| 摘要 |
Mouldable non-porous polyurethane polymers are produced by a process which comprises reacting in the presence of a reaction accelerator (1) an NCO-containing pre-polymer prepared by reacting an excess of an aliphatic di-isocyanate, cycloaliphatic di-isocyanate or araliphatic di-isocyanate with an organic compound having a molecular weight of at least 250 and containing active hydrogen atoms which are reactive towards NCO groups (the excess of di-isocyanate being calculated on the free active hydrogen atoms of the organic compound) with (2) from 5 to 30 molecules of water for each two NCO groups. Solvents, e.g. acetone, dioxan, tetrahydrofuran and dimethylformamide, may be present during the reaction. The organic compound may be a polyester, polyhydric polyalkylene ether, polyhydric polyalkylene polythioether, polyacetal, polyesteramide, polyesterurethane or polyetherester and starting materials for the production of these are listed. The di-isocyanates specified include polymethylene di-isocyanates; cyclohexane di-isocyanates; di-cyclohexane-4, 41-di-isocyanate; p-xylylene-o , o 1-di-isocyanate; hexahydrotoluene di-isocyanates; di-isocyanates obtained by phosgenating hydrogenated or partially hydrogenated aromatic amines; aliphatic di-isocyanates with hetero atoms in the aliphatic chain, such as those obtained by the addition of acrylonitrile to hydrogen sulphide, water or glycols and subsequent conversion to isocyanates; polymerized hexamethylene di-isocyanates; and di-isocyanates modified by reaction with less than the equivalent quantity of water. Minor amounts of aliphatic, cycloaliphatic and aromatic mono-isocyanates may also be added. Reaction accelerators specified include alkali metal hydroxides, quaternary ammonium bases, tertiary amines, alcoholates and organometallic compounds. The accelerators may be chemically incorporated in the prepolymer (1) e.g. by using polyesters made from amines such as triethanolamine or by using amine initiated polyethers. The reaction mixtures may be cast or centrifugally cast to give moulded articles, used as sealing compounds, to give pavement and road surfaces, as moulding compounds, as adhesives, to give self-supporting foils, as impregnants, as coating compositions and to make printing cylinders, driving belts and conveyer bands. Specifications 798,209, 840,097, 842,420 and 876,503 are referred to. |
