Chlorides vinyl

Vinyl chloride is used in the production of polymer (polyvinyl chloride), for use in plastics. It is classified as a human carcinogen (EPA Group A). 

Vinyl chloride was first prepared by Regnier in 1835 when working with Liebig. He chlorinated ethylene, or olefiant gas, as it was then known, and converted the ethylene dichloride, or oil of Dutch chemists (1795), to vinyl chloride by reaction with caustic potash solution  

The first reference to the compound as viityl chloride was by Kolbe in 1854. Baumann later described polyviiyl chloride in 1872 when he gave a good sum-maiy of its properties.  

Around 1900, when indusby began to take an interest in acetylene chemis-tiy, Fritz Klatte produced viiyl chloride at 180°C from acetylene and hydrogen chloride  

Patents for his process were issued to Griesheim-Electron in 1912/1913. They described a mercuric chloride catalyst supported on coke or pumice. The early catalysts described in 1912 could only operate for short periods because mercury compounds sublime at reaction temperature. Although the 1913 patent described reaction in aqueous solution with the mercuric chloride catalyst, this process was never used industrially. A further patent in 1913 claimed that the process only took place in the presence of the mercury catalyst that accelerated the reaction.  

Reactor Tubes 50-80 mm diameter x 3 m long (vessel 2 m diameter) 

The manufacture of polyvinyl chloride is still very important com-mercially8,45-47 and the synthesis of the monomer is therefore an important step in this synthesis (see Section 13.2)  

The earliest investigations on vinyl chloride using Zieglei Natta catalysts suggested that they were rather unsatisfactory initiators of polymerization. Yields and molecular weights were low, possibly due to participation of monomer in side reactions with catalyst components, and it was considered that polymerization resulted from free radicals produced by decomposition of unstable organo-metal compounds. 

Recent investigations [259] have indicated that the polymerization is not conventional free radical in character but is likely to be coordinated anionic. In support of this view are the reactivity ratio coefficients in copolymerization of vinyl chloride with vinyl acetate and methyl methacrylate, which are different from those found with free radical initiators. 

The catalyst was VOCl3/Al(i-Bu)3 in THF/benzene at 30°C and the free radical coefficients given in brackets. 

The reactivity ratios, although numerically different for the Ziegler and free radical catalysts, do show the same orders of monomer reactivity, vinyl acetate being less reactive and methyl methacrylate much more reactive than vinyl chloride. With the rather wide scatter in literature values for reactivity ratios — particularly with coordination systems — the data on VC/MM A cannot be regarded as completely indicative of a non-radical reaction however, the very low value of rj in the VA/VC system is more definitive. 

The general kinetic features of the polymerization show the rate to be first order in monomer and vanadium oxychloride concentrations, and independent of Al/V ratio above 5/1. The rate was increased in the presence of the polar solvent up to THF/V = 6 but then became independent of THF concentration. The catalyst underwent a rapid decomposition, accounting for declining polymerization rates with time, which was shown to be second order. The rate coefficient for decompo- 

The Reduction of Heat Distortion Temperature (HDT) in Vinylchloride-Eliiylene Copolymers Content as a Function of Ethylene. 

One method of producing PVC copolymers with higher heat distortion temperatures than a comparable PVC homopolymer is to employ n-substituted maleimides as comonomers. The bulkiness introduced by the ring structure is beUevedto result in the improved heat distortion temperature (81). 

Adding other polymeric ingredients is a common method of increasing the api ications for PVC. The miscible mixing of polymers with PVC to improve specific properties such as impact or plasticization, is covered in sections niB and niF. In contrast to miscible mixtures, there exist mixtures with nitrile (NBR) rubber of specific comonomer content which do approach the thermodynamic requirements for solid solutions. This present discussion will be directed towards alloys of PVC and other polymers, where some miscibility is a characteristic of the final formulation, and where some benefit fiom each polymer ingredient is noted. 

The major polymers with whieh PVC ean be alloyed are aerylonitrile-butadiene eopolymers, aerylonitrile-butadiene-styrene terpolymer, ethylene-vinylacetate copolymers, chlorinated polyethylene, chlorosulfonated polyethylene, thermoplastic polyurethanes, acrylics and methacrylics, and polycaprolactone. Table 18 lists the property enhancements achieved by blending these polymers with PVC. 

NBR flexibility, permanent plasticization, oil resistance, impact powdered and crumb NBR preferable most common is 33% ACN,67%BD 

The Bellar [514] purge and trap method has been applied to the determination of vinyl chloride in potable water. Chloroform, bromidi-chloromethane and dibromochloromethane are common to chlorinated drinking waters and result from the chlorination process. Low levels of methylene chloride are often observed in samples anal3rsed by this technique. These are attributed to method backgrormd. 

Not leaa than 95% diatilla over before the temperature of the liquid reache a 10 C 

Flash Point (Tag closed cup) °f Explosive limits in air (28°C), % Aulo-ignition temperature, °F Q Value e Value 

Liquid Monomer, A Hr k cal/mole Gaseous Monomer, A Hr k cal/mole 

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Example 2.1 Given that the objective is to manufacture vinyl chloride, there are at least three reaction paths which can be readily exploited. ... 

In summary, path 2 from Example 2.1 is the most attractive reaction path if there is a large market for hydrogen chloride. In practice, it tends to be difficult to sell the large quantities of hydrogen chloride produced by such processes. Path 4 is the usual commercial route to vinyl chloride. 

Polymerization reactions. There are two broad types of polymerization reactions, those which involve a termination step and those which do not. An example that involves a termination step is free-radical polymerization of an alkene molecule. The polymerization requires a free radical from an initiator compound such as a peroxide. The initiator breaks down to form a free radical (e.g., CH3 or OH), which attaches to a molecule of alkene and in so doing generates another free radical. Consider the polymerization of vinyl chloride from a free-radical initiator R. An initiation step first occurs ... 

Consider vinyl chloride production (see Example 2.1). In the oxychlorination reaction step of the process, ethylene, hydrogen chloride, and oxygen are reacted to form dichloroethane ... 

Figure 10.4 The oxychlorination step of the vinyl chloride process. (From Smith and Petela, Chem. Eng., 513 24, 1991 reproduced by permission of the Institution of Chemical Engineers.)...

A fiowsheet for this part of the vinyl chloride process is shown in Fig. 10.5. The reactants, ethylene and chlorine, dissolve in circulating liquid dichloroethane and react in solution to form more dichloroethane. Temperature is maintained between 45 and 65°C, and a small amount of ferric chloride is present to catalyze the reaction. The reaction generates considerable heat. 

Figure 10.5 The direct chlorination step of the vinyl chloride process using a liquid phase reactor. (From McNaughton, Chem. Engg., December 12, 1983, pp. 54-58 reproduced by permission.)...

Aldrin is obtained from the Diels-Alder addition product of cyclopentadiene and vinyl chloride by dehydrochlorination followed by condensation with hexachlorocyclopenta-diene. 

Most of the ethylene dichloride produced is utilized for the manufacture of vinyl chloride, which may be obtained from it by pyrolysis or the action of caustic soda. Large quantities are also used in anti-knock additives for gasoline. As a solvent It has been displaced by trichloroethylene and tetrachloroelhyJene. U.S. production 1978 4-75 megatonnes. 

Ethyne is the starting point for the manufacture of a wide range of chemicals, amongst which the most important are acrylonitrile, vinyl chloride, vinyl acetate, ethanal, ethanoic acid, tri- and perchloro-ethylene, neoprene and polyvinyl alcohol. Processes such as vinylation, ethinylation, carbonylation, oligomerization and Reppe processes offer the possibility of producing various organic chemicals cheaply. Used in oxy-acetylene welding. 

Isopropenyl acetate gives spinnable fibres on copolymerization with vinyl chloride. 

Vinyl chloride is used almost exclusively for the manufacture of polymers and copolymers. U.S. production 1983 2-6 megatonnes. See vinyl chloride polymers. 

Polymers can be classified as addition polymers and condensation polymers. Addition polymers are formed by iiitermolecular reactions of the monomeric units without the elimination of atoms or groups. An example is vinyl chloride, which can be made to combine with itself to yield polyvinyl chloride ... 

Vinyl compounds. Vinyl chloride (prepared from acetylene and hydrogen chloride) 3 ields polyvinyl chloride (P.V.C.), which is employed as a rubber substitute and for other purposes. Vinyl acetate (from... 

Copolymerisation of vinyl acetate and vinyl chloride yields resins of desirable properties they are strong and adhesive, thermoplastic, and are suitable for the manufacture of synthetic fibre (Vinyon). 

Vinylidene chloride and vinyl chloride lead to the copolymer known as Saran. Other commercial copolymers are produced from vinyl chloride and acrylonitrile (Dynel), and from maleic anhydride and styrene. 

C/760 mmHg) sulfur dichloride After the addition stirring v/as stopped and the flask was allowed to stand for 15 h in the ice-bath. The condenser was replaced with a drying tube containing CaCl (refluxing of the vinyl chloride had stopped completely after the addition of sulfur dichloride). 

Unsaturated nitriles are formed by the reaction of ethylene or propylene with Pd(CN)2[252]. The synthesis of unsaturated nitriles by a gas-phase reaction of alkenes. HCN, and oxygen was carried out by use of a Pd catalyst supported on active carbon. Acrylonitrile is formed from ethylene. Methacrylonitrile and crotononitrile are obtained from propylene[253]. Vinyl chloride is obtained in a high yield from ethylene and PdCl2 using highly polar solvents such as DMF. The reaction can be made catalytic by the use of chloranil[254]. 

Alkenyl chlorides are generally not very reactive, bnt vinyl chloride is exceptionally reactive and its carbonyiation with NH3 at 100 "C gave the Michael adduct of acrylamide 506 in high yields[360]. 

The rather unreactive chlorine of vinyl chloride can be displaced with nucleophiles by the catalytic action of PdCb. The conversion of vinyl chloride to vinyl acetate (797) has been studied extensively from an industrial standpoint[665 671]. DMF is a good solvent. 1,2-Diacetoxyethylene (798) is obtained from dichloroethylene[672]. The exchange reaction suffers steric hindrance. The alkenyl chloride 799 is displaced with an acetoxy group whereas 800 and 801 cannot be displaccd[673,674]. Similarly, exchange reactions of vinyl chloride with alcohols and amines have been carried out[668]. 

Copolymerization can be carried out with styrene, acetonitrile, vinyl chloride, methyl acrylate, vinylpyridines, 2-vinylfurans, and so forth. The addition of 2-substituted thiazoles to different dienes or mixtures of dienes with other vinyl compounds often increases the rate of polymeriza tion and improves the tensile strength and the rate of cure of the final polymers. This allows vulcanization at lower temperature, or with reduced amounts of accelerators and vulcanizing agents. 

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