JP6988303B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having excellent molding processability, low air permeability and tire durability.

In order to reduce the load on the global environment, studies are being conducted to reduce the rolling resistance of pneumatic tires and improve fuel efficiency. When the air pressure of a pneumatic tire decreases, the tire deformation during running increases, which causes an increase in rolling resistance and eventually a deterioration in fuel efficiency. Therefore, suppressing the air permeability of the pneumatic tire leads to reducing the rolling resistance and improving the fuel efficiency. Further, by suppressing the air permeability, deterioration of the tire reinforcing material such as a steel cord can be suppressed, and the tire durability can be further improved.

In order to reduce air permeability, Patent Document 1 describes 100 parts by weight of a rubber component made of butyl rubber, 10 to 50 parts by weight of clay having an average aspect ratio of 3 or more and less than 30, and 10 to 60 parts by weight of carbon black. It is described that the rubber composition for an inner liner containing the above reduces air permeability. However, in recent years, it has been required to improve the air permeability of pneumatic tires, improve tire durability, and not deteriorate tire workability, and pneumatic tires that meet such requirements are still available. Not developed.

Japanese Unexamined Patent Publication No. 2002-88206

An object of the present invention is to provide a pneumatic tire having improved moldability, low air permeability and tire durability beyond the conventional level.

The pneumatic tire of the present invention that achieves the above object has an inner liner layer, a tie rubber layer and a carcass layer from the inside to the outside in the tire radial direction, and the rubber composition for tie rubber forming the tie rubber layer is a diene rubber. 100 parts by weight, has an inorganic filler 3-50 weight parts, and its 100% deformation tensile stress (M _tie), 100% deformation tensile stress of the rubber composition for an inner liner forming the inner liner layer (M _IL ) difference between the (M _tie -M _IL) is characterized in that it is a 0～2.0MPa.

The pneumatic tire of the present invention, the rubber composition is blended with inorganic filler for the tie rubber, and its 100% tensile deformation stress (M _tie), and 100% deformation tensile stress of rubber composition for an inner liner (M _IL) because of the difference of (M _tie -M _IL) was 0～2.0MPa, moldability, a low air permeability and tire durability can be improved in a conventional level or higher.

The aspect ratio Ar of the inorganic filler is preferably 0.5 to 0.95, and the air permeability can be made smaller. Further, the rubber composition for an inner liner _{has an A IL} mass part in 100 parts by mass of the rubber component thereof, and the blending amount of the inorganic filler with respect to 100 parts by mass of the diene rubber in the rubber composition for tie rubber is A. _{When it is a tie} mass part, the ratio of the blending amounts of these inorganic fillers (A _IL / A _tie ) is preferably 2/3 or less, and 100% deformation tensile stress of the rubber composition for tie rubber and the rubber composition for inner liner. The difference (M _tie - _MIL ) can be easily optimized. Further, the inorganic filler may be at least one selected from clay, talc, calcium carbonate and magnesium oxide.

In the present specification, the pneumatic tire has an inner liner layer, a tie rubber layer and a carcass layer in this order from the inner side to the outer side in the tire radial direction. That is, the pneumatic tire has an inner liner layer on the innermost side in the tire radial direction, a carcass layer on the outer side thereof, and a tie rubber layer is interposed between the inner liner layer and the carcass layer. The inner liner layer and the tie rubber layer are formed of the inner liner rubber composition and the tie rubber rubber composition.

The rubber composition for tie rubber has 3 to 50 parts by mass of an inorganic filler in 100 parts by mass of a diene-based rubber. Examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like. It is preferable that the natural rubber is contained in an amount of 30 to 70% by mass based on 100% by mass of the diene rubber.

Examples of the inorganic filler include clay, talc, calcium carbonate, magnesium oxide, mica, bituminous coal and the like. Among them, at least one selected from clay, talc, calcium carbonate, and magnesium oxide is preferable. In this specification, carbon black is excluded from the types of inorganic fillers.

The aspect ratio Ar of the inorganic filler is preferably 0.5 to 0.95, more preferably 0.5 to 0.9, and even more preferably 0.6 to 0.9. By setting the aspect ratio Ar of the inorganic filler within such a range, it is possible to secure tackiness, adhesiveness, etc. while suppressing air permeability resistance. In the present specification, the aspect ratio Ar measures 50% particle size Ds by the centrifugal sedimentation method using a Cedigrag 5100 particle size measuring device manufactured by Micromeritex Instrument Co., Ltd., and a laser Malvern Mastersizer 2000 diffraction manufactured by Malvern Co., Ltd. The 50% particle diameter Dl can be measured using the formula particle distribution measuring device, and can be obtained by the following formula (1).
Ar = (Ds-Dl) / Ds (1)
(In the formula, 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 diameter determined by the cumulative distribution measured by the laser diffraction method of coherent light. Represents the diameter.)

The inorganic filler is blended in an amount of 3 to 50 parts by mass, preferably 5 to 30 parts by mass, based on 100 parts by mass of the diene rubber. In the present specification, it is assumed that the blending amount of the inorganic filler with respect to 100 parts by mass of the diene rubber is A _{tie mass parts.} If the blending amount of the inorganic filler is less than 3 parts by mass, the effect of reducing the air permeability cannot be sufficiently obtained. Further, when the blending amount of the inorganic filler exceeds 50 parts by mass, the molding processability is lowered, the non-defective product rate is lowered, the tire is liable to fail, and the tire durability is lowered.

In the pneumatic tire of the present invention, the difference between _{the 100% deformation tensile stress (M tie} ) of the rubber composition for tie rubber and the 100% deformation tensile stress (M _{IL ) of the rubber composition for inner liner (M tie −} M _IL ). Is 0 to 2.0 MPa, preferably 0 to 1.5 MPa. By setting the difference in 100% deformation tensile stress (M _tie - _MIL ) within such a range, it is possible to suppress the occurrence of opening of the mouth during tire molding and increase the non-defective rate. Further, when the tire is deformed, the stress concentration can be reduced and the tire durability can be improved. In the present specification, 100% tensile deformation stress of the tie rubber for the rubber composition (M _tie) and 100% deformation tensile stress of the inner liner rubber composition (M _IL) conforms to JIS K6251, 3 No. dumbbell test The piece shall be subjected to a tensile test under the conditions of 20 ° C. and a tensile speed of 500 mm / min, and the tensile stress at 100% elongation shall be measured.

In the rubber composition for an inner liner, an inorganic filler can be blended in an _{A IL mass part in 100 parts by mass of the rubber component.} The blending amount of the inorganic filler (A _IL mass part) in the rubber composition for the inner liner can be determined by the ratio with the blending amount of the inorganic filler (A _{tie mass portion) in the rubber composition for tie rubber.} The ratio (A _IL / A _tie ) of the blending amount of the inorganic filler of the rubber composition for the inner liner (A _IL mass part) and the blending amount of the inorganic filler of the _tie rubber rubber composition (A tie mass part) is preferably 2. It is 3/3 or less, more preferably 1/5 to 1/3. By setting the ratio of the blending amount of the inorganic filler (A _IL / A _tie ) to 2/3 or less, the difference in 100% deformation tensile stress between the rubber composition for _{tie rubber and the rubber composition for inner liner (M tie-} M _IL). ) Can be easily optimized. The inorganic filler contained in the rubber composition for the inner liner can be appropriately selected from clay, talc, calcium carbonate, magnesium oxide, mica, bituminous coal and the like. The inorganic filler contained in the rubber composition for inner liner may be of the same type or different from the inorganic filler contained in the rubber composition for tie rubber.

The rubber component of the rubber composition for the inner liner is mainly butyl rubber composed of butyl rubber, brominated butyl rubber, chlorinated butyl rubber and the like. That is, it is preferable that the butyl rubber is contained in an amount of 50% by mass or more, preferably 70 to 100% by mass, based on 100% by mass of the rubber component. The rubber composition for the inner liner can contain a rubber component other than the butyl rubber. Examples of other rubber components include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and the like.

In the present invention, the rubber composition for tie rubber and the rubber composition for inner liner may contain, in addition to the above-mentioned compounding agent, a compounding agent to be blended in a normal rubber composition for tie rubber and a rubber composition for inner liner. can. That is, the present invention comprises various additives generally used in rubber compositions such as vulcanization agents / cross-linking agents, vulcanization accelerator aids, antiaging agents, scouring accelerators, various oils, and plasticizers. Such additives can be kneaded by a general method to obtain a rubber composition for tie rubber and a rubber composition for an inner liner, and can be used for vulcanization or crosslinking.

Hereinafter, the present invention will be further described with reference to Examples, but the scope of the present invention is not limited to these Examples.

Ten kinds of rubber compositions for tie rubber (Standard Example, Examples 1 to 5, Comparative Examples 1 to 4) having the common composition shown in Table 2 and having the composition shown in Table 1 are prepared. In the formulation of the rubber composition for Thai rubber, the components excluding sulfur and the vulcanization accelerator were weighed and kneaded with a 1.7 L sealed Banbury mixer for about 5 minutes, and the obtained mixture was released and cooled to room temperature. The cooled mixture was subjected to a roll, sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for Thai rubber. The ratio (A _IL / A _{tie ) of the blending amount (A IL} ) of the inorganic filler in the rubber composition for inner liner below to the blending amount (A _tie ) of the inorganic filler in the rubber composition for tie rubber was calculated. It is described in Table 1.

Three types of rubber compositions for inner liners (compositions A, B, and C) having the formulations shown in Table 3 are weighed with components excluding sulfur and a vulcanization accelerator, and about 5 with a 1.7 L sealed Banbury mixer. After kneading for minutes, the resulting mixture was released and cooled to room temperature. The cooled mixture was subjected to a roll, sulfur and a vulcanization accelerator were added and mixed to prepare a rubber composition for an inner liner.

Using the obtained rubber composition for tie rubber and rubber composition for inner liner, vulcanize and mold at 160 ° C. for 30 minutes using a mold having a predetermined shape to prepare a test sample, and 100 by the method shown below. % Tensile stress was measured. Moreover, the air permeability was measured by the method shown below using the test sample of the rubber composition for tie rubber.

100% tensile stress From the obtained test sample, a JIS No. 3 dumbbell type test piece was cut out in accordance with JIS K6251. A tensile test was conducted under the conditions of a temperature of 20 ° C. and a tensile speed of 500 mm / min in accordance with JIS K6251, and the tensile stress at 100% elongation was measured. The results obtained are shown in Tables 1 and 3. Also to calculate the difference between 100% tensile stress and 100% tensile stress (M _tie) and the inner liner rubber composition for the tie rubber for the rubber composition _{(M IL) (M tie -M} IL), as described in Table 1.

Air permeability The air permeability of the obtained test sample of the rubber composition for tie rubber is determined in accordance with JIS K7126 "Plastic film and sheet-Gas permeability test method-Part 1: Differential pressure method". Was measured. The reciprocal of the obtained air permeability coefficient was calculated and used as an index with the standard example as 100, and is shown in the column of "Air permeability of Thai rubber" in Table 1. The larger this index is, the smaller the air permeability is and the better the barrier property is.

As shown in Table 1, 10 types of rubber compositions for tie rubber (Standard Examples, Examples 1 to 5, Comparative Examples 1 to 4) and 3 types of rubber compositions for inner liners (compositions A, B, C). ) And a tire size (195 / 65R15) pneumatic tire was vulcanized and molded. Here, when manufacturing 1000 pneumatic tires each, the good product rate from green molding to vulcanization molding was obtained, and the standard example was set to 100, which was set as an index and described in "Good product rate during tire molding" in Table 1. .. The higher this index, the higher the non-defective rate and the better.
Further, using the obtained pneumatic tire, the tire durability test and the tire air leakage performance were measured by the methods shown below.

Tire durability test The obtained pneumatic tire was assembled to the JATTA standard rim, and a steel drum tester with a diameter of 1707 mm was used to control the ambient temperature to 38 ± 3 ° C., internal pressure 200 kPa, load 4 The mileage until a tire failure occurred at 0.7 kN and a speed of 80 km / h was calculated. The obtained results were indexed with the standard example as 100 and listed in the "Tire durability" column of Table 1. The larger this index is, the better the tire durability is.

Tire air leakage performance A pneumatic tire was assembled on a JATTA standard rim and pressurized to an air pressure of 230 kPa. After each pneumatic tire was left at room temperature for one month, the air pressure was measured and the amount of air leakage (air pressure leakage rate) was calculated. The obtained results are shown in the column of "tire air leakage performance" in Table 1 by calculating the reciprocal of each and making an index with the standard example as 100. The larger this index is, the less air leaks, and the better the tire air leak performance.

The types of raw materials used in Table 1 are shown below.
-NR: natural rubber, TSR20, Tg: -65 ° C
-SBR: Styrene butadiene rubber, Nippon Zeon Nipol 1520, Tg: -60 ° C
-Carbon black: Tokai Carbon Co., Ltd. Seast V, nitrogen adsorption specific surface area: 27 m ² / g
・ Clay: Catalpo Y-K manufactured by Sanyo Clay, aspect ratio Ar: 0.85
・ Talc: Mistron vapor manufactured by Japan Mistron, aspect ratio Ar: 0.65

The types of raw materials used in Table 2 are shown below.
・ Zinc oxide: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: Beaded stearic acid manufactured by NOF Corporation ・ Resin: Hitanol 1502Z manufactured by Hitachi Kasei Kogyo Co., Ltd.
・ Sulfur: Shikoku Kasei Kogyo Co., Ltd. Mucron OT-20
・ Vulcanization accelerator: Noxeller CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

The types of raw materials used in Table 3 are shown below.
-IIR: Butyl rubber, EXXON BROMOBUTYL 2255 manufactured by ExxonMobil
-NR: natural rubber, TSR20, Tg: -65 ° C
-Carbon black: Tokai Carbon Co., Ltd. Seast V, nitrogen adsorption specific surface area: 27 m ² / g
・ Clay: Catalpo Y-K manufactured by Sanyo Clay, aspect ratio Ar: 0.85
・ Zinc oxide: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: Bead stearic acid manufactured by NOF Corporation ・ Sulfur: Mucron OT-20 manufactured by Shikoku Kasei Kogyo Co., Ltd.
・ Vulcanization accelerator: Noxeller CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

As is clear from Table 1, the pneumatic tires of Examples 1 to 6 are excellent in molding processability, low air permeability and tire durability.

In the pneumatic tire of Comparative Example 1, the rubber composition for tie rubber does not contain an inorganic filler, and the rubber composition for an inner liner contains an inorganic filler, so that the non-defective rate at the time of tire molding deteriorates.
The pneumatic tire of Comparative Example 2, the tie rubber for the rubber composition contains no inorganic filler, the difference between 100% deformation tensile stress (M _tie -M _IL) exceeds 2.0 MPa, the yield rate at the time of tire molding And tire durability deteriorates.
In the pneumatic tire of Comparative Example 3, the inorganic filler exceeds 50 parts by mass and the difference in 100% deformation tensile stress (M _tie - _MIL ) exceeds 2.0 MPa in the rubber composition for tie rubber, so that during tire molding. The non-defective rate and tire durability deteriorate.
The pneumatic tire of Comparative Example 4, the rubber composition for the tie rubber, the difference in a 100% deformation tensile stress (M _tie -M _IL) because less than 0 MPa, the yield rate at the time of tire molding is remarkably deteriorated.

Claims (4)

The rubber composition for tie rubber having an inner liner layer, a tie rubber layer and a carcass layer from the inside to the outside in the tire radial direction and forming the tie rubber layer comprises 100 parts by mass of a diene rubber and 3 to 50 parts by mass of an inorganic filler. The difference (M _{tie −} M _IL ) between the 100% deformation tensile stress (M _{tie ) and the 100% deformation tensile stress (M IL} ) of the rubber composition for the inner liner forming the inner liner layer is 0. Pneumatic tires characterized by ~ 2.0 MPa. The pneumatic tire according to claim 1, wherein the inorganic filler has an aspect ratio Ar of 0.5 to 0.95. _{The rubber composition for an inner liner has an A IL} mass part in 100 parts by mass of the rubber component thereof, and the blending amount of the inorganic filler with respect to 100 parts by mass of the diene rubber in the rubber composition for _{tie rubber is tie.} The pneumatic tire according to claim 1 or 2, wherein _{the ratio (A IL} / A _tie ) of the blending amounts of these inorganic fillers is 0 or more and 2/3 or less in terms of parts by mass. The pneumatic tire according to any one of claims 1 to 3, wherein the inorganic filler contained in the rubber composition for tie rubber is at least one selected from clay, talc, calcium carbonate, and magnesium oxide.