JP7516174B2 - Gas separation membrane and method for producing same - Google Patents

Description

The present invention relates to a gas separation membrane and a manufacturing method thereof, and is particularly effective when applied to the separation of nitrogen gas and oxygen gas, or the separation of nitrogen gas and carbon dioxide gas, etc.

For example, the one described in Patent Document 1 below is known as a gas separation membrane that separates a specific type of gas from a mixture of multiple types of gas. This gas separation membrane has a separation layer made of an inorganic material provided on a porous substrate membrane made of an inorganic material, and gas permeability and selectivity are improved by making the surface roughness of the separation layer 10 μm or less, providing a protective layer made of an organic material on the separation layer, and forming an impregnation layer in which the separation layer is impregnated into the porous substrate membrane.

JP 2018-167149 A Patent No. 5626950

There is a strong demand for further improvement in the gas separation performance of gas separation membranes such as those mentioned above.

For this reason, the present invention aims to provide a gas separation membrane and a method for producing the same that can further improve gas separation performance.

In order to solve the above-mentioned problems, the gas separation membrane of the present invention comprises a porous substrate and a separation layer made of a polymeric material having gas permeability, which is arranged so as to cover one side of the porous substrate, and is characterized in that clusters of agglomerated particles are arranged within the pores of the porous substrate so as to be in contact with the separation layer , and the clusters are arranged within the pores of the porous substrate to a depth of 200 nm or less from the interface of the separation layer .
In addition, in order to solve the above-mentioned problems, the gas separation membrane of the present invention comprises a porous substrate and a separation layer made of a polymeric material having gas permeability, which is arranged so as to cover one side of the porous substrate, and clusters of agglomerated particles are arranged within the pores of the porous substrate so as to be in contact with the separation layer, the separation layer contains a plurality of agglomerated particles, and the clusters are present in the polymeric material having gas permeability.

In addition, the method for producing a gas separation membrane according to the present invention comprises a porous substrate, and a separation layer made of a polymeric material having gas permeability and arranged so as to cover one side of the porous substrate, in which clusters of agglomerated particles are arranged within the pores of the porous substrate so as to be in contact with the separation layer, and is characterized in that the method for producing a gas separation membrane comprises adding raw materials for the particles and the polymeric material to a solvent, mixing and stirring the raw materials to prepare a coating liquid, applying the coating liquid to one side of the porous substrate in a manner to push the coating liquid into the porous substrate, and then drying the resulting membrane.

According to the gas separation membrane of the present invention, the gas separation performance can be further improved.
Furthermore, according to the method for producing a gas separation membrane of the present invention, the gas separation membrane of the present invention can be easily produced.

1 is a cross-sectional view showing a schematic configuration of a main embodiment of a gas separation membrane according to the present invention. FIG. 2 is a schematic diagram of the particle of FIG. 1. 1 is a transmission electron microscope photograph of specimen 2 in an example of a gas separation membrane according to the present invention. 1 is a transmission electron microscope photograph of test piece 20.

The gas separation membrane and its manufacturing method according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments described with reference to the drawings.

[Main embodiment]
A gas separation membrane and a method for producing the same according to a preferred embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the gas separation membrane 100 according to this embodiment comprises a porous substrate 110 having a large number of holes 111, and a separation layer 120 made of a polymeric material having gas permeability and arranged to cover one side (the upper side in FIG. 1) of the porous substrate 110. Clusters 130 of particle groups having a plurality of aggregated particles 131 are arranged in the holes 111 of the porous substrate 110 so as to contact the separation layer 120.

The porous substrate 110 is made of a resin in a sheet shape, such as polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), etc.

Such a porous substrate 110 preferably has a thickness t1 of 5 μm or more and 50 μm or less, and more preferably 15 μm or more and 25 μm or less. If the thickness t1 is less than 5 μm, it is undesirable because it is too thin and the particles 131 have difficulty penetrating inside, and if it exceeds 50 μm, it is undesirable because it is too thick and gas permeability (permeation rate) is likely to decrease.

In addition, the porous substrate 110 preferably has a diameter d1 of the pores 111 of 10 nm or more and 100 nm or less. If the diameter d1 is less than 10 nm, it is undesirable because the pores are too small and the particles 131 have difficulty entering the interior, whereas if the diameter d1 exceeds 100 nm, it is undesirable because the pores are too large and the particles 131 easily pass through the interior.

Furthermore, it is preferable that the porosity of the porous substrate 110 is 35% or more and 85% or less. If the porosity is less than 35%, the particles 131 that penetrate into the interior will be too few, which is not preferable, and if it exceeds 85%, the particles 131 that penetrate into the interior will be too many, which is not preferable.

The separation layer 120 is made of a polymeric material in the form of a sheet, such as a polymer of intrinsic microporosity (PIM), poly(1-trimethylsilyl-1-propyne) (PTMSP), polydimethylsiloxane (PDMS), polyimide (PI), polycarbonate (PC), polyethyleneimine (PEI), etc. Among these, "PIM" is preferred, and "PIM-1" obtained by reacting 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane with tetrafluoroterephthalonitrile is even more preferred.

In addition, the separation layer 120 preferably has a thickness t2 of 50 nm or more and 500 nm or less. If the thickness t2 is less than 50 nm, it is undesirable because it is too thin and prone to defects, and if it exceeds 500 nm, it is undesirable because it is too thick and prone to reducing gas permeability (permeation rate).

The clusters 130 are preferably provided within the pores 111 of the porous substrate 110 to a depth t3 of 200 nm or less from the interface with the separation layer 120, and more preferably to a depth t3 of 100 nm or less. If the depth t3 exceeds 200 nm, this is not preferable as it tends to cause a decrease in gas permeability (permeation rate).

In addition, it is preferable that the clusters 130 are equal to or smaller than the diameter d1 of the holes 111 of the porous substrate 110. If the diameter is larger than d1, it is difficult for the clusters 130 to penetrate into the holes 111 of the porous substrate 110, which is likely to lead to a decrease in gas permeability (permeation rate), and this is not preferable.

As shown in FIG. 2, the particles 131 of the cluster 130 are preferably surface-modified particles in which multiple modifying groups 133 are linked to the surface of a particle core 132 made of an inorganic material. The modifying groups 133 are preferably organic molecules that extend in a chain shape. For example, organic polymers that extend in a chain shape while branching, such as the "hyperbranched polymers" and "dendrimer polymers" disclosed in the above-mentioned Patent Document 2, are very bulky, making it easier to form spaces (nanospaces) 134 around the particle core 132 and facilitating the aggregation of the particles 131, and are therefore highly preferred.

The separation layer 120 contains a plurality of aggregated particles 131 (not shown), and the clusters 130 are present in a matrix of the aforementioned polymeric material having gas permeability (not shown). In such a separation layer 120 and clusters 130, it is preferable that the particles 131 are present in a ratio of 20% by mass to 60% by mass. If it is less than 20% by mass, the amount of aggregated particles 131 becomes too small, which is not preferable, and if it exceeds 60% by mass, the aggregated particles 131 become too large, which is not preferable.

The gas separation membrane 100 according to this embodiment having such a structure can be easily manufactured by adding the particles 131 and the raw materials of the aforementioned polymeric material to a solvent such as tetrahydrofuran (THF), mixing and stirring to prepare a coating liquid, applying the coating liquid to one side of the porous substrate 110 in a pushing manner, and then drying.

At this time, it is preferable that the pressure of the coating liquid against the porous substrate 110 is 0.1 Pa/m ² or more and 0.4 Pa/m ² or less. If it is less than 0.1 Pa/m ² , it is difficult to push a sufficient amount of the coating liquid into the inside of the holes 111 of the porous substrate 110, which is not preferable, and if it exceeds 0.4 Pa/m ² , not only is there a risk that the coating liquid is pushed too far into the inside of the holes 111 of the porous substrate 110, but there is also a risk that the porous substrate 110 may be damaged, which is not preferable.

In addition, it is preferable that the coating liquid contains a mixture of polymer material in a ratio of 2% by mass to 5% by mass relative to the mass of the solvent. If it is less than 2% by mass, the separation layer 120 tends to become thin, which is likely to lead to a decrease in gas separation performance, and if it exceeds 5% by mass, the separation layer 120 tends to become thick, which is likely to lead to a decrease in gas permeability (permeation rate), and this is not preferable.

In the gas separation membrane 100 according to this embodiment obtained in this manner, when a mixed gas containing different types of gases (e.g., a mixed gas of nitrogen gas and oxygen gas, or a mixed gas of nitrogen gas and carbon dioxide gas, etc.) is circulated on the separation layer 120 side and the porous substrate 110 side is placed in a reduced pressure environment, the mixed gas penetrates into the separation layer 120.

The mixed gas that has entered the separation layer 120 permeates through the inside of the separation layer 120 at different speeds depending on the type of gas, such as molecular size, so there is a difference in the time it takes for each gas to permeate to the porous substrate 110, and the gases are separated (concentrated) within the separation layer 120.

The gas that has permeated through the separation layer 120 and reached the porous substrate 110 enters the nanospace 134 formed by the modification group 133 of the particles 131 of the cluster 130 from the separation layer 120, passes between the nanospaces 134 of the aggregated particles 131, and is sent into the pores 111 of the porous substrate 110, and is collected outside the porous substrate 110.

At this time, when the gas separated (concentrated) in the separation layer 120 enters the pores 111 of the porous substrate 110 where Knudsen diffusion occurs, it is desorbed from the separation layer 120 more quickly by passing through the clusters 130. Therefore, in the gas separation membrane 100 according to this embodiment, the gas permeation in the separation layer 120 can be accelerated, and the gas permeability can be greatly improved.

Therefore, according to the gas separation membrane 100 of this embodiment, the gas separation performance (particularly the permeability) can be further improved. And, according to the manufacturing method of the gas separation membrane 100 of this embodiment, the gas separation membrane 100 of this embodiment can be easily manufactured.

[Other embodiments]
In the above-described embodiment, the gas separation membrane 100 is provided with the separation layer 120 and the clusters 130 using the same particles 131 and polymeric material, but the present invention is not limited thereto. As another embodiment, for example, a gas separation membrane provided with a separation layer and clusters using different particles and polymeric materials may be used.

However, as in the above-mentioned embodiment, a gas separation membrane 100 having a separation layer 120 and clusters 130 made of the same particles 131 and polymeric material is highly preferable because the formation of the separation layer 120 and the formation of the clusters 130 can be carried out simultaneously, further simplifying manufacturing.

In addition, in the above-mentioned embodiment, the gas separation membrane 100 having a separation layer 120 containing particles 131 has been described, but the present invention is not limited to this. As another embodiment, for example, it is also possible to provide a gas separation membrane having a separation layer made of the above-mentioned polymer material that does not contain particles 131.

However, as in the above-mentioned embodiment, a gas separation membrane 100 having a separation layer 120 containing particles 131 is highly preferable because it can further increase the gas permeation rate through the separation layer 120 and further improve the gas separation performance (particularly permeability).

In addition, in the above-mentioned embodiment, the gas separation membrane 100 in which the clusters 130 are present in the matrix of the above-mentioned polymer material having gas permeability has been described, but the present invention is not limited to this. As another embodiment, for example, a gas separation membrane having clusters formed by agglomerating a plurality of particles 131 can be used in the same manner as in the above-mentioned embodiment.

However, as in the above-mentioned embodiment, a gas separation membrane 100 in which clusters 130 exist in a matrix of the above-mentioned polymeric material having gas permeability is highly preferable because it can increase the permeation rate of the gas in the clusters 130 and further improve the gas separation performance (particularly permeability).

We will explain examples that were conducted to confirm the effects of the gas separation membrane and its manufacturing method according to the present invention, but the present invention is not limited to the following specific examples.

[Preparation of test specimen]
<Test piece 1>
A coating liquid was prepared by adding surface hyperbranched silica nanoparticles (see Patent Document 2) in which a modification group was provided on the surface of a silica nanoparticle core having a particle diameter of 15 nm by reacting 3,5-diaminobenzoic acid via a silane coupling agent (3-aminopropyltriethoxysilane: APTES) and PIM-1 to a THF solvent and stirring and mixing for 6 hours. At this time, the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to be 2 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to be 10 mass%.

Next, a porous substrate (320 mm x 320 mm) made of polyethylene (PE) with a thickness of 15 μm, a pore size of 50 nm, and a porosity of 55% was placed on a multi-coater (K404 (product number) manufactured by Matsuo Sangyo Co., Ltd.), and 1.5 mL of the above coating liquid was applied to the porous substrate at a coating pressure (indentation pressure) of 0.19 Pa/ ^m2 and a coating speed of 3 m/min, and then dried to prepare a gas separation membrane specimen 1.

<Test piece 2>
Gas separation membrane specimen 2 was produced under the same conditions as specimen 1, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 20 mass%.

<Test piece 3>
Gas separation membrane specimen 3 was produced under the same conditions as specimen 1, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 2.5 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 40 mass%.

<Test piece 4>
Gas separation membrane specimen 4 was produced under the same conditions as specimen 1, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 2.5 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 50 mass%.

<Test piece 5>
Gas separation membrane specimen 5 was produced under the same conditions as specimen 1, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 60 mass %.

Test specimen 6
Gas separation membrane specimen 6 was produced under the same conditions as specimen 1, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 80 mass %.

<Test piece 7>
A porous substrate (320 mm x 320 mm) made of polytetrafluoroethylene (PTFE) with a thickness of 20 μm, a pore diameter of 100 nm, and a porosity of 80 to 85% was used, and the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 4 mass%. Except for this, the conditions were the same as those of specimen 1. Specimen 7 of the gas separation membrane was produced.

<Test piece 8>
Gas separation membrane specimen 8 was produced under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 20 mass%.

<Test piece 9>
Gas separation membrane specimen 9 was produced under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 30 mass%.

<Test piece 10>
Gas separation membrane specimen 10 was produced under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 50 mass%.

<Test piece 11>
Gas separation membrane specimen 11 was produced under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 60 mass%.

<Test piece 12>
Gas separation membrane specimen 12 was produced under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 80 mass %.

<Test piece 13>
Gas separation membrane specimen 13 was produced under the same conditions as specimen 7, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 3.5 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 50 mass%.

<Test piece 14>
Gas separation membrane specimen 14 was prepared under the same conditions as specimen 13, except that a porous substrate (320 mm x 320 mm) made of PTFE with a thickness of 10 μm, a pore diameter of 50 nm, and a porosity of 50 to 60% was used.

<Test piece 15>
Gas separation membrane specimen 15 was prepared under the same conditions as specimen 13, except that a PTFE porous substrate (320 mm x 320 mm) with a thickness of 10 μm, a pore diameter of 10 nm, and a porosity of 35 to 40% was used.

<Test piece 16>
Gas separation membrane specimen 16 was produced under the same conditions as specimen 7, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 3.5 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was 0 mass%, i.e., the addition of particles was omitted.

<Test piece 17>
Gas separation membrane specimen 17 was prepared under the same conditions as specimen 7, except that the mass ratio of the particles to the total mass of the particles and PIM-1 was 0 mass%, i.e., the addition of the particles was omitted.

<Test piece 18>
Gas separation membrane specimen 18 was produced under the same conditions as specimen 7, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 4.5 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was 0 mass%, i.e., the addition of particles was omitted.

<Test piece 19>
Gas separation membrane specimen 19 was produced under the same conditions as specimen 1, except that the ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 3 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was 0 mass%, i.e., the addition of particles was omitted.

<Test piece 20>
The ratio of the mass of PIM-1 to the mass of the solvent was adjusted to 3 mass%, and the mass ratio of the particles to the total mass of the particles and PIM-1 was adjusted to 20 mass%, and further, the coating liquid was applied to the porous substrate at a coating pressure (indentation pressure) of less than 0.1 Pa/ ^m2 . Except for this, a gas separation membrane specimen 20 was produced under the same conditions as specimen 1.

[evaluation]
<Transmission electron microscope (TEM)>
TEM images of the specimen 2 and the specimen 20 were taken. The results are shown in Figures 3 and 4. In the specimen 2 (coating pressure: 0.19 Pa), as can be seen from Figure 3, clusters (depth: about 190 nm) were formed in the pores of the porous substrate so as to contact the separation layer (thickness: about 400 nm). In contrast, in the specimen 20 (coating pressure: less than 0.1 Pa), as can be seen from Figure 4, only particles were present in the separation layer, and no clusters were formed in the pores of the porous substrate.

Gas Permeability and Gas Selectivity
After one side and the other side of the test specimens 1 to 20 were evacuated, one side of the test specimens 1 to 20 was evacuated to an oxygen or nitrogen atmosphere, and gas was passed from one side to the other side of the test specimens 1 to 20. The time until the pressure difference between the one side and the other side disappeared was measured, and the gas permeation rate (permeation amount) was calculated to obtain gas permeability (permeability), and the ratio of the oxygen gas permeation amount to the nitrogen gas permeation amount was calculated to obtain gas selectivity. Then, the separation performance was evaluated from these results. The results are shown in Table 2.

In Table 2, permeability was judged as "◎" (excellent) for 10,000 GPU or more, "○" (good) for 1,000 GPU or more but less than 10,000 GPU, "△" (passable) for 300 GPU or more but less than 1,000 GPU, and "×" (fail) for less than 300 GPU. Selectivity was judged as "◎" (excellent) for 1.20 or more, "○" (good) for 1.10 or more but less than 1.20, "△" (passable) for over 1.00 but less than 1.10, and "×" (fail) for 1.00 or less. The lower of the permeability and selectivity judgments was used as the evaluation of separation performance.

As can be seen from Table 2, specimen 19 (substrate pore size "medium", no particles) and specimen 20 (substrate pore size "medium", no clusters) showed high selectivity but low permeability, making it impossible to evaluate separation. On the other hand, specimens 16 to 18 (substrate pore size "large", no particles) showed high permeability but low selectivity, making it impossible to evaluate separation.

In addition, test specimen 1 (substrate pore size "medium" and particle amount "small"), test specimen 6 (substrate pore size "medium" and particle amount "large"), and test specimen 7 (substrate pore size "large" and particle amount "small") showed high permeability, but had low selectivity, making it impossible to evaluate separation.

In contrast, specimens 2 to 5 (medium substrate pore size and medium particle amount), specimens 8 to 12 (large substrate pore size and medium to large particle amount), and specimens 13 to 15 (small to large substrate pore size and medium particle amount) demonstrated satisfactory performance in both permeability and selectivity, and were rated as acceptable or better in separation.

Therefore, it was confirmed that the gas separation membrane of the present invention can further improve gas separation performance.

The gas separation membrane and its manufacturing method according to the present invention can be used to significantly improve gas separation performance when applied to the separation of nitrogen gas and oxygen gas, or the separation of nitrogen gas and carbon dioxide gas, and can also be easily manufactured, making it extremely useful in industry.

100 Gas separation membrane 110 Porous substrate 111 Hole 120 Separation layer 130 Cluster 131 Particle 132 Particle core 133 Modification group 134 Space (nanospace)

Claims (13)

A porous substrate;
A separation layer made of a gas-permeable polymer material provided so as to cover one surface of the porous substrate;
Equipped with
A plurality of aggregated particle clusters are provided in the pores of the porous substrate so as to contact the separation layer ,
The clusters are provided in the pores of the porous substrate to a depth of 200 nm or less from the interface of the separation layer.
A gas separation membrane characterized by: A porous substrate;
A separation layer made of a gas-permeable polymer material provided so as to cover one surface of the porous substrate;
Equipped with
A plurality of aggregated particle clusters are provided in the pores of the porous substrate so as to contact the separation layer,
The separation layer contains a plurality of aggregated particles,
The gas separation membrane, wherein the clusters are present in a polymer material having gas permeability. 3. The gas separation membrane according to claim 1, wherein the porous substrate has pores with diameters of 10 nm or more and 100 nm or less. The gas separation membrane according to claim 1 , wherein the porosity of the porous substrate is 35% or more and 85% or less. The gas separation membrane according to any one of claims 1 to 4 , wherein the porous substrate has a thickness of 5 µm or more and 50 µm or less. 6. The gas separation membrane according to claim 1, wherein the porous substrate is made of at least one resin selected from the group consisting of polytetrafluoroethylene, polyethylene, and polypropylene. The gas separation membrane according to claim 1 , wherein the separation layer has a thickness of 50 nm or more and 500 nm or less. 3. The gas separation membrane of claim 2, wherein the polymeric material of the separation layer and the clusters is at least one of an intrinsic microporous polymer, poly(1-trimethylsilyl-1-propyne), polydimethylsiloxane, polyimide, polycarbonate, and polyethyleneimine. 9. The gas separation membrane according to claim 2 or 8 , wherein the particles are present in the separation layer and the clusters at a ratio of 20% by mass to 60% by mass. 10. The gas separation membrane according to claim 2, wherein the clusters and the particles of the separation layer are surface-modified particles having a plurality of modifying groups bonded to the surface of a particle core made of an inorganic material. The gas separation membrane according to claim 10 , wherein the modifying group is an organic molecule extending in a chain form. A porous substrate;
A separation layer made of a gas-permeable polymer material provided so as to cover one surface of the porous substrate;
Equipped with
A method for producing a gas separation membrane, wherein clusters of a plurality of aggregated particles are provided in the pores of the porous substrate so as to be in contact with the separation layer,
adding the particles and the raw material of the polymer material to a solvent and mixing and stirring them to prepare a coating liquid;
The coating liquid is applied to one surface of the porous substrate in a pressing manner,
and drying the resulting gas separation membrane. The method for producing a gas separation membrane according to claim 12 , wherein the coating liquid contains the polymer material at a ratio of 2% by mass to 5% by mass relative to the mass of the solvent.

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