SU536193A1 - Method of coagulation of synthetic latex - Google Patents

Description

The invention relates to a method of coagulation with solutions of electrolytes of synthetic latexes of unsaturated polymers, obtained by using carboxylic acid salts (stearic, oleic, synthetic fatty acids, rosin resin acids and others or their combination) as an emulsifier.

The known method of coagulation of synthetic latexes with electrolyte solutions: various salts (sodium chloride, barium, calcium, magnesium, iron, calcium nitrate, calcium acetate and others) and acids (salt, acetic, sulfuric, and others) 1.

iB of general purpose rubber production The main electrolytes for coagulating latex are sodium chloride and sulfuric acid 2.

The extraction of the lower molecular weight of the habits is also carried out with a solution of sodium chloride in combination with sulfuric acid 3.

Sodium chloride, used to coagulate latexes, is preliminarily purified from mechanical impurities and divalent metal ions, which requires cation exchangers, tanks, and production areas.

The use of sodium chloride involves the thorough washing of the coagulum from water-soluble impurities in order to obtain

the final product with an ash content of less than 0, b%. For washing, softened water is used, the consumption of which for high molecular weight rubbers is 20-30 rubber and for low molecular weight copolymers 60-, 80 rubber. When coagulating latexes of some low molecular weight rubbers (for example, butadiene-p-diethylaminoethyl methacrylate SKAE-SOJ latex) using sodium chloride solution, it is not possible to obtain rubber with an ash content of less than 1.5-2.0% even with a large amount of wash water ( more than 90 rubber). In the process of separating high molecular weight structured rubbers of raST1 thorax and chlorine sodium and sulfuric acid, a crumb of small size (1-2 mm) is formed, which leads to loss of rubber when it is separated from the serum and with the wash water.

The aim of the invention is to obtain a large crumb of rubbers, a reduction in their ash content and a reduction in the consumption of water for washing.

This goal is achieved by introducing into the latex a 16–17% solution of hydrolyzed polyacrylonitrile in the amount of 0.5–4.0 weight before acid treatment. h on uo weight. rubber h.

The use of hydrolyzed polyacrylonitrile instead of sodium chloride makes it possible to reduce by 2–4 times the amount of softened water to wash the rubbers before they are dried. It should be noted that even with the complete elimination of washing, the ash content in rubber is only 0.15-0.35%, which is significantly lower than the norm stipulated by the technical specifications for rubbers.

Complete replacement of sodium chloride with a solution of hydrolyzed polyacrylonitolil. Upon coagulation of latex results in an enlarged rubber crumb of 5-10 mm in size, and thereby improves the conditions for the release of rubber, eliminating the loss of separation of the coagulum crumb from the serum and crushing.

Coagulation of the latexes of these polymers with solutions of hydrolyzed polyacrylonitrile and acid is observed only if the rubbers are obtained by using various salts of carboxylic acids (usually sodium or potassium) as an emulsifier.

Example 1. For coagulation, a latex of a high molecular weight copolymer of divi is taken. Coagulation conditions of high molecular weight and latex coats

n: silt with styrene SKS-ZOARKP with a dry residue of 21%. 300 ml of latex, filled with neozone D (1.5% for rubber), stir in a glass beaker and with stirring

5.6 ml of a 16.8% solution of hydrolyzed polyacrylonitrile are poured. After stirring for 5 minutes, 79 ml of a 2.4% sulfuric acid solution are added to the vial. At pH 2.2, complete coagulation of the latex is observed. The rubber crumbled is separated from the serum and washed with 750 ml of distilled water with stirring for 10 minutes. Then the rubber is drained and dried in an oven at

90-100 ° C.

A control rubber sample was obtained by coagulating the latex with solutions of sodium chloride and sulfuric acid, followed by washing and drying.

A comparative assessment of coagulation and consumption coefficients of electrolytes and wash water is given in Table. I; Physical and chemical properties of rubber - in Table. : 2. Table of low molecular weight copolymers

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The effect of rubber isolation method from latex on their properties

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table 2

Example 2. For coEGulation, a high molecular weight divinylbenzene-structured divinylbenzene copolymer with styrene CKC-EPCS with a dry residue of 34% is taken as a latex.

300 ml of latex, charged with neozone D (1.5% for rubber), is poured into a glass beaker and, with stirring, 6.1 liters {l of a 16.8% solution of hydrolyzed polyacrylonitrile are poured. After stirring for 5 minutes, 130 ml of a 2.4% sulfuric acid solution are added to the flocculant. With an RP of 2.5, a complete coagulation of the latex is observed: the rubber is excreted in the form of a crumb of mm. The rubber is separated from the serum and washed with 1430 ml of distilled water at

stirring for 10 min. Then the rubber is squeezed and dried in a drying cabinet at 90-100 ° C.

A control rubber sample was obtained by coagulating the latex with solutions of sodium chloride and sulfuric acid, followed by washing and drying.

A comparative assessment of the coagulation conditions and consumption coefficients of electrolytes and leaching is given in Table. one; physical and mechanical properties of rubber - in Table. 2

EXAMPLE 3: To coagulate, a latex of a low-molecular-weight copolymer of divinyl with p-diethylaminoethyl methacrylate, SCAE10G, taken when using synthetic potassium salts of synthetic fatty acids (potassium paraffinate) with a dry residue of 35%, is used for coagulation. 300 ml of latex, filled with neozone D (1.5% for rubber), is poured into a glass beaker, to which, with stirring, 12.5 ml of a 16.8% solution of hydrolyzed polyacrylonitrile is added. After stirring for 5 minutes, 36.8 ml of a 10% acetic acid solution is poured into the floc. At pH 5.1, complete coagulation is observed. Characteristic low

The characteristics of low molecular weight rubbers are in Table. 3

Example 4. For coagulation, a latex of a low-molecular-weight copolymer of divinyl with acrylic acid nitrile SKN-40G was obtained, obtained by using cal. I as a paraffinate emulsifier, with a dry residue of 36%.

300 ml of latex, charged with neozone D (1.5% for rubber), is poured into a glass beaker and 6.4 ml of a hydrolyzed polyacrylonitrile solution is added with stirring. After stirring for 5 minutes, 194 ml of a 1.4% solution of sulfuric acid are poured into the floc. At pH 3, complete coagulation of the latex is observed. The rubber is separated from the serum and washed with 2000 ml of tempered water with stirring for 15 minutes. Then the rubber is separated from industrial water and dried at 70-75 ° C under vacuum of 600-700 mm Hg. Art. in a vacuum drying oven.

| Control rubber sample obtained by coagulating latex with chloride solutions

sodium and sulfuric acid, followed by washing and drying.

A comparative assessment of the coagulation conditions and flow rates of electrolytes and wash water is given in Table. one; the characteristics of low molecular weight rubbers are in the table. 3

Example 5. For coagulation, a low molecular weight triple copolymer latex is taken 70 wt. h. divinyl, 25 wt. including styrene and 5 wt. h | 2-methyl-5-vinylpyridine SKS25M: V1P- .5G, obtained using B as an emulsifier of the Pure salts of synthetic fatty acids of the Cie-Cis fraction, with a dry residue of 34%.

The coagulum of the SCS-25MWP-5G latex with solutions of hydrolyzed polyacrylonitrile and sulfuric acid, rubber washing and drying are carried out as in Example 4.

A control rubber sample was obtained by coagulating the latex with solutions of sodium chloride and sulfuric acid, followed by washing and drying.

Comparative assessment of coagulation conditions and electrolytex consumption coefficients. The rubber is separated from the serum and washed with 2100 ml of softened water with stirring for 15 minutes. Then the rubber is separated from the wash water. And dried with 70–75 ° C irri and 600– 700 mm Hg under vacuum. Art. in a vacuum drying oven. A control rubber sample was obtained by coagulating the latex with sodium and acetic acid, followed by washing and drying. A comparative assessment of coagulation conditions and flow rates of electrolytes, rolites, and wash water is given in Table. one; Ha-. Table 3 of ecologically pure rubbers

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Commodity and wash water are given in Table. one; the characteristics of low molecular weight rubbers are in the table. 3

Example 6. For coagulation, the latex of a low molecular weight polymer of SKD-L divinyl, obtained by using the potassium salts of synthetic fatty acids of the Ciu-Xi fraction, as an emulsifier, with a dry residue of 33.2% Coagulation of the CAPS-F by solutions of hydrolyzed polyacrylonitrile and cesium acid, the washing of rubber "its drying is carried out analogously to example 4.

A control rubber sample was obtained by coagulating the latex with solutions of sodium chloride and sulfuric acid, followed by washing and drying.

A comparative assessment of the coagulation conditions and flow rates of electrolytes and wash water is given in Table. one; the characteristic of eismolecular rubber - in the table. 3

Example 7. For coagulation, a latex of a high molecular weight copolymer of divinyl with styrene, SKS-SOARKP, with a dry residue of 21%, is taken. 300 ml of latex filled with neozone D (1.5% for rubber) are placed in a glass beaker and, while stirring, 94 ml of a 1% solution of hydrolyzed polyacrylonitrile are poured. After stirring for 5 minutes, 79 ml of a 2.4% solution of sulfuric acid are added to the flocculant. When: pH 2.4, complete coagulation of the latex is observed. The isolation of the rubber, its washing and the substance is carried out analogously to example 1.

Example 8. For coagulation, a latex of a low-molecular-weight copolymer of divinyl with p-diethylaminoethyl methacrylate, SKA-SOJ, prepared using F4 sodium salts of FFA as an emulsifier, is taken. Syu-Ci6, with a dry residue of 35%. 300 ml of latex filled with neozone D (1.5% for rubber) are poured into a glass beaker, to which 25 ml of an 8% solution of hydrolyzed polyacrylonitrile is added with stirring. After stirring for 5 minutes, 37 ml of a 10% acetic acid solution are added to the floccule. At pH 5, complete coagulation of the latex is observed. Isolation of the SCAE-SOZh rubber, its washing: And the substance is carried out analogously to example 3.

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Example 9. For coagulation of be, rut latex is a high-molecular-weight structured divinylbenzene copolymer of divinyl with a scrolling SKS-ZOPS with a dry residue of 34%. 300 ml of latex filled with neozone D (1.5% for rubber) are poured into a glass beaker: 5 ml of 20% hydrolyzed polyacrylonitrile are poured in with stirring. After grilling for 5 minutes

130 ml of a 2.4% sulfuric acid solution are added to the flocculant. With RP 2.5, a complete coagulation of the latex is observed. The scaling of the SCS-KEPS rubber, its washing and drying are carried out analogously to Example 2.

Use for coagulation of latex 1-20% solution of hydrolyzed polyacrylonitrile in the amount of 0.5-4 weight. hours per 100 weight. The rubber does not cause changes in the coagulation conditions and flow rates of electrolytes and wash water, as well as the physicomechanical and chemical characteristics of the rubbers (Tables 1-3 with additions). Thus, the use of a solution of hydrolyzed polyacrylonitrile makes it possible to obtain a large crumb of rubbers, to significantly reduce their ash content, and to reduce the water consumption for washing.

Claims (3)

1.N. I. Smirnov. "Synthetic rubber, M.-L., Goskhilshzdat, 1949, p. 327- 328 (prototype). 2.P. A. Kirpichnikov. And others. “Chem and technologists SK, L., Himizdat, 1970, p. 398- 399. 3.L. V. Kosmodem Nsky and others. “Rubber and rubber, No. 9, 1973, pp. 10-11.