RU2554343C1 - Method of obtaining bromobutyl rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method consists in interaction of molecular bromine and butyl rubber, synthesised by method of low-temperature copolymerisation of isobutylene with isoprene. Molar ratio of quantity of isoprene units in base butyl rubber and amount of halogen in bromobutyl rubber is preserved within 1.5-1.26. Residual content of non-halogenated double bonds in bromobutyl rubber is lower than 0.7 mol %, preferably 0.6-0.3 mol %.

EFFECT: improvement of technological properties of raw rubber mixtures based on bromobutyl rubber by hermolayer formulation with preservation of gas-impermeability index in obtained vulcanisates, obtained on its base.

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Description

The invention relates to a method for producing halogenated polymers, in particular bromobutyl rubbers, and can be used in the petrochemical and chemical industries. The bromobutyl rubbers obtained by the bromination of butyl rubber are mainly used to obtain a hermetic layer of tubeless tires and, therefore, their properties must correspond to this application, i.e. they must have high gas impermeability and good technological properties when processing raw rubber compounds according to the hermetic compounding.

Known halogenated 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 wt.%, And the content of non-halogenated double bonds of more than 0.7 mol.%, while the halogenated rubber contains 1.0-2.2 wt. substances that control the processes of anti-agglomeration and vulcanization [RF patent 2212417, C08C 19/12, 19/14, C08F 8/18, 8/20, publ. 09/20/2009]. The disadvantage of this method is that for the synthesis of halobutyl rubber, butyl rubber with high polydispersity is used, the value of which follows from the method for producing basic butyl rubber, carried out in accordance with the patent of the Russian Federation [RF patent 2373234, C08L 23/18, 23/20, 23/22, 25 / 08, 25/16, publ. November 20, 2009]. In accordance with this patent, the dosage of the polymerization catalyst in the synthesis of the base polymer is more than 0.5 wt.% On isobutylene, which leads to a wide molecular weight distribution of base butyl rubber and, accordingly, halobutyl rubber based on it. The high polydispersity of halobutyl rubber reduces the gas impermeability of rubbers based on it, to increase it, it is necessary to increase the halogen content of the rubber, and this, in turn, entails the need to increase the number of stabilizing additives that worsen the drying process of rubber on extrusion machines.

There is also known 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, with the bromine being separated from the wash water and returning it to halogenation, RF Patent No. 218/206/8 6/06, C08C 19/12, publ. 01/10/2002]. In this method, halogenated butyl rubber is prepared by copolymerizing isobutylene with isoprene in chloromethyl in the presence of a Friedel-Crafts catalyst. At the same time, isoprene is dosed into the mixture in amounts that ensure 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 of producing butyl rubber and, accordingly, halobutyl rubber with low polydispersity, which allows obtaining rubber with increased gas impermeability with a reduced content of halogen and stabilizing additives.

Closest to the claimed is a method for producing bromobutyl 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, while isobutylene contains at least 99.97 wt.% Of the basic substance, while the dosage of aluminum chloride is 0.01-0.1 wt.% on isobutylene and the catalyst is used in the presence of a protogenic type activator, and the dosage of isoprene is 2.0-3.5% on isobutylene [Pat NT RF 2439084, C08F 8/20, C08F 8/22, C08C 19/12, C08C 19/14, publ. 01/10/2012]. This allows to reduce the halogen content in halobutyl rubber while increasing the gas impermeability of the rubbers obtained from it. Halobutyl rubber is characterized by low polydispersity in comparison with analogues. The main disadvantage of this method is the increased number of non-halogenated double bonds in halobutyl rubber, which, together with its low polydispersity, leads to an increase in the viscosity and stiffness of raw rubber compounds according to the hermetic layer formulation, as well as to a deterioration of scorching performance and, accordingly, to a deterioration of technological properties during processing.

The objective of the invention is to improve the technological properties of crude rubber compounds based on bromobutyl rubber according to the hermetic layer formulation while maintaining the gas impermeability index of vulcanizates obtained on its basis.

This problem is achieved in that the bromobutyl rubber is prepared by the interaction of molecular bromine and butyl rubber synthesized by low-temperature copolymerization of isobutylene with isoprene, characterized in that the molar ratio of the number of isoprene units in the base butyl rubber and the amount of halogen in the bromobutyl rubber is kept within the range of 1.5-1.2, 6 6 and the residual content of non-halogenated double bonds in bromobutyl rubber is below 0.7 mol%, preferably 0.6-0.3 mol%.

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. Isobutylene used for polymerization contains 99.99 wt.% Of the basic substance, isoprene - 99.5 wt.% Of the main substance. The isoprene content in the charge is 0.75 wt.%, The dosage of aluminum chloride is 0.05% per isobutylene. The uncertainty of the base rubber is 2.0 mol%. When bromination, the dosage of bromine is maintained so that its amount in rubber is 1.7 wt.%, The residual content of non-halogenated double bonds is 0.73 mol.%. An anti-agglomerator (calcium stearate) is dosed into a solution of bromobutyl rubber before degassing at the rate of 1.6 wt.%, A dehydrohalogenation stabilizer (epoxidized soybean oil) is calculated at 1.2 wt.% Per polymer.

The resulting bromobutyl rubber is analyzed for bromine content, its molecular weight distribution, vulcanization rate, Mooney viscosity of the crude rubber compound in the hermetic layer formulation, scorching indices (T35), and gas impermeability of the vulcanizates are determined.

Example 2

The experiment is carried out as in example 1, except that the unsaturation of the base butyl rubber is maintained at 1.7 mol.%, The molar ratio of the number of isoprene units in the basic butyl rubber and the amount of halogen in bromobutyl rubber is maintained at 1.4, and the residual content of non-halogenated double bonds in bromobutyl rubber is 0.5 mol.%.

Example 3

The experiments are carried out as in example 2, except that the unsaturation of the base rubber is maintained at 1.8 mol%, the molar ratio of the number of isoprene units in the base butyl rubber and the amount of halogen in the bromobutyl rubber is 1.5, and the residual content of non-halogenated double bonds in bromobutyl rubber is 0.6 mol.%.

Example 4

The experiments are carried out as in example 2, except that the unsaturation of the base rubber is maintained at the level of 1.5 mol%, the molar ratio of the number of isoprene units in the base butyl rubber and the amount of halogen in the bromobutyl rubber is 1.26, and the residual content of non-halogenated double bonds in bromobutyl rubber is 0.3 mol.%.

Example 5

The experiments are carried out as in example 2, except that the unsaturation of the base rubber is maintained at the level of 1.9 mol%, the molar ratio of the number of isoprene units in the base butyl rubber and the amount of halogen in the bromobutyl rubber is 1.6, and the residual content of non-halogenated double bonds in bromobutyl rubber is 0.71 mol.%.

Example 6

The experiments are carried out as in example 2, except that the unsaturation of the base rubber is maintained at 1.4 mol.%, The molar ratio of the number of isoprene units in the base butyl rubber and the amount of halogen in bromobutyl rubber is 1.2, and the residual content of non-halogenated double bonds in bromobutyl rubber is 0.25 mol.%.

Data on the analysis of rubbers obtained in accordance with examples 1-6 are shown in table 1.

From the data of the table it can be seen that the purpose of the invention is achieved if the molar ratio of the number of isoprene units in the basic butyl rubber is maintained in the range of 1.5-1.26. When this ratio is increased (as in the prototype), the viscosity of the crude rubber compound according to the hermetic layer formulation significantly increases, which significantly complicates the processing. In addition, scorching performance deteriorates - the time of vulcanization is reduced (T5 and T35). When this ratio decreases, the gas permeability index worsens - the gas permeability coefficient increases.

To achieve the objective of the invention, the residual amount of non-halogenated double bonds should be below 0.7 mol%. With an increase in this indicator, the viscosity of the crude rubber compound increases and scorching performance deteriorates. The optimal limits of 0.6-0.3 mol.%. By reducing the number of bonds below 0.3, the goal is achieved, but this increases gas permeability.

Claims (1)

A method of producing bromobutyl rubber by the interaction of molecular bromine and butyl rubber synthesized by the low-temperature copolymerization of isobutylene with isoprene, characterized in that the molar ratio of the number of isoprene units in the basic butyl rubber and the amount of halogen in the bromobutyl rubber is kept in the range of 1.5-1.26, and the residual bonds in bromobutyl rubber below 0.7 mol. %, preferably 0.6-0.3 mol. %