| 摘要 |
PROBLEM TO BE SOLVED: To provide an impact modifier which, even when added in a small amount, imparts excellent discoloration resistance and impact strength to a resin by selecting, as the modifier, a graft copolymer prepared by grafting a vinyl monomer onto a composite polyalkyl (meth)acrylate rubber which contains at least two acrylic rubber components different in glass transition point and has a specified particle size distribution. SOLUTION: The composite polyalkyl (meth)acrylate rubber contains at least two acrylic rubber components different in glass transition point, and each rubber component contains up to 20 wt.% monomer units, each of which has at least two unsaturated bonds. The particle size distribution of the rubber is a polydisperse distribution wherein there are at least two peaks in the range of 0.05-0.4μm and at least 70 wt.% of the particles have particle sizes of 0.05-0.4μm. The objective modifier is an acrylic rubber-based graft copolymer prepared by grafting 20-0.1 wt.% vinyl monomer onto 80-99.9 wt.% above-mentioned composite rubber. Preferably, the composite rubber has at least two glass transition points equal to or lower than 10 deg.C.
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