JP6474583B2 - Method for manufacturing separation filter - Google Patents

Description

  The present invention relates to a method for manufacturing a separation filter.

  Separation membranes having permselectivity are widely used when collecting and separating a target substance from liquid or gas or when obtaining pure water from seawater. Since inorganic membranes containing ceramic materials such as silica have excellent gas strength, heat resistance, and solvent resistance, they have been researched and developed as porous membrane materials. In recent years, high separation properties that surpass polymer membranes, It has become clear to show permeability. On the other hand, inorganic membranes have drawbacks such as heavy weight per module, hardness, and brittleness.

  For this reason, an attempt has been made to develop a separation membrane having lightness and flexibility by combining an organic base material and a separation layer made of an inorganic or inorganic-organic hybrid material. For example, in Non-Patent Document 1, an attempt is made to form a hybrid silica film on an organic substrate. This separation membrane uses a plasma CVD (Chemical Vapor Deposition) method to form a hybrid silica membrane (film forming raw material: bistriethoxysilylethane (BTESE)) on polyamideimide.

JP 2012-254449 A

Patrick H. T. Ngamou, et al .; Plasma-deposited hybrid silica membranes with a controlled retention of organic bridges; Journal of Materials Chemistry A, 05 March 2013, 5567-5576

  In film formation by the plasma CVD method of Non-Patent Document 1, the Si—C—C—Si bond in BTESE, which is a film forming raw material, disappears, and only about 30% remains. That is, there is a problem that formation of pores in which Si—C—C—Si bonds are formed by bonds through oxygen atoms is insufficient. In addition, since the plasma CVD method requires an expensive apparatus, there is a problem that the manufacturing cost of the separation membrane is high.

  The present invention has been made in view of the above matters, and the object of the present invention is that the Si—X—Si bond (X is a linear saturated alkyl chain or a linear unsaturated alkyl chain) of the film forming raw material. An object of the present invention is to provide a method of manufacturing a separation filter that is maintained and low in manufacturing cost.

A method for producing a separation filter according to the present invention includes:
A polymer sol preparation step of preparing a polymer sol by mixing a compound represented by (RO) ₃ Si—X—Si (OR) ₃ and a solvent containing water;
An application step of applying the polymer sol on a heat-resistant polymer support composed of a film-like or hollow porous material having a pore diameter of 1 to 3 nm ;
Firing to form an inorganic-organic hybrid film having —Si—X—Si— bonds on the heat-resistant polymer support.
It is characterized by that.
(The above X represents a linear saturated hydrocarbon chain or a linear unsaturated hydrocarbon chain in which one or more hydrogens may be substituted, and R represents an alkyl group.)

  The heat-resistant polymer support is formed from a polymer compound selected from the group consisting of polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, and derivatives thereof. It is preferable that

  Moreover, it is preferable to bake at a temperature higher than 100 ° C. and lower than 400 ° C.

  Moreover, it is preferable to bake at 100 degreeC or more and 200 degrees C or less.

  In the method for manufacturing a separation filter according to the present invention, the Si—X—Si bond of the film forming raw material is maintained, and the pores in which the Si—X—Si bond is formed by a bond through an oxygen atom are sufficiently formed. Moreover, since the separation filter can be manufactured without using an expensive device, there is an advantage that the manufacturing cost is low.

It is process drawing of the manufacturing method of a separation filter. It is a schematic diagram which shows schematic structure of an inorganic organic hybrid film | membrane. 3A is a SEM photograph showing the surface of the SPES porous film, and FIG. 3B is a SEM photograph showing the surface of NTR7450-BTESE150. 4A is a cross-sectional view of the SPES porous membrane, and FIG. 4B is a SEM photograph showing a cross-section of NTR7450-BTESE150. It is a schematic block diagram of the apparatus used for experiment. It is a graph which shows the relationship between a separation factor and a calcination temperature. It is the graph (FIG. 7 (A)) which shows the time-dependent change of the flow rate of water and IPA of NTR7450-150, and the graph (FIG. 7 (B)) which shows the time-dependent change of the separation coefficient. It is a graph (FIG. 8 (A)) which shows the time-dependent change of the flow rate of water and IPA of NTR7450-BTESE150, and a graph (FIG. 8 (B)) which shows the time-dependent change of the separation coefficient. FIG. 9 is a graph showing changes over time in the flow rates of water and IPA of NTR7450-200 (FIG. 9A), and a graph showing changes over time in the separation coefficient (FIG. 9B). It is a graph (FIG. 10 (A)) which shows the time-dependent change of the flow rate of water and IPA of NTR7450-BTESE200, and a graph (FIG. 10 (B)) which shows the time-dependent change of the separation coefficient. 11A is a SEM photograph showing the surface of the PSf porous film, and FIG. 11B is a SEM photograph showing the surface of PSf-BTESE150. 12A is a SEM photograph showing a cross section of the PSf porous film, and FIG. 12B is a SEM photograph showing a cross section of PSf-BTESE150. It is a graph (FIG. 13 (A)) which shows the time-dependent change of the flow volume of water and IPA of PSf-BTESE150, and a graph (FIG. 13 (B)) which shows the time-dependent change of the separation coefficient. It is a graph which shows the time-dependent change of the water permeability coefficient of NTR7410-150-2, and the rejection rate of NaCl. It is a graph which shows the time-dependent change of the water permeation coefficient of NTR7410-BTESE150-2, and the rejection of NaCl.

  A method for producing a separation filter according to an embodiment of the present invention is a method of forming an inorganic-organic hybrid membrane that functions as a separation layer on a polymer support that is a base material. As shown in the process diagram of FIG. And a polymer sol preparation step, a coating step, and a baking step.

(Polymer sol preparation process)
A polymer sol is prepared by mixing a compound represented by (RO) ₃ SiXSi (OR) ₃ and a solvent containing water. In the above formula, R represents an alkyl group, and examples thereof include a methyl group, an ethyl group, and a propyl group.

In the above formula, X represents a linear saturated hydrocarbon chain or a linear unsaturated hydrocarbon chain in which one or more hydrogen atoms may be substituted, and X represents a linear saturated hydrocarbon residue. A linear olefinic hydrocarbon residue or a linear acetylene hydrocarbon residue is preferable. For _example, -C _{n H 2n} - in or linear saturated hydrocarbon residues _{represented, -C n H (2n-2} ) - a linear olefinic hydrocarbon residue represented, _-C n H _{And a} linear acetylene hydrocarbon residue represented by _(2n-4) -. In this case, n of the linear saturated hydrocarbon residue, that is, the number of carbon atoms is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less. Further, n of the linear olefinic hydrocarbon residue and the linear acetylene hydrocarbon residue is preferably 2 or more and 6 or less, more preferably 2 or more and 4 or less. This is because if the hydrocarbon chain is long, the structure becomes bent, the pore diameter of the formed inorganic-organic hybrid membrane tends to be non-uniform, and it may not function as a separation filter.

Specific examples of the compound represented by (RO) ₃ SiXSi (OR) ₃ include, for example, bistriethoxysilylethane, bistriethoxysilylbutane, bistriethoxysilyloctane, bistriethoxysilylethylene, bistriethoxysilylacetylene, and the like. .

When represented by (RO) ₃ SiXSi (OR) ₃ , an alkoxy group (OR) is hydrolyzed by mixing with a solvent containing water, and adjacent compounds are bonded to each other by Si—O—Si bond by dehydration condensation. To polymerize. More specifically, the above compound is dissolved in a solvent containing water (ethanol, propyl alcohol, etc.), and an acid (hydrochloric acid, nitric acid, etc.) or a base (ammonia, etc.) is added as a catalyst, followed by hydrolysis and polycondensation. A polymer sol can be prepared by stirring for a time sufficient for the reaction.

(Coating process)
The polymer sol prepared as described above is coated on a heat resistant polymer support. The polymer sol can be applied by various methods such as spin coating and dip coating, as well as immersing a non-woven fabric in the polymer sol and applying it onto a heat resistant polymer support.

  The heat-resistant polymer support is composed of a porous material having a plurality of fine pores, and has a heat resistance that can withstand the firing temperature in the subsequent firing step. As the heat-resistant polymer support, a hollow material such as a membrane or a hollow fiber membrane is used. The heat resistant polymer support is preferably a film having a heat resistance of 100 ° C. or higher, and more preferably a heat resistance of 200 ° C. or higher. Examples of the heat resistant polymer support include polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, and derivatives thereof. As the heat-resistant polymer support, a commercially available one (for example, NTR-7450 (product number): Nitto Denko Corporation as a film-shaped heat-resistant polymer support) may be used as it is.

(Baking process)
The applied polymer sol is dried and then baked. By performing the firing, the dehydration condensation further proceeds and the network becomes dense. The firing temperature is preferably set to a temperature higher than 100 ° C. from the examples described later. In addition, when firing at 400 ° C. or higher, the Si—X—Si alkyl chain is decomposed and pores are not formed. Therefore, firing at a temperature lower than 400 ° C. is preferable. Furthermore, it is preferable that it is 100 degreeC or more and 200 degrees C or less.

As described above, a separation filter in which an inorganic-organic hybrid film having a —Si—X—Si— bond is formed on a heat resistant polymer support is obtained. FIG. 2 shows a schematic diagram of an inorganic-organic hybrid film (in the figure, Si—X—Si bonds are Si—C ₂ H ₄ —Si bonds), but pores formed by dehydration condensation (see FIG. 2). The pore shown) serves to permeate one substance of the mixture while blocking the other substance.

  The separation filter manufacturing method described above does not require an expensive film forming apparatus unlike the plasma CVD method. For this reason, there exists an advantage that the manufacturing cost of a separation filter is cheap.

  By performing the firing temperature at such a low temperature that Si—X—Si bonds do not disappear, in the formed inorganic-organic hybrid film, pores due to —Si—X—Si—O— bonds are sufficiently formed.

  The obtained separation filter has a laminated structure of a heat-resistant polymer support as a base material and an inorganic-organic hybrid membrane. Since the heat-resistant polymer support is a polymer, it has flexibility. Since the inorganic-organic hybrid film also includes an organic component, it is excellent in flexibility. Since both have flexibility, the separation filter is also excellent in flexibility. Moreover, the separation filter is lighter than the inorganic separation membrane. For this reason, in the case of a flat plate-like separation filter formed using a film-like heat-resistant polymer support, it can be wound and used for a spiral type module or the like.

(Preparation of separation filter)

  BTESE (bistriethoxysilylethane) was added to water and stirred to prepare a polymer sol (BTESE sol). The weight% concentration of BTESE was 5 wt%, and the molecular weight of the BTESE sol was 5000 to 20000 wt / mol as measured by Zetasizer Nano (manufactured by Malverm).

  SPES (sulfonated polyethersulfone) porous membrane (NaCl blocking rate 50%, estimated pore diameter 1 nm, NTR-7450HG (product number), Nitto Denko Corporation) was washed with methanol and hydrochloric acid for 30 minutes, washed with ion-exchanged water and dried did. BTESE sol was applied to the SPES porous film by spin coating. And it baked for 30 minutes at 100 degreeC in nitrogen atmosphere. Application and baking were performed twice. In this way, an inorganic-organic hybrid membrane was formed on the surface of the SPES porous membrane, and a separation filter was produced. This separation filter is referred to as NTR7450-BTESE100.

  Moreover, the separation filter was produced by the same method as described above except that the baking was performed at 150 ° C. This separation filter is referred to as NTR7450-BTESE150.

  Moreover, the separation filter was produced by the same method as described above except that baking was performed at 200 ° C. This separation filter is referred to as NTR7450-BTESE200.

  In addition, as a reference example, a SPEF porous membrane was fired at 100 ° C., 150 ° C., and 200 ° C. in the same manner as described above without applying 5% BTESE sol. These are referred to as NTR7450-100, NTR7450-150, and NTR7450-200, respectively.

  An SEM photograph of the surface of the SPES porous film and an SEM photograph of the surface of the produced NTR7450-BTES150 are shown in FIGS. 3 (A) and 3 (B), respectively. Moreover, the SEM photograph of the cross section of SPES porous film and the SEM photograph of the cross section of NTR7450-BTESE150 are shown to FIG. 4 (A) and (B), respectively. It can be seen that an inorganic-organic hybrid film is formed on the surface of the SPES porous film by the coating and baking of the BTESE sol.

  Subsequently, the separation ability of the produced separation filter was verified using the apparatus shown in FIG.

  The suction pressure of the vacuum pump was -95 kPa, 90 wt% isopropyl alcohol aqueous solution (hereinafter, IPA aqueous solution) filled in the feed tank was sucked, and the IPA aqueous solution was permeated through the separation filter. And IPA and water which permeate | transmitted the separation filter with the cold trap using liquid nitrogen were collected. The heating was performed at an oven temperature of 105 ° C., and the separation filter was at a temperature of 103 ° C.

And while measuring the flow volume and molar concentration of IPA and water which permeate | transmitted the separation filter, the separation factor (separation factor) was computed. The higher the value of the separation factor, the higher the selectivity of the target substance to be separated. The separation factor was determined by the following formula.
Separation factor = (Y _W / Y _A ) / (X _W / X _A )
In the above formula, Y _W and Y _A represent the molar concentration of water downstream of the separation filter and the molar concentration of IPA, respectively. X _W and X _A represent the molar concentration of water upstream of the separation filter and IPA, respectively. Represents the molar concentration of.

  FIG. 6 shows the relationship between the separation factor and the firing temperature, and Table 1 shows the flow rate and the separation factor. FIGS. 7A and 7B show the change with time of the flow rate and the change with time of the separation coefficient in NTR7450-150, respectively. FIGS. 8A and 8B show the change over time in the flow rate and the change over time in the separation coefficient in NTR7450-BTESE150, respectively. FIGS. 9A and 9B show the change over time in the flow rate and separation coefficient of the NTR7450-200 in FIGS. 9A and 10B, and FIGS. Each change over time is shown.

  NTR7450-BTESE100, NTR7450-BTESE150, and NTR7450-BTESE200 all have higher separation factors than NTR7450-100, NTR7450-150, and NTR7450-200, respectively, and prevent IPA transmission. It can be seen that is significantly improved. This is because a dense network inorganic-organic hybrid film was formed by applying BTESE and baking. NTR7450-200 also has an improved separation factor, but it is thought that the holes formed in SPES itself have been reduced by firing.

  Moreover, even if the time-dependent change of the water which passes the separation filter of FIGS. 7-10, the flow volume of IPA, and a separation coefficient is seen, there are not many changes with time, and it has changed by the substantially constant value. Therefore, it can be seen that even when used for a long time, it has a resistance to exhibit a certain resolution.

  In place of NTR-7450HG, NTR-7410HG (product number, Nitto Denko Corporation; NaCl rejection 10%, estimated pore diameter 2-3 nm) was used as the heat-resistant polymer support in the same manner as in Example 1. A separation filter was produced. The firing temperature was 100 ° C. and 150 ° C. This separation filter is referred to as NTR7410-BTESE100 and NTR7410-BTESE150.

  As a reference example, NTR7410 was fired at 100 ° C. and 150 ° C. in the same manner as in Example 1 without applying 5% BTESE sol. These are referred to as NTR7410-100 and NTR7410-150, respectively.

  About the separation power of each produced separation filter, the separation of IPA was performed under the same conditions as described above using the apparatus of FIG. Table 2 shows the respective flow rates and separation factors.

  NTR7410-BTESE100 and NTR7410-BTESE150 have higher separation factors than NTR7410-100 and NTR7410-150, respectively, which prevents IPA permeation and greatly improves selectivity. I understand.

  Further, a PSf (polysulfone) porous membrane (pore size: 30-40 nm) was prepared as a heat resistant polymer support, washed with methanol and hydrochloric acid for 30 minutes, washed with ion-exchanged water and dried. BTESE sol was applied to the PSf porous film by spin coating. And it baked for 20 minutes at 150 degreeC in nitrogen atmosphere. Coating and baking were performed 5 times. In this way, a separation filter was produced. This separation filter is referred to as PSf-BTESE150.

  FIGS. 11A and 11B show an SEM photograph of the surface of the PSf porous film and an SEM photograph of the surface of PSf-BTESE 150, respectively. Moreover, the SEM photograph of the cross section of a PSf porous film and the SEM photograph of the cross section of PSf-BTESE150 are shown to FIG. 12 (A) and (B), respectively. It can be seen that an inorganic-organic hybrid film is formed on the surface of the PSf porous film.

  Regarding the separation ability of the produced separation filter, IPA was separated under the same conditions as described above using the apparatus of FIG. 5 described above and the IPA aqueous solution.

  Table 3 shows the flow rate and separation factor of PSf150 and PSf-BTESE150. FIGS. 13A and 13B show the change with time of the flow rates of water and IPA and the change with time of the separation coefficient in PSf-BTESE 150, respectively.

  In PSf150, the separation factor was 1, and IPA could not be separated. On the other hand, in PSf-BTESE150, the separation factor is improved to 762, and it can be seen that the selectivity is greatly improved by forming the inorganic-organic hybrid membrane on the PSf porous membrane. Moreover, even if it sees a time-dependent change, it turns out that the separation factor and the flow volume are substantially constant, and it has the tolerance to exhibit a constant separation ability even when used for a long time.

  Separation filters were produced in the same manner as in Example 1 except that NTR-7450HG and NTR-7410HG were used and the firing time was 15 minutes. The firing temperature was 150 ° C. The produced separation filters are referred to as NTR7450-BTES150-2 and NTR7410-BTES150-2, respectively.

  Further, as a reference example, NTR7450 and NTR7410 were fired at 150 ° C. in the same manner as in Example 1 without applying 5% BTESE sol in the same manner as described above. These are referred to as NTR7450-150-2 and NTR7410-150-2, respectively.

  About each created separation filter, NaCl aqueous solution (2000 ppm) was flowed on 25 degreeC and feed pressure 1.5MPa conditions, and the water permeability coefficient and the rejection rate of NaCl were measured. The results are shown in Table 4. FIG. 14 shows changes with time of the water permeability coefficient and NaCl rejection of NTR7410-150-2, and FIG. 15 shows changes with time of the water permeability coefficient and NaCl rejection of NTR7410-BTES150-2.

  In NTR7450-BTESE150-2 and NTR7410-BTESE150-2, compared with NTR7450-150-2 and NTR7410-150-2, it confirmed that the rejection rate of NaCl was improved and it can be used also as a reverse osmosis membrane.

  The separation membrane manufactured by the method for manufacturing a separation filter according to the present invention can be used for collection, separation, reverse osmosis membrane, and the like of a target substance from a liquid or gas.

Claims (4)

A polymer sol preparation step of preparing a polymer sol by mixing a compound represented by (RO) ₃ Si—X—Si (OR) ₃ and a solvent containing water;
An application step of applying the polymer sol on a heat-resistant polymer support composed of a film-like or hollow porous material having a pore diameter of 1 to 3 nm ;
Firing to form an inorganic-organic hybrid film having —Si—X—Si— bonds on the heat-resistant polymer support.
A method for manufacturing a separation filter.
(The above X represents a linear saturated hydrocarbon chain or a linear unsaturated hydrocarbon chain in which one or more hydrogens may be substituted, and R represents an alkyl group.) The heat-resistant polymer support is formed from a polymer compound selected from the group consisting of polysulfone, polyethersulfone, sulfonated polysulfone, sulfonated polyethersulfone, polyimide, polytetrafluoroethylene, polyvinylidene fluoride, and derivatives thereof. Being
The method for manufacturing a separation filter according to claim 1. Firing at a temperature higher than 100 ° C. and lower than 400 ° C.
The method for manufacturing a separation filter according to claim 1 or 2. Firing at 100 ° C. or more and 200 ° C. or less,
The method for manufacturing a separation filter according to claim 3.