用SN型催化剂合成苯乙烯一丙烯嵌段共聚物的研究──Ⅰ．聚合条件对共聚合反应的影响

SYNTHESIS OF iPS-b -iPP BLOCK COPOLYMER WITH SN CATALYST Ⅰ.EFFECT OF POLYMERIZATION PARAMETERS ON SEQUENTIAL BLOCK COPOLYMERIZATION OF STYRENE WITH PROPYLENE

用稀土化合物改性的钛系载体催化剂（ＳＮ催化剂）进行苯乙烯和丙烯顺序嵌段共聚合（Ｓｅｑｕｅｎｔｉａｌｂｌｏｃｋｃｏｐｏｌｙｍｅｒｉｚａｔｉｏｎ）的研究．考察了苯乙烯预聚时间、单体比、外加给电子体（ＥＢ）、烷基铝浓度、催化剂浓度和聚合温度等条件对共聚合的影响．发现外加酯（ＥＢ）降低了共聚合反应催化活性，在ＥＢ／Ｔｉ摩尔比为５范围内，外酯有助于提高嵌段共聚物（ｉＰＳ—ｂ—ｉＰＰ）中ＰＳ段和ＰＰ段的等规度及增加苯乙烯链节含量．ＳＮ型催化剂对苯乙烯一丙烯嵌段共聚合有较高的催化活性，催化效率在１００ｇ聚合物／ｇ－Ｔｉ以上．共聚物通过溶剂革取分级除去均聚物后，所得嵌段共聚物中苯乙烯链节含量可在１５～８５ｍｏｌ％之间调节．其结构表征续见第ＩＩ报．

Sequential block copolymerization of styrene with prOPylene were carried out with TiO4-NdojOR), /MgCI2 /Ph2SiO2 / EB catalyst (called SN catalyst) which was developed in our laboratory. The influence of various polymerization conditions such as styrene prepolymerization time, monomer feed ratio, extend donor (EB),Al(iBu). concentration, catalyst concentration and temperature on the copolymerization were studied in detail' Ethyl benzoate was found to reduce the activity of the catalyst.A much higher incorporation of styrene and higher stereoregularity of each segmentsof copolymer, however, were observed withinmole ratio EB /Ti=5; while futheraddition of EB reduced incorporation of styrene and suppressed the stereospecificity of PS segment. SN catalyst was found to give higher catalytic yield (over 1000 gp /gTi)and conversion yield of styrene. The styrene-whiz of copolymer obtained werewhithin 15 to 85 mole%, depending upon the polymerization conditions.