Grades 1,3-butadiene

Over 70% of the total volume of thermoplastics is accounted for by the commodity resins polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) (PVC) (1) (see Olefin polymers Styrene plastics Vinyl polymers). They are made in a variety of grades and because of their low cost are the first choice for a variety of appHcations. Next in performance and in cost are acryhcs, ceUulosics, and acrylonitrile—butadiene—styrene (ABS) terpolymers (see... 

Except for the solvent process above, the cmde product obtained is a mixture of chloroprene, residual dichlorobutene, dimers, and minor by-products. Depending on the variant employed, this stream can be distiUed either before or after decantation of water to separate chloroprene from the higher boiling impurities. When the concentration of 1-chloro-1,3-butadiene [627-22-5] is in excess of that allowed for polymerisation, more efficient distillation is required siace the isomers differ by only about seven degrees ia boiling poiat. The latter step may be combiaed with repurifying monomer recovered from polymerisation. Reduced pressure is used for final purification of the monomer. All streams except final polymerisation-grade monomer are inhibited to prevent polymerisation. 

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. 

Third Monomers. In order to achieve certain property improvements, nitrile mbber producers add a third monomer to the emulsion polymerization process. When methacrylic acid is added to the polymer stmcture, a carboxylated nitrile mbber with greatly enhanced abrasion properties is achieved (9). Carboxylated nitrile mbber carries the ASTM designation of XNBR. Cross-linking monomers, eg, divinylbenzene or ethylene glycol dimethacrylate, produce precross-linked mbbers with low nerve and die swell. To avoid extraction losses of antioxidant as a result of contact with fluids duriag service, grades of NBR are available that have utilized a special third monomer that contains an antioxidant moiety (10). FiaaHy, terpolymers prepared from 1,3-butadiene, acrylonitrile, and isoprene are also commercially available. 

The refined grade s fastest growing use is as a commercial extraction solvent and reaction medium. Other uses are as a solvent for radical-free copolymerization of maleic anhydride and an alkyl vinyl ether, and as a solvent for the polymerization of butadiene and isoprene usiag lithium alkyls as catalyst. Other laboratory appHcations include use as a solvent for Grignard reagents, and also for phase-transfer catalysts. 

The butadiene-acrylonitrile rubbers were first prepared about 1930 about five years after the initial development of free-radical-initiated emulsion polymerisation. Commercial production commenced in Germany in 1937, with the product being known as Buna N. By the late 1980s there were about 350 grades marketed by some 20 producers and by the early 1990s world production was of the order of 250000 tonnes per annum, thus classifying it as a major special purpose rubber. 

All grades of regular butyl rubber are tacky, rubbery and contain less unsaturation than natural rubber or styrene-butadiene rubber. On the other hand, low molecular weight grades of polyisobutylene are permanently tacky and are clear white semi-liquids, so they can be used as permanent tackifiers for cements, PSAs, hot-melt adhesives and sealants. Low molecular weight polyisobutylenes also provide softness and flexibility, and act as an adhesion promoter for difficult to adhere surfaces (e.g. polyolefins). 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Acrylated rubber These are based on styrene butadiene and have become commercially available only relatively recently. They are manufactured in several grades but most have the advantage over other materials in this class of being based on white spirit solvent rather than the stronger and more obnoxious xylol. In other respects, they are similar to chlorinated rubber and cost approximately the same, although they are easier to airless spray and the dried film contains less pores. They are considered to have superior weather resistance to chlorinated rubber and vinyl. 

Enamels. The flexibility grades for the eight enamels (Table I) that were irradiated with 3-4 Mrad and 6-7.5 Mrad at 5, —30, and —90°C are shown in Table II. These data indicate that the epoxy-based enamels showed the best initial flexibility at — 90 °C and maintained their flexibility after irradiation. The preferred enamels were the epoxy phenolic with aluminum pigment, epoxy-wax and butadiene-styrene copolymer with aluminum pigment, and epoxy-wax with aluminum pigment. Tinplate adhesion before and after irradiation was satisfactory for the eight enamels. 

Commercial grades Inhibited butadiene is shipped as a liquid in tank trucks, tank cars, and steel cylinders. It is stored cold to prevent dimerization. ... 

Acrylonitrile butadiene styrene resins The information refers to a general purpose moulding grade material. 

The polymerisation of butadiene results in a polymer with a narrow molecular weight distribution which can be difficult to process. Indeed, commercially available grades present a compromise between processibility and performance. Most polybutadiene rubbers are inherently difficult to break down during mixing and milling, have low inherent tack, and the inherent elasticity of the polymer gives poor extrudability. Peptisers can be used to facilitate breakdown and hence aid processing. 

High-impact grades present better impact resistances even at low temperature, higher flexibility and environmental stress cracking resistance (ESCR). The butadiene-styrene block copolymers are transparent but the alloys made of polystyrene and polybutadiene are not. 

PS Sensitivity to UV, low temperatures, impact (apart from butadiene-modified grades), solvents, heat readily flammable with dripping and dense black smoke sometimes difficult machining. 

Uses. Plastics and synthetic rubber are the major uses for styrene. They account for the exponential growth from a few million pounds per year in 1938 to more than 8 billion pounds today. The numerous plastics include polystyrene, styrenated polyesters, acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), and styrene-butadiene (SB). Styrene-butadiene rubber (SBR) was a landmark chemical achievement when it was comrner-cialized during World War II. The styrene derivatives are found everywhere—in food-grade film, coys, construction pipe, foam, boats, latex paints, tires, luggage, and furniture. 

Homopolymers of butadiene, isoprene, and styrene were prepared under similar conditions. It should be noted that DVB was a commercial grade and, therefore, consisted of meta/para isomers and ethyl vinyl benzene. 

Iodine is used in many dyes and as a colorant for foods and cosmetics. Its silver salt is used in photographic negative emulsions. Other industrial applications include dehydrogenation of butane and butylenes to 1,3-butadiene as a catalyst in many organic reactions in treatment of naphtha to yield high octane motor fuel and in preparation of many metals in high purity grade, such as titanium, zirconium and hafnium. 

To a large bottle are added 470.0 gm (5.6 moles) of 2-methyl-3-butyne-2-ol, 1000 ml of 48 % technical grade hydrobromic acid, 200.0 gm (2.04 moles) of ammonium bromide, and 70.0 gm (0.71 mole) of cuprous chloride. The bottle is sealed, shaken at room temperature for 4J hr, opened, and the organic layer is separated. The organic layer is washed twice with sodium bicarbonate solution, once with a saturated sodium bisulfite solution, dried over calcium chloride, and fractionally distilled through a glass-helix-packed column to afford 500 gm (61 %) of almost pure product (ir 1956 cm-1 allene), b.p. 34°C (18 mm), d5 1.5163. The ir showed that the product contained a trace of l-bromo-3-methyl-1,3-butadiene (1580 and 1620 cm-1). 

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