JP7315837B2 - Heavy duty pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heavy duty pneumatic tire, and more particularly to a heavy duty pneumatic tire in which air permeation prevention performance, fuel economy performance and durability are well balanced at a high level.

A pneumatic tire is mainly composed of a pair of left and right bead portions and sidewall portions, and a tread portion connected to both sidewall portions and composed of a cap tread and an undertread. A carcass layer is provided inside the tire, and both ends of the carcass layer are folded back so as to wrap the bead core from the inside to the outside of the tire.
In addition, an inner liner rubber composed mainly of butyl rubber, which has excellent air permeation prevention performance, is provided on the innermost surface of the pneumatic tire in the tire radial direction to prevent air leakage.

On the other hand, as for pneumatic tires for heavy loads such as tires for trucks and buses, emphasis is placed on safe and comfortable operation and economic efficiency, and tires with excellent total balance are required. Therefore, heavy-duty pneumatic tires are required to have a high-level balance between durability and fuel efficiency. For example, in order to improve fuel efficiency, it is effective to suppress air leakage from the tire, and for that purpose, increasing the thickness of the inner liner rubber is conceivable. However, simply increasing the thickness of the inner liner rubber causes the inner liner rubber to generate heat and accumulate heat, which causes the temperature of the tire to rise, degrading the casing (tire components other than the tread) and reducing tire durability. It gets worse. In addition, fuel efficiency is not improved.
A technique has also been proposed in which silica and a specific silane coupling agent are blended into the inner liner rubber (Patent Document 1). not fully satisfied.
Therefore, it is recognized in the industry that it is difficult to improve air permeation prevention performance, fuel economy performance and durability at the same time.

JP 2011-126929 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heavy-duty pneumatic tire in which air permeation prevention performance, fuel efficiency performance and durability are well balanced at a high level.

As a result of intensive research, the present inventor has made the inner liner rubber a two-layer structure of rubber layers (A) and (B), the composition of the rubber layer (A) on the inner side in the tire radial direction, the thickness of the cap tread rubber (Ga Cap) and the thickness (Ga. IL) of the rubber layer (A), and the relationship between the tan δ (60°C) of the cap tread rubber and the tan δ (60°C) of the rubber layer (A). As a result, the inventors have found that the above problems can be solved, and have completed the present invention.
That is, the present invention is as follows.

1. A heavy-duty pneumatic tire comprising an inner liner rubber arranged as an air sealing layer and a cap tread rubber forming a tire contact surface,
The inner liner rubber has a tire radially inner rubber layer (A) and a tire radially outer rubber layer (B),
The ratio of butyl-based rubber is 50 parts by mass or more in 100 parts by mass of rubber constituting the rubber layer (A),
10 parts by mass or more of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 25 to 100 m ² /g as a filler with respect to 100 parts by mass of rubber constituting the rubber layer (A),
The thickness (Ga. cap) of the cap tread rubber and the thickness (Ga. IL) of the rubber layer (A) satisfy the following formula,
tan δ (60 ° C.) (tan δ cap) at 60 ° C. of the cap tread rubber and tan δ (60 ° C.) (tan δ IL) at 60 ° C. of the rubber layer (A) satisfy the following formula. pneumatic tires.
(Ga. cap) / (Ga. IL) ≤ 30
(tanδcap)/(tanδIL) ≤ 1
2. 2. The heavy duty pneumatic tire according to 1 above, wherein the gas permeability coefficient (permeation coefficient cap) of the cap tread rubber and the gas permeability coefficient (permeation coefficient IL) of the rubber layer (A) satisfy the following formula. .
3 ≤ (transmission coefficient cap) / (transmission coefficient IL)
3. 3. The pneumatic pneumatic container for heavy load according to 1 or 2 above, wherein the total thickness (Ga. All-IL) of the rubber layer (A) and the rubber layer (B) is 1.5 mm to 7.5 mm. tire.
4. In the rubber layer (A), 50 parts by mass or less of a plate-like inorganic filler having a particle diameter of 4.9 to 7.5 μm and an aspect ratio of 3.0 to 7.0 is blended with 100 parts by mass of rubber. and the rubber layer (B) is characterized in that 0.05 to 0.5 parts by mass of an organic metal salt as a metal content is blended with 100 parts by mass of rubber containing 50 parts by mass or more of natural rubber. 4. The heavy duty pneumatic tire according to any one of 1 to 3 above.
5. 5. The heavy-duty pneumatic tire according to any one of 1 to 4, wherein the inner liner rubber is arranged on the innermost surface in the tire radial direction.

The heavy duty pneumatic tire of the present invention comprises an inner liner rubber arranged as an air sealing layer and a cap tread rubber constituting a tire ground contact surface, and the inner liner rubber is a rubber layer on the inner side in the tire radial direction. (A) and a rubber layer (B) on the outer side in the tire radial direction, wherein the ratio of butyl-based rubber is 50 parts by mass or more in 100 parts by mass of rubber constituting the rubber layer (A), and the rubber layer With respect to 100 parts by mass of rubber constituting (A), 10 parts by mass or more of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 25 to 100 m ² /g is included as a filler, and the thickness of the cap tread rubber (Ga cap) and the thickness (Ga. IL) of the rubber layer (A) satisfy (Ga. cap) / (Ga. IL) ≤ 30, and the tan δ at 60 ° C. of the cap tread rubber (60 ° C.) ( tan δ cap) and tan δ (60° C.) (tan δ IL) of the rubber layer (A) at 60° C. satisfy (tan δ cap)/(tan δ IL) ≦ 1, so air permeation prevention performance, Low fuel consumption performance and durability can be balanced at a high level.

As mentioned above, suppressing air leakage from tires is an effective way to improve fuel efficiency, and one way to do this is to increase the thickness of the inner liner rubber, but simply increasing the thickness of the inner liner rubber If only the inner liner rubber heats up and accumulates heat, the temperature of the tire rises, causing deterioration of the casing (tire components other than the tread), deterioration of tire durability, and no improvement in fuel efficiency. . On the other hand, if the thickness of the inner liner rubber is reduced, air leakage during running becomes large, and low fuel consumption cannot be obtained. Even if the thickness of the cap tread is increased, problems such as air leakage and heat generation occur during running.
In the present invention, the inner liner rubber has a two-layer structure of rubber layers (A) and (B), and the composition of the rubber layer (A) on the inner side in the tire radial direction, the thickness of the cap tread rubber (Ga. cap) and the rubber layer ( A) thickness (Ga. IL) and the relationship between tan δ (60°C) of the cap tread rubber and tan δ (60°C) of the rubber layer (A) are specified. It is possible to balance permeation prevention performance, fuel efficiency performance and durability at a high level.

The present invention will now be described in more detail.

(inner liner rubber)
The inner liner rubber used in the heavy-duty pneumatic tire of the present invention (hereinafter sometimes simply referred to as a pneumatic tire) is used as an air sealing layer and direction).
The inner liner rubber in the present invention has a rubber layer (A) on the inner side in the tire radial direction and a rubber layer (B) on the outer side in the tire radial direction, and one feature is the composition of the rubber layer (A).

That is, in 100 parts by mass of rubber constituting the rubber layer (A), the ratio of butyl rubber is 50 parts by mass or more, and for 100 parts by mass of rubber constituting the rubber layer (A), as a filler It contains 10 parts by mass or more of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 25 to 100 m ² /g.

When the ratio of the butyl rubber is less than 50 parts by mass, when the blending ratio of the carbon black is less than 10 parts by mass, and/or the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is 25 to 100 m If it is outside the range of ² /g, air permeation prevention performance, fuel efficiency performance and durability cannot be well balanced at a high level.

Any butyl rubber used for inner liners, such as butyl rubber (IIR) and halogenated butyl rubber (Br-IIR, Cl-IIR), can be used as the butyl rubber. Examples of commercially available butyl-based rubbers include brominated butyl rubbers such as BROMOBUTYL2255 manufactured by EXXON MOBILE.

As the rubber constituting the rubber layer (A), a rubber component other than the butyl-based rubber, such as a diene-based rubber, can be used. Preferred diene rubbers include natural rubber (NR) and synthetic isoprene rubber (IR).

Here, from the viewpoint of improving the effects of the present invention, the following forms are preferable.
(1) The ratio of the butyl rubber to 100 parts by mass of the rubber constituting the rubber layer (A) is preferably 60 to 90 parts by mass.
(2) The mixing ratio of the carbon black is preferably 20 to 90 parts by mass, more preferably 25 to 80 parts by mass, based on 100 parts by mass of the rubber constituting the rubber layer (A).
(3) The rubber layer (A) contains 50 parts by mass or less of a plate-like inorganic filler having a particle diameter of 4.9 to 7.5 μm and an aspect ratio of 3.0 to 7.0 with respect to 100 parts by mass of rubber. , for example, 5 to 45 parts by mass are preferably blended. Examples of plate-like inorganic fillers include flat talc, mica, clay, and bituminous coal. Moreover, the aspect ratio can be measured by the following formula (1).
Ar=(Ds−Dl)/Ds (1)
(Wherein, Ar is the aspect ratio, Ds is the 50% particle diameter determined by the cumulative distribution measured by the centrifugal sedimentation method, and Dl is the 50% particle determined by the cumulative distribution measured by the coherent light laser diffraction method. diameter.)
The nitrogen adsorption specific surface area (N ₂ SA) is a value measured according to JIS K 6217-2:2001 "Part 2: Determination of specific surface area--Nitrogen adsorption method--single point method".

The rubber layer (B) is arranged outside in the tire radial direction with respect to the rubber layer (A).
The rubber layer (B) preferably contains a diene rubber as a rubber component. Natural rubber (NR) is preferable as the diene rubber, and the content of NR is preferably 50 parts by mass or more, more preferably 80 to 100 parts by mass in 100 parts by mass of the diene rubber. As the rubber constituting the rubber layer (B), other than natural rubber, for example, butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene rubber (NBR), etc. can be used. can.
In addition, the NR referred to in the present invention includes synthetic isoprene rubber (IR).

Further, the rubber layer (B) preferably contains an organic metal salt. Adhesion with the rubber layer (A) can be enhanced by blending the organic metal salt. Adhesion between adjacent carcass layers can also be enhanced.

Examples of the metal in the organic metal salt include cobalt, nickel, chromium, manganese and the like. Among them, nickel and cobalt are preferable from the viewpoint of adhesiveness and hardness. Examples of organic components include naphthenic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, palmitic acid, neodecanoic acid, octylic acid, benzoic acid, acetic acid, methacrylic acid, rosin acid, tall oil acid, and trineodecane borate. An acid etc. can be illustrated. Organic metal salts that can be used in the present invention include, for example, cobalt stearate, cobalt naphthenate, cobalt neodecanoate orthoborate, cobalt oleate, cobalt octylate, cobalt benzoate, cobalt acetate, cobalt methacrylate, tall oil. Examples include cobalt acid, cobalt rosinate, nickel naphthenate, nickel stearate, nickel octylate, and nickel rosinate.

The organic metal salt is preferably added in an amount of 0.05 to 0.5 parts by mass in terms of metal content per 100 parts by mass of the rubber constituting the rubber layer (B).

In the rubber layer (A) and the rubber layer (B), in addition to the above-mentioned components, various fillers, various oils, anti-aging agents, plasticizers, zinc oxide, etc. are generally added to the inner liner rubber. Various additives that are used can be blended. Further, at the time of vulcanization, a known vulcanization or cross-linking agent, vulcanization or cross-linking accelerator can be used without limitation. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

The cap tread rubber in the pneumatic tire of the present invention constitutes the tire contact surface.
In the present invention, the composition of the cap tread rubber is not particularly limited as long as it satisfies the following relationships of (Ga. cap)/(Ga. IL) ≤ 30 and (tan δ cap)/(tan δ IL) ≤ 1. It can be selected as appropriate.
For example, diene rubber, various fillers such as silica and carbon black, coupling agents, various oils, anti-aging agents, plasticizers, zinc oxide and other components that are generally blended in cap tread rubber are blended. be able to. Further, at the time of vulcanization, a known vulcanization or cross-linking agent, vulcanization or cross-linking accelerator can be used without limitation. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

In the present invention, it is necessary that the thickness of the cap tread rubber (Ga. cap) and the thickness of the rubber layer (A) (Ga. IL) satisfy the following formula.
(Ga. cap) / (Ga. IL) ≤ 30
If (Ga. cap)/(Ga. IL) exceeds 30, air permeation prevention performance, fuel economy performance and durability cannot be well balanced at a high level.
The thickness of the cap tread rubber (Ga. cap) is the thickness of the cap tread from the contact surface between the cap tread and the undertread to the ground contact surface of the cap tread in the cross section of the vulcanized pneumatic tire cut in the meridian direction. is the thickness (mm) in the tire radial direction located at the center of the
The thickness (Ga. IL) of the rubber layer (A) is the thickness (mm) in the tire radial direction located at the center of the cap tread in a cross section of the vulcanized pneumatic tire cut in the meridian direction.

The (Ga. cap)/(Ga. IL) is preferably 2 mm to 25 mm, more preferably 3 mm to 23 mm.
(Ga. cap) is preferably 5 mm to 35 mm, more preferably 8 mm to 32 mm.
(Ga. IL) is preferably 1.0 mm to 5.0 mm, more preferably 1.0 mm to 4.0 mm.
Furthermore, the thickness of the rubber layer (B) measured in the same manner as (Ga. IL) is preferably 0.5 mm to 2.5 mm, more preferably 0.5 mm to 2.0 mm. The total thickness (Ga. All-IL) of the rubber layer (A) and the rubber layer (B) is preferably 1.5 mm to 7.5 mm, more preferably 1.5 mm to 6.0 mm.

In the present invention, tan δ (60° C.) at 60° C. (tan δ cap) of the cap tread rubber and tan δ (60° C.) (tan δ IL) at 60° C. of the rubber layer (A) satisfy the following formula. is necessary.
(tanδcap)/(tanδIL) ≤ 1
If (tan δ cap)/(tan δ IL) exceeds 1, air permeation prevention performance, fuel efficiency performance and durability cannot be well balanced at a high level.

The (tan δ cap)/(tan δ IL) is preferably 0.3 to 1.0, more preferably 0.35 to 1.0.
Tan δ (60°C) is measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of initial strain of 10%, amplitude of ±2%, frequency of 20 Hz, and temperature of 60°C.

From the viewpoint of improving the effect of the present invention, it is preferable that the gas permeability coefficient (permeation coefficient cap) of the cap tread rubber and the gas permeability coefficient (permeation coefficient IL) of the inner liner rubber satisfy the following formula.
3 ≤ (transmission coefficient cap) / (transmission coefficient IL)
The (transmission coefficient cap)/(transmission coefficient IL) is preferably 3.0 to 10.0, more preferably 3.0 to 9.0.
The gas permeability coefficient is a gas permeability coefficient measured at 30°C according to JIS K7126 A method.

In addition, in the other members of the pneumatic tire of the present invention, such as members constituting the bead portion and the sidewall portion, the compounding ratio of each component is not particularly limited and can be appropriately selected.
For example, as the rubber composition for other members, various commonly used components such as diene rubbers, various fillers, various oils, antioxidants, plasticizers, and zinc oxide can be blended. Further, at the time of vulcanization, a known vulcanization or cross-linking agent, vulcanization or cross-linking accelerator can be used without limitation. The blending amount of these additives can also be a conventional general blending amount as long as it does not contradict the object of the present invention.

The tan δ (60° C.) (tan δ cap) and (tan δ IL) of the cap tread rubber and the inner liner rubber can be adjusted, for example, by increasing or decreasing fillers, vulcanizing agents or cross-linking agents.
The gas permeability coefficient (permeability coefficient cap) and (permeability coefficient IL) of the cap tread rubber and the inner liner rubber can be adjusted, for example, by increasing or decreasing the plasticizer, filler, vulcanizing agent, or cross-linking agent.

Also, the heavy duty pneumatic tire of the present invention can be manufactured according to the conventional method for manufacturing heavy duty pneumatic tires.

The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1-6 and Comparative Examples 1-4
In the formulation (parts by weight) shown in Table 1, the vulcanization accelerator and components other than sulfur were kneaded for 5 minutes in a 1.6-liter internal Banbury mixer, and the rubber was discharged out of the mixer and cooled to room temperature. Next, the rubber is placed in the same mixer again, a vulcanization accelerator and sulfur are added, and the mixture is further kneaded to obtain a tire radially inner rubber layer (A) and a tire radially outer rubber layer (B) of various inner liner rubbers. got

On the other hand, cap tread rubbers were prepared according to a conventional method, and cap tread rubbers having various thicknesses, tan δ (60°C) and gas permeability coefficients were obtained by increasing or decreasing the amount of plasticizer or filler.

The tan δ (60°C) (tan δ cap) and (tan δ IL) of the cap tread rubber and the inner liner rubber were measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., with an initial strain of 10% and an amplitude of ±2%. , a frequency of 20 Hz, and a temperature of 60°C.
The gas permeability coefficient (permeability coefficient cap) and (permeability coefficient IL) of the cap tread rubber and the inner liner rubber were measured at 30°C in accordance with JIS K7126 A method (unit = [mol/(m ² s・Pa)]).
Table 1 shows the results.

Various test tires with tire sizes of 275/80R22.5 and 151/148J were manufactured by incorporating the inner liner rubber and the cap tread rubber. The conditions for each member other than the inner liner rubber and the cap tread rubber were the same among the various test tires.

The following evaluations were performed on the obtained various test tires. Table 1 shows the results.

Actual driving fuel consumption performance: Various test tires were mounted on a wheel with a rim size of 22.5 x 8.25, mounted on a test vehicle, and run for 50,000 km on a paved test course at an air pressure of 900 kPa. In addition, refilling of air is not performed during the test. The scores were A: Actual fuel consumption of 3.5 km/liter or more, B: Actual fuel consumption of 2 km/liter or more and less than 3.5 km/liter, and C: Actual fuel consumption of less than 2 km/liter.

Tire Air Leakage Performance: Each test tire was mounted on a wheel with a rim size of 22.5×8.25, mounted on a test vehicle, air was introduced into each test tire at an air pressure of 900 kPa, and the test tire was run for 20,000 km. The air pressure of each test tire was then measured. The results are indexed with the value of Example 1 as 100. A smaller index value indicates that air leakage is prevented.

Tire durability: Each test tire was mounted on a wheel with a rim size of 22.5×8.25, air pressure was set to 900 kPa, and the tires were run in the market for 100,000 km to evaluate residual durability during running on a durability test drum. The results are indexed with the value of Example 1 as 100. A larger index value indicates better tire durability.

*1: Br-IIR (BROMOBUTYL2255 manufactured by EXXON MOBIL)
*2: NR (TSR20)
*3: Carbon black 1 (trade name SEAST V manufactured by Tokai Carbon Co., Ltd., N ₂ SA = 27 m ² /g)
*4: Talc (trade name HARtalc manufactured by Imerys, particle size = 5.7 m, aspect ratio Ar = 4.7)
*5: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.)
*6: Zinc oxide (Type 3 zinc oxide manufactured by Seido Chemical Industry Co., Ltd.)
*7: Vulcanization accelerator (Suncellar DM-PO manufactured by Sanshin Chemical Industry Co., Ltd.)
*8: Sulfur (Hosoi Chemical Industry Co., Ltd. oil refinery processing sulfur)

*11: NR (TSR20)
*12: Carbon black 2 (product name Seast 300 manufactured by Tokai Carbon Co., Ltd., N ₂ SA = 84 m ² /g)
*13: Organometallic salt (cobalt naphthenate, content of cobalt is 10.0% by mass, cobalt naphthenate manufactured by DIC)
*14: Zinc oxide (Type 3 zinc oxide manufactured by Seido Chemical Industry Co., Ltd.)
*15: Stearic acid (industrial stearic acid manufactured by Chiba Fatty Acid Co., Ltd.)
* 16: Anti-aging agent (Ozonon 6C manufactured by Seiko Chemical Co., Ltd.)
*17: Vulcanization accelerator (Suncellar DM-PO manufactured by Sanshin Chemical Industry Co., Ltd.)
*18: Sulfur (Hosoi Chemical Industry Co., Ltd. oil processing sulfur)

As is clear from Table 1 above, in each example, the inner liner rubber has a two-layer structure of rubber layers (A) and (B), the composition of the rubber layer (A) on the inner side in the tire radial direction, the cap tread rubber The relationship between the thickness (Ga.cap) of the rubber layer (A) and the thickness (Ga.IL) of the rubber layer (A), and the relationship between the tan δ (60°C) of the cap tread rubber and the tan δ (60°C) of the rubber layer (A) Since it is specified, compared with each comparative example, air permeation prevention performance, fuel efficiency performance and durability are well balanced at a high level.
On the other hand, in Comparative Example 1, (Ga. cap) / (Ga. IL) exceeds 30, so air permeation prevention performance, fuel efficiency performance and durability are all deteriorated compared to Example 1. there is
In Comparative Example 2, since (tan δ cap)/(tan δ IL) exceeds 1, air permeation prevention performance, fuel economy performance and durability are all worse than those of Example 1.
In Comparative Example 3, (Ga. cap)/(Ga. IL) exceeds 30, so air permeation prevention performance, fuel economy performance and durability are all worse than in Example 1.
In Comparative Example 4, since the ratio of the butyl rubber is less than the lower limit specified in the present invention, air permeation prevention performance, fuel economy performance and durability are all worse than in Example 1.

Claims (5)

A heavy-duty pneumatic tire comprising an inner liner rubber arranged as an air sealing layer and a cap tread rubber forming a tire contact surface,
The inner liner rubber has a tire radially inner rubber layer (A) and a tire radially outer rubber layer (B),
The ratio of butyl-based rubber is 50 parts by mass or more in 100 parts by mass of rubber constituting the rubber layer (A),
10 parts by mass or more of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 25 to 100 m ² /g as a filler with respect to 100 parts by mass of rubber constituting the rubber layer (A),
The thickness (Ga. cap) of the cap tread rubber and the thickness (Ga. IL) of the rubber layer (A) satisfy the following formula,
A load characterized in that tan δ (60° C.) (tan δ cap) at 60° C. of the cap tread rubber and tan δ (60° C.) (tan δ IL) at 60° C. of the rubber layer (A) satisfy the following formula: Heavy-duty pneumatic tires.
(Ga. cap) / (Ga. IL) ≤ 30
(tanδcap)/(tanδIL) ≤ 1 2. The heavy duty pneumatic pneumatic according to claim 1, wherein a gas permeability coefficient (permeation coefficient cap) of said cap tread rubber and a gas permeability coefficient (permeation coefficient IL) of said rubber layer (A) satisfy the following formula. tire.
3 ≤ (transmission coefficient cap) / (transmission coefficient IL) 3. The heavy load air according to claim 1 or 2, wherein the total thickness (Ga. All-IL) of the rubber layer (A) and the rubber layer (B) is 1.5 mm to 7.5 mm. entered tire. In the rubber layer (A), 50 parts by mass or less of a plate-like inorganic filler having a particle diameter of 4.9 to 7.5 μm and an aspect ratio of 3.0 to 7.0 is blended with 100 parts by mass of rubber. and the rubber layer (B) is characterized in that 0.05 to 0.5 parts by mass of an organic metal salt as a metal content is blended with 100 parts by mass of rubber containing 50 parts by mass or more of natural rubber. The heavy duty pneumatic tire according to any one of claims 1 to 3. The heavy duty pneumatic tire according to any one of claims 1 to 4, wherein the inner liner rubber is arranged on the innermost surface in the tire radial direction.