Polyisoprene epoxidation

Other patents include Ternary Blend of Polyisoprene, Epoxidized Natural Rubber and Chlorosulfonated Polyethylene to Goodyear Tire Rubber, U.S. Patent 5,736,593, April 7, 1998, and Truck Tire With Cap/Base Construction Tread to Goodyear Tire Rubber, U.S. Patent... 

As with many polymers, polyisoprene exhibits non-Newtonian flow behavior at shear rates normally used for processing. The double bond can undergo most of the typical reactions such as carbene additions, hydrogenation, epoxidation, ozonolysis, hydrohalogena-tion, and halogenation. As with the case of the other 1,4-diene monomers, many copolymers are derived from polyisoprene or isoprene itself. 

Synthetic polymers from alkene monomers are also a major target for epoxidizers. Polyisoprenes,26 polybutenes and polybutadienes have all been epoxidized by general in situ peracid methods. In the case of liquid polybutadienes, a wide range of types is available. Products with varying contents of 1,4-cis, 1,4-trans, and 1,2-vinyl alkene groups are available (Figure 3.6). 

Polyenes (i.e., unsaturated aliphatic polymers) such as polyisoprenes, and polybutadiens may be hydrogenated, halogenated, hydrohalo-genated, cyclized, and epoxidized. 

Photoinitiated Ring-Opening Polymerization of Epoxidized Polyisoprene... 

From the conversion dependence of the insolubilization process, it was concluded that both inter- and intramolecular propagation reactions occur during the polymerization of the epoxy ring. Blends of epoxidized polyisoprene and difunctional vinyl ether or aciylate monomers were shown to undergo a fast and extensive cross-linking polymerization, with formation of interpenetrating polymer networks. 

THF structures have indeed been characterized by C-NMR spectroscopy in epoxidized polyisoprene exposed to UV radiation in the presence of a sulfonium photoinitiator... 

Photocross-Hnking of epoxidized polyisoprene - vinyl ether blends... 

Photocross-linking of epoxidized polyisoprene-acrylate blends... 

The photoinitiated cationic polymerization of liquid epoxidized polyisoprene is an efficient method to generate rapidly crosslinked elastomers. In the presence of a triarylsulfonium salt, the reaction develops readily upon UV exposure, with formation of both inter and intramolecular ether linkages. The formulation reactivity can be substantially enhanced by the addition of a difunctional vinyl ether or acrylate monomer, which acts as a reactive diluent and leads to the formation of an... 

Another route of carbonyl oxide deactivation is double-bond epoxi-dation. Various schemes of olefin epoxidation during ozonolysis have been suggested but the epoxidation through Cl (Scheme 2, reaction 9) is presumed to be the most probable with the C=C bonds in polyisoprenes [20, 21], Since a peak at 2.73 ppm has also been observed under similar conditions on ozonolysis of acrylonitrile—butadiene copolymers [31], as well as during ozonolysis of polybutadienes, it can be assumed that the epoxidation reaction takes place with the participation of both types of CL... 

The basic functional groups— products from the rubbers ozonolysis were identified and quantitatively characterized by means of IR-spectros-copy and H-NMR spectroscopy. The aldehyde—ozonide ratio was 11 89 and 27 73 for E-BR and BR, respectively. In addition, epoxide groups were detected, only in the case of BR, their yield was about 10 per cent of that of the aldehydes. On polyisoprenes the ozonide—ketone—aldehyde ratio was 40 37 23 and 42 39 19 for E-IR and Z-IR, respectively. Besides the already-specified functional groups, epoxide groups were also detected, their yields being 8 and 7 per cent for E-IR and Z-IR, respectively, with respect to reacted ozone. In the case of 1,4-rrara-polychloroprene, the chloroanhydride group was found to be the basic carbonyl product. 

Bromohydration, Bromolactonization, and Other Additions to C=C. The preferred conditions for the bromohydration of afkenes involves the portionwise addition of solid or predissolved NBS (recrystallized) to a solution of the alkene in 50-75% aqueous DME, THF, or f-butanol at 0 °C. The formation of dibromide and a-bromo ketone byproducts can be minimized by using recrystallized NBS. High selectivity for Markovrukov addition and anti stereochemistry results from attack of the bromonium ion intermediate by water. Aqueous DMSO can also be used as the solvent however, since DMSO is readily oxidized under the reaction conditions, significant amounts of the dibromide byproduct may be produced. In the bromohydration of polyalkenic compounds, high selectivity is regularly achieved for attack of the most electron-rich double bond (eq 20). With famesol acetate, squalene, and other polyisoprenes, choice of the optimum proportion of water is used to effect the selective bromohydration at the terminal double bond (eq 21), and the two-step sequence shown is often the method of choice for the preparation of the corresponding epoxides. ... 

When the respective component glass transition temperatures are close, the blend Tg is not a useful measure of blend homogeneity. In fact, excess mixing volumes and specific interactions can cause anomalous behavior. The Tg of such a blend can be lower (as seen in polychloroprene/epoxidized polyisoprene blends (McGrath and Roland, 1994)) or higher (as seen in polylepichlorohydrin/polyvinylmethylether blends (Alegria et al., 1995)), than Tg of either neat component. In blends of polymers having nearly equivalent... 

Uncontrolled oxidation of rubber is detrimental to its physical properties. Oxidation reactions take place readily at unsaturated groups in polymers and are often referred to collectively as epoxidation however, oxidation under controlled conditions can lead to useful products such as the epoxidized natural rubber introduced by the Malaysian Rubber Producers Association (Schults etal., 1983 Cunneen and Porter, 1965 Ceresa, 1965 Avery and Watson, 1956). Natural rubber in the latex form is treated with hydrogen peroxide dissolved in acetic acid. This gives 50% epoxidized natural rubber. This rubber shows very interesting physical properties and excellent carbon black dispersion. Similarly, nonaqueous epoxidizations of synthetic polyisoprene can be achieved... 

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