申请人:Asahi Kasei Kogyo Kabushiki Kaisha
公开号:EP0123412A1
公开(公告)日:1984-10-31
Manufacture of a diphenylmethane diisocyanate for an N-phenylcarbamate is economically accomplished in high yield with high selectivity by a method which comprises (A) a process of methylenation forthe formation of a condensation product containing at least 80 mol% of a dinuclear diphenylmethane dicarbamate by the steps of 1) causing a methylenating agent to react upon at least 2 moles of an N-phenylcarbamate, based on 1 mole of the methylene group of said methylenating agent, in a liquid phase in the presence of an aqueous inorganic acid solution, 2) separating the resultant reaction mixture into the aqueous inorganic acid solution and an organic phase reaction mixture containing substantially none of said inorganic acid, and 3) subsequently treating said organic phase reaction mixture in the presence of an N-phenylcarbamate and a carboxylic acid having a pKa of not more than 4 in an aqueous solution at a temperature of25°C or a solid acid or an acid consisting of said two acids thereby converting a reaction intermediate possessing a methylene-amino bond and contained in said organic phase reaction mixture to a diphenylmethane dicarbamate, and (B) a process of thermal decomposition by the steps of allowing a mixture comprising 1 to 50% by weight of the condensation product obtained in said process of (A) and 99 to 50% by weight of a thermal decomposition solvent having a boiling point under atmospheric pressure in the range of 120 to 350%C and being inactive to isocyanates to flow down into a reactor maintained attemperatu res in the range of 180 to 380°C through the upper part thereof, causing said mixture to come into counterflow contact with a carrier introduced into said reactor upwardly via the lower part thereof thereby producing an organic hydroxyl compound, allowing said organic hydroxyl compound to be discharged from said reactor in the form of vapor in conjunction with said carrier through the upper part thereof, and withdrawing the resultant isocyanate solution from said reactor through the lower part thereof.
用 N-苯基氨基甲酸酯制造二苯基甲烷二异氰酸酯是一种高产率和高选择性的经济 方法,该方法包括 (A) 通过以下步骤形成含有至少 80 摩尔二核二苯基甲烷二氨基甲酸酯的缩合产物的亚 甲基化过程:1) 使亚甲基化剂与至少 2 摩尔的 N-苯基氨基甲酸酯反应、1) 在无机酸水溶液存在下,使亚甲基化剂在液相中与至少 2 摩尔的 N-苯基氨基甲酸酯发生反应,以所述亚甲基化剂的 1 摩尔亚甲基为基准、2) 将生成的反应混合物分离为无机酸水溶液和基本上不含所述无机酸的有机相反应混合物、3) 随后在温度为 25°C 的水溶液中,在 N-苯基氨基甲酸酯和 pKa 不大于 4 的羧酸或固体酸或由上述两种酸组成的酸的存在下处理上述有机相反应混合物,从而将上述有机相反应混合物中含有的具有亚甲基氨基键的反应中间体转化为二苯基甲烷二氨基甲酸酯、(B) 热分解工艺,其步骤为:使包含 1 至 50%(按重量计)在所述(A)工艺中获得的缩合产物和 99 至 50%(按重量计)的热分解溶剂的混合物流下,该溶剂在大气压下的沸点在 120 至 350℃之间,对异氰酸酯不活泼,并通过其上部流入温度保持在 180 至 380℃之间的反应器中、使所述混合物与通过其下部向上进入所述反应器的载体逆流接触,从而产生有机羟基化合物,使所述有机羟基化合物与所述载体一起通过其上部以蒸汽的形式排出所述反应器,并通过其下部将由此产生的异氰酸酯溶液从所述反应器中抽出。