JPH0948210A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air permeation resistance, cornering performance, and durability, by compounding together a specific polyamide short fiber containing composition, isoprene-isobutylene rubber and/or its halide, and diene type rubber, so as to constitute an air permeation preventing layer. SOLUTION: Polyamide short fiber to be used is thermoplastic polymer having fine fibrous-C(=O)-NH group in molecule, the mean diameter is under 1m, the mean length is 100-2000m, and the fiber is oriented in the axial direction during molding a tire. The mixed quantity of polyamide short fiber is set 0.5-8 weight part against the whole rubber content 100 weight part, and the mixed quantity of polyolefine is set 0.5-8 weight part against the whole rubber content 100 weight part. The polyamide short fiber contained composition is constituted by dispering polyamide short fiber and natural rubber and/or polyisoprene rubber into the continuous phase of polyolefine, and chemically binding them together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more specifically to a pneumatic tire having a rubber composition containing a specific polyamide short fiber in an air permeation preventive layer to improve air permeation resistance, cornering performance and durability. An excellent pneumatic radial tire.

[0002]

2. Description of the Related Art The inner surface of a pneumatic radial tire is provided with an air permeation preventive layer such as an inner liner layer made of a rubber having a low gas permeability such as butyl rubber and halogenated butyl rubber in order to keep the tire air pressure constant. It is well known that it is provided. By the way, recently, the average short fiber diameter of the inner liner layer of a tire mainly composed of butyl rubber or halogenated butyl rubber is 0.02 to 0.
It has been proposed to blend organic short fibers having an average short fiber length of 0.5 to 30 μm with a diameter of 8 μm to reduce the air permeability of a pneumatic tire and to improve fatigue resistance and fuel economy (( (See JP-A-57-151402). However, the effect is not yet sufficient with such a method, and the breaking strength and cracking resistance (fatigue resistance) of the matrix are significantly reduced, probably because the organic short fibers enter as foreign matter in the rubber matrix, resulting in tire durability. There is a problem that

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide an air permeation preventive layer having excellent air permeation resistance, cornering performance and durability. It is to provide a pneumatic radial tire having the same.

[0004]

According to the present invention, (A)
Average diameter less than 1 μm, average fiber length 100-2000 μm
(B) Isoprene-isobutylene rubber, wherein the polyamide-based short fiber and the natural rubber and / or polyisoprene rubber are dispersed in a continuous phase of polyolefin, and these are chemically bonded to each other. And / or a halide thereof and (C) a diene rubber, and (i) the amount of the polyamide short fibers is 0.
5 to 8 parts by weight, and (ii) a pneumatic radial tire having an air permeation preventive layer formed of a thin film of a rubber composition in which the amount of the polyolefin is 0.5 to 8 parts by weight based on 100 parts by weight of all rubber components. Will be provided.

[0005]

According to the present invention, as described above, by using the short fiber-containing composition in which the specific short fiber is blended in the natural rubber and / or the polyisoprene rubber in the specific amount, the rubber matrix, the polyamide system is used. The short fibers and the polyolefin phase are made uniform to prevent reduction in breaking strength and cracking resistance and improve tire durability. Further, since these components are strongly chemically bonded to each other and the gas barrier property of the polyolefin phase is high, the air permeation resistance of the air permeation preventive layer is further improved. Furthermore, since the entire layer has a uniform phase, the rigidity is dramatically increased,
This leads to an increase in tire rigidity. In particular, the rigidity in the tire circumferential direction is greatly increased and the steering stability is improved. The center of rigidity of the tire is the carcass line, and it is generally the outer surface of the carcass layer to arrange something like a chafer to improve the rigidity, and it is arranged only on the outer surface of the carcass layer, which is the center of rigidity. Is less effective. However, arranging something like a chafer on the inner surface of the carcass layer has the drawback of increasing the weight of the tire, which is not common. However, by arranging the air permeation preventive layer on the inner surface of the carcass layer according to the present invention, both the effect of preventing air permeation and the effect of increasing rigidity can be obtained.

The polyamide-based short fibers used in the present invention are thermoplastic polymers having a fine fibrous —C (═O) —NH— group in the molecule and have an average diameter of less than 1 μm.
The average length is preferably 0.05 to 0.8 μm and 100 to 2
000 μm, preferably 200 to 1000 μm,
It is desirable to orient along the fiber axis during tire building.
If the average diameter of the polyamide-based short fibers is 1 μm or more, stress concentration becomes large when strain is applied, and durability is deteriorated, which is not preferable. Similarly, when the fiber length of the polyamide-based short fibers is long, the stress concentration becomes large when strain is applied, and sufficient durability cannot be obtained. Conversely, if it is too short, the effect of improving tire rigidity is low, which is not preferable. .

If the amount of the polyamide short fibers is less than 0.5 parts by weight based on 100 parts by weight of the total rubber component, the desired effect cannot be obtained sufficiently, and if it exceeds 8 parts by weight, rolling during processing, Alternatively, it is not preferable because the extrusion speed cannot be increased and the productivity is reduced.

Examples of the polyolefin used in the present invention include polyethylene, polypropylene, polyethylethylene, polydimethylethylene and polystyrene. If this blending amount is less than 0.5 parts by weight with respect to 100 parts by weight of all rubber components, the adhesion between the short fibers and the rubber is not sufficient, which is not preferable. On the contrary, if it exceeds 8 parts by weight,
It is not preferable because the speed of rolling or extrusion cannot be increased and productivity is reduced. The molecular weight of these polyolefins is not particularly limited, but especially polypropylene,
Preference is given to using polyethylene, polyethylethylene, polystyrene, polydimethylethylene.

As the natural rubber and / or polyisoprene rubber used for blending the polyamide short fiber-containing composition in the present invention, any natural rubber and / or polyisoprene rubber conventionally blended in tires can be used. .

Examples of the polyamide short fibers used in the present invention 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, -C (= in polymer molecules such as polyurea such as polyundecamethylene urea and polyurethane
O) —NH— group-containing thermoplastic polymers, preferably nylon, and having an average diameter of less than 1 μm, preferably of substantially circular cross section and having an average fiber length of 100 to 200.
It is preferably 0 μm, preferably 200 to 1000 μm, and is incorporated in the rubber composition in the form of fine short fibers in which molecules are arranged in the fiber axis direction.

Such polyamide short fibers are dispersed in polyolefin together with natural rubber and / or polyisoprene rubber in advance, and the polyamide short fibers and the rubber are chemically bonded to each other in the natural rubber and / or Compounded with polyisoprene rubber and diene rubbers other than these. Moreover, the polyamide-based short fibers are graft-bonded in the rubber mixture via, for example, an initial condensation product of a phenol-formaldehyde-based resin or a silane coupling agent. Examples of the initial condensate of the phenol formaldehyde resin include a resol type or novolak type phenol formaldehyde resin initial condensate, and a compound capable of generating formaldehyde upon heating according to a conventional method (eg, hexamethylenetetramine, acetaldehyde ammonia). : [CH ₃ -CH
(OH) -NH ₂ ] ₃ , paraformaldehyde, α-polyoxymethylene, polyvalent methylol melamine derivative, oxazolidine derivative, polyvalent methylol acetylene urea, etc.) can be used for grafting to obtain a desired composition. it can.

By blending the polyamide type 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. It is possible to obtain a pneumatic radial tire having an air permeation preventive layer having excellent cornering power and durability as well as excellent air permeation resistance.

The rubber composition according to the present invention contains the above-mentioned components in a conventional manner, for example, by adding the above-mentioned components to a Banbury mixer,
It can be obtained by kneading using a kneading machine such as a roll.

The isoprene-isobutylene rubber (so-called butyl rubber IIR) and its halide compounded as the component (B) in the rubber composition used in the present invention are any of those generally used in the inner liner layer of pneumatic tires. Can be used.

As the diene rubber compounded as the component (C) in the rubber composition used in the present invention, any diene rubber compound conventionally compounded for tires can be used. Is natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (B
R), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR),
Examples thereof include chloroprene rubber (CR), butyl rubber (IIR) and ethylene / propylene terpolymer rubber (EPDM). Particularly preferred are NR, IR,
It is SBR.

The above component (A) of the composition according to the present invention,
The mixing ratio of the component (B) is not particularly limited, but the weight ratio is preferably (A) :( B) = 1: 2 to 2: 1.

In addition to the above-mentioned essential components, the rubber composition according to the present invention contains a reinforcing agent such as carbon black, sulfur,
Various additives commonly used for tires, such as vulcanization accelerators, antioxidants, fillers, softeners, and plasticizers, can be added, and such compounds can be vulcanized by a general method. It can be manufactured. The amount of these additives may be a general amount.

FIG. 1 is a half sectional view in the meridian direction illustrating a typical example of the arrangement of the air permeation preventive layer of a pneumatic tire. In FIG. 1, a carcass layer 2 is mounted between a pair of left and right bead cores 1, 1, and an inner liner layer 3 is provided on the inner surface of the tire inside the carcass layer 2. The inner liner layer 3 is composed of the polymer composition for a tire in the present invention. In FIG. 1, reference numeral 4 denotes a sidewall.

Regarding an example of a method for producing a pneumatic tire having an air permeation preventive layer comprising a thin film of the polymer composition according to the present invention, as shown in FIG. 1, when the inner liner layer 3 is arranged inside the carcass layer 2. For example,
The polymer composition of the present invention is extruded in advance into a thin film having a predetermined width and thickness, which can be adhered to a cylinder on a tire molding drum. Members such as a carcass layer made of unvulcanized rubber, a belt layer, and a tread layer, which are used in ordinary tire manufacturing, are successively laminated on top of this, and the drum is removed to obtain a green tire. Next, by heating and vulcanizing the green tire according to a conventional method, a desired lightweight pneumatic tire can be manufactured. In addition, also when providing an air permeation prevention layer on the outer peripheral surface of a carcass layer, it can be performed according to this.

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

[0021]

[Examples] Standard Example 1, Examples 1 to 3 and Comparative Examples 1 to 3 Raw rubbers and compounding agents excluding a vulcanization accelerator and sulfur by mixing the respective components in the compounding contents (parts by weight) shown in Table I 16
After mixing with a liter Banbury mixer for 5 minutes, a vulcanization accelerator and sulfur were kneaded into pellets by a twin-screw kneader, and then the mixture was extruded with a width of 1000 mm and a thickness of 1.5 mm.
Was obtained. Steel radial tires (rim 13 × 4 1/2 B) of size 165SR13 were prepared using these films as an inner liner layer, various tests were conducted, and the physical properties thereof were measured. The results obtained are shown in Table I.

[0022]

[Table 1]

The test methods used in the evaluation tests of Table I are as follows. Air permeation resistance 165SR13 Steel radial tire (rim 13
The pressure was measured at an interval of 4 days with an initial pressure of 200 kPa and no load at room temperature of 21 ° C. for 3 months. As the measured pressure Pt, the initial pressure Po, and the number of elapsed days t, an α value is obtained by regressing on the function: Pt / Po = exp (−αt). Using the obtained α, t = 30
Is substituted into the following equation to obtain β = [1-exp (−αt)] × 100 β value. This β value is calculated as the pressure drop rate per month (% /
Month) and indexed with the value of Standard Example 1 as 100.
The smaller this value is, the better the air permeation resistance is.

Cornering Power Each test tire was mounted on the rim (13 × 4 1/2 B),
The internal pressure was set to 186.3 kPa, and the evaluation was performed by an indoor flat belt type tester under the conditions of a speed of 10 km / h and a load of 425 kg. The larger this value is, the larger the cornering power is.

Durability Each test tire was filled with the same internal pressure on the same rim as described above, and the drum diameter was 1707 mm, and JIS D 4230 and JATMA were used.
After completion of the specified load durability test, the load was increased by 20% every 5 hours and the test was continued until the tire broke. The value of Standard Example 1 was set to 100 and displayed as an index. The larger this value is, the higher the durability is.

The standard example 1 is an inner liner layer composed of a conventional typical brominated butyl rubber (80) / natural rubber (20), and the comparative example 1 is a partial replacement of the natural rubber with short cellulose fibers. This is the case, but with this composition, the air permeation resistance is slightly improved, but the durability is poor. Comparative Example 2 is a case where a part of the natural rubber was replaced with polyamide-based short fibers in the formulation of Standard Example 1, but the improvement effect was not recognized because the blending amount was insufficient. In Comparative Example 3, on the contrary, when the amount of the short fibers is too large, the air permeation resistance and the cornering power are increased, but the durability is poor. In contrast,
In Examples 1 to 3 according to the present invention, the air permeation resistance and the cornering power are improved, and the durability retains the value of the standard example.

[0027]

As described above, according to the present invention,
Average diameter less than 1 μm, average fiber length 100-2000 μm
Polyamide short fibers and natural rubber and / or polyisoprene rubber are dispersed in a continuous phase of polyolefin, and a polyamide short fiber-containing composition in which these are chemically bonded to each other is used for air permeation of a pneumatic radial tire. By compounding in the prevention layer, a pneumatic radial tire having excellent air permeation resistance, cornering power and durability can be obtained.

[Brief description of drawings]

FIG. 1 is a half sectional view in the meridian direction showing a structure of an inner liner portion of a pneumatic tire of the present invention.

[Explanation of symbols]

 1 ... Bead core 2 ... Carcass layer 3 ... Inner liner layer 4 ... Sidewall

Claims (1)

[Claims] 1. (A) Polyamide-based short fibers having an average diameter of less than 1 μm and an average fiber length of 100 to 2000 μm and natural rubber and / or polyisoprene rubber are dispersed in a continuous phase of polyolefin, and these are chemically bonded to each other. A composition containing a bound polyamide short fiber, (B) isoprene-isobutylene rubber and / or a halide thereof, and (C) a diene rubber, and (i) the total amount of the short polyamide fiber is 0.1 parts by weight per 100 parts by weight of the rubber component.
5 to 8 parts by weight, and (ii) a pneumatic radial tire having an air permeation preventive layer formed of a thin film of a rubber composition in which the amount of the polyolefin is 0.5 to 8 parts by weight based on 100 parts by weight of all rubber components. .