GB739634A - Improvements in chemically modified elastomers - Google Patents

Abstract

Synthetic elastomers are dry mixed with maleic anhydride and the mixture is heated, in the absence of organic peroxide or solvent and in the presence of an inhibitor of free radical polymerization, to at least 150 DEG C., preferably while mechanically mixing and desirably in the substantial absence of oxygen. Elastomers specified are copolymers of butadiene, isoprene, piperylene and 2,3-dimethylbutadiene, with styrene, methylstyrenes, acrylonitrile, methacrylonitrile, acrylic and methacrylic acids and their alkyl esters, acrylamide, N-substituted acrylamides, vinyl pyridines, fumarate esters, methylene malonic acid esters, vinylidine chloride, methyl vinyl ketone and methyl isopropenyl ketone. The examples also include a terpolymer of isoprene, butadiene and styrene (11) and mixtures of elastomers (10). The inhibitors of which many are listed belong to the following classes: phenol derivatives, aromatic amines and their quinonoid derivatives, condensation products of aromatic amines with aldehydes or ketones, organic phosphites and phosphate esters including those specified in U.S.A. Specification 2,587,477. To obtain a product having substantially no cross-linking a mixture of inhibitors, one of which inhibits self cross-linking at 150 DEG C. (e.g. aryl phosphites), is desirably used. Ingredients which may be included before, during or after the reaction are further inhibitor; softeners such as pine tar, coal tar (Bardol) and petroleum oil; plasticizers such as polyesters (Paraflux), dinitrochlorobenzene and xylyl mercaptans; and inert fillers or pigments such as carbon black, clay, titanium dioxide, lithopone, blanc fixe and diatomaceous earth. The adducts may be cold milled to reduce their viscosity, they may be blended together and they are of equal or lower viscosity than the original elastomer and are soluble in the same solvents, e.g. benzene and methyl ethyl ketone. The adducts may be vulcanized with the oxides, hydroxides and carbonates of zinc, magnesium, calcium, barium and divalent lead and are useful as water-resistant coatings or for making composite articles of metal and rubber.