| 摘要 |
Cross-linked polyurethane elastomers containing urea groups are prepared by spraying a mixture comprising a linear polymer containing urethane groups and terminal aromatic primary -NH2 groups and of M.W. 800-3000, an aromatic primary diamine of M.W. below 500 and an organic diisocyanate present in an excess calculated on the sum of the end groups of the mixture of amino compounds on to a foundation and allowing the reaction to be completed on the foundation. The linear polymer of M.W. 800-3000 may be prepared by reaction of a nitroaryl isocyanate with a polyhydroxyl compound followed by catalytic reduction of the nitro groups; or alternatively by reacting 1 mol of aromatic diisocyanate per hydroxyl group of a polyhydroxyl compound and converting the -NCO end groups with HCOOH to formylamide groups which can then be hydrolysed with acids or alkali metal hydroxides to -NH2 groups. In Example (1) 1 mol of polypropylene glycol was reacted with 2 mols of p-nitrophenyl isocyanate in chlorobenzene and the product hydrogenated in the presence of Raney nickel. The hydrogenated product was mixed with 3:31 - dichloro - 4:41 - diaminodiphenylmethane in a spray apparatus and the mixture so formed continuously mixed in the nozzle of said apparatus with diphenylmethane 4,41-diisocyanate and sprayed. In Example (3) the hydrogenated product prepared as in Example (1) was mixed 1:5-naphthylene diamine and then with hexamethylene 1:6-diisocyanate.ALSO:Cross linked polyurethane elastomers containing urea groups are prepared by spraying a mixture of a linear poly addition or condensation product containing urethane groups and terminal aromatic -NH2 groups and having a M.W. of 800-3000, an aromatic primary diamine of M.W. below 500 and an organic diisocyanate present in an excess calculated on the sum of the end groups of the mixture of amino compounds on to a foundation and allowing the reaction of the components to be completed on the foundation. The spraying may be done from nozzles. Surfaces mentioned are suitable for coating on leather, metal, paper, wood, solid and porous synthetic resins, rubber and woven fabrics. In examples the reaction mixture was sprayed on to (2) a vertical wall and (3) a metal plate. |
