KR850001090B1 - Method for electrolysis of alkali chloride - Google Patents

Abstract

Alkali chloride is electrolyzed in the manufacture of alkali hydroxide in an electrolyte cell, which is divided into a cathode chamber and anode chamber by a fluorine uniform cation exchange membrane of sulfonic acid type, sulfonamide type, or carbonic acid type. The surface of the membrane is coarse, having more than 20 concavo-convexity per 1 mm. The maximum height of the crosssection is more than 0.05 , and surface roughness is more than 0.05 . The coarse surface of the membrane creates a cathode in the cell.

Description

Electrolytic Method of Alkali Chloride

1 is a method of obtaining the maximum height from the recorded rough curve,

2 is a method of obtaining the number of t1 of roughness of 0.05 micron or more in the recorded rough curve.

The present invention relates to an economical alkali chloride electrolysis method by ion exchange membrane method.

)하는 것을 특징으로 하고, 전해 전압의 저 염화알카리의 전해방법에 관한 것이다.Specifically, in the production of alkali hydroxide by electrolyzing alkali chloride in an electrolytic cell divided into a positive electrode chamber and a negative electrode chamber by a cation exchange membrane, a homogeneous cation exchange membrane having at least one surface is roughly used as the cation exchange membrane. And into the electrolytic cell so that the rough surface of the cation exchange membrane becomes the cathode side (

It relates to an electrolytic method of low alkali chloride of the electrolytic voltage.

The homogeneous cation exchange membrane referred to in the present invention is a cation exchange membrane formed from only an ion exchange resin without branding a thermoplastic resin having no ion exchange group. Of course, in order to increase the film strength, the fiber may be spun into a porous film or the like. Moreover, you may laminate the membrane from which the kind of ion exchanger and exchange capacity differ. In the heterogeneous ion exchange membrane which is conventionally mixed with an ion exchange resin and a thermoplastic resin, the membrane resistance is decreased, so that the surface of the membrane is roughened by brushing or framing, and the ion exchange resin is exposed on the membrane surface. It became. (See, for example, Japanese Patent Application Laid-Open No. 52-47590.) However, in a homogeneous ion exchange membrane consisting of only ion exchange resins, the ion exchange resin is originally exposed on the surface of the membrane, and such a roughening treatment does not lower the membrane resistance. . In addition, Japanese Patent Application Laid-Open No. 52-20980 discloses that the surface of the membrane is discharge treated, radiation treated or flame treated, but the purpose is to make the cation exchanger incapable of ion exchange, and there is no indication about the shape of the membrane surface. . In the case where the cation exchanger on the surface of the membrane is modified, the resistance of the membrane increases and the electrolytic voltage increases, which is not preferable.

)에 매입하는 방법(열프레스 적층법)압출 성형하여 제조한 열용융성의 이온 교환막 중간체의 한쪽의 면만을 가수분해 하여 열불용성으로 한 후 반대의 열용융성면에 지지 섬유를 접촉하고 전체를 가열하면서 지지 섬유에 접촉한 측을 감압으로 하여 지지 섬유를 막에 매입하는 방법(진공적층법, 특공소 52-14670) 등을 들 수 있다. 열프레스 적층법에서는 양면이 평활하게 되며, 종래에는 이 평활한면이 음극측이 되도록 전해조에 조입하였다. 그러나, 본 발명자등은 전해상태를 상세하게 관찰한 결과, 놀랍게도 균질양이온 교환막의 음극면이 적당히 조면화(粗面化) 되어 있을 때에 전해에 의하여 음극에서 발생한 수소가스 기포의 막면 부착량이 가장 적어서 전해 전압이 가장낮은 것을 발견하였다. 즉, 본 발명은 양이온 교환막에 의하여 양극실과 음극실로 분할된 전해조에 염화 알카리를 전해하여 수산화 알카리를 제조함에 있어서 그 양이온 교환막으로서 적어도 편면이 조면화된 균질양이온 교환막을 사용하고, 또한 그 양이온 교환막의 조면이 음극측이 되게 전해조에 조입하는 것을 요지로하고 그 효과는 전류 효율은 저하시키지 않고 전해전압을 현저히 저하시키는 것이다.In the present invention, the surface of the membrane is roughened without denaturing the cation exchanger to lower the electrolytic voltage. In addition, in a homogeneous cation exchange membrane, if the cathode surface of the membrane is not smooth, it is known that bubbles of hydrogen gas generated from the cathode adhere to the membrane surface due to electrolysis and the electrolytic voltage is increased, and conventionally, the membrane is smoothly inserted into the electrolytic cell so that the smooth surface of the membrane becomes the cathode side. It was common sense. (See, for example, Japanese Patent Application Laid-Open No. 51-131489.) In general, the thickness of the cation exchange membrane method used for alkali chloride electrolysis of the ion exchange membrane method is 1000 microns or less, preferably 200 microns or less, because the membrane resistance is small. Is insufficient, and thus the strength of the membrane is added by the support fibers. A method of embedding the support fibers in the cation exchange membrane is, for example, exposing and hot pressing the heat-melt ion exchange membrane intermediate and the support fibers produced by extrusion molding. Support fabric for waist (

) (Heat press lamination method) by heat-molding only one side of the heat-melting ion exchange membrane intermediate produced by extrusion molding to make it heat insoluble, and then contacting the supporting fiber to the opposite heat-melting side and heating the whole. The method which embeds a support fiber in a film | membrane by making the side which contacted the support fiber into a pressure reduction (vacuum lamination method, the special rape 52-14670) etc. are mentioned. In the hot press lamination method, both surfaces are smoothed, and in the related art, the smooth surface is incorporated into the electrolytic cell so that the smooth side is the cathode side. However, the present inventors have observed the electrolytic state in detail, and surprisingly, when the negative electrode surface of the homogeneous cation exchange membrane was moderately roughened, the amount of film surface adhesion of hydrogen gas bubbles generated at the negative electrode by electrolysis was the smallest. The lowest voltage was found. That is, the present invention uses a homogeneous cation exchange membrane having at least one surface roughened as the cation exchange membrane in producing alkali hydroxide by electrolyzing alkali chloride into an electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane. It is a main point to insert into a electrolytic cell so that a rough surface may become a cathode side, and the effect is to reduce an electrolytic voltage remarkably, without reducing a current efficiency.

Ion Exchange Membrane Method The two-chamber method of dividing the anode and cathode chambers in a single cation exchange membrane is also advantageous in alkaline chloride electrolysis, and is a fluorine homogeneous cation exchange membrane having excellent heat resistance, chemical resistance, and mechanical strength as the cation membrane. This is used. Thus, various improvements to the fluorine-based cation exchange membrane have been studied in the prior art for the purpose of increasing the current efficiency of alkali hydroxide production and lowering the electrolytic voltage. However, in general, in the fluorine-based cation exchange membrane, it is difficult to introduce a crosslinked structure. Therefore, when the current efficiency is increased, the electrolytic voltage also increases, and when the electrolytic voltage is decreased, the current efficiency also often decreases.

This is because the change in force yield of the ion exchange membrane is affected. However, according to the present invention, the electrolytic voltage can be lowered by keeping the current efficiency of the homogeneous cation exchange membrane high. The reason why the electrolytic voltage decreases when the surface of the cation exchange membrane is inserted into the cathode is that the surface of the cation exchange membrane is lowered when the bubble of hydrogen gas generated from the cathode is injected into the cathode surface of the membrane. This is because bubbles of hydrogen gas are difficult to adhere to the cathode surface of the membrane, and the voltage rise caused by bubbles of hydrogen gas adhere to the cathode surface of the membrane results in (1) electrical shielding of the adhesion bubbles (2) high concentration of the membrane-liquid interface. This is because the diffusion rate of alkali hydroxide is lowered.

이 1mm당 30개 이상 존재하면 막면으로의 가스 부착은 극히 적다.On the other hand, the chlorine gas generated in the anode by electrolysis is difficult to adhere to the anode surface of the homogeneous cation exchange membrane because the bubble diameter is very large in comparison with the sorghum gas. Therefore, roughening of the positive electrode surface of the homogeneous cation exchange membrane is not necessary for lowering the electrolytic voltage. The rough surface in this invention is a concept about a mirror surface, Specifically, what is necessary is just to exist 20 or more t2 per 1 mm of a maximum height of 0.05 micron or more and roughness 0.05 micron or more on a film surface. More preferably, the maximum height is 0.05-5 microns, and roughness of 0.05 microns or more

If there are more than 30 of these 1mm, gas adhesion to the membrane surface is extremely small.

이 1mm당 20개 이하의 경우에도 막면으로의 가스부착 방지 효과가 불충분하다. 따라서, 본 발명의 양이온 교환막은 상기 범위의 조면을 가지는 것이 좋다.If the maximum height of the rough surface is 0.05 micron or less, the effect of leaving the gas on the membrane surface is small. In addition, roughness of 0.05 micron

In the case of 20 pieces or less per 1 mm, the gas adhesion prevention effect to the membrane surface is insufficient. Therefore, the cation exchange membrane of the present invention preferably has a rough surface in the above range.

에 따라 촉침이 상하한다. 이 상하 운동을 전기 신호로 변환하여 기록지에 기록한다. 통상 양이온 교환막은 유연하기 때문에 촉침에 의한 변형을 받기 쉽기 때문에 표면 거치름의 측정에 있어서는 촉침의 선단 형상이 10μmR이상으로 측정력이 0.1g이하의 피이크 압(Peak up)을 사용하는 것이 바람직하다.In order to confirm the degree of gas adhesion to the membrane surface, for example, a membrane may be incorporated into a transparent electrolytic set made of acrylic resin or the like, and the membrane surface may be observed. The surface roughness of the cation exchange membrane can be measured by a stylus method using a universal surface shape measuring instrument (type Saf Rubber 60B Tokyo Precision K.K). In other words, when the stylus is placed on the membrane surface and moved,

Depending on the stylus up and down. The vertical motion is converted into an electrical signal and recorded on a recording sheet. Since the cation exchange membrane is usually flexible, it is easy to be deformed by the stylus. Therefore, when measuring surface roughness, it is preferable to use a peak pressure of 0.1 g or less with a tip shape of 10 탆 R or more and a measuring force of 0.1 g or less.

(표면 굴곡)이 있다.In the present invention, the tip shape of the stylus tip was 13 µmR, and the measurement force was measured using a peak pressure of 0.07 g. In addition, in the cation exchange membrane, the strength of the supporting fibers is often added, and in this case, the membrane surface is large due to the supporting fibers.

(Surface curvature).

In order to distinguish the surface roughness, it is preferable to cut off the long wavelength at a specific wavelength through an electric filter in order to distinguish the surface roughness. In the present invention, the cut off value was set to 0.032 mm and measured.

The maximum height referred to in the present invention is obtained by the following method in accordance with JIS0601. In other words, the distance between the two straight lines that is equal to the average line of the portion of the roughness curve measured at the cut-off value of 0.032 mm and only the reference length of 0.1 mm is measured in the direction of the longitudinal magnification of the roughness curve. For example, in FIG. 1, the distance Rmdx of a straight line is called the maximum height through the straight line through the maximum value P1 and the minimum value P1 of the parallel lines parallel to the average line of 0.1 mm excerpted part. The measurements are averaged over 10 measurements taken at different locations in the same sample. In addition, when the maximum height is found, it is extracted as much as the reference length from the part that is not the minimum value of the special maximum tooth that can be regarded as a flaw.

In addition, the number per 1 mm of roughness 0.05 micron or more said by this invention was calculated | required by the following method according to US SAE standard J911. In other words, draw a straight line of two (+) 0.025 microns and (-) 0.025 microns levels by the average line of 0.1 mm of the reference length from the roughness curve measured at 0.032 mm of cut-off value (R and V lines, respectively). ), Count the maximum value through the P-line and the maximum value through the P-line to the maximum, and find the number per 0.1mm. For example, in FIG. 2, the maximum number of peaks through the P-line and then through the P-line is three of a, b, and c. For the measurement, the number per 1 mm is obtained by averaging the values obtained by measuring 10 times by changing the place in the same sample.

The homogeneous cation exchange membrane used by roughening at least one surface in the present invention is preferably a fluorine-based homogeneous cation exchange membrane in which the anolyte or catholyte by the hydraulic flow substantially prevents passage of the membrane. If the anolyte or catholyte passes through the membrane due to hydraulic pressure, it is not good because the quality of the product produced by brine electrolysis is lowered.

Examples of the fluorine homogeneous cation exchange membrane include (1) sulfonic acid type cation exchange membranes, (2) sulfonamide type cation exchange membranes, and (3) carboxylic acid type cation exchange membranes.

However, the present invention is not limited to these, but applies to all homogeneous cation exchange membranes. An example of the specific manufacturing method of these fluorine-type homogeneous cation exchange membrane is given to the following.

(1) As the sulfonic acid type cation exchange membrane, a method of hydrolyzing a copolymer film of CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F and ethylene tetrafluoride (trade name Nafion, manufactured by E.I DuPont) Etc,

(2) As the sulfone amide type cation exchange membrane, a method of reacting the copolymerized film ammonia, alkyl monoamine or diamine (JP-A Nos. 48-44360, 50-66488, 51-64495, 51-64496, etc.)

(3) As the carboxylic acid type cation exchange membrane, fluorinated olefin and CF ₂ = CFO (CF ₂ ) _n A or CF = CFOCF _2- (CFXOCF ₂ )-(CFX ') _m- (CF ₂ OCFX ") _-n A (A is CN, COF, COOH, C

OOM, COOR, CONR ₂ R ₃ ; A method of introducing an ion exchange group required for a copolymer of X, X ', X "F or CF ₃ ) (Japanese Patent Application Laid-Open No. 51-130495, 52-36486, etc.)

(4) A method of reducing the copolymer of a fluorinated olefin and a copolymer of (Y is halogen, OH group, alkyl group, etc.) (Japanese Patent Laid-Open Nos. 52-24175, 52-24176, 52-24155, etc.) may be mentioned.

As a method of roughening a homogeneous cation exchange membrane;

부분을 갖는 것을 사용하는방법1. When the ion exchange membrane is roughened by an extruded membrane, a predetermined die as a molding die

How to use having a part

부분을 갖는 이지(梨地) 회전롤의 사이를 통과시키는 방법.2. Predetermined while heating the ion exchange membrane

The method of passing between the easy rotation rolls which have a part.

3. A method of thermal pressing by overlapping an ion exchange membrane with fine powder of cloth, paper organic matter or inorganic matter.

4. A method of polishing the surface of an ion exchange membrane with an abrasive.

5. The method of passing an ion exchange membrane between the rolling rolls which wound the sand paper on the surface.

6. A method of attaching an abrasive to the surface of an ion exchange membrane.

7. Method of polishing the surface of the ion exchange membrane by a metal brush.

8. A method of discharging such as arc discharge and glow discharge.

9. Method of irradiating the surface with ultraviolet rays, X-rays, electron beams, and radiation.

10. Treatment with gas salt or heated air.

11. Method of treating ion exchange membrane with solvent.

12. A method of attaching a mesh or a nonwoven fabric made of ion exchange resin to a membrane surface may be mentioned, but is not limited to these methods.

It is also important not to denature the surface cation exchanger without ion exchange capacity when the roughening treatment is performed. In the case of change, the resistance of the film rises and the electrolytic voltage increases, which is not preferable. Although the roughening process may be performed on both surfaces of an ion exchange membrane, when the surface membrane which becomes a cathode side at the time of injecting into an electrolytic cell is performed, the reduction of the electrolysis voltage as desired is achieved. In membranes having two equivalent weights, membranes having a sulfonic acid base layer and a weak acid base layer, etc., it is preferable to perform the layer having a high equivalent weight or weak acid group layer.

The roughening treatment of the present invention also acts on the ion exchange membrane intermediate, and the ion exchange membrane intermediate is used as a cation exchange membrane after undergoing treatment such as hydrolysis, introduction of an ion exchanger, etc. after the roughening treatment. Examples of the alkali chloride of the present invention include lithium chloride, sodium chloride, potassium chloride and the like. Moreover, as alkali hydroxide, a lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. are mentioned.

In the case of carrying out the electrolytic method of the present invention, the most important thing is to insert into the electrolytic cell so that the rough surface of the homogeneous cation exchange membrane becomes the cathode side. In the case where the rough surface is inserted into the electrolytic cell so as to be the anode side, the drop of the electrolytic voltage cannot be achieved.

The electrolyzer and electrolysis conditions which are preferable to this invention are described. Salt water is supplied to the anode chamber and water or lean hydroxide alkali solution is supplied to the cathode chamber to control the concentration of alkali hydroxide at the outlet of the cathode chamber.

The brine supplied to the anode chamber is purified in the same manner as in the conventional alkali chloride electrolytic method. In other words, the return brine circulated from the anode chamber is subjected to sedimentation and neutralization of dechlorination, saturated solution of alkali chloride, magnesium, calcium, iron, etc. All of these processes are performed in the same manner as in the conventional method. . However, it is preferable to purify the feed brine again with a granular ion exchange resin, in particular a chelate resin, if necessary, and to allow calcium to an acceptable limit, preferably 1 ppm or less. The concentration of the brine is rich and should be close to saturation. The utilization rate of the alkali chloride supplied to the anode chamber is 5-95%, which is different by the method of current density and heat removal, but is generally high.

Electrolytic temperature can be performed at 0-150 degreeC. Since work occurs by electrolysis, a part of the anolyte or the catholyte is cooled to de-heat. Chlorine and hydrogen are generated in the anode chamber and the cathode chamber, respectively. In particular, the electrolyzer which introduce | generates a generated gas to the back side of an electrode and raises it has the effect of reducing electrolytic voltage and power consumption. The flow rate in each chamber is preferably a mixture of the liquid in the room by the gas generated from the cathode chamber and the anode chamber separately from the flow rate supplied from the outside, and for this purpose, an electrode with a large supply such as a metal mesh electrode is used. It is preferable to circulate and stir the liquid in each chamber according to the upward flow of the gas. The electrode is preferably plated with nickel or a nickel compound on iron or iron as an anode at the point of overvoltage. In general, the anode is preferably an electrode of a metal mesh coated with an oxide of a noble metal such as ruthenium. Although an Example is given to the following and it concretely demonstrates, this invention is not limited to this.

Example 1

Detrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octensulfonyl fluoride to 1,1,2-trichloro-1,2,2, -trifluoroethane Perfluoro propionyl peroxide as a polymerization initiator in the above, and the polymerization temperature of 45 ℃, tetrafluoroethylene pressure 3kg /

Copolymerization was maintained at cm ² -G. After wash and saponification of the obtained polymer, an equivalent weight (dry resin weight including 1 equivalent of an ion exchanger) was measured by a titration method and found to be 1090. The polymerized product is heat molded to form a film having a uniform thickness of 250 microns and then roughened by a liquid honing method. The liquid honing method is a method of attaching and polishing abrasive suspended in water to a workpiece using compressed air.In this embodiment, alumina having an average particle diameter of 10 microns (trade name WA # 1500, manufactured by Fujigen Abrasives Co., Ltd.) 3.5kg / c in an aqueous solution

이 1mm당 약 55개 존재하는 조면화막을 얻었다. 그 조면화 처리막을 2.5N 가성소다 150%메타놀즐 60℃로 16시간 검화하였다. 검화후의 막의 조면화면에는

부분이 거의 변동없이 남아있었다. 이와같이 하여 얻은 막을 조면화면이 음극측이 되도록 아크릴 수지로 제작한 투명한 전해조에 조입하고, 전류밀도 50A/dm², 전해온도 90℃에서 식염 전해를 행하였다. 양극은 티탄 기재에 산화루테늄을 피복한 촌법 안정성 전극음극은 철제 금망인 것이다. 양극실에는 pH2의 3N식염수를 공급하고, 음극실에는 5N가성소다를 공급하였다. 전해전압은 2.97V이고, 전류효율은 60%이었다. 양이온 교환막의 음극면에서는 수소가스 기포의 부착은 없었다. 그 막을 교류법에 의하여 0.1N 가성소다 중에서 저항을 측정한바, 2.2Ω. cm²이었다.It was mounted on one side of the membrane with compressed air of m ² and roughened. The mounting time was 2 minutes per 1 dm ² membrane. The treatment results in a film with a maximum height of 0.25 microns and roughness of 0.05 microns or more.

About 55 roughening films existed per 1 mm. The roughened film was saponified at 60 ° C. for 150 hours with 2.5N caustic soda. On the rough surface of the film after the sword

The part remained almost unchanged. The membrane thus obtained was inserted into a transparent electrolytic cell made of acrylic resin such that the roughened surface was at the cathode side, and salt electrolysis was performed at a current density of 50 A / dm ² and an electrolysis temperature of 90 ° C. The positive electrode is a steel-based metal mesh, which is a stable electrode cathode coated with ruthenium oxide on a titanium substrate. 3N brine of pH 2 was supplied to the anode chamber, and 5N caustic soda was supplied to the cathode chamber. The electrolytic voltage was 2.97V and the current efficiency was 60%. There was no adhesion of hydrogen gas bubbles at the cathode surface of the cation exchange membrane. The membrane was measured for resistance in 0.1 N caustic soda by the alternating current method to find 2.2Ω. cm ² .

[Comparative Example-1.]

The same polymer as in Example-1 was electrolyzed in the same manner as in Example-1 without performing the roughening treatment. The electrolytic voltage was 3.20V and the current efficiency was 59.5%. Hydrogen gas bubbles were strongly adhered to the cathode surface of the film which had not been roughened. Moreover, the resistance of the film which was not roughened was 2.2 ohm * cm <^2> .

[Example-2.]

이 1mm당 약 45개 되어 있었다. 이와같이 A면이 음극측이되게 아크릴수지로 제작한 투명한 전해조에 조입하고, 실시예-1과 동일하게 식염 전해를 행하였다. 전해 전압은 3.75V이고, 전류효율 80%이었다. 그 막의 음극면에는 수소 가스 기포의 부착은 없었다. 그 막의 저항은 6.3Ω. cm²이었다.Detrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octensulfonyl fluoride to 1,1,2-trichloro-1,2,2, -trifluoroethane In the above, perfluoro propionyl peroxide was used as a polymerization initiator, and copolymerization was carried out while maintaining a polymerization temperature of 45 ° C. and tetrafluoro ethylene at a pressure of 5 kg / cm ² -G. This is referred to as Polymer 1. In the same operation, tetrafluoro copolymerized while maintaining the pressure of ethylene at 3 kg / cm ² -G. This is referred to as Polymer 2. Some of these polymers were washed with water, and the equivalent weight was measured by titration after saponification. As a result, polymer 1 was 1500 and polymer 2 was 1110. The polymers 1 and 2 were heat-molded to form a two-layer laminate having a thickness of 50 microns and 100 microns, respectively, and a saponic acid type ion exchange membrane was obtained by saponifying a composite agent in which the Teflon R fabric was buried by vacuum lamination from the polymer 2 side. It was. The sulfonic acid type ion exchange membrane was roughened by the following method. 3mm thick silicone rubber sheet (top) A hard magnesium oxide powder (manufactured by Wako Jun Baseball Co., Ltd. KK) layer, a wet sulfonic acid type cation exchange membrane (top surface A), silicon 3mm thick The rubber sheet and the 60 mesh mesh net (bottom) were laminated | stacked, and heat-pressed at 10 kg / cm <^2> for 10 minutes, heating at 280 degreeC. Next, it is attached to the membrane with a maximum height of 0.6 microns and roughness of 0.05 microns or more.

There were about 45 pieces per 1mm. In this way, the A side was inserted into a transparent electrolytic cell made of acrylic resin with the negative electrode side, and salt electrolysis was performed in the same manner as in Example-1. The electrolytic voltage was 3.75V and the current efficiency was 80%. There was no adhesion of hydrogen gas bubbles to the cathode surface of the film. The membrane's resistance is 6.3Ω. cm ² .

Example-3.

이 1mm당 약 30개 되었다. 이와같이 하여 얻은 막을 A면이 음극측이 되도록 아크릴수지로 제작한 투명한 전해조에 조입하고 실시예-1과 동일하게 식염 전해를 행하였다. 전해 전압은 3.80V이고, 전류효율 80%이었다. 그 막의 음극면에는 수소 가스 기포의 부착은 없었다. 그 막의 저항은 6.3Ω. cm²이었다.The sulfonic acid type cation exchange membrane reinforced with the Teflon R fabric of Example-2 was roughened by the following method. 3mm thick silicone rubber sheet (top), cotton cloth, and wet sulfonic acid type ion exchange membrane (top surface A). 3mm thick silicone rubber sheet 60 mesh is laminated and heated to 250 ° C, 10kg / cm ² was heat pressed for 10 minutes at a pressure of. Next, the cotton cloth adhered to the membrane was removed by treatment with a thermal aqueous solution of sodium hypochlorite. The surface roughness of the surface A of the roughened cation exchange membrane was measured, and the maximum height was 2.5 microns, and 0.05 micron or more.

About 30 per 1 mm. The membrane thus obtained was incorporated into a transparent electrolytic cell made of acrylic resin so that the A side was the cathode side, and salt electrolysis was performed in the same manner as in Example-1. The electrolytic voltage was 3.80V and the current efficiency was 80%. There was no adhesion of hydrogen gas bubbles to the cathode surface of the film. The membrane's resistance is 6.3Ω. cm ² .

[Comparative Example-2.]

Instead of the thermally pressed roughened film of Example-2, a non-roughened film was prepared in the same manner as in Example-2, and electrolytically treated in the same manner. The electrolytic voltage was 4.05V and the current efficiency was 79.5%. Hydrogen gas bubbles were strongly adhered to the cathode surface of the unroughened film. In addition, the resistance of the unroughened film was 6.3 Ω. cm ² .

[Example-4, 5, 6 Comparative Examples-3, 4]

In the same manner as in Example-1, tetrafluoro ethylene and perfluoro-3, 6-dioxy-4-octyl-7-octene sulfonyl fluoride were copolymerized to obtain a polymer having the equivalent weight of 1350 (polymer 1) and A polymer (polymer 2) having an equivalent weight of 1090 was obtained. These polymers were heat-molded to form two-layer laminates of 35 microns (polymer 1) and 100 microns (polymer 2), respectively, and Teflon R woven fabric was embedded by vacuum lamination in terms of polymer 2. Only the surface of polymer 1 of the sulfonic acid type cation exchange membrane obtained by saponifying the laminate was reduced and converted into a carboxylic acid group. (A side) Next, the A side of this cation exchange membrane was roughened by the liquid honing method. In this example, an aqueous solution in which an emery powder having an average particle diameter of 10 microns (trade name FO # 1200, manufactured by Fujigen Abrasive Providing Method KK) was suspended was mounted with compressed air of 3 kg / cm ² . Mounting time is just 1dm 10, 30, 60 and was 120 seconds per ^second. The surface roughness of the A surface of the roughened film thus obtained was measured. The results are shown in the first table. In addition, these membranes were joined to the electrolytic cell so that the A side was the cathode side, and electrolytically was electrolyzed in the same manner as in Example-1, and the gas adhering state to the membrane surface, the electrolytic voltage and the current efficiency were measured. The results are shown in the first table.

[Table 1]

[Example-7.]

Tetrafluoro ethylene and perfluoro-3 and 6-dioxy-4-methyl-7-octensulfonyl fluoride were copolymerized in the same manner as in Example-1 to obtain a polymer having an equivalent weight of 1200. The polymer was heat molded to a thickness of 125 microns and then treated only with one side with ammonia gas to produce a 20 micron sulfonic acid amide layer. (A side) Teflon R woven fabric by the following vacuum lamination method was embedded in the surface opposite to A side, and saponified to obtain a sulfone amide type cation exchange membrane. The cation exchange membrane was roughened by the dry paste method. The dry blasting method is a method of attaching an abrasive to a workpiece to be ground by compressed air, and in this embodiment, an average particle diameter of 20 microns is ² kg / cm ² of alumina (trade name WA # 800, manufactured by Fuji Industries Co., Ltd.). Was mounted on surface A with compressed air. Mounting time was 1 minute per membrane 1 dm ² . As a result of the roughening treatment, the membrane surface had a maximum height of 0.5 microns, and the roughness of t 14 of 0.05 microns or more was 45 pieces per mm. The electrolytic bath was introduced so that the rough surface (A surface) of the cation exchange membrane thus obtained was the cathode side, and was electrolyzed in the same manner as in Example-1. In this embodiment, the electrolytic density was performed at 30 A / dm ² . The electrolytic voltage was 3.55 V and the current efficiency was 84%. Hydrogen gas bubbles were hardly attached to the cathode surface of the cation exchange membrane.

[Comparative Example-5.]

Instead of the roughened sulfonamide cation exchange membrane of Example-7, electrolysis was carried out in the same manner as in Example-7 using a sulfonamide type cation exchange membrane not subjected to roughening treatment. The electrolytic voltage was 3.85V and the current efficiency was 83.5%. Hydrogen gas bubbles were strongly adhered to the cathode surface of the cation exchange membrane.

[Example -8.]

Teflon R woven fabric was embedded in a copolymer of ethylene tetrafluoride and CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ by a hot press lamination method in a film having an equivalent weight of 650 and a thickness of 250 microns.

The laminate was hydrolyzed after roughening only one surface in the same manner as in Example-1 to obtain a carboxylic acid type ion exchange membrane. The surface roughness of the ion exchange membrane was measured. The roughened surface (A surface) had a maximum height of 0.25 microns and a roughness of about 55 t15 of 0.5 microns or more per mm.

에는 1mm당 3개 만이었다. 그 이온 교환막을 전해조에 매입하여 실시예-1과 동일한 방법으로 전해하였다. 또, 본실시예에서는 전류 밀도는 20A/dm², 식염수의 pH는 3, 또 가성소다 농도는 13N로 실시하였다. 결과는 다음과 같다.On the surface without roughening, the maximum height is 0.04 microns and the roughness is 0.05 microns or more.

It was only three per 1mm. The ion exchange membrane was embedded in an electrolytic cell and electrolyzed in the same manner as in Example-1. In this example, the current density was 20 A / dm ² , the pH of the saline solution was 3, and the sodium hydroxide concentration was 13 N. The result is as follows.

Claims (1)

In the production of alkali hydroxide by electrolyzing alkali chloride in an electrolytic cell divided into a positive electrode chamber and a negative electrode chamber by a fluorine-based homogeneous cation exchange membrane, the cation exchange membrane has a maximum height of at least 0.05 µm and a roughness of 0.05 µm or greater.

An electrolytic method of alkali chloride, characterized in that there are more than 20 rough surfaces per 1 mm, and a cation exchange membrane is used and the electrolytic bath is joined so that the rough surface of the cation exchange membrane is the cathode side.

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