Water reducible polyurethane

Such polyurethanes have excellent hydrolytic stability compared to water-reducible polyesters and superior abrasion resistance. In view of the importance of developing low solvent emission coatings, considerable effort is being devoted to new types of water-borne urethane resins (62,63). 

Chem. Descrip. Blend of silica and organic solids Uses Surfactant, defoamer, air release agent in water-reducible coatings such as polyurethanes, interior and exterior paints, aq. printing inks Features Min. contribution to VOC... 

Water-reducible polyunsaturated acid substituted aqueous polyurethane dispersions are also being used (40). They can be made by reacting a diisocyanate with a polyol, monoglyceride of a drying oil, and dimethylolpropionic acid. The carboxylic acid groups are neutralized with a tertiary amine and dispersed in water. If aliphatic isocyanates are used, good color retention can be obtained. They are much more resistant to hydrolysis than conventional alkyd resins. Films also have excellent abrasion resistance. Cost can be reduced by blending in 10-20% of acrylic latex. 

The hydroxy-functional polyurethane dispersions can be cross-linked with MF resins or blocked isocyanates. Blocked isocyanates can also be used with water-reducible anionic acrylic or polyester resins instead of an MF resin oxime blocked isocyanates are commonly used, owing to their high reactivity. Oxime blocked aliphatic isocyanates are more stable to hydrolysis than oxime blocked aromatic isocyanates (32). As mentioned earlier alcohol blocked isocyanates are used in cationic electrodeposition coatings. 

Ley DA, Fiori DE, Quinn RJ. Optimization of acrylic polyols for low VOC two-component water reducible polyurethane coatings using tertiary isocyanate crosslinkers. 

Waterborne Polyurethane Coatings Reduce VOCs by 50% New polyurethane coatings from Bayer use water to replace most or all of the organic solvents used in conventional two-component (2K), solvent-bome polyurethane coatings. These 2K waterborne polyurethane coatings reduce volatile organic compound (VOC) emissions by 50—90% and hazardous air pollutant (HAP) emissions by 50—99%. 

Water-reducible urethanes - In recent years, advances have been made incorporating polyurethane coating attributes into aqueous vehicles. One approach is to prepare a hydroxyl-terminated polyurethane (using NCO/OH... 

Water reducible polyurethane systems are also now commercially available. These systems compare favourably with their solvent based counterparts for gloss, resistance properties, mechanical properties and appearance, but they have inferior weathering performance. Nevertheless, they do present a viable commercial alternative to the alkyd based products, which are presently used in a large range of industrial applications. 

For cleaning/priming operations there are also new developments. One trend is to apply the primer in a water-based form. In this invention, a water based primer was developed using water reducible polyurethanes. The primer is for general use but has been... 

The tank is typically about sixteen inches in diameter and about four to five feet tall. The top of the tank is domed upward and the bottom of the tank is also domed upward in a concave manner. The outside of the tank is insulated with a polyurethane foam insulation that is squirted into the gap between the tank and a thinner sheet metal jacket. The polyurethane is made of two different components that react and harden when mixed. Included in the mixture is a blowing agent that causes the polyurethane to expand in a foam-like manner. Prior to about 1980, water heaters were insulated with fiberglass insulation. The foam insulation process was developed to allow automation and increased manufacturing speed and reduced costs. A side benefit was improved insulating ability leading to a slight increase in efficiency. 

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