Process for producing flow-in closure sealing gaskets from hot melt compositions

Claim 2

Process for producing a gasket in a closure to thereby render the closure capable of sealing a container, said process being characterized by the steps of: (a) providing a vinyl chloride free, elastomeric hot melt composition having a viscosity index less than about 40 meter-grams torque at 175° C and being capable of retaining a given shape when cooled; (b) heating the composition to cause it to flow; (c) depositing a metered amount of the flowable, heated composition from a nozzle into a closure shell; (d) shaping the composition in the closure shell to form a gasket; and (e) cooling the shaped gasket.

Claim 3

The process of claim 1 wherein the hot melt composition comprises between about 20 to about 55 percent of a thermoplastic elastomer chosen from the group consisting of: (a) triblock copolymers of the type having the general formula ABA, wherein A is a thermoplastic segment of a polymerized alkenyl aromatic compound of average molecular weight within the range of about 2,000 to about 30,000 and wherein B is an elastomeric segment of polymerized diene selected from the class consisting of conjugated diene hydrocarbon compounds formed from monomers having four to eight carbon atoms and elastomeric copolymers of ethylene with butylene, said elastomeric segment having an average molecular weight within the range of 10,000 to 200,000, the total polymerized alkenyl aromatic compound content constituting from about 15 to about 65 percent by weight of the triblock molecule; and (b) radial block copolymers of the type having a plurality of chains having the general formula BA wherein B is linked to a central hub and is an elastomeric segment of a polymerized diene selected from the class consisting of conjugated diene hydrocarbon compounds formed from monomers having four to eight carbon atoms and elastomeric copolymers of ethylene with butylene, said elastomeric segment having an average molecular weight within the range of about 10,000 to about 200,000, and A is a thermoplastic segment of a polymerized alkenyl aromatic compound of average molecular weight within the range of about 2,000 to about 30,000, the total polymerized alkenyl aromatic compound content constituting between about 20 to about 50 percent by weight of the radial block copolymer molecule.

Claim 4

The process of claim 1 wherein, in said heating step, the composition is heated to between 160° C and 210° C.

Claim 5

The process of claim 1 wherein the closure shell is heated.

Claim 6

The process of claim 1 wherein said shaping step is effected by contacting the composition in the closure shell with a die.

Claim 7

The process of claim 5 wherein the die is cooled.

Claim 8

The process of claim 1 wherein the hot melt composition comprises a blend of a polyethylene and at least one member of the class consisting of copolymers of ethylene/vinyl acetate and terpolymers of acid/ethylene/vinyl acetate.