RU2373225C2 - Method of emulsion polymerisation rubber stabilisation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: N (4-anilinophenyl)amide of alkenylsuccinic acid of general formula

, where n=6-18 is used as a stabiliser of phenylenediamine type. The stabiliser is introduced into latex in amount 0.1-1.5 weight fractions per 100 weight fractions of rubber as aqueous alkaline liquor. While using the stabiliser of low content of ballast substance less than 3% and high content of fragments of phenylenediamine type, is suitable to be introduced into latex.

EFFECT: maintained effective stabilisation and eliminated odour nuisance.

4 tbl, 12 ex

Description

The invention relates to the field of stabilization of unsaturated elastomers, in particular emulsion polymerization rubbers.

There is a method of stabilizing unsaturated elastomers by introducing N, N'-diphenylphenylenediamine-1,4 (diaphene FF) into them at the stage of producing rubbers or vulcanizates (Chemical additives to polymers. Handbook. - M .: Chemistry, 1984, p. 28). Diafen FF is used in dosages of 0.5-1% per rubber. The disadvantages of this method are associated with the poor solubility of FF diaphen in polymers and the difficulties of introducing it into emulsion polymerization rubbers, as a result of which this method is not used in industry to stabilize emulsion polymerization rubbers and latexes.

There is also a method of stabilizing rubbers and rubbers using N-isopropyl-N'-phenyl-n-phenylenediamine (AF diaphene) as an antioxidant by introducing it into rubber at the rubber isolation stage or into the rubber mixture when it is prepared on rollers or in a rubber mixer ( Handbook of rubber worker. - M.: Chemistry, 1971, p.330). Diafen AF is used in dosages of 0.5-1.5%, usually in combination with other antioxidants. The disadvantages of this method are the high volatility and high solubility of the resulting antioxidant in acidic aqueous solutions, as a result of which its use to stabilize the rubbers of emulsion polymerization is limited - when coagulating, it is largely washed out of the rubber and into sewage.

There is also known a method of stabilizing synthetic polymers by introducing into them the product of the interaction of a copolymer of maleic anhydride with ethylene or α-olefins, or styrene, or octadecene, or methyl vinyl ether with compounds containing both a hydrazide or amine group and groups of spatially hindered phenol or spatially hindered amine and other groups responsible for the stabilizing effect (US No. 4863999, MKI T08F 8/30, 09/05/1989). The disadvantage of this method is the poor compatibility of the resulting antioxidants with the most common rubbers, such as styrene butadiene, polybutadiene, polyisoprene.

A stabilization method is also known, according to which an antioxidant, which is the product of the interaction of epoxidized linseed oil with an aromatic amine, such as naphthylamine, aniline, toluidine, anisidine, is introduced into natural or synthetic rubber (B.M. Badran, AFYouman, ea High - MW material as antioxidant and antiradiations agent. Elastomerics, V.122, No. 2. p. 26-33, 1990). The antioxidant is introduced into the composition of the rubber mixture in an amount of 2-3 wt.h. per 100 parts by weight rubber. The disadvantages of this method are that the antioxidant must be used in sufficiently large quantities (2-3 wt.%); during the synthesis of the antioxidant, parallel reactions of intermolecular crosslinking take place, leading to difficult to control increase in molecular weight and deterioration of the technological properties of the resulting product; it is also difficult to introduce the resulting product into the rubber latexes of emulsion polymerization due to the difficulties in preparing a stable emulsion.

The closest is a way to stabilize rubbers by using as an antioxidant the product of the interaction of maleated tall oil containing tar and fatty acids in a mass ratio of 1-2: 1, respectively, with a mass fraction of bound maleic anhydride from 10 to 30%, with n-aminodiphenylamine in mass the ratio of maleized tall oil: n-aminodiphenylamine 100: 18-54, supplied in an amount of 1.5-5.0 parts by weight per 100 parts by weight rubber in the form of an aqueous alkaline solution (RU No. 2130031, IPC 6 C08A 6/14, 236/10, 236/12, C08L 5/20, 12/25/1996). The disadvantages of this method are as follows:

1. The content of phenylenediamine fragments responsible for the stabilizing effect in the product is 15-30%, which necessitates the use of a stabilizer in sufficiently high dosages to effectively protect the rubber from aging: as a rule, 1.5-5.0 wt.% Per rubber .

2. Maleinized tall oil may contain up to 20% of neutral substances, which are “ballast” - a product that does not protect elastomers from aging.

3. The disadvantage is the unpleasant smell of tall oil products.

The task of the invention is to develop a method for stabilizing the rubbers of emulsion polymerization, which does not require high doses of the stabilizer, but at the same time retains its effectiveness at the same level as the known methods.

The technical result consists in the use of an antioxidant with a high content of phenylenediamine type fragments, with a low content of “ballast substances” and impurities, and also not causing an unpleasant smell of emulsion polymerization rubbers stabilized by it.

The technical result is achieved by the fact that the method of stabilizing the rubbers of emulsion polymerization involves the introduction of latex stabilizer phenylenediamine type N (4-anilinophenyl) amide alkenylamine acid of the General formula:

where n = 6-18,

in an amount of 0.1-1.5 parts by weight per 100 parts by weight rubber in the form of an aqueous alkaline solution.

The stabilizer used according to the claimed method, N (4-anilinophenyl) amide of alkenyl succinic acid is characterized by a content of the basic substance of at least 97%, that is, it contains a small amount of "ballast" impurities. Also, the content in the stabilizer phenylenediamine fragment, responsible for the stabilizing effect, varies depending on the length of the hydrocarbon radical from 35.5 to 49.0%, and therefore, significantly higher than in the known method. Due to this, the stabilizer is used in small doses: from 0.1 to 1.5% per rubber (the best option is 0.2-0.6%, depending on the type of rubber). In addition, emulsion polymerization rubbers stabilized according to the claimed method have no unpleasant odor.

Table 1 presents data on the properties of rubber Nitrilast-26M, stabilized by various antioxidants (examples 1, 2).

Table 2 presents data on the properties of rubber Nitrilast 18M, stabilized by various variants of antioxidants (examples 3-8).

Table 3 presents data on the properties of the rubber BNKS-28AMN and its vulcanizates, stabilized by various antioxidants (examples 9-10).

Table 4 presents data on the properties of rubber SKS-30ARKM-27 and its vulcanizates, stabilized by various antioxidants (examples 11-12).

To introduce an antioxidant into rubber, a 15-25% aqueous alkaline emulsion is prepared from it. The emulsion is mixed with latex in every way. In this case, there is no decrease in the aggregate stability of latex. When rubber is released from latex, the antioxidant remains in the rubber and is not washed out with wastewater. Isolation can be carried out in various ways: 1) using a mixture of electrolytes for coagulation: salt (sodium chloride) + acid, 2) using a salt-free coagulant (quaternary ammonium base, protein) in combination with acid, 3) using polyvalent metal salts as coagulants ( calcium chloride, magnesium chloride, aluminum sulfate).

In accordance with this method, stabilization of any rubbers of emulsion polymerization can be carried out; for example, nitrile butadiene, styrene butadiene (methyl styrene), polybutadiene, as well as commodity latexes.

In carrying out the invention, the following test methods were used:

Physico-mechanical properties of rubbers and vulcanizates were evaluated by the following methods:

Butadiene-nitrile rubbers;

Nitrilast - TU 38.40.350-99

BNKS-TU 38.30313-98

Styrene-butadiene rubbers;

SKS-30ARKM-27-TU 38.303-03-020-2001

The synthesis of the stabilizer is carried out in accordance with the following General procedure:

Alkenyl succinic anhydride or a mixture of alkenyl succinic anhydrides and n-aminodiphenylamine in a 1: 1 molar ratio of components is charged into a reactor equipped with a stirrer, a jacket for a coolant. The process is carried out with stirring, at a temperature of 65-75 ° C for 1.5 hours. The product has the appearance of a dark, viscous, oily liquid. To introduce the stabilizer into the rubber, a 20 ± 5% concentration aqueous-alkaline emulsion with a pH of 9-11 is prepared from it.

The synthesis of the stabilizer can also be carried out in a solvent. In this case, after preparing the emulsion, the solvent is distilled from it.

The invention is illustrated by examples of specific performance.

Example 1

A coagulation apparatus equipped with a mechanical stirrer and a heating jacket serves 5 kg of nitrilest-26M nitrile butadiene rubber latex (rubber manufactured by Voronezhsintezkauchuk OJSC, mass fraction of bound acrylic acid nitrile in rubber is 27.5%). The dry matter content in latex is 18.5%, pH 10.3. The stirrer is turned on and 14.0 g of a 20% aqueous alkaline solution of dodecenyl succinic acid amide N (4-anilinophenyl) amide are fed into it (stabilizer dosage of 0.3 parts by weight per 100 parts by weight of rubber). The mixture is stirred for 10 minutes, heated to 50 ° C, 1250 g of a solution of sodium chloride in water are added (concentration of 24%), a 0.3% solution of sulfuric acid is poured into the resulting flocculate to a pH of 3.0. Separated crumb of rubber is separated from serum, washed three times with softened water, squeezed out of moisture on a worm unit (moisture content - 7.2%) and dried in an air dryer at a temperature of 80-100 ° C (content of volatile in rubber 0.25%).

In order to verify the stabilizing properties of the product, the rubber is tested in accelerated aging conditions:

1. Heat treatment in an air thermostat, t = 150 ° C, time 60 min. The solubility of rubber before and after aging is evaluated.

2. A rubber mixture is prepared from rubber, the mixture is vulcanized and the vulcanizate is subjected to thermal aging in an air thermostat (t = 100 ° C, aging time - 120 hours). A comparative assessment of the physicomechanical properties of the vulcanizate before and after aging is carried out. The test results are shown in table 1.

Example 2 (prototype)

All operations are carried out analogously to example 1. In this case, the product is used as a stabilizer for the interaction of maleated tall oil with n-aminodiphenylamine (mass ratio of maleized tall oil and n-aminodiphenylamine 100: 20) in an amount of 1% per rubber. The rubber and vulcanizate obtained on its basis are analyzed analogously to example 1. The properties of rubber and vulcanizate are shown in table 1.

Examples 3-7

All operations are carried out in accordance with example 1. In this case, Nitrilast-18 rubber latex is used (the content of the bound acrylic acid nitrile is 18.6%). As a stabilizer, N (4-anilinophenyl) alkenyl succinic acid amide with various hydrocarbon radicals is used, and the dosages of the stabilizer are varied from 0.1 to 1.5 parts by weight. per 100 parts by weight rubber. The test results are shown in table 2.

Example 8 (prototype)

All operations are carried out in accordance with examples 3-8. In this case, the product of the interaction of maleated tall oil with n-aminodiphenylamine with a ratio of 100: 20 is used as an antioxidant. The test results are shown in table 2.

Thus, from examples 1-2, it follows that the antioxidant stabilized by the claimed method effectively protects nitrile butadiene rubbers and vulcanizates based on them from aging, while not inferior to the known method.

Example 9

Analogously to example 1, an emulsion of N (4-anilinophenyl) alkenyl succinic amide (a mixture of amides with n = 12 and n = 14 in the ratio of 70:30) is introduced into the latex of rubber BNKS-28AMN (the content of the bound acrylic acid nitrile is 29%) 0.35 parts by weight stabilizer per 100 parts by weight rubber. The mixture is stirred for 10 minutes, heated to 55 ° C and a solution of calcium chloride is fed into it. The resulting rubber crumb is separated from serum, washed with softened water, squeezed on a worm aggregate and dried in an air dryer. Rubber and vulcanizate based on it are subjected to aging tests. The test results are shown in table 3.

Example 10 (prototype)

Analogously to example 10, rubber stabilized in a known manner is obtained using the product of the interaction of maleated tall oil with n-aminodiphenylamine (component ratio 100: 20). The test results of the rubber and its vulcanizate are shown in table 3, from which it follows that the rubber stabilized by the claimed method is not inferior in properties to the rubber stabilized in a known manner. In this case, the dosage of the stabilizer in the first embodiment is almost three times less.

Examples 11 and 12

Get samples of oil-filled styrene-butadiene rubber SKS-30ARKM-27, stabilized by the known and claimed methods. For this, emulsions are introduced into rubber latex with a dry matter content of 21.2% according to the known and claimed methods in dosages of 1.7 and 0.4 parts by weight, respectively. per 100 parts by weight rubber. In the known method, the product of the interaction of maleated tall oil with n-aminodiphenylamine in a mass ratio of 100: 20 is used, in the claimed method, succinic acid alkenylamide with n = 12-14 (70:30 ratio). Latexes are heated to 60 ° C, sodium chloride is supplied, the filler PN-6 is introduced into the resulting flocculate in an amount of 16.5 wt.% (Oil content in the finished rubber), acidified with sulfuric acid to pH 3.2. The crumb of rubber is separated, washed with water, squeezed, dried. Rubber and vulcanizate are analyzed by accelerated aging. The results are shown in table 4.

Claims (1)

A method for stabilizing emulsion polymerization rubbers by introducing a phenylenediamine type stabilizer, N (4-anilinophenyl) alkenyl succinic acid amide of the general formula:

where n = 6-18,
fed into latex in an amount of 0.1-1.5 parts by weight per 100 parts by weight rubber in the form of an aqueous alkaline solution.