JP3108111B2 - Conjugated diene rubber composition and tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying a conjugated diene rubber composition, and more particularly to a method for polymerizing a conjugated diene compound using an organic alkali compound as an initiator in a hydrocarbon solvent, or a method for modifying the conjugated diene compound. The present invention relates to a method for modifying a conjugated diene rubber composition obtained by copolymerizing a vinyl aromatic compound with a vinyl aromatic compound. Further, the present invention provides a
The present invention also relates to a conjugated diene rubber composition excellent in low heat build-up and a tire using the same in a tread.

[0002]

2. Description of the Related Art In recent years, demands for safety and low fuel consumption of automobiles have become more and more strict, and accordingly, low fuel consumption, safety and wear resistance have been strongly required for rubber materials of automobile tires. It has become required. In order to meet such demands, methods for improving conjugate diene-based rubber materials to simultaneously improve contradictory characteristics such as low fuel consumption and safety have been studied. For example, JP-B-44-4996, JP-A-57-205414, and U.S. Pat. No. 3,956,232 disclose that after butadiene is polymerized using an organolithium initiator in a hydrocarbon solvent, or After copolymerizing butadiene and styrene,
A modification method has been proposed and implemented in which a tin halide compound or an alkenyltin compound is reacted to obtain a conjugated diene polymer excellent in safety and low heat generation, that is, excellent in safety and low fuel consumption.

[0003] Other reforming methods are disclosed in
No. 162604 discloses a method for modifying a diene-based polymer rubber with an aromatic ketone compound, and JP-A-60-137913.
No. 3-4, a modification method using an amide compound, etc.
No. 0737 proposes a modification method using a tin carboxylate compound, and JP-A No. 62-161844 proposes a modification method using a carbodiimide compound.

[0004]

However, the above-mentioned conventional reforming methods do not sufficiently improve the low heat build-up and safety of the conjugated diene-based polymer rubber, and the industrial practice of these reforming methods. Faced difficult problems in terms of: For example,
Since the polymer modified by reacting with the above-mentioned tin halide compound or alkenyltin compound has a carbon-tin bond at the terminal of the polymer, acidic substances such as inorganic acids, organic carboxylic acids and Lewis acids, and organic phosphorus The carbon-tin bond at the terminal of the polymer is easily cleaved by chemical reaction with the compound and the organic sulfur compound, or hydrolysis reaction under strong acid or strong alkali, whereby the molecular weight is largely changed and unstable. Was. Furthermore, the vulcanizates of the conjugated diene-based polymer rubber having undergone such molecular cleavage have a problem that the rebound resilience and the tensile strength are significantly reduced. In order to prevent such a molecular cleavage phenomenon from occurring, the type of polymerization terminator and antioxidant used in the production of these polymers, the conditions for desolvation, the type of extender oil to be added, and the type of other polymers to be blended There were significant restrictions on the choice of such items.

The present invention has been made in order to overcome the problems of the prior art, and it has been found that the properties of the vulcanized product, particularly the low heat build-up and the breaking strength, can be improved without causing a change in the molecular weight of the polymer. It is an object of the present invention to provide a method for modifying a conjugated diene rubber composition so as to improve it. Further, another object of the present invention is to provide a rubber composition having excellent properties of a vulcanized product, particularly, low heat build-up and breaking strength.

[0006]

SUMMARY OF THE INVENTION In order to achieve this object,
Therefore, the reforming method according to the present invention has the following features.
That is, an organolithium compound is used as an initiator in a hydrocarbon solvent.
Conjugated diene compound is polymerized or conjugated
Obtained by copolymerizing a diene compound and a vinyl aromatic compound
The conjugated diene polymer rubber has the general formula R¹ R³  > C = NN <(1) R² R⁴  Reacting a hydrazone compound represented by
Where R in the formula¹, R², R³, R⁴Is hydrogen,
Alkyl group, cycloalkyl group, alkenyl group,
Aryl group, phenyl group or their partial substitution
Show.

The polymer rubber modified by the method according to the present invention is obtained by polymerizing a conjugated diene compound or a conjugated diene compound with a vinyl aromatic compound by using an organic alkali compound as an initiator in a hydrocarbon solvent. And a conjugated diene polymer rubber obtained by copolymerizing Examples of the conjugated diene compound constituting the linear polymer main chain of the polymer to be modified include conjugated diolefins such as butadiene, isoprene and pentadiene, but butadiene is preferred. The glass transition temperature (Tg temperature) of the conjugated diene compound is desirably −10 ° C. or less. This is because a Tg temperature of −10 ° C. or more is not preferable because rebound resilience and elongation at break are inferior. Examples of the vinyl aromatic compound that can be copolymerized with the conjugated diene compound, which constitutes the copolymer, include styrene, vinyltoluene, and α-methylstyrene, but styrene is preferred. The content of the conjugated diene compound constituting the linear polymer main chain is preferably 50% by weight or more from the viewpoint of elongation, tensile strength and abrasion resistance.

The polymerization solvent to be used may be any as long as it is stable with respect to the organic alkali compound used as the polymerization initiator. For example, pentane, hexane, heptane,
Cyclohexane, methylcyclohexane, benzene, toluene, xylene and mixtures thereof are examples. The ratio of the solvent amount to the monomer is 2 to 20 times the weight or the weight ratio of the monomer to the solvent is 1/20 to 1/20.
2 range. As the organic alkali metal compound used as a polymerization initiator, sodium naphthalene, potassium naphthalene, n-butyllithium, sec-butyllithium, phenyllithium and the like are used, and an organic lithium compound, particularly n-butyllithium is preferable. is there.

In the polymerization or copolymerization, terahydrofuran, dimethoxybenzene, ethylene glycol dimethyl ether,
Ether compounds such as diglyme, N, N, N ', N'
Amine compounds such as -tetramethylethylenediamine, triethylenediamine or the like, potassium salts of t-butanol, potassium salts of amyl alcohol, potassium salts of nonylphenol and the like can be added.

The hydrazone compound represented by the above formula (1) used as a modifier in the present invention may be any condensation product of a disubstituted alkyl and / or aryl hydrazine with an aldehyde or ketone. For example, benzaldehyde-N, N-dimethylhydrazone, benzaldehyde-N, N-diphenylhydrazone, benzaldehyde-N, N-methylphenylhydrazone, p-methylbenzaldehyde-N, N-dimethylhydrazone, p- (N, N-dimethyl Amino) benzaldehyde-N, N-dimethylhydrazone, p- (N,
N-dimethylamino) benzaldehyde-N, N-diphenylhydrazone, p- (N, N-methylphenylamino) benzaldehyde-N, N-dimethylhydrazone,
p- (N, N-methylphenylamino) benzaldehyde-N, N-diphenylhydrazone, p- (N, N-diphenylamino) benzaldehyde-N, N-dimethylhydrazone, p- (N, N-diphenylamino) benzaldehyde -N, N-diphenylhydrazone, benzophenone-N, N-dimethylhydrazone, benzophenone-N, N-diphenylhydrazone, 4,4'-bis (dimethylamino) benzophenone-N, N-dimethylhydrazone, 4,4'- Examples include, but are not limited to, hydrazone compounds such as bis (dimethylamino) benzophenone-N, N-diphenylhydrazone. The compounding ratio of the above-mentioned modifier is different depending on the type of the conjugated diene-based polymer rubber and the modifier, but 0.01 to 2 equivalents of the modifier is used based on the number of moles of the organic alkali metal used as the polymerization initiator. Added.
The amount of the organic alkali metal varies depending on the type of the organic alkali metal and the molecular weight of the conjugated diene polymer or copolymer to be produced.
It is about 0.1 to 3 mmol per 100 g.

The modification reaction with the modifier is carried out in a step subsequent to the polymerization reaction step for producing a conjugated diene polymer or copolymer. The equipment required for the reaction is a conventional reaction equipment and does not require any special equipment for performing the method according to the present invention. First, a conjugated diene polymer or copolymer is produced in a usual polymerization reaction step operated in a batch or continuous manner. A conjugated diene compound such as butadiene is dissolved at a predetermined concentration in a hydrocarbon solvent such as cyclohexane to prepare a monomer solution, and the prepared solution is charged into a reaction vessel. The reaction vessel is a general pressure-resistant reaction vessel equipped with a stirrer inside and a heating jacket provided on the outer periphery of the vessel. When modifying a copolymer of a conjugated diene compound and a vinyl aromatic compound, a vinyl aromatic compound such as styrene is further charged into the reaction tank.

Next, predetermined amounts of an appropriate randomizing agent and an organic alkali compound as a polymerization initiator are added, respectively.
The polymerization reaction is carried out at a temperature of 0 to 100 ° C. while heating with a heating jacket and stirring with a stirrer. After a lapse of a predetermined time required for the polymerization reaction, the process proceeds to the step of performing the modification method according to the present invention, that is, the modification reaction step. A predetermined amount of a hydrazone compound is added to a solution of the polymer formed by the above polymerization reaction. While stirring for a predetermined time, approximately 30 minutes to 4 hours, a predetermined reaction temperature, a range of 0 to 120 ° C., preferably 40 to 100 ° C.
The reaction is performed while maintaining the temperature in the range of ° C. Next, a solvent removal operation and a drying operation are performed by a usual method to obtain a modified conjugated diene polymer rubber as a product.

In order to achieve the object of providing a rubber composition having excellent vulcanizate breaking strength and low heat build-up, the rubber composition according to the present invention comprises a conjugate modified by the modification method according to the present invention. It is characterized in that the raw material rubber contains 30% by weight or more of diene polymer rubber. The diene polymer modified by the modification method of the present invention may be used alone or as a natural rubber, cis 1,4 polyisoprene, emulsion polymerized styrene butadiene copolymer, solution polymerized styrene butadiene copolymer, high cis 1 1,4 polybutadiene, low cis 1,4 polybutadiene, halogenated butyl rubber and the like. The rubber composition of the present invention,
It is necessary to contain at least 30% by weight or more of the conjugated diene polymer rubber modified by the modification method according to the present invention. If the content is less than 30% by weight, the effect of improving the breaking strength and low heat generation properties of the vulcanized product is weak. Further, the diene-based polymer composition of the present invention can be oil-extended and used with a highly aromatic process oil, a naphthene-based process oil, or the like, if necessary.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the examples unless it exceeds the gist of the present invention. Unless otherwise specified, parts and percentages in Examples and Comparative Examples are based on weight. Example 1 800 g of a cyclohexane solution in which butadiene was dissolved at a concentration of 15% by weight was poured into a pressure-resistant reactor having a capacity of 2 liters and having a stirrer attached on the inner side and a heating jacket provided on the outer periphery, and a monomer solution was added. Was prepared. Next, tetrahydrofuran was added as a randomizing agent to the prepared solution.
g, and 0.08 g of n-butyllithium as a polymerization initiator was added and heated to carry out a polymerization reaction at a polymerization temperature of 20 ° C to 90 ° C. The molecular weight after the modification reaction of the resulting conjugated diene polymer by a polymerization reaction was determined by gel permeation chromatography (GPC), it showed a weight-average molecular weight M ^W calculated in polyethylene terms in Table 1. Further, Table 1 shows the microstructure of the diene portion in terms of the proportions of cis, trans, and vinyl in the butadiene portion determined by an infrared analysis method (Morello method).

Approximately 3 hours after the completion of the polymerization reaction, n-butyllithium was used as a modifier with the hydrazone compound, benzaldehyde-N, N'-diphenylhydrazone, described in Example 1 of the polymerization recipe shown in Table 1. And a denaturation reaction was carried out with stirring at about 50 ° C. for about 2 hours. Then, the solvent was removed by a usual method and dried to obtain a polymer A, which was used as a conjugated diene polymer rubber modified by Example 1 of the method according to the present invention.
Further, necessary additives are added to the obtained polymer A in accordance with the formulation shown in Table 2, and the resulting mixture is kneaded.
The mixture was vulcanized for 33 minutes to obtain a vulcanized polymer A rubber. The properties of the obtained vulcanizate (Example product 1) were evaluated as described below, and the results are shown in Table 3.

Example 1 In order to evaluate the breaking strength of the product 1, J
The tensile strength according to IS K-6301 was measured, and the tensile strength measured at 100 ° C. according to JIS K-6301 as a high-temperature strength was measured. In order to evaluate the low heat build-up of the product of Example 1, 50
The mechanical loss coefficient tan δ at ° C. and the strain dependence Δtan δ of tan δ were measured, and the results are shown in Table 3, respectively. Note that tan δ and the strain dependency Δ of tan δ
The smaller the value of both tan δ, the better the low heat generation. Here, Δtan δ is a value obtained by changing the dynamic strain from 0.1% to 20%.
% Is the difference between the maximum value and the minimum value of tan δ when changed to%. Tan δ was measured by a shear type viscoelasticity meter manufactured by Rheometrics. Example product 1
In order to evaluate the abrasion resistance of Comparative Example 1, a value at a constant slip ratio measured using a Lambourn abrasion tester was shown as an index with respect to Comparative Example 1. As other characteristics, elongation at room temperature was measured, and the results are also shown in Table 3.

Examples 2 to 5 Polymers B to E were obtained in the same manner as in Example 1 except that the hydrazone compounds described in the rows of Examples 2 to 5 in Table 1 were used as modifiers. A conjugated diene-based polymer rubber was obtained by Examples 2 to 5 of the method according to the present invention. Furthermore, vulcanized products (Example products 2 to 5) were obtained in the same manner as in Example 1, and the physical properties were evaluated. The results are shown in Table 3. Comparative Example 1 In Example 1, 4 g of tetrahydrofuran as a randomizing agent and 0.08 g of n-butyllithium as a polymerization initiator were added to the prepared solution, and the mixture was heated to initiate polymerization at a polymerization temperature of 20 ° C. to 90 ° C. After a lapse of time, the polymerization reaction was stopped with isopropyl alcohol, and thereafter the solvent was removed by a usual method without performing a denaturation reaction, followed by drying to obtain a polymer F. It was a polymer rubber. Furthermore, a vulcanized product (comparative product 1) was obtained in the same manner as in Example 1, and the physical properties were evaluated. The results are shown in Table 3.

[0018]

[Table 1]

[0019]

[Table 2] ポ リ マ ー Polymer 100 parts by weight HAF carbon 50 Aroma oil 10 Stearic acid 2 Antioxidant 6C ¹ ) 1 Zinc white 3 Anti-aging agent TP ² ) 0.8 Accelerator DPG ³ ) 0.6 Accelerator DM ⁴ ) 1.2 Sulfur 1.5 ──────────────────────── 1) N- Phenyl- (1,3-dimethylbutyl) -p-phenylenediamine 2) mixed diaryl-p-phenylenediamine 3) 1,3-diphenylguanidine 4) dibenzothiazyl disulfide

[Table 3]

Example 6 To the pressure-resistant reactor used in Example 1, 800 g of a solution of butadiene in a concentration of 15% by weight was added, and then 30 g of styrene was mixed and mixed to prepare a monomer solution. Next, 5 g of tetrahydrofuran as a randomizing agent and 0.1 g of n-butyllithium as a polymerization initiator were added to the prepared solution and heated to carry out polymerization at a polymerization temperature of 20 ° C to 90 ° C. In the microstructure column of Table 1, nuclear magnetic resonance (NM)
R) The amount of bound styrene determined from the absorption intensity of aromatic protons in the spectrum is shown. About 3 hours after the completion of the polymerization reaction, the hydrazone compound described in the row of Example 6 in Table 1 and benzaldehyde-N, N'-diphenylhydrazone were added as modifiers in an equimolar amount to n-butyllithium for about 2 hours. The denaturation reaction was carried out while maintaining the temperature at 00 ° C with stirring. Subsequently, the solvent was removed by a usual method and dried to obtain a polymer G, which was used as a polymer G rubber modified by Example 6 of the method according to the present invention. Further, a vulcanized product (Example product 6) was obtained in the same manner as in Example 1, and its properties were evaluated. The results are shown in Table 4.

Examples 7 to 11 Polymers H to L were obtained in the same manner as in Example 6, except that the hydrazone compounds described in the rows of Examples 7 to 11 in Table 1 were used as modifiers. The modified conjugated diene-based polymer rubber was obtained according to Examples 7 to 11 of the method according to the present invention. Further, a vulcanized product (Example products 7 to 11) was obtained in the same manner as in Example 1, and its properties were evaluated.
Table 4 shows the results. Comparative Example 2 In Example 6, 5 g of tetrahydrofuran as a randomizing agent and 0.1 g of n-butyllithium as a polymerization initiator were added to the prepared solution, and the mixture was heated to initiate polymerization at a polymerization temperature of 20 ° C. to 90 ° C. After a lapse of time, the polymerization reaction was stopped with isopropyl alcohol, and thereafter the solvent was removed by a usual method without performing a denaturation reaction, followed by drying to obtain a polymer M. The polymer M was obtained by the method of Comparative Example 2. This was a diene polymer rubber. Further, a vulcanized product (Comparative Example Product 2) was obtained in the same manner as in Example 1, and its properties were evaluated.
Table 4 shows the results.

[0022]

[Table 4]

Example 12 The necessary additives were added to 40 parts of the polymer L obtained in Example 11 and 60 parts of natural rubber (NR) in accordance with the formulation shown in Table 2, kneaded, and kneaded at a temperature of 145 ° C. After vulcanization for 33 minutes, a rubber composition containing a conjugated diene polymer rubber modified by the method according to the present invention was obtained. The characteristics were evaluated, and the results are shown in Table 5. Comparative Example 3 40 parts of polymer L and natural rubber (NR) 60 in Example 12
Example 11 was repeated except that 40 parts of the polymer M obtained in Comparative Example 2 and 60 parts of natural rubber (NR) were blended in place of the blending with 30 parts by weight.
A vulcanizate was obtained in the same manner as described above, and its properties were evaluated. The results are shown in Table 5. Comparative Example 4 40 parts of polymer L and natural rubber (NR) 60 in Example 12
Parts of polymer L20 and natural rubber (N
R) A vulcanizate was obtained in the same manner as in Example 11 except that 80 parts was blended, and its properties were evaluated. The results are shown in Table 5.

[0024]

[Table 5]

The vulcanized butadiene polymer modified by the method according to the present invention (Examples 1 to 5) is compared with the unmodified butadiene polymer vulcanized (Comparative Example 1). The tensile strength at room temperature and at 100 ° C. increases, the tan δ and the strain dependency Δtan δ of tan δ decrease, the wear resistance index increases, and the degree of increase and decrease is remarkable, respectively.
In other words, the vulcanizate of the butadiene polymer modified by the method according to the present invention has both excellent breaking strength and low heat build-up than the vulcanizate of the unmodified butadiene polymer. I have. The vulcanizates of the butadiene-styrene copolymer modified by the method according to the present invention (Examples 6 to 11) can be evaluated in the same manner. Further, as shown in Table 5, the rubber composition of Example 12 according to the present invention containing 40% of a butadiene-styrene copolymer modified by the method according to the present invention was unmodified butadiene-styrene copolymer. 40% polymer
Compared with the rubber composition of Comparative Example 3 including the rubber composition, its characteristics are superior. The rubber composition of Comparative Example 4 containing only 20% of the butadiene-styrene copolymer modified by the method according to the present invention has higher tensile strength than Example 12, but is inferior in low heat generation. However, the object of the present invention has not been achieved.

[0026]

The modification method according to the present invention changes the molecular weight of the vulcanizate of conjugated diene polymer rubber in the breaking strength characteristic and the low fuel consumption characteristic in the modification reaction step added continuously to the polymerization reaction step. It is possible to provide a conjugated diene-based polymer rubber having excellent vulcanizate breaking strength characteristics and low fuel consumption characteristics at a low cost, and the conjugated diene-based polymer rubber composition according to the present invention is economically improved. The vulcanized product has excellent breaking strength characteristics and low fuel consumption characteristics and can be suitably used as a rubber composition for a tire tread satisfying the requirements of the automobile industry.

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Claims (5)

(57) [Claims] 1. A polymer or copolymer obtained by polymerizing a conjugated diene compound or copolymerizing a conjugated diene compound and a vinyl aromatic compound by using an organic alkali compound as an initiator in a hydrocarbon solvent. And the general formula (Wherein R ₁ , R ₂ , R ₃ , and R ₄ represent hydrogen, an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, a phenyl group, or a partially substituted product thereof). The conjugated diene polymer rubber obtained by the reaction
A conjugated diene-based rubber composition comprising a raw rubber containing at least 30% by weight and carbon black. 2. The conjugated diene rubber composition according to claim 1, wherein the conjugated diene compound is 1,3-butadiene, and the vinyl aromatic compound is styrene. 3. The conjugated diene rubber composition according to claim 1, wherein the carbon black is HAF. 4. The conjugated diene rubber composition according to claim 1, further comprising sulfur. 5. A tire using the rubber composition according to claim 1 for a tread.