Process for manufacturing polysiloxane microcapsules that are functionalized and are not very porous

摘要

A method is provided for encapsulating products that can have lipophilic or hydrophilic, including volatile, properties in a polysiloxane membrane that is particularly impervious. A method is also provided for evaluating the imperviousness of capsules. The present method includes the following steps:
a) formation of droplets by an emulsion between an oily phase containing the product to be encapsulated and an acidic aqueous phase heated to around 50° C. and in the presence of surfactants;b) addition and hydrolysis of at least one silane in order to obtain a silanol;c) increasing the pH in order to start condensation of the silanol to form a first membrane around the droplets of the product to be encapsulated;d) lowering the pH;e) increasing the pH, optionally preceded by adding a silane, in order to obtain a new condensation of silanol around the droplets of the product to be encapsulated.

主权项

1. A method for encapsulating one or more products that can have lipophilic or hydrophilic properties in a polysiloxane double membrane, the method consisting of the following steps:
a) forming droplets by an emulsion between an oily phase containing the product to be encapsulated and an acidic aqueous phase heated between 40° C. and 70° C., at pH between 2.5 and 4.5, and in the presence of surfactants; b) adding and hydrolyzing at least one silane in order to obtain a silanol; c) increasing the pH from 2 to 3 up to a value in the range from 4.5 to 6 by adding at least one base in order to start condensation of the silanol to form a first membrane around the droplets of the product to be encapsulated; d) lowering the pH to a value in the range from 2.5 to 4.5 by adding one or more weak acids to stop the condensation; e) adding and hydrolyzing at least one other silane which can be different from or the same as the silane or silanes added during step b); f) increasing the pH up to a value in the range from 4.5 to 7 by adding at least one base in order to obtain new or better condensation of the silanol to form a second membrane around the droplets of the product to be encapsulated, the condensation being carried out between the silanol groups still present of the first membrane and those of the silane of step e), resulting in the formation of a second membrane around the droplets of the product to be encapsulated.