JP2012197416A - Method for improving heat resistance possessed by vulcanized rubber - Google Patents

Abstract

In the field of automobile tires, there has been a demand for a method for improving the heat resistance of vulcanized rubber more easily.
In order to improve the heat resistance of a vulcanized rubber, the use of a composition obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic anhydride, and the following steps (1), (1) 2,2,4-trimethyl-1,2-dihydroquinoline and polymer thereof, and a total of 100 parts by mass thereof A mixture containing 2 to 6 parts by mass of a primary amine with respect to 1 mol of the primary amine and 3 to 10 mol of a carboxylic acid anhydride with respect to 1 mol of the primary amine (2) Step of kneading rubber component and sulfur component (3) Step of vulcanizing the kneaded product obtained in step (2) to obtain vulcanized rubber [Selection] None

Description

  The present invention relates to a method for improving the heat resistance of a vulcanized rubber.

  A condensation reaction product of aniline and acetone is known as an anti-aging agent for vulcanized rubber used in the manufacture of automobile tires (Patent Document 1). However, the vulcanized rubber obtained using such an anti-aging agent may not always have sufficient heat resistance.

  As a method for improving the heat resistance of the vulcanized rubber, 2,2,4-trimethyl-1,2-dihydroquinoline, which is a condensate of aniline and acetone, is distilled from the condensation reaction product of aniline and acetone. There is known a method including a step of taking out and a step of polymerizing 2,2,4-trimethyl-1,2-dihydroquinoline obtained in the step (Patent Document 2).

JP-A-53-145854 JP-A-6-228375

  In the field of automobile tires, a method for improving the heat resistance of vulcanized rubber more simply has been demanded.

The present invention includes the following inventions.
[1] Use of a composition obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic acid anhydride to improve the heat resistance of the vulcanized rubber.

[2] A method for improving the heat resistance of a vulcanized rubber, comprising the following steps (1), (2) and (3).
(1) 2,2,4-trimethyl-1,2-dihydroquinoline and a polymer thereof, a mixture containing 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total, and 1 mol of the primary amine Obtained by the step (2) of kneading the mixture obtained in the step (2) step (1), the rubber component and the sulfur component. Of vulcanizing the kneaded material to obtain vulcanized rubber

[3] The improvement method according to [2], wherein step (1) is performed in the absence of a rubber component.

[4] The improvement method according to [2] or [3], wherein the step (1) is performed in the absence of a sulfur component.

[5] The amount of carboxylic anhydride used in step (1) is 0.6 to 5 mol per 1 kg of the condensation reaction product of aniline and acetone, according to any one of [2] to [4] How to improve.

[6] A heat resistance improver for vulcanized rubber obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic acid anhydride.

[7] A condensation reaction product of aniline and acetone is a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, 2,2,4-trimethyl-1,2-dihydroquinoline, and primary The heat resistance improver for vulcanized rubber according to [6], which is a mixture containing an amine.

[8] A condensation reaction product of aniline and acetone is a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, 2,2,4-trimethyl-1,2-dihydroquinoline, and 2 , 2,4-trimethyl-1,2-dihydroquinoline and 2,2,4-trimethyl-1,2-dihydroquinoline in a total of 100 parts by mass, a mixture containing 2 to 6 parts by mass of a primary amine The heat resistance improver for vulcanized rubber according to [6] or [7].

[9] Obtained by mixing a condensation reaction product of aniline and acetone with 3 to 10 moles of carboxylic acid anhydride per mole of primary amine contained in the condensation reaction product of aniline and acetone. [7] or [8].

[10] The product according to any one of [6] to [9], wherein the condensation reaction product of aniline and acetone is a product produced by condensation reaction of aniline and acetone in the absence of a sulfur component. Heat resistance improver for vulcanized rubber.

  According to the present invention, it is possible to provide a method for more easily improving the heat resistance of a vulcanized rubber used for manufacturing a tire.

  In this specification, “to improve the heat resistance of a vulcanized rubber” means, for example, modifying the tensile properties (JIS K6251) of a test piece in a heat resistance test (JIS K6257) of a vulcanized rubber as described later. Etc.

The present invention includes a method for improving the heat resistance of a vulcanized rubber having the following steps (1), (2) and (3).
(1) 2,2,4-trimethyl-1,2-dihydroquinoline and a polymer thereof, a mixture containing 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total, and 1 mol of the primary amine Obtained by the step (2) of kneading the mixture obtained in the step (2) step (1), the rubber component and the sulfur component. Of vulcanizing the kneaded material to obtain vulcanized rubber

  Hereinafter, each of the steps (1), (2) and (3) will be described. In addition, such an explanation will also explain an invention relating to the use of a composition obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic acid anhydride to improve the heat resistance of the vulcanized rubber. .

  First, the above step (1), that is, 2,2,4-trimethyl-1,2-dihydroquinoline and a polymer thereof, and a mixture containing 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total. And a step of bringing 3 to 10 moles of carboxylic acid anhydride into contact with 1 mole of the primary amine.

（式中、ｎは０以上の整数を表す。ｎは０〜５が好ましい。） 2,2,4-Trimethyl-1,2-dihydroquinoline and a polymer thereof, and a mixture containing 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total are produced by condensation reaction of aniline and acetone. It is preferable that it is a thing.
The condensation reaction product of aniline and acetone contains a condensation reaction product of aniline and acetone represented by the following formula (usually a mixture of compounds having different n) as a main component.

(In the formula, n represents an integer of 0 or more. N is preferably 0 to 5.)

  The condensation reaction product of aniline and acetone is preferably obtained by reacting 2 to 20 mol of acetone with respect to 1 mol of aniline, and reacting acetone with aniline in the presence of an acidic catalyst in a heated state. More preferably, it is produced by a dehydration polycondensation reaction. After mixing the aniline and the acidic catalyst, it is preferable from the standpoint of maintaining the reaction temperature under normal pressure that the excess acetone is continuously fed and the unreacted component is recovered together with the produced water by distillation.

The reaction between acetone and aniline is usually carried out in the presence of an acidic catalyst. Examples of the acidic catalyst include hydrogen halides such as hydrogen chloride, hydrogen bromide, and hydrogen fluoride; organic acids such as organic sulfone; Lewis acids such as boron fluoride; and the like. Hydrogen halide is preferable, and hydrogen chloride is more preferable. The acidic catalyst may be used as an aqueous solution, may be used as a liquid other than the aqueous solution, may be used as a solid, or may be introduced as a gas into the reaction system. When hydrogen halide is used, it is preferably used as an aqueous solution. When hydrochloric acid is used, the concentration is preferably 15 to 35% by mass. The amount of the acidic catalyst used is preferably 0.05 to 0.5 mol with respect to 1 mol of aniline.
If the amount of the acidic catalyst used is 0.05 mol or more, the reaction time is short, and if it is 0.5 mol or less, the amount of the condensation reaction product in which n is 2 or more in the above formula decreases, so that aging occurs. Prevention performance is improved.

The reaction between acetone and aniline may be carried out in the presence of an organic solvent inert to the reaction between acetone and aniline, or may be carried out without substantially using an organic solvent. The reaction temperature is preferably in the range of 100 to 150 ° C. When the reaction temperature is 100 ° C. or higher, the amount of unreacted aniline decreases, and the amount of 2,2,4-trimethyl-1,2-dihydroquinoline and its polymer increases. When the reaction temperature is 150 ° C. or lower, the amount of acetone used is small, which is economically preferable.
Such a reaction is usually completed in a reaction time of 2 to 16 hours. When a relatively large amount of acidic catalyst is used, the reaction time is relatively short.
The reaction end point may be appropriately determined by analyzing the aniline content in the reaction mixture by a general analysis means such as high performance liquid chromatography or gas chromatography.
After completion of the reaction, the catalyst is removed by a method such as neutralization, and then this is distilled under reduced pressure to remove the organic solvent and unreacted aniline, whereby the condensation reaction product of aniline and acetone is removed from the reaction mixture. It is preferred to isolate.

  The resulting reaction mixture may be directly mixed with a carboxylic acid anhydride as a condensation reaction product of aniline and acetone, or a mixture obtained by removing the acidic catalyst by post-treatment such as neutralization, washing, and concentration. May be mixed with a carboxylic acid anhydride as a condensation reaction product of aniline and acetone. These condensation reaction products contain 2,6 parts by weight of primary amines with respect to 2,2,4-trimethyl-1,2-dihydroquinoline and its polymer, and a total of 100 parts by weight thereof.

（式中、ｍは０以上の整数を表す。）

The “primary amine” in the present specification is mainly generated due to aniline and can take various structures, but typical examples include two of the following structures.

(In the formula, m represents an integer of 0 or more.)

Thus, primary amine is a generic name for a plurality of types of compounds, and in this specification, the content of primary amine is an amount expressed by considering all primary amines as aniline (molecular weight: 93.13). . That is, 1 mol of amino group (—NH ₂ ) is converted as 93.13 g of primary amine. Specifically, the primary amine content is determined by dissolving the mixture in chloroform, adding hydrochloric acid and p-dimethylaminobenzaldehyde to prepare a sample solution, measuring the absorbance of the obtained sample solution, It is obtained from the calibration curve used.

  Examples of carboxylic anhydrides include intramolecular anhydrides of aromatic dicarboxylic acids such as phthalic anhydride and pyromellitic anhydride; intramolecular anhydrides of aliphatic dicarboxylic acids such as succinic anhydride, glutaric anhydride, and maleic anhydride. An intermolecular anhydride of an aliphatic carboxylic acid such as acetic anhydride; an intermolecular anhydride of an aromatic carboxylic acid such as benzoic anhydride; and the like. Of these, an intramolecular anhydride of an aromatic dicarboxylic acid or an intramolecular anhydride of an aliphatic dicarboxylic acid is preferable, an intramolecular anhydride of an aromatic dicarboxylic acid is more preferable, and phthalic anhydride is more preferable.

  As for the usage-amount of carboxylic acid anhydride, 3-10 mol is preferable with respect to 1 mol of primary amines, More preferably, it is 3-5 mol.

  The amount of the carboxylic anhydride used is preferably 0.6 to 5 mol, more preferably 0.6 to 2 mol, per 1 kg of the condensation reaction product of aniline and acetone. If the amount of carboxylic acid anhydride used is in the above range, the composition obtained by mixing the condensation reaction product of aniline and acetone and the carboxylic acid anhydride, the rubber component and the sulfur component are kneaded, then The heat resistance of the vulcanized rubber obtained by vulcanization tends to be improved, which is preferable.

  Mixing of the condensation reaction product of aniline and acetone and the carboxylic acid anhydride may be carried out in the presence of a solvent inert to the reaction of the condensation reaction product of aniline and acetone and the reaction of the carboxylic acid anhydride, You may implement without using such a solvent substantially. Examples of such solvents include aromatic hydrocarbon solvents such as xylene and toluene; aliphatic hydrocarbon solvents such as heptane, octane and dimethylhexane; When using a solvent, the usage-amount is 0.5-10 mass parts normally with respect to 1 mass part of condensation reaction products of aniline and acetone, Preferably it is 0.5-2 mass parts.

Mixing of the condensation reaction product of aniline and acetone and the carboxylic anhydride is preferably carried out in the absence of a sulfur component. The sulfur component will be described in detail in step (2).
Mixing of the condensation reaction product of aniline and acetone and the carboxylic anhydride is preferably carried out in the absence of a rubber component.

  The temperature at which the condensation reaction product of aniline and acetone and the carboxylic acid anhydride are mixed is preferably 100 to 150 ° C.

  The obtained composition may be used in the step (2) as it is, or may be used in the step (2) after being subjected to post-treatment such as neutralization, washing and concentration as necessary. The composition thus obtained may be hereinafter referred to as “the present composition”.

  Next, the step (2), that is, the step of kneading the composition (this composition) obtained in the step (1), the rubber component and the sulfur component will be described. Hereinafter, the kneaded product obtained in this step may be referred to as “the rubber composition”.

  Examples of the rubber component include rubber selected from the group consisting of natural rubber and diene rubber.

  Examples of natural rubber include unmodified natural rubber, epoxidized natural rubber, deproteinized natural rubber, and other modified natural rubber.

  Examples of the diene rubber include highly unsaturated rubbers such as styrene / butadiene copolymer rubber and polybutadiene rubber.

  Examples of the sulfur component include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Usually, powdered sulfur is preferred, and insoluble sulfur is preferred when used for tire members having a large amount of sulfur such as belt members. Although the usage-amount is not specifically limited, Preferably it is 2-10 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 3-6 mass parts.

  The amount of the composition used is preferably 0.5 to 5 parts by mass, more preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the rubber component.

  The rubber composition may further contain a filler, a vulcanization accelerator, zinc oxide, fatty acids, cobalt salt and the like.

  Examples of the filler include carbon black, silica, talc, clay, aluminum hydroxide, titanium oxide and the like that are usually used in the rubber field, preferably carbon black and silica are used, and more preferably carbon black. Is used. Although the usage-amount of this filler is not specifically limited, 5-100 mass parts is preferable with respect to 100 mass parts of rubber components, and 30-80 mass parts is more preferable.

  Examples of the carbon black include those described on page 494 of “Rubber Industry Handbook <Fourth Edition>” edited by the Japan Rubber Association. HAF (High Abrasion Furnace), SAF (Super Abrasion Furnace), ISAF (Intermediate). Carbon blacks such as SAF), FEF (Fast Extrusion Furnace), MAF, GPF (General Purpose Furnace), and SRF (Semi-Reinforcing Furnace) are preferred.

Examples of the silica include silica having a CTAB specific surface area of 50 to 180 m ² / g and silica having a nitrogen adsorption specific surface area of 50 to 300 m ² / g. “AQ” and “AQ-N” manufactured by Tosoh Silica Co., Ltd. Degussa's "Ultra Gil (registered trademark) VN3", "Ultra Gil (registered trademark) 360", "Ultra Gil (registered trademark) 7000", Rhodia "Zeosil (registered trademark) 115GR", "Zeosil (registered) (Trademark) 1115MP "," Zeosil (registered trademark) 1205MP "," Zeosil (registered trademark) Z85MP ", and" Nip Seal (registered trademark) AQ "manufactured by Nippon Silica Co., Ltd. are preferable. Further, silica having a pH of 6 to 8 or silica containing 0.2 to 1.5% by mass of sodium, true spherical silica having a roundness of 1 to 1.3, silicone oil such as dimethyl silicone oil, or ethoxysilyl group It is also preferable to blend a silica having a surface treatment with an alcohol such as ethanol or polyethylene glycol, or a silica having two or more different nitrogen adsorption specific surface areas.

  When silica is blended, it is preferable to blend 5 to 50 parts by mass of carbon black per 100 parts by mass of the rubber component, and the blending ratio of silica / carbon black is particularly preferably 0.7 / 1 to 1 / 0.1. When silica is usually used as a filler, bis (3-triethoxysilylpropyl) tetrasulfide ("Si-69" manufactured by Degussa) or bis (3-triethoxysilylpropyl) disulfide ("Si-" manufactured by Degussa) 75 ") or the like, or a compound having a functional group such as silicon or an element such as silicon that can be bonded to silica, a so-called silane coupling agent is preferably added.

Examples of the aluminum hydroxide include aluminum hydroxide having a nitrogen adsorption specific surface area of 5 to 250 m ² / g and aluminum hydroxide having a DOP oil supply amount of 50 to 100 ml / 100 g.

  Examples of vulcanization accelerators include thiazole-based vulcanization accelerators and sulfur compounds described on pages 412 to 413 of Rubber Industry Handbook <Fourth Edition> (issued by the Japan Rubber Association on January 20, 1994). Examples thereof include phenamide vulcanization accelerators and guanidine vulcanization accelerators.

  Specifically, for example, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N, N-dicyclohexyl-2 -Benzothiazolylsulfenamide (DCBS), 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), diphenylguanidine (DPG). Also, morpholine disulfide, which is a known vulcanizing agent, can be used. When carbon black is used as the filler, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N, N-dicyclo When hexyl-2-benzothiazolylsulfenamide (DCBS) or dibenzothiazyl disulfide (MBTS) is used in combination with diphenylguanidine (DPG), silica and carbon black are used in combination as fillers N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N, N-dicyclohexyl-2-benzothiazoli Rusulfenamide (DCBS), dibenzothiazyl disulfide It is preferred that either the de (MBTS) in combination with diphenyl guanidine (DPG).

  Although the usage-amount of this vulcanization accelerator is not specifically limited, 0.5-5 mass parts is preferable with respect to 100 mass parts of rubber components, and 0.5-2 mass parts is more preferable.

  The amount of zinc oxide used is preferably 1 to 15 parts by mass and more preferably 3 to 8 parts by mass with respect to 100 parts by mass of the rubber component.

  The fatty acids are preferably stearic acid, and the amount used is preferably 1 to 15 parts by weight, more preferably 1 to 7 parts by weight, based on 100 parts by weight of the rubber component.

  An example of the cobalt salt is cobalt naphthenate. The amount used is preferably 0.02 to 2 parts by mass, more preferably 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the rubber component as a cobalt content.

  Furthermore, various rubber chemicals commonly used in the rubber industry, such as anti-degradation agents, crosslinking agents, retarders, peptizers, softeners, petroleum resins, lubricants, plasticizers, tackifiers, resorcins and resorcin resins Such an adhesive may be used in combination as necessary.

  As a procedure for kneading each component, a rubber component and a filler are kneaded (hereinafter sometimes referred to as “procedure 1”), and then the composition obtained in procedure 1 and a sulfur component are kneaded. (Hereinafter also referred to as “procedure 2”). The composition is preferably kneaded in the procedure 1.

  The kneading temperature in Procedure 1 is preferably 80 to 200 ° C, more preferably 110 to 160 ° C.

  The kneading temperature in Procedure 2 is preferably 60 to 110 ° C.

  The rubber composition thus kneaded is particularly preferably used for an internal member of an automobile tire. Examples of the internal member of the automobile tire include a belt, a carcass, an inner liner, and an under tread.

  Finally, the step (3), that is, the step of vulcanizing the kneaded product (present rubber composition) obtained in the step (2) to obtain a vulcanized rubber will be described.

  The rubber composition is processed into a specific state and then vulcanized to obtain a target product.

  Vulcanization conditions vary depending on the target product, but are usually selected from the range of about 120 to 200 ° C. and about 1 minute to 2 hours.

  A rubber composition is obtained by blending a condensation reaction product of aniline and acetone (not mixed with a carboxylic acid anhydride), and this rubber composition is added in comparison with a vulcanized rubber obtained by vulcanizing the rubber composition. Vulcanized rubber obtained by vulcanization has improved heat resistance.

  EXAMPLES Hereinafter, although an Example, a test example, a manufacture example, etc. are given and this invention is demonstrated concretely, this invention is not limited to these.

Production Example 1
A 300 mL round bottom flask equipped with a thermometer, a stirrer, and a distillation apparatus was charged with 46.5 g of aniline and 4.4 g of 35 mass% hydrochloric acid and heated to 110 ° C. Acetone 290.4g was dripped there over 110 hours at 110 to 140 degreeC, Then, it heat-retained at 135 to 140 degreeC for 4 hours. Thereafter, the reaction mixture was cooled to 90 ° C., diluted with toluene, neutralized with an aqueous sodium hydroxide solution, and allowed to stand for separation to remove the aqueous layer. After toluene in the oil layer was distilled off, the low boiling point component was distilled off by distillation at an internal temperature of 200 ° C. and a reduced pressure of 2 mmHg to obtain 80.3 g of a condensation reaction product of aniline and acetone.

Production Example 2: Step (1)
In a 100 mL four-necked round bottom flask equipped with a thermometer, stirrer, Dean-Stark apparatus and condenser, 25.0 g of a condensation reaction product of aniline and acetone obtained according to Production Example 1 and 3.46 g of phthalic anhydride were added. The mixture was charged and kept at 140 ° C. for 2 hours to obtain the present composition.

Production Example 3: Step (1)
In Production Example 2, the present composition was obtained in the same manner as in Production Example 2 except that the temperature was kept at 120 ° C. for 4 hours.

Production Example 4: Step (1)
In a 100 mL four-necked round bottom flask equipped with a thermometer, stirrer, Dean-Stark apparatus and condenser, 20.0 g of the condensation reaction product of aniline and acetone obtained in Production Example 1, 11.2 g of phthalic anhydride and xylene 40 0.0 mL was charged and kept at 140 ° C. for 3 hours to obtain the present composition.

Production Example 5: Step (1)
In Production Example 4, this composition was obtained in the same manner as in Production Example 4 except that the amount of phthalic anhydride was changed to 22.3 g.

Example 1
<Step (2) Procedure 1>
Using a Banbury mixer (600 ml Labo Plast Mill manufactured by Toyo Seiki Co., Ltd.), 100 parts by mass of natural rubber (RSS # 1), 45 parts by mass of carbon black (N330), 10 parts by mass of hydrous silica (Nipsil AQ), 3 parts by mass of stearic acid Then, 5 parts by mass of zinc oxide and 2 parts by mass of the present composition obtained in Production Example 2 were blended and kneaded to obtain a composition.
<Step (2) Procedure 2>
The composition obtained by the step (2) procedure 1 and the vulcanization accelerator (N, N-dicyclohexyl-2-benzothiazolylsulfenamide) 0 at a temperature of 60 to 80 ° C. in an open roll machine. .7 parts by mass, 6 parts by mass of insoluble sulfur (as sulfur component) and 2 parts by mass of cobalt naphthenate were blended and kneaded to obtain the rubber composition.
<Step (3)>
Step (2) The rubber composition obtained in the procedure 2 was vulcanized at 150 ° C. to obtain a vulcanized rubber.

Examples 2 and 3
In Example 1, this rubber composition and vulcanized rubber were obtained in the same manner as in Example 1 except that the present composition obtained in Production Examples 3 and 4 was used in place of the present composition obtained in Production Example 2. It was.

Comparative Example 1
In Example 1, a rubber composition and a vulcanized rubber were obtained in the same manner as in Example 1 except that the condensation reaction product of aniline and acetone obtained in Production Example 1 was used instead of the present composition obtained in Production Example 2. Got.

Comparative Example 2
In Example 1, a rubber composition and a vulcanized rubber were obtained in the same manner as in Example 1 except that the present composition obtained in Production Example 5 was used instead of the present composition obtained in Production Example 2.

Test Examples 1 to 3, Comparative Test Examples 1 and 2
The following heat resistance tests were performed on the rubber compositions and vulcanized rubbers obtained in Examples 1 to 3 and Comparative Examples 1 and 2, respectively.
Heat resistance test: A heat resistance test at 100 ° C. for 48 hours was performed by a JIS K6257 B-1 method using a dumbbell No. 3 test piece according to JIS K6251. The elongation at break (EB) was measured according to JIS K6251 using the test piece after the heat resistance test. The relative EB when the value using the rubber composition and vulcanized rubber obtained in Comparative Example 1 is taken as 100 is shown.

  It can be said that the greater the relative EB, the better the heat resistance. Therefore, if this composition is used, the heat resistance which the vulcanized rubber used for manufacture of a tire has can be improved more easily.

  According to the present invention, it is possible to provide a method for more easily improving the heat resistance of a vulcanized rubber used for manufacturing a tire.

Claims (10)

Use of a composition obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic anhydride to improve the heat resistance of a vulcanized rubber. A method for improving the heat resistance of a vulcanized rubber, comprising the following steps (1), (2) and (3).
(1) 2,2,4-trimethyl-1,2-dihydroquinoline and a polymer thereof, a mixture containing 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total, and 1 mol of the primary amine Obtained by the step (2) of kneading the mixture obtained in the step (2) step (1), the rubber component and the sulfur component. Of vulcanizing the kneaded material to obtain vulcanized rubber The improvement method of Claim 2 with which process (1) is implemented in absence of a rubber component. The improvement method according to claim 2 or 3, wherein step (1) is carried out in the absence of a sulfur component. The improvement method according to any one of claims 2 to 4, wherein the amount of the carboxylic acid anhydride used in the step (1) is 0.6 to 5 mol with respect to 1 kg of the condensation reaction product of aniline and acetone.   A heat resistance improver for vulcanized rubber obtained by mixing a condensation reaction product of aniline and acetone and a carboxylic acid anhydride.   The condensation reaction product of aniline and acetone contains 2,2,4-trimethyl-1,2-dihydroquinoline, a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, and a primary amine. The heat resistance improver for vulcanized rubber according to claim 6, which is a mixture.   The condensation reaction product of aniline and acetone is a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, 2,2,4-trimethyl-1,2-dihydroquinoline, and 2,2,4- A mixture comprising 2 to 6 parts by mass of a primary amine with respect to 100 parts by mass in total of a polymer of 4-trimethyl-1,2-dihydroquinoline and 2,2,4-trimethyl-1,2-dihydroquinoline. Item 8. The heat resistance improver for vulcanized rubber according to Item 6 or 7.   The product obtained by mixing a condensation reaction product of aniline and acetone and 3 to 10 moles of carboxylic acid anhydride with respect to 1 mole of primary amine contained in the condensation reaction product of aniline and acetone. 8. The heat resistance improving agent for vulcanized rubber according to 8.   The heat resistance for vulcanized rubber according to any one of claims 6 to 9, wherein the condensation reaction product of aniline and acetone is a product produced by condensation reaction of aniline and acetone in the absence of a sulfur component. Sex improver.