JPWO2018181224A1 - Rubber composition and method for producing the same - Google Patents

Abstract

An object of the present invention is to provide a rubber composition containing a rubber component and a cellulosic fiber and having good strength at high strain, and a method for producing the same. That is, the present invention provides a rubber composition containing (A) component: modified cellulose nanofiber, (B) component: rubber component, and (C) component: surfactant, and step [I]: (A) component. And a component (B): a step of mixing a rubber component to obtain a mixture, and a step [II]: a step of adding and kneading the component (C) to the obtained mixture and kneading to obtain a rubber composition. [I]: a step of mixing the components (A), (B) and (C) to obtain a mixture, and a step [ii]: kneading the obtained mixture to obtain a rubber composition. A method for producing a rubber composition is provided.

Description

  The present invention relates to a rubber composition and a method for producing the same, and more particularly, to a rubber composition containing modified cellulose nanofibers and a method for producing the same.

  It is known that a rubber composition 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.

  Generally, the compatibility between the rubber component and the cellulosic fiber is low. For example, Patent Literature 2 describes that adding a cellulose nanofiber and a silane coupling agent to a rubber component improves dispersibility. Patent Document 3 discloses that a finely modified cellulose fiber obtained by treating a carboxyl group-containing fine cellulose fiber having a predetermined amount of a carboxyl group with a hydrophobic modifying agent having a hydrocarbon group has a rubber component when compounded with a rubber component. It is described that the dispersibility in the composition becomes excellent.

JP 2006-206864 A JP 2009-191198 A JP 2014-125607 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. In particular, improvement in strength at high strain (for example, strain of 100% or more) has been required.

  Accordingly, an object of the present invention is to provide a rubber composition containing a rubber component and a cellulosic fiber, which has good strength at the time of high strain, and a method for producing the same.

The present invention provides the following [1] to [15].
[1] Component (A): modified cellulose nanofiber,
Component (B): a rubber component, and component (C): a rubber composition containing a surfactant.
[2] The rubber composition according to [1], wherein the component (A) contains oxidized cellulose nanofibers.
[3] The rubber composition according to [2], wherein the carboxyl group content of the oxidized cellulose nanofiber is 0.5 mmol / g to 3.0 mmol / g based on the absolute dry mass of the oxidized cellulose nanofiber.
[4] The rubber composition according to [2] or [3], wherein the oxidized cellulose nanofiber is an acid-type oxidized cellulose nanofiber.
[5] The rubber composition according to [1], wherein the component (A) contains carboxymethylated cellulose nanofibers.
[6] The rubber composition according to [5], wherein the carboxymethylated cellulose nanofiber has a carboxymethyl substitution degree per glucose unit of 0.01 to 0.50.
[7] The rubber composition according to [5] or [6], wherein the carboxymethylated cellulose nanofiber is an acid-type carboxymethylated cellulose nanofiber.
[8] The rubber composition according to any one of [1] to [7], wherein the component (B) contains a diene rubber.
[9] The rubber composition according to any one of [1] to [8], wherein the component (B) contains a natural rubber.
[10] The rubber composition according to any one of [1] to [9], wherein the component (C) contains a cationic surfactant or an amphoteric surfactant.
[11] The rubber composition according to any one of [1] to [10], wherein the component (C) contains an aliphatic amine.
[12] Component (C) is oleylamine, stearylamine, tetradecylamine, 1-hexenylamine, 1-dodecenylamine, 9,12-octadecadienylamine, 9,12,15-octadecatrienylamine, and The rubber composition according to any one of [1] to [11], comprising at least one aliphatic amine selected from the group consisting of linoleylamines.
[13] The method for producing a rubber composition according to any one of [1] to [12], comprising the following steps [I] and [II].
Step [I]: Step of mixing a modified cellulose nanofiber with a rubber component to obtain a mixture Step [II]: Step of adding and kneading a surfactant to the obtained mixture to obtain a rubber composition [14] The following [ The method for producing a rubber composition according to any one of [1] to [12], having [i] and [ii].
Step [i]: Step of mixing the components (A), (B) and (C) to obtain a mixture, and Step [ii]: Step of kneading the obtained mixture to obtain a rubber composition [15] The following steps The method for producing a rubber composition according to [13] or [14], further comprising [IA].
Step [IA]: a step of drying the mixture obtained in step [I] or [i] prior to step [II] or [ii].

  The rubber composition of the present invention contains a rubber component and modified cellulose nanofibers, and can exhibit good strength at high strain. According to the production method of the present invention, such a rubber composition can be produced efficiently.

  The present invention relates to a rubber composition containing (A) component: modified cellulose nanofiber, (B) component: rubber component, and (C) component: surfactant, and a method for producing the same.

  When the rubber composition contains the components (A) to (C), good strength can be exhibited at high strain.

<(A) component: modified cellulose nanofiber>
Modified cellulose nanofibers are fine fibers made from modified cellulose. The average fiber diameter of the modified cellulose nanofiber is not particularly limited, but the length-weighted average fiber diameter is usually about 2 to 500 nm, and preferably 2 to 50 nm. The average fiber length of the modified cellulose nanofiber is not particularly limited, but the length-weighted average fiber length is preferably 50 to 2000 nm. The length-weighted average fiber diameter and the length-weighted average fiber length (hereinafter, also simply referred to as “average fiber diameter” and “average fiber length”) are measured using an atomic force microscope (AFM) or a transmission electron microscope (TEM). Observed for each fiber. The average aspect ratio of the modified cellulose nanofiber is 10 or more. The upper limit is not particularly limited, but is 1000 or less. The average aspect ratio can be calculated by the following equation (1).

(1): average aspect ratio = average fiber length / average fiber diameter

  Modified cellulose is 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-derived cellulosic materials include wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (eg, softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood Bleached 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). 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 (for example, carboxymethylation), 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 ion and potassium ion, 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 mmol / g or more, or 0.8 mmol / g or more, and still more preferably 1 mmol / g or more based on the absolute 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 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 carbon atom having a 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.

  An N-oxyl compound refers to a compound that can generate a nitroxy radical. 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"). 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 oxide, and peroxide. 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 make the oxidation reaction proceed efficiently, it is preferable to maintain the pH of the reaction solution within the above range by adding an alkaline solution such as an aqueous solution of sodium hydroxide. 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 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. By desalting, a salt-type carboxyl group can be converted to an acid-type carboxyl group. In this specification, the oxidized cellulose (nanofiber) that has undergone desalting is referred to as acid-type oxidized cellulose (nanofiber) or oxidized cellulose (nanofiber) (acid-type), respectively. In addition, oxidized cellulose and oxidized cellulose (nanofiber) which have not been subjected to desalination are referred to as salt-type oxidized cellulose (nanofiber) or oxidized cellulose (nanofiber) (salt-type). 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 contacting oxidized cellulose or oxidized cellulose nanofiber 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 used in the present invention, the ratio of the acid-type carboxyl group is preferably 40% or more, more preferably 60% or more, and 85% or more. Is 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 a 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 is added, and the mixture is shaken for 3 hours to convert a carboxymethyl cellulose salt (carboxymethylated cellulose) into a carboxymethylated cellulose having a carboxyl group (hereinafter, “acid-type carboxymethyl”) Cellulose cellulose). 3) 1.5 to 2.0 g of acid-type carboxymethylated cellulose (absolutely dried) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the acid-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 ′ − (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of acid-type carboxymethylated cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralization of 1 g of acid-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. By desalting, a salt-type carboxyl group can be converted to an acid-type carboxyl group. In the present specification, carboxymethylated cellulose (nanofiber) that has undergone desalting is referred to as acid-type carboxymethylated cellulose (nanofiber) or carboxymethylated cellulose (nanofiber) (acid-type). 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. As an example, the ratio of the aqueous dispersion of the carboxymethylated cellulose nanofiber 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. can do. The cation exchange resin after the contact may be collected by a conventional method such as suction filtration.

  In the acid-type carboxymethylated cellulose and the acid-type carboxymethylated cellulose nanofiber used in the present invention, the ratio of the acid-type carboxyl group is preferably 40% or more, more preferably 60% or more, and 85% or more. % Is 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 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 salt in the cationized cellulose can be converted to a base by desalting. In the present specification, cationized cellulose (nanofiber) that has undergone desalting is referred to as basic cationized cellulose (nanofiber) or cationized cellulose (nanofiber) (base type). Further, cationized cellulose and cationized cellulose nanofibers that have not been subjected to desalination are referred to as salt-type cationized cellulose (nanofiber) or cationized cellulose (nanofiber) (salt type). The desalting may be performed at any point before (after cationized cellulose) or after (after cationized cellulose nanofiber) defibration. Desalting means that the salt (for example, Cl ⁻ ) contained in the cationized cellulose (salt type) and the cationized cellulose nanofiber (salt type) is replaced with a base to form a base type. 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 the cation 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 thereof, and salts thereof. These compounds are low-cost, easy to handle, and improve the defibration efficiency by introducing a phosphate group into cellulose. 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, dipotassium hydrogen phosphate, Examples include 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, and hexamethylenediamine. 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 from being easily dissolved, and to improve the yield of the phosphate esterified 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 (preferably 110 ° C or less) while water is contained. Is more preferable.

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

The device used for defibration 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, an apparatus of an ultrasonic type and the like, and a high pressure or ultra high pressure homogenizer is preferable, and a wet type High pressure or ultra high pressure homogenizers are 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 at least 50 MPa, more preferably at least 100 MPa, further preferably at least 140 MPa.

  The defibration 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 defibration is performed on a dispersion of a cellulose-based material or a dispersion of a modified cellulose, the lower limit of the solid content concentration of the cellulose-based material or the modified cellulose in the dispersion is usually 0.1% by mass or more, preferably Is 0.2% by mass or more, more preferably 0.3% by mass or more. Thus, the amount of the liquid is appropriate for the amount of the cellulosic raw material or the modified cellulose to be treated, which is efficient. The upper limit is usually 10% by mass or less, preferably 6% by mass or less. Thereby, fluidity can be maintained.

[Filtration]
After the fibrillation, filtration may be performed if necessary, and it is preferable to perform the filtration after fibrillation of the modified cellulose. Foreign matter such as unfibrillated fibers may remain in the dispersion of modified cellulose nanofibers due to insufficient fibrillation, but such foreign matter can be removed by filtration. In the case where the rubber composition is formed in a state where the foreign matter remains, the rubber composition tends to be broken starting from the foreign matter, and disadvantages such as a decrease in strength may occur. Therefore, this can be prevented by filtration.

  As the filtration treatment, for example, a treatment of applying a pressure difference of 0.01 MPa or more, preferably 0.01 to 10 MPa to a dispersion of a modified cellulose nanofiber (usually an aqueous dispersion), or performing pressure filtration or vacuum filtration is performed. No. When the differential pressure is 0.01 MPa or more, a sufficient filtration treatment amount can be obtained without performing substantial dilution (preferably, dilution is not performed in consideration of the subsequent steps). When the pressure difference is 0.01 to 10 MPa, a sufficient amount of filtration treatment can be obtained even when the concentration of the modified cellulose nanofibers in the dispersion or the viscosity of the dispersion is high. The concentration of the modified cellulose nanofibers in the dispersion of the modified cellulose nanofibers at the time of filtration is usually 0.1 to 5% by mass, preferably 0.2 to 4% by mass, more preferably 0.5% by mass. ３3% by mass. Examples of an apparatus used for filtration include a Nutsche type, a candle type, a leaf disk type, a drum type, a filter press type, a belt filter type and the like.

The filtration amount is preferably 10 L / m ² or more per hour, more preferably 100 L / m ² or more. Examples of the method of filtration include auxiliary filtration using a filter aid and filter media filtration using a porous filter medium. One filtration method may be selected and performed, or two or more filtration methods may be used. You may use together. In this case, the order of the filtration methods can be arbitrarily selected. When performing two or more filtration steps, any one of the filtration steps may be performed at the filtration pressure difference, but all the filtration steps may be performed at the filtration pressure difference.

  Among the filtration methods, auxiliary filtration using a filter auxiliary is preferable. According to this method, clogging of the filter medium caused by the filtration process can be easily eliminated by removing the filtration layer formed by the filter aid, and a continuous filtration process can be performed. The filter aid is preferably substantially granular. The average particle size of the granular material is preferably 150 μm or less, more preferably 1 to 150 μm, further preferably 10 to 75 μm, still more preferably 15 to 45 μm, and particularly preferably 25 to 45 μm. When the average particle diameter exceeds 1 μm, a decrease in filtration speed can be suppressed. When the average particle diameter is less than 150 μm, foreign substances can be sufficiently captured, and the filtration can be performed efficiently.

  Examples of the shape of the filter aid include a substantially spherical shape such as diatomaceous earth and a rod shape such as powdered cellulose. Regardless of the shape, the average particle diameter can be measured by a laser diffraction measuring instrument in accordance with JIS Z8825-1.

  Auxiliary filtration using a filtration aid is performed by precoat filtration in which a layer of the filter aid is formed on the filter medium, and body feed filtration in which the dispersion of the filter aid and the modified cellulose nanofiber are previously mixed and filtered. Either method may be used, or both methods may be used in combination. The combination of the two is more preferable because the throughput is improved and the quality of the filtrate is improved. Further, a multi-stage filter filtration may be performed by changing the type of the filter aid. When performing two or more filtration steps using a filtration aid, any one of the filtration steps may be performed at the filtration pressure difference, and all the filtration steps may be performed at the filtration pressure difference. Good.

  Either an inorganic compound or an organic compound may be used as the filter aid, but a granular one is preferable. Preferred examples of the filter aid include diatomaceous earth, powdered cellulose, perlite, and activated carbon.

Diatomaceous earth refers to soft rock or soil mainly composed of diatom shells, and has silica as a main component. Diatomaceous earth may contain components other than silica, such as alumina, iron oxide, and oxides of alkali metals. Further, a porous material having a high porosity and a cake bulk density of about 0.2 to 0.45 g / cm ³ is preferable. Among the diatomaceous earths, a calcined product and a flux calcined product are preferable, and freshwater diatomaceous earth is also preferable. Examples of such diatomaceous earth include Celite (registered trademark) manufactured by Celite Corporation and Seratom (registered trademark) manufactured by Eagle Pitcher Minerals.

  Powdered cellulose refers to rod-shape particles made of microcrystalline cellulose obtained by removing an amorphous portion of wood pulp by an acid hydrolysis treatment, followed by pulverization and sieving. The polymerization degree of cellulose in the powdered cellulose is preferably about 100 to 500. The crystallinity of the powdered cellulose by X-ray diffraction is preferably 70 to 90%. The volume average particle size measured by a laser diffraction type particle size distribution analyzer is preferably 100 μm or less, more preferably 50 μm or less. When the volume average particle size is 100 μm or less, a cellulose nanofiber dispersion having excellent fluidity can be obtained. As the powdered cellulose, for example, a rod-shape manufactured by a method of purifying and drying an undecomposed residue obtained after acid hydrolysis of a selected pulp, pulverizing, and sieving, having a certain particle size distribution Examples include crystalline cellulose powder, KC Floc (registered trademark) manufactured by Nippon Paper Industries, Ceolus (registered trademark) manufactured by Asahi Kasei Chemicals, and Avicel (registered trademark) manufactured by FMC.

  As the filter medium, for example, a filter made of a material such as metal fiber, cellulose, polypropylene, polyester, nylon, glass, cotton, polytetrafluoroethylene, polyphenylene sulfide, a filter, a membrane, a filter cloth, and a filter obtained by sintering metal powder Or a slit filter. 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 filtering is performed using only the filter medium without using the above-mentioned filter aid, the average pore diameter of the filter medium is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm, and still more preferably 1 to 50 μm. ３０30 μm. If the average pore size is smaller than 0.01 μm, a sufficient filtration rate may not be obtained. On the other hand, if it is larger than 100 μm, the foreign matter cannot be caught, and it may be difficult to obtain a filtering effect.

  It is preferable to evaluate the dispersibility of the modified cellulose nanofiber dispersion after filtration by the following method. The modified cellulose nanofiber dispersion is formed into a thin film after adding a surface tension modifier. A pair of polarizing plates are arranged on both surfaces of the thin film so that the polarizing 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 specify the foreign matter area, and the foreign matter area ratio per 1 g of the absolute dry mass of the cellulose nanofiber is calculated. The filtered cellulose nanofiber dispersion preferably has a foreign matter area ratio of 25% or less in the evaluation method.

  The component (A) may be a single type of modified cellulose nanofiber or a combination of two or more types of modified cellulose nanofibers. The component (A) preferably contains at least one carboxyl group-containing cellulose nanofiber such as an oxidized cellulose nanofiber or a carboxymethylated cellulose nanofiber. More preferably, it is included. As a result, the hydrophilic group of the surfactant (C) and the carboxyl group of the carboxyl group-containing cellulose nanofiber strongly interact with each other, and the compatibility between the cellulose nanofiber and the rubber component (B). Is improved, the cellulose nanofibers can be more uniformly dispersed in the rubber component, and the strength of the rubber composition can be remarkably improved.

  The component (A) may be a mixture of a modified cellulose nanofiber and a water-soluble polymer. 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.

<(B) component: 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). Among these, natural rubber and diene rubber are preferable, and diene natural rubber (natural rubber (NR) in a narrow sense without chemical modification) is more preferable.

  As the component (B), one type may be used alone, or two or more types may be used in combination.

<(C) component: surfactant>
Surfactants are substances that can have at least one hydrophilic group and at least one hydrophobic group in a molecule, and precursors thereof (for example, can have both of the above groups in the presence of a metal salt). Substance). 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, linoleylamine, dodecylamine, propylamine, monoalkylamine such as propylamine, methylamine, dialkylamine, trialkylamine), tetramethylammonium salt (for example, tetramethylammonium chloride, water Tetramethylammonium oxide), tetrabutylammonium salt (eg, tetrabutylammonium chloride), alkyltrimethylammonium salt (eg, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, salt) Decyltrimethylammonium, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, alkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide), benzyltrialkylammonium salt (for example, benzyltrimethyl chloride) Ammonium, benzyltriethylammonium chloride, benzalkonium chloride (dodecyldimethylbenzylammonium chloride), benzalkonium bromide), dibenzyldialkylammonium salt (eg, benzethonium chloride), dialkyldimethylammonium salt (eg, didecyldimethylammonium chloride) , Distearyl dimethyl ammonium chloride), alkyl pyridinium (E.g., butyl pyridinium chloride, dodecyl pyridinium, cetyl pyridinium 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, sodium N-lauroyl sarcosine, 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 octylbenzene sulfonate, naphthalene sulfonic acid Thorium, disodium naphthalene disulfonic acid, trisodium naphthalene trisulfonic acid, sodium butyl naphthalene sulfonate), sulfates (eg, sodium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkylphenol sulfonate, ammonium lauryl sulfate), Phosphate esters (eg, lauryl phosphoric acid, sodium lauryl phosphate, potassium lauryl phosphate) may be mentioned.

  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) Aminomethyldimethylsulfopropylbetaine, cocamidopropylbetaine, cocamidopropylhydroxylbetaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine), alkyl amino acid salts (eg, sodium lauroylglutamate, potassium lauroylglutamate) , Lauroylmethyl-β-alanine), alkylamine oxides (eg, lauryldimethylamine N-oxide, Yl dimethylamine N- oxide) and the like.

  The component (C) is preferably an amphoteric surfactant or a cationic surfactant, more preferably a cationic surfactant, and further 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. Preferably, at least one is satisfied, more preferably, all are satisfied, oleylamine, stearylamine, or 1-hexenylamine is still more preferable, and oleylamine is still more preferable.

  The component (C) may be a single surfactant or a combination of two or more surfactants.

<Composition>
The content of each of the components (A) to (C) in the rubber composition is not particularly limited, but the preferred usage is as follows.

  The content of the component (A) 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, per 100 parts by mass of the component (B). Thereby, the effect of improving the tensile strength can be sufficiently exhibited. The upper limit is preferably equal to or less than 50 parts by mass, more preferably equal to or less than 40 parts by mass, and still more preferably equal to or less than 30 parts by mass. 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 component (C) is preferably at least 5 or 10 parts by mass, more preferably at least 15 or 20 parts by mass, and even more preferably at least 40 parts by mass, per 100 parts by mass of the component (A). 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 or 10 to 100 parts by mass is preferable, 15 to 80 parts by mass or 20 to 80 parts by mass is more preferable, and 40 to 70 parts by mass is more preferable.

<Optional components>
The rubber composition may further include one or two or more optional components according to the demands such as the use of the rubber composition described later. Optional components include, for example, a reinforcing agent (eg, carbon black, silica), a silane coupling agent, a crosslinking agent, a vulcanization accelerator, a vulcanization accelerator (eg, zinc oxide, stearic acid), an oil, and a cured resin. And compounding agents that can be used in the rubber industry, such as waxes, antioxidants, coloring agents and the like. Among these, a vulcanization accelerator and a vulcanization accelerator are preferable. The content of the optional component may be appropriately determined according to conditions such as 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 at least a crosslinking agent as an optional component. Examples of the crosslinking agent include sulfur, sulfur halide, organic peroxides, 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, and even more preferably at least 1.7 parts by mass, per 100 parts by mass of the component (B). 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 at least 0.1 part by mass, more preferably at least 0.3 part by mass, even more preferably at least 0.4 part by mass based on 100 parts by mass of the component (B). 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 components (A) to (C) and the optional component may be present independently of each other, or may be present as a reactant of at least two components. The reactant includes, for example, a reactant formed by ionic bonding of the component (C) and the component (A), and specific examples include an aliphatic amine-modified cellulose oxidized cellulose nanofiber. 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 devices such as automobiles, trains, ships, and airplanes; electric appliances such as personal computers, televisions, telephones, and watches; mobile communication devices such as mobile phones; Reproduction equipment, printing equipment, copying equipment, sporting goods; building materials; office equipment such as stationery; containers; 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 method>
The rubber composition of the present invention is preferably produced by a production method comprising the following steps [I] and [II] or by a production method comprising the following steps [i] and [ii]. More preferably, it is produced by the production method of
Step [I]: Step of mixing components (A) and (B) to obtain a mixture Step [II]: Step of adding and kneading component (C) to the obtained mixture to obtain a rubber composition Step [ i]: Step of mixing components (A), (B) and (C) to obtain a mixture Step [ii]: Step of kneading the obtained mixture to obtain a rubber composition

  Through the steps [I] and [II] or the steps [i] and [ii], a rubber composition having good strength at high strain can be produced. In the method of the present invention, specific examples and the amounts of the components (A) to (C) and the optional components are as described above.

<Steps [I] and [i]: Mixing Step>
In the steps [I] and [i], the form of the component (B) subjected to mixing is not particularly limited. For example, there are a solid rubber component, a dispersion (latex) in which the rubber component is dispersed in a dispersion medium, and 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 form of the component (A) to be mixed is not particularly limited. For example, a dispersion in which the modified cellulose nanofibers are dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion are included. 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). In the present specification, the wet solid is a solid in an intermediate state 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 modified cellulose nanofibers. By the addition or further drying of the liquid, the amount of dispersion medium in the wet solid can be adjusted accordingly.

  As described above for the component (A), the component (A) may be a combination of two or more modified cellulose nanofibers. The form in which the mixture of the modified cellulose nanofiber as the component (A) and the water-soluble polymer solution is subjected to mixing is not particularly limited, and examples thereof include a mixed solution, a dry solid of the mixed solution, and a mixed solution. Liquid wet solids. The amount of liquid in the mixture and its dry solids may be in the above ranges.

  In the step [i], the time of addition of the component (C) is not particularly limited, and the components (A) to (C) may be added and mixed at the same time. Component B) may be added, the latter being preferred.

<Step [IA]: drying step>
The mixture obtained in the steps [I] and [i] is preferably subjected to the step [IA] before being subjected to the steps [II] and [ii]. In step [IA], the mixture obtained in step [I] or [i] is dried. The drying method is not particularly limited, and may be any of a heating method, a coagulation method, and a combination thereof, but a heat treatment is preferred. The conditions for the heat treatment are not particularly limited, but the following is one example. The heating temperature is preferably 40 ° C. or more and less than 100 ° C. The processing time is preferably 1 hour to 24 hours. By setting the heating temperature or the heating time under the above conditions, damage to the rubber component can be suppressed. The mixture after drying may be in a completely dry state or a solvent may remain. The drying method is not limited to the above method, and a conventionally known method for removing a solvent may be appropriately selected.

<Steps [II] and [ii]: Kneading step>
In steps [II] and [ii], the mixture obtained through steps [I], [i] or [IA] is kneaded. The kneading may be performed using a kneading machine according to a known method. Examples of the kneading machine include open-type kneading machines such as two-roll and three-roll mills, and closed kneading machines such as an intermeshing-type Banbury mixer, a tangential-type Banbury mixer, and a pressure kneader. Steps [II] and [ii] may be steps through multi-stage kneading. For example, a combination of kneading with a closed kneader in the first stage and re-kneading with an open kneader thereafter.

  In the step [II], the component (C): a surfactant is added to the mixture. The addition of the component (C) is performed when the mixture obtained in the step [I] or the mixture obtained through the step [IA] is kneaded using the above kneader. The time of addition is not particularly limited, and includes, for example, at the start of kneading, during kneading, and both.

  The method of adding the component (C) is not particularly limited, and includes, for example, batch addition of a predetermined amount and sequential addition. Any method may be used as long as the surfactant is uniformly kneaded with the mixture, and the method is not particularly limited.

  In the steps [II] and [ii], optional additives (compounding agents) such as a filler and a vulcanizing agent may be added and kneaded together with the mixture. The order of addition of the mixture, the component (C) and the optional additives is not limited. After the mixture is first charged into the kneading machine, the surfactant and any additives may be charged and kneaded, and conversely, after the component (C) and any additives have been charged first, the mixture may be mixed. It may be charged and kneaded. The component (C) and any additives may be previously blended into a mixture and added to the kneader. When a vulcanizing agent is added, it is preferable to add the vulcanizing agent at the last stage of kneading. The kneading time may be any as long as the component (C) is uniformly kneaded with the mixture, but is usually about 3 to 20 minutes.

  The kneading temperature may be about room temperature (for example, about 15 to 30 ° C.), but may be heated to a relatively high temperature. For example, the upper limit of the temperature is usually 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 it is as a master batch. On the other hand, the obtained kneaded material may be used as a final product. When used as a final product, it is preferable that an optional additive such as a rubber component and a vulcanizing agent is additionally added to the kneaded material, and the kneaded material is kneaded again.

  In the steps [II] and [ii], after the kneading is completed, molding may be performed if necessary. Molding includes, for example, mold molding, injection molding, extrusion molding, hollow molding, and foam molding, and the apparatus may be appropriately selected according to the shape, use, and molding method of the final product.

  In the steps [II] and [ii], it is preferable to heat after completion of kneading, preferably after molding. When the rubber composition contains a crosslinking agent (preferably, a crosslinking agent and a vulcanization accelerator), a crosslinking (vulcanization) treatment is performed by heating. Even when the rubber composition does not contain a crosslinking agent and a vulcanization accelerator, the same effect can be obtained by adding the rubber composition before heating. The heating temperature is preferably 150 ° C. or higher, and the upper limit is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. Therefore, about 150 to 200 ° C. is preferable, and about 150 to 180 ° C. is more preferable. Examples of the heating device include vulcanization devices such as mold vulcanization, can vulcanization, and continuous vulcanization.

  Before making the kneaded product into a final product, a finishing treatment may be performed as necessary. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, and chlorine treatment. Only one of these treatments may be performed, or a combination of two or more of these treatments may be performed.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Unless otherwise stated, the method of measuring the values such as the physical property values is the measurement method described in the present specification.

[Physical property measurement method]
According to JIS K 6251 "Vulcanized rubber thermoplastic rubber-Determination of tensile properties", 50% tensile stress (50% modulus; described as "M50"), 100% tensile stress (100% modulus; described as "M100"). ) And 300% tensile stress (300% modulus; described as “M300”). The larger the value is, the higher the reinforcing effect of the rubber composition is, and the more excellent the mechanical strength of the rubber composition is.

  In the present invention, “at the time of high strain” is defined as a measurement condition of M100 or more.

<Production Example 1> Production of oxidized cellulose nanofibers 5.00 g (absolutely dry) of bleached unbeaten kraft pulp (85% whiteness) derived from softwood was 39 mg of TEMPO (Sigma Aldrich) (0 g for 1 g of absolutely dry cellulose). 0.05 mmol) and 514 mg of sodium bromide (1.0 mmol per 1 g of absolutely dry cellulose) were added to 500 ml of an aqueous solution, and the mixture was 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 pulp, and the separated pulp was sufficiently washed with water to obtain oxidized pulp (oxidized (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. This was adjusted to 1.0% (w / v) with water, and treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized (carboxylated) cellulose nanofiber dispersion (1% by weight). Was. The average fiber diameter was 3 nm, and the aspect ratio was 250. HCl was added to this aqueous dispersion of oxidized cellulose nanofibers (salt type) until the pH reached 2.4, thereby obtaining a gel-like aggregate. After dehydration and washing with water, water was added again and the mixture was treated with a mixer to obtain a slurry having a solid content of 1% by weight. This slurry was treated three times with an ultrahigh-pressure homogenizer (processing pressure: 140 MPa) to obtain a washed acid-type oxidized cellulose nanofiber aqueous dispersion (1% by weight). The ratio of the acid-type carboxyl groups in the obtained acid-type oxidized cellulose nanofiber aqueous dispersion was 97%.

<Production Example 2> Production of oxidized cellulose nanofibers 5.00 g (bright dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood was 39 mg of TEMPO (Sigma Aldrich) (0 g per 1 g of absolute dry cellulose). 0.05 mmol) and 514 mg of sodium bromide (1.0 mmol per 1 g of absolutely dry cellulose) were added to 500 ml of an aqueous solution, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that sodium hypochlorite became 3.5 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 pulp, and the separated pulp was sufficiently washed with water to obtain oxidized pulp (oxidized (carboxylated) cellulose). The pulp yield at this time was 91%, the time required for the oxidation reaction was 80 minutes, and the amount of carboxyl groups was 1.0 mmol / g. This was adjusted to 1.0% (w / v) with water, and treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized (carboxylated) cellulose nanofiber dispersion (1% by weight). Was. The average fiber diameter was 3 nm, and the aspect ratio was 270. HCl was added to the aqueous dispersion of the oxidized cellulose nanofibers (salt type) until the pH reached 2.4, thereby obtaining a gel aggregate. After dehydration and washing with water, water was added again and the mixture was treated with a mixer to obtain a slurry having a solid content of 1% by weight. This slurry was treated three times with an ultrahigh-pressure homogenizer (processing pressure: 140 MPa) to obtain a washed acid-type oxidized cellulose nanofiber aqueous dispersion (1% by weight). The ratio of the acid-type carboxyl group in the obtained aqueous dispersion of the acid-type cellulose oxide nanofiber was 95%.

<Production Example 3> Production of carboxymethylated cellulose nanofibers 200 g of pulp (NBKP (softwood bleached kraft pulp), manufactured by Nippon Paper Industries Co., Ltd.) was dried in a stirrer capable of mixing pulp, and sodium hydroxide was dried. 111 g by mass (2.25 moles per anhydrous glucose residue of the starting material) was added, and water was added so that the pulp solid content became 20% (w / v). Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (1.5 times as much as an active ingredient, per mol of glucose residue in pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and the mixture was stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. The solid content was adjusted to 1% with water, and the mixture was treated five times with a high-pressure homogenizer at 20 ° C. and a pressure of 150 MPa to obtain carboxymethylated cellulose nanofibers (1% by weight). The average fiber diameter was 15 nm, and the aspect ratio was 50. A cation exchange resin (Amberjet 1020, manufactured by Organo Corporation) was added to the aqueous carboxymethylated cellulose nanofiber dispersion (salt type) until the pH reached 2.9, followed by stirring. The cation exchange resin was recovered by suction filtration to obtain an acid-type carboxymethylated cellulose nanofiber aqueous dispersion (1% by weight). The ratio of the acid-type carboxyl group in the obtained aqueous dispersion of the acid-type carboxymethylated cellulose nanofiber was 91%.

<Production Example 4> Production of cationized cellulose nanofiber To a pulper capable of stirring pulp, 200 g of pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) in a dry mass and 24 g of sodium hydroxide in a dry mass were added. % Water was added. Thereafter, the mixture was stirred at 30 ° C. for 30 minutes and then heated to 70 ° C., and 200 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cation-modified pulp having a cation substitution degree of 0.05 per glucose unit. This was adjusted to a solid concentration of 1%, and treated twice with a high-pressure homogenizer at 20 ° C. and a pressure of 140 MPa to obtain cationized cellulose nanofibers (1% by weight). The average fiber diameter was 25 nm, and the aspect ratio was 50. An anion exchange resin (Amberjet 4400, manufactured by Organo Corporation) was added to the aqueous cationized cellulose nanofiber dispersion (salt type) until the pH reached 11, and the mixture was stirred. The anion exchange resin was recovered by suction filtration to obtain a base-type cationized cellulose nanofiber aqueous dispersion (1% by weight).

  The carboxyl group content, the degree of carboxymethyl substitution, and the degree of cation substitution in the above Production Examples were measured by the methods described in the upper section.

<Example 1>
500 g of an aqueous dispersion (1% by weight) of the acid-type oxidized cellulose nanofiber obtained in Production Example 1 and 162.9 g of natural rubber latex (trade name: HA-LATEX, manufactured by Redtex Co., Ltd., solid concentration: 61.4%) Was mixed so that the mass ratio of the rubber component to the cellulose nanofiber became 100: 5, and the mixture was stirred at 23 ° C. for 10 minutes with a TK homomixer (8000 rpm). The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture.

  105 g of the obtained mixture was placed in a Labo Plastomill (Toyo Seiki Seisaku-sho, Ltd.) and masticated for one minute. Then, 2.1 g of oleylamine was sequentially added and kneaded until the whole became uniform. The set temperature of the Labo Plastomill was 70 ° C., and the total kneading time was 10 minutes. To the obtained kneaded material, 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 were added. Using an open roll (manufactured by Kansai Roll Co., Ltd.), the mixture was kneaded at 40 ° C. for 15 minutes to obtain a sheet of an unvulcanized rubber composition. This sheet was inserted into a mold and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the physical properties were evaluated. That is, the tensile strength, which is one of the reinforcing properties, was measured in accordance with JIS K6251 "Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties" of each test piece.

<Example 2>
A sheet of a rubber composition was obtained in the same manner as in Example 1, except that the acid-type carboxymethylated cellulose nanofiber aqueous dispersion (1% by weight) obtained in Production Example 3 was used, and the physical properties were evaluated. .

<Example 3>
A sheet of a rubber composition was obtained in the same manner as in Example 1, except that the aqueous base-type cationized cellulose nanofiber dispersion (1% by weight) obtained in Production Example 4 was used, and the physical properties were evaluated.

<Example 4>
A sheet of the rubber composition was obtained in the same manner as in Example 1 except that 2.1 g of stearylamine was used as the surfactant, and the physical properties were evaluated.

<Example 5>
A sheet of a rubber composition was obtained in the same manner as in Example 1 except that 0.8 g of 1-hexenylamine was used as a surfactant, and physical properties were evaluated.

<Example 6>
A sheet of a rubber composition was obtained in the same manner as in Example 1 except that 500 g of the aqueous dispersion of the acid-type oxidized cellulose nanofiber (1% by weight) obtained in Production Example 2 was used, and the physical properties were evaluated.

<Example 7>
A sheet of a rubber composition was obtained in the same manner as in Example 1 except that the amount of oleylamine added as a surfactant was changed to 1.0 g, and physical properties were evaluated.

<Example 8>
A sheet of a rubber composition was obtained in the same manner as in Example 1, except that the oxidized (carboxylated) cellulose nanofiber dispersion (salt type, 1% by weight) obtained before desalting was used. , Physical properties were evaluated.

<Example 9>
1000 g of the aqueous dispersion (1% by weight) of the acid-type oxidized cellulose nanofiber obtained in Production Example 1 and 162.9 g of natural rubber latex (trade name: HA-LATEX, manufactured by Redtex Co., Ltd., solid content: 61.4%) Was mixed so that the mass ratio of the rubber component to the cellulose nanofiber was 100: 10, and the mixture was stirred at 23 ° C. for 10 minutes with a TK homomixer (8000 rpm). The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture.

  To 110 g of the obtained mixture, 2.1 g of oleylamine was successively added using a Labo Plastomill (Toyo Seiki Seisakusho), and kneaded at 70 ° C. for 10 minutes. To the obtained kneaded material, 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 were added. Using an open roll (manufactured by Kansai Roll Co., Ltd.), the mixture was kneaded at 40 ° C. for 15 minutes to obtain a sheet of an unvulcanized rubber composition. This sheet was inserted into a mold and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the physical properties were evaluated.

<Example 10>
2000 g of an aqueous dispersion (1% by weight) of the acid-type oxidized cellulose nanofiber obtained in Production Example 1 and 162.9 g of a natural rubber latex (trade name: HA-LATEX, manufactured by Redex Corporation, solid concentration: 61.4%) Was mixed so that the mass ratio of the rubber component to the cellulose nanofiber was 100: 20, and the mixture was stirred at 23 ° C. for 10 minutes with a TK homomixer (8000 rpm). The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture.

  To 120 g of the obtained mixture, 2.1 g of oleylamine was successively added using a Labo Plastomill (Toyo Seiki Seisaku-sho, Ltd.), and kneaded at 70 ° C. for 10 minutes. To the obtained kneaded material, 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 were added. Using an open roll (manufactured by Kansai Roll Co., Ltd.), the mixture was kneaded at 40 ° C. for 15 minutes to obtain a sheet of an unvulcanized rubber composition. This sheet was inserted into a mold and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the physical properties were evaluated.

<Comparative Example 1>
A sheet of the rubber composition was obtained in the same manner as in Example 1 except that oleylamine was not added, and the physical properties were evaluated.

<Comparative Example 2>
A sheet of the rubber composition was obtained in the same manner as in Example 2 except that oleylamine was not added, and the physical properties were evaluated.

<Comparative Example 3>
A sheet of the rubber composition was obtained in the same manner as in Example 3 except that oleylamine was not added, and the physical properties were evaluated.

<Example 11>
Natural rubber latex (trade name: HA-LATEX, manufactured by Redtex, 61.4% solids concentration) with respect to 500 g of the aqueous dispersion (1% by weight) of the acid-type oxidized cellulose nanofiber obtained in Production Example 1. 162.9 g was mixed so that the mass ratio of the rubber component to the cellulose nanofiber was 100: 5, and 2.1 g of oleylamine was further mixed, followed by stirring at 23 ° C. for 10 minutes with a TK homomixer (8000 rpm). . The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture.

  105 g of the obtained mixture was kneaded at 70 ° C. for 10 minutes using Labo Plastomill (Toyo Seiki Seisakusho). To the obtained kneaded material, 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 were added. Using an open roll (manufactured by Kansai Roll Co., Ltd.), the mixture was kneaded at 40 ° C. for 15 minutes to obtain a sheet of an unvulcanized rubber composition. This sheet was inserted into a mold and press-crosslinked at 150 ° C. for 15 minutes to obtain a sheet of a rubber composition having a thickness of about 2 mm. This was cut into a test piece having a predetermined shape, and the physical properties were evaluated.

<Comparative Example 4>
A sheet of the rubber composition was obtained in the same manner as in Example 9 except that oleylamine was not added, and the physical properties were evaluated.

<Comparative Example 5>
A sheet of a rubber composition was obtained in the same manner as in Example 10 except that oleylamine was not added, and physical properties were evaluated.

<Example 12>
To 500 g of the aqueous dispersion (1% by weight) of the acid-type oxidized cellulose nanofiber obtained in Production Example 1, 2.1 g of oleylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added, and the mixture was stirred at room temperature for 3 hours to be modified with oleylamine It was obtained _{^{- (NH 3 + -R TOCN-}} COO) oxidized cellulose nanofibers.

  To 502.1 g of oleylamine-modified oxidized cellulose nanofibers, 162.9 g of natural rubber latex (trade name: HA-LATEX, manufactured by Redex Corporation, solid content concentration: 61.4%) was mixed, and a rubber component and cellulose nanofibers were mixed. And the mixture was stirred at 23 ° C. for 10 minutes with a TK homomixer (8000 rpm). The aqueous suspension was dried in a heating oven at 70 ° C. for 19 hours to obtain a mixture. Except that the obtained mixture was used in place of the kneaded product in Example 1, vulcanization and molding were performed in the same manner as in Example 1 to obtain a sheet of a rubber composition, and physical properties were evaluated.

<Example 13>
A sheet of a rubber composition was obtained and the physical properties were evaluated in the same manner as in Example 12, except that the acid-type carboxymethylated cellulose nanofiber aqueous dispersion (1% by weight) obtained in Production Example 3 was used. .

  Table 1 shows the results. The tensile stress of the example is higher than that of the comparative example in M100 and M300 at the time of high strain, and the strength of the rubber composition of the example at the time of high strain is improved.

Claims (15)

Component (A): modified cellulose nanofiber,
Component (B): a rubber component, and component (C): a rubber composition containing a surfactant.   The rubber composition according to claim 1, wherein the component (A) includes oxidized cellulose nanofibers.   The rubber composition according to claim 2, wherein the carboxyl group content of the oxidized cellulose nanofiber is 0.5 mmol / g to 3.0 mmol / g based on the absolute dry mass of the oxidized cellulose nanofiber.   The rubber composition according to claim 2 or 3, wherein the oxidized cellulose nanofiber is an acid-type oxidized cellulose nanofiber.   The rubber composition according to claim 1, wherein the component (A) includes carboxymethylated cellulose nanofibers.   The rubber composition according to claim 5, wherein the carboxymethylated cellulose nanofiber has a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50.   The rubber composition according to claim 5, wherein the carboxymethylated cellulose nanofiber is an acid-type carboxymethylated cellulose nanofiber.   The rubber composition according to any one of claims 1 to 7, wherein the component (B) includes a diene rubber.   The rubber composition according to any one of claims 1 to 8, wherein the component (B) contains a natural rubber.   The rubber composition according to any one of claims 1 to 9, wherein the component (C) contains a cationic surfactant or an amphoteric surfactant.   The rubber composition according to any one of claims 1 to 10, wherein the surfactant comprises an aliphatic amine.   Component (C) is oleylamine, stearylamine, tetradecylamine, 1-hexenylamine, 1-dodecenylamine, 9,12-octadecadienylamine, 9,12,15-octadecatrienylamine, and linoleylamine The rubber composition according to any one of claims 1 to 11, comprising at least one aliphatic amine selected from the group consisting of: The method for producing a rubber composition according to any one of claims 1 to 12, having the following [I] and [II].
Step [I]: a step of mixing the components (A) and (B) to obtain a mixture, and Step [II]: a step of adding the component (C) to the obtained mixture and kneading to obtain a rubber composition. The production method according to any one of claims 1 to 12, having the following [i] and [ii].
Step [i]: a step of mixing the components (A), (B) and (C) to obtain a mixture, and Step [ii]: a step of kneading the obtained mixture to obtain a rubber composition. The method according to claim 13 or 14, further comprising the following step [IA].
Step [IA]: a step of drying the mixture obtained in step [I] or [i] prior to step [II] or [ii].