| 摘要 |
<p>Microcapsules, having a nucleus of liquid, water-immiscible material which is or which carries a first of two chemical reactants which react upon contact, the nucleous being retained by a rupturable wall of hydrophilic, film-forming polymer material which is coated on the outside with the second reactant which is a water-soluble particulate solid, are prepared by forming an emulsion of the nucleous material in an aqueous sol of one or more film-forming, hydrophilic polymers which are caused to coacervate, e.g. by lowering the pH of the system) and to deposit around and enclose the droplets of nucleous material, the polymer material then being gelled and the particulate solid coated thereupon and the capsule hardened, e.g. by treatment with glutaraldehyde solution. In a modification of the process, the conditions are adjusted so that initially single capsules are formed which subsequently form "clumps" which are coated by more polymer material to give single units which may be coated with the second reactant as described above. Preferably, the capsules have an inner wall of ethyl cellulose between the nucleous and polymer wall this being obtained by dissolving ethyl cellulose in the liquid of the nucleous whereby a film of this material forms around each droplet when it comes into contact with the aqueous polymer sol. The capsules find application in the manufacture record material sheets (see Group VIII). Specification 896,458 is referred to.</p> |
