RU2179173C1 - Rubber production process - Google Patents

Abstract

FIELD: rubber industry. SUBSTANCE: process is accomplished by water-emulsion polymerization technique and can be used to obtain a variety of brands of butadiene-based synthetic rubbers. Process involves carrying out polymerization in presence of radical initiator, molecular weight regulator, and emulsifiers. Rubber latex, before distilling off monomers, is diluted with 5-10 wt parts (per 100 wt parts of monomers) of water-alkali solution of trisodium phosphate or soda ash, disperser, and phenol-type stabilizer taken at ratio, respectively, 1:(0.01-0.03):(0.01- 0.05):(0.01-0.05), after which rubber is isolated and dried. EFFECT: enlarged assortment of rubber products. 1 tbl

Description

 The invention relates to a method for producing rubbers.

 The invention can be used to obtain various grades of synthetic rubbers based on butadiene and vinyl monomers by water-emulsion polymerization.

A known method of producing nitrile butadiene rubbers (BNK) by water-emulsion copolymerization of butadiene with acrylic acid nitrile (NAC) at 0-40 ^o C using ionic and non-ionic emulsifiers in an amount of 2-4 wt.h. per 100 parts by weight monomers, radical initiators, a regulator, or a mixture of molecular weight regulators. Upon reaching the conversion of monomers 65-90%, the process is interrupted by the supply of stoppers, for example sodium dimethyldithiocarbamate. Unpolymerized monomers are then distilled off from the latex in columns using hot steam under vacuum. Latex is coagulated using electrolytes or a mixture of polyelectrolyte and electrolyte, then the crumb of rubber is washed and dried [Rivin E.M., Moiseev V.V., Yadreev F.I. Nitrile butadiene rubbers. Synthesis and application. M., Central Research Institute of Petroleum Engineering and Natural Resources, 1982]
However, this method has a significant drawback: low aggregate stability of latexes during the distillation of monomers.

 The NAC hydrolysis product formed during distillation, dicyandiethyl ether, is a strong coagulant. This leads to increased clogging of the stripping columns with the coagulum, which reduces their mileage when switching from one brand of rubber to another.

There are various ways to increase the aggregate stability of latexes at the stage of monomer distillation, using nonionic additives, various antifoam agents, microemulsifying monomers in the presence of higher alcohols, lowering the NAC distillation temperature by using countercurrent columns [Rivin EM, Skulsky AS, Korablin V .G. Degassing of synthetic latexes. M., TsNIITEneftekhim, 1990]
However, although these methods increase the stability of latexes during the distillation of monomers, it is not possible to suppress the hydrolysis of NAC, which leads to the formation of coagulum and, accordingly, to clogging of columns.

 There is a method of increasing the aggregate stability of latex in the preparation of styrene-butadiene rubbers by introducing into the rubber latex ~ 20% of the dispersant — leucanol of the total polymerization recipe before degassing (A.S. NRB N 50658, IPC C 08 F 236/06, publ. 15.10. 92 g., BI N 9 1994).

 However, this method, although it reduces coagulum formation, does not give a significant effect.

 The closest in technical essence and the achieved result to the proposed one is a method for producing rubbers by water-emulsion polymerization of butadiene and NAC in the presence of radical initiators, emulsifiers, electrolytes, according to which the process is carried out in the presence of 0.5- 1.5 parts by weight emulsifiers per 100 wt. including comonomers, and the resulting latex before distillation of the monomers is diluted 20-50 wt.h. water per 100 weight. including comonomers. [A. C. USSR N 663696, IPC C 08 F 236/06, C 08 F 2/24, published. 05/25/79, BI N 19].

 Dilution of latex with water before distillation of the monomers helps to increase the resistance of latexes to mechanical and thermal effects by 3-12 times.

However, this method has disadvantages:
- dilution with water leads to a decrease in the dry residue of latex and, accordingly, to a decrease in the productivity of the equipment;
- low dry residue of latex leads to an increase in the consumption of electrolyte - sodium chloride during coagulation;
- this method does not inhibit the hydrolysis of NAC, which leads to the formation of coagulum.

 The technical task of the invention is to increase the stability of latex and reduce coagulum formation during degassing of latexes, reduce electrolyte consumption and, accordingly, reduce its discharge into wastewater.

 The problem is achieved by introducing into the latex before distillation of monomers 5-10 wt. including an aqueous-alkaline solution of a mixture of trisodium phosphate or soda ash, a dispersant and a phenolic stabilizer in the following weight ratios 1: (0.01 - 0.03) :( 0.01 - 0.05) :( 0.01 - 0, 05).

This method has the following advantages over the known:
- the presence of trisodium phosphate or soda ash maintains the pH of the latex in the range of 10-11, which leads to a reduction in the formation of coagulum;
- the addition of a dispersant immediately before distillation increases the resistance of rubber latex to mechanical, thermal and thermomechanical effects;
- the presence of a phenolic type stabilizer reduces the rate of polymerization and the formation of polymers in the gas phase of the distillation columns and the condensation system.

 All of the above factors reduce the formation of coagulum and increase the mileage of distant columns by 3-5 times.

 Conventional monomers are used as vinyl monomers: styrene, nitrile of acrylic acid, (meth) acrylic monomers-acids, esters of (meth) acrylic acids, etc.

 The invention is illustrated by the following examples.

Example 1. Latex of nitrile butadiene rubber receive the recipe SKN-18ASM, parts by weight:
Butadiene - 83
Acrylic Acid Nitrile - 17
Tall Oil Potassium Soap - 3.0
Leucanol with an aqueous phase - 0.3
Trisodium phosphate with an aqueous phase - 0.2
Rongalit - 0.08
Trilon "B" - 0.016
Iron sulfate (heptahydrate) - 0.008
Pinan hydroperoxide - 0.06
Regulator - tertiary dodecyl mercaptan - 0.3
Water - 200
The copolymerization is terminated by feeding a stopper solution of sodium dimethyldithiocarbamate in an amount of 0.2 wt.% Per rubber at a monomer conversion of ~ 70%.

Before distillation, 5 parts of an aqueous alkaline solution consisting of 0.01 wt.% Trisodium phosphate are added to latex; 0.01 wt.% Dispersant - leucanol; 0.01 wt.% Stabilizer BC-30 A (2,4,6-trialkylphenol). The latex resistance to mechanical stress was evaluated on a Maron-Ulevich instrument, the latex resistance to thermomechanical stress was evaluated on the same instrument when heated to 80 ^o C; to thermal effects - steam treatment of latex.

 The test results are shown in the table.

 Example 2. Obtaining rubber latex is carried out, as in example 1, only the ratio of butadiene and NAC is 74:26 parts by weight, and 7.0 parts by weight are added to latex before degassing. aqueous alkaline solution consisting of 0.02 wt.% soda ash; 0.02 wt.% Dispersant - leucanol; 0.02 wt.% Stabilizer BC-30A. The test results are shown in the table.

 Example 3. Obtaining rubber latex is carried out, as in example 1, only the ratio of butadiene and NAC is 58:42, and 10 parts by weight are introduced into latex before distillation. aqueous alkaline solution consisting of 0.03 wt.% soda ash; 0.03 wt. % dispersant, 0.05 wt.% stabilizer BC-30 A. Evaluation of latex is carried out as in example 1. The test results are shown in the table.

 Example 4. The prototype. In the latex obtained in example 2, 20.0 parts by weight are added. softened water. The run of distant aggregates until the time of clogging with coagulum was 5 days. Evaluation of latex is carried out as in example 1. The test results are shown in the table.

 Example 5. The prototype. In the latex obtained in example 3, with a content of nitrile of acrylic acid in a copolymer of 40 wt.% Was introduced 50 wt.h. softened water. Evaluation of latex was carried out as in example 1. The test results are shown in the table.

 Example 6. The copolymerization of butadiene with nitrile of acrylic acid (NAC) is carried out according to the recipe SKN-18ASM (Example 1) in a continuous polymerisation battery. When the conversion of monomers to 70% is achieved, the latex is filled with stopper - dimethyldithiocarbomate (DDK) in an amount of 0.2 wt.% Per polymer and antifoam in an amount of 0.02 wt.% Per polymer. Then, 5.0 wt. including a water-alkaline solution consisting of 0.01 wt.% soda ash, a dispersant - leucanol in an amount of 0.05 wt.% and a stabilizer BC-30 A - in an amount of 0.01 wt.% Run of distant aggregates until clogging coagulum was 30 days. Analysis of latex on resistance to mechanical, thermal and thermomechanical effects is carried out, as in example 1. The test results are shown in the table.

 Example 7. Rubber latex obtained in example 6, only the amount of NAC in the copolymer was 26 wt.%. After stoppering, 7.0 wt. including a water-alkaline solution consisting of 0.02 wt.% buffer - trisodium phosphate; 0.05 wt.% Dispersant - leucanol; 0.02 wt.% Stabilizer BC-30 A. Mileage run-off units until clogging with coagulum was 35 days. Latex is evaluated as in example 1, the test results are shown in the table.

 Latex after distillation of unpolymerized monomers was averaged in containers and coagulated with sodium chloride with serum recycle and sulfuric acid at pH 4-6. The consumption of sodium chloride in this case amounted to 240 kg per ton of rubber. In the known method of the prototype (examples 4 and 5), the consumption of sodium chloride is 330 kg per 1 ton of rubber.

 Example 8. The latex obtained in example 6, only the amount of bound NAC in the copolymer was 40%. After stoppering, 9 wt.h. an aqueous-alkaline solution consisting of 0.03 wt.% buffer - trisodium phosphate; 0.05 wt.% Dispersant - leucanol, 0.02 wt.% Stabilizer BC-30 A. Latex is evaluated according to example 1. The test results are shown in the table. The consumption of sodium chloride per ton of rubber was 280 kg.

 Example 9. Rubber latex is obtained according to example 7, only in the amount of phenolic stabilizer use Agidol-2 (NG-2246) - 2,2-methylenebis- (4-methyl-6-tert-butylphenol) in an amount of 0.02 wt.%. Latex was evaluated as in example 1. The test results are shown in the table.

 Example 10. The latex of styrene-butadiene rubber is obtained in a continuously operating polymerization battery, consisting of 10 series-connected polymerizers, according to a typical recipe for rubber SKS-30ARK, (parts by weight per 100 parts by weight of monomers): butadiene 70; styrene 30; emulsifier potassium soap of rosin-tall mixture 5.4; leucanol 0.15; rongalit 0.08; Trilon B 0.02; ferrous sulfate 0.01; trisodium phosphate 0.2; pinan hydroperoxide 0.06; tertiary dodecyl mercaptan 0.2; water 190.

 The copolymerization was terminated when the monomer conversion was achieved by 70% by applying the DEG stopper in an amount of 0.04 wt.% Per polymer and POS-2 antifoam in an amount of 0.02 wt.% Per polymer. Before the distillation is introduced 5.0 wt.h. aqueous alkaline solution, consisting of 0.05 wt.% dispersant, - leucanol; 0.02 wt.% Trisodium phosphate and 0.01 wt.% Stabilizer BC-30A. The run of distant aggregates up to the moment of clogging with the coagulum was 35 days. Latex was evaluated for resistance to mechanical and thermomechanical influences. The test results are shown in the table. The consumption of sodium chloride per ton of rubber was 200 kg.

 Example 11. Control (production) on the method of producing rubber latex SKS-30ARK.

 Latex receive example 10.

 Unpolymerized monomers are distilled off without additional additives. The run of distant aggregates until the time of clogging with coagulum was 20 days. The consumption of sodium chloride per ton of rubber was 240 kg.

 Data on latex stability are given in the table.

 Analysis of the results shown in the table shows that the proposed method provides a reduction in coagulum formation for all types of rubbers in comparison with the known method.

 The latex stability, estimated by the amount of coagulum formed during mechanical, thermomechanical and thermal stresses, increases by 1.3-2.0 times in comparison with the known method.

 In real production conditions, a decrease in coagulum formation by the proposed method increased the mileage of distant aggregates from 5-12 days to 30-35 days for nitrile rubber latexes and from 20-25 days to 30-35 days for styrene butadiene rubber latexes, butadiene (styrene or NAC) (meth) acrylate latexes.

 In addition, the proposed method allows to reduce for butadiene-nitrile rubbers the discharge of sodium chloride into wastewater by 90 kg / t, for butadiene-styrene rubbers by 40 kg / t.

 The quality of the rubbers produced fully met the technical specifications of TU 38.40350-99 for Nitrilast-18 and Nitrilast-26 and GOST 15627-79 for styrene-butadiene rubbers SKS-30ARK.

Claims (1)

 A method of producing rubbers by water-emulsion polymerization in the presence of a radical initiator, molecular weight regulator and emulsifiers, dilution of rubber latex before distillation of monomers, characterized in that dilution before distillation is carried out by adding 5-10 wt. hours per 100 wt. including monomers of an aqueous-alkaline solution of a mixture of trisodium phosphate or soda ash, a dispersant and a phenolic stabilizer, taken in the ratio latex: trisodium phosphate or soda ash: dispersant: a phenolic stabilizer 1: (0.01-0.03): (0.01 -0.05): (0.01-0.05), followed by isolation and drying of the resulting rubber.

Images