JPH07315015A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance controllability, low rolling resistance and durability of a bead section, and eliminate dislocation in a rim by employing as gum-chafers a specified rubber composition which is made up of a fiber composed of at least a kind of rubber constituent and thermal plastic elastomer having amide groups, and of resin in an olefin system. CONSTITUTION:In the pneumatic tire having a carcass ply composed of bead wires and a rubber coated cord layer, and bead fillers and gum chafers in the radiative direction of each bead wire, each gum chafer is formed out of a rubber composition which is made up of 3 to 70 parts of fibers by weight composed of thermal plastic elastomer having amid groups, and of 3 to 70 parts of resin in an olefin system by weight with respect to 100 parts of a king of rubber constituent by weight, which is selected out of natural rubber and synthetic rubber in a dien system where a compounding ratio of the aforesaid fibers to resin in an olefin system is 3/7 to 7/3. Each fiber is used, in which an average diameter is o.1 to 1.0mum, and a ratio of an average length to an average diameter is equal to or more than 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire using a rubber composition suitable for a gum chafer, and more specifically, it has excellent maneuverability and low rolling resistance (fuel economy),
In addition, the present invention relates to a pneumatic tire having a bead portion with excellent durability without rim displacement.

[0002]

2. Description of the Related Art Various studies have been conducted on the bead structure of a pneumatic tire in order to satisfy the dynamic performance and durability required of the tire. In addition, there is concern about global warming due to the increase in carbon dioxide emissions in recent years, and measures to improve fuel economy are required for automobiles and automobile parts, and rolling resistance is also reduced for tires. Is required to improve fuel efficiency.

As a countermeasure against this, an attempt has been made to improve a tire's kinetic performance and durability performance by disposing a gum chafer layer at the bead portion. Had a drawback that it was significantly inferior.

As another attempt, it is known to improve the kinetic performance by arranging a super-hard rubber in the bead portion, as disclosed in Japanese Utility Model Publication No. 47-16084, French Patent Nos. 1,260,13.
No. 8 and U.S. Pat. No. 4,067,373. However, in these publications, it is almost considered that the function as a gum chafer rubber that is under complicated input while the tire is running is sufficiently exerted, and that the tire has durability and the like necessary for it. Absent.

On the other hand, with the development of highways and the speeding up of vehicles, high-speed performance of tires has also been demanded, and the gum chafer arranged between the rim and the bead has an increasing force. Therefore, the need for a gum chafer with maneuverability, low rolling resistance, and durability is increasing.

On the other hand, in order to obtain a reinforced rubber composition having a high elastic modulus, it has been conventionally practiced to mix vulcanizable rubber with short fibers. For example, Japanese Patent Publication 1-174
Japanese Patent Publication No. 94 describes a reinforced rubber in which a rubber and a nylon fiber embedded therein are graft-bonded via an initial condensation product of a resol type alkylphenol formaldehyde resin. However, in this method, since a resole-type alkylphenol resin having high reactivity to heat is used, it is difficult to control the graft bond between the nylon fiber and the rubber, and the usable rubber is limited. Only a small amount of reinforced rubber composition could be obtained.

To solve this, Japanese Patent Publication No. 3-215
No. 72, a method in which fine fibrous material of thermoplastic polyamide is dispersed in a synthetic rubber mixed with a tackifier, and the polyamide and the synthetic rubber are graft-bonded at this interface via a novolac type phenol resin. However, in this method, since a resin curing agent is mixed with a kneaded product of rubber, polyamide and resin and the mixture is cured in the rubber, there are various problems as described above. In addition, special fair 3
JP-A-49932 describes that by kneading an aromatic polyamide pulp and a phenolic resin into rubber, short fiber reinforcement and resin reinforcement are performed, and by these, a high elastic modulus can be obtained. However, in this technology, the rubber molecules and the polyamide pulp short fibers are not directly bonded, so the reinforcing efficiency is low, and the short fibers themselves act as fracture nuclei in the rubber to improve the fatigue durability and creep properties of the rubber. Disadvantages that significantly reduce, because pulp-like fibers are dispersed in rubber using a kneading machine such as a Banbury mixer, the dispersion level is extremely low. However, when the amount is further increased, it has a drawback that kneading and extrusion become extremely difficult.

[0008]

As described above, the pneumatic tire using the conventional rubber composition for the gum chafer has reached the present without being able to solve the above-mentioned problems. Therefore, the present invention is a pneumatic tire which is excellent in handleability, low rolling resistance (fuel consumption) by using a rubber composition suitable for a gum chafer, and excellent in durability of a bead portion without rim displacement. The purpose is to provide.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to solve the above problems, and as a result, the intended pneumatic tire can be obtained by using a specific rubber composition for a gum chafer. They found out the present invention and completed the present invention. That is, the present invention consists of a bead wire located at a bead portion and a rubberized cord layer in which a large number of cords are arranged in parallel, and both ends are folded back at the bead portion and are radiated from the carcass ply and the bead wire. A pneumatic tire having a bead filler and a gum chafer arranged in a direction, having an amide group with respect to 100 parts by weight of at least one rubber component selected from the group consisting of natural rubber and diene synthetic rubber. Fibers 3 to 70 made of thermoplastic elastomer
A rubber composition comprising 3 parts by weight and 3 to 70 parts by weight of an olefin resin, and the compounding ratio of the fiber made of the thermoplastic elastomer having an amide group and the olefin resin is 3/7 to 7/3. A pneumatic tire used for gum chafers. The fibers made of the thermoplastic elastomer of the rubber composition used for the gum chafer have an average diameter D
Is 0.1 to 1.0 μm, and the ratio (L / D) of the average length L and the average diameter D is preferably 8 or more.

[0010]

The pneumatic tire of the present invention comprises a bead wire located at a bead portion and a rubberized cord layer in which a large number of cords are arranged in parallel, and both ends are folded back at the bead portion and are retained by the bead wire. It has a ply and a bead filler and a gum chafer that are arranged in the radial direction of the bead wire, and in the gum chafer, a fiber composed of a diene rubber and a thermoplastic elastomer having an amide group is chemically Being combined,
An olefin resin is embedded in the polyamide in a fusion-bonded state, and the properties of the polyamide fiber, such as break resistance and fatigue resistance, are improved, and the anisotropy, which is a property of the olefin resin, is improved. Since it is made of rubber, it has excellent maneuverability, low rolling resistance (fuel economy), and excellent durability of the bead portion without rim displacement.

The contents of the present invention will be described below. Examples of rubber components that can be preferably used in the present invention include natural rubber (NR), synthetic polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), chloroprene. Examples thereof include rubber (CR), chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR) and ethylene-propylene rubber (EPDM), and these rubbers can be used alone or in combination of two or more kinds.

Examples of the amide group-containing thermoplastic elastomer (hereinafter referred to as "polyamide") used in the present invention include nylon 6, nylon 11, nylon 12, nylon 610, nylon 611, nylon 61.
2, polyamides including copolymerization of nylon 6/66, and mixed polyamides of two or more of these may be mentioned. The molecular weight of the polyamide used is preferably 8,000 or more, and the melting point thereof is preferably in the range of 170 to 240 ° C. in consideration of the temperature of kneading when preparing a masterbatch. The blending amount of this polyamide can be appropriately adjusted by, for example, further kneading a diene rubber with a reinforcing rubber of a polyamide as a masterbatch and an olefin resin described later. Further, in the rubber composition of the present invention, the polyamide is contained in the form of short fibers, and from the viewpoint of physical properties and processed surface, it is necessary to consider the amount of polyamide as short fibers, and the amount thereof is the above diene type. It is 3 to 70 parts by weight, preferably 5 to 50 parts by weight, and more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of the polyamide compounded is less than 3 parts by weight, the effect of the present invention cannot be exhibited, and if it exceeds 70 parts by weight, the workability is markedly reduced and the workability becomes difficult, which is not preferable.

In the present invention, the polyamide in the rubber composition used for the gum chafer may be in any bonding state with the rubber molecule, but is preferably chemically bonded such as graft bonding. This polyamide has a circular cross section or a shape similar thereto, and has an average diameter D of 0.1 to 1.0 μm, preferably 0.1 to 1.0 μm.
0.8 μm, more preferably 90% by weight thereof
The above is 1.0 μm or less, and the average fiber length L is 10
μm or more, and 90% by weight or more is 1000 μm
The following are preferred. If the average diameter D exceeds 1.0 μm, the stress concentration at the fiber ends causes the fatigue durability to decrease. Further, the larger the ratio (L / D) of the average length L and the average diameter D of the polyamide, the easier the orientation and the effect of increasing the anisotropy. Therefore, it can be said that the ideal characteristics of polyamide are that the diameter is small and the L / D is large. Therefore, L / D needs to be 8 or more, and preferably 50 to 5000. L /
When D is less than 8, anisotropy cannot be increased, which is not preferable. Since the polyamide used in the present invention is melt-stretched in rubber, it is an extremely microfiber, and can significantly improve fatigue durability.

Examples of the olefin resin used in the present invention include low density polyethylene (L-PE), high density polyethylene (H-PE), polypropylene (P).
P) and the like. The melting point of olefin resin is 13
It is 0 to 200 ° C, preferably 150 to 170 ° C. If the melting point is less than 130 ° C, the exothermic property, which is a physical property of rubber after vulcanization, cannot be lowered, and the melting point is 200 ° C.
If it exceeds, the workability will deteriorate and it will not dissolve when kneading rubber,
Not preferable.

The blending amount of the olefin resin can be appropriately adjusted by further kneading the olefin resin as the masterbatch and the reinforcing rubber of the above polyamide with the diene rubber, and 100 parts by weight of the diene rubber component. The amount is 3 to 70 parts by weight, preferably 5 to 50 parts by weight, and more preferably 5 to 30 parts by weight. If the amount of the olefin resin blended is less than 3 parts by weight, the effect of the present invention cannot be exhibited, and if it exceeds 70 parts by weight, the workability is markedly reduced and the workability becomes difficult, which is not preferable. Further, the compounding ratio of the polyamide and the olefin resin is 3/7 to 7/3, and preferably 4/6 to 6
/ 4 and the compounding ratio is less than 3/7, the anisotropy and fatigue property are deteriorated, which is not preferable, and the compounding ratio is 7 /
Exceeding 3 is not preferable because the heat buildup becomes high.

The rubber composition used in the gum chafer of the present invention is an unsaturated fatty acid having two or more carbon-carbon double bonds in the molecule, and the unsaturated fatty acid is a conjugated diester in the molecule. Conjugated diene-based acid having one or more sets of heavy bonds
You may add the thing comprised by weight% or more. here,
The “conjugated diene-based acid” means at least one set of two carbon-carbon double bonds having a conjugated relationship in the molecule (for example, —C).
H = CH-CH = CH-) containing unsaturated monocarboxylic acid. The unsaturated fatty acid containing two or more carbon-carbon double bonds in the molecule containing 10% by weight or more of the conjugated diene-based acid (hereinafter, simply referred to as "organic unsaturated fatty acid") naturally contains the conjugated diene-based acid. However, other organic unsaturated fatty acids include two or more carbon-carbon double bonds, but they are in a non-conjugated relationship with each other. The unsaturated fatty acid is preferably within the range of a fatty acid having a carbon number of 10 to 22 which is a conventionally used vulcanization accelerator, including conjugated diene acids.

The content of the conjugated diene-based acid in the unsaturated fatty acid must be 10% by weight or more, preferably 25% by weight or more, and 100% by weight, that is, the unsaturated fatty acids are all conjugated diene-based acids. May be. If the content of the conjugated diene-based acid is less than 10% by weight, the effect of addition cannot be obtained. Examples of the conjugated dienoic acid include 2,4-pentadienoic acid, 2,4-hexadienoic acid, 2,4-decadienoic acid,
2,4-dodecadienoic acid, 9,11-octadecadienoic acid, eriostearic acid, 9,11,13,15-octadecatetraenoic acid, 9,11,13-octadecatrienoic acid and the like are mentioned. Are used alone, in a mixture, or in a form contained in the unsaturated fatty acid.

Preferred examples of the organic unsaturated fatty acid include dehydrated castor oil fatty acid. This dehydrated castor oil fatty acid is obtained by dehydrating castor oil. The content of the conjugated dienoic acid can be changed depending on the dehydration method, and for example, 35% by weight and 50% by weight can be obtained. In the case of this dehydrated castor oil fatty acid, as the conjugated diene acid,
The main component is 9,11-octadecadienoic acid, and other organic unsaturated fatty acids mainly include non-conjugated octadecadienoic acid. Examples of the non-conjugated unsaturated fatty acid also include linoleic acid and linoleic acid. The amount of the organic unsaturated fatty acid compounded is 1 to 10 parts by weight, preferably 3 to 6 parts by weight, based on 100 parts by weight of the rubber component. The organic unsaturated fatty acid is 1 to 100 parts by weight of the rubber component.
By blending 10 parts by weight, workability and anisotropy can be significantly improved. Even when the amount of the organic unsaturated fatty acid compounded exceeds 10 parts by weight or less than 1 part by weight, a sufficient elastic modulus of the rubber, which is an effect of addition, cannot be obtained, and moreover,
If the amount is less than 1 part by weight, the breaking strength improving effect cannot be obtained. Furthermore, in the rubber composition of the present invention, it is more preferable to use, in addition to the above-mentioned organic unsaturated fatty acid, a conventionally used fatty acid represented by stearic acid.

Next, an example of the method for producing the rubber composition according to the present invention will be described. The materials and their amounts used here are as described above. First, a diene rubber and an amine anti-aging agent are kneaded for about 1 to 3 minutes, and then a polyamide and an olefin resin are added and kneaded to raise the temperature to a temperature equal to or higher than the melting points of the polyamide and the olefin resin and melt them. . Then, if necessary, a coupling agent such as a phenol resin oligomer is added and further kneaded to obtain a masterbatch. Then, this masterbatch is extruded by an extruder and stretched to obtain a rubber composition reinforced with a polyamide fiber / olefin resin.

Further, to the obtained masterbatch (the diene rubber is reinforced by polyamide and olefin resin by graft bonding), the diene rubber is added to adjust the amount of the polyamide and olefin resin in the blend to a desired amount. Rubber is appropriately added to the above-mentioned organic unsaturated fatty acids, as well as carbon black usually used in the rubber industry, sulfur, vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, antioxidants, other than carbon black, for example. A rubber composition for a gum chafer can be obtained by appropriately adding a filler such as silica, process oil and the like and kneading the mixture with a Banbury mixer, a kneader or the like. This kneading is carried out for 30 seconds to 10 minutes in a kneading stage containing no vulcanization accelerator or vulcanizing agent so that the final kneading temperature is 3 ° C. or more higher than the melting point of the olefin resin. The final kneading temperature after the above kneading is set to a temperature higher than the melting point of the olefin resin by 3 ° C. or more in order to completely melt the olefin resin and promote good dispersion of the olefin resin and fusion with the polyamide. Is. The vulcanization temperature is preferably set higher than the melting point of the olefin resin by 3 ° C. or more. This is because if the temperature is raised to 3 ° C. or higher, the olefin resin is easily dispersed and fused to the polyamide.

In the rubber composition used in the present invention, a diene rubber and fibers made of a thermoplastic elastomer having an amide group are chemically bonded, and the polyamide is fused with an olefin resin. It is embedded in rubber and has a breaking resistance characteristic of the polyamide fiber,
Improvement of fatigue resistance and improvement of anisotropy, which is a characteristic of olefin resin, are compounded into a rubber. Therefore, when this rubber composition is used as a gum chafer rubber, a pneumatic tire excellent in handleability, low rolling resistance (fuel economy), and excellent in bead portion without rim displacement is achieved. The Rukoto.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The polyamide fibers [nylon 6 (Ny-6)] used in this example are various types shown in Table 1 below.

[0024]

[Table 1]

Polypropylene (PP) was used as the olefin resin. The melting point was measured by the following method. (Measurement of melting point) Suggested thermal analyzer DS by Seiko Instruments Inc.
Using C200, the temperature rise rate is 10 ° C / min.
The temperature was raised in the temperature range up to 50 ° C., and the melting point temperature was measured from the obtained endothermic peak.

Examples 1 to 4 and Comparative Examples 1 to 9 100 parts by weight of natural rubber and N- (3-methacryloyloxy-2)
-Hydroxypropyl) -N'-phenyl-P-phenylenediamine [trade name "Nocrac G-1", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.] 1.0 part by weight, and then a molecular weight of 3
50 parts by weight of 6-nylon resin having a melting point of 220.degree.
-Nylon was melted, 2 parts by weight of novolak-type phenol formaldehyde initial condensate was added, and 0.2 part by weight of hexamethylenetetramine was further added to obtain a masterbatch. Then, the master batch was stretched by an extruder to obtain a short fiber polyamide / olefin resin reinforced rubber master batch. In addition, this master batch is
By further kneading with a diene rubber in a Banbury mixer, the compounding amounts of polyamide (6-nylon) and olefin resin (polypropylene) can be adjusted appropriately. Further, by changing the average particle diameter of the polyamide powder used, the average diameter (D) and length (L) of the polyamide (6-nylon) in the masterbatch were obtained as shown in Table 3. Moreover, the olefin resin of the melting point shown in Table 3 was used.

Next, the reinforcing rubber masterbatch was blended with the compounding agents shown in Table 3 below in a Banbury mixer to prepare various rubber compositions, which were vulcanized to obtain a dynamic elastic modulus E'and a dynamic loss coefficient. Tan δ and anisotropy were evaluated. The results are shown in Table 3 below.

Next, in order to study the effect on the tire, the tire shown in FIG. 1, that is, a 2-ply steel cord layer as a belt layer and a 1500 d / 2 PE as a carcass layer.
In a test pneumatic tire including one ply of a layer made of T fiber and having the folded back of the carcass ply kept at a low position near the rim flange, as a rubber composition of gum chafer, Examples 1 to 3 shown in Table 3 were used. 4, using the compounded rubbers of Comparative Examples 1 to 9 and combining the bead filler rubbers shown in Table 2 below to produce tires of size 205 / 60R15, RRC index (rolling resistance), maneuverability (linearity) dry. The rim displacement wear amount was evaluated. The results are shown in Table 3.

[0029]

[Table 2]

Various evaluation methods are as follows. (1) Dynamic elastic modulus E ′, dynamic loss coefficient tan δ Using a viscoelastic spectrometer (VES / F type) manufactured by Iwamoto Seisakusho, sample piece thickness 2 mm, width 4.7 mm, length 2
It was measured at room temperature under the conditions of 0 mm, dynamic strain of 2% statically stretched by 5% and frequency of 50 Hz. The fiber orientation direction is indicated as p, and the direction perpendicular to the fiber orientation direction is indicated as v.

(2) Rolling resistance index (RRC index) Internal pressure of 2.0 kg / cm ³ on a drum having an outer diameter of 1708 mm.
A test tire that is fully covered is placed and the load is 300 kg.
After f was loaded, it was preliminarily run at a speed of 80 km / h for 30 minutes, the air pressure was readjusted, the drum rotation speed was increased to a speed of 200 km / h, and then the drum was coasted.
It was calculated from the moment of inertia until the drum rotation speed decreased from 185 km / h to 20 km / h. (Rolling resistance of the tire) = [- ds / dt (Id / Rd 2 + It / Rt 2 - ( resistance of drum itself)] In the formula, Id drum inertia moment, It is the moment of inertia of the tire, Rd drum Radius and Rt are tire radii.The rolling resistance value at 50 km / h obtained by the above formula was calculated as a representative value, and the measurement was performed in a room controlled at 24 ± 2 ° C. The value of the following formula is rounded off to the nearest whole number.

(Rolling resistance index) = [(representative value of test tire) / (representative value of control tire)] × 100 As a result, the smaller the rolling resistance index, the better the fuel economy. Comparative Example 2 was used as a control tire. The load when measuring the rolling resistance index is 300 kg
f, and the method for measuring the rolling resistance index is the uniaxial coasting method.

(3) Maneuverability (Linearity) Dry In an actual vehicle test, the driver's steering feeling on the dry asphalt road surface (the better the reaction of the vehicle was, the better) was made to be linearity, and the feeling was evaluated.

(4) Amount of rim displacement wear Tire internal pressure on the drum is 1.0 kg / cm ² , load is 450
Rim displacement depth (rim displacement wear amount) on the rubber chafer surface after traveling 10,000 kg at a speed of 60 km / h and kgf
Was measured and displayed as an index.

[0035]

[Table 3]

[Discussion of Table 3] As is clear from the results of Table 3, Examples 1 to 4, which are within the scope of the present invention, are different from Comparative Examples 1 to 9 which are outside the scope of the present invention. The composition has high anisotropy and low loss, and a pneumatic tire using this rubber composition as a gum chafer has good maneuverability,
It was found that it has excellent low rolling resistance (fuel efficiency) and is excellent in all without rim displacement. On the other hand, Comparative Example 1
4 to 4 are respectively compared with Examples 1 to 4, Comparative Examples 1 to 3 are cases where only an olefin resin is not blended, and Comparative Example 4 is a case where only polyamide is not blended. In these cases, It was found that the anisotropy was low, and the maneuverability, low rolling resistance (fuel efficiency), and rim displacement were not all satisfied. Comparative Example 5 is to be compared with Example 2, and since the amount of the olefin resin is large and the compounding ratio is out of the range (1/3), the anisotropy is lowered, and the maneuverability and the rim displacement are also deteriorated. It turned out to be. Comparative Example 6
In contrast with Example 3, since there are many polyamides and the compounding ratio is out of the range (3/1), the anisotropy is lowered and the low rolling resistance (fuel economy) is deteriorated. It has been found. Comparative Example 7 is to be compared with Example 2, and it was found that the average diameter (D) of the polyamide was out of the range, so that the rim displacement was deteriorated. Comparative Example 8 is to be compared with Example 2, and it was found that the L / D of the polyamide was out of the range, so that the anisotropy was small and the maneuverability was also deteriorated. Comparative Example 9 is a case in which the polyamide and the olefin resin are not blended at all, and it was found that the maneuverability and the low rolling resistance (fuel economy) are deteriorated.

[0037]

EFFECTS OF THE INVENTION According to the present invention, by using a rubber composition suitable for a gum chafer, the maneuverability and low rolling resistance (fuel consumption) are excellent, and the bead portion is durable without rim displacement. A pneumatic tire having excellent properties is provided.

Claims (2)

[Claims] 1. A carcass ply which is composed of a bead wire located at a bead portion and a rubberized cord layer in which a large number of cords are arranged in parallel, both ends are folded back at the bead portion and locked to the bead wire, and a radial direction of the bead wire. In a pneumatic tire having a bead filler and a gum chafer disposed in the rubber composition, at least one rubber component 1 selected from the group consisting of natural rubber and diene-based synthetic rubber.
3 to 70 parts by weight of a fiber made of a thermoplastic elastomer having an amide group and 3 to 70 parts by weight of an olefin resin with respect to 00 parts by weight, and a fiber made of the thermoplastic elastomer having an amide group and an olefin resin. A pneumatic tire using a rubber composition having a compounding ratio of 3/7 to 7/3 for a gum chafer. 2. The fibers made of a thermoplastic elastomer of the rubber composition used for the gum chafer have an average diameter D of 0.1 to 1.0 μm, and a ratio of the average length L to the average diameter D (L / D) is 8 or more, The pneumatic tire according to claim 1.