Styrene butadiene copolymer production

The most common VI improvers are methacrylate polymers and copolymers, acrylate polymers (see Acrylic ester polymers), olefin polymers and copolymers, and styrene—butadiene copolymers. The degree of VI improvement from these materials is a function of the molecular weight distribution of the polymer. VI improvers are used in engine oils, automatic transmission fluids, multipurpose tractor fluids, hydrautic fluids, and gear lubricants. Their use permits the formulation of products that provide satisfactory lubrication over a much wider temperature range than is possible using mineral oils alone. 

Elastomers. Elastomers are polymers or copolymers of hydrocarbons (see Elastomers, synthetic Rubber, natural). Natural mbber is essentially polyisoprene, whereas the most common synthetic mbber is a styrene—butadiene copolymer. Moreover, nearly all synthetic mbber is reinforced with carbon black, itself produced by partial oxidation of heavy hydrocarbons. Table 10 gives U.S. elastomer production for 1991. The two most important elastomers, styrene—butadiene mbber (qv) and polybutadiene mbber, are used primarily in automobile tires. 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

Many of the synthetic elastomers now made are still polymerized by a free radical mechanism. Polychloroprene, polybutadiene, polyisoprene, and styrene-butadiene copolymer are made this way. Initiation by peroxides is common. Many propagation steps create high molecular weight products. Review the mechanism of free radical polymerization of dienes given in Chapter 14, Section 2.2. 

The production of ABS and SAN resins consumes the second largest quantity of acrylonitrile. The ABS resins are produced by grafting acrylonitrile and styrene onto polybutadiene or a styrene-butadiene copolymer and contain about 25 wt% acrylonitrile. These products are used to make components for automotive and recreational vehicles, pipe fittings, and appliances. The SAN resins are styrene-acrylonitrile copolymers containing 25-30 wt% of acrylonitrile. The superior clarity of SAN resin allows it to be used in automobile instrument panels, for instrument lenses and for houseware items (Langvardt, 1985 Brazdil, 1991). 

Of the 17 billion lb of butadiene consumed in 1999, almost two thirds went into the production of elastomers (styrene-butadiene latex rubber (SBR), polybutadiene, nitrile, and polychloroprene). Adiponitrile, ABS resins, styrene-butadiene latex, styrene block copolymers, and other smaller polymer uses accounted for the remainder. The largest single use was for styrene-butadiene copolymers (SBR and latex). Most of it was made by an emulsion process using a free-radical initiator and a styrene-butadiene ratio of about 1 3. More detailed description of the rubber and polymer used can be found in Chapters 16 and 15. 

NOTE Ibtals for plastics are for those products listed and exclude some small-volume plastics. Synthetic rubber data include Canada. Dry-weight basis unless otherwise specified Density 0.940 and below " Data include Canada from 2001 Density above 0.940 Data include Canada from 1995 Data include Canada from 2000 Data include Canada from 1994 Includes styrene-butadiene copolymers and othm styrene-based polymers Unmodified Includes butyl styrene-butadiene rubber latex, nitrile latex, polyisoprene, and miscellaneous others. SOURCES American Plastics Council, International Institute of Synthetic Rubber Producers. 

Significant developments in synthetic rubber began at this time. Outstanding were the introduction of polychloroprene (neoprene) by Carothers, and of the oil-resistant polysulfide rubber Thiokol by Patrick. These were soon followed by styrene-butadiene copolymers, nitrile rubber, butyl rubber, and various other types, some of which were rushed into production for the war effort in the early 1940s. The stereospecific catalysts researched by Ziegler and Natta aided this development, including synthesis of true rubber hydrocarbon (polyisoprene). Since 1935 synthetic rubbers have been referred to as elastomers. 

Polyurethanes and Rubbers - The photooxidation of polyether-polyurethanes exhibits sensitivity due to the ether segments. Formates were the primary products of photorearrangement. The addition of styrene-butadiene copolymers to polyolefins significantly enhances their susceptibility to photooxidation via the butadiene component. Horizontal attenuated FTIR spectroscopy has been found useful for detecting the products of photooxidation of rubbers ... 

Zmierczak et al.4 have investigated the catalytic hydrocracking of non-vulcanized rubber (SBR, styrene-butadiene copolymers) over superacid solids, consisting of sulfated Zr and Fe oxides. Figure 6.7 shows the GC-MS analysis of the liquids produced at 400 °C over sulfated Fe203, with assignments of the main peaks. Three types of product are observed C5-C9 paraffins produced from the butadiene blocks of the polymer, alkylbenzenes derived from the... 

Mastral et al.23,24 have also investigated the effect of the main components present in tyres (carbon black, styrene-butadiene copolymer and polybutadiene) on the liquefaction of coal. Coprocessing of coal and carbon black confirmed the catalytic role of the latter, as it promotes hydrocracking reactions leading mainly to the formation of gaseous products. The addition of SBR to coal improves the yield of gases, oil and asphalt fractions, even at relatively low temperatures (350-375 °C). It is proposed that SBR favours the stabilization of the radicals involved in the process through alkylation reactions... 

Several other common industrial polymers are also used in biomedical applications [51]. Because of its low cost and easy processibility, polyethylene is frequently used in the production of catheters. High-density polyethylene is used to produce hip prostheses, where durability of the polymer is critical. Polypropylene, which has a low density and high chemical resistance, is frequently employed in syringe bodies, external prostheses, and other non-implanted medical applications. Polystyrene is used routinely in the production of tissue culture dishes, where dimensional stability and transparency are important. Styrene-butadiene copolymers or acrylonitrile-butadiene-styrene copolymers are used to produce opaque, molded items for perfusion, dialysis, syringe connections, and catheters. 

Copolymerization of styrene with other monpmers has become of great industrial importance in the production of synthetic rubber. GR-S type, rubbers are made from styrene and butadiene, and the necessity to produce this synthetic rubber during World War II brought about a high output of monostyrene, which in turn stimulated further industrial development and use of polystyrene. A more detailed discussion of styrene-butadiene copolymers is found later in the section on Diene Elastomers. 

Acrylonitrile is used in the production of acrylic fibers, resins, and surface coating as an intermediate in the production of pharmaceuticals and dyes as a polymer modifier and as a fumigant. It may occur in fire-effluent gases because of pyroly-ses of polyacrylonitrile materials. Acrylonitrile was found to be released from the acrylonitrile-styrene copolymer and acrylonitrile-styrene-butadiene copolymer bottles when these bottles were filled wifh food-simulating solvents such as water, 4% acetic acid, 20% ethanol, and heptane and stored for 10 days to 5 months (Nakazawa et al. 1984). The release was greater with increasing temperature and was attributable to the residual acrylonitrile monomer in the polymeric materials. 

The most important application of SBR is in car tires and tire products, but there is also widespread use of the rubber in mechanical and industrial goods. SBR latexes, which are emulsions of styrene-butadiene copolymers (containing about 23-25% styrene), are used for the manufacture of foam rubber backing for carpets and for adhesive and molded foam applications. 

Rubber consumption is dominated by tyre production. In these, conveyor belts, and pressure hoses, thin layers of either steel wire or polymeric fibre reinforcement take the main mechanical loads. These layers, with rubber interlayers, allow flexibility in bending, whereas the reinforcement limits the in-plane stretching of the product. The applications are dominated by natural rubber and styrene butadiene copolymer rubber (SBR). Other rubbers have specialised properties butyl rubbers have low air permeability, nitrile rubbers have good oil resistance, while silicone rubbers have high and low temperature resistance. Rubbers play a relatively small role in this book, but the rubbery behaviour of the amorphous phase in semi-crystalline thermoplastics is important. 

Fig. 9. Spectra of styrene-butadiene copolymer (A) and its hydrogenated product (B)...

Waterborne dispersed polymers include both synthetic polymer dispersions and natural rubber. Synthetic polymer dispersions are produced by emulsion polymerization. A substantial part of the synthetic polymer dispersions is commercialized as dry products these include SBR for tires, nitrile rubbers, about 10% of the total PVC production, 75% of the total ABS and redispersable powders for construction materials. Carboxylated styrene-butadiene copolymers, acrylic and styrene-acrylic latexes and vinyl acetate homopolymer and copolymers are the main polymer classes commercialized as dispersions. The main markets for these dispersions are paints and coatings, paper coating, adhesives and carpet backing. 

Next to ethylene and vinyl chloride, styrene is the most important monomer building block in the production of plastic materials in addition, it is used to make synthetic rubber, such as styrene-butadiene copolymer (SBR) and other polymers. The first mention of styrene appeared in the Dictionary of Practical and Theoreti-... 

Styrene-butadiene copolymers are used in toys, housewares, and medical applications.Thermoformed products include disposable food packaging such as cups, bowls, clam shells, deli containers, and lids. Bhster packs and other display packaging also use styrene-butadiene copolymers. Other packaging apphcations include shrink wrap and vegetable wrap. ... 

Looking at the historical development of the emulsion pol)nnerization, it is seen that the trigger factor in this development was the necessity for synthetic rubber in the wartime. The production of styrene/butadiene rubber (SBR) satisfied this requirement. Today, millions of tons of S)mthetic latexes are produced by the emulsion pol3merization process for use in wide variety of applications. In the S)mthetic latexes, the most important groups are styrene/butadiene copolymers, vinyl acetate homopol)rmers and copol)nners, and polyacrylates. Other synthetic latexes contain copolymers of ethylene, styrene, vinyl esters, vinyl chloride, vinylidene chloride, acrylonitrile, cloroprene and polyurethane. 

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