JP2014122289A - Method for producing fine cellulose fiber dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine cellulose fiber dispersion which, in a fine cellulose fiber-containing vulcanized rubber composition which contains the fine cellulose fiber, carbon black, and a rubber component, has high breaking strength and high breaking elongation.SOLUTION: Provided is a method for producing a fine cellulose fiber dispersion containing a fine cellulose fiber and carbon black, comprising fibrillating the cellulose fiber in a raw material dispersion containing the cellulose fiber and the carbon black.

Description

The present invention relates to a method for producing a fine cellulose fiber dispersion. Specifically, the present invention relates to a method for producing a fine cellulose fiber dispersion in which cellulose fibers are defibrated in the presence of carbon black.
The present invention also provides a fine cellulose fiber dispersion obtained from the method for producing a fine cellulose fiber dispersion, a fine cellulose fiber-containing rubber composition produced using the fine cellulose fiber dispersion, and the fine cellulose fiber-containing composition. The present invention relates to a vulcanized rubber composition containing fine cellulose fibers obtained by vulcanizing a rubber composition.

  Various proposals have been made so far for rubber compositions obtained by blending reinforcing agents such as fibers and inorganic compounds with rubber, and as a result, techniques for improving the physical properties of rubber products using the rubber composition. None of them were sufficient.

  For example, in order to increase the strength of rubber and reduce loss, it is an effective technique to add a reinforcing agent such as an inorganic compound such as fiber or carbon black in the rubber component. In order to sufficiently obtain the blending effect, it is necessary to uniformly disperse these reinforcing agents in the rubber component. However, when rubber, fiber, and inorganic compound are combined, the fibers tend to aggregate in the mixing step or rubber kneading step, and it is difficult to uniformly disperse the inorganic compound.

  Therefore, establishment of the technique for solving these various problems and improving the reinforcement of a rubber composition further is calculated | required.

In Patent Document 1, nanofillers, which are inorganic fillers having an average particle diameter of 2 to 200 nm, are added to an aqueous dispersion of fibrillated fibers such as fine fibrous cellulose fibers in an amount of 0.1 to 0. 0 of the fiber weight. A method for producing a rubber reinforcing agent is disclosed in which a composite of fibrillated fibers and nanofillers is obtained by mixing in an amount five times and drying.
However, in the case of using a fine cellulose fiber / nanofiller-containing aqueous dispersion obtained by mixing a nanofiber filler of an inorganic filler with an aqueous dispersion of cellulose fiber that has been refined in advance, fiber aggregation or an inorganic filler is also used. As a rubber reinforcing agent, a sufficient reinforcing effect in terms of breaking strength and breaking elongation cannot be obtained.

JP 2011-102451 A

  The present invention achieves a fine cellulose fiber-containing vulcanized rubber composition having high breaking strength and high elongation at break in a fine cellulose fiber-containing vulcanized rubber composition containing fine cellulose fibers, carbon black and a rubber component. An object is to provide a fine cellulose fiber dispersion to be obtained.

  As a result of intensive studies on the above-mentioned problems, the present inventor has conducted a fibrillation treatment of cellulose fibers in a dispersion containing cellulose fibers and carbon black, thereby providing fine cellulose fibers having high breaking strength and high breaking elongation. It turned out that the fine cellulose fiber dispersion liquid which can implement | achieve the containing vulcanized rubber composition can be manufactured, and this invention was reached | attained.

  That is, the present invention is a method for producing a fine cellulose fiber dispersion containing fine cellulose fibers and carbon black, comprising the step of defibrating cellulose fibers in a raw material dispersion containing cellulose fibers and carbon black. It is obtained by removing the dispersion medium from the method for producing a fine cellulose fiber dispersion, the fine cellulose fiber dispersion produced by the production method, and the fine cellulose fiber dispersion containing a rubber component. The present invention resides in a fine cellulose fiber-containing rubber composition and a fine cellulose fiber-containing vulcanized rubber composition obtained by vulcanizing the fine cellulose fiber-containing rubber composition.

  ADVANTAGE OF THE INVENTION According to this invention, the fine cellulose fiber containing vulcanized rubber composition which has high breaking strength and high breaking elongation can be provided.

  The fine cellulose fiber dispersion of the present invention and the production method thereof, the fine cellulose fiber-containing rubber composition, and the fine cellulose fiber-containing vulcanized rubber composition will be described in detail below.

[I. Method for producing fine cellulose fiber dispersion]
The method for producing a fine cellulose fiber dispersion of the present invention is a method for producing a fine cellulose fiber dispersion containing fine cellulose fibers and carbon black, and the cellulose in the raw material dispersion containing the cellulose fibers and carbon black. It is characterized by having a defibrating step of defibrating the fiber.

  In the present invention, as described above, by performing a defibrating process on the cellulose fibers together with the carbon black in the presence of the carbon black, the cellulose fibers are refined and the carbon black particles are further finely dispersed and finely divided. A fine cellulose fiber dispersion can be obtained in which the dispersed carbon black and fine cellulose fibers are uniformly dispersed in the dispersion without agglomeration or uneven distribution. Using this fine cellulose fiber dispersion Thus, a fine cellulose fiber-containing vulcanized rubber composition having significantly improved breaking strength and breaking elongation can be obtained.

  First, materials (cellulose fibers, carbon black, rubber components, etc.) used in the present invention will be described in detail.

<Cellulose fiber>
The cellulose fiber used in the present invention is a material used as a raw material for fine cellulose fiber, and if it is a substance containing cellulose (cellulose-containing material) or a material containing a refined cellulose-containing material (cellulose fiber raw material), The type is not particularly limited. As the cellulose fiber, cellulose may be used, or cellulose partially containing impurities may be used. Especially, it is preferable that the cellulose fiber used by this invention remove | eliminated the impurity from the cellulose containing material through refinement | purification.

(Cellulose-containing material)
Cellulose-containing materials include, for example, wood such as conifers and hardwoods, cotton such as cotton linter and cotton lint, pomace such as sugar cane and sugar radish, bast fibers such as flax, ramie, jute, kenaf, sisal, pineapple, etc. Plant-derived raw materials such as leaf vein fibers, abaca, banana and other petiole fibers, coconut palm and other fruit fibers, bamboo and other stem stem fibers, bacterial cellulose produced by bacteria, seaweeds such as valonia and falcons and squirts of squirts Natural cellulose is mentioned. These natural celluloses are preferable because of their high crystallinity and low linear expansion and high elastic modulus. In particular, cellulose fibers obtained from plant-derived materials are preferred. When wood is used as the cellulose fiber of the present invention, it is preferably used after being cut or crushed into a state of wood chips or wood flour. In this case, cutting or crushing of the cellulose-containing material may be performed at any timing before the purification treatment, during the treatment, or after the purification treatment.

(Purification method)
In the present invention, the cellulose-containing material is subjected to a purification treatment as necessary (purification step) to remove substances other than cellulose in the cellulose-containing material, such as lignin, hemicellulose, and resin (resin). Use.
The method for purifying the cellulose-containing material is not particularly limited, and examples thereof include degreasing treatment, delignification treatment, and dehemicellulose treatment. As an example, there may be mentioned a method in which a cellulose-containing material is degreased with benzene-ethanol, then subjected to delignification treatment by the Wise method, and dehemicellulose treatment with alkali.

As delignification treatment, in addition to the above Wise method, a method using peracetic acid (pa method), a method using a peracetic acid persulfuric acid mixture (pxa method), and the like are also used.
If necessary, bleaching treatment may be performed with chlorine, ozone, sodium hypochlorite, hydrogen peroxide, chlorine dioxide, or the like.
Moreover, as a refinement | purification method, the manufacturing method of a general chemical pulp, for example, the manufacturing method of a kraft pulp, a sulphid pulp, an alkali pulp, and a nitrate pulp, is also mentioned. In addition, there may be mentioned a method in which the cellulose-containing material is heat-treated in a digester to perform delignification or the like, and further bleaching or the like.

  In the purification treatment, water is generally used as a dispersion medium. However, an aqueous solution of an acid or base or other treatment agent may be used, and in this case, it may be finally washed with water.

  In the purification treatment of the cellulose-containing material, an acid, a base, or other treatment agent is usually used, but the type is not particularly limited. Examples of the treating agent include sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium sulfide, magnesium sulfide, sodium sulfite, calcium sulfite, magnesium sulfite, ammonium sulfite, sodium sulfate, sodium thiosulfate. , Sodium oxide, magnesium oxide, calcium oxide, acetic acid, oxalic acid, sodium hypochlorite, calcium hypochlorite, sodium chlorite, sodium chlorate, chlorine dioxide, chlorine, sodium perchlorate, sodium thiosulfate, Hydrogen peroxide, ozone, hydrosulfite, anthraquinone, dihydrodihydroxyanthracene, tetrahydroanthraquinone, anthrahydroquinone, alcohols such as ethanol, methanol, 2-propanol And water-soluble organic solvent such as Le acids and acetone and the like. These treatment agents may be used alone or in combination of two or more.

  Further, two or more purification treatments can be performed using two or more treatment agents. In that case, it is preferable to wash with water between purification treatments using different treatment agents.

  The temperature and pressure during the purification treatment are not particularly limited, and the temperature is preferably selected in the range of 0 ° C. or more and 100 ° C. or less. In the case of treatment under pressure exceeding 1 atm, the temperature is 100 ° C. or more and 200 ° C. The following is preferable.

Cellulose fibers obtained by purifying the cellulose-containing material are usually obtained in a water-containing state (aqueous dispersion). The cellulose fiber obtained by refining the cellulose-containing material may be hereinafter referred to as a cellulose fiber raw material.
As the cellulose fiber raw material, hardwood kraft pulp, softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp, hardwood bleached kraft pulp, softwood bleached kraft pulp, linter pulp and the like may be used.

(Fiber diameter)
The cellulose fiber used in the present invention is preferably used in a size within the following range by subjecting the cellulose-containing material to purification treatment, cutting, crushing, or the like. For example, when using a cellulose-containing chip having a size of several centimeters, it is preferable to perform mechanical treatment with a disintegrator such as a refiner or a beater to make the thickness about several millimeters. As described above, when the cellulose-containing material is cut or crushed, the cellulose-containing material may be cut or crushed at any time before, during, or after the treatment. For example, an impact pulverizer or a shear pulverizer may be used before the purification treatment, and a refiner or the like may be used during the purification treatment or after the treatment.

  In the present invention, the fiber diameter of the cellulose fiber to be subjected to the defibrating treatment (usually, the cellulose fiber raw material) is not particularly limited, and from the viewpoint of the defibrating efficiency at the time of defibrating treatment described later, and handleability The number average fiber diameter is preferably 1 μm to 1000 μm, and more preferably 5 μm to 500 μm. Usually, the average fiber diameter of the cellulose fiber raw material that has undergone general purification is about several hundred μm, preferably about 50 to 500 μm.

  The method for measuring the number average fiber diameter is not particularly limited. For example, the number average fiber diameter is observed with a scanning electron microscope (hereinafter referred to as SEM) or a transmission electron microscope (hereinafter referred to as TEM). 12 fibers are randomly extracted, and 10 measured values obtained by removing the thickest fiber and the thinnest fiber can be averaged.

(Oxidation treatment)
A carboxy group may be introduced into the cellulose constituting the cellulose fiber by performing an oxidation treatment or the like.
Although there is no restriction | limiting in particular as a specific method of oxidation treatment, the method of making a cellulose fiber raw material contact the gas which has oxidizing property (henceforth "oxidizing gas"), or a cellulose fiber raw material to the solution containing an oxidizing chemical species Examples of the method include suspension or immersion.

Although it does not specifically limit as oxidizing gas, Ozone, chlorine gas, fluorine gas, chlorine dioxide, nitrous oxide, etc. are mentioned, These 2 or more types may be included. In particular, ozone can be generated in a timely and required place by supplying oxygen-containing gas such as air, oxygen gas, oxygen-added air, etc. to the ozone generator, and the ozone generator is commercially available. It is preferable because it can be used easily.
When ozone is used as the oxidizing gas, the amount of ozone added is preferably 0.1 to 1000% by weight, more preferably 1 to 100% by weight, and 5 to 50% by weight based on the dry mass of the cellulose fiber raw material. % Is more preferable.

  As the oxidizing chemical species, a reagent that can oxidize alcohol to an aldehyde or carboxylic acid can be generally used, and is not particularly limited. However, a hexavalent chromic acid sulfuric acid mixture, Jones reagent (chromic anhydride (Sulfuric acid solution), chromic acid oxidizing reagents such as pyridinium chlorochromate (PCC reagent), activated dimethyl sulfoxide reagent used for Swern oxidation, and tetrapropylammonium perruthenad (catalytic oxidation) TPAP) and N-oxyl compounds such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (Japanese Patent Laid-Open No. 2008-1728). In particular, it is known that the oxidation of cellulose fibers by TEMPO is known to proceed under mild conditions in an aqueous dispersion.

An oxidation treatment step may be further added after the above oxidation treatment. By adding the oxidation treatment, oxidizing the formyl group in the cellulose fiber to the carboxy group is more preferable because the defibration property is further improved.
Although it does not specifically limit as a chemical species used for an additional oxidation process, Chlorite, such as sodium chlorite, is mentioned. Specifically, the cellulose fiber raw material after the oxidation treatment is suspended in a solution prepared by adding an acid such as hydrochloric acid or acetic acid to a 0.1 to 5% by weight aqueous solution of sodium chlorite to adjust the pH to 4 to 5. Then, the additional oxidation treatment can be performed by holding for a certain time, for example, 1 to 100 hours. The temperature during this additional oxidation treatment is usually 0 ° C to 100 ° C, preferably 20 ° C to 80 ° C.

  It is preferable that the cellulose fiber raw material after the additional oxidation treatment is sufficiently suspended and washed with water. When the cellulose fiber raw material is stored in a strongly acidic or strongly basic state, the crystallinity of the cellulose may be lowered. Therefore, when washing, the pH of the washed water is in the range of 4 to 9. It is preferable to repeat the washing until

  By this oxidation treatment, a carboxy group is usually introduced into the cellulose of the cellulose fiber. The amount of carboxy groups after introduction is usually 0.1 to 5 mmol / g, preferably 0.2 to 2 mmol / g, based on the weight of the cellulose fiber.

  If the introduction amount of the carboxy group representing the degree of the oxidation treatment is too small, the effect of improving the fibrillation efficiency by the oxidation treatment cannot be obtained sufficiently. However, if the amount of carboxy groups introduced is too large, there is a possibility that desired cellulose nanofibers cannot be obtained.

  The amount of carboxy groups (mmol / g) relative to the weight of the cellulose fiber can be quantified, for example, according to the method of “Test Method T237 cm-08 (2008): Carboxyl Content of pulp” of TAPPI, USA. At this time, as the absolutely dry cellulose fiber used as a measurement sample, one obtained by freeze-drying is used in order to avoid alteration of cellulose due to heating that may occur in heat drying. In addition, the amount of carboxy groups in the cellulose fiber is increased by the amount of chemical modification groups added to the cellulose when the chemical modification treatment described later is performed, so the numerical value per gram of dry cellulose changes. Therefore, when the cellulose fiber according to the present invention is further subjected to chemical modification treatment, the amount of carboxy group of the cellulose fiber needs to be obtained as a value after substitution with the chemical modification group.

  Usually, the cellulose fiber after the oxidation treatment is subjected to a purification treatment by washing with water or filtration.

(Modification processing)
The cellulose fiber according to the present invention may be subjected to a modification treatment for modifying (substituting) a hydroxyl group in cellulose with another group. Specific examples thereof include those derivatized by chemical modification (chemically modified cellulose fibers). For example, hydroxyl groups in cellulose have been modified (replaced by reacting with a chemical modifier). It is a thing. The chemical modification in the present invention means that a hydroxyl group in cellulose is derived or substituted with another group by a chemical reaction.

  Chemical modification may be performed in any process until the fine cellulose fiber dispersion of the present invention is obtained, but from the viewpoint of efficient reaction of the chemical modifier, it is applied to cellulose after purification (cellulose fiber raw material). It is preferable to perform chemical modification treatment.

  Substituents introduced into the hydroxyl groups of cellulose by chemical modification (groups introduced by substitution with hydrogen atoms in the hydroxyl groups) are not particularly limited, and are close to the skeleton of the rubber component in consideration of the affinity with the rubber component used. A structural group or the like may be selected. For example, acetyl group, acryloyl group, methacryloyl group, propionyl group, propioroyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, dodecanoyl group, myristoyl Group, palmitoyl group, stearoyl group, acyl group such as pivaloyl group, isocyanate group such as 2-methacryloyloxyethylisocyanoyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-Butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, stearyl group and other alkyl groups, oxirane group, oxetane group, thiirane group , Ethane group. Among these, acyl groups having 2 to 12 carbon atoms such as acetyl group, acryloyl group, and methacryloyl group are particularly preferable.

(Enzyme treatment)
The cellulose fiber used in the present invention may be subjected to an enzyme treatment.
The enzyme treatment is performed using a cellulase enzyme that cleaves the β-1,4-glucoside bond of cellulose by hydrolysis and causes depolymerization, and the cellulose fiber raw material is fibrillated by the enzyme treatment to obtain the fiber diameter and fiber length. Can be reduced.
The enzyme treatment is usually performed by adding a cellulase enzyme to an aqueous dispersion of cellulose fiber raw material.

  Cellulase-producing microorganisms include aerobic bacteria, anaerobic bacteria, rumen bacteria, actinomycetes, yeast, filamentous fungi (ascomycetes, basidiomycetes, etc.) present in the digestive organs of animals and insects. Produces a novel cellulase.

  Cellulase-based enzymes include the genus Trichoderma, the genus Acremonium, the genus Aspergillus, the genus Phanerochaete, the trametes, Trametes, Genus, Humicola (Bacteria), Bacillus (Bacteria), Suehirotake (Basidiomycetes), Streptomyces (Bacteria), Pseudomonas (Pseudomonas, Bacteria), etc. Enzymes. Such a cellulase enzyme can be purchased as a reagent or a commercial product. Examples thereof include cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor), cellulase enzyme GC220 (manufactured by Genencor). Among these cellulase enzymes, filamentous fungal cellulase enzymes are preferred, and among the filamentous fungal cellulase enzymes, cellulase enzymes produced by Trichoderma bacterium (Trichoderma reesei or Hyporea jerorina) are cellulase enzymes. It is particularly preferred because of its wide variety of enzymes and high productivity.

  A hemicellulase-based enzyme is an enzyme that hydrolyzes hemicellulose. Among hemicellulase-based enzymes, xylanase, which is an enzyme that degrades xylan, mannanase, which is an enzyme that degrades mannan, and arabanase, an enzyme that degrades araban. In addition, pectinase, which is an enzyme that degrades pectin, can also be used as a hemicellulase-based enzyme. Microorganisms that produce hemicellulase enzymes often also produce cellulase enzymes.

  Hemicellulose is a polysaccharide excluding pectins between cellulose microfibrils in the plant cell wall. Hemicelluloses are diverse and differ between plant types and cell wall layers. In wood, glucomannan is the main component in the secondary wall of conifers, and 4-O-methylglucuronoxylan is the main component in the secondary walls of hardwood. Therefore, in order to obtain fine fibrous cellulose from conifers, it is preferable to use mannase, and in the case of hardwoods, it is preferable to use xylanase.

  The amount of cellulase enzyme added to the cellulose fiber raw material is preferably 0.1 to 3% by weight, and more preferably 0.3 to 2.5% by weight. If the addition amount of the cellulase enzyme is less than 0.1% by weight, the fibrillation efficiency by the enzyme may be reduced. If the addition amount exceeds 3% by weight, the cellulose is saccharified and the yield of fine cellulose fibers is reduced. There is a risk.

  The pH of the aqueous dispersion of cellulose fiber raw material during the cellulase enzyme treatment is preferably a weakly acidic region of pH 3.0 to 6.9, but an optimal pH region may be appropriately selected depending on the type of cellulase enzyme.

  Further, the pH of the aqueous dispersion of the cellulose fiber raw material when the treatment with the hemicellulase-based enzyme is preferably pH 7.1 to 10.0 which is a weak alkaline region, but the optimum pH region depending on the type of the hemicellulase-based enzyme. May be selected.

  The temperature of the aqueous dispersion of the cellulose fiber raw material during the enzyme treatment is preferably 30 to 70 ° C, more preferably 35 to 65 ° C, and particularly preferably 40 to 60 ° C. If the temperature is less than 30 ° C., the enzyme activity decreases and the treatment time becomes longer, which is not preferable. If the temperature exceeds 70 ° C., the enzyme is deactivated, which is not preferable. The treatment time is adjusted by the enzyme type, temperature, and pH, but preferably 30 minutes to 24 hours. If the treatment time is less than 30 minutes, the effect of the enzyme treatment may hardly be exhibited. If it exceeds 24 hours, the decomposition of the cellulose fibers proceeds too much by the enzyme, and the number average fiber length of the obtained fine cellulose fibers may be too short.

  If the enzyme remains active, the decomposition of the cellulose fiber proceeds too much. Therefore, an aqueous sodium hydroxide solution of about 20% by weight is added to the aqueous dispersion of the cellulose fiber raw material after the reaction with the enzyme for a predetermined time. Usually, the enzyme is deactivated by adding the dispersion so that the pH is about 12, or the temperature of the aqueous dispersion of the cellulose fiber raw material is increased to 90 ° C. to deactivate the enzyme. Although it is simpler to add a sodium hydroxide aqueous solution, dehydration may be deteriorated in the subsequent cleaning treatment, and it is necessary to deal with it. Washing with water may be carried out with 2 to 4 times the amount of water of cellulose fibers, so that almost no enzyme remains.

<Carbon black>
There is no restriction | limiting in particular as carbon black, From what is conventionally used as a reinforcing filler of rubber | gum, arbitrary things can be selected suitably and can be used. For example, SRF, GPF, FEF, HAF, ISAF, and SAF are used, and HAF, ISAF, and SAF that are particularly excellent in wear resistance are preferable.
Carbon black may be used individually by 1 type, and may be used in combination of 2 or more type.

<Dispersion medium (solvent)>
In the present invention, the solvent (dispersion medium) used for the raw material dispersion for defibrillating cellulose fibers in the presence of carbon black is not particularly limited as long as it has excellent dispersibility of carbon black and cellulose fibers. Examples thereof include protic polar solvents such as water and alcohol solvents, ketone solvents, glycol ether solvents, amide solvents, aromatic hydrocarbons, aprotic polar solvents, and the like. Preferred are water, amide solvents, alcohol solvents, and ketone solvents. These solvents may be used alone or in combination of two or more.

  In addition, since the solvent used by this invention has the process of removing a solvent at a next process, it is preferable that a boiling point is not too high. The boiling point of the solvent is preferably 300 ° C. or lower, preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Moreover, 70 degreeC or more is preferable from points, such as handleability.

  Examples of alcohol solvents include methanol, ethanol, propanol, butanol and the like.

  Examples of the ketone solvent (referring to a liquid having a ketone group) include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diisopropyl ketone, di-tert-butyl ketone, 2-heptanone, 4-heptanone, 2-octanone, Examples include cyclopentanone, cyclohexanone, cyclohexyl methyl ketone, acetophenone, acetylacetone, and dioxane. Among these, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone are preferable, and methyl ethyl ketone (MEK) and cyclohexanone are more preferable.

  Specific examples of the glycol ether solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol. Examples include mono-n-butyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol mono-n-butyl ether, propylene glycol monomethyl ether acetate.

Specific examples of the aromatic hydrocarbon include benzene, toluene, xylene and the like.
Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, 2-pyrrolidone, N- Examples include methyl pyrrolidone.

<Procedure for producing fine cellulose fiber dispersion>
In the production method of the present invention, the cellulose fibers are defibrated in a raw material dispersion containing cellulose fibers and carbon black subjected to enzyme treatment or the like as necessary to obtain fine cellulose fibers.

(Production method of raw material dispersion)
The manufacturing method of a raw material dispersion liquid is not specifically limited, It can prepare by mixing each component used. Usually, it can prepare by mixing the dispersion liquid (cellulose fiber dispersion liquid) which disperse | distributed the said cellulose fiber, and carbon black.

As a dispersion medium for dispersing cellulose fibers, water is usually used, but an organic solvent (dispersion medium) may be used. When using an organic solvent, when using a cellulose fiber raw material obtained as an aqueous dispersion of cellulose fibers, the water in the aqueous dispersion may be replaced with an organic solvent in advance (solvent replacement step).
The method for substituting the solvent is not particularly limited, but water is removed from the aqueous dispersion containing cellulose fibers by filtration, etc., an organic solvent used for defibration is added thereto, the mixture is stirred and mixed, and the organic solvent is again filtered. The method of removing is mentioned. By repeating the addition of organic solvent and filtration, the medium in the dispersion can be replaced with water from the organic solvent.
In addition, when the organic solvent to be used is water-insoluble, after substituting with a water-soluble organic solvent once, you may substitute with a water-insoluble organic solvent.

  When mixing the cellulose fiber dispersion and carbon black, carbon black may be added directly to the cellulose fiber dispersion and mixed, or after preparing a liquid in which carbon black is dispersed in a solvent (dispersion medium), the liquid is mixed. May be added and mixed. A cellulose fiber dispersion may be added to the liquid and mixed, and the mixing order may be any.

  The solvent for dispersing the carbon black may be the same as the solvent used in the solvent substitution step, or may be different as long as it is compatible.

  The content of cellulose fibers in the raw material dispersion is not particularly limited, but from the viewpoint of handleability such that the viscosity and liquid stability of the resulting fine cellulose fiber dispersion are suitable, the total amount of raw material dispersion, 0.01 wt% or more is preferable, 0.05 wt% or more is more preferable, 0.1 wt% or more is particularly preferable, 30 wt% or less is preferable, 20 wt% or less is more preferable, and 15 wt% or less is particularly preferable preferable.

  The carbon black content in the raw material dispersion is not particularly limited, but in terms of handleability such that the viscosity and liquid stability of the resulting fine cellulose fiber dispersion are suitable, the fine cellulose fiber and the carbon black are also included. From the viewpoint of the reinforcing effect on the rubber component by using together, in the raw material dispersion, the content of cellulose fibers is preferably 1 part by weight or more, more preferably 2 parts by weight or more, with respect to 100 parts by weight of carbon black. The amount is particularly preferably 5 parts by weight or more, preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and particularly preferably 30 parts by weight or less.

  The content of the dispersion medium in the raw material dispersion is not particularly limited, but from the viewpoint of handleability such that the viscosity and liquid stability of the obtained fine cellulose fiber dispersion are suitable, It is preferably 1% by weight or more, more preferably 2% by weight or more, particularly preferably 3% by weight or more, preferably 99.9% by weight or less, more preferably 98% by weight or less, and particularly preferably 95% by weight or less.

(Defibration method)
In the present invention, cellulose fibers are defibrated in the raw material dispersion prepared as described above. In the present invention, defibration means unraveling the fiber, and usually the fiber can be made smaller.

  The specific method of the defibrating step (defibrating treatment) is not particularly limited. For example, a ceramic bead having a diameter of about 1 mm is a raw material having a cellulose fiber concentration of 0.01 to 30% by weight, for example, about 0.5% by weight. Examples thereof include a method in which the cellulose fiber is defibrated by putting it in a dispersion and applying vibration using a paint shaker or a bead mill.

  Cellulose fibers can also be obtained by blending with a blender-type disperser or slits that rotate at high speed, using a raw material dispersion to break the fiber (high-speed rotating homogenizer), or by suddenly reducing the pressure from high pressure. Examples include a method in which a shearing force is generated in the middle (high pressure homogenizer method), a method using a counter-impact type disperser (Masuko Sangyo) such as the massomizer X, and the like. That is, a defibrating process using a bead mill, a defibrating (miniaturizing) process using jets, a defibrating process using a rotary defibrating method, or a defibrating process using ultrasonic treatment can be used.

  In particular, the treatment with a high-speed rotation homogenizer and a high-pressure homogenizer further improves the efficiency of defibration.

  In the case of defibration by these treatments, the solid content concentration (total amount of cellulose fibers and carbon black) in the raw material dispersion is not particularly limited, but is preferably 2.5% by weight or more, more preferably 3% by weight or more. 99% by weight or less is preferable, and 50% by weight or less is more preferable. If the solid content concentration in the raw material dispersion used in the defibrating step is too low, the amount of liquid is too large with respect to the amount of cellulose to be treated, and the efficiency deteriorates. If the solid content concentration is too high, the fluidity deteriorates.

In the case of a high-speed rotating homogenizer, the higher the peripheral speed, the higher the defibrating efficiency. The peripheral speed is 15 m / s or more, preferably 30 m / s or more, and 100 m / s or less, preferably 50 m / s or less. The following relationship holds between the peripheral speed and the rotational speed.
Peripheral speed (m / sec) = 2 × radius of rotating blades (m) × π × rotational speed (rpm) / 60
Therefore, if a rotating blade having a radius of 15 mm is used, the rotational speed is preferably, for example, about 10,000 rpm or more, and particularly preferably about 20000 rpm or more. The upper limit of the rotational speed is not particularly limited, but is preferably about 30000 rpm or less from the viewpoint of the performance of the apparatus. When the rotational speed is 5000 rpm or less, the cellulose fibers are not sufficiently defibrated.

The treatment time is preferably 1 minute or longer, more preferably 5 minutes or longer, and particularly preferably 10 minutes or longer. The treatment time is preferably 6 hours or less from the viewpoint of productivity. When heat is generated by shearing, it is preferable to cool the solution so as not to exceed 50 ° C.
Further, it is preferable to stir or circulate so that the raw material dispersion is uniformly sheared.

  When using a high-pressure homogenizer, the raw material dispersion is preferably pressurized to 30 MPa or more, more preferably 100 MPa or more, more preferably 150 MPa or more, particularly preferably 220 MPa or more with a pressure intensifier, and ejected from a nozzle having a pore diameter of 50 μm or more. The pressure is reduced so that the pressure difference is preferably 30 MPa or more, more preferably 80 MPa or more, and further preferably 90 MPa or more. The cellulose fiber is defibrated by the cleavage phenomenon caused by this pressure difference.

Here, when the pressure under the high pressure condition is low, or when the pressure difference from the high pressure to the decompression condition is small, the defibrating efficiency is lowered, and it is necessary to increase the number of repeated ejections to obtain a desired fiber diameter. Absent.
The higher the high pressure condition at the time of jetting, the more cleavage can be achieved by a large cleavage phenomenon due to the pressure difference, but the upper limit of the apparatus specification is usually 245 MPa or less.

  Similarly, it is preferable that the pressure difference from the high pressure condition to the reduced pressure is large, but generally, the upper limit of the pressure difference is usually 245 MPa or less by ejecting from the pressurizing condition by the pressure intensifier to the atmospheric pressure. .

  In addition, when the pore diameter of the pores from which the raw material dispersion is ejected is too large, a sufficient defibrating effect cannot be obtained. In this case, even if the ejection treatment is repeated, cellulose having a desired fiber diameter is obtained. There is also a possibility that fibers cannot be obtained. If the diameter of the pores through which the raw material dispersion is ejected is small, a high-pressure state can be easily created, but if it is too small, the ejection efficiency is deteriorated. The pore diameter is preferably 50 μm or more, more preferably 100 μm or more, further preferably 150 μm or more, preferably 800 μm or less, more preferably 500 μm or less, and even more preferably 350 μm or less.

  The ejection of the raw material dispersion is repeated a plurality of times as necessary, thereby increasing the degree of fineness and obtaining cellulose fibers having a desired fiber diameter. The number of repetitions (pass number) is usually 1 or more, preferably 3 or more, and usually 20 or less, preferably 15 or less. As the number of passes increases, the degree of miniaturization can be increased. However, an excessively large number of passes is not preferable because the cost increases.

  Although there is no restriction | limiting in particular in the temperature (dispersion liquid temperature) at the time of ejection, Usually, it is 5 to 100 degreeC. If the temperature is too high, there is a possibility that the apparatus, specifically, the liquid feed pump, the high-pressure seal part, and the like may be deteriorated, which is not preferable.

  One or two ejection nozzles may be used, and the ejected raw material dispersion may be hit against a wall, ball, or ring provided at the ejection destination. Furthermore, when there are two nozzles, the raw material dispersions may collide with each other at the ejection destination.

  Although the specific apparatus of a high pressure homogenizer is not restrict | limited in particular, For example, the "starburst system" by a Gaulin company or a Sugino machine company can be used.

  In addition, it is possible to obtain the fine cellulose fiber dispersion of the present invention only by the treatment with such a high-pressure homogenizer, but when the treatment efficiency is poor with a large number of repetitions for obtaining a sufficient degree of fineness, It is preferable to refine by performing the following ultrasonic treatment after the high-pressure homogenizer treatment about 1 to 5 times.

  In the case of performing ultrasonic treatment, the cellulose concentration in the raw material dispersion after defibration treatment, which is subjected to ultrasonic treatment (hereinafter referred to as the ultrasonic treatment raw material dispersion as appropriate), is 0. 5 wt% or more is preferable, 1 wt% or more is more preferable, 50 wt% or less is preferable, and 40 wt% or less is more preferable. If the cellulose concentration in the ultrasonic treatment raw material dispersion to be irradiated with ultrasonic waves is too low, it is inefficient, and if it is too high, the viscosity increases and the fibrillation treatment becomes non-uniform.

  In the present invention, the cellulose fiber is defibrated by subjecting the raw material dispersion containing cellulose fiber and carbon black, not the cellulose fiber dispersion containing only cellulose fiber, to defibrate the cellulose fiber, and carbon black particles In addition, a fine cellulose fiber dispersion in which fine cellulose fibers and fine carbon black particles are uniformly dispersed can be obtained.

[II. Fine cellulose fiber dispersion]
In the fine cellulose fiber dispersion obtained through the above defibration process, fine cellulose fibers and carbon black are uniformly dispersed, and aggregation and sedimentation of fine cellulose fibers and carbon black are suppressed, and excellent liquid stability. Have sex.
Further, in the vulcanized rubber composition containing fine cellulose fibers described in detail below, the fine cellulose fibers and carbon black are uniformly dispersed in the vulcanized rubber component, and exhibit a high elastic modulus and low exothermic property.

The content of fine cellulose fibers in the fine cellulose fiber dispersion is appropriately adjusted according to the amount of cellulose fiber that is the starting material used, but from the viewpoint of the stability of the dispersion, % By weight or more is preferable, 0.05% by weight or more is more preferable, 30% by weight or less is preferable, 20% by weight or less is more preferable, and 15% by weight or less is more preferable.
The content of the dispersion medium and carbon black in the fine cellulose fiber dispersion is the same as the content of each component of the raw material dispersion described above, and the preferred range is also the same.
If the amount of cellulose fiber and carbon black in the fine cellulose fiber dispersion is small, the reinforcing effect is not sufficient, and conversely if large, the processability of rubber may be lowered.

<Cellulose type I crystal>
It is preferable that the fine cellulose fiber obtained by the said defibration process has a cellulose I type crystal structure. Cellulose I-type crystals are preferable because they have higher crystal elastic modulus than other crystal structures, and thus have high elastic modulus, high strength, and low linear expansion coefficient.
The fact that the fine cellulose fiber has the I-type crystal structure is typical at two positions near 2θ = 14-17 ° and 2θ = 22-23 ° in the diffraction profile obtained by wide-angle X-ray diffraction image measurement. It can be identified from having a peak.

<Number average fiber diameter of fine cellulose fibers>
The number average fiber diameter of the fine cellulose fibers in the fine cellulose fiber dispersion obtained by the above method can be obtained by measuring by observing with SEM, TEM, etc. after drying and removing the dispersion medium in the dispersion. it can.
The number average fiber diameter of the fine cellulose fibers defibrated obtained by the present invention is preferably 400 nm or less, and preferably 100 nm or less, from the point that the obtained fine cellulose fiber-containing vulcanized rubber composition exhibits more excellent low linear expansion. It is more preferable that it is 50 nm or less. The lower limit of the number average fiber diameter is usually 4 nm or more.
When the average fiber diameter of the fine cellulose fibers is less than the above lower limit, the cellulose I-type crystals are broken and the strength and elastic modulus of the fibers themselves are lowered, so that it is difficult to obtain a reinforcing effect. Moreover, since the contact area with rubber | gum becomes small when exceeding the said upper limit, the reinforcement effect becomes small.

  The number average fiber diameter was observed with SEM, TEM, etc., a line was drawn on the diagonal line of the photograph, and 12 fibers in the vicinity were randomly extracted to remove the thickest and thinnest fibers. It is the value obtained by measuring points and averaging.

<Rubber component>
The fine cellulose fiber dispersion of the present invention may further contain a rubber component. When the fine cellulose fiber dispersion contains a rubber component, the dispersion medium (solvent) is removed from the fine cellulose fiber dispersion. Thus, the fine cellulose fiber-containing composition of the present invention can be obtained and vulcanized to obtain the fine cellulose fiber-containing vulcanized rubber composition of the present invention.

  The rubber component can be broadly classified into natural rubber and synthetic rubber, but either one of them may be used alone or a mixture of natural rubber and synthetic rubber may be used. Synthetic rubbers are selected from known ones according to the purpose, but diene rubbers are preferable, and styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene rubber, chloroprene. Examples thereof include rubber and butyl rubber (IIR). These may be used alone or in combination of two or more.

  When the fine cellulose fiber dispersion of the present invention contains a rubber component, the content of the rubber component in the fine cellulose fiber dispersion is not particularly limited, but handling properties such as viscosity and liquid stability of the fine cellulose fiber dispersion are not limited. In terms of the total amount of the fine cellulose fiber dispersion, 2% by weight or more is preferable, 2.5% by weight or more is more preferable, 95% by weight or less is preferable, and 80% by weight or less is more preferable.

  Further, when the fine cellulose fiber dispersion of the present invention contains a rubber component, the weight ratio of the rubber component and the dispersion medium in the fine cellulose fiber dispersion is not particularly limited, but the viscosity or liquid of the fine cellulose fiber dispersion is not limited. From the viewpoint of handleability such as stability, the content of the dispersion medium is preferably 5 to 2000 parts by weight and more preferably 25 to 1000 parts by weight with respect to 100 parts by weight of the rubber component.

  In addition, when the fine cellulose fiber dispersion of the present invention contains a rubber component, the weight ratio of the cellulose fiber to the rubber component in the fine cellulose fiber dispersion is not particularly limited, but the viscosity of the obtained fine cellulose fiber dispersion is not limited. From the viewpoint of handleability such as liquid stability, the content of cellulose fibers is preferably 2.5 parts by weight or more, more preferably 3 parts by weight or more, with respect to 100 parts by weight in total of the cellulose fibers and the rubber component. 5 parts by weight or more is more preferable, 97.5 parts by weight or less is preferable, 97 parts by weight or less is more preferable, and 95 parts by weight or less is more preferable.

  Further, when the fine cellulose fiber dispersion of the present invention contains a rubber component, the weight ratio of carbon black and rubber component in the fine cellulose fiber dispersion is not particularly limited, but the viscosity of the resulting fine cellulose fiber dispersion is not limited. From the viewpoint of handleability such as liquid stability, the content of carbon black is preferably 1 part by weight or more, more preferably 10 parts by weight or more, and further preferably 30 parts by weight or more with respect to 100 parts by weight of the rubber component. 90 parts by weight or less, preferably 70 parts by weight or less, more preferably 60 parts by weight or less.

  In addition, when the fine cellulose fiber dispersion of the present invention contains a rubber component, from the viewpoint of handleability such as viscosity and liquid stability of the obtained fine cellulose fiber dispersion, the total solid content in the fine cellulose fiber dispersion is obtained. The content is preferably 0.1% by weight or more, more preferably 1% by weight or more, preferably 90% by weight or less, and more preferably 80% by weight or less with respect to the total amount of the fine cellulose fiber dispersion. Therefore, the content of the dispersion medium in the fine cellulose fiber dispersion is preferably 10% by weight or more, more preferably 20% by weight or more, and preferably 99.9% by weight or less based on the total amount of the fine cellulose fiber dispersion. More preferably, it is less than wt%.

  The fine cellulose fiber dispersion of the present invention containing a rubber component may be produced by defibrating cellulose fibers in a raw material dispersion containing cellulose fiber, carbon black and a rubber component, Even if it is manufactured by further mixing rubber components to the fine cellulose fiber dispersion produced by defibrating the dispersion in a raw material dispersion containing cellulose fibers and carbon black Good.

  The cellulose fibers in the raw material dispersion containing the cellulose fiber, carbon black and rubber component are defibrated in the same manner as the method for defibrating the cellulose fibers in the raw material dispersion containing the cellulose fiber and carbon black. Can be done. When a rubber component is further mixed with a fine cellulose fiber dispersion obtained by defibrating cellulose fibers in a raw material dispersion containing cellulose fibers and carbon black, the rubber component is directly added to the fine cellulose fiber dispersion. You may mix, and after preparing the liquid which melt | dissolved or disperse | distributed the rubber component in a solvent, you may add and mix this liquid. A fine cellulose fiber dispersion may be added to the liquid and mixed, and the mixing order may be any. An emulsion such as latex may be used as the rubber component.

  As the solvent for dissolving or dispersing the rubber component, those exemplified as the dispersion medium (solvent) used in the above-mentioned raw material dispersion can be used, and may be the same as the solvent in the fine cellulose fiber dispersion. However, they may be different as long as they are compatible.

  Moreover, the fine cellulose fiber dispersion of the present invention further contains additives exemplified as other compounding agents that may be contained in the composition of the present invention, which will be described later, if necessary. Also good.

[III. Fine cellulose fiber-containing composition]
The fine cellulose fiber-containing composition of the present invention is obtained by removing a dispersion medium (solvent) from the fine cellulose fiber dispersion of the present invention containing the rubber component described above.

  That is, when the fine cellulose fiber dispersion of the present invention is subjected to the vulcanization reaction described in detail below to obtain the vulcanized rubber composition containing the fine cellulose fibers of the present invention, it is usually subjected to heat treatment, reduced pressure treatment, etc. Thus, the fine cellulose fiber dispersion containing the rubber component is dried and solidified, and the solvent (dispersion medium) in the dispersion is removed to obtain a fine cellulose fiber-containing rubber composition. An appropriate amount of the solvent (dispersion medium) may be removed in accordance with the subsequent steps. In the case of heat treatment, the heating temperature is usually about 100 ° C. when the solvent (dispersion medium) is water, and can be appropriately changed depending on the type of the solvent (dispersion medium) contained in the dispersion.

<Other additives>
In the fine cellulose fiber-containing rubber composition of the present invention obtained by removing the fine cellulose fiber dispersion of the present invention or the solvent (dispersion medium) from the fine cellulose fiber dispersion, fine cellulose fibers and carbon black may be used as necessary. In addition to the rubber component, other compounding agents conventionally used in the rubber industry may be added. Other additives that can be added to the fine cellulose fiber-containing rubber composition of the present invention or the fine cellulose fiber-containing rubber composition obtained by removing the solvent (dispersion medium) from the fine cellulose fiber dispersion are, for example, other than carbon black Other reinforcing agents such as silica particles and fibers, inorganic and organic fillers, silane coupling agents, vulcanizing agents described below, vulcanization accelerators such as stearic acid, amines, zinc oxide and magnesium oxide And vulcanization accelerators, oils, curing resins, waxes, anti-aging agents and the like. These additives are usually added to the fine cellulose fiber-containing rubber composition obtained by removing the solvent (dispersion medium) from the fine cellulose fiber dispersion after the fibrillation treatment or the fine cellulose fiber dispersion, It may be added in advance to the raw material dispersion.

<Vulcanizing agent>
As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. Various organic peroxides conventionally used in the rubber industry can be used, among which dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferable. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example, and sulfur is preferable. These vulcanizing agents may be used alone or in combination of two or more.

  The compounding amount of the vulcanizing agent in the fine cellulose fiber-containing rubber composition of the present invention or in the fine cellulose fiber-containing rubber composition obtained by removing the solvent (dispersion medium) from the fine cellulose fiber dispersion is 100 wt. In the case of sulfur with respect to parts, it is 7.0 parts by weight or less, preferably 6.0 parts by weight or less. Moreover, it is 0.5 weight part or more normally, Preferably it is 1.0 weight part or more, More preferably, it is 3.0 weight part or more, Especially 4.0 weight part or more.

[IV. Vulcanized rubber composition containing fine cellulose fibers]
The fine cellulose fiber-containing vulcanized rubber composition of the present invention is obtained from the fine cellulose fiber dispersion of the present invention containing a rubber component obtained through the production method of the fine cellulose fiber dispersion of the present invention. After the production of the rubber composition containing fine cellulose fibers according to the present invention, the rubber composition containing fine cellulose fibers is vulcanized. Specifically, a fine cellulose fiber-containing rubber composition obtained by removing a solvent (dispersion medium) from the fine cellulose fiber dispersion of the present invention containing a rubber component is vulcanized to add fine cellulose fibers and carbon black. A fine cellulose fiber-containing vulcanized rubber composition of the present invention containing a vulcanized rubber component is obtained. In addition, the method for producing the vulcanized rubber composition containing fine cellulose fibers according to the present invention includes, as necessary, additional addition in which a rubber component is further added to and mixed with the fine cellulose fiber-containing rubber composition before the vulcanization step. A process may be provided. In this case, the additional addition of the rubber component can be performed in the same manner as the addition and mixing of the rubber component to the fine cellulose fiber dispersion.

<Vulcanization process>
In the vulcanization step, a fine cellulose fiber-containing vulcanized rubber composition containing fine cellulose fibers, carbon black, and a vulcanized rubber component is obtained using the above-described fine cellulose fiber-containing rubber composition. That is, by subjecting a fine cellulose fiber-containing rubber composition to a vulcanization reaction (vulcanization step), a fine cellulose fiber-containing vulcanized rubber composition containing fine cellulose fibers, carbon black, and a vulcanized rubber component can be obtained. it can. Usually, the fine cellulose fiber-containing vulcanized rubber composition of the present invention is a fine cellulose fiber-containing rubber composition obtained by removing the solvent from the fine cellulose fiber dispersion of the present invention as necessary. The compounding agent is obtained by mixing using a known method such as a kneader for rubber, and then molding and vulcanizing by a known method.

Various methods are possible for the molding prior to the vulcanization process. For example, a fine cellulose fiber dispersion may be applied onto a substrate to form a coating film, poured into a mold, or extruded. May be. At this time, if necessary, a drying treatment may be performed to remove the solvent.
For example, taking a tire as a fine cellulose fiber-containing vulcanized rubber composition as an example, the tire is produced by a conventionally known method using the fine cellulose fiber dispersion of the present invention containing a rubber component. That is, moisture and other solvents are removed from fine cellulose fibers and carbon black dispersed in the rubber component to obtain a fine cellulose fiber-containing rubber composition, and additives are added as necessary, kneaded, and unvulcanized. An unvulcanized tire is formed by extruding in accordance with the shape of a desired application member of the tire in a state and molding the tire together with other members of the tire by a normal method on a tire molding machine. By heating and pressing this unvulcanized tire in a vulcanizer, a tire using the vulcanized rubber composition containing fine cellulose fibers of the present invention can be obtained. Such a tire has low rolling resistance and good steering stability and durability.

  The conditions for the vulcanization step are not particularly limited as long as the temperature is equal to or higher than the temperature at which the rubber component can be converted to vulcanized rubber. Especially, the heating temperature is preferably 60 ° C. or higher, more preferably 100 ° C. or higher, from the viewpoint that the organic solvent can be volatilized and removed. In addition, from the point which suppresses decomposition | disassembly of a fine cellulose fiber, 250 degreeC or less is preferable and the heating temperature has more preferable 200 degreeC or less. The heating time is 5 minutes or more, preferably 10 minutes or more, more preferably 15 minutes or more, and preferably 180 minutes or less from the viewpoint of productivity. The heat treatment may be performed multiple times by changing the temperature and the heating time.

<Number average fiber diameter of fine cellulose fibers>
The number average fiber diameter of the fine cellulose fiber in the fine cellulose fiber-containing vulcanized rubber composition of the present invention obtained by the above method is obtained by cutting out the fine cellulose fiber-containing vulcanized rubber composition as necessary, SEM or TEM. It can be measured and obtained by observing with the above.

  The number average fiber diameter of the fine cellulose fibers in the fine cellulose fiber-containing vulcanized rubber composition of the present invention is preferably 400 nm or less from the point that the obtained vulcanized rubber composition exhibits more excellent low linear expansion, and is 100 nm. More preferably, it is more preferably 50 nm or less. The lower limit of the number average fiber diameter is usually 4 nm or more.

  When the average fiber diameter of the fine cellulose fibers in the vulcanized rubber composition containing the fine cellulose fibers is less than the above lower limit, the cellulose I-type crystal structure cannot be maintained, the strength and elastic modulus of the fibers themselves are lowered, and the reinforcing effect Is difficult to obtain. Moreover, since the contact area with rubber | gum becomes small when exceeding the said upper limit, the reinforcement effect becomes small.

  In addition, the number average fiber diameter of the fine cellulose fiber is observed with SEM, TEM, etc., a line is drawn on the diagonal line of the photograph, and 12 points of fibers in the vicinity are extracted at random, the thickest fiber and the thinnest fiber. It is a value obtained by measuring and averaging 10 points from which.

<Content of fine cellulose fiber and carbon black>
The content of the fine cellulose fiber in the fine cellulose fiber-containing vulcanized rubber composition is appropriately adjusted according to the purpose, but from the point of reinforcement, the content of the fine cellulose fiber-containing vulcanized rubber composition is 0.5%. % By weight or more is preferable, 1% by weight or more is more preferable, 50% by weight or less is preferable, 40% by weight or less is more preferable, and 30% by weight or less is more preferable. If the amount of fine cellulose fiber in the fine cellulose fiber-containing vulcanized rubber composition is small, the reinforcing effect is not sufficient, and conversely if large, the processability of rubber may be lowered.

  Further, from the viewpoint of the reinforcing effect on the rubber component by using a combination of fine cellulose fibers and carbon black, the content of carbon black and fine cellulose fibers in the vulcanized rubber composition containing fine cellulose fibers is 100 parts by weight of carbon black. On the other hand, the cellulose fiber content is preferably 1 part by weight or more, more preferably 5 parts by weight or more, particularly preferably 10 parts by weight or more, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, particularly preferably. The amount is preferably 20 parts by weight or less.

  The weight ratio between the fine cellulose fibers and the rubber component contained in the fine cellulose fiber-containing vulcanized rubber composition is the cellulose in the raw material dispersion and the fine cellulose fiber dispersion when no rubber component is added. The weight ratio of the fiber and the rubber component is the same. If there is a rubber component additional step, the total weight ratio of the cellulose fibers in the fine cellulose fiber dispersion, the rubber component in these dispersions and the added rubber component, the weight ratio is As described above, when the total of the fine cellulose fiber and the rubber component is 100 parts by weight, the content of the fine cellulose fiber is 2.5 parts by weight or more, particularly 3 parts by weight or more, especially 5 parts by weight or more. The amount is preferably 5 parts by weight or less, particularly 97 parts by weight or less, particularly 95 parts by weight.

  The weight ratio of the carbon black and the rubber component contained in the fine cellulose fiber-containing vulcanized rubber composition is such that the carbon black is 1 part by weight or more, particularly 10 parts by weight or more, especially 30 parts per 100 parts by weight of the rubber component. A vulcanized rubber composition having high rubber properties such as high breaking strength and high elongation at break is obtained when the amount is not less than 90 parts by weight, particularly not more than 70 parts by weight, particularly not more than 60 parts by weight. preferable.

<Dispersed state of fine cellulose fiber and carbon black>
The fine cellulose fiber-containing vulcanized rubber composition of the present invention thus obtained has a number average fiber diameter of 4 to 400 nm, preferably 4 to 100 nm, more preferably 4 to 50 nm, and agglomerates are formed. Without being uniformly dispersed in the vulcanized rubber component, and carbon black is also uniformly dispersed as fine fine particles, and at the same time a high elastic modulus is achieved by the reinforcing effect of fine cellulose fibers, It is considered that a high elongation at break is achieved because the original elongation of the rubber is not hindered because the fiber diameter of the cellulose fiber is thin. Moreover, a high elongation at break can be obtained due to the reinforcing effect of carbon black. That is, as a reinforcing rubber, it exhibits excellent durability and rigidity, and can be suitably used for rubber products such as tires.
The dispersion state of the fine cellulose fibers and carbon black in the fine cellulose fiber-containing vulcanized rubber composition of the present invention can be confirmed by observing the cross-sectional structure with SEM or the like.

<Elastic modulus>
The preferred one of the fine cellulose fiber-containing vulcanized rubber composition of the present invention has an elastic modulus of 15 MPa or more, particularly 4 MPa or more and 10 GPa or less.
In addition, the elastic modulus produced a rubber slab sheet 1 mm thick from the vulcanized rubber composition containing fine cellulose fibers, cut out a test piece of 7 × 25 × 2 mm, and used a viscoelastic device such as DMS6100 manufactured by SII. Thus, it can be determined by measuring E * (complex elastic modulus) under conditions of a temperature of 70 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz.

<Elongation at break and strength at break>
The preferable one of the fine cellulose fiber-containing vulcanized rubber composition of the present invention has a breaking elongation of 200% or more, particularly 400% or more and 10,000% or less, preferably 2000% or less.
The fine cellulose fiber-containing vulcanized rubber composition of the present invention preferably has a breaking strength of 15 MPa or more, particularly 20 MPa or more and 40 MPa or less, preferably 35 MPa or less.
The elongation at break and the strength at break can be measured according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”.

<Application>
The fine cellulose fiber-containing vulcanized rubber composition of the present invention has high breaking strength and breaking elongation, tires such as pneumatic tires for passenger cars, trucks, buses, heavy vehicles, etc., and other rubber crawlers It can be applied to various rubber products such as conveyor belts.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, unless this invention exceeds the summary, it is not limited by a following example.

[Production Example 1: Preparation of cellulose fiber 1 (enzyme-treated cellulose fiber)]
Softwood bleached kraft pulp (NBKP, Oji Paper's bay pine product) is used as a cellulose fiber raw material, beaten with Niagara beater (capacity 23 liters, manufactured by Tozai Seiki Co., Ltd.) for 200 minutes, and a pulp dispersion (pulp concentration 2% by weight, A weighted average fiber length after beating: 1.61 mm) was obtained.
The pulp dispersion was dehydrated to a concentration of 3% by weight, adjusted to pH 6 with 0.1% by weight sulfuric acid, warmed in a water bath until 50 ° C., and then enzyme GC220 (Genencor) was pulped (converted to solid content) 1% by weight with respect to) and allowed to react with stirring at 50 ° C. for 1 hour. Then, it heated at 95 degreeC or more for 20 minutes, the enzyme was deactivated, and the enzyme treatment cellulose fiber dispersion liquid was obtained.

[Example 1]
<Manufacture of fine cellulose fiber dispersion>
The solid content of carbon black (“Dia Black G” manufactured by Mitsubishi Chemical Corporation) of 12.8 g and the dispersion of enzyme-treated cellulose fibers obtained in Production Example 1 are such that the solid content of cellulose fibers is 1.6 g. By adding carbon black to the cellulose fiber dispersion and treating with a rotary high speed homogenizer (CLEAMIX 0.8S manufactured by M Technique Co., Ltd.) for 60 minutes at 20000 rpm, the cellulose fibers are defibrated. A nanofiberized carbon black-containing fine cellulose fiber dispersion (slurry 1) was obtained. The solid content concentration of the carbon black of the slurry 1 was 4% by weight, and the solid content concentration of the enzyme-treated cellulose fiber was 0.5% by weight.

  Next, with respect to 100 parts by weight as the solid content of the natural rubber latex (solid content concentration 61% by weight), the slurry 1 is added to 5 parts by weight as the solid content of cellulose, and then mixed using a homogenizer. A rubber-carbon black-containing fine cellulose fiber mixture (carbon black-containing rubber latex dispersion) was obtained. As a result of visual evaluation of the dispersibility of the fine cellulose fibers made into nanofibers in the obtained carbon black-containing rubber latex dispersion, the dispersibility was good.

<Production of Fine Cellulose Fiber Containing Composition and Fine Cellulose Fiber Containing Vulcanized Rubber Composition>
Next, the obtained carbon black-containing rubber latex dispersion was put in a vat and dried and solidified in an oven at 110 ° C. to obtain a rubber composition (fine cellulose fiber-containing composition) containing slurry 1.
The obtained rubber composition (hereinafter referred to as rubber composition 1) contains 5 parts by weight of fine cellulose fibers that have been made into nanofibers with respect to 100 parts by weight of the natural rubber component. Carbon black is contained in an amount of 40 parts by weight with respect to 100 parts of the natural rubber component. Furthermore, 3 parts by weight of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.) in a ratio to 100 parts by weight of the natural rubber component, a vulcanization accelerator (N-tert-butyl-2-benzothiazole sulfenamide), 1 part by weight of Wako Pure Chemical Industries, Ltd.), 2 parts by weight of sulfur (5% oil-treated powder sulfur, manufactured by Tsurumi Chemical Co., Ltd.), 3 parts by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd.) It was.
Specifically, the rubber composition 1 is added with components other than the vulcanization accelerator and sulfur, kneaded at 140 ° C. for 3 minutes using a kneading apparatus (laboroplast mill μ, manufactured by Toyo Seiki Co., Ltd.), and further added. A sulfur accelerator and sulfur were added and kneaded at 80 ° C. for 3 minutes.
This was pressure-press vulcanized at 160 ° C. for 10 minutes to obtain a vulcanized rubber composition 1 having a thickness of 1 mm (a vulcanized rubber composition containing fine cellulose fibers).

[Comparative Example 1]
Using the solid content of 1.6 g of the enzyme-treated cellulose fiber 1 obtained in Production Example 1, it was treated at 20000 rpm for 60 minutes with a rotary high-speed homogenizer (Cleamix 0.8S manufactured by Mtec Co., Ltd.) to defibrate the cellulose fiber. Was performed to obtain a slurry 2 of fine cellulose fibers made into nanofibers. The solid content concentration of the enzyme-treated cellulose fiber at this time was 0.5% by weight.
Next, to 100 parts by weight as the solid content of the natural rubber latex (solid concentration 61% by weight), the slurry 2 is added so as to be 5 parts by weight as the solid content of cellulose, and then mixed using a homogenizer, A rubber-containing cellulose fiber mixture (rubber latex dispersion 1) was obtained. As a result of visual evaluation of the dispersibility of the nanofiberized fine cellulose fibers in the obtained rubber latex dispersion 1, the dispersibility was good.
Next, the obtained rubber latex dispersion 1 was put in a vat and dried and solidified in an oven at 110 ° C. to obtain a rubber composition containing slurry 2.
The obtained rubber composition (hereinafter referred to as rubber composition 2) contains 5 parts by weight of fine cellulose fibers that are made into nanofibers with respect to 100 parts by weight of natural rubber. Furthermore, for 100 parts by weight of the natural rubber component, 40 parts by weight of carbon black (“Dia Black G” manufactured by Mitsubishi Chemical Corporation), 3 parts by weight of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.), Sulfur accelerator (N-tert-butyl-2-benzothiazolesulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight, sulfur (5% oil-treated powdered sulfur, manufactured by Tsurumi Chemical Co., Ltd.), 2 parts by weight, stearic acid 3 parts by weight (manufactured by Wako Pure Chemical Industries, Ltd.) was blended and kneaded.
Specifically, the rubber composition 2 is added with components other than the vulcanization accelerator and sulfur, kneaded at 140 ° C. for 3 minutes using a kneading apparatus (laboroplast mill μ, manufactured by Toyo Seiki Co., Ltd.), and further added. A sulfur accelerator and sulfur were added and kneaded at 80 ° C. for 3 minutes.
This was pressure-press vulcanized at 160 ° C. for 10 minutes to obtain a vulcanized rubber composition 2 having a thickness of 1 mm.

[Comparative Example 2]
100 parts by weight as a solid content of natural rubber latex (solid content concentration 61% by weight) was put into a vat and dried and solidified in an oven at 110 ° C.
This contains only 100 parts by weight of the natural rubber component. Furthermore, for 100 parts by weight of the natural rubber component, 40 parts by weight of carbon black (“Dia Black G” manufactured by Mitsubishi Chemical Corporation), 3 parts by weight of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.), Sulfur accelerator (N-tert-butyl-2-benzothiazolesulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.) 1 part by weight, sulfur (5% oil-treated powdered sulfur, manufactured by Tsurumi Chemical Co., Ltd.), 2 parts by weight, stearic acid 3 parts by weight (manufactured by Wako Pure Chemical Industries, Ltd.) was blended and kneaded.
Specifically, a vulcanization accelerator and components other than sulfur are added to natural rubber, and the mixture is kneaded at 140 ° C. for 3 minutes using a kneading apparatus (Laboplast Mill μ, manufactured by Toyo Seiki Co., Ltd.), and further vulcanization is accelerated. The agent and sulfur were added and kneaded at 80 ° C. for 3 minutes.
This was pressure-press vulcanized at 160 ° C. for 10 minutes to obtain a vulcanized rubber composition 3 having a thickness of 1 mm.

[Evaluation test]
The vulcanized rubber composition 1, the vulcanized rubber composition 2, and the vulcanized rubber composition 3 obtained in Example 1 and Comparative Examples 1 and 2 were made into predetermined dumbbell-shaped test pieces, and the breaking strength and breaking elongation were obtained. The results are shown in Table 1.
The breaking strength and breaking elongation were measured by a tensile test according to JIS K6251, and the breaking strength and breaking elongation of the vulcanized rubber composition were measured.
The larger the index, the better the reinforcement.

From Table 1, the vulcanized rubber composition 1 of Example 1 obtained from the production method of the present invention does not use fine cellulose fibers, and has higher breaking strength than Comparative Example 2 in which carbon black is added during kneading. The elongation at break was shown. Also, after mixing and drying and solidifying the refined cellulose fibers and the rubber latex, compared with the vulcanized rubber composition 2 of Comparative Example 1 in which carbon black was added during kneading, the breaking strength was the same and the high breaking elongation was high. As a result, it was found that the reinforcing property was excellent.
This is because cellulose fibers and carbon black are simultaneously defibrated, so that the cellulose fibers are refined and the carbon black particles are finely dispersed, and the finely dispersed carbon black particles are uniformly mixed with the fine cellulose fibers. It is thought that it was because of.

  According to the present invention, a fine cellulose fiber-containing vulcanized rubber composition having improved reinforcing properties can be produced, so that it can be suitably used for rubber members, hoses, belts, vibration-proof sheets and the like of various tires.

Claims (7)

  A method for producing a fine cellulose fiber dispersion containing fine cellulose fibers and carbon black, comprising a step of defibrating cellulose fibers in a raw material dispersion containing cellulose fibers and carbon black A method for producing a fine cellulose fiber dispersion.   The manufacturing method of the fine cellulose fiber dispersion liquid of Claim 1 whose density | concentration of the cellulose fiber in the said raw material dispersion liquid is 0.01-30 weight%.   The manufacturing method of the fine cellulose fiber dispersion liquid of Claim 1 or 2 with which the said raw material dispersion liquid contains 1-50 weight part of cellulose fibers with respect to 100 weight part of carbon black.   The fine cellulose fiber dispersion liquid manufactured by the manufacturing method as described in any one of Claims 1 thru | or 3.   Furthermore, the fine cellulose fiber dispersion liquid of Claim 4 containing a rubber component.   The fine cellulose fiber containing composition obtained by removing a dispersion medium from the fine cellulose fiber dispersion liquid of Claim 5.   A fine cellulose fiber-containing vulcanized rubber composition obtained by vulcanizing the fine cellulose fiber-containing composition according to claim 6.