TWI650350B - Method of producing cellulose nanofiber film - Google Patents

Abstract

A method for producing a cellulose nanofiber membrane according to an embodiment of the present invention comprises: atomizing a cellulose nanofiber dispersion solution containing a cellulose nanofiber and a solvent for diluting the cellulose nanofiber to obtain a raw material solution a mist atomization step; a coating step of supplying the mist of the raw material solution and applying the mist of the raw material solution on the surface of the substrate to form a liquid film of the raw material solution; calcining the liquid film of the raw material solution to dry it, on the surface of the substrate a film forming step of forming a cellulose nanofiber film; and a peeling step of peeling the formed cellulose nanofiber film formed from the substrate.

Description

Method for producing cellulose nanofiber membrane

An embodiment of the present invention relates to a method for producing a cellulose nanofiber membrane.

Cellulose nanofibers (hereinafter, referred to as CNF) can be made of plants, tunicates, algae, bacteria, etc., and thus are very rich in resources. CNF has chemical processing methods and physical processing methods. The chemical treatment methods include TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) catalytic oxidation method, cationization method, acid hydrolysis method, enzyme treatment method, etc., and the physical treatment method has high pressure homogenization method, Grinding method, biaxial mixing method, and the like.

The CNF has a diameter ranging from several nanometers (nm) to several tens of nanometers and a length of several hundred nanometers to several micrometers (μm). CNF has superior properties such as light weight (one-fifth of the density of steel), high strength (more than five times that of steel), and low linear thermal expansion (equivalent to quartz glass).

Since CNF has excellent performance, the film manufactured by CNF is transparent, and is considered to be used in a transparent sheet, a gas barrier film, or the like.

The method for producing the CNF film includes a solvent casting method, a melt extrusion method, and a suction filtration method. Solvent casting method and melt extrusion method have been disclosed in Document 1, the suction filtration method has been disclosed in Patent Document 2.

[Previous Technical Literature] (Patent Literature)

Patent Document 1: Japanese Patent Laid-Open Publication No. 2014-24928

Patent Document 2: JP-A-2015-40358

The melt extrusion method disclosed in Patent Document 1 is a method in which a film precursor containing CNF and an optional additive is melted at a high temperature, and the obtained melt is extruded to be cast into a support for casting and formed into a film. .

On the other hand, the solvent casting method is a method in which CNF and an optional additive are dissolved in a solvent to prepare a dopant, and the obtained doping stream is cast and dried on a metal support.

The suction filtration method disclosed in Patent Document 2 is a method in which CNF is dispersed in an aqueous medium to prepare an aqueous dispersion, and the aqueous dispersion is retained and subjected to suction filtration and dehydration drying.

However, in the melt extrusion method, the solvent casting method, and the suction filtration method, it is necessary to cast or suction-filter the molten stream, and thus it is difficult to adjust the thickness of the CNF membrane and to have a long drying time.

The object of the present embodiment is to solve the above problems and to provide a method for producing a CNF film by a mist coating film formation method.

According to an embodiment of the present invention, a fiber is provided A method for producing a sonic fiber membrane, comprising: atomizing a cellulose nanofiber dispersion solution containing a cellulose nanofiber and a solvent for diluting the cellulose nanofiber to obtain a mist of a raw material solution mist a step of applying a mist of the raw material solution and applying a mist of the raw material solution on a surface of the substrate to form a liquid film of the raw material solution; calcining the liquid film of the raw material solution to dry it, and forming a cellulose naphthalene on the surface of the substrate a film forming step of the rice fiber membrane; and a peeling step of peeling the formed cellulose nanofiber membrane from the substrate.

According to the method for producing a cellulose nanofiber membrane of the embodiment, after the raw material solution mist is formed on the surface of the substrate to form a raw material solution liquid film, the raw material solution liquid film is calcined/dried on the surface of the substrate by a calcination/drying mechanism. A film containing a specific raw material is formed thereon. At this time, a CNF dispersion solution was used as a raw material solution.

As a result, in the method for producing a cellulose nanofiber membrane of the embodiment, the thickness of the film which is a constituent material of the specific raw material contained in the cellulose nanofiber dispersion solution can be arbitrarily adjusted, and the drying time can be shortened. A cellulose nanofiber membrane can be formed on the surface of a substrate having good uniformity.

1‧‧‧Supersonic oscillator

2‧‧‧Sink

3‧‧‧ water

4‧‧‧Atomizing container

5‧‧‧ raw material solution

6‧‧‧Material solution fog

8‧‧‧Mist coating head

8b‧‧‧The bottom of the head of the mist coating head

9‧‧‧Substrate

10‧‧‧Mobile Station

11‧‧‧Mist coating room

13‧‧‧heating plate

14‧‧‧calcining/drying room

16‧‧‧Carrier Gas Supply Department

18‧‧‧Fog spray

21‧‧‧ Carrier gas introduction line

21b, 23b, 24b‧‧‧ valves

22‧‧‧Fog supply line

23, 24‧‧‧ exhaust output line

35‧‧‧Fog Control Department

37‧‧‧Mobile Control Department

50‧‧‧Material solution atomization mechanism

61‧‧‧ raw material solution liquid film

62‧‧‧CNF film

70‧‧‧Mist coating mechanism

90‧‧‧calcining/drying mechanism

100‧‧‧Mist coating film forming device

Fig. 1 is a schematic view showing a mist coating film forming apparatus of an embodiment.

Fig. 2 is a plan view showing the structure of the bottom surface of the mist coating head of Fig. 1.

Fig. 3 is a view showing a method of manufacturing a CNF film by a mist coating film forming apparatus flow chart.

Fig. 4 is a schematic view showing a state on the surface of the substrate when the mist coating film forming method of the present embodiment is carried out.

Fig. 5 is a schematic view showing the positional relationship of the bottom surface of the head of the mist coating head with respect to the substrate.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings.

In addition, the drawings are schematic or conceptual drawings, and the relationship between the thickness and the width of each portion, the dimensional ratio between the portions, and the like are not necessarily limited to the same as the actual articles. Further, even if the same portions are shown, there are cases in which the sizes or ratios of the respective portions are different.

In the present specification and the drawings, the same components as those described above are denoted by the same reference numerals, and the detailed description is omitted as appropriate.

(First embodiment, mist coating film forming apparatus)

Fig. 1 is a schematic view showing the configuration of the mist coating film forming apparatus 100 of the present embodiment. As shown in the figure, the mist coating film forming apparatus 100 of the present embodiment has a raw material solution atomizing mechanism 50, a mist applying mechanism 70, and a calcining/drying mechanism 90 as main constituent elements.

The raw material solution atomization mechanism 50 performs a raw material solution mist generation process. The atomization treatment of the raw material solution is subjected to atomization to produce a mist 6 of the raw material solution. By using the ultrasonic oscillator 1 that generates ultrasonic waves, The raw material solution 5 charged in the atomization container 4 is atomized to have a droplet having a center particle diameter of about 4 μm and a particle size distribution (σ is ±20% or less). The raw material solution mist 6 is transported to the mist application mechanism 70 via the mist supply line 22 via the carrier gas supplied from the carrier gas supply unit 16 .

The mist application mechanism 70 performs a mist coating processing of a raw material solution. In the raw material solution mist coating treatment, the raw material solution mist 6 supplied through the mist supply line 22 is coated on the surface of the substrate 9 (substrate to be coated) to form a raw material solution liquid film. In the raw material solution mist coating treatment, the raw material solution mist 6 is supplied from the mist coating head 8 to the surface of the substrate 9 (substrate on which the film formation target) is carried on the moving table 10 (bearing portion).

The calcination/drying mechanism 90 performs a calcination/drying treatment. The calcination/drying treatment is a treatment in which a CNF raw material contained in a liquid film of a raw material solution is formed on a surface of the substrate 9 as a constituent material. In the calcination/drying treatment, the substrate 9 on which the raw material solution liquid film is formed on the surface is calcined/dried on the hot plate 13, and the solvent of the raw material solution liquid film is evaporated.

(raw material solution atomization mechanism 50)

In the raw material solution atomizing mechanism 50, the ultrasonic oscillator 1 is oscillated, for example, at a frequency set in the range of 1.5 to 2.5 MHz. The water tank 3 on which the ultrasonic oscillator 1 is placed is introduced into the water 3 as an ultrasonic wave propagation medium. The raw material solution 5 introduced into the atomization container 4 is atomized by driving the ultrasonic oscillator 1 at a set oscillation frequency. The atomized raw material solution 5 is a raw material solution mist 6 containing micron-sized droplets having a center particle diameter of about 4 μm and having a narrow particle size distribution (σ of ±20% or less).

Further, the raw material solution 5 is assumed to be a low-viscosity raw material solution. The low viscosity raw material solution may be diluted with a solvent such as acetone, methyl ethyl ketone, dichloromethane, methanol, toluene, water, hexane, methyl acetate, ethyl acetate, vinyl acetate or ethyl chloride.

Consider the case where the raw material solution 5 is a CNF dispersion solution. At this time, the raw material solution 5 can be obtained by diluting with a solvent such as acetone, methyl ethyl ketone, methanol or water.

Further, the CNF dispersion solution is a fibrous material having a fiber diameter of 3 nm or more and 70 nm or less, and is a solution in which the CNF is floating insoluble in a solvent such as water or ethanol.

The carrier gas system supplied from the carrier gas supply unit 16 is supplied into the atomization container 4 from the carrier gas introduction line 21. Thereby, the droplet-form raw material solution mist 6 atomized in the internal space of the atomization container 4 is conveyed to the mist application head 8 of the mist application mechanism 70 via the mist supply line 22.

In the carrier gas, nitrogen or air is mainly used to transport the raw material solution mist 6. The carrier gas flow rate is controlled by the mist control unit 35 at 2 to 10 (L/min). Valve 21b is used to adjust the carrier gas flow. The valve 21b is provided on the carrier gas introduction line 21.

The mist control unit 35 controls the degree of opening and closing of the valve 21b and controls the flow rate of the carrier gas supplied from the carrier gas supply unit 16. The mist control unit 35 controls the opening and closing of the ultrasonic oscillation circuit of the ultrasonic oscillator 1 or the opening and closing of the ultrasonic oscillation circuit for the ultrasonic ultrasonic oscillator having different ultrasonic frequencies while controlling the flow rate of the carrier gas.

(Mist coating mechanism 70)

The mist application mechanism 70 is configured to carry the mist application head 8 and the film formation substrate 9 on the upper portion. The mist application mechanism 70 has a mobile station 10 (bearing portion) that is movable under the control of the movement control unit 37 as a main constituent element.

Fig. 2 is a plan view showing the structure of the bottom surface of the mist coating head 8. Figure 2 shows the XY coordinate axis. As shown in the figure, a mist discharge port 18 having a slit shape in the Y direction (predetermined direction) as a longitudinal direction is formed on the head bottom surface 8b of the mist application head 8.

The substrate 9 is placed such that its surface faces the head bottom surface 8b of the mist coating head 8. That is, the substrate 9 is placed on the lower side of the head bottom surface 8b. In Fig. 2, the assumed planar position of the substrate 9 is indicated by a broken line. In the figure, the substrate 9 has a side in the X direction of the long side and a side in the Y direction of the short side.

As shown in Fig. 2, the mist discharge port 18 is provided on the head bottom surface 8b. The mist discharge port 18 is provided in a slit shape in which the short side direction (Y direction) of the substrate 9 is a longitudinal direction. The formation length (length in the Y direction) of the mist discharge port 18 is set to be the same as the width of the short side of the substrate 9.

For example, while the substrate 9 is moved in the X direction (the short side direction of the mist discharge port 18) by the moving table 10, the raw material solution mist 6 rectified in the mist coating head 8 is supplied from the mist discharge port 18. Thereby, the raw material solution mist 6 can be applied substantially uniformly on the surface of the substrate 9, and a liquid film of the raw material solution can be formed on the surface of the substrate 9. The mist discharge port 18 is formed in a slit shape. Therefore, by adjusting the formation length of the longitudinal direction (Y direction, predetermined direction) of the mist application head 8, the short side width of the substrate 9 as the substrate for film formation is made wide. The degree is not limited, and can also be applied to the substrate 9 having a wide width of the short side. Specifically, by making the mist application head 8 have a width in the longitudinal direction that coincides with the maximum short side width of the assumed substrate 9, the length of formation of the mist discharge port 18 can almost coincide with the maximum short side width of the substrate 9.

The mobile station 10 carries the substrate 9 at its upper portion. The mobile station 10 is separated from the head bottom surface 8b of the mist application head 8 by 2 to 5 mm, and is movable in the X direction under the control of the movement control unit 37. Thereby, the raw material solution mist 6 can be applied to substantially the entire surface of the substrate 9, and a raw material solution liquid film can be formed on the surface of the substrate 9.

At this time, the thickness of the liquid film of the raw material solution can be adjusted by changing the moving speed of the mobile station 10 by the movement control unit 37.

In other words, the movement control unit 37 moves the moving table 10 in the moving direction (the X direction in FIG. 2) that coincides with the short-side direction of the mist ejection port 18 of the mist application head 8, and variably controls the movement direction. The moving speed of the mobile station 10.

Further, the mist coating head 8 and the moving table 10 are provided in the mist application chamber 11. The mixed gas of the solvent vapor and the carrier gas of the raw material solution mist 6 volatilized in the mist coating chamber 11 is treated by an exhaust gas treatment device (not shown) and then released into the atmosphere. Further, the valve 23b is a valve provided to the exhaust gas output line 23.

The substrate 9 on which the liquid film of the raw material solution is formed can be moved to the next step by batch processing, or can be moved to the next step with the mobile station 10 to carry out a continuous manufacturing step.

(calcining/drying mechanism 90)

The calcination/drying mechanism 90 has a heating plate 13 provided in the calcination/drying chamber 14 as a main structure. In the calcination/drying chamber 14, the substrate 9 on which the raw material solution liquid film is formed by applying the raw material solution mist 6 by using the mist application mechanism 70 is carried on the heating plate 13.

The substrate 9 on which the liquid film of the raw material solution is formed on the surface is subjected to calcination/drying treatment using the heating plate 13. By the calcination/drying treatment, the solvent of the raw material solution liquid film formed by the application of the raw material solution mist 6 is evaporated, and the raw material (specific raw material) contained in the raw material solution 5 can be formed as a constituent material on the surface of the substrate 9. The CNF membrane. Further, the solvent vapor of the raw material solution 5 generated by the calcination/drying treatment is treated by an exhaust gas treatment device (not shown), and then released into the atmosphere from the exhaust gas output line 24. The exhaust output line 24 is opened and closed by a valve 24b.

Further, in the example shown in Fig. 1, the calcination/drying treatment is performed using the hot plate 13, but the calcination/drying mechanism 90 may be configured to supply hot air in the calcination/drying chamber 14 without using the hot plate 13. .

(Second embodiment, method for producing CNF film)

Fig. 3 is a flow chart showing the procedure for forming a CNF film by the mist coating film forming method shown in Fig. 1. Fig. 4 is a schematic view showing a state on the surface of the substrate 9 when the mist coating film formation method is carried out. Hereinafter, the processing procedure of the mist coating film formation method will be described with reference to Figs. 3 and 4 .

In step S1, the raw material solution in the atomization container 4 is made by the ultrasonic wave oscillator 1 by the raw material solution atomization mechanism 50. 5 A mist of a raw material solution which is atomized and produces a droplet-like raw material solution mist 6 is formed. Hereinafter, a case where a CNF dispersion solution is used as the raw material solution 5 will be described.

Specifically, the two ultrasonic oscillators 1 (only one ultrasonic oscillator 1 is shown in FIG. 1) are driven to atomize the raw material solution 5, which is used as the CNF of the raw material solution 5. 0.4 wt% (% by weight) of the dispersion solution was shaken at 1.6 MHz. A nitrogen carrier gas system having a carrier gas flow rate of 2 L/min is supplied from the carrier gas supply unit 16. Thereby, the raw material solution mist 6 generated in the atomization container 4 can be transported to the mist application head 8 in the mist application mechanism 70 via the mist supply line 22.

In this manner, the mist control unit 35 as the atomization control unit sets the number of oscillators that operate in the plurality of ultrasonic oscillators 1 to adjust the opening and closing of the ultrasonic oscillation circuit, and controls the supply from the carrier gas supply unit 16. The carrier gas flow rate of the carrier gas. Thereby, the raw material solution mist 6 can be accurately supplied to the mist application head 8 in the mist application mechanism 70.

Next, in step S2, the raw material solution mist 6 is supplied from the mist discharge port 18 of the mist application head 8 by the mist application mechanism 70. The substrate 9 as a substrate to be coated is carried on the mobile station 10. In the mist application mechanism 70, the raw material solution mist 6 is applied onto the surface of the substrate 9 to be carried. As shown in Fig. 4(a), a raw material solution mist coating treatment for forming a raw material solution liquid film 61 (raw material solution liquid film) is performed on the surface of the substrate 9.

Specifically, the raw material solution mist 6 that has been rectified in the mist coating head 8 is supplied to the surface of the substrate 9 through the mist discharge port 18 formed in a slit shape, whereby the raw material solution mist coating treatment is performed.

The substrate 9 carried (placed) on the mobile station 10 is stored It is located at a position 2 mm to 5 mm below the bottom surface 8b of the spacer head. Under the control of the movement control unit 37, the mobile station 10 is moved (scanned) in the X direction of FIG. 2, whereby the raw material solution liquid film 61 on which the raw material solution mist 6 is applied is formed substantially entirely on the surface of the substrate 9. Further, the moving speed of the mobile station 10 can be variably controlled in the range of 1 to 50 (mm/sec) by the movement control unit 37.

In order to apply the raw material solution mist 6 on the surface of the substrate 9 and form the raw material solution liquid film 61, it is necessary to sufficiently wet the raw material solution mist 6 on the surface of the substrate 9 (improving the wettability). In order to sufficiently wet the raw material solution mist 6 on the surface of the substrate 9, it is necessary to reduce the surface tension of the raw material solution mist 6 and increase the surface tension of the substrate 9. Since the raw material solution 5 is a CNF dispersion solution, the solvent water is diluted with a solvent such as methyl ethyl ketone, ethyl acetate, toluene, acetone, benzene or methanol to reduce the surface tension of the raw material solution mist 6. At the same time, the surface tension of the substrate 9 can be increased by performing the hydrophilization treatment on the surface of the substrate 9. As a result, the wettability on the surface of the substrate 9 on which the raw material solution mist 6 is applied is improved, and a liquid raw material solution liquid film 61 can be formed on the surface of the substrate 9.

In this manner, by using a solvent which decomposes CNF and has a small surface tension in the raw material solution 5, and hydrophilization treatment of the surface of the substrate 9, the coated raw material solution mist 6 is sufficiently wetted on the surface of the substrate 9 to form a raw material solution liquid. Membrane 61. Moreover, by fixing the mist coating head 8, only the moving stage 10 of the carrier substrate 9 is moved, and the raw material solution mist 6 is applied onto the surface of the substrate 9, whereby the raw material solution liquid film 61 can be formed relatively easily on the surface of the substrate 9.

Fig. 5 is a schematic view showing the positional relationship of the head bottom surface 8b with respect to the substrate 9. In Figure 5, the XZ coordinate axis is also displayed. As shown in the figure As shown in the drawing, the direction of the surface formation of the substrate 9 (the X direction of FIG. 5) has an inclination θ angle, and the raw material solution mist 6 can be ejected from the mist ejection port 18 in a direction inclined by θ from the vertical line L9 of the substrate 9. .

In this manner, by making the head bottom surface 8b of the mist application head 8 have an inclination θ angle with respect to the surface forming direction of the substrate 9, the raw material solution mist 6 can be effectively controlled to contact the substrate due to the carrier gas flow rate of the carrier gas supply portion 16. The liquid film generated at the surface of 9 is disordered, and the raw material solution mist 6 can be more uniformly applied on the surface of the substrate 9, and the uniformity of the raw material solution liquid film 61 can be improved.

Next, in step S3, the raw material solution liquid film 61 formed on the surface of the substrate 9 is calcined/dried by the calcination/drying mechanism 90. As shown in FIG. 4(b), a calcination/drying treatment for forming a CNF film 62 which is a constituent material of a CNF raw material (specific raw material) contained in a CNF dispersion solution is performed on the surface of the substrate 9. It is thinner and transparent than the thickness of the raw material solution liquid film 61.

In step S4, the CNF film 62 formed on the surface of the substrate 9 is peeled off from the substrate 9 by a peeling mechanism (not shown) such as FIG. By using the ceramic substrate as the substrate 9, the formed CNF film 62 can be easily peeled off. The peeled CNF film 62 can be wound around the drum by, for example, a winder.

By the mist coating film forming method of the above steps S1 to S4, the CNF film 62 capable of adjusting the thickness can be formed on the surface of the substrate 9 with a short drying time.

In this way, implementing step S1 shown in FIG. 3 is performed. The mist coating film forming method of the present embodiment in the mist coating film forming method of S4 is a film coating device 70 that uses a CNF dispersion solution as a raw material solution 5, and applies a raw material solution mist 6 to form a surface of the substrate 9. Raw material solution liquid film 61. In addition, the raw material solution liquid film 61 is calcined/dried by the calcination/drying mechanism 90, and a functional CNF film using the raw material (specific raw material) of the raw material solution 5 as a constituent material is formed on the surface of the substrate 9.

As a result, the mist coating film forming method of the present embodiment can form the CNF film which is a constituent material of the raw material solution 5 contained in the CNF dispersion solution as a constituent material on the surface of the substrate 9 with good uniformity.

The embodiments of the present invention have been described above, but the embodiments are not intended to limit the scope of the present invention. The present invention may be embodied in various other forms, and various omissions, substitutions and changes can be made without departing from the scope of the invention. The scope of the invention and the modifications thereof are included in the scope and spirit of the invention, and are included in the scope of the invention described in the claims.

Claims (8)

A method for producing a cellulose nanofiber membrane, comprising: dissolving a cellulose nanofiber dispersion solution containing a cellulose nanofiber and a solvent for diluting the cellulose nanofiber to obtain a mist of a raw material solution; An atomization step; a coating step of supplying the mist of the raw material solution, applying a mist of the raw material solution on the surface of the substrate to form a liquid film of the raw material solution; calcining the liquid film of the raw material solution to dry it, and forming a fiber on the surface of the substrate a film forming step of the sonic fiber membrane; and a peeling step of peeling the formed cellulose nanofiber membrane from the substrate. The method for producing a cellulose nanofiber membrane according to the above aspect of the invention, wherein the solvent comprises any one of methyl ethyl ketone, ethyl acetate, toluene, acetone, benzene, and methanol. The method for producing a cellulose nanofiber membrane according to the second aspect of the invention, wherein the surface of the substrate is subjected to a hydrophilization treatment. The method for producing a cellulose nanofiber membrane according to the above aspect of the invention, wherein the cellulose nanofiber has a fiber diameter ranging from a minimum of 3 nm to a maximum of 70 nm. The method for producing a cellulose nanofiber film according to claim 1, wherein the coating step comprises: coating the raw material solution through a mist coating head having a mist discharge port disposed opposite to a surface of the substrate; a step of misting, wherein the mist ejection outlet is disposed to be parallel to a surface of the substrate The direction is at a specific angle. The method for producing a cellulose nanofiber membrane according to the above aspect of the invention, wherein the raw material solution mist comprises droplets having an average particle diameter of 4 μm. The method for producing a cellulose nanofiber film according to the first aspect of the invention, wherein the coating step includes: moving the substrate through a mist discharge port provided to face the surface of the substrate; The mist coating head applies a step of applying the mist of the raw material solution, and after the coating step, a step of moving the substrate coated with the mist of the raw material solution to the film forming step. The method for producing a cellulose nanofiber membrane according to claim 7, wherein the peeling step further comprises a winding step of winding the peeled cellulose nanofiber membrane.