JP2013177540A - Rubber modifying material, rubber latex-dispersed solution and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber modifying material which uses a cellulose fiber, exhibits excellent dispersibility in a dispersion liquid and can provide a rubber composition having high elastic modulus and low heat generation properties.SOLUTION: A rubber modifying material contains a cellulose fiber, wherein a cellulose constituting the cellulose fiber is a cellulose having a phosphoric acid-derived group and/or a carboxylic acid-derived group. A rubber latex-dispersed solution contains the rubber modifying material and rubber latex. A rubber composition contains the rubber modifying material and rubber. A rubber composition is produced by using the rubber latex-dispersed solution.

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 latex dispersion and a 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

  The present invention relates to a rubber modifier using cellulose fibers, which is a rubber modifier exhibiting good dispersibility in a dispersion, and has a high elastic modulus and low exothermic property. It is an object to provide a rubber modifying material that can be obtained.

  As a result of intensive studies by the present inventors, it was found that the above-mentioned problems can be solved by using cellulose fibers having phosphoric acid-derived groups and / or carboxylic acid-derived groups as modifiers, and the present invention has been achieved.

  That is, the present invention is a rubber modifying material containing cellulose fiber, wherein the cellulose constituting the cellulose fiber is a cellulose having a group derived from phosphoric acid and / or a group derived from carboxylic acid, A rubber latex dispersion containing the rubber modifier and rubber latex, a rubber composition containing the rubber modifier and rubber, and a rubber composition produced using the rubber latex dispersion. .

  The rubber modifier of the present invention exhibits excellent dispersibility in a rubber latex dispersion, and further disperses well in a rubber composition and contains the rubber modifier of the present invention. The rubber composition produced using the rubber latex dispersion of the invention has a high elastic modulus, a high rubber reinforcing effect, and 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 containing cellulose fiber, and the cellulose constituting the cellulose fiber is cellulose having a group derived from phosphoric acid and / or a group derived from carboxylic acid. Features.
Hereinafter, cellulose having a group derived from phosphoric acid may be referred to as “cellulose phosphate”, and cellulose having a group derived from carboxylic acid may be referred to as “carboxyl cellulose”.
However, the cellulose fiber according to the present invention may be one in which both a group derived from phosphoric acid and a group derived from carboxylic acid are introduced into cellulose. Cellulose fibers in which the cellulose has a group derived from phosphoric acid and / or a group derived from carboxylic acid, contained in the rubber modifier of the present invention, may be hereinafter referred to as “phosphoric acid / carboxylic acid cellulose fibers”.

  The phosphoric acid / carboxylic acid cellulose fiber contained in the rubber modifier of the present invention may have a group derived from phosphoric acid and / or a group derived from carboxylic acid. For example, the cellulose fiber raw material described in detail below Or defibrated cellulose fiber may be sufficient.

  First, the cellulose fiber used as the rubber modifier of the present invention will be described.

The cellulose fiber contained in the rubber modifier of the present invention may be produced by any production method.
For example, a phosphoric acid-derived group or a carboxylic acid-derived group may be introduced into the cellulose fiber raw material described in detail below, or the cellulose fiber raw material is subjected to defibrating treatment to prepare a desired fiber diameter. A group derived from phosphoric acid and / or a group derived from carboxylic acid may be introduced later (defibrated cellulose fiber).
As will be described later, the rubber modifying material using cellulose fibers before defibration may be defibrated after being mixed with rubber latex.

<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, as a cellulose fiber raw material, you may use 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.

  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 crystalline α-cellulose content of the cellulose fiber raw material can be determined by measuring an insoluble part in the concentrated alkaline solution in accordance with ISO 699-1982. The crystalline α-cellulose content of the cellulose fiber raw material of the present invention is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 85% by weight or more. If the crystalline α-cellulose content increases the purification degree of the cellulose fiber raw material, a highly pure cellulose fiber raw material exceeding 98% by weight can be obtained. Since the extreme refining (purification) of the cellulose fiber raw material may reduce the yield of the cellulose fiber raw material, the content of crystalline α-cellulose in the cellulose fiber raw material should be 95% by weight or less. Is more practical and preferred.

  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.

<Cellulose phosphate>
First, the case where the cellulose which comprises a cellulose fiber is the cellulose (phosphoric acid cellulose) which has group derived from phosphoric acid is demonstrated.

Here, the group derived from phosphoric acid is a group that binds to cellulose by the reaction between phosphoric acid or a phosphoric acid derivative and 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 for introducing a phosphate-derived group into cellulose, a method of mixing a powdered or aqueous solution of phosphoric acid or a phosphoric acid derivative with a dried or wet cellulose fiber raw material or defibrated cellulose fiber, a cellulose fiber raw material or Examples thereof include a method of adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a dispersion of fine cellulose fibers.
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 aqueous alkaline solution after the treatment with the phosphoric acid or 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 cellulose phosphate. For example, two or more types of phosphoric acid-derived groups in which hydrogen atoms are substituted with different groups may be introduced into cellulose phosphate.

<Carboxylate cellulose>
Next, the case where the cellulose which comprises a cellulose fiber is the cellulose (carboxylate cellulose) which has group derived from carboxylic acid is demonstrated.

  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.

  In addition, in order to make the group derived from the carboxylic acid introduced into the cellulose 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 phosphoric acid-derived group and / or carboxylic acid-derived group>
It is preferable that 0.1-2.0 mmol / g of phosphoric acid-derived groups is introduced into cellulose phosphate.
Moreover, it is preferable that 0.1-2.0 mmol / g of carboxylic acid-derived groups are usually introduced into the cellulose carboxylate.
When cellulose has a group derived from phosphoric acid and a group derived from carboxylic acid, it is preferable that 0.1 to 2.0 mmol / g of the cellulose is introduced into the cellulose in total.

  When the introduction amount of phosphoric acid-derived groups and / or carboxylic acid-derived groups into cellulose is too small, the effect of improving dispersibility in the dispersion due to the introduction of these groups cannot be sufficiently obtained. There is.

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

  The amount of phosphoric acid-derived group or carboxylic acid-derived group introduced can be controlled by adjusting the amount of phosphoric acid, phosphoric acid derivative or carboxylic acid compound used for introducing these groups.

<Chemical modification treatment>
In addition to the group derived from phosphoric acid and / or the group derived from carboxylic acid, another group may be further introduced into the cellulose constituting the cellulose fiber used in the rubber modifier of the present invention.

  The chemical modification treatment for introducing other groups into the cellulose may be performed on the cellulose fiber raw material or may be performed on the cellulose fiber after defibration. Further, it may be performed before or after the introduction of the group derived from phosphoric acid or the group derived from carboxylic acid, or may be performed simultaneously with the introduction, and may be performed in any step as long as the effect of the present invention is not impaired. Also good.

(Chemical modification group types)
Chemical modification groups introduced into cellulose by chemical modification include acetyl group, acryloyl group, methacryloyl group, propionyl group, propioyl 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, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, cinnamoyl group and other acyl groups, 2-methacryloyloxyethyl isocyania Isocyanate group such as noyl 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, Group, decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, an alkyl group such as a stearyl group, an oxirane group, an oxetane group, a thiirane group, include one or more of such thietane group. Among these, an acyl group having 2 to 12 carbon atoms such as an acetyl group, an acryloyl group, a methacryloyl group, a benzoyl group and a naphthoyl group, and an alkyl group having 1 to 12 carbon atoms such as a methyl group, an ethyl group and a propyl group are preferable. .

(Chemical modification method)
Although it does not specifically limit as a chemical modification method, There exists the method of making a cellulose fiber raw material and the following chemical modifiers react. 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.

  Examples of the chemical modifier include one or more selected from the group consisting of cyclic ethers such as acids, acid anhydrides, alcohols, halogenating reagents, isocyanates, alkoxysilanes, and oxiranes (epoxies).

Examples of the acid include acetic acid, acrylic acid, methacrylic acid, propanoic acid, butanoic acid, 2-butanoic acid, and pentanoic acid.
Examples of the acid anhydride include acetic anhydride, acrylic anhydride, methacrylic anhydride, propanoic anhydride, butanoic anhydride, 2-butanoic anhydride, and pentanoic anhydride.
Examples of the halogenating reagent include acetyl halide, acryloyl halide, methacryloyl halide, propanoyl halide, butanoyl halide, 2-butanoyl halide, pentanoyl halide, benzoyl halide, naphthoyl halide, and the like.
Examples of the alcohol include methanol, ethanol, propanol, and 2-propanol.
Examples of the isocyanate include methyl isocyanate, ethyl isocyanate, propyl isocyanate, and the like.
Examples of the alkoxysilane include methoxysilane and ethoxysilane.
Examples of cyclic ethers such as oxirane (epoxy) include ethyl oxirane and ethyl oxetane.

Among these, acetic anhydride, acrylic acid anhydride, methacrylic acid anhydride, benzoyl halide, and naphthoyl halide are particularly preferable.
These chemical modifiers may be used alone or in combination of two or more.

(Degree of substitution)
The degree of substitution here refers to the number of the previously mentioned chemical modification groups introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, it is defined as “a value obtained by dividing the number of moles of the introduced chemical modification group by the total number of moles of the glucopyranose ring”. Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of substitution of the phosphoric acid / carboxylic acid cellulose fiber of the present invention is {3- (derived from phosphoric acid) And / or the degree of substitution of the carboxylic acid-derived group)} (minimum value is 0).
The degree of substitution of the chemical modifying group can be measured and determined by the following titration method.

0.05 g of dry cellulose is precisely weighed, and 1.5 ml of ethanol and 0.5 ml of distilled water are added thereto. This is left to stand in a hot water bath at 60 to 70 ° C. for 30 minutes, and then 2 ml of 0.5 M aqueous sodium hydroxide solution is added. After leaving this in a 60-70 degreeC hot water bath for 3 hours, it ultrasonically shakes for 30 minutes with an ultrasonic cleaner. This is titrated with 0.2 M hydrochloric acid standard solution using phenolphthalein as an indicator.
Here, from the amount Z (ml) of 0.2 M hydrochloric acid aqueous solution required for titration and the amount Z ₀ (ml) of 0.2 N hydrochloric acid aqueous solution required for titration of the blank sample (= sample without dry cellulose), The total amount Q (mol) of the group derived from phosphoric acid and / or the group derived from carboxylic acid and the chemical modification group is determined by the formula.
Q (mol) = (Z ₀ −Z) × 0.2 / 1000
The mass of dry cellulose (= 0.05 g exact balance, denoted A by symbol) is the unmodified glucopyranose ring structure (C ₆ H ₁₀ O ₅ , Mw = 162), phosphoric acid-derived groups and A glucopyranose structure substituted with a carboxylic acid-derived group (C ₆ H ₈ O _6, Mw = 145 + S, S is the molecular weight of a phosphate-derived group and / or a carboxylic acid-derived group), and a chemical modification group It can be considered that the total mass of each of the glucopyranose structures (Mw = 145 + T, T is the molecular weight of the chemical modification group) substituted with. If the number of moles of each structure is x, y, z (mol),
A (g) = 162 × x + (145 + S) × y + (145 + T) × z Equation 1
Further, the following relationship is established for Q (mol) previously obtained by titration.
When a group derived from phosphoric acid is introduced Q (mol) = y + z Formula 2
When a carboxylic acid-derived group is introduced Q (mol) = 2y + z Formula 2 ′
In addition, the phosphoric acid-derived group and / or carboxylic acid-derived group amount (mmol / g, denoted by B as a symbol) in the cellulose fiber obtained by the method described in the above section can be converted to y. .
y (mol) = B (mmol / g) × A (g) / 1000 Formula 3
Here, the degree of substitution is defined as “a value obtained by dividing the number of moles of the introduced substituent by the total number of moles of the glucopyranose ring”, and the degree of substitution of the chemical modifying group is expressed as the following formula. Can do.
Degree of substitution of chemical modification group (dimensionless number) = z / (x + y + z) Formula 4
When formulas 1 to 4 are used to arrange A, B, Q, and T, the degree of substitution of the chemical modification group can be obtained by formulas 5 and 5 ′ below.

  In the present invention, when a chemically modifying group is introduced into the phosphoric acid / carboxylic acid cellulose fiber, the degree of substitution of the chemically modifying group is usually 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more. More preferably, it is 0.3 or more, preferably 2.0 or less, more preferably 1.8 or less, still more preferably 1.5 or less, particularly preferably 1.2 or less, and most preferably 1.0 or less. .

  By introducing chemical modification groups other than phosphoric acid-derived groups and / or carboxylic acid-derived groups by chemical modification, the decomposition temperature of cellulose increases and the heat resistance increases, but the chemical modification rate is too high. Then, since the cellulose structure is destroyed and the crystallinity is lowered, there is a problem that the elastic modulus and the strength are lowered, which is not preferable.

<Defibration processing>
Cellulose fiber raw material is defibrated cellulose fiber by defibrating treatment. The cellulose fiber used in the present invention preferably has an average fiber diameter of 400 nm or less, and is usually obtained by performing this defibrating treatment.

  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 organic solvents 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 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 refinement | 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.

(Average fiber diameter of fibrillated cellulose fiber raw material)
The fiber diameter of the cellulose fiber (defibrated cellulose fiber) in the cellulose fiber dispersion defibrated or further refined by the above-mentioned method is determined after the dispersion medium in the dispersion is dried and removed (after sheet formation), SEM or TEM It can be measured and obtained by observing with the above.

  The number average fiber diameter of the fibrillated cellulose fiber is usually 400 nm or less, preferably 100 nm or less, more preferably 80 nm or less, and particularly preferably 50 nm or less. Further, the number average fiber diameter is preferably as small as possible. However, in order to develop a high reinforcing effect, it is important to maintain the crystallinity of cellulose, and the fiber diameter of the cellulose crystal unit is substantially 2 nm or more. Preferably, it is 4 nm or more.

  As described above, phosphoric acid / carboxylic acid cellulose fibers having an average fiber diameter of 400 nm or less can be obtained.

<Rubber modifier>
The rubber modifier of the present invention is usually provided as a dispersion of phosphoric acid / carboxylic acid cellulose fibers. Therefore, the rubber modifier of the present invention may contain a dispersion medium in addition to the phosphoric acid / carboxylic acid cellulose fiber, or may be composed of the phosphoric acid / carboxylic acid cellulose fiber and the dispersion medium. In addition, additives and the like may be included within a range not impairing the effects of the present invention. However, in particular, in the rubber composition of the present invention, the rubber modifier is not limited to being present as a dispersion. In this case, if the rubber composition contains phosphoric acid / carboxylate cellulose fibers. Good.
The phosphoric acid / carboxylic acid cellulose fiber dispersion was obtained by centrifuging the phosphoric acid / carboxylic acid cellulose fiber dispersion obtained by defibration as shown in Examples 3 to 8 described later. , A supernatant containing only ultrafine cellulose fibers is obtained, and when this supernatant is used as a rubber modifier of the present invention, dispersibility in vulcanized rubber is further improved, and higher elastic modulus and strength are obtained. Can do.

  The phosphoric acid / carboxylic acid cellulose fiber contained in the rubber modifier of the present invention may be any cellulose as long as the cellulose has a group derived from phosphoric acid and / or a group derived from carboxylic acid. Alternatively, cellulose fibers after defibration may be used. When cellulose fibers before defibration are used, the rubber modifier of the present invention may be mixed with rubber latex and then defibrated.

  The content of phosphoric acid / carboxylic acid cellulose fiber in the phosphoric acid / carboxylic acid cellulose fiber dispersion of the rubber modifier of the present invention is not particularly limited, but the handling property such that the viscosity and liquid stability are suitable. From the viewpoint of the total amount of the dispersion, 0.01% by weight or more is preferable, 0.1% by weight or more is more preferable, 0.5% by weight or more is further preferable, 1% by weight or more is particularly preferable, and 50% by weight or less. Is preferable, and 40 weight% or less is more preferable.

  Examples of the dispersion medium include water, alcohol solvents, ketone solvents, glycol ether solvents, amide solvents, aromatic hydrocarbons, aprotic polar solvents, and the like. Preferred are water, aprotic polar solvents (particularly amide solvents), alcohol solvents, and ketone solvents. These solvents may be used alone or in combination of two or more.

  In addition, it is preferable that the boiling point of the solvent used as the dispersion medium of the rubber modifier is not too high 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 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.

  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 methylpyrrolidone and tetrahydrofuran.

  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.

[Rubber latex dispersion]
The rubber latex dispersion of the present invention contains the rubber modifier of the present invention and a rubber latex. In the preparation of the rubber latex dispersion of the present invention, the aforementioned phosphoric acid / carboxylate cellulose fiber raw material is used. In order to obtain good dispersibility, it is preferable to mix with a rubber latex and perform a defibration treatment in this mixed solution. In this case, the rubber modifier of the present invention is in a state in which the phosphoric acid / carboxylate cellulose fiber raw material is dispersed in the rubber latex, which is further defibrated to have a high dispersibility. A rubber latex dispersion of the present invention containing a material can be obtained.

The defibrating process in this case will be described below.
As a dispersion medium for dispersing the phosphoric acid / carboxylic acid cellulose fiber raw material, water is usually used, but an organic solvent may be used. In that case, 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 containing cellulose fiber (preferably cellulose fiber after purification or after introduction of phosphoric acid-derived groups and / or carboxylic acid-derived groups) is used. There is a method in which water is removed from the dispersion by filtration or the like, an organic solvent used at the time of defibration is added thereto, the mixture is stirred and mixed, and the organic solvent is removed by filtration again. 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 once with a water-soluble organic solvent, you may substitute with a water-insoluble organic solvent.

Next, a cellulose fiber raw material dispersion containing a phosphoric acid / carboxylic acid cellulose fiber raw material and a rubber latex are mixed. In mixing, rubber latex may be directly added to the dispersion and mixed.
The content of the phosphoric acid / carboxylate cellulose fiber raw material in the pre-defibration rubber latex dispersion is not particularly limited, but is preferably 0.01% by weight or more based on the total amount of the rubber latex dispersion before defibration. 1% by weight or more is more preferable, 1% by weight or more is more preferable, 50% by weight or less is preferable, and 40% by weight or less is more preferable.

  The solid content of the 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, and 95% by weight with respect to the total amount of the rubber latex dispersion before defibration. % Or less is preferable, and 80% by weight or less is more preferable.

  The content of the solvent 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, and 97.5% by weight with respect to the total amount of the rubber latex dispersion before defibration. The following is preferable, and 95% by weight or less is more preferable.

  The weight ratio of the rubber component and the solvent in the dispersion in the rubber latex before defibration is not particularly limited, but handling such that the viscosity and liquid stability of the obtained rubber latex dispersion after defibration are suitable. From the viewpoint of properties, the content of the solvent 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.

  The weight ratio of the phosphoric acid / carboxylic acid cellulose fiber raw material and the rubber component in the rubber latex dispersion before defibration is not particularly limited, but the content of the phosphoric acid / carboxylic acid cellulose fiber raw material is phosphoric acid / carboxylic acid cellulose cellulose. 2.5 weight% or more is preferable with respect to the total amount (100 weight%) of a fiber raw material and a rubber component, 3 weight% or more is more preferable, 5 weight% or more is further more preferable, and 97.5 weight% or less is preferable. 97 wt% or less is more preferable, and 95 wt% or less is more preferable.

The method of defibrating treatment when the defibrating rubber latex dispersion before defibrating is the same as the defibrating method of the cellulose fiber raw material described above.
In the rubber latex dispersion obtained through the defibrating step, the fibrillated phosphoric acid / carboxylate cellulose fibers are uniformly dispersed, and aggregation and sedimentation of the phosphoric acid / carboxylate cellulose fibers are suppressed, Excellent liquid stability.
In the composite after the vulcanization step obtained by using the rubber latex dispersion of the present invention containing phosphoric acid / carboxylate cellulose fibers and rubber latex, phosphoric acid / carboxylate cellulose fibers are vulcanized rubber. It is uniformly dispersed in the components and exhibits high modulus and low loss tangent.

  The content of phosphoric acid / carboxylate cellulose fibers 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 material used. From the viewpoint of the stability of the dispersion, the total amount of the dispersion Is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, further preferably 0.5% by weight or more, particularly preferably 1% by weight or more, preferably 50% by weight or less, and 40% by weight. % Or less is more preferable, and 30% by weight or less is more preferable.

  The solvent and the rubber component in the rubber latex dispersion are 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.

  Further, the phosphoric acid / carboxylic acid 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 further preferably 10 parts by weight with respect to 100 parts by weight of the rubber component. It is at least 100 parts by weight, preferably at most 70 parts by weight, more preferably at most 50 parts by weight. 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 the phosphoric acid / carboxylate cellulose fiber and the rubber component, 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 contains the rubber modifier of the present invention and rubber. Or the rubber composition of this invention is manufactured using the rubber latex dispersion liquid of this invention. The rubber composition of the present invention may be before vulcanization or after vulcanization.

Below, the manufacturing method of the 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 rubber composition containing phosphoric acid / carboxylate cellulose fibers and a vulcanized rubber component is obtained by vulcanizing the rubber latex dispersion (vulcanization step).
In the rubber composition of the present invention, the solvent is removed from the rubber latex dispersion of the present invention as necessary, and the rubber component and the various compounding agents described above are mixed using a known method such as a rubber kneader. Then, it is molded and obtained by a vulcanization reaction by a known method.

  Various methods are possible for the molding prior to the vulcanization process. For example, a rubber latex 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, 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 before vulcanization 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 pressurizing the pre-vulcanized rubber composition in a vulcanizer. Such a vulcanized rubber composition has good 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. The heating temperature is preferably 250 ° C. or lower, more preferably 200 ° C. or lower, from the viewpoint of suppressing the decomposition of phosphoric acid / carboxylic acid cellulose fibers. In view of productivity, the heating time is usually 3 minutes or longer, preferably 5 minutes or longer, more preferably 10 minutes or longer, still more preferably 15 minutes or longer, and preferably 180 minutes or shorter.
The heat treatment may be performed multiple times by changing the temperature and the heating time.

<Content of phosphoric acid / carboxylic acid cellulose fiber>
The content of phosphoric acid / carboxylic acid cellulose fibers in the rubber composition of the present invention is appropriately adjusted according to the purpose, but from the viewpoint of the reinforcing effect, 0.5% by weight or more is preferable based on the total amount of the rubber composition. 1 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.

<Weight ratio of phosphoric acid / carboxylic acid cellulose fiber and rubber component>
The weight ratio of the phosphoric acid / carboxylic acid cellulose fiber and the rubber component contained in the rubber composition of the present invention is the same as the weight ratio of the phosphoric acid / carboxylic acid cellulose fiber and the rubber component in the rubber latex dispersion of the present invention. It is.
The phosphoric acid / carboxylic acid 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, still more preferably 10 parts by weight or more, usually 100 parts by weight with respect to 100 parts by weight of the rubber component. The amount is preferably 70 parts by weight or less, more preferably 50 parts by weight or less. If the amount of phosphoric acid / carboxylic acid cellulose fiber in the rubber composition is small, the reinforcing effect is not sufficient, and if it is large, the processability of the rubber is lowered.

<Average fiber diameter of phosphoric acid / carboxylic acid cellulose fiber>
The number average fiber diameter of phosphoric acid / carboxylic acid cellulose fibers in the rubber composition of the present invention is usually 400 nm or less, preferably 100 nm or less, more preferably 80 nm or less, and 50 nm or less. Is particularly preferred. The smaller the number average fiber diameter, the better. However, as described above, in order to maintain the crystallinity of cellulose, it is substantially 2 nm or more, preferably 4 nm or more, which is the fiber diameter of the cellulose crystal unit. When the average fiber diameter of the phosphoric acid / carboxylic acid cellulose fiber is less than the above lower limit value, the I-type crystal structure of cellulose cannot be maintained, the strength and elastic modulus of the fiber itself are lowered, and the reinforcing effect is hardly obtained. Further, when the average fiber diameter of the phosphoric acid / carboxylic acid cellulose fibers exceeds the above upper limit, the contact area with the rubber becomes small, so that the reinforcing effect becomes small.

  In addition, the number average fiber diameter of the phosphoric acid / carboxylic acid cellulose fiber in the rubber composition can be measured and determined by cutting the rubber composition as necessary and observing it with SEM, TEM or the like.

<Dispersion state of phosphoric acid / carboxylic acid cellulose fiber>
In the rubber composition of the present invention, phosphoric acid / carboxylate cellulose fibers are stably dispersed in the vulcanized rubber component without forming aggregates, and a high elastic modulus is achieved by the reinforcing effect of nanofiber cellulose. At the same time, because the fiber diameter is thin, the original elongation of the rubber is not hindered, and it is considered that high breakage and low heat generation are achieved.
In addition, the dispersion state of the phosphoric acid / carboxylic acid cellulose fiber in the 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.

[Production Example 1: Production of cellulose phosphate]
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 immersing this pulp sheet 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 dry pulp), an air dryer at 105 ° C. (manufactured by Yamato Chemical Co., Ltd.) , DKM400) for 1 hour, and further heat-treated with a 150 ° C. blower dryer (DKM400, supra) for 1 hour to obtain a pulp sheet having phosphate groups 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.

By X-ray diffraction, this cellulose maintained the cellulose I type crystal, and further, absorption based on a phosphate group was observed at 1320 to 1290 cm ⁻¹ by FT-IR (infrared absorption spectrum) measurement. Group addition was confirmed.
The amount of phosphate group introduced was 0.592 mmol / g.

[Production Example 2: Production of cellulose succinate]
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 maintains the cellulose type I crystal, and FT-IR (infrared absorption spectrum) measurement shows absorption based on carboxy groups in the vicinity of 1580 and 1720 cm ⁻¹ . The addition was confirmed.
The amount of succinic acid group introduced was 0.323 mmol / g.

[Production Example 3: Production of cellulose maleate]
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 filled in 100 parts by weight of the obtained dried pulp in an autoclave and treated at an internal temperature of 120 to 135 ° C. for 2 hours.
Subsequently, the pulp treated with maleic anhydride was added to a 0.8 wt% aqueous sodium hydroxide solution to adjust the pH 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 maleated cellulose.
By X-ray diffraction, this cellulose maintained the cellulose I type crystal, and the crystallinity was 84%. By FT-IR (infrared absorption spectrum) measurement, absorption based on a carboxy group was observed in the vicinity of 1580 and 1720 cm ⁻¹ , and addition of maleic acid to cellulose was confirmed.
The amount of maleic acid introduced was 0.25 mmol / g.

[Production Example 4: Production of acetylated cellulose maleate]
To 100 parts by weight of cellulose maleate obtained in Production Example 3, 2000 parts by weight of acetic anhydride was added, the inside of the flask was replaced with nitrogen gas, and then the temperature was raised to 60 ° C. and held for 1 hour. Then, it heated up to 115 degreeC and made it react for 5 hours. After the reaction, acetic anhydride was removed by filtration, and suspension washing with methanol was repeated three times. Thereafter, suspension washing was repeated with ion-exchanged water, and the washing end point was determined when the pH of the washing water was 5 or more. Then, it filtered under reduced pressure using a filter paper, and obtained the acetylation cellulose maleate.
The degree of substitution with acetyl groups of this maleated acetylated cellulose was 0.4.

[Production Example 5: Production of acetylated cellulose phosphate]
Cellulose phosphate was obtained in the same manner as in Production Example 1 except that hardwood kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd.) was used as the cellulose fiber raw material. The amount of phosphate groups introduced into this cellulose phosphate was 0.556 mmol / g.
To 100 parts by weight of the obtained cellulose phosphate, 2000 parts by weight of acetic anhydride was added, the inside of the flask was replaced with nitrogen gas, and then the temperature was raised to 60 ° C. and held for 1 hour. Then, it heated up to 115 degreeC and made it react for 5 hours. After the reaction, acetic anhydride was removed by filtration, and suspension washing with methanol was repeated three times. Thereafter, suspension washing was repeated with ion-exchanged water, and the washing end point was determined when the pH of the washing water was 5 or more. Then, it filtered under reduced pressure using the filter paper, and obtained the phosphoric acid acetylation cellulose.
The degree of substitution of this acetylated cellulose phosphate with an acetyl group was 0.53.

[Production Example 6: Production of cellulose phthalate]
Hardwood kraft pulp (LBKP, 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 phthalic anhydride was added to the flask with respect to 100 parts by weight of the dried pulp, and the atmosphere was purged with nitrogen, followed by treatment at 150 ° C. for 2 hours.
Subsequently, the pulp treated with phthalic anhydride was added to a 0.8 wt% aqueous sodium hydroxide solution to adjust the pH 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, and finally cellulose phthalate was obtained.
The amount of phthalic acid introduced was 0.10 mmol / g.

[Production Example 7: Production of acetylated cellulose phthalate]
To 100 parts by weight of cellulose phthalate obtained in Production Example 6, 2000 parts by weight of acetic anhydride was added, the inside of the flask was replaced with nitrogen gas, and then the temperature was raised to 60 ° C. and held for 1 hour. Then, it heated up to 115 degreeC and made it react for 5 hours. After the reaction, acetic anhydride was removed by filtration, and suspension washing with methanol was repeated three times. Thereafter, suspension washing was repeated with ion-exchanged water, and the washing end point was determined when the pH of the washing water was 5 or more. Then, it filtered under reduced pressure using the filter paper, and obtained the acetylated cellulose phthalate.
The degree of substitution with acetyl groups of this acetylated cellulose phthalate was 0.48.

[Example 1]
The dispersion of cellulose phosphate fibers obtained in Production Example 1 was diluted with water so that the solid content concentration was 0.6% by weight, and a rotary high-speed homogenizer (“CLEAMIX 0.8S” manufactured by M Technique Co., Ltd.) was used. ) At 20,000 rpm for 60 minutes to defibrate the cellulose fibers, and a dispersion (rubber modifier) of defibrated cellulose phosphate fibers was obtained.
Next, with respect to 100 parts by weight of natural rubber latex (“NR-LATEX” manufactured by Hiratec Co., Ltd., solid content concentration: 61% by weight), the above-described cellulose phosphate fiber dispersion (rubber modifier) is dried by weight of cellulose. Was mixed using a rotary homogenizer to obtain a rubber latex dispersion. This dispersion was put into a vat and dried and solidified in an oven at 110 ° C. to obtain a rubber composition before vulcanization.

  Next, a compounding agent was added to 100 parts by weight of the rubber component of the rubber composition before vulcanization so as to have the composition shown in Table 1 below, and kneading was performed. Specifically, 3 parts by weight of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.) and 3 parts by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd.) are added to the pre-vulcanized rubber composition at 140 ° C. And kneading for 5 minutes (first step). As a kneading apparatus, “Laboplast Mill μ” manufactured by Toyo Seiki Co., Ltd. was used. To the mixture obtained in the first step, 1 part by weight of a vulcanization accelerator (N-tert-butyl-benzothiazole sulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.) and sulfur (5% oil-treated powder sulfur, Tsurumi Chemical Co., Ltd.) 2 parts by weight) was added and kneaded at 80 ° C. for 3 minutes (second step). The mixture obtained in the second step was pressure-press vulcanized at 160 ° C. for 20 minutes to obtain a vulcanized rubber composition having a thickness of 2 mm.

[Example 2]
A rubber modifier and a rubber composition before vulcanization were obtained in the same manner as in Example 1 except that the cellulose succinate fiber dispersion obtained in Production Example 2 was used instead of the cellulose phosphate fiber dispersion. And a vulcanized rubber composition was obtained.

[Example 3]
After the cellulose maleate fiber dispersion obtained in Production Example 3 was diluted with water so that the solid content concentration was 0.6% by weight, a rotary high-speed homogenizer (“CLEAMIX 0.8S manufactured by M Technique Co., Ltd.) was used. The cellulose fiber was defibrated for 60 minutes at 20000 rpm. Next, the supernatant was collected by centrifuging at 12000 G for 10 minutes with a centrifuge to obtain a dispersion (rubber modifier) of defibrated cellulose maleate fibers.
A rubber latex dispersion, a pre-vulcanized rubber composition, and a vulcanization were prepared in the same manner as in Example 1 except that the above-described defibrated maleate cellulose fiber dispersion was used instead of the cellulose phosphate fiber dispersion. A vulcanized rubber composition was obtained.

[Example 4]
The rubber modification was performed in the same manner as in Example 3 except that the dispersion of cellulose acetylated cellulose fibers obtained in Production Example 4 was used instead of the dispersion of cellulose maleate fibers obtained in Production Example 3. A material, a pre-vulcanized rubber composition and a vulcanized rubber composition were obtained.

[Example 5]
A rubber modifier in the same manner as in Example 3, except that the cellulose phosphate fiber dispersion obtained in Production Example 1 was used instead of the cellulose maleate fiber dispersion obtained in Production Example 3. A rubber composition before vulcanization and a vulcanized rubber composition were obtained.

[Example 6]
The rubber modification was performed in the same manner as in Example 3 except that the dispersion of cellulose acetylated cellulose fibers obtained in Production Example 5 was used instead of the dispersion of cellulose maleate fibers obtained in Production Example 3. A material, a pre-vulcanized rubber composition and a vulcanized rubber composition were obtained.

[Example 7]
A rubber modifier in the same manner as in Example 3 except that the cellulose phthalate fiber dispersion obtained in Production Example 6 was used instead of the cellulose maleate fiber dispersion obtained in Production Example 3. A rubber composition before vulcanization and a vulcanized rubber composition were obtained.

[Example 8]
The rubber modification was conducted in the same manner as in Example 3 except that the dispersion of cellulose phthalate acetylated fiber obtained in Production Example 7 was used instead of the dispersion of cellulose maleate fiber obtained in Production Example 3. A material, a pre-vulcanized rubber composition and a vulcanized rubber composition were obtained.

[Comparative Example 1]
A rubber composition before vulcanization and a vulcanized rubber composition were obtained in the same manner as in Example 1 according to the composition shown in Table 1 below without using cellulose fibers.

[Comparative Example 2]
A dispersion of defibrated cellulose fibers and a rubber composition before vulcanization were carried out in the same manner as in Example 1 except that hardwood bleached kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd.) was used instead of the cellulose phosphate fiber dispersion. And a vulcanized rubber composition were obtained.

[Evaluation test]
The vulcanized rubber compositions obtained in Examples 1 to 8 and Comparative Examples 1 and 2 were processed into predetermined dumbbell-shaped test pieces, and the following evaluations were performed.

<Breaking strength and M300>
The tensile strength in accordance with JIS K6251 was measured for each vulcanized rubber composition and the tensile stress (M300) at 300% elongation, and displayed as an index with the value of natural rubber only (Comparative Example 1) as 100. did. The larger the index, the better the reinforcement.
<Tan δ>
In accordance with JIS K6394, the loss factor tan δ was measured 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%. The smaller the index, the smaller the tan δ, and the less the heat is generated.
The results are shown in Table 1.

From the results shown in Table 1, for the vulcanized rubber compositions of Examples 1 to 8 using the rubber modifier of the present invention, Comparative Example 1 which is only natural rubber and cellulose fibers having no functional group are used. Compared with the comparative example 2, the high elastic modulus and the high fracture strength are shown, and it can be seen that the reinforcing property is excellent.
Moreover, it turns out that the vulcanized rubber composition of Examples 1-8 is excellent in the low exothermic property compared with the rubber composition of the comparative example 2.
This result is considered to be a result of the cellulose fibers becoming finer and the dispersibility in the vulcanized rubber component being remarkably excellent by using the modifier of the present invention.

Claims (5)

A rubber modifier containing cellulose fibers,
A rubber modifier, wherein the cellulose constituting the cellulose fiber is a cellulose having a group derived from phosphoric acid and / or a group derived from carboxylic acid.   The rubber modifier according to claim 1, wherein an average fiber diameter of the cellulose fibers is 400 nm or less.   A rubber latex dispersion comprising the rubber modifier according to claim 1 or 2 and a rubber latex.   A rubber composition comprising the rubber modifying material according to claim 1 or 2 and rubber.   A rubber composition produced by using the rubber latex dispersion according to claim 3.