JP2002080635A - Bead filler rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire, improved in durability and workability during manufacture and providing excellent controllability and riding comfort, by improving the bead filler rubber composition. SOLUTION: The bead filler rubber composition is prepared by adding a master batch, in which a thermoplastic polyamide is dispersed fiber-wise in the matrix comprising a polyolefin and an elastomer with 1-8 pts.wt. of the polyamide fiber component, and a carbon blend system comprising 30-70 pts.wt. of hard carbon and 10-50 pts.wt. of soft carbon is added to 100 pts.wt. of the material rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bead filler rubber composition provided with anisotropy by blending a single fiber and a pneumatic tire using the same, and more particularly to a pneumatic tire using the same while ensuring steering stability. The present invention relates to a pneumatic tire capable of improving comfort performance.

[0002]

2. Description of the Related Art In recent years, with the development of expressways, tires have been increasingly demanded, and driving stability as well as riding comfort have been demanded. One example of high-speed running is the occurrence of a tire standing wave phenomenon, which is known to lead to tire destruction. One of the means for suppressing this phenomenon is to improve the rigidity of the bead portion, and the high elasticity of the bead portion is also effective in reducing the rolling resistance. Those having a high elastic modulus are preferred.

[0003] However, in general, methods for obtaining a rubber composition having a high elastic modulus include a method of blending a large amount of carbon black, a method of blending a large amount of sulfur, a method of adding a thermosetting resin, and a method of blending short fibers. Although each has its own characteristics, the former three are not preferred from the viewpoint of the tire molding operation and the life of the tire. On the other hand, it has been pointed out that in the latter method of blending short fibers with rubber, the bonding between the short fibers and rubber is generally insufficient, so that the creep property increases and the fatigue life decreases.

Now, in a pneumatic radial tire,
In order to improve tire performance, it is necessary to satisfy driving stability as well as driving stability.However, from the viewpoint of the bead structure, there is a conflict between steering stability and riding comfort. It is.

In general, the rigidity of a bead filler is increased for the purpose of improving the steering stability of a pneumatic radial tire. If the rigidity is insufficient, a steel reinforcing material or the like is arranged around the bead filler. There are cases.
However, when a steel reinforcing material or the like is arranged in the bead portion, the rigidity in the tire radial direction becomes too high, and the riding comfort performance is greatly reduced. On the other hand, if no steel reinforcement is used, the steering stability may be insufficient because the bead portion is too soft in some cases. Therefore, it has been difficult to secure the same steering stability as when no steel reinforcing material is used around the bead filler, to improve the riding comfort performance, and to further reduce the weight of the tire.

As described above, in consideration of the riding comfort performance of the tire, it is preferable that the elastic modulus of the bead filler rubber composition is made anisotropic. Proposals have been made.

A technique for blending short fibers with a bead filler rubber composition has been proposed, for example, in Japanese Patent Application Laid-Open No. 7-330962. However, blending short fibers in the bead filler rubber composition has an advantage in workability as compared with increasing the amount of carbon black or thermosetting resin, but also causes a decrease in the fatigue characteristics of the vulcanized rubber. Become. Therefore, in such a proposal, a thermoplastic polyamide is dispersed in a matrix composed of a polyolefin and an elastomer, and the polyamide fiber and the matrix are compounded with a masterbatch chemically bonded by a silane coupling agent, a phenol resin, or the like. It is a thing obtained. The vulcanization properties of this rubber composition are superior to those of conventional rubber compositions in terms of crack growth resistance, and are supposed to eliminate the above-mentioned problems when blending fibers. However, although the conventional problems have been improved on the one hand by the incorporation of such short fibers, it is also a fact that some points have to be considered further. And the process requires much labor and time. It is also a fact that the fatigue property deteriorates as the blending amount of the short fiber increases with respect to the fatigue property. In particular, the number of breaks in a region where the load is large (4 Kpa or more) becomes extremely poor when the fiber is blended. I will.

Short fibers are mixed with the bead filler rubber composition to make the anisotropy, that is, the ratio of the elastic modulus in the tire radial direction and the elastic modulus in the direction perpendicular to the tire different, to achieve both steering stability and ride comfort. This technique is disclosed in JP-A-11-129711. In such a proposal, the short fiber is a blend of a water-soluble fiber such as polyvinyl alcohol and a thermoplastic polyamide, thereby increasing the elastic modulus in a wide strain range. A phenolic resin or a silane coupling agent or the like is blended for the purpose of improving the convergence and dispersion of the fiber and for grafting the elastomer component of the matrix onto the fiber surface. As described above, although measures are taken to improve the binding between the short fibers and the matrix elastomer, deterioration in workability and fatigue is still unavoidable due to the blending of the short fibers.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to improve the bead filler rubber composition to improve durability and workability during tire production, and at the same time, to improve tire handling stability and ride comfort. It is to provide a compatible pneumatic tire.

[0010]

Means for Solving the Problems The present invention has been made to solve the above problems, and the first invention is a thermoplastic polyamide comprising a polyolefin and an elastomer based on 100 parts by weight of a raw rubber. A masterbatch dispersed in a matrix in a fibrous form has a polyamide fiber content of 1
-8 parts by weight, and hard carbon 3
The present invention relates to a bead filler rubber composition containing a carbon blend of 0 to 70 parts by weight and 10 to 50 parts by weight of soft carbon.

The second invention provides a pneumatic tire in which a bead filler is arranged on the outer peripheral side of a bead core.
A thermoplastic polyamide short fiber is oriented in the rubber constituting the bead filler in a direction perpendicular to the tire radial direction, and the ratio of the elastic modulus a in the tire circumferential direction to the elastic modulus b in the radial direction (a / b).
Is a pneumatic tire with 1.5 or more, specifically, the bead filler rubber composition provided in the first invention is arranged on the outer peripheral side of a bead core.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the present invention will be described in further detail with reference to the first invention. A short fiber is compounded in a bead filler rubber, and the fiber is extruded to orient the fiber in the extrusion direction. One object is to obtain a material having an anisotropy in which the ratio of the elastic modulus a in the direction to the elastic modulus b in the radial direction is a / b> 1.5. The anisotropy of the elastic modulus achieves both the steering stability and ride comfort of the tire, and the addition of short fibers raises the elastic modulus of the entire bead filler to reduce the weight of the tire. And low rolling properties.

A thermoplastic polyamide short fiber dispersed in a polyolefin-elastomer is blended so as not to impair the fatigue resistance. The polyamide short fiber is dispersed in such a matrix, and a bond is formed between the matrices. It is formed to reduce deterioration of fatigue resistance. The composition of the composition is composed of about 5 to 100 parts by weight of a polyamide short fiber and about 5 to 70 parts by weight of a polyolefin for 100 parts by weight of an elastomer. It is grafted with a phenolic thermoplastic resin or a silane coupling agent. The elastomer used here is desirably the same as the polymer (for example, natural rubber) constituting the bead filler composition.

However, the incorporation of short fibers inevitably impairs the workability such as roll heatability and the fatigue characteristics when vulcanized rubber is used.
The balance was maintained by taking measures to keep the weight below the weight level. Thereby, the ratio of the elastic modulus a in the fiber orientation direction to the elastic modulus b in the orthogonal direction is in the range of about 1.5 <a / b <4.

The compounding of the carbon blend system of the present invention aims at improving the overall elastic modulus. In this case, the purpose of blending a blend of soft carbon and hard carbon as the carbon black is to increase the balance between the total carbon filling and the reinforcing property and increase the elastic modulus of the bead filler. Here, as the hard carbon black, carbon black having an average particle diameter of 40 μm or less, preferably about 20 to 30 μm can be used, and examples thereof include SAF, ISAF, and HAF. As the soft carbon black, carbon black having an average particle diameter of preferably 40 μm or more, preferably about 50 to 100 μm can be used. For example, FEF, GPF, SRF, HPF, APF
PF and the like can be mentioned. The hard carbon black has an element adsorption amount (IA) of 60 to 170 mg /
g is preferable, and 70 to 110 mg / g is more preferable. On the other hand, soft carbon black has an IA of 10
-60 mg / g, preferably about 20-50 mg / g, more preferably. The above IA is ASTM D-1510
-95 and DBP are values measured according to ASTM D-2414-97, respectively.

In order to achieve both the steering stability of the tire and the ride comfort, it is desirable that the ratio of the elastic modulus in the circumferential direction to the elastic modulus in the radial direction is conditionally large as described above. In a normal tire structure, since it is smaller than the sidewall, it is not advisable to increase the elastic modulus by increasing the blend of short fibers until the workability and the fatigue property are deteriorated. For these reasons, the blending amount of the short fibers has an upper limit, and accordingly, an increase in the overall elastic modulus can be suppressed. To compensate for this, the present invention balances the reinforcement and filling effects by further filling soft carbon into a hard carbon-based carbon system, and it is possible to improve the elastic modulus especially in the low strain region. And thereby contribute to the improvement of steering stability. In addition, advantages of the carbon blend system include excellent workability and fatigue resistance, such as a low Mooney viscosity and the like, and a reduction in elongation at break can be suppressed in proportion to the amount of carbon black.

Regarding the numerical limitation of carbon black,
10 to 70 parts by weight of soft carbon
If the amount is less than 0 parts by weight, there is no effect as a carbon blend, and if it exceeds 70 parts by weight, the compounding amount of the whole carbon combined with the hard carbon is too large, resulting in a decrease in workability and fatigue. Occurs. The numerical limitation of the hard carbon is 30 to 70 parts by weight, and if it is less than 30 parts by weight, a sufficient reinforcing effect cannot be obtained, and if it exceeds 70 parts by weight, the total compounding amount is too large. Because.

As another method of increasing the elastic modulus, there is a method of blending a phenolic thermoplastic resin.
It is desirable to mix about parts.

According to a second aspect of the present invention, there is provided a pneumatic tire employing the above-described bead filler rubber composition having a high elastic modulus in anisotropy. The ratio of the elastic modulus b in the direction is a / b
A pneumatic tire having an anisotropy of> 1.5 was obtained, and the anisotropy of the elasticity of the bead portion employing such a bead filler made it possible to achieve both steering stability and ride comfort of the tire. In addition, the elastic modulus of the entire bead filler is increased, and the weight reduction and the low rolling property can be achieved.

The thermoplastic polyamide used in the present invention is a short fiber having an average length of 10 mm or less.
Nylon 6, Nylon 66, Nylon 6-Nylon 66
Copolymer, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, nylon MXD
6, selected from polycondensates of aliphatic diamines and aromatic dicarboxylic acids.

The elastomer component forming the matrix is a vulcanizable rubber component and includes, for example, natural rubber, polyisoprene, polybutadiene, styrene butadiene rubber, butyl rubber and the like, alone or in combination. Among them, those common to the raw material rubber of the bead filler are particularly preferable.

The polyolefin component forming the matrix preferably has a softening point of 50 ° C. or higher or a melting point in the range of 80 to 250 ° C., for example, C ₂ to C _2.
8 olefin homopolymers and copolymers, copolymers of C _{2 to} C ₈ olefins with aromatic vinyl compounds such as styrene, chlorostyrene and α-methylstyrene, copolymers with vinyl acetate, acrylics A copolymer with an acid or methacrylic acid may be used. More specific examples include high-density polyethylene, low-density polyethylene, polypropylene, ethylene-propylene block copolymer, polybutene-1, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-styrene copolymer. Examples thereof include a coalesce and a propylene / styrene copolymer, and these can be used alone or in combination.

Examples of the binder incorporated in the matrix include a silane coupling agent, a titanate coupling agent, a novolak type alkylphenol formaldehyde precondensate, and a resol type alkylphenol formaldehyde precondensate. Preferably, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, or the like is selected. In addition, it can also be used together with the organic oxide.

In the matrix production method, melting and kneading may be performed by using a Banbury mixer, a kneader, a kneader extruder, an open roll, a single-axis kneader, a twin-axis kneader, etc., which are usually used for kneading resins and rubbers. No. The same applies to the kneading of the matrix and the rubber raw material.

In the bead filler rubber composition, a usual compounding agent, for example, a vulcanizing agent represented by sulfur, a thermosetting resin, a reinforcing agent such as white carbon, activated carbon, lignin, clay, zinc Filler such as flower, other vulcanization accelerator,
Various compounding agents such as an antioxidant and a process oil are arbitrarily selected and compounded.

As for the production of a tire using the rubber composition, for example, a sheet-shaped bead filler member is prepared by kneading and extruding with an extruder calender or the like, and this is placed on a molding drum. Then, a green tire is prepared by laminating the green tire with another member, the green tire is placed in a tire mold, and vulcanization is performed while applying pressure from the inside.

[0027]

EXAMPLES The bead filler rubber composition referred to in the first invention will be further described below with reference to Examples and Comparative Examples. Table 1
Indicates the composition of the bead filler rubber composition and the vulcanized properties of the vulcanized rubber composition.

Tables 1) to 5) are as follows. 1): Polyamide dispersed in a matrix of a polyolefin and an elastomer in a fibrous form. For example, UBE-FRR _NR manufactured by Ube Industries, Ltd. can be used. The weight ratio of polyamide: polyolefin: elastomer of the composition is about 1: 1: 2. 2): As the hard carbon black, for example, Asahi Carbon Co., Ltd. Asahi # 55 (IA = 70, DBP = 10
0) can be used. 3): As soft carbon black, for example, Asahi Carbon Co., Ltd. Asahi # 70 (IA = 30, DBP = 80)
Can be used. 4): As the phenol resin, for example, Sumireto Bakelite Co., Ltd. Sumilite Resin PR50253 can be used. 5): As the phenol resin curing agent, for example, Noxeller H of Ouchi Shinko Chemical Co., Ltd. can be used.

The kneading conditions were two-stage kneading, and the non-pro (first stage) kneading conditions were a rotor rotation speed of 70.
rpm / min, temperature 80-170 ° C, kneading time 4mi
n, and the professional (second stage) kneading conditions are 50r each.
pm / min, 70-110 ° C, 1 min. The dark kneading conditions are such that the kneading temperature in non-pro kneading is sufficiently higher than the softening temperature of the polyolefin constituting the short fiber-containing composition so that the short fibers are well dispersed. The vulcanization conditions were a vulcanization temperature of 160 ° C., a vulcanization pressure of 10 kgf / cm ² , and a vulcanization time of 15 minutes.

The fatigue resistance test was performed using a hydraulic fatigue test, for example, a servo pulser EHF-E series manufactured by Shimadzu Corporation. As a test piece, a strip-shaped test piece having a width of 6.0 mm, a length of 70 mm and a thickness of 2.0 mm with an initial crack of about 0.5 mm in the center was used. A constant repetitive stress that forms a sine function is applied to a time of about 1.0 to 3.0 Mpa, a minimum stress of 0.1 Mpa, and a frequency of 5 Hz, and the number of times until the test piece breaks for each maximum stress is determined. Was.

(Comparison of Physical Properties of Bead Filler Composition) Comparative Example 1 is a conventional bead filler composition containing no short fiber, and has an anisotropy of M50 or E '(2%) as physical properties. Can not. Comparative Example 2 is a case where the blending amount of the short fiber is about 12 parts by weight per 100 parts by weight of the elastomer, the number of breaks in the fatigue test at the maximum stress of 2.5 Mpa becomes extremely small, and deterioration of the fatigue resistance is remarkably exhibited. I do. Comparative Example 3 was a system in which only hard carbon was blended without using a hard and soft blend system with carbon. In this case, the elastic modulus such as M50 and E '(2%) was higher than that of the carbon blend system. It can be seen that the resistance is reduced by about 30% and the fatigue resistance is also reduced.

On the other hand, in Examples 1 to 3, short fibers were blended in an amount of about 3 to 7 parts by weight per 100 parts by weight of the elastomer, whereby the elastic modulus ratio was 2 at M50 and E '(2%).
The anisotropic characteristics described above were achieved. Also, compared to Comparative Example 1 in which short fibers are not blended, an increase in the elastic modulus of 60 to 100% can be realized, and when applied to a tire, the weight reduction and low rolling characteristics of the tire are realized. You can do it.

FIG. 1 is a meridional half-sectional view of a tire (second invention) using the bead filler rubber composition of the first invention. Reference numeral 1 denotes a bead portion, 2 denotes a carcass layer, 3 denotes a bead core, 4 denotes a bead filler disposed on the outer peripheral side of the bead core 3, 5 denotes a tread portion, and 6 denotes a belt layer. And
The belt layer 6 has three steel cord layers, and the carcass layer 2 has one ply layer made of PET fiber.
The turn-back of the carcass ply reaches a position on the outer peripheral side of about 30 mm from the outer peripheral end of the bead.

The produced tire has a size of 215 / 45Z.
R17, a bead filler was arranged on the outer peripheral side of the bead core, and the above-described Comparative Example 1 was used as the bead filler member.
2 and the rubber compositions of Examples 1 to 3 were used. When making a tire using a bead filler member containing short fibers, the orientation direction of the short fibers, that is, the extrusion direction of the bead filler member is made to coincide with the circumferential direction of the tire,
The elastic modulus ratio of the bead filler member in the tire circumferential direction and the radial direction was set to 2 or more.

(Tire evaluation test / actual tire performance test)
A vehicle equipped with the prepared tires was driven on a test course, and ride comfort and dry steering stability were evaluated by a test driver. Table 2 shows the results of the evaluation test.

[0036]

According to the present invention, a high elastic modulus of a bead filler rubber composition can be realized by blending a short fiber and a carbon blend. In a tire using the same, steering stability and rolling resistance are improved, and By making the directional elastic modulus larger than the radial elastic modulus, it was possible to reduce the deterioration of ride comfort. In addition, fatigue (such as collision with curbstones or running on rough roads) that particularly applied a large load ), A tire with reduced deterioration of durability can be obtained.

[0037]

[Table 1]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a meridian half sectional view of a tire according to a second invention.

[Description of Signs] 1) bead portion, 2) carcass layer, 3) bead core, 4) bead filler disposed on the outer peripheral side of bead core, 5) tread portion, 6) belt layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/04 C08K 3/04 9/04 9/04 C08L 9/00 C08L 9/00 15/00 15 / 00 23/02 23/02 23/22 23/22 77/00 77/00 F term (reference) 4F070 AA04 AA12 AC04 AC90 AD02 FA03 FA13 FA17 FB03 FC03 FC05 4F072 AA02 AA07 AB06 AC06 AC10 AD02 AD04 AF01 AG05 AH04 AH23 AK04 AL18 4J002 AC011 AC031 AC061 AC081 AC114 BB032 BB062 BB082 BB102 BB122 BB142 BB152 BB172 BB181 CL013 CL023 CL033 CL053 DA036 FA043 FB263 GN01

Claims (9)

[Claims] 1. A master batch in which a thermoplastic polyamide is dispersed in a fibrous form in a matrix composed of a polyolefin and an elastomer is blended with 100 parts by weight of a raw rubber so that the polyamide fiber content is 1 to 8 parts by weight. Furthermore, 30 to 70 parts by weight of hard carbon and 10 parts of soft carbon
A bead filler rubber composition containing about 50 parts by weight of a carbon blend. 2. The bead filler rubber composition according to claim 1, wherein the thermoplastic polyamide is a short fiber having an average length of 10 mm or less. 3. The thermoplastic polyamide short fiber is nylon 6,
A fiber selected from nylon 66, nylon 6-nylon 66 copolymer, nylon 610, nylon 612, nylon 46, nylon 11, nylon 12, nylon MXD6, and a polycondensate of an aliphatic diamine and an aromatic dicarboxylic acid. Item 4. A bead filler rubber composition according to Item 2. 4. The hard carbon black has an average particle diameter of 40.
The pneumatic tire according to claim 1, wherein the pneumatic tire is carbon black having a size of not more than μm. 5. The soft carbon black has an average particle diameter of 40.
The pneumatic tire according to claim 1, wherein the pneumatic tire is carbon black having a particle size of at least μm. 6. A matrix comprising an elastomer and a polyolefin in which a thermoplastic polyamide is dispersed in a fibrous form is converted into 5-70 parts by weight of a polyolefin and 5-100 parts by weight of a short thermoplastic polyamide fiber per 100 parts by weight of an elastomer. 2. A thermoplastic polyamide short fiber and an elastomer component are grafted with a phenolic thermoplastic resin or a silane coupling agent.
The bead filler rubber composition according to the above. 7. A bead filler rubber composition is extruded in the circumferential direction of the tire, and the ratio (a / b) of the elastic modulus a in the tire circumferential direction to the elastic modulus b in the radial direction is 1.5 or more. The bead filler rubber composition according to claim 1. 8. A pneumatic tire in which a bead filler is arranged on the outer peripheral side of a bead core, wherein the thermoplastic polyamide short fibers in the bead filler rubber composition are oriented in a direction perpendicular to the tire radial direction, and have an elastic modulus in a tire circumferential direction. A pneumatic tire wherein the ratio (a / b) of a to the elastic modulus b in the radial direction (a / b) is 1.5 or more. 9. The pneumatic tire according to claim 8, wherein the bead filler rubber composition according to any one of claims 1 to 5 is arranged on an outer peripheral side of the bead core.