Rubber composition for metal bonding, and tires

Abstract

To provide a rubber composition for metal bonding having excellent hygrothermal adhesion, and a tire made from the rubber composition for metal bonding.SOLUTION: A rubber composition for metal bonding comprises a diene rubber of 100 pts.mass, the diene rubber comprising natural rubber of 80 pts.mass or more, a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxy groups at adjacent carbon atoms of 1-30 pts.mass, and sulfur of 4-10 pts.mass.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a rubber composition for metal adhesion and a tire.

Background Art

[0002] Since strong impacts and large loads are applied to tires, tires usually have a belt layer in which a belt made of steel cords is coated with a rubber composition for metal adhesion.

[0003] As a rubber composition for metal adhesion for coating such steel cords, for example, Patent Document 1 discloses, "0.1 to 10 parts by mass of an organic acid cobalt salt, a nitrogen adsorption specific surface area (N2SA) of 100 m 2 / g or less of carbon black 40 to 80 parts by mass, the following resin solution, 0.1 to 20 parts by mass as the mass of a novolac-type phenolic resin, and 0.1 to 20 parts by mass of a curing agent are blended, and a rubber composition for steel cord coating is characterized in that." (Claim 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Recently, the demand for durability of tires has been increasing. And since rubber deterioration tends to progress when exposed to a wet heat (high temperature and high humidity) environment, a rubber composition for metal adhesion that exhibits excellent adhesion to steel cords even when exposed to such an environment is required. Hereinafter, the adhesion after exposure to a wet heat environment is also referred to as "wet heat adhesion". In this context, when the present inventors examined the rubber composition for steel cord coating described in Patent Document 1, it became clear that further improvement in moist heat adhesion is desirable when considering future requirements.

[0006] Therefore, in view of the above circumstances, the present invention aims to provide a rubber composition for metal bonding that has excellent moist heat adhesion properties, and a tire manufactured using the above-mentioned rubber composition for metal bonding. [Means for solving the problem]

[0007] As a result of diligent research into the above-mentioned problems, the inventors of this invention discovered that the above-mentioned problems can be solved by incorporating a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups between adjacent carbon atoms, and thus arrived at the present invention. In other words, the inventors have found that the above problem can be solved by the following configuration.

[0008] (1) A rubber composition for metal bonding containing 100 parts by mass of a diene rubber containing 80 parts by mass or more of natural rubber, 1 to 30 parts by mass of a modified conjugated diene polymer which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, and 4 to 10 parts by mass of sulfur. (2) The metal bonding rubber composition according to (1) above, further containing 5 to 12 parts by mass of zinc oxide. (3) A tire manufactured using the metal bonding rubber composition described in (1) or (2) above. [Effects of the Invention]

[0009] As shown below, the present invention provides a rubber composition for metal bonding that exhibits excellent wet heat adhesion, and a tire manufactured using the above-mentioned rubber composition for metal bonding. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic partial cross-sectional view showing an example of an embodiment of the tire of the present invention. [Modes for carrying out the invention]

[0011] The following describes the rubber composition for metal bonding according to the present invention, and a tire manufactured using the above-described rubber composition for metal bonding. In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Furthermore, each component may be used alone or in combination of two or more. When two or more components are used in combination, the "content" of each component refers to the total content unless otherwise specified. Furthermore, the superior moist heat adhesion, low heat generation, and rigidity are also referred to as "the effects of the present invention being excellent."

[0012] [I] Rubber composition for metal bonding The rubber composition for metal bonding of the present invention (hereinafter also referred to as "the composition of the present invention") is This is a rubber composition for metal bonding, containing 100 parts by mass of a diene rubber containing 80 parts by mass or more of natural rubber, 1 to 30 parts by mass of a modified conjugated diene polymer which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, and 4 to 10 parts by mass of sulfur.

[0013] As described above, the modified conjugated diene polymer contained in the composition of the present invention has hydroxyl groups on adjacent carbon atoms. Therefore, it is believed that adjacent hydroxyl groups interact with each other, and that hydroxyl groups also interact with each other within the polymer chain. Furthermore, when the composition of the present invention is used for bonding metals such as steel cords, it is believed that the hydroxyl groups also interact with the metal. Therefore, when the composition of the present invention is used for metal bonding, it is believed that the modified conjugated diene polymer and the metal form an extremely strong and dense network, resulting in excellent moist heat adhesion.

[0014] The components contained in the composition of the present invention will be described below. [1] Diene rubber The composition of the present invention contains a diene rubber, including natural rubber. Note that the above diene rubber does not include the modified conjugated diene polymer described later.

[0015] [Natural rubber] The content of natural rubber is 80 parts by mass with respect to 100 parts by mass of the diene rubber. The content of natural rubber is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, based on 100 parts by mass of the diene rubber, for the reason that the effects of the present invention are more excellent. The upper limit is not particularly limited and is 100 parts by mass.

[0016] [Other diene rubbers] The above diene rubber may contain diene rubbers other than natural rubber. Specific examples of such diene rubbers include butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), and the like. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene butadiene rubber (SBR), styrene isoprene copolymer rubber, and the like.

[0017] [Molecular weight] The number average molecular weight (Mn) of the above diene rubber is not particularly limited, but is preferably 50,000 to 2,500,000, more preferably 100,000 to 1,500,000, and even more preferably 150,000 to 1,000,000, for the reason that the effects of the present invention are more excellent. The weight average molecular weight (Mw) of the above diene rubber is not particularly limited, but is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000, for the reason that the effects of the present invention are more excellent.

[0018] In this specification, Mn and Mw are standard polystyrene equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions. • Solvent: tetrahydrofuran • Detector: RI detector

[0019] [2] Modified conjugated diene polymers The composition of the present invention contains a modified conjugated diene polymer (hereinafter also simply referred to as "modified conjugated diene polymer") which is a conjugated diene polymer having hydroxyl groups between adjacent carbon atoms.

[0020] [Conjugated diene polymers] A conjugated diene polymer refers to a polymer obtained using a conjugated diene as a monomer. However, a conjugated diene polymer does not necessarily have to be obtained using a conjugated diene, as long as it has the same structure as a polymer obtained using a conjugated diene as a monomer. For example, natural rubber has the same structure as a polymer obtained using isoprene as a monomer, and therefore falls under the category of a conjugated diene polymer.

[0021] [Conjugated diene] The above-mentioned conjugated diene is not particularly limited, but it is preferably butadiene (especially 1,3-butadiene) or isoprene, for reasons that the effects of the present invention are superior. In other words, the above-mentioned conjugated diene is preferably a butadiene polymer or an isoprene polymer, for reasons that the effects of the present invention are superior.

[0022] [Specific examples] Specific examples of the above-mentioned conjugated diene polymers include polybutadiene (butadiene rubber) (BR), polyisoprene (isoprene rubber) (IR), natural rubber (NR), aromatic vinyl-conjugated diene copolymer, acrylonitrile-butadiene copolymer (nitrile rubber) (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the above-mentioned aromatic vinyl-conjugated diene copolymers include styrene-butadiene copolymer (styrene-butadiene rubber) (SBR) and styrene-isoprene copolymer (styrene-isoprene copolymer rubber).

[0023] [Preferred Embodiment] The above-mentioned conjugated diene polymer is preferably a butadiene polymer (especially polybutadiene), an isoprene polymer (especially polyisoprene, natural rubber), or an aromatic vinyl-conjugated diene copolymer (especially styrene-butadiene copolymer), and more preferably a butadiene polymer (especially polybutadiene), for reasons that the effects of the present invention are superior.

[0024] The conjugated diene content of the above-mentioned conjugated diene polymer is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, particularly preferably 70 mol% or more, and most preferably 90 mol% or more. The upper limit is not particularly limited, but is 100 mol%. The conjugated diene content refers to the proportion of units derived from conjugated dienes (hereinafter also referred to as "conjugated diene units") among all monomer units constituting the conjugated diene polymer.

[0025] [Hydroxyl group] As described above, modified conjugated diene polymers have hydroxyl groups between adjacent carbon atoms. Modified conjugated diene polymers are preferable in that they have hydroxyl groups between adjacent carbon atoms as units derived from the conjugated diene (conjugated diene units), for reasons that the effects of the present invention are superior. In particular, it is preferable that they have hydroxyl groups between adjacent carbon atoms as units represented by formula (A3) or formula (B3) described later.

[0026] [Degeneration rate] The modification rate of the modified conjugated diene polymer is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 0.1 to 99 mol%, more preferably 1.0 to 50 mol%, even more preferably 3.0 to 50 mol%, and particularly preferably 5.0 to 20 mol%. Here, the modification rate is the proportion of conjugated diene units in a modified conjugated diene polymer that have a hydroxyl group on an adjacent carbon atom (for example, the unit represented by formula (A3) or formula (B3) described later).

[0027] [Molecular weight] The number-average molecular weight (Mn) of the modified conjugated diene polymer is not particularly limited, but is preferably 5,000 to 5,000,000, more preferably 50,000 to 2,000,000, and even more preferably 100,000 to 1,000,000, for reasons that the effects of the present invention are superior.

[0028] The weight-average molecular weight (Mw) of the modified conjugated diene polymer is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 10,000 to 10,000,000, more preferably 100,000 to 4,000,000, and even more preferably 200,000 to 2,000,000.

[0029] The molecular weight distribution (PDI) of the modified conjugated diene polymer is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less, for reasons that the effects of the present invention are superior. The lower limit of the molecular weight distribution is not particularly limited, but is usually 1.0 or higher.

[0030] [Preferred embodiment] For reasons that the effects of the present invention are superior, the modified conjugated diene polymer is preferably a conjugated diene polymer having units represented by the following formulas (A1) to (A3), (B1) to (B3), or (C) (provided that it must have at least one of formulas (A3) and (B3)) (hereinafter also referred to as "specific modified conjugated diene polymer"). Here, the units represented by (A1) to (A3) and the units represented by (B1) to (B3) are all units derived from conjugated dienes (conjugated diene units). Furthermore, the unit represented by formula (A2) corresponds to the epoxidized form of formula (A1), and the unit represented by formula (A3) corresponds to the ring-opened form of formula (A2). Similarly, the unit represented by formula (B2) corresponds to the epoxidized form of formula (B1), and the unit represented by formula (B3) corresponds to the ring-opened form of formula (B2). Furthermore, the unit represented by formula (C) is derived from aromatic vinyl (e.g., styrene).

[0031] [ka]

[0032] In formulas (A1) to (A3), (B1) to (B3), and (C), R represents a hydrogen atom or an aliphatic hydrocarbon group. Multiple Rs may be the same or different. In formula (C), Ar represents an aromatic hydrocarbon group. The above aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the above aliphatic hydrocarbon group include linear or branched alkyl groups (especially those with 1 to 30 carbon atoms), linear or branched alkenyl groups (especially those with 2 to 30 carbon atoms), and linear or branched alkynyl groups (especially those with 2 to 30 carbon atoms). Examples of the above-mentioned aromatic hydrocarbon groups include aromatic hydrocarbon groups having 6 to 18 carbon atoms, such as phenyl groups, tolyl groups, xylyl groups, and naphthyl groups.

[0033] In equations (A1) to (A3), (B1) to (B3), and (C), a1 to a3, b1 to b3, and c represent the proportion (mol%) of each unit. For reasons that the effects of the present invention are superior, a1 is preferably 1 to 99.9 mol%, more preferably 50 to 99 mol%, even more preferably 70 to 97 mol%, and particularly preferably 80 to 95 mol%. For b1, the effects of the present invention are better, and the amount is preferably 1 to 99.9 mol%, more preferably 50 to 99 mol%, even more preferably 70 to 97 mol%, and particularly preferably 80 to 95 mol%. For reasons that the effects of the present invention are superior, a1+b1 is preferably 1 to 99.9 mol%, more preferably 50 to 99 mol%, even more preferably 70 to 97 mol%, and particularly preferably 80 to 95 mol%. For reasons that the effects of the present invention are superior, a2 is preferably 0 to 99 mol%, more preferably 0 to 50 mol%, even more preferably 0 to 30 mol%, and particularly preferably 0 to 10 mol%. For b2, it is preferably 0 to 99 mol%, more preferably 0 to 50 mol%, even more preferably 0 to 30 mol%, and particularly preferably 0 to 10 mol%, for reasons that the effects of the present invention are superior. For reasons that the effects of the present invention are superior, a1+b2 is preferably 0 to 99 mol%, more preferably 0 to 50 mol%, even more preferably 0 to 30 mol%, and particularly preferably 0 to 10 mol%. For reasons that the effects of the present invention are superior, a3 is preferably 0.1 to 99 mol%, more preferably 1.0 to 50 mol%, even more preferably 3.0 to 30 mol%, and still more preferably 5.0 to 20 mol%. For b3, the amount is preferably 0.1 to 99 mol%, more preferably 1.0 to 50 mol%, even more preferably 3.0 to 30 mol%, and even more preferably 5.0 to 20 mol%, for reasons that the effects of the present invention are superior. For reasons that the effects of the present invention are superior, the amount of a3+b3 is preferably 0.1 to 99 mol%, more preferably 1.0 to 50 mol%, even more preferably 3.0 to 30 mol%, and still more preferably 5.0 to 20 mol%. c is preferably 0 to 90 mol%, more preferably 0 to 50 mol%, even more preferably 0 to 30 mol%, and particularly preferably 0 to 25 mol%, for reasons that the effects of the present invention are superior.

[0034] [Manufacturing method] The method for producing modified conjugated diene rubber is not particularly limited, but it is preferable to use a method comprising the following steps (hereinafter also referred to as "the method of the present invention") for the reason that the effects of the present invention are superior in the resulting modified conjugated diene rubber. Hereinafter, the fact that the effects of the present invention are superior in the resulting modified conjugated diene rubber will also simply be referred to as "the effects of the present invention are superior." (1) Epoxy process A process to obtain an epoxidized conjugated diene polymer by reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bond of the conjugated diene polymer. (2) Ring-opening process A process to obtain a modified conjugated diene polymer, which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, by reacting the epoxidized conjugated diene polymer obtained in the epoxidation process with water, thereby opening the epoxy ring (oxirane ring) of the epoxidized conjugated diene polymer.

[0035] Below, one embodiment in which 1,4-cis polybutadiene (1,4-cis BR) is used as the conjugated diene polymer will be explained using its structural formula.

[0036] First, 1,4-cis polybutadiene (see below) is reacted with a peroxide.

[0037] [ka]

[0038] This process epoxidizes at least a portion of the carbon-carbon double bonds of 1,4-cis polybutadiene to obtain epoxidized 1,4-cis polybutadiene (see below) (epoxidation step).

[0039] [ka]

[0040] Next, the epoxidized 1,4-cis polybutadiene obtained in the epoxidation step is reacted with water. This opens at least a portion of the epoxy ring of the epoxidized 1,4-cis polybutadiene to obtain 1,4-cis polybutadiene (modified 1,4-cis polybutadiene) (see below) having hydroxyl groups on adjacent carbon atoms (ring-opening step).

[0041] [ka]

[0042] The following details each step.

[0043] [Epoxy treatment process] The epoxidation process involves reacting a conjugated diene polymer with a peroxide to epoxidize the carbon-carbon double bonds of the conjugated diene polymer, thereby obtaining an epoxidized conjugated diene polymer. Epoxy-conjugated diene polymers are polymers in which at least some of the carbon-carbon double bonds (C=C) of the units (conjugated diene units) derived from the conjugated diene in the polymer are epoxidized (formed into epoxy rings).

[0044] <Conjugated diene polymers> The definition, specific examples, and preferred embodiments of the conjugated diene polymer used in the epoxidation process are the same as those of the modified conjugated diene polymer described above. Furthermore, the preferred molecular weight of the conjugated diene polymer used in the epoxidation process is the same as that of the modified conjugated diene polymer described above.

[0045] <Peroxides> The peroxide used in the epoxidation process is not particularly limited.

[0046] (Specific example) Examples of the above-mentioned peroxides include inorganic peroxides and organic peroxides. Examples of the inorganic peroxides mentioned above include hydrogen peroxide; persulfate compounds such as persulfuric acid, sodium persulfate, and potassium persulfate. Examples of the above-mentioned organic peroxides include t-butyl hydroperoxide, m-chloroperbenzoic acid (mCPBA), performic acid, peracetic acid, and perpropionic acid.

[0047] (Preferred embodiment) The above-mentioned peroxide is preferably an organic peroxide, and more preferably m-chloroperbenzoic acid (mCPBA), for reasons that it provides superior effects of the present invention.

[0048] (Amount used) The amount of peroxide used is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 10 to 200% by mass, and more preferably 50 to 100% by mass, relative to the amount of conjugated diene polymer used.

[0049] <Procedure for the Epoxy Process> The procedure for the epoxidation process is not particularly limited, and examples include a method in which a conjugated diene polymer and a peroxide are mixed and stirred, and then the reaction product is recovered.

[0050] <Epoxy-conjugated diene polymers> The epoxidized conjugated diene polymer obtained in the epoxidation process is one in which at least some of the carbon-carbon double bonds (C=C) of the units (conjugated diene units) derived from the conjugated diene in the conjugated diene polymer have been epoxidized (formed into epoxy rings).

[0051] (Epoxylization rate) The epoxidation rate of the above epoxidized conjugated diene polymer is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 0.1 to 99 mol%, more preferably 1.0 to 50 mol%, even more preferably 3.0 to 30 mol%, and even more preferably 5.0 to 20 mol%. Here, the epoxidation rate is the percentage of carbon-carbon double bonds in the conjugated diene units (e.g., butadiene units) of the conjugated diene polymer used in the epoxy process that are epoxidized (formed into epoxy rings). For example, if there are 100 carbon-carbon double bonds in the conjugated diene polymer used in the epoxidation process, and 10 of them are epoxidized, the epoxidation rate of the epoxidized conjugated diene polymer is 10 mol%.

[0052] (molecular weight) The preferred molecular weight of the above-mentioned epoxidized conjugated diene polymer is the same as that of the modified conjugated diene polymer described above.

[0053] [Ring opening process] The ring-opening step is a step in which the epoxy-conjugated diene polymer obtained in the epoxidation step described above is reacted with water to open the epoxy ring of the epoxidated conjugated diene polymer, thereby obtaining a modified conjugated diene polymer which is a conjugated diene polymer having hydroxyl groups on adjacent carbon atoms. By opening the epoxy ring, hydroxyl groups are introduced to the two carbon atoms (adjacent carbon atoms) that made up the epoxy ring. In other words, the modified conjugated diene polymer obtained in the ring-opening step is one in which at least a portion of the epoxy ring in the epoxidized conjugated diene polymer has been opened, and hydroxyl groups have been introduced to the two carbon atoms (adjacent carbon atoms) that constituted the opened epoxy ring. In addition, a group other than a hydroxyl group (for example, an alkoxy group) may be introduced to some of the two carbon atoms (adjacent carbon atoms) that make up the opened epoxy ring.

[0054] In the ring-opening step, it is preferable to use a catalyst for activating the epoxy ring, as this provides superior effects compared to the present invention.

[0055] <Epoxy-conjugated diene polymers> The epoxidized conjugated diene polymer used in the ring-opening step is the epoxidized conjugated diene polymer obtained in the epoxidation step described above. The epoxidized conjugated diene polymer is as described above.

[0056] <Catalyst> As described above, in the ring-opening step, it is preferable to use a catalyst for activating the epoxy ring because the effects of the present invention are superior.

[0057] (Specific example) Specific examples of the catalysts mentioned above include protic acids (hydrochloric acid and sulfuric acid), Lewis acids (aluminum chloride, etc.), and the like. It is preferable to add a base such as a hydroxide along with the catalyst.

[0058] (Preferred embodiment) The catalyst is preferably hydrazinium, and more preferably hydrazinium sulfate, for reasons that it provides superior effects of the present invention.

[0059] (Amount used) The amount of catalyst used is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 100% by mass, and more preferably 10 to 50% by mass, relative to the amount of epoxidized conjugated diene polymer used.

[0060] <Ring Opening Procedure> The procedure for the ring-opening step is not particularly limited, and examples include a method in which an epoxidized conjugated diene polymer is mixed and stirred with water and a catalyst, and then the reaction product is recovered.

[0061] <Modified conjugated diene polymers> The modified conjugated diene polymer obtained in the ring-opening process is one in which at least a portion of the epoxy ring in the epoxidized conjugated diene polymer is opened, and hydroxyl groups are introduced to the two carbon atoms (adjacent carbon atoms) that constituted the opened epoxy ring.

[0062] (Ring opening rate) The ring-opening rate is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 60 mol% or more, particularly preferably 70 mol% or more, and most preferably 90 mol% or more. The upper limit of the ring-opening rate is not particularly limited, but is 100 mol%. Here, the ring-opening rate is the percentage of epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening process that were opened. For example, if there are 10 epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening process and all of them are opened, the ring-opening rate of the modified conjugated diene polymer is 100 mol%.

[0063] (Epoxy ring retention rate) The epoxy ring retention rate is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 90 mol% or less, more preferably 70 mol% or less, even more preferably 50 mol% or less, even more preferably 40 mol% or less, particularly preferably 30 mol% or less, and most preferably 10 mol% or less. The lower limit of the epoxy ring retention rate is not particularly limited and is 0%. Here, the epoxy ring retention rate is the percentage of epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step that did not open. For example, if there are 10 epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step and all of them open, the epoxy ring retention rate of the modified conjugated diene polymer is 0 mol%.

[0064] (Diol conversion rate) The diolation rate is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 1 mol% or more, more preferably 10 mol% or more, even more preferably 30 mol% or more, particularly preferably 60 mol% or more, and most preferably 70 mol% or more. The upper limit of the diolation rate is not particularly limited, but is 100 mol%. Here, the diolation rate is the percentage of the epoxidized conjugated diene polymer used in the ring-opening step in which a hydroxyl group was introduced to two carbon atoms (adjacent carbon atoms) that made up the opened epoxy ring. For example, if there are 10 epoxy rings in the epoxidized conjugated diene polymer used in the ring-opening step, and all of them are opened, and a hydroxyl group is introduced to the adjacent carbon atoms (a total of 12 carbon atoms) that made up 6 of those epoxy rings, then the diolation rate is 60%.

[0065] [Content] In the composition of the present invention, the content of the modified conjugated diene polymer is 1 to 30 parts by mass per 100 parts by mass of the diene rubber described above. In particular, it is preferably 2 to 25 parts by mass, and more preferably 5 to 20 parts by mass, for reasons that the effects of the present invention are superior.

[0066] [3] sulfur The composition of the present invention contains sulfur.

[0067] [Content] In the composition of the present invention, the sulfur content is 4 to 10 parts by mass per 100 parts by mass of the diene rubber described above.

[0068] [4] Optional component The composition of the present invention may optionally contain other components (optional components) as long as they do not impair its effects or purpose. Examples of the optional components mentioned above include carbon black, silica, fillers other than carbon black and silica, silane coupling agents, terpene resins (e.g., aromatically modified terpene resins), thermally expandable microcapsules, zinc oxide, stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents other than sulfur, and various other additives commonly used in rubber compositions.

[0069] [Carbon Black] The composition of the present invention preferably contains carbon black because it provides superior effects and other benefits. The carbon black mentioned above is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF can be used.

[0070] [Content] In the composition of the present invention, the carbon black content is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 1 to 100 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass, per 100 parts by mass of the diene rubber described above.

[0071] [Zinc oxide] The composition of the present invention preferably contains zinc oxide because it provides superior effects and other benefits.

[0072] [Content] In the composition of the present invention, the zinc oxide content is not particularly limited, but it is preferably 5 to 12 parts by mass per 100 parts by mass of the diene rubber described above, for reasons that the effects of the present invention are superior.

[0073] [5] Manufacturing method The method for producing the composition of the present invention is not particularly limited, and specific examples include, for example, a method of kneading each of the above-mentioned components using known methods and equipment (e.g., Banbury mixer, kneader, roll, etc.). If the composition of the present invention contains sulfur, a vulcanization accelerator, and a vulcanization retarder, it is preferable to first mix the components other than sulfur, a vulcanization accelerator, and a vulcanization retarder at a high temperature (preferably 130 to 190°C), cool them, and then mix in the sulfur, vulcanization accelerator, and vulcanization retarder. Furthermore, the compositions of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0074] [6]Applications The composition of the present invention is suitably used for coating steel cords (especially for tires).

[0075] [II] Tires The tire of the present invention is a tire manufactured using the composition of the present invention described above. In particular, it is preferable that the tire is manufactured using the composition of the present invention described above as the coating for the steel cord. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, and other gases. Figure 1 shows a schematic partial cross-sectional view of a tire representing an example of an embodiment of the tire of the present invention, but the tire of the present invention is not limited to the embodiment shown in Figure 1.

[0076] In Figure 1, reference numeral 1 represents the bead portion, reference numeral 2 represents the sidewall portion, and reference numeral 3 represents the tire tread portion. Furthermore, a carcass layer 4 with embedded fiber cords is installed between the pair of left and right bead sections 1, and the ends of this carcass layer 4 are folded back and wrapped around the bead core 5 and bead filler 6 from the inside to the outside of the tire. Furthermore, in the tire tread portion 3, a belt layer 7 is arranged around the entire circumference of the tire on the outside of the carcass layer 4. Here, the belt layer 7 is a belt made of steel cords covered with the composition of the present invention described above. Furthermore, a rim cushion 8 is positioned in the bead portion 1 where it contacts the rim.

[0077] The tire of the present invention can be manufactured, for example, by conventionally known methods. In addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used as the gas to fill the tire. [Examples]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0079] [Production of Modified Conjugated Diene Polymers] The modified conjugated diene polymer was prepared as follows. The prepared modified conjugated diene polymer is a polybutadiene having hydroxyl groups between adjacent carbon atoms, and therefore corresponds to the modified conjugated diene polymer described above.

[0080] [Epoxy treatment process] To a solution of polybutadiene (1,4-cis BR, Mn=199,000, Mw=490,000, PDI=2.5, 10.2g) in methylene chloride (Kanto Chemical Co., Ltd., 150mL), a solution of m-chloroperbenzoic acid (mCPBA) (Kanto Chemical Co., Ltd., 25% water content, 7.0g) in methylene chloride (100mL) was added dropwise at room temperature, and the mixture was stirred at room temperature for 24 hours. The resulting solution was added dropwise to methanol (Kanto Chemical Co., Ltd., 1.5L), and the solid component was separated. The solid component was dissolved in tetrahydrofuran (THF) (Kanto Chemical Co., Ltd., 200mL), and reprecipitation purification was performed by adding the dissolved solid to methanol dropwise, yielding a white solid (10.4g). Regarding the obtained white solid 1 ¹H-NMR (CDCl3) measurement revealed that 2.9 ppm of epoxy ring-derived material was present. 1 A hydrogen (H) signal was observed, indicating that the carbon-carbon double bond of polybutadiene was epoxidized, resulting in epoxidized polybutadiene with an epoxidation rate of 16 mol% (Mn=205,000, Mw=495,000, PDI=2.4).

[0081] [Ring opening process] The epoxidized polybutadiene (10.3 g) obtained in the epoxidation process described above was dissolved in toluene (Kanto Chemical Co., Ltd., 150 mL). A solution of hydrazinium sulfate (Kanto Chemical Co., Ltd., 5.2 g) in water (80 mL) was added to the resulting solution, and the mixture was stirred under reflux conditions for 48 hours. Subsequently, the insoluble components of the resulting solution were removed, and water (100 mL) was added to these insoluble components. The mixture was stirred at room temperature to remove the inorganic components. This process was repeated twice. The insoluble components were dried to obtain a pale yellow solid component (10.3 g) that was insoluble in THF. Regarding the obtained pale yellow solid component 13 1C-NMR (CPMAS) measurements revealed that the epoxy ring originated at around 60 ppm. 13 The C signal disappears, and the 73 ppm signal originates from an adjacent carbon atom with a hydroxyl group. 13A 13C signal was observed (no 13C signal originating from a single carbon atom with a hydroxyl group around 70 ppm (a non-adjacent carbon atom) was observed), indicating that all epoxy rings of the epoxidized polybutadiene opened, resulting in a modified polybutadiene (ring-opening rate: 100 mol%, diolation rate: 50 mol% or more, modification rate: 8-16 mol%) (Mn=205,000, Mw=495,000, PDI=2.4) having hydroxyl groups on adjacent carbon atoms. The obtained modified polybutadiene corresponds to the specific modified conjugated diene polymer described above. Here, R in formulas (A1) and (A3) is all hydrogen, a1 is 84 mol%, and a3 is 8-16 mol%.

[0082] [Preparation of rubber compositions for metal bonding] The components shown in Tables 1 to 5 below were blended in the proportions (parts by mass) shown in the same tables. Specifically, first, the components shown in Tables 1 to 5 below were mixed for 5 minutes using a 1.7-liter sealed Banbury mixer, released at approximately 160°C, and cooled to room temperature to obtain a masterbatch. Furthermore, sulfur and a vulcanization accelerator were mixed into the obtained masterbatch using the same Banbury mixer to obtain a rubber composition for metal bonding.

[0083] [Adhesion test] The wire pull-out force and rubber adhesion amount of the obtained metal bonding rubber compositions were measured in accordance with ASTM-D-2. The measurements were performed after leaving the test samples in a humid heat environment (temperature: 70°C, humidity: 96%RH) for two weeks. The results are shown in Tables 1 to 5. The results (wire pull-out force after aging, rubber adhesion amount after aging) are expressed as follows: Table 1 uses an index with Comparative Example 1-1 set to 100; Table 2 uses an index with Comparative Example 2-1 set to 100; Table 3 uses an index with Comparative Example 3-1 set to 100; Table 4 uses an index with Comparative Example 4-1 set to 100; and Table 5 uses an index with Comparative Example 5-1 set to 100. A higher index indicates better humid heat adhesion.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] [Table 4]

[0088] [Table 5]

[0089] The details of each component in Tables 1-5 are as follows. • NR: Natural rubber (RSS#3) • Carbon Black: Carbon black (manufactured by Tokai Carbon Co., Ltd., Seast 300) • Zinc oxide: Manufactured by Seido Chemical Industry Co., Ltd. (3 types of zinc oxide) • Cobalt stearate: Cobalt stearate (manufactured by DIC Corporation) • Anti-aging agent: Amine-based anti-aging agent (Santoflex 6PPD, manufactured by Flexis) • Vulcanization accelerator: Noxellar DZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: AkzoNobel Crystex HS OT 20 • Modified conjugated diene polymer: The modified conjugated diene polymer prepared as described above. • Comparatively modified conjugated diene polymer: Liquid polybutadiene with hydroxyl groups at one end (R-45HT, weight-average molecular weight: 2800, manufactured by Idemitsu Kosan Co., Ltd.) • Comparative conjugated diene polymer: Polybutadiene (Nipol BR1220, weight-average molecular weight: 500,000, manufactured by Nippon Zeon Corporation)

[0090] As can be seen from Tables 1 to 5, Examples 1-1 to 1-3, 2-1 to 2-3, 3-1 to 3-3, 4-1 to 4-3, and 5-1 to 5-3, which contain modified conjugated diene polymers, showed excellent wet heat adhesion. In particular, Examples 1-2 to 1-3, 2-2 to 2-3, 3-2 to 3-3, 4-2 to 4-3, and 5-2 to 5-3, in which the content of modified conjugated diene rubber was 5 parts by mass or more per 100 parts by mass of diene rubber, showed even better wet heat adhesion (especially the amount of rubber adhered after aging). Among these, Examples 1-3, 2-3, 3-3, 4-3, and 5-3, in which the content of modified conjugated diene rubber was 15 parts by mass or more per 100 parts by mass of diene rubber, showed even better wet heat adhesion (especially the amount of rubber adhered after aging).

[0091] On the other hand, Comparative Examples 1-1 to 1-3, Comparative Example 2-1, Comparative Example 3-1, Comparative Examples 4-1 to 4-2, and Comparative Example 5-1, which did not contain a modified conjugated diene polymer, exhibited insufficient moist heat adhesion. [Explanation of Symbols]

[0092] 1. Bead section 2 Sidewall section 3. Tire tread section 4. Carcass layer 5 Bead core 6. Bead Filler 7 Belt layer 8 Rim Cushion

Claims

1. 100 parts by mass of diene rubber containing 80 parts by mass or more of natural rubber, A modified conjugated diene polymer having hydroxyl groups on adjacent carbon atoms, a weight-average molecular weight of 200,000 or more, and being in solid form, comprising 1 to 30 parts by mass of a modified conjugated diene polymer, A rubber composition for metal bonding containing 4 to 10 parts by mass of sulfur. However, the diene rubber does not include conjugated diene polymers having hydroxyl groups on adjacent carbon atoms.

2. Furthermore, the metal adhesive rubber composition according to claim 1 contains 5 to 12 parts by mass of zinc oxide.

3. A tire manufactured using the metal-bonding rubber composition described in claim 1 or 2.

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