JP3148372B2 - Conjugated diene rubber composition - Google Patents

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 having excellent vulcanizate breaking strength, abrasion resistance and low heat build-up.

[0002]

2. Description of the Related Art In recent years, demands for safety and low fuel consumption of automobiles have become more and more severe, and rubber materials for automobile tires have been required to have high fuel efficiency, safety and wear resistance. It has become. Conventionally, rubber compositions using styrene-butadiene copolymer rubber (E-SBR) obtained by emulsion polymerization have been widely used as treads for tires because of their excellent abrasion resistance. However, E-SB
The rubber composition using R 2 has a large energy loss and easily generates heat, and thus is not suitable for a tread aiming at low fuel consumption.

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

Further, S-SBR is described in JP-B-44-4996, JP-A-57-205414, US Pat. No. 3,953,232, etc. by utilizing the activity of the terminal after polymerization. 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 carbon black or the like is blended into a composition. However, S-SBR has low heat build-up, i.e., excellent fuel economy when it is made into a composition, but is inferior to E-SBR in terms of strength and wear resistance. It was difficult to synthesize S-SBR satisfying both characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems of the prior art, and it is an object of the present invention to provide a conjugated diene excellent in low heat build-up, breaking strength and abrasion resistance of a vulcanized product. An object of the present invention is to provide a rubber composition.

[0006]

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

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, an alkenyl group) , An aryl group or a partially substituted product thereof, and M represents Na, K, Rb, or Cs.) At least one alkali metal compound selected from the group consisting of alkali metal compounds represented by the following formula: And 1,
At least 30 parts by weight of styrene-butadiene copolymer rubber obtained by copolymerizing 3-butadiene and styrene at a weight ratio of 80:20 to 50:50 and further modifying the polymerization active terminal with a modifier. 100 parts by weight of gen-based rubber
Nitrogen adsorption specific surface area of 70m ² / g or more, DBP oil absorption amount 70~150m
A conjugated diene rubber composition comprising 30 to 80 parts by weight of l / 100 g of carbon black.

The present invention relates to a conjugated diene rubber composition containing S-SBR, another diene rubber and reinforcing carbon black as essential components produced under the above-mentioned conditions, and is 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 a weight percentage ratio of 1,3-butadiene and styrene in the range from 80:20 to 50:50. And copolymerized. Here, the styrene content of 20 to 50% by weight means that the amount of styrene is
If the amount is less than 20% by weight, the abrasion resistance is inferior, and if it exceeds 50% by weight, the heat generation increases, and the fuel economy performance deteriorates. Under such polymerization conditions, a microblock having a chain length of 4 or more and 10 or less occupies 20% by weight or more of the total styrene amount.

The organic lithium compounds used for the polymerization include alkyl lithiums such as ethyl lithium, propyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium; aryl lithiums such as phenyl lithium and tolyl lithium; vinyl Alkenyllithium such as lithium and propenyllithium; alkylenedilithium such as tetramethylenedilithium, pentamethylenedilithium, decamethylenedilithium; 1,3-
Arylene dilithium such as dilithiobenzene and 1,4-dilithiobenzene; 1,3,5-trilithiocyclohexane,
1,2,5-Trilithionaphthalene or the like is used, and alkyllithium, particularly n-butyllithium, is preferred.

The amount of the organolithium initiator used is determined by the molecular weight of the target copolymer.
It is 0.05 to 4.0 milligram atoms, preferably 0.1 to 2.0 milligram atoms as lithium atoms per 100 g.

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 (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 partially substituted product thereof;
Represents Na, K, Rb, and Cs. ), And specific examples include the following compounds. As R ¹ M, methyl sodium, ethyl potassium, n-propyl rubidium, ethyl cesium, t-butyl sodium, t-amyl potassium, n-hexyl rubidium, 4-methyl cyclohexyl sodium, 3-hexenyl potassium, 2,5
-Decadienyl rubidium, sodium 4,6-di-n-butyldecyl, phenyl potassium, benzyl sodium, 4-tolyl potassium and the like.

The compound represented by R ² OM is a monohydric or polyhydric alcohol, an alkali metal salt of monohydric or polyhydric phenol, and specifically, methyl alcohol, ethyl alcohol, n-propyl alcohol, 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
Sodium, potassium, rubidium and cesium salts such as -tri-t-butylphenol, n-nonylphenol and 1,12-dodecanediol.

The compounds represented by R ³ COOM include alkali metal salts of mono- and polycarboxylic acids, specifically lauric acid, myristic acid, palmitic acid, stearic acid, arachiic acid, linoleic acid, linolenic acid, Sodium, potassium, rubidium and cesium salts such as phenylacetic acid, benzoic acid, sebacic acid, phthalic acid and 1,8,16-hexadecanthrylcarboxylic acid.

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, dibenzylamine,
Cesium salts may be mentioned. Styrene and butadiene are copolymerized using one or more of the above alkali metal compounds in an amount of 0.01 to 0.3 mol per gram equivalent of lithium of the organolithium initiator. If the amount of the alkali metal compound is less than 0.01 mol per gram atomic 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 undesirably reduced.

As the polymerization solvent, any solvent may be used as long as it is stable to the organolithium compound, and pentane, hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene and a mixture thereof are used. After the polymerization, various terminal modifiers shown below are added to modify the terminal of SBR. This makes it possible to obtain a rubber composition having more excellent 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, and 2,4-tolylene diisocyanate. Nart, 2,
6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate and dimer and trimer aromatic polyisocyanate compounds thereof, 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 Benzaldehyde-N, N-dimethylhydrazone, p- (N, N-dimethylamino) benzaldehyde-N, N-dimethylhydrazone and the like.

[0016] At least 30 parts by weight of the styrene / butadiene copolymer rubber thus obtained is combined with another diene rubber different from the styrene / butadiene copolymer rubber, for example, natural rubber or synthetic poly- ene. Isoprene rubber, E-SBR, polybutadiene rubber and the like are used alone or in combination of two or more kinds as the remainder to make a rubber component of 100 parts by weight. The reason why the composition of the styrene-butadiene copolymer rubber obtained by the above-described method is set to 30 parts by weight or more of 100 parts by weight of the rubber component is that when less than 30 parts by weight, the effect of improving the properties of the vulcanized rubber composition is improved. Is less.

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 the characteristics of 150ml / 100g 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 preferred because the vulcanizate has poor strength and abrasion resistance. Add these carbon blacks to 100 parts by weight of rubber component
30 to 80 parts by weight. If the amount of carbon black is less than 30 parts by weight, it is inferior in strength and abrasion resistance, and if it exceeds 80 parts by weight, heat generation becomes large, and durability and fuel economy performance deteriorate.
If necessary, the conjugated diene rubber 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.

[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 the examples unless it exceeds the gist of the present invention. Parts and percentages in the examples are by weight unless otherwise specified. In addition, various measurements in the examples depended on the following. The molecular weight was measured by gel permeation chromatography (GPC) for the diene polymer before the reaction with the denaturing agent, and the results were shown based on polystyrene.

The microstructure of the diene portion was determined by an infrared method (Morello method). The amount of bound styrene is determined by nuclear magnetic resonance
(NMR) It was 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 a tensile strength measured at 100 ° C. according to JIS K-6301. As a criterion for evaluating low heat build-up (low fuel consumption), the mechanical loss coefficient at 50 ° C in viscoelasticity measurement
Dependence of strain on n δ and tan δ (tanδ max-tanδ 0.1%
(Strain) Δtan δ (all values are better). The abrasion resistance is shown by indexing values at a constant slip ratio measured using a Lambourn abrasion tester with respect to Comparative Examples 1 and 3.

Polymers A to F used in the following Examples and Comparative Examples were obtained by the following methods. (Polymer of Example) Polymer A: 2 with stirrer and heating jacket
1000 g of cyclohexane in which butadiene was previously dissolved at a concentration of 12% by weight was injected into a liter pressure-resistant reactor, and 80 g of styrene was further added to prepare a monomer solution. Next, potassium t-butoxide (t-BuOK) is used as an alkali metal compound.
Was added and 0.11 g of n-butyllithium was added as an organolithium initiator to initiate polymerization. It was kept at a polymerization temperature of about 50 ° C. for a polymerization time of about 3 hours. Thereafter, 0.13 g of tin tetrachloride (SnCl ₄ ) was added as a modifier, and the mixture was further reacted for 2 hours to modify the polymer terminals. The solvent was removed and dried in a conventional manner to obtain a copolymer of polymer A with styrene / butadiene copolymer. A coalescence was obtained.

Polymer B: A styrene / butadiene copolymer of polymer B was obtained in the same manner as in polymer A, except that 0.3 g of dibutyltin dichloride (Bu ₂ SnCl ₂ ) was added as a modifier instead of tin tetrachloride. . Polymer C: After polymerization in the same manner as in Polymer A, 0.2 g of 1,3-dimethyl-2-imidaridinone (DMI) was added as a modifier instead of tin tetrachloride, and the reaction was further performed for 2 hours to modify the polymer terminals. Then, the mixture was stopped with isopropyl alcohol, and the solvent was removed and dried in a usual manner to obtain a styrene-butadiene copolymer of Polymer C. Polymer D: Polymerization was carried out in the same manner as in Polymer A, except that 0.025 g of potassium norylphenoxy was added instead of potassium t-butoxide as an alkali metal compound, and 0.13 g of tin tetrachloride was added as a modifier, followed by a reaction for 2 hours. The terminal of the polymer was modified, and the solvent was removed and dried in a usual manner to obtain a styrene / butadiene copolymer of polymer D.

(Polymer of Comparative Example) Polymer E: 2 having a stirrer and a heating jacket
1000 g of cyclohexane in which butadiene was previously dissolved at a concentration of 12% by weight was 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 organolithium initiator were added to initiate polymerization. about
The polymerization temperature was maintained at a polymerization temperature of 50 ° C. for about 3 hours. Thereafter, the reaction was stopped with isopropyl alcohol, and the solvent was removed and dried in a usual manner to obtain a styrene-butadiene copolymer of polymer E. Polymer F: After polymerization in the same manner as in Polymer A, the reaction was stopped with isopropyl alcohol without performing a denaturation reaction, and the solvent was removed and dried by a conventional method to obtain styrene.
A butadiene copolymer was obtained.

The molecular weight and microstructure of each synthesized polymer 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 represented by the ratio to the butadiene portion, and the molecular weight is represented by a value in terms of polystyrene.

The polymers A to F were independently kneaded according to the formulation shown in Table 2 to obtain rubber compositions of Examples 1 to 4 and Comparative Examples 1 and 2. After vulcanizing each of the rubber compositions at 145 ° C. for 33 minutes, physical properties were evaluated, and the results are shown in Table 3.
Further, the polymer A and the natural rubber (NR) selected as the other diene rubber composition described above were kneaded while changing the number of blended parts to obtain rubber compositions of Examples 5 and 6 and Comparative Example 3. .
After this rubber composition was vulcanized at 145 ° C. for 33 minutes, physical properties were evaluated. The results are shown in Table 4.

[0025]

[Table 2]

[0026]

[Table 3] The vulcanized conjugated diene-based rubber compositions of Examples 1 to 4 according to the present invention have higher elongation (%) and higher tensile strength than the vulcanized conjugated diene-based rubber compositions of Comparative Examples 1 and 2. It has a small δ and a large Rambo abrasion index, that is, it has high breaking strength, large abrasion resistance, and low heat generation.

[0027]

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

[0028]

Industrial Applicability The conjugated diene rubber composition of the present invention is suitable for use as a rubber composition for tire treads because it has excellent vulcanizate breaking strength, abrasion resistance and low fuel consumption. Can be.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-278501 (JP, A) JP-A-1-230647 (JP, A) JP-A-64-70541 (JP, A) JP-A-3- 239737 (JP, A) JP-A-62-149708 (JP, A) JP-A-2-129241 (JP, A) JP-A-63-97646 (JP, A) JP-A-62-96546 (JP, A) JP-A-62-215639 (JP, A) JP-B-44-4996 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/06 C08F 4/48 C08F 8/00 C08F 236/06 C08K 3/04

Claims (1)

(57) [Claims] 1. An organolithium compound as an initiator in a hydrocarbon solvent, comprising:
0.3 mol of the general formula: R ¹ M, R ² OM, R ³ COOM and R ⁴ R ⁵ NM (where R ¹ , R ² , R ³ , R ⁴ and R ⁵ are alkyl groups, A cycloalkyl group, an alkenyl group, an aryl group, or a partially substituted product thereof, and M represents Na, K, Rb, or Cs.) At least one kind selected from the group consisting of alkali metal compounds represented by Styrene-butadiene obtained by copolymerizing 1,3-butadiene and styrene at a weight ratio of 80:20 to 50:50 using an alkali metal compound and further modifying the polymerization active terminal with a modifier. 100 parts by weight of a diene rubber containing at least 30 parts by weight of a copolymer rubber, a nitrogen adsorption specific surface area of 70 m ² / g or more, and a DBP oil absorption of 70 to 150 m
A conjugated diene rubber composition comprising 30 to 80 parts by weight of l / 100 g of carbon black.