| 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 an acid of the formula RCOOH, in which R denotes an alkyl radical of 1-3 carbon atoms, 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 solution of p,p1-diphenylmethane diisocyanate in dimethyl formamide is pretreated with acetic acid and then 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 an acid of the formula RCOOH, in which R denotes an alkyl radical of 1-3 carbon atoms, 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-diphenyl methane diisocyanate in dimethyolformamide solution with acetic acid. A number of other diisocyanates which may be treated are also specified. |
