Increasing the Functionality of Interior Architectural Coatings

Interior architectural coatings today do much more than hide blemishes in walls and ceilings. They often play a key role in the overall decorating scheme and are chosen in concert with furnishings and room accessories. In addition, consumers today expect these coatings to have minimal impact on the environment and have low odor while also offering a multitude of performance properties, from high hiding power to stain resistance. Increasingly, consumers also want interior architectural coatings to have advanced functionality, from biocidal properties to the ability to degrade harmful chemicals in the air. The growing demand for higher and more varied performance is occurring at a time when the market for these coatings is expanding. Driven by healthy construction sectors in mature economies and rising incomes in emerging markets, the value of the global interior architectural coatings segment is growing from $39.8 billion in 2018 at a CAGR of 6.4% and will, according to IMARC Group, reach $57.8 billion by 2024.

Many Fundamental Properties

Opacity and brightness are two of the most important attributes for interior architectural paints, along with color, and much research revolves around color trends, according to Aggie Lotz, vice president of The ChemQuest Group and the ChemQuest Technology Institute. “The most important attributes for an interior paint are to provide color as well as protection to the surface,” agrees Stan Cook, Architectural Coatings marketing director at Dow Coating Materials. Flatter sheens are also becoming a strong consumer desire. From the pigment perspective, color consistency is the most important attribute that end users look for from interior architectural coatings, both from a can-to-can and visit-to-visit standpoint, adds Michael T. Venturini, marketing director for Coatings with Sun Chemical. “There is an expectancy that no matter what day of the week and no matter the can of paint, that color will be a seamless match. That puts a big demand on ensuring pigment color consistency, tinter consistency, and dosing,” he observes.

Other required attributes for interior architectural coatings vary based on the project and overall demand of the paint job, according to Nate Hardy, product manager at Kelly-Moore Paint Company. “More heavily used or high traffic areas, such as kitchens, bathrooms, commercial buildings, schools, and doors and trim, may require a coating with higher durability to provide resistance to cleaning, moisture, scuffing, and damage. In low-traffic areas such as living spaces or offices, however, the most important attribute may be the coating’s aesthetics. Determining the most important attributes of a coating really comes down to the specific project and desired outcome,” he explains. For residential consumers, for instance, Mark Coward, technical leader Paints & Coatings, BU Industrial & Consumer Specialties at Clariant, notes that in high-humidity areas, premium paints contain additives to prevent mold and mildew formation, while in kitchen and dining areas, coatings should provide resistance to fingerprints and food staining. Commercial and institutional end users, on the other hand, prefer low-VOC paints with consistent gloss, low odor, and quick drying times for fast return to service. “Consumers and contractors expect a competitively priced, low-VOC paint that applies easily, with minimal splattering or running, exhibits maximum hiding/coverage, holds up to daily wear and tear, and delivers color,” he summarizes.

Increasingly, consumers also want interior architectural coatings to have advanced functionality, from biocidal properties to the ability to degrade harmful chemicals in the air.

Some of the basic requirements for interior architectural coatings do depend on the applicator, however. In addition to being brand loyal, contractors require paint that applies quickly and easily, hides well, touches up, and minimizes call backs. “Generally, how the paint applies with a brush, roller, or sprayer is a key selection criterion,” notes Eric Dumain, global marketing director, Liquid Resins, Arkema. In addition, for commercial and institutional jobs, the paint must have the appropriate Master Painters Institute (MPI) specification. Do-it-yourselfers, on the other hand, are influenced by consumer marketing ads, available color palette, social media trends, and third-party testing (i.e., Consumer Reports®). They are, according to Dumain, looking for decorating help, durability, stain resistance, and one-coat hide. An overall trend, he adds, is a desire for anti-scuff capability for coatings used in hallways, while trim paints need to provide excellent block and hardness, and bathroom paints must exhibit superior humidity resistance. “Protection has evolved into a more sophisticated concept that includes resistance to stains, burnishing, and other conditions previously understood as normal wear and tear,” comments Pablo León Escobar, global marketing director at OMNOVA Solutions. Surface cleanability is also part of enhanced protection especially with regards to matte finishes and texturized applications, he observes.

Sustainability is a key driver of new coatings technology research. End users (both consumers and manufacturers) seek paints that can be applied with simpler techniques, that have lower energy footprints, and reduced coating-related waste. There is also growing interest in plant-based resins and coatings based on recycled materials, according to Lotz. “Environmental regulations continue to become stricter, especially at international and state levels, and that could affect architectural coatings, while a surging awareness of the value of sustainable products (low/no-VOCs and isocyanate-, NMP-, BPA-, formaldehyde-, and metal-free) is leading to higher demand for ‘green’ coatings,” she says. In particular, Lotz points to LEED and other third-party certifications as becoming increasingly important to the interior architectural coatings market.

Shift to Greater Functionality

Another key shift for interior architectural coatings, according to Lotz, is a move from decorative to functional. “The main functionality drivers for coatings remain aesthetics and protection; end users want the coating to make the surface look good, reduce wear over time, and be able to be maintained easily,” Hardy remarks. “Coatings,” he continues, “must retain their color and finish, adhere to the surface, resist damage, and be able to be cleaned and touched up. Some coatings also need special functionalities, such as moisture, mildew, or chemical resistance, in order to protect against exposure to certain environments.” In general, according to Coward, people are looking to change the interior appearance of their homes, personalizing them to their unique tastes, in part to create a “look” that is brought alive by paint. They want this look to last, and to remain fresh, through the use of various functionalities.
More “basic” multifunctional coatings, therefore, can be anti-microbial, anti-corrosion, self-cleaning and/or self-healing. “Consumers want functionality that will ease their pain points and deliver on unmet needs. They aren’t, however, looking for specific functionality, but to have their unmet needs addressed,” notes Michael Burriss, Industrial Coatings industry manager at DSM Coating Resins.

Examples of properties that are still sought, according to Jan van Dongen, AkzoNobel marketing director for Innovation and Insights, are dirt repellency/easy-to-clean and anti-scratch/anti-scuff. The former paints would be longer lasting and stay clean longer, while the latter would stay bright longer, particularly in high-traffic areas. “Overall,” says Cook, “end users across the board are looking for paints and coatings that do more. Paints and coatings are being asked to provide properties that go beyond the traditional decorative and protective functions, from anti-microbial and sound absorbing properties to formaldehyde abatement and many more.”

Paint + Primer in One products are one example of highly functional coatings, according to Cook. “These products were initially developed from binder technology solutions to deliver outstanding stain-blocking functionality without jeopardizing the classic topcoat properties of a premium interior architectural coating,” he says. Easy-clean coatings have also been on the market for several years, but improvements are still being introduced with next-generation products, according to van Dongen. He notes that anti-scratch solutions and brighter colors are on the market as well, but here again new insights are enabling continually improved performance.

. . . for commercial and institutional jobs, the paint must have the appropriate Master Painters Institute (MPI) specification. Do-it-yourselfers, on the other hand, are influenced by consumer marketing ads, available color palette, social media trends, and third-party testing.

Coward points to surfactants with increasingly broad compatibility and improved thickener technologies combined with better economics on pigments that allow more pigments to be used in the architectural arena as other important advances. Recently, wetting and dispersing additives containing both hydrophilic groups and hydrophobic groups that, upon drying, orientate so the hydrophilic groups face towards the pigment particles and the hydrophobic groups face out into the coating have been introduced that hydrophobize the entire paint film and thus reduce the tendency for water uptake, according to Christopher Mosinski, BYK’s end-use manager for Wood Coatings in the United States. “These additives provide great pigment stabilization and viscosity reduction, while also minimizing any negative impacts on other important properties such as stain resistance,” he says.

For Shandi Ramirez, Architectural Coatings industry manager with DSM Coating Resins, the fact that the coatings industry has waterborne paints is a testament to the need for functionality. “Across our industry we have been able to develop polymers not meant to go into water. There is an intended functionality to every paint that is designed and part of that functionality is to ease the pain points of a consumer and deliver on unmet needs. For example, faster drying resins were developed that still delivered excellent gloss development. Coatings that erode vs peel have better toughness by adding various functionalities. The trend for paint has always been moving toward improving efficiency. Painting is a laborious job; when we can make it easier on the consumer, that is the functionality that will be used,” she states.

Indeed, some interior architectural coatings today have “smart” functionality, although the definition of this type of coating can vary widely. For van Dongen, smart coatings for interior applications may be antibacterial or aseptic coatings; have active air-cleaning capability; exhibit thermal activities, such as insulation coatings; provide sound isolation; or act as sensors. Escobar considers smart functionalities to include self-cleaning properties, odor-absorption technology, and thermochromic capabilities to monitor disinfection in hospitals or temperature changes in specific rooms. He also includes anti-microbial coatings that provide resistance to mold and/or mildew formation. Hardy adds that coatings that are breathable, stain-release, self-cleaning, rust-converting, etc. are available to meet specific project needs. “Smart functionalities at their core are attribute benefits beyond aesthetics and protection,” he concludes.

Need to Achieve Balance

Developing these highly functional coatings requires the ability to balance many opposing properties and expectations. “One of the largest challenges we tend to forget is that a coating is a very thin layer. Laws of physics are restricting the effect that a thin layer can have on thermal and sound isolating properties, for instance,” says van Dongen. Creating functional interior architectural coatings at a product cost that makes sense for the market is also difficult. “Technology exists to produce extremely high-performance coatings. Unfortunately, this technology is expensive and does not always fit architectural painting budgets,” Hardy observes.  There are, agrees Escobar, many raw materials and process technologies commercially available and transferable from other industries with relative success in coatings, but that come at a cost. “Consumers, contractors, and retailers must be willing to adopt these new functionalities for the added value gained despite the higher price tags for such coatings,” he states.

It becomes important for formulators to find not only the best solution for viscosity reduction and pigment stabilization, but also minimize the impact that doing so can have on water sensitivity and stain resistance.

It is also essential to balance the critical performance needs per application, according to Ramirez. “For example,” she says, “in wall paint, some key performance requirements are low VOCs, wash and scrub resistance, and stain resistance. Achieving these requirements can become a balancing act.  This issue is particularly apparent when considering the addition of a functionality such as adhesion to various substrates, especially engineered substrates,” she notes. Other challenges exist when formulating functional coatings such as compatibility of ingredients, Hardy adds. “Often times, when one ingredient is added to improve a functionality, other functionalities are negatively impacted,” he explains. As an example, Mosinski points to the need for wetting and dispersing additives in waterborne coatings, which in turn creates the need to find ways to eliminate the negative impact their hydrophilic nature can have on such properties. “It becomes important for formulators to find not only the best solution for viscosity reduction and pigment stabilization, but also minimize the impact that doing so can have on water sensitivity and stain resistance,” he explains.

Smart coatings for interior applications may be antibacterial or aseptic coatings; have active air-cleaning capability; exhibit thermal activities, such as insulation coatings; provide sound isolation; or act as sensors.

The situation is complicated by the need to create formulations that are zero-VOC, odor-free, and do not contain many traditional ingredients due to environmental concerns. “Designers and formulators have fewer degrees of freedom in material selection,” Dumain asserts. Finally, van Dongen notes that safety has to be kept in mind, which can be particularly challenging for functional coatings that interact with electrical power. Finding multifunctional raw materials and streamlining formulas is often the best route, according to Coward.

Many Areas of Exploration

Interior coatings are waterborne and, therefore, normally acrylics. Some paints are based on pure acrylics, while others rely on acrylic hybrid resins to increase the range of properties exhibited. For many functionalities, other ingredients are added to the formulation to create the desired effect, according to van Dongen, but for some attributes such as easy-clean and anti-scratch coatings, the nature and quality of the resin is clearly important. “It is less important to understand the resin chemistries used, and more important to understand the problem that is trying to be solved. One resin or chemistry cannot do it all. Formulators need many technologies in their toolbox in order to be able to develop the best-performing products that address customer challenges,” Burriss says. He also notes that polymer design has become more complex to balance the various performance requirements and today requires “thinking outside of the box” to identify resin chemistries that have multi-functions to them, such as hybrids and tribrids. Furthermore, Burriss stresses that a deeper understanding of all ingredients used in the formulation is required, and not just a focus on the resin or polymer itself.

Companies that are exploring biobased and/or recycled materials will have an advantage, because these ingredients represent different chemistries and provide the opportunity to leverage new polymerization and crosslinking technologies.

As this understanding increases, ingredient suppliers and formulators will continue to develop more advanced interior architectural coatings with increasingly complex functionalities. “Because each paint ingredient plays a part in overall performance, many raw material manufacturers are striving to innovate to consumer demands,” Coward states. He also expects that end users will be willing to pay for game-changing coatings that bring tangible benefits.

Researchers are exploring new hybrid and multiphase technologies to provide stain-resistant systems and higher levels of block and hardness at zero VOC, according to Dumain. In the pigment realm, Venturini notes that the desire is to continuously improve sustainability, lightfastness in certain color spaces, dispersibility, and achieving these developments at the necessary price point. Dow is interested in simplifying the painting process through the development of technologies that can be combined to deliver a coating that enables a painting prep process that is significantly less onerous—less taping, spackling, and sanding, while also serving as a first coat in the painting process. “This is a very demanding requirement to fulfill, but would serve a part of the market that is typically in need of solutions to increase speed and efficiency while minimizing dusting and EHS concerns,” Cook observes. Work is also needed, notes van Dongen, on antibacterial/antiseptic coatings given the limited options available in different places due to varying regulations. AkzoNobel is also interested in safe conductive coatings that function as sensors, which is a challenging target. “Several layers are needed to create a functional system, and in case of small damages, it must remain safe for all customers,” he says. Technologies that could improve indoor air quality in all its aspects from chemicals to particulate matter are being investigated, but most are still in very explorative phases. The holy grail, according to van Dongen, would be a coating that generates electricity from light that enters a room, but this technology is very far away from anything currently in scope.

In ACA’s recently released U.S. Market Analysis for the Paint and Coatings Industry (2018–2023) (see www.paint.org/market), ChemQuest has identified several notable development areas as well, including: multifunctional pigments for multiple surfaces; connectivity and/or conductivity through paint technology for lighting and other applications; inclusion of biocides and/or bacteria resistance in paints (desired by the older community who fear that one bad staph infection will be life threatening); odor absorbing/grease resistance for home kitchens and medical applications, hospitality, and other venues where odors/grease could be a concern; radon blocking for radon-producing regions; and changeable wall technology whereby colors change from solar impacts (time of day), upon exposure to artificial lighting, or through controls sent via a phone.

Researchers are exploring new hybrid and multiphase technologies to provide stain-resistant systems and higher levels of block and hardness at zero VOC.

Multiple Expectations Always a Factor

Underlying the development of these novel functional coatings, the key trends outlined above will continue to be important going forward. “Sustainability is going to impact the interior architectural coatings market and will play a role in how the coatings will evolve, whether functional or not,” Venturini insists. Technologies that increase application efficiency, solve routine problems, and reduce the cost of labor for commercial and residential do-it-for-me jobs will be in demand, and these coatings will need to perform more functions, according to Dumain. “Consumers will continue to look for new solutions to common issues but no longer be willing to sacrifice finish appearance for performance,” Hardy asserts. They will also look for more cost-effective offerings with better convenience and reduced maintenance time and costs, adds Escobar. “Customers will expect more added value benefits in the field of performance as well as well-being; from passive to active coatings,” van Dongen concludes.

Achieving these goals in the face of ever-tightening restrictions on the materials available for use in coatings is creating the need for a new problem-solving approach, according to Dumain. Arkema is working with its customer partners and looks forward to developing effective solutions, he notes. Clariant, too, is positioning its offerings in the paints and coating market to address the demand for enhanced functionality while becoming greener and addressing a globalized market, according to Coward. “As industries shift and materials change in cost structure and functionality, new approaches can be incorporated and brought to the architectural market,” he says. Collaborations will, in fact, be necessary to help the industry overcome the challenges they face with respect to the need to balance the right amount of performance with the price demands of the market, according to Hardy. Companies that are exploring biobased and/or recycled materials will have an advantage, because these ingredients represent different chemistries and provide the opportunity to leverage new polymerization and crosslinking technologies, observes van Dongen. He also says that, particularly for interior coatings, aesthetics continue to be extremely important. “Color guidance to support customers in selecting the right color combination will be as important as the selection of the right functional formulation, with color visualization technology and color science contributing to significant changes in the landscape.”

CoatingsTech | Vol. 17, No. 2 | February 2020

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