CoatingsTech asked several industry experts about various aspects of rheology modifiers, including market needs and trends, remaining challenges, and new products.
Q. How does your company participate in the rheology modifier market for paints and coatings?
Williams, Dow Coating Materials: Dow is a leading supplier of HEUR and HASE rheology modifiers for the waterborne coating industry. We have a long history of inventing in this space. Today our ACRYSOL™ product line is extensive and well adapted to serve multiple end-use markets and applications.
Sullivan, Münzing: Münzing produces HEUR and HASE type of rheology additives for water-based coatings, paints, tints, adhesives and inks. The product portfolio of polyurethane thickeners covers the entire rheological profile from highly pseudoplastic, through pseudoplastic to Newtonian.
Moore, BASF: BASF offers a broad portfolio of rheology modifier chemistries for water-based, solvent-based, and solvent-free systems in the paint and coatings markets. RHEOVIS additives are synthetic rheology modifiers designed for aqueous systems, including non-ionic associative (HEUR / HMPE), anionic associative (HASE) and non-associative anionic (ASE) technologies. EFKA
additives are specifically designed for solvent-based and solvent-free systems consisting of polyamide wax and hydrogenated castor oil chemistries. ATTAGEL attapulgite rheology modifiers perform as thickening and suspension aids for improved sag resistance and long-term stability. Each product class has its own properties and applications to enable formulators to achieve their desired rheology profile with all types of resins. Our rheology modifiers also provide additional functionalities like wetting properties and health or environmental benefits such as suitability for formulations free of VOCs, odors, APEOs and heavy metals.
Sieto, Elementis: Elementis is a significant supplier in this market. We have a broad portfolio in the market, which includes associative, acrylic, organic thixoptropes, and clay-based thickeners.
Q. What are some of the key industry needs and trends driving innovations for rheological additives?
Sorrell, BASF: Customers have requested thickeners that provide thickening in only one part of the rheology curve for targeted viscosity control. Another request we have received is for synthetic versions of the cellulosic chemistries. Also, there is a focus on more sustainable and environmentally free additives (tin-free, low/no VOC, etc.). Additionally, rheology modifiers that provide performance uniformity across different application methods is driving our innovation efforts. Rheology modification has become an increasingly targeted technology. Unique formulations require technologies that can offer varying profile development. Ease of use in formulation preparation and in the final product are key innovation perspectives.
Sieto, Elementis: Developing thickeners which maintain performance or increase efficiency while having no impact on the resin performance. We are always looking to improve sag, scratch resistance, and anti-staining properties in architectural and industrial paints.
Williams, Dow Coating Materials: Consumers are demanding higher performance paints in terms of appearance and resistance properties. We see properties such as hiding and surface smoothness and “toughness” as key features beyond traditional premium products. Attaining these attributes relies heavily on finding the right additives to help take paint performance to the next level.
Sullivan, Münzing: Due to regulations on harmful substances and growing end-user concerns about environmental and health hazards in coatings, the entire industry is working on more
pollutant-free formulations to include no APEOs, parabens, VOCs, and solvents. Additionally, Europe and parts of Asia have noticed a major trend in preservative-free paints and coatings with high pH value. In response, we have been working towards the development of new, pH-stable rheological additives.
Q. Is the use of biobased materials finding its way into the manufacture of rheology modifiers, and are you seeing interest in biosourced materials from coatings manufacturers or their customers?
Sieto, Elementis: Yes, more customers are asking us for biobased and naturally derived product. We have both. Our clay-based thickeners are based on natural hectorite, which is mined. Our organic thixotropes are based on castor beans which are biobased.
Iyer, Dow Coating Materials: Consumers are also looking for more sustainable paints which is helping to drive the industry to replace petrochemical-based ingredients with progressively increasing amounts of biobased materials. A life-cycle assessment of a paint containing only petrochemical sourced materials typically shows a higher carbon footprint (CO2 emissions) versus a paint with equivalent performance that is made in part from biobased sources. It is important that the sourcing of biobased raw materials is done in a thoughtful way from regions where advanced farming practices are pursued and where there are no known water-scarcity challenges. As rheology modifiers are used in small quantities, their contribution to greenhouse gas (GHG) emissions is low in the manufacturing process, but they also offer functional benefits in the storage and use phase of a paint. The progress of EU Green Deal legislation is expected to accelerate more sustainable paints with better environmental profile beyond low odor and VOC.
Sullivan, Münzing: Recently, we have noticed an increased demand from our customers for additives based on renewable raw materials. We have therefore just launched a new series of HEUR rheology modifiers, TAFIGEL PUR R (R = renewable), to meet this demand.
Achord, BASF: For many years, sustainability has been a core pillar at BASF where we focus on developing products that make the best use of our available resources and enhance the quality of life for the world’s future. Our ATTAGEL line and some of our EFKA rheology modifiers are derived from natural resources. BASF is also evaluating the conversion of many raw materials that make up our synthetic rheology modifiers to sustainable and biobased alternatives.
Q. Are there any regulatory issues or environment/health/safety (EHS) concerns, such as materials of concern, that is driving new research and product development efforts in rheological additives?
Sullivan, Münzing: The biggest regulatory concern we are grappling with is to make more rheology modifiers acceptable to be used in products that have contact with food. We are looking into new product development for more food contact applications. Again, our industry is working on more pollutant-free formulations (no APEOs, parabens, VOCs and solvents) because of both regulations and end-user concerns about environmental and health hazards in paints and coatings.
Achord, BASF: Nearly all newly developed rheology modifiers in the industry are developed as low or zero VOC. On top of this trend, which has been in the works for some time, APEO-based products are being replaced within the markets we serve. This enhances the overall environmental compatibility and reduces potential health hazards in the final products offered to the market. Increasingly, food contact is becoming more of a focus in development. Our rheology modifier portfolio offers versatile offerings that also support USDA food compliance for functional and flexible packaging applications. This ensures our customers can formulate for all desired applications.
Sieto, Elementis: One area of huge concern is the use of biocides. We are currently limited on what we can use, and we continue to test and develop products that are biocide free.
Wang, Dow Coating Materials: We are always working to develop new solutions that perform better and are more sustainable throughout the life cycle of paints. We want the products we develop to have minimal environmental impact, which is why we continually try to develop the next generation of sustainable paints.
Q. From a rheology perspective, what do you consider as the top challenges for paint and coatings formulators, and do solutions exist today or is innovation required?
Wang, Dow Coating Materials: Formulators have many choices to optimize overall compatibility of paint ingredients while delivering on paint stability and paint performance. Choice is influenced in part, by what is on the shelf—that is, by formulator experience. But delivering on new paint attributes dictates utilizing new additives and sometimes new rheology modifiers. It is this process of optimizing choice for a given final performance balance that continues to be both an opportunity and source of complexity for our industry.
Sullivan, Münzing: It is possible to solve many problems with available rheological additives; however, this requires profound formulation expertise on the part of coating developers. For example, viscosity drop on tinting is best addressed by formulating pigment concentrates with polymeric dispersants instead of surfactants.
Sorrell, BASF: The biggest challenge is finding the right rheology balance with newer latexes that are on the market. Latexes are being pushed to smaller and smaller particle sizes, which can be a challenge to stabilize with rheology modifiers. A smaller particle size means more surface area, and thus the response to thickeners is much more profound. While the requirement of less thickener may be viewed as a benefit, a certain amount of rheology modifier is needed for good application performance and storage stability. Furthermore, next-generation latexes are doing more by providing improved features in certain performance properties, such as stain resistance or opacity, but can also negatively impact rheology. The efficiency of rheology modifiers while maintaining the desired profile is also a key focus. Many times, the highest efficiency products come with drawbacks such as incorporation difficulty, equilibration time, and final product stability. Final film properties can be impacted strongly using rheology modifiers, and key innovations are required to either eliminate drawbacks or introduce additional functionality to the coating.
Sieto, Elementis: There are a few examples that we solved during the past few years. One example is the use of certain solvents in industrial coatings that cause a reduction in the efficiency of the rheology modifier and reduce sag. We created a product called THIXATROL PM 8058, which has much higher efficiency in these systems. One other example is viscosity drop on adding colorants to deep tint bases. Again, we developed associative thickeners that hold up very well.
Q. Have you introduced any recent products for controlling the rheology of paints and coatings?
Moore, BASF: BASF is working on several new rheology modifiers and adjusting our production to maximize our supply to customers. Our newest innovations, Rheovis PU 1192/1193, are higher-efficiency pseudoplastic thickeners and scheduled to launch in 2022. Additionally, we are exploring new concepts for a HASE product that could be used to partially, or completely, replace HEC use in formulations. We are also continually researching new techniques and test methods for evaluating the performance of our additive portfolio. Our focus for rheology modifiers includes visual methods for identifying flow and leveling potential as well as real-time-force measurements for application ease. Also, BASF is in the process of relocating our associative rheology portfolio to Castelbisbal, Spain. This site previously supplied many of the same products to regions outside North America. The move to Castelbisbal will ensure that our quality of supply will be uniform throughout the globe and strengthen our global knowledge on market trends and R&D efforts to better support our global customers.
Sieto, Elementis: Elementis recently introduced THIXATROL PM 8058, a new amide-based organic thixotrope for use in solvent-based coatings such as high-performance industrial coatings for marine and industrial maintenance applications. It provides high viscosity, thixotropy, and thick-layer sag control in high-build systems that contain aromatic solvents (e.g., xylene) and polar solvents (e.g., n-butanol, benzyl alcohol, etc). THIXATROL PM 8058 is activated at low temperatures, enhancing manufacturing efficiencies, storage stability and improved process control. It also has a high percentage of biobased raw materials to help customers meet high sustainability demands.
Williams, Dow Coating Materials: We recently developed new products such as ACRYSOL™ RM-725, ACRYSOL™ RM-3030, and ACRYSOL™ RM-1600. These products allow for formulating across a very broad spectrum of formulations from economy flats to specialty coatings. We optimized formulations that allow for benefits in both professional and do-it-yourself paints. We are prepared to highlight full formulating guidelines for optimizing features with these products, such as hiding, sheen uniformity, levelling, and cleanabilty at all sheen levels.
Sullivan, Münzing: Münzing is working to introduce a series of HEUR thickeners using biobased building blocks in NAFTA (TAFIGEL PUR R), which are currently available in Europe. We are also working to introduce a new series of HASE thickeners for high pH value formulations.
Q. What advice would you give formulators who are designing a waterborne coating formulation and trying to optimize rheology with additives?
Sullivan, Münzing: For a truly in-depth understanding of the properties of rheology for finished products during manufacturing, storage and processing, developers should be aware of the basic properties of various rheology additives (e.g. cellulose ether, HASE, HEUR, ASE, etc.). Also,
rheology issues may be improved by selecting more appropriate pigments, fillers and dispersing additives as well as appropriate processing conditions (e.g. shear rate, rate and order of addition). Furthermore, the use of a high-end rheometer and the performance of rotational, oscillatory, and combined measurements is essential to identify the causes of problems.
Sorrell, BASF: Optimizing rheology can be tricky with heterogenous mixtures such as paints. There are many components that can add to or detract from your rheology performance. Therefore, if you are working with a formulation that has evolved over the years, I recommend returning the formulation to the basics. To solve problems, formulating by addition can unnecessarily complicate rheology optimization. More than any other paint ingredient, rheology modifiers are expected to perform different functions under varying circumstances from in-can particle suspension, in-can feel, brush/roller-applied feel, and drag, spatter resistance, flow, and sag balance.
Achord, BASF: One needs to consider the entire rheology curve when selecting rheology modifiers. Most often a single thickener is not sufficient to provide good in-can storage stability and sag resistance as these two attributes are on opposite ends of the rheology curve. It is best to select a low-mid-shear thickener in combination with a high-shear thickener to provide the best rheology profile for the application. How it will be applied and the environment where the paint will be applied is yet another important factor in rheology modifier selection. For instance, if the coating will be spray applied, select a thickener that is strongly pseudoplastic for improved atomization. If the coating will be subjected to exterior exposure, water resistance will be a key factor, and therefore, the water sensitivity of the thickener choice should be considered.
Sieto, Elementis: Make sure you are open to working with a supplier who can recommend the right product based on your paint system. This will speed up your development time and give you the performance you need.
Wang, Dow Coating Materials: Think rheology early! Your choice could greatly influence film and application properties, as well as overall end user experience. Take advantage of the best measurement science. Design of experiments coupled with high throughput capabilities can speed your journey to the best solution. Test and refine your model with real-world application methods.
Williams, Dow Coating Materials: Be open to change and recognize that a new solution sometimes demands new products (i.e., products not on your shelf). Formulators and suppliers alike have a role to play here in demystifying rheology. We are not alone, but we pride ourselves in providing experts who can translate paint rheology from basics to optimizing solutions for most formulation spaces.