JP2616978B2 - Rubber composition and pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a rubber composition having particularly excellent wet skid characteristics, rolling friction resistance characteristics (fuel consumption characteristics), and reinforcing properties at high temperatures, and to a tire surface layer. The present invention relates to a pneumatic tire provided for a vehicle.

(Prior Art) In recent years, with the demand for safety and low fuel consumption for automobiles, in order to simultaneously improve wet skid characteristics, fuel consumption characteristics and reinforcing properties of a rubber material for tires, a polymer system and Improvements in rubber compositions for tires have been made separately from both carbs.

Patents relating to polymer systems, particularly the technology for improving with conjugated diene polymers, are JP-B-44-4996, U.S. Pat.No. 3,953,232, JP-A-57-205414 and JP-A-61-141741. Etc. These are related to an improved technology for reacting a tin compound or an isocyanate compound with a polymer, thereby improving fuel efficiency and reinforcing properties.

On the other hand, there is a technique of improving fuel efficiency by increasing the particle size of carbon black as an improvement technique using carbon, but in this case, there is a problem that the reinforcing property is reduced. Also, JP-A-62-18446 discloses that
It is disclosed that -OH groups are selectively introduced into the surface of carbon black to thereby achieve both fuel efficiency and reinforcement.

(Problems to be Solved by the Invention) However, as in the prior art described above, further improvement is desired from the standpoint of improving both fuel consumption characteristics and reinforcement at high temperatures in the polymer or carbon alone improvement technology. It is.

That is, when the polymer improved by the conventional technique as described above is combined with ordinary carbon black, the fuel consumption characteristics are not sufficiently improved due to a small number of reactive active points on the surface of the carbon black, and the polymer at high temperatures The interaction force between the carbon blacks is reduced, and no improvement in reinforcement is seen. Conversely, when carbon black obtained by improving the prior art as described above is combined with a normal diene-based polymer, the interaction with the polymer is not sufficient because only carbon black is reactive, After all, there was a practical problem in terms of reinforcement at high temperatures.

Therefore, an object of the present invention is to achieve a further improvement in wet skid characteristics, fuel efficiency characteristics, and reinforcement at high temperatures by comprehensively improving the pneumatic tire from both a polymer system and a carbon system. Aim.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have (co) polymerized a diene-based monomer using an initiator composed of an alkali metal and / or an alkaline earth metal. rear,
By combining a conjugated diene (co) polymer obtained by reacting a specific polymerization terminal modifier with the specific carbon black, the interaction between the polymer and the carbon black is sufficient even in a high temperature region. The present inventors have found that a rubber composition having particularly excellent wet skid properties, rolling friction resistance properties and reinforcing properties at high temperatures can be obtained, thereby completing the present invention.

That is, the present invention provides a conjugated diene compound obtained by polymerizing or copolymerizing a conjugated diene compound or a conjugated diene compound and one or more aromatic vinyl compounds using a lithium-based polymerization initiator in a hydrocarbon solvent. A terminal obtained by reacting at least one or more reactive compounds selected from the group consisting of an isocyanate compound, a dialkylamino-substituted aromatic compound and an aromatic heterocyclic compound with a polymerization active terminal of the (co) polymer. With respect to 100 parts by weight of the modified conjugated diene-based (co) polymer alone or a blend with another diene-based polymer containing 30% by weight or more of the (co) polymer, the following properties, nitrogen adsorption specific surface area (N ₂ SA): 60 ~ 270m ² / g Compressed dibutyl phthalate oil absorption (24M ₄ DBP oil absorption): 80 ~
140ml / 100g Number of oxygen-containing functional groups on the surface per 100 carbon atoms: 2.2
The present invention relates to a rubber composition containing 20 to 150 parts by weight of carbon black having a pH of 2 to 6 and a pneumatic tire provided with the rubber composition in a tire surface layer.

Here, the tire surface layer means a tread, a sidewall or various cover rubbers.In a tread having a plurality of layers, not only the tread outer layer, but also the tread inner layer exposed on the tire outer surface after running. Also included. In the present invention, the above rubber composition is preferably provided in a tread.

Examples of the aromatic vinyl compound include styrene, p-methylstyrene, vinyltoluene, vinylnaphthalene, α
-Methylstyrene, p-tert-butylstyrene, and the like, with styrene being preferred.

As the conjugated diene compound, 1,3-butadiene,
Examples include isoprene, 1,3-pentadiene, and 2,3-dimethylbutadiene, with 1,3-butadiene being preferred.

The vinyl content of the butadiene part in the (co) polymer of such a butadiene rubber compound is 15% or more, preferably 20%
It is more preferably 30% or more. Further, it is preferably 90% or less from the viewpoint of production and effects.

If it is less than 15%, it is difficult to simultaneously improve wet skid characteristics and rolling friction resistance characteristics. That is, when the wet skid characteristics are to be improved, the rolling friction resistance characteristics are inferior, and when the rolling friction resistance characteristics are to be improved, the wet skid characteristics are inferior.

The above-mentioned butadiene (co) polymer preferably has a glass transition temperature (Tg) of −70 ° C. or higher, more preferably −60 ° C.
That is all. From the viewpoint of the effect, the temperature is preferably -30 ° C or lower. If the glass transition temperature is lower than this temperature, the wet skid characteristics are inferior, and this is not preferred. The glass transition temperature (T
g) shows the value measured by DSC. Incidentally, Li-butadiene rubber having a vinyl bond content of 12% is -180 ° C, and natural rubber is -7 ° C.
6 ° C, emulsion polymerized styrene-butadiene copolymer rubber (SBR #
1500: trade name) is -64 ° C.

The conjugated diene-based (co) polymer of the present invention comprises a conjugated diene alone or a conjugated diene and one or more other conjugated dienes or aromatic vinyl compounds in a hydrocarbon solvent using a lithium-based initiator. It is obtained by reacting a reactive compound such as an isocyanate compound after performing solution polymerization.

In particular, a styrene-butadiene copolymer having a styrene content of 5% by weight or more is preferable because it has excellent wet skid characteristics, excellent rolling friction resistance, and high tensile strength and workability.

Although the content of the styrene is not particularly limited, 50
% By weight, preferably 45% by weight or less.

Further, as the hydrocarbon solvent, pentane, hexane,
Heptane, octane, methylcyclopentane, cyclohexane, benzene, xylene and the like can be mentioned.

The lithium initiator used is an alkyl lithium such as n-butyllithium, sec-butyllithium or 1,4-dilithiobutane, or an organic lithium amide such as N-methylbenzyllithiumamide or dioctyllithiumamide.

The lithium initiator is used in an amount of 0.1 to 100 mg as a lithium atom per 100 g of the monomer.

In particular, a combination of a polyfunctional monomer such as 1,4-dilithiobutane or alkyl monolithium with divinylbenzene, and reacting a polyfunctional polymer terminal obtained by copolymerizing a conjugated diene monomer with an isocyanate compound. A (co) polymer with excellent tensile strength is obtained.

Among the reactive compounds, as the isocyanate compound, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate,
Naphthalene diisocyanate, tolidine diisocyanate, triphenylmethane triisocyanate, p-phenylene diisocyanate, tris (isocyanatophenyl) thiophosphate, xylylene diisocyanate, benzene-1,2,4-triisocyanate, Naphthalene-1,2,5,7-tetraisocyanate, naphthalene-1,
3,7-triisocyanate, phenyl isocyanate,
Hexamethylene diisocyanate, methylcyclohexane diisocyanate and the like can be mentioned. Preferably, aromatic diisocyanate or triisocyanate or an aromatic isocyanate compound such as a dimer, a trimer of various aromatic isocyanate compounds and an adduct obtained by reacting the aromatic isocyanate with a polyol or a polyamine is used. Used. More preferably, aromatic polyisocyanate compounds such as 2,4-tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate are used.

Dialkylamino-substituted aromatic compounds include N, N '
-Dimethylaminobenzophenone, N, N'-diethylaminobenzophenone, N-dimethylaminobenzaldehyde, N-diethylaminobenzaldehyde, N-dimethylaminobenzoyl chloride, methyl ester of N-dimethylaminobenzoic acid, p-diethylaminostyrene, p-dimethylamino There are styrene, p-dimethylaminomethylstyrene, 1- (N-dimethylamino) -4-chlorobenzene and the like.

Examples of the aromatic heterocyclic compound include 4-vinylpyridine, 2-vinylpyridine, bis (2-pyridyl) ketone, bis (4-pyridyl) ketone, and the like.

These reactive compounds, i.e., modifiers, are used in an amount of 0.1 to 10 equivalents, preferably 0.2 to 10 equivalents, of the reactive group per mole of lithium atom.
Use within a range of 3 equivalents. If the amount is less than 0.1 equivalent, the reactivity to carbon black described below is not sufficient, and the fuel efficiency and the reinforcing property at high temperatures are small.On the other hand, if the amount exceeds 10 equivalents, the above-mentioned improvement effect reaches saturation and becomes economically disadvantageous. Is not preferred.

(Co) polymerization reaction with lithium initiator and (co)
The coupling reaction between the active terminal and the modifying agent after the polymerization reaction is carried out in the range of 0 ° C. to 150 ° C., and may be performed under isothermal conditions or elevated temperature conditions.

The polymerization method may be either a batch polymerization method or a continuous polymerization method.

When polymerizing the conjugated diene compound or the conjugated diene compound and the aromatic vinyl compound, for the purpose of controlling the microstructure of the obtained polymer, for example, the degree of randomness in the vinyl content or the polymer molecular structure, tetrahydrofuran, diethyl Ether compounds such as ether, dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine and dipiperidinoethane, tertiary amine compounds, phosphine compounds and potassium salts can be used.

The content of the aromatic vinyl compound in the conjugated diene polymer obtained in the present invention is preferably 50% by weight or less, more preferably 5 to 35% by weight, and it is randomly distributed in the polymer molecular chain. Is preferred.

The conjugated diene compound content of the conjugated diene (co) polymer is preferably 30% by weight or more from the viewpoint of tensile strength. The conjugated diene-based (co) polymer as described above must contain at least 30% by weight, more preferably at least 40% by weight, based on 100 parts by weight of the raw rubber in the composition of the present invention. It is not possible to obtain the desired rubber composition having excellent wet skid properties, rolling friction resistance properties and tensile strength.

The conjugated diene-based (co) polymer of the present invention is a polymer having a uniform composition along the molecular chain of an aromatic vinyl derivative, such as a side-chain conjugate such as a vinyl bond, or a conjugated diene-based (co) polymer which is continuously changing. , Or those connected in blocks.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the conjugated diene (co) polymer of the present invention is preferably in the range of 10 to 150, and if it is less than 10, the tensile properties and the rolling friction resistance properties are inferior. On the other hand, when it exceeds 150, it is not preferable because it is inferior in workability.

Next, the carbon black used in the present invention limits the number of oxygen-containing functional groups introduced to the surface thereof to a range of 2.2 to 10.5 per 100 carbon atoms.
When the number of oxygen-containing functional groups is less than 2.2, the reactivity with a modifying group such as the isocyanate is low, and therefore, the effect of improving the fuel efficiency and reinforcing property at high temperatures is small. If the number is more than 10.5, the oxygen-containing functional group which has not reacted with the isocyanate-modified group or the like remains on the surface of the carbon black, so that the vulcanization rate is significantly reduced.

The number of such oxygen-containing functional groups is preferably 2.7 to 7.8, and the pH value is 2 to 6, preferably 3 to 5. Thus, the reason that the pH value due to the introduction of the oxygen-containing functional group is in the range of 2 to 6 is that the vulcanization is unfavorably delayed when the pH value is less than 2, whereas the oxygen-containing functional group decreases when the pH value exceeds 6. This is because the object of the present invention cannot be achieved.

Specific examples of the carbon black to be used include, for example, JP-A-62-184463 and Kinki University Faculty of Engineering Research Report No. 2
Furnace black obtained by the vacuum low-temperature plasma processing method presented in 1 and furnace black oxidized with HNO ₃ , H ₂ O ₂ , O _{3, and the} like. A similar effect can be obtained with channel black that satisfies the above-described conditions of the present invention.

Such carbon black, 24M N ₂ SA is at 60~270m ² / g
₄ It is required that the DBP oil absorption is in the range of 80 to 140 ml / 100 g.This is because the N ₂ SA value and the 24M ₄ DBP oil absorption are smaller than the respective lower limits, the dispersibility improvement effect is small. ,
Also, when the amount exceeds the upper limit, the dispersibility is poor, and the heat generation increases.

In the present invention, the amount of carbon black to be filled is in the range of 20 to 150 parts by weight.
If the amount is less than 10 parts by weight, sufficient elasticity cannot be obtained as a rubber composition for a tire, and the reinforcing property cannot be secured.On the other hand, if the amount exceeds 150 parts by weight, sufficient carbon dispersion cannot be obtained, and the reinforcing property is reduced, which is not desirable. Because.

The rubber composition used in the pneumatic tire of the present invention contains the conjugated diene-based (co) polymer as an essential component, and contains natural rubber, high cis-polyisoprene, emulsion-polymerized styrene-butadiene copolymer, and bound styrene in 10 parts. ~ 40 wt%, other solution polymerized styrene-butazine copolymer having a vinyl content of 10-80%, high cis polybutadiene, ethylene-propylene-diene ternary copolymer obtained using nickel, cobalt, titanium, neodymium catalyst Coalesced, halogenated butyl rubber, blended with one or more rubbers selected from halogenated ethylene-propylene-diene terpolymer, and carbon black is mainly composed of the carbon black, if necessary. Furnace black, such as HAF, ISAF, SAF, and the like used in ordinary rubber compositions for tires can be used in combination. When the total parts by weight of carbon black must be in the range of 20 to 150 parts by weight from the reason.

(Function) Conjugated diene system (co) used in the rubber composition of the present invention
The polymer has a specific modifying group at the polymerization terminal by reacting a lithium atom at the polymerization terminal with a reactive compound such as an isocyanate compound, and the modified group and the carbon black surface according to the present invention have a specific modifying group. The introduced oxygen-containing functional group has an extremely large interaction.

As a result, the loss due to the interaction between the carbon black and the polymer is reduced, and the high-temperature reinforcing property is improved due to the reinforcing effect of the interaction.

(Example) Next, the present invention will be described more specifically with reference to examples.

Synthesis of Polymers (A to H, N to P) Cyclohexane, a monomer, and tetrahydrofuran were charged into a nitrogen-purged reactor having an inner volume of 5 according to the formulation shown in Table 1 below. The polymerization reaction was carried out at 30 to 90 ° C. under adiabatic condition by adding an initiator.

After the polymerization addition ratio reached 100%, the reactive compounds shown in Table 1 were added and reacted in the amounts shown in the same table. Next, 0.7 g of di-tert-butyl-p-cresol was added as an antioxidant to 100 g of rubber, and the mixture was desolvated and dried by a conventional method.

Synthesis of Polymers (I to J) A butadiene copolymer was obtained in the same manner as in A except that silicon tetrachloride and diethyl adipate were used instead of the isocyanate compound, respectively.

Synthesis of Polymers (K to M) A butadiene-based copolymer was obtained in the same manner as in Polymer A except that no isocyanate compound was used.

The microstructure (vinyl bond content) of the butadiene portion of the (co) polymer thus obtained was determined by infrared spectroscopy (Morello method).

The styrene content was measured by infrared spectroscopy based on the absorption of a phenyl group at 699 cm ^-1 by a calibration curve previously determined.

Mooney viscosity: 1 minute residual heat, 4 minutes measurement time, 100 temperature
Measured in ° C.

 Tg was measured by a differential scanning calorimeter (DSC).

 The measurement results are shown in Table 2 below.

Preparation of carbon black i) Vacuum low-temperature plasma treatment (carbon Q to T) 50 g of carbon black is placed in a 500 ml Pyrex flask-type plasma chamber, and the flask is rotated at least 5 rpm or more to uniformize the treatment and suppress incineration. Vacuum low-temperature plasma treatment was performed while performing.

This vacuum low-temperature plasma treatment uses a high-frequency output (13.56 MHz).
z) The processing was performed under the conditions of 25 W, a degree of vacuum of 0.3 Torr, and a processing gas flow rate of 50 ml / min, using the processing gas and processing time shown in Table 3 below.

ii) Liquid phase oxidation treatment (carbon U, X) 100 g of carbon black was added to an aqueous solution containing 10 g of H ₂ O ₂ in water 1 and reacted at 30 to 70 ° C. for 30 minutes while heating and stirring. After the completion of the reaction, the carbon black suspension was filtered, and then dried in a dryer at 120 ° C. for 12 hours to adjust the carbon used.

The carbon black and CK3 (E
Table 3 shows the characteristics of PC) channel black (carbon V) and untreated furnace black (W, Y, Z).

Incidentally, the number of carbon atoms relative to the surface oxygen-containing functional groups introduced to the surface of each carbon black by such treatment and
The pH value was measured as follows.

The number of carbon atoms in the oxygen-containing functional group was measured under the following conditions using JPS-80 manufactured by JEOL Ltd.

X-ray: M _g K [alpha accelerating voltage: 12 kV Emission Current: The number of carbon atoms comparison 25mA surface oxygen-containing functional groups, the following C
The peak area of 1S of O and O was determined, and the ratio was used as the ratio of the number of atoms.

O _1S : 528 eV to 542 eV C _1S : 280 eV to 300 eV pH value 1 g of a sample is added to 100 ml of ion-exchanged water, boiled for 15 minutes, and left for 48 hours. It was measured with a meter.

Table 3 also shows the measurement results of the number of carbon atoms and the pH value of the surface oxygen-containing functional groups.

The above-mentioned polymer and carbon black were kneaded and compounded using a 250 cc blast mill according to the compounding recipe shown in Table 4 below to obtain various test rubber compositions. These compounds were vulcanized at 145 ° C. by 30 press vulcanization to obtain vulcanized products, which were tested for the following properties.

The vulcanization characteristics were measured according to JIS K6301.

 The following method was used for the wear resistance test.

Two test tires were mounted on a drive shaft of a passenger car having a displacement of 1500 cc, and were run at a predetermined speed on a concrete road surface of a test course. The amount of change in the groove depth was measured, and the result was indicated as an index with the tire of Comparative Example 1 as 100. The larger the numerical value, the better the wear resistance performance. Internal loss (tan
δ) was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of a tensile dynamic strain of 1%, a frequency of 10 Hz, and 50 ° C. The test piece used was a slab sheet having a thickness of about 2 mm and a width of 5 mm, and the initial load was 100 g with a distance between sample sandwiches of 2 cm.

The rolling resistance index was evaluated by the following equation from the value calculated from the moment of inertia at a predetermined speed by rotating the drum by bringing the tire into contact with the drum having an outer diameter of 1.7 m, rotating the drum to a certain speed, coasting the drum, and calculating the moment of inertia at a predetermined speed. .

The skid resistance (wet skid property) of wet road surface is
On a wet concrete road surface at a depth of 3 mm, the distance from the wheel was locked to the stop after sudden braking from a speed of 80 km / h was measured, and the skid resistance of the test tire was evaluated by the following equation.

The high-temperature reinforcement is obtained by using the above spectrometer.
Temperature dispersion measurement was performed at a dynamic strain of 1% and a frequency of 50 Hz.
The evaluation was made based on the ratio of storage elastic modulus (E ') at 0 ° C.

Here, the closer to 1 the value is, the higher the high-temperature reinforcing property is.

Table 5 below shows the test rubber compositions and the test results of pneumatic tires using these rubber compositions for treads.

(Effect of the Invention) As can be seen from the measurement results shown in Table 5 above, a diene compound modified with a specific reactive compound satisfying the requirements of the present invention or a blend rubber with the compound,
Reinforcing properties of pneumatic tires, especially at high temperatures, by using carbon black having oxygen-containing functional groups on the surface that satisfies the requirements of the present invention alone or in combination with carbon black blended with ordinary reinforcing furnace black. The effect is obtained that the reinforcing properties, wet skid properties and fuel economy properties can be simultaneously improved.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C09C 1/48 PBE C09C 1/48 PBE // (C08L 15/00 7:00) (C08L 15 / 00 9:06) (56) References JP-A-63-191844 (JP, A)

Claims (8)

(57) [Claims] 1. A conjugated diene compound obtained by polymerizing or copolymerizing a conjugated diene compound or a conjugated diene compound and one or more aromatic vinyl compounds in a hydrocarbon solvent using a lithium-based polymerization initiator. Terminal modification obtained by reacting at least one reactive compound selected from the group consisting of an isocyanate compound, a dialkylamino-substituted aromatic compound and an aromatic heterocyclic compound with a polymerization active terminal of a (co) polymer. With respect to 100 parts by weight of the conjugated diene-based (co) polymer alone or a blend with another diene-based polymer containing 30% by weight or more of the (co) polymer, the following properties, nitrogen adsorption specific surface area (N ₂ SA): 60 ~ 270m ² / g Compressed dibutyl phthalate oil absorption (24M ₄ DBP oil absorption): 80 ~
140ml / 100g Number of oxygen-containing functional groups on the surface per 100 carbon atoms: 2.2
A rubber composition comprising 20 to 150 parts by weight of carbon black having a pH of 2 to 6. 2. A pneumatic tire comprising the rubber composition according to claim 1 in a tire surface layer. 3. The pneumatic tire according to claim 2, wherein the tire surface layer is a tread. 4. The pneumatic tire according to claim 2, wherein said conjugated diene polymer is a butadiene polymer. 5. The pneumatic tire according to claim 2, wherein said conjugated diene polymer is a styrene-butadiene copolymer. 6. The method of claim 1, wherein the other diene polymer is natural rubber and / or
The pneumatic tire according to claim 2, which is a polyisoprene rubber. 7. The pneumatic tire according to claim 2, wherein said reactive compound is an isocyanate compound. 8. The terminal-modified conjugated diene-based (co) polymer is a butadiene-based (co) polymer, and the butadiene portion has a vinyl bond content of 15% by weight or more and the glass transition of the (co) polymer. The pneumatic tire according to claim 2, wherein the temperature is -70C or higher.