Abstract: The present invention provides a new separation functional layer suitable for separating an acid gas from a gas mixture containing the acid gas. A separation functional layer of the present invention includes polyimide. The polyimide includes a structural unit A1 derived from a tetracarboxylic dianhydride having a six-membered ring acid anhydride structure, and a structural unit B1 derived from diamine. At least one of the structural unit A1 and the structural unit B1 has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a thiol group, and metal salts of these groups.

Abstract: The present invention provides a separation membrane suitable for suppressing variation in separation performance. A separation membrane 10 of the present invention includes a separation functional layer 1, a porous support member 3 supporting the separation functional layer 1, and an intermediate layer 2 that is disposed between the separation functional layer 1 and the porous support member 3 and is formed from an emulsion resin composition. The emulsion resin composition includes, for example, a silicone-based polymer, a hydrophilic polymer, etc.

Abstract: The present invention provides a method for manufacturing a separation membrane suitable for transferring a separation functional layer and an intermediate layer from a release liner to a porous support member. The manufacturing method of the present invention is a method for manufacturing a separation membrane 10 including a separation functional layer 1, a porous support member 3, and an intermediate layer 2. The manufacturing method includes: forming the intermediate layer 2 on a first laminate 15 having a release liner 5 and the separation functional layer 1; bonding the intermediate layer 2 of a second laminate 16 having the release liner 5, the separation functional layer 1, and the intermediate layer 2 in this order to the porous support member 3 and thereby forming a third laminate 17; and removing the release liner 5 from the third laminate 17.