RU2155194C1 - Butyl rubber production process - Google Patents

Abstract

FIELD: rubber industry. SUBSTANCE: process consists in isobutylene-isoprene copolymerization in methyl chloride diluent in presence of Friedel-Crafts catalyst and includes deactivation of catalyst, degassing of rubber, condensation, compression, drying, and rectification of non-polymerized monomers and diluent. Process also includes separation and drying of rubber and preparation of charge mixture. Before the latter operation, isobutylene is regenerated by hydration into trimethyl carbinol, which is dehydrated back into isobutylene. The latter is further purified by washing with water to remove carbonyl- and nitrogen-containing soluble compounds followed by additional removal of butylenes and butadiene, azeotropic drying, treatment with dry alkali at liquid isobutylene supply volume rate from 2.5 to 10.0 and temperature 35 to 65 C. EFFECT: enhanced process efficiency. 1 dwg, 10 ex

Description

 The invention relates to a technology for the production of synthetic rubbers, in particular butyl rubber, used for the manufacture of automobile cameras, rubber products, halobutyl rubber, and can be used in the petrochemical industry.

 A known method of producing butyl rubber by copolymerization of isobutylene with isoprene in a hydrocarbon solvent in the presence of a catalyst, followed by deactivation of the catalyst, distillation of the diluent and non-polymerized monomers in several stages of degassing, condensation of distilled off degassing vapors, their compression, drying and distillation, isopolymerization, including , isoprene and return methyl chloride-isobutylene fraction, averaging the dispersion of rubber, concentration rirovanie rubber and drying in a worm-nip drying units [ "Synthetic Rubber", edited by I. Garmonova.- L .: Chemistry, 1983, p. 293-300].

 One of the main disadvantages of this method is that isobutylene rectified is not subjected to purification from water-insoluble compounds such as propionic and acetic aldehyde, urea compounds, acetonitrile and other impurities that inhibit the copolymerization process.

 The impurities formed during the copolymerization process are also not purified by return isobutylene. All this reduces the uniformity of rubber, worsens its technical and economic indicators.

The closest in technical essence to the claimed method is a method for producing butyl rubber, which consists in the copolymerization of isobutylene with isoprene at a temperature of about -100 ^o C in a medium of methyl chloride in the presence of an aluminum chloride catalyst, in the subsequent conclusion of the reaction mixture containing polymer, non-polymerized monomers and methyl chloride for degassing at 70 ^o C and processing return product - hydrocarbon condensate degassing vapors - distillation and the direction of them for the preparation of the charge d polymerization in the form of a return methyl chloride-isobutylene fraction, withdrawal of isobutylene and isoprene, distilled off during rectification of the hydrocarbon condensate for regeneration, isolation of rubber from the aqueous dispersion and its drying, which also includes isolation of isobutylene from isobutylene-containing fractions obtained from the dehydrogenation of isobutene isomerization, pyrolysis normal butylene, by hydration in trimethylcarbinol and its dehydration [P.A. Kirpichnikov, V.V. Beresnev, L.M. Popova, "The album of technological schemes of the main industries of the synthetic rubber industry" .- L .: Chemistry, 1976, p. 43-44, 70-74].

The disadvantage of this method is the lack of a scheme for the deep purification of isobutylene rectified or its mixture with return isobutylene from both soluble and practically water-insoluble impurities that inhibit the copolymerization of isobutylene with isoprene. Even with stable operation, the washing stage of the initial isobutylene-containing fractions used for hydration of isobutylene to trimethylcarbinol from nitrogen-containing and carbonyl compounds, the washing stage of trimethylcarbinol and the separation of isobutylene dimers from the decomposition products of trimethylcarbinol in isobutylene do not exclude the inclusion of trace impurities from heavy impurities from isobutylene with isobutylene dimers and trimers of isobutylene, sec-butanol, C ₅ hydrocarbons, ethers and heavy residue, especially when concurrently Hinnom isobutylene using different fractions.

 The carbonyl, nitrogen-containing and urea compounds remaining in the dried isobutylene rectified product reduce the efficiency of the copolymerization of isobutylene with isoprene and worsen the uniformity of butyl rubber.

 The aim of the invention is to increase the efficiency of the copolymerization process, the uniformity of butyl rubber and reduce energy costs.

This goal is achieved by the fact that in the proposed method for producing butyl rubber, including the production of isobutylene by hydration to trimethylcarbinol and the dehydration of trimethylcarbinol to isobutylene, the preparation of a mixture from isobutylene and isoprene, copolymerization of the mixture in a diluent - methyl chloride in the presence of a Friedel-Crafting catalyst, a deactivation catalyst, and catalyst rubber, processing of unpolymerized monomers and diluent - methyl chloride by condensation, compression, drying and rectification, effluent, drying of rubber, isobutylene with other decomposition products of trimethylcarbinol obtained by dehydration of trimethylcarbinol to isobutylene, or its mixture with return isobutylene formed during the processing of non-polymerized monomers during rectification, is first washed with water from carbonyl and nitrogen-containing impurities and then separated from soluble impurities, then separated butenes and butadiene, azeotropic drying, is treated with dry alkali at a volumetric feed rate of liquid isobutylene of 2.5-10.0 h ^-1 and a temperature of 35-65 ^o C and served on the preparation of the mixture.

 In contrast to the known method, these techniques will allow due to aldol-proton condensation and chemical interaction with dry alkali at high temperatures, as well as due to optimal washing with water, significantly reduce the content of propionic and acetic aldehyde, urea compounds, acetonitrile and other nitrogen-containing compounds in isobutylene -fixed.

 The proposed method is carried out according to the scheme shown in the drawing, as follows.

The isobutylene-containing fraction obtained by the pyrolysis of hydrocarbon feedstock, isobutane dehydrogenation, normal butenes isomerization, after washing from nitrogen-containing compounds, is sent via line 1 to stage 2 of isobutylene hydration to trimethylcarbinol (tert-butyl alcohol) in the presence of water and the sulfated solution is separated, the solution is separated by water, C ₄ hydrocarbons and C _5, in particular from α-β-butenes and butene output line 3 for processing and fed through line 4 to step 5 concentration aqueous sol Dr. trimethyl carbinol.

The purified and concentrated aqueous solution of trimethylcarbinol through line 6 is sent to stage 7 of dehydration of trimethylcarbinol in the presence of sulfocationite, the reaction products are sent via line 8 and washed in column 9 from trimethylcarbinol and carbonyl compounds with water supplied through line 10, and isobutylene is isolated via line 11 by distillation in column 12, the heavy residue, esters, dimers and trimers of isobutylene, secondary butanol and C ₅ hydrocarbons from the bottom of the column 12 through line 13 are led to line 1 for supplying feedstock to hydration, and isobutylene at the top of column 12 is sent via line 14 to column 15 of azeotropic drying of isobutylene. Water from the bottom of the dehydrator 7 is returned to stage 2 of isobutylene hydration (not shown in the diagram).

 In contrast to the known method, washing the reaction products of the decomposition of trimethylcarbinol from alcohols and carbonyl compounds with water is carried out without an internal circulation circuit only when using direct flow, which improves the quality of the products and significantly reduces the content of trace elements in isobutylene rectified.

The volumetric flow rate of water for washing 0.5-1.5 h ^-1 . Dried isobutylene rectified from the bottom of the column 15 through line 16 is fed for treatment with dry alkali (potassium hydroxide or sodium hydroxide) to the apparatus 17. The processing of isobutylene rectified is carried out at a volumetric feed rate of liquid isobutylene of 2.5-10.0 h ^-1 and a temperature of 35-65 ^o C, and the isobutylene rectified is served in several streams, one is sent to line 16 to the apparatus 17 and passed through several shelves loaded with granular solid alkali (on the carrier or without it), the second stream is fed through lines 18 and 19 for keeping volume I have the feed rate of isobutylene in the range of 2.5-10.0 h ^-1 with a change in the consumption of isobutylene for blending, and the third stream can be sent along line 20 to achieve the same goal and stabilize the pH of the total flow of isobutylene rectified within 7.0- 8.0.

 If necessary, solid alkali in the form of pieces can be used. In contrast to the known method, maintaining the volumetric rate of processing of isobutylene with dry alkali within the indicated limits allows only the content of carbonyl compounds to be reduced by 7-8 times, and the use of two streams, one of which is treated with dry alkali, the second is passed without treatment, allows to withstand the pH of isobutylene in such ranges as to stabilize the pH of the mixture for polymerization at the level of 6.5-7.0.

 The use of several shelves for solid alkali significantly increases the efficiency of alkali and improves cleaning.

The implementation of the processing of isobutylene with solid dry alkali at a temperature of 35-65 ^o C allows you to clean not only poorly washed carbonyl compounds due to the condensation reaction and turning them into resins, but also to bind cyclopentadiene, carbonyl compounds and some nitrogen-containing compounds.

 Product discharged from the top of column 15 via line 21 is fed to column 9.

 The purified isobutylene rectified on line 22 is fed into the tank 23, where return isobutylene extracted from the hydrocarbon condensate of the degassing vapors by distillation is introduced via line 24, and the return methyl chloride-isobutylene fraction, also distilled during rectification of the hydrocarbon condensate from butyl rubber degassing vapors, is introduced through line 25. After mixing with isoprene sent via line 26, a hydrocarbon mixture is obtained for the copolymerization of isobutylene with isoprene, which is introduced via line 27 to the inlet of pump 28 and then fed through line 29 to copolymerization in a reactor 30 carried out in the presence of a Friedel-Crafts catalyst, for example, chloride aluminum fed through line 31. The reaction products — a dispersion of butyl rubber in methyl chloride, unpolymerized isobutylene and isoprene — are withdrawn from the reactor 30 through line 32 to degass the butyl rubber in the presence of circulating water vapor hot water, an anti-agglomerator of rubber crumb and an antioxidant (these flows are not shown in the diagram), carried out in a degassing system 33, consisting of two or more degassing stages, operating under slight overpressure in the first stage and a vacuum of 0.04-0.08 MPa subsequent stages of degassing. The dispersion of rubber in water is taken out through line 34 to concentrate, isolate and dry the rubber in compartment 35, and the degassing vapors containing methyl chloride, non-polymerized isobutylene and isoprene, water is fed through line 36 to condensation, compression and drying (not shown in the diagram) and further the hydrocarbon condensate of the degassing vapors is collected in a container 37, from where, through a line 38, a pump 39 is sent through a line 40 to a column 41. At the top of the column 41, methyl chloride is taken via line 42 to prepare a Friedel-Crafts catalyst solution.

 The bottoms product from column 41 is sent through line 43 to column 44. From the upper part of column 44, the methyl chloride isobutylene fraction is withdrawn via line 25 to a vessel 23 for preparing a charge for polymerization. The bottoms product from column 44 via line 45 is fed to column 46 to distill off the isobutylene return from line 24. Return products can also be processed in a different way. The return isobutylene stream is divided into two streams, the first in the amount of 30-70% of the total mass is sent via line 24 to the preparation of the charge, and the second in the amount of 70-30% of the total mass is sent for purification from butenes and butadiene together with the isobutylene-containing fraction of hydrocarbons the process of producing isobutylene along line 47 and then along lines 48 or 49, respectively, for mixing with an isobutylene-containing fraction supplied through line 1 to stage 2 of hydration of isobutylene into trimethylcarbinol, where α-butene and β-butene are distilled off, but also butadiene, or with the products of dehydration of trimethyl carbinol.

 An aqueous solution of alkali and resinous products from the apparatus 17 are sent along line 50 to mix with water discharged from the isobutylene hydration compartment, and then fed to the afterburner.

The finished rubber is brought to packaging on line 51. At the stage of trimethylcarbinol hydration, butenes and butadiene are distilled off with a C ₃ -C ₅ hydrocarbon fraction, which is separated from the aqueous trimethylcarbinol solution in the process of its concentration at stage 5. With minor amounts of butenes and butadiene in the isobutylene return the latter is directed to mixing with the products of dehydration of trimethylcarbinol in stage 7, in particular, before water washing the decomposition products of trimethylcarbinol or before the isolation of isobutylene and its azeotropic by drying.

 The method is illustrated by the following examples.

 Example 1

 Butyl rubber is produced by a known method (prototype).

A mixture of isobutylene, isoprene and methyl chloride, containing 25 wt.% Isobutylene, 0.75 wt.% Isoprene and 74.25 wt.% Methyl chloride, is introduced in an amount of 50 g into a laboratory reactor with a volume of 100 ml, cooled to a temperature of -100 ^o C and serves 0.05% aluminum chloride by weight of the monomers.

In this case, isobutylene rectified of the following composition is used, wt.%:
isobutane = 0.001
α-butene = 0.002
β-butene = 0.002
carbonyl compounds = 0.0013
trimethylcarbinol = 0.0001
acetylene compounds = traces
butadiene = 0.00003
isobutylene = 99.99
Isoprene rectified of the following composition, wt.%:
isoprene = 92.0
acetylene compounds = 0,0004
cyclopentadiene = 0,0005
nitrogen containing compounds = 0,0003
isopentane = 6.5
isoamylene = 1.5
The copolymerization time was 15 minutes, the polymerization temperature increased from -98 to -92 ^o C. The concentration of the catalyst in methyl chloride was 0.12 wt.%.

Key indicators of the copolymerization process:
polymer yield - 65.1%
unsaturation - 1.53 mol.%
the molecular weight of the polymer x 10 ³ ,
units Staudinger - 80.3
Examples 2-4.

The copolymerization is carried out according to the proposed method. Isobutylene rectified composition similar to that shown in example 1, is subjected to further purification by treatment with solid potassium alkali. The processing temperature is varied in the range of 35-65 ^o C, the volumetric feed rate of liquid isobutylene rectified is 10.0 h ^-1 . All copolymerization modes are similar to example 1.

Return isobutylene is fed via line 48 to the hydration step.
The main indicators of the copolymerization process are given in table. 1.

 Examples 5-7.

The copolymerization is carried out according to the proposed method. Isobutylene rectified is subjected to additional purification by feeding with dry potassium alkali before being fed to the batch. Processing temperature 45 ^o C. Volumetric feed rate of 2.5-10.0 h ^-1 . The copolymerization mode is similar to Example 1. Return isobutylene is fed through line 49.

 The main indicators of alkali treatment and copolymerization are given in table. 2.

With an increase in the volumetric rate of processing of isobutylene with solid alkali to 15.0 h ^{-1, the} content of carbonyl compounds was 0,00045 wt.%.

 Examples 8-10.

The copolymerization of isobutylene with isoprene is carried out according to the known and proposed methods. According to the known method, the decomposition products of trimethylcarbinol in isobutylene are washed with water at a water supply of 1 h ^-1 and a working internal circulation circuit (example 8). According to the proposed method, the decomposition products of trimethylcarbinol in isobutylene are washed with water only when it is supplied countercurrently without its internal circulation, the water flow rate is also maintained for 1 h ^-1 , and the isolated isobutylene rectified is treated with dry potassium alkali at a temperature of 40 ^o C and a feed rate of liquid isobutylene 10 h ^-1 (example 9). In example 10, the proposed method is used, only 80% of isobutylene is subjected to alkali treatment, the remaining 20% is sent without contact with alkali.

 In examples 9 and 10, the return isobutylene is fed through line 49.

 The main process indicators are given in table. 3.

 As can be seen from the examples, the proposed method for producing butyl rubber allows, due to cleaner isobutylene, to significantly improve the quality of butyl rubber, to increase the productivity of the copolymerization process by 10-15%.

Claims (1)

A method of producing butyl rubber, including the production of isobutylene by hydration to trimethylcarbinol and the dehydration of trimethylcarbinol to isobutylene, the preparation of a mixture from isobutylene and isoprene, copolymerization of the mixture in a diluent-methyl chloride medium in the presence of a Friedel-Crafts catalyst, deactivation of the catalyst, degassing methyl chloride by condensation, compression, drying and rectification, isolation, drying of rubber, characterized in that with other decomposition products of trimethylcarbinol obtained by dehydration of trimethylcarbinol into isobutylene, or a mixture of it with refluxing isobutylene formed during the processing of unpolymerized monomers during distillation, is first washed with water from carbonyl and nitrogen-containing soluble impurities, then after separation from butene and butene butene and butene and drying the treated dry alkali at a volumetric flow rate of liquid isobutylene 2.5 - 10.0 hr ^-1 and a temperature of 35 - 65 ^o C and fed to the preparation of ihty.

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