RU2281295C1 - Method for production of modified cis-1,4-polyisoprene - Google Patents

Abstract

FIELD: polymers, rubber industry, in particular production of stereoblock polymers of conjugated dienes, such as cis-1,4-polyisoprene.

SUBSTANCE: modified cis-1,4-polyisoprene is obtained by polymerization pf isoprene in isopentane medium in presence of Ziegler-Natta catalyst. Then catalyst is deactivated; polymer is stabilized and modified with nitrogen-containing compound; polymer in isolated and dried. As nitrogen-containing compound reaction product of maleic anhydride and N-alkyl-N'-phenyl-n-phenylenediamine in amount of 0.5-2 % based on polymer is used.

EFFECT: simplified method for production of polymers having heat oxidative stability.

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Description

The invention relates to the production of stereoregular polymers of conjugated dienes, in particular cis-1,4-polyisoprene (cis-1,4-PI), and can be used in the synthetic rubber industry, and the modified rubbers themselves in the tire and rubber industries.

A known method of producing a modified cis-1,4-PI, which consists in the polymerization of isoprene in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst, deactivation of the catalyst, stabilization and modification with nitrogen-containing compounds, isolation of rubber from the polymerizate and drying it, while using as a modifying agent p-nitrosodiphenylamine / ed. certificate 587138 dated 03.10.75 /.

The disadvantage of this method is the difficulty in obtaining the modified cis-1,4-PI, since, along with p-nitrosodiphenylamine, it is necessary to introduce other chemical compounds into the polymerization mass: a Ziegler-Natta catalyst deactivator and a polymer stabilizer. At the same time, if the most common methanol deactivator is used as a deactivator, it must be removed from the polymerizate, as methanol poisoning the catalyst when it passes through a return solvent system. In addition, the modifying agent used is obtained by multistage synthesis, the last stage of which is the acidification of an aqueous solution of p-nitrosodiphenylamine sodium salt, followed by dehydration.

A known method of producing a modified cis-1,4-PI polymerization of isoprene in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst, followed by deactivation of the catalyst in the resulting polymer solution with N-phenylmaleamic acid, which is also a modifying agent. The deactivated N-phenylmaleamic acid polymerizate is stabilized by any of the antioxidants commonly used to stabilize cis-1,4-PI, after which it is subjected to aqueous degassing. The isolated polymer is dried. The modification reaction is carried out simultaneously with drying or at the stage of degassing (Aut. Certificate 689212 with prior. From 01.09.76, С 08 F 136/06).

The disadvantage of this method is the multistage production of the modified cis-1,4-PI, since the stabilization of the polymer is carried out in a separate stage. In addition, the stability level of the modified cis-1,4-PI is relatively small. So, according to the authors of this application, the index of conservation of rubber ductility ranges from 65-70%.

The most mucilous analogue in technical essence of the proposed technical solution is a method for producing modified cis-1,4-polyisoprene in isopentane in the presence of a Ziegler-Natta catalyst. Catalyst deactivation, stabilization and modification of the polymer is carried out by one chemical compound in one stage - processing of the polymerizate after the end of the polymerization with an aqueous solution of 0.1-1.0 wt.% Based on the polymer of an alkali metal salt and p-quinone- (N-phenyl) - iminooxime formula

/ USSR Copyright Certificate No. 675870 with prior. from 29.03.79, C 08 F 136/08, C 08 G 19/22).

The disadvantage of this method is that the resulting polymers have low thermal oxidative stability, which ultimately leads to a change in the properties of the polymer during processing, since the ductility retention index of the modified cis-1,4-PI is only 65-78%. The objective of the proposed technical solution is to develop a simplified method for producing modified cis-1,4-PI, allowing to obtain polymers with high thermal oxidative stability.

The problem is solved in that in the known method for producing mediated cis-1,4-PI polymerization of isoprene in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst, deactivation, modification and stabilization of a nitrogen-containing compound, followed by isolation of rubber and drying, use nitrogen-containing compound the product of the interaction of maleic anhydride and N-alkyl-N'-phenyl-p-phenidenediamine, with a mass ratio of components (15-50) :( 85-50), respectively, in an amount of 0.5-2 wt.% based on olimer.

The essence of the proposed method is as follows: polymerization of isoprene in isopentane in the presence of a Ziegler-Natta catalyst, then the product of the interaction of maleic anhydride and N-alkyl-N'-phenyl-p-phenylenediamine in the form of a solution in toluene in an amount of 0 is introduced into the obtained polymerizate 5-2 wt.% Per polymer (in terms of dry matter).

The interaction of N-alkyl-N'-phenyl-p-phenylenediamine with maleic anhydride is carried out, for example, as follows: a 60-70% solution of N-alkyl-N'-phenyl-p-phenylenediamine in toluene is prepared at room temperature, which is then heated to 50-60 ° C, after which meleic anhydride is introduced with stirring. The mass ratio of maleic anhydride N-alkyl-N'-phenyl-p-phenylenediamine is (15-50) :( 85-50). The reaction continues until complete dissolution of maleic anhydride (3-16 hours). The resulting solution is pumped to the polymerization unit and introduced into the polymer.

From derivatives of N-alkyl-N'-phenyl-p-phenylenediamine, for example, compounds containing alkyl substituents can be used:

(CH ₃ ) ₂ CH-; C ₇ H ₁₅ -C ₁₀ H ₂₁ -;

(CH ₃ ) ₂ CH-CH ₂ -CH (CH ₃ );

a mixture of (CH ₃ ) ₂ CH-CH ₂ -CH (CH ₃ ) and (CH ₃ ) ₂ CH- (CH ₂ ) ₂ -CH (CH ₃ ).

As a Ziegler-Natta catalyst, for example, the reaction product of triisobutylaluminum and titanium tetrachloride can be used.

Isopentane is preferably used as a solvent for the polymerization.

After polymerization is complete, the polymer is isolated by degassing to remove the solvent and the polymer is dried, and then the plasticity retention index is determined, which characterizes the thermo-oxidative stability of the modified cis-1,4-polyisoprene. Based on the modified rubber, a crude rubber mixture is prepared and the conditional stress modulus is determined at 300% elongation of the mixture and its cohesive strength.

The plasticity conservation index is determined by the following method: 20 g of modified rubber is passed 3 times through the rollers at room temperature and released in the form of skins with a thickness of 1.6-1.8 mm. Then the skin is folded in half and tightly pressed by hand. Six washers with a thickness of 3.5 mm and a diameter of 10 mm are cut out of the skin with a special knife. Determines the plasticity according to Wallace of the three initial samples and find their average value.

Then three washers are placed in a thermostat, in which they maintain the temperature (140 ± 0.2) ° С and hold there for 30 minutes, after which the ductility is determined and the average value is calculated. The plasticity conservation index is the ratio of the plasticity of the oxidized sample to the plasticity of the initial sample of the modified polymer, expressed as a percentage.

Based on the modified polymer, a composition of the following composition is prepared:

Modified polymer 100 parts by weight Stearic acid 2.0 parts by weight Zinc white 5.0 parts by weight Sulfur 2.0 parts by weight Sulfenamide C 0.80 parts by weight Carbon black 50.0 parts by weight

For this, the polymer is mixed with the ingredients on the rollers at a front roll rotation speed of 23:25 rpm and a roll surface temperature of (90 ± 5) ° C. From the resulting rubber compound sheet with a thickness of (2.0 ± 0.2) mm, a plate with a size of (120 × 140) mm is cut out and cooled at room temperature.

Next, the plate is placed in an oven heated to a temperature of (100 ± 3) ° C and kept at room temperature for at least 60 minutes. Five samples are cut from the plate in the direction of rolling with a knife of type 1 in accordance with GOST 270 and their tests are carried out in accordance with GOST 270, namely, they determine the conditional stress at 300% elongation and cohesive strength of the samples, after which their average value is found.

The alleged invention is illustrated by the following examples.

Example 1

The polymerization of isoprene in isopentane is carried out in the presence of 0.3 wt.% (By weight of isoprene) of the catalytic complex, which is the product of the interaction of triisobutylaluminum and titanium tetrachloride, and then into the polymerization mass containing 13.6 wt.% Cis-1,4- polyisoprene, the product of the interaction of maleic anhydride and Santoflex 134 PD is introduced in the form of a solution in toluene in an amount of 0.6 wt.% (dry matter) per polyisoprene. Next, the polymer is isolated by degassing to remove the solvent, and the polymer is dried in a worm dryer. Then determine the index of conservation of plasticity of the modified polymer and the properties of the crude rubber compound obtained on its basis.

The test results are shown in the table.

The conditions of examples 2-8, as well as example 1 and the test results of polymers and compositions are summarized in the following table. Thus, the proposed method for producing modified cis-1,4-polyisoprene is not only relatively simple in its technological design, because allows deactivation of the catalyst, stabilization and modification of the polymer in one step, using the same compound, but also allows you to obtain a modified cis-1,4-polyisoprene with high thermal oxidative stability, rubber raw materials based on which have high cohesive strength .

Table No. / No. of example The structure of the alkyl radical used N-alkyl-N'-phenyl-p-phenylenediamine Trade name of the used N-acyl-N'-phenyl-p-phenylenediamine The amount of modifying additives introduced into the rubber, wt.% Mass ratio of maleic anhydride and N-alkyl-N'-phenyl-p-phenylenediamine Properties of the modified polymer and raw rubber compounds based on it Plasticity Conservation Index%. Conditional stress at 300% elongation Cohesive Strength, MPa one. Mixture
(CH ₃ ) ₂ CH — CH ₂ —CH (CH ₃ ); and
(CH ₃ ) ₂ CH- (CH ₂ ) ₂ -CH (CH ₃ ) Santoflex 134 PD 0.6 30/70 96.6 0.56 2.20 2. - "- Flexson 11 L 0.6 20/80 94.5 0.39 1.85 3. - "- Santoflex 134 PD 0.8 25/75 95.4 0.45 2.04 four. - "- Santoflex 134 PD 1.3 30/70 93.5 0.44 2.42 5. (CH ₃ ) ₂ —CH— Diafen FP 2.0 15/85 96.0 0.72 3.11 6. (CH ₃ ) ₂ CH — CH ₂ —CH (CH ₃ ) Diafen 13 0.5 50/50 97.3 0.45 1.98 7. C ₇ H ₁₅ -C ₁₀ H ₂₁ Diafen FA 2.0 15/85 98.1 0.46 1.37 8*. (CH ₃ ) ₂ CH-CH ₂ -CH (CH ₃ ) Dusantox L 1.4 30/70 97.5 0.63 3.22 ^*) in a mixture with N- (1,3-dimethylbutyl) -N'- / 4- (α, α'-dimethylbenzyl) phenyl /.

Claims (1)

A method of producing a modified cis-1,4-polyisoprene by polymerization of isoprene in isopentane in the presence of a Ziegler-Natta catalyst, deactivating the catalyst, stabilizing the polymer and modifying it with a nitrogen-containing compound, isolating the polymer and drying it, characterized in that the reaction product is used as a nitrogen-containing compound maleic anhydride and N-alkyl-N'-phenyl-p-phenylenediamine, in an amount of 0.5-2 wt.% based on the polymer.