Process for the production of a transparent rubber-modified monovinylidene aromatic resin

A process for production of a transparent rubber-modified monovinylidene aromatic resin is performed by polymerization of the monovinylidene aromatic monomers, ester of (meth)acrylic acid monomers and optionally copolymerizable monomers with presence of the rubbery copolymer;

• wherein, the final conversion of said polymerization is 60˜98%, and content of the residual volatile components in said transparent rubber-modified monovinylidene aromatic resin is less than 1 wt. %;
• wherein, said transparent rubber-modified monovinylidene aromatic resin comprises (i) 1˜25 wt. % of dispersed rubber particle (A) comprising rubbery copolymer and (ii) 99˜75 wt. % of continuous phase matrix copolymer (B);
• wherein said copolymer (B) is prepared from monomers comprising 20˜70 parts by weight of monovinylidene aromatic monomers, 30˜80 parts by weight of ester of (meth)acrylic acid monomers and 0˜40 parts by weight of copolymerizable monomers;
• wherein the maximum height difference (ΔHmax) of the surface of a piece molding for testing of said transparent rubber-modified monovinylidene aromatic resin is less than 3,200 Å and the average height difference (ΔHave) is less than 2,000 Å;
• wherein said piece molding is produced by injection with a mirror mold, wherein the surface roughness of said mirror mold is about 0.1 μm according to JIS B0601, Ra method;
• and
• wherein the ratio of A1/A2 of the rubber particles of dispersed rubber particle (A) having a major diameter of greater than 0.3 μm and located at a depth of 1.8˜2.2 μm from a surface of said piece molding is in the range of 1.08˜2.35;
• wherein A1 and A2 represent the average ratio of major diameter to minor diameter of said rubber particles before and after annealing at 120° C. for 40 minutes of said piece molding, respectively.