JPH1087705A5 - - Google Patents

Description

[0023]
Example 2
The same operations as in Example 1 were carried out except that no distillation operation was performed. Bulk polymerization was performed. That is, the monomer solution supplied to the polymerization reactor was 97.9% by weight of methyl methacrylate and 2.1 % by weight of methyl acrylate. The same operations as in Example 1 were also carried out except that the polymerization initiator and chain transfer agent were slightly modified so as to obtain approximately the same polymerization conversion rate and molecular weight as in Example 1. The methyl acrylate content in the obtained methacrylic resin pellets was 2.0% by weight, the intrinsic viscosity was 54 ml/g, and the residual monomer content was 2200 ppm. Furthermore, the number of small foreign matters did not change significantly, remaining at 2000 to 3000 particles/g of polymer even after six months of continuous operation.

[0024]
Comparative Example 1
The same procedure as in Example 1 was carried out under the same conditions as in Example 1, except that an ion exchange column was not used . The methyl acrylate content in the resulting methacrylic resin pellets was 1.9 wt %, the intrinsic viscosity was 56 ml/g, and the residual monomer content was 2,300 ppm, the same as in Example 1. The number of minute foreign matters was slightly high at the start, at about 5,000 particles/g of polymer, due to the effects of the initial step, but after two days it had risen to 2,000 to 3,000 particles/g of polymer, which was almost the same as in Example 1. However, after four months it had risen to 5,000 to 6,000 particles/g of polymer, and after six months it had risen to more than 10,000 particles/g of polymer, resulting in a significant deterioration in optical properties.