JP4294607B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire capable of improving steering stability while maintaining crack growth resistance and riding comfort performance of a sidewall.

  In recent years, tires have been increasingly required to improve steering performance such as braking performance and riding comfort especially at high speeds. As a method for improving the braking performance of a tire, a method for increasing the longitudinal rigidity of the tire has been conventionally used, and for example, a method using a high-hardness sidewall is known.

  Patent Document 1 proposes a radial tire in which a rubber composite material layer containing organic single fibers oriented in the tire circumferential direction is arranged on a sidewall. According to the method of Patent Document 1, the rigidity in the tire circumferential direction is improved, but since the strength in the radial direction is not sufficient, it is difficult to obtain sufficient durability such as crack growth resistance.

  In Patent Document 2, the sidewall rubber is composed of an inner layer adjacent to the carcass and an outer layer that forms the outer wall surface outside the inner layer, and the inner layer includes a rubber composition including short fibers made of organic fibers. Pneumatic radial tires have been proposed. However, the organic fiber used in the method of Patent Document 2 is generally economically expensive because it is generally used by cutting a newly spun fiber for reinforcing short fibers.

  Patent Document 3 discloses a polyolefin, a vulcanizable rubber, a heat having an amide group in the main chain for the purpose of obtaining a rubber composition for a base tread in which the vulcanizate has low exothermic property, low Mooney viscosity and die swell. A rubber composition for a base tread in which a plastic polymer and a carbon book are blended at a predetermined quantitative ratio has been proposed. However, Patent Document 3 does not consider the compatibility between crack growth resistance and ride comfort performance.

Patent Document 4 uses a foamed rubber containing polybutadiene containing a predetermined amount of 1,2-syndio-polybutadiene crystals, and preferably has a complex elastic modulus E ₁ ^{* in} the circumferential direction of the tire and a complex elastic modulus in the radial direction of the tire. E ₂ ^* and the side wall to meet the ^{_{1.05 ≦ E 1 * / E 2}} * ≦ 1.25 is proposed. According to the method of Patent Document 4, it is possible to reduce the rolling resistance and reduce the weight while maintaining the durability. However, since the entire side wall is formed using the foamed rubber, in terms of cost and durability. There is room for improvement.

  In Patent Document 5, regarding bead fillers, thermoplastic polyamide, polyolefin, hard carbon and A bead filler rubber composition containing soft carbon has been proposed.

Patent Document 6 proposes a pneumatic radial tire in which the sidewall rubber is formed in a multilayer rubber structure, and the rubber modulus of the inner rubber layer of the sidewall rubber is set larger than the rubber modulus of the outer rubber layer. . According to the method of Patent Document 6, it is possible to improve the braking performance by increasing the longitudinal rigidity while avoiding the deterioration of the riding comfort performance, but there is still room for improvement in the crack growth resistance.
JP-A-4-191105 JP-A-6-255321 JP-A-8-3369 JP-A-8-85303 JP 2003-128844 A JP 2003-31213 A

  An object of the present invention is to solve the above-described problems and to provide a pneumatic radial tire that can improve steering stability while maintaining crack growth resistance and riding comfort performance of a sidewall.

  The present invention is a tire having two or more sidewall rubbers including at least an inner rubber layer and an outer rubber layer, and the inner rubber layer contains at least an olefin compound, a diene rubber, and a thermoplastic polymer. A rubber composition for the inner rubber layer containing the fiber-reinforced thermoplastic composition, and at the tire maximum width position in a state where the tire is mounted on the rim and filled with the specified internal pressure, The ratio E * a / E * b of the complex elastic modulus E * a to the radial complex elastic modulus E * b is 1.5 or more, and the inner rubber layer has a total thickness of the sidewall rubber. The present invention relates to a pneumatic radial tire having a thickness of 10 to 80%.

  The thermoplastic polymer blended in the present invention preferably contains an amide group in the main chain.

  Moreover, it is preferable that melting | fusing point of an olefin type compound exists in the range of 130-140 degreeC, and a thermoplastic polymer is thermoplastic polyamide which has melting | fusing point in the range of 240 degreeC or more.

  In the fiber reinforced thermoplastic composition of the present invention, the olefinic compound is blended in the range of 70 to 80 parts by weight and the thermoplastic polymer is blended in the range of 80 to 90 parts by weight with respect to 100 parts by weight of the diene rubber. It is preferable.

  In this invention, it is preferable that the content rate of the fiber reinforced thermoplastic composition in the rubber composition for inner side rubber layers exists in the range of 1-30 mass%.

  In the present invention, it is preferable that the complex elastic modulus in the tire circumferential direction of the inner rubber layer is set to be larger than the complex elastic modulus in the tire circumferential direction of the outer rubber layer.

  In the present invention, under the measurement conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 1%, the complex elastic modulus E * a of the inner rubber layer in the tire circumferential direction is in the range of 5 to 40 MPa, and the radial direction The complex elastic modulus E * b is preferably in the range of 3 to 10 MPa.

  According to the present invention, at least two or more sidewall rubbers including an inner rubber layer containing a fiber-reinforced thermoplastic composition containing at least an olefin compound, a diene rubber, and a thermoplastic polymer are formed, Steering stability while maintaining crack growth resistance and riding comfort performance by setting the stiffness so that the complex elastic modulus in the tire circumferential direction in the rubber layer is above a certain level in relation to the complex elastic modulus in the radial direction Thus, it is possible to provide a pneumatic radial tire with improved performance.

  The sidewall in the pneumatic tire of the present invention comprises two or more layers including at least an inner rubber layer and an outer rubber layer, and the inner rubber layer includes at least an olefin compound, a diene rubber, and a thermoplastic polymer. It consists of a rubber composition for an inner rubber layer containing a fiber reinforced thermoplastic composition.

  The fiber-reinforced thermoplastic composition can be obtained as a composition in which a thermoplastic polymer is dispersed in a fine fiber form in a matrix composed of an olefin compound and a diene rubber. In the fiber-reinforced thermoplastic composition, the thermoplastic polymer is dispersed in the form of fibers in the matrix, and preferably has a chemical bond at the interface between the thermoplastic polymer and the matrix, thereby providing good rigidity and moderate flexibility. An inner rubber layer having both of the above can be obtained.

  The thermoplastic polymer blended in the present invention preferably has an amide group in the main chain. In this case, the thermoplastic polymer and the olefinic compound and the diene rubber are phase-separated, and at the same time, the thermoplastic polymer can be chemically bonded to the olefinic compound and the diene rubber, and the thermoplastic polymer is desired in the matrix. Therefore, the rigidity of the inner rubber layer can be easily adjusted within a desired range.

  The melting point of the olefinic compound is preferably 130 ° C. or higher and 140 ° C. or lower. If the melting point of the olefinic compound is 130 ° C or higher, there is little risk that the physical properties of the inner rubber layer will be extremely lowered, and if it is 140 ° C or lower, the handling property during processing is good, and the diene rubber and olefin A matrix in which the system compound is uniformly mixed is formed, and adhesion between the matrix and the fibrous thermoplastic polymer is improved.

  The melting point of the thermoplastic polymer is preferably 240 ° C. or higher. If the melting point of the thermoplastic polymer is 240 ° C. or higher, the shape of the short fiber can be maintained without melting the thermoplastic polymer in the kneading step.

  In the fiber reinforced thermoplastic composition of the present invention, the blending amount of the olefin compound is preferably 70 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the diene rubber. Moreover, it is preferable that the compounding quantity of a thermoplastic polymer shall be 80 to 90 mass parts. If the blending amount of the olefinic compound is 70 parts by mass or more, it is preferable from the viewpoint that it can be easily pelletized and the handling is good, and if it is 80 parts by mass or less, it is preferable from the viewpoint that physical property deterioration can be prevented. . Further, if the blending amount of the thermoplastic polymer is 80 parts by mass or more, it is preferable in terms of obtaining a good reinforcing effect on the inner rubber layer, and if it is 90 parts by mass or less, riding due to the inner rubber layer becoming too hard. This is preferable in that deterioration of comfort performance is prevented.

  In addition, it is preferable that the compounding quantity of said olefin type compound shall be 0.2 mass part or more and 10 mass parts or less with respect to 100 mass parts of all the diene rubbers in the rubber composition for inner side rubber layers. If it is 0.2 parts by mass or more, it can be easily formed into a pellet form and the handling property is good, and if it is 10 parts by mass or less, deterioration of physical properties can be prevented.

  Moreover, it is preferable that the compounding quantity of said thermoplastic polymer shall be 1 to 30 mass parts with respect to 100 mass parts of all the diene rubbers in the rubber composition for inner side rubber layers. If it is 1 part by mass or more, the reinforcing effect on the inner rubber layer is good, and if it is 30 parts by mass or less, deterioration in riding comfort performance is prevented.

  The diene rubber compounded in the fiber reinforced thermoplastic composition used in the present invention is as follows: kneading, reaction, and spinning with a thermoplastic polymer such as a thermoplastic polymer having an amide group in the main chain. Those which do not cause gelation at high temperatures can be used. Specifically, natural rubber, polyisoprene, ethylene-propylene-diene rubber (EPDM), nitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR) ) And the like. In particular, ethylene-propylene-diene rubber (EPDM) can be preferably used.

  The olefinic compound blended in the fiber-reinforced thermoplastic composition used in the present invention contains an olefin component in the molecule, and is, for example, a homopolymer or copolymer of an olefin having 2 to 5 carbon atoms. Preferred examples include block copolymers or random copolymers of polymers, olefins having 2 to 5 carbon atoms, and acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, vinyl silane, acrylonitrile, vinyl acetate, and the like. . Specifically, for example, low density polyethylene, high density polyethylene, polypropylene, polybutene, polyhexene, polystyrene, polymethylpentene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene copolymer Copolymer, ethylene-pentene-1 copolymer, ethylene-octene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene -Propyl acrylate copolymer, ethylene-hydroxyethyl acrylate copolymer, ethylene-vinyltrimethoxysilane copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-tetracyclodone Decene copolymer, acrylonitrile Styrene copolymers, acrylonitrile - butadiene - styrene copolymer, polymethacrylic styrene, ethylene - vinyl acetate copolymer, and the like.

As the thermoplastic polymer blended in the fiber reinforced thermoplastic composition used in the present invention, for example, a thermoplastic polymer having an amide group in the main chain is preferably exemplified, and among them, a heat having an amide group in the main chain is preferable. A plastic polymer is preferred. Examples of the thermoplastic polymer having an amide group in the main chain include thermoplastic polyamide and urea resin. Among these, examples of preferable thermoplastic polyamides include nylon 6 (registered trademark) , nylon 66 (registered trademark) , nylon 610 (registered trademark) , nylon 612 (registered trademark) , nylon 7 (registered trademark) , nylon 11 ( (Registered trademark) , nylon 12 (registered trademark) and the like are preferable.

  The fiber reinforced thermoplastic composition used in the present invention can be obtained, for example, by the following method. First, a diene rubber and an olefin compound are kneaded in, for example, a closed kneader, and the diene rubber and the olefin compound are reacted. Thereby, the matrix component of the sea island structure in which a diene system forms an island structure in an olefin type compound is obtained. Next, a thermoplastic polymer is added to the matrix component, and further kneaded using, for example, a twin screw extruder, and the matrix component and the thermoplastic polymer are reacted to form a ternary composite. Next, the ternary composite is extruded from, for example, a nozzle installed at the tip of a twin-screw extruder, and is drawn and spun while being drafted. Thereby, a fiber reinforced thermoplastic composition in which a thermoplastic polymer is dispersed in a fiber form in a matrix composed of a diene rubber and an olefin compound is obtained. An example of a more detailed method for producing the fiber-reinforced thermoplastic composition used in the present invention is described in, for example, Journal of Japanese Rheological Society, Vol. 25 (1997) pages 275-282.

As a commercial product of a preferred fiber reinforced thermoplastic composition, a trade name “SHP” sold by Daiwa Polymer Co., Ltd. is known. Depending on the composition ratio, “PA3060” (EPDM / PP / nylon 6 (registered trademark) = 100/100/100), “HA1060” (NR / HDPE / nylon 6 (registered trademark) = 100/75/87), “LA1060” (NR / LDPE / nylon 6 (registered trademark) = 100/75/87) "LA3080" (EPDM / LDPE / nylon 6 (registered trademark) = 100/40/105), "LA5060" (H-NBR / LDPE / nylon 6 (registered trademark) = 100/100/100), "Z040NB" (NBR / LDPE / nylon 6 (registered trademark) = 100/75/75) . Here, NR means natural rubber, HDPE means high density polyethylene, LDPE means low density polyethylene, NBR means acrylonitrile-butadiene rubber, and H-NBR means hydrogenated NBR. The composition ratio is shown in parts by mass.

  In the fiber reinforced thermoplastic composition used in the present invention, the average fiber length (L) of the fibers formed by the thermoplastic polymer is preferably 10 μm or more, and more preferably 50 μm or more. The average fiber length (L) is preferably 1000 μm or less. When the average fiber length (L) is 10 μm or more, the desired effect of improving the rigidity of the sidewall is obtained. When the average fiber length (L) is 1000 μm or less, the durability is lowered due to insufficient adhesion between the matrix and the thermoplastic polymer. It is possible to prevent the non-uniform physical properties of the inner rubber layer.

  Further, the ratio (L) / (D) of the average fiber length (L) to the average fiber diameter (D) of the fibers is preferably 10 or more, more preferably 20 or more, and more preferably 2000 or less. When (L) / (D) is 10 or more, the surface area of the interface between the matrix and the thermoplastic polymer is sufficiently large so that the adhesion is good, and when it is 1000 or less, the dispersion size of the fibers is large. Insufficient adhesion between the matrix and the thermoplastic polymer can be prevented.

  In addition, said average fiber length (L) and average fiber diameter (D) can be evaluated by SEM observation, for example.

  In the present invention, the ratio E * a / E * b of the complex elastic modulus E * a in the tire circumferential direction of the inner rubber layer and the complex elastic modulus E * b in the radial direction is set to be 1.5 or more. The When the rigidity of the inner rubber layer is anisotropic and the relationship between the complex elastic modulus in the circumferential direction and the radial direction satisfies the above, it is possible to achieve both steering stability and ride comfort performance. The E * a / E * b is preferably 1.7 or more, and more preferably 2.0 or more. The E * a / E * b is preferably 10 or less, more preferably 8 or less, from the viewpoint that the handling property during processing and the bending crack growth resistance of the inner rubber layer are not significantly impaired.

  In the present invention, the complex elastic modulus in the tire circumferential direction of the inner rubber layer is preferably set larger than the complex elastic modulus in the tire circumferential direction of the outer rubber layer. In this case, steering stability can be ensured by the contribution of the inner rubber layer having relatively high rigidity in the circumferential direction, and riding comfort performance can be ensured by the contribution of the outer rubber layer having relatively low rigidity in the radial direction. In particular, the complex elastic modulus E * a in the tire circumferential direction in the inner rubber layer is within a range of 5 to 40 MPa under the measurement conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 1%. When the complex elastic modulus in the direction is in the range of 3 to 10 MPa under the measurement conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 1%, it is preferable because steering stability and riding comfort performance are both excellent.

  The complex elastic modulus of the inner rubber layer and the outer rubber layer in the side wall rubber of the pneumatic tire of the present invention is measured at the tire maximum width position in a state where the tire is mounted on the rim and the specified internal pressure is filled.

  In the pneumatic tire of the present invention, the thickness of the inner rubber layer accounts for 10 to 80% of the total thickness of the sidewall rubber. If the thickness of the inner rubber layer relative to the total thickness of the sidewall rubber is 10% or more, the crack growth resistance and steering stability are good, and if it is 80% or less, the riding comfort performance is good.

  The hardness of the inner rubber layer of the present invention is preferably set within a range of 60 to 80, for example. If the hardness is 60 or more, the desired degree of steering stability of the tire can be secured, and if it is 80 or less, the ride comfort is good. The hardness can be measured according to ISO-7619.

  Preferred examples of the rubber component used in the sidewall rubber of the present invention include natural rubber (NR) and / or diene synthetic rubber. 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, a sufficient reinforcing effect on the tire rubber composition can be obtained, thereby improving the tire wear resistance. On the other hand, when the nitrogen adsorption specific surface area is 300 m ² / g or less, the processability of the rubber composition for tires 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 blended in the rubber composition for tires of the present invention, a silane coupling agent, preferably a sulfur-containing silane coupling agent is blended in an amount of 1% by mass or more and 20% by mass or less with respect to the mass of silica. It is preferable. By adding a silane coupling agent, the wear resistance and steering stability of the tire can be improved. When the amount of the silane coupling agent is 1% by mass or more, the effect of improving the wear resistance and steering stability is good. 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 baking (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.

Here, the 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. Here, 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 suitable in terms of the reinforcing effect on the tire rubber composition.

  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, 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 group 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 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, 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.

  For the side wall rubber of the present invention, as a scorch preventing agent for preventing or delaying scorch, for example, organic acids such as phthalic anhydride, salicylic acid, benzoic acid, nitroso compounds such as N-nitrosodiphenylamine, N-cyclohexylthiophthalimide Etc. can be used.

  FIG. 1 is a diagram illustrating the right half of a cross-sectional view of a pneumatic tire according to the present invention. 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 5 is bridged between the bead portions 4 and 4, and a belt layer 6 having a tagging effect is disposed 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 at an angle of, for example, 70 to 90 ° with respect to the tire equator. The carcass ply is connected to the bead portion from the tread portion 2 through the sidewall portion 3. 4 around the bead core 7 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 belt layer 6 includes two or more belt plies in which belt cords are arranged at an angle of, for example, 45 ° or less with respect to the tire equator, and the belt cords are stacked in different directions so that the belt cords cross each other. . Further, a band layer (not shown) may be provided outside the belt layer 6. At this time, the band layer is formed by a continuous ply spirally wound with a low modulus organic fiber cord substantially parallel to the tire equator.

  In the present invention, the side wall portion 3 has a structure of two or more layers having at least the inner rubber layer 3a and the outer rubber layer 3b, and the inner rubber layer is formed using a predetermined rubber composition. It is possible to improve the steering stability while maintaining the crack growth resistance of the wall and the riding comfort performance. The structure of the pneumatic tire according to the present invention is not limited to that described above.

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

[Examples 1-6, Comparative Examples 1-3]
Of the blending components shown in Table 1, the components excluding sulfur and the vulcanization accelerator were kneaded at about 150 ° C. for 5 minutes using a banbury, and further added with sulfur and the vulcanization accelerator and about 80 using a biaxial open roll. It knead | mixed for 5 minutes at 0 degreeC, and obtained the rubber composition for inner side rubber layers. Moreover, the components excluding sulfur and the vulcanization accelerator shown in Table 2 were kneaded at about 150 ° C. for 5 minutes using a banbury, and further added with sulfur and the vulcanization accelerator and a biaxial open roll was used. The mixture was kneaded at about 80 ° C. for 5 minutes to obtain a rubber composition for the outer rubber layer.

  The obtained rubber composition for the inner rubber layer and the rubber composition for the outer rubber layer are extruded by coextrusion to produce a rubber sheet, which is molded as a tire sidewall, and is 150 ° C., 30 minutes, 25 kgf (245. A test tire was produced by vulcanization under the condition of 16625N).

[Conventional example 1]
Of the blending components shown in Table 1, the components excluding sulfur and the vulcanization accelerator were kneaded at about 150 ° C. for 5 minutes using a banbury, and further added with sulfur and the vulcanization accelerator and about 80 using a biaxial open roll. The mixture was kneaded at 5 ° C. for 5 minutes to obtain a rubber composition for the outer rubber layer. The rubber composition for the outer rubber layer thus obtained is extruded to produce a rubber sheet, molded as a tire sidewall, and vulcanized under conditions of 150 ° C., 30 minutes, 25 kgf (245.16625N) and tested. A tire was prepared.

(Complex modulus)
A strip-shaped sample having a width of 4 mm, a length of 30 mm, and a thickness of 1.5 mm was prepared from the sidewall portion at the tire maximum width position in a state in which the tire was mounted on the rim and filled with the specified internal pressure. Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., the complex elastic modulus was measured in the tire circumferential direction and radial direction under conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 1%. The results are shown in Table 1.

(Maneuvering stability, ride comfort)
Wear tires of size 195 / 65R15 on the car, run at 40-100 km / h on the test course, evaluate steering stability by feeling test of steering wheel response, rigidity and grip, and ride comfort performance Evaluation was performed. The evaluation was performed on the basis of the following criteria for each of the steering stability and the ride comfort performance with a maximum of 5 points, and the average value of the three drivers was represented by an index with the conventional example 1 being 100. Larger values indicate better handling stability and ride comfort. The results are shown in Table 1.
5 points: Very good.
4 points: Good.
3 points: normal.
2 points: Slightly inferior.
1 point: Inferior.

(Flexible crack growth resistance)
In accordance with a flex crack test according to JIS-K6260, the crack growth property 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 the crack to grow by 1 mm was measured, and the conventional example 1 was indicated as an index. The results are shown in Table 1.

Note 1: NR is “RSS # 3” made in Thailand.
Note 2: BR is “BR150B” manufactured by Ube Industries.
Note 3: Carbon black is “N550” manufactured by Tokai Carbon Co., Ltd.
Note 4: SHP (fiber reinforced thermoplastic composition) is “HA1060” (NR / HDPE / nylon 6 (registered trademark) = 100/75/87) manufactured by Daiwa Polymer.
Note 5: Anti-aging agent 6C is “Ozonon 6C” manufactured by Seiko Chemical Co., Ltd.
Note 6: Wax is “Sannokk Wax” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 7: Aroma oil is “Diana Process AH40” manufactured by Idemitsu Kosan Co., Ltd.
Note 8: Stearic acid is “paulownia” manufactured by NOF Corporation.
Note 9: Zinc oxide is “Ginbae R” manufactured by Toho Zinc Co., Ltd.
Note 10: Sulfur is manufactured by Tsurumi Chemical.
Note 11: The vulcanization accelerator is “Noxeller NS” (Nt-butyl 2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

  From the results shown in Table 1, Comparative Example 1 in which the ratio E * a / E * b of the complex elastic modulus E * a in the tire circumferential direction and the complex elastic modulus E * b in the radial direction in the inner rubber layer is smaller than 1.5 Compared with Comparative Example 3 and Comparative Example 2 in which the thickness of the inner rubber layer occupies 90% of the total thickness of the sidewall rubber, a sidewall comprising the inner rubber layer and the outer rubber layer according to the present invention was provided. In Examples 1 to 6, the crack growth resistance and the ride comfort were not reduced, but the steering stability was remarkably improved.

  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.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the pneumatic radial tire which improved steering stability, maintaining the crack growth growth property etc. of a sidewall, and riding comfort performance.

It is the figure which illustrated the right half of the sectional view of the pneumatic tire concerning the present invention.

Explanation of symbols

  1 tire, 2 tread portion, 3 sidewall portion, 3a inner rubber layer, 3b outer rubber layer, 4 bead portion, 5 carcass, 5a folded portion, 6 belt layer, 7 bead core.

Claims (4)

A tire having two or more sidewall rubbers including at least an inner rubber layer and an outer rubber layer,
The inner rubber layer comprises a rubber composition for an inner rubber layer containing a thermoplastic composition in which at least an olefin compound, a diene rubber, and a thermoplastic polymer are blended.
The ratio E * of the complex elastic modulus E * a in the tire circumferential direction and the complex elastic modulus E * b in the radial direction of the inner rubber layer at the position of the maximum tire width when the tire is mounted on the rim and the specified internal pressure is filled. a / E * b is 1.5 or more,
And the thickness of the inner rubber layer accounts for 10 to 80% of the total thickness of the sidewall rubber ,
The melting point of the olefinic compound is in the range of 130 to 140 ° C,
The thermoplastic polymer is nylon 6 (registered trademark), nylon 66 (registered trademark), nylon 610 (registered trademark), nylon 612 (registered trademark), nylon 7 (registered trademark), nylon 11 (registered trademark), and nylon 12 (Registered trademark) at least one selected from the group consisting of:
In the thermoplastic composition, with respect to 100 parts by mass of the diene rubber, the olefin compound is blended within a range of 70 to 80 parts by mass, and the thermoplastic polymer is blended within a range of 80 to 90 parts by mass,
A pneumatic radial tire in which the content of the thermoplastic composition in the rubber composition for the inner rubber layer is in the range of 1 to 30% by mass .   The pneumatic radial tire according to claim 1, wherein the thermoplastic polymer is nylon 6 (registered trademark).   The pneumatic radial tire according to claim 1, wherein a complex elastic modulus E * a of the inner rubber layer in the tire circumferential direction is set to be larger than a complex elastic modulus of the outer rubber layer in the tire circumferential direction.   Under the measurement conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 1%, the complex elastic modulus E * a in the tire circumferential direction of the inner rubber layer is in the range of 5 to 40 MPa, and the complex elastic modulus E in the radial direction. The pneumatic radial tire according to claim 1, wherein * b is in a range of 3 to 10 MPa.

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