T h e discovery that polyamines were effective reducers for the hydroperoxide initiator system of cold rubber prompted a further study in the preparation of butadienestyrene copolymers and an attempt to apply them to the preparation of butadiene-acrylonitrile copolymers.In the preparation of butadiene-styrene copolymers a mixture of polyamines composed of 80% diethylenetriamine and 20% tetraethylenepentamine was found best for uniform rates of conversion. The rate of conversion could be adjusted by adding ferrous iron or an iron complexing agent. Similar amines were found to be ineffective activators in the copolymerization of butadiene and acrylonitrile. The reason appeared to be the cyanoethylation of the amines with loss of reducing power. This was prevented or slowed by the addition of digested D-glucose or other source of enediol to the amine solution, whereby a reducer was formed which was not destroyed by reaction with acrylonitrile. Such hydroperoxide-reducer systems are suitable for commercial use. The advantages appear to be ease of preparation of the activator, reduced sensitivity to oxygen, preparation of synthetic rubbers in the virtual absence of iron salts, and, for butadiene-styrene copolymers, preparation in the abssnce of the sugar which tends to ferment in the latex on standing.HE use of peroxy compounds and reducers as initiator sys-T tems for free radical polymerization reactions has been studied extensively for many yeam The use of amines as reducers has also received considerable study. One aspect of the work ( 8 ) is that in which a water-soluble amine is used with a water-soluble peroxy compound in emulsion polymerization, or an oil-soluble amine is used with an oil-soluble peroxy compound in bulk polymerization. Several papers have appeared describing amines as activators in redox polymerizations of butadiene and styrene of the type in which a water-soluble reducer is used in combination with an oil-soluble peroxy compound and usually with a heavy metal carrier such rm ferrous iron. (Ethylenedinitri1o)tetraacetic acid and other chelate-forming organic nitrogen compounds (19) were effective reducers (activatnrs) in the preAence of digested wglucose and ferrous sulfate. The ferrous sulfate could be reduced in quantity or eliminated entirely with practical rates of Conversion being achieved.A significant advance waa made by Whitby el al. (21) who observed that polyethylene polyamines were effective activators without digested -glucose or ferrous sulfate. The present authors (80) enlarged this study and indicated that ferrous sulfate and digested wglucose could play important roles in the activation of a commercial recipe using polyamines. Such recipes have been used by others (6, 19). Under optimal conditions the activators are simple to prepare, the solution need not be handled with exclusion of oxygen, and the resulting recipe appears to be less sensitive to oxygen contamination (6, 19, 21). The chief disadvantage appears to be extreme sensitivity to iron contamination; this effect can be...
The copolymerization of b~rtadiene and acrylonitrile is very similar to the copolymerization of butadiene and styrene. Polymers predominantly butadiene may be studied by conventional solution techniques but the study of polymers rich in acrylonitrile requires improved solvents for these materials. Polymerization rates are greatest for monomer ratios approximating equal proportions. The mercaptan modilier disappears much more slowly than in the b~~tadiene-styrene system, the regulating index approximating unity. The n~unber average molecular weights calculated from the mercaptan disappearance curves indicate uniform polymer molecular weights to relatively high conversions after which there is a decrease. T h e viscosity data indicate a rise in viscosity \vith conversion, which elfect is overcome for charges rich in acrylonitrile by the lessening of branching, the more rapid disappearance of mcrcaptan a t high conversion, and the tendency of polymers containing over 50% acrylonitrile to show very low dilute s o l~~t i o n viscosities in the solvents tested. Viscosity molecular weights have been calculated and estimates of the molecular weight tlistributjon made. These distributions appear to be quite narrow and the ~~s u a l broaden~ng a t higher conversions is prevented by tlre increased nrodiher consun~ption and increased vinyl content of the poly~ner prepared with 50 parts acrylonitrile in the charge. The bountl acrylonitrile has been determined a t various conversions and the reactivity ratios have been found to be r, = 0 . 2 s and r2 = 0.02 for emulsions and rl = 0. 18 and r? = 0.03 for oil phase portion only. Q is 0.74 and e is 1.17 as calculated by the Alfrey-Price equations.
ability of heavy metals such as copper, manganese, and iron to catalyze the breakdown of natural rubber during storage and processing is well known (ß, 8). Use is made of this effect in certain peptizing agents like ferrous naphthenate and in rubber reclaiming agents (6). In the early days of the "cold rubber" development it was feared that the ferrous pyrophosphate, present as an activator for peroxide-catalyzed polymerization recipes, would have a deleterious effect on the aging of these polymers. Synthetic polymers were proved, however, to be more resistant to degradation during aging (4, 7), and production has been successful for almost 7 years.These polymer types, when produced to high viscosity and extended with oil, are much more susceptible to raw polymer breakdown during processing in the copolymer plant and in storage than the normal unextended cold rubbers (9). This undesirable degradation has occurred mainly where relatively highiron, sugar-free recipes are used for the polymerization of the parent polymer. When the polymerization recipe is a sulfoxylateactivated type of very low iron content, deterioration of Sundex 53-extended product during drying and subsequent storage, for as long as 12 months, is negligible. The effect of heavy metals, especially iron, in promoting the breakdown of polymer-oil masterbatches was studied in the pilot plant. EXPERIMENTAL of latex solids. This masterbatch was heated to 100°to 120°F. and stirred continuously during the coagulation process. For several experiments, ferrous sulfate heptahydrate and/or complexing agents were added to the latex before masterbatching.Coagulation was effected at 110°F. by adding the oil-latex masterbatch with agitation to 4% sodium chloride serum at pH 5 to 6. The pH was maintained at 5 to 6 during the coagulation by the addition of 0.5% sulfuric acid. After the precipitation was essentially completed, the pH of the slurry was reduced to 4.0 by the addition of more acid, and leaching was continued for 30 minutes at, 100°to 110°F. for soap conversion. Various metal salts were added to the dilute coagulating acid to determine their relative effects on the heat softening of the crumb during the drying cycle. After the leaching, the serum was decanted, replaced with water at 100°to 110°F ., and stirred for 20 to 30 minutes. The water was then decanted and the washing repeated, using fresh water. Finally, the crumb was spread on a tray and loaded into a circulating air oven dryer. LITERATURE CITED
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