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:
Feb. 18, 1992
Filed:
Sep. 25, 1989
Shin-Etsu Chemical Co., Ltd., Tokyo, JP;
Abstract
A highly heat-resistant and thermally stable polyvinyl chloride resin can be prepared by copolymerizing vinyl chloride monomer and an N-substituted maleimide compound without decreasing the ingerently excellent properties of polyvinyl chloride resins when the monomer mixture is suspension-copolymerized in an aqueous medium containing a suspending agent which is a combination of three different polymers including: (a) a first partially saponified polyvinyl alcohol having an average degree of polymerization in the range from 700 to 3000 and a degree of saponification in the range from 70 to 95%; (b) a second partially saponified polyvinyl alcohol having an average degree of polymerization in the range from 300 to 600 and a degree of saponification in the range from 35 to 55%; and (c) a water-soluble cellulose derivative of which a 0.2% by weight aqueous solution has a surface tension not exceeding 55 dyn/cm at 25.degree. C., in a specified proportion.