RU2442795C2 - Method of salt-free congelation of rubber latexes - Google Patents

Abstract

FIELD: petrochemical industry.

SUBSTANCE: invention refers to manufacture of synthetic rubbers that are obtained by means of emulsion copolymerization, notable to the stage of their extraction from latex, and can be applied in petrochemical industry. In the salt-free congelation method rubbers that contain leukanol-oil dispersing agent are employed. The rubbers are obtained by emulsion copolymerization of butadiene with the monomers of the vinylic row. As a coagulating agent, quaternary ammonium compounds are used that are based on resin acids and colophony Biozic by means of introduction of 3-5 kg of an active substance into the latex per 1 t of the rubber.

EFFECT: production of the rubber at one stage in the form of big, unadhesive, homogeneous, finely set chips in the acid environment, improvement of the quality of the obtained rubber.

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Description

The invention relates to the production of synthetic rubbers obtained by emulsion copolymerization, in particular to the stage of their separation from latex, and can be used in the petrochemical industry.

There is a known and widespread method of isolating rubbers from latexes by coagulation with electrolytes - sodium chloride and sulfuric acid (P.P. Kirpichnikov, L.N. Averko-Antonovich, Chemistry and technology of synthetic rubber, - L., Chemistry, 1970, p.395- 399; 402-403). The main disadvantage of this relatively inexpensive method is the high environmental load on water bodies, because a large amount of salt (190-250 kg per 1 ton of rubber) is discharged into water bodies, which leads to their pollution. In addition, this method causes rubber losses due to the formation of dust particles, which is removed from the process with washing water. Residues of chloride ions in rubber lead to a significant deterioration in its quality and consumer properties due to a decrease in the effectiveness of antioxidants and the rate of vulcanization.

These environmental, technological and economic disadvantages can be significantly avoided by the use of salt-free methods of coagulation of synthetic latexes, which consist in processing the obtained latexes with organic coagulants.

A known method of isolating rubbers from latexes by the action of alkaline solutions of amine plant proteins. (French application 240138, IPC C 08/22, published in 1981). However, it is not without drawbacks: coagulants form difficult to separate suspensions, which necessitates the use of special equipment for the isolation of rubber. In addition, the shelf life of coagulants is small, and food and feed products are used for its production.

There is also a method for the isolation of styrene-butadiene rubbers from latexes using protein hydrolysates as coagulants (AS USSR, 1131883 IPC С08С 1/15, published 12/30/1984, bull. 48). However, this method also has a number of disadvantages, the main of which are the insufficiently physicomechanical properties of the vulcanizates (low strength, gelation) obtained from rubbers isolated by this method, low vulcanization rate and, very importantly, increased stickiness of the resulting rubber crumb to equipment. The latter seriously complicates the stable operation of the entire coagulation cascade, reduces the productivity of the process, and leads to a decrease in the rubber yield. In addition, hydrolysates have an extremely limited shelf life, especially in the hot season, because are exposed to bacterial infection, rot and become unsuitable for use.

Known methods for salt-free isolation of synthetic rubbers from latexes using cationic polyelectrolytes as coagulants (GDR Patent No. 221739, MKI S082C 1/15; AS USSR, No. 859377, IPC S08C 2/06 C 1/14, 1979), including quaternary ammonium compounds (GDR patent 142345, 1979; AS USSR 556604, 1975; AS USSR, No. 1700007, IPC С08С 1/15, 1991). These methods have significant advantages over the above. In particular, the proposed coagulants require a relatively small consumption of reagents (2-7 kg per 1 kg of rubber), they do not cause a slowdown in vulcanization and do not reduce the strength of the vulcanizates. The ash content of rubber is also reduced due to the exclusion of the use of sodium chloride at the coagulation stage. In addition, the environmental load is reduced as a result of the binding of a biodegradable leucanol due to the formation of an insoluble complex in the aqueous medium that remains in the rubber, which allows the reuse of wash water at the rubber isolation stage. However, in these cases, there is a significant increase in the stickiness resulting from the coagulation of rubber crumb, which causes difficulties in the process of coagulation of rubbers, namely: complication of equipment operation, decrease in the productivity of the entire rubber production process, and decrease in rubber yield.

The closest in technical essence and the achieved result to the present invention is a method for salt-free coagulation of latexes in an acidic environment using a cationic polyelectrolyte as a coagulant - poly-N, N-dimethyl-N, N-diallylammonium chloride (PDMDAAH, prototype), which is the basis of industrial flocculant VPK-402 (RF Patent No. 2067592, IPC C08F 236/10, С08С 1/15, 1994).

The disadvantage of this method is that when using PDMDAAH, the isolated rubber also has an increased stickiness, and the rubber isolation process is two- or three-stage, since in this case additional flocculation of the latex with sulfuric acid is required. This causes an increase in the cost of sulfuric acid and, importantly, does not help to reduce the cost of emulsifiers at the copolymerization stage. Moreover, in comparison with salt coagulation, rubbers obtained with the coagulant PDMDAAH cure faster. However, their quality is significantly lower than the best foreign samples, which is generally the main disadvantage of domestic emulsion rubbers.

The aim of the invention is to improve the manufacturability of the process of salt-free coagulation of synthetic latex, eliminating the stickiness of the resulting rubber crumb, improving the quality of rubber to the level of the best foreign analogues and reducing the cost of sulfuric acid and emulsifiers used.

This goal is achieved by the fact that at the stage of coagulation of latexes, a new quaternary ammonium compound obtained on the basis of resin acids and rosin according to the patent of the Russian Federation 2256649, 2004 (published on July 25, 2005, bull. No. 20), called " Biotsik "and having fungicidal, bactericidal and surface-active properties.

The coagulating ability of Biocic was established by us for the first time. It is based on the fact that Biotsik easily interacts with the biodegradable dispersant leucanol (NF dispersant) always present in latex to form a water-insoluble complex containing rosin products. Due to this, latex is destabilized, and the complex itself remains in rubber, significantly improving its quality indicators and consumer properties. In particular, this circumstance contributes to increasing the productivity of the rubber production process as a result of conducting the coagulation process in one stage; Significant reduction in rubber stickiness increasing the proportion of organic acids in rubber; acceleration of its vulcanization, etc.

The essence of the invention is confirmed by the following examples.

Example 1 (prototype). Technical latex of the SKS-30 ARK, SKMS-30 ARK, SKS-30 ARKM-15 or SKMS-30 ARKM-15 brand latex, obtained according to the generally accepted formulation using EDiSCAN 1010-1418 as an emulsifier and in the established generally accepted mode, coagulate in two stages . Latex containing 18-20% solids; pH 10-10.5, in the first stage it is mixed with a 4% solution of sulfuric acid containing PDMDAAH as a coagulating additive, introduced in an amount of 1.7 kg per 1 ton of rubber at a total pH of the resulting mixture 5-6. In the second stage, again add a 4% solution of sulfuric acid to a pH of the mixture 3.5-4.5. The coagulation process is carried out at a temperature of 55-60 ° C. At the end of the dosage, the mixture is continued to mix until the end of coagulation, the completeness of which is assessed visually by the transparency of the serum.

The rubber is separated from the serum, washed with distilled water and dried. The consumption of sulfuric acid is 13 kg per 1 ton of rubber with a ratio of latex and serum 1: 2.

The quality indicators of the selected rubbers are shown in table 1.

Table 1 Mark Quality indicators latex mass fraction of org. acids,% stickiness, g / cm ² adherence, g / cm ² ICP,% SKMS-30 ARK 5.5 75 17 59 SKS-30 ARK 5.2 76 16 61 SKMS-30 ARKM-15 6.0 64 13 62 SKS-30 ARKM-15 6.3 67 fifteen 72

The selected rubber samples of the prototype are characterized by increased stickiness.

Example 2. Everything, as in example 1, but the coagulation processes are carried out in one stage, and as a coagulant use a 2% solution of Biocic according to TU 2453-01225588394-2005. To coagulate latex of a certain brand, serum (0.5% H ₂ SO ₄ solution) is loaded into a reactor equipped with a mixing device, it is heated to a temperature of 55-60 ° C and, with constant stirring, an aqueous solution of Biocic in the amount of 3 , 0-5 kg of the active substance of the product per ton of rubber.

In the same reactor, latex is pre-heated to 40-50 ° C in portions, adjusting the feed rate by the rate of rubber crumb formation. After dosing, the mixture in the reactor is kept under constant stirring for 5-10 minutes, determining the completeness of coagulation visually by the transparency of the serum. The resulting rubber is separated, washed with water and dried. Serum analysis revealed the absence of leucanol.

The rubbers stood out in the form of a large, non-sticky, well-formed uniform crumb.

The quality indicators of the rubbers are shown in table 2.

It can be seen that the use of Biotsik as a coagulant leads to a noticeable improvement in the quality of rubber: the stickiness of rubber is 1.2 times lower than that of the prototype, adhesion is 1.4-1.7 times lower, and ICP is 1.4-1.5 times higher.

table 2 Mark Quality indicators latex mass fraction of org. acids,% stickiness, g / cm ² adherence, g / cm ² ICP,% SKMS-30 ARK 6.3 60 10 86 SKS-30 ARK 6.6 62 eleven 91 SKMS-30 ARKM-15 6.5 56 8 96 SKS-30 ARKM-15 6.9 57 9 96

Example 3. Everything is as in example 2, but for coagulation we used technical acrylonitrile-butadiene latex of the ABS-2020 brand, and as a coagulant we use a 2% solution of Biocic in water in the amount of 3-3.5 kg of active substance per 1 t rubber. Received ABS rubber in the form of granules, the quality indicators of which fully met the requirements of TU 6-05-1587-90 "ABS-emulsion". The data obtained are shown in table 3.

Table 3 Name of indicator Norm according to TU 6-05-1587-90 Factual data Appearance Granules with a diameter of not more than 3 mm, length 2-5 mm Compliant Izod Impact, kJ / m ² 24.5 22.0 Tensile Strength, MPa 38,2 38.3 Melt yield strength at 220 ° С, g / 10 min, not less than 5 7.5 Relative elongation,%, not less 22 twenty Vicat softening temperature, ° С, not less 97 107 Ash content not standardized 0.02

It can be seen that the obtained ABS rubber fully complies with the requirements of the current regulatory and technical document. Moreover, the ash content (non-rated) is significantly lower.

Example 4. Everything, as in example 2, but for coagulation using technical nitrile butadiene rubber brand SKN-26CM, and as a coagulant - 2% aqueous solution of Biocic in the amount of 3.5 kg of active substance per 1 ton of rubber. The properties of the obtained rubber were studied in a standard rubber compound according to GOST 7738-79.

The results are shown in table 4.

Table 4 Name of indicator Factual data A) Rubber Mooney viscosity MB 1-4 (100 ° C) 48 Rigidity, gf 690 Recoverability, mm 2.1 Plastic 0.43 Email recovery mm 1.49 Mass loss on drying 105 ° C 0.41 Mas. ash fraction,% 0.04 Mas. AO share,% 2.25 Mas. share of associated NAC,% 29.4 Mas. the proportion of alkyl sulfonate,% 0.46 Solubility in methyl ketone,% one hundred ICP (160 °, 60 min),% 96 B) Rubber compounds Mooney Viscosity 54.0 The vulcanization time at 143 ° C, min 40 fifty 60 80 Conditional stress at 300% elongation, MPa 5,6 6.0 6.1 6.5 Conditional tensile strength, MPa 28.1 28,4 28.7 28.9 Relative extension, % 745 720 705 690 Residual elongation,% thirty 28 23 23

It can be seen that the inventive coagulant Biotsik provides the production of SKN rubbers, the vulcanization of which is also not inferior to rubbers obtained using known coagulants, including sodium chloride.

Example 5. Everything, as in example 2, but all technical butadiene-styrene latexes were coagulated with a 2% aqueous solution of Biocic in the amount of 3 kg of active substance per 1 ton of rubber, and crude rubber compounds and their vulcanizates were prepared using the generally accepted method for determination of the vulcanimetric characteristics of mixtures and the physicomechanical properties of rubber vulcanizates. The results are shown in table 5. Here, for comparison, the specification for rubbers of SBR-1502 and SBR-1712 grades manufactured by Goodyear is also given.

Table 5 The name of indicators Oil-free rubbers Oil-filled rubbers SBP-1502 Goodyear SKS-30 ARK SKMS-30 ARK SBR-1712, Goodyear SKS-30-ARKM-15 SKMS-30-ARKM-15 Vulcometric characteristics (rheometer-100, 160 °, 1 °) Minimum torque, N.m. 0.9 ± 0.2 1,07 1D2 - 0.9 1,02 Maximum torque, N.M. 4.8 ± 0.3 5.1 4.94 - 4.65 4.76 Ts min 4.2 ± 1 4D 3.6 2 4.3 4.0 T ₅₀ min. 10 ± 0.5 7.35 7.4 10.5 ± 1.5 7.8 8.0 T ₉₀ min. 16 ± 2 14.1 12.6 15.6 ± 3 13.3 13.5 Vulcanizers, T _volc = 145 ° С (ISO) 25 ^/ - 17,2 16.7 8.6 ± 1.7 12.0 11.6 Stress at 300% elongation, MPa 35 ^/ 15.7 ± 2.5 21,2 20,4 - 15.8 15.4 Conditional Strength at 25 ^/ 26 ± 4,2 25.8 25,2 min 18.3 25.0 24.5 stretching 35 ^/ - 27.4 26.0 - 27.1 26.8

It can be seen that the proposed coagulant not only has a coagulating ability, but also modifies the rubber: the vulcanization rate of rubber significantly exceeds not only the coagulation of the prototype, but also the required performance of foreign rubber samples, in particular the Goodyear company. The strength of the vulcanizates is consistent with the level specified in the Goodyear specification, even if the vulcanization time is reduced to 25 minutes.

Example 6. Everything, as in example 2, but when conducting coagulation of technical latex SKMS-ARK 30 or SKS-ARK 30, the dosage of Biotsik was 3.0 kg of active substance per 1 ton of rubber.

The results are shown in table 6.

Table 6 No. The composition of the coagulant (per 100 m. Of rubber) pH of serum Exit p / p Sulphuric acid Water (dist) Biocyc rubber,% one 4.70 997 0.95 1,50 one hundred 2 0.70 950 0.95 2.15 one hundred 3 0.60 950 0.95 2.80 one hundred four 0.55 952 0.95 3.20 98.7 5 0.48 952 0.95 3.40 98.2

It can be seen that the effectiveness of the coagulant used remains at its maximum when the mass fraction of sulfuric acid in serum is reduced to 0.6 mass parts per 100 mass parts of rubber.

Example 7. Everything, as in example 2, but for coagulation of technical butadiene-styrene latexes, serum was reused with the introduction in each cycle of a 2% solution of the proposed coagulant in an amount of 4-4.5 kg of the active substance Biocic per 1 ton of rubber.

The data obtained are shown in table 7.

It is seen that the proposed coagulant is possible at least four times the recycling of serum with the release of rubber up to 100% without compromising its quality.

Table 7 The name of indicators Cycle number one 2 3 four 5 pH of the original serum 1.20 1,50 1.70 2.05 2.85 1.20 1,50 1.65 2.00 2.95 1.30 1,59 1,69 2.10 2.80 pH of the final serum 1.35 1,60 1.90 2.85 3.20 1,50 170 2.00 2.95 3.40 1,59 1.65 2.00 2.80 3.17 The completeness of coagulation,% one hundred one hundred one hundred one hundred 98.7 M. d. Leucanol in serum,% 0,0006 0.0011 0.0011 0.0012 0,0007 0,0009 0,0009 0,0006 0.0010 0.0014 0.0010 0,0005 M. d. Organic acids in serum,% 0,023 0,034 0,031 0,031 - 0,040 0,040 0,030 0,040 0,037 0,043 0,046 0,046 The stickiness of the rubber, g / cm ² 56.3 62,2 55.1 56.3 - Adhesion, g / cm 9.7 12.6 9.5 10.6 -

The proposed salt-free method of coagulation using a quaternary ammonium compound based on rosin and resin acids as a coagulant - Biotsik (biocidal rosin), which is an environmentally friendly plant product with fungicidal, bactericidal and surface-active properties - made it possible for the first time to obtain high-quality rubber, not inferior in terms of quality and consumer properties to the best foreign counterparts, in particular the company Goodyear. The biocidal properties of the proposed coagulant can protect rubbers and products based on them from biocorrosion, which is of no small importance, especially at present. The composition of Biocic reduces not only the consumption of scarce and expensive rosin both in the production of rubber and in its use in the manufacture of rubber products, especially in the tire industry, but also the consumption of sulfuric acid and other chemicals in their production.

The implementation of the proposed method in enterprises producing rubber by the emulsion method does not require capital expenditures and creates the possibility of efficient use of existing existing equipment.

Claims (1)

The method of salt-free coagulation of rubber latexes obtained by copolymerization of butadiene with vinyl monomers and containing leucanol-dispersant NF by introducing an organic coagulant into latex, characterized in that quaternary ammonium compounds based on rosin and resin acids - Biotsik, in an amount of 3 are used as a coagulant -5 kg of active substance per 1 ton of rubber.