Composite materials comprising water-soluble glass particles

Claim 1

A coherent composite structure releasably incorporating an active material therein, said composite structure comprising a polymeric matrix material and a particulate glass composition dispersed in said matrix material, said polymeric matrix material being essentially insoluble in aqueous medium and said particulate glass composition being soluble at a controlled dissolution rate in said aqueous medium whereby said composite structure shields said active material from release until contacted by said aqueous medium and when said composite structure is contacted by said aqueous medium, said particulate glass composition dissolves at a controlled rate thereby increasing the aqueous permeability of said composite structure to release said active material incorporated therein at a controlled rate, said particulate glass composition consisting essentially of from 50-75 mole percent of phosphorus pentoxide as a glass forming oxide; from 1-20 mole percent of an alkali metal oxide as the principal glass modifier, the remainder including from 1-25 mole percent of an oxide selected from the group consisting of an alkaline earth metal oxide, an oxide of a metal of Group III A of the Periodic Table, a transition metal oxide and combinations of the foregoing.