Interpolymer cures of blends comprising halogenated isoolefin/para-alkylstyrene elastomers and unsaturated elastomers

Claim 1

A vulcanizable, partially cured compatibilized elastomeric composition, the composition exhibiting a maximum rheometer torque increase ratio in accordance with the formula; ΔM a+b /(ΔM a f a +ΔM b f b ) of greater than 1.25, wherein: ΔM a+b =the torque increase observed for the blend of polymer (a) and polymer (b); ΔM a =the torque increase observed for polymer (a) on its own; f a =the weight fraction of polymer (a) in the blend; ΔM b =the torque increase observed for polymer (b) on its own; and f a =the weight fraction of polymer (b) in the blend; produced by mixing: a) a halogenated random copolymer having a number average molecular weight of at least 10,000 comprising at least about 80 weight % of polymerized isomonoolefin containing from 4 to 7 carbon atoms and from about 0.05 up to about 20 mole % of aromatic monomer units comprising a mixture of the following structures randomly distributed therein: ##STR2## wherein R and R' are independently selected from the group consisting of hydrogen and C 1 to C 4 alkyl and X is bromine or chlorine; b) polybutadiene or copolymers of butadiene with styrene or acryonitrile; and c) from about 0.05 to less than 3 parts by weight per 100 parts by weight of the polymer content of the mixture of a curing agent comprising a hydrocarbon soluble compound selected from the group consisting of one or a mixture of aluminum, iron, tin and zinc compounds of a carboxylic acid selected from the group consisting of naphthenic, salicylic and C 10 to C 28 fatty acids; wherein said mixing is performed at a temperature of from about 80° C. to about 150° C. and the weight ratio of said random copolymer and unsaturated polymer present prior to mixing being within the range of about 1:99 to 99:1, said rheometer torque is measured using an oscillating disc rheometer, cure time 60 minutes at 160° C. and 3° arc.