Method of forming sealing gaskets in container closures
AssigneeW. R. Grace & Co.
InventorGaston A. Stroud
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Abstract
Method of forming a sealing gasket made from vinyl chloride resin plastisol in container closures made of a high-melting olefin polymer, especially polypropylene. The invention employs a combination of microwave heating and controlled heating by conventional means. The controlled conventional heating raises the temperature of the closure to from 5.degree. to 35.degree. C., preferably 5.degree. to 15.degree. C., below its melting point; at this temperature microwave heating is then introduced to flux the plastisol.
Claims6
In a method of forming a sealing gasket in a container closure made of polypropylene which is substantially transparent to microwave radiation, in which one introduces into the closure a vinyl chloride resin plastisol, forms it therein into the configuration of a gasket, and heats the thus formed plastisol in the closure with the aid of microwave energy until the plastisol is completely fluxed and cools the plastisol to form the gasket, the improvement which comprises heating also the closure, so that it acquires at the time of the microwave heating a temperature of from 130.degree. to 160.degree. C.
Dependencies are inferred from the claim text.