JP7342431B2 - Rubber compositions and pneumatic tires - Google Patents

Description

The present invention relates to a rubber composition and a pneumatic tire made using the rubber composition.

Rubber compositions are required to have excellent strength and the like, and the inclusion of various organic short fibers is being considered. For example, a rubber composition may be prepared by blending predetermined amounts of a predetermined organic short fiber and a predetermined surfactant (for example, see Patent Document 1), or a rubber composition containing modified natural rubber and microfibrillated vegetable fibers. Producing a rubber composition using a masterbatch (for example, see Patent Document 2) has been considered.

However, with these methods, it is not possible to obtain sufficiently good kneading processability, rubber strength, fuel efficiency, etc. required for the rubber composition. Additionally, there is a need for a method that can provide excellent overall performance in terms of fuel efficiency.

Japanese Patent Application Publication No. 2002-146109 JP2013-253222A

The present invention has been made in view of the above-mentioned current situation, and provides a rubber composition that has excellent overall performance in terms of kneading processability, rubber strength, and fuel efficiency, and a pneumatic tire manufactured using the rubber composition. The purpose is to provide.

The present invention provides a rubber composition comprising a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil, a rubber component, and a filler, the rubber component comprising natural rubber, and the rubber composition comprising: In the dispersion, the content of the microfibrillated vegetable fibers is 1 to 30 parts by mass relative to 100 parts by mass of the oil, the content of the dispersion is 3 to 20 parts by mass relative to 100 parts by mass of the rubber component, and the rubber The present invention relates to a rubber composition in which the content of the filler is 20 to 55 parts by mass based on 100 parts by mass of the components.

The oil is preferably a plant-derived glycerol fatty acid triester, and the blending ratio of the dispersion is preferably 30% by mass or more based on 100% by mass of the acetone extract.

The glycerol fatty acid triester preferably satisfies the following formula (A).
80≦Content of monounsaturated fatty acids having 1 unsaturated bond in 100% by mass of constituent fatty acids (mass%) x 1 (number of unsaturated bonds) + 2 unsaturated bonds in 100% by mass of constituent fatty acids Content of diunsaturated fatty acids (mass %) × 2 (number of unsaturated bonds) + content of trivalent unsaturated fatty acids having 3 unsaturated bonds (mass %) in 100 mass % of constituent fatty acids × 3 (Number of unsaturated bonds)≦200 Formula (A)

The microfibrillated plant fibers preferably have an average fiber diameter of 3 to 200 nm and an average fiber length of 0.3 to 10 μm, and the dispersion preferably has a viscosity of 1000 to 100000 mPa·s at 40°C.

The present invention also relates to a pneumatic tire made using the above rubber composition.

The present invention provides a rubber composition comprising a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil, a rubber component, and a filler, the rubber component comprising natural rubber, and the rubber composition comprising: In the dispersion, the content of the microfibrillated vegetable fibers is 1 to 30 parts by mass relative to 100 parts by mass of the oil, the content of the dispersion is 3 to 20 parts by mass relative to 100 parts by mass of the rubber component, and the rubber Since the rubber composition has a filler content of 20 to 55 parts by mass based on 100 parts by mass of the components, it has excellent overall performance of kneading processability, rubber strength, and fuel efficiency.

The rubber composition of the present invention includes a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil, a rubber component, and a filler, the rubber component includes natural rubber, and the dispersion includes: The content of microfibrillated vegetable fibers is 1 to 30 parts by mass per 100 parts by mass of oil, the content of the dispersion is 3 to 20 parts by mass per 100 parts by mass of rubber component, and the content of filler per 100 parts by mass of rubber component is The content is 20 to 55 parts by mass. Such a rubber composition has excellent overall performance of kneading processability, rubber strength, and fuel efficiency.

As mentioned above, it has been considered in the past to incorporate various organic short fibers into rubber compositions, but as a method to achieve excellent overall performance in terms of kneading processability, rubber strength, and fuel efficiency. was insufficient. In this regard, the present inventors have found that if a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil is blended into a rubber composition and a rubber composition having the above-mentioned structure is obtained, kneading processing is possible. It has been found that it is possible to achieve excellent overall performance in terms of hardness, rubber strength, and fuel efficiency.

The following mechanism is presumed to be the reason why such effects are obtained.
Oil has high plasticity and low viscosity, so when oil is blended into a rubber composition, it easily adsorbs to the filler during the preparation of the rubber composition, resulting in filler agglomerates. However, when a dispersion obtained by mixing and dispersing oil and microfibrillated plant fibers is blended into a rubber composition, the dispersion has a high viscosity. Therefore, the adsorption rate of oil to the filler is low, and since the oil is adsorbed to the microfibrillated plant fibers, a uniform dispersion form of the microfibrillated plant fibers is obtained, which prevents the formation of filler aggregates. As a result, energy loss is reduced and fuel efficiency is improved, and furthermore, the proportion of rubber that is not reinforced with filler is reduced, resulting in an improvement in the strength of the rubber composition. In addition, by blending a high-viscosity dispersion into a rubber composition, the viscosity of the rubber composition also increases, which improves kneading processability, and improves the dispersibility of fillers due to improved processability. This contributes to improvements in rubber strength and fuel efficiency. As a result, when a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil is blended into a rubber composition to form a rubber composition having the above-mentioned structure, kneading processability, rubber strength, and , the overall performance of low fuel consumption is excellent.

(rubber component)
The rubber composition includes a rubber component containing natural rubber. Natural rubber may be modified. For example, examples of modified natural rubber include epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), hydrogenated natural rubber (HNR), and grafted natural rubber. . These natural rubbers may be used alone or in combination of two or more.

The natural rubber is not particularly limited, and for example, those commonly used in the tire industry, such as SIR20, RSS#3, and TSR20, can be used.

The content of natural rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, from the viewpoint of fuel efficiency. The upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less.

The rubber component may further contain rubber other than natural rubber.
As the other rubber, common rubbers used in the rubber industry can be used, such as isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), Examples include diene rubbers such as ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), butyl rubbers such as halogenated butyl rubber (X-IIR) and butyl rubber (IIR), and fluororubbers. It will be done. Note that these rubbers may be modified rubbers, and examples of the modified rubbers include modified rubbers into which functional groups similar to modified BR described below are introduced. These other rubbers may be used alone or in combination of two or more. Among these, from the viewpoint of fatigue resistance, it is preferable to blend BR and/or SBR as other rubbers other than the above-mentioned natural rubber, and it is more preferable to blend BR.

BR is not particularly limited, and includes, for example, BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (BR containing SPB), butadiene rubber synthesized using a rare earth catalyst (rare earth BR) and tin-modified butadiene rubber modified with a tin compound (tin-modified BR), which are common in the tire industry. As a commercially available BR, products manufactured by Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used. These may be used alone or in combination of two or more.

The cis content of BR is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more. This provides good bending fatigue resistance.
Note that in this specification, the cis content is a value calculated by infrared absorption spectrum analysis.

As the BR, either non-denatured BR or modified BR can be used.
As the modified BR, BR having a functional group that interacts with a filler such as silica can be used. For example, at least one end of BR is modified with a compound (modifier) having the above functional group (terminally modified BR having the above functional group at the end), or a main chain having the above functional group in the main chain. Chain-modified BR, main chain end-modified BR having the above-mentioned functional groups on the main chain and ends (for example, main chain end-modified BR having the above-mentioned functional groups on the main chain and at least one end modified with the above-mentioned modifier) ), terminal-modified BR in which a hydroxyl group or an epoxy group is introduced by modification (coupling) with a polyfunctional compound having two or more epoxy groups in the molecule, and the like.

Examples of the above functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, and disulfide groups. group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. . Note that these functional groups may have a substituent. Among these, an amino group (preferably an amino group in which the 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), an alkoxysilyl group ( An alkoxysilyl group having 1 to 6 carbon atoms is preferred.

When blending BR, the content of BR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of low-temperature properties. . Further, the upper limit of the content is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less.

(dispersion)
The rubber composition includes a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil.

The above-mentioned dispersion is produced by a manufacturing method including a step of mixing and dispersing microfibrillated plant fibers and oil, that is, mixing and dispersing microfibrillated plant fibers and oil to prepare a dispersion. will be produced.

Examples of the oil include process oil, vegetable oil, and mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, low PCA (polycyclic aromatic) process oil such as TDAE, MES, etc. can be used. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

Examples of the above-mentioned oils include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu Co., Ltd., and Fuji Kosan Co., Ltd. ) and other products can be used.

Among the above-mentioned oils, plant-derived glycerol fatty acid triester (vegetable oil) is preferable. By using vegetable oil, the vegetable oil also functions as a surfactant for both microfibrillated vegetable fibers and rubber materials, which further improves the dispersibility of microfibrillated vegetable fibers in dispersions and rubber compositions. Therefore, the effects of the present invention can be made more suitable. Here, the glycerol fatty acid triester is an ester of fatty acid and glycerin, and is also called triglyceride or tri-O-acylglycerin.

The fatty acids constituting the above plant-derived glycerol fatty acid triester are usually palmitic acid (16 carbon atoms, 0 unsaturated bonds), stearic acid (18 carbon atoms, 0 unsaturated bonds), and oleic acid (carbon atoms 0). It is known that the main components are linoleic acid (18 carbon atoms, 2 unsaturated bonds), and palmitic acid, stearic acid, oleic acid, The total content of linoleic acid is usually 80% by mass or more, preferably 90% by mass or more.

The glycerol fatty acid triester preferably has a saturated fatty acid content of 10 to 25% by mass based on 100% by mass of the constituent fatty acids, the lower limit is more preferably 12% by mass or more, and the upper limit is more preferably 20% by mass or more. It is not more than 18% by mass, more preferably not more than 18% by mass, particularly preferably not more than 15% by mass. When the content of saturated fatty acids is 10% by mass or more, it is possible to sufficiently prevent the number of unsaturated bonds in the glycerol fatty acid triester from becoming too large, and a better softening effect can be obtained without having too many reaction points. Better fuel efficiency can be achieved. Further, when it is blended into a rubber composition, it is possible to prevent the crosslinking efficiency of the rubber component from decreasing, and better adhesion can be obtained. On the other hand, when the content of saturated fatty acids is 25% by mass or less, it is possible to sufficiently prevent the number of unsaturated bonds in the glycerol fatty acid triester from becoming too small, and when it is blended into a rubber composition, the glycerol fatty acid triester is It can be appropriately bound to the rubber, and the surface precipitation of glycerol fatty acid triester can be sufficiently suppressed, resulting in better fuel efficiency, rubber strength, and kneading processability. Furthermore, since the amount of saturated fatty acids with a relatively high melting point is small, the melting point of the glycerol fatty acid triester is lowered, energy loss is reduced, and better fuel efficiency is obtained.

In the glycerol fatty acid triester, the content of monounsaturated fatty acids having one unsaturated bond in 100% by mass of the constituent fatty acids is preferably less than 50% by mass, more preferably 45% by mass or less, and Preferably it is 40% by mass or less, even more preferably 35% by mass or less, particularly preferably 30% by mass or less. As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are further enhanced. Suitably obtained. Although the lower limit is not particularly limited, it is preferably 8% by mass or more, more preferably 14% by mass or more, and even more preferably 20% by mass or more, because the effects of the present invention can be more suitably obtained.

In the glycerol fatty acid triester, the content of polyunsaturated fatty acids having two or more unsaturated bonds in 100% by mass of the constituent fatty acids is preferably 50% by mass or more, more preferably 55% by mass or more, and Preferably it is 60% by mass or more. As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when it is blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are enhanced. It can be obtained more suitably. Although the upper limit is not particularly limited, it is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, because the effects of the present invention can be more suitably obtained.

The glycerol fatty acid triester preferably has a content of diunsaturated fatty acids having two unsaturated bonds in 100% by mass of the constituent fatty acids, preferably 35 to 80% by mass, more preferably 40 to 70% by mass, and Preferably it is 45 to 65% by mass. As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when it is blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are enhanced. It can be obtained more suitably.

In the glycerol fatty acid triester, the content of trivalent unsaturated fatty acids having three unsaturated bonds in 100% by mass of the constituent fatty acids is preferably 3 to 25% by mass, more preferably 5 to 15% by mass. . As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when it is blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are enhanced. More suitably obtained.

The above-mentioned glycerol fatty acid triester has a total content of unsaturated fatty acids of 100% by mass of the constituent fatty acids, preferably 75 to 90% by mass, more preferably 80 to 88% by mass, even more preferably 82 to 88% by mass, Particularly preferred is 85 to 88% by mass. As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when it is blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are enhanced. It can be obtained more suitably.

The glycerol fatty acid triester preferably satisfies the following formula (A). As a result, the number of unsaturated bonds in the glycerol fatty acid triester can be further optimized, and when it is blended into a rubber composition, it is possible to achieve both an appropriate softening effect and an appropriate restraint to the rubber, and the effects of the present invention are enhanced. It can be obtained more suitably.
For the reason that the effects of the present invention can be obtained more suitably, the lower limit of the following formula (A) is preferably 100 or more, more preferably 120 or more, still more preferably 140 or more, particularly preferably 150 or more, and the following formula The upper limit of (A) is preferably 190 or less, more preferably 180 or less, even more preferably 170 or less.
80≦Content of monounsaturated fatty acids having 1 unsaturated bond in 100% by mass of constituent fatty acids (mass%) x 1 (number of unsaturated bonds) + 2 unsaturated bonds in 100% by mass of constituent fatty acids Content of diunsaturated fatty acids (mass %) × 2 (number of unsaturated bonds) + content of trivalent unsaturated fatty acids having 3 unsaturated bonds (mass %) in 100 mass % of constituent fatty acids × 3 (Number of unsaturated bonds)≦200 Formula (A)

When the above-mentioned glycerol fatty acid triester is a plant-derived glycerol fatty acid triester, the unsaturated bond that the constituent fatty acid has is usually a double bond.

The above-mentioned glycerol fatty acid triester preferably has an average carbon number of 15 to 21, more preferably 16 to 20, and still more preferably 17 to 19, because the effects of the present invention can be more preferably obtained. .
In this specification, the average carbon number of constituent fatty acids is calculated by the following formula (D).
Average number of carbon atoms of constituent fatty acids = Σ Content of fatty acids with carbon number n in 100 mass% of constituent fatty acids (mass%) x n (number of carbons)/100 Formula (D)

The glycerol fatty acid triester is preferably liquid at room temperature (25° C.). The melting point of the glycerol fatty acid triester is preferably 20°C or lower, more preferably 17°C or lower, even more preferably 0°C or lower, particularly preferably -5°C or lower. This provides better fuel efficiency, rubber strength, and kneading processability.
Although the lower limit is not particularly limited, it is preferably -100°C or higher, more preferably -90°C or higher because good fuel efficiency can be obtained.
Note that the melting point of the glycerol fatty acid triester can be measured by differential scanning calorimetry (DSC).

The iodine value of the glycerol fatty acid triester is preferably 60 or more, more preferably 70 or more, even more preferably 80 or more, particularly preferably 100 or more, and most preferably 120 or more. Further, the iodine value is preferably 160 or less, more preferably 150 or less, even more preferably 135 or less. When the iodine value is within the above range, the effects of the present invention can be more suitably obtained.
In addition, in this specification, the iodine value is the amount of halogen that is converted into grams of iodine when 100 g of glycerol fatty acid triester is reacted with halogen, and is determined by potentiometric titration method (JIS K0070). This is the measured value.

Examples of the plant-derived glycerol fatty acid triester include soybean oil, sesame oil, rice oil, safflower oil, corn oil, olive oil, rapeseed oil, and the like. Among these, soybean oil, sesame oil, rice oil, and rapeseed oil are preferred, soybean oil, sesame oil, and rice oil are more preferred, and soybean oil is even more preferred because they are inexpensive, available in large quantities, and highly effective in improving performance. .

Note that the above fatty acid composition can be measured by GLC (gas-liquid chromatography).

Examples of the glycerol fatty acid triester include Nisshin Oilio Co., Ltd., J-Oil Mills Co., Ltd., Showa Sangyo Co., Ltd., Fuji Oil Co., Ltd., Miyoshi Yushi Co., Ltd., Boso Yushi Co., Ltd., etc. products can be used.

As the above-mentioned oil, one obtained by saponifying a plant-derived glycerol fatty acid triester (vegetable oil or fat) (saponified vegetable oil or fat) can also be suitably used.
The saponification treatment can be carried out by adding an alkali to the vegetable oil and allowing it to stand at a predetermined temperature for a predetermined period of time. Note that stirring or the like may be performed as necessary.

Examples of the alkali that can be used in the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, and amine compounds. It is preferable to use

The amount of the alkali added is not particularly limited, but for example, the lower limit is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and 1 part by mass or more with respect to 100 parts by mass of the vegetable oil. More preferred. Moreover, the upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. When the amount of alkali added is within this range, saponification treatment can be performed efficiently.

The temperature for the above saponification treatment can be set as appropriate within a range where the saponification reaction with alkali can proceed at a sufficient reaction rate and within a range where vegetable oils and fats do not deteriorate, but it is usually 20 to 70°C. The temperature is preferably 30 to 70°C, and more preferably 30 to 70°C. In addition, when processing vegetable oils and fats while leaving them still, the processing time depends on the processing temperature, but considering both sufficient processing and productivity improvement, it takes 30 minutes to 48 hours. It is preferable that the time is 1 to 24 hours, and more preferably 1 to 24 hours.

As the microfibrillated plant fiber, cellulose microfibrils are preferred from the viewpoint of breaking strength and abrasion resistance. Cellulose microfibrils are not particularly limited as long as they are derived from natural products, such as resource biomass such as fruits, grains, and root vegetables, wood, bamboo, hemp, jute, kenaf, and pulps and kenaf obtained from these materials. Waste biomass such as paper, cloth, crop residue, food waste, and sewage sludge; unused biomass such as rice straw, wheat straw, and thinned wood; and materials derived from cellulose produced by ascidians, acetic acid bacteria, etc. It will be done. These microfibrillated plant fibers may be used alone or in combination of two or more.

In addition, in this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, and more typically mean fiber diameters formed by an aggregation of cellulose molecules. It means cellulose fibers having a microstructure of 500 nm or less. Note that typical cellulose microfibrils can be formed, for example, as an aggregate of cellulose fibers having the average fiber diameter as described above.

The method for producing the microfibrillated plant fibers is not particularly limited, but for example, after chemically treating the raw material for the cellulose microfibrils with an alkali such as sodium hydroxide as necessary, using a refiner, a twin-screw kneader (two-screw kneading machine), etc. Extruder), twin-screw kneading extruder, high-pressure homogenizer, medium stirring mill, stone mill, grinder, vibration mill, sand grinder, etc. may be used to mechanically grind or beat the material. In these methods, since lignin is separated from the raw material by chemical treatment, microfibrillated plant fibers containing substantially no lignin can be obtained. Other methods include a method in which the raw material for the cellulose microfibrils is subjected to ultra-high pressure treatment.

As the microfibrillated plant fibers, for example, products manufactured by Sugino Machine Co., Ltd., Daicel Finechem Co., Ltd., etc. can be used.

The above-mentioned microfibrillated plant fibers include those obtained by the above-mentioned production method and further subjected to oxidation treatment and various chemical modification treatments, and natural products that can be the source of the above-mentioned cellulose microfibrils (for example, Wood, pulp, bamboo, hemp, jute, kenaf, agricultural crop residues, cloth, paper, ascidian cellulose, etc.) are used as cellulose raw materials and are subjected to oxidation treatment and various chemical modification treatments, followed by defibration treatment as necessary. It is also possible to use those that have been subjected to the following steps.

Examples of the chemical modification of the microfibrillated plant fibers include esterification treatment, etherification treatment, acetalization treatment, and the like. More specifically, acylation such as acetylation, cyanoethylation, amination, sulfone esterification, phosphoric acid esterification, alkyl esterification, alkyl etherification, complex esterification, β-ketoesterification, alkyl esterification such as butylation, etc. Preferred examples include chlorination, chlorination, and the like. Further examples include alkyl carbamate formation and aryl carbamate formation. Among these, amination is particularly preferable because it can further improve the dispersibility of the microfibrillated plant fibers in the dispersion and can make the effects of the present invention more suitable.

That is, the microfibrillated plant fiber is a chemically modified microfibrillated plant fiber, and the chemical modification in the chemically modified microfibrillated plant fiber includes acetylation, amination, sulfone esterification, alkyl esterification, and composite esterification. , β-keto esterification, alkyl carbamate formation, and aryl carbamate formation. All of these chemical modification treatments are treatments that hydrophobize microfibrillated plant fibers, and by using microfibrillated plant fibers that have been subjected to such chemical modification treatments, microfibrillation in the dispersion can be improved. The dispersibility of plant fibers can be further improved, and the effects of the present invention can be made more suitable.

The chemically modified microfibrillated plant fibers are preferably chemically modified so that the degree of substitution is within the range of 0.2 to 2.5. Here, the degree of substitution refers to the average number of hydroxyl groups per glucose ring unit that are substituted with other functional groups by chemical modification among the hydroxyl groups of cellulose, and the theoretical maximum value is 3. When the degree of substitution is 0.2 or more, the dispersibility of the chemically modified microfibrillated vegetable fibers in oil becomes particularly good, and when it is 2.5 or less, the chemically modified microfibrillated vegetable fibers have a particularly good dispersibility in oil. It has particularly excellent dispersibility in oil and particularly excellent flexibility, and the effects of the present invention can be more suitably obtained. The degree of substitution is more preferably within the range of 0.3 to 2.5, even more preferably within the range of 0.5 to 2.3, and even more preferably within the range of 0.5 to 2.0. It is particularly preferable that there be.

In addition, when the chemically modified microfibrillated plant fibers are a combination of two or more types, the degree of substitution is calculated as the average of the entire chemically modified microfibrillated plant fibers.

The degree of substitution in the chemically modified microfibrillated plant fiber can be confirmed, for example, by titration using 0.5N-NaOH and 0.2N-HCl, NMR, infrared absorption spectrum, or the like.

The chemically modified microfibrillated plant fibers particularly preferably used in the present invention include aminated microfibrillated plants having a degree of substitution within the range of 0.3 to 2.5 (more preferably 0.3 to 2.0). An example is fiber. The degree of substitution of the aminated microfibrillated plant fibers is preferably within the range of 0.5 to 2.3, more preferably within the range of 0.7 to 2.0, even more preferably 0.9. ~1.8.

In addition, when the chemically modified microfibrillated plant fiber is an acetylated microfibrillated plant fiber, the degree of substitution is 0.3 to 2.5, and when it is a sulfone-esterified microfibrillated plant fiber, the degree of substitution is 0.3 to 2.5. 0.3 to 1.8, the degree of substitution is 0.3 to 1.8 in the case of alkyl esterified microfibril cellulose, and the degree of substitution is 0.4 to 1.8 in the case of composite esterified microfibril cellulose. 8. In the case of β-ketoesterified microfibril cellulose, the degree of substitution is 0.3 to 1.8, in the case of alkyl carbamate microfibril cellulose, the degree of substitution is 0.3 to 1.8, and aryl carbamate In the case of microfibrillar cellulose, the degree of substitution is preferably within the range of 0.3 to 1.8.

The acetylation can be carried out, for example, by adding acetic acid, concentrated sulfuric acid, or acetic anhydride to microfibrillated plant fibers and reacting them. More specifically, for example, microfibrillated plant fibers are reacted with acetic anhydride in a mixed solvent of acetic acid and toluene in the presence of a sulfuric acid catalyst to advance the acetylation reaction, and then the solvent is replaced with water. This can be carried out by any conventionally known method.

The above amination is carried out, for example, after performing an oxidation treatment using an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and then using alcohol (for example, ethanol, etc.). Among alcohols having 1 to 10 carbon atoms (preferably alcohols having 1 to 5 carbon atoms, more preferably primary alcohols having 1 to 4 carbon atoms), amine compounds (for example, alcohols having 1 to 30 carbon atoms such as oleylamine) Primary amine compound (preferably a primary amine compound having 3 to 25 carbon atoms having a saturated bond or unsaturated bond, more preferably a primary amine compound having 6 to 23 carbon atoms having an unsaturated bond, even more preferably is a primary amine compound having 10 to 20 carbon atoms having an unsaturated double bond) or a quaternary alkyl ammonium salt (preferably a quaternary alkylammonium salt having 1 to 30 carbon atoms, more preferably hexadecyltrimethyl This can be carried out by a known method such as a nucleophilic substitution reaction by reacting with a quaternary alkyl ammonium halide having 1 to 20 carbon atoms such as ammonium chloride, or tosyl esterification.

The above-mentioned sulfone esterification can be carried out, for example, by simply dissolving the microfibrillated plant fibers in sulfuric acid and adding the solution to water. Other methods include anhydrous sulfuric acid gas treatment, treatment with chlorosulfonic acid and pyridine, and the like.

The above-mentioned phosphoric acid esterification can be carried out, for example, by a method of treating microfibrillated plant fibers that have been treated with dimethylamine or the like with phosphoric acid and urea.

The alkyl esterification can be carried out, for example, by the Schotten-Baumann method, in which microfibrillated plant fibers are reacted with a carboxylic acid chloride under basic conditions; , the Williamson method, etc., in which microfibrillated plant fibers are reacted with an alkyl halide under basic conditions.

The above chlorination can be carried out, for example, by adding thionyl chloride in DMF (dimethylformamide) and heating the mixture.

The above composite esterification can be carried out, for example, by a method in which microfibrillated plant fibers are reacted with two or more types of carboxylic acid anhydrides or carboxylic acid chlorides under basic conditions.

The above β-ketoesterification can be carried out, for example, by reacting microfibrillated plant fibers with diketene or alkyl ketene dimer, or by transesterifying microfibrillated plant fibers with a β-ketoester compound such as alkyl acetoacetate. can.

The alkyl carbamate formation can be carried out, for example, by reacting microfibrillated plant fibers with an alkyl isocyanate in the presence of a basic catalyst or a tin catalyst.

The above aryl carbamate formation can be carried out, for example, by a method in which microfibrillated plant fibers are reacted with an aryl isocyanate in the presence of a basic catalyst or a tin catalyst.

The average fiber diameter of the microfibrillated plant fibers is preferably 10 μm or less. When the average fiber diameter of the microfibrillated plant fibers is within such a range, the dispersibility of the microfibrillated plant fibers in the dispersion can be further improved, and the effects of the present invention can be more preferably achieved. It can be done. Furthermore, breakage of microfibrillated plant fibers during processing tends to be suppressed. The average fiber diameter is more preferably 500 nm or less, still more preferably 200 nm or less, even more preferably 100 nm or less, and particularly preferably 50 nm or less, since the effects of the present invention can be obtained more suitably. The lower limit of the average fiber diameter of the microfibrillated plant fibers is not particularly limited, but it is preferably 3 nm or more, and more preferably 4 nm or more, because the microfibrillated plant fibers are difficult to untangle and disperse. It is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 20 nm or more.

The average fiber length of the microfibrillated plant fibers is preferably 100 nm or more. The thickness is more preferably 300 nm or more, and even more preferably 500 nm or more. Further, the thickness is preferably 5 mm or less, more preferably 1 mm or less, even more preferably 50 μm or less, even more preferably 10 μm or less, particularly preferably 3 μm or less, and most preferably 1 μm or less. When the average fiber length is less than the lower limit or exceeds the upper limit, there is a tendency similar to the average fiber diameter described above. In addition, by using microfibrillated plant fibers having such an average fiber length, when blended into a rubber composition, it is possible to suppress concentration of distortion in the rubber matrix near the fiber edges, and improve fracture strength and abrasion resistance. properties tend to be better.

When the microfibrillated plant fibers are a combination of two or more types, the average fiber diameter and the average fiber length are calculated as the average of the entire microfibrillated plant fibers.

In this specification, the average fiber diameter and average fiber length of the microfibrillated plant fibers are determined by image analysis using scanning electron microscopy, image analysis using transmission electron microscopy, image analysis using atomic force microscopy, and X-ray It can be measured by analysis of scattering data, pore electrical resistance method (Coulter principle method), etc.

The above-mentioned microfibrillated plant fibers may be mixed and dispersed with oil in the form of an aqueous solution (microfibrillated plant fiber aqueous solution) dispersed in water, or after solvent substitution of the microfibrillated plant fiber aqueous solution with ethanol etc. , may be mixed and dispersed with oil, or microfibrillated plant fibers may be mixed and dispersed with oil as they are. In addition, when the microfibrillated plant fiber aqueous solution is mixed with oil, if necessary, a strong acid such as hydrochloric acid or sulfuric acid is added and heated (for example, 120 to 200°C, preferably 140 to 180° C.) and remove water by azeotroping or the like. Note that when a dispersion aid, which will be described later, is used when mixing and dispersing the microfibrillated plant fibers and oil, the dispersion aid is also removed during the process of removing the water.

The microfibrillated plant fiber aqueous solution can be produced by a known method, for example, by dispersing microfibrillated plant fibers in water using a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, or the like. The temperature and time during preparation can also be appropriately set within the usual range so that the microfibrillated plant fibers are sufficiently dispersed in water.

The content (solid content) of microfibrillated plant fibers in the microfibrillated plant fiber aqueous solution is preferably 0.2 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 0.2% to 20% by mass. It is 5 to 3% by mass.

The step of mixing and dispersing microfibrillated plant fibers and oil to prepare a dispersion involves sequentially dropping or injecting them, or mixing microfibrillated plant fibers and oil, and then, for example, It can be prepared by dispersing by a known method using a high-speed homogenizer, an ultrasonic homogenizer, a colloid mill, a blender mill, or the like. The temperature and time during preparation are appropriately set within the usual range so that the microfibrillated plant fibers are sufficiently dispersed in the oil, and the viscosity of the dispersion is measured so that the dispersion has the desired viscosity. You can adjust it.

When preparing the above dispersion, in addition to oil and microfibrillated plant fibers, inorganic minerals and/or water-soluble polymers may be blended. By blending inorganic minerals and/or water-soluble polymers, the compatibility of the inorganic minerals and/or water-soluble polymers with microfibrillated plant fibers and oil increases, and the microfibrillated plant fibers and oil become more uniform. As a result, the generation of filler agglomerates is reduced, energy loss is further reduced, and fuel efficiency can be significantly improved.

The above-mentioned inorganic minerals are not particularly limited, but include, for example, kaolin group such as kaolinite, nacrite, endeleite, dickite, halloysite, and chrysotile; antigorite group such as antigorite, amethite, and cronstedite; Vermiculite group such as vermiculite, tri-vermiculite; smectite group such as montmorillonite, beidellite, nontronite, saponite, laponite, hectorite, sauconite, stevensite; illite, glauconite, celadonite, talc, pyrophyllite, mica (masco phyllosilicates such as margarite, clintonite, muscovite, biotite, phlogopite, synthetic mica, fluorinated mica, paragolite, phlogopite, lepidolite, tetrasilylic mica, and teniolite; donpasite, sudolite , chlorite, such as cookite, clinochlore, chamosite, chlorite, nantite; piolite-palygoskite, such as sepiolite, attapulgite, attapulga clay, palygorskite; clay minerals, such as bentonite; hydrotalcite; diamond, graphite, Examples include boehmite, magnesium hydroxide, hydroxyapatite, diatomaceous earth, and zeolite. These inorganic minerals may be used alone or in combination of two or more.

Among the above-mentioned inorganic minerals, clay minerals are preferable from the viewpoint of compatibility with microfibrillated vegetable fibers and oil, and kaolin group, antigorite group, vermiculite group, smectite group, phyllosilicate, and chlorite are preferable. More preferred are the kaolin group, antigorite group, vermiculite group, and smectite group, even more preferred are the kaolin group and smectite group, and particularly preferred are kaolinite and montmorillonite.

The above-mentioned water-soluble polymer is not particularly limited as long as it has a hydrophilic group introduced into the main chain or side chain of the polymer and exhibits water solubility, but examples include synthetic water-soluble polymers, natural polysaccharides, and cellulose derivatives. , starches, glycerin, hyaluronic acids, etc. Examples of synthetic water-soluble polymers include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, carboxyvinyl polymers, polyvinyl alcohol, alkyl methacrylate/acrylic acid copolymers, polyvinylpyrrolidone, sodium polyacrylate, polyacrylamide, polyurethane, and polyester. , polyamide, polyimide, etc. Examples of natural polysaccharides include xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, pullulan, carrageenan, and pectin. Examples of cellulose derivatives include carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose. Examples of starches include cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, amylose, and the like. Examples of glycerins include polyglycerin. Examples of hyaluronic acids include hyaluronic acid and metal salts of hyaluronic acid. Note that the terminals of these water-soluble polymers may be substituted with various substituents. These water-soluble polymers may be used alone or in combination of two or more.

Among the above-mentioned water-soluble polymers, from the viewpoint of compatibility with microfibrillated vegetable fibers and oil, synthetic water-soluble polymers are preferred, such as polyalkylene glycol, carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate/acrylic acid. More preferred are copolymers, polyvinylpyrrolidone, sodium polyacrylate, and polyacrylamide. In particular, in view of the balance between hydrophilicity and hydrophobicity, polyalkylene glycols having repeating alkylene units having 2 to 6 carbon atoms are more preferred, and polyethylene glycol and polypropylene glycol are particularly preferred.

The number average molecular weight of the water-soluble polymer is not particularly limited, but is preferably 300 or more, more preferably 500 or more, and even more preferably 1000 or more. Further, it is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 100,000 or less.

When blending an inorganic mineral and/or a water-soluble polymer into the above-mentioned dispersion, the above-mentioned preparation step involves dispersing the microfibrillated plant fibers in water from the viewpoint of dispersibility of the microfibrillated plant fibers in oil. It is preferable to prepare the microfibrillated plant fiber aqueous solution by replacing the solvent with ethanol etc., mixing it with an inorganic mineral and/or a water-soluble polymer, and then adding oil, mixing, and dispersing. It can be mentioned as one. By using such a method for preparing a dispersion, the dispersibility of microfibrillated plant fibers in oil can be further improved.

When blending an inorganic mineral and/or a water-soluble polymer into the above-mentioned dispersion, the blending amount of the inorganic mineral and/or water-soluble polymer is 1 part by mass per 100 parts by mass of the above-mentioned microfibrillated vegetable fiber (solid content). The amount is preferably 2000 parts by mass. By blending the inorganic mineral and/or water-soluble polymer into the dispersion in such a proportion, the compatibility of the inorganic mineral and/or water-soluble polymer with the microfibrillated plant fiber and oil can be further improved. I can do it. The blending amount is more preferably 2 parts by mass or more, still more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, particularly preferably 50 parts by mass or more, and most preferably 100 parts by mass or more. Further, it is more preferably 1,800 parts by mass or less, even more preferably 1,500 parts by mass or less, even more preferably 1,000 parts by mass or less, particularly preferably 500 parts by mass or less, and most preferably 400 parts by mass or less.

Further, when an inorganic mineral and/or a water-soluble polymer is blended into the dispersion, the content of the inorganic mineral and/or water-soluble polymer in the dispersion is 1% by mass based on 100% by mass of the dispersion. The content is preferably 2% by mass or more, and more preferably 2% by mass or more. Further, it is preferably 80% by mass or less, more preferably 60% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less. By blending the inorganic mineral and/or water-soluble polymer into the dispersion in such a proportion, the compatibility of the inorganic mineral and/or water-soluble polymer with the microfibrillated plant fiber and oil can be further improved. I can do it.

Further, when preparing the above-mentioned dispersion, other components such as a dispersion aid may be added in addition to the oil and the microfibrillated vegetable fibers.

Examples of the dispersion aid include toluene and N-methylpyrrolidone.

When blending the above-mentioned dispersion aid, the blending amount of the dispersion aid is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 50 parts by mass or more, and 80 parts by mass, based on 100 parts by mass of the oil. Parts or more are particularly preferred. Further, it is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, and even more preferably 150 parts by mass or less. When the amount of the dispersion aid is within this range, the dispersibility of the microfibrillated plant fibers in the dispersion can be further improved.

The above-mentioned dispersion preferably has a viscosity at 40° C. of 1000 mPa·s or more, preferably 5000 mPa·s, from the viewpoint of improving fuel efficiency, rubber strength, and kneading processability when blended into a rubber composition. It is more preferable that it is above, and even more preferably that it is 10000 mPa·s or more. Further, it is preferably 100,000 mPa·s or less, more preferably 50,000 mPa·s or less, even more preferably 25,000 mPa·s or less, even more preferably 20,000 mPa·s or less, and even more preferably 15,000 mPa·s or less. It is particularly preferable that
The viscosity of the above dispersion is a value measured at 40° C. using a tuning fork vibratory viscometer.

In addition, the viscosity of the above dispersion can be adjusted by mixing and dispersing microfibrillated plant fibers and oil to prepare the dispersion, or by further dispersing and dissolving a resin in the dispersion after preparing the dispersion. can.

Examples of the resin include terpene resin, epoxy resin, and rosin resin. These resins may be used alone or in combination of two or more.
The above-mentioned terpene resins are represented by resins obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphor, and dipetene, and terpene phenols, which are resins obtained from terpene compounds and phenolic compounds as raw materials. It is a terpene resin.

Examples of the epoxy resin include alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate; glycidyl ester type epoxy resins such as hexahydrophthalic acid diglycidyl ester; bisphenol A; Bisphenol-type epoxy resins derived from bisphenols such as bisphenol F and epihalohydrins, and modified epoxy resins further modified with novolac resins; phenol novolak resins, cresol novolak resins, bisphenol A novolak resins, naphthol novolak resins, biphenyl novolaks Epoxidized products of novolac resins such as resins; glycidyl ether type derived from dihydric alcohols such as hydrogenated bisphenol F, hydrogenated bisphenol A, 1,4-cyclohexanedimethanol, alkylene oxide adducts of bisphenol A, and epihalohydrins. Epoxy resins include epoxy resins derived from polyhydric phenols such as hydroquinone and catechol and epihalohydrins.

Examples of the rosin resin include natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

In the dispersion, the content (solid content) of the microfibrillated vegetable fibers is 1 to 30 parts by mass based on 100 parts by mass of the oil. By dispersing microfibrillated plant fibers in oil at such a ratio, the effect of dispersing microfibrillated plant fibers in oil can be sufficiently obtained, and the effects of using microfibrillated plant fibers can also be obtained. The effect of the present invention can be sufficiently obtained. The content is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. Further, it is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 7 parts by mass or less.

The content of the oil in the dispersion is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more based on 100% by mass of the dispersion. It is preferably at least 80% by mass, particularly preferably at least 90% by mass. Further, it is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. When the oil content in the dispersion is within this range, the effects of the present invention can be more suitably achieved.

The content (solid content) of the microfibrillated plant fibers in the dispersion is preferably 1% by mass or more, more preferably 2% by mass or more based on 100% by mass of the dispersion. Further, the content is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass or less. When the content of microfibrillated plant fibers in the dispersion is within this range, the effects of the present invention can be more suitably obtained.

In the rubber composition, the content of the dispersion per 100 parts by mass of the rubber component is 3 to 20 parts by mass. By blending the above-mentioned dispersion in such a content, the above-mentioned effects can be obtained. The content is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 12 parts by mass or more, and particularly preferably 15 parts by mass or more.

In the rubber composition, the content (solid content) of the microfibrillated vegetable fibers is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, based on 100 parts by mass of the rubber component. More preferably, the amount is .5 parts by mass or more. Further, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less. When the content of microfibrillated plant fibers in the rubber composition is within this range, the above effects can be more suitably obtained.

In the rubber composition, the content of the oil is preferably 0.9 parts by mass or more, more preferably 4 parts by mass or more, even more preferably 9 parts by mass or more, and 12 parts by mass based on 100 parts by mass of the rubber component. The above is even more preferable, and 13 parts by mass or more is particularly preferable. Further, it is preferably 25 parts by mass or less, more preferably 23 parts by mass or less, and even more preferably 20 parts by mass or less. When the oil content in the rubber composition is within this range, the above effects can be more suitably obtained.

The blending ratio of the dispersion to 100% by mass of acetone extracts such as oil is preferably 30% by mass or more. When the above dispersion is blended in such a blending ratio, the above effect can be more suitably obtained. The blending ratio is more preferably 40% by mass or more, further preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 85% by mass or more. Further, it is preferably 110% by mass or less, more preferably 100% by mass or less, even more preferably 95% by mass or less, even more preferably 90% by mass or less, and particularly preferably 88% by mass or less.
The amount of acetone extract can be measured by the method described in Examples below.

(filler)
The rubber composition includes a filler. A reinforcing effect can be obtained by adding a filler.

Examples of the filler include those commonly used in rubber compositions for tires, such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica. These fillers may be used alone or in combination of two or more. Among them, it is preferable to use carbon black and/or silica as the filler, and it is more preferable to use carbon black, since the effects of the present invention can be obtained more suitably.

Examples of the carbon black include, but are not limited to, N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, and the like. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Nippon Kayaku Carbon Co., Ltd., and Columbia Carbon Co., Ltd. can. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 m ² /g or more, more preferably 35 m ² /g or more. By setting it above the lower limit, good rubber strength and fuel efficiency tend to be obtained. Further, the N ₂ SA is preferably 150 m ² /g or less, more preferably 120 m ² /g or less. By setting the amount below the upper limit, good dispersion of carbon black tends to be obtained.
Note that the nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

Examples of the silica include dry process silica (anhydrous silica), wet process silica (hydrated silica), and the like. Among these, wet process silica is preferred because it has a large number of silanol groups. As commercially available products, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of the silica is preferably 70 m ² /g or more, more preferably 140 m ² /g or more, even more preferably 160 m ² /g or more. By setting it above the lower limit, good rubber strength and fuel efficiency tend to be obtained. Further, the upper limit of N ₂ SA of silica is not particularly limited, but is preferably 500 m ² /g or less, more preferably 300 m ² /g or less, and still more preferably 250 m ² /g or less. By setting the amount below the upper limit, good dispersibility tends to be obtained.
Note that the N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

The content of the filler is 20 to 55 parts by mass based on 100 parts by mass of the rubber component. Within the above range, the effects of the present invention can be sufficiently achieved, and particularly good fuel efficiency can be achieved. The content is preferably 25 parts by mass or more, more preferably 35 parts by mass or more, still more preferably 40 parts by mass or more. Moreover, it is preferably 50 parts by mass or less.

In particular, when carbon black is used as the filler, the content of carbon black is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 35 parts by mass or more, based on 100 parts by mass of the rubber component. , and even more preferably 40 parts by mass or more. By setting it above the lower limit, good rubber strength, fuel efficiency, etc. tend to be obtained. Moreover, the said content becomes like this. Preferably it is 55 parts by mass or less, More preferably, it is 50 parts by mass or less. When the amount is below the upper limit, good kneading processability of the rubber composition tends to be obtained.

In addition, especially when silica is used as the filler, the content of silica is preferably 25 parts by mass or more, more preferably 35 parts by mass or more, still more preferably 40 parts by mass or more, based on 100 parts by mass of the rubber component. It is. By setting it above the lower limit, good rubber strength and fuel efficiency tend to be obtained. The upper limit of the content is not particularly limited, but is preferably 55 parts by mass or less, more preferably 50 parts by mass or less. By setting the amount below the upper limit, good dispersibility tends to be obtained.

(Silane coupling agent)
When the rubber composition contains silica, it is preferable that it further contains a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, 3- Sulfide types such as triethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, mercapto types such as NXT and NXT-Z manufactured by Momentive, vinyltriethoxysilane, and vinyl triethoxysilane. Vinyl type such as methoxysilane, amino type such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, glycidoxy such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc. Examples include nitro types such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloro types such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Kasei Kogyo Co., Ltd., Azumax Co., Ltd., Toray Dow Corning Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, based on 100 parts by mass of silica. When the amount is 3 parts by mass or more, good breaking strength etc. tend to be obtained. Moreover, the said content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When the amount is 20 parts by mass or less, effects commensurate with the amount blended tend to be obtained.

The rubber composition may contain a plasticizer other than the oil. Other plasticizers include, but are not particularly limited to, liquid polymers (liquid diene polymers), liquid resins, and the like. These plasticizers may be used alone or in combination of two or more.

The liquid polymer (liquid diene polymer) is a diene polymer that is in a liquid state at room temperature (25° C.).
The liquid diene polymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) of 1.0×10 ³ to 2.0×10 ⁵ as measured by gel permeation chromatography (GPC); 3. More preferably, it is 0×10 ³ to 1.5×10 ⁴ .
In this specification, the Mw of the liquid diene polymer is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

Examples of liquid diene-based polymers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), etc. It will be done.

The liquid resin is not particularly limited, and examples thereof include liquid aromatic vinyl polymers, coumaron indene resins, indene resins, terpene resins, rosin resins, and hydrogenated products thereof.

Liquid aromatic vinyl polymer is a resin obtained by polymerizing α-methylstyrene and/or styrene, and includes a styrene homopolymer, an α-methylstyrene homopolymer, and a combination of α-methylstyrene and styrene. Examples include liquid resins such as copolymers.

Liquid coumaron indene resin is a resin containing coumaron and indene as main monomer components constituting the skeleton (main chain) of the resin, and other monomer components that may be included in the skeleton besides coumaron and indene are Examples include liquid resins such as , styrene, α-methylstyrene, methylindene, and vinyltoluene.

Liquid indene resin is a liquid resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

Liquid terpene resins are resins obtained by polymerizing terpene compounds such as α-pinene, β-pinene, camphor, and dipetene, and liquid terpene resins such as terpene phenols, which are resins obtained using terpene compounds and phenolic compounds as raw materials. It is a terpene resin.

The liquid rosin resin is a liquid rosin resin typified by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, or hydrogenated products thereof.

A solid resin (a polymer that is solid at room temperature (25° C.)) may be blended into the rubber composition.

When containing a solid resin, the content thereof is preferably 1 part by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. Further, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 20 parts by mass or less. Within the above range, the effects of the present invention can be more suitably obtained.

Examples of solid resins include, but are not limited to, solid styrene resins, coumaron indene resins, terpene resins, pt-butylphenol acetylene resins, acrylic resins, and dicyclopentadiene resins (DCPD resins). , C5 petroleum resin, C9 petroleum resin, C5C9 petroleum resin and the like. These may be used alone or in combination of two or more.

The solid styrene-based resin is a solid polymer using a styrene-based monomer as a constituent monomer, and includes polymers polymerized with a styrene-based monomer as a main component (50% by mass or more). Specifically, styrenic monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, Homopolymers of o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), copolymers of two or more styrene monomers, and styrene monomers. and copolymers of other monomers that can be copolymerized therewith.

Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, acrylics, unsaturated carboxylic acids such as methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, chloroprene, and butadiene. Examples include dienes such as isoprene; olefins such as 1-butene and 1-pentene; α,β-unsaturated carboxylic acids such as maleic anhydride, or acid anhydrides thereof; and the like.

Among these, solid α-methylstyrene resins (α-methylstyrene homopolymer, copolymers of α-methylstyrene and styrene, etc.) are preferred.

Examples of the solid coumaron indene resin include solid resins having the same structural units as the liquid coumaron indene resin described above.

Examples of solid terpene resins include polyterpenes, terpene phenols, aromatic modified terpene resins, and the like.
Polyterpenes are resins obtained by polymerizing terpene compounds and hydrogenated products thereof. Terpene compounds are hydrocarbons and their oxygen-containing derivatives represented by the composition (C ₅ H ₈ ) _n , including monoterpenes (C ₁₀ H ₁₆ ), sesquiterpenes (C ₁₅ H ₂₄ ), and diterpenes (C ₂₀ H _{32 )} . ) and other compounds whose basic skeletons are terpenes, such as α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, and terpinolene. , 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, and the like.

Solid polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene/limonene resin made from the above-mentioned terpene compounds, as well as hydrogenated terpene resins. Also included are solid resins such as treated hydrogenated terpene resins.

Examples of solid terpene phenols include solid resins obtained by copolymerizing the above-mentioned terpene compounds and phenolic compounds, and solid resins obtained by hydrogenating the above-mentioned resins. Examples include solid resins made by condensing formalin. Note that examples of the phenolic compound include phenol, bisphenol A, cresol, xylenol, and the like.

Examples of solid aromatic modified terpene resins include solid resins obtained by modifying terpene resins with aromatic compounds, and solid resins obtained by hydrogenating the resins. The aromatic compound is not particularly limited as long as it has an aromatic ring, but examples include phenol compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol, alkylnaphthol, alkoxynaphthol, Naphthol compounds such as unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumaron, indene, and the like.

Examples of the solid pt-butylphenol acetylene resin include solid resins obtained by subjecting pt-butylphenol and acetylene to a condensation reaction.

Although the solid acrylic resin is not particularly limited, a solvent-free acrylic solid resin can be suitably used since it contains few impurities and can yield a resin with a sharp molecular weight distribution.

Solid solvent-free acrylic resin is produced using a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (U.S. Patent No. 4,414) without using as many auxiliary materials as polymerization initiators, chain transfer agents, and organic solvents. , 370 specification, JP-A-59-6207, JP-A-5-58005, JP-A-1-313522, U.S. Patent No. 5,010,166, Toagosei Research Annual Report TREND 2000 No. 3 Examples include (meth)acrylic resins (polymers) synthesized by the method described in No. 42-45, etc. In addition, in this specification, (meth)acrylic means methacryl and acrylic.

It is preferable that the solid acrylic resin does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, etc., which serve as auxiliary raw materials. The acrylic resin preferably has a relatively narrow composition distribution and molecular weight distribution obtained by continuous polymerization.

As mentioned above, the solid acrylic resin is preferably one that does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, etc. as auxiliary raw materials, that is, one that has high purity. The purity of the solid acrylic resin (the proportion of resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

Examples of monomer components constituting the solid acrylic resin include (meth)acrylic acid, (meth)acrylic esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic esters. Examples include (meth)acrylic acid derivatives such as acrylamide derivatives.

In addition to (meth)acrylic acid and (meth)acrylic acid derivatives, monomer components constituting solid acrylic resins include styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, divinyl Aromatic vinyls such as naphthalene may also be used.

The solid acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component.
Furthermore, the solid acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, and the like.

Other plasticizers and solid resins include, for example, Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, and Nichijo Chemical ( Products from Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Corporation, Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. can be used.

The rubber composition preferably contains an anti-aging agent from the viewpoint of crack resistance, ozone resistance, etc.

The anti-aging agent is not particularly limited, but includes naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents 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, N,N'-di-2-naphthyl-p-phenylene p-phenylenediamine type anti-aging agents such as diamines; quinoline type anti-aging agents such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methyl Monophenolic anti-aging agents such as phenol and styrenated phenol; bis, tris, and polyphenols such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane; Examples include anti-aging agents. Among these, p-phenylenediamine-based antiaging agents and quinoline-based antiaging agents are preferred, including N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred. As commercially available products, for example, products manufactured by Seiko Kagaku Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis Co., Ltd., etc. can be used.

The content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, based on 100 parts by mass of the rubber component. By setting the value above the lower limit, sufficient ozone resistance tends to be obtained. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less. By keeping it below the upper limit, a good appearance tends to be obtained.

The rubber composition preferably contains stearic acid. From the viewpoint of the performance balance, the content of stearic acid is preferably 0.5 to 10 parts by mass or more, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the rubber component.

As the stearic acid, conventionally known ones can be used; for example, products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. are used. can.

The rubber composition preferably contains zinc oxide. From the viewpoint of the performance balance, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the rubber component.

As the zinc oxide, conventionally known zinc oxides can be used, such as those manufactured by Mitsui Kinzoku Mining Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. products can be used.

The rubber composition may contain wax. The wax is not particularly limited, and includes petroleum waxes, natural waxes, etc. Synthetic waxes obtained by refining or chemically processing multiple waxes can also be used. These waxes may be used alone or in combination of two or more.

Examples of petroleum waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are waxes derived from resources other than petroleum; for example, vegetable waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; beeswax, lanolin, spermaceti wax, etc. animal waxes; mineral waxes such as ozokerite, ceresin, and petrolactam; and purified products thereof. As commercially available products, for example, products manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used. Note that the wax content may be appropriately set from the viewpoint of ozone resistance and cost.

Sulfur is preferably blended into the rubber composition from the standpoint of forming appropriate crosslinks in the polymer chains and imparting good overall performance.

The content of sulfur is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 0.7 parts by mass or more, based on 100 parts by mass of the rubber component. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, still more preferably 3.0 parts by mass or less. By keeping it within the above range, there is a tendency for good overall performance to be obtained.

Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, soluble sulfur, etc. commonly used in the rubber industry. As commercially available products, products manufactured by Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis, Nippon Kanditsu Kogyo Co., Ltd., Hosoi Chemical Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The rubber composition preferably contains a vulcanization accelerator.
The content of the vulcanization accelerator is not particularly limited and may be determined freely according to the desired vulcanization rate and crosslinking density, but it is usually 0.3 to 10 parts by mass per 100 parts by mass of the rubber component. , preferably 0.5 to 7 parts by mass.

The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of vulcanization accelerators include thiazole vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; tetramethylthiuram disulfide (TMTD); ), thiuram-based vulcanization accelerators such as tetrabenzylthiuram disulfide (TBzTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); N-cyclohexyl-2-benzothiazolesulfenamide, N-t-butyl- 2-Benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide, etc. Examples include sulfenamide vulcanization accelerators; guanidine vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more. Among these, from the viewpoint of the overall performance, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

In addition to the above-mentioned components, the rubber composition may also contain appropriate additives such as release agents and pigments, which are commonly used in applications depending on the field of application.

The rubber composition can be produced by a known method, for example, by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the composition. .

As for the kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, the kneading temperature is usually 50 to 200°C, preferably 80 to 190°C, and the kneading time is usually 30°C. The time is from seconds to 30 minutes, preferably from 1 minute to 30 minutes. In the final kneading step of kneading the vulcanizing agent and vulcanization accelerator, the kneading temperature is usually 100°C or less, preferably room temperature to 80°C. Further, a composition obtained by kneading a vulcanizing agent and a vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200°C, preferably 140 to 180°C.

The above rubber composition can be used for tires, shoe sole rubber, floor rubber, anti-vibration rubber, seismic isolation rubber, butyl frame rubber, belts, hoses, packing, medicine plugs, and other rubber industrial products. In particular, it is preferable to use it as a rubber composition for tires because it has excellent overall performance of rubber strength, fuel efficiency, and kneading processability.

The above tire rubber composition is suitably used for sidewalls, but also for tire members other than sidewalls, such as tread (cap tread), base tread, undertread, clinch apex, bead apex, breaker cushion rubber, It may be used for carcass cord covering rubber, insulation, chafer, inner liner, etc., and for side reinforcing layers of run-flat tires.

The above rubber composition can be suitably used for pneumatic tires. The pneumatic tire described above is manufactured by a conventional method using the rubber composition described above. In other words, a rubber composition mixed with various materials as necessary is extruded to match the shape of tire components such as sidewalls at an unvulcanized stage, and then processed together with other tire components on a tire molding machine. After forming an unvulcanized tire by the method described above, it is possible to manufacture a tire by heating and pressurizing it in a vulcanizer. By manufacturing a tire using the rubber composition in this manner, a pneumatic tire manufactured using the rubber composition can be obtained.

The above pneumatic tires can be suitably used as tires for passenger cars, tires for large passenger cars, tires for large SUVs, tires for heavy loads such as trucks and buses, tires for light trucks, tires for motorcycles, run-flat tires, and competition tires. It is. In particular, it can be used more suitably as a passenger car tire.

The present invention will be specifically explained based on examples, but the present invention is not limited to these examples.

Below, various chemicals used in Examples and Comparative Examples will be collectively explained.
Microfibrillated plant fiber: Biomass nanofiber manufactured by Sugino Machine Co., Ltd. (product name "BiNFi-s Cellulose", solid content: 2% by mass, moisture: 98% by mass, average fiber diameter: 10 to 50 nm, average fiber length) :2~5μm)
Oil: Soybean oil manufactured by Nisshin Oilio Co., Ltd. (Each property is shown in Table 1. The content of fatty acids in Table 1 is the content (mass%) of each fatty acid in 100% by mass of the constituent fatty acids. means.)
TEMPO: 2,2,6,6-tetramethylpiperidine-1-oxyl Sodium bromide: Fujifilm Wako Pure Chemical Industries, Ltd. Sodium hypochlorite: Tokyo Chemical Industry Co., Ltd. NaOH: Fujifilm Wako Pure Chemical Industries, Ltd. NaOH manufactured by Co., Ltd.
NR: Natural rubber, TSR20
BR: Butadiene rubber, BR150B manufactured by Ube Industries, Ltd. (95% by mass or more of cis)
Carbon black: Diablack N550 (N ₂ SA: 41 m ² /g) manufactured by Mitsubishi Chemical Corporation
Zinc oxide: Type 2 zinc oxide manufactured by Mitsui Mining & Mining Co., Ltd. Stearic acid: Camellia anti-aging agent manufactured by NOF Corporation: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Sulfur: Seimi sulfur manufactured by Nippon Karidome Kogyo Co., Ltd. Vulcanization accelerator: Noxel NS manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

<Preparation of dispersion>
(Manufacturing example 1)
1000 g of pure water was added to 500 g of microfibrillated plant fibers to prepare a suspension of 0.5% by mass (solid content concentration) of microfibrillated plant fibers, and a high-speed homogenizer ("T50" manufactured by IKA Japan Co., Ltd., rotating A homogeneous aqueous dispersion was prepared by stirring at a speed of 8,000 rpm for about 5 minutes.
The aqueous dispersion prepared above was added to 100 parts by mass of oil so that the dry weight (solid content) of the microfibrillated plant fibers was 5 parts by mass, and 100 parts by mass of toluene was added to 100 parts by mass of oil. part was added and mixed. A small amount of hydrochloric acid was added to the mixture, and the mixture was heated to 150°C to azeotropically remove water. The mixture after water removal was stirred and mixed for 5 minutes at 50° C. using a high-speed homogenizer (“T50” manufactured by IKA Japan, rotation speed: 8000 rpm) to prepare a dispersion (dispersion 1). The viscosity of Dispersion 1 at 40° C. was measured using a tuning fork vibratory viscometer and was found to be 5000 mPa·s.

(Manufacturing example 2)
After dispersing 10 g of microfibrillated vegetable fibers, 150 mg of TEMPO, and 1000 mg of sodium bromide in 1000 mL of water, a 15% by mass aqueous solution of sodium hypochlorite was added to 1 g of microfibrillated vegetable fibers (bone dry) with hypochlorite. The reaction was started by adding sodium chloride in an amount of 5 mmol. During the reaction, a 3M NaOH aqueous solution was added dropwise to maintain the pH at 10.0. The reaction is considered complete when no change in pH is observed, and the reaction product is filtered through a glass filter, followed by washing with a sufficient amount of water and filtration 5 times to impregnate it with water with a solid content of 15% by mass. A reactant fiber was obtained. Then, water was added to the reactant fibers to form a slurry having a solid content of 1% by mass.
Hydrochloric acid was added dropwise to the oxidized microfibrillated plant fibers (solid content: 1% by mass) to adjust the pH to 2. Thereafter, 0.5 g of hexadecyltrimethylammonium chloride was added to produce aminated microfibrillated plant fibers. The average fiber diameter of the obtained aminated microfibrillated plant fibers was 10 nm, the average fiber length was 2 μm, and the degree of substitution was 0.5.
Here, the aminated microfibrillated plant fibers fixed on the mica section were observed (3000 nm x 3000 nm) using a scanning probe microscope (manufactured by Hitachi High-Tech Science), the fiber widths of 50 fibers were measured, and the average The fiber diameter was calculated. The average fiber length was calculated from the obtained observation image using image analysis software WinROOF (manufactured by Mitani Shoji Co., Ltd.).
Further, the degree of amino substitution of the aminated microfibrillated plant fibers was measured by FTIR (Fourier transform infrared spectrophotometer).

To 100 parts by mass of oil, 5 parts by mass of aminated microfibrillated plant fibers were added in terms of dry weight (solid content) and mixed. The mixture was stirred and mixed at 50° C. for 5 minutes using a high-speed homogenizer (“T50” manufactured by IKA Japan, rotation speed: 8000 rpm) to prepare a dispersion (dispersion 2). The viscosity of Dispersion 2 at 40° C. was measured using a tuning fork vibratory viscometer and was found to be 12,000 mPa·s.

(Manufacturing example 3)
A dispersion (Dispersion 3) was prepared in the same manner as in Production Example 2 , except that 10 parts by mass of the aminated microfibrillated plant fibers were added by dry weight (solid content) to 100 parts by mass of the oil. The viscosity of Dispersion 3 at 40° C. was measured using a tuning fork vibratory viscometer and was found to be 30,000 mPa·s.

(Manufacturing example 4)
A dispersion (Dispersion 4) was prepared in the same manner as in Production Example 2 , except that 1 part by mass of aminated microfibrillated plant fibers was added by dry weight (solid content) to 100 parts by mass of oil. The viscosity of Dispersion 4 at 40° C. was measured using a tuning fork vibratory viscometer and was found to be 6000 mPa·s.

(Manufacturing example 5)
A dispersion (Dispersion 5) was prepared in the same manner as in Production Example 2 , except that 30 parts by mass of aminated microfibrillated plant fibers were added by dry weight (solid content) to 100 parts by mass of oil. The viscosity of Dispersion 5 at 40° C. was measured using a tuning fork vibratory viscometer and was found to be 95,000 mPa·s.

<Preparation of vulcanized rubber composition>
(Example and comparative example)
According to the formulation shown in Table 2, materials other than sulfur and the vulcanization accelerator were kneaded for 4 minutes at 150° C. using a 1.7 L Banbury mixer. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product using an open roll, and the mixture was kneaded at 80° C. for 4 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized at 170° C. for 12 minutes using a 2 mm thick mold to obtain a vulcanized rubber composition.

<Evaluation items and test methods>
The following evaluations were performed on the obtained unvulcanized rubber composition and vulcanized rubber composition. The results are shown in Table 2.

(Amount of acetone extract)
The amount of the substance extracted by acetone contained in the vulcanized rubber composition was measured according to the method for measuring the amount of acetone extracted in accordance with JIS K6229. The amount of the acetone extract serves as an index of the concentration of organic low molecular compounds such as oil and wax contained in the vulcanized rubber composition. Note that JIS K6229 (1998) stipulates two methods, method A and method B, but method A is adopted in this application.

(Kneading processability)
The Mooney viscosity of the unvulcanized rubber composition was measured at 130° C. according to JIS K6300, and the measurement results were expressed as an index using the following formula. The larger the index, the higher the Mooney viscosity and the better the kneading processability.
(Kneading processability) = (Mooney viscosity of each formulation) / (Mooney viscosity of Comparative Example 1) x 100

(rubber strength)
A tensile test was conducted according to JIS K6251 to measure the elongation at break of the vulcanized rubber composition, and the measurement results were expressed as an index using the following formula. The larger the index, the higher the rubber strength and the more excellent the durability.
(Rubber strength) = (Elongation at break of each formulation) / (Elongation at break of Comparative Example 1) x 100

(Fuel efficiency)
The tan δ of the vulcanized rubber composition was measured using a spectrometer manufactured by Uejima Seisakusho Co., Ltd. at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50°C. The measurement results were expressed as an index using the following calculation formula. The larger the index, the lower the rolling resistance and the better the fuel efficiency.
(Fuel efficiency) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Overall performance)
In Table 2, the sum of each index of kneading workability, rubber strength, and fuel efficiency was evaluated as the overall performance.

From Table 2, a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil, containing a rubber component and a filler, the rubber component containing natural rubber, and microfibrillation based on 100 parts by mass of oil. The content of the vegetable fiber is 1 to 30 parts by mass, the content of the dispersion is 3 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and the content of the filler is 20 to 55 parts by mass with respect to 100 parts by mass of the rubber component. In the example shown in Section 1, it was revealed that the overall performance of kneading processability, rubber strength, and fuel efficiency was excellent.

Claims (5)

A rubber composition comprising a dispersion obtained by mixing and dispersing microfibrillated plant fibers and oil, a rubber component, and a filler,
the rubber component contains natural rubber,
the filler contains carbon black and/or silica,
The oil is a plant-derived glycerol fatty acid triester,
The dispersion has a content of the microfibrillated vegetable fibers of 1 to 30 parts by mass based on 100 parts by mass of the oil,
The content of the dispersion per 100 parts by mass of the rubber component is 3 to 20 parts by mass,
A rubber composition characterized in that the content of the filler is 20 to 55 parts by mass based on 100 parts by mass of the rubber component. The rubber composition according to claim 1 , wherein the blending ratio of the dispersion is 30% by mass or more based on 100% by mass of the acetone extract. The rubber composition according to claim 1 or 2, wherein the glycerol fatty acid triester satisfies the following formula (A).
80≦Content of monounsaturated fatty acids having 1 unsaturated bond in 100% by mass of constituent fatty acids (mass%) x 1 (number of unsaturated bonds) + 2 unsaturated bonds in 100% by mass of constituent fatty acids Content of diunsaturated fatty acids (mass %) × 2 (number of unsaturated bonds) + content of trivalent unsaturated fatty acids having 3 unsaturated bonds (mass %) in 100 mass % of constituent fatty acids × 3 (Number of unsaturated bonds)≦200 Formula (A) The microfibrillated plant fibers have an average fiber diameter of 3 to 200 nm and an average fiber length of 0.3 to 10 μm, and the dispersion has a viscosity of 1000 to 100000 mPa·s at 40° C. The rubber composition according to any one of. A pneumatic tire produced using the rubber composition according to any one of claims 1 to 4.