Tire curing bladder with improved release characteristics
First Claim
1. In a curing press for a rubber composition of the type which uses an expandable bladder to assist in shaping and curing said rubber composition wherein the bladder is a molded crosslinked formulation includingone or more rubbery polymers, wherein at least 50 weight percent of said rubbery polymers of said bladder are at least one isobutylene rubbery polymer having at least 80 weight percent repeat units from isobutylene;
- one or more curatives for said one or more rubbery polymers;
the improvement wherein the bladder further comprises from about 1 to about 20 parts by weight of corn oil dispersed throughout said bladder formulation and wherein said corn oil reduces the Hot Peel Adhesion value of the crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil;
at least 10 weight percent of said at least one isobutylene rubbery polymer is one or more copolymers of isobutylene and a para-alkylstyrene; and
wherein said parts by weight are based on 100 parts by weight of the rubbery polymers in said bladder formulation.
1 Assignment
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Accused Products
Abstract
Disclosed are expandable bladders for use in curing presses for rubber compositions such as pneumatic tires. The bladders are a crosslinked elastomer comprising an isobutylene rubbery polymer. The bladder composition includes corn oil which improves the release characteristics of the cured bladder from a tire innerliner cured in contact with said bladder. The improved release characteristics have been observed to allow rubber compositions such as tires to be molded with fewer defects caused during release of the bladder from the tires or caused by abraded or deformed bladders. The use of corn oil also has been observed to increase the useful life time of the bladder allowing more tires to be cured without changing bladders. A preferred isobutylene rubbery polymer is a brominated copolymer of isobutylene and p-methylstyrene. The bladder compositions have also been observed to have an enhanced flexibility due to the corn oil.
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Citations
20 Claims
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1. In a curing press for a rubber composition of the type which uses an expandable bladder to assist in shaping and curing said rubber composition wherein the bladder is a molded crosslinked formulation including
one or more rubbery polymers, wherein at least 50 weight percent of said rubbery polymers of said bladder are at least one isobutylene rubbery polymer having at least 80 weight percent repeat units from isobutylene; -
one or more curatives for said one or more rubbery polymers; the improvement wherein the bladder further comprises from about 1 to about 20 parts by weight of corn oil dispersed throughout said bladder formulation and wherein said corn oil reduces the Hot Peel Adhesion value of the crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil; at least 10 weight percent of said at least one isobutylene rubbery polymer is one or more copolymers of isobutylene and a para-alkylstyrene; and wherein said parts by weight are based on 100 parts by weight of the rubbery polymers in said bladder formulation. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An expandable curing bladder being the molded crosslinkstar from a formulation comprising:
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one or more rubbery polymers, wherein at least 50 weight percent of said rubbery polymers are at least one isobutylene rubbery polymer having at least 80 weight percent units from isobutylene; wherein at least 10 weight percent of said at least one isobutylene rubber polymer is one or more copolymers of isobutylene and para-alkylstyrene; from about 1 to about 20 phr of corn oil dispersed throughout said bladder and wherein said corn oil reduces the Hot Peel Adhesian value of said crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil; and one or more curatives for said rubbery polymers; wherein phr is parts by weight based upon 100 parts by weight of said one or more rubbery polymers in said bladder. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of using an expandable rubber bladder to cure an uncured rubber composition, said method comprising the sequential steps of:
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first inserting an uncured rubber composition into a curing press having an expandable rubber bladder positioned therein and having one or more molding surfaces; second expanding said expandable rubber bladder by filling the internal portion of said bladder with a fluid to expand the bladder outwardly against an inner surface of the uncured rubber composition to force said uncured rubber composition against said one or more molding surfaces and curing the rubber composition into a cured article under conditions of heat and pressure; and third deflating said expandable rubber bladder and removing the cured article from said curing press, the improvement wherein the expandable bladder is a molded and crosslinked rubber formulation wherein said rubber formulation comprises; one or more rubbery polymers, at least 50 weight percent of said rubbery polymers being at least one rubbery isobutylene polymer having at least 80 weight percent repeat units from isobutylene, and wherein at least 10 weight percent of said at least one isobutylene rubbery polymer is one or more copolymers of isobutylene and para-alkylstyrene; and from about 1.0 to about 20 parts by weight of corn oil dispersed throughout said bladder and wherein said corn oil reduces the Hot Peel Adhesion value of said crosslinked bladder formulation at least 10 percent as compared to the same bladder formulation without said corn oil; wherein said parts by weight are based upon 100 parts by weight of said one or more rubbery polymers in said bladder. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification