JPS60128277A - Manufacture of diaphragm for electrolysis - Google Patents

Abstract

PURPOSE:To obtain a diaphragm for electrolysis with superior strength and dimensional stability by dispersing fibers in an aqueous slurry of a synthetic mica type mineral, adding NaOH to disintegrate the fibers, and forming a film by a paper making process using the resulting treating liq. CONSTITUTION:A water-swellable synthetic mica type mineral represented by a formula W1/3-1.0[X2.5-3.0(Z4O10)F2] (where W is Na or Li, X is Li or Mg, and Z is Si or Al) is dispersed in water to prepare an aqueous slurry. Asbestos fibers or asbestos-base fibers are dispersed in the slurry, and an aqueous NaOH soln. or a mixed aqueous soln. contg. NaOH and NaCl is further added and stirred to disintegrate the fibers. A film is formed on a cathode substrate by a paper making process using the resulting treating liq. When a diaphragm for electrolysis manufactured by this mothod is used, NaOH of high concn. can be obtd. by electrolysis at low voltage with high current efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a diaphragm used in diaphragm electrolysis of a saline solution.

Specifically, asbestos fiber alone or a dispersion of fibers mainly composed of asbestos fibers is used to form paper on a cathode substrate or without a substrate, and the paper is still wet and has sufficient strength as an electrolytic diaphragm. The present invention relates to a method for producing an electrolytic diaphragm having dimensional stability and excellent electrolytic performance.

Conventionally, asbestos diaphragms have been used for diaphragm electrolysis of saline solutions. That is, asbestos has been dispersed in water, a saline solution, a caustic soda aqueous solution, etc., and then paper is made on a cathode wire mesh to create a diaphragm, which has been put to practical use. The strength of the diaphragm is weak, and it expands significantly in a few hours, becoming soft, and is easily damaged by the gas generated at the electrode and the liquid flow that accompanies it, and cannot adequately fulfill the role of a diaphragm to separate liquids and gases. It often disappeared. Furthermore, along with these phenomena, the electrolysis voltage has also increased rapidly, reducing the productivity of caustic soda.

To solve these problems, heat treatment (e.g. 110°
A number of methods have been proposed for improving dimensional stability by bonding organic polymeric substances to fiber base materials.

However, in these conventional methods, in addition to the deterioration of asbestos due to high-temperature treatment, the asbestos is deionized by the adhesive used for adhesion, so when trying to increase the concentration of caustic soda in the catholyte, the current efficiency decreases, and the concentration of caustic soda decreases. Currently, there is a limit to how much energy can be raised, and a large amount of energy is currently consumed in concentrating the electrolyte.

The inventors of the present invention filed a patent application in 1592-1982 for a diaphragm with little water swelling and no damage even after manufacturing, and a method for manufacturing the same.
It was proposed in 1981.

This production method is based on the general formula %) or Mg, Z is Si and or A, 0 is oxygen, F
is a method of adding and dispersing a fiber base material such as asbestos in an aqueous slurry in which at least a portion of a water-swellable synthetic mica-based mineral represented by (is fluorine) is dispersed in a sol, followed by paper-making and drying; A method in which paper is made by uniformly mixing a slurry in which a fiber base material such as asbestos is dispersed in an aqueous solution of caustic soda and/or common salt, which is an aqueous slurry in which at least a portion of a synthetic mica-based mineral is dispersed in the form of a sol, and then dried. be.

All of these proposed methods involve drying the paper after papermaking.

As a result of further research into the method for producing a diaphragm containing the water-swellable synthetic mica-based mineral, the present inventors have found that a fiber base material such as asbestos is dried after papermaking on a cathode wire mesh or without using the wire mesh. It has sufficient strength even in a wet state without
The present invention has been completed by discovering a method that is substantially dimensionally stable even when used in electrolysis for producing caustic soda, has a low electrolytic voltage, and can obtain highly concentrated caustic soda with high current efficiency.

That is, the gist of the present invention is that water-swellable synthetic mica-based minerals represented by the general formula % or Mg, Z is Si and or AfL, 0 is oxygen, and F is fluorine) are mainly composed of asbestos fibers or asbestos fibers. In the method for manufacturing an electrolytic diaphragm that is present in the gap between a fiber base material, the water-swellable synthetic mica mineral is dispersed in water to form an aqueous slurry, and asbestos fibers or an S fiber base material mainly composed of asbestos fibers are added to the aqueous slurry. Add and mix and disperse, and further add and stir an aqueous solution of caustic soda or a mixture of caustic soda and common salt to this dispersion.
A method for manufacturing an electrolytic diaphragm includes preparing a cotton opening treatment solution and making paper and forming a film using the treatment solution.

The contents of the present invention will be explained in detail below.

The water-swellable synthetic mica mineral represented by the above general formula is Na[M
g(Si0)F], Li[MgLi(S
14010) F2], 2.54102 2 Na1/3 [Mg8/3LI 1/3 (S14010
)F2], and when these fine powders are immersed in water and swelled, a sol is finally created. This solization phenomenon is thought to occur when water is sucked between the crystalline layers of the mineral, causing it to swell and eventually unfold into ultrafine powder.

When the above-mentioned sol is dried or put into an aqueous solution containing a high concentration of Na + etc., it solidifies, but when it is immersed in water again, it swells again and finally becomes the original sol.

Furthermore, this water-swellable synthetic mica-based mineral can be found in a fine powder state, a swollen state, a sol state, and a resolidified state (film-like, granular, etc.).
In either case, there is a cation exchange property, and the exchange capacity is 200 when the W component composition in the above general formula is Wt, o.
~250meq/100g, 100m for W%
It is said to be eq/100g.

Asbestos or a mixed tam containing asbestos, such as ion-exchangeable fluorine fibers, fluorine-based potassium titanate-containing fluorine-based materials, are prepared by adding asbestos or a mixed tam containing asbestos to an aqueous slurry in which the water-swellable synthetic mica-based mineral is added to water and at least a portion thereof is dispersed in the form of a sol. Mixed fibers with fibers such as fibers, glass fibers, and polyolefin fibers that are normally used for various diaphragms, furnace materials, etc. are added, and the fibers are thoroughly stirred to disperse the fibers as much as possible. A slurry is created by uniformly mixing minerals.

Note that the concentration of mica-based minerals in the aqueous slurry is 1.0~
20 g/kg is preferable in terms of preparing an aqueous slurry and efficiently incorporating the mica-based mineral into the fiber base material. Also,
The mixing ratio of the fiber base material and the water-swellable synthetic mica mineral greatly affects the performance of the diaphragm obtained in the present invention; Parts by weight are preferably used, more preferably 15 to 30 parts by weight. If the mica-based mineral is less than 5% by weight, the strength of the final diaphragm is not only weak, but also the electrolytic performance is poor, making it impractical. On the other hand, if it exceeds 50% by weight, the amount of water permeation (liquid) decreases significantly, and the essential function as a diaphragm is likely to be lost.

As mentioned above, a caustic soda aqueous solution or a mixed aqueous solution of caustic soda and common salt is added to the slurry in which the fiber base material is dispersed, but the concentration after addition is 200 to 3 in the case of the former.
00g/J2. , in the latter case, the molar ratio 1/1.4 to 1
10.7 and 300 to 350 g/i is preferably used. The amount added is 1000 to 35 parts by weight of caustic soda or caustic soda and common salt in solid content per 100 parts by weight of the above mica mineral.
000 parts by weight is added.

There is no particular restriction on the temperature of the aqueous solution when it is added to and mixed with the slurry.

#1! By selecting the weight ratio of the fiber base material to the mica-based mineral, the concentration of the caustic soda aqueous solution, etc., and the weight ratio of the mica-based mineral to the fiber base material as described above, the performance of the prepared diaphragm can be significantly improved. In other words, by adopting the above conditions, although the cause is not clear, it has the strength to be immediately used as an electrolytic diaphragm for producing caustic soda even in an undried or wet state, and the diaphragm has good dimensional stability, so it can be used for electrolysis. The voltage does not increase, the caustic soda concentration in the cathode chamber increases, and the current efficiency does not decrease.

The post-addition of the caustic soda aqueous solution and the subsequent stirring to open the cotton are important constituent elements of the present invention, and exhibit even more excellent effects compared to the effects of the invention disclosed in the above-mentioned Japanese Patent Application No. 1511281-1983. This is considered to be a possible cause.

The present invention will be explained below with reference to Examples.

(Example 1) A water-swellable synthetic mica-based mineral represented by Na[Mg2.5(Si40□.)F2] was placed in water and mixed with aeration stirring to form a sol with a concentration of 12 and θg/A. , add warm asbestos (Bellmine, 3T-700) in an amount equivalent to 40 g 1 liter.
A slurry was formed by stirring and stirring for 1 hour. This slurry was mixed with a 48% by weight aqueous solution of caustic soda,
The concentration of the above synthetic mica mineral is 8.4g/l, the concentration of asbestos is 28.7g 7 sentences, and the concentration of caustic soda is 2e0g/l.
A slurry was prepared, which was aerated and stirred for 24 hours to homogenize the slurry, and the asbestos was opened. From this slurry, 3.5 g of the above synthetic mica mineral was placed on the cathode wire mesh.
/d, m', asbestos was deposited in an amount equivalent to 1 g/drn' by vacuum suction, and then vacuum suction was continued for 1 hour to pass room temperature air through the diaphragm to remove excess moisture. The electrolysis conditions, electrolysis results, etc. using this cathode are shown in Table 1 and will be described later.

(Example 2) A water-swellable synthetic mica-based mineral represented by Na[Mg2.5(Si401o)F2] was added to water and mixed by aeration with stirring until the concentration was 8.3 g/f1. After forming a sol of warm asbestos (
3T-700 (manufactured by Bellmine Co., Ltd.) was added in an amount equivalent to 40 g/l, and mixed with aeration for 1 hour to form a slurry. This slurry was mixed with a 48% by weight aqueous solution of caustic soda, and the concentration of the synthetic mica mineral was 4.2 g/l, the asbestos concentration was 28.7 g/l, and the concentration of caustic soda was 2E10.
The slurry was made into a slurry having a weight of 1.5 g/mt, and was aerated and stirred for 24 hours to homogenize the slurry, and the asbestos was opened. From this slurry, 1.
After depositing asbestos in an amount equivalent to 7 g/dm' and 11 g/dm' by vacuum suction, vacuum suction was continued for 1 hour to pass room temperature air through the diaphragm to remove excess water. The electrolysis conditions, electrolysis results, etc. using this cathode are shown in Table 1 and will be described later.

(Example 3) When the cathode with a diaphragm prepared in Example 2 was subjected to salt electrolysis for 24 hours under the same conditions as above and the condition of the diaphragm was inspected, the surface was a little soft, but the inside contained about There was a hard layer of 211 shoes.

(Comparative Example 1) A water-swellable synthetic mica-based mineral represented by Na[Mg2.5(S14010)F2] was placed in water and mixed with aeration stirring to form a sol with a concentration of 8.3 g/u. Warm asbestos (Bellmine, 3T-700) was added in an amount equivalent to 40g 1fL, and stirred with a mixer to form a uniform slurry. From this slurry, 10g/d of asbestos was deposited on a cathode wire mesh using a vacuum suction method.
rrf, 1.13 g/dIT1' of the above water-swellable mineral
After a considerable amount was deposited, vacuum suction was continued for 1 hour to remove as much moisture as possible from the diaphragm. Next, 18 at 120°C
After drying for an hour, electrolysis was carried out under the same conditions as in Examples 1 and 2. The data after 2 weeks are shown in Table 1.

The following is a reference example in which a water-swellable synthetic mica-based mineral is not used.

(Reference Example 1) Warm asbestos (Bellmine, 3T-700) was added to a caustic soda aqueous solution to form a slurry with an asbestos concentration of 30 g/l and a caustic soda concentration of 280 g/4Q, and the slurry was aerated and stirred for 24 hours. In addition to homogenizing the asbestos, the asbestos was opened. From this slurry, one layer of asbestos was deposited on the cathode wire mesh.
After depositing an amount equivalent to 4 g/dm' by vacuum suction, vacuum suction was continued for 1 hour to pass room temperature air through the diaphragm, excess moisture was removed, and the membrane was dried at 120°C for 16 hours. The electrolytic conditions, electrolytic results, etc. using this cathode are shown in Table 1 and are also described later.

(Reference Example 2) The cathode with a diaphragm prepared in Reference Example 1 was heated to 120°C.
When salt electrolysis was carried out for 24 hours under the same conditions as in Example 3 without drying, and the condition of the diaphragm was inspected, it was found to be soft and swollen to the inside, and had no strength at all.

In addition, aeration stirring was carried out under conditions of approximately 5417 m1n per liquid volume 11 in all cases of Examples, Comparative Examples, and Reference Examples.

Examples 1 and 2. Comparative example 1. Table 1 shows the results when salt electrolysis was performed continuously for two weeks under the following conditions using the diaphragm described in Reference Example 1.

(1) Salt solution composition; Mail 310g/41,
Ca 1mg/ JlMg 0.2mg/text (2) Difference between catholyte and anolyte heads; 50cm (3) Temperature of electrolytic cell, 70°C (4) Current density; 20A/dm" Table 1

Claims (2)

[Claims] (1) General formula %) or Kg, Z is Sj and or Ai, 0 is oxygen,
In a method for manufacturing an electrolytic diaphragm in which a water-swellable synthetic mica-based mineral (F is fluorine) is present in the gaps between asbestos fibers or a fiber base material mainly composed of asbestos fibers, the water-swellable synthetic mica-based mineral is To this, asbestos fibers or a fiber base material mainly composed of asbestos fibers is added and mixed and dispersed, and then an aqueous solution of caustic soda or a mixture of caustic soda and common salt is added and stirred to form fibers. A method for producing a diaphragm for electrolysis, characterized by preparing a cotton opening treatment solution, and using the treatment solution for paper making and film formation. (2) A method for manufacturing an electrolytic diaphragm according to claim 1, wherein papermaking is carried out on a cathode substrate.