JP2010180507A - Cellulose fiber dispersing liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose dispersing liquid having high concentration and remarkably improved dispersion stability, free from gelation trouble and keeping transparency and to improve the productivity. <P>SOLUTION: The cellulose fiber dispersing liquid contains surface-treated cellulose fibers having an average fiber diameter of ≥2 nm and ≤200 nm, and the cellulose fiber concentration is ≥1 mass% and ≤30 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cellulose fiber dispersion, and more particularly to a high concentration cellulose fiber dispersion.

  BACKGROUND ART Fiber reinforced composite materials whose strength and rigidity are greatly improved by blending various fibrous reinforcing agents into resins are widely used in industrial fields such as electric / electronics, machinery, automobiles, and building materials. As the fibrous reinforcing material blended in the fiber-reinforced composite material, glass fibers having excellent strength and lightness are mainly used.

  However, in the glass fiber reinforced material, although high rigidity is achieved, the specific gravity is large, so there is a limit to weight reduction. On the other hand, fiber reinforcement made of organic materials such as polyester fiber, polyamide fiber, and aramid fiber has been studied as a fibrous reinforcement, but fiber reinforcement materials containing these reinforcements are lightweight and thermal recyclable. Although it can be secured, there is a problem that the mechanical reinforcement effect is not sufficient.

  On the other hand, in recent years, high-performance materials using plant-derived materials are attracting attention from the viewpoint of carbon neutral, and fiber composite materials in which cellulose fibers obtained by fibrillating and fibrillating these plant fibers have been proposed. . As a method for dispersing these fibers in the resin, a method of mixing the fibers and the resin and using a biaxial kneader is generally used, but it is difficult to disperse the fibers in the resin at the nano level. Therefore, sufficient mechanical strength has not been secured.

  On the other hand, techniques for surface-treating fibers to uniformly disperse such fibers in the resin and improving compatibility with the resin have been reported (for example, Patent Documents 1 and 2).

  However, with respect to Document 1, it is a method in which a cellulose fiber film is first prepared and the film is immersed in a silane coupling material solution, and it cannot be said that the fibers are uniformly dispersed in the resin. Further, in Document 2, a resin is added to cellulose fiber dispersed at 1% by mass in a solvent and adsorbed onto the cellulose fiber. However, the concentration of the dispersion of cellulose fiber is low, and it can be developed in the industrial field. Not satisfied with productivity.

  Further, when the concentration of the dispersion of cellulose fibers is increased without surface treatment, gelation occurs due to hydrogen bonding between a large number of hydroxyl groups present in cellulose, and the fluidity of the solution (dispersion) is significantly impaired. Moreover, aggregation of the molecules accompanying the hydrogen bond between the hydroxyl groups of the cellulose fiber occurs, and the transparency of the dispersion is lost. This mixing of transparent resin and cellulose fiber has a problem with this decrease in transparency. In addition, with aggregation, the cellulose fibers aggregate and settle over time, resulting in a non-uniform dispersion.

JP 2008-266630 A JP 2008-184492 A

  Conventional cellulose fiber dispersions are difficult to handle because gelation occurs when the concentration is increased in order to increase production efficiency, and the fluidity of the solution is significantly impaired. Moreover, aggregation of molecules accompanying gelation occurred, and the transparency of the dispersion was lost. An object of the present invention is to provide a high-concentration cellulose dispersion that can significantly improve dispersion stability and maintain transparency without causing gelation. Furthermore, it is to obtain productivity that can be developed in the industrial field by using the dispersion of cellulose fiber of the present invention.

  The object of the present invention is achieved by the following configurations.

  1. A cellulose fiber dispersion containing surface-treated cellulose fibers having an average fiber diameter of 2 nm to 200 nm, wherein the cellulose fibers have a concentration of 1% by mass to 30% by mass Dispersion.

  2. 2. The cellulose fiber dispersion according to 1 above, wherein the concentration of the cellulose fiber is 5% by mass or more and 30% by mass or less.

  3. 3. The cellulose fiber dispersion according to 1 or 2, wherein the surface treatment is a treatment with a hydrophobic silane coupling agent or an amphiphilic polymer.

  When the concentration of the dispersion of cellulose fibers is increased without surface treatment, gelation occurs due to hydrogen bonding between hydroxyl groups present in a large number of cellulose, and the fluidity of the solution is significantly impaired. In addition, in a dispersion liquid in which cellulose fibers are microfibrillated, the specific surface area is increased by decreasing the fiber diameter, and the gelation rate is increased by exposing more hydroxyl groups to the surface.

  According to the present invention, by subjecting the cellulose fiber to surface treatment, when the cellulose fiber has reached the nano-order fiber diameter, gelation can be prevented and the fluidity of the liquid can be maintained. Very convenient on top. Further, since the hydroxyl group is protected by the surface treatment agent, the aggregation of the fibers is small, and the transparency of the dispersion can be maintained even when the cellulose fibers have a nano-order fiber diameter. By applying such a nano-order fiber diameter cellulose dispersion to a transparent polymer film or creating a polymer composite that is uniformly dispersed in a transparent resin, the polymer is maintained while maintaining transparency. Mechanical properties such as tensile strength, bending strength, scratch resistance, and low linear expansion of the film or polymer composite alone can be greatly improved.

  Hereinafter, although this invention is demonstrated based on embodiment, it is not limited to these.

  The present invention is a cellulose fiber dispersion containing surface-treated cellulose fibers having an average fiber diameter of 2 nm or more and 200 nm or less, wherein the concentration of the cellulose fibers is 1% by mass or more and 30% by mass or less. It is said.

  Hereinafter, the present invention will be described in more detail.

(Cellulose fiber)
The cellulose fiber of the present invention only needs to be fibrillated to the microfibril state, and the fiber surface is further subjected to surface treatment by chemical modification or physical modification.

  Examples of the raw material cellulose fiber used in the present invention include plant-derived pulp, wood, cotton, hemp, bamboo, cotton, kenaf, hemp, jute, banana, coconut, seaweed, tea leaves, etc. Examples include fibers separated from animal fibers produced by sea squirts, and bacterial cellulose produced from acetic acid bacteria.

  Among these, fibers separated from plant fibers can be preferably used, but fibers obtained from plant fibers such as pulp and cotton are more preferable.

  In the present invention, these fibers are defibrated using a homogenizer, a grinder or the like to obtain a microfibrillated cellulose fiber, but as long as the contained cellulose maintains the fiber state, There is no restriction | limiting about the defibrillation processing method.

  In addition, hard materials such as wood may need to be pulverized with a dry pulverizer as pre-crushing if they cannot be processed directly with a homogenizer.

  As a specific example, cellulose fibers such as pulp are introduced into a dispersion container containing water so as to be 0.1 to 3% by mass, and this is defibrated with a high-pressure homogenizer to obtain an average fiber diameter of 0.1 to 3%. An aqueous dispersion of cellulose fibers defibrated to about 10 μm microfibrils is obtained. Further, by repeatedly grinding with a grinder or the like, nano-order cellulose fibers having an average fiber diameter of about 2 to 500 nm can be obtained. Examples of the grinder used for the grinding treatment include a pure fine mill (manufactured by Kurita Machinery Co., Ltd.).

  As another method, there is a method using a high-pressure homogenizer in which cellulose fiber dispersion is jetted from a pair of nozzles at a high pressure of about 250 MPa, and the jet fibers collide with each other at a high speed to pulverize the cellulose fibers. Are known. Examples of the apparatus used include “Homogenizer” manufactured by Sanwa Machinery Co., Ltd., “Artemizer System” manufactured by Sugino Machine Co., Ltd., and the like.

  The average fiber diameter of the cellulose fibers obtained by fibrillation in this manner is 2 nm or more and 200 nm or less, more preferably 2 nm or more and 100 nm or less, and further preferably 4 nm or more and 40 nm or less.

  The average fiber diameter shown here is an average value of the diameters of the fibers dispersed in the resin, and is obtained from an image observation result by an electron microscope.

  In this invention, when the average fiber diameter of a cellulose fiber exceeds 200 nm, there exists a possibility that the intensity | strength of a fiber composite material may become inadequate. On the other hand, cellulose fibers having an average fiber diameter of less than 2 nm are difficult to obtain by the above-described defibrating treatment, grinding treatment and the like.

  Moreover, although it does not specifically limit about the length of a cellulose fiber, 50 nm or more is preferable by average fiber length, More preferably, it is 100 nm or more. If the average fiber length is shorter than 50 nm, the strength of the fiber composite material may be insufficient.

  In the present invention, the average fiber diameter and the average fiber length are measured after observing the obtained fiber at a magnification of 10,000 times using a transmission electron microscope, H-1700FA type (manufactured by Hitachi, Ltd.). Randomly, 100 fibers were selected from the obtained images, and the fiber diameter and fiber length of each fiber were analyzed using image processing software (WINROOF), and their simple number average values were obtained.

(Surface treatment method of cellulose)
Although the microfibrillated cellulose fiber maintains good dispersibility, the specific surface area of the fiber increases and the number of hydroxyl groups on the surface increases as the fiber diameter decreases to the nano level. As a result, the hydrogen bonding between the hydroxyl groups increases, and the fibers tend to aggregate due to hydrogen bonding over time. Moreover, this aggregate embeds water molecules, and the dispersion causes gelation. For this reason, in order to prevent re-aggregation of the dispersion in which microfibril fibers are dispersed, as a surface treatment means for cellulose fibers, the hydroxyl groups of cellulose are modified to reduce the aggregation due to hydrogen bonding, thereby modifying the surface of the cellulose fibers. There is a way.

  The surface modification of the cellulose fiber includes chemical modification or physical modification, but a chemical modification method is preferable, and the chemical modification will be described more specifically.

  In the present invention, the hydroxyl group of the cellulose fiber is chemically modified using a modifying agent such as an acid, an alcohol, a halogenating reagent, an acid anhydride, an isocyanate, or a silane coupling agent. It is also preferable to use a modifier such as a polymer. The surface is modified by adsorbing on cellulose fibers through hydrogen bonding with a hydroxyl group of cellulose.

  The chemical modification can be carried out according to a known method. For example, after cellulose fiber that has been defibrated is added to water or an appropriate solvent and dispersed, then a chemical modifier is added to the reaction to perform an appropriate reaction. What is necessary is just to make it react on conditions. In this case, in addition to the chemical modifier, a reaction catalyst can be added as necessary. For example, pyridine, N, N-dimethylaminopyridine, triethylamine, sodium methoxide, sodium ethoxide, sodium hydroxide, etc. A basic catalyst or an acidic catalyst such as acetic acid, sulfuric acid, or perchloric acid can be used, but a basic catalyst such as pyridine is preferably used in order to prevent a decrease in reaction rate and degree of polymerization. As reaction temperature, about 40-100 degreeC is preferable at the point which suppresses deterioration, such as yellowing of a cellulose fiber, and the fall of a polymerization degree, and ensuring reaction rate. The reaction time may be appropriately selected depending on the modifier used and the processing conditions.

  Examples of functional groups introduced into cellulose fibers by chemical modification include, for example, acetyl group, methacryloyl group, propanoyl group, butanoyl group, iso-butanoyl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, methyl group, ethyl group, Examples include propyl group, iso-propyl group, butyl group, iso-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group and the like.

  In the present invention, when introducing these functional groups, among the modifiers, for example, silane coupling agents capable of introducing these functional groups are preferably used.

  Moreover, in addition to the said silane coupling agent, it is also preferable to use an amphiphilic polymer as a modifier (polymer modifier) which performs the surface treatment of a cellulose fiber in this invention.

  On the other hand, recently, there are reports that defibration treatment and surface modification are performed simultaneously. Natural cellulose obtained by removing and purifying impurities such as lignin from plant resources is dissolved in a solvent, and the raw material is regenerated cellulose. 2,2,6,6-tetramethylpiperidine-N-oxyl (hereinafter, TEMPO) In the presence of the above, an oxidizing agent such as hypochlorous acid is allowed to act to advance the oxidation reaction. According to this, the cellulose chain forming the regenerated cellulose is at the molecular chain level, and only the primary hydroxyl group at the C6 position in the glucopyranose ring, which is a constituent monomer unit of the cellulose chain, is selectively oxidized and passes through the aldehyde. It is oxidized to a carboxyl group. The method of this report ("Cellulose" Vol. 5, 1998, pages 153 to 164, article entitled "Preparation of polyuronic acid from cellulose by TEMPO-catalyzed oxidation" by A. Isogai and Y. Kato) cellulose fiber It is also possible to use it for the cellulose fiber produced by this method for producing the nanofiber. Nanofibers of cellulose fibers prepared by this method can also be used as cellulose fibers having surface hydroxyl groups modified in the same manner as the above chemical modification method.

  Cellulose fibers that have been surface-treated by such a method are modified with hydroxyl groups on the surface, so that the concentration of cellulose fibers with respect to the solvent (dispersion medium) can be 1% by mass or more and 30% by mass or less. . Moreover, it is also possible to make it 5 mass% or more and 30 mass% or less preferably, and a yield can be raised.

  The cellulose fiber is defibrated with water as a solvent (dispersion medium) at a concentration of cellulose fiber of 0.1% by mass or more and 3% by mass or less. As a method of concentrating, a concentration method such as an evaporator or a membrane separation method may be used.

  The fiber surface treatment may be performed by once drying the cellulose fiber after defibration treatment by means of air drying, oven drying, vacuum drying, freeze drying, etc., and then dispersing it in a solvent at a concentration necessary for the surface treatment. Good.

  Moreover, when performing surface treatment, the density | concentration of the cellulose fiber immediately after defibration is 0.1 mass% or more and 3 mass% or less, and after the surface treatment, the density | concentration with respect to the solvent of a cellulose fiber is 1 mass% or more and 30 mass%. The concentration method after the surface treatment in which concentration is performed by a concentration method such as an evaporator or a membrane separation method is preferable so as to be less than or equal to%. If possible, the concentration of the cellulose fiber immediately after defibration may be 0.1% by mass or more and 3% by mass or less of a cellulose dispersion by concentrating it by a concentration method such as an evaporator or a membrane separation method, followed by surface treatment. However, before the surface treatment, many hydroxyl groups are exposed on the surface of the cellulose fiber and cause gelation. Therefore, a method of concentrating after the surface treatment is preferable.

  There is no particular limitation on the solvent used for the defibrating treatment of the cellulose fiber serving as the dispersion medium, but it is preferable to use water or a solvent mainly composed of water. The solvent mainly composed of water refers to a solvent containing 90% or more of water and one or more organic solvents as described later mixed therewith.

  Further, when the surface treatment is performed after the defibration treatment, water or a solvent mainly composed of water may be used, but those which do not hinder the reaction or interaction between the modifier and the hydroxyl group of the cellulose fiber are preferable. Depending on the type, a solvent selected from alcohols, ketones such as acetone and methyl ethyl ketone, ether solvents such as acetonitrile, acetamide, tetrahydrofuran and dioxane, pyridine and the like can be used. In order to change the solvent, for example, a method of gradually replacing the cellulose fiber dispersion defibrated with water using a membrane separation method or a method of gradually replacing the solvent by distillation is used. Thereby, the dispersion medium can be replaced.

  Next, silane coupling agents preferably used for surface modification (surface treatment) of cellulose fibers are listed below.

(Silane coupling agent)
Surface treatment includes hydrophilic treatment and hydrophobic treatment, but general versatile resins or films are often hydrophobic, and the cellulose fiber of the present invention is uniformly mixed with such resins and films. When it is going to perform, it is preferable to hydrophobize the surface of a cellulose fiber, and it is good to use the silane coupling agent with many kinds generally marketed as a hydrophobization means.

As a specific silane coupling agent as a hydrophobizing agent,
Silazanes: vinylsilazane, hexamethyldisilazane, tetramethyldisilazane,
Chlorosilanes: trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, vinyltrichlorosilane,
Alkoxysilanes: trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane,
Silane coupling agents: vinyltriacetoxysilane, vinyltris (methoxyethoxy) silane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, etc. are applicable, trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxy Silane, hexamethyldisilazane, trimethylchlorosilane and the like are preferable.

  These hydrophobizing agents may be appropriately diluted with hexane, toluene, methanol, ethanol, acetone, pyridine, water or the like.

  These hydrophobizing agents may be used alone or in combination, and the hydrophobized cellulose fibers obtained by the hydrophobizing agent may be further hydrophobized. The proportion of the hydrophobizing agent is not particularly limited, but the proportion of the hydrophobizing agent is preferably 10% by mass or more and 99% by mass or less with respect to the cellulose fiber after the hydrophobizing treatment, and 30% by mass. % To 98% by mass is more preferable.

  The amphiphilic polymers preferably used for the surface modification (surface treatment) of cellulose fibers are listed below.

(Amphiphilic polymer)
An amphiphilic polymer is a polymer having both a hydrophilic component and a lipophilic component in a polymer unit, and has a property of dissolving and dispersing in both an organic solvent and water. Since the surface treatment with the amphiphilic polymer is performed by adsorbing on the cellulose fiber due to affinity (including hydrogen bonding) with the hydroxyl group, it is added to, mixed with, and adsorbed to the cellulose dispersion.

  The polymer may be a homopolymer composed of a single monomer having both a hydrophilic component and a lipophilic component in the side chain, or may be a copolymer polymer obtained by copolymerizing a hydrophilic component monomer and a lipophilic component monomer.

  For example, (polyoxyalkylene) acrylate and methacrylate are commercially available hydroxypoly (oxyalkylene) materials such as “Pluronic” (Pluronic (manufactured by Asahi Denka Kogyo Co., Ltd.)), Adeka Polyether (Asahi Denka Kogyo Co., Ltd.). )), Carbowax [Carbowax (Glyco Products)], Triton [Toriton (from Rohm and Haas)] and P.I. E. What is generally sold as G (Daiichi Kogyo Seiyaku Co., Ltd.) can be used.

  Alternatively, an amphiphilic polymer may be synthesized by copolymerizing a hydrophilic component monomer and a lipophilic component monomer. In this case, an acrylic resin that is easy to polymerize and has a wide variety of monomers is preferred. The acrylic resin may be a homopolymer based only on the acrylic monomer, or may be copolymerized with other monomers based on the acrylic monomer. May be.

  Examples of the acrylic monomer include general acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylic chloride, methacrylic chloride, and acrylic acid anhydride.

  As a commercially available product having a special structure, as a polyalkylene glycol mono (meth) acrylate manufactured by NOF Corporation, Blemmer PE-90, Blemmer PE-200, Blemmer PE-350, Blemmer AE-90, Blemmer AE -200, Blemmer AE-400, Blemmer PP-1000, Blemmer PP-500, Blemmer PP-800, Blemmer AP-150, Blemmer AP-400, Blemmer AP-550, Blemmer AP-800, Blemmer 50 PEP-300, Blemmer 70 PEP -350B, Blemmer AEP series, Blemmer 55PET-400, Blemmer 30PET-800, Blemmer 55PET-800, Blemmer AET series, Blemmer 30PPT-800, Buremer Ma 50PPT-800, Blemmer 70PPT-800, Blemmer APT series, Brenmer 10PPB-500B, such as Brenmer 10APB-500B and the like. Similarly, Blemmer PME-100, Blemmer PME-200, Blemmer PME-400, Blemmer PME-1000, Blemmer PME-4000, Blemmer AME-400, Blemmer as alkyl-terminated polyalkylene glycol mono (meth) acrylates manufactured by NOF Corporation. 50POEP-800B, Blemmer 50AOEP-800B, Blemmer PLE-200, Blemmer ALE-200, Blemmer ALE-800, Blemmer PSE-400, Blemmer PSE-1300, Blemmer ASE series, Blemmer PKEP series, Blemmer AKEP series, Blemmer AE-300 , Blemmer ANE-1300, Blemmer PNEP series, Blemmer PNPE series, Blemmer 43ANE -500, BLEMMER 70ANEP-550, etc., and Kyoeisha Chemical Co., Ltd. light ester MC, light ester 130MA, light ester 041MA, light acrylate BO-A, light acrylate EC-A, light acrylate MTG-A, light acrylate 130A, light Acrylate DPM-A, light acrylate P-200A, light acrylate NP-4EA, light acrylate NP-8EA and the like can be mentioned, and these can be selected and used.

  Other than acrylic monomers, acrylimides typically include diacetone acrylamide, acrylamide, N-isopropyl acrylamide (NIPAM), N-ethyl acrylamide, N-pyrrolidinyl acrylamide, N-cyclopropyl acrylamide, N -Diethylacrylamide, N-methyl, N-isopropylacrylamide, N-propylacrylamide, N-methyl, N-isopropylpropylacrylamide, N-piperidinylacrylamide, N-propylacrylamide and the like.

  Examples of the vinyl monomer include vinyl alcohol and vinyl acetate.

  By copolymerizing these monomers at an arbitrary ratio, the hydrophilicity and hydrophobicity of the polymer can be controlled.

Examples of the synthesis of amphiphilic polymers include isopropylacrylamide (manufactured by Kojin Co., Ltd.), Bremer PME-400 (manufactured by NOF Corporation), and the like. (Blenmer PME-400: methacrylate with — (CH ₂ CH ₂ O) _m —CH ₃ (m≈9))
The molecular weight of the amphiphilic polymer is not particularly limited, but preferably 10,000 or more and 500,000 or less.

  In the surface treatment with the amphiphilic polymer, the ratio of the hydrophobizing agent to the cellulose fiber is not particularly limited, but is 10% by mass to 99% by mass with respect to the cellulose fiber after the hydrophobizing treatment. Is preferable, and it is more preferable that it is 30 mass% or more and 98 mass% or less.

(Evaluation method of cellulose fiber (dispersion))
(1) Measurement of light transmittance Using a spectrophotometer (visible ultraviolet spectrophotometer UV-2500PC, Shimadzu Corporation), the total transmitted light amount and scattered light with respect to the incident light amount of visible light were measured in accordance with ASTM D-1003 standard. The measurement results at 550 nm are shown in Table 1 below.
(2) Stability evaluation of dispersion over time After the prepared sample was stagnated for 1 week, similarly, using the spectrophotometer described in (1) above, total transmission with respect to the incident light amount of visible light according to the ASTM D-1003 standard The amount of light and scattered light were measured. The measurement results at 550 nm are shown in Table 1 below.
(3) Evaluation of gelation After making a cellulose fiber dispersion, the state after standing still for one day was evaluated visually, and the gelled state was evaluated with and without gelation. The results are shown in Table 1 below.
(4) Yield Evaluation After the cellulose fiber dispersion was filtered through a 10 μm glass filter, x (g) was collected in an aluminum dish and dried at 120 ° C. for 2 hours to completely evaporate the solvent. The remainder remaining in the subsequent aluminum pan was measured and defined as y (g).

  y / x × 100 = yield (%) was used as a measure of aggregation.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<About cellulose fiber>
Cellulose fibers (dispersion liquid) were prepared according to the following production examples, and the surface treatment, concentration, etc. were changed as described in Table 1 on the basis of this and dispersion liquid No. 1-30 were created.

(Comparative Production Example 1)
Sulfuric acid bleached pulp obtained from conifers was added to pure water at 1.0% by mass, and the cellulose fibers were defibrated at 3000 rpm for 15 minutes using an Excel Auto Homogenizer. This aqueous dispersion was designated as cellulose fiber A. From the observation result of the scanning electron microscope, the obtained cellulose fiber was confirmed to be fibrillated to an average fiber diameter of 500 nm and to be microfibrillated. This was also referred to as dispersion 1.

(Comparative Example 2)
Cellulose fiber B was prepared in the same manner except that the rotational speed of Comparative Production Example 1 was changed to 15 minutes at 10,000 rpm. It was confirmed that the fiber was fibrillated to an average fiber diameter of 250 nm and microfibrillated. This was also referred to as dispersion 2.

(Comparative Production Example 3)
The cellulose fiber B aqueous dispersion prepared in Comparative Production Example 2 was filtered, washed with pure water, and dried at 70 ° C. to obtain cellulose fiber C.

  To 100 parts by mass of ethanol and 1 part by mass of pure water, 5 parts by mass of cellulose fiber C was added and dispersed. While stirring this dispersion at 50 ° C., 5 parts by mass of tetraethoxysilane was added over 60 minutes. The mixture was then stirred for a further 2 hours. The obtained cellulose fiber was kept at an average fiber diameter of 250 nm by a scanning electron microscope observation result. This was designated as Dispersion Liquid 3.

(Comparative Production Example 4)
Disperse 100 parts by mass of the cellulose fiber B aqueous dispersion prepared in Comparative Production Example 2, add 1 part by mass of tetraethoxysilane over 60 minutes while stirring this dispersion at 50 ° C., and then add the mixture further. Stir for 2 hours. Further, the solvent was removed with a rotary evaporator, and the cellulose fiber obtained was the end point when the concentration of the cellulose fiber reached 5% by mass. From the result of observation with a scanning electron microscope, the average fiber diameter was kept at 250 nm. It was. This was also referred to as dispersion 4.

(Production Example 1)
A cellulose fiber D was prepared in the same manner except that the rotational speed of Comparative Production Example 1 was changed to 30 minutes at 10,000 rpm. It was confirmed that the fiber was fibrillated to an average fiber diameter of 200 nm and microfibrillated. This was also referred to as dispersion 5.

  Similarly to the comparative example, the surface treatment was not performed, the solvent was removed by a rotary evaporator, and a sample having an end point when the concentration of the cellulose fiber became 5% by mass was prepared. The results are listed in Table 1. This was also referred to as dispersion 6.

(Production Example 2)
Cellulose fiber E was obtained by drying the cellulose fiber D aqueous dispersion prepared in Production Example 1 with a freeze dryer.

(Production Example 3)
Cellulose fiber B prepared in Comparative Production Example 2 was dispersed with Ultra Apex Mill UAM-105 (manufactured by Kotobuki Industries Co., Ltd.) using 0.5 mm beads for 1 hour at a peripheral speed of 6 m / sec. The cellulose fiber F was obtained by adjusting with water so that the cellulose fiber was 5% by mass. The obtained cellulose fiber had an average fiber diameter of 50 nm.

(Production Example 4)
Cellulose fiber F prepared in Production Example 3 was dried in the same manner as in Production Example 2 to obtain cellulose fiber G. The obtained cellulose fiber had an average fiber diameter of 50 nm.

(Production Example 5)
The cellulose fiber B produced in Comparative Production Example 2 was pulverized 180 times at 200 MPa with a high-pressure pulverization system Altemizer HJP-2005 (manufactured by Sugino Machine Co., Ltd.).

  The cellulose fiber B was adjusted with water so that the cellulose fiber B might be 5 mass%, and the cellulose fiber H was obtained. The obtained cellulose fiber had an average fiber diameter of 20 nm.

(Production Example 6)
Cellulose fiber H prepared in Production Example 5 was dried in the same manner as in Production Example 2 to obtain Cellulose Fiber I. The obtained cellulose fiber had an average fiber diameter of 20 nm.

(Production Example 7)
Cellulose fibers B prepared in Comparative Production Example 2 were dispersed in 100 ml of water with 1 g equivalent of dry mass, 0.0125 g of TEMPO and 0.125 g of sodium bromide, and then 12% by mass of sodium hypochlorite. The reaction was started by adding sodium hypochlorite to the aqueous solution so that the amount of sodium hypochlorite was 2.5 mmol. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10.5. When no change in pH is observed, the reaction is considered to be complete, the reaction product is filtered through a glass filter, washed with a sufficient amount of water and filtered five times, so that the cellulose fiber B becomes 5% by mass. Dilute with water.

  Furthermore, it processed with the ultrasonic disperser for 1 hour and the cellulose fiber J was obtained. The average fiber diameter was 4 nm.

(Production Example 8)
Cellulose fiber J prepared in Production Example 7 was dried in the same manner as in Production Example 2 to obtain cellulose fiber K. The obtained cellulose fiber had an average fiber diameter of 4 nm.

(Production Example 9)
Manufacture of treatment agent (amphiphilic polymer) E A 0.5 liter four-necked separable flask was equipped with a dropping device, a thermometer, a nitrogen gas inlet tube, a stirring device and a reflux condenser, and 93 g of methyl ethyl ketone, 50 g of Kojin Co., Ltd., 50 g of Bremer PME400, and 0.12 g of lauryl peroxide were added and heated to the temperatures shown in Table 1. Thereafter, the temperature was raised over 1 hour, and polymerization was carried out for 2 hours under reflux. Further, a solution obtained by dissolving 0.17 g of lauryl peroxide in 33 g of methyl ethyl ketone was dropped into the flask over 2 hours, and the reaction was further performed at the same temperature for 3 hours. Thereafter, a solution obtained by dissolving 0.33 g of methyl hydroquinone in 107 g of methyl ethyl ketone was added and cooled, and a polymer solution of 30% by mass of polymer was obtained.

The obtained polymer solution was poured into 300 g of water to precipitate the polymer. Thereafter, the polymer was decanted, water was removed, dissolved, water was added, reprecipitation was repeated, and decantation was repeated. Then, 33 g of polymer was collected. The molecular weight was 50,000 (inherent viscosity method).
BLEMMER PME-400: Methacrylate (EO; ethyleneoxy group) having — (EO) _m —CH ₃ (m≈9), manufactured by NOF Corporation.

  It used as a 30 mass% methyl ethyl ketone solution.

  Using the cellulose fibers (dispersions) A to K obtained in Production Examples 1 to 8, Dispersions 1 to 30 were prepared as shown in Table 1. Cellulose fibers in aqueous solution were dispersed in a solvent in the same manner as in Comparative Example 4 and dried ones in the same manner as in Comparative Example 3, and surface treatment was performed. Further, as a method of changing the solvent from water to an organic solvent in the surface treatment, a method of gradually substituting the organic solvent with a membrane separation method was used.

  Table 1 shows the cellulose fiber, the surface treatment agent, the amount added, the reaction solvent for the surface treatment (hence the final solvent), the concentration method, and the concentration used for each dispersion.

  In addition, even in the case of using the same cellulose fiber, those having different surface treatments are shown in Table 1 with the surface treatment agent, the ratio of the treatment agent and cellulose fiber, and the surface treatment solvent changed in Table 1. It was. The differences in concentration, reaction solvent, concentration method, etc. are also shown in Table 1. Moreover, the method of changing the solvent from water to an organic solvent was gradually replaced by a membrane separation method.

  The obtained dispersion was subjected to the various measurements described above.

  The composition of each dispersion is shown in Table 1, and the evaluation results are shown in Table 2.

a: Tetraethoxysilane b: Trimethylchlorosilane c: Hexamethyldisilazane d: Pluronic L44 (Asahi Denka: block copolymer composed of ethylene oxide and propylene oxide)
e: Isopropylacrylamide / Blemmer PME400 = 5/5 copolymer, molecular weight 50,000

  As can be seen from Tables 1 and 2, the present invention was a high-concentration cellulose fiber dispersion, and it was found that the solution was not gelled, had little aggregation and could maintain transparency. In addition, the dispersion stability over time is good and the concentration is high, so that it has become possible to develop applications in the industrial field.

Claims (3)

  A cellulose fiber dispersion containing surface-treated cellulose fibers having an average fiber diameter of 2 nm to 200 nm, wherein the cellulose fibers have a concentration of 1% by mass to 30% by mass Dispersion.   The cellulose fiber dispersion according to claim 1, wherein the concentration of the cellulose fiber is 5% by mass or more and 30% by mass or less.   The cellulose fiber dispersion according to claim 1 or 2, wherein the surface treatment is a treatment with a hydrophobic silane coupling agent or an amphiphilic polymer.