| 摘要 |
A gellable hydrophilic colloid material is caused to form around oil droplets by coacervation and is then gelled to form microscopic oil-containing capsules. The coacervation may be brought about by addition of a salt solution or by mixing two sols having different ionic charges followed by dilution or adjustment of the pH until coacervation occurs. Suitable colloid materials are gelatin, albumen, alginates, casein, agar-agar, starch, pectins, carboxymethylcellulose, Irish moss and gum arabic. Sodium or ammonium sulphate may be used to coacervate gelatin, or gelatin and gum arabic sols may be mixed to provide a complex coacervate. The oil may be emulsified in the colloid, or in either colloid in the case of complex coacervation. Specified oils include mineral oils, fish oils such as halibut liver oil, vegetable oils such as cotton seed oil, corn oil, castor oil and coconut oil, essential oils and synthetic oils such as methyl salicylate and chlorinated diphenyl. The oil may contain additives such as dyes used in making inks, medicines, perfumes, oil-soluble vitamins and adhesives. The gelled coacervate may be used to coat paper to form a transfer film, the oil containing a marking ink or a reactive material such as trichlorodiphenyl containing crystal violet lactone. On bringing such paper into contact with paper coated with attapulgite and rupturing the capsules with a stylus or other instrument a dark blue impression is formed. Detailed descriptions of methods of producing coacervation are given. |
