PET fiber-rubber composite and tire

Abstract

The purpose of the present invention is to provide a PET fiber-rubber composite which achieves excellent strength and excellent low rolling resistance when applied to a tire without increasing the total fineness of cords or the thickness of a sheet. In order to solve the above-mentioned problem, a sheet-like PET fiber-rubber composite according to the present invention is obtained by coating a PET fiber cord with a coating rubber and is characterized by satisfying expression (1). (1): A / B / total fineness of the cord is greater than or equal to 0.3, A: cord strength (N) * fiber occupancy; fiber occupancy: cross-sectional area (mm2) of the PET fiber cord / (thickness (mm) of the composite * (diameter (mm) of the PET fiber cord + cord pitch (mm) of the PET fiber cord)). B: tan delta * rubber occupancy of the coating rubber; the rubber occupancy is 1-the fiber occupancy; the total denier of the cord is the total denier of the PET fibers constituting the cord.

Description

Technical Field

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

[0002] In recent years, cords made of polyethylene terephthalate (PET) fibers are mainly used as carcass materials for pneumatic tires. This is mainly because PET fibers show a more excellent balance in properties such as strength, modulus, and dimensional stability compared to conventional materials such as nylon fibers and rayon fibers, and PET fibers are low-cost materials.

[0003] However, conventional PET fibers are not satisfactory in terms of contribution to tire strength and lightweight. In view of recent environmental requirements related to motor vehicles, there is an increasing demand for cords having even higher strength and contributing more significantly to tire lightweighting. Therefore, it has become a pursuit to develop a PET fiber-rubber composite having higher strength and lower rolling resistance by replacing conventional PET fibers with PET fibers having even higher strength.

[0004] As a technique for increasing the strength of a PET fiber-rubber composite, for example, a technique for increasing the total fineness of a PET fiber cord is known. However, although increasing the total fineness of the fiber can increase the strength, it also results in thicker cords, forcing the PET fiber-rubber composite to be thicker. This in turn has a negative impact on the rolling resistance when the PET fiber-rubber composite is applied to a tire.

[0005] As a technology for improving rolling resistance when a PET fiber-rubber composite is applied to a tire, PTL 1 discloses a method of reducing hysteresis loss during running by forming a cross-sectional shape of a PET fiber cord closer to a perfect circle.

[0006] According to this technology, the rolling resistance when the composite is applied to a tire can be reduced while maintaining durability (hereinafter referred to as "excellent in low rolling resistance characteristics").

[0007] However, although the technology in PTL 1 achieves a certain effect in maintaining durability and reducing rolling resistance, it is desired to balance both strength and low rolling resistance characteristics at an even higher level.

[0008] Prior art literature

[0009] Patent Literature

[0010] PTL 1: JP 2011-251582 A Summary of the invention

[0011] (Problem to be solved by the invention)

[0012] To this end, an object of the present invention is to provide a PET fiber-rubber composite excellent in strength and low rolling resistance characteristics when the PET fiber-rubber composite is applied to a tire without causing an increase in the total fineness of a cord or the thickness of a sheet.

[0013] Furthermore, another object of the present invention is to provide a tire excellent in both strength and low rolling resistance characteristics.

[0014] (Solutions used to solve problems)

[0015] The main features of the present disclosure for solving the above problems are as follows:

[0016] The PET fiber-rubber composite of the present invention is a sheet-shaped PET fiber-rubber composite obtained by coating a PET fiber cord with a coating rubber.

[0017] The PET fiber-rubber composite satisfies the following formula (1):

[0018] (A / B) / Total cord fineness ≥ 0.3... (1)

[0019] Where A is defined as: cord strength (N) × fiber occupancy,

[0020] Fiber occupancy is defined as: cross-sectional area of ​​PET fiber cord (mm 2 ) / (thickness of the composite (mm)×(diameter of the PET fiber cord (mm)+cord spacing of the PET fiber cord (mm))), and

[0021] B is defined as: tanδ of the coated rubber × rubber occupancy,

[0022] The rubber share is defined as: 1-fiber share, and

[0023] The total fineness of the cord is defined as the sum of the finenesses of the PET fibers constituting the cord.

[0024] The above configuration can improve strength and low rolling resistance characteristics when the PET fiber-rubber composite is applied to a tire without causing an increase in the total fineness of the cord or the thickness of the sheet.

[0025] The tire of the present disclosure includes the PET fiber-rubber composite of the present disclosure described above.

[0026] The above configuration can achieve excellent strength and low rolling resistance characteristics.

[0027] (Effects of the Invention)

[0028] According to the present disclosure, a PET fiber-rubber composite having excellent strength and low rolling resistance when the PET fiber-rubber composite is applied to a tire without increasing the total fineness of the cord or the thickness of the sheet can be provided. In addition, according to the present disclosure, a tire having excellent durability and low rolling resistance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the accompanying drawings, Figure 1 is a diagram schematically showing a cross section of a PET fiber-rubber composite according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Hereinafter, the PET fiber-rubber composite and the tire of the present disclosure are described in detail based on the embodiments of the present disclosure.

[0031] Here, Figure 1 A cross section of a PET fiber-rubber composite according to an embodiment of the present disclosure is schematically shown.

[0032] <PET fiber-rubber composite>

[0033] like Figure 1 As shown, the PET fiber-rubber composite of the present disclosure is a sheet-shaped PET fiber-rubber composite 100 , which includes a PET fiber cord 10 coated with a coating rubber 20 .

[0034] The PET fiber-rubber composite of the present disclosure satisfies the following formula (1):

[0035] (A / B) / Total cord fineness ≥ 0.3... (1)

[0036] Here, A in the above formula (1) represents "cord strength (N) × fiber occupancy". By increasing the value of A, the strength of the PET fiber-rubber composite can be increased. In addition, the fiber occupancy in A is defined as "cross-sectional area of ​​PET fiber cord (mm 2 ) / (thickness of PET fiber-rubber composite (mm) × (diameter of PET fiber cord (mm) + cord spacing of PET fiber cord (mm)))". By increasing this value, the thickness of the coating rubber 20 can be reduced, which helps to reduce rolling resistance. In addition, B in the above formula (1) represents the "rubber occupancy". By setting B to a small value, the volume of rubber in the PET fiber-rubber composite is reduced, which helps to reduce weight and rolling resistance. In addition, the total cord fineness in the above formula (1) represents the sum of the fineness of the PET fiber 11. As this value increases, the thickness of the PET fiber 10 increases, which means higher strength but also increased mass.

[0037] In the present disclosure, by adjusting the ratio of A / B to the total fineness of the cord to 0.3 or more, the strength of the PET fiber-rubber composite can be increased even when a cord of low fineness is used (when the mass of the PET fiber cord is small).

[0038] From a similar viewpoint, the PET fiber-rubber composite of the present disclosure preferably satisfies the following formula (1)':

[0039] (A / B) / Total cord fineness ≥ 0.45...(1)'

[0040] Hereinafter, the PET fiber cord and the coating rubber constituting the PET fiber-rubber composite of the present disclosure will be described.

[0041] (PET fiber cord)

[0042] The PET fiber cord is a cord made of polyethylene terephthalate (PET) fiber and has an excellent balance of properties such as strength, modulus, dimensional stability, and manufacturing cost.

[0043] The PET fiber cords may be single-twisted cords or multi-twisted cords each consisting of two or more cords. The structure of the PET fiber cord may be appropriately selected according to the desired performance of the PET fiber cord.

[0044] The raw material of the PET fiber cord is not particularly limited, and for example, may be derived from a synthetic product, may be derived from biological resources such as plant-based resources, animal-based resources or microbial resources, may be obtained by mechanical recycling involving pulverizing, melting and re-spinning a resin product, or may be obtained by chemical recycling involving depolymerizing and repolymerizing a resin product.

[0045] Furthermore, the cord strength of the PET fiber cord is preferably 160 N or more, and more preferably 165 N or more, because the strength of the PET fiber-rubber composite can be further increased.

[0046] It should be noted that the cord strength of the PET fiber cord can be appropriately controlled by adjusting, for example, the total fineness of the cord, the number of twists, and the raw yarn strength, as well as other factors.

[0047] In addition, the raw yarn strength of the PET fiber constituting the PET fiber cord is preferably 7.8 cN / dtex or more, and more preferably 8.0 cN / dtex or more. Since this leads to an increase in the strength of the PET fiber cord, the strength of the PET fiber-rubber composite can be further increased.

[0048] It should be noted that the raw yarn strength of PET fibers can be increased by adjusting the molecular weight, crystallinity and crystal orientation of the PET resin, as well as other factors.

[0049] In addition, the total fineness of the PET fiber cord is preferably 1000 to 4800 dtex, and more preferably 2000 to 4000 dtex. When the total fineness of the PET fiber cord is 1000 dtex or more, the strength of the PET fiber-rubber composite can be further increased. On the other hand, when the total fineness of the PET fiber cord is 4800 dtex or less, the deterioration of the rolling resistance when the PET fiber-rubber composite is applied to a tire can be more reliably suppressed.

[0050] Here, the total fineness of the PET fiber cord refers to the sum of the finenesses of the PET fibers constituting the cord, and the total fineness can be controlled by adjusting the fineness and twist number of the PET fiber and other factors.

[0051] In addition, from the viewpoint of maintaining plunger energy, the diameter of the PET fiber cord is preferably 0.45 mm or more, and more preferably 0.50 mm or more. In addition, from the viewpoint of reducing rolling resistance, the diameter of the PET fiber cord is preferably 0.80 mm or less, and more preferably 0.70 mm or less.

[0052] In addition, the fineness of the PET fiber is preferably 550 to 2200 dtex, and more preferably 1100 to 1670 dtex. When the fineness of the PET fiber is 550 dtex or more, the strength of the PET fiber-rubber composite can be further increased. On the other hand, when the fineness of the PET fiber is 2200 dtex or less, the deterioration of the rolling resistance when the PET fiber-rubber composite is applied to a tire can be more reliably suppressed.

[0053] It should be noted that the denier of PET fibers can be controlled by adjusting the type of fiber and manufacturing conditions, among other factors.

[0054] In addition, the cord density of the PET fiber cord is preferably 120 / 10 cm or more, and more preferably 140 / 10 cm or more, because the strength of the PET fiber-rubber composite can be further increased.

[0055] It should be noted that the cord density of the PET fiber cord refers to the number of PET fiber cords per 10 cm in the cord arrangement direction in the PET fiber-rubber composite (in Figure 1 In the figure, the cord density corresponds to the number of PET fiber cords per 10 cm in the transverse direction).

[0056] Furthermore, the fiber occupancy rate in the PET fiber-rubber composite is not particularly limited as long as the above formula (1) is satisfied. However, from the viewpoint of balancing high strength at an even higher level with low rolling resistance characteristics when the composite is applied to a tire, the fiber occupancy rate is preferably 30% or more and 40% or less, and more preferably 35% or more and 40% or less.

[0057] It should be noted that the fiber occupancy ratio as described above is determined as: the cross-sectional area of ​​the PET fiber cord (mm 2 ) / (thickness of PET fiber-rubber composite (mm)×(diameter of PET fiber cord (mm)+cord spacing of PET fiber cord (mm))).

[0058] Here, if Figure 1 As shown, the diameter of the PET fiber cord refers to the diameter D of the cross section of the PET fiber cord 10 constituting the PET fiber-rubber composite 100 .

[0059] In addition, if Figure 1 As shown, the cross-sectional area of ​​the PET fiber cord refers to the area S of the cross section of the PET fiber cord 10 constituting the PET fiber-rubber composite 100 .

[0060] In addition, if Figure 1 As shown, the cord pitch of the PET fiber cord refers to the shortest distance P between adjacent cords 10 in a cross section of the PET fiber cords 10 constituting the PET fiber-rubber composite 100 .

[0061] (Adhesive composition)

[0062] Furthermore, it is preferred that the PET fiber cords be subjected to an adhesive treatment using an adhesive composition.

[0063] The adhesive composition may include, for example, a thermoplastic polymer (A) having at least one side group with a crosslinkable functional group and substantially free of addition-reactive carbon-carbon double bonds in its main chain structure, a heat-reactive water-based urethane resin (B) and an epoxy compound (C), and optionally further includes a rubber latex (D). By using such an adhesive composition to perform an adhesive treatment on a PET fiber cord, the adhesion between the PET fiber cord and the elastomer (coating rubber) under high temperature conditions can be improved.

[0064] Generally, the adhesive treatment of PET fiber cords involves a so-called two-bath method, in which an epoxy or isocyanate is applied to the surface of the cord, and then treated with a resin formed by mixing resorcinol, formaldehyde and latex (hereinafter referred to as RFL resin). However, with this method, the resin used in the first-stage bath becomes very hard, and the strain input into the PET fiber cord increases, which reduces 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 above 130°C. In contrast, using a single-stage bath mixture (adhesive composition) comprising a thermoplastic polymer (A) having at least one side group with a crosslinking functional group and 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), sufficient adhesion with the elastomer (coating rubber) can be ensured without hardening the PET fiber cord even at high temperatures above 180°C.

[0065] The main chain of the thermoplastic polymer (A) is mainly a linear structure, and for example, the main chain is preferably a vinyl addition polymer such as an acrylic polymer, a vinyl acetate polymer, and a vinyl acetate-ethylene copolymer; or a urethane high molecular polymer; etc. However, the thermoplastic polymer (A) is not limited to the above-mentioned vinyl addition polymer or urethane high molecular polymer as long as it can suppress the fluidity of the resin at high temperature by cross-linking of the functional group on the side group and ensure the fracture toughness of the resin.

[0066] Preferred examples of the functional group on the side group of the thermoplastic polymer (A) include an oxazoline group, a bismaleimide group, a (blocked) isocyanate group, an aziridine group, a carbodiimide group, a hydrazine group, an epoxy group and an epithio group.

[0067] The above-mentioned thermoplastic polymer (A), heat-reactive aqueous urethane 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.

[0068] In the adhesive treatment of the PET fiber cord, a three-component mixture (adhesive composition) of a thermoplastic polymer (A), a heat-reactive aqueous urethane resin (B) and an epoxy compound (C) is preferably 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 mixture (adhesive composition) of a thermoplastic polymer (A), a heat-reactive aqueous urethane resin (B), an epoxy compound (C) and a rubber latex (D) may also be used for a single-stage bath treatment.

[0069] 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 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 less than 20%.

[0070] Meanwhile, 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 PET fiber cords. Examples of such an impregnation treatment liquid are, for example, a composition containing a rubber latex (a) having an unsaturated diene and one or more compounds (b) selected from a compound containing 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 containing, in addition to the above-mentioned rubber latex (a) and compound (b), 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).

[0071] In addition, as an immersion treatment liquid not containing resorcinol and formaldehyde, a composition containing polyphenols (I) and aldehydes (II) can also be used. In addition to polyphenols (I) and aldehydes (II), this composition can further contain at least one of isocyanate compounds (III) and rubber latex (IV).

[0072] When the adhesive composition for treating (coating) the PET 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.

[0073] -Polyphenols (I)

[0074] When the adhesive composition contains polyphenols (I) as a resin component, the adhesiveness to the PET fiber cord can be enhanced. Here, polyphenols (I) are generally water-soluble polyphenols and are not particularly limited 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.

[0075] From the viewpoint of achieving further excellent adhesion, the polyphenols (I) preferably have two or more hydroxyl groups, and more preferably have three or more hydroxyl groups. When the polyphenols have three or more hydroxyl groups, the polyphenols or their condensates are dissolved in an adhesive composition (immersion treatment liquid) containing water. Since this allows the polyphenols to be uniformly distributed in the adhesive composition, further excellent adhesion can be achieved. In addition, if the polyphenols (I) are polyphenols containing two or more aromatic rings, each aromatic ring may have two or three hydroxyl groups located at the ortho, meta or para positions.

[0076] As the polyphenols (I), for example, the polyphenol compounds disclosed in WO 2022 / 130879 A1 can be used. These polyphenols (I) can be used alone or in combination of two or more thereof.

[0077] -aldehydes (II)

[0078] When the adhesive composition contains aldehydes (II) as a resin component in addition to the above-mentioned polyphenols (I), high adhesiveness can be achieved together with the above-mentioned polyphenols (I). Here, the aldehydes (II) are not particularly limited and can be appropriately selected according to the desired performance. It should be noted that in this specification, the aldehydes (II) encompass derivatives of aldehydes derived from aldehydes.

[0079] Examples of aldehydes (II) include, for example, monoaldehydes such as formaldehyde, acetaldehyde, butyraldehyde, acrolein, propionaldehyde, trichloroacetaldehyde, 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 thereof.

[0080] 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) preferably do not contain formaldehyde. Here, "does not contain formaldehyde" means, for example, that the formaldehyde content is less than 0.5% by mass of the total mass of the aldehydes.

[0081] 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 a similar 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.

[0082] The above-mentioned mass ratio refers to a mass ratio (solid content ratio) based on the mass of a dry substance.

[0083] In addition, the total content of the polyphenols (I) and the aldehydes (II) in the adhesive composition is preferably 3 to 30% by mass, since further excellent adhesiveness is ensured without impairing processability, etc. From a similar 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.

[0084] The above-mentioned total content also means the total content (solid content ratio) based on the mass of the dry substance.

[0085] -Isocyanate compound (III)

[0086] 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).

[0087] Here, the isocyanate compound (III) is a compound having an adhesion promoting effect with 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 thereof.

[0088] The isocyanate compound (III) is not particularly limited, but from the viewpoint of further improving adhesion, it is preferred to include 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 PET 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 to the PET fiber cord.

[0089] 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.

[0090] The content of the isocyanate compound (III) in the above adhesive composition is not particularly limited, but from the viewpoint of more reliably ensuring further excellent adhesion, the content is preferably 5 to 65% by mass. From a similar 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.

[0091] It should be noted that the above content is a content based on the mass of a dry substance (solid content ratio).

[0092] -Rubber latex (IV)

[0093] 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.

[0094] Here, the 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 thereof.

[0095] 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).

[0096] 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.

[0097] The production method of 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) followed by further aging. In the case where the raw materials of the adhesive composition contain an isocyanate compound (III), the method may include adding rubber latex (IV), aging the mixture, and then adding the isocyanate compound (III).

[0098] (Rubber coating)

[0099] The coating rubber refers to the rubber coating the PET fiber cord.

[0100] In the PET fiber-rubber composite of the present disclosure, there is no particular limitation on the coating rubber except that the rubber occupancy of the coating rubber is limited to satisfy the above formula (1). The composition and physical properties of the coating rubber can be appropriately selected according to the desired performance.

[0101] For example, from the viewpoint of further improving the low rolling resistance characteristics when the PET fiber-rubber composite is applied to a tire, it is preferred that the coating rubber includes a rubber component containing 60% by mass or more of natural rubber and 40% by mass or less of non-oil-extended styrene-butadiene rubber, and 30 to 60 parts by mass of a nitrogen adsorption specific surface area (N2SA) of 60 m2 per 100 parts by mass of the rubber component. 2 Such a coating rubber composition has excellent low heat build-up properties and can further reduce rolling resistance when the composite is applied to a tire.

[0102] There is no particular limitation on the rubber component of the coating rubber; however, as described above, the rubber component preferably contains 60% by mass or more of natural rubber and 40% by mass or less of non-oil-extended styrene-butadiene rubber. The inclusion of 60% by mass or more of natural rubber and 40% by mass or less of non-oil-extended styrene-butadiene rubber can contribute to low rolling resistance characteristics when the PET fiber-rubber composite is applied to a tire.

[0103] In addition to the above-mentioned natural rubber and non-oil-extended SBR, the rubber component may also include, for example, various synthetic rubbers or non-diene rubbers, such as polyisoprene rubber (IR), polybutadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), isoprene-isobutylene copolymer rubber (IIR), ethylene-propylene-diene copolymer rubber (EPDM), halogenated butyl rubber (HR) and chloroprene rubber (CR).

[0104] Furthermore, it is preferred that the coating rubber contains 30 to 60 parts by mass of a nitrogen adsorption specific surface area (N2SA) of 60 m 2 / g or less carbon black.

[0105] By including N2SA in the coating rubber, 60m 2 / g or less carbon black can maintain the high strength of the PET fiber-rubber composite while suppressing the deterioration of rolling resistance when the PET fiber-rubber composite is applied to a tire. From a similar point of view, it is more preferred that the N2SA of the carbon black is 45m 2 / g or less.

[0106] By adjusting the content of carbon black in the coating rubber to 30 parts by mass or more relative to 100 parts by mass of the rubber component, the strength of the PET fiber-rubber composite can be enhanced. By adjusting the content of carbon black to 60 parts by mass or less relative to 100 parts by mass of the rubber component, the deterioration of the rolling resistance when the PET fiber-rubber composite is applied to a tire can be suppressed. From a similar viewpoint, it is more preferable that the content of carbon black is 35 to 45 parts by mass relative to 100 parts by mass of the rubber component.

[0107] In addition to the above-mentioned rubber components and carbon black, the coating rubber may appropriately include additives commonly used in the rubber industry, such as fillers (e.g., silica), vulcanizing agents, vulcanization accelerators, bismaleimide compounds, softeners, stearic acid, zinc oxide, resins, waxes and oils, etc., as long as the effects of the present disclosure are not impaired.

[0108] In lamellar complexes, e.g. Figure 1 As shown, from the viewpoint of the durability of the tire during high-speed running, the cord pitch P of the PET fiber cord is preferably 0.15 mm or more, and more preferably 0.17 mm or more. In addition, from the viewpoint of maintaining the compression energy, the cord pitch P of the PET fiber cord is preferably 0.45 mm or less, and more preferably 0.40 mm or less.

[0109] (Flake complex)

[0110] like Figure 1 As shown, the PET fiber-rubber composite of the present disclosure is a sheet-shaped composite 100 .

[0111] Here, the sheet-like composite is not particularly limited as long as it satisfies the above formula (1). However, from the viewpoint of obtaining further excellent strength, its tensile strength is preferably greater than 23,000 N / dm. The strength (N / dm) of the composite is calculated as the tensile toughness of a single cord measured according to ASTM D885 multiplied by the number of cords per 10 cm width.

[0112] In addition, the thickness of the sheet-like composite body is preferably 1.8 mm or less, more preferably 1.5 mm or less, even more preferably 1.2 mm or less, and most preferably 1.0 mm or less.

[0113] When the thickness of the sheet-like composite is 1.8 mm or less, the PET fiber-rubber composite can be made lightweight, thereby more reliably suppressing deterioration in rolling resistance when the composite is applied to a tire.

[0114] It should be noted that Figure 1 As shown, the thickness of the sheet-like composite body refers to the thickness T of the composite body when cut along a plane perpendicular to the direction in which the cords in the composite body extend.

[0115] Regarding the sheet-like composite, from the viewpoint of reducing rolling resistance, it is preferred that tan δ of the coating rubber measured using a spectrometer (manufactured by Kamishima Seisakusho Co., Ltd.) under the conditions of temperature 24°C, strain 1% and frequency 52 Hz is 0.15 or less, more preferably 0.10 or less.

[0116] It should be noted that tan δ of the coating rubber described in this specification refers to a value of tan δ measured using a spectrometer (manufactured by Kamishima Seisakusho Co., Ltd.) under the conditions of a temperature of 24° C., a strain of 1%, and a frequency of 52 Hz.

[0117] As described above, the PET fiber-rubber composite of the present disclosure needs to satisfy the above formula (1), and preferably satisfies the above formula (1)'.

[0118] As the value of A (cord strength x fiber occupancy) in the above formula (1) increases, the strength of the PET fiber-rubber composite increases. As the value of B (tan δ of coating rubber x rubber occupancy) decreases, the rolling resistance decreases.

[0119] As described above, by adjusting the value of (A / B) / total cord fineness to 0.3 or more (adjusting so as to satisfy the above-mentioned formula (1)), it is possible to achieve high strength while reducing the number of cords and the rolling resistance.

[0120] The manufacturing method of the PET fiber-rubber composite of the present disclosure is not particularly limited and the PET fiber-rubber composite may be produced by a known method.

[0121] As a method of coating the PET fiber cord with the coating rubber, for example, the following method can be used.

[0122] A prescribed number of PET fiber cords are arranged in a reed curtain shape. An unvulcanized rubber sheet made of a rubber composition and having a certain thickness is placed on both the top and bottom of the PET fiber cords so that the PET fiber cords are sandwiched by the unvulcanized rubber sheet. Thereafter, vulcanization is performed at a temperature of about 160° C. for about 20 minutes to obtain a PET fiber-rubber composite.

[0123] <Tires>

[0124] The tire of the present disclosure includes the PET fiber-rubber composite of the present disclosure described above.

[0125] By using the PET fiber-rubber composite of the present disclosure as a member forming a tire, excellent durability and low rolling resistance characteristics can be achieved.

[0126] The application site of the PET fiber-rubber composite disclosed in the present invention is not particularly limited.

[0127] For example, the PET fiber-rubber composite can be suitably used for reinforcing members such as belt reinforcement layers, carcass plies, and chafers of various automotive radial tires, as well as other reinforcing members. Among these, the PET fiber-rubber composite is preferably used for the belt reinforcement layer or the carcass ply, and more preferably for the carcass ply.

[0128] The carcass ply is a member constituting the carcass, and the carcass may be constituted by a single carcass ply, or the carcass may be constituted by two or more carcass plies.

[0129] When the PET fiber-rubber composite is used as a carcass ply, the angle of the PET fiber cords may be substantially perpendicular to the tire circumferential direction, for example, the angle may be 80° to 90°.

[0130] Furthermore, the locking structure of the carcass ply of the bead portion is not limited to the structure in which the carcass ply is wound around the bead core and locked. A structure in which the edge of the carcass ply is sandwiched between two layers of bead cores is also used.

[0131] The tire of the present disclosure includes a belt layer. The belt layer may be composed of, for example, a first belt layer and a second belt layer stacked on the outer side of the first belt layer in the tire radial direction.

[0132] The first belt layer and the second belt layer are each composed of a plurality of cords embedded in the coating rubber. The thickness of the first belt layer and the thickness of the second belt layer in the central portion of the tire are each 1.00 mm or less. When the shortest distance between the cords in the second belt layer in the central portion of the tire and the cords in the first belt layer is defined as "a" and the shortest distance between the cords at the outermost end of the second belt layer and the cords in the first belt layer is defined as "b", the ratio b / a is preferably 1.8 or more and 4.0 or less.

[0133] This configuration ensures excellent durability at the belt edges while reducing rolling resistance.

[0134] As described above, by setting the thickness of each belt layer in the central portion of the tire to 1.00 mm or less, rolling resistance can be reduced while achieving lightweight. From a similar point of view, the thickness of the first belt layer in the central portion of the tire is preferably 0.90 mm or less. In addition, the thickness of the second belt layer in the central portion of the tire is preferably 0.90 mm or less. In order to achieve these thicknesses, the diameter of the cord embedded in the first belt layer and the second belt layer and the thickness of the coating rubber 5B and 6B are appropriately selected. It should be noted that the "central portion of the tire" refers to an area within one-quarter of the tire ground contact width from the tire equatorial plane in the tire width direction.

[0135] Furthermore, when the shortest distance between the cords in the second belt layer in the central portion of the tire and the cords in the first belt layer is defined as "center" and the shortest distance between the cords at the outermost end of the second belt layer and the cords in the first belt layer is defined as "second", the reason for adjusting the value of the ratio b / a to be greater than 1.8 and less than 4.0 is that by increasing the spacing between the cords in the first belt layer and the second belt layer at the belt edge, the strain that may cause the belt edge separation can be suppressed. In the tire of the present disclosure, adjusting the value of b / a to greater than 1.8 improves durability at the belt edge, in particular, durability against belt edge separation. In addition, adjusting the value of b / a to less than 4.0 ensures sufficiently low rolling resistance required for the tire. From a similar point of view, the value of b / a is preferably greater than 1.95, preferably greater than 2.00, and preferably less than 3.90.

[0136] It should be noted that "the shortest distance b between the outermost cord in the second belt layer and the cord in the first belt layer" substantially refers to the shortest distance between the outermost cord in the second belt layer and the tangent line of the plurality of cords arranged in the first belt layer.

[0137] In the tire of the present disclosure, when the PET fiber-rubber composite of the present disclosure is applied to the carcass ply, the reinforcing fiber cord of the belt reinforcement layer can be appropriately selected. For example, it is preferable to use an organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus of 6.0 mN / (dtex·%) or more at 7% elongation.

[0138] Organic fiber cords with a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus of 6.0 mN / (dtex·%) or more at 7% elongation exhibit high breaking strength, significant breaking elongation, and high elastic modulus at 7% elongation. By applying organic fiber cords having such properties to the belt reinforcement layer, it is possible to improve the handling stability of the tire while suppressing the reduction in the plunger durability of the tire.

[0139] Here, the breaking strength, breaking elongation and elastic modulus at 7% elongation of the organic fiber cord are values ​​measured at room temperature (23° C.) Various physical properties of the organic fiber cord can be measured in accordance with JIS L1013 “Testing methods for chemical fiber filament yarns”.

[0140] In addition, the tire of the present disclosure is preferably a pneumatic tire. The gas filled in the pneumatic tire is ordinary air or air with an adjusted oxygen partial pressure, and an inert gas such as nitrogen, argon, and helium may also be used.

[0141] The manufacturing method of the tire of the present disclosure is not particularly limited and the tire can be manufactured based on conventional methods. Generally, the rubber composition containing various components is processed into components without vulcanization, and is attached and formed by conventional methods in a tire forming machine to form a green tire. The green tire is then heated and pressurized in a vulcanizer to produce a tire.

[0142] For example, a rubber composition is obtained by kneading. The obtained rubber composition is used to apply rubber on a PET fiber cord. The unvulcanized belt, unvulcanized carcass and other unvulcanized components are stacked. The unvulcanized stack is vulcanized to obtain a tire.

[0143] Example

[0144] The present disclosure is described in more detail below with reference to Examples, but the present disclosure is not intended to be limited by these Examples in any way.

[0145] <Examples 1 to 2 and Comparative Examples 1 to 3>

[0146] The PET fiber-rubber composites for the carcass ply were prepared according to the conditions summarized in Table 1.

[0147] In the preparation of the PET fiber-rubber composite, the PET fiber cords and rubber compositions summarized in Table 1 were used to obtain samples of the PET fiber-rubber composite under the conditions listed in Table 1 (cord count, cord spacing, and composite coarseness).

[0148] Table 1 summarizes the formulation of the rubber composition for the coating rubber applied to each sample, the conditions of the PET fiber cord (various physical properties and arrangement conditions), and the conditions of the composite (fiber occupancy, thickness, coating rubber occupancy, and tanδ, A, B, and (A / B) / total cord fineness of the coating rubber).

[0149] <Evaluation>

[0150] Each sample of the PET fiber-rubber composite was incorporated into a pneumatic tire (tire size: 195 / 65R15) as a carcass ply produced using a rolling device under the following conditions, and the following evaluation was performed.

[0151] (1) Ply strength

[0152] The ply strength was calculated using the following formula based on the tenacity of each PET fiber cord and the cord count per unit measured according to ASTM D885. The results are summarized in Table 1. A higher value indicates a greater ply strength.

[0153] Formula: cord layer strength (N / dm) = toughness of each PET fiber cord (N) × cord count per unit (pieces / 10cm).

[0154] (2) Rolling resistance

[0155] The drum test was performed according to ISO 28580. The rolling resistance coefficient of the tires of Comparative Example 2 and Example 1 was calculated with respect to the measured rolling resistance coefficient of the tire of Comparative Example 3 being set to 100. The results are summarized in Table 1. For Example 2, the rolling resistance coefficient was predicted based on the test results of Comparative Example 2 and Example 1 and the tan δ and volume ratio of the rubber. The results are also summarized in Table 1. The smaller the index value, the lower the rolling resistance. It should be noted that the rolling resistance coefficient of the tire of Comparative Example 1 was not evaluated due to the low strength of the cord layer.

[0156] [Table 1]

[0157]

[0158] 1*SBR1: solution polymerized SBR, non-oil-filled 2*SBR2: emulsion polymerized SBR, oil-filled 27.3% by mass

[0159] 3*CB1: N2SA is 28m 2 / g and DBP of 89mL / 100g GPF grade carbon black 4*CB2: N2SA of 71m 2 / g and HAF grade carbon black with a DBP of 103mL / 100g

[0160] As can be understood from the results in Table 1, Comparative Examples 1 and 2 have low ply strengths. When the results of Comparative Example 3 are compared with those of Examples 1 and 2, the tires of Examples 1 and 2 exhibit lower rolling resistance despite the ply strength being at the same level. Therefore, it can be concluded that the ply strength and low rolling resistance characteristics of the samples of the Examples are balanced at a higher level than those of the Comparative Examples.

[0161] Industrial Applicability

[0162] According to the present disclosure, a PET fiber-rubber composite having excellent strength and low rolling resistance when the PET fiber-rubber composite is applied to a tire without increasing the total fineness of the cord or the thickness of the sheet can be provided. In addition, according to the present disclosure, a tire having excellent durability and low rolling resistance can be provided.

[0163] Description of Reference Numerals

[0164] 10PET fiber cord

[0165] 11PET fiber

[0166] 20 Rubber coating

[0167] 100PET fiber-rubber composite

Claims

1. A PET fiber-rubber composite, which is a sheet-shaped PET fiber-rubber composite obtained by coating a PET fiber cord with a coating rubber, The PET fiber-rubber composite satisfies the following formula (1): (A / B) / Total cord fineness ≥ 0.3 ... (1) Where A is defined as: cord strength (N) × fiber occupancy, Fiber occupancy is defined as: cross-sectional area of ​​PET fiber cord mm 2 / (thickness of the composite body, mm×(diameter of the PET fiber cord, mm+cord spacing of the PET fiber cord, mm)), and B is defined as: tanδ of the coated rubber × rubber occupancy, The rubber share is defined as: 1-fiber share, and The total fineness of the cord is defined as the sum of the finenesses of the PET fibers constituting the cord. 2 . The PET fiber-rubber composite according to claim 1 , wherein the cord strength of the PET fiber cord is 160 N or more.

3. The PET fiber-rubber composite according to claim 1 or 2, wherein the tensile strength of the sheet-like PET fiber-rubber composite is greater than 2300 N / cm. 4 . The PET fiber-rubber composite according to claim 1 , wherein the fineness of the PET fiber cord is 1100 / 2 to 2000 / 2 dtex. 5 . The PET fiber-rubber composite according to claim 1 , wherein the thickness of the sheet-shaped PET fiber-rubber composite is 1.2 mm or less.

6. The PET fiber-rubber composite according to claim 1 or 2, wherein the PET fiber-rubber composite satisfies the following formula (1)': (A / B) / total cord fineness ≥ 0.45...(1)'.

7. The PET fiber-rubber composite according to claim 1 or 2, wherein the coating rubber comprises: A rubber component comprising 60% by mass or more of natural rubber and 40% by mass or less of non-oil-extended styrene-butadiene rubber; and The nitrogen adsorption specific surface area (N2SA) of 30 to 60 parts by mass of the rubber component per 100 parts by mass is 60 m 2 / g or less carbon black.

8. A tire comprising the PET fiber-rubber composite according to claim 1 or 2.

9. The tire according to claim 8, wherein the PET fiber-rubber composite is used for a carcass ply.

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