| 摘要 |
1,205,765. Preparation of hydrophilic polymers. NATIONAL PATENT DEVELOPMENT CORP. 26 July, 1967 [5 July, 1967], No. 3696/70. Divided out of 1,205,764. Heading C3P. [Also in Division A5] Hydrophilic polymers in the form of finely divided spheres or beads are prepared by rapidly agitating a water-soluble polymerizable monoester of an olefinically unsaturated carboxylic acid having at least one hydrophilic functional group in the alcohol moiety of the monoester in a non-polar liquid suspending medium in which the monoester and the polymer formed are insoluble, the agitating being effected in the presence of an amount of a free radical vinyl polymerization catalyst sufficient to polymerize the monoester. Suitable suspending media include silicone oils, and paraffinic and/or aromatic hydrocarbons, e.g. mineral oils and xylene. Polymerization can be effected in the presence of a minor amount (relative to the monoester) of a cross-linking monomer. Also, the polymers obtained can be mixed with further monoester, and catalyst and with cross-linking monomer to form a casting composition which can be cured to form shaped articles. The monoester is preferably a hydroxyalkyl acrylate or methacrylate, e.g. a hydroxypropyl or 2- hydroxyethyl (meth)acrylate; and the optional diester is suitably a diacrylate or dimethacrylate, e.g. a dimethacrylate of ethylene glycol, 1,3 - butylene glycol or 1,4 - butylene glycol. Polymerization catalysts specified are isopropyl percarbonate, t-butyl peroctoate, cumene hydroperoxide and benzoyl peroxide. The polymer beads can be used to form shaped articles, e.g. by injection moulding, extrusion or calendering. The polymers can also be adhered to metal, glass, rubber, plastics and other surfaces, and can be formed and ground into toric contact lenses. When used in dental applications, an amine polymerization accelerator can be included in the casting syrup. The hydrophilic polymers formed are also useful in body implant applications and in medicinal, flavouring and fragrance compositions. Other uses include cigarette filter elements or tips, filter media, chromatographic filters, thickening agents in foods, bandages and dressings, nutrient carriers, and light-transmitting coatings. |
