| 摘要 |
A diol monochloroformate is made by the phosgenation of an aromatic diol, the hydroxyl groups of which are bonded to aromatic carbon atoms the phosgene being mixed with an aqueous alkaline solution of the diol in a proportion to provide substantially complete precipitation of the monochloroformate of the diol. The products are employed in the production of polycarbonate resins. Representative of dihydroxy aromatic compounds employed as starting materials in examples are p,p1-isopropylidenebisphenol and its 2,21-dichloro- and 2,21,5,51-tetrabromo derivatives and 4,41 - dihydroxybenzophenone.ALSO:Polycarbonate resins are obtained by dispersing one or more monochloroformates, obtained by phosgenation of aromtic dihydroxy compounds (see Division C2) in a solevnt, admixing the solution with aqueous alkali and a condensation catalyst and thereafter subjecting the mixture to condensation polymerization. Many examples are furnished in which such monochloroformates as those of bisphenol A and its 2,21 - dichloro - and 2,21,5,51 - tetrabromo derivatives are converted to polycarbonates in the presence of organic solvents and benzyl trimethylammonium chloride. |
