JP5004457B2 - Rubber composition for tire and pneumatic tire using the same - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention can be used for an inner liner and / or insulation of a pneumatic tire, and can provide a pneumatic tire that has good rubber properties even with a small gauge, is lightweight, and has excellent durability performance. The present invention relates to a tire rubber composition and a pneumatic tire using the same.

  2. Description of the Related Art In recent years, tire rolling resistance has been reduced and weight has been reduced based on social demands for lower fuel consumption of vehicles. As a method for reducing the weight of a tire, a method of reducing the gauge (thickness) of rubber at each portion is conceivable. However, if the gauge is simply reduced, the durability performance required for the tire may be lost.

  If the tire inner liner or the gauge of the insulation between the inner liner and the ply is made small, the rubber of the inner liner and the insulation is sucked up between the plies due to the pressure from the bladder during molding vulcanization. There is a phenomenon that the ply cord appears to be exposed when viewed from the inside. When this phenomenon occurs, the durability performance of the tire is significantly reduced.

  Further, particularly when reducing the gauge of the inner liner, if the air permeability of the inner liner is increased, the internal pressure holding performance of the tire is lowered, which causes a decrease in durability performance. As a method for reducing the air permeability of the inner liner, for example, a method of filling a rubber composition for an inner liner with mica to form a laminate structure of three or more layers has been proposed. Since a process is required, it is not advantageous in terms of cost.

  In Patent Document 1, as a method of reducing the air permeability of the inner liner layer, a method of using, for an insulation layer, a rubber composition containing organic short fibers and having a rubber component composed of an epoxidized natural rubber and a diene rubber. Has been proposed. However, in this method, organic short fibers need to be newly spun and cut, so there is room for further improvement in terms of cost.

Patent Document 2 contains waste paper, for example, a rubber composition used for bead apex, Patent Document 3 contains a tire rubber composition containing waste paper and silica, and Patent Document 4 contains short fibers, waste paper. And rubber compositions for studless tires containing silica have been proposed, but methods for maintaining good rubber physical properties and tire durability even when the inner liner and insulation gauge are reduced are considered. Absent.
JP 7-82420 A JP 2002-37929 A JP 2002-226634 A Japanese Patent Laid-Open No. 2002-249619

  The present invention solves the above-mentioned problems, and produces a pneumatic tire having good rubber properties, light weight and good durability even when the gauge of the inner liner rubber and / or the insulation rubber is reduced. An object of the present invention is to provide a rubber composition and a pneumatic tire using the rubber composition.

  The present invention relates to a rubber composition for tires used as an inner liner rubber and / or an insulation rubber of a pneumatic tire, and an average major axis (A) and an average minor axis (B) with respect to 100 parts by mass of a rubber component. ) And a rubber composition for a tire formed by blending paper fibers having a ratio (A) / (B) within a range of 1.1 to 30 within a range of 1 to 15 parts by mass.

  The average length (C) of the paper fibers blended in the present invention is preferably in the range of 10 to 1000 μm.

  Moreover, it is preferable that ratio (C) / (A) of the average length (C) of paper fiber and an average major axis (A) exists in the range of 10-2000.

  The present invention also relates to a pneumatic tire in which the rubber composition for tire is used as at least an insulation rubber, and an insulation gauge is set within a range of 0.5 to 2.0 mm.

  The present invention also relates to a pneumatic tire using the above rubber composition for a tire as at least an inner liner rubber. In this case, it is more preferable that the gauge of the inner liner be in the range of 0.5 to 2.0 mm.

  The rubber composition of the present invention is used for an inner liner rubber and / or an insulation rubber, and good rubber properties are secured even if the gauge of the insulation rubber and / or the inner liner rubber is reduced. Therefore, according to the present invention, it is possible to obtain a pneumatic tire that is light in weight and excellent in durability performance, which is effective for reducing fuel consumption of a vehicle.

  The rubber composition for tires of the present invention is used as an inner liner rubber and / or an insulation rubber of a pneumatic tire. Inner liner rubber is a member to ensure air seal performance at the innermost side of the tire, and insulation rubber improves adhesion between the case and inner liner on the inner side of the case, and sucks up the inner liner rubber during vulcanization. It is a member for preventing. In the tire rubber composition of the present invention, the ratio (A) / (B) of the average major axis (A) to the average minor axis (B) is 1.1 to 30 with respect to 100 parts by mass of the rubber component. The paper fiber which is in the range is blended in the range of 1 to 15 parts by mass.

  In the present invention, flat paper fibers are contained in the rubber composition, and when the unvulcanized rubber composition is formed into a sheet by extrusion, the longitudinal direction of the paper fibers and the sheet extrusion direction are generated by shearing force. It is easy to arrange the paper fiber so that the major axis direction and the sheet width direction of the paper fiber and the minor axis direction of the paper fiber and the sheet thickness direction are horizontal. When such a rubber composition is used for an inner liner and particularly for an insulation, the paper fiber in the rubber composition is applied to the inner liner and the insulation in the internal pressure filling process by the bladder against the pressure of the bladder. The sucking phenomenon between the unvulcanized rubber compositions between the ply cords is suppressed, and the inner liner and the insulation are vulcanized and molded into a desired shape. This can prevent the ply cord from being exposed and improve the durability of the tire.

  In particular, by using the tire rubber composition of the present invention for the inner liner, higher air leak resistance can be ensured, and therefore the gauge of the inner liner can be reduced.

  If the ratio (A) / (B) of the average major axis (A) to the average minor axis (B) of the paper fiber is 1.1 or more, the paper fiber has a sufficiently flat shape, and thus the above suction phenomenon. If it is 30 or less, the processability at the time of manufacturing the rubber composition is not impaired. The ratio (A) / (B) is particularly preferably in the range of 2 to 25, and more preferably in the range of 3 to 20. The average major axis (A) can be calculated as the number average value of the major axis of each paper fiber obtained by image measurement in, for example, cross-sectional observation of the paper fiber by SEM (scanning electron microscope), and the average minor axis (B) is It can be calculated as the number average value of the minor axis of each paper fiber obtained by the same image measurement.

  In the present invention, the paper fiber is blended in the range of 1 to 15 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of the paper fiber with respect to 100 parts by mass of the rubber component is 1 part by mass or more, the effect of suppressing the above-mentioned sucking phenomenon is obtained, and if it is 15 parts by mass or less, the hardness of the rubber composition is prevented from becoming too large. The tire characteristics such as ride comfort performance can be ensured, and the processability during the production of the rubber composition is not impaired. The blending amount of the paper fiber is particularly preferably in the range of 2 to 10 parts by mass, and more preferably in the range of 3 to 8 parts by mass.

  In the present invention, the average length (C) of the paper fibers is preferably in the range of 10 to 1000 μm. When the average length (C) is 10 μm or more, the suppression effect of the sucking phenomenon is good. When the average length (C) is 1000 μm or less, the hardness of the rubber composition is prevented from becoming too large, and tire characteristics such as riding comfort performance are improved. It can be ensured and the processability during the production of the rubber composition is not impaired. The average length (C) of the paper fibers is preferably in the range of 50 to 1000 μm. The average length (C) of the paper fibers can be calculated as, for example, the number average value of the lengths of the respective paper fibers obtained by image measurement in the observation of the paper fibers with an SEM (scanning electron microscope).

  Moreover, it is preferable that ratio (C) / (A) of the average length (C) of paper fiber and an average major axis (A) shall be in the range of 10-2000. When the ratio (C) / (A) is 10 or more, the suppression effect of the sucking phenomenon is good. When the ratio (C) / (A) is 2000 or less, the hardness of the rubber composition is prevented from being excessively increased, and riding comfort performance, etc. The tire characteristics can be secured and the processability during the production of the rubber composition is not impaired. The ratio (C) / (A) is preferably in the range of 20 to 2000.

  Since the rubber composition for tires of the present invention has an effect of suppressing rubber sucking, it is useful as tire insulation. In this case, the gauge of the insulation is preferably set within a range of 0.5 to 2.0 mm. When the gauge of insulation is 0.5 mm or more, the durability performance of the tire is good, and when it is 2.0 mm or less, the effect of reducing fuel consumption due to weight reduction of the tire is good. It is particularly preferable that the gauge of the insulation is further in the range of 0.6 to 1.0 mm.

  Moreover, since the rubber composition for tires of the present invention has an effect of improving air leak resistance, it is useful as an inner liner. In this case, the gauge of the inner liner is preferably in the range of 0.5 to 2.0 mm. When the gauge of the inner liner is 0.5 mm or more, the durability performance of the tire is good, and when it is 2.0 mm or less, the effect of reducing fuel consumption by reducing the weight of the tire is good. It is particularly preferable that the gauge of the inner liner is further in the range of 0.6 to 1.0 mm.

  Examples of the paper fiber to be blended in the present invention include newspaper, kraft paper, pulp pulverized material, etc., but when the rubber composition of the present invention is used for insulation, a paper fiber made of kraft paper is particularly preferred. Preferably used. Kraft paper refers to all paper obtained by making kraft pulp (KP), and includes unbleached kraft paper and bleached kraft paper. Kraft pulp is the mainstream of those classified as chemical pulp, and since it has a relatively long fiber length, kraft paper is widely used for packaging applications and the like as paper having excellent strength.

  Kraft pulp is generally produced by the following method. First, impurities of the chip as a raw material are removed, and the thickness, length, etc. are made uniform within a certain range. Next, the chips are steamed with chemicals such as caustic soda and sodium sulfide at a high temperature of, for example, about 150 to 160 ° C. to elute mainly lignin in the chips and pulp. After passing through a washing step for separating the eluted lignin and chemicals from the pulp, the pulp is further treated with oxygen and alkali to further elute residual lignin in the pulp. Finally, foreign matter is removed and washed to obtain unbleached kraft pulp. Unbleached kraft pulp can be made bleached kraft pulp through a bleaching process. By making unbleached kraft pulp, unbleached kraft paper and by making bleached kraft pulp can be produced.

  As the kraft pulp used as the raw material for kraft paper, either softwood kraft pulp or hardwood kraft pulp can be used. Moreover, all of the raw material of the kraft paper may be virgin kraft pulp, but derived from pulp, kenaf, bagasse, bamboo, cotton, seaweed, etc. obtained by other pulping methods such as semi-chemical pulp and mechanical pulp Non-wood pulp, used copy paper, used newspaper, used paper pulp obtained by deinking used paper, etc. may be mixed to the extent that desired properties are not impaired.

  The rubber hardness of the tire rubber composition of the present invention can be in the range of 40 to 65. When the hardness is 40 or more, it is preferable from the viewpoint of excellent effect of suppressing the rubber sucking, and when it is 65 or less, it is preferable from the viewpoint that crack growth from the inner liner can be suppressed. The rubber hardness can be measured according to ISO-7619.

  As the rubber component of the present invention, natural rubber (NR) and / or diene synthetic rubber is preferably used. Diene-based synthetic rubbers include styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR). Butyl rubber (IIR) and the like, and rubber components containing one or more of these are preferred. The ethylene-propylene-diene rubber (EPDM) is an ethylene-propylene rubber (EPM) containing a third diene component. Examples of the third diene component include non-conjugated dienes having 5 to 20 carbon atoms such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5. -Hexadiene and 1,4-octadiene, cyclic dienes such as 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5 Preferred examples include alkenyl norbornene such as -norbornene and 2-isopropenyl-5-norbornene. In particular, dicyclopentadiene, 5-ethylidene-2-norbornene and the like can be preferably used.

  In the rubber composition for tires of the present invention, a silane coupling agent, preferably a sulfur-containing silane coupling agent, is added in an amount of 0.1 to 10 parts by mass, preferably 0.5 to 100 parts by mass of the rubber component. It is preferable to blend in an amount of 3 parts by mass or more. Steering stability can be improved by blending the silane coupling agent. When the blending amount of the silane coupling agent is 0.1 parts by mass or more, the steering stability improving effect is particularly good. Moreover, when the compounding quantity of a silane coupling agent is 10 mass parts or less, there is little danger that the rubber | gum kneading | mixing and the burning (scorch) in an extrusion process will arise.

  In the present invention, other coupling agents such as aluminate coupling agents and titanium coupling agents can be used alone or in combination with a silane coupling agent depending on the application.

  In the tire rubber composition of the present invention, fillers such as calcium carbonate, silica, clay, alumina, talc, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide are used alone or in combination. Can be used.

Carbon black may also be used in the tire rubber composition of the present invention. Here, the carbon black is preferably 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the rubber component. The physical properties of carbon black are such that the nitrogen adsorption specific surface area (BET method) is in the range of 20 to 300 m ² / g, the DBP oil absorption is in the range of 5 to 300 ml / 100 g, and the iodine adsorption is in the range of 100 to 170 mg / g. The inner one is suitable in terms of the reinforcing effect on the tire rubber composition.

  In addition to the above, a vulcanizing agent, a vulcanization accelerator, a softening agent, a plasticizer, an anti-aging agent, a foaming agent, an anti-scorch agent, and the like can be added to the tire rubber composition of the present invention. .

  As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy-diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di- t-butylperoxy-3,3,5-trimethylsiloxane, n-butyl-4,4 And the like can be used di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

  Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Examples thereof include sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide.

  Examples of the thiazole type include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Phenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole and the like.

  Examples of thiurams include TMTD (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide. , Tetrabutyl thiuram disulfide, pentamethylene thiuram tetrasulfide and the like.

  Examples of thiourea compounds include thiourea compounds such as thiacarbamide, diethyl thiourea, dibutyl thiourea, trimethyl thiourea, and diortolyl thiourea.

  Examples of guanidine compounds include guanidine compounds such as diphenyl guanidine, diortolyl guanidine, triphenyl guanidine, orthotolyl biguanide, and diphenyl guanidine phthalate.

Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate Such Okarubamin acid compounds.

  Examples of the aldehyde-amine system or aldehyde-ammonia system include acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, and the like.

  As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

  In the present invention, a softener may be used in combination in order to further improve kneading processability. Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum jelly such as petroleum jelly, fatty oil softener such as castor oil, linseed oil, rapeseed oil, coconut oil, tall oil, , Waxes such as beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid.

  Furthermore, a plasticizer can be mix | blended with the rubber composition for tires of this invention as needed. Specifically, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Acid diisodecyl), BBP (butylbenzyl phthalate), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), DOS (Dioctyl sebacate), acetyl triethyl citrate, acetyl tributyl citrate, DBM (dibutyl maleate), DOM (2-ethylhexyl maleate), DBF (dibutyl fumarate) and the like.

  The tire rubber composition of the present invention includes, as a scorch inhibitor for preventing or retarding scorch, for example, organic acids such as phthalic anhydride, salicylic acid, benzoic acid, nitroso compounds such as N-nitrosodiphenylamine, N-cyclohexyl Thiophthalimide or the like can be used.

  The rubber composition for tires of the present invention is suitably used for pneumatic tires, and particularly preferably used for inner liner parts and insulation parts. Hereinafter, it demonstrates according to drawing. FIG. 1 is a diagram illustrating a left half of a cross-sectional view of a pneumatic tire according to the present invention, and FIG. 2 is an enlarged cross-sectional view illustrating an installation portion and an inner liner portion of the pneumatic tire according to the present invention. is there. The tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 positioned at an inner end of each sidewall portion 3. A carcass 6 is bridged between the bead portions 4 and 4, and a belt layer 7 having a tagging effect is disposed on the outer side in the radial direction of the carcass 6.

  The carcass 6 is formed of one or more carcass plies 6a in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C, for example. The bead portion 4 is bent around the bead core 5 from the inner side to the outer side in the tire axial direction and locked.

  The belt layer 7 is composed of two or more belt plies 7a and 7b in which belt cords are arranged at an angle of 45 ° or less with respect to the tire equator C, for example. It is location. Further, a band layer (not shown) may be provided on the outer side of the belt layer 7. At this time, the band layer is formed by a continuous ply in which a low modulus organic fiber cord is spirally wound substantially parallel to the tire equator C.

  A bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 that forms a tire lumen surface and the inner liner rubber 9 are disposed inside the carcass 6. And the carcass 6 are adjacent to each other, and the outside of the carcass 6 is protected by the chafer rubber 4G and the side wall rubber 3G.

  The tire rubber composition according to the present invention can be used as an inner liner rubber 9 and an insulation rubber 10 in a pneumatic tire, particularly when the gauge of the inner liner rubber or the insulation rubber is reduced. In addition, good tire durability is given by good rubber properties. In addition, the structure of the pneumatic tire in which the rubber composition for tires of this invention is used is not limited to the above-mentioned thing.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  Of the blending components (unit: parts by mass) shown in Table 1 and Table 2, components other than sulfur and a vulcanization accelerator were kneaded at 150 ° C. for 4 minutes using a 1.7 L Banbury manufactured by Kobe Steel. Subsequently, sulfur and a vulcanization accelerator were added and kneaded for 4 minutes at 80 ° C. using a biaxial roller. Using the obtained unvulcanized rubber composition, rubber sheets of gauges shown in Tables 1 and 2 were prepared as installation rubbers and inner liner rubbers, and used for the tire installation parts and inner liner parts. It was molded and vulcanized at 150 ° C. for 35 minutes under the conditions of 25 kf (245.16625N) to produce a 175 / 70R13 test tire.

<Appearance evaluation>
For the test tires prepared using the blending components shown in Table 1, the inside appearance of the tire was visually observed, and the presence or absence of the sucking phenomenon of the insulation rubber and the inner liner rubber between the carcass ply cords, that is, the ply cords Checked for exposure. Table 1 shows the results of the presence or absence of the sucking phenomenon.

<Machine durability test>
Test tires prepared using the ingredients shown in Table 1 and Table 2 were placed in an oven at 80 ° C. for 1 week, and then traveled for 30,000 km at an internal pressure of 200 kPa, a load of 340 kgf (333.261 N), and a speed of 80 km / h. Then, the presence or absence of damage to the inner liner and insulation, that is, the presence or absence of cracks was evaluated visually. The results are shown in Tables 1 and 2.

<Evaluation of air permeability>
The inner liner and the insulation part of the test tire prepared by the above method are cut to prepare a sample having a diameter of 90 mm and a thickness of 1 mm as a test rubber composition, and the air permeation amount is measured according to ASTM D-1434-75M. The air permeability coefficient (cc · cm / cm ² · sec · cmHg) was calculated. For the measurement, a constant temperature gas permeability measuring device M-C1 manufactured by Toyo Seiki Seisakusho Co., Ltd. was used. The results are shown in Table 2.

<Tensile test>
Using the rubber composition for test produced by the above method, the tensile strength was evaluated using dumbbell-shaped No. 3 based on JIS K6251. The results are shown in Table 2.

<Bending crack test>
Using the test rubber composition produced by the above method, a sample was produced based on JIS K6260, and 30% strain was applied to evaluate the number of occurrences of bending cracks. The results are shown in Table 2.

<Air leak test>
After using the test tires prepared using the blending components in Table 2, the rim was assembled, the internal pressure was set to 200 kPa, and the degree of decrease in the internal pressure was calculated by the following formula by placing it in an 80 ° C. oven for one week.
(Internal pressure of each Example or Comparative Example: MPa) / (Internal pressure of Comparative Example 3: MPa) The larger the index, the better the internal pressure retention performance.

  The inner liner gauge was the same in all examples, comparative examples, and conventional examples.

Note 1: Natural rubber is RSS # 3 made in Thailand.
Note 2: SBR is “SBR1502” manufactured by Sumitomo Chemical.
Note 3: Carbon black is “N660” manufactured by Mitsubishi Chemical Corporation.
Note 4: Calcium carbonate is “Success 200S” manufactured by Omi Chemical Co., Ltd.
Note 5: Paper fiber is “Mill Five # 100” (average length 1000 μm, average length / short diameter = 10) manufactured by Sankyo Flour Milling Co., Ltd.
Note 6: Stearic acid is “paulownia” manufactured by NOF Corporation.
Note 7: Zinc oxide is “Silver R” manufactured by Toho Zinc Co., Ltd.
Note 8: The adhesive resin is “SP1068” manufactured by Nippon Shokubai Co., Ltd.
Note 9: Process oil is “Diana Process PS32” manufactured by Idemitsu Kosan Co., Ltd.
Note 10: Sulfur is manufactured by Tsurumi Chemical Co., Ltd.
Note 11: The vulcanization accelerator is “Sun Cellar CM” (N-cyclohexyl-2-benzothiazyl-sulfenamide) manufactured by Sanshin Chemical Co., Ltd.
Note 12: Halogenated butyl rubber is “bromobutyl 2255” (brominated butyl rubber) manufactured by Nippon Butyl Co., Ltd.

  As shown in Table 1, in each of the comparative examples, the sucking phenomenon and / or cracking of the insulation rubber and the inner liner rubber was observed, whereas in Examples 1 to 4, the insulation rubber and the inner liner Neither rubber sucking up nor cracking was observed.

As shown in Table 2, in Comparative Example 3 in which no paper fiber was blended, the amount of air permeation and the number of bending cracks were large. In Comparative Example 4 in which the amount of paper fiber was large, the tensile strength and machine durability were not good. On the other hand, in Reference Examples 1 and 2 , good results were obtained in the amount of air permeation, tensile strength, flex crack, air leak, and machine durability. The rubber composition for tires of the present invention is resistant to flex crack. It can be seen that it is excellent in physical strength and durability and has low air permeability.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rubber composition for tires of the present invention is used for inner liners and / or insulation of pneumatic tires. A pneumatic tire using the rubber composition for a tire is lightweight and excellent in durability performance, and is therefore preferably used as a pneumatic tire that can reduce fuel consumption of a vehicle.

It is the figure which illustrated the left half of sectional drawing of the pneumatic tire which concerns on this invention. It is an expanded sectional view explaining the installation part and inner liner part of the pneumatic tire which concern on this invention.

Explanation of symbols

  1 tire, 2 tread portion, 3 sidewall portion, 3G sidewall rubber, 4 bead portion, 4G chafer rubber, 5 bead core, 6 carcass, 6a carcass ply, 7 belt layer, 7a, 7b belt ply, 8 bead apex rubber , 9 Inner liner rubber, 10 Insulation rubber.

Claims (5)

A rubber composition for a tire used as an inner liner rubber and / or an insulation rubber of a pneumatic tire, wherein an average major axis (A) and an average are obtained with respect to 100 parts by mass of a rubber component composed of natural rubber and styrene butadiene rubber. The ratio (A) / (B) to the minor axis (B) is in the range of 3 to 20 , and the paper fiber having the average length (C) in the range of 50 to 1000 μm is in the range of 1 to 15 parts by mass. A rubber composition for tires, which is formulated inside. 2. The tire rubber composition according to claim 1, wherein a ratio (C) / (A) of the average length (C) of the paper fibers to the average major axis (A) is within a range of 20 to 2,000.   A pneumatic tire in which the rubber composition for tire according to claim 1 or 2 is used as at least an insulation rubber, and an insulation gauge is set within a range of 0.5 to 2.0 mm.   A pneumatic tire using the tire rubber composition according to claim 1 as at least an inner liner rubber.   The pneumatic tire according to claim 4, wherein a gauge of the inner liner is in a range of 0.5 to 2.0 mm.

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