| 摘要 |
A compsn. for use in an aqs. environment comprises (a) a formulation contg. a water-soluble active ingredient (I), (b) a semipermeable membrane (II) surrounding the formulation and (c) particulate water-soluble pore-forming material (III) dispersed within the membrane. In use in an aqs. environment, (III) is dissolved forming pores in (II), (I) is taken up in soln. thus creating an asmotic pressure gradient across the membrane between the soln. and the aqs. environment, and water from the aqs. environment is diffused through (II) into contact with (I) concurrently while a soln. of (I) is discharged through the pores of the membrane into the aqs. environment. Pref. the formulation is in the form of a prill seed having a coating of a water-permeable polymer e.g. cellulose acetate. (II) is pref. made from a cellulose ester, a cellulose ether, nylon, a polycarbonate, a poly(dialkylsiloxane), a poly(methacrylic acid)ester, a poly(acrylic acid) ester, a poly(phenylene oxide), a poly(vinyl alcohol), an aromatic N-contg. polymer, a polymeric epoxide or regenerated cellulose (III) is e.g. a water-soluble sugar or a salt.
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