| abstract |
1,236,885. Multi-wall capsules. FUJI PHOTO FILM CO. Ltd. 26 Sept., 1969 [28 Sept., 1968], No. 47476/69. Heading B8C. Multi-wall capsules, each consisting of one or more single-wall capsules enclosed within one or more further polymeric walls are prepared by dispersing single wall capsules in an aqueous solution of a water-soluble, film-forming, high molecular weight material having hydroxyl, acid or basic groups, and adding portions (e.g. drops, or extruded portions) of the dispersion to an aqueous solution of a hardener for the said high molecular weight material. If desired, the procedure may be repeated to give capsules having 3 or more wall layers. Specified high M.W. materials (together with the appropriate hardener) are: sodium alginate (Ca<SP>++</SP>, Al<SP>+++</SP>, acid); carageenin (Ca<SP>++</SP>); dextran (Ca<SP>++</SP>, Ba<SP>++</SP>); carboxy methyl-cellulose and -starch (Al<SP>++</SP><SP>+</SP>, Fe<SP>++</SP><SP>+</SP>, Cu<SP>+</SP> <SP>+</SP>); collagen (alkali), polyvinyl alcohol (borax) ; polyvinyl methyl ether/ maleic anhydride copolymer; agar (tannic acid with cooling); milk casein (Ca<SP>++</SP>, acid); chitosan oxalate (alkali) and glucomannan (Ca<SP>++</SP>, alkali). |