| 摘要 |
1. A process for producing a solid, microencapsulated product which comprises (a) preparing a film-forming aqueous medium comprising a film-forming polymer and an aqueous suspension of a microencapsulated material, (b) casting the aqueous medium thus formed onto a substrate and (c) drying the cast medium to form a cast of the film-forming polymer containing the microencapsulated material. 2. A process according to claim 1 wherein the film-forming polymer is polyvinylpyrrolidone, polyvinyl alcohol, partially hydrolysed polyvinyl acetate, a polyvinylpyrrolidone/vinyl acetate copolymer, polyethylene oxide, ethylene/maleic anhydride copolymer, methyl vinyl ether/maleic anhydride copolymer, water-soluble cellulose, water-soluble polyamide or polyesters, a copolymers or homopolymers of acrylic acid, starch, a natural gum or a protein or a mixture of two or more thereof. 3. A process according to claim 2 wherein the film-forming polymer comprises a polyvinylpyrollidone having a molecular weight in the range from 30,000 to 360,000. 4. A method according to any one of preceding claims wherein the film-forming polymer mixture comprises a mixture of a polyvinylpyrollidone of molecular weight from 40,000 to 80,000 and a polyvinylpyrollidone of molecular weight from 8,000 to 30,000. 5. A method according to any of claims 1-3 wherein the film-forming polymer comprises a polyvinylpyrollidone of molecular weight from 40,000 to 50,000 and carboxymethylcellulose. 6. A method according to any one of preceding claims wherein the concentration of the film-forming polymer in the film-forming aqueous medium is from 5 to 50% by weight. 7. A method according to any one of preceding claims wherein a plasticiser is present in the film-forming medium. 8. A method according to any one of preceding claims wherein a surfactant, a viscosity aid, an anti-foam or an inert filler is present in the film-forming medium. 9. A method according to any one of preceding claims wherein the cast medium is dried at a temperature of from 40 C to 60 C. 10. A method according to any one of preceding claims wherein the surface of the cast product is protected by lamination or co-casting with a layer of water-soluble polymer which contains no microencapsulated product. 11. A solid microencapsulated product prepared by a process according to any one of preceding claims. |
