JP2020007457A - Cellulose nanofiber, and manufacturing method of rubber composition containing cellulose nanofiber - Google Patents

Abstract

To provide a manufacturing method of a rubber composition, good in strength and manufactured by a master batch containing a rubber composition and a cellulosic fiber.SOLUTION: There is provided a manufacturing method of a master batch including following processes of <1> to <2>. <1> a process for fibrillating a dispersion prepared with chemically modified treated cellulose fiber of 2.0 wt.% concentration or more to obtain a cellulose nanofiber. <2> a process for conducting a drying treatment after mixing the cellulose nanofiber obtained in <1> and rubber latex to obtain the master batch. The cellulose nanofiber preferably contains a carboxyl group-containing cellulose nanofiber such as an oxidized cellulose nanofiber or carboxylated cellulose nanofiber.SELECTED DRAWING: None

Description

  The present invention relates to a masterbatch containing cellulose nanofibers using chemically modified cellulose fibers as a raw material, and a method for producing a rubber composition produced using the same.

  It is known that a rubber composition produced by a master batch containing a rubber component and a cellulosic fiber has excellent mechanical strength. For example, Patent Document 1 discloses that a short fiber having an average fiber diameter of less than 0.5 μm is fibrillated in water, mixed with a rubber latex, and dried, so that the short fiber is uniformly dispersed in rubber. It describes that a dispersed rubber / short fiber masterbatch can be obtained, and that a rubber composition having an excellent balance between rubber reinforcement and fatigue resistance can be produced from the masterbatch.

JP 2006-206864 A

  However, in order for a conventional rubber composition containing a rubber component and a cellulosic fiber to be applied to various fields, further improvement in strength is required.

  Therefore, an object of the present invention is to provide a method for producing a rubber composition produced by a master batch containing a rubber component and a cellulosic fiber and having good strength.

The present invention provides the following [1] to [8].
[1] A method of manufacturing a master batch including the following steps <1> and <2><1> After adjusting the chemically modified cellulose fiber to a dispersion having a concentration of 2.0% by weight or more, the dispersion is prepared. <2> Step of obtaining cellulose nanofibers by mixing the cellulose nanofibers obtained in <1> and rubber latex, followed by drying treatment to obtain a master batch [2] Chemical modification treatment The method for producing a masterbatch according to [1], wherein the method is a oxidation treatment, and the method for producing a masterbatch according to [1], wherein the chemical modification treatment is a carboxymethylation treatment. 4] The method for producing a masterbatch according to [1], wherein the chemical modification treatment is a cationization treatment. [5] A phosphate esterification treatment. [1] The method for producing a master batch described in [1] [6] The method for producing a master batch according to [1] to [5], wherein the fibrillation treatment is an ultra-high pressure homogenizer treatment. The method of [6], wherein the product of the pressure (MPa) and the number of treatments (times) is 200 MPa · times or more. For producing rubber composition prepared by using the method

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the rubber composition which contains a rubber component and cellulose nanofiber and has favorable intensity | strength can be provided.

[Chemically modified cellulose fiber]
Chemically modified cellulose fibers are obtained by modifying cellulose contained in a cellulosic material. The cellulosic material is not particularly limited as long as it contains cellulose, and is derived from, for example, plants, animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), and microorganism products. Things. Examples of plant-based cellulosic materials include wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft Pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulphite pulp (NUSP), softwood bleached sulphite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.). The cellulosic material may be any of these, or a combination of two types of cellulosic materials, preferably a cellulosic material derived from a plant or a microorganism, more preferably a cellulosic material derived from a plant, and still more preferably. Is pulp.

  The cellulosic material usually contains fibrous cellulose (cellulose fiber). The average fiber diameter of the cellulosic fibers is not particularly limited, but the average fiber diameter of the cellulosic material derived from a common pulp, softwood kraft pulp, is usually about 30 to 60 μm, and the cellulose derived from hardwood kraft pulp The average fiber diameter of the system raw material is usually about 10 to 30 μm. The average fiber diameter of the cellulosic raw material derived from pulp after general purification other than softwood kraft pulp and hardwood kraft pulp is usually about 50 μm.

  Cellulose has three hydroxyl groups per glucose unit and can be variously modified. Examples of the modification (generally, chemical modification) include esterification such as oxidation, etherification, and phosphate esterification, silane coupling, fluorination, and cationization. Among them, oxidation (carboxylation), etherification (carboxymethylation and the like), cationization and esterification are preferred, and oxidation (carboxylation) and carboxymethylation are more preferred.

In the present invention, if the hydroxyl groups of the cellulose by oxidation and etherification is denatured carboxyl group, a group that actually represented by -COOH, -COO ^- group represented by are mixed. So based on the acid type carboxyl group represented by -COOH (acid form), - COO ^- group represented by the called salt type carboxyl group (salt form). The counter cation of the salt-type carboxyl group is not particularly limited, and examples thereof include alkali metal ions such as sodium ions and potassium ions, and other metal ions.

[Oxidation (carboxylation)]
The modified cellulose (oxidized cellulose) and the modified cellulose nanofiber (oxidized cellulose nanofiber) obtained through oxidation preferably have a structure in which at least one of the hydroxyl groups of cellulose is selectively oxidized.

  In the oxidized cellulose nanofiber, it is preferable that at least one of the hydroxyl groups of the glucopyranose ring constituting the cellulose has a carboxyl group, and the hydroxyl group at the 6-position of at least one glucopyranose ring constituting the cellulose has a carboxyl group. preferable.

  The carboxyl group content of the oxidized cellulose and the oxidized cellulose nanofiber is preferably 0.5 mmol / g or more, more preferably 0.6 mol / g or more, or 0.8 mmol or / g or more, even more preferably, based on the absolute dry mass. Is 1.0 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 even more preferably 2.0 mmol / g or less. Therefore, the amount is preferably 0.5 to 3.0 mmol / g, more preferably 0.6 to 2.0 mmol / g or 0.8 to 2.5 mmol / g, and 1.0 to 2.0 mmol / g. More preferred. The carboxyl group content of the oxidized cellulose nanofiber is usually the same as that of the oxidized cellulose before fibrillation.

  The oxidation method is not particularly limited, and includes, for example, a method of oxidizing a cellulosic 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 generate a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. The concentration of the cellulosic material during the reaction is not particularly limited, but is preferably 5% by mass or less.

  As the N-oxyl compound, for example, 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter, also referred to as “TEMPO”) or 4-hydroxy-2,2,6,6 -Tetramethyl-1-piperidine-N-oxy radical (hereinafter, also referred to as "4-hydroxyTEMPO").

  An N-oxyl compound refers to a compound that can generate 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 a desired oxidation reaction. The amount of the N-oxyl compound used may be an amount that catalyzes the oxidation reaction of cellulose as a raw material. For example, the amount is preferably 0.01 mmol or more, more preferably 0.02 mmol or more, based on 1 g of absolutely dried cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.02 to 0.5 mmol, based on 1 g of absolutely dried cellulose.

  Bromide is a compound containing bromine, for example, an alkali metal bromide that can be dissociated and ionized in water. Further, iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used is not particularly limited, and 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, based on 1 g of absolutely dried cellulose. 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. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and even more preferably 0.5 to 5 mmol, based on 1 g of absolutely dried cellulose.

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

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

  The reaction time in the oxidation can be appropriately set according to the degree of progress of the oxidation, and is usually 0.5 hours or more, and the upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in the oxidation is usually 0.5 to 6 hours, preferably about 0.5 to 4 hours. The oxidation may be performed in two or more stages of the reaction. 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 of the oxidized cellulose can be reduced without being inhibited by the salt produced as a by-product in the first-stage reaction. Can be well oxidized.

  Another example of the carboxylation (oxidation) method is ozone oxidation. By this oxidation reaction, at least the hydroxyl groups at the 2- and 6-positions 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 into contact with a cellulosic material.

The ozone treatment is usually performed by bringing a gas containing ozone into contact with a cellulosic material. 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, more preferably 220 g / m ^3. Therefore, the ozone concentration in the gas is preferably ^{50~250g / m 3, 50~220g / m} 3 and more preferably. The amount of ozone added is preferably at least 0.1 part by mass, more preferably at least 5 parts by mass, based on 100 parts by mass of the solid content of the cellulosic raw material. The upper limit of the amount of added ozone is usually 30 parts by mass or less. Therefore, the amount of added ozone is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the solid content of the cellulosic raw material. The ozone treatment temperature is usually 0 ° C. or higher, preferably 20 ° C. or higher, and the upper limit is usually 50 ° C. or lower. Therefore, the ozone treatment temperature is preferably from 0 to 50 ° C, more preferably from 20 to 50 ° C. The ozone treatment time is usually at least 1 minute, preferably at least 30 minutes, and the upper limit is usually at most 360 minutes. Therefore, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of the ozone treatment are within the above-mentioned range, excessive oxidation and decomposition of cellulose can be prevented, and the yield of oxidized cellulose can be improved.

  The ozone-treated cellulose may be further subjected to an 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, and peracetic acid. Examples of the method of the post-oxidation treatment include a method in which an oxidizing agent is dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the cellulose-based material is immersed in the oxidizing agent solution. The amounts 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 amount of the oxidizing agent added and the reaction time.

[Acid-type oxidized cellulose]
It is preferable that the oxidized cellulose after oxidation is converted to acid-type oxidized cellulose or acid-type oxidized cellulose nanofiber by desalting. The desalting may be performed at any point before (after oxidized cellulose) and after (after oxidized cellulose nanofibers) defibration. Desalting means that a salt (for example, a sodium salt) contained in oxidized cellulose (salt type) or oxidized cellulose nanofiber (salt type) is replaced with a proton to obtain an acid type. Examples of the desalting method after the oxidation include a method of adjusting the inside of the system to be acidic and a method of bringing oxidized cellulose or oxidized cellulose nanofiber into contact with a cation exchange resin. When the inside of the system is adjusted to be acidic, the pH in the system is preferably adjusted to 2 to 6, more preferably 2 to 5, and still more preferably 2.3 to 5. To adjust the acidity, an acid (eg, an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrous acid, or phosphoric acid; or an organic acid such as acetic acid, lactic acid, oxalic acid, citric acid, or formic acid) is generally used. After the addition of the acid, a washing treatment may be appropriately performed. As the cation exchange resin, any of a strongly acidic ion exchange resin and a weakly acidic ion exchange resin can be used as long as the counter ion is H ⁺ . When the oxidized cellulose is brought into contact with the cation exchange resin, the ratio between the two is not particularly limited, and those skilled in the art can appropriately set the ratio from the viewpoint of efficiently performing proton substitution. The cation exchange resin after the contact may be collected by a conventional method such as suction filtration.

  In the acid-type oxidized cellulose and the acid-type oxidized cellulose nanofiber of the present invention, the ratio of the acid-type carboxyl group is preferably 40% or more, more preferably 60% or more, and further preferably 85% or more. preferable.

The ratio of the acid-type carboxyl group can be calculated by the following method. First, 250 mL of a 0.1% by mass slurry of oxidized cellulose nanofiber (salt type) before desalting treatment is prepared. To the prepared slurry, a 0.1 M aqueous hydrochloric acid solution is added to adjust the pH to 2.5, and then a 0.1 N aqueous sodium hydroxide solution is added to measure the electric conductivity until the pH becomes 11. From the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid having a gradual change in electric conductivity, the amount of acid-type carboxyl groups and the amount of salt-type carboxyl groups, that is, Calculate the amount of carboxyl groups.

(2): Total amount of carboxyl groups (mmol / g oxidized cellulose nanofiber (salt type)) = a (ml) × 0.1 / mass (g) of oxidized cellulose nanofiber (salt type)

Next, 250 mL of a 0.1% by mass slurry of the desalted acid-type oxidized cellulose nanofiber is prepared. A 0.1N aqueous sodium hydroxide solution is added to the prepared slurry, and the electric conductivity is measured until the pH becomes 11. The amount of acid-type carboxyl group is calculated from the amount of sodium hydroxide (b) consumed in the neutralization step of a weak acid having a gradual change in electric conductivity using the following formula (3).

(3): Amount of acid-type carboxyl group (mmol / g acid-type oxidized cellulose nanofiber) = b (ml) × 0.1 / mass of acid-type oxidized cellulose nanofiber (g)

From the calculated total amount of the carboxyl groups and the amount of the acid type carboxyl groups, the ratio of the acid type carboxyl groups can be calculated using the following formula (4).

(4): Ratio of acid type carboxyl group (%) = (acid type carboxyl group amount / total carboxyl group amount) × 100

[Etherification]
Examples of the etherification include etherification by carboxymethylation, etherification by methylation, etherification by ethylation, etherification by cyanoethylation, etherification by hydroxyethylation, etherification by hydroxypropylation, and ethylhydroxyethylation. And etherification by hydroxypropylmethylation. The carboxymethylation method is described below as an example.

  The modified cellulose (carboxymethylated cellulose) and cellulose nanofiber (carboxymethylated cellulose nanofiber) obtained through carboxymethylation preferably have a structure in which at least one of the hydroxyl groups of cellulose is carboxymethylated.

  The degree of carboxymethyl substitution per anhydroglucose unit of carboxymethylated cellulose and carboxymethylated cellulose nanofibers is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. The upper limit of the substitution degree is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less. Therefore, the degree of carboxymethyl substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and even more preferably 0.10 to 0.35. The degree of carboxymethyl substitution of carboxymethylated cellulose nanofibers is usually the same as that of carboxymethylated cellulose before fibrillation.

The degree of carboxymethyl substitution per glucose unit is measured, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dried) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 2) 100 mL of a solution obtained by adding 100 mL of special-grade concentrated nitric acid to 1000 mL of methanol nitrate, and shaken for 3 hours to convert a carboxymethylcellulose salt (carboxymethylated cellulose) into a carboxymethylated cellulose having a carboxyl group (hereinafter, “H-type carboxy”). Methylated cellulose "). 3) 1.5-2.0 g of H-type carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 4) Wet H-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake for 3 hours at room temperature. 5) Back titrate excess NaOH with 0.1 N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following equation (5).

(5): A = [(100 × F ′ − (0.1N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of H-type carboxymethylated cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralization of 1 g of H-type carboxymethylated cellulose
F: Factor of 0.1N H ₂ SO ₄ F ′: Factor of 0.1N NaOH

  The carboxymethylation method is not particularly limited, and includes, for example, a method in which a cellulosic material as a starting material is mercerized and then etherified. Usually, a solvent is used in the method. Examples of the solvent include water, alcohol (for example, lower alcohol), and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, isobutyl alcohol, and tertiary butyl alcohol. The mixing ratio of the lower alcohol in the mixed solvent is preferably from 60 to 95% by mass. The amount of the solvent is usually at least 3 times the mass of the cellulosic material. The upper limit of the amount is not particularly limited, but is usually not more than 20 times by mass. Therefore, the amount of the solvent is preferably 3 to 20 times by mass.

  Mercerization is usually performed by mixing a starting material and a mercerizing agent. Examples of the mercerizing agent include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent to be 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. The upper limit of the amount is usually 20 times or less, preferably 10 times or less, more preferably 5 times or less. Therefore, the amount of the mercerizing agent used is preferably 0.5 to 20 times mol, more preferably 1.0 to 10 times mol, and still more preferably 1.5 to 5 times mol.

  The reaction temperature for mercerization is usually 0 ° C. or higher, preferably 10 ° C. or higher, and the upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. Therefore, the reaction temperature is usually 0 to 70 ° C, preferably 10 to 60 ° C. The reaction time is usually at least 15 minutes, preferably at least 30 minutes. The upper limit of the time is usually 8 hours or less, preferably 7 hours or less. Therefore, 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. As the carboxymethylating agent, monochloroacetic acid and sodium monochloroacetate are preferable.

  The addition amount of the carboxymethylating agent is usually preferably 0.05 times or more, more preferably 0.5 times or more, more preferably 0.8 times or more per glucose residue of cellulose contained in the cellulose-based material. preferable. The upper limit of the amount is usually 10.0 mol or less, preferably 5 mol or less, more preferably 3 mol or less, and therefore the amount is preferably 0.05 to 10.0 mol. It is more preferably 0.5 to 5 moles, and still more preferably 0.8 to 3 moles. The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. Therefore, the reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C. The reaction time is usually at least 30 minutes, preferably at least 1 hour, and the upper limit is usually at most 10 hours, preferably at most 4 hours. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. The reaction solution may be stirred during the carboxymethylation reaction, if necessary.

[Acid carboxymethylated cellulose]
The carboxymethylated cellulose after etherification is preferably converted to acid-type carboxymethylated cellulose or acid-type carboxymethylated cellulose nanofiber by desalting. The desalting may be performed at any point before (after carboxymethylated cellulose) and after (after carboxymethylated cellulose nanofiber) defibration. Desalting means that a salt (for example, a sodium salt) contained in carboxymethylated cellulose (salt type) and carboxymethylated cellulose nanofiber (salt type) is replaced with a proton to form an acid type. Examples of the desalting method after the etherification (for example, carboxymethylation) include a method of bringing carboxymethylated cellulose or carboxymethylated cellulose nanofibers into contact with a cation exchange resin. As the cation exchange resin, any of a strongly acidic ion exchange resin and a weakly acidic ion exchange resin can be used as long as the counter ion is H ⁺ . The ratio of the carboxymethylated cellulose to the cation exchange resin when the carboxymethylated cellulose is brought into contact with the cation exchange resin is not particularly limited, and those skilled in the art can appropriately set the ratio from the viewpoint of performing efficient proton substitution. For example, the ratio is adjusted so that the pH of the aqueous dispersion after the addition of the cation exchange resin is preferably 2 to 6, more preferably 2 to 5, with respect to the aqueous dispersion of carboxymethylated cellulose nanofibers. can do. The collection of the cation exchange resin after the contact may be performed by a conventional method such as suction filtration.

  In the acid-type carboxymethylated cellulose and the acid-type carboxymethylated cellulose nanofiber of the present invention, the ratio of the acid-type carboxyl group is preferably 40% or more, more preferably 60% or more, and more preferably 85% or more. It is more preferred that there be.

The ratio of the acid-type carboxyl group can be calculated by the following method. First, 250 mL of a 0.1% by mass slurry of carboxymethylated cellulose nanofibers (salt type) before desalting treatment is prepared. To the prepared slurry, a 0.1 M aqueous hydrochloric acid solution is added to adjust the pH to 2.5, and then a 0.1 N aqueous sodium hydroxide solution is added to measure the electric conductivity until the pH becomes 11. From the amount (a) of sodium hydroxide consumed in the neutralization stage of the weak acid having a gradual change in electric conductivity, the amount of acid-type carboxyl groups and the amount of salt-type carboxyl groups, that is, Calculate the amount of carboxyl groups.

(6): Total amount of carboxyl groups (mmol / g carboxymethylated cellulose nanofiber (salt type)) = a (ml) x 0.1 / mass (g) of carboxymethylated cellulose nanofiber (salt type)

Next, 250 mL of a 0.1% by mass slurry of the desalted acid-type carboxymethylated cellulose nanofiber is prepared. A 0.1N aqueous sodium hydroxide solution is added to the prepared slurry, and the electric conductivity is measured until the pH becomes 11. The amount of acid-type carboxyl group is calculated from the amount (b) of sodium hydroxide consumed in the neutralization step of a weak acid having a gradual change in electric conductivity using the following formula (7).

(7): Amount of acid-type carboxyl group (mmol / g acid-type carboxymethylated cellulose nanofiber) = b (ml) × 0.1 / mass of acid-type carboxymethylated cellulose nanofiber (g)

From the calculated total amount of carboxyl groups and the amount of acid type carboxyl groups, the ratio of acid type carboxyl groups can be calculated using the following formula (8).

(8): Ratio (%) of acid type carboxyl groups = (acid type carboxyl group amount / total carboxyl group amount) × 100

[Cationization]
Modified cellulose (cationized cellulose) and cellulose nanofiber (cationized cellulose nanofiber) obtained through cationization contain at least one cation such as ammonium, phosphonium, sulfonium, or a group having the cation in the molecule. It is preferable to include at least one group having ammonium, and it is more preferable to include at least one group having quaternary ammonium.

  The degree of cation substitution per glucose unit of the cationized cellulose and the cationized cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, and still more 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 even more preferably 0.20 or less. Therefore, the degree of cation substitution is preferably 0.01 to 0.40, more preferably 0.02 to 0.30, and still more preferably 0.03 to 0.20. By introducing a cation substituent into cellulose, the celluloses repel each other electrically. For this reason, the modified cellulose into which the cation substituent is introduced (cationized cellulose) can be easily nanofibrillated. When the degree of cation substitution per glucose unit is 0.01 or more, nanofibrillation 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 morphology can be maintained, and the situation where nanofibers cannot be obtained can be prevented. The cation substitution degree of the cationized cellulose nanofiber is usually the same as that of the cationized cellulose before fibrillation.

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

  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 equation. The degree of cation substitution can be determined as the average value of the number of moles of the substituent per 1 mol of anhydroglucose unit using the following formula (9).

(9): Degree of cation substitution = (162 × N) / (1-116 × N)
N: Nitrogen content (mol) per 1 g of cationized cellulose

  The method of cationization is not particularly limited, and examples thereof include a method in which a cationizing agent and a catalyst are reacted with a cellulose-based material in the presence of water or an alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydride), and halohydrin types thereof. By using any of these, cationized cellulose having a group containing a quaternary ammonium can be obtained. Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Examples of the alcohol include an alcohol having 1 to 4 carbon atoms. The amount of the cationizing agent is preferably at least 5 parts by mass, more preferably at least 10 parts by mass, based on 100 parts by mass of the cellulosic raw material. The upper limit of the amount is usually 800 parts by mass or less, preferably 500 parts by mass or less. The amount of the catalyst is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more based on 100 parts by mass of the cellulosic raw material. The upper limit of the amount is usually 20 parts by mass or less, preferably 15 parts by mass or less. The amount of the alcohol is preferably at least 50 parts by mass, more preferably at least 100 parts by mass, per 100 parts by mass of the cellulosic raw material. The upper limit of the amount is usually 50,000 parts by mass or less, preferably 500 parts by mass or less.

  The reaction temperature at the time of cationization is usually 10 ° C. or higher, preferably 30 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. The reaction time is usually at least 10 minutes, preferably at least 30 minutes, and the upper limit is usually at most 10 hours, preferably at most 5 hours. The reaction solution may be agitated as needed during the cationization reaction.

[Basic cationized cellulose]
It is preferable that the cationized cellulose after cationization is converted into basic cationized cellulose or basic cationized cellulose nanofiber by desalting. The desalting may be performed at any point before (after cationized cellulose) or after (after cationized cellulose nanofiber) defibration. Desalting, cationized cellulose (salt type), and salts contained in the cationized cellulose nanofibers (salt form) ^- chlorine (Cl, etc.) means that the substituted basic base form. As a desalting method after cationization, for example, a method of bringing cationized cellulose or cationized cellulose nanofibers into contact with an anion exchange resin may be mentioned. As the anion exchange resin, any of a strongly basic ion exchange resin and a weakly basic ion exchange resin can be used as long as the counter ion is OH ⁻ . When the modified cellulose is brought into contact with the anion exchange resin, the ratio between the two is not particularly limited, and those skilled in the art can appropriately set the ratio from the viewpoint of efficiently performing proton substitution. For example, the ratio is adjusted such that the pH of the aqueous dispersion after the addition of the anion exchange resin is preferably 8 to 13, more preferably 9 to 13, relative to the aqueous dispersion of the cationized cellulose nanofiber. be able to. The collection of the anion exchange resin after the contact may be performed by a conventional method such as suction filtration.

[Esterification]
The esterification method is not particularly limited, and includes, for example, a method of reacting a compound having a phosphate group with a cellulose-based material (phosphate esterification method). Examples of the phosphoric esterification method include a method of mixing a powder or an aqueous solution of a compound having a phosphate group with a cellulose-based material, a method of adding an aqueous solution of a compound having a phosphate group to a slurry of a cellulose-based material, and the like. The latter is preferred. Thereby, the uniformity of the reaction can be improved, and the esterification efficiency can be increased.

  Examples of the compound having a phosphate group include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, esters and salts thereof. These compounds are low-cost, easy to handle, and improve the defibration efficiency by introducing a phosphate group into cellulose. 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, and hydrogen dihydrogen phosphate. Examples include potassium, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. The compound having a phosphate group may be one type or a combination of two or more types. Among them, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of phosphate group introduction, easy defibration in the following defibration step, and easy industrial application. Is preferred, the sodium salt of phosphoric acid is more preferred, and sodium dihydrogen phosphate and disodium hydrogen phosphate are even more preferred. In addition, it is preferable to use an aqueous solution of a compound having a phosphate group in the esterification because the uniformity of the reaction is increased and the efficiency of introducing the phosphate group is increased. The pH of the aqueous solution of the compound having a phosphate group is preferably 7 or less because the efficiency of phosphate group introduction is increased. From the viewpoint of suppressing hydrolysis of the pulp fiber, pH 3 to 7 is more preferable.

  The phosphoric esterification method will be described below by way of an example. A compound having a phosphate group is added to a suspension of the cellulosic raw material (for example, a solid content concentration of 0.1 to 10% by mass) with stirring to introduce a phosphate group into the cellulose. When the amount of the cellulose-based material is 100 parts by mass, the amount of the compound having a phosphoric acid group is preferably 0.2 parts by mass or more, more preferably 1 part by mass or more, as the amount of phosphorus atoms. Thereby, the yield of the esterified cellulose or the esterified cellulose nanofiber can be further improved. The upper limit is preferably 500 parts by mass or less, more preferably 400 parts by mass or less. As a result, a yield commensurate with the amount of the compound having a phosphate group can be efficiently obtained. Therefore, 0.2 to 500 parts by mass is preferable, and 1 to 400 parts by mass is more preferable.

  When reacting a compound having a phosphate group with a cellulose-based material, a basic compound may be further added to the reaction system. As a method of adding a basic compound to the reaction system, for example, a method of adding a basic compound to a slurry of a cellulose-based material, an aqueous solution of a compound having a phosphate group, or a slurry of a cellulose-based material and a compound having a phosphate group Is mentioned.

  The basic compound is not particularly limited, but preferably shows basicity, and more preferably a nitrogen-containing compound showing basicity. "Showing basicity" generally means that the aqueous solution of the basic compound exhibits a pink to red color in the presence of the phenolphthalein indicator, and / or that the pH of the aqueous solution of the basic compound is greater than 7. . The basic compound is preferably a compound having a basic nitrogen atom, and more preferably a compound having a basic amino group. Examples of the compound having a basic amino group include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Of these, urea is preferred because it is low in cost and easy to handle. The addition amount of the basic compound is preferably from 2 to 1,000 parts by mass, more preferably from 100 to 700 parts by mass. The reaction temperature is preferably from 0 to 95 ° C, more preferably from 30 to 90 ° C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the conditions of the esterification reaction are within any of these ranges, it is possible to suppress the cellulose from being excessively esterified and being easily dissolved, and to improve the yield of the phosphorylated cellulose. .

  After reacting the compound having a phosphate group with the cellulosic material, a suspension of the phosphorylated cellulose or the phosphorylated cellulose nanofiber is usually obtained. The suspension of phosphorylated cellulose or phosphorylated cellulose nanofibers is dehydrated as needed. After the dehydration, heat treatment is preferably performed. Thereby, hydrolysis of cellulose can be suppressed. The heating temperature is preferably from 100 to 170 ° C. During the heat treatment, heating is performed at 130 ° C or less (more preferably 110 ° C or less) while water is contained, and after removing water, heating is performed at 100 to 170 ° C. Processing is more preferred.

  By the phosphoric esterification reaction, a phosphate group substituent is introduced into the cellulose, and the celluloses are electrically repelled. Therefore, phosphate esterified cellulose can be easily defibrated into cellulose nanofibers. The phosphoric acid-substituted cellulose preferably has a degree of substitution of phosphate groups per glucose unit of 0.001 or more. Thereby, sufficient fibrillation (for example, nano-fibrillation) can be performed. The upper limit is preferably 0.40 or less. Thereby, the swelling or dissolution of the phosphated cellulose is suppressed, and the occurrence of a situation where cellulose nanofibers cannot be obtained can be suppressed. Therefore, the phosphate group substitution degree is preferably 0.001 to 0.40. The phosphate group substitution degree per glucose unit of the phosphate esterified cellulose nanofiber is more preferably 0.001 to 0.40.

  It is preferable that the phosphate esterified cellulose is subjected to a washing treatment such as washing with cold water after boiling. Thereby, defibration can be performed efficiently.

[Fibrillation processing (nano-fibrillation)]
The fibrillation treatment may be performed on the cellulosic raw material before denaturation or on the denatured cellulose, but the latter is preferable because the energy required for fibrillation is reduced by denaturation. The defibration treatment may be performed once or plural times, but preferably 2 to 5 times. When desalting is performed in the production of modified cellulose or modified cellulose nanofibers, defibration may be performed before and after desalting.

The apparatus used for the defibrating treatment is not particularly limited, and examples thereof include a high-speed rotation type, a colloid mill type, a high pressure type, a roll mill type, and an apparatus of an ultrasonic type, and a high pressure or ultra high pressure homogenizer is preferable, and a wet type is used. Of these, a high pressure or ultra high pressure homogenizer is more preferred. These devices are preferable because a strong shearing force can be applied to the modified cellulose. The shear rate is preferably 1000 sec ^-1 or more. This makes it possible to uniformly form nanofibers with a small aggregate structure. The pressure applied to the modified cellulose is preferably 100 MPa or more, more preferably 125 MPa or more, and even more preferably 150 MPa or more.

  The defibration treatment is usually performed in a dispersion. The dispersion is usually an aqueous dispersion such as an aqueous dispersion. Prior to dispersion, preliminary processing may be performed as necessary. The pretreatment includes, for example, mixing, stirring, and emulsification, and may be performed using a known device (for example, a high-speed shear mixer).

  When the defibration treatment is performed on a dispersion of a cellulosic raw material or a dispersion of a modified cellulose, the lower limit of the concentration by weight of the cellulose fiber dispersion in the dispersion is usually 2.0% by mass or more. Features. The preferred concentration of the cellulose fiber dispersion is 2.0 to 5.0% by weight, more preferably 2.5 to 4.0% by weight, and even more preferably 3.0 to 3.5% by weight. is there. By performing the defibration treatment at this concentration, a rubber composition having good strength can be obtained.

[Product of applied pressure and the number of times of defibration]
When the product obtained by multiplying the pressure (MPa) of the ultrahigh-pressure homogenizer treatment by the number of treatments (times) is 200 MPa · times or more, cellulose nanofibers having a rubber composition having good strength can be obtained. From the viewpoint of the physical property value of the obtained rubber composition and the production cost of the cellulose nanofiber, it is preferably 200 to 800 MPa · times, more preferably 250 to 650 MPa · times, and still more preferably 300 to 500 MPa · times.

  The cellulose nanofiber may be one kind or a combination of two or more kinds of cellulose nanofibers.

  Further, the dispersion liquid of the cellulose nanofibers may be a mixture of water-soluble polymers. Examples of the water-soluble polymer include cellulose derivatives (eg, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, Hardened flour, kudzu flour, positive starch, phosphorylated starch, corn starch, gum arabic, gellan gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein solubles, peptone, polyvinyl alcohol, polyacrylamide , Sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, Gin sizing agent, petroleum resin sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethylene imine, 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. Among them, carboxymethylcellulose or a salt thereof is preferably used from the viewpoint of solubility.

[Rubber component]
The rubber component is a raw material of rubber and refers to a material which is crosslinked to form rubber. The rubber component includes a rubber component for natural rubber and a rubber component for synthetic rubber. Examples of the rubber component for natural rubber include 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; hydrogenated 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 coalesced rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber; butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydrid Non-diene rubbers such as rubber (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), and chlorosulfonated polyethylene (CSM). Of these, diene rubbers are preferred, and diene natural rubbers are more preferred.

  The rubber component may be used alone or in combination of two or more.

[Manufacturing method of master batch]
<Mixing process>
In the mixing step, the solid component of the rubber component may be used for mixing, or may be used as a dispersion liquid (latex) in which the rubber component is dispersed in a dispersion medium or a solution in which the rubber component is dissolved in a solvent. Examples of the dispersion medium and the solvent (hereinafter, also collectively referred to as “liquid”) include, for example, water and an organic solvent. The amount of the liquid is preferably from 10 to 1000 parts by mass based on 100 parts by mass of the rubber component (when two or more rubber components are used, the total amount).

  The mixing can be performed using a known device such as a homomixer, a homogenizer, a propeller stirrer, and the like. The mixing temperature is not limited, but is preferably room temperature (20 to 30 ° C.). The mixing time may be appropriately adjusted.

  The cellulose nanofiber can be provided for mixing in the form of a dispersion dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion. The concentration of the modified cellulose nanofibers in the dispersion may be 0.1 to 5% (w / v) when the dispersion medium is water, and when the dispersion medium contains water and an organic solvent such as alcohol. , 0.1 to 20% (w / v). A wet solid is a solid that is intermediate between the dispersion and the dry solid. The amount of the dispersion medium in the wet solid obtained by dehydrating the dispersion in a usual manner is preferably 5 to 15% by mass based on the cellulose, but the amount of the dispersion medium is appropriately adjusted by adding a liquid or further drying. I can do it.

  The cellulose nanofiber may be a combination of two or more cellulose nanofibers. When the mixture is a mixture of modified cellulose nanofibers and a water-soluble polymer solution, a mixture, a dry solid of the mixture, a wet solid of the mixture, and the like can be used for mixing. The amount of liquid in the mixture and its dry solids may be in the above ranges.

<Drying process>
The mixture obtained in the mixing step is preferably dried. The method of drying is not particularly limited, and a coagulation treatment may be performed before drying.

<Kneading process>
The kneading of the mixture in the kneading step of the present invention may be performed in a known manner, for example, an open kneader such as a two-roll or three-roll mixer, a meshing Banbury mixer, a tangential Banbury mixer, a pressure kneader. Such a closed kneader can be used. In addition, a process through a multi-stage kneading process is also possible. For example, in the first stage, kneading is performed by a closed kneader, and then re-kneading can be performed by an open kneader.

  In the present invention, a surfactant may be added in the kneading step. The addition of the surfactant is performed when the mixture obtained in the mixing step or the mixture obtained through the drying step is kneaded using the above kneader. The addition is performed at the start of kneading, during kneading, or both.

  Further, as a method of addition, there is a method of adding a predetermined amount at a time or a method of adding sequentially, but any method may be used as long as the surfactant is uniformly kneaded with the mixture.

  In addition to the surfactant, an optional additive such as a filler, a vulcanizing agent, and other compounding agents can be added. The order of addition of the mixture, the surfactant, and other optional additives is not limited. After the mixture has been charged into the kneader first, the additives can be charged and kneaded. Alternatively, after the additives have been charged first, the mixture can be charged and kneaded. Further, a surfactant and other additives may be previously blended and added to the kneader. However, when a vulcanizing agent is added, it is desirable to add the vulcanizing agent at the final stage of kneading. The kneading time may be any as long as the surfactant is uniformly kneaded with the mixture, but is usually about 3 to 20 minutes.

  The kneading temperature may be about room temperature (about 15 to 30 ° C.), but may be heated to some high temperature. For example. The upper limit of the temperature is 150 ° C. or lower, preferably 140 ° C. or lower, and more preferably 130 ° C. or lower. The lower limit of the temperature is 15 ° C. or higher, preferably 20 ° C. or higher, and more preferably 30 ° C. or higher. The kneading temperature is preferably from 15 to 150C, more preferably from 20 to 140C, even more preferably from 30 to 130C.

  The obtained kneaded material is preferably used as a master batch. When used as a final product, it is preferable that a rubber component, a vulcanizing agent, an optional component, and the like are additionally added to the kneaded material and the kneaded material is kneaded again.

[Surfactant]
After mixing the cellulose nanofiber and the rubber component, the master batch obtained by performing a drying treatment may contain a surfactant.

  Surfactants are substances that have at least one hydrophilic group and at least one hydrophobic group in the molecule. Examples of the surfactant include a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  Examples of the cationic surfactant include aliphatic amines (eg, oleylamine, stearylamine, tetradecylamine, 1-hexenylamine, 1-dodecenylamine, 9,12-octadecadienylamine (linolamine), 9 , 12,15-octadecatrienylamine, alkylamines such as linoleylamine), tetramethylammonium salts (eg, tetramethylammonium chloride, tetramethylammonium hydroxide), tetrabutylammonium salts (eg, tetrabutyl chloride) Ammonium), alkyltrimethylammonium salts (eg, alkyltrimethylammonium salts (eg, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyl chloride) Limethylammonium, tetradecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, alkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide), benzyltrialkylammonium salt (for example, benzyltrimethylammonium chloride, benzyltriethyl chloride) Ammonium, benzalkonium chloride (dodecyldimethylbenzylammonium chloride), benzalkonium bromide), dibenzyldialkylammonium salt (eg, benzethonium chloride), dialkyldimethylammonium salt (eg, didecyldimethylammonium chloride, distearyldimethyl chloride) Ammonium), alkylpyridinium salts (eg, butylpyridinium chloride, dodechloride) Rupirijiniumu, cetylpyridinium chloride), aliphatic amine salts (e.g., monomethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine hydrochloride) and the like.

  Examples of the anionic surfactant include carboxylic acids (for example, sodium octoate, sodium decanoate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, perfluorononanoic acid, N-lauroyl sarcosine sodium, Sodium cocoyl glutamate, alpha sulfo fatty acid methyl ester salt), sulfonic acids (eg, sodium 1-hexanesulfonate, sodium 1-octanesulfonate, sodium 1-decanesulfonate, sodium 1-dodecanesulfonate, perfluorobutanesulfonic acid, Sodium linear alkyl benzene sulfonate, sodium toluene sulfonate, sodium cumene sulfonate, sodium octyl benzene sulfonate, sodium naphthalene sulfonate, na Disodium phthalene sulfonate, trisodium naphthalene trisulfonate, sodium butyl naphthalene sulfonate), sulfates (eg, sodium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkylphenol sulfonate, ammonium lauryl sulfate), phosphorus Acid esters (eg, lauryl phosphoric acid, sodium lauryl phosphate, potassium lauryl phosphate).

  Examples of the nonionic surfactant include glycerin fatty acid esters (eg, glycerin laurate, glyceryl monostearate), sorbitan fatty acid esters, polyoxyethylene alkyl ethers (eg, pentaethylene glycol monododecyl ether, octaethylene glycol monoester) Dodecyl ether), alkylphenol alkylate (eg, polyoxyethylene alkylphenyl ether, octylphenol ethoxylate, nonylphenol ethoxylate), polyoxyalkylene glycol (eg, polyoxyethylene polyoxypropylene glycol), polyoxyalkylene sorbitan fatty acid ester (eg, , Polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hexitan fatty acid ester Terol, sorbitan fatty acid ester polyethylene glycol), alkanolamides (eg, lauric acid diethanolamide, oleic acid diethanolamide, stearic acid diethanolamide, cocamide DEA), and alkyl glucosides (eg, octyl glucoside, decyl glucoside, lauryl glucoside). .

  Examples of the amphoteric surfactant include higher alcohols (eg, cetanol, stearyl alcohol, oleyl alcohol), betaine compounds (eg, lauryl dimethylamino acetate betaine, stearyl dimethylamino acetate betaine, dodecylaminomethyldimethylsulfopropyl betaine, octadecyl) Aminomethyldimethylsulfopropyl betaine, cocamidopropyl betaine, cocamidopropyl hydroxyl betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, alkyl amino acid salt (for example, sodium lauroylglutamate, potassium lauroylglutamate, Lauroylmethyl-β-alanine), alkylamine oxides (eg, lauryldimethylamine N-oxide, Le dimethylamine N- oxide) and the like.

  The surfactant is preferably an amphoteric surfactant or a cationic surfactant, more preferably a cationic surfactant, and still more preferably an aliphatic amine. The aliphatic amine is selected from the group consisting of having 15 to 20 carbon atoms, having at least one (preferably one) unsaturated bond in its structure, and being a primary amine. It is preferable to satisfy at least one, more preferably all, and even more preferably oleylamine.

  The surfactant may be one kind or a combination of two or more kinds of surfactants.

<Composition>
The content of each component in the rubber composition is not particularly limited, but the preferred content is as follows.

  The content of the cellulose nanofiber is preferably at least 1 part by mass, more preferably at least 2 parts by mass, even more preferably at least 3 parts by mass with respect to 100 parts by mass of the rubber component. Thereby, the effect of improving the tensile strength can be sufficiently exhibited. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Thereby, workability in the manufacturing process can be maintained. Therefore, 1 to 50 parts by mass is preferable, 2 to 40 parts by mass is more preferable, and 3 to 30 parts by mass is further preferable.

  The content of the surfactant is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 40 parts by mass or more based on 100 parts by mass of the cellulose nanofiber. Thereby, the effect of improving the tensile strength can be sufficiently exhibited. The upper limit is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. Thereby, workability in the manufacturing process can be maintained. Therefore, 5 to 100 parts by mass is preferable, 20 to 80 parts by mass is more preferable, and 40 to 70 parts by mass is further preferable.

<Optional components>
The rubber composition may include one or more optional components depending on the use of the rubber composition described later. Optional components include, for example, reinforcing agents (eg, carbon black, silica, etc.), silane coupling agents, cross-linking agents, vulcanization accelerators, vulcanization accelerators (eg, zinc oxide, stearic acid), oils, and curing. Examples include compounding agents that can be used in the rubber industry, such as resins, waxes, antioxidants, and coloring agents. Among these, a vulcanization accelerator and a vulcanization accelerator are preferable. The content of the optional component may be appropriately determined according to the type of the optional component, and is not particularly limited.

  When the rubber composition is an unvulcanized rubber composition or a final product, it preferably contains a crosslinking agent. Examples of the crosslinking agent include sulfur, sulfur halide, organic peroxide, quinone dioximes, organic polyamine compounds, and alkylphenol resins having a methylol group. Of these, sulfur is preferred. The content of the crosslinking agent is preferably at least 1.0 part by mass, more preferably at least 1.5 parts by mass, even more preferably at least 1.7 parts by mass based on 100 parts by mass of the rubber component. The upper limit is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less.

  Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazolesulfenamide and N-oxydiethylene-2-benzothiazolylsulfenamide. The content of the vulcanization accelerator is preferably 0.1 parts by mass, more preferably 0.3 parts by mass or more, and still more preferably 0.4 parts by mass or more based on the rubber component. The upper limit is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less.

  In the rubber composition, the rubber component, the cellulose nanofiber, and the optional component may exist independently of each other, or may exist as a complex such as a reactant of at least two components. The content of each component in the rubber composition generally conforms to the amount used as a raw material.

<Application>
The use of the rubber composition of the present invention is not particularly limited as long as it is a composition for obtaining rubber as a final product. That is, it may be an intermediate (master batch) for rubber production, an unvulcanized rubber composition containing a vulcanizing agent, or rubber as a final product. The use of the final product is not particularly limited. For example, transportation equipment such as automobiles, trains, ships, and airplanes; electric appliances such as personal computers, televisions, telephones, and watches; mobile communication equipment such as mobile phones; Equipment, video playback equipment, printing equipment, copying equipment, sports equipment, etc .; building materials; office equipment such as stationery, containers, containers and the like. 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.

[Production Example 1: Production of oxidized cellulose nanofiber]
5.00 g of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood (absolutely dry) was mixed with 39 mg of TEMPO (manufactured by Sigma Aldrich) (0.05 mmol per 1 g of absolutely dry cellulose) and 514 mg of sodium bromide ( The solution was added to 500 mL of an aqueous solution in which 1.0 mmol of absolutely dried cellulose was dissolved in 1 g of cellulose, and stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that sodium hypochlorite became 5.5 mmol / g, and an oxidation reaction was started at room temperature. During the reaction, the pH in the system decreased, but the pH was adjusted to 10 by sequentially adding a 3M aqueous sodium hydroxide solution. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). At this time, the pulp yield 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 3.0% by weight (w / v), and the mixture was treated twice with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3.9 nm, and the average fiber length was 620 nm.

[Production Example 2: Production of oxidized cellulose nanofiber]
Water was added to the oxidized pulp produced in Production Example 1 to adjust the concentration to 1.0% by weight (w / v), and treated twice with an ultra-high pressure homogenizer (20 ° C., 150 Mpa) to disperse oxidized cellulose nanofibers. A liquid was obtained. The average fiber diameter was 2.4 nm, and the average fiber length was 570 nm.

<Example 1>
A 100% natural rubber latex (trade name: HA latex, Redtex Co., solid content concentration: 61.5% by weight) was added to a 1% by weight aqueous dispersion of the cellulose nanofiber of Production Example 1 above, based on the absolute dry solid content. The nanofibers were mixed at 5% by weight on a dry basis and stirred with a TK homomixer (8000 rpm) for 30 minutes to obtain a mixture. The mixture was dried in a heating oven at 70 ° C. for 15 hours to obtain a master batch.

  Zinc oxide and stearic acid were mixed at 6% by weight and 0.5% by weight with respect to the rubber component in the masterbatch, respectively, with respect to the masterbatch obtained by the above method. A kneaded material was obtained by kneading at 30 ° C. for 10 minutes. To this kneaded material, sulfur and a vulcanization accelerator (BBS, Nt-butyl-2-benzothiazolesulfenamide) were added at 3.5% by weight and 0.7% by weight, respectively, to the rubber component in the kneaded material. %, And kneaded at 30 ° C. for 10 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.) to obtain a sheet of an unvulcanized rubber composition. The obtained unvulcanized rubber composition sheet was sandwiched between molds and press-vulcanized at 150 ° C. for 15 minutes to obtain a vulcanized rubber sheet having a thickness of 2 mm. The obtained vulcanized rubber sheet is cut into a test piece having a predetermined shape, and according to JIS K6251 “Vulcanized rubber and thermoplastic rubber—How to determine tensile properties”, a sheet having a tensile strength of 50% strain ( M50) and at 100% strain (M100), stress, breaking strength, and breaking elongation were measured. As for the measured value, the value of Comparative Example 2 was set to 100, and the values of the other Examples and Comparative Examples were used as index display. A larger value indicates that the vulcanized rubber composition is satisfactorily reinforced and has excellent mechanical strength.

<Comparative Example 1>
The procedure was performed in the same manner as in Example 1 except that the cellulose nanofiber of Production Example 2 was used.

<Comparative Example 2>
The procedure was performed in the same manner as in Example 1 except that the cellulose nanofiber was not used.

実施例のゴム組成物は、良好に補強されており、機械強度に優れる。 table

The rubber compositions of Examples are satisfactorily reinforced and have excellent mechanical strength.

Claims (8)

<1> A method for manufacturing a master batch including the following steps <1> and <2>: <1> After adjusting the chemically modified cellulose fiber to a dispersion having a concentration of 2.0% by weight or more, the dispersion is defibrated. Step of processing to obtain cellulose nanofiber <2> Step of mixing cellulose nanofiber obtained in <1> and rubber latex, and then performing drying treatment to obtain a master batch The method for producing a master batch according to claim 1, wherein the chemical modification treatment is an oxidation treatment. The method for producing a master batch according to claim 1, wherein the chemical modification treatment is a carboxymethylation treatment. The method for producing a master batch according to claim 1, wherein the chemical modification treatment is a cationization treatment. 2. The method for producing a master batch according to claim 1, wherein the chemical modification treatment is a phosphorylation treatment. The method for producing a master batch according to any one of claims 1 to 5, wherein the defibrating treatment is an ultra-high pressure homogenizer treatment. The method for producing a master batch according to any one of claims 1 to 6, wherein the product of the pressure (MPa) and the number of treatments (times) of the defibration treatment is 200 MPa · times or more. A method for producing a rubber composition produced using the master batch according to claim 1.