JP2018119072A - Master batch, rubber composition, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master batch that makes it possible to produce a rubber having high stress at low strain without deterioration of breaking elongation.SOLUTION: A master batch has a rubber component, a cellulose fiber and a silane coupling agent as the raw material, wherein the master batch contains a heated product of a mixture containing at least the rubber component and the cellulose fiber.SELECTED DRAWING: None

Description

  The present invention relates to a master batch, an uncured bridge rubber composition and a rubber composition, and methods for producing them.

  It is known that rubber compositions containing rubber and cellulosic fibers have excellent mechanical strength. As a raw material for such a rubber composition, a master batch of rubber / short fiber obtained by stirring and mixing cellulose short fibers having an average fiber diameter of less than 0.5 μm and rubber latex is known (for example, patent document). 1). The rubber / short fiber master batch is prepared by mixing a dispersion obtained by fibrillating short fibers having an average fiber diameter of less than 0.5 μm in water and a rubber latex and drying the mixture to dry the short fibers in the rubber. It is described that a rubber composition having a good balance between rubber reinforcement and fatigue resistance can be produced.

  In general, since rubber and cellulosic fibers have low compatibility, it has been studied to improve the compatibility of rubber and cellulosic fibers in the rubber composition. For example, use of a coupling agent or introduction of a long-chain alkyl group into cellulose fibers has been studied (for example, Patent Documents 2 and 3).

JP 2006-206864 A JP 2009-191198 A JP 2014-125607 A

  However, in the above method, the reactivity may be poor, and the improvement of the compatibility between rubber and cellulosic fibers may be insufficient. Therefore, the physical property improvement effect of the rubber composition may not be sufficient.

  The subject of this invention is providing the masterbatch which can manufacture the rubber | gum with high stress in low distortion, without impairing break elongation.

As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by heat-treating a mixture containing at least a rubber component and cellulosic fibers, and have completed the present invention.
That is, the present inventors provide the following [1] to [21].
[1] A masterbatch containing a heat-treated product of a mixture containing at least the rubber component and the cellulose fiber, using the rubber component, the cellulose fiber and the silane coupling agent as raw materials.
[2] The master batch as described in [1] above, which contains a kneaded product of the heat-treated product A of the mixture A containing the rubber component and the cellulose fiber and the silane coupling agent.
[3] The master batch according to [1] above, which includes a heat-treated product B of the mixture B containing the rubber component, the cellulose fiber, and the silane coupling agent.
[4] The above [1] to [1], wherein the blending ratio of the cellulose fiber and the silane coupling agent (silane coupling agent / cellulose fiber) is 0.1 / 10 to 5/10 in terms of parts by mass. 3]. The master batch according to any one of [3].
[5] The master batch according to any one of [1] to [4], wherein the cellulosic fiber is oxidized cellulose.
[6] The masterbatch according to any one of [1] to [5], wherein the cellulosic fiber has a length-weighted average fiber length of 50 to 2000 nm and a length-weighted average fiber diameter of 2 to 500 nm. .
[7] The silane coupling agent according to any one of [1] to [6], wherein the silane coupling agent has at least one group selected from the group consisting of a mercapto group, an isocyanate group, a sulfide group, and an amino group. Master Badge.
[8] The master batch according to any one of [1] to [7], wherein the rubber component includes natural rubber.
[9] An uncrosslinked rubber composition containing the master batch according to any one of [1] to [8] above and a crosslinking agent.
[10] A rubber composition containing a crosslinked product of the uncrosslinked rubber composition according to [9].
[11] (a1) A step of mixing a rubber component and cellulosic fiber to obtain a mixture A, and (b1) heating the mixture A at a temperature of 100 to 300 ° C. for 5 to 600 minutes. And (c1) a step of kneading the heat-treated product A and a silane coupling agent to obtain a kneaded product.
[12] The step (a1) is mixed using a solvent A derived from at least one of the dispersion or solution of the rubber component and the dispersion of the cellulose fiber, and the solvent A is dried to The production method according to the above [11], which is a step of obtaining the mixture A.
[13] (a2) A step of obtaining a mixture B by mixing a rubber component, a cellulosic fiber and a silane coupling agent, and (b2) heating the mixture B at a temperature of 100 to 300 ° C. for 5 to 600 minutes. And a step of obtaining a heat-treated product B.
[14] The step (a2) is derived from at least one selected from the group consisting of a dispersion or solution of the rubber component, a dispersion of the cellulose fiber, and a dispersion or solution of the silane coupling agent. The production method according to [13] above, wherein the solvent B is mixed and dried to obtain the mixture B.
[15] The above [11] to [11], wherein the blending ratio of the cellulose fiber and the silane coupling agent (silane coupling agent / cellulose fiber) is 0.1 / 10 to 5/10 in terms of parts by mass. [14] The production method according to any one of [14].
[16] The production method according to any one of [11] to [15], wherein the cellulosic fiber is oxidized cellulose.
[17] The production method according to any one of [11] to [16], wherein the cellulosic fiber has a length-weighted average fiber length of 50 to 2000 nm and a length-weighted average fiber diameter of 2 to 500 nm. .
[18] The [11] to [17], wherein the silane coupling agent has at least one group selected from the group consisting of a mercapto group, an isocyanate group, a sulfide group, and an amino group. Production method.
[19] The production method according to any one of [11] to [18], wherein the rubber component contains natural rubber.
[20] Production of an uncrosslinked rubber composition comprising a step of preparing a master batch by the production method according to any one of [11] to [19], and a step of kneading a crosslinking agent in the master batch. Method.
[21] A method for producing a rubber composition, comprising: a step of preparing an uncrosslinked rubber composition by the production method according to [20]; and a step of crosslinking the uncrosslinked rubber composition.

  The master batch of the present invention can produce a rubber having a high stress at a low strain without impairing the elongation at break.

In the present specification, the “master batch” refers to a product obtained by mixing a rubber component, a cellulosic fiber, and a silane coupling agent with a mixer or roll.
In addition, the term “mixture” means both the mixture A and the mixture B, and the term “heat-treated product” means both the heat-treated product A and the heat-treated product B.
Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

(1) Master batch:
The masterbatch of the present invention contains a heat-treated product of a mixture containing at least a rubber component and cellulosic fibers using a rubber component, cellulosic fibers and a silane coupling agent as raw materials. More specifically, it has the following two embodiments. In Embodiment A, the master batch contains a kneaded product of a heat-treated product A of a mixture A containing a rubber component and cellulosic fibers, and a silane coupling agent. In Embodiment B, the master batch contains a heat-treated product B of a mixture B containing a rubber component, a cellulosic fiber, and a silane coupling agent.
In the master batch of the present invention, the compatibility between the hydrophobic rubber component and the hydrophilic cellulosic fiber is improved by using a heat-treated product. Regarding the mechanism of improving the compatibility, it is presumed that, at present, a conjugated double bond is formed by the desorption of the hydroxyl group of cellulose by heating, and the hydrophobicity of the cellulose fiber is improved.

It is known that when a silane coupling agent is added to the rubber component, low strain stress can be increased, but elongation at break decreases. In addition, when heat treatment is performed on the rubber component, low strain stress can be slightly improved, but no improvement to the extent that a silane coupling agent is added is observed.
On the other hand, in the masterbatch of the present invention, when the heat-treated product B is produced, a silane coupling agent is blended, or after the heat-treated product A is produced, the silane coupling agent is blended, thereby increasing the elongation at break. Low strain stress can be increased while maintaining a certain degree. Such an effect is an effect that cannot be assumed because the compatibility between the hydrophobic rubber component and the hydrophilic cellulosic fiber is improved.
Hereinafter, the masterbatch of the present invention will be described, but the description regarding the “rubber component”, “cellulosic fiber”, and “silane coupling agent” is the masterbatch of Embodiment A and the masterbatch of Embodiment B. Not distinguished.

(1-1) Rubber component:
The rubber component is a raw material of rubber and is crosslinked to become rubber. Although there are a rubber component for natural rubber and a rubber component for synthetic rubber, any of them may be used in the masterbatch of the present invention, or both may be used in combination.
The rubber component for natural rubber includes, for example, natural rubber (NR) in a narrow sense without chemical modification; chemically modified natural rubber such as chlorinated natural rubber, chlorosulfonated natural rubber, and epoxidized natural rubber; Rubber; Deproteinized natural rubber.
Examples of rubber components for synthetic rubber include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber, and styrene-isoprene copolymer. Diene rubbers such as united rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber; butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydride Non-diene rubbers such as rubber (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), and chlorosulfonated polyethylene (CSM).
These rubber components may be used alone or in combination of two or more. Among these, NBR, NR, SBR, chloroprene rubber, and BR are preferable.

(1-2) Cellulosic fiber:
Cellulosic fibers include cellulose fibers having a fiber diameter on the order of microns, or cellulose fibers as cellulose raw materials (hereinafter, cellulose fibers to be chemically modified may be referred to as “cellulose raw materials”), and if necessary, chemical After modification, cellulose nanofibers having a nano-order fiber diameter obtained by defibration (hereinafter, cellulose fibers defibrated after chemical modification are referred to as “cellulose nanofibers”) can be used.
In the present specification, “cellulosic fiber” refers to a general concept including cellulose fiber and cellulose nanofiber. The “cellulose fiber” refers to a cellulosic fiber that has not been chemically modified.

Cellulose fibers are not particularly limited, and examples thereof include those derived from plants, animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), and microorganism products.
Plant-derived cellulose fibers include, for example, wood, bamboo, hemp, jute, kenaf, farmland residue, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, and the like.
The cellulosic fibers used in the masterbatch of the present invention may be any one or a combination thereof, preferably a plant or microorganism-derived cellulose fiber, more preferably a plant-derived cellulose fiber, more preferably It is a cellulose nanofiber having a nano-order fiber diameter obtained by chemically modifying a cellulose raw material and then defibrating.

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

The average fiber diameter of the cellulose nanofiber is usually about 2 to 500 nm, preferably 2 to 50 nm, as a length-weighted average fiber diameter. The average fiber length is preferably a length-weighted average fiber length of 50 to 2000 nm.
Length-weighted average fiber diameter and length-weighted average fiber length (hereinafter, simply referred to as “average fiber diameter” or “average fiber length”) are measured using an atomic force microscope (AFM) or a transmission electron microscope (TEM). Then, each fiber can be observed and determined.
The average aspect ratio of the cellulose nanofiber is usually 10 or more. Although an upper limit is not specifically limited, Usually, it is 1000 or less. The average aspect ratio can be calculated by the following (Formula 1).
(Formula 1): Average aspect ratio = Average fiber length / Average fiber diameter

Cellulose has three hydroxyl groups per glucose unit, and can be subjected to various chemical modifications (hereinafter simply referred to as “modification”). In the masterbatch of the present invention, both modified cellulose fibers and unmodified cellulose fibers can be used. However, when modified cellulose fibers are used, the cellulose fibers are sufficiently refined, and cellulose nanofibers having a uniform average fiber length and average fiber diameter can be obtained by defibration. Therefore, a sufficient reinforcing effect can be exhibited when compounded with a rubber component. From such a viewpoint, modified cellulose fibers are preferred.
Examples of the modification include esterification such as oxidation, etherification, and phosphoric esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation), etherification, cationization and esterification are preferred, and oxidation (carboxylation) is more preferred.

(Oxidation)
The amount of the carboxyl group in the oxidized cellulose fiber or the oxidized cellulose nanofiber is preferably 0.5 mmol / g or more, more preferably 0.8 mmol / g or more, further preferably 1 with respect to the absolutely dry mass. 0.0 mmol / g or more. The upper limit of the amount is preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and still more preferably 2.0 mmol / g or less. The amount of the carboxyl group is preferably 0.5 to 3.0 mmol / g, more preferably 0.8 to 2.5 mmol / g, and further preferably 1.0 to 2.0 mmol / g.

  Although the oxidation method is not particularly limited, an example is a method of oxidizing a cellulose raw material in water using an oxidizing agent in the presence of an N-oxyl compound and at least one of bromide and iodide. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to produce at least one group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. Although the density | concentration of the cellulose raw material at the time of reaction is not specifically limited, 5 mass% or less is preferable.

  An N-oxyl compound refers to 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 promotes the target oxidation reaction. The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize 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 an absolutely dry cellulose raw material. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and still more preferably 0.5 mmol or less. The amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.02 to 0.5 mmol with respect to 1 g of the absolutely dry cellulose raw material.

Bromide refers to a compound containing bromine. For example, an alkali metal bromide such as sodium bromide that can be dissociated and ionized in water can be used. The iodide means a compound containing iodine. An example is alkali metal iodide.
The amount of bromide or iodide used can be selected within a range that can promote the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, with respect to 1 g of the absolutely dry cellulose raw material. The upper limit of the amount is preferably 100 mmol or less, more preferably 10 mmol or less, and even more preferably 5 mmol or less. The total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of the cellulose raw material.

Although it does not specifically limit as an oxidizing agent, For example, a halogen, hypohalous acid, a halous acid, perhalogen acid, these salts, a halogen oxide, a peroxide, etc. are mentioned. Among them, hypohalous acid or a salt thereof is preferable because it is inexpensive and has a low environmental burden, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is more preferable.
The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and still more preferably 3 mmol or more with respect to 1 g of the absolutely dry dry cellulose raw material. The upper limit of the amount is preferably 500 mmol or less, more preferably 50 mmol or less, and even more preferably 25 mmol or less. The amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 1 to 50 mmol, and still more preferably 3 to 25 mmol with respect to 1 g of the absolutely dry cellulose raw material.
When using N-oxyl compound, the usage-amount of an oxidizing agent has preferable 1-40 mol with respect to 1 mol of N-oxyl compounds.

Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, 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 of the temperature is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. The reaction 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 more, and more preferably 10 or more. The upper limit of pH is preferably 12 or less, and more preferably 11 or less. The pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11.
Usually, as the oxidation reaction proceeds, carboxyl groups are generated in the cellulose, so that the pH of the reaction solution is lowered. Therefore, in order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution during the reaction to maintain the pH of the reaction solution in the above range. The reaction medium during the oxidation is preferably water for reasons such as ease of handling and the difficulty of side reactions.

The reaction time in oxidation can be appropriately set according to the progress of oxidation. The reaction time is usually 0.5 hours or longer. The upper limit is usually 6 hours or less, preferably 4 hours or less. The reaction time in the oxidation is usually 0.5 to 6 hours, and preferably about 0.5 to 4 hours.
Oxidation may be carried out in two or more stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is ozone oxidation. By this oxidation reaction, at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting cellulose are oxidized, and the cellulose chain is decomposed. The ozone treatment is usually performed by bringing a gas containing ozone and a cellulose raw material into contact with each other.
The ozone concentration in the gas is preferably 50 g / m ³ or more. The upper limit is preferably 250 g / m ³ or less, and more preferably 220 g / m ³ or less. Ozone concentration in the gas is preferably 50 to 250 g / m ^3, more preferably 50~220g / m ^3.
The amount of ozone added is preferably 0.1% by mass or more and more preferably 5% by mass or more with respect to 100% by mass of the solid content of the cellulose raw material. The upper limit is usually 30% by mass or less. The amount of ozone added is preferably 0.1 to 30% by mass and more preferably 5 to 30% by mass with respect to 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. The ozone treatment temperature is preferably 0 to 50 ° C, and 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. The ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes.
When the condition of the ozone treatment is within the above range, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

  The ozone-treated cellulose may be further subjected to additional oxidation treatment using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. Examples of the method for the additional oxidation treatment 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 immersed in the oxidizing agent solution. The amount of the carboxyl group, carboxylate group, and aldehyde group contained in the oxidized cellulose nanofiber can be adjusted by controlling the oxidizing conditions such as the addition amount of the oxidizing agent and the reaction time.

An example of a method for measuring the amount of the carboxyl group will be described below. Prepare 60 mL of 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N sodium hydroxide aqueous solution dropwise to adjust pH to 11. Measure the electrical conductivity until From the amount (a) of sodium hydroxide consumed in the weak acid neutralization stage where the change in electrical conductivity is gradual, it can be calculated using the following (formula 2).
(Formula 2): Amount of carboxyl group [mmol / g (oxidized cellulose or oxidized cellulose nanofiber)] = a [mL] × 0.05 / oxidized cellulose mass or oxidized cellulose nanofiber mass [g]

(Etherification)
As etherification, carboxymethyl (ether), methyl (ether), ethyl (ether), cyanoethyl (ether), hydroxyethyl (ether), hydroxypropyl (ether), ethyl hydroxyethyl (ether) And hydroxypropylmethyl (ether). As an example, the method of carboxymethylation will be described below.

  The degree of substitution of carboxymethyl groups per anhydroglucose unit in cellulose fibers or cellulose nanofibers subjected to carboxymethylation treatment is preferably 0.01 or more, more preferably 0.05 or more, and further preferably 0.10 or more. preferable. The upper limit of the degree of substitution is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.35 or less. The degree of substitution of the carboxymethyl group is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and still more preferably 0.10 to 0.35.

The carboxymethylation method is not particularly limited, and examples thereof include a method in which a cellulose raw material as a starting material is mercerized and then etherified. In the reaction, a solvent is usually used. Examples of the solvent include at least one of water and alcohol (for example, lower alcohol). Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, isobutyl alcohol, and tertiary butyl alcohol.
The mixing ratio of the lower alcohol in the mixed solvent is preferably 60 to 95% by mass.
The amount of the solvent is about 3 times that of the cellulose raw material in terms of mass. Although the upper limit of the amount is not particularly limited, it is 20 times or less. The amount of the solvent is preferably 3 to 20 times that of the cellulose raw material in terms of mass.

Mercerization is usually performed by mixing starting materials and mercerizing agents. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
The amount of mercerizing 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 per anhydroglucose residue of the starting material in terms of mole. The upper limit of the amount is usually 20 times or less, preferably 10 times or less, and more preferably 5 times or less. The amount of the mercerizing agent used is preferably 0.5 to 20 times, more preferably 1.0 to 10 times, and even more preferably 1.5 to 5 times in terms of mole.

The mercerization reaction temperature 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. The reaction temperature is usually 0 to 70 ° C, preferably 10 to 60 ° C.
The mercerization 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. The reaction time is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

The etherification reaction is usually performed by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate.
The addition amount of the carboxymethylating agent is preferably 0.05 times or more, more preferably 0.5 times or more, and further preferably 0.8 times or more per glucose residue of the cellulose raw material in terms of mole. The upper limit of the amount is usually 10.0 times or less, preferably 5 times or less, and more preferably 3 times or less. The addition amount of the carboxymethylating agent is preferably 0.05 to 10.0 times, more preferably 0.5 to 5 times, and still more preferably 0.8 to 3 times in terms of mole.

The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher. The upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. 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. The reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours.
During the carboxymethylation reaction, the reaction solution may be stirred as necessary.

The measurement of the substitution degree of the carboxymethyl group per glucose unit of the cellulose fiber or cellulose nanofiber subjected to the carboxymethylation treatment is performed, for example, by the following method.
About 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 100 mL of nitric acid methanol 1000 mL of special concentrated nitric acid 100 mL was added and shaken for 3 hours to desalinate carboxymethylcellulose salt (carboxymethylated cellulose), and carboxyl group-containing carboxymethylated cellulose (hereinafter, “ Also referred to as “H-type carboxymethylated cellulose”). 1.5-2.0 g of H-type carboxymethylated cellulose (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. Wet H-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. Excess NaOH is back titrated with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. The degree of substitution (DS) of the carboxymethyl group is calculated by the following (Formula 3) and (Formula 4).
(Formula 3): A = [(100 × F ′ − (0.1N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of H-type carboxymethylated cellulose (g) )
(Formula 4): DS = 0.162 × A / (1−0.058 × A)
(A shows 1N NaOH amount (mL) required for neutralizing 1 g of H-type carboxymethylated cellulose, F shows a factor of 0.1 N H ₂ SO ₄ , and F ′ shows 0.1 N Indicates the factor of NaOH.)

(Cationization)
Cationized cellulose fibers and cellulose nanofibers contain cations such as ammonium, phosphonium and sulfonium, or groups having such cations in the molecule. The cationized cellulose fiber or cellulose nanofiber preferably contains a group having ammonium, and more preferably contains a group having quaternary ammonium.

The cationization method is not particularly limited, and examples thereof include a method in which a cellulose raw material, a cationizing agent, and a catalyst are reacted in the presence of water or alcohol.
Examples of the cationizing agent include 3-chloro-2-hydroxypropyltrialkylammonium hydrates such as glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium hydride, or halohydrin type thereof. . By using any of these, a cationized cellulose having a group containing quaternary ammonium can be obtained.
The amount of the cationizing agent is preferably 5 parts by mass or more and more preferably 10 parts by mass or more with respect to 100 parts by mass of the cellulose raw material. The upper limit of the amount is usually 800 parts by mass or less, preferably 500 parts by mass or less.
Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.
The amount of the catalyst is preferably 0.5 parts by mass or more and more preferably 1 part by mass or more with respect to 100 parts by mass of the cellulose raw material. The upper limit of the amount is usually 7 parts by mass or less, preferably 3 parts by mass or less.

As alcohol, C1-C4 alcohol is mentioned, for example.
The amount of alcohol is preferably 50 parts by mass or more and more preferably 100 parts by mass or more with respect to 100 parts by mass of the cellulose raw material. The upper limit of the amount is usually 50000 parts by mass or less, preferably 500 parts by mass or less.

The reaction temperature during cationization is usually 10 ° C or higher, preferably 30 ° C or higher. 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. During the cationization reaction, the reaction solution may be stirred as necessary.

The degree of cation substitution per glucose unit in cationized cellulose can be adjusted by the amount of cationizing agent added and the composition ratio of water or alcohol.
The degree of cation substitution refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. That is, the degree of cation substitution is defined as “a value obtained by dividing the number of moles of the introduced substituent 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 degree of cation substitution per glucose unit of the cationized cellulose fiber or cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, and further preferably 0.03 or more. The upper limit of the degree of substitution is preferably 0.40 or less, more preferably 0.30 or less, and still more preferably 0.20 or less. The degree of cation substitution is preferably from 0.01 to 0.40, more preferably from 0.02 to 0.30, and even more preferably from 0.03 to 0.20. By introducing a cation substituent into the cellulose raw material, the cationized celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the cation substituent can be nano-defibrated easily.
When the degree of cation substitution per glucose unit is 0.01 or more, nano-defibration can be sufficiently 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 form can be maintained.

An example of a 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 (manufactured by Mitsubishi Chemical Corporation). For example, when 3-chloro-2-hydroxypropyltrimethylammonium chloride is used as the cationizing agent, the degree of cationization is calculated by the following (formula 5). In addition, the cation substitution degree calculated by the following (Formula 5) means the average value of the number of moles of substituents per mole of anhydroglucose unit.
(Formula 5): Degree of cation substitution = (162 × N) / (1-116 × N)
(N represents the nitrogen content (mol) per gram of cationized cellulose)

(Esterification)
Although the method of esterification is not specifically limited, For example, the method of making the compound which has a phosphoric acid group react with a cellulose raw material is mentioned. Examples of a method of reacting a phosphoric acid group-containing compound with a cellulose raw material include, for example, a method of mixing a phosphoric acid group compound powder or an aqueous solution with a cellulose raw material, a cellulose raw material slurry having a phosphoric acid group compound Examples include a method of adding an aqueous solution. Among these, since the uniformity of the reaction is enhanced and the esterification efficiency is increased, a method of mixing an aqueous solution of a compound having a phosphoric acid group with a cellulose raw material or a slurry thereof is preferable.
Among these, a method of mixing an aqueous solution of a compound having a phosphate group with a cellulose raw material or a slurry thereof is preferable because the uniformity of the reaction is increased and the introduction efficiency of the phosphate group is increased. The pH of the aqueous solution of the compound having a phosphoric acid group is preferably 7 or less from the viewpoint of increasing the efficiency of introduction of the phosphoric acid group, and more preferably 3 to 7 from the viewpoint of suppressing hydrolysis.

Examples of the compound having a phosphoric acid group include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, esters and salts thereof, and the like. These compounds are low-cost, easy to handle, and can introduce a phosphate group into cellulose to improve the fibrillation efficiency. Specific examples of the compound having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dihydrogen phosphate. Examples include potassium, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. Among them, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid ammonium salt are preferable because of the high introduction efficiency of phosphoric acid groups, easy defibration in the defibrating process, and industrial application. A salt is preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable.
In addition, the compound which has a phosphate group may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the esterification method include the following methods. A compound having a phosphoric acid group is added to a suspension of a cellulose raw material (for example, a solid content concentration of 0.1 to 10% by mass) while stirring to introduce the phosphoric acid group into the cellulose. When the compound having a phosphoric acid group is a phosphoric acid compound, the addition amount of the compound having a phosphoric acid group is preferably 0.2 parts by mass or more, preferably 1 part by mass or more in terms of phosphorus atoms, relative to 100 parts by mass of the cellulose raw material. Is more preferable. Thereby, the yield of esterified cellulose can be improved more. The upper limit of the amount is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. By being in such a range, the yield corresponding to the usage-amount of the compound which has a phosphate group can be obtained efficiently. The addition amount of the compound having a phosphoric acid group is preferably 0.2 to 500 parts by mass and more preferably 1 to 400 parts by mass in terms of phosphorus atom.

When the cellulose raw material and the compound having a phosphate group are reacted, a basic compound may be further added to the reaction system. Examples of the method of adding the basic compound to the reaction system include a method of adding to a slurry of a cellulose raw material, an aqueous solution of a compound having a phosphoric acid group, or a slurry of a cellulose raw material and a compound having a phosphoric acid group.
Although a basic compound is not specifically limited, The nitrogen-containing compound which shows basicity is preferable. “Show basic” usually means that the aqueous solution of the basic compound is pink to red in the presence of the phenolphthalein indicator, or the pH of the aqueous solution of the basic compound is greater than 7.
Although it does not specifically limit as a nitrogen-containing compound which shows basicity, The compound which has an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned. Among these, urea is preferable because it is easy to handle at low cost.
The amount of the basic compound added is preferably 2 to 1000 parts by mass, more preferably 100 to 700 parts by mass with respect to 100 parts by mass of the cellulose raw material. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. Although reaction time is not specifically limited, Usually, it is about 1 to 600 minutes, and 30 to 480 minutes are preferable. When the conditions for the esterification reaction are in any of these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and to improve the yield of phosphorylated esterified cellulose. .

After reacting the cellulose raw material with a compound having a phosphate group, an esterified cellulose suspension is usually obtained. The esterified cellulose suspension is preferably dehydrated as necessary, and is subjected to heat treatment after dehydration. Thereby, hydrolysis of a cellulose raw material can be suppressed.
The heating temperature is preferably 100 to 170 ° C. While water is included in the heat treatment, heating is performed at 130 ° C or less (preferably 110 ° C or less), and after removing water, the temperature is 100 to 170 ° C. It is more preferable to heat-process with.

In phosphate esterified cellulose, a phosphate group substituent is introduced into the cellulose raw material, and cellulose repels electrically. Therefore, phosphorylated esterified cellulose can be easily nano-defibrated.
The degree of phosphate group substitution per glucose unit in the phosphate esterified cellulose is preferably 0.001 or more. Thereby, sufficient defibration (for example, nano defibration) can be implemented. The upper limit of the degree of substitution is preferably 0.60. Thereby, swelling or melt | dissolution of phosphate esterified cellulose can be prevented, and the situation where a nanofiber cannot be obtained can be prevented. The degree of substitution is preferably 0.001 to 0.60. The phosphorylated cellulose is preferably subjected to a washing treatment such as washing with cold water after boiling. Thereby, defibration can be performed efficiently.

(Defibration)
When defibrating as a cellulose fiber, the defibrating may be performed on the cellulose raw material before chemical modification or may be performed on the modified cellulose. The defibrating process may be performed once or a plurality of times. In the case of multiple times, each defibration period 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, and ultrasonic type apparatuses. Among these, a high pressure or ultra high pressure homogenizer is preferable, and a wet high pressure or ultra high pressure homogenizer is more preferable. When a wet high-pressure or ultrahigh-pressure homogenizer is used, a strong shearing force can be applied to the cellulose raw material or the modified cellulose (usually a dispersion), and defibration can be performed efficiently.
The pressure applied by the apparatus is preferably 50 MPa or more, more preferably 100 MPa or more, and further preferably 140 MPa or more.

  When defibration is performed on a dispersion of 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 Is 0.3% by mass or more. Within such a range, the amount of liquid with respect to the solid content of the cellulose raw material becomes an appropriate amount and can be efficiently defibrated. The upper limit of the concentration is usually 10% by mass or less, preferably 6% by mass or less. Thereby, fluidity | liquidity can be hold | maintained.

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

(Filtration)
When cellulose nanofibers are used as the cellulosic fibers, foreign substances such as undefibrated fibers due to insufficient defibration may exist in the cellulose nanofibers. If the rubber composition contains foreign matters, the rubber composition is likely to break starting from the foreign matters, resulting in a decrease in strength. Therefore, when using a cellulose nanofiber as a cellulose-type fiber, it is preferable to use the cellulose nanofiber isolated from the cellulose nanofiber dispersion liquid which performed the filtration process, or the cellulose nanofiber dispersion liquid after the said filtration process.

In the filtration treatment, the cellulose nanofiber dispersion is preferably subjected to pressure filtration or reduced pressure filtration with a differential pressure of 0.01 MPa or more, and preferably subjected to pressure filtration or reduced pressure filtration at a differential pressure of 0.01 to 10 MPa. . By performing filtration with a filtration differential pressure in such a range, even if the concentration and viscosity of the cellulose nanofiber dispersion are high, a sufficient amount of filtration can be obtained. If the differential pressure is less than 0.01 MPa, a sufficient amount of filtration treatment cannot be obtained, and considerable dilution is required to obtain a sufficient amount of filtration treatment, which is not preferable in consideration of the subsequent steps.
The density | concentration of the cellulose nanofiber in the cellulose nanofiber dispersion liquid used for filtration is 0.1-5 mass% normally, Preferably it is 0.2-4 mass%, More preferably, it is 0.5-3 mass %.
Examples of the apparatus used for filtration include Nutsche type, candle type, leaf disk type, drum type, filter press type, belt filter type and the like.

The amount of filtration treatment is preferably 10 L / m ² or more per hour, and more preferably 100 L / m ² or more.
Examples of the filtration method include auxiliary agent filtration using a filter aid, filter medium filtration using a porous filter medium, and the like. In the present invention, a method can be appropriately selected, and the two filtration methods may be used in combination. In this case, the order of the filtration methods can be arbitrarily selected. Furthermore, when implementing two or more filtration processes, any one filtration process should just be implemented with the said filtration differential pressure, All the filtration processes may be implemented with the said filtration differential pressure.

Auxiliary filtration using a filter aid is preferable because clogging of the filter medium caused by the filtration treatment can be easily eliminated by removing the filter layer formed with the filter aid. Therefore, it is possible to perform continuous filtration.
The filter aid is preferably a granular material having an average particle size of 150 μm or less, more preferably a granular material having an average particle size of 1 to 150 μm, a granular material having an average particle size of 10 to 75 μm, and an average particle size of 15 It is more preferable to be a granular material having a particle size of ˜45 μm and an average particle diameter of 25 to 45 μm. When the average particle size is smaller than 1 μm, the filtration rate may decrease. On the other hand, when the average particle size is larger than 150 μm, foreign matter cannot be captured, and the effect of the filtration treatment may not be obtained.
As will be described later, the filter aid can take various shapes such as a substantially spherical shape such as diatomaceous earth or a rod shape such as powdered cellulose. In either case, the average particle diameter can be measured by a laser diffraction measuring instrument in accordance with JIS Z8825-1.

Auxiliary filtration using a filter aid is performed by any of precoat filtration that forms a layer of filter aid on the filter medium, and body feed filtration in which the filter aid and cellulose nanofiber dispersion are mixed in advance and filtered. May be. Combining both is more preferable because the throughput is improved and the quality of the filtrate is improved. Moreover, you may perform multistage adjuvant filtration by changing the kind of filter aid. When carrying out two or more stages of filtration steps using a filter aid, it is sufficient that any one filtration step is carried out at the filtration differential pressure, and all filtration steps are carried out at the filtration differential pressure. Good.
As the filter aid, either an inorganic compound or an organic compound may be used, but a granular one is preferred. Preferable examples of the filter aid include diatomaceous earth, powdered cellulose, pearlite, activated carbon and the like.

Diatomaceous earth refers to soft rock or soil mainly composed of diatom shell, and is mainly composed of silica. In addition to silica, alumina, iron oxide, alkali metal oxides, and the like may be included. Further, it is preferably porous and has a high porosity and a cake bulk density of about 0.2 to 0.45 g / cm ³ . Among the diatomaceous earths, fired products and flux fired products are preferable, and freshwater diatomaceous earth is more preferable. Examples of such diatomaceous earth include Celite (registered trademark) manufactured by Celite and Ceratom (registered trademark) manufactured by Eagle Pitcher Minerals.

Powdered cellulose refers to rod-like particles made of microcrystalline cellulose obtained by removing a non-crystalline portion of wood pulp by acid hydrolysis, and then pulverizing and sieving.
The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 500.
The crystallinity of the powdered cellulose by X-ray diffraction method is preferably 70 to 90%.
The volume average particle size measured by the laser diffraction particle size distribution analyzer is preferably 100 μm or less, more preferably 50 μm or less. When the volume average particle diameter is 100 μm or less, a cellulose nanofiber dispersion excellent in fluidity can be obtained.
The powdered cellulose used in the present invention is, for example, a rod shaft produced by a method in which an undegraded residue obtained after acid hydrolysis of a selected pulp is purified and dried, pulverized and sieved, and has a certain particle size. Examples thereof include crystalline cellulose powder having a diameter distribution, KC Flock (registered trademark) manufactured by Nippon Paper Industries, Theolas (registered trademark) manufactured by Asahi Kasei Chemicals, and Avicel (registered trademark) manufactured by FMC.

  Filter media include filters made of metal fibers, cellulose, polypropylene, polyester, nylon, glass, cotton, polytetrafluoroethylene, polyphenylene sulfide, etc., membranes, filter cloth, filters made by sintering metal powder, or slits Shape filter and the like. Among these, a metal filter or a membrane filter is preferable.

  The preferred average pore size of the filter medium is not particularly limited when used in combination with the above filter aid. On the other hand, when not filtering together with said filter aid and filtering only with a filter medium, the average pore diameter of a filter medium becomes like this. Preferably it is 0.01-100 micrometers, More preferably, it is 0.1-50 micrometers, More preferably, it is 1. ˜30 μm. When the average pore size is smaller than 0.01 μm, a sufficient filtration rate may not be obtained. On the other hand, when it is larger than 100 μm, it is difficult to obtain a filtering effect because foreign matters cannot be captured.

The dispersibility of the cellulose nanofiber dispersion after filtration is preferably evaluated by the following method.
After adding a surface tension adjusting agent to the cellulose nanofiber dispersion, it is thinned. A pair of polarizing plates are arranged on both surfaces of the thin film so that the polarization axes are orthogonal to each other. Light is irradiated from one polarizing plate side, and a transmission image is acquired from the other polarizing plate side. The image is subjected to image analysis to determine the foreign matter area, and the foreign matter area ratio per 1 g of the cellulose nanofiber dry mass is calculated.
The cellulose nanofiber dispersion after filtration preferably has a foreign matter area ratio of 25% or less in the evaluation method.

Moreover, a mixture of a cellulose fiber and a water-soluble polymer can be used as the cellulose fiber.
Examples of water-soluble polymers include cellulose derivatives (for example, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, Snack flour, scrap flour, positive starch, phosphorylated starch, corn starch, gum arabic, gellan gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide , Sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, Gin-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 cross-linked polymer, polyacrylate, starch Examples include polyacrylic acid copolymers, tamarind gum, guar gum, and colloidal silica, and mixtures thereof.
Of these, carboxymethylcellulose or a salt thereof is preferably used from the viewpoint of solubility.

  The amount of cellulosic fibers used can be adjusted to achieve the desired physical properties when made into a rubber composition. For example, 0.1-100 mass parts is preferable with respect to 100 mass parts of rubber components, 1-50 mass parts is more preferable, 2-40 mass parts, and 3-30 mass parts is further more preferable.

(1-3) Silane coupling agent:
There is no restriction | limiting in particular as a silane coupling agent. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, 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-trimethoxysilylbutyl) trisulfide, bis (3- bird Toxisilylpropyl) 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-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl Ethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetra Silane coupling agents having sulfide groups such as rufide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Silane coupling agents having a mercapto group such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; etc .; having a vinyl group such as vinyltriethoxysilane and vinyltrimethoxysilane Silane coupling agent; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane Silane coupling agents having amino groups such as lan, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycid Silane coupling agents having a glycidoxy group such as xylpropylmethyldiethoxysilane and γ-glycidoxypropylmethyldimethoxysilane; Silane cups having a nitro group such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane Ring agent; Silane coupling agent having a chloro group such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane; 3-glycidoxy Propyltrime Silane coupling agents having an epoxy group such as xylsilane, 5,6-epoxyhexyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; p A silane coupling agent having a styryl group such as styryltrimethoxysilane, α-methylstyryldimethylmethoxysilane, and p-styryltriethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3 -Methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, γ- (methacryloyloxypropyl) trimethoxysilane, γ- (methacryloyloxypropylmethyl) dimethoxysilane, etc. Methacrylic group-containing silane coupling agent; acrylic group such as 3-acryloxypropyltrimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, 3-acryloxypropyltriethoxysilane Γ-ureidopropyltrimethoxysilane, β-ureidoethyltrimethoxysilane, α-ureidomethyltrimethoxysilane, γ-ureidopropylmethyldimethoxysilane, β-ureidoethylmethyldimethoxysilane, α-ureido Methylmethyldimethoxysilane, γ-ureidopropyltriethoxysilane, β-ureidoethyltriethoxysilane, α-ureidomethyltriethoxysilane, γ-ureidopropylmethyldiethoxysilane β-ureidomethyldiethoxysilane, α-ureidomethylmethyldiethoxysilane, 1-methyl-1- (3- (trimethoxysilyl) propyl) urea, 1-methyl-3- (3- (trimethoxysilyl) propyl ) Urea, 1-methyl-1- (3- (methyldimethoxysilyl) propyl) urea, 1-methyl-3- (3- (methyldimethoxysilyl) propyl) urea, 1-ethyl-1- (3- (tri Methoxysilyl) propyl) urea, 1-ethyl-3- (3- (trimethoxysilyl) propyl) urea, 1-ethyl-1- (3- (methyldimethoxysilyl) propyl) urea, 1-ethyl-3- ( 3- (methyldimethoxysilyl) propyl) urea, 1,3-dimethyl-1- (3- (trimethoxysilyl) propyl) urea, 1,3- Methyl-3- (3- (trimethoxysilyl) propyl) urea, 1,3-dimethyl-1- (3- (methyldimethoxysilyl) propyl) urea, 1,3-dimethyl-3- (3- (methyldimethoxy) Silyl) propyl) urea, 1,3-diethyl-1- (3- (trimethoxysilyl) propyl) urea, 1,3-diethyl-3- (3- (trimethoxysilyl) propyl) urea, 1,3- Silane coupling agents having a ureido group such as diethyl-1- (3- (methyldimethoxysilyl) propyl) urea and 1,3-diethyl-3- (3- (methyldimethoxysilyl) propyl) urea; trimethoxysilylmethyl Isocyanate, triethoxysilylmethyl isocyanate, tripropoxysilylmethyl isocyanate, 2-trimethoxysilyl Ruethyl isocyanate, 2-triethoxysilylethyl isocyanate, 2-tripropoxysilylethyl isocyanate, 3-trimethoxysilylpropyl isocyanate, 3-triethoxysilylpropyl isocyanate, 3-tripropoxysilylpropyl isocyanate, 4-trimethoxysilylbutyl Examples thereof include silane coupling agents having an isocyanate group such as isocyanate, 4-triethoxysilylbutyl isocyanate, and 4-tripropoxysilylbutyl isocyanate. Among these, a silane coupling agent having at least one group selected from the group consisting of a mercapto group, an isocyanate group, a sulfide group, and an amino group is preferable.
In addition, these silane coupling agents may be used individually by 1 type, and may use 2 or more types together.

  The amount of the silane coupling agent used is such that the mixing ratio of the cellulose fiber and the silane coupling agent (silane coupling agent / cellulosic fiber) is 0.1 / 10 to 5/10 in terms of parts by mass. It is preferable that the amount is 0.5 / 10 to 3/10, and more preferable. When the blending ratio (silane coupling agent / cellulosic fiber) is 0.1 / 10 or more, the effect of improving stress with low strain can be sufficiently exhibited. On the other hand, the elongation at break can be maintained to some extent by being 5/10 or less.

(1-4) Mixture:
The mixture includes a mixture A containing a rubber component and cellulosic fibers, and a mixture B containing a rubber component, cellulosic fibers and a silane coupling agent. Although the mixing method will be described later, the mixture is preferably a dried product from which the solvent has been removed.

(1-5) Heat-treated product:
The heat-treated product is obtained by heat-treating the mixture. The mixture A is heat-treated and the mixture B is heat-treated A. The heating method will be described later.

(1-6) Kneaded product:
The kneaded product is obtained by kneading the heat-treated product A and the silane coupling agent. The kneading method will be described later.

(2) Masterbatch manufacturing method:
The masterbatch production method of the present invention has the following two embodiments. In the embodiment A, (a1) a step of obtaining a mixture A by mixing a rubber component and cellulosic fibers, and (b1) heating the mixture A at a temperature of 100 to 300 ° C. for 5 to 600 minutes. And (c1) kneading the heat-treated product A and a silane coupling agent to obtain a kneaded product. In Embodiment B, (a2) a step of obtaining a mixture B by mixing a rubber component, cellulosic fibers and a silane coupling agent; and (b2) heating the mixture B at a temperature of 100 to 300 ° C. for 5 to 600 minutes. And obtaining a heat-treated product B.
In the manufacturing method of the masterbatch of this invention, since it has the process of heating a mixture for 5 to 600 minutes at the temperature of 100-300 degreeC, and obtaining a heat processing thing, a hydrophobic rubber component and hydrophilic cellulose type The compatibility of the fibers is improved.

(2-1) Mixing step:
The mixing step is a step (a1) of mixing the rubber component and the cellulosic fiber, or a step (a2) of mixing the rubber component, the cellulosic fiber and the silane coupling agent.
Mixing can be carried out using a known apparatus such as a homomixer, a homogenizer, or a propeller stirrer. Although the temperature to mix is not limited, Room temperature (20-30 degreeC) is preferable. You may adjust mixing time suitably.

  The rubber component may be used for mixing a solid material, but may be used for mixing in a dispersion solution (latex) in which the rubber component is dispersed in a dispersion medium or a solution dissolved in a solvent. Examples of the dispersion medium and the solvent (hereinafter, collectively referred to as “liquid”) include water and organic solvents. The amount of the liquid is preferably 10 to 1000 parts by mass with respect to 100 parts by mass of the rubber component.

Cellulose fibers can be used for mixing in the form of a dispersion in which cellulose fibers are dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion.
The density | concentration of the cellulose fiber in a dispersion liquid can be 0.1-5% (w / v), when a dispersion medium is water. When the dispersion medium contains an organic solvent such as alcohol in addition to water, the concentration can be 0.1 to 20% (w / v). The wet solid is a solid in an intermediate form between the dispersion and the dry solid. The amount of the dispersion medium in the wet solid obtained by dehydrating the dispersion by a usual method is preferably 5 to 15% by mass with respect to the cellulosic fiber. The amount of can be adjusted as appropriate.

  Moreover, when using the mixture of a cellulose fiber and a water-soluble polymer solution as a cellulose fiber, a liquid mixture, the dry solid of a liquid mixture, the wet solid of a liquid mixture, etc. can be used for mixing. The amount of liquid in the mixture and its dry solids may be in the above range.

Dry solids and wet solids can be prepared by drying a dispersion of cellulosic fibers or a mixture of cellulosic fibers and a water-soluble polymer. Although a drying method is not specifically limited, For example, spray drying, pressing, air drying, hot air drying, or vacuum drying is mentioned.
Examples of the drying apparatus include a continuous tunnel drying apparatus, a band drying apparatus, a vertical drying apparatus, a vertical turbo drying apparatus, a multistage disk drying apparatus, an aeration drying apparatus, a rotary drying apparatus, an airflow drying apparatus, and a spray dryer drying. Equipment, spray dryer, cylindrical dryer, drum dryer, screw conveyor dryer, rotary dryer with heating tube, vibration transport dryer, batch box dryer, aerated dryer, vacuum box dryer, agitation A drying apparatus is mentioned. Among these, a drum drying apparatus is preferable because heat energy can be directly supplied uniformly to the material to be dried, so that the energy efficiency is high and the dried material can be recovered immediately without applying more heat than necessary.
These drying apparatuses may be used alone or in combination of two or more.

As the silane coupling agent, a dried product may be used for mixing, but a dispersion or solution of a silane coupling agent may be used for mixing. Among these, it is preferable to use a dispersion or solution of a silane coupling agent for mixing.
When the silane coupling agent is liquid, the stock solution may be used for mixing as it is, or may be diluted for mixing. When diluting, the concentration of the silane coupling agent solution or dispersion is preferably about 0.1 to 20% by mass. The solvent or dispersion medium used for dilution is preferably a hydrophilic solvent such as water or alcohol.

The mixing step is a step of mixing using a solvent A derived from at least one of a dispersion or solution of a rubber component and a dispersion of a cellulosic fiber, and drying the solvent A to obtain a mixture A. Mixing using a solvent B derived from at least one selected from the group consisting of a dispersion or solution, a dispersion of cellulose fibers, and a dispersion or solution of a silane coupling agent, and drying the solvent B The step of obtaining B is preferred.
A uniform mixture can be obtained by mixing using a solvent. Moreover, the processing time in a heating process can be shortened by performing a drying process.
The drying temperature is preferably 50 to 80 ° C. You may adjust drying time suitably. The mixture after drying may be in an absolutely dry state, but contains a solvent of 10% by mass or less based on the total amount of the rubber component and the cellulosic fiber, or the total amount of the rubber component, the cellulosic fiber and the silane coupling agent. Also good. Moreover, it does not restrict | limit especially as a method of removing solvents other than the above, It can carry out by a conventionally well-known method. For example, there is a method of coagulating the mixture by adding an acid or salt, dehydrating, washing and drying.

In the step (a2), mixing can be performed in the following four modes.
Aspect 1: A mixture (B1) of a rubber component and a cellulosic fiber is mixed with a silane coupling agent.
Aspect 2: A mixture (B2) of a rubber component and a silane coupling agent is mixed with a cellulosic fiber.
Aspect 3: The mixture (B3) of the cellulosic fiber and the silane coupling agent is mixed with the rubber component.
Aspect 4: A rubber component, a cellulosic fiber, and a silane coupling agent are mixed.
In Embodiments 1 to 3, if a solvent or a dispersion medium is used in the process of obtaining the previous mixture, the material to be added in the subsequent mixing may be added as a solid substance, or is dissolved in a solution or dispersed in the dispersion medium. You may add in a state. In the aspect 4, it is preferable to use a material in which any material is dissolved or dispersed.

(2-2) Heating step:
A heating process is a process of heating a mixture for 5 to 600 minutes on 100-300 degreeC conditions. This heat treatment improves the compatibility between the cellulosic fibers and the rubber component. If the heating temperature is less than 100 ° C., the compatibility improving effect may not be sufficiently exhibited. On the other hand, when it exceeds 300 ° C., the rubber component and the like may deteriorate. On the other hand, if the heating time is less than 5 minutes, the heat treatment may not sufficiently proceed and the compatibility improving effect may not be sufficiently exhibited. On the other hand, when it exceeds 600 minutes, a rubber component etc. may deteriorate.
The lower limit of the heating temperature is preferably 105 ° C. or higher, and more preferably 110 ° C. or higher. The upper limit of the heating temperature is preferably 200 ° C. or less, and more preferably 180 ° C. or less. The heating temperature is preferably 105 to 200 ° C, more preferably 110 to 180 ° C.
The heating time is preferably 5 to 300 minutes, more preferably 10 to 120 minutes, and still more preferably 15 to 70 minutes.

  The heat treatment can be performed using a known apparatus such as a ventilating oven. The heating atmosphere may be in the presence of oxygen or in the absence of oxygen. Moreover, it is preferable that the pressure of a heating atmosphere is a normal pressure (1 atmosphere).

(2-3) Kneading step:
The kneading step is a step of obtaining a kneaded product by kneading the heat-treated product A and the silane coupling agent in the embodiment A.
The method for adding the silane coupling agent to the heat-treated product A is not limited, but it is preferable to add the silane coupling agent without using a solvent.
The kneading may be performed as known, for example, using a Banbury mixer, a kneader, an open roll, or the like.

  The kneading temperature may be about room temperature (about 15 to 30 ° C.), but may be heated to a certain high temperature. For example. The upper limit of the temperature is 140 ° C. or lower, preferably 100 ° C. or lower. The lower limit of the temperature is 15 ° C or higher, preferably 20 ° C or higher. The kneading temperature is preferably 15 to 140 ° C, more preferably 20 to 100 ° C.

  You may shape | mold as needed after a heating process (b2) or a kneading | mixing process (c1) completion | finish. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, hollow molding, and foam molding. What is necessary is just to select suitably according to the shape of a masterbatch, a use, and a shaping | molding method.

(3) Unkahashi rubber composition:
The unvulcanized rubber composition of the present invention contains the masterbatch described in “(1) Masterbatch” and a crosslinking agent. Moreover, the uncured bridge rubber composition may contain a known additive used for the rubber composition. Further, the uncured rubber composition may contain a rubber component separately from the rubber component used in the preparation of the masterbatch. The rubber component may be the same as or different from the rubber component used in the preparation of the masterbatch.
Hereinafter, the crosslinking agent and the additive will be described.

(3-1) Crosslinking agent:
Examples of the crosslinking agent include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, alkylphenol resins having a methylol group, and the like. Among these, sulfur is preferable.
The compounding amount of the crosslinking agent is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, with respect to 100 parts by mass of the rubber component in the uncured bridge rubber composition. Preferably it is 0.5-5 mass parts.

(3-2) Additive:
Examples of additives include vulcanization accelerators such as sulfenamide (for example, Nt-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide), zinc oxide and stearin. Examples include vulcanization accelerating aids such as acids, reinforcing agents such as carbon black and silica, silane coupling agents, oils, curing resins, waxes, anti-aging agents, peptizers, colorants, and pH adjusters. Among these, zinc oxide and a vulcanization accelerator are preferable.
The blending amount of the additive is appropriately selected according to the additive used. For example, when it is zinc oxide, it is about 1-10 mass parts with respect to 100 mass parts of rubber components in an unvulcanized rubber composition, and it is about 0.1-5 mass parts when it is a vulcanization accelerator. It is.

(4) Manufacturing method of uncured bridge rubber composition:
The method for producing an uncured bridge rubber composition of the present invention comprises a step of preparing a master batch by the method described in “(2) Method of producing master batch” and a step of kneading a crosslinking agent in the master batch. Have. When kneading the cross-linking agent, additives and rubber components may be blended as necessary. By further blending the rubber component in the kneading step, desired physical properties can be easily achieved when a rubber composition is obtained.
Hereinafter, the process of kneading the crosslinking agent in the master batch will be described.

Kneading refers to a step of uniformly dispersing a crosslinking agent and additives in a masterbatch. The kneading can be carried out by a known method, for example, using a Banbury mixer, a kneader, an open roll, or the like.
Further, an unvulcanized rubber composition in which the rubber component is further added to the master batch together with a crosslinking agent and additives and kneaded to dilute the compounding concentration of the cellulosic fibers can be obtained.

  The kneading temperature may be about room temperature (about 15 to 30 ° C.), but may be heated to a high temperature so that the rubber component does not undergo a crosslinking reaction. For example, the upper limit of the temperature is 140 ° C. or lower, more preferably 100 ° C. or lower. The lower limit of the temperature is 15 ° C or higher, preferably 20 ° C or higher. The kneading temperature is preferably 15 to 140 ° C, more preferably 20 to 100 ° C.

  You may shape | mold as needed after completion | finish of kneading | mixing. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, hollow molding, and foam molding. What is necessary is just to select suitably according to the shape of an unvulcanized rubber composition, a use, and a shaping | molding method.

(5) Rubber composition:
The rubber composition of the present invention contains a crosslinked product of the uncrosslinked rubber composition described in “(3) Uncrosslinked rubber composition”.
The use of the rubber composition of the present invention is not particularly limited, for example, transportation equipment such as automobiles, trains, ships, airplanes, etc .; electrical appliances such as personal computers, televisions, telephones, watches, etc .; mobile communication equipment such as mobile phones Etc .; AV equipment such as portable music playback equipment and video playback equipment; printing equipment; copying equipment; sports equipment; building materials; office equipment such as stationery; Other than these, application to members using rubber or flexible plastic is possible, and application to tires is preferable. Examples of the tire include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

(5-1) Physical properties:
The rubber composition of the present invention has a high stress at low strain while maintaining the elongation at break to some extent even when using the master batch of any of Embodiment A and Embodiment B.
The value of elongation at break is preferably 550% or more, more preferably 560% or more, and further preferably 570% or more.
The stress at low strain can be evaluated by the modulus value. The 50% modulus value (MPa) is preferably 0.9 or more, more preferably 1.0 or more, and further preferably 1.1 or more. The 100% modulus value (MPa) is preferably 1.7 or more, more preferably 1.9 or more, and further preferably 2.0 or more. The 300% modulus value (MPa) is preferably 7.6 or more, more preferably 8.0 or more, and further preferably 8.5 or more.
In addition, about the measuring method of breaking elongation and a modulus value, it is a method as described in an Example.

(6) Manufacturing method of rubber composition:
The method for producing a rubber composition of the present invention comprises a step of preparing an uncrosslinked rubber composition by the method described in “(4) Method for producing an uncrosslinked rubber composition”, and crosslinking the prepared uncrosslinked rubber composition. And a process.
Hereinafter, the step of crosslinking the prepared uncrosslinked rubber composition will be described.

Crosslinking is not particularly limited in temperature as long as the crosslinking reaction proceeds. Usually, when an uncrosslinked rubber composition obtained by kneading is heated and crosslinked (also referred to as vulcanization when sulfur is contained), a rubber composition is obtained. The lower limit of the heating temperature is preferably 140 ° C. or higher. The upper limit is preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. The heating temperature is preferably 140 to 200 ° C, more preferably 140 to 180 ° C.
For crosslinking, for example, a vulcanizing apparatus that performs mold vulcanization, can vulcanization, continuous vulcanization, or the like can be used. In the manufacturing method of the rubber composition of this invention, it exists in the tendency for a crosslinking reaction to advance rapidly compared with the case where a cellulose nanofiber is not included. The reason for this is not limited, but it is presumed that functional groups such as carboxyl groups in cellulose nanofibers may promote the crosslinking reaction.

After the cross-linking, a final treatment may be performed as necessary before making the final product. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, and chlorination.
These processes may be performed only by a single process or may be performed by combining two or more processes.

  Hereinafter, the present invention will be described in detail with reference to examples. The following examples are for explaining the present invention preferably and are not intended to limit the present invention. In addition, unless otherwise indicated, the measuring methods, such as a physical-property value, are the measuring methods described above.

[Measurement method of physical properties]
According to JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”, 50% tensile stress (50% modulus, described as “M50”), 100% tensile stress (100% modulus, “M100”) Described), 300% tensile stress (300% modulus; described as “M300”), breaking stress and breaking elongation. It shows that the reinforcement effect of a rubber composition is so high that each numerical value is large, and it is excellent in the mechanical strength of a rubber composition.

(Production Example 1: Production of oxidized cellulose nanofiber)
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%) 5.00 g (absolutely dried), TEMPO (manufactured by Sigma Aldrich) 39 mg (0.05 mmol for 1 g of absolutely dried cellulose) and 514 mg of sodium bromide ( The solution was added to 500 mL of an aqueous solution in which 1.0 mmol) of 1 g of absolutely dry cellulose was dissolved, and 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 the oxidation reaction was started at room temperature. During the reaction, since the pH in the system was lowered, a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The reaction mixture was filtered through a glass filter to separate the 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. Water was added to the reaction mixture to adjust the concentration to 1.0 mass% (w / v), and the mixture was treated 3 times with an ultrahigh pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3 nm and the aspect ratio was 250.

Below, the material used for manufacture of a masterbatch by the reference example described in Table 1, Examples 1-4, and Comparative Examples 1-4 is described.
NR: Natural rubber (trade name “HA-LATEX”, manufactured by Restex, solid content concentration 61.7%)
TOCN: Oxidized cellulose nanofiber produced in Production Example 1 SC agent: (trade name “A-1310”, manufactured by Momentive Performance Materials Japan LLC, isocyanate-based)

Below, the additive used for manufacture of a rubber composition by a reference example, Examples 1-4, and Comparative Examples 1-4 is described.
Stearic acid: (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.)
Zinc oxide: (special reagent grade, manufactured by Wako Pure Chemical Industries, Ltd.)
Sulfur: (for chemical use, manufactured by Wako Pure Chemical Industries, Ltd.)
MSA-G :: (trade name “Noxeller MSA-G”, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

(Reference example)
The natural rubber was dried in a heating oven at 70 ° C. for 19 hours. To 100 g of the natural rubber, add 3.5 g of sulfur, 0.7 g of a vulcanization accelerator (N-oxydiethylene-2-benzothiazolylsulfenamide), 6.0 g of zinc oxide, and 0.5 g of stearic acid, and open roll. (Kansai Roll Co., Ltd.) was used and kneaded at 50 ° C. for 20 minutes to obtain a sheet of an unvulcanized rubber composition. The sheet was sandwiched between molds and press-crosslinked at 150 ° C. for 15 minutes to obtain a reference rubber composition sheet having a thickness of about 2 mm. Using the reference rubber composition sheet, the physical properties of the rubber composition were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 1)
A rubber component and cellulose nano were prepared by mixing 673.1 g of a solid content concentration of 1.04% (w / v) (1% by mass) of the oxidized cellulose nanofiber obtained in Production Example 1 and 56.7 g of natural rubber. The mass ratio with respect to the fiber was adjusted to 100: 20, and the mixture was stirred with a TK homomixer (8000 rpm) for 10 minutes. This aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture.
Natural rubber dried for 19 hours in a heating oven at 70 ° C. is added to 42 g of the dried mixture three times as much as the natural rubber component of the mixture, and 3.5 g of sulfur and a vulcanization accelerator (N-oxydiethylene- 2-benzothiazolylsulfenamide) 0.7 g, zinc oxide 6.0 g and stearic acid 0.5 g were added, and kneaded at 50 ° C. for 20 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.). The sheet | seat of the unvulcanized rubber composition whose mass ratio with a cellulose nanofiber is 100: 5 was obtained. The rubber composition sheet of Comparative Example 1 was obtained in the same manner as the reference example, and the physical property values were evaluated. The evaluation results are shown in Table 1.

Example 1
Mass of rubber component and cellulose nanofiber by mixing 673.1 g of water dispersion liquid of 1.04% (w / v) solid content of oxidized cellulose nanofiber obtained in Production Example 1 and 56.7 g of natural rubber The ratio was 100: 20, 0.7 g of SC agent was further added, and the mixture was stirred for 10 minutes with a TK homomixer (8000 rpm). This aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture B.
The mixture B was heated in an oven at 120 ° C. for 30 minutes to obtain a heat-treated product B (master batch).
Natural rubber dried in a heating oven at 70 ° C. for 19 hours is added to 43.3 g of the heat-treated product B three times as much as natural rubber in the mixture B, and 3.5 g of sulfur and a vulcanization accelerator (N-oxygen) are added. Diethylene-2-benzothiazolylsulfenamide) 0.7 g, zinc oxide 6.0 g and stearic acid 0.5 g were added, and kneaded at 50 ° C. for 20 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.). A sheet of vulcanized rubber composition was obtained. The mass ratio between the rubber component and the cellulose nanofiber is 100: 5, the mass ratio between the rubber component and the SC agent is 100: 0.5, and the mass ratio between the cellulose nanofiber and the SC agent is 5: 0.5. Met.
The sheet was sandwiched between molds and press-crosslinked at 150 ° C. for 15 minutes to obtain a rubber composition sheet having a thickness of about 2 mm. This was cut into test pieces of a predetermined shape, and the physical property values were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 2)
A rubber composition sheet was obtained in the same manner as in Example 1 except that the mixture B was not heated in an oven, and the physical properties were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 3)
When obtaining the mixture B, a rubber composition sheet was obtained in the same manner as in Example 1 except that the SC agent was not added, and the physical properties were evaluated. The evaluation results are shown in Table 1.

(Example 2)
Mass of rubber component and cellulose nanofiber by mixing 673.1 g of water dispersion liquid of 1.04% (w / v) solid content of oxidized cellulose nanofiber obtained in Production Example 1 and 56.7 g of natural rubber The ratio was 100: 20, and the mixture was stirred for 10 minutes with a TK homomixer (8000 rpm). This aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture A.
The mixture A was heated in an oven at 120 ° C. for 30 minutes to obtain a heat-treated product A.
Natural rubber dried for 19 hours in a heating oven at 70 ° C. is added to 42 g of the heat-treated product A 3 times in terms of natural rubber in the mixture A, and further SC agent 0.7 g, sulfur 3.5 g, vulcanization accelerator (N-oxydiethylene-2-benzothiazolylsulfenamide) 0.7 g, zinc oxide 6.0 g and stearic acid 0.5 g are added and kneaded at 50 ° C. for 20 minutes using an open roll (manufactured by Kansai Roll). Thus, a sheet of an unvulcanized rubber composition was obtained. The mass ratio between the rubber component and the cellulose nanofiber is 100: 5, the mass ratio between the rubber component and the SC agent is 100: 0.5, and the mass ratio between the cellulose nanofiber and the SC agent is 5: 0.5. Met.
The sheet was sandwiched between molds and press-crosslinked at 150 ° C. for 15 minutes to obtain a rubber composition sheet having a thickness of about 2 mm. This was cut into test pieces of a predetermined shape, and the physical property values were evaluated. The evaluation results are shown in Table 1.

(Example 3)
A sheet of the rubber composition was obtained in the same manner as in Example 1 except that the heating temperature was 150 ° C., and the physical properties were evaluated. The evaluation results are shown in Table 1.

Example 4
A rubber composition sheet was obtained in the same manner as in Example 2 except that the heating temperature was 150 ° C., and the physical properties were evaluated. The evaluation results are shown in Table 1.

(Comparative Example 4)
A rubber composition sheet was obtained in the same manner as in Comparative Example 3 except that the heating temperature was 150 ° C., and the physical properties were evaluated. The evaluation results are shown in Table 1.

In Table 1, parts indicate parts by mass. “Before” in the order of SC agent addition means that the SC agent is blended before the heating step, that is, the mixing step, and “after” means that the SC agent is blended after the heating step, that is, the kneading step. To do.
As can be seen from Table 1, when the SC agent is added, the low strain stress increases, but the elongation at break decreases (see Comparative Examples 2 and 3). On the other hand, the heat treatment alone does not reduce the elongation at break, but does not improve the stress as low as adding the SC agent (see Comparative Examples 1 to 4).
On the other hand, when the SC agent is added and the heating step is performed, a low strain stress can be improved while suppressing a decrease in elongation at break as compared with the case of the SC agent alone (Comparative Example 2, Implementation). See Examples 1-4). Moreover, the addition of the SC agent is not significantly different before and after the heat treatment.
Therefore, a heterogeneous effect that could not be expected simply by improving the compatibility between the rubber component and the cellulose fiber was recognized.

Claims (21)

Using rubber components, cellulosic fibers and silane coupling agents as raw materials,
A master batch containing a heat-treated product of a mixture containing at least the rubber component and the cellulosic fiber. A heat-treated product A of a mixture A containing the rubber component and the cellulosic fibers;
The masterbatch of Claim 1 containing the kneaded material with the said silane coupling agent.   The masterbatch of Claim 1 containing the heat-processed material B of the mixture B containing the said rubber component, the said cellulosic fiber, and the said silane coupling agent.   The blending ratio of the cellulosic fiber and the silane coupling agent (silane coupling agent / cellulosic fiber) is 0.1 / 10 to 5/10 in terms of parts by mass. The master batch described in the item.   The masterbatch according to any one of claims 1 to 4, wherein the cellulosic fiber is oxidized cellulose.   The masterbatch according to any one of claims 1 to 5, wherein the cellulosic fibers have a length-weighted average fiber length of 50 to 2000 nm and a length-weighted average fiber diameter of 2 to 500 nm.   The master batch according to any one of claims 1 to 6, wherein the silane coupling agent has at least one group selected from the group consisting of a mercapto group, an isocyanate group, a sulfide group, and an amino group.   The master batch according to any one of claims 1 to 7, wherein the rubber component includes natural rubber.   The uncrosslinked rubber composition containing the masterbatch of any one of Claims 1-8, and a crosslinking agent.   A rubber composition containing a crosslinked product of the uncrosslinked rubber composition according to claim 9. (A1) mixing the rubber component and the cellulosic fiber to obtain a mixture A;
(B1) heating the mixture A at a temperature of 100 to 300 ° C. for 5 to 600 minutes to obtain a heat-treated product A;
(C1) A method for producing a masterbatch comprising: kneading the heat-treated product A and a silane coupling agent to obtain a kneaded product.   The step (a1) is mixed using a solvent A derived from at least one of the dispersion or solution of the rubber component and the dispersion of the cellulose fiber, the solvent A is dried, and the mixture A is dried. The manufacturing method according to claim 11, which is a step of obtaining. (A2) mixing the rubber component, cellulosic fiber and silane coupling agent to obtain a mixture B;
(B2) A step of heating the mixture B at a temperature of 100 to 300 ° C. for 5 to 600 minutes to obtain a heat-treated product B.   The step (a2) is a solvent B derived from at least one selected from the group consisting of a dispersion or solution of the rubber component, a dispersion of the cellulose fiber, and a dispersion or solution of the silane coupling agent. The production method according to claim 13, wherein the mixture B is mixed to obtain the mixture B by drying the solvent B.   The blending ratio (silane coupling agent / cellulosic fiber) of the cellulose fiber and the silane coupling agent is 0.1 / 10 to 5/10 in terms of parts by mass. The production method according to item.   The manufacturing method according to any one of claims 11 to 15, wherein the cellulosic fiber is oxidized cellulose.   The length-weighted average fiber length of the said cellulose-type fiber is 50-2000 nm, The manufacturing method of any one of Claims 11-16 whose length weighted average fiber diameter is 2-500 nm.   The production method according to any one of claims 11 to 17, wherein the silane coupling agent has at least one group selected from the group consisting of a mercapto group, an isocyanate group, a sulfide group, and an amino group.   The manufacturing method according to claim 11, wherein the rubber component includes natural rubber. A step of preparing a masterbatch by the production method according to any one of claims 11 to 19,
And a step of kneading a crosslinking agent in the master batch.   A method for producing a rubber composition, comprising: a step of preparing an uncrosslinked rubber composition by the production method according to claim 20; and a step of crosslinking the uncrosslinked rubber composition.