Deproteinization of Natural Rubber Latex and Synthesis of Highly Purified Natural Rubber Latex

采用脱蛋白和酯交换的方法对天然橡胶进行了精制。在表面活性剂存在下，用蛋白水解酶处理天然胶乳，使其含氮量从0.3%降至0.01(w/w)。推测残留的含氮化合物是与橡胶相连的寡肽。脱蛋白后凝胶含量显著降低，相对分子质量略有下降。尽管硫化胶的吸水率和电阻有较大改善，但脱蛋白对硫化胶的物理性能影响不大。橡胶的酯交换反应分解支点形成线性橡胶分子。橡胶的绿色强度经酯交换处理后显著降低，而脱蛋白处理不会改变。脱蛋白过程伴随着天然抗氧剂的减少。在甲苯溶液中的二氯化钴或胶乳中的过硫酸钾等催化剂的存在下，脱蛋白橡胶易被空气氧化分解为低分子量液体橡胶。这些液体橡胶的两个末端基团都被推测为羰基。

Purification of natural rubber was curried out by deproteinization and transesterification. Nitrogen content in commercial natural rubber latex was reduced from 0.3% to 0.01 (w/w) by treatment with proteolytic enzyme in the presence of surfactants. The residual nitrogenous compound was presumed to be oligo peptide linked to rubber. Deproteinization resulted in a significant decrease in gel content and a slight decrease in molecular weight. The physical properties of vulcanizates were unchanged by deproteinization, although a large improvement for water adsoptivity and electric resistance were observed. Transesterification of rubber decomposed the branch-points to form linear rubber molecules. The green strength of rubber decreased significantly after transesterification, while not changed by deproteinization.The deproteinization process was accompanied with the reduction of naturally occurring antioxidants. The deproteinized rubber was easily decomposed to low molecular weight liquid rubber by air oxidation in the presence of catalyst such as cobalt dichloride in toluene solution or potassium persulfate in latex. Both terminal group of these liquid rubbers were presumed to be carbonyl groups.