Cured vinyl chloride resin-epoxidized linseed oil compositions as closure cap gaskets

摘要

The basic constituents for a cross-linked plastics gasket or liner composition is applied to an inner surface of a container closure cap are vinyl chloride base resin and epoxidized linseed oil having a minimum oxirane content by weight of 90% and a maximum iodine value of 5, the content by weight of vinyl chloride base resin exceeding the content of epoxidized linseed oil, and the two constituents together constituting 90% by weight of the composition. The liners may be prepared as plastisols and then flowed into the cap, or may be extruded as sheet stock with fusing of the plasticizer and polyvinyl chloride resin in the extruder, or calendering or moulding techniques may be employed. The vinyl chloride base resin may be any vinyl polymer. The linseed oil epoxidation process is accomplished with the aid of hydrogen peroxide a carrier acid such as formic acid and a catalyst such as sulfuric acid. A lubricant selected from the group comprising fatty acids, petroleum waxes, and silicone oils is normally included and fillers or pigments are optional ingredients. The composition may contain 100 parts by weight of the vinyl chloride base resin for every 50-90 parts of epoxidized linseed oil for every 1-5 parts of filler or pigment for every 1-7 parts of lubricant. Specification 844,400 is referred to.