| 摘要 |
The prodn. of expandable (co)polymers of styrene comprises (co)polymerising styrene and opt. at least one comonomer in aq. suspension in the presence of a polymerisation initiator and at least one mercaptan as chain transfer agent, the mercaptan(s) being added to the polymerisation medium in an amt. of 0.005-3 pts. wt. per 100 pts. wt. styrene and any comonomers when the level of conversion of the styrene and opt. comonomers is 30-39 (32-38), (33-37) %. Pref. mercaptan is tert. dodecyl mercaptan. Pref. an aq. phase preheated to 80-120 deg C is mixed with the organic phase preheated to 30-60 deg C to give a polymerisation mixt. which is at a temp. of 70-100 deg C at which polymerisation is initiated immediately, and polymerisation is advanced by raising the temp. continuously or stepwise at 4-20 deg C/h to a final polymerisation temp. of 105-150 deg C. The (co)polymerisation is pref. continued until the content of residual styrene and comonomer(s) in the (co)polymer is less than 0.2 wt.%.
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