PURPOSE: To provide the captioned polymers that are obtained in a short polymerization time and are high in light transmittance by polymerization using peroxide initiators having different decomposition temperatures in which the difference between the decomposition temperature of the initiator having the lowest decomposition temperature of them and the decomposition temperature of the initiator having the highest decomposition temperature of them falls in specified conditions.
CONSTITUTION: In polymerizing (A) 80 to 100 wt.% methyl methacrylate and (B) 0 to 20 wt.% further monomers capable of undergoing free radical polymerization at a temperature of from 100 to 140°C which is virtually constant over the major part of the polymerization time by means of an initiator system consisting of two or more peroxide initiators I having different decomposition temperatures T at which in each case half of the initiator has decomposed after 1 hour, the initiator Imin having the lowest decomposition temperature has a decomposition temperature Tmin of from 60 to 100°C, the initiator Imax having the highest decomposition temperature has a decomposition temperature Tmax of from 100 to 140°C, the difference between Tmax and Tmin is greater than 10°C, and Imax is a perketal of the formula (R1 and R2 are each 1-5C alkyl or the like and R3 is tert-butyl or tert-amyl).
BUIRUFURIITO SHIEEN
KAARUURUUTOBUITSUHI ENTORITSUH
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