tire

Abstract

The present invention addresses the problem of providing a tire in which deterioration in steering stability is suppressed even when polyamide fibers having a low amide density are used. Provided is a tire which is the solution to the foregoing problem and which is characterized in that: the tire comprises a carcass layer, belt layers (60A, 60B), and a belt reinforcement layer; the carcass layer and the belt reinforcement layer include reinforcement cords; the reinforcement cords of at least one of the carcass layer and the belt reinforcement layer include polyamide fibers having an amide density of 14.0 or less; and (i) angles (α, β) formed by the reinforcement cords (60A-1, 60B-1) of the belt layers (60A, 60B) with respect to the tire circumferential direction (DC) are 25 degrees to 65 degrees, inclusive, or (ii) angles formed by the reinforcement cords of the carcass layer with respect to the tire circumferential direction are 70 degrees or more and less than 90 degrees.

Description

tire

[0001] The present invention relates to a tire.

[0002] Conventionally, a carcass layer including reinforcing cords is disposed inside a tire to reinforce the strength and rigidity of the tire, and a belt layer including reinforcing cords is disposed radially outward of the carcass layer. Furthermore, a belt reinforcing layer (also called a "cap layer") including reinforcing cords may be disposed radially outward of the belt layer to reinforce the belt layer. Among these tire components, organic fiber cords such as polyamide (nylon) fiber cords are widely used as reinforcing cords for the carcass layer and the belt reinforcing layer.

[0003] On the other hand, in recent years, there has been a demand for reducing the use of fossil resources such as petroleum and coal in order to reduce environmental impact. Therefore, the replacement of fossil-resource-derived organic fiber cords with biomass-derived (biological resource-derived) cords has also been considered, and such replacement must be able to sufficiently maintain tire performance. For example, Patent Document 1 listed below discloses a reinforcing ply having a reinforcing element containing a multifilament yarn made of nylon 4,10, and a pneumatic vehicle tire including such a reinforcing ply, and teaches that one of the two monomers of nylon 4,10 is based on a renewable raw material, making it environmentally friendly.

[0004] Special table 2019-511411 publication

[0005] As described above, polyamide fiber cords are widely used as reinforcing cords for carcass layers and belt reinforcing layers, and polyamide 6,6 (PA66) fiber cords are commonly used. However, polyamide 6,6, the raw material for polyamide 6,6 (PA66) fiber cords, is difficult to synthesize from biomass. In response to this, the present inventors have conducted research and found that although polyamide 4,10 (i.e., nylon 4,10) can be easily synthesized from biomass, it has a lower amide density and fewer hydrogen bonds between amide bonds than polyamide 6,6, resulting in poor thermal properties. Therefore, organic fiber cords using such polyamide 4,10 deteriorate in physical properties at high temperatures. Furthermore, tires using organic fiber cords using polyamide 4,10 as reinforcing cords for carcass layers and belt reinforcing layers have poor steering stability.

[0006] Therefore, an object of the present invention is to provide a tire that suppresses a decrease in steering stability while using polyamide fiber that has a lower amide density than polyamide 6,6 fiber.

[0007] The gist of the tire of the present invention that solves the above problems is as follows.

[0008] [1] A tire having a pair of bead portions, a pair of sidewall portions, and a tread portion continuous with both sidewall portions, and comprising: at least one carcass layer extending in a toroidal shape spanning the pair of bead portions; at least one belt layer disposed radially outward of a crown portion of the carcass layer; and at least one belt reinforcing layer disposed radially outward of the belt layer, wherein the carcass layer, the belt layer, and the belt reinforcing layer each contain a reinforcing cord, and the reinforcing cord of at least one of the carcass layer and the belt reinforcing layer contains a polyamide fiber having an amide density of 14.0 or less, and the angle of the reinforcing cord of the belt layer with respect to the circumferential direction of the tire is 25 degrees or more and 65 degrees or less.

[0009] [2] A tire having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and comprising: at least one carcass layer extending in a toroidal shape spanning the pair of bead portions; at least one belt layer disposed radially outward of a crown portion of the carcass layer; and at least one belt reinforcing layer disposed radially outward of the belt layer, wherein the carcass layer and the belt reinforcing layer contain reinforcing cords, and the reinforcing cords of at least one of the carcass layer and the belt reinforcing layer contain polyamide fibers having an amide density of 14.0 or less, and the angle of the reinforcing cords of the carcass layer with respect to the circumferential direction of the tire is equal to or greater than 70 degrees and less than 90 degrees.

[0010] [3] The tire according to [1], wherein the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction is 25 degrees or more and 40 degrees or less.

[0011] [4] The tire according to any one of [1] to [3], wherein the reinforcing cords of both the carcass layer and the belt reinforcing layer contain polyamide fibers having an amide density of 14.0 or less.

[0012] [5] The tire according to any one of [1] to [4], wherein the polyamide fiber having an amide density of 14.0 or less is a polyamide 4,10 fiber.

[0013] According to the present invention, it is possible to provide a tire that suppresses deterioration in steering stability while using polyamide fiber that has a lower amide density than polyamide 6,6 fiber.

[0014] Fig. 1 is a cross-sectional view of an example of tires according to a first embodiment and a second embodiment of the present invention, Fig. 2 is a partial developed view illustrating an angle of a reinforcing cord of a belt layer of a tire according to a first embodiment of the present invention with respect to the tire circumferential direction, Fig. 3 is a partial developed view illustrating an angle of a reinforcing cord of a carcass layer of a tire according to a second embodiment of the present invention with respect to the tire circumferential direction,

[0015] The tire of the present invention will be described in detail below by way of example based on an embodiment thereof.

[0016] <Definition> In this specification, the term "biomass content rate" refers to the content rate of carbon derived from biomass, and is calculated using the following formula (1): Biomass content rate (%) = number of carbon atoms derived from biomass / total number of carbon atoms × 100 (1).

[0017] In addition, in this specification, the "biomass content rate of the entire cord" refers to the content rate of biomass-derived carbon in the entire cord, and is calculated using the following formula (2): Biomass content rate of the entire cord (%) = number of biomass-derived carbon atoms in the entire cord / total number of carbon atoms in the entire cord × 100 (2).

[0018] In this specification, the heat shrinkage of the reinforcing cord is measured in accordance with ASTM D885 and ASTM D4974, and is a value measured by heating at 177°C for 2 minutes.

[0019] In this specification, the "amide density" of a polyamide is calculated from the following formula (3): Amide density = number of amide groups in polyamide / number of atoms in the main chain of polyamide × 100 (3) Here, the "number of amide groups in polyamide" and the "number of atoms in the main chain of polyamide" are calculated from the "number of amide groups" and the "number of atoms in the main chain" in one repeating unit of the polyamide. 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.

[0020] In addition, in this specification, "biomass-derived" refers to being derived from biological resources such as plant resources, animal resources, and microbial resources, and is synonymous with "bio-derived."

[0021] The compounds described herein may be derived in part or entirely from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0022] <Tire> A tire according to a first embodiment of the present invention includes at least one carcass layer having a pair of bead portions, a pair of sidewall portions, and a tread portion continuous with both sidewall portions, and extending toroidally across the pair of bead portions, at least one belt layer disposed radially outward of a crown portion of the carcass layer, and at least one belt reinforcing layer disposed radially outward of the belt layer. The tire according to the first embodiment of the present invention is characterized in that the carcass layer, the belt layer, and the belt reinforcing layer each include a reinforcing cord, the reinforcing cord of at least one of the carcass layer and the belt reinforcing layer including a polyamide fiber having an amide density of 14.0 or less, and the reinforcing cord of the belt layer forms an angle of 25 degrees or more and 65 degrees or less with respect to the circumferential direction of the tire.

[0023] The polyamide fibers having an amide density of 14.0 or less have lower amide densities and fewer hydrogen bonds between amide bonds than polyamide 6,6 fibers, resulting in poor thermal properties. Therefore, polyamide fibers having an amide density of 14.0 or less have reduced rigidity at high temperatures, and carcass layers and belt reinforcing layers containing reinforcing cords containing polyamide fibers having an amide density of 14.0 or less have reduced shear rigidity. As a result, tires using reinforcing cords containing polyamide fibers having an amide density of 14.0 or less as reinforcing cords in carcass layers and belt reinforcing layers have reduced cornering power and steering stability. In contrast, in the tire of the first embodiment of the present invention, the reinforcing cords in the belt layer are angled at an angle of 25 degrees to 65 degrees relative to the tire circumferential direction, thereby improving the shear rigidity of the belt layer and compensating for the reduced shear rigidity of the carcass layer and belt reinforcing layer. As a result, the tire of the first embodiment of the present invention suppresses a decrease in cornering power and a decrease in steering stability, even though it uses polyamide fibers having an amide density of 14.0 or less.

[0024] A second embodiment of the tire according to the present invention includes a carcass layer having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, the carcass layer including at least one toroidally extending carcass layer between the pair of bead portions, at least one belt layer disposed radially outward of a crown portion of the carcass layer, and at least one belt reinforcing layer disposed radially outward of the belt layer. The second embodiment of the tire is characterized in that the carcass layer and the belt reinforcing layer include reinforcing cords, the reinforcing cords of at least one of the carcass layer and the belt reinforcing layer including polyamide fibers having an amide density of 14.0 or less, and the angle of the reinforcing cord of the carcass layer with respect to the tire circumferential direction is 70 degrees or more and less than 90 degrees.

[0025] The polyamide fibers having an amide density of 14.0 or less have lower amide densities and fewer hydrogen bonds between amide bonds than polyamide 6,6 fibers, resulting in poor thermal properties. Therefore, polyamide fibers having an amide density of 14.0 or less have reduced rigidity at high temperatures, and carcass layers and belt reinforcing layers containing reinforcing cords containing such polyamide fibers have reduced shear rigidity. As a result, tires using reinforcing cords containing such polyamide fibers as reinforcing cords in carcass layers and belt reinforcing layers have reduced cornering power and steering stability. In contrast, in a tire according to a second embodiment of the present invention, the angle of the reinforcing cords in the carcass layer relative to the tire circumferential direction is set to 70 degrees or more and less than 90 degrees, thereby improving the rigidity against lateral inputs and compensating for the reduced shear rigidity of the carcass layer and belt reinforcing layer. As a result, the tire according to the second embodiment of the present invention suppresses the reduction in cornering power and steering stability, even though it uses polyamide fibers having an amide density of 14.0 or less.

[0026] (Carcass Layer and Belt Reinforcing Layer) The carcass layer and the belt reinforcing layer contain the reinforcing cords, and are usually formed by coating the reinforcing cords with a coating rubber.

[0027] In the tire according to the first embodiment of the present invention, the angle of the reinforcing cord of the carcass layer relative to the tire circumferential direction is not particularly limited.

[0028] In a tire according to a second embodiment of the present invention, the angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction is 70 degrees or more but less than 90 degrees, and preferably 80 degrees or more but less than 89 degrees. The angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction correlates with the rigidity of the tire against lateral input. In the tire according to the second embodiment of the present invention, by setting the angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction to 70 degrees or more but less than 90 degrees, it is possible to sufficiently compensate for the decrease in shear rigidity of the carcass layer and belt reinforcing layer using reinforcing cords containing polyamide fibers having an amide density of 14.0 or less. As a result, it is possible to suppress a decrease in the cornering power of the tire and a decrease in the handling stability of the tire. Note that if the angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction is less than 70 degrees, strain during tire running is concentrated on the reinforcing cords, resulting in reduced tire durability. On the other hand, if the angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction is 90 degrees, it is not possible to sufficiently improve the rigidity of the tire against lateral input.

[0029] On the other hand, the angle of the reinforcing cords of the belt reinforcing layer relative to the tire circumferential direction is not particularly limited. For example, the reinforcing cords of the belt reinforcing layer may be arranged substantially parallel to the tire circumferential direction (for example, at an angle of 0 to 5 degrees relative to the tire circumferential direction).

[0030] In the carcass layer, the end count of the reinforcement cords is preferably 20 / 50 mm to 70 / 50 mm, and more preferably 50 / 50 mm to 70 / 50 mm. By setting the end count of the reinforcement cords in the carcass layer to 20 / 50 mm or more, the strength of the carcass layer can be improved, and by setting the end count of the reinforcement cords in the carcass layer to 70 / 50 mm or less, an excessive increase in tire weight can be avoided.

[0031] In the carcass layer, the cord diameter of the reinforcing cord is preferably 0.4 mm to 1.2 mm, and more preferably 0.5 mm to 1.0 mm. By setting the cord diameter of the reinforcing cord in the carcass layer to 0.4 mm or more, the strength of the carcass layer can be improved, and by setting the cord diameter of the reinforcing cord in the carcass layer to 1.2 mm or less, an excessive increase in tire weight can be avoided.

[0032] In the belt reinforcing layer, the end count of the reinforcing cords is preferably 20 / 50 mm to 70 / 50 mm, and more preferably 30 / 50 mm to 60 / 50 mm. By setting the end count of the reinforcing cords in the belt reinforcing layer to 20 / 50 mm or more, the strength of the belt reinforcing layer can be improved, and by setting the end count of the reinforcing cords in the belt reinforcing layer to 70 / 50 mm or less, an excessive increase in tire weight can be avoided.

[0033] In the belt reinforcing layer, the cord diameter of the reinforcing cord is preferably 0.4 mm to 1.2 mm, and more preferably 0.5 mm to 1.0 mm. By setting the cord diameter of the reinforcing cord in the belt reinforcing layer to 0.4 mm or more, the strength of the belt reinforcing layer can be improved, and by setting the cord diameter of the reinforcing cord in the belt reinforcing layer to 1.2 mm or less, an excessive increase in tire weight can be avoided.

[0034] -Coating Rubber- As the coating rubber for the carcass layer and the belt reinforcing layer, a rubber composition can be used in which a rubber component such as natural rubber or synthetic rubber is blended with a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, etc.

[0035] The rubber components used in the coating rubber of the carcass layer and the belt reinforcing layer are preferably natural rubber (NR) or synthetic isoprene rubber (IR). The natural rubber may be modified. In the case of modified natural rubber, for example, the modified natural rubber preferably has a nitrogen content of 0.1 to 0.3 mass%. Furthermore, the modified natural rubber is preferably one from which proteins have been removed by a centrifugation process, enzyme treatment, or urea treatment. Furthermore, the modified natural rubber preferably has a phosphorus content of more than 200 ppm and not more than 900 ppm.

[0036] The carbon black used in the coating rubber of the carcass layer and the belt reinforcing layer is not particularly limited, and examples include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination. The carbon black content is preferably 40 to 80 parts by mass, more preferably 50 to 70 parts by mass, per 100 parts by mass of the rubber component. The carbon black may also be recycled carbon black. Here, "recycled carbon black" refers to carbon black recovered from recycled waste raw materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including unnecessary scraps generated during the production or repair of rubber products, as well as rubber generated from rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is fine rubber generated during the buffing process of tire retreading, which removes the tread portion remaining on the base tire. Peeled rubber is a long piece of rubber, for example, 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to cross-linked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing stage of final products. Used tires may be, for example, tires to be retreaded, or tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELT (End-of-Life Tire) tires that have reached the end of their lifespan. Waste oil is not limited to oil generated during the decomposition of plastics or rubber, but may also include, for example, animal and vegetable oils, lubricating oils, insulating oils, cutting oils, and used oils discharged from industry. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Moreover, the waste oil is preferably one that has carbon black or rubber containing carbon black mixed in it."Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., non-recycled carbon black. Note that "used" here does not only include carbon black that has been discarded after actual use, but also carbon black that has been manufactured but discarded without actually being used.

[0037] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0038] Furthermore, when the recycled carbon black is recovered from solid residue, it is more preferably carbon black that has been subjected to a surface treatment or surface modification. Examples of surface treatments or surface modifications include treatment with hydrofluoric acid, or treatment with an acid such as hydrochloric acid or sulfuric acid, or with a peroxide. Furthermore, the surface treatment or surface modification may be performed at room temperature, preferably at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C or higher and 100°C or lower.

[0039] Preferably, the recycled carbon black has three or more lines 10 mm or longer when measured with a grind gauge, and the third-largest particle among the particles that produce the lines 10 mm or longer has a particle size of 20 μm or less. If the particle size of the third-largest particle is 20 μm or less, the recycled carbon black can be well dispersed in the rubber composition even when blended with the recycled carbon black, and deterioration of the durability of the rubber composition, particularly its performance after aging, can be suppressed. In the measurement using a grind gauge, a paste of the recycled carbon black can be prepared as the measurement sample in accordance with JIS K5101-1-5, and the load applied is preferably set to 0.4 to 0.5 kN and the rotation speed of the glass plate is preferably set to 90 to 110 r / min. Furthermore, for the method of evaluating the occurrence of linear scratches, it is preferable to use a sample that complies with JIS K5400 and has a range of 0 to 25 μm. A grind gauge with an upper limit of the range greater than 20 μm can be used because it can determine whether the particle size of the third largest particle is 20 μm or less. When using the gauge for other purposes (performance other than durability of the rubber composition containing recycled carbon black), the range of the grind gauge to be used can be appropriately selected depending on the purpose.

[0040] The recycled carbon black 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, a tire with sufficient reinforcing properties may not be obtained. In consideration of the reinforcing properties of the tire, the ash content is preferably 10% by mass or less, and more preferably 6% by mass or less.

[0041] - Reinforcement cords containing polyamide fibers having an amide density of 14.0 or less - The reinforcing cords of at least one of the carcass layer and the belt reinforcing layer contain polyamide fibers having an amide density of 14.0 or less. Compared to widely used polyamide 6,6 (PA66) fibers, polyamide fibers having an amide density of 14.0 or less have a lower amide density and fewer hydrogen bonds between amide bonds, resulting in poor thermal properties and low rigidity at high temperatures. Furthermore, when reinforcing cords containing such polyamide fibers having an amide density of 14.0 or less are used in the carcass layer or belt reinforcing layer, the shear rigidity of the carcass layer or belt reinforcing layer decreases, resulting in a decrease in tire handling stability. In contrast, in the tire of the first embodiment of the present invention, the angle of the reinforcing cords in the belt layer relative to the tire circumferential direction is set to be 25 degrees or more and 65 degrees or less, thereby improving the shear rigidity of the belt layer and compensating for the decrease in shear rigidity of the carcass layer or belt reinforcing layer, thereby suppressing a decrease in tire handling stability. In addition, in the tire of the second embodiment of the present invention, the angle of the reinforcing cord of the carcass layer with respect to the tire circumferential direction is set to be equal to or greater than 70 degrees and less than 90 degrees, thereby improving the rigidity against lateral input of the tire, compensating for the decrease in shear rigidity of the carcass layer and the belt reinforcing layer, and as a result, suppressing the decrease in steering stability of the tire. Although the lower limit of the amide density of the polyamide fiber is not particularly limited, the amide density of the polyamide fiber is preferably 10.5 or more. When the amide density of the polyamide fiber is 10.5 or more, some hydrogen bonds are formed between the amide bonds, thereby mitigating the decrease in thermal properties.

[0042] Polyamide fibers with a high bio-based content are easily used as the polyamide fibers with an amide density of 14.0 or less, and such polyamide fibers with a high bio-based content are highly effective in reducing the environmental impact. Therefore, a tire in which a reinforcing cord containing polyamide fibers with an amide density of 14.0 or less is used in at least one of the carcass layer and the belt reinforcing layer can easily reduce the environmental impact.

[0043] The reinforcing cords of both the carcass layer and the belt reinforcing layer preferably contain polyamide fibers having an amide density of not more than 14.0. A tire in which the reinforcing cords of both the carcass layer and the belt reinforcing layer contain polyamide fibers having an amide density of not more than 14.0 facilitates the application of biomass-derived polyamide fibers to the reinforcing cords of the carcass layer and the belt reinforcing layer, facilitating a reduction in the environmental load.

[0044] A reinforcing cord containing polyamide fibers having an amide density of 14.0 or less preferably has a biomass-derived carbon content (biomass content) of 15% or more throughout the cord. A biomass content of 15% or more throughout the cord enhances the effect of reducing the environmental impact. To further reduce the environmental impact, the biomass content of the reinforcing cord is preferably 20% or more, and may be 100%.

[0045] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably contains fibers with a biomass-derived carbon content (biomass content) of 40% or more. Reinforcing cords containing fibers with a biomass content of 40% or more are more effective in reducing environmental impact. Examples of fibers (polyamide fibers) with a biomass content of 40% or more include polyamide 11 (PA11) fiber, polyamide 4,10 (PA410) fiber, polyamide 6,10 (PA610) fiber, and polyamide 10,10 (PA1010). The polyamides used as the raw material for these polyamide fibers can be synthesized from biomass-derived components. Here, biomass-derived components refer to components derived from biological resources such as plant resources, animal resources, and microbial resources.

[0046] Polyamide 11 (PA11) is obtained by polymerization of aminoundecanoic acid, which is obtained from plant resources such as castor beans. Polyamide 4,10 (PA410) is obtained by condensation polymerization of tetramethylenediamine (carbon number 4) and sebacic acid (carbon number 10), which is obtained from plant resources such as sugarcane. Polyamide 6,10 (PA610) is obtained by condensation polymerization of hexamethylenediamine (carbon number 6) and sebacic acid (carbon number 10), which is obtained from plant resources such as castor beans. Polyamide 10,10 (PA1010) is obtained by the condensation polymerization reaction of decamethylenediamine (C10) and sebacic acid (C10). Decamethylenediamine and sebacic acid are obtained from plant resources such as castor beans. For example, tetramethylenediamine, also known as "putrescine," can be obtained by fermenting sugarcane to produce glutamic acid, biochemically producing ornithine from the glutamic acid, and decarboxylating the resulting ornithine. Sebacic acid can be obtained by mechanically pressing castor beans to obtain castor oil, methanolyzing the castor oil to obtain methyl ricinoleate, and then saponifying the methyl ricinoleate.

[0047] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably contains the fiber whose bio-based content is 100% (i.e., entirely derived from biomass). By including the fiber whose bio-based content is 100%, the effect of reducing the environmental load is further enhanced. Examples of the fiber whose bio-based content is 100% include polyamide 11 (PA11) fiber, polyamide 4,10 (PA410) fiber, and polyamide 10,10 (PA1010) fiber.

[0048] Examples of polyamide fibers having 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 these, polyamide 4,10 (PA410) fibers are preferred. Polyamide 4,10 fibers with a 100% bio-based content can be used, and such 100% bio-based polyamide 4,10 fibers are highly effective in reducing environmental impact. Therefore, a tire in which reinforcing cords containing polyamide 4,10 fibers are used in at least one of the carcass layer and the belt reinforcing layer facilitates reducing environmental impact.

[0049] The reinforcing cord may contain organic fibers other than polyamide fibers having an amide density of 14.0 or less. Here, the raw material of the organic fibers other than polyamide fibers having an amide density of 14.0 or less is not particularly limited, and may be derived from synthetic products, biological resources such as plant resources, animal resources, or microbial resources, mechanically recycled by crushing, melting, and re-spinning a resin product, or chemically recycled by depolymerizing and repolymerizing a resin product.

[0050] The material of the organic fiber is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethylene furan dicarboxylate (PEF); polyamides such as 6-nylon (registered trademark), 6,6-nylon (registered trademark), 4,6-nylon (registered trademark), and aramid; and celluloses such as rayon and lyocell.

[0051] Examples of the polyethylene terephthalate (PET) include polyethylene terephthalate obtained by mechanically or chemically recycling PET products, clothing, and the like.

[0052] Examples of the polyamide include polyamides 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 (also referred to as PA6:6-nylon (registered trademark)), and polyamide 6,6 (also referred to as PA66:6,6-nylon (registered trademark)).

[0053] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably a cord obtained by twisting together the fiber having a bio content of 40% or more and aramid fiber. Such a reinforcing cord has rigidity and excellent thermal properties due to the aramid fiber, and is also effective in reducing the environmental load due to the bio content of the fiber being 40% or more.

[0054] The reinforcing cord containing polyamide fiber having an amide density of 14.0 or less is preferably a cord twisted together with polyamide 4,10 fiber and aramid fiber. Such a reinforcing cord has rigidity and excellent thermal properties due to the aramid fiber, and is also effective in reducing the environmental load due to the polyamide 4,10 fiber, which can be used with a 100% bio-based content.

[0055] The reinforcing cord containing polyamide fibers having an amide density of 14.0 or less is also preferably a cord formed by twisting two to four fibers together. A reinforcing cord formed by twisting two to four fibers together can achieve a lightweight tire while ensuring sufficient rigidity as a tire reinforcing material. From the same viewpoint, a cord formed by twisting two fibers together is preferred.

[0056] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably a cord twisted together of two aramid fibers and one polyamide 4,10 fiber. Such a reinforcing cord has rigidity and excellent thermal properties due to the two aramid fibers, and is also effective in reducing the environmental load due to the polyamide 4,10 fiber, which can be used with a 100% bio-based content.

[0057] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably made exclusively of polyamide fiber having a biomass-derived carbon content (biomass content) of 15% or more. By making the reinforcing cord exclusively of polyamide fiber having a biomass content of 15% or more, the effect of reducing the environmental load is enhanced.

[0058] The reinforcing cord may have a single twist structure or a twisted structure (such as a double twist structure). In the case of a single twist structure, for example, raw yarns are pulled together and twisted in one direction to obtain a twisted cord. Here, the number of twists is preferably in the range of 4 to 20 times per 10 cm. If the number of twists in a single twist structure exceeds 20 times per 10 cm, the strength of the twisted cord may decrease, and if it is less than 4 times per 10 cm, the twisted cord may not have sufficient fatigue resistance. In the case of a double twist structure, for example, raw yarns are first twisted, and then multiple such twists are combined and then second twisted in the opposite direction to obtain a twisted cord. Here, the number of first twists is preferably in the range of 10 to 60 times per 10 cm, and the number of second twists is preferably in the range of 10 to 60 times per 10 cm. If the number of first twists exceeds 60 times / 10 cm, the strength of the twisted cord may decrease, and if it is less than 10 times / 10 cm, the twisted cord may not have sufficient fatigue resistance.If the number of final twists exceeds 60 times / 10 cm, the strength of the twisted cord may decrease, and if it is less than 10 times / 10 cm, the twisted cord may not have sufficient fatigue resistance.

[0059] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably has a heat shrinkage rate of 12.0% or less. When the reinforcing cord has a heat shrinkage rate of 12.0% or less, deterioration of physical properties (particularly modulus of elasticity and strength) at high temperatures can be suppressed. The reinforcing cord more preferably has a heat shrinkage rate of 9.0% or less. When the reinforcing cord has a heat shrinkage rate of 9.0% or less, uniformity is improved, particularly during high-speed running.

[0060] The total fineness of the reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably in the range of 1000 to 6000 dtex. If the total fineness of the reinforcing cord is less than 1000 dtex, sufficient strength as a tire reinforcing cord may not be obtained, and if it exceeds 6000 dtex, the treat becomes thick, increasing the tire weight.

[0061] The breaking strength of the reinforcement cord containing the polyamide fiber having an amide density of 14.0 or less is preferably 6.0 cN / dtex or more. The breaking strength of the reinforcement cord is preferably 180 N or more. Here, the breaking strength is measured at room temperature (23°C) in accordance with ASTM D855M. A sufficient reinforcing effect can be obtained when the breaking strength of the reinforcement cord is 6.0 cN / dtex or more, or 180 N or more.

[0062] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably has a breaking elongation (elongation at break) of 8.0% or more. Here, the breaking elongation is measured at room temperature (23°C) in accordance with ASTM D855M. When the breaking elongation of the reinforcing cord is 8.0% or more, a sufficient reinforcing effect can be obtained.

[0063] The moisture regain of the reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably 3.0% or less. Here, the moisture regain is measured in accordance with JIS L 1013. If the moisture regain of the reinforcing cord exceeds 3.0%, the physical properties will be deteriorated and a sufficient reinforcing effect will not be obtained.

[0064] -Other Reinforcing Cords- When one of the carcass layer and the belt reinforcing layer includes a reinforcing cord containing a polyamide fiber having an amide density of 14.0 or less, the other of the carcass layer and the belt reinforcing layer does not need to include a reinforcing cord containing a polyamide fiber having an amide density of 14.0 or less. In this case, the reinforcing cord can be a reinforcing cord containing any organic fiber, and in addition to a polyamide fiber cord, a polyester fiber cord or the like can also be used.

[0065] -Adhesive Composition- The reinforcing cords used in the carcass layer and the belt reinforcing layer are preferably treated with an adhesive composition.

[0066] Examples of the adhesive composition include an adhesive composition containing a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially no addition-reactive carbon-carbon double bonds in its main chain structure, a heat-reactive aqueous urethane resin (B), and an epoxy compound (C), and optionally further containing a rubber latex (D). Treating the reinforcing cord with such an adhesive composition can improve the adhesion between the reinforcing cord and elastomer (coating rubber) at high temperatures.

[0067] Conventionally, adhesive treatment of organic fiber cords has been performed using a so-called two-bath process, in which epoxy or isocyanate is applied to the cord surface, followed by treatment with a resin (hereinafter referred to as RFL resin) composed of a mixture of resorcinol, formaldehyde, and latex. However, this method can result in the resin used in the first bath becoming very hard, increasing strain input to the organic fiber cord and reducing cord fatigue resistance. Furthermore, while such RFL resins can exhibit sufficient cord-to-elastomer adhesion at room temperature, they can experience a significant decrease in adhesion at temperatures above 130°C. In contrast, by using a one-bath mixture (adhesive composition) containing a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially free of addition-reactive carbon-carbon double bonds in its main chain structure, a thermally reactive aqueous urethane resin (B), and an epoxy compound (C), sufficient adhesion to the elastomer (coating rubber) can be ensured without curing the reinforcing cord, even at temperatures above 180°C.

[0068] The main chain of the thermoplastic polymer (A) mainly has a linear structure, and the main chain is preferably, for example, an ethylenic addition polymer such as an acrylic polymer, a vinyl acetate polymer, or a vinyl acetate-ethylene polymer; a urethane high molecular weight polymer; etc. However, the thermoplastic polymer (A) is not limited to the above-mentioned ethylenic addition polymer and urethane high molecular weight polymer, as long as it has the function of suppressing resin fluidity at high temperatures and ensuring the breaking strength of the resin by crosslinking the functional groups of the pendant groups.

[0069] The functional group of the pendant group of the thermoplastic polymer (A) is preferably an oxazolidine group, a bismaleimide group, a (blocked) isocyanate group, an aziridine group, a carbodiimide group, a hydrazino group, an epoxy group, an epithio group, or the like.

[0070] In addition, with respect to the above-mentioned thermoplastic polymer (A), heat-reactive aqueous urethane resin (B), epoxy compound (C), and rubber latex (D), those described in Japanese Patent Application No. 2023-040157 and those described in Japanese Patent Application No. 2023-030762 can be used.

[0071] In the adhesive treatment of the reinforcing cord, it is preferable to use a three-type mixed liquid (adhesive composition) of the thermoplastic polymer (A), the heat-reactive aqueous urethane resin (B), and the epoxy compound (C) as a one-bath treatment liquid, and to use a normal RFL resin liquid as a two-bath treatment liquid. In addition, in the adhesive treatment, it is also possible to treat with only one bath using a mixed liquid (adhesive composition) of the thermoplastic polymer (A), the heat-reactive aqueous urethane resin (B), the epoxy compound (C), and the rubber latex (D).

[0072] In the adhesive composition, the proportion (dry mass ratio) of the thermoplastic polymer (A) is preferably 2 to 75%, the proportion (dry mass ratio) of the heat-reactive aqueous urethane resin (B) is preferably 15 to 87%, the proportion (dry mass ratio) of the epoxy compound (C) is preferably 11 to 70%, and the proportion (dry mass ratio) of the rubber latex (D) is preferably 20% or less.

[0073] On the other hand, from the viewpoint of environmental protection, it is preferable to use a dip treatment liquid that does not contain resorcinol or formalin as the adhesive composition for the reinforcing cord. Examples of such dip treatment liquids include a composition containing (a) a rubber latex having an unsaturated diene and (b) one or more compounds selected from a compound having a polyether skeleton structure and an amine functional group, a compound having an acrylamide structure, a polypeptide, a polylysine, and a carbodiimide. Examples of such dip treatment liquids include a composition containing, in addition to the rubber latex (a) having an unsaturated diene and the compound (b), one or more compounds selected from (c) an aqueous compound having a (thermally dissociable blocked) isocyanate group, a polyphenol (d), and a polyvalent metal salt (e).

[0074] Other examples of the dipping treatment liquid that does not contain resorcinol or formalin include a composition containing polyphenols (I) and aldehydes (II). Such a composition may further contain at least one of an isocyanate compound (III) and a rubber latex (IV) in addition to the polyphenols (I) and aldehydes (II).

[0075] By including polyphenols (I) and aldehydes (II) in the adhesive composition used to treat (coat) the reinforcing cord with an adhesive, good adhesive properties can be achieved even when resorcinol is not used in consideration of the environmental impact.

[0076] --Polyphenols (I)-- The adhesive composition contains polyphenols (I) as a resin component, thereby improving adhesion to the reinforcing cord. The polyphenols (I) are typically water-soluble polyphenols, and are not particularly limited as long as they are polyphenols other than resorcinol (resorcinol). The number of aromatic rings or the number of hydroxyl groups in the polyphenols (I) can be appropriately selected.

[0077] From the viewpoint of realizing better adhesive properties, the polyphenols (I) preferably have two or more hydroxyl groups, and more preferably three or more hydroxyl groups. When the polyphenols have three or more hydroxyl groups, the polyphenol or polyphenol condensate is soluble in the adhesive composition (dip treatment liquid) containing water. This allows the polyphenols to be uniformly distributed in the adhesive composition, thereby realizing better adhesive properties. Furthermore, when the polyphenols (I) are polyphenols containing multiple (two or more) aromatic rings, each of the aromatic rings has two or three hydroxyl groups at the ortho, meta, or para positions.

[0078] As the polyphenols (I), for example, those described as polyphenol compounds in WO 2022 / 130879 can be used. These polyphenols (I) may be used alone or in combination of two or more.

[0079] --Aldehydes (II)-- The adhesive composition contains aldehydes (II) as a resin component in addition to the polyphenols (I) described above, thereby achieving high adhesiveness together with the polyphenols (I). The aldehydes (II) are not particularly limited and can be appropriately selected depending on the required performance. In this specification, the aldehydes (II) also include derivatives of aldehydes that are generated from aldehydes.

[0080] Examples of the aldehydes (II) include monoaldehydes such as formaldehyde, acetaldehyde, butylaldehyde, acrolein, propionaldehyde, chloral, butylaldehyde, caproaldehyde, and allylaldehyde, and aliphatic dialdehydes such as glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, and adipaldehyde, aldehydes having an aromatic ring, and dialdehyde starch. These aldehydes (II) may be used singly or in combination of two or more.

[0081] The aldehydes (II) are preferably aldehydes having an aromatic ring or contain aldehydes having an aromatic ring, because this allows for better adhesiveness to be obtained. Furthermore, the aldehydes (II) preferably do not contain formaldehyde. Here, "does not contain formaldehyde" means, for example, that the formaldehyde content of the total mass of the aldehydes is less than 0.5 mass%.

[0082] In the adhesive composition, polyphenols (I) and aldehydes (II) are in a condensed state, and the mass ratio of the polyphenols to the aldehydes having an aromatic ring (content of aldehydes having an aromatic ring / content of polyphenols) is preferably 0.1 or more and 3 or less. In this case, the hardness and adhesive properties of the resin, which is the product of the condensation reaction between the polyphenols and the aldehydes having an aromatic ring, are more suitable. From the same viewpoint, the mass ratio of the polyphenols to the aldehydes having an aromatic ring (content of aldehydes having an aromatic ring / content of polyphenols) in the adhesive composition is more preferably 0.25 or more and more preferably 2.5 or less. Note that the above mass ratio is the mass of the dry product (solid content ratio).

[0083] The total content of polyphenols (I) and aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass. This is because better adhesion can be ensured without deteriorating workability, etc. From the same viewpoint, 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. The above total content is the mass of the dry product (solid content ratio).

[0084] --Isocyanate Compound (III)--The adhesive composition preferably further contains an isocyanate compound (III) in addition to the polyphenols (I) and aldehydes (II) described above. In this case, the adhesive composition can further enhance the adhesiveness due to a synergistic effect with the polyphenols (I) and the aldehydes (II).

[0085] Here, the isocyanate compound (III) is a compound that has the effect of promoting adhesion of the adhesive composition to a resin material (e.g., a phenol / aldehyde resin obtained by condensing polyphenols (I) and aldehydes (II)) that is the adherend, and is a compound that has an isocyanate group as a polar functional group. These isocyanate compounds (III) may be used alone or in combination of two or more.

[0086] The isocyanate compound (III) is not particularly limited, but from the viewpoint of further improving adhesion, it preferably contains a (blocked) isocyanate group-containing aromatic compound. When the adhesive composition contains a (blocked) isocyanate group-containing aromatic compound, the (blocked) isocyanate group-containing aromatic compound is distributed in a position near the interface between the reinforcing cord and the adhesive composition, resulting in a further adhesion-promoting effect, and this effect can further improve the adhesion of the adhesive composition to the reinforcing cord.

[0087] As the (blocked) isocyanate group-containing aromatic compound, those described in Japanese Patent Application No. 2023-040157 and Japanese Patent Application No. 2023-030762 can be used.

[0088] The content of the isocyanate compound (III) in the adhesive composition is not particularly limited, but from the viewpoint of more reliably ensuring excellent adhesion, it is preferably 5 to 65% by mass. From the same viewpoint, the content of the isocyanate compound (III) in the adhesive composition is more preferably 10% by mass or more, and more preferably 45% by mass or less. The above content is the mass of the dry product (solid content ratio).

[0089] --Rubber Latex (IV)-- The adhesive composition may further contain substantially rubber latex (IV) in addition to the polyphenols (I), aldehydes (II), and isocyanate compound (III) described above, which allows the adhesive composition to have even greater adhesion to rubber members.

[0090] Here, the rubber latex (IV) is not particularly limited, and examples thereof include natural rubber (NR), as well as synthetic rubbers such as polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), and vinylpyridine-styrene-butadiene copolymer rubber (Vp). These rubber latexes (IV) may be used alone or in combination of two or more.

[0091] When preparing the adhesive composition containing the rubber latex (IV), it is preferable to mix the rubber latex (IV) with the phenol (I) and the aldehyde (II) before compounding the isocyanate compound (III).

[0092] The content of the rubber latex (IV) in the adhesive composition is preferably 20% by mass or more, more preferably 25% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less.

[0093] The method for producing the adhesive composition is not particularly limited, and examples thereof include a method of mixing raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV) and aging the mixture, or a method of mixing polyphenols (I) and aldehydes (II) and aging the mixture, and then adding rubber latex (IV) and aging the mixture. When an isocyanate compound (III) is contained in the raw materials, the method for producing the adhesive composition may also be a method of adding rubber latex (IV), aging the mixture, and then adding the isocyanate compound (III).

[0094] (Belt Layer) The tires of the first and second embodiments of the present invention include a belt layer on the radially outer side of the crown portion of the carcass layer. The number of belt layers is not particularly limited, and may be one, two, or three or more.

[0095] In the tire of the first embodiment of the present invention, the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction is 25 degrees or more and 65 degrees or less, and preferably 25 degrees or more and 40 degrees or less. The angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction is correlated with the shear rigidity of the belt layer. As a result of intensive research by the present inventors, it has been found that the shear rigidity of the belt layer is highest when the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction is 45 degrees, and that the shear rigidity of the belt layer gradually decreases as the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction becomes smaller or larger than 45 degrees. Furthermore, by setting the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction to 25 degrees or more and 65 degrees or less, it is possible to sufficiently compensate for the decrease in shear rigidity of the carcass layer and the belt reinforcing layer using reinforcing cords containing polyamide fibers having an amide density of 14.0 or less, and as a result, it is possible to suppress a decrease in the cornering power of the tire and suppress a decrease in the handling stability of the tire. Furthermore, when the angle of the reinforcing cord of the belt layer with respect to the tire circumferential direction is 25 degrees or more and 40 degrees or less, the shear rigidity of the belt layer is improved and the balance of the entire tire is improved, making it possible to improve the steering stability of the tire.

[0096] In the tire of the first embodiment of the present invention, the belt layer is typically formed by reinforcing cords extending at an angle of 25 degrees to 65 degrees with respect to the tire circumferential direction (tire equatorial plane) and coated with a coating rubber, preferably by steel cords coated with a coating rubber. Also, typically, two or more belt layers are laminated such that the reinforcing cords constituting the belt layers cross each other with the tire equatorial plane in between, and are disposed on the tire radially outer side of the crown portion of the carcass layer. Also, when the belt layer has two layers, the reinforcing cords constituting the belt layers may be inclined at the same angle with respect to the circumferential direction (for example, may be inclined plane-symmetrically with respect to the tire equatorial plane), or may be inclined at different angles.

[0097] In the tire according to the second embodiment of the present invention, the belt layer is typically formed by coating reinforcing cords, preferably steel cords, with a coating rubber, the reinforcing cords extending at an angle inclined with respect to the tire equatorial plane (for example, at an angle of 15 to 40 degrees). Also, typically, two or more belt layers are laminated such that the reinforcing cords constituting the belt layers cross each other with the tire equatorial plane in between, and the belt layers are disposed radially outward of the crown portion of the carcass layer.

[0098] -Coating Rubber- As the coating rubber of the belt layer, a rubber composition can be used in which a rubber component such as natural rubber or synthetic rubber is blended with a filler such as carbon black, an antioxidant, an adhesion promoter such as a cobalt compound containing a cobalt salt, a vulcanizing agent such as sulfur, a vulcanization accelerator, etc.

[0099] The rubber component used for the coating rubber of the belt layer is preferably natural rubber (NR) or synthetic isoprene rubber (IR). The natural rubber may be modified. In the case of modified natural rubber, for example, the modified natural rubber preferably has a nitrogen content of 0.1 to 0.3 mass%. Furthermore, the modified natural rubber is preferably one from which proteins have been removed by a centrifugation process, enzyme treatment, or urea treatment. Furthermore, the modified natural rubber preferably has a phosphorus content of more than 200 ppm and not more than 900 ppm.

[0100] The carbon black used in the coating rubber of the belt layer is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination. The carbon black content is preferably 40 to 80 parts by mass, more preferably 50 to 70 parts by mass, per 100 parts by mass of the rubber component. The carbon black may also be recycled carbon black. Here, "recycled carbon black" refers to carbon black obtained by recovering recycled waste from raw materials, and is the same as the "recycled carbon black" described above as an example of the carbon black used in the coating rubber of the carcass layer and belt reinforcing layer. Examples of the recycled waste include rubber products (particularly vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. Further details of the waste are the same as those described above. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., non-recycled carbon black. Note that "used" here does not only include carbon black that has been discarded after actual use, but also carbon black that has been manufactured but discarded without actually being used.

[0101] The recycled carbon black for the coating rubber of the belt layer is also preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. The recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is easily available because there are a large number of vulcanized rubber products containing carbon black and it can be easily obtained by pyrolysis. Details of the pyrolysis of vulcanized rubber products containing carbon black are the same as those described above.

[0102] Furthermore, when the recycled carbon black for the coating rubber of the belt layer is recovered from solid residue, it is preferably carbon black that has been subjected to a surface treatment or surface modification. Examples of the surface treatment or surface modification include treatment with hydrofluoric acid, or treatment with an acid such as hydrochloric acid or sulfuric acid, or with a peroxide. The surface treatment or surface modification may be performed at room temperature, preferably at 70°C or higher, more preferably at 90°C or higher, and particularly preferably at 90°C or higher and 100°C or lower.

[0103] The recycled carbon black for the coating rubber of the belt layer also preferably has three or more lines of 10 mm or more in length when measured with a grind gauge, and the particle size of the third-largest particle among the particles that produce the lines of 10 mm or more in length is 20 μm or less. If the particle size of the third-largest particle is 20 μm or less, even when recycled carbon black is blended, the recycled carbon black has good dispersibility in the rubber composition, and the durability of the rubber composition, particularly the deterioration of performance after aging, can be suppressed. Details of the grind gauge measurement are the same as above.

[0104] The recycled carbon black for the coating rubber of the belt layer also 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, a tire with sufficient reinforcement may not be obtained. In consideration of the reinforcement of the tire, the ash content is preferably 10% by mass or less, and more preferably 6% by mass or less.

[0105] -Reinforcement Cord- The reinforcing cord used in the belt layer is not particularly limited, but is preferably a steel cord. The structure of the steel cord is not particularly limited. However, from the viewpoint of effectively achieving both improved tire durability and low rolling resistance, the steel cord may have a 1×N structure (N is an integer of 2 or more) formed by twisting together N filaments, an M+N structure in which N sheath filaments (N is an integer greater than 1) are twisted spirally around M core filaments (here, M is an integer of 1 or more) (here, the core filaments may be twisted together or may be bundled together without twisting), or a multi-twist structure in which a plurality of the 1×N structure or M+N structure are twisted together. Furthermore, the cord is preferably a monofilament that is pulled parallel to one another without being twisted together. In addition, in tires, steel cords can be used, for example, as belt cords in belt layers (usually arranged in the tread portion), as well as belt reinforcing layer cords in belt reinforcing layers; carcass cords; reinforcing cords in wire chafers (usually arranged on the outer side of the folded-up portion of the carcass in the tire width direction); bead cords in bead cores (usually arranged in the bead portion); etc.

[0106] The filaments constituting the above-mentioned steel cord preferably satisfy the following formula: 4000-2000X≦Y≦4500-2000X, where X (mm) is the diameter of the filament and Y (MPa) is the tensile strength of the filament. By using filaments that satisfy the above formula, the strength of the steel cord can be improved, and the cut resistance of the tire can be improved. Here, the tensile strength of the filament is determined in accordance with the provisions of ISO 17832:2009.

[0107] From the viewpoint of fatigue resistance, the hardness of the surface layer of the filament constituting the above-mentioned steel cord is preferably 90 to 110%, and particularly preferably 100%, of the hardness of the inner layer. The hardness can be measured, for example, by Vickers hardness. The surface layer of the filament refers to the layer extending from the outermost surface to a depth of 0.01 mm, and the inner layer refers to the layer extending further inside. The hardness can be measured in a region 0.005 mm deep from the outermost surface for the surface layer, and in a region 0.04 mm deep for the inner layer.

[0108] The steel filaments constituting the above-mentioned steel cord may be steel filaments derived from recycled iron.

[0109] The raw material of the recycled iron is not particularly limited, and examples thereof include scrap iron, steel cords extracted from tires, etc. ２ From the viewpoint of reducing emissions, recycled iron obtained from an electric furnace (electric furnace steelmaking method) is preferred.

[0110] The steel filaments derived from recycled iron preferably have an N (nitrogen) content of 60 ppm to 200 ppm by mass, preferably 60 ppm to 89 ppm by mass, a C (carbon) content of 0.7 to 1.0% by mass, a Cu (copper) content of 0.01 to 0.4% by mass, and a Cr (chromium) content of 0.05 to 0.3% by mass. Such steel filaments can be produced using, as a raw material, general recycled iron having an N (nitrogen) content of 60 ppm to 200 ppm by mass, a C (carbon) content of 0.7 to 1.0% by mass, a Cu (copper) content of 0.01 to 0.4% by mass, and a Cr (chromium) content of 0.05 to 0.3% by mass. Such steel filaments do not require advanced refining during production, and therefore the production process is not complicated. Furthermore, such steel filaments can reduce energy consumption during production and also reduce CO ２ This is also preferable from an environmental perspective, as it reduces emissions.

[0111] The steel filaments derived from recycled iron preferably contain iron as the main component and have an Fe (iron) element content of 98% by mass or more.

[0112] In the belt layer, the end count of the reinforcement cord is preferably 40 / dm to 100 / dm, more preferably 60 / dm to 95 / dm. By setting the end count of the reinforcement cord in the belt layer to 40 / dm or more, the strength of the belt layer can be improved, and by setting the end count of the reinforcement cord in the belt layer to 100 / dm or less, an excessive increase in tire weight can be avoided.

[0113] In the belt layer, the cord diameter of the reinforcement cord is preferably 0.4 mm or more and 1.2 mm or less, and more preferably 0.5 mm or more and 1.0 mm or less. By making the cord diameter of the reinforcement cord in the belt layer 0.4 mm or more, the strength of the belt layer can be improved, and by making the cord diameter of the reinforcement cord in the belt layer 1.2 mm or less, an excessive increase in tire weight can be avoided.

[0114] (Specific Example) Next, an example of a tire according to the first and second embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of an example of a tire according to the first and second embodiments of the present invention. Fig. 2 is a partially developed plan view, seen from the tire tread side, illustrating the angle of a reinforcing cord of a belt layer of a tire according to the first embodiment of the present invention relative to the tire circumferential direction. Fig. 3 is a partially developed plan view, seen from the tire tread side, illustrating the angle of a reinforcing cord of a carcass layer of a tire according to the second embodiment of the present invention relative to the tire circumferential direction.

[0115] The tire 100 shown in FIG. 1 has a pair of bead portions 10, a pair of sidewall portions 20, and a tread portion 30 connected to both sidewall portions 20, and is equipped with a carcass layer 50 extending in a toroidal shape between bead cores 40 embedded in the pair of bead portions 10, two belt layers 60A, 60B arranged on the tire radial outside of the crown portion of the carcass layer 50, a belt reinforcing layer (also called a "cap layer") 70A arranged on the tire radial outside of the belt layers 60A, 60B so as to cover the entire belt layers 60A, 60B, and a pair of belt reinforcing layers (also called "layer layers") 70B arranged so as to cover only both end portions of the belt reinforcing layer 70A. In the tire 100 shown in FIG. 1, at least one of the carcass layer 50 or the belt reinforcing layers 70A, 70B, or at least one of the carcass layer 50 and the belt reinforcing layers 70A, 70B, includes a reinforcing cord containing the above-mentioned polyamide fiber having an amide density of 14.0 or less.

[0116] 1, the tire 100 has one carcass layer 50, but the tires of the first and second embodiments of the present invention may have two or more carcass layers. Also, in the tire 100 shown in Fig. 1, the carcass layer 50 is composed of a main body portion extending in a toroidal shape between a pair of bead cores 40 each embedded in the bead portion 10, and a folded-up portion wound up radially outward from the inner side toward the outer side in the tire width direction around each bead core 40, but the shape and structure of the carcass layer 50 are not limited to this in the tires of the first and second embodiments of the present invention.

[0117] In the tire of the first embodiment of the present invention, the carcass layer 50 is preferably formed by covering a plurality of organic fiber cords (such as the above-mentioned reinforcing cords) that extend in a direction substantially perpendicular to the tire circumferential direction (for example, extending at an angle of 70 degrees to 90 degrees) with a coating rubber; that is, the carcass layer 50 is preferably a radial carcass.

[0118] In the tire according to the second embodiment of the present invention, the carcass layer 50 is formed in a shape similar to that shown in FIG. ＣThe reinforcing cord 50-1 extends at an angle γ of 70 degrees or more but less than 90 degrees with respect to the tire circumferential direction D. Ｃ The direction perpendicular to the tire equatorial plane CL is the tire width direction D Ｗ In addition, in FIG. Ｃ and the tire equatorial plane CL are parallel to each other, so the tire circumferential direction D Ｃ The angle γ with respect to the tire equatorial plane CL is the same as the angle with respect to the tire equatorial plane CL.

[0119] Furthermore, although the tire 100 shown in FIG. 1 has two belt layers 60A, 60B, the number of belt layers in the tires of the first and second embodiments of the present invention may be one layer or three or more layers.

[0120] In the tire according to the first embodiment of the present invention, the belt layers 60A and 60B are arranged in the tire circumferential direction D as shown in FIG. Ｃ The reinforcing cords 60A-1, 60B-1 extend at an angle α, β of 25 degrees or more and 65 degrees or less with respect to the tire equatorial plane CL, and are covered with coating rubber 60A-2, 60B-2. Preferably, the reinforcing cords 60A-1, 60B-1 are steel cords covered with coating rubber. Ｃ The direction perpendicular to the tire equatorial plane CL is the tire width direction D Ｗ In addition, in FIG. Ｃ and the tire equatorial plane CL are parallel to each other, so the tire circumferential direction D Ｃ The angles α and β with respect to the tire circumferential plane CL are the same as the angles with respect to the tire equatorial plane CL. Ｃ and the angle α with respect to the tire circumferential direction D of the reinforcement cord 60B-1 constituting the belt layer 60B. Ｃ The angle β to the axial direction of the belt layer 60A is in a different direction from the axial direction of the tire equatorial plane CL. The reinforcement cord 60A-1 constituting the belt layer 60A and the reinforcement cord 60B-1 constituting the belt layer 60B are layered so as to intersect with each other with the tire equatorial plane CL in between.

[0121] In the tire according to the second embodiment of the present invention, each belt layer 60A, 60B is usually formed by coating reinforcing cords, which extend at an angle inclined with respect to the tire equatorial plane (for example, at an angle of 15 degrees to 40 degrees), with a coating rubber, and is preferably formed by coating steel cords with a coating rubber, and further, the two belt layers 60A, 60B are laminated such that the reinforcing cords constituting the belt layers 60A, 60B intersect with each other with the tire equatorial plane in between.

[0122] In the tire 100 shown in FIG. 1 , the belt reinforcing layers 70A, 70B are formed by coating reinforcing cords arranged substantially parallel to the tire circumferential direction (e.g., at an angle of 0 to 5 degrees relative to the tire circumferential direction) with a coating rubber. The belt reinforcing layers 70A, 70B are formed by continuously spirally winding narrow strips of organic fiber cords (such as the reinforcing cords described above) in the tire circumferential direction. In this case, the absence of joint portions in the tire circumferential direction improves tire uniformity, and the absence of joint portions also prevents strain concentration at the joint portions. While the tire 100 shown in FIG. 1 includes the belt reinforcing layers 70A and 70B, a tire in which either the belt reinforcing layer 70A or the belt reinforcing layer 70B is omitted is also an example of the tire of the first and second embodiments of the present invention. In the tire 100 shown in FIG. 1, each of the belt reinforcing layer (cap layer) 70A and the belt reinforcing layer (layer layer) 70B is one layer, but may be two or more layers.

[0123] <Tire Manufacturing Method> Depending on the type of tire to be applied, the tires of the first and second embodiments of the present invention may be obtained by molding an unvulcanized rubber composition or an unvulcanized treat (rubber-organic fiber cord composite), etc., and then vulcanizing the molded tire. Alternatively, they may be obtained by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like instead of the unvulcanized rubber composition, and then further vulcanizing the molded tire. Note that the components of the tires of the first and second embodiments of the present invention other than the carcass layer and the belt reinforcing layer are not particularly limited, and known components can be used. Furthermore, the tires of the first and second embodiments of the present invention are preferably pneumatic tires, and the gas to be filled into the pneumatic tires can be normal air or air with an adjusted oxygen partial pressure, as well as inert gases such as nitrogen, argon, and helium.

[0124] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0125] Comparative Example 1 Two 1400 dtex polyamide 6,6 (PA66) fibers (amide density 14.3) were first twisted, then paralleled and second twisted to produce a twisted cord [cord structure: 1400 / / 2 / 2]. The number of first twists was 22 per 10 cm, and the number of second twists was 22 per 10 cm.

[0126] Example 1 Two 1400 dtex polyamide 4,10 (PA410) fibers (amide density 12.5) were first twisted, then paralleled and second twisted to produce a twisted cord (cord structure: 1400 / / 2 / 2). The number of first twists per 10 cm was 22, and the number of second twists per 10 cm was 22.

[0127] <Measurement of Heat Shrinkage of Cord> According to ASTM D885 and ASTM D4974, the cord was heated at 177°C for 2 minutes to measure the heat shrinkage of the cord.

[0128] <Evaluation of Cord Properties> A tensile test was carried out on the cord obtained as described above in accordance with JIS L 1013 "Testing methods for chemical fiber filament yarns," and the load (N)-elongation (%) curve of the cord was measured. The strength (N) and elongation (%) at break at 100°C of Comparative Example 1 were set to 100, and the respective values ​​were expressed as indices.

[0129]

[0130] Comparing Comparative Example 1 with Example 1, it is clear that the cord made of PA410 fiber has a greater decrease in strength at break at high temperatures than the cord made of PA66 fiber.

[0131] In contrast, according to the first embodiment of the present invention, by setting the angle of the reinforcing cords of the belt layer relative to the tire circumferential direction to be 25 degrees or more and 65 degrees or less, the decrease in shear rigidity of the carcass layer and belt reinforcing layer using reinforcing cords containing polyamide fibers with an amide density of 14.0 or less can be compensated for, and as a result, the decrease in cornering power of the tire can be suppressed, and the decrease in steering stability of the tire can be suppressed.

[0132] Furthermore, according to the second embodiment of the present invention, by setting the angle of the reinforcing cords of the carcass layer relative to the tire circumferential direction to be equal to or greater than 70 degrees and less than 90 degrees, the rigidity of the tire against lateral input is improved, compensating for the decrease in shear rigidity of the carcass layer and belt reinforcing layer that use reinforcing cords containing polyamide fibers with an amide density of 14.0 or less, and as a result, it is possible to suppress a decrease in the cornering power of the tire and suppress a decrease in the handling stability of the tire.

[0133] 100: Tire 10: Bead portion 20: Sidewall portion 30: Tread portion 40: Bead core 50: Carcass layer 50-1: Reinforcement cord 50-2: Coating rubber 60A, 60B: Belt layer 60A-1, 60B-1: Reinforcement cord 60A-2, 60B-2: Coating rubber 70A: Belt reinforcing layer (cap layer) 70B: Belt reinforcing layer (layer layer) D Ｃ : Tire circumferential direction D Ｗ: tire width direction CL: tire equatorial plane α, β: angle of reinforcing cord of belt layer with respect to tire circumferential direction γ: angle of reinforcing cord of carcass layer with respect to tire circumferential direction

Claims

1. A tire having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and comprising: at least one carcass layer extending in a toroidal shape spanning the pair of bead portions; at least one belt layer disposed radially outward of a crown portion of the carcass layer; and at least one belt reinforcing layer disposed radially outward of the belt layer, wherein the carcass layer, the belt layer, and the belt reinforcing layer each contain a reinforcing cord, and the reinforcing cord of at least one of the carcass layer and the belt reinforcing layer contains a polyamide fiber having an amide density of 14.0 or less, and the angle of the reinforcing cord of the belt layer relative to the circumferential direction of the tire is between 25 degrees and 65 degrees.

2. A tire having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and comprising: at least one carcass layer extending toroidally across the space between the pair of bead portions; at least one belt layer disposed radially outward of a crown portion of the carcass layer; and at least one belt reinforcing layer disposed radially outward of the belt layer, wherein the carcass layer and the belt reinforcing layer contain reinforcing cords, and the reinforcing cords of at least one of the carcass layer and the belt reinforcing layer comprise polyamide fibers with an amide density of 14.0 or less, and the angle of the reinforcing cords of the carcass layer relative to the circumferential direction of the tire is equal to or greater than 70 degrees and less than 90 degrees.

3. The tire according to claim 1, wherein the angle of the reinforcing cords of the belt layer with respect to the tire circumferential direction is equal to or greater than 25 degrees and equal to or less than 40 degrees.

4. A tire according to claim 1 or 2, wherein the reinforcing cords of both the carcass layer and the belt reinforcing layer contain polyamide fibers having an amide density of 14.0 or less.

5. A tire according to claim 1 or 2, wherein the polyamide fiber having an amide density of 14.0 or less is a polyamide 4,10 fiber.

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