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:
May. 08, 1990
Filed:
Mar. 26, 1987
Wilhelm E Walles, Freeland, MI (US);
Donald L Tomkinson, Auburn, MI (US);
The Dow Chemical Company, Midland, MI (US);
Abstract
A controlled release composition for use with liquid acids, and a method of preparation is disclosed. The composition comprises (1) a porous matrix comprising and substantially inert to an absorbed acid; (2) a midlayer surrounding the matrix, this midlayer consisting essentially of a salt of the absorbed acid; and (3) a membrane surrounding the matrix, the membrane being exterior of the midlayer, the membrane further being substantially inert to the midlayer and permeable to a selected environment, the thickness and permeability of the membrane comprising means for controlling diffusion of the environment therethrough. The midlayer can be applied as a coating to the acid-bearing matrix, or it can be evolved by exposing the acid-bearing matrix to a base such as ammonia gas or a solid metal oxide for a time sufficient to allow reaction of a proportion of the acid at or near the surface of the matrix with the base to form a layer of the corresponding salt.