CLAIM OF PRIORITY

This application is a national phase filing under 35 USC § 371 from PCT Patent Application serial number PCT/CA2019/051835 filed on Dec. 17, 2019 and published as WO 2020/0124222 A1 on Jun. 25, 2020, which claims priority to European Patent Application Number EP 18215140.7 filed on Dec. 21, 2018. PCT Patent Application serial number PCT/CA2019/051835 and European Patent Application Number EP 18215140.7 are each incorporated by reference herein in its entirety.

FIELD

This application relates to a process for halogenating an unsaturated isoolefin copolymer.

BACKGROUND

In the standard process for brominating butyl rubber to form bromobutyl rubber, molecular bromine (Br2) is used as the brominating agent. The process results in the evolution of hydrogen bromide (HBr), as a by-product which, under normal conditions, does not further brominate the butyl rubber polymer. Therefore, the theoretical maximum fraction of bromine present in the reaction mixture which can be introduced into the butyl rubber polymer is 50%. However, in practice the fraction is usually less than 45%, and is less than 35% in both laboratory and production plant settings.

Known methods (US 2014/0309362, U.S. Pat. Nos. 3,018,275, 5,681,901) to enhance bromine utilization during butyl rubber bromination involve the application of at least 0.5 mol per mol of brominating agent of a water-soluble oxidizing agent, such as hydrogen peroxide, which re-oxidizes the hydrogen bromide back to elemental bromine. The oxidizing agent can be an aqueous solution, or an aqueous emulsion in an organic solvent. Since the oxidizing agent is only soluble in water, the rate of reaction is governed by the rate in which the reactants can exchange between the organic and aqueous phases, thus requiring a longer reaction time. Further, these methods require very low concentrations of water to be present in the bromination medium. The benefits observed from the use of an oxidizing agent in the bromination medium decrease dramatically with water concentrations greater than 1 wt %, presenting significant challenges and cost industrial, because additional equipment and energy may be needed to reduce the water content in the bromination medium from 10-20 wt % down to below 1 wt %. With specific reference to U.S. Pat. No. 5,681,901, peracid is mentioned as a route to forming hydrogen peroxide. Especially when considering the partition coefficients of peracids, there is no expectation that peracids would perform any better than the combination of hydrogen peroxide and emulsifier.

It is known to brominate alkyl rubbers with bromine in the presence of organic azo compounds and/or hypochlorites (U.S. Pat. No. 5,569,723). Also, halogenated butyl rubber may be produced by using N-halo organic compounds as the halogen source, in the presence of minor proportions of peroxide catalysts (U.S. Pat. No. 2,948,709), but such a process relies on the addition of a specific halogen source (N-halo compounds) as a means of halogen addition to butyl rubber, instead of conventional use of molecular halogens (bromine, chlorine), catalyzed by peroxides.

In addition, some processes involve post-halogenation recycling by neutralizing HBr to yield sodium bromide (NaBr), washing the NaBr from the halogenated butyl rubber into the aqueous stream, and converting the NaBr to Br2using Cl2gas, for example by the Blowout Process. This ex situ recycling method is limited by extraction efficiency of NaBr into the aqueous phase and dilution of the NaBr in the aqueous phase. Further, performing such an ex situ process is cost ineffective and energy intensive.

There remains a need for a cost-effective, efficient in-situ process for improving halogen utilization during halogenation of an isoolefin copolymer, for example butyl rubber.

SUMMARY

In one aspect, there is provided a process for producing a halogenated isoolefin copolymer, the process comprising contacting an unsaturated isoolefin copolymer cement, the cement comprising an unsaturated isoolefin copolymer dissolved in an organic solvent and having a water content of 1 wt % or greater based on total weight of the cement, under halogenation conditions with a halogenating agent and an aqueous solution of a C1-20organic peracid oxidant to form a two-phase reaction medium comprising an organic phase and an aqueous phase, the organic peracid oxidant capable of converting hydrogen halide to free halogen.

In another aspect, there is provided a process for producing a halogenated isoolefin copolymer, the process comprising contacting an unsaturated isoolefin copolymer cement, the cement comprising an unsaturated isoolefin copolymer dissolved in an organic solvent, under halogenation conditions with a halogenating agent and an aqueous solution of a C1-4organic peracid oxidant to form a two-phase reaction medium comprising an organic phase and an aqueous phase, the organic peracid oxidant capable of converting hydrogen halide to free halogen.

The process may further comprise recovering halogenated isoolefin copolymer containing at least 0.05 mol % of chemically combined halogen.

The present halogenation process advantageously results in increased halogen utilization by oxidizing hydrogen halide (HX) formed during halogenation of the unsaturated isoolefin copolymer back to molecular halogen (X2) without the necessity for a low water content in the halogenation medium and without the need to use a surfactant to disperse the oxidant in the organic phase of the halogenation medium.

Further features will be described or will become apparent in the course of the following detailed description. It should be understood that each feature described herein may be utilized in any combination with any one or more of the other described features, and that each feature does not necessarily rely on the presence of another feature except where evident to one of skill in the art.

