JP6143187B2 - Cellulose nanofiber-containing rubber masterbatch - Google Patents

Description

  The present invention relates to a rubber masterbatch containing cellulose nanofibers.

  Conventionally, a technique for improving hardness and modulus by reinforcing rubber with short fibers such as aramid and cellulose and crystalline polymers such as syndiotactic polybutadiene is known (see Patent Document 1).

  Patent Document 1 proposes a rubber composition comprising a diene rubber component, starch and cellulose for the purpose of providing a rubber composition having excellent abrasion resistance, and also proposes using bacterial cellulose as the cellulose. ing. However, the technique of Patent Document 1 has a problem that the breaking property is poor due to poor compatibility between rubber and cellulose.

  Patent Document 2 discloses a rubber composition in which finely powdered cellulose fibers prepared from natural plant fibers are blended with a diene rubber. However, the technique of Patent Document 2 has room for improvement in terms of obtaining rigidity and reinforcing properties commensurate with the blended amount of cellulose fiber because the fiber length of the cellulose fiber is short due to its production method.

  Therefore, it is still difficult to obtain a vulcanized rubber composition that is environmentally friendly and excellent in breaking properties.

JP 2005-133025 A JP-A-2005-75856

  An object of the present invention is to provide a cellulose nanofiber-containing rubber masterbatch that is a raw material for a vulcanized rubber composition that is environmentally friendly and has excellent fracture characteristics.

  The present inventors have found that the dispersibility of cellulose nanofibers in rubber significantly affects the strength characteristics in the vulcanized rubber composition. Moreover, it discovered that the dispersibility in a vulcanized rubber of a cellulose nanofiber was greatly influenced by the conditions at the time of manufacture of a cellulose nanofiber containing rubber masterbatch. And based on these knowledge, it discovered that the vulcanized rubber composition which used the cellulose containing rubber dispersion masterbatch manufactured from the following cellulose nanofiber dispersions as a raw material had the outstanding fracture | rupture characteristic.

The present invention has the following aspects.
[1] From an aqueous dispersion containing a cellulose nanofiber having an average fiber width of less than 100 nm, a rubber latex, and a component for aggregating the cellulose nanofiber and the rubber latex and having a solid content concentration of 3% by mass or less , moisture is removed. Cellulose nanofiber-containing rubber masterbatch obtained by removal.
[2] The cellulose nanofiber-containing rubber masterbatch according to [1], wherein the aqueous dispersion contains a cationic polymer.
[3] The cellulose nanofiber-containing rubber masterbatch according to [1] or [2], wherein the aqueous dispersion contains a cationic surfactant.

  By using the cellulose nanofiber-containing rubber masterbatch of the present invention as a raw material, a vulcanized rubber composition having excellent breaking properties can be obtained.

"Cellulose nanofiber"
Cellulose nanofibers are cellulose fibers or rod-like particles having a type I crystal structure that is much thinner and shorter than pulp fibers normally used in papermaking applications.
The fact that the cellulose nanofiber has the I-type crystal structure is that 2θ = 14 to 17 ° in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks in the vicinity and two positions near 2θ = 22 to 23 °.
The crystallinity of the cellulose nanofibers determined by the X-ray diffraction method is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. If the degree of crystallinity is not less than the lower limit, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. The degree of crystallinity can be obtained by measuring an X-ray diffraction profile and using a conventional method (Segal et al., Textile Research Journal, 29, 786, 1959).

<Fiber width>
Cellulose nanofibers are cellulose having an average fiber width of less than 100 nm determined by observation with an electron microscope. The average fiber width of the cellulose nanofiber is preferably 2 nm or more and less than 100 nm, more preferably 2 to 50 nm, further preferably 2 to 30 nm, and particularly preferably 2 to 15 nm. When the average fiber width of the cellulose nanofiber exceeds the above upper limit, the characteristics as the cellulose nanofiber (high strength, high rigidity, high dimensional stability, high dispersibility when combined with resin, transparency) are obtained. Becomes difficult. When the average fiber width of the cellulose nanofibers is less than the lower limit value, the cellulose nanofibers are dissolved in the dispersion medium as cellulose molecules, so that characteristics (high strength, high rigidity, high dimensional stability) as cellulose nanofibers can be obtained. It becomes difficult.

The measurement of the average fiber width of the cellulose nanofibers by observation with an electron microscope is performed as follows. A cellulose nanofiber-containing slurry is prepared, and the slurry is cast on a carbon film-coated grid subjected to a hydrophilization treatment to obtain a transmission electron microscope (TEM) observation sample. When wide fibers are included, an operation electron microscope (SEM) image of the surface cast on glass may be observed. Observation by an electron microscope image is performed at any magnification of 1000 times, 5000 times, 10000 times, 20000 times, 50000 times or 100,000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicularly intersecting the straight line X is drawn in the same image, and 20 or more fibers intersect the straight line Y.
For the electron microscope observation image as described above, the width (minor axis of the fiber) of at least 20 fibers (that is, at least 40 in total) is read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y. . In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber width of at least 40 × 3 sets (that is, at least 120 sets) is read. The fiber widths thus read are averaged to obtain the average fiber width. This average fiber width is equal to the number average fiber diameter.

  The maximum fiber width of the cellulose nanofiber is preferably 50 nm or less, and more preferably 30 nm or less. When the maximum fiber width of the cellulose nanofiber is not more than the above upper limit, the strength of the composite material obtained by mixing with rubber is increased.

<Fiber length>
As for the average fiber length of a cellulose nanofiber, 0.1-5.0 micrometers is preferable. If average fiber length is more than the said lower limit, the strength improvement effect at the time of mix | blending a cellulose nanofiber with resin is fully acquired. If average fiber length is below the said upper limit, the mixability at the time of mix | blending a cellulose nanofiber with resin will become more favorable. The fiber length can be determined by analyzing the electron microscope observation image used when measuring the average fiber width. That is, at least 20 fibers (that is, a total of at least 40 fibers) are read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y with respect to the electron microscope observation image as described above. In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber length of at least 40 × 3 sets (that is, at least 120 sets) is read. The average fiber length is obtained by averaging the fiber lengths thus read.
When cellulose nanofibers are applied to uses such as a transparent substrate that require strength, the fiber length is preferably long (specifically, 500 nm to 4 μm). Is preferably shorter (specifically, 200 nm to 2 μm).

<Anionic group>
The cellulose nanofiber may have an anion group and a negative surface charge.
When the cellulose nanofiber has an anionic group, the content is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, 0.2 to More preferably, it is 1.2 mmol / g. When the content of the anionic group is within the above range, the hydration property of the cellulose nanofiber is not excessively increased, and the viscosity when slurried is decreased. If the content of the anionic group exceeds the above upper limit, the hydration property becomes too high and the cellulose nanofibers may be dissolved.
Note that cellulose has a small amount (specifically, less than 0.1 mmol / g) of carboxy groups even without a treatment for introducing carboxy groups.

Examples of the anionic group include a carboxy group, a phosphoric acid group, and a sulfonic acid group.
The content of the anionic group is determined using a method of “Test Method T237 cm-08 (2008): Carboxyl Content of pull” of TAPPI, USA. In order to make it possible to measure the content of anionic groups over a wider range, among the test solutions used in the test method, sodium hydrogen carbonate (NaHCO 3) / sodium chloride (NaCl) = 0.84 g / 5.85 g was added with distilled water. The test solution dissolved and diluted in 1000 ml is based on TAPPI T237 cm-08 (2008) except that the concentration of the test solution is changed to 1.60 g of sodium hydroxide so that the concentration of the test solution is substantially 4 times. Moreover, when an anion group is introduced, the difference in the measured value in the cellulose fiber before and after the introduction of the anion group is regarded as a substantial anion group content. In addition, the absolutely dry cellulose fiber used as a measurement sample is one obtained by freeze-drying in order to avoid alteration of cellulose that may occur due to heating during heat drying.
Since the anion group content measurement method is a measurement method for a monovalent anion group (carboxy group), when the anion group to be quantified is multivalent, it is obtained as the monovalent anion group content. A value obtained by dividing the obtained value by the acid number is defined as an anion group content.

"Production method of cellulose nanofiber"
<Cellulose fiber raw material>
In the present invention, the fiber raw material containing cellulose, which is a raw material of cellulose nanofiber, includes pulp for papermaking, cotton pulp such as cotton linter and cotton lint, non-wood pulp such as hemp, straw, bagasse, sea squirt and seaweed And cellulose isolated from the above. Among these, paper pulp is preferable in terms of availability. Paper pulp includes hardwood kraft pulp (bleached kraft pulp (LBKP), unbleached kraft pulp (LUKP), oxygen bleached kraft pulp (LOKP), etc.), softwood kraft pulp (bleached kraft pulp (NBKP), unbleached kraft pulp) (NUCKP, oxygen bleached kraft pulp (NOKP), etc.), sulfite pulp (SP), chemical pulp such as soda pulp (AP), semi-chemical pulp (SCP), semi-chemical pulp such as chemiground wood pulp (CGP) In addition, mechanical pulp such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP), non-wood pulp using raw material such as cocoon, sardine, hemp, kenaf and the like, and deinked pulp using raw paper as a raw material. Among these, kraft pulp, deinked pulp, and sulfite pulp are preferable because they are more easily available.
A cellulose fiber raw material may be used individually by 1 type, and may be used in mixture of 2 or more types.

<Chemical treatment process>
The fiber raw material containing cellulose may be used as it is as a raw material for cellulose nanofibers. However, since the micronization is promoted in the micronization process, a substituent composed of at least one of a polar group and a bulky group is not added. It is preferable to perform chemical treatment to contain 1 to 2.0 mmol / g.
Examples of the polar group include an anion group (specifically, a carboxy group, a phosphate group, a sulfate ester group, a sulfonate group, a phenol group, and a nitrate ester group), and a carboxy group and a phosphate group are preferable.
Examples of the bulky group include an alkyl group, a benzyl group (benzene ring) and a benzene derivative-containing group, an acyl group, a silyl group, a trityl group, and a tosyl group.

[Introduction of carboxy group]
As a method of introducing a carboxy group into a cellulose fiber raw material, a method of oxidizing a part of the hydroxyl group of cellulose to a carboxy group using an oxidizing agent can be mentioned.
Oxidizing agents include ozone, chlorine dioxide, hydrogen peroxide, peracetic acid, persulfuric acid, permanganic acid, chlorine, hypochlorous acid, chlorous acid, chloric acid, perchloric acid or an aqueous solution thereof such as six salts. Chromic acid sulfuric acid mixture, Jones reagent (acidic sulfuric acid solution of chromic anhydride), chromic acid oxidizing reagent such as pyridilinium chlorochromate (PCC reagent), activated dimethyl sulfoxide reagent used for Swern oxidation, etc., and catalytic oxidation And N-oxyl compounds such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and the like. Of these, ozone, TEMPO, hydrogen peroxide, and chlorine dioxide are preferred, and ozone and TEMPO are more preferred because of the high efficiency of introducing carboxy groups into cellulose fibers.

[Treatment with ozone]
In the treatment with ozone, some hydroxyl groups of cellulose are replaced with carbonyl groups or carboxy groups. Thereby, the bond strength between cellulose fibers becomes weak and defibration improves.
Ozone can be generated by supplying an oxygen-containing gas such as air, oxygen gas, or oxygen-added air to a known ozone generator.

The treatment with ozone is performed by exposing the cellulose fiber raw material to a closed space or atmosphere in which ozone exists. If the ozone concentration in the gas containing ozone is 250 g / m ² or more, there is a possibility of explosion, so it is necessary to be less than 250 g / m ² . However, if the concentration is low, the amount of ozone used increases, so the ozone concentration is preferably 50 to 215 g / m ² . If the ozone concentration is equal to or higher than the lower limit, it is easy to handle ozone, and the effect of improving the yield of cellulose nanofibers in the miniaturization step is further increased.
The amount of ozone added to the cellulose fiber raw material is not particularly limited, but is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the solid content of the cellulose fiber raw material. If the amount of ozone added is equal to or greater than the lower limit, the effect of improving the yield of cellulose nanofibers in the miniaturization step will be higher. However, exceeding the upper limit causes a decrease in yield before and after the ozone treatment and a deterioration in dewaterability. In addition, the effect of improving the yield of cellulose nanofiber reaches its peak in the miniaturization process.

The ozone treatment temperature is not particularly limited, and is appropriately adjusted within a range of 0 to 50 ° C. Further, the ozone treatment time is not particularly limited, and is appropriately adjusted within a range of 1 to 360 minutes.
In addition, you may perform a post-oxidation process after performing an ozone process to a cellulose fiber raw material. Examples of the oxidizing agent used for the additional oxidation treatment include oxygen, hydrogen peroxide, persulfuric acid, peracetic acid, and the like, in addition to chlorine compounds such as chlorine dioxide and sodium chlorite.

Moreover, after ozone treatment, it is preferable to perform the alkali treatment which processes with the alkaline solution with respect to the processed cellulose fiber raw material. Although it does not specifically limit as a method of alkali treatment, For example, the method of immersing the cellulose fiber raw material which carried out ozone treatment in the alkaline solution is mentioned.
The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound.

Examples of inorganic alkali compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphoric acids. Salt.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of the alkaline earth metal hydroxide include calcium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate.
Examples of the alkali metal phosphate include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.

Examples of the organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums, aromatic ammoniums, heterocyclic compounds and their hydroxides, carbonates, and phosphates. For example, ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, etc. Can be mentioned.
The said alkali compound may be single 1 type, and may combine 2 or more types.

The solvent in the alkaline solution may be either water or an organic solvent, but is preferably a polar solvent (polar organic solvent such as water or alcohol), and more preferably an aqueous solvent containing at least water. Among alkaline solutions, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia aqueous solution are particularly preferred because of their high versatility.
The pH at 25 ° C. of the alkaline solution in which the ozone-treated cellulose fiber raw material is immersed is preferably 9 or more, more preferably 10 or more, and even more preferably 11-14. If the pH of the alkaline solution is equal to or higher than the lower limit, the yield of cellulose nanofibers becomes higher. However, when the pH exceeds 14, not only the handling property of the alkaline solution is lowered, but also dissolution of the cellulose nanofiber occurs.

[Processing by TEMPO]
In the treatment with TEMPO, a cellulose fiber raw material is reacted with an oxidizing agent in the presence of TEMPO and an alkali halide to change a part of the hydroxyl groups of cellulose to carboxy groups. Thereby, the bond strength between cellulose fibers becomes weak and defibration improves.
The alkali halide used as an oxidation catalyst together with TEMPO is not particularly limited, and alkali iodide, alkali bromide, alkali chloride, alkali fluoride and the like can be appropriately selected and used.
The oxidizing agent is not particularly limited, and sodium hypochlorite, sodium chlorite, sodium hypobromite, sodium bromite and the like can be appropriately selected and used.

Although the usage-amount of TEMPO and an alkali halide is not restrict | limited in particular, It is preferable that it is 0.1-15 mass parts, respectively with respect to 100 mass parts of solid content of a cellulose fiber raw material. If the addition amount of TEMPO and an alkali halide is each more than the said lower limit, the yield improvement effect of the cellulose nanofiber in a refinement | miniaturization process will become higher. However, if the upper limit is exceeded, the yield enhancement effect of cellulose nanofibers in the miniaturization process may reach a peak.
The amount of the oxidizing agent used is not particularly limited, but is preferably 1 to 80 parts by mass with respect to 100 parts by mass of the solid content of the cellulose fiber raw material.
The pH of the dispersion when the dispersion containing the cellulose fiber raw material is treated with TEMPO is appropriately adjusted according to the type of oxidizing agent to be used. The pH of the cellulose fiber raw material dispersion is adjusted by appropriately adding a basic substance such as potassium hydroxide or ammonia, or an acidic substance such as acetic acid or oxalic acid.
The treatment temperature for treating the cellulose fiber raw material with TEMPO is preferably in the range of 20 to 100 ° C., and the treatment time is preferably 0.5 to 4 hours.

[Treatment with carboxylic acid compound]
As a method for introducing a carboxy group into a cellulose fiber raw material, a method using a carboxylic acid compound having two or more carboxy groups in the molecule is also preferred.
In the treatment with the carboxylic acid compound, the hydroxy group of the cellulose molecule and the carboxylic acid compound undergo a dehydration reaction to form a polar group (—COO ⁻ ). Thereby, the bond strength between cellulose fibers becomes weak and defibration improves.

  Specific methods for treating the cellulose fiber raw material with the carboxylic acid compound include a method of mixing the gasified carboxylic acid compound with the cellulose fiber raw material, a method of adding the carboxylic acid compound to the dispersion of the cellulose fiber raw material, and the like. Can be mentioned. Among these, since the process is simple and the efficiency of introducing a carboxy group is high, a method of mixing a gasified carboxylic acid compound with a cellulose fiber raw material is preferable. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid compound used in this treatment is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. Of the compounds having two carboxy groups, compounds having two carboxy groups (dicarboxylic acid compounds) are preferred.
The compounds having two carboxy groups include propanedioic acid (malonic acid), butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), 2-methylpropanedioic acid, 2 -Methylbutanedioic acid, 2-methylpentanedioic acid, 1,2-cyclohexanedicarboxylic acid, 2-butenedioic acid (maleic acid, fumaric acid), 2-pentenedioic acid, 2,4-hexadienedioic acid, 2-methyl 2-butenedioic acid, 2-methyl-2-pentenedioic acid, 2-methylidenebutanedioic acid (itaconic acid), benzene-1,2-dicarboxylic acid (phthalic acid), benzene-1,3-dicarboxylic acid (isophthalic acid) ), Benzene-1,4-dicarboxylic acid (terephthalic acid), ethanedioic acid (oxalic acid), and the like.
Acid anhydrides of compounds having two carboxy groups include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, 1,2-cyclohexanedicarboxylic anhydride Examples thereof include acid anhydrides of dicarboxylic acid compounds such as acids and compounds containing a plurality of carboxy groups.
The acid anhydride derivative of the compound having two carboxy groups includes at least a part of the acid anhydride of the compound having a carboxy group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. The hydrogen atom is substituted with a substituent (for example, an alkyl group, a phenyl group, etc.).
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.

The mass ratio of the carboxylic acid compound to the cellulose fiber raw material is preferably 0.1 to 500 parts by mass, preferably 10 to 200 parts by mass with respect to 100 parts by mass of the solid content of the cellulose fiber raw material. More preferably. If the ratio of a carboxylic acid type compound is more than the said lower limit, the yield of a cellulose nanofiber can be improved more. However, even if the upper limit is exceeded, the effect of improving the yield reaches its peak, and the carboxylic acid compound is merely used in vain.
The treatment temperature is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose. Furthermore, when water is contained in the treatment, the temperature is preferably 80 to 200 ° C, more preferably 100 to 170 ° C.
In this treatment, a catalyst can be used as necessary. As the catalyst, it is preferable to use a basic catalyst such as pyridine, triethylamine, sodium hydroxide or sodium acetate, or an acidic catalyst such as acetic acid, sulfuric acid or perchloric acid.
After the treatment with the carboxylic acid compound, the treated cellulose fiber raw material is preferably subjected to an alkali treatment with an alkaline solution, similarly to the treatment with ozone.

[Introduction of phosphate group]
As a method for introducing a phosphate group into cellulose, a method of mixing a powder or aqueous solution of phosphoric acid or a phosphoric acid derivative with a dry or wet cellulose fiber raw material, a phosphoric acid or phosphoric acid with a dispersion of a cellulose fiber raw material Examples thereof include a method of adding an aqueous solution of a derivative. In these methods, dehydration treatment, heat treatment, and the like are usually performed after mixing or adding a powder or aqueous solution of phosphoric acid or phosphoric acid derivative.
Examples of the phosphoric acid or phosphoric acid derivative used here include at least one compound selected from an oxo acid, a polyoxo acid or a derivative thereof containing a phosphorus atom. Specifically, phosphoric acid; sodium salt of phosphoric acid such as sodium dihydrogen phosphate, disodium hydrogen phosphate and trisodium phosphate; sodium salt of polyphosphoric acid such as sodium pyrophosphate and sodium metaphosphate; Potassium salts of phosphoric acid such as potassium hydrogen, dipotassium hydrogen phosphate and tripotassium phosphate; potassium salts of polyphosphoric acid such as potassium pyrophosphate and potassium metaphosphate; ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphoric acid Examples thereof include ammonium salts of phosphoric acid such as triammonium; ammonium salts of polyphosphoric acid such as ammonium pyrophosphate and ammonium metaphosphate. These may be used alone or in combination of two or more. Among the above, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable.

  The mass ratio of phosphoric acid or phosphoric acid derivative to the cellulose fiber raw material is such that phosphoric acid or phosphoric acid derivative is 0.2 to 500 parts by mass as the amount of phosphorus element with respect to 100 parts by mass of the solid content of the cellulose fiber raw material. Preferably, it is 1-400 mass parts, More preferably, it is 2-200 mass parts. If the ratio of phosphoric acid or a phosphoric acid derivative is more than the said lower limit, the yield of a cellulose nanofiber can be improved more. However, even if the upper limit is exceeded, the effect of improving the yield reaches its peak, and only phosphoric acid or phosphoric acid derivatives are used in vain.

It is preferable that the heat processing temperature is 250 degrees C or less from the point of the thermal decomposition temperature of a cellulose. Moreover, it is preferable that the heat processing temperature is 100-170 degreeC from a viewpoint of suppressing hydrolysis of a cellulose. Furthermore, regarding the heating while water is contained in the system to which phosphoric acid or a phosphoric acid derivative is added during the heat treatment, it is preferably 130 ° C. or less, more preferably 110 ° C. or less to sufficiently absorb moisture. Remove and dry. After that, it is preferable to heat-process at 100-170 degreeC. Further, when removing moisture, a vacuum dryer may be used.
After the treatment with phosphoric acid or a phosphoric acid derivative, the treated cellulose fiber raw material may be subjected to an alkali treatment, similarly to the treatment with ozone.

By the above treatment, the cellulose has phosphoric acid-derived groups (—PO ₄ ²⁻ , —PO ₄ H ⁻ ). Cellulose may have two or more phosphoric acid-derived groups. For example, cellulose may have two types of phosphoric acid derived from different numbers of hydrogen ions.

[Enzyme treatment]
The cellulose fiber raw material used in the present invention does not necessarily have the above polar group or bulky group, but when it does not have the above polar group or bulky group, the cellulose fiber raw material is produced by an enzyme collectively referred to as so-called cellulase. Is preferably processed. Cellulase is an enzyme having cellobiohydrolase activity, endoglucanase activity, and beta-glucosidase activity.
As the enzyme used in the enzyme treatment, an enzyme having the above activity may be mixed and used in an appropriate amount, or a commercially available cellulase preparation may be used.
Commercial cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerocheet, Trametes, Humicola, and Humicola. Cellulase preparations derived from the above.
Commercially available products of such cellulase preparations are all trade names, for example, cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika Co., Ltd.), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor) ) And the like.
In addition, many commercially available cellulase preparations have hemicellulase activity as well as various cellulase activities described above.

  In the enzyme treatment, in addition to cellulase, a hemicellulase-based enzyme may be used alone, or a cellulase and a hemicellulase-based enzyme may be used in combination. Among hemicellulase enzymes, it is preferable to use xylanase, which is an enzyme that degrades xylan, mannanase, which is an enzyme that degrades mannan, and arabanase, which is an enzyme that degrades araban. In addition, pectinase, which is an enzyme that degrades pectin, can also be used as a hemicellulase-based enzyme.

The pH of the dispersion during the enzyme treatment is preferably maintained in a range where the activity of the enzyme used is high. For example, in the case of a commercially available enzyme derived from Trichoderma, the pH is preferably between 4-8.
Further, the temperature of the dispersion during the enzyme treatment is preferably maintained within a range in which the activity of the enzyme used is increased. For example, in the case of a commercially available enzyme derived from Trichoderma, the temperature is preferably 40 ° C to 60 ° C. If the temperature is less than the lower limit, the enzyme activity decreases and the treatment time becomes longer. If the temperature exceeds the upper limit, the enzyme may be deactivated. The treatment time for the enzyme treatment is preferably in the range of 10 minutes to 24 hours. If the treatment time of the enzyme treatment is less than 10 minutes, the effect of the enzyme treatment is hardly exhibited. If it exceeds 24 hours, the decomposition of cellulose fibers proceeds too much by the enzyme, and the average fiber length of the resulting cellulose nanofibers may be too short.
It should be noted that when the enzyme remains active for a predetermined time or longer, the decomposition of cellulose proceeds excessively as described above. Therefore, when the predetermined enzyme treatment is completed, it is preferable to perform an enzyme reaction stop process. . The enzyme reaction is stopped by washing the enzyme-treated dispersion with water, removing the enzyme, adding sodium hydroxide to the enzyme-treated dispersion to a pH of about 12, and then adding the enzyme. Examples thereof include a method for inactivation and a method for inactivating the enzyme by raising the temperature of the dispersion treated with the enzyme to a temperature of 90 ° C.

<Refining process>
The refinement step is a step of obtaining a cellulose nanofiber dispersion containing cellulose nanofibers by subjecting the cellulose fiber raw material dispersion to a refinement treatment so that cellulose nanofibers having an average fiber width of less than 100 nm are obtained.
In the miniaturization process, a miniaturization processing apparatus is usually used. High-speed rotary defibrator, grinder (stone mill type grinder), high-pressure homogenizer and ultra-high pressure homogenizer, high-pressure collision type grinder, ball mill, bead mill, disk type refiner, conical refiner, twin-screw kneader, vibration A wet pulverizing apparatus such as a mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used as appropriate. These may be used alone, a plurality of the same devices may be used, or different types of devices may be combined. When combining different types of apparatuses, it is preferable to combine any two of a refiner, a high-pressure homogenizer, and a high-speed rotary defibrator.

It is preferable that the solid content concentration of the cellulose fiber raw material dispersion supplied to the micronization treatment is 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. If the solid content concentration of the cellulose fiber raw material dispersion is equal to or higher than the lower limit, the efficiency of the refining treatment is improved, and if it is equal to or lower than the upper limit, blockage in the refining treatment apparatus can be prevented.
Examples of the dispersion medium for dilution include water, an organic solvent, and a mixture of water and an organic solvent.

<Purification process>
A refinement | purification process is a process of refine | purifying a cellulose nanofiber dispersion so that an average fiber width may be 2-100 nm after a refinement | miniaturization process. If a cellulose nanofiber dispersion liquid is refine | purified by a refinement | purification process, the fiber which has a big fiber diameter will be removed, the external appearance of a cellulose nanofiber can be improved, and a physical property can be improved more. When cellulose nanofibers are used for applications where strength is important, the number of fracture nuclei consisting of large fibers is reduced by the purification process, so that variations in strength and reduction can be prevented.

In the refining process, a refining apparatus is used that removes large fibers of cellulose nanofibers and concentrates those having an average fiber width of less than 100 nm.
Examples of the refining device include a decanter using a difference in specific gravity, a centrifuge, a cleaner, a screen and a filter using a difference in shape, a flotator for separating by flotation, and a pressure levitation device. These may be used singly or a plurality of different types may be combined.

"Aqueous dispersion containing cellulose nanofiber"
The cellulose nanofiber-containing rubber masterbatch of the present invention is obtained by removing water from an aqueous dispersion containing cellulose nanofibers and a rubber latex and having a solid content concentration of 3% by mass or less. In addition to cellulose nanofibers and rubber latex, the aqueous dispersion contains components such as formic acid, a cationic polymer, and a cationic surfactant that function to aggregate these components. Furthermore, other compounding agents conventionally used in the rubber industry may be added. For example, silica particles, carbon black, inorganic such as fiber, organic filler, silane coupling agent and the like can be mentioned.

  The solid content of the aqueous dispersion is preferably 0.01% by mass to 3% by mass, more preferably 0.05% by mass to 2.8% by mass, and further preferably 0.08% by mass to 2.5% by mass. preferable. If it is 0.01% by mass or less, it requires a lot of energy and cost to remove water, which is not preferable. On the other hand, if the solid content concentration is higher than 3% by mass, cellulose nano-nanofibers aggregate in the aqueous dispersion and become aggregates in the resulting cellulose nanofiber-containing rubber composite, causing a decrease in strength.

  The cellulose nanofibers in the cellulose nanofiber-containing aqueous dispersion are usually 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and usually 100 parts by mass or less, preferably with respect to 100 parts by mass of the rubber component. Is 70 parts by mass or less, more preferably 50 parts by mass or less. When the amount of cellulose nanofiber is small, the reinforcing effect is not sufficient, and when it is large, the processability of rubber is lowered.

<Cationic polymer>
Examples of the cationic polymer include polyamide polyamine resins, polyamide polyurea resins, polyamine resins, and the like, and one or more of these cationic resins are used as appropriate. Incidentally, specific examples of the polyamide polyamine resin include polyamide polyamine-epichlorohydrin resin, polyamide polyamine-glyoxal resin, polyamide polyamine-formaldehyde resin, and the like.
Specific examples of the polyamide polyurea resin include a polyamide polyurea-epichlorohydrin resin, a polyamide polyurea-glyoxal resin, and a polyamide polyurea-formaldehyde resin. Furthermore, specific examples of the polyamine resin include polyalkylene polyamine-epichlorohydrin resin, polyalkylene polyamine-epichlorohydrin-dialkyl sulfate resin, alkylene diamine-alkylene dihalide resin, polyethyleneimine, and the like.

  When the cationic polymer is blended in the cellulose nanofiber-containing aqueous dispersion, it is usually 0.1 parts by mass or more, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, with respect to 100 parts by mass of the rubber component. Usually 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less. When the cationic polymer is less than 0.1 parts by mass, it is insufficient to agglomerate the cellulose nanofibers and the rubber latex. Since the ratio of the conductive polymer increases, it causes a problem such as a decrease in water resistance of the obtained master batch, which is not preferable.

<Cationic surfactant>
Cationic surfactants include alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, acylaminoethyldiethylammonium salt, acylaminoethyldiethylamine salt, alkylamidopropyldimethylbenzylammonium salt, alkylpyridinium salt, alkyl Quaternary ammonium salts such as pyridinium sulfate, stearamide methylpyridinium salt, alkylquinolinium salt, alkylisoquinolinium salt, fatty acid polyethylene polyamide, acylaminoethylpyridinium salt, acylcoraminoformylmethylpyridinium salt, stearo Oxymethylpyridinium salt, fatty acid triethanolamine, fatty acid triethanolamine formate, trioxyethylene fatty acid tri Ester-bonded amines and ether-bonded quaternary ammonium salts such as tanolamine, cetyloxymethylpyridinium salt, p-isooctylphenoxyethoxyethyldimethylbenzylammonium salt, alkylimidazolines, 1-hydroxyethyl-2-alkylimidazolines, 1-acetyl Heterocyclic amines such as aminoethyl-2-alkylimidazoline, 2-alkyl-4-methyl-4-hydroxymethyloxazoline, polyoxyethylene alkylamine, N-alkylpropylenediamine, N-alkylpolyethylenepolyamine, N-alkylpolyethylenepolyamine Examples thereof include amine derivatives such as dimethyl sulfate, alkyl biguanide, and long chain amine oxide.

  When the cationic surfactant is blended in the cellulose nanofiber-containing aqueous dispersion, it is usually 0.1 parts by mass or more, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, relative to 100 parts by mass of the rubber component. The amount is usually 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less. When the cationic surfactant is less than 0.1 parts by mass, it is insufficient to agglomerate the cellulose nanofibers and the rubber latex. When the cationic surfactant is 20 parts by mass or more, the cellulose nanofiber-containing rubber masterbatch obtained Since the ratio of the cationic surfactant is increased, it is not preferable because it causes problems such as reduction in water resistance of the obtained master batch.

<Rubber latex>
Examples of rubber latex used include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), nitrile rubber (NBR), and chloroprene. It is preferable to use rubber latex (preferably concentration: 5 to 60% by mass) such as rubber (CR), acrylic rubber (ACM), and fluoro rubber (FKM).

  In the step of preparing the cellulose nanofiber-containing rubber latex aqueous dispersion, there is no particular limitation on the method of mixing the cellulose nanofiber aqueous dispersion, the latex dispersion, and other components. It can be performed by a general method such as an apparatus, an electromagnetic stirring device, manual stirring, or natural diffusion without stirring.

  Water can be removed from the cellulose nanofiber-containing rubber latex aqueous dispersion by, for example, general methods such as natural drying, oven drying, freeze drying, and spray drying. After separation, the water can be efficiently removed by drying.

"Preparation of rubber composition"
The rubber composition is produced from the cellulose nanofiber-containing masterbatch of the present invention. Specifically, it is produced by vulcanizing a cellulose nanofiber-containing rubber masterbatch or, if necessary, adding a rubber latex to the cellulose nanofiber-containing rubber masterbatch and then vulcanizing. In addition, it is obtained by mixing other compounding agents used in the conventional rubber industry as described above using a known method such as a kneader for rubber before vulcanization, and then molding and vulcanizing by a known method. . Compounding agents include silica particles, carbon black, fibers, inorganic and organic fillers, silane coupling agents, vulcanizing agents, stearic acid, vulcanization accelerators, vulcanization accelerators, oils, cured resins, waxes, Anti-aging agent can be raised.

  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 is usually 7.0 parts by mass or less, preferably 6.0 parts by mass or less in the case of sulfur with respect to 100 parts by mass of the rubber component. Moreover, it is 1.0 mass part or more normally, Preferably it is 3.0 mass part or more, Especially 4.0 mass part or more.

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

  The vulcanized rubber composition produced from the cellulose nanofiber-containing rubber masterbatch of the present invention has high breaking strength and elastic modulus, such as pneumatic tires for passenger cars, trucks, buses, heavy vehicles, etc. It can be applied to various rubber products such as tires, rubber crawlers, conveyor belts and the like.

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

<Preparation of cellulose nanofiber>
As a fiber material containing cellulose, a hardwood bleached kraft pulp (LBKP) having a carboxy group content of 0.06 mmol / g, a solid content concentration of 30% by mass (water content of 70% by mass), and an absolute dry mass conversion was prepared.
The LBKP was housed in a container, and 5 L of an ozone / oxygen mixed gas having an ozone concentration of 200 g / m ³ was introduced into the container and shaken at 25 ° C. for 2 minutes. The ozone addition rate at this time was 5 mass% with respect to the pulp dry mass. After standing for 6 hours, ozone and air in the container were removed, and the ozone oxidation treatment was completed.
After the treatment, the suspension was washed with ion-exchanged water, and the washing was repeated until the pH of the washing water reached 6 or higher. Then, it filtered under reduced pressure using the filter paper, and obtained the oxidation process pulp with a solid content concentration of 20 mass%.
Ion exchange water was added to the oxidized pulp (20 g in terms of absolute dry mass) to prepare a slurry having a solid content concentration of 2% by mass. Sodium hydroxide was added to the slurry so that the sodium hydroxide concentration was 0.3% by mass, and the mixture was stirred for 5 minutes and then allowed to stand at room temperature for 30 minutes. Subsequently, the suspension was washed with ion-exchanged water, and washing was repeated until the pH of the washing water became 8 or less to obtain a slurry containing alkali-treated pulp.
Subsequently, ion-exchanged water was added to prepare a cellulose fiber aqueous dispersion having a cellulose fiber concentration of 0.5% by mass. The cellulose fiber aqueous dispersion was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) at 21500 rpm. Thereafter, using a centrifuge (“H-200NR” manufactured by Kokusan Co., Ltd.), the resultant was treated with about 12000 G for 10 minutes, and the supernatant thus separated was recovered as an aqueous dispersion of cellulose nanofibers.
It was 4 nm when the aqueous dispersion liquid of the obtained cellulose nanofiber was observed with the transmission electron microscope, and the average fiber width was measured.

<Manufacture of master batch>
Production Example 1
After diluting natural rubber latex (solid content concentration 20% by mass) to 0.2% by mass and stirring at 11000 rpm using IKA homogenizer for 100 parts of natural rubber latex, the above <Preparation of cellulose nanofiber> 5 parts of the obtained cellulose nanofiber aqueous dispersion (0.2% by mass) was added, and the mixture was further stirred for 10 minutes. 20 parts of formic acid (5% by mass) was slowly added while stirring at 500 rpm using a three-one motor. After standing for 2 hours, the rubber suspension was recovered. After drying with a cylinder dryer at 110 ° C. for 10 minutes, the mixture was dried with a vacuum dryer at 110 ° C. for 3 hours to prepare Masterbatch 1 (MB1).

Production Example 2
Masterbatch 2 (MB2) was produced in the same manner as in Production Example 1 except that 5 parts of WS4024 (manufactured by Seiko PMC, 1 mass%) was added in place of formic acid in Production Example 1.

Production Example 3
Masterbatch 3 (MB3) was prepared in the same manner as in Production Example 1 except that 1.25 parts of Cathiogen DDM-PG (Daiichi Kogyo Seiyaku Co., Ltd., 1% by mass) was added instead of formic acid in Production Example 1. ) Was manufactured.

Production Example 4
A master batch 4 (MB4) was produced in the same manner as in Production Example 1 except that natural rubber latex (solid content concentration 20% by mass) was used without being diluted to 0.2% by mass in Production Example 1. .

Production Example 5
20 parts of formic acid (5% by mass) was slowly added while stirring at 500 rpm using a three-one motor with respect to 100 parts by mass as the solid content of the natural rubber latex (solid content 20% by mass). After standing for 2 hours, the rubber suspension was recovered. After drying at 110 ° C. for 10 minutes with a cylinder dryer, drying was performed at 110 ° C. for 3 hours in a vacuum dryer to prepare Masterbatch 5 (MB5).

  Table 1 shows the composition of the master batch prepared in Production Example 1 to Production Example 5 and the solid content concentration of the cellulose nanofiber-containing aqueous dispersion before removing water.

Example 1
M.C. obtained in Production Example 1 B. 1 contains 5 parts by mass of cellulose fiber 1 per 100 parts by mass of the rubber component (natural rubber latex). Furthermore, 3 parts by mass of zinc white (No. 1 zinc white, manufactured by Asaoka Ceramics Co., Ltd.), 1 mass of vulcanization accelerator (N-tert-butyl-2-benzothiazole sulfenamide, manufactured by Wako Pure Chemical Industries, Ltd.) 2 parts by mass of sulfur (5% oil-treated powdered sulfur, manufactured by Tsurumi Chemical Co., Ltd.) and 3 parts by mass of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed and kneaded.
Specifically, a vulcanization accelerator and components other than sulfur are added to Masterbatch 1, and the mixture is kneaded at 140 ° C. for 3 minutes using a kneading apparatus (Laboplast Mill μ, manufactured by Toyo Seiki Co., Ltd.), and further vulcanization is accelerated. A rubber composition was obtained by adding an agent and sulfur and kneading at 80 ° C. for 3 minutes. This rubber composition was pressure-press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition 1 having a thickness of 1 mm.

Example 2
M.I obtained in Production Example 2 B. A vulcanized rubber composition 2 was obtained in the same manner as in Example 1 except that 2.

Example 3
M. obtained in Production Example 3 B. A vulcanized rubber composition 3 was obtained in the same manner as in Example 1 except that 3 was used.

Comparative Example 1
M.I obtained in Production Example 4 B. A vulcanized rubber composition 4 was obtained in the same manner as in Example 1 except that 4 was used.

Comparative Example 2
A vulcanized rubber composition 5 was obtained in the same manner as in Example 1 except that the natural rubber (MB5) obtained in Production Example 5 was used.

[Evaluation test]
The vulcanized rubber composition 1, the vulcanized rubber composition 2, the vulcanized rubber composition 3, the vulcanized rubber composition 4, and the vulcanized rubber composition 5 obtained in Example 1 and Comparative Examples 1 and 2 were predetermined. The dumbbell-shaped test piece was evaluated for breaking strength and M300. The results are shown in Table 2. The breaking strength and M300 were measured by the tensile test according to JIS K6251 and the rupture strength and M300 of the vulcanized rubber composition were measured and displayed as an index with the value of Comparative Example 2 as 100. The larger the index, the better the reinforcement.

From Table 2, the rubber compositions of Examples 1 to 3 using the cellulose nanofiber-containing rubber masterbatch of the present invention showed higher elastic modulus and higher breaking strength than Comparative Example 2 which is only natural rubber. It can be seen that the vulcanized rubber composition prepared from the cellulose nanofiber-containing rubber masterbatch of the invention has excellent strength characteristics.
On the other hand, M.C. produced from an aqueous dispersion containing cellulose nanofibers and rubber latex having a solid content concentration exceeding 3% by mass. B. The vulcanized rubber composition obtained from No. 4 did not have a high reinforcing effect.

Claims (3)

Moisture was removed from the aqueous dispersion containing a cellulose nanofiber having an average fiber width of less than 100 nm, a rubber latex, and a component for aggregating the cellulose nanofiber and the rubber latex and having a solid content of 3% by mass or less. Cellulose nanofiber-containing rubber masterbatch obtained.   The cellulose nanofiber-containing rubber masterbatch according to claim 1, wherein the aqueous dispersion contains a cationic polymer.   The cellulose nanofiber-containing rubber masterbatch according to claim 1 or 2, wherein the aqueous dispersion contains a cationic surfactant.