Process for producing a methyl methacrylate series polymer translucent or opaque plate

Claim 1

A process for preparing a translucent or opaque sheet, which comprises: polymerizing 100 parts by weight of styrene monomer with from about 0.5 to 10 parts by weight of peroxide having the formula ##STR7## wherein R 1 is alkylene having 1 to 15 carbon atoms or phenylene, R 2 is alkylene having 2 to 10 carbon atoms, --(CH 2 ) 2 O(CH 2 ) 2 --, --(CH 2 ) 2 O(CH 2 ) 2 O(CH 2 ) 2 -- ##STR8## and n is a number from 2 to 20 at a temperature of from about 60° to about 90° C., for from about 2 to about 6 hours, to obtain polystyrene having peroxy groups therein; then partially polymerizing a mixture comprised of from about 0.5 to about 20 parts by weight of said polystyrene having peroxy groups therein and 100 parts by weight of second monomer consisting essentially of more than 80 wt. % of methyl methacrylate and less than 20 wt. % of one or more acrylic monomers and optionally a coloring agent at a temperature of from about 60° to about 90° C., for from about 1 to about 2 hours, to convert about 10 to about 30 wt. % of said second monomer to polymer whereby to obtain a syrup; then casting said syrup into a sheet-forming mold and maintaining the contents of said mold at a temperature of from about 40° to about 70° C., for from about 4 to about 10 hours, followed by heating at from about 100° to about 120° C. for from about 2 to about 6 hours, whereby to obtain a translucent or opaque sheet.