It has been shown that dual functional compounds bearing antioxidant and polymerizable functions can be copolymerized with numerous monomers in emulsion systems. Somewhat higher initiator levels and/or increased temperature appear to be required for normal polymerization rates in the presence of these monomers. The only incompatible initiator—monomer combinations found are those of persulfate and benzoyl peroxide with amine antioxidants. The dual functional monomers retain their normal antioxidant characteristics in the copolymerized form and are not removed by solvent extraction nor volatilization except under conditions that destroy the polymer. The amine antioxidants, in the copolymerized state, cause comparatively little discoloration on aging and cause no migratory stain while providing antioxidant protection equivalent to high-quality, conventional amine antioxidants.

No abstract

A versatile family of elastomers has been prepared by free radical addition of aliphatic mercaptans to the double bonds of diene polymers. High saturation levels were readily achieved without degradation of the basic polymer chain. The technology is similar to ordinary emulsion polymerization. By varying the nature of the base polymer, the mercaptan used, and the extent of saturation, a wide range of compositions and of physical properties were attained in the adducts. In general, resistance to aging, ozone attack, heat, solvent swelling, and to permeation by gases increased with increasing extent of saturation. Outstanding performance in these qualities was achieved by adducts of polymers whose double bonds had been over 90 per cent saturated. A highly saturated methyl mercaptan adduct of polybutadiene showed (1) stress-strain and air aging properties at 400° and 500° F better than commercially available ethylacrylate copolymers and various semicommercial heat resistant elastomers; (2) permeability resistance equivalent to butyl; (3) solvent swell intermediate between neoprene and medium nitrile content butadiene-acrylonitrile rubbers, with a Tg below −30° C; (4) ozone resistance comparable to the better commercially available saturated rubbers. Increased solvent resistance was obtained by preparing adducts of the appropriate butadiene-acrylonitrile copolymers. Adducts with saturation levels up to about 85 per cent could be cured by the same procedures used for the base polymers. Activated or butyl-type curing systems were required for higher saturation levels. The relative rates at which aliphatic mercaptans add to the several types of double bonds present in emulsion diene polymers have been examined in a preliminary way.

In view of the failure to obtain quantitative yields of the expected carboxylic acids by permanganate oxidation of the several butadiene polymers studied, definite conclusions about their structures cannot be made. The results have a qualitative significance, however, in that the −10° emulsion polymer was found to produce a larger amount of succinic acid than the 50° emulsion polymer and less tricarballylic acid, and thus they correlate with general thinking that lowered temperature of polymerization results in a polymer of more regular structure and less branching. The Alfin polymer, although prepared in a system entirely different from the emulsion system, gave results which indicated a microstructure similar to that of 50° emulsion polybutadiene. Sodium polybutadiene was less completely characterized than the others, but the large amounts of carbon dioxide and β-carboxyadipic acid isolated correlated well with the high percentage of external double bonds known to be present from other methods of analysis.

Natural rubber was the subject of intensive investigation with respect to its chemical reactions and the preparation of commercially useful derivatives. General reviews in this field have been written by Fisher, Schidrowitz, Jones, Sibley, Memmler, Dawson and Schidrowitz, and Farmer. Before World War II several of these reaction products, such as rubber hydrochloride (Pliofilm), isomerized rubber (Pliolite), and chlorinated rubber (Parlon), had been marketed successfully. During the past five years drastic restriction of the commercial use of natural rubber for chemical derivatives prompted the study of synthetic rubbers for this purpose. Endres recently reported on chlorinated and cyclized synthetic lubbers, with special emphasis on GR-S as the starting material. This paper deals particularly with derivatives of polyisoprene and other isoprene-containing synthetic rubbers which behave chemically very much like natural rubber because of the similarity in structure. It is shown that GR-S and other butadiene-containing synthetic rubbers, under the same conditions, are either nonreactive or behave differently. Because of its similarity to the natural rubber product, isomerized synthetic polyisoprene has been designated Pliolite S-1. Chlorinated synthetic polyisoprene is referred to as Pliochlor.