WO2019230719A1

WO2019230719A1 - Master batch containing carboxymethylated cellulose nanofibers and method for producing same

Info

Publication number: WO2019230719A1
Application number: PCT/JP2019/021087
Authority: WO
Inventors: 裕亮多田; 井上　一彦; 丈史中谷; 玲子大島; 貴史川崎; 俊則藤本; 隼人加藤; 喜威山田; 康太郎伊藤; 芽衣高木
Original assignee: 日本製紙株式会社
Priority date: 2018-05-29
Filing date: 2019-05-28
Publication date: 2019-12-05
Also published as: JPWO2019230719A1

Abstract

A master batch which contains a rubber component and carboxymethylated cellulose nanofibers; and a method for producing this master batch. The carboxymethylated cellulose nanofibers have a crystallinity of cellulose type I of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and a light transmittance at the wavelength of 660 nm of 60% or more if measured in the form of an aqueous dispersion that has a solid content of 1% (w/v).

Description

Carboxymethylated cellulose nanofiber-containing masterbatch and method for producing the same

The present invention relates to a carboxymethylated cellulose nanofiber-containing masterbatch. Specifically, the present invention relates to a masterbatch containing carboxymethylated cellulose nanofibers having a specific range of carboxymethyl substitution degree and a crystallinity degree of cellulose type I and exhibiting high transparency when made into an aqueous dispersion, and a method for producing the same. .

It is known that a rubber composition produced by a masterbatch containing a rubber component and cellulosic fibers has excellent mechanical strength. For example, in Patent Document 1, a dispersion obtained by fibrillating short fibers having an average fiber diameter of less than 0.5 μm in water and a rubber latex are mixed and dried to uniformly distribute the short fibers in the rubber. It is described that a master batch of dispersed rubber / short fibers can be obtained, and that a rubber composition having an excellent balance between rubber reinforcement and fatigue resistance can be produced from this master batch.

JP 2006-206864 A

However, in order to apply a conventional rubber composition containing a rubber component and cellulosic fibers to various fields, it is necessary to further improve the strength of the rubber composition.

Therefore, an object of the present invention is to provide a method for producing a rubber composition having a good strength and produced by a masterbatch containing a rubber component and cellulosic fibers.

As a result of intensive studies on the above object, the present inventors have conducted mercerization (cellulose alkali treatment) in a carboxymethylation of cellulose in a solvent mainly composed of water, and then carboxymethylation. (Also referred to as etherification) in a mixed solvent of water and an organic solvent, so that a conventional aqueous medium method (a method in which both mercerization and carboxymethylation are carried out using water as a solvent) or a solvent method (Mercel). Compared with carboxymethylated cellulose obtained by a method in which both glycation and carboxymethylation are carried out in a solvent mainly composed of an organic solvent, when defibrated, a cellulose nanofiber dispersion having a higher transparency than before is obtained. It has been found that the carboxymethylating agent can be produced economically with a high effective utilization rate. Moreover, it discovered that the rubber composition with favorable intensity | strength can be manufactured using this carboxymethylated cellulose nanofiber and the masterbatch containing a rubber component.

The present invention includes, but is not limited to, the following.
[1] A method for producing a masterbatch,
Mixing the rubber component and carboxymethylated cellulose nanofibers,
The carboxymethylated cellulose nanofiber is an aqueous dispersion having a cellulose I type crystallinity of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and a solid content of 1% (w / v). The said manufacturing method whose transmittance | permeability of the light of the wavelength of 660nm at the time is 60% or more.
[2] A mercerization reaction is performed in a solvent mainly containing water, and then a carboxymethylation cellulose is produced by performing a carboxymethylation reaction in a mixed solvent of water and an organic solvent. The production method according to [1], further comprising producing carboxymethylated cellulose nanofibers by defibrating carboxymethylated cellulose.
[3] The production method according to [2], wherein the solvent mainly containing water is a solvent containing more than 50% by mass of water.
[4] The production method according to any one of [1] to [3], wherein the amount of foreign matter contained in the carboxymethylated cellulose nanofiber is 20% or less.
[5] A rubber composition comprising: producing a masterbatch by the method according to any one of [1] to [4]; and producing a rubber composition using the obtained masterbatch. Manufacturing method [6] A masterbatch containing carboxymethylated cellulose nanofibers,
The carboxymethylated cellulose nanofiber is an aqueous dispersion having a cellulose I type crystallinity of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and a solid content of 1% (w / v). A master batch in which the transmittance of light having a wavelength of 660 nm is 60% or more.
[7] The master batch according to [6], wherein the amount of foreign matter in the carboxymethylated cellulose nanofiber is 20% or less.
[8] A rubber composition produced using the master batch according to [6] or [7].
[9] Light having a wavelength of 660 nm when the cellulose I type has a crystallinity of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and an aqueous dispersion having a solid content of 1% (w / v). A filler for rubber containing carboxymethylated cellulose nanofibers having a transmittance of 60% or more.

According to the present invention, it is possible to provide a method for producing a rubber composition containing a rubber component and modified cellulose fibers and having good strength.

<Carboxymethylated cellulose nanofiber>
The wavelength of the present invention when an aqueous dispersion having a carboxymethyl substitution degree of 0.50 or less and a cellulose I type crystallinity of 60% or more and a solid content of 1% (w / v) is used. The present invention relates to a masterbatch containing carboxymethylated cellulose nanofibers having a light transmittance of 660 nm of 60% or more. Carboxymethylated cellulose has a structure in which a part of hydroxyl groups in a glucose residue constituting cellulose is ether-bonded to a carboxymethyl group.

The carboxymethylated cellulose nanofibers are those obtained by converting carboxymethylated cellulose having the above structure into nanofibers having nanoscale fiber diameters. The carboxymethylated cellulose may be in the form of a salt such as a metal salt such as a sodium salt of carboxymethylated cellulose, and the nanofibers of carboxymethylated cellulose may be in the form of a salt.

The carboxymethylated cellulose nanofiber used in the present invention maintains at least a part of the fibrous shape even when dispersed in water. That is, when an aqueous dispersion of carboxymethyl cellulose nanofibers is observed with an electron microscope, a fibrous substance can be observed. Moreover, when the carboxymethylated cellulose nanofiber is measured by X-ray diffraction, the peak of the cellulose I-type crystal can be observed.

<Crystallinity of cellulose type I>
The crystallinity of cellulose in the carboxymethylated cellulose nanofiber used in the present invention is 60% or more, preferably 65% or more, for the crystalline I type. When the crystallinity of cellulose I type is as high as 60% or more, the ratio of cellulose that maintains the crystal structure without dissolving in the solvent is high, so that the strength can be improved when added to rubber or resin. Is obtained. The crystallinity of cellulose can be controlled by the concentration of mercerizing agent and the temperature during processing, as well as the degree of carboxymethylation. In mercerization and carboxymethylation, a high concentration of alkali is used, so cellulose type I crystals are easily converted to type II. However, the amount of modification can be reduced by adjusting the amount of alkali (mercellizing agent) used. The desired crystallinity can be maintained by adjusting the degree. The upper limit of the crystallinity of cellulose type I is not particularly limited. In reality, it is considered that the upper limit is about 90%.

A method for measuring the crystallinity of cellulose type I of carboxymethylated cellulose nanofibers is as follows:
The sample is placed on a glass cell and measured using an X-ray diffractometer (LabX XRD-6000, manufactured by Shimadzu Corporation). The degree of crystallinity is calculated using a method such as Segal, and the diffraction intensity of 2θ = 10 ° to 30 ° in the X-ray diffraction diagram is used as a baseline, and the diffraction intensity of the 002 plane of 2θ = 22.6 ° and 2θ = It is calculated by the following formula from the diffraction intensity of the amorphous part at 18.5 °.
Xc = (I002c−Ia) / I002c × 100
Xc = Crystallinity of cellulose type I (%)
I002c: 2θ = 22.6 °, diffraction intensity of 002 plane Ia: 2θ = 18.5 °, diffraction intensity of amorphous part.

The ratio of the type I crystal in the carboxymethylated cellulose nanofiber is usually the same as that in the carboxymethylated cellulose before the nanofiber.

<Carboxymethyl substitution degree>
The carboxymethylated cellulose nanofibers used in the present invention have a carboxymethyl substitution degree per cellulose anhydroglucose unit of 0.50 or less. If the degree of carboxymethyl substitution exceeds 0.50, it will be dissolved in water and the fiber shape cannot be maintained. In consideration of operability, the degree of substitution is preferably 0.02 to 0.50, more preferably 0.05 to 0.50, still more preferably 0.10 to 0.40, More preferably, it is 0.20 to 0.40. By introducing a carboxymethyl group into cellulose, cellulose repels each other, so that it can be fibrillated into nanofibers, but the degree of carboxymethyl substitution per anhydroglucose unit is 0.02 If it is small, defibration becomes insufficient and cellulose nanofibers with high transparency may not be obtained. In the conventional aqueous medium method, it is difficult to obtain nanofibers of carboxymethylated cellulose having a cellulose I type crystallinity of 60% or more when the degree of carboxymethyl substitution is in the range of 0.20 to 0.40. However, the present inventors, for example, by the method described later, carboxymethylation in which the degree of carboxymethyl substitution is in the range of 0.20 to 0.40 and the degree of crystallinity of cellulose type I is 60% or more. It has been found that cellulose nanofibers can be produced. The degree of carboxymethyl substitution can be adjusted by controlling the amount of carboxymethylating agent to be reacted, the amount of mercerizing agent, the composition ratio of water and organic solvent, and the like.

In the present invention, an anhydroglucose unit means an individual anhydroglucose (glucose residue) constituting cellulose. The degree of carboxymethyl substitution (also referred to as etherification degree) is the proportion of hydroxyl groups in the glucose residues constituting cellulose that are substituted with carboxymethyl ether groups (carboxymethyl per glucose residue). The number of ether groups). The degree of carboxymethyl substitution may be abbreviated as DS.

The method for measuring the degree of carboxymethyl substitution is as follows:
About 2.0 g of sample is precisely weighed and placed in a 300 mL conical flask with a stopper. Add 100 mL of methanol nitric acid (a solution obtained by adding 100 mL of special concentrated nitric acid to 1000 mL of methanol) and shake for 3 hours to convert carboxymethylated cellulose nanofiber salt (CMC) to H-CMC (hydrogen-type carboxymethylated cellulose nanofiber). Convert to Accurately weigh 1.5-2.0 g of the absolutely dry H-CMC and place it in a 300 mL conical flask with a stopper. Wet H-CMC with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. Using phenolphthalein as an indicator, excess NaOH is back titrated with 0.1N—H ₂ SO ₄ , and the degree of carboxymethyl substitution (DS value) is calculated by the following formula.
A = [(100 × F′−0.1N—H ₂ SO ₄ (mL) × F) × 0.1] / (absolute dry mass of H-CMC (g))
Carboxymethyl substitution = 0.162 × A / (1−0.058 × A)
F ′: Factor of 0.1N—H ₂ SO ₄ F: Factor of 0.1N—NaOH

The degree of carboxymethyl substitution in the carboxymethylated cellulose nanofiber is usually the same as the degree of carboxymethyl substitution in the carboxymethylated cellulose before the nanofiber.

<Transparency in water dispersion>
The nanofibers of carboxymethylated cellulose used in the present invention have a characteristic of exhibiting high transparency when water is used as a dispersion medium (water dispersion). Nanofibers with high transparency can be used as additives for applications where transparency is required, which is preferable. In addition, since nanofibers with high transparency are considered to have few unfibrillated cellulose fibers, it is thought that when they are contained in rubber, the occurrence frequency of cracks that cause a decrease in the strength of the rubber can be reduced. It is done. In this specification, transparency refers to the transmittance of light having a wavelength of 660 nm when carboxymethylated cellulose nanofibers are made into an aqueous dispersion having a solid content of 1% (w / v). A method for measuring the transparency of carboxymethylated cellulose nanofibers is as follows:
A cellulose nanofiber dispersion (solid content 1% (w / v), dispersion medium: water) was prepared, and a UV-VIS spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) was used to form a square cell with an optical path length of 10 mm. Used to measure the transmittance of light at 660 nm.

The transparency of the carboxymethylated cellulose nanofiber of the present invention is 60% or more. More preferably, it is 60 to 100%, still more preferably 70 to 100%, still more preferably 80 to 100%, and further preferably 90 to 100%. Such cellulose nanofibers can be optimally used for applications requiring transparency. It also reduces the frequency of cracking in the rubber and contributes to improving the strength of the rubber. The above-mentioned cellulose I type crystallinity and carboxymethyl substitution degree, and such transparency, carboxymethylated cellulose nanofibers can be produced, for example, by the method described later.

<Fiber diameter, aspect ratio>
The carboxymethylated cellulose nanofiber used in the present invention has a nanoscale fiber diameter. The average fiber diameter is preferably 1 nm to 500 nm, more preferably 1 nm to 150 nm, further preferably 1 nm to 20 nm, more preferably 3 nm to 10 nm, and further preferably 3 nm to 6 nm.

The aspect ratio of the carboxymethylated cellulose nanofiber is not particularly limited, but is preferably 350 or less, more preferably 300 or less, further preferably 200 or less, and further preferably 120 or less. 100 or less, more preferably 80 or less. When the aspect ratio is 350 or less, the fibers are not excessively long, the entanglement of the fibers is reduced, the generation of lump of cellulose nanofibers can be reduced, and it can be used as an additive. Suitable. Further, since the fluidity is high, it is easy to use even at a high concentration, and there is an advantage that it is easy to use even in applications requiring a high solid content. Although the minimum of an aspect-ratio is not specifically limited, Preferably it is 25 or more, More preferably, it is 30 or more. When the aspect ratio is 25 or more, an effect of improving thixotropy can be obtained from the fibrous shape. The aspect ratio of the carboxymethylated cellulose nanofiber can be controlled by the mixing ratio of the solvent and water at the time of carboxymethylation, the chemical addition amount, and the degree of carboxymethylation, and can be produced, for example, by the production method described later. .

The average fiber diameter and average fiber length of nanofibers of carboxymethylated cellulose are determined using an atomic force microscope (AFM) when the diameter is 20 nm or less, and a field emission scanning electron microscope (FE-SEM) when the diameter is 20 nm or more. Then, it is possible to measure 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.

<Viscosity and thixotropy in aqueous dispersion>
The nanofibers of carboxymethylated cellulose used in the present invention preferably exhibit high thixotropy when water is used as a dispersion medium (water dispersion). The thixotropy (thixotropy) refers to a property in which the viscosity gradually decreases by receiving a shearing stress, and the viscosity gradually increases when resting. In the present specification, a value obtained by dividing the viscosity measured at a low shear rate by the viscosity measured at a high shear rate is used as an index of thixotropy. Specifically, viscosity and thixotropy are measured by the following methods:
A cellulose nanofiber dispersion (solid content: 1% (w / v), dispersion medium: water) was prepared, allowed to stand at 25 ° C. for 16 hours, then stirred at 3000 rpm for 1 minute using a stirrer, and a sample for viscosity measurement And About a part of obtained sample for viscosity measurement, using a B-type viscometer (made by Toki Sangyo Co., Ltd.) The viscosity after 3 minutes is measured at 4 rotors / rotation speed 6 rpm. Further, using another part of the sample for measuring viscosity (those whose viscosity has not been measured yet), using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.), The viscosity after 3 minutes is measured at 4 rotors / 60 rpm. The viscosity is measured according to the method of JIS-Z-8803. A value obtained by dividing the obtained viscosity at 6 rpm by the viscosity at 60 rpm is used as an index of thixotropy.

The carboxymethylated cellulose nanofiber used in the present invention is an aqueous dispersion having a solid content of 1% (w / v) at 25 ° C. and 6 rpm when the aqueous dispersion has a solid content of 1% (w / v). The value divided by the viscosity at 25 ° C. and 60 rpm (also simply referred to as “the value obtained by dividing the viscosity at 6 rpm by the viscosity at 60 rpm”) is preferably 6.0 or more. The higher this value, the greater the change in viscosity due to the difference in shear stress, and the higher the thixotropy. Cellulose nanofibers with high thixotropy are suitable for use as a shape-retaining agent or a viscosity modifier. Although the upper limit of the value obtained by dividing the viscosity at 6 rpm by the viscosity at 60 rpm is not limited, it is considered that the upper limit is actually about 15.0.

The viscosity at 6 rpm of the carboxymethyl cellulose nanofiber (aqueous dispersion with a solid content of 1% (w / v), 25 ° C.) is preferably 15000 mPa · s or more, and more preferably 20000 mPa · s or more. . The higher the viscosity at a low shear rate (6 rpm), the higher the thixotropy can be. The upper limit of the viscosity at 6 rpm is not particularly limited, but in reality, it is considered to be about 50000 mPa · s.

The viscosity at 60 rpm of the carboxymethylated cellulose nanofiber (aqueous dispersion with a solid content of 1% (w / v), 25 ° C.) is preferably about 1500 to 8400 mPa · s, and about 2000 to 7000 mPa · s. More preferably, it is about 2500 to 7000 mPa · s, more preferably about 3000 to 7000 mPa · s.

<Measurement of amount of foreign matter in cellulose nanofiber>
In cellulose nanofibers, undefibrated cellulose fibers may remain as foreign substances. In general, it is considered that the strength against breakage, abrasion, tearing, etc. of rubber can be improved by suppressing the occurrence and growth of rubber cracks. If a foreign substance having a size of several tens of μm or more is present in the rubber, it can be a starting point of cracking. Therefore, the amount of the foreign substance in the cellulose nanofiber is preferably small.

In the present invention, the amount of foreign matter in the carboxymethylated cellulose nanofiber is measured using the following method. In this method, fine cellulose nanofibers are not detected through two orthogonal polarizing plates because they do not block the light that has passed through the polarizing plates, whereas foreign substances such as undefibrated fibers cause irregular reflection, so It utilizes the property of being specifically detected through the two polarizing plates:
Add 1.0 g of polyethylene glycol (PEG, molecular weight 600) to an aqueous suspension containing 0.5 g of cellulose nanofibers, and stir for 2 hours using a stirrer. Foaming was performed to prepare a cellulose nanofiber (CNF) dispersion.

A rubber frame was placed on a polyethylene terephthalate (PET) film and fixed firmly, poured in pure water, and after confirming that it did not leak, the water inside was discarded. Thereby, the dust adhering to the PET film was also removed. The CNF dispersion was poured into a rubber frame on the dried PET film so as not to be bubbled, and was allowed to stand at 40 ° C. overnight. After confirming that the drying was sufficient, the CNF film was taken out. The obtained CNF film had a size of 18 cm × 18 cm and a thickness of 0.1 mm.

Next, a plate-shaped LED light was installed in the dark curtain, and the CNF film as the sample was sandwiched between the two polarizing plates on the LED light while removing dust with an air duster. . These two polarizing plates were arranged in a state in which their polarization axes were orthogonal to each other. In addition, the said CNF film was taken as the magnitude | size of 18 cm x 18 cm, and it was set as the magnitude | size which can cover the whole CNF film also about two polarizing plates.

Then, light was emitted from the lower LED light, and a transmission image was taken from above with a digital camera so that the entire film was in view.

The presence / absence of foreign matter in the CNF dispersion was confirmed based on the obtained photographed image, and the area ratio of the foreign matter was calculated by image analysis of the obtained photographed image to obtain the amount of foreign matter. For image analysis, image analysis software ImageJ provided by Wayne Rasband was used.

The amount of foreign matter in the cellulose nanofiber of the present invention is preferably 20% or less. More preferably, it is 15% or less, More preferably, it is 10% or less. Thereby, a rubber composition excellent in mechanical strength is obtained.

The carboxymethylated cellulose nanofiber having such a degree of carboxymethyl substitution, viscosity and thixotropy, and the amount of foreign matter can be produced, for example, by the method described later.

<Hydrophobicization>
The carboxymethylated cellulose nanofibers used in the present invention may be those obtained by appropriately modifying a carboxyl group (—COOH) derived from a carboxymethyl group within a range not inhibiting the effects of the present invention. As such modification, for example, an amine compound or phosphorus compound having an alkyl group, an aryl group, an aralkyl group or the like is bonded to a carboxyl group to hydrophobize the carboxymethylated cellulose nanofiber.

<Method for producing carboxymethylated cellulose nanofiber>
Cellulose I type crystallinity of 60% or more, carboxymethyl substitution degree of 0.50 or less, and light transmittance at a wavelength of 660 nm when an aqueous dispersion having a solid content of 1% (w / v) is obtained. Nanofibers of carboxymethylated cellulose having a ratio of 60% or more are not limited to this, but can be produced by defibrating carboxymethylated cellulose produced by the following method.

In general, carboxymethylated cellulose is obtained by treating cellulose with an alkali (mercelization), and then reacting the obtained mercerized cellulose (also referred to as alkali cellulose) with a carboxymethylating agent (also referred to as an etherifying agent). Can be manufactured. Carboxymethylated cellulose capable of forming nanofibers having the above characteristics of the present invention is subjected to mercerization (alkali treatment of cellulose) in a solvent mainly containing water, and then carboxymethylation (also referred to as etherification). .) In a mixed solvent of water and an organic solvent. The carboxymethylated cellulose thus obtained can be obtained by using a conventional aqueous medium method (a method in which both mercerization and carboxymethylation are performed using water as a solvent) and a solvent method (in which both mercerization and carboxymethylation are performed using an organic solvent). Compared to the carboxymethylated cellulose obtained in the main solvent), the cellulose nanofiber dispersion is highly transparent when defibrated while having a high effective utilization rate of the carboxymethylating agent. Can be converted.

<Cellulose>
In the present invention, cellulose means a polysaccharide having a structure in which D-glucopyranose (simply referred to as “glucose residue” or “anhydroglucose”) is linked by β-1,4 bonds. Cellulose is generally classified into natural cellulose, regenerated cellulose, fine cellulose, microcrystalline cellulose excluding non-crystalline regions, and the like, based on the origin, production method, and the like. In the present invention, any of these celluloses can be used as a raw material for mercerized cellulose. However, in order to maintain a cellulose I type crystallinity of 60% or more in carboxymethylated cellulose nanofibers, cellulose I It is preferable to use cellulose having a high mold crystallinity as a raw material. The cellulose I type crystallinity of the raw material cellulose is preferably 70% or more, and more preferably 80% or more. The method for measuring the crystallinity of cellulose type I is as described above.

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, and the like. 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. Moreover, the manufacturing method of a bleached pulp or an unbleached pulp is not specifically limited, either, a mechanical method, a chemical method, or the method which combined two in the middle may be sufficient. Examples of bleached or unbleached pulp classified according to the production method include mechanical pulp (thermomechanical pulp (TMP), groundwood pulp), chemical pulp (conifer unbleached sulfite pulp (NUSP), conifer bleach sulfite pulp (NBSP). ) And the like, and softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), and kraft pulp such as hardwood bleached kraft pulp (LBKP)). Furthermore, dissolving pulp may be used in addition to papermaking pulp. Dissolving pulp is chemically refined pulp, which is mainly used by dissolving in chemicals, and is a main raw material for artificial fibers, cellophane and the like.

Examples of the regenerated cellulose include those obtained by dissolving cellulose in some solvent such as a copper ammonia solution, a cellulose xanthate solution, and a morpholine derivative and spinning again.

The fine cellulose is obtained by depolymerizing a cellulose-based material such as the above natural cellulose or regenerated cellulose (for example, acid hydrolysis, alkali hydrolysis, enzyme decomposition, explosion treatment, vibration ball mill treatment, etc.). And those obtained by mechanically treating the cellulose-based material.

<Mercelization>
The cellulose described above is used as a raw material, and mercerized cellulose (also referred to as alkali cellulose) is obtained by adding a mercerizing agent (alkali). According to the method described in this specification, water is mainly used as a solvent in this mercerization reaction, and a mixed solvent of an organic solvent and water is used in the next carboxymethylation, so that Carboxymethylated cellulose that can be made into a cellulose nanofiber dispersion having a very high transparency can be obtained economically.

The main use of water as a solvent (a solvent mainly containing water) refers to a solvent containing water in a proportion higher than 50% by mass. Water in the solvent mainly composed of water is preferably 55% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, More preferably, it is 90 mass% or more, More preferably, it is 95 mass% or more. Particularly preferably, the solvent mainly composed of water is 100% by mass of water (that is, water). The greater the proportion of water during mercerization, the greater the transparency of the cellulose nanofiber dispersion obtained by defibrating carboxymethylated cellulose. Examples of the solvent other than water (used by mixing with water) in the solvent mainly containing water include organic solvents used as a solvent in the subsequent carboxymethylation. For example, alcohols such as methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol and tertiary butanol, ketones such as acetone, diethyl ketone and methyl ethyl ketone, and dioxane, diethyl ether, benzene and dichloromethane These can be used alone or a mixture of two or more thereof can be added to water in an amount of less than 50% by mass and used as a solvent for mercerization. The organic solvent in the solvent mainly composed of water is preferably 45% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and further preferably 20% by mass or less. More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less, More preferably, it is 0 mass%.

Examples of mercerizing agents include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and any one of these or a combination of two or more thereof can be used. The mercerizing agent is not limited to this, but these alkali metal hydroxides are added to the reactor as an aqueous solution of, for example, 1 to 60% by mass, preferably 2 to 45% by mass, more preferably 3 to 25% by mass. Can be added.

The amount of the mercerizing agent used is an amount capable of maintaining a cellulose I type crystallinity of 60% or more in carboxymethylated cellulose. In one embodiment, 0.1 mol or more and 2 mol per 100 g of cellulose (absolutely dry). 0.5 mol or less is preferable, 0.3 mol or more and 2.0 mol or less is more preferable, and 0.4 mol or more and 1.5 mol or less is more preferable.

The amount of the solvent mainly composed of water at the time of mercerization is preferably 1.5 to 20 times by mass and more preferably 2 to 10 times by mass with respect to the cellulose raw material. By using such an amount, the raw materials can be easily stirred and mixed, and the raw materials can be uniformly reacted.

In the mercerization treatment, the bottoming material (cellulose) and a solvent mainly composed of water are mixed, and the temperature of the reactor is adjusted to 0 to 70 ° C., preferably 10 to 60 ° C., more preferably 10 to 40 ° C. Then, an aqueous solution of mercerizing agent is added and stirred for 15 minutes to 8 hours, preferably 30 minutes to 7 hours, more preferably 30 minutes to 3 hours. Thereby, mercerized cellulose (alkali cellulose) is obtained.

The pH during mercerization is preferably 9 or more, whereby the mercerization reaction can proceed. The pH is more preferably 11 or more, still more preferably 12 or more, and may be 13 or more. The upper limit of pH is not particularly limited.

The soot mercerization can be performed using a reactor capable of mixing and stirring the above components while controlling the temperature, and various reactors conventionally used in mercerization reactions can be used. For example, a batch type stirring apparatus in which two shafts are stirred and the above components are mixed is preferable from the viewpoints of both uniform mixing and productivity.

<Carboxymethylation>
Carboxymethylated cellulose is obtained by adding a carboxymethylating agent (also referred to as an etherifying agent) to mercerized cellulose. According to the method described in this specification, water is mainly used as a solvent for mercerization, and a mixed solvent of water and an organic solvent is used for carboxymethylation. Carboxymethylated cellulose that can be made into a cellulose nanofiber dispersion having a very high transparency can be obtained economically.

Examples of the carboxymethylating agent include monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate, isopropyl monochloroacetate and the like. Of these, monochloroacetic acid or sodium monochloroacetate is preferable from the viewpoint of easy availability of raw materials.

The amount of the carboxymethylating agent used is an amount that can maintain a crystallinity of 60% or more of cellulose type I, and an amount that provides a carboxymethyl substitution degree of 0.50 or less. Although not particularly limited, in one embodiment, it is preferably added in the range of 0.5 to 1.5 mol per anhydroglucose unit of cellulose. The lower limit of the above range is more preferably 0.6 mol or more, still more preferably 0.7 mol or more, and the upper limit is more preferably 1.3 mol or less, still more preferably 1.1 mol or less. The carboxymethylating agent is not limited to this, but for example, it can be added to the reactor as an aqueous solution of 5 to 80% by mass, more preferably 30 to 60% by mass. You can also.

The molar ratio of mercerizing agent to carboxymethylating agent (mercelling agent / carboxymethylating agent) is generally 0.9 to 2.45 when monochloroacetic acid or sodium monochloroacetate is used as the carboxymethylating agent. Adopted. The reason is that if it is less than 0.9, the carboxymethylation reaction may be insufficient, and unreacted monochloroacetic acid or sodium monochloroacetate may remain, resulting in waste, and 2.45. If it exceeds 1, the side reaction between the excess mercerizing agent and monochloroacetic acid or sodium monochloroacetate may proceed to produce an alkali metal glycolate, which may be uneconomical.

In carboxymethylation, the effective utilization rate of the carboxymethylating agent is preferably 15% or more. More preferably, it is 20% or more, more preferably 25% or more, and particularly preferably 30% or more. The effective utilization rate of a carboxymethylating agent refers to the proportion of carboxymethyl groups introduced into cellulose among carboxymethyl groups in the carboxymethylating agent. By using a solvent mainly composed of water at the time of mercerization and using a mixed solvent of water and an organic solvent at the time of carboxymethylation, the effective utilization rate of the carboxymethylating agent is high (ie, the carboxymethylating agent). Carboxymethylated cellulose capable of obtaining a cellulose nanofiber dispersion having high transparency when defibrated can be produced economically without greatly increasing the use amount of. The upper limit of the effective utilization rate of the carboxymethylating agent is not particularly limited, but in reality, the upper limit is about 80%. The effective utilization rate of the carboxymethylating agent may be abbreviated as AM.

The calculation method of the effective utilization rate of the carboxymethylating agent is as follows:
AM = (DS × number of moles of cellulose) / number of moles of carboxymethylating agent DS: Degree of carboxymethyl substitution (measurement method is as described above)
Number of moles of cellulose: Pulp mass (dry mass when dried at 100 ° C. for 60 minutes) / 162
(162 is the molecular weight of cellulose per glucose unit).

The concentration of the cellulose raw material in the carboxymethylation reaction is not particularly limited, but is preferably 1 to 40% (w / v) from the viewpoint of increasing the effective utilization rate of the carboxymethylating agent.

Simultaneously with the addition of the carboxymethylating agent, or before or immediately after the addition of the carboxymethylating agent, an organic solvent or an aqueous solution of the organic solvent is appropriately added to the reactor, or water other than the water used in the mercerization process by reducing the pressure. The organic solvent is appropriately reduced to form a mixed solvent of water and the organic solvent, and the carboxymethylation reaction proceeds under the mixed solvent of the water and the organic solvent. The timing of addition or reduction of the organic solvent may be from the end of the mercerization reaction to immediately after the addition of the carboxymethylating agent, and is not particularly limited. For example, 30 minutes before and after adding the carboxymethylating agent Is preferred.

Examples of the organic solvent include alcohols such as methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol and tertiary butanol, ketones such as acetone, diethyl ketone and methyl ethyl ketone, and dioxane, diethyl ether, Benzene, dichloromethane, etc. can be mentioned, These alone or a mixture of two or more thereof can be added to water and used as a solvent for carboxymethylation. Of these, monohydric alcohols having 1 to 4 carbon atoms are preferred and monohydric alcohols having 1 to 3 carbon atoms are more preferred because of their excellent compatibility with water.

The ratio of the organic solvent in the mixed solvent in the carboxymethylation is preferably 20% by mass or more, more preferably 30% by mass or more, based on the sum of water and the organic solvent, It is more preferably 40% by mass or more, further preferably 45% by mass or more, and particularly preferably 50% by mass or more. As the proportion of the organic solvent is higher, an advantage that the transparency when the cellulose nanofiber dispersion is obtained becomes higher. The upper limit of the ratio of the organic solvent is not limited, and may be 99% by mass or less, for example. Considering the cost of the organic solvent to be added, it is preferably 90% by mass or less, more preferably 85% by mass or less, still more preferably 80% by mass or less, and further preferably 70% by mass or less.

The reaction medium at the time of carboxymethylation (a mixed solvent of water and an organic solvent, which does not contain cellulose) has a smaller proportion of water than the reaction medium at the time of mercerization (in other words, the proportion of the organic solvent is lower). Many). By satisfying this range, it becomes easy to increase the degree of carboxymethyl substitution while maintaining the crystallinity of the resulting carboxymethylated cellulose, and becomes a highly transparent cellulose nanofiber dispersion when fibrillated. Can be obtained more efficiently. In addition, when the reaction medium at the time of carboxymethylation is less than the reaction medium at the time of mercerization (the ratio of the organic solvent is large), when shifting from the mercerization reaction to the carboxymethylation reaction, There is also an advantage that a mixed solvent for the carboxymethylation reaction can be formed by a simple means of adding a desired amount of an organic solvent to the reaction system after completion of the mercerization reaction.

After forming a mixed solvent of water and an organic solvent and adding a carboxymethylating agent to mercerized cellulose, the temperature is preferably kept constant in the range of 10 to 40 ° C. for 15 minutes to 4 hours, preferably 15 Stir for about 1 to 1 hour. The mixing of the mercerized cellulose-containing liquid and the carboxymethylating agent is preferably performed in a plurality of times or by dropping in order to prevent the reaction mixture from becoming high temperature. After adding a carboxymethylating agent and stirring for a certain time, the temperature is raised if necessary, and the reaction temperature is set to 30 to 90 ° C, preferably 40 to 90 ° C, more preferably 60 to 80 ° C, and 30 minutes to The etherification (carboxymethylation) reaction is carried out for 10 hours, preferably 1 to 4 hours to obtain carboxymethylated cellulose.

In the carboxymethylation, the reactor used in the mercerization may be used as it is, or another reactor capable of mixing and stirring the above components while controlling the temperature may be used. .

After the reaction, the remaining alkali metal salt may be neutralized with a mineral acid or an organic acid. If necessary, by-product inorganic salts, organic acid salts, and the like may be removed by washing with water-containing methanol, dried, pulverized, and classified to obtain carboxymethylated cellulose or a salt thereof. When washing for removing by-products, the acid form may be linearized in advance, and the salt form may be restored after washing. Examples of the apparatus used in the dry pulverization include impact mills such as a hammer mill and a pin mill, medium mills such as a ball mill and a tower mill, and jet mills. Examples of the apparatus used in the wet pulverization include apparatuses such as a homogenizer, a mass collider, and a pearl mill.

<Disentanglement to nanofiber>
By defibrating the carboxymethylated cellulose obtained by the above method, it can be converted into cellulose nanofibers having nanoscale fiber diameters.

In the case of defibration, a dispersion of carboxymethylated cellulose obtained by the above method is prepared. The dispersion medium is preferably water from the viewpoint of ease of handling. The concentration of carboxymethylated cellulose in the dispersion during defibration is preferably 0.01 to 10% (w / v) in consideration of the efficiency of defibration and dispersion.

The apparatus used for defibrating carboxymethylated cellulose is not particularly limited, and apparatuses such as a high speed rotation type, a colloid mill type, a high pressure type, a roll mill type, and an ultrasonic type can be used. In defibration, it is preferable to apply a strong shearing force to the carboxymethylated cellulose dispersion. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 50 MPa or more to the dispersion and can apply a strong shearing force. The pressure is more preferably 100 MPa or more, and further preferably 140 MPa or more. Further, prior to defibration and dispersion treatment with a high-pressure homogenizer, if necessary, the dispersion may be pretreated using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. .

High-pressure homogenizer is emulsified and dispersed by total energy such as collision between particles and shear force due to pressure difference by pressurizing (high pressure) the fluid with a pump and ejecting it from a very delicate gap provided in the flow path. , A device that performs de-pulverization, pulverization, and ultra-miniaturization.

The reason why high-transparency cellulose nanofibers can be obtained by the above method is not clear, but according to the above-mentioned method, it is possible to maintain a relatively high degree of crystallinity of cellulose type I. The present inventors have confirmed that the fibrous shape of carboxymethylated cellulose can be maintained even if it is relatively high. The ability to increase the degree of carboxymethyl substitution while maintaining the fibrous shape (that is, introducing more carboxymethyl groups) is thought to lead to improved defibration of carboxymethylated cellulose, which is highly transparent It is speculated that this is one of the reasons why a nanofiber dispersion is obtained. However, it is not limited to this.

<Rubber component>
The rubber component is a raw material of rubber and refers to 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, NBR, NR, SBR, chloroprene rubber, and BR are preferable.

The rubber component may be used alone or in combination with two or more carboxymethylated cellulose nanofibers.

<Mixing process>
The manufacturing method of a masterbatch includes mixing a rubber component and carboxymethylated cellulose nanofibers. The form of the rubber component and the carboxymethylated cellulose nanofiber during mixing is not particularly limited. For example, the form which mixes the dispersion liquid of a cellulose nanofiber, the dry solid substance of this dispersion liquid, or the wet solid substance of the said dispersion liquid, and a rubber component (solid substance) or its dispersion liquid is mentioned. Among these, the form which mixes the dispersion liquid of a cellulose nanofiber and the dispersion liquid of a rubber component is preferable.

The mixing ratio of the rubber component and the cellulose nanofiber is not particularly limited, but is preferably as follows.

The content of carboxymethylated cellulose nanofibers is preferably 0.5 parts by mass or more, more preferably 1 part 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 25 parts by mass or less, preferably 20 parts by mass or less, and more preferably 15 parts by mass or less. Thereby, the workability in the manufacturing process can be maintained. Therefore, 0.5 to 25 parts by mass is preferable, 1 to 20 parts by mass is more preferable, and 3 to 15 parts by mass is further preferable.

The present invention provides a master batch by mixing carboxymethyl cellulose nanofibers having the above-mentioned specific degree of carboxymethyl substitution, cellulose type I crystallinity, and transparency with a rubber component. It has been found that a vulcanized rubber composition obtained from a batch has high strength. The carboxymethylated cellulose nanofiber having the above-described properties used in the present invention is useful as a filler (rubber filler) in the finally obtained rubber product.

<Coagulation process>
The carboxymethylated cellulose nanofiber and the rubber component may be mixed and then coagulated. In the coagulation step, it is preferable to use a polyvalent metal or an acid. Moreover, you may use a polyvalent metal and an acid together. The acid may be either an organic acid or an inorganic acid as long as it does not inhibit coagulation. Examples of the organic acid include formic acid and acetic acid, and examples of the inorganic acid include sulfuric acid, hydrochloric acid, and carbonic acid. What is necessary is just to select an acid suitably according to the polyvalent metal used together. One or a combination of two or more acids may be used.

When an acid is used, the addition timing of the acid is not particularly limited, and the acid may be added simultaneously with the polyvalent metal, or may be added before or after the addition of the polyvalent metal. The amount of the acid used is preferably such that the pH in the mixed solution is 3.0 to 6.0, more preferably the pH is 3.5 to 5.0.

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

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

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

<Master batch>
As described above, a master batch can be obtained by mixing carboxymethylated cellulose nanofibers and a rubber component and optionally performing one or more of a coagulation step, a solid-liquid separation step, a water washing step, and a drying step. In the present specification, a composition containing an uncrosslinked rubber component and not containing a crosslinking component is referred to as a “masterbatch” for convenience. Therefore, in addition to the above-mentioned carboxymethylated cellulose nanofibers and the uncrosslinked rubber component, the master batch of the present invention includes a crosslinking component (crosslinking agent, vulcanization acceleration) described in the column of <Kneading Step> described later It may be in a state containing components other than the agent and the vulcanization accelerating aid), or it may be in a state before adding these components. In this specification, what blended a crosslinking component with the masterbatch and knead | mixed as needed is called a "rubber composition" for convenience. Of the rubber compositions, those vulcanized (crosslinked) are called vulcanized rubber compositions, and those that are not vulcanized are called unvulcanized rubber compositions. In addition, a rubber composition that has been molded, vulcanized, and subjected to finishing treatment as necessary may be referred to as “rubber” or “rubber product” as a final product.

<Kneading process, kneading process>
Next, the above-described master batch is kneaded and / or kneaded as it is or optionally with optional components. The kneading and kneading temperature may be about room temperature (for example, about 15 to 30 ° C.), but may be heated to a high temperature so that the rubber component does not undergo a crosslinking reaction. For example, it is 140 ° C. or lower, more preferably 120 ° C. or lower. Moreover, a minimum is 40 degreeC or more, Preferably it is 60 degreeC or more. Accordingly, the heating temperature is preferably about 40 to 140 ° C., more preferably about 60 to 120 ° C.

Examples of optional components that may be added during kneading include, for example, reinforcing agents (for example, carbon black, silica, etc.), silane coupling agents, crosslinking agents (sulfur, peroxides, etc.), vulcanization accelerators, Vulcanization accelerator (zinc oxide, stearic acid), oil, curing resin, wax, anti-aging agent, colorant, peptizer, softener, plasticizer, curing agent (eg phenol resin, high styrene resin, etc.) ), Foaming agents, fillers (carbon black, silica, etc.), coupling agents, adhesives (eg, macron resins, phenols, terpene resins, petroleum hydrocarbon resins, rosin derivatives, etc.), dispersants (eg, fatty acids) Etc.), adhesion promoters (for example, organic cobalt salts, etc.), lubricants (for example, paraffins, hydrocarbon resins, fatty acids, fatty acid derivatives, etc.) and the like, which can be used in the rubber industry. That. Of these, sulfur and vulcanization accelerators are preferred. Examples of the vulcanization accelerator include Nt-butyl-2-benzothiazole sulfenamide (BBS) and N-oxydiethylene-2-benzothiazolyl sulfenamide. When adding an arbitrary component, 1 type may be added and 2 or more types may be added.

The addition timing of optional ingredients is not particularly limited. The addition timing of sulfur and the vulcanization accelerator is preferably after the addition timing of other optional components. It is preferable to start kneading by mixing other optional components without adding sulfur and a vulcanization accelerator, and then further kneading by adding sulfur and a vulcanization accelerator.

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

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

After kneading and kneading, molding may be performed as necessary. Examples of the molding apparatus include mold molding, injection molding, extrusion molding, hollow molding, and foam molding, and may be appropriately selected according to the shape, application, and molding method of the final product.

<Vulcanization and crosslinking process>
It is preferable to heat (vulcanize, crosslink) the rubber composition after mastication and kneading, preferably after molding. Thereby, an unvulcanized rubber composition can be converted into a vulcanized rubber composition, and the rubber composition can be effectively reinforced. The heating temperature is preferably 150 ° C. or higher, and the upper limit is preferably 200 ° C. or lower, more preferably 180 ° C. or lower. Therefore, about 150 to 200 ° C. is preferable, and about 150 to 180 ° C. is more preferable. Examples of the heating device include vulcanization devices such as mold vulcanization, can vulcanization, and continuous vulcanization.

After vulcanization, it may be subjected to finishing treatment as necessary before making the final product. Examples of the finishing treatment include polishing, surface treatment, lip finishing, lip cutting, and chlorination, and only one of these treatments may be performed, or two or more may be performed in combination.

<Rubber composition>
In the present specification, as described above, the “rubber composition” is obtained by blending a crosslinking component into a master batch and kneading as necessary, and includes a crosslinking component but in an uncrosslinked state. Both the rubber composition and the rubber composition after vulcanization are included. Further, rubber as a final product is also included in the rubber composition.

The rubber composition may contain one or more optional components depending on the above-described use. The optional components are those described in the <Kneading step> column. Among these, it is preferable that a vulcanization accelerator and a vulcanization acceleration auxiliary (for example, zinc oxide and stearic acid) are contained. What is necessary is just to determine suitably content of an arbitrary component according to the kind etc. of an arbitrary component, and it does not specifically limit. For example, the contents of sulfur and vulcanization accelerator are as described above.

In the rubber composition, the rubber component and the optional component may be present independently, or may be present as a composite such as a reaction product of at least two components.

<Application>
The use of the rubber product obtained using the rubber composition of the present invention is not particularly limited, and examples thereof include transportation equipment such as automobiles, trains, ships, airplanes, and belt conveyors; personal computers, televisions, telephones, watches, and the like. Electrical appliances, etc .; mobile communication equipment such as mobile phones; portable music playback equipment, video playback equipment, printing equipment, copying equipment, sports equipment, etc .; building materials; office equipment such as stationery, containers, containers, etc. Other than these, application to members using rubber or flexible plastic is possible, and application to industrial belts and tires is preferable. Examples of the industrial belt include a flat belt, a conveyor belt, a cogged belt, a V belt, a rib belt, and a round belt. Examples of the tire include pneumatic tires for passenger cars, trucks, buses, heavy vehicles, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, a part and% show a mass part and mass%.

(Production Example 1)
Add 130 parts of water and 20 parts of sodium hydroxide dissolved in 100 parts of water to a biaxial kneader whose rotational speed is adjusted to 150 rpm, and hardwood pulp (NBK, LBKP) at 100 ° C. 60 100 parts were charged in a dry mass when dried for a minute. Mercerized cellulose was prepared by stirring and mixing at 35 ° C. for 80 minutes. Further, 230 parts of isopropanol (IPA) and 60 parts of sodium monochloroacetate were added with stirring, and the mixture was stirred for 30 minutes, and then heated to 70 ° C. to cause carboxymethylation reaction for 90 minutes. The concentration of IPA in the reaction medium during the carboxymethylation reaction is 50%. After completion of the reaction, the reaction mixture was neutralized with acetic acid until pH 7 and washed with water-containing methanol, lysed, dried and ground to obtain a sodium salt of carboxymethylated cellulose.

The obtained sodium salt of carboxymethylated cellulose was dispersed in water to obtain a 1% (w / v) solid content aqueous dispersion. This was treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain a nanofiber dispersion of carboxymethylated cellulose. The transparency and viscosity of the obtained dispersion, the average fiber diameter of cellulose nanofibers, the degree of carboxymethyl substitution, and the crystallinity of cellulose type I were measured by the methods described above.

(Production Example 2)
A dispersion of nanofibers of carboxymethylated cellulose was obtained in the same manner as in Production Example 1, except that the ultrahigh pressure homogenizer treatment at 150 MPa was performed 5 times.

(Production Example 3)
A dispersion of nanofibers of carboxymethylated cellulose was obtained in the same manner as in Production Example 1, except that the 150 MPa ultrahigh pressure homogenizer treatment was performed once.

(Production Example 4)
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%) is dispersed in water to a solid content of 1% (w / v), and TEMPO (Sigma Aldrich) and sodium bromide are completely dried in 1 g of cellulose. It added to 0.05 mmol and 1.0 mmol with respect to this, and it stirred until it disperse | distributed uniformly. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 6.0 mmol / g, and the oxidation reaction was started. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed. The mixture after the reaction was filtered through a glass filter to separate the 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 1.6 mmol / g. This was adjusted to 1.0% (w / v) with water and treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa) to obtain an oxidized (carboxylated) cellulose nanofiber dispersion.

(Example: Masterbatch, rubber composition)
<Example 1>
325 g of an aqueous dispersion of carboxymethylated cellulose nanofibers obtained in Production Example 1 having a solid content concentration of 1% and 100 g of natural rubber latex (trade name: HA latex, Restex, solid content concentration of 65%) are mixed. The mass ratio of the rubber component (solid content of natural rubber latex) and the solid content of carboxymethylated cellulose nanofibers was 100: 5, and the mixture was stirred for 10 minutes with a TK homomixer (8000 rpm). Thereafter, the obtained mixed solution was dried in a heating oven at 70 ° C. for 5 hours to obtain a master batch.

The above master batch was kneaded with an open roll (manufactured by Kansai Roll Co., Ltd.) at 30 ° C. for 10 minutes. Next, 2.3 g of sulfur (3.5% by mass with respect to the rubber component), 0.5 g of vulcanization accelerator (BBS, Nt-butyl-2-benzothiazolesulfenamide) (0.2% with respect to the rubber component). 5 mass%) was added, and an unrolled rubber composition sheet was obtained by kneading at 30 ° C. for 10 minutes using an open roll (manufactured by Kansai Roll Co., Ltd.).

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 is cut into a test piece of a predetermined shape, and in accordance with JIS K6251 “vulcanized rubber and thermoplastic rubber-Determination of tensile properties”, tensile strength and elongation, which are one of reinforcing properties, and stress at 50% elongation ( M50), stress at 100% elongation (M100) was measured. The larger each value, the better the vulcanized rubber composition is reinforced and the better the mechanical strength of the rubber.

<Example 2>
The same procedure as in Example 1 was performed except that the carboxymethylated cellulose nanofibers obtained in Production Example 1 were changed to the carboxymethylated cellulose nanofibers obtained in Production Example 2.

<Comparative Example 1>
The same procedure as in Example 1 was performed except that the carboxymethylated cellulose nanofiber obtained in Production Example 1 was changed to the carboxymethylated cellulose nanofiber obtained in Production Example 3.

<Comparative Example 2>
The same procedure as in Example 1 was performed, except that the carboxymethylated cellulose nanofiber obtained in Production Example 1 was changed to the oxidized cellulose nanofiber obtained in Production Example 4.

<Comparative Example 3>
It carried out by the same method as Example 1 except not having blended carboxymethylated cellulose nanofiber.

From the results shown in Table 1, the carboxymethyl substitution degree is 0.50 or less, and the transmittance of light having a wavelength of 660 nm when an aqueous dispersion having a solid content of 1% (w / v) is 60% or more. The vulcanized rubber compositions (Examples 1 and 2) obtained using the master batch containing methylated cellulose nanofibers had a tensile strength, an elongation, as compared with the vulcanized rubber compositions of Comparative Examples 1 to 3. It can be seen that the stress at 50% elongation (M50) and the stress at 100% elongation (M100) are large. It can be seen that the rubber compositions of Examples 1 and 2 are well reinforced and excellent in the mechanical strength of the rubber.

Claims

A method for manufacturing a masterbatch,
Mixing the rubber component and carboxymethylated cellulose nanofibers,
The carboxymethylated cellulose nanofiber is an aqueous dispersion having a cellulose I type crystallinity of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and a solid content of 1% (w / v). The said manufacturing method whose transmittance | permeability of the light of the wavelength of 660nm at the time is 60% or more.
Producing a carboxymethylated cellulose by carrying out a mercerization reaction under a solvent mainly containing water and then carrying out a carboxymethylation reaction under a mixed solvent of water and an organic solvent, and the obtained carboxymethylation The production method according to claim 1, further comprising producing carboxymethylated cellulose nanofibers by defibrating cellulose.
The production method according to claim 2, wherein the solvent mainly containing water is a solvent containing more than 50% by mass of water.
The production method according to any one of claims 1 to 3, wherein the amount of foreign matter contained in the carboxymethylated cellulose nanofiber is 20% or less.
A method for producing a rubber composition, comprising producing a master batch by the method according to any one of claims 1 to 4, and producing a rubber composition using the obtained master batch.
A masterbatch containing carboxymethylated cellulose nanofibers,
The carboxymethylated cellulose nanofiber is an aqueous dispersion having a cellulose I type crystallinity of 60% or more, a carboxymethyl substitution degree of 0.50 or less, and a solid content of 1% (w / v). A master batch in which the transmittance of light having a wavelength of 660 nm is 60% or more.
The master batch according to claim 6, wherein the amount of foreign matter of the carboxymethylated cellulose nanofiber is 20% or less.
A rubber composition produced using the master batch according to claim 6 or 7.
Cellulose I type crystallinity of 60% or more, carboxymethyl substitution degree of 0.50 or less, and light transmittance at a wavelength of 660 nm when an aqueous dispersion having a solid content of 1% (w / v) is obtained. A filler for rubber containing carboxymethylated cellulose nanofibers having a selenium content of 60% or more.