| 摘要 |
1,202,054. Polyurethane laminates. MINNESOTA MINING & MFG. CO. 14 Aug., 1967 [15 Aug., 1966; 28 June, 19671, No. 37311/67. Heading B5N. [Also in Divisions B2 and C3] A laminate comprises a porous substrate bonded to a layer of a microporous material, comprising a matrix of cross-linked, chain extended polyurethane particles chemically bonded together at cross-linkable and chain-extendable sites therein, the major amount of cross-links being urethane and/or urea linkages, and the average M.W. between the urethane and/or urea cross-links being 1000 to 50,000, the material being substantially insoluble in dimethylformamide-tetrahydrofuran mixtures and may be prepared by effecting an NCO-amine reaction in a polyurethane forming reaction mixture comprising a liquid organic vehicle in which the reactants either dissolve or form a highly solvated dispersion and in which the reaction product is insoluble, a polyisocyanate, an organic polyamine and a cross-linking component having at least three reactive groups per molecule, agitating the reaction mixture until a dispersion of insoluble gel-like polyurethane particles having chain-extendable sites therein has been produced, casting this dispersion on to a substrate prior to completion of the NCO-amine reaction to form a matrix of the particles, and substantially preventing evaporation of the liquid organic vehicle until the reaction is completed and the matrix has formed a self-supporting structure containing inter-particulate bonding. The polyurethane is suitably prepared by reacting an organic polyisocyanate, a polyalkylene ether glycol, an organic polyamine and a cross-linking component which is suitably a polyalkylene ether polyol having at least three hydroxyl groups. Evaporation of the liquid organic vehicle may be prevented by immersing the cast dispersion in a mineral spirits bath until a self-supporting structure is formed. The microporous material may then be stripped from the substrate and then adhesively bonded to suitable backings, e.g. a porous latex impregnated non-woven fibrous material (see. Example II). In Example II, the dispersion was knife coated on to a carrier film of polyethylene terephthalate and a polyester-cotton cloth was applied over the wet coating. |
