Process for producing ion exchange membrane for electrolysis, and ion exchange membrane for electrolysis
To provide a process for producing an ion exchange membrane for electrolysis which has a low membrane resistance and which is capable of reducing the electrolysis voltage during the electrolysis, even if the membrane strength is increased, an ion exchange membrane for electrolysis, a precursor membrane of an ion exchange membrane for electrolysis, and an electrolysis apparatus. In a fluorinated polymer having groups convertible to ion exchange groups, a reinforcing fabric 20 A formed by weaving covered yarns 21 each comprising a reinforcing fabric 22 and a sacrificial material covering at least a portion of the outer peripheral surface of the reinforcing yarn 22 , to produce a precursor membrane of an ion exchange membrane, and from the precursor membrane, at least a portion of the sacrificial material in the reinforcing fabric is eluted to form a reinforcing material and at the same time, the groups convertible to ion exchange groups are converted to ion exchange groups, to produce an ion exchange membrane for electrolysis.
1. A process for producing an ion exchange membrane, the process comprising:
(a) embedding, in a fluorinated polymer having groups convertible to ion exchange groups, a reinforcing fabric formed by weaving covered yarns each comprising a reinforcing yarn and a sacrificial material covering at least a portion of the outer peripheral surface of the reinforcing yarn, to produce a precursor membrane of an ion exchange membrane; and
(b) eluting, from the precursor membrane, at least a portion of the sacrificial material in the reinforcing fabric to form a reinforcing material and at the same time, converting the groups convertible to ion exchange groups to ion exchange groups;
wherein between the outer peripheral surface of at least a portion of the reinforcing yarns and the fluorinated polymer, a region (p) which is either a region (p 1 ) formed by a void or a region (p 2 ) formed by a void and the sacrificial material, is continuously formed along an entire length of the reinforcing yarn.
2. The process of claim 1 , therein the covered yarns are covered twisted yarns each having the reinforcing yarn as a core yarn and a wrap yarn composed of the sacrificial material wound on at least a portion of the outer peripheral surface of the core yarn.
3. The process of claim 1 , wherein the region (p) is formed in a tubular form along the longitudinal direction of the reinforcing yarn on the outer peripheral surface of the reinforcing yarn or is formed in a spiral form so as to be wound on the outer peripheral surface of the reinforcing yarn.
4. The process of claim 1 , wherein in a cross section at right angles to the lengthwise direction of at least a portion of the reinforcing yarns, the following angle (x) of a portion facing the region (p) based on the outer periphery of the reinforcing yarn, is from 60 to 360°:
angle (x): an angle formed by two lines drawn from a centroid Pc of the reinforcing yarn in the cross section so as to sandwich a portion (T) facing the region (p) formed on the outer peripheral surface of the reinforcing yarn; in a case where there are two or more portions (T), the angle (x) is the sum of the angles corresponding to the respective portions (T); and in a case where the portion (T) is present on the entire outer periphery of the reinforcing yarn, the angle (x) is 360°.
5. The process of claim 1 , wherein in a cross section at right angles to the lengthwise direction of at least a portion of the reinforcing yarns, the ratio of a cross sectional area (y 2 ) of the region (p) formed on the outer periphery of the reinforcing yarn to the sum of a cross sectional area (y 1 ) of the reinforcing yarn and the cross sectional area (y 2 ) of the region (p), i.e. [y 2 /(y 1 +y 2 )] is from 5 to 50%.
6. The process of claim 1 , wherein the thickness of the reinforcing fabric is from 10 to 300 μm.
7. The process of claim 1 , wherein the reinforcing fabric is a reinforcing fabric formed by weaving the covered yarns and sacrificial yarns composed of the sacrificial material, and at least a portion of the sacrificial yarns is eluted in (b).
8. A process of electrolyzing an aqueous alkali chloride solution, the process comprising contacting the aqueous alkali chloride solution with an ion exchange membrane obtained by the process of claim 1 .