사이크로헥실아민과 무수말레인산으로부터 N-사이크로헥실말레이미드의 합성 및 정제입자의 제조

Abstract

N-cyclohexylmaleimide(CHMI) is a radical copolymer with excellent crosslinking property and thermal stability, and thus has been used for the synthesis of various functional polymers. However, the synthesis of CHMI is not so easy, because the synthesis proceeds under vacuum condition and generates lots of reaction heat. CHMI has been conventionally synthesized from cyclohexylamine and maleic anhydride in ortho-xylene. This method is simple one step reaction, but the maximum yield of CHMI is only 70%. To overcome the low yield of CHMI, an effective three step synthetic method via intermediates has been proposed. In this study, a series of experimental research was performed to improve the three step synthetic process of CHMI via N-cyclohexylmaleiamic acid(CHMA) and N-cyclohexylmaleiamic acid isobutyl ester(CHMAIE) further. For the first step, a series of intermediates were synthesized. Initially, CHMA was synthesized by drop-wise mixing of cyclohexylamine with maleic anhydride in toluene and 98.2% of theoretical CHMA production was obtained by precipitation at 10 ℃ for 2 hours. And the esterfication of CHMA was followed for the preparation of CHMAIE. The optimum reaction temperature of the esterfication was 68 ℃, and equilibrium conversion at the optimum temperature was 98.5%. Equilibrium reaction time decreased with increasing reaction temperature, and 4 hours was taken to reach equilibrium at the optimum reaction temperature. Toluene in the final reaction product was recovered by vacuum distillation. The recovery of toluene was increased with distillation temperature and 98% of toluene was recovered at 55 ℃. Finally CHMI was synthesized from CHMAIE in organic solvents. And CHMI was purified and precipitated to give CHMI particles with high purity. It turned out that n-heptane reflux imidation is more beneficial than toluene put-out imidation not only to the synthesis but also to the precipitation of CHMI. By washing the synthetic CHMI with cold n-heptane twice, purified CHMI with 99.7% purity was obtained at the cost of 11.7% weight loss. And CMHI particles were effectively prepared by spouting molten CHMI through the spiral nozzle with 3 mm diameter under the pressure of 1.5～2.0 kg/cm2.