RU2439084C1 - Method of producing halobutyl rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing halobutyl rubber by reacting halogen and butyl rubber obtained via low-temperature suspension copolymerisation of isobutylene with isoprene on an aluminium chloride catalyst in a chloromethyl medium, wherein the isobutylene contains not less than 99.97 wt % basic substance, the isoprene contains not less than 99.1 wt % basic substance, wherein the dosage of aluminium chloride is equal to 0.01-0.1 wt % per isobutylene and the catalyst is used in the presence of a protogenic or cationogenic activator, taken in amount of 1.0-0.01 mol per 1 mol of aluminium chloride, the dosage of isoprene during copolymerisation is equal to 2.0-3.5 wt % per isobutylene.

EFFECT: low content of halogen and stabilising reagents in halobutyl rubber with simultaneous increase in gas-permeability of rubber obtained therefrom; also, the halobutyl rubber is characterised by lower polydispersity compared to the prototype.

1 cl, 1 tbl, 21 ex

Description

The invention relates to a method for producing halogenated polymers, in particular halogenated butyl rubbers, and can be used in the petrochemical and chemical industries.

Known halogenated butyl rubbers and a method for their preparation, characterized in that the butyl rubber is treated with a halogenating agent in the gas phase or in the presence of an organic solvent until the halogen content in the rubber reaches 0.5-2.5% by weight and the content of non-halogenated double bonds is more than 0.7 % mol., while the halogenated butyl rubber contains 1.0-2.2% wt. substances that control the processes of anti-agglomeration and vulcanization [RF Patent 2212417, С08С 19/12, 19/14, C08F 8/18, 8/20, publ. 09/20/2003]. For halogenation in accordance with this invention using standard butyl rubber from Bayer-Rabber - Polysar Butyl 301, obtained in a known manner, including described in the patent [RF No. 2373234, C08L 23/18, 23/20, 23/22, 25/08, 25/16, publ. November 20, 2009]. The disadvantage of this method is that in the synthesis of further halogenated butyl rubber isobutylene is used, containing less than 99.97% wt. the main substance, and isoprene containing less than 99.1% of the main substance, the dosage of the catalyst is more than 0.5% wt. on isobutylene. This leads to the production of butyl rubber with a fairly wide molecular weight distribution (the polydispersity of the polymer is in the range 2.5-3.1).

The introduction of halogen in the polymer chain of butyl rubber significantly changes its properties: adhesion, vulcanization activity and one of the main properties are gas impermeability of rubbers based on the obtained polymer. It is the increased gas impermeability of rubbers based on halogenated butyl rubber that makes it suitable for the production of the base of a hermetic layer of tubeless tires. The value of gas impermeability substantially depends on the halogen content in halobutyl rubber - it grows with its increase. However, an increased halogen content in rubber requires an increased content of stabilizing agents such as salts of fatty acids (e.g., calcium stearate) and epoxidized oils (e.g., epoxidized soybean oil). Stabilizing agents interfere with the dehydrohalogenation reaction and, accordingly, premature vulcanization (scorching). The gas impermeability also substantially depends on the molecular weight distribution of the butyl rubber in the polymer: the higher the polydispersity, the lower the gas impermeability. The use of basic butyl rubber with high polydispersity for the production of halobutyl rubber leads to the need to introduce an increased amount of halogen into it (at the upper limit of specification values), and this in turn requires an increased amount of stabilizing agents, which worsen the polymer drying process on extrusion machines. Therefore, it is precisely the increased polydispersity of basic butyl rubber that is the main disadvantage of the method for producing halobutyl rubber in accordance with the analogue.

Closest to the claimed one is a method for producing bromobutyl rubber by treating a solution of butyl rubber in an inert hydrocarbon solvent with a brominating agent, neutralizing the brominated butyl rubber solution with an aqueous alkali solution, water degassing and drying the brominated butyl rubber, recovering the bromine from the wash water and returning it to Patent RF 95 8/20, 6/06, C08C 19/12, publ. 01/10/2002]. In this method, halogenated butyl rubber is prepared by copolymerizing isobutylene with isoprene in chloromethyl medium in the presence of a Friedel-Crafts catalyst. The content of isobutylene in the mixture is maintained in the range of 20-30% wt. Isoprene is metered into the charge in quantities that ensure the unsaturation of butyl rubber in the range of 1.6-2.0 mol%. This method involves the production of butyl rubber specifically for halogenation, but does not have the technology for the production of basic butyl rubber with low polydispersity, which allows, with a reduced content of halogen and stabilizing reagents in halobutyl rubber, made from such specially produced butyl rubber, to obtain rubber for a hermetic layer with increased gas impermeability.

The objective of the invention is to reduce the number of stabilizing reagents in halobutyl rubber with a simultaneous increase in the gas impermeability of the rubber obtained from it.

This problem is achieved in that halobutyl rubber is obtained by the method of interaction of halogen and butyl rubber obtained by the method of low-temperature suspension copolymerization of isobutylene with isoprene on a catalyst aluminum chloride in chloromethyl medium, characterized in that isobutylene contains at least 99.97% wt. the main substance, isoprene contains at least 99.1% wt. the main substance, while the dosage of aluminum chloride is 0.01-0.1% wt. for isobutylene and the catalyst is used in the presence of an activator of the protogenic or cationogenic type, taken in an amount of 1.0-0.01 mol per 1 mol of aluminum chloride, the dosage of isoprene is 2.0-3.5% wt. on isobutylene.

As a protogenic or cationogenic activator, for example, water, hydrogen chloride, benzyl chloride, ethyl chloride, isopropyl chloride, tert-butyl chloride, a chlorinated isobutylene dimer, etc. can be used.

The proposed method is illustrated by the following examples.

Example 1 (prototype). Butyl rubber is obtained by copolymerization of isobutylene with isoprene in the presence of a catalyst - aluminum chloride. The isobutylene content in the charge is 25% wt., Isoprene - 0.9 wt.%, Chloromethyl - 74.2 wt.%. The dosage of the catalyst is aluminum chloride - 0.2 wt.% On isobutylene. Polymerization temperature minus 95 ° C. After degassing, butyl rubber crumbs are dissolved in hexane. The resulting solution of butyl rubber in hexane with a polymer concentration of 17.5% at a temperature of 20 ° C is fed for halogenation with bromine and bromine-containing hydrocarbon solvent solution. The total dosage of bromine is maintained so that the bromine content in the rubber reaches 2.4%. The brominated rubber solution is washed with water, neutralized with alkali, degassed and, after averaging, sent to extrusion apparatuses, where the rubber is dried at a temperature of 147-150 ° C. Before degassing, an antioxidant (Irganox 1076) is introduced into the rubber solution at a rate of 0.08% per polymer, an anti-agglomerator (calcium stearate) at a rate of 2.0% per polymer, and a dehydrohalogenation stabilizer (epoxidized soybean oil) at a rate of 1.5% per polymer.

The resulting bromobutyl rubber is analyzed for the bromine content, the content of antioxidant, anti-agglomerating and stabilizing components, the molecular weight distribution (polydispersity), the rate of vulcanization and the gas-tightness of rubber are determined according to the recipe for the hermetic layer of tubeless tires. To assess the gas tightness, the diffusion coefficient of compressed air at 25 ° C for 8 hours is determined. The lower this indicator, the higher the gas impermeability.

Example 2. The process is carried out as in example 1, except that the isobutylene used for copolymerization contains 99.99 wt.% The basic substance, and isoprene - 99.5 wt.% The basic substance. The isoprene content in the charge is 0.75%, the dosage of aluminum chloride is 0.05% for isobutylene. Benzyl chloride (cationogen) is dosed into the charge line in an amount of 0.05 mol per 1 mol of aluminum chloride. When bromination, the dosage of bromine is maintained so that its amount in rubber is 1.8% wt. An anti-agglomerator (calcium stearate) is dosed into a solution of bromobutyl rubber before degassing at a rate of 1.6 wt.%, A dehydrohalogenation stabilizer (epoxidized soybean oil) at a rate of 1.2 wt.% Per polymer.

Examples 3-4. The experiments are carried out as in example 2, except that the isobutylene used for copolymerization contains 99.97% (example 3) and 99. 95% (example 4) of the main substance.

Examples 5-6. The experiments are carried out as in example 2, except that the isoprene used for copolymerization contains 99.1% (example 5) and 89.5% of the main substance (example 6).

Examples 7-10. The experiments are carried out as in example 2, except that the dosage of aluminum chloride during copolymerization is 0.007% wt. (example 7), 0.01% wt. (example 8), 0.1% wt. (example 9), 0.15% wt. (example 10).

Examples 11-13. The experiments are carried out as in example 2, except that benzyl chloride is dosed into the charge line in an amount of 0.005 moles per 1 mol of aluminum chloride (example 11), 0.01 mol per 1 mol of aluminum chloride (example 12), from 0.1 mol per 1 mol of aluminum chloride (example 13).

Example 14-15 The experiments are carried out as in example 2, except that water is used as a protogenic agent in an amount of 1.5 moles per 1 mol of aluminum chloride (example 14) and 1 mol per 1 mol of aluminum chloride (example 15).

Example 16. The experiment is carried out as in example 2, except that the polymerization is carried out without a protogenic or cationogenic agent.

Example 17. The experiment is carried out as in example 2, except that chlorine is used as a halogenating agent with a dosage such that its rubber content is 1.2% wt. and before degassing, an antioxidant (Irganox 1010) is introduced into the rubber solution at a rate of 0.08% per polymer, an anti-agglomerator (calcium stearate) at a rate of 1.0% per polymer and a dehydrohalogenation stabilizer (epoxidized soybean oil) at a rate of 0.3% per polymer.

Examples 18-21. The experiments are carried out as in example 2, except that the concentration of isoprene in the mixture is 0.45% (example 18), 0.5% (example 19), 0.87% (example 20), 0.95% (example 21).

The data obtained during the implementation of the methods in accordance with examples 1-21 are shown in the table.

It can be seen from the table that the objective of the invention is achieved if the isobutylene used to obtain the base polymer contains at least 99.97% of the basic substance, with a decrease in this value, the polydispersity of the polymer increases and, accordingly, the gas impermeability of rubber based on halobutyl rubber obtained by this method is significantly reduced. The same is observed when using isoprene with a basic substance content below 99.1%. The optimal dosage of the catalyst is 0.01-0.1% wt. on isobutylene.

When reducing the dosage of the catalyst below 0.01% wt. good quality halobutyl rubber is obtained, but the yield of the base polymer is significantly reduced. With an increase in the dosage of the catalyst above 0.1% wt. on isobutylene, the polydispersity of rubber increases and gas impermeability worsens.

When polymerization is carried out without a protonogenic or cationogenic agent, the dosage of the catalyst increases, the polydispersity of both the base polymer and, accordingly, GBK increases, and if this does not increase the bromine content in the rubber, but leave it at 1.8, which allows an acceptable polymerization rate at a low dosage of stabilizing agents then the gas impermeability of the rubber will decrease significantly. The optimal amount of protogenic or cationogenic agent is 1.0-0.01 mol per 1 mol of aluminum chloride. When using a cationic agent (benzyl chloride) in an amount of less than 0.01 mol per 1 mol of aluminum chloride, the catalyst consumption increases, which in turn increases the polydispersity of rubber and reduces the gas impermeability of rubber. An increase in the dosage of the protogenic agent (water) over 1 mol per 1 mol of aluminum chloride can lead to a significant decrease in the Mooney viscosity of both the base polymer and GBA. The optimal dosage of isoprene upon receipt of the base polymer is 2.0-3.5% wt. on isobutylene. With a decrease in this dosage, it is impossible to introduce the required amount of halogen into the base polymer without a significant drop in Mooney viscosity, the amount of polymer introduced is 1.5% per polymer, which significantly impairs the rheometric properties of halobutyl rubber, increases above the optimal T90, and accordingly the gas impermeability of rubber based on it decreases.

With an increase in the dosage of isoprene above 3.5% for isobutylene, the gas impermeability index increases, but the vulcanization process accelerates and the T90 index is much lower than the optimal limits.

Claims (1)

The method of producing halobutyl rubber by the interaction of halogen and butyl rubber obtained by the method of low-temperature suspension copolymerization of isobutylene with isoprene on a catalyst aluminum chloride in chloromethyl medium, characterized in that isobutylene contains at least 99.97 wt.% Of the basic substance, isoprene contains at least 99.1 wt.% Of the main substance wherein the dosage of aluminum chloride is 0.01-0.1 wt.% on isobutylene and the catalyst is used in the presence of an activator of protogenic or cationogenic type, taken if 1.0–0.01 mol per 1 mol of aluminum chloride; the dosage of isoprene during copolymerization is 2.0–3.5 wt% per isobutylene.