WO2018199191A1 - Masterbatch, rubber composition, and production methods for both - Google Patents

Abstract

In order to provide a rubber composition which contains cellulose nanofibers and is excellent in terms of strength including rupture strength, a method for producing a masterbatch is provided, the method comprising: (1) a step in which a pulp B is prepared, the pulp B having been produced from a raw wood material which, when pulped under the kraft pulp production conditions of an active-alkali addition amount of 15%, a degree of sulfurization of 25%, a liquid ratio of 2.5 L/kg, and an H-factor of 830, gives a pulp A having a fiber length distribution in which the proportion of fibers each having a length of 1.00 mm or longer as measured in accordance with ISO 16065-2 is 20% or less; (2) a step in which the pulp B is fibrillated to obtain cellulose nanofibers having a length-weighted mean fiber length of 500 nm or less and a length-weighted mean fiber diameter of 100 nm or less; and (3) a step in which the cellulose nanofibers are mixed with a rubber ingredient.

Description

Masterbatch, rubber composition and production method thereof

The present invention relates to a masterbatch, a rubber composition, and a production method thereof, and more particularly, to a masterbatch containing chemically modified cellulose nanofibers, a rubber composition using the same, and a production method thereof.

In recent years, a technique for improving various strengths in a rubber composition, such as tensile strength, has been proposed by incorporating into a rubber composition a material called cellulose nanofiber, which is produced by finely loosening plant fibers to the nano level. .
For example, Patent Document 1 discloses that after mixing rubber latex and an aqueous dispersion of cellulose fibers having a carboxyl group, at least a part of water is removed to obtain a cellulose fiber / rubber composite, and this composite. And a method of producing a rubber composition having excellent hardness and tensile strength.

JP 2013-018918 A

However, although the hardness and tensile strength of the rubber composition obtained by the method of Patent Document 1 are good to some extent, they are not sufficient as expected. The reason why the hardness and tensile strength of the rubber composition are not sufficient as expected is presumed that the cellulose fibers are not uniformly dispersed in the rubber composition for the following reason.
When the rubber latex and the aqueous dispersion of cellulose fiber are mixed to obtain a rubber composition, the carboxyl group in the cellulose fiber forms a salt such as a sodium salt, and the cellulose fiber is in a highly hydrophilic state. Therefore, when removing the water of a dispersion liquid, it is estimated that a hydrophilic cellulose fiber aggregates strongly mutually and a dispersibility falls. That is, it is presumed that cellulose fibers can exhibit their original reinforcing properties when dispersed uniformly in the system, but cannot sufficiently exhibit their original reinforcing properties when aggregated.
Accordingly, an object of the present invention is to provide a master batch capable of producing a rubber composition containing cellulose nanofibers and having excellent strength such as breaking strength, a rubber composition using the same, and a production method thereof. To do.

The above-mentioned problems are solved by the present invention [1] to [8] below.
[1]: (1): Measured according to ISO 16065-2 when pulped under kraft pulp production conditions of 15% active alkali addition, 25% sulfidity, liquid ratio 2.5 L / kg, H-factor 830 A step of preparing a pulp B made of wood from which a pulp A having a fiber length distribution in which the ratio of fiber length components of 1.00 mm or more is 20% or less is obtained;
(2): a step of defibrating the pulp B to obtain cellulose nanofibers having a length weighted average fiber length of 500 nm or less and a length weighted average fiber diameter of 100 nm or less; and (3): the cellulose nanofibers. Mixing rubber components,
A method for producing a masterbatch including
[2]: The wood from which the pulp A is obtained in which the ratio of the fiber length component of 0.20 mm or less is 20% or less in the fiber length distribution when the wood is pulped under the kraft pulp production conditions. [1] The production method according to [1].
[3]: The production method according to [1] or [2], including a step of anion-modifying the pulp B after the step (1) and before the step (2).
[4]: The cellulose nanofiber is an oxidized cellulose nanofiber, and the amount of carboxyl groups and the like is 0.1 to 3.0 mmol / g with respect to the absolute dry weight of the cellulose nanofiber. The manufacturing method as described.
[5]: The production method according to [3], wherein the cellulose nanofiber is carboxymethylated cellulose nanofiber, and the degree of carboxymethyl substitution per glucose unit of the cellulose nanofiber is 0.01 to 0.50. .
[6]: A master batch produced by the production method according to any one of [1] to [5].
[7]: A step of producing a master batch by the production method according to any one of [1] to [5], and a step of kneading the obtained master batch and a rubber component to obtain a rubber composition. The manufacturing method of the rubber composition containing.
[8]: A rubber composition produced by the production method according to [7].

The present invention can provide a master batch capable of producing a rubber composition containing cellulose nanofibers and having excellent strength such as breaking strength, a rubber composition using the same, and a production method thereof.

FIG. 1 is a diagram showing the fiber length distribution of pulp B used in Example 1 and Comparative Example 1. FIG.

Hereinafter, the present invention will be described in detail. In the present invention, “˜” includes values at both ends thereof. That is, “X to Y” includes X and Y.

≪Method for producing cellulose nanofiber≫
In the present invention, the cellulose nanofiber refers to a fiber having a length weighted average fiber length of 500 nm or less and a length weighted average fiber diameter of 100 nm or less. The fiber diameter is preferably 20 nm or less, more preferably 2 to 10 nm. The fiber length is preferably 490 nm or less, more preferably 250 to 480 nm. The length-weighted average fiber length and length-weighted average fiber diameter of the cellulose nanofiber can be measured by observing the cellulose nanofiber with a microscope such as an electron microscope or an atomic force microscope. The manufacturing method of the cellulose nanofiber of this invention includes the process (1) of preparing the pulp B prepared from the specific wood, and the process (2) of defibrating the said pulp B.

<Step (1)>
In this step, pulp B prepared from specific wood is prepared. Specifically, when the wood is pulped under specific pulping conditions (hereinafter also referred to as “specific pulping conditions”), the ratio of fiber length components of 1.00 mm or more measured according to ISO 16065-2 (2014) The wood from which pulp A having a fiber length distribution of 20% or less (hereinafter also referred to as “long fiber ratio”) is obtained. The fiber length distribution of the pulp can be measured by using a pulp analyzer “FiberLab” manufactured by Metso Automation. In the fiber length distribution, the ratio of fiber length components of 0.20 mm or less (hereinafter also referred to as “short fiber ratio”) is preferably 20% or less. Moreover, it is preferable that the length weight average fiber length of the pulp A is 0.65 mm or less.
In addition, the lower limit of the long fiber ratio and the short fiber ratio of the pulp A is usually 3% or more. Moreover, the minimum of the length weighted average fiber length of the pulp A is 0.3 mm or more normally.

The specific pulping conditions refer to the conditions for producing kraft pulp using wood chips with an active alkali addition of 15%, a sulfidity of 25%, a liquid ratio of 2.5 L / kg, and an H-factor of 830.

An active alkali means the term prescribed | regulated to JISP0001 (1998), and shows the alkalinity of a Kraft method cooking solution and a soda method cooking solution. The amount of active alkali is represented by NaOH + Na ₂ S.

The degree of sulfidization is a term defined in JIS P0001 (1998) and is the amount of sulfide in the kraft process cooking liquor. The degree of sulfidation (%) is expressed as Na ₂ S / (NaOH + Na ₂ S) × 100.

H-factor is a term defined in JIS P0001 (1998), and is a cooking degree that comprehensively represents the effects of cooking temperature and cooking time in a chemical pulping method. The pulping effect when digested for 1 hour at 100 ° C. is defined as H-factor 1.

<Step (1-1): Preparation of wood>
The wood species is not limited as long as it is a wood from which the above fiber length distribution is obtained, but it is preferably a hardwood material. The tree species of the hardwood is not particularly limited, and examples thereof include Eucalyptus (eucalyptus), Fagus (beech), Quercus (nara, oak, etc.), Beluta (hippo), and Acacia (acacia). Among these, tree species belonging to the genus Eucalyptus are preferred. Since these generally have good growth and a large number of tree species belong to them, it is relatively easy to search for suitable tree species for the plantation. The tree species belonging to the genus Eucalyptus is preferably at least one selected from the group consisting of Eucalyptus globulas, Eucalyptus grandis, Eucalyptus nighttens, Eucalyptus eurofila, Eucalyptus perita, and Eucalyptus camaldrensis. Moreover, these hybrids etc. may be sufficient.
It is preferable to use a wood material having a low tree age, more preferably a wood material having a tree age of 1 to 5 years, and even more preferably a wood material having a tree age of 2 to 3 years.

<Process (1-2): Pulp>
Examples of the pulping method of hardwood include a mechanical pulp method using a kraft pulp method, a soda pulp method, a sulfite pulp method, a refiner, and the like. In addition to pulp obtained by these methods, pulp obtained by pulverizing these pulps with a high-pressure homogenizer, a cutting mill, or the like, or pulp purified by chemical treatment such as acid hydrolysis can be used. However, if a large amount of lignin remains in the pulp material, chemical modification in the next step may be hindered. Use chemical pulp produced by the kraft pulp method, soda pulp method, sulfite pulp method, etc. Is preferred.

Pulp preparation conditions for obtaining pulp B prepared in step (1) (also referred to as “pulp preparation conditions in step (1)”) need not be the same as the above-mentioned “specific pulping conditions”. That is, the pulp preparation conditions in step (1) may be milder conditions or severer conditions than the specific pulping conditions. However, the “long fiber ratio” of the pulp B prepared in the step (1) is preferably 20% or less. The “short fiber ratio” of the pulp B is preferably 20% or less. Furthermore, it is preferable that the length weight average fiber length of the pulp B is 0.65 mm or less.
In addition, the minimum of the long fiber ratio of the pulp B and a short fiber ratio is 3% or more normally. Moreover, the minimum of the length weight average fiber length of the pulp B is 0.3 mm or more normally.

The pulp B may be the same as or different from the pulp A as long as it is a pulp having few extreme short fibers and a relatively narrow fiber length distribution. The viscosity of pulp B at a concentration of 1% (w / v) at 20 ° C. and 60 rpm is preferably 1 to 12 mPa · s, more preferably 3 to 10 mPa · s.

<Step (1-3): Bleaching>
In order to further remove lignin, the pulp B is preferably subjected to a known bleaching treatment. The bleaching method is not particularly limited, but chlorine treatment (C), chlorine dioxide bleaching (D), alkali extraction (E), hypochlorite bleaching (H), oxygen treatment (O), hydrogen peroxide bleaching (P ), Alkaline hydrogen peroxide treatment stage (Ep), alkaline hydrogen peroxide / oxygen treatment stage (Eop), ozone treatment (Z), chelate treatment (Q) and the like. For example, C / DE / OHD, ZE / OD, C / DEHD, ZEDP, Z / DEpD, Z / D-Ep-DP, D-Ep-D, D-Ep-DP, D-Ep-PD, ZEop-DD, Z / D-Eop-D, Z / D-Eop- Bleaching can be performed in a sequence such as DED. “/” In the sequence means that the processes before and after “/” are continuously performed without cleaning. The amount of lignin in the pulp B is preferably small, and the pulp B (bleached kraft pulp B, bleached sulfite pulp B) obtained using the pulping treatment and the bleaching treatment has a whiteness (ISO 2470) of 80. % Or more is more preferable.

<Step (1-4): Chemical modification>
In order to efficiently perform defibration in the next step, the pulp B is preferably subjected to chemical modification such as anion modification or cation modification.

<Step (1-4-1) Anion Modification>
i) Carboxymethylation The pulp B is used as a starting material, and a solvent mixture of 3 to 20 times lower alcohol and water is usually used in terms of weight. Specific examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butyl alcohol, isobutyl alcohol, tertiary butanol and the like. The lower alcohol may be a single alcohol or a mixture of two or more. In the case of a mixture of two or more, the mixing ratio of the lower alcohol is 60 to 95% by weight in the mixed medium. As the mercerizing agent, 0.5 to 20 times alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide is used in terms of mole per glucose residue of the starting material. A starting material, a solvent, and a mercerizing agent are mixed and subjected to mercerization treatment under the conditions of a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Do. Thereafter, a carboxymethylating agent is added 0.05 to 10.0 times in terms of mole per glucose residue, the reaction temperature is 30 to 90 ° C., preferably 40 to 80 ° C., and the reaction time is 30 minutes to 10 hours. The etherification reaction is preferably carried out under conditions of 1 hour to 4 hours.

The degree of carboxymethyl substitution per glucose unit in the anion-modified cellulose is preferably 0.01 to 0.50. By introducing a carboxymethyl group into cellulose, the celluloses repel each other electrically. For this reason, the cellulose which introduce | transduced the carboxymethyl group can be nano-defibrated easily. If the degree of carboxymethyl substitution per glucose unit is less than 0.01, nano-defibration may not be sufficient. On the other hand, if the degree of carboxymethyl substitution per glucose unit is greater than 0.50, it may swell or dissolve, and may not be obtained as a nanofiber.

ii) Oxidation Pulp B 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 bromides, iodides and mixtures thereof, thereby converting the carboxyl group into cellulose. Oxidized cellulose introduced in can be obtained.

N-oxyl compound refers to a compound capable of generating a nitroxy radical. The N-oxyl compound used in the present invention is not limited as long as it is a compound that promotes the target oxidation reaction.

The amount of the N-oxyl compound is not particularly limited as long as it is a catalyst amount that can sufficiently oxidize pulp B to such an extent that the resulting oxidized pulp can be made into nanofibers. For example, it is about 0.01 to 10 mmol, preferably about 0.02 to 1 mmol, and more preferably about 0.05 to 0.5 mmol with respect to 1 g of absolutely dry pulp.

The bromide used in the oxidation of pulp B refers to a compound containing bromine, and examples thereof include alkali metal bromides that can be dissociated and ionized in water. Iodide refers to a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, about 0.1 to 100 mmol, preferably 0.1 to 10 mmol, and more preferably about 0.5 to 5 mmol with respect to 1 g of absolutely dry pulp.

As the oxidizing agent used in the oxidation of the pulp B, known oxidizing agents such as halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, and peroxide can be used. Sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The amount of the oxidizing agent used can be selected within a range that can promote the oxidation reaction. The amount is, for example, about 0.5 to 500 mmol, preferably 0.5 to 50 mmol, and more preferably about 2.5 to 25 mmol with respect to 1 g of absolutely dry pulp.

The temperature during the oxidation reaction may be a room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at about 9 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

By the above oxidation reaction, the primary hydroxyl group at the 6-position in the cellulose Pyranose ring of pulp B is oxidized to a carboxyl group or a salt thereof. A pyranose ring is a six-membered ring carbohydrate consisting of five carbon atoms and one oxygen atom. The 6-position primary hydroxyl group means an OH group bonded to a 6-membered ring via a methylene group. In the oxidation reaction of cellulose using an N-oxyl compound, this primary hydroxyl group is selectively oxidized. The cellulose thus oxidized is easily nano-defibrated in the next defibrating process. This mechanism is explained as follows. Natural celluloses are nanofibers when they are biosynthesized, but many of them converge by hydrogen bonding to form fiber bundles. When the cellulose fiber is oxidized using an N-oxyl compound, the primary hydroxyl group at the C6 position of the pyranose ring is selectively oxidized, and this oxidation reaction remains on the surface of the microfibril, so that the concentration is high only on the surface of the microfibril. A carboxyl group is introduced. Since the carboxyl groups are negatively charged and repel each other, when dispersed in water, the aggregation of the microfibrils is hindered. As a result, the fiber bundle is unraveled in units of microfibrils, and cellulose single microfibrils. It becomes a certain cellulose nanofiber.

The carboxyl group introduced at the C6 position of the cellulose may form a salt with an alkali metal or the like. In the present invention, the amount of the carboxyl group and a salt thereof (hereinafter collectively referred to as “carboxyl group and the like”) is 0.10 mmol / g or more with respect to the dry mass of the cellulose nanofiber. Further, the lower limit of this amount is preferably 0.50 mmol / g or more, more preferably 1.20 mmol / g or more, and further preferably 1.40 mmol / g or more. Under conditions where a large amount of carboxyl group or the like is obtained, the cellulose is likely to be cleaved as a side reaction during the oxidation reaction, and the yield decreases, which is uneconomical. For this reason, the upper limit of the amount of carboxyl groups and the like is preferably 3.00 mmol / g or less, and more preferably 2.00 mmol / g or less.

The amount of carboxyl groups and the like is adjusted by adding 60 ml of a 0.5% by mass slurry of oxidized pulp and adding 0.1 M hydrochloric acid aqueous solution to pH 2.5, then adding 0.05 N sodium hydroxide aqueous solution dropwise to adjust the pH. The electric conductivity is measured until it becomes 11, and the amount can be calculated from the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electric conductivity is slow, using the following formula.

Amount of carboxyl group etc. [mmol / g pulp] = a [ml] × 0.05 / oxidized pulp mass [g]
The amount of carboxyl groups and the like of cellulose nanofibers and the amount of carboxyl groups and the like of oxidized pulp are usually the same value.

As another example of the oxidation method, a method of oxidizing by contacting a gas containing ozone and pulp can be mentioned. By this oxidation reaction, at least the 2-position and 6-position hydroxyl groups of the glucopyranose ring are oxidized and the cellulose chain is decomposed. The ozone concentration in the gas containing ozone is preferably 50 to 250 g / m ³ , more preferably 50 to 220 g / m ³ . The amount of ozone added to the pulp B is preferably 0.1 to 30 parts by mass and more preferably 5 to 30 parts by mass when the solid content of the pulp B is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50 ° C., and more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the conditions for the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, an additional oxidation treatment may be performed 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. For example, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the oxidized pulp can be immersed in the solution for additional oxidation treatment. The amount of carboxyl group and the like of oxidized cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidizing agent added and the reaction time.

iii) Phosphorylation The method of phosphorylation is not particularly limited, and examples thereof include a method of reacting compound A with pulp B. Compound A will be described below. Examples of the method of reacting compound A with pulp B include a method of mixing a powder or an aqueous solution of compound A with pulp B, a method of adding an aqueous solution of compound A to a slurry of pulp B, and the like. Among these, since the uniformity of the reaction is increased and the esterification efficiency is increased, a method of mixing an aqueous solution of Compound A into Pulp B or a slurry thereof is preferable.

Examples of the 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. As the compound A, 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 the cellulose of the 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 type or a combination of two or more types. Among these, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid, from the viewpoint that phosphoric acid group introduction efficiency is high, is easy to be defibrated in the following defibrating process, and is industrially applicable. Are preferred, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferred. 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 enhanced and the efficiency of introduction of phosphoric acid groups 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 introduction of 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 pulp B (for example, a solid concentration of 0.1 to 10% by mass) with stirring to introduce phosphate groups into the cellulose. When the pulp B is 100 parts by mass, when the compound A is a phosphoric acid compound, the addition amount of the compound A is preferably 0.2 parts by mass or more and more preferably 1 part by mass or more as the mass in terms of phosphorus element. . Thereby, the yield of fine fibrous cellulose can be improved more. The upper limit is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. Thereby, the yield corresponding to the usage-amount of the compound A can be obtained efficiently. Therefore, 0.2 to 500 parts by mass is preferable, and 1 to 400 parts by mass is more preferable.

When reacting compound A with pulp B, 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 pulp, an aqueous solution of compound A, or a slurry of pulp B and compound A.

Compound B is not particularly limited, but preferably exhibits basicity, more preferably a nitrogen-containing compound exhibiting basicity. “Shows basicity” usually means that the aqueous solution of Compound B is pink to red in the presence of a phenolphthalein indicator and / 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. Examples include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among 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 mass, and more preferably 100 to 700 parts by mass. The reaction temperature is preferably 0 to 95 ° C, more preferably 30 to 90 ° C. 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 pulp B, 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 the pulp B 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, phosphate groups are introduced into pulp B, and cellulose repels electrically. Therefore, the phosphate esterified 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 is preferably 0.40 or less. 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, it is preferable that the degree of phosphate group substitution be 0.001 to 0.40. The phosphorylated cellulose is preferably subjected to a washing treatment such as washing with cold water after boiling. Thereby, defibration can be performed efficiently.

<Step (1-4-2) Cation Modification>
The above pulp B is used as a starting material, and the above pulp B is mixed with a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydride or a halohydrin type thereof, and an alkali metal as a catalyst. A cation-modified cellulose can be obtained by reacting hydroxide (sodium hydroxide, potassium hydroxide, etc.) in the presence of water or an alcohol having 1 to 4 carbon atoms. The degree of cation substitution per glucose unit in the resulting cation-modified cellulose can be adjusted by controlling the amount of the cationizing agent to be reacted and the composition ratio of water or an alcohol having 1 to 4 carbon atoms.

In the present invention, the cation substitution degree per glucose unit of the cation-modified cellulose is preferably 0.02 to 0.50. 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-defibrated easily. In addition, when the cation substitution degree per glucose unit is smaller than 0.02, nano-defibration may not be sufficiently performed. On the other hand, if the degree of cation substitution per glucose unit is more than 0.50, it may swell or dissolve, and may not be obtained as a nanofiber. In order to efficiently perform the next defibration, the cation-modified cellulose obtained above is preferably washed.

<Step (2): defibration>
In this step, the pulp B or the pulp B subjected to chemical modification is defibrated to obtain cellulose nanofibers. Defibration can be performed by mixing or stirring, emulsifying or dispersing devices such as a high-speed shear mixer and a high-pressure homogenizer, singly or in combination of two or more as required. At this time, the size of the pulp (fiber diameter) decreases simultaneously with the loosening of the fibers. In particular, when using an ultra-high pressure homogenizer that enables a pressure of 100 MPa or more, preferably 120 MPa or more, more preferably 140 MPa or more, defibration and dispersion of cellulose nanofibers proceed efficiently, and when an aqueous dispersion is obtained, This is preferable because cellulose nanofibers having a low viscosity can be produced efficiently.

Since the pulp subjected to the above-mentioned chemical modification is easily defibrated, in the present invention, a process for further cutting the cellulose chain (shortening the cellulose chain) (also referred to as “low viscosity treatment”) is not performed. Is preferred. However, a low viscosity treatment that does not cause coloring or the like may be applied to the chemically modified pulp. Examples of such a viscosity-reducing treatment include, for example, a treatment of irradiating chemically modified pulp with ultraviolet rays, a treatment of oxidizing and decomposing with hydrogen peroxide and ozone, a treatment of hydrolyzing with an acid, a treatment of hydrolyzing with an alkali, Examples thereof include treatment with an enzyme such as cellulase, or a combination thereof.

For example, for the hydrolysis with alkali, a dispersion of oxidized pulp (preferably an aqueous dispersion) is prepared, and the pH of the dispersion is adjusted to 8 to 14, preferably 9 to 13, and more preferably 10 to 12. By reacting at a temperature of 20 to 120 ° C., preferably 50 to 100 ° C., more preferably 60 to 90 ° C., for 0.5 to 24 hours, preferably 1 to 10 hours, more preferably 2 to 6 hours. It can be carried out. For adjusting the pH of the dispersion, an alkaline aqueous solution such as sodium hydroxide can be used. Moreover, it is preferable to add an oxidizing agent or a reducing agent as an auxiliary agent. As the oxidizing agent or reducing agent, those having activity in an alkaline region of pH 8 to 14 can be used. Examples of the oxidizing agent include oxygen, ozone, hydrogen peroxide, and hypochlorite. Of these, oxygen, hydrogen peroxide, hypochlorite, and the like that do not easily generate radicals are preferable. Hydrogen oxide is more preferred. Examples of the reducing agent include sodium borohydride, hydrosulfite, and sulfite.

<Cellulose nanofiber dispersion>
Cellulose nanofibers can be used as a dispersion. A dispersion is a liquid in which cellulose nanofibers are dispersed in a dispersion medium. The dispersion medium is a medium, and water is preferable from the viewpoint of handleability. The dispersion is useful from the viewpoint of industrial use of cellulose nanofibers.

The upper limit of the B-type viscosity of the cellulose nanofiber dispersion is 2000 mPa · s or less at a concentration of 1% (w / v). The viscosity was 20 ° C., 60 rpm, rotor No. 4 is measured. The lower limit of the B-type viscosity is not particularly set, but actually, it will be about 10 mPa · s at a concentration of 1% (w / v).

The aqueous dispersion of cellulose nanofibers is a liquid that is visually transparent because cellulose nanofibers are uniformly dispersed in water. The transparency of the cellulose nanofiber dispersion can be determined by measuring the transmittance of light having a wavelength of 660 nm with a spectrophotometer. The light transmittance (wavelength 660 nm) at a concentration of 0.1% (w / v) of the cellulose nanofiber aqueous dispersion is preferably 90% or more, and more preferably 95% or more.

The dispersion can be prepared by any method. For example, after preparing oxidized pulp, a dispersion medium such as water is added and dispersed while defibrating using an ultrahigh pressure homogenizer or the like, whereby a dispersion can be prepared.

The B-type viscosity (60 rpm, 20 ° C.) of the cellulose nanofiber dispersion (1% (w / v)) obtained by the conventional method is about 2000 to 10000 mPa · s, whereas the dispersion of step (1) The viscosity of the cellulose nanofiber dispersion (1% (w / v)) prepared using the pulp obtained under the pulp preparation conditions is as low as 2000 mPa · s or less. Therefore, it is possible to increase the concentration of the cellulose nanofiber dispersion. For example, the concentration of the cellulose nanofiber dispersion prepared by the above method is preferably 1.1 to 10% (w / v), and more preferably 2 to 8% (w / v). Cellulose nanofibers are characterized by improving the breaking strength of the rubber composition by being contained in the rubber component.

The reason why cellulose nanofibers having such performance can be produced by using a specific pulp is considered as follows.

When a conventional alkali treatment is performed on pulp, some fibers are excessively cut, resulting in extremely short fibers. In addition, if wood flour is used as the raw material, the fibers are mechanically excessively broken, so that there are many cellulose nanofibers that are extremely shortened, which lowers the reinforcing effect. On the other hand, from the wood used in the present invention, pulp B having a relatively narrow fiber length distribution with few extreme short fibers, without making wood powder or conventional alkali treatment, etc. Can be prepared. Therefore, when it is made to contain in a rubber component, it is guessed that the cellulose nanofiber excellent in breaking strength can be manufactured.

≪Masterbatch manufacturing method≫
The manufacturing method of the masterbatch of this invention includes the process of mixing the cellulose nanofiber obtained at the said process (2) like the following process (3). After mixing, a kneading step may be further included. It is also possible to provide a drying step after mixing and before the kneading step.

<Step (3): Mixing>
In this step, the cellulose nanofiber and the rubber component are mixed.

<Rubber component>
A rubber component is a raw material of rubber and means a material that is crosslinked to become rubber. As the rubber component, there are a rubber component for natural rubber and a rubber component for synthetic rubber. The rubber component for natural rubber includes, for example, natural rubber (NR) in a narrow sense without chemical modification; chemically modified natural rubber such as chlorinated natural rubber, chlorosulfonated natural rubber, and epoxidized natural rubber; Rubber; Deproteinized natural rubber. Examples of rubber components for synthetic rubber include butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber, and styrene-isoprene copolymer. Diene rubbers such as united rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber; butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), acrylic rubber (ACM), epichlorohydride Non-diene rubbers such as rubber (CO, ECO), fluoro rubber (FKM), silicone rubber (Q), urethane rubber (U), and chlorosulfonated polyethylene (CSM). Among these, a diene rubber is preferable, and a diene natural rubber is more preferable.

The rubber component may be a single type or a combination of two or more types.

In step (3), the solid of the rubber component may be used for mixing, but may also be used for mixing in a dispersion solution (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”) include water and organic solvents. The amount of the liquid is preferably 10 to 1000 parts by mass with respect to 100 parts by mass of the rubber component (the total amount when two or more rubber components are used).

<Mixed>
Mixing can be carried out using a known apparatus such as a homomixer, a homogenizer, or a propeller stirrer. The mixing temperature is not limited, but room temperature (20 to 30 ° C.) is preferable. You may adjust mixing time suitably.

The cellulose nanofibers used for mixing can be used for mixing in the form of a dispersion dispersed in a dispersion medium, a dry solid of the dispersion, and a wet solid of the dispersion. When the dispersion medium is water, the concentration of cellulose nanofibers in the dispersion may be 0.1 to 20% (w / v). When the dispersion medium contains water and an organic solvent such as alcohol, It may be 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 liquid by a usual method is preferably 5 to 15% by mass with respect to the cellulose nanofibers. Can be adjusted as appropriate.

The cellulose nanofiber may be a combination of two or more cellulose nanofibers as long as the cellulose nanofiber obtained in the step (2) is used. Moreover, the mixture of a cellulose nanofiber and a water-soluble polymer solution is also good. In the case of such a mixture, a mixed solution, a dry solid of the mixed solution, a wet solid of the mixed solution, or the like can be used for mixing. The amount of liquid in the mixture and its dry solids may be in the above range.

<Composition of the mixture>
Each content of the cellulose nanofiber and the rubber component in the mixture of the step (3) is not particularly limited, but preferable contents are as follows.

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

<Drying process>
The mixture is preferably, but not necessarily, dried before the following kneading step. The drying method is not particularly limited, and any of a heating method, a coagulation method, and a combination thereof may be used, but a heat treatment is preferable. The conditions for the heat treatment are not particularly limited, but an example is as follows. The heating temperature is preferably 40 ° C. or higher and lower than 100 ° C. The treatment time is preferably 1 to 24 hours. By setting it as the said conditions, the damage with respect to a rubber component can be suppressed. The mixture after drying may be completely dried or the solvent may remain. Moreover, it does not restrict | limit especially as a method of removing solvents other than the above, It can carry out by a conventionally well-known method.

<Kneading process>
When performing the kneading step, the mixture may be kneaded in a known manner, for example, an open kneader such as a two-roll or three-roll, a meshing Banbury mixer, a tangential Banbury mixer, a pressure kneader, or the like. A closed kneader can be used. Moreover, the process which passes through a multistage kneading | mixing process is also possible, for example, kneading | mixing with a closed kneading machine can be performed at a 1st stage, and it can re-knead with an open kneading machine after that.

In addition, during kneading, reinforcing agents (for example, carbon black, silica, etc.), silane coupling agents, fillers, vulcanizing agents, vulcanization accelerators, vulcanization accelerators (for example, zinc oxide, stearic acid) Any additives such as oil, hardened resin, wax, anti-aging agent, colorant, and other compounding agents can be added to the mixture. What is necessary is just to determine suitably content of an additive according to the kind etc. of an additive, and it does not specifically limit.

The obtained kneaded material is used as a master batch of the rubber composition of the present invention as shown below.

≪Master batch≫
The master batch of the present invention is obtained by the above production method. In the production method of the present invention, by using a specific wood, a pulp having a relatively narrow fiber length distribution with few extreme short fibers, without making wood flour or conventional alkali treatment, etc. Can be prepared. Therefore, when it is made to contain in a rubber component, it is guessed that the cellulose nanofiber excellent in breaking strength can be manufactured. Therefore, it is guessed that it will become a masterbatch which can manufacture a rubber composition containing cellulose nanofibers and having excellent strength such as breaking strength.

≪Method for producing rubber composition≫
The manufacturing method of the rubber composition of this invention includes the process of manufacturing a masterbatch by said manufacturing method of a masterbatch, and the process of knead | mixing the obtained masterbatch and a rubber component and obtaining a rubber composition.
The details of the process for producing the master batch are as described above. Examples of the rubber component used in the step of obtaining the rubber composition include those described in step (3) of the masterbatch production method. Moreover, as a kneading | mixing method, the method described by the above <kneading | mixing process> is mentioned.

≪Rubber composition≫
The rubber composition of the present invention is a rubber composition produced by the method for producing a rubber composition described above. Therefore, even if it contains a cellulose nanofiber, it can be set as the rubber composition excellent in strength, such as breaking strength.

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

Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazole sulfenamide and N-oxydiethylene-2-benzothiazolyl sulfenamide. The content of the vulcanization accelerator is preferably 0.1 parts by mass, more preferably 0.3 parts by mass or more, and still more preferably 0.4 parts by mass or more with respect to 100 parts by mass of the rubber component. The upper limit is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and still more preferably 2 parts by mass or less.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In addition, the physical-property value shown below is a value by an above-described measuring method unless there is particular notice.

<B-type viscosity>
B-type viscosity (60 rpm, 20 ° C.) was measured using a TV-10 viscometer (Toki Sangyo Co., Ltd.).

<Pulp viscosity>
The measurement of pulp viscosity is described in J. Am. It carried out according to TAPPI 44.

<Length-weighted average fiber length of cellulose nanofiber>
The fiber length was measured from the atomic force microscope image (3000 nm × 3000 nm) of the cellulose nanofiber fixed on the mica section, and the length weighted average fiber length was calculated. The fiber length was measured using image analysis software WinROOF (Mitani Corporation) in the range of 100 nm to 2000 nm in length.

<Length-weighted average fiber diameter of cellulose nanofiber>
A cellulose nanofiber aqueous dispersion diluted so that the concentration of the cellulose nanofibers was 0.001% by mass was prepared. The diluted dispersion is thinly spread on a mica sample stage, heated and dried at 50 ° C. to prepare an observation sample, the cross-sectional height of the shape image observed with an atomic force microscope (AFM) is measured, and the length is measured. The weighted average fiber diameter was calculated.

<Pulp length weighted average fiber length and fiber length distribution>
It was measured according to ISO 16065-2 (2014).

<Preparation of wood>
The following wood was prepared. The ratio of long fiber components (long fiber ratio) of 1.00 mm or more measured according to ISO 16065-2 (2014) when each wood was pulped under specific pulping conditions was as follows.

Specific pulping conditions:
Kraft pulp using wood chips with active alkali addition of 15%, sulfidity of 25%, liquid ratio of 2.5L / kg, H-factor 830 (maximum temperature is 160 ° C, hold for 90 minutes after maximum temperature is reached) Production conditions Wood A: Eucalyptus maldrensis 2 years old, long fiber ratio 8.8%, short fiber ratio 5.5%
Wood B: 3 years old Eucalyptus maldrensis, long fiber ratio 17.6%, short fiber ratio 9.6%
Wood C: 3 years old acacia, long fiber ratio 10.1%, short fiber ratio 8.1%
Wood D: 8 year old hardwood mixed material, long fiber ratio 28.6%, short fiber ratio 7.1%

[Example 1]
<Step (1): Preparation of pulp>
Wood A (2 years old Eucalyptus maldrensis) was used. Bleached unbeaten kraft pulp (whiteness 85%) (manufactured by Nippon Paper Industries Co., Ltd.) obtained by pulping wood A chips as raw materials under the same conditions as the specific pulping conditions was prepared. FIG. 1 shows the fiber length distribution of this pulp. The long fiber ratio was 8.8%, and the short fiber ratio was 5.5%.

5 g (absolutely dry) of the pulp is added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Tokyo Kasei) and 756 mg (7.35 mmol) of sodium bromide (Wako Pure Chemical Industries) are dissolved, until the pulp is uniformly dispersed. Stir. To this, 2.3 mmol of sodium hypochlorite (Wako Pure Chemicals, aqueous solution) was added in the form of an aqueous solution, and then sodium hypochlorite was fed at a rate of 0.23 mmol / min per gram of pulp. Was added gradually to oxidize the pulp. The addition was continued until the total amount of sodium hypochlorite added was 22.5 mmol. During the reaction, since the pH in the system was lowered, a 3N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. Addition from the start of the addition of the aqueous sodium hydroxide solution (that is, from the start of the oxidation reaction to decrease the pH), when the decrease in pH stops and the addition of the aqueous sodium hydroxide solution ends The reaction time was defined as the time until completion (that is, until the time when the oxidation reaction was finished and no pH decrease was observed). The pulp aqueous dispersion after the reaction was filtered through a glass filter and washed thoroughly with water to obtain an oxidized pulp having an amount of carboxyl groups per glucose unit of 1.60 mmol / g.

<Process (2): Defibration of oxidized pulp>
When a slurry of 500 mL of oxidized pulp having a concentration of 1% (w / v) was treated five times with an ultrahigh pressure homogenizer (20 ° C., 140 MPa), an oxidation with a length weighted average fiber length of 290 nm and a length weighted average fiber diameter of 2.9 nm was performed. A transparent and low-viscosity oxidized cellulose nanofiber dispersion having a transparency of 99.4% and a B-type viscosity of 940 mPa · s in which cellulose nanofibers were dispersed was obtained.

<Manufacture of master batch>
A rubber component obtained by mixing 325 g of a 1% solid concentration aqueous dispersion of oxidized cellulose nanofibers obtained in step (2) and 100 g of natural rubber latex (trade name: HA latex, Restex, solid content concentration 65%). And the weight ratio of the modified cellulose nanofibers was 100: 5, and the mixture was stirred for 60 minutes with a TK homomixer (8000 rpm). This aqueous suspension was dried in a heating oven at 70 ° C. for 10 hours to obtain a master batch.

To 100 g of this master batch, add 3.5 g of sulfur, 0.7 g of vulcanization accelerator (BBS, Nt-butyl-2-benzothiazolesulfenamide), 6 g of zinc oxide, and 0.5 g of stearic acid. A roll (manufactured by Kansai Roll Co., Ltd.) was used and kneaded at 30 ° C. for 10 minutes to obtain a sheet of an unvulcanized rubber composition.

This sheet was sandwiched between molds and press vulcanized at 150 ° C. for 10 minutes to obtain a vulcanized rubber composition sheet having a thickness of 2 mm. This was cut into a test piece of a predetermined shape, and the rupture strength was measured according to JIS K6251 “vulcanized rubber and thermoplastic rubber—how to obtain tensile properties”, indicating the tensile strength which is one of the reinforcing properties. . The larger this value, the better the vulcanized rubber composition is reinforced and the better the mechanical strength of the rubber.

[Example 2]
Wood B (3 years old Eucalyptus maldrensis) was used. Pulp obtained by pulping the wood chips under the same conditions as the above specific pulping conditions (long fiber ratio 17.6%, short fiber ratio 9.6%, pulp viscosity 8.8 mPa · s, carboxyl A cellulose nanofiber dispersion was obtained in the same manner as in Example 1 except that the amount of the group and the like was 1.64 mmol / g (manufactured by Nippon Paper Industries Co., Ltd.). As a result, transparent and low-viscosity oxidized cellulose nanos having a transparency of 99.1% and a B-type viscosity of 1250 mPa · s in which oxidized cellulose nanofibers having a length-weighted average fiber length of 350 nm and a length-weighted average fiber diameter of 3.7 nm were dispersed. A fiber dispersion was obtained. Using this oxidized cellulose nanofiber dispersion, a master batch was prepared in the same manner as in Example 1, and then a vulcanized rubber composition sheet was prepared, and then the breaking strength was measured.

[Example 3]
Wood C (3-year-old acacia) was used. Pulp obtained by pulping the wood chips under the same conditions as the above specific pulping conditions (long fiber ratio 10.1%, short fiber ratio 8.1%, pulp viscosity 5.0 mPa · s, carboxyl A cellulose nanofiber dispersion was obtained in the same manner as in Example 1 except that the amount of the group and the like was 1.55 mmol / g (manufactured by Nippon Paper Industries Co., Ltd.). As a result, transparent and low-viscosity oxidized cellulose nanos having a transparency of 98.7% and a B-type viscosity of 1300 mPa · s in which oxidized cellulose nanofibers having a length-weighted average fiber length of 400 nm and a length-weighted average fiber diameter of 4.0 nm were dispersed. A fiber dispersion was obtained. Using this oxidized cellulose nanofiber dispersion, a master batch was prepared in the same manner as in Example 1, and then a vulcanized rubber composition sheet was prepared, and then the breaking strength was measured.

[Example 4]
Similar to Example 1, bleached unbeaten kraft pulp (whiteness 85%) (long fiber ratio 8.8%, short fiber ratio 5.5%, pulp viscosity 4.6 mPa · s) (Nippon Paper Industries Co., Ltd.) Prepared).

In a stirrer capable of mixing pulp, the above bleached unbeaten kraft pulp is 200 g in terms of dry mass and sodium hydroxide is 111 g in dry mass (2.25 times in terms of mol per anhydroglucose residue of the starting material) In addition, 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 (as an active ingredient, 1.5 times in terms of 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 0.26 per glucose unit. This was made into 1% solids with water, and treated with a high-pressure homogenizer at 20 ° C. and a pressure of 150 MPa for 5 times to obtain a carboxymethyl cellulose cellulose having a length weighted average fiber length of 470 nm and a length weighted average fiber diameter of 5.1 nm. A low-viscosity carboxymethylated cellulose nanofiber dispersion having a transparency of 49.6% and a B-type viscosity of 1500 mPa · s was obtained. Using this carboxymethylated cellulose nanofiber dispersion, a master batch was prepared in the same manner as in Example 1, and then a vulcanized rubber composition sheet was prepared, and then the breaking strength was measured.

[Comparative Example 1]
Wood D (8-year-old hardwood mixed material) was used. Pulp obtained by pulping the wood chip under the same conditions as the above specific pulping conditions (long fiber ratio 28.6%, short fiber ratio 7.1%, pulp viscosity 14.5 mPa · s, carboxyl A cellulose nanofiber dispersion was obtained in the same manner as in Example 1 except that the amount of the group and the like was 1.30 mmol / g, manufactured by Nippon Paper Industries Co., Ltd. As a result, oxycellulose nanofibers having a length-weighted average fiber length of 560 nm and a length-weighted average fiber diameter of 5.5 nm were dispersed, the transparency was 78.2%, the B-type viscosity was 1500 mPa · s, the transparency was low, and the viscosity was high. An oxidized cellulose nanofiber dispersion was obtained. Using this oxidized cellulose nanofiber dispersion, a master batch was prepared in the same manner as in Example 1, and then a vulcanized rubber composition sheet was prepared, and then the breaking strength was measured.

Table 1 shows the results of the examples and comparative examples. It can be seen that the breaking strengths of the examples are higher than those of the comparative examples and have excellent strength.

Claims (8)

1. (1): 1.00 mm measured according to ISO 16065-2 when pulped under kraft pulp production conditions of 15% active alkali addition, sulfidity 25%, liquid ratio 2.5 L / kg, H-factor 830 A step of preparing a pulp made from wood from which a pulp having a fiber length distribution in which the ratio of the above fiber length components is 20% or less is obtained;
   (2): a step of defibrating the pulp to obtain a cellulose nanofiber having a length weighted average fiber length of 500 nm or less and a length weighted average fiber diameter of 100 nm or less; and (3): the cellulose nanofiber and rubber. Mixing the ingredients,
   A method for producing a masterbatch including
2. 2. The wood according to claim 1, wherein when the wood is pulped under the kraft pulp production conditions, a pulp having a fiber length component of 0.20 mm or less in a fiber length distribution of 20% or less is obtained. The manufacturing method as described.
3. The manufacturing method according to claim 1 or 2, comprising a step of anion-modifying the pulp after the step (1) and before the step (2).
4. The cellulose nanofiber is an oxidized cellulose nanofiber,
   The production method according to claim 3, wherein the amount of carboxyl groups and the like is 0.1 to 3.0 mmol / g based on the absolute dry weight of the cellulose nanofiber.
5. The cellulose nanofiber is a carboxymethylated cellulose nanofiber,
   The production method according to claim 3, wherein the cellulose nanofibers have a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50.
6. A master batch produced by the production method according to any one of claims 1 to 5.
7. Production of a rubber composition comprising a step of producing a master batch by the production method according to any one of claims 1 to 5, and a step of kneading the obtained master batch and a rubber component to obtain a rubber composition. Method.
8. A rubber composition produced by the production method according to claim 7.

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