JPH0816274B2 - Method for producing quaternary ammonium hydroxide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for synthesizing quaternary ammonium hydroxide from an organic quaternary ammonium salt by an electrolysis reaction using an ion exchange membrane. More specifically, it relates to an improved process for electrolytically synthesizing high-purity tetraalkylammonium hydroxide using a special cation exchange membrane.

[Conventional technology]

Quaternary ammonium hydroxide is a chemical useful as a strong organic base such as a phase transfer catalyst in chemical reactions, and particularly as the electronics industry has expanded in recent years, it has come into the limelight as a developer for positive photoresists in the manufacture of ICs, LSIs, etc. Demand is growing. This quaternary ammonium hydroxide can be produced by reacting an organic tertiary amine with an alkyl halide to form a quaternary ammonium halide, which is converted into a hydroxide, a tertiary amine and dimethylsulfate. And a quaternary ammonium sulfate to form a hydroxide, or a tertiary amine and dimethyl carbonic acid to form a quaternary ammonium carbonate to form a hydroxide. However, in general, a tertiary amine and an alkyl halide are often reacted for ease of synthesis. As a method of converting the above quaternary ammonium salt into a hydroxide, there are a method using an ion exchange resin, a method of adding silver hydroxide and precipitating it as silver chloride to obtain a quaternary ammonium hydroxide. A complicated operation is required, and a high-purity quaternary ammonium hydroxide is not always obtained. In addition, in recent years, along with the improvement of the performance of the ion exchange membrane, a method by an electrolysis reaction using the ion exchange membrane has been carried out. That is, the anode chamber and the cathode chamber are fractionated by a cation exchange membrane, a quaternary ammonium salt is added to the anode chamber, the quaternary ammonium ions are transmitted through the cation exchange membrane, and hydrogen gas is generated on the cathode. And producing hydroxide ions, and also dividing into three chambers, an anode chamber, an anion exchange membrane-an intermediate chamber of a cation exchange membrane and a cathode chamber, and supplying a quaternary ammonium halide to the intermediate chamber. , Permeate quaternary ammonium ions into the cation exchange membrane, permeate ions such as halide into the anion exchange membrane, and generate hydroxide in the cathode chamber,
There is a method of producing by producing a halogen gas in the anode chamber. However, the process using these ion-exchange membranes can obtain high-purity quaternary ammonium hydroxide, but when using a normal anion-exchange membrane, the hydroxide which is easy to permeate the membrane is essentially intermediate. The target hydroxide can be obtained only with low current efficiency because it diffuses back into the chamber and anode chamber. Therefore, improvements have been made such as the use of a cation exchange membrane having a carboxylic acid base layer on one surface of the membrane used for salt electrolysis.

[Problems to be solved by the invention]

Among the various conventional techniques described above, the method of converting an organic quaternary ammonium salt into a hydroxide by an ion exchange resin is a regeneration treatment with an acid and / or an alkali as a characteristic property of the ion exchange resin. However, from the viewpoint of high purity, no matter what is used for the regenerating reagent, the residue of the regenerating reagent in the resin and the quaternary ammonium hydroxide contaminating them are contaminated. I have a problem to do. Further, the method using silver hydroxide is complicated in operation, some loss of expensive silver salt is unavoidable, and silver halide also has some solubility, so that the product is contaminated.

By the way, for the purpose of obtaining high-purity quaternary ammonium hydroxide by an economical method, it is essential that the raw material quaternary ammonium salt is of high purity and contains no impurities. However, a trace amount of metal ions may be mixed in from the reaction step or from the material of the reactor, especially when used as a photoresist developing solution, a trace amount of metal ions, especially alkali metal ions such as Na ⁺ . Since its presence is not preferable, it is generally necessary to use it in a content of 100 ppm or less. When using a normal cation exchange membrane, comparing the membrane permeability of quaternary ammonium ions and alkali metal ions, alkali metal ions such as Na ^{+ with} a small ionic radius are more quaternary ammonium ions. Permeable through the membrane more easily than organic ions. Therefore, even if a trace amount of the alkali metal ions are mixed in the quaternary ammonium salt in the raw material, the alkali metal ions will be present in the product obtained from the cathode chamber in a concentrated state, and therefore the purity will be too high. It was difficult to obtain high-purity quaternary ammonium hydroxide unless a high quaternary ammonium salt was used.

[Means for solving problems]

The inventors of the present invention have made earnest studies to obtain higher purity quaternary ammonium hydroxide more easily and economically, and as a result, surprisingly, a solution of a quaternary ammonium salt of a cation exchange membrane. Using a cation-exchange membrane in which a thin layer having a cationic group is present on the side in contact with the cation, organic quaternary ammonium ions with a large ionic radius are compared with other heavy metal ions including alkali metal ions. Then, they have found that the intended purpose can be achieved by selective membrane permeation, and have completed the present invention. That is, the present invention uses an electrolytic cell in which the anode and the cathode are separated by one or more cation exchange membranes, and an anode chamber and a cathode chamber are formed, and a quaternary ammonium salt is supplied to the anode chamber for electrolysis. In the method for obtaining quaternary ammonium hydroxide from the cathode chamber, at least one cation exchange membrane to be used is present in a thin layer having a cationic group on the surface layer thereof, and A method for producing quaternary ammonium hydroxide, characterized in that the layer is provided facing the side facing the anode.

The present invention uses an electrolytic cell in which one or more ion exchange membranes are arranged between an anode and a cathode, an aqueous solution of quaternary ammonium salt is supplied to the anode side, that is, the anode chamber, and a high-purity aqueous solution is supplied from the cathode chamber. A quaternary ammonium hydroxide solution is obtained. One or more cation exchange membranes are arranged between the cathode and the anode, and when two or more cation exchange membranes are used, the intermediate room is filled with an aqueous solution of quaternary ammonium hydroxide. .
The cation exchange membrane may be any of hydrocarbon type, fluorocarbon type and perfluorocarbon type.
It has a thickness of 2 mm, the ion exchange capacity is generally 0.3 to 3.0 milliequivalents per 1 g of the dry membrane, preferably the side facing the cathode of the cation exchange membrane is bonded with a carboxylic acid group as a cation exchange group. However, it is desirable that a sulfonic acid group is bonded to the remaining portion, or that the surface has an anisotropic structure in which a sulfonic acid group corresponding to 2/3 or less of the ion exchange capacity of the membrane body is bonded.

The feature of the cation exchange membrane used in the present invention is that a thin tank having a cation group is present on the side of the membrane facing the anode.

When forming a thin layer having a cationic group on a cation exchange membrane, if the thin layer having a cationic group is too thick, it becomes a bipolar-ion exchange membrane, resulting in an abnormal increase in the electric resistance of the membrane and its result. As a result, heat is generated in the film, film performance is deteriorated, and current efficiency is also reduced. Therefore, the thickness of the thin layer having a cationic group is 10 to 50000Å, preferably 20 to 10000Å
It is preferable that the cationic group is a strongly basic functional group. A conventionally known method is widely adopted as a method for forming such a layer. That is, by immersing the cation exchange membrane in a solution or dispersion of the cationic polyelectrolyte, or by coating and spraying a concentrated solution, or by keeping the temperature at the time of adhesion high, One method is to penetrate the inside of the film in a swollen state.
However, there is a possibility that the cationic polyelectrolyte that has adhered may be released over time during use. Therefore, it is preferable to bond to the membrane surface by a stable covalent bond. For example, a method in which a cationic polymer having a primary, secondary, or tertiary amine, such as poly-4-vinylpyridine, is bound to a cation exchange membrane having an epoxy group and then alkylated, a sulfonic acid group or a carboxylic acid is used. In the present invention, a method for introducing a sulfonic acid carboxylic acid group or the like into a thin layer of a cation exchange membrane before introducing a group, a cationic group is formed into a thin layer by chlormethylation treatment-amination treatment only on one surface, This is an effective method. In addition, since 4-vinylpyridine undergoes matrix polymerization as a product utilizing the entanglement of polymer chains, the cation exchange membrane is made into an acid type, and this is
There is a method in which only one side of the membrane is immersed in a solution of vinylpyridine for a short time to form a polymer of 4-vinylpyridine on the surface layer of the membrane, and then neutralized, and then the pyridine ring is alkylated. A cationic polymer is in a state of being entangled in the polymer matrix of the cation exchange membrane, which is one preferable embodiment. Generally, when a thin layer having a cationic group is formed on a cation exchange membrane, the electric resistance of the membrane increases. When this increase was measured in 1.0 N tetramethylammonium hydroxide at a current density of 1.0 A / dm ² , the electric resistance of a cation-exchange membrane that did not form a thin layer with cationic groups was measured. 10 times or more, and particularly preferably 5 times or more. If it is too thin, the ability to block permeation of metal ions such as Na ⁺ through the quaternary ammonium ion is lost. Further, it is desirable that the concentration of the cationic group in the thin layer having the cationic group is as high as possible, and the fixed ion concentration when only the thin layer having the cationic group is taken out is generally 5% by weight. It is necessary that the concentration is not less than molar. In particular, the higher the concentration of the quaternary ammonium salt or the hydroxide thereof facing the thin layer having a cationic group, the higher the above-mentioned fixed ion concentration is desirable.

The quaternary ammonium salt used as a raw material in the present invention has a general formula R ₄ NX (R is, for example, a methyl group, an ethyl group,
Alkyl groups such as propyl group and butyl group, aryl groups such as phenyl, or derivatives thereof, which may be the same or different, and X is, for example, halogen ion such as chlorine ion or bromion ion, sulfate ion,
An organic compound represented by an acid group such as a carbonate ion, a nitrate ion, and a phosphate ion), and a quaternary ammonium halide is particularly preferably used. Also, quaternary ammonium hydroxide obtained by the present invention, the general formula [R ₄ N] ⁺ OH ^-
(R is the same as above).

The concentration of the quaternary ammonium salt supplied to the anode chamber is
Generally, it is desirable that the standard is 0.2 to 4.0. If this concentration is too low, the electrical resistance of the solution will be large, and if the concentration is too high, the solution will become viscous, which is not preferable. In addition, the concentration of quaternary ammonium hydroxide, which is the product obtained at the cathode, is generally selected to be the optimum concentration within the range of 0.1 normal to 4.5 normal, but if the concentration is lower than this, it may be further increased depending on the purpose of use. There is a fear that impurities will be mixed in because it requires a concentration operation and becomes complicated, and if it is too concentrated, the current efficiency for hydroxylation generation is reduced due to the characteristics of the ion exchange membrane, which is industrially disadvantageous. When a plurality of cation exchange membranes are used, the room between the cation exchange membranes is generally filled with 0.1 to 4.5 normal hydroxide. Liquid is preferably circulated independently in each chamber, the liquid flow rate is generally 0.5 to 100 cm / sec, and a plastic net is preferably arranged to disturb the streamlines.

As the anode, a conventionally known anode that is stable in an oxidizing atmosphere is used, and a so-called loose insoluble anode in which carbon, platinum-coated titanium, Ru, Ir, etc. are coated on titanium is preferably used, and the cathode is stable in a strongly basic atmosphere. The active cathode which is widely used in insoluble salt electrolysis of SUS316, platinum, Raney nickel, etc. is used without any limitation.

Further, the shape of the electrode is not particularly limited, and for example, a plate shape, a net shape, an expanded metal, a rod shape such as a perforated porous body such as a perforated plate, or the like is used.

In electrolysis, it usually depends on the concentration of the solution,
Although operating at a current density of ~50A / dm ^2, quaternary ammonium salts and quaternary ammonium hydroxide is unstable at high temperatures, the temperature in the electrolytic cell is operated at a range not exceeding 90 ° C. is necessary.

[Effect]

According to the present invention, by using at least one cation exchange membrane having a thin film having a cationic group on the surface layer portion of the cation exchange membrane, the metal contained in the quaternary ammonium salt as a raw material is used. High-purity quaternary ammonium hydroxide can be stably and industrially produced without particularly removing ions or without using a particularly high-purity quaternary ammonium salt.

〔Example〕

Hereinafter, the content of the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 For an anodic property using an electrolytic cell having a three-chamber structure with an effective energization area of 20 cm ² , an extract band methane anode coated with RuO ₂ · TiO ₂ on a titanium plate was placed, and 1.5 N tetramethylammonium was used. A solution containing a carbonate solution and a thin layer having a cationic group formed on the surface of a perfluorocarbon-based cation exchange membrane (trade name, Nafion 901) manufactured by DuPont between the second chamber The second room is 1.0
Nafion 901, which is filled with a specified tetramethylammonium hydroxide aqueous solution and has a thin layer having the same cationic group as the boundary with the third chamber (cathode chamber), is placed in the cathode chamber, and 1.5N Methylammonium hydroxide was filled and pure water was supplied so as to maintain this concentration.

Nafion 901 having a thin layer having a cationic group used here was prepared by contacting the membrane surface having a sulfonic acid group of Nafion 901 with 1.0 N hydrochloric acid for 1 minute to make the membrane surface layer a sulfonic acid type. This was immersed in a solution of 20 parts of 4-vinylpyridine dissolved in 50 parts of methanol for 30 minutes, taken out, washed with methanol and washed with water. By this operation, 4-vinylpyridine was polymerized on the surface layer of the film by matrix polymerization, and a thin layer of poly-4-vinylpyridine was formed. Then, after immersing this in 0.5 N ammoni water, a 16: 4 mixed solution of hexane-methyl iodide was added to the solution.
After immersing for a period of time, the pyridine ring of the polymer of 4-vinylpyridine which was matrix-polymerized was N-methylated. The obtained membrane was used for electrolysis with the side having a thin layer having a cationic group facing the anode side. After electrolysis at a current density of 20 A / dm ² and reaching an equilibrium state, the amount of Na ⁺ in the generated quaternary ammonium hydroxide solution in the cathode chamber was analyzed and found to be 5 ppb, and carbonate ion was 0.05 ppm or less. It was

In addition, N in 1.5N tetramethylammonium carbonate
The amount of a ⁺ was 1.2 ppm. Also, quaternary ammonium hydroxide (tetramethylammonium hydroxide)
The current efficiency of the formation was 80%.

The electrical resistance of the thin layer containing cationic groups is
It is 52 Ω-cm ² and the electric resistance of the film without thin layer is 44
Ω-cm ² .

Comparative Example 1 Electrolysis was carried out under exactly the same conditions as in Example 1 except that Nafion 901 was used as a cation exchange membrane in the same three-chamber electrolytic cell, and Na ^{+ in} 1.5 ^N tetramethylammonium hydroxide in the cathode chamber was used. Amount of 2.3ppm
It was. The content of carbonate ion was 0.05 ppm.

The current efficiency for producing tetramethylammonium hydroxide was 80%.

Example 2 Ti was used as an anode in an electrodialysis tank with a three-chamber structure with an effective current-carrying area of ² dm ^2.
A plate coated with platinum was used. Next, the same Nafion 901 membrane used in Example 1 was treated with a special treatment, and then a 2 mm gasket and a polypropylene spacer were used, and a Ti plate was coated with platinum to form a three-chamber configuration. The electrodialysis tank of
The special processing for Nafion 901 used here is N, N,
A monomer having a bifunctional quaternary ammonium group obtained by reacting N ′, N′-tetramethylethylenediamine with two equivalents of chloromethylstyrene was synthesized, and one side of Nafion 901 was added to a 1% aqueous solution of the monomer. Only (sulphonic acid group side) was dipped and adsorbed for 4 hours, and then an aqueous solution of ammonium persulfate and potassium sulfite was added for redox polymerization.

Pour a 2.5N solution of triethylmonomethylammonium sulfate obtained by reacting triethylamine and dimethylsulfate between the cation exchange membrane and anion exchange membrane of an electrodialysis tank, fill the anode chamber with 0.1N sulfuric acid, and charge the cathode. The chamber and the chamber composed of two cation exchange membranes were filled with an aqueous solution of 1.5 N of the above ammonium salt hydroxide. A liquid flow rate of 25 cm / sec was applied to each chamber, and electrodialysis was performed at a current density of 20 A / dm ² to produce 1.8 N of high-purity quaternary ammonium hydroxide from the cathode chamber.

As a result of analysis of the product, the content of Na ⁺ was 5 ppb, and SO ₄ ^2-
Was 0.3 ppm. None of the other metal ions exceeded 20 ppb. The current efficiency for obtaining quaternary ammonium hydroxide was 76%. The amount of Na ⁺ in the raw material was 1 ppm.

For comparison, electrodialysis was performed under exactly the same conditions using Nafion 901 (raw membrane), which was not subjected to the special treatment used in the present invention, and the amount of Na ^{+ in} the product was 1.8 pp.
m, the content of SO ₄ ^2- is 0.03 ppm, and other heavy metal ions are 2
Nothing exceeded 0 ppb, but it was a little more than that observed from the analysis chart. The current efficiency for producing quaternary ammonium hydroxide was 76%.

In addition, the cation exchange membrane formed with a thin layer having a cationic group has a lower electrification resistance than the untreated cation exchange membrane.
It was 2.1 times.

Claims (4)

[Claims] 1. An electrolytic cell in which an anode and a cathode are divided by one or more cation exchange membranes to form an anode chamber and a cathode chamber, respectively, and a quaternary ammonium salt is supplied to the anode chamber for electrolysis. In the method for obtaining quaternary ammonium hydroxide from the cathode chamber, at least one of the cation exchange membranes to be used has a cationic group present in a thin layer on the surface layer thereof, and Is provided toward the side facing the anode, the method for producing quaternary ammonium hydroxide. 2. The method for producing quaternary ammonium hydroxide according to claim 1, wherein the cation exchange group of the cation exchange membrane is a carboxylic acid group. 3. An electrolytic cell in which two or more cation exchange membranes are used, and an aqueous solution of quaternary ammonium hydroxide is supplied to an intermediate chamber defined by the two cation exchange membranes. The method for producing quaternary ammonium hydroxide according to claim 1. 4. The method for producing a quaternary ammonium hydroxide according to claim 1, wherein the quaternary ammonium salt is at least one salt selected from halides, carbonates and sulfates.