Hybrid cord, rubber-fiber composite, and tire

Abstract

The present invention addresses the problem of providing an organic fiber cord capable of reducing environmental load while maintaining physical properties at high temperatures. The solution to this problem is a hybrid cord comprising at least two types of polyamide fibers, the hybrid cord being characterized in that at least one type of polyamide fiber among the polyamide fibers contains a biomass-derived component, and the average amide density of the hybrid cord is 10.5 or more.

Description

Technical Field

[0001] The present disclosure relates to hybrid cords, rubber-fiber composites, and tires. Background Art

[0002] Conventionally, a carcass including reinforcing cords is arranged inside the tire to improve the strength and rigidity of the tire, and a belt portion including reinforcing cords is arranged on the radially outer side of the carcass. In addition, a belt reinforcement layer (also called a "cap layer") including reinforcing cords may be arranged on the radially outer side of the belt portion to reinforce the belt portion. In these tire components, organic fiber cords such as polyamide (nylon) fiber cords and polyester fiber cords are generally used as reinforcing cords for the carcass and belt reinforcement layers.

[0003] On the other hand, in recent years, it is required to reduce the use of fossil resources such as oil and coal to reduce the environmental load. Therefore, research has been conducted to replace these organic fiber cords derived from fossil resources with cords derived from biomass (biological resource sources). In this replacement, it is crucial to keep the tire properties at a sufficient level. For example, PTL 1 discloses a pneumatic tire provided with a reinforcing member (rubber-fiber composite), the reinforcing member including a cord coated with rubber, the cord including a polyester fiber made at least partially from a component derived from biomass as a raw material. It is understood that the tire is able to suppress the reduction of tire properties while reducing the environmental load.

[0004] Citation List

[0005] Patent Literature

[0006] PTL 1: WO 2019 / 021747A1 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] The above-mentioned PTL 1 belongs to a technology of replacing polyester fiber cords used in tires with alternative materials. However, in addition to polyester fiber cords, various organic fiber cords are also applied to tires according to their purposes. Among such organic fiber cords, polyamide fiber cords, particularly polyamide 6,6 (PA66) fiber cords are widely used. However, it is challenging to synthesize polyamide 6,6 (PA66) used as a cord raw material from biomass.

[0009] In order to solve this problem, the present inventors have studied polyamide fiber cords using polyamide at least partially derived from biomass as a substitute for polyamide 6,6. However, these polyamide fiber cords exhibit low physical properties (particularly elastic modulus and tenacity) at high temperatures. When such polyamide fiber cords are applied to tires, tire properties are reduced.

[0010] In addition, organic fiber cords are also used in other rubber products such as conveyor belts and hoses, which also require a reduction in environmental load.

[0011] Therefore, the present disclosure aims to provide an organic fiber cord capable of reducing environmental load while maintaining physical properties at high temperatures, and a rubber-fiber composite including such an organic fiber cord.

[0012] Furthermore, the present disclosure is directed to providing a tire which includes such an organic fiber cord and is capable of reducing environmental load while maintaining tire characteristics.

[0013] Solutions for solving problems

[0014] Main features of the organic fiber cord (hybrid cord), rubber-fiber composite, and tire of the present disclosure for solving the above-mentioned problems are as follows.

[0015] [1] A hybrid cord comprising at least two polyamide fibers,

[0016] wherein at least one of the polyamide fibers comprises a component derived from biomass, and

[0017] The hybrid cord has an average amide density of 10.5 or more.

[0018] [2] The hybrid cord according to [1], which is a cord formed by twisting together an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less.

[0019] [3] The hybrid cord according to [2],

[0020] wherein the volume ratio of the organic fiber A having an amide density of 10.0 or more is 50% or more, and

[0021] The volume ratio of the organic fiber B having an amide density of 13.0 or less is 50% or less.

[0022] [4] The hybrid cord according to [2] or [3], wherein the organic fiber B has an amide density of 8.0 or more.

[0023] [5] The hybrid cord according to any one of [2] to [4], wherein the organic fiber A is an aramid fiber.

[0024] [6] The hybrid cord according to any one of [2] to [5], wherein the organic fiber B is a polyamide 4,10 fiber.

[0025] [7] The hybrid cord according to any one of [1] to [6], which is a cord formed by twisting two aramid fibers and one polyamide 4,10 fiber together.

[0026] [8] A rubber-fiber composite comprising the hybrid cord according to any one of [1] to [7].

[0027] [9] A tire comprising the hybrid cord according to any one of [1] to [7].

[0028] Effects of the Invention

[0029] According to the present disclosure, it is possible to provide a hybrid cord and a rubber-fiber composite that can reduce environmental load while maintaining physical properties at high temperatures.

[0030] In addition, according to the present disclosure, it is possible to provide a tire capable of reducing environmental load while maintaining tire characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the attached picture:

[0032] Figure 1 is a cross-sectional view of one embodiment of a tire according to the present disclosure. DETAILED DESCRIPTION

[0033] The hybrid cord, the rubber-fiber composite, and the tire according to the present disclosure are exemplified and described in detail with reference to the embodiments thereof.

[0034] <Definition>

[0035] In this specification, the term "hybrid cord" refers to a cord including at least two kinds of fibers, and is also referred to as a "composite cord". Here, the expression "including at least two kinds of fibers" means including two or more kinds of fibers made of different materials. In addition, the fibers included in the cord are also referred to as "fiber bundles" or "filament bundles".

[0036] In the present specification, the "amide density" of polyamide is defined by the following formula (1).

[0037] Amide density = number of amide groups in polyamide / number of atoms in the polyamide backbone × 100 (1)

[0038] Here, the “number of amide groups in polyamide” and the “number of atoms in the main chain of polyamide” are calculated based on the “number of amide groups” and the “number of atoms in the main chain” in one repeating unit of polyamide.

[0039] 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.

[0040] In addition, in this specification, the "average amide density" of the hybrid cord is calculated using the following formula (2).

[0041] Average amide density = [(fineness of fiber A (dtex) × number of fibers A × amide density of fiber A) + (fineness of fiber B (dtex) × number of fibers B × amide density of fiber B) + ...] / (fineness of fiber A (dtex) × number of fibers A + fineness of fiber B (dtex) × number of fibers B + ...] (2)

[0042] Here, fiber A represents the first fiber and fiber B represents the second fiber. When the hybrid cord contains three or more fibers, the "..." part of the numerator is supplemented with "the fineness (dtex) of the fiber in question × the number of the fibers × the amide density of the fibers" and the "..." part of the denominator is supplemented with "the fineness (dtex) of the fiber in question × the number of the fibers".

[0043] As an example, in the case of a cord formed by twisting together two fibers A having a fineness of 1100 dtex and a amide density of 10.3 and one fiber B having a fineness of 940 dtex and a amide density of 12.5, the average amide density is calculated as follows:

[0044] Average amide density = [(1100×2×10.3)+(940×1×12.5)] / (1100×2+940)=10.96.

[0045] In other words, when the cord includes n types of fibers and the nth fiber is represented as "fiber n ", the average amide density can be calculated by the following formula (2').

[0046] Average amide density = Σ(fiber n Denier × Fiber n Amount × Fiber n amide density) / Σ(fiber n Denier × Fiber n Number of (2')

[0047] In addition, in the present specification, the term "biobased ratio" refers to the ratio of carbon derived from biomass, and is calculated using the following formula (3).

[0048] Bio-based ratio (%) = number of carbon atoms derived from biomass / total number of carbon atoms × 100 (3)

[0049] In this specification, the term "derived from biomass" means that the material in question is derived from biological resources, such as plant resources, animal resources and microbial resources, and is synonymous with "biogenic".

[0050] As described later, the hybrid cord of the present embodiment includes a polyamide fiber containing a component derived from biomass, but in addition to the component derived from biomass, the polyamide fiber may also include a component not derived from biomass. In addition, for those other than the polyamide fiber containing a component derived from biomass, the compounds described in this specification may be partially or entirely derived from fossil resources, biological resources such as plant resources (biomass-derived), or recycled resources such as used tires. Alternatively, they may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0051] <Hybrid cord>

[0052] The hybrid cord of the present embodiment comprises at least two polyamide fibers. In the hybrid cord of the present embodiment, at least one of the polyamide fibers contains a component derived from biomass, and the average amide density of the hybrid cord is 10.5 or more. It should be noted that the hybrid cord of the present embodiment comprises at least two polyamide fibers, but may also comprise other fibers (fiber bundles).

[0053] Since the hybrid cord of the present embodiment includes at least two kinds of polyamide fibers, and at least one of the polyamide fibers contains a component derived from biomass, environmental load can be reduced.

[0054] In addition, since the average amide density of the hybrid cord of the present embodiment is 10.5 or more, hydrogen bonds between amide groups are tightly formed, sufficient strength can be ensured and thermal properties can be improved. As a result, properties such as elastic modulus and strength are maintained even at high temperatures. In addition, since the average amide density of the hybrid cord of the present embodiment is 10.5 or more, physical properties equivalent to those of cords made of polyamide 6,6 (PA66) derived from petroleum fibers can be achieved.

[0055] Therefore, the hybrid cord of the present embodiment can reduce environmental load while maintaining physical properties at high temperatures, particularly elastic modulus and strength.

[0056] The hybrid cord of the present embodiment comprises at least two polyamide fibers (fiber bundles), and at least one of the polyamide fibers comprises a component derived from biomass. Here, the component derived from biomass refers to a component derived from biological resources such as plant resources, animal resources or microbial resources. Examples of polyamides comprising a component derived from biomass include polyamide 4 (PA4), polyamide 11 (PA11), polyamide 4,4 (PA44), polyamide 5,4 (PA54), polyamide 4,6 (PA46), polyamide 5,6 (PA56), polyamide 4,10 (PA410), polyamide 6 (PA6), polyamide 6,6 (PA66), polyamide 6,10 (PA610), polyamide 10,10 (PA1010), etc. It should be noted that the hybrid cord of the present embodiment comprises at least two polyamide fibers, but may also comprise other fibers (fiber bundles).

[0057] Polyamide 4 (PA4) is obtained by ring-opening polymerization of γ-butyrolactam, which is derived from glucose, glutamic acid, etc.

[0058] Polyamide 11 (PA11) is obtained by polymerization of aminoundecanoic acid. Aminoundecanoic acid is derived from plant resources, such as castor oil plants.

[0059] Polyamide 4,4 (PA44) is obtained by the polycondensation reaction of tetramethylene diamine (having four carbon atoms) and succinic acid (having four carbon atoms). Tetramethylene diamine is derived from plant resources such as sugar cane, while succinic acid is derived from plant resources such as sugar cane and corn.

[0060] Polyamide 5,4 (PA54) is obtained by the polycondensation reaction of pentamethylene diamine (having five carbon atoms) and succinic acid (having four carbon atoms). Pentamethylene diamine is derived from plant resources such as corn, while succinic acid is derived from plant resources such as sugar cane and corn.

[0061] Polyamide 4,6 (PA46) is obtained by the polycondensation of tetramethylene diamine (having four carbon atoms) and adipic acid (having six carbon atoms). Tetramethylene diamine is derived from plant resources such as sugar cane.

[0062] Polyamide 5,6 (PA56) is obtained by the polycondensation reaction of pentamethylene diamine (having five carbon atoms) and adipic acid (having six carbon atoms). Pentamethylene diamine is derived from plant resources such as corn.

[0063] Polyamide 4,10 (PA410) is obtained by the polycondensation reaction of tetramethylene diamine (having four carbon atoms) and sebacic acid (having ten carbon atoms). Tetramethylene diamine is derived from plant resources such as sugar cane, and sebacic acid is derived from plant resources such as castor beans.

[0064] Polyamide 6 (PA6) is obtained by ring-opening polymerization of ε-caprolactam (having six carbon atoms), which is derived from plant resources.

[0065] Polyamide 6,6 (PA66) is obtained by the polycondensation reaction of hexamethylenediamine (having six carbon atoms) and adipic acid (having six carbon atoms). Hexamethylenediamine and adipic acid are derived from plant resources.

[0066] Polyamide 6,10 (PA610) is obtained by the polycondensation reaction of hexamethylenediamine (having six carbon atoms) and sebacic acid (having ten carbon atoms). Sebacic acid is derived from plant resources such as castor beans.

[0067] Polyamide 10,10 (PA1010) is obtained by the polycondensation reaction of decamethylenediamine (having ten carbon atoms) and sebacic acid (having ten carbon atoms). Decamethylenediamine and sebacic acid are derived from plant resources such as castor beans.

[0068] For example, tetramethylenediamine is also known as "putrescine" and can be obtained by fermenting sugar cane to produce glutamate, biochemically converting the glutamate to ornithine, and then decarboxylating the resulting ornithine.

[0069] Additionally, sebacic acid can be obtained by mechanically pressing castor beans to extract castor oil, methanolyzing the castor oil to produce ricinoleic acid methyl ester, and then saponifying the ricinoleic acid methyl ester.

[0070] Among the polyamides containing a component derived from biomass, polyamides derived entirely from biomass (i.e., having a bio-based ratio of 100%) are preferred from the viewpoint of further reducing the environmental load. Specifically, polyamide 4 (PA4), polyamide 11 (PA11), polyamide 4,4 (PA44), polyamide 5,4 (PA54), polyamide 4,10 (PA410), and polyamide 10,10 (PA1010) are preferred.

[0071] The average amide density of the hybrid cord of the present embodiment is 10.5 or more. If the average amide density of the hybrid cord is less than 10.5, hydrogen bonding between amide groups will be insufficient, resulting in a decrease in physical properties such as elastic modulus and strength at high temperatures. From the perspective of further improving physical properties at high temperatures, an average amide density of 12.0 or more is preferred, and even more preferably 12.5 or more. In order to obtain ease, an average amide density of 20.0 or less is preferred.

[0072] The hybrid cord of the present embodiment is preferably a cord formed by twisting together an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less. Here, the organic fiber A and the organic fiber B are made of different materials from each other. The polyamide fiber containing a component derived from biomass can be an organic fiber A, an organic fiber B, or both. By combining an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less, a polyamide fiber having various amide densities containing a component derived from biomass can be used, thereby reducing the environmental load while maintaining the physical properties at high temperatures. In addition, the physical properties (thermal properties) at high temperatures sufficient for use as a tire cord can be ensured while increasing the bio-based ratio of the hybrid cord.

[0073] Here, as the amide density of the organic fiber (polyamide fiber) increases, hydrogen bonds between amide groups are formed more tightly. As a result, the melting point (Tm), glass transition temperature (Tg), moisture content, elastic modulus (E') tend to increase, while the thermal shrinkage tends to decrease. Therefore, organic fibers with a higher amide density tend to exhibit excellent physical properties (thermal characteristics) at high temperatures.

[0074] In the hybrid cord, preferably, the volume fraction of the organic fiber A having an amide density of 10.0 or more is 50% or more, and the volume fraction of the organic fiber B having an amide density of 13.0 or less is 50% or less. When the volume fraction of the organic fiber A having an amide density of 10.0 or more is 50% or more, the overall amide density (i.e., average amide density) of the cord improves, and the thermal characteristics of the hybrid cord improve.

[0075] The amide density of the organic fiber A is preferably 20.0 or less. The organic fiber A (polyamide fiber) having an amide density of 20.0 or less is easily available.

[0076] Furthermore, the amide density of the organic fiber B is preferably 8.0 or more. When the amide density of the organic fiber B is 8.0 or more, even if the polyamide fiber containing a component derived from biomass is the organic fiber B, the proportion of the organic fiber B in the hybrid cord can be increased, thereby improving the bio-based ratio of the entire cord and further reducing the environmental load. From the viewpoint of further increasing the proportion of the organic fiber B in the hybrid cord, the amide density of the organic fiber B is even more preferably 12.0 or more.

[0077] Examples of the organic fiber A (polyamide fiber) having an amide density of 10.0 or more include polyamide 4 (PA4) fiber, polyamide 4,4 (PA44) fiber, polyamide 5,4 (PA54) fiber, polyamide 4,6 (PA46) fiber, polyamide 5,6 (PA56) fiber, polyamide 6 (PA6) fiber, polyamide 6,6 (PA66) fiber, aramid fiber, polyamide 4,10 (PA410) fiber, polyamide 6,10 (PA610) fiber, and polyamide 9,T (PA9T) fiber.

[0078] Here, the organic fiber A is preferably aramid fiber. Aramid fiber fully compensates for the physical properties (thermal characteristics) at high temperatures of organic fiber B having an amide density of 13.0 or less. In addition, since aramid fibers are rigid and have excellent thermal characteristics, they can further improve the thermal characteristics of the hybrid cord.

[0079] On the other hand, examples of the organic fiber B (polyamide fiber) having an amide density of 13.0 or less include polyamide 4,10 (PA410) fiber, polyamide 6,10 (PA610) fiber, polyamide 9,T (PA9T) fiber, polyamide 10,10 (PA1010) fiber, polyamide 11 (PA11) fiber, and the like.

[0080] Here, the organic fiber B is preferably polyamide 4,10 fiber. Since polyamide 4,10 fiber can achieve a 100% bio-based ratio (i.e., a fiber having a 100% bio-based ratio can be used), the environmental load can be further reduced. In addition, polyamide 4,10 fiber has physical properties similar to those of polyamide 6,6 fiber except for thermal properties, and a hybrid cord containing polyamide 4,10 fiber exhibits sufficient performance as a tire cord.

[0081] The hybrid cord of the present embodiment is preferably a cord formed by twisting three fibers together. Compared with a cord formed by twisting two fibers together, a cord formed by twisting three fibers together can ensure sufficient rigidity as a reinforcing material for a tire, and can also achieve lightness compared with a cord formed by twisting four fibers together.

[0082] The hybrid cord of this embodiment is particularly preferably a cord formed by twisting two aramid fibers and one polyamide 4,10 fiber together. Since it is two kinds of aramid fibers, this hybrid cord is rigid and has excellent thermal characteristics, and the inclusion of polyamide 4,10 fibers that can achieve a 100% bio-based ratio has the effect of significantly reducing environmental load.

[0083] The hybrid cord of the present embodiment comprises at least two polyamide fibers, and can be obtained as a twisted cord by, for example, applying a primary twist to each polyamide fiber (raw yarn), and then combining a plurality of fibers and applying a final twist in the opposite direction. Here, the primary twist number is preferably in the range of 10 to 60 twists / 10cm, and the final twist number is preferably in the range of 10 to 60 twists / 10cm. If the primary twist number is less than 10 twists / 10cm, the twisted yarn cord may not have sufficient fatigue resistance. On the other hand, if it exceeds 60 twists / 10cm, the strength of the twisted cord may be reduced. In addition, if the final twist number is less than 10 twists / 10cm, the twisted yarn cord may not have sufficient fatigue resistance. On the other hand, if it exceeds 60 twists / 10cm, the strength of the twisted yarn cord may be reduced.

[0084] In the case of a cord (twisted yarn cord) formed by twisting together an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less, the number of initial twists of the organic fiber A having an amide density of 10.0 or more is preferably in the range of 10 to 60 twists / 10 cm, and the number of initial twists of the organic fiber B having an amide density of 13.0 or less is also preferably in the range of 10 to 60 twists / 10 cm. If the number of initial twists of the organic fiber A having an amide density of 10.0 or more is less than 10 twists / 10 cm, the twisted yarn cord may not have sufficient fatigue resistance. On the other hand, if it exceeds 60 twists / 10 cm, the strength of the twisted yarn cord may be reduced. If the number of initial twists of the organic fiber B having an amide density of 13.0 or less is less than 10 twists / 10 cm, the twisted yarn cord may not have sufficient fatigue resistance. On the other hand, if it exceeds 60 twists / 10 cm, the strength of the twisted yarn cord may be reduced.

[0085] The total fineness of the hybrid cord of the present embodiment is preferably in the range of 1000 to 6000 dtex. If the total fineness of the hybrid cord is less than 1000 dtex, sufficient strength as a tire fiber may not be achieved. On the other hand, if it exceeds 6000 dtex, the processing thickness increases, resulting in an increase in the weight of the tire.

[0086] In the case of a cord (twisted yarn cord) formed by twisting together an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less, it is preferred that the fineness of the organic fiber A having an amide density of 10.0 or more is in the range of 1000 to 4000 dtex, and the fineness of the organic fiber B having an amide density of 13.0 or less is in the range of 400 to 3000 dtex. If the fineness of the organic fiber A having an amide density of 10.0 or more is less than 1000 dtex, sufficient strength as a fiber for a tire may not be achieved. On the other hand, if it exceeds 4000 dtex, the processing thickness increases, resulting in an increase in the weight of the tire. If the fineness of the organic fiber B having an amide density of 13.0 or less is less than 400 dtex, sufficient strength as a fiber for a tire may not be achieved. On the other hand, if it exceeds 3000 dtex, the processing thickness increases, resulting in an increase in the weight of the tire.

[0087] The heat shrinkage of the hybrid cord of the present embodiment is preferably 4.0% or less. Here, the heat shrinkage is a value measured by heating at 177°C for 2 minutes according to ASTM D885 and ASTM D4974. When the heat shrinkage of the hybrid cord is 4.0% or less, the physical properties (especially elastic modulus and strength) at high temperatures can be fully maintained, and excellent uniformity can be achieved during high-speed driving.

[0088] The breaking strength of the hybrid cord of the present embodiment is preferably 6.0 cN / dtex or more. In addition, the breaking strength of the hybrid cord is preferably 200 N or more. Here, the breaking strength is measured at room temperature (23 ° C) according to ASTM D855M. This is because when the breaking strength of the hybrid cord is 6.0 cN / dtex or more, or 200 N or more, a sufficient reinforcement effect can be achieved.

[0089] The elongation at break (elongation at break) of the hybrid cord of the present embodiment is preferably 8.0% or more. Here, the elongation at break is measured at room temperature (23° C.) according to ASTM D855M. If the elongation at break of the hybrid cord is less than 8.0%, a sufficient reinforcement effect may not be achieved.

[0090] The water content in the hybrid cord of the present embodiment is preferably 3.0% or less. Here, the water content is measured according to JIS L 1013. If the water content in the hybrid cord exceeds 3.0%, physical properties may be degraded, and sufficient reinforcing effect may not be achieved.

[0091] As described above, since the hybrid cord of the present embodiment can reduce the environmental load while maintaining the physical properties at high temperatures, it is particularly suitable as a tire cord that requires excellent physical properties at high temperatures such as elastic modulus and strength. In addition, since the hybrid cord of the present embodiment has sufficient physical properties (thermal characteristics) at high temperatures, it is also suitable for uses other than tires such as conveyor belts and hoses.

[0092] <Adhesive Composition>

[0093] The hybrid cords (organic fiber cords) are preferably treated with an adhesive composition.

[0094] The adhesive composition may include, for example, a thermoplastic polymer (A) having at least one side group having a crosslinking functional group and substantially free of carbon-carbon double bonds having addition reactivity in its main chain structure, a heat-reactive waterborne polyurethane resin (B) and an epoxy compound (C), and optionally further includes rubber latex (D). By treating the hybrid cord (organic fiber cord) with such an adhesive composition, the adhesion of the hybrid cord (organic fiber cord) to the elastomer (coating rubber) at high temperatures can be improved.

[0095] Conventionally, adhesive treatment of organic fiber cords involves a so-called two-bath treatment in which epoxy or isocyanate is applied to the surface of the cord and then treated with a resin (hereinafter referred to as RFL resin) obtained by mixing resorcinol, formaldehyde and latex. However, with this method, the resin used in the first-stage bath may become very hard, increasing the strain input into the organic fiber cord, which may reduce the fatigue resistance of the cord. In addition, although such RFL resin can achieve sufficient adhesion between the cord and the elastomer at room temperature, the adhesive force may be significantly reduced at high temperatures of 130°C or above. In contrast, the use of a single-stage bath mixture (adhesive composition) comprising a thermoplastic polymer (A) having at least one side group having a crosslinking functional group and substantially free of addition-reactive carbon-carbon double bonds in its main chain structure, a heat-reactive aqueous polyurethane resin (B) and an epoxy compound (C) can ensure sufficient adhesion to the elastomer (coating rubber) even at high temperatures of 180°C or above without hardening the hybrid cord (organic fiber cord).

[0096] The main chain of the thermoplastic polymer (A) mainly has a linear structure, and for example, the main chain is preferably an ethylene addition polymer such as an acrylic polymer, a vinyl acetate polymer, a vinyl acetate-ethylene copolymer, etc.; a polyurethane high molecular polymer; etc. However, the thermoplastic polymer (A) is not limited to the above-mentioned ethylene addition polymer or polyurethane high molecular polymer as long as it can suppress the fluidity of the resin at high temperature and ensure the rupture tenacity of the resin by crosslinking the functional groups on the side groups.

[0097] Preferred examples of the functional group on the side group of the thermoplastic polymer (A) include oxazoline groups, bismaleimide groups, (blocked) isocyanate groups, aziridine groups, carbodiimide groups, hydrazine groups, epoxy groups and epithio groups.

[0098] The above-mentioned thermoplastic polymer (A), heat-reactive aqueous polyurethane resin (B), epoxy compound (C) and rubber latex (D) which can be used may be those disclosed in JP 2023-040157A or those disclosed in JP 2023-030762A.

[0099] In the adhesive treatment of the hybrid cord (organic fiber cord), it is preferred that a three-component mixture (adhesive composition) of a thermoplastic polymer (A), a heat-reactive waterborne polyurethane resin (B) and an epoxy compound (C) is used as the treatment liquid of the first-stage bath, and a conventional RFL resin liquid is used as the treatment liquid of the second-stage bath. In addition, in the above-mentioned adhesive treatment, a single-stage bath treatment may be performed using a mixture (adhesive composition) of a thermoplastic polymer (A), a heat-reactive waterborne polyurethane resin (B), an epoxy compound (C) and a rubber latex (D).

[0100] In the above-mentioned 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 water-based polyurethane 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 less than 20%.

[0101] At the same time, from the viewpoint of environmental protection, it is preferred to use an impregnation treatment liquid that does not contain resorcinol and formaldehyde as an adhesive composition for hybrid cords (organic fiber cords). Examples of such an impregnation treatment liquid include, for example, a composition containing a rubber latex (a) having an unsaturated diene and one or more compounds (b) selected from a compound having a skeleton structure composed of a polyether and an amine functional group, a compound having an acrylamide structure, a polypeptide, polylysine, and a carbodiimide. In addition, an example of such an impregnation treatment liquid is a composition that, in addition to the above-mentioned rubber latex (a) and compound (b), contains one or more selected from an aqueous compound (c) having a (thermally dissociable blocked) isocyanate group, a polyphenol (d), and a polyvalent metal salt (e).

[0102] In addition, as an immersion treatment liquid free of resorcinol and formaldehyde, a composition containing polyphenols (I) and aldehydes (II) may be used. In addition to polyphenols (I) and aldehydes (II), such a composition may further contain at least one of isocyanate compounds (III) and rubber latex (IV).

[0103] When the adhesive composition for treating (coating) the hybrid cord (organic fiber cord) with an adhesive contains the polyphenols (I) and the aldehydes (II), good adhesiveness can be achieved even when resorcinol is not used in consideration of environmental load.

[0104] [Polyphenols (I)]

[0105] When the adhesive composition contains polyphenols (I) as a resin component, the adhesiveness with the mixed cord (organic fiber cord) can be improved. Here, polyphenols (I) are generally water-soluble polyphenols, and there is no particular limitation as long as they are polyphenols other than resorcinol (resorcinol). In polyphenols (I), the number of aromatic rings or hydroxyl groups can be appropriately selected.

[0106] From the viewpoint of achieving further excellent adhesion, the polyphenol (I) preferably has 2 or more hydroxyl groups, more preferably 3 or more hydroxyl groups. When the polyphenol has 3 or more hydroxyl groups, the polyphenol or its condensate is dissolved in the adhesive composition (immersion treatment liquid) containing water. Since this allows the polyphenol to be uniformly distributed in the adhesive composition, further excellent adhesion can be achieved. In addition, if the polyphenol (I) is a polyphenol containing two or more aromatic rings, each aromatic ring may have two or three hydroxyl groups located at the ortho position, meta position or para position.

[0107] As the polyphenols (I), for example, the polyphenol compounds disclosed in WO 2022 / 130879A1 can be used. These polyphenols (I) can be used alone or in combination of two or more.

[0108] [Aldehydes(II)]

[0109] When the adhesive composition further comprises aldehydes (II) as a resin component in addition to the above-mentioned polyphenols (I), high adhesiveness can be achieved in combination with the above-mentioned polyphenols (I). Here, aldehydes (II) are not particularly limited and can be appropriately selected according to the desired performance. It should be noted that in this specification, aldehydes (II) encompass aldehyde derivatives derived from aldehydes.

[0110] Examples of aldehydes (II) include monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, chloral, butyraldehyde, hexanal, and allylaldehyde, etc.; aliphatic dialdehydes such as glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, and adipaldehyde, etc.; aldehydes containing aromatic rings; and dialdehyde starch. These aldehydes (II) can be used alone or in combination of two or more.

[0111] Aldehydes (II) are preferably aldehydes having an aromatic ring or containing aldehydes having an aromatic ring, because they provide further excellent adhesion. In addition, aldehydes (II) are preferably free of formaldehyde. Here, "free of formaldehyde" means, for example, that the formaldehyde content is less than 0.5% by mass of the total mass of the aldehydes.

[0112] In the adhesive composition, it is preferred that the polyphenols (I) and the aldehydes (II) are in a condensed state, and the mass ratio of the aldehydes having an aromatic ring to the polyphenols (the content of the aldehydes having an aromatic ring / the content of the polyphenols) is 0.1 or more and 3 or less. This is because the ratio optimizes the hardness and adhesiveness of the resin formed as a condensation product of the polyphenols and the aldehydes having an aromatic ring. From the same viewpoint, in the adhesive composition, the mass ratio of the polyphenols to the aldehydes having an aromatic ring (the content of the aldehydes having an aromatic ring / the content of the polyphenols) is more preferably 0.25 or more, and more preferably 2.5 or less.

[0113] The above-mentioned mass ratio refers to a mass ratio (solid content ratio) based on the mass of a dry substance.

[0114] In addition, the total content of polyphenols (I) and aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass. This is because further excellent adhesiveness is ensured without impairing workability, etc. From a similar 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.

[0115] The above-mentioned total content also means the total content (solid content ratio) based on the mass of the dry substance.

[0116] [Isocyanate compound (III)]

[0117] In addition to the above-mentioned polyphenols (I) and aldehydes (II), the adhesive composition preferably contains an isocyanate compound (III). In this case, the adhesiveness of the adhesive composition is further enhanced by the synergistic effect with the polyphenols (I) and aldehydes (II).

[0118] Here, the isocyanate compound (III) is a compound having an adhesion promoting effect on a resin material (e.g., a phenol / aldehyde resin obtained by condensation of a polyphenol (I) and an aldehyde (II)) as an adherend of the adhesive composition, and is a compound containing an isocyanate group as a polar functional group. The isocyanate compound (III) can be used alone or in combination of two or more.

[0119] The isocyanate compound (III) is not particularly limited, but from the viewpoint of further improving adhesion, it is preferred to contain an aromatic compound containing a (blocked) isocyanate group. Including an aromatic compound containing a (blocked) isocyanate group in the adhesive composition causes the aromatic compound containing a (blocked) isocyanate group to be distributed near the interface between the hybrid cord (organic fiber cord) and the adhesive composition, thereby providing an effect of further promoting adhesion. This effect allows the adhesive composition to achieve an even higher level of adhesion with the hybrid cord (organic fiber cord).

[0120] Examples of the (blocked) isocyanate group-containing aromatic compound that can be used include those described in JP 2023-040157 A and those described in JP 2023-030762 A.

[0121] The content of the isocyanate compound (III) in the adhesive composition is not particularly limited, but from the perspective of more reliably ensuring further excellent adhesion, the content is preferably 5 to 65% by mass. From a similar perspective, 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.

[0122] It should be noted that the above content is a content based on the mass of a dry substance (solid content ratio).

[0123] [Rubber latex (IV)]

[0124] The adhesive composition may substantially contain the rubber latex (IV) in addition to the above-mentioned polyphenols (I), aldehydes (II) and isocyanate compounds (III). This allows the adhesive composition to further enhance the adhesiveness to the rubber member.

[0125] Here, rubber latex (IV) is not particularly limited, and examples include synthetic rubbers such as polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR) or vinylpyridine-styrene-butadiene copolymer rubber (Vp) in addition to natural rubber (NR). These rubber latexes (IV) can be used alone or in combination of two or more.

[0126] When preparing an adhesive composition containing the rubber latex (IV), it is preferred to mix the rubber latex (IV) with the phenol (I) and the aldehyde (II) before adding the isocyanate compound (III).

[0127] 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.

[0128] The method for producing the adhesive composition is not particularly limited, but examples include, for example, a method of mixing and aging raw materials such as polyphenols (I), aldehydes (II), and rubber latex (IV), or a method of first mixing and aging polyphenols (I) and aldehydes (II), then adding rubber latex (IV), and further aging. In the case where the raw materials of the adhesive composition include an isocyanate compound (III), the method may include adding rubber latex (IV), aging the mixture, and then adding the isocyanate compound (III).

[0129] <Rubber-fiber composite>

[0130] The rubber-fiber composite of the present embodiment includes the hybrid cord of the present embodiment described above. Since the rubber-fiber composite of the present embodiment includes the hybrid cord of the present embodiment described above, the environmental load can be reduced. It should be noted that the fiber portion of the rubber-fiber composite corresponds to the hybrid cord described above.

[0131] In one example, the rubber-fiber composite includes a hybrid cord and a coating rubber covering the hybrid cord. Here, the coating rubber that can be used can be a rubber composition containing a rubber component such as natural rubber or synthetic rubber mixed with a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, and a vulcanization accelerator.

[0132] <Tires>

[0133] The tire of the present embodiment includes the hybrid cord of the present embodiment described above. Since the tire of the present embodiment includes the hybrid cord described above, it is possible to reduce environmental load while maintaining tire characteristics.

[0134] In the tire of the present embodiment, the region to which the hybrid cord is applied is preferably the carcass and the belt reinforcement layer (also referred to as "cap ply"), and particularly preferably the carcass.

[0135] Next, one embodiment of a tire according to the present disclosure will be described in detail with reference to the accompanying drawings.

[0136] Figure 1 is a cross-sectional view of one embodiment of a tire according to the present disclosure. Figure 1The tire 100 shown includes: a pair of bead portions 10, a pair of sidewall portions 20, a tread portion 30, a carcass 50 extending in a ring shape between a bead core 40 buried in the bead portion 10, a belt portion 60 composed of two belt layers 60A and 60B arranged on the tread portion 30 (more specifically, arranged on the radially outer side of the crown portion of the carcass 50), a belt reinforcement layer 70A (also called a "cap layer") arranged on the radially outer side of the belt portion 60 and covering the entire belt portion 60, and a pair of belt reinforcement layers (also called "cord layers") 70B arranged to cover only the two end portions of the belt reinforcement layer 70A.

[0137] exist Figure 1 In the tire 100 shown, the carcass 50 is composed of a single carcass ply, and includes a main body portion extending in a ring shape between a pair of bead cores 40 buried in the bead portion 10, and a turn-back portion wound around each bead core 40 from the inside in the tire width direction toward the outside and radially outward. However, the number and structure of the carcass ply of the carcass 50 in the tire of the present disclosure are not limited thereto. Here, the carcass ply constituting the carcass 50 is preferably formed by coating a plurality of reinforcing cords extending in a direction substantially perpendicular to the tire circumferential direction (for example, extending at an angle of 70° to 90°) with a coating rubber. In other words, the carcass 50 is preferably a radial carcass. As the reinforcing cord of the carcass 50, the above-mentioned hybrid cord is preferred, but if the above-mentioned hybrid cord is applied to other tire components, other organic fiber cords or steel cords may also be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords. As the coating rubber, a rubber composition including a rubber component such as natural rubber or synthetic rubber mixed with a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, and a vulcanization accelerator can be used.

[0138] in addition, Figure 1 The belt portion 60 of the tire 100 shown is composed of two belt layers 60A and 60B. Each belt layer 60A, 60B is generally formed by coating a reinforcing cord extending obliquely (e.g., inclined at an angle of 15° to 40°) relative to the tire equatorial plane with a coating rubber, preferably a steel cord coated with the coating rubber. In addition, the two belt layers 60A, 60B are stacked so that the reinforcing cords constituting the belt layers 60A, 60B cross across the tire equatorial plane, thereby forming the belt portion 60.

[0139] Although the belt portion 60 in the figure is constituted by two belt layers 60A and 60B, in the tire of the present disclosure, the number of belt layers constituting the belt portion may be three or more.

[0140] exist Figure 1In the tire 100 shown, the belt reinforcement layer 70A, 70B is formed by coating the reinforcing cords configured substantially parallel to the tire circumference (for example, at an angle of 0° to 5° relative to the tire circumference) with a coating rubber. The belt reinforcement layer 70A, 70B is formed by continuously spirally winding along the tire circumference with a narrow strip made of coating rubber reinforcing cords. In this case, the absence of a joint on the tire circumference improves tire uniformity, and the absence of a joint prevents strain concentration at the joint. As the reinforcing cords for the belt reinforcement layers 70A, 70B, the above-mentioned hybrid cords are preferred, but if the above-mentioned hybrid cords are applied to other tire components, other organic fiber cords can also be used. Examples of other organic fiber cords include polyethylene terephthalate cords and rayon cords. As the coating rubber, a rubber composition containing a rubber component such as natural rubber or synthetic rubber mixed with a filler such as carbon black, an antioxidant, a vulcanizing agent such as sulfur, and a vulcanization accelerator can be used.

[0141] It should be noted that although Figure 1 The tire 100 shown includes the belt reinforcement layers 70A and 70B, but a tire omitting the belt reinforcement layer 70A or the belt reinforcement layer 70B is also an embodiment of the tire according to the present disclosure. Figure 1 In the tire 100 shown, the belt reinforcing layers 70A and 70B are each composed of a single layer, but they may be composed of two or more layers.

[0142] <Conveyor Belt>

[0143] The conveyor belt of the present embodiment includes the hybrid cord of the present embodiment described above. Since the conveyor belt of the present embodiment includes the hybrid cord of the present embodiment described above, the environmental load can be reduced.

[0144] In one embodiment, the hybrid cords may be used as reinforcement material for conveyor belts.

[0145] <Hose>

[0146] The hose of the present embodiment includes the hybrid cord of the present embodiment described above. Since the hose of the present embodiment includes the hybrid cord of the present embodiment described above, it is possible to reduce environmental load.

[0147] In one embodiment, the hose includes an inner rubber layer (inner tube rubber) disposed radially inside, an outer rubber layer disposed radially outside, and a reinforcement layer disposed between the inner rubber layer and the outer rubber layer, wherein a hybrid cord is used in the reinforcement layer.

[0148] Example

[0149] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to the following examples.

[0150] <Manufacturing of cord>

[0151] (Comparative Example 1)

[0152] Two 1100 dtex aramid fibers (manufactured by Toray DuPont, amide density 12.5) and one 940 dtex polyamide 6,6 (PA66) fiber (amide density 14.3) were twisted together to produce a hybrid cord [cord structure: (1100×2,940) / 3]. Here, the initial twist number of the aramid fiber was 52 twists / 10 cm, the initial twist number of the PA66 fiber was 46 twists / 10 cm, and the final twist number of these fibers was 52 twists / 10 cm.

[0153] (Example 1)

[0154] Two 1100 dtex aramid fibers (manufactured by Toray DuPont, amide density 12.5) and one 940 dtex polyamide 4,10 (PA410) fiber (amide density 12.5) were twisted together to produce a hybrid cord [cord structure: (1100×2,940) / 3]. Here, the initial twist number of the aramid fiber was 52 twists / 10 cm, the initial twist number of the PA410 fiber was 46 twists / 10 cm, and the final twist number of these fibers was 52 twists / 10 cm.

[0155] (Comparative Example 2)

[0156] Two 1400 dtex polyamide 6,6 (PA66) fibers (amide density 14.3) were preliminarily twisted, then aligned and final twisted to produce a twisted cord [cord structure: 1400 / / 2 / 2]. Here, the preliminary twist number was 22 twists / 10 cm and the final twist number was 22 twists / 10 cm.

[0157] (Comparative Example 3)

[0158] Two 1400 dtex polyamide 4,10 (PA410) fibers (amide density 12.5) were preliminarily twisted, then doubling and final twisting to produce a twisted cord [cord structure: 1400 / / 2 / 2]. Here, the preliminary twist number was 22 twists / 10 cm, and the final twist number was 22 twists / 10 cm.

[0159] <Evaluation of Physical Properties of Cord>

[0160] The cord obtained as described above was subjected to a tensile test according to JIS L 1013 "Testing Methods for Chemical Fiber Filament Yarns", and the load (N)-elongation (%) curve of the cord was measured. In Table 1, the strength (N) and elongation (%) at break at 100° C. are expressed as indices with the corresponding results of Comparative Example 1 being 100. In addition, in Table 2, the strength (N) and elongation (%) at break at 100° C. are expressed as indices with the corresponding results of Comparative Example 2 being 100.

[0161] [Table 1]

[0162]

[0163] [Table 2]

[0164]

[0165] From the comparison between Comparative Example 2 and Comparative Example 3, it can be understood that the cord composed of only PA410 fibers has a greater decrease in breaking strength at high temperature than the cord composed of only PA66 fibers.

[0166] On the other hand, it can be understood from the comparison between Comparative Example 1 and Example 1 that the hybrid cord of PA410 fiber and aramid fiber has a breaking strength at high temperature comparable to that of the hybrid cord of PA66 fiber and aramid fiber.

[0167] Industrial Applicability

[0168] The hybrid cords and rubber-fiber composites of the present disclosure may be applied not only to tires but also to conveyor belts, hoses, and other products.

[0169] Description of Reference Numerals

[0170] 100: tire, 10: bead portion, 20: sidewall portion, 30: tread portion, 40: bead core, 50: carcass, 60: belt portion, 60A, 60B: belt layer, 70A: belt reinforcement layer (cap layer), 70B: belt reinforcement layer (cord layer)

Claims

1. A hybrid cord, characterized in that: comprising at least two polyamide fibers, wherein at least one of the polyamide fibers comprises a component derived from biomass, and The hybrid cord has an average amide density of 10.5 or more. 2 . The hybrid cord according to claim 1 , which is a cord formed by twisting together an organic fiber A having an amide density of 10.0 or more and an organic fiber B having an amide density of 13.0 or less.

3. The hybrid cord according to claim 2, wherein the volume ratio of the organic fiber A having an amide density of 10.0 or more is 50% or more, and The volume ratio of the organic fiber B having an amide density of 13.0 or less is 50% or less. 4 . The hybrid cord according to claim 2 , wherein the organic fiber B has an amide density of 8.0 or more. 5 . The hybrid cord according to claim 2 , wherein the organic fiber A is an aramid fiber.

6. The hybrid cord according to claim 2, wherein the organic fiber B is a polyamide 4,10 fiber.

7. The hybrid cord according to claim 1, which is a cord formed by twisting two aramid fibers and one polyamide 4,10 fiber together.

8. A rubber-fiber composite, characterized in that: Comprising the hybrid cord according to claim 1.

9. A tire, characterized in that: Comprising the hybrid cord according to claim 1.

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