GB1529867A - Impregnating protein-based materials with polyisocyanates - Google Patents

Abstract

1529867 Impregnating protein based materials BAYER AG 8 Oct 1975 [9 Oct 1974] 41210/75 Heading D1P A process for impregnating protein-based material in the form of sheets, e.g. leather or collagen fleece comprises applying to the material a solvent-free mixture comprising 20-99% of at least one involatile (defined) polyisocyanate and from 1-80% by weight, of a selected involatile (defined), viscosityreducing, non-migrating liquid organic plasticiser for the polyisocyanate. The mixture may be applied as an emulsion in water by spray coating, printing or plush-coating. The isocyanate compound, which may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic, may be applied unmodified or modified e.g. by reaction with water and/or a preferably high molecular weight compound containing at least two isocyanate-reactive hydrogen atoms, such as polyesters, polyethers, polythioethers, polyacetals, polycarbonates or polyesteramides. The plasticiser is free from hydroxyl and amino groups, and may be a leather greasing agent, a chlorinated paraffin hydrocarbon, a phenol ester of a long chain sulphonic acid, a phthalic or phosphoric acid ester, a monocarbonylic acid ester, a dibenzyl ether or a chlorinated aromatic hydrocarbon. The isocyanate compound may be pre-reacted with 1-20 mol % of an organic dye which contains isocyanate-reactive groups. In Examples 1 and 2, a NCO prepolymer formed by reacting a dehydrated polypropylene glycol ether (MW 2,000) with a six-fold excess of 1, 6-hexane di-isocyanate and plasticised with dibutyl phthalate or a compound of formula RSO 2 OPh in which R is an alkyl mixture (10-18C) is applied to leather e.g. by spraying or plush coating followed by a nitro-cellulose emulsion lacquer or polyurethane lacquer dressing. In Example 3 the reaction product of an 80:20 by weight mixture of 2, 4- and 2, 6-tolylene di-isocyanate and a polyester of adipic acid, 1, 6-hexamethylene glycol and 2, 2-dimethyl- 3-propane diol plasticised with dioctyl phthalate is applied to buffed upper leathers, grain leathers and split leathers which are subsequently surface coated with pigment dispersions and aqueous acrylate or butadiene-based polymer dispersions and nitro-cellulose emulsion lacquers or reactive polyurethane dressings e.g. by pneumatic spray gun, airless spray gun, coating machine or printing machine to provide softness and resistance to water penetration. Sheepskin and pigskin may also be treated.