Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2007-07-10
2007-07-10
Zemel, Irina S. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S060000
Reexamination Certificate
active
10901970
ABSTRACT:
A process of producing expandable styrene resin particles, wherein in suspension polymerization of styrene monomers, the concentration of oxygen in a reaction vessel is kept low at least in a late stage of the polymerization, and the resulting styrene resin particles are impregnated with an expanding agent before or after completion of the polymerization. Preferably, at a polymerization rate of 60% or higher, the concentration of oxygen in the reaction vessel is kept at 7 volt % or lower. When additional styrene monomers are added during the polymerization, they are added and adsorbed to styrene resin particles in the course of polymerization while the concentration of oxygen is kept low. By this method, the particles whose internal portion has a low molecular weight and surface portion has a high molecular weight are obtained. A foamed article produced from the particles has high strength and a good appearance.
REFERENCES:
patent: 05-295160 (1993-11-01), None
patent: 7-188454 (1995-07-01), None
patent: 7188454 (1995-07-01), None
patent: 07-330943 (1995-12-01), None
patent: 8295756 (1996-11-01), None
Akima Toshio
Katou Tetsuya
Kunimi Makoto
Nakaguki Hiroshi
Saitou Makoto
Antonelli, Terry Stout & Kraus, LLP.
Hitachi Chemical Co. Ltd.
Zemel Irina S.
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