Method for producing gas separation composite membrane, liquid composition, gas separation composite membrane, gas separation module, gas separation apparatus, and gas separation method

1. A method for producing a gas separation composite membrane, the method comprising:

applying a mixed liquid containing a crosslinkable polysiloxane compound (a) below and a crosslinkable polysiloxane compound (b) below onto a porous support to form a coating film; and

curing the coating film to form a crosslinked polysiloxane compound layer:

(a) a crosslinkable polysiloxane compound that has a structural unit represented by formula (a1) below, a structural unit represented by formula (a2) below, and at least one structural unit selected from the group consisting of a structural unit represented by formula (a3) below and a structural unit represented by formula (a4) below and that does not have a hydrosilyl group, and

(b) a crosslinkable polysiloxane compound that has a structural unit represented by formula (b1) below, a structural unit represented by formula (b2) below, and at least one structural unit selected from the group consisting of a structural unit represented by formula (b3) below and a structural unit represented by formula (b4) below and that does not have a vinyl group,

where R 1a to R 1f and R 2a to R 2f represent a substituent that is not reactive with a vinyl group or a hydrosilyl group and * represents a linking site, where a linking site * in *—Si— and —O—* is a linking site in a siloxane bond and a linking site * in —CH 2 —CH 2 —* is a linking site with a Si atom constituting a siloxane bond.

2. The method for producing a gas separation composite membrane according to claim 1 , wherein the crosslinkable polysiloxane compound (a) and the crosslinkable polysiloxane compound (b) are obtained by reacting a polysiloxane compound (c) below and a polysiloxane compound (d) below:

(c) a polysiloxane compound that has a structural unit represented by formula (c1) below and at least one structural unit selected from the group consisting of a structural unit represented by formula (c3) below and a structural unit represented by formula (c4) below, and

(d) a polysiloxane compound that has a structural unit represented by formula (d1) below and at least one structural unit selected from the group consisting of a structural unit represented by formula (d3) below and a structural unit represented by formula (d4) below,

where R 3a to R 3c and R 4a to R 4e represent a substituent that is not reactive with a vinyl group or a hydrosilyl group and * represents a linking site in a siloxane bond.

3. The method for producing a gas separation composite membrane according to claim 1 , wherein the crosslinkable polysiloxane compound (a) and/or the crosslinkable polysiloxane compound (b) has a structural unit represented by formula (e1) below and/or a structural unit represented by formula (e2) below:

where R 5a represents a substituent that is not reactive with a vinyl group or a hydrosilyl group and * represents a linking site in a siloxane bond.

4. The method for producing a gas separation composite membrane according to claim 1 , wherein R 1a to R 1f , R 2a to R 2f , R 3a to R 3e , R 4a to R 4e , and R 5a represent a non-aromatic substituent.

5. The method for producing a gas separation composite membrane according to claim 1 , wherein after the crosslinked polysiloxane compound layer is formed, a gas separation layer is formed on the crosslinked polysiloxane compound layer.

6. The method for producing a gas separation composite membrane according to claim 5 , wherein after the crosslinked polysiloxane compound layer is formed and before the gas separation layer is formed, an oxygen atom is caused to permeate into the crosslinked polysiloxane compound layer.

7. The method for producing a gas separation composite membrane according to claim 5 , wherein the gas separation layer is a layer having a polyimide compound.

8. A liquid composition comprising a crosslinkable polysiloxane compound (a) below and a crosslinkable polysiloxane compound (b) below:

(a) a crosslinkable polysiloxane compound that has a structural unit represented by formula (a1) below, a structural unit represented by formula (a2) below, and at least one structural unit selected from the group consisting of a structural unit represented by formula (a3) below and a structural unit represented by formula (a4) below and that does not have a hydrosilyl group, and

(b) a crosslinkable polysiloxane compound that has a structural unit represented by formula (b1) below, a structural unit represented by formula (b2) below, and at least one structural unit selected from the group consisting of a structural unit represented by fomnnula (b3) below and a structural unit represented by formula (b4) below and that does not have a vinyl group,

where R 1a to R 1f and R 2a to R 2f represent a substituent that is not reactive with a vinyl group or a hydrosilyl group and * represents a linking site, where a linking site * in *—Si— and —O—* is a linking site in a siloxane bond and a linking site * in —CH 2 —CH 2 —* is a linking site with a Si atom constituting a siloxane bond.

9. The liquid composition according to claim 8 , wherein a molar ratio of a total content β of a hydrosilyl group in the crosslinkable polysiloxane compound (b) to a total content α of a vinyl group in the crosslinkable polysiloxane compound (a) in the liquid composition is β/α=0.8 to 2.0.

10. The liquid composition according to claim 8 , wherein R 1a to R 1f and R 2a to R 2f represent a non-aromatic substituent.

11. A gas separation composite membrane comprising a crosslinked polysiloxane compound layer on a porous support,

wherein the crosslinked polysiloxane compound layer has a structural unit represented by formula (f1) below and a structural unit represented by formula (f2) below,

a Si ratio of the crosslinked polysiloxane compound layer before and after immersion in chloroform, the Si ratio being calculated from mathematical formula (I) below, is 0.65 to 1.00, and

a surface of the crosslinked polysiloxane compound layer has an arithmetical mean roughness of 70 nm or less,

where R 6a to R 6c represent a substituent that is not reactive with a vinyl group or a hydrosilyl group and * represents a linking site, where a linking site * in *—Si— and —O—* is a linking site in a siloxane bond and a linking site * in —CH 2 —CH 2 —* is a linking site with a Si atom constituting a siloxane bond,

Si ratio=(Si-Kα X-ray intensity after immersion in chloroform)/(Si-Kα X-ray intensity before immersion in chloroform).  Mathematical formula (1)

12. The gas separation composite membrane according to claim 11 , wherein the crosslinked polysiloxane compound layer has a structural unit represented by formula (e1) below and/or a structural unit represented by formula (e2) below:

where R 5a represents a substituent and * represents a linking site in a siloxane bond.

13. The gas separation composite membrane according to claim 11 , wherein the crosslinked polysiloxane compound layer has a hardness of 30 N/mm 2 or more.

14. The gas separation composite membrane according to claim 11 , wherein a volume swelling ratio obtained when the crosslinked polysiloxane compound layer is exposed to a toluene-saturated atmosphere for 10 minutes is 100% to 155%.

15. The gas separation composite membrane according to claim 11 , wherein R 6a to R 6c represent a non-aromatic substituent.

16. The gas separation composite membrane according to claim 12 , wherein R 5a represents a non-aromatic substituent.

17. The gas separation composite membrane according to claim 11 , comprising a gas separation layer on the crosslinked polysiloxane compound layer.

18. The gas separation composite membrane according to claim 17 , wherein the gas separation layer contains a polyimide compound.

19. A gas separation module comprising the gas separation composite membrane according to claim 11 .

20. A gas separation apparatus comprising the gas separation module according to claim 19 .