Pneumatic tire

Abstract

The present invention solves the following problem: providing a pneumatic tire in which the reduction of tire performance is suppressed even when using polyamide fibers with low amide density. The solution is a pneumatic tire, characterized in that it comprises a carcass layer (50), belt layers (60A, 60B) and a belt reinforcement layer (70A), wherein the reinforcing cords (50-1, 70A-1) in the carcass layer (50) and / or the belt reinforcement layer (70A) comprise polyamide fibers with an amide density of 14.0 or less, and (i) when the measured thickness A from the outer peripheral surface of the reinforcing cord (50-1) of the carcass layer (50) on the tire inner surface side to the tire inner surface is measured at 100 equally spaced points, the average measured thickness A is 1.5 mm or less, or (ii) when the measured thickness D from the outer peripheral surface of the reinforcing cord (70A-1) of the belt reinforcement layer (70A) on the tire outer surface side to the tire outer surface is measured at 100 equally spaced points, the measured thickness D is 6.0 mm or less in more than 80% of the measured points.

Description

Technical Field

[0001] This invention relates to a pneumatic tire. Background Technology

[0002] Typically, inside a tire, a carcass layer containing reinforcing cords is configured to enhance the tire's strength and rigidity, and a belt layer containing reinforcing cords is configured on the radially outer side of the carcass layer. Furthermore, a belt reinforcement layer (also called a "cap layer") containing reinforcing cords can be provided on the radially outer side of the belt layer to further reinforce it. In these tire components, organic fiber cords such as polyamide (nylon) fiber cords are widely used as reinforcing cords for both the carcass layer and the belt reinforcement layer.

[0003] Meanwhile, in recent years, from the perspective of reducing environmental impact, it has become necessary to reduce the use of fossil resources such as oil and coal. Therefore, for the aforementioned organic fiber cords, consideration has been given to replacing cords derived from fossil resources with cords derived from biomass (biological resources), and in this replacement, it is necessary to fully maintain tire performance.

[0004] For example, Patent Document 1 discloses a reinforced ply having a reinforcing element comprising multifilament yarns made of nylon 4,10, and an inflatable vehicle tire including the reinforced ply, and teaches how to achieve environmental friendliness by making one of the two monomers of nylon 4,10 based on renewable raw materials.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: JP 2019-511411 A Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] As mentioned above, polyamide fiber cords are widely used as reinforcing cords in the carcass and belt reinforcement layers, and polyamide 6,6 (PA66) fiber cords are commonly used in these applications. However, polyamide 6,6 (PA66), the raw material for polyamide 6,6 fiber cords, is difficult to synthesize from biomass.

[0010] In contrast, as a result of the inventors' research, it was found that polyamide 4,10 (i.e., nylon 4,10) is readily synthesized from biomass, but compared to polyamide 6,6, it has a lower amide density and fewer hydrogen bonds between amide bonds, resulting in lower thermal properties. Therefore, organic fiber cords using such polyamide 4,10 exhibit reduced physical properties at high temperatures, and when such organic fiber cords are applied to tires, tire performance is degraded.

[0011] Therefore, the object of the present invention is to provide a pneumatic tire in which the reduction in tire performance is suppressed even when polyamide fibers with an amide density lower than that of polyamide 6,6 fibers are used.

[0012] Solution for solving the problem

[0013] The key features of the pneumatic tire of the present invention, which solves the above problems, are as follows.

[0014] [1] A pneumatic tire comprising:

[0015] A pair of tire bead sections;

[0016] A pair of tire sidewalls;

[0017] The tummy area that connects to the two sidewalls;

[0018] At least one carcass layer that extends in a ring shape across a pair of bead portions;

[0019] At least one belt layer disposed on the radially outer side of the tire crown portion of the carcass layer;

[0020] At least one belt reinforcement layer disposed on the radially outer side of the belt layer of the tire; and

[0021] At least one airtight layer is disposed adjacent to the inner surface side of the tire carcass ply, wherein

[0022] The carcass and belt reinforcement layers include reinforcing cords.

[0023] The reinforcing cords of at least one of the carcass layer and the belt reinforcement layer comprise polyamide fibers with an amide density of less than 14.0, and

[0024] In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the thickness of the reinforcing cord of the carcass layer from the outer circumferential surface on the tire inner surface to the tire inner surface is measured at 100 equally spaced points, the average measured thickness is less than 1.5 mm.

[0025] [2] A pneumatic tire comprising:

[0026] A pair of tire bead sections;

[0027] A pair of tire sidewalls;

[0028] The tummy area that connects to the two sidewalls;

[0029] At least one carcass layer that extends in a ring shape across a pair of bead portions;

[0030] At least one belt layer disposed on the radially outer side of the crown portion of the tire carcass; and

[0031] At least one belt reinforcement layer disposed on the radially outer side of the belt layer of the tire, wherein

[0032] The carcass and belt reinforcement layers include reinforcing cords.

[0033] The reinforcing cords of at least one of the carcass layer and the belt reinforcement layer comprise polyamide fibers with an amide density of less than 14.0, and

[0034] In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the thickness of the belt reinforcement layer's reinforcing cord on the tire outer surface side from the outermost position in the tire radial direction to the tire outer surface is measured at 100 equally spaced points, the measurement points with a thickness of 6.0 mm or less account for more than 80%.

[0035] [3] The pneumatic tire according to [1] or [2], wherein the reinforcing cords of both the carcass layer and the belt reinforcement layer comprise polyamide fibers with an amide density of less than 14.0.

[0036] [4] The pneumatic tire according to any one of [1] to [3], wherein the polyamide fiber with an amide density of 14.0 or less is polyamide 4,10 fiber.

[0037] [5] The pneumatic tire according to any one of [1], [3] and [4], wherein the total thickness of the airtight layer is less than 1.0 mm.

[0038] The effects of the invention

[0039] According to the present invention, a pneumatic tire can be provided in which the reduction of tire performance is suppressed even when polyamide fibers with an amide density lower than that of polyamide 6,6 fibers are used. Attached Figure Description

[0040] In the attached diagram:

[0041] [ Figure 1 [I] is a cross-sectional view showing an example of a pneumatic tire according to a first embodiment of the present invention;

[0042] [ Figure 2 ]yes Figure 1 A magnified view of the tread portion of the pneumatic tire shown.

[0043] [ Figure 3 [A] is a cross-sectional view illustrating an example of a pneumatic tire according to a second embodiment of the present invention; and

[0044] [ Figure 4]yes Figure 3 A magnified view of the tread portion of the pneumatic tire shown. Detailed Implementation

[0045] In the following text, the pneumatic tire of the present invention will be described in detail based on its embodiments.

[0046] <Definition>

[0047] In this specification, "biodegradation rate" refers to the proportion of carbon derived from biomass and is calculated according to the following formula (1):

[0048] Bioavailability (%) = (Number of carbon atoms derived from biomass / Total number of carbon atoms) × 100 (1)

[0049] Furthermore, in this specification, "the bioavailability of the entire cord" refers to the proportion of carbon derived from biomass in the entire cord, and is calculated according to the following formula (2):

[0050] Bioavailability of the entire cord (%) = (Number of carbon atoms derived from biomass in the entire cord / Total number of carbon atoms in the entire cord) × 100 (2)

[0051] Furthermore, in this specification, the heat shrinkage rate of the reinforcing cord is measured according to ASTM D885 and ASTM D4974, and is the value measured after heating at 177°C for 2 minutes.

[0052] Furthermore, in this specification, the "amide density" of the polyamide is calculated according to the following formula (3):

[0053] Amide density = (Number of amide groups in polyamide / Number of atoms in the main chain of polyamide) × 100 (3)

[0054] Here, the "number of amide groups in the polyamide" and the "number of atoms in the main chain of the polyamide" are calculated from the "number of amide groups" and the "number of atoms in the main chain" of a repeating unit of the polyamide.

[0055] For example, the amide density of polyamide 4 and polyamide 4,4 is 20.0, the amide density of polyamide 5,4 is 18.2, the amide density of polyamide 4,6 is 16.7, the amide density of polyamide 5,6 is 15.4, the amide density of polyamide 6 and polyamide 6,6 is 14.3, the amide density of polyamide 4,10 is 12.5, the amide density of polyamide 6,10 is 11.1, the amide density of polyamide 9,T is 10.5, the amide density of polyamide 10,10 is 9.1, and the amide density of polyamide 11 is 8.3.

[0056] In this specification, "derived from biomass" means derived from biological resources such as plant resources, animal resources or microbial resources, and is synonymous with "derived from organisms".

[0057] Furthermore, the compounds described in this specification may be derived in whole or in part from fossil resources, from biological resources such as plant resources, or from renewable resources such as waste tires. They may also be derived from any mixture of two or more of fossil resources, biological resources, and renewable resources.

[0058] <Pneumatic Tires>

[0059] According to a first embodiment of the present invention, a pneumatic tire includes a pair of bead portions, a pair of sidewall portions, and a tread portion connected to the two sidewall portions, and includes at least one carcass layer extending annularly across the pair of bead portions, at least one belt layer disposed on the outer side of the tire radial direction of the crown portion of the carcass layer, at least one belt reinforcement layer disposed on the outer side of the tire radial direction of the belt layer, and at least one airtight layer disposed adjacent to the inner surface side of the carcass layer.

[0060] In the pneumatic tire of the first embodiment of the present invention, the carcass layer and the belt reinforcement layer include reinforcing cords, and the reinforcing cords of at least one of the carcass layer and the belt reinforcement layer contain polyamide fibers with an amide density of 14.0 or less. In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the thickness of the reinforcing cord of the carcass layer at 100 equally spaced points is measured from the outer peripheral surface on the tire inner surface side of the innermost position in the tire radial direction to the tire inner surface, the average measured thickness is 1.5 mm or less.

[0061] Compared to polyamide 6,6 fibers, polyamide fibers with an amide density of 14.0 or less have a lower amide density and fewer hydrogen bonds between amide bonds, resulting in lower thermal properties. Therefore, polyamide fibers with an amide density of 14.0 or less exhibit reduced physical properties at high temperatures, and thus the carcass layer and / or belt reinforcement layer of reinforcing cords containing polyamide fibers with an amide density of 14.0 or less will experience performance degradation at high temperatures.

[0062] In contrast, in the pneumatic tire of the first embodiment of the present invention, in the region where the belt reinforcement layer is disposed, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, by making the average thickness (i.e., the sum of the total thickness of the airtight layer and the thickness of the coated rubber of the tire carcass layer at the innermost position in the tire radial direction) from the outer peripheral surface of the reinforcing cord on the inner surface of the tire carcass layer at the innermost position in the tire radial direction to the inner surface of the tire 1.5 mm or less, the heat generated inside the tire during driving can be dissipated quickly, and the high temperature inside the tire during driving can be suppressed, thereby suppressing the degradation of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less, and maintaining tire performance.

[0063] Therefore, even when using polyamide fibers with an amide density of 14.0 or less, the pneumatic tire of the first embodiment of the present invention suppresses the reduction of tire performance.

[0064] The average thickness of the tire from the outer circumferential surface of the reinforcing cord of the carcass ply at the innermost position in the radial direction to the inner surface of the tire (i.e., the sum of the total thickness of the airtight layer and the thickness of the coated rubber of the carcass ply at the innermost position in the radial direction) is preferably 1.0 mm or less. Pneumatic tires with an average measured thickness of 1.0 mm or less are suitable for use as racing tires.

[0065] Furthermore, according to a second embodiment of the present invention, the pneumatic tire includes a pair of bead portions, a pair of sidewall portions, and a tread portion connected to the two sidewall portions, and includes at least one carcass layer extending annularly across the pair of bead portions, at least one belt layer disposed on the outer side of the tire radial direction of the crown portion of the carcass layer, and at least one belt reinforcement layer disposed on the outer side of the tire radial direction of the belt layer.

[0066] In the pneumatic tire of the second embodiment of the present invention, the carcass layer and the belt reinforcement layer include reinforcing cords, and the reinforcing cords of at least one of the carcass layer and the belt reinforcement layer contain polyamide fibers with an amide density of 14.0 or less. In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the thickness of the reinforcing cord of the belt reinforcement layer at the outermost position in the tire radial direction is measured at 100 equally spaced points from the outer peripheral surface on the tire outer surface side to the tire outer surface, the measurement points with a thickness of 6.0 mm or less account for more than 80%.

[0067] Compared to polyamide 6,6 fibers, polyamide fibers with an amide density of 14.0 or less have a lower amide density and fewer hydrogen bonds between amide bonds, resulting in lower thermal properties. Therefore, polyamide fibers with an amide density of 14.0 or less exhibit reduced physical properties at high temperatures, and thus the carcass layer and / or belt reinforcement layer of reinforcing cords containing polyamide fibers with an amide density of 14.0 or less will experience performance degradation at high temperatures.

[0068] In contrast, in the pneumatic tire of the second embodiment of the present invention, in the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, by ensuring that when the thickness of the reinforcing cord of the belt reinforcement layer at the outermost position in the tire radial direction is measured at 100 equally spaced points from the outer peripheral surface on the tire outer surface side to the tire outer surface, the measurement points with a thickness of 6.0 mm or less account for more than 80%, the heat generated inside the tire during driving can be dissipated quickly, and the high temperature inside the tire during driving can be suppressed, thereby suppressing the reduction of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less, and maintaining tire performance.

[0069] Therefore, even when using polyamide fibers with an amide density of 14.0 or less, the pneumatic tire of the second embodiment of the present invention suppresses the reduction of tire performance.

[0070] (Carcass layer and belt reinforcement layer)

[0071] The carcass and belt reinforcement layers consist of reinforcing cords and are typically formed by covering the reinforcing cords with coated rubber.

[0072] -Coated rubber-

[0073] As a coating rubber used for the carcass layer and belt reinforcement layer, a rubber composition in which rubber components such as natural rubber or synthetic rubber are mixed with fillers such as carbon black, antioxidants, vulcanizing agents such as sulfur, and vulcanization accelerators can be used.

[0074] The coated rubber preferably has a loss tangent tanδ(24°C) of less than 0.15, measured under the conditions of temperature 24°C, initial strain 6%, amplitude ±1%, and frequency 52Hz, and (ii) a loss tangent tanδ(60°C) of less than 0.10, measured under the conditions of temperature 60°C, initial strain 1.5%, amplitude ±1%, and frequency 52Hz. By ensuring that the loss tangent tanδ(24°C) is less than 0.15 and less than 0.10 under the conditions of temperature 60°C, initial strain 1.5%, amplitude ±1%, and frequency 52Hz, the hysteresis loss of the coated rubber from near room temperature to driving temperature can be reduced, and heat generation inside the tire can be suppressed. Furthermore, by suppressing the heat generated inside the tire, the high temperature inside the tire can be suppressed, thereby suppressing the reduction in the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less. As a result, the performance of the carcass layer and / or belt reinforcement layer containing the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less can be maintained.

[0075] Here, the loss tangent tanδ of the coated rubber can be measured using a viscoelasticity measuring device (manufactured by Rheometric Scientific).

[0076] The coated rubber preferably has (i) a loss tangent tanδ (24°C) of 0.15 or less, more preferably 0.12 or less. When the loss tangent tanδ (24°C) of the coated rubber is 0.12 or less, heat generation inside the tire near room temperature can be further suppressed, and the degradation of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less can be further suppressed, so that the performance of the carcass layer and / or belt reinforcement layer containing the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less can be maintained more reliably. Therefore, using a coated rubber carcass layer and / or belt reinforcement layer with a loss tangent tanδ (24°C) of 0.12 or less can further suppress the degradation of tire performance.

[0077] The coated rubber preferably has (ii) a loss tangent tanδ (60°C) of 0.10 or less, more preferably 0.07 or less. When the loss tangent tanδ (60°C) of the coated rubber is 0.07 or less, heat generation inside the tire during driving can be further suppressed, and high temperatures inside the tire can be further suppressed, thereby further suppressing the degradation of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less. This allows the performance of the carcass layer and / or belt reinforcement layer containing the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less to be maintained more reliably. Therefore, using a coated rubber carcass layer and / or belt reinforcement layer with a loss tangent tanδ (60°C) of 0.07 or less can further suppress the degradation of tire performance.

[0078] There are no particular limitations on the rubber components used in rubber compositions for coating rubber, and a variety of elastomers can be applied. Examples of such elastomers include natural rubber (NR), synthetic isoprene rubber (IR), epoxidized natural rubber, styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR, high cis BR and low cis BR), nitrile rubber (NBR), hydrogenated NBR, hydrogenated SBR and other diene rubbers and their hydrogenated products; ethylene-propylene rubber (EPDM, EPM), maleic acid modified ethylene-propylene rubber (M-EPM), butyl rubber (IIR), copolymers of isobutylene and aromatic vinyl or diene monomers, acrylic rubbers (ACM), ionomers and other olefin rubbers; brominated butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-IIR), brominated copolymers of isobutylene and p-methylstyrene (Br-IPMS), chloroprene rubber (CR), epichlorohydrin rubber (hydrin chlorosulfonated polyethylene rubber (CHR), chlorinated polyethylene rubber (CSM), maleic acid modified chlorinated polyethylene rubber (M-CM) and other halogenated rubbers; methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber and other silicone rubbers; polysulfide rubber and other sulfur-containing rubbers; vinylidene fluoride rubbers, fluorinated vinyl ether rubbers, tetrafluoroethylene-propylene rubbers, fluorinated silicone rubbers, fluorinated phosphazene rubbers and other fluororubbers; and styrene elastomers, olefin elastomers, ester elastomers, urethane elastomers, polyamide elastomers and other thermoplastic elastomers.

[0079] Natural rubber (NR) and synthetic isoprene rubber (IR) are preferred as rubber components used in the coating rubber for the carcass and belt reinforcement layers. The natural rubber may be modified. For example, in the case of modified natural rubber, a nitrogen content of 0.1 to 0.3% by mass is preferred. Furthermore, it is preferred that the modified natural rubber has had proteins removed through centrifugation, enzymatic treatment, or urea treatment. It is also preferred that the modified natural rubber has a phosphorus content exceeding 200 ppm and below 900 ppm.

[0080] The rubber composition used for coating preferably comprises natural rubber and styrene-butadiene copolymer rubber as rubber components, and the content of natural rubber in 100 parts by weight of the rubber component is preferably 70 parts by weight or more. The content of natural rubber in the rubber composition for coating is more preferably 70 to 90 parts by weight relative to 100 parts by weight of the rubber component. Furthermore, the content of styrene-butadiene copolymer rubber in the rubber composition for coating is preferably 10 to 30 parts by weight relative to 100 parts by weight of the rubber component. When the rubber composition comprises natural rubber and styrene-butadiene copolymer rubber as rubber components, and the content of natural rubber is 70 parts by weight or more relative to 100 parts by weight of the rubber component, the hysteresis loss of the coated rubber becomes even smaller, further suppressing heat generation inside the tire and more reliably suppressing high temperatures inside the tire. Therefore, using such coated rubber in the carcass layer and / or belt reinforcement layer can further suppress the reduction of tire performance.

[0081] As the styrene-butadiene copolymer rubber, non-oil-extended styrene-butadiene copolymer rubber is preferred. By including non-oil-extended styrene-butadiene copolymer rubber in the rubber composition, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, using the carcass layer and / or belt reinforcement layer of the coated rubber containing non-oil-extended styrene-butadiene copolymer rubber can further suppress heat generation inside the tire and further suppress the degradation of tire performance.

[0082] There are no particular limitations on the carbon black used in the coated rubber for the carcass and belt reinforcement layers, and examples include GPF, FEF, HAF, ISAF, and SAF grades of carbon black. These carbon blacks can be used alone or in combination of two or more. The carbon black content is preferably in the range of 40 to 80 parts by weight relative to 100 parts by weight of the rubber composition, more preferably in the range of 50 to 70 parts by weight.

[0083] In one embodiment, GPF, FEF, and HAF grade carbon black are preferred as the carbon black used in coating the rubber. The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 40 m². 2 / g or less, preferably 34m 2 / g or less, especially preferably 30m 2 / g or less. The nitrogen adsorption specific surface area (N2SA) of carbon black can also be 25m². 2 / g or more. The carbon black content is preferably 30 to 60 parts by weight, more preferably 40 to 50 parts by weight, relative to 100 parts by weight of the rubber component. When the rubber composition for coating rubber contains 30 to 60 parts by weight of carbon black relative to 100 parts by weight of the rubber component, and the nitrogen adsorption specific surface area (N2SA) of the carbon black is 40 m² / g or more. 2 At g / g or below, the hysteresis loss of the coated rubber becomes even smaller, further suppressing heat generation inside the tire and more reliably suppressing high temperatures inside the tire. Therefore, using carcass layers and / or belt reinforcement layers with this type of coated rubber can further suppress the degradation of tire performance when applied to tires.

[0084] Carbon black can be recycled carbon black. Here, "recycled carbon black" refers to carbon black obtained through recycling from waste materials that have already undergone recycling. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber is not limited to that generated from rubber products, but refers to all waste rubber, including unwanted scraps generated during the production or repair of rubber products. Examples of such scraps include, for example, polishing powder and stripping rubber. Polishing powder is, for example, fine rubber produced in a polishing process in tire retreading where the tread remaining on the base tire is scraped off. Stripping rubber is, for example, a long strip of rubber about 1 to 2 cm wide peeled from the surface of a rubber product such as a tire. Stripping rubber is produced by scraping the surface of a rubber product such as a tire using a knife with a U-shaped or V-shaped tip as a stripper. Furthermore, waste rubber is not limited to cross-linked rubber, but also includes unvulcanized rubber. Rubber products include, for example, finished products such as tires and rubber hoses, as well as rubber parts or components in the manufacturing stage of the finished products. Used tires can be retreaded tires, tires generated in connection with tire replacement or vehicle scrapping, tires that have reached the end of their service life (ELT), or any tire discarded for any reason. Waste oil is not limited to waste oil generated from the decomposition of plastics or rubber, but includes, for example, used oils from industrial emissions, such as animal or vegetable oils, lubricating oils, insulating oils, and cutting oils. Preferably, the waste oil used contains no components other than organic matter, such as those derived from silicone rubber or polyvinyl chloride. It is also preferred that the waste oil contains carbon black or carbon black-containing rubber.

[0085] "Recycled carbon black" is different from carbon black produced directly from hydrocarbons such as petroleum, natural gas, or coal; that is, it is not recycled carbon black. Note that "used" here includes not only items that have been actually used and then discarded, but also items that were manufactured but discarded and not actually used.

[0086] Furthermore, it is preferable to obtain recycled carbon black through the thermal decomposition of vulcanized rubber articles containing carbon black. Recycled carbon black obtained through the thermal decomposition of vulcanized rubber articles containing carbon black is readily available because there are large quantities of vulcanized rubber articles containing carbon black, and it can be easily obtained through thermal decomposition. Furthermore, it is preferable to obtain recycled carbon black from the solid residue generated by the thermal decomposition of vulcanized rubber articles containing carbon black. When the rubber articles containing carbon black are thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black can be recovered from either.

[0087] When recovering carbon black from volatile components, oil fractions with a specific gravity suitable for carbon black manufacturing can be recovered and used to manufacture carbon black using existing carbon black manufacturing methods (e.g., see JP 2015-520259 A). In this case, unlike carbon black recovered from solid residues, there are advantages such as the absence of impurities and the absence of mixing of different grades. Furthermore, in the manufacture of carbon black with a low environmental impact, various options exist, such as using not only oil obtained by recovering volatile components from the aforementioned thermal decomposition of rubber, but also vegetable oil and oil derived from waste plastics. However, due to demand for other uses such as food, there are issues in ensuring sufficient quantities of edible resources like vegetable oil, and the environmental impact associated with the expansion of arable land must also be considered. Additionally, oil derived from waste plastics is used for other purposes, such as the horizontal recycling of plastics, thus potentially causing supply-side problems. On the other hand, when using volatile components (oil) generated from the thermal decomposition of vulcanized rubber products, especially tires, existing materials in the tire industry can be reused, thereby reducing the consumption of new materials in new tire manufacturing and contributing to a reduction in the environmental impact of industry. There are no particular restrictions on the grade of carbon black, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550 and N762, etc.

[0088] Furthermore, when recovering regenerated carbon black from solid residues, it is more preferable that the carbon black has undergone surface treatment or surface modification. Examples of surface treatment or surface modification include treatment with acids such as hydrofluoric acid, hydrochloric acid, or sulfuric acid, or peroxides. Surface treatment or surface modification can be carried out at room temperature, but is preferably carried out at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C to 100°C.

[0089] Preferably, when measured with a grind gauge, the recycled carbon black has three or more lines with a length of 10 mm or more, and among the particles that produce lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less. If the particle size of the third largest particle is 20 μm or less, the reclaimed carbon black has good dispersibility in the rubber composition, even when blended, and the durability of the rubber composition, especially the reduction in performance after degradation, can be suppressed. For measurement with a grind gauge, a paste of reclaimed carbon black can be prepared as the measurement sample according to JIS K5101-1-5, and it is preferable to set the applied load to 0.4 to 0.5 kN and the rotation speed of the glass plate to 90 to 110 r / min. Furthermore, the evaluation method based on the appearance of linear marks can be based on JIS K5400, and it is preferable to use a grind gauge with a range of 0 to 25 μm. If a grind gauge with an upper limit greater than 20 μm is used, it can be determined whether the particle size of the third largest particle is 20 μm or less, and therefore it can be used. Furthermore, when used for other purposes (other than the properties of rubber compositions containing recycled carbon black), the range of fineness gauges to be used can be appropriately selected according to the purpose.

[0090] Preferably, the ash content of the recycled carbon black is 0.5% by mass or more and 20% by mass or less. If the ash content in the recycled carbon black exceeds 20% by mass, there is a risk that tires with sufficient reinforcement cannot be obtained. Considering the reinforcement of the tire, it is preferable that the ash content is 10% by mass or less, more preferably 6% by mass or less.

[0091] In addition to carbon black, antioxidants, sulfur, and vulcanization accelerators, rubber compositions for coating rubber may also suitably include zinc oxide (zinc white) and stearic acid, which are commonly used in rubber products such as tires. Here, the amount of zinc white in the rubber composition is preferably greater than 3 parts by weight and less than 5 parts by weight relative to 100 parts by weight of the rubber component. If the amount of zinc white is 5 parts by weight or more, aggregation may occur and dispersibility may deteriorate; and if it is 3 parts by weight or less, there is a risk of adversely affecting the vulcanization reaction.

[0092] Preferably, the rubber composition for coating rubber does not contain oil derived from the polymer. Here, "does not contain oil derived from the polymer" means that the rubber composition does not contain oil indirectly blended as a component included in the polymer, such as rubber components. By setting the content of polymer-derived oil in the rubber composition for coating rubber to zero, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, using the carcass layer and / or belt reinforcement layer of the rubber composition for coating rubber that does not contain polymer-derived oil can further suppress the reduction of tire performance.

[0093] Further preferably, the oil content in the rubber composition for coating is 0.2% by mass or less. By setting the oil content in the rubber composition for coating to 0.2% by mass or less, the loss tangent tanδ (24°C) of the rubber composition can be further reduced. Therefore, using the carcass layer and / or belt reinforcement layer of the rubber composition for coating with an oil content of 0.2% by mass or less can further suppress the reduction in tire performance.

[0094] -Reinforced cords containing polyamide fibers with an amide density of 14.0 or less-

[0095] The reinforcing cord of at least one of the carcass layer and the belt reinforcement layer comprises polyamide fibers with an amide density of less than 14.0. Compared with widely used polyamide 6,6 (PA66) fibers, polyamide fibers with an amide density of less than 14.0 have a lower amide density and fewer hydrogen bonds between amide bonds, resulting in lower thermal properties and reduced physical properties at high temperatures.

[0096] In contrast, in the tire of the first embodiment of the present invention, by making the measured thickness (distance) from the outer peripheral surface of the reinforcing cord of the carcass layer at the innermost position in the radial direction of the tire to the inner surface of the tire (in other words, the sum of the total thickness of the airtight layer and the thickness of the coated rubber of the carcass layer at the innermost position in the radial direction of the tire) average 1.5 mm or less, the heat generated inside the tire during driving can be dissipated quickly, and the tire performance can be maintained by suppressing the high temperature inside the tire during driving.

[0097] Furthermore, in the tire of the second embodiment of the present invention, by ensuring that when the thickness of the reinforcing cord of the belt reinforcement layer at the outermost position in the radial direction of the tire is measured at 100 equally spaced points, the measurement points with a thickness of 6.0 mm or less account for more than 80% (i.e., by making the sum of the total thickness of the tread rubber layer and the thickness of the coated rubber of the belt reinforcement layer thin), the heat generated inside the tire during driving can be dissipated quickly, and the tire performance is maintained by suppressing the high temperature inside the tire during driving.

[0098] There is no particular limitation on the lower limit of the amide density of polyamide fibers, but it is preferred that the amide density of polyamide fibers be 10.5 or higher. If the amide density of polyamide fibers is 10.5 or higher, some hydrogen bonds are formed between the amide bonds, which can mitigate the decrease in thermal properties.

[0099] Polyamide fibers with an amide density of 14.0 or less are readily available, and such polyamide fibers with high biocompatibility have a significant effect on reducing environmental impact. Therefore, in pneumatic tires in which reinforcing cords containing polyamide fibers with an amide density of 14.0 or less are applied to at least one of the carcass ply and the belt reinforcement ply, environmental impact can be easily reduced.

[0100] Preferably, the reinforcing cords of both the carcass ply and the belt reinforcement ply comprise polyamide fibers with an amide density of 14.0 or less. In tires where the reinforcing cords of both the carcass ply and the belt reinforcement ply comprise polyamide fibers with an amide density of 14.0 or less, it is easy to apply biomass-derived polyamide fibers to the reinforcing cords of the carcass ply and the belt reinforcement ply, thereby easily reducing environmental impact.

[0101] Preferably, for the entire cord, the carbon content (bioavailability) of the biomass source of the reinforcing cord, including polyamide fibers with an amide density of 14.0 or less, is 15% or more. If the bioavailability of the entire cord is 15% or more, the reduction in environmental impact is significant. From the viewpoint of further reducing environmental impact, it is preferable that the bioavailability of the reinforcing cord is 20% or more, and may be 100%, for the entire cord.

[0102] Preferably, the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less comprises fibers with a biomass-derived carbon content (bioavailability) of 40% or more. By including fibers with a bioavailability of 40% or more in the reinforcing cord, the reduction in environmental impact is significant. Examples of fibers (polyamide fibers) with a bioavailability of 40% or more include polyamide 11 (PA11) fibers, polyamide 4,10 (PA410) fibers, polyamide 6,10 (PA610) fibers, and polyamide 10,10 (PA1010), etc. The polyamide used as a raw material for these polyamide fibers can be synthesized from biomass-derived components. Here, biomass-derived components are components derived from biological resources such as plant resources, animal resources, and microbial resources.

[0103] Polyamide 11 (PA11) is obtained by the polymerization of aminoundecanoic acid, which is obtained from plant resources such as castor beans.

[0104] Polyamide 4,10 (PA410) is obtained by the condensation polymerization of tetramethylenediamine (4 carbons) and sebacic acid (10 carbons). Tetramethylenediamine is obtained from plant resources such as sugarcane, and sebacic acid is obtained from plant resources such as castor beans.

[0105] Polyamide 6,10 (PA610) is obtained by the condensation polymerization of hexamethylenediamine (6 carbons) and sebacic acid (10 carbons), and sebacic acid is obtained from plant resources such as castor beans.

[0106] Polyamide 10,10 (PA1010) is obtained by the condensation polymerization of decamethylenediamine (10 carbon atoms) and sebacic acid (10 carbon atoms), and the decamethylenediamine and sebacic acid are obtained from plant resources such as castor beans.

[0107] For example, tetramethylenediamine, also known as "putrescine", can be obtained by fermenting sugarcane to produce glutamic acid, biochemically producing ornithine from glutamic acid, and then decarboxylating the obtained ornithine.

[0108] In addition, sebacic acid can be obtained by mechanically pressing castor beans to obtain castor oil, by methanol decomposition of castor oil to obtain methyl ricinoleate, and by saponification of methyl ricinoleate.

[0109] Preferably, the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less comprises fibers with a bioavailability of 100% (i.e., completely biomass-derived). By including fibers with a bioavailability of 100%, the reduction effect on environmental impact is further enhanced. Examples of fibers with a bioavailability of 100% include polyamide 11 (PA11) fibers, polyamide 4,10 (PA410) fibers, and polyamide 10,10 (PA1010) fibers.

[0110] Examples of polyamide fibers with an amide density of 14.0 or less include polyamide 4,10 (PA410) fibers, polyamide 6,10 (PA610) fibers, polyamide 9,T (PA9T) fibers, polyamide 10,10 (PA1010) fibers, and polyamide 11 (PA11) fibers, among which polyamide 4,10 (PA410) fibers are preferred. Polyamide 4,10 fibers with a 100% biocompatibility can be used, and such polyamide 4,10 fibers with a 100% biocompatibility have a significant effect on reducing environmental impact. Therefore, in pneumatic tires in which reinforcing cords containing polyamide 4,10 fibers are applied to at least one of the carcass ply and belt reinforcement ply, environmental impact can be easily reduced.

[0111] The reinforcing cord may contain organic fibers other than polyamide fibers with an amide density of 14.0 or less. Here, there are no particular restrictions on the raw materials of organic fibers other than polyamide fibers with an amide density of 14.0 or less, and they may be derived from synthetic products; plant resources, animal resources or microbial resources, etc.; or they may be derived from mechanical recycling of resin products through crushing, melting and respinning; or from chemical recycling through depolymerization and repolymerization of resin products.

[0112] There are no particular restrictions on the materials used for organic fibers, and examples include polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethylene furanate (PEF); polyamides such as 6-nylon® (nylon is a registered trademark in Japan, other countries, or both), 6,6-nylon®, 4,6-nylon®, and aromatic polyamides; and cellulose fibers such as rayon and lyocell.

[0113] Examples of polyethylene terephthalate (PET) include polyethylene terephthalate obtained through mechanical or chemical recycling of PET articles or fabrics.

[0114] Examples of polyamides include those derived from biological resources, such as polyamide 4 (PA4), polyamide 4,4 (PA44), polyamide 5,4 (PA54), polyamide 4,6 (PA46), polyamide 5,6 (PA56), polyamide 6 (PA6: also known as 6-nylon®), and polyamide 6,6 (PA66: also known as 6,6-nylon®).

[0115] Preferably, the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less is a cord in which fibers with a bioavailability of 40% or more are twisted together with aromatic polyamide fibers. Due to the aromatic polyamide fibers, such reinforcing cords are rigid and have excellent thermal properties, and due to the fibers with a bioavailability of 40% or more, they have a significant effect on reducing environmental impact.

[0116] Preferably, the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less is obtained by twisting polyamide 4,10 fibers and aromatic polyamide fibers together. Due to the aromatic polyamide fibers, such reinforcing cords are rigid and have excellent thermal properties, and because polyamide 4,10 fibers with a biocompatibility of 100% can be used, the reduction in environmental impact is significant.

[0117] It is also preferred that the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less is obtained by twisting 2 to 4 fibers together. Reinforcing cords twisted from 2 to 4 fibers can achieve tire weight reduction while ensuring sufficient rigidity as a tire reinforcement component. From the same viewpoint, cords twisted from 2 fibers are preferred.

[0118] Preferably, the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less is obtained by twisting two aromatic polyamide fibers and one polyamide 4,10 fiber together. Due to the two aromatic polyamide fibers, this type of reinforcing cord is rigid and has excellent thermal properties, and because 100% biodegradable polyamide 4,10 fibers can be used, it significantly reduces environmental impact.

[0119] Preferably, the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is composed solely of polyamide fibers with a carbon content (bioavailability) of 15% or more from biomass sources. When the reinforcing cord is composed solely of polyamide fibers with a bioavailability of 15% or more, the environmental impact reduction effect is further enhanced.

[0120] Reinforcing cords can have a single-twist structure or a twist structure (such as a double-twist structure).

[0121] In the case of a single-twist structure, for example, the original yarns are aligned and twisted in one direction to obtain a twisted yarn cord. Here, the twist count is preferably in the range of 4 to 20 turns / 10cm. If the twist count in the single-twist structure exceeds 20 turns / 10cm, the strength of the twisted yarn cord may be reduced, and if it is less than 4 turns / 10cm, the twisted yarn cord may not achieve sufficient fatigue resistance.

[0122] In the case of a double-twist structure, for example, the original yarn is first given a single twist, and then combined and given a second twist in the opposite direction to obtain a twisted yarn cord. Here, the single twist is preferably in the range of 10 to 60 turns / 10cm, and the second twist is also preferably in the range of 10 to 60 turns / 10cm. If the single twist exceeds 60 turns / 10cm, the strength of the twisted yarn cord may decrease, and if it is less than 10 turns / 10cm, the twisted yarn cord may not achieve sufficient fatigue resistance. Similarly, if the second twist exceeds 60 turns / 10cm, the strength of the twisted yarn cord may decrease, and if it is less than 10 turns / 10cm, the twisted yarn cord may not achieve sufficient fatigue resistance.

[0123] Preferably, the heat shrinkage rate of the reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less is 12.0% or less. When the heat shrinkage rate of the reinforcing cord is 12.0% or less, the decrease in physical properties (especially elastic modulus and strength) at high temperatures can be suppressed. More preferably, the heat shrinkage rate of the reinforcing cord is 9.0% or less. When the heat shrinkage rate of the reinforcing cord is 9.0% or less, the uniformity is improved, particularly during high-speed operation.

[0124] The total fineness of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is preferably in the range of 1,000 to 6,000 dtex. If the total fineness of the reinforcing cord is less than 1,000 dtex, sufficient strength as a reinforcing cord for tires may not be obtained, and if it exceeds 6,000 dtex, the processing becomes thicker and the weight of the tire increases.

[0125] The breaking strength of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is preferably 6.0 cN / dtex or higher. Furthermore, the breaking strength of the reinforcing cord is preferably 180 N or higher. Here, the breaking strength is measured at room temperature (23°C) according to ASTM D855M. Sufficient reinforcement effect can be obtained when the breaking strength of the reinforcing cord is 6.0 cN / dtex or higher or 180 N or higher.

[0126] The elongation at break (elongation at break) of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is preferably 8.0% or more. Here, the elongation at break is measured at room temperature (23°C) according to ASTM D855M. When the elongation at break of the reinforcing cord is 8.0% or more, sufficient reinforcement effect can be obtained.

[0127] The moisture content of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is preferably 3.0% or less. Here, the moisture content is measured according to JIS L 1013. If the moisture content of the reinforcing cord exceeds 3.0%, the physical properties deteriorate and a sufficient reinforcing effect cannot be obtained.

[0128] -Other reinforcing cords-

[0129] When one of the carcass layer and the belt reinforcement layer includes a reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less, the other of the carcass layer and the belt reinforcement layer may not include a reinforcing cord comprising polyamide fibers with an amide density of 14.0 or less. In this case, any reinforcing cord comprising organic fibers can be used as the reinforcing cord, and in addition to polyamide fiber cords, polyester fiber cords, etc., can also be used.

[0130] -Adhesive Composition-

[0131] Preferably, the reinforcing cords used in the carcass layer and the belt reinforcement layer are treated with an adhesive composition.

[0132] As an adhesive composition, for example, one may mention an adhesive composition comprising at least one thermoplastic polymer (A), a heat-reactive waterborne polyurethane resin (B), and an epoxy compound (C), and optionally further comprising a rubber latex (D), wherein the thermoplastic polymer (A) has crosslinking functional groups as side groups and substantially does not contain addition-reactive carbon-carbon double bonds in its main chain structure. By treating the reinforcing cord with such an adhesive composition, the adhesion between the reinforcing cord and the elastomer (rubber-coated) at high temperatures can be improved.

[0133] Typically, a so-called two-bath treatment has been used as an adhesive treatment for organic fiber cords, in which an epoxy or isocyanate is applied to the cord surface, followed by the application of a resin (hereinafter referred to as RFL resin) obtained by mixing resorcinol, formaldehyde, and latex. However, with this method, the resin used in the first bath becomes very hard, increasing the strain input to the organic fiber cord and potentially reducing the cord's fatigue resistance. Furthermore, while this RFL resin can provide sufficient cord-elastomer adhesion at room temperature, the adhesion strength decreases significantly at temperatures above 130°C. In contrast, by using a first-bath mixed solution (adhesive composition) comprising at least one thermoplastic polymer (A), a thermally reactive waterborne polyurethane resin (B), and an epoxy compound (C), where the thermoplastic polymer (A) has crosslinking functional groups as side groups and substantially does not contain addition-reactive carbon-carbon double bonds in its main chain structure, sufficient adhesion to the elastomer (coated rubber) can be ensured even at temperatures above 180°C in the case of uncured reinforcing cords.

[0134] The thermoplastic polymer (A) has a main chain that is primarily linear, and preferred main chains include, for example, acrylic polymers, vinyl acetate polymers, vinyl acetate-ethylene copolymers, and other vinyl addition polymers; as well as polyurethane polymers. However, the thermoplastic polymer (A) only needs to have the function of suppressing the flowability of the resin at high temperatures and ensuring the resin's tensile strength through crosslinking of the functional groups of the side groups, and is not limited to the aforementioned vinyl addition polymers and polyurethane polymers.

[0135] As functional groups of the side groups of the thermoplastic polymer (A), oxazoline, bismaleimide, (terminated) isocyanate, aziridinyl, carbodiimide, hydrazine, epoxy, and epithio group are preferred.

[0136] The aforementioned thermoplastic polymer (A), thermally reactive waterborne polyurethane resin (B), epoxy compound (C), and rubber latex (D) may be those described in Japanese Patent Application No. 2023-040157 and Japanese Patent Application No. 2023-030762, respectively.

[0137] In the adhesive treatment of reinforcing cords, it is preferable to use a mixture of thermoplastic polymer (A), thermally reactive waterborne polyurethane resin (B), and epoxy compound (C) as the first bath treatment liquid (adhesive composition), and to use conventional RFL resin liquid as the second bath treatment liquid. Alternatively, in the above adhesive treatment, a mixture of thermoplastic polymer (A), thermally reactive waterborne polyurethane resin (B), epoxy compound (C), and rubber latex (D) can be used for a single-bath treatment.

[0138] In the above adhesive composition, the proportion (dry mass ratio) of thermoplastic polymer (A) is preferably 2 to 75%, the proportion (dry mass ratio) of heat-reactive waterborne polyurethane resin (B) is preferably 15 to 87%, the proportion (dry mass ratio) of epoxy compound (C) is preferably 11 to 70%, and the proportion (dry mass ratio) of rubber latex (D) is preferably 20% or less.

[0139] On the other hand, from an environmental protection point of view, it is preferable to use an impregnation treatment liquid that does not contain resorcinol and formaldehyde as the adhesive composition for reinforcing the cord. For example, a composition comprising a rubber latex having an unsaturated diene (a) and a compound (b) selected from compounds comprising a backbone structure composed of polyethers and amine functional groups, compounds having an acrylamide structure, polypeptides, polylysine, and carbodiimide can be mentioned as such an impregnation treatment liquid. Furthermore, in addition to the aforementioned rubber latex having an unsaturated diene (a) and compound (b), a composition further comprising at least one of an aqueous compound (c) having a (thermally dissociable-terminated) isocyanate group, polyphenols (d), and polyvalent metal salts (e) can be mentioned as such an impregnation treatment liquid.

[0140] Furthermore, compositions containing polyphenols (I) and aldehydes (II) may also be mentioned as impregnation treatment solutions free of resorcinol and formaldehyde. In addition to polyphenols (I) and aldehydes (II), such compositions may further contain at least one of isocyanate compounds (III) and rubber latex (IV).

[0141] When the adhesive composition used for adhesive treatment (coating) to reinforce cords contains polyphenols (I) and aldehydes (II), it can exhibit good adhesion even when resorcinol is not used, taking into account environmental impact.

[0142] --Polyphenols (I)--

[0143] When an adhesive composition contains polyphenols (I) as a resin component, its adhesion to reinforcing cords can be enhanced. Here, the polyphenols (I) are typically water-soluble polyphenols, and there are no particular limitations as long as they are polyphenols other than resorcinol (1,3-benzenehydrin). The number of aromatic rings or hydroxyl groups in the polyphenols (I) can be appropriately selected.

[0144] From the viewpoint of achieving or even better adhesion, it is preferable that the polyphenol (I) has two or more hydroxyl groups, more preferably three or more hydroxyl groups. When the polyphenol has three or more hydroxyl groups, the polyphenol or its condensate dissolves in the aqueous adhesive composition (impregnation treatment solution). As a result, the polyphenol can be uniformly distributed in the adhesive composition, thereby achieving or even better adhesion. Furthermore, when the polyphenol (I) is a polyphenol containing multiple (two or more) aromatic rings, in each of these aromatic rings, two or three hydroxyl groups are present at the ortho, meta, or para positions.

[0145] As polyphenols (I), for example, those described as polyphenol compounds in International Publication No. 2022 / 130879 can be used. These polyphenols (I) can be used alone or in combination of two or more.

[0146] --Aldehydes (II)--

[0147] When the adhesive composition contains an aldehyde (II) as a resin component in addition to the polyphenol (I) described above, high adhesion can be achieved together with the polyphenol (I). Here, the aldehyde (II) is not particularly limited and can be appropriately selected according to the desired performance. In this specification, the aldehyde (II) also includes aldehyde derivatives derived from aldehydes.

[0148] As aldehydes (II), examples include monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, chloraldehyde, butyraldehyde, hexanal, and allyl aldehyde; aliphatic dialdehydes such as glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, and adipaldehyde; aldehydes containing aromatic rings; and dialdehyde starch, etc. These aldehydes (II) can be used alone or in combination of two or more.

[0149] Preferably, the aldehyde (II) is an aldehyde containing an aromatic ring or includes aldehydes containing an aromatic ring. This is because even better adhesion can be obtained. Furthermore, it is preferred that the aldehyde (II) is formaldehyde-free. Here, "formaldehyde-free" means, for example, that the formaldehyde content in the total mass of the aldehyde is less than 0.5% by mass.

[0150] In the adhesive composition, it is preferable that, in the condensed state of the polyphenols (I) and aldehydes (II), the mass ratio of the polyphenols to the aromatic aldehydes (content of aromatic aldehydes / content of polyphenols) is 0.1 or more and 3 or less. In this case, the hardness and adhesiveness of the resin, as the product of the condensation reaction between the polyphenols and the aromatic aldehydes, become more suitable. From the same viewpoint, the mass ratio (content of aromatic aldehydes / content of polyphenols) in the adhesive composition is more preferably 0.25 or more, and more preferably 2.5 or less.

[0151] It should be noted that the above mass ratios are based on the mass of the dried product (solid content ratio).

[0152] Furthermore, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass. In this case, even better adhesion can be ensured without deterioration of workability, etc. From the same point of view, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is more preferably 5% by mass or more, and more preferably 25% by mass or less.

[0153] It should be noted that the total content mentioned above is based on the mass of the dried product (solid content ratio).

[0154] --Isocyanate compound (III)--

[0155] Preferably, in addition to the polyphenols (I) and aldehydes (II) described above, the adhesive composition further comprises an isocyanate compound (III). In this case, the adhesive properties of the adhesive composition can be further enhanced through the synergistic effect with the polyphenols (I) and aldehydes (II).

[0156] Here, the isocyanate compound (III) is a compound that promotes the bonding of resin materials (e.g., phenol / aldehyde resins obtained by condensing polyphenols (I) with aldehydes (II)) to the adhesive composition, and is a compound having an isocyanate group as a polar functional group. These isocyanate compounds (III) can be used alone or in combination of two or more.

[0157] There are no particular limitations on the isocyanate compounds (III), but from the viewpoint of further improving adhesion, it is preferred that they include aromatic compounds containing (terminated) isocyanate groups. When the adhesive composition contains aromatic compounds containing (terminated) isocyanate groups, the aromatic compounds containing (terminated) isocyanate groups are distributed near the interface between the reinforcing cord and the adhesive composition, resulting in a further adhesion-promoting effect, and due to this effect, the adhesion between the adhesive composition and the reinforcing cord can be further enhanced.

[0158] As aromatic compounds containing (terminated) isocyanate groups, those described in Japanese Patent Application No. 2023-040157 and Japanese Patent Application No. 2023-030762 can be used.

[0159] There is no particular limitation on the content of isocyanate compound (III) in the adhesive composition; however, from the viewpoint of more reliably ensuring excellent adhesion, it is preferably 5 to 65% by mass. From the same viewpoint, the content of isocyanate compound (III) in the adhesive composition is more preferably 10% by mass or more, and even more preferably 45% by mass or less.

[0160] It should be noted that the above contents are based on the mass of the dried product (solid content ratio).

[0161] --Rubber Latex (IV)--

[0162] In addition to the polyphenols (I), aldehydes (II), and isocyanate compounds (III) mentioned above, the adhesive composition may further substantially contain rubber latex (IV). By this means, the adhesive composition can further enhance the adhesion to rubber components.

[0163] Here, there are no particular limitations on the rubber latex (IV), and examples include synthetic rubbers in addition to natural rubber (NR), 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 vinylpyridine-styrene-butadiene copolymer rubber (Vp). These rubber latexes (IV) can be used alone or in combination of two or more.

[0164] When preparing an adhesive composition containing rubber latex (IV), it is preferable to blend the rubber latex (IV) with phenols (I) and aldehydes (II) before blending the isocyanate compound (III).

[0165] The content of rubber latex (IV) in the adhesive composition is preferably 20% by mass or more, more preferably 25% by mass or more, preferably 70% by mass or less, and more preferably 60% by mass or less.

[0166] There are no particular limitations on the method of manufacturing the adhesive composition, but examples include methods in which raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV) are mixed and cured, or methods in which polyphenols (I) and aldehydes (II) are mixed and cured, and then rubber latex (IV) is further added and cured. When the raw materials include isocyanate compound (III), the method may be to add rubber latex (IV) and cure it, and then add isocyanate compound (III).

[0167] (Belt layer)

[0168] The pneumatic tires of the first and second embodiments of the present invention include belt layers on the radially outer side of the crown portion of the carcass ply. The number of belt layers is not particularly limited and can be one, two, or three or more layers. The belt layers are typically formed by covering reinforcing cords extending at an angle (e.g., 15 to 40°) relative to the tire equator with coated rubber, and preferably, the steel cords are covered with coated rubber. Furthermore, typically, two or more belt layers are stacked such that the reinforcing cords constituting the belt layers cross each other across the tire equator, and the two or more belt layers are disposed on the radially outer side of the crown portion of the carcass ply.

[0169] -Coated rubber-

[0170] As a coating rubber for the belt layer, a rubber composition can be used in which rubber components such as natural rubber or synthetic rubber are mixed with fillers such as carbon black, antioxidants, adhesion promoters such as cobalt compounds containing cobalt salts, vulcanizing agents such as sulfur, and vulcanization accelerators.

[0171] Natural rubber (NR) and synthetic isoprene rubber (IR) are preferred rubber components used as coating rubber for the belt layer. The natural rubber may be modified. For example, in the case of modified natural rubber, it is preferred to have a nitrogen content of 0.1 to 0.3% by mass. Furthermore, it is preferred that the modified natural rubber has had proteins removed through centrifugation, enzyme treatment, or urea treatment. Additionally, the phosphorus content of the modified natural rubber is preferably greater than 200 ppm and less than 900 ppm.

[0172] There are no particular limitations on the carbon black used in the coated rubber of the belt layer, and examples include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks can be used alone or in combination of two or more. The carbon black content is preferably in the range of 40 to 80 parts by weight relative to 100 parts by weight of the rubber composition, more preferably in the range of 50 to 70 parts by weight. The carbon black can also be recycled carbon black. Here, "recycled carbon black" refers to carbon black obtained by recycling from waste materials that have undergone recycling, and is the same as the "recycled carbon black" mentioned above as an example of carbon black used in the coated rubber for the carcass layer or belt reinforcement layer. Examples of such recycled waste materials include rubber products containing carbon black (especially vulcanized rubber products), such as used rubber and used tires, as well as waste oil, and other details of the waste are as described above. "Recycled carbon black" is different from carbon black directly produced from hydrocarbons such as petroleum, natural gas, or coal, i.e., carbon black that is not recycled. Note that "used" here includes not only those that have been actually used and then discarded, but also those that were manufactured but discarded and not actually used.

[0173] Recycled carbon black for use in the belt layer coating rubber is preferably obtained through the thermal decomposition of a vulcanized rubber product containing carbon black. Since vulcanized rubber products containing carbon black are abundant and readily available through thermal decomposition, recycled carbon black obtained through the thermal decomposition of these products is readily available. Details of the thermal decomposition of vulcanized rubber products containing carbon black are described above.

[0174] Furthermore, the recycled carbon black used for coating the belt layer is preferably carbon black that has undergone surface treatment or surface modification when recovered from solid residues. Examples of surface treatment or surface modification include treatment with hydrofluoric acid, acids such as hydrochloric acid or sulfuric acid, or peroxides. Surface treatment or surface modification can be carried out at room temperature, but is preferably carried out at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C or higher and below 100°C.

[0175] The recycled carbon black used for coating rubber in the belt layer is preferably such that, when measured with a fineness gauge, there are three or more lines with a length of 10 mm or more, and among the particles that produce lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less. If the particle size of the third largest particle is 20 μm or less, the dispersibility of the recycled carbon black in the rubber composition is good even when it is blended, and the durability of the rubber composition, especially the reduction in performance after deterioration, can be suppressed. Details of the fineness gauge measurement are as described above.

[0176] The recycled carbon black used for coating rubber in the belt layer preferably has an ash content of 0.5% by mass or more and 20% by mass or less. If the ash content in the recycled carbon black exceeds 20% by mass, there is a risk that tires with sufficient reinforcement cannot be obtained. Considering the reinforcement of the tire, the ash content is preferably 10% by mass or less, more preferably 6% by mass or less.

[0177] -Reinforced Cord-

[0178] There are no particular limitations on the reinforcing cords used for the belt layer, but steel cords are preferred. The structure of the steel cords is not particularly limited. However, from the viewpoint of effectively achieving both improved tire durability and reduced rolling resistance, the steel cords can have a 1×N structure in which N filaments (where N is an integer greater than 2) are twisted together, an M+N structure in which N spirally twisted sheath filaments (where N is an integer greater than 1) surround M core filaments (where M is an integer greater than 1; the core filaments may be twisted together or bundled without twisting), or a compound twist structure in which multiple of the above 1×N or M+N structures are further twisted together. The cord can also be a monofilament in which the filaments are aligned parallel to each other without being twisted together.

[0179] Furthermore, in tires, steel cords can be used, for example, not only as belt cords in the belt layer (usually located in the tread), but also as belt reinforcement cords in the belt reinforcement layer; as carcass cords; as reinforcement cords in the steel bead wrap (usually located on the outer side of the carcass in the tire width direction); and as bead cords in the bead core (usually located in the bead portion); etc.

[0180] When the diameter of the wires constituting the above-mentioned steel wire cord is X (mm) and the tensile strength of the wires is Y (MPa), the following formula is preferably satisfied:

[0181] 4000-2000X≤Y≤4500-2000X

[0182] By using wires that satisfy the above formula, the strength of steel cord can be improved, and the cut resistance of tires can be enhanced. Here, the tensile strength of the wire is determined according to ISO 17832:2009.

[0183] From the viewpoint of fatigue resistance, the hardness of the surface layer of the wires constituting the aforementioned steel wire cord is preferably 90 to 110% relative to the hardness of the inner layer, and particularly preferably 100%. Hardness can be measured, for example, by Vickers hardness. The surface layer of the wire refers to the layer from the outermost surface to a depth of 0.01 mm, and the inner side refers to the inner layer of the wire. For the surface layer, hardness can be measured from the outermost surface to a depth of 0.005 mm, and for the inner layer, it can be measured in a region deeper than 0.04 mm.

[0184] The steel wires that make up the above-mentioned steel wire cords can be steel wires derived from recycled iron.

[0185] There are no particular restrictions on the raw materials for recycled iron, and examples include scrap iron and steel cord extracted from tires. Furthermore, from the viewpoint of reducing CO2 emissions, recycled iron obtained through electric arc furnaces (electric arc furnace steelmaking) is preferred.

[0186] The steel wire derived from recycled iron preferably has a nitrogen (N) content of 60 ppm to 200 ppm by mass, more preferably 60 ppm to 89 ppm by mass, a carbon (C) content of 0.7 to 1.0 wt%, a copper (Cu) content of 0.01 to 0.4 wt%, and a chromium (Cr) content of 0.05 to 0.3 wt%. This type of steel wire can be manufactured using general recycled iron with a nitrogen (N) content of 60 ppm to 200 ppm by mass, a carbon (C) content of 0.7 to 1.0 wt%, a copper (Cu) content of 0.01 to 0.4 wt%, and a chromium (Cr) content of 0.05 to 0.3 wt%. This type of steel wire does not require extensive refining during manufacturing, thus simplifying the manufacturing process. Furthermore, this type of steel wire reduces energy consumption during manufacturing and also reduces CO2 emissions, which is preferable from an environmental perspective.

[0187] The steel wire derived from recycled iron preferably has iron as its main component, and the Fe (iron) content is preferably 98% by mass or more.

[0188] (Airtight layer)

[0189] The pneumatic tire of the first embodiment of the present invention includes an airtight layer disposed adjacent to the inner surface side of the tire carcass layer. Furthermore, the pneumatic tire of the second embodiment of the present invention preferably includes an airtight layer disposed adjacent to the inner surface side of the tire carcass layer. The number of airtight layers is not particularly limited, and can be one or more layers. The airtight layer serves to maintain the internal pressure of the pneumatic tire, and a rubber with low air permeability is used in the airtight layer. As such a rubber with low air permeability, a rubber composition in which a rubber component such as butyl rubber or halogenated butyl rubber is blended with fillers such as carbon black, antioxidants, vulcanizing agents such as sulfur, and vulcanization accelerators can be used.

[0190] (specific example)

[0191] Next, examples of an inflatable tire according to a first embodiment of the present invention will be shown and described in detail with reference to the accompanying drawings.

[0192] Figure 1 This is a cross-sectional view of an example of a pneumatic tire according to the first embodiment of the present invention (more specifically, a cross-sectional view of the tire section orthogonal to the tire circumferential direction).

[0193] Figure 1 The tire 100 shown includes a pair of bead portions 10, a pair of sidewall portions 20, a tread portion 30 connected to the two sidewall portions 20, a carcass layer 50 extending in an annular shape between bead cores 40 embedded in the pair of bead portions 10, two belt layers 60A and 60B disposed on the outer side of the crown portion of the carcass layer 50 in the tire radial direction, a belt reinforcement layer (also called "crown belt layer") 70A disposed on the outer side of the belt layers 60A and 60B in the tire radial direction to cover the entire belt layers 60A and 60B, a pair of belt reinforcement layers (also called "layer ply") 70B configured to cover only the two ends of the belt reinforcement layer 70A, and an airtight layer 80 disposed adjacent to the inner surface side of the carcass layer 50.

[0194] exist Figure 1 In the tire 100 shown, the carcass layer 50 is a single layer, but in the pneumatic tire of the first embodiment of the present invention, the number of carcass layers can be two or more. Furthermore, in Figure 1 In the tire 100 shown, the carcass layer 50 includes a main body extending annularly between a pair of bead cores 40 embedded in the bead portion 10, and a turn-up portion that is wound radially outward from the inner side in the tire width direction around each bead core 40. However, the shape and structure of the carcass layer 50 in the pneumatic tire of the first embodiment of the present invention are not limited thereto. Here, the carcass layer 50 is preferably formed by multiple reinforcing cords extending in a direction substantially perpendicular to the tire circumferential direction (e.g., at an angle of 70° to 90°) covered with coated rubber; that is, the carcass layer 50 is preferably a radial carcass. As reinforcing cords of the carcass layer 50, reinforcing cords containing the aforementioned polyamide fibers are preferred, but when reinforcing cords containing the aforementioned polyamide fibers are applied to the belt reinforcement layers 70A and 70B, other organic fiber cords or steel wire cords can be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords.

[0195] In addition, Figure 1 In the tire 100 shown, belt layers 60A and 60B are two layers, but in the pneumatic tire of the first embodiment of the present invention, the number of belt layers can be one or more layers. Furthermore, in Figure 1 In the tire 100 shown, each of the belt layers 60A and 60B is typically formed by covering reinforcing cords that extend at an angle (e.g., 15° to 40°) relative to the tire equatorial plane with coated rubber, preferably by covering steel cords with coated rubber. Furthermore, the two belt layers 60A and 60B are stacked in such a way that the reinforcing cords constituting the belt layers 60A and 60B cross each other across the tire equatorial plane.

[0196] In addition, Figure 1 In the tire 100 shown, belt reinforcement layers 70A and 70B are formed by covering reinforcing cords arranged substantially parallel to the tire circumferential direction (e.g., at an angle of 0° to 5° relative to the tire circumferential direction) with coated rubber. Belt reinforcement layers 70A and 70B are formed by continuously spirally winding narrow strips prepared by covering the reinforcing cords with coated rubber in the tire circumferential direction. In this case, since there are no joints in the tire circumferential direction, the uniformity of the tire is improved, and since there are no joints, strain concentration at the joints is also prevented. Reinforcing cords containing the aforementioned polyamide fibers are preferred as reinforcing cords for belt reinforcement layers 70A and 70B; however, when reinforcing cords containing the aforementioned polyamide fibers are applied to the carcass layer 50, other organic fiber cords can be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords.

[0197] Notice, Figure 1 The tire 100 shown includes both belt reinforcement layer 70A and belt reinforcement layer 70B, but a tire in which either belt reinforcement layer 70A or belt reinforcement layer 70B is omitted is also an example of a pneumatic tire according to the first embodiment of the present invention. Furthermore, in Figure 1 In the tire 100 shown, each belt reinforcement layer (crown belt layer) 70A and belt reinforcement layer (ply layer) 70B is a single layer, but may be two or more layers.

[0198] In addition, Figure 1 In the tire 100 shown, the airtight layer 80 is a single layer, but in the pneumatic tire of the first embodiment of the present invention, the number of airtight layers can be two or more. The airtight layer 80 has the function of maintaining the internal pressure of the tire, and a rubber with low air permeability is used in the airtight layer 80.

[0199] Figure 2 yes Figure 1 An enlarged view of the portion of the tread 30 of the tire 100 shown, enclosed by dashed line II. Figure 2 In this embodiment, the carcass layer 50 and the belt reinforcement layer 70A include reinforcing cords 50-1 and 70A-1. Here, the carcass layer 50 is composed of reinforcing cords 50-1 and coated rubber 50-2 covering the reinforcing cords 50-1, and similarly, the belt reinforcement layer 70A is composed of reinforcing cords 70A-1 and coated rubber 70A-2 covering the reinforcing cords 70A-1. Furthermore, at least one of the reinforcing cords 50-1 of the carcass layer 50 and the reinforcing cords 70A-1 of the belt reinforcement layer 70A comprises polyamide fibers with an amide density of 14.0 or less.

[0200] Note that even the reinforcing cords 50-1 in the carcass layer 50 and the reinforcing cords 70A-1 in the belt reinforcing layer 70A do not contain polyamide fibers with an amide density of less than 14.0, but Figure 2 When the reinforcing cords of the belt reinforcement layer (ply layer) 70B (not shown) contain polyamide fibers with an amide density of 14.0 or less, such a tire is also an example of a pneumatic tire according to the first embodiment of the present invention.

[0201] exist Figure 1 and Figure 2 In the tire width direction D of the tire cross-section orthogonal to the tire circumferential direction. W In region R of the belt reinforcement layers 70A and 70B observed above, when measurements were taken from the tire radial direction D at 100 equally spaced points... R When measuring the thickness (distance) A from the outer circumferential surface of the reinforcing cord 50-1 of the innermost layer of the tire carcass 50 to the inner surface of the tire, the average measured thickness A is less than 1.5 mm. Figure 2 In the figure, the measured thickness A from the outer peripheral surface of the reinforcing cord 50-1 of the carcass ply 50 to the inner surface of the tire corresponds to the total thickness B of the airtight layer 80 and the tire radial direction D. R The thickness C of the coated rubber 50-2 at the innermost position of the carcass layer 50 is the sum of (i.e., A = B + C). As described above, by making the average measured thickness A less than 1.5 mm, and therefore thinner, heat generated inside the tire during driving can be dissipated quickly, and high temperatures inside the tire during driving can be suppressed. By suppressing high temperatures inside the tire during driving, the degradation of the physical properties of the reinforcing cords containing polyamide fibers with an amide density of less than 14.0 can be suppressed, thereby maintaining tire performance.

[0202] Furthermore, it is preferable that the average measured thickness A (i.e., the sum of the total thickness B of the airtight layer 80 and the thickness C of the coated rubber 50-2 of the carcass layer 50 at the innermost position in the radial direction of the tire) is 1.0 mm or less. Pneumatic tires with an average measured thickness A of 1.0 mm or less are suitable as racing tires.

[0203] In the pneumatic tire of the first embodiment of the present invention, it is preferable that both the reinforcing cords of the carcass layer 50 and the reinforcing cords of the belt reinforcement layers 70A and 70B contain polyamide fibers with an amide density of 14.0 or less. By making both the reinforcing cords of the carcass layer 50 and the reinforcing cords of the belt reinforcement layers 70A and 70B contain polyamide fibers with an amide density of 14.0 or less, it is easy to apply biomass-derived polyamide fibers to the reinforcing cords of the carcass layer 50 and the belt reinforcement layers 70A and 70B, and it is also easy to reduce the environmental impact.

[0204] In the pneumatic tire of the first embodiment of the present invention, it is preferable that the total thickness C of the airtight layer 80 is 1.0 mm or less. When the total thickness C of the airtight layer 80 is 1.0 mm or less, the radial direction D of the tire... R The average thickness A of the reinforcing cord 50-1 of the carcass layer 50 at the innermost position of the tire can be even thinner than the outer peripheral surface of the tire inner surface. This allows heat generated inside the tire during driving to dissipate even faster, further suppressing high temperatures inside the tire during driving, and further suppressing the degradation of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of less than 14.0, thereby ensuring more reliable maintenance of tire performance.

[0205] Next, examples of a pneumatic tire according to a second embodiment of the present invention will be shown and described in detail with reference to the accompanying drawings.

[0206] Figure 3 This is a cross-sectional view of an example of a pneumatic tire according to the second embodiment of the present invention (more specifically, a cross-sectional view of the tire section orthogonal to the tire circumferential direction).

[0207] Figure 3 The tire 100 shown includes a pair of bead portions 10, a pair of sidewall portions 20, and a tread portion 30 connected to the two sidewall portions 20. It also includes a carcass layer 50 extending in an annular shape between bead cores 40 embedded in the pair of bead portions 10, two belt layers 60A and 60B disposed on the outer side of the crown portion of the carcass layer 50 in the tire radial direction, a belt reinforcement layer (also called "crown belt layer") 70A disposed on the outer side of the belt layers 60A and 60B in the tire radial direction to cover the entire belt layers 60A and 60B, a pair of belt reinforcement layers (also called "ply layers") 70B disposed to cover only the two ends of the belt reinforcement layer 70A, and an airtight layer 80 disposed adjacent to the inner surface side of the carcass layer 50.

[0208] exist Figure 3 In the tire 100 shown, the carcass layer 50 is a single layer, but in the pneumatic tire of the second embodiment of the present invention, the number of carcass layers can be two or more. Furthermore, in Figure 3In the tire 100 shown, the carcass layer 50 is composed of a main body extending annularly between a pair of bead cores 40 embedded in the bead portion 10, and a folded portion that winds radially outward from the inner side in the tire width direction around each bead core 40. However, in the pneumatic tire of the second embodiment of the present invention, the shape and structure of the carcass layer 50 are not limited thereto. Here, it is preferred that the carcass layer 50 is formed by multiple reinforcing cords that are covered with rubber and extend in a direction substantially perpendicular to the tire circumferential direction (e.g., at an angle of 70° to 90°), i.e., the carcass layer 50 is preferably a radial carcass. As the reinforcing cords of the carcass layer 50, reinforcing cords containing the aforementioned polyamide fibers are preferred, but when reinforcing cords containing the aforementioned polyamide fibers are applied to the belt reinforcement layers 70A and 70B, other organic fiber cords or steel wire cords can be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords.

[0209] In addition, Figure 3 In the tire 100 shown, belt layers 60A and 60B are two layers, but in the pneumatic tire of the second embodiment of the present invention, the number of belt layers can be one or more layers. Furthermore, in Figure 3 In the tire 100 shown, each of the belt layers 60A and 60B is typically formed by covering reinforcing cords that extend at an angle (e.g., 15° to 40°) relative to the tire equatorial plane with coated rubber, and preferably by covering steel cords with coated rubber. Furthermore, the two belt layers 60A and 60B are stacked in such a manner that the reinforcing cords constituting the belt layers 60A and 60B cross each other across the tire equatorial plane.

[0210] In addition, Figure 3 In the tire 100 shown, belt reinforcement layers 70A and 70B are formed by covering reinforcing cords arranged substantially parallel to the tire circumferential direction (e.g., at an angle of 0° to 5° relative to the tire circumferential direction) with a coated rubber. Belt reinforcement layers 70A and 70B are formed by continuously spirally winding a narrow strip prepared by covering the reinforcing cords with a coated rubber in the tire circumferential direction. In this case, since there is no joint in the tire circumferential direction, the uniformity of the tire is improved, and since there is no joint, strain concentration at the joint is also prevented. Reinforcing cords containing the aforementioned polyamide fibers are preferred as the reinforcing cords of belt reinforcement layers 70A and 70B; however, when reinforcing cords containing the aforementioned polyamide fibers are applied to the carcass layer 50, other organic fiber cords can be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords.

[0211] Notice, Figure 3The tire 100 shown includes both belt reinforcement layer 70A and belt reinforcement layer 70B, but a tire in which either belt reinforcement layer 70A or belt reinforcement layer 70B is omitted is also an example of a pneumatic tire according to the second embodiment of the present invention. Furthermore, in Figure 3 In the tire 100 shown, each belt reinforcement layer (crown belt layer) 70A and belt reinforcement layer (ply layer) 70B is a single layer, but may be two or more layers.

[0212] In addition, Figure 3 In the tire 100 shown, the airtight layer 80 is a single layer, but in the pneumatic tire of the second embodiment of the present invention, the number of airtight layers can be two or more. The airtight layer 80 serves to maintain the internal pressure of the tire, and a rubber with low air permeability is used in the airtight layer 80. As such a rubber with low air permeability, a rubber composition in which a rubber component such as butyl rubber or halogenated butyl rubber is mixed with fillers such as carbon black, antioxidants, vulcanizing agents such as sulfur, and vulcanization accelerators can be used.

[0213] also, Figure 3 The tire 100 shown includes a tread rubber layer 90 located at the outermost surface of the tread portion 30. The tread rubber layer 90 can be a rubber composition in which a rubber component, such as natural or synthetic rubber, is blended with fillers such as carbon black, antioxidants, vulcanizing agents such as sulfur, and vulcanization accelerators. Note that... Figure 3 The tire 100 shown has a single tread rubber layer 90, but in the pneumatic tire of the second embodiment of the present invention, the number of tread rubber layers can be two or more. For example, Figure 3 The tread rubber layer 90 of the tire 100 shown can be divided into a crown rubber at the position of the outermost surface side and a base rubber at the position of the inner side in the radial direction of the tire.

[0214] Figure 4 yes Figure 3 An enlarged view of the portion of the tread 30 of the tire 100 shown, enclosed by the dashed line IV. Figure 4 In this embodiment, the carcass layer 50 and the belt reinforcement layer 70A include reinforcing cords 50-1 and 70A-1. Here, the carcass layer 50 is composed of reinforcing cords 50-1 and coated rubber 50-2 covering the reinforcing cords 50-1, and similarly, the belt reinforcement layer 70A is composed of reinforcing cords 70A-1 and coated rubber 70A-2 covering the reinforcing cords 70A-1. Furthermore, at least one of the reinforcing cords 50-1 of the carcass layer 50 and the reinforcing cords 70A-1 of the belt reinforcement layer 70A comprises polyamide fibers with an amide density of 14.0 or less.

[0215] Note that even the reinforcing cords 50-1 in the carcass layer 50 and the reinforcing cords 70A-1 in the belt reinforcing layer 70A do not contain polyamide fibers with an amide density of less than 14.0, but Figure 4 When the reinforcing cords of the belt reinforcement layer (ply layer) 70B (not shown) contain polyamide fibers with an amide density of 14.0 or less, such a tire is also an example of a pneumatic tire according to the second embodiment of the present invention.

[0216] exist Figure 3 and Figure 4 In the tire width direction D of the tire cross-section orthogonal to the tire circumferential direction. W In region R of the belt reinforcement layers 70A and 70B observed above, when measurements were taken from the tire radial direction D at 100 equally spaced points... R When measuring the thickness (distance) D from the outer circumferential surface of the reinforcing cord 70A-1 of the outermost belt reinforcement layer 70A on the tire's outer surface (more specifically, the virtual line connecting the outer circumferential surfaces of each reinforcing cord 70A-1 of the belt reinforcement layer 70A on the tire's outer surface), measurement points with a thickness D of 6.0 mm or less account for more than 80%. Figure 4 In the figure, the measured thickness D from the outer peripheral surface of the reinforcing cord 70A-1 of the belt reinforcement layer 70A to the outer surface of the tire corresponds to the total thickness of the tread rubber layer 90 and the tire radial direction D. R The sum of the thicknesses of the coated rubber 70A-2 of the belt reinforcement layer 70A at the outermost position. As described above, by making the measurement points with a thickness D of 6.0 mm or less occupy more than 80% (i.e., by making the sum of the total thickness of the tread rubber layer 90 and the thickness of the coated rubber 70A-2 of the belt reinforcement layer 70A thinner), the heat generated inside the tire during driving can be dissipated quickly, and the high temperature inside the tire during driving can be suppressed. By suppressing the high temperature inside the tire during driving, the degradation of the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less can be suppressed, thereby maintaining tire performance.

[0217] In the pneumatic tire of the second embodiment of the present invention, it is preferable that both the reinforcing cords of the carcass layer 50 and the reinforcing cords of the belt reinforcement layers 70A and 70B contain polyamide fibers with an amide density of 14.0 or less. By making both the reinforcing cords of the carcass layer 50 and the reinforcing cords of the belt reinforcement layers 70A and 70B contain polyamide fibers with an amide density of 14.0 or less, it is easy to apply biomass-derived polyamide fibers to the reinforcing cords of the carcass layer 50 and the belt reinforcement layers 70A and 70B, and it is also easy to reduce the environmental impact.

[0218] <Manufacturing Method of Pneumatic Tires>

[0219] The pneumatic tires of the first and second embodiments of the present invention can be obtained by molding and then vulcanizing an unvulcanized rubber composition or an unvulcanized treatment (in which the reinforcing cords are covered with rubber-coated cord-rubber composites), depending on the type of tire to be applied, or by molding and then further vulcanizing a semi-vulcanized rubber that has undergone a pre-vulcanization process instead of an unvulcanized rubber composition.

[0220] Note that there are no particular limitations on the components other than the carcass layer and belt reinforcement layer of the pneumatic tire of the first and second embodiments of the present invention, and known components can be used.

[0221] Furthermore, in addition to ordinary air or air with an adjusted oxygen partial pressure, the gas to be filled in the pneumatic tires of the first and second embodiments of the present invention can be an inactive gas such as nitrogen, argon or helium.

[0222] Example

[0223] The present invention will now be described in further detail with reference to embodiments, but the present invention is not limited in any way to the following embodiments.

[0224] (Comparative Example 1)

[0225] After initial twisting two 1400 dtex polyamide 6,6 (PA66) fibers (amide density 14.3), the fibers are aligned and final twisted to produce a twisted yarn cord [cord structure: 1400 / / 2 / 2]. Here, the initial twist is 22 turns / 10cm, and the final twist is 22 turns / 10cm.

[0226] (Example 1)

[0227] After initial twisting two 1400 dtex polyamide 4,10 (PA410) fibers (amide density 12.5), the fibers are aligned and final twisted to produce a twisted yarn cord [cord structure: 1400 / / 2 / 2]. Here, the initial twist is 22 turns / 10cm, and the final twist is 22 turns / 10cm.

[0228] Measurement of the thermal shrinkage rate of cords

[0229] The thermal shrinkage rate of the cord was measured by heating the cord at 177°C for 2 minutes according to ASTM D885 and ASTM D4974.

[0230] <Evaluation of Cord Properties>

[0231] Tensile tests were performed on the cords obtained as described above according to JIS L 1013 "Test Methods for Chemical Fiber Filament Yarns", and the load (N)-elongation (%) curves of the cords were measured. The breaking strength (N) and breaking elongation (%) at 100°C in Comparative Example 1 were set to 100, and each result was expressed as an exponent.

[0232] [Table 1]

[0233]

[0234] As can be seen from the comparison between Comparative Example 1 and Example 1, the cord made of PA410 fiber exhibits a greater reduction in strength when it breaks at high temperature compared to the cord made of PA66 fiber.

[0235] In contrast, according to the first embodiment of the invention, by making the average measured thickness of the reinforcing cord of the carcass layer from the outer peripheral surface on the inner surface of the tire to the inner surface of the tire average less than 1.5 mm and thus thinner, heat generated inside the tire during driving can be dissipated quickly, high temperatures inside the tire during driving can be suppressed, and the reduction in the physical properties of the reinforcing cord containing polyamide fibers with an amide density of less than 14.0 can be suppressed, thereby maintaining tire performance.

[0236] Furthermore, according to a second embodiment of the present invention, when measurements are taken at 100 equally spaced points, by ensuring that more than 80% of the measurement points have a measurement thickness of 6.0 mm or less from the outer peripheral surface of the reinforcing cord of the belt reinforcement layer at the outermost position in the radial direction of the tire to the tire outer surface, heat generated inside the tire during driving can be dissipated quickly, high temperatures inside the tire during driving can be suppressed, and the reduction in the physical properties of the reinforcing cord containing polyamide fibers with an amide density of 14.0 or less can be suppressed, thereby maintaining tire performance.

[0237] Explanation of reference numerals in the attached figures

[0238] 100: Tires

[0239] 10: Bead area

[0240] 20: Sidewall

[0241] 30: Tire face

[0242] 40: Tire bead core

[0243] 50: Fetal body layer

[0244] 50-1: Reinforced Cord

[0245] 50-2: Coated rubber

[0246] 60A, 60B: Belt layer

[0247] 70A: Belt reinforcement layer (coronal belt layer)

[0248] 70A-1: Reinforced Cord

[0249] 70A-2: Coated Rubber

[0250] 70B: Belt reinforcement layer (cord layer)

[0251] 80: Airtight layer

[0252] 90: Tread rubber layer

[0253] R: Region for configuring the belt reinforcement layer

[0254] A: The measured thickness (distance) from the outer circumferential surface of the reinforcing cord of the carcass ply at the innermost position in the radial direction of the tire to the inner surface of the tire.

[0255] B: Total thickness of the airtight layer

[0256] C: Thickness of the rubber coating on the innermost part of the tire carcass in the radial direction.

[0257] D: The measured thickness (distance) from the outer circumferential surface of the reinforcing cord of the belt reinforcement layer at the outermost position in the radial direction of the tire to the outer surface of the tire.

[0258] D R : Tire radial direction

[0259] D W : Tire width direction

Claims

1. A pneumatic tire comprising: A pair of tire bead sections; A pair of tire sidewalls; The tread portion that connects to the two sidewalls; At least one carcass layer extending in a ring shape across the pair of bead portions; At least one belt layer disposed on the radially outer side of the tire crown portion of the carcass layer; At least one belt reinforcement layer disposed on the outer side of the belt layer in the radial direction of the tire; and At least one airtight layer is disposed adjacent to the inner surface side of the tire carcass ply, wherein The carcass layer and the belt reinforcement layer include reinforcing cords. The reinforcing cord of at least one of the carcass layer and the belt reinforcement layer comprises polyamide fibers with an amide density of less than 14.0, and In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the measured thickness from the outer circumferential surface of the reinforcing cord of the carcass layer at the innermost position in the tire radial direction to the inner surface of the tire is measured at 100 equally spaced points, the average measured thickness is less than 1.5 mm.

2. A pneumatic tire, comprising: A pair of tire bead sections; A pair of tire sidewalls; The tread portion that connects to the two sidewalls; At least one carcass layer extending in a ring shape across the pair of bead portions; At least one belt layer disposed on the radially outer side of the crown portion of the carcass ply; and At least one belt reinforcement layer disposed on the outer side of the belt layer in the radial direction of the tire, wherein The carcass layer and the belt reinforcement layer include reinforcing cords. The reinforcing cord of at least one of the carcass layer and the belt reinforcement layer comprises polyamide fibers with an amide density of less than 14.0, and In the region where the belt reinforcement layer is configured, viewed in the tire width direction of the tire cross section orthogonal to the tire circumferential direction, when the thickness of the belt reinforcement layer's reinforcing cord on the tire outer surface side from the outermost position in the tire radial direction to the tire outer surface is measured at 100 equally spaced points, the measurement points with a thickness of 6.0 mm or less account for more than 80%.

3. The pneumatic tire according to claim 1 or 2, wherein the reinforcing cords of both the carcass layer and the belt reinforcement layer comprise polyamide fibers with an amide density of 14.0 or less.

4. The pneumatic tire according to claim 1 or 2, wherein the polyamide fiber with an amide density of 14.0 or less is polyamide 4,10 fiber.

5. The pneumatic tire according to claim 1, wherein the total thickness of the airtight layer is less than 1.0 mm.

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