JP6689082B2 - Rubber composition for oil seal - Google Patents

Description

  The present invention relates to a rubber composition for oil seals.

  The oil seal prevents fluids such as lubricating oil, water, chemicals, and gas from leaking through the gaps at the end of the rotary shaft of mechanical products such as automobile engines and geared motors, and also allows dust and dirt to enter from the outside. Used to prevent In addition to automobiles, it is used as a sealing device for machines in various fields such as aircrafts, ships, railway vehicles, construction machinery, agricultural machinery, petrochemical plants, and home appliances.

  As a structure of an oil seal, usually, a rubber that constitutes a seal lip is baked and adhered to a metal ring, and a built-in spring appropriately holds the shaft, so that a moving part can be sealed.

The properties required of rubber compositions for oil seals are usually oil resistance, mechanical strength (tensile strength, wear resistance, etc.), heat resistance, cold resistance, ozone resistance, water resistance, solvent resistance, acid resistance. , Alkali resistance, chemical resistance and the like. Further, in the manufacturing process, workability is required such that the Mooney viscosity at the time of kneading is not too high and the vulcanization rate is sufficiently fast within an appropriate range. Appropriate rubber components and additives are blended depending on the required performance, processability, cost and the like.
Among the above performances required for a rubber composition for an oil seal, a method of blending carbon black or silica with rubber is generally known as a method of improving mechanical strength. For example, in Patent Document 1, by blending carbon black having a DBP oil absorption amount within a certain range with hydrogenated nitrile rubber, it is possible to provide a seal member having appropriate hardness and excellent moldability and wear resistance. It is said that.

  As another method, Patent Document 2 discloses a method in which powdered cellulose is blended as a filler with nitrile rubber. According to this method, the tensile strength is improved, and by blending powdered cellulose produced from plant raw materials, petroleum-based materials are reduced, and combustion residues do not occur during incineration treatment, so that the waste is discarded. It is said that it will be possible to reduce goods.

Special WO12-070677 JP-A-2003-336745

However, in the method of Patent Document 1, although the tensile strength and the wear resistance are improved, if the compounding amount of the filler such as carbon black or silica is too large, the specific gravity of the rubber composition increases, so that the energy efficiency is increased. In addition to the decrease, the Mooney viscosity of the rubber when unvulcanized increases and the processability decreases. Therefore, there is an upper limit to the amount that can be blended. Further, although the method of Patent Document 2 certainly improves the tensile strength and the wear resistance, there is still room for improvement. Therefore, the present invention provides a rubber for an oil seal having sufficient mechanical strength (tensile strength, wear resistance), low specific gravity, and suppressing an increase in Mooney viscosity during unvulcanization in the manufacturing process. It is intended to provide a composition.

The present invention provides the following (1) to (7).
(1) A rubber composition for an oil seal, comprising the following components A, B and C.
Component A: Rubber component Component B: Filler containing at least one selected from carbon black, silica and powdery cellulose
Component C: Cellulose nanofiber (2) The compounding ratio of the following component A, component B, and component C is A: B: C = 100: 5 to 100: 1 to 50 (mass%). The rubber composition for an oil seal according to (1).
(3) The rubber composition for oil seals according to any one of (1) and (2), wherein the rubber component (component A) contains nitoacrylonitrile-butadiene rubber.
(4) The rubber composition for oil seals according to any one of (1) to (3), wherein the rubber component (component A) contains ethylene-propylene rubber.
(5) The cellulose nanofiber (component C) contains an oxidized cellulose nanofiber in which a part of the hydroxyl group at the C6 position in the glucose unit of cellulose is oxidized to a carboxyl group, and the carboxyl group of the oxidized cellulose nanofiber is The amount is 0.1 mmol / g to 3.0 mmol / g with respect to the absolute dry weight of the oxidized cellulose nanofibers, (1) to (4) according to any one of the oil seals. Rubber composition.
(6) The cellulose nanofiber (component C) contains carboxymethylated cellulose nanofiber in which a part of hydrogen atoms of a hydroxyl group in a glucose unit of cellulose is replaced with a carboxymethyl group, and carboxymethylated cellulose nanofiber The rubber composition for oil seals according to any one of (1) to (4), wherein the degree of carboxymethyl substitution per glucose unit of the fiber is 0.01 to 0.50.
(7) The cellulose nanofiber (component C) contains a cationized cellulose nanofiber in which a part of hydrogen atoms of a hydroxyl group in a glucose unit of cellulose is replaced with a cationic group, and glucose of the cationized cellulose nanofiber is included. The degree of cation substitution per unit is 0.01 to 0.40, the rubber composition for oil seals according to (1) to (4).

According to the present invention, a rubber for an oil seal having sufficient mechanical strength (tensile strength, abrasion resistance), low specific gravity, and suppressing an increase in Mooney viscosity during unvulcanization in the manufacturing process. A composition can be provided.

  The rubber composition for an oil seal of the present invention is characterized by containing at least component A: a rubber component, component B: carbon black and / or silica, and component C: cellulose nanofibers. Hereinafter, each of these components (materials) and a method for producing a rubber composition containing them will be described in detail.

[Component A: Rubber component]
The rubber component is usually a component containing an organic polymer as a main component and having a high elastic limit and a low elastic modulus. The rubber component is roughly classified into natural rubber and synthetic rubber, but in the present invention, either may be used, or a combination of both may be used.
Natural rubber may be a natural rubber in a narrow sense without chemical modification, and natural rubber such as chlorinated natural rubber, chlorosulfonated natural rubber, epoxidized natural rubber, hydrogenated natural rubber, and deproteinized natural rubber. May be chemically modified.
Examples of the synthetic rubber include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), styrene- Diene rubbers such as isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydrin rubber ( CO, ECO), fluororubber (FKM), silicone rubber (Q), urethane rubber (U) and chlorosulfonated polyethylene (CSM). Among these, acrylonitrile-butadiene rubber (NBR) or ethylene-propylene rubber (EPM, EPDM) is particularly preferable. Due to the polymer structure, acrylonitrile-butadiene rubber (NBR) has improved heat resistance and oil resistance when the acrylonitrile group is increased, and cold resistance is improved when the butadiene group is increased. Therefore, by changing the copolymerization ratio, heat resistance and cold resistance can be improved. The oil resistance can be widely changed. In addition, since ethylene-propylene rubber (EPM, EPDM) does not have a double bond in the polymer molecular chain, it has excellent properties in ozone resistance and heat resistance. It also exhibits excellent resistance to polar solutions such as steam resistance, cold resistance, and LLC resistance.
As the acrylonitrile-butadiene rubber (NBR), any of medium nitrile content (CN: 25 to 30%), medium high nitrile content (CN: 31 to 35%) and high nitrile content (CN: 36 to 42%) is used. However, those having a medium to high nitrile content are particularly preferable.
The rubber component may be a single type or a combination of two or more types. The rubber component may be solid or liquid. Examples of the liquid rubber component include a rubber component dispersion liquid and a rubber component solution. Examples of the solvent include water and organic solvents.

[Component B: Filler (carbon black, silica, powdered cellulose)]
In the present invention, in order for the rubber composition for oil seals to obtain sufficient tensile strength and abrasion resistance, it is important to contain a filler containing at least one selected from carbon black, silica and powdered cellulose. . The compounding amount of the filler is 5 to 100% by mass, more preferably 20 to 60%, and further preferably 30 to 45% by mass based on 100% by mass of the rubber component. If it is less than 5% by mass, sufficient mechanical strength and abrasion resistance cannot be obtained, and if it is more than 100% by mass, the Mooney viscosity in the unvulcanized state in the manufacturing process is excessively increased, resulting in poor processability. Further, other fillers can be used together within the range that does not impair the effects of the present invention.
The details of carbon black and silica will be described below.

[Component B-1: Carbon black]
In the present invention, carbon black is fine particles of carbon having a diameter of about 3-500 nm, which are manufactured by industrially controlling the quality. In addition, those having a property of being well compatible with rubber by controlling the functional groups on the particle surface are also included. As a method for producing carbon black, generally, a thermal method, an acetylene decomposition method, a contact method, a lamp / pine smoke method, a gas furnace method, an oil furnace method, etc. can be mentioned. A carbon black having characteristics such as the agglomeration structure (structure) of is produced. In the present invention, the type of carbon black is not particularly limited, and it is preferable to select and use the most suitable carbon black in order to exert a desired effect.

[Component B-2: Silica]
In the present invention, silica is a general term for silicon dioxide (SiO2) or a substance composed of silicon dioxide. In addition to the name silica, it is sometimes called silicic acid anhydride, silicic acid, or silicon oxide.
Examples of the type of silica that can be used in the present invention include natural silica and synthetic silica (precipitated silica, dry silica, wet silica), and are not particularly limited. For example, tire fillers The silica used as can be used.

  By treating the surface of silica with a silane coupling agent, the affinity for various rubbers is improved. Therefore, in the present invention, it is preferable to treat silica with 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. Sulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, Bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis ( 4-tri Toxysilylbutyl) 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, 3-triethoxysilylpropyl-N, N -Dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyltetrasulfide, -Trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide and other sulfides, 3-mercapto Propyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and other mercapto-based compounds, vinyltriethoxysilane, vinyltrimethoxysilane and other vinyl-based compounds, 3-amino Propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) Amino) aminopropyltrimethoxysilane, etc., γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyl Glycidoxy-based compounds such as dimethoxysilane, 3-nitropropyltrimethoxysilane, nitro-based compounds such as 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane , 2-chloroethyltriethoxysilane and other chloro-based compounds. These may be used alone or in combination of two or more.

[Component B-3: Powdered cellulose]
In the present invention, powdery cellulose is fine particles that can be obtained by pulverizing pulp that has been subjected to acid hydrolysis treatment with a mineral acid such as hydrochloric acid, sulfuric acid, or nitric acid, or by mechanically pulverizing pulp that has not been subjected to acid hydrolysis treatment. is there.

  The average particle size is preferably 20 to 50 μm, more preferably 15 to 50 μm, and further preferably 22 to 36 μm. If the average particle size is large, the rubber hardness becomes high and the mechanical properties deteriorate. On the other hand, when the average particle size is small, the moldability is improved, but the effect of reinforcing mechanical properties is reduced.

  The degree of polymerization is preferably 150 to 1200, more preferably 400 to 800. If the degree of polymerization is high, the rubber hardness will be high and the mechanical properties will be poor. On the other hand, when the degree of polymerization is low, the effect of reinforcing the mechanical properties becomes small.

  The crystallinity is preferably 70 to 90, more preferably 80 to 90. The crystallinity of the powdery cellulose is mainly affected by the raw material pulp and the manufacturing method, and the powdery cellulose produced only by mechanical treatment without acid treatment has a low crystallinity. When the crystallinity is low, the time required for heat vulcanization is long and workability deteriorates. When the crystallinity is 80 or more, the influence on the vulcanization rate is hardly permanent.

  The apparent specific gravity is preferably 0.2 to 0.6 g / ml, more preferably 0.3 to 0.45. If the apparent specific gravity is less than 0.2, the powder is bulky and does not mix well when kneading with rubber or the like, causing poor dispersion. When the apparent specific gravity exceeds 0.6, the powder has a low bulk and is compact, so that the dispersibility is good, but the average particle diameter of the powder is small, so that the effect of reinforcing the mechanical properties is small.

  The angle of repose is preferably 45 to 60 °, more preferably 48 to 56 °. If the angle of repose exceeds 60 °, the powder fluidity is poor, which is not preferable in terms of work. If the angle of repose is less than 45 °, the powder dropping speed is high, but on the other hand, the powder is extremely sloppy, which is not preferable in terms of work.

The water content is preferably 5% or less, more preferably 3% or less. When the water content of the powdery cellulose is high, it causes vulcanization delay when the rubber is heated and vulcanized. In addition, the mechanical properties after molding are also adversely affected.

[C: Cellulose Nanofiber]
In the present invention, the cellulose nanofibers are fine fibers obtained by subjecting a cellulose raw material to a chemical modification treatment, if necessary, followed by defibration and, if necessary, drying treatment. The average fiber diameter of cellulose nanofibers is usually about 2 to 500 nm. The average fiber diameter and the average fiber length are measured, for example, by preparing a 0.001% by mass aqueous dispersion of cellulose nanofibers, thinly diluting the diluted dispersion on a mica sample stand, and heating and drying at 50 ° C. for observation. It is possible to calculate the number average fiber diameter or the fiber length by preparing a sample for use and measuring the cross-sectional height of the shape image observed with an atomic force microscope (AFM).

The average aspect ratio of cellulose nanofibers is usually 50 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula. Aspect ratio = average fiber length / average fiber diameter In the present invention, by blending cellulose nanofibers with the rubber component, sufficient tensile strength and durability can be obtained while keeping the blending amount of carbon black and silica within a certain range. Wearability can be obtained.

The content of cellulose nanofibers in the rubber composition is preferably 1 to 50% by mass or more, more preferably 1 to 40% by mass or more, and further preferably 1 to 30% by mass or more in terms of solid content relative to 100% by mass of the rubber component. preferable. If it is less than 1% by mass, a sufficient effect cannot be obtained, and if it is more than 50% by mass, the Mooney viscosity at the time of unvulcanization increases in the manufacturing process, resulting in poor processability.
The raw materials of cellulose nanofibers and the manufacturing process will be described in detail below.

[C-1: Cellulose raw material]
The origin of the cellulose raw material that is the raw material of the cellulose nanofibers is not particularly limited, and examples thereof include plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural land waste, cloth and pulp (soft bleached unbleached kraft pulp (NUKP)). , Softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulphite pulp (NUSP), softwood bleached sulphite pulp (NBSP) thermomechanical pulp (TMP) , Recycled pulp, waste paper, etc.), animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (acetobacter)), microbial products, etc. The cellulose raw material used in the present invention is any of these. It may be a combination of two or more kinds, but preferably Mono or microbial origin cellulosic material (e.g., cellulosic fibers), more preferably a cellulose material of plant origin (e.g., cellulose fibers).

  The number average fiber diameter of the cellulose raw material is not particularly limited, but it is about 30 to 60 μm in the case of a softwood kraft pulp, which is a general pulp, and about 10 to 30 μm in the case of a hardwood kraft pulp. In the case of other pulps, those that have undergone general refining have a size of about 50 μm. For example, when a chip or the like having a size of several cm is purified, it is preferable to perform mechanical treatment with a disintegrator such as a refiner or beater to adjust the size to about 50 μm.

[C-2: Modified]
The cellulose raw material has three hydroxyl groups per glucose unit and can be subjected to various chemical modification treatments. In the present invention, these may or may not be modified, but the chemical modification treatment may exert sufficient reinforcing properties when incorporated into the rubber composition. preferable. The reason is that the modification of the cellulose raw material sufficiently promotes the miniaturization of the fibers, and a uniform fiber length and fiber diameter can be obtained. In addition, it is possible to secure a sufficient number of fibers having a fiber length and a fiber diameter effective for exerting the reinforcing property.

In the present invention, the modification method is not particularly limited, and examples thereof include oxidation (carboxylation), etherification, phosphorylation, esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation), etherification, cationization, and esterification are preferable. The cellulose nanofiber contained in the rubber composition for oil seals may be a single cellulose nanofiber or a combination of two or more modified cellulose nanofibers.
Hereinafter, detailed methods of oxidation, etherification, cationization, and esterification will be described.

[C-2-1: Oxidation]
When the cellulose raw material is modified by oxidation, the amount of carboxyl groups with respect to the absolute dry weight of the obtained oxidized cellulose or cellulose nanofibers is preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, and further preferably It is 1.0 mmol / g or more. The upper limit is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, still more preferably 2.0 mmol / g or less. Therefore, 0.5 mmol / g to 3.0 mmol / g is preferable, 0.8 mmol / g to 2.5 mmol / g is more preferable, and 1.0 mmol / g to 2.0 mmol / g is further preferable.

  The method of oxidation is not particularly limited, but as one example, N-oxyl compound and cellulose in water using an oxidizing agent in the presence of a substance selected from the group consisting of bromide, iodide or a mixture thereof. Examples include a method of oxidizing the raw material. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized, and a group selected from the group consisting of an aldehyde group, a carboxyl group and a carboxylate group is produced. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by mass or less.

  The N-oxyl compound means a compound capable of generating a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction.

  The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable, and 0.02 mmol or more is more preferable with respect to 1 g of absolutely dried cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, still more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, still more preferably 0.02 to 0.5 mmol, per 1 g of absolutely dry cellulose.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromide capable of dissociating and ionizing in water, such as sodium bromide. Further, iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used may be selected within a range that can accelerate the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, based on 1 g of absolutely dried cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and further preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, still more preferably 0.5 to 5 mmol, per 1 g of absolutely dried cellulose.

  The oxidizing agent is not particularly limited, and examples thereof include halogen, hypohalous acid, halogenous acid, perhalogenic acid, salts thereof, halogen oxides, peroxides and the like. Of these, hypohalous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable, because it is inexpensive and has a low environmental load. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, still more preferably 3 mmol or more, based on 1 g of absolutely dried cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, further preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol per 1 g of absolutely dry cellulose. When the N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more per 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol per 1 mol of the N-oxyl compound.

  Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and generally, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C or higher, more preferably 15 ° C or higher. The upper limit is preferably 40 ° C or lower, more preferably 30 ° C or lower. Therefore, the temperature is preferably 4 to 40 ° C., and may be about 15 to 30 ° C., that is, room temperature. The pH of the reaction solution is preferably 8 or higher, more preferably 10 or higher. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably 8 to 12, more preferably 10 to 11. Usually, a carboxyl group is generated in cellulose as the oxidation reaction progresses, so that the pH of the reaction solution tends to decrease. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous solution of sodium hydroxide to maintain the pH of the reaction solution in the above range. Water is preferable as the reaction medium for the oxidation because it is easy to handle and side reactions are unlikely to occur.

  The reaction time in oxidation can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours or more. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually 0.5 to 6 hours, for example, 0.5 to 4 hours.

  The oxidation may be carried out in two or more steps. For example, by oxidizing the oxidized cellulose obtained by filtering after the completion of the first step reaction again under the same or different reaction conditions, the reaction efficiency due to the salt by-produced in the first step reaction is not affected. Can be well oxidized.

  Another example of the carboxylation (oxidation) method is a method of oxidizing by ozone treatment. This oxidation reaction oxidizes at least the hydroxyl groups at the 2nd and 6th positions of the glucopyranose ring constituting the cellulose and causes the decomposition of the cellulose chain. Ozone treatment is usually performed by bringing a gas containing ozone into contact with a cellulose raw material. The ozone concentration in the gas is preferably 50 g / m3 or more. The upper limit is preferably 250 g / m3 or less, more preferably 220 g / m3 or less. Therefore, the ozone concentration in the gas is preferably 50 to 250 g / m3, and more preferably 50 to 220 g / m3. The amount of ozone added is preferably 0.1 part by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the solid content of the cellulose raw material. The upper limit is usually 30 mass% or less. Therefore, the amount of ozone added is preferably 0.1 to 30% by mass, and more preferably 5 to 30% by mass, based on 100% by mass of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C or higher, preferably 20 ° C or higher. The upper limit is usually 50 ° C or lower. Therefore, the ozone treatment temperature is preferably 0 to 50 ° C, more preferably 20 to 50 ° C. The ozone treatment time is usually 1 minute or longer, preferably 30 minutes or longer. The upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of the ozone treatment are within the above range, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of the oxidized cellulose will be good.

  The resulting product obtained after the ozone treatment may be subjected to additional oxidation treatment using an oxidant. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples thereof include chlorine-based compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. Examples of the counteroxidation method include a method in which these oxidizing agents are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the cellulose raw material is dipped in the oxidizing agent solution.

  The amounts of the carboxyl group, carboxylate group and aldehyde group contained in the oxidized cellulose nanofibers can be adjusted by controlling the oxidizing conditions such as the addition amount of the oxidizing agent and the reaction time.

An example of the method for measuring the amount of carboxyl groups will be described below. After preparing 60 ml of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose and adding 0.1 M hydrochloric acid aqueous solution to pH 2.5, 0.05 N sodium hydroxide aqueous solution was added dropwise to adjust the pH to 11. Measure electrical conductivity until It can be calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of a weak acid with a gradual change in electrical conductivity using the following formula:
Amount of carboxyl group [mmol / g oxidized cellulose or cellulose nanofiber] = a [ml] × 0.05 / weight of oxidized cellulose [g].

[C-2-2: Etherification]
Etherification includes carboxymethyl (ether), methyl (ether), ethyl (ether), cyanoethyl (ether), hydroxyethyl (ether), hydroxypropyl (ether), ethyl hydroxyethyl (ether) And hydroxypropylmethyl (ether) conversion. The method of carboxymethylation will be described below as an example.

  When the cellulose raw material is modified by carboxymethylation, the carboxymethyl substitution degree per anhydroglucose unit in the obtained carboxymethylated cellulose or cellulose nanofiber is preferably 0.01 or more, more preferably 0.05 or more, and 0 More preferably, it is 10 or more. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and further preferably 0.35 or less. Therefore, the carboxymethyl group substitution degree is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and further preferably 0.10 to 0.30.

  The method for carboxymethylation is not particularly limited, and examples thereof include a method in which a cellulose raw material as a bottoming raw material is mercerized and then etherified. A common solvent is used in the carboxymethylation reaction. Examples of the solvent include water, alcohol (for example, lower alcohol), and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol. The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by mass or more or 95% by mass or less, and preferably 60 to 95% by mass. The amount of the solvent is usually 3 times the weight of the cellulose raw material. The upper limit is not particularly limited, but is 20 times by weight. Therefore, the amount of the solvent is preferably 3 to 20 times by weight.

  The mercerization is usually performed by mixing the bottoming raw material and the mercerizing agent. Examples of the mercerizing agent include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerization agent used is preferably 0.5 times or more, more preferably 1.0 times or more, and even more preferably 1.5 times or more, with respect to the anhydrous glucose residue of the bottoming raw material. The upper limit is usually 20 times mol or less, preferably 10 times mol or less, more preferably 5 times mol or less, therefore, 0.5 to 20 times mol is preferable, 1.0 to 10 times mol is more preferable, and 1 It is more preferably 0.5 to 5 times mol.

  The reaction temperature for mercerization is usually 0 ° C or higher, preferably 10 ° C or higher. The upper limit is usually 70 ° C or lower, preferably 60 ° C or lower. Therefore, the reaction temperature is usually 0 to 70 ° C, preferably 10 to 60 ° C. The reaction time is usually 15 minutes or longer, preferably 30 minutes or longer. The upper limit is usually 8 hours or less, preferably 7 hours or less. Therefore, it is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

  The etherification reaction is usually carried out by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate. The amount of the carboxymethylating agent added is usually preferably 0.05 times or more, more preferably 0.5 times or more, and even more preferably 0.8 times or more, per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times or less, preferably 5 times or less, more preferably 3 times or less, and therefore preferably 0.05 to 10.0 times, and more preferably 0.5 to 10. 5 and more preferably 0.8 to 3 times mol. The reaction temperature is usually 30 ° C or higher, preferably 40 ° C or higher, and the upper limit is usually 90 ° C or lower, preferably 80 ° C or lower. Therefore, the reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C. The reaction time is usually 30 minutes or longer, preferably 1 hour or longer. The upper limit is usually 10 hours or less, preferably 4 hours or less. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. The reaction solution may be stirred during the carboxymethylation reaction if necessary.

The carboxymethyl substitution degree per glucose unit of the carboxymethyl cellulose nanofiber may be measured, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dried) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a ground stopper. 2) Add 100 mL of a solution containing 100 mL of special grade concentrated nitric acid to 1000 mL of methanol, and shake for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) 1.5 to 2.0 g of hydrogen-type carboxymethyl cellulose (extra dry) is precisely weighed and put in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the hydrogen-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. 5) Back titration of excess NaOH with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. 6) Calculate the degree of carboxymethyl substitution (DS) by the following formula:
A = [(100 × F ′ − (0.1N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass (g) of hydrogen-type carboxymethyl cellulose)
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required to neutralize 1 g of hydrogen-type carboxymethylated cellulose
F: 0.1 N H ₂ SO ₄ factor F ′: 0.1 N NaOH factor

[C-2-3: Cationization]
When the cellulose raw material is modified by cationization, the cationized cellulose nanofiber obtained may contain a cation such as ammonium, phosphonium, or sulfonium, or a group having the cation in the molecule. The cationized cellulose nanofiber preferably contains an ammonium-containing group, more preferably a quaternary ammonium-containing group.

  The method of cationization is not particularly limited, and examples thereof include a method of reacting a cellulose raw material with a cationizing agent and a catalyst in the presence of water and / or alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydrate), and halohydrin-type compounds thereof. By using any of these, cationized cellulose having a group containing a quaternary ammonium can be obtained. Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Examples of the alcohol include alcohols having 1 to 4 carbon atoms. The amount of the cationizing agent is preferably 5% by mass or more, and more preferably 10% by mass or more, based on 100% by mass of the cellulose raw material. The upper limit is usually 800 mass% or less, preferably 500 mass% or less. The amount of the catalyst is preferably 0.5% by mass or more, and more preferably 1% by mass or more based on 100% by mass of the cellulose fiber. The upper limit is usually 7 mass% or less, preferably 3 mass% or less. The amount of alcohol is preferably 50% by mass or more, and more preferably 100% by mass or more, based on 100% by mass of the cellulose fiber. The upper limit is usually 50,000% by mass or less, preferably 500% by mass or less.

  The reaction temperature during cationization is usually 10 ° C. or higher, preferably 30 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. The reaction time is usually 10 minutes or longer, preferably 30 minutes or longer. The upper limit is usually 10 hours or less, preferably 5 hours or less. The reaction solution may be stirred during the cationization reaction, if necessary.

  The cation substitution degree of the cationized cellulose per glucose unit can be adjusted by controlling the addition amount of the cationizing agent and the composition ratio of water and / or alcohol. The cation substitution degree indicates the number of introduced substituents per unit structure (glucopyranose ring) constituting cellulose. In other words, the degree of cation substitution is defined as “a value obtained by dividing the number of moles of introduced substituents by the total number of moles of hydroxyl groups of the glucopyranose ring”. Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of cation substitution is 3 (the minimum value is 0).

  The cation substitution degree per glucose unit of the cationized cellulose nanofibers is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more. The upper limit is preferably 0.40 or less, more preferably 0.30 or less, and further preferably 0.20 or less. Therefore, it is preferably 0.01 to 0.40, more preferably 0.02 to 0.30, and further preferably 0.03 to 0.20. By introducing a cationic substituent into cellulose, the cellulose electrically repels each other. Therefore, the cellulose having the cationic substituent introduced therein can be easily nano-disentangled. When the degree of cation substitution per glucose unit is 0.01 or more, sufficient nano-defibration can be performed. On the other hand, when the degree of cation substitution per glucose unit is 0.40 or less, swelling or dissolution can be suppressed, whereby the fiber morphology can be maintained, and a situation where nanofibers cannot be obtained is prevented. be able to.

  An example of the method for measuring the degree of cation substitution per glucose unit will be described below. After drying the sample (cationized cellulose), the nitrogen content is measured with a total nitrogen analyzer TN-10 (Mitsubishi Chemical), and the degree of cationization is calculated by the following formula. The cation substitution degree here is an average value of the number of moles of the substituent per mole of anhydrous glucose unit.

Degree of cation substitution = (162 × N) / (1-151.6 × N)
N: Nitrogen content

[C-2-4: Esterification]
The esterification method is not particularly limited, and examples thereof include a method of reacting the cellulosic raw material with the compound A. The compound A will be described below. Examples of the method of reacting the compound A with the cellulosic material include a method of mixing a powder or an aqueous solution of the compound A with the cellulosic material, a method of adding an aqueous solution of the compound A to a slurry of the cellulosic material, and the like. Among these, the method of mixing the aqueous solution of the compound A with the cellulosic material or the slurry thereof is preferable because the uniformity of the reaction is enhanced and the esterification efficiency is enhanced.

  Examples of the compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid and esters thereof. Compound A may be in the form of salt. Among the above, the phosphoric acid-based compounds are preferable because they are low in cost, easy to handle, and can introduce a phosphoric acid group into the cellulose of the pulp fiber to improve the defibration efficiency. The phosphoric acid compound may be a compound having a phosphoric acid group, and examples thereof include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, and diphosphate. Examples include potassium hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. . The phosphoric acid compound used may be one kind or a combination of two or more kinds. Among these, phosphoric acid, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of phosphate group introduction, easy to defibrate in the following defibration step, and easy to apply industrially Ammonium salts are preferred, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferred. In addition, it is preferable to use an aqueous solution of a phosphoric acid-based compound in the esterification because the homogeneity of the reaction is enhanced and the efficiency of introducing the phosphate group is enhanced. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less because the efficiency of introducing a phosphate group is high, and more preferably 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fiber.

  Examples of the esterification method include the following methods. Compound A is added to a suspension of a cellulosic material (for example, a solid content concentration of 0.1 to 10% by mass) with stirring to introduce a phosphate group into cellulose. When the amount of the cellulosic raw material is 100 parts by weight and the compound A is a phosphoric acid compound, the addition amount of the compound A is preferably 0.2 parts by weight or more, more preferably 1 part by weight or more, as the amount of phosphorus element. Thereby, the yield of fine fibrous cellulose can be further improved. The upper limit is preferably 500 parts by weight or less, more preferably 400 parts by weight or less. This makes it possible to efficiently obtain a yield commensurate with the amount of the compound A used. Therefore, 0.2 to 500 parts by weight is preferable, and 1 to 400 parts by weight is more preferable.

  When the compound A is reacted with the cellulosic material, the compound B may be further added to the reaction system. Examples of the method of adding the compound B to the reaction system include a method of adding it to the slurry of the cellulosic raw material, the aqueous solution of the compound A, or the slurry of the cellulosic raw material and the compound A.

  The compound B is not particularly limited, but preferably shows basicity, more preferably a nitrogen-containing compound showing basicity. "Showing basicity" usually means that the aqueous solution of compound B exhibits a pink to red color in the presence of a phenolphthalein indicator, and / or the pH of the aqueous solution of compound B is greater than 7. The nitrogen-containing compound having basicity is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. Examples thereof include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine and hexamethylenediamine. Of these, urea is preferable because it is inexpensive and easy to handle. The addition amount of the compound B is preferably 2 to 1000 parts by weight, more preferably 100 to 700 parts by weight. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the conditions of the esterification reaction are in any of these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and it is possible to improve the yield of the phosphorylated esterified cellulose. .

  After reacting the cellulosic material with the compound A, an esterified cellulose suspension is usually obtained. The esterified cellulose suspension is dehydrated if necessary. It is preferable to perform heat treatment after dehydration. Thereby, hydrolysis of the cellulosic raw material can be suppressed. The heating temperature is preferably 100 to 170 ° C, and is heated to 130 ° C or lower (more preferably 110 ° C or lower) while water is included in the heat treatment, and is heated to 100 to 170 ° C after removing water. It is more preferable to treat.

  In the phosphate esterified cellulose, a phosphate group substituent is introduced into the cellulosic raw material, and the celluloses electrically repel each other. Therefore, phosphate esterified cellulose can be easily nano-disentangled. The phosphate group substitution degree of glucose esterified cellulose is preferably 0.001 or more per glucose unit. Thereby, sufficient defibration (for example, nano defibration) can be performed. The upper limit is preferably 0.40. This can prevent swelling or dissolution of the phosphoric acid esterified cellulose and prevent the situation where nanofibers cannot be obtained. Therefore, it is preferably 0.001 to 0.40. The phosphate esterified cellulose is preferably subjected to a washing treatment such as washing with cold water after boiling. Thereby, the defibration can be efficiently performed.

[C-3: disentanglement]
The defibration of the cellulose raw material may be performed before or after the modification treatment of the cellulose raw material. Moreover, the defibration may be performed once or a plurality of times. In the case of multiple times, each defibration time may be any time.

  The apparatus used for defibration is not particularly limited, and examples thereof include high-speed rotation type, colloid mill type, high pressure type, roll mill type, ultrasonic type, and other types of devices, and high pressure or ultra high pressure homogenizers are preferable, and wet high pressure is used. Alternatively, an ultrahigh pressure homogenizer is more preferable. The device is preferably capable of applying a strong shearing force to the cellulose raw material or modified cellulose (usually a dispersion). The pressure that can be applied by the device is preferably 50 MPa or more, more preferably 100 MPa or more, and further preferably 140 MPa or more. The apparatus is preferably a wet high-pressure or ultrahigh-pressure homogenizer, which can apply the above-mentioned pressure to the cellulose raw material or modified cellulose (usually a dispersion liquid) and can apply a strong shearing force. Thereby, defibration can be efficiently performed.

  When defibrating the dispersion of the cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more. It is at least mass%. As a result, the amount of liquid relative to the amount of cellulose fiber raw material becomes a proper amount, which is efficient. The upper limit is usually 10 mass% or less, preferably 6 mass% or less. This makes it possible to maintain fluidity.

  Prior to defibration (preferably defibration with a high-pressure homogenizer) or, if necessary, a dispersion treatment performed before defibration, a preliminary treatment may be performed. The pretreatment may be performed by using a mixing, stirring, emulsifying and dispersing device such as a high speed shear mixer.

[C-4: Dry]
The above-mentioned cellulose nanofiber may be used as it is as a dispersion, but may be used as a wet solid or a dry solid by partially or completely removing the solvent by performing a drying treatment if necessary. Here, the wet solid matter is a solid matter in an intermediate mode between the dispersion liquid and the dry solid matter.
When performing the drying treatment, in order to improve the redispersibility, the water-soluble polymer may be mixed in advance with the dispersion liquid of the cellulose nanofibers and then the drying treatment may be performed. Examples of the water-soluble polymer include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, starch starch, and kudzu. Powder, positive starch, phosphorylated starch, corn starch, gum arabic, locust bean gum, gellan gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein melt, peptone, polyvinyl alcohol, poly Acrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, Tex, rosin-based sizing agent, petroleum resin-based sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic crosslinked polymer, polyacrylate , Starch polyacrylic acid copolymers, tamarind gum, gellan gum, pectin, guar gum and colloidal silica and mixtures of one or more thereof. Among these, it is preferable to use carboxymethyl cellulose and salts thereof from the viewpoint of compatibility.

The dried solid matter and the wet solid matter of the cellulose nanofibers may be prepared by drying the dispersion liquid of the cellulose nanofibers or the mixed liquid of the cellulose nanofibers and the water-soluble polymer. The drying method is not particularly limited, and examples thereof include spray drying, pressing, air drying, hot air drying, and vacuum drying. Examples of the drying device include a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disc drying device, an aeration drying device, a rotary drying device, an air flow drying device, a spray dryer drying device. , Spray dryers, cylinder dryers, drum dryers, screw conveyor dryers, rotary dryers with heating tubes, vibration transport dryers, batch-type box dryers, aeration dryers, vacuum box dryers, and A stirring and drying device and the like can be mentioned. These drying devices may be used alone or in combination of two or more. The dryer is preferably a drum dryer. As a result, heat energy can be directly directly supplied to the material to be dried, so that energy efficiency can be improved. Further, the dried product can be immediately recovered without applying more heat than necessary.
[Production of rubber composition]
The rubber composition of the present invention requires the above materials and, if necessary, various additives to be mixed in advance, and then kneaded, molded, heated (vulcanized when sulfur is contained), necessary. It is manufactured by finishing according to the above.

  The additive may be any additive that can be used in the rubber industry, and examples thereof include mastication accelerators, softeners / plasticizers, curing agents (phenolic resins, high styrene resins, etc.), crosslinking compounding agents (such as sulfur, etc.). Crosslinking agents, vulcanization accelerators (N-t-butyl-2-benzothiazolesulfenamide, etc.), vulcanization acceleration aids, scorch inhibitors, etc.), antioxidants, foaming agents, coupling agents, adhesives ( Macron resin, phenol, terpene resin, petroleum hydrocarbon resin, rosin derivative, etc.), dispersant (fatty acid etc.), adhesion promoter (organic cobalt salt etc.), lubricant (paraffin and hydrocarbon resin, fatty acid and fatty acid derivative etc.) ), A colorant, and the like. One additive may be used or a combination of two or more may be used, and the amount used may be appropriately determined according to need.

  The kneading can be performed by a conventionally known kneading device. Examples of the kneading device include a Banbury mixer, a kneader, and an open roll. When sulfur or a vulcanization accelerator is blended, the temperature during kneading is preferably a temperature at which the rubber component does not undergo a crosslinking reaction during kneading, for example, 10 ° C or higher is preferable, and 20 ° C or higher is more preferable. . The upper limit is preferably 140 ° C or lower, more preferably 120 ° C or lower. Therefore, the temperature is preferably 10 ° C or higher to about 140 ° C, more preferably about 20 to 120 ° C.

  Molding is usually performed by a molding device. As the molding apparatus, for example, mold molding, injection molding, extrusion molding, blow molding, foam molding, etc. can be performed, and the apparatus can be selected according to the application and molded into a desired shape.

  Vulcanization is usually performed by adding sulfur and a vulcanization accelerator. As a result, the rubber component can be vulcanized, and a crosslinked structure can be formed between the modified substituent in the modified cellulose fiber and the rubber component. The amount of sulfur used is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, based on 100 parts by weight of the rubber component. The upper limit is preferably 50 mass% or less, more preferably 35 mass% or less, and further preferably 20 mass% or less. Therefore, it is preferably about 0.1 to 50 parts by weight, more preferably about 0.5 to 35 parts by weight, still more preferably about 1 to 20 parts by weight. The amount of the vulcanization accelerator used is preferably 0.1% by mass, more preferably 0.3% by mass or more, still more preferably 0.4% by mass or more, based on the rubber component. The upper limit is preferably 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.

  The vulcanization temperature is preferably 150 ° C. or higher. The upper limit is preferably 200 ° C or lower, more preferably 180 ° C or lower. Therefore, the temperature is preferably about 150 to 200 ° C, more preferably about 150 to 180 ° C. Examples of the heating device include vulcanization devices such as mold vulcanization, can vulcanization, and continuous vulcanization. Examples of the vulcanization method include press vulcanization.

  If necessary, finishing treatment may be performed before the final product. Examples of the finishing treatment include conventionally known treatments such as polishing, surface treatment, lip finishing, lip cutting, and chlorine treatment. Only one of these treatments may be performed, or a combination of two or more treatments. May be.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example 1>
[Production of oxidized cellulose nanofibers]
Bleached unbeaten kraft pulp from softwood (whiteness 85%) 5.00 g (absolutely dry) TEMPO (Sigma Aldrich) 39 mg (0.05 mmol to absolute dryness 1 g of cellulose) and sodium bromide 514 mg (absolutely dry) It was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and an oxidation reaction was started at room temperature. Although the pH in the system was lowered during the reaction, the pH was adjusted to 10 by sequentially adding a 3M aqueous sodium hydroxide solution. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system stopped changing.
The mixture after the reaction was filtered with a glass filter to separate pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to 1.0% (w / v) with water and treated three times with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) to obtain an aqueous dispersion of oxidized cellulose nanofibers. The oxidized cellulose nanofibers had an average fiber diameter of 3 nm and an aspect ratio of 250.
This aqueous dispersion of oxidized cellulose nanofibers was dried in a drum dryer until the solid content concentration became 50%, to obtain a wet solid of oxidized cellulose nanofibers.

[Production of rubber composition]
Nitrile rubber (manufactured by KUMHO PETROCHEMICAL, product name: KNB35L, bound acrylonitrile content 34%, Mooney viscosity 41) is used, and carbon black (manufactured by Sid Richardson, product name: N550) is 40 mass with respect to 100 mass% of nitrile rubber. %, 5% by mass of the wet solid matter of the oxidized cellulose nanofibers in terms of solid content, 3% by mass of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.), and 6% by mass of a plasticizer (manufactured by ADEKA, product name: RS107). 2% by mass of an anti-aging agent (manufactured by Chemutra, product name: Naugard 445) and 4.9% by mass of a crosslinking auxiliary (manufactured by Kawaguchi Chemical Industry Co., Ltd., product name: Trialic), respectively, and added to a kneader and an open roll. Kneaded in. The above kneaded material was press-vulcanized at 160 ° C. for 12 minutes to obtain a plate-shaped test piece of a vulcanized rubber composition having a thickness of 2 mm.
The tensile strength, wear depth, and specific gravity of each of the obtained vulcanized rubber compositions were evaluated by the methods described below. The Mooney viscosity was evaluated by the method described below using the rubber composition at the time of unvulcanization.

[Tensile strength]
The stress (M100) at 100% strain was measured according to JIS K6251 "Vulcanized rubber and thermoplastic rubber-Determination of tensile properties". Specifically, the sheet of the rubber composition was cut into a test piece having a predetermined shape and measured using a universal tensile compression tester (UTM-10T manufactured by A & D Company). The larger each value is, the better the vulcanized rubber composition is reinforced, and the more excellent the mechanical strength of the rubber is. Regarding the measurement results, based on the case where cellulose nanofibers were not blended (Comparative Example 1 described later), the case where the tensile strength was large was marked with ◯, the case where the tensile strength was equivalent was marked with Δ, and the case where it was small was marked with x.

[Abrasion depth]
Using a ring-on-disc friction and wear tester (manufactured by Kobe Zoki Co., Ltd.), the test piece was immersed in a designated lubricating oil (IRM-903, designated in JIS oil wear test) heated to 100 ° C. for 72 hours, and then the ring The rotation speed was 250 rpm, a load of 10 kgf was applied for 1 minute from the start of rotation, the load was increased to 40 kgf, and the wear depth of the test piece after 120 minutes was measured at an average of 3 points. The smaller the wear depth, the higher the resistance to repeated sliding. Regarding the measurement results, the case where the wear depth was small was marked with ◯, the case where the wear depth was equivalent was marked with Δ, and the case where the wear depth was large was marked with x, based on the case where cellulose nanofibers were not blended (Comparative Example 1 described later).

[specific gravity]
It was measured according to the method of JIS K6268 "Vulcanized rubber-Density measurement". Regarding the measurement results, based on the case where cellulose nanofiber was not blended (Comparative Example 1 described later), the case where the specific gravity was small was marked with ◯, the case where it was equivalent was marked with Δ, and the case where it was large was marked with x.

[Moonie viscosity]
An unvulcanized rubber sheet was prepared as a sample and measured according to the method of JIS K6300 "Unvulcanized rubber-Physical properties-Part 1: Determination of viscosity and scorch time by Mooney viscometer". Specifically, a Mooney viscometer (SMV-300, manufactured by Shimadzu Corporation) was used to measure the Mooney viscosity of the sample at 100 ° C. for 1 minute of preheating and 4 minutes after the start of rotation. The lower the Mooney viscosity, the better the processability during production. Regarding the measurement results, the case where the Mooney viscosity was low was evaluated as ◯, the case where the Mooney viscosity was low was evaluated as Δ, and the case where it was high was evaluated as x, based on the case where cellulose nanofiber was not blended (Comparative Example 1 described later).

<Example 2>
A rubber composition was obtained in the same manner as in Example 1 except that the oxidized cellulose nanofibers in Example 1 were changed to carboxymethylated cellulose nanofibers produced by the following method.

[Production of carboxymethyl cellulose nanofiber]
In a stirrer with which pulp can be mixed, pulp (NBKP (softwood bleached kraft pulp), made by Nippon Paper Industries) in a dry mass of 200 g, and sodium hydroxide in a dry mass of 111 g (2. 25 times mol), and water was added so that the pulp solid content was 20% (w / v). Then, after stirring for 30 minutes at 30 ° C., 216 g of sodium monochloroacetate (calculated as an active ingredient, 1.5 times mol per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and the mixture was stirred for 1 hour.
Then, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. This was made to have a solid content of 1% with water, and fibrillated by treatment with a high-pressure homogenizer at 20 ° C. and a pressure of 150 MPa five times to obtain carboxymethyl cellulose nanofibers. The average fiber diameter was 15 nm and the aspect ratio was 50.
The aqueous dispersion of carboxymethyl cellulose nanofibers was dried in a drum dryer until the solid content concentration became 50%, to obtain a wet solid of carboxymethyl cellulose nanofibers.

<Example 3>
A rubber composition was obtained in the same manner as in Example 1 except that the oxidized cellulose nanofibers in Example 1 were changed to cationized cellulose nanofibers produced by the following method.

[Production of cationized cellulose nanofibers]
To a pulper that can stir the pulp, 200 g of pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) by dry weight and 24 g of sodium hydroxide by dry weight are added, and water is added so that the pulp solid concentration becomes 15%. It was Then, after stirring at 30 ° C. for 30 minutes, the temperature was raised to 70 ° C., and 200 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride (as an active ingredient) was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cation-modified pulp having a cation substitution degree of 0.05 per glucose unit. This was made to have a solid concentration of 1%, and was treated twice with a high pressure homogenizer at 20 ° C. and a pressure of 140 MPa. The average fiber diameter was 25 nm and the aspect ratio was 50.
This aqueous dispersion of cationized cellulose nanofibers was dried in a drum dryer until the solid content concentration reached 50%, to obtain a wet solid of cationized cellulose nanofibers.

<Example 4>
In Example 1, the carbon black was changed to silica (manufactured by Rhodia, product name: Z-175), and 4% by mass of a silane coupling agent (manufactured by Evonik Degussa, product name: Dynasylan Si-69) was added. A rubber composition was obtained in the same manner as in Example 1 except that the kneading was carried out. The reference of the measurement result was Comparative Example 2 shown below.

<Comparative Example 1>
A rubber composition was produced in the same manner as in Example 1 except that cellulose nanofibers were not added during kneading.

<Example 5>
A rubber composition was obtained in the same manner as in Example 1 except that the nitrile rubber was changed to ethylene propylene diene rubber (KUMHO PETROCHEMICAL, product name: KEP570P, Mooney viscosity 53).

<Comparative example 2>
A rubber composition was produced in the same manner as in Example 1 except that cellulose nanofibers were not added during kneading.

As is clear from Table 1, when acrylonitrile-butadiene rubber was used as the rubber component, in Examples 1 to 4 containing cellulose nanofibers, the specific gravity and Mooney viscosity were higher than those of Comparative Example 1 containing no cellulose nanofibers. It can be seen that tensile strength and wear depth are improved while maintaining. Similarly, even when ethylene-propylene rubber was used, in Example 5 containing cellulose nanofibers, tensile strength and wear were maintained, while maintaining specific gravity and Mooney viscosity, as compared with Comparative Example 2 containing no cellulose nanofibers. It can be seen that the depth has improved.

Claims (5)

A rubber composition for an oil seal, comprising the following components A, B and C.
Component A: Rubber component containing ethylene-propylene rubber Component B: Filler containing at least one selected from carbon black, silica and powdery cellulose
Component C: Modified cellulose nanofiber   The blending ratio of the component A, the component B, and the component C is component A: component B: component C = 100: 5 to 100: 1 to 50 (mass%), The claim 1 characterized by the above-mentioned. Rubber composition for oil seals. The modified cellulose nanofiber (component C) contains an oxidized cellulose nanofiber in which a part of the hydroxyl group at the C6 position in the glucose unit of cellulose is oxidized to a carboxyl group, and the amount of the carboxyl group of the oxidized cellulose nanofiber is The rubber composition for an oil seal according to any one of claims 1 and 2 , wherein the dry weight of the oxidized cellulose nanofiber is 1.6 mmol / g to 2.0 mmol / g. The modified cellulose nanofiber (component C) contains a carboxymethylated cellulose nanofiber in which a part of hydrogen atoms of a hydroxyl group in a glucose unit of cellulose is replaced with a carboxymethyl group, and The rubber composition for oil seals according to any one of claims 1 to 2 , wherein the degree of carboxymethyl substitution per glucose unit is 0.01 to 0.50. The modified cellulose nanofiber (component C) contains a cationized cellulose nanofiber in which a part of hydrogen atoms of a hydroxyl group in a glucose unit of cellulose is replaced with a cationic group, and The degree of cation substitution is 0.01 to 0.40, and the average fiber diameter is 25 nm or more and 500 nm or less, The rubber composition for oil seals according to claim 1 or 2 .