Coating rubber composition for tire-reinforcing material, and tire
Patent Information
- Application Number
- JP2023563552
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Priority Date
- 2022-10-13
- Filing Date
- 2022-10-13
- Publication Date
- 2025-10-07
Smart Images
Figure 2023095480000001
Abstract
Description
Coating rubber composition for tire reinforcement, and tire
[0001] The present invention relates to a coating rubber composition for tire reinforcing materials, and a tire.
[0002] Conventionally, metal reinforcing materials such as steel cords have been used in rubber products such as tires and industrial belts. Various studies have been conducted on rubber compositions that have excellent adhesion durability to the metal reinforcing materials and rubber degradation resistance. For example, Patent Document 1 below discloses a rubber composition containing a rubber component, a sulfenamide vulcanization accelerator with a specific structure, a compound containing a di- or tri-substituted benzene ring having at least one hydroxyl group as a substituent, a methylene group donor, and a cobalt compound. The rubber composition is disclosed to have significantly less rubber burn, excellent degradation resistance, a high elastic modulus, and excellent adhesion to metal reinforcing materials such as steel cords.
[0003] JP 2010-37546 A
[0004] On the other hand, tires are subjected to various heat histories during manufacture and use, and are subject to thermal degradation throughout their product lifespan, so each component of the tire is required to have heat degradation resistance. In relation to this point, the inventors have conducted studies and found that rubber compositions used in conventional coating rubbers for tire reinforcing materials have insufficient heat degradation resistance, and that there is room for improvement, particularly in terms of crack resistance after heat degradation.
[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional art and to provide a coating rubber composition for tire reinforcing materials that has excellent crack resistance after heat degradation.A further object of the present invention is to provide a tire that uses such a coating rubber composition for tire reinforcing materials and has excellent durability.
[0006] The gist of the present invention, which solves the above-mentioned problems, is that the coating rubber composition for tire reinforcing material and the tire are as follows.
[0007] [1] A rubber composition comprising a rubber component, carbon black, a cobalt compound, and an amine-based antiaging agent, wherein the rubber component contains 60 to 100 mass% of an isoprene-skeleton rubber, and the amine-based antiaging agent is represented by the following general formula (1): [In the formula, R １ and R ２ and each independently represents a monovalent saturated hydrocarbon group, the content of the amine-based antiaging agent is 0.1 part by mass or more per 100 parts by mass of the rubber component, and the content (parts by mass) of the cobalt compound in terms of cobalt and the content (parts by mass) of the amine-based antiaging agent per 100 parts by mass of the rubber component satisfy the relationship of the following formula (1): (content of cobalt compound in terms of cobalt)×6<(content of amine-based antiaging agent) (1).
[0008] [2] The carbon black has a dibutyl phthalate (DBP) absorption of 50 to 100 cm ３ The coating rubber composition for tire reinforcement according to [1], wherein the coating rubber composition is 0.1g / 100g.
[0009] [3] R in the above general formula (1) １ and R ２ are each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.
[0010] [4] The coating rubber composition for tire reinforcing material according to any one of [1] to [3], wherein the rubber component contains 1 to 20 mass% of synthetic isoprene rubber as the isoprene skeleton rubber.
[0011] [5] The coating rubber composition for tire reinforcing material according to any one of [1] to [4], which does not contain silica or has a silica content of 1 part by mass or less per 100 parts by mass of the rubber component.
[0012] [6] The coating rubber composition for tire reinforcing material according to any one of [1] to [5], which does not contain a thermoplastic resin.
[0013] [7] The coating rubber composition for tire reinforcing material according to any one of [1] to [6], which contains a thermosetting resin.
[0014] [8] The coating rubber composition for tire reinforcing material according to any one of [1] to [7], wherein the content of the carbon black is 50 parts by mass or less per 100 parts by mass of the rubber component.
[0015] [9] The coating rubber composition for tire reinforcing material according to any one of [1] to [8], which does not contain 2,2'-methylenebis(4-methyl-6-tert-butylphenol).
[0016]
[10] The coating rubber composition for tire reinforcing material according to any one of [1] to [9], which does not contain N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine.
[0017]
[11] A tire comprising a reinforcing material coated with the coating rubber composition for tire reinforcing material according to any one of [1] to
[10] .
[0018]
[12] The tire according to
[11] , which is for heavy loads.
[0019] According to the present invention, it is possible to provide a coating rubber composition for tire reinforcing materials that has excellent crack resistance after heat degradation. Furthermore, according to the present invention, it is possible to provide a tire that uses such a coating rubber composition for tire reinforcing materials and has excellent durability.
[0020] 1 is a cross-sectional view of one embodiment of a tire of the present invention.
[0021] The coating rubber composition for tire reinforcing material and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.
[0022] <Coating Rubber Composition for Tire Reinforcement> The coating rubber composition for tire reinforcement of the present invention (hereinafter sometimes abbreviated as "coating rubber composition" or "rubber composition") contains a rubber component, carbon black, a cobalt compound, and an amine-based antiaging agent. In the coating rubber composition of the present invention, the rubber component contains 60 to 100% by mass of an isoprene-skeleton rubber, and the amine-based antiaging agent is a compound represented by the following general formula (1): [In the formula, R １ and R ２ are each independently a monovalent saturated hydrocarbon group], the amount of the amine-based antiaging agent is 0.1 part by mass or more per 100 parts by mass of the rubber component, and the amount (parts by mass) of the cobalt compound in terms of cobalt and the amount (parts by mass) of the amine-based antiaging agent per 100 parts by mass of the rubber component satisfy the relationship of the following formula (1): (amount of cobalt compound in terms of cobalt)×6<(amount of amine-based antiaging agent) (1).
[0023] The coating rubber composition of the present invention contains a cobalt compound that improves adhesion of the rubber composition to a reinforcing material, and an amine-based antioxidant represented by the general formula (1) that improves heat degradation resistance of the rubber composition. A high cobalt-equivalent content of the cobalt compound tends to reduce the heat degradation resistance of the rubber composition, particularly the elongation at break (EB) after heat degradation. However, in the coating rubber composition of the present invention, when the cobalt-equivalent content (parts by mass) of the cobalt compound and the amine-based antioxidant content (parts by mass) per 100 parts by mass of the rubber component satisfy the relationship of formula (1) above (i.e., when the amine-based antioxidant content is more than six times the cobalt-equivalent content of the cobalt compound), the improving effect of the amine-based antioxidant on the heat degradation resistance of the rubber composition becomes dominant over the reducing effect of the cobalt compound on the heat degradation resistance of the rubber composition, improving the heat degradation resistance of the rubber composition and suppressing a decrease in elongation at break (EB) after heat degradation. As a result, the coating rubber composition of the present invention has excellent crack resistance after heat degradation.
[0024] (Rubber Component) The coating rubber composition of the present invention contains a rubber component, which provides rubber elasticity to the composition. The rubber component contains an isoprene-skeleton rubber, and the content of the isoprene-skeleton rubber in the rubber component is 60 to 100% by mass, preferably 80 to 100% by mass. When the content of the isoprene-skeleton rubber in the rubber component is 60% by mass or more, the durability of the coating rubber composition is improved. Here, the isoprene-skeleton rubber is a rubber whose main skeleton is isoprene units, and specific examples include natural rubber (NR) and synthetic isoprene rubber (IR).
[0025] The rubber component preferably contains 1 to 40 mass % of synthetic isoprene rubber (IR) as the isoprene skeleton rubber, and more preferably 1 to 20 mass %. When the content of synthetic isoprene rubber in the rubber component is 1 mass % or more, workability in kneading the coating rubber composition is improved, and when it is 20 mass % or less, the content of isoprene skeleton rubbers other than the synthetic isoprene rubber in the rubber component increases, further improving the durability of the coating rubber composition.
[0026] The rubber component may contain a rubber other than the isoprene skeleton rubber, and such other rubber is preferably a diene rubber, for example, styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), etc. The total content of the isoprene skeleton rubber and the diene rubber other than the isoprene skeleton rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. The rubber component may be one type alone or a blend of two or more types.
[0027] (Carbon Black) The coating rubber composition of the present invention contains carbon black. The carbon black reinforces the rubber composition, improving the reinforcing properties of the rubber composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more.
[0028] From the viewpoint of crack resistance, the carbon black has a dibutyl phthalate (DBP) absorption of 50 to 100 cm ３ / 100g. DBP absorption is preferably 50 to 100 cm ３ By using carbon black with a relatively low structure, i.e., a DBP absorption of 50 cm3 / 100 g, it is possible to achieve both reinforcement and appropriate flexibility of the rubber composition, and to obtain better crack resistance. ３ When the amount of DBP absorption is 100 cm or more, the reinforcing property of the rubber composition is improved. ３When the carbon black has a DBP absorption of 90 cm / 100 g or less, the structure is not too high, so that the reinforcing property of the rubber composition is not too high, and flexibility is ensured, thereby obtaining better crack resistance. ３ / 100g or less is preferable, and 80cm ３ It is more preferable that the dibutyl phthalate (DBP) absorption is 50 to 100 cm ３ Any hard carbon produced by the oil furnace method can be used as the carbon black having a carbon black content of 100 g / 100 g. Among these, HAF grade carbon black is preferred from the viewpoint of achieving superior low loss and crack resistance. Here, the carbon black structure refers to the size of the structure (carbon black particle aggregate) formed as a result of spherical carbon black particles fusing and connecting with each other. The DBP absorption of the carbon black is the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black (cm ３ ) and can be measured in accordance with JIS K 6217-4 (2008).
[0029] The amount of carbon black is preferably 30 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component. When the amount of carbon black is 30 parts by mass or more per 100 parts by mass of the rubber component, the reinforcement and crack resistance of the rubber composition are improved, and when the amount of carbon black is 50 parts by mass or less per 100 parts by mass of the rubber component, the low loss property of the rubber composition is improved. Furthermore, from the viewpoint of the reinforcement and crack resistance of the rubber composition, the amount of carbon black is more preferably 40 parts by mass or more per 100 parts by mass of the rubber component, and from the viewpoint of the low loss property of the rubber composition, the amount is more preferably 48 parts by mass or less.
[0030] (Cobalt Compound) The coating rubber composition of the present invention contains a cobalt compound, which can improve the adhesion of the rubber composition to a reinforcing material.
[0031] From the viewpoint of adhesion to the reinforcing material, the cobalt compound is preferably an organic acid cobalt salt or a composite salt in which part of the organic acid in the organic acid cobalt salt is replaced with boric acid, etc. The organic acid cobalt salt may be saturated, unsaturated, linear, or branched, and examples thereof include cobalt stearate, cobalt versatate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt abietic acid, cobalt caprylate, cobalt 2-ethylhexanoate, cobalt octylate, cobalt pivalate, cobalt n-heptanoate, cobalt 2,2-dimethylpentanoate, cobalt 2-ethylpentanoate, cobalt 4,4-dimethylpentanoate, Examples of the composite salt include cobalt n-octanoate, cobalt 2,2-dimethylhexanoate, cobalt 2-ethylhexanoate, cobalt 4,4-dimethylhexanoate, cobalt 2,4,4-trimethylpentanoate, cobalt n-nonanoate, cobalt 2,2-dimethylheptanoate, cobalt 6,6-dimethylheptanoate, cobalt 3,5,5-trimethylhexanoate, cobalt n-decanoate, cobalt 2,2-dimethyloctanoate, cobalt 7,7-dimethyloctanoate, and cobalt n-undecanoate. Specific examples of the composite salt include Manobond (trademark: manufactured by OMG).
[0032] The content of the cobalt compound in terms of cobalt is preferably 0.1 parts by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the rubber component. When the content of the cobalt compound in terms of cobalt is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the adhesion of the rubber composition to a reinforcing material is improved. Furthermore, when the content of the cobalt compound in terms of cobalt is 3 parts by mass or less per 100 parts by mass of the rubber component, the deterioration of the heat degradation resistance (degradation durability) of the rubber composition can be suppressed.
[0033] (Amine-Based Antiaging Agent) The coating rubber composition of the present invention contains an amine-based antioxidant, which is represented by the above general formula (1). The amine-based antioxidant represented by general formula (1) contains a phenylenediamine moiety, similar to the general-purpose antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD), but differs from antioxidant 6PPD in that it does not contain a double bond outside of the phenylenediamine moiety. The amine-based antioxidant represented by general formula (1) improves the heat degradation resistance of the rubber composition, inhibits a decrease in elongation at break (EB) after heat degradation, and also has the effect of improving crack resistance after heat degradation.
[0034] In the above general formula (1), R １ and R ２ are each independently a monovalent saturated hydrocarbon group. １ and R ２ may be the same or different, but from the viewpoint of synthesis, they are preferably the same.
[0035] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass is large, which increases the anti-aging effect and further improves the heat degradation resistance and crack resistance after heat degradation of the rubber composition. １ and R ２ and each independently represent a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms, from the viewpoint of further improving the heat degradation resistance and crack resistance after heat degradation of the rubber composition.
[0036] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.
[0037] Specific examples of the amine-based antioxidant represented by the general formula (1) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N,N'-dicyclohexyl-p-phenylenediamine (antiaging agent CCPD). Of these, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) and N,N'-dicyclohexyl-p-phenylenediamine (CCPD) are preferred, with N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) being particularly preferred. The amine-based antioxidants may be used alone or in combination of two or more.
[0038] The content of the amine-based antiaging agent is preferably 0.1 parts by mass or more and 11 parts by mass or less per 100 parts by mass of the rubber component. If the content of the amine-based antiaging agent is less than 0.1 parts by mass per 100 parts by mass of the rubber component, the heat degradation resistance of the rubber composition cannot be sufficiently ensured, the decrease in elongation at break (EB) after heat degradation of the rubber composition cannot be sufficiently suppressed, and the decrease in crack resistance after heat degradation cannot be sufficiently suppressed. Furthermore, if the content of the amine-based antiaging agent is 11 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber properties other than heat degradation resistance and crack resistance after heat degradation (heat buildup, etc.) are reduced, making the rubber suitable for tire applications. The amount of the amine-based antiaging agent is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component from the viewpoint of crack resistance after thermal degradation, and is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component from the viewpoint of influence on other physical properties of the rubber.
[0039] The content (parts by mass) of the cobalt compound in terms of cobalt equivalent and the content (parts by mass) of the amine-based antioxidant per 100 parts by mass of the rubber component satisfy the relationship of the above formula (1). When the content (parts by mass) of the cobalt compound in terms of cobalt equivalent and the content (parts by mass) of the amine-based antioxidant per 100 parts by mass of the rubber component satisfy the relationship of the above formula (1) (i.e., when the content of the amine-based antioxidant is more than six times the content of the cobalt compound in terms of cobalt equivalent), the heat degradation resistance of the rubber composition is improved, and a decrease in elongation at break (EB) after heat degradation is suppressed, resulting in improved crack resistance after heat degradation. Furthermore, from the viewpoint of heat degradation resistance, the content of the amine-based antioxidant is preferably 10 times or more the content of the cobalt compound in terms of cobalt equivalent, and from the viewpoint of adhesion, it is preferably 30 times or less the content of the cobalt compound in terms of cobalt equivalent.
[0040] (Quinoline-Based Antiaging Agent) The coating rubber composition of the present invention may contain a quinoline-based antioxidant. The quinoline-based antioxidant is an antioxidant having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety). The quinoline-based antioxidant has the effect of improving the heat degradation resistance of the rubber composition and suppressing a decrease in elongation at break (EB) after heat degradation.
[0041] The quinoline-based antioxidant preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. The quinoline-based antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). Quinoline-based antioxidants containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline are highly effective in improving the heat degradation resistance of rubber compositions and also have the advantage of being less likely to discolor the rubber composition. The polymer of 2,2,4-trimethyl-1,2-dihydroquinoline includes a dimer, trimer, tetramer, etc. of 2,2,4-trimethyl-1,2-dihydroquinoline.
[0042] The content of the quinoline-based antioxidant is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. When the content of the quinoline-based antioxidant is 0.1 part by mass or more per 100 parts by mass of the rubber component, the heat degradation resistance of the rubber composition is improved, and the decrease in elongation at break (EB) of the rubber composition after heat degradation can be further suppressed. On the other hand, when the content of the quinoline-based antioxidant is 5 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber physical properties other than heat degradation resistance (heat buildup, etc.) can be suppressed, making the rubber more suitable for tire applications. From the viewpoint of heat degradation resistance, the content of the quinoline-based antioxidant is more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of effects on other rubber physical properties, the content is more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component.
[0043] (Silica) The coating rubber composition of the present invention preferably does not contain silica or contains 1 part by mass or less of silica per 100 parts by mass of the rubber component. Silica deteriorates workability in kneading the rubber composition, so when the coating rubber composition does not contain silica or contains 1 part by mass or less of silica per 100 parts by mass of the rubber component, workability in kneading the rubber composition can be improved.
[0044] (Thermoplastic Resin) The coating rubber composition of the present invention preferably does not contain a thermoplastic resin. A thermoplastic resin makes a rubber composition prone to creep and reduces durability against repeated inputs. Therefore, when the rubber composition does not contain a thermoplastic resin, the durability of the rubber composition can be improved. Here, the thermoplastic resin is preferably C ５ based resin, C ５ -C ９ based resin, C ９ resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, alkylphenol resins, and the like.
[0045] (Thermosetting Resin) The coating rubber composition of the present invention preferably contains a thermosetting resin. The thermosetting resin reduces the hysteresis loss of the rubber composition (improves low loss properties) and also improves crack resistance, thereby improving durability. Therefore, when the coating rubber composition contains a thermosetting resin, the low loss properties of the rubber composition can be improved, and the crack resistance (durability) can be further improved.
[0046] The thermosetting resin is preferably a phenolic resin. By including a phenolic resin (preferably together with a methylene donor, which will be described later) in the rubber composition, the rubber composition can maintain low loss properties while improving reinforcement and crack resistance. The phenolic resin is not particularly limited and can be appropriately selected depending on the required performance. Examples include those produced by condensing a phenol such as phenol, cresol, resorcinol, or tert-butylphenol, or a mixture thereof, with formaldehyde in the presence of an acid catalyst such as hydrochloric acid or oxalic acid. Modified phenolic resins can also be used, and can be modified with oils such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, or linolenic acid. The phenolic resins can be used singly or in combination.
[0047] The content of the thermosetting resin is preferably 2 to 10 parts by mass, and more preferably 3 to 7 parts by mass, per 100 parts by mass of the rubber component. By setting the content of the thermosetting resin to 2 parts by mass or more per 100 parts by mass of the rubber component, crack resistance can be further improved, and by setting the content to 10 parts by mass or less, deterioration of low loss properties can be suppressed.
[0048] (Methylene Donor) When the coating rubber composition of the present invention contains a phenolic resin as a thermosetting resin, it is preferable that the coating rubber composition further contains a methylene donor. By containing a melamine donor as a curing agent for the phenolic resin, the reinforcement of the rubber composition can be improved while maintaining the low loss property of the rubber composition.
[0049] The methylene donor is not particularly limited and can be appropriately selected depending on the required performance. Examples of the methylene donor include hexamethylenetetramine, hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, hexakis-(methoxymethyl)melamine, N,N',N"-trimethyl-N,N',N"-trimethylolmelamine, N,N',N"-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, N,N',N"-tributyl-N,N',N"-trimethylolmelamine, and paraformaldehyde. Among these methylene donors, hexamethylenetetramine, hexamethoxymethylmelamine, hexamethoxymethylolmelamine, and paraformaldehyde are preferred. These methylene donors may be used alone or in combination.
[0050] From the viewpoint of achieving both low loss properties and crack resistance at a higher level, the ratio of the content of the phenolic resin to the content of the methylene donor (phenolic resin content / methylene donor content) is preferably 0.6 to 7, and more preferably 1 to 5. When the ratio of the content of the phenolic resin to the content of the methylene donor is 0.6 or more, the crack resistance is further improved, and when the ratio is 7 or less, the low loss properties are further improved.
[0051] (Antioxidant o-MBp14) The coating rubber composition of the present invention preferably does not contain 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (antioxidant o-MBp14). When the antioxidant o-MBp14 is not contained, the rubber composition becomes more environmentally friendly.
[0052] (Antioxidant 6PPD) The coating rubber composition of the present invention preferably does not contain N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD). When the antioxidant 6PPD is not contained, the rubber composition becomes more environmentally friendly.
[0053] (Wax) The coating rubber composition of the present invention may contain a wax. When the rubber composition contains a wax, the ozone resistance of the rubber composition is improved. Examples of the wax include paraffin wax and microcrystalline wax. The wax content is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. When the wax content is 0.1 part by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition is further improved. Furthermore, when the wax content is 5 parts by mass or less per 100 parts by mass of the rubber component, the influence on rubber physical properties other than ozone resistance is small. From the viewpoint of ozone resistance, the wax content is more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of the influence on other rubber physical properties, the wax content is more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component.
[0054] (Sulfur) The coating rubber composition of the present invention preferably contains sulfur. The inclusion of sulfur in the rubber composition makes it possible to vulcanize the rubber composition, improving its durability (particularly, elongation at break (EB) and tensile strength (TB)). Various types of sulfur can be used, but ordinary sulfur (soluble sulfur (powdered sulfur), etc.) is preferred over insoluble sulfur, and oil treat sulfur is also preferred. Here, insoluble sulfur refers to sulfur insoluble in carbon disulfide (amorphous polymeric sulfur), while soluble sulfur (powdered sulfur) refers to sulfur soluble in carbon disulfide. The sulfur content is preferably in the range of 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component. When the sulfur content is 0.1 part by mass or more per 100 parts by mass of the rubber component, the durability of the vulcanized rubber can be ensured. When the sulfur content is 10 parts by mass or less per 100 parts by mass of the rubber component, sufficient rubber elasticity can be ensured.
[0055] (Others) In addition to the aforementioned rubber component, carbon black, cobalt compound, amine-based antioxidant, quinoline-based antioxidant, thermosetting resin, wax, sulfur, etc., the coating rubber composition of the present invention may contain various components commonly used in the rubber industry, such as fillers other than carbon black and silica (e.g., calcium carbonate), silane coupling agents, softeners, processing aids, surfactants, organic acids (e.g., stearic acid), zinc oxide (zinc white), vulcanization accelerators, vulcanizing agents other than sulfur, selected as needed within the scope of the present invention. Commercially available products can be suitably used as these compounding ingredients. The amine-based antioxidant represented by the general formula (1) may be supported on any carrier. For example, the amine-based antioxidant represented by the general formula (1) may be supported on an inorganic filler such as calcium carbonate. The amine-based antioxidant represented by the general formula (1) may also constitute a masterbatch together with the rubber component. The rubber component used in preparing the masterbatch is not particularly limited, and may be a diene rubber such as natural rubber (NR), or an ethylene-propylene-diene rubber (EPDM). The amine-based antioxidant represented by the general formula (1) may be a salt with an organic acid. The organic acid used in preparing the salt is not particularly limited, but examples thereof include stearic acid.
[0056] (Method for producing coating rubber composition) The method for producing the coating rubber composition is not particularly limited, but the coating rubber composition can be produced, for example, by blending the above-mentioned rubber component, carbon black, cobalt compound, and amine-based antioxidant with various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.
[0057] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.
[0058] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.
[0059] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.
[0060] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.
[0061] (Reinforcing Material) The reinforcing material to be coated with the coating rubber composition of the present invention is preferably made of metal, i.e., the reinforcing material is preferably a metal reinforcing material. A metal reinforcing material-rubber composite can be formed by coating the metal reinforcing material with the coating rubber composition (coating rubber). Examples of metal reinforcing materials include wire, plate, and chain-shaped reinforcing materials made of metals such as steel, iron, stainless steel, lead, aluminum, copper, brass, bronze, Monel metal alloys, nickel, and zinc. Steel cords are particularly preferred as the metal reinforcing material. The diameter of the steel cord is appropriately selected depending on the application. The metal reinforcing material may also have a plating layer on its surface. Examples of plating layers include a brass plating layer, a zinc plating layer, and a copper plating layer. Among these, a brass plating layer is preferred from the viewpoints of initial adhesion to the coating rubber composition (coating rubber) and heat-resistant adhesion (adhesion after thermal degradation). The copper to zinc ratio in the brass plating layer is preferably in the range of 60:40 to 70:30 by mass.
[0062] <Tire> The tire of the present invention is characterized by comprising a reinforcing material coated with the above-mentioned coating rubber composition for tire reinforcing material. Because the tire of the present invention comprises a reinforcing material coated with the above-mentioned coating rubber composition for tire reinforcing material, the tire has high crack resistance after heat degradation and excellent durability.
[0063] The tire of the present invention is preferably for heavy loads, i.e., is preferably a heavy load tire. Heavy load tires have thick portions, which tend to have high temperatures during vulcanization and during driving. Furthermore, they tend to be retreaded and used, resulting in long total driving distances. Therefore, high heat degradation resistance, particularly crack resistance after heat degradation, is required. In response to this, by applying the above-mentioned coating rubber composition, which has excellent crack resistance after heat degradation, high crack resistance after heat degradation can be maintained. Therefore, the tire of the present invention is particularly preferred as a heavy load tire, and can be suitably used as a heavy load tire for, for example, trucks, buses, off-the-road vehicles (e.g., construction vehicles, mining vehicles, etc.), small trucks (light trucks), industrial vehicles, aircraft, etc.
[0064] Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire shown in Fig. 1 comprises a pair of bead portions 1, a pair of sidewall portions 2, a tread portion 3, a carcass (preferably a radial carcass) 5 extending toroidally between bead cores 4 embedded in the bead portions 1, and a belt 6 consisting of two belt layers arranged in the tread portion 3 (more specifically, arranged radially outward of the crown portion of the carcass 5).
[0065] 1, the carcass 5 is made up of one carcass ply and includes a main body portion extending in a toroidal shape between a pair of bead cores 4 each embedded in the bead portion 1, and a turn-up portion wound up radially outward from the inner side to the outer side in the tire width direction around each bead core 4, but the number and structure of the plies of the carcass 5 in the tire of the present invention are not limited to this. Here, the carcass ply constituting the carcass 5 is made up of a plurality of reinforcing cords (reinforcing materials such as steel cords and organic fiber cords) covered with a coating rubber.
[0066] 1 is made up of two belt layers, each of which usually consists of a rubberized layer of reinforcing cords (reinforcing material) extending at an angle to the tire equatorial plane, preferably a rubberized layer of steel cords (reinforcing material), and further, the two belt layers are laminated such that the reinforcing cords constituting the belt layers cross each other with the tire equatorial plane in between to constitute the belt 6. Note that, although the belt 6 in FIG. 1 is made up of two belt layers, the number of belt layers constituting the belt 6 in the tire of the present invention may be one or more and is not limited to this.
[0067] Suitable tire components to which the reinforcing material coated with the coating rubber composition (reinforcing material-rubber composite) is applied include the belt 6, carcass 5, bead core 4, and the like.
[0068] Depending on the type of tire to be applied, the tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it. The tire of the present invention may be a pneumatic tire or a solid tire. Here, when the tire of the present invention is a pneumatic tire, the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.
[0069] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.
[0070] (Preparation of Rubber Compositions) Rubber compositions of Comparative Example 1 and Example 3 were produced according to the compounding recipes shown in Table 1. The elongation at break (EB) after thermal aging and the retention of elongation at break (EB) after thermal aging were evaluated for the resulting rubber compositions by the following methods. Rubber compositions of Comparative Examples 2 to 4, Examples 1 and 2, and Examples 4 to 6 were produced according to the compounding recipes shown in Table 1. The elongation at break (EB) after thermal aging and the retention of elongation at break (EB) after thermal aging were evaluated for the resulting rubber compositions by the following methods.
[0071] (1) Elongation at Break (EB) After Heat Aging The rubber compositions of Comparative Example 1 and Example 3 were vulcanized to prepare vulcanized rubber test specimens. The vulcanized rubber test specimens were then left at 100°C for 24 hours to allow for thermal aging. Tensile tests were conducted on the thermally aged test specimens in accordance with JIS K 6251 to measure the elongation at break (EB) after thermal aging. The rubber compositions of Comparative Examples 2 to 4, Examples 1 and 2, and Examples 4 to 6 were vulcanized to prepare vulcanized rubber test specimens. The vulcanized rubber test specimens were then left at 100°C for 24 hours to allow for thermal aging. Tensile tests were conducted on the thermally aged test specimens in accordance with JIS K 6251 to measure the elongation at break (EB) after thermal aging. The elongation at break (EB) after thermal aging of Comparative Example 1 was set at 100, and the results are expressed as an index. A higher index value indicates a higher elongation at break (EB) after thermal aging and higher resistance to thermal aging (durability after thermal aging).
[0072] (2) Retention of Elongation at Break (EB) after Thermal Aging The rubber compositions of Comparative Example 1 and Example 3 were vulcanized to prepare vulcanized rubber test pieces. Immediately after preparation, the test pieces were subjected to a tensile test in accordance with JIS K 6251 to measure the initial elongation at break (EB). Next, the vulcanized rubber test pieces were left at 100°C for 24 hours to undergo thermal aging. After thermal aging, the test pieces were subjected to a tensile test in accordance with JIS K 6251 to measure the elongation at break (EB) after thermal aging. The retention of elongation at break (EB) after thermal aging was calculated from the initial elongation at break (EB) and the elongation at break (EB) after thermal aging according to the following formula: Retention of elongation at break (EB) after thermal aging = elongation at break (EB) after thermal aging / initial elongation at break (EB) × 100 (%). Furthermore, the retention of elongation at break (EB) after thermal aging in Comparative Example 1 was set to 100, and the results were expressed as an index. The larger the index value, the higher the retention of elongation at break (EB) after thermal degradation, and the higher the resistance to thermal degradation (durability after thermal degradation).
[0073] (Production of Tire) The rubber composition in Table 1 is used as the coating rubber for the belt, and the steel cord is used as the reinforcing material for the belt to produce a tire of size 225 / 50R17 having the structure shown in Fig. 1. The durability of the obtained tire is evaluated by the following method.
[0074] (3) Tire durability (belt edge separation length) Four identical tires were mounted on an actual vehicle and driven for 10,000 km, after which the tires were removed and cut to measure the circumferential length of the portion where separation occurred at the belt end [belt edge separation length (BES length)], and the result was expressed as an index, with the belt edge separation length of Comparative Example 1 set at 100. The smaller the index value, the shorter the belt edge separation length and the higher the durability.
[0075]
[0076] *1 NR: Natural rubber *2 Carbon black: Asahi Carbon Co., Ltd., product name "Asahi #70L", DBP absorption capacity = 75 cm ３ / 100g *3 Silica: Tosoh Silica Corporation, trade name "Nipsil AQ" *4 Zinc oxide: Hakusui Tech Co., Ltd., trade name "Zinc oxide type 2" *5 Thermoplastic resin: C ５ -C ９ Resin, manufactured by Tonen Chemical Co., Ltd., trade name "T-REZ RD104" * 6 Alkylphenol formaldehyde resin: Manufactured by SUMITOMO BAKELITE EUROPE, trade name "DUREZ 19900" * 7 Thermosetting phenolic resin: Manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilite Resin PR-50235" * 8 Antiaging agent o-MBp14: Bisphenol-based antiaging agent, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac NS-6" * 9 Cobalt compound: Organic acid cobalt, manufactured by OMG, trade name "Manobond C", cobalt content = 22.0 mass%, the content in cobalt equivalent is shown in the table * 10 Antiaging agent TMDQ: Quinoline-based antioxidant, polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, manufactured by Seiko Chemical Co., Ltd., trade name "Nonflex RD" *11 Antioxidant 6PPD: R in general formula (1) １ and R ２An amine-based antioxidant in which one of R is an unsaturated hydrocarbon group (phenyl group), N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Sumitomo Chemical Co., Ltd., trade name "Antigen 6C" *12 Antioxidant 77PD: １ and R ２ is a saturated hydrocarbon group (1,4-dimethylpentyl group), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, manufactured by Eastman Corporation, trade name "Santoflex 77PD" *13 Sulfur: manufactured by Eastman MFG Japan, trade name "CRYTEX HS OT20"
[0077] It can be seen from Table 1 that the rubber compositions of the Examples according to the present invention have improved elongation at break (EB) after thermal aging, and that the tires of the Examples using these rubber compositions have improved durability. It can also be seen that the rubber composition of Example 3 according to the present invention has a higher retention rate of elongation at break (EB) after thermal aging than the rubber composition of Comparative Example 1.
[0078] 1: bead portion, 2: sidewall portion, 3: tread portion, 4: bead core, 5: carcass, 6: belt
Claims
1. The rubber composition includes a rubber component, carbon black, a cobalt compound, and an amine-based antioxidant, The rubber component contains 60 to 100% by mass of an isoprene skeleton rubber, The amine-based antiaging agent is represented by the following general formula (1): 【Chemical 1】 [In the formula, R １ and R ２ are each independently a monovalent saturated hydrocarbon group; the content of the amine-based antioxidant is 0.1 parts by mass or more per 100 parts by mass of the rubber component, The content (parts by mass) of the cobalt compound in terms of cobalt and the content (parts by mass) of the amine-based antioxidant relative to 100 parts by mass of the rubber component are expressed as follows: (Content of cobalt compound in cobalt equivalent) × 6 < (content of amine-based antioxidant) ... (1) A coating rubber composition for tire reinforcement, characterized in that the following relationship is satisfied:
2. The carbon black has a dibutyl phthalate (DBP) absorption of 50 to 100 cm ３ 2. The coating rubber composition for tire reinforcement according to claim 1, wherein the coating weight is 100g / 100g.
3. R in the above general formula (1) １ and R ２ The coating rubber composition for tire reinforcing material according to claim 1, wherein each of the groups independently represents a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.
4. 2. The coating rubber composition for tire reinforcing material according to claim 1, wherein the rubber component contains 1 to 20 mass % of synthetic isoprene rubber as the isoprene skeleton rubber.
5. 2. The coating rubber composition for tire reinforcing material according to claim 1, which does not contain silica or contains silica in an amount of 1 part by mass or less per 100 parts by mass of the rubber component.
6. 2. The coating rubber composition for tire reinforcement according to claim 1, which does not contain a thermoplastic resin.
7. The coating rubber composition for tire reinforcement according to claim 1, which contains a thermosetting resin.
8. 2. The coating rubber composition for tire reinforcing material according to claim 1, wherein the content of the carbon black is 50 parts by mass or less based on 100 parts by mass of the rubber component.
9. 2. The coating rubber composition for tire reinforcement according to claim 1, which does not contain 2,2'-methylenebis(4-methyl-6-tert-butylphenol).
10. 2. The coating rubber composition for tire reinforcement according to claim 1, which does not contain N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine.
11. A tire, characterized in that it comprises a reinforcing material coated with the coating rubber composition for tire reinforcing material described in claim 1.
12. 12. Tire according to claim 11 for heavy loads.