JP4280860B2 - Method for producing porous material formed on substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a porous material on a substrate or a support. The production method of the present invention is suitably used for producing a porous plate for thin layer chromatography and a gel for electrophoretic analysis.
[0002]
[Prior art]
As a thin-layer chromatography carrier, one in which inorganic fine particles such as silica gel are applied in close contact on a glass plate is known. As the size of the inorganic fine particles is smaller and the shape is uniform, the analysis sensitivity is improved. However, the developing speed of the solution containing the sample is reduced as the particle diameter is reduced. In addition, although it is important to form a thin and uniform coating layer, it is difficult to form a coating layer with good reproducibility with a thickness of about 0.1 mm or less in the conventional manufacturing method.
[0003]
In general, an inorganic porous material such as silica gel is produced by a sol-gel method which is a liquid phase reaction. The sol-gel method refers to a general method for producing a low molecular compound capable of polymerization and finally obtaining an aggregate or a polymer. For example, hydrolysis of metal alkoxides, hydrolysis of metal chlorides, hydrolysis of metal salts or coordination compounds having hydrolyzable functional groups such as carboxyl groups and β-diketones, hydrolysis of metal amines Is mentioned. In addition, the carrier for thin-layer chromatography is generally non-uniformly shaped gel particles that have been gelled by adding strong acid to inexpensive water glass, and spherical particles mainly made of water glass. Has been used.
A thin layer chromatography carrier has been produced by applying a slurry in which silica gel fine particles are dispersed in a high concentration, and depositing physically aggregated fine particles in a layer form on a glass plate.
[0004]
[Problems to be solved by the invention]
However, the thin-phase chromatography support by the coating method generally has a porosity of 30 to 40% or less, and there is no method other than enlarging the particle diameter in order to increase the developing speed of the sample solution. Led to a decline. Further, a carrier having a thickness of about 0.1 mm requires a development distance of about 10 cm in order to separate a plurality of components. Although the method of controlling the porosity of a thin-layer chromatography carrier over a wide range and further reducing the thickness while maintaining the uniformity of the structure is sufficient, the separation performance of the resulting carrier is greatly improved. Was not developed.
[0005]
Therefore, the present inventors have studied that a gel film having a solvent-rich phase or a skeleton phase serving as a support portion having a pore size of about 100 nm or more on a substrate is first prepared by a sol-gel method, followed by heating. By performing the treatment, the shape of the solvent-rich phase region and the skeletal phase region becomes a cylindrical shape that penetrates the thickness of the gel phase, or the solvent-rich phase and the skeleton phase both penetrate the thickness of the gel phase and are parallel to the substrate. It has been found that a gel having a homogeneous porous structure with a film thickness of about 5 to 10 μm is formed which is composed of a co-continuous form or a solvent-rich phase region dispersed in a disk shape and a droplet shape smaller than the gel phase thickness. It was.
The present invention has been made based on such knowledge. The purpose is to provide a pore structure having a desired central pore diameter and a narrow distribution that could not be produced by a conventional coating method with good reproducibility, and has a homogeneous structure with high reproducibility over the entire membrane area. The result is to establish a method for producing an inorganic porous body formed on a substrate, which gives high separation performance and surface reaction characteristics.
[0006]
[Means for Solving the Problems]
The means is that a gel film having a solvent-rich phase that becomes giant vacancies of about 100 nm or more or a skeleton phase that becomes a carrier part of about 100 nm or more is formed on a substrate by a sol-gel method, followed by heat treatment. Therefore, the shape of the solvent-rich phase region or the skeletal phase region is a cylindrical shape that penetrates the thickness of the gel phase, or both the solvent-rich phase and the skeleton phase penetrate the thickness of the gel phase and are co-continuous in the dimension parallel to the substrate. The method is characterized in that a gel having a homogeneous porous structure composed of a solvent-rich phase region dispersed in a certain form or a disk shape and a droplet shape smaller than the thickness of the gel phase is produced.
[0007]
Here, the average size of the solvent-rich phase or the skeleton phase region is preferably about 100 nm or more, and more preferably 100 nm or more and 30 μm or less.
[0008]
In the present invention, the most effective method for producing an inorganic porous material that can control the pore structure is to use a metal alkoxide as a starting material, and if necessary, add an appropriate coexisting material to the raw material, And a sol-gel method that produces a structure having a solvent-rich phase. A suitable coexisting substance is a substance having a function of simultaneously inducing a sol-gel transition and a phase separation process, whereby it is separated into a solvent-rich phase and a skeleton phase and simultaneously gelled. As the coexisting substance, a polymer soluble in a solvent such as polyethylene oxide is desirable.
[0009]
As the metal compound having a hydrolyzable functional group used in the sol-gel method, a metal alkoxide or an oligomer thereof can be used. These compounds have, for example, a methoxy group, an ethoxy group, a propoxy group and the like having a carbon number. Less is preferred. Further, as the metal, an oxide metal finally formed, for example, Si, Ti, Zr, or Al is used. The metal may be one type or two or more types. On the other hand, any oligomer can be used as long as it can be uniformly dissolved and dispersed in alcohol. In addition, alkylalkoxysilanes in which some of the alkoxy groups of these silicon alkoxides are substituted with alkyl groups, and oligomers of up to about 10-mers thereof are preferably used. An alkyl-substituted metal alkoxide in which the central metal element is replaced with titanium, zirconium, aluminum or the like instead of silicon can also be used.
[0010]
Moreover, as acidic aqueous solution, the thing of 0.001 N or more of mineral acids, such as hydrochloric acid and nitric acid, or 0.1 N or more of organic acids, such as formic acid and acetic acid, is preferable normally.
[0011]
When the starting material is a silicon alkoxide that is not alkyl-substituted, it is effective to add a component that induces phase separation such as a water-soluble polymer such as polyethylene oxide or a surfactant as a coexisting material.
Here, the water-soluble polymer is theoretically a water-soluble organic polymer that can be formed into an aqueous solution having an appropriate concentration, and in a reaction system including an alcohol generated by a metal compound having a hydrolyzable functional group. The polymer metal salt is a sodium salt or potassium salt of polystyrene sulfonic acid, which is a polymer metal salt, polyacrylic acid which is a polymer acid and dissociates to form a polyanion, Polyallylamine and polyethyleneimine which are molecular bases and generate polycations in aqueous solution, or neutral polymers such as polyethylene oxide having an ether bond in the main chain, polyvinylpyrrolidone, and the like are preferable.
[0012]
In addition, the reaction rate and form can be controlled by adding a solvent to the above starting materials. The added solvent is not particularly limited as long as it improves the affinity between the silicate polymer and the water / alcohol mixed solvent, but the solubility parameter value of the organic silicate polymer and the water / alcohol mixed solvent is about 8 to 15. Methanol, ethanol, propanol, N, N-dimethylformamide, N-methylformamide, and the like having an intermediate polarity and relatively low vapor pressure are suitable.
[0013]
Metal, glass, and polymer can be used as the substrate for film formation, but there is no particular limitation on polymer substrates with extremely high water repellency, except that the adhesion of the film to the substrate is weakened. . When it is necessary to perform the heat treatment after film formation at a high temperature, a glass substrate is preferably used. In addition to a flat substrate, a film can be formed on a porous substrate having a through hole or a substrate having unevenness of about several tens of micrometers.
Particularly desirable in this means is the case where the skeleton phase is silica or organic silicate, the substrate is soda lime silica glass or polyester resin, and the additive solvent is N, N-dimethylformamide. Further, the composition of the coating solution is preferably 2.0 to 4.0 g of nitric acid aqueous solution and 0 to 5.0 g of N, N-dimethylformamide with respect to 9.55 g of methyltrimethoxysilane. More desirably, the aqueous nitric acid solution is 2.5 to 3.5 g and the N, N-dimethylformamide is 0 to 3.0 g with respect to 9.55 g of methyltrimethoxysilane.
[0014]
In the dip method in which the substrate is immersed vertically in the coating liquid and pulled up at a constant speed, the solvent phase in the coating liquid is obtained by rapid vaporization and evaporation of low-boiling components from the liquid film formed on the substrate near the liquid surface. If the composition changes and this causes a reduction in the chemical affinity between the dissolved oxide polymer and the solvent phase, phase separation is induced in the membrane. In a membrane that has undergone phase separation, a microscopic phase region is formed between a phase rich in an oxide polymer that easily forms a gel and a solvent phase that forms a fluid phase and becomes a pore after drying and heat treatment. Happens. Since the size of each phase region increases as the phase separation process lasts longer due to coarsening, the time from the preparation of the coating solution to the dipping operation is short, and the larger phase is obtained when the polymer is not sufficiently grown. After the region has a long time to dipping and the polymer has grown, the fine phase region is frozen as a film structure.
The pulling speed of the dip method is preferably 0.1 to 10 mm / sec.
[0015]
In the spin method in which the substrate is rotated at a constant speed to spread the coating solution in the planar direction and the excess solution is removed, it can be obtained by adjusting the time from preparation of the coating solution to film formation in exactly the same manner. The fine structure of the film can be controlled. In addition, as for the rotational speed in a spin method, 100-5000 rpm is preferable.
[0016]
Thus, since the phase separation structure in the film depends on the growth behavior of the metal oxide polymer in the coating liquid, the film forming characteristics of the coating liquid are impaired by some means such as inactivation of the polymerization site. If the growth of the polymer is stopped halfway, a certain film structure can be obtained thereafter regardless of the coating time.
[0017]
When the reaction time from the preparation of the solution to the coating increases, the volume fraction of the skeletal phase increases due to the growth of the polymer, so that the membrane structure is from a microporous membrane or a dispersed skeletal phase, It changes in the order of the continuous skeleton phase and the dispersed solvent-rich phase through a co-continuous structure of the solvent-rich phase and the skeleton phase. As the reaction time increases, the form of the dispersed solvent-rich phase changes from a cylindrical shape penetrating the thickness of the membrane to a disc shape thinner than the thickness of the membrane while reducing the diameter in the membrane surface direction.
[0018]
The structure of the film in the region where the reaction time from preparation of the coating solution to coating is short becomes microporous when a substrate having a high affinity with an organic silicate polymer such as a glass plate is used, When a substrate having the same degree of affinity as that of a solvent-rich phase such as polyester or an organic silicate phase is used, a dispersed skeleton phase is obtained. When using a substrate with extremely strong water repellency, such as a fluorocarbon resin, the reaction solution is dispersed in droplets before the film is formed and slips down, resulting in a film with very low adhesion. It is not suitable for the production of a porous membrane.
[0019]
Increasing the pulling speed when the coating is performed by the dip method or decreasing the rotation speed when the coating method is performed by the spin method increases the film thickness of the gel obtained by using the reaction solution under the same conditions, and the dispersed skeletal phase. The reaction time during which a change in morphology from a dispersed to a solvent-rich phase occurs moves to the short time side. The form control of this method is performed by the time from preparation of the reaction solution to film formation, and is also affected by the polarity of the substrate surface during film formation, the application / development speed of the solution, the atmosphere in the film formation chamber, etc. However, by maintaining the same reaction container and film forming apparatus and keeping the temperature history of the reaction solution the same, a porous film having a form depending on the reaction time from solution preparation to film formation can be obtained with good reproducibility.
[0020]
The sample after film formation becomes a dry gel film adhered to the substrate by evaporation of the solvent. In this dry gel film, coexisting substances in the starting solution may remain. Therefore, heat treatment is performed at an appropriate temperature, and organic matter is thermally decomposed as necessary. You can get a body. In addition, drying is performed by leaving at 40-100 degreeC for several hours-several dozen hours, and heat processing is heated at about 120-700 degreeC.
[0021]
【Example】
Example 1
First, 0.95 g of dimethylformamide was added to 3.09 g of 1 molar nitric acid aqueous solution to obtain a homogeneous solution, and then 9.55 g of methyltrimethoxysilane was added with stirring under ice-cooling for hydrolysis. After stirring for 5 minutes, the reaction solution was kept at 20 ° C., and a polymer was grown for a predetermined reaction time, and then a gel film was formed on the slide glass substrate by the dipping method. The substrate pulling rate in the dipping operation was 2 cm / min, and the film forming atmosphere was saturated water vapor.
[0022]
As a result, the microporous film adhered to the substrate until the reaction time of 210 minutes consists of a skeleton phase continuous with the dispersed macropores in the form of a cylinder or disk until the gelation time reaches 245 minutes. A porous membrane having a thickness of about 5 μm was obtained. The size of the macropores observed by SEM observation gradually decreased from about 3 to 5 μm in diameter at 215 minutes to about 1 to 2 μm in diameter at 240 minutes. FIG. 1 is a diagram (micrograph) showing the results of observing a three-dimensional structure of the former film and FIG. 2 using a laser confocal microscope.
[0023]
-Example 2-
In the reaction composition of Example 1, only the addition amount of dimethylformamide was changed, and the other conditions were the same to obtain a gel film. When dimethylformamide was not added, the reaction time for changing from the microporous membrane to the macroporous membrane was 95 minutes, and the gelation time was shortened to 150 minutes. When dimethylformamide was 0.48 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 160 minutes, and the gelation time was 195 minutes. In the case of 1.43 g of dimethylformamide, the reaction time for changing from the microporous membrane to the macroporous membrane was 262 minutes, and the gelation time was 300 minutes. When dimethylformamide was 1.9 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 340 minutes, and the gelation time was 370 minutes. Thus, the gelation time increases as the amount of dimethylformamide added increases, and the reaction time for changing from the microporous membrane to the macroporous membrane relatively approaches the gelation time.
[0024]
Example 3
In the reaction composition of Example 1, only the amount of the nitric acid aqueous solution was changed, and the other conditions were the same to obtain a gel film. When the nitric acid aqueous solution was 2.42 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 170 minutes, and the gelation time was 370 minutes. When the nitric acid aqueous solution was 2.69 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 190 minutes, and the gelation time was 305 minutes. When the nitric acid aqueous solution was 2.82 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 205 minutes, and the gelation time was 275 minutes. When the nitric acid aqueous solution was 2.96 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 210 minutes, and the gelation time was 270 minutes. When the nitric acid aqueous solution was 3.23 g, the reaction time for changing from the microporous membrane to the macroporous membrane was 215 minutes, and the gelation time was 230 minutes. Thus, the gelation time decreases as the amount of nitric acid aqueous solution increases, and the reaction time for changing from the microporous membrane to the macroporous membrane relatively approaches the gelation time.
[0025]
Example 4
In the reaction composition of Example 1, only a pulling rate was changed, and other conditions were the same to obtain a gel film. When the pulling rate was 1 cm / min, the time for changing from the microporous membrane to the macroporous membrane was 220 minutes, and when the pulling rate was 4 cm / min, the same time was 205 minutes. Thus, when the pulling speed is increased and the film thickness at the time of film formation is increased, the time for obtaining a continuous skeletal phase moves to the short time side.
[0026]
-Example 5
First, 0.95 g of dimethylformamide was added to 3.09 g of 1 molar nitric acid aqueous solution to obtain a homogeneous solution, and then 9.55 g of methyltrimethoxysilane was added with stirring under ice-cooling for hydrolysis. After stirring for 5 minutes, the reaction solution was kept at 20 ° C., and a polymer was grown for a predetermined reaction time, and then a gel film was formed on the polyester substrate by the dipping method. The substrate pulling rate in the dipping operation was 2 cm / min, and the film forming atmosphere was saturated water vapor.
As a result, a membrane in which a skeletal phase in the micrometer region is dispersed until a reaction time of 205 minutes, and then a skeleton phase continuous with dispersed macropores in a cylindrical or disk shape until a gelation time of 250 minutes is reached. A porous membrane having a thickness of about 5 μm was obtained. The size of the macropores observed by SEM observation gradually decreased from about 3 to 5 μm in diameter at 205 minutes to about 1 to 2 μm in diameter at 240 minutes.
[0027]
-Example 6
In the reaction composition of Example 5, only the addition amount of dimethylformamide was changed, and other conditions were the same to obtain a gel film. In the case of 0.48 g of dimethylformamide, only a film in which the skeleton phase was dispersed was obtained in all the reaction times up to 195 minutes of gelation time. In the case of 0.76 g of dimethylformamide, the reaction time for changing the structure in which the skeleton phase and the macropores are both continuous from the film in which the skeleton phase is dispersed is 170 minutes, and between 170 minutes and 185 minutes, Obtained. In a longer reaction time, a film in which macropores were dispersed was obtained, and the gelation time was 235 minutes. In the case of 1.14 g of dimethylformamide, the reaction time for changing from the membrane in which the skeleton phase was dispersed to the macroporous membrane was 255 minutes, and the gelation time was 310 minutes. Thus, the gelation time increases as the amount of dimethylformamide added increases, and the reaction time for changing from the membrane in which the skeleton phase is dispersed to the macroporous membrane is relatively close to the gelation time.
[0028]
-Example 7-
In the reaction composition of Example 5, only the amount of the nitric acid aqueous solution was changed, and the other conditions were the same to obtain a gel film. When the nitric acid aqueous solution was 2.96 g, only a film in which the skeleton phase was dispersed was obtained in all the reaction times up to the gelation time of 270 minutes. When the nitric acid aqueous solution is 3.03 g, the reaction time for changing the structure in which the skeleton phase and the macropores are both continuous from the film in which the skeleton phase is dispersed is 190 minutes, and the co-continuous structure is between 190 minutes and 205 minutes. Obtained. In a longer reaction time, a film in which macropores were dispersed was obtained, and the gelation time was 250 minutes. When the nitric acid aqueous solution was 3.23 g, the reaction time for changing from the membrane in which the skeleton phase was dispersed to the macroporous membrane was 220 minutes, and the gelation time was 235 minutes. When the nitric acid aqueous solution was 3.30 g, the reaction time for changing from the membrane in which the skeleton phase was dispersed to the macroporous membrane was 210 minutes, and the gelation time was 220 minutes. Thus, the gelation time decreases as the amount of nitric acid aqueous solution increases, and the reaction time for changing from a membrane in which the skeletal phase is dispersed to a macroporous membrane relatively approaches the gelation time.
[0029]
【The invention's effect】
As described above, according to the present invention, a pore structure having a desired central pore diameter and a narrow distribution, which could not be produced by a conventional coating method, is provided with good reproducibility and has a homogeneous structure over the entire membrane area. As a result, it is possible to obtain an inorganic porous body formed on a substrate that gives high separation performance and surface reaction characteristics in thin-layer chromatography.
[Brief description of the drawings]
FIG. 1 is a three-dimensional observation image of a gel produced in Example 1, with a macropore diameter of 3 to 5 μm.
2 is a three-dimensional observation image of the gel prepared in Example 1, with a macropore diameter of 1 to 2 μm. FIG.

Claims (1)

Inducing a sol-gel transition and phase separation to produce a gel film having a solvent-rich phase that is a giant pore of about 100 nm or more and a skeleton phase that is a carrier part of about 100 nm or more on a substrate , followed by heat treatment By doing so, the shape of the solvent-rich phase region or the skeletal phase region is a cylindrical shape that penetrates the thickness of the gel phase, or the solvent-rich phase and the skeletal phase penetrate through the gel phase thickness and are co-continuous in the dimension parallel to the substrate. Porous material for thin layer chromatography characterized by producing a gel with a homogeneous porous structure consisting of a solvent-rich phase region dispersed in a certain form or in a disk shape and droplet shape smaller than the gel phase thickness Manufacturing method.

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