Pneumatic tire

Abstract

To provide a pneumatic tire that is excellent in durability at the time of running at a high speed.SOLUTION: A pneumatic tire 1 according to the present invention comprises; a radial carcass 3 extending in a toroidal shape; a belt 6 position at an outer periphery side of a crown part 4 of the radial carcass 3 and made of at least two belt layers 5a and 5b formed of cords covered with rubber; at least one belt reinforcement layer 7 positioned outside in the tire radial direction of the belt 6 and formed of a cord extending in a nearly tire circumferential direction covered with rubber, where when the belt reinforcement layer 7 is partitioned into a center region W1 and a shoulder region W2 when viewed from a cross section in a tire width direction, a ratio (rigidity of the shoulder region / rigidity of the center region) of rigidity (an elastic modulus of the cord × frequencies of punching) per unit width of the belt reinforcement layer 7 in the center region W1 to the rigidity in the shoulder region W2 is 2.05-12.00.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] With the recent advancement and high-quality improvement of vehicles, especially in passenger cars, the improvement of durability during high-speed driving has been rapidly progressing, and high-speed durability is also required for tires.

[0003] Here, as a method for improving the durability of a tire during high-speed driving, various techniques have been devised. One of them is to rubberize a cord made of polyethylene terephthalate, which is a high-rigidity fiber, and wind it spirally on the upper part of a cross belt layer (main belt) to form a belt reinforcing layer to suppress the vibration of the belt part. However, there is still room for improvement in the durability during further high-speed driving with this technique.

[0004] In order to further improve the durability during high-speed driving, there is a technique of arranging a high-rigidity belt reinforcing layer only at the belt end and not providing a belt reinforcing layer at the center of the belt. However, there is still room for improvement in durability with this technique as well.

[0005] Also, in Patent Documents 1 to 3, for the purpose of achieving both reduction of road noise and reduction of rolling resistance, a technique is disclosed in which a high-rigidity belt reinforcing layer such as polyethylene-2,6-naphthalate is arranged at the belt end, and a low-rigidity belt reinforcing layer such as nylon 6,6 is installed at the center of the belt.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, even for tires having a belt reinforcing layer with a structure as in Patent Documents 1 to 3, further improvement in durability during high-speed driving has been desired. In addition, when fibers with excessively low rigidity such as nylon 6,6 are applied to the reinforcing layer at the center of the belt, the amount of tire diameter growth due to centrifugal force during high-speed driving becomes significantly larger at the center of the belt than at the belt ends. Therefore, the contact length at the center of the tread becomes extremely long, and the contact length at the outer side in the tread width direction becomes extremely short. As a result, it was also considered that the high-speed durability and handling stability would be significantly reduced.

[0008] Therefore, an object of the present invention is to provide a pneumatic tire excellent in durability during high-speed driving.

Means for Solving the Problems

[0009] As a result of earnestly studying a pneumatic tire including a radial carcass extending in a toroidal shape, a belt composed of at least two belt layers located on the outer peripheral side of the crown portion of the carcass and formed by rubber-coating cords, and at least one belt reinforcing layer located on the outer side in the tire radial direction of the belt and formed by rubber-coating cords extending substantially in the tire circumferential direction, in order to solve the above problems, when the belt reinforcing layer is divided into a center region and a shoulder region in a cross-section in the tire width direction, regarding the rigidity per unit width of the belt reinforcing layer, it has been found that the durability during high-speed driving can be enhanced by controlling the ratio between the center region and the shoulder region within a specific range.

[0010] The gist configuration of the present invention for solving the above problems is as follows. (1) A pneumatic tire comprising a radial carcass extending in a toroidal shape, a belt composed of at least two belt layers located on the outer peripheral side of the crown portion of the carcass and formed by rubber-coating cords, and at least one belt reinforcing layer located on the outer side of the belt in the tire radial direction and formed by rubber-coating cords extending substantially in the tire circumferential direction. When the belt reinforcing layer is divided into a center region and a shoulder region in a cross-section in the tire width direction, the ratio (rigidity of the shoulder region / rigidity of the center region) of the rigidity per unit width (elastic modulus of the cord × number of plies) of the belt reinforcing layer between the center region and the shoulder region is 2.05 to 12.00. The pneumatic tire is characterized by this. The pneumatic tire having the above configuration is excellent in durability during high-speed driving.

[0011] (2) The pneumatic tire according to (1), characterized in that cords of different materials are used in the center region and the shoulder region of the belt reinforcing layer. The pneumatic tire having the above configuration is more excellent in durability during high-speed driving.

[0012] (3) The pneumatic tire according to (2), characterized in that the cords constituting the shoulder region of the belt reinforcing layer have a higher elastic modulus than the cords constituting the center region. The pneumatic tire having the above configuration is more excellent in durability during high-speed driving.

[0013] (4) The pneumatic tire according to (1), characterized in that polyethylene terephthalate (PET) cords are used in both the center region and the shoulder region of the belt reinforcing layer. The pneumatic tire having the above configuration is excellent in durability during high-speed driving without causing manufacturing costs or manufacturing complexity.

[0014] (5) The pneumatic tire according to (4), wherein the number of cords constituting the shoulder region in the belt reinforcing layer is larger than the number of cords constituting the center region. The pneumatic tire having the above configuration is excellent in durability during high-speed driving.

[0015] (6) The pneumatic tire according to (4), wherein the number of twists of the cords constituting the shoulder region in the belt reinforcing layer is larger than the number of twists of the cords constituting the center region. The pneumatic tire having the above configuration is excellent in durability during high-speed driving.

[0016] (7) The pneumatic tire according to any one of (1) to (6), wherein the belt reinforcing layer is composed of a single layer of belt reinforcing layer. The pneumatic tire having the above configuration is excellent in durability during high-speed driving without causing manufacturing costs and manufacturing complexity.

[0017] (8) The pneumatic tire according to any one of (1) to (6), wherein the belt reinforcing layer includes a center portion belt reinforcing layer covering the central portion in the width direction of the belt and a shoulder portion belt reinforcing layer covering the end portion of the belt. The pneumatic tire having the above configuration is excellent in durability during high-speed driving.

Advantages of the Invention

[0018] According to the present invention, a pneumatic tire excellent in durability during high-speed driving can be provided.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a cross section in the tire width direction in order to explain one embodiment of the pneumatic tire of the present invention. The pneumatic tire of the present invention includes a carcass 3 extending in a toroidal shape between bead portions 2, 2, a belt 6 composed of at least two layers (two layers in FIG. 1) of belt layers 5a, 5b located on the outer periphery of the crown portion 4 of the carcass 3, and at least one layer (one layer in FIG. 1) of a belt reinforcing layer 7 located on the outer side in the tire radial direction of the belt 6.

[0021] The belt reinforcing layer 7 is formed by rubber-coating a cord and is arranged such that the cord extends in a substantially circumferential direction. In a tire having a cross-belt layer, when the tire rolls under load, shear strain occurs between adjacent belt layers constituting the cross-belt layer, and belt layer separation is likely to occur. However, by disposing the belt reinforcing layer on the outer periphery of the belt and suppressing the elongation of the belt in the tire circumferential direction, the reinforcing property and durability can be enhanced. Note that the "substantially tire circumferential direction" means a direction within a range of ±10°, preferably ±5°, centered on the tire circumferential direction.

[0022] And in the pneumatic tire of the present invention, when the belt reinforcing layer 7 is divided into a center region W1 and a shoulder region W2 in a cross section in the tire width direction, the ratio of the rigidity per unit width of the belt reinforcing layer 7 between the center region W1 and the shoulder region W2 (rigidity of the shoulder region / rigidity of the center region) is required to be 2.05 to 12.00, and preferably 2.40 to 8.00.

[0023] By increasing the rigidity of the belt reinforcing layer 7, the rigidity of the belt 5 can be reinforced, and the durability of the tire during high-speed running can be enhanced. Further, by controlling the ratio of the rigidity of the shoulder region / the rigidity of the center region to be 2.05 or more and 12.00 or less, the durability of the tire during high-speed running can be further enhanced. If the rigidity ratio is less than 2.05, strain concentrates in the shoulder region, and if it exceeds 12.00, strain concentrates in the center region, and sufficient high-speed durability cannot be obtained.

[0024] Here, the shoulder region W2 of the belt reinforcing layer 7 refers to a region with a width of 6 to 10% of the width W from both side ends of the belt reinforcing layer 7 toward the equatorial plane E respectively. Also, the center region W1 of the belt reinforcing layer 7 refers to the region of the belt reinforcing layer 7 including the tire equatorial plane E when viewed in the tire width direction cross-section as shown in FIG. 1. More specifically, it is the region other than W2 centered on the tire equatorial plane E.

[0025] Also, the rigidity per unit width of the belt reinforcing layer 7 refers to the rigidity of the aggregate of cords excluding rubber, and specifically, it is defined by the elastic modulus of the cords × the number of cords driven in. By increasing the elastic modulus and the number of cords driven in of the cords, higher rigidity can be obtained. Regarding the unit width of the belt reinforcing layer, there is no particular limitation as long as the center region 2a and the shoulder region 2b have the same width, but for example, it can be set to 1 mm for ease of measurement.

[0026] Therefore, in order to control the ratio (rigidity of the shoulder region / rigidity of the center region) of the rigidity per unit width of the belt reinforcing layer 7 between the center region W1 and the shoulder region W2 within a desired range, it is necessary to adjust the rigidity of the shoulder region and the rigidity of the center region respectively. Specifically, by selecting the cord material constituting the belt reinforcing layer 7, the number of cords driven in, the twist number of the fibers constituting the cords, etc., the ratio between the center region W1 and the shoulder region W2 of the rigidity per unit width of the belt reinforcing layer 7 can be controlled within a specific range.

[0027] Also, regarding the elastic modulus of the cords constituting the belt reinforcing layer 7, the ratio (rigidity of the shoulder region / rigidity of the center region) between the center region W1 and the shoulder region W2 If it can be set as described above, there are no particular limitations. Note that the elastic modulus of the cords used for the rigidity per unit width of the belt reinforcing layer 7 is the elastic modulus when a 2% strain is applied to the cords.

[0028] Furthermore, regarding the number of cords constituting the belt reinforcing layer 7, the ratio of the center region W1 to the shoulder region W2 (rigidity of the shoulder region / rigidity of the center region) If it can be set as described above, there are no particular limitations. For example, from the viewpoint of increasing the rigidity of the belt reinforcing layer 7 and obtaining more excellent high-speed durability, the number of cords constituting the center region W1 is preferably 20 to 80 cords / 50 mm, and more preferably 25 to 60 cords / 50 mm. From the same viewpoint, the number of cords constituting the shoulder region W2 is preferably 30 to 70 cords / 50 mm, and more preferably 40 to 60 cords / 50 mm.

[0029] In the pneumatic tire 1 of the present invention, cords of different materials can be used in the center region W1 and the shoulder region W2 of the belt reinforcing layer 7.

[0030] When cords of different materials are used in the center region W1 and the shoulder region W2 of the belt reinforcing layer 7, it is preferable that the elastic modulus of the cords constituting the shoulder region W2 is higher than the elastic modulus of the cords constituting the center region W1. Since the rigidity per unit width of the belt reinforcing layer 7 can be changed more reliably and easily, the durability during high-speed driving can be further enhanced. Note that for the cords of different materials, it is sufficient that the types of resins used are the same, and even if there are slight differences in composition or differences in wire drawing, they are regarded as the same material.

[0031] The material of the cords constituting the belt reinforcing layer 7 is not particularly limited, and examples thereof include aramid fiber, nylon fiber, polyethylene terephthalate (PET) fiber, polyethylene naphthalate (PEN) fiber, trimethylene terephthalate fiber, polybutylene terephthalate fiber, and the like.

[0032] When the belt reinforcing layer 7 uses cords of different materials in the center region W1 and the shoulder region W2, for example, cords made of nylon fiber are used in the center region W1, and polyethylene terephthalate (PET) fiber, polyethylene naphthalate (PEN) fiber, aramid fiber, or the like is used in the shoulder region W2, whereby the elastic modulus of the cords constituting the shoulder region W2 can be set higher than that of the cords constituting the center region W1.

[0033] Also, the belt reinforcing layer 7 may use cords of the same material in the center region W1 and the shoulder region W2. In this case, while reducing the cost and complexity involved in manufacturing, the durability during high-speed driving can be enhanced.

[0034] The raw material of the cords constituting the reinforcing layer 7 is not particularly limited, and it may be derived from synthetic products, biological products, mechanical recycling obtained by pulverizing, melting, and re-spinning PET products such as PET bottles, or chemical recycling obtained by depolymerizing and repolymerizing PET products such as PET bottles.

[0035] Furthermore, when the belt reinforcing layer 7 uses cords of the same material in the center region W1 and the shoulder region W2, it is more preferable to use polyethylene terephthalate (PET) cords in both cases. Since the rigidity per unit width of the belt reinforcing layer 7 can be changed more reliably and easily depending on the number of cords driven in and the number of twists of the fibers, the durability during high-speed driving can be further enhanced.

[0036] The cord constituting the reinforcing layer 7, especially the PET cord, is preferably adhesively treated with an adhesive composition containing a thermoplastic polymer (A), a heat-reactive aqueous urethane resin (B), and an epoxy compound (C), or an adhesive composition containing a rubber latex (D) in addition to these components (A) to (C), and the main chain of the component (A) substantially has no addition-reactive carbon-carbon double bond and has at least one crosslinkable functional group as a pendant group. By adhesively treating with such an adhesive composition, the adhesiveness between the cord and the coating rubber at high temperatures can be improved.

[0037] Conventionally, as an adhesive treatment for organic fiber cords, especially PET cords, a so-called two-bath treatment is performed in which epoxy or isocyanate is applied to the cord surface and then treated with a resin (RFL resin) obtained by mixing resorcinol, formaldehyde, and latex. However, with such means, the resin used in one bath becomes very hard, the strain input to the cord increases, and the fatigue resistance of the cord may decrease. In addition, such a resin can exhibit sufficient adhesion between the cord and the elastomer at room temperature, but at high temperatures of 130 °C or higher, the adhesion may decrease extremely. In contrast, by using a one-bath mixture containing a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially not containing an addition-reactive carbon-carbon double bond in the main chain structure, a heat-reactive aqueous urethane resin (B), and an epoxy compound (C), it is possible to ensure sufficient adhesion to the coating rubber even at high temperatures of 180 °C or higher without curing the cord.

[0038] The main chain of the thermoplastic polymer (A) is mainly a linear structure. As the main chain, for example, an ethylenically addition polymer such as an acrylic polymer, a vinyl acetate polymer, a vinyl acetate-ethylene polymer, or a urethane-based polymer is preferable. However, the thermoplastic polymer (A) only needs to have a function of suppressing the resin fluidity at high temperatures and ensuring the breaking strength of the resin by crosslinking the functional groups of the pendant groups, and is not limited to ethylenically addition polymers and urethane-based polymers.

[0039] Moreover, as the functional group of the pendant group of the thermoplastic polymer (A), an oxazoline group, a bismaleimide group, a (blocked) isocyanate group, an aziridine group, a carbodiimide group, a hydrazino group, an epoxy group, an episulfide group, etc. are preferable.

[0040] Examples of the monomers constituting the ethylenically unsaturated polymer include ethylenically unsaturated monomers having one carbon-carbon double bond and monomers containing two or more carbon-carbon double bonds.Among these, examples of ethylenically unsaturated monomers having one carbon-carbon double bond include α-olefins such as ethylene, propylene, butylene, and isobutylene; α,β-unsaturated aromatic monomers such as styrene, α-methylstyrene, monochlorostyrene, vinyltoluene, vinylnaphthalene, and sodium styrenesulfonate; ethylenically carboxylic acids such as itaconic acid, fumaric acid, maleic acid, acrylic acid, methacrylic acid, and butenetricarboxylic acid and their salts; acid anhydrides such as maleic anhydride and itaconic anhydride; esters of unsaturated carboxylic acids such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-aminoethyl (meth)acrylate; mono-esters of ethylenically dicarboxylic acids such as monoethyl itaconate, monobutyl fumarate, and monobutyl maleate; di-esters of ethylenically dicarboxylic acids such as diethyl itaconate and dibutyl fumarate; amides of α,β-ethylenically unsaturated acids such as acrylamide, maleic amide, N-methylolacrylamide, N-(2-hydroxyethyl)acrylamide, methacrylamide, N-methylolmethacrylamide, N-(2-hydroxyethyl)methacrylamide, and maleic amide; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate and polyethylene glycol mono(meth)acrylate; unsaturated nitriles such as acrylonitrile, methacrylonitrile, fumaronitrile, and α-chloroacrylonitrile; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl ketone; vinyl amide; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; vinyl compounds such as vinyl acetate, vinyl valerate, vinyl caprylate, and vinyl pyridine; addition-polymerizable oxazolines such as 2-isopropenyl-2-oxazoline; heterocyclic vinyl compounds such as vinyl pyrrolidone; unsaturated bond-containing silane compounds such as vinyl ethoxysilane and α-methacryloxypropyltrimethoxysilane, etc. These may be used alone or in combination of two or more.In the present invention, it is preferable to obtain the thermoplastic polymer (A) by radical addition polymerization of these monomers. Further, as monomers constituting the main chain skeleton and containing two or more carbon-carbon double bonds, conjugated diene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, halogen-substituted butadienes such as chloroprene, etc. can be mentioned. As non-conjugated diene monomers, non-conjugated diene monomers such as vinyl norbornene, dicyclopentadiene, 1,4-hexadiene, etc. can be mentioned. These may be used alone or in combination of two or more.

[0041] The ethylenically unsaturated polymer consists of units derived from an ethylenically unsaturated monomer having one carbon-carbon double bond and a monomer containing two or more carbon-carbon double bonds. Based on the charged amount of all monomers, the sulfur-reactive carbon-carbon double bond is preferably 10 mol% or less in the monomer composition ratio, and more preferably 0 mol%.

[0042] The method of introducing a crosslinkable functional group into the ethylenically unsaturated polymer to obtain the thermoplastic polymer (A) is not particularly limited. For example, a method of copolymerizing an addition polymerizable monomer having an oxazoline, an addition polymerizable monomer having an epoxy group, an addition polymerizable monomer having a maleimide, an addition polymerizable monomer having a blocked isocyanate group, an addition polymerizable monomer having an episulfide group, etc. when polymerizing the ethylenically unsaturated polymer can be adopted.

[0043] Further, the urethane-based polymer is a polymer having a large number of bonds in the molecule due to the reaction of an isocyanate group and an active hydrogen, such as a urethane bond or a urea bond, which is mainly obtained by polyaddition reaction of a polyisocyanate and a compound having two or more active hydrogens. Note that it may be a polymer containing not only bonds resulting from the reaction of an isocyanate group and an active hydrogen, but also ester bonds, ether bonds, amide bonds contained in the active hydrogen compound molecule, and uretdione, carbodiimide, etc. generated by the reaction of isocyanate groups.

[0044] As the heat-reactive aqueous urethane resin (B), a resin having two or more thermally dissociable blocked isocyanate groups in one molecule is preferable. For example, a heat-reactive aqueous polyurethane compound represented by the following general formula (4) is particularly preferable. TIFF2025088362000002.tif27157In formula (4), A represents an isocyanate residue of an organic polyisocyanate compound having 3 to 5 functional groups, Y represents an active hydrogen residue of a blocking agent compound that releases an isocyanate group by heat treatment, Z represents an active hydrogen residue of a compound having at least one active hydrogen atom and at least one anion-forming group in the molecule, X represents an active hydrogen residue of a polyol compound having 2 to 4 hydroxyl groups and an average molecular weight of 5000 or less, n is an integer of 2 to 4, and p + m is an integer of 2 to 4 (m ≧ 0.25).

[0045] As the epoxy compound (C), a compound containing two or more, preferably four or more epoxy groups in one molecule may be used, and a compound containing an epoxy group, a reaction product of a polyhydric alcohol and epichlorohydrin is preferable. Specific examples of the epoxy compound include reaction products of polyhydric alcohols such as diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, sorbitol polyglycidyl ether and epichlorohydrin; novolak type epoxy resins such as phenol novolak type epoxy resin, cresol novolak type epoxy resin; bisphenol A type epoxy resin and the like.

[0046] As the rubber latex (D), vinyl pyridine-styrene-butadiene copolymer latex, styrene-butadiene copolymer latex and the like are preferable, but it is not particularly limited.

[0047] For the adhesive treatment of organic fiber cords, especially PET cords, it is preferable to use the three components of (A), (B), and (C) as a one-bath treatment liquid, and to use a normal RFL resin as a two-bath treatment liquid. It is also possible to perform the treatment with only one bath using the mixed liquid of the components (A), (B), (C), and (D). In addition, these components are in terms of dry weight ratio, the component (A) is 2 to 75% of the dry weight of the adhesive composition, the component (B) is 15 to 87% of the dry weight of the adhesive composition, the component (C) is 11 to 70% of the dry weight of the adhesive composition, and the component (D) is preferably 20% or less of the dry weight of the adhesive composition.

[0048] On the other hand, from the perspective of environmental protection, it is preferable to use a dip treatment liquid that does not contain resorcinol and formalin as the adhesive composition for organic fiber cords. Examples of such a dip treatment liquid include a composition containing a rubber latex (a) having an unsaturated diene and one or more compounds (b) selected from a compound containing a skeletal structure composed of a polyether and an amine functional group, a compound having an acrylamide structure, a polypeptide, a polylysine, and a carbodiimide. In addition, examples of such a dip treatment liquid include a composition containing one or more selected from an aqueous compound (c) having a (thermally dissociable blocked) isocyanate group, a polyphenol (d), and a polyvalent metal salt (e) in addition to the rubber latex (a) having an unsaturated diene and the compound (b).

[0049] In addition, examples of the dip treatment liquid that does not contain resorcinol and formalin include a composition containing polyphenols (I) and aldehydes (II). Further, such a composition may further contain at least one of an isocyanate compound (III) and a rubber latex (IV) in addition to the polyphenols (I) and aldehydes (II).

[0050] In addition, by using an adhesive composition for treating, i.e., coating, the organic fiber cord, which contains polyphenols (I) and aldehydes (II), good adhesiveness can be exhibited even when resorcinol is not used in consideration of the environmental load.

[0051] By containing polyphenols (I) as a resin component, the adhesiveness with the organic fiber cord can be enhanced. Here, the polyphenols (I) are typically water-soluble polyphenols, and are not particularly limited as long as they are polyphenols other than resorcinol (resorcinol). In the polyphenols (I), the number of aromatic rings or the number of hydroxyl groups can be appropriately selected.

[0052] From the viewpoint of realizing more excellent adhesiveness, the polyphenols (I) preferably have two or more hydroxyl groups, and more preferably have three or more hydroxyl groups. When the polyphenols have three or more hydroxyl groups, polyphenols or condensates of polyphenols are water-soluble in the adhesive composition (dip treatment solution) containing moisture. As a result, the polyphenols can be uniformly distributed in the adhesive composition, so that more excellent adhesiveness can be realized. Further, when the polyphenols (I) are polyphenols containing a plurality of, i.e., two or more aromatic rings, two or three hydroxyl groups are present at the ortho position, meta position or para position in each of those aromatic rings.

[0053] As the polyphenols (I), for example, those described as polyphenol compounds in International Publication No. 2022 / 130879 can be used. These polyphenols (I) may be used alone or in combination of two or more.

[0054] By containing aldehydes (II) as a resin component in addition to the above-mentioned polyphenols (I), high adhesiveness can be achieved together with the above-mentioned polyphenols (I). Here, the aldehydes (II) are not particularly limited and can be appropriately selected according to the required performance. In this specification, the aldehydes (II) include derivatives of aldehydes that are the source of aldehydes.

[0055] Examples of the aldehydes (II) include monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, chloral, butyraldehyde, caproaldehyde, allyl aldehyde, etc., or aliphatic dialdehydes such as glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipaldehyde, etc., aldehydes having an aromatic ring, dialdehyde starch, and the like. These aldehydes (II) may be used alone or in combination of two or more.

[0056] The aldehydes (II) are preferably aldehydes having an aromatic ring or aldehydes containing an aldehyde having an aromatic ring. This is because more excellent adhesiveness can be obtained. Also, the aldehydes (II) preferably do not contain formaldehyde. Here, "not containing formaldehyde" means, for example, that the content of formaldehyde in the total mass of aldehydes is less than 0.5% by mass.

[0057] In the above adhesive composition, polyphenols (I) and aldehydes (II) are in a condensed state, and the mass ratio of aldehydes having an aromatic ring to polyphenols (content of aldehydes having an aromatic ring / content of polyphenols) is preferably 0.1 or more and 3 or less. This is because the hardness and adhesiveness of the resin, which is the product of the condensation reaction occurring between polyphenols and aldehydes having an aromatic ring, become more suitable. From the same perspective, in the above adhesive composition, the mass ratio of aldehydes having an aromatic ring to polyphenols (content of aldehydes having an aromatic ring / content of polyphenols) is more preferably 0.25 or more, and more preferably 2.5 or less. Note that the above mass ratio is the mass of the dried product (solid content ratio).

[0058] Also, the total content of polyphenols (I) and aldehydes (II) in the above adhesive composition is preferably 3 to 30% by mass. This is because excellent adhesiveness can be ensured without deteriorating workability and the like. From the same perspective, in the above adhesive composition, the total content of polyphenols (I) and aldehydes (II) is more preferably 5% by mass or more, and more preferably 25% by mass or less. Note that the above total content is the mass of the dried product (solid content ratio).

[0059] The above adhesive composition preferably further contains an isocyanate compound (III) in addition to the above-mentioned polyphenols (I) and aldehydes (II). In this case, the adhesiveness of the adhesive composition can be further enhanced by the synergistic effect with polyphenols (I) and aldehydes (II).

[0060] Here, the isocyanate compound (III) is a compound that has the effect of promoting adhesion to a resin material that is an adherend of the adhesive composition, for example, a phenol / aldehyde resin obtained by condensing polyphenols (I) and aldehydes (II), and is a compound having an isocyanate group as a polar functional group. These isocyanate compounds (III) may be used alone or in combination of two or more.

[0061] The isocyanate compound (III) is not particularly limited, but from the viewpoint of further improving adhesiveness, it preferably contains a (blocked) isocyanate group-containing aromatic compound. By the adhesive composition containing a (blocked) isocyanate group-containing aromatic compound, as a result, the (blocked) isocyanate group-containing aromatic compound is distributed in the vicinity of the interface between the organic fiber cord and the adhesive composition, and a further adhesion promoting effect can be obtained. Due to this effect, the adhesiveness of the adhesive composition to the organic fiber cord can be further enhanced.

[0062] For the (blocked) isocyanate group-containing aromatic compound, those described in Japanese Patent Application No. 2023-040157 or those described in Japanese Patent Application No. 2023-030762 can be used.

[0063] The content of the isocyanate compound (III) in the adhesive composition is not particularly limited, but from the viewpoint of more surely ensuring excellent adhesiveness, it is preferably 5 to 65% by mass. From the same viewpoint, the content of the isocyanate compound (III) in the adhesive composition is more preferably 10% by mass or more, and more preferably 45% by mass or less. Note that the content is the mass of the dried product (solid content ratio).

[0064] In addition to the above-described polyphenols (I), aldehydes (II), and isocyanate compound (III), the adhesive composition can substantially further contain a rubber latex (IV). Thereby, the adhesiveness of the adhesive composition to a rubber member can be further enhanced.

[0065] Here, the rubber latex (IV) is not particularly limited. In addition to natural rubber (NR), synthetic rubbers such as polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), or vinyl pyridine-styrene-butadiene copolymer rubber (Vp) can be mentioned. These rubber latices (IV) may be used alone or in combination of two or more.

[0066] When preparing the adhesive composition containing the rubber latex (IV), it is preferable to mix the rubber latex (IV) with phenols (I) and aldehydes (II) before blending the isocyanate compound (III).

[0067] In the adhesive composition, the content of the rubber latex (IV) is preferably 20% by mass or more, more preferably 25% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less.

[0068] The method for producing the adhesive composition is not particularly limited. For example, a method of mixing raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV) and aging them, or a method of mixing polyphenols (I) and aldehydes (II), aging them, and then further adding rubber latex (IV) and aging them can be mentioned. When the raw materials contain the isocyanate compound (III), the method of adding the rubber latex (IV), aging it, and then adding the isocyanate compound (III) may also be used as the method for producing the adhesive composition.

[0069] Further, when the same material cords are used in the center region W1 and the shoulder region W2 of the belt reinforcing layer 7, for example, by making the number of cords driven in the center region W1 larger than the number of cords driven in the shoulder region W2, the rigidity per unit width of the shoulder region W2 can be set higher than the rigidity per unit width of the center region W1.

[0070] Furthermore, when the same material cords are used in the center region W1 and the shoulder region W2 of the belt reinforcing layer 7, by making the twist number of the fibers of the cords forming the center region W1 larger than the twist number of the fibers of the cords forming the shoulder region W2, the rigidity per unit width of the shoulder region W2 can be set higher than the rigidity per unit width of the center region W1.

[0071] The conditions for twisting the fibers constituting the cords are not particularly limited, and can be appropriately selected according to the required performance. For example, it can be single-twisted or double-twisted with the same kind of fibers, or can be single-twisted or double-twisted with a combination of different kinds of fibers.

[0072] In the tire 1 of the present invention, as shown in FIG. 1, it can be composed of one layer of the belt reinforcing layer 7, or as shown in FIG. 2, it can be composed of two or more layers (in FIG. 2, three layers of belt reinforcing layers 7 and 8) of belt reinforcing layers.

[0073] When the belt reinforcing layer 7 consists of a single layer (Fig. 1), for example, among the belt reinforcing layer 7, the rigidity per unit width of the shoulder region W2 can be set higher than the rigidity per unit width of the center region W1 by changing the material of the cords used in the center region W1 and the shoulder region W2, or by changing the number of cords driven and the number of twists of the fibers in the center region W1 and the shoulder region W2. Also, all the conditions of the material of the cords used, the number of cords driven, and the number of twists of the fibers can be changed between the center region W1 and the shoulder region W2.

[0074] When the belt reinforcing layer 7 consists of two or more layers (Fig. 2), for example, for one belt reinforcing layer 7, cords of the same material are used with a uniform number of drivings, and then, by providing an additional belt reinforcing layer 8 only in the shoulder region W2, the rigidity per unit width of the shoulder region W2 can be set higher than the rigidity per unit width of the center region W1. When there are two belt reinforcing layers 7 and 8 in the shoulder region W2, the total value of the rigidity per unit width of each of the belt reinforcing layers 7 and 8 becomes the rigidity per unit width of the shoulder region W2.

[0075] Note that what has been described above only shows a part of the embodiments of this invention, and combinations of these configurations with each other or various changes can be made without departing from the gist of this invention. For example, in the illustrated embodiments, the belt layer is two layers in all cases, but depending on the load conditions under which the tire is used, the belt layer can also be four layers or six layers. In the present invention, there are no particular limitations on the configurations other than the belt reinforcing layer described above, and they can be appropriately selected according to the performance required for a pneumatic tire.

Examples

[0076] Examples will be given below to explain the present invention in more detail, but the present invention is not limited to the following examples at all.

[0077] <Examples 1 - 5, Comparative Examples 1 - 3> It is assumed that samples of pneumatic tires equipped with belt reinforcing layers under the conditions shown in Table 1 are each produced. The tire size is 205 / 55R16, and except for the conditions shown in Table 1, all samples have the same configuration. Also, for the center region of the belt reinforcing layer, it has a width of 40% of the maximum belt width with the tire equatorial plane E in between, and the part excluding the center region of the belt reinforcing layer (about 8% of the maximum belt width × 2) is defined as the shoulder region. Among the samples of pneumatic tires, for Comparative Examples 1 - 2 and Examples 1 - 4, as shown in Fig. 1, they are configured to consist of a single layer of belt reinforcing layer. Furthermore, among the samples of pneumatic tires, for Comparative Example 3 and Example 5, as shown in Fig. 2, they are configured to have two layers of belt reinforcing layers provided in the shoulder region W2. For each sample, the modulus of elasticity used for the stiffness per millimeter in the shoulder region and the center region is the modulus of elasticity when a 2% strain is applied. Also, regarding the stiffness per millimeter in the shoulder region and the center region, it is expressed as an index value when the stiffness of Comparative Example 1 is set to 100, and the stiffness of the shoulder region / the stiffness of the center region is calculated based on this index value.

[0078] <Evaluation> The following evaluations were performed on the obtained samples of pneumatic tires. The results are shown in Table 1.

[0079] (1) Durability during high - speed driving Each sample of pneumatic tire was assembled on a 6.5J rim, and under an internal pressure filling of 240 kPa, it was run at a speed of 100 km / h for 10 minutes. If there was no failure, the speed was increased by 10 km / h each time, and it was indexed based on the speed at which failure occurred. The speed at which failure occurred was calculated based on past test data not shown in the table and the stiffness ratio of each belt reinforcing layer. The speed at the time of failure is shown in Table 1 as an index when the speed of Comparative Example 1 is taken as 100. Note that the larger the index value in the table, the better the high-speed durability.

[0080]

Table 1

[0081] From the results in Table 1, it was found that for each sample of Examples 1 to 5, all showed better results compared to the samples of Comparative Examples 1 to 3.

Industrial Applicability

[0082] According to the present invention, it is possible to provide a pneumatic tire excellent in durability during high-speed driving.

Explanation of Reference Numerals

[0083] 1 Pneumatic tire 2 Bead part 3 Carcass 4 Crown part 5a First belt layer 5b Second belt layer 6 Belt 7 Belt reinforcing layer 8 Belt reinforcing layer

Claims

1. A pneumatic tire comprising a radial carcass extending in a toroidal shape, a belt composed of at least two belt layers located on the outer peripheral side of the crown portion of the carcass and formed by rubber-coating cords, and at least one belt reinforcing layer located on the outer side of the belt in the tire radial direction and formed by rubber-coating cords extending substantially in the tire circumferential direction, wherein when the belt reinforcing layer is divided into a center region and a shoulder region in a cross-section in the tire width direction, the ratio (rigidity of the shoulder region / rigidity of the center region) of the rigidity per unit width (elastic modulus of the cord × number of plies) of the belt reinforcing layer between the center region and the shoulder region is 2.05 to 12.

00.

2. The pneumatic tire according to claim 1, wherein cords of different materials are used in the center region and the shoulder region of the belt reinforcing layer.

3. The pneumatic tire according to claim 2, wherein the cords constituting the shoulder region of the belt reinforcing layer have a higher elastic modulus than the cords constituting the center region of the belt reinforcing layer.

4. The pneumatic tire according to claim 1, wherein polyethylene terephthalate (PET) cords are used in both the center region and the shoulder region of the belt reinforcing layer.

5. The pneumatic tire according to claim 4, wherein the number of plies of the cords constituting the shoulder region of the belt reinforcing layer is larger than the number of plies of the cords constituting the center region of the belt reinforcing layer.

6. The pneumatic tire according to claim 4, wherein the number of twists of the cords constituting the shoulder region of the belt reinforcing layer is larger than the number of twists of the cords constituting the center region of the belt reinforcing layer.

7. The pneumatic tire according to any one of claims 1 to 6, wherein the belt reinforcing layer is composed of one belt reinforcing layer.

8. The pneumatic tire according to any one of claims 1 to 6, wherein the belt reinforcing layer comprises a center portion belt reinforcing layer covering the central portion in the width direction of the belt and a shoulder portion belt reinforcing layer covering the end portion of the belt.

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