Patent GB-922833-A (GB)
Title: Method of producing gaskets for container closures
IPC: B29C43/00
Filed: 1961-02-01
Abstract: A gasket for a container closure is formed by applying to the closure a rubber latex composition having air finely dispersed therein so that it dries to an open cellular composition and thereafter applying pressure thereto to compress it to shape.  The rubber latex composition comprises natural or synthetic rubber mixed with an ammoniacal soap and finely divided filler materials such as iron oxide and barytes, which filler material introduces air in a finely dispersed state.  The composition is applied through a nozzle to the closures, e.g. metal caps for bottles, which are heated to a temperature between 250 DEG  and 400 DEG F., e.g. 380 DEG F., for one minute which converts the composition to a cellular mass.  The caps are passed under a die where pressure is applied to the gasket material.  The synthetic rubber materials may be latices or water dispersions of butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, butadiene-styrene-acrylonitrile terpolymers, neoprene, polysulphide rubber and butyl rubber.  In an example to a mixture of 50 parts of oleic acid, 50 parts paraffin, 100 parts water and 20 parts of 28% ammonia was added 15 parts iron oxide and 2000 parts barytes.  600 parts of a 60% concentrated natural rubber latex followed by 300 parts of talc were then added and stirred in and then 14% bentonite and 5% gum karaya solutions were added.  To avoid pre-curing, a curing compound of 3 parts sulphur, 3 parts butyl zimate, 10 parts zinc oxide and 16 parts water was added immediately before use.  The resulting composition was applied to metal cups which were placed in an oven at 380 DEG F. for one minute, which converted the composition to a cellular mass which was subsequently compressed in a die.  Specification 665,773 is referred to.ALSO:A gasket for a container closure is formed by applying to the closure a rubber latex composition having air finely dispersed therein so that it dries to an open cellular composition and thereafter applying pressure thereto to compress it to shape.  The rubber latex composition comprises natural or synthetic rubber mixed with an ammoniacal soap and finely divided filler materials such as iron oxide and barytes, which filler material introduces air in a finely dispersed state.  The composition is applied through a nozzle to the closures, e.g. metal caps for bottles, which are heated to a temperature between 250 DEG F. and 400 DEG F., e.g. 380 DEG F., for 1 minute to convert the composition to a cellular mass.  The caps are then passed under a die when pressure is applied to the gasket material.  The synthetic rubber materials may be latices or water dispersions of butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, butadiene-styrene-acrylonitrile terpolymers, neoprene, polysulphide rubber and butyl rubber.  In an example, to a mixture of 50 parts oleic acid, 50 parts paraffin, 100 parts water and 20 parts of 28% ammonia was added 15 parts iron oxide and 2000 parts barytes. 600 parts of a 60% concentrated natural rubber latex followed by 300 parts talc were then added and stirred in and then 14% bentonite and 5% gum keraya solutions were added.  To avoid pre-curing, a curing compound of 3 parts sulphur, 3 parts butyl zimate, 10 parts zinc oxide and 16 parts water was added immediately before use.  The resulting composition was applied to metal caps which were placed in an oven at 380 DEG F. for one minute, which converted the composition to a cellular mass which was subsequently compressed in a die. Specification 665,773 is referred to.