RU2453560C2 - Method of extracting butadiene-nitrile rubber from latex - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of extracting butadiene-nitrile rubber from latex is carried out by feeding sodium sulphite or sodium bisulphite or sodium pyrosulphite in amount of 0.05-0.8 wt % per latex, into a stream of latex degassed beforehand, into which an antioxidant emulsion is also fed. Further, the stream of latex, containing sulphite, is directed into a coagulation apparatus into which aqueous sulphuric acid and an organic amine coagulant in form of a quaternary polymer ammonium salt are also simultaneously fed, said salt being selected from: polydimethyl diallyl ammonium chloride, a methacrylamide and dimethyl aminoethyl methacrylate hydrochloride copolymer, and polydiethyl aminoethyl methacrylate hydrochloride. The amount of the polymer ammonium salt varies from 0.2-0.5 wt %, per rubber, depending on content of leukanol content in latex in the range of 0.1-0.4 wt %, per rubber, at coagulation pH 3-6 and temperature 30-70°C.

EFFECT: invention improves environmental friendliness of the process, specifically reduces content of unreacted monomer - free acrylic acid nitrile, avoids excess synthetic coagulant and the amount of salt used for coagulation.

3 tbl, 7 ex

Description

The invention relates to the field of isolation of synthetic rubbers from latexes and can be used in the petrochemical and oil refining industries.

The most common industrial method for isolating synthetic rubbers from latexes obtained using carboxylic acid soaps as emulsifiers and NF dispersants (leucanol) is to isolate rubbers using sodium chloride and sulfuric acid. Consumption of sodium chloride even with serum recycle ranges from 200 to 400 kg per ton of rubber. All sodium chloride, as well as biodegradable leucanol, is washed into wastewater, which causes environmental problems (P.A. Kirpichnikov, L.A. Averko-Antonovich, Yu.O. Averko-Antonovich. Chemistry and technology of synthetic rubber. Chemistry. Leningrad department ., 1970, p. 395-399, 402-403).

A known method of isolating synthetic rubbers from latexes with mineral acids in the presence of high molecular weight amino-containing coagulating additives of synthetic or natural origin:

- polyalkylene polyamines (US No. 3112299, IPC C08F 6/00, C08F 6/02);

- sodium lignate and water-soluble polyamine (US No. 4025711, IPC C08F 6/22, publ. 24.05.77);

- polyhexamethylene guanidine hydrochloride (metacide) (RU No. 1700007, IPC C08C 1/15, publ. 23.02.91).

A common drawback of these technical solutions is the need to withstand low pH values (1.5-2.5), which causes equipment corrosion, increased sulfate content in wastewater, leaching of coagulants and antioxidants in serum.

Some of them, such as sodium lignate, give the rubbers a dark color, which makes it impossible to use them when obtaining light grades of rubbers.

A coagulant such as metacid is a highly hygroscopic substance, which complicates its storage and preparation of working solutions.

A known method of isolating synthetic rubbers from latexes by the action of an organic coagulant, followed by separation of the resulting rubber crumbs from serum and washing and drying thereof. As an organic coagulant, a protein collagen hydrolyzate with a content of 0.07-20 wt.% Carboxyl groups is used (AS USSR No. 1065424 with priority from 09.09.1982, IPC C08C 1/15, publ. 07.01.1984), and also methods using mixtures of collagen hydrolyzate or phenolamine resin (a condensation product of nonylphenol and hexamethylenetetramine with diethanolamine) with anti-agglomerators, calcium chloride, magnesium chloride or bischofite (RU No. 2140928 with prior, from 04.02.98. IPC C08C 1/14, C08 C 1/14, C14 15; C08F 6/22, publ. 10.11.99, BI No. 31), as well as with the introduction of vinegar anti-agglomerators in various devices to skag coagulation and washing of crumb rubber, with the additional introduction of potassium hydroxide or sodium hydroxide and sodium chloride (RU No. 2203287 with prior, from 24.06.02, IPC C08C 1/14, C08C 1/15, publ. 04/27/2003, BI No. 12).

The disadvantages of these methods are the ability of proteinaceous matter of animal origin to rot during storage and transportation with the release of volatile sharply smelling decomposition products, such as hydrogen sulfide, ammonia, etc. In addition, the contact of working personnel with a protein product during loading for hydrolysis can cause allergic diseases ("Belcosin" is a dusty powdery product).

The relatively high consumption of protein coagulants is explained by the fact that proteins of both animal and plant origin are high molecular weight products. In aqueous solutions, macromolecules, as a rule, are in the form of tangles or twisted fibril spirals, and access to nitrogen atoms is difficult. Since the efficiency of coagulation is largely determined by the rate of interaction of the leukanol sulfo group with the amino group of the protein, isolation of the amino group significantly slows down the speed of the process and reduces the effectiveness of the coagulant.

A significant disadvantage of these methods is that the aqueous solution of the coagulant has an acidic environment. Its introduction into latex causes local point-wise premature coagulation. The additional introduction of anti-agglomerators, potassium, sodium and sodium chloride hydroxides significantly complicates the hardware design and the process of rubber separation.

A known method of coagulation of synthetic rubber latexes, styrene-butadiene or nitrile butadiene, followed by separation of serum and drying the rubber crumbs in an air belt dryer in an acidic environment created by a 1% solution of acetic or sulfuric acid, using a saturated aqueous solution as a coagulant sodium chloride in an amount of 0.1-60 wt.%, counting on latex, and polydimethyldialkylammonium chloride in an amount of 0.05-0.5 wt.% (DD No. 142345, IPC C08C 1/14).

This method provides a friable, well-drying crumb of rubber. However, it has a significant drawback: during its implementation, significant amounts of salt, sodium chloride, are used.

There is also a method of isolating synthetic rubber from latex using a water-soluble copolymer of epichlorohydride with dimethylamine with a molecular weight of 200-2000, at a pH of 1.5-7.0, with a molar ratio of epichlorohydrin: dimethylamine 1: 0.75-0.98 (US No. 4001486, IPC C08F 6/22).

This method provides effective coagulation without the use of inorganic salts. However, it has a significant drawback - both the starting products, dimethylamine and epichlorohydrin, and the copolymer are toxic substances, and the copolymer is a biodegradable product.

The closest technical solution to the proposed one is a method for isolating synthetic rubbers from latexes (styrene-butadiene and nitrile butadiene) stabilized with carboxylic acid soaps, the action of mineral acid and an organic amine coagulant, served in two stages: the first portion of the coagulant, in the amount of 50- 90 wt.%, Incubated with stirring and a temperature of 20-70 ° C for 0.5 hours, the second portion of the coagulant or its mixture with mineral salt in a mass ratio of amine coagulant: mineral salt from 1.0: 0.0 to 1.0: 1500.0 is introduced into the coagulation apparatus together with recycled serum in a mass ratio of latex: serum from 1.0: 1.0 to 1.0: 2.0 (RU No. 22253656 C1, IPC С08С 1 / 15, published on 06/10/2005).

This method of isolation allows both salt-free isolation of rubber from latex and the use of a mixture of amine coagulant in combination with a mineral salt. At the same time, the biologically non-degradable product present in the synthesis recipe, leucanol, binds into an insoluble salt, as a result of which its ingress into waste water is prevented. The introduction of part of the coagulant into the recycled serum allows you to quickly influence the quality of the coagulant.

But this method is not free from disadvantages:

1. The two-stage variant of coagulation complicates the process technology.

2. The unreacted monomer contained in latex, nitrile of acrylic acid (its amount in latex supplied to coagulation is 0.01-0.2 wt.%).

3. The amount of amine coagulant is not consistent with the amount of leucanol present in the latex, but is given with a known excess, and if sodium alkyl sulfonate is used as an emulsifier in addition to carboxylic acids, this excess is especially significant.

The technical task of the invention is to improve the environmental performance of the process and more efficient management of coagulation.

The problem is solved in that the isolation of nitrile butadiene rubbers from latexes is carried out by feeding into the latex stream, degassed, containing 0.01-0.2 wt.% Free acrylic acid nitrile, sodium sulfite or sodium bisulfite, or sodium pyrosulfite in an amount of 0 , 05-0.8 wt.%, Counting on latex, a solution of sulfuric acid and an organic amine coagulant in the form of a quaternary polymer ammonium salt, selected from the group: polydimethyl diallylammonium chloride, copolymer of methacrylamide with dimethylamino hydrochloride are dosed ethyl methacrylate, polydiethylaminoethyl methacrylate hydrochloride, varying the amount of quaternary polymer ammonium salt in the range of 0.2-0.5 wt.%, based on rubber, depending on the content in the latex of leucanol in the range of 0.1-0.4 wt.%, counting on rubber, with a coagulation pH of 3-6 units and a temperature of 30-70 ° C.

This selection method provides:

- chemical bonding of free nitrile of acrylic acid with the formation of a non-toxic product of sodium cyanethyl sulfonate:

CH ₂ = CH ₂ —CN + Na ₂ SO ₃ + H ₂ O → NaSO ₃ —CH ₂ —CH ₂ —CN + NaOH;

- in the process of coagulation, sodium cyanethyl sulfonate reacts with a quaternary polymer ammonium salt:

- the resulting polymer ammonium salt (II) mainly binds to leucanol and remains in rubber, without falling into waste water;

- the polymer ammonium salt is supplied together with the acid to the coagulation apparatus, balanced with the amount of leucanol contained in the latex, therefore, an excess of synthetic coagulant is excluded and it does not enter the waste water.

The invention is illustrated by examples of specific performance.

Example 1 (control)

To 5 kg of nitrileast-26M latex nitrile butadiene rubber latex stabilized by the emulsifier EDiSCAN 1010, an antioxidant emulsion BC-30A is added at the rate of 1.0 wt.% Per rubber. The dry matter content in latex is 20 wt.%. The first portion of the OMP coagulant (the product of the interaction of polyethylene polyamine with (3,5-di-tert-butyl-4-hydroxybenzene) -dimethylamine) is fed in the form of a 10% emulsion, in the amount of 0.025 kg, which is 50% of the total dosage of amine coagulant . The total dosage is 0.5 wt.% Per rubber. Stand for 0.5 hours with stirring at a temperature of 50 ° C. Latex is fed into a coagulation apparatus containing sulfuric acid and a second portion of WMD. Sulfuric acid is dosed in an amount providing a pH of serum of 4.0 units. The crumb of rubber is separated from serum, washed with softened water, squeezed and dried in an air dryer at a temperature of 80-90 ° C. The selection parameters are shown in table No. 2.

Example 2

The degassed rubber latex Nitrilast-26AM, synthesized according to the recipe shown in Table 1, using EDiscan 1010 as an emulsifier, is pumped into the collection, while 40 ml of a 10% sodium sulfite solution are dosed into the latex stream. The latex is heated to a temperature of 60 ° C, an emulsion of antioxidant BC-30A is introduced (1 wt.% Per rubber) and fed to a coagulation apparatus, simultaneously with the supply of a solution of polydimethyl diallylammonium chloride heated to a temperature of 60 ° C in an amount of 0.3 wt.% Sulfuric acid . pH during the coagulation process is maintained at 5.0 units. by feeding additional portions of sulfuric acid. Separated crumb of rubber is separated from serum, washed with softened water, squeezed and dried in an air dryer at a temperature of 80-90 ° C. The selection parameters are shown in table No. 2.

Example 3

Latex was prepared according to the recipe shown in Table 1 for Nitrilast-18AM rubber using a mixture of potassium soap disproportionate rosin (EDISCAN 5600) and potassium soap of vegetable fatty acids (Polynor 1618) in an amount of 2.8 wt.% For monomers.

Subsequent operations were carried out analogously to example 2. Polydimethyldiallylammonium chloride was used as a coagulant. The dosage of the coagulant was 0.2 wt.% On rubber, the dosage of sodium bisulfite was 0.05 wt.% On latex. The selection parameters are shown in table 2.

Example 4

Latex was obtained according to the recipe shown in table 1 for Nitrilast-40AM rubber using EDISCAN 1010 as an emulsifier in an amount of 3.2 wt.% For monomers, a dispersant content of leucanol 0.4 wt.% For monomers and water - 270 wt. % on monomers.

Subsequent operations were carried out analogously to example 2. Polydimethyldiallylammonium chloride was used as a coagulant. The dosage of the coagulant was 0.5 wt.% Per rubber, the dosage of sodium pyrosulfite was 0.8 wt.% Per latex. The selection parameters are shown in table 2.

Example 5

Latex was obtained according to the recipe shown in table 1 for Nitrilast-26AM rubber using vegetable fatty acids (Polinor 1618) as an emulsifier in potassium soap in an amount of 2.8 wt.% Per monomer, the dispersant content was 0.3 wt.% Leucanol. on monomers.

Subsequent operations were carried out analogously to example 2. As a coagulant, a copolymer of methacrylamide with dimethylaminoethyl methacrylate hydrochloride (SMHD) was used. The dosage of the coagulant was 0.4 wt.% On rubber, the dosage of sodium sulfite was 0.07 wt.% On latex. The selection parameters are shown in table 2.

Example 6

Latex was obtained according to the recipe shown in table 1 for Nitrilast-26AM rubber using EDISCAN 1010 as an emulsifier in an amount of 2.8 wt.% For monomers, the dispersant content of leucanol 0.3 wt.% For monomers.

Subsequent operations were carried out analogously to example 2. Polydiethylaminoethyl methacrylate hydrochloride was used as a coagulant. The dosage of the coagulant was 0.4 wt.% On rubber, the dosage of sodium sulfite was 0.07 wt.% On latex. The selection parameters are shown in table 2.

Example 7 (production)

Latex was obtained according to the recipe shown in table 1 for Nitrilast-26AM rubber using EDISCAN 1010 as an emulsifier, the content of the dispersant was 0.3 wt% leucanol per monomer.

The polymerization was carried out in a continuously operating polymerization battery consisting of 10 polymerizers. Upon the conversion of the monomers to the polymer, 70% of the latex was charged with a DEG stopper and degassed in distillation columns using humidified steam from divinyl under slight pressure and from acryl acid nitrile under vacuum to its content in latex - 0.02 wt.%.

Degassed latex was fed for isolation, while an aqueous solution of sodium sulfite in an amount of 0.07 wt.% Per latex was continuously introduced into the latex stream.

Latex was charged with BC-30A antioxidant in an amount of 1.2 wt.% Per rubber and fed into the first coagulation apparatus, where an aqueous solution of sulfuric acid and an aqueous solution of a coagulant, polydimethyl diallylammonium chloride, were fed in an amount of 0.3 wt.% Per rubber. The temperature was maintained at 60-65 ° C, pH - (5.0 ÷ 5.2) units. The coagulated pulp of rubber crumb was fed into a second coagulation apparatus in which potassium soap of rosin and fatty acids were converted into the corresponding free acids.

Then the rubber crumb was separated from the serum in the concentrator, washed with water, separated from the water, wrung out, dried and briquetted. The selection modes are shown in table 2.

The analysis of table 2 shows that in the example obtained by the prototype, the amount of wastewater remains unchanged, the ash content in rubber is at the level of a known technical solution, the amount of amines in wastewater is reduced due to the adjustable dosage of coagulant depending on the leucanol content in latex. In addition, as shown by the industrial production of rubber Nitrilast-26AM according to the proposed scheme, the amount of wastewater is significantly reduced due to a decrease in the amount of water for washing rubber.

As follows from table 3, the rubber obtained by the claimed method fully complies with the TU standards and is not inferior in quality to the rubber obtained in a known manner.

Table 1 Polymerization Recipes No. p / p Recipe Components Dosage, wt.% Nitrilast-18AM Nitrilast-26AM Nitrilast-40AM one Butadiene 84 74 60 2 Acrylic Acid Nitrile 16 26 40 3 Emulsifier: EDISCAN 1010 ¹ - 2,8 3.2 EDISCAN 5600 ² 1.43 - - Polynor 1618 ³ 1.43 2,8 - four Dispersant NF - Leucanol ⁴ 0.1 0.2-0.25-0.3 0.4 5 Pinan hydroperoxide 0.06 0.04 0,03 6 Iron sulfate (II), 7-water 0.01 0.008 0.006 7 Trilon B ⁵ 0.02 0.016 0.012 8 Rongalit ⁶ 0.08 0,07 0.06 9 Tert-dodecyl mercaptan 0.4 0.45 0.6 10 Water 200 200 270 eleven DEGA ⁷ 0.12 0.11 0.1 Notes: 1 - A mixture of potassium salts of a disproportionate rosin and fatty acids (TU 2253-038-00278-893-2003), taken in a ratio of 1: 1; 2 - Potassium soap of a disproportionate rosin (TU 2253-038-00279-893-2003); 3 - A mixture of distilled fatty acids of plant origin (TU 9146-039-58604719-2005); 4 - The product of the interaction of naphthalenesulfonic acid with formaldehyde, neutralized with sodium hydroxide (GOST 6848-79); 5 - Disodium salt of ethylene-diamine-tetraacetic acid (TU 2484-005-22657427-99); 6 - Formaldehyde sodium sulfoxylate (TU 6-14-61-79); 7 - Diethyl hydroxylamine (TU 38.103528-2000).

VS-30A was used as an antioxidant, a product of the interaction of nonylphenol with isobutylene (TU 38.40367-87), introduced into latex in the form of an aqueous-alkaline emulsion.

Latexes were obtained in polymers at a volume of 60 dm ³ , stripping was performed at a temperature of 60 ° C, degassing from acrylic acid nitrile was carried out in a distillation column with water vapor under vacuum.

table 2 Latex rubber selection parameters No. p / p Analyzed components and selection parameters Sample Numbers 1 counter 2 3 four 5 6 7 one. Mark of emitted rubber Nitrilast-26AM Nitrilast-26AM BNK-18M BNK-40M BNK-26AM BNK-26AM Nitrilast-26AM 2 Coagulant type WMD MIC ¹ Defense industry Defense industry SMGD ² GPA ³ Defense industry 3 Coagulant dosage, wt.% On rubber 0.5 0.3 0.2 0.5 0.4 0.4 0.3 four The content of leucanol in latex, wt.%, Rubber 0.25 0.25 0.1 0.4 0.3 0.3 0.2 5 The content of free nitrile of acrylic acid in latex, wt.% 0,025 0,025 0.01 0.2 0.02 0.02 0.02 6 Dosage of sodium sulfite, counting on latex, wt.% - 0.08 0.05 ⁴ 0.80 ⁵ 0,07 0,07 0,07 7 pH coagulation, units 4.0 5,0 3.0 6.0 4.0 4.0 5,0 8 Coagulation temperature, ° С 60 60 70 thirty fifty fifty 65 9 The content of leucanol in wastewater, mg / DM ³ 10 5 8 10 7 9 5 10 The content of cyanethyl sulfonate in wastewater, mg / DM ³ - 2 3 8 3 3 3 eleven The amine content in wastewater, mg / DM ³ 0.29 0.14 0.13 0.15 0.17 0.16 0.13 12 The ash content in rubber, wt.% 0.15 0.15 0.10 0.20 0.14 0.16 0.12 13 The amount of wastewater, m ³ / ton of rubber 17 17 17 17 17 17 10 Note: 1 - VPK-402 - polydimethyldiallylammonium chloride; 2 - SMHD - a copolymer of methacrylamide with dimethylaminoethyl methacrylate hydrochloride; 3 - GPA - polydimethylaminoethyl methacrylate hydrochloride; 4 - in this example, sodium bisulfite is used; 5 - sodium pyrosulfite is used in this example.

Table 3 Qualitative characteristics of the resulting rubbers No. p / p Indicators Norm according to TU * The value of the indicator in the example: one 2 5 6 one Defo stiffness, N 5.8-8.3 7.1 7.1 7.5 7.7 2 Conditional tensile strength, MPa, not less 25.5 26.5 27.0 27.5 27.4 3 Elongation at break,%, not less than 625 640 650 645 650 four Change in the mass of vulcanizate in isooctane / toluene,%, no more 34 28 29th 28 29th 5 Mass loss during drying,%, no more 1,0 0.5 0.5 0.45 0.40 6 Mass fraction of ash,%, no more 0.6 0.15 0.14 0.15 0.12 7 Mass fraction of organic acids,%, no more 6.5 5,4 5.3 5.5 5,6 8 Mass fraction of soaps of organic acids,%, no more 0.4 0.2 0.25 0.2 0.18 * - Analysis performed according to TU 38.40350-99

Claims (1)

Method for isolating nitrile butadiene rubbers from latexes stabilized with leucanol and potassium soaps of carboxylic acids selected from the group: synthetic and natural fatty acids with a number of hydrocarbon atoms from 12 to 18 or mixtures thereof, rosin acids or mixtures of fatty acids with rosin, the action of mineral acids and an organic amine coagulant, characterized in that sodium sulfite, or sodium bisulfite, or sodium pyrosulfite in an amount of 0.05-0.8 wt.%, based on latex, is fed to the latex degassed stream ok latex containing sulfite is sent to a coagulation apparatus, where at the same time an aqueous solution of sulfuric acid and an organic amine coagulant in the form of a quaternary polymer ammonium salt, selected from the group: polydimethyl diallylammonium chloride, copolymer of methacrylamide with dimethylaminoethyl methacrylate, hydrochloride in the range of 0.2-0.5 wt.%, considering rubber, depending on the content of leucanol in the latex in the range of 0.1 -0.4 wt.%, Based on rubber, with a coagulation pH of 3-6 units and a temperature of 30-70 ° C.