WO2020100979A1 - Master batch containing anionically modified cellulose nanofibers and method for producing rubber composition - Google Patents

Abstract

The present invention provides a method for producing a rubber composition with low power consumption, said rubber composition containing anionically modified cellulose nanofibers and having a high strength. According to the present invention, a master batch is produced by mixing a rubber component with anionically modified cellulose nanofibers that are obtained by fibrillating anionically modified celluloses with use of a cavitation jet device; and a rubber composition is produced by crosslinking the master batch.

Description

Masterbatch containing anion-modified cellulose nanofiber and method for producing rubber composition

The present invention relates to a masterbatch containing a rubber component and anion-modified cellulose nanofibers and a method for producing a rubber composition.

Rubber compositions containing rubber and cellulosic fibers are known to have excellent mechanical strength. For example, Patent Document 1 describes a rubber / short fiber masterbatch obtained by stirring and mixing cellulose short fibers having an average fiber diameter of less than 0.5 μm and rubber latex. According to the document, a rubber in which short fibers having an average fiber diameter of less than 0.5 μm are uniformly dispersed in rubber by mixing a dispersion obtained by fibrillating in water with a rubber latex and drying the mixture / It is said that a rubber composition having an excellent balance between rubber reinforcement and fatigue resistance can be produced from a masterbatch of short fibers.

Japanese Patent Laid-Open No. 2006-206864

A method using a high-pressure homogenizer is generally known as a method for fibrillating cellulose to reduce the average fiber diameter to the nano order (less than 1.0 μm). The high-pressure homogenizer is excellent in that it can easily give high energy to the object to be treated, but it usually requires a very high pressure to reduce the average fiber diameter of the nanometer order, and the power consumption Becomes higher. If there is a method capable of defibrating cellulose to a nano-order average fiber diameter with low power consumption instead of a high-pressure homogenizer, at a lower cost when producing a rubber composition containing fibrillated cellulose having a small average fiber diameter. It is desirable because it enables manufacturing.

Further, when the cellulose short fibers are mixed with the rubber, if the short fibers are inhomogeneous, specifically, if large fibers that have not been defibrated remain, a force is applied to the obtained rubber composition. In that case, the rubber is likely to break from the portion where the large fiber remains as a starting point. Therefore, the cellulosic fibers mixed with the rubber are preferably homogeneous.

As a result of intensive studies by the present inventors, cellulose was anion-modified to anion-modified cellulose, which was defibrated by using a cavitation jet device to reduce the amount of power consumption compared to a high-pressure homogenizer with nano-sized particles. It has been found that anion-modified cellulose (nanofiber of anion-modified cellulose) having an average fiber diameter of the order can be obtained. It was also found that the strength of the rubber composition can be increased by incorporating the nanofiber of the anion-modified cellulose into the rubber composition. The present invention includes, but is not limited to:
(1) Step 1 of preparing anion-modified cellulose,
Step 2 of defibrating anion-modified cellulose using a cavitation jet device to produce anion-modified cellulose nanofibers, and step 3 of mixing the anion-modified cellulose nanofibers obtained in step 2 with a rubber component to obtain a masterbatch ,
A method for producing a masterbatch, which comprises:
(2) The cavitation jet device provides the anion-modified cellulose with an impact force when the cavitation bubbles generated by the liquid jet injected through the nozzle or the orifice are collapsed, and the upstream pressure of the liquid jet injected through the nozzle or the orifice is The method according to (1), which is 0.01 MPa or more and 30.00 MPa or less, and the ratio of the downstream pressure / upstream pressure is 0.001 to 0.500.
(3) The method according to (1) or (2), wherein the anion-modified cellulose is a cellulose having a carboxyl group.
(4) The method according to (3), wherein the amount of carboxyl groups in the anion-modified cellulose is 0.4 mmol / g to 3.0 mmol / g based on the absolute dry mass of the anion-modified cellulose.
(5) The method according to (1) or (2), wherein the anion-modified cellulose is a cellulose having a carboxymethyl group.
(6) The method according to (5), wherein the anion-modified cellulose has a degree of carboxymethyl substitution of 0.01 or more and less than 0.40.
(7) The method according to any one of (1) to (6), wherein the rubber component contains a diene rubber polymer.
(8) A method for producing a rubber composition, comprising a step of producing a masterbatch by the method described in any one of (1) to (7), and a step of crosslinking the masterbatch.

Anion-modified cellulose is used as the cellulose used for fibrillation, and by defibrating it using a cavitation jet device, anion having an average fiber diameter on the order of nanometers is used with less power consumption than when using a high-pressure homogenizer. A modified cellulose nanofiber can be obtained. In addition, the strength of the rubber composition can be increased by incorporating the nanofiber of the anion-modified cellulose into the rubber composition.

Further, when blending the cellulose fiber into the rubber composition, such as a large amount of undisentangled fibers remaining, if it is inhomogeneous, in the rubber composition which is the final product, the undisintegrated large fibers are ruptured from the starting point. Although the problem that it is easy to occur may occur, since the anion-modified cellulose nanofibers obtained by defibrating anion-modified cellulose using a cavitation jet device are homogeneous, the above-mentioned problems are less likely to occur.

The present invention relates to a masterbatch containing anion-modified cellulose nanofibers and a rubber component, and a method for producing a rubber composition.

(1) Step 1
In step 1, anion-modified cellulose is prepared. Anion-modified cellulose is one in which an anionic group is introduced into the molecular chain of cellulose. Specifically, an anionic group is introduced into the pyranose ring of cellulose by oxidation or substitution reaction.

(1-1) Cellulose The type of cellulose used as a raw material for the anion-modified cellulose is not particularly limited. Cellulose is generally classified into natural cellulose, regenerated cellulose, fine cellulose, and microcrystalline cellulose excluding the non-crystalline region according to the origin, production method, and the like. In the present invention, any of these celluloses can be used as a raw material.

Examples of natural cellulose include bleached pulp or unbleached pulp (bleached wood pulp or unbleached wood pulp); linters, refined linters; cellulose produced by microorganisms such as acetic acid bacteria. The raw material of bleached pulp or unbleached pulp is not particularly limited, and examples thereof include wood, cotton, straw, bamboo, hemp, jute, kenaf, and the like. The method for producing the bleached pulp or the unbleached pulp is not particularly limited, and may be a mechanical method, a chemical method, or a method in which the two are combined in between. Examples of the bleached pulp or unbleached pulp classified by the production method include mechanical pulp (thermo-mechanical pulp (TMP), groundwood pulp), chemical pulp (softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP). ) And the like, sulfite pulp such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and hardwood bleached kraft pulp (LBKP) and the like). Further, dissolving pulp may be used in addition to the papermaking pulp. Dissolving pulp is chemically refined pulp, which is mainly used by dissolving it in chemicals and is a main raw material for artificial fibers, cellophane, and the like.

The regenerated cellulose is exemplified by one in which cellulose is dissolved in any solvent such as a copper ammonia solution, a cellulose xanthate solution, a morpholine derivative, and then spun again.

The fine cellulose can be obtained by depolymerizing a cellulosic material such as the above natural cellulose or regenerated cellulose (for example, acid hydrolysis, alkali hydrolysis, enzymatic decomposition, explosion treatment, vibration ball mill treatment, etc.). Examples thereof include those obtained by mechanically treating the above cellulose-based material.

(1-2) Anion modification Anion modification means introducing an anionic group into cellulose, and specifically, introducing an anionic group into the pyranose ring of cellulose by oxidation or substitution reaction. In the present invention, the oxidation reaction means a reaction of directly oxidizing a hydroxyl group of a pyranose ring to a carboxyl group. In the present invention, the substitution reaction means a reaction of introducing an anionic group into the pyranose ring by a substitution reaction other than the oxidation.

(1-2-1) Carboxylation (oxidation)
As an example of anion modification, carboxylation (introduction of carboxyl group into cellulose, also referred to as “oxidation”) can be mentioned. In the present specification, the carboxyl group refers to —COOH (acid type) and —COOM (metal salt type) (in the formula, M is a metal ion). Carboxylated cellulose (also referred to as “oxidized cellulose”) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. Although not particularly limited, the amount of the carboxyl group is preferably 0.4 mmol / g to 3.0 mmol / g, and 0.6 mmol / g to 2.0 mmol based on the absolute dry mass of the anion-modified cellulose or anion-modified cellulose nanofibers. / G is more preferable, 1.0 mmol / g to 2.0 mmol / g is further preferable, and 1.1 mmol / g to 2.0 mmol / g is further preferable.

The amount of carboxyl groups of anion-modified cellulose or anion-modified cellulose nanofibers can be measured by the following method:
60 ml of a 0.5% by mass slurry of carboxylated cellulose (aqueous dispersion) was prepared and adjusted to pH 2.5 by adding a 0.1 M hydrochloric acid aqueous solution, and then a 0.05 N sodium hydroxide aqueous solution was added dropwise to adjust the pH to 11 The electric conductivity is measured until it becomes, and it is calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid with a gradual change in electric conductivity using the following formula:
Amount of carboxyl group [mmol / g carboxylated cellulose] = a [ml] × 0.05 / mass of carboxylated cellulose [g].

As an example of a carboxylation (oxidation) method, a cellulose raw material is oxidized in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide, and a mixture thereof. Can be mentioned. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and the cellulose fiber having an aldehyde group and a carboxyl group (—COOH) or a carboxylate group (—COO ⁻ ) on the surface. Can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

“N-oxyl compound” refers to a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (eg 4-hydroxy TEMPO). The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol to 10 mmol is preferable, 0.01 mmol to 1 mmol is more preferable, and 0.05 mmol to 0.5 mmol is further preferable to 1 g of absolutely dried cellulose. Further, it is preferably about 0.1 mmol / L to 4 mmol / L with respect to the reaction system.

Bromide is a compound containing bromine, examples of which include alkali metal bromide that can be dissociated and ionized in water. 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 accelerate the oxidation reaction. The total amount of bromide and iodide is, for example, preferably 0.1 mmol to 100 mmol, more preferably 0.1 mmol to 10 mmol, still more preferably 0.5 mmol to 5 mmol, per 1 g of absolutely dried cellulose. The modification is a modification due to an oxidation reaction.

As the oxidizing agent, known ones can be used, for example, halogen, hypohalous acid, halogenous acid, perhalogenic acid or salts thereof, halogen oxides, peroxides and the like can be used. Of these, sodium hypochlorite, which is inexpensive and has a low environmental load, is preferable. The appropriate amount of the oxidizing agent used is, for example, preferably 0.5 mmol to 500 mmol, more preferably 0.5 mmol to 50 mmol, still more preferably 1 mmol to 25 mmol, most preferably 3 mmol to 10 mmol, per 1 g of absolutely dried cellulose. . Further, for example, 1 mol to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

The cellulose oxidation process allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 ° C to 40 ° C, and may be room temperature of about 15 ° C to 30 ° C. Since a carboxyl group is generated in the cellulose as the reaction progresses, the pH of the reaction solution is lowered. In order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous solution of sodium hydroxide to maintain the pH of the reaction solution at 8 to 12, preferably about 10 to 11. As the reaction medium, water is preferable because it is easy to handle and side reactions are unlikely to occur. The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours to 6 hours, for example, 0.5 hours to 4 hours.

Also, the oxidation reaction may be carried out in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first step reaction again under the same or different reaction conditions, the reaction efficiency due to the salt by-produced in the first step reaction is not affected. Can be well oxidized.

As another example of the carboxylation (oxidation) method, a method of oxidizing by bringing a gas containing ozone into contact with a cellulose raw material can be mentioned. This oxidation reaction oxidizes at least the 2- and 6-position hydroxyl groups of the glucopyranose ring and causes decomposition of the cellulose chain. The ozone concentration in the gas containing ozone is preferably 50 g / m ³ to 250 g / m ³ , and more preferably 50 g / m ³ to 220 g / m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 parts by mass to 30 parts by mass, and more preferably 5 parts by mass to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. .. The ozone treatment temperature is preferably 0 ° C to 50 ° C, more preferably 20 ° C to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 minute to 360 minutes, preferably about 30 minutes to 360 minutes. When the conditions of ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose will be good. After performing the ozone treatment, an additional oxidizing treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples thereof include chlorine-based compounds such as chlorine dioxide and sodium chlorite, and oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. For example, an additional oxidization treatment can be performed by dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

The amount of carboxyl groups of oxidized cellulose can be adjusted by controlling the reaction conditions such as the addition amount of the above-mentioned oxidizing agent and the reaction time. The amount of carboxyl groups in oxidized cellulose and the amount of carboxyl groups when the same oxidized cellulose is used as nanofibers are usually the same.

(1-2-2) Carboxyalkylation As an example of anion modification, introduction of a carboxyalkyl group such as a carboxymethyl group can be mentioned. In the present specification, the carboxyalkyl group refers to -RCOOH (acid type) and -RCOOM (metal salt type). Here, R is an alkylene group such as a methylene group or an ethylene group, and M is a metal ion.

The carboxyalkylated cellulose may be obtained by a known method, or a commercially available product may be used. The degree of carboxyalkyl substitution of anhydrous glucose unit of cellulose is preferably less than 0.40. Further, when the anionic group is a carboxymethyl group, the carboxymethyl substitution degree is preferably less than 0.40. If the degree of substitution is 0.40 or more, the crystallinity of cellulose will decrease. The lower limit of the degree of carboxyalkyl substitution is preferably 0.01 or more. Considering operability, the substitution degree is particularly preferably 0.02 or more and 0.35 or less, further preferably 0.10 or more and 0.35 or less, and 0.15 or more and 0.35 or less. Is more preferable and 0.15 or more and 0.30 or less is further preferable. The anhydrous glucose unit means each anhydrous glucose (glucose residue) that constitutes cellulose, and the degree of carboxyalkyl substitution means the carboxyalkyl group among the hydroxyl groups (—OH) in the glucose residue that constitutes cellulose. The ratio (number of carboxyalkyl ether groups per glucose residue) of those substituted with ether groups (-ORCOOH or -ORCOOM) is shown.

An example of a method for producing carboxyalkylated cellulose is a method including the following steps. The modification is modification by substitution reaction. Description will be made by taking carboxymethyl cellulose as an example.
i) The bottoming raw material, the solvent and the mercerizing agent are mixed, and the reaction temperature is 0 ° C. to 70 ° C., preferably 10 ° C. to 60 ° C., and the reaction time is 15 minutes to 8 hours, preferably 30 minutes to 7 hours, and mercerization is performed. Process,
ii) Then, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times mol per glucose residue, the reaction temperature is 30 ° C to 90 ° C, preferably 40 ° C to 80 ° C, and the reaction time is 30 minutes to 10 hours. A step of performing the etherification reaction for preferably 1 to 4 hours.

The above-mentioned cellulose raw material can be used as the bottoming raw material. As the solvent, 3 to 20 times by mass of water or lower alcohol, specifically water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc., or 2 One or more mixed media can be used. When a lower alcohol is mixed, the mixing ratio is preferably 60% by mass to 95% by mass. As the mercerizing agent, it is preferable to use 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, per anhydrous glucose residue of the bottoming raw material.

As described above, the degree of carboxymethyl substitution per glucose unit of cellulose is less than 0.40, preferably 0.01 or more and less than 0.40. By introducing a carboxymethyl substituent into the cellulose, the cellulose electrically repels each other. Therefore, the cellulose having the carboxymethyl substituent introduced therein can be nano-defibrated. If the carboxymethyl substituent is less than 0.01 per glucose unit, nano-defibration may not be sufficiently performed. The carboxymethyl substitution degree is more preferably 0.10 or more and less than 0.40, further preferably 0.15 or more and less than 0.40, and further preferably 0.20 or more and less than 0.40. The degree of carboxyalkyl substitution in carboxyalkylated cellulose and the degree of carboxyalkyl substitution when the same carboxyalkylated cellulose is used as nanofibers are usually the same.

The degree of carboxymethyl substitution per glucose unit can be measured by the following method:
About 2.0 g of carboxymethyl cellulose (extra-dried) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 100 mL of a solution prepared by adding 100 mL of special grade concentrated nitric acid to 900 mL of methanol is added and shaken for 3 hours to convert the carboxymethylated cellulose salt (CMized cellulose) into hydrogenated CM-modified cellulose. Precisely weigh 1.5 g to 2.0 g of hydrogenated CM cellulose (absolutely dried) and put it in a 300 mL Erlenmeyer flask with a ground stopper. The hydrogenated CM cellulose is wetted with 15 mL of 80 mass% methanol, 100 mL of 0.1 N NaOH is added, and the mixture is shaken at room temperature for 3 hours. Excess NaOH was back titrated with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. The degree of carboxymethyl substitution (DS) is calculated by the formula:
A = [(100 × F ′ − (0.1N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of hydrogenated CM cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required to neutralize 1 g of hydrogenated CM-modified cellulose
F: Factor of 0.1 N H ₂ SO ₄ F ′: Factor of 0.1 N NaOH.

The degree of substitution of a carboxyalkyl group other than the carboxymethyl group can be measured by the same method as above.

(1-2-3) Esterification Esterification can be mentioned as an example of anion modification. Examples of the esterification method include a method of mixing a powder or aqueous solution of a phosphoric acid compound with a cellulose raw material, a method of adding an aqueous solution of a phosphoric acid compound to a slurry of a cellulose raw material, and the like. Examples of phosphoric acid compounds include phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among the above, a compound having a phosphoric acid group is preferable because of its low cost, easy handling, and introduction of a phosphoric acid group into the cellulose of the pulp fiber to improve the defibration efficiency. Examples of the compound having a phosphoric acid group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite and potassium hypophosphite. , Sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate , Ammonium pyrophosphate, ammonium metaphosphate and the like. A phosphate group can be introduced into cellulose by using one kind or a combination of two or more kinds of them. Among these, phosphoric acid, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of phosphate group introduction, easy to defibrate in the following defibration step, and easy to apply industrially Ammonium salts are preferred. Particularly, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable. In addition, the phosphoric acid compound is preferably used as an aqueous solution because the reaction can proceed uniformly and the efficiency of introducing a phosphoric acid group can be increased. The pH of the aqueous solution of the phosphoric acid compound is preferably 7 or less because the efficiency of phosphoric acid group introduction is high, but a pH of 3 to 7 is preferable from the viewpoint of suppressing hydrolysis of pulp fibers.

The following method can be mentioned as an example of the method for producing phosphate esterified cellulose. A phosphoric acid compound is added to a suspension of a cellulose raw material having a solid content concentration of 0.1% by mass to 10% by mass while stirring to introduce a phosphoric acid group into the cellulose. When the amount of the cellulose raw material is 100 parts by mass, the amount of the phosphoric acid compound added is preferably 0.2 parts by mass to 500 parts by mass, and more preferably 1 part by mass to 400 parts by mass, as the amount of phosphorus element. More preferable. When the proportion of the phosphoric acid compound is at least the above lower limit, the yield of fine fibrous cellulose can be further improved. However, if the upper limit is exceeded, the effect of improving the yield will reach the ceiling, which is not preferable in terms of cost.

In addition to phosphoric acid compounds, powders of other compounds or aqueous solutions may be mixed. The compound other than the phosphoric acid compound is not particularly limited, but a nitrogen-containing compound having basicity is preferable. The term "basic" as used herein is defined as a pink to red color of an aqueous solution in the presence of a phenolphthalein indicator, or a pH of the aqueous solution of greater than 7. The basic nitrogen-containing compound used in the present invention is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. Examples thereof include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Of these, urea is preferable because it is inexpensive and easy to handle. The amount of the other compound added is preferably 2 parts by mass to 1000 parts by mass, and more preferably 100 parts by mass to 700 parts by mass, relative to 100 parts by mass of the solid content of the cellulose raw material. The reaction temperature is preferably 0 ° C to 95 ° C, more preferably 30 ° C to 90 ° C. Although the reaction time is not particularly limited, it is about 1 minute to 600 minutes, more preferably 30 minutes to 480 minutes. When the conditions of the esterification reaction are within these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and the yield of the phosphorylated esterified cellulose becomes good. After dehydrating the obtained phosphoric acid esterified cellulose suspension, it is preferable to heat-treat at 100 ° C. to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. Further, it is preferable to heat at 130 ° C. or lower, preferably 110 ° C. or lower while water is contained in the heat treatment, remove water, and then heat treatment at 100 ° C. to 170 ° C.

The degree of phosphoric acid group substitution per glucose unit of the phosphorylated cellulose is preferably 0.001 or more and less than 0.40. By introducing a phosphate group substituent into the cellulose, the cellulose repels each other electrically. Therefore, the cellulose having the phosphate group introduced therein can be easily nano-disentangled. When the phosphate group substitution degree per glucose unit is less than 0.001, nanofibrillation cannot be sufficiently carried out. On the other hand, if the phosphate group substitution degree per glucose unit is greater than 0.40, the nanofibers may not be obtained because they swell or dissolve. In order to efficiently perform defibration, it is preferable that the phosphoric acid esterified cellulose raw material obtained above is boiled and then washed with cold water. The modification by esterification is modification by a substitution reaction. The degree of substitution in esterified cellulose and the degree of substitution when the same esterified cellulose is used as nanofibers are usually the same.

The degree of phosphate group substitution per glucose unit can be measured by the following method:
A phosphoric acid esterified cellulose slurry having a solid content of 0.2% by mass is prepared. Next, 1/10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo, conditioned) was added to the slurry, shaken for 1 hour, and then poured onto a mesh having an opening of 90 μm. The phosphoric acid esterified cellulose is converted into hydrogen type phosphoric acid esterified cellulose by separating the resin and the slurry with. Then, a change in the value of electric conductivity of the slurry is measured while adding 0.1 N sodium hydroxide aqueous solution to the slurry after the treatment with the ion exchange resin once every 30 seconds by 50 μL. Of the measurement results, the amount of alkali (mmol) required in the region where the electrical conductivity sharply decreases is divided by the solid content (g) in the slurry to be titrated to give 1 g of hydrogen phosphate esterified cellulose. The amount of phosphoric acid groups (mmol / g) is calculated. Furthermore, the degree of phosphate group substitution (DS) per glucose unit of phosphated cellulose is calculated by the following formula:
DS = 0.162 × A / (1-0.079 × A)
A: Phosphoric acid group amount (mmol / g) per 1 g of hydrogen-type phosphorylated esterified cellulose.

(1-3) Anion-Modified Cellulose The anion-modified cellulose can be obtained by subjecting the cellulose as a raw material to anion modification as exemplified above. Moreover, you may use a commercially available thing. The type of anion-modified cellulose is preferably cellulose having a carboxyl group or cellulose having a carboxyalkyl group. In particular, carboxylated cellulose obtained by oxidizing cellulose with an N-oxyl compound and an oxidizing agent has uniformly introduced carboxylic groups, is easily disentangled uniformly, and has high transparency. Is preferred in that

As anion-modified cellulose, use one that maintains at least part of its fibrous shape when dispersed in water or a water-soluble organic solvent. Nanofibers cannot be obtained using a material that does not maintain a fibrous shape (that is, a material that dissolves). That at least a part of the fibrous shape is maintained when dispersed means that a fibrous substance can be observed by observing the dispersion of anion-modified cellulose with an electron microscope. Further, anion-modified cellulose capable of observing the peak of cellulose type I crystal when measured by X-ray diffraction is preferable.

The crystallinity of the cellulose in the anion-modified cellulose is preferably 50% or more, and more preferably 60% or more in the crystal type I. By adjusting the crystallinity within the above range, it is possible to sufficiently obtain crystalline cellulose fibers that do not dissolve even after the fibers are made fine by defibration. The crystallinity of cellulose can be controlled by the crystallinity of the raw material cellulose and the degree of anion modification. The method for measuring the crystallinity of anion-modified cellulose is as follows:
The sample is placed on a glass cell and measured using an X-ray diffraction measurement device (LabX XRD-6000, manufactured by Shimadzu Corporation). The degree of crystallinity was calculated using a method such as Segal, and the diffraction intensity of 2θ = 22.6 ° and the 2θ = 2θ = 22.6 ° were used as the baseline with the diffraction intensity of 2θ = 10 ° to 30 ° of the X-ray diffraction diagram as the baseline. It is calculated by the following formula from the diffraction intensity of the amorphous portion at 18.5 °.
Xc = (I002c-Ia) / I002c × 100
Xc: Type I crystallinity of cellulose (%)
I002c: 2θ = 22.6 °, diffraction intensity Ia: 2θ = 18.5 °, amorphous region diffraction intensity.

The proportion of cellulose type I crystals of anion-modified cellulose and the proportion of cellulose type I crystals of the same anion-modified cellulose as nanofibers are usually the same.

(2) Step 2
In step 2, anion-modified cellulose nanofibers are produced by treating (defibrating) anion-modified cellulose with a cavitation jet device.

(2-1) Anion-modified cellulose dispersion For defibration, an anion-modified cellulose dispersion is prepared. As the dispersion medium, water, an organic solvent, or a mixture thereof can be appropriately selected. The type of organic solvent is not limited, but for example, a polar solvent having a high affinity for hydroxyl groups in cellulose is preferable, and methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol are preferred. , Glycerin, ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and the like. The above dispersion media may be used alone or in combination of two or more. For example, a form in which two or more kinds of organic solvents are mixed, a form containing water and an organic solvent, a form containing only water, and the like can be appropriately selected. It is preferable to use only water as the dispersion medium (that is, 100% of water) from the viewpoint of easy handling. The mixing ratio when water and the organic solvent are mixed is not particularly limited, and the mixing ratio may be appropriately adjusted depending on the type of the organic solvent used.

The solid content concentration of the anion-modified cellulose dispersion used in the cavitation jet device is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and further preferably 0.1 to 5.0% by mass. It is preferable to treat within the range from the viewpoint of bubble generation efficiency.

The pH of the anion-modified cellulose dispersion is preferably pH 6 to 13, more preferably pH 6 to 12, and still more preferably pH 6 to 10. If the pH is 6 or more, defibration of the anion-modified cellulose is likely to proceed. On the other hand, if the pH exceeds 13, alkaline burning of the pulp fiber occurs and the whiteness decreases, which is not preferable.

(2-2) Cavitation jet device The cavitation jet device compresses the jetted liquid and jets it toward the jetted liquid from the tip of the nozzle at high speed, thereby producing an extremely high shearing force in the vicinity of the nozzle and a sudden depressurization of the liquid. Is a device that shreds solid lumps in the jetted liquid and the jetted liquid by the collapse energy of cavitation bubbles generated by the expansion of the. Since there is no physical contact of the blade with the fiber, it is difficult to cause the fiber to become short.

As the jetting liquid, the dispersion medium used in the above-mentioned anion-modified cellulose dispersion or the anion-modified cellulose dispersion itself can be used. The above-mentioned anion-modified cellulose dispersion is used as the liquid to be ejected. By jetting the jetted liquid toward the anion-modified cellulose dispersion that is the jetted liquid and generating a jet flow, cavitation is generated in the jetted liquid, and the anion-modified cellulose in the jetted liquid is generated by the collapse energy of the cavitation bubbles. Can be defibrated. It is preferable to use an anion-modified cellulose dispersion as the jet liquid from the viewpoint of efficient defibration. When an anion-modified cellulose dispersion is used as the jetting liquid, in addition to the effect of cavitation generated around the jet flow, hydrodynamic shearing force at the time of jetting from a nozzle or orifice at high pressure is obtained, so efficient defibration is performed. be able to.

Cavitation occurs when the liquid is accelerated and the local pressure becomes lower than the vapor pressure of the liquid, so the flow velocity and pressure are important to control the generation of cavitation. The basic dimensionless number representing the cavitation state, the cavitation number σ, is defined by the following mathematical formula 1 (Yoji Kato, New Edition Cavitation Basics and Recent Advances, Maki Shoten, 1999).

A large cavitation number means that the flow field is in a state where cavitation is unlikely to occur. When cavitation is generated through a nozzle or orifice such as a cavitation jet, the cavitation number σ is calculated from the upstream pressure p _{1 of} the nozzle or orifice, the downstream pressure p ₂ of the nozzle or orifice, and the saturated vapor pressure p _v of the sample water. It can be rewritten as Equation 2 below, and in the cavitation jet, the pressure difference between p ₁ , p ₂ , and p _v is large, and p ₁ >> p ₂ >> p _v , so the cavitation number σ Can be further approximated to p ₂ / p ₁ (H. Soyama, J. Soc. Mat. Sci. Japan, 47 (4), 381 1998).

In the present invention, the cavitation condition is that the cavitation number σ (that is, the downstream pressure / upstream pressure) that can be approximated to p ₂ / p ₁ described above is preferably 0.001 or more and 0.500 or less, It is preferably 0.003 or more and 0.200 or less, and particularly preferably 0.010 or more and 0.100 or less. When the cavitation number σ is less than 0.001, the defibration effect is small because the pressure difference between the cavitation bubbles and the surroundings is low, and when it is larger than 0.500, the flow pressure difference is low. Cavitation is less likely to occur.

When jetting the jetting liquid through a nozzle or an orifice to generate cavitation, the pressure of the jetting liquid (upstream pressure) is preferably 0.01 MPa or more and 30.00 MPa or less, and 0.70 MPa or more and 20.00 MPa or less. Is preferable, and it is particularly preferable that the pressure is 2.00 MPa or more and 10.00 MPa or less. When the upstream pressure is less than 0.01 MPa, a pressure difference is less likely to occur between the upstream pressure and the downstream pressure, and the effect is small. Further, when it is higher than 30.00 MPa, energy consumption becomes large, which is disadvantageous in terms of cost. On the other hand, the pressure (downstream pressure) in the container is preferably 0.05 MPa or more and 0.50 MPa or less in static pressure.

The jetting speed of the jetted liquid is preferably in the range of 1 m / sec or more and 200 m / sec or less, and more preferably in the range of 20 m / sec or more and 100 m / sec or less. If the injection speed is less than 1 m / sec, the pressure drop is low and cavitation is unlikely to occur, so the effect is weak. On the other hand, when it is higher than 200 m / sec, high pressure is required and a special device is required, which is disadvantageous in cost.

The cavitation jet device has a pipe or container of a certain size, which is a place where cavitation occurs immediately after a nozzle or orifice for injecting a liquid. If the inner diameter of the pipe immediately after this nozzle or orifice (the inner diameter not including the wall thickness of the pipe or container) is the same as the maximum width of the cavitation jet generated by the liquid jet injected through the nozzle or orifice, anion modification This is preferable because the defibration of cellulose will proceed efficiently. For example, it is preferable to adjust the maximum width of the cavitation jet generated by the liquid jet jetted through the nozzle or the orifice to be 50% or more of the inner diameter of the pipe immediately after the nozzle or the orifice, and more preferably 55% or more, 60% or more is more preferable, 65% or more is further preferable, 70% or more is further preferable, 80% or more is further preferable, and 85% or more is further preferable. The length is preferably adjusted to 130% or less, more preferably 110% or less, and further preferably less than 100%. Here, the nozzle is a pipe-shaped component for ejecting a liquid in a certain direction, and generally, the liquid can be discharged at high speed by reducing the area of the circular cross section of the pipe (or reducing the inner diameter of the pipe). Refers to the parts that are ejected. An orifice is a hole made in a wall for ejecting a liquid. When liquid is ejected from the nozzle or orifice, a group of cavitation bubbles generated by the liquid jet appears in a conical shape with the outlet of the nozzle or orifice as the apex. This group of cavitation bubbles is called a cavitation jet. The maximum width of the cavitation jet means the maximum width of the width (diameter) perpendicular to the jet direction of the cavitation jet. The maximum width of the cavitation jet changes depending on conditions such as the nozzle or orifice used, the jet liquid, the jet liquid, the jet velocity, the downstream pressure / upstream pressure ratio, and the temperature. When measuring the maximum width of the cavitation jet, if the width of the cavitation jet is large and it contacts the inner wall of the pipe immediately after the nozzle or orifice, use a larger pipe so that the cavitation jet does not contact the inner wall under the same conditions. Injection is performed and the maximum width of the cavitation jet is determined. Further, a plurality of nozzles or orifices may be connected to the pipe immediately after the nozzle or orifice, and a liquid may be jetted into the pipe from each nozzle or orifice to generate a plurality of cavitation jets. The maximum width of the cavitation jet is the maximum width when the cavitation jet generated from each nozzle or orifice is regarded as one cavitation jet. That is, when a plurality of cavitation jets coalesces at the end, it is the maximum width of the coalesced cavitation jet, while on the other hand, when at least some of the cavitation jets do not coalesce and are independent of each other. Is the maximum width obtained by connecting the outermost positions of the plurality of observed cavitation jets (the side away from the center of the plane perpendicular to the jet direction of each jet toward the inner wall of the pipe). ..

Further, the pipe immediately after the nozzle or orifice means any container or pipe to which the nozzle or orifice is connected and which is a place where a cavitation jet is formed. The shape of the pipe may be any of a cylindrical shape, a rectangular tube shape, a conical shape, a pyramidal shape, and the like, and is preferably a cylindrical shape in order to prevent the fibers from staying after the defibration. The pipe diameter immediately after the nozzle or the orifice means the width (inner diameter of the pipe) perpendicular to the jetting direction of the cavitation jet of the pipe. When the pipe has a tubular shape other than a cylindrical shape, such as a square tubular shape, the smallest width of the widths perpendicular to the jet direction of the cavitation jet is meant. Further, when the pipe has a conical shape or a pyramid shape, it means the pipe diameter of the cross section where the width of the cavitation jet is maximum (in the case of the pyramid shape, the minimum width of the cross section).

If the maximum width of the cavitation jet generated by the liquid jet jetted through the nozzle or orifice is less than 50% of the inner diameter of the pipe immediately after the nozzle or orifice, the pipe (or container) immediately after the nozzle or orifice becomes the cavitation jet. On the other hand, since it is too large, the anion-modified cellulose and the anion-modified cellulose nanofibers are retained in the pipe (or container), and the defibration is difficult to proceed. On the other hand, when the length is more than 130%, many parts of the cavitation jet flow may come into direct contact with the pipe immediately after the nozzle or the orifice, causing erosion of the pipe. When the maximum width of the cavitation jet is 100% or more and 130% or less of the inner diameter of the pipe immediately after the nozzle or the orifice, a part (end) of the cavitation jet comes into contact with the pipe immediately after the nozzle or the orifice. The contact is partial, and the impact of the end of the cavitation jet (the part far from the nozzle or orifice) is rather weak, and it has little influence on the piping, so it can be used. When the maximum width of the cavitation jet is less than 100% of the inner diameter of the pipe immediately after the nozzle or the orifice, erosion of the pipe immediately after the nozzle or the orifice does not occur, which is preferable.

The ratio between the maximum width of the cavitation jet and the inner diameter of the pipe immediately after the nozzle or the orifice is adjusted by adjusting the inner diameter of the pipe immediately after the nozzle or the orifice, by adjusting the ratio of the downstream pressure / the upstream pressure, and This can be adjusted by changing the maximum width of the cavitation jet by adjusting the jet speed of the jet liquid.

The injection of liquid for generating cavitation may be performed in an atmospherically open container such as a pulper, but it is preferable to perform injection in a pressure container to control cavitation.

Cavitation is affected by the amount of gas in the liquid, and when there is too much gas, bubbles collide with each other and coalesce, resulting in a cushioning effect that the collapse impact force is absorbed by other bubbles, weakening the impact force. Since the amount of gas in the liquid is affected by the dissolved gas and vapor pressure, it is preferable to adjust the impact force of cavitation by controlling the treatment temperature within a certain range. The treatment temperature depends on the type of dispersion medium, but is preferably 0 ° C. or higher and 70 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. In general, it is considered that the impact force becomes maximum at the midpoint between the melting point and the boiling point, so that when water is used as the dispersion medium, about 50 ° C. is preferable, but at other temperatures, within the above range. If so, a sufficient defibration effect can be obtained.

A surfactant may be added to the jet liquid and / or the jet liquid in order to reduce the energy required to generate cavitation. The surfactant used is not particularly limited, and examples thereof include nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, and alkylene oxide adducts of fatty acids, anionic surfactants. Agents, cationic surfactants, amphoteric surfactants and the like. You may use these individually or in combination of 2 or more types. When the surfactant is added, the addition amount may be an amount necessary to reduce the surface tension of the jet liquid and / or the jet liquid.

The treatment with the cavitation jet device may be repeated multiple times until the desired degree of defibration is achieved. When the treatment is performed a plurality of times, it may be circulated in a single device as many times as necessary, or the treatment may be performed by using a plurality of devices in parallel or by sequentially flowing the plurality of devices.

(2-3) Anion-Modified Cellulose Nanofibers By defibration with the above cavitation jet device, anion-modified cellulose can be defibrated until the average fiber diameter on the order of nanometers is obtained to obtain nanofibers. The nano-order average fiber diameter means an average fiber diameter of less than 1 μm. In the present invention, the anion-modified cellulose nanofibers preferably have an average fiber diameter of about 3 nm to 500 nm, more preferably about 3 nm to 150 nm, further preferably about 3 nm to 20 nm. The aspect ratio is 30 or more, preferably 50 or more, more preferably 100 or more. The upper limit of the aspect ratio is not limited, but is about 500 or less.

The average fiber diameter and the average fiber length of the anion-modified cellulose nanofibers are determined by using an atomic force microscope (AFM) when the diameter is less than 20 nm and a field emission scanning electron microscope (FE-SEM) when the diameter is 20 nm or more. The measurement can be performed by analyzing 200 randomly selected fibers and calculating an average. Also, the aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length / average fiber diameter.

As the anion-modified cellulose nanofibers, those having high transparency when formed into a dispersion are preferable. Clarity is measured, for example, by the following method:
A cellulose nanofiber dispersion having a predetermined concentration was prepared, and a UV-VIS spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) was used, and a 660 nm light transmittance (%) was measured using a prismatic cell having an optical path length of 10 mm. ) Is measured and used as the transparency.

In the present invention, for example, with respect to an anion-modified cellulose nanofiber dispersion having a solid content of 1.0 mass% with water as a dispersion medium, it is preferably 70% or more, more preferably 80% or more, and 90%. It is more preferable that the above is satisfied. The high transparency means that the number of undisentangled fibers is small and the disentanglement proceeds uniformly. When the undisentangled fibers remain, when the rubber composition is mixed with the rubber component to give a rubber composition, a problem may occur in that the rubber tends to break from the large fibers in the rubber composition as a starting point. Anion-modified cellulose nanofibers having high transparency and defibration progressing uniformly are preferable because such problems are less likely to occur. The upper limit of transparency is not particularly limited, but is 99%, for example.

The viscosity of the anion-modified cellulose nanofibers is not particularly limited, but those having a high viscosity when made into a dispersion are preferable. Viscosity is measured, for example, by the following method:
A cellulose nanofiber dispersion having a predetermined concentration was prepared, and a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.) was used in accordance with the method of JIS-Z-8803 at 25 ° C., and the rotation speed was 60 rpm or 6 rpm. Measure the value after a minute.

For example, regarding an anion-modified cellulose nanofiber dispersion having a solid content of 1.0% by mass with water as a dispersion medium, the B-type viscosity at 6 rpm measured by the above method is 5000 mPa · s or more, or 7,000 mPa · s or more, or It may be 10000 mPa · s or more, or 15000 mPa · s or more, or 17000 mPa · s or more, and the B-type viscosity at 60 rpm is 1000 mPa · s or more, or 2000 mPa · s or more, or 3000 mPa · s or more, or It may be 4000 mPa · s or more. However, it is not limited to these. Higher viscosity means less damage to the fiber during defibration. Since the cavitation jet device has a lower processing pressure than the ultrahigh pressure homogenizer, it is considered that the damage to the fiber during defibration is reduced. The upper limit of the viscosity is not particularly limited.

(3) Step 3
In step 3, the anion-modified cellulose nanofibers obtained in step 2 are mixed with a rubber component to produce a masterbatch.

(3-1) Rubber Component The rubber component is a raw material of rubber, which is crosslinked to form rubber. Although there are rubber components for natural rubber and rubber components for synthetic rubber, any of them may be used in the present invention, or both may be combined. For convenience, the rubber component for natural rubber or the like is referred to as "natural rubber polymer" or the like.

As a natural rubber (NR) polymer, a natural rubber polymer in a narrow sense that is not chemically modified; a chemically modified natural rubber polymer such as a chlorinated natural rubber polymer, a chlorosulfonated natural rubber polymer, an epoxidized natural rubber polymer; a hydrogenated natural Rubber polymer: Deproteinized natural rubber polymer can be mentioned. Examples of synthetic rubber polymers include butadiene rubber (BR) polymer, styrene-butadiene copolymer rubber (SBR) polymer, isoprene rubber (IR) polymer, acrylonitrile-butadiene rubber (NBR) polymer, chloroprene rubber (CR) polymer, styrene. -Diene rubber polymers such as isoprene copolymer rubber polymers, styrene-isoprene-butadiene copolymer rubber polymers, isoprene-butadiene copolymer rubber polymers; butyl rubber (IIR) polymers, ethylene-propylene rubber (EPM, EPDM) polymers , Acrylic rubber (ACM) polymer, epichlorohydrin rubber (CO, ECO) polymer, fluororubber (FKM) polymer, silicone rubber (Q) polymer, urethane rubber (U) polymer, chlorosulfonated polyethylene (CSM) polymer, etc. Examples include non-diene rubber polymers. These rubber polymers may be used alone or in combination of two or more. Among these, diene rubber polymers including natural rubber (NR) polymers are particularly preferable from the viewpoint of reinforcement. Preferred diene rubber polymers include natural rubber (NR) polymers, isoprene rubber (IR) polymers, butadiene rubber (BR) polymers, styrene-butadiene copolymer rubber (SBR) polymers, butyl rubber (IIR) polymers, acrylonitrile-butadiene. Examples thereof include rubber (NBR) polymers and the above-mentioned modified natural rubber polymers.

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

(3-2) Form of Cellulose Nanofiber Used for Mixing with Rubber Component The form of cellulose nanofiber mixed with the rubber component is not particularly limited. For example, a dispersion of anion-modified cellulose nanofibers, a dry solid of the dispersion, and a wet solid of the dispersion may be provided for mixing. The concentration of cellulose nanofibers in the dispersion can be 0.1 to 5.0 mass% when the dispersion medium is water. When the dispersion medium contains an organic solvent such as alcohol in addition to water, the concentration may be 0.1 to 20.0% by mass. A wet solid is a solid in the intermediate form between the dispersion and the dry solid. The amount of the dispersion medium in the wet solid obtained by dehydrating the dispersion by a usual method may be about 5 to 15% by mass with respect to the cellulose nanofibers. The amount of the dispersion medium may be adjusted appropriately.

The cellulose nanofibers mixed with the rubber component may be a mixture of the cellulose nanofiber dispersion and a water-soluble polymer, a dry solid product of the mixture, or a wet solid product of the mixture. The amount of liquid medium in the mixture and dry solids may be in the ranges mentioned above. Examples of the water-soluble polymer include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucan, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, pullulan, starch, starch starch, and kudzu. Powder, positive starch, phosphorylated starch, corn starch, gum arabic, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soy protein solution, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylate , Polyvinylpyrrolidone, polyvinyl acetate, polyamino acid, polylactic acid, polymalic acid, polyglycerin, latex, rosin sizing agent, petroleum resin sizing agent, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, Mention may be made of polyethyleneimine, polyamines, vegetable gums, polyethylene oxide, hydrophilic cross-linked polymers, polyacrylates, starch polyacrylic acid copolymers, tamarind gums, guar gums and colloidal silicas, and mixtures thereof. Among these, carboxymethyl cellulose or a salt thereof is preferable from the viewpoint of solubility. The carboxymethyl cellulose referred to here is completely soluble in water and has no fiber shape in water, and is distinguished from carboxymethylated cellulose nanofibers having a fiber shape in water.

The dry and wet solids can be prepared by drying a dispersion of cellulose nanofibers or a mixture of a dispersion of cellulose nanofibers and a water-soluble polymer. The drying method is not particularly limited, and examples thereof include spray drying, pressing, air drying, hot air drying, and vacuum drying. 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 disc drying device, an aeration drying device, a rotary drying device, an air flow drying device, a spray dryer drying device. , Spray dryers, cylinder dryers, drum dryers, screw conveyor dryers, rotary dryers with heating tubes, vibration transport dryers, batch-type box dryers, aeration dryers, vacuum box dryers, or A stirring and drying device and the like can be mentioned. These drying devices may be used alone or in combination of two or more. The drum dryer is preferable because it can directly supply heat energy to the material to be dried uniformly, has high energy efficiency, and can immediately recover the dried material without applying more heat than necessary.

The mixing ratio of the anion-modified cellulose nanofibers and the rubber component may be adjusted so as to achieve the ratio when the rubber composition described below is used. For example, the anion-modified cellulose nanofiber is added to 100.0 parts by mass of the rubber component. The fiber (solid content) is preferably 0.1 to 100.0 parts by mass.

(3-3) Other compounding agents In step 3, in addition to the rubber component and the cellulose nanofibers, other compounding agents may be mixed. Other compounding agents include, but are not limited to, reinforcing agents (carbon black, silica, etc.), silane coupling agents, cross-linking agents (sulfur, peroxide, etc.), vulcanization accelerators (zinc oxide, stearin). Acids, sulfenamides, etc.), vulcanization accelerating aids, oils, cured resins, waxes, antioxidants, peptizers, colorants, pH adjusters, and other compounding agents that can be used in the rubber industry. Examples of the vulcanization accelerator sulfenamide include Nt-butyl-2-benzothiazole sulfenamide.

When compounding sulfur, the compounding amount thereof is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and further preferably 1.7% by mass or more based on the rubber component. The upper limit is preferably 10% by mass or less, more preferably 7% by mass or less, and further preferably 5% by mass or less.

When the vulcanization accelerator is compounded, the compounding amount thereof is preferably 0.1% by mass, more preferably 0.3% by mass or more, still more preferably 0.4% by mass or more, based on the rubber component. The upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less.

(3-4) Mixing A masterbatch is produced by mixing the anion-modified cellulose nanofibers and the rubber component described above with the above-mentioned other compounding agents as necessary.

The order of adding the materials in the mixing is not particularly limited, and the respective components may be mixed at once, or one of the materials may be mixed first and then the remaining materials may be mixed. A first example is a method in which the anion-modified cellulose nanofibers and the rubber component are first mixed and then the other masterbatch is mixed with the resulting masterbatch. Specifically, for example, a dispersion of anion-modified cellulose nanofibers and a dispersion liquid (latex) of a rubber component are mixed (eg, stirring with a mixer or the like), water is removed, and the resulting mixture is blended with another compound. Add the agent and knead (eg, equipment such as open roll). This allows the anion-modified cellulose nanofibers to be uniformly dispersed in the rubber component.

A second example is a method of removing water by mixing anion-modified cellulose nanofibers, a rubber component, and other compounding agents at once. Specifically, for example, an anion-modified cellulose nanofiber dispersion, a rubber component dispersion (latex), and other compounding agents are mixed (eg, stirring with a mixer or the like), and water is removed from the resulting mixture. This makes it possible to uniformly disperse any component.

The method of removing water from the mixture is not particularly limited, and examples thereof include a method of drying with a dryer such as an oven and a method of adjusting pH to 2 to 6 to solidify and dehydrating and drying. ：

A third example is a method of adding other components to the rubber component in any order and mixing. Specifically, for example, the solid substance of the rubber component is mixed with the solid substance of the anion-modified cellulose nanofibers and another compounding agent in any order, and similarly kneaded with an apparatus such as an open roll. Thereby, the step of removing water can be omitted.

Examples of the masticating and kneading device include a Banbury mixer, a kneader, and an open roll.

The temperature during mixing (for example, during mastication and kneading) may be room temperature (about 15 to 30 ° C.), or may be heated at a high temperature so that the rubber component does not undergo a crosslinking reaction. For example, it is 140 ° C. or lower, and more preferably 120 ° C. or lower. The lower limit is 70 ° C or higher, preferably 80 ° C or higher. Therefore, the heating temperature is preferably about 80 to 140 ° C, more preferably about 80 to 120 ° C.

After completion of mixing, molding may be performed if necessary. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, blow molding, foam molding, and the like, and may be appropriately selected depending on the shape, application, and molding method of the final product.

(3-5) Masterbatch A masterbatch can be produced by the above method. The masterbatch is a precursor of rubber and refers to a composition containing a rubber component in an uncrosslinked state that can be made into a rubber by crosslinking. In the present specification, the masterbatch contains at least an uncrosslinked rubber component and anion-modified cellulose nanofibers, and other compounding agents containing sulfur and a vulcanization accelerator may be added, It may be in a state before being added. Further, it may be molded depending on the form of the final product, or may be in a state before being molded.

(4) Production of rubber composition By using a masterbatch with a crosslinking agent added, the masterbatch can be converted into a rubber composition by crosslinking.

(4-1) Crosslinking Crosslinking may be carried out under the condition that the crosslinking reaction proceeds, and the conditions such as temperature are not particularly limited. Generally, the heating temperature is preferably 140 ° C. or higher, preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Therefore, the heating temperature is preferably about 140 to 200 ° C, more preferably about 140 to 180 ° C. For the crosslinking, for example, but not limited to, a vulcanizer that performs mold vulcanization, can vulcanization, continuous vulcanization, or the like can be used. The rubber composition of the present invention tends to have a faster crosslinking reaction than a composition containing no cellulose nanofibers. The reason for this is not limited, but it is presumed that the functional group such as a carboxyl group in the cellulose nanofiber accelerates the crosslinking reaction.

After cross-linking, if necessary, finishing treatment may be performed before the final product. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, chlorine treatment and the like, and only one of these treatments may be performed or a combination of two or more may be performed.

(4-2) Rubber composition In the present specification, the rubber composition means a composition obtained by crosslinking the above masterbatch. The content of the anion-modified cellulose nanofibers (solid content) in the rubber composition is preferably 0.1 to 100.0 parts by mass with respect to 100.0 parts by mass of the rubber component. From the viewpoint of improving the tensile strength, the content is more preferably 1.0 part by mass or more, further preferably 2.0 parts by mass or more, and 3.0 parts by mass or more based on 100.0 parts by mass of the rubber component. Even more preferable. The upper limit of the amount is more preferably 50.0 parts by mass or less, further preferably 40.0 parts by mass or less, and further preferably 30.0 parts by mass or less. By the amount, the workability in the manufacturing process can be maintained.

The use of the rubber composition of the present invention is not particularly limited, and examples thereof include transportation equipment such as automobiles, trains, ships, and planes; electric appliances such as personal computers, televisions, telephones, and watches; mobile communication equipment such as mobile phones. Etc .; AV equipment such as portable music reproduction equipment and video reproduction equipment; printing equipment; copying equipment; sports equipment; building materials; office equipment such as stationery; packaging goods such as containers and containers. Other than these, it can be applied to a member using rubber or flexible plastic, and is preferably applied to a tire. Examples of tires include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

The rubber composition obtained by the present invention exhibits higher mechanical strength than a rubber composition containing no cellulose nanofiber. Further, as the cellulose nanofibers to be mixed with the rubber component, by using anion-modified cellulose nanofibers obtained by defibrating anion-modified cellulose using a cavitation jet device, in the production process of the masterbatch and the rubber composition, the power consumption is reduced. A rubber composition that can be reduced and has high mechanical strength can be produced cost-effectively.

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

<Production Example 1: Production of carboxylated cellulose nanofiber (cavitation defibration)>
Bleached unbeaten kraft pulp from softwood (whiteness 85%) 5.00 g (absolute dryness), TEMPO (manufactured by Sigma Aldrich) 39 mg (0.05 mmol with respect to absolute dryness 1 g of cellulose) and sodium bromide 514 mg ( It was added to 500 mL of an aqueous solution in which 1.0 mmol of absolutely dried cellulose was dissolved and stirred until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and the oxidation reaction was started at room temperature. Although the pH of the system was lowered during the reaction, the pH was adjusted to 10 by sequentially adding a 3M sodium hydroxide aqueous solution. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system stopped changing. The mixture after the reaction was filtered with a glass filter to separate pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.4 mmol / g. Water was added to the reaction mixture to adjust the concentration to 1% by mass (w / v), and the cavitation treatment was repeated for 1 to 24 passes using a cavitation jet device at an upstream pressure of 9 MPa and a downstream pressure of 0.4 MPa to obtain a carboxyl group. A cellulose nanofiber dispersion was obtained. The number of passes in the cavitation process was calculated using the following formula:
Number of passes = Nozzle flow rate × Processing time / Sample volume

<Production Example 2>
Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 1 except that sodium hypochlorite was added at 6.0 mmol / g to start the oxidation reaction. The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device (internal diameter of the pipe immediately after the nozzle was 2.3 cm) in which the nozzle hole shape was adjusted (upstream pressure: 9 MPa, downstream pressure: 0) Cavitation treatment was performed for 24 passes at 0.45 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 70%.

<Production Example 3>
Using 500 mL of an aqueous solution in which TEMPO (manufactured by Sigma Aldrich) 80 mg (0.1 mmol for 1 g of absolutely dried cellulose) and 800 mg of sodium bromide (1.47 mmol for 1 g of completely dried cellulose) were used, sodium hypochlorite was used. Was added at a rate of 8.6 mmol / g to start the oxidation reaction, and an oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 1. The pulp yield at this time was 86%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.9 mmol / g. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 16 passes at a pressure of 0.45 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 59%.

<Production Example 4>
Production Example except that 20 mg of TEMPO (manufactured by Sigma Aldrich) (0.025 mmol with respect to 1 g of absolutely dried cellulose) was used and sodium hypochlorite was added to 2.2 mmol / g to start the oxidation reaction. Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in 1. The pulp yield at this time was 93%, the time required for the oxidation reaction was 60 minutes, and the amount of carboxyl groups was 0.7 mmol / g. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 70 passes at a pressure of 0.40 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 61%.

<Production Example 5>
Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 2. Water was added to the reaction mixture to adjust the concentration to 2.5% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 63 passes at a pressure of 0.40 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 62%.

<Production Example 6>
Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 2. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.9 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 30 passes at a pressure of 0.04 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 51%.

<Production Example 7>
Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 2. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.9 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 30 passes at a pressure of 0.27 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 50%.

<Production Example 8>
A carboxylated cellulose nanofiber dispersion was obtained in the same manner as in Production Example 6 except that the upstream pressure was 9 MPa, the downstream pressure was 0.45 MPa, and the pipe inner diameter immediately after the nozzle was 2.3 cm. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 65%.

<Production Example 9>
A carboxylated cellulose nanofiber dispersion was obtained in the same manner as in Production Example 8 except that the upstream pressure was 9 MPa and the downstream pressure was 0.63 MPa. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 66%.

<Production Example 10>
Oxidized pulp (carboxylated cellulose) was obtained in the same manner as in Production Example 1. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 30 passes at a pressure of 0.54 MPa to obtain a carboxylated cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 60%.

<Production Example 11>
To a twin-screw kneader whose rotation speed was adjusted to 100 rpm, 130 parts by mass of water and 20 parts by mass of sodium hydroxide dissolved in 100 parts by mass of water were added, and a hardwood pulp (NBK, LBKP) was added. 100 parts by mass of the dry mass when dried at 100 ° C. for 60 minutes were charged. The mixture was stirred and mixed at 30 ° C. for 90 minutes to prepare mercerized cellulose. While further stirring, 230 parts by mass of isopropanol (IPA) and 60 parts by mass of sodium monochloroacetate were added, and after stirring for 30 minutes, the temperature was raised to 70 ° C. to carry out a carboxymethylation reaction for 90 minutes. After completion of the reaction, neutralization, deliquoring, drying and pulverization were carried out to obtain a sodium salt of carboxymethylated cellulose having a carboxymethyl substitution degree of 0.31 and a cellulose type I crystallinity of 67%. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 40 passes at a pressure of 0.40 MPa to obtain a carboxymethyl cellulose nanofiber dispersion. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 63%.

<Production Example 12>
Sodium dihydrogen phosphate dihydrate (6.75 g) and disodium hydrogen phosphate (4.83 g) were dissolved in 19.62 g of water to obtain an aqueous solution of a phosphoric acid compound (hereinafter referred to as "phosphorylation reagent"). It was Water was added to softwood unbleached kraft pulp (NUKP, water content 80%, Canadian Standard Freeness (CSF) 580 ml measured according to JIS P8121) so that the concentration was 4% by mass. Then, using a double disc refiner, anomalous CSF (plain weave 80 mesh, conforming to JIS P8121 except that the amount of pulp collected was 0.3 g) was 200 ml and beaten until the average fiber length was 0.66 mm. The cellulose suspension thus obtained was diluted to 0.3% to obtain a pulp sheet (thickness: 200 μm) having a water content of 90% and a solid content (absolute dry mass) of 3 g by a papermaking method. This pulp sheet was immersed in 31.2 g of the phosphorylation reagent (80 parts by mass as the amount of phosphorus element based on 100 parts by mass of dry pulp), and heated for 1 hour with a blow dryer (Yamato Scientific Co., Ltd. DKM400) at 105 ° C Further, it was heat-treated at 150 ° C. for 1 hour to introduce a phosphate group into the cellulose fiber. Next, 500 ml of ion-exchanged water was added to the pulp sheet in which the phosphoric acid groups were introduced into the cellulose fibers, and the mixture was washed with stirring and then dehydrated. The dehydrated sheet was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N sodium hydroxide aqueous solution was added little by little while stirring to obtain a cellulose suspension having a pH of 12 to 13. Then, this cellulose suspension was dehydrated, and washed with 500 ml of ion-exchanged water. This dehydration washing was repeated twice more. At this time, the phosphoric acid group substitution degree was 0.34. Water was added to the reaction mixture to adjust the concentration to 1.0% by mass, and a cavitation jet device equipped with the same nozzle as in Production Example 2 (diameter inside the pipe immediately after the nozzle was 2.3 cm) was used for upstream pressure 9 MPa and downstream. Cavitation treatment was performed for 30 passes at a pressure of 0.4 MPa to obtain a phosphoric acid esterified cellulose nanofiber dispersion liquid. The ratio of the maximum width of the jet flow to the inner diameter of the pipe immediately after the nozzle was 61%.

<Production Example 13: Production of carboxylated cellulose nanofibers (high pressure homogenizer defibration)>
Water was added to the reaction mixture (carboxylated cellulose) obtained in the same manner as in Production Example 1 to adjust the concentration to 1.0% by mass (w / v), and the ultrahigh pressure homogenizer (20 ° C., 150 Mpa) was used for 1 to It was treated for 3 passes to obtain a carboxylated cellulose nanofiber dispersion.

<Production Example 14: Production of carboxylated cellulose nanofibers (high pressure homogenizer defibration)>
Water was added to the reaction mixture (carboxylated cellulose) obtained in the same manner as in Production Example 4 to adjust the concentration to 1.0% by mass (w / v), and 5 passes with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa). It processed and the carboxylated cellulose nanofiber dispersion liquid was obtained.

<Example 1>
A 1.0% by mass aqueous dispersion of the cellulose nanofibers of the above Production Example 1 was mixed with natural rubber latex (trade name: HA latex, Redex Co., solid content concentration 61.5% by mass). The mixing ratio of the natural rubber latex (extra-dry solid content) and the cellulose nanofibers (extra-dry solid content) was 5.0 parts by mass when the natural rubber latex was 100 parts by mass. These were stirred for 30 minutes with a TK homomixer (8000 rpm) to obtain a mixture. The mixture was dried in a 70 ° C. heating oven for 15 hours.

To the obtained mixture, zinc oxide and stearic acid were mixed in an amount of 6.0% by mass and 0.5% by mass, respectively, with respect to the rubber component in the mixture, and the mixture was mixed with an open roll (manufactured by Kansai Roll Co., Ltd.) at 30 ° C. A kneaded material was obtained by kneading for 10 minutes. Sulfur and a vulcanization accelerator (BBS, Nt-butyl-2-benzothiazole sulfenamide) were added to the kneaded material in amounts of 3.5% by mass and 0.7% by mass, respectively, based on the rubber component in the kneaded material. %, And the mixture was kneaded at 30 ° C. for 10 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.) to obtain a sheet of uncrosslinked rubber composition (masterbatch). The obtained sheet of uncrosslinked rubber composition was sandwiched between molds and pressed at 150 ° C. for 15 minutes to obtain a crosslinked rubber sheet having a thickness of 2 mm.

The obtained crosslinked rubber sheet was cut into a test piece (dumbbell-shaped No. 3 shape) having a predetermined shape, and as a piece showing tensile strength in accordance with JIS K6251 "Vulcanized rubber and thermoplastic rubber-Determination of tensile properties" The stress at 50% strain (M50), 100% strain (M100), and 300% strain (M300), and the breaking strength were measured. The larger each value is, the better the crosslinked rubber composition is reinforced, and the more excellent the mechanical strength is.

<Examples 2 to 12>
Crosslinked rubber sheets of Examples 2 to 12 were obtained in the same manner as in Example 1 except that the cellulose nanofibers of Production Examples 2 to 12 were used instead of the cellulose nanofibers of Production Example 1.

<Comparative Example 1>
A crosslinked rubber sheet of Comparative Example 1 was obtained in the same manner as in Example 1 except that cellulose nanofibers were not mixed.

<Reference Examples 1 and 2>
Crosslinked rubber sheets of Reference Examples 1 and 2 were obtained in the same manner as in Example 1 except that the cellulose nanofibers of Production Example 13 or 14 were used.

Stress at 50% strain (M50), 100% strain (M100), and 300% strain (M300) of the crosslinked rubber sheets of Examples 1 to 12, Comparative Example 1, and Reference Examples 1 and 2, and fracture. The strength is shown in Table 1.

Further, in Production Examples 1 to 14, the amount of power consumed by the defibration device when defibrating anion-modified cellulose into anion-modified cellulose nanofibers, and the obtained anion-modified cellulose nanofibers were dispersed in water as a dispersion medium. Table 1 shows the viscosity of the dispersion (solid concentration 1.0% by mass) and the transparency of the dispersion. The methods for measuring the viscosity and the transparency are as follows.

<Measurement of viscosity>
In a glass beaker, 300 g of an aqueous dispersion is prepared so that the solid content concentration of anion-modified cellulose nanofibers is 1.0% by mass. The temperature of the aqueous dispersion is set to 25 ° C., and the viscosity after 3 minutes is measured at a rotation speed of 60 rpm or 6 rpm using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.) according to the method of JIS-Z-8803.

<Measurement of transparency>
An anion-modified cellulose nanofiber aqueous dispersion was prepared so that the solid content concentration was 1.0% by mass, and then a UV-VIS spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) was used to form a prismatic type with an optical path length of 10 mm. Using a cell, the transmittance (%) of 660 nm light is measured and taken as the transparency.

From the results shown in Table 1, it can be seen that the rubber compositions obtained in Examples 1 to 12 have significantly higher mechanical strength than the rubber compositions of Comparative Example 1 containing no anion-modified cellulose nanofibers.

In addition, in the method of using the cavitation jet apparatus in the production of the carboxylated cellulose nanofibers of Examples 1 to 3, 5 to 10, compared with the method of using the ultrahigh pressure homogenizer of Reference Example 1, the power consumption was smaller and the same or more. It can be seen that a rubber composition exhibiting mechanical strength can be produced. In addition, in the method of using the cavitation jet device in the production of the carboxylated cellulose nanofibers of Example 4, the rubber composition showing the same or higher mechanical strength with less power consumption than the method of using the ultrahigh pressure homogenizer of Reference Example 2. It turns out that the thing can be manufactured. In addition, the carboxymethylated cellulose nanofibers of Example 11 and the phosphorylated esterified cellulose nanofibers of Example 12 also use the cavitation jet device to produce cellulose nanofibers of high mechanical strength with low power consumption. You can see that you can.

Further, it can be seen that the methods of Examples 1 to 3 and 5 to 10 can produce anion-modified cellulose nanofibers having high transparency and high viscosity with less power consumption than the method of Reference Example 1. . In addition, it can be seen that the method of Example 4 can produce anion-modified cellulose nanofibers having a high viscosity and having the same transparency with less power consumption than the method of Reference Example 2. The carboxymethylated cellulose nanofibers of Example 11 and the phosphorylated esterified cellulose nanofibers of Example 12 also use a cavitation jet device and have a low power consumption, high transparency, and high viscosity. It can be seen that can be manufactured. The high transparency of the anion-modified cellulose nanofibers indicates that the defibration proceeded homogeneously, and when mixed with the rubber component to form a rubber composition, it may become a starting point of rupture. Indicates that there are few large fibers. Further, the high viscosity means that the fiber is less damaged. The ability to produce such an anion-modified cellulose nanofiber having high transparency and high viscosity with low power consumption leads to the production of a masterbatch and a rubber composition at low cost, which makes it difficult to break, which is advantageous. You can say that.

Claims (8)

1. Step 1 of preparing anion-modified cellulose,
   Step 2 of defibrating anion-modified cellulose using a cavitation jet device to produce anion-modified cellulose nanofibers, and step 3 of mixing the anion-modified cellulose nanofibers obtained in step 2 with a rubber component to obtain a masterbatch ,
   A method for producing a masterbatch, which comprises:
2. The cavitation jet device gives the anion-modified cellulose an impact force when the cavitation bubbles generated by the liquid jet jetted through the nozzle or orifice are collapsed, and the upstream pressure of the liquid jet jetted through the nozzle or orifice is 0.01 MPa. The method according to claim 1, wherein the ratio is not less than 30.00 MPa and not more than 30.00 MPa, and the ratio of the downstream pressure / upstream pressure is 0.001 to 0.500.
3. The method according to claim 1 or 2, wherein the anion-modified cellulose is a cellulose having a carboxyl group.
4. The method according to claim 3, wherein the amount of carboxyl groups in the anion-modified cellulose is 0.4 mmol / g to 3.0 mmol / g based on the absolute dry mass of the anion-modified cellulose.
5. The method according to claim 1 or 2, wherein the anion-modified cellulose is a cellulose having a carboxymethyl group.
6. The method according to claim 5, wherein the anion-modified cellulose has a degree of carboxymethyl substitution of 0.01 or more and less than 0.40.
7. The method according to any one of claims 1 to 6, wherein the rubber component contains a diene rubber polymer.
8. A method for producing a rubber composition, comprising the steps of producing a masterbatch by the method according to any one of claims 1 to 7, and a step of crosslinking the masterbatch.