Gas separation composite membrane, method of producing the same, gas separating module using the same, and gas separation apparatus and gas separation method

1. A gas separation composite membrane comprising:

a gas-permeable supporting layer; and

a gas separating layer containing a crosslinked polyimide resin, over the gas-permeable supporting layer,

wherein the crosslinked polyimide resin is composed of a polyimide compound having been crosslinked through an ester linking group, the polyimide compound containing a repeating unit represented by the following formula (I), a repeating unit represented by the following formula (II-a) or (II-b), and a repeating unit represented by the following formula (III-a) or (III-b):

wherein, in formula (I), R is a group of atoms selected from the group consisting of groups represented by any one of the following formulas (I-a) to (I-g):

wherein, in formulas (I-a) to (I-g), X 1 represents a single bond or a divalent linking group; Y 1 represents a methylene group or a vinylene group; R 1 and R 2 each independently represent a hydrogen atom or a substituent; and the symbol “*” represents a binding site;

wherein, in formulas (II-a) and (II-b), R 3 , R 4 and R 5 each independently represent a substituent; l1, m1 and n1 each independently are an integer of from 0 to 4; and X 2 represents a single bond or a divalent linking group; and

wherein, in formulas (III-a) and (III-b), R 6 , R 7 and R 8 each independently represent a substituent; J 1 , J 2 and W 1 each independently represent a single bond or a divalent linking group; l2, m2 and n2 each independently are an integer of from 0 to 3; L 1 represents a divalent linking group; L 2 represents a crosslinkable functional group which is capable of forming an ester covalent bond or a crosslinkable functional group which crosslinks other than by the ester covalent bond and when the ester linking group is other than a reaction-produced site of L 2 , J 1 or J 2 is the ester linking group; p represents an integer of 0 or more; X 3 represents a single bond or a divalent linking group; and -J 1 -W 1 -(L 1 -J 2 ) p -L 2 is a site for forming a crosslinked chain mediated by the ester linking group upon being crosslinked, and

wherein a ratio [κ] of the site for forming the crosslinked chain mediated by the ester linking group to imide groups in the polyimide compound (number of the site forming the crosslinked chain mediated by the ester linking group/number of the imide groups in the polyimide compound) is more than 0.4 and less than 0.5.

2. The gas separation composite membrane according to claim 1 , wherein a gas to be supplied is a mixed gas of carbon dioxide and methane, wherein a transmission rate of the carbon dioxide at 40° C. and 40 atmospheric pressure is more than 20 GPU, and wherein a ratio of the transmission rate of the carbon dioxide to a transmission rate of the methane (R CO2 /R CH4 ) is 15 or more.

3. The gas separation composite membrane according to claim 1 , wherein the supporting layer contains a porous layer on a side of the gas separating layer and a nonwoven fabric layer on a side reverse thereto.

4. The gas separation composite membrane according to claim 3 , wherein the porous layer has a molecular weight cut-off of 100,000 or less.

5. A method of producing the gas separation composite membrane according to claim 1 comprising:

providing the polyimide compound containing the repeating unit represented by the following formula (I), the repeating unit represented by the following formula (II-a) or (II-b), and the repeating unit represented by the following formula (III-a) or (III-b):

wherein, in formula (I), R is the group of atoms selected from the group consisting of groups represented by any one of the following formulas (I-a) to (I-g):

wherein, in formulas (I-a) to (I-g), X 1 represents the single bond or the divalent linking group; Y 1 represents the methylene group or the vinylene group; R 1 and R 2 each independently represent the hydrogen atom or the substituent; and the symbol “*” represents the binding site;

wherein, in formulas (II-a) and (II-b), R 3 , R 4 and R 5 each independently represent the substituent; l1, m1 and n1 each independently are the integer of from 0 to 4; and X 2 represents the single bond or the divalent linking group; and

wherein, in formulas (III-a) and (III-b), R 6 , R 7 and R 8 each independently represent the substituent; J 1 , J 2 and W 1 each independently represent the single bond or the divalent linking group; l2, m2 and n2 each independently are the integer of from 0 to 3; L 1 represents the divalent linking group; L 2 represents a radical crosslinkable ester functional group; p represents the integer of 0 or more; X 3 represents the single bond or the divalent linking group; and -J 1 -W 1 -(L 1 -J 2 ) p -L 2 is the site for forming the crosslinked chain mediated by the ester linking group upon being crosslinked, and

wherein the ratio [κ] of the site for forming the crosslinked chain mediated by the ester linking group to imide groups in the polyimide compound (number of the site for forming a the crosslinked chain mediated by the ester linking group/number of the imide groups in the polyimide compound) is more than 0.4 and less than 0.5;

applying a coating liquid containing the polyimide compound, over the gas-permeable supporting layer to form the gas separating layer; and

subjecting the radical crosslinkable ester functional group to a crosslinking reaction by irradiating an active radiation or applying heat to the coating liquid, to crosslink the polyimide compound.

6. The method of producing the gas separation composite membrane according to claim 5 , wherein a crosslinking conversion ratio [α] [a crosslinked site/a crosslinkable site] is set to be 5% or more and 100% or less, in the crosslinking reaction of the polyimide compound.

7. The method of producing the gas separation composite membrane according to claim 5 , wherein the crosslinking of the polyimide compound is carried out under the conditions of 10 to 120° C.

8. A method of producing the gas separation composite membrane according to claim 1 , comprising:

providing the polyimide compound containing the repeating unit represented by the following formula (I), the repeating unit represented by the following formula (II-a) or (II-b), and the repeating unit represented by the following formula (III-a) or (III-b):

wherein, in formula (I), R is the group of atoms selected from the group consisting of groups represented by any one of the following formulas (I-a) to (I-g):

wherein, in formulas (I-a) to (I-g), X 1 represents the single bond or the divalent linking group; Y 1 represents the methylene group or the vinylene group; R 1 and R 2 each independently represent the hydrogen atom or the substituent; and the symbol “*” represents the binding site;

wherein, in formulas (II-a) and (II-b), R 3 , R 4 and R 5 each independently represent the substituent; l1, m1 and n1 each independently are the integer of from 0 to 4; and X 2 represents the single bond or the divalent linking group; and

wherein, in formulas (III-a) and (III-b), R 6 , R 7 and R 8 each independently represent the substituent; J 1 , J 2 and W 1 each independently represent the single bond or the divalent linking group; l2, m2 and n2 each independently are the integer of from 0 to 3; L 1 represents the divalent linking group; L 2 represents a crosslinkable functional group; p represents an integer of 0 or more; X 3 represents the single bond or the divalent linking group; and -J 1 -W 1 -(L 1 -J 2 )-L 2 is the site for forming the crosslinked chain mediated by the ester linking group upon being crosslinked, and

wherein the ratio [κ] of the site for forming the crosslinked chain mediated by the ester linking group to imide groups in the polyimide compound (number of the site for forming a the crosslinked chain mediated by the ester linking group/number of the imide groups in the polyimide compound) is more than 0.4 and less than 0.5;

applying a coating liquid containing both of the polyimide compound and a compound having at least two functional groups selected from an oxirane group and an oxetane group in the molecule thereof, over the gas-permeable supporting layer to form the gas separating layer; and

subjecting the crosslinkable functional group to a crosslinking reaction by irradiating an active radiation or applying heat to the coating liquid, to crosslink the polyimide compound.

9. The method of producing the gas separation composite membrane according to claim 8 , wherein a crosslinking conversion ratio [α] [a crosslinked site/a crosslinkable site] is set to be 5% or more and 100% or less, in the crosslinking reaction of the polyimide compound.

10. The method of producing the gas separation composite membrane according to claim 8 , wherein the crosslinking reaction of the polyimide compound is carried out under the conditions of 10 to 120° C.

11. A gas separation module, containing the gas separation composite membrane according to claim 1 .

12. A gas separation apparatus, containing the gas separation module according to claim 11 .

13. A gas separation method, which comprises: a step of selectively permeating carbon dioxide from a gas containing carbon dioxide and methane, by using the gas separation composite membrane according to claim 1 .