JP4738283B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, for example, a pneumatic tire having improved steering stability performance and durability performance while maintaining ride comfort performance.

  In recent years, in addition to the remarkable enhancement of the equipment and performance of automobiles, the road network has expanded and developed, so in addition to the demand for stable maneuverability of tires, especially high braking performance at high speeds, high performance in terms of ride comfort Is being requested. In order to increase the braking performance of the tire, a method for increasing the longitudinal rigidity of the tire has been conventionally used. For example, a method using a high-hardness sidewall is known.

  For example, Japanese Patent Application Laid-Open No. 2002-37929 (Patent Document 1) discloses a rubber composition for tires in which 1 to 10 parts by weight of cut old paper is blended with 100 parts by weight of a rubber component. With the tire rubber composition disclosed in Patent Document 1, a tire with high hardness can be obtained.

JP-A-2002-249619 (Patent Document 2) discloses 2 to 15 parts by weight of short fibers, 1 to 6 parts by weight of waste paper, and 5 to 5 parts of silica based on 100 parts by weight of natural rubber and / or diene synthetic rubber. A rubber composition for studless tires containing 30 parts by weight is disclosed. With the rubber composition for studless tires disclosed in Patent Document 2, the grip performance on ice can be improved.
JP 2002-37929 A Japanese Patent Laid-Open No. 2002-249619

  However, when the tire rubber composition disclosed in Patent Document 1 is used for the sidewall portion, although the braking performance can be improved, there is a problem that durability performance and riding comfort performance required as the sidewall portion are impaired.

  Moreover, when the rubber composition for studless tires disclosed in Patent Document 2 is used for the sidewall portion, although the grip performance on ice and the wear resistance performance can be maintained, there is a problem that riding comfort performance is impaired.

  Therefore, an object of the present invention is to solve the above-described problems, and to provide a tire that improves the steering stability performance and the durability performance while maintaining the riding comfort performance.

  The pneumatic tire of the present invention is a pneumatic tire including a sidewall rubber including an inner rubber layer and an outer rubber layer, and a breaker. The inner rubber layer is mixed with 0.5 to 20 parts by mass of paper fiber with respect to 100 parts by mass of the rubber component. The average thickness of the inner rubber layer with respect to the total thickness of the sidewall rubber is 20 to 80%. The inner rubber layer is in contact with both ends of the breaker, and the outer rubber layer is not in contact with the breaker.

  In the pneumatic tire, preferably, the average length of the paper fibers is 10 μm or more.

  In the pneumatic tire, preferably, the average major axis of the paper fiber is 10 to 1000 μm.

  The pneumatic tire is preferably characterized in that the ratio of the average length of the paper fibers to the average major axis is 10 or more.

  According to the tire of the present invention, it is possible to improve steering stability performance and durability performance while maintaining riding comfort performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a cross-sectional view showing a right half of a pneumatic tire according to an embodiment of the present invention. Referring to FIG. 1, a pneumatic tire 1 according to an embodiment of the present invention is a pneumatic tire provided with a sidewall rubber including an inner rubber layer 3a and an outer rubber layer 3b, and a breaker 6. The inner rubber layer 3a is blended with 0.5 to 20 parts by mass of paper fiber with respect to 100 parts by mass of the rubber component. The average thickness of the inner rubber layer 3a with respect to the total thickness of the sidewall rubber is 20 to 80%. The inner rubber layer 3a is in contact with both ends of the breaker 6, and the outer rubber layer 3b is not in contact with the breaker.

  Specifically, as shown in FIG. 1, the pneumatic 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 an inner end of each sidewall portion 3. The bead part 4 located and the clinch apex 8 located in the outer end of each sidewall part 3 are provided. A carcass 5 is bridged between the bead portions 4 and 4, and a breaker 6 having a tagging effect is arranged on the outer side in the radial direction of the carcass 5. The carcass 5 is formed of one or more carcass plies in which the carcass cord is arranged with respect to the tire equator C at an angle of 70 to 90 °, for example. Around the bead core 7 of the portion 4 is folded back from the inner side to the outer side in the tire axial direction and is locked by the turned-up portion 5a.

  The breaker 6 is composed of two or more belt plies in which the belt cords are arranged with respect to the tire equator C at an angle of 45 ° or less, for example, and the belt cords are stacked in different directions so that the belt cords cross each other. Yes. Further, a band layer (not shown) may be provided outside the breaker 6, and at this time, the band layer is formed of a continuous ply spirally wound with a low modulus organic fiber cord substantially parallel to the tire equator C.

  In the pneumatic tire 1 of the present invention, the sidewall portion 3 has a structure of two or more layers having at least an inner rubber layer 3a and an outer rubber layer 3b. The inner rubber layer 3 a is in contact with both ends of the breaker 6, and the outer rubber layer 3 b is not in contact with the breaker 6. In the sidewall part 3, it is preferable that both end parts of the inner rubber layer 3 a are in contact with both end parts of the breaker 6. Furthermore, the inner rubber layer 3a is preferably in contact with both ends of the breaker 6 on the side opposite to the side facing the tread portion 2 (the inner peripheral side of the pneumatic tire 1). Since the inner rubber layer 3a and the breaker 6 are in contact with each other, a reinforcing effect can be obtained inside the sidewall portion 3, so that steering stability can be improved. Since the outer rubber layer 3b and the breaker 6 are not in contact with each other, desired performance can be provided outside the sidewall portion 3, so that the wear resistance performance can be improved and the riding comfort performance can be maintained. Further, since the outer rubber layer 3b is not restricted by the movement of the breaker 6, the durability performance can be improved.

  The width X (in FIG. 1, (2X / W) × 100%) where the inner rubber layer 3a and the breaker 6 are in contact with the width W of the breaker 6 is preferably in the range of 10% to 50%. More preferably, it is in the range of 20% to 45%. It is because the reinforcement effect by constraining the motion of a breaker edge within a desired range is more acquired by setting it as 10% or more. This is because the reinforcing effect can be further obtained by setting it to 20% or more. On the other hand, by setting it to 50% or less, the durability performance and the riding comfort performance can be sufficiently improved. This is because by setting it to 45% or less, the durability performance and riding comfort performance can be improved more sufficiently. The width X at which the inner rubber layer 3a is in contact with the breaker 6 refers to one overlap in the width direction at the cross section of the pneumatic tire 1 in the portion where the inner rubber layer 3a and the breaker 6 are in contact. It means the length that is.

  The average thickness of the inner rubber layer 3a with respect to the total thickness of the sidewall rubber of the sidewall portion 3 is 20 to 80%, preferably 30 to 70%, and more preferably 40 to 60%. If the average thickness of the inner rubber layer 3a is less than 20%, the reinforcing effect of the inner rubber layer 3a cannot be sufficiently obtained, and the steering stability performance cannot be maintained. By setting it to 30% or more, the reinforcing effect of the inner rubber layer 3a can be sufficiently obtained, so that the steering stability performance can be maintained. By setting it to 40% or more, the reinforcing effect of the inner rubber layer 3a can be more sufficiently obtained, so that the steering stability performance can be improved. On the other hand, if the average thickness of the inner rubber layer 3a exceeds 80%, the proportion occupied by the inner rubber layer 3a having the reinforcing effect becomes too large, the ride performance deteriorates, and the bending resistance decreases, so the durability performance is reduced. Deteriorate. By setting it to 70% or less, riding comfort performance can be maintained and durability performance can be further improved. By setting it to 60% or less, riding comfort performance can be improved, and durability performance can be further improved.

  The inner rubber layer 3a contains 0.5 to 20 parts by mass, preferably 1 to 18 parts by mass, and more preferably 2 to 15 parts by mass of paper fiber with respect to 100 parts by mass of the rubber component. When the blending amount of the paper fiber is less than 0.5 parts by mass, the reinforcing effect by blending the paper fiber cannot be obtained. By setting it to 1 part by mass or more, the reinforcing effect by blending paper fibers can be obtained more sufficiently. By setting it to 2 parts by mass or more, the reinforcing effect can be obtained more sufficiently. On the other hand, when the compounding amount of the paper fiber exceeds 20 parts by mass, the rubber composition becomes hard and processability and ride comfort performance deteriorate. By setting it as 18 mass parts or less, a rubber composition does not become hard too much and the deterioration of workability and riding comfort performance can be prevented more. By setting it to 15 parts by mass or less, deterioration of workability and riding comfort performance can be further prevented.

  Note that the paper fiber refers to paper obtained by shortening the fiber by grinding or the like. In the present invention, by blending the above-mentioned blending amount of paper fiber with the inner rubber layer 3a, the rigidity of the inner rubber layer 3a can be improved at low cost, and the type and blending amount of the paper fiber can be reduced. By appropriately setting, the rigidity of the inner rubber layer 3a can be easily and arbitrarily controlled. Moreover, since paper fiber is inexpensive, the cost can be reduced by using the paper fiber as a reinforcing material.

  Paper fibers blended in the inner rubber layer 3a are non-wood pulp derived from pulp, kenaf, bagasse, bamboo, cotton, seaweed, etc. obtained by pulping methods such as kraft pulp, semi-chemical pulp, mechanical pulp, etc. It can be prepared using one or a mixture of two or more raw papers obtained from used paper pulp obtained by deinking used paper such as finished copy paper, old newspaper, and old corrugated cardboard. It is preferable to use paper fibers having a relatively large physical strength such as a pulverized paper product. 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. As the kraft pulp, either softwood kraft pulp or hardwood kraft pulp can be used, but softwood kraft pulp is preferable because of its relatively long fiber length.

  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.

  The average length (L) of the paper fibers blended in the inner rubber layer 3a is preferably 10 μm or more, and more preferably in the range of 50 to 1000 μm. By setting the average length (L) to 10 μm or more, the reinforcing effect of the inner rubber layer 3a can be sufficiently obtained. By setting it to 50 μm or more, the reinforcing effect of the inner rubber layer 3a can be more sufficiently obtained. On the other hand, when the average length (L) is 1000 μm or less, poor dispersion of paper fibers and non-uniform physical properties of the inner rubber layer 3a can be well prevented.

  Moreover, it is preferable that the average long diameter (D) of the paper fiber mix | blended with the inner side rubber layer 3a is in the range of 10-1000 micrometers, It is more preferable in the range of 30-700 micrometers, The range of 30-200 micrometers It is even more preferable that it is within. By setting the average major axis (D) to 10 μm or more, the reinforcing effect of the inner rubber layer 3a can be sufficiently obtained. By setting it to 30 μm or more, the reinforcing effect of the inner rubber layer 3a can be more sufficiently obtained. On the other hand, by setting the average major axis (D) to 1000 μm or less, poor dispersion of paper fibers and non-uniform physical properties of the inner rubber layer 3a can be satisfactorily prevented. By setting the thickness to 700 μm or less, poor dispersion of paper fibers and non-uniform physical properties of the inner rubber layer 3a can be prevented better. By setting it to 200 μm or less, poor dispersion of paper fibers and non-uniform physical properties of the inner rubber layer 3a can be prevented even better.

  Further, the ratio (L / D) of the average length (L) and the average long diameter (D) of the paper fibers blended in the inner rubber layer 3a is preferably 10 or more, and within the range of 20 to 2000. More preferably. By setting L / D to 10 or more, the reinforcing effect of the inner rubber layer 3a can be sufficiently obtained. By setting it to 20 or more, the reinforcing effect of the inner rubber layer 3a can be more sufficiently obtained. On the other hand, when L / D is 2000 or less, poor dispersion of paper fibers and non-uniform physical properties of the inner rubber layer 3a can be satisfactorily prevented.

  The hardness of the inner rubber layer 3a is preferably set within a range of 35 to 65, for example. If the hardness is 35 or more, a desired degree of steering stability of the tire can be secured, and if it is 65 or less, the riding comfort performance is good. Moreover, it is preferable that the hardness of the outer rubber layer 3b is set within a range of 40 to 60, for example. If the hardness is 40 or more, the desired degree of steering stability of the tire can be secured, and if it is 60 or less, the riding comfort performance is good. The hardness can be measured according to ISO-7619.

  As a rubber component used for the sidewall rubber of the present invention, at least one of natural rubber (NR) and diene synthetic rubber is preferably mentioned. 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.

  The following components generally blended in other rubber products can be appropriately blended with the sidewall rubber in the present invention.

  As the filler, for example, silica can be blended in an amount of, for example, 5 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component. As the silica, those generally used for general-purpose rubber can be used, and examples thereof include dry method white carbon, wet method white carbon and colloidal silica used as a reinforcing material. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable. If the compounding amount of silica is 5 parts by mass or more, the tire rubber composition has a satisfactory reinforcing effect by sufficiently obtaining a reinforcing effect on the tire rubber composition, and if it is 100 parts by mass or less, the tire rubber composition is used. It is possible to prevent a decrease in processability and an excessive increase in cost due to an increase in the viscosity of the unvulcanized rubber composition during the production of.

Nitrogen adsorption specific surface area (BET method) of silica used in the above, for example 50 to 300 m ² / g, it is preferably further in the range of 100 to 200 m ² / g. When the nitrogen adsorption specific surface area of silica is 50 m ² / g or more, the abrasion resistance of the pneumatic tire 1 is improved satisfactorily by obtaining a sufficient reinforcing effect on the rubber composition used for the sidewall rubber. On the other hand, when the nitrogen adsorption specific surface area is 300 m ² / g or less, the processability of the rubber composition used for the sidewall rubber is good, and the steering stability is sufficiently secured. Here, the nitrogen adsorption specific surface area is a value measured by the BET method according to ASTM D3037-81.

  When silica is compounded in the rubber composition used for the sidewall rubber of the present invention, a silane coupling agent, preferably a sulfur-containing silane coupling agent, is, for example, 1% by mass or more and 20% by mass with respect to the mass of silica. It is preferable to mix | blend below%. The abrasion resistance and steering stability of the pneumatic tire 1 can be improved by blending the silane coupling agent. When the blending amount of the silane coupling agent is 1% by mass or more, the abrasion resistance and steering stability are improved. Good effect is obtained. Moreover, when the compounding quantity of a silane coupling agent is 20 mass% or less, there is little danger that the rubber | gum kneading | mixing and the burning (scorch) in an extrusion process will arise. As sulfur-containing silane coupling agents, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxymethyl Examples include silylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, 3-mercaptopropyltrimethoxysilane and the like.

  Other silane coupling agents include vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ- (2-aminoethyl) Aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like can be used.

  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 addition, the sidewall rubber of the present invention may contain other fillers such as carbon black, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide alone or in combination. Can be used.

Carbon black is preferably blended in an amount of 10 to 150 parts by mass 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 70 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 146 to 152 mg / g. The inner one is preferable in terms of the reinforcing effect on the rubber composition used for the sidewall rubber.

  In addition to the above, it is possible to add 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 to the sidewall rubber 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, And 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 blended in the sidewall rubber of the present invention as necessary. Specifically, DMP (dimethyl phthalate), DEP (diethyl phthalate), DBP (dibutyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (phthalate) Acid diisodecyl), BBP (butyl benzyl 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 side wall rubber of the present invention includes, for example, an organic acid such as phthalic anhydride, salicylic acid and benzoic acid, a nitroso compound such as N-nitrosodiphenylamine, and N-cyclohexylthiophthalimide as a scorch preventing agent for preventing or delaying scorch. Etc. can be used.

  In addition, about parts other than the sidewall part 3 in the pneumatic tire 1, it does not specifically limit, The component mix | blended generally is mixed suitably.

  As described above, according to the pneumatic tire 1 in the embodiment of the present invention, the pneumatic tire 1 includes the sidewall rubber including the inner rubber layer 3a and the outer rubber layer 3b, and the breaker 6. The inner rubber layer 3a is mixed with 0.5 to 20 parts by mass of paper fiber with respect to 100 parts by mass of the rubber component, and the average thickness of the inner rubber layer 3a with respect to the total thickness of the sidewall rubber is 20 to 20 parts. The inner rubber layer 3a is in contact with both ends of the breaker 6 and the outer rubber layer 3b is not in contact with the breaker 6. Thereby, the inner rubber layer 3a has a reinforcing effect. Therefore, the steering stability performance including the braking performance can be maintained by enhancing the reinforcing effect by the inner rubber layer 3a having a predetermined thickness connected to the breaker 6. By setting the outer rubber layer 3b having a predetermined thickness that is not connected to the breaker 6 to a composition that can improve the ride comfort and wear resistance, the ride comfort and wear resistance can be improved.

  In the pneumatic tire 1, preferably, the average length of the paper fibers is 10 μm or more. Thereby, the reinforcement effect of the side wall part 3 can be improved more. Therefore, the steering stability performance can be further improved.

  In the pneumatic tire 1, preferably, the average major axis of the paper fiber is 10 to 1000 μm. Thereby, while the reinforcement effect of the side wall part 3 can be improved more, the dispersibility of paper fiber and the uniformity of the physical property of the inner side rubber layer 3a can be improved.

  The pneumatic tire 1 is preferably characterized in that the ratio of the average length of the paper fibers to the average major axis is 10 or more. Thereby, while the reinforcement effect of the side wall part 3 can be improved more, the dispersibility of paper fiber and the uniformity of the physical property of the inner side rubber layer 3a can be improved.

〔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 shown in Tables 1 and 2, the components excluding sulfur and the vulcanization accelerator were kneaded at 150 ° C. for 5 minutes using 1.7 L Banbury (manufactured by Kobe Steel) to obtain a mixture. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained mixture and kneaded at 80 ° C. for 5 minutes using an 8-inch biaxial roller to obtain a rubber composition. And the rubber sheet for a test was produced using the obtained rubber composition. Moreover, the rubber sheet for a test was shape | molded as a side wall part of a tire, and it vulcanized | cured on the conditions of 150 degreeC, 35 minutes, and 25 kgf (245.16625N), For the test of Example 1 and Comparative Examples 1-5 A tire was produced.

  In addition, as shown in FIG. 1, in the side walls of Example 1 and Comparative Examples 3 to 5, the inner rubber layer 3 a is in contact with both ends of the breaker 6, and the outer rubber layer 3 b is in contact with the breaker 6. No structure. As shown in FIG. 2, Comparative Example 1 has a single-layer structure in which the inner rubber layer 3a is not provided. In Comparative Example 2, as shown in FIG. 3, the outer rubber layer 3 b is in contact with both end portions of the breaker 6, and the inner rubber layer 3 a is in contact with portions other than both end portions of the breaker 6.

  Moreover, each component of Example 1 and Comparative Examples 2 to 5 was a blending component of the inner rubber layer 3a shown in Table 1, and the outer rubber layer 3b was a blending component shown in Table 2. The comparative example 1 was made into the compounding component shown in Table 1 which consists of one layer.

  Below, the various compounding agents used in Example 1 and Comparative Examples 1-5 are demonstrated. In addition, the unit of the compounding quantity in Table 1 and Table 2 is a mass part.

(Note 1) As natural rubber, RSS3 manufactured by Thailand was used.
(Note 2) As butadiene rubber, BR150B manufactured by Ube Industries, Ltd. was used.
(Note 3) N550 manufactured by Mitsubishi Chemical Corporation was used as the carbon black.
(Note 4) Neofiber manufactured by Oji Bags Co., Ltd. was used as the paper fiber. (The average length was 1000 μm, the average major axis was 20 μm, and the ratio of the average length to the average major axis was 50 paper fibers.)
(Note 5) Ozonon 6C manufactured by Seiko Chemical Co., Ltd. was used as an anti-aging agent.
(Note 6) As the wax, Sannoc Wax manufactured by Ouchi Chemical Shinsei Chemical Co., Ltd. was used.
(Note 7) As the aroma oil, Diana Process AH40 manufactured by Idemitsu Kosan Co., Ltd. was used.
(Note 8) As stearic acid, paulownia made by NOF Corporation was used.
(Note 9) As zinc oxide, Toho Zinc Co., Ltd. silver candy R was used.
(Note 10) Sulfur manufactured by Tsurumi Chemical Co., Ltd. was used as sulfur.
(Note 11) As the vulcanization accelerator, Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. was used.

(Maneuvering stability)
A pneumatic tire of size 195 / 65R15 was attached to the car, and it was run at 40 to 100 km / h on a test course, and steering stability was evaluated by a feeling test of steering wheel response, rigidity, and grip. . The evaluation was performed by a 10-point scale method, and the average value of the three drivers was represented by an index with Comparative Example 1 being 100. The results are shown in Table 1. The larger the value, the better the steering stability. At 110 or more, the steering stability has an effect.

(Ride comfort performance)
The above pneumatic tire was mounted on a vehicle, and the vehicle was run at 40 to 100 km / h on a test course, and the ride performance was evaluated by a ride comfort feeling test. The evaluation was performed by a 10-point scale method, and the average value of the three drivers was represented by an index with Comparative Example 1 being 100. The results are shown in Table 1. The larger the value, the better the steering stability, and 95 or less means that the riding comfort performance is poor.

(Durability)
After putting the above pneumatic tires in an oven at 80 ° C. for one week, running at an internal pressure of 200 kPa, a load of 340 kgf (about 3334.278 N), at a speed of 80 km / h, the distance until each pneumatic tire is damaged is compared. Example 1 was represented by an index of 100. The results are shown in Table 1. The larger the value, the better the durability performance. At 105 or more, the durability performance is effective.

(Evaluation results)
As shown in Table 1, the inner rubber layer is blended with 0.5 to 20 parts by mass of paper fiber with respect to 100 parts by mass of the rubber component, and the average thickness of the inner rubber layer with respect to the total thickness of the sidewall rubber is In Example 1 in which the inner rubber layer was in contact with both ends of the breaker and the outer rubber layer was not in contact with the breaker, the riding comfort performance was maintained, and the steering stability performance and durability performance were maintained. I was able to improve.

  On the other hand, Comparative Example 1 in which the inner rubber layer containing the paper fiber was not provided had poor handling stability and durability performance as compared with Example 1. In Comparative Example 2 in which the outer rubber layer was connected to the breaker, the endurance performance was not improved because the movement of the breaker end was restricted. In Comparative Example 3 in which a large amount of paper fiber was blended, the durability performance was degraded because the flex resistance performance was degraded. In Comparative Example 4 where the inner rubber layer was thin, the steering rubber stability and durability performance were poor compared to Example 1 because the effect of the inner rubber layer was small. Since Comparative Example 5 in which the inner rubber layer is thick has strong front-rear rigidity, the steering stability performance was poor compared to Example 1.

  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.

It is sectional drawing which shows the right half of the pneumatic tire with which this invention is applied. 2 is a cross-sectional view showing a right half of a pneumatic tire showing Comparative Example 1. FIG. 5 is a cross-sectional view showing a right half of a pneumatic tire showing a comparative example 2. FIG.

Explanation of symbols

  1 pneumatic tire, 2 tread portion, 3 sidewall portion, 3a inner rubber layer, 3b outer rubber layer, 4 bead portion, 5 carcass, 5a folded portion, 6 breaker, 7 bead core, 8 clinch apex, C tire equator.

Claims (4)

A pneumatic tire including a sidewall rubber including an inner rubber layer and an outer rubber layer, and a breaker,
The inner rubber layer is blended in an amount of 0.5 to 20 parts by weight of paper fiber with respect to 100 parts by weight of the rubber component.
The average thickness of the inner rubber layer with respect to the total thickness of the sidewall rubber is 20 to 80%,
The inner rubber layer is in contact with both end portions of the breaker, and the ratio of the contacting width X to the breaker width W ((2X / W) × 100) is in the range of 10 to 50%,
The pneumatic rubber tire is characterized in that the outer rubber layer is not in contact with the breaker.   The pneumatic tire according to claim 1, wherein an average length of the paper fibers is 10 μm or more.   The pneumatic tire according to claim 1, wherein an average major axis of the paper fiber is 10 to 1000 μm.   The pneumatic tire according to any one of claims 1 to 3, wherein a ratio of an average length of the paper fibers to an average major axis is 10 or more.

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