JPH05186639A - Conjugated diene-based rubber composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, composed of a specific styrene- butadiene copolymer rubber, specified carbon black and a specific diene-based rubber in a specified proportion, excellent in low heat build-up properties, breaking strength and abrasion resistance and suitable as tire treads, etc. CONSTITUTION:The objective composition is obtained by blending (A) 100 pts.wt diene-based rubber prepared by copolymerizing 1,3-butadiene with styrene at a wt.% ratio within the range of (80/10) to (50/50) using one or more alkali metallic compounds selected from the group consisting of alkali metallic compound expressed by the formulas R<1>M, R<2>OM, R<3>COOM and R<4>R<5>NM [R<1> to R<5> are alkyl, cycloalkyl, etc. ; M is Na, K, Rb or Cs] in an amount of 0.01-0.3 mol based on 1 gram equiv. lithium in an organolithium compound as an initiator in a hydrocarbon solvent, further modifying the polymerization active terminals with a modifying agent and blending >=30 pts.wt. prepared rubber therein with (B) 30-80 pts.wt. carbon black having >=70m<2>/g nitrogen adsorption specific surface area and 70-150ml/100g DBP oil absorption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conjugated diene rubber composition which has excellent breaking strength, wear resistance and low heat buildup.

[0002]

2. Description of the Related Art In recent years, the demands on automobiles for safety and low fuel consumption have become more and more strict, so that rubber materials for automobile tires are strongly required to have low fuel consumption and safety as well as abrasion resistance. It's coming. BACKGROUND ART Conventionally, a rubber composition using a styrene / butadiene copolymer rubber (E-SBR) obtained by an emulsion polymerization method has been widely used as a tread for tires because of its excellent wear resistance. However, E-SB
The rubber composition containing R was unsuitable for a tread aiming at low fuel consumption because of large energy loss and easy heat generation.

In order to solve these problems, a rubber composition using a styrene / butadiene copolymer (S-SBR) prepared by a solution polymerization method is used. S-SBR is obtained by copolymerizing butadiene and styrene with an organic lithium initiator in a hydrocarbon solvent, and is characterized by a narrow molecular weight distribution. Therefore, compared to E-SBR, it does not contain low molecular weight components, so it has less hysteresis loss and is suitable for treads that aim for low fuel consumption.

Further, S-SBR is described in JP-B-44-4996, JP-A-57-205414, US Pat. No. 3956232. As described above, a terminal-modified S-SBR can be obtained by reacting a tin halide compound or an alkenyl tin compound. This S-SBR
Is a rubber composition having low heat build-up, that is, excellent fuel economy characteristics, when a composition is prepared by blending carbon black or the like. However, S-SBR has a low heat build-up, that is, low fuel consumption, when it is made into a composition, but it is inferior in strength and wear resistance to E-SBR. It was difficult to synthesize S-SBR that satisfies both characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems of the prior art, and is a conjugated diene excellent in low exothermic property, breaking strength and abrasion resistance of a vulcanized product. The purpose is to provide a rubber composition.

[0006]

The object of the present invention has been achieved by the conjugated diene rubber composition according to the present invention having the following characteristics. That is, the characteristic feature of the conjugated diene rubber composition according to the present invention is that an organolithium compound as an initiator is used in a hydrocarbon solvent, and 0.01 to 0.3 mol of the general formula is used per 1 gram equivalent of lithium of the organolithium compound.

[Formula 2] R ¹ M, R ² OM, R ³ COOM and R ⁴ R ⁵ NM (wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are an alkyl group, a cycloalkyl group or an alkenyl group) , An aryl group and a partial substitution product thereof, and M represents Na, K, Rb, Cs), and at least one alkali metal compound selected from the group consisting of alkali metal compounds represented by , 1,
At least 30 parts by weight of styrene-butadiene copolymer rubber obtained by copolymerizing 3-butadiene and styrene at a weight% ratio in the range of 80:20 to 50:50, and further modifying the polymerization active terminal with a modifier. To 100 parts by weight of Gen rubber
Nitrogen adsorption specific surface area is 70m ² / g or more, DBP oil absorption is 70 ~ 150m
A conjugated diene rubber composition is characterized by containing 30 to 80 parts by weight of carbon black of 1/100 g.

The present invention is a conjugated diene rubber composition containing S-SBR, another diene rubber and reinforcing carbon black produced under the above-mentioned conditions as essential components, and used as a tread material for tires. It has excellent wear resistance and low fuel consumption. The S-SBR in the present invention comprises an organolithium initiator in the presence of one or more of the above-mentioned alkali metal compounds in the weight percent ratio of 1,3-butadiene and styrene in the range 80:20 to 50:50. It is used and copolymerized. Here, the amount of styrene is set to 20 to 50% by weight because the amount of styrene is
This is because if it is less than 20% by weight, abrasion resistance is poor, and if it exceeds 50% by weight, heat generation is increased and fuel efficiency is deteriorated. Under such polymerization conditions, microblocks having a chain length of 4 or more and 10 or less account for 20% by weight or more of the total styrene content.

Examples of the organolithium compound used for the polymerization include alkyllithium such as ethyllithium, propyllithium, n-butyllithium, sec-butyllithium and tert-butyllithium; aryllithium such as phenyllithium and tolyllithium; vinyl. Alkenyllithium such as lithium and propenyllithium; alkylenedilithium such as tetramethylenedilithium, pentamethylenedilithium and decamethylenedilithium; 1,3-
Allylene dilithium such as dilithiobenzene and 1,4-dilithiobenzene; 1,3,5-trilithiocyclohexane,
1,2,5-trilithionaphthalene or the like is used, preferably alkyllithium, particularly n-butyllithium.

The amount of the organolithium initiator used is determined by the molecular weight of the desired copolymer, but it is usually a monomer.
The amount of lithium atom per 100 g is 0.05 to 4.0 mg, preferably 0.1 to 2.0 mg.

The alkali metal compound used in the present invention is
R ¹ M, R ² OM, R ³ COOM and R ⁴ R ⁵ NM (wherein R ¹ , R ² , R ³ ,
R ⁴ and R ⁵ represent an alkyl group, a cycloalkyl group, an alkenyl group, an aryl group or a partial substitution product thereof,
Indicates Na, K, Rb and Cs. ) And specifically include the following compounds. R ¹ M includes methyl sodium, ethyl potassium, n-propyl rubidium, ethyl cesium, t-butyl sodium, t-amyl potassium, n-hexyl rubidium, 4-methylcyclohexyl sodium, 3-hexenyl potassium, 2,5
-Decadienyl rubidium, 4,6-di-n-butyldecyl sodium, phenyl potassium, benzyl sodium, 4-tolyl potassium and the like can be mentioned.

The compounds represented by R ² OM include monohydric and polyhydric alcohols, alkali metal salts of monohydric and polyhydric phenols such as methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol. , T-butyl alcohol, t-amyl alcohol,
n-hexyl alcohol, cyclohexyl alcohol,
2-butenyl alcohol, 4-methylcyclohexenyl alcohol, 3-cyclopentenyl alcohol, 3-hexenyl alcohol, 2,5-decadienyl alcohol,
Allyl alcohol, 1,3-dihydrohexane, 1,5,9-
Trihydroxytridecane, benzyl alcohol, phenol, catechol, resorcinol, hydroquinone, pyrogallol, 1-naphthol, 2-naphthol,
2,6-di-t-butyl-4-methylphenol, 2,4,6
Examples thereof include sodium, potassium, rubidium and cesium salts of tri-t-butylphenol, n-nonylphenol, 1,12-dodecanediol and the like.

The compound represented by R ³ COOM is an alkali metal salt of a mono- or polycarboxylic acid, specifically, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, linoleic acid, linolenic acid, Examples thereof include sodium, potassium, rubidium and cesium salts of phenylacetic acid, benzoic acid, sebacic acid, phthalic acid, 1,8,16-hexadecanetolylcarboxylic acid and the like.

The compound represented by R ⁴ R ⁵ NM is an alkali metal salt of a secondary amine, specifically dimethylamine,
Di-n-butylamine, methyl-n-hexylamine,
Sodium, potassium, rubidium such as di (3-hexenyl) amine, diphenylamine and dibenzylamine,
Examples include cesium salts. Copolymerization of styrene and butadiene is carried out by using one or more of the above-mentioned alkali metal compounds and 0.01 to 0.3 mol per 1 gram equivalent of lithium of the organolithium initiator. If the amount of the alkali metal compound is less than 0.01 mol per 1 gram atom equivalent of lithium of the organolithium initiator, it is difficult to obtain a random SBR, and if it exceeds 0.3 mol, the polymerization activity is lowered, which is not desirable.

Any solvent can be used as the polymerization solvent as long as it is stable with respect to the organic lithium compound, and pentane, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene and a mixture thereof are used. After the polymerization is completed, various terminal modifiers shown below are added to modify the terminal of SBR. This makes it possible to obtain a rubber composition that is more excellent in strength, abrasion resistance, fuel economy and the like.

Examples of the terminal modifier include tin halides such as tin tetrachloride, diethyldichlorotin, dibutyldichlorotin, tributyltin chloride, diphenyldichlorotin and triphenyltin chloride, phenyl isocyanate, 2,4-tolylene diisocyanate. Nart, 2,
6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and their dimeric and trimeric aromatic polyisocyanate compounds, N, N'-dimethylaminobenzophenone, N, N'-
Diethylaminobenzophenone, N-dimethylaminobenzaldehyde, N-diethylaminobenzaldehyde, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, N-methylacrylamide, tetramethylurea, N-methyl -2-pyrrolidone, N-methyl-ε-caprolactam, dimethylcarbodiimide, dipropylcarbodiimide, dibutylcarbodiimide, dicyclohexylcarbodiimide, diphenylcarbodiimide, benzaldehyde-N, N-dimethylhydrazone, benzaldehyde-N, N-diphenylhydrazone, p-methyl Examples thereof include benzaldehyde-N, N-dimethylhydrazone and p- (N, N-dimethylamino) benzaldehyde-N, N-dimethylhydrazone.

At least 30 parts by weight of the styrene / butadiene copolymer rubber thus obtained and another diene rubber of a different type from the styrene / butadiene copolymer rubber, for example, natural rubber or synthetic poly rubber Isoprene rubber, E-SBR, polybutadiene rubber, etc. may be used alone or in combination with each other, with the balance being 100 parts by weight of the rubber component. The composition of the styrene-butadiene copolymer rubber obtained by the above-mentioned method is set to 30 parts by weight or more of 100 parts by weight of the rubber component because the effect of improving the physical properties of the vulcanized product of the rubber composition is less than 30 parts by weight Because there are few.

The carbon black compounded in the rubber component has a nitrogen adsorption specific surface area of 70 m ² / g or more and a DBP oil absorption of 70 to
It has a characteristic of 150 ml / 100 g and is equivalent to HAF, ISAF, and SAF. Carbon black having a nitrogen adsorption specific surface area of less than 70 m ² / g is not preferable because the vulcanizate has poor strength and abrasion resistance. These carbon blacks per 100 parts by weight of rubber component
Add 30 to 80 parts by weight. If the amount of carbon black is less than 30 parts by weight, it is strong and inferior in abrasion resistance, and if it exceeds 80 parts by weight, heat generation becomes large and durability and fuel consumption performance deteriorate.
If necessary, the conjugated diene rubber composition of the present invention may be oil-extended with a highly aromatic process oil, a naphthene-based process oil, or the like.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded. Parts and% in the examples are by weight unless otherwise specified. The various measurements in the examples are as follows. For the measurement of the molecular weight, the weight average molecular weight of the diene polymer before reacting the modifier was measured by gel permeation chromatography (GPC), and polystyrene was used as a reference.

The microstructure of the diene portion was determined by the infrared method (Morero method). The amount of bound styrene is determined by nuclear magnetic resonance.
(NMR) Determined from the absorption intensity of aromatic protons in the spectrum. The breaking strength was evaluated and measured by the tensile strength according to JIS K-6301. The high temperature strength was evaluated and measured by the tensile strength measured at 100 ° C according to JIS K-6301. Mechanical loss coefficient at 50 ℃ in viscoelasticity measurement as a criterion for low heat buildup (fuel economy)
Strain dependence of n δ and tan δ (tan δ max-tan δ 0.1%
Strain) Δtan δ (smaller values are better in each case) was measured. The abrasion resistance was shown by indexing the value at a constant slip ratio measured using a Lambourn abrasion tester to Comparative Examples 1 and 3.

Polymers A to F used in the following examples and comparative examples were obtained by the following methods. Polymers of Examples Polymer A: 2 with stirrer and heating jacket
To a liter pressure resistant reactor, 1000 g of cyclohexane in which butadiene was dissolved in a concentration of 12% by weight was previously injected, and 80 g of styrene was further added to prepare a monomer solution. Next, potassium t-butoxide (t-BuOK) as an alkali metal compound
0.01 g and 0.11 g of n-butyllithium as an organolithium initiator were added to initiate polymerization. The polymerization temperature was maintained at about 50 ° C. for about 3 hours. After that, 0.13 g of tin tetrachloride (SnCl ₄ ) was added as a modifier, and the reaction was continued for 2 hours to modify the polymer terminal, followed by desolvation and drying by a conventional method to carry out styrene-butadiene copolymerization of polymer A. Got united.

Polymer B: A styrene-butadiene copolymer of Polymer B was obtained in the same manner as Polymer A except that 0.3 g of dibutyltin dichloride (Bu ₂ SnCl ₂ ) was added as a modifier in place of tin tetrachloride. .. Polymer C: After polymerizing in the same manner as Polymer A, 0.2 g of 1,3-dimethyl-2-imidazolidinone (DMI) was added in place of tin tetrachloride as a modifier, and the mixture was further reacted for 2 hours to modify the polymer terminal. Then, the reaction was stopped with isopropyl alcohol, desolvation and drying were carried out by a conventional method to obtain a styrene-butadiene copolymer of polymer C. Polymer D: Polymerized in the same manner as Polymer A except that 0.025 g of norylphenoxypotassium was added instead of t-butoxypotassium as the alkali metal compound, and then 0.13 g of tin tetrachloride was added as a modifier and further reacted for 2 hours. The polymer terminal was modified, and the solvent was removed and dried by a conventional method to obtain a styrene-butadiene copolymer of polymer D.

Comparative Polymer Polymer E: 2 with stirrer and heating jacket
1000 g of cyclohexane in which butadiene was dissolved in a concentration of 12% by weight was previously injected into a liter pressure resistant reactor, and 80 g of styrene was further added to prepare a monomer solution. Next, 2.0 g of tetrahydrofuran and 0.11 g of n-butyllithium as an organic lithium initiator were added to initiate polymerization. about
The polymerization temperature was maintained at 50 ° C. for about 3 hours. Thereafter, the reaction was stopped with isopropyl alcohol, and the solvent was removed and dried by a conventional method to obtain a styrene-butadiene copolymer of polymer E. Polymer F: Polymerized in the same manner as Polymer A, stopped the reaction with isopropyl alcohol without carrying out a modification reaction, and desolvated and dried by a conventional method to obtain styrene of Polymer F.
A butadiene copolymer was obtained.

The molecular weight and microstructure of each polymer synthesized are shown in Table 1 (Mn: number average molecular weight, Mw: weight average molecular weight).

[Table 1] In Table 1, the amounts of cis, trans, and vinyl are shown as a ratio to the butadiene portion, and the molecular weight is shown as a polystyrene-converted value.

Polymers A to F were individually kneaded according to the formulation shown in Table 2 to obtain rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2. The rubber compositions were each vulcanized at 145 ° C. for 33 minutes and then evaluated for physical properties. The results are shown in Table 3.
Further, the polymer A and the above-mentioned natural rubber (NR) selected as another diene-based rubber composition were kneaded at different compounding parts to obtain rubber compositions of Examples 5 and 6 and Comparative Example 3. ..
After vulcanizing this rubber composition at 145 ° C. for 33 minutes, the physical properties were evaluated, and the results are shown in Table 4.

[0025]

[Table 2]

[0026]

[Table 3] The vulcanized conjugated diene rubber compositions of Examples 1 to 4 according to the present invention have higher elongation (%), higher tensile strength and tan than the vulcanized conjugated diene rubber compositions of Comparative Examples 1 and 2. It has a small δ and a large Lambeau wear resistance index, that is, has high fracture strength, large wear resistance, and low heat buildup.

[0027]

[Table 4] The comparison between the vulcanized conjugated diene rubber compositions of Examples 5 and 6 according to the present invention and the vulcanized conjugated diene rubber composition of Comparative Example 3 shows that as the NR ratio increases, the value of Δtan δ increases. It shows that the low heat buildup is impaired.

[0028]

EFFECTS OF THE INVENTION The conjugated diene rubber composition of the present invention is excellent in breaking strength properties, abrasion resistance and fuel economy properties of vulcanized products, and therefore, it is suitable for use as a rubber composition for tire treads. You can

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Claims (1)

[Claims] 1. An organolithium compound as an initiator in a hydrocarbon solvent, and 0.01 to about 1 gram equivalent of lithium of the organolithium compound.
0.3 mol of R ¹ M, R ² OM, R ³ COOM and R ⁴ R ⁵ NM (wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are alkyl groups, A cycloalkyl group, an alkenyl group, an aryl group and partial substitution products thereof, and M represents Na, K, Rb, Cs), and at least one selected from the group consisting of alkali metal compounds represented by Styrene-butadiene, in which 1,3-butadiene and styrene were copolymerized with an alkali metal compound at a weight% ratio in the range of 80:20 to 50:50, and the polymerization active end was modified with a modifier. 100 parts by weight of diene rubber made by blending at least 30 parts by weight of copolymer rubber, nitrogen adsorption specific surface area of 70 m ² / g or more, DBP oil absorption of 70 ~ 150 m
A conjugated diene rubber composition comprising 30 to 80 parts by weight of carbon black of 1/100 g.