JP4080467B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a two-layer sidewall.

  In recent years, in order to protect the global environment, energy saving of resources (in the case of automobiles, low fuel consumption) has been demanded. For this reason, reduction in rolling resistance is also demanded for automobile tires, and in particular, heavy reduction in rolling resistance is desired for heavy duty tires used in heavy vehicles such as trucks and buses with large displacement and heavy fuel consumption. ing.

  The rolling resistance of the tire is largely attributed to energy loss accompanying repeated deformation during traveling. Therefore, in order to reduce rolling resistance, for example, the rubber of the tread portion having the highest contribution ratio (about 34%) is made into two layers, the compounded rubber having a small energy loss is provided on the inside, and the grip performance is excellent on the outside. A structure with each compounded rubber has been proposed.

  However, the tread part has a large contribution ratio to the reduction of rolling resistance, but also has a large contribution ratio to wear resistance performance, performance on snow and snow, wet grip performance, etc. In general, there is often a trade-off relationship. Therefore, there is a problem that the above-mentioned traveling performance is easily impaired by reducing the rolling resistance.

  On the other hand, Patent Document 1 discloses a pneumatic tire having a two-layered sidewall, but the rolling resistance has not been sufficiently reduced.

JP-A-4-362405

  The present invention provides a heavy duty tire that reduces rolling resistance and further reduces costs without impairing running performance such as wear resistance, performance on ice and snow, and wet grip performance, and further, durability of the sidewall portion. It is an object.

  The present invention relates to a pneumatic tire having two sidewalls, an inner layer and an outer layer, wherein the ratio of the thickness of the sidewall inner layer to the thickness of the entire sidewall is 0.2 to 0.8, The present invention relates to a pneumatic tire in which the content of an anti-aging agent in the wall inner layer and the outer layer is the same.

  The sidewall inner layer preferably contains 5 to 50 parts by weight of calcium carbonate with respect to 100 parts by weight of the rubber component.

  The sidewall inner layer preferably contains 1 to 20 parts by weight of kraft paper pulverized powder with respect to 100 parts by weight of the rubber component.

  It is preferable that the complex elastic modulus of the inner wall layer is 3 to 25 MPa under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%.

  The loss tangent of the inner sidewall layer is preferably 0.03 to 0.07 under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%.

  It is preferable that the sidewall outer layer does not contain calcium carbonate.

  According to the present invention, the sidewall has a two-layer structure of an inner layer and an outer layer, the ratio of the thickness of the sidewall inner layer to the thickness of the entire sidewall is defined, and the anti-aging agent for the sidewall inner layer and the sidewall outer layer By setting the content of each to the same amount, it is possible to provide a pneumatic tire with reduced rolling resistance and reduced cost without impairing the durability of the sidewall.

  As shown in FIG. 1 (a), the pneumatic tire of the present invention has a sidewall composed of two layers: a sidewall inner layer positioned on the inner side in the tire axial direction and a sidewall outer layer positioned on the outer side.

  The thickness of the sidewall inner layer is preferably 0.4 mm or more, and more preferably 0.5 mm or more. When the thickness of the sidewall inner layer is less than 0.4 mm, the effect obtained by providing the inner layer tends to be small.

  The thickness of the sidewall outer layer is preferably 1.0 mm or more, and more preferably 1.2 mm or more. If the thickness of the sidewall inner layer is less than 1.0 mm, the bending crack resistance tends to deteriorate and cracks from the outer layer tend to grow.

The ratio of the thickness of the sidewall inner layer to the thickness of the entire sidewall is 0.2 or more, preferably 0.25 or more, more preferably 0.3 or more. If the thickness ratio of the sidewall inner layers is smaller than 0.2, the rolling resistance is not sufficiently reduced, and the cost is not reduced. Further, the ratio of the thickness of the sidewall inner layer to the thickness of the entire sidewall is 0.8 or less, preferably 0.7 or less, more preferably 0.65 or less, and further preferably 0.6 or less. When the ratio of the thickness of the sidewall inner layer to the thickness of the entire sidewall is greater than 0.8, the bending crack resistance performance is degraded. Here, the ratio of thickness represents the ratio of T _{1 to} the sum of T ₁ and T ₂ in FIG.

  The sidewall inner layer and the outer layer are made of a rubber composition containing a rubber component and an antioxidant.

  As rubber components used in the sidewall inner layer and outer layer, natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber, butadiene-isoprene rubber, styrene -Diene rubbers such as butadiene-isoprene rubber. Of these, NR and BR are preferable from the viewpoint of suppressing flex crack growth.

  Examples of the anti-aging agent include anti-aging agent 6C and the like. In particular, anti-aging agent 6C is preferably used because it has a function of moving to the sidewall surface and protecting the rubber surface from ozone.

  The content of the anti-aging agent in the sidewall inner layer is preferably 1.5 parts by weight or more and more preferably 2 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall inner layer. If the content is less than 1.5 parts by weight, sufficient anti-aging agent on the side wall surface does not reach the side wall inner layer, and on the contrary, the anti-aging agent is absorbed from the side wall outer layer. The content is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less. If the content exceeds 10 parts by weight, the cost increases.

  The content of the anti-aging agent in the sidewall outer layer is preferably 1.5 parts by weight or more and more preferably 2 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall outer layer. If the content is less than 1.5 parts by weight, ozone cracks are likely to occur from the sidewall surface. The content is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less. When the content exceeds 10 parts by weight, the cost is increased and the surface is remarkably brown.

The content of the anti-aging agent in the side wall inner layer and the content of the anti-aging agent in the side wall outer layer are the same. Here, the same amount means that the content of the anti-aging agent in the sidewall outer layer is A, and the content of the anti-aging agent in the sidewall inner layer is B. Is 0.95, preferably 0.98, and the upper limit of α is 1.05, preferably 1.03.
A = αB

  When α is larger than 1.05, that is, when the content of the antioxidant in the sidewall outer layer is larger than the content of the antioxidant in the sidewall inner layer, the migration of the antioxidant to the sidewall circular layer becomes large, Ozone craft tends to be generated from the wall surface.

  The sidewall inner layer preferably contains calcium carbonate, and the average particle size of the calcium carbonate is preferably 0.5 to 10 μm. If the average particle size is less than 0.5 μm, the cost tends to increase and the merit of filling tends to decrease. If the average particle size exceeds 10 μm, cracks tend to occur starting from the particles.

  The content of calcium carbonate in the sidewall inner layer is preferably 5 parts by weight or more and more preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall inner layer. If the content is less than 5 parts by weight, the cost tends not to be sufficiently reduced. The calcium carbonate content is preferably 50 parts by weight or less, and more preferably 45 parts by weight or less. When the content exceeds 50 parts by weight, the flex crack resistance tends to be inferior.

  The sidewall inner layer is preferably blended with pulverized kraft paper. Here, the pulverized powder of kraft paper is obtained by pulverizing kraft paper with a shredder and further finely pulverizing with a stone mill. When the sidewall inner layer contains kraft paper pulverized powder, the elastic modulus (E *) can be greatly improved while suppressing an increase in loss tangent (tan δ). By arranging the side wall inner layer containing kraft paper on the side wall, it is possible to improve the driving stability performance while reducing the fuel consumption of the vehicle.

  The content of the pulverized powder of kraft paper is preferably 1 part by weight or more and more preferably 5 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall inner layer. If the content is less than 1 part by weight, the steering stability performance is inferior or the effect of adding kraft paper tends to be small. The content of the pulverized powder of kraft paper is preferably 20 parts by weight or less, and more preferably 15 parts by weight or less. When the content exceeds 20 parts by weight, the bending crack resistance tends to be inferior or the workability tends to deteriorate.

  Under conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%, the complex elastic modulus of the sidewall inner layer is preferably 3 MPa or more, and more preferably 6 MPa or more. When the complex elastic modulus is less than 3 MPa, the steering stability performance tends to deteriorate. Further, the complex elastic modulus is preferably 25 MPa or less, and more preferably 20 MPa or less. When the complex elastic modulus exceeds 25 MPa, the flex crack resistance tends to be inferior.

  Under conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%, the loss tangent is preferably 0.03 or more. Further, the loss tangent is preferably 0.07 or less, and more preferably 0.06 or less. When the loss tangent exceeds 0.07, the rolling resistance reduction effect tends to be small.

  The sidewall inner layer can further contain carbon black.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black used in the sidewall inner layer is preferably 20 to 300 m ² / g. If N ₂ SA is less than 20 m ² / g, sufficient reinforcement tends to be difficult to obtain, and if it exceeds 300 m ² / g, dispersibility tends to deteriorate and heat generation tends to increase. Examples of the carbon black satisfying the N ₂ SA include FEF (N550), GPF (N660), SAF (N110), ISAF (N220), and HAF (N330).

  The content of carbon black in the sidewall inner layer is preferably 30 parts by weight or more and preferably 35 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall inner layer. If the carbon black content is less than 30 parts by weight, the hardness tends to be low, and the steering stability tends to deteriorate. Further, the carbon black content is preferably 80 parts by weight or less, and more preferably 70 parts by weight or less. When the carbon black content exceeds 80 parts by weight, heat generation tends to increase.

  In addition to the rubber component, anti-aging agent, calcium carbonate, kraft paper pulverized powder, and carbon black, the sidewall inner layer is a normal tire such as a vulcanizing agent, a vulcanization accelerator, zinc oxide, a softening agent, and wax. The filler used for the rubber composition can be blended.

  The sidewall outer layer in the present invention is the same vulcanizing agent, vulcanization accelerator, softening agent, zinc oxide, softening agent, wax, etc. as those used in the sidewall inner layer in addition to the rubber component and anti-aging agent described above. These fillers can be used.

  It is preferable that the sidewall outer layer does not contain calcium carbonate. By containing calcium carbonate in the sidewall outer layer, there is a disadvantage that cracks grow starting from large particles.

  The sidewall outer layer can contain carbon black.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black used in the sidewall outer layer is preferably 20 to 300 m ² / g. If N ₂ SA is less than 20 m ² / g, sufficient reinforcement tends to be difficult to obtain, and if it exceeds 300 m ² / g, dispersibility tends to deteriorate and heat generation tends to increase. Examples of the carbon black satisfying N ₂ SA include ISAF (N220), GPF (N660), SAF (N110), ISAF (N220), and HAF (N330).

  The content of carbon black in the sidewall outer layer is preferably 30 parts by weight or more and preferably 35 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall outer layer. If the carbon black content is less than 30 parts by weight, the hardness tends to be low, and the steering stability tends to deteriorate. Further, the carbon black content is preferably 80 parts by weight or less, and more preferably 70 parts by weight or less. When the carbon black content exceeds 80 parts by weight, heat generation tends to increase.

  The sidewall outer layer can contain silica. There is no restriction | limiting in particular as a silica, The thing manufactured by the wet method or a dry process can be used.

  The content of silica in the sidewall outer layer is preferably 20 parts by weight or more and more preferably 25 parts by weight or more with respect to 100 parts by weight of the rubber component in the sidewall outer layer. If the silica content is less than 20 parts by weight, the dispersibility tends to deteriorate. Further, the content of silica is preferably 60 parts by weight or less, and more preferably 55 parts by weight or less. When the silica content exceeds 60 parts by weight, heat generation tends to increase.

  The pneumatic tire of the present invention can be manufactured by a known method. For example, the above components are kneaded using a rubber kneader such as an open roll or a Banbury mixer to obtain unvulcanized rubber compositions for the sidewall inner layer and the sidewall outer layer. Each of the obtained unvulcanized rubber compositions is formed into a sheet and bonded to a predetermined shape, or is inserted into two extruders and formed into two layers at the head outlet of the extruder. A two-layer sidewall is obtained. This is laminated | stacked with another tire member on a tire molding machine, and an unvulcanized tire is formed by shape | molding by a normal method. A pneumatic tire is manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not restrict | limited only to these.

Various chemicals used in the examples will be described below.
NR: RSS # 3
BR: BR150B manufactured by Ube Industries, Ltd.
Carbon black 1: ISAF N220 (N ₂ SA: 114 m ² / g) manufactured by Mitsubishi Chemical Corporation
Carbon black 2: FEF N550 (N ₂ SA: 41 m ² / g) manufactured by Mitsubishi Chemical Corporation
Silica: Silica calcium carbonate manufactured by Degussa Co., Ltd .: White gloss flower CC (average particle size: 1 μm) manufactured by Shiroishi Kogyo Co., Ltd.
Anti-aging agent: 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock wax aroma oil manufactured by Ouchi Shinsei Chemical Industry Co., Ltd .: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Stearic acid: Tungsten zinc oxide manufactured by Nippon Oil & Fats Co., Ltd .: Ginseng R manufactured by Toho Zinc Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator CZ manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.

  Moreover, the pulverized kraft paper used in the examples was obtained by pulverizing kraft paper with a shredder and further pulverizing with a stone mill.

Examples 1-9 and Comparative Examples 1-11
<Method for producing unvulcanized rubber composition>
According to the blending contents shown in Tables 1, 2 and 3, various chemicals other than sulfur and vulcanization accelerator were kneaded at 150 ° C. for 5 minutes using a Banbury mixer. Next, by adding sulfur and a vulcanization accelerator and kneading at 80 ° C. for 5 minutes using an open roll, the rubber for the sidewall outer layers “A-1” to “A-3” and for the sidewall inner layers Rubbers “B-1” to “B-13” were obtained.

<Tire manufacturing method>
The side wall outer layer rubbers “A-1” to “A-3” and the side wall inner layer rubbers “B-1” to “B-13” obtained by the production method described above are combined according to Tables 4 to 6, respectively. Two types of rubber were laminated and extruded to form a sidewall comprising two layers, a sidewall inner layer and a sidewall outer layer. The obtained sidewall and other tire members were bonded together and vulcanized to produce a heavy-duty radial tire, which was used in the following measurements.

(Rubber hardness)
According to JIS K6253, the rubber hardness of the sample cut out from the sidewall inner layer of the radial tire at 25 ° C. was measured using a JIS-A hardness meter.

(Loss tangent (tan δ) and complex elastic modulus (E *))
A strip-shaped sample of 4 mm width × 30 mm length × 1.5 mm thickness was prepared, using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of temperature 70 ° C., frequency 10 Hz, and dynamic strain ± 2%. It was measured.

(Rolling resistance)
Using a rolling resistance tester, each tire was mounted on a regular rim (22.5 × 8.25 15 ° deep rim), and the rolling resistance was measured at an internal pressure of 700 kPa, an speed of 80 km / h, and a load of 24.52 kN. The tires of Comparative Examples 1 and 9 are shown as an index when the tire is 100. The smaller the value, the smaller the rolling resistance and the better.

(Bend crack resistance)
In accordance with a flex crack test according to JIS K6260, the resistance to flex crack growth was tested using a Dematcher flex crack tester. In the test, a sample was cut out from the tire, a prescribed crack was given, the number of bendings required for this crack to grow by 1 mm was measured, and each of Comparative Examples 1, 6 and 9 was taken as 100 and expressed as an index. It shows that it is excellent in the bending crack-proof performance, so that a numerical value is large.

(Maneuvering stability)
The test tire is mounted on the front wheel of a 2-D-4 10-ton constant load test vehicle, and the characteristics relating to handle response, rigidity, etc. are evaluated by the driver's sensory evaluation, and Comparative Examples 1 and 9 are set to 6. The point method was used for evaluation. The larger the value, the better the steering stability performance.

(cost)
Each material unit price was multiplied by the filled weight and divided by the total weight.

  The measurement results are shown in Tables 4, 5 and 6.

(A) is sectional drawing of the sidewall of the pneumatic tire in this invention, (b) is the figure which expanded the area | region X. FIG.

Explanation of symbols

1 Sidewall outer layer 2 Sidewall inner layer 3 Carcass T ₁ Side wall inner layer thickness T ₂ Side wall outer layer thickness

Claims (5)

A pneumatic tire comprising two layers of an inner layer and an outer layer,
The ratio of the thickness of the inner layer side wall to the thickness of the entire sidewall is 0.2 to 0.8, Ri content equal amount der antioxidant in addition the side wall inner and outer layers, sidewall inner layer A pneumatic tire comprising a rubber composition containing 1 to 20 parts by weight of kraft paper ground powder with respect to 100 parts by weight of the rubber component . The pneumatic tire according to claim 1, wherein the sidewall inner layer is made of a rubber composition containing 5 to 50 parts by weight of calcium carbonate with respect to 100 parts by weight of the rubber component. Temperature 70 ° C., at a frequency 10Hz and a dynamic strain of ± 2% condition, the pneumatic tire according to claim 1 or 2, wherein the sidewall lining of the complex elastic modulus is 3～25MPa. The pneumatic tire according to claim 1, 2, or 3 , wherein the loss tangent of the sidewall inner layer is 0.03 to 0.07 under conditions of a temperature of 70 ° C, a frequency of 10 Hz, and a dynamic strain of ± 2%. Sidewall outer layer, the pneumatic tire according to claim 1, 2, 3 or 4, wherein without calcium carbonate.

Images