Rubber composition and tire

Abstract

To provide: a rubber composition that comprises natural rubber but is less malodorous and has excellent workability; and a tire.SOLUTION: A rubber composition contains a rubber component containing natural rubber, and chaff ash. The chaff ash contains ash of 40 mass% or more. The content of the chaff ash is 0.1-3.0 pts.mass relative to 100 pts.mass of the rubber component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to rubber compositions and tires. [Background technology]

[0002] Natural rubber contains large amounts of non-rubber components such as proteins, lipids, and sugars, which can cause foul odors when the non-rubber components spoil during storage of the raw material or decompose due to thermal decomposition during the drying process.

[0003] Proposed methods for reducing the odor of natural rubber include, for example, a method in which the removal temperature when masticating natural rubber in a Banbury mixer is set to 145°C or lower (see, for example, Patent Document 1), and a method in which at least one antioxidant selected from tocopherol and phenol is added to natural rubber latex before coagulation, followed by drying at a drying temperature of 115°C to 100°C (see, for example, Patent Document 2).However, these methods are insufficient to suppress the odor of rubber compositions containing natural rubber, and there is room for improvement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-257237 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-74392 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to solve the above problems and provide a rubber composition and a tire that are excellent in odor suppression and processability despite containing natural rubber. [Means for solving the problem]

[0006] The present disclosure relates to a rubber composition comprising a rubber component containing natural rubber and rice husk ash, wherein the rice husk ash has an ash content of 40 mass% or more and the content of the rice husk ash is 0.1 to 3.0 mass parts per 100 mass parts of the rubber component. [Effects of the Invention]

[0007] According to the present disclosure, the rubber composition includes a rubber component containing natural rubber and rice husk ash, the rice husk ash having an ash content of 40 mass% or more, and the content of the rice husk ash is 0.1 to 3.0 mass parts per 100 mass parts of the rubber component.Therefore, despite the incorporation of natural rubber, a rubber composition and tire can be provided that have excellent odor suppression properties and processability. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present disclosure provides a rubber composition comprising a rubber component containing natural rubber and rice husk ash, the ash content of which is a predetermined amount. Despite the incorporation of natural rubber, the rubber composition exhibits excellent odor suppression and processability.

[0009] The odor of natural rubber is thought to be caused by the spoilage of non-rubber components of natural rubber, such as proteins, lipids, and sugars, during storage or decomposition during drying, which generates odor-causing lower fatty acids and other odorous substances.However, this disclosure was completed based on the discovery that blending a predetermined amount of rice husk ash with a rubber composition containing such natural rubber can make the rubber composition excellent in odor suppression without compromising processability.In addition to the odor originating from natural rubber, the rubber composition of the present disclosure can also suppress odors originating from substances other than natural rubber.

[0010] [Rubber component] The natural rubber (NR) is not particularly limited, and examples that can be used include those commonly used in the rubber industry, such as SIR20, RSS#3, TSR20, SVR5S, deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. However, in this disclosure, by blending a predetermined amount of rice husk ash with a predetermined ash content into the rubber composition, excellent odor suppression properties can be achieved without deteriorating processability. Therefore, even when SIR20, RSS#3, TSR20, SVR5S, or the like is used as the natural rubber, the odor of the rubber composition can be sufficiently suppressed without deteriorating processability.

[0011] The content of NR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be better obtained.

[0012] The rubber composition may contain rubber components other than NR. Examples of other rubber components that can be used include other diene-based rubbers. Examples of other diene-based rubbers include isoprene-based rubbers other than NR, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Other examples include butyl-based rubbers and fluororubbers. These may be used alone or in combination of two or more types. However, from the viewpoint of rubber physical properties, it is preferable to use BR.

[0013] Examples of isoprene-based rubbers other than NR include isoprene rubber (IR) and modified IR. The IR is not particularly limited, and for example, IR2200 or other commonly used IRs in the rubber industry can be used. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0014] The BR is not particularly limited, and examples thereof include high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare earth catalyst (rare earth BR). These may be used alone or in combination of two or more. Of these, high-cis BR with a cis content of 90% by mass or more is preferred because it improves wear resistance. These may be used alone or in combination of two or more.

[0015] The BR may be a non-modified BR or a modified BR. The modified BR may be any BR having a functional group that interacts with a filler such as silica. Examples include terminal-modified BR (terminal-modified BR having the functional group at the terminal) in which at least one terminal of the BR has been modified with a compound (modifier) ​​having the functional group, main-chain-modified BR having the functional group in the main chain, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal (for example, main-chain terminal-modified BR having the functional group in the main chain and at least one terminal modified with the modifier), and terminal-modified BR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0016] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0017] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0018] In the rubber composition, when the rubber component contains BR, the content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0019] In the rubber composition, when the rubber component contains BR, the total content of NR and BR in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be more favorably obtained.

[0020] [Filler] The rubber composition contains rice husk ash. Rice husk ash can be obtained by carbonizing rice husks. The carbonization method is not particularly limited, and known methods can be used, such as a method of heating rice husks. Commercially available rice husk ash may be used, such as rice husk ash manufactured by Kansai Sangyo Co., Ltd.

[0021] The main components contained in rice husk ash are carbon and ash, but the ratio of carbon and ash in rice husk ash can be adjusted by changing the carbonization conditions such as heating temperature and heating time. For example, by increasing the heating temperature and / or increasing the heating time, the carbonization reaction can be promoted more, and rice husk ash with a higher ash content can be prepared.

[0022] In the present disclosure, the rice husk ash contains 40% by mass or more of ash. That is, the ash content in 100% by mass of rice husk ash is 40% by mass or more. By setting the ash content of the rice husk ash within this range, the rubber composition can be made to have excellent odor suppression properties. The ash content in 100% by mass of rice husk ash is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 75% by mass or more, and particularly preferably 85% by mass or more. Furthermore, the ash content in 100% by mass of rice husk ash is preferably 99.7% by mass or less, more preferably 99.5% by mass or less, even more preferably 99.3% by mass or less, and particularly preferably 99.0% by mass or less. In this specification, the ash content of rice husk ash can be measured by the method described in the examples below.

[0023] The carbon content in 100% by mass of rice husk ash is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and particularly preferably 1.0% by mass or more. It is also preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, even more preferably 25% by mass or less, and particularly preferably 15% by mass or less. If the carbon content in 100% by mass of rice husk ash is within the above range, the effects of the present disclosure can be further enhanced. In this specification, the carbon content of rice husk ash is calculated as the amount remaining after subtracting the ash content in the rice husk ash.

[0024] The most frequent pore size of the rice husk ash is preferably 0.50 to 0.80 nm. It is more preferably 0.55 nm or more, and even more preferably 0.60 nm or more. It is also more preferably 0.75 nm or less, even more preferably 0.70 nm or less, and even more preferably 0.65 nm or less. By setting the most frequent pore size of the rice husk ash within the above range, the effects of the present disclosure can be further enhanced.

[0025] The maximum pore diameter of the rice husk ash is preferably 2.0 to 2.5 nm. It is more preferably 2.1 nm or more, and even more preferably 2.2 nm or more. It is also more preferably 2.4 nm or less, and even more preferably 2.3 nm or less. By setting the maximum pore diameter of the rice husk ash within the above range, the effects of the present disclosure can be further enhanced.

[0026] The minimum pore diameter of the rice husk ash is preferably 0.10 to 0.30 nm. It is more preferably 0.12 nm or more, and even more preferably 0.14 nm or more. It is also more preferably 0.25 nm or less, even more preferably 0.20 nm or less, and even more preferably 0.17 nm or less. By setting the minimum pore diameter of the rice husk ash within the above range, the effects of the present disclosure can be further enhanced. In the present disclosure, the most frequent pore size, maximum pore size, and minimum pore size of rice husk ash can be measured by the method described in the examples below.

[0027] The pore sizes (modal pore size, maximum pore size, and minimum pore size) of rice husk ash can be adjusted by washing the rice husk ash with acid or alkali. Specifically, washing the rice husk ash with acid can reduce the modal pore size and minimum pore size and increase the maximum pore size, while washing the rice husk ash with alkali can reduce the modal pore size and minimum pore size and increase the maximum pore size.

[0028] Methods for washing rice husk ash with acid or alkali include, for example, applying an acidic solution of pH 1 to 3 (such as an aqueous solution of an acidic compound or an alcohol solution) or a basic (alkaline) solution of pH 6 to 9 (such as an aqueous solution of a basic compound or an alcohol solution) to the rice husk ash, spraying it with a spray or shower, or immersing the rice husk ash in the acidic or basic solution, thereby bringing the rice husk ash into contact with the acidic or basic solution, and then removing the acidic or basic solution remaining on the surface of the rice husk ash.

[0029] The contact time and temperature of the rice husk ash with the acidic or basic solution are not particularly limited and can be adjusted as appropriate. The concentration of the acidic or basic solution is also not particularly limited and can be adjusted as appropriate.

[0030] The method for removing the acidic or basic solution remaining on the surface of the rice husk ash is not particularly limited, but examples include placing the rice husk ash that has been contacted with the acidic or basic solution in running water, diluting the rice husk ash that has been contacted with the acidic or basic solution with water and then centrifuging it, and leaving the rice husk ash that has been contacted with the acidic or basic solution in a water bath to float it, and then discharging only the aqueous phase to remove the rice husk ash.

[0031] The acidic compound is not particularly limited, and examples thereof include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, metaphosphoric acid, boric acid, boronic acid, sulfanilic acid, and sulfamic acid; formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, salicylic acid, methanesulfonic acid, itaconic acid, benzenesulfonic acid, and toluenesulfonic acid. Examples of organic acids include naphthalenedisulfonic acid, trifluoromethanesulfonic acid, styrenesulfonic acid, trifluoroacetic acid, barbituric acid, acrylic acid, methacrylic acid, cinnamic acid, 4-hydroxybenzoic acid, aminobenzoic acid, naphthalenedisulfonic acid, hydroxybenzenesulfonic acid, toluenesulfinic acid, benzenesulfinic acid, α-resorcylic acid, β-resorcylic acid, γ-resorcylic acid, gallic acid, phloroglycine, sulfosalicylic acid, ascorbic acid, erythorbic acid, and bisphenol acid.

[0032] The basic compound is not particularly limited, and examples thereof include metal hydroxides such as alkali metal hydroxides and alkaline earth metal hydroxides; metal carbonates such as alkali metal carbonates and alkaline earth metal carbonates; metal bicarbonates such as alkali metal bicarbonates; metal phosphates such as alkali metal phosphates; metal acetates such as alkali metal acetates; metal hydrides such as alkali metal hydrides; and ammonia. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the alkaline earth metal hydroxide include magnesium hydroxide, calcium hydroxide, and barium hydroxide. Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of the alkaline earth metal carbonate include magnesium carbonate, calcium carbonate, and barium carbonate. Examples of the alkali metal hydrogen carbonate include lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. Examples of the alkali metal phosphate include sodium phosphate and sodium hydrogen phosphate. Examples of the alkali metal acetate include sodium acetate and potassium acetate. Examples of the alkali metal hydride include sodium hydride and potassium hydride.

[0033] The content of rice husk ash is 0.1 to 3.0 parts by mass per 100 parts by mass of the rubber component. By setting the content of rice husk ash within this range, the rubber composition can be made excellent in odor suppression and processability. The content of rice husk ash is preferably 0.2 parts by mass or more, and more preferably 0.3 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, the content is preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less, even more preferably 1.0 part by mass or less, and particularly preferably 0.6 parts by mass or less.

[0034] The rubber composition may contain carbon black. Examples of carbon black include, but are not limited to, GPF, FEF, HAF, ISAF, SAF, etc. Commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0035] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 20 m 2 / g or more, more preferably 50m 2 / g or more, more preferably 70m 2 The upper limit of the N2SA of the carbon black is not particularly limited, but is preferably 150 m 2 / g or less, more preferably 130m 2 / g or less, more preferably 120m 2 Within the above range, there is a tendency for the effect to be better obtained. The nitrogen adsorption specific surface area of ​​carbon black can be determined according to JIS K6217-2:2001.

[0036] In the rubber composition, the carbon black content is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The carbon black content is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above ranges, the effects tend to be more favorably obtained.

[0037] Fillers other than carbon black that can be used in the rubber composition include those known in the rubber field, such as silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica, etc. Of these, silica is preferred.

[0038] In the rubber composition, the filler content (total amount) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0039] The carbon black content in 100% by mass of the filler contained in the rubber composition is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. When it is within the above range, better effects tend to be obtained.

[0040] Examples of silica that can be used in the rubber composition include dry process silica (anhydrous silica), wet process silica (hydrated silica), etc. Among these, wet process silica is preferred because it has a large number of silanol groups.

[0041] In the rubber composition, the content of silica is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the rubber component. The content of silica is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less. Within the above ranges, the effects tend to be more favorable.

[0042] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 50 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 150m 2 / g or more. The N2SA of the silica is preferably 250m 2 / g or less, more preferably 220m 2 / g or less, more preferably 200m 2 Within the above range, there is a tendency for the effect to be better obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0043] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0044] [Silane coupling agent] The rubber composition preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include sulfide-based agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, and bis(3-trimethoxysilylpropyl)tetrasulfide, mercapto-based agents such as 3-mercaptopropyltrimethoxysilane, vinyl-based agents such as vinyltriethoxysilane, amino-based agents such as 3-aminopropyltriethoxysilane, glycidoxy-based agents such as γ-glycidoxypropyltriethoxysilane, nitro-based agents such as 3-nitropropyltrimethoxysilane, and chloro-based agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane.Among these, sulfide-based agents are preferred from the viewpoint of obtaining better effects.

[0045] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0046] In the rubber composition, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of silica, and is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above ranges, the effect tends to be more favorable.

[0047] [Plasticizer] The rubber composition may contain a plasticizer. In this specification, the term "plasticizer" refers to a material that imparts plasticity to a rubber component, and is a concept that includes liquid plasticizers (plasticizers that are liquid (liquid) at 25°C) and solid plasticizers (plasticizers that are solid at 25°C). Specifically, it is a component that can be extracted from a rubber composition using acetone. These may be used alone or in combination of two or more types.

[0048] In the rubber composition, the total content of plasticizers (total content of liquid plasticizer and solid plasticizer) is preferably 5.0 parts by mass or more, more preferably 8.0 parts by mass or more, even more preferably 10.0 parts by mass or more, and particularly preferably 12.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50.0 parts by mass or less, more preferably 30.0 parts by mass or less, and even more preferably 20.0 parts by mass or less. Within the above range, better effects tend to be obtained. The amount of plasticizer included also includes the amount of oil contained in rubber (oil-extended rubber), sulfur (oil-containing sulfur), etc.

[0049] Examples of liquid plasticizers include oils, liquid polymers (diene-based, olefin-based, ester-based, etc.), liquid resins, essential oils derived from natural products such as turpentine, and ester-based plasticizers. Examples of solid plasticizers include solid resins that are solid at 25°C and are commonly used in the tire industry. These may be used alone or in combination of two or more. Of these, oils, liquid polymers, and liquid resins are preferred, oils are more preferred, and process oils are even more preferred.

[0050] The oil is not particularly limited, and conventionally known oils can be used, such as process oils such as paraffin-based process oil, aromatic process oil, naphthenic process oil, low PCA (polycyclic aromatic) process oil such as TDAE or MES, vegetable oil, and mixtures thereof. These may be used alone or in combination of two or more. Among them, aromatic process oil is preferred.

[0051] As the oil, for example, products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu KK, Fuji Kosan Co., Ltd., etc. can be used.

[0052] Examples of liquid resins include terpene-based resins (including terpene phenol resins and aromatic modified terpene resins) that are liquid at 25°C, rosin resins, styrene-based resins, C5-based resins, C5C9-based resins, coumarone-indene-based resins (including coumarone and indene simple resins), olefin-based resins, polyurethane resins, and acrylic resins.

[0053] Examples of liquid resins that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0054] Examples of liquid diene polymers include liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), and liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), which are liquid at 25° C. The terminals or main chains of these polymers may be modified with polar groups.

[0055] As the liquid diene polymer, for example, products manufactured by Sartomer Co., Ltd., Kuraray Co., Ltd., etc. can be used.

[0056] In the rubber composition, the content of the liquid plasticizer (preferably oil) is preferably 5.0 parts by mass or more, more preferably 8.0 parts by mass or more, even more preferably 10.0 parts by mass or more, and particularly preferably 12.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50.0 parts by mass or less, more preferably 30.0 parts by mass or less, and even more preferably 20.0 parts by mass or less. Within the above range, the effect tends to be more favorably obtained. The amount of plasticizer included also includes the amount of oil contained in rubber (oil-extended rubber), sulfur (oil-containing sulfur), etc.

[0057] As the solid plasticizer, solid resins commonly used in tire compounds can be used. Specific examples include terpene resins, rosin resins, styrene resins, olefin resins, C5 resins, C9 resins, C5 / C9 resins, coumarone resins, indene resins, coumarone-indene resins, acrylic resins, and urethane resins. These may be used alone or in combination, or the resin itself may be a copolymer of monomer components derived from multiple sources.

[0058] Examples of solid plasticizers that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Nippon Oil & Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0059] The softening point of the solid plasticizer is preferably 30° C. or higher, more preferably 50° C. or higher, even more preferably 80° C. or higher, and is preferably 200° C. or lower, more preferably 160° C. or lower, even more preferably 140° C. or lower, and particularly preferably 120° C. or lower. By keeping the softening point within the above range, the above-mentioned effects tend to be more suitably obtained. In this specification, the softening point of a solid plasticizer is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0060] When the rubber composition contains a solid plasticizer (preferably a resin), the content of the solid plasticizer is preferably 5.0 parts by mass or more, more preferably 8.0 parts by mass or more, even more preferably 10.0 parts by mass or more, and particularly preferably 12.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 50.0 parts by mass or less, more preferably 30.0 parts by mass or less, and even more preferably 20.0 parts by mass or less. Within the above range, better effects tend to be obtained.

[0061] [Other ingredients] The rubber composition preferably contains zinc oxide from the viewpoint of obtaining better effects. As the zinc oxide, a conventionally known product can be used, for example, a product manufactured by Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0062] In the rubber composition, the content of zinc oxide is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 2.5 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of obtaining better effects. The upper limit is not particularly limited, but is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. Within the above range, better effects tend to be obtained.

[0063] The rubber composition preferably contains a vulcanizing agent. The vulcanizing agent can be one commonly used in the rubber industry, such as sulfur. Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. These may be used alone or in combination of two or more.

[0064] As the vulcanizing agent, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0065] In the rubber composition, the content of the vulcanizing agent (preferably sulfur) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, even more preferably 5.5 parts by mass or less, and particularly preferably 4.0 parts by mass or less. Within the above ranges, the effect tends to be more favorable.

[0066] The rubber composition preferably contains a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolyl sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators are preferred.

[0067] As the vulcanization accelerator, for example, products manufactured by Kawaguchi Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Rhein Chemie AG, etc. can be used.

[0068] In the rubber composition, the content of the vulcanization accelerator is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, better effects tend to be obtained.

[0069] The rubber composition preferably contains stearic acid. As the stearic acid, conventionally known ones can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0070] In the rubber composition, the content of stearic acid is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, the content is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. Within the above ranges, the effects tend to be more favorable.

[0071] The rubber composition may contain an antioxidant. Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of antioxidants include p-phenylenediamine-based antioxidants such as quinoline; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and p-phenylenediamine-based antioxidants are more preferred.

[0072] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0073] In the rubber composition, the content of the antioxidant is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. Within the above ranges, the effect tends to be more favorably obtained.

[0074] The rubber composition may contain a wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0075] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0076] In the rubber composition, the wax content is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The wax content is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 5.0 parts by mass or less. Within the above ranges, the effect tends to be more favorable.

[0077] In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, such as vulcanizing agents other than sulfur (e.g., organic crosslinking agents, organic peroxides), etc. The content of each of these components is preferably 0.1 part by mass or more and preferably 200 parts by mass or less per 100 parts by mass of the rubber component.

[0078] The rubber composition can be produced, for example, by kneading the components using a rubber kneading device such as an open roll or a Banbury mixer, followed by vulcanization.

[0079] As for kneading conditions, in the base kneading step in which additives other than the crosslinking agent (vulcanizing agent) and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 80 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0080] The rubber composition can be used (as a rubber composition for tires) in tire components such as tread, sidewall, base tread, undertread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, etc., and side reinforcing layer of run-flat tires, etc. Among these, it is preferably used in tread (particularly the portion (cap tread) that comes into contact with the road surface during driving) and sidewall.

[0081] 〔tire〕 The tire of the present disclosure is manufactured by a conventional method using the rubber composition. That is, the rubber composition, to which various additives are optionally blended, is extruded in an unvulcanized state to match the shapes of the tire components such as the tread, molded in a tire building machine by a conventional method, and laminated together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0082] The tire is not particularly limited, and examples thereof include pneumatic tires, solid tires, airless tires, etc. Among these, pneumatic tires are preferred.

[0083] The tires can be used as passenger car tires, large passenger car tires, large SUV tires, heavy load tires (truck and bus tires, etc.), motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc. [Example]

[0084] The present disclosure will be specifically described based on examples, but the present disclosure is not limited to these examples.

[0085] [Ash content measurement] The dried rice husk ash was placed in an alumina crucible and heated in an electric furnace at 550°C for 4 hours. The ash content was then calculated using the following formula. Ash content (mass%) = (mass of rice husk ash after heating / mass of rice husk ash before heating) x 100

[0086] [Pore size distribution measurement] Pore ​​diameter was measured by nitrogen adsorption testing and analysis using the MP method. The MP method assumes that the pores are cylindrical and calculates the diameter from the correlation with the adsorption layer thickness. The measurement device used was a BELSORP MAX manufactured by Microtrac-Bell Corporation.

[0087] The various chemicals used in the examples and comparative examples will be collectively described below. NR:TSR20 BR: BR150B (cis content: 98% by mass) manufactured by Ube Industries, Ltd. Carbon black: Show Black N220 (N2SA: 111m) manufactured by Cabot Japan Co., Ltd. 2 / g) Rice husk ash A: Prepared by carbonizing rice husks at temperatures ranging from 500 to 700°C (Ash content: 60% by mass, Carbon content: 40% by mass, Modest pore diameter: 0.75nm, Maximum pore diameter: 2.0nm, Minimum pore diameter: 0.23nm) Rice husk ash B: Produced by further burning rice husk ash A at 700°C or higher (Ash content: 99.0 mass%, carbon content: 1.0 mass%, mode pore diameter: 0.75 nm, maximum pore diameter: 2.0 nm, minimum pore diameter: 0.23 nm) Rice husk ash C: Prepared by washing rice husk ash A with an acidic solution (pH 1-3) (Ash content: 60% by mass, Carbon content: 40% by mass, Modest pore diameter: 0.70nm, Maximum pore diameter: 2.1nm, Minimum pore diameter: 0.20nm) Rice husk ash D: Prepared by washing rice husk ash B with an acidic solution (pH 1-3) (Ash content: 99.0 mass%, carbon content: 1.0 mass%, mode pore diameter: 0.70 nm, maximum pore diameter: 2.1 nm, minimum pore diameter: 0.20 nm) Rice husk ash E: Prepared by washing rice husk ash A with an alkaline solution (pH 6-9) (Ash content: 60% by mass, Carbon content: 40% by mass, Modest pore diameter: 0.65nm, Maximum pore diameter: 2.3nm, Minimum pore diameter: 0.17nm) Rice husk ash F: Prepared by washing rice husk ash B with an alkaline solution (pH 6-9) (Ash content: 99.0 mass%, carbon content: 1.0 mass%, mode pore diameter: 0.65 nm, maximum pore diameter: 2.3 nm, minimum pore diameter: 0.17 nm) Aroma oil: Diana Process AH-24 (aroma process oil) manufactured by Idemitsu Kosan Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS (N-tert-butyl-2-benzothiazylsulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0088] <Examples and Comparative Examples> According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded using a Banbury mixer to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were kneaded into the obtained kneaded mixture using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170°C for 12 minutes to produce a vulcanized rubber sheet with a thickness of 2 mm.

[0089] The vulcanized rubber sheets obtained were subjected to the following evaluations, and the evaluation results are shown in Table 1.

[0090] (Smell rating) 20g of vulcanized rubber sheet was placed in a 200mL glass airtight container and heated in an oven at 60℃ for 3 hours, after which a sensory evaluation was carried out according to the following criteria. The sensory evaluation was carried out by two people, and the average score of the two people was used as the sensory evaluation score. The evaluation criteria were as follows: Comparative Example 1, which had a strong putrid smell, was 5 points; 4 points: Smells putrid 3 points: A slightly faint smell of decay 2 points: If you smell carefully, you can smell a slight putrid smell. 1 point: Odorless (no putrid smell) It was judged as such.

[0091] (Mooney viscosity (ML1+4, 130°C) (processability)) Processability was evaluated by measuring the Mooney viscosity (ML1+4, 130°C). The Mooney viscosity of the unvulcanized rubber composition was measured at 130°C in accordance with JIS K6300. The smaller the measured value, the better the processability.

[0092] [Table 1]

[0093] As can be seen from Table 1, the rubber compositions of the examples, which contain a rubber component containing natural rubber and rice husk ash, and in which the ash content of the rice husk ash is a specified amount, and in which the rice husk ash content is a specified amount, were excellent in odor suppression and processability despite containing natural rubber.

[0094] The present disclosure (1) is a rubber composition comprising a rubber component containing natural rubber and rice husk ash, wherein the rice husk ash contains an ash content of 40 mass% or more, and the content of the rice husk ash is 0.1 to 3.0 parts by mass per 100 parts by mass of the rubber component.

[0095] The present disclosure (2) is the rubber composition according to the present disclosure (1), in which the rice husk ash has a mode pore size of 0.50 to 0.80 nm, a maximum pore size of 2.0 to 2.5 nm, and a minimum pore size of 0.10 to 0.30 nm.

[0096] The present disclosure (3) is a tire having a tread and / or a sidewall made of the rubber composition according to the present disclosure (1) or (2).

Claims

1. The rubber component contains natural rubber and rice husk ash, The rice husk ash contains 40% by mass or more of ash, has a mode pore size of 0.50 to 0.80 nm, a maximum pore size of 2.0 to 2.5 nm, and a minimum pore size of 0.10 to 0.30 nm; The content of the rice husk ash in the rubber composition is 0.1 to 3.0 parts by mass per 100 parts by mass of the rubber component.

2. A tire having a tread and / or sidewalls made from the rubber composition of claim 1.

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