JPH0219848B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a fluorine-containing ion exchange resin membrane, and more specifically, an improved fluorine-containing ion exchange method that involves uniformly mixing specific inorganic fine substances to form a fluorine-containing ion exchange resin membrane. Concerning a method for manufacturing a resin film. Conventionally, various electrolysis methods have been proposed using water, an aqueous acid or alkali solution, an aqueous solution such as an alkali halide or an alkali carbonate solution, and the like. In recent years, from the viewpoint of pollution prevention, the diaphragm method has been used instead of the mercury method to obtain caustic alkali and chlorine by electrolyzing such aqueous solutions, especially aqueous alkaline chloride solutions. A method using an ion exchange membrane has been put into practical use for the purpose of obtaining this. On the other hand, from the viewpoint of energy saving, it is required in this type of electrolysis to lower the electrolysis voltage as much as possible, and various means for this purpose have been proposed. For example, so-called SPE (Solid Solid
Polymer Electrolyte) type electrolysis method (for example, JP-A-Sho
53-52297, JP-A-52-78788, etc.) are known. In addition, a fluorine-containing ion exchange resin membrane with at least one rough surface is used,
A method of arranging the rough surface toward the cathode side (Japanese Patent Application Laid-open No. 1983
-Refer to Publication No. 110786, etc.) have also been proposed.
Further, a method of using a fluorine-containing ion exchange resin membrane having a gas- and liquid-permeable porous layer formed on its surface that does not function as an electrode has been proposed in Japanese Patent Application Laid-open No. 75583/1983. The present inventor unexpectedly discovered the following by forming a film by uniformly mixing inorganic fine particles such as silicon carbide and titanium oxide with a fluorine-containing ion exchange resin in a specific ratio. That is, a blend film obtained by uniformly mixing such inorganic fine substances can reduce the cell voltage of an electrolytic cell using the blend film. Furthermore, such a blend membrane has the advantage that the hydrophilicity of the membrane surface is increased and the mechanical strength of the membrane is significantly improved. Thus, the present invention provides a method for producing a fluorine-containing ion-exchange resin membrane, which comprises forming a film of a fluorine-containing ion-exchange resin having an ion-exchange group, from an oxide of a group B or iron group metal in the periodic table. The inorganic fine particles are added to the fluorine-containing ion exchange resin 100.
Forming a film by uniformly mixing 0.5 to 50 parts by weight per part by weight In the present invention, it is important to form a film by uniformly mixing inorganic fines in a specific ratio with a fluorine-containing ion exchange resin. The mixing ratio of inorganic fines is 0.5 to 50 parts by weight per 100 parts by weight of fluorine-containing ion exchange resin.
It is preferably selected from a range of 5 to 30 parts by weight.
If the mixing ratio of the inorganic fine particles is too small, the above-mentioned effects such as reducing the electrolytic voltage in the present invention will be slight, and if it is too large, the various electrolytic performances of the fluorine-containing ion exchange membrane will tend to be impaired. There is a problem in that as the voltage increases, the electrolytic voltage also increases. It is important that the inorganic fine particles are mixed uniformly, and from the viewpoint of such uniform mixing, the particle size is 0.1
Fine particles of ~100 microns, preferably 0.1-50 microns or diameters of 0.1-100 microns, preferably
Fine fibers of 0.1 to 50 microns and lengths of 1 micron to 5 mm are used. The above-mentioned inorganic fine particles are selected depending on the purpose and conditions of use of the fluorine-containing ion exchange resin membrane blended with these fine particles or fine fibers.
(preferably titanium, zirconium, hafnium) or iron group metals (preferably iron, cobalt,
Oxides of the elements (nickel) are used. Specific examples include TiO ₂ , ZrO ₂ , Fe ₂ O ₃ , Fe ₃ O ₄ and the like. In the present invention, the fluorine-containing ion exchange resin includes carboxylic acid groups, sulfonic acid groups, phosphoric acid groups,
A resin made of a fluorine-containing polymer having an ion exchange group such as a phenolic hydroxyl group is preferred. Such a resin preferably has a copolymer structure of a vinyl monomer such as tetrafluoroethylene or chlorotrifluoroethylene and a fluorovinyl monomer containing an ion exchange group such as a sulfonic acid, carboxylic acid, or phosphoric acid group. In particular, it is preferable to use polymers having the following structures (a) and (b). where X is F, Cl, H or _-CF3 , X' is X or _CF3 ( _CF2 ) _-n , m is 1 to 5,
Y is selected from the following: ( _-CF2 ) _-x A, -O(-- _CF2 ) _-x A,

[Formula] −CF ₂ −O(−−CF ₂ ) − _x A,

【formula】

x, y, z are all 0 to 10, and Z, R _f
is selected from -F or a perfluoroalkyl group having 1 to 10 carbon atoms. Also, A is −SO ₃ M, −COOM
or can be converted into these groups by hydrolysis -
SO ₂ F, -CN, -COOF or -COOR, M represents hydrogen or an alkali metal, and R represents an alkyl group having 1 to 10 carbon atoms. The fluorine-containing ion exchange resin membrane of the present invention preferably has an ion exchange capacity of 0.5 to 4.0 meq/g dry resin, particularly preferably 0.8 to 2.0 meq/g dry resin. In order to provide such an ion exchange capacity, in the case of an ion exchange resin membrane made of a copolymer consisting of the polymerized units of (a) and (b) above,
Preferably, the amount of polymerized units (b) is preferably 1 to 40 mol%, particularly 3 to 25 mol%. The fluorine-containing ion exchange resin membrane used in the present invention does not necessarily need to be formed from one type of polymer, nor does it need to have only one type of ion exchange group. For example, two types of polymers may be used in combination for the ion exchange capacity, or an ionic resin membrane may be used in combination with a weakly acidic exchange group such as a carboxylic acid group and a strongly acidic exchange group such as a sulfonic acid group. The inorganic fine particles and the fluorine-containing ion exchange resin are uniformly mixed to form a film. Film formation can be performed by various conventionally known methods. Further, the specific blend membrane can be reinforced, if necessary, with a cloth, a woven fabric such as a net, a nonwoven fabric, a metal mesh, a porous body, etc., preferably made of a fluorine-containing polymer such as polytetrafluoroethylene. The thickness of the specific blend film of the present invention is usually 20 to 500μ, preferably 50 to 400μ. In the present invention, uniform mixing of the inorganic fine particles and the fluorine-containing ion exchange resin and film formation are carried out by various means as described above. For example, using an aqueous dispersion, an organic solution, a dispersion, etc. of a fluorine-containing ion exchange resin, homogeneous mixing with inorganic fines is carried out in a wet manner, or such an organic solution mixed with inorganic fines, It is also possible to form a film from a dispersion or the like by a casting method. Of course, it is also possible to form a film by employing a dry blending method or by heat-melting a blended product. In the latter case, when forming a film by hot melt molding, the fluorine-containing ion exchange resin has an appropriate form of ion exchange group that does not cause decomposition of the ion exchange group it has, for example, an acid or ester type in the case of a carboxylic acid group. In the case of a sulfonic acid group, −SO ₂ F
It is preferable to do this in a mold. Furthermore, the blend may be heated and melt-molded to form pellets, and the pellets may be formed into a film by extrusion molding or press molding. Special blend membranes are used extensively in various electrolysis applications, in which either type of electrode may be used. For example, a hollow electrode such as a perforated plate, mesh or expanded metal is used. As a hollow electrode, the major axis is 1.0 to 10 mm, and the minor axis is 0.5 mm.
An example is expanded metal with a wire diameter of ~10 mm, a wire diameter of 0.1 to 1.3 mm, and a porosity of 30 to 90%. Although a plurality of plate-shaped electrodes may be used, it is preferable to use a plurality of plate electrodes with different porosity, with the one with the smaller porosity being used on the side closer to the membrane. As the anode material, a platinum group metal, its conductive oxide, or its conductive reduced oxide, etc. are usually used, while as the cathode, a platinum group metal, its conductive oxide, or an iron group metal, etc. are used. Examples of platinum group metals include platinum, rhodium, ruthenium, palladium, and rhidium, and examples of iron group metals include iron, cobalt, nickel, Raney nickel, stabilized Raney nickel, stainless steel, and alkali-etched stainless steel (Special Publication No. 54-19229). (Japanese Patent Application Laid-Open No. 1983-1999)
112785) and a Rodan-Nickelmecki cathode (Japanese Patent Application Laid-Open No. 115676/1983). If a porous metal is used, the electrode may be formed from the material itself forming the anode or cathode. However, when platinum group metals or conductive oxides thereof are used, it is preferable to coat the surface of an expanded valve metal such as titanium or tantalum with these substances. In the case of arranging electrodes in the present invention, the electrodes may be arranged in contact with the specific blend film, or may be arranged at appropriate intervals. Rather than firmly pressing the metal against the ion exchange membrane surface, the electrode is preferably gently pressed against the ion exchange membrane surface at, for example, 0 to 2.0 kg/cm ² . The electrolytic cell using the blend membrane of the present invention may be of a monopolar type or a bipolar type. In addition, in the case of electrolysis of an aqueous alkali chloride solution, for example, materials resistant to aqueous alkali chloride and chlorine are used for the anode chamber, such as valve metal and titanium, and for the cathode chamber. Iron, stainless steel, or nickel, which are resistant to alkali hydroxide and hydrogen, are used. Known conditions can be employed as process conditions for electrolyzing an aqueous alkali chloride solution using the blend membrane of the present invention. For example, an aqueous alkali chloride solution of 2.5 to 5.0 normal (N) is preferably supplied to the anode chamber, and water or diluted alkali hydroxide is supplied to the cathode chamber, preferably at a temperature of 80°C to 120°C and a current density of 10 to 100°C.
Electrolyzed at A/dm ² . In such cases, heavy metal ions such as calcium and magnesium in the aqueous alkali chloride solution cause deterioration of the ion exchange membrane;
It is preferable to make it as small as possible. Further, in order to prevent the generation of oxygen at the anode as much as possible, an acid such as hydrochloric acid can be added to the aqueous alkali chloride solution. The above describes the use of the specific blend membrane of the present invention mainly for the example of electrolysis of an aqueous alkali chloride solution, but it is equally applicable to the electrolysis of water, halogen membranes (hydrochloric acid, hydrobromic acid), and alkali carbonate. Of course it is possible. It can also be applied as a diaphragm in various electrolytic synthesis reactions of organic compounds using ion exchange membranes. Next, examples of the present invention will be described in more detail, but it goes without saying that the present invention is not limited by such explanations. Incidentally, parts in the examples are parts by weight unless otherwise specified. Example 1 Ion exchange consisting of 1 part of iron oxide powder with a particle size of 25μ or less, a copolymer of tetrafluoroethylene and CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ with an ion exchange capacity of 1.43 meq/g dry resin 9 parts of resin powder and 50 parts of methanol were mixed for 1 hour using an automatic mortar and then dried to obtain a mixed powder consisting of iron oxide powder and ion exchange resin powder. The mixed powder is heated to 220℃ using a press molding machine.
An ion exchange membrane having a thickness of 300μ was obtained. The ion exchange membrane was immersed in a 25% by weight aqueous sodium hydroxide solution at 90° C. for 16 hours to hydrolyze the ion exchange membrane. Then, on the anode side of the ion exchange membrane, an anode with a low chlorine overvoltage made of expanded titanium metal (2.5 mm short axis, 5 mm long axis) coated with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide was installed on the anode side of the ion exchange membrane. SUS-304 expanded metal (short diameter 2.5 mm, long diameter 5 mm) is placed on the cathode side of the
The cathode, which has been etched at 150°C for 52 hours in a 52% caustic soda aqueous solution to have a low hydrogen overvoltage, is brought into contact with pressure, and the anode chamber is chlorinated while supplying a 5N-NaCl aqueous solution to the anode chamber and water to the cathode chamber. Electrolysis was carried out at 90°C while maintaining the sodium concentration at 4N and the caustic soda concentration in the catholyte at 35% by weight, and the following results were obtained. Current density (A/dm ² ) Cell voltage (V) 20 2.84 40 3.23 60 3.60 Furthermore, the current efficiency of caustic soda generation at a current density of 40 A/dm ² was 92%. Furthermore, the current density
When electrolysis was continued for one month at 40 A/dm ² , the cell voltage remained almost constant. Comparative Example Example 1 except that a 300μ thick ion exchange membrane formed only from ion exchange resin powder without blending iron oxide powder was used in Example 1.
An electrolytic cell was assembled in the same manner as above, and a saline solution was electrolyzed to obtain the following results. Current density (A/dm ² ) Cell voltage (V) 20 3.07 40 3.50 60 3.90 Furthermore, the current efficiency of caustic soda generation at a current density of 40 A/dm ² was 94%. Example 2 Example 1 except that 0.5 parts of iron oxide powder and 9.5 parts of ion exchange resin powder were used in Example 1.
A film was formed in the same manner as above and electrolyzed under the same conditions, and the following results were obtained. Current density (A/dm ² ) Cell voltage (V) 20 2.95 40 3.37 60 3.72 Furthermore, the current efficiency for caustic soda generation at a current density of 40 A/dm ² was 92.5%. Example 3 In Example 1, instead of iron oxide powder, particle size
Electrolysis was carried out in the same manner and under the same conditions as in Example 1, except that zirconium oxide of 25μ or less was used, and the following results were obtained. Current density (A/dm ² ) Cell voltage (V) 20 2.92 40 3.30 60 3.64 Furthermore, the current efficiency of caustic soda generation at a current density of 40 A/dm ² was 92%. Example 4 Electrolysis was carried out in the same manner and under the same conditions as in Example 1, except that zirconium oxide fibers with an average fiber length of 1.6 mm and a diameter of 3 microns were used instead of iron oxide powder, and the following results were obtained. I got it. Current density (A/dm ² ) Cell voltage (V) 20 2.96 40 3.40 60 3.84 Furthermore, the current efficiency of caustic soda production at a current density of 40 A/dm ² was 92.5%.

Claims (1)

[Scope of Claims] 1. A method for producing a fluorine-containing ion-exchange resin membrane comprising forming a fluorine-containing ion-exchange resin having an ion-exchange group, the oxidation of a group B or iron group metal in the periodic table. 0.5 to 50 parts by weight of inorganic fine matter consisting of
A method for producing a fluorine-containing ion exchange resin membrane, which is characterized in that the membrane is formed by uniformly mixing parts by weight. 2. The manufacturing method according to claim 1, wherein the inorganic fine particles are fine particles having a particle size of 0.1 to 100 microns. 3. Claim 1 in which the inorganic fine particles are fine particles of 0.1 to 100 microns and 1 micron to 5 mm in length.
Manufacturing method described in section. 4. The production method according to claim 1, wherein the ion exchange group is a carboxylic acid type, sulfonic acid type, or phosphoric acid type ion exchange group.