JP3876433B2 - Porous silica membrane for membrane emulsification - Google Patents

Description

表１の１、３は上記製造法で疎水化処理をしなかった膜、２、４は上記疎水化処理を施した膜である。
【００１９】
該疎水化膜（多孔質膜）を図３の膜乳化システムに装着した。図３中（３）は、筒状のシリカハウジングであって、該ハウジング（３）は、分散媒（１）の入った容器（６）に収容されている。ハウジング（３）の先端には、本発明の多孔質膜（４）が装着されている。なお、ハウジング（３）は図示しない支持体で容器（６）に固定されている。
（７）は分散相（２）の入った密閉円筒容器であり、該容器の上端には開口が２個あいてあり、１つは配管により前記ハウジング（３）と連結し、もう一つは窒素ガスボンベ（５）からの配管と接続される。したがって、密閉円筒容器（７）内の分散相（２）は窒素ガス加圧により、ハウジング（３）に供給される。
【００２０】
図３の膜乳化システムを用い、次の方法でシリカ粒子を製造した。
先ず、多孔質膜（４）をシリカハウジング（３）に取り付け、これをソルビタンモノラウレート５ｇをケロシン５００ｍｌに溶解した分散媒（１）中に設置した。ハウジング内にシリカゾル（日産化学：スノーテックスＮ）を満たして分散相（２）とし、これを窒素ガスで加圧して乳化を行った。得られたエマルション分散液に、０．５Ｍ塩化アンモニウム水溶液を５ｍｌ添加し、３０分撹拌後１晩放置した。沈殿物をろ取し、乾燥後６００℃で５時間熱処理した。
得られたシリカ粒子のSEM写真を図４に示した。図4-1は合成膜の膜乳化60〜120分で得られたシリカ粒子、図4-2は合成膜の膜乳化120〜180分で得られたシリカ粒子を示す。本発明の多孔質膜を使用すれば、乳化時間にかかわらず均一な径を有するシリカ粒子を製造することができる。
【００２１】
＜比較例１＞
市販のＳＰＧ膜を購入した。
膜のSEM写真を図５に、水銀圧入測定による細孔分布を図６に示す。膜細孔径は1.6μｍ、細孔径は均一である。
ＳＰＧ膜を、ジエチルアミノ−オクタデシルジメチルシラン２ｍｌのトルエン溶液１０ｍｌに浸漬し、８０℃で１０時間反応させた。さらにヘキサメチルジシラザン２ｍｌのトルエン溶液１０ｍｌ中、８０℃で２時間反応させ、洗浄後乾燥した。
得られた疎水化ＳＰＧ膜の元素分析結果を前述の表１に示した。表１の５のＳＰＧは疎水化処理をしないもの（図５のSEM写真の膜）、６は上記疎水化処理をした膜である。
【００２２】
該疎水化ＳＰＧ膜を前述した図３のハウジング（３）に取り付け、これをソルビタンモノラウレート５ｇをケロシン５００ｍｌに溶解した分散媒（１）中に設置した。ハウジング内にシリカゾル（日産化学：スノーテックスＮ）を満たして分散相（２）とし、これを窒素ガスで加圧して乳化を行った。得られたエマルション分散液に、０．５Ｍ塩化アンモニウム水溶液を５ｍｌ添加し、３０分撹拌後１晩放置した。沈殿物をろ取し、乾燥後６００℃で５時間熱処理した。
得られたシリカ粒子のSEM写真を図７に示した。図7-1はSPG膜の膜乳化60〜120分で得られたシリカ粒子、図7-2はSPG膜の膜乳化120〜180分で得られたシリカ粒子を示す。図４との対比で分かるように、SPG膜を用いた膜乳化では、乳化初期はほぼ均一なシリカ粒子が製造できるが、乳化時間が長くなると、次第に粒径分布が広がることが分かる。これは膜の導入炭素量が少ないため、すなわち、疎水化が十分でないため、乳化時間につれて膜の濡れが起こり、粒径の均一性がくずれるためと考えられる。
【００２３】
【発明の効果】
本発明の多孔質シリカ膜は、主成分がSiO₂であるため、表面化学修飾に必要な活性シラノール基を、従来の多孔質膜と比較して多く含むことができる。
それと同時に本多孔質シリカ膜は、膜乳化に適した貫通孔からなり、さらにその細孔分布は従来の膜乳化用膜と同等以上の均一性を有する。また細孔の中心サイズは、０．３?５０ミクロンの範囲でコントロールでき、併せて５０ナノメートル以下の細孔を有することもできる。
【図面の簡単な説明】
【図１】合成した膜のSEM像
【図２】合成した膜の細孔分布
【図３】膜乳化システム
【図４】合成膜の膜乳化で得られたシリカ粒子
【図５】SPG膜のSEM像
【図６】SPG膜の細孔分布
【図７】SPG膜の膜乳化で得られたシリカ粒子
【符号の説明】
１：分散媒
２：分散相
３：ハウジング
４：多孔質膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous membrane used in a so-called membrane emulsification method in which an emulsion is produced by dispersing one of liquids that are not mixed together into the other liquid via a porous membrane.
[0002]
[Prior art]
Conventionally, in various industrial fields, fluids having different properties have been mixed. As an example, there is a mixture of water and oil, which are fluids having different properties, and the oil is made into fine particles in water. There is so-called emulsification which is dispersed and emulsified. As a method of producing this emulsion, a mechanical method of adding a liquid to be a dispersed phase and an emulsifier such as a surfactant to a liquid to be a continuous phase, and stirring the resulting mixture with a machine such as a stirrer 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 the emulsion particles, which greatly affects the performance of the polymer by suspension polymerization, and the latter method is generally used.
Conventional porous membranes used in the latter membrane emulsification method include CaO-B ₂ O ₃ —SiO ₂ —Al ₂ O ₃ porous glass, CaO—B ₂ O ₃ —SiO ₂ there are _{-Al 2 O 3 -Na 2 O-} MgO -based porous glass. Both are manufactured using the phase separation of multicomponent glass.
[0003]
[Problems to be solved by the invention]
In order to adapt membrane emulsification to various combinations of dispersed phases and dispersion media, the surface of the porous membrane needs to have properties corresponding to each emulsification system. For this purpose, a technique of modifying the surface of the film by chemical modification is very effective.
On the other hand, a silanol group can exist on the surface of the SiO ₂ gel, and the silanol group plays a role of a functional group that becomes a reaction site during surface chemical modification. However, conventional porous membranes for membrane emulsification have a problem that the raw material is multicomponent glass and contains a large amount of components other than silica, so that 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 provides a porous silica membrane for membrane emulsification comprising SiO ₂ as a main component and having pores of 0.3 to 50 microns and 50 nanometers or less.
The porous silica membrane of the present invention is preferably prepared by a sol-gel method using phase separation. Examples of the precursor of the network component that causes gel formation used in the sol-gel reaction include metal alkoxides, complexes, metal salts, organically modified metal alkoxides, organic cross-linked metal alkoxides, and partial hydrolysis products and partial polymerization products thereof. Can be used. Sol-gel transition by changing the pH of water glass and other silicate aqueous solutions can be used as well.
More specifically, the above-mentioned means for achieving the object is to dissolve a water-soluble polymer and a thermally decomposable compound in an acidic aqueous solution, and add a metal compound having a hydrolyzable functional group to perform a hydrolysis reaction. After the product has solidified in the groove of the shaped member, the wet gel is then heated to thermally decompose the low molecular weight compound previously dissolved during gel preparation, and then dried and heated. Is preferred.
[0005]
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 that are molecular bases that generate polycations in aqueous solution, or neutral polymers that are polyethylene oxide having an ether bond in the main chain and polyvinylpyrrolidone having a carbonyl group in the side chain are suitable. . In addition, formamide, polyhydric alcohol, or surfactant may be used in place of the organic polymer. In this case, glycerin is optimal as the polyhydric alcohol, and polyoxyethylene alkyl ethers are optimal as the surfactant.
[0006]
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 a methoxy group, an ethoxy group, and a propoxy group are preferable. As the metal, a metal of an oxide finally formed, such as Si, Ti, Zr, or Al, is used, but Si is preferable. 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. Specifically, it can be used up to about 10-mer.
[0007]
Moreover, as acidic aqueous solution, the thing of 0.001 mol concentration or more of mineral acids, such as hydrochloric acid and nitric acid, or 0.01 mol concentration or more of organic acids, such as an acetic acid and a formic acid, is preferable normally.
[0008]
The phase separation and 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 is a process in which an initially transparent solution becomes cloudy, causing phase separation between a silica phase and an aqueous phase and finally gelling. By this phase separation / gelation, the water-soluble polymers are in a dispersed state and their precipitation does not substantially occur.
[0009]
Specific examples of the thermally decomposable compound that coexists in advance include urea or hexamethylenetetramine, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide and the like. However, since the pH value of the solvent after heating is an important condition, there is no particular limitation as long as it is a compound that makes the solvent basic after thermal decomposition.
Although the thermally decomposable compound to coexist depends on the kind of the compound, for example, in the case of urea, it is 0.05 to 0.8 g, preferably 0.1 to 0.7 g, with respect to 10 g of the reaction solution. The heating temperature is preferably 40 to 200 ° C. in the case of urea, for example, and the pH value of the solvent after heating is preferably 6.0 to 12.0.
Moreover, what produces the compound with the property to melt | dissolve a silica like hydrofluoric acid by thermal decomposition can be utilized similarly.
[0010]
In the above method, when a water-soluble polymer is dissolved in an acidic aqueous solution and a hydrolysis reaction is performed by adding a metal compound having a hydrolyzable functional group thereto, a solvent-rich phase and a skeleton phase are separated in the groove. A gel is formed. After the product (gel) has solidified, an appropriate aging time has passed, and then the wet gel is heated to thermally decompose the amide compound dissolved in the reaction solution in advance. The pH of the solvent in contact with increases. The solvent erodes the inner wall surface, and gradually changes the pore size by changing the uneven state of the inner wall surface.
In the case of gels 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 vigorous and the basicity of the aqueous solution increases, the part constituting the pore dissolves. Then, by reprecipitation in a flatter portion, a reaction in which the average pore diameter becomes large occurs remarkably.
[0011]
In gels that have only three-dimensionally confined pores without huge pores, the elution substance cannot be diffused to the external solution even if it can be dissolved as an equilibrium condition. Remains in a considerable proportion. On the other hand, in a gel having a solvent-rich phase that becomes giant pores, there are many pores that are restricted only two-dimensionally, and exchange of substances with an external aqueous solution occurs frequently enough. In parallel with the development, small pores disappear and the entire pore size distribution does not spread significantly.
[0012]
In the heating process, it is effective to place the gel in a hermetically sealed condition so that the vapor pressure of the pyrolysis product is saturated and the pH of the solvent quickly takes a steady value.
[0013]
The heat treatment time required for the dissolution / reprecipitation reaction to reach a steady state and obtain the corresponding pore structure varies depending on the size of the huge pores and the volume of the sample. It is necessary to determine the shortest processing time at which the pore structure does not change.
[0014]
The gel after the heat treatment becomes a dry gel by evaporating the solvent. Since the coexisting substances in the starting solution may remain in this dry gel, the target inorganic porous material can be obtained by heat-treating at an appropriate temperature and thermally decomposing organic matter. it can. In addition, drying is performed by leaving at 30-80 degreeC for several hours-several dozen hours, and heat processing is heated at about 200-1200 degreeC.
[0015]
The porous silica membrane for membrane emulsification of the present invention obtained by the above method has SiO2 as a main component and has pores of 0.3 to 50 microns and 50 nanometers or less. Here, the “main component” means that most of the component is SiO ₂ , and it is most preferable that it contains 99.0% or more of SiO ₂ , but is not limited thereto. Control of the pores can be performed by changing the heating time, temperature, etc. of the above-described production method. Preferable pores have a through-pore (through-hole) of 0.6 to 20 microns, and the mesopore may be any pore including 0 as long as it is 50 nanometers or less. This is because the strength is insufficient when the thickness is 50 nanometers or more.
[0016]
In the present invention, since the main component is SiO ₂ , sufficient surface chemical modification can be achieved by containing a large amount of active silanol groups. The surface chemical modifier is not particularly limited. For example, silane coupling agents such as methyltrimethoxysilane, hexamethyldisilane, vinyltrimethoxysilane, trimethylchlorosilane, and octadecyldimethylsilane, and cyclic rings such as dihydrogenhexamethylcyclosiloxane. Thermosetting silicone oils such as silicone compounds and dimethylpolysiloxane can be used. Among these chemical modifiers, a chemical modifier with a carbon chain is preferable. Thereby, various grains 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. In addition, weight% here is a ratio with respect to the total weight which added the silica gel and the modification group.
[0017]
An inorganic microsphere can be produced by dispersing a dispersed phase having a particle raw material in a 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, and other polymer raw materials can be used. Examples of the polymer raw material include vinyl monomers such as styrenes, divinylbenzene, (meth) acrylic acid esters, hydroxyalkyl (meth) acrylates, and dicarboxylic acid diols and dicarboxylic acid diamines as condensation monomers. The vinyl ether can be monofunctional to tetrafunctional, preferably bifunctional or less vinyl ether.
As the dispersion medium, any organic solvent having low hydrophilicity may be used, and alcohols, hydrocarbons and the like can be used. Specifically, hexane, cyclohexane, toluene, kerosene, chloroform, soybean, oil and the like can be used.
DETAILED DESCRIPTION OF THE INVENTION
<Example 1>
(Membrane production)
Polyethylene oxide (molecular weight 10,000) 4.2g was melt | dissolved in 0.01M acetic acid aqueous solution 50ml, tetramethoxysilane 24.7ml was added under ice-cooling, and it stirred, and was set as the uniform solution. The homogeneous solution was reacted in a sealed solution at 40 ° C. for 3 days, and the resulting gel was treated in a 0.5 M urea aqueous solution at 110 ° C. for 4 hours.
The obtained gel was dried and then heat-treated at 1050 ° C. or 950 ° C. for 5 hours, and formed into a disk shape of 25 mmφ and 1 mm thickness with abrasive paper. The SEM photograph of the membrane is shown in FIG. 1, and the pore distribution by mercury intrusion measurement is shown in FIG. FIG. 2 shows that the membrane of the present invention has 1.2 μm pores and the pore diameter is uniform.
[0018]
(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. Furthermore, it was reacted at 80 ° C. for 2 hours in 10 ml of a toluene solution of 2 ml of hexamethyldisilazane, washed and dried.
Table 1 shows the results of elemental analysis of the resulting hydrophobic membrane.
[Table 1]

In Table 1, 1 and 3 are membranes that were not hydrophobized by the above production method, and 2 and 4 are membranes that were hydrophobized.
[0019]
The hydrophobic membrane (porous membrane) was attached to the membrane emulsification system of FIG. In FIG. 3, (3) is a cylindrical silica housing, and the housing (3) is accommodated in a container (6) containing a dispersion medium (1). 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) with a support (not shown).
(7) is a sealed cylindrical container containing the dispersed phase (2), and there are two openings at the upper end of the container, one is connected to the housing (3) by piping, and the other is It is connected to the piping from the nitrogen gas cylinder (5). Therefore, the dispersed phase (2) in the sealed cylindrical container (7) is supplied to the housing (3) by nitrogen gas pressurization.
[0020]
Silica particles were produced by the following method using the membrane emulsification system of FIG.
First, the porous membrane (4) was attached to the 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 emulsified by pressurization with nitrogen gas. 5 ml of 0.5M ammonium chloride aqueous solution was added to the obtained emulsion dispersion, stirred for 30 minutes, and left overnight. The precipitate was collected by filtration, dried and then heat treated at 600 ° C. for 5 hours.
An SEM photograph of the obtained silica particles is shown in FIG. Fig. 4-1 shows silica particles obtained in 60 to 120 minutes of membrane emulsification of the synthetic membrane, and Fig. 4-2 shows silica particles obtained in 120 to 180 minutes of membrane emulsification of the synthetic membrane. If the porous membrane of the present invention is used, silica particles having a uniform diameter can be produced regardless of the emulsification time.
[0021]
<Comparative Example 1>
A commercially available SPG membrane was purchased.
The SEM photograph of the membrane is shown in FIG. 5, and the pore distribution 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 and reacted at 80 ° C. for 10 hours. Furthermore, it was reacted at 80 ° C. for 2 hours in 10 ml of a toluene solution of 2 ml of hexamethyldisilazane, washed and dried.
The results of elemental analysis of the obtained hydrophobic SPG film are shown in Table 1 above. SPG of 5 of Table 1 is a thing which does not hydrophobize (film | membrane of the SEM photograph of FIG. 5), 6 is a film | membrane which carried out the said hydrophobization process.
[0022]
The hydrophobized SPG membrane was attached to the housing (3) of FIG. 3 described above, 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 emulsified by pressurization with nitrogen gas. 5 ml of 0.5M ammonium chloride aqueous solution was added to the obtained emulsion dispersion, stirred for 30 minutes, and left overnight. The precipitate was collected by filtration, dried and then heat treated at 600 ° C. for 5 hours.
An SEM photograph of the obtained silica particles is shown in FIG. Fig. 7-1 shows silica particles obtained in 60 to 120 minutes of SPG membrane emulsification, and Fig. 7-2 shows silica particles obtained in 120 to 180 minutes of SPG membrane emulsification. As can be seen from comparison with FIG. 4, in the membrane emulsification using the SPG membrane, almost uniform silica particles can be produced at the initial stage of emulsification, but as the emulsification time increases, the particle size distribution gradually increases. This is presumably because the amount of carbon introduced into the film is small, that is, the hydrophobicity is not sufficient, so that the film wets with the emulsification time and the uniformity of the particle size is lost.
[0023]
【The invention's effect】
Since the main component of the porous silica film of the present invention is SiO ₂ , it can contain more active silanol groups necessary for surface chemical modification than a conventional porous film.
At the same time, the present porous silica membrane comprises through-holes suitable for membrane emulsification, and the pore distribution has a uniformity equal to or higher than that of a conventional membrane emulsification membrane. The center size of the pores 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 the drawings]
Fig. 1 SEM image of synthesized membrane 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 SPG membrane SEM image [Fig. 6] Pore distribution of SPG membrane [Fig. 7] Silica particles obtained by membrane emulsification of SPG membrane [Explanation of symbols]
1: Dispersion medium 2: Dispersed phase 3: Housing 4: Porous membrane

Claims (1)

A porous silica membrane for emulsification prepared by a sol - gel method using phase separation, containing SiO ₂ as the main component, having 0.6 to 20 micron through pores and mesopores of 50 nanometers or less, and introducing carbon A porous silica membrane for membrane emulsification, which is chemically modified with a carbon chain whose amount is 3 weight percent or more .

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