JP7270689B2 - CNF molded article manufacturing method, CNF molded article and CNF molded article as ivory substitute material - Google Patents

Description

The present invention relates to a CNF molded article and a method for producing a CNF molded article.

Cellulose is naturally found in fibrous form in plants such as woody plants such as broadleaf trees and conifers, herbaceous plants such as bamboo and reeds, some animals such as sea squirts, and some acetic acid bacteria. is known to be produced by fungi and the like. A structure in which cellulose molecules are aggregated in a fibrous form is called a cellulose fiber. In particular, cellulose fibers with a fiber width of 100 nm or less and an aspect ratio of 100 or more are generally called cellulose nanofibers (hereinafter sometimes referred to as CNF), and have excellent properties such as light weight, high strength, and low coefficient of thermal expansion. have.

In recent years, there has been an active movement to create CNF compacts using CNF having such excellent properties as a material and to utilize it for various purposes as a high-strength material derived from sustainable raw materials.

Ivory is beautiful and easy to process, so it was used for stamps, kotozume, bridges, piano keyboards and other musical instrument parts. However, the ivory trade is currently severely restricted due to animal protection concerns. Therefore, the development of substitute materials for ivory is underway.

Patent Literature 1 discloses a method for producing a molded composite material containing acicular hydroxyapatite. In addition, US Pat. No. 6,200,000 discloses a method for producing a multi-purpose isotropic hydroxyapatite/gelatin composite.

On the other hand, CNF is usually dispersed in water, and the CNF content in the dispersion is about 0.1 to 10%. In order to obtain a CNF molded body that can be cut, the amount of CNF dispersion is inevitably increased, and the time for removing the solvent from the CNF aqueous dispersion is increased.

Therefore, the inventors of the present invention proposed a means for solving the above problems in Japanese Patent No. 6864816.

Re-table 2018-159417 Special table 2020-528469 Patent No. 6864816

“Experimental study on the face-to-face friction coefficient between the enamel surface of human teeth and its cut surface and the dentin cut surface and the dental alloy rolled plate and precision cast plate surface”, [online], [Reiwa 3rd year 8 Search on the 6th of the month], Internet <URL: https://www.jstage.jst.go.jp/article/jjps1957/8/1/8_1_44/_pdf>

The composite material compacts and composite materials described in Patent Documents 1 and 2 are useful materials from the viewpoint of using them as substitute materials for ivory.
The CNF molded body described in Patent Document 3 describes an example in which cutting was performed, and disclosed a CNF molded body that can be cut.
However, there is still a demand for suitable ivory replacement materials for different applications.

Therefore, the present invention provides a high-strength, lightweight CNF molded body that has a volume that allows for more types of processing such as cutting, drilling, and polishing, and is homogeneous and free from cracks, a method for producing the CNF molded body, and ivory. An object of the present invention is to provide a CNF molded body that can be an alternative material such as.

That is, the present invention puts a CNF-containing slurry into a CNF molding device, applies pressure to the CNF-containing slurry using a gas permeable means, and performs a step of supplying a heated gas to the CNF molding device to form a first molded body. and applying pressure to the first molded body using a gas permeable means, and performing a step of supplying heated gas to the CNF molding device to desolvate the first CNF molded body. A method for producing a CNF molded body including steps.

According to the CNF production method of the present invention, a high-strength lightweight CNF molded body that has a volume that allows for more types of processing such as cutting, drilling, and polishing, and is homogeneous and does not cause cracks, and the CNF molded body It is possible to obtain a CNF molded body that can be used as a manufacturing method and an alternative material such as ivory.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the conceptual diagram of the CNF shaping|molding apparatus of one embodiment of this invention. 10 is a photograph of a cross-sectional view of a CNF molded body in Example 5. FIG. 11 is a photograph of a cross-sectional view of a CNF molded body in Example 8. FIG. 10 is a photograph of a cross-sectional view of a CNF molded body in Example 9. FIG. 2 is a photograph of a shamisen piece produced using the CNF molded body obtained in Example 5. FIG. 4 is a photograph of an erhu piece produced using the CNF molded body obtained in Example 5. FIG. FIG. 12 is a laser chart showing the evaluation results of the koto in Example 13. FIG. It is the figure which showed the evaluation result of the erhu in Example 13 on the laser chart.

Next, embodiments of the present invention will be described in detail. However, the following embodiments are intended to aid understanding of the invention, and are not intended to limit the invention.

(Definition of terms)
The term “CNF” as used herein refers to cellulose fibers having an average thickness of 3 to 200 nm and an average length of 0.1 μm or more, so-called single cellulose nanofibers having an average width of 3 to 4 nm, and single Cellulose nanofibers include single cellulose nanofiber aggregates with an average width of 10 to 200 nm, in which several cellulose nanofibers are aggregated to form multiple layers. In addition, not only cellulose fibers without branches in the longitudinal direction but also those with branches are present.
The term "gas permeation means" in the present specification refers not only to means for permeating a solvent volatilized and becoming a gas, but also means for absorbing and adsorbing this gas and/or means for allowing the solvent to permeate and pass through. Alternatively, it broadly includes means for absorbing and adsorbing the solvent.
The term "first molded body" in the present invention means a molded body obtained by the molding step in the present invention, and the CNF concentration in the molded body is about 10 to 25%. shall be said.

A method for producing a CNF molded article according to the present invention is a method for producing a CNF molded article including (1) a molding step and (2) a solvent removal step.
Furthermore, (3) it is preferable to include a suction step of sucking gas in the CNF forming apparatus. In addition, the manufacturing method according to the present invention may further have other processes other than these processes. The manufacturing method according to the present invention will be described in detail below.

(CNF-containing slurry)
The CNF-containing slurry used in the present invention is a CNF dispersion, a CNF aqueous dispersion in which the solvent is water, or a CNF dispersion containing a metal salt, hardwood, softwood or bamboo pulp as a raw material, or crosslinked The one to which the agent is added can also be used as the CNF-containing slurry. Furthermore, the thing which replaced the water solvent with the organic solvent can also be used as a CNF containing slurry. Furthermore, known materials such as thermosetting resins, polyamides, polyamines, epichlorohydrin-based, melamine-formalin-based, urea-formalin-hydroxyl group and dehydration-condensing carboxylic acid-based materials, wet paper strength agents, dry paper strength agents, A waterproofing agent, a sizing agent, and the like can be added. In addition, a CNF dispersion liquid is mentioned later.

The CNF concentration in the CNF-containing slurry should be in the range of 0.1% to 18%. If the content is less than 0.1%, a dense and uniform structure is obtained, but the manufacturing time is lengthened, resulting in an increase in cost. When the thickness is 15% to 18%, the manufacturing time is shortened, but dents are likely to occur to some extent. Furthermore, in the case of a CNF content of 18% or more, partial hydrogen bonding progresses, so that a homogeneous compact cannot be obtained in the system, resulting in separation into many layers.

(CNF dispersion)
Examples of CNF dispersions that can be used in the present invention include a method for producing fine fibers described in Japanese Patent No. 6867613, and cellulose nanofibers and cellulose nanofibers using cellulose as a natural polymer described in Japanese Patent No. 6704551. Reference can be made to the method for preparing an aqueous crystal solution and the method for producing fine fibers derived from other raw materials described in both publications.

These raw materials for the CNF dispersion may be used singly or in combination of two or more. As the raw polysaccharide, it is preferable to use pulp having an α-cellulose content of 60% to 99% by mass. If the purity has an α-cellulose content of 60% by mass or more, it is easy to adjust the fiber diameter and fiber length, and compared to the case where the α-cellulose content is less than 60% by mass, the thermal stability is high and the coloration is high. Good inhibitory effect. On the other hand, when 99% by mass or more is used, it becomes difficult to defibrate the fibers to the nano level.

The crystallinity of CNF is preferably 50 or more. The degree of crystallinity can be measured by X-ray diffractometry or the like. If the degree of crystallinity is less than 50, the characteristics of natural cellulose crystals cannot be sufficiently brought out, and deterioration over time during storage due to putrefaction etc. There is a risk of causing

CNF having an average thickness of 3 to 200 nm and an average length of 0.1 μm or more can be obtained by the ACC method (underwater counter-collision method) described in paragraph 0018 of Japanese Patent No. 6704551 . For the measurement of the average thickness and average fiber length, a scanning electron microscope (SEM), a transmission electron microscope (TEM), etc. are appropriately selected, CNF is observed and measured, and 20 or more are selected from the obtained photographs. , are obtained by averaging them respectively. In addition, a method of observing with a fluorescence microscope using fluorescence amplification may be employed.

(CNF molding equipment)
FIG. 1 is a cross-sectional view of a conceptual diagram of a CNF forming apparatus according to one embodiment of the present invention. The CNF forming apparatus 1 will be described below with reference to FIG.
The CNF molding device 1 includes a first cylindrical portion 3 having a plurality of holes 2 on the top, a second cylindrical portion 4 one size larger than the diameter of the first cylindrical portion 3, and a lid connected to the top of these and a pedestal 8 into which the main body portion 6 can be inserted and provided with a support shaft portion 7 .
Inside the first cylindrical portion 3, a molding cavity 11 is formed by vertically fitting a top plate 9 and a bottom plate 10 of a pair of gas permeable means.
The upper plate 9 passes through the lid portion 5 via the shaft portion 12 , and various pressing machines (not shown) are mounted on the shaft portion 12 .
The lid portion 5 includes a gas supply port 13 for supplying gas/vapor to the body portion 6 .
The lower plate 10 is fixed to the support shaft portion 7 .
The pedestal 8 has a gas supply port 14 and a gas suction port 15 .
A seal portion 16 is provided at a contact portion between the upper plate 9 , the bottom plate 10 , and the pedestal 8 and the main body portion 6 .
In this specification, the body portion 6 has been described as having a cylindrical shape, but it may have a shape other than this.

An air supply pipe 17 and an air supply pipe 18 are connected to the gas supply ports 13 and 14, respectively. A heating device is arranged in the vicinity of the air supply pipe 16 and the air supply pipe 17 . Such an arrangement makes it possible to supply heated gas to the body portion 6 .
Also, by installing various gas suction devices 19 such as a vacuum pump at the gas suction port 15, the inside of the main body 6 can be reduced in pressure or brought into a vacuum state.
Furthermore, the CNF-containing slurry can be charged into the molding cavity 11 through the CNF slurry charging pipe 20 . As a charging means, a charging nozzle may be installed on the first cylindrical portion 3 or a charging nozzle may be installed on the lid portion 5 . Without this nozzle, the size of the obtained CNF molded body is extremely small compared to the size of the molding cavity 11, but by adding the CNF-containing slurry from the injection nozzle , the volume of the resulting CNF molded body can be arbitrary. By keeping the valve valve 24 closed, backflow can be prevented except during supply.
The water removed from the CNF slurry can be collected and accumulated in the drain reservoir 22 and discharged out of the system through the solvent discharge pipe 23 . The presence of the drain reservoir 22 prevents the liquid from being discharged from the gas suction port 15 to the vacuum pump, so that the production can be stably continued without failure.

According to the CNF shaping|molding apparatus 1 of the above this Embodiment, when pressure is applied using various press machines, the CNF containing slurry can be pressurized by the upper plate 9 to the baseplate 10 direction.
In addition, while maintaining the pressurized state, it becomes possible to supply heated gas to the inside of the main body portion 6 and/or reduce the pressure or create a vacuum state.
Further, the actual volume of the molding cavity 11 is calculated from the cross-sectional areas of the top plate 9 and the bottom plate 10, the distance between them, and the like. It is possible to derive these relational expressions from the water content, the distance, etc., and convert the volume and concentration from the distance value to the upper part of the pedestal 8 measured using the distance measuring device 25 .

(Gas Permeable Means)
As the gas permeation means, means for concentrating using an object permeable to vapor can be used. Objects that allow vapor to permeate include textiles, felt, various filters such as membrane filters and sintered filters, filter paper, substances with permeation mechanisms such as holes, stacks of plates and bars, porous and fine-grained substances. Aggregates (fine particles of sand, silica, etc. forming a pseudo-porous structure) can be used. In addition, water can be easily removed by using a hydrophilic base material. Furthermore, if the pore diameter of the gas permeation mechanism is 1 μm or less, the outflow of CNF can be prevented. In addition, if a fibrous CNF mat is produced, outflow of CNF can be prevented even if the pore size is 200 μm or more.
Furthermore, these single use or combination use is considered. In addition, the load applied to the CNF slurry and the direction of steam permeation are not limited. Moreover, it is possible to allow vapor to permeate under vacuum conditions or reduced pressure conditions, and the means is not particularly limited.

As another means of the gas permeation means, a porous body using a porous material can be used. As the porous material, organic, inorganic, metal, or composites thereof, specifically, various materials such as stainless steel, SiC, ceramic, resin, rubber, glass, and paper can be used. . Moreover, you may use these in combination as needed. In addition, with regard to the average pore diameter, porosity, or opening of the porous body to be used, those having an average pore diameter of 5 to 800 μm and a porosity of 30 to 85% or openings of 20 to 1000 μm can be used, preferably. should have an average pore diameter of 5 to 600 μm and a porosity of 40 to 70% or an opening of 200 to 800 μm.
The porosity is (1) the sum of the volume of pores communicating with the outside and the volume of pores enclosed inside, divided by the total volume (apparent volume), and (2) the volume of pores communicating with the outside. There are two types of pore volume divided by the total volume. In the present invention, any calculation method can be used, but pores leading to the outside are always necessary.

(Molding process)
(1) The molding step uses a gas permeable means to
(1-1) While applying pressure to the CNF-containing slurry,
(1-2) Performing a step of supplying heated gas to the CNF molding device,
This is the step of obtaining the first compact.
In the molding step, the CNF-containing slurry is desolvated, and when the CNF concentration in the first molded body reaches about 10 to 25%, pressurization using the gas permeation means is stopped, and this step is performed. finish. This is because if the CNF concentration in the first compact is set to about 40% in this step, an excessive amount of time will be required.

Further, in the molding step, instead of (1-1),
(1-3) After applying pressure to the CNF-containing slurry, a step of reducing the pressure multiple times, and a step of supplying heated gas to the CNF molding device, that is, a step of performing pressurization and decompression multiple times. and stopping the step of supplying heated gas to the CNF molding device or the step of supplying heated gas to the CNF molding device along with the step of reducing the pressure applied to the CNF-containing slurry, The step of resuming may be performed along with the step of applying pressure to the CNF-containing slurry.

Moreover, in the molding step, a step of adding a CNF-containing slurry into the molding cavity 11 can be further performed.
At this time, the CNF concentration near the surface of the already added CNF-containing slurry and the CNF concentration in the CNF-containing slurry to be added should be less than 18%. If the CNF-containing slurry is added when any of the slurries has a concentration of 18% or more, the CNFs in each CNF-containing slurry partially proceed with hydrogen bonding, and the already added Hydrogen bonding does not progress between the CNF-containing slurry and the CNF-containing slurry added later, resulting in separate layers and a single homogeneous material. Therefore, a large number of layers are formed inside the CNF molded body, and a homogeneous CNF molded body cannot be obtained.

(Desolvation step)
(2) The desolvation step is
(2-1) applying pressure to the first compact using a gas permeable means,
(2-2) A desolvation step of performing a step of supplying a heated gas to the CNF molding device and desolvating the first CNF molded body.
In the desolvation step, the first molded body is dried and desolvated, and when the CNF concentration reaches 80 to 100%, pressurization using the gas permeation means is stopped, and this step is completed.

Further, in the solvent removal step, instead of (2-1),
(2-3) A step of stepwise applying pressure to the gas permeation means to the first compact and supplying heated gas to the CNF molding apparatus may be performed.

(Suction process)
(3) The suction step is a step in which various gas suction devices such as a vacuum pump are installed at the gas suction port 14, and the CNF molding device, that is, the main body 6 is decompressed or vacuumed using this. . The suction step is performed as a step added to the molding step and the solvent removal step.
In addition, in (1-3), the process including the step of performing pressurization and decompression multiple times is performed, and the step of reducing the pressure applied to the CNF-containing slurry and the step of sucking the gas in the CNF molding device are stopped. Then, again, the step of applying pressure to the CNF-containing slurry and the step of resuming the step of sucking the gas in the CNF molding device may be performed.

(4) A distance measuring device may be used to control the molding step and/or the desolvation step, that is, to control the step of pressurizing and/or depressurizing.

The steps in each of the above steps will be described in detail below.
Applying pressure to the CNF-containing slurry in (1-1) is a step of pressurizing the CNF-containing slurry in the molding cavity 11 in the thickness direction as shown in FIG. . Due to this pressurization, water in the CNF-containing slurry moves to the gas permeable means and is discharged out of the molding cavity system.
The pressurization method in this process can be performed by a known method, but is preferably performed by a pneumatic press. This is because the pneumatic press facilitates fine adjustment of the pressure.
A hydraulic press or servo press can also be used. In the case of a hydraulic press, it is easy to apply higher pressure. In the case of a servo press, fine control can be performed. In the case of a servo, energy can be saved because no force is required when the distance (position) is not changed. A servo hydraulic press that combines these can also be used.

In (1-1), while maintaining the state in which the upper surface of the CNF-containing slurry and the upper plate 9 are in contact, after performing the step of (3) sucking the gas in the CNF molding apparatus described later, gradually Applying pressure or applying constant pressure is preferred.
Before performing the process of applying pressure to the CNF-containing slurry, by performing the suction step in advance, the air bubbles originally present in the CNF-containing slurry and / or when the CNF-containing slurry is introduced into the CNF molding device It is possible to remove the generated air bubbles, and to make the bonding state of the CNF inside the finally obtained CNF compact uniform.

The step of supplying heated gas into the CNF forming apparatus in (1-2) is a step of supplying heated gas into the CNF forming apparatus to create a circulating air flow. By performing such a process, it is possible to create a flow of air that circulates in the gas area above the upper plate 9 and the gas area below the bottom plate 10 .
As the heated gas in this step, a heated gas of 30 to 95°C, preferably 35 to 93°C, more preferably 40 to 90°C is used. By using a heated gas in such a range, the temperature of the CNF-containing slurry can be increased, the CNF can be swollen and expanded, and the dehydration rate can be accelerated. can increase the removal rate of the solvent of However, if a heated gas of 30° C. or less is used, the temperature of the CNF-containing slurry is lowered, the water removal rate cannot be increased, and desolvation takes time. In addition, if a heated gas of 95° C. or higher is used, the water content in the CNF-containing slurry may be boiled, and a large amount of air bubbles may be generated in the CNF-containing slurry.

In order not to cause a difference in the moisture content between the inside and the surface of the CNF-containing slurry in the molding cavity, the amount of heating gas supplied is less than the exhaust amount of the vacuum pump, and the amount of heating gas is about 1 minute. It is preferably 0.001 to 10 times the volume of the molding cavity 11. It is preferably 0.002 to 5 times. If the amount of supply is small, the circulation of the gas area will be insufficient, and conversely, if the amount of supply is large, the loss of heat energy from the exhaust system will increase.

After applying pressure to the CNF-containing slurry in (1-3), the step of performing the step of reducing the pressure one or more times is the step of reducing the applied pressure in (1-1). When such a step is performed, the CNF-containing slurry expands in the thickness direction, and the solvent inside the CNF-containing slurry moves inside the CNF-containing slurry. Then, by applying pressure again, the water in the CNF-containing slurry can be desolvated more quickly. Furthermore, when the solvent on the surface side is significantly reduced compared to the inside, the hydrogen bonding of CNF on the surface portion progresses, and it is possible to prevent the passage speed of the solvent from being significantly reduced. In this process, it is sufficient if the pressure applied in the process (1) is reduced below that pressure.

(3) The step of sucking the gas inside the CNF forming device is a step of reducing the pressure inside the CNF forming device or making the inside of the CNF forming device into a vacuum state by sucking the gas inside the CNF forming device. By performing such a step, air bubbles in the CNF-containing slurry can be removed as described above. The suction method in this step can be performed by a known method using a vacuum pump or the like.

Applying pressure to the first molded body using a gas permeable means in (2-1) is a step of the same meaning as applying pressure to the CNF-containing slurry in (1-1), A pressurizing method similar to (1-1) can be used. It is preferable to use a hydraulic press or a servo press. This is because the hydraulic press can apply a greater pressure and desolventize the first CNF compact in a short time. In the case of the servo type, fine control is possible and energy saving can be achieved.
As a method of applying pressure in this step, it is preferable to first apply a small pressure (initial pressure), then gradually increase this pressure, and finally apply a constant pressure (final pressure). .
As a specific pressure value, the initial pressure is preferably 8 kg/cm ² , more preferably 7 kg/cm ² , and even more preferably 5 kg/cm ² . Also, the final pressure is preferably 500 kg/cm ² , more preferably 700 kg/cm ² , and even more preferably 900 kg/cm ² .

From the above, the CNF molding apparatus 1 may use the same CNF molding apparatus on the premise that different press machines are exchanged between the molding process and the desolvation process, You may make it perform the said shaping|molding process and the said desolvation process using the CNF shaping|molding apparatus of 2 or more types which installed the different press machine.

The step of supplying heated gas to the CNF forming apparatus in (2-2) has the same meaning as the step of supplying heated gas into the CNF forming apparatus in (1-2).

Stepwise application of pressure to the gas permeable means in (2-3) means the step of gradually stepwise application of pressure in (2-1). This is because if the first molded body is rapidly pressurized, the first molded body cracks in the horizontal direction, so it is preferable to apply a small pressure in the initial stage and then apply the pressure gradually.

Controlling the molding step and/or the desolvation step using a distance measuring device in (4) means pressurization and/or in (1-1), (1-3) and (2-1) It is a step of controlling the step of depressurizing according to the distance value measured using the distance measuring device.
As described above, the CNF forming apparatus 1 can convert the volume and the concentration value from the distance value measured using the distance measuring device, so such a process can be performed. By setting it as such a process, it becomes possible to perform sequence control etc., for example.

(CNF molded body)
The CNF compact obtained as described above has a density of 1.30 to 1.61 g/cm ³ . If the density of the CNF molded body is less than 1.3 g/cm ³ , the strength is insufficient due to the reduction of hydrogen bonding points, or there are cavities and voids inside. On the other hand, if various processing such as cutting, drilling, polishing, etc. are performed, the CNF molded body will be peeled, destroyed, or damaged, and various processing cannot be performed. The density of the compact is a value measured according to JIS-P-8118:2014.

The lower limit of the thickness of the CNF molded body is 3 mm or more. When the thickness of the CNF molded body is less than 3 mm, it becomes difficult to perform polishing and cutting.
On the other hand, the upper limit in the thickness direction of the CNF molded body is not particularly limited as long as the CNF concentration in the CNF-containing slurry is 18% or less as described in paragraph 0031. By stretching the first cylindrical portion 3 in the height direction, the height of the obtained CNF molded article can be adjusted.

As described above, the method for manufacturing the CNF molded body and the embodiment of the CNF molded body have been described in detail. , various modifications and alterations are possible.

The CNF molded product manufactured by the manufacturing method of the present invention can be used as a substitute material for precious woods such as ivory, rosewood, ebony, and iron blade wood, which are currently difficult to obtain.
In addition, the CNF molded body can be processed into a desired shape by performing various processes such as cutting, piercing, and polishing, depending on the specific application, as a high-strength material derived from a sustainable raw material.
Furthermore, the CNF molded body can also be used as an acoustic material.
In addition, as lightweight and high-strength members, pillars, pedestals, windings for connection, noses, girders, eaves support rings, joints, weighing joints, frame joints, squares, girder, beams, bolts, floor materials , construction parts such as tiles, machine parts such as gears, sliding parts, screws, screws, and bolts, furniture parts such as chairs, desks, tables, chests, etc. It can be used as a high-strength member for daily necessities such as fishing rods, go bamboo shoots, go boards, shogi pieces, shogi stands, chopsticks, and fountain pens, as well as wooden swords, knife handles, buttstocks, and shields.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

(Examples 1 to 4)
(Comparative example 1)
2,038 g of CNF 7.7% aqueous dispersion (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) obtained by the ACC method described in paragraph 0018 of Japanese Patent No. 6704551 using bamboo pulp as a raw material as a cellulose-derived component. was used as a CNF-containing slurry.
Then, it was put into a CNF molding apparatus having a cylindrical main body, and a molding step and a desolvation step were performed under the conditions shown in Table 1 below to create a CNF molded body with a thickness of 10 mm. Also, the CNF concentration in the first compact is shown.

From the results in Table 1, it has become clear that the time required for desolvation in the molding process can be significantly shortened by setting the heated gas temperature to 35° C. or higher.

(Examples 5-8)
(Comparative example 2)
Using bamboo pulp as a cellulose-derived component as a raw material, the CNF aqueous dispersion obtained by the ACC method (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) is the CNF raw material concentration described in Table 2 below, and each is CNF A containing slurry was prepared.
Then, it was put into a CNF molding apparatus with a cylindrical main body, and under the conditions shown in Table 2, each CNF-containing slurry was subjected to a molding process and a solvent removal process to create a CNF molded body.
Next, the density and thickness of the obtained CNF compact were measured. The density was measured according to JIS-P-8118:2014.
Moreover, as appearance evaluation, the cross-sectional view of the obtained CNF molded body was observed and evaluated using the following evaluation criteria. Table 2 shows the results.
○: No layer is formed inside the CNF compact ×: A layer is formed inside the CNF compact In addition, if a layer is formed inside the CNF compact, cutting, polishing, drilling, etc. There is a possibility that the CNF molded body will separate along this layer during processing. From this, when the appearance evaluation is ◯, there is no such possibility, so it can be said that the CNF molded body has excellent workability.

From the results in Table 2, it was clarified that a CNF compact in which no layer is formed inside the CNF compact can be produced by setting the final pressure to 354 kg/cm ² in the desolvation step.
2 and 3 show cross-sectional views of CNF molded bodies in Examples 5 and 8. FIG.

(Examples 9-11)
Using bamboo pulp as a cellulose-derived component as a raw material, the CNF aqueous dispersion obtained by the ACC method (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) is the CNF raw material concentration described in Table 3 below, and each is CNF A containing slurry was prepared.
Next, the CNF molding apparatus with a cylindrical main body is divided into the number of times of raw material injection in each example, and under the conditions shown in Table 3, each CNF-containing slurry is subjected to a molding process and a desolvation process. , to create a CNF compact.
Next, the density and thickness of the obtained CNF compact were measured. The density was measured according to JIS-P-8118:2014, and the contact surface CNF concentration was measured by the dry weight method by scooping the supernatant of the CNF paste in the molding apparatus.
In addition, the appearance evaluation was performed in the same manner as in Examples 5 to 8 and Comparative Example 2. Table 3 shows the results.

(Comparative Example 3)
Using bamboo pulp as a raw material as a cellulose-derived component, a CNF aqueous dispersion (average fiber width 20 nm to 200 nm, average length 3 μm to 30 μm) obtained by the ACC method is used as a CNF raw material concentration described in Table 3 below, and a CNF-containing slurry. and
Then, it was put into a CNF molding apparatus having a cylindrical main body, and under the conditions shown in Table 3, the CNF-containing slurry was subjected to a molding process to prepare a first CNF molded body. Moreover, the contact surface CNF density|concentration of the obtained CNF compact was 18%. The same operation was performed three times to prepare three first compacts.
Next, three of the obtained first molded bodies were stacked, and the solvent was removed to obtain a CNF molded body.
In addition, the appearance evaluation was performed in the same manner as in Examples 5 to 8 and Comparative Example 2. Table 3 shows the results.

From the results of Table 3, if the contact surface CNF concentration is less than 18% in the desolvation process, even if the number of CNF raw material inputs is set to 2 or more, a CNF molded body that satisfies the evaluation criteria for appearance evaluation is obtained. It became clear that it was obtained. From these results, it was clarified that the height of the CNF molded body can be increased in the height direction by paying attention to the CNF concentration at the contact surface.
Moreover, the cross-sectional view of the CNF compact in Example 9 is shown in FIG.

(Example 12)
After polishing the CNF molded body obtained in Example 5 using a round bar and a carbide bar, the CNF molded body was polished using a stylus roughness measuring machine (Tokyo Seimitsu Co., Ltd., model: Surfcom 480A). The surface roughness before (i) and after polishing (ii) was measured. Table 5 shows the measurement results.
In addition, the surface roughness (iii) of the metal material titanium (Ti) and the enamel value (iv) shown in Non-Patent Document 1 are shown as reference examples.
Furthermore, the CNF molded body obtained in Example 5 was polished with sandpaper in the order of #80, #120, #240, #400, #1000, and #2500, and then the surface roughness was measured ( v). Table 5 shows the measurement results.

Table 5 reveals that the CNF molded body according to the present invention can be polished. In addition, it was found that the value of Ti shown as a reference example and the value of enamel shown in Non-Patent Document 1 are comparable. Furthermore, it has also become clear that a molded article having a lower surface roughness value than that of the metal material titanium (Ti) can be obtained.
From the above, it was clarified that the molded body is homogeneous inside at a level equal to or higher than that of human tooth enamel, which is similar to ivory.

(Example 13)
Using the CNF molded body obtained in Example 5, kotozume, erhu piece and shamisen piece were created. Fig. 5 shows the pieces of the shamisen that were made. Moreover, the created erhu piece is shown in FIG. Of these, koto and erhu were provided to professional musicians and compared with current products (koto made of ivory and plastic, erhu made of high-grade wood and general-purpose wood). The evaluation results of the koto are shown in Table 6 and FIG. 7, and the evaluation results of the erhu are shown in Table 7 and FIG.
The evaluation was made up of 5 points, and the higher the score, the better the evaluation. The evaluation items were noise, sound quality, volume, workability, preference, and, in the case of the erhu, the ease of handling. The presence or absence of noise was evaluated for noise, the texture was evaluated for sound quality, and the volume due to the reverberation of koto and erhu was evaluated for volume. The easiness of adjusting and processing at the stage of use by each person was evaluated as workability. Preference was scored based on the expert's preference, taking into account not only performance but also availability, cost, and environmental impact. In terms of handling, which was added to the evaluation of the erhu, the ease of wearing was scored.

Here, I would like to introduce the opinion of a professional koto player. Regarding the CNF compact, I think it is more appropriate to consider it as a new material different from ivory and comparable to ivory. After 1 to 2 months, nails of any material deteriorate severely, so it is necessary to improve the strength, but in consideration of sustainability, CNF molded products are the most preferred. Considering the burden on the thread, ivory is the most natural and easy to play, but considering the future of the koto world, it is becoming an indispensable material. Also, the plastic has an unfriendly sound, and the CNF molded body has a smooth tone.

From the evaluation results, it can be seen that the CNF molded body has suitability equivalent to that of the conventional material for koto (Japanese harp) claws and erhu pieces. In addition, it is comparable to ivory, which is a high-grade material that is difficult to obtain for koto picks, and all musicians evaluate it as an excellent material in terms of palatability, and it is recognized as an indispensable material.
The erhu pieces also received evaluations similar to those of rare woods such as rosewood and ebony, and the handling properties were evaluated to be exactly the same.
In addition, the CNF molded body provided does not have any additives, etc., and after receiving feedback from professional musicians, we added various additives to improve water resistance, durability, slipperiness, workability, etc. It is possible to improve various qualities of

Claims (12)

Cellulose nanofiber (hereinafter referred to as CNF) containing slurry is put into a CNF molding device,
Applying pressure to the CNF-containing slurry using a gas permeable means,
A method for producing a CNF molded body, comprising a step of supplying a heated gas to the CNF molding device to obtain a first molded body. Put the CNF-containing slurry in the CNF molding device,
Applying pressure to the CNF-containing slurry using a gas permeable means,
A molding step of obtaining a first molded body by performing a step of supplying a heated gas to the CNF molding device;
CNF molded body including a solvent removal step of applying pressure to the first molded body using a gas permeable means and supplying heated gas to the CNF molding device to remove the solvent from the first CNF molded body. manufacturing method A method for producing a CNF molded body according to claim 1,
In the molding step and the solvent removal step,
Furthermore, the manufacturing method of a CNF molded object including performing the suction process which sucks the gas in the said CNF molding apparatus once or more. A method for producing a CNF molded body according to claim 1 or claim 2,
A method for producing a CNF molded body, wherein the CNF-containing slurry is divided two or more times and put into a CNF molding device. A method for producing a CNF molded body according to claim 1,
The density of the obtained CNF molded body is 1.41 to 1.61 g / cm ³ Method for producing a CNF molded body A method for producing a CNF molded body according to claim 2,
The density of the obtained CNF molded body is 1.38 to 1.45 g / cm ³ Method for producing a CNF molded body A method for producing a CNF molded body according to any one of claims 1 to 3,
The obtained CNF molded body can be processed by one or more of cutting, polishing, and drilling. Method for manufacturing a CNF molded body A CNF molded article obtained by the method for producing a CNF molded article according to any one of claims 1 to 7 The CNF molded article according to claim 8,
A CNF molded body having a thickness of 3 mm or more and 30 mm or less and a density of 1.38 g/cm ³ or more and 1.61 g/cm ³ or less. The CNF molded article according to claim 8,
The thickness of the CNF molded body is 3 mm or more and 30 mm or less, the density of the CNF molded body is 1.38 g/cm ³ or more and 1.61 g/cm ³ or less, and it is processed by any one of cutting, polishing, and piercing. CNF molded body that can be processed as above The CNF molded article according to any one of claims 8 to 10 , for use as a substitute material for any one or more of ivory, bone, precious wood, building members, machine members, furniture members, and tea ceremony utensils. CNF molded body according to any one of claims 8 to 10 for use as an acoustic material

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