Styrene-butadiene cold latex

The polymerization process parallels the emulsion process used for styrene-butadiene rubber. Either a hot or a cold process can be used, with the cold polymerization providing the same improved processing and vulcanizate properties as seen in SBR. Polymerizations are carried to 70-80 percent conversion and terminated to avoid gel formation. The latex must be stripped to remove unreacted butadiene and acrylonitrile. 

Table 7. Resins Recommended for use with Styrene-Butadiene Latexes - Hot, Cold or Carboxylated (2)...

Adhesives have long represented a market, albeit relatively small, for styrene-butadiene rubbers. The original commercial SBR was used successfully in this application and today all of the SBRs, solution types as well as hot and cold emulsion types, are used in a variety of adhesive compositions. They are used by adhesive formulators as latexes or as solid rubbers. 

The most successful method developed for the production of a general-purpose synthetic rubber was the emulsion copolymerization of butadiene and styrene (SBR), which still represents the main process in use today [54,64-69]. The general principles of copolymerization will be discussed in a later section, but it is instructive at this point to examine the other main features of this system. The types of recipes used are seen in Table V [67]. The recipes shown are to be considered only as typical, as they are subject to many variations. It should be noted that the initiator in the SO C recipe (hot rubber) is the persulfate, whereas in the recipe (cold rubber) the initiator consists of a redox system comprising the hydroperoxide-iron(II)-sulfoxylate-EDTA. In the latter case, the initiating radicals are formed by the reaction of the hydroperoxide with the ferrous iron, whose concentration is controlled by the EDTA complexing agent the sulfoxylate is needed to convert the oxidized ferric(III) back to ferrous iron. The phosphate salt serves as a stabilizing electrolyte for the latex. 

A 75/25 butadiene-styrene latex with a total sohds content of 68%, produced by cold emulsion polymerisation reaction and subsequently concentrated and evaporated, was incrementally fractionated through the technique of fractionated creaming with sodium alginate. The fractions were analysed in relation to the average particle size by photon correlation spectrometry. 13 refs. 

A significant development was disclosed by Lin. He replaced part of the vinyl pyridine terpolymer latex in the adhesive recipe with poly butadiene latex. Glass cords dipped in this polybutadiene latex adhesive were more resistant to fracture under cold weather conditions. This was attributed to the lower tg of polybutadiene compared to vinylpyridine-styrene-bu-tadiene rubber. 

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