| 摘要 |
<p>Styrene/ alpha-methylstyrene graft copolymers with high heat-resistance, good electrical properties and low ash content, useful foe electrical industry, also foils and sheets and contg. 30-60% alpha-methylstyrene and having >60 K-value are prepd. by (i) a first step where a styrene/ alpha-methylstyrene copolymer contg. 0-60% alpha-methylstyrene and having 70-160 K-value is prepd. in emulsion at 0-100 degrees C, in presence of usual polymsn. auxiliaries and with >=50% conversion of monomers used; and (ii) a second step, where 1 pt. styrene/ alpha-methylstyrene monomer mixt., with 80:20 to 25:75 monomer wt. ratio, is grafted, in suspension, on 0.05-1 pts. of emulsion polymer, at 50-150 degrees C, in presence of usual polymsn. assistants, to >=50% monomer conversion, followed by (iii) expelling any monomer still present in polymer.</p> |
