The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 29, 2003
Filed:
Feb. 23, 2000
Makoto Ooura, Hasaki-machi, JP;
Tadashi Amano, Kamisu-machi, JP;
Shin-Etsu Chemical Co., Ltd., Tokyo, JP;
Abstract
A process for producing a vinyl chloride polymer, the process including the steps of charging into a polymerization vessel, vinyl chloride or a monomer mixture containing vinyl chloride, water, and other materials necessary for polymerization, and polymerizing in an aqueous medium the vinyl chloride or the monomer mixture. An antioxidant is added to a mixture of materials before polymerization, or to a polymerization reaction mixture during polymerization or after polymerization. The antioxidant is added in the state of an aqueous dispersion and by means of a uniaxial eccentric screw pump. The aqueous antioxidant dispersion can be added at a constant rate and stably, without causing any block-up of the interior of the pump even when the polymerization vessel is held at a high internal pressure. Hence, vinyl chloride polymers having less uneven plasticizer absorption and having good anti-initial discoloration properties and thermal stability can be produced stably.