KR101503339B1 - Process for preparing diene based rubbers having excellent color and thermal resistance - Google Patents

Abstract

The present invention relates to a method for manufacturing diene based rubbers with vivid colors and excellent heat resistance, the method comprising the steps of polymerizing diene based monomers with use of negative ions of an alkyl lithium initiator and accordingly manufacturing living polymers; stopping the polymerization step by adding a polymerization inhibitor; and obtaining stabilized diene based rubbers by adding an anti-oxidant. The present invention relates to a method for manufacturing diene based rubbers with improved functions, which can stabilize rubbers with use of mixing a styrenated phenol compound with a thiomethylphenol as an anti-oxidant, leading to improved heat resistance wherein the diene based rubber manufactured by the method has excellent resistance to heat, thereby being applicable as a material for heat melting adhesive, plastic modifier, tires, etc.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for preparing a diene rubber having excellent color and thermal resistance,

More particularly, the present invention relates to a process for producing a living polymer by anionic polymerization using a diene monomer and an alkyl lithium initiator, a process for adding a polymerization inhibitor to a polymerization reaction product And a step of adding an antioxidant to the polymerization reaction to obtain a stabilized diene rubber. In carrying out the conventional process for producing a diene rubber, the styrene-based phenol compound And a thiomethylphenol compound are mixed with each other to stabilize the rubber to improve the heat resistance without yellowing.

Synthetic rubber is a universal material widely used not only for industrial use but also for everyday life due to its excellent chemical and physical properties. In general, rubber products can exert high product value only if their color is superior, regardless of their physical properties. When the color of the rubber itself directly affects the final product, for example when used as an adhesive or a plastic modifier, it becomes an important quality factor to judge character high and low. Even in the case of rubber used for tires or asphalt, where the importance of color is relatively low, if the color of the product is poor, consumers may be hesitant to use the product due to the prejudice of the property level. Therefore, color is an important factor to consider when manufacturing rubber.

Heat resistance is also an important quality determining factor in choosing rubber products. The reason is that when the rubber product is processed, the process proceeds for a long time at a high temperature condition. Generally, heat resistance is closely related to discoloration resistance, and rubber that is resistant to discoloration at high temperature is excellent in heat resistance. As such, efforts have been made to improve the initial color and heat resistance at the same time when manufacturing rubber products.

As a method for increasing the color and heat resistance of rubber, a method of adding an appropriate antioxidant to rubber is known. The antioxidant acts to prevent the progress of aging by grabbing or decomposing the radicals or peroxides generated in the aging process of the rubber, or preventing the aging phenomenon due to long-term storage.

Examples of such antioxidants include phenol-based, phosphorus-based, sulfur-based, and amine-based ones. Phenolic antioxidants have excellent thermal stability at the beginning, but their use is limited because they are frequently colored after oxidation. Phosphorus antioxidants have the disadvantage of being hydrolyzed by water and decomposing during vulcanization during rubber synthesis. In addition, the amine antioxidant has excellent heat resistance effect, but it easily becomes reddish due to poor coloration and is classified as a cancer-inducing substance, so its use is limited.

In general, in the field of rubber production, 2,6-di- t -butyl-4-methylphenol (BHT) is used as an antioxidant or octadecyl 3- (3,5- Phenyl) propionate (Irganox 1076) and tris- (nonylphenol) phosphite (TNPP). However, BHT has a disadvantage that it has to be used in a large amount in rubber because of its low antioxidative effect, and it easily changes into a dimer in aging process and causes yellowing. When the temperature is low during the drying or processing of rubber due to low sublimation temperature, The amount of BHT remaining in the rubber is reduced, and as a result, the effect as an antioxidant can not be sufficiently exhibited. The combination of Irganox 1076 and TNPP as an antioxidant exhibits excellent effects in terms of color, so that it is widely used as a rubber for reforming plastics, in which color is an important factor, but has a disadvantage in that it is somewhat inferior in terms of heat resistance. In addition, TNPP is easily hydrolyzed at high temperature or acidic conditions in the rubber manufacturing process to produce nonylphenol. Nonylphenol is classified as an endocrine disrupter that affects the human hormone system, There are disadvantages.

Therefore, many studies have been done to overcome these drawbacks and have had considerable effects over the years, for example as follows.

U.S. Patent Nos. 4,857,572 and 5,059,661 disclose 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520) which simultaneously contains a phenolic and a sulfur- Can be used alone, or it can be used with other antioxidants. However, in this case, there is a problem that the lithium oxide generated in the anion polymerization process using the alkyl lithium catalyst reacts with the dimer impurity contained in the Irganox 1520 itself, causing the rubber to yellow.

Korean Patent No. 0340711 discloses a method of using an Irganox 1520 and an octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Irganox 1076) together as an antioxidant of a rubber polymer Method is disclosed. In this case, however, the rubber is yellowed by Irganox 1520.

Korean Patent No. 0340711 discloses a rubber composition comprising octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Irganox 1076) and pentyl tri- (3-dodecylthiopropionate) are used together. Irganox 1076, however, is difficult to process due to flaking in the process of putting the powder into the polymerization tank.

An object of the present invention is to provide a process for producing a diene rubber excellent in heat resistance without yellowing by using a specific antioxidant.

In order to solve the above problems,

a) preparing a living polymer by anionic polymerization using a diene-based monomer and an alkyl lithium initiator;

b) adding an aqueous solution of an alkyl carboxylic acid to the polymerization reactant to stop the activity of the living polymer; And

c) stabilizing a diene rubber prepared by adding a styrenated phenol compound represented by the following formula (1) and a thiomethyl phenol compound represented by the following formula (2) as an antioxidant to the polymerization reaction product;

The present invention also provides a method for producing a diene rubber excellent in color and heat resistance.

[Chemical Formula 1]

(Wherein, in the formula (1), St represents -CH (CH ₃ ) (C ₆ H ₅ ), and n represents the number of substitution of St and is an integer of 1,

(2)

(Wherein R ¹ and R ² are the same or different and each represents an alkyl group having 5 to 16 carbon atoms)

According to the production method of the present invention, it is possible to produce a diene rubber having a transparent color without yellowing and having excellent heat resistance.

Further, according to the production process of the present invention, the thiomethylphenol compound represented by the general formula (2), which tends to be easily crystallized at a low temperature, can be easily handled. That is, the thiomethylphenol compound represented by Formula 2 tends to be easily crystallized at a temperature of about 14 ° C., so that it is cumbersome to perform a separate dissolution process to dissolve crystals in the winter season. However, when it is stored in a state mixed with the styrylated phenol compound represented by the above formula (1), it is kept in a liquid state even at a low temperature of minus 15 ° C, so that it is advantageous in that the addition is simple and the dispersibility is improved.

The present invention relates to a method for producing a rubber by anionic polymerization of a diene monomer, characterized in that a styrenated phenol compound represented by the formula (1) and a thiomethylphenol compound represented by the formula (2) are used together as an antioxidant To a process for producing a diene rubber.

The styrenated phenol compound represented by Formula 1 and the thiomethylphenol compound represented by Formula 2 used in the present invention are each known as an antioxidant. However, the present invention is an invention for providing a high quality diene rubber having a remarkably improved color and heat resistance as compared with the case where each of these two compounds is used as an antioxidant.

The antioxidant used in the diene rubber manufacturing method according to the present invention will be described in more detail as follows.

The chemical structure and manufacturing method of the styrylated phenol compound represented by the above formula (1), wherein the present invention is used as an antioxidant, is disclosed in Korean Patent Registration Nos. 1,111,248 and 1,205,508 in detail. The styrenated phenol compound in the present invention may be monostyranide phenol (MSP) in which one styrene group is substituted at the C2 or C4 position of the phenol. The styrenated phenol compound in the present invention may be a diesteriented phenol (DSP) in which two styrene groups are substituted at C2 and C4 positions of phenol, or at C2 and C6 positions. In addition, the styrenated phenol compound in the present invention may be tris (phenylene) trisilane (TSP) in which three styrene groups are substituted at the C2, C4, and C6 positions of the phenol.

In the present invention, a single compound can be used in the use of the styrenated phenol compound represented by the above formula (1). However, considering that the styrenated phenol compound is prepared from a mixture of two or more kinds, good. When the styrylated phenol compound is used in the form of a mixture, monostyrylated phenol (MSP), diestered phenol (DSP) and tristilene phenol (TSP) are preferably used in a mixture of 7: : 30 to 45% by weight. The reason for this is that when the content of the tristilated phenol contained in the mixture is too large, the viscosity of the antioxidant becomes very high, which makes the use of the antioxidant inconvenient and the performance may be poor. On the other hand, when the content of the monostyranide phenol contained in the mixture is relatively large, the viscosity is very low, which is easy to use and has an advantage of improving the performance. However, there may be a problem that the amount of residual phenol is increased and the smell is generated.

The chemical structure of the thiomethylphenol compound represented by Formula 2 as a further antioxidant and the preparation method thereof are disclosed in detail in Korean Patent Registration Nos. 813,173, 813,174 and 926,796. Specific examples of the thiomethylphenol compound represented by Formula 2 include 2,4-bis (n-pentylthiomethyl) -6-methylphenol, 2,4-bis (n-hexylthiomethyl) Phenol, 2,4-bis (n-heptylthiomethyl) -6-methylphenol, 2,4-bis (n-octylthiomethyl) Methylphenol, 2,4-bis (n-decanylthiomethyl) -6-methylphenol, 2,4-bis (n-dodecanylthiomethyl) (n-tridecanylthiomethyl) -6-methylphenol, 2,4-bis (n-pentadecanylthiomethyl) -6 -Methylphenol, 2,4-bis (n-hexadecanylthiomethyl) -6-methylphenol, and the like. In the present invention, a single compound may be used in the use of the thiomethylphenol compound represented by the general formula (2), but a mixture containing two or more compounds may be used.

In the present invention, the styrenated phenol compound represented by the formula (1) and the thiomethylphenol compound represented by the formula (2) are used together as an antioxidant. The antioxidant may be added to the polymerization reaction separately However, if the antioxidant to be added is first mixed and agitated and then added to the polymerization reaction mixture in the form of a liquid phase, the antioxidant may be dispersed evenly, which makes it easier to control the polymerization reaction. The reason for this is that since the crystallization temperature of the thiomethylphenol compound represented by the above formula (2) is as high as about 14 ° C, it is necessary to use a crystallized antioxidant dissolved in the polymerization reactor during the winter, so that it must be heated at a high temperature for a long time, There is a problem in that the color of the display panel is discolored or the performance is deteriorated, which is troublesome to use. However, when the thiomethylphenol compound represented by Formula 2 is mixed with the styrylated phenol compound represented by Formula 1, the crystallization temperature is lowered to approximately -15 ° C or lower and the viscosity is reduced to 100 to 1,500 cps It is easy to handle because it can be put into a polymerization reactor in a short time at a low temperature in a polymerization reactor and it is easy to control the physical properties of the rubber by inducing uniform dispersion of the antioxidant in the polymerization reaction product.

[0030] Further refinement of the process for producing a diene rubber using the above-described antioxidant as described above comprises the steps of: a) preparing a living polymer by anionic polymerization using a diene monomer and an alkyl lithium initiator; b) adding an aqueous solution of an alkyl carboxylic acid to the polymerization reactant to stop the activity of the living polymer; And c) stabilizing the diene rubber prepared by adding a styrenated phenol compound represented by the following formula (1) and a thiomethyl phenol compound represented by the following formula (2) as an antioxidant to the polymerization reaction product; .

The manufacturing method of the present invention will be described in detail as follows.

Step a) is a step of polymerizing the diene-based monomer. That is, the living polymer is prepared by anionic polymerization using a diene monomer as an alkyl lithium initiator. The anion polymerization is preferably carried out by a solution polymerization method commonly used in the art, and the amount of the solvent to be used is preferably 2 to 10 weight ratio, and the polymerization temperature is maintained in the range of 30 to 150 占 폚. The diene-based monomer is not particularly limited as it is generally used in the art, and specifically includes one or more selected from the group consisting of 1,3-butadiene (BR), isoprene, acrylonitrile and styrene . The diene rubbers produced using such monomers may be selected from butadiene rubber (BR), styrene-butadiene-styrene rubber (SBS), styrene-isoprene-styrene rubber (SIS), butadiene- Rubber (NBR) may be included. The alkyllithium initiator is not particularly limited as it is generally used in the art, but specifically n -butyllithium or secondary-butyllithium may be used. The amount of the alkyl lithium initiator to be used may vary depending on the target molecular weight of the rubber, but it is usually 0.02 to 0.2 wt%, preferably 0.015 to 0.15 wt%, based on the weight of the monomer .

Step b) is a step of stopping the anionic polymerization. That is, the step of removing the activity of the living polymer by replacing the living polymer P ^- Li ⁺ (where P is a polymer chain) terminal with the active hydrogen of the reaction terminator by adding an aqueous alkylcarbonic acid solution as a polymerization terminator to the polymerization reaction product. The alkylcarboxylic acid is an organic acid substituted with an alkyl group having 5 to 16 carbon atoms and specifically includes acetic acid, propionic acid, malonic acid, maleic acid and citric acid. acid) may be used alone or in combination of two or more. The amount of the alkylcarboxylic acid to be used may be 1: 3 to 2 molar ratio with respect to 1 mol of the alkyllithium of the living polymer. If the activity of the living polymer is not completely removed by the addition of the alkylcarboxylic acid, the color may be adversely affected. Therefore, the activity of the living polymer is completely removed by thoroughly mixing in a high-performance line mixer or a stirrer so that the activity of the living polymer can be completely removed It is possible.

Step c) is a step of stabilizing the diene rubber prepared by adding an antioxidant to the polymerization reaction product. That is, the styrylated phenol compound represented by Formula 1 and the thiomethylphenol compound represented by Formula 2 are added to the polymerization reaction product to prepare the desired diene rubber.

0.05 to 2.0 parts by weight of the styrylated phenol compound represented by the formula (1) and 0.01 to 1.0 part by weight of the thiomethylphenol compound represented by the formula (2), based on 100 parts by weight of the discontinued polymer produced in the step b) . The content ratio of the styrenated phenol compound represented by the formula (1) and the thiomethyl phenol compound represented by the formula (2), which are added as an antioxidant, is preferably maintained in a weight ratio of 10: 1 to 1: 1. At this time, in the case of the styrylated phenol compound represented by the above-mentioned formula (1), in order to maintain the required performance of the rubber product, a relatively large amount of the styrylated phenol compound should be used. However, Therefore, it is recommended to use in the above content range. If the amount of the thiomethylphenol compound represented by Formula 2 is less than 0.01 part by weight, the color tends to deteriorate during drying of the rubber at a high temperature. If the amount of the thiomethylphenol compound is more than 1.0 part by weight, rubber compounding property The problem of degradation occurs.

The antioxidant is convenient in the process of mixing the styrenated phenol compound represented by Formula 1 and the thiomethylphenol compound represented by Formula 2 in a solution state. If necessary, it may be dissolved in a non-polar hydrocarbon solvent and used in a solution state. Specific examples of the non-polar hydrocarbon solvents include cyclohexane, n-hexane, heptane, and mixed solvents thereof. It is preferable that the antioxidant is prepared and used as a solution of about 5 to 50% by weight based on the solvent. If the content is less than 5% by weight, the total amount of the antioxidant-added solution may excessively fall below the rubber production amount per unit time, resulting in a decrease in productivity. If the content exceeds 50% by weight, complete dissolution is possible, It is preferable to maintain the above range because it is difficult to control the amount of the antioxidant.

The objects and advantages of the present invention as described above are that, compared with the prior art, particularly, they maintain excellent thermal stability even after prolonged elapse of time, and other objects and effects will become more apparent through the embodiments described later.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

[Example]

Example 1. Preparation of butadiene rubber

Under a nitrogen atmosphere, 5 kg of cyclohexane containing 50 ppm of tetrahydrofuran and 0.6 kg of 1,3-butadiene were added to a 10 L reactor and the temperature was adjusted to 40 ° C. Then 0.018 mol of n -butyllithium was added To initiate the reaction. Five minutes after the reaction reached the maximum temperature, 0.4 kg of styrene was added to continue the reaction. After 15 minutes after the reaction temperature reached the maximum temperature, 0.01 mol (based on citric acid) of citric acid aqueous solution as a reaction stopper was added and stirred to completely remove the living polymer activity. 0.16 part by weight of styrenated phenol (MSP: DSP: TSP = 13:43:44 by weight) and 0.16 part by weight of 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520) 0.08 parts by weight were added to the reactor and mixed.

Then, water of a volume of the polymer solution was poured into the stainless dispersion vessel, the polymer solution was put into the dispersion vessel, and steam was added while stirring to remove the solvent, thereby obtaining rubber crums. The rubber crumb obtained above was dried in a 110 占 폚 roll mill, and a sheet was cut out to a thickness of 2 mm and cut into a rectangular shape of 5 cm 占 5 cm 占 2 mm. The color and the Mooney viscosity of the prepared specimen were measured and are shown in Table 1 below. The Mooney viscosity (ML _{1 + 4} , 100 ° C) was measured using a Mooney viscometer (Mooney MV 2000; ALPHA Technology) after thermally aging the specimen at 100 ° C to confirm the heat resistance of the prepared specimen The results are shown in Table 1 below.

Example 2. Preparation of butadiene rubber

0.14 part by weight of styrene-phenol (MSP: DSP: TSP = 13: 43: 44 weight ratio) as an antioxidant and 0.14 part by weight of 2,4-bis [(octylthio) Methyl] -o -cresol (Irganox 1520) was used to prepare a butadiene rubber specimen. The results of comparative analysis of the color of the specimen and the change in Mooney viscosity after thermal aging at 100 ° C are shown in Table 1 below.

Example 3: Preparation of styrene-butadiene rubber

Except that 0.4 kg of 1,3-butadiene and 0.2 kg of styrene were used instead of butadiene as a monomer and styrene-phenol (MSP: DSP: TSP = 13) as an antioxidant was prepared in the same manner as in Example 1, : 43: 44 weight ratio) and 0.8 parts by weight of 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520) were used to prepare styrene-butadiene rubber specimens. The results of comparative analysis of the color of the specimen and the change in Mooney viscosity after thermal aging at 100 ° C are shown in Table 1 below.

Example 4: Preparation of styrene-butadiene rubber

0.4 kg of 1,3-butadiene and 0.2 kg of styrene were used in place of butadiene as a monomer, and styrene-phenol (MSP: DSP: TSP = 13 : 43: 44 weight ratio) and 0.1 part by weight of 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520) were used to prepare a styrene-butadiene rubber specimen. The results of comparative analysis of the color of the specimen and the change in Mooney viscosity after thermal aging at 100 ° C are shown in Table 1 below.

Comparative Example 1. Preparation of butadiene rubber

A butadiene rubber specimen was prepared in the same manner as in Example 1 except that 0.24 parts by weight of styrene-phenol (MSP: DSP: TSP = 13: 43: 44 weight ratio) was used as an antioxidant. The results of comparative analysis of the color of the specimen and the change in Mooney viscosity after thermal aging at 100 ° C are shown in Table 1 below.

Comparative Example 2. Preparation of butadiene rubber

A butadiene rubber specimen was prepared in the same manner as in Example 1 except that 0.24 parts by weight of 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520) was used as an antioxidant. The results of comparative analysis of changes in color and Mooney viscosity of the specimen after thermal aging at 100 ° C are shown in Table 1 below.

division Diene rubber Antioxidant (parts by weight) Properties of rubber specimens after thermal aging Styrenated phenol ¹⁾ Thiomethyl phenol ²⁾ color
³⁾  Pattern viscosity 24 hours 0 hours 12 hours 24 hours Example 1 Butadiene rubber 0.16 0.08 4 43.3 40.4 35.5 Example 2 Butadiene rubber 0.14 0.10 3 43.2 41.2 39.2 Example 3 Styrene-butadiene rubber 0.16 0.08 4 43.0 39.9 36.0 Example 4 Styrene-butadiene rubber 0.14 0.10 3 43.3 41.5 38.9 Comparative Example 1 Butadiene rubber 0.24 - 10 43.4 51.9 94.7 Comparative Example 2 Butadiene rubber - 0.24 One 43.1 42.5 41.9 1) mixture of styrylated phenol: MSP: DSP: TSP (13:43:44 by weight)
2) thiomethyl phenol: 2,4-bis [(octylthio) methyl] -o -cresol (Irganox 1520)
3) Degree of discoloration: Good 1 << 10 Poor

According to the above Table 1, in the rubber specimens of Examples 1 to 4 prepared by mixing the styrenated phenol compound and the thiomethylphenol compound as the antioxidants, the larger the content of thiomethylphenol is, the better the heat-resistant color and heat resistance Has been confirmed. On the other hand, the rubber specimen of Comparative Example 1 prepared by using the styrenated phenol compound alone as the antioxidant exhibited extremely poor heat-resistant color and heat resistance, and in order to maintain the existing performance of the rubber product, But the use of an excess of styrenated phenol may lead to another problem of deteriorating rubber properties. The rubber specimen of Comparative Example 2, which was prepared using a thiomethylphenol compound alone as an antioxidant, exhibited excellent heat resistant color and heat resistance. However, it was inconvenient to handle due to the low crystallization temperature of the thiomethylphenol compound, There is a problem with the use of Irganox 1520 alone as pointed out in the technical section.

[Reference Example]

This Reference Example is intended to confirm the physicochemical properties of each of the styrenated phenol compound and the thiomethylphenol compound used as an antioxidant and the property change due to the combination thereof.

The melting point of each antioxidant was measured in Table 2 below, and the viscosity was measured and compared at 25 ° C.

Antioxidant Melting point (캜) Viscosity (cps) Styrenated phenol <-15 4,000-4,600 Thiomethylphenol 14 69 Styrylated phenol + thiomethyl phenol (2: 1) <-15 300 to 500  Mixture of styrenated phenol: MSP: DSP: TSP (13:43:44 weight ratio)

According to the above Table 2, the styrenated phenol compound has a high-viscosity liquid state property which is unfavorable for use in the polymerization process, having a melting point of -15 DEG C or less and a viscosity of 4,000 to 4,600 cps. The 2,4-bis (n-octylthiomethyl) -6-methylphenol has a melting point of 14 ° C and a viscosity of 69 cps, which facilitates the formation of crystals. However, when the styrylated phenol compound and 2,4-bis (n-octylthiomethyl) -6-methylphenol are mixed, the melting point is lowered to -15 ° C or lower and the viscosity is in the range of 100 to 1,500 cps, So it is easy to handle. Therefore, it is convenient to mix the styrenated phenol compound and the thiomethyl phenol compound in a mixed state under the condition that a low ambient temperature is maintained as in the winter season in the manufacturing method of the present invention.

Therefore, the diene rubber produced by the production method of the present invention is widely applicable to tire material, hot melt adhesive material and the like because it has excellent color and excellent heat resistance characteristics.

Claims (6)

a) preparing a living polymer by anionic polymerization using a diene-based monomer and an alkyl lithium initiator;
b) adding an aqueous solution of an alkyl carboxylic acid to the polymerization reactant to stop the activity of the living polymer; And
c) stabilizing a diene rubber prepared by adding a styrenated phenol compound represented by the following formula (1) and a thiomethyl phenol compound represented by the following formula (2) as an antioxidant to the polymerization reaction product;
Wherein the rubber is a thermoplastic resin.
[Chemical Formula 1]

(In the formula (1), St represents -CH (CH ₃ ) (C ₆ H ₅ ), and n represents the number of substitution of St and represents an integer of 1, 2 or 3.)
(2)

(Wherein R ¹ and R ² are the same or different and each represents an alkyl group having 5 to 16 carbon atoms)
The method according to claim 1,
Wherein the diene monomer is at least one member selected from the group consisting of 1,3-butadiene (BR), isoprene, acrylonitrile and styrene.
The method according to claim 1,
The alkylcarboxylic acid may be one or two or more selected from the group consisting of acetic acid, propionic acid, malonic acid, maleic acid and citric acid. Which is excellent in color and heat resistance.
The method according to claim 1,
0.05 to 2.0 parts by weight of a styrylated phenol compound represented by the formula (1) and 0.01 to 1.0 part by weight of a thiomethylphenol compound represented by the formula (2) are added as antioxidants based on 100 parts by weight of the polymer in which the activity is stopped Which is excellent in color and heat resistance.
5. The method of claim 4,
Wherein the content of the styrenated phenol compound represented by the formula (1) and the thiomethyl phenol compound represented by the formula (2) to be added as the antioxidant is 10: 1 to 1: 1 by weight. A method for producing a diene rubber.
The method according to claim 1, 4, or 5,
The antioxidant is a mixture of the styrenated phenol compound represented by Formula 1 and the thiomethylphenol compound represented by Formula 2, and has a melting point of -15 ° C or less and a viscosity of 100 to 1,500 cps By weight based on the total weight of the diene-based rubber.