| 摘要 |
Co-polymers are formed by the polymerization of approximately equimolar amounts of a half-ester of an a , b -unsaturated carboxylic acid and a water-insoluble monomeric vinyl compound in the presence of a small amount (0,1 to 0,3 mole per mole of half ester) of acrylic and/or methacrylic acid. Polymerization may be carried out in a suitable solvent, e.g. esters, ketones, alcohols or low aliphatic hydrocarbon halides (or mixtures thereof) in the presence of a catalyst e.g. organic peroxides, hydroperoxides, azo compounds, inorganic "per" compounds such as hydrogen peroxide. Specified half-esters are those of maleic, fumaric and itaconic acids with C1-8 aliphatic alcohols. Specified vinyl compounds are styrene and its derivatives, vinyl esters, acrylic esters, methacrylic esters and vinyl chloride. An example relates to the preparation of a preferred co-polymer using butyl maleate half-ester (9,000 gms.), styrene (6,920 gms.) and anhydrous methacrylic acid (1,000 gms.) in dioxan with benzoyl peroxide (51 gms.) as catalyst at 105 DEG C. for 15 hours. Plasticizers, e.g. fatty oils, fatty acids, polyhydric alcohols, solid hydrocarbons, dioctyl phthalate, sorbitan trioleate and glyceryl monostearate may be incorporated into the polymers. The products find application as compositions with and as coatings on pharmaceutical agents.ALSO:Solid pharmaceutical preparations, e.g. tablets, pills, and granules, are granulated with or enterically coated by conventional methods, e.g. pan-coating, with a protective layer or layers of a copolymer formed by the polymerization of approximately equimolecular amounts of a half-ester of an a ,b -unsaturated dicarboxylic acid and a water-soluble monomeric vinyl compound in the presence of a small amount (0.1 to 0.3 mol. per mol. of half ester) of acrylic and/or methacrylic acid. Suitable hemi-esters are those of maleic, fumaric and itaconic acids with C1-8 aliphatic alcohols, suitable vinyl compounds are styrene and derivatives thereof, acrylic and methacrylic esters and vinyl chloride. A preferred copolymer comprises 1.1 mols. styrene, 0.1 to 0.3 mol. methacrylic acid and 1 mol. of the butyl half-ester of maleic acid. The coating material of the invention may also be dissolved in a solvent together with a solid hydrocarbon or with glyceryl monostearate or aliphatic acids of high molecular weight and the resulting solution used for coating. Plasticizers may also be incorporated, examples of those given being fatty oils, fatty acids, polyhydric alcohols, solid hydrocarbons, dioctyl phthalate, sorbitan trioleate, glyceryl monostearate. Specific medicaments mentioned are: para-aminosalicylic acid, phenyl-ethyl-barbituric acid and 7-chloro-4-(41-diethylamino-11 - methyl - butylamino) - quinoline diphosphate. |
