Xanthogen disulfides chain transfer

Latex products are manufactured in an identical fashion as the dry polymers described earlier. One major exception is that the primary and auxiUaiy surfactants used in latex manufacture are not destroyed prior to shipment to the end user. Molecular weight control is identical with mercaptan, organic halides, and xanthogen disulfides chain-transfer agents typically used. Copolymerizations are conducted with the same variety of comonomers that include... 

Xanthogen disulfide modification has been used in the manufactin-e of all dry and latex types including chloroprene-sulfur copolymers. The chain-transfer agents have heen used in comhination with all conventional comonomers. In contrast to dodecylmercaptan modifiers, xanthogen disulfide modification has the advantage that it can be used with chloroprene-sulfur copolymerizations without concerns with reaction with sulfiir. 

Sulfides. A wide range of various disulfides have been employed as chain transfer agents dialkyl disulfides (211), diaryl disulfides (212,213), diaroyl disulfides (214), and xanthogens (215). The reaction of these compounds leads to the incorporation of sulfiir-containing end groups at both ends of the polymer, as shown in equations 34 and 35. They therefore have foimd some applications in the preparation of telechelic polymers. 

The transfer coefficients of disulfides are extremely low for styrene and methyl methacrylate (see Table 4), but are close to one for the vinyl acetate polymerization. In general the xanthogens and thiurams have higher chain transfer ability, which has been attributed to the iniferter mechanism described above. Monosulfides have lower transfer coefficients in comparison to disulfides. This may refiect steric factors and the relative strength of the C—S bond, which is significantly stronger than the S—S bond. 

Formulation example n-dodecyl mercaptan (and sometimes xanthogen disulfide) is used as a chain transfer agent in linear grades slow crystallizing grades are copolymerized with 2,3-dichloro-1,3-butadiene ... 

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