有机硅氧烷接枝改性天然胶乳的制备及结构表征

Preparation and Structural Characters of Natural Rubber Latex Graft-modified by Organosiloxane

采用接枝共聚制备有机硅氧烷接枝改性天然胶乳,着重考察偶联剂种类和用量、引发剂用量、胶乳浓度、反应温度、反应时间和有机硅氧烷种类及用量等对有机硅在接枝共聚反应中的转化率和接枝率的影响,并采用正交设计试验,探索有机硅氧烷改性天然胶乳的适宜工艺条件。结果表明:VD4接枝改性天然胶乳的转化率和接枝率均比D4的要高;与其他偶联剂相比,A-171的接枝率也较高;随着有机硅单体用量的增加、反应时间延长、反应温度升高,有机硅单体的转化率和接枝率都升高。有机硅氧烷改性天然胶乳的适宜工艺条件:胶乳浓度为50%,反应温度为55℃,反应时间为4h,偶联剂A-171用量为1.2%(占橡胶的质量百分率,下同),有机硅用量为15%,引发剂用量为1.0%。IR分析结果表明:有机硅氧烷与天然橡胶分子链存在接枝共聚。

Natural rubber latex modified by polyorganosiloxane was prepared by the method of grafi-copolymerization. An attempt was made to study the effect of the coupling agents and dosages, NR latex concentration, dosage of initiator, reaction temperature, reaction time and the organosilixane agents and their dosages to the monomers conversion and monomers grafting percentage in graft copolymerization reaction. An orthogonal experiment was arranged to seek suitable technological conditions through statistical analysis of the available experimental data. The results showed that VD4 had higher monomers conversion and monomers grafting rate than D4 in graft copolymerization reaction. The A-171 was the best coupling agent as against the other agents： KH-550, KH-570 and A-151. The monomers conversion and the grafting rate were increased significantly with an increase in ratio of D4 or VD4/NR, in reaction time and in reaction temperature. The optimum technological conditions observed for modifieation of NR grafted by organosilixane were： NR latex concentration 50 %, reaction temperature 55 ℃, reaction time 4h, the dosage of A-171 1.2 %, the dosage of organosilixane 15 % and the dosage of initiator 1.0 %. The IR proved that polyorganosiloxane was definitely grafted onto NR.