JP2005296821A - Gas separation composite membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas separation composite membrane manufacturable at a low cost, having superior gas permeability, while preventing lifting up and breakage of a gas separation layer. <P>SOLUTION: This gas separation composite membrane 100 is provided with the gas separation layer on a support body. The support body 10 comprises un-oriented ethylenic high polymer-based porous body. The gas separation layer 20 comprises a high polymer thin film phase-separated into a rubbery state or molten state phase and a vitreous state or crystallized state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas separation composite membrane and a method for producing a porous body for use in a support provided in the gas separation composite membrane.

  The gas separation membrane is for the purpose of separating gases such as oxygen, nitrogen and carbon dioxide from the air, or increasing (concentrating) the concentration of these gases, or carbon monoxide and nitrogen oxidation mixed from the combustion system, reaction system, etc. Used for the purpose of removing highly toxic gases such as substances and sulfur oxides. In particular, in the fields of combustion equipment, air conditioning equipment, medical equipment, health equipment, etc., the concentration of oxygen in the air has attracted attention, and is referred to as a gas separation membrane (hereinafter referred to as “oxygen-rich membrane”) for the purpose of oxygen enrichment. ) Has been developed in the past.

For example, a siloxane polymer known as a material used for an oxygen-enriched film has an oxygen / nitrogen separation coefficient (PO ₂ / PN ₂ ) of 1.5 to 2.5 [−] and an oxygen transmission coefficient. 1 × 10 ⁻⁸ to 1 × 10 ⁻⁹ [cm ³ (STP) · cm / cm ² · sec · cmHg] (see, for example, Patent Document 1), and a film thickness of about 100 nm made of this siloxane-based polymer. By allowing air to pass through the thin film, oxygen-enriched air is obtained.

  Since such a thin film is difficult to handle by itself, a gas separation composite membrane in which the thin film is laminated on a support as a gas separation membrane is usually used for the purpose of oxygen enrichment or the like.

  As the support on which the thin film is laminated, a porous body having air permeability is often used. As the porous body used for the gas separation composite membrane, for example, a porous body made of polyimide (for example, see Patent Document 2), a porous body made of a fluororesin (for example, see Patent Document 3), and the like are known. However, since these porous bodies are excellent in terms of mechanical strength and the like, but are expensive, porous bodies made of an ethylene-based polymer, which is a cheaper material, are generally used.

As a method for obtaining a porous body composed of an ethylene polymer, a stretching method obtained by stretching an ethylene polymer mixed with particles such as silica to open the particle interface (see, for example, Patent Document 4). Alternatively, an extraction method (for example, see Patent Document 5) obtained by extracting a liquid agent from an ethylene-based polymer mixed with a liquid agent into a predetermined shape, and sintering an ethylene-based polymer fine powder. There are known sintering methods obtained (for example, see Patent Document 6). Among these, the porous body by the extending | stretching method is the cheapest, and is used for various uses, such as an electronic device and a building material.
JP-A-56-26504 JP 2001-145826 A JP-A-3-179038 Japanese Patent Laid-Open No. 3-80923 Japanese Patent Laid-Open No. 4-170446 JP 2002-265657 A

  As a method of obtaining a gas separation composite membrane, a polymer organic solvent solution is developed on the water surface by utilizing surface tension, and a polymer thin film is formed. The method (hereinafter referred to as “water surface development method”) is preferably used. According to the water surface development method, a gas separation layer composed of a thin film having a thickness of 100 nm or less can be efficiently formed.

  However, when a porous body of an ethylene polymer obtained by a stretching method is used as a support, in a gas separation composite membrane obtained by a production method involving contact between a material and water, such as a water surface expansion method However, there is a problem that the gas separation layer laminated on the support tends to float from the support or the gas separation layer is easily broken.

  When such lifting and tearing occur, it is difficult to fulfill the function of the gas separation composite membrane.In particular, when employing a water surface expansion method or the like, in order to efficiently obtain the gas separation composite membrane, There is a strong demand to suppress the occurrence of tears.

  The present invention has been made in view of the above circumstances, and it is possible to manufacture a gas separation composite membrane that can be manufactured at low cost while suppressing the occurrence of breakage and tearing of the gas separation layer, and that is excellent in gas permeability. The purpose is to provide.

  In order to solve the above problems, the gas separation composite membrane of the present invention is a gas separation composite membrane having a gas separation layer on a support, and the support is a porous body of an unstretched ethylene polymer. The gas separation layer is composed of a polymer thin film that is phase-separated into a rubbery or molten phase and a glassy or crystalline phase.

  By combining such a support and a gas separation layer, it is possible to manufacture the gas separation layer at a low cost while suppressing the floating and tearing of the gas separation layer, and a gas having excellent gas permeability. A separation composite membrane is obtained.

  When adopting the water surface development method, since water absorption and dehydration are involved in the support, it is possible to use a porous body having excellent dimensional stability in the process of water absorption and dehydration as a support, It is considered effective for suppressing the occurrence of tearing.

  The unstretched ethylene polymer porous body has superior dimensional stability in the process of water absorption and dehydration as compared with the ethylene polymer porous body obtained by the stretching method. They found out. This is because, in a stretched porous polymer of an ethylene polymer, the strain applied during stretching remains, and the permeation occurs when water that has filled the open pores of the porous material is removed by water absorption. In response to release from pressure, the porous body contracts so that the above distortion is eliminated, whereas in the porous body made of unstretched ethylene polymer, the above strain remains. It is guessed that this is because they have not.

  However, even if a support having excellent dimensional stability as described above is used, if the adhesion between the support and the gas separation layer is insufficient, lifting may occur easily, and this adhesion is improved. Was also found to be important.

  As a result of further studies based on this knowledge, the support was phase-separated into a specific polymer, that is, a phase in a rubber state or a molten state and a phase in a glass state or a crystalline state. In combination as a gas separation layer, while maintaining the strength and heat resistance of the gas separation layer, the adhesion between the support and the gas separation layer is enhanced, and sufficient effects such as prevention of lifting can be obtained. The headline and the present invention were completed.

  Since the polymer as described above has a property that the phase in a rubber state or a molten state is easily deformed, the polymer as a whole is easily stretched. Therefore, the gas separation layer has excellent shape followability, and even if there is a place where the air separation layer floats due to the air being embraced between the support and the gas separation layer, it follows the shape of the support surface. As described above, the gas separation layer is gradually deformed to suppress the final lifting.

  The ethylene polymer constituting the support is generally considered to have poor chemical affinity with other polymers. However, in combination with the specific polymer thin film as described above, good adhesion is obtained. Sex is obtained.

  The gas separation layer may be a polymer thin film containing an organopolysiloxane skeleton represented by the following general formula (1) and an imide skeleton represented by the following general formula (2).

［式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４はそれぞれ独立に１価の脂肪族基又は１価の芳香族基、Ｘは４価の芳香族基、Ｙ、Ｚ^１及びＺ^２はそれぞれ独立に２価の脂肪族基又は２価の芳香族基、ｒは正の整数、をそれぞれ示す。］

[Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a monovalent aliphatic group or a monovalent aromatic group, X is a tetravalent aromatic group, Y, Z ¹ and Z ² are Each independently represents a divalent aliphatic group or a divalent aromatic group, and r represents a positive integer. ]

  Such a thin film containing a polymer containing an organopolysiloxane skeleton and an imide skeleton (hereinafter referred to as “polyimide siloxane”) has an excellent shape following property by containing an organopolysiloxane skeleton, and is an ethylene polymer. Adhesion with the porous body made of is improved. Therefore, the combination with the support having excellent dimensional stability as described above suppresses the occurrence of lifting and tearing, and a gas separation layer particularly suitable for oxygen enrichment can be obtained.

  The above-mentioned polyimidesiloxane has a structure in which a linear molecular chain composed of an organopolysiloxane skeleton is spirally wound in its structure, and this spiral functions as a gas-permeable path. Is considered high. Furthermore, since the organopolysiloxane skeleton contains abundant oxygen atoms and the solubility of oxygen gas is high, it is considered that oxygen penetrates preferentially.

  The polyimidesiloxane preferably contains the above-mentioned organopolysiloxane skeleton in an amount of 35% by mass or more based on the mass of the polyimidesiloxane. By setting the content of the organopolysiloxane skeleton to 35% by mass or more, the thin film becomes more easily stretched, and the gas permeability of the obtained gas separation composite membrane is further increased.

  The polyimidesiloxane as described above is usually a phase mainly composed of an organopolysiloxane skeleton (hereinafter referred to as “siloxane phase”) and a phase mainly composed of an imide skeleton (hereinafter referred to as “imide phase”). )), And at room temperature, the siloxane phase is in a rubber state or a molten state, and the imide phase is in a glass state. By having an imide phase, the heat resistance and mechanical strength of the entire polyimidesiloxane are maintained.

  The polymer is preferably a polymer having an elongation of 80% or more in order to further improve the adhesion to the support.

  In addition, the polymer thin film is a thin film obtained by spreading the polymer on the water surface, and it is easy to reduce the thickness of the gas separation layer, and the gas separation composite membrane is excellent in gas permeability. Is preferable because it is obtained efficiently.

  The unstretched ethylene polymer porous material preferably has a shrinkage of 0 to 10% when immersed in water at 20 ° C. for 10 seconds and further left at 23 ± 2 ° C. for 1 hour. By making the shrinkage rate in the above range, it becomes easier to obtain the effect of suppressing lifting and tearing.

  In addition, the porous body is formed with open pores in which cohesive fine particles are attached to the pore wall, and the dimensional stability is particularly excellent, and the production of the porous body of the present invention as described below It is preferable at the point which can obtain efficiently by employ | adopting a method.

  The present invention is also a method for producing a porous body for use as a support for a gas separation composite membrane, wherein the liquid agent is removed from a mixture of cohesive fine particles, a liquid agent, and an unstretched ethylene polymer. It is characterized by doing. The porous body obtained by this production method is excellent in dimensional stability, and can be suitably used, for example, as a support for the gas separation composite membrane of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the gas separation composite membrane which can be manufactured at low cost, suppressing the generation | occurrence | production of a gas separation layer and generation | occurrence | production of a tear, and excellent in gas permeability is obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

(Gas separation composite membrane)
FIG. 1 is a cross-sectional view schematically showing a gas separation composite membrane according to an embodiment of the present invention. A gas separation composite membrane 100 shown in FIG. 1 includes a sheet-like support 10 and a gas separation layer 20 provided on the support 10.

  The support 10 is made of a porous body containing an unstretched ethylene polymer. Since the ethylene polymer is a hydrophobic polymer, it is suitable for adopting a water surface expansion method or the like as a method for forming the gas separation layer 20. Moreover, it has the advantage that it is cheap compared with other hydrophobic polymers, such as a fluororesin and a polyimide resin.

  The ethylene polymer is a polymer mainly composed of a polyethylene skeleton, for example, polyethylene, polypropylene, ethylene-acrylic acid copolymer, ethylene-α olefin copolymer, ethylene-unsaturated ester copolymer, ethylene-unsaturated copolymer. Examples thereof include saturated carboxylic acid copolymers.

  Among these, polyethylene is preferable because it has a high degree of crystallinity, is inexpensive, and is suitable for obtaining a porous material by a method (extraction method) described later. Furthermore, the crystallinity of polyethylene is preferably 90% or more, and more preferably 95% or more. A high degree of crystallinity is advantageous in that it is difficult to take in the liquid used in the extraction method, heat resistance, and the like.

Further, as the polyethylene, high-density polyethylene (density: 0.95 to 0.98 g / cm ³ ) is preferable from the viewpoint of few short chain branches and high crystallinity. Furthermore, among high-density polyethylene, the so-called ultra-high molecular weight polyethylene having a molecular weight of 1 million or more has high mechanical properties such as breaking strength, and also flows and deforms even at its melting point of 135 ° C. or higher. It is more preferable in that it has excellent heat resistance.

  The unstretched ethylene-based polymer is an ethylene-based polymer that has not been subjected to a stretching operation in the production process, and the support made of a porous body containing the unstretched ethylene-based polymer has moisture content. Excellent dimensional stability in the process of adsorption and dehydration. Usually, an ethylene-based polymer obtained by a stretching method is produced by being stretched at a stretch ratio of about 2 times or more for the purpose of improving its mechanical strength, but in the present invention, such a stretch is not performed. Ethylene polymer is used.

  Generally, in a material made of a crystalline polymer such as an ethylene polymer, a crystal called a lamellar crystal is generated when cooled from a molten state. When the material is stretched, the lamellar crystals tend to disappear as the molecular chain is oriented along the stretched direction. It may be confirmed from the fact that most of the lamellar crystals remain.

  In addition, although the porous body as the support body 10 is preferably composed of only unstretched ethylene polymer, it may further include other components such as a plasticizer as necessary.

  The porous body used as the support 10 is preferably 0 to 10% shrinkage when immersed in water at 20 ° C. for 10 seconds and further left at 23 ± 2 ° C. for 1 hour. It is more preferable that Here, when the sheet-like porous body having a length of 50 to 150 mm, a width of 50 to 150 mm, and a thickness of 0.05 to 1.00 mm is treated under the above-described conditions, the shrinkage rate is the length before and after the treatment. Alternatively, the value is defined as the rate of change of the horizontal length (after processing / before processing). In the case of a porous body obtained by a method described later using an unstretched ethylene-based polymer, the shrinkage rate is usually within the above range.

  Further, it is preferable that the support 10 is made of a porous body in which open pores in which agglomerated fine particles are attached to the pore wall from the viewpoint of particularly excellent dimensional stability.

  The shape of the support 10 is a sheet shape in the gas separation composite membrane 100, but as a modified form, it may be a tube shape, a granular shape, a bulk shape, or the like. However, in consideration of simplicity when air is permeated and separated, a sheet shape is preferable. When the support 10 is a sheet, the thickness is preferably 20 to 300 μm, and more preferably 50 to 100 μm. If the thickness of the support 10 is less than 20 μm, the mechanical strength tends to decrease and the handleability tends to deteriorate, and if it exceeds 300 μm, the resistance tends to increase during the permeation of air.

  In the porous body used for the support 10, open pores communicating with the outside air are preferably formed, and the average pore diameter is preferably 3 times or less with respect to the thickness of the gas separation layer 20. . When the average pore diameter is larger than this, the gas separation layer 20 tends to be broken when the gas separation composite membrane 100 is used. In the present invention, the thickness of the gas separation layer 20 is preferably 10 to 1000 nm, but the average pore diameter in the porous body combined therewith is preferably 30 to 3000 nm, and more preferably 30 to 100 nm. preferable.

  When the porosity of the porous body is less than 30% by volume, the resistance tends to increase during the permeation of air, and when it exceeds 80% by volume, the mechanical strength tends to decrease and the handleability tends to deteriorate. Therefore, it is preferable that it is 30-80 volume%, and it is more preferable that it is 40-60 volume%.

  The support 10 made of a porous material as described above can be suitably obtained by, for example, an extraction method using coherent fine particles, as will be described later.

  The gas separation layer 20 is a high phase phase-separated into a phase in a rubber state or a molten state (hereinafter referred to as “soft phase”) and a phase in a glass state or a crystalline state (hereinafter referred to as “hard phase”). It consists of a thin film of a molecule or a polymer (polyimide siloxane) containing an organopolysiloxane skeleton represented by the general formula (1) and an imide skeleton represented by the general formula (2). In the soft phase, a rubbery region and a molten region may be mixed, and in a hard phase, a glassy region and a crystalline region may be mixed.

  In the above-described polymer that is phase-separated into a soft phase and a hard phase, a microphase separation structure composed of these two phases is usually formed. The soft phase is a phase that exhibits a glass transition phenomenon in a region at a temperature lower than room temperature and is in a rubber state or a molten state at room temperature. On the other hand, the hard phase is a phase in which glass transition does not occur at room temperature or lower, and glass transition or melting occurs at a higher temperature exceeding room temperature. The component constituting the soft phase and the component constituting the hard phase are preferably at least partially bonded by a covalent bond from the viewpoint of heat resistance. As such a polymer, for example, a copolymer containing a skeleton (soft segment) mainly constituting a soft phase and a skeleton (hard segment) mainly constituting a hard phase is suitable.

  The fact that the polymer is phase-separated into such a soft phase and a hard phase means that, for example, when a dynamic viscoelasticity measurement is performed, a glass transition point (first transition point) below normal temperature and a high temperature. This can be confirmed by observing the glass transition point or melting point (second transition point).

  This first transition point is usually 20 ° C. or lower, and more preferably −20 ° C. or lower. On the other hand, the second transition point is usually 100 ° C. or higher, and more preferably 130 ° C. or higher. These transition points are values measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a heating rate of 10 ° C./min.

  One of the effects of suppressing the phenomenon that a part of the gas separation layer 20 peels off from the support 10 (floating) is that the polymer thin film as described above has the property of being easily stretched. This is thought to be due to the fact that

  When the gas separation layer 20 is formed on the support 10, air is trapped between the ethylene polymer 11 constituting the support and the gas separation layer 20, for example, as shown in FIG. 30 may be formed, and the gas separation layer 20 in that portion may be in a lifted state. Even in such a state, if the gas separation layer 20 has a property of being easily extended, the gas separation layer 20 in the vicinity of the void 30 is deformed so as to follow the irregularities on the surface of the ethylene polymer 11 over time. Thus, it is considered that the gap 30 disappears within several tens of seconds to several minutes, and as a result, there is no lift.

  In order to further enhance the effect of suppressing lifting, the polymer constituting the thin film as the gas separation layer 20 has an elongation of preferably 80% or more, and more preferably 500% or more. However, this elongation is a value obtained by conducting a tensile test on a test piece made of a polymer constituting the thin film by a method defined in JIS K7311. As a result of the study by the present inventors, it is clear that using this parameter as an index is effective as an index of adhesion between the support 10 composed of the ethylene polymer 11 and the gas separation layer 20. became.

  When the elongation is less than 80%, the state in which the voids 30 are formed as shown in FIG. 2 tends to be maintained for a long time. In this case, even when a slight external force is applied to the gas separation composite membrane 100, the portion of the gas separation layer forming the gap 30 may be torn. On the other hand, in the case of a polymer whose elongation exceeds 500%, even if the void 30 is formed, it disappears in a very short time.

  Further, in the case of a thin film having an elongation of 80% or more, when compressed air is blown onto the portion where the gap 30 is formed, the air in the gap 30 escapes through the open pores of the support 10, so that the gap 30 disappears. Time can also be shortened. This method can be carried out almost without problems in the case of a thin film having an elongation of 80% or more. However, if this method is employed when the elongation of the thin film is less than 80%, the thin film tends to be easily broken by air pressure. .

  The thickness of the gas separation layer 20 is preferably 10 to 1000 nm, and more preferably 50 to 200 nm. If the thickness exceeds 1000 nm, the gas permeability tends to be insufficient, and if it is less than 10 nm, the handleability tends to decrease. Note that the thickness of the gas separation layer 20 is such that, for example, a part of the gas separation layer 20 is removed from the support 10 and the step between the place where the gas separation layer 20 remains and the place where the gas separation layer 20 is removed is determined by AFM or the like. It can be quantified by measuring with.

  In the above polymer, examples of the skeleton (soft segment) mainly constituting the soft phase include a skeleton made of an ethylene-butylene copolymer, an ethylene-styrene copolymer, an acrylate polymer, an organopolysiloxane, and the like. It is done. Among these, an organopolysiloxane skeleton is preferable from the viewpoint of gas permeability.

  Examples of the skeleton (hard segment) mainly constituting the hard phase include a crystalline polymer such as polyethylene, or an amorphous rigid skeleton such as polyimide and polycarbonate. Among these, polyimide is preferable from the viewpoint of heat resistance and the like.

  In polyimidesiloxane, a microphase-separated structure is generally formed, which is composed of a soft phase mainly composed of an organopolysiloxane skeleton and a hard phase mainly composed of an imide skeleton. The gas separation layer 20 is particularly preferably formed of a thin film containing polyimidesiloxane from the viewpoints of gas permeability, oxygen enrichment, heat resistance, mechanical strength, and the like.

  As the polyimidesiloxane, those containing the above-mentioned organopolysiloxane skeleton represented by the following general formula (1) and the imide skeleton represented by the following general formula (2) are preferable. The organopolysiloxane skeleton and the imide skeleton may be bonded to each other in a block shape or may be bonded at random.

  In the above-described polyimidesiloxane, the content of the organopolysiloxane skeleton that is a soft segment is preferably 35% by mass or more, more preferably 35 to 97% by mass, based on the entire polyimidesiloxane, and 40 to 40%. More preferably, it is 97 mass%. When the content of the organopolysiloxane is large, the mechanical properties of the polyimidesiloxane are more likely to be elastomeric and rich in flexibility and stretchability. By making this content 35% by mass or more, the gas separation layer 20 is particularly easily stretched, and the adhesion to the support 10 becomes better as compared with the case of less than 35% by mass. Moreover, when this content exceeds 97 mass%, it exists in the tendency for heat resistance and mechanical strength to fall.

  This polyimidesiloxane is, for example, a repeating unit composed of a skeleton represented by the following general formula (3) (including an organopolysiloxane skeleton represented by the above general formula (1)) and the above general formula (2). And a repeating unit composed of an imide skeleton represented by

  Further, the polyimidesiloxane may have a repeating unit represented by the following general formula (4). In the formula (4), n represents a positive integer.

R ¹ , R ² , R ³ and R ⁴ in the general formulas (1) to (4) each independently represent a monovalent aliphatic group or a monovalent aromatic group, and these are substituted with a fluorine atom. It may be. Examples of the monovalent aliphatic group include a monovalent saturated hydrocarbon group and a monovalent unsaturated hydrocarbon group. Examples of the monovalent saturated hydrocarbon group include an alkyl group having 1 to 22 carbon atoms, and examples thereof include a methyl group, an ethyl group, and a propyl group. Examples of the monovalent unsaturated hydrocarbon group include alkenyl groups having 2 to 22 carbon atoms, and examples thereof include a vinyl group and a propenyl group. Examples of the monovalent aromatic group include an aryl group having 6 to 24 carbon atoms and an aralkyl group. As R ¹ , R ² , R ³ and R ⁴ , a methyl group or a phenyl group is particularly preferable. R represents a positive integer and is preferably an integer of 10 to 10,000.

  X in the general formulas (1) to (4) represents a tetravalent aromatic group, and the following general formulas (5a) to (5k), (5m), (5n), (5p) and (5q) It is preferable that it is a tetravalent aromatic group represented by each.

In the above formulas (5a) to (5k), (5m), (5n), (5p) and (5q), R ⁵ and R ⁶ are each independently a hydrogen atom, a methyl group, a trifluoromethyl group or a phenyl group. R ⁷ and R ⁸ each independently represents a hydrogen atom, a trifluoromethyl group or a phenyl group. s shows a positive integer, Preferably it is an integer of 1-20. R ⁹ and R ¹⁰ each independently represent a trifluoromethyl group or a phenyl group, and A represents an ethylene group or a divalent aromatic group represented by the following general formulas (6a) to (6c). .

In the general formulas (1) to (4), Z ¹ and Z ² each independently represent a divalent aliphatic group or a divalent aromatic group, and these groups are substituted with a fluorine atom. May be. Examples of the divalent aliphatic group include a divalent saturated hydrocarbon group or a divalent unsaturated hydrocarbon group. As a bivalent saturated hydrocarbon group, a C1-C22 alkylene group is mentioned, For example, a methylene group, ethylene group, and a propylene group can be illustrated. As a bivalent unsaturated hydrocarbon group, a C2-C22 unsaturated carbon group is mentioned, For example, the alkylene group which has an unsaturated double bond at the terminal can be illustrated, for example, vinylene group, propenylene group. Examples of the divalent aromatic group include a phenylene group having 6 to 24 carbon atoms, a phenylene group substituted with an alkyl group, and an aralkylene group. Z ¹ and Z ² are particularly preferably a propylene group, a phenylene group, and an aralkylene group.

  Y in the general formulas (1) to (4) represents a divalent aliphatic group or a divalent aromatic group, and is represented by the following general formula (7) or the following general formula (8). A valent aromatic group is preferred. In the formula (8), t represents a positive integer and is preferably an integer of 1 to 22.

  The polyimidesiloxane used in the gas separation layer 20 preferably has a weight average molecular weight (Mw) in terms of standard polystyrene by gel permeation chromatography (GPC) of 1,000 to 100,000, preferably 5,000 to 50,000. It is more preferable that

  The polyimidesiloxane having the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is an organopolysiloxane having an amino group at the terminal represented by the following general formula (9). Obtained by a dehydration condensation reaction of a diamine (hereinafter referred to as “siloxane diamine”) and a diamine mixture not containing a siloxane represented by the following general formula (10) and a polybasic acid dianhydride. Can do. This dehydration condensation reaction can be carried out by employing a conventionally known method. In addition, the code | symbol in chemical formula in the following description shows the structure similar to the content in the said chemical formula.

  As the dianhydride of polybasic acid, a dianhydride of tetracarboxylic acid represented by the following general formula (11) is preferably used.

  As what can be obtained as a commercial item of the siloxane diamine represented by the general formula (9), X-22-9409, X-22-1660B, X-22-161AS, X-22-161A, X-22- 161B (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like. These can be used alone or in combination of two or more.

  As the diamine represented by the general formula (10), an aromatic diamine is preferably used. Examples of the aromatic diamine include compounds represented by the following formula (12) or the following general formula (13).

  Examples of the aromatic diamine represented by the general formula (13) include 4,4′-diaminophenoxymethane, 1,2-bis (4-aminophenoxy) ethane, and 1,3-bis (4-aminophenoxy) propane. 1,4-bis (4-aminophenoxy) butane, 1,5-bis (4-aminophenoxy) pentane, 1,6-bis (4-aminophenoxy) hexane, 1,7-bis (4-aminophenoxy) ) Heptane, 1,8-bis (4-aminophenoxy) octane, 1,9-bis (4-aminophenoxy) nonane, 1,10-bis (4-aminophenoxy) decane, 1,11-bis (4- Aminophenoxy) undecane, 1,12-bis (4-aminophenoxy) dodecane, 1,13-bis (4-aminophenoxy) tridecane, 1,14-bis (4-a Nophenoxy) tetradecane, 1,15-bis (4-aminophenoxy) pentadecane, 1,16-bis (4-aminophenoxy) hexadecane, 1,17-bis (4-aminophenoxy) heptadecane, 1,18-bis ( 4-aminophenoxy) octadecane, 1,19-bis (4-aminophenoxy) nonadecane, 1,20-bis (4-aminophenoxy) icosane and the like. These can be used alone or in combination of two or more.

  Examples of the tetracarboxylic dianhydride represented by the general formula (11) include pyromellitic dianhydride, methyl pyromellitic dianhydride, trifluoromethylpyromellitic dianhydride, phenyl pyro Mellitic acid dianhydride, diphenylpyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2′-diphenyl-3,3 ′, 4,4′-biphenyl Tetracarboxylic dianhydride, 2,2'-ditrifluoromethyl-3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfate Fonte Lacarboxylic acid dianhydride, 3,3 ′, 4,4′-diphenylhexafluoroisopropylidenetetracarboxylic dianhydride, 1,1′-bis (3,4-dicarboxyphenyl) -1-phenyl-2, 2,2-trifluoroethane dianhydride, 3,3 ′, 4,4′-diphenylisopropylidenetetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylmethanetetracarboxylic dianhydride, 3 , 3 ′, 4,4′-benzosulfide tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzosulfide tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylamine tetracarboxylic Acid dianhydride, 3,3 ′, 4,4′-diphenylamide tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, bis (3 4-dicarboxyphenoxy) benzene dianhydride, bis (3,4-dicarboxyphenoxy) ethane dianhydride, bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′-bis ( 3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) phosphine oxide dianhydride, and the like. These can be used alone or in combination of two or more.

  The polyimidesiloxane having the repeating unit represented by the general formula (4) can be obtained by reacting the siloxane diamine represented by the general formula (9) with a polyimide having an acid anhydride group at the terminal.

  The thin film as the gas separation layer 20 is preferably composed only of a polymer such as polyimidesiloxane as described above, but further includes other components such as a plasticizer and inorganic particles as necessary. But you can.

(Method for producing gas separation composite membrane)
About the suitable manufacturing method for obtaining the gas separation composite membrane 100 as described above, the following is the order of the manufacturing method of the porous body used as the support 10 and the method of forming the gas separation layer 20 on the support 10. Will be described in detail.

  The porous body used as the support 10 can be suitably obtained by a method of removing the liquid agent from a mixture obtained by mixing the cohesive fine particles, the liquid agent, and the unstretched ethylene polymer. By using the coherent fine particles, the volume change of the entire porous body when removing the liquid agent can be reduced, and the dimensional stability of the obtained porous body is particularly excellent.

  In this method, first, a mixture in which cohesive fine particles, a liquid agent, and an unstretched ethylene polymer are mixed is obtained. At this time, an adhering body as shown in FIG. 4 in which a liquid agent is adhered to the aggregating fine particles may be separately prepared, and the adhering body and the ethylene polymer may be mixed, or the aggregating fine particles, the liquid agent, and ethylene may be mixed. The high molecular weight polymer may be mixed by, for example, charging it into a kneader.

  In the mixing, in order to uniformly disperse the coherent fine particles 1 and the liquid agent 2, it is preferable to knead at a temperature higher than the melting point of the ethylene polymer by a kneading device such as an extruder or a kneader. Normally, the agglomeration state of particles changes as needed depending on the kneading history, but kneading can be performed with good reproducibility by controlling the product of torque output and kneading time and the resin temperature in kneading.

  Moreover, the porosity of the obtained porous body can be controlled by the amount of the liquid agent contained in the mixture. In order to make the porosity of the obtained porous body into a preferable range, the amount of the liquid agent is preferably 30 to 80% by volume, more preferably 40 to 60% by volume based on the whole mixture.

  The kneaded mixture is once processed into pellets, veils, belts, etc., and then formed into sheets by an extruder, calender, roll, belt, etc., and used as a precursor of a porous body. Is preferred. When an extruder is used, kneading and molding can be performed at once. The apparatus used for kneading may be other than the above.

  FIG. 5 is a cross-sectional view schematically showing a sheet-like precursor 10a made of the above mixture after kneading and forming. In the precursor 10 a, a region formed by incorporating the liquid agent 2 into the aggregate of the coherent fine particles 1 is dispersed in the ethylene polymer 11. At the stage where the ethylene polymer is melted during kneading, the liquid 2 is also taken into the ethylene polymer, but after molding, the mixture is cooled to grow ethylene polymer crystals (lamellar crystals). As a result, the liquid agent 2 is discharged from the ethylene polymer, and is taken into the aggregate of the aggregating fine particles 1 again, resulting in a state like the precursor 10a shown in FIG.

  FIG. 4 is a cross-sectional view schematically showing an adherent used for mixing. In the adhering body 5 shown in FIG. 4, the liquid agent 2 adheres so as to penetrate into the gap between the aggregates of primary particles of the aggregating fine particles 1 (hereinafter referred to as “aggregates”). Since the aggregating fine particles 1 form an aggregate, by attaching the liquid agent 2, it is possible to easily obtain the adhered body 5 as shown in FIG. 2. The adhering body 5 is obtained, for example, by kneading a mixture of the coherent fine particles 1 and the liquid agent 2 using a pressure kneader or the like.

  Examples of the aggregating fine particles 1 include ketjen black, silica, synthetic wet calcium carbonate, and acrylic crosslinked particles. However, the aggregating fine particles 1 have high aggregability and have a property of easily retaining a liquid agent even in a mixture with an ethylene polymer. Silica is preferred. This silica refers to silicon oxide (silicic acid), and is obtained by pulverizing natural anhydrous silicic acid such as quartz, or synthetic silica such as wet silica or fumed silica. Among these, the cohesive fine particles 1 are preferably synthetic silica in terms of cohesiveness.

It is generally known that the cohesive force of the cohesive fine particles can be quantified by the absorption amount of the oil or the like. For example, in ASTM D2414-93, the fine particle is determined by the absorption amount (DBP oil absorption amount) of DBP (dibutyl phthalate). A method for quantifying the cohesiveness of the water is defined. For cohesive fine particles 1, DBP oil absorption of above, preferably at ⁵⁰ [cm 3 / 100g] or more, more preferably 200~400 ^[cm 3 / 100g]. DBP oil absorption tends ^{to 50} [cm 3 / 100g] less than a is a holding force of the liquid becomes insufficient.

  Further, the primary particle diameter of the aggregating fine particles 1 is desirably 1.0 μm or less, and more desirably 0.05 μm or less. When the primary particle diameter exceeds 1.0 μm, the cohesive force tends to decrease. The particle diameter of the aggregate composed of the aggregating fine particles 1 is preferably 100 μm or less, and more preferably 10 μm or less when the aggregate is regarded as a particle. When this particle diameter exceeds 100 μm, the pore diameter of the pores formed in the resulting porous body increases, and the gas separation layer 20 tends to be easily broken.

In attachment member 5, the content of aggregated particles 1 may be suitably determined depending on the type, for example, when the DBP oil absorption amount of cohesive fine particles 1 is 200~400 ^[cm 3 / 100g] Is preferably 1/5 to 1/2 in weight ratio to the liquid agent 2.

  As the liquid agent 2, it is preferable to use a liquid that can efficiently absorb the aggregate of the aggregating fine particles 1. Specifically, paraffinic oil, phthalate ester and the like are preferable.

  The paraffinic oil preferably has a molecular weight of 500 or less and more preferably 10 to 100 in order to increase the efficiency of removal from the precursor 10a. The viscosity is preferably 1000 mPa · s or less, and more preferably 10 to 100 mPa · s.

  Phthalates are diesters of phthalic acid and alcohol, such as dioctyl phthalate (DOP) and diisonolyl phthalate (DINP). The alcohol preferably has 3 to 12 carbon atoms, more preferably 7 to 10 carbon atoms. When the number of carbon atoms is 3 or less, the boiling point is low and tends to be lost due to volatilization during mixing or molding. When the number of carbon atoms exceeds 18, the fluidity is lost at room temperature and is attached to the coherent fine particles 1. Tend to be difficult.

  Next, pores are formed by removing the liquid agent 2 from the precursor 10a, and a sheet-like support 10 made of a porous material as shown in FIG. 6 is obtained. FIG. 6 is a cross-sectional view schematically showing the support 10 in which open pores in which the cohesive fine particles 1 are adhered to the pore walls are formed.

  The removal of the liquid agent 2 can be suitably performed by extracting the liquid agent 2 with an extraction solvent. For example, the extraction is performed by immersing the precursor 10a in an extraction solvent such as toluene, hexane, xylene, various alcohols, rubber volatile oil, hot water, or boiling water. What is necessary is just to determine suitably the conditions which perform extraction according to the extraction solvent etc. to be used. After the immersion, the extraction solvent adhering to the porous body is removed (dried) to obtain the support 10. This drying may be natural drying or forced drying by heating or blowing.

  The gas separation composite membrane 100 is obtained by laminating the gas separation layer 20 on the support 10 obtained as described above. As a method for forming a thin film of the gas separation layer 20, a water surface expansion method in which a polymer is expanded on the water surface is suitable.

  In this water surface development method, a polymer solution in which a polymer is dissolved in a solvent is dropped onto the water surface, and the polymer is developed as a solution on the water surface to form a thin film. The dropped polymer solution immediately develops on the water surface due to surface tension, and the solvent evaporates almost simultaneously with the development to form a polymer thin film. Subsequently, when the formed thin film is scooped with the support 10 that has been submerged in water and brought into contact with the surface, the thin film adheres to the support 10 and is integrated. Furthermore, the gas separation composite membrane 100 can be obtained by removing water adhering to the support 10 and the thin film (gas separation layer 20).

  The solvent used in the polymer solution is preferably selected from those having good solubility of the polymer constituting the gas separation layer 20. For example, when the polymer is polyimide siloxane, an organic solvent such as toluene, methyl ethyl ketone, or N-methylpyrrolidone is preferable. The polymer concentration in this solution is preferably 5 to 30% by mass based on the whole polymer solution.

  In order to drop the polymer solution onto the water surface, a dispenser, a syringe, a dropper, or the like can be preferably used. Alternatively, the polymer solution supply device may be installed in water and floated on the surface of the water by the buoyancy of the solution.

  In the case where the support 10 is a long sheet, the support 10 is sent out by a feeding device and once passed through the water, and the thin film formed on the water surface is scooped up, and the winding device is sequentially wound up. A continuous process can also be employed. When such a continuous process is employed, it is preferable to adjust the supply amount of the solution in accordance with the feed rate of the support. In addition, the thickness of the gas separation layer 20 can be adjusted by repeating the lamination of the thin film on the support 10 a plurality of times.

  The content of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Example 1)
<Preparation of porous body A>
100 parts by weight of paraffin oil (Lucant 360, trade name, manufactured by Mitsui Chemicals) and wet silica particles having an average particle diameter of 9 μm formed by agglomeration of primary particles having an average particle diameter of 16 nm (Nipseal LP, trade name, Nippon Silica) (Made by Kogyo Co., Ltd.) A mixture of 50 parts by weight was kneaded with a pressure kneader at room temperature to obtain an adherent in which paraffin oil as a liquid agent was adhered to an aggregate of silica particles as an agglomerated fine particle It was.
Next, using a two-roll whose temperature is adjusted to about 160 ° C., high-density ultra-high molecular weight polyethylene having a molecular weight of about 3 million (Hi-Zex Million 220, trade name, molecular weight of about 3 million, manufactured by Mitsui Petrochemical Co., Ltd.) ) 100 parts by weight and 300 parts by weight of the adherent obtained above were mixed and kneaded to obtain a sheet-like precursor made of a white mixture and having a thickness of about 0.2 mm. In this precursor, 100 parts by weight of ultrahigh molecular weight polyethylene, 200 parts by weight of paraffin oil, and 100 parts by weight of silica particles are mixed, and about 44.5% by volume with respect to the total volume of the precursor. Paraffin oil was occupied.

Subsequently, the above-mentioned precursor cut to 15 × 15 cm is sandwiched between a pair of mirror-finished stainless steel plates, and this is held at a pressure of 100 kgf / cm ² for 3 minutes with a pair of press machines adjusted to 180 ° C. Pressed. And while maintaining a pressurization state, the temperature of a press board was cooled to 60 degreeC by flowing cooling water in a press board for 5 minutes, Then, the precursor was taken out. Further, this precursor was immersed in toluene in a vat at room temperature for 3 hours, then taken out, left to stand overnight at room temperature, and further heated with a dryer to obtain a white opaque porous body A. . The porous body A was cut into 100 × 100 mm and the thickness and weight were measured. As a result, the thickness was 195 μm and the weight was 1.0271 g. Therefore, from the following formula (1), the porosity φ of the porous body A was calculated to be 41%. However, the true specific gravity of the porous body A was 1.285 g / cm ³ .
φ = {M / (C · V)} · 100 (1)
(In the formula, M represents the mass [g] of the support, C represents the true specific gravity [g / cm ³ ] of the support, and V represents the volume [cm ³ ] of the support).

  When the surfaces of the front and back surfaces of the porous body A were observed with an electron microscope, it was confirmed that innumerable pores of 30 to 60 nm were formed on any surface. Further, the sheet-like porous body A, whose dimensions were measured in advance, was immersed in water at 20 ° C. for 10 seconds, and further allowed to stand at 23 ° C. for 1 hour, the shrinkage rate was 0.5%. From this, it was found that the porous body A obtained by the extraction method using silica particles as described above has small shrinkage in the process of water absorption and dehydration and is suitable for thin film lamination by the water surface expansion method.

(Comparative Example 1)
<Preparation of porous body B>
In a pressure kneader adjusted to a temperature of about 160 ° C., 100 parts by weight of high-density polyethylene (Hi-Zex 5500S, trade name, manufactured by Mitsui Petrochemical Co., Ltd.) having a molecular weight of about 100,000, and wet silica particles (Nipseal LP , Trade name, manufactured by Nippon Silica Industry Co., Ltd.) and 20 parts by weight were kneaded to obtain a mixture. The obtained mixture was crushed with two rolls adjusted to a temperature of 150 ° C. to obtain a white sheet precursor having a thickness of about 0.2 mm.

The precursor was heated in a thermal drum adjusted to 120 ° C. and then stretched by a stretching roll in the longitudinal direction and the vertical direction by 2.15 times and 1.85 times, respectively. After stretching, the removed silica was removed to obtain a white opaque porous body B. The porous body B was cut to 100 × 100 mm, and the thickness and weight were measured. As a result, the thickness was 103 μm and the weight was 0.303 g. Therefore, from the above formula (1), the porosity φ of the porous body B was calculated to be 28%. However, the true specific gravity of the porous body B was 1.050 g / cm ³ .
When the front and back surfaces of the porous body B were observed with an electron microscope, it was confirmed that numerous pores of 10 to 50 nm were formed. Further, the shrinkage percentage of the porous body B measured in the same manner as in Example 1 was 48%.

(Example 2)
<Creation of gas separation composite membrane>
Polyimidesiloxane (Shin-Etsu Chemical Co., Ltd.) having a structure represented by the following general formula (14) (wherein p and q each independently represents a positive integer) and containing 50% by mass of an organopolysiloxane skeleton When a tensile test was performed on a sheet of SMP4001 (made by Co., Ltd.) formed into a sheet having a thickness of 2 mm and the breaking strength and elongation were measured, the breaking strength of SMP4001 was 9.87 MPa and the elongation was 578%. . In addition, the tensile test was performed using a No. 2 dumbbell piece and a tensile tester (manufactured by Toyo Seiki Co., Ltd., Tensilon) according to the test method of JIS K7311.

  This polyimidesiloxane was dissolved in a mixed solvent of toluene and N-methylpidridon to prepare a polymer solution having a solid content of 10% by mass. When 0.01 mL of this polymer solution was dropped onto a water surface in a 30 × 30 × 20 cm bat containing 5 L of water by a burette, a polymer film was formed into a clean concentric shape having a diameter of about 20 cm. Expanded. The thickness of the developed thin film is calculated to be about 30 nm. A few seconds after the development, the support obtained by cutting the porous body A obtained in Example 1 into a sheet of 15 × 15 cm in size is dropped into water and gently so as to scoop the thin film. Raised. Immediately after pulling up, there was a floating part with a slight air layer at the end of the support, and this part was rainbow-colored, but after a few seconds this floating part disappeared and the entire surface was It turned white. And it left at room temperature, the water | moisture content adhering to a support body and a thin film (gas separation layer) was removed, and the gas separation composite membrane was obtained.

When the gas separation layer of the obtained gas separation composite membrane was faced down and floated on the water surface, it was not confirmed that water had entered the support, so the gas separation layer was free of defects such as tearing. confirmed. Further, when the moisture was removed, the gas separation layer was not peeled off from the support when the compressed air was wiped onto the gas separation layer.
When the gas separation composite membrane was cut into a circle having a diameter of 60 mm and subjected to a gas permeation test (23 ± 2 ° C., 1 atm reduced pressure), the oxygen permeability coefficient was 9.11 × 10 ⁻⁸ [cm ³ ( STP) · cm / cm ² · sec · cmHg], nitrogen permeability coefficient is 4.25 × 10 ⁻⁸ [cm ³ (STP) · cm / cm ² · sec · cmHg], and has excellent gas permeability It was a thing. Further, the separation factor PO ₂ / PN ₂ between oxygen and nitrogen was 2.14 [−], and the oxygen enrichment performance was also excellent.

(Example 3)
<Production of gas separation composite membrane>
The polyimidesiloxane having a structure represented by the general formula (14) and having an organopolysiloxane skeleton content of 40% by mass (SMP5010, manufactured by Shin-Etsu Chemical Co., Ltd.) is the same as in Example 2. When the tensile test was performed, the breaking strength was 15.43 MPa and the elongation was 88%.
A gas separation composite membrane was produced in the same manner as in Example 2 except that polyimide siloxane was replaced with SMP5010. When the support was lifted from the surface of the water, a portion that was not supported on the support due to the gas separation layer turning over at the end of the support was slightly observed. When this was left at room temperature, the part that was not turned up gradually turned white, and after 45 minutes, the turned up part and the part other than its surroundings became almost white, and gas separation occurred. The layer adhered to the support.

When the obtained gas separation composite membrane was floated on the water surface in the same manner as in Example 2, it was not confirmed that water had entered the support, and thus there was no defect such as tearing in the gas separation layer. confirmed. In addition, when the compressed air was wiped onto the gas separation layer during the removal of moisture, the gas separation layer was partially blown off and blown off, but most did not appear to peel off from the support. .
When this gas separation composite membrane was subjected to a gas permeation test in the same manner as in Example 2, the oxygen permeation coefficient was 8.67 × 10 ⁻¹⁰ [cm ³ (STP) · cm / cm ² · sec · cmHg]. The permeability coefficient of nitrogen was 2.03 × 10 ⁻¹⁰ [cm ³ (STP) · cm / cm ² · sec · cmHg], and the gas permeability was excellent. Further, the separation factor PO ₂ / PN ₂ between oxygen and nitrogen was 4.27 [−], and the oxygen enrichment performance was also excellent.

Example 4
<Production of gas separation composite membrane>
When a tensile test was conducted in the same manner as in Example 2 for polyimidesiloxane having an organopolysiloxane skeleton content of 30% by mass (manufactured by Shin-Etsu Chemical Co., Ltd., SMP3001), the breaking strength was 51.21 MPa. The elongation was 76%.
A gas separation composite membrane was produced in the same manner as in Example 2 except that polyimide siloxane was replaced with SMP3001. When it pulled up from the water surface, the part which was not supported on the support body by the gas separation layer turning over at the edge part of the support body was recognized. In this gas separation composite membrane, the gas separation layer was almost adhered to the support as a whole, but the part where the gas separation layer was lifted in addition to the part that was turned up after standing at room temperature for 1 hour However, when compared with the gas separation composite membrane of Example 3, a little more was observed.

(Comparative Example 2)
A gas separation composite membrane was produced in the same manner as in Example 2 except that the porous material A was replaced with the porous material B obtained in Comparative Example 2. However, when the moisture contained in the support was removed, the whole was severely distorted. When this gas separation composite membrane was floated on the water surface, it was confirmed that water entered the support over the entire surface in contact with the water surface. Therefore, this gas separation composite membrane did not provide a gas separation function.

FIG. 1 is a cross-sectional view schematically showing a gas separation composite membrane according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a state where voids are formed in a part of the gas separation composite membrane. FIG. 3 is a cross-sectional view schematically showing a state after the gap shown in FIG. 2 disappears in a part of the gas separation composite membrane. FIG. 4 is a cross-sectional view schematically showing an adhering body in which a liquid agent adheres to coherent fine particles. FIG. 5 is a cross-sectional view schematically showing a precursor of a porous body. FIG. 6 is a cross-sectional view schematically showing a support made of a porous body.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Aggregating fine particle, 2 ... Liquid agent, 5 ... Adherence body, 10 ... Support body, 10a ... Precursor, 11 ... Ethylene polymer, 20 ... Gas separation layer, 30 ... Gap, 100 ... Gas separation composite membrane.

Claims (8)

A gas separation composite membrane comprising a gas separation layer on a support,
The support comprises a porous body of unstretched ethylene polymer,
The gas separation layer is a gas separation composite membrane comprising a polymer thin film that is phase-separated into a phase in a rubber state or a molten state and a phase in a glass state or a crystal state. A gas separation composite membrane comprising a gas separation layer on a support,
The support comprises a porous body of unstretched ethylene polymer,
The gas separation layer is
An organopolysiloxane skeleton represented by the following general formula (1);
A gas separation composite membrane comprising a polymer thin film containing an imide skeleton represented by the following general formula (2).

[Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a monovalent aliphatic group or a monovalent aromatic group, X is a tetravalent aromatic group, Y, Z ¹ and Z ² are Each independently represents a divalent aliphatic group or a divalent aromatic group, and r represents a positive integer. ]   The gas separation composite membrane according to claim 2, wherein the polymer contains the organopolysiloxane skeleton in an amount of 35% by mass or more based on the mass of the polymer.   The gas separation composite membrane according to any one of claims 1 to 3, wherein the polymer is a polymer having an elongation of 80% or more.   The gas separation composite membrane according to any one of claims 1 to 4, wherein the thin film is a thin film obtained by spreading the polymer on a water surface.   6. The porous body according to claim 1, wherein the porous body has a shrinkage of 0 to 10% when immersed in water at 20 ° C. for 10 seconds and further left at 23 ± 2 ° C. for 1 hour. The gas separation composite membrane described.   The gas separation composite membrane according to any one of claims 1 to 6, wherein the porous body is a porous body in which open pores in which cohesive fine particles are attached to a pore wall are formed. A method for producing a porous body for use as a support for a gas separation composite membrane,
A method for producing a porous body, wherein the liquid agent is removed from a mixture obtained by mixing cohesive fine particles, a liquid agent, and an unstretched ethylene polymer.

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