RU2351610C1 - Method of emulsion rubber recovery from latex - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention refers to emulsion rubber recovery from latex and can be used in chemical rubber industry. There is disclosed method of emulsion rubber recovery from latex through coagulation with using bivalent metal salts from magnesium chloride, magnesium sulphate, calcium chloride. Thereafter rubber crumb is separated from serum, it is followed with wringing and drying, differing that mixing latex and bivalent metal salt is preceded with pre-acidification of latex with diluted sulphuric acid concentrated 0.3-4% to pH 2.5-7.0 units. Within mixing range of acidulous latex and bivalent metal salt, concentration of the latter is kept within 0.05-0.8%, while produced rubber crumb is wrung out thus maintaining pH of wringing water within 2.5-6.9 units with sulphuric acid supplied to pre-acidification of latex.

EFFECT: making uniform rubber compatible with the requirements of related GOST and rubber TOR specifications in characteristics - mass fraction of organic acid soaps and mass fraction of organic acids, improved technological effectiveness and ecological compatibility of process.

2 cl, 1 tbl, 14 ex

Description

The invention relates to the field of separation of emulsion rubbers from latexes and can be used in the manufacture of synthetic rubbers.

The modern industry of SK around the world is a consumer of a huge amount of non-renewable natural raw materials and has a negative impact on the environment, including air and water pools.

In general, at the present stage, the anthropogenic impact of mankind on nature is so great that, when implementing technical solutions, such problems as greening production and saving natural resources come to the fore.

In particular, the production of emulsion rubbers is associated with the use of a large amount of sodium chloride (190-300 kg per 1 ton of emitted rubber) for their isolation. Each year, a large rubber manufacturing plant discharges 20-30 thousand tons of sodium chloride into water bodies, which leads to an irreversible loss of valuable raw materials (sodium chloride) and irreversible salinization of fresh water bodies and, as a result, to their environmental degradation (change in the species composition of biocenoses, deterioration fresh water quality).

In accordance with the requirements for environmental protection, the standards for maximum permissible discharges (MPD) of chlorides in fresh water have been established (List of fishery standards: maximum permissible concentrations (MPC) and tentatively safe levels of exposure (SEC) of harmful substances to water of water bodies having fishery values / Publisher VNIRO. M. 1999).

Physicochemical methods for the extraction of chlorides from wastewater are laborious and expensive, and therefore have not received industry recognition. In addition, sodium chloride has a negative effect on the work of biological structures, inhibiting the work of aeration tanks.

Thus, the stage of separation of emulsion rubbers from latexes is problematic from an environmental point of view.

In the absence of economically acceptable methods of wastewater desalination, it is possible to reduce the chloride content in discharged effluents and to prevent salinization of fresh water bodies in the production of emulsion rubbers by introducing a salt-free or low-salt rubber separation technology. Therefore, the above environmental, technological and economic problems arising from the release of rubbers by sodium chloride make the development of methods for salt-free or low-salt release of rubbers from latexes highly relevant.

Many technical solutions are known that exclude the use of sodium chloride in the isolation of emulsion rubbers from latexes. Products offered as coagulants instead of sodium chloride in known solutions can be divided into five groups:

1 - protein coagulants;

2 - synthetic amine coagulants;

3 - aluminum salts;

4 - calcium salts;

5 - magnesium salts.

However, to date, the problem of eliminating sodium chloride in the allocation of emulsion rubbers from latexes on an industrial scale remains unresolved for several reasons.

So, despite the fact that protein coagulants have a clear advantage over other known coagulants, as they are biodegradable, affordable and effective coagulants, widely tested in the production of synthetic rubbers (SC), however, their use is complicated by the need to preserve protein solutions from decay and thorough disinfection of equipment during their storage and use.

Synthetic amine coagulants as biodegradable products pose a particular danger to the environment, due to their solubility in water or in an acidic environment, they are able to wash out in serum during coagulation, accumulate in water bodies and worsen their sanitary and hygienic condition.

Synthetic amine coagulants have a negative effect on the biological treatment of wastewater, inhibiting the work of aeration tanks of biological treatment facilities, up to the death of activated sludge. Therefore, the use of synthetic coagulants in industry requires special care and in-depth study of any coagulants, and synthetic ones in particular, since it is impossible to predict the long-term effects of the latter on human health and the environment.

Aluminum salts are highly toxic. The maximum permissible concentration (MPC) of aluminum ion for water of fishery facilities is very low and amounts to 0.04 mg / l, which, for example, is 4,500 times lower than the MPC for calcium ions (List of fishery standards for maximum permissible concentrations (MPC) and tentatively safe exposure levels (SECS) of harmful substances for water of water bodies of fishery value. Publishing House VNIRO, M. 1999). Therefore, for SK plants located near large fresh water bodies (the Volga, Yenisei, Belaya, Voronezh reservoirs), the use of aluminum salts for the rubber production is unacceptable.

Of the above coagulants, the most interesting for the SC industry are calcium and magnesium salts (magnesium chloride, magnesium sulfate, calcium chloride) and, from the point of view of environmental friendliness and manufacturability, the stages of emulsion rubber isolation from latexes.

The advantage of calcium and magnesium salts is:

- availability;

- low cost;

- relatively low consumption for coagulation;

- non-toxicity of calcium and magnesium salts.

However, a significant drawback that prevents the widespread use of calcium salts in industry for the isolation of rubbers obtained with emulsifiers based on organic acid soaps is the non-standard nature of rubber in the composition regulated by the normative and technical documentation (NTD) for rubber, since rubbers released by calcium salts do not meet the requirements corresponding to GOST and TU.

It is known that the release of rubber from latex using divalent metal salts leads to the formation of sparingly soluble emulsifier salts that impede the formation of granular coagulum of controlled dispersion and impair the quality of the rubber (synthetic rubber / Ed. By I.V. Garmonov- 2 ed., Revised. - L .: Chemistry, 1983. - p.203-204).

For the above reasons, the use of calcium salts in the industry for the isolation of rubbers over many years has been brought only to the production of special rubbers (butadiene-nitrile rubbers of the BNK brand and the BNKS brand at the Krasnoyarsk plant SK) [V.V. Moiseev, Yu.V. Perina. Rubbers of Russia and materials for their production, Voronezh, 2001].

1. Small tonnage BNK obtained by isolating calcium or magnesium chloride from latex based on emulsifiers (alkyl sulfonates, alkylbenzenesulfonates, sulfoethoxylates) giving water-soluble salts that are completely washed from rubber to serum ("pure" rubber).

2. Nitrile butadiene rubber released by calcium or magnesium chloride without using latex acid based on an emulsifier — synthetic fatty acids that form insoluble calcium (magnesium) salts that remain completely in the rubber (TU 38.30313-98 “Synthetic butadiene-nitrile rubbers BNKS )

However, in the world practice in the tire industry, emulsion rubbers are traditionally used, which are necessarily obtained from latexes based on synthetic fatty acids and must meet the requirements of scientific and technical documentation on the content of emulsifiers in rubber in the form of free and bound organic acids (organic acid soaps).

At the same time, for each brand of tire rubbers, in accordance with the requirements of NTD (GOST, TU), its own maximum content of soap of organic acids (from no more than 0.15 to no more than 0.3%) is regulated and the content of free organic acids in them should be in the range from 4 to 7% (also individual for each brand of rubber).

The above requirements are ensured by the industrial technology for emulsion rubbers separation using a large amount of sodium chloride and sulfuric acid.

The traditional serial technology for the allocation of emulsion rubbers includes the following sequence of flows:

- latex is mixed with a sodium chloride coagulant in a dip or in a separate mixer;

- then the mixture (flocculate) enters the first coagulation apparatus, where a stream of return serum and sulfuric acid is simultaneously fed;

- the resulting rubber pulp is then transferred to the next apparatus — a breeder, and then to the first concentrator, where the crumb is separated from the serum and transferred to a washing tank with partially softened water (PUF);

- the crumb of rubber in CHU enters the second concentrator for separation from the washing water and to the squeezing machine and then to the dryer.

The control of the rubber release process is as follows:

- completeness of coagulation - visually by periodically monitoring the turbidity of serum in the apparatus (coagulator and ripener);

- the serum pH is measured and recorded in these apparatuses and the concentration of sodium chloride in the serum is periodically measured by density.

The use according to the industrial method described above for the isolation of rubbers of magnesium or calcium salts instead of sodium chloride leads to a significant change in the composition of the rubber, which differs from the requirements of NTD for rubbers.

For the above reasons (non-standard rubber composition, the mandatory use of carboxylic acid soaps as emulsifiers) rubbers isolated by divalent metal salts have not received recognition in the tire industry.

Known technical solutions in this area, offering the use of coagulants as salts of divalent metals, also do not eliminate the above disadvantages.

For example, there is a known method for producing rubber, in which 0.75 or more equivalents of salts of two or more valence metals per carboxylic acid soap are added to a latex containing carboxylic acid soaps (Japanese Patent No. 8301/85, C08C 1 / 14, C08L 21/00. Application 60-8301. Japan, application 29.06.83, publ. 17.01.85).

In the examples of the above known method, two equivalents of salts of two or more valence metals are used as coagulants, in particular, ZnCl ₂ , CdCl ₂ · H ₂ O, Mg (NO ₃ ) ₂ · 6H ₂ O, CaCl ₂ · 2H ₂ O , BaCl ₂ · 2H ₂ O, SnCl ₄ · H ₂ O without the use of acid. When coagulating with salts of two or more valence metals without the use of acid, insoluble salts of carboxylic acids precipitate on the surface and inside the rubber crumb. The resulting rubber has improved processability. The best results are obtained with magnesium nitrate, surpassing in this respect calcium chloride and the sodium chloride - sulfuric acid system.

There is a method of producing high-purity (without nitrogen) natural rubber by first isolating it from natural latex with magnesium chloride or magnesium stearate in the presence of soaps (sodium laurate or sodium palmitate or ammonium salts of fatty acids), followed by treating the isolated crumbs with a solution of sulfuric acid (or without adding acid) and an alkaline solution of the proteolytic enzyme trypsin (England Patent No. 846290, С08С, publ. 08.31.1960). Coagulation of natural latex with magnesium chloride or magnesium stearate in the presence of soap - laurate or sodium palmitate (soaps are added to form crumbs) without adding acid is carried out for a long time (within 10 to 12 hours), only after that the crumb is then treated with sulfuric acid solution (or without treatment with a solution of sulfuric acid) and an alkaline solution of the proteolytic enzyme - trypsin.

Natural rubber isolated by the above-mentioned method has a low nitrogen content and thus is not subjected to scorching during processing.

All the above-mentioned known methods for the isolation of rubbers using magnesium and calcium salts are carried out without the addition of acid during coagulation, therefore, along with the advantages consisting in improving some properties of the isolated rubbers (in particular, improving mixing with fillers, increasing oxidation resistance compared to rubbers, excreted by sodium chloride, reducing the negative impact on the environment), they have significant disadvantages:

- non-standard rubber content of bound organic acids (soap organic acids) and organic acids;

- increased ash content of rubber.

It is also known that salts of various metals, including magnesium sulfate, increase the oxidation stability of natural rubber and GR-S, as well as vulcanizates based on them (Jnd. End. Chem., 1952, 44, No. 3, p. 576- 580). In the above-mentioned well-known work, a method for producing a GR-S sample in which magnesium sulfate was supplied in sulfuric acid is described.

However, this known method also does not solve the problem of producing rubber that meets the requirements of technical documentation on the content of organic acids and soaps of organic acids.

In addition, the supply of coagulant in acid limits the ability to control the flow of coagulant while maintaining the coagulation pH in the required range, which greatly complicates the technology of rubber isolation: it leads either to excessive consumption of electrolytes (acid, salt), or to latex coagulation and its loss.

It is known to use salts of magnesium (magnesium chloride, bischofite) and calcium (calcium chloride) as anti-agglomerators that prevent the crumb from sticking together when coagulated with proteins or phenolamine resin.

1. A method for isolating synthetic rubbers from latexes in an acidic environment by introducing an organic amine coagulant of a collagen protein hydrolyzate or phenoamine resin — a condensation product of nonylphenol with hexamethylenetetramine and diethanolamine and calcium chloride or magnesium chloride or bischofite in a weight ratio of 10 amine coagulant: 1 to 1:10 with a total dosage of a mixture of coagulants of 0.01-2.00 wt.% On rubber, followed by separation of the resulting rubber crumbs from serum (RF Patent No. 2140928, IPC С08С 1/14, 1/15, C08F 6/22 , priority 4.02 .98, publ. 10.11.99, Bull. No. 31). In this case, a mixture of an organic amine coagulant with calcium or magnesium chloride or bischofite is added to latex simultaneously or separately by feeding the coagulant for mixing with latex, and a solution of calcium chloride or magnesium or bischofite is added to return serum (p. 5-6 of this patent) .

Industrial tests of this method showed its obvious advantages over the serial technology for the isolation of rubbers (sodium chloride - sulfuric acid), calcium or magnesium chlorides, or bischofite act as anti-agglomerators that prevent the adhesion of rubber crumb, the formation of large agglomerates, and polymer overgrowing of equipment.

However, the above method allows without technological complications with high efficiency to carry out the process of rubber isolation from latex in a batch mode; during industrial tests in a continuous long-term isolation mode according to the cascade scheme, the following disadvantages were identified:

- at a high dosage of the anti-agglomerator supplied to the return serum line to the lower part of the first cascade apparatus (at the level of supply of a mixture of latex and coagulant), substandard crumbs of non-uniform size are formed (dusty crumb appears);

- the performance of squeezing machines (expeller) is reduced due to poor grip of pulverized crumbs, the crumb after spinning and drying has an overestimated moisture content (does not correspond to the standards of the technological regulations for serial rubbers isolated with sodium chloride), which complicates the operation of drying units;

- the content of organic acid soaps in commodity rubber increases to much higher values than is regulated by normative and technical documentation (NTD), i.e. rubber does not meet the standards of GOST in terms of the indicator “Mass fraction of soaps of organic acids” and cannot be considered conditional;

- at a low dosage of the anti-agglomerator supplied to the return serum line to the lower part of the first cascade apparatus (at the level of supply of the latex-coagulant mixture), crumbling occurs, crushing of the squeezing machines also decreases, the crumb after drying and drying has an overestimated moisture content (does not meet the standards technological regulations for this indicator), the drying time of rubber increases;

- rubber compounds made from this rubber have delayed vulcanization and, according to the indicator, “vulcanization speed does not meet the requirements of the corresponding technical documentation.

2. There is also a method of isolating synthetic rubbers from latexes in an acidic environment by introducing an organic amine coagulant and an antiagglomerator selected from the group: calcium chloride, magnesium chloride, bischofite, followed by separation of the resulting rubber crumb from serum, washing it with water, and separating it from wash water, dehydration and drying, the separation process is carried out according to a cascade scheme, including coagulation apparatus and washer, when the anti-agglomerator is fed from the group into the pulp zone - to the top of the first coa apparatus or a second coagulation apparatus and / or into the washing apparatus in an amount providing a concentration of the anti-agglomerator in serum and / or in the washing water in the anti-agglomerator supply apparatus of 0.004-0.200% by weight, at the same time potassium hydroxide or sodium hydroxide is additionally introduced into the washing apparatus or sodium carbonate in an amount that maintains the pH of the wash water is 4-8 units, and in the case of supplying an anti-agglomerator to the top of the first coagulation apparatus or to the second coagulation apparatus or to the washing apparatus, an additional itelnoe administering to the washer sodium chloride in an amount to provide a concentration of 0,004-0,200% of its weight in the washing water. (RF patent No. 2203287, IPC С08С priority 24.06.2004, publ.).

Magnesium and calcium salts in the specified known method play the role of an anti-agglomerator and are already supplied to coagulated chips (in the pulp zone to the upper part of the apparatus or to crumbs in the second coagulation apparatus or washer), coagulation is carried out by proteins or synthetic amine coagulants.

The disadvantages of this known method is:

- the complexity of handling protein coagulants due to their ability to rot;

- the use of biodegradable synthetic amine coagulants that are hazardous to the environment;

- the complexity of the technology of the stage of rubber isolation due to the additional supply of sodium chloride in the washing tank.

The closest in technical essence and the achieved result to the proposed is a method for producing rubber using coagulation of magnesium salts, in which the magnesium salt is supplied for coagulation in the form of a solution in sulfuric acid (US Pat. Italy No. 580939, С08С 1/00, 1958).

However, the above known method has significant drawbacks.

1. Rubbers isolated from magnesium salts from latexes obtained on emulsifiers of potassium or sodium salts of carboxylic acids are non-standard in quality (heterogeneous in composition), do not meet the requirements of scientific and technical documentation and are non-standard in terms of mass fraction of soaps of organic acids and mass fraction of organic acids.

The heterogeneity of rubber in the composition of the batch (the batch is 54 tons of rubber - 1800 briquettes) creates great problems in the processing of rubber by the consumer, since it does not allow to adjust the composition of the rubber mixture, which is uniform for the entire batch, which leads to non-standard properties of vulcanizates from product to product obtained from this batch of rubber.

2. This method is not technologically advanced, as it makes it difficult to adjust the optimal consumption of coagulant and acid. Either excessive consumption of both electrolytes occurs, or latex undercoagulation (if they are insufficiently supplied), leading to rubber losses and pollution of effluents.

The technical task of the invention is to obtain using salts of divalent metals of standard quality (uniform in composition) rubber that meets the requirements of the relevant GOST and TU for rubbers in terms of indicators - mass fraction of soaps of organic acids and mass fraction of organic acids, improving processability and environmental friendliness of the process.

The problem is solved as follows.

1. The method of separation of emulsion rubbers from coagulation latexes using salts of divalent metals from a series of magnesium chloride, magnesium sulfate, calcium chloride, followed by separation of rubber crumbs from serum, extraction and drying, characterized in that before mixing with the divalent metal salt, the latex is pre-acidified diluted sulfuric acid with a concentration of 0.3-4% to a pH of 2.5-7.0 units, in the zone of acidified latex with a divalent metal salt, the concentration of the latter is maintained in the range of 0.05-0.8%, and the resulting crumb is squeezed, under erzhivaya squeezing water pH in the range of 2,5-6,9 units. using sulfuric acid supplied to the preliminary acidification of latex.

2. The method according to claim 1, characterized in that the magnesium chloride is used in a mixture with magnesium sulfate or calcium chloride in a mass ratio of from 1:10 to 10: 1, respectively.

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

When implementing the proposed method is used as coagulants:

magnesium chloride - magnesium chloride according to GOST 4209-77 or

natural bischofite - technical magnesium chloride (bischofite) according to GOST 7759-73 or TU 2152-005-5356.1075-03;

calcium chloride - technical calcium chloride according to GOST 450-77;

magnesium sulfate - magnesium sulfate 7-water in accordance with GOST 4523-77.

To pre-acidify the latex (before it contacts the divalent metal salt), it is preferable to use a solution of sulfuric acid with a concentration of 0.3-4% (most preferably 0.5-2%).

The mass fraction of soaps of organic acids and organic acids is determined by the method described in GOST 19816.1-74 “Styrene-butadiene rubber. Determination of the content of organic acids and their soaps. ”

To verify in industry the proposed method for the isolation of emulsion rubbers using salts of divalent metals as coagulants and to obtain the indicated rubbers of standard composition, an improved technological scheme of isolation is mounted. A distinctive feature of this scheme is the following.

1. The sequence of flows of electrolytes (acid and salt) is changing.

2. Changes are made to the process mode:

- latex for coagulation with salts of divalent metals comes with a pH in the range of 2.5-7.0 units, while in technology with sodium chloride and the prototype latex has an alkaline environment (pH 9-10);

- a new operation is introduced to maintain the pH of squeezing water in the range of 2.5-6.9 units.

EXAMPLE 1

Isolation of styrene-butadiene rubber SKS-30ARK magnesium sulfate.

15 m ³ / h of rubber latex SKS-30ARK and a 1% solution of sulfuric acid to a pH of latex of 5.0 units are fed into the mixer of the improved cascade of separation Then, the acidified latex enters the first apparatus of the cascade through the cascade, into which a mixture composed of return serum and magnesium sulfate to its concentration in serum of 0.8% is supplied from below at the level of acidified latex exit from the cascade.

The coagulated crumb together with serum (pulp) then goes to the batching apparatus, then to the washing tank (or bypassing it), to the hub to separate the crumbs from the serum and to the squeezer and dryer.

In this case, the pH of squeezed water is maintained in the range of 2.5-6.9 units. supply of sulfuric acid to acidify latex.

The SKS-30ARK rubber isolated by the proposed method is standard, uniform in composition, meets the requirements of NTD (GOST 15627-79 “Synthetic butadiene-methylstyrene rubbers SKMS-30ARK and styrene butadiene SKS-Z0ARK).

1. The mass fraction of organic acids amounted to 5.5% (the norm for scientific and technical documentation is 5.0-6.5%).

2. The mass fraction of soaps of organic acids in rubber is 0.07% (the norm for scientific and technical documentation is not more than 0.15%).

3. The consumption of coagulant magnesium sulfate was 25 kg per ton of rubber.

The conditions for the allocation of rubber SKS-30ARK magnesium sulfate in industry by the proposed method with preliminary acidification of latex, as well as the results are presented in the table.

EXAMPLE 2 (prototype).

Isolation of styrene-butadiene rubber SKS-30ARK according to the prototype with the supply of coagulant magnesium sulfate in the form of a solution in sulfuric acid.

By lowering, SKS-30ARK rubber latex is fed into the first apparatus of the cascade; at the same time, magnesium sulfate in a 0.25% solution of sulfuric acid is dosed to the same level at the lowering level along the return serum line to its concentration in serum of 0.8%.

The coagulated crumb together with serum (pulp) first goes to the batching apparatus, and then to the first concentrator, where the crumb is separated from the serum and transferred to a washing tank with partially-softened water (PUF). The washed crumb enters the second concentrator for separation from water and is then transported to the squeezing machine and to the dryer.

Squeezing water has a pH value of 7.5 units. The consumption of magnesium sulfate when it was supplied as a solution in acid was 30 kg per ton of rubber.

SKS-30ARK commercial rubber did not meet the requirements of NTD (GOST 15627-79) for the content of organic acids (OK) and organic acid soaps (IOC) in it and was not considered conditional.

1. The mass fraction of OK in rubber was 3.57% (norm on standardized technical documentation is 5.0-6.5%).

2. The mass fraction of the IOC is 1.93% (the norm for scientific and technical documentation is not more than 0.15%).

The conditions for the allocation of rubber on the prototype and the results are presented in the table.

EXAMPLE 3

Isolation of styrene-butadiene oil-filled rubber SKS-30-ARKM-15 with bischofite.

Rubber SKS-30ARKM-15 from latex is isolated by bischofite according to the method of example 1 of the description.

The latex-oil emulsion and a 4% solution of sulfuric acid are fed into the mixer of the improved cascade to a pH of the latex-oil emulsion of 7.0 units.

The concentration in the coagulation zone of the divalent metal salt (bischofite) is 0.3%, squeezing water has a pH of 6.9 units.

Commodity rubber SKS-30ARKM-15, isolated by the proposed method under industrial conditions with preliminary acidification of the latex-oil emulsion with sulfuric acid and subsequent coagulation with bischofite, is standard, uniform in composition and meets the requirements of NTD (GOST 11138-78 “Synthetic butadiene-methyl styrene rubbers SKMS -30ARKM-15 and styrene-butadiene SKS-Z0ARKM-15 ”).

1. The mass fraction of OK in rubber amounted to 5.3% (norm on technical standards is 5.0-6.4%).

2. The mass fraction of the IOC is 0.11% (the norm for scientific and technical documentation is not more than 0.25%).

3. The consumption of bischofite for coagulation amounted to 18 kg per ton of rubber.

The conditions for the allocation of rubber SKS-30ARKM-15 according to the proposed method and the results obtained are presented in the table.

EXAMPLE 4

Isolation of styrene-butadiene rubber SKS-30ARKPN with magnesium chloride.

The allocation of rubber SKS-30ARKPN magnesium chloride from latex, previously acidified with a 0.3% solution of sulfuric acid to pH 4.5, is carried out according to example 1 of the description.

The concentration of divalent metal salt (magnesium chloride) in the coagulation zone is 0.25%, the pH of squeezed water is 5.0 units.

Rubber SKS-30ARKPN obtained by the proposed method is standard and uniform in composition and meets the requirements of NTD (TU 38.303-03-070-2001).

1. The mass fraction of OK in rubber was 6.0% (norm on standardized technical documentation is 5.0-7.2%).

2. The content of the IOC - 0% - no (norm on technical documentation is not more than 0.3%).

3. The consumption of magnesium chloride for coagulation was 19 kg per ton of rubber.

The conditions for the allocation of the specified rubber and the results are presented in the table.

EXAMPLE 5

Isolation of oil-filled rubber SKMS-30ARKM-27 with bischofite without washing rubber crumbs.

Isolation of rubber SKMS-30ARKM-27 with bischofite from pre-acidified latex to pH 5.5 with sulfuric acid with a concentration of 2% is carried out according to example 1 of the description. The stage of washing the rubber crumb with partially-softened water (PUF) is excluded. Savings in NWF are 10.3 m ³ per ton of rubber and, accordingly, the amount of contaminated water discharged to water treatment is reduced.

The concentration of bischofite in the coagulation zone is 0.20%, the pH of squeezed water is 6.0 units.

At the same time, the composition rubber fully complies with the NTD requirements (TU 38.303-03-070-2001 “Synthetic butadiene-methyl styrene rubbers SKMS-30ARKM-27 and styrene butadiene rubbers SKS-30ARKM-27”).

1. The mass fraction of OK amounted to 4.9% (norm on technical documentation is 4.0-5.6%).

2. The mass fraction of the IOC is 0.12% (the norm for scientific and technical documentation is not more than 0.15%).

3. The consumption of bischofite was 17 kg per ton of rubber.

The conditions for the isolation of rubber SKMS-Z0ARKM-27 by bischofite and the results obtained are presented in the table.

EXAMPLE 6

Isolation of calcium chloride with nitrile butadiene rubber brand Nitrilast 33M, produced on emulsifiers - a mixture of carboxylic acids.

Isolation of rubber Nitrilast 33M calcium chloride is carried out in accordance with example 1 of the description of the present invention.

The latex of this rubber, before contact with a divalent metal salt (calcium chloride), is pre-acidified by supplying a 1.5% solution of sulfuric acid to a pH of 2.5 units.

The concentration of the divalent metal salt in the coagulation zone is 0.05%, squeezing water has a pH of 2.5 units.

Commodity rubber Nitrilast 33M, isolated under industrial conditions by the proposed method with preliminary acidification of latex and maintaining the pH of squeezed water, is standard, uniform in composition and meets the requirements of NTD (TU 38.40350-99 "Synthetic rubber nitrile butadiene-nitrile Nitrilast 33M").

1. The mass fraction of OK in rubber amounted to 3.0% (norm on technical documentation is not more than 4.0%).

2. The mass fraction of the IOC is 0.1% (the norm for scientific and technical documentation is not more than 0.4%).

3. The consumption of calcium chloride was 23 kg per ton of rubber.

The conditions for the release of rubber Nitrilast 33M calcium chloride and the results are presented in the table.

EXAMPLE 7 (control).

Isolation of styrene-butadiene rubber SKS-30ARK with bischofite with preliminary acidification of latex to pH 7.5 5% sulfuric acid solution, maintaining the concentration of the divalent metal salt in the coagulation zone of 1.0% and the pH of squeezed water of 7.2 units

Rubber SKS-30ARK control experience isolated by the method of example 1 of the description. Bischofite is used as the salt of the bivalent metal.

The latex of this rubber is pre-acidified with sulfuric acid with a concentration of more than 4% (5% solution) to a latex pH of 7.5 units.

The concentration of bischofite in the coagulation zone is 1.0%, squeezing water has a pH of 7.2 units.

Insufficient preliminary acidification of the latex before its contact with the divalent metal salt (pH of latex 7.2 units) leads to an increase in the pH of squeezed water (more than 6.9%) and, as a result, commodity rubber is non-standard and does not meet the requirements of the technical documentation ( GOST 15627-79).

1. The mass fraction of OK in rubber amounted to 4.8% (norm on standardized technical documentation is 5.0-6.5%).

2. The mass fraction of the IOC is 0.30% (the norm for scientific and technical documentation is not more than 0.15%).

3. The consumption of bischofite for coagulation was 24 kg per ton of rubber.

Thus, increasing the pH of the latex to contact with the coagulant and the pH of the squeezed water above the claimed intervals leads to non-standard and non-standard rubber composition.

Maintaining a salt concentration of divalent metal above 0.8% leads to the formation of large chips (lump coagulation) with the capture of uncoagulated latex, while the stickiness of the rubber increases, leading to fouling of the equipment.

Transporting along the cascade and spinning of large agglomerates is difficult, latex gets into waste water during spinning.

An increase in the concentration of an acid solution above 4%, applied to the preliminary acidification of latex, leads to partial coagulation of the latex, clogging of mixers and pipelines with coagulum and frequent stops of the cascade for cleaning equipment.

The conditions for the implementation of the control experiment and the results are presented in the table.

EXAMPLE 8 (control).

Isolation of styrene-butadiene rubber SKS-30ARK with calcium chloride with preliminary acidification of latex to a pH of 2.0 units. a solution of sulfuric acid of 0.2% concentration, maintaining a pH of squeezed water of 2.2 units and a concentration of a divalent metal salt in the coagulation zone of 0.04%.

Isolation of rubber SKS-30ARK calcium chloride from pre-acidified latex to a pH of 2.0 units carried out according to example 1 of the description, the pH of squeezed water was 2.2 units. The consumption of calcium chloride per ton of rubber is 25 kg, the concentration of the specified salt of the divalent metal in the coagulation zone was 0.04%.

Commodity rubber SKS-30ARK isolated by calcium chloride in the above coagulation mode, different from the proposed method, meets the requirements of technical documentation on composition (GOST 15627-79)

1. The mass fraction of OK in rubber is 6.5% (the norm for technical documentation is 5.0-6.5%).

2. The mass fraction of the IOC - 0% (absence) - the norm for scientific and technical documentation is not more than 0.15%.

However, despite the fact that rubber SKS-30ARK, released by a divalent metal salt (calcium chloride) under the above conditions, complies with the requirements of the technical documentation, the application of the proposed method in the modes of this example is characterized by a number of negative disadvantages.

1. Acidification of latex and maintaining the pH of squeezed water less than 2.5 units. leads to excessive consumption of acid, to severe corrosion of equipment and increased pollution of waste water with sulfates.

2. Due to the low concentration of the divalent metal salt in the coagulation zone, incomplete latex coagulation is observed, leading to the loss of rubber in the form of latex and its pollution of effluents.

Thus, the deviation in the proposed method of separation from the claimed parameters leads to a deterioration of economic and environmental indicators of the process.

The conditions for isolating the control experiment and the results obtained are presented in the table.

EXAMPLE 9

Isolation of styrene-butadiene rubber SKS-30-ARKPN with a mixture of magnesium chloride: magnesium sulfate in a mass ratio of 1:10, respectively.

Before coagulation, the latex of this rubber is pre-acidified with a 0.3% solution of sulfuric acid to a pH of 2.5 units, maintaining the pH of squeezed water equal to 2.5 units, the concentration of a mixture of salts of divalent metals in the coagulation zone is maintained at 0.05%.

Coagulation is carried out in accordance with example 1 of the description.

Commodity rubber is homogeneous in composition and meets the requirements of NTD (TU 38.40384-99).

1. The mass fraction of OK in rubber is 6.8% (the norm for technical documentation is 5.0-7.2%).

2. The mass fraction of the IOC - 0% (absence) - the norm for scientific and technical documentation is not more than 0.3%.

The consumption of the salt mixture per ton of rubber was 18 kg.

The selection conditions and the results are presented in the table.

EXAMPLE 10

Isolation of oil-filled styrene-butadiene rubber SKS-30ARKM-15 with a mixture of salts of divalent metals MgCl ₂ : MgSO ₄ in a mass ratio of 1: 1, respectively.

The allocation of rubber SKS-30ARKM-15 with a mixture of salts of MgCl ₂ : MgSO ₄ in a mass ratio of 1: 1 is carried out according to example 1 of the description.

The latex-oil emulsion of this rubber is pre-acidified to a pH of 5.0 units. 1.5% solution of sulfuric acid, maintaining the pH of squeezed water equal to 5.5 units.

The concentration of the mixture of salts of divalent metals in the coagulation zone is maintained in the form of a 0.3% concentration.

Commodity rubber is homogeneous in composition and meets the requirements of NTD (GOST 11138-78).

1. The mass fraction of OK in rubber is 6.0% (norm on standardized technical documentation is 5.0-6.4%).

2. The mass fraction of the IOC is 0.09% (the norm for scientific and technical documentation is not more than 0.25%).

3. The consumption of a mixture of salts of divalent metals is 16 kg per ton of rubber.

The implementation conditions of the proposed method and the results are presented in the table.

EXAMPLE 11

The selection of oil-filled alpha-methylstyrene rubber SKMS-30ARKM-27 with a mixture of salts of divalent metals MgCl ₂ : MgSO ₄ in a mass ratio of 10: 1, respectively.

Isolation of rubber SKMS-30ARKM-27 with a mixture of salts of MgCl ₂ : MgS04 in a mass ratio of 10: 1, respectively, is carried out according to example 1 of the description.

The latex of this rubber is pre-acidified with a 4% solution of sulfuric acid to a pH of 7.0 units, maintaining the pH of squeezed water equal to 6.9 units.

The concentration of salts of divalent metals in the coagulation zone is maintained equal to 0.8% concentration.

Commodity rubber is homogeneous in composition and meets the requirements of NTD (TU 38.303-03-070-2001).

1. The mass fraction of OK in rubber is 5.3% (norm on standardized technical documentation 4.0-5.6%).

2. The mass fraction of the IOC is 0.10% (the norm for scientific and technical documentation is not more than 0.12%).

3. The consumption of the salt mixture per ton of rubber was 15 kg.

The implementation conditions of the proposed method and the results are presented in the table.

EXAMPLE 12

Isolation of nitrile butadiene rubber NITRILAST-18M with a mixture of divalent metal salts of magnesium chloride: calcium chloride in a mass ratio of 1:10, respectively.

The selection of rubber NITRILAST-18M with a mixture of salts of MgCl ₂ : CaCl ₂ in a mass ratio of 1:10, respectively, is carried out according to example 1 of the description.

The latex of this rubber is pre-acidified to a pH of 2.5 units. 0.3% solution of sulfuric acid, maintaining the pH of squeezed water equal to 2.5 units.

The concentration of the mixture of these salts of divalent metals withstand equal to 0.05%.

Commodity rubber is homogeneous in composition and meets the requirements of NTD (TU 38.40350-99 Synthetic butadiene-nitrile rubber "NITRILAST" 18M).

1. The mass fraction of OK in rubber is 3.2% (the norm for scientific and technical documentation is not more than 4.0%).

2. The mass fraction of the IOC is 0.01% (the norm for scientific and technical documentation is not more than 0.4%).

3. The consumption of a mixture of salts of divalent metals per ton of rubber amounted to 20 kg

EXAMPLE 13

Isolation of oil-filled styrene-butadiene rubber SKS-30ARKM-27 with a mixture of salts of divalent metals MgCl ₂ : CaCl ₂ in a mass ratio of 1: 1.

The allocation of rubber SKS-30ARKM-27 with a mixture of salts of MgCl ₂ : CaCl ₂ in a mass ratio of 1: 1 is carried out according to example 1 of the description.

The latex-oil emulsion of this rubber is pre-acidified with 2.0% sulfuric acid to a pH of 5.9 units, maintaining a pH of squeezed water of 6.1 units.

The concentration of the mixture of these salts in the coagulation zone is maintained equal to 0.32%.

Commodity rubber is homogeneous in composition and corresponds to NTD (TU 38.303-03-070-2001).

1. The mass fraction of OK in rubber was 5.0% (norm on standardized technical documentation 4.0-5.6%).

2. The mass fraction of the IOC is 0.09% (the norm for scientific and technical documentation is not more than 0.15%).

3. The consumption of a mixture of salts of divalent metals per ton of rubber amounted to 14 kg

The conditions for the implementation of the proposed method and the results are presented in the table.

EXAMPLE 14

Isolation of styrene-butadiene rubber SKS-30ARK with a mixture of salts of divalent metals MgCl ₂ : CaCl ₂ in a mass ratio of 10: 1, respectively.

The allocation of rubber SKS-30ARK with a mixture of salts of MgCl ₂ : CaCl ₂ in a mass ratio of 10: 1, respectively, is carried out according to example 1 of the description.

The latex of this rubber is pre-acidified to a pH of 7.0 units. 4% solution of sulfuric acid, maintaining the pH of squeezed water equal to 6.9 units.

The concentration of the mixture of these salts in the coagulation zone is maintained equal to 0.8%.

Commodity rubber is homogeneous in composition and meets the requirements of NTD (GOST 15627-79).

1. The mass fraction of OK in rubber amounted to 6.3% (norm on technical standards is 5.0-6.5%).

2. The mass fraction of the IOC is 0.12% (the norm for scientific and technical documentation is not more than 0.15%).

3. The consumption of a mixture of salts of divalent metals per ton of rubber was 15 kg

The conditions for the implementation of the proposed method and the results are presented in the table.

As can be seen from the data shown in examples 1-14 and in the table, the proposed method allows to solve the technical problem - obtaining using salts of divalent metals of standard quality (uniform in composition) emulsion rubbers that meet the requirements of technical documentation on rubber in their organic content acids and soaps of organic acids, improving the manufacturability and environmental friendliness of the process of rubber separation from latexes.

Claims (2)

1. The method of separation of emulsion rubbers from latexes by coagulation using salts of divalent metals from a series of magnesium chloride, magnesium sulfate, calcium chloride, followed by separation of rubber crumbs from serum, extraction and drying, characterized in that before mixing the latex with a divalent metal salt, the latex is pre-acidified diluted sulfuric acid with a concentration of 0.3-4% to a pH of 2.5-7.0 units, in the mixing zone of acidified latex with a divalent metal salt, the concentration of the latter is maintained in the range of 0.05-0.8%, and the resulting cr shku rubber squeeze, squeezing of water while maintaining the pH in the range of 2,5-6,9 units. using sulfuric acid supplied to the preliminary acidification of latex. 2. The method according to claim 1, characterized in that the magnesium chloride is used in a mixture with magnesium sulfate or calcium chloride in a mass ratio of from 1:10 to 10: 1, respectively.