Download this slide presentation from a Bayer Webinar to learn more about the chemistry of polyurethane dispersions and how they can help you formulate more environmentally friendly coatings.

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In their ongoing quest to provide the safest, highest-quality products possible, scientists from Bayer MaterialScience LLC are exploring new pathways to make aqueous polyurethane dispersions without the co-solvent n-methylpyrolidone (NMP) ? a suspected fetotoxin ? for use as coatings for wood floors, among other applications. In this July 2007 presentation, BMS provides an overview of potential alternatives to NMP, which has been labeled toxic by the EU Commission Working Group on the Classification and Labeling of Dangerous Substances.

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This paper describes fundamental developments in two-component (two-pack, 2K) waterborne polyurethanes for automotive OEM clearcoats. The focus is on work in progress concerning: raw materials, relevant chemistry and application considerations.

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This paper will examine the effect of substrate choice on the resistance of automotive interior “soft feel” coatings to suntan lotion. Analytical methods such as scanning electron microscopy (SEM) were employed to observe morphological changes to the substrates upon exposure to suntan lotion. Results showed that failure times after exposure to suntan lotion were much more dependent on substrate choice than on the coating for this type of system.

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The automotive industry has built up a network of production facilities, affiliates and joint ventures with the aim of further strengthening its own position. The progressive globalisation of the supplier and raw material industries is the logical and unavoidable consequence of this development.

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Two-component, flexible polyurethane coatings are used as protective aesthetic coatings for many automotive plastic applications. Adjusting the coating flexibility to match the flexibility of the plastic allows the coated plastic to retain the impact resistance of the uncoated plastic. New developments in polyurethane chemistry allow the formulation of coatings with much lower VOC’s than conventional flexible polyurethanes.

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One of the major requirements of the automotive manufacturers has been to improve the corrosion protection of their vehicles. Recently, speical polyurethane dispersions containing minimal amounts of co-solvent have been developed that provide even higher performance than current solventborne systems. The present work deals with the technical development of new waterborne primer surfacers by presenting a review of the chemistry and properties of these unique coatings.

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This paper investigates two critical properties, scratch and mar resistance and environmental etch resistance of automotive clearcoats, the top layer of a “basecoat/clearcoat” automobile finish. Polyurethane clearcoats based on two commercially available polyisocyanates and two developmental polyisocyanates were tested for scratch and mar resistance by two different methods: a car wash test and a dry abrasion test. In addition, outdoor acid etch resistance of the same clearcoat systems was tested by summer outdoor exposure in Vero Beach, Florida, and in Pittsburgh, Pennsylvania.

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In the development of automotive coatings, the focus is on improving quality and reducing the emissions of organic solvents. At the same time, this should not involve any increase in the cost of the overall coating process.

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Continual demands from consumers for highly durable coatings with excellent appearance motivate automotive manufactures and paint suppliers to introduce new coating systems into the marketplace to meet those demands. However, because of the potential risk inherent in introducing new coating systems, significant testing of paint systems must be completed before commercial introduction. Unfortunately, testing programs require significant time and resources to reduce the risk of long-term failure to acceptable levels. Typically, automotive manufacturers required up to five years of Florida exposure for a new paint system before they will implement new technology. This time constraint could be significantly reduced if a trustworthy accelerated test were available to the industry that would rapidly and accurately assess the long-term weatherability of automotive coating systems.

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Whether it is new construction for the refurbishment of steel structures, economics is becoming more and more important. This is especially true for refurbishment of steel structures where the question is being asked whether the structure should be completely refurbished or only spot repaired.

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Latent hardeners, based on urethane bisoxazolidine, for example, can react with water to provide isocyanate reactive compounds. As a result of the unique chemistry involved, stable, one-component, moisture-curable systems can be made with prepolymers of a variety of isocyanate types. Oxazolidine chemistry, as it pertains to polyurethane coatings technology, will be discussed.

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This paper will discuss the fundamentals of blocked isocyanates as well as some of the results of a current study examining the potential of developmental blocking agents such as diisopropyl amine (DIPA) and t-butyl benzyl amine (BEBA) for these low temperature applications.

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There is a growing interest to lower the cure temperature of powder coatings and expand the application of this technology to heat sensitive substrates. For the first time solid DEM based crosslinker was successfully designed and developed having significant application potential in the powder coatings field. Examples of the coatings formulations and the details of the coating properties are presented.

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The blocked polyisocyanates belong to the group of baking resins, therefore they are also called crosslinking baking urethanes. For this type of resin two characteristics are of importance: the baking process and the resulting film properties. In the case of the crosslinking baking urethanes these characteristics are determined by the incorporated diisocyanate, the structure of the prepolymer and the blocking agent employed.

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The report presented below gives an account of a new method for the internal plasticizing of cold-curing epoxy resins using special grades of urethane polymers.

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Ketimines derived from aliphatic polyamines and ketones have long been used as latent moisture cure resins in epoxy coatings. It is found that combinations of ketimines with polyisocyanates could have very rapid viscosity builds without moisture. This paper details our identification of a previously unidentified direct reaction between aliphatic isocyanates and ketimines that is responisble for the increase in viscosity. Also detailed is how the rate of this reaction can be controlled and what the implications of it are for a coatings formulator.

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Polyaspartic esters are a new type of amine functional coreactant for aliphatic polyisocyanates. Currently, a number of polyaspartic ester products are coming to market for use in very high solids two component automotive coatings. In addition to providing tough, high gloss finishes, the polyurea coatings produced by this chemistry show superior weathering and environmental etch performance.

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An overview concerning tris-3-(1-aziridino)propionate chemistry and their uses are given. The overview is based on an exhaustive literature search, which covers the chemical literature up to March 2002, and concentrates on the three most commercially significant tris-3-(1-aziridino)propionate crosslinkers: trimethylolpropane tris-(1-(2-methyl)aziridino)propionate (TTMAP), trimethylolpropane tris-3-(1-aziridinopropionate) (TTAP) and pentaerythritol tris-3-(1-aziridinopropionate) (PTAP).

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This paper compares the use of ketimines and aldimines as blocked primary amines in such formulations. These are low viscosity materials that are significantly less reactive than the parent amines. Aspects of imine- isocyanate chemistry presented include the direct reaction of imines with polyisocyanates as well as the relative hydrolytic stability and

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This paper describes experimental formulations with solvent levels at or below 2.0 pounds/gallon with target properties for the automotive refinish, industrial maintenance and wood finishes markets. Comparison of performance properties and cure times of conventional and high solids coatings systems vs. aldimine-isocyanate systems will be discussed. Control of the reaction through catalysis and inhibition along with compatibility of aldimines with various polyisocyanates will also be addressed.

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Two-component polyurethanes are particularly suited for high-solids coatings because they are comprised of lower molecular weight oligomers, which react on the substrate to form a polymeric network. The choice of catalyst for high-solids polyurethane coating formulations, using low molecular weight resins, can be critical since multiple reactions must take place to achieve high molecular weight polymers.

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This paper will describe the growth of polyurethanes in the coatings area both from a technological as well as a market standpoint. In addition to an overview of the current state of polyurethane chemistry, some observations as to the future of polyurethane chemistry in coatings will be shared.

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Polyurethane raw-material suppliers have developed low-viscosity polyisocyanates and coreactants for low VOC polyurethane coatings to address environmental concerns. Development of these resins, as well as many new corrosion inhibitives are providing increased flexibility in formulating polyurethane coatings with excellent corrosion protection.

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This paper presents the development of a new polyuretdione hardener that demonstrates improvements in melt viscosity, processability and appearance as well as powder coating formulations that demonstrate an acceptable performance level for a range of industrial coating applications.

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In order to further penetrate the current markets and, if possible, establish new ones, optimization of the presently used powder coatings systems as well as introduction of new technology is necessary. The goals of such developments are as follows: 1. Reduction of the baking temperature required for crosslinking; 2. Improvement of the flow properties especially at lower film builds. The following article describes the recent wide-ranging efforts to achieve these goals utilizing the versatility of polyurethane chemistry.

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Low temperature cure powder coatings have attracted significant research and development efforts in recent years, for their low energy requirements that can lead to considerable economic benefits. Curing at low temperatures will also help powder coatings as a technology to enter new markets for temperature-sensitive substrates.

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Weather-stable coatings, which yield matte films, are an important field of application for powder coating systems in Europe and as well as in the North American market. Because of their outstanding weather stability and excellent flow and surface properties, polyurethane powder coatings are among the systems used, for example, in the coating of wall cladding elements, garage doors, door and window profiles and car accessories.

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Weathering performance of 2-component polyurethane topcoats used in corrosion protection applications, e.g. bridges, marine, stadiums, etc., is discussed with emphasis on some key formulating variables. Variables such as isocyanate index and resin selection are compared in an accelerated weathering study using various polyurethane topcoats. The results are referenced to SSPC polyurethane coating specifications which are often used in the industry to define performance criteria.

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In recent experiments, sealers based on UV-curable polyurethane dispersions have proven to successfully reduce and eliminate the occasion of defects, especially under the condition of stressing after sealer application. This paper will examine the use and limitations of UV- curable polyurethane dispersions in sealers for SMC, and attempt to explain the spontaneous random delamination observed with some of the sealers in the study.

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The preparation, composition, and properties of aqueous dispersions of crosslinked polyurethanes will be presented. In addition, a review of established polyurethane dispersion technology will be included.

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The performance of coatings prepared from one-component waterborne polyurethane dispersions is generally inferior to one- or two-component cross-linked films in terms of chemical resistance and mechanical durability, particularly in soft-touch coatings. By incorporation of double bond functionality via reacting polyester acrylates into the backbone of the polymer we can greatly reduce cure time of these films to as little as three minutes (elevated flash off temperature, UV cure).

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In this paper, the process and characterization of mixing will be described for two-component waterborne polyurethane coatings that combine either hydrophobic or hydrophilic polyisocyanates with polyol. The physical parameters such as flow rates, viscosities, particle sizes and distributions, polydispersities, refractive indices and percent solid volumes were determined for each type of polyisocyanate and polyol. From this data, the mixing process was optimized and the spray equipment was used as a useful mixing tool instead of hand mixing or impellar mixing in the two-component waterborne technology.

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Recent regulations have mandated the development of primers with a maximum volatile organic content of 2.1 pounds per gallon for the automotive refinish market. Two waterborne resins have been developed which meet the requirements of this application: a co-solventless, oxidatively drying, hydrocarbon backbone resin and a newly developed polyurethane dispersion with low organic co-solvent content. The goal of this study was to examine the use of these resins in formulations which comply with the new, VOC restrictive regulations in consideration of whether these formulations provide the performance required by the market.

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Using rheological methods, the stability and dispersibility of modified polyisocyanates were evaluated. Evaluating the particle size results indicated that the polyisocyanate particles became softer (more deformable) and were emulsified easier at low shear when the level of polyether was increased. Thus, the polyether helps to protect the polyisocyanate/water interface. Overall, this work demonstrates that rheology can be used to characterize the stability and the dispersibility of new materials in a water medium.

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The use of waterborne coatings has been increasing over the past decade with the need to produce more environmentally-friendly products through reducing the needed solvents which make up the Volatile Organic Content (VOC). To meet this need in the wood market, a two-component waterborne polyurethane system (2K-WB/PUR) was developed. This system is based on an acrylic polyol emulsion and a water dispersible polyisocyanate (WDP).

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In response to the need for ambient temperature curing coatings with low solvent emission levels, Bayer has developed two-component waterborne polyurethane coatings with properties similar to those of two-component solvent-borne polyurethane coatings. In this paper, we discuss the hydroxy-functional polyurethane dispersions and the water-dispersible polyurethane crosslinkers that make up this reactive waterborne system. We also discuss the properties of clear and pigmented films from these formulations as well as the factors which affect film properties.

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Reactive two-component polyurethane coatings historically have been stringently protected from water, but in the early 1990's it was shown that such reactive systems could actually be formulated using water as the carrier and still produce films with outstanding appearance and barrier properties. This paper details the current status of work being done in the area of two-component waterborne polyurethane coatings.

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The decision to convert a coating line to a new technology must be a broad-based decision which encompasses all aspects of the operation including VOC and HAPS as well as price and performance. This paper discusses the advantages that have lead several end-users to consider and convert to two-component and one-component waterborne polyurethane coating systems.

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Waterborne polyurethanes (PUR) are not simply scientific curiousities but rather viable commerical industrial products. The earliest application areas for this class of polymetric materials were as coatings and adhesives. Here the use of solvents was precluded due to either the sensitivity of the substrate towards solvent attack or because of the flammability of the solvents. These waterborne products have now begun to penetrate application areas previously serviced only by solventborne polymeric resins.

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This paper describes the development and properties of a fast drying, two- component, crosslinking waterborne polyurethane coating with ultra low Volatile Organic Compound (VOC) emissions and ultra low Hazardous Air Pollutants (HAPS) that was specifically designed for the wood coatings industry.

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This paper will discuss in detail the status of polyurethanes in European and US wood market. An overview of the basic chemistry of polyurethane coatings will be presented. In addition, the performance characteristics of solventborne polyurethane coating systems will be described. Formulation strategies for both one-component moisture curing and two- component solventborne systems will also be discussed.

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With the development of a Water-Dispersible Polyisocyanate (WDP) technology in conjunction with hydroxy-functional acrylic resin it is now possible to formulate an ultra low Volatile Organic Compounds (VOC) and Volatile Hazardous Air Pollutants (VHAPs) wood coating system. This Two- Component Waterborne Polyurethane (2K WB/PUR) gives acceptable “open pore effect” with reduced amounts of flammable solvent than the normal lacquer systems.

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Statistical analysis revealed several key variables in the design of the BFGoodrich hydroxy functional acrylic emulsions, and in the formulation of the coating. These variables were found to significantly influence performance properties of the finished wood coating. The methods used and the results obtained will be discussed.

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In a cooperative effort between Bayer Corp. and the Rohm and Haas Company a waterborne, ultra low VOC and HAPS polyurethane coating has been designed which is not only chemically resistant but also comparable in price to many thermoplastic acrylic coatings.

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With the development of a Water-Dispersible Polyisocyanate (WDP) technology in conjunction with hydroxy-functional acrylic resin it is now possible to formulate an ultra low Volatile Organic Compounds (VOC) and Volatile Hazardous Air Pollutants (VHAPs) wood coating system. This Two- Component Waterborne Polyurethane (2K WB/PUR) gives acceptable “open pore effect” with reduced amounts of flammable solvent than the normal lacquer systems.

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This paper discusses an improved method to UV-cure, high-build, pigmented wood coatings that are based on non-air-inhibited unsaturated polyesters (NAI/UPEs). In covering these topics, the paper describes the development of NAI/UPEs supplied in styrene monomer, NAI/UPEs reduced in solvent and NAI/UPEs that are free of monomer and solvent but are reduced in water.

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