The present invention provides a gel having an interpenetrating network formed from a first network structure and a second network structure, the first network structure being composed of a first crosslinked polymer formed from at least one noncrosslinkable compound selected from the group consisting of a compound represented by the following formula (I) and a compound represented by the following formula (II), and at least one crosslinkable compound selected from the group consisting of a compound represented by the following formula (III) and a compound represented by the following formula (IV), and the second network structure being composed of a second crosslinked polymer having at least one selected from the group consisting of an acidic dissociative group, an acidic dissociative group in a salt form, and a derivative group of an acidic dissociative group:

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wherein the groups are as defined in the DESCRIPTION.

The present invention provides a gel containing a crosslinked polymer having at least one selected from the group consisting of an acidic dissociative group, an acidic dissociative group in a salt form, and a derivative group of an acidic dissociative group, and a condensate of a compound represented by the following formula (I): Si{R.sup.1N(R.sup.2)(R.sup.3)}(OR.sup.4)(OR.sup.5)(R.sup.6) (wherein each group is as defined in the DESCRIPTION).

An acidic gas separation membrane sheet causes an acidic gas to selectively permeate therethrough. The acidic gas separation membrane sheet includes a first porous layer, a hydrophilic resin composition layer, and a second porous layer in this order. A second peel strength between the second porous layer and the hydrophilic resin composition layer is less than a first peel strength between the first porous layer and the hydrophilic resin composition layer. An average value of the second peel strength is within a range of greater than or equal to 5 N/m and less than or equal to 500 N/m.

The present invention provides a gel containing a crosslinked polymer having at least one selected from the group consisting of an acidic dissociative group, an acidic dissociative group in a salt form, and a derivative group of an acidic dissociative group, and a condensate of a compound represented by the following formula (I): Si{R.sup.1N(R.sup.2)(R.sup.3)}(OR.sup.4)(OR.sup.5)(R.sup.6) (wherein each group is as defined in the DESCRIPTION).

Provided is a method for separating, from a raw gas containing a specific gas, the specific gas using a gas separation membrane module. The gas separation membrane module includes a housing and a gas separation membrane element enclosed in the housing. The gas separation membrane element includes a gas separation membrane including a hydrophilic resin composition layer for selectively allowing for permeation of the specific gas. The method includes the steps of: increasing pressure in an interior of the gas separation membrane module; increasing a temperature in the interior of the gas separation membrane module; and feeding a raw gas to the interior of the gas separation membrane module in that order.

The gas separation membrane element contains a gas separation membrane, and a sealing portion for preventing mixture of a source gas and a specific gas permeated through a gas separation membrane. The gas separation membrane has a first porous layer including a porous membrane, and a hydrophilic resin composition layer disposed on the first porous layer. The sealing portion is a region in which a cured material of a sealant penetrates in at least the first porous layer in the gas separation membrane, and a thermal expansion coefficient A of the sealing portion and a thermal expansion coefficient B of a material forming the first porous layer satisfy a relation (I):

0.35A/B1.0 (I).

Provided is a method for separating a specific gas from a raw gas using a gas separation membrane module that includes a gas separation membrane element enclosed in a housing. The element includes a gas separation membrane including a hydrophilic resin composition layer. The method includes: preparing the module; increasing pressure in an interior of the module; increasing a temperature in the interior; and feeding a raw gas to the interior. The layer of the module prepared is adjusted to contain moisture, and a moisture content thereof is an amount that allows an equilibrium relative humidity at a temperature of 23 C. of a gas phase portion in the housing to be 10% RH or more. The raw gas feeding step is performed after the preparation step. The pressure increase step and the temperature increase step are performed after the preparation step and before the raw gas feeding step.

Provided is a method for separating, from a raw gas containing a specific gas, the specific gas using a gas separation membrane module. The gas separation membrane module includes a housing and a gas separation membrane element enclosed in the housing. The gas separation membrane element includes a gas separation membrane including a hydrophilic resin composition layer for selectively allowing for permeation of the specific gas. The method includes the steps of: increasing pressure in an interior of the gas separation membrane module; increasing a temperature in the interior of the gas separation membrane module; and feeding a raw gas to the interior of the gas separation membrane module in that order.

Provided is a method for separating a specific gas from a raw gas using a gas separation membrane module that includes a gas separation membrane element enclosed in a housing. The element includes a gas separation membrane including a hydrophilic resin composition layer. The method includes: preparing the module; increasing pressure in an interior of the module; increasing a temperature in the interior; and feeding a raw gas to the interior. The layer of the module prepared is adjusted to contain moisture, and a moisture content thereof is an amount that allows an equilibrium relative humidity at a temperature of 23? C. of a gas phase portion in the housing to be 10% RH or more. The raw gas feeding step is performed after the preparation step. The pressure increase step and the temperature increase step are performed after the preparation step and before the raw gas feeding step.

A spiral-wound acid gas separation membrane element (1) includes a wound body which includes a laminate and a perforated core (5), the laminate being wound around the perforated core tube (5) and including: a separation membrane (2), a feed-side channel component (3), and an element constituent layer (e.g., permeate-side channel component (4)). The separation membrane (2) is provided with a sealing section (25) present at both widthwise ends of the separation membrane (2). The sealing section (25) is sealed with an adhesive. This makes it possible not only to separate acid gas from mixed gas more efficiently as compared to a conventional spiral-wound acid gas separation membrane element but also to save energy.