JP2018199755A - Modified cellulose fiber - Google Patents

Abstract

To provide a modified cellulose fiber capable of exhibiting good dispersibility to a rubber component and an application thereof.SOLUTION: There are provided a modified cellulose fiber having a carboxyl group, and Land bin a CIELab color space of 1 mass% of a water dispersion of 75≤L≤95 and 5≤b≤35 respectively; a dispersion thereof, a manufacturing method of the fiber or the dispersion, including conducting an anion modification treatment of a cellulose raw material to obtain an anion modified cellulose fiber, and conducting a heating treatment by heating the anion modified cellulose fiber or the dispersion at 105°C to 135°C for 20 min. to 180 min. to obtain a heating treated article; a master batch or a rubber composition containing the fiber and a rubber component; and a manufacturing method of the master batch or the rubber composition, including adding the rubber component to the fiber or the dispersion.SELECTED DRAWING: None

Description

  The present invention relates to a modified cellulose fiber, and more particularly to a modified cellulose fiber, a dispersion thereof, a production method thereof, and an application.

  It is known that modified cellulose fibers such as cellulose fibers containing carboxy groups can improve the mechanical properties of resins such as rubber (for example, Patent Document 1). However, since the carboxy group present on the surface of the cellulose fiber is hydrophilic, it is known that the dispersibility in the resin component is poor, and an improvement in dispersibility is required. In Patent Document 2, an oxidized cellulose fiber in which an oxidized cellulose fiber having a predetermined carboxy group content is thermally modified under a predetermined condition to reduce the carboxy group content becomes hydrophobic due to partial elimination of the carboxy group on the fiber surface. It is described that the dispersibility in the resin is improved.

JP 2011-140632 A JP 2014-141772 A

  However, when the carboxy group content is reduced as in the method of Patent Document 2, there is a possibility that the effect of improving the strength of the rubber component by oxidized cellulose cannot be obtained sufficiently. An object of this invention is to provide the cellulose fiber which can show favorable dispersibility with respect to a rubber component, and its use.

The present invention provides the following [1] to [19].
[1] Modified cellulose fiber in which b ^* in the CIELab color space of a 1% by mass aqueous dispersion is 5 ≦ b ^* ≦ 35.
[2] The fiber according to [1], wherein L ^* and a ^* in the CIELab color space of the 1% by mass aqueous dispersion satisfy 75 ≦ L ^* ≦ 95 and −2 ≦ a ^* ≦ 2, respectively.
[3] The fiber according to [1] or [2], wherein the 1% by mass aqueous dispersion has a yellow index of 8.5 or more.
[4] The fiber according to any one of [1] to [3], which is a carboxy-modified cellulose fiber.
[5] The fiber according to [4], which is a carboxy-modified cellulose fiber having a carboxy group content of 0.5 mmol / g to 3.0 mmol / g with respect to the absolutely dry mass of the modified cellulose fiber.
[6] The fiber according to any one of [1] to [3], which is a carboxymethyl-modified cellulose fiber.
[7] The fiber according to [6], which is a carboxymethyl-modified cellulose fiber having a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50.
[8] The fiber according to any one of [1] to [7], which is a cellulose nanofiber.
[9] The fiber according to any one of [1] to [8], which is an acid-type cellulose fiber or a salt-type cellulose fiber.
[10] A dispersion containing the fiber according to any one of [1] to [9].
[11] The dispersion according to [10], which is an aqueous dispersion.
[12] Anion-modified cellulose fiber is obtained by anion-modifying the cellulose-based raw material;
The method according to any one of [1] to [9], comprising heat-treating the anion-modified cellulose fiber or dispersion thereof at 105 to 150 ° C. for 20 to 180 minutes to obtain a heat-treated product. Or a method for producing a dispersion according to [10] or [11].
[13] The color difference of the 1% by mass aqueous dispersion of the anion-modified cellulose fiber after the heat treatment to that of the 1% by mass aqueous dispersion of the anion-modified cellulose fiber before the heat treatment is 1 or more and 50 or less. ] The method of description.
[14] The method according to [12] or [13], wherein the heat treatment is performed under a pressure of 10 kPa (gage) to 400 kPa (gage).
[15] The method according to any one of [12] to [14], wherein the heat treatment is performed using an autoclave.
[16] A masterbatch or a rubber composition comprising the fiber and the rubber component according to any one of [1] to [9].
[17] The masterbatch or rubber composition according to [16], wherein the rubber component includes at least one selected from the group consisting of acrylonitrile-butadiene rubber, natural rubber, chloroprene rubber, and styrene-butadiene copolymer rubber. .
[18] A masterbatch or rubber comprising adding a rubber component to the fiber according to any one of [1] to [9] or to the dispersion according to [10] or [11] A method for producing the composition.
[19] The method according to [18], wherein the rubber component includes at least one selected from the group consisting of acrylonitrile-butadiene rubber, natural rubber, chloroprene rubber, and styrene-butadiene copolymer rubber.

  ADVANTAGE OF THE INVENTION According to this invention, the modified cellulose fiber which can show favorable dispersibility with respect to a rubber component, and its use are provided.

1. Modified cellulose fiber [cellulose fiber, cellulose nanofiber]
In this specification, a modified cellulose fiber means the cellulose fiber obtained through a modification process from a cellulosic raw material. The cellulose fiber is fibrous cellulose and may further contain a fibrous cellulose derivative. The size of the cellulose fiber is not particularly limited. The fiber diameter of the cellulose fiber may be either micron order or nano order, and nano order is preferable. Cellulose fibers having a fiber diameter of nano-order are referred to as cellulose nanofibers. The length weighted average fiber diameter of the cellulose nanofiber is preferably about 2 to 500 nm, more preferably 2 to 50 nm. The length weighted average fiber length is preferably 50 to 2000 nm. Length-weighted average fiber diameter and length-weighted average fiber length (hereinafter, simply referred to as “average fiber diameter” or “average fiber length”) are measured using an atomic force microscope (AFM) or a transmission electron microscope (TEM). It is obtained by observing each fiber. The average aspect ratio of the cellulose nanofiber is 10 or more. Although an upper limit is not specifically limited, It is 1000 or less. The average aspect ratio can be calculated by the formula: average aspect ratio = average fiber length / average fiber diameter. In this specification, a cellulose fiber includes both an unmodified cellulose fiber and a modified cellulose fiber.

[Anion-modified cellulose fiber, acid-type / salt-type cellulose fiber]
The modified cellulose fiber of the present invention is preferably an anion-modified cellulose fiber. An anion-modified cellulose fiber means a modified cellulose fiber obtained through an anion-modifying treatment. Examples of the anion modification treatment include oxidation, carboxymethylation, and phosphate esterification. Each anion-modified cellulose fiber that has been subjected to anion-modified treatment is further subjected to a desalting treatment of a metal salt such as sodium to obtain acid-type cellulose fibers, which are distinguished from salt-type cellulose fibers that have not undergone desalting treatment. The anion modification treatment and desalting treatment will be described in the description of the modification treatment in the subsequent stage.

[Coloring degree of modified cellulose fiber]
The degree of coloring of the modified cellulose fiber can be expressed by a numerical value in the CIELab color space of the 1 mass% aqueous dispersion. Examples of numerical values include the coordinate axes (L ^* , a ^* , b ^* ) of the CIELab color space, and the yellow index (conforming to the YI (E) standard ASTM E313). L ^* of the 1% by weight aqueous dispersion of modified cellulose fibers is usually 95 or less, preferably 94 or less, more preferably 93 or less, and still more preferably 92 or less. The lower limit is usually 75 or more, for example, 76 or more, 77 or more, 78 or more, or 79 or more, preferably 80 or more, more preferably 81 or more. The b ^{* of the} modified cellulose fiber is usually 5 or more, preferably 5.5 or more, more preferably 6 or more. The upper limit is usually 35 or less, for example, 34 or less, 33 or less, 32 or less, 31 or less, or 30 or less, preferably 29 or less, more preferably 28 or less. The a ^{* of the} modified cellulose fiber is usually 2 or less, for example 1.5 or less, 1 or less, or 0.5 or less, preferably less than 0, more preferably −0.1 or less. The lower limit is usually −2 or more or −1.5 or more, preferably −1 or more. The hydrophilicity of the modified cellulose fiber surface is presumed to contribute to the carboxy group and hydroxyl group in the fiber. L ^*, a ^*, and b ^* of the numerical values including at least b ^* is preferably L ^*, a ^* and a numerical value including a b ^* are more preferably all figures, satisfy any of the above The modified cellulose fiber has an appropriate hydrophobicity on the fiber surface, and can exhibit a good interfacial bonding force to the rubber component.

  YI (E) of the modified cellulose fiber 1% by mass aqueous dispersion is usually 8.5 or more, for example, 9 or more, 9.5 or more, 10 or more, or 10.5 or more, preferably 11 or more. More preferably, it is 11.5 or more. Although an upper limit is not specifically limited, Usually, it is 70 or less. The cellulose fiber in which YI (E) satisfies any of the above has a more appropriate hydrophobicity on the fiber surface, and can exhibit a good interfacial bonding force to the rubber component.

The measurement of L ^* , a ^* , b ^* , YI (E) may be performed according to the conditions of the example.

2. Modified Cellulose Fiber Dispersion The modified cellulose fiber of the present invention may be used as a dispersion, a wet solid or a dry solid, but is preferably used as a dispersion. The lower limit of the solid content concentration of the modified cellulose fiber in the dispersion is usually 0.1% by mass (w / v%) or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more. . An upper limit is 20 mass% or less normally, Preferably it is 10 mass% or less, More preferably, it is 6 mass% or less, More preferably, it is 5 mass% or less. When the aqueous solvent is water, it is preferably 0.1 to 5% by mass, and when the aqueous solvent is a combination of water and another solvent, it is preferably 0.1 to 20% by mass.
The wet solid is a solid in an intermediate form between the dispersion and the dry solid, and is usually prepared by dehydrating the dispersion. The content of the aqueous solvent in the wet solid is preferably 5 to 15% by mass with respect to the modified cellulose fiber, but addition or further drying of a liquid such as an aqueous solvent (for example, spray drying, pressing, air drying, hot air drying, or vacuum) The amount of the dispersion medium can be appropriately adjusted by drying. The dispersion is usually a dispersion in an aqueous solvent such as water.

  Examples of the aqueous solvent include water, water-soluble solvents, and combinations thereof. Examples of water-soluble solvents include alcohols (for example, methanol, ethanol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, methyl cellosolve, ethyl cellosolve, ethylene glycol, glycerin), ethers (Eg, ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran), ketones (eg, acetone, methyl ethyl ketone), N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and these Or a combination of two or more. The aqueous solvent preferably contains at least water, and more preferably water.

  The dispersion may contain components other than the modified cellulose fiber. Examples of components other than the modified cellulose fiber include water-soluble polymers.

  Examples of water-soluble polymers include cellulose derivatives (for example, carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, Snack flour, scrap flour, positive starch, phosphorylated starch, corn starch, gum arabic, gellan gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide , Sodium polyacrylate, polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, Gin sizing agent, petroleum resin sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide-polyamine resin, polyethyleneimine, polyamine, plant gum, polyethylene oxide, hydrophilic cross-linked polymer, polyacrylate, starch Examples thereof include polyacrylic acid copolymers, tamarind gum, guar gum, colloidal silica, and one or more combinations selected from these. Among these, carboxymethyl cellulose or a salt thereof is preferable from the viewpoint of compatibility.

  The method for preparing the dispersion is not particularly limited, and examples thereof include a method including adding and dispersing the modified cellulose fiber in an aqueous solvent such as water. Addition may be either batch addition or stepwise addition. If necessary, other components such as a water-soluble polymer may be added together with the modified cellulose fiber or before or after the addition of the modified cellulose fiber. The preparation may be performed using an apparatus capable of applying a shearing force such as a homogenizer. Prior to dispersion, preliminary processing may be performed as necessary. Examples of the pretreatment include mixing, stirring, and emulsification, and may be performed using a known device (for example, a high-speed shear mixer).

3. Process for producing modified cellulose fiber or dispersion thereof [cellulose-based raw material]
The modified cellulose fiber of the present invention can be obtained from a cellulosic material. Although the raw material (cellulose-type raw material) of a cellulose fiber is not specifically limited, For example, a plant, an animal (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), and microbial products are mentioned. Examples of plant-derived cellulosic materials include wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleach kraft pulp (NBKP), hardwood unbleached kraft Pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.). The cellulosic raw material may be any of these, or a combination of two types of cellulosic raw materials, preferably a plant or microbial cellulosic raw material, more preferably a plant derived cellulosic raw material, and even more preferably. Is pulp.

  The method for producing the modified cellulose fiber of the present invention from the cellulosic material is not particularly limited as long as it includes a step of modifying the cellulosic material. Hereinafter, each step will be described.

[Modification]
The modification treatment is a treatment for modifying the cellulosic material to obtain modified cellulose fibers. The modification treatment preferably includes at least an anion modification treatment and a heat treatment.

[Modification Example 1: Anion Modification Treatment]
Anion-modifying treatment is a treatment for introducing an anionic functional group (eg, carboxy group, carboxymethyl group, phosphate ester group, sulfone group, nitro group). For example, oxidation, carboxymethylation, phosphate esterification Is mentioned. Although an anion modification site | part is not specifically limited, For example, what is necessary is just at least 1 of three hydroxy groups contained in the glucopyranose ring of a cellulose, and a cellulose fiber surface is preferable. The anion modification is preferably introduction of a carboxy group into a hydroxy group. Examples of the anion modification treatment for introducing a carboxy group include oxidation and carboxymethylation. In the present specification, modified cellulose fibers obtained through oxidation treatment, carboxymethylation treatment, and phosphate esterification treatment are referred to as carboxy-modified cellulose fiber, carboxymethyl-modified cellulose fiber, and phosphate ester-modified cellulose fiber, respectively.

[Example of anion modification treatment 1: oxidation]
An oxidized material (hereinafter referred to as oxidized cellulose) of a cellulose-based raw material has a structure in which at least one of three hydroxy groups contained in a glucopyranose ring constituting cellulose is oxidized. Preferably, it has a structure in which a carbon atom having a hydroxy group at the C6 position of a glucopyranose ring is selectively oxidized.

Oxidized cellulose contains a carboxy group. Carboxy group, although strictly group represented by -COOH, carboxylate group (-COO ^- group represented by or -COO ^- group represented by A (where, A is a counter cation (e.g. It may be an alkali metal ion such as sodium ion or potassium ion))). The carboxy group of oxidized cellulose may be composed of only a group represented by —COOH, may be composed of a combination of a group represented by —COOH and a carboxylate group, or is composed of only a carboxylate group. May be. The carboxy group content of the oxidized cellulose is usually 0.5 mmol / g or more, preferably 0.6 mmol / g or more, more preferably 0.8 mmol / g or more, and still more preferably 1. 0 mmol / g or more. The upper limit of the amount is usually 3.0 mmol / g or less, preferably 2.5 mmol / g or less, 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 2.5 mmol / g, still more preferably 0.8 to 2.5 mmol / g, and 1.0 to 2. Even more preferred is 0 mmol / g. The carboxy group content of modified cellulose fibers derived from oxidized cellulose (carboxy-modified cellulose fibers) is usually the same as that of oxidized cellulose that has or has not undergone defibrating treatment.

  An example of a method for measuring the carboxy group content will be described below. Prepare 60 mL of 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N sodium hydroxide aqueous solution dropwise to adjust pH to 11. Measure the electrical conductivity until From the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electrical conductivity is gradual, it can be calculated by the following equation.

(formula)
Carboxy group amount [mmol / g oxidized cellulose] = a [mL] × 0.05 / oxidized cellulose mass [g]

  The oxidation method is not particularly limited, and examples thereof include a method of oxidizing a cellulosic raw material in water using an oxidizing agent in the presence of an N-oxyl compound and at least one of bromide and iodide. According to this method, the carbon atom having the primary hydroxyl group at the 6-position of the glucopyranose ring is selectively oxidized to produce a group selected from the group consisting of an aldehyde group and a carboxy group. Although the density | concentration of the cellulose raw material at the time of reaction is not specifically limited, 5 mass% or less is preferable.

  Examples of the N-oxyl compound include 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-hydroxy TEMPO”).

  An N-oxyl compound refers to a compound capable of generating a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction. The amount of the N-oxyl compound used may be an amount that catalyzes the oxidation reaction of cellulose as a raw material. For example, 0.01 mmol or more is preferable and 0.02 mmol or more is more preferable with respect to 1 g of absolutely dry 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 with respect to 1 g of absolutely dry cellulose.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water. Further, the 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, with respect to 1 g of absolutely dry 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 still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  The oxidizing agent is not particularly limited, and examples thereof include halogen, hypohalous acid, halous acid, perhalogen acid, salts thereof, halogen oxide, and peroxide. Among them, hypohalous acid or a salt thereof is preferable because it is inexpensive and has a low environmental burden, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is more preferable. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and further preferably 3 mmol or more with respect to 1 g of absolutely dry cellulose. The upper limit of the amount is preferably 500 mmol or less, more preferably 50 mmol or less, further preferably 25 mmol or less, and still more preferably 10 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and even more preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. When the N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound, and the upper limit is preferably 40 mol or less. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

  Conditions such as pH and temperature during the oxidation reaction are not particularly limited. In general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C or higher, more preferably 15 ° C or higher. The upper limit of the temperature is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. 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, and more preferably 10 or more. The upper limit of pH is preferably 12 or less, and more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, as the oxidation reaction proceeds, carboxy groups are generated in the cellulose fiber, and therefore the pH of the reaction solution tends to decrease. Therefore, in order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. The reaction medium for the oxidation is preferably water for reasons such as ease of handling and the difficulty of side reactions.

  The reaction time in the oxidation can be appropriately set according to the 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. Accordingly, the reaction time in the oxidation is usually 0.5 to 6 hours, preferably about 0.5 to 4 hours. Oxidation may be carried out in two or more stages. For example, by oxidizing the oxidized cellulose fiber obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the reaction is not inhibited by the salt produced as a by-product in the first-stage reaction, It can be oxidized efficiently.

  Another example of oxidation is ozone oxidation. Ozone oxidation oxidizes carbon atoms having hydroxyl groups at least at the 2nd and 6th positions of the glucopyranose ring constituting cellulose, and also causes degradation of the cellulose chain.

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 0.1 parts by mass or more and more preferably 5 parts by mass or more with respect to 100 parts by mass of the solid content of the cellulosic material. The upper limit of the amount of ozone added is usually 30 parts by mass or less. Therefore, 0.1-30 mass parts is preferable with respect to 100 mass parts of solid content of a cellulose raw material, and, as for ozone addition amount, 5-30 mass parts is more preferable. 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, 0-50 degreeC is preferable and, as for ozone treatment temperature, 20-50 degreeC is more preferable. The ozone treatment time is usually 1 minute or longer, preferably 30 minutes or longer, and the upper limit is usually 360 minutes or shorter. Accordingly, the ozone treatment time is usually about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the condition of the ozone treatment is within the above range, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose can be improved.

  Further, the ozone-treated cellulose may be subjected to a further 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 for the additional 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 a cellulose-based raw material is immersed in the oxidizing agent solution. The amount of carboxy group, carboxylate group, and aldehyde group contained in the oxidized cellulose nanofiber can be adjusted by controlling the oxidizing conditions such as the addition amount of the oxidizing agent and the reaction time.

The product after oxidation may be subjected to a desalting treatment. Desalting means that a salt (which is a counter cation of a carboxylate group, such as a sodium salt) contained in a reaction product (salt form) is replaced with a proton to form an acid form. By the desalting treatment, the counter cation of the carboxylate group introduced into the reaction product is proton-substituted to obtain an acid-type carboxy group-modified cellulose fiber. Desalting can be performed at any time before and after the defibrating process described below. Examples of the desalting method after oxidation include a method of adjusting the inside of the system to acidity and a method of contacting oxidized cellulose with a cation exchange resin. When adjusting the inside of the system 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. In order to adjust to acidity, an acid (for example, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrous acid and phosphoric acid; organic acids such as acetic acid, lactic acid, succinic acid, citric acid and formic acid) is usually used. After the addition of the acid, a washing treatment may be appropriately performed. As the cation exchange resin, both a strong acid ion exchange resin and a weak acid ion exchange resin can be used as long as the counter ion is H ⁺ . The ratio between the oxidized cellulose and the cation exchange resin is not particularly limited, and those skilled in the art can appropriately set the ratio from the viewpoint of efficiently performing proton substitution. The collection of the cation exchange resin after contact may be performed by a conventional method such as suction filtration.

[Example 2 of Anion Modification Treatment: Carboxymethylation]
Cellulose-based raw material carboxymethylated product (hereinafter referred to as carboxymethylated cellulose) usually has a structure in which at least one of three hydroxy groups contained in a glucopyranose ring constituting cellulose is carboxymethylated.

  The degree of carboxymethyl substitution per anhydroglucose unit of carboxymethylated cellulose 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 degree of substitution is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.35 or less. Therefore, the degree of carboxymethyl substitution is preferably from 0.01 to 0.50, more preferably from 0.05 to 0.40, and even more preferably from 0.10 to 0.35. The degree of carboxymethyl substitution of the modified cellulose fiber of the present invention (carboxymethyl modified cellulose fiber) derived from carboxymethylated cellulose is usually equivalent to that of carboxymethylated cellulose that has or has not undergone defibrating treatment.

An example of a method for measuring the degree of carboxymethyl substitution per glucose unit will be described below. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. 2) Add 100 mL of a solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol, and shake for 3 hours to replace the salt of the carboxymethyl group with a proton to form acid-type carboxymethylated cellulose. 3) 1.5-2.0 g of acid-type carboxymethylated cellulose (absolutely dry) is precisely weighed and put into a 300 mL Erlenmeyer flask with a stopper. 4) Wet the acid carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following formula.

(formula)
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 / (1-0.058A)
A: 1N NaOH amount (mL) required for neutralizing 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 examples thereof include a method in which a cellulose-based raw material that is a starting material is mercerized and then etherified. In the method, a solvent is usually used. As a solvent, water, alcohol (for example, lower alcohol), and these mixed solvents are mentioned, for example. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, isobutyl alcohol, and tertiary butyl alcohol. The mixing ratio of the lower alcohol in the mixed solvent is preferably 60 to 95% by mass. The amount of the solvent is usually at least 3 times the mass of the cellulosic material. Although the upper limit of the said amount is not specifically limited, Usually, it is 20 mass times or less. Therefore, the amount of the solvent is preferably 3 to 20 times by mass.

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

  The mercerization reaction temperature 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 15 minutes or longer, preferably 30 minutes or longer. The upper limit of the time is usually 8 hours or less, preferably 7 hours or less. Accordingly, 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 mol or more, more preferably 0.5 times mol or more, further preferably 0.8 times mol or more per glucose residue of cellulose contained in the cellulosic raw material. . The upper limit of the amount is usually 10.0 times mol or less, preferably 5 times mol or less, more preferably 3 times mol or less, and therefore the amount is preferably 0.05 to 10.0 times mol, More preferably, it is 0.5-5 times mole, More preferably, it is 0.8-3 times mole. 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. Accordingly, the reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C. The reaction time is usually 30 minutes or longer, preferably 1 hour or longer, and the upper limit is usually 10 hours or shorter, preferably 4 hours or shorter. Accordingly, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. The reaction solution may be stirred as necessary during the carboxymethylation reaction.

The product after carboxymethylation may be subjected to a desalting treatment. Desalination is the same as desalting after oxidation, in which a salt (a counter cation of a carboxylate group, such as a sodium salt) contained in a reaction product (salt form) is replaced with a proton to form an acid form. means. Desalting can be performed at any time before and after the defibrating process described below. Examples of the desalting method after carboxymethylation include a method of bringing carboxymethylated cellulose into contact with a cation exchange resin. As the cation exchange resin, both a strong acid ion exchange resin and a weak acid ion exchange resin can be used as long as the counter ion is H ⁺ . The ratio between the carboxymethylated cellulose and the cation exchange resin when they are brought into contact with each other is not particularly limited, and those skilled in the art can appropriately set them from the viewpoint of efficiently performing proton substitution. For example, the ratio can be adjusted so that the pH of the aqueous carboxymethylated cellulose dispersion after addition of the cation exchange resin is preferably 2 to 6, more preferably 2 to 5. The collection of the cation exchange resin after contact may be performed by a conventional method such as suction filtration.

[Example 3 of Anion Modification Treatment: Phosphate Esterification]
The phosphoric acid esterification method may be a method in which a cellulose raw material is treated with a compound having a phosphoric acid group. For example, a method of mixing a powder or an aqueous solution of a compound having a phosphoric acid group with a cellulose raw material, a cellulose raw material The method of adding the aqueous solution of the compound which has a phosphoric acid group to this slurry etc. is mentioned, The latter is preferable. Thereby, the uniformity of reaction can be improved and the esterification efficiency of the hydroxy group and phosphoric acid group of a cellulose raw material can be improved.

  Examples of the compound having a phosphoric acid group include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters and salts thereof. These compounds are low-cost, easy to handle, and can introduce a phosphate group into cellulose to improve the fibrillation efficiency. Examples of compounds 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 , Tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. The compound having a phosphate group may be one kind or a combination of two or more kinds. Among these, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid, from the viewpoint that phosphoric acid group introduction efficiency is high, is easy to be defibrated in the following defibrating process, and is industrially applicable. Ammonium salt is preferable, sodium salt of phosphoric acid is more preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, since the uniformity of the reaction is increased and the efficiency of introducing phosphate groups is increased, it is preferable to use an aqueous solution of a compound having a phosphate group in the esterification. The pH of the aqueous solution of the compound having a phosphoric acid group is preferably 7 or less because the efficiency of introducing a phosphoric acid group is increased. From the viewpoint of suppressing hydrolysis of cellulosic materials such as pulp fibers, pH 3 to 7 is more preferable.

  An example of the phosphoric acid esterification method will be described below. A compound having a phosphoric acid group is added to a suspension of a cellulose-based raw material (for example, a solid content concentration of 0.1 to 10% by mass) while stirring to introduce the phosphoric acid group into the cellulose. When the cellulose-based raw material is 100 parts by mass, the amount of the phosphoric acid group-containing compound is preferably 0.2 parts by mass or more, and more preferably 1 part by mass or more as the amount of phosphorus atoms. Thereby, the yield of the cellulose-based raw material of the phosphoric acid esterified product (hereinafter referred to as phosphoric esterified cellulose) or the phosphoric acid ester-modified cellulose fiber can be further improved. The upper limit is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. Thereby, the yield corresponding to the usage-amount of the compound which has a phosphate group can be obtained efficiently. Therefore, 0.2 to 500 parts by mass is preferable, and 1 to 400 parts by mass is more preferable.

  When reacting a cellulose-based material with a compound having a phosphate group, a basic compound may be further added to the reaction system. As a method of adding a basic compound to a 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.

  Although a basic compound is not specifically limited, It is preferable to show basicity and the nitrogen-containing compound which shows basicity is more preferable. "Show basic" usually means that the aqueous solution of the basic compound is pink to red in the presence of the phenolphthalein indicator and / or the pH of the aqueous solution of the basic compound is greater than 7. . The basic compound is preferably a compound having a nitrogen atom exhibiting basicity, and more preferably a compound having an amino group exhibiting basicity. Examples of the compound having an amino group showing basicity include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Of these, urea is preferable because it is easy to handle at low cost. The amount of the basic compound added is preferably 2 to 1000 parts by mass, and more preferably 100 to 700 parts by mass. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. Although reaction time is not specifically limited, Usually, it is about 1 to 600 minutes, and 30 to 480 minutes are preferable. When the conditions for the esterification reaction are in any of these ranges, it is possible to suppress the cellulose from being excessively esterified and easily dissolved, and to improve the yield of phosphorylated esterified cellulose. .

  After reacting the cellulose raw material with a compound having a phosphate group, a suspension of phosphate esterified cellulose or phosphate ester-modified cellulose fibers is usually obtained. The suspension is dehydrated as necessary. Heat treatment is preferably performed after dehydration. Thereby, hydrolysis of cellulose can be suppressed. The heating temperature is preferably 100 to 170 ° C., and is heated at 130 ° C. or less (more preferably 110 ° C. or less) while water is contained in the heat treatment, and after removing water, it is heated at 100 to 170 ° C. More preferably, it is processed.

  The amount of phosphate group introduced into the phosphate esterified cellulose is preferably 0.1 to 3.5 mmol / g, more preferably 0.2 to 3.0 mmol / g, per 1 g (mass) of fine fibrous cellulose. 0.4 to 2.5 mmol / g is more preferable, and 0.6 to 2.3 mmol / g is particularly preferable. Thereby, refinement | miniaturization of a fiber raw material can be made easy and stability of a fine fibrous cellulose can be improved. Moreover, the viscosity of the slurry of fine fibrous cellulose can be adjusted to an appropriate range. The amount of phosphate group introduced into the modified cellulose fiber of the present invention (carboxymethyl-modified cellulose fiber) derived from phosphate esterified cellulose is usually the same as that of phosphate esterified cellulose that has or has not undergone defibrating treatment.

  The amount of phosphate group introduced can be measured by a conductivity titration method. Specifically, after treating the phosphorylated esterified cellulose-containing slurry after the defibration treatment described later with an ion exchange resin, the amount introduced is measured by determining the change in electrical conductivity while adding an aqueous sodium hydroxide solution. be able to.

  In the conductivity titration, when alkali is added, the electrical conductivity suddenly decreases at first (hereinafter referred to as “first region”). Thereafter, the conductivity starts to increase slightly (hereinafter referred to as “second region”). Thereafter, the conductivity increment increases (hereinafter referred to as “third region”). That is, three areas appear. Among these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is the amount of weakly acidic groups in the slurry used for titration. Will be equal. When the phosphoric acid group undergoes condensation, apparently weakly acidic groups are lost, and the amount of alkali required in the second region is reduced compared to the amount of alkali required in the first region. On the other hand, the amount of strongly acidic groups coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation, so that the amount of phosphate groups introduced (or the amount of phosphate groups) or the amount of substituent introduced (or the amount of substituents) is simply When said, it represents the amount of strongly acidic group.

  The product after phosphoric acid esterification may be subjected to a desalting treatment. The desalting means that the salt (for example, sodium salt) contained in the reaction product (salt form) is replaced with a proton to form an acid form, similar to desalting after oxidation and desalting after carboxymethylation. To do. Desalting can be performed at any time before and after the defibrating process described below. Examples of the desalting method after the phosphoric esterification include a method of bringing the phosphoric esterified cellulose into contact with a cation exchange resin.

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

[Heat treatment]
The heat treatment is a treatment for heating the anion-modified cellulose fiber or dispersion thereof obtained after the anion-modification treatment. The carboxy group and hydroxyl group in the anion-modified cellulose fiber contribute to the hydrophilicity of the cellulose fiber, but it is presumed that these groups are appropriately modified by heat treatment and can exhibit hydrophobicity. The temperature during the heat treatment is usually 105 ° C. or higher, preferably 110 ° C. or higher, more preferably 115 ° C. or higher. The upper limit is usually 150 ° C. or lower, preferably 140 ° C. or lower, more preferably 130 ° C. or lower. The time for the heat treatment is usually 20 minutes or longer, preferably 23 minutes or longer, more preferably 25 minutes or longer. The upper limit is usually 180 minutes or less, preferably 160 minutes or less, more preferably 140 minutes or less.
When the temperature or time of the heat treatment is in the above range, preferably both the temperature and time are in the above range, the cellulose fiber of the present invention can be efficiently produced.

  The pressure of the heat treatment is usually 10 kPa (gage) or more, preferably 40 kPa (gage) or more, more preferably 70 kPa (gage) or more. The upper limit is usually 400 kPa (gage) or less, preferably 250 kPa (gage) or less, more preferably 150 kPa (gage) or less. Thereby, the cellulose fiber of this invention can be manufactured more efficiently.

It is preferable that the degree of coloring of the heat-treated product, that is, the anion-modified cellulose fiber after heating is higher than that before heating. The degree of coloring can be expressed by a numerical value representing the CIELab color space of the anion-modified cellulose fiber before and after heating, and a color difference (ΔE). The b ^* after heating is preferably +1 or more of b ^* before heating, more preferably +1.5 or more, and further preferably +2 or more. The a ^* after heating is preferably −0.1 or less of the a ^* before heating, more preferably −0.2 or less, and further preferably −0.3 or less. YI (E) after heating is preferably +2.5 or more, more preferably +3.5 or more, and further preferably +4.0 or more of YI (E) before heating. The color difference (color difference before and after heating: ΔE) is preferably +50 or less, more preferably +40 or less, and still more preferably +30 or less. The upper limit is usually 1 or more. The fiber surface has a more appropriate hydrophobicity and can exhibit a good interfacial bonding force to the rubber component.

  The heat treatment is usually performed using a heating device. As a heating apparatus, the apparatus which can be heat-processed under pressure, such as an autoclave, is mentioned, for example, An autoclave is preferable.

  The heat treatment may be performed on the anion-modified cellulose fiber or its dispersion. The definition and concentration of the dispersion, the aqueous solvent, examples of the method for preparing the dispersion and preferred embodiments are the same as those described in Item 2. The heat-treated product obtained through the heat treatment can be used as it is as the cellulose fiber of the present invention or a dispersion thereof. When the heat-treated product is a dispersion of cellulose fibers, the dispersion can be dried and used as cellulose fibers with reduced moisture content (dried product), or further obtained by redispersing the dried product. It can be used as a cellulose fiber redispersion.

  The heat-treated product obtained through the modification treatment can be used as it is as the modified cellulose fiber of the present invention. In the method of the present invention, at least one or more arbitrary treatments other than the denaturation treatment may be performed at arbitrary points as necessary. Examples of such optional treatment include fibrillation treatment, filtration treatment, fiber shortening treatment, and combinations of two or more thereof.

[Defibration (nanodefibration) treatment]
The timing of performing the defibration (nano-defibration) treatment is not particularly limited and may be any one or both before and after the modification treatment, but is preferably performed at least after the anion modification treatment. Thereby, the defibrating process can be performed with less energy than the energy required for the defibrating process before the anion modification process. The number of times of defibrating treatment is not particularly limited, and may be one or more times. When performing the above-mentioned desalting treatment, the desalting treatment may be performed before or after the defibrating treatment.

A defibrating apparatus is usually used for the defibrating process. The defibrating apparatus is not particularly limited, and examples thereof include high-speed rotating type, colloid mill type, high pressure type, roll mill type, ultrasonic type apparatus, high pressure or ultra high pressure homogenizer is preferable, wet type, high pressure or An ultra-high pressure homogenizer is more preferable. These apparatuses are preferable because a strong shearing force can be applied to the modified cellulose. The shear rate is preferably 1000 sec ^-1 or more. Thereby, there are few aggregation structures and it can be made into nanofibers uniformly. The pressure applied to the modified cellulose is preferably 50 MPa or more, more preferably 100 MPa or more, and further preferably 140 MPa or more. The defibrating treatment is usually performed in 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 fibers in the dispersion is usually 0.1% by mass (w / v%) or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more. The upper limit is usually 10% by mass or less, preferably 6% by mass or less. Other definitions of the dispersion, concentration, aqueous solvent, examples of the method of preparing the dispersion and preferred embodiments are the same as those described in Item 2.

[Filtration treatment]
Although the time for performing the filtration treatment is not particularly limited, it is usually after the fibrillation treatment, and a dispersion of the modified cellulose after the fibrillation treatment (eg, an aqueous dispersion such as an aqueous dispersion) may be filtered. Thereby, foreign matters (for example, undefibrated fibers) remaining due to insufficient defibrating treatment can be removed. Furthermore, when the modified cellulose fiber is used for the production of a rubber composition, it is possible to suppress the breakage of the rubber composition starting from the remaining foreign matter and problems caused by this (eg, a decrease in strength of the rubber composition).

  Examples of the filtration treatment include pressure filtration treatment and vacuum filtration treatment. The pressure condition (differential pressure) in the pressure filtration treatment and the vacuum filtration treatment is not particularly limited, but is, for example, 0.01 MPa or more, and preferably 0.01 to 10 MPa. When the differential pressure is 0.01 MPa or more, the dilution of the dispersion liquid performed to obtain a sufficient amount of filtration treatment can be omitted (dilution is preferably not performed in consideration of the subsequent steps). When the differential pressure is 0.01 to 10 MPa, a sufficient amount of filtration treatment can be obtained even when the concentration of the modified cellulose fiber in the dispersion or the viscosity of the dispersion is high. The density | concentration of the modified cellulose fiber in the case of filtration is 0.1-5 mass% normally, Preferably it is 0.2-4 mass%, More preferably, it is 0.5-3 mass%.

A filtration device is usually used for the filtration treatment. The filtration device is not particularly limited, and examples thereof include Nutsche type, candle type, leaf disk type, drum type, filter press type, belt filter type and the like. The amount of filtration treatment is not particularly limited, but is preferably 10 L / m ² or more per hour, and more preferably 100 L / m ² or more.

  Examples of filter media used for the filtration treatment include filters made of materials such as metal fibers, cellulose, polypropylene, polyester, nylon, glass, cotton, polytetrafluoroethylene, polyphenylene sulfide, and combinations thereof; membrane filters; filter cloths; metals A filter formed by sintering a material such as powder; or a slit filter. Among these, a filter made of metal fiber and a membrane filter are preferable.

  The average pore diameter of the filter medium is not particularly limited when a filter aid is used in combination. On the other hand, when a filter aid is not used in combination, the average pore size of the filter medium is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm, and still more preferably 1 to 30 μm. When the average pore size is 0.01 μm or more, the filtration rate can be sufficient. On the other hand, when the thickness is 100 μm or less, foreign matters can be sufficiently captured, and a filtration effect is easily obtained.

  In the case of a filtration process, you may use a filter aid as needed. In the filtration treatment using a filter aid (auxiliary filtration treatment), the filter layer formed on the filter medium can be removed using the filter aid, so that the filter medium can be easily clogged and continuously removed. Can be filtered. The average particle diameter of the filter aid is preferably 150 μm or less, more preferably 1 to 150 μm, still more 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 rate can be suppressed. When the average particle diameter is less than 150 μm, foreign matters can be sufficiently captured, and filtration can be performed efficiently.

  The shape of the filter aid is not particularly limited, and examples thereof include substantially spherical shapes (eg, diatomaceous earth) and substantially rod-like shapes (eg, powdered cellulose). Measurement of the average particle diameter of the filter aid can be performed by a laser diffraction measuring instrument in conformity with JIS Z8825-1 regardless of its shape.

  The form of the auxiliary filter treatment is not particularly limited. For example, precoat filtration that forms a filter aid layer on the filter medium, and body feed that filters a mixture obtained by adding the filter aid to the modified cellulose fiber dispersion. Examples include filtration and a combination of both. Of these, the latter combination is preferred. Thereby, the amount of filtration processing improves and the filtrate of favorable quality can be obtained. The auxiliary filtration treatment may be a multistage treatment consisting of two or more filtration steps using different filter aids. In the case of multistage treatment, it is preferable that at least one of the filtration steps is a pressure filtration treatment or a vacuum filtration treatment.

  A filter aid is not specifically limited, For example, an inorganic compound and an organic compound are preferable. Preferable examples of the filter aid include diatomaceous earth, powdered cellulose, pearlite, and activated carbon.

Diatomaceous earth refers to soft rock or soil mainly composed of diatom shell, and is mainly composed of silica. Components other than silica, such as alumina, iron oxide and alkali metal oxides, may be included. Diatomaceous earth is usually porous and has a high porosity. The cake bulk density of diatomaceous earth is preferably about 0.2 to 0.45 g / cm ³ . Diatomaceous earth is preferably a fired product or a flux fired product. The origin of diatomaceous earth is not particularly limited, but freshwater diatomaceous earth is preferred. Examples of diatomaceous earth include Celite (registered trademark) manufactured by Celite, and Ceratom (registered trademark) manufactured by Eagle Pitcher Minerals.

  Powdered cellulose is powdered cellulose, and its shape is usually rod-shaped particles. The method for producing the powdered cellulose is not particularly limited. For example, the wood pulp is subjected to an acid hydrolysis treatment to remove the non-crystalline portion, and then pulverized and sieved. The undegraded residue obtained after the acid hydrolysis of the selected pulp is purified and The method of drying, grinding | pulverizing, and sieving is mentioned. Powdered cellulose can be crystalline or microcrystalline cellulose and preferably has a certain particle size distribution. The degree of cellulose polymerization of the powdered cellulose is preferably about 100 to 500. The crystallinity of the powdered cellulose by X-ray diffraction method is preferably 70 to 90%. The volume average particle size of the powdered cellulose measured by a laser diffraction particle size distribution analyzer is preferably 100 μm or less, more preferably 50 μm or less. Thereby, the modified cellulose fiber excellent in the fluidity | liquidity after filtration can be obtained. Examples of the powdered cellulose include KC Flock (registered trademark) manufactured by Nippon Paper Industries Co., Ltd., Theolas (registered trademark) manufactured by Asahi Kasei Chemicals Corporation, and Avicel (registered trademark) manufactured by FMC.

  The foreign matter area ratio of the dispersion of modified cellulose fibers after filtration is preferably 25% or less. The foreign matter area ratio is calculated by the following method. First, a surface tension adjuster is added to a dispersion of modified cellulose fibers, and then thinned. A pair of polarizing plates are arranged on both surfaces of the thin film so that the polarization axes are orthogonal to each other. Light is irradiated from one polarizing plate side, and a transmission image is acquired from the other polarizing plate side. The image is subjected to image analysis to determine the foreign matter area, and the foreign matter area ratio per gram of the modified cellulose fiber absolutely dry mass is calculated. The modified cellulose fiber dispersion after filtration preferably has a foreign matter area ratio of 25% or less in the evaluation method. The foreign matter area ratio is an index of dispersibility, and when the ratio is 25% or less, it has good dispersibility.

[Short fiber treatment]
The fiber shortening treatment is a treatment for appropriately cutting (shortening fibers) the cellulose chain before the treatment, and examples include ultraviolet irradiation treatment, oxidative decomposition treatment, hydrolysis treatment, and combinations of two or more thereof. It is done. The short fiber treatment is preferably a hydrolysis treatment or a combination of hydrolysis treatment and other treatment.

  It is preferable to perform a washing treatment for washing the cellulose fibers before the shortening treatment. Thereby, a side reaction can be suppressed. The conditions for the cleaning treatment are not particularly limited, and can be performed by a known method.

  Examples of the hydrolysis treatment include acid hydrolysis treatment in which an acid is added to cellulose fibers to hydrolyze cellulose chains, and alkali hydrolysis treatment in which alkali is added to cellulose fibers to hydrolyze cellulose chains. The reaction medium for the hydrolysis treatment is usually water. Thereby, a side reaction can be suppressed.

  Examples of the acid include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. The hydrolysis treatment is preferably performed on a dispersion of cellulose fibers (eg, a dispersion in an aqueous dispersion medium such as water). Thereby, a hydrolysis reaction can be performed efficiently. The cellulose fiber concentration in the dispersion is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass.

  The conditions for the acid hydrolysis treatment may be any conditions that allow the acid to act on the amorphous part of the cellulose molecule. Examples are as follows. The addition amount of the acid is preferably 0.01 to 0.5% by mass, and more preferably 0.1 to 0.5% by mass with respect to the absolutely dry mass of the cellulose fiber. When the added amount of the acid is 0.01% by mass or more, hydrolysis of the cellulose fiber can proceed and the efficiency of nanofiber formation can be improved. When the amount added is 0.5% by mass or less, excessive hydrolysis of the cellulose fibers can be prevented, and a decrease in the yield of the cellulose fibers can be suppressed.

  The pH value of the dispersion medium during the acid hydrolysis treatment is preferably 2.0 to 4.0, and more preferably 2.0 or more and less than 3.0. The pH value can be adjusted, for example, by adjusting the acid addition amount. For example, when the alkali remains in the dispersion medium, the acid addition amount may be increased. The reaction temperature is, for example, 70 to 120 ° C., and the reaction time is, for example, 1 to 10 hours. After the acid hydrolysis treatment, it is preferable to neutralize by adding an alkali such as sodium hydroxide. Thereby, the nanofiberization can be performed efficiently.

  The conditions for the alkaline hydrolysis treatment are not particularly limited, but examples are as follows. The pH value of the reaction solution is preferably 8 to 14, more preferably 9 to 13, and still more preferably 10 to 12. When the pH value is 8 or more, hydrolysis proceeds and the cellulose fibers can be sufficiently shortened. On the other hand, when the pH value is 14 or less, coloring of the cellulose fiber after hydrolysis and a decrease in transparency can be suppressed. The pH value may be adjusted by adding an alkali. The alkali used is usually water-soluble, and sodium hydroxide is preferable from the viewpoint of production cost.

  In the alkaline hydrolysis treatment, it is preferable to use an auxiliary agent (eg, oxidizing agent, reducing agent). When cellulose fibers having a carboxy group are hydrolyzed in an alkaline solution, the cellulose fibers may be colored yellow due to the formation of double bonds during β elimination, and the transparency may decrease. Result application technology may be limited. However, by using an auxiliary agent, the double bond can be oxidized or reduced, and coloration and transparency can be prevented from lowering. The auxiliary agent only needs to have activity in the alkaline region. From the viewpoint of reaction efficiency, the amount of the auxiliary added is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and further 0.5 to 2% by mass with respect to the absolutely dried cellulose fiber. preferable.

  Examples of the oxidizing agent include oxygen, ozone, hydrogen peroxide, and hypochlorite. Among them, the oxidizing agent is less likely to generate radicals, and oxygen, hydrogen peroxide, and hypochlorite are preferable, and hydrogen peroxide is more preferable. One oxidizing agent can be used alone, or two or more oxidizing agents can be used in combination.

  Examples of the reducing agent include sodium borohydride, hydrosulfite, and sulfite. A reducing agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The reaction temperature of the hydrolysis treatment is not particularly limited, but hydrolysis may be insufficient at low temperatures, resulting in insufficient fiber shortening, and cellulose fibers after hydrolysis may be colored at high temperatures. Since it can suppress such a problem and improve reaction efficiency, 40-120 degreeC is preferable, 50-100 degreeC is more preferable, and 60-90 degreeC is further more preferable. The reaction time for the hydrolysis treatment is preferably 0.5 to 24 hours, more preferably 1 to 10 hours, and further preferably 2 to 6 hours.

  From the viewpoint of reaction efficiency, the concentration of the cellulose fiber in the alkaline solution is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and further preferably 5 to 10% by mass.

  The ultraviolet irradiation treatment is a treatment for irradiating the cellulose fiber with ultraviolet rays. The reason why cellulose fibers are shortened by ultraviolet irradiation is presumed as follows. Ultraviolet rays directly act on cellulose and hemicellulose to cause low molecular weight and shorten the cellulose chain.

  The wavelength of the ultraviolet light is preferably 100 to 400 nm, more preferably 100 to 300 nm, and still more preferably 135 to 260 nm. By using ultraviolet rays having a wavelength of 135 to 260 nm, it can directly act on cellulose and hemicellulose to easily cause a reduction in molecular weight.

  As a light source for irradiating ultraviolet rays, it is only necessary to irradiate light in a wavelength region of 100 to 400 nm, and examples thereof include a xenon short arc lamp, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a deuterium lamp, and a metal halide lamp. . These light sources may be used alone or in any combination of two or more. The combination of two or more light sources is preferably a combination of a plurality of light sources having different wavelength characteristics. Thereby, the cut | disconnection location in a cellulose chain or a hemicellulose chain can be increased by irradiating simultaneously with the ultraviolet-ray of a different wavelength.

  When performing ultraviolet irradiation, a container that contains a cellulose fiber dispersion is usually used. For example, when using ultraviolet rays of 300 to 400 nm, a hard glass container may be used. When ultraviolet rays having a wavelength shorter than 300 nm are used, a quartz glass container that transmits ultraviolet rays more may be used. What is necessary is just to select suitably from the material with little deterioration with respect to the wavelength of the ultraviolet-ray used about the material of the part which does not participate in the light transmission reaction of a container.

  The density | concentration of the cellulose fiber in the dispersion liquid at the time of irradiating an ultraviolet-ray becomes like this. Preferably it is 0.1-12 mass%, More preferably, it is 0.5-5 mass%, More preferably, it is 1-3 mass%. Energy efficiency can be improved as the density | concentration of carboxymethylated cellulose is 0.1 mass% or more. When the concentration of the cellulose fiber is 12% by mass or less, the fluidity of the cellulose fiber in the ultraviolet irradiation device becomes good, and the reaction efficiency can be increased.

  The temperature when irradiating with ultraviolet rays is preferably 20 to 95 ° C, more preferably 20 to 80 ° C, and still more preferably 20 to 50 ° C. A temperature of 20 ° C. or higher is preferable because the efficiency of the photooxidation reaction is increased. If the temperature is 95 ° C. or lower, there is no risk of adverse effects such as deterioration of the quality of carboxymethylated cellulose, and there is no possibility that the pressure in the reaction apparatus will exceed atmospheric pressure, and it is necessary to design an apparatus that takes pressure resistance into consideration. This is preferable because the property is lost.

  Although the pH value at the time of irradiating with ultraviolet rays is not particularly limited, in view of simplification of the process, the neutral region, for example, the pH value is preferably about 6.0 to 8.0.

  The amount of ultraviolet rays received by the cellulose fibers can be controlled as necessary. Control methods include, for example, adjustment of the residence time of cellulose fibers in the irradiation reaction apparatus, adjustment of the energy amount of the irradiation light source, adjustment of the concentration of cellulose fibers in the irradiation apparatus (eg, adjustment by dilution with water, air or nitrogen, etc. Adjustment by blowing an inert gas into cellulose fibers). The extent to which the residence time and concentration are controlled can be appropriately set according to the target quality of the cellulose fibers after irradiation with ultraviolet rays (fiber length, degree of cellulose polymerization, etc.).

  When the ultraviolet irradiation treatment is performed in the presence of an auxiliary agent such as oxygen, ozone, peroxide (hydrogen peroxide, peracetic acid, sodium percarbonate, sodium perborate, etc.), the efficiency of the photooxidation reaction is increased. preferable.

  In the case of irradiating ultraviolet rays in the wavelength region of 135 to 242 nm, ozone is generated from air present in the gas phase portion (light source peripheral portion) around the light source. Ozone generated in this way can be used as an auxiliary agent for ultraviolet irradiation treatment. Thereby, the amount of ozone supplied from outside the system can be reduced, or the supply can be omitted. The method of using ozone purified from the air present in the periphery of the light source as an auxiliary agent for the ultraviolet irradiation treatment is not particularly limited. For example, while continuously supplying air to the periphery of the light source, the generated ozone is continuously And extracting the extracted ozone into cellulose fibers. By supplying oxygen to the periphery of the light source, a larger amount of ozone can be generated in the system, and the generated ozone can also be used as an auxiliary agent for the photooxidation reaction.

  The ultraviolet irradiation treatment may be repeated a plurality of times. The number of repetitions can be appropriately set according to conditions such as target quality of the cellulose fiber. For example, when the wavelength of ultraviolet rays is 100 to 400 nm, more preferably 135 to 260 nm, it is preferably 1 to 10 times, more preferably 2 to 5 times. The irradiation time per time is preferably 0.5 to 10 hours, more preferably 0.5 to 3 hours.

  The oxidative decomposition treatment is usually performed using hydrogen peroxide and ozone in combination. Ozone can be generated by a known method using an ozone generator using air or oxygen as a raw material. The amount of ozone added (in terms of mass) is preferably 0.1 to 3 times, more preferably 0.3 to 2.5 times, and more preferably 0.5 to 1.5 times the absolute dry mass of the cellulose fiber. Further preferred. If it is 0.1 times or more, the amorphous part of cellulose can be sufficiently decomposed. When it is 3 times or less, excessive decomposition of cellulose can be suppressed, and a decrease in the yield of cellulose fibers can be prevented. The amount of hydrogen peroxide added (in terms of mass) is preferably 0.001 to 1.5 times, more preferably 0.1 to 1.0 times the absolute dry mass of the cellulose fiber. When it is 0.001 times or more, the synergistic effect of ozone and hydrogen peroxide can be exhibited. If it is 1.5 times or less, the oxidative decomposition can proceed sufficiently, and the cost can be suppressed.

  The conditions (for example, pH and temperature) of the oxidative decomposition treatment are not particularly limited, but when ozone and hydrogen peroxide are used, the conditions are as follows. The pH value is preferably 2 to 12, more preferably 4 to 10, more preferably 6 to 8, and the temperature is preferably 10 to 90 ° C, more preferably 20 to 70 ° C, and further preferably 30 to 50. The reaction time is preferably 1 to 20 hours, more preferably 2 to 10 hours, still more preferably 3 to 6 hours. Thereby, the treatment can be carried out with good reaction efficiency.

  The apparatus used for the oxidative decomposition treatment may be a known apparatus. Examples of the apparatus include a reaction chamber, a stirrer, a chemical injection device, a heater, and a normal reactor equipped with a pH electrode.

  When defibrating treatment is performed after oxidative decomposition treatment using ozone and hydrogen peroxide, ozone and hydrogen peroxide remaining in the aqueous solution can act effectively in the defibrating process, so that the shortening of cellulose fibers is further shortened. Can be promoted.

4). Masterbatch and Rubber Composition The modified cellulose fiber of the present invention can be used as a component of a masterbatch and a rubber composition. The masterbatch is an intermediate for rubber production. The rubber composition is a composition for obtaining a rubber as a final product, and examples thereof include an unvulcanized rubber composition containing a vulcanizing agent and a rubber as a final product.

  The masterbatch and the rubber composition may contain one type of the modified cellulose fiber of the present invention or two or more types. Since the surface of the modified cellulose fiber has hydrophobicity, the interfacial bond strength between the fiber and the rubber component is good, so that a high-strength rubber composition or a master batch for obtaining a rubber composition can be obtained.

[Rubber component]
The masterbatch and the rubber composition usually contain a rubber component. The rubber component is a raw material of rubber and refers to a material that is crosslinked to become rubber. Examples of the rubber component include a rubber component for natural rubber and a rubber component for synthetic rubber. Examples of the rubber component for natural rubber include, for example, natural rubber (NR) in a narrow sense not subjected to chemical modification; chemically modified natural rubber such as chlorinated natural rubber, chlorosulfonated natural rubber, and epoxidized natural rubber; hydrogenated natural rubber Deproteinized natural rubber. Examples of the rubber component 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 rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber; butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydrin rubber Non-diene rubbers such as (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), chlorosulfonated polyethylene (CSM), and the like. Among these, NBR, NR, SBR, chloroprene rubber and BR are preferable, and NBR, NR, SBR and chloroprene rubber are more preferable. The rubber component may be a single type or a combination of two or more types.

[composition]
The content of the modified cellulose fiber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. Thereby, the improvement effect of tensile strength can fully express. The upper limit is preferably 50 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less. Thereby, the workability in the manufacturing process can be maintained. Therefore, 1-50 mass parts is preferable, 2-40 mass parts is more preferable, and 3-30 mass parts is further more preferable.

[Optional ingredients]
A masterbatch and a rubber composition may contain an arbitrary component as needed. Examples of optional components include surfactants (for example, cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants), polyvalent metals, and modified cellulose fibers of the present invention. Cellulose fibers, and compounding agents that can be used in the rubber industry. Examples of compounding agents that can be used in the rubber industry include reinforcing agents (eg, carbon black, silica, etc.), silane coupling agents, crosslinking agents, vulcanization accelerators, and vulcanization accelerators (eg, zinc oxide, stearic acid). ), Oils, cured resins, waxes, anti-aging agents, colorants and the like, which can be used in the rubber industry. Of these, vulcanization accelerators and vulcanization accelerators are preferred. What is necessary is just to determine suitably content of an arbitrary component according to the kind etc. of an arbitrary component, and it does not specifically limit.

  When the rubber composition is an unvulcanized rubber composition or a final product, it is preferable to include a crosslinking agent. Examples of the crosslinking agent include sulfur, sulfur halides, organic peroxides, quinone dioximes, organic polyvalent amine compounds, alkylphenol resins having a methylol group, and the like. Among these, sulfur is preferable. 1.0 mass part or more is preferable with respect to 100 mass parts of rubber components, as for content of a crosslinking agent, 1.5 mass parts or more is more preferable, and 1.7 mass parts or more is further more preferable. The upper limit is preferably 10 parts by mass or less, preferably 7 parts by mass or less, and more preferably 5 parts by mass or less.

  Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazole sulfenamide and N-oxydiethylene-2-benzothiazolyl sulfenamide. The content of the vulcanization accelerator is preferably 0.1 parts by mass, more preferably 0.3 parts by mass or more, and still more preferably 0.4 parts by mass or more with respect to the rubber component. The upper limit is preferably 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass or less.

  Each component in the rubber composition may exist independently, or may exist as a complex such as a reaction product of at least two components. The content of each component in the rubber composition usually conforms to the amount used as a raw material.

[Use of rubber]
The use of rubber, which is the final product of the masterbatch and rubber composition of the present invention, is not particularly limited, for example, transportation equipment such as automobiles, trains, ships, airplanes, etc .; electrical appliances such as personal computers, televisions, telephones, watches, etc. Mobile communication equipment such as mobile phones; portable music playback equipment, video playback equipment, printing equipment, copying equipment, sports equipment, etc .; building materials; office equipment such as stationery, containers, containers, etc. Other than these, application to members using rubber or flexible plastic is possible, and application to tires is preferable. Examples of the tire include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

5. Production Method The production method of the masterbatch and rubber composition of the present invention is not particularly limited, but it is preferably produced by a method comprising adding a rubber component to the modified cellulose fiber of the present invention or a dispersion thereof. Thereby, the rubber composition of this invention mentioned above can be manufactured efficiently.

  The form of the rubber component added to the modified cellulose fiber or dispersion thereof is not particularly limited, and may be a solid rubber component or a liquid containing a rubber component (for example, a rubber component dispersion (latex) or a rubber component solution). But you can. Examples of the dispersion medium of the rubber component dispersion and the solvent of the solution (hereinafter, collectively referred to as “liquid”) include water and organic solvents. The amount of the liquid is preferably 10 to 1000 parts by mass with respect to 100 parts by mass of the rubber component (the total amount when two or more rubber components are used).

  After the rubber component is added to the modified cellulose fiber dispersion, it is usually mixed. Mixing can be carried out using a known apparatus such as a homomixer, a homogenizer, or a propeller stirrer. The temperature at the time of mixing is preferably room temperature (20 to 30 ° C.). What is necessary is just to determine suitably the addition time of an arbitrary component according to each component.

  After coagulation, dehydration (drying) may be performed. The method of dehydration is not particularly limited, but is preferably by heat treatment. The conditions for the heat treatment are not particularly limited, but an example is as follows. The heating temperature is preferably 40 ° C. or higher and lower than 100 ° C. The treatment time is preferably 1 to 24 hours. By setting it as the said conditions, the damage with respect to a rubber component can be suppressed. The mixture after drying may be in an absolutely dry state, but the solvent may remain. Moreover, it does not restrict | limit especially as a method of removing solvents other than the above, It can carry out by a conventionally well-known method. For example, there is a method of coagulating the mixture by adding an acid or salt, dehydrating, washing and drying.

  The recovered coagulum is preferably washed. Thereby, since an impurity can be removed efficiently, it can lead to various performance improvement of a rubber composition.

  The recovered coagulum can be used as it is as a master batch. When obtaining a final product from the coagulated product, it is preferable to add a rubber component to the coagulated product and mix (for example, kneading and kneading).

  The temperature at the time of mixing (for example, during mastication and kneading) may be about room temperature (for example, about 15 to 30 ° C.), or may be heated to a high temperature so that the rubber component does not undergo a crosslinking reaction. . For example, it is 140 ° C. or lower, more preferably 120 ° C. or lower. Moreover, a minimum is 40 degreeC or more normally, Preferably it is 60 degreeC or more. Accordingly, the heating temperature is preferably about 40 to 140 ° C, more preferably about 60 to 120 ° C. Mixing can be performed using apparatuses, such as a Banbury mixer, a kneader, and an open roll, for example.

  You may shape | mold as needed after completion | finish of mixing. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, hollow molding, and foam molding, and may be appropriately selected according to the shape, application, and molding method of the final product.

  You may perform a finishing process as needed before making a solidified material into a final product. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, and chlorination, and only one of these treatments may be performed, or a combination of two or more may be used.

  Hereinafter, although an example is given and the present invention is explained still in detail, the present invention is not limited to these.

<Example 1>
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Industries) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (manufactured by Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 14 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. Since the pH in the system was lowered during the reaction, a 0.5N sodium hydroxide aqueous solution was sequentially added to maintain the pH at 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain oxidized cellulose having a carboxyl group content of 1.6 mmol / g.

  Subsequently, the obtained slurry of oxidized cellulose was adjusted to 1% (w / v) with water, treated with an ultra-high pressure homogenizer (20 ° C., 140 MPa) three times, and a transparent gel-like carboxylated cellulose nanofiber salt was obtained. A dispersion (1% (w / v): aqueous dispersion A) was obtained.

  The aqueous dispersion A was heated in an autoclave at 120 ° C. (Yamato Scientific Co., Ltd., SB310) for 30 minutes to obtain a heat-treated acid-type carboxy group-containing cellulose nanofiber aqueous dispersion A1.

<Example 2>
Except having changed the heat time in the heat processing of the aqueous dispersion A into 60 minutes, the process similar to Example 1 was performed and the heat-processed carboxyl group containing cellulose nanofiber aqueous dispersion A2 was obtained.

<Example 3>
Except having changed the heat time in the heat processing of the aqueous dispersion A into 120 minutes, the process similar to Example 1 was performed and the heat-processed carboxyl group containing cellulose nanofiber aqueous dispersion A3 was obtained.

<Comparative Example 1>
The aqueous dispersion A obtained in Example 1 was used as it was.

L ^* , a ^* , b ^* , ΔE, YI (E), transmittance and contact angle of each aqueous dispersion obtained in Examples 1 to 3 and Comparative Example 1 were measured and calculated under the following conditions. The results are shown in Tables 1 and 2.

<Measurement of L ^* , a ^* , b ^* , ΔE, YI (E)>
Using a spectral color difference meter (trade name: SE7700, manufactured by Nippon Denshoku Industries Co., Ltd.) under the conditions of a C light source and a 2 ° field of view, L ^* , a ^* , b ^* , YI (E), The color difference (ΔE) before and after heating was measured and calculated.

<Measurement of transmittance>
The transmittance of 660 nm light of each dispersion was measured using a UV-VIS spectrophotometer UV-265FS (manufactured by Shimadzu Corporation).

<Measurement of contact angle>
After applying each dispersion obtained in Examples and Comparative Examples using a Meyer bar so that the dry coating amount is ² g / m ² per side with respect to glassine paper (basis weight 30 g / m ² ). The sample was obtained by drying with a cylinder dryer. 5 μl of water is dropped onto the surface of the sample, and after 0.1 seconds, 1 second, and 10 seconds after dropping, the contact angle of water is measured by a contact angle measuring device (trade name: DAT1122, manufacturer: Fibro). Was measured under the conditions of a temperature of 23 ° C. and a humidity (relative humidity) of 50%.

  In addition, the amount of carboxy groups and the degree of carboxymethyl substitution in the above production examples were measured by the method described above.

From Tables 1 and 2, the following can be understood. The heat-treated carboxy group-containing cellulose nanofiber aqueous dispersions A1 to A3 of Examples 1 to 3 satisfy 75 ≦ L ^* ≦ 95 and 5 ≦ b ^* ≦ 35. On the other hand, b ^* of the aqueous dispersion A of Comparative Example 1 is smaller than that of the aqueous dispersions A1 to A3 (b ^* <5). On the other hand, the contact angles of the aqueous dispersions A1 to A3 of Examples 1 to 3 are larger than the contact angle of the aqueous dispersion A of Comparative Example 1, which is a carboxy group-containing cellulose contained in the aqueous dispersions A1 to A3. Nanofibers show high surface hydrophobicity.

  These results show that the carboxy group-containing cellulose nanofibers of the present invention can have good surface hydrophobicity, can exhibit good interfacial bonding force with hydrophobic materials such as rubber, and rubbers containing the nanofibers It shows that the composition can have good strength.

Claims (19)

Modified cellulose fiber in which b ^* in the CIELab color space of the 1% by mass aqueous dispersion is 5 ≦ b ^* ≦ 35. The fiber according to claim 1, wherein L ^* and a ^* in the CIELab color space of the 1% by mass aqueous dispersion are 75 ≦ L ^* ≦ 95 and −2 ≦ a ^* ≦ 2, respectively.   The fiber according to claim 1 or 2, wherein the yellow index of the 1 mass% aqueous dispersion is 8.5 or more.   The fiber according to any one of claims 1 to 3, which is a carboxy-modified cellulose fiber.   The fiber according to claim 4, which is a carboxy-modified cellulose fiber having a carboxy group content of 0.5 mmol / g to 3.0 mmol / g with respect to the absolutely dry mass of the modified cellulose fiber.   The fiber according to any one of claims 1 to 3, which is a carboxymethyl-modified cellulose fiber.   The fiber according to claim 6, which is a carboxymethyl-modified cellulose fiber having a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50.   The fiber according to any one of claims 1 to 7, which is a cellulose nanofiber.   The fiber according to any one of claims 1 to 8, which is an acid-type cellulose fiber or a salt-type cellulose fiber.   Dispersion liquid containing the fiber of any one of Claims 1-9.   The dispersion according to claim 10, which is an aqueous dispersion. Obtaining an anion-modified cellulose fiber by anion-modifying the cellulose-based raw material;
The fiber according to any one of claims 1 to 9, comprising heat-treating the anion-modified cellulose fiber or dispersion thereof at 105 ° C to 150 ° C for 20 minutes to 180 minutes to obtain a heat-treated product. Or the manufacturing method of the dispersion liquid of Claim 10 or 11.   It is performed so that the color difference with respect to 1 mass% aqueous dispersion of the anion modified cellulose fiber before heat processing of the 1 mass% aqueous dispersion of the anion modified cellulose fiber after heat processing may be 1 or more and 50 or less. the method of.   The method according to claim 12 or 13, wherein the heat treatment is performed under a pressure of 10 kPa (gage) to 400 kPa (gage).   The method according to claim 12, wherein the heat treatment is performed using an autoclave.   A masterbatch or a rubber composition comprising the fiber according to any one of claims 1 to 9 and a rubber component.   The masterbatch or rubber composition according to claim 16, wherein the rubber component includes at least one selected from the group consisting of acrylonitrile-butadiene rubber, natural rubber, chloroprene rubber, and styrene-butadiene copolymer rubber.   The manufacturing method of a masterbatch or a rubber composition including adding a rubber component to the fiber of any one of Claims 1-9, or the dispersion liquid of Claim 10 or 11.   The method according to claim 18, wherein the rubber component includes at least one selected from the group consisting of acrylonitrile-butadiene rubber, natural rubber, chloroprene rubber, and styrene-butadiene copolymer rubber.