JP2002105248A - Rubber composition for bead filler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a bead filler increasing effectively a modulus without loss of elongation at break and workability, and making a tire light keeping a driving stability to contribute to improvement of a fuel consumption. SOLUTION: The rubber composition for the bead filler and a pneumatic tire consisting of 100 pts.wt. of a rubber component, 30-100 pts.wt. of a hard carbon black, and 10-50 pts.wt. of a soft carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, passenger cars,
The present invention relates to a rubber composition for bead filler that can be suitably used as a bead filler for tires of trucks, buses, motorcycles, and the like, and a pneumatic tire using the same.

[0002]

2. Description of the Related Art To increase the rigidity of a bead filler, the aim is to improve steering stability or reduce the weight by reducing the gauge. Conventionally, high rigidity has been achieved by adding phenolic resin or changing the type of carbon black. However, from the viewpoint of further suppressing fuel consumption, the physical properties (destructive properties, workability) of the bead filler are further reduced. It is required to achieve high rigidity.

[0003] In order to increase the modulus of the rubber composition, there is known a means of increasing the filling amount of carbon black. And the workability is remarkably deteriorated.

Further, in order to obtain high rigidity as a rubber composition for bead fillers such as pneumatic tires, Japanese Patent Application Laid-Open No.
JP-A-8-4611 proposes a method using a combination of soft carbon black and a phenol resin. However, soft carbon black alone had low reinforcing properties and could not obtain a sufficient elastic modulus.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for a bead filler in which the modulus of elasticity is effectively increased while suppressing the elongation at break and the decrease in workability.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned circumstances, and as a result, by using a system in which hard carbon black and soft carbon black are blended as a filler for a rubber composition, The present inventors have found that the bead filler can be made highly rigid, and have completed the present invention.

That is, the present invention provides the following (1) to (8)
Exists. (1) A rubber composition for a tire bead filler comprising 100 parts by weight of a rubber component, 30 to 100 parts by weight of hard carbon black, and 10 to 50 parts by weight of soft carbon black. object. (2) The rubber composition according to the above (1), wherein the hard carbon black is a carbon black having a nitrogen adsorption specific surface area of 60 m ² / g or more. (3) The rubber composition according to the above (1), wherein the soft carbon black is a carbon black having a nitrogen adsorption specific surface area of 50 m ² / g or less. (4) The total compounding amount of the hard carbon black and the soft carbon black is 7 with respect to 100 parts by weight of the rubber component.
The rubber composition according to any one of the above (1) to (3), which is 0 to 130 parts by weight. (5) The rubber composition according to any one of the above (1) to (4), wherein the compounding ratio of the hard carbon black and the soft carbon black is 10: 1 to 1: 1. (6) The above (1) to (5), further comprising blending 5 to 40 parts by weight of a phenolic thermosetting resin and hexamethylenetetramine with respect to 100 parts by weight of the rubber component. The rubber composition according to any one of the above. (7) The rubber composition as described in (6) above, further comprising a melamine derivative in addition to hexamethylenetetramine. (8) having a bead filler disposed in the bead portion,
A pneumatic tire, wherein the bead filler contains the rubber composition according to any one of the above (1) to (7).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the present invention includes, for example, natural rubber, styrene butadiene rubber, butadiene rubber, isoprene rubber, butyl rubber, halobutyl rubber, crosslinked polyethylene rubber, chloroprene rubber, nitrile rubber and the like. These can be used as a mixture of two or more kinds. In the present invention, it is particularly preferable to use natural rubber, isoprene rubber, or a mixture thereof.

In the rubber composition of the present invention, as a filler,
Hard carbon black and soft carbon black are combined and compounded. Here, hard carbon black refers to SAF, ISAF, and HAF, and is preferably a carbon having a nitrogen adsorption specific surface area (N ₂ SA) of 60 m ² / g or more, more preferably about 70 m ² / g to about 200 m ² / g. Black can be used. In addition, soft carbon black refers to FEF, GPF, SRF, FT, M
T, preferably having a nitrogen adsorption specific surface area (N ₂ SA) of 50 m ² / g or less, more preferably 25 m ² / g to 40 m ² / g.
Carbon black of about m ² / g can be used.

The hard carbon black preferably further has the following characteristics. Iodine adsorption (IA) is 6
0 mg / g to 170 mg / g is preferable,
g / g to 150 mg / g is more preferable.
It is particularly preferable if the amount is about g / g to 120 mg / g.
Dibutyl phthalate oil absorption (DBP) is 40 ml / 1
It is preferably from about 00 g to about 200 ml / 100 g.
More preferably, it is about 150 ml / 100 g, more preferably about 60 ml / 100 g to 120 ml / 100 g.
It is particularly preferable if the degree is about the same.

The soft carbon black preferably further has the following characteristics. IA is 10 mg / g
To about 60 mg / g, preferably 20 mg / g
It is more preferable if the amount is from about 50 mg / g. DBP
Is preferably about 40 ml / 100 g to 170 ml / 100 g, and 50 ml / 100 g to 150 ml / 10
About 0 g is more preferable. The above IA is A
STM D1510-95, DBP is ASTM D24
14-97 and N ₂ SA are values measured according to ASTM D3037-88, respectively.

The amount of hard carbon black is, for example, from 30 parts by weight to 100 parts by weight of the rubber component.
Parts by weight, particularly 50 to 70 parts by weight.
It is preferably about parts by weight. On the other hand, the amount of the soft carbon black is, for example, 10 parts by weight per 100 parts by weight of the rubber component.
From 50 parts by weight to about 50 parts by weight,
It is preferably from about 40 parts by weight to about 40 parts by weight. Further, the total compounding amount of the hard carbon black and the soft carbon black can be, for example, about 70 to 130 parts by weight, and particularly preferably about 80 to 100 parts by weight, based on 100 parts by weight of the rubber component. Further, the mixing ratio of the hard carbon black and the soft carbon black can be, for example, about 10: 1 to 1: 1.
It is preferably about 1 to 1.5: 1.

The rubber composition of the present invention preferably contains a phenolic resin, especially a novolak type phenolic resin. As a novolak type phenolic resin,
For example, a novolak type phenol resin, a novolak type cresol resin, a novolak type resorcin resin, or the like, or a resin obtained by modifying the above resin with an oil such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and linoleic acid, and the like. be able to.

The amount of the novolak type phenolic resin to be added can be 40 parts by weight or less based on 100 parts by weight of the rubber component, and more preferably 5 to 30 parts by weight.

As the curing agent for the phenolic resin,
Known ones, for example, hexamethylenetetramine, paraformaldehyde, melamine derivatives, acetaldehyde ammonia, α-polyoxymethylene, polymethylol melamine derivatives, oxazolidine derivatives, polymethylolated acetylene urea, and the like, and mixtures thereof can be used. .

In the present invention, it is particularly preferable to use hexamethylenetetramine, or a mixed system of hexamethylenetetramine and a melamine derivative. By adding a mixed system of hexamethylenetetramine and a melamine derivative, it is possible to further increase rigidity by increasing the amount of a curing agent and to improve elongation at break. This improvement in elongation at break is presumed to be due to the fact that the crosslinked form of the phenolic resin has a structure that is more flexible than when only hexamethylenetetramine is used as a curing agent. Further, by using hexamethylenetetramine and the melamine derivative in combination, it is possible to secure high rigidity and elongation at break from room temperature to high temperature. Here, as the melamine derivative, for example, hexamethoxymethylmelamine (H
MMMM) or a partial condensate of hexamethylolmelamine pentamethyl ether.
Is a commercially available product of, for example, Mitsui Cytec Co., Ltd.
RA100 (trademark) and the like.

The amount of the curing agent can be appropriately set according to the type. For example, when using hexamethylenetetramine as a curing agent, the amount can be about 4 to 20 parts by weight, more preferably about 6 to 15 parts by weight, based on 100 parts by weight of the phenolic resin. When a melamine derivative is used, 10 parts by weight to 80 parts by weight of phenolic resin is used.
The amount can be about 30 parts by weight, more preferably about 30 parts by weight to 60 parts by weight.

Further, when a mixed system of hexamethylenetetramine and a melamine derivative is used as the curing agent, the amount of hexamethylenetetramine should be about 4 to 20 parts by weight based on 100 parts by weight of the phenolic resin. Preferably, the amount is about 6 to 15 parts by weight, and the melamine derivative can be about 10 to 80 parts by weight, preferably about 30 to 60 parts by weight. Here, the total amount of hexamethylenetetramine and the melamine derivative can be about 15 to 85 parts by weight, preferably about 40 to 65 parts by weight, based on 100 parts by weight of the phenol resin. . Further, the mixing ratio of hexamethylenetetramine and the melamine derivative can be about 1: 3 to 1:16 by weight, preferably about 1: 4 to 1: 8.

The rubber composition of the present invention may contain, if necessary, other components usually used, for example, a vulcanizing agent, a vulcanization accelerator,
Vulcanization retarders, antioxidants, antioxidants, softeners, lubricants,
Vulcanization aids, tackifiers, peptizers and the like can be appropriately compounded.

The rubber composition of the present invention can be produced by kneading the above components with, for example, a Banbury mixer or a kneader. Further, in the manufacture of a tire using the rubber composition, for example, a sheet-shaped bead filler member is prepared by kneading and extruding with an extruder calendar or the like, and this is bonded to another member on a molding drum. A green tire is prepared by placing the green tire in a tire mold, and vulcanizing while applying pressure from the inside. The inside of the tire of the present invention can be filled with nitrogen and an inert gas in addition to air.

[0021]

Next, the present invention will be described in more detail with reference to examples and test examples, but the present invention is not limited to these examples.

Examples 1 to 5, Comparative Example 1 Rubber compositions were prepared according to the formulations shown in Table 1, and their physical properties were tested. The results are shown in Table 1.

The method of each test is as follows. (1) Hardness: In accordance with JIS K6253-1993, the hardness is determined from the indentation depth of the indenter using an A-type durometer.

(2) Vulcanized rubber tensile test: JIS K62
In accordance with the provisions of 51-1993, a dumbbell test piece of JIS No. 3 is used, benchmarks are made at intervals of 20 ± 0.1 mm on parallel portions of the test piece, and the test piece is pulled at a temperature of 25 ± 2 ° C. and a tensile strength of 500 ± 25 mm / min. . The meaning of each parameter in this test is as follows. T _B (tensile strength, unit: Mpa): wherein _{T B = F B / A,} F B; load when the test piece cut [N], A; is a cross-sectional area of the specimen [m ^2]. E _B (elongation at break; unit%): E _B = (L ₁ · L ₀ ) / L ₀ × 100 where L _{1 is} a benchmark distance at the time of cut, and L _{0 is a} first benchmark distance. Elastic modulus at 100% elongation (unit: Mpa): Elastic modulus at 100% elongation = F ₁₀₀ / A where F ₁₀₀ ; load at 100% elongation [N], A; cross-sectional area of test specimen [m ² ].

(3) Dynamic viscoelasticity test: Using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., width 5 mm, thickness 2 m
The measurement is performed at room temperature under the conditions of a dynamic strain of 2% and a frequency of 50 Hz while a test piece having a length of 50 mm and a length of 50 mm is statically elongated. The meaning of each parameter in this test is
It is as follows. Dynamic elastic modulus (E '): storage elastic modulus in the above viscoelastic spectrometer test. Dynamic loss coefficient (tan δ): The ratio between the loss elastic modulus and the storage elastic modulus in the viscoelastic spectrometer test.

(4) Mooney viscosity (ML _{1 + 4} ; 130)
° C): Using a rotorless Mooney measuring device manufactured by Toyo Seiki Co., Ltd., a value obtained by preheating the unvulcanized rubber at 130 ° C for 1 minute and then measuring the torque value 4 minutes later in Mooney units.

[0027]

[Table 1]

As is apparent from Table 1, the conventional hard carbon black is partially replaced by the soft carbon black and the total amount of carbon black is increased, so that the breaking strength and workability are not significantly reduced. ,
Dynamic elastic modulus can be greatly increased.

[0029]

The rubber composition for a bead filler of the present invention has improved dynamic elastic modulus, so that the steering stability can be improved for tires of the same weight. Further, a tire having a lighter weight can be manufactured while maintaining the same level of steering stability as in the past, which contributes to improvement in fuel efficiency.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 61:06) C08L 61:06)

Claims (8)

[Claims] 1. A bead filler for a tire, comprising 100 parts by weight of a rubber component, 30 to 100 parts by weight of hard carbon black, and 10 to 50 parts by weight of soft carbon black. Rubber composition. 2. The rubber composition according to claim 1, wherein the hard carbon black is a carbon black having a nitrogen adsorption specific surface area of 60 m ² / g or more. 3. The rubber composition according to claim 1, wherein the soft carbon black is a carbon black having a nitrogen adsorption specific surface area of 50 m ² / g or less. 4. The rubber composition according to claim 1, wherein the total amount of the hard carbon black and the soft carbon black is 70 to 130 parts by weight based on 100 parts by weight of the rubber component. object. 5. The rubber composition according to claim 1, wherein the mixing ratio of the hard carbon black to the soft carbon black is from 10: 1 to 1: 1. 6. Further, based on 100 parts by weight of the rubber component,
5 to 40 parts by weight of a phenolic thermosetting resin,
The rubber composition according to any one of claims 1 to 5, wherein the rubber composition is mixed with hexamethylenetetramine. 7. The rubber composition according to claim 6, further comprising a melamine derivative in addition to hexamethylenetetramine. 8. A pneumatic tire having a bead filler disposed in a bead portion, wherein the bead filler contains the rubber composition according to any one of claims 1 to 7.