2-Chlorobutadiene polymers

Hargreaves, C. A. and Thompson, D. C., 2-chlorobutadiene polymers Chapter in Encyclopaedia of Polymer Science and Technology, Vol. 3, Wiley, New York (1965). 

Chloro-1,3-butadiene homopolymer Chlorobutadiene polymer 2-Chloro-1,3-butadiene polymer. See Polychloroprene Chlorocosane. See Paraffin, chlorinated... 

Synonyms 1,3-Butadiene, 2-chloro-, polymers 2-Chloro-1,3-butadiene homopolymer Chlorobutadiene polymer 2-Chloro-1,3-butadiene polymer Chloroprene polymer Chloroprene resin Chloroprene rubber CR Neoprene Neoprene rubber Poly (2-chlorobutadiene) Poly (2-chloro-1,3-butadiene) Poly (chloroprene)... 

Polymerization-grade chloroprene is typically at least 99.5% pure, excluding inert solvents that may be present. It must be substantially free of peroxides, polymer [9010-98-4], and inhibitors. A low, controlled concentration of inhibitor is sometimes specified. It must also be free of impurities that are acidic or that will generate additional acidity during emulsion polymerization. Typical impurities are 1-chlorobutadiene [627-22-5] and traces of chlorobutenes (from dehydrochlorination of dichlorobutanes produced from butenes in butadiene [106-99-0]), 3,4-dichlorobutene [760-23-6], and dimers of both chloroprene and butadiene. Gas chromatography is used for analysis of volatile impurities. Dissolved polymer can be detected by turbidity after precipitation with alcohol or determined gravimetrically. Inhibitors and dimers can interfere with quantitative determination of polymer either by precipitation or evaporation if significant amounts are present. 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

This is the preferred designation for all chloroprene polymers and copolymers. Chloroprene rubber was first introduced commercially in 1931 by DuPont and their trade name, originally DuPrene, later Neoprene, has almost become a generic term for all such rubber. See Chlorobutadiene. 

The main by-products are 1-chlorobutadiene, produced from the residual dichloro 2-butenes or formed during the reaction, polymers, sodium chloride and monochloro-butenes (l-chloro 1-butene, 2-diloro 2-butenes, 2-chloro 1-butene, etc.) To control the undesirable polymerizations, the reaction takes place in an oxygen-free environment, at the lowest possible temperature, and with an inhibitor. Also effective is the presence of a solvent (methanol, ethanol) or a catalyst In this case, however, it is necessary to raise the caustic soda concentrations (30 per cent) or to employ other bases (liquid ammonia, ion exchange resins, etc.). In the absence of catalyst, the residence time is 3 to 5 h. and selectivity exceeds 95 molar percent for a once-through conversion of nearly 95 per cent... 

Many hundreds of diene polymers were investigated for their suitability as elastomers. Only three of these have achieved widespread commercial acceptance butadiene-styrene copolyipers, butadiene-aciylonitrile copolymers, and poly-2-chlorobutadienes. Other essentially non-diene elastomers such as butyl rubber from isobutene, Thiokol from ethylene dihalides and polysulfides, and silicones have become important for special applications. 

The parts of the structural elements of three most important diene monomers butadiene, isoprene and chloroprene (2-chlorobutadiene) in the structure of different polymers obtained by free radical polymerization at different temperatures are given in Table 8.5. 

One of the drawbacks to solvent-based adhesives based on rigid polymers is the shrinkage that results when the solvent evaporates. This can set up stresses that weaken the joint. An example of this type of adhesive is the familiar model airplane cement, basically a cellulose nitrate solution, with perhaps some plasticizer. Rubber cements, of course, maintain their flexibility, but cannot support as great a stress. Commercial rubber cements are based on natural, SBR oly(butadiene-co-styrene)), nitrile (poly(butadiene-co-acrylonitriIe)), chloro-prene (poIy(2-chlorobutadiene)), and reclaimed (devulcanized) rubbers. Examples are household rubber cement and Pliobond . Rubber cements may also... 

Fig. 35. Dissipation factor vs frequency for polar polymers at 25°C. A, Clear cast phenolic B, plasticized PVC C, poly(vinyl chloride-co-vinylidene chloride) (saran) D, unplasticized PVC E, poly(methyl methacrylate) G, poly(hexamethylene adipamide) (nylon) H, poly(2-chlorobutadiene) I, plasticized ethyl cellulose J, cast epoxy K, methyl silicone rubber L, polyurethane foam (d = 33 g/L) and M, 50% polystyrene-50% chlorinated biphenyl.

He also produced neoprene, a synthetic rubber, in 1931. He did so by treating viny-lacetylene with hydrochloric add. This produced the monomer chlorobutadiene which readily polymerizes to give the polymer neoprene. In the search to find artifical versions of silk and cellulose he used many types of condensation polymers. In 1935 he discovered the polyamide usually known as nylon by the condensation of adipic acid and hexamethylenediamine. Carothers suffered from depression and committed suidde in 1937. He therefore did not live to see the commercial production of nylon in 1940. 

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