Patent ID: 6147181
Filing Date: 2000-11-14
Classification: C08G

Abstract:
A two-stage process for the production of semi-rigid, solid polyurethane molded articles having a high transparency and/or translucency, even at different thicknesses of molded articles, comprising reacting:a) at least one organic and/or modified organic polyisocyanate, withb) at least one high molecular weight compound containing at least two isocyanate-reactive hydrogen atoms, comprising(1) at least one OH-terminated prepolymer having an OH number of from 7 to 56 mg KOH/g, which contains no reactive isocyanate groups, and comprises the reaction product of(1A) a polyether polyol component being selected from the group consisting of:(I) a linear ethylene oxide/propylene oxide polyether polyol having terminal ethylene oxide groups, and an ethylene oxide/propylene oxide ratio of from 15:85 to 40:60, an OH number of from 28 to 56, and having a functionality of 2.0,(II) a mixture of (a) a polyether polyol as specified by (I) above, with (b) another higher functional ethylene oxide/propylene oxide polyether polyol initiated with glycerine, trimethylol-propane, pentaerythritol or sugar, having an ethylene oxide propylene oxide ratio of from 15:85 to 40:60, and having an OH number of from 25 to 60,(III) mixtures of several linear and branched polyether polyols, each of which comprises components (I) and/or (II)(b),(IV) a poly-tetrahydrofuran-ether having an average molecular weight of 500 to 2,000, and(V) mixtures thereof; with(1B) an isocyanate component being selected from the group consisting of:(A) isomers of toluene diisocyanate in any ratio, and/or prepolymers thereof,(B) toluene diisocyanate based polynuclear isocyanates and/or prepolymers thereof,(C) isomers of diphenylmethane diisocyanate in any ratio and/or prepolymers thereof,(D) diphenylmethane diisocyanate based polynuclear isocyanates and/or prepolymers thereof,(E) an aromatic isocyanate having a functionality of at least two and which is obtainable on an industrial scale, and/or prepolymers thereof,(F) an aliphatic isocyanate having a functionality of at least two and which is obtainable on an industrial scale, and/or prepolymers thereof, and(G) mixtures thereof;c) at least one low molecular weight chain extender and/or crosslinking agent,in the presence of, optionally,d) at least one amine and/or metal salt catalysts, and/ore) additives.