JP2013241586A - Rubber modifying material, rubber latex dispersion and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber modifying material, which shows satisfactory dispersibility in a dispersion liquid and has an excellent rubber modifying effect such as rubber reinforcing property.SOLUTION: A rubber modifying material is composed of cellulose fibers, and has a number average fiber diameter of 5-35 nm. A rubber latex dispersion containing the rubber modifying material and a dispersion medium, a rubber latex dispersion containing the rubber modifying material and a rubber latex, a rubber composition containing the rubber modifying material and a rubber component, and a vulcanized rubber composition produced by vulcanizing the rubber composition are also provided. This rubber modifying material can provide a rubber composition and a vulcanized rubber composition which have high elastic modulus, high breaking strength and low-heat-generating property.

Description

The present invention relates to a rubber modifier, and more particularly to a rubber modifier using cellulose fibers.
The present invention also relates to a rubber modifier dispersion, a rubber latex dispersion, a rubber composition, and a vulcanized rubber composition containing the rubber modifier.

  The technology to improve the hardness and modulus by mixing fibers with rubber is already known. Fibers with a large diameter are easy to disperse into rubber, but the physical properties such as fatigue resistance decrease, and conversely when the diameter is thin Although fatigue resistance is improved, there is a tendency that the dispersibility in rubber tends to deteriorate due to entanglement of fibers.

  Therefore, in Patent Document 1, a blended fiber having a sea-island cross section is dispersed in rubber and fibrillated by a shearing force during mixing to increase the contact area with the rubber, thereby achieving both dispersibility and fatigue resistance. Proposed fibers have been proposed. However, since this fiber forms a sea-island structure by phase separation of the resin, the thickness and length are non-uniform, the diameter is as thick as 1 μm and 0.7 μm, and the contact area with the rubber is not sufficiently large, A large reinforcing effect cannot be expected.

  Patent Document 2 discloses that when cellulose cellulose having a fine diameter of 0.1 μm is mixed with diene rubber together with starch as a reinforcing agent for the purpose of improving wear resistance, the wear resistance is higher than when blended with starch alone. It is disclosed that the sex index is improved. However, cellulose alone is considered to have a problem in processability, and starch is blended 5 times or more of cellulose. Bacterial cellulose is dispersed in nano-size in water, but tends to aggregate in rubber. Therefore, it is thought that dispersibility was improved by blending starch. This is offset and it is expected that the reinforcing effect is not yet sufficient.

Japanese Patent Laid-Open No. 10-7811 JP 2005-133025 A

It is an object of the present invention to provide a rubber modifying material using cellulose fibers, which exhibits good dispersibility in a dispersion and is excellent in rubber modifying effects such as rubber reinforcement. And
Another object of the present invention is to provide a rubber modifier having a high elastic modulus and a high breaking strength and capable of obtaining a low exothermic rubber composition and a vulcanized rubber composition.

  As a result of intensive studies by the present inventors, it has been found that the above problems can be solved by using cellulose fibers having a number average fiber diameter of 5 to 35 nm as rubber modifiers, and the present invention has been achieved.

  That is, the present invention is a rubber modifying material comprising cellulose fibers, the number average fiber diameter of 5 to 35 nm, a rubber modifying material containing the rubber modifying material and a dispersion medium. , Rubber latex dispersion containing the rubber modifier and rubber latex, rubber composition containing the rubber modifier and rubber component, and vulcanized rubber produced by vulcanizing the rubber composition Composition.

  The rubber modifier of the present invention exhibits excellent dispersibility in the rubber latex dispersion, and further disperses well in the rubber composition and contains the rubber modifier of the present invention and the present rubber composition. The vulcanized rubber composition produced by vulcanizing the rubber composition of the invention has a high elastic modulus and a high breaking strength, has a high rubber reinforcing effect, and has a low exothermic property.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. The content of is not specified.

[Rubber modifier]
The rubber modifier of the present invention is a rubber modifier made of cellulose fibers, and the number average fiber diameter of the cellulose fibers is 5 to 35 nm.

  The cellulose fiber contained in the rubber modifier of the present invention may be produced by any production method.

  The rubber modifier of the present invention may be produced, for example, by subjecting the cellulose fiber raw material to be described in detail below to fibrillation and adjusting the fiber diameter, or by dispersing the cellulose fiber raw material in rubber latex. In this state, the fiber diameter may be adjusted by performing a defibrating process.

<Number average fiber diameter of cellulose fibers>
The cellulose fiber used as the rubber modifier of the present invention has a number average fiber diameter of 35 nm or less. The number average fiber diameter of the cellulose fibers is preferably 30 nm or less, more preferably 25 nm or less, further preferably 20 nm or less, further preferably 17 nm or less, particularly preferably 15 nm or less, and most preferably 10 nm or less. The number average fiber diameter of the cellulose fibers is 5 nm or more, more preferably 6 nm or more, and particularly preferably 7 nm or more. By using the cellulose fiber in this range, the rubber composition and the vulcanized rubber composition containing the rubber modifier of the present invention can express a high elastic modulus, a high breaking strength, and a low tan δ in a balanced manner.

  The fiber diameter of the cellulose fiber of the rubber modifier of the present invention is determined by drying and removing the dispersion medium in the rubber modifier dispersion (after forming a sheet), and then using a scanning electron microscope (hereinafter SEM) or transmission electron. It can be determined by observing with a microscope (hereinafter referred to as TEM), an atomic force microscope (hereinafter referred to as AFM), an X-ray small angle scattering (hereinafter referred to as SAXS) or the like.

<Cellulose fiber raw material>
In the present invention, the cellulose fiber raw material is obtained by removing impurities from a cellulose-containing material as shown below through a general purification process.

(Cellulose-containing material)
Examples of cellulose-containing materials include woods such as conifers and hardwoods (wood flour, etc.), cotton such as cotton linter and cotton lint, pomace such as sugar cane and sugar radish, bast fibers such as flax, ramie, jute and kenaf Vegetal vein fibers such as sisal and pineapple, petiole fibers such as abaca and banana, fruit fibers such as coconut palm, stem-derived fibers such as bamboo, bacterial cellulose produced by bacteria, seaweed and squirts such as valonia and falcon Natural cellulose such as encapsulates. 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.

Bacterial cellulose is preferred in that it can be easily obtained with a fine fiber diameter. Cotton is also preferable in that it is easy to obtain a fine fiber diameter, and more preferable in terms of easy acquisition of raw materials.
In addition, wood of conifers and hardwoods with fine fiber diameters can be obtained, and it is the largest amount of biological resources on the planet. It is a sustainable resource that produces about 70 billion tons per year. Therefore, it contributes greatly to the reduction of carbon dioxide that affects global warming, which is advantageous from an economic point of view.

(Cellulose fiber raw material)
The cellulose fiber raw material is obtained by refining the above cellulose-containing material by a usual method.
For example, it is obtained by degreasing with benzene-ethanol or sodium carbonate aqueous solution, followed by delignification treatment with chlorite (Wise method) and dehemicellulose treatment with alkali. In addition to the 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 as purification methods. Moreover, a bleaching process etc. are further performed suitably.

  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.

The cellulose fiber raw material may be obtained by a general method for producing chemical pulp, for example, a method for producing kraft pulp, salified pulp, alkali pulp, or nitrate pulp.
That is, pulps such as hardwood kraft pulp, softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp, hardwood bleached kraft pulp, softwood bleached kraft pulp, and linter pulp may be used as the cellulose fiber raw material.

  In addition, as a raw material for cellulose fiber, CGP (Chemical Groundwood Pulp) or the like which is subjected to light chemical treatment with ground pulp, such as SGW (Stone Groundwood) or sodium sulfite, and then crushed, can be used. Groundwood pulp is preferably used.

  In addition, the cellulose-containing material may be crushed into a state such as wood chips or wood powder, and this crushing may be performed at any timing before, during or after the purification treatment.

  The degree of purification of the cellulose fiber raw material obtained by refining the cellulose-containing material is not particularly defined, but it is preferable that the fat content of the cellulose fiber raw material is less because the fat and oil and lignin are less and the cellulose component content is higher. The content of the cellulose component is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more.

  The cellulose component of the cellulose fiber raw material can be classified into a crystalline α-cellulose component and an amorphous hemicellulose component. It is preferable that the content of crystalline α-cellulose is large because effects of a low linear expansion coefficient, a high elastic modulus, and a high strength are easily obtained when a rubber composition is obtained. The α-cellulose content of the cellulose fiber raw material is preferably 70% by weight or more, more preferably 75% by weight or more, more preferably 80% by weight or more.

  Although the fiber diameter of the cellulose fiber raw material is not particularly limited, the number average fiber diameter is usually 1 μm to 1 mm. What has undergone general purification is about 50 μm.

<Pretreatment of cellulose fiber>
Although the fine cellulose fiber having a number average fiber diameter of 5 to 35 nm according to the present invention can be obtained by defibrating the cellulose fiber raw material as it is, the fine cellulose fiber having a number average fiber diameter of 5 to 35 nm is efficiently obtained by defibration. In order to obtain well, you may pre-process.
Examples of the pretreatment include cellulose oxidation treatment and enzyme treatment.

(Oxidation treatment)
Carboxy group can be introduce | transduced with respect to the cellulose which comprises a cellulose fiber by performing an oxidation process.
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 introduction amount of the carboxy group is too large, there is a possibility that a desired fine cellulose fiber 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 above oxidation treatment is subjected to a purification treatment by washing with water or filtration.

(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. For example, 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), and the like can be mentioned. 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.

<Modified cellulose fiber>
The cellulose fiber used for the rubber modifier of the present invention may contain a modified cellulose fiber in which a part of the hydroxyl group of cellulose constituting the cellulose fiber is substituted with another group. At least some of the cellulose fibers may be modified cellulose fibers, or all may be modified cellulose fibers. When the rubber modifier of the present invention contains a modified cellulose fiber, the affinity with the rubber is preferably increased at the time of compounding with the rubber in the subsequent step.

In order to produce the modified cellulose fiber, for example, other groups are introduced into the hydroxyl group of cellulose by chemical or physical treatment. For example, a carboxy group or the like may be introduced by the aforementioned oxidation treatment.
The introduction of other groups may be performed on the cellulose fiber raw material or may be performed on the cellulose fiber after the defibrating treatment.

  Other groups introduced into the hydroxyl group of cellulose include carboxy group, acyl group, isocyanate group, alkyl group, oxirane group, oxetane group, thiirane group, thietane group, amino group, group derived from carboxylic acid group, and phosphate group 1 type or 2 types or more, such as these groups.

Specific examples of the acyl group include acetyl, acryloyl, methacryloyl, propionyl, propioyl, butyryl, 2-butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, and undecanoyl. Group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, cinnamoyl group and the like.
Specific examples of the isocyanate group include a 2-methacryloyloxyethylisocyanoyl group.
Specific examples of the alkyl group include 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, Examples include decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, stearyl group and the like.

  Among these, acyl groups having 2 to 12 carbon atoms such as acetyl group, acryloyl group, methacryloyl group, benzoyl group and naphthoyl group, alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group and propyl group, A group derived from an acid group and a group derived from a phosphate group are preferred.

  The method for introducing the other group by chemical treatment is not particularly limited, but a method of reacting a cellulose fiber raw material or cellulose fiber after defibration treatment with the following chemical modifiers There is. Although there are no particular limitations on the reaction conditions, a solvent, a catalyst, or the like may be used, or heating, decompression, or the like may be performed as necessary.

  Chemical modifiers include acids, acid anhydrides, alcohols, halogenating reagents, isocyanates, alkoxysilanes, cyclic ethers such as oxiranes (epoxies), glycidyltrialkylammonium halides or their halohydrins, phosphoric acids or phosphoric acid derivatives. 1 type (s) or 2 or more types chosen from the group which consists of are mentioned.

(Cellulose phosphate fiber)
In the following, a cellulose fiber (hereinafter referred to as “phosphorus”) in which a part of the hydroxyl group of cellulose constituting the cellulose fiber, which is suitable as the modified cellulose fiber used in the present invention, is substituted with a group derived from phosphoric acid and a group derived from phosphoric acid is introduced. The “acid cellulose fiber” may be referred to.).

Here, the group derived from phosphoric acid is a group that binds to cellulose by a reaction between phosphoric acid or a phosphoric acid derivative and a hydroxyl group of cellulose. Usually, the cellulose phosphate referred to in the present invention is at least one phosphoric acid selected from the group consisting of a part of the hydroxyl group of cellulose consisting of a phosphoric acid group, a phosphorous acid group, a phosphonic acid group, a polyphosphoric acid group, and a polyphosphonic acid group. Substituted with a group derived from, preferably substituted with a phosphate group (HPO ₄ ²⁻ or H ₂ PO ₄ ⁻ ) or a polyphosphate group, more preferably substituted with a phosphate group For example, this HPO ₄ ²⁻ or H ₂ PO ₄ ⁻ is a group derived from phosphoric acid. In addition, the hydrogen atom in this phosphoric acid-derived group may be substituted with another group, for example, may form a salt. More specifically, alkali metal ions such as sodium, potassium and lithium, alkaline earth metal ions such as calcium and magnesium, and ammonium such as ammonia, aliphatic amine, aromatic amine, aliphatic ammonium and aromatic ammonium A salt may be formed with system ions and the like.

As a method of introducing phosphoric acid-derived groups into cellulose, a method of mixing phosphoric acid or phosphoric acid derivative powder or aqueous solution into a dried or wet cellulose fiber raw material or cellulose fiber after defibration treatment, cellulose fiber Examples thereof include a method of adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a raw material or a dispersion of cellulose fibers after defibrating treatment.
In these methods, after mixing or adding a powder or aqueous solution of phosphoric acid or phosphoric acid derivative, usually, dehydration, heating or the like is performed.
For example, two types of sodium dihydrogen phosphate and disodium hydrogen phosphate are mixed to prepare a phosphorylating reagent aqueous solution adjusted to pH 5-7, and this phosphorylating reagent aqueous solution is immersed or mixed in a wet cellulose fiber raw material Thereafter, a method of heating at a temperature of 130 ° C. or less (particularly preferably 110 ° C. or less) to sufficiently remove the moisture of the cellulose fiber raw material and heating at 130 to 170 ° C. is exemplified.

  Examples of the phosphoric acid or phosphoric acid derivative used herein include at least one compound selected from an oxo acid containing a phosphorus atom, a polyoxo acid or a derivative thereof. Specifically, phosphoric acid, polyphosphoric acid, Examples thereof include phosphorous acid, phosphonic acid, polyphosphonic acid, and salts or esters thereof. Among these, phosphoric acid, polyphosphoric acid, or a salt thereof is preferable, and the salt is preferably an alkali metal salt such as sodium or potassium, an ammonium salt, or an amine salt. Among these, phosphoric acid, sodium salt, potassium salt or ammonium salt of phosphoric acid, phosphoric acid, polyphosphoric acid, etc. from the viewpoint of high introduction efficiency of phosphoric acid-derived groups, easy defibration, and industrial application. Acid, sodium salt, potassium salt, and ammonium salt of polyphosphoric acid are preferable, and phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, and ammonium salt of phosphoric acid are more preferable.

  In order to make the group derived from phosphoric acid introduced into cellulose into a salt form, it may be treated with an alkaline aqueous solution or the like after the treatment with the phosphoric acid or the phosphoric acid derivative. After these treatments, the dispersion is usually washed with water until the pH of the dispersion becomes neutral.

  Specific examples of phosphoric acid or phosphoric acid derivatives include phosphoric acid; sodium salts of phosphoric acid such as sodium dihydrogen phosphate, disodium hydrogen phosphate, and trisodium phosphate; sodium pyrophosphate, sodium metaphosphate, etc. Sodium salt of polyphosphoric acid; potassium salt of phosphoric acid such as potassium dihydrogen phosphate, dipotassium hydrogen phosphate and tripotassium phosphate; potassium salt of polyphosphoric acid such as potassium pyrophosphate and potassium metaphosphate; ammonium dihydrogen phosphate And ammonium salts of phosphoric acid such as diammonium hydrogen phosphate and triammonium phosphate; ammonium salts of polyphosphoric acid such as ammonium pyrophosphate and ammonium metaphosphate. In particular, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferred.

  These may be used alone or in combination of two or more. That is, two or more types of phosphoric acid-derived groups may be introduced into the cellulose phosphate fiber. For example, two or more types of phosphoric acid-derived groups substituted with different groups of hydrogen atoms may be introduced into the cellulose phosphate fiber.

(Carboxylic acid cellulose fiber)
Next, a cellulose fiber (hereinafter referred to as “carboxyl”) in which a part of the hydroxyl group of cellulose constituting the cellulose fiber, which is suitable as the modified cellulose fiber used in the present invention, is substituted with a group derived from a carboxylic acid and a group derived from a carboxylic acid is introduced. The “acid cellulose fiber” may be referred to.).

  Here, the carboxylic acid-derived group is a group that binds to cellulose by the reaction of a carboxylic acid compound and cellulose, and two or more carboxylic acid-derived groups (—O (CO) —group) in the group. It is group which has.

  Usually, the carboxylate cellulose referred to in the present invention is one in which a part of hydroxyl groups of cellulose is substituted with —O (CO) —R— (CO) OH, and this —O (CO) —R— (CO). OH becomes a group derived from carboxylic acid. Here, R is an alkylene group, an aromatic hydrocarbon group, or a group combining these. In addition, a plurality of terminal carboxy groups may be bonded to R.

  Further, the terminal hydrogen atom of the carboxylic acid-derived group may be substituted with another group, for example, may form a carboxylate salt, an alkali metal ion such as sodium, potassium, lithium, etc. Further, salts may be formed with alkaline earth metal ions such as calcium and magnesium, and ammonium ions such as ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums and aromatic ammoniums.

  Examples of a method for introducing a carboxylic acid-derived group into cellulose include a method of mixing a gasified carboxylic acid compound into cellulose fibers, a method of adding a carboxylic acid compound to a dispersion of cellulose fiber raw materials, and the like. Among these, since the process is simple and the introduction efficiency of the group derived from the carboxylic acid is increased, a method of mixing the gasified carboxylic acid compound with the cellulose fiber is preferable. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid-based compound used for introducing a carboxylic acid-derived group into cellulose is a compound having a carboxy group, and preferably a compound having two or more carboxy groups in the molecule. Examples of such carboxylic acid compounds include maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, itaconic acid, pyromellitic acid, 1,2-cyclohexanecarboxylic acid and other dicarboxylic acids, maleic anhydride And dicarboxylic anhydrides such as succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, and 1,2-cyclohexanecarboxylic acid anhydride. In addition, derivatives of the above-exemplified carboxylic acids such as an acid anhydride imidized product, dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, and the like are also included.
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.
These may be used alone or in combination of two or more. That is, two or more carboxylic acid-derived groups may be introduced into the carboxylic acid cellulose fiber.

  In addition, in order to make the group derived from the carboxylic acid introduced into the cellulose fiber into a salt form, the group may be treated with an alkaline aqueous solution after being treated with the carboxylic acid compound. After these treatments, the dispersion is usually washed with water until the pH of the dispersion becomes neutral.

(Introduction amount of other group of modified cellulose fiber)
In the modified cellulose fiber, it is preferable that 0.1 to 2.0 mmol / g of other groups such as a group derived from phosphoric acid and a group derived from carboxylic acid are usually introduced to the cellulose fiber.
When the modified cellulose fiber has two or more of other groups such as a group derived from phosphoric acid and a group derived from carboxylic acid, 0.1 to 2.0 mmol / g is usually introduced to the cellulose fiber in total. It is preferable that

  Increasing the amount of other groups introduced into the cellulose fiber is preferable because, when combined with rubber in a later step, the affinity with the rubber is increased, but if it is too small, the rubber resulting from the introduction of these groups. In some cases, the effect of improving the affinity cannot be sufficiently obtained.

  Here, the amount of other groups introduced, for example, the amount of phosphoric acid-derived groups or carboxylic acid-derived groups introduced into cellulose fibers can be determined by the following method.

<Introduction amount of carboxylic acid-derived group>
About the calculation method of the introduction amount of group derived from carboxylic acid, it calculated using TAPPI T237 cm-08 (2008). Specifically, in order to make it possible to calculate the introduction number of acidic groups (here, carboxy groups) over a wider range, among the test solutions used in the test method, sodium bicarbonate (NaHCO ₃ ) / sodium chloride (NaCl) = 0.84 g / 5.85 g of the test solution dissolved in 1000 ml with distilled water, sodium bicarbonate / sodium chloride = 3.36 g / 23.23 so that the concentration of the test solution is substantially quadrupled. The amount is calculated according to TAPPI T237 cm-08 (2008) except that the difference is 40 g, and the difference between the calculated values in the cellulose fiber before and after the introduction of the substituent is set to the substantial substituent introduction amount.

<Introduction amount of phosphoric acid-derived group>
The amount of phosphoric acid-derived groups introduced into cellulose was calculated using TAPPI T237 cm-08 (2008). Specifically, in order to make it possible to calculate the introduction amount of phosphoric acid-derived acidic groups introduced into cellulose over a wider range, among the test solutions used in the test method, sodium bicarbonate (NaHCO ₃ ) / sodium chloride The test solution in which (NaCl) = 0.84 g / 5.85 g was dissolved and diluted in 1000 ml with distilled water was changed to a test solution in which 1.60 g of sodium hydroxide was dissolved and diluted in 1000 ml with distilled water. The difference in the calculated values of the cellulose fibers was calculated according to TAPPI T237 cm-08 (2008) as a substantial substituent introduction amount (monovalent acidic group). Furthermore, in order to calculate the introduction amount of the phosphoric acid-derived group that is a polyvalent acidic group, the value obtained by dividing the obtained substituent introduction amount by the acid number of the phosphoric acid-derived group is derived from the phosphoric acid-derived group. The amount introduced was the group.

<Defibration processing>
By subjecting the above-mentioned cellulose fiber raw material to a defibrating treatment, a rubber modifier made of fine cellulose fibers having a number average fiber diameter of 5 to 35 nm can be obtained.

  A specific method of the defibrating treatment is not particularly limited. For example, ceramic beads having a diameter of about 1 mm are dispersed in a cellulose fiber raw material concentration of 0.1 to 10% by weight, for example, about 1% by weight. A method of defibrating the cellulose fiber raw material by putting it in a liquid (hereinafter sometimes referred to as “cellulose fiber dispersion”) and applying vibration using a paint shaker, a bead mill, or the like.

  In addition, as a dispersion medium of a cellulose fiber dispersion liquid, an organic solvent, water, or a mixed liquid of an organic solvent and water can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, n-butanol, ethylene glycol, and ethylene glycol mono-t-butyl ether, ketones such as acetone and methyl ethyl ketone, and cyclic ethers such as tetrahydrofuran. In addition, one or more water-soluble organic solvents can be used. The dispersion medium is preferably a mixed liquid of an organic solvent and water or water, and particularly preferably water.

  Defibration methods include a blender-type disperser and a high-speed rotating slit that uses a cellulose fiber dispersion to apply a shearing force (using a high-speed rotating homogenizer), or a sudden decrease in pressure from high pressure. By using a high-pressure homogenizer method, a method using a counter-impact type disperser such as “Masscomizer X (Masuyuki Sangyo)”, etc. Is mentioned. In particular, the efficiency of defibration is improved by adopting a treatment using a high-speed rotation type homogenizer or a high-pressure homogenizer.

  In the case of defibration by these treatments, the solid content concentration as the cellulose fiber raw material is 0.1% by weight or more, preferably 0.2% by weight or more, particularly 0.3% by weight or more, and 10% by weight or less, particularly It is preferable to perform a defibrating treatment on 6% by weight or less of the cellulose fiber dispersion. If the solid content concentration in the cellulose fiber dispersion to be subjected to the defibrating process is too low, the amount of liquid will be excessive with respect to the amount of cellulose fiber raw material to be processed, and the efficiency will be poor. Therefore, the concentration of the cellulose fiber dispersion used for the defibrating treatment is adjusted by adding water as appropriate.

  In addition, you may perform the fibrillation (miniaturization) process which combined the ultrasonic process after the process by such a high voltage | pressure homogenizer and the process by a high-speed rotation type homogenizer.

[Rubber modifier dispersion]
The rubber modifier of the present invention is usually provided as a dispersion of cellulose fibers (rubber modifier dispersion). The rubber modifier dispersion of the present invention may contain a dispersion medium in addition to cellulose fibers, and may be composed of the cellulose fibers and the dispersion medium, or other additives and the like as long as the effects of the present invention are not impaired. May be included.

Examples of the dispersion medium include water, alcohol, ketone, ether, glycol ether, cyclic ether, amide, aromatic hydrocarbon, aprotic polar dispersion medium, and the like. These dispersion media may be used individually by 1 type, and may use 2 or more types together.
In addition, it is preferable that the solvent used as a dispersion medium of the rubber modifier dispersion liquid is not too high in boiling point because there is a step of removing the solvent in a later step. 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.

  Specific examples of the aromatic hydrocarbon as the dispersion medium include benzene, toluene, xylene and the like.

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

  As ketones (referring to liquids having ketone groups), acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), diisopropyl ketone, di-tert-butyl ketone, 2-heptanone, 4-heptanone, 2-octanone, cyclopenta Non, cyclohexanone, cyclohexyl methyl ketone, acetophenone, acetylacetone, dioxane and the like can be mentioned. Among these, preferred are methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone and cyclohexanone, and more preferred are methyl ethyl ketone (MEK) and cyclohexanone.

  Examples of the ether include diethyl ether, dimethyl ether, methyl ethyl ether, furan, dibenzofuran and the like. Of these, diethyl ether and furan are preferable.

  Examples of the aprotic polar dispersion medium include dimethyl sulfoxide (DMSO), formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, 2-pyrrolidone, N -Methylpyrrolidone and the like.

  Specific examples of the glycol ether 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 mono- Examples thereof include 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 and the like.

  Examples of the cyclic ether include tetrahydrofuran.

  The content of the cellulose fiber (rubber modifier) in the rubber modifier dispersion is not particularly limited, but it is 0 with respect to the total amount of the dispersion from the viewpoint of handleability such that the viscosity and the liquid stability are suitable. 0.05% by weight or more is preferable, 0.1% by weight or more is more preferable, 50% by weight or less is preferable, and 40% by weight or less is more preferable.

  In addition, in this dispersion liquid, only one of a cellulose fiber (non-modified cellulose fiber) and a modified cellulose fiber may be contained, or both may be contained. That is, the rubber modifier of the present invention may be composed of only unmodified cellulose fibers or modified cellulose fibers, or may be a mixture of unmodified cellulose fibers and modified cellulose fibers.

[Rubber latex dispersion]
The rubber latex dispersion of the present invention contains the rubber modifier of the present invention and a rubber latex. In preparing the rubber latex dispersion of the present invention, the cellulose fiber raw material is directly used as the rubber latex. The fibers may be mixed and defibrated in this mixed solution. In this case, the cellulose fiber raw material is in a state of being dispersed in the rubber latex, and the rubber of the present invention containing the rubber modifier of the present invention having high dispersibility by further defibration treatment. A latex dispersion can be obtained.
The defibrating process in this case will be described below.

As the dispersion medium for dispersing the cellulose fiber raw material, water is usually used, but the organic solvent or the like exemplified above as the dispersion medium for the rubber modifier dispersion liquid may be used. In that case, since the cellulose fiber raw material is usually in the state of an aqueous dispersion, the water in the aqueous dispersion of the cellulose fiber raw material may be replaced with an organic solvent in advance. The method for substituting the solvent in the solvent replacement step is not particularly limited, but water is removed from the aqueous dispersion containing the cellulose fiber raw material by filtration, etc., and an organic solvent used during defibration is added thereto, followed by stirring and mixing. The method of removing an organic solvent by filtration again 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.

  Next, the cellulose fiber raw material dispersion containing the cellulose fiber raw material and the rubber latex are mixed. In mixing, rubber latex may be directly added to the dispersion and mixed.

  The content of the cellulose fiber raw material in the rubber latex dispersion before defibration is not particularly limited, but is preferably 0.01% by weight or more, and 0.05% by weight relative to the total amount of the rubber latex dispersion before defibration. The above is more preferable, 50% by weight or less is preferable, and 40% by weight or less is more preferable.

  The solid content of rubber in the rubber latex dispersion before defibration is not particularly limited, but is preferably 2% by weight or more, more preferably 2.5% by weight or more, based on the total amount of rubber latex dispersion before defibration, 10 wt% or more is more preferable, 20 wt% or more is particularly preferable, 95 wt% or less is preferable, and 80 wt% or less is more preferable.

  The content of the solvent (dispersion medium) in the rubber latex dispersion before defibration is not particularly limited, but is preferably 1% by weight or more, more preferably 5% by weight or more, based on the total amount of the rubber latex dispersion before defibration. 97.5% by weight or less, preferably 95% by weight or less.

  The weight ratio of the rubber component and the solvent in the dispersion in the rubber latex before defibration is not particularly limited, but the viscosity and liquid stability of the obtained rubber latex dispersion after defibration treatment are suitable. From the viewpoint of handleability, the solvent content is preferably 5 parts by weight or more, more preferably 25 parts by weight or more, preferably 2000 parts by weight or less, more preferably 1000 parts by weight or less, relative to 100 parts by weight of the rubber component. preferable.

  The weight ratio of the cellulose fiber raw material to the rubber component is not particularly limited in the rubber latex dispersion before defibration, but the content of the cellulose fiber raw material is the total amount (100% by weight) of the cellulose fiber raw material and the rubber component. On the other hand, it is preferably 2.5% by weight or more, more preferably 3% by weight or more, still more preferably 4% by weight or more, preferably 97.5% by weight or less, more preferably 97% by weight or less, and 95% by weight or less. Further preferred.

  The method of defibrating treatment when the rubber latex dispersion before defibrating is defibrated is the same as the method of defibrating the cellulose fiber raw material.

In the rubber latex dispersion obtained through the defibrating step, the defibrated cellulose fibers are uniformly dispersed, aggregation and sedimentation of the cellulose fibers are suppressed, and excellent liquid stability is obtained.
In the vulcanized rubber composition after the vulcanization step obtained using the rubber latex dispersion of the present invention containing cellulose fibers and rubber latex, the cellulose fibers are uniformly dispersed in the vulcanized rubber component. High elastic modulus and low loss tangent.

  The cellulose fiber content in the rubber latex dispersion of the present invention is appropriately adjusted depending on the amount of cellulose fiber raw material that is a starting raw material used. From the viewpoint of the stability of the dispersion, the content of cellulose fiber is 0%. 0.01 wt% or more is preferable, 0.05 wt% or more is more preferable, 50 wt% or less is preferable, 40 wt% or less is more preferable, and 30 wt% or less is more preferable.

  In addition, the content of the solvent and the rubber component in the rubber latex dispersion is the same as the content of each component of the rubber latex dispersion before defibration described above, and the preferred range is also the same.

  The cellulose fiber in the rubber latex dispersion is usually 1 part by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and usually 100 parts by weight or less with respect to 100 parts by weight of the rubber component (solid content). , Preferably 70 parts by weight or less, more preferably 50 parts by weight or less. If the amount of fiber is small, the reinforcing effect is not sufficient, and if it is large, the processability of rubber is lowered.

  In addition to cellulose fibers and rubber components, other compounding agents conventionally used in the rubber industry may be added to the rubber latex dispersion of the present invention. For example, other reinforcing materials such as silica particles, carbon black and fibers, inorganic and organic fillers, silane coupling agents, vulcanizing agents, stearic acid, vulcanization accelerators, vulcanization accelerators, oils, curing resins , Wax, anti-aging agent and the like.

  Of these, organic peroxides or sulfur vulcanizing agents can be used as the vulcanizing agent. 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. One of these vulcanizing agents may be used alone, or two or more thereof may be used in combination.

  The compounding amount of the vulcanizing agent in the rubber latex dispersion of the present invention is usually 7.0 parts by weight or less, preferably 6.0 parts by weight or less in the case of sulfur with respect to 100 parts by weight of the rubber component. Moreover, it is 1.0 weight part or more normally, Preferably it is 3.0 weight part or more, Especially 4.0 weight part or more.

[Rubber composition]
The rubber composition of the present invention comprises the rubber modifier of the present invention and a rubber component. Usually, the rubber composition of the present invention is produced using the rubber latex dispersion of the present invention.
The rubber composition of the present invention can be applied, for example, by applying the rubber latex dispersion of the present invention onto a substrate to form a coating film, pouring into a mold, or extruding, and drying as necessary. It is obtained by applying a treatment to remove the solvent. For example, by using the rubber latex dispersion of the present invention, moisture is removed from cellulose fibers dispersed in the rubber latex, and a necessary compounding agent is added to obtain a rubber composition, which is kneaded and desired in an unvulcanized state. The rubber composition is formed by extruding in accordance with the shape of the applied member and molding by a normal method on a molding machine. A vulcanized rubber composition can be obtained by heating and pressing the rubber composition in a vulcanizer. Such a vulcanized rubber composition has good durability.

Below, the manufacturing method of the rubber composition and vulcanized rubber composition of this invention is demonstrated.
In addition, the manufacturing method of the rubber composition of this invention may be provided with the addition process of adding a rubber component before the compounding process of detailed description below as needed.

<Composite process>
In the compounding step, a vulcanized rubber composition containing cellulose fibers and a vulcanized rubber component is obtained by vulcanizing the rubber composition (vulcanization step).
The vulcanized rubber composition of the present invention is obtained by removing the solvent from the rubber latex dispersion of the present invention as necessary, and further using a known method such as a rubber kneader to mix the rubber component and the above-mentioned various compounding agents. Are mixed and then molded and vulcanized by a known method.

The conditions for the vulcanization step are not particularly limited as long as the temperature is such that the rubber component can be converted into 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 cellulose fiber, 250 degreeC or less is preferable and the heating temperature has more preferable 200 degreeC or less. The heating time is usually 3 minutes or longer, preferably 5 minutes or longer, and preferably 180 minutes or shorter from the viewpoint of productivity.
The heat treatment may be performed multiple times by changing the temperature and the heating time.

<Content of cellulose fiber>
The cellulose fiber content in the rubber composition or vulcanized rubber composition of the present invention is appropriately adjusted depending on the purpose, but from the point of reinforcing effect, it is 0 with respect to the total amount of the rubber composition or vulcanized rubber composition. 0.5 wt% or more, preferably 1 wt% or more, more preferably 50 wt% or less, further preferably 40 wt% or less, and then 30 wt% or less, 10 wt% or less, 8 wt% or less, 5 wt% % Or less in order.

<Content of rubber component>
The content of the rubber component (solid content) in the rubber composition or vulcanized rubber composition of the present invention is appropriately adjusted according to the purpose. From the viewpoint of the reinforcing effect, the total amount of the rubber composition or vulcanized rubber composition is used. On the other hand, 10 weight% or more is preferable, 20 weight% or more is more preferable, 30 weight% or more is preferable, 99 weight% or less is more preferable, 95 weight% or less is further more preferable.

<Weight ratio between cellulose fiber and rubber component>
The weight ratio of the cellulose fiber and the rubber component contained in the rubber composition or vulcanized rubber composition of the present invention is the same as the weight ratio of the cellulose fiber and the rubber component in the rubber latex dispersion of the present invention.
The cellulose fiber is usually 1 part by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more, usually 100 parts by weight or less, preferably 70 parts by weight or less, relative to 100 parts by weight of the rubber component (solid content). More preferably, it is 50 parts by weight or less. If the amount of cellulose fiber in the rubber composition or vulcanized rubber composition is small, the reinforcing effect is not sufficient, and conversely if it is large, the processability of the rubber is lowered.
In addition to cellulose fibers and rubber components, other compounding agents used in the conventional rubber industry may be added to the rubber composition or vulcanized rubber composition of the present invention.

<Dispersion state of cellulose fiber>
In the rubber composition or vulcanized rubber composition of the present invention, the cellulose fiber is stably dispersed in the rubber component or the vulcanized rubber component without forming an agglomerate, and has a high elastic modulus due to the reinforcing effect of the cellulose fiber. At the same time, it is considered that high elongation at break and low exothermic property are achieved because the original elongation of the rubber is not hindered because the fiber diameter is thin.
In addition, the dispersion state of the cellulose fiber in the rubber composition or vulcanized rubber composition of the present invention can be confirmed by observing the cross-sectional structure with SEM or the like.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless the gist of the present invention is exceeded.

  In the following, the amount of phosphoric acid-derived group, carboxylic acid-derived group, or carboxy group introduced into cellulose was determined by the method described above.

Moreover, the number average fiber diameter of the fine cellulose fiber was measured as follows using an atomic force microscope (AFM).
Method: Atomic force microscopy (tapping mode)
Probe: Unmodified Si cantilever (NCH)
Environment: Room temperature and air (humidity about 50%)
Apparatus: Digital Instrument Nanoscope III manufactured by Bruker
Number of data sampling: 512 × 512 points AFM image type: height image, phase image (to recognize each fiber)
Image analysis method: A fiber is traced from the AFM observation image, and the fibers are extracted one by one.
The maximum height of one fiber was measured as the fiber thickness.
The measured values were averaged to obtain a number average fiber diameter.

[Production Example 1: Preparation of cellulose fiber 1 (cellulose phosphate fiber)]
6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate were dissolved in 19.62 g of water to obtain a phosphorylating reagent aqueous solution. The pH of this phosphorylating reagent aqueous solution was 6.0 at 25 ° C.
As cellulose fiber raw material, soft water bleached kraft pulp (manufactured by Oji Paper Co., Ltd., moisture 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121) was added with water to a concentration of 4% by weight. Then, a double slurry refiner was used to beat the irregular CSF (plain mesh 80 mesh, according to JIS P8121 except that the amount of pulp collected was 0.3 g) until the average fiber length was 0.68 mm to obtain a pulp slurry. After the obtained pulp slurry was diluted to 0.3% by weight, a pulp sheet having a moisture content of 90% (3 g as an absolute dry mass, thickness 200 μm) was obtained by a papermaking method. After this pulp sheet was immersed in 31.2 g of the phosphorylating reagent aqueous solution (80.2 parts by weight as the amount of phosphorus element with respect to 100 parts by weight of the dried pulp), a blow dryer at 105 ° C. (manufactured by Yamato Chemical Co., Ltd., DPM400) was dried for 1 hour, and further heat-treated with a 150 ° C. blast dryer (DKM400, supra) for 1 hour to obtain a pulp sheet in which phosphate groups were introduced into cellulose.

  Subsequently, 500 ml of ion-exchanged water was added to the pulp sheet into which phosphate groups had been introduced, and after stirring and washing, filtration and dehydration were performed to obtain dehydrated pulp. The obtained dehydrated pulp was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a pulp slurry having a pH of 12 to 13. Thereafter, this pulp slurry was filtered and dehydrated, and washing with 500 ml of ion-exchanged water and filtration and dehydration were repeated a total of three times to finally obtain cellulose phosphate.

As a result of X-ray diffraction, the cellulose maintained a cellulose I-type crystal, and further, absorption based on a phosphate group was observed at 1230 to 1290 cm ⁻¹ by measurement of an infrared absorption spectrum by FT-IR. Group addition was confirmed.
The amount of phosphate group introduced was 0.59 mmol / g (cellulose fiber 1).

[Production Example 2: Preparation of cellulose fiber 2 (cellulose maleate fiber)]
As a cellulose fiber raw material, hardwood kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd.) was dried at 105 ° C. for 3 hours to obtain a dry pulp having a moisture content of 3% by weight or less. Next, 50 parts by weight of maleic anhydride was charged into the autoclave with respect to 100 parts by weight of the dried pulp and treated at an internal temperature of 120 to 135 ° C. for 2 hours.
Next, the pulp treated with maleic anhydride was added to a 0.08N aqueous sodium hydroxide solution to adjust the pH of the slurry to 12 to 13, and the pulp was alkali treated. Thereafter, the alkali-treated pulp was washed with water and filtered and dehydrated repeatedly until the pH became 8 or less, and finally cellulose maleate was obtained.

By X-ray diffraction, the cellulose maintained the cellulose type I crystal and the crystallinity was 84%. Measurement of an infrared absorption spectrum by FT-IR showed absorption based on a carboxy group in the vicinity of 1580 and 1720 cm ⁻¹ , confirming the addition of maleic acid.
The amount of maleic acid group introduced was 0.25 mmol / g (cellulose fiber 2).

[Production Example 3: Preparation of cellulose fiber 3 (cellulose succinate fiber)]
As a cellulose fiber raw material, hardwood kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd.) was dried at 105 ° C. for 3 hours to obtain a dry pulp having a moisture content of 3% by weight or less. Next, 4 g of the obtained dried pulp and 4 g of succinic anhydride (100 parts by weight with respect to 100 parts by weight of the dried pulp) were filled in an autoclave and treated at 150 ° C. for 2 hours.
Next, the pulp treated with succinic anhydride was washed with 500 ml of water and filtered and dehydrated three times, and then ion-exchanged water was added to prepare 490 ml of slurry.
Then, while stirring the slurry, 10 ml of 4N aqueous sodium hydroxide solution was added little by little to adjust the pH of the slurry to 12 to 13, and the pulp was alkali-treated. Thereafter, the alkali-treated pulp was repeatedly washed with water and filtered and dehydrated until the pH became 8 or less, to finally obtain cellulose succinate.

By X-ray diffraction, the cellulose maintained the cellulose type I crystal, and the absorption based on the carboxy group was observed in the vicinity of 1580 and 1720 cm ⁻¹ by the measurement of the infrared absorption spectrum by FT-IR. The addition was confirmed.
The amount of succinic acid group introduced was 0.32 mmol / g (cellulose fiber 3).

[Production Example 4: Preparation of cellulose fiber 4 (enzyme-treated cellulose fiber)]
Softwood bleached kraft pulp (NBKP, Oji Paper's bay pine product) is used as a cellulose fiber raw material, beaten for 200 minutes with a Niagara beater (capacity 23 liters, manufactured by Tozai Seiki Co., Ltd.), and a pulp dispersion (pulp concentration 2% by weight, A weighted average fiber length after beating: 1.61 mm) was obtained.
The pulp dispersion is dehydrated to a pulp concentration of 3% by weight, adjusted to pH 6 with 0.1% by weight sulfuric acid, warmed to 50 ° C. in a water bath, and then enzyme (cellulase, GC220, Genencor) is added to the pulp. 1 wt% was added to (in terms of solid content) and reacted at 50 ° C. with stirring for 2 hours. Then, it heated at 95 degreeC or more for 20 minutes, the enzyme fiber was deactivated, and the cellulose fiber by which the enzyme process was carried out was obtained (cellulose fiber 4).

[Production Example 5: Preparation of cellulose fiber 5 (enzyme-treated oxidized cellulose fiber)]
Prepared 6L of hardwood bleached kraft pulp (LBKP, Oji Paper Co., Ltd. bay pine) diluted with water to a solid content of 4.5% by weight as a raw material for cellulose fiber, and a rotary high-speed homogenizer (M Technique) (Creamix 2.2S) for 3 hours, adjusted to pH 6 with 0.1% by weight sulfuric acid, warmed to 50 ° C in a water bath, and then enzyme (cellulase, GC220, Genencor) Was added at 1% by weight to the pulp (in terms of solid content) 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 fiber was deactivated, and the enzyme-treated cellulose fiber was obtained.
After adding 20 g and 2 L of air as a pulp dry weight, 15 L of ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was added, shaken at 25 ° C. for 2 minutes, and allowed to stand for 6 hours in sequence. Ozone treatment (oxidation treatment) was performed by removing ozone and air in the container. This operation was performed twice to obtain a cellulose fiber which was sufficiently washed / dehydrated with ion-exchanged water and subjected to ozone treatment.
200 g of 0.2% by weight sodium chlorite aqueous solution adjusted to pH 4-5 with hydrochloric acid with respect to the cellulose fiber (solid content concentration 20% by weight) after the ozone treatment (dry weight of cellulose fiber) Was added as sodium chlorite (corresponding to 3% by weight) and stirred, and then allowed to stand at room temperature for 48 hours. This was repeatedly suspended and washed with ion-exchanged water to obtain cellulose fibers having a carboxy group introduced. The amount of carboxy groups of this cellulose fiber was 0.41 mmol / g (cellulose fiber 5).

[Example 1]
Cellulose fiber 1 obtained in Production Example 1 is diluted with water so that the solid content concentration is 0.5% by weight, and is rotated at 20000 rpm with a rotary high-speed homogenizer (Cleamix 0.8S manufactured by M Technique Co., Ltd.). The cellulose fiber 1 (rubber modifier 1) slurry obtained by carrying out the partial processing and performing the defibrating process of the cellulose fiber was obtained. When the fiber diameter of the nanofiberized cellulose fiber 1 was measured, the number average fiber diameter was 5.4 nm.

  Next, the slurry of the rubber modifier 1 is added to 100 parts by weight of natural rubber latex (solid content concentration: 61% by weight) so that the solid content of cellulose is 5 parts by weight, and demineralized water is added to the cellulose and rubber. The solid content concentration was adjusted to 0.3% by weight. Subsequently, it mixed using the homogenizer and the rubber- cellulose fiber liquid mixture (rubber latex dispersion liquid) was obtained. As a result of visual evaluation of the dispersibility of the rubber modifier 1 in the obtained rubber latex dispersion, the dispersibility was good.

  Next, the obtained rubber latex dispersion was put into a vat and dried and solidified in an oven at 110 ° C. to obtain a rubber composition containing the rubber modifier 1. As a result of visual evaluation of the dispersibility of the rubber modifier 1 in the obtained rubber composition, the dispersibility was good.

The obtained rubber composition (hereinafter referred to as rubber composition 1) contains 5 parts by weight of rubber modifier 1 with respect to 100 parts by weight of the rubber component (natural rubber latex). Furthermore, 3 parts by weight of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.), 1 weight of vulcanization accelerator (N-tert-butyl-2-benzothiazole sulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.) 2 parts by weight of sulfur (5% oil-treated powdered sulfur, manufactured by Tsurumi Chemical Co., Ltd.) and 3 parts by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed and kneaded.
Specifically, a rubber composition is added to rubber composition 1 by adding components other than a vulcanization accelerator and sulfur and kneading at 140 ° C. for 3 minutes using a kneading apparatus (Laboplast Mill μ, manufactured by Toyo Seiki Co., Ltd.). Product 2 was obtained. A rubber composition 3 was obtained by adding a vulcanization accelerator and sulfur to the rubber composition 2 and kneading at 80 ° C. for 3 minutes. This rubber composition 3 was pressure-press vulcanized at 160 ° C. for 10 minutes to obtain a rubber composition 4 (vulcanized rubber composition) having a thickness of 1 mm.

As a result of visual evaluation of the dispersibility of the rubber modifier 1 in the obtained vulcanized rubber composition, the dispersibility was good.
The obtained vulcanized rubber composition was made into a predetermined dumbbell-shaped test piece, and the breaking strength, M300, and tan δ were evaluated.
The breaking strength and M300 are indices obtained by measuring the breaking strength of the vulcanized rubber composition and the tensile stress at 300% elongation by a tensile test according to JIS K6251, and taking the value of Comparative Example 1 of natural rubber alone as 100. displayed. The larger the index, the better the reinforcement.
tan δ was measured in accordance with JIS K6394 under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2%, and expressed as an index with the value of Comparative Example 1 as 100. The smaller the index, the smaller the tan δ, and the less the heat is generated, that is, the low heat buildup is excellent (the energy loss is small).
The vulcanized rubber composition had a breaking strength of 179, M300 of 404, and tan δ of 235.

[Example 2]
The cellulose fiber 3 obtained in Production Example 3 is diluted with water so that the solid content concentration is 0.6% by weight, and is 60 at 20000 rpm with a rotary high-speed homogenizer (Cleamix 0.8S manufactured by M Technique Co., Ltd.). This was subjected to a minute treatment, and the cellulose fibers were defibrated. Next, the supernatant was collected by centrifuging at 12000 G for 10 minutes using a centrifuge, and a slurry of 0.5% by weight of nanofiberized cellulose fibers 3 (rubber modifier 2) was obtained. When the fiber diameter of the nanofiberized cellulose fiber 3 was measured, the number average fiber diameter was 5.5 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 2 was used as a rubber modifier. As a result of visual evaluation of the dispersibility of the rubber modifier 2 in the rubber latex dispersion and the vulcanized rubber composition, the dispersibility was good.
Further, when the rupture strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1, the rupture strength of the vulcanized rubber composition was 148, M300 was 304, and tan δ was 257.

[Example 3]
A rubber modifier 3 was obtained in the same manner as in Example 2 except that hardwood kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd.) was used as the cellulose fiber instead of the cellulose fiber 3. When the fiber diameter of the nanofiberized cellulose fiber was measured, the number average fiber diameter was 16 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 3 was used as the rubber modifier. As a result of visual evaluation of the dispersibility of the rubber modifier 3 in the rubber latex dispersion and the vulcanized rubber composition, the dispersibility was good.
Further, when the rupture strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1, the rupture strength of the vulcanized rubber composition was 210, M300 was 348, and tan δ was 170.

[Example 4]
6 L of cellulose fiber 4 obtained in Production Example 4 diluted with water so as to have a solid content concentration of 4.8% by weight was prepared, and a rotary high-speed homogenizer (Cleamix 2.2S manufactured by M Technique Co., Ltd.) was prepared. The cellulose fiber was continuously treated at 20000 rpm for 3 hours, and 6 L diluted with water to a solid content concentration of 0.9% by weight was continuously treated for 9 hours, and the cellulose fibers were defibrated. Next, the supernatant was collected by centrifugation at 12000 G for 10 minutes in a centrifuge to obtain a slurry of nanofiberized cellulose fibers 4 (rubber modifier 4). When the fiber diameter of the nanofiberized cellulose fiber 4 was measured, the number average fiber diameter was 7.9 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 4 was used as the rubber modifier. As a result of visual evaluation of the dispersibility of the rubber modifier 4 in the rubber latex dispersion and the vulcanized rubber composition, the dispersibility was good.
Further, when the rupture strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1, the rupture strength of this vulcanized rubber composition was 252, M300 was 338, and tan δ was 146.

[Example 5]
4 L of cellulose fiber 4 obtained in Production Example 4 diluted with water so that the solid content concentration is 3% by weight is prepared, treated with Homo Disper (manufactured by Primics) for 4 hours, Cellulose fibers were defibrated by continuous treatment at 20000 rpm for 5 hours with a rotary high-speed homogenizer (Cleamix 2.2S manufactured by M Technique Co., Ltd.). Furthermore, what was diluted to a solid content concentration of 0.5% by weight was continuously centrifuged at 12000 G, and the supernatant was collected to obtain a slurry of nanofiberized cellulose fibers 4 (rubber modifier 5). When the fiber diameter of the nanofiberized cellulose fiber 4 was measured, the number average fiber diameter was 18 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 5 was used as a rubber modifier. As a result of visual evaluation of the dispersibility of the rubber modifier 5 in the rubber latex dispersion and the vulcanized rubber composition, the dispersibility was good.
Further, the rupture strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1. The rupture strength of the vulcanized rubber composition was 219, M300 was 269, and tan δ was 142.

[Example 6]
A rubber modifier 6 was obtained in the same manner as in Example 2 except that the cellulose fiber 5 was used instead of the cellulose fiber 3. When the fiber diameter of the nanofiberized cellulose fiber was measured, the number average fiber diameter was 7.1 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 6 was used as the rubber modifier. As a result of visual evaluation of the dispersibility of the rubber modifier 6 in the rubber latex dispersion and the vulcanized rubber composition, the dispersibility was good.
Further, when the rupture strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1, the rupture strength of the vulcanized rubber composition was 250, M300 was 304, and tan δ was 132.

[Comparative Example 1]
A vulcanized rubber composition was obtained in the same manner as in Example 1 except that cellulose fibers were not used, and the breaking strength, M300, and tan δ were measured in the same manner, and the measured values of breaking strength, M300, and tan δ were 100. It was.

[Comparative Example 2]
A rubber modifier 7 was obtained in the same manner as in Example 2 except that the cellulose fiber 2 obtained in Production Example 2 was used. When the fiber diameter of the nanofiberized cellulose fiber 2 was measured, the number average fiber diameter was 4.2 nm.
A rubber latex dispersion, a rubber composition, and a vulcanized rubber composition were obtained in the same manner as in Example 1 except that this rubber modifier 7 was used as a rubber modifier.
When the breaking strength, M300, and tan δ of the vulcanized rubber composition were evaluated in the same manner as in Example 1, the breaking strength of this vulcanized rubber composition was 185, M300 was 260, and tan δ was 239.

  The results of Examples 1-6 and Comparative Examples 1-2 are summarized in Table 1.

From Table 1, the vulcanized rubber compositions of Examples 1 to 6 using the rubber modifiers 1 to 6 of the present invention show a high elastic modulus and high breaking strength as compared with Comparative Example 1 which is only natural rubber. It can be seen that the rubber modifier of the present invention is excellent in reinforcement.
Moreover, when the vulcanized rubber compositions of Examples 1 to 6 using the rubber modifiers 1 to 6 of the present invention and the vulcanized rubber composition of Comparative Example 2 were compared, the fiber diameter of the cellulose fibers was 5 nm to 35 nm. It can be seen that a high elastic modulus, high fracture strength, and low tan δ can be expressed in a balanced manner.

Claims (6)

A rubber modifier made of cellulose fiber,
A rubber modifier having a number average fiber diameter of 5 to 35 nm.   The rubber modifier according to claim 1, comprising a modified cellulose fiber in which a part of a hydroxyl group of cellulose constituting the cellulose fiber is substituted with another group as at least a part of the cellulose fiber.   A rubber modifier dispersion liquid comprising the rubber modifier according to claim 1 or 2 and a dispersion medium.   A rubber latex dispersion, comprising the rubber modifier according to claim 1 and rubber latex.   A rubber composition comprising the rubber modifier according to claim 1 and a rubber component.   A vulcanized rubber composition produced by vulcanizing the rubber composition according to claim 5.