Method for producing protective-layer-covered gas separation membrane, protective-layer-covered gas separation membrane, gas separation membrane module, and gas separation apparatus

1. A method for producing a protective-layer-covered gas separation membrane, the method comprising:

forming a gas separation membrane having a resin layer containing a compound having a siloxane bond by surface oxidation treatment of a resin layer precursor containing a siloxane bond with an input power of 23 W or more; and

providing a protective layer on the resin layer before winding,

wherein the gas separation membrane satisfies one of conditions 1, 3, and 4:

condition 1: the resin layer satisfies inequalities 1 and 2:

0.9≥ A/B≥ 0.55  inequality 1:

B≥ 1.7  inequality 2:

wherein A represents an O/Si ratio that is a ratio of the number of oxygen atoms to the number of silicon atoms contained in the resin layer at a depth of 10 nm from a surface of the resin layer, and B represents an O/Si ratio that is a ratio of the number of oxygen atoms to the number of silicon atoms in the surface of the resin layer;

condition 3: a minimum percentage Si 0 of Si 2+ and Si 3+ peaks relative to all Si peaks in ESCA depth profiling of the resin layer is 1% to 40%; and

condition 4: a positron lifetime τ3 of a third component formed by implantation of a positron with an energy of 1 keV into the surface of the resin layer is 3.40 to 4.20 ns.

2. The method for producing a protective-layer-covered gas separation membrane according to claim 1 ,

wherein the gas separation membrane has a porous support A and the resin layer disposed on the porous support A and satisfies condition 2:

condition 2: the compound having a siloxane bond has a repeating unit represented by general formula (2) and a repeating unit represented by general formula (3):

wherein R 11 represents a substituent, * represents a site linked to # in general formula (2) or (3), and # represents a site linked to * in general formula (2) or (3),

the gas separation membrane includes a region GLi where the compound having a siloxane bond is present in the porous support A and a region GLe where the resin layer is present on the porous support A,

GLe has a thickness of 50 to 1,000 nm,

GLi has a thickness of 20 nm or more, and the thickness of GLi is 10% to 350% of the thickness of GLe, and

a difference between a content of the repeating unit represented by general formula (3) in a surface layer of GLe extending to a depth of 20 nm and a content of the repeating unit represented by general formula (3) in a surface layer of GLi extending to a depth of 20 nm is 30% to 90%.

3. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , wherein the surface oxidation treatment is atmospheric-pressure plasma treatment, ultraviolet ozone treatment, corona discharge treatment, or low-pressure plasma treatment.

4. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , wherein the protective layer is provided by coating or vapor deposition.

5. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , wherein the protective layer is provided within 12 hours after completion of the surface oxidation treatment.

6. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , wherein the protective layer contains a silicone resin.

7. The method for producing a protective-layer-covered gas separation membrane according to claim 6 , wherein the silicone resin contains a Si 4+ component.

8. The method for producing a protective-layer-covered gas separation membrane according to claim 6 , wherein an O/Si ratio that is a ratio of the number of oxygen atoms to the number of silicon atoms in an inner portion of the protective layer is less than 1.7.

9. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , wherein the protective layer contains a polyimide resin.

10. The method for producing a protective-layer-covered gas separation membrane according to claim 1 , further comprising:

unwinding a composite having the resin layer precursor from a roll; and

winding the protective-layer-covered gas separation membrane obtained by providing the protective layer into a roll.

11. A protective-layer-covered gas separation membrane comprising:

a gas separation membrane having a resin layer containing a compound having a siloxane bond; and

a protective layer on the resin layer,

wherein the gas separation membrane satisfies one of conditions 3and 4:

condition 3: a minimum percentage Si 0 of Si 2+ and Si 3+ peaks relative to all Si peaks in ESCA depth profiling of the resin layer is 1% to 40%; and

condition 4: a positron lifetime τ3 of a third component formed by implantation of a positron with an energy of 1 keV into the surface of the resin layer is 3.40 to 4.20 ns.

12. The protective-layer-covered gas separation membrane according to claim 11 ,

wherein the gas separation membrane comprises a porous support A and the resin layer disposed on the porous support A and satisfies condition 2:

condition 2: the compound having a siloxane bond has a repeating unit represented by general formula (2) and a repeating unit represented by general formula (3):

wherein R 11 represents a substituent, * represents a site linked to # in general formula (2) or (3), and # represents a site linked to * in general formula (2) or (3),

the gas separation membrane includes a region GLi where the compound having a siloxane bond is present in the porous support A and a region GLe where the resin layer is present on the porous support A,

GLe has a thickness of 50 to 1,000 nm,

GLi has a thickness of 20 nm or more, and the thickness of GLi is 10% to 350% of the thickness of GLe, and

a difference between a content of the repeating unit represented by general formula (3) in a surface layer of GLe extending to a depth of 20 nm and a content of the repeating unit represented by general formula (3) in a surface layer of GLi extending to a depth of 20 nm is 30% to 90%.

13. The protective-layer-covered gas separation membrane according to claim 11 , wherein the gas separation membrane is roll-shaped.

14. A gas separation membrane module comprising the protective-layer-covered gas separation membrane according to claim 11 .

15. A gas separation membrane module comprising a protective-layer-covered gas separation membrane cut from the protective-layer-covered gas separation membrane according to claim 13 .

16. A gas separation apparatus comprising the gas separation membrane module according to claim 15 .