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:
Apr. 25, 1989
Filed:
Oct. 24, 1986
Gunter Pietsch, Isernhagen, DE;
Karl-Heinz Schrader, Hanover, DE;
Abstract
A process for microencapsulating hydrophobic oils with color reactants, dissolved therein, of color reaction systems by reacting a water-soluble non-ionic melamine/formaldehyde precondensate and a water-soluble polymer in an oil-in-water dispersion for forming the capsule envelope is described. The special feature of this process is that, for stabilizing the oil-in-water dispersion, an aqueous solution of a cationic melamine/formaldehyde precondensate and the aqueous solution of a water-soluble polymer are mixed with vigorous stirring, a solid precipitating as a very fine suspension in the mixture, the mixture thus obtained and containing the very finely suspended solid is mixed with ther oil, containing the color reactant in solution, with vigorous stirring, the oil-in-water dispersion thus obtained in acidified and an aqueous solution of a water-soluble non-ionic melamine/formaldehyde precondensate is added with stirring, in order to form the capsule envelope. The use of the cationic melamine/formaldehyde precondensate leads to the precipitation of a very finely suspended reaction product thereof, whereby all the reaction systems in the course of the process are stabilized. Excellent capsules can be obtained without formation of agglomerates. The invention also relates to the microcapsules obtainable by the above process and to their advantageous use in color reaction recording systems.