JPH0924705A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of a pneumatic tire by eliminating a problem, separation the pneumatic tire caused at a belt end part. SOLUTION: Compounded are: (A) a compsn. formed by dispersing a polyamide-based short fiber having an average diameter of less than 1μm and an average fiber length of 100-2000μm, and natural rubber or polyisoprene rubber into a polyolefin continuous phase, and in which they are chemically bonded to each other; with (B) diene-based rudder using natural rubber and/or polyisoprene rubber as its main component. In a pneumatic radial tire, a tire belt edge cushion, a belt edge tape and/or an edge cover sheet uses a rubber compsn. satisfying the conditions that: (i) an amt. of the polyamide-bassed short fiber is 0.5-2.0 parts by weight; and (ii) the amt. of the polyolefin is 0.5-20 parts by weight per 100 parts by weight of the entire rubber component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, more specifically, a continuous phase polyolefin having an average diameter of less than 1 μm and an average length of 100 to 20.
A rubber formed by dispersing 0.5 to 20 parts by weight of a polyamide-based short fiber-containing composition in which 100 μm of polyamide-based short fibers and a diene rubber are dispersed and which are chemically bonded to each other is used as a belt edge portion. The present invention relates to a pneumatic radial tire with improved durability used for a rubber sheet.

[0002]

2. Description of the Related Art The belt layer of a conventional pneumatic radial tire has a structure as shown in FIG. 1, and the end portion of the belt layer has a discontinuity in rigidity between the belt layer and the rubber on the extension thereof. Occurs, and stress concentration is likely to occur there, resulting in the problem of separation of the belt end portion. Therefore, the same kind of rubber as the coat rubber of the belt layer is arranged in a tape shape on the edge portion of the belt layer of the radial tire (belt edge cushion 2), or the same kind of rubber as the coat rubber is arranged so as to wrap around the end portion of the belt layer. It is well known that the durability of the belt edge portion is improved by (belt edge tape 3). It is necessary for the coat rubber to have a high hardness in order to improve the durability of the belt portion, and for the adhesion between the coat rubber and the cord, it is better to use a resorcin resin, a melanin derivative, and silica together with a cobalt salt as an adhesion promoter. Has been.
However, in the above formulation, the breaking property of the coated rubber itself is deteriorated due to the thermosetting reaction, and when used as a belt edge cushion, there is a problem that the separation resistance of the belt edge portion is deteriorated. In FIG. 1, 4 is an edge cover sheet, 5 is a belt (in FIG. 1, steel belts 1 to 4 are used), and 6 is a carcass.

As a proposal for improving the durability of the end portion of the belt layer, a short fiber having an average diameter of 1 μm or less and a ratio (L / D) of the average length L and the average diameter D of 8 or more is provided at the end portion of the belt layer. (See JP-A-61-119406 and JP-A-61-119408) and use of short fibers of natural rubber grafted with nylon through an alkylphenol formaldehyde resin (JP-A-62-24).
4702). However, these proposals have a problem that desired durability cannot be obtained.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the problem of separation of a pneumatic tire due to the above belt end portion and to provide a pneumatic tire having excellent durability. .

[0005]

According to the present invention, (A)
An average fiber length of less than 1 μm and an average fiber length of 100 to 2000 μm
(B) Natural rubber and / or polyisoprene, and a polyamide short fiber-containing composition obtained by dispersing the above polyamide-based short fibers and natural rubber or polyisoprene rubber in a continuous phase of polyolefin, and chemically bonding them to each other. A diene rubber containing rubber as a main component is blended, and (i) the amount of the polyamide short fibers is 100% of the total rubber component.
0.5 to 20 parts by weight relative to parts by weight (ii) The amount of the polyolefin is 0.5 to 100 parts by weight of all rubber components.
A pneumatic radial tire using a rubber composition satisfying conditions (i) and (ii) of 20 parts by weight to at least one of a belt edge cushion, a belt edge tape and an edge cover sheet of the tire is provided.

[0006]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a specific polyamide short fiber is dispersed in a polyolefin together with a rubber, and a specific rubber composition chemically bonded is arranged at a belt edge portion of a radial tire. It is possible to reduce the separation generated at the belt edge portion, obtain a radial tire having excellent durability, improve workability and extrusion processability, and enhance high-speed durability and belt rigidity.

The rubber, which is the main component of the rubber composition used in the present invention, contains natural rubber (NR); polyisoprene rubber (IR) as a main component, and if necessary, styrene-butadiene copolymer rubber ( SBR) and polybutadiene (BR) are blended with a diene rubber, and these rubber components include, for example, any NR and / or IR (and SBR, which have been conventionally used for compounding a tire rubber.
BR). The diene rubber blend preferably contains NR and / or IR in the range of 80 to 100% of the total rubber.

The polyamide short fibers to be blended in the rubber composition used in the present invention have the average diameter and average length as described above, and the blending amount thereof is diene rubber 1.
It is 0.5 to 20 parts by weight per 00 parts by weight. If the blending amount of the polyamide-based short fibers is less than 0.5 parts by weight, the desired blending amount cannot be obtained because the blending amount is too small, and if it exceeds 20 parts by weight, the fatigue resistance tends to deteriorate, which is not preferable. The preferred blending amount of polyamide short fibers is 1 to 15 parts by weight, more preferably 3 to 10 parts by weight, per 100 parts by weight of rubber.

The polyamide type short fibers to be blended in the rubber composition used in the present invention are fine fine fibers of a thermoplastic polymer having a —C (═O) —NH— group in the molecule (hereinafter referred to as polyamide type fibers). Is preferred. Examples of such polyamide short fibers include nylons such as nylon 6, nylon 610, nylon 12, nylon 611, nylon 612 and the like having a melting point of about 190 to 235 ° C., polyheptamethylene urea, polyundecamethylene urea, and the like. -C (= in polymer molecules such as urea and polyurethane
O) -NH-group-containing thermoplastic polymer, preferably nylon, and having an average diameter of preferably 1 μm or less,
More preferably, it is 0.05 to 0.8 μm, has a substantially circular cross section, an average fiber length of 2000 μm or less, more preferably 200 to 1000 μm, and a form of fine short fibers in which molecules are arranged in the fiber axis direction. Preferably in the rubber composition. Such polyamide short fibers are preferably 0.5 to 20 parts by weight of polyolefin (for example, polypropylene, polyethylene, polyethylethylene, polydimethylethylene, polystyrene, etc.) per 100 parts by weight of the total rubber component, in advance of the polyamide short fibers. Disperse and mix with diene rubber. In the rubber composition, the polyamide-based short fibers are further grafted and chemically bonded to the rubber through, for example, an initial condensation product of a phenol-formaldehyde-based resin or a silane coupling agent.

Examples of the above-mentioned initial condensation product of the phenol-formaldehyde resin include a resol-type or novolac-type phenol-formaldehyde-based resin initial condensation product, and a compound capable of generating formaldehyde upon heating according to a conventional method (eg, hexamethylene). Tetramine, acetaldehyde ammonia)

[0011]

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The desired composition can be obtained by graft-bonding with parapormaldehyde, α-polyoxymethylene, polyvalent methylol melamine derivative, oxazolidine derivative, polyvalent methylol acetylene urea, etc.). By blending the polyamide-based short fibers in the rubber composition as described above, the short fibers (and the polymer) are well dispersed in the rubber, and are chemically bonded to the rubber, and thus are extremely high. A rubber composition having rigidity and good fatigue resistance can be obtained.

In the rubber composition used in the present invention, in addition to the above-mentioned respective components, various additives such as sulfur, a vulcanization accelerator, an antioxidant, a filler and a plasticizer which are generally blended for tires. Can be compounded, and such a compound can be vulcanized by a general method and then BEC, BET or E of the belt edge portion.
The pneumatic tire can be used for CS. When an organic acid cobalt salt (for example, 0.5 to 5.0 parts by weight based on 100 parts by weight of rubber) is used, the adhesiveness between the belt portion and the steel cord is improved, and the fatigue property of the rubber composition is improved. Therefore, it is preferable.

It is preferable that a part or all of the diene rubber used in the rubber composition used in the present invention (40 to 100% by weight of the total rubber component) is dispersed in the polyolefin continuous phase. In addition, this rubber composition usually uses the same compound as the belt coat compound in many cases, and the present invention can also comply with this.

[0015]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

The ingredients used in the following examples and comparative examples are as follows. NR: RSS # 1 Carbon black: HAF Anti-aging agent: Antigen 6C (Sumitomo Chemical Co., Ltd.) Vulcanization accelerator: N, N'-dicyclohexylbenzothiazolesulfenamide Short fiber 1: Cellulose short fiber (average diameter 12 μm average length 1500 μm ) SBR masterbatch (fiber: SB
R = 2: 1) Short fibers 2: Nylon 6 short fibers (average diameter 0.5 μm average length 200 μm) and NR are dispersed in a continuous phase of polypropylene and are master-batch (composition: 6 nylon). : Polypropylene: NR = 1: 1: 1
1) Cobalt naphthenate: containing 10% by weight of cobalt element Metactezol resin: Sumicanol 610 (manufactured by Sumitomo Chemical) Hexamethoxymethyl melamine: Active ingredient of Cyletz 964 (manufactured by American Sunanamid)

Examples 1 and 2 and Comparative Examples 1 to 4 The components other than sulfur and the vulcanization accelerator having the compositions shown in Table I were mixed for 5 minutes in a closed Banbury mixer, and the mixture was discharged at 160 ° C. This rubber was mixed with sulfur and a vulcanization accelerator with an open roll to obtain compositions 1 to 3. A belt edge cushion (BEC) 2, a belt edge tape (BET) 3 and an edge cover sheet (ECS) 4 of a tire having a structure as shown in FIG. The tire was prepared according to the method and an evaluation test of the separation resistance of the obtained tire was performed. The composition 1 is a conventional standard rubber composition, the composition 2 is a short fiber material outside the scope of the present invention, and the composition 3 is a short fibrous material according to the present invention. The results are shown in Table II.

[0018]

[Table 1]

[0019]

[Table 2]

As is clear from the results of Tables I and II, Comparative Example 2 is an example in which an edge cover sheet is provided on a conventional tire, as compared with Comparative Example 1 which is a conventional typical tire. Improvement of is recognized. Comparative Example 3 is an example in which the composition 2 containing short fibers in the belt edge portion (BEC and BET) of Comparative Example 1 is used, and since the short fiber shape is large, fatigue resistance is poor and durability (separation resistance) is reduced. are doing. In Comparative Example 4, the edge cover sheet (EC
In the example in which S) is arranged, some improvement is recognized as compared with Comparative Example 3, but durability is poor and not practical for the same reason as Comparative Example 3.

On the other hand, Examples 1 and 2 are examples in which the composition 3 according to the present invention was blended, and the durability was clearly improved in all cases.

[0022]

As described above, according to the present invention,
The durability of the pneumatic tire can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a partial view of a pneumatic tire showing a belt edge cushion, a belt edge tape and an edge cover sheet using a specific rubber composition according to the present invention.

[Explanation of symbols]

 1 ... Pneumatic tire 2 ... Belt edge cushion 3 ... Belt edge tape 4 ... Edge cover sheet 5 ... Belt 6 ... Carcass

Claims (1)

[Claims] 1. (A) Polyamide short fibers having an average diameter of less than 1 μm and an average fiber length of 100 to 2000 μm and natural rubber or polyisoprene rubber are dispersed in a continuous phase of polyolefin, and these are chemically bonded to each other. A polyamide short fiber-containing composition and (B) natural rubber and / or
Or a diene rubber containing polyisoprene rubber as a main component, and (i) the amount of the polyamide short fibers is 0.5 to 20 parts by weight based on 100 parts by weight of all rubber components (ii). The amount of the polyolefin is 100% of the total rubber component.
A rubber composition satisfying conditions (i) and (ii) of 0.5 to 20 parts by weight based on parts by weight is used in at least one of a belt edge cushion, a belt edge tape and an edge cover sheet of a tire. Pneumatic radial tire featuring.