Novel urethane reaction products of aromatic nitroso compounds with isocyanates are used to improve the resistance of unsaturated rubbers to oxidative degradation by providing antioxidant groups bound to the rubber molecules. Dry rubber or rubber latex is conveniently reacted with decomposition products of the urethane during normal vulcanization.
A system for cross-linking, curing, or "vulcanizing" elastomers containing a moderate to high degree of olefinic unsaturation is described which employs synergistic mixtures of known urethane and maleimide cross-linking agents in conjunction with a known accelerator for the urethane component. The proportion of maleimide to urethane cross-linking agent in the curing composition may range from about 4:1 to about 0.1:5 and is preferably about 3:2 to about 1:4 parts by weight. The curing compositions are employed at curing temperatures known to the art, i.e., in the range from about 250.degree. to 400.degree.F; the amount of the curing composition containing the mixed urethane-maleimide cross-linking agents required to obtain a given density of cure being less than the amount of cross-linking agent required if either a urethane or maleimide cross-linking agent is employed alone. Vulcanizates having good processing safety, high reversion resistance, low compression set, excellent dynamic properties and resistance to thermal and oxidative degradation on aging are obtained.
An aqueous binder dispersion for use in the production of composite bodies by vulcanizing a vulcanizable rubber composition on a substrate which is stable under vulcanization conditions comprising water and at least one emulsifier and a solids content of from 20% to 50% by weight of a solids composition of, (a) per 1000 parts by weight of a polymer selected from the group consisting of polyvinylidene chloride, vinylidene chloride/alkyl acrylate copolymers, butadiene/acrylonitrile copolymers and mixtures thereof, (b) from 100 to 500 parts by weight of at least one aromatic poly-C-nitroso compound, (c) from 50 to 300 parts by weight of masked polyfunctional isocyanates, (d) from 20 to 100 parts by weight of a water-soluble polymer selected from the group consisting of polyvinyl pyrrolidone and water-soluble copolymers of vinyl pyrrolidone, and (e) from 5 to 500 parts by weight of customary fillers and pigments, adhesion-improving resins based on formaldehyde condensation products, adhesion-improving condensation products based on epichlorohydrin condensation products; emulsifiers and antifoam agents; as well as the method of bonding rubbers to solid substrates employing said aqueous binder dispersion.
A process for the cross-linking or chain extension of hycrocarbon polymers which contain ethylenically unsaturated groups which comprises forming an intimate mixture of the polymer with a carbamate of the formula: ##STR1## WHEREIN R.sub.1 is an optionally substituted hydrocarbyl radical, m is an integer, and A is H or an optionally substituted hydrocarbyl radical of valency m, and subjecting the mixture to heat. Novel compounds of preferred use include those in which m=1 and at least one of R and A is alkyl or 7 or more carbon atoms, or in which m=2 and A is phenylene or alkylene or alkenylene of 2 to 4 carbon atoms.
Vulcanizable compositions contain in admixture a synthetic high molecular weight polymer and a compatible low molecular weight polymer containing a multiplicity of antioxidant functional groups chemically bound to the polymer. Vulcanizates derived from these compositions have improved aging characteristics.
It now has been found that uncured modified rubber compositions comprising mixtures of elastomers and a reinforcing filler can be prepared having improved properties. More particularly, such uncured modified rubber compositions can be prepared by a process which comprises the steps of (A) preparing a first mixture comprising an elastomer, at least one reinforcing filler and at least one chemical agent capable of promoting the formation of filler-elastomer linkages; (B) preparing a second mixture comprising (i) an elastomer, at least one reinforcing filler and at least one chemical agent capable of promoting the formation of filler-elastomer linkages, wherein at least one of the elastomer, filler or chemical agent in the second mixture is different from the elastomer, filler or chemical agent in the first mixture; or (ii) an elastomer and at least one reinforcing filler; or (iii) at least one reinforcing filler and at least one chemical agent capable of promoting the formation of filler-elastomer linkages; or (iv) an elastomer and at least one chemical agent capable of promoting the formation of filler-elastomer linkages; and (C) blending the first and second mixtures to form a third mixture. Examples of such useful chemical agents include aromatic furazan oxides, heterocyclic di-N-oxides, 1-hydroxy-benzimidazole-3-oxide compounds, 1,3-dihydroxy-benzimidazolinone compounds, and aromatic nitroso compounds. The invention also includes filled vulcanizates prepared by vulcanizing the uncured modified rubber compositions prepared in accordance with the above method. Rubber articles and portions thereof made from such vulcanizates such as tires, hoses, belts, treads, sidewalls and the like are also within the scope of the present invention as well as methods of reducing the rolling resistance of tires.
