JPH06270603A - Pneumatic tyre - Google Patents

Abstract

PURPOSE:To obtain excellent wet skid resistance and wear resistance and improve fuel consumption by producing preparatory paste works in which end modified styrene-butadiene copolymer containing a specific rate of carbon black whose iodine suction amount is a specific value natural rubber are mixed and kneaded individually and these preparatory paste works are mixed and kneaded together. CONSTITUTION:A rubber component for a tyre tread contains end modified styrene-butadiene copolymer whose glass transition temperature is more than -50 deg.C and whose combined styrene content is less than 45% and natural rubber and carbon black. Here, the rubber component for the tyre tread is made by mixing and kneading a material containing the preparatory paste work in which carbon black (more than 100mg/g of an iodine suction amount) more than 40weight% of an entire carbon black amount contained in the rubber component is mixed and kneaded with end modified styrene-butadiene copolymer, with a material containing the preparatory paste work in which carbon black (less than 80mg/g of the iodine suction amount) more than 10weight% of the entire carbon black amount contained in the rubber component is mixed and kneaded with the natural rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition containing a terminal-modified styrene-butadiene copolymer, natural rubber and carbon black, and a pneumatic tire having a tread processed by using the composition in a tread portion. .

[0002]

2. Description of the Related Art In recent years, with the demand for safety and low fuel consumption for automobiles, attempts to simultaneously improve wet skid resistance, low fuel consumption, and reinforcement as a rubber material for tires are included in the rubber material. Made from both sides of polymer and carbon black.

For example, Japanese Patent Publication No. 62-10530 discloses that
Random copolymerization of styrene and 1.3 butadiene,
It has a bond of at least one metal selected from silicon, germanium, tin and lead with butadienyl in the main chain, and the content of bonded styrene is 3 to 30% by weight and 1.2 vinyl bond of butadiene moiety. Content is 60-95
It has been shown that a rubber composition for tires containing a blended rubber of styrene-butadiene copolymer rubber and natural rubber in an amount of wt% and carbon black has improved running safety and rolling resistance.

Further, JP-A-61-141741 discloses that a rubber composition containing a butadiene copolymer modified with an isocyanate compound and having a glass transition temperature of −70 ° C. or more is excellent in wet skid resistance, rolling friction resistance and tensile strength. Is disclosed. Further, Japanese Patent Publication No. 61-362 discloses a method for modifying a diene polymer rubber with a benzophenone compound, and describes that impact resilience is improved.

However, the fuel consumption characteristics obtained by these modification techniques are insufficient for the recent trend toward low fuel consumption.
On the other hand, carbon black improves fuel economy by increasing the particle size, but in this case, there is a drawback that abrasion resistance is greatly reduced and reinforcement is poor. When the terminal-modified polymer is combined with carbon black having a small particle size, abrasion resistance is improved, but fuel consumption cannot be obtained at a satisfactory level.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. A rubber composition containing a terminal-modified styrene-butadiene copolymer rubber, natural rubber and carbon black. By providing a rubber composition for a tire tread that has excellent wet skid resistance and abrasion resistance and at the same time has improved fuel economy, and by further providing a pneumatic tire used for a tread having excellent fuel economy. is there.

[0007]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventors produced a pre-kneaded product in which an end-modified styrene-butadiene copolymer and natural rubber were separately kneaded in advance, and The inventors have found that a rubber composition for a tire tread having improved fuel economy can be obtained by kneading a preliminary kneaded product, and have completed a rubber composition for a tire tread of the present invention and a pneumatic tire having the tread. That is,

The rubber composition for tire tread of the present invention is
The polymerization active terminal of the styrene-butadiene copolymer polymerized in the presence of an organic lithium catalyst in a hydrocarbon solvent is treated with a tin halide compound, an isocyanate compound, a compound represented by the formula-CX.
A glass transition temperature obtained by reacting with a compound having a group represented by -N = (X represents an oxygen atom or a sulfur atom), at least one terminal modifier selected from benzophenones and thiobenzophenones- A vulcanizable rubber composition for a tire tread, which contains a terminal-modified styrene-butadiene copolymer having a bound styrene content of 50% or more and a bound styrene content of 45% or less, and natural rubber and carbon black, and (a) is included in the rubber composition. 40% by weight or more of the total carbon black amount (a) (iodine adsorption amount 100 mg / g or more) and the terminal-modified styrene-butadiene copolymer are kneaded in advance, and (b) the rubber 10% by weight or more of the total amount of carbon black contained in the composition (b)
It is characterized in that a material containing (amount of iodine adsorbed by 80 mg / g or less) and a pre-kneaded product of natural rubber is kneaded. Further, preferably, the weight content ratio of the terminal-modified styrene-butadiene copolymer and the natural rubber is 80:20 to 20:80, and the content of carbon black is 20 to 110 parts by weight based on 100 parts by weight of the total rubber. It is a department.

A pneumatic tire having a tread of the present invention is characterized by being processed by using the rubber composition for a tire tread as a tread.

The composition of the present invention comprises a pre-kneaded product (a) obtained by previously kneading a terminal-modified styrene-butadiene copolymer and carbon black (a), and a natural rubber and carbon black (b) in advance. The characteristic is that the carbon black is unevenly distributed by kneading the kneaded (b) preliminary kneaded product, and the carbon black contained at that time is distinguished as follows. The carbon black (a) to be pre-kneaded with the terminal-modified styrene-butadiene copolymer needs to have an iodine adsorption amount of 100 mg / g or more. If it is less than 100 mg / g, the reinforcing property is poor and the wear resistance is low. Also, its content is
The total amount of carbon black contained in the composition is 40% by weight or more. If it is 40% by weight or less, no effect is produced and the amount of heat generated is large, which is not preferable. Carbon black (B) to be pre-kneaded with natural rubber needs to have an iodine adsorption amount of 80 mg / g or less. If it exceeds 80 mg / g, the calorific value becomes large, and there is no effect of improving fuel economy. The content is 10% by weight or more of the amount of carbon black contained in the entire composition. If it is less than 10% by weight, the effect of uneven distribution of carbon black is not exerted and the amount of heat generation is increased, which is not preferable.

The content of total carbon black in the composition is 20 to 110 parts by weight based on 100 parts by weight of total rubber. When it exceeds 110 parts by weight, the workability of kneading is poor and the dispersion of carbon black is poor. However, the fracture resistance and wear resistance are deteriorated. When it is less than 20 parts by weight, the reinforcing property is poor and the fracture resistance and wear resistance are poor, which is not preferable. The compounding ratio of the terminal-modified styrene-butadiene copolymer and the natural rubber in the composition is 80:20 to 20:80, preferably 7.
It is 0:30 to 30:70. When kneading both pre-kneaded products during the production of the composition of the present invention (sometimes referred to as main kneading), an aromatic oil, stearic acid, and an anti-aging agent can be mixed if necessary. Although a part of the carbon black of the entire composition may be mixed in the main kneading, the amount thereof is preferably 50% by weight or less of the total carbon black in the composition.

The terminal-modified styrene-butadiene copolymer contained in the composition of the present invention is obtained by copolymerizing styrene and butadiene in a hydrocarbon solvent in the presence of an organolithium catalyst and then modifying the polymerization active terminal. Is.

As the organolithium catalyst, alkyllithium such as n-butyllithium, sec-butyllithium, 1.4-dilithioptan or an organolithium amide such as N-methylbenzyllithium amide or dioctyllithium amide is used. The organolithium catalyst is
0.2 to 20 as lithium atom per 100 g of monomer
Used in millimoles. Examples of the hydrocarbon solvent include pentane, hexane, heptane, octane, methylcyclopentane, cyclohexane, benzene, xylene and the like.

The modification of the polymerization active terminal is carried out by modifying a tin halide compound, an isocyanate compound, a compound having a group represented by the formula --CX--N = (X represents an oxygen atom or a sulfur atom), benzophenones and thiobenzophenones. At least one compound selected from the above is reacted with the active end of the styrene-butadiene copolymer.

Examples of the tin halide compound include tetrachlorotin, monophenyltrichlorotin, diphenyldichlorotin, dibutyldichlorotin, triphenylmonochloroszu, tributylmonochlorosuzu and the like.

Examples of the isocyanate compound include 2.4-tolylene diisocyanate, 2.6-tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate and p-phenylene diisocyanate. Nato, tris (isocyanatophenyl) thiophosphate, xylene diisocyanate, benzene-1.2.4
-Triisocyanate, naphthalene-1.2.5.7-
Tetraisocyanate and the like can be shown.

The compound having a group represented by the formula -CX-N = (X represents an oxygen atom or a sulfur atom) is
N, N-dimethylformamide, N, N-diethylformamide, N, N-diethylacetamide, aminoacetamide, N, N-dimethyl-N ′, N′-dimethylaminoacetamide, N-phenyldiacetamide, N,
N-dimethylacrylamide, N, N-dimethylmethacrylamide, propionamide, N, N-dimethylpropionamide, 4-pyridylamide, N, N-dimethyl-4-pyridylamide, N, N-dimethylbenzamide, p-amino Benzamide, N ', N'-(p-dimethylamino) benzamide, N, N-dimethyl-N'-
(P-Ethylamino) benzamide, N-acetyl-N
-2-naphthylbenzamide, nicotinamide, N, N
-Diethylnicotinamide, succinic acid amide, maleic acid amide, N, N, N ', N'-tetramethylmaleic acid amide, succinimide, maleimide, N-methylmaleimide, N-methylphthalimide, 1,2-cyclohexanedicarboxyl Amide, N-methyl-1,2-cyclohexanecarboxide, oxamide, 2-furamide, N,
N, N ', N'-tetramethyloxamide, N, N-dimethyl-2-furamide, N, N-dimethyl-3-quinolinecarboxamide, N, N-dimethyl-p-amino-
Benzalacetamide, N, N-dimethyl-N ', N'
-(P-Dimethylamino) cinnamylidene acetamide, N, N-dimethyl-N ', N'-(2-dimethylamino) vinylamide, N '-(2-methylamino) -vinylamide, urea, N, N' -Dimethylurea, N, N,
N ', N'-tetramethylurea, methyl carbamate,
Ethyl N, N-diethylcarbamate, ε-caprolactam, N-methyl-ε-caprolactam, N-acetyl-ε-caprolactam, 2-pyrrolidone, N-methyl-
2-pyrrolidone, N-acetyl-2-pyrrolidone, N-
Vinylpyrrolidone, 2-piperidone, N-methyl-2-
Piperidone, 2-quinolone, N-methyl-2 quinolone,
2-indolinone, N-methyl-2-indolinone, isocyanuric acid, N, N ', N'-trimethylisocyanuric acid, 1,3-diethyl-2-imidazolidinone, 1,
3-Dimethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-
2-imidazolidinone, 1-methyl-3-butyl-2-
Imidazolidinone, 1-methyl-3- (2-methoxyethyl) -2-imidazolidinone, 1-methyl-3- (2
-Ethoxyethyl) -2-imidazolidinone, 1,3-
Di- (2-ethoxyethyl) -2-imidazolidinone,
1,3-dimethylethylenethiourea, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone, and sulfur-containing compounds corresponding thereto,
Among these, a particularly preferable compound is a compound having an alkyl group bonded to nitrogen.

Examples of benzophenones and thiobenzophenones are 4-aminobenzophenone, 4-dimethylaminobenzophenone and 4-dimethylamino-.
4'-methylbenzophenone, 4,4'-diaminobenzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, 4,4'-bis (ethylamino) benzophenone, 3 , 3'-Dimethyl-4,4'-bis (diethylamino) benzophenone, 3,3'-dimethoxy-4,
4'-bis (dimethylamino) benzophenone, 3,
3 ', 5,5'-tetraaminobenzophenone, 2,
4,6-triaminobenzophenone, 3,3 ', 5
5'-tetra (diethylamino) benzophenone, etc.,
And their corresponding thiobenzophenones.

The reaction between the active end and the modifier is 0 ° C to 15 ° C.
It is carried out in the range of 0 ° C. and may be under isothermal conditions or elevated temperature conditions. The polymerization method may be either a batch polymerization method or a continuous polymerization method. The microstructure of the butadiene part is tetrahydrofuran, diethyl ether,
Add ethers such as dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine, N, N, N ', N'-tetramethylethylenediamine, dipiperidinoethane and tertiary amine compounds to the polymerization system. Thus, the vinyl bond content can be freely changed.

The terminal-modified styrene-butadiene copolymer contained in the composition of the present invention has a glass transition temperature of -50 ° C.
Or higher, preferably -45 ° C or higher. When the glass transition temperature is lower than -50 ° C, the wet skid resistance is deteriorated, which is not preferable. Also, the bound styrene content is 45% by weight.
Below, preferably 10 to 45% by weight, more preferably 2
It is 0 to 40% by weight. Bound styrene content is 45% by weight
If it exceeds the range, the fuel efficiency is deteriorated, which is not preferable.

The composition of the present invention contains, in addition to carbon black, softening agents such as aroma oil and spindle oil, antiaging agents, vulcanization accelerators, vulcanization accelerators such as stearic acid and zinc white, vulcanizing agents and the like. The rubber compounding agent can be compounded with the rubber within the usual range. It is preferable that, during the main kneading, these compounding agents are mixed with a softening agent, an antioxidant, stearic acid and the like in the first step, and are kneaded with a vulcanization accelerator and a vulcanizing agent in the second step.

A preferred embodiment of the pneumatic tire having the tread of the present invention is a tread portion having a cap and a base.
In a pneumatic tire having a layered structure, the base portion is processed using the composition. Further, the pneumatic tire may be reinforced with any of organic fiber cords such as nylon, vinylon, polyester and Kepler or organic fiber cords such as steel, glass and carbon, and the carcass has either a radial structure or a bias structure. It may be present, but it is preferably a radial structure.

[0023]

The present invention will be described below with reference to examples.
The invention is not limited to these examples. Various measurements in the examples were carried out as follows.

Bound styrene content: The bound styrene content of the copolymer properties was determined using an analytical curve using the absorbance of the phenyl group at 699 cm ^-1 by an infrared spectrometer. Vinyl content: The vinyl content of copolymer properties (butadiene 1: 2 bond content) is determined by the method of D. Morero [Chem. & I
nd. 41 , 758 (1959)].

Abrasion resistance: The amount of abrasion loss was measured using a Lambourn abrasion tester, and the comparative example 1 was set to 100 and displayed as an index. The larger the number, the better. Wet skid resistance: Measured at room temperature (° C) using a Stanley portable skid resistance tester. An asphalt surface sprayed with water at 20 ° C was selected as the contact road surface. Comparative Example 1 was set to 100 and displayed as an index, and the larger the value, the better. Fuel economy (rolling friction resistance): tan δ at 60 ° C. is shown as an index of rolling friction resistance. Tan δ was measured at 1% with a spectrometer manufactured by Iwamoto Seisakusho. The copolymer used in the examples was prepared by the following method.

(Modified Copolymer A) Nitrogen-substituted 5 liter autoclave was charged with cyclohexane 20 as a solvent.
00 g, styrene 100 g and butadiene 400 g as monomers, and tetrahydrofuran as a polar compound 20
g prepared. While stirring the contents, n as a polymerization initiator
-Butyllithium (6 mmol) was added, and adiabatic polymerization was carried out from 20 ° C. After the completion of polymerization, 2 mmol of tin tetrachloride was added as a terminal modifier. 2.5 g of di-t-butylcresol was added, and the solvent was dried by a conventional method. (Modified Copolymers B to D) The modified copolymer A was prepared in the same manner as the modified copolymer A except that the modifier was changed. (Modified copolymer E) The modified copolymer A was prepared in the same manner as the modified copolymer A except that the ratio of styrene and butadiene was changed.

(Modified Copolymer F) The same procedure as in Modified Copolymer A was carried out except that the ratio of styrene and butadiene was changed.
Bound styrene content exceeds 45% by weight (50% by weight)
A modified copolymer of was obtained. (Modified copolymer G) The procedure of A was repeated except that the ratio of styrene and butadiene was changed. Bound styrene content 10
A modified copolymer having a weight percentage of Tg <-50 ° C. was obtained. (Unmodified Copolymer H) The same procedure as in A was repeated except that no modifier was used. That is, it is an unmodified styrene-butadiene copolymer. Table 1 shows the characteristics of the copolymer obtained as described above and the modifier used.

[0028]

[Table 1]

Example 1 100 parts by weight of modified copolymer A and 50 parts by weight of ISAF carbon black (iodine adsorption amount 119 mg / g) were added to OO.
Using a C type Banbury mixer, kneading was carried out for 2 minutes at 60 rpm, a filling rate of 70% and a starting temperature of 100 ° C. to prepare a preliminary kneaded product (a). 100 parts by weight of natural rubber and 50 parts by weight of FEF carbon black (iodine adsorption amount: 45 mg / g) were kneaded in the same manner as above to prepare a preliminary kneaded product (b). Then, these preliminary kneaded products were put together, and 5 parts by weight of aromatic oil, 3 parts by weight of stearic acid and an antioxidant (Ouchi Shinko Chemical Industry Co., Ltd., trade name "81
0NA ″) 1.0 part by weight was added, and the mixture was kneaded for 3 minutes at 60 rpm, a filling rate of 70% and a starting temperature of 100 ° C. 100 parts by weight of the obtained kneaded product was 3.0 parts by weight of zinc white and 1.5 parts of sulfur. By weight, vulcanization accelerator (Ouchi Shinko Chemical Industry Co., Ltd., trade name "MSA") 1.0 part by weight was added and kneaded at 50 ° C. for 1 minute at 80 ° C. to obtain a rubber composition for tire tread. The composition obtained was press-vulcanized at 150 ° C. for 40 minutes and then subjected to a predetermined test at room temperature, and the results are shown in Table 2.

Examples 2 to 5 The procedure of Example 1 was repeated, except that the modified copolymers were changed to B, C, D and E, respectively.

Comparative Examples 2 and 3 The same procedure as in Example 1 was carried out except that the modified copolymer was used outside the range of the modified polymer used in the composition of the present invention. Comparative Example 4 Example 1 except that the modified copolymer was changed to an unmodified copolymer.
I went the same way.

Comparative Example 6 As shown in Table 3, the procedure of Example 1 was repeated except that the amount of FEF carbon black was changed to reduce the amount in the preliminary kneading product (b) and to use it in the main kneading. Comparative Example 7 The procedure of Example 1 was repeated except that the carbon black was changed to HAF carbon black (adsorption amount of iodine: 90 mg / g).

Comparative Examples 1 and 5 Only the main kneading was carried out in the same manner as in Example 1 except that the pre-kneaded product was not used and the formulation of Table 3 was used.

[0034]

[Table 2]

[0035]

[Table 3]

Examples 6 to 8 Preliminary kneading was carried out in the same manner as in Example 1 with the formulations shown in Table 4, and the main kneading was carried out at a weight ratio of natural rubber / modified copolymer = 30/70,
Others were the same as in Example 1.

Comparative Example 10 The procedure of Example 6 was repeated, except that the modified copolymer A was changed to the unmodified copolymer H. Comparative Example 11 As shown in Table 4, carbon black was also used in the main kneading,
Others were the same as in Example 6.

Comparative Example 9 Only the main kneading was carried out with the formulation of Example 6 without carrying out the preliminary kneading. Comparative Example 8 All the carbon was changed to HAF carbon black (iodine adsorption amount 90 mg / g), and pre-kneading was not carried out, but only main kneading was carried out with the formulation of Example 6.

[0039]

[Table 4]

[0040]

INDUSTRIAL APPLICABILITY The present invention provides a rubber composition for a tread and a pneumatic tire, which have excellent wet skid resistance and abrasion resistance and at the same time have fuel economy as a rubber material for a tire.

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[Procedure amendment]

[Submission date] July 8, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

[0034]

[Table 2]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

[0035]

[Table 3]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction content]

[0039]

[Table 4]

Claims (4)

[Claims] 1. A polymerization active terminal of a styrene-butadiene copolymer polymerized in a hydrocarbon solvent in the presence of an organic lithium catalyst is treated with a tin halide compound, an isocyanate compound, a compound represented by the formula: -CX-N = (X is A compound having a group represented by an oxygen atom or a sulfur atom), a glass transition temperature of −50 ° C. or higher obtained by reacting with at least one terminal modifier selected from benzophenones and thiobenzophenones, and bound styrene. A vulcanizable rubber composition for tire treads containing a terminal modified styrene-butadiene copolymer having a content of 45% or less, and natural rubber and carbon black, wherein (a) the total amount of carbon black contained in the rubber composition. 40% by weight or more of carbon black (a) (iodine adsorption amount of 100 mg / g or more) and the terminal-modified styrene A pre-kneaded product obtained by previously kneading with a tadiene copolymer, and (b) 10% by weight or more of the total carbon black contained in the rubber composition (b) (iodine adsorption amount of 80 mg / g or less) and natural A rubber composition for a tire tread, which is obtained by kneading a material containing a preliminary kneaded product obtained by kneading rubber in advance. 2. The weight content ratio of the terminal-modified styrene-butadiene copolymer and the natural rubber is 20:80 to 80:20.
The rubber composition for a tire tread according to claim 1, wherein the content of carbon black is 20 to 100 parts by weight based on 100 parts by weight of the total rubber. 3. A pneumatic tire using a vulcanizable rubber composition for a tire tread containing a diene copolymer, natural rubber and carbon black as a tread,
(A) The polymerization active terminal of a styrene-butadiene copolymer polymerized in a hydrocarbon solvent in the presence of an organolithium catalyst is treated with a tin halide compound, an isocyanate compound, a formula-CX-N = (X is an oxygen atom). Or represents a sulfur atom)
A compound having a group represented by, a glass transition temperature of -50 obtained by reacting with at least one terminal modifier selected from benzophenones and thiobenzophenones.
C. or higher and a bound styrene content of 45% or less, a terminal-modified styrene-butadiene copolymer and 40% by weight or more of the total carbon black contained in the rubber composition (a) (iodine adsorption amount of 100 mg / g or more). And (b) 10% by weight or more of the total amount of carbon black contained in the rubber composition (b) (iodine adsorption amount 80 mg /
g) or less) and a pre-kneaded product in which natural rubber is kneaded in advance, and a pneumatic tire having a tread, which is processed by using a rubber composition for a tire obtained by kneading a material containing the same in a tread portion. 4. The weight content ratio of the terminal-modified styrene-butadiene copolymer to the natural rubber is 20:80 to 80:20.
The pneumatic tire having a tread according to claim 3, wherein the content of carbon black is 20 to 110 parts by weight with respect to 100 parts by weight of the total rubber.