Polyurethanes coatings have long been used in solventborne systems. Polyurethanes can be made waterborne, and have been used successfully as such or in acrylic-urethane hybrids. However, the hydrolytic sensitivity of the commonly used adipate polyester backbones has often resulted in poor storage stability and film durability.
This problem can be countered through a range of hydrolytically stable polyester polyols developed by Uniqema, based on dimerized fatty acids.
Natural oils and fats have for years provided polyurethane chemists with a variety of building blocks, such as glycerin and castor oil. Less known is the use of a fatty acid derivative, the so-called dimerized fatty acids, for polyurethane chemistry. These dimerized acids are obtained by the conversion of unsaturated fatty acids (from sources like soybean oil or tall oil) by a combination of pressure, temperature and catalysis. This process generates a mixture of products, the most important being dimerized fatty acid. Others are trimerized fatty acid and isostearic acid. Figure 1 gives an overview of the dimerization process