Bruno Zorn

Porous Polyurethane Films and Coatings

In addition to the transfer coating process for textile substrates which has been known for a long time, the coagulation process has aroused considerable interest. It makes it possible to manufacture imitation leather which is very similar to genuine leather in its handle and appearance. As the solvent used is recovered, pollution of the environment is minimal. The coagulation process is not suitable for coating leather, because it would mean producing a microporous film onto which splits would be pasted. Practice has shown this to be too expensive. For coating leather, a transfer process in which a reactive two-component PUR coating is applied on the leather via moulds has become widely used. The advantages and disadvantages of this method are discussed. The purpose in manufacturing imitation leather is usually to obtain a material which resembles genuine leather. One imitation leather which enjoyed-and still enjoys-great success consists of a raised fabric transfer-coated with polyurethane. This construction is intended to imitate the handle and grain break of leather, but it does so with only limited success. Because of the compact top coat, the material has very poor water vapour permeability, and it is only soft if the PUR coat penetrates as little as possible into the nap, which means, however, that the adhesion of the synthetic resin coat is reduced.