JP5311017B2 - Surface treatment method of a substrate having nanoscale unevenness by metal alkoxide - Google Patents

Description

  The present invention relates to a technique for forming a thin film on a substrate having nanoscale irregularities and / or functionalization of the substrate, and in particular, forms a thin film on the substrate by treatment with a metal alkoxide solution or the substrate. The present invention relates to a surface treatment method for functionalizing a surface and a substrate having nanoscale irregularities, which has been treated with a metal alkoxide solution by the surface treatment method.

  Surface treatment technology that adds new functions to the surface of existing substances is classified into dry processes and wet processes. In the wet process, the substance to be functionalized or coated is added to the chemical solution and immersed in this chemical solution. Or, add new functions by casting, dip coating, spin coating, alternating lamination, etc.

By the way, it is well known that metal oxide sols or gels are produced when metal alkoxides are hydrolyzed.
In the above-described thin film formation or functionalization method, a method using a sol / gel method of this metal alkoxide is used. In addition, a new function is added to the surface of the base material by dipping / stirring treatment, dip coating treatment, spin coating treatment or the like. In addition, examples of tackling surface functionalization using an anhydrous solvent for metal alkoxides are also seen.

For example, in Non-Patent Document 1, after preparing a stable sol solution of a metal alkoxide using a chelating agent in an anhydrous solvent, a photocatalyst is generated on the paper by dipping the paper into this solution. In the case of this method, a large amount of metal alkoxide can be attached to the substrate.
Further, in Patent Document 1, a metal halide alkoxide is stabilized with an anhydrous solvent, a substrate is immersed in the solution, and then a stoichiometric amount of “water” for at least hydrolyzing the halogenated alkoxide is added to the solution. It is added.

  On the other hand, surface modification technology that adds a new function to the surface of an existing substance can be used to remove harmful molecules in the gas phase or liquid phase, such as adsorbents and filters, or water-repellent or hydrophilic coatings on fibers. It is also an important problem in the field, and modification with metal alkoxide is used.

That is, the performance of the adsorbent and the filter is basically determined by the number of functional groups per area and the surface area. Existing filters, such as activated carbon, have a high surface area, and because the number of chemical functional groups per area is small, the amount of adsorption seems large, but desorption occurs. That is, the adsorbed and removed molecules are released again.
Therefore, it has been proposed to apply the above-mentioned metal alkoxide modification to the adsorbent and the filter surface.
For example, in Patent Document 2, activated carbon and a metal alkoxide are placed separately in a sealed container or in a dry air stream to generate a vapor of the metal alkoxide, then adsorbed to the activated carbon, and then contacted with water vapor to be adsorbed. The activated carbon carrying the metal oxide was obtained by hydrolyzing the metal alkoxide.

In addition, the water repellency of the base material is manifested by both the physical structure and chemical properties of the surface. That is, it is necessary to form a physical concavo-convex structure on the surface of the base material on which the water repellent coating is to be applied, and to make the surface have low surface energy. At present, there are a method of forming irregularities by dip coating, spin coating, spraying, and then performing chemical treatment, a method of simultaneously forming irregularities and chemical treatment by the above-described method, and the like.
In any of the methods, the uneven structure is fragile, so that there is a drawback that it lacks durability. That is, in order to perform highly durable water-repellent processing, it is necessary to reinforce the physical uneven structure while maintaining the uneven structure contributing to water repellency.
As an example, in Non-Patent Document 2, TEOS (tetraethyl orthosilane), colloidal silica, and FOETES ((heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane) are used as raw materials to coat fluorinated alkyl functional groups. A film of silica particles is produced in one stage. In this technique, a metal alkoxide is used as a binder that promotes necking (adhesion) between fine particles and between the fine particles and the substrate surface.
JP-A-8-239202 JP-A-8-245210 Akira Uramoto, Masaki Takahashi, Hideaki Ichiura “Development Research on the Creation of Nano Thin Films Using the Sol-Gel Method” Ehime Industrial Research Report No. 45 Pages 64-65 M.M. Hikita, et al. , Langmuir, 21, 7299 (2005).

However, in the thin film formation or surface functionalization using metal alkoxide, the actual situation is that thin film formation or functionalization is not performed up to the inside of the nanoscale unevenness present on the surface of the substrate.
That is, when the process of adding water to the solution and promoting the hydrolysis / polycondensation of metal alkoxide as in Patent Document 1 is taken, the nanoscale fine uneven surface cannot be effectively modified. . For this reason, when a thin film is formed by this method, the inside of the nanoscale irregularities cannot be filled, so that a film having low adhesion and poor durability is produced. On the other hand, when the porous material is functionalized by this method, the nanoscale uneven inner surface cannot be effectively functionalized, so that the modification method has a low modification efficiency, that is, a low functional level.

In the case of the technique of Non-Patent Document 1, a large amount of metal alkoxide can be attached to the substrate. However, as will be described in detail later, since the influence of moisture on the surface of the base material is not taken into account, the adhesion between the base material and the metal alkoxide is weak, and the nanoscale minute irregularities cannot be modified.
Similarly, when the activated carbon is chemically modified with a metal alkoxide, there is a high possibility that the nanoscale pores originating from the high surface area are blocked. Moreover, when using steam like patent document 2, not only a large-scale apparatus is required but the possibility of clogging pores on the order of several nm due to condensation of gas molecules in the pores is high.
Furthermore, in the technique of Non-Patent Document 2, since the binder is a metal alkoxide, moisture between nanoscale irregularities is not taken into consideration, so that an effective and efficient binding effect is not expressed.

As described above, in the conventional thin film formation or surface functionalization method using metal alkoxide, the thin film formation or functionalization is not performed to the inside of the nanoscale unevenness existing on the substrate surface, and the functionalization efficiency is When the amount of the metal alkoxide is increased to increase the thickness, only the surface of the base material is covered with the metal alkoxide, so that the nanoscale unevenness is blocked, or the necking force (adhesiveness with the base material) ) Was missing.
This invention is made | formed in view of the above situations, Comprising: The objective of this invention forms the thin film on this base material by processing the base-material surface which has a nanoscale unevenness | corrugation with a metal alkoxide solution. In the method of functionalizing the surface of the substrate, the object is to fill the nanoscale irregularities with metal alkoxide, or to effectively functionalize the nanoscale irregularities inside surface with metal alkoxide It is. In other words, the present invention is intended to realize high-adhesion thin film formation and high-density surface functionalization in consideration of nanoscale unevenness.
Here, “high adhesion” means that the coating agent is filled even inside the nanoscale irregularities, and there is no air interface between the coating agent and the substrate, and “high density functionalization” The state in which the metal alkoxide is attached to the inner surface while maintaining the nanoscale unevenness, that is, the case where the number of functional groups per specific surface area considering the nanoscale fine unevenness is higher than the conventional functionalization.

The inventors have studied to achieve the above-mentioned object, and the nanoscale irregularities present on the surface of the base material are not formed or functionalized into a thin film because the metal alkoxide easily reacts with water, and the nanoscale. It was found that this was caused by water adsorbing inside the irregularities. That is, in conventional thin film formation or surface functionalization methods using metal alkoxides, the influence of moisture in the solvent is taken into consideration (see Patent Document 1), but exists on the substrate surface (outer surface and fine irregularities inside). The above-mentioned problem arises because the effect of water is not taken into consideration.
Therefore, the present inventors considered that it is important to remove the moisture adhering to the inner and outer surfaces of the irregularities on the surface of the base material, and as a result of examination, the base material was previously heat-treated in an anhydrous solvent. As a result, it has been found that moisture adhering to the inside and outside of the irregularities can be removed.

The present invention has been completed based on these findings, and provides the following inventions.
[1] A method for forming a thin film on a substrate by treating a substrate surface having nanoscale irregularities with a metal alkoxide solution or functionalizing the substrate surface, the substrate In the anhydrous solvent, the surface is provided with a step of removing moisture adhering to the inner and outer surfaces of the irregularities by heat treatment at a temperature not lower than the boiling point of water and not higher than the boiling point of the anhydrous solvent. Processing method.
[2] The anhydrous solvent is toluene, hexane, DMF, 2-aminoethanol, 1-butanol, dimethyl sulfoxide, ethyl acetoacetate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, anisole / ethyl lactate , diethylene glycol dimethyl ether, surface treatment methods are described you wherein a is selected from polyethylene glycol monomethyl ether and anhydrides thereof [1].
[3] The surface treatment method according to the above [1] or [2], wherein the metal alkoxide has at least one functional group necessary for the functionalization.
[4] The metal alkoxide solution, any surface treatment method of the above-mentioned [1] to [3], wherein the metal alkoxide is dissolved in anhydrous solvent.
[5] The surface treatment method according to any one of the above [1] to [4], wherein the thin film is formed or functionalized by immersing the substrate in a metal alkoxide solution.
[6] Any of the above-mentioned [1] to [5], wherein the substrate having nanoscale irregularities is any one of activated alumina, activated carbon, mesoporous silica, nanofibers, or alternating laminated films Surface treatment method.
[7] A substrate having nanoscale irregularities, characterized in that the surface thereof is treated with a metal alkoxide solution by the surface treatment method of any one of [1] to [6] above. Base material.

ADVANTAGE OF THE INVENTION According to this invention, it can be filled with a metal alkoxide to the inside of a nanoscale unevenness | corrugation, or a nanoscale uneven | corrugated internal surface can be effectively functionalized with a metal alkoxide. In other words, it is possible to realize thin film formation with high adhesion and high-density surface functionalization in consideration of nanoscale unevenness.
The filter performance is improved by applying the present invention to an air / water purification filter. That is, according to the present invention, the metal alkoxide can be functionalized without clogging the nanoscale fine irregularities, so that the desired functional groups can be generated at high density while maintaining the surface area of the substrate. it can. Therefore, it is possible to realize a harmful molecule removal filter that has a large adsorption amount per unit weight and does not cause desorption.
In addition, by applying the present invention to the water-repellent coating method, highly durable water-repellent processing can be performed without reducing water repellency. In other words, while maintaining the concavo-convex structure necessary for water repellency, the concavo-convex structure and the necking (adhesion) between the concavo-convex and the substrate surface can be strengthened, thereby significantly improving the physical durability of the water-repellent surface. Can do.

The present invention relates to a method of forming a thin film on a substrate by treating a substrate surface having nanoscale irregularities with a metal alkoxide solution or functionalizing the substrate surface, It is characterized by providing a step of removing moisture adhering to the inside and outside surfaces of the irregularities by heat treatment in an anhydrous solvent.
FIG. 1 is a diagram schematically illustrating the difference between the method of the present invention and a conventional method.
That is, as shown in the upper part of the figure, conventionally, moisture remains inside the nanoscale unevenness, and the metal alkoxide easily reacts with water, resulting in covering the uneven surface. Has not been thinned or functionalized.
In the present invention, by providing a step of removing moisture adhering to the inside and outside of the unevenness, as shown in the lower part of the figure, the nanoscale unevenness is filled with metal alkoxide, or the nanoscale unevenness The internal surface can be effectively functionalized with a metal alkoxide.

  In the present invention, the substrate having nanoscale unevenness is not particularly limited in shape and material as long as the surface can be treated with a metal alkoxide solution to form a thin film or functionalize the surface. Examples thereof include polymers used as adsorbents or filter materials, such as fibrous materials such as polymers having a textured structure, activated carbon, activated alumina, mesoporous silica, nylon nanofibers, and carbon nanofibers.

  When the method of the present invention is used to form a thin film on the surface of a substrate having nanoscale irregularities or to functionalize the surface of the substrate, specifically, the following four steps are performed.

Step 1: A step of heating the base material having nanoscale unevenness in an anhydrous solvent to reduce the moisture inside the unevenness of the substrate. This step reduces the moisture inside the unevenness of the substrate. In the subsequent steps, the metal alkoxide molecules can penetrate into the irregularities.
In the present invention, the temperature of the heat treatment necessary to reduce the moisture inside the irregularities by heat treatment in an anhydrous solvent is not less than the boiling point of water and not more than the boiling point of the anhydrous solvent, and the heat resistant temperature of the substrate It is necessary to select the following temperature.

The anhydrous solvent used in Step 1 is toluene, hexane, DMF, 2-aminoethanol, 1-butanol, dimethyl sulfoxide, ethyl acetoacetate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, anisole / ethyl lactate , Diethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, and the like, and anhydrides thereof can be used.
The reason why such a solvent can be used is that the metal alkoxide can be stably present in the solvent and the amount of water present in the substrate can be reduced.

Step 2: Step of creating a stable solution of metal alkoxide Next, a metal alkoxide having a desired metal or a metal alkoxide having a desired functional group is added to an anhydrous solvent to obtain a stable solution of metal alkoxide.
In the present invention, by applying this step, the metal alkoxide can stably exist as a metal alkoxide molecule.

As the desired metal, for example, titanium is used to form a superhydrophilic thin film, and metal alkoxide having a plurality of metals to be combined is used to form a composite metal thin film.
In addition, as the desired functional group, a functional group capable of adding the function to the base material to be functionalized by the method of the present invention is used. For example, an amine group is added to add a function of removing aldehyde, If a function for removing amine is added, a carboxyl group is used. If a water-repellent coating is applied, one having F or a methyl group is used.

In this step, when the activity of the metal alkoxide is high, a stabilizer such as a chelating agent is added. A chelating agent binds to a metal ion by a coordination bond and exhibits a reaction suppressing effect. Ethanolamines and alkoxyalcohols exhibit effects as chelating agents.
Metal alkoxide is a molecule having a metal atom as a nucleus and an alkoxy group in a side chain. Many of these side chains have been replaced with functional groups, so that new metallic properties and functional properties can be added by selecting the type of metal alkoxide.
The functional property is the property of the side chain of the metal alkoxide that does not cause hydrolysis or dealcoholization. For example, in the case of 3-aminopropyltrimethoxysilane (APTMS), the three methoxy groups are hydrolyzed and dealcoholized. However, the remaining aminopropyl groups do not undergo these reactions and remain in the final material. In the case of APTMS, since aminopropyl groups remain, properties such as protein fixation and aldehyde adsorption are exhibited.
In the subsequent steps, the metal alkoxide reacts with water and starts hydrolysis and polycondensation.

Step 3: Immersion and Stirring Step of Substrate The substrate obtained by reducing moisture in Step 1 is added to the solution obtained in Step 2 above, and dipped and stirred.
In the step, the metal alkoxide in the solution is adsorbed on the surface of the target substrate as a molecule and then diffuses. Although the water on the substrate surface is reduced by the treatment in step 1, since the water is trapped in a very small nanoscale region (small mesopore or micropore region), the surface-diffused metal alkoxide is It diffuses until it meets this innumerable water, and then begins hydrolysis and polycondensation. However, since the amount of water existing at one site is very small, the unevenness is not completely blocked by polycondensation.
In this step, a metal alkoxide gel is formed on the nanoscale uneven inner surface, and the nanoscale space is filled with unreacted metal alkoxide.

Step 4 (No. 1): Step of drying without washing When producing a highly adherent thin film, the substrate is pulled up from the solution and dried as it is.
In the drying process, drying is performed for several hours at a temperature equal to or higher than the boiling point of the anhydrous solvent. For example, when anhydrous toluene is selected as the solvent, the process is performed at 120 ° C. for 3 hours.
The nanoscale space is composed of a substrate wall, a metal alkoxide gel, and an unreacted metal alkoxide.
In this step, two phenomena occur when the substrate is dried without washing. The first is that the gel is solidified and firmly connected to the substrate, and the second is that the unreacted metal alkoxide starts hydrolysis and polycondensation, and is firmly connected to the original gel, thus To fill.
By applying this process, the nanoscale uneven space is filled with metal alkoxide, and a highly adhesive thin film is generated.
In the present invention, a state in which fine concavo-convex portions are filled with metal alkoxide is referred to as “high adhesion”. On the other hand, when the nanoscale fine irregularities are not filled with metal alkoxide and there is an air interface between the nanoscale fine irregularities and the thin film, it is called "low adhesion" And

Step 4 (No. 2): Step of drying after washing On the other hand, when realizing high-density surface functionalization, the substrate is taken out from the solution, the substrate is washed with a solvent, and then dried.
The drying process in this step is also performed for several hours at a temperature equal to or higher than the boiling point of the anhydrous solvent. For example, when anhydrous toluene is selected as the solvent, the process is performed at 120 ° C. for 3 hours.
In the present invention, the state in which the metal alkoxide is attached to the inner surface of the fine unevenness without blocking the fine uneven space is referred to as “high density surface functionalization”.

  Hereinafter, although this invention is demonstrated concretely using various base materials, this invention is not limited at all by these.

Example 1
In this example, commercially available activated alumina (manufactured by Sumitomo Chemical Co., Ltd., KHD-12 60604) having an average particle diameter of about 2 mm was used.
(Preprocessing)
First, impurities on the surface of the activated alumina were removed by ultrasonic treatment and dried at 60 ° C. for 24 hours. Hereinafter, this is referred to as “untreated activated alumina”.
(Dehydration treatment)
1.0 g of this untreated activated alumina was added to 20 ml of anhydrous toluene and subjected to heat treatment at 105 ° C. for 0 to 5 hours. The heat treatment time was counted as “dehydration treatment time 0 hours” when the substrate was placed on a hot plate having a volume of 55 ml and a bottom area of a circle having a diameter of 36 mm. Once reached, the temperature was maintained at 105 ° C.
(Treatment with metal alkoxide solution and drying)
Next, the activated alumina after the dehydration treatment was added to a solution obtained by dissolving 4.0 g of APTMS in 2.5 ml of anhydrous toluene, and the mixture was immersed and stirred for 6 hours. Thereafter, it was washed with toluene and 2-propanol and dried at 120 ° C. for 3 hours.

Since the water content inside the nanoscale irregularities cannot be directly measured, the degree of APTMS modification was observed by a nitrogen adsorption method (apparatus shimazu micromeritics ASAP2010).
FIG. 2 is a physical adsorption isotherm of nitrogen gas of the obtained activated alumina, and FIG. 3 is a diagram showing a pore size distribution of the obtained activated alumina.
In each figure, “WR0h”, “WR1h”, “WR3h”, and “WR5h” indicate that the heat treatment time is 0 hour, 1 hour, 3 hours, and 5 hours, respectively, and “Control” Represents untreated activated alumina.

According to FIG. 2, it can be seen that there is a relationship between the heat treatment time and the degree of metal alkoxide (APTMS) modification.
That is, there is an optimum value for the heat treatment time. In Example 1, in the heat treatment time (WR3h) of 3 hours, the nitrogen adsorption amount is the maximum, and it can be seen that the residual moisture amount between the fine substrate irregularities is an optimum value for internal functioning. Moreover, the physical adsorption isotherm in the dehydration treatment time of 3 hours has a hysteresis, which indicates that the nanoscale unevenness remains without being blocked.
If the dehydration process is excessively performed (see WR5h), it is considered that the amount of water inside the fine unevenness is excessively reduced and the unevenness cannot be efficiently covered.
In addition, untreated activated alumina (WR0h) has a larger adsorption amount than activated alumina (WR1h) after 1 hour of heat treatment, but this is because the liquid temperature has increased during this time, but the water can be removed at 100 degrees. This is probably because water was pushed into the irregularities due to the poor compatibility of anhydrous toluene and water.

Further, as is apparent from FIG. 3, the uneven structure inside the pores of the activated alumina is reduced by modification with APTMS.
That is, the pore size distribution of the optimal dehydration time of 3 hours (WR3h) had a nano-size peak as in the case of untreated activated alumina. The peak was that of untreated activated alumina. It is getting smaller. From this, it can be seen that even after modification with APTMS, the nano-sized uneven space is not blocked, and metal alkoxide is attached to the uneven inner surface to reduce the size.

The reason why such a phenomenon (optimum value) appears is considered as follows.
That is, by adding the base material to the anhydrous solvent, the water existing on the outer surface of the base material or inside the fine irregularities strongly adheres to the base material. For this reason, when the dehydration treatment is insufficient, the inside of the unevenness cannot be modified, and the metal alkoxide blocks the entrance of the unevenness. As the dehydration time elapses, the moisture inside the irregularities decreases, and the metal alkoxide can be adsorbed inside the irregularities. Hydrolysis and polycondensation proceed from the inside of the concavo-convex to the outside by the reaction between the water remaining in the concavo-convex and the metal alkoxide. On the other hand, since excessive dehydration process excessively reduces the moisture inside the irregularities, polycondensation does not occur on the inner surfaces of the irregularities even if metal alkoxide is adsorbed inside the pores. Therefore, the excessive dehydration treatment causes the metal alkoxide to be filled into the concavo-convex portions and closes the small fine concavo-convex portions.

Example 2
In this example, the heat treatment time was set to 3 hours which was optimal in Example 1, and the treatment time in the APTMS solution dissolved in anhydrous toluene was increased to 14 hours. In the same manner as above, activated alumina modified with APTMS was obtained.
FIG. 4 is a physical adsorption isotherm of nitrogen gas of the obtained activated alumina, and FIG. 5 is a diagram showing a pore size distribution of the obtained activated alumina. In each figure, “Control” represents untreated activated alumina.
As is clear from FIG. 4, the obtained activated alumina has a reduced amount of nitrogen gas adsorbed than the untreated activated alumina, but has hysteresis as in the case of Example 1, and FIG. As can be seen from FIG. 5, since the peak of the pore size distribution is smaller than that of the untreated activated alumina, the nano-sized uneven space is not blocked even after modification with APTMS, and the uneven inner surface It can be seen that the metal alkoxide is attached to the metal and the size is reduced.

FIG. 6 is a TEM image showing the functionalization inside the pores of activated alumina. The upper left is untreated, the upper right is APTMS modified by a conventional method (using ethanol as a solvent), and the lower left is dehydrated. Without APTMS modification, the lower right is APTMS modification by the method of the present invention.
A photograph (scale bar: 2 nm) in the upper left (untreated alumina) shows a lattice image unique to alumina and shows that there are mesopores. Moreover, in the upper right (conventional method) photograph (scale bar: 20 nm), a part of the lattice image is visible, and many amorphous images peculiar to APTMS are not seen, so the surface modification (functionalization) is incomplete. I understand that. Furthermore, it can be seen from the lower left photo (without dehydration) (scale bar: 10 nm) that the mesopores are completely filled with APTMS.
On the other hand, in the lower right photo (by the method of the present invention) (scale bar: 10 nm), it can be seen that the surface is completely covered with APTMS, but mesopores are present.

  From the above, it can be said that by the method of the present invention, mesopores of the substrate (activated alumina) can be utilized and the inner surface of the pores can be functionalized with APTMS.

Example 3
An APTMS-treated mesoporous silica was obtained in the same manner as in Example 2 except that mesoporous silica (TMPS-4 manufactured by Taiyo Kagaku Co., Ltd.) was used as the substrate.
FIG. 7 is a physical adsorption isotherm of nitrogen gas of the obtained mesoporous silica, and FIG. 8 is a diagram showing a pore size distribution of the obtained mesoporous silica. In each figure, “Control” represents untreated mesoporous silica.
7 and 8 show the same results as those of the activated alumina modified with APTMDS obtained in Examples 1 and 2, respectively. In the case of mesoporous silica, the nanosized particles were also modified after modification with APTMS. It can be seen that the metal alkoxide is attached to the inner surface of the unevenness without blocking the uneven space, and the size is reduced.

FIG. 9 is a TEM image showing the functionalization inside the pores of mesoporous silica. The upper part is untreated, the lower part is APTMS-modified by the method of the present invention, and the left is a low magnification (scale bar). : 100 nm), and the right is a photograph with a high magnification (scale bar: 20 nm).
It can be seen from the low magnification TEM image on the left that an APTMS coating film is formed on the surface of the mesoporous silica fine particles. Moreover, it can be seen from the high-magnification TEM image on the right that APTMS has been introduced into the micropores.

Example 4
In this example, nylon nanofibers are used as the base material, (1) only the surface of the fiber base material can be effectively coated with metal alkoxide (APTMS) (surface functionalization), and (2) nanofibers It was confirmed that the nano-scale space between the fibers existing in the fiber can be filled and a highly adhesive thin film of metal alkoxide and nanofiber can be formed (filling).
(1) Functionalization of nylon Nylon was dissolved in 88% formic acid at 15 wt%, and this solution was fiberized by electrospinning (voltage 25.0 kV, flow rate 0.1 ml / h, collector syringe distance 15 cm).
Next, the produced nylon nanofibers were added to anhydrous toluene, and dehydrated for 3 hours in the same manner as in Example 1. Thereafter, the dehydrated nylon nanofibers were immersed in an APTMS solution dissolved in 5.2 g / 10 ml of anhydrous toluene for 2 hours. After immersion, the substrate was thoroughly washed with toluene and dried at 120 ° C. for 3 hours. At this time, the nanoscale gap existing as the gap between the nanofibers is maintained.
(2) Filling The method for producing nylon nanofibers is the same as the surface functionalization treatment in Example 4.
The produced nylon nanofibers are dehydrated by the same method and immersed in an APTMS solution having the same concentration. After soaking, it was taken out from the solution and directly subjected to a drying treatment at 120 ° C. for 3 hours.

FIG. 10 is an SEM image (scale bar: 2 μm) of nylon nanofiber. In the figure, the upper part is a cross-sectional observation, and the lower part is an observation from directly above.
In the figure, the left side is an untreated nylon nanofiber, the center is an SEM image of the nylon nanofiber obtained by the processing method (1), and the right side is obtained by the processing method (2). 2 is an SEM image of a nylon nanofiber.
As is apparent from the SEM image at the center, it can be seen that the surface-functionalized nylon nanofibers can be obtained by washing and removing the APTMS solution on the substrate surface and then drying. That is, the inside of the fiber has a higher density of trapped water than the fiber surface, and the metal alkoxide grows fine particles with the place where hydrolysis and polycondensation is started as the nucleus. Thus, the inside of the fiber (inner fiber surface) is functionalized with the metal alkoxide. This is to improve the mechanical strength of the nanofiber and the function as an air filter / underwater filter.
Further, as is apparent from the SEM image on the right side, it can be seen that the metal alkoxide (APTMS) fills the nanoscale gap of the nylon nanofiber without any gap. If preliminary hydrolysis (immersion treatment in a solution) is not performed, filling as shown in the right figure does not occur, and a gap is generated at the interface between the nanofiber and the metal alkoxide.

Example 5
In this example, nylon nanofibers were used as the base material, and treatment with Tip (titanium isopropoxide) was performed.
The method for producing the nylon nanofiber is the same as in Example 4.
Next, the produced nylon nanofibers were added to anhydrous toluene, and dehydrated for 3 hours in the same manner as in Example 4. Thereafter, the dehydrated nylon nanofibers were immersed for 2 hours in a Tip solution in which 5.2 g / 10 ml of anhydrous toluene was dissolved.
After immersion, thoroughly washed with toluene and dried at 120 ° C for 3 hours (surface functionalization); after immersion, taken out from the solution and subjected to drying treatment at 120 ° C for 3 hours (filling) Was made.

FIG. 11 is an SEM image (scale bar: upper 2 μm, lower 1 μm), upper is untreated nylon nanofiber, lower left is nylon nanofiber surface-functionalized with Tip by the method of the present invention, lower On the right is a nylon nanofiber filled with Tip by the method of the present invention.
As is apparent from the left SEM image, it can be seen that the surface-functionalized nylon nanofibers can be obtained by washing and removing the APTMS solution on the substrate surface and then drying. Further, as is apparent from the right SEM image, the metal alkoxide (APTMS) fills the nanoscale gap of the nylon nanofiber without any gap.

Example 6
In this example, an alumina PVP composite nanofiber was used as a base material, and the treatment with APTMS was performed.
First, an alumina PVP composite nanofiber was prepared by the following procedure.
(1) Alumina precursor sec trioxide butoxide (4.0 g) was dissolved in 29 ml of water.
(2) To this, 3.6 ml of nitric acid was slowly added dropwise to obtain a transparent and stable alumina sol.
(3) Next, 1.5 g of PVP was dissolved.
(4) 2.0 g of an aqueous ammonia solution was slowly added dropwise to this and sufficiently stirred.
(5) Using this solution, a fiber was formed by electrospinning. The formation conditions are: voltage: 25 kV, flow rate (solution extrusion speed); 1 m / h, TCD (distance from the tip of the syringe from which the solution is ejected to the collector); 20 cm, room temperature and normal pressure (6) 120 nanofibers obtained. Dry at ℃.

The alumina PVP composite nanofiber thus obtained was subjected to the same method as in Example 4 to obtain a nanofiber whose surface was functionalized with APTMS.
FIG. 12 is an SEM image (scale bar: 5 μm) of the obtained alumina PVP composite nanofiber. The left side is an unprocessed SEM image, and the right side is a SEM image of the surface functionalized by APTMS. From the left and right SEM images, it can be seen that surface-functionalized nylon nanofibers are obtained in this example.

Example 7
In this example, an alternating laminated film was used as a base material, and a treatment with TEOS (tetraethoxysilane) was performed.
First, an alternate laminated film was prepared by the following procedure.
(1) 0.1 mol / l PDDA (poly (diallyl dimethyl ammonium chloride)) was prepared.
(2) Separately, a mixed solution of PVA (Poly (vinyl alcohol)) and PAA (poly (acrylic acid)) was adjusted to a concentration of 1 wt% for the former and 20 mmol / l for the latter.
(3) The glass substrate was immersed in the PDDA solution for 15 minutes, and then immersed in pure water for 4 minutes.
(4) The glass substrate after the step (3) was immersed in a PVA / PAA mixed solution for 15 minutes, and then immersed in pure water for 4 minutes.
(5) The steps (3) and (4) were repeated a total of 5 times.
(6) After the alternate lamination (step (5)), the film was dried at 80 ° C. for 1 hour.

The alternating laminated film thus obtained was added to anhydrous toluene and subjected to dehydration treatment for 3 hours in the same manner as in Example 1. Thereafter, the alternately laminated film was immersed in a TEOS solution dissolved in 16 g / 10 ml of anhydrous toluene for 3 hours. After immersion, the substrate was thoroughly washed with toluene and dried at 80 ° C. for 3 hours.
FIG. 13 is an SEM image of the obtained alternating laminated film, the left side is an unprocessed SEM image, and the right side is a SEM image of a surface functionalized by TEOS. From the left and right SEM images, it can be seen that an alternating layered film having a surface function is obtained in this example.

Example 8
In this example, in order to confirm the performance when the present invention is applied to an aldehyde removal filter, the basic physical properties of activated alumina treated with APTMS obtained in Example 2 and various filters were compared.
The results are shown in Table 1.

Example 9
In this example, the adsorption amount of p-aminobenzenesulfonic acid per specific surface area was measured in order to compare the functional group density of the activated alumina treated with APTMS obtained in Example 2 and various filters.
The result is shown in FIG. In order from the left end, activated carbon (untreated), activated alumina (untreated), conventional APTMS-modified activated alumina (no dehydration treatment), and APTMS-modified activated alumina obtained in Example 2 (right end) are shown. .
From FIG. 14, when the method of the present invention is applied to activated alumina with APTMS treatment, the amount of p-aminobenzenesulfonic acid adsorbed per specific surface area is 27 times that of untreated alumina, which is higher than that of the conventional production method. It can be seen that it has a large adsorption capacity.

Example 10
In this example, the acetaldehyde removal performance of activated alumina treated by the method of the present invention was compared using other porous materials.
First, in order to reduce the moisture inside the pores of alumina, alumina was added to anhydrous toluene (1.0 g / 20 ml), followed by heat treatment at 105 ° C. for 3 hours. Next, 1.0 g of activated alumina in a slurry state was added to 2.5 ml of anhydrous toluene, and then 1.0 g of APTMS was added and stirred for 12 hours. After stirring, it was thoroughly washed with toluene, then washed with IPA, and finally dried at 120 ° C. for 3 hours.
For comparison, an APTMS-treated activated alumina was obtained in the same manner except that the heat treatment in anhydrous toluene was not performed.

For each of these two types of APTMS-treated activated alumina, and activated carbon and mesoporous silica, 135 ppm of acetaldehyde gas was added as an initial concentration to a 9-liter system, and the change with time in concentration was measured by gas chromatography.
The results are shown in FIGS.
FIG. 15 is a graph comparing the amount of aldehyde removed between activated alumina surface-functionalized by APTM of the present invention and activated alumina surface-functionalized by APTM without dehydration by heat treatment, and FIG. It is the figure which compared the aldehyde removal amount about the activated alumina, activated carbon, and mesoporous silica which surface-functionalized by APTM.
As is apparent from FIGS. 15 and 16, it can be seen that the product obtained by the method of the present invention has about 2.4 times the performance after 80 minutes as compared with the high adsorption amount activated carbon.

Further, it was confirmed by FTIR (infrared spectroscopy) that the acetaldehyde adsorbed did not desorb in the activated alumina surface-functionalized by the APTM of the present invention.
FIG. 17 is a diagram showing an infrared absorption spectrum. In the figure, the solid line is the one before adsorbing acetaldehyde (control), the dotted line is the adsorbed acetaldehyde, and the broken line is heated at 60 ° C. for 3 hours. After that.
In FIG. 17, the arrow represents the presence of acetaldehyde chemisorbed on the amine group derived from APTMS, and it can be seen that it has not been desorbed even after heating.

  As is clear from this example, the present invention is applied to a porous material such as mesoporous silica or activated alumina, and shows a molecular removal performance superior to activated carbon known as a high performance adsorbent. Further, when activated alumina is treated with APTMS (3-aminopropyltrimethoxysilane), desorption does not occur, and the acetaldehyde removal filter is superior to untreated activated carbon.

Example 11
In this example, in order to confirm that the physical durability of the uneven structure formed on the substrate surface can be enhanced, the present invention was applied to the silica fine particle unevenness produced on the substrate surface.
First, 40 nm silica fine particles were dispersed in an alcohol solvent (ethanol), and a concavo-convex structure was formed on the substrate surface by dip coating.
Next, this base material was immersed in anhydrous toluene and heat-treated at 105 ° C. to reduce the moisture inside the irregularities. Next, FAS (fluoroalkylsilane) was dispersed in anhydrous toluene, and the substrate after dehydration was immersed for 4 hours. Thereafter, the substrate was transferred to a toluene solvent and heated at 105 ° C. Finally, drying was performed at 120 ° C.
For comparison, a conventional method (EtOH method), that is, the substrate was immersed in an FAS solution dispersed in ethanol at 2 wt% for 4 hours and then dried at 120 ° C. was used.

In order to examine the durability of the obtained water-repellent coating layer, a peelability test using an adhesive tape was performed as follows.
A 3M Scotch tape is used as the adhesive tape, and the tape is brought into close contact with the surface of the substrate so that no air bubbles enter. Then peel off at once. This process was counted as one tape test, and the contact angle of the base material subjected to the tape test a specified number of times was measured to examine the durability.

FIG. 18 is a diagram showing the results for the irregular surface of the silica fine particles obtained by the method of the present invention, and FIG. 19 is a diagram showing the results for the irregular surface of the silica fine particles obtained by the conventional method. As shown in FIG. 18, what was obtained by the method of the present invention did not show a large change in the contact angle of the substrate even after 80 times of the tape test, but what was obtained by the conventional method was the tape test After 17 times, the contact angle is reduced by half, and the water repellent coating layer can be seen to be peeled off.
From these figures, it was found that a highly durable water-repellent coating can be achieved by applying the present invention to the silica fine particle irregularities produced on the substrate surface.

FIG. 20 is an SEM image (scale bar: 1 μm) of the silica fine particle irregularities produced on the substrate surface, the left is FAS-coated by the above-mentioned conventional method, and the right is FAS by the method of the present invention. It is a coating.
From the figure, it can be seen that in the case of applying the method of the present invention, the necking (adhesion) between the fine particles and the necking (adhesion) between the particles and the substrate are enhanced as compared with the conventional technique shown on the left.

The figure which illustrates typically the difference of the method of this invention, and the conventional method N2 adsorption isotherm of activated alumina treated with APTMS (aminopropyltrimethylsilane). The figure which shows the pore size distribution of the activated alumina which processed APTMS. N2 adsorption isotherm of the APTMS-treated activated alumina obtained in Example 2. The figure which shows the hole size distribution of the activated alumina by which the APTMS process obtained in Example 2 was carried out. It is a TEM image showing functionalization inside the pores of activated alumina, the upper left is untreated, the upper right is APTMS modified by the conventional method (using ethanol as solvent), the lower left is APTMS modified without dehydration The lower right is the APTMS-treated activated alumina obtained in Example 2. N2 adsorption isotherm of APTMS-treated mesoporous silica obtained in Example 3. The figure which shows the hole size distribution of the mesoporous silica by which the APTMS process obtained in Example 3 was carried out. It is a TEM image showing the functionalization inside the pores of mesoporous silica, the upper row is untreated, the lower row is APTMS-treated mesoporous silica obtained in Example 3 (left: low magnification, right: high magnification) ). It is a SEM image (upper section: cross section, lower section: observation from directly above) of nylon nanofibers, the left side is untreated nylon nanofibers, and the center is nylon nanofibers surface-functionalized with APTMS obtained in Example 4 Fiber, right side is nylon nanofiber filled with APTMS obtained in Example 4. It is a SEM image of a nylon nanofiber, the upper stage is an untreated nylon nanofiber, the lower stage left side is the nylon nanofiber functionalized with Tip obtained in Example 5, and the lower stage right side is obtained in Example 5. Nylon nanofiber filled with Tip. It is a SEM image of an alumina PVP composite nanofiber, the left side is an untreated one, and the right side is a surface functionalized by APTMS obtained in Example 6. It is a SEM image of an alternating laminated film, the left side is an unprocessed alternating laminated film, and the right side is an alternating laminated film surface-functionalized by TEOS obtained in Example 7. The figure which shows adsorption | suction of p-aminobenzenesulfonic acid per specific surface area of the active alumina by which the APTMS process obtained in Example 2 was carried out. The figure which compared the amount of aldehyde removal of the activated alumina surface-functionalized by APTM obtained in Example 10, and the thing without the dehydration process by heat processing. The figure which compared the amount of aldehyde removal of the activated alumina surface-functionalized by APTM obtained in Example 10, and another porous body. The figure which shows the infrared absorption spectrum of the activated alumina surface-functionalized by APTM of Example 10. The figure which shows the result of the tape test of the silica fine particle uneven | corrugated surface which carried out FAS coating by the method of this invention. The figure which shows the result of the tape test of the silica fine particle uneven | corrugated surface which carried out FAS coating by the conventional method. It is a SEM image of the silica fine particle unevenness | corrugation produced on the base-material surface of Example 11, the left is what FAS-coated by the conventional method, and the right is what FAS-coated by the method of this invention.

Claims (7)

A method of forming a thin film on a substrate by treating a substrate surface having nanoscale irregularities with a metal alkoxide solution or functionalizing the substrate surface, wherein the substrate is previously treated with an anhydrous solvent. A surface treatment method comprising a step of removing moisture adhering to the inside and the outer surface of the irregularities by heat treatment at a temperature not lower than the boiling point of water and not higher than the boiling point of an anhydrous solvent . The anhydrous solvent is toluene, hexane, DMF, 2-aminoethanol, 1-butanol, dimethyl sulfoxide, ethyl acetoacetate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, anisole / ethyl lactate, diethylene glycol dimethyl ether the surface treatment method according to claim 1 you wherein a is selected from polyethylene glycol monomethyl ether and anhydrides thereof.   The surface treatment method according to claim 1, wherein the metal alkoxide has at least one functional group necessary for the functionalization. The metal alkoxide solution, the surface treatment method according to any one of claims 1 to 3, the metal alkoxide is characterized Tei Rukoto are dissolved in anhydrous solvent.   The surface treatment method according to claim 1, wherein the substrate is immersed in a metal alkoxide solution to form or functionalize a thin film.   The surface treatment according to any one of claims 1 to 5, wherein the substrate having nanoscale irregularities is any one of activated alumina, activated carbon, mesoporous silica, nanofibers, and alternating laminated films. Method.   A substrate having nanoscale irregularities, the surface of which is treated with a metal alkoxide solution by the surface treatment method according to any one of claims 1 to 6. Wood.