Neoprene chlorination

Properties Vise. 69 cps pH 12.0 59% solids 38% chlorine Neoprene Liq. Disp. 735A [DuPont DuPont Canada]... 

Uses Polychloroprene for mfg. of cellulose and asbestos paper, blending with other Neoprene latexes to improve wet-gel strength used for adhesives, bonded batts, coatings, saturants Properties Vise. 5 cps pH 11.5 45% solids 38.5% chlorine Neoprene Liq. Disp. 750 [DuPont DuPont Canada]... 

Featmes Good low temp, props. compat. with SBR, NR, butyl, chlorinated, neoprene mbber. EVA, SBS, PE, PP, acrylic, phihalale and polyester plasticizers, all d and hydrocarbon resins Regiriat FDA 21CFR 175.105... 

At one time, the only commercial route to 2-chloro-1,3-butadiene (chloroprene), the monomer for neoprene, was from acetylene (see Elastomers, synthetic). In the United States, Du Pont operated two plants in which acetylene was dimeri2ed to vinylacetylene with a cuprous chloride catalyst and the vinyl-acetylene reacted with hydrogen chloride to give 2-chloro-1,3-butadiene. This process was replaced in 1970 with a butadiene-based process in which butadiene is chlorinated and dehydrochlorinated to yield the desired product (see Chlorocarbonsandchlorohydrocarbons). 

Other Accelerators. Amine isophthalate and thiazolidine thione, which are used as alternatives to thioureas for cross-linking polychloroprene (Neoprene) and other chlorine-containing polymers, are also used as accelerators. A few free amines are used as accelerators of sulfur vulcanization these have high molecular weight to minimize volatility and workplace exposure. Several amines and amine salts are used to speed up the dimercapto thiadiazole cure of chlorinated polyethylene and polyacrylates. Phosphonium salts are used as accelerators for the bisphenol cure of fluorocarbon mbbers. 

Neoprene latex type Comonomer Emulsifiers Chlorine content, wt % pH at 25° C Standard soHds, wt % Distinguishing features Primary appHcations... 

Vulcanization. Some of the chlorine atoms along the chain (1,2 units) are very labile and reactive, and provide excellent sites for cross-linking. Hence neoprene is not vulcanized by sulfur but by metal oxides, eg, magnesium and zinc oxides, although sulfur is generally included in the compound to control the rate of vulcanization. 

Processing ndProperties. Neoprene has a variety of uses, both in latex and dry mbber form. The uses of the latex for dipping and coating have already been indicated. The dry mbber can be handled in the usual equipment, ie, mbber mills and Banbury mixers, to prepare various compounds. In addition to its excellent solvent resistance, polychloroprene is also much more resistant to oxidation or ozone attack than natural mbber. It is also more resistant to chemicals and has the additional property of flame resistance from the chlorine atoms. It exhibits good resiUence at room temperature, but has poor low temperature properties (crystallization). An interesting feature is its high density (1.23) resulting from the presence of chlorine in the chain this increases the price on a volume basis. 

Neoprene 250 Excellent mechanical properties. Good resistance to uouaromatic petroleum, fatty oils, solvents (except aromatic, chlorinated, or ketone types). Good water and alkali resistance. Fair acid resistance. 

Neoprene 400. It contains a fast-crystallizing polymer with the highest chlorine content and the highest uncured cohesive strength among all anionic latexes. However, this latex has a relatively short open time and requires high lamination pressures to achieve coalescence. 

Various polymeric materials were tested statically with both gaseous and liquefied mixtures of fluorine and oxygen containing from 50 to 100% of the former. The materials which burned or reacted violently were phenol-formaldehyde resins (Bakelite) polyacrylonitrile-butadiene (Buna N) polyamides (Nylon) polychloroprene (Neoprene) polyethylene polytriflu-oropropylmethylsiloxane (LS63) polyvinyl chloride-vinyl acetate (Tygan) polyvinylidene fluoride-hexafluoropropylene (Viton) polyurethane foam. Under dynamic conditions of flow and pressure, the more resistant materials which binned were chlorinated polyethylenes, polymethyl methacrylate (Perspex) polytetraflu-oroethylene (Teflon). 

Chlorine is used to make plastics such as neoprene and polyvinyl chloride (vinyl). It is used to make insecticides, fireworks, explosives, and paint pigments pharmaceuticals, chloroform, and chlorofluorocarbons (ClFCs) and chlorohydfocarbons (ClHCs). 

Chloroprene, used for the production of neoprene rubber, is obtained by the dehydrochlorination of dichlorobutene. The latter is produced by the chlorination of 1,3-butadiene, which in turn is synthesized from acetylene. 

Plastics and elastomers Degrades chlorinated polyethylene, neoprene, nitrile rubber, polysulfide, polyurethane... 

Neoprene Comonomer Emulsifiers Chlorine pH Standard Distinguishing features Primary applications... 

Another chlorinated compound which, like vinyl chloride, is used only in its polymeric form, is chloroprene (2-chloro-l,3-butadiene), which is polymerized to make neoprene, first produced in 1940. As far as is known (17) y the monomer is made commercially only from acetylene via addition of hydrochloric acid to monovinylacetylene in the presence of cuprous chloride, but syntheses from butylenes or butadiene have been described. The production of chloroprene exceeded 100,000,000 pounds per year at the wartime peak and has been somewhat lower since then, but in view of the many valuable properties of the neoprene rubber it will continue to be important. 

Exterior surface corrosion or rusting of pipes occurs by the formation of iron oxides. Painting to an appropriate specification will significantly extend the period to the onset of corrosion, but the durability of the paint finish is largely dependent on the quality of the surface preparation as well as the thickness of the coated film. Improperly installed insulation can provide ideal conditions for corrosion and should be weatherproofed or otherwise protected from moisture and spills to avoid contact of the wet material on equipment surfaces. Application of an impervious coating such as bitumen to the exterior of the pipes is beneficial in some circumstances. Hypalon and neoprene rubber-based anticorrosive coatings admixed with chlorinated rubber are finding use in many installations. 

The resilience of gum neoprene vulcanizates is little lower than natural rubber but it decreases with increased filler incorporation. Therefore, the resilience of most practical neoprene compounds is higher than that of natural rubber with comparable volume loading. Because of the presence of chlorine in the neoprene molecule, products made from neoprene resist combustion to a greater degree than products made from non-halogen bearing rubbers. This means neoprene can be compounded to meet the flammability requirements of the Mine Safety and Health Administration (MSHA) USA or similar requirements as might be stipulated by any other countries,... 

Chlorinated rubber is also an effective bonding agent. It can be used for bonding neoprene, nitrile and natural rubbers to metals. Phenol formaldehyde resins have been used alone or in conjunction with chlorinated rubbers, but curing time is lengthy. 

Small amounts of other polymers are used in certain niche applications, including chlorinated polyethylene (CPE), neoprene, chlorosulfonated polyethylene, nylon, and TPU. 

At about the same time, Wallace Carothers and his colleagues discovered a chlorine derivative of butadiene that polymerized to give a rubbery polymer that DuPont eventually marketed as Neoprene. Note the similarity in the structures of isoprene and 2-chloro-1,3-butadiene (chloroprene) ... 

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