JP2003181262A - Porous silica membrane for membrane emulsification - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous silica membrane which includes surface chemical modification groups in a large amount and has pores suitable for membrane emulsification. <P>SOLUTION: The porous silica membrane for membrane emulsification contains SiO<SB>2</SB>as a main component and has pores having diameters of 0.3 to 50 μm and diameters of ≤50 nm. It is preferable to produce the porous silica membrane by a sol-gel process utilizing phase separation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous membrane used in a so-called membrane emulsification method in which one liquid of immiscible liquids is dispersed in the other liquid through a porous membrane to produce an emulsion. Regarding

[0002]

2. Description of the Related Art Conventionally, fluids having different properties have been mixed in various industrial fields, and one example thereof is mixing fluids having different properties, water and oil. There is so-called emulsification, which is a mixture in which fine particles are dispersed and emulsified. As a method for producing this emulsion, a mechanical method in which a liquid to be a continuous phase and a liquid to be a dispersed phase and an emulsifier such as a surfactant are added, and the resulting mixed liquid is stirred by a machine such as a stirrer Then, there is a membrane emulsification method in which a liquid to be a dispersed phase is pressed into a liquid to be a continuous phase through a microporous membrane. In the former method, it is difficult to freely change the particle size of emulsion particles, which greatly affects the performance of the polymer by suspension polymerization, and the latter method is generally used. Heretofore, those listed as a porous membrane for use in the latter membrane emulsification _{method, CaO-B 2 O 3 -SiO} 2 -Al 2 O 3 based porous _{glass, CaO-B 2 O 3 -SiO} 2 -Al ₂ O ₃ -Na ₂ O-MgO based porous glass is available. Both are manufactured by utilizing the phase separation of multi-component glass.

[0003]

In order to adapt the film emulsification to various combinations of the disperse phase and the dispersion medium, the surface of the porous film needs to have a property corresponding to each emulsification system. For that purpose, a method of modifying the surface of the film by chemical modification is very effective. On the other hand, a silanol group can be present on the surface of the SiO ₂ gel, and the silanol group plays a role of a functional group which becomes a reaction site during surface chemical modification. However, the conventional porous membrane for membrane emulsification has a problem that the raw material is multi-component glass and contains a large amount of components other than silica, so that the surface functional groups are insufficient and sufficient surface chemical modification cannot be achieved. It was

[0004]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention comprises a porous silica for membrane emulsification containing SiO ₂ as a main component and having pores of 0.3 to 50 μm and 50 nm or less. Provide a membrane. The porous silica membrane of the present invention is preferably prepared by a sol-gel method utilizing phase separation. As the precursor of the network component that causes gel formation used in the sol-gel reaction, metal alkoxide,
Complexes, metal salts, organic modified metal alkoxides, organic crosslinked metal alkoxides, and partial hydrolysis products thereof,
A multimer which is a partial polymerization product can be used. The sol-gel transition by changing the pH of water glass as well as the aqueous silicate solution can be utilized in the same manner. More specifically, the means for achieving the above-mentioned object is to dissolve a water-soluble polymer and a thermally decomposable compound in an acidic aqueous solution, and then add a metal compound having a hydrolyzable functional group to carry out a hydrolysis reaction. After the product is solidified in the groove of the strip-shaped member, the wet gel is then heated to thermally decompose the low-molecular weight compound that was dissolved in advance when the gel was prepared, and then dried and heated to produce the product. Is preferred.

Here, the water-soluble polymer is theoretically a water-soluble organic polymer which can be formed into an aqueous solution having an appropriate concentration.
Any compound that can be uniformly dissolved in a reaction system containing an alcohol formed by a metal compound having a hydrolyzable functional group may be used, and specifically, a sodium salt or potassium salt of polystyrenesulfonic acid, which is a polymer metal salt, may be used. Salts, polyacrylic acids that are polymeric acids that dissociate into polyanions, polyallylamine and polyethyleneimine that are polymeric bases that produce polycations in aqueous solution, or neutral polymers that are ether-bonded to the main chain Polyethylene oxide having, and polyvinylpyrrolidone having a carbonyl group in the side chain are preferable. Further, formamide, polyhydric alcohol, or a surfactant may be used in place of the organic polymer, in which case glycerin is optimal as the polyhydric alcohol and polyoxyethylene alkyl ethers are optimal as the surfactant.

As the metal compound having a hydrolyzable functional group, a metal alkoxide or an oligomer thereof can be used, and those having a small number of carbon atoms such as methoxy group, ethoxy group and propoxy group are preferable. . Further, as the metal, a metal of an oxide finally formed, for example, Si, Ti, Zr, Al is used, and Si is preferable. The metal may be one kind or two or more kinds. On the other hand, the oligomer may be any oligomer that can be uniformly dissolved and dispersed in alcohol, and specifically, 1
It can be used up to about 0 mer.

The acidic aqueous solution is usually preferably a mineral acid such as hydrochloric acid or nitric acid having a concentration of 0.001 mol or more, or an organic acid such as acetic acid or formic acid having a concentration of 0.01 mol or more.

Phase separation / gelation can be achieved by storing the solution at room temperature of 40 to 80 ° C. for 0.5 to 5 hours. Phase separation / gelation involves a process in which an initially transparent solution becomes cloudy to cause phase separation between a silica phase and an aqueous phase and finally gelate. Due to this phase separation / gelation, the water-soluble polymer is in a dispersed state and their precipitation is substantially not caused.

Specific examples of the thermally decomposable compound to be coexisted in advance include urea or hexamethylenetetramine, formamide, N-methylformamide, N,
Organic amides such as N-dimethylformamide, acetamide, N-methylacetamide, and N, N-dimethylacetamide can be used, but since the pH value of the solvent after heating is an important condition, the solvent should be basic after thermal decomposition. There is no particular limitation as long as it is a compound. The thermally decomposable compound to coexist depends on the type of compound, but in the case of urea, for example,
The amount is 0.05 to 0.8 g, preferably 0.1 to 0.7 g per 10 g of the reaction solution. The heating temperature is, for example, 40 to 200 ° C. in the case of urea, and the pH of the solvent after heating.
The value is preferably 6.0 to 12.0. Further, a compound which produces a compound having a property of dissolving silica, such as hydrofluoric acid, by thermal decomposition can be similarly used.

In the above method, when a water-soluble polymer is dissolved in an acidic aqueous solution and a metal compound having a hydrolyzable functional group is added to carry out a hydrolysis reaction, a solvent-rich phase and a skeletal phase are formed in the groove. A gel that separates is produced. After the product (gel) has solidified and after an appropriate aging time, by heating the gel in a wet state, the amide compound previously dissolved in the reaction solution is thermally decomposed, and the inner wall surface of the skeletal phase The pH of the solvent in contact with is increased. Then, the solvent erodes the inner wall surface and changes the concave-convex state of the inner wall surface to gradually increase the pore diameter. In the case of a gel containing silica as the main component, the degree of change is very small in the acidic or neutral region, but as thermal decomposition becomes more active and the basicity of the aqueous solution increases, the part that constitutes the pores dissolves. Then, by re-precipitating in a flatter portion, the reaction in which the average pore diameter becomes large becomes remarkable.

In a gel having only three-dimensionally bound pores without giant pores, even if it is a soluble portion under equilibrium conditions, the eluting substance cannot diffuse to the external solution, so Pore structure remains in a considerable proportion. On the other hand, in a gel with a solvent-rich phase that becomes giant pores, many pores are bound only in two dimensions, and the exchange of substances with the external aqueous solution occurs frequently enough. The small pores disappear in parallel with the development of the, and the entire pore size distribution does not significantly expand.

In the heating process, the gel is placed under a closed condition, the vapor pressure of the thermal decomposition product is saturated, and the p
It is effective to set H to a steady value promptly.

The heat treatment time required for the dissolution / reprecipitation reaction to reach a steady state and to obtain a pore structure corresponding to the steady state changes depending on the size of the giant pores and the volume of the sample. It is necessary to determine the shortest treatment time at which the pore structure does not substantially change.

The gel that has undergone the heat treatment becomes a dry gel by evaporating the solvent. Since the coexisting substances in the starting solution may remain in this dried gel, it is possible to obtain the desired inorganic porous body by thermally decomposing organic substances and the like by performing heat treatment at an appropriate temperature. it can. The drying is performed by leaving it at 30 to 80 ° C for several hours to several tens of hours, and the heat treatment is performed at about 200 to 1200 ° C.

The porous silica membrane for membrane emulsification of the present invention obtained by the above method contains SiO2 as a main component and has pores of 0.3 to 50 microns and 50 nanometers or less. Here, the term “main component” means that most of the components are SiO ₂ , and it is most preferable that the content of SiO ₂ is 99.0% or more, but the present invention is not limited to this. The pores can be controlled by changing the heating time, temperature, etc. of the above-mentioned manufacturing method. Preferred pores are through pores
Is 0.6 to 20 microns, and the mesopores may be any pores including 0 as long as they are 50 nanometers or less.
This is because the strength becomes insufficient at 50 nm or more.

In the present invention, since the main component is SiO ₂ , a large amount of active silanol groups are contained and sufficient surface chemical modification can be achieved. The surface chemical modifier is not particularly limited, for example, methyltrimethoxysilane, hexamethyldisilane, vinyltrimethoxysilane, trimethylchlorosilane, silane coupling agents such as octadecyldimethylsilane,
Cyclic silicone compounds such as dihydrogenhexamethylcyclosiloxane and thermosetting silicone oils such as dimethylpolysiloxane can be used. Among these chemical modifiers, a chemical modifier having a carbon chain is preferable. As a result, various particles can be manufactured stably for a long time. The amount of carbon introduced by the modification is 3% by weight or more, preferably 10% by weight or more, from the viewpoint of stability.
The weight% here is the ratio to the total weight of silica gel and the modifying group.

Inorganic microspheres can be produced by dispersing the dispersed phase containing the particle raw material in the dispersion medium through the porous silica membrane of the present invention. As the dispersed phase, water or alcohol dispersion of metal oxide sol such as silica sol, metal, or other polymer raw material can be used. Examples of the polymer raw material include vinyl monomers such as styrenes, divinylbenzene, (meth) acrylic acid esters, and hydroxyalkyl (meth) acrylates, and condensation-type monomers such as dicarboxylic acid diols and dicarboxylic acid diamines. , As vinyl ether 1
It is possible to use vinyl ethers having a functionality of 4 to 4 and preferably a functionality of 2 or less. As the dispersion medium,
Any organic solvent with low hydrophilicity, such as alcohols,
Hydrocarbons and the like can be used. Specifically, hexane, cyclohexane, toluene, kerosene, chloroform, soybean, oil and the like can be used.

BEST MODE FOR CARRYING OUT THE INVENTION <Example 1> (Membrane production) Polyethylene oxide (molecular weight: 10,000)
0) 4.2 g was dissolved in 0.01 M acetic acid aqueous solution 50 ml, and tetramethoxysilane 24.7 ml was added under ice cooling and then stirred to obtain a uniform solution. The homogeneous solution in a closed solution,
The reaction was carried out at 40 ° C for 3 days, and the obtained gel was treated in a 0.5M aqueous urea solution at 110 ° C for 4 hours. After drying the obtained gel, it was heat-treated at 1050 ° C. or 950 ° C. for 5 hours, and formed into a disc shape having a diameter of 25 mm and a thickness of 1 mm with abrasive paper. The SEM photograph of the film is shown in Fig. 1, and the pore distribution measured by mercury intrusion measurement is shown in Fig. 2. From FIG. 2, it can be seen that the membrane of the present invention has pores of 1.2 μm and has a uniform pore diameter.

(Hydrophobic treatment) The obtained film was immersed in 10 ml of a toluene solution of 2 ml of diethylamino-octadecyldimethylsilane and reacted at 80 ° C. for 10 hours. Hexamethyldisilazane 2 ml toluene solution 10
The mixture was reacted in 80 ml at 80 ° C. for 2 hours, washed and dried. Table 1 shows the results of elemental analysis of the obtained hydrophobic film.

[Table 1] In Table 1, 1 and 3 are membranes not subjected to the hydrophobizing treatment by the above manufacturing method, and 2 and 4 are membranes subjected to the hydrophobizing treatment.

The hydrophobized membrane (porous membrane) was attached to the membrane emulsification system shown in FIG. In FIG. 3, (3) is a cylindrical silica housing, and the housing (3) is a dispersion medium (1).
It is housed in a container (6) containing. The porous membrane (4) of the present invention is attached to the tip of the housing (3). The housing (3) is fixed to the container (6) by a support (not shown). (7) is a closed cylindrical container containing the dispersed phase (2), and the upper end of the container has 2 openings.
Individually, one is the housing by piping (3)
The other is connected to the pipe from the nitrogen gas cylinder (5). Therefore, the dispersed phase (2) in the closed cylindrical container (7) is supplied to the housing (3) by pressurizing nitrogen gas.

Silica particles were produced by the following method using the membrane emulsification system of FIG. First, the porous membrane (4) was attached to a silica housing (3), and this was placed in a dispersion medium (1) in which 5 g of sorbitan monolaurate was dissolved in 500 ml of kerosene. The housing was filled with silica sol (Nissan Chemical: Snowtex N) to form a dispersed phase (2), and this was pressurized with nitrogen gas for emulsification. To the obtained emulsion dispersion, 5 ml of a 0.5 M ammonium chloride aqueous solution was added, and the mixture was stirred for 30 minutes and allowed to stand overnight. The precipitate was collected by filtration, dried and then heat-treated at 600 ° C. for 5 hours. The SEM photograph of the obtained silica particles is shown in FIG. Fig. 4-1 shows the silica particles obtained by the membrane emulsification of the synthetic membrane at 60 to 120 minutes, and Fig. 4-2 shows the silica particles obtained at the membrane emulsification of the synthetic membrane at 120 to 180 minutes. By using the porous membrane of the present invention, silica particles having a uniform diameter can be produced regardless of the emulsification time.

Comparative Example 1 A commercially available SPG film was purchased.
The SEM photograph of the film is shown in FIG. 5, and the pore distribution measured by mercury intrusion measurement is shown in FIG. The membrane pore diameter is 1.6 μm, and the pore diameter is uniform. The SPG film was immersed in 10 ml of a toluene solution of 2 ml of diethylamino-octadecyldimethylsilane,
The reaction was carried out at 0 ° C for 10 hours. Further, it was reacted in 80 ml of a toluene solution of 2 ml of hexamethyldisilazane at 80 ° C. for 2 hours, washed and dried. The results of elemental analysis of the obtained hydrophobic SPG film are shown in Table 1 above. SPG 5 in Table 1 is not subjected to the hydrophobic treatment (membrane of SEM photograph of FIG. 5), and 6 is the membrane subjected to the above hydrophobic treatment.

The hydrophobized SPG film was attached to the above-mentioned housing (3) of FIG. 3, and this was placed in a dispersion medium (1) in which 5 g of sorbitan monolaurate was dissolved in 500 ml of kerosene. The housing was filled with silica sol (Nissan Chemical: Snowtex N) to form a dispersed phase (2), and this was pressurized with nitrogen gas for emulsification. To the obtained emulsion dispersion, add 5 ml of 0.5 M ammonium chloride aqueous solution.
The mixture was added, stirred for 30 minutes and then left overnight. The precipitate is collected by filtration,
After drying, it was heat-treated at 600 ° C. for 5 hours. The SEM photograph of the obtained silica particles is shown in FIG. Figure 7-1 shows the film emulsification of SPG 60
Silica particles obtained in ~ 120 minutes, Figure 7-2 shows SPG membrane emulsification 1
The silica particles obtained in 20 to 180 minutes are shown. As can be seen from the comparison with FIG. 4, in the film emulsification using the SPG film, almost uniform silica particles can be produced in the initial stage of the emulsification, but as the emulsification time increases, the particle size distribution gradually widens. It is considered that this is because the amount of introduced carbon in the film is small, that is, the hydrophobicity is not sufficient, so that the film becomes wet with the emulsification time and the uniformity of the particle size is deteriorated.

[0023]

The porous silica film of the present invention is mainly composed of Si.
Since it is O ₂ , it can contain a large amount of active silanol groups necessary for surface chemical modification as compared with the conventional porous membrane.
At the same time, the present porous silica membrane is composed of through-holes suitable for membrane emulsification, and its pore distribution is as uniform as or higher than that of conventional membrane emulsification membranes. The center size of the pores is
It can be controlled in the range of 0.3 to 50 microns, and can also have pores of 50 nanometers or less.

[Brief description of drawings]

[Figure 1] SEM image of the synthesized film

FIG. 2 Pore distribution of synthesized membrane

[Fig. 3] Membrane emulsification system

FIG. 4 Silica particles obtained by membrane emulsification of synthetic membrane

FIG. 5: SEM image of SPG film

FIG. 6 Pore distribution of SPG membrane

FIG. 7: Silica particles obtained by film emulsification of SPG film

[Explanation of symbols]

1: Dispersion medium 2: Dispersed phase 3: Housing 4: Porous membrane

Continued front page    (72) Inventor Kazuki Nakanishi             64-10 Shimogamo Tatekura-machi, Sakyo-ku, Kyoto (72) Inventor Ken Hosoya             1 Uni, 1 Matsuchidai Chikuzen, Momoyama-cho, Fushimi-ku, Kyoto-shi             Heim Momoyama Goryoku 109 (72) Inventor Hiroyoshi Mizuguchi             59, Shakadani, Omiya, Kita-ku, Kyoto-shi (72) Inventor Tomoko Fuchigami             12-1 Tamachi, Matsugasaki Ichimachi, Sakyo-ku, Kyoto F-term (reference) 4G035 AB40 AC26                 4G072 AA28 AA41 BB02 BB15 HH30                       JJ47 KK01 KK17 LL17 MM01                       MM31 MM36 QQ06 QQ07 QQ09                       TT08

Claims (4)

[Claims] 1. A porous silica membrane containing SiO ₂ as a main component and having a pore size of 0.3 to 50 microns and 50 nanometers or less for emulsification. 2. The porous silica film according to claim 1, wherein the surface is chemically modified. 3. The porous silica membrane according to claim 2, wherein the chemical modification is a chemical modification with a carbon chain. 4. The porous silica film according to claim 3, wherein the amount of carbon introduced is 3% by weight or more.