Preparation Of Allyl Acrylate

Allyl acrylate is a special acrylate, because its molecular contains two double bonds with high reactivity which can provide effective secondary cross-linking in the second stage to unit two polymer chains(or molecular groups) with unsaturated bonds, so ALA can be used as agents to improve toughening effect of PVC impact modifier. It may also be used as rubber modifier, paint modifier to improve the resistance, impact strength, adhesion hardness and low shrinkage and so on. Because of the two double bonds and active a-H in its molecular, ALA can polymerize easier than the usual acrylate, which leads to its synthesis and refined with great difficulty and low yield, therefore, the study of its synthesis conditions and technology has great significance.According to the synthesis theory of ester and referred literature, by comparative analysis, and we ultimately determined four possible synthesis routes:Direct Esterification with acrylic acid (AA) and allyl alcohol (AL) as raw materials,Acyl Halide Method with acryloyl chloride (AC) and allyl alcohol (AL),Carboxylate Method with acrylic acid salts (SA) and allyl chloride (ALC),Transesterification with methyl acrylate (MA) and allyl alcohol (AL). The experimental research fixed the most suitable conditions of ALA synthesis. The four methods were compared comprehensively, to reach that the best laboratory method was Acyl Halide Method and the method suit for industrial prospect was Transesterification.Optimizing the synthesis conditions of ALA with Direct Transesterification, the most suitable reaction condition was obtained:the ratio of MA and AL was3.5:1. selected p-toluenesulfonic acid as catalyst, the amount was about 8 g/1 molAL, and concentrated sulfuric acid had a strong oxidizing and dehydration, made the product darker; selected the inhibition of hydroquinone and p-methoxy phenol(the ratio of 1:1), with the amount of 9 g (1 mol AL), could play the role of inhibitor effectively. Under the above reaction conditions, the esterification rate reached up to 84%, with products having light color and good quality.Optimizing the synthesis conditions of ALA with Acyl Halide Method, the most suitable reaction condition was obtained:the ratio of AC and AL was 1:1.2. selected methylpyridine as acid binding agent, and the amount was 25g/lmol AC,flow was 3ml/min. Under these conditions, the yield could reach up to 90%, and the product was easily purified with high purity.Optimizing the purifying conditions of crude ALA, the optimal purifying conditions were obtained:selected the inhibition of methoxyphenol and CuCl(the ratio of 1:1) for the rectification, and the amount was 7g(100g crude ester), and the experiment collected the fractions at 51～53℃,2.5kPa. Finally, the yield of ALA reached up to 94% and the purity was above 98%.