Butene butyl rubber

Butyl mbber, a copolymer of isobutjiene with 0.5—2.5% isoprene to make vulcanization possible, is the most important commercial polymer made by cationic polymerization (see Elastomers, synthetic-butyl rubber). The polymerization is initiated by water in conjunction with AlCl and carried out at low temperature (—90 to —100° C) to prevent chain transfer that limits the molecular weight (1). Another important commercial appHcation of cationic polymerization is the manufacture of polybutenes, low molecular weight copolymers of isobutylene and a smaller amount of other butenes (1) used in adhesives, sealants, lubricants, viscosity improvers, etc. 

Butyl rubber is a copolymer of 1 -butene, (CH3)2C = CH2, and small amounts (about 2%-3%) of isoprene or other unsaturated compounds. The unsaturation allows subsequent cross-linking of the material. 

Isobutylene is more reactive than n-butene and has several industrial uses. It undergoes dimerization and trimerization reactions when heated in the presence of sulfuric acid. Isobutylene dimer and trimers are use for alkylation. Polymerization of isobutene produces polyisobutenes. Polyisobutenes tend to be soft and tacky, and do not set completely when used. This makes polyisobutenes ideal for caulking, sealing, adhesive, and lubricant applications. Butyl rubber is a co-polymer of isobutylene and isoprene containing 98% isobutene and 2% isoprene. 

Polymers account for about 3—4% of the total butylene consumption and about 30% of nonfuels use. Homopolymerization of butylene isomers is relatively unimportant commercially. Only stereoregular poly(l-butene) [9003-29-6] and a small volume of polyisobutylene [25038-49-7] are produced in this manner. High molecular weight polyisobutylenes have found limited use because they cannot be vulcanized. To overcome this deficiency a butyl mbber copolymer of isobutylene with isoprene has been developed. Low molecular weight viscous liquid polymers of isobutylene are not manufactured because of the high price of purified isobutylene. Copolymerization from relatively inexpensive refinery butane—butylene fractions containing all the butylene isomers yields a range of viscous polymers that satisfy most commercial needs (see OLEFIN POLYMERS ELASTOMERS, SYNTHETIC-BUTYL rubber). 

Another approximately 1.5 billion lb of isobutylene goes into other chemical uses. These applications include polybutenes and derivatives of high-purity isobutylene such as butyl rubber, polyisobutylenes, and substituted phenols. Isobutylene is more reactive than the n-butenes, but many of its reactions are readily reversible under relatively mild conditions. 

More recently, the dehydrohalc enation of chlorinated butyl rubber, i. e. iso-butene-isoprene copolymer containing 1.4—1.6 wt % of chlorine, essentially in allylic positions, was performed successfully thus poljdsobutraie chains carrying randcxn groups of two conjugated double bonds were obtained. 

As it will be discussed In Sect. III.B.2.d), isobutene homopolymer and isoprene-iso-butene copolymer (butyl rubber) are prone to degrade under the attack of free radicals Therefore, these polymers cannot cross-link (unless h comonomer content is present) in the presence of free radicals and usually are not used in grafting reactions since a low degree of graft is observed (Tdrle 9, n 1,2). 

Previously it has been reported that biacetyl, bibutyryl, pyruvic acid, and butyl nitrite produce ozone upon irradiation without the addition of nitrogen dioxide. In the absence of nitrogen dioxide, ozone formation can be established by irradiation of biacetyl at a concentration of 40 p.p.m. in its presence the rate of formation is still pronounced in the 1-p.p.m. range, and equals that of 2-butene. Butyl nitrite without the addition of nitrogen dioxide is even more active than 2-butene. After 94 hours the total crack depth of the rubber pieces corresponds to the production of 80 p.p.m. of ozone, demonstrating again a chain mechanism in its formation. 

Similarly, 2-methylpropene (isobutene) is an important monomer. It only polymerizes by a cationic mechanism, and its copolymers with dienes are known as butyl rubber. Higher 1-alkenes (1-butene, 1-hexene, 1-octene) are important copolymerization components [4, 5] they produce tailored branching of some polyethylene types prepared by a coordination mechanism. Longer-chain alkenes (Cjq, C,2, Cj ) are also sometimes used as comonomers... 

Polybutenes have heen used for almost a century and while they are still used, most of this type sealant contains butyl rubber, which is a copolymer of butene and isoprene. Most building specifications, including Federal Specification, TT-S-001637, require solutions of butyl rubber instead of oil-based caulking compositions. Self curing butyl rubber sealants may contain phenolic resins,IS. resorcinol and hexamethylenetetramine. ... 

The remaining components are common to many refinery streams, and thus isobutene and w-butenes may be derived from either source. Isobutene is generally recovered from the butadiene-free raffinate by chemical means. For example, by contacting the mixture with 65% sulphuric acid, r-butanol is formed in the acid phase, from which fairly pure isobutene (for butyl rubber ) may be regenerated. Alternatively, the isobutene within the mixed C4 stream may be converted directly to the dimer and trimer by contact with solid acidic catalysts, to viscous polybutenes by treatment with Lewis acid catalysts, or to a /-butyl ether (section 12.9.3). The reported 1993 U.S. production of isobutene was about 500 kt, but this refers only to isolated material (including dehydration of Arco s co-product /-butanol) derivatives possibly consumed 7-8 Mt in the U.S. compared with roughly 2Mt in Europe. 

Figure 1 Polymer interpretation chart. PAI, polyamideimide PC, polycarbonate UP, unsaturated polyester PDAP, diarylate phtalate resin VC-VAc, vinyl chloride-vinyl acetate copolymer PVAc, polyvinyl acetate PVFM, polyvinyl formal PUR, polyurethane PA, polyamide PMA, methacrylate ester polymer EVA, ethylene-vinyl acetate copolymer PF, phenol resin EP, epoxide resin PS, polystyrene ABS, acrylonitrile-butadiene-styrene copolymer PPO, polyphenylene oxide P-SULFONE, poly-sulfone PA, polyamide UF, urea resin CN, nitrocellulose PVA, polyvinyl acetate MC, methyl cellulose MF, melamine resin PAN, polyacrylonitrile PVC, polyvinyl chloride PVF, polyvinyl fluoride CR, polychloroprene CHR, polyepichlorohydrin SI, polymethylsiloxane POM, polyoxy-methylene PTFE, polytetrafluoroethylene MOD-PP, modified PP EPT, ethylene-propylene terpolymer EPR, ethylene-propylene rubber PI, polyisoprene BR, butyl rubber PMP, poly(4-methyl pentene-1) PE, poly(ethylene) PB, poly(butene-l). (Adapted from Ref. 22, p. 50.)...

Poly butylene n Any of a family of low-molecular-weight polymers of mixed 1-butene, ds-2-butene, trans-2-butene, and isobutene. Depending on molecular weight, these polymers range from oils through tacky waxes, crystalline waxes, and rubbery solids. See also Butyl Rubber and Polybutylene Resin. Poly(l-butene) shown below. 

The C4 olefins go into three types of sealants polybutenes, butyl rubber, and polyisobutylene. Polybutenes are largely linear, low molecular weight homopolymers of butene-1, used in sealants either as prime vehicles or as modifying polymers. They are relatively low cost, nondrying, tacky polymers. They are used in the formulation of three types of compounds ... 

Zso-butene (2-methylpropene) and isoprene can be copolymerized to give butyl rubber. Only about 2 % of isoprene is needed to give the desired properties (to give sites for vulcanization), and the polymer is prepared by a cationic process. 

High performance elastomeric butyl tapes are available for large window lite glazing in high-rise structures and for windshield sealing. These usually contain crosslinked butyl elastomers (20-40%) plus poly butenes, resinous tackifiers, and reinforcing fillers such as carbon black and platy talc. Chlorobutyl rubber compositions are available for faster and more thorough vulcanization. 

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