Paint & Coating Industry January 2011

January 2011 VOLUME 27, NUMBER 1

INSIDE A New Solvent-Free Defoamer/Deaerator

Paint

Coatings Industry

Renewable Products The Anatomy of Colorants

Globally Serving Liquid and Powder Formulators and Manufacturers

Nanotechnology

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Mason Color’s high performance pigment technology for coatings provides the ultimate in heat resistance, UV durability, and chemical resistance. Our mixed metal oxide pigments meet the most exacting color and durability requirements of the defense, architectural, stove and heating products, and roofing industries. These pigments add vibrant color to building facades, stove equipment, exhaust parts and outdoor furnishings and equipment. These advanced technology pigments can be incorporated into any coating platform including powder coatings, electrocoat, high solids and waterborne paints.

Mason Color Works, Inc. A History of Pigment Technology Excellence Mason Color Works has been manufacturing high temperature, inorganic pigments since 1842. For more than 40 years Mason Color has been a global supplier of high performance pigments to all sectors of the ceramic industry including pottery, artware, bricks, sanitaryware and roofing materials. In the last 45 years, Mason Color has expanded into the high technology Investment Casting Industry. Our ISO Compliant Cobalt Aluminate products are integral in the manufacturing jet turbine blades and medical devices. In the 1990s heralded the emergence of the fireplace gas log industry and Mason Color's participation as a supplier of high quality, high temperature pigments for this use. Soon thereafter, the Swimming Pool and Spa colorant industry embraced Mason's pigment technology. Our high quality pigment exceed the demands for resistance to punishing UV energy and the aggressive chemicals used in swimming pools. Our fully outfitted Powder Coating Laboratory and skilled technicians will help you choose the perfect color for your most demanding requirements.

See you at the American Coatings Show, April 2010 in Charlotte, NC.

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CONTENTS PA I N T & C O AT I N G S I N D U S T RY , V O L U M E 2 7 , N U M B E R 1

January 2011

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ONLINE FEATURES w w w. pcimag.com Topographic Confocal Raman Imaging – The Next Evolutionary Leap in Cutting-Edge Microscope Configurations, WITec Sansin Introduces Color System for its Interior Enviro Stain, Sansin Corp. Dehumidification Alleviates Pressure To Meet Blasting and Coating Challenges, Polygon

FEATURES 24 The Anatomy of Multipurpose Solventborne Colourants, Resene Paints Ltd. 28 Current and Impending Developments in Silica Nanoparticle Use in UV-Curable Systems, Nissan Chemical America Corporation 32 Design and Performance of Radiation-Curable Acrylates with High Renewable Carbon Content, Sartomer USA, LLC 36 A New Solvent-Free Defoamer/Deaerator, Cytec Austria GmbH 39 UV-Curable Anti-Fog Coatings, DSM Desotech

Laser Diffraction Particle Size Analyzer Helps Manufacturer Optimize Furniture Coating, Malvern Instruments Color Trends 2011, PQI, CIL Paints and Sico

DEPARTMENTS 6 8 14 16 22 45 48 50

Viewpoint Industry News Calendar of Events Company News Names in the News Products Classifieds Advertiser Index

42 New Applications for Conductive Carbon Nanotube Inks Now Possible, SouthWest NanoTechnologies

BUSINESS TOOLS 44 Green Showcases

PCI - PAINT & COATINGS INDUSTRY (ISSN 0884-3848) is published 12 times annually, monthly, by BNP Media, 2401 W. Big Beaver Rd., Suite 700, Troy, MI 48084-3333. Telephone: (248) 362-3700, Fax: (248) 362-0317. No charge for subscriptions to qualified individuals. Annual rate for subscriptions to nonqualified individuals in the U.S.A.: $115.00 USD. Annual rate for subscriptions to nonqualified individuals in Canada: $149.00 USD (includes GST & postage); all other countries: $165.00 (int’l mail) payable in U.S. funds. Printed in the U.S.A. Copyright 2011, by BNP Media. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the publisher. The publisher is not responsible for product claims and representations. Periodicals Postage Paid at Troy, MI and at additional mailing offices. POSTMASTER: Send address changes to: PCI - PAINT & COATINGS INDUSTRY, P.O. Box 2145, Skokie, IL 60076. Canada Post: Publications Mail Agreement #40612608. GST account: 131263923. Send returns (Canada) to Pitney Bowes, P.O. Box 25542, London, ON, N6C 6B2. Change of address: Send old address label along with new address to PCI - PAINT & COATINGS INDUSTRY, P.O. Box 2145, Skokie, IL 60076. For single copies or back issues: contact Ann Kalb at (248) 244-6499 or [email protected].

Audited by BPA Worldwide

Associate Member

Printed in the U.S.A.

V I EWPOINT

Color Trends I always find it so interesting when the coatings manufacturers release their color forecasts. Do they really know what color themes consumers will gravitate toward, or are they setting the trends by issuing their reports? Whatever the answer, a lot of time and research goes into these projections. I spent some time with Jane Harrington, Manager, Color Styling, at PPG Industries, during the company’s annual Automotive Color Trend Show. She spends much of her year surfing the net, attending events and shows, and clipping photos out of newspapers, magazines and brochures in order to analyze the latest trends in culture, fashion, movies, media, electronics and many consumer products. She then comes up with a theme that best describes the automotive color palette that her team develops. This year’s theme is titled InSite and draws on the influences of insights from PPG’s other color- and coatings-oriented businesses, such as architectural, industrial, protective and marine, and aerospace coatings. PPG presented automotive designers new colors such as Denim, a classic true blue with a high-effect sparkle; Cognac, a rich, coppery, warm brown with an iridescent highlight; Silky Silver, a liquid silver look with a slight bronze cast; Moonshine Blue, a pale silvery blue like the reflection of the moon on a lake; and Wicked, a sinister green color inspired by couture fashion. I have also reviewed several other coatings manufacturers’ 2011 color trend forecasts and found that all of them are inspired by the global mood following the economic crisis. Each is worded in its own unique way, but the general theme is the same. According to Canadian paint brand CIL Paints, the forecast for 2011 is sunny. The hottest color is a light, citrus yellow, symbolizing a sense of fun, freedom and positive energy. “The new yellow is associated with warmth and sunshine,” said Martin Tustin-Fuchs, Marketing Manager for CIL Paints. “It’s a very optimistic, cheerful and refreshing color, sending a clear message that, as a society,

we’re done with tough times and look forward to brighter days ahead.” Sico, another Canadian paint brand, feels that consumers are looking for the simple pleasures in life and want to surround themselves with heart-warming colors. From timeless denim blues and earthy clay and wood tones, to leafy greens, strawberry reds, sunny yellows and airy pastels, its 2011-2012 paint palette is dominated by warm, homey and comforting colours – a reflection of the public mood, said Dominique Pépin, Marketing Manager for Sico and a Chairholder of the international color forecaster Color Marketing Group. Sherwin-Williams celebrates individualism – a trend toward not being trendy at all – through its Colormix™ 2011 collection. “We’ve seen reactions to the economy move from panic to acceptance, if not appreciation, because people are finding they have the opportunity to be true to themselves,” said Jackie Jordan, Director of Color Marketing for Sherwin-Williams. Akzo Nobel’s color theme for 2011 is Appreciation, as this is a time of acceptance and appreciation of things we so often take for granted. The Color of the Year is a light, airy, citrus yellow that symbolizes a freer spirit, sense of fun and positive energy. There are many other forecasts out there, but it is clear from these that the global mood is changing from dreary to hopeful, with a new sense of appreciation for what we have. Here’s hoping that 2011 will indeed reflect that mood in more than just the colors we choose!

By Kristin Johansson, Editor | PCI



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Markets:

Architectural Coatings

Industrial Coatings

Container Automotive

Civil Aerospace Engineering

Coatings Technologies:

SolventBorne Coatings

WaterBorne Coatings

Powder Coatings

Surface/Substrate:

Wood

Brick

Concrete

Marine & Maintenance

UV Coatings

Metal

Stucco

High Solids Coatings

Vinyl

Plastic

Brenntag understands change is normal for the Coatings Industry. As the Coatings Industry has evolved through the years, Brenntag’s Paint and Coatings Team continues to provide our customers with the products and services to stay competitive in the marketplace. Whether you face different markets, technologies, or substrate applications, Brenntag’s Paint and Coatings Team can help you to adapt and make change work to your advantage.

Brenntag offers a complete specialty and industrial product portfolio, technical assistance with product development, formulations and applications know-how, superior logistics with versatile blending and re-packaging capabilities, and last, but not least, commitment to quality and safety. Change demands innovation and creativity. Brenntag Understands. Brenntag North America, Inc. (610) 926-6100 Ext: 3858 [email protected] brenntagnorthamerica.com

The Glocal® Chemical Distributor.

I NDUSTRY NEWS

UMass Team Creates Biomass Alternative to Petroleum Production AMHERST, MA – A research team from the UMass Amherst Chemical Engineering department reports in the November 26 issue of Science that it has developed a way to produce high-volume chemical feedstocks, including benzene, toluene, xylenes and olefins, from pyrolytic biooils, the cheapest liquid fuels available today derived from biomass. As George Huber, the Armstrong Associate Professor in the Chemical Engineering Department at UMass Amherst, explained, “Thanks to this breakthrough, we can meet the need to make commodity chemical feedstocks entirely through processing pyrolysis oils. We are making the same molecules from biomass that are currently being produced from petroleum, with no infrastructure changes required.” The new process could reduce or eliminate industry’s reliance on fossil fuels to make industrial chemicals worth an estimated $400 billion annually. Instead of buying petroleum

by the barrel, chemical manufacturers will now be able to use relatively cheaper, widely available pyrolysis oils made from waste wood, agricultural waste and non-food energy crops to produce the same highvalue materials for making everything from solvents and detergents to plastics and fibers. In the paper, Huber and doctoral students Tushar Vispute, Aimaro Sanno and Huiyan Zhang show how to make olefins such as ethylene and propylene, the building blocks of many plastics and resins, plus aromatics such as benzene, toluene and xylenes found in dyes, plastics and polyurethane, from biomass-based pyrolysis oils.

Nanotechnology Helps Profits by Cutting Energy Costs BOSTON – A report by Lux Research, titled “Nanotech’s Answer Key to the Energy Problem,” quantifies the potential impact that six nanotechnology innovations could have on energy consumption in three representative regions: the United States, Germany and Japan. The six technologies are low-friction tribological coatings in automotive engines, nanofiber air filters, nano-enabled insulation, lightweight nanocomposite automotive parts, thermochromic windows and quantum dot (QD)-enabled light sources. “Full adoption of all six nanotechnologies listed could reduce total energy consumption by 12 percent, which would be comparable to shutting down all the coal plants in the U.S.,” said David Hwang, an Analyst for Lux Research and the report’s lead author. “A more realistic adoption scenario could see a 1.6 percent drop in consumption that, while less impressive, is still substantial compared to the potential impact of energy conservation or renewable energy generation.” Visit www.luxresearchinc.com for more information.

EPA Unveils New Tool to Promote Safer Chemicals WASHINGTON, DC – The U.S. Environmental Protection Agency (EPA) has announced new criteria to help companies and other groups, such as states and environmental organizations, identify safer chemicals. As part of the agency’s Design for the Environment (DfE) program, EPA unveiled the new criteria, which are an important tool under its DfE Alternatives Assessments for 8

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A pilot plant on the UMass Amherst campus is now producing these chemicals on a liter-quantity scale using this new method. The technology has been licensed to Anellotech Corp., co-founded by Huber and David Sudolsky of New York City. Anellotech is also developing UMass Amherst technology invented by the Huber research team to convert solid biomass directly into chemicals. Thus, pyrolysis oil represents a second renewable feedstock for Anellotech. Sudolsky, Anellotech’s CEO, said, “There are several companies developing technology to produce pyrolysis oil from biomass. The problem has been that pyrolysis oils must be upgraded to be useable. But with the new UMass Amherst process, Anellotech can now convert these pyrolysis oils into valuable chemicals at higher efficiency and with very attractive economics. This is very exciting.”

identifying safer alternatives to chemicals that pose a concern to human health and the environment. Information on chemical hazards from DfE Alternatives Assessments is combined with industry data on performance and cost to guide the choice of safer alternatives. To distinguish among alternatives, DfE evaluates data for each chemical and assigns hazard levels of high, moderate or low for human health and environmental concerns. DfE Alternatives Assessments will be conducted for bisphenol A, phthalates, decabromodiphenyl ether, hexabromocyclododecane, and nonylphenol and nonylphenol ethoxylates. EPA will accept comment on the criteria through January 31, 2011. For additional information, visit http://epa.gov/dfe/alternative_assessments.html.

Study of Nanocomposites Market Now Available BIRMINGHAM, UK – A new market research report by Future Markets Inc. provides a detailed discussion of the global nanocomposites market. Global revenues for polymeric nanocomposites were approximately $390 million in 2009. A diverse range of markets are being impacted by polymer nanocomposites. Clay nanocomposites have the largest market share, with revenues of approximately $220 million in 2009 and main application markets in packaging, flame retardants, and aerospace and aviation (including military applications). Nanofiber composites accounted for $79.5 million in global revenues in 2009, with main application markets in filtration. Metal and metal oxide nanocom-

I NDUSTRY NEWS posites accounted for $41 million in global revenues in 2009, with main application markets in aerospace and electronics. Carbon nanotube nanocomposites accounted for $37 million in global revenues in 2009, with main application markets in aerospace, consumer, and military and defense. The report, titled “The World Market for Nanocomposites (Metal Nanoparticles, Nanotubes, Nanoclays, Nanofibers, Graphene, Fullerenes and POSS),” was published in October 2010. For additional information about the report, visit http:// marketpublishers.com.

Hydraulic Institute Updates Standards PARSIPPANY, NJ – The Hydraulic Institute has updated the 2000 edition of the ANSI/HI standard on sealless centrifugal pumps and published ANSIHI 5.1-5.6 – 2010 Sealless Rotodynamic Pumps for Nomenclature, Definitions, Application, Operation and Test. The revised standard covers sealless rotodynamic pumps driven by canned motors or through magnetic couplings with conventional motors. The Hydraulic Institute has also updated its standard ANSI/HI 4.1-4.6 – 2010 Sealless, Magnetically Driven Rotary Pumps. This standard covers the unique features of these pumps and includes sections on types and nomenclature; definitions; design and applications; installation, operation, and maintenance; and testing of these pumps. Additionally, the Hydraulic Institute has updated the ANSI/HI Standard for Rotary Pump Tests version 2000 and has introduced ANSI/HI 3.6 – 2010, Rotary Pump Tests. This updated standard applies to industrial/commercial rotary positive displacement pumps and includes

detailed procedures on the setup and methods for conducting hydrostatic test and performance tests of such pumps.

NCCA Offers Online Resources CLEVELAND – The National Coil Coating Association (NCCA) is now offering its “Key to the Toolbox” pocket guide, a free publication designed to unlock the NCCA’s array of online educational resources. Because there are so many educational tools available from NCCA, the organization has created a key to help you select the right tool for your needs. Categorized for current prepaint users, potential users, building and construction manufacturers, and employee training, the “Key to the Toolbox” guide helps users drill down to the online assets they need, including videos, e-tutorials, case studies, tool kits, articles, press releases and more. All of these tools are free and ready to view or download on the NCCA’s manufacturers’ Web site, www.coilcoatinginstitute.org. Looking for even more specific information about the benefits of coil coating? Be sure to try the handy online “Resource Wizard” search engine, which is also available on the NCCA’s manufacturers’ Web site. To order a free copy of “The Key to the Toolbox,” complete the online form at www.coilcoating.org/toolboxrequest.

CalPoly Offers Short Course in February SAN LUIS OBISPO, CA – The Polymers and Coatings Program at California Polytechnic State University, San Luis Obispo, CA, will offer a Polymers and Coatings Introductory Short Course during the week of February 7-11, 2011.

OBITUARY Industry Loses R. Emmett Carroll Jr. TRENTON, NJ – R. Emmett Carroll Jr., CEO of R.E. Carroll Inc., passed away on Monday, November 15, 2010, at the age of 81. Carroll was with R.E. Carroll Inc. for over 50 years, including his tenure as President from 1987 to 2009, and most recently as Chief Executive Officer. He was well known throughout the rubber, paint and coatings, and process oils industries. He served in varying capacities within the Rubber division of the American Chemical Society and the Philadelphia Society of Coatings Technology (PSCT). Carroll was a past-President of the Philadelphia Rubber Group and a Board member of the 25th Year Club of the Rubber division. Carroll is survived by his wife of 51 years Marilyn, his daughter Linda, two sons Robert and David (both of whom are employees of R.E. Carroll Inc.), seven grandchildren, and two step-grandchildren.

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The early registration deadline for this course is January 16, 2011. More detailed information is available at w w w.polymerscoatings.calpoly.edu/ short%20courses.htm.

Powder Coating Forum to Take Place in June COLUMBUS, OH – The Powder Coating Forum is scheduled for June 7-8, 2011, at the The Westin, Columbus, OH. This twoday workshop and symposium provides the basics of powder coating formulation, emerging technologies and trends, and networking with leading industry providers to discuss best practices. On day one, attendees receive hands-on learning experience at a live demonstration of the powder coating manufacturing process at a local research lab. Day two consists of a symposium led by industry experts illuminating the latest powder coating materials and processing technology. For more information, visit www.powdercoatingsforum.com.

Canada Takes Further Action on Bisphenol A OTTAWA, Canada – The Government of Canada is proposing a new regulatory instrument to address releases of bisphenol A (BPA) through industrial effluent. The proposed new instrument comes days after the Government of Canada announced that BPA, a chemical that can be harmful to both human health and the environment, is being added to Schedule 1 of Canadian Environmental Protection Act, 1999 (CEPA 1999). “The Government of Canada is taking a comprehensive approach to managing risks associated with bisphenol A, and this latest step addresses industrial use of the chemical in Canada,” said Canada’s Environment Minister, Jim Prentice, “The proposed rules will require facilities to develop and implement plans to limit releases of BPA to the environment and to submit ongoing progress reports to the Government of Canada.” The regulatory instrument is a Pollution Prevention Planning Notice that was published in the Canada Gazette Part 1 on October 16, 2010. The Pollution Prevention Planning Notice is the latest in a series of government actions to manage the risks of BPA, including the prohibition on the advertising, importation and sale of polycarbonate baby bottles containing the substance and

How to make your products greener and their performance pure gold. Our customers come to us to help them stay ahead of competitive pressures by helping to re-formulate existing products and innovate new ones – meeting “green” goals while preserving and even enhancing performance. We call it Greenability. You’ll call it genius.  Another fine result of the Innovation Principle – . Let us help you work through the formula for Greenability.

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I NDUSTRY NEWS ongoing work with Canada’s provincial and municipal counterparts to address potential releases that could occur during the disposal or recycling of products.

Mark Your Calendars Now to Attend CTT in 2011 TROY, MI – Coatings Trends & Technologies (CTT) is scheduled for September 13-14, 2011, at the Doubletree Chicago in Oak Brook, IL. The theme this year is “Innovate to Survive.” Coatings professionals, including formulators, technical managers, R&D personnel, applicators, raw material suppliers, quality control personnel, analytical testing personnel, technicians, technical directors, purchasing directors and students, are encouraged to attend. The conference will benefit anyone who wants to stay abreast of the latest developments, and will provide an excellent chance to interact with industry experts. See page 47 for information on the call for papers.

EuroNanoForum to Cover Entire Lifecycle of Nanotechnology BUDAPEST, Hungary – EuroNanoForum will take place at the Budapest Congress and World Trade Center in Budapest, Hungary, from May 30 to June 1, 2011. The event will cover the whole lifecycle of nanotechnology, from basic research to nanotechnology-enabled products. In addition to a full conference program, a matchmaking program and exhibition will maximize opportunities for networking.

out the supply chain, major aerospace and defense OEMs are working with SME to create a vertically integrated event that will help manufacturing professionals keep current with new technologies and advanced manufacturing processes. To register for AeroDef, visit www. xpressreg.net/register/aero041/start.asp. 䡲

February 23-25, Orlando, FL

OEMs Join SME to Sponsor Conference

Join us for an update on

DEARBORN, MI – The Society of Manufacturing Engineers (SME) is partnering with aerospace and defense OEMs to sponsor the AeroDef Manufacturing Exposition and Conference, to be held April 5-7, 2011, at the Anaheim Convention Center in Anaheim, CA. With mounting pressure to innovate and drive technology development through-

the most recent emerging technologies and opportunities in coatings, functional polymers, processes and allied materials presented by world-renowned scientists and technologists.

www.smartcoatings.org

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INNOVATION = VALUE COATINGS:

Go ‘green’ with innovative binder and additive technologies.

ADHESIVES & SEALANTS: Conserve energy in production and product use.

ELASTOMERS:

Formulate with alternative raw materials, and do it competitively.

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C ALENDAR Meetings, Shows and Educational Programs JAN 28-30 The India International Coatings Show 2011 www.coatingsindia.com

FEB. 1-2 Kuwait Laboratory Technology Conference www.kuwaitlabex.com

31-Feb. 3 SSPC 2011 Greencoat www.sspc.org/sspc2011

7-11 Polymers and Coatings Introductory Short Course

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www.polymerscoatings.calpoly.edu/short%20 courses.htm 14-16 TiO2 2011 www.tio2conference.com

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MARCH 1-3 Middle East Coatings Show www.coatings-group.com 8-9 uv.eb West www.radtech.org 13-18 Pittcon www.pittcon.org 15-16 Principles of Waterborne Coatings www.pra-world.com/nandl/training/courses

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5-7 AeroDef Manufacturing www.aerodefevent.com 10-12 Radiation Curing Technology www.pra-world.com/nandl/training/courses 13-15 PDA 2011 Annual Meeting www.pda-online.org/polyurea_annual_ conference.asp 17-19 ASC Spring Convention www.ascouncil.org 27-28 Windy City Coatings Course http://chicagocoatings.org

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C O M PA N Y NEWS

Celanese Develops Technology for Production of Industrial-Use Ethanol DALLAS – Celanese Corp. is planning to construct manufacturing facilities in China and the United States to utilize recently developed advanced technology for the production of ethanol for chemical applications and other industrial uses. Celanese’s process technology builds on the company’s acetyl platform and integrates new technologies to produce ethanol using basic hydrocarbon feedstocks. Following necessary approvals, Celanese intends to construct one, and possibly two, industrial ethanol complexes in China to serve the fast-growing Asia region. Initial annual production capac-

ity of each complex is expected to be approximately 400,000 tons. The company could begin industrial ethanol production within 30 months after project approvals. Celanese’s technology allows capacity to be more than doubled at sig-

DSM to Acquire 51 Percent of AGI Corp. HEERLEN, The Netherlands – Royal DSM N.V. announced that it intends to acquire a 51 percent stake in AGI Corp. of Taiwan (AGI) through a subscription for newly to-be-issued shares combined with a public tender offer, subject to AGI corporate approvals and to regulatory and other customary conditions, approvals and notifications. AGI offers a broad range of environmentally friendly UV-curable resins and other products. AGI reported net sales in 2009 of NTD 3,561 million (approximately EUR 90 million).

Eckart America Corp. Consolidates Distribution Network LOUISVILLE, KY – Eckart America Corp. is consolidating its sales agency and distribution network within the United States. The Northeast has been expanded, with DN Lukens as Eckart’s regional representative to include eastern New York, eastern Pennsylvania and New Jersey. This will effectively give DN Lukens coverage from Maine to New Jersey. The upper Midwest has been expanded, with Hall Technologies as the regional representative to include North and South Dakota, Minnesota, Wisconsin, Iowa and Illinois. In addition, Hall Technologies has announced its acquisition of Sexton Inc., covering southern Ohio and Indiana. As a result, Eckart will further expand Hall’s territory to include Michigan, western Pennsylvania, western New York and Kentucky.

Arkema Plans to Acquire Total’s Photocure and Coatings Resins PARIS – Arkema has announced plans to acquire the Coatings Resins (Cray Valley and Cook Composite Polymers) and Photocure Resins (Sartomer) businesses of Total’s Specialty Chemicals activities for a EUR 550 million enterprise value. The project would establish Arkema as a leader in the global coatings resins market. 16

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nificantly less than the original investment to meet future demand. The China units would utilize coal as the primary raw material. Celanese also intends to build an approximately 40,000-ton industrial ethanol production unit at its Clear Lake, TX, facility for either internal use or merchant demand. The unit will also support continuing technology development efforts over the next several years. Following approvals, construction of the unit is anticipated to begin in mid-2011 and to be completed by the end of 2012. The Clear Lake facility would utilize natural gas as its primary raw material.

It would further increase the downstream integration of its acrylics chain, while offering major potential for growth and synergies. The businesses comprise the coatings resins of Cray Valley (Europe, Asia and South Africa) and Cook Composite Polymers (United States), as well as the photocure resins of Sartomer (Europe, United States and Asia).

Clariant Adds Polyetheramines to Product Offerings MUTTENZ, Switzerland – In response to increasing demand, Clariant has added polyetheramines to its range of industrial and consumer specialty products. A new reactor in the company’s nitril-amine plant in Gendorf, Germany, has started production to facilitate the portfolio extension.

D&F Distribution Inc. Partners With OMG Americas CLEVELAND – D&F Distribution Inc. has been named OMG Americas’ technical partner for the Advanced Organic business group. The company will represent the OMG Borchi® coatings additive business in Texas, Oklahoma, Louisiana and Arkansas.

BASF and INEOS to Establish Styrenics Company LUDWIGSHAFEN, Germany/LYNDHURST, UK – BASF SE, Ludwigshafen, Germany, and INEOS Industries Holdings Limited, Lyndhurst, UK, have announced their intention to combine their global business activities in styrene monomers (SM), polystyrene (PS), acrylonitrile butadiene styrene (ABS), styrene-butadiene block copolymers (SBC) and other styrene-based copolymers, as well as copolymer blends, into a new joint venture called Styrolution. BASF’s styrenics activities now operate as a separate company with the name Styrolution. INEOS plans to acquire the other 50-percent shareholding in its 50-50 styrenics joint venture, INEOS NOVA, from NOVA Chemicals. Upon completion of the

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C O M PA N Y NEWS proposed joint venture with BASF, INEOS will transfer these activities into the new Styrolution group. BASF and INEOS will retain their expandable polystyrene businesses. The SM/PS capacities in Ludwigshafen used to produce foam will also remain with BASF as well as the SM/PS business of BASFYPC Co. Ltd. in Nanjing, China. Styrolution headquarters will be located in Frankfurt/Main, Germany. BASF and INEOS will each own 50 percent of the joint venture. BASF and INEOS will continue to operate as strictly independent companies until the completion of the deal, which is anticipated in 2011.

Key Finishes LLC Celebrates Grand Opening COLUMBUS, OH – Key Finishes LLC, Columbus, OH, has announced the grand opening of its toll bonding facility. Located in a 5500-square-foot facility on the west side of Columbus, the company

fills an open niche in the powder coatings industry by providing a full-service, cradle-to-grave metallic bonding operation. Key Finishes’ ability to control the process from base formulation to bonded product is critical to producing a highquality metallic finish. Initially, the company has capacity to make approximately two million pounds of bonded metallic powder coatings per year, with future expansion planned as required.

Dow Implements Improvements in Stade Plant STADE, Germany – The Dow Chemical Co. has increased its monopropylene glycol capacity by 15 percent, an additional 35 kilotons per annum (KTA), in the Stade, Germany, plant after completion of an advanced energy improvement and technology optimization project. The Stade expansion was completed in August 2010 during planned maintenance; it raises the plant’s propylene glycol nameplate capacity to approximately 270 KTA.

Nubiola Expands Manufacturing Capacity BARCELONA, Spain – Nubiola has recently expanded its manufacturing capacity of micronized red iron oxides (Nubifer Red 5000 series) by 20 percent in its Girardota (Colombia) production plant. The investment was approved last year; the expanded line has been working at full capacity since mid-2010.

Sherwin-Williams Coatings Meet Strict NRC Requirements CLEVELAND – Design engineers, contractors and equipment manufacturers doing business with the U.S. Department of Energy/Nuclear Regulatory Commission (DOE/NRC) can look to Sherwin-Williams for guidance in specifying a full range of nuclear safety-related protective coating and lining systems manufactured to the requirements of ANSI/ASME NQA-1, Quality Assurance Program Requirements for Nuclear Facilities, and 10 CFR 50 Appendix B, Quality Assurance

C O M PA N Y N E W S

Criteria for Nuclear Power Plants and Fuel Reprocessing Plants. Products manufactured under this program are available for use in nuclear power plants, nuclear fuel facilities and nuclear waste facilities.

Munters MCS is Now Named Polygon STOCKHOLM, Sweden – The Munters Moisture Control Services (MCS) division has separated from Munters Group and is now an independent company known as Polygon. The former MCS division is wholly owned by Triton and operates in all countries on a standalone basis. Polygon serves the property damage restoration and temporary humidity control markets.

Dow Advanced Materials Breaks Ground on Plant in Vietnam MIDLAND, MI – Dow Advanced Materials, a division of The Dow Chemical Co., has broken ground on a new manufacturing facility in Dong Nai Province in southern Vietnam

for the production of acrylic and styreneacrylic polymers used in the paint, coatings, construction, packaging, home and personal care industries. The new plant, scheduled to go on-stream in September 2011, will be shared by three Dow Advanced Materials businesses: Dow Coating Materials, Dow Building & Construction and Dow Adhesives & Functional Polymers.

PPG Partners With ACCESSA Coatings Solutions

capabilities in India with the formation of a new Indian subsidiary, Arch Protection Chemicals Pvt. Ltd. (APCPL). Capitalizing on the indigenous availability of raw materials and cost-effective production, APCPL will offer biocide products and services that are tailored to meet the needs of Indian customers.

H.B. Fuller Announces Expansion into India

INDIANAPOLIS – PPG has entered into an agreement with ACCESSA Coatings Solutions for its line of TrueFinish® Industrial Coatings. ACCESSA will serve as PPG’s sales and distribution partner. PPG joins the current general industrial segment of ACCESSA’s product segment offerings.

ST. PAUL, MN – H.B. Fuller Co. has broken ground on construction of a $12 million manufacturing facility to support the expansion of business into India. The plant will be located near the city of Pune, approximately 100 kilometers south of Mumbai. The plant is expected to be operational by August 2011.

Arch Chemicals Launches New Company in India

Hall Technologies Acquires Sexton & Co.

MUMBAI, India – Arch Chemicals Inc. is expanding its marketing presence and establishing new manufacturing

ST. LOUIS, MO – Hall Technologies Inc., St. Louis, MO, has acquired Sexton & Co. Inc., Cincinnati, OH. Sexton & Co. Inc.

watch for further developments. As a fully integrated global resource for

coatings formulators, Arkema Emulsion Systems provides the strategic manufacturing, logistics and technical support you need, wherever you need it. For example, our recently announced emulsions plant, scheduled for a 2012 start-up in Changshu, China, will enable improved support to formulators already operating in or expanding into the region. Equally important, our focus on global product offerings gives you seamless technology transfer to ensure consistent product performance throughout the world. More developments are coming at the speed of light, so keep an eye out. At Arkema Emulsion Systems, we’re focused on your future.

©2011 Arkema Inc.

arkemaemulsionsystems.com

C O M PA N Y NEWS is a specialty chemical distributor that has served the graphic arts, paint and coatings, and plastics industries for over 40 years. The acquisition expands Hall Technologies’ coverage range into Ohio, Kentucky, Indiana, Michigan, West Virginia, southwestern New York and western Pennsylvania.

Songwon Announces Two New Joint Ventures ULSAN, Korea – Songwon Industrial Co. Ltd., Ulsan, Korea, has announced two new joint ventures, one with Tangshan Baifu Chemical Co. Ltd., Tangshan, China, and one with HPL Additives Ltd. (HPL), Delhi, India. Songwon and HPL have signed a letter of intent to form Songwon HPL Additives PVT LTD. HPL will transfer all its business and assets related to polymer stabilizers to the new entity, which will be owned 40 percent by HPL and 60 percent by Songwon. The parties expect

the new company to be operational by the second quarter of 2011. Songwon and Tangshan Baifu Chemical Co. Ltd. have signed an agreement to establish a joint venture to manufacture and sell Thioester antioxidants. The new company will be named Songwon Baifu Chemical Co. Ltd. and will have a capacity of 6,000 tons of Thioester antioxidants.

AMETEK Inc. Acquires Material Testing Technology PAOLI, PA – AMETEK Inc., Paoli, PA, has acquired Atlas Material Testing Technology LLC, a provider of weathering test instruments and related testing and consulting services, from Industrial Growth Partners. Atlas is headquartered in Chicago, with additional manufacturing operations in Germany and a network of outdoor and laboratory testing facilities around the globe.

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Archway Sales Acquires DH Litter Co. ST. LOUIS, MO – Archway Sales Inc., St. Louis, MO, has acquired D.H. Litter Co., Elmsford, NY. D.H. Litter Co. is a specialty chemical distributor that has served the northeast and mid-Atlantic United States since 1921. The acquisition enhances Archway’s coverage, product line portfolio and distribution network in the northeast and mid-Atlantic states.

Momentive Specialty Chemicals to Sell Ink and Adhesive Resins Business COLUMBUS, OH – Momentive Specialty Chemicals Inc. has signed a definitive agreement to sell its global Ink & Adhesive Resins (IAR) business to Harima Chemicals Inc., a producer of pine-based products. IAR is a supplier of resins and additives to the graphics arts, adhesives, aroma chemical, synthetic rubber and specialty coating industries. 䡲

N AMES IN THE NEWS 䡲 Bill Alhofen has been promoted to National Sales Manager for Charles Ross and Son Co. Alhofen will handle general sales management duties as well as work with the company’s network of sales representatives.

additive and metal carboxylate sales for the Advanced Organics business into the coatings, composites and inks markets.

䡲 Robert Quesnette

䡲 Don Deihs has been named President of Fitz Chem Corp. Bob Becker, Fitz Chem’s founder, will assume the role of Chairman.

Alhofen

䡲 Antoine Fady has been appointed Chief Executive Officer (CEO)

of Flint Group. Fady will succeed Charles Knott, who will hand over the responsibilities in order to separate the duties of the Chairman and CEO. Knott will continue on as Chairman.

䡲 Shaun Julian has joined E.W. Kaufmann Co. He is responsible for a territory that includes central and northern New Jersey, metro New York City through Albany, NY, western Connecticut, and western Massachusetts.

䡲 BASF has appointed Michael McHenry Vice President, Resins and Additives, in North America. He will be based in Wyandotte, MI.

䡲 OMG Americas

has hired Christopher Niblock as Regional Account Manager for the Midwest territory. He is responsible for

Gaco’s WallFoam division covering New England. Jeff Dawdy has joined Gaco Western as a Regional Sales Manager for the WallFoam Peterson division in the newly formed Midwest region. Shawn Wate joins Gaco Western as a Field Service Technician for the Northwest region. Eric Peterson has been appointed the company’s new Chief Financial Officer.

䡲 Steve Randall has joined Archway Sales Inc. as a member of the Customer Service team for the St. Louis branch. Rosemarie AyalaOlson and Erica Gerner have also joined Archway Sales. They will work in the company’s Midwest region. 䡲 Evonik Degussa Corp. announced the appointment of Bonnie Tully as Vice President and Site Manager for the company’s Mobile, AL, operations. Tully has been Plant Manager for Evonik’s lubricant additives facility in Singapore. She will take over from Tom Bates, President of Evonik's North America region, who will now concentrate on the growth and development of Evonik in North America. 䡲

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has been appointed

Gaco Western’s Regional Sales Manager for

JANUARY 2011 | W W W . P C I M A G . C O M

T

oday’s consumer has become much more demanding, and this is a trend unlikely to be reversed. These demands obviously include enhanced product appearance, which extends even to utilitarian items. Colour is a very important element of appearance, and the paint industry has responded with a broad palette of beautiful colours for architectural finishes, as well as for highly prized items such as automobiles and pleasure marine craft. In the past, coatings for heavy industrial structures always emphasized protective qualities over and above decorative qualities, and were generally offered in a limited colour range. The term ‘industrial colour match’ indicated that if the supplied colour was somewhere near the same hue as the desired colour, then that was all that could be expected for a heavy-duty protective coating. This situation rarely exists in today’s world, and the protective coating supplier is expected to approach the other, above-named markets for colour offering and quality. Concentrated pigment pastes, which exhibit compatibility with a broad range of coatings chemistry, are a useful tool in achieving this goal, and we will examine the technology of such pastes in this presentation.

Pigments Pigments are naturally the heart of the pigment paste and, in addition to the obvious properties of shade, tinting strength, lightfastness etc., for colourants designed for protective coatings, one must especially be aware of solvent resistance and surface reactivity. Inorganic pigments exhibit excellent solvent resistance properties mainly due to their inherent chemistry. Their ionic crystal lattices have an interlocking arrangement of metal cations and non-metallic anions, which doesn’t allow this class of pigments to dissolve in solvents. On the other hand, organic pigments exist in the form of molecular crystals where individual molecules are linked

FIGURE 1 | Enhancing solvent stability in a pigment.

SO3-

SO3- Na+ 2 N

N

H O

2 Ca++

COO- Na+ Soluble

N

N

H O

-OOC Ca++

Ca++ -O3S COOInsoluble PR 57:1

O H

N

N

together by means of weak hydrogen bonds and π-π interactions. The solvent stability of an organic pigment depends upon the strength and extent of the interactions between the constituent molecules in its crystal lattice. In addition to this, the chemistry of the basic molecule also plays a significant role in determining the solvent stability of the resulting pigment crystals. The stability of the pigment can be enhanced by maximizing intermolecular contacts/interaction in a crystal lattice, and this can be designed into the basic structure. This is illustrated in Figure 1. Strong bonding can also be serendipitous, as exhibited by the NH – CO interactions in the β quinacridone crystal (Figure 2). Some pigments undergo phase change when used in combination with certain solvents. Alpha modification of copper phthalocyanine is a classic example of this. The crystal phase of this pigment is relatively unstable compared to its other polymorphs. When this pigment is used in applications containing aromatic solvents, the shade of the system will change from reddish blue to greenish blue, accompanied by a reduction in colour strength. This is due to the dissolution of the α form into the solvent and its re-crystallization into the more stable (but greener) β form. Because the re-crystallization is uncontrolled, nonideal particle sizes can also lead to poorer tint strength and reduced durability. Bivalent metal ions used in the lake pigments can sometimes cause gelling of paints containing carboxylic binders. This is due to the possible crosslinking of two carboxylic polymer chains through the bivalent metal ions. Improper processing of certain inorganic pigments can often create problems in systems containing reactive binders. Over grinding of such pigments results in the delamination of its surface treatment followed by the release of reactive metal ions to the continuous phase. These metal ions can sometime accelerate isocyanate/polyol reactions and thereby reduce the pot life. They can also act as driers and cause in-can skinning of alkyd paints. Certain organic pigments can interact with reactive polymers and, for example, when used in an amine-cured epoxy system, can cause unacceptable shade changes. Pigment Orange 5 and Pigment Red 4 are examples of pigments that come in this category. The photograph in Figure 3 clearly shows the dramatic difference in shade when PO 5 was used in the colouration of an alkyd and an amine-cured epoxy paint system. The treatment of pigments with their derivatives is a common practice in the pigment industry. This is carried out mainly on those pigments that have inert surfaces (i.e., have no groups or atoms that can form linkages with the surfactant or resin moieties). The idea is to derivatize the same pig-

By Colin Gooch, F.T.S.C. Technical Director and Dr. Ajith M. Aravindakshan, Colourant Development Manager | Resene Paints Ltd., New Zealand 24

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ment pre-cursor via sulphonation, chloromethylation, chlorosulphonation, phthalimidomethylation, etc., and attach these derivatives (or suitably converted derivatives) onto the pigment surfaces (Figure 4). This attachment is very strong, as the surface chemistry of the pigment and the molecular chemistry of the pre-cursors are very much alike. The attachment of these groups will alter the polarity of the pigment surface, which aids in the wetting of the pigment surface by wetting agents and solvents. One can also build polymeric chains onto these derivatives to generate sufficient steric hindrance to stabilize the resulting dispersions. These pigments can be customized to one application by introducing specific polymer tails to these derivatives, or they can be made universal by linking the derivatives with more than one type of polymeric chains. The pigment derivative of choice can be made separately and it can be utilized during the manufacture of pigment dispersions. In this case, the dispersion chemist can choose one or a combination of derivatives depending on the requirement of the dispersion in various applications. The quantity of derivatives used for the treatment is very important, as excess amount will cause solvent bleeding (owing to its molecular nature). Pigment surface treatment is mainly carried out to optimize its performance in various applications. Certain treatments are designed to impart high performance only in specific applications, and usage of these pigments in some other area can cause unwanted results. For example, amine-treated pigments are generally easy to disperse and stabilize but can significantly reduce the pot-life of epoxy-based systems.

Dispersants Pigments are highly complex materials with varying morphologies and surface chemistries. The surface chemistry may not be what one could deduce from the bulk chemistry of the pigments, as the crystallization process and/or the closely guarded ‘finishing techniques’ of the pigment manufacturer may radically alter what might be expected. Pigments are also delivered in a highly agglomerated form that must be broken down and stabilized in order to make a useful tint paste. This is not a trivial matter, and dispersants are the most useful tool in achieving success. Dispersants are a subset of surfactants that show usefulness in dispersing a discrete, solid phase into a continuous (liquid) phase. A very simple example is oleic acid, which contains a carboxylic ‘‘head’ that has some pigment affinity and a C17 ‘tail’, which would be expected to show compatibility with hydrocarbon solvents and oil-modified vehicles. The single carboxyl group would not be expected to show strong affinity to a pigment surface (unless the surface was very basic), and desorption leads to dispersion instability. A successful ploy is to string many carboxyls

FIGURE 2 | Hydrogen bonding in the β-quinacridone crystal structure.

FIGURE 3 | Shade differences for PO 5 colourant in an alkyd versus an aminecured epoxy coating. PO 5 dispersed in alkyd paint

O

H N

PO 5 dispersed in amine-cured epoxy paint

N H

O H N

O

N H

O

FIGURE 4 | Pigment derivative examples.

Pigment

CH 2 Cl

Pigment

SO 2 Cl

Pigment

SO 3 H

n

n

Chloromethylated Pigment Derivative

Chlorosulphonated Pigment Derivative Sulphonated Pigment Derivative

n O Pigment

C N H2

Phthalimido Methyl Derivative n

O together into a polymer where it is expected that, whilst the adsorption of each single carboxyl remains relatively weak, the combined adsorption of the polyacid is relatively strong and total desorption much less likely. Useful pigment affinic groups include carboxyls, hydroxyls (and usefully hydroxy acids), phosphates, phosphonates, sulphonates, phenyls, PEO, PPO, and a range of nitrogen-bearing chemistries including amines, amides, amino-alcohol, urea derivatives, betaines, taurides etc. One can recognize from this partial list that some of these will be reactive to commonly used protective coatings systems. The wide variety of listed pigment-affinic groups is also a reflection of the variety of anchor sites on pigment surfaces. The greater the knowledge that can be gleaned about the nature of the surface of any one pigment, the greater the chances of making a successful pigment dispersion. It is worth raising the question of the ability or the desirability of the coating resin to adsorb onto and thus easily PA I N T & C O A T I N G S I N D U S T R Y

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25

The Anatomy of Multipurpose Solventborne Colourants

disperse and stabilize a pigment. When the pigment affinic group used is not needed for film formation (such as the hydroxyl on an air drying alkyd) then the effect is desirable. But what happens if the hydroxyl is needed for reaction with an MF resin or an isocyanate? What happens to the amine group of the polyaminoamide that is adsorbed onto an acidic oxide? Are these groups available for reaction with their respective co-reactants or is the stoichiometry of the system compromised? And if they are available for reaction, does this mean that the pigment surface is stripped bare in the latter stages of film formation leading to increased porosity? Suitable stabilization with an appropriate dispersant seems to be the prudent path. Turning our attention to the ‘tail’ of the dispersant, it is clear that it needs to be solvated by a wide range of solvents and/or be compatible with a wide range of binders. It is our observation that solvation is more important for low-molecular-weight dispersants and binder compatibility with high-molecular-weight variants. It is also clear that no one simple A-B configured dispersant will satisfy the needs of all pigments – or even a single pigment. Let us consider the crystal shape of Pigment Red 122 (Figure 5). This crystal has 26 different facets and, because the plane of the base molecules runs on a slightly different plane to the main crystal face, each of the 26 facets can have subtly different chemistries and charge. One can see that even if the vast majority of these surfaces could be separated and stabilized with suitable surfactants, agglomerated networks could still exist if the corners (which constitute c.1% of the entire surface) are not satisfied.

Whilst the most elegant solution may comprise a unique mixture of strongly adhering monomeric surfactants with pigment affinic groups calculated to cover the various facets of the pigment, attached to tails of varying polarity, the most likely commercial ‘universal’ dispersant will be a ‘comb polymer’ combining a variety of pigment affinic groups on one side of the ‘comb’ and a series of ‘tails’ on the other side, with repeats of differing polarities.

Dispersing Resins If the pigment pastes are intended solely for factory use and, treated like millbases, can be stabilized with judicious amounts of binder, there is little need for the use of dispersing resins. However, when pigment pastes are post-added to various coatings, systems that are stabilized only with dispersants may not be robust enough to withstand the ‘shock’ of their introduction into the new environment. The use of dispersing resins significantly increases this ‘robustness’. One cannot, however, simply dismiss the utility of dispersing resins; they also show a wide range of compatibilities with a variety of binders and also the ability to adsorb onto some pigments. Experience shows that some classes of dispersing resin interact better with some pigments than do others, and also exhibit synergies with specific dispersants. Some regimes recommend examining systems by blending dispersant, dispersing resin and binder, and examining the cast, dried films for clarity as a guide to system ‘compatibility’. We believe this to be of limited value, as absorbed species (onto pigment surfaces) behave very differently to the unabsorbed material.

FIGURE 5 | Crystal shape of Pigment Red 122.

FIGURE 6 | Condensation product formed from the reaction of isobutyraldehyde

Typical dispersing resins are: 1. Ketone/Aldehyde Resins The most well known and utilized resin of this class is the BASF product Laropal A81. This material is the further condensed product of the aldehyde formed by condensing 1 mol of urea with 3 mols of isobutyraldehyde (Figure 6).1 This polydisperse hexahydropyrimidine exhibits excellent compatibility with a wide range of coating resins. This compatibility may be influenced by the wide molecular mass distribution, from 500 to 35,000 daltons. It is soluble in a wide range of solvents but with only limited solubility in hydrocarbons with high levels of aliphatics. The product has low solution viscosity, pale colour, good heat resistance and good durability. Resins based on methyl cyclohexanone show improved solubility in aliphatic hydrocarbons but generally with poorer pigment wetting, whereas resins based on acetophenone show improved pigment wetting with lower solubility and compatibility.

and urea.

3

O H H

O

O +

Isobutyraldehyde

H2N

NH2

Urea

H

H N H

N

H O H

+ H

Condensation Aldehyde Resin

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2. Acrylic Resins The wide array of acrylic monomers, including functional monomers, can be used to produce resins with suitable solubilities and varying degrees of pigment affinity. Newer, sophisticated means of assembling acrylic monomers into precise formations, blocks and stars blur the distinction between acrylic dispersing resins and polymeric acrylic dispersants. Acrylics generally enjoy good durability.

3. Saturated Polyesters The ease of condensation chemistry and the wide range of monomers available make polyesters a suitable means of assembling dispersing resins. Polyesters also provide reasonable durability but do remain susceptible to saponification.

Solvents Solvents play an important role in the manufacture of pigment pastes as well as in their subsequent use. Solvents with mid-range solubility parameters have greatest utility, as are solvents with mid-range evaporation rates. Too high a volatility can lead to rapid drying out of the pigment pastes, whereas too low a volatility can lead to solvent entrapment in the cured film. Blends of PM Acetate and Aromatic 100 (C-9 aromatic hydrocarbon blend) are generally favoured, but increasing pressure on the use of aromatics may result in a change away from this. In the preparation of the pastes, the solvent is often the first thing that the pigment ‘sees’. A solvent that absorbs strongly onto the pigment surface may compete with the dispersant for that surface: a solvent that is an excellent solvent for the dispersant may hinder the partition of the dispersant from solution to the interface. The solvent blend therefore is at an optimum when it a) does not absorb strongly onto the pigment surface; b) is not a good solvent for the dispersant; and c) is a good solvent for the ‘tails’ of the dispersant.

Viscosity and Rheology These properties, at first sight, would seem relatively obvious. At the highest pigment loading, one requires a low viscosity in the mid to high shear range to allow for easy machine dispensing. High pigment loadings often tend to dilatency, which must be avoided at all costs. Similarly, one needs high viscosity at very low shear rates to prevent pigment settling, especially for the heavy metal oxide pigments. The main dilemma springs from the fact that liquids of similar rheological profile mix more easily with each other than liquids of dissimilar rheological profile. Shaking is often the most convenient and preferred method of incorporation, and significant mismatches of viscosity can preclude successful mixing. Compromise viscosities are sought to optimize mixing but, in some cases, the shear provided by shaking is insufficient, and mechanical stirring will be required.

Compatibility Compatibility means different things to different disciplines. We use the following when we consider tinted pigmented coatings: a system is deemed to be compatible if the liquid components show no phase separation on a molecular scale and the solid phase fillers and prime pigments exhibit interfacial adhesion to the liquid phase, such that the whole is homogeneous on the macroscale. This definition is idealistic and debatable. The obvious question is how are the dispersants defined? In our view, strongly adsorbed dispersants should be viewed as part of the pigment as would any other supplied ‘pigment finishing system’.

There are some obvious requirements for achieving compatibility such as the need for the solvents of the tinter paste to be miscible with the solvents of the paint system; that the solvents of the paint system are not so good that they can strip the dispersant from the pigment, nor so bad that they collapse the dispersants ‘tails’ and that the dispersing resin in the paste is compatible with the resin in the paint system at the normal levels of addition. Mixed resin systems do not always achieve compatibility on the molecular scale but can co-exist in phase-separated domains. A simple example is an epoxy/polyamide mix, which will not achieve full compatibility until some reaction has taken place to produce a pre-curser hybrid species that will link the separate phases together. This is what happens during the ‘induction’ stage. Where separate phases exist, the tinter paste will often show a preference for one of them, which can lead to reduced tinter acceptance. The dispersing resin can be of significant assistance in compatibilizing such systems, but often other compatibilizers may need to be added directly to the paint system. There is an increasingly wide range of block polymers that are very useful in this area, but their selection can only be sensibly done with a full knowledge of the various resins in the paint system and knowledge of the structure of the block polymer.

Effect on Final Films An assessment of the effect of tint pastes is really an assessment of the effect of excess dispersant and the dispersing resin. This also means that pastes based on metal oxides with high pigment loading and low surfactant resin levels will have less effect than pastes based on ‘difficult’ organic pigments with the reverse properties. For thermoplastic paint systems such as chlorinated rubber, solution acrylics and vinyls, there are very few negative side effects at typical use levels (0-10% by vol). For thermoset systems, these excipient materials from the pastes can reduce chemical and solvent resistance in critical areas. Low level additions are scarcely an issue but, at higher levels, specific property testing is recommended.

Conclusion The design of a successful multipurpose solventborne colourant demands a deep knowledge of the wide array of possible raw materials that can be utilized to make them, as well as knowledge of the likely systems they are to be used in. Because of the wide range of coating formulating protocols and styles used around the world, it is highly unlikely that such tinters will show the full universal compatibility that is desired. This is why the coatings formulating chemist will always be an integral part in the successful utilization of such products. Only they have the intimate knowledge of the coating formulation and the ability to ‘tweak’ it to achieve optimum colourant performance. 䡲

Reference 1

Hughes, D.K; Robb, I.D. Langmuir 1999, 15, 8796.

For more information, e-mail [email protected] or [email protected], or visit www.totalcolor.co.nz. PA I N T & C O A T I N G S I N D U S T R Y

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Current and Impending Developments

UV-CURABLE

N

anoscale colloidal silicon dioxide particles are currently widely used in UVcurable systems for surface abrasion resistance and in nanocomposites, among other applications. The use of silica nanoparticles as they are currently available is not without drawbacks, however. The natural hydrophilic surface chemistry of the silica particle has low compatibility with most UV-curable resins and crosslinkers. Monodispersed silica nanoparticles are currently either provided in a volatile solvent that must be substituted or removed, or are provided in a narrow range of monomer. This paper will review the current use of silica nanoparticles in UV-curable coatings and introduce effective approaches that have been developed for delivering silica nanoparticles to UV-curable resin formulations without the drawbacks of current solvent- or monomer-based silica nanoparticle dispersions.

Introduction The use of monodispersed nanoparticle oxides can greatly improve the durability and performance of UV-curable coatings and composites. Colloidal silica (SiO2), one of the first commercially produced nanoparticles, is still one of the most widely used in coatings applications. Silica’s natural, glass-like hardness imparts scratch resistance to coatings while providing a clear, highgloss finish, however the active surface chemistry of silica and the necessity to provide it in a carrier system to keep it monodispersed creates challenges for the end user. End users can overcome some of these problems through treating the surface of silica particles with silane coupling agents, however commercially pretreated silica particles, silica particles dispersed in more versatile system components, and carrier-free monodispersed silica promise to increase ease of use of silica nanoparticles in UV-curable systems.

FIGURE 1 |Transmission electron micrograph of silica nanoparticles.

FIGURE 2 | Silica particle structure and surface. H H H

Si

Si Si

H Si

H Si

H Si

Si

Si

Si Si Si H Si Si Si Si H Si Si Si H Si Si Si Si H Si Si H Si Si H Si Si Si Si H Si Si Si H Si Si H H

Si

H

Si

Si

H

Si

Si Si

Si

Si

Si

Si

Si

Si

Si Si

H

Si

Si

H H

H

H

By Mark Myers | Nissan Chemical America Corporation, Houston, TX 28

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JANUARY 2011 | W W W . P C I M A G . C O M

Traditional Silica Nanoparticle Use in UV-Curable Applications Silica nanoparticles are particles of silicon dioxide (SiO2) generally between 5 and 500 nanometers in diameter. They are usually spherical, but elongated, and other novel shapes are available (Figure 1). Silica nanoparticles generally have a density of 2.2 grams per cubic centimeter (cm3) ,1 and the surface chemistry is dominated by hydroxyl groups, with between 4 and 5 per square nanometer (nm2).1 These hydroxyl groups, attached to silicon atoms, comprise silanols. Silica is naturally anionic and always has a negative zeta potential. Its isoelectric and point of zero charge are at about pH 2.1 Figure 2 provides a graphical representation of the silica nanoparticle structure and surface chemistry. Colloidal silica nanoparticles are most commonly incorporated into coatings to provide scratch and abrasion resistance, but can also be used to enhance nanocomposite strength, modulus, control refractive index and provide a host of other surface properties including but not limited to, antiblocking and self-cleaning properties, porosity, surface roughness and hydrophilicity. Nanoscale silica is used to provide scratch and abrasion resistance to coatings because it has a natural Mohs hardness of 6-7, is optically colorless and imparts a glossy finish to coatings. Silica particles that extend slightly above the surface of the coating become the point of first contact for foreign materials, keeping them from making full contact with the resin surface. Figure 3 illustrates the orientation of silica nanoparticles in a hard coating. Note that nanoparticles that do not protrude from the coating surface do not have an effect on scratch resistance, but may provide other benefits. Many antiscratch and antiabrasion applications in UV-curable systems require optical clarity, therefore a particle diameter below 50 nanometers, and ideally below 20 nanometers, is used. Silica solids loading for such applications is usually 10-15% for optimal scratch resistance without compromising optical clarity, coating mechanical strength and substrate adhesion. Silica nanoparticles for UV coating applications are most commonly used in commercially available monodispersions, either in organic solvents or mono-, di- or trifunctional acrylate monomers (which will be discussed later). Solvent-based dispersions are available in a wide range of solvents, including alcohols, ketones, esters and aromatics.

Drawbacks For all the potential benefits silica nanoparticles can impart to a coating, there are drawbacks to using them in UV-curable systems.

in Silica Nanoparticle Use in

SYSTEMS Solvent Issues Several significant drawbacks that present themselves when using common commercially available organic solvent-based silicas relate to the solvent itself. The first is compatibility of the solvent with the resin system. While there are many types of solvent dispersions currently available, there are still gaps where there is no commercially available silica sol dispersed in a preferred solvent. One option that is frequently employed by end users of solvent-based silica dispersions is to redisperse the silica particles in a preferred monomer. This can be very difficult due to silica’s hydrophilic nature, and frequently risks agglomeration of the silica. This also adds another step to an end user’s process, which increases cost. Solvent presence may also cause environmental, safety (flammability) and human health (toxicity) concerns, which low-VOC coatings seek to avoid. Even when a compatible solvent dispersion is available, the presence of solvent is not ideal. Solvents can affect rheology and cause coating defects in the cured coating. Also, solvents can offset the benefit of fast coating and curing time that UV curing can provide, as the solvent must usually be completely evaporated before curing can take place.

Effect on Coating Properties and Behavior Like the addition of any new additive to a polymerizable formulation, the addition of nanoscale silica can affect properties, positively or negatively, outside the targeted function of the additive. Nanoscale silica can increase system viscosities, changing the rheology of the resulting formulation.2 In UV-curable systems, the presence of silica nanoparticles can also alter the curing behavior of the system. Researchers have found that using silica nanoparticles at levels below 10 wt% accelerated the cure reaction and cure rate in UV-curable polyester acrylate systems, but at levels above 10%, this trend was reversed. The reaction rate acceleration below 10% can possibly be explained by the silica nanoparticles behaving as an effective flow or diffusion-aid agent for the photopolymerization process, or a lengthening of the path of the UV light by partial scattering or reflection (by aggregated silica particles). Cure rate reduction at silica nanoparticle concentrations above 10% could be explained by the higher concentrations of silica nanoparticles increasing the concentration of larger aggregates, hindering absorption of UV radiation by the photoinitiator, and thus reducing the efficiency.3

Silica-Resin Incompatibility As stated before, silica is naturally a hydrophilic material and, as such, can be difficult to employ in UV-curable polymer systems, which are often hydrophobic in nature. This can result in agglomeration of the silica and an

FIGURE 3 | Silica nanoparticles in a hardcoat.

overall hazy appearance in the coating, if not total failure of the formulation. Other components in the coating, such as cationic photoinitiators, can also cause agglomeration of the silica due to its anionic nature.

Conventional Remedies Use of Silane Coupling Agents When organic polymers are mixed with inorganic substances such as colloidal silica particles, the interphase, or interphase region, is a complex interaction of physical and chemical forces. Many mechanisms can disrupt the interphase, including water. A coupling agent creates a bond at the interphase that resists debonding, thus creating a stable bond between two otherwise poorly bonding surfaces. Silane coupling agents also enhance overall bond strength. In composites, a substantial increase in flexural strength is achievable with the appropriate silane coupling agent, as is resistance to humidity, better wetting of inorganic substrates, lower viscosities during compounding, less catalyst inhibition of thermoset composites,4 and clearer coatings when using silane coupling agents with silica nanoparticles. Silane coupling agents are silicon-based chemicals that contain two types of reactivity (inorganic and organic) in the same molecule. The typical silane coupling agent structure is (RO)3SiCH2CH2CH2-X, where RO is a hydrolyzable group such as methoxy, ethoxy or acetoxy, and X is an organofunctional group such as amino, methacryloxy, epoxy, etc. They function to act as interphases between the inorganic colloidal silica and an organic resin. Not all silane coupling agents can be used with all silica nanoparticle dispersions. For instance, amine-type silane coupling agents such as γ-aminopropyl triethoxysilane cannot be used with silica sol, as the cationic amino group will cause gelation of the anionic colloidal silica. Care PA I N T & C O A T I N G S I N D U S T R Y

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Current and Impending Developments in Silica Nanoparticle Use in UV-Curable Systems

TABLE 1 | Silane coupling agent compatibility with silica organosols. Silane Coupling Agent Type

3-aminopropyltrimethoxysilane (APTMS) 3-glycidoxypropyltrimethoxysilane (GPTMS)

Isopropanol, 30% solids

No change

No change

No change

No change

No change Solid cloudy gel No change

No change White gel on bottom No change

No change

No change

Solid cloudy gel

Slight cloudiness

Slight bubble formation

No change

should also be taken to choose a silane coupling agent that is compatible with the solvent that silica nanoparticles are dispersed into (Table 1). Before binding to silica nanoparticles, alkoxysilanes must undergo hydrolysis by the reaction shown in Figure

FIGURE 4 | Hydrolysis reaction of alkoxysilanes.

RSi (OCH3)3 H2O

CH3OH RSi (OH)3 H2O R

R

R

HO-Si-O-Si-O-Si-OH O

O

O

H

H

H

FIGURE 5 | The alkoxysilane-silica bond produced via a dehydration reaction. R

R

R H2O

HO-Si-O-Si-O-Si-OH

R

R

R

O O O H HH HH H O O O

HO-Si-O-Si-O-Si-OH

SiO2

SiO2

Hydrogen Bonding

Bond Formation

O

O

FIGURE 6 | Interpenetrating network bonding mechanism. Si - - - O - - Si - Si - - - O - - Si - Silica

Si - - - O - - Si - Si - - - O - - Si - -

Coupling agent 30

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Polymer

JANUARY 2011 | W W W . P C I M A G . C O M

Methyl ethyl ketone, 30% solids

Methanol, 30% solids Vinyltrimethoxysilane (VTMO) Methacryloxypropyltrimethoxysilane (MPS)

Dispersion Type Propylene gylcol monomethylether acetate, 30% solids

O

4. The water that facilitates the hydrolysis reaction is often present in small amounts in commercially available silica nanoparticle solutions, but can be added if necessary. Once the alkoxysilane is hydrolyzed, it is ready to bond to the surface of a silica nanoparticle, as shown in Figure 5. Note that the alkoxysilane-silica bond is produced via a dehydration reaction, which evolves free water that is then available to perpetuate the process of hydrolysis of other still-unreacted alkoxysilane molecules. Generally, the optimal silica nanoparticle size to use in clear, hard coatings is 10 to 12 nanometers, as larger sizes tend to cause haze. Commercially available silica nanoparticle dispersions in organic solvents are generally provided in 30% solutions. For a typical commercial 12 nanometer silica solution of 30% by weight, an amount of alkoxysilane equivalent to 1% of the total solution weight being used should be added. The general method for preparing silica nanoparticles with silane coupling agents is to add the alkoxysilane to the silica sol and agitate at 55 °C for 3 h. This will cause approximately 20% of the –OH groups on each silica nanoparticle to be replaced by an alkoxysilane group, which is usually sufficient for promoting silica compatibility with most common monomers (Figure 6). The use of silane coupling agents with silica nanoparticles not only improves the compatibility of the silica with the resin system, but also provides additional hardness to the final coating, through both covalent bonding (crosslinking) of the silica to the polymer matrix and a short-range interpenetrating network with the polymer matrix resulting from a ladder-like structure of grafted polysiloxanes.5

Monomer-Based Silica Sols As previously discussed, for UV-curable systems the use of silica particles dispersed in volatile organic solvents is not preferred, so one solution has been to attempt to disperse silica nanoparticles into monomers. Examples of monomers that have had silica nanoparticles successfully dispersed in them for commercial resale include 2-hydroxyethyl methacrylate, hexanediol diacrylate (HDDA) and trimethylol propane triacrylate (TMPTA). Because of the high viscosity of multifunctional monomers, commercial silica monomer dispersions generally consist of a mono, di or trifunctional monomer. While tri- and lower functionality may be acceptable levels of monomer functionality for some users, for others who require higher levels of functionality, this means that the monomer is acting as a reactive diluent, not a primary

Ask the Expert monomer or oligomer. Low-functionality acrylates give rise to low crosslink density and ineffective surface crosslinking, due to oxygen inhibition. This inefficient crosslinking and low crosslink density can reduce the hardness of a hard coating. Monofunctional acrylate-based silica dispersions also have high vapor pressure, causing concerns for flammability and health exposure similar to that of organic solvent-based dispersions.

Anticipated Developments The majority of the drawbacks of using silica nanoparticles in UV-curable systems arise from the carriers into which most commercially available silica nanoparticles are dispersed, and the surface chemistry of the silica particles themselves. Therefore, logical developments to increase the ease of use of silica nanoparticles in UV systems for end users will focus on functionalization of the silanols on the particle surfaces and dispersion of silica nanoparticles into more versatile carrier systems, or elimination of a carrier system altogether. As previously discussed, end users can increase the compatibility of solventdispersed silica nanoparticles with resin systems by treating the surface with trialkoxysilane coupling agents to reduce the number of exposed, active silanol groups on the particle surfaces. This process requires additional equipment, time and raw materials, increasing the expense and decreasing the ease of use for the end user. The commercial availability of silica dispersions that have already been pretreated would make silica nanoparticle dispersions much easier to use, and developments along this line are in progress. The concept behind monomer-based silica nanoparticle dispersions is to eliminate a solvent that would not be added to a coating system if silica were not being used, but the monomers have limitations of their own, such as the low functionality of the monomers and the limited selection of monomers that are available with silica predispersed. Predispersing silica into another common system component, one that is more versatile in a variety of resin systems, is another option. Polyisocyanates with silica nanoparticles predispersed in them have recently been released commercially, and as polyisocyanates can be used in a variety of polyurethane systems, this is a very versatile delivery medium for silica nanoparticles.

The ideal form for silica nanoparticles for use in UV-curable systems would be without any carrier at all. However, when untreated silica dries, it naturally agglomerates into large, permanent clusters that cannot be redispersed as individual spherical nanoparticles. This nullifies the benefits of using nanoparticles, and results in a cloudy, high-viscosity mixture when dispersed into a resin. Therefore, in order to have commercially available monodispersed silica nanoparticles in dry form, the surface of the silica particles must be extensively modified. Research is currently underway in this endeavor.

Conclusion Silica nanoparticles are used in UV-curable systems primarily to promote scratch and abrasion resistance, but also to provide a variety of other mechanical and surface properties. The anionic, hydrophilic surface chemistry of silica is imparted by the silanol groups that dominate the surface of silica nanoparticles, and it creates challenges for the end user of silica in UV-curable polymer systems. The conventional availability of silica nanoparticles in either organic solvents or a limited range of monomers also limits the versatility of these products in UV-curable systems. End users can overcome some of these problems through treating the surface of silica particles with silane coupling agents, however, commercially pretreated silica particles, silica particles dispersed in more versatile system components, and carrier-free monodispersed silica promise to increase ease of use of silica nanoparticles in UV-curable systems. 䡲

References 1 Iler, R. The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties, and Biochemistry. Wiley & Sons: New York, 1979. 2 Fernando, R. JCT CoatingsTech 2004, 1(5), (32-38). 3 Cho J.D.; Kim, Y.B.; Ju, H.T.; Hong, J.W. Macromolecular Research. Vol. 13, No. 4, 2005, (362-365). 4 A Guide to Silane Solutions from Dow Corning [Brochure]. Dow Corning. 2005. 5 Bauer, F. et al. Nucl. Instr, and Meth. In Phys. Res. B 265. 2007, (87-91).

This paper was presented at the RadTech 2010 Technology Expo and Conference, Baltimore, MD, www.radtech.org.

Jim Reader Lead Research Chemist

Q

I’m confused by the bewildering number of defoamers available. Do you have any simple guideline to help me choose a defoamer?

A

As waterborne coatings contain many different ingredients, it can be difficult to predict a defoamer’s performance. However, some simple elements to consider first are the VOC and viscosity of the formulation. High-PVC (pigment volume concentration) formulations and high-viscosity formulations need strong defoamers, like mineral oils, such as Surfy¯nol® DF75 defoamer. In high-gloss systems, mineral oils can cause haze, so in these systems silicone defoamers, such as Surfy¯nol DF58 defoamer or Surfy¯nol DF62 defoamer, can give effective foam control without haze. It can be difficult to control foam in lowviscosity formulations and clear coats, because strong defoamers can cause incompatibility problems like craters and fish-eyes. In these cases, molecular defoamers such as Surfy¯nol DF110D defoamer or EnviroGem® AD01 defoamer work best.

tell me more www.airproducts.com/ surfactants © Air Products and Chemicals, Inc., 2010 (31894) B39

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31

Design and Performance of Radiation-Curable Acrylates with

High Renewable Carbon Content

R

adiation curing technology is widely recognized as a “green” or sustainable technology because of the avoidance of VOC emissions and its low energy use compared to solvent- or water-based coating and printing technologies. The use of radiation-curable materials based at least partially on renewable raw materials brings another level of sustainability. While renewablebased radiation-curable materials are currently being used commercially (primarily in printing inks), there are many opportunities to design new materials with higher renewable content and enhanced performance. The properties of new materials with high renewable content in targeted coating and ink applications will be discussed.

Introduction Chemicals derived from renewable resources have long been widely used in a variety of industrial, household and cosmetic applications. Nearly all of the renewable raw materials used are plant-based and are all ultimately

derived from plant sugars formed by conversion of CO2 by photosynthesis (Figure 1). These raw materials are converted to final products using a range of chemical processes such as esterification, epoxidation, hydrogenation, fermentation, hydrolysis, dehydration or polymerization. Like the chemical industry, radiation-cure applications have also long used renewable raw materials in a variety of ways. Materials like rosin esters, sucrose esters and vegetable oil derivatives are used as inert ingredients for pigment wetting, thickening or plasticization. There are also a significant number of reactive acrylate monomers and oligomers on the market that are at least partially based on renewable raw materials. Some examples are shown in Figure 2, along with their biorenewable carbon content.1 While there are several different ways to express the renewable content of a chemical product, this paper uses the biorenewable carbon content, or %BRC. The %BRC has the advantages of being easy to understand and calculate, reasonably widely accepted and verifiable by analytical testing.2,3 The %BRC can be calculated by the equation:

FIGURE 1 | Chemicals derived from renewable resources and their applications. Coatings Thickeners Paper Fibers Cellulose

Soaps Coatings Biodiesel Lipids (oil, fat)

Starch

Hemicellulose

Sugars

Energy

Terpenes Rosin Natural Rubber

Proteins

Lignin Surfactants Concrete Additives Dyes

Adhesives Paper Industry Polymers

Adhesives

Solvents Inks Rubber

By Jeffrey Klang, Ph.D. | Sartomer USA, LLC, Exton, PA 32

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JANUARY 2011 | W W W . P C I M A G . C O M

%BRC = 100 x (# of Biorenewable Carbon Atoms/# of Total Carbon Atoms) Some of the current commercial examples have impressively high %BRC values, but until there is a viable commercial supply of bio-sourced acrylic acid it will be impossible to make 100%-renewable acrylates. While there is development activity in this area, availability at reasonable prices is still likely several years away.4 Despite the commercial availability of radiation-curable acrylates with partial biorenewable carbon content and their widespread use in some applications, there is still a need for new offerings with higher %BRC and improved properties. In particular, there are needs for multifunctional lowviscosity diluents and for oligomers with low color and properties suitable for general coatings applications.

Results and Discussion Table 1 introduces a series of six new radiation-curable acrylates with BRC contents of 50 to almost 90%, and functionalities of 2 to 12 acrylate groups per molecule.

The products are all derived from readily available renewable raw materials and were converted to acrylates using standard techniques such as esterification, epoxy addition and urethane formation. The properties of each are discussed in more detail below. As noted above, there is a need for low-viscosity, multifunctional monomer diluents with high BRC. Monomer 1 is a higher-molecular-weight analogue of 1,6-hexanediol diacrylate (HDDA) made by conventional acrylate processing techniques using a raw material derived from a common vegetable oil. Table 2 shows a comparison of the basic properties of Monomer 1 to HDDA. Monomer 1 has liquid properties similar to HDDA with the benefits of reduced volatility, less skin irritancy, higher Tg and better flexibility. Diluency power, cure efficiency and weathering performance have been found to be nearly identical to HDDA. Its balance of properties make Monomer 1 well suited for applications such as ink jet, screen and flexo inks and exterior coatings. The performance of Monomer 1 as a diluent in simple, highBRC formulations is discussed below. The basic physical properties of Oligomers 1 through 5 are shown in Table 3. Each oligomer will be discussed separately in more detail below. Oligomer 1 is one of several urethane acrylates that have been made from hydroxyl-functional vegetable oils or derivatives. In addition to varying the vegetable oil portion of the product, the use of urethane chemistry allows for adjustment of properties by choice of isocyanate and acrylating agent. Oligomer 1 exhibits the high flexibility and toughness typical of many urethane acrylates. Other urethane acrylates with modified structures are being tested. Oligomer 2 and Oligomer 5 are both made from raw materials that have undergone one or more chemical processing steps and are quite chemically pure. One result of this is that the color of resulting acrylates is low compared to most acrylated oligomers with high renewable carbon content. In addition, chemical processing provides structures and resulting properties that are not available directly from nature or from petrochemical sources. Oligomers 3 and 4 can be considered higherfunctionality versions of conventional epoxidized oil acrylates such as epoxy soybean oil (ESO) and epoxy linseed oil (ELO) acrylates. They are made by reaction of a well-defined fatty acid stream with a high-functionality, naturally derived polyol core followed by epoxidation and acrylation using standard methods. Oligomer 3 differs from Oligomer 4 in that only about 50% of the available epoxy groups are converted to acrylate. So in addition to six acrylates/molecule, Oligomer 3 also contains about six epoxies/molecule, offering opportunities for dualcure uses. As they are based on a raw material that is chemically processed with relatively pure and welldefined precursors, Oligomers 3 and 4 should exhibit less of the year-to-year and regional variations seen with products that use vegetable oil precursors more directly. All of the experimental oligomers were tested for basic coating properties as neat materials and in a simple, high-BRC formulation consisting of 50% oligomer, 23% Monomer 1, 23% IBOA, 3% Esacure KIP100F

FIGURE 2 | Examples of current commercial acrylates with renewable raw material content. Propoxylated glycerol triacrylate Modified epoxy acrylate Lauryl acrylate Tetrahydrofurfuryl acrylate Isobornyl acrylate Hexafunctional polyester acrylate Tetrafunctional polyester acrylate Epoxidized linseed oil acrylate Epoxidized soybean oil acrylate 0

20

40

60

80

100

%BRC TABLE 1 | Experimental monomers and oligomers. Description Monomer 1 Oligomer 1 Oligomer 2 Oligomer 3 Oligomer 4 Oligomer 5

Low-viscosity hydrophobic monomer Vegetable oil urethane acrylate Hydrophobic oligomer Modified vegetable oil epoxy acrylate Modified vegetable oil epoxy acrylate Low-viscosity oligomer

%BRC

Acrylate Functionality

Color

Viscosity (cPs)

62.5

2

50 APHA

10*

55.9

3

2G

18,800

74.7

2

300 APHA

40

88.5

6

1G

5800

79.3

12

1G

24,000

50.0

2

50 APHA

45

*At 25 º C, all others at 60 º C.

TABLE 2 | Comparison of high-%BRC monomer to HDDA. APHA Color Monomer 1 HDDA*

Tg Viscosity @ Surface Tension Volatility** º ( C by DSC) 25 ºC (dynes/cm)

< 50

10 cPs

33.4

1.8%

91

20

9 cPs

35.7

12.5%

43

*Sartomer SR238 ** Measured by TGA as weight loss at 80 º C over 240 minutes.

TABLE 3 | Physical properties of experimental oligomers. Tg by DMA, ºC

Tensile Properties

Loss Strength Elong. Modulus Energy @ Max Tan Δ Modulus (psi) (%) (psi) Load (ft-lb) Oligomer 1 Oligomer 2 Oligomer 3 Oligomer 4 Oligomer 5

31 -3 -30 4 -27

63 11 16 76 63

3350 150 470 1000

51 75,119 0.4582 5 3314 0.0008 6 8783 0.0033 1.8 65,205 0.0022 Too brittle to be tested.

Cure Conditions: 1880 mJ/cm2 energy as measured by Power Puck II radiometer with 3% Esacure KIP100F (70:30 blend of oligomer 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl] propanone and 2-hydroxy-2-methyl-1-phenyl propan-1-one) and 1% Esacure TZT (2,4,6-trimethylbenzophenone) photoinitiators.

PA I N T & C O A T I N G S I N D U S T R Y

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Design and Performance of Radiation-Curable Acrylates with High Renewable

Rub resistance measured by change in gloss after Sutherland rub test.

by pencil and Persoz hardness tests. Within the series, the higher-functionality Oligomer 4 does show higher hardness compared to the others. All of the experimental oligomers do show quite good MEK resistance and are much improved over ESO acrylate in this regard. Interestingly, Oligomers 1 and 3 both provide very good adhesion to PLA (polylactic acid), which is an increasingly popular choice for packaging because of its renewability.5 Test results on the high-BRC formulations are somewhat disappointing given the fairly encouraging neat oligomer results. However, no attempt was made to adjust or optimize the formulations, and it seems likely that much better results could be achieved. Analogous studies to those above were carried out on Oligomers 2 and 5. Although the two materials are based on quite different raw materials, they do have some similarities: both are at least partially cyclic in structure, have low viscosity and are diacrylate functional. In this case a standard bisphenol A epoxy acrylate oligomer (Sartomer CN120), which shares the cyclic structure and difunctionality, was used as the comparison. In these tests the performance of Oligomers 2 and 5 equals or exceeds that of the epoxy acrylate oligomer in some respects (Tables 6 and 7). In particular, Oligomer 5 has very good hardness, chemical resistance and rub resistance both as a neat material and in the high-BRC formulation. In other work that is being reported on separately, Oligomer 2 has shown very good performance as a moisture vapor barrier material.6

TABLE 5 | Properties of a high-BRC formulation containing Oligomers 1, 3 and 4.

Conclusion

(70:30 blend of oligomer 2-hydroxy-2-methyl-1-[4-(1methylvinyl)phenyl] propanone and 2-hydroxy-2methyl-1-phenyl propan-1-one) and 1% Esacure TZT (2,4,6-trimethylbenzophenone). All samples were cured with a Fusion 600 W/in H bulb at 861 mJ/cm2 total UV energy as measured by a Power Puck II radiometer. Oligomers 1, 3 and 4, which are all vegetable oil derived, were compared to a commercial ESO acrylate (Sartomer CN111US). Neat oligomer results are summarized in Table 4 and formulation results in Table 5. As they are all based on vegetable oils and contain long-chain fatty acids, Oligomers 1, 3 and 4, as well as ESO acrylate, all cure to relatively soft films as measured

TABLE 4 | Neat Oligomer 1, 3 and 4 coating properties vs ESO acrylate. Hardness

Adhesion MEK Rub Rubs Resistance Pencil Persoz PET PLA Glass Aluminum Oligomer 1 Oligomer 3 Oligomer 4 ESO acrylate

8B

35

200+

+

--

+++

--

+

8B

40

195

+

++

+++

--

+

3B

90

200+

++

--

+

+

--

6B

50

60

+

--

--

--

--

-- poor/fail, + fair, ++ good, +++ very good

Formulation

Hardness

MEK Rub Oligomer %BRC Pencil Persoz Rubs Resistance PET 1 3 4 ESO acrylate

Adhesion PLA

Glass Al

57.2 72.8 68.4

4B 8B 2B

30 40 120

30 94 °C > 97% (1 hour, 110 °C 1 g)

When h talking lk about b ffoam one h has to d distinguish hb between macrofoam and microfoam. Macrofoam is mostly located on the coating surface and is surrounded by a duplex film with two liquid/air interfaces (double layer), whereas microfoam occurs inside of a coating film (air entrapment) and is characterized by a single liquid/air interface. These two types of foam also differentiate defoamers from deaerators. Defoamers are mostly effective against macrofoam, whereas deaerators suppress microfoam. In practice, the terms “defoamer” and “deaerator” are often mixed up, and several commercial products are optimized to prevent macro- as well as microfoam. Both kinds of foam impair surface optics of coatings, causing surface irregularities and reducing gloss and transparency. Microfoam also adversely affects the protective properties of coatings, as the effective film thickness is reduced and pinholes may be formed out of small bubbles. The function of defoamers is based on disturbance of the double layer of the macrofoam lamella. Substances with very low surface tension are used, as they cannot be wetted by the foam bubble. Foam-stabilizing substances move away from the defoamer droplet, which finally causes collapse of the bubble. Surfactants are often used together with defoaming substances to improve the spreading behavior of the defoamer droplet on the bubble surface. The mode of action of deaerators is still not fully understood, but a couple of trustful theories have been published on this topic.1 Deaerators seem to prevent microfoam during application while reducing the droplet size of spray coatings. These small droplets have less air entrapment than bigger droplets do, and therefore a reduction in microfoam formation is observed.2 Small air bubbles more likely dissolve in the surrounding liquid phase or collapse with bigger bubbles because of their higher internal pressure (Young-Laplace equation).3 As a consequence, small air bubbles disappear while big ones flow to the coating surface with higher velocity (Stokes’ law, valid for nonvertical surfaces).4 The Young-Laplace equation is

Pin = Pout +

2σ r

where pin is the internal pressure, pout is the external pressure, σ is the surface tension, and r is the bubble radius. Stoke’s law (simplified version) is ν ~ r 2 /η where v is rising velocity of the foam bubble, r is the bubble radius, and η is the dynamic viscosity of the fluid. Another theory refers to the incompatibility of deaerating substances in the coating. Due to this partial insolubility, deaerators accumulate at the air (bubble)/ coating surface and displace foam-stabilizing substances.5

By Bernhard Hirschmann, Thomas Schönbacher and Armin Temel | Coating Additives, Cytec Austria GmbH 36

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JANUARY 2011 | W W W . P C I M A G . C O M

Defoamer/Deaerator Spray Application Application A li ti Ef Eff Effects f t

New Cl N Class off D Defoamer/Deaerator f /D t

Modern application techniques like airless or airassisted airless, as well as the desire to apply thick layers of coating in one application, challenge coating producers to deaerate systems. Airless spray does not use compressed air. Instead, paint is pumped at increased fluid pressures (34 to 450 bar ≈ 500 to 6500 psi)) n through a small opening at the tip of the spray gun to achieve atomization. When the pressurized paintt enters the low-pressure region in front of the gun, thee n sudden drop in pressure causes the paint to become an aerosol. Airless spraying has several distinct advantagess over conventional air-spray methods. This method iss more efficient than the air spray because the airlesss spray is softer and less turbulent, thus less paint iss y lost in bounce back. The droplets formed are generally larger than conventional spray guns and produce a o heavier paint coat in a single pass. This system is also d more portable. Production rates are nearly double, and transfer efficiencies are usually greater (65% to 70%).. Other advantages include the ability to utilize high-d viscosity coatings (without thinning with solvents) and the ability to have good penetration in recessed areas off y work pieces. The major disadvantage of the airless spray is that due to the thick layer buildup and high viscosity off the airless coating formulations, the resulting films aree very sensitive to form pinholes due to air entrapments.6 Air-assisted airless application is similar to airlesss g application, except that a small amount of atomizing d air is used to further improve coating atomization and therefore improve the appearance of the end product.. The amount of atomizing air is typically between 0.3-1.38 bar (5-20 psi), and is another source of shear,, leading to entrainment of air into the coating system.

ADDITOL® XW 6544 addresses many of the limitations of traditional defoamer and dearating technologies. It enables coating formulators the latitude to improve the application properties of low-VOC, high-viscosity coatings used in typically difficult application techniques. This is equ eq ua all all lly y important im impo mp po ort r ta an nt for for bo fo both th ccoatings oati oa ting ngs as ng as w elll as as ssolvent-free ollve ol v n ve ntt-f t-f -freee equally well

Traditional Defoamers Mineral oils, silicones and modified polydimethylsiloxaness are widely used in waterborne coatings. To a lesser extent,, glycol and glycol blends with surfactants are also used forr defoaming and deaerating. Mineral oils and mineral oilss with finely dispersed particles of wax or silica are effectivee defoamers, and typically dispensed in some type of solvent like mineral spirits, which contribute to VOCs. Silicones and modified polydimethylsiloxanes can be used with or without finely dispersed particles. Although effective in both defoaming and deaerating, they can sometimes be difficult to disperse in coatings. Further, they can re-agglomerate, causing craters, recoating and other defects. In the case of modified polydimethylsiloxanes, they can hydrolyze and lose effectiveness during coating storage. Both silicones and modified polydimethylsiloxanes are often avoided in appearance-critical applications like automotive coatings. Like mineral oil, glycols and glycolsurfactant blends often contain VOCs. They can be more compatible with waterborne coating systems to reduce potential defects, but by design could also be less effective.

TABLE 2 | Formulation for 2K waterborne epoxy coating. Comp. 1 BECKOPOX™ EP 386w/52 WA1 ADDITOL VXW 63941 MODAFLOW® 92001 Blank Defoamer A Defoamer B Defoamer C ADDITOL XW 65442 Deionized water Micro Talk IT extra3 Kronos® 21904 Bayferrox® 39205 Bayferrox® 3065 EWO6 Texanol™ 7 Blank Defoamer A Defoamer B Defoamer C ADDITOL XW 65442 ADDITOL VXW 63881 ADDITOL XW 65361

Comp. 2

33.54

0 0.5 0.5 0.5  

 

 

 

 

 

0.50% 6.57

 

 

Production

Part B

0.61

Part C

0.5 0.5 0.5

 

 

 

 

0.50% 0.5 0.5 100.01 9.65

 

 

 

 

ca. 10%

Stoichimetric quantity of hardener: approx. 75%

Mix part A in mentioned order and add part B. Disperse for 30 minutes at 10 m/s. The temperature should be below 40 °C. Add part C in mentioned order and stir on the dissolver for 10 minutes at 4 m/s. Add the diluted hardener of component B shortly before application. Paint solid: Comp. A: approx. 74% Comp. A + B: approx. 65% Density: Comp. A + B: approx. 1.55 g/L VOC (calculated) Comp. A + B: approx. 41 g/L Dynamical viscosity, DIN EN ISO 3219/23 °C, Shear rate: 25 mPa.s

7.59 26.77 0.3 1.11 21.01

0

BECKOPOX™ VEH 2188w / 55 WA1 Deionized water

Part A

1 0.5

s-1,

Comp. A+B: approx. 1700

Airless Application Nozzle size: 0.46 mm 50° Pressure: approx. 200 bar

Pigment/binder ratio: approx. 2.5:1 Potlife/23 °C: approx. 2 h Approximately 10% deionized water was added just before application to adjust the spray viscosity of approximately 1600 mPa.s (DIN EN ISO 3219, shear rate 100 s-1, 23 °C). 1

Cytec Industries Inc.

2

Defoamer, which was varied throughout this study

3

Mondo Minerals BV

4

Kronos

5

Lanxess

6

Sachtleben Chemie GmbH

7

Eastman

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A New Solvent-Free Defoamer/Deaerator

pigment concentrates used in point-of-sale (POS) tinting machines. Table 1 discusses the physical properties of this new defoamer/deaerator. To demonstrate some of the key benefits, comparative work in both a coating and pigment concentrate application is discussed.

Performance in 2K Waterborne Epoxy Coating Systems A 2K waterborne epoxy coating for airless application was produced according to the formulation found in Table 2. A series of coatings was prepared in order to test several defoamers with different chemical compositions. The

FIGURE 1 | Performance of defoamers in 2K waterborne epoxy coating. Number of Pinholes/dm2

35

Performance in Solvent-Free, Black Pigment Concentrate

30 25 20 15 10 5 0 Blank

Defoamer A

Defoamer B

Defoamer C

ADDITOL XW 6544

TABLE 3 | Formulation for solvent-free, waterborne, black pigment concentrate. ADDITOL XW 6535 Deionized water Blank Defoamer A Defoamer B Defoamer C ADDITOL XW 6544 ADDITOL VXW 6372 Lamp Black 1011   1

47.2 25.6 0 2 2

 

 

 

 

2 0.2 25 100

(defoamer) (preserver)

Pigment concentration (%): 25 Non-volatile material DIN EN ISO 3251 (%): approx. 46.3 (1 h; 125 °C; 1 g)

Production Each pigment concentrate was agitated for 60 minutes using lab bead mill. The pigment concentrates were then evaluated for foam height and the results are found in Figure 2.

Dynamic viscosity DIN EN ISO 3219 (mPa.s): approx. 300 (100 s-1; 23 °C) Grind fineness (μm): < 5

FIGURE 2 | Comparison of defoaming performance in low-VOC pigment concentrates. Volume in ml (right after grinding)

A series of solvent-free, waterborne, black pigment concentrates were prepared according to the formulations in Table 3. As with many black pigments and other highsurface-area pigments like organic red and blue pigments, foaming and deaerating are difficult and can lead to long processing times, poor pigment wetting, flocculation and pigment settling. Several defoamers were evaluated according to manufacturers’ recommendations and are summarized in Table 3. The series of pigment pastes from Table 3 were then evaluated for foam inclusions by measuring the volume in a glass cylinder directly after the grinding process. The results are shown in Figure 2. ADDITOL XW 6544 compared to commercial defoamers and the pigment concentrate without defoamer (blank) provides much improved efficiency to deaerate solvent-free pigment concentrates using high-surface-area black pigment. This is demonstrated by decreased volume of pigment concentrate, right after the grinding process, where less foam is stabilized.

2

Evonik

38

finished coatings were applied on steel substrates and the number of pinholes in the cured film was determined. The performances of the defoamers were tested in application trials. The different coatings were applied with airless equipment (SATA® shark™ M 3227) at a working pressure of 7 bar (corresponding to 224 bar spray pressure) with a 46/50 nozzle. The substrates were untreated steel panels. The coating was applied in increasing film thickness from 60 to 200 µm dry film thickness (dft, determined by bykotest 8500 basic Fe/NFe, BYK Gardner). Twenty minutes after application the panels were cured in the oven at 70 °C. These panels were examined for pinholes in an area of dft from 120 to 140 µm. The number of pinholes per dm² was determined. The results are given in Figure 1.

Conclusions and Future Developments ADDITOL XW 6544 represents a new class of defoamer/ deaerator technology that allows for improved appearance as well as effective defoaming characteristics, especially in low-VOC, high-viscosity coatings applied by airless application. Further, it has been demonstrated that ADDITOL XW 6544 is well suited for solventfree pigment concentrates. Future work includes the development of a range of defoamers to be used in highgloss topcoats and clearcoats. 䡲 For more information, visit www.cytec.com.

References 1

250

2

200 150

3

100

4

50

5

0 Blank

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Defoamer A

Defoamer B

Defoamer C

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ADDITOL XW 6544

6

Heilen, W. Additives for Waterborne Coatings, Vincentz Network, 2009, S.122. Bell, G. C. Jr. Mechanism of Bubble Entrapment in Spray Coatings. Presented at the 42nd Annual Meeting of the Federation of Societies for Paint Technology in Chicago IL, November 1964. Semmler, H.; Heilen, W. Elimination and prevention of microfoam, European Coatings Journal, 2000. www.p2pays.org/ref%5C01/00777/appltech.htm. Butt, H-J.; Graf, K.; Kappl, M. Physics and Chemistry of Interfaces; Wiley VCH, 2003; page 9. Schramm, L. L. Dictionary of Nanotechnology, Colloid and Interface Science; Wiley VCH, 2008; page 229.

UV-Curable

Anti-Fog Coatings

A

t certai certain in temperature temp mperatur ure and an nd humidity, hu umi m di d ty, t vapor in i air i condenses d lid water on solid surfaces. Because water has much higher surface energy than most solid surfaces, the condensed water usually takes the form of small droplets, which scatter light and cause haziness. Fogging is a severe problem for a lot of optical devices, such as lenses, mirrors, windshields and visors et al. Basically, there are two ways to avoid hazy water condensation. One is to control the temperature and humidity so that water condensation can not happen. For example, some devices use heating elements to keep the temperature high enough that water cannot condense; some devices are purged by inert gases or dry air to remove moisture. These approaches are very effective, but consume energy and they are expensive. The other approach is to use anti-fog coatings on the optical devices. Anti-fog coatings can prevent hazy water condensation and maintain the optical clarity. Obviously, this is a better approach, because anti-fog coatings are cheaper and consume no energy to operate. Considering the anti-fog mechanism, it is possible to categorize anti-fog coatings into three types. Type I: The coatings remove water condensation by absorbing liquid water into the coating. Type I coatings can be saturated when moisture level is too high, and do not respond to water condensation quickly; therefore they are not very effective. Type II: The coatings lower the surface energy of water, and the condensed water evenly wets the surface. Usually, Type II anti-fog coatings carry extractable surfactants.1 When water condenses on the coating surface, the surfactants dissolve into the liquid water and bring down its surface energy so that water will wet the surface evenly. Type II coatings work effectively as long as enough surfactants can be extracted into water; however, surfactants can be washed away by water, and Type II anti-fog coatings will lose their anti-fog property gradually. In addition, because it takes time for water to dissolve surfactants, Type II coatings will not respond to water condensation very quickly. When suddenly exposed to high humidity, some Type II coatings can immediately get fogged and it will take some time for them to turn clear. Type III: These coatings have a super-hydrophilic surface. Water has a very low contact angle, less than 5°, on superhydrophilic surfaces, and water condensed on a super-hydrophilic surface will evenly spread out very quickly. No surfactants need to be extracted from the

supe su perr-h pe r-hy hydro hydr ophilicc coatings; coat co atin at ngs gs;; they t ey th y work worrk instantly insttan antl tly y with wiith little littl itttl tlee super-hydrophilic 2 perform d l time. ti S h d hili coatings ti f b better ttt delay Super-hydrophilic than the other two types of anti-fog coatings. In this paper, we discuss UV-curable super-hydrophilic anti-fog coatings. UV-curable anti-fog coatings3 can be cured instantaneously. They consume less energy to produce and, more importantly, they can be produced in a roll-to-roll process at high speed.

Experimental Silica nanoparticles, as a 10-15 nm particle size, 30% dispersion in methanol, were used either directly without modification or were modified by polyethylene glycolmodified silane and acrylate/methacrylate-modified silanes.

Synthesis of Polyethylene Glycol-Modified Silane Monomethyl ether polyethylene glycol (mPEG) (Mw = 1100) was dissolved in toluene and the mixture was dried. At room temperature and under nitrogen, a molar equivalent (with respect to the mPEG) of 3-isocyantopropyl trimethoxysilane was added drop wise to the reaction mixture. A few drops of dibutyl tin dilaurate were added as a catalyst. The reaction mixture was then stirred continuously for 24 h at 50 ºC. The reaction was monitored by infrared spectroscopy; the isocyanate signal is at 2271 cm-1. Upon completion, approximately two thirds of the toluene was removed by rotary evaporation and the mPEG trimethoxysilane was precipitated into hexane and washed several times. The resulting solid was dried and characterized by 1H NMR. Reaction yields of > 90% were obtained.

Silica Nanoparticle Surface Modification The surface of silica nanoparticles was functionalized with mPEG triethoxysilane and 3-(trimethoxysilyl)propyl

FIGURE 1 | Polycarbonate sheet (left) and PET sheet (right) coated by a roll-to-roll process.

By Wenguang Li, Guido Meijers, Jens Thies and Atze Nijenhuis | DSM Desotech, Elgin, IL PA I N T & C O A T I N G S I N D U S T R Y

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UV-Curable Anti-Fog Coatings

TABLE 1 | Modification of silica nanoparticles. Modified Silicon Oxide Particle A B

Material Silicon oxide nanoparticles, 30% solid in methanol 3-(trimethoxysilyl)propyl acrylate 3-(trimethoxysilyl)propyl methacrylate mPEG trimethoxysilane Hydroquinone monoethyl ether Methanol (solvent) Total

29.0 1.1

28.8 1.1 3.0 0.02 67.1 100

2.1 0.02 67.7 100

TABLE 2 | Anti-fog coating formulation. Material Silicon oxide nanoparticle Modified silicon oxide particle A Modified silicon oxide particle B PEG diacrylate PEG dimethacrylate Sulfo propyl acrylate potassium salt Sulfo propyl methyacrylate potassium salt Water Irgacure 184 Methanol (solvent) Total

C (%)

Formulation D (%) E (%)

28.9 6.8 0.3

20.4 5.1 0.2

2.4 0.4 61.3 100

1.8 0.3 72.2 100

29.7 7.0 0.3 2.5 0.3 60.4 100

F (%) 28.9 6.8 2.4 0.4 61.6 100

TABLE 3 | Rating of anti-fogging performance. Antifogging Performance

Rating

No No Poor Fair

1 2 4 6

Good

8

Excellent

10

Annotations Zero visible, poor light transmission Zero visible, poor light transmission Poor visible Discontinuous film of water Discontinuous film of water, mostly transparent Completely transparent

TABLE 4 | Performance of the anti-fog coatings. Anti-Fogging Rating Before Water Wash After Water Wash* Formulation C Formulation D Formulation E Formulation F

10 10 10 2

10 10 10 2

* The coated samples were washed with water for 10 seconds.

TABLE 5 | Properties of anti-fog coatings produced by roll-to-roll process. Properties

Value

Pencil hardness Refractive index Thickness Transmittance (%) Clarity Yellowness index Haze Steel wool abrasion* ΔHaze

H on PET, 2B on polycarbonate 1.48 6 μm 93.4 99.8 No change from the uncoated substrate 0.27 1.87

*250 g load, #0000 steel wool, 10 double rub, and then measure haze value

40

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JANUARY 2011 | W W W . P C I M A G . C O M

acrylate or 3-(trimethoxysilyl)propyl methacrylate. Table 1 shows the amount of each component used in the reaction. The mixtures were stirred at room temperature overnight to finish the reaction.

Coating Formulation Formulations were prepared by mixing modified or unmodified silicon oxide nanoparticles with reactive diluents, polyethylene glycol diacrylate (Mw = 575 g mol-1), sulfopropyl acrylate potassium salt, and a photoinitiator, 1-hydroxycyclohexyl benzophenone. The sulfopropyl acrylate potassium salt was added as a solution in water. The exact weights used for coatings are shown in Table 2. All the liquid coatings have a solid content of about 12%. Coatings were applied on PET or polycarbonate sheets using #16 wire wound rod. The coatings were dried for half a minute, and then cured under a 300 W per inch mercury vapor lamp at a dose of 1 J/cm2 in a nitrogen atmosphere. The thicknesses of the cured coatings were about 5 micrometers. The coated samples were characterized by cross-hatch adhesion test, pencil hardness, optical properties and steel wool scratch test.

Results and Discussion All cured coatings have 100% adhesion on treated PET and polycarbonate substrate, 99% optical clarity and over 90% transmittance. The anti-fog properties of the coatings were tested by holding a coated substrate for 15 seconds above warm water at 50 °C. The coating performance is rated to the degree of fogging/transparency. If the coating fogs completely, having no transparency, it is rated as 1. If the coating does not fog at all, staying completely transparent, it is rated as 10. A complete description of the rating and degree of fogging is given in Table 3. Anti-fog performance of coatings is listed in Table 4. All the coatings with the sulfonate salt have perfect anti-fog properties; the coating without sulfonate salt has poor anti-fog properties. Typically, ionic groups are more hydrophilic than ethylene glycol groups, and that is probably the reason that coatings containing sulfonate salt have better performance in the fogging test. Because all the components are crosslinked into a polymer network, after the coatings were washed by water their anti-fog performance did not change. It also has no effect on anti-fog performance whether acrylates or methacrylates were used. However, methyacrylates polymerize much slower than acrylates. When coating E is cured in air, the coating is very tacky because of the oxygen inhibition. There is no obvious difference between coating C and coating E, when they are cured in nitrogen. The modification of silica nanoparticles has no effect on anti-fog performance of the coatings. Because the modified silica nanoparticles are covalently linked into the polymer network, the modified silica nanoparticles should give the coating better scratch resistance. Since silica nanoparticles without modification can already give good mechanical properties, surface modification of silica nanoparticles is not always necessary. The coating with non-modified silica particles was applied by a roller coater on flexible PET and polycarbonate sheet. The coating was applied and cured continuously

and 90 ºC. As shown in Figure 2, a piece of partially coated polycarbonate plate was placed on a cup of 90 ºC coffee. The plate was initially at room temperature. When it was exposed to the moisture from 90 ºC coffee, the uncoated area was immediately fogged, while the coated area always stayed clear. In the low-temperature test, the coated samples were cooled down to -20 ºC, and then were exposed to 60% humidity room temperature air. The coated area stayed clear, while the uncoated area was quickly fogged.

FIGURE 2 | Coffee cup fogging test.

Uncoated area

Coated area

Conclusion UV-curable anti-fog coatings were developed. The coatings comprise inorganic nanoparticles and UV-curable hydrophilic materials. The coatings can prevent fogging at temperatures between -20 ºC and 90 ºC. The coatings show excellent optical clarity, good hardness and scratch resistance. 䡲

References 1 2

at 5 m/min in a roll-to-roll process. As shown in Table 5 and Figure 1, the coated transparent sheets have good optical and mechanical properties and uniform thickness. Anti-fog coatings were also tested at both high and low temperatures, and they worked very well between -20 ºC

3

Radisch, Helmer; Scholz, Werner. US Patent, 4,609,688. Cebeci, F.Ç.; Wu, Z.; Zhai, L.; Cohen, R.E.; Rubner, M.F. Langmuir 2006, 22, 2856-2862. Meijers, Guido, Thies, Jens Christoph; Nijenhuis, Atze Jan. International Patent Application, 2009, WO 2009/118415.

This paper was presented at the RadTech 2010 Technology Expo and Conference, Baltimore, MD, www.radtech.org.

Elcometer 456 Coating Thickness Gauge. One gauge–A world full of applications. The key to the superiority of the 456 is its measurement system featuring a range of interchangeable probes 씰 씰 씰 씰 씰 씰 씰 씰

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NEW APPLICATIONS Carbon Nanotube Inks Using Standard Commercial Printing Equipment

C

arbon nanotubes (CNTs) offer unique mechanical, optical and electrical properties and, as a result, researchers are investigating their use in electronic, mechanical and optical devices. Inks comprised of carbon nanotubes are commercially available from a variety of sources. However many, if not all, of these CNT inks have properties that limit their use in printing with common commercial printing equipment at high rates. Some of these limitations are listed below. • Most inks have very low CNT concentration, requiring multiple passes to achieve the desired CNT deposition, resulting in cost and resolution penalties. • Oftentimes, non-volatile dispersants and surfactants are used, which must be removed in order for the optimal performance of the CNT to be realized. This requires an added rinsing operation and/or a high-temperature baking process. These added steps increase cost and may not be compatible with other layers in the device. • Most CNT inks do not have sufficiently high viscosity for commercial printing processes such as screen, flexo or gravure.

FIGURE 1 | Viscosity curve of CNT ink formulated for screen print application.

FIGURE 2 | V2V ink screen printed using commercial printing equipment.

• Traditional techniques that have been used to coat CNTs, such as spin coating and aerosol spraying, are not well suited for roll-to-roll coating. They also require an additional step of subtractive patterning via photolithographic etching or laser ablation. Ink jet printing has been successfully demonstrated for CNTs, but this technique is better suited for prototyping versus highrate manufacturing.

Viscosity (cP)

100,000 These limitations have been significant barriers to commercialization of CNT inks for printed electronic applications. The ability to print CNT inks in large areas, at high rates, with standard commercial printing equipment, will enable a wide range of printed electronics applications.

10,000

Novel CNT Inks

1,000 0

5

10

15

20

25

30 -1

Shear Rate (sec )

35

Using novel chemistry, new CNT coating fluids and inks have been developed by SouthWest NanoTechnologies (SWeNT®) that overcome many of the limitations described above. These inks use a proprietary technology, developed by CHASM Technologies, called V2V™ Ink Technology. V2V (Viscous-to-Vapor) employs unique chemistry that has several features that make printing CNTs safe and easy to use for a variety of commercial coating and printing techniques. These features include:

By Dr. William Hurley and Dave Arthur, CEO | SouthWest NanoTechnologies, Norman, OK 42

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JANUARY 2011 | W W W . P C I M A G . C O M

for Conductive NOW POSSIBLE • Ability to tailor ink viscosity over the workable range of 50 to 5000 cP (compatible with screen, flexo and gravure); • No residual surfactants or dispersants need to be removed, as the viscous fluid is completely vaporized during standard drying conditions (100 °C); • No CNT airborne species; • Direct printing means no need for subtractive patterning. Overall, V2V technology overcomes the limitations of prior state-of-the-art CNT inks and fluids, allowing printing with standard commercial equipment. This greatly expands the range of applications for CNTs. V2V technology simply combines a CNT paste, containing no surfactants or dispersing aids, and a viscous media. When combined and blended together, the resultant CNT ink fluid is a stable dispersion of CNTs that can be easily printed with commercial printing equipment. The V2V viscous media completely vaporizes at standard drying temperatures, leaving no significant traces of residual material that need to be removed in post processing or that affect the performance of the deposited CNT in the dried coating. The media viscosity can be easily adjusted to the desired range for the specific coating application through small chemistry changes. Changes to the viscous media component chemistry can also be altered to affect drying or substrate compatibility. Coating the ink on polymeric materials may require changes to the viscous media formulation to minimize dilution and salvation effects of the ink fluid into the substrate layer. This is a straightforward process using the V2V technology, as the chemistries involved are compatible with a wide range of substrate materials. SWeNT CNT ink fluids have been successfully demonstrated on commercial screen printing equipment with relatively high CNT loadings (1 g/L). Commercial applications such as LED lighting and touch pads/screens are being investigated. Figure 1 is a representative curve of ink developed for a screen print application. Figure 2 is the ink being printed using commercial screen-printing equipment. Figure 3 shows screen-printed electrodes using the V2V CNT ink. Figure 4 shows an SEM of screenprinted film showing the CNT structure.

Conclusions Employing a novel chemistry, CNT inks can now be printed

FIGURE 3 | Screen-printed electrodes using V2V-based CNT ink.

FIGURE 4 | SEM of screen-printed film showing CNT structure.

using standard commercial printing equipment. The new fluids have several key advantages over current state-of-theart CNT fluids: • CNT concentrations, up to at least 1 g/L, which allow single-pass printing operations or higher coverage per pass; • No residual viscosity modifiers, surfactants or dispersing aids to remove to achieve optimal performance. 100% volatile ink base; • Rheological properties that allow potential line speeds up to 300 ft/min.; • Easy to dry at relatively low temperatures (