RU2758384C1 - Method for producing styrene-butadiene rubber - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of styrene-butadiene rubbers produced by emulsion (co)polymerisation. The method for producing styrene-butadiene rubber is implemented by copolymerisation of butadiene with styrene in an emulsion in the presence of radical initiators. Executed then are stoppering of the process, degassing, introduction of an antioxidant, and isolation of rubber from latex by coagulation. The latex is mixed with nitrogen-containing coagulating and acidifying agents at 0 to 10°C. The rubber chips are washed at 50 to 70°C. An aqueous phase (serum) is used in order to prepare solutions of the coagulating and acidifying agents.

EFFECT: reduction in the consumption of coagulating agents, the environmental pollution by products of rubber production by emulsion copolymerisation, improvement in the physical and mechanical parameters of vulcanisates.

1 cl, 5 tbl, 5 ex

Description

The invention relates to the production of styrene-butadiene rubbers obtained by emulsion (co) polymerization.

A known method of producing styrene-butadiene rubbers using poly-N, N-dimethyl-N, N-diallyl-ammonium chloride as a coagulating agent (Nikulin S.S., Verezhnikov V.N., Poyarkova T.N., Vostrikova G.Yu. Influence of the concentration of the dispersed phase on the regularities of the release of rubber from latex. Journal of Applied Chemistry, vol. 73, Issue 10, 2000, pp. 1720-1724), produced on an industrial scale under the brand name VPK-402. The consumption of this coagulant for the extraction of one ton of SKS-30 ARK rubber is 3-5 kg.

The disadvantages of this method for producing styrene-butadiene rubber are a rather high consumption of VPK-402 and, most importantly, a high sensitivity of the process to an overdose of this coagulating agent, which creates increased difficulties when working with it in real industrial conditions. In case of an overdose of VPK-402, the components of the emulsion system are lost, the productivity of the process decreases and the contamination of industrial wastewater by the components of the emulsion system increases.

The closest in technical essence is a method of producing styrene-butadiene rubber by copolymerizing butadiene with styrene in an emulsion in the presence of radical initiators, stopping the process, degassing, introducing an antioxidant and isolating rubber from latex by coagulation [Kirpichnikov P.A., Averko-Antonovich L. A., Averko-Antonovich Yu.O. Chemistry and technology of synthetic rubber: Textbook for universities. - 3rd ed., Rev. - L .: Chemistry, 1987. - 424 p., Ill.] Using sodium chloride as a coagulating agent.

The main disadvantages of this method for producing styrene-butadiene rubbers are:

- high consumption of sodium chloride per 1 ton of emitted rubber -150-200 kg;

- environmental pollution with a coagulating agent, sodium chloride, components of the emulsion system, etc.;

- low resistance to thermal oxidative effects;

- pollution of natural water bodies with a hepatotoxic dispersant with leukanol.

The technical problem to be solved by this invention is to stabilize the process of extracting rubber from latex, reducing the consumption of coagulating agents, environmental pollution by products of rubber production by emulsion copolymerization, improving the physical and mechanical properties of vulcanizates.

The task is achieved by the fact that in the method of producing styrene-butadiene rubber by copolymerizing butadiene with styrene in an emulsion in the presence of radical initiators, stopping the process, introducing an amine or phenolic antioxidant, degassing and isolating rubber from latex by the coagulation method, it is new that mixing latex with nitrogen-containing coagulating and acidifying agents, it is carried out at 0-10 ° C and using an aqueous phase (serum) to prepare solutions of coagulating and acidifying agents.

The proposed method for producing styrene-butadiene rubber allows to reduce the consumption of coagulating agents, environmental pollution by products from the production of rubbers by emulsion copolymerization, to improve the physical and mechanical properties of vulcanizates.

In order to use some nitrogen-containing organic compounds in the processes of extracting rubber from latex, it was necessary to convert them into a water-building state. For example, benzotriazole is insoluble in water. However, benzotriazole gives salts with strong acids that become water-soluble. For this, benzotriazole was dissolved in hydrochloric acid with a concentration of 30-35% at a temperature of 30 ° C. The excess of hydrochloric acid in the preparation of the salt was 10-15%. The pH of the resulting solution was 1.5-2.0, the dry residue was 6%. This salt was subsequently used to isolate rubber from latex.

The method is carried out as follows

Copolymerization of butadiene with styrene is carried out in a battery consisting of 10-12 polymerization apparatus in the presence of radical initiators (for example, pinane hydroperoxide). After reaching the conversion of 65-70%, a radical process stopper (sodium nitrite, rongalit, etc.) is introduced into the system, and the resulting latex is fed to degassing, where unpolymerized monomers (styrene, butadiene and other low-boiling products) are distilled off. From the degassing department, latex is fed to coagulation. Before coagulation, an antioxidant (antioxidant) in the form of an aqueous dispersion is introduced into the latex and subjected to coagulation, i.e. mixing with an aqueous solution of sodium chloride, compounds containing nitrogen and sulfuric acid. The resulting crumb of rubber is fed for washing, dehydration, drying and packaging [Raspopov IV, Nikulin SS, Garshin A.P. and others. Improvement of equipment and technology for the separation of butadiene- (α-methyl) styrene rubbers from latexes. M .: TsNIITEneftekhim, 1997. 68 p.].

Styrene-butadiene latex SKS-30 ARK is mixed in coagulating agents at a given temperature. After the introduction of the coagulating agents and stirring for 1-2 minutes, a solution of the acidifying agent (an aqueous solution of sulfuric acid with a concentration of 2%) was introduced and the coagulated system was stirred for 3-5 minutes. The resulting rubber crumb is separated from the serum, washed with water and dried at a temperature of 80 -85 ° C. The completeness of coagulation was assessed visually (the serum is transparent, without inclusions - the coagulation is complete), as well as by the mass of the resulting rubber crumb.

The method is illustrated by the following examples.

Example 1 (prototype)

Copolymerization of butadiene with styrene is carried out in a continuous scheme on a battery consisting of 12 polymerizers. In the first polymerizer during the process, the aqueous and hydrocarbon phases (a mixture of 70% butadiene and 30% styrene), a radical initiator (hydroperoxides of isopropylbenzene, pinane, etc.) and a molecular weight regulator (tertiary dodecyl mercaptan) are fed. Additional amounts of molecular weight regulator are added to the process before the fifth and ninth polymerizers. Polymerizers are equipped with stirrers. Copolymerization of butadiene with styrene is carried out at 4-8 ° C. The process is carried out until conversion of 65-68%. When leaving the last polymerizer, the latex is continuously filled with a stopper - a solution of sodium dimethyldithiocarbamate with sodium nitrite. The latex filled with the stopper passes through the filter and is directed to the distillation of unpolymerized monomers to the upper part of the preliminary degassing column, where the main amount of butadiene is distilled off. After the preliminary degassing column, the latex is sent to a vacuum stripper, where styrene and the remaining butadiene are stripped off.

Latex, from the degassing section, is fed to coagulation. Before coagulation, an antioxidant (amine or phenolic type antioxidant) in the form of an aqueous dispersion is introduced into the latex and subjected to coagulation. To do this, the latex is kept at a predetermined temperature for 10-15 minutes and a 24% aqueous solution of sodium chloride is introduced with constant stirring. To complete the coagulation process, an acidifying agent is introduced in the form of a 2% aqueous solution of sulfuric acid. Sulfuric acid consumption - 15.0 kg / t of rubber. After coagulation, the resulting rubber crumb is separated from the aqueous phase (serum), washed with water and dried at a temperature of 80-85 ° C.

The test results are presented in table 1.

Example 2

A distinctive feature of the studies in example 2 from example 1 is that the butadiene-styrene latex SKS-30 ARK was cooled to a temperature of 0-10 ° C and fed for sequential mixing with aqueous solutions of benzotriazole hydrochloride cooled to a temperature of 0-10 ° C and an aqueous solution of sulfuric acid.

The concentration of benzotriazole hydrochloride in an aqueous solution is 6.0%, sulfuric acid is 2.0%. The introduction of benzotriazole hydrochloride into the latex was carried out with constant stirring and homogenized for 1-2 minutes. Then the acidifying agent was introduced and stirred for 3-5 minutes. The resulting rubber crumb was separated from the aqueous phase (serum) and washed with warm water at a temperature of 50-70 ° C. After separation from the aqueous phase, the crumb was dehydrated in an air dryer at a temperature of 80-85 ° C. The results are shown in Table 2.

The analysis of the presented results shows that the completeness of the extraction of rubber from latex was achieved at a consumption of benzotriazole of 4-5 kg / t of rubber.

The use of an acidic salt of benzotriazole makes it possible to reduce the consumption of sulfuric acid to 9 kg / t of rubber (Table 2).

Example 3

Triethanolamine hydrochloride was used in the technology for separating SKS-30 ARK rubber from latex. This salt was prepared in the same way as the benzotriazole salt. A distinctive feature in this case is that triethanolamine is a water-soluble product and, like it, gives an ammonium salt. Interest in the use of triethanolamine in the production of emulsion rubbers is based on the fact that it is used as an additive inhibiting corrosion processes, as a component of rubber softeners, etc. strong sulfuric acid is used in the manufacture of emulsion rubbers.

Isolation of rubber from latex was carried out according to example 2. Used 10% aqueous solution of triethanolamine acidified with hydrochloric acid to pH = 2. The results are shown in Table 3.

Analysis of the experimental results shows that the smallest consumption of the coagulating agent is achieved at a temperature of 0-10 ° C and the consumption of triethanolamine hydrochloride 50-70 kg / t of rubber, which is 3-4 times less than sodium chloride.

Example 4

Phenazine hydrochloride was used in the technology for separating SKS-30 ARK rubber from latex. Phenazine is insoluble in water. To obtain an aqueous solution based on phenazine, a salt was prepared by dissolving it in a solution of hydrochloric acid with a concentration of 30-35% at 20 ° C. The concentration of the salt of phenazine hydrochloride in the solution is 1.7%. The pH of the resulting solution is 1.0-1.5.

Isolation of SKS-30 ARK rubber from latex was carried out according to the method described in example 2.

The results are shown in Table 4.

It can be seen from the above data that phenazine in its coagulating ability is close to polymeric quaternary ammonium salts (VPK-402) (3-5 kg / t of rubber, at 20 ° C), and even surpasses them. The consumption of phenazine was 1.0-1.5 kg / t of rubber at 0-10 ° C.

Based on the experimental data obtained, the following conclusions can be drawn:

Carrying out the coagulation process at 0-10 ° C allows achieving the completeness of the release of rubber from latex at lower consumption rates of coagulating agents than at elevated temperatures (more than 20 ° C). The use of organic ammonium salts makes it possible to reduce the content of lecanol in serum by tens of times. This product is resistant to biodegradation and waste water is not purified from it at treatment facilities, which leads to pollution of natural water bodies. In addition, the organic nitrogen-containing compounds used in the technology for the isolation of organic nitrogen-containing compounds with anticorrosive activity create good prerequisites for extending the service life of technological equipment, since a strong oxidizing agent is used in the production of emulsion rubbers - a solution of sulfuric acid.

Example 5

To assess the properties of SKS-30 ARK rubber isolated from latex using a traditional coagulant (sodium chloride) and the above coagulants, rubber mixtures and vulcanizates were prepared to assess physical and mechanical properties. The test results are presented in table. 5.

Analysis of rubber mixtures and vulcanizates prepared on the basis of SKS-30 ARK rubber isolated from latex by sodium chloride and the above coagulants meet the requirements of TU. In terms of aging resistance, vulcanizates based on experimental rubber samples are superior to control ones.

Claims (1)

A method for producing styrene-butadiene rubber by copolymerizing butadiene with styrene in an emulsion in the presence of radical initiators, stopping the process, degassing, introducing an antioxidant and isolating rubber from latex by the coagulation method, characterized in that the latex is mixed with nitrogen-containing coagulating and acidifying agent 10 ° С, washing of rubber crumbs - at 50-70 ° С and using an aqueous phase (serum) to prepare solutions of coagulating and acidifying agents.