JP2788398B2 - tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire having a tread comprising two layers, a base tread and a cap tread, having low rolling resistance, excellent steering stability and ride comfort.

[0002]

2. Description of the Related Art Conventionally, treads have been improved in order to improve both rolling resistance, riding comfort and steering performance of tires. For example, a technique of blending short fibers with tread rubber has been disclosed (Japanese Patent Publication No. 64-506).
0, Japanese Patent Publication No. 64-5608). It is also known that the tread is formed into two layers: a cap tread having excellent wet skid resistance for improving steering performance and a base tread having small energy loss for reducing rolling resistance. / A rubber composition for a base tread having a base structure has been proposed (JP-A-59-204637).

[0003]

However, when the tread according to the prior art as described above is applied, the rolling resistance is sufficiently reduced, but the steering performance is not significantly improved.
In particular, steering response is deteriorated, and steering stability is reduced.

[0004] In addition, since the steering stability and the riding comfort are mutually contradictory characteristics, there is a problem that if the steering stability is improved, the riding comfort is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a base tread capable of reducing the rolling resistance of a tire and improving steering stability while maintaining a good ride quality. In providing tires.

[0006]

An object of the present invention is to provide a tire comprising a cap / base tread having a base tread thickness of 6 mm or less, wherein the base tread has a total of 100 parts of a rubber component. (Parts by weight; the same applies hereinafter)
A tire containing 16 to 30 parts of short fibers and 30 to 60 parts of carbon black having an iodine adsorption amount of 60 to 130 mg / g (hereinafter referred to as "the first invention").
).

Another object of the present invention is a pneumatic radial tire including a tread having a cap / base structure, wherein the base tread comprises (i) 50 to 80 parts of natural rubber and 20 to 50 parts of butadiene rubber. Rubber component,
And (ii) 10 to 3 parts per 100 parts of the rubber component.
Obtained from a rubber composition containing 0 parts of short fibers and 5 to 30 parts of carbon black, wherein the short fibers are oriented at an angle of 90 ° ± 20 ° with respect to the circumferential direction of the tire,
The ratio E ^* _a / E ^* _b of the complex elastic modulus E ^* _{a in} the orientation direction of the base tread to the complex elastic modulus E ^* _{b in the} direction perpendicular to the orientation direction.
Is 3 or more, the thickness of the base tread is 6 mm or less, and the flatness of the tire is 60% or more (hereinafter referred to as “the second invention”).

[0008]

The tire tread of the present invention has a cap / base structure comprising a base tread and a cap tread. In this tire, the base tread has an action of reducing rolling resistance and improving steering stability, and the cap tread has an action of providing desired steering performance, for example, excellent wet skid properties and wear resistance.

The thickness of the base tread used in the tire of the present invention depends on the size of the tire, but usually the thickness of the tread crown portion is 6 mm or less, preferably 1 mm or more in a state where the tire is manufactured. . 1m thick
When it is smaller than m, the effect of the base tread is not seen, and when it is larger than 6 mm, the orientation of the short fibers is deteriorated, and the handle responsiveness, grip feeling, and riding comfort tend to be deteriorated. The preferred thickness is 2-5 mm.

Hereinafter, the first invention of the present case will be described first.

The base tread used in the tire of the first invention has a rubber content of 16 to 3 with respect to a total of 100 parts of the rubber component.
0 parts of a short fiber as a reinforcing material and 30 to 60 parts of carbon black having an iodine adsorption amount of 60 to 130 mg / g are blended, and other general additives are blended.

The short fibers have a number average diameter D of 0.1 to 0.5 μm.
m, number average length L50-500 μm, L / D 100-5
000 fibers. Outside of these ranges, the orientation tends to decrease and the desired effect cannot be obtained. Preferably number average diameter 0.2 to 0.4 μm, number average length 100
４００400 μm, L / D 300〜2000. Examples of the short fibers include short fibers such as aramids such as nylon, polyester, rayon, and Kevlar, and short fibers such as cotton, and short fibers obtained by surface-treating these to improve adhesiveness with a rubber component. Specifically, short fibers such as 6-nylon grafted to natural rubber or the like are preferably used.

The content of short fibers is 16 to 30 parts based on 100 parts of the rubber component in total. If less than 16 parts,
Although the rolling resistance is reduced, the handle response tends to be deteriorated. If it exceeds 30 parts, the rolling resistance tends to increase, and the ride comfort tends to deteriorate. The preferred short fiber content is about 20-30 parts.

Carbon black has an iodine adsorption amount of 60.
130 to 130 mg / g, and 30 to 60 parts per 100 parts in total of the rubber component. The iodine adsorption amount is, for example, J
It is measured by a method based on ISK-6221-1982 "Test method for carbon black for rubber". When the iodine adsorption amount is less than 60 mg / g, although the rolling resistance is improved, the steering stability tends to deteriorate, and the
/ G tends to deteriorate the rolling resistance. The iodine adsorption amount is preferably 65 to 125 mg / g.
Examples of such carbon black include N351 (iodine adsorption amount: 68 mg / g) and N339 in ASTM.
(90 mg / g), N375 (90 mg / g), N34
3 (92 mg / g), N299 (108 mg / g), I
SAF (N220) (121 mg / g), N234 (1
20 mg / g), and ISAF, N351,
N339 and the like are preferable. When N351 is used, the rolling resistance tends to decrease. When ISAF is used, steering stability tends to be improved. When the carbon black content is less than 30 parts, the steering stability tends to deteriorate. If it is more than 60 parts, the rolling resistance tends to increase, and the riding comfort tends to deteriorate. The preferred content of carbon black is 30 to 50 parts.

As the rubber component of the base tread, natural rubber (NR), isoprene rubber (IR), emulsion-polymerized styrene-butadiene rubber (SBR), solution-polymerized SBR, butadiene rubber (BR), etc. are used to form a rubber elastic body by vulcanization. All rubbers given are used, especially NR, SBR, BR
Are preferred. These rubbers are used alone or in combination of two or more. Preferred combinations are, for example, NR / BR (50-80 / 50-20).

Other additives include a vulcanizing agent such as sulfur, a vulcanizing aid such as zinc white and stearic acid, and an accelerating agent CZ.
(N-cyclohexyl-2-benzothiazolesulfenamide), accelerator NS (Nt-butyl-2-benzothiazolesulfenamide) and other vulcanization accelerators, antioxidant 13 (N, N′-phenyl-) antioxidants such as p-phenylenediamine) and anti-aging IPPD (N-isopropyl-N'-phenyl-p-phenylenediamine); process oils such as aromatic oils, naphthenic oils and paraffin oils; and waxes. Is also good. The amounts of these additives are not particularly limited. However, the additives are formulated so as to achieve the object of the first invention of the present invention in that the rolling resistance of the tire is reduced and the steering stability is improved.

It is preferable that the short fibers in the base tread are oriented in a certain direction, since the intended effect can be obtained particularly strongly. In particular, as shown in FIG. 1, 90% or more of the short fibers have an angle in a direction of 90 ° (hereinafter referred to as a “radial direction”) ± 20 ° with respect to the circumferential direction of the tire 5 in a range of ± 20 °. When the short fibers are oriented, the handle responsiveness and the grip at the time of cornering are excellent, and as shown in FIG.
% Or less, the short fibers are oriented in the base tread 1 such that the angle is within the range of ± 20 ° with respect to the circumferential direction of the tire 5, when the rolling resistance, the steering stability and the riding comfort are balanced. Excellent in point.

In any of the orientations, the ratio E ^* _a / E ^* _b of the complex elastic modulus E ^* _a in the orientation direction to the complex elastic modulus E ^* _{b in the} direction perpendicular to the orientation direction is preferably 3 or more. Is 3 ~
When it is 5, the intended effect of the orientation is particularly excellent. The complex elastic modulus is measured by a viscoelastic spectrometer manufactured by Iwamoto Seisakusho (10 Hz, 70 ° C., ±
1% dynamic strain).

The base tread used in the first invention of the present invention can be manufactured, for example, by the following method.

Base Tread Production Method 1 The rubber, carbon black, short fibers and other additives are kneaded using a Banbury mixer to prepare a rubber composition for a base tread. This rubber composition 4
Is rolled using a calender roll 3 as shown in FIG. 3 to obtain a sheet having a thickness of 1 to 6 mm. In the case of the circumferential orientation, as shown in FIG. 3, a sheet piece of a predetermined length whose longitudinal direction is the rolling direction is cut out to obtain a base tread. In the case of the radial orientation, as shown in FIG. 3, sheet pieces having a longitudinal direction perpendicular to the rolling direction are cut out and joined so as to have a predetermined length to form a base tread.

Base Tread Manufacturing Method 2 The rubber composition for the base tread and the rubber composition for the cap tread prepared by kneading as described above are mixed with a triple box or a Y-box generally used in the rubber industry. Extrude with an extruder to produce a base tread and a cap tread simultaneously. According to this method, a base tread having a circumferential orientation is obtained.

Base Tread Preparation Method 3 The rubber composition for the base tread prepared by kneading as described above is extruded into a tube by an extruder. Thereby, the short fibers in the rubber composition are oriented parallel to the longitudinal direction of the tube. As shown in FIG. 4, this tubular extruded product is cut at a predetermined cutting angle θ (an angle with respect to a direction perpendicular to the tube axis).
To form a base tread by spirally cutting out a sheet piece. If the diameter of the tube is sufficiently large and the cutting angle θ is small, the base tread will be oriented in the radial direction.

The cap tread is obtained by vulcanizing a rubber composition having a general composition. The compounding is, for example, as a main rubber component, any one or a mixture of solution polymerization SBR, emulsion polymerization SBR, NR, IR, BR,
It is a commonly used compound such as carbon black such as N220 (ISAF) and N110 (SAF), process oil, vulcanizing agent and the like.

The tire of the first invention is manufactured using the base tread manufactured as described above, for example, as follows. In the case of radial tires, after attaching a carcass, bead, chefer, and sidewall tread on a molding drum, inflate in an annular shape, attach a breaker, attach the base tread, and attach a cap tread on it. To form a green tire. When using method 2, the base tread and cap tread are already obtained in a laminated form,
The laminated tread is bonded and formed. The green tire thus obtained is put into a mold and vulcanized. Thereafter, through a predetermined operation, the tire according to the first aspect of the present invention is obtained.

The technique using the base tread as disclosed in the first invention can reduce the rolling resistance and improve the steering stability while maintaining the riding comfort.
High performance tires such as radial tires, especially with a flatness of 7
It is preferably applied to a radial tire of 0% or less, preferably 35 to 70%.

Next, the second invention will be described.

As described above, the second invention of the present invention relates to a tire excellent in rolling resistance, steering performance and ride comfort even when the amount of carbon black is small, particularly a pneumatic radial tire having an aspect ratio of 60% or more. The base tread is obtained from a rubber composition containing 10 to 30 parts of short fibers and 5 to 30 parts of carbon black with respect to 100 parts of a rubber component, and 90% or more of the short fibers have a radial direction of the tire of ± 20 °. Oriented in a range of angles and E ^* _a /
E ^* _b is 3 or more.

The rubber component for the base tread that can be used in the second invention is the same as the rubber component of the first invention, but NR and BR are particularly preferred, and NR50
A rubber component is obtained by mixing 20 to 50 parts of BR with about 80 parts.

The carbon black has, for example, an iodine adsorption amount of 30 to 90 mg / g, preferably 40 to 85 mg / g.
mg / g can be used. 30mg of iodine adsorption
If it is less than / g, the reinforcing property is low, and the strength and the cut resistance are inferior.
If it is 90 mg / g or more, heat generation is high and rolling resistance increases. Preferred carbon black is N550 (FE
F) (Iodine adsorption amount: 43 mg / g), N330 (HA
F) (82 mg / g), N351 (68 mg / g) and the like, for example, those available from Showa Cabot Co., Ltd. and Mitsubishi Kasei Kogyo Co., Ltd., and N550 is particularly preferable. In the second invention, the addition amount of the carbon black is 5 to 30 parts based on 100 parts of the rubber component. If the amount is less than 5 parts by weight, the reinforcing property is reduced and the strength is inferior, and if it exceeds 30 parts, the heat generation of the rubber is increased and the rolling resistance is increased.

The raw materials of the short fibers used in the second invention are the same as those in the first invention. As for the dimensions, the number average length is longer than 30 μm, particularly preferably 50 to 500 μm, and the number average diameter is preferably 0.1 to 0.5 μm. Further, L / D is preferably larger than 50, particularly preferably 100 to 5000. If the ratio is less than 50, sufficient short fiber orientation cannot be imparted to the rubber.

The amount of the short fibers is 5 to 30 parts, preferably 10 to 25 parts, per 100 parts of the rubber component. If the short fiber content is less than 5 parts, there is no effect on the improvement of steering stability, and 3
If it is 0 or more, the rolling resistance is deteriorated and the riding comfort is also deteriorated.

In the second invention, 90% of the short fibers
It is important to orient the above at an angle in the range of ± 20 ° in the radial direction of the tire (90 ° with respect to the circumferential direction of the tire), thereby improving the radial rigidity of the tire, that is, the lateral rigidity. In addition, steering stability such as handle responsiveness and grip feeling can be improved. If the short fibers are not oriented in the predetermined direction, the lateral rigidity as described above does not improve, and the steering stability does not improve. In addition, the ratio E
^* _a / E ^* _b needs to be 3 or more, preferably 3 to 5. When E ^* _a / E ^* _b is less than 3, steering stability is not improved, which is not preferable.

The rubber composition constituting the radial tire of the second invention of the present invention further contains the same process oil, antioxidant, wax, vulcanization aid, vulcanization accelerator and the like as the first invention as additives. You may mix.

The rubber composition for cap tread is the first of the present invention.
The same as the invention can be used.

The manufacture of the radial tire of the second invention is as follows.
Except for the composition of the rubber for the base tread, in the first invention of the present invention, it can be manufactured by a manufacturing method for orienting the short fibers in the base tread in the radial direction, for example, the manufacturing method 1 described above.

In the second aspect of the present invention, it is important that the base tread thickness of the tire is 6 mm or less, preferably 1 to 6 mm, and the flatness is 60% or more. Can be secured in a specific direction,
Steering stability and rolling resistance can be balanced. If the thickness exceeds 6 mm, the orientation of the internal fibers decreases, and the rolling resistance also deteriorates.

Next, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples. The amounts in the examples, comparative examples and tables are parts by weight.

Example 1 40 parts of natural rubber (NR RSS # 3), 20 parts of styrene-butadiene copolymer rubber (SBR1500), number average diameter 0.3 μm, number average length 300 μm, L / D 100
Short fiber reinforced natural rubber (UBEPOL-HE manufactured by Ube Industries, Ltd.) 60 containing 33% by weight of nylon 6 fiber 60
Parts, 40 parts of carbon black (ISAF) with an iodine adsorption amount of 121 mg / g, 3 parts of process oil (aromatic oil), 2 parts of antioxidant (age 13), 2 parts of stearic acid, 3 parts of zinc white, vulcanization A rubber composition was obtained by kneading with a Banbury mixer using 1.75 parts of an agent (sulfur) and 1 part of a vulcanization accelerator (CZ). This rubber composition 4
Was rolled by a calender roll 3 shown in FIG. 3 to produce a sheet, and the sheet was cut in a direction perpendicular to the rolling direction and joined to produce a base tread 1.

After a carcass, bead, chefer, and sidewall tread having a general composition and structure separately prepared are pasted on a molding drum, they are inflated in an annular shape, and a breaker is pasted to obtain a low cover 2, and the above-mentioned raw cover 2 is obtained. The base tread 1 obtained as described above was adhered, and a cap tread was adhered thereon to form a green tire. The green tire was placed in a mold and vulcanized. Thereafter, through a predetermined operation, a radial tire of the present invention having a dimension represented by 205 / 60R15 was obtained.

When the thickness of the base tread of this tire was measured, it was 4 mm at maximum and 3.5 mm on average. In addition, the orientation direction of the short fibers in the base tread is the radial direction with respect to the tire, and the complex elastic modulus E ^* _{a in the} orientation direction.
Is 210 kgf / cm ² , the complex modulus E ^* _{b in the} direction perpendicular to the orientation direction is 50 kgf / cm ² , and E ^* _a / E ^*
_b was 4.2.

Table 1 shows the composition of the base tread and the structure of the tire.

Table 2 shows the results obtained by measuring the rolling resistance, steering performance (handle response and grip feeling), and riding comfort of the obtained tire.

The rolling resistance of the manufactured tire

[0044]

(Equation 1)

On the 60 inch drum
Speed 80km / h, internal pressure 2.0kgf / cm^Two, Load 3
It was measured by running under the condition of 50 kg. The results are compared
Example 1 is set to 100 and shown as a relative value. Number is
The smaller, the smaller the rolling resistance and the better the tire performance.
You. Handle responsiveness, grip feeling and ride performance are
The manufactured tire is mounted on a 2000cc passenger car,
Pressure 1.8kgf / cm ^TwoThe JARI Comprehensive Test Road
Was evaluated by riding with one person. Conclusion
The results are based on Comparative Example 1 (3).
Expressed as being. + On the right shoulder of the number is slightly better
And-mean a little inferior.

Example 2 A rubber composition having the base tread composition shown in Table 1
A rubber composition having the same cap tread composition as that used in Example 1 was extruded with a triple box extruder to produce a tread having a double cap / base structure.

After a separately prepared carcass, bead, chefer, and sidewall tread having a general composition and structure are pasted on a molding drum, they are inflated in a ring shape, and a breaker is pasted to obtain a low cover. The tread produced in the above was glued to form a green tire. The green tire was placed in a mold and vulcanized. Thereafter, through a predetermined operation, a radial tire of the present invention having a dimension represented by 205 / 60R15 was obtained.

When the thickness of the base tread of this tire was measured, it was 4 mm at maximum and 3.5 mm on average. The orientation direction of the short fibers in the base tread is circumferential to the tire. That is, 90% or more of the short fibers are oriented in a range of ± 20 ° with respect to the circumferential direction of the tire, and the complex elastic modulus E ^* _{a in the} circumferential direction is 210 kgf / cm ² , and the complex elastic modulus in the direction perpendicular thereto is The rate E ^* _b is 50 kgf / cm ²
And the ratio E ^* _a / E ^* _b was 4.2. Table 1 shows the composition of the base tread and the structure of the tire. Formulations are given in parts by weight.

Table 2 shows the results obtained by measuring the rolling resistance, steering wheel responsiveness, grip feeling, and riding comfort of the obtained tires.

Examples 3 and 4 The same method as in Example 1 except that the composition of the base tread was changed as shown in Table 1, the same size as in Example 1 and radial fibers having short fibers oriented in the radial direction. Tires were manufactured. When the thickness of the base tread of these tires was measured, the tire of Example 3 had a maximum thickness of 4 m.
m, 3.5 mm on average, and 2.5 mm at maximum and 2.2 mm on average for Example 4.

Table 2 shows the results of measuring the rolling resistance, steering wheel responsiveness, grip feeling, and riding comfort of these tires in the same manner as in Example 1.

Example 5 The thickness of the base tread was the same as in Example 4 except that the composition of the base tread was changed as shown in Table 1, and the short fibers were oriented in the radial direction. A radial tire having the same dimensions as in Example 4 was manufactured.

Table 2 shows the results of the same performance test as in Example 1 for this tire.

Comparative Example 1 A cap tread was extruded thickly without using a base tread, a tire was molded using Method 2, and then vulcanized to produce a radial tire having the same dimensions as in Example 1.

Table 2 shows the results of measuring the rolling resistance, steering wheel responsiveness, grip feeling, and riding comfort of this tire in the same manner as in Example 1.

Comparative Example 2 A radial tire having the same dimensions as in Example 2 was produced in the same manner as in Example 2 except that the composition of the base tread was changed as shown in Table 1 (not including short fibers). When the thickness of the base tread of this tire was measured, it was 4 mm at maximum and 3.5 mm on average.

Table 2 shows the results of measuring the rolling resistance, steering wheel responsiveness, grip feeling, and riding comfort of this tire in the same manner as in Example 1.

Comparative Examples 3 and 4 The same method as in Example 1 was used except that the composition of the base tread was changed as shown in Table 1. Radial in which short fibers were oriented in the radial direction in the same size as in Example 1. Tires were manufactured. When the thickness of the base tread of these tires was measured, the tire of Comparative Example 3 had a maximum thickness of 4 m.
m, an average of 3.5 mm, and a maximum of 4 mm and an average of 3.5 mm for Comparative Example 4.

Table 2 shows the results of measuring the rolling resistance, handle response, grip feeling, and riding comfort of these tires in the same manner as in Example 1.

Comparative Example 5 A rubber composition having the base tread shown in Table 1 was obtained by kneading in the same manner as in Example 1. This rubber composition was extruded by an extruder to form a tube-shaped extrudate having a wall thickness of 8 mm. This tubular extrudate was spirally cut out as shown in FIG. 4 to produce a base tread.

Using this base tread, a radial tire having the same dimensions as in Example 1 and short fibers oriented substantially in the radial direction was produced in the same manner as in Example 1. When the thickness of the base tread was measured, the maximum was 7 mm, and the average was 6.
3 mm.

Table 2 shows the results of measuring the rolling resistance, handle responsiveness, grip feeling and riding comfort of this tire in the same manner as in Example 1.

Comparative Example 6 The thickness of the base tread was the same as in Example 1 except that the composition of the base tread was changed as shown in Table 1, and the short fibers were oriented in the radial direction. A radial tire having the same dimensions as in Example 1 was manufactured. In this case, the short fibers are more than 90% in the radial direction, and the ratio of the complex elastic modulus in the radial direction E ^* _a and a direction perpendicular thereto of complex elastic modulus E ^* _b is less than 3.

Table 2 shows the results of a performance test performed on this tire in the same manner as in Example 1.

Comparative Example 7 The thickness of the base tread was the same as that of Example 3 except that the composition of the base tread was changed as shown in Table 1, and the short fibers were blended in the radial direction. A radial tire having the same dimensions as in Example 3 was manufactured.

Table 2 shows the results of the same performance test as in Example 1 for this tire.

[0067]

[Table 1]

[0068]

[Table 2]

Tables 1 and 2 show the following. Comparative Example 2 shows that even when a base tread containing no short fiber is provided, the rolling resistance is reduced, but the handle response is deteriorated. From Comparative Example 3, it can be seen that even if the base tread containing short fibers is provided, if the amount is as large as 40 parts, the rolling resistance increases and the riding comfort performance deteriorates. From Comparative Example 4, even when a base tread containing an appropriate amount of short fibers was provided, the carbon black content was 70%.
It can be seen that when there are many parts, the rolling resistance is considerably large and the riding comfort performance is also deteriorated. From Comparative Example 5, even if a base tread containing an appropriate amount of short fibers and an appropriate amount of carbon black is provided, if the thickness is as thick as 7 mm, handle responsiveness, grip feeling, and ride comfort deteriorate. I understand. In Comparative Example 6, the amount of short fibers was as small as 10 parts, and improvement in steering stability could not be achieved. In contrast, the tires of Examples 1 to 5 of the present invention have low rolling resistance, handle responsiveness,
It is understood that the grip feeling and the riding comfort are excellent. Further, from Examples 1 and 2, it is understood that when the orientation of the short fibers in the base tread is in the radial direction with respect to the tire, the handle response is particularly good. Further, ISA as carbon black was obtained from Examples 1 and 3.
It is understood that when N351 is used instead of F, the rolling resistance becomes smaller.

Examples 6 to 10 The following components were used to prepare rubber compositions for base treads.

Component Amount (parts by weight) Rubber component Table 3 Short fiber Table 3 Carbon black Table 3 Naphthenic oil 5 Adhesive resin (SP-1068) 3 Wax 1.5 Antioxidant (aging IPPD) 2 Zinc stearate 2 Hua 4 Sulfur 2 Accelerator CZ 1.3 A sheet-like rubber composition having a thickness of 2 to 6 mm was prepared in the same manner as in Example 1, and this was rolled with a calender roll having a width of 2 m or more, and the orientation of short fibers was obtained. At right angles to the direction, a sheet of the tread width is cut out, pasted on a breaker on a tire forming machine, and a cap tread extruded thereon is further pasted thereon to produce a tire (tire size: 185/65).
R14) was obtained. Table 3 shows E ^* _a , E ^* _b and E ^* _a / E ^* _b of the base tread. The thickness of the base tread was constant at 4 mm, and the flatness was constant at 65%. The tire was mounted on a 6JJ × 14-inch rim, and a rolling resistance test, a driving stability test, and a riding comfort test were performed using an actual vehicle. The evaluation methods are described below. Table 4 shows the results of these tests.

(1) Rolling resistance test: tire 6JJ × 1
4 rim, speed 80 on 60 inch drum
km / h, internal pressure 2.5 kgf / cm ² , load 350 kg
The rolling resistance was measured by running under the conditions described in (1), and the rolling resistance was converted into an index when the tire of Comparative Example 8 was set to 100. The smaller the index, the better.

(2) Maneuvering stability test: Tire displacement 1
The vehicle was mounted on a 600 cc passenger car, and a turning test was performed on a dry, flat asphalt road with one passenger. Characteristics such as handle responsiveness and grip were scored by sensory evaluation of the driver. The score is better when the numerical value is larger based on 3.

(3) Ride comfort test: Similar to the above, sensory evaluation was carried out on a stepped portion on a dry road, a Belgian road, a Bitzmann road and the like, with respect to ruggedness, thrust-up, and dumping, and a score was given. The score is based on three points as in the case of the steering stability, and the larger the numerical value, the better.

[0075]

[Table 3]

Comparative Examples 8 to 13 Using a rubber composition for base tread having the composition shown in Table 3, a base tread was produced in the same manner as in Example 6 so as to have the short fiber orientation shown in the table. A radial tire was manufactured in the same manner. With respect to the obtained radial tire, the same rolling resistance, steering stability and riding comfort performance as in Example 6 were examined. Table 4 shows the results.

[0077]

[Table 4]

As is clear from Tables 3 and 4, the radial tires of Examples 6 to 10 have better balance in rolling resistance, steering stability and ride comfort than the tires of Comparative Examples 8 to 12. Comparative Example 1 in which short fibers are oriented in the circumferential direction
Tire No. 3 is clearly inferior in steering stability to the tire of Example 6 in which short fibers are oriented in the radial direction.

[0079]

As described above, the tire of the present invention has a low rolling resistance, a small dynamic loss and a good fuel economy. Steering stability, such as grip, has been improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a state in which short fibers in a base tread are oriented in a radial direction of a tire.

FIG. 2 is a schematic perspective view showing a state in which short fibers in a base tread are oriented in a circumferential direction of a tire.

FIG. 3 is a process chart showing a method for producing a base tread.

FIG. 4 is a schematic perspective view showing a method of cutting out a base tread from a tubular extrudate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base tread 2 Low cover 3 Calender roll 4 Rubber composition 5 Tire

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C08L 9/02 C08L 9/02 (56) References JP-A-4-143104 (JP, A) JP-A-57-104405 (JP) JP-A-57-151405 (JP, A) JP-A-54-132907 (JP, A) JP-A-5-339427 (JP, A) JP-A-3-152140 (JP, A) 1-5060 (JP, B2) JP-B-57-4527 (JP, B2) JP-B-58-3842 (JP, B2) JP-B 64-5060 (JP, B2) Patent 2565953 (JP, B2) (58) ) Field surveyed (Int. Cl. ⁶ , DB name) B60C 1/00 B60C 11/00 C08L 7/00

Claims (7)

(57) [Claims] 1. A tire comprising a base tread having a thickness of 6 mm or less, wherein the base tread has 16-30 parts by weight of short fibers and 30-60 parts by weight based on 100 parts by weight of a total of rubber components. Iodine adsorption amount 60-130mg
/ Der which carbon black is blended in g is, the circumferential direction more than 90% of the tire of the short fibers in the base tread
Oriented at an angle in the range of 90 ° ± 20 ° to the
Complex elastic modulus E ^* _{a in the} direction and the complex
The ratio E ^* _a / E ^* _b of the elastic modulus E ^* _b is 3 or more
Ya . 2. A tire comprising a base tread having a thickness of 6 mm or less, wherein the base tread has 16-30 parts by weight of short fibers and 30-60 parts by weight based on 100 parts by weight of a total of rubber components. Iodine adsorption amount 60-130mg
/ Der which carbon black is blended in g is, the circumferential direction more than 90% of the tire of the short fibers in the base tread
Orientation at an angle in the range of ± 20 ° to the orientation
The direction perpendicular to the complex elastic modulus of the complex elastic modulus E ^* _a and the alignment direction of
Tire ratio E ^* _a / E ^* _b of the E ^* _b is 3 or more. 3. The short fiber has a number average diameter D of 0.1 to 0.5.
μm, the number average length L is 50 to 500 μm, and L
The tire according to claim 1 or 2 , wherein / D is 100 to 5,000. 4. A tire according to any one of claims 1 to 3 aspect ratio of the tire is less radial tires 70%. 5. A pneumatic radial tire having a tread having a cap / base structure, said base tread comprising: (i) a rubber component comprising 50 to 80 parts by weight of natural rubber and 20 to 50 parts by weight of butadiene rubber; (Ii) A rubber composition containing 10 to 30 parts by weight of short fibers and 5 to 30 parts by weight of carbon black with respect to 100 parts by weight of the rubber component, wherein the short fibers are located in the circumferential direction of the tire. Oriented at an angle in the range of 90 ° ± 20 °, and the ratio E ^* _a / E ^* _b of the complex elastic modulus E ^* _a in the orientation direction to the complex elastic modulus E ^* _{b in the} direction perpendicular to the orientation direction is 3 or more; The thickness of the base tread is 6 mm or less and the flatness is 60
% Radial tires. 6. The carbon black having an iodine adsorption amount of 30.
The radial tire according to claim 5 , wherein the amount is from 90 to 90 mg / g. 7. The short fiber has a number average diameter D of 0.1 to 0.5.
μm, the number average length L is 50 to 500 μm, and L
/ D is a radial tire according to claim 5 or 6, wherein 100 to 5,000.