JP2015071848A - Method for producing fine cellulose fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of obtaining a fine cellulose fiber at a high yield even in low input energy and producing a fine cellulose fiber at high productivity.SOLUTION: Provided is a method for producing a fine cellulose fiber with the number average fiber size of 200 nm or lower by subjecting a cellulose fiber to splitting treatment, as the cellulose fiber, the cellulose fiber into which a cationic group is introduced by 0.05 to 3.0 mmol/g is used, and the splitting treatment is performed by a high speed rotary type dispersion machine and a high pressure type dispersing machine.

Description

The present invention relates to a method for producing fine cellulose fibers having a number average fiber diameter of 200 nm or less. Specifically, by carrying out mechanical defibrating using a high-speed rotary disperser and a high-pressure disperser, The present invention relates to a method for efficiently producing cellulose fibers.
The present invention also relates to a dispersion containing fine cellulose fibers obtained by this production method, a cellulose fiber sheet, and a cellulose fiber composite material.

  In recent years, it has been studied to produce a dispersion of fine cellulose fibers that are biodegradable in industrial products, structural materials, cosmetics, foods, gas barrier materials, and the like. It is known that cellulose exhibits a low linear expansion coefficient, a high elastic modulus, and a high strength because of its extended chain crystal. In addition, it has attracted attention as a material exhibiting high transparency when it is miniaturized to be combined with a resin to form a composite material. Examples of applications of cellulose fiber composite materials (cellulosic fiber composite materials) having such a high transparency and low linear expansion coefficient include electricity / representatives such as flat panel displays, organic LED lighting, and photovoltaic power generation panels. There are substrate materials for electronic devices.

  Conventionally, in order to obtain such cellulose fine fibers, for example, Patent Document 1 proposes a method of mechanically defibrating wood flour with a high-pressure homogenizer, a high-speed rotary homogenizer, an ultrasonic homogenizer, or the like. Yes. However, this method requires a large amount of energy in order to improve defibration. Moreover, in order to obtain a desired fine fiber, although centrifugation operation is performed after a fibrillation process, the further improvement of the recovery rate in that case and the improvement of productivity are calculated | required.

  Further, for example, in Patent Document 2, a cationic microfibrillated plant fiber cation-modified with a compound containing a quaternary ammonium group is used as a cellulose fiber, and the fine cellulose fiber is obtained by defibration with a refiner. However, although fine fibers can be obtained by this method, problems of fiber recovery and productivity remain.

Japanese Unexamined Patent Publication No. 2009-167397 JP 2011-162608 A

  An object of the present invention is to provide a method capable of obtaining fine cellulose fibers with higher productivity than conventional methods even on an industrial scale.

  As a result of intensive studies by the present inventors, it was found that by using a specific cellulose fiber as a cellulose fiber to be subjected to a defibrating treatment and performing a specific defibrating treatment, fine cellulose fibers can be produced with high productivity. Reached.

That is, the present invention
In the method for producing fine cellulose fibers having a number average fiber diameter of 200 nm or less by defibrating the cellulose fibers, the cellulose fibers introduced with 0.05 to 3.0 mmol / g of a cationic group as the cellulose fibers , A method for producing fine cellulose fibers, characterized by performing a defibrating treatment with a high-speed rotary disperser and a high-pressure disperser,
A dispersion containing fine cellulose fibers obtained by this production method,
A cellulose fiber sheet containing fine cellulose fibers obtained by this production method,
And a cellulose fiber composite material containing fine cellulose fibers and a matrix material obtained by this production method,
Exist.

  According to the present invention, fine cellulose fibers can be obtained in high yield even with low input energy, and desired fine cellulose fibers can be produced with high productivity even on an industrial scale.

  DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described in detail below. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is specified by these contents. It is not a thing.

[Production method of fine cellulose fiber]
The method for producing fine cellulose fibers of the present invention is a method for producing fine cellulose fibers having a number average fiber diameter of 200 nm or less by defibrating the cellulose fibers. A cellulose fiber introduced with ~ 3.0 mmol / g is used for defibration treatment with a high-speed rotary disperser and a high-pressure disperser.

First, cellulose fibers will be described. Hereinafter, the cellulose fiber subjected to the defibrating treatment is referred to as “cellulose fiber raw material”. Moreover, the fine cellulose fiber obtained by the manufacturing method of the fine cellulose fiber of this invention is called "the fine cellulose fiber of this invention."
The fine cellulose fiber of this invention is manufactured through the process of introduce | transducing a cationic group into the following cellulose fiber raw materials, and the process of defibrating the cellulose fiber raw material into which the cationic group was introduce | transduced.

<Cellulose fiber raw material>
In this invention, it is preferable that a cellulose fiber raw material removes an impurity from the cellulose containing material as shown below through a general refinement | 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, a cellulose-containing material obtained from a plant-derived raw material is preferable.

(Method for purifying cellulose-containing material)
The cellulose fiber raw material used in the present invention is preferably obtained by purifying the above cellulose-containing material by a usual method.

  As this purification method, for example, there is a method in which a cellulose-containing material is degreased with a mixed solvent of benzene-ethanol or an aqueous sodium carbonate solution, then subjected to delignification treatment with chlorite (Wise method), and dehemicellulose treatment with alkali. Can be mentioned. In addition to the Wise method, a method using peracetic acid (pa method), a method using a mixture of peracetic acid and persulfuric acid in combination with peracetic acid and persulfuric acid (pxa method), and a chlorine / monoethanolamine method are also used as purification methods. Used. Moreover, you may perform a bleaching process etc. further suitably.

Cellulose-containing materials can be refined according to a general chemical pulp production method, for example, kraft pulp, sulfide pulp, alkali pulp, nitrate pulp production method, and the cellulose-containing material can be heat-treated in a digester. A method of performing a treatment such as delignification and further performing a bleaching treatment may be used.
That is, pulps such as hardwood kraft pulp, softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp, hardwood bleached kraft pulp, softwood bleached kraft pulp, and linter pulp may be used as the cellulose fiber raw material.

  In addition, 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.

  Although there is no particular limitation on the degree of purification of the cellulose fiber raw material obtained by refining the cellulose-containing material, 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 of the cellulose fiber raw material obtained by refining the cellulose-containing material 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 can be classified into a crystalline α-cellulose component and an amorphous hemicellulose component. A higher ratio of crystalline α-cellulose is preferable because a low linear expansion coefficient, high elastic modulus, and high strength can be easily obtained when a cellulose fiber composite material is obtained. The ratio (weight ratio) between the crystalline α-cellulose component and the amorphous hemicellulose component of the cellulose fiber raw material obtained by refining the cellulose-containing material is preferably 70 to 30 or more, more preferably 75 to 25 or more. More preferably, it is 80:20 or more and the ratio of the crystalline α-cellulose component is high.

(Fiber diameter of cellulose fiber raw material)
The fiber diameter of the cellulose fiber raw material used in the present invention is not particularly limited, and the number average fiber diameter is 1 μm to 1 mm. What has undergone general purification is about 50 μm. For example, when a chip or the like having a size of several centimeters is refined, it is preferable to perform a mechanical treatment with a disintegrator such as a refiner or a beater to make it about 50 μm.

<Introduction of cationic group>
In the present invention, a cationic group is usually introduced into the cellulose fiber raw material. Although it is possible to introduce a cationic group after the defibrating treatment, if a cationic group is introduced into the cellulose fiber raw material before the defibrating treatment, the fibrillation efficiency of the cellulose fiber raw material is improved. In the present invention, it is preferable to introduce a cationic group into the cellulose fiber raw material before the defibrating treatment, because miniaturization with low input energy becomes possible.

(Cationic group)
The cationic group is introduced by substituting a part of the hydroxyl group of cellulose constituting the cellulose fiber with a cationic group.

The cationic group is a group having an onium such as ammonium, phosphonium, or sulfonium in the group, and is usually a group having a molecular weight of about 1000 or less. Specific examples of the cationic group include ammonium, phosphonium, sulfonium, and a group having ammonium, phosphonium or sulfonium. In the present invention, the cationic group is preferably a group having ammonium, and particularly preferably a group containing quaternary ammonium.
In the present invention, only one of the cationic groups may be introduced into the cellulose fiber raw material, or two or more thereof may be introduced.

These cationic groups can be introduced by reacting a compound having a cationic group with a cellulose fiber raw material.
That is, the cationic group is preferably introduced by reacting a cellulose fiber raw material with a compound having a cationic group such as ammonium, phosphonium or sulfonium and a group capable of reacting with a hydroxyl group of cellulose. The group that reacts with the hydroxyl group of cellulose is not particularly limited as long as it is a reactive group that reacts with the hydroxyl group to form a covalent bond. For example, an epoxy group or a halohydrin group capable of forming it, an active halogen group, an active group A vinyl group, a methylol group, etc. are mentioned. Among these, an epoxy group or a halohydrin group capable of forming it is preferable from the viewpoint of reactivity.

  As a compound having a cationic group and a group that reacts with a hydroxyl group of cellulose (hereinafter sometimes referred to as “compound having a cationic group”) used for introducing a cationic group into a cellulose fiber raw material. Examples thereof include glycidyltrialkylammonium halides such as glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride, and halohydrins thereof. These may be used alone or in combination of two or more.

  As a method for reacting a compound having a cationic group with a cellulose fiber raw material (hereinafter sometimes referred to as “cationization reaction”), for example, when glycidyltrialkylammonium halide is used, cellulose fiber is used in a reaction solvent. The method of making it react by making glycidyl trialkyl ammonium halide and the alkali metal hydroxide salt which is a catalyst act on a raw material is mentioned.

  As the reaction solvent, water or a general organic solvent is used. In particular, water or a lower alcohol, specifically methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, etc. One or more kinds of about 4 lower alcohols, or a mixed solvent of these lower alcohols and water can be used, and the amount used is about 1 to 30 times the weight of the cellulose fiber raw material. Is preferred.

  As the alkali metal hydroxide salt of the catalyst, one or more of sodium hydroxide, potassium hydroxide and the like can be used.

  The cationization reaction is usually 0 ° C. or higher, preferably 20 ° C. or higher, usually 90 ° C. or lower, preferably 80 ° C. or lower, usually 30 minutes or longer, preferably 1 hour or longer, usually 10 hours or shorter, preferably 4 hours or shorter. .

  In addition, the usage-amount of the compound and catalyst which have a cationic group is suitably adjusted with the cellulose fiber raw material to be used, the solvent composition of a reaction system, the mechanical conditions of a reactor, and other factors.

  After completion of the reaction, the remaining alkali metal hydroxide salt is neutralized with a mineral acid or an organic acid, and then washed and purified by a conventional method to obtain a cellulose fiber raw material having a cationic group.

  Specifically, the cationic group introduced into the cellulose fiber raw material by the reaction with the compound having a cationic group is preferably a group represented by the following formula (1).

(In the formula (1), R ¹ , R ² and R ³ each independently represents an alkyl group (preferably an alkyl group having 1 to 10 carbon atoms, particularly preferably a methyl group), and X ⁻ represents a halogen such as Cl ⁻ or the like. (Ce represents cellulose, and -O- in Ce-O- represents an ether bond formed by the reaction between a hydroxyl group of cellulose and a glycidyltrialkylammonium halide.)

  The introduction amount of the cationic group is 0.05 to 3.0 mmol / g, preferably 0.14 mmol / g or more, and 0.21 mmol / g as the degree of substitution of the cationic group with respect to cellulose of the cellulose fiber raw material. The above is more preferable, 2.14 mmol / g or less is preferable, and 2.07 mmol / g or less is more preferable. When the introduction amount of the cationic group is within this range, an electrostatic repulsion force acts between the cellulose fiber raw materials to improve the fibrillation treatment efficiency, and fine cellulose fibers can be produced with high productivity.

  The degree of substitution of the cationic group can be determined by quantifying elements such as nitrogen contained in the cationic group by elemental analysis, or by quantifying the peak of the molecular structure unique to the cationic group by solid-state NMR.

<Defibration processing>
In the present invention, a cellulose fiber raw material into which a cationic group has been introduced (hereinafter sometimes referred to as “cationized cellulose fiber raw material”) is subjected to a defibrating treatment with a high-speed rotary disperser and a high-pressure disperser. Since the manufacturing method of the fine cellulose fiber of the present invention is characterized by using a high-speed rotary disperser and a high-pressure disperser in combination, the order thereof does not matter, but it is better to first process with a high-speed rotary disperser. From the viewpoint of the defibration efficiency of the high-concentration cellulose fiber raw material and the prevention of clogging in the system due to the cellulose fibers.
The dispersion liquid of the present invention containing the fine cellulose fibers of the present invention is obtained by performing a defibrating treatment with a high-speed rotary disperser and a high-pressure disperser.

(Defibration processing using a high-speed rotating disperser)
The cationized cellulose fiber raw material is preferably subjected to a fibrillation treatment with a high-speed rotary disperser after preparing a dispersion having a preferable solid content concentration described later.

The high-speed rotating disperser disperses and refines a workpiece by shearing force, impact force, and cavitation generated in the vicinity of a rotating body that rotates at high speed. There are various types of stirring blades in various shapes, and various types of high-speed rotating dispersers such as those in which the tank itself rotates are known.
The high-speed rotary disperser is of the type in which the dispersion of the cationized cellulose fiber raw material to be processed is passed through the gap between the rotating body and the fixed part, or the inner rotation rotates in a certain direction. And the outer rotating body rotating in the opposite direction on the outer side of the inner rotating body, and the dispersion of the cationized cellulose fiber raw material to be treated is passed through the gap between the inner rotating body and the outer rotating body. The type of fiber processing is preferable.

  High-speed rotating dispersers include, for example, M Technique Co., Ltd. Claremix, Taihei Koki Co., Ltd. Milder, Primix Co., Ltd. TK Robotics Co., Ltd., Taihei Koki Co., Ltd. Type disperser (Cabitron), high-speed rotating disperser (Sharp Flow Mill) manufactured by Taihei Koki Co., Ltd., thin film swirl type high-speed rotating disperser (Filmix etc.) manufactured by Primix Co., Ltd. In addition, a medium agitating type disperser (SC mill) manufactured by Mitsui Mining Co., Ltd. can be used as an effect equivalent to that of a high-speed rotary disperser.

By passing the dispersion of the cationized cellulose fiber raw material through a narrow gap while rotating at a high speed in this way, a high shear rate (unit s ⁻¹ ) can be generated. That is, as compared with a case where a mechanical means having a large gap and a low shear rate is used as in a domestic juicer mixer), the miniaturization process can be effectively performed. The size of the gap through which the cationized cellulose fiber raw material of the high-speed rotary disperser passes is preferably 10 mm or less, more preferably 5 mm or less, still more preferably 2 mm or less, and usually 0.01 mm or more.
The operation speed of the high-speed rotary disperser is preferably 1000 to 40000 rpm, more preferably 12000 to 22000 rpm.

The defibrating process by the high-speed rotary disperser may be performed only once, but may be repeated twice or more. Here, the two or more defibrating processes mean that the one processed by the high-speed rotary disperser is processed again, and the first processing is one pass, then the second processing. This process is referred to as two passes, and the same three processes are referred to as three passes.
Since the temperature of the dispersion rises as the number of passes increases, it is preferable that the dispersion after being processed by the high-speed rotary disperser is cooled by passing through a heat exchanger such as a cooling pipe. Alternatively, it is preferable to perform the fibrillation treatment while cooling the dispersion in the high-speed rotary disperser with a heat exchanger such as a cooling device.

  The number of passes varies depending on processing conditions in a high-pressure disperser described later, but two or more passes are preferable from the viewpoint of productivity and input energy (kWh / kg-cellulose).

  Although it does not specifically limit about processing temperature, It is preferable to process on the conditions of 100 degrees C or less.

  When defibrating twice or more times, the method is to disperse the dispersion of the cationized cellulose fiber raw material sent from the raw material tank with a pump using a high-speed rotary disperser and to perform high-speed rotary dispersion. The defibrated dispersion discharged from the machine is returned to the raw material tank via a heat exchanger such as a cooling pipe, and sent to the high-speed rotary disperser again by a liquid feed pump, etc. Alternatively, a continuous circulation process may be performed.

(Defibration processing with a high-pressure disperser)
The cationized cellulose fiber raw material is preferably subjected to a fibrillation treatment with a high-pressure disperser after preparing a dispersion having a preferable solid content concentration described later.

  Examples of the high-pressure disperser include a high-pressure homogenizer manufactured by Invensys System Co., Ltd., a nanomizer (Nanovaita) manufactured by Yoshida Kikai Kogyo Co., Ltd., and MFIC Corp. Microfluidizer manufactured by Sugino Machine Co., Ltd., Optimizer system manufactured by Sugino Machine Co., Ltd., soundless high-pressure emulsifying and dispersing device manufactured by Migrain Co., Ltd., microfluidizer manufactured by Mizuho Industry Co., Ltd. .

  These devices, when the inhaled object to be treated (dispersion of cationized cellulose fiber raw material) is passed through a fine channel at high pressure, the fluid and wall surface generated by the high shearing force generated in the channel and the device of the channel And the like, the impact force caused by the collision between fluids, cavitation generated when discharged from a fine flow path, and the like.

  The operating pressure of the high-pressure disperser is preferably 10 to 500 MPa, more preferably 20 to 350 MPa, and still more preferably 30 to 300 MPa.

The defibrating treatment by the high-pressure disperser may be performed only once, but may be repeated two or more times, for example, 2 to 100 times. Here, the two or more defibrating treatments mean that the one treated with the high-pressure disperser is treated again, and the first treatment is one pass and then the second treatment. Processing is referred to as two passes, and processing three times in the same manner is referred to as three passes.
Since the temperature of the dispersion rises as the number of passes increases, it is preferable that the dispersion after being processed by the high-pressure disperser is cooled by passing through a heat exchanger such as a cooling pipe. Alternatively, it is preferable to perform the fibrillation treatment while cooling the dispersion in the high-pressure disperser with a heat exchanger such as a cooling device.

  The number of passes varies depending on the processing conditions in the high-speed rotary disperser described above, but 1 to 20 passes is preferable from the viewpoint of productivity and input energy (kWh / kg-cellulose).

  Although it does not specifically limit about processing temperature, It is preferable to process on the conditions of 100 degrees C or less.

  In the case of two or more times of defibrating treatment, as a method, the defibrating treatment is performed by defibrating the dispersion liquid pumped from the raw material tank with a high-pressure disperser and discharging from the high-pressure disperser. In this method, the spent dispersion liquid is returned to the raw material tank via a heat exchanger such as a cooling pipe, and sent to a high-pressure disperser by a liquid feed pump or the like to perform a defibrating process. There may be.

(Other defibrating treatment)
The method for producing fine cellulose fibers of the present invention is characterized by using a high-speed rotary disperser and a high-pressure disperser in combination. Further fiber processing may be performed.
Defibration devices other than high-speed rotary dispersers and high-pressure dispersers include, for example, blender-type dispersers such as mixers, ball mills and bead mills, grinders and ultrasonic homogenizers. Examples thereof include a miniaturization apparatus such as a freezer mill under a low temperature condition of 0 ° C. or lower.

(Dispersion solvent)
As a solvent (dispersion medium) for the dispersion of the cationized cellulose fiber raw material to be subjected to the defibrating treatment, an organic solvent, water, or a mixed liquid of an organic solvent and water can be used. As the organic solvent, one or more organic solvents such as alcohols, ketones, aromatic hydrocarbons, ethers, glycol ethers, aprotic polar solvents, and cyclic ethers can be used.

  Examples of alcohols include propanol such as methanol, ethanol, isopropyl alcohol and n-propyl alcohol, butanol such as n-butanol, and ethylene glycol.

  Ketones (referring to liquids having a ketone group) include acetone, methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ketone, di-tert-butyl ketone, 2-heptanone, 4-heptanone, 2-octanone, cyclopentanone, cyclohexanone, cyclohexyl Examples include methyl ketone, acetophenone, acetylacetone, and dioxane. Among these, preferred are methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone, and more preferred are methyl ethyl ketone and cyclohexanone.

  Aromatic hydrocarbons include benzene, toluene, xylene and the like.

  Examples of ether include diethyl ether, dimethyl ether, methyl ethyl ether and the like. Among these, diethyl ether is preferable.

  As glycol ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl Examples include ether, diethylene glycol 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 and the like.

  Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, 2-pyrrolidone, N- Examples include methyl pyrrolidone.

  Examples of the cyclic ether include tetrahydrofuran, furan, dibenzofuran and the like. Of these, furan is preferred.

In addition, since the solvent used as a dispersion medium has the process of removing a solvent by a next process, it is preferable that a boiling point is not too high. The boiling point of the solvent is preferably 300 ° C. or lower, preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Moreover, 70 degreeC or more is preferable from points, such as handleability.
The solvent of the cellulose fiber raw material dispersion is preferably a mixed liquid of organic solvent and water or water, and particularly preferably water.

(Solid concentration of dispersion)
The solid content concentration (cellulose fiber raw material concentration) of the cationized cellulose fiber raw material dispersion used for the defibrating treatment is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, More preferably 0.2% by weight or more, particularly preferably 0.3% by weight or more, and usually 50% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, particularly preferably 6% by weight or less. It is preferable to do. If the solid content concentration in the cationized cellulose fiber raw material dispersion to be subjected to the defibrating process is too low, the amount of liquid becomes too large with respect to the amount of the cationized cellulose fiber raw material to be processed, the efficiency is poor, and the solid content concentration is too high. Therefore, the concentration of the cationized cellulose fiber raw material dispersion used for the defibrating treatment is adjusted by appropriately adding water.

(Centrifuge)
Centrifugation may be performed on the dispersion liquid after the above-described defibrating treatment to separate and remove cellulose fibers with poor defibration. By centrifuging, a more uniform and fine supernatant of fine cellulose fibers can be obtained. The conditions for the centrifugation are not particularly limited because they depend on the applied defibrating treatment and the required degree of refinement. For example, it is preferable to apply a centrifugal force of 3000 G or more, preferably 10,000 G or more. Moreover, as processing time, it is preferable to apply centrifugal force, for example for 1 minute or more, Preferably it is 5 minutes or more. If the centrifugal force is too small or the treatment time is too short, separation and removal of cellulose fibers with poor defibration may be insufficient.

In addition, when the centrifugal separation is performed, it is not preferable that the viscosity of the dispersion to which the centrifugal force is applied is high because the separation efficiency is lowered. As the viscosity of this dispersion, the viscosity at a shear rate of 10 s ⁻¹ measured at 25 ° C. is preferably 500 mPa · s or less, particularly preferably 100 mPa · s or less.

<Fine cellulose fiber>
The number average fiber diameter of the fine cellulose fiber of the present invention obtained by the defibrating treatment and, if necessary, the centrifugal separation after the defibrating treatment is usually 200 nm or less, more preferably 100 nm or less, particularly preferably 50 nm or less, most preferably. Is 10 nm or less, usually 2 nm or more. When the number average fiber diameter of the fine cellulose fibers is within this range, the fiber diameter is nano-sized and light scattering is small, so that an effect of showing high transparency can be obtained. Further, when combined with a matrix material, high strength, high elastic modulus, and low linear expansion coefficient can be obtained.

  The number average fiber length of the cellulose fiber of the present invention is usually 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less, more preferably 10 μm or less, and particularly preferably 5 μm or less. When the number average fiber length of the fine cellulose fibers is not more than the above upper limit, the effect of eliminating the entanglement between the fine cellulose fibers and reducing the mass due to the fibers is obtained.

  The fiber diameter and fiber length of the fine cellulose fibers are obtained by drying and removing the solvent of the fine cellulose fiber dispersion of the present invention, then scanning electron microscope (SEM), transmission electron microscope (TEM), and atomic force microscope (AFM). It can be measured and obtained by observing with various microscopes.

[Cellulose fiber aggregate]
Next, a cellulose fiber aggregate using the fine cellulose fibers of the present invention (hereinafter, may be referred to as “the cellulose fiber aggregate of the present invention”) will be described.

<Manufacture of cellulose fiber aggregate>
The cellulose fiber aggregate of the present invention contains the fine cellulose fiber of the present invention. Usually, the cellulose fiber aggregate of the present invention consists of only the fine cellulose fibers of the present invention after drying described later, but may contain other fibers and particles.

The cellulose fiber aggregate of the present invention is produced using the fine cellulose fiber of the present invention refined by defibrating treatment. Here, in the present invention, the cellulose fiber aggregate usually means that a dispersion medium is volatilized by filtering a cellulose fiber dispersion containing fine cellulose fibers or by applying the dispersion to a suitable substrate. An aggregate of cellulose fibers obtained by removal by a method such as, for example, a sheet, a particle, or a gel.
In the production of the cellulose fiber aggregate, the fine cellulose fiber dispersion after the defibration treatment is subjected to a centrifugal separation treatment to obtain a supernatant liquid containing only ultrafine cellulose fibers, and this supernatant liquid is used for the cellulose fiber aggregate. When used for production, a highly transparent cellulose fiber composite material can be obtained from the obtained cellulose fiber aggregate.

(Sheet)
It can be set as the cellulose fiber sheet of this invention containing the fine cellulose fiber of this invention using the fine cellulose fiber of this invention. By using a cellulose fiber sheet, a resin resin can be impregnated into a fiber resin composite material, or a fiber resin composite material can be sandwiched between resin sheets. Specifically, the cellulose fiber sheet is produced by filtering the fine cellulose fiber dispersion containing the fine cellulose fibers of the present invention, which has been subjected to the above-described defibrating treatment, or by applying to a suitable substrate. The

  When the cellulose fiber sheet is produced by filtering the fine cellulose fiber dispersion, the fine cellulose fiber concentration of the fine cellulose fiber dispersion used for filtration is 0.01% by weight or more, preferably 0.05% by weight. More preferably, the content is 0.1% by weight or more. If the fine cellulose fiber concentration of the fine cellulose fiber dispersion is too low, it takes an enormous amount of time for filtration, which is inefficient. Further, the fine cellulose fiber concentration of the fine cellulose fiber dispersion to be subjected to filtration is 1.5% by weight or less, preferably 1.2% by weight or less, more preferably 1.0% by weight or less. If the fine cellulose fiber concentration is too high, a uniform sheet may not be obtained.

When filtering the fine cellulose fiber dispersion, it is important that the finely divided cellulose fibers do not pass through and the filtration speed is not too slow as a filter cloth at the time of filtration. As such a filter cloth, a sheet made of an organic polymer, a woven fabric, and a porous membrane are preferable. The organic polymer is preferably a non-cellulose organic polymer such as polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) or the like.
Specifically, a porous film of polytetrafluoroethylene having a pore diameter of 0.1 to 20 μm, for example, 0.5 to 1 μm, a polyethylene terephthalate having a pore diameter of 0.1 to 20 μm, for example, 0.5 to 1 μm, a polyethylene woven fabric, or the like. .

The cellulose fiber sheet can have various porosity depending on the production method.
When the cellulose fiber sheet is impregnated with a resin to obtain a cellulose fiber composite material, it is preferable that the cellulose fiber sheet has a certain degree of porosity because the resin is difficult to be impregnated when the porosity of the cellulose fiber sheet is small. The porosity in this case is usually 10% by volume or more, preferably 20% by volume or more. However, when the porosity of the cellulose fiber sheet is excessively high, when a cellulose fiber composite material is obtained, a sufficient reinforcing effect by the cellulose fibers cannot be obtained, and the linear expansion coefficient and the elastic modulus may be insufficient. It is preferable that it is below volume%.

The porosity of a cellulose fiber sheet here is calculated | required by a following formula simply.
Porosity (volume%) = {(1-B / (M × A × t)} × 100
Here, A is the area (cm ² ) of the cellulose fiber sheet, t is the film thickness (cm), B is the weight (g) of the sheet, M is the density of cellulose, and in the present invention, M = 1.5 g / cm Assume ³ .
The film thickness of the cellulose fiber sheet is measured at 10 points at various positions on the sheet using a film thickness meter (PDN-20 manufactured by PEACOK), and the average value is adopted.

Examples of a method for obtaining a cellulose fiber sheet having a large porosity include a method in which water in the cellulose fiber sheet is finally replaced with an organic solvent such as alcohol in a film forming process by filtration.
In this method, water is removed by filtration, and an organic solvent such as alcohol is added when the cellulose content reaches 5 to 99% by weight. Alternatively, after the fine cellulose fiber dispersion is put into the filtration device, the organic solvent such as alcohol is gently put into the upper part of the dispersion, so that the water in the cellulose fiber sheet is removed from the organic solvent such as alcohol at the end of the filtration. Can be substituted.

  The organic solvent such as alcohol used here is not particularly limited. For example, in addition to alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and ethylene glycol, ethylene glycol mono- Examples thereof include one or more organic solvents such as t-butyl ether, acetone, methyl ethyl ketone, tetrahydrofuran, cyclohexane, toluene, carbon tetrachloride and the like. When using a water-insoluble organic solvent, it is preferable to use a water-soluble organic solvent or a mixed solvent with the water-soluble organic solvent, and then replace with a water-insoluble organic solvent.

  Thus, the film thickness of a cellulose fiber sheet can also be controlled by controlling the porosity.

Moreover, as a method for controlling the porosity, a method in which a solvent having a boiling point higher than that of the above-described alcohol or the like is mixed with a dispersion of fine cellulose fibers and dried at a temperature lower than the boiling point of the solvent can be mentioned. In this case, if necessary, the solvent having a high boiling point remaining after drying can be replaced with another solvent, and then impregnated into a resin to obtain a cellulose fiber composite material. The cellulose fiber sheet from which the solvent has been removed by filtration is then dried, but in some cases, it may proceed to the next step without drying.
That is, when the heat-treated fine cellulose fiber dispersion is filtered and then impregnated into the resin, the resin can be impregnated as it is without passing through a drying step.
Also, when the fine cellulose fiber dispersion is filtered and the sheet is heat-treated, it can be carried out without a drying step.
However, it is preferable to perform drying in the sense of controlling the porosity, the film thickness, and strengthening the sheet structure.

  This drying may be air drying, vacuum drying, or pressure drying. Moreover, you may heat-dry. When heating, the temperature is preferably 50 ° C or higher, more preferably 80 ° C or higher, 250 ° C or lower is more preferable, and 150 ° C or lower is more preferable. If the heating temperature is too low, drying may take time or drying may be insufficient. If the heating temperature is too high, the cellulose fiber sheet may be colored or the cellulose may be decomposed. Moreover, when pressurizing, 0.01 MPa or more is preferable, 0.1 MPa or more is more preferable, 5 MPa or less is preferable, and 1 MPa or less is more preferable. If the pressure is too low, drying may be insufficient, and if the pressure is too high, the cellulose fiber sheet may be crushed or cellulose may be decomposed.

  Although there is no limitation in particular in the thickness of a cellulose fiber sheet, Preferably it is 1 micrometer or more, More preferably, it is 5 micrometers or more. Moreover, it is 1000 micrometers or less normally, Preferably it is 250 micrometers or less.

(particle)
Fine cellulose fibers can be used to make cellulose fiber particles.
Cellulose fiber particles are particularly suitable for compounding by kneading with a thermoplastic resin, taking advantage of their properties such as high elastic modulus, low linear expansion coefficient, and surface smoothness to make various structural materials, especially surface designs. It is useful for automotive panels with excellent properties and exterior wall panels for buildings.

  As a method for granulating the fine cellulose fiber of the present invention, the fine cellulose fiber dispersion of the present invention is produced by, for example, spraying from a spray nozzle or the like using a known spray drying apparatus to remove the dispersion medium. The method of granulating is mentioned. Specific examples of the injection method include a method using a rotating disk, a method using a pressure nozzle, and a method using a two-fluid nozzle. You may dry the particle | grains obtained by spray-drying further using another drying apparatus. In this case, infrared rays or microwaves can be used as the thermal energy source.

  Cellulose fiber particles can also be obtained by freeze-drying and pulverizing the fine cellulose fiber dispersion of the present invention. In this case, specifically, after cooling the fine cellulose fiber dispersion of the present invention with liquid nitrogen or the like, a method of pulverizing with a grinder, a rotary blade or the like can be mentioned.

  Although there is no restriction | limiting in particular in the particle size of a cellulose fiber particle, Usually, 1 micrometer or more and 1 mm or less are preferable. The particle size is more preferably 5 μm or more and 100 μm or less, and particularly preferably 5 μm or more and 50 μm or less. If the particle size of the cellulose fiber particles is too large, poor dispersion occurs when they are combined with the resin, and if they are too small, they are fluffy and difficult to handle.

<Gel>
The fine cellulose fiber of the present invention can be combined with a matrix material other than cellulose to obtain a cellulose fiber composite material (fiber resin composite material). The composite with the matrix material other than cellulose may be performed in the dispersion medium without removing the dispersion medium from the fine cellulose fiber dispersion of the present invention, and the cellulose is obtained by removing the dispersion medium after the composite. A fiber composite material can also be obtained. The dispersion medium of the fine cellulose fiber dispersion of the present invention is replaced with a dispersion medium species suitable for complexing with a matrix material other than cellulose, from water to another organic solvent, or from an organic solvent to water. It is more preferable to perform complexing from the above.

In the process of removing or replacing the dispersion medium in the composite, the fine cellulose fiber dispersion of the present invention may be in a cellulose fiber gel state.
In the cellulose fiber gel, cellulose fibers form a three-dimensional network structure, which is wetted or swollen by a dispersion medium, and the network structure is formed by chemical crosslinking or physical crosslinking. When the gel contains a predetermined amount of the dispersion medium, the three-dimensional network structure of the fine cellulose fibers in the gel is maintained.

  The content of the dispersion medium in the cellulose fiber gel is usually 10% by weight or more, preferably 50% by weight or more, and more preferably 70% by weight or more. When the content of the dispersion medium in the gel is less than 10% by weight, the optical isotropy and surface smoothness of the resulting cellulose fiber composite material are impaired. Moreover, as an upper limit, it is 99 weight% or less normally, 97 weight% or less is preferable and 95 weight% or less is more preferable. When the content of the dispersion medium in the gel exceeds 99% by weight, the handling property of the gel is deteriorated and the productivity is lowered.

  Moreover, content of the fine cellulose fiber in a cellulose fiber gel is 90 weight% or less normally, 50 weight% or less is preferable and 30 weight% or less is more preferable. When content of the fine cellulose fiber in a gel exceeds 90 weight%, the optical isotropy and surface smoothness of the cellulose fiber composite material obtained will be impaired. Moreover, as a minimum, it is 1 weight% or more normally, 3 weight% or more is preferable and 5 weight% or more is more preferable. When the content of the fine cellulose fiber in the gel is less than 1% by weight, the handling property of the gel is deteriorated and the productivity is lowered.

  The weight ratio of the dispersion medium to the fine cellulose fibers in the cellulose fiber gel (fine cellulose fibers / dispersion medium) is preferably 9/1 to 1/99, more preferably 1/1 to 3/97, and even more preferably. Is 3/7 to 5/95. When this ratio exceeds 9/1, the optical isotropy and surface smoothness of the resulting cellulose fiber composite material are impaired. When this ratio is less than 1/99, the shape of the cellulose fiber gel cannot be maintained, and handling becomes very difficult.

  The dispersion medium contained in the cellulose fiber gel is usually the dispersion medium of the fine cellulose fiber dispersion of the present invention and is generally water, but is a mixed dispersion medium of one or more organic solvents. May be. Further, a mixed dispersion medium of water and an organic solvent may be used.

The dispersion medium contained in the cellulose fiber gel can be replaced with another type of dispersion medium as necessary as long as the content of the dispersion medium is within the above range. That is, after the gel production process, if necessary, a dispersion medium replacement process is performed in which the dispersion medium (first dispersion medium) in the cellulose fiber gel is replaced with another dispersion medium (second dispersion medium). Also good.
As a replacement method, for example, after removing a predetermined amount of the dispersion medium contained in the dispersion by the above-described filtration method, an organic solvent such as alcohol is added to produce a gel containing the organic solvent such as alcohol. can do. More specifically, the first dispersion medium is water and the second dispersion medium is an organic solvent.

  In addition, the kind of said 2nd dispersion medium is not specifically limited, In addition to alcohols, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, cyclohexane, toluene, tetrachloride One or more organic solvents such as carbon may be used.

  The shape of the cellulose fiber gel is not particularly limited, and can be appropriately controlled such as a sheet or a film (for example, a thickness of 10 μm or more and 10 cm or less), a particle, and the like.

[Cellulose fiber composite material]
The cellulose fiber composite material of the present invention can be obtained by compounding a cellulose fiber aggregate such as the above-described cellulose fiber sheet, cellulose fiber particles, or cellulose fiber gel with a matrix material. In addition, the cellulose fiber composite material of this invention can also be directly manufactured without going through a cellulose fiber aggregate from the fine cellulose fiber dispersion of this invention. That is, the cellulose fiber composite material of the present invention only needs to include the fine cellulose fiber of the present invention and a matrix material.

  The cellulose fiber composite material of the present invention is useful for various display substrate materials, solar cell substrates, window materials, etc. by taking advantage of its high transparency, low linear expansion coefficient, and non-coloring properties. Utilizing characteristics such as elastic modulus, low linear expansion coefficient, and surface smoothness, it is useful for various structural materials, particularly for automobile panels having excellent surface design and for building outer wall panels.

<Composite method>
Hereinafter, a method for producing a fiber resin composite material which is a cellulose fiber composite material of the present invention by combining a cellulose fiber aggregate or a cellulose fiber dispersion with a matrix material will be described.

The cellulose fiber composite material of the present invention is a composite of a cellulose fiber sheet obtained by the above-described method, a cellulose fiber aggregate such as cellulose fiber particles or cellulose fiber gel, or a fine cellulose fiber dispersion and a matrix material other than cellulose. It has been made.
Here, the matrix material refers to a polymer material or a precursor thereof (for example, a monomer) that is bonded to a cellulose fiber sheet, fills a void, or kneads granulated cellulose fiber particles.
Suitable materials for this matrix material include thermoplastic resins that become fluid when heated, and active energy ray-curable resins that cure and cure when irradiated with active energy rays such as ultraviolet rays and electron beams , Sometimes referred to as “photo-curing resin”) or the like, or a precursor thereof.

  In the present invention, the precursor of the polymer material is a so-called monomer or oligomer, such as each monomer described later as a polymerization or copolymerization component in the section of thermoplastic resin (hereinafter referred to as “thermoplastic resin precursor”). And the precursors described later in the section of the photo-curable resin.

Examples of the method for combining the cellulose fiber sheet, the cellulose fiber particles, the cellulose fiber gel, or the fine cellulose fiber dispersion and the matrix material include the following methods (a) to (j). The polymerization curing process of the curable resin will be described in detail in the section <Polymerization curing process>.
(A) Cellulose fiber sheet, cellulose fiber particle or cellulose fiber gel is impregnated with a liquid thermoplastic resin precursor and polymerized (b) Cellulose fiber sheet, cellulose fiber particle or cellulose fiber gel is photocurable resin precursor (C) Cellulose fiber sheet, cellulose fiber particle or cellulose fiber gel is impregnated with a resin solution (one or more solutes selected from thermoplastic resins, thermoplastic resin precursors and photocurable resin precursors). (Solution solution) is dried and then adhered by a heating press or the like, and polymerized and cured as necessary (d) A cellulose fiber sheet, cellulose fiber particles or cellulose fiber gel is impregnated with a thermoplastic resin melt. (E) Thermoplastic resin sheet and cellulose A method of alternately arranging fiber sheets or cellulose fiber gels and closely adhering them with a heating press or the like (f) A liquid thermoplastic resin precursor or a photocurable resin precursor is placed on one or both sides of a cellulose fiber sheet or cellulose fiber gel. Method of applying and curing by polymerization (g) One or more solutes selected from a resin solution (a thermoplastic resin, a thermoplastic resin precursor, and a photocurable resin precursor) are applied to one or both sides of a cellulose fiber sheet or cellulose fiber gel. (H) A method in which cellulose fiber particles and a thermoplastic resin are melt-kneaded and then formed into a sheet or a desired shape (i) Fine cellulose fiber dispersion and monomer solution or dispersion (1 selected from thermoplastic resin precursor and photocurable resin precursor) After mixing a solution or dispersion) and contains a solute or dispersoid above, a method of solvent removal, it is polymerized and cured.
(J) A method of removing the solvent after mixing the fine cellulose fiber dispersion and the polymer solution or dispersion (thermoplastic resin solution or dispersion).

  Among these, the methods (a), (b), (c), (d), (e), (f), and (g) are preferable for cellulose fiber sheets, and (h) for cellulose fiber particles. This method is preferred.

<Matrix material>
In the present invention, as a resin other than cellulose which is a matrix material to be combined with a cellulose fiber sheet, cellulose fiber particles, cellulose fiber gel, or fine cellulose fiber dispersion, active energy ray curing such as a thermoplastic resin or a photocurable resin is used. Resin. By using an active energy ray curable resin such as a thermoplastic resin or a photocurable resin, a highly transparent fiber resin composite material can be obtained. For example, when a thermosetting resin is used, since the curing time is long, the transparency may decrease in the process.

  In the present invention, a thermoplastic resin refers to a resin that can be molded by being softened by heating, and has a property of solidifying when it is cooled (this may also be reversible).

  In the present invention, the active energy ray (light) curable resin is a resin that changes from a liquid state to a solid state (photocuring) by the action of the active energy ray (light energy) and is cured.

  In the present invention, among the following matrix materials (polymer materials or precursors thereof), in the case of a polymer material or precursor, the polymer is an amorphous compound having a high glass transition temperature (Tg). A polymer is preferable for obtaining a highly durable cellulose fiber composite material having excellent transparency. Among these, the degree of amorphousness is 10% or less, particularly 5% or less in terms of crystallinity. The Tg is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, and particularly preferably 130 ° C. or higher. If Tg is low, there is a risk of deformation when touched with hot water, for example, which causes a practical problem. Moreover, in order to obtain a low water-absorbing cellulose fiber composite material, it is preferable to select a polymer material having few hydrophilic functional groups such as a hydroxyl group, a carboxy group, and an amino group. The Tg of the polymer material can be obtained by a general method. For example, it is obtained by measurement by the DSC method. The degree of crystallinity of the polymer can be calculated from the density of the amorphous part and the crystalline part, and can also be calculated from the tan δ, which is the ratio of the elastic modulus to the viscosity, by dynamic viscoelasticity measurement. .

(Thermoplastic resin)
The thermoplastic resin is not particularly limited, but polyvinyl alcohol resin, styrene resin, acrylic resin, aromatic polycarbonate resin, aliphatic polycarbonate resin, aromatic polyester resin, aliphatic polyester resin. And aliphatic polyolefin resins, cyclic olefin resins, polyamide resins, polyphenylene ether resins, thermoplastic polyimide resins, polyacetal resins, polysulfone resins, amorphous fluorine resins, and the like.

(Active energy ray curable resin)
Although it does not specifically limit as active energy ray curable resins, such as photocurable resin, Precursors, such as an epoxy resin, an acrylic resin, an oxetane resin, are mentioned.
Specific examples of the thermoplastic resin and the active energy ray curable resin include those described in JP-A-2009-299043.

(Other ingredients)
The thermoplastic resin and the active energy ray curable resin are appropriately used as a composition (hereinafter referred to as a curable composition) blended with a chain transfer agent, an ultraviolet absorber, a filler, a silane coupling agent, and the like.

<Chain transfer agent>
The curable composition may contain a chain transfer agent for the purpose of causing the reaction to proceed uniformly. As the chain transfer agent, for example, a polyfunctional mercaptan compound having two or more thiol groups in the molecule can be used, and thereby moderate toughness can be imparted to the cured product. Examples of mercaptan compounds include pentaerythritol tetrakis (β-thiopropionate), trimethylolpropane tris (β-thiopropionate), and tris [2- (β-thiopropionyloxyethoxy) ethyl] triisocyanurate. It is preferable to use 1 type (s) or 2 or more types. When the mercaptan compound is contained in the curable composition, the chain transfer agent is usually contained in a proportion of 30% by weight or less with respect to the total of the radically polymerizable compounds in the curable composition.

<Ultraviolet absorber>
For the purpose of preventing coloring, the curable composition may contain an ultraviolet absorber. For example, the ultraviolet absorber is selected from a benzophenone-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber, and the ultraviolet absorber may be used alone or in combination of two or more. . When an ultraviolet absorber is contained in the curable composition, the ultraviolet absorber is usually contained at a ratio of 0.01 to 1 part by weight with respect to 100 parts by weight of the radically polymerizable compound in the curable composition. .

<Fillers other than cellulose>
The curable composition may contain a filler other than cellulose fibers. Examples of the filler include inorganic particles and organic polymers. Specifically, inorganic particles such as silica particles, titania particles, alumina particles, transparent cycloolefin polymers such as ZEONEX (ZEON CORPORATION) and ARTON (JSR), general-purpose thermoplastic polymers such as polycarbonate and polymethyl methacrylate, etc. Is mentioned. Among these, use of nano-sized silica particles is preferable because transparency can be maintained. In addition, it is preferable to use a polymer having a structure similar to that of the ultraviolet curable monomer because the polymer can be dissolved to a high concentration.

<Silane coupling agent>
A silane coupling agent may be added to the curable composition. Examples of the silane coupling agent include γ-((meth) acryloxypropyl) trimethoxysilane, γ-((meth) acryloxypropyl) methyldimethoxysilane, and γ-((meth) acryloxypropyl) methyldiethoxy. Silane, γ-((meth) acryloxypropyl) triethoxysilane, γ- (acryloxypropyl) trimethoxysilane, and the like, which have a (meth) acryl group in the molecule and other monomers Is preferable because it can be copolymerized. When the curable composition contains a silane coupling agent, the silane coupling agent is usually 0.1 to 50% by weight, preferably 1 to 20%, based on the total amount of radically polymerizable compounds in the curable composition. It is made to contain so that it may become weight%. If the blending amount is too small, the effect of containing it is not sufficiently obtained, and if it is too large, optical properties such as transparency of the cured product may be impaired.

<Polymerization curing process>
The curable composition for forming the cellulose fiber composite material of the present invention can be polymerized and cured by a known method.
Examples of the curing method include radiation curing. Examples of radiation include active energy rays such as infrared rays, visible rays, ultraviolet rays, and electron beams, with light being preferred. More preferred is light having a wavelength of about 200 nm to 450 nm, and more preferred is ultraviolet light having a wavelength of 250 to 400 nm.

  Specifically, a method in which a photopolymerization initiator that generates radicals by radiation such as ultraviolet rays is added to the curable composition in advance and polymerized by irradiation with radiation (hereinafter sometimes referred to as “photopolymerization”), etc. Is mentioned.

  As the photopolymerization initiator, a photoradical generator is usually used. As the photoradical generator, a known compound that can be used for this purpose can be used. Examples include benzophenone, benzoin methyl ether, benzoin propyl ether, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the like. Among these, 2,4,6-trimethylbenzoyldiphenylphosphine oxide is preferable. These photopolymerization initiators may be used alone or in combination of two or more.

  The blending amount of the photopolymerization initiator is 0.001 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0, when the total amount of radically polymerizable compounds in the curable composition is 100 parts by weight. 0.01 parts by weight or more. The upper limit is usually 1 part by weight or less, preferably 0.5 part by weight or less, more preferably 0.1 part by weight or less. When the blending amount of the photopolymerization initiator is too large, the polymerization proceeds rapidly, and not only the birefringence of the resulting cured product is increased, but also the hue is deteriorated. For example, when the amount of the initiator is 5 parts by weight, absorption of the initiator causes light to not reach the side opposite to the irradiation of the ultraviolet rays, resulting in an uncured portion. Further, it is colored yellow and the hue is markedly deteriorated. On the other hand, if the amount is too small, the polymerization may not proceed sufficiently even if ultraviolet irradiation is performed.

  Moreover, the curable composition may contain a thermal polymerization initiator simultaneously. Examples of the thermal polymerization initiator include hydroperoxide, dialkyl peroxide, peroxy ester, diacyl peroxide, peroxy carbonate, peroxy ketal, and ketone peroxide. Specifically, benzoyl peroxide, diisopropyl peroxy carbonate, t-butyl peroxy (2-ethylhexanoate) dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, t-butyl hydroperoxide Side, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide and the like can be used. When thermal polymerization is initiated at the time of light irradiation, it becomes difficult to control the polymerization. Therefore, these thermal polymerization initiators preferably have a 1 minute half-life temperature of 120 ° C. or higher. These polymerization initiators may be used alone or in combination of two or more.

The amount of radiation to be irradiated upon curing is arbitrary as long as the photopolymerization initiator generates radicals. However, when the amount is extremely small, the polymerization is incomplete, so that the cured product has sufficient heat resistance and mechanical properties. If it is not expressed and is extremely excessive, on the contrary, it will cause deterioration due to light such as yellowing of the cured product. Therefore, ultraviolet rays having a wavelength of 300 to 450 nm are used in accordance with the composition of the monomer and the type and amount of the photopolymerization initiator. preferably irradiated with 0.1 J / cm ² or more 200 J / cm ² or less. More preferably, irradiation is performed in the range of 1 J / cm ² or more and 20 J / cm ² . More preferably, the radiation is divided into a plurality of times. That is, when the first irradiation is performed for about 1/20 to 1/3 of the total irradiation amount and the necessary remaining amount is irradiated for the second and subsequent times, a cured product with smaller birefringence is obtained. Specific examples of the lamp used include a metal halide lamp, a high-pressure mercury lamp lamp, an ultraviolet LED lamp, and an electrodeless mercury lamp lamp.

  For the purpose of promptly completing the polymerization, photopolymerization and thermal polymerization may be performed simultaneously. In this case, the curable composition is heated and cured in the range of 30 ° C. or more and 300 ° C. or less simultaneously with the radiation irradiation. In this case, a thermal polymerization initiator may be added to the curable composition in order to complete the polymerization, but if added in a large amount, the birefringence of the cured product is increased and the hue is deteriorated. The agent is generally used in an amount of from 0.1% by weight to 2% by weight, more preferably from 0.3% by weight to 1% by weight, based on the total of radically polymerizable compounds in the curable composition.

<Laminated structure>
The cellulose fiber composite material of the present invention may be a laminated structure of a layer of the cellulose fiber sheet of the present invention and a planar structure layer made of a polymer other than cellulose as described above, and the cellulose fiber of the present invention. A laminated structure of the sheet layer and the cellulose fiber composite material layer of the present invention may be used, and the number of laminated layers and the laminated structure are not particularly limited.

  Further, a plurality of the cellulose fiber sheets or plate-like cellulose fiber composite materials of the present invention can be stacked to form a laminate. In that case, you may laminate | stack the cellulose fiber composite material of this invention, and the resin sheet which does not contain a cellulose fiber. In this case, in order to adhere the cellulose fiber composite materials or the resin sheet and the cellulose fiber composite material, an adhesive may be applied or an adhesive sheet may be interposed. Moreover, it can also integrate by adding a heat press process to a laminated body.

<Inorganic membrane>
The cellulose fiber composite material of the present invention may be obtained by further laminating an inorganic film on the cellulose fiber composite material layer according to its use, and further laminating an inorganic film on the above laminated structure. There may be.

The inorganic film used here is appropriately determined according to the use of the cellulose fiber composite material, for example, metals such as platinum, silver, aluminum, gold, copper, silicon, ITO, SiO ₂ , SiN, SiOxNy, ZnO, etc. A TFT etc. are mentioned, The combination and film thickness can be designed arbitrarily.

<Characteristics and physical properties of cellulose fiber composite material>
Hereinafter, suitable characteristics or physical properties of the cellulose fiber composite material of the present invention will be described.

(Cellulose content)
The cellulose content in the cellulose fiber composite material of the present invention (the content of the fine cellulose fiber of the present invention) is usually 1% by weight to 99% by weight, and the content of the matrix material other than cellulose is 1% by weight or more. 99% by weight or less. In order to develop low linear expansion, it is necessary that the content of cellulose is 1% by weight or more and the content of a matrix material other than cellulose is 99% by weight or less. In order to express transparency, it is necessary that the content of cellulose is 99% by weight or less and the content of a matrix material other than cellulose is 1% by weight or more. A preferred range is 5% to 90% by weight of cellulose, a matrix material other than cellulose is 10% to 95% by weight, and a more preferred range is 10% to 80% by weight of cellulose, The matrix material other than cellulose is 20% by weight or more and 90% by weight or less. In particular, the content of cellulose is preferably 30% by weight or more and 70% by weight or less, and the content of matrix materials other than cellulose is preferably 30% by weight or more and 70% by weight or less.

  The content of the cellulose and the matrix material other than cellulose in the cellulose fiber composite material can be determined from, for example, the weight of the cellulose fiber before composite and the weight of the cellulose fiber composite material after composite. Alternatively, the cellulose fiber composite material is immersed in a solvent in which the matrix material is soluble to remove only the matrix material, and the weight can be obtained from the remaining fine cellulose fibers. In addition, the functional group of the resin or cellulose can also be quantified and determined using the specific gravity of the resin that is the matrix material, NMR, or IR.

(Thickness)
The thickness of the cellulose fiber composite material of the present invention is preferably 10 μm or more and 10 cm or less, and by using such a thickness, the strength as a structural material can be maintained. The thickness of the cellulose fiber composite material is more preferably 50 μm or more and 1 cm or less, and further preferably 80 μm or more and 250 μm or less.
The cellulose fiber composite material of the present invention is, for example, a film shape (film shape) or a plate shape having such a thickness, but is not limited to a flat film or a flat plate, and is a film shape or a plate shape having a curved surface. You can also. Other irregular shapes may also be used. Further, the thickness is not necessarily uniform and may be partially different.

(Coloring)
The cellulose fiber composite material of the present invention is characterized in that coloring by heating is small.
Cellulose is sometimes yellowish by using raw materials derived from wood. This may be the case where the cellulose itself is colored or the remaining substance other than cellulose depending on the degree of purification. The fine cellulose fiber and cellulose fiber composite material of the present invention are small in color even when a heating step is performed, and can withstand heat treatment in actual device forming steps such as transparent substrates of various devices.
When the cellulose fiber composite material of the present invention is used as various transparent materials, the degree of coloring of the fine cellulose fiber is preferably 30 or less, more preferably 15 or less, particularly preferably 10 or less, as the YI of the cellulose fiber composite material. It is preferable that the YI does not increase even after the heat treatment, and it is preferable that the YI is preferably maintained at 30 or less, more preferably 15 or less, and particularly preferably 10 or less after the heating. The YI of the cellulose fiber composite material is measured using, for example, a color computer manufactured by Suga Test Instruments.

(Haze)
The cellulose fiber composite material of the present invention can be a cellulose fiber composite material having high transparency, that is, low haze.
When used as various transparent materials, the haze of the cellulose fiber composite material is preferably 2.0 or less, more preferably 1.8 or less, particularly preferably 1.5 or less. If the haze is larger than 2.0, it becomes difficult to apply it to transparent substrates of various devices.
A haze can be measured about a cellulose fiber composite material using the Suga Test Instruments haze meter, and the value of C light source is used. For example, a fiber resin composite material having a thickness of 10 to 250 μm, preferably 10 to 100 μm is measured.

(Total light transmittance)
The cellulose fiber composite material of the present invention can be a cellulose fiber composite material having high transparency, that is, low haze. When used as various transparent materials, this fiber resin composite material has a total light transmittance of 60% or more, further 70% or more, particularly 80% or more, especially 90%, as measured in the thickness direction in accordance with JIS standard K7105. % Or more is preferable. If this total light transmittance is less than 60%, it becomes translucent or opaque, and it may be difficult to use it in applications requiring transparency.
The total light transmittance can be measured, for example, for a cellulose fiber composite material using a Suga Test Instruments haze meter, and the value of a C light source is used. For example, the measurement is performed on a cellulose fiber composite material having a thickness of 10 to 250 μm, preferably 10 to 100 μm.

(Linear expansion coefficient)
The cellulose fiber composite material of the present invention can be made into a cellulose fiber composite material having a low linear expansion coefficient by using cellulose having a low linear expansion coefficient (elongation rate per 1K). The cellulose fiber composite material preferably has a linear expansion coefficient of 1 to 50 ppm / K, more preferably 1 to 30 ppm / K, particularly preferably 1 to 20 ppm / K, and 1 to 15 ppm / K. Most preferably.
That is, for example, in the substrate application, since the linear expansion coefficient of the inorganic thin film transistor is about 15 ppm / K, when the linear expansion coefficient of the cellulose fiber composite material exceeds 50 ppm / K, the laminated composite with the inorganic film is formed. The difference in linear expansion coefficient between the two layers becomes large, and cracks and the like are generated. Therefore, the linear expansion coefficient of the cellulose fiber composite material is particularly preferably 1 to 20 ppm / K.

The linear expansion coefficient is measured by, for example, the following method.
Cellulose fiber composite material was cut into 3 mm width x 40 mm length with a laser cutter, and this was stretched at a rate of 5 mm / min from room temperature to 180 ° C. in a nitrogen atmosphere at 20 mm between chucks in a tensile mode using TMA6100 made by SII. The temperature was raised and then from 180 ° C. to 25 ° C. at 5 ° C./min. The linear expansion coefficient is obtained from the measured value from 60 ° C. to 100 ° C. during the second temperature increase when the temperature is further decreased from 25 ° C. to 180 ° C. at a rate of 5 ° C./min. The temperature range to be measured is appropriately adjusted depending on the matrix material used.

(Tensile strength)
The tensile strength of the cellulose fiber composite material of the present invention is preferably 40 MPa or more, more preferably 100 MPa or more. If the tensile strength is lower than 40 MPa, sufficient strength cannot be obtained, which may affect the use of a structural material or the like to which a force is applied.

(Tensile modulus)
The tensile elastic modulus of the cellulose fiber composite material of the present invention is preferably 0.2 to 100 GPa, more preferably 1 to 50 GPa, and still more preferably 5.0 to 30 GPa. When the tensile elastic modulus is lower than 0.2 GPa, sufficient strength cannot be obtained, which may affect the use of a structural material or the like to which a force is applied.

<Application>
The cellulose fiber composite material of the present invention has high transparency, high strength, low water absorption, high transparency, low coloration, small haze, and excellent optical properties, so that it can be used for liquid crystal displays, plasma displays, organic EL displays, field emission displays. It is suitable as a display, a substrate or a panel of a rear projection television. Moreover, it is suitable for substrates for solar cells such as silicon-based solar cells and dye-sensitized solar cells. The substrate may be laminated with a barrier film, ITO, TFT or the like. In particular, the cellulose fiber composite material of the present invention is small in color even when subjected to heat treatment, and can withstand heat treatment in actual device forming steps such as transparent substrates of various devices.

The cellulose fiber composite material of the present invention can also be suitably used for window materials for automobiles, window materials for railway vehicles, window materials for houses, window materials for offices and factories, and the like. As the window material, a film such as a fluorine film or a hard coat film or a material having impact resistance or light resistance may be laminated as necessary.
In addition, the cellulose fiber composite material of the present invention can be used as a structure other than the use of a transparent material by taking advantage of characteristics such as a low linear expansion coefficient, high elasticity, and high strength. In particular, it is suitably used as automobile materials such as interior materials, outer plates, bumpers, etc., personal computer casings, home appliance parts, packaging materials, building materials, civil engineering materials, marine materials, and other industrial materials.

  Examples 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 it exceeds the gist.

  In addition, the calculation method of the input energy amount required for the nano-ized yield of the fine cellulose fiber and the defibration process in the following examples and comparative examples is as follows.

<Calculation method of nano-ized yield>
(1) The fine cellulose fiber dispersion after defibration is diluted to a solid content concentration of 0.2% by weight and uniformly dispersed.
(2) The diluted fine cellulose fiber dispersion is placed in an aluminum dish, dried at 105 ° C. for 2 hours or more, and weighed to obtain the solid content concentration (C ₀ ) of the dispersion in (1).
(3) Weigh 30 g of the dispersion of (1) in a centrifuge tube and centrifuge at 12000 G for 10 minutes using a centrifuge (CR23 manufactured by Hitachi Koki Co., Ltd.).
(4) Weigh the whole centrifuge tube (W ₁ ).
(5) Carefully separate the supernatant so that no precipitate enters, and determine the solid content concentration as in (2) (C ₁ ).
(6) Weigh the centrifuge tube where the precipitate remains (W ₂ ).
(7) centrifuge tube of mass and W _0.
The nanonization yield is calculated by the following formula.

 (8) Since the supernatant contains a large amount of fine fine cellulose fibers having a number average fiber diameter of 200 nm or less, the higher the nanofibration yield, the higher the fibrillation efficiency.

<Calculation method of input energy amount>
(When using only a high-speed rotating disperser)
The following formula was used for calculation.
Input energy (kWh / kg-cellulose) =
{Current x voltage x fibrillation treatment time} / {put into high-speed rotary disperser
Cellulose fiber raw material amount (g)}
(When using high-speed rotary disperser and high-pressure disperser)
The input energy amount in the defibrating process by the high-pressure disperser was calculated by the following formula, and the sum of the input energy amount in the defibrating process by the high-speed rotary disperser was defined as the input energy amount.
Input energy (kWh / kg-cellulose) =
{Current x Voltage x Defibration treatment time} / {Putted into high-pressure disperser
Cellulose fiber raw material amount (g)}

[Example 1]
To 250 g of 2-propanol, 32.4 g of hardwood bleached kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd., solid content of 30% by weight) is added as a cellulose fiber raw material, and then 5.83 g of 1 mol / L sodium hydroxide aqueous solution and glycidyltrimethyl 4.86 g of an 80% by weight aqueous solution of ammonium chloride (Cathiomaster G (registered trademark), Yokkaichi Gosei Co., Ltd.) was added, and the mixture was stirred at room temperature for 3 hours, and then reacted at 50 ° C. for 90 minutes. After the reaction, the cake separated by filtration was dispersed in 600 mL of demineralized water, neutralized with a 10 wt% aqueous acetic acid solution, and then filtered again. Next, the filtrate is washed with demineralized water until the electric conductivity is less than 50 μS / cm, and the groups represented by the formula (1) (R ¹ , R ² , R ³ are methyl groups, X ⁻ is Cl ⁻ ) are removed. The introduced cationized cellulose fiber raw material was obtained.
When the introduction amount of the cationic group of the obtained cationized cellulose fiber raw material was measured according to JIS-K2609 using a nitrogen measuring device (TN-10, manufactured by Mitsubishi Chemical Analytech), 0.50 mmol / g.

Using the obtained cationized cellulose fiber raw material, 5400 g of an aqueous dispersion adjusted to a solid content concentration of 0.5% by weight (cellulose solid content 27 g) was prepared.
Next, this aqueous dispersion was supplied to a high-speed rotary disperser (CLEAMIX-2.2S, manufactured by M Technique Co., Ltd.), and the cationized cellulose fiber was defibrated for 30 minutes at 20000 rpm. The amount of energy input at this time was 32 kWh / kg-cellulose as shown in the following formula, and the nano-ized yield was 15%.
Input energy (kWh / kg-cellulose) =
1750W × (30/60) time / 27g ≒
32kWh / kg-cellulose

  Using a part of the aqueous dispersion 1000g (cellulose solid content 5g) after defibration with a high-speed rotary disperser, press the pressure with a high-pressure disperser (Ultimizer System, manufactured by Sugino Machine Co., Ltd.). Two-pass treatment was performed at 245 MPa for 2 minutes each. The nano-ized yield after the defibrating process by the high-pressure disperser was 92%.

The amount of energy input when using a high-pressure disperser is a discharge amount of 1000 g (cellulose amount: 5.0 g) / 2 minutes, and a two-pass treatment makes the defibration time 4 minutes. Therefore, the input energy amount (kWh / kg-cellulose) is calculated by the following formula.
Input energy (kWh / kg-cellulose) =
11200W × (4/60) time / 5.0g ≒
149kWh / kg-cellulose

  When the cationized cellulose fiber raw material is defibrated with a high-speed rotary disperser and then defibrated with a high-pressure disperser, the nanofibrization yield is 92%, and the total input energy required for the defibrating process is It was 181 (= 32 + 149) kWh / kg-cellulose.

[Comparative Example 1]
320 g of a 0.5 wt% aqueous dispersion of a cationized cellulose fiber raw material (amount of cationic group introduced: 0.50 mmol / g) prepared in the same manner as in Example 1 was added to a high-speed rotary disperser (CLEAMIX-0. 8S, manufactured by M Technique Co., Ltd., with a maximum capacity of 320 g), and the cationized cellulose fiber raw material was defibrated for 60 minutes at 20000 rpm.
The nano-sized yield of fine cellulose fibers in the aqueous dispersion after the defibration treatment was 85%.
Moreover, the input energy amount required for the defibrating process was 450 kWh / kg-cellulose.

[Comparative Example 2]
24 g of 25 wt% sodium hydroxide aqueous solution was added to 100.5 g of hardwood bleached kraft pulp (LBKP, manufactured by Oji Paper Co., Ltd., solid content of 30 wt%), stirred for 10 minutes with a spatula, and then stirred with a meniscus stirring blade for 20 minutes. . After stirring, 750 g of 2-propanol was added, and then 25.6 g of a 65 wt% aqueous solution of 3-chloro-2-hydroxy-propyltrimethylammonium chloride (Cathiomaster C (registered trademark), Yokkaichi Gosei Co., Ltd.) was added. The reaction was performed at 90 ° C. for 90 minutes. After the reaction, the filtered cake was dispersed in 900 mL of demineralized water, neutralized with acetic acid, and then filtered again. Subsequently, the filtrate was washed with demineralized water until the electric conductivity of the filtrate was less than 50 μS / cm to obtain a cationized cellulose fiber raw material.
With respect to this cationized cellulose fiber raw material, the amount of cationic groups introduced was measured in the same manner as in Example 1. As a result, it was 0.29 mmol / g.
Using the obtained cationized cellulose fiber raw material, 320 g of an aqueous dispersion adjusted to a solid content concentration of 0.5% by weight was prepared.
In the same manner as in Comparative Example 1, the aqueous dispersion was defibrated using a high-speed rotary disperser.
The nano-sized yield of fine cellulose fibers in the aqueous dispersion after the defibrating treatment was 50%.
Moreover, the input energy amount required for the defibrating process was 450 kWh / kg-cellulose.

  The above results are summarized in Table 1.

  As is clear from Table 1, for Comparative Examples 1 and 2 that were defibrated using only a high-speed rotating disperser, defibrating was performed using a high-speed rotating disperser and a high-pressure disperser. In Example 1, a high nanonization yield can be achieved with a small amount of input energy.

Claims (4)

In the method for producing fine cellulose fibers having a number average fiber diameter of 200 nm or less by defibrating cellulose fibers,
As the cellulose fiber, a cellulose fiber introduced with a cationic group of 0.05 to 3.0 mmol / g is used.
A method for producing fine cellulose fibers, which comprises performing a fibrillation treatment with a high-speed rotary disperser and a high-pressure disperser.   The dispersion liquid containing the fine cellulose fiber obtained by the manufacturing method of Claim 1.   The cellulose fiber sheet containing the fine cellulose fiber obtained by the manufacturing method of Claim 1.   The cellulose fiber composite material containing the fine cellulose fiber and matrix material which were obtained by the manufacturing method of Claim 1.