WO2018070387A1

WO2018070387A1 - Method for producing rubber composition

Info

Publication number: WO2018070387A1
Application number: PCT/JP2017/036701
Authority: WO
Inventors: 康太郎伊藤; 雄介安川; 昌浩森田
Original assignee: 日本製紙株式会社
Priority date: 2016-10-13
Filing date: 2017-10-10
Publication date: 2018-04-19
Also published as: JP6990190B2; JPWO2018070387A1

Abstract

The purpose of the present invention is to provide a rubber composition having sufficient reinforcing properties and improved compatibility of rubber and cellulose-based fiber. That is, the present invention provides a method for producing a rubber composition, the method comprising a step in which a mixture of a chloroprene rubber-containing rubber component and a cellulose-based fiber (e.g., oxidized cellulose fiber, carboxymethylated cellulose fiber, cationized cellulose fiber, etc.) is coagulated by a metal salt, or by a metal salt and an acid. The rubber composition obtained by this production method exhibits excellent strength characteristics.

Description

Method for producing rubber composition

The present invention relates to a method for producing a rubber composition containing cellulosic fibers.

Rubber compositions containing rubber and cellulosic fibers are known to have excellent mechanical strength. For example, Patent Document 1 discloses a rubber / short fiber master batch obtained by stirring and mixing an aqueous dispersion of short fibers having an average fiber diameter of less than 0.5 μm and rubber latex, and removing water from the mixed liquid. Are listed. This document describes that a short fiber having an average fiber diameter of less than 0.5 μm is uniformly dispersed in rubber by mixing and drying a dispersion obtained by fibrillating short fibers in water and a rubber latex. ing. It is also described that a rubber composition having an excellent balance between rubber reinforcement and fatigue resistance can be produced from this rubber / short fiber master batch. However, since rubber and cellulosic fiber are generally poorly compatible, the strength of the rubber composition containing rubber and cellulosic fiber has been insufficient. Then, in order to improve compatibility, using a silane coupling agent and introduce | transducing a long-chain alkyl group into a cellulose fiber are examined (for example, patent document 2, 3).

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

However, there is a problem that the reagents used in the methods described in Patent Documents 2 and 3 are expensive. Furthermore, these methods have a problem that the reaction rate is low and a sufficient strength improvement effect cannot be obtained.
An object of the present invention is to provide a rubber composition that has good compatibility between rubber and cellulosic fibers and can exhibit sufficient reinforcement.

The present invention provides the following [1] to [6].
[1] A step of adding a divalent or trivalent metal salt, or a divalent or trivalent metal salt and an acid to a mixed solution containing chloroprene rubber and cellulosic fiber to coagulate the rubber component. The manufacturing method of a rubber composition.
[2] The method for producing a rubber composition according to [1], wherein the metal salt is a calcium salt.
[3] The method for producing a rubber composition according to [1] or [2], wherein the acid is acetic acid or sulfuric acid.
[4] The rubber composition according to any one of [1] to [3], wherein the cellulosic fiber includes at least one selected from the group consisting of oxidized cellulose fiber, carboxymethylated cellulose fiber, and cationized cellulose fiber. Manufacturing method.
[5] The method for producing a rubber composition according to any one of [1] to [4], wherein the length-weighted average fiber length of the cellulosic fibers is 50 to 2000 nm.
[6] The method according to any one of [1] to [5], wherein the cellulosic fiber has a length-weighted average fiber diameter of 2 to 500 nm.

According to the present invention, it is possible to provide a rubber composition that has good compatibility between rubber and cellulosic fibers and can exhibit sufficient reinforcement.

The present invention relates to a method for producing a rubber composition, comprising a step of coagulating chloroprene rubber by adding a metal salt or a metal salt and an acid to a mixed solution containing chloroprene rubber and cellulosic fibers. The rubber composition produced by this method has good compatibility between the rubber and the cellulosic fiber, can exhibit sufficient reinforcement, and can maintain the reinforcement even when a large strain is applied. In addition, the effect of this invention expresses specifically in the rubber composition containing a chloroprene rubber and a cellulosic fiber.

<1. Solidification process>
In the present invention, solidification (coagulation method) means that a rubber component is aggregated by adding an acid or a metal salt to a liquid such as a suspension (dispersion) containing the rubber component, and as a result, the rubber component is separated (solidified). Liquid separation) (process, method).

The coagulation step includes mixing chloroprene rubber and cellulosic fibers to obtain a mixed solution containing these, and adding a metal salt, or an acid or a metal salt to the mixed solution.

<1.1. Metal salt>
The metal salt used for solidification is preferably a divalent or trivalent metal salt. It is presumed that divalent or trivalent metal ions contribute to the improvement of the compatibility between the chloroprene rubber and the cellulosic fiber, and the reinforcing property of the rubber composition can be improved. Examples of the divalent or trivalent metal salt include calcium salts such as calcium chloride and calcium nitrate, magnesium salts such as magnesium chloride and magnesium sulfate, and aluminum salts such as aluminum chloride and aluminum sulfate. Salts are preferred, calcium salts are more preferred, and calcium chloride is even more preferred. Calcium ions are presumed to have a high contribution to improving compatibility between chloroprene rubber and cellulosic fibers and reinforcing the rubber composition. One or a combination of two or more metal salts may be used.
The amount of the metal salt added to the mixed solution is not particularly limited, but the metal salt concentration in the whole mixed solution is preferably adjusted to 0.1% by weight or more, more preferably 0.3% by weight or more. That's fine. Although an upper limit is not specifically limited, Preferably it is 3.0 weight% or less, More preferably, it is 2.0 weight% or less. Therefore, the concentration of the metal salt in the premixed solution is preferably adjusted to 0.1 to 3.0% by weight, more preferably 0.3 to 2.0% by weight.

<1.2. Acid>
As the acid used for coagulation, either an organic acid or an inorganic acid can be used. As the organic acid, formic acid, acetic acid and the like are preferable. As the inorganic acid, sulfuric acid, hydrochloric acid, carbonic acid and the like are preferable. Of these, acetic acid and sulfuric acid are more preferable. The acid addition conditions vary depending on the type of metal salt, but in general, the pH in the mixed solution after acid addition is preferably 3.0 or more, more preferably 3.5 or more, and even more preferably 4.0 or more. do it. Although an upper limit is not specifically limited, Preferably it is 8.0 or less, More preferably, it is 7.0 or less, More preferably, it is 6.0 or less, More preferably, it is 5.0 or less. Accordingly, the pH is preferably 3.0 to 8.0, more preferably 3.5 to 7.0, still more preferably 4.0 to 7.0, 4.0 to 6.0, or pH 4.0 to 5 Adjust to 0. One or a combination of two or more acids may be used.

In solidification, it is preferable to add a metal salt, or to add both a metal salt and an acid, and to add a divalent or trivalent metal salt, or to add a divalent or 3 It is more preferable to perform both addition of a valent metal salt and addition of an acid. When both the addition of the metal salt and the addition of the acid are performed, the timing of the addition of the metal salt and the addition of the acid is not particularly limited, but it is preferable to add the acid after the addition of the metal salt.

<1.3. Cellulosic fiber>
In the present invention, the cellulose fiber may be a cellulose fiber having a fiber diameter of micron order or a cellulose nanofiber having a fiber diameter of nano order obtained by chemically modifying the cellulose fiber after chemical modification as necessary.

The origin of the cellulose fiber is not particularly limited, and examples thereof include plants, animals (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (Acetobacter)), and microorganism products. Plant-derived cellulose fibers include, for example, wood, bamboo, hemp, jute, kenaf, farmland residue, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, and the like. Although the raw material of the cellulose fiber used by this invention may be any of these or a combination, it is preferably a plant or microorganism-derived cellulose fiber, more preferably a plant-derived cellulose fiber.

The average fiber diameter of the cellulose fibers is not particularly limited, but is usually about 30 to 60 μm in the case of softwood kraft pulp, which is a general pulp, and is usually about 10 to 30 μm in the case of hardwood kraft pulp. The average fiber diameter of pulp other than softwood kraft pulp and hardwood kraft pulp that has undergone general refining is usually about 50 μm. For example, when a raw material obtained by refining a material such as a chip of several centimeters is used, it is preferable to obtain a cellulose fiber by performing mechanical treatment with a disintegrator such as a refiner or beater and adjusting the average fiber diameter to about 50 μm.

The average fiber diameter of cellulosic fibers (for example, cellulose nanofibers) is usually about 2 to 500 nm, preferably 2 to 50 nm in terms of length-weighted average fiber diameter. The average fiber length is preferably 50 to 2000 nm in terms of length-weighted average fiber length. 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 cellulosic fiber (for example, cellulose nanofiber) is usually 10 or more. Although an upper limit is not specifically limited, Usually, it is 1000 or less. The average aspect ratio can be calculated by the following formula.

Average aspect ratio = average fiber length / average fiber diameter

Hereinafter, a method for producing cellulose nanofiber will be described. For convenience, the cellulose fiber that is the raw material of the cellulose nanofiber is also referred to as “cellulose raw material”.

[Modification]
The cellulose raw material has three hydroxyl groups per glucose unit and can be subjected to various chemical modifications. In the present invention, both the cellulose raw material subjected to chemical modification and the cellulose raw material not subjected to chemical modification can be used as the cellulosic fiber. When the chemically modified cellulose raw material is used, the fineness of the fibers is sufficiently advanced to obtain cellulose nanofibers having a uniform fiber length and fiber diameter, so that a sufficient reinforcing effect can be exhibited when combined with rubber. Therefore, as the cellulose fiber, a cellulose fiber obtained through chemical modification is preferable. Examples of the chemical modification include oxidation, etherification, phosphorylation, esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation), etherification, cationization and esterification are preferred. Hereinafter, chemical modification will be described.

[Oxidation]
The amount of carboxyl groups in the oxidized cellulose or cellulose nanofiber obtained by this treatment is preferably 0.5 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 preferably 3.0 mmol / g or less, more preferably 2.5 mmol / g or less, and still more preferably 2.0 mmol / g or less. Accordingly, the amount is preferably 0.5 to 3.0 mmol / g, more preferably 0.8 to 2.5 mmol / g, and further preferably 1.0 to 2.0 mmol / g. In addition, the amount of carboxyl groups of oxidized cellulose and the amount of carboxyl groups of oxidized cellulose nanofibers obtained from the oxidized cellulose are usually the same value.

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

The N-oxyl compound is a compound capable of generating a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). The N-oxyl compound is not particularly limited as long as it is a compound that promotes the target oxidation reaction. The amount of the N-oxyl compound used is not particularly limited as long as it is a catalyst amount that can oxidize cellulose as a raw material. For example, 0.01 mmol or more is preferable and 0.02 mmol or more is more preferable with respect to 1 g of 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.

Bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected within a range that can promote the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, with respect to 1 g of 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. Accordingly, the total amount of bromide and iodide is preferably from 0.1 to 100 mmol, more preferably from 0.1 to 10 mmol, and even more preferably from 0.5 to 5 mmol, based on 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, and even more preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and particularly preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. When an 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. Accordingly, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

The conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C or higher, more preferably 15 ° C or higher. The upper limit of the temperature is preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. Accordingly, 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. Accordingly, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, a carboxyl group is generated in cellulose as the oxidation reaction proceeds, 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. Therefore, the reaction time in the oxidation is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours. Oxidation may be carried out in two or more stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is ozone oxidation. By this oxidation reaction, at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting cellulose are oxidized, and the cellulose chain is decomposed. The ozone treatment is usually performed by bringing a gas containing ozone and a cellulose raw material into contact with each other. The ozone concentration in the gas is preferably 50 g / m ³ or more. The upper limit is preferably 250 g / m ³ or less, more preferably 220 g / m ^3. Therefore, the ozone concentration in the gas is preferably 50 ~ 250g / m ^3, more preferably 50 ~ 220g / m ^3. The amount of ozone added is preferably 0.1% by weight or more and more preferably 5% by weight or more with respect to 100% by weight of the solid content of the cellulose raw material. The upper limit of the amount of ozone added is usually 30% by weight or less. Accordingly, the amount of ozone added is preferably 0.1 to 30% by weight and more preferably 5 to 30% by weight with respect to 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C. or higher, preferably 20 ° C. or higher, and the upper limit is usually 50 ° C. or lower. Accordingly, the ozone treatment temperature is preferably 0 to 50 ° C., more preferably 20 to 50 ° C. The ozone treatment time is usually 1 minute or longer, preferably 30 minutes or longer, 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, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

Further, the ozone-treated cellulose may be further oxidized 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 these oxidizers are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizer solution, and the cellulose raw material is immersed in the oxidizer solution. The amount of the carboxyl group, carboxylate group, and aldehyde group contained in the oxidized cellulose nanofiber can be adjusted by controlling the oxidizing conditions such as the addition amount of the oxidizing agent and the reaction time.

An example of a method for measuring the carboxyl group amount will be described below. Prepare 60 mL of 0.5 wt% 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 It can be calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid where the change in electrical conductivity is gradual, using the following equation.

Carboxyl group amount [mmol / g oxidized cellulose or cellulose nanofiber] = a [mL] × 0.05 / oxidized cellulose weight [g]

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 the inside of the system is adjusted to be acidic, the pH in the system is preferably adjusted to 2 to 6, more preferably 2 to 5, and still more preferably 2.3 to 5. 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.

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

The degree of carboxymethyl substitution per anhydroglucose unit in carboxymethylated cellulose or cellulose nanofiber obtained by carboxymethylation is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. The upper limit of the substitution degree is preferably 0.50 or less, more preferably 0.40 or less, and further preferably 0.35 or less or 0.30 or less. Accordingly, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and even more preferably 0.10 to 0.35 or 0.10 to 0.30. In addition, the amount of carboxyl groups of carboxymethylated cellulose and the amount of carboxyl groups of carboxymethylated cellulose nanofibers obtained from the carboxymethylated cellulose are usually the same value.

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

Mercerization is usually performed by mixing the bottoming material and mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of mercerizing agent used is preferably 0.5 times mol or more, more preferably 1.0 times mol or more, and 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. Accordingly, the amount of 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 reaction temperature for mercerization is usually 0 ° C. or higher, preferably 10 ° C. or higher, and the upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. Accordingly, 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. Examples of the carboxymethylating agent include sodium monochloroacetate. 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 the cellulose raw material. The upper limit of the amount is usually 10.0 moles or less, preferably 5 moles or less, and more preferably 3 moles or less. Therefore, the amount is preferably 0.05 to 10.0 times mol, more preferably 0.5 to 5 times mol, and still more preferably 0.8 to 3 times mol. The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. 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. Therefore, 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 carboxymethyl substitution degree per glucose unit of the carboxymethyl cellulose nanofiber is measured, for example, by the following method. 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 nitric acid methanol solution prepared by adding 100 mL of special concentrated nitric acid to 1000 mL of methanol, and shake for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into acid-type carboxymethylated cellulose. 3) Weigh accurately 1.5 to 2.0 g of acid-type carboxymethylated cellulose (absolutely dry) 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:
A = [(100 × F ′ − (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of acid-type carboxymethylated cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralizing 1 g of acid-type carboxymethylated cellulose
F: Factor of 0.1N H ₂ SO ₄ F ′: Factor of 0.1N NaOH

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. As an 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.

[Cationization]
The cationized cellulose nanofiber obtained by cationization may contain a cation such as ammonium, phosphonium, or sulfonium, or a group having the cation in the molecule. The cationized cellulose nanofiber preferably includes a group having ammonium, and more preferably includes a group having quaternary ammonium.

The method of cationization is not particularly limited, and examples thereof include a method of reacting a cellulose raw material with a cationizing agent and a catalyst in the presence of water or alcohol. Examples of the cationizing agent include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride (eg, 3-chloro-2-hydroxypropyltrimethylammonium hydride) or a halohydrin type thereof. By using any of these, a cationized cellulose having a group containing quaternary ammonium can be obtained. Examples of the catalyst include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Examples of the alcohol include alcohols having 1 to 4 carbon atoms. The amount of the cationizing agent is preferably 5% by weight or more, more preferably 10% by weight or more with respect to 100% by weight of the cellulose raw material. The upper limit of the amount is usually 800% by weight or less, preferably 500% by weight or less. The amount of the catalyst is preferably 0.5% by weight or more, more preferably 1% by weight or more with respect to 100% by weight of the cellulose fibers. The upper limit of the amount is usually 70% by weight or less, preferably 30% by weight or less. The amount of alcohol is preferably 50% by weight or more, more preferably 100% by weight or more, based on 100% by weight of cellulose fibers. The upper limit of the amount is usually 50000% by weight or less, preferably 500% by weight or less.

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

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

The cation substitution degree per glucose unit of the cationized cellulose nanofiber is preferably 0.01 or more, more preferably 0.02 or more, and further preferably 0.03 or more. The upper limit of the degree of substitution is preferably 0.40 or less, more preferably 0.30 or less, and still more preferably 0.20 or less. Accordingly, the degree of cation substitution is preferably from 0.01 to 0.40, more preferably from 0.02 to 0.30, and even more preferably from 0.03 to 0.20. By introducing a cationic substituent into cellulose, the celluloses repel each other electrically. For this reason, the cellulose which introduce | transduced the cation substituent can be nano-fibrillated easily. When the cation substitution degree per glucose unit is 0.01 or more, nano-defibration can be sufficiently achieved. On the other hand, when the degree of cation substitution per glucose unit is 0.40 or less, swelling or dissolution can be suppressed, whereby the fiber form can be maintained, and a situation where nanofibers cannot be obtained can be prevented. In addition, the amount of carboxyl groups of cationized cellulose and the amount of carboxyl groups of cationized cellulose nanofibers obtained from the cationized cellulose are usually the same value.

An example of a method for measuring the degree of cation substitution per glucose unit will be described below. After drying the sample (cationized cellulose), the nitrogen content is measured with a total nitrogen analyzer TN-10 (manufactured by Mitsubishi Chemical Corporation). For example, when 3-chloro-2-hydroxypropyltrimethylammonium chloride is used as the cationizing agent, the degree of cation substitution is calculated by the following formula. The cation substitution degree here is an average value of the number of moles of substituents per mole of anhydroglucose unit.

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

[Esterification]
Although the method of esterification is not specifically limited, For example, the method of making the compound A mentioned later react with a cellulose raw material is mentioned. Examples of the method of reacting compound A with a cellulose raw material include a method of mixing a powder or an aqueous solution of compound A with a cellulose raw material, a method of adding an aqueous solution of compound A to a slurry of a cellulose raw material, and the like. Among these, a method of mixing an aqueous solution of Compound A into a cellulose raw material or a slurry thereof is preferable because the uniformity of the reaction is enhanced and esterification efficiency can be increased.

Examples of compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. Compound A may be in the form of a salt. Among them, a phosphoric acid compound is preferable because it is low in cost and easy to handle, and a phosphoric acid group can be introduced into cellulose of pulp fiber to improve the fibrillation efficiency. The phosphate compound may be any compound having a phosphate group. For example, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, diphosphate Examples include potassium hydrogen, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. . The phosphoric acid compound used may be one or a combination of two or more of these. Among these, phosphoric acid group introduction efficiency is high, it is easy to defibrate in the defibrating process, and is easy to apply industrially, from the viewpoint of phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid Ammonium salts are preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable. In addition, it is preferable to use an aqueous solution of a phosphoric acid compound in the esterification because the uniformity of the reaction is increased and the efficiency of introducing a phosphate group is increased. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less from the viewpoint of increasing the efficiency of introducing phosphate groups, and more preferably 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fibers.

Examples of the esterification method include the following methods. Compound A is added to a suspension of cellulose raw material (for example, solid content concentration of 0.1 to 10% by weight) with stirring to introduce phosphate groups into the cellulose. When compound A is a phosphoric acid compound, the amount of compound A added is preferably 0.2 parts by weight or more and more preferably 1 part by weight or more as the amount of phosphorus element with respect to 100 parts by weight of the cellulose raw material. Thereby, the yield of fine fibrous cellulose can be improved more. The upper limit of the amount is preferably 500 parts by weight or less, and more preferably 400 parts by weight or less. Thereby, the yield corresponding to the usage-amount of the compound A can be obtained efficiently. Therefore, 0.2 to 500 parts by weight is preferable, and 1 to 400 parts by weight is more preferable.

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

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

In phosphate esterified cellulose, a phosphate group substituent is introduced into the cellulose raw material, and the cellulose repels electrically. Therefore, phosphorylated cellulose can be easily nano-defibrated. The degree of phosphate group substitution per glucose unit in the phosphate esterified cellulose is preferably 0.001 or more. Thereby, sufficient defibration (for example, nano defibration) can be implemented. The upper limit of the degree of substitution is preferably 0.60. Thereby, swelling or melt | dissolution of phosphate esterified cellulose can be prevented, and the situation where a nanofiber cannot be obtained can be prevented. Therefore, the degree of substitution is preferably 0.001 to 0.60. In addition, the amount of carboxyl groups of phosphate esterified cellulose and the amount of carboxyl groups of phosphate esterified cellulose nanofibers obtained from the phosphate esterified cellulose are usually the same value.

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

[Defibration]
The fibrillation of the cellulose raw material may be performed before or after chemical modification of the cellulose raw material. The defibrating process may be performed once or a plurality of times. In the case of multiple times, each defibration period may be any time. The defibrating process is usually physical defibrating.

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

When defibration is performed on a dispersion of cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3%. % By weight or more. Thereby, the liquid quantity with respect to the quantity of a cellulose fiber raw material becomes an appropriate quantity, and can become efficient. The upper limit of the concentration is usually 10% by weight or less, preferably 6% by weight or less. Thereby, fluidity can be maintained.

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

The cellulosic fiber preferably includes at least one cellulose nanofiber obtained through the above-described chemical modification, and includes at least one selected from the group consisting of oxidized cellulose fiber, carboxymethylated cellulose fiber, and cationized cellulose fiber. It is more preferable.

Cellulose nanofibers may be subjected to treatment other than chemical modification and defibration treatment usually performed in the production process. Examples of such treatment include filtration treatment, fiber shortening treatment, and combinations of two or more thereof.

[Filtration treatment]
Although the timing for performing the filtration treatment is not particularly limited, it is usually after the defibration treatment and may be performed on the modified cellulose dispersion (eg, an aqueous dispersion such as an aqueous dispersion) after the defibration treatment. 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 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, 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 concentration of the modified cellulose fiber during filtration is usually 0.1 to 5% by mass, preferably 0.2 to 4% by mass, and more preferably 0.5 to 3% by 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 size of the filter medium is not particularly limited when a filter aid is used in combination. On the other hand, when no filter aid is 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 filtration treatment, a filter aid may be used as necessary. 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 size 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 shapes (eg, powdered cellulose). Measurement of the average particle diameter of the filter aid can be performed with a laser diffraction measuring instrument in accordance 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, a combination of both 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, at least one of the filtration steps is preferably pressure filtration treatment or vacuum filtration treatment.

The filter aid is not particularly limited, and for example, inorganic compounds and organic compounds 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 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 modified cellulose fiber dispersion 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 from 0.1 to 20% by mass, more preferably from 0.5 to 10% by mass, and even more preferably from 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 amount of acid added is preferably 0.01 to 0.5% by mass, more preferably 0.1 to 0.5% by mass, based on the absolute 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, 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 further 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 alkali 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 preferably 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. In order to suppress such problems and improve the reaction efficiency, the temperature is preferably 40 to 120 ° C, more preferably 50 to 100 ° C, and further preferably 60 to 90 ° C. 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 cellulose fibers 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 reduce the 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. 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 ultraviolet rays of 300 to 400 nm are used, 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 concentration of the cellulose fiber in the dispersion upon irradiation with ultraviolet rays is preferably 0.1 to 12% by mass, more preferably 0.5 to 5% by mass, and further preferably 1 to 3% by 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 at the time of irradiation with ultraviolet rays is preferably 20 to 95 ° C., more preferably 20 to 80 ° C., and further 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.

The pH value when irradiating with ultraviolet rays is not particularly limited, but considering the simplification of the process, the neutral value, 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.

When irradiating ultraviolet rays in the wavelength region of 135 to 242 nm, ozone is generated from the air present in the gas phase around the light source (light source periphery). 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, 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.

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 the oxidative decomposition treatment (for example, pH and temperature) 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, further 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, and further 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.

<1.4. Form of cellulosic fiber used for mixing>
When preparing a liquid mixture in a coagulation process, the form of the cellulosic fiber mixed with a rubber component is not particularly limited. Examples of the form include a dispersion in which cellulosic fibers are dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion. The concentration of the cellulosic fibers in the dispersion is usually 0.1 to 5% (w / v) when the dispersion medium is water. When the dispersion medium contains an organic solvent such as alcohol in addition to water, the concentration is usually 0.1 to 20% (w / v). The wet solid is a solid in an intermediate form between the dispersion and the dry solid. The amount of the dispersion medium in the wet solid obtained by dehydrating the dispersion by a conventional method is preferably 5 to 15% by weight based on the cellulosic fiber, but the amount of the dispersion medium can be increased by adding a liquid medium or further drying. Can be adjusted as appropriate.

Also, examples of the form include a mixed solution of a cellulosic fiber and a water-soluble polymer solution, a dry solid of the mixed solution, and a wet solid of the mixed solution. The amount of the liquid medium in the mixed liquid and the dry solid may be in the range of the amount of the dispersion medium of the wet solid described above. Examples of water-soluble polymers include cellulose derivatives (carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, ethylcellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, hard starch, crumbs Flour, positive starch, phosphorylated starch, corn starch, gum arabic, locust bean gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein lysate, peptone, polyvinyl alcohol, polyacrylamide, Polyvinyl pyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, rosin sizing agent, petroleum Fat sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide-polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic cross-linked polymer, polyacrylate (eg, polyacrylic acid soda) , Starch polyacrylic acid copolymer, tamarind gum, guar gum, and colloidal silica, and mixtures thereof. Among these, carboxymethylcellulose and its salt are preferable from the viewpoint of solubility.

The dry solid and wet solid can be prepared by drying a dispersion of cellulose fibers or a mixture of cellulose fibers and a water-soluble polymer. Although a drying method is not specifically limited, For example, spray drying, pressing, air drying, hot air drying, or vacuum drying is mentioned. Examples of the drying device include a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disk drying device, an aeration drying device, a rotary drying device, an air flow drying device, and a spray dryer drying device. , Spray dryer, cylindrical dryer, drum dryer, screw conveyor dryer, rotary dryer with heating tube, vibration transport dryer, batch dryer (eg box dryer, aerated dryer, vacuum box) A drying device or a stirring drying device). These drying apparatuses may be used alone or in combination of two or more. The drum drying apparatus is preferable because it can supply heat energy uniformly and directly to the material to be dried, so that energy efficiency is high and the dried material can be recovered immediately without applying more heat than necessary.

<1.5. Rubber component>
In the present invention, chloroprene rubber is used as the rubber component. Chloroprene rubber (CR) exhibits crystallinity similar to that of natural rubber (NR). Chloroprene rubber is characterized by satisfying various properties such as heat resistance, oil resistance, ozone resistance, chemical resistance, fatigue resistance, flame resistance, weather resistance, and adhesiveness in a well-balanced manner.

In the present invention, chloroprene rubber and other rubber components can be used in combination as long as the desired effects are not impaired. Examples of other rubber components include natural rubber, chlorinated natural rubber, hydrogenated natural rubber, chlorosulfonated natural rubber, epoxidized natural rubber, deproteinized natural rubber, butadiene rubber (BR), and styrene-butadiene copolymer. Rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, etc. Diene rubber, ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydrin rubber (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), chloro Examples include sulfonated polyethylene (CSM).

The form of mixing the chloroprene rubber and the rubber component used as necessary with the cellulosic fiber is not particularly limited. For example, a dispersion of cellulose fibers, a dry solid of the dispersion, or a wet solid of the dispersion is mixed with chloroprene rubber and a rubber component (solid) used as necessary or a dispersion thereof. A form is mentioned. Among these, the form which mixes the dispersion liquid of a cellulosic fiber, the dispersion liquid of the chloroprene rubber and the rubber component used as needed is preferable.

<1.6. Addition amount>
The addition amount of the cellulosic fibers in the preparation of the mixed solution is preferably 1% by weight or more with respect to 100% by weight of the rubber component (the total of the chloroprene rubber and the other rubber component when other rubber components are included), and 2% by weight. % Or more is more preferable, and 3% by weight or more is more preferable. Thereby, the improvement effect of the tensile strength of the rubber composition obtained can fully be expressed. The upper limit is preferably 50% by weight or less, more preferably 40% by weight or less, and still more preferably 30% by weight or less. Thereby, the workability in the manufacturing process can be maintained. Therefore, 1 to 50% by weight is preferable.

<2. Solid-liquid separation process (dehydration process), water washing process>
The production method of the present invention preferably further includes at least one step selected from the group consisting of a solid-liquid separation step and a water washing step, and more preferably further includes both steps. Thereby, content of the impurity in a rubber composition can be reduced and the intensity | strength of a rubber composition can be improved. The aspect of a solid-liquid separation process and a water washing process has a preferable aspect which repeats the set of solid-liquid separation and water washing twice or more.

The solid-liquid separation step (dehydration step) is a step for solid-liquid separation of the liquid mixture containing the solidified rubber component obtained in the coagulation step. Therefore, the time for performing the solid-liquid separation step is usually after the coagulation step. Solid-liquid separation is preferably performed using a filter medium. Examples of filter media include filters made of materials such as metal fibers, cellulose, polypropylene, polyester, nylon, glass, cotton, polytetrafluoroethylene, polyphenylene sulfide, membranes, filter cloths, filters made by sintering metal powder, Or a slit filter is mentioned. Among these, a nylon filter is preferable. A preferable average pore diameter of the filter medium is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm, and further preferably 1 to 30 μm.

The water washing step is a step of washing the solid phase obtained in the solid-liquid separation step.

<3. Drying process>
The production method of the present invention may further include a drying step. Thereby, a masterbatch with little moisture content can be obtained. A drying process is a process which uses for the drying by heating the processing liquid obtained by a coagulation process, or the processing liquid obtained by the solid-liquid separation process and washing | cleaning process performed after that as needed. Conditions such as heating temperature and heating time are not particularly limited. The heating temperature is preferably 40 ° C. or higher. The upper limit is preferably less than 100 ° C. The heating time is preferably 1 hour or longer. The upper limit is preferably 24 hours or less. By setting the heating condition within the above range, damage to the rubber component can be suppressed. Heating may be performed using a dryer such as an oven.

<4. Methylene acceptor compound and / or methylene donor compound addition step>
The production method of the present invention may further include a step of adding a methylene acceptor compound and / or a methylene donor compound.
The methylene acceptor compound is usually a compound that can accept a methylene group and can undergo a curing reaction by mixing with a methylene donor compound and heating. Examples of the methylene acceptor compound include phenol compounds such as phenol, resorcinol, resorcin, and cresol and derivatives thereof, resorcin resin, cresol resin, and phenol resin. Examples of the phenol resin include condensates of the above phenol compounds and derivatives thereof with aldehyde compounds such as formaldehyde and acetaldehyde. Phenol resins can be classified into novolak resins (acidic catalysts) and resol resins (alkaline catalysts) depending on the catalyst used in the condensation, and any of them may be used in the present invention. The phenol resin may be modified with oil or fatty acid. Examples of the oil and fatty acid include rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and linolenic acid.

The methylene donor compound is usually a compound that can donate a methylene group and can undergo a curing reaction by mixing with a methylene acceptor compound and heating. Examples of the methylene donor compound include hexamethylenetetramine and melamine derivatives. Examples of the melamine derivative include hexamethylol melamine, hexamethoxymethyl melamine, pentamethoxymethyl melamine, pentamethoxymethylol melamine, hexaethoxymethyl melamine, and hexakis- (methoxymethyl) melamine.

Examples of the combination of the methylene acceptor compound and the methylene donor compound include, for example, cresol, a cresol derivative or a combination of a cresol resin and pentamethoxymethylmelamine, a resorcin, a resorcin derivative or a combination of a resorcin resin and hexamethylenetetramine, a cashew-modified phenol. Examples include a combination of a resin and hexamethylenetetramine, and a combination of a phenol resin and hexamethylenetetramine. Among these, a combination of cresol, a cresol derivative or a cresol resin and pentamethoxymethylmelamine, and a combination of resorcin, a resorcin derivative or resorcin resin and hexamethylenetetramine are preferable.

The amount of the methylene acceptor compound added is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, further preferably 1.3% by weight or more, and more preferably 1.5% by weight with respect to 100% by weight of the rubber component. % Or more is even more preferable. Thereby, the improvement effect of tensile strength can fully express. The upper limit is preferably 50% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less. Thereby, the workability in the manufacturing process can be maintained. Accordingly, 0.5 to 50% by weight is preferable, 1.0 to 50% by weight or 1.0 to 20% by weight is more preferable, 1.3 to 20% by weight is further preferable, and 1.5 to 10% by weight is more preferable. Even more preferred.

The addition amount of the methylene donor compound is preferably 10% by weight or more, more preferably 20% by weight or more, and further preferably 25% by weight or more with respect to 100% by weight of the methylene acceptor compound. Thereby, the improvement effect of tensile strength can fully express. The upper limit is preferably 100% by weight or less, preferably 90% by weight or less, and more preferably 85% by weight or less. Thereby, the workability in the manufacturing process can be maintained. Therefore, 10 to 100% by weight is preferable, 20 to 90% by weight is more preferable, and 25 to 85% by weight is further preferable.

The time for performing this step may be either during or after the solidification step. For example, when preparing a mixed liquid of chloroprene and cellulosic fibers, a mode in which a methylene acceptor compound / methylene donor compound is mixed together with them; a methylene acceptor compound / methylene donor compound is added to a master batch obtained after the drying step An embodiment is mentioned.

<5. Mixing process>
The mixing step is a step of mixing the processed product (master batch) after the coagulation step (obtained through other steps as necessary) as it is or adding an optional component as necessary. The temperature during mixing (for example, during kneading and kneading) may be about room temperature (for example, about 15 to 30 ° C.), but may be heated to a high temperature so that the rubber component does not undergo a crosslinking reaction. . For example, it is 140 ° C. or lower, more preferably 120 ° C. or lower. Moreover, a minimum is 40 degreeC or more, 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.

Optional components include, for example, reinforcing agents (for example, carbon black, silica, etc.), silane coupling agents, sulfur, zinc oxide, stearic acid, vulcanization accelerators, vulcanization accelerators, oils, cured resins, waxes, aging Inhibitors, colorants, peptizers, softeners, plasticizers, curing agents (eg, phenol resins, high styrene resins, etc.), foaming agents, fillers (carbon black, silica, etc.), coupling agents, adhesives (E.g., macron resin, phenol, terpene resin, petroleum hydrocarbon resin, rosin derivative, etc.), dispersant (e.g., fatty acid, etc.), adhesion promoter (e.g., organic cobalt salt, etc.), lubricant (e.g., paraffin, Compounding agents that can be used in the rubber industry, such as hydrocarbon resins, fatty acids, fatty acid derivatives, etc.). Of these, sulfur and vulcanization accelerators are preferred. Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazole sulfenamide (BBS). The optional component may be one type or two or more types.

The addition timing of optional ingredients is not particularly limited. The addition timing of sulfur and the vulcanization accelerator is preferably after the addition timing of the methylene acceptor compound and / or the methylene donor compound. When the methylene acceptor compound and / or methylene donor compound addition step is performed in the middle of the mixing step, the methylene acceptor compound and the material containing the methylene donor compound are mixed and kneaded without adding sulfur and a vulcanization accelerator. It is preferable to start and then add sulfur and a vulcanization accelerator to further masticate and knead. As a result, the methylene acceptor compound and the methylene donor compound are preliminarily condensed by heating, and the interaction between the condensate, the rubber component, and the cellulosic fiber can be effectively exhibited.

The amount of sulfur added is preferably 1.0% by weight or more, more preferably 1.5% by weight or more, and still more preferably 1.7% by weight or more based on the rubber component. The upper limit is preferably 10% by weight or less, preferably 7% by weight or less, and more preferably 5% by weight or less.

The addition amount of the vulcanization accelerator is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, and further preferably 0.4% by weight or more based on the rubber component. The upper limit is preferably 5% by weight or less, preferably 3% by weight or less, and more preferably 2% by weight or less.

In the mixing step, after mixing is completed, molding may be performed as necessary. 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.

In the mixing step, it is preferable to heat (vulcanize, crosslink) after completion of mixing, preferably after molding. Thereby, the rubber composition can be effectively reinforced. When a methylene acceptor compound and / or a methylene donor compound is added, these compounds undergo a condensation reaction by heating to form a three-dimensional network structure, and this structure interacts with the rubber component and the cellulosic fiber, respectively. The rubber composition can be reinforced more effectively. The heating temperature is preferably 150 ° C. or higher, and the upper limit is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. Therefore, about 150 to 200 ° C. is preferable, and about 150 to 180 ° C. is more preferable. Examples of the heating device include vulcanization devices such as mold vulcanization, can vulcanization, and continuous vulcanization.

In the mixing step, finishing may be performed as necessary at the end (before 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.

<6. Applications of rubber composition>
The use of the rubber composition obtained by the production method of the present invention is not particularly limited, and includes, for example, transportation equipment such as automobiles, trains, ships, airplanes, and belt conveyors; electrical appliances such as personal computers, televisions, telephones, and watches; Mobile communication equipment such as telephones; portable music playback equipment, video playback equipment, printing equipment, copying equipment, sports equipment; building materials; office equipment such as stationery, containers, and containers. Other than these, application to members using rubber or flexible plastic is possible, and application to industrial belts is preferable. Examples of the industrial belt include a flat belt, a conveyor belt, a cogged belt, a V belt, a rib belt, and a round belt.

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

<Production Example 1> Production of oxidized cellulose nanofiber (1)
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%), 5.00 g (absolutely dry), 39 mg of TEMPO (Sigma Aldrich) and 0.05 mmol of sodium bromide (absolutely dry) The solution was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and the oxidation reaction was started at room temperature. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed. The mixture after the reaction was filtered through a glass filter to separate pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (oxidized (carboxylated) cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to 1.0% (w / v) with water and treated with an ultra-high pressure homogenizer (20 ° C., 150 Mpa) three times to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 3 nm and the aspect ratio was 250.

<Production Example 2> Production of oxidized cellulose nanofiber (2)
A 5% (w / v) slurry of the oxidized cellulose of Production Example 1 was prepared, and 30% (w / v) hydrogen peroxide solution was added 2% (in terms of active ingredient) with respect to the solid content of the oxidized cellulose. The pH was adjusted to 12 with sodium hydroxide. This slurry was hydrolyzed at 80 ° C. for 2 hours. Then, it filtered with the glass filter and washed thoroughly with water. The hydrolyzed 5% (w / v) oxidized cellulose slurry was treated three times with an ultrahigh pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized cellulose nanofiber dispersion. The average fiber diameter was 5 nm and the aspect ratio was 60.

<Manufacture example 3> Manufacture of carboxymethylated cellulose nanofiber In a stirrer which can mix pulp, pulp (NBKP (coniferous bleached kraft pulp), made by Nippon Paper Industries Co., Ltd.) is 200 g in dry mass and sodium hydroxide in dry mass. 111 g (2.25 moles per anhydroglucose residue of the bottoming raw material) was added, and water was added so that the pulp solid content was 20% (w / v). Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 times mol per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. This was defatted by treating it with water at a solid content concentration of 1% and treating it with a high-pressure homogenizer five times at 20 ° C. and a pressure of 150 MPa to obtain carboxymethylated cellulose nanofibers. The average fiber diameter was 15 nm and the aspect ratio was 50.

<Manufacture example 4> Manufacture of cationized cellulose nanofiber To pulper which can stir pulp, pulp (NBKP, made by Nippon Paper Industries Co., Ltd.) is added by dry weight 200g, sodium hydroxide 24g by dry weight, and pulp solid concentration is 15%. Water was added so that Then, after stirring for 30 minutes at 30 ° C., the temperature was raised to 70 ° C., and 200 g (in terms of active ingredient) of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added as a cationizing agent. After reacting for 1 hour, the reaction product was taken out, neutralized and washed to obtain a cation-modified pulp having a cation substitution degree of 0.05 per glucose unit. This was made into 1% of solid content concentration, and it processed twice with the high pressure homogenizer at 20 degreeC and the pressure of 140 Mpa. The average fiber diameter was 25 nm and the aspect ratio was 50.

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

<Example 1>
1000 g of a solid dispersion of 0.5% solid content concentration of oxidized cellulose nanofiber obtained in Production Example 1 and 1000 g of a 10% suspension of chloroprene rubber latex solid content are mixed, and rubber component: weight of modified cellulose nanofiber The ratio was 100: 5, and the mixture was stirred for 30 minutes with a TK homomixer (6000 rpm). While stirring this mixed solution with a three-one motor (150-300 rpm), 10% calcium chloride was added so that the concentration in the total mixed solution would be 0.5%, and solid-liquid separation was performed with a nylon mesh with an opening of 5 μm. Then, a master batch was obtained by drying in a heating oven at 70 ° C. for 10 hours. This master batch 168g was kneaded with an open roll (manufactured by Kansai Roll Co., Ltd.) at 60 ° C for 5 minutes. Next, stearic acid is 0.5% by weight based on the rubber component, zinc oxide is 6% by weight based on the rubber component, sulfur is 3.5% by weight based on the rubber component, and a vulcanization accelerator (BBS, Nt -Butyl-2-benzothiazolesulfenamide) is added to the rubber component by 0.7% by weight and kneaded at 60 ° C. for 10 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.). A sheet of material was obtained. This sheet was sandwiched between molds and press vulcanized at 160 ° C. for 15 minutes to obtain a vulcanized rubber composition sheet having a thickness of 2 mm. This is cut into test pieces of a predetermined shape, and tensile strength (50% tensile stress (M50), 100), which is one of reinforcing properties, according to JIS K6251 “vulcanized rubber and thermoplastic rubber—how to obtain tensile properties”. % Tensile stress (M100), 300% tensile stress (M300), and breaking strength) were measured. The results are shown in Table 1. The larger each value, the better the vulcanized rubber composition is reinforced and the better the mechanical strength of the rubber.

<Example 2>
After solidification, solid-liquid separation was performed with a nylon mesh having an opening of 5 μm after solidification, and the obtained solid was washed with water, and again solid-liquid separated with a nylon mesh having an opening of 5 μm, and the solid was recovered. Went in the way. The results are shown in Table 1.

<Example 3>
The same procedure as in Example 2 was performed except that the oxidized cellulose nanofiber obtained in Production Example 2 was used. The results are shown in Table 1.

<Example 4>
The same procedure as in Example 2 was performed except that the coagulant was magnesium chloride. The results are shown in Table 1.

<Example 5>
The same procedure as in Example 2 was performed except that the coagulant was aluminum sulfate. The results are shown in Table 1.

<Example 6>
In the same manner as in Example 2, except that calcium chloride was added so that the concentration in the total mixed solution was 0.3%, and then 5% by weight acetic acid was added until the pH in the mixed solution reached 5. went. The results are shown in Table 1.

<Example 7>
In the same manner as in Example 2, except that calcium chloride was added so that the concentration in the total mixed solution was 0.3%, and then 5 wt% sulfuric acid was added until the pH in the mixed solution reached 5. went. The results are shown in Table 1.

<Example 8>
The same procedure as in Example 1 was performed, except that 20 parts by weight of the oxidized cellulose nanofiber obtained in Production Example 1 was blended with respect to 100 parts of the rubber component. The results are shown in Table 1.

<Example 9>
After solidification, solid-liquid separation was performed with a nylon mesh having a mesh opening of 5 μm, and the obtained solid was washed with water, and again solid-liquid separated with a nylon mesh having a mesh opening of 5 μm, and the solid was recovered. Went in the way. The results are shown in Table 1.

<Example 10>
The same procedure as in Example 2 was performed except that the carboxymethylated cellulose nanofiber obtained in Production Example 3 was used. The results are shown in Table 1.

<Example 11>
This was carried out in the same manner as in Example 2 except that the cationized cellulose nanofiber obtained in Production Example 4 was used. The results are shown in Table 1.

<Example 12>
Instead of kneading 168 g of the master batch at 60 ° C. for 10 minutes using an open roll, 1.3 wt% of resorcin for the rubber component and 0.8 wt% of hexamethylenetetramine for the rubber component are added to the master batch of 168 g. This was performed in the same manner as in Example 2 except that it was added and kneaded with an open roll (manufactured by Kansai Roll Co., Ltd.) at 60 ° C. for 10 minutes. The results are shown in Table 1.

<Comparative Example 1>
The same method as in Example 1 was performed except that the coagulation treatment was not performed. The results are shown in Table 1.

<Comparative example 2>
The same method as in Example 3 was performed except that the coagulation treatment was not performed. The results are shown in Table 1.

<Comparative Example 3>
The same procedure as in Example 1 was performed except that the coagulant was sodium chloride. With this coagulant, coagulation did not proceed well, and it was difficult to produce an evaluation sample, so no measurement results of tensile strength were obtained. The results are shown in Table 1.

<Comparative example 4>
The same method as in Example 10 was performed except that the coagulation treatment was not performed. The results are shown in Table 1.

<Comparative Example 5>
The same procedure as in Example 11 was performed except that the coagulation treatment was not performed. The results are shown in Table 1.

<Comparative Example 6>
It carried out by the same method as Example 2 except not having blended cellulose nanofiber. The results are shown in Table 1.

<Comparative Example 7>
The same process as in Comparative Example 6 was performed except that the coagulation treatment was not performed. The results are shown in Table 1.

Claims

A rubber composition comprising a step of coagulating a rubber component by adding a divalent or trivalent metal salt, or a divalent or trivalent metal salt and an acid to a mixed liquid containing chloroprene rubber and cellulose fiber. Manufacturing method.
The method according to claim 1, wherein the metal salt is a calcium salt.
The method according to claim 1 or 2, wherein the acid is acetic acid or sulfuric acid.
The method according to any one of claims 1 to 3, wherein the cellulosic fiber comprises at least one selected from the group consisting of oxidized cellulose fiber, carboxymethylated cellulose fiber and cationized cellulose fiber.
The method according to any one of claims 1 to 4, wherein the length-weighted average fiber length of the cellulosic fibers is 50 to 2000 nm.
The method according to any one of claims 1 to 5, wherein the length-weighted average fiber diameter of the cellulosic fibers is 2 to 500 nm.