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Acrylic resins: new technologies for new times.

Coatings based on acrylic resins perform well in a wide variety of applications, from architectural (exterior, deck, concrete, and flooring) to automotive and industrial to road marking. They can be formulated as liquid, powder, or 100% solids, and can form films by evaporation or UV or thermal curing depending on the choice of monomers used to prepare the resin. New hybrid acrylic coatings--epoxy acrylates, vinyl acrylates, alkyd acrylates, urethane acrylates, etc.--are further expanding the versatility of this important class of resins. Acrylic binders are attractive because they provide good UV resistance and are also abrasion resistant and flexible while offering reasonable chemical resistance and high gloss if desired. Furthermore, acrylic binders are available as water-based systems prepared through emulsion polymerization, making them attractive as greener alternatives to solvent-based resins.

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Even so, many liquid coatings based on acrylates still require or contain solvents to aid in film formation. As regulatory requirements and consumer expectations have driven demand for very low- or no-VOC coatings, acrylate resin manufacturers have been challenged to develop alternative systems that meet this need yet continue to provide the same or higher levels of coating performance. To complicate matters, regulations as well as customer expectations can vary significantly from one region to another. Within the different regions, many customers are also looking for increased functionality in all types of coating resins, including acrylates, and they want it all at the same or lower price. Resin producers must meet these customer demands while facing steadily rising raw material costs due to tightness in the market for acrylates and the rising cost of propylene, the major feedstock for the acrylate chain.

"The acrylic acid and acrylates markets remain very tight on the supply-side going into the 2011 paint season due to a series of planned and unplanned outages starting in late 2009 and continuing through early 2011. Inventories remain low and the industry is having trouble rebuilding, even 18 months into the recovery," notes Michael D. Brown, managing partner with TZ Chemicals International Pty Ltd, a Perth-based consultancy. Tightness is also coming from the demand side, with modest recovery growth in the paint and coatings sector combining with strong demand for acrylic fibers in China caused by high cotton prices. New capacity will come in Asia and the Middle East later this year through 2013, and there is an expectation that a significant amount of this capacity will be exported to North America and Europe, but many do not believe the added production will be enough to meet the expected growth in demand, particularly in the U.S.

"Coatings suppliers are working hard to displace acrylics with lower cost and more readily available resins such as VAE," Brown observes. "This theme is being repeated with Ti[O.sub.2] as formulators work hard to incrementally displace this key ingredient with minerals. Paint guys are getting hit hard by +20% price increases for these two commodities in the last 12 months, and allocations loom on the horizon for the coming paint season."

To overcome these significant challenges, resin manufacturers have turned to technology to find solutions. Arkema Emulsion Systems is advising its customers to look closely at alternatives to 100% acrylic systems, according to Wayne Devonport, Arkema's global product development leader for coatings. "For many applications, alternative binder technologies may provide a significant improvement in the cost/performance ratio that will allow formulators to meet both performance and value targets in their end products," he says. The company's NEOCAR[R] line of vinyl versatate-containing latexes for architectural applications, for example, which have extensive field testing results, provide a low-risk choice for formulators who need to find a solution to unavoidable acrylate price escalation.

Dow Coating Materials (DCM) has focused on process technology to the waterborne traffic paint market which can help to lower a paint's dependence on both the level of acrylic latex binder and Ti[O.sub.2], the two most important components of a traffic paint formulation. FASTRACK[TM] HE-2706 Acrylic Binder enables the formulation of waterborne traffic paints that will have the same performance as formulations based on its existing FASTRACK resins but with up to 50% lower Ti[O.sub.2] levels and up to 30% less latex in the formulation, according to the company. The resin, which is based on an innovative high efficiency emulsion technology, offers notably higher pigment binding efficiency that facilitates higher pigment loadings and a reduction of Ti[O.sub.2] pigments without sacrificing the important dry time performance of water-based traffic paints or properties such as hiding, visibility, durability, sprayability, or stability, according to DCM traffic paint market manager Stan Cook. As an added benefit, an ISO 14040 Life Cycle Analysis showed, in a cradle to grave analysis, that waterborne traffic paint formulations based on FASTRACK HE-2706 Acrylic Binder consume less energy, and have less of an impact on the ecosystem and human health versus paints used today.

Environmental issues are of importance in other sectors as well. For the household, institutional, and industrial flooring markets, field applied coatings in hospitals, industrial warehouses, and retail centers protect vinyl, tile, and concrete substrates, with shine being a critical performance characteristic. Acrylic emulsions crosslinked with zinc materials are the dominant technology, according to Eric Dumain, product manager for New Product Development with Cook Composites and Polymers (CCP). Concerns have been raised, however, about zinc solubility in wastewater, and so there has been a push to eliminate zinc from floor finishes.

To address this problem, self-crosslinked acrylic emulsion polymers have recently been introduced. "These internally crosslinked polymers offer similar performance application properties while being much more environmentally friendly and, in some cases, have better gloss and chemical resistance than their zinc-crosslinked counterparts," Dumain states. Furthermore, workability can be an issue with the zinc systems. Floor coatings need to have good barrier properties yet be readily strippable when it is time to recoat. Self-crosslinked systems have hard and soft segments with an overall lower glass transition temperature for strippability but higher molecular weight for good film formation and resistance properties. CCP's new emulsion polymer Esi-Cryl[R] RAIN, which incorporates amine chemistry into the resin for self-crosslinking capability, can be formulated into floor finishes that are compliant with Green Seal, Design for Environment, and Ecologo certification requirements while offering excellent gloss, buffability, and resistance to black heel scuffing and a wide array of chemicals, according to Dumain.

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OMNOVA Solutions also offers zinc-free acrylic alternatives for floor coatings. Its NM[R]-128 non-zinc polymer is based on calcium crosslinking technology, which, according to senior market development manager Russ Craig, has proven to be very effective in achieving high performing polishes. "Floor polish manufacturers and their suppliers are continually improving 'greener' products in an effort to match the cost/performance of conventional polishes. Their acceptance in the marketplace is growing and is expected to continue to grow in the future," he notes.

Currently, CCP is looking to see what other applications would be suitable for its self-crosslinking technology. The company is also working to reformulate all of its flooring resin to be alkylphenol ethoxylate (APE)-free. "There have been a lot of advancements made in surfactant technology in the last four to five years that are making it possible to develop APE-free acrylate resin systems that continue to provide excellent performance," Dumain comments. He expects the company to have all products reformulated by the end of 2011.

Arkema and Dow have both also developed APE-free acrylic rheology modifiers. RHEOTECH[TM] 2800 and RHEOTECH[TM] 4800 acrylic associative thickeners from Coatex, part of the Arkema Group, are both APE- and solvent-free and are designed to provide improved performance in water-based coatings.

DCM's ACRYSOL[TM] RM-845 Rheology Modifier is a solvent-free, low-odor additive based on ACID SUPPRESION[TM] Technology, which allows formulators to achieve extremely efficient KU levels, low- to high-shear viscosity levels across many applications, and excellent flow and leveling, according to Kendall Justiniano, strategic marketing & product line manager for Additives with DCM. "This technology is an innovative solution, as the high KU-builder efficiency that is necessary for good thickening in latex coatings often leads to a very high viscosity solution that is not easily poured or pumped, but the co-solvents used to suppress this product viscosity, such as propylene glycol or butyl carbitol, result in higher VOC levels and overall cost," he explains. "ACID SUPPRESSION Technology targets the root cause of associative viscosity build, thereby producing a high efficiency HEUR (hydrophobically-modified ethoxylated- urethane) composition paint formulation that offers low VOC and odor levels, helping our customers achieve new performance attributes with more sustainable chemistries."

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VOC reduction is a major issue for all coating manufacturers, and resin suppliers have been very active in developing low- and no-VOC alternative binders that still behave like solvent-based systems. "In general the continuing challenge of acrylic-based resins is to develop polymers that deliver high performance at lower VOC levels," says Steve Wilson, marketing manager coating resins for OMNOVA Solutions, which recently acquired specialty resin manufacturer Eliokem. "Improving our resins without compromising performance remains a primary focus of our synthesis and technology team," he adds. Specifically, the company is looking at acrylic resins for improved water-based stain-blocking technologies. "Water-based stains generally re-wet when topcoated with a water-based coating, and the stain bleeds through. OMNOVA is developing resins to prohibit the migration of these types of stains," Wilson explains.

Arkema Emulsion Systems has taken a unique approach to addressing customer concerns about the sustainability of its resin products, introducing the EnVia[TM] certification program. "EnVia-certified products meet strict compositional standards that call for removal or minimization of components such as APE surfactants, formaldehyde, and other substances listed in Proposition 65," says Devonport. The favorable response from the coatings industry has led the company to commit to having any new product meet EnVia certification prior to commercial introduction.

The company is also addressing the VOC issue with a new technology platform. "The two solutions being used by the industry to afford lower VOC coatings include softening the backbone of the polymer binder or incorporation of a non-VOC plasticizer. Both approaches bring inherent performance challenges to properties such as hardness, block resistance (especially in highly pigmented coatings), washability, and dirt pick-up resistance that result from a softer coating," Devonport says. Arkema's solution is its new SNAP[TM] structured nano-acrylic polymer technology. SNAP 720 is the first product launched from that platform that incorporates a nano-structured acrylic polymer particle into an ammonia free/low odor binder system and provides excellent gloss, block resistance, and hardness, even in highly tinted systems, according to Devonport. The company is continuing to develop new prototypes across the sheen range to expand the breadth of the technology.

Dow offers an acrylic resin that addresses the susceptibility of low-VOC acrylate paints to produce softer films with block resistance problems, especially in tinted systems. Its RHOPLEX[TM] HG-706 acrylic emulsion, according to field marketing manager for Architectural Coatings, J. Rusty Johnson, offers improved enamel performance over that of other reduced-VOC latex polymers, providing excellent adhesion, block resistance, and stain removal. DCM also has introduced RHOPLEX[TM] PR-295 Emulsion Polymer with AVANSE[TM] Technology, an improved stain-blocking resin for aqueous stain-blocking primers that is effective over common interior household stains, and enables enhanced adhesion and durability. "To offer innovations like these we continually work on crafting the basic chemistry of a product to enhance certain performance attributes of the final paint, including adhesion, hardness, and film formation," Johnson remarks.

The polymerization process is indeed very important for the production of acrylic resins. "In a lot of cases, the process drives the performance of acrylic resins. The process can influence acrylic emulsion particle size and size distribution, crosslink density, and morphology," asserts Vick Stanislawcyzk, technology manager for performance coatings with Lubrizol Advanced Materials, Inc. "By carefully designing the process, it is possible to design acrylic particles with a specific architecture that will drive end coating performance properties."

Incorporation of specialty acrylate monomers is another way to improve performance or add new characteristics to acrylic resins. These specialty monomers may often be used at only a few percent in the overall polymer, but can provide important and unusual functionality. "As one example, copolymerizable phosphate or surfactant-like monomers can enable the improved adhesion and stabilization of the polymer in an aqueous environment," Stanislawcyzk says. He also adds that improving efficiency, throughput, and site-to-site consistency on a global basis is also critical for developing successful emulsion polymerization processes and acrylic resins for an increasingly global coatings marketplace.

Lubrizol's newest product--Carboset[R] resin CA-600--is a water-based, acrylic, self-crosslinking emulsion specifically developed for clear, stain, and opaque horizontal masonry coatings. Carboset CA-600 based coatings, according to Stanislawcyzk, are fast drying with good early water resistance, allowing faster application and fewer concerns with rain after application. They also do not blush and have good chemical resistance, durability, and adhesion, and can be applied directly to concrete or used over sealers, stains, or other latex coatings. The new resin is an addition to many other resins that Lubrizol has developed for specific applications. For example, Carboset[R] CR-795 and Permax[R] 805 polyvinylidene dichloride acrylic copolymers are ideal for the OEM metal market. Carboset resin CR-795 is a thermoplastic acrylic emulsion designed to provide an excellent balance of gloss and adhesion to various metal and nonmetal substrates and offers superior corrosion protection, according to Stanislawcyzk. In addition, low-VOC, APEO-free Permax acrylic copolymer 805 is an acrylic emulsion that demonstrates excellent corrosion resistance and adhesion over a variety of metal substrates.

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Innovation clearly is a must for resin producers as both regulatory requirements and customer expectations become more extensive. "Customers constantly expect their suppliers to innovate and provide resins for current and evolving technologies. In addition to improving conventional coating properties, many customers are asking for resins to provide advanced performance in terms of electrical, barrier, weathering, printing, formability, etc.," observes Jim Horgan, vice president of technology with Sartomer USA.

In addition, adds Sjaak Griffioen, business director for the global architectural business at DSM NeoResins, "The acrylics market is changing because the desire for higher gloss system-sas well as enhanced flow, leveling, and open-time-means that we now need to look beyond pure acrylic technology." As a result hybrid, and even tribrid, systems that combine urethane and/or alkyd technology are now the name of the game." Hybrid technologies have been receiving interest for a few years now as researchers attempt to combine the best properties of solventborne resins with waterborne resins into architectural coatings, according to Devonport.

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DSM is thus now designing true hybrids and tribrids for many customers--from high-gloss, no-yellowing trim paints to waterborne stain locking to high-performance zero-VOC systems, according to Griffioen. "This approach has proven extremely successful, delivering performance beyond just cold blending, and shows that we are doing the right things here in a sustainable way." Arkema, mean-while, has introduced a unique class of fluoropoly-mer-acrylic hybrids under the Kynar Aquatec[TM] brand. "These products deliver outstanding exterior performance similar to traditional Kynar[TM] PVDF binders, but with the flexibility of waterborne acrylic and vinyl chemistry," Devonport notes.

DSM is also tackling the sustainability issue through the use of renewable resources with the goal of achieving higher performance at a lower carbon footprint. Renewable raw materials are already finding their way into the so-called acrylic-based coatings market, according to Griffioen. "We believe that our investments in such sustainable technologies will be the means for differentiating ourselves as the topic moves higher up the corporate agenda," he comments.

Radiation-cured coatings provide another environmentally friendly alternative. UV/EB cured resin systems from Sartomer are fully reactive, 100% solids systems that generate no VOCs during use. UV/EB technology is also energy efficient and does not result in emission of the greenhouse gases that are generated by heated drying ovens required by solvent- or water-based coatings, according to Horgan. New products from the company include CN9030, a urethane acrylate oligomer for UV/EB coatings and inks that offers adhesion to a wide variety of substrates, along with a combination of hardness and toughness with excellent weathering resistance, and CN9026, a high functionality, scratch-resistant urethane acrylate for hard coatings on glass, metal, and plastic that retains gloss very well even upon exposure to exterior weathering.

For all of these resin producers which serve the global coatings industry, the issues of regulatory compliance and customer expectations are multiplied several times due to the different requirements found in different regions of the world. "Customers in Asia, Europe, and the Americas may have different performance requirements, formulation types, modes of use, and application processes for many products," explains Stanislawcyzk. "It is quite a challenge to provide products that meet specific regional demands while simultaneously meeting differing inter-regional regulatory requirements."

Lubrizol's approach to this challenge is to study and understand the performance, formulating, and application needs of customers in different regions as early as possible in the product development process. In addition, the research group is tasked with understanding the regulatory requirements of different agencies around the world and working with Lubrizol's health, safety, and environment (HSE) regulatory specialists to ensure that new products are compliant.

Underlying all of this activity is the recognition that new chemistries and technologies are fundamental to the continued use of acrylic resins in coatings applications. "The changing dynamics of the coatings industry--whether in floor coatings for hospitals in Asia, UV-cured OEM coatings in Europe, or concrete coatings in the U.S.--demand that coating formulators, and thus acrylic resin producers, provide sustainable solutions that perform at ever higher levels, offering increased functionality with a minimized environmental footprint at a reasonable cost. To that end, acrylic resin producers are striving to meet this challenge head-on by exploring numerous technology platforms and developing innovative polymers with enhanced performance profiles using more efficient production processes.

By Cynthia Challener Coatings Tech Contributing Writer
COPYRIGHT 2011 American Coatings Association, Inc.
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Author:Challener, Cynthia
Publication:JCT CoatingsTech
Date:May 1, 2011
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