JP2021159915A - Polymer composite thin film - Google Patents

Abstract

To provide a polymer composite thin film 1 comprising a high gas separation function by being formed extremely thin, by a more simplified structure in which, a nano film having flexible functionality and a nano support medium excellent in mechanical strength are combined (conjugated), and comprising practical structure stability (self standing properties).SOLUTION: There is provided a polymer composite thin film 1 in which, a polymer thin film 2 whose thickness is equal to or smaller than 100 nm is conjugated to a fibrous structure (cellulose nanofiber 3) having a diameter smaller than the thickness of the polymer thin film 2, therefore the polymer composite thin film having self standing properties, can be acquired.SELECTED DRAWING: Figure 1

Description

The present invention mainly relates to a polymer composite thin film containing a polymer material, particularly a polymer composite thin film having high functionality and significantly improved film strength.

Recently, interest in organic / inorganic nanofilms is increasing. In the inorganic system, the peculiar physical properties of Graphene, which is an inorganic carbon compound, have attracted worldwide attention, and international development competition has intensified at once. This tendency has further _{spread to other inorganic materials with nano-thickness such as MoS 2} , and now it has created a new research field as a two-dimensional material.

On the other hand, in organic systems, there is an enormous amount of research on biomembranes with nano-order thickness from a biochemical and biophysical standpoint. In addition, organic nanofilms as industrial materials can be expected to have unique characteristics as two-dimensional materials, but in order to promote practical application, it is necessary to realize large area, defect-free, independence, structural stability, etc. Become.

As an example of an organic nanomembrane as an industrial material, there are high expectations for the development of an excellent separation membrane utilizing the thickness of nanoorders. In order to maximize the separation function of the separation membrane, it is desirable to make the film thickness as thin as possible from the viewpoint of ensuring high permeability. However, in that case, there is a high possibility that the mechanical strength is lowered and the film becomes fragile and cannot be put into practical use. That is, there is a trade-off relationship between making the separation membrane thin from a functional point of view and mechanical strength. In order to solve this problem, it is considered effective to combine a functional film having a film thickness as thin as possible with a tough support and a skeletal structure that do not interfere with its function.

As a technique for such a polymer composite thin film, it is a gas separation membrane having a gas separation layer containing a crosslinked cellulose resin and cellulose nanofibers, and the crosslinked cellulose resin has a ^* −O in the crosslinked structure. -M-O- ^* , ^* -S-M-S- ^* , ^* -NR ^a C (= O)- ^* , ^* -NR ^b C (= O) NR ^{b- *} , ^* -O-CH _2- O- ^* , ^* -S- (CH ₂ ) ₂ -S- ^* , ^* -OC (= O) O- ^* , ^* -SO ₃ ^- N ⁺ (R ^c ) _3- ^* and ^* -P (= O) ^{) (OH) O - N +} (R d) 3 - at least one coupling structure is selected from the group consisting of ^* the gas separation layer contains 10ppm~5000ppm the organic solvent, the gas separation membrane (in the formula , M represents a 2- to 4-valent metal atom, and ^Ra , R ^b , R ^c and R ^d each independently represent a hydrogen atom or an alkyl group. ^{* Indicates} a linking site). .. (Patent Document 1)

According to Patent Document 1, by forming a gas separation membrane in which a gas separation layer is formed by using a crosslinked cellulose resin having a specific linking structure in the crosslinked structure, excellent gas permeability and excellent gas separation selectivity can be obtained. It also has excellent gas separation performance that is hard to plasticize even when used under high temperature, high pressure and high humidity conditions, and is not easily affected by toluene, which is an impurity component present in natural gas, and has good folding resistance. It is said that it can be excellently processed into various module forms, can be manufactured with a high yield, and can provide a gas separation membrane exhibiting stable gas separation performance from the initial stage of use.

Japanese Patent No. 6349026

However, according to the technique described in Patent Document 1, cellulose nanofibers may be added to the gas separation layer constituting the gas separation membrane, and the thickness of the gas separation layer is preferably 50 nm to 1 μm. However, it is premised that the gas separation layer containing the crosslinked cellulose resin is formed on the upper side of the gas permeable support layer (porous layer). More specifically, in the composite membrane having both the gas separation layer and the porous layer, a coating liquid (dope) containing a component (cellulose resin and a cross-linking agent) forming the gas separation layer is applied to at least the surface of the porous support. It is formed by applying. With such a configuration, the thickness of the gas separation membrane is 10 μm to 200 μm as a result.

That is, the gas separation layer described in Patent Document 1 functions as a gas separation membrane by being formed on the porous layer, and the gas separation layer having the thickness of the nanoorder is independently self-supporting and gas. There is no suggestion that it can form a separation membrane and that this gas separation membrane can exert a gas separation function.

Further, although the porous layer is composed of, for example, a porous membrane of an organic polymer, no mention is made of gas permeability in a portion other than the voids of the porous layer, and the porous layer is interposed. This may reduce the total gas permeability of the gas separation membrane.

Further, the gas separation membrane described in Patent Document 1 uses a specific metal complex as a cross-linking agent in order to form the gas separation layer with a cross-linked cellulose resin having a specific linking structure in the cross-linked structure, and uses a specific metal complex as a cross-linking agent. A metal crosslink is formed by the ligand exchange reaction between the two. In this case, the concentration of the cellulose resin in the coating liquid and the metal complex as a cross-linking agent is kept below a certain level to suppress the ligand exchange reaction in the coating liquid, and the coating liquid is further thinned on the porous support layer. By coating, the ligand exchange reaction rapidly proceeds with the rapid evaporation of the solvent, and a metal crosslinked structure is formed in the cellulose resin. Therefore, the microstructure of the gas separation layer becomes complicated, and as a result, the manufacturing process becomes complicated.

The present invention has been devised to solve the problems of the prior art, and rather than combining (compositing) a nanofilm having flexible functionality and a nanosupport having excellent mechanical strength. It is an object of the present invention to provide a polymer composite thin film having a simple structure and an extremely thin structure, which is highly functional and has practical structural stability (independence).

The present invention made to solve the above problems is self-sustaining because a polymer thin film having a film thickness of 100 nm or less is composited with a fibrous structure having a diameter smaller than the film thickness of the polymer thin film. It is a polymer composite thin film characterized by having.

This makes it possible to obtain a polymer composite thin film having both high functionality and high mechanical strength even when the polymer thin film is not self-supporting.

Further, the present invention is a polymer composite thin film in which a self-supporting polymer thin film having a film thickness of 100 nm or less is composited with a fibrous structure having a diameter smaller than the film thickness of the polymer thin film.

As a result, when the polymer thin film itself is self-supporting, it is possible to obtain a polymer composite thin film having both high functionality and higher mechanical strength.

Further, in the present invention, the fibrous structure is composed of an organic polymer.

This makes it possible to manufacture a polymer composite thin film at a lower cost.

Further, in the present invention, the fibrous structure is made into cellulose nanofibers.

As a result, since the material cost of the cellulose nanofibers is extremely small, it becomes possible to manufacture the polymer composite thin film at a lower cost.

Further, in the present invention, the polymer thin film is mainly composed of polysiloxane.

As a result, since the thin film generally composed of polysiloxane has independence, it becomes possible to obtain a polymer composite thin film having more excellent mechanical strength.

Further, in the present invention, the polymer thin film is mainly composed of a crosslinkable polymer.

This makes it possible to obtain a polymer composite thin film having high functionality and high mechanical strength by using a crosslinkable polymer such as an epoxy resin, which is a more general polymer material.

Further, in the present invention, the polymer thin film has gas separability.

This makes it possible to remove a predetermined gas from the gas with the polymer composite thin film.

Further, in the present invention, the polymer thin film selectively permeates carbon dioxide.

This makes it possible to remove (separate) carbon dioxide from the gas using the polymer composite thin film.

Further, in the present invention, the polymer thin film separates oxygen and nitrogen in the air.

As a result, the polymer composite thin film functions as an air separation membrane, and it becomes possible to increase or decrease the oxygen concentration and the nitrogen concentration in the air.

As described above, according to the present invention, it is possible to obtain a polymer composite thin film having high functionality and high mechanical strength.

(A) to (d) are explanatory views which show the structure of the polymer composite thin film 1 which concerns on this invention. (A) to (d) are photographs showing the bending of the films when the same load is applied to the films obtained in Comparative Example 1 and Example 1. A graph showing the relationship between stress (σ) and deflection (ε) in the films obtained in Comparative Example 1 and Example 1. Photograph showing the appearance of CNF / PDMS film with circular damage

1 (a) to 1 (d) are explanatory views showing the structure of the polymer composite thin film 1 according to the present invention. Hereinafter, embodiments of the present invention will be described with reference to FIG. The polymer composite thin film 1 is composed of a polymer thin film 2 and cellulose nanofibers 3 as a fibrous structure.

As shown in FIGS. 1 (a) to 1 (d), the polymer composite thin film 1 has a structure in which the cellulose nanofibers 3 are included in the film of the polymer thin film 2. Specifically, as shown in FIGS. 1 (a) and 1 (b), all the cellulose nanofibers 3 are contained inside the polymer thin film 2, and on one side of the surface formed by the polymer thin film 2. A mode in which the cellulose nanofibers 3 are unevenly distributed, a mode in which a part of the cellulose nanofibers 3 is exposed to the outside of the polymer thin film 2 as shown in the same (c), or a mode in which the cellulose nanofibers 3 are exposed to the outside, or as shown in the same (d). It may be any of the embodiments in which all 3 are contained inside the polymer thin film 2 and the cellulose nanofibers 3 are uniformly dispersed in the film of the polymer thin film 2.

As described above, the polymer composite thin film 1 of the present embodiment has a configuration in which the polymer thin film 2 and the cellulose nanofibers 3 are composited. Cellulose nanofibers 3, which are organic polymers, form fibrils as small fibers (fibrous structures). Fibril has high mechanical strength as a material, and by combining with the polymer thin film 2, the polymer composite thin film 1 exhibits extremely high mechanical strength. Further, the cellulose nanofiber 3 is produced from wood or the like, which is abundant as a resource, at low cost by mechanical defibration or the like, and is an environmentally friendly material because it is a plant fiber.

As a material constituting the polymer thin film 2, for example, a vinyl polymer, a polysiloxane, or a crosslinkable polymer can be preferably used. Here, it is said that vinyl polymer and polysiloxane cannot secure mechanical strength (independence) by themselves at a film thickness (for example, 100 nm or less) at which functionality such as gas separability can be effectively exhibited. In this case, by combining the polymer thin film 2 containing a vinyl polymer or polysiloxane as a main component and the cellulose nanofibers 3, the functionality and independence of the polymer composite thin film 1 containing these components are compatible. It becomes possible to do.

On the other hand, the crosslinkable polymer is said to have self-sustaining property by itself even at a film thickness (similar to vinyl polymer and polysiloxane, for example, 100 nm or less) at which the functionality can be effectively exhibited. Here, the crosslinkable polymer (crosslinked polymer) refers to a polymer having a three-dimensional network structure (crosslinked structure) by bonding a plurality of linear polymer chains by a chemical reaction, for example, a functional group. Includes an epoxy resin in which an epoxy group and an amino group are crosslinked by a chemical reaction.

As for the epoxy resin, an example of a polymer thin film having a film thickness of 20 nm and having self-supporting property is "A Large, Freestanding, 20 nm Stick Nanomembrane Based on Epixy Resin, H. Watanabe T. Kunitake, H. Watanabe T. Kune , Pages 909-912, 2007 "
(Https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.200601630)
It is published in.

By combining a polymer thin film 2 containing a crosslinkable polymer as a main component and a cellulose nanofiber 3, the polymer composite thin film 1 containing these components is to ensure not only functionality but also tougher mechanical strength. Is possible.

By the way, in this embodiment, the film thickness D2 of the polymer thin film 2 is set to 100 nm or less. By setting the film thickness D2 of the polymer thin film 2 to 100 nm or less, the functionality (here, gas separability) of the polymer composite thin film 1 can be significantly enhanced. Further, in the present embodiment, the film thickness D1 of the polymer composite thin film 1 is also set to 100 nm or less.

That is, in the configurations of FIGS. 1A, 1B, and 1D, the polymer thin film 2 completely including the cellulose nanofibers 3 in the film is the polymer composite thin film 1 itself, so that the polymer composite thin film 1 is used. The film thickness D1 = the film thickness D2 of the polymer thin film 2, and in the configuration in which a part of the cellulose nanofibers 3 is exposed from the polymer thin film 2 as shown in FIG. 1C, the film of the polymer composite thin film 1 Thickness D1> Thickness D2 of the polymer thin film 2.

The cellulose nanofiber 3 has a diameter (for example, 4 nm to 90 nm) smaller than the film thickness of the polymer thin film 2. By making the diameter of the cellulose nanofibers 3 smaller than the thickness of the polymer thin film 2, the functionality of the polymer thin film 2 is fully exhibited. On the contrary, when the diameter of the cellulose nanofibers 3 is set to a size equal to or larger than the film thickness of the polymer thin film 2, the substantial surface area of the film is reduced, and it becomes difficult to exhibit the functionality.

In addition, although it is described in FIG. 1 that the cellulose nanofibers 3 having the same fiber length are aligned in a specific direction, it is merely schematically described. In reality, the fiber lengths of the cellulose nanofibers 3 vary (5 μm or more), and the cellulose nanofibers 3 are oriented in all directions and are included in the polymer thin film 2 in a complicatedly entangled state.

By the way, in this embodiment, as the fibrous structure, cellulose nanofibers which are organic polymers such as cellulose oxide nanofiber (CNF oxide) and a mixture of cellulose nanofiber 3 and cellulose oxide nanofiber can be preferably used. However, other organic polymers may be used as the fibrous structure. As other organic polymers, for example, polymers produced by a manufacturing method such as electrolytic spinning, fibrin, peptide, collagen, etc., which are proteins involved in blood coagulation in which fine fibers are bundled, can be used, and further. Deoxyribonucleic acid (DNA: deoxyribonucleic acid) or ribonucleic acid (RNA: ribonucleic acid) may be used.

Here, for example, when DNA is adopted as the fibrous structure, since the DNA is a fiber having a diameter of 2 nm, if the film thickness of the polymer composite thin film 1 is larger than 2 nm, both functionality and mechanical strength can be achieved. Become. That is, the film thickness of the polymer composite thin film 1 according to the present invention can be in the range of 2 nm to 100 nm by selecting a fibrous structure. Further, even when the fibrous structure is limited to the cellulose nanofiber 3, the film thickness can be in the range of 4 nm to 100 nm.

Hereinafter, Example 1 of the present invention will be described. First, cellulose nanofiber 3 (hereinafter sometimes referred to as "CNF") (Nanoforcest-S (Nanoforcest is a registered trademark) manufactured by Chuetsu Pulp & Paper Co., Ltd.) produced a 0.11 weight% CNF dispersion, and ions were prepared therein. Exchange water was added to prepare a CNF aqueous solution having a predetermined CNF concentration, which was used in the subsequent operations.

Separately, the main agent and curing agent of polydimethylsilicone (PDMS) resin (manufactured by Toray Dow Corning, SYLGARD 184 (SYLGARD is a registered trademark)), which is one of the polysiloxanes, are mixed at a ratio of 10: 1. Hexane was added to prepare a 10 wt% PDMS / hexane solution. A predetermined amount of hexane was added thereto to prepare PDMS / hexane solutions having different concentrations, which were used for the subsequent operations.

Prior to the preparation of the polymer composite thin film 1, a polyhydroxystyrene (PHS) / ethanol solution (15% by weight) was first spin-coated (3000 rpm / 1 minute) on a glass substrate to form a PHS layer, and then dried. The substrate was treated with oxygen plasma to make the surface hydrophilic.

The CNF aqueous solution prepared by the above operation was spin-coated on this substrate, then the PDMS / hexane solution was spin-coated, and then the substrate was heated at 100 ° C. for 30 minutes.

After allowing to cool to room temperature, this substrate was immersed in ethanol (stripping liquid), and the film was peeled from the substrate in the stripping liquid. The film thus obtained (polymer composite thin film 1) is hereinafter referred to as a CNF / PDMS film. This CNF / PDMS film was fixed to a concentric circular frame produced using a Kapton film, and the film was taken out from the release liquid. It was visually confirmed that the CNF / PDMS film fixed to the concentric circular frame had no defects and was self-supporting.

For use in the bulge test described later, a plurality of samples were obtained in which the number of rotation coating operations of the CNF aqueous solution (hereinafter, may be referred to as “CNF spin coating operation”) was changed in the above step.

As Comparative Example 1, a film in which a PDMS layer was directly formed on a glass substrate coated with PHS was produced without performing a CNF spin coating operation. This is hereinafter referred to as PDMS film.

The mechanical strength of the film prepared as Example 1 and Comparative Example 1 was evaluated by a bulge test. The film used in the test was (i) PDMS film as Comparative Example 1, and (ii) a film obtained by performing PDMS spin coating on the sample prepared in Example 1 by performing (ii) CNF spin coating operation once. (CNF / PDMS film), (iii) CNF spin coating operation was performed 5 times, and PDMS spin coating was performed on the film (CNF-5 / PDMS film), and (iv) CNF spin coating operation was performed 10 times. There are four types of films (CNF-10 / PDMS film) that have been used.

The film thicknesses of the polymer composite thin films 1 of (ii) to (iv) prepared in Example 1 were all 100 nm or less, specifically in the range of 50 nm to 75 nm. The PDMS film (i) as Comparative Example 1 was exceptionally formed with a film thickness of 150 nm. This is because (i) when the film thickness of the PDMS film is set to 50 nm to 75 nm, which is the same as the other samples obtained in Example 1, it breaks immediately when taken out into the air (it does not become self-supporting), and Example 1 This is because it cannot be compared with.

The samples prepared in Comparative Example 1 and Example 1 were attached to the bottom surface of a cylindrical glass tube, ion-exchanged water was dropped from the upper side of the glass tube, a weight was applied to the film, and the film was expanded by the weight load ( The stress (σ) and strain (ε) were calculated from the shape of the (deflected) film.

2 (a) to 2 (d) are photographs showing the bending of the films when the same load is applied to the films obtained in Comparative Example 1 and Example 1. Specifically, the film deflection was observed when the same load (water: 3.5 mL was introduced, hydraulic pressure: about 437 Pa) was applied to Comparative Example 1 and Example 1. Here, FIG. 2A shows the state of the PDMS film, FIG. 2B shows the state of the CNF / PDMS film, FIG. 2C shows the state of the CNF-5 / PDMS film, and FIG. 2D shows the state of the CNF-10 / PDMS film. ..

FIG. 3 is a graph showing the relationship between stress (σ) and deflection (ε) in the films obtained in Comparative Example 1 and Example 1. Specifically, FIG. 3 shows the relationship between the stress (σ) and the deflection (ε) calculated from the load pressure, the film radius, the film thickness, the bending length, and the film arc length at the time of bending for each film.

From FIGS. 2 and 3, it is clear from the film in which the CNF and PDMS obtained in Example 1 are layered (having the configuration shown in any of FIGS. 1A to 1C depending on the production conditions). A difference was seen in the film deflection under hydraulic load, and the amount of deflection decreased as the amount of CNF introduced increased. In addition, as the number of CNF layers increased, the stress also increased (conversely, the deflection decreased). Therefore, it was confirmed that the introduction of CNF improved the mechanical strength of the entire film.

FIG. 4 is a photograph showing the appearance of a CNF / PDMS film in which circular damage has occurred. The circular damage was created by piercing a CNF / PDMS film with a needle having a sharp tip. As shown in FIG. 4, even if some external damage was applied to the CNF / PDMS film, the damage did not spread to the whole but was limited to a part. Further, the same was true when circular damage was caused to the CNF-5 / PDMS film and the CNF-10 / PDMS film.

On the other hand, in the PDMS film, when such damage is formed, the entire film shrinks and breaks in an instant, and the film structure cannot be maintained. Considering together with the other evaluation results of Example 1, it can be determined that CNF is present in the obtained polymer composite thin film 1. Moreover _{, the selectivity between CO 2} and N ₂ was maintained at about 10. In the case of PDMS film alone, the CO ₂ / N ₂ selectivity is about 10 to 11 (references: Shigenori Fujikawa, Miho Ariyoshi, Roman Seliyanchin, Toyoki Kunitake, Chemistry Letters, Chemistry Letters, Chemistry Letters. ), It can be said that none of the produced films has defects that cause gas leaks.

Hereinafter, Example 2 of the present invention will be described. Ion-exchanged water was further added to the CNF dispersion having a CNF of 0.11% by weight prepared in Example 1 to prepare diluted solutions having different CNF concentrations. CNF / PDMS films were prepared using the prepared dilutions. The film thickness of the CNF / PDMS film as the polymer composite thin film 1 obtained in Example 2 was about 50 nm to 75 nm.

The CNF / PDMS film and the PDMS film were placed on a porous polyacrylonitrile film, and a gas permeation test was performed. The permeability of carbon dioxide (CO ₂ ) and nitrogen (N ₂ ) of the _{CNF / PDMS film and the CO 2} / N ₂ selectivity are shown in [Table 1]. The results of the gas permeability test of the PDMS film are shown in the leftmost column of [Table 2] described later.

Since the same selectivity was observed in all the CNF / PDMS films produced as Example 2, it can be seen that all the films were obtained without defects such as gas leaks. The CO ₂ and N ₂ permeability are lower than those of a PDMS film having the same film thickness (about 50 nm as described later). In general, a film made of CNF has low gas permeability, and it is supported that CNF is also introduced in this film.

Hereinafter, Example 3 of the present invention will be described. A CNF / ethanol dispersion was prepared so that the cellulose nanofiber 3 (CNF) (Nanoforcest-S manufactured by Chuetsu Pulp & Paper Co., Ltd.) was 0.072% by weight.

Separately, the main agent and curing agent of a commercially available polydimethylsilicone (PDMS) resin (Toray Dow Corning, SYLGARD 184) were mixed at a volume ratio of 10 to 1, respectively, and the CNF / ethanol dispersion and hexane prepared above were mixed thereto. To prepare a 0.5 volume% CNF / PDMS / hexane solution, which was used for subsequent operations.

Next, a polyhydroxystyrene (PHS) / ethanol solution (15% by weight) was spin-coated on a glass substrate (3000 rpm / 1 minute) to form a PHS layer, and then the substrate was subjected to oxygen plasma treatment to surface the surface. It became hydrophilic. The CNF / PDMS / hexane solution prepared in the above operation was added dropwise onto this substrate, the substrate was rotated at 4000 rpm for 1 minute, and then the substrate was heated at 100 ° C. for 30 minutes.

After allowing to cool to room temperature, this substrate was immersed in an ethanol substrate, and the film was peeled off from the substrate. The film thus obtained is hereinafter referred to as a CNF-PDMS film. This CNF-PDMS film is composed of a polydimethylsilicone resin in which CNF is evenly dispersed, and is different from the CNF / PDMS film (CNF and PDMS are layered) described in Example 1 and the like. The structure is different. That is, the CNF-PDMS film obtained in Example 2 has the configuration shown in FIG. 1 (d).

This CNF-PDMS film was placed on a porous polyacrylonitrile film and a gas permeation test was performed. As Comparative Example 2, a film (PDMS film) using only SYLGARD 184 as a raw material without mixing the cellulose nanofibers 3 was also produced.

[Table 2] shows _{the permeability of CO 2} and N ₂ and the CO ₂ / N ₂ transmission selectivity of films prepared by changing the concentration of each film solution. That is, in [Table 2], the relationship between the mixed amount of the CNF dispersion liquid and the characteristics of the obtained CNF-PDMS film (No. 1 to No. 5) is shown.

Here, whether or not the film is self-supporting is determined by peeling the thin film (film) from the base material in the stripping liquid and then pulling the film suspended in the liquid into the air without breaking the flat film shape. Judgment is based on whether or not it can be retained. That is, when the film structure is maintained without breaking even in the air, it is "self-supporting", and when it is taken out into the air, it retains the film structure when it is suspended in the release liquid after the substrate is peeled off. The case of easy breakage is judged to be "non-self-supporting" (described as "easy breakage in air" in [Table 2]).

The film thickness of the PDMS film is limited to about 150 nm to be self-supporting, and if the film thickness is made thinner than that, the film breaking rate becomes extremely high. Therefore, for the PDMS film shown in [Table 2], the gas permeation test is performed by scooping up the thin film onto the porous polyacrylonitrile film in the stripping solution without pulling it up into the air.

The film produced in Example 3 has a film thickness of about 50 nm, including the PDMS film. As described above, with the PDMS film not mixed with CNF, the flat film shape could not be maintained by itself, and a flat film having self-supporting property that could be used for a gas permeation test could not be obtained due to shrinkage fracture. All the films mixed with CNF had independence.

Hereinafter, Example 4 of the present invention will be described. In Example 4, the polymer material constituting the polymer thin film 2 is a crosslinkable polymer. First, an aqueous dispersion was prepared so that the cellulose nanofiber 3 (CNF) (Chuetsu Pulp & Paper Co., Ltd., Nanoforcest-S) was 0.11% by weight, and this was used for the subsequent operations.

Further, Poly [(o-formaldehyde) -co-formaldehyde] (hereinafter, may be referred to as “PCGF”) (ALDRICH, Mn870) and Polyethylenimine, brunched (hereinafter, referred to as “PCGF”) as a crosslinkable polymer (epoxy resin). , "PEI".) (ALDRICH, Mn ~ 10,000) was prepared as a PCGF-PEI / chloroform solution having a content of 4% by weight. After stirring this solution at 40 ° C. for 4 hours, chloroform was further added to prepare a 1 wt% PCGF-PEI / chloroform solution, which was used in the subsequent operations.

A polyhydroxystyrene (PHS) / ethanol solution (15% by weight) was spin-coated on a glass substrate (3000 rpm / 1 minute) to form a PHS layer, and then the substrate was subjected to oxygen plasma treatment to hydrophilize the surface. .. The CNF aqueous dispersion prepared by the above operation was spin-coated (1500 rotations, 2 minutes) on this substrate, and the substrate was heated at 100 ° C. for 1 minute.

The substrate was then spin-coated (3000 rpm, 1 minute) with the previously engineered 1 wt% PCGF-PEI / chloroform solution. After this, the substrate was heated at 100 ° C. for 5 minutes. After allowing to cool to room temperature, this substrate was immersed in ethanol, and the film (polymer composite thin film 1) was peeled off from the substrate. The thickness of the film obtained in Example 4 was 75 nm.

It was visually confirmed that the polymer composite thin film 1 obtained in Example 4 had no defects and was self-supporting. In addition, a test for applying a hydraulic load was conducted in the same manner as described in Example 1. As a result, the amount of deflection decreased as the amount of CNF introduced increased.

Hereinafter, Example 5 of the present invention will be described. In Example 5, instead of the above-mentioned CNF aqueous solution, a 0.05 wt% CNF + CNF oxide aqueous solution in which CNF and CNF oxide (cellulose oxide nanofibers) are mixed in equal amounts is used, and the PDMS concentration of the PDMS / hexane solution is adjusted. It was 0.5 v / v%. Further, the rotary coating (spin coating) operation of the CNF + CNF oxide aqueous solution was performed once, and a film (CNF + CNF oxide / PDMS film) was prepared in the same process as in Example 1. When the cross section of the prepared film was observed with a scanning electron microscope, the film thickness of the CNF + oxidized CNF / PDMS film was 30 nm.

This CNF + oxidized CNF / PDMS film was placed on a porous polyacrylonitrile film and a gas permeation test was performed. The permeability of carbon dioxide (CO ₂ ), nitrogen (N ₂ ) and oxygen (O ₂ ) and the _{selectivity of CO 2} / N ₂ , CO ₂ / O _{2 and O 2} / N ₂ are shown in [Table 3].

As shown in [Table 3], also in the CNF + oxidized CNF / PDMS film of Example 5, _{the transmittance of CO 2} is very large, _{and the transmittance of O 2} and N ₂ is also high. Focusing on O ₂ and N ₂ , the O ₂ / N ₂ selectivity is 2.3, and the CNF + oxidized CNF / PDMS film has an air separation function for separating oxygen and nitrogen in the air. It is clearly shown. That is, the polymer composite thin film 1 according to the present invention functions as an air separation membrane, and can increase or decrease the oxygen concentration and the nitrogen concentration in the air.

The air separation function of CNF + CNF oxide / PDMS film is exhibited by a layer composed of PDMS (polymer thin film, hereinafter sometimes referred to as "PDMS layer"), but the thickness of the PDMS layer is large. Indeed, the transparency becomes small, which becomes a practical barrier. However, when the PDMS layer is composited with a layer composed of CNF (or CNF + CNF oxide), the mechanical strength is improved, and the PDMS layer in the polymer composite thin film 1 is thinned (thinned) to the utmost limit. It becomes possible.

In Example 5, as described above, the film thickness of the CNF + CNF oxide / PDMS film is 30 nm, and the film thickness of the PDMS layer excluding the thickness of the layer composed of CNF + CNF oxide is considered to be about 10 nm to 20 nm. .. By making the PDMS layer ultra-thin in this way, it is possible to realize _{high O 2} and N _{2 transmittance exceeding 1000 GPU (3000 GPU).}

Since the polymer composite thin films 1 shown in Examples 1 to 3 also contain a thinned PDMS layer, it is clear that these polymer composite thin films 1 have an air separation function.

Since the polymer composite thin film 1 according to the present invention has high functionality and high mechanical strength, for example, CO ₂ which is a greenhouse gas generated by combustion of fossil fuel is emitted from a source such as a power plant or a factory. It can be suitably applied to a gas separation membrane or the like used in CCS (Carbon dioxide Capture and Storage) for separation and recovery. Further, the polymer composite thin film 1 according to the present invention is an oxygen enricher utilizing air having a high concentration of oxygen (air having a low concentration of nitrogen), a high concentration oxygen mask, a plant factory, and oxygen combustion power generation. It can be suitably applied to plants, oxygen combustion boilers, and the like, and inert gas fire extinguishing equipment that utilizes air with a high concentration of nitrogen (air with a low concentration of oxygen).

1 Polymer composite thin film 2 Polymer thin film 3 Cellulose nanofiber 10 Circular damage

Claims (9)

A polymer composite thin film having a thickness of 100 nm or less, which is self-supporting by being composited with a fibrous structure having a diameter smaller than the thickness of the polymer thin film. A polymer composite thin film having a self-supporting polymer thin film having a film thickness of 100 nm or less, which is composited with a fibrous structure having a diameter smaller than the film thickness of the polymer thin film. The polymer composite thin film according to claim 1 or 2, wherein the fibrous structure is composed of an organic polymer. The polymer composite thin film according to claim 3, wherein the fibrous structure is made of cellulose nanofibers. The polymer composite thin film according to any one of claims 1 to 4, wherein the polymer thin film is mainly composed of polysiloxane. The polymer composite thin film according to any one of claims 1 to 4, wherein the polymer thin film is mainly composed of a crosslinkable polymer. The polymer composite thin film according to any one of claims 1 to 6, wherein the polymer thin film has gas separability. The polymer composite thin film according to any one of claims 1 to 7, wherein the polymer thin film selectively permeates carbon dioxide. The polymer composite thin film according to any one of claims 1 to 7, wherein the polymer thin film separates oxygen and nitrogen in the air.

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