JPWO2018220759A1 - Method for producing cellulose nanofiber film - Google Patents

Abstract

The method for producing a cellulose nanofiber film according to an embodiment includes a mist forming step of misting a cellulose nanofiber dispersion solution containing cellulose nanofibers and a solvent for diluting the cellulose nanofibers to obtain a raw material solution mist, and the raw material solution mist And applying the raw material solution mist on the surface of the substrate to form a raw material solution liquid film, baking the raw material solution liquid film, and drying the cellulose nanofiber film on the surface of the substrate And a peeling step of peeling the formed cellulose nanofiber film from the substrate.

Description

  Embodiments of the present invention relate to a method for producing a cellulose nanofiber film.

  Cellulose nanofibers (hereinafter referred to as CNF) can be made from plants, cysts, algae, bacteria, and the like, and thus are abundant in resources. CNF has a chemical processing method and a physical processing method. Chemical treatment methods include TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) catalyzed oxidation method, cationization method, acid hydrolysis method, enzyme treatment method, etc. There are homogenizer method, grinder method, biaxial kneading method and so on.

  CNF has a diameter of several nm to several tens of nm and a length of several hundred nm to several μm. CNF has excellent properties such as light weight (density is one fifth that of steel), high strength (more than 5 times that of steel), and low linear thermal expansion (equivalent to quartz glass).

  CNF has excellent performance, and since the film made of CNF is transparent, it can be used for transparent sheets, gas barrier films and the like.

  The CNF film production method includes a solvent casting method, a melt extrusion method, and a suction filtration method. The solvent casting method and the melt extrusion method are disclosed in Patent Document 1, and the suction filtration method is disclosed in Patent Document 2.

JP 2014-24928 A Japanese Patent Laying-Open No. 2015-40358

  In the melt extrusion method disclosed in Patent Document 1, a film precursor containing CNF and, if necessary, an additive is melted at a high temperature, and the resulting melt is extruded onto a casting support. This is a method of forming a film.

  On the other hand, the solvent casting method is a method in which a dope is prepared by dissolving CNF and, if necessary, an additive in a solvent, and the obtained dope is cast on a metal support and dried.

  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, the aqueous dispersion is stored, subjected to suction filtration, and dehydrated and dried.

  However, in the melt extrusion method, solvent casting method, and suction filtration method, it is necessary to cast the melt or perform suction filtration, so that it is difficult to adjust the thickness of the CNF film and the drying time is long. It was.

  An 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 forming method.

  According to an embodiment of the present invention, a mist forming step of misting a cellulose nanofiber dispersion solution containing cellulose nanofibers and a solvent for diluting the cellulose nanofibers to obtain a raw material solution mist, and supplying the raw material solution mist, Applying the raw material solution mist on the surface of the substrate to form a raw material solution liquid film; firing the raw material solution liquid film; and drying to form a cellulose nanofiber film on the surface of the substrate There is provided a method for producing a cellulose nanofiber film having a film forming step and a peeling step of peeling the formed cellulose nanofiber film from the substrate.

  According to the manufacturing method of the cellulose nanofiber film of the embodiment, after forming the raw material solution liquid film on the surface of the substrate by applying the raw material solution mist, the raw material solution liquid film is baked and dried by a baking / drying mechanism. A film containing a predetermined raw material is formed on the surface of the substrate. At this time, a CNF dispersion solution is used as a raw material solution.

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

It is typical explanatory drawing which illustrates the mist coating film-forming apparatus concerning an embodiment. It is a top view which shows the bottom face structure of the mist application | coating head of FIG. It is a flowchart which illustrates the manufacturing method of the CNF film by the mist coating film-forming apparatus of FIG. It is explanatory drawing which shows typically the state on the surface of a board | substrate at the time of execution of the mist coating film-forming method of this Embodiment. It is explanatory drawing which shows typically the positional relationship of the head bottom face with respect to a board | substrate.

Embodiments of the present invention will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
Note that, in the present specification and each drawing, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

(First embodiment, mist coating film forming apparatus)
FIG. 1 is an explanatory view schematically showing a configuration of a mist coating film forming apparatus 100 according to the present embodiment. As shown in the figure, the mist coating film forming apparatus 100 of the present embodiment has a raw material solution mist forming mechanism 50, a mist coating mechanism 70, and a baking / drying mechanism 90 as main components.

  The raw material solution mist generating mechanism 50 executes a raw material solution mist generation process. In the raw material solution mist processing, the raw material solution mist 6 is generated by misting (atomization). By using the ultrasonic transducer 1 that generates ultrasonic waves, the raw material solution 5 put in the mist container 4 is a liquid having a narrow center particle size of about 4 μm and a particle size distribution (σ is ± 20% or less). Can be misted into drops. The raw material solution mist 6 is conveyed to the mist coating mechanism 70 via the mist supply line 22 by the carrier gas supplied from the carrier gas supply unit 16.

  The mist coating mechanism 70 performs a raw material solution mist coating process. In the raw material solution mist coating process, the raw material solution mist 6 supplied via the mist supply line 22 is coated on the surface of a substrate 9 (film formation target substrate) to form a raw material solution liquid film. . In the raw material solution mist coating process, the raw material solution mist 6 is supplied from the mist coating head 8 onto the surface of the substrate 9 (film formation target substrate) placed on the moving stage 10 (mounting unit).

  The firing / drying mechanism 90 executes a firing / drying process. The firing / drying process is a process of forming a film using the CNF raw material contained in the raw material solution liquid film as a constituent material on the surface of the substrate 9. In the baking / drying process, the substrate 9 having the raw material solution liquid film formed on the surface is baked and dried on the hot plate 13 to evaporate the solvent of the raw material solution liquid film.

(Raw material mist mechanism 50)
In the raw material solution mist making mechanism 50, the ultrasonic vibrator 1 oscillates at a frequency set within a range of 1.5 to 2.5 MHz, for example. Water 3 is introduced into a water tank 2 provided on the ultrasonic vibrator 1 as an ultrasonic propagation medium. By driving the ultrasonic vibrator 1 at a set oscillation frequency, the raw material solution 5 put into the mist container 4 is misted (atomized). The misted raw material solution 5 is a raw material solution mist 6 including micrometer-sized droplets having a narrow particle size distribution (σ is ± 20%) with a central particle size of about 4 μm.

  As the raw material solution 5, a low viscosity raw material solution is assumed. The low viscosity raw material solution is diluted with a solvent such as acetone, methyl ethyl ketone, methylene chloride, 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. In this case, the raw material solution 5 is obtained by diluting with a solvent such as acetone, methyl ethyl ketone, methanol, or water.

  The CNF dispersion solution is a solution in which CNF floats and does not dissolve in a fibrous material having a fiber diameter of 3 nm or more and 70 nm or less in a solvent such as water or alcohol.

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

  Nitrogen gas or air is mainly used as the carrier gas, and the raw material solution mist 6 is conveyed. The carrier gas flow rate is controlled to 2 to 10 (L / min) by the mist control unit 35. The valve 21b is a valve for adjusting the carrier gas flow rate. The valve 21 b is provided in the carrier gas introduction line 21.

  The mist control unit 35 controls the flow rate of the carrier gas supplied from the carrier gas supply unit 16 by controlling the degree of opening and closing of the valve 21b. The mist control unit 35 controls the opening and closing of the ultrasonic oscillation circuit of the ultrasonic transducer 1 and the opening and closing of the ultrasonic oscillation circuit for ultrasonic transducers having different ultrasonic frequencies as well as the control of the carrier gas flow rate. To do.

(Mist application mechanism 70)
The mist application mechanism 70 has the mist application head 8 and the film forming substrate 9 placed on top. The mist application mechanism 70 includes a movable stage 10 (mounting unit) that can move under the control of the movement control unit 37 as a main component.

  FIG. 2 is a plan view showing the bottom structure of the mist application head 8. FIG. 2 shows the XY coordinate axes. As shown in the figure, a slit-like mist outlet 18 having a longitudinal direction in the Y direction (predetermined direction) is formed on the head bottom surface 8 b of the mist application head 8.

  The substrate 9 is placed so that the surface thereof faces the head bottom surface 8 b of the mist application head 8. That is, the substrate 9 is placed below the head bottom surface 8b. In FIG. 2, a virtual plane position of the substrate 9 is indicated by a broken line. In the drawing, the substrate 9 has a long side in the X direction and a short side in the Y direction.

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

  For example, the raw material solution mist 6 rectified in the mist application head 8 is supplied from the mist ejection port 18 while the substrate 9 is moved along the X direction (short direction of the mist ejection port 18) by the moving stage 10. Thus, the raw material solution mist 6 can be applied to almost the entire surface of the substrate 9 to form a liquid film of the raw material solution on the surface of the substrate 9. The mist outlet 18 is formed in a slit shape. Therefore, by adjusting the formation length of the mist application head 8 in the longitudinal direction (Y direction, predetermined direction), the short side width is not limited to the short side width of the substrate 9 that is a film forming substrate. It can also be applied to the substrate 9. Specifically, by providing the mist application head 8 with a width in the longitudinal direction that matches the assumed maximum short side width of the substrate 9, the formation length of the mist ejection port 18 is substantially equal to the maximum short side width of the substrate 9. Can be matched.

  The moving stage 10 has a substrate 9 placed on the top thereof. The moving stage 10 can move along the X direction under the control of the movement control unit 37 while being 2 to 5 mm away from the head bottom surface 8 b of the mist application head 8. Thereby, the raw material solution mist 6 can be applied on almost 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 raw material solution liquid film can be adjusted by changing the moving speed of the moving stage 10 by the movement control unit 37.

  That is, the movement control unit 37 moves the moving stage 10 along a moving direction (X direction in FIG. 2) that matches the short direction of the mist ejection port 18 of the mist application head 8, and moves along the moving direction. 10 moving speeds are variably controlled.

  Further, the mist application head 8 and the moving stage 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 discharged to the atmosphere after being processed by an exhaust processing device (not shown) through the exhaust gas output line 23. The valve 23b is a valve provided in the exhaust gas output line 23.

  The substrate 9 on which the raw material solution liquid film is formed may be moved collectively to the next step by batch processing, or may be moved to the next step together with the moving stage 10 to be a continuous manufacturing step. .

(Baking and drying mechanism 90)
The firing / drying mechanism 90 has a hot plate 13 provided in the firing / drying chamber 14 as a main component. By applying the raw material solution mist 6 using the mist application mechanism 70, the substrate 9 having the raw material solution liquid film formed on the surface is placed on the hot plate 13 in the baking / drying chamber 14.

  Using the hot plate 13, the substrate 9 on which the raw material solution liquid film is formed is baked and dried. By evaporating the solvent of the raw material solution liquid film formed by the applied raw material solution mist 6 by the baking / drying process, the raw material (predetermined raw material) itself contained in the raw material solution 5 is formed on the surface of the substrate 9 as a constituent material. A CNF film can be formed. In addition, the solvent vapor | steam of the raw material solution 5 produced | generated by baking / drying process is discharge | released to air | atmosphere after processing with the exhaust-gas treatment apparatus which is not shown in figure from the exhaust gas output line 24. FIG. The exhaust gas output line 24 is opened and closed by a valve 24b.

  In the example shown in FIG. 1, the firing / drying process is performed using the hot plate 13, but the firing / drying mechanism 90 is configured so as to supply hot air into the firing / drying chamber 14 without using the hot plate 13. May be configured.

(2nd Embodiment, the manufacturing method of a CNF film)
FIG. 3 is a flowchart showing a CNF film forming procedure of the mist coating film forming method shown in FIG. FIG. 4 is an explanatory view schematically showing a state on the surface of the substrate 9 during execution of the mist coating film forming method. Hereinafter, the processing procedure of the mist coating film forming method will be described with reference to FIGS.

  In step S1, a raw material solution mist generating mechanism 50 generates a droplet-shaped raw material solution mist 6 by making the raw material solution 5 in the mist container 4 mist by using the ultrasonic vibrator 1 by the raw material solution mist generating mechanism 50. Execute. Hereinafter, a case where a CNF dispersion solution is used as the raw material solution 5 will be described.

  Specifically, two ultrasonic vibrators 1 that vibrate a 0.4 wt% (weight percent) CNF dispersion solution that is the raw material solution 5 at 1.6 MHz (only one ultrasonic vibrator 1 is shown in FIG. 1). To mist the raw material solution 5. A nitrogen carrier gas having a carrier gas flow rate of 2 L / min is supplied from the carrier gas supply unit 16. Thus, the raw material solution mist 6 generated in the mist container 4 can be conveyed to the mist application head 8 in the mist application mechanism 70 via the mist supply line 22.

  As described above, the mist control unit 35 serving as the atomization control unit sets the number of operating transducers among the plurality of ultrasonic transducers 1 to adjust the opening / closing of the ultrasonic oscillation circuit, and the carrier gas supply unit 16. The carrier gas flow rate of the carrier gas supplied from is controlled. Thereby, the raw material solution mist 6 can be supplied to the mist coating head 8 in the mist coating mechanism 70 with high accuracy.

  Next, in step S <b> 2, the raw material solution mist 6 is supplied from the mist outlet 18 of the mist application head 8 by the mist application mechanism 70. A substrate 9 that is a substrate to be coated is placed on a moving stage 10. In the mist application mechanism 70, the raw material solution mist 6 is applied on the surface of the substrate 9 placed thereon. As shown in FIG. 4A, a raw material solution mist coating process for forming a raw material solution liquid film 61 (raw material solution liquid film) on the surface of the substrate 9 is executed.

  Specifically, the raw material solution mist 6 rectified in the mist coating head 8 is supplied to the surface of the substrate 9 through a mist ejection port 18 formed in a slit shape, whereby the raw material solution mist coating process is executed.

  The substrate 9 placed (set) on the moving stage 10 is present at a position 2 mm to 5 mm below the head bottom surface 8b. By moving (scanning) the moving stage 10 in the X direction in FIG. 2 under the control of the movement control unit 37, a raw material solution liquid film 61 is formed on the entire surface of the substrate 9 by applying the raw material solution mist 6. The The movement control unit 37 can variably control the moving speed of the moving stage 10 in the range of 1 to 50 (mm / sec).

  In order to apply the raw material solution mist 6 to form the raw material solution liquid film 61 on the surface of the substrate 9, the raw material solution mist 6 needs to be well wetted (enhance wettability) on the surface of the substrate 9. In order for the raw material solution mist 6 to wet well 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, the surface tension of the raw material solution mist 6 can be reduced by diluting the solvent water with a solvent such as methyl ethyl ketone, ethyl acetate, toluene, acetone, benzene, or methanol. At the same time, the surface tension of the substrate 9 can be increased by hydrophilizing the surface of the substrate 9. As a result, the wettability of the applied raw material solution mist 6 on the surface of the substrate 9 is increased, so that a liquid raw material solution liquid film 61 can be formed on the surface of the substrate 9.

  In this way, by using a solvent capable of decomposing CNF in the raw material solution 5 and having a low surface tension and subjecting the surface of the substrate 9 to hydrophilic treatment, the applied raw material solution mist 6 is well wetted on the surface of the substrate 9 and the raw material solution A liquid film 61 is formed. Further, by moving only the moving stage 10 on which the substrate 9 is placed while the mist coating head 8 is fixed, the raw material solution mist 6 is coated on the surface of the substrate 9, so that the surface of the substrate 9 can be relatively easily applied. The raw material solution liquid film 61 can be formed.

  FIG. 5 is an explanatory diagram schematically showing the positional relationship of the head bottom surface 8 b with respect to the substrate 9. In the figure, the XZ coordinate axes are also shown. As shown in the figure, by providing an inclination θ with respect to the surface formation direction of the substrate 9 (X direction in FIG. 5), the raw material solution is obliquely inclined by an angle θ from the perpendicular L9 of the substrate 9 from the mist outlet 18. Mist 6 can be ejected.

  In this way, by providing the head bottom surface 8b of the mist coating head 8 with an inclination θ with respect to the surface formation direction of the substrate 9, the raw material solution mist 6 due to the carrier gas flow rate from the carrier gas supply unit 16 strikes the surface of the substrate 9. The uniformity of the raw material solution liquid film 61 is improved by effectively suppressing the disturbance of the liquid film that occurs at the time so that the raw material solution mist 6 can be applied more uniformly on the surface of the substrate 9.

  Next, in step S <b> 3, the raw material solution liquid film 61 formed on the surface of the substrate 9 is baked and dried by the baking / drying mechanism 90. As shown in FIG. 4B, a transparent CNF film 62 having a thickness smaller than that of the raw material solution liquid film 61 and comprising a CNF raw material (predetermined raw material) itself contained in the CNF dispersion solution on the surface of the substrate 9 as a constituent material. A baking / drying process is performed to form the film.

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

  The CNF film 62 whose thickness can be adjusted can be formed on the surface of the substrate 9 in a short drying time by the mist coating film forming method according to the above steps S1 to S4.

  As described above, the mist coating film forming method according to the present embodiment that executes the mist coating film forming method including steps S1 to S4 shown in FIG. 3 is performed by using the mist coating mechanism 70 to convert the CNF dispersion solution as the raw material solution 5. The raw material solution mist 6 is applied and a raw material solution liquid film 61 is formed on the surface of the substrate 9. Then, the raw material solution liquid film 61 is fired and dried by the firing / drying mechanism 90 to form a functional CNF film having the raw material of the raw material solution 5 (predetermined raw material) as a constituent material on the surface of the substrate 9. Yes.

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

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims (8)

A misting step of misting a cellulose nanofiber dispersion solution containing cellulose nanofibers and a solvent for diluting the cellulose nanofibers to obtain a raw material solution mist;
An application step of supplying the raw material solution mist and applying the raw material solution mist on a surface of a substrate to form a raw material solution liquid film;
A film forming step of firing the raw material solution liquid film and drying to form a cellulose nanofiber film on the surface of the substrate;
A peeling step of peeling the formed cellulose nanofiber film from the substrate;
The manufacturing method of the cellulose nanofiber film which has this.   The method for producing a cellulose nanofiber film according to claim 1, wherein the solvent contains any one of methyl ethyl ketone, ethyl acetate, toluene, acetone, benzene, and methanol.   The method for producing a cellulose nanofiber film according to claim 2, wherein the surface of the substrate is hydrophilized.   The method for producing a cellulose nanofiber film according to claim 1, wherein the cellulose nanofiber has a fiber diameter in a range of a minimum of 3 nm and a maximum of 70 nm. The application step includes a step of applying the raw material solution mist through a mist application head having a mist outlet provided to face the surface of the substrate,
The method for producing a cellulose nanofiber film according to claim 1, wherein the mist ejection port is provided at a predetermined angle from a direction parallel to the surface of the substrate.   The method for producing a cellulose nanofiber film according to claim 1, wherein the raw material solution mist includes droplets having an average particle diameter of 4 μm. The application step includes a step of applying the raw material solution mist through a mist application head having a mist ejection port provided to face the surface of the substrate while moving the substrate,
The method for producing a cellulose nanofiber film according to claim 1, further comprising a step of moving the substrate coated with the raw material solution mist to the film forming step after the coating step.   The manufacturing method of the cellulose nanofiber film of Claim 7 which further has a winding-up process which winds up the peeled said cellulose nanofiber film after the said peeling process.

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