Tire

Abstract

To provide a tire that has suppressed deterioration in tire performance despite the use of polyamide fiber with low amide density.SOLUTION: In a tire 100 including a carcass layer 50, belt layers 60A and 60B, and belt reinforcement layers 70A and 70B, and having a rubber part, the carcass layer 50 and the belt reinforcement layers 70A and 70B contain a reinforcement cord. The reinforcement cord of at least one of the carcass layer 50 and the belt reinforcement layers 70A and 70B contains polyamide fiber with amide density of 14.0 or less. The rubber part of the tire 100 contains regenerated carbon black. One mass% or more of carbon black contained in all the rubber parts of the tire 100 is a regenerated carbon black.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Conventionally, a carcass layer containing reinforcing cords is disposed inside a tire to reinforce the strength and rigidity of the tire, and a belt layer containing reinforcing cords is disposed radially outward of the carcass layer. Furthermore, a belt reinforcing layer (also called a "cap layer") containing 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, from the viewpoint of reducing the environmental load, there has been a demand for reducing the amount of fossil resources used, such as petroleum and coal. Therefore, with regard to the organic fiber cords, the replacement of cords derived from fossil resources with cords derived from biomass (biological resources) 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 the reinforcing ply, and teaches that one of the two monomers of nylon 4,10 is based on renewable raw materials, making it environmentally friendly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2019-511411 Summary of the Invention [Problem to be solved by the invention]

[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 particularly 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 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. As a result, an organic fiber cord using such polyamide 4,10 exhibits reduced physical properties at high temperatures, and when such an organic fiber cord is used in a tire, tire performance is reduced.

[0006] Therefore, an object of the present invention is to provide a tire that suppresses deterioration in tire performance while using polyamide fiber that has a lower amide density than polyamide 6,6 fiber. [Means for solving the problem]

[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 connected to both sidewall portions, At least one carcass layer extending in a toroidal shape across the pair of bead portions; At least one belt layer arranged on the tire radially outer side of the crown portion of the carcass layer; At least one belt reinforcing layer is disposed radially outward of the belt layer, In a tire having a rubber portion, the carcass layer and the belt reinforcing layer contain reinforcing cords, a 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, The rubber portion of the tire contains recycled carbon black, A tire, characterized in that 1% by mass or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black. The tire of the present invention described in [1] above uses polyamide fibers having an amide density of 14.0 or less, yet the degradation of tire performance is suppressed.

[0009] [2] As the rubber portion, a tread rubber arranged on the tire radial outer side of the belt reinforcing layer of the tread portion; a side rubber disposed on the outer side of the carcass layer in the tire width direction of the sidewall portion; a gum chafer disposed at a contact portion of the bead portion with the rim, The tire according to [1], wherein at least one of the tread rubber, the side rubber, and the gum chafer contains the recycled carbon black. In the tire described in [2] above, the deterioration of tire performance is more reliably suppressed.

[0010] [3] The tire according to [1] or [2], wherein the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. The tire described in [3] above recycles resources, further contributing to improving sustainability.

[0011] [4] The tire according to any one of [1] to [3], wherein the recycled carbon black has an ash content of 20% by mass or less. In the tire described in [4] above, the physical properties of the rubber portion are improved.

[0012] [5] The tire according to any one of [1] to [4], 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. In the tire described in [5] above, biomass-derived polyamide fibers can be easily applied to the reinforcing cords of the carcass layer and the belt reinforcing layer, which facilitates reducing the environmental load.

[0013] [6] The tire according to any one of [1] to [5], wherein the polyamide fiber having an amide density of 14.0 or less is a polyamide 4,10 fiber. The tire described in [6] above can easily reduce the environmental impact. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a tire in which degradation of tire performance is suppressed even when using polyamide fiber having a lower amide density than polyamide 6,6 fiber. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The tire of the present invention will be described in detail below by way of example based on an embodiment thereof.

[0017] <Definition> In this specification, the term "biomass content" refers to the content rate of carbon derived from biomass, and is calculated using the following formula (1): Biomass ratio (%) = number of carbon atoms derived from biomass / total number of carbon atoms × 100 (1) It is calculated from

[0018] 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-derived carbon atoms in the entire code (%) = Number of carbon atoms in the entire code / Total number of carbon atoms in the entire code × 100 (2) It is calculated from

[0019] 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.

[0020] In this specification, the "amide density" of a polyamide is calculated by the following formula (3): Amide density = number of amide groups in polyamide / number of atoms in the main chain of polyamide × 100 (3) It is calculated from 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" 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.

[0021] 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."

[0022] The compounds described herein may be derived partially or entirely from fossil resources, biological resources such as plant resources, or recycled resources such as used tires, or may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0023] <Tires> The tire of this embodiment has a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and is equipped with at least one carcass layer extending toroidally across the pair of bead portions, at least one belt layer arranged radially outward of the crown portion of the carcass layer, and at least one belt reinforcing layer arranged radially outward of the belt layer, and has a rubber portion. In the tire of this embodiment, 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 rubber portion of the tire contains recycled carbon black, and 1% by mass or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black.

[0024] The polyamide fibers having an amide density of 14.0 or less have a lower amide density and fewer hydrogen bonds between amide bonds than polyamide 6,6 fibers, resulting in poor thermal properties. As a result, the physical properties of polyamide fibers having an amide density of 14.0 or less deteriorate at high temperatures, and therefore the physical properties of a carcass layer and / or belt reinforcing layer including reinforcing cords containing polyamide fibers having an amide density of 14.0 or less deteriorate at high temperatures. In contrast, in the tire of the present embodiment, recycled carbon black is contained in the rubber portion of the tire, and further, 1 mass % or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black. This makes it difficult for heat to be generated inside the tire while the tire is running, prevents the inside of the tire from becoming too hot while the tire is running, and prevents deterioration in the physical properties of the reinforcing cords containing polyamide fibers with an amide density of 14.0 or less, thereby making it possible to maintain tire performance. Therefore, in the tire of this embodiment, even though polyamide fibers having an amide density of 14.0 or less are used, degradation of tire performance is suppressed.

[0025] (Carcass layer and belt reinforcing layer) The carcass layer and the belt reinforcing layer contain the reinforcing cords, and the reinforcing cords are usually coated with a coating rubber.

[0026] -Coated rubber- The coating rubber for the carcass layer and the belt reinforcing layer can be a rubber composition containing a rubber component such as natural rubber or synthetic rubber, a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, etc.

[0027] The rubber component used for the coating rubber of the carcass layer and the belt reinforcing 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 nitrogen content is preferably 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 phosphorus content of the modified natural rubber is preferably more than 200 ppm and not more than 900 ppm.

[0028] The carbon black used in the coating rubber of the carcass layer and the belt reinforcing 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 recovered from recycled waste raw materials. Examples of recycled waste include rubber products (especially vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" differs from carbon black produced directly from hydrocarbon raw materials such as petroleum and natural gas, i.e., non-recycled carbon black. Note that "used" here refers not only to carbon black discarded after actual use, but also to carbon black produced but discarded without actually being used.

[0029] -Reinforcing cord containing polyamide fiber with 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 with an amide density of 14.0 or less. Compared to widely used polyamide 6,6 (PA66) 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 poor thermal properties and reduced physical properties at high temperatures. However, in the tire of this embodiment, recycled carbon black is contained in the rubber portion of the tire, and by using recycled carbon black to account for 1% by mass or more of the carbon black contained in all rubber portions of the tire, heat generation inside the tire is reduced during driving, preventing the tire from becoming too hot during driving and maintaining tire performance. While there is no particular lower limit for the amide density of the polyamide fiber, 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 deterioration of thermal properties.

[0030] 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 a polyamide fiber 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.

[0031] 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.

[0032] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably has a biomass-derived carbon content (biomass content) of 15% or more throughout the entire cord. When the biomass content of the entire cord is 15% or more, the effect of reducing the environmental load is significant. From the viewpoint of further reducing the environmental load, the biomass content of the entire reinforcing cord is preferably 20% or more, and may be 100%.

[0033] 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 raw materials for these polyamide fibers can be synthesized from biomass-derived components. Biomass-derived components are components derived from biological resources such as plant resources, animal resources, and microbial resources.

[0034] Polyamide 11 (PA11) is obtained by polymerization of aminoundecanoic acid, which is obtained from plant sources such as castor beans. Polyamide 4,10 (PA410) is obtained by the condensation polymerization reaction of tetramethylenediamine (carbon number 4) and sebacic acid (carbon number 10). Tetramethylenediamine is obtained from plant resources such as sugarcane, and sebacic acid is obtained from plant resources such as castor beans. Polyamide 6,10 (PA610) is obtained by a condensation polymerization reaction between hexamethylenediamine (carbon number 6) and sebacic acid (carbon number 10), and sebacic acid is obtained from plant resources such as castor beans. Polyamide 10,10 (PA1010) is obtained by a condensation polymerization reaction between decamethylenediamine (having 10 carbon atoms) and sebacic acid (having 10 carbon atoms), and 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 also be obtained by mechanically pressing castor beans to obtain castor oil, methanolysing the castor oil to obtain methyl ricinoleate, and then saponifying the methyl ricinoleate.

[0035] The reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less preferably contains the fiber whose bio content is 100% (i.e., entirely derived from biomass). By including the fiber whose bio content is 100%, the effect of reducing the environmental load is further enhanced. Examples of the fiber whose bio content is 100% include polyamide 11 (PA11) fiber, polyamide 4,10 (PA410) fiber, and polyamide 10,10 (PA1010) fiber.

[0036] 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 pneumatic tire in which a reinforcing cord containing polyamide 4,10 fibers is applied to at least one of the carcass layer and the belt reinforcing layer can easily reduce environmental impact.

[0037] 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.

[0038] 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.

[0039] Examples of the polyethylene terephthalate (PET) include polyethylene terephthalate obtained by mechanically or chemically recycling PET products, clothing, and the like.

[0040] 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)).

[0041] 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.

[0042] 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.

[0043] The reinforcing cord containing polyamide fibers having an amide density of 14.0 or less is also preferably a cord made by twisting two to four fibers together. A reinforcing cord made 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 made by twisting two fibers together is preferred.

[0044] The reinforcing cord containing 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 environmental impact due to the polyamide 4,10 fiber, which can be made 100% bio-based.

[0045] The reinforcing cord containing polyamide fibers having an amide density of 14.0 or less is preferably made exclusively of polyamide fibers with a biomass-derived carbon content (biomass content) of 15% or more. By making the reinforcing cord exclusively of polyamide fibers with a biomass content of 15% or more, the effect of reducing the environmental load is enhanced.

[0046] 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 the 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. Furthermore, in the case of a two-twist structure, for example, a twisted cord can be obtained by first twisting an original yarn, then combining multiple twists and then final twisting them in the opposite direction. Here, the number of first twists is preferably in the range of 10 to 60 times per 10 cm, and the number of final twists is preferably in the range of 10 to 60 times per 10 cm. If the number of first twists exceeds 60 times per 10 cm, the strength of the twisted cord may decrease, and if it is less than 10 times per 10 cm, the twisted cord may not have sufficient fatigue resistance. If the number of final twists exceeds 60 times per 10 cm, the strength of the twisted cord may decrease, and if it is less than 10 times per 10 cm, the twisted cord may not have sufficient fatigue resistance.

[0047] 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.

[0048] 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, and the tire becomes heavy.

[0049] 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. When the breaking strength of the reinforcement cord is 6.0 cN / dtex or more or 180 N or more, a sufficient reinforcing effect can be obtained.

[0050] 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.

[0051] The moisture content of the reinforcing cord containing the polyamide fiber having an amide density of 14.0 or less is preferably 3.0% or less, as measured in accordance with JIS L 1013. If the moisture content of the reinforcing cord exceeds 3.0%, the physical properties will be reduced and a sufficient reinforcing effect will not be obtained.

[0052] -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, etc. may also be used.

[0053] -Adhesive composition- The reinforcing cords used in the carcass layer and the belt reinforcing layer are preferably treated with an adhesive composition.

[0054] Examples of the adhesive composition include an adhesive composition containing a thermoplastic polymer (A) that has at least one crosslinkable functional group as a pendant group and that is substantially free of 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.

[0055] Conventionally, adhesive treatment of organic fiber cords has been performed using a so-called two-bath process, in which an 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 drastically reduce adhesion at temperatures above 130°C. In contrast, 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) can be used to ensure sufficient adhesion to the elastomer (coating rubber) without curing the reinforcing cord, even at temperatures above 180°C.

[0056] 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.

[0057] 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.

[0058] In addition, for 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.

[0059] 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 liquid of a normal RFL resin as a two-bath treatment liquid. Also, in the adhesive treatment, it is 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).

[0060] 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 thermally 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.

[0061] 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).

[0062] Other examples of the dip treatment liquid that does not contain resorcinol or formalin include a composition containing polyphenols (I) and aldehydes (II). In addition to the polyphenols (I) and aldehydes (II), such a composition may further contain at least one of an isocyanate compound (III) and a rubber latex (IV).

[0063] The adhesive composition used to treat (coat) the reinforcing cord with an adhesive contains polyphenols (I) and aldehydes (II), so that good adhesive properties can be achieved even when resorcinol is not used in consideration of the environmental impact.

[0064] --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 hydroxyl groups in the polyphenols (I) can be appropriately selected.

[0065] 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.

[0066] As the polyphenols (I), for example, those described as polyphenol compounds in International Publication No. 2022 / 130879 can be used. These polyphenols (I) may be used alone or in combination of two or more.

[0067] --Aldehydes (II)-- The adhesive composition contains aldehydes (II) as a resin component in addition to the polyphenols (I), thereby achieving high adhesiveness together with the polyphenols (I). Here, 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.

[0068] 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.

[0069] 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%.

[0070] 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. This is because 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, become 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. The above mass ratio is the mass of the dried product (solid content ratio).

[0071] The total content of the polyphenols (I) and the aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass, because this ensures better adhesion without impairing workability, etc. From the same viewpoint, the total content of the polyphenols (I) and the aldehydes (II) in the adhesive composition is more preferably 5% by mass or more and more preferably 25% by mass or less. The total content is the mass of the dry matter (solid content ratio).

[0072] --Isocyanate compound (III)-- The adhesive composition preferably further contains an isocyanate compound (III) in addition to the polyphenols (I) and aldehydes (II), which can further enhance the adhesiveness of the adhesive composition due to a synergistic effect with the polyphenols (I) and aldehydes (II).

[0073] Here, the isocyanate compound (III) is a compound that has the effect of promoting adhesion to a resin material (for example, a phenol / aldehyde resin obtained by condensing a polyphenol (I) and an aldehyde (II)) that is the adherend of the adhesive composition, 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.

[0074] 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 the vicinity of 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.

[0075] As the (blocked) isocyanate group-containing aromatic compound, those described in Japanese Patent Application No. 2023-040157 and those described in Japanese Patent Application No. 2023-030762 can be used.

[0076] The content of the isocyanate compound (III) in the adhesive composition is not particularly limited, but is preferably 5 to 65% by mass from the viewpoint of more reliably ensuring excellent adhesiveness. 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 matter (solid content ratio).

[0077] --Rubber latex (IV)-- The adhesive composition may further contain substantially a rubber latex (IV) in addition to the polyphenols (I), aldehydes (II), and isocyanate compound (III), thereby further enhancing the adhesiveness of the adhesive composition to rubber members.

[0078] 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.

[0079] When preparing the adhesive composition containing the rubber latex (IV), it is preferable to mix the rubber latex (IV) with the phenols (I) and the aldehydes (II) before compounding the isocyanate compound (III).

[0080] 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.

[0081] 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 the raw materials contain an isocyanate compound (III), the method for producing the adhesive composition may also include a method of adding rubber latex (IV), aging the mixture, and then adding the isocyanate compound (III).

[0082] (Belt layer) The tire of this embodiment includes 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. The belt layer is usually formed by coating reinforcing cords that extend at an angle (for example, at an angle of 15 to 40°) with a coating rubber with respect to the tire equatorial plane, and preferably by coating steel cords with a coating rubber. Also, usually, 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 arranged on the radially outer side of the crown portion of the carcass layer.

[0083] -Coated 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 compounded 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.

[0084] 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 nitrogen content is preferably 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 phosphorus content of the modified natural rubber is preferably more than 200 ppm and not more than 900 ppm.

[0085] 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 recovered from recycled waste raw materials. Examples of recycled waste include rubber products (especially vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" differs from carbon black produced directly from hydrocarbon raw materials such as petroleum and natural gas, i.e., non-recycled carbon black. Note that "used" here refers not only to carbon black that is discarded after actual use, but also to carbon black that is produced but discarded without actually being used.

[0086] -Reinforcement cord- The reinforcing cords used in the belt layer are not particularly limited, but are preferably steel cords. The structure of the steel cord is also not particularly limited. However, from the viewpoint of effectively achieving both improved tire durability and reduced rolling resistance, the steel cord may have a 1×N structure (N is an integer of 2 or more) in which N filaments are twisted together, an M+N structure in which N sheath filaments (N is an integer greater than 1) are twisted spirally around M core filaments (M is an integer of 1 or more) (the core filaments may be twisted or may be bundled without twisting), or a multi-twist structure in which multiple 1×N or M+N structures 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.

[0087] The filaments constituting the above-mentioned steel cord have a diameter of X (mm) and a tensile strength of Y (MPa) that satisfies the following formula: 4000-2000X≦Y≦4500-2000X It is preferable that the following formula be satisfied. By using a filament that satisfies 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.

[0088] 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.

[0089] The steel filaments constituting the above-mentioned steel cord may be steel filaments derived from recycled iron.

[0090] The raw material of the recycled iron is not particularly limited, and examples thereof include scrap iron, steel cord extracted from tires, etc. From the viewpoint of reducing CO2 emissions, the recycled iron is preferably recycled iron obtained by an electric furnace (electric furnace steelmaking method).

[0091] The steel filament derived from recycled iron preferably has an N (nitrogen) content of 60 to 200 ppm by mass, preferably 60 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 typical recycled iron as a raw material, with an N (nitrogen) content of 60 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, resulting in a simple manufacturing process. Furthermore, such steel filaments are preferable from an environmental perspective, as they can reduce energy consumption and CO2 emissions during production.

[0092] The steel filaments derived from recycled iron preferably contain iron as the main component and have an Fe (iron) element content of 98 mass % or more.

[0093] (Rubber part) The tire of this embodiment has a rubber portion. The location of the rubber portion is not particularly limited. The rubber portion of the tire may be the carcass layer, belt reinforcing layer, or coating rubber of the belt layer described above, or may be tread rubber, side rubber, bead filler, inner liner, gum chafer, or other tire components. Here, the tread rubber is disposed radially outward of the belt reinforcing layer in the tread portion of the tire. The side rubber is disposed radially outward of the carcass layer in the sidewall portion of the tire. The bead filler is disposed radially outward of the bead core embedded in the bead portion, between the main portion and the turned-up portion of the carcass layer. The inner liner is disposed adjacent to the carcass layer on the inner surface of the tire. The gum chafer is disposed in the contact portion of the bead portion with the rim, and in one embodiment, is disposed radially outward of the contact portion with the rim and the turned-up portion of the carcass layer.

[0094] In the tire of this embodiment, it is preferable that at least one of the tread rubber, side rubber, and gum chafer (i.e., any one, any two, or all three) contains the recycled carbon black. The tread rubber and / or side rubber occupy a large volume within the tire, which further reduces the generation of heat inside the tire during running, and is highly effective in preventing the tire's interior from becoming too hot during running. Furthermore, strain tends to concentrate in the side rubber and / or gum chafer during running, making them prone to heat generation. Therefore, a tire in which at least one of the tread rubber, side rubber, and gum chafer contains the recycled carbon black more reliably prevents degradation of tire performance.

[0095] The rubber portion of the tire of this embodiment contains recycled carbon black, and 1% by mass or more of the carbon black contained in all rubber portions of the tire is recycled carbon black. Recycled carbon black has the effect of reducing hysteresis loss in the rubber portion of the tire compared to virgin carbon black. Therefore, rubber portions containing recycled carbon black are less likely to generate heat compared to rubber portions containing virgin carbon black. The tire of this embodiment, which has rubber portions containing recycled carbon black, suppresses heat generation inside the tire during driving, prevents the tire from becoming too hot, and suppresses deterioration of the physical properties of reinforcing cords containing polyamide fibers with an amide density of 14.0 or less. Furthermore, the tire of this embodiment uses recycled carbon black, which can contribute to improved sustainability.

[0096] The rubber portion can be made of a rubber composition containing a rubber component such as natural rubber or synthetic rubber, a filler such as recycled carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, etc.

[0097] The rubber component used in the rubber portion is preferably natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), or styrene-butadiene rubber (SBR). The natural rubber may be modified. In the case of modified natural rubber, the nitrogen content is preferably 0.1 to 0.3% by mass. Furthermore, the modified natural rubber is preferably one in which proteins have been removed by a centrifugation process, enzyme treatment, or urea treatment. Furthermore, the phosphorus content of the modified natural rubber is preferably greater than 200 ppm and less than or equal to 900 ppm.

[0098] The recycled carbon black used in the rubber portion is a material derived from recycled resources (recycled resources). Therefore, by blending recycled carbon black into the rubber composition, the proportion of sustainable materials in the rubber portion to which the rubber composition is applied can be increased.

[0099] In this specification, "recycled carbon black" refers to carbon black recovered from raw materials that are waste materials that have been recycled. Examples of the waste materials that have been recycled include rubber products (particularly vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" differs from carbon black that is produced directly from hydrocarbon raw materials such as petroleum and natural gas, i.e., non-recycled carbon black. Note that "used" here includes not only carbon black that has been discarded after actual use, but also carbon black that has been produced but discarded without actually being used.

[0100] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. This enables the recycling of resources, further contributing to improving sustainability. Additionally, 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. However, the recycled carbon black preferably does not include carbon black recovered from oil.

[0101] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. For this reason, recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content in the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and even more preferably 89% by mass or more. The carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the above carbon content does not include adsorbed moisture.

[0102] Specific examples of ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residues obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. The lower limit of the ash content of the recycled carbon black may be 0.5% by mass. Meanwhile, considering the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 5.0% by mass or less. When the ash content of the recycled carbon black is 20% by mass or less, the various physical properties of the rubber portion to which the rubber composition is applied can be improved. In this specification, the ash content of carbon black is calculated from the mass of unburned components (ash content) obtained by burning carbon black at 550°C ± 25°C to convert it to incineration.

[0103] The recycled carbon black can also be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes the carbon black as being obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in

[0004] of Japanese Patent No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercial Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0104] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent No. 6,856,781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0105] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0106] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again with a rubber component, a rubber composition with better performance can be obtained.

[0107] Furthermore, when the crosslinked rubber product used in the decomposition is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, trucks, buses, large vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.), and the decomposition step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the decomposition step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the decomposition step may be carried out for each group. When the decomposition step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0108] The nitrogen adsorption specific surface area (N2SA) of the recycled carbon black is not particularly limited, but is preferably 70 m 2 / g or more, and 2 / g or more, and 2 / g or more is more preferable, and 2 / g or less, and 2 / g or less is more preferable, and 2The recycled carbon black preferably has a dibutyl phthalate (DBP) oil absorption of 50 mL / 100 g or more, more preferably 60 mL / 100 g or more, and even more preferably 70 mL / 100 g or more, and preferably 100 mL / 100 g or less, more preferably 90 mL / 100 g or less, and even more preferably 80 mL / 100 g or less. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is determined according to JIS K 6217-2:2017 (ISO 4652:2012), and the DBP oil absorption of carbon black is determined according to JIS K 6217-4:2017.

[0109] The amount of recycled carbon black is preferably 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the rubber component. In this case, crack resistance and low loss properties can be more highly balanced, and sustainability can be further improved. From the same viewpoint, the amount of recycled carbon black is more preferably 15 parts by mass or less per 100 parts by mass of the rubber component.

[0110] The rubber portion of the tire of this embodiment may contain carbon black other than the above-mentioned recycled carbon black, and preferably contains carbon black having a larger nitrogen adsorption specific surface area than the above-mentioned recycled carbon black. The nitrogen adsorption specific surface area of ​​the carbon black other than the recycled carbon black is 110 m or less. 2 / g or more, and 115m 2 / g or more is preferable, and 120m 2 / g or more is more preferable, and 140m 2 / g or less, and 136m 2 / g or less, and 134m 2The carbon black other than the recycled carbon black preferably has a dibutyl phthalate (DBP) oil absorption of 75 mL / 100 g or more, more preferably 80 mL / 100 g or more, and even more preferably 87 mL / 100 g or more, and preferably 110 mL / 100 g or less, more preferably 105 mL / 100 g or less, and even more preferably 97 mL / 100 g or less.

[0111] The content of the carbon black other than the recycled carbon black is preferably 5 parts by mass or more per 100 parts by mass of the rubber component. In this case, crack resistance can be further improved. Furthermore, the content of the carbon black other than the recycled carbon black is preferably 70 parts by mass or less per 100 parts by mass of the rubber component. In this case, low loss properties can be better maintained. From the same viewpoint, the content of the carbon black other than the recycled carbon black is more preferably 10 parts by mass or more and more preferably 60 parts by mass or less per 100 parts by mass of the rubber component.

[0112] In the rubber portions of the tire of this embodiment, it is preferable that 1% by mass or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black, and 10% by mass or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black. When 1% by mass or more of the carbon black contained in all rubber portions of the tire is recycled carbon black, heat generation inside the tire is suppressed during driving, preventing the inside of the tire from becoming too hot during driving. This suppresses deterioration of the physical properties of the reinforcing cords containing polyamide fibers with an amide density of 14.0 or less, thereby maintaining tire performance. Furthermore, when 10% by mass or more of the carbon black contained in all rubber portions of the tire is recycled carbon black, heat generation inside the tire is further suppressed during driving, and tire performance can be more reliably maintained.

[0113] (One embodiment) Next, an embodiment of the tire of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of one embodiment of a tire of the present invention.

[0114] 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 radially outward of the crown portion of the carcass layer 50, a belt reinforcing layer (also called a "cap layer") 70A arranged radially outward 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.

[0115] In the tire 100 shown in FIG. 1, the carcass layer 50 is a single layer, but the tire of the present invention may have two or more carcass layers. In the tire 100 shown in FIG. 1, the carcass layer 50 includes a main body portion extending in a toroidal shape between a pair of bead cores 40 embedded in the bead portion 10, and a folded-up portion wound radially outward around each bead core 40 from the inner side to the outer side in the tire width direction. However, in the tire of the present invention, the shape and structure of the carcass layer 50 are not limited to this. Here, the carcass layer 50 is preferably formed by coating a plurality of reinforcing cords with a coating rubber, the reinforcing cords extending in a direction substantially perpendicular to the tire circumferential direction (e.g., extending at an angle of 70 to 90°). In other words, the carcass layer 50 is preferably a radial carcass. The reinforcing cords of the carcass layer 50 are preferably the reinforcing cords containing the polyamide fibers described above. However, when the reinforcing cords containing the polyamide fibers described above are used in the belt reinforcing layers 70A and 70B, other organic fiber cords or steel cords may also be used. Other organic fiber cords include polyethylene terephthalate cords and rayon cords.

[0116] 1 has two belt layers 60A, 60B, but the tire of the present invention may have one or three or more belt layers. In the tire 100 shown in Fig. 1, each of the belt layers 60A, 60B is usually formed by coating reinforcing cords that extend at an angle inclined with respect to the tire equatorial plane (for example, at an angle of 15 to 40°) with a coating rubber, and preferably 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.

[0117] In the tire 100 shown in FIG. 1 , the belt reinforcing layers 70A, 70B are formed by coating reinforcing cords with a coating rubber, the reinforcing cords being arranged substantially parallel to the tire circumferential direction (for example, at an angle of 0 to 5° relative to the tire circumferential direction). The belt reinforcing layers 70A, 70B are formed by continuously spirally winding narrow strips of reinforcing cords coated with a coating rubber in the tire circumferential direction. In this case, the absence of joints in the tire circumferential direction improves tire uniformity, and the absence of joints also prevents strain concentration at the joints. The reinforcing cords of the belt reinforcing layers 70A, 70B are preferably reinforcing cords containing the polyamide fibers described above. However, when the reinforcing cords containing the polyamide fibers described above are applied to the carcass layer 50, other organic fiber cords may also be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords. 1 includes a belt reinforcing layer 70A and a belt reinforcing layer 70B, but a tire in which either the belt reinforcing layer 70A or the belt reinforcing layer 70B is omitted is also an embodiment of the tire of the present invention. In addition, in the tire 100 shown in FIG. 1, the belt reinforcing layer (cap layer) 70A and the belt reinforcing layer (layer layer) 70B each have one layer, but may have two or more layers.

[0118] 1, the tire 100 has a pair of bead portions 10 in contact with the rim and a folded portion of the carcass layer 50 in the tire width direction D. W The outer surface is provided with a pair of gum chafers 15. The gum chafers 15 can be made of a rubber composition that contains a rubber component such as natural rubber or synthetic rubber, a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, etc.

[0119] In addition, the tire 100 shown in FIG. 1 has a pair of sidewall portions 20, and the carcass layer 50 has a width D of the tire. WThe tire has a pair of side rubbers 25 on the outside. The side rubbers 25 can be made of a rubber composition that contains a rubber component such as natural rubber or synthetic rubber, a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, and the like.

[0120] 1, the tire 100 has a tread portion 30 having the belt reinforcing layers 70A and 70B in the tire radial direction D. R The tire has a tread rubber 35 on the outside. The tread rubber 35 can be a rubber composition made by compounding a rubber component such as natural rubber or synthetic rubber with a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, a vulcanization accelerator, and the like. Note that although the tread rubber 35 of the tire 100 shown in FIG. 1 is a single layer, the tread rubber of the tire of the present invention may be two or more layers. For example, the tread rubber 35 of the tire 100 shown in FIG. 1 can be divided into a cap rubber located on the outermost surface side and a base rubber located radially inward of the cap rubber.

[0121] In the tire of this embodiment, it is preferable that at least one of the gum chafer 15, side rubber 25, and tread rubber 35 contains the recycled carbon black. Strain tends to concentrate in the gum chafer 15 and / or the side rubber 25 when the tire is running, and heat tends to be generated. Furthermore, when the side rubber 25 and / or the tread rubber 35 contain recycled carbon black, there is a significant effect of suppressing high temperatures inside the tire during running.

[0122] In the tire of the present embodiment, the reinforcing cords of both the carcass layer 50 and the belt reinforcing layers 70A, 70B preferably contain polyamide fibers having an amide density of not more than 14.0. When the reinforcing cords of both the carcass layer 50 and the belt reinforcing layers 70A, 70B contain polyamide fibers having an amide density of not more than 14.0, it becomes easy to apply biomass-derived polyamide fibers to the reinforcing cords of the carcass layer 50 and the belt reinforcing layers 70A, 70B, and it becomes easy to reduce the environmental load.

[0123] <Tire manufacturing method> Depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition or an unvulcanized treat (a cord-rubber composite in which reinforcing cords are covered with coating rubber) or the like, followed by vulcanization, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process or the like instead of the unvulcanized rubber composition, followed by further vulcanization. The components of the tire of the present embodiment other than the carcass layer and the belt reinforcing layer are not particularly limited, and known components can be used. Furthermore, the tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[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 first twist was 22 times per 10 cm, and the second twist was 22 times 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 first twist was 22 times per 10 cm, and the second twist was 22 times per 10 cm.

[0127] (1) Measurement of the thermal shrinkage rate of the 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. The results are shown in Table 1.

[0128] (2) Evaluation of cord properties The cord obtained as described above was subjected to a tensile test 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 at 100, and the results were expressed as an index. The results are shown in Table 1.

[0129] [Table 1]

[0130] (Example 2 and Comparative Example 2) Rubber compositions were produced using a conventional Banbury mixer according to the compounding recipes shown in Table 2. The loss tangent (tan δ) of the resulting rubber compositions was measured by the following method. The results are shown in Table 2.

[0131] (3) Measurement of loss tangent (tanδ) of rubber composition The rubber composition was vulcanized at 145°C for 33 minutes to obtain a vulcanized rubber test piece. The loss tangent (tanδ) of the obtained vulcanized rubber test piece was measured using a viscoelasticity measuring device (manufactured by Rheometrics) under conditions of a temperature of 60°C, a strain of 1%, and a frequency of 52 Hz, and expressed as an index, with the reciprocal of the loss tangent (tanδ) of Comparative Example 1 set to 100. A larger index value indicates a smaller loss tangent (tanδ) and better low heat buildup (i.e., low loss).

[0132] (4) Sustainable material ratio Furthermore, the sustainable material ratio for the above-mentioned rubber composition was calculated using the following formula. The results are shown in Table 1. Sustainable material ratio = Total sustainable materials (B in Table 1) / Total of all materials (A in Table 1) x 100

[0133] [Table 2]

[0134] *1 Low Tg modified SBR: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -65°C *2 High Tg modified SBR: Modified styrene-styrene-butadiene copolymer rubber synthesized using the following method. Contains 10.0 parts by mass of oil per 100 parts by mass of rubber component. Weight average molecular weight (Mw) = 85.2 x 10 4 , molecular weight 200×10 4 Over 500 x 10 4 The following percentages = 4.6%, and the amounts of rubber components are shown in Table 2. *3 Unused carbon black: Asahi Carbon Co., Ltd., product name "#78" *4 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *5 Silica: Tosoh Silica Industries Co., Ltd., product name "Nipsil AQ" *6 Silane coupling agent: Evonik, product name "Si75" *7 Aluminum hydroxide: Manufactured by Resonac, product name "Hijilite H-43M" *8 Other chemicals: Total amount of sulfur, vulcanization accelerator, retarder, adhesion inhibitor, antioxidant, wax, resin, and softener. The same ratio for each rubber composition.

[0135] <Synthesis method of low Tg modified SBR(*1)> A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the total weight of the mixture was 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were then added, and polymerization was carried out at 50°C for 1.5 hours. At this point, the polymerization conversion rate of the polymerization reaction system reached nearly 100%, and 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50°C for 30 minutes. The reaction was then quenched by adding 2 mL of a 5% by weight solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol. The mixture was then dried in the usual manner to obtain modified SBR (low Tg modified SBR). Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass and the glass transition temperature (Tg) was -65°C.

[0136] <Method for synthesizing high Tg modified SBR(*2)> The polymerization reactor was a tank-type pressure vessel with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a jacket for temperature control. 1,3-butadiene, which had been pre-dehydrated, was mixed at 17.2 g / min, styrene at 10.5 g / min, and n-hexane at 145.3 g / min. n-butyllithium, used for inert treatment of remaining impurities, was added at 0.117 mmol / min in a static mixer installed in the piping supplying this mixed solution to the inlet of the reactor. After mixing, the mixture was continuously fed to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.019 g / min and n-butyllithium as a polymerization initiator at a rate of 0.242 mmol / min were fed into the bottom of the polymerization reactor, which was being vigorously mixed with a stirrer, and the polymerization reaction was continued continuously. The temperature of the polymerization solution at the top outlet of the reactor was controlled to 75 °C. When the polymerization was sufficiently stabilized, a small amount of the polymer solution before the addition of the coupling agent was withdrawn from the top outlet of the reactor, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer, after which the solvent was removed. The Mooney viscosity at 110 °C and various molecular weights were measured. Next, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, diluted to 2.74 mmol / L, was continuously added to the polymer solution flowing out of the reactor outlet at a rate of 0.0302 mmol / min (n-hexane solution containing 5.2 ppm water) as a coupling agent. The polymer solution with the added coupling agent was mixed by passing it through a static mixer, allowing the coupling reaction to occur. The time until the coupling agent was added to the polymer solution flowing out of the reactor outlet was 4.8 minutes, the temperature was 68°C, and the temperature difference between the polymerization process and the temperature before the modifier was added was 7°C. The antioxidant (BHT) was continuously added to the coupled polymer solution at 0.055 g / min (n-hexane solution) to give 0.2 g per 100 g of polymer, and the coupling reaction was completed. Simultaneously with the antioxidant, oil (JOMO Process NC140, manufactured by JX Nippon Oil & Energy Corporation) was continuously added at a ratio of 10.0 g per 100 g of polymer, and the mixture was mixed in a static mixer. The solvent was removed by steam stripping to obtain a modified conjugated diene polymer (high Tg modified SBR). The modified conjugated diene polymer obtained by the above method was confirmed to contain nitrogen atoms and silicon atoms. The modified conjugated diene polymer has a "degree of branching" of 8, which corresponds to the number of branches estimated from the number of functional groups of the coupling agent and the amount added (this can also be confirmed from the value of the shrinkage factor), and a "number of SiOR residues" of 4, which corresponds to the value obtained by subtracting the number of SiOR removed by the reaction from the total number of SiOR in one molecule of the coupling agent.

[0137] A comparison between Comparative Example 1 and Example 1 in Table 1 reveals that the cord made of PA410 fiber exhibits a greater decrease in strength at break at high temperatures than the cord made of PA66 fiber.

[0138] In contrast, according to the present invention, by applying a rubber composition with excellent low heat buildup properties (low loss properties) as shown in Example 2 of Table 2 to the rubber portion of the tire, heat generation inside the tire during running is suppressed, and deterioration in the physical properties of the reinforcing cord containing polyamide fiber with an amide density of 14.0 or less is suppressed, thereby making it possible to maintain tire performance.

[0139] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is thought to be a technology that can contribute to the achievement of goals such as "No. 12: Responsible Consumption and Production" and "No. 13: Take concrete action against climate change." [Explanation of symbols]

[0140] 100: Tire 10: Bead section 15: Gum Chafer 20: Sidewall 25: Side rubber 30: Tread section 35: Tread rubber 40:Bead core 50: Carcass layer 60A, 60B: belt layer, 70A: Belt reinforcement layer (cap layer) 70B: Belt reinforcement layer (layer) D R : Tire radial direction D W : Tire width direction

Claims

1. a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, at least one carcass layer extending in a toroidal shape across the pair of bead portions; At least one belt layer disposed radially outward of a crown portion of the carcass layer; At least one belt reinforcing layer is disposed radially outward of the belt layer, In a tire having a rubber portion, the carcass layer and the belt reinforcing layer contain reinforcing cords, a 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, The rubber portion of the tire contains recycled carbon black, A tire, characterized in that 1 mass % or more of the carbon black contained in all rubber portions of the tire is the recycled carbon black.

2. As the rubber portion, a tread rubber disposed on the outer side of the belt reinforcing layer in the tire radial direction of the tread portion; a side rubber disposed on the outer side of the carcass layer in the tire width direction of the sidewall portion; a gum chafer disposed at a contact portion of the bead portion with the rim, 2. The tire of claim 1, wherein at least one of the tread rubber, side rubber, and gum chafer contains the recycled carbon black.

3. 10. The tire of claim 1, wherein the recycled carbon black is obtained by pyrolysis of a vulcanized rubber product containing carbon black.

4. The tire according to claim 1 , wherein the recycled carbon black has an ash content of 20% by mass or less.

5. The tire according to claim 1 , 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.

6. 2. The tire of claim 1, wherein the polyamide fiber having an amide density of 14.0 or less is a polyamide 4,10 fiber.

Images