GB893637A - Method of producing laminated sheet materials - Google Patents

Abstract

893,637. Polyurethane coatings. DUNLOP RUBBER CO. Ltd. Sept. 9, 1958 [Oct. 12, 1957], No. 31933/57. Class 140. A laminated sheet material is produced by casting on a non-metallic backing sheet a layer of a liquid polyurethane intermediate product, said intermediate product being a reaction product of a polymer containing terminal hydroxy groups and an aromatic polyisocyanate having a cross-linking agent incorporated therein, and completing the polymerization of the intermediate product in situ. The polyurethane intermediate product may be prepared by heating a polymer containing terminal hydroxy groups, such as a polyester, e.g. polyethylene adipate or sebacate, polyether, e.g. polyethylene glycol, or polyesteramide, with an aromatic polyisocyanate, to form a syrup and immediately prior to casting stirring a crosslinking agent therein. Alternatively, the intermediate product may be prepared by reacting the polymer containing terminal hydroxy groups with a slight excess of polyisocyanate and then with a further quantity of the polymer to form the syrup into which the cross-linking agent is subsequently stirred. The crosslinking agent may be water, a glycol, e.g. butylene 1,4-glycol or propylene glycol, or an amine, e.g. ethylene diamine or triethylamine. The backing sheet may be a sheet of fibrous material such as leather, e.g. chrome leather, leather-board, paper, and textile materials including cotton duck, canvas and like woven fabrics such as an open-weave nylon monofil fabric, or a sheet of non-fibrous material such as natural or synthetic rubber. It is preferable that the surface of the sheets of non-fibrous material be provided with a layer of adhesive prior to casting the polyurethane intermediate product thereon. The adhesive may be based on polyurethane which may comprise a reaction product of a polyester and an aromatic diisocyanate to which an aromatic triisocyanate is added, or the reaction product of trimethylol propane and toluene diisocyanate. Examples of polyisocyanates are toluene and naphthalene diisocyanates, and triphenylmethane triisocyanate. Pigments, colouring materials, fillers, plasticizers, and modifiers may be added to the intermediate product, preferably prior to the addition of the cross-linking agent. The backing sheet may be held on a heated vacuum mould during the casting operation. The intermediate product may be allowed to set in the mould, the laminated sheet removed from the mould and polymerization completed by heating. Fabric or paper may be stretched in a framework and/or held on a hot plate, during the casting operation. It may be desirable to store the laminated material in a curved position to counteract shrinkage of the polyurethane coating.