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:
Jan. 12, 2021
Filed:
Oct. 30, 2017
Shin-etsu Chemical Co., Ltd., Tokyo, JP;
SHIN-ETSU CHEMICAL CO., LTD., Tokyo, JP;
Abstract
There are provided HPMCAS (hypromellose acetate succinate) having such a property that a solution of the HPMCAS in a solvent has a controlled viscosity; and a method for producing the HPMCAS. More specifically, provided are HPMCAS having such property that a solution of 10 parts by weight of the HPMCAS in 100 parts by weight of a mixed solvent having a weight ratio of methylene chloride to methanol of 1:1 has a viscosity at 20° C. of 135 mPa·s or less; and a method for producing the HPMCAS including an esterification step of adding acetic anhydride and succinic anhydride to a solution of hypromellose in glacial acetic acid in the presence of sodium acetate to obtain a reaction product mixture, wherein the succinic anhydride is added intermittently, and a precipitation step of mixing the reaction product mixture with water to precipitate the HPMCAS.