RU2436813C1 - Unsaturated carbon-chain natural rubber-based rubber modifier - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: modifier is a mechanical mixture of molecular complexes of hexamethylene tetramine and fumaric acid and hexamethylene tetramine and maleic acid, in which the proton donor used is fumaric acid and maleic acid, taken in weight ratio hexamethylene tetramine: proton donor equal to 1:0.86.

EFFECT: proposed engineering solution enables to widen the raw material base of the rubber industry, increase the strength of the bond between rubber and textile and metallic reinforcing materials, and improve physical and mechanical properties of vulcanising agents.

3 ex, 6 tbl

Description

The invention relates to modifiers for rubbers based on unsaturated carbochain rubbers and can be used in the rubber industry to produce rubbers having high bond strength with textile and metal reinforcing materials in a wide temperature range, as well as improving the physico-mechanical properties of vulcanizates (fracture, dynamic endurance, tear resistance).

Known modifier for rubbers based on the molecular complex of hexamethylenetetramine and a proton donor, as a proton donor, which uses resorcinol, and which contains hydrocarbon wax and mineral oil (USSR Author's Certificate No. 697532, class C08L 9/00; Publ. 15.11.79 )

However, this modifier does not provide a high set of physicomechanical parameters of vulcanizates for lining the textile layers of the carcass, as well as for rubberizing a metal cord broker.

The task was set for the developers: to develop a rubber compound modifier based on available starting materials, expanding the raw materials base of the rubber industry, and providing increased bond strength of rubbers with textile and metal reinforcing materials in a wide temperature range, as well as improving the physical and mechanical properties of vulcanizates.

The purpose of the invention is to increase the durability and performance of pneumatic tires, which is realized by improving the physicomechanical characteristics of vulcanizates of rubber compounds: fracture work, bond strength between rubber and reinforcing materials over a wide temperature range, fatigue resistance, tear resistance.

The goal is achieved in that a molecular complex of hexamethylenetetramine and a proton donor is used as a modifier of rubber compounds for lining a textile carcass and a metal cord breaker for pneumatic tires, where maleic and (or) fumaric acids are used as a proton donor, with a mass ratio of 1: 0.86 (molar ratio 1: 1). As a modifier, molecular complexes of individual maleic and fumaric acids with hexamethylenetetramine or a mechanical mixture of complexes of these individual acids with hexamethylenetetramine can be used.

At present, molecular complexes formed by phenols (both mono- and polyatomic) and amines are widespread. The components in such molecular complexes are linked by a hydrogen bond formed between the hydroxyl groups of phenols and a lone electron pair in amines. In this case, phenol acts as a proton donor, and the amine as an acceptor. Hexamethylenetetramine and hexamethoxymethylmelamine are the most widely used proton-amine acceptors.

The electronic structure of the proton donor has a great influence on the ability to complexation. Proton-donor functions, and hence complex formation, are determined by the electron density on the oxygen atom in the hydroxyl group. Having a high polarity and the ability to form hydrogen bonds, organic acids are also capable of complexation with amines and, in particular, with hexamethylenetetramine.

According to the quantum chemical calculations carried out by the authors, to maximize the decomposition of hexamethylenetetramine under the conditions of manufacture of rubber compounds and their vulcanization, a maximum degree of polarization of tertiary nitrogen is required. This is achieved through the use of molecular complexes that arise not due to the formation of hydrogen bonds, but during the formation of salt-like compounds such as quaternary bases that arise between hexamethylenetetramine and organic unsaturated dibasic acids, which are proposed as fumaric and maleic acids.

A modifier for rubber compounds is obtained by mixing alcohol solutions of hexamethylenetetramine and a proton donor; maleic and fumaric acid are used as a proton donor. Prepare 4-10% (mol.) Alcohol solution of hexamethylenetetramine and 3-5% (mol.) Alcohol solution of proton donor. The prepared solutions are poured in a mass ratio of hexamethylenetetramine: proton donor = (54:46), respectively (molar ratio 1: 1) and mixed. The molecular complex of hexamethylenetetramine with a proton donor begins to precipitate immediately after the solutions are drained. The output of the modifier is 80-95% of theoretical. To obtain a modifier, the precipitate is filtered and dried at room temperature. As a modifier in rubbers, one can use a mechanical mixture of molecular complexes obtained using individual maleic and fumaric acids. The ratio of molecular complexes in the modifier obtained by mechanical mixing of the components depends on what property of the rubber requires improvement.

Modifiers are introduced into raw rubber compounds intended for lining the textile layers of the carcass and rubberizing the metal cord broker in an amount of 0.5-1.5 parts by weight. per 100 parts by weight rubber. The introduction of modifiers into the crude rubber compounds is carried out by conventional methods on rollers or in rubber mixers at the end of mixing using a single-stage process or at the final stage using multi-stage mixing processes. Modifiers do not affect the kinetics of vulcanization of rubber compounds and do not require changes in the technological regimes of vulcanization.

Example 1.7 g of hexamethylenetetramine is dissolved in 200 ml of isopropyl alcohol. 6 g of fumaric acid is dissolved in 200 ml of isopropyl alcohol. While stirring, an alcoholic solution of hexamethylenetatramine is added to the alcoholic solution of fumaric acid. In this case, there is an increase in temperature, turbidity of the solution, and then the formation of a crystalline white precipitate - a molecular complex of hexamethylenetetramine and fumaric acid. The crystalline precipitate is filtered off and dried. The yield of the molecular complex is 80-95% of theoretical.

Example 2.7 g of hexamethylenetetramine is dissolved in 200 ml of isopropyl alcohol. 6 g of maleic acid are dissolved in 200 ml of isopropyl alcohol. While stirring, an alcoholic solution of hexamethylenetatramine is added to the alcoholic solution of maleic acid, with an increase in temperature, turbidity of the solution, and then the formation of a crystalline white precipitate - a molecular complex of hexamethylenetetramine and maleic acid. The crystalline precipitate is filtered off and dried. The yield of the molecular complex is 80-95% of theoretical.

Example 3. The finished molecular complexes prepared according to examples 1 and 2, are thoroughly mixed mechanically at room temperature in any ratio.

Tables 1-6 show the physical and mechanical properties of the vulcanizates based on the proposed modifiers (mixture of modifiers) and the prototype. Elastic strength properties were determined according to GOST 270-75; bond strength of rubber with reinforcing materials according to the N-method - according to GOST 14863-69; indicators of thermal aging and temperature resistance - according to GOST 9.024-74; tear resistance of rubbers - according to GOST 262-93; fatigue endurance with repeated stretching - according to GOST 261-79; resistance to crack propagation with a puncture - according to GOST 9983-74; destruction work - according to GOST 23020-78.

Rubber mixtures containing the proposed modifiers were made in a rubber mixer with a mixing chamber volume of 2.4 dm ³ according to a two-stage mixing mode. Powdered modifiers in the form of a molecular complex of hexamethylenetetramine and a proton donor were introduced at the second (final) stage of the mixing process. Vulcanization was carried out at a temperature of 155 ± 2 ° C; the duration of vulcanization was 15 ± 1 min.

According to the data given in tables 1-6, the use of the proposed modifier can significantly improve such properties as bond strength in rubber-textile cord and rubber-metal cord systems, fracture work, fatigue resistance under repeated stretching, temperature resistance, heat aging resistance, resistance tear apart. The ratio of molecular complexes in the modifier obtained by mechanical mixing of the components depends on what property of the rubber requires improvement.

Table 1 Physico-mechanical properties of vulcanizates for rubberizing a metal cord breaker Indicators Modifying system Cobalt stearate * (1.00 wt.h) PKU * (0.5-1.5 wt.h) The coefficient of thermal aging in strength at 100 ° C × 72 h,% -54.0 -46.4 Cohesive strength, MPa 0,065 0,084 The work of destruction, MJ / m ³ 62.3 74.5 The bond strength according to the N-method with steel cord 9l20 / 35NT, kgf at 20 ° C 45.1 48.0 at 120 ° C 32,0 35.1 Strength according to the N-method with metal cord 4l27, kgf at 20 ° C 31,0 32,4 at 120 ° C 25.6 26.6 Tear resistance, kN / m 120 131 Note: * PKU - modifier - molecular complex of fumaric acid and hexamethylenetetramine; cobalt stearate - a serial modifier to increase the bond strength of rubber with metal.

table 2 Physico-mechanical properties of vulcanizates for rubberizing a metal cord breaker Indicators Modifying system Cobalt stearate * (1.00 wt.h) MKU * (0.5-1.5 wt.h) Thermal aging at 100 ° C × 72 h in strength,% -54 -47 Cohesive strength, MPa 0,065 0.103 The bond strength according to the N-method with steel cord 9l20 / 35NT, kgf at 20 ° C 45.1 47.9 at 120 ° C 32,0 36.9 Fatigue endurance with repeated stretching at 20 ° C, thousand cycle. 384 414 Tear resistance, kN / m 120 140 Note: * MKU - modifier - molecular complex of maleic acid and hexamethylenetetramine; cobalt stearate - a serial modifier to increase the bond strength of rubber with metal.

Table 3 Physico-mechanical properties of vulcanizates for lining textile layers of the frame Indicators Modifying system RU * (1.2 wt.h) MKU * (0.5-1.5 wt.h) Thermal aging at 100 ° C × 72 h in strength,% -35 -31 The work of destruction, MJ / m ³ 39.5 42.6 The strength of communication according to the N-method with cord 30KNTS, kgf at 20 ° C 13.7 14.7 at 120 ° C 10.9 11.5 Fatigue endurance with repeated stretching at 20 ° C, thousand cycle. 53 75 Conditional tensile strength, MPa 16.3 16.6 Resistance to crack growth with a puncture up to 12 mm, thousand cycle. 68 72 Note: * MKU - modifier - molecular complex of fumaric acid and hexamethylenetetramine; RU - serial modifier - molecular complex of resorcinol and urotropin

Table 4 Physico-mechanical properties of vulcanizates for lining textile layers of the frame Indicator Modifying system RU * (1.2 wt.h) MKU + PKU * (0.5-1.5 wt.h) taken in the ratio 1: 1 Thermal aging at 100 ° C × 72h in strength,% -fifty -48 Temperature resistance at 100 ° C in strength,% -46 -42 The work of destruction, MJ / m ³ 48.51 60.50 The strength of communication according to the N-method with cord 30KNTS, kgf at 20 ° C 10.5 11.1 at 120 ° C 8.0 8.3 Fatigue endurance with repeated stretching at 20 ° C, thousand cycle. 70 121 Note: * PKU - modifier - molecular complex of fumaric acid and hexamethylenetetramine; MKU - modifier - a molecular complex of fumaric acid and hexamethylenetetramine; RU - serial modifier - molecular complex of resorcinol and urotropin

Table 5 Physico-mechanical properties of vulcanizates for lining textile layers of the frame Indicator Modifying system RU * (1.2 wt.h) PKU * (0.5-1.5 wt.h) Thermal aging at 100 ° C × 72 h in strength,% -35 -31 Temperature resistance at 100 ° C in strength,% -42 -41 The work of destruction, MJ / m ³ 39.5 41 The strength of communication according to the N-method with cord 30 KNTS, kgf at 20 ° C 13.7 14.1 at 120 ° C 10.9 11.8 Dynamic endurance during repeated stretching at 20 ° С, thousand cycles. 53 121 Conditional tensile strength, MPa 16.3 16.7 Cohesive strength, kgf / cm ² 0.3 0.34 Resistance to crack propagation with a puncture up to 12 mm, thousand cycle. 68 75 Note: * PKU - modifier - molecular complex of fumaric acid and hexamethylenetetramine; RU - serial modifier - molecular complex of resorcinol and urotropin

Table 6 Physico-mechanical properties of vulcanizates for rubberizing metal cord breaker Indicator Modifying system Cobalt stearate (1.00 wt.h) MKU and PKU * (0.5-1.5 wt.h) taken in the ratio 1: 1 Thermal aging at 100 ° C × 72 h in strength,% -68 -62 The bond strength according to the N-method with steel cord 9l20 / 35NT, kgf at 20 ° C 44,2 49.7 at 120 ° C 31.3 37 after heat aging at 100 ° C × 72 h 37.5 43.0 Temperature resistance at 100 ° C in strength,% -fifty -41 Note: * PKU - modifier - molecular complex of fumaric acid and hexamethylenetetramine; MKU - modifier - a molecular complex of fumaric acid and hexamethylenetetramine; cobalt stearate - a serial modifier to increase the bond strength of rubber with metal.

Claims (1)

A rubber modifier based on unsaturated carbochain rubbers, which is a mechanical mixture of molecular complexes of hexamethylenetetramine and fumaric acid and hexamethylenetetramine and maleic acid, in which fumaric and maleic acid taken in the mass ratio of hexamethylenetetramine (donor = 1: donor , 86).