| 摘要 |
In the manufacture of fibre-forming elastomeric polyurethanes by processes involving the addition of a solution of an organic diisocyanate to a polymeric diol, the diisocyanate solution is pretreated with phosphoric acid in a proportion of about 0.001-1%, based on the diisocyanate. The pretreatment nullifies the tendency for gel-formation to occur during the manufacture of the polyurethane. An example is given in which a pretreated solution of p,p1 - diphenylmethane diisocyanate in dimethyl formamide is reacted with a solution of a mixture of 80/20 mol. per cent polyethylene/propylene adipate of molecular weight 1800 in the presence of dibutyl tin dilaurate, whereafter the prepolymer solution so obtained is extended with 1,4 - bis - (methylamino) benzene. A number of other diisocyanates which may be pretreated are specified.ALSO:Solutions of organic diisocyanates are treated with phosphoric acid in a proportion of about 0.001-1%, based on the diisocyanate. The treatment nullifies the tendency for gel-formation to occur when the solutions are used in the manufacture of polyurethanes (see Division C3). An example is given of the treatment of p,p1-diphenylonethane diisocyanate in dimethylformamide solution. A number of other diisocyanates which may be treated are also specified. |
