Isoprene

These products are especially useful as thermoplastic rubbers and as pressure-sensitive or thermosetting adhesives. ... Smaller amounts of isoprene are used in the production of butyl rubber (isobutene - isoprene rubber, IIR), a copolymerizate with isobutene.

Manufacture of "synthetic" natural rubber, butyl rubber. Copolymer in the production of synthetic elastomers.

Some of the many uses in which rubbers are employed include pneumatic tires and inner tubes, tubing and hose, rubber footware, inflatable and sectional seals, elastic thread and tape, rubber/metal bonded products, inflatable life-rafts and dinghies, chemically resistant tank linings, conveyor belting, foam cushioning for upholstery and bedding, floor coverings, proofed material for clothing, adhesives and solutions, washers, gaskets, diaphrams, floating bulk liquid containers and hose, tennis, squash and golf balls.

Acetonitrile is the most common solvent, but dimethylformamide is also used commercially.

The synthesis of isoprene from propylene is a three-step process. The propylene is dimerized to 2-methyl-1-pentene, which is then isomerized to 2-methyl-2-pentene in the vapor phase over silica alumina catalyst. The last step is the pyrolysis of 2-methyl-2-pentene in a cracking furnace in the presence of ((NH4)2-S). Isoprene is recovered from the resulting mixture by conventional distillation.

The starting material here is a fraction which is cut from catalytic cracking of petroleum. Two of the tertiary amylene isomers, 2-methyl-1-butene and 2-methyl-2-butene, are recovered in high purity by formation of methyl tertiary butyl ether and cracking of this to produce primarily 2-methyl-2-butene. The amylenes are mixed with steam and dehydrogenated over a catalyst.