JPH0277591A - Method for producing quaternary phosphonium hydroxide - Google Patents

Abstract

PURPOSE:To obtain high purity quat. phosphonium hydroxide in a high yield from the cathode chamber of an electrolytic cell provided with a cation exchange membrane as a diaphragm by electrolyzing an aq. soln. of a specified quat. phosphonium salt with DC in the anode chamber. CONSTITUTION:An aq. soln. of a quat. phosphonium salt represented by the formula (where each of R1-R4 is 1-8C alkyl, aryl, etc., and X is an anion) is fed into the anode chamber of an electrolytic cell provided with one or more cation exchange membranes as diaphragms. Water is fed into the cathode chamber and DC is supplied between both electrodes. Only quat. phosphonium cations permeate the cation exchange membranes and move from the anode to the cathode and high purity quat. phosphonium hydroxide corresponding to the quat. phosphonium salt is obtd. in the cathode chamber. This product is useful as a polymn. catalyst, a curing catalyst, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing quaternary phosphonium hydroxide. Furthermore, polymerization catalysts useful in the production of polysiloxanes (UK Patent No. 794,119) and intermediate raw materials used in the production of quaternary phosphonium salts for electrolytes in electrolytic capacitors (JP-A-62-272-512) , Japanese Unexamined Patent Publication No. 62-272, 51:1).

Furthermore, we are using an electrolytic method to produce intermediate raw materials for high-purity quaternary phosphonium salts, which are useful as curing catalysts for epoxy resins with excellent electrical properties, which are widely used for sealing and impregnating electronic components such as semiconductor devices and electronic devices. The present invention relates to a manufacturing method.

[Prior art] and [Problem to be solved by the invention'x
U] Conventionally, as a method for producing quaternary phosphonium hydroxide, a method of reacting an aqueous solution of tetra-n-butylphosphonium iodide with silver oxide to obtain quaternary phosphonium hydroxide (British Patent No. 794, 119) specification) is known. The reaction formula is shown below.

(n-C,H,), PI+1/2AgO+1/2HzO
-+ (n-Cjl,,)4POH+Agl However, this method is not an industrially desirable method because silver oxide is expensive and the manufacturing cost is high.

On the other hand, co-authored by G.M. Kozolahoff and El Meyer, “
Organic Phosphorous Compound” Willy
Published by Interscience (G, M, KO30LAP)
OFF and L, MAIERrORGANIc
PtlO5PHPt105PHORUSGOWILEY
-INTER3CIENCE, a Division
of John Wiley & 5ons, Inc.
) Vol. 2, p. 201.

(1972) describes that quaternary phosphonium salts can be ion-exchanged using an ion-exchange resin.

However, as stated in the same book.

When ion exchange is performed using an ion exchange resin, it is generally necessary to dilute the concentration of the stock solution, which has the disadvantage that ion exchange requires a long time.

In addition, in order to overcome this point, Japanese Patent Application Laid-Open No. 62-212,397
The publication describes a method for obtaining quaternary phosphonium hydroxide by contacting quaternary phosphonium halide with a strongly basic anion exchange resin (OH type) in a relatively high concentration range and performing ion exchange. However, in the case of this method, as described in the examples, ion exchange is not completely performed (yield 66.4-90.8
%), it is unavoidable that the raw material quaternary phosphonium halide is mixed into the effluent.Therefore, it is necessary to remove the mixed quaternary phosphonium halide using an organic solvent such as a halogenated hydrocarbon. It is.

Furthermore, even if the quaternary phosphonium halide used as a raw material is removed using a solvent, it is difficult to completely recover it from the effluent, and analysis of the halogen in the effluent shows that the amount ranges from several hundred to several 11,000 pp. include.

As mentioned above, in all conventional methods, highly pure quaternary phosphonium hydroxide cannot be obtained, or they cannot be applied industrially at all.

As a result of intensive and detailed research in view of the above-mentioned problems, the present inventors electrolyzed a quaternary phosphonium salt aqueous solution in an electrolytic cell configured with a cation exchange membrane as a diaphragm, and found that it had unexpectedly high purity and The present invention was completed by discovering a method for producing quaternary phosphonium hydroxide in high yield.

[Means for Solving the Problems] That is, the present invention provides an electrolytic cell having one or more cation exchange membranes as a diaphragm, which has the following general formula [I] (wherein R1, R2, R) and R4 has 1 or more carbon atoms
represents an aqueous solution of a quaternary phosphonium salt represented by The present invention relates to a method for producing quaternary phosphonium hydroxide, which is characterized by obtaining quaternary phosphonium hydroxide from a cathode chamber by direct current electrolysis.

The present invention will be explained in detail below.

In the method for producing quaternary phosphonium hydroxide of the present invention, a quaternary phosphonium salt aqueous solution is subjected to direct current electrolysis using an electrolytic cell having one or more cation exchange membranes as a diaphragm. A method using an ion exchange membrane will be explained.

The specific method is to supply a quaternary phosphonium salt aqueous solution to the anode chamber and water to the cathode chamber of an electrolytic cell divided by one cation exchange membrane, and to pass a direct current between the two electrodes. , is a method for obtaining quaternary phosphonium hydroxide from the cathode chamber.

In the present invention, ordinary cation exchange membranes can be used as the cation exchange membrane, such as styrene-divinylbenzene copolymer membranes and fluororesin membranes having cation exchange groups such as sulfone groups and carboxyl groups. is used.

In addition, as for the material constituting the electrode, it is preferable to use a stable material that is durable against halogen, oxygen, etc. generated by electrolysis of quaternary phosphonium salt for the anode.1For example, graphite,
It is preferable to use electrodes made of lead, alloys thereof, various metals coated with white metal, or the like. Further, it is preferable to use an alkali-resistant material for the cathode, such as stainless steel or nickel.

As for the materials constituting the electrolytic cell, synthetic resins such as fluororesin, polypropylene, and polyethylene are used for the anode chamber, and synthetic resins used for the anode chamber, as well as alkali-resistant stainless steel, etc., are sufficient for the cathode chamber. can be used.

The quaternary phosphonium salt supplied as an aqueous solution to the anode chamber of the electrolytic cell in the present invention has the following general formula [I] C, where RIn RIn nff and R<a alkyl group having 1 to 8 carbon atoms, Represents an aryl group, an aralkyl group, or at least one group thereof substituted with a hydroxyl group or an alkoxyl group,
Xo represents an anion) is used.

In the general formula [11], the alkyl group for R1-R1 is, for example, methyl, ethyl, propyl, butyl, pentyl, and octyl, the aryl group is, for example, phenyl, tolyl, or xylyl, and the aralkyl group is, for example, Examples include benzyl and phenityl, and examples include those in which at least one of the above six groups is substituted with a hydroxyl group or an alkoxyl group. Further, 81 to R4 may be of the same type or different types.

Also, ze represents an anion (# group), such as fluorine,
Halogen ions such as chlorine, bromine, and iodine, formic acid, acetic acid,
Organic carboxyl ions such as oxalic acid, sulfuric acid, dimethyl and diethyl sulfate ions, nitrate ions, phosphate ions, methyl and dimethyl phosphate ions, organic phosphate ions such as ethyl and diethyl phosphate, hydroxyl groups (OH-), etc. Examples include, but are not limited to, these anions.

When electrolyzing the quaternary phosphonium salt aqueous solution of the present invention, a DC voltage is applied, and the current density at that time is usually l
~SOA/da", preferably 2-30A/da"
The temperature of the electrolyte is sufficient at room temperature, but in order to prevent corrosion of the anode and decomposition of the target substance in the catholyte,
It is preferable to maintain the temperature at 50°C or lower.

The method for supplying the quaternary phosphonium salt aqueous solution to the electrolytic cell is as follows:
It can be carried out in any of the circulation type, continuous type, and semi-continuous type. This quaternary phosphonium salt aqueous solution is supplied to the anode chamber, and the concentration at that time varies depending on the type of quaternary phosphonium salt and the quality of the target quaternary phosphonium hydroxide produced in the cathode chamber. Usually 2~
The content is set to 50 wt%, preferably 3 to 30 wt%. The reason for this is that when a high concentration of quaternary phosphonium salt exceeding 50 wt % is supplied to the anode chamber, anions (ugly groups) are somewhat back-diffused into the cathode chamber through the cation exchange membrane. in this case,
By maintaining the concentration in the anode chamber within the range of 2 to 50 wt%, it is possible to suppress back diffusion of anions to the cathode chamber. Furthermore, in the case of anion or hydroxyl group, the method according to the present invention can also be applied to the purification of crude quaternary phosphonium hydroxide. Quaternary phosphonium hydroxide has poor stability and decomposes into the corresponding phosphine oxide at high concentrations, so 50
It is not preferable to use it at an excessively high concentration of wt% or more.

On the other hand, either pure water is supplied to the cathode, or at the beginning of operation, a small amount of quaternary phosphonium hydroxide, which is the target product, is added as an electrolyte at 0°C, since electrolysis is difficult to occur with pure water. O1-10. It is preferable to add about Owt%.

As the electrolysis progresses, the concentration of the desired product, quaternary phosphonium hydroxide, in the cathode chamber solution increases, or the desired concentration is up to 50 wt% considering the stability of the quaternary phosphonium hydroxide. Collect continuously or in batches when this is reached. It goes without saying that before starting electrolysis, the electrodes, electrolytic cell, and other systems should be sufficiently washed with pure water to prevent any impurities from entering.

Next, a method of using two or more cation exchange membranes as diaphragms in an electrolytic cell will be described.

The specific method is to supply an acidic electrolyte to the anode chamber, water to the cathode chamber, and a quaternary phosphonium salt aqueous solution to the intermediate chamber of an electrolytic cell partitioned by two or more cation exchange membranes. In this method, quaternary phosphonium hydroxide is obtained from the cathode chamber by passing a direct current between the two.

In this method, the same cation exchange membrane, electrode, and electrolytic cell as used in the method using one cation exchange membrane described above can be used.

Furthermore, the quaternary phosphonium salt supplied as an aqueous solution to the intermediate chamber of the electrolytic cell can be the same as that used in the method using one of the cation exchange membranes described above, but in this method, .

In particular, if the quaternary phosphonium salt aqueous solution contains halogen ions or nitrate ions as a main component or as an impurity, if they reach the anode during electrolysis, they will cause harmful and highly corrosive halogen and nitrogen oxidation. The anode itself is corroded by the generation of high concentrations of gases from materials, etc., and the corrosion products migrate to the catholyte side, resulting in a decrease in the purity of the target product, quaternary phosphonium hydroxide, as well as damage to synthetic resins. This may cause deterioration of the manufactured anode chamber and cation exchange membrane. Therefore, in order to prevent corrosive anions, typically halogen ions, liberated from the quaternary phosphonium salt aqueous solution supplied to the intermediate chamber from migrating from the intermediate chamber to the anode chamber during electrolysis, the anode chamber and the intermediate chamber The important significance of this method lies in the use of a cation exchange membrane as a diaphragm.

That is, by using a cation exchange membrane as a diaphragm between the anode chamber and the intermediate chamber, it is possible to suppress the generation of corrosive gases that cause deterioration of the anode, anode chamber, and cation exchange membrane during electrolysis. .

On the other hand, due to the presence of a cation exchange membrane that is a partition between the cathode chamber and the intermediate chamber, only the quaternary phosphonium cations for two purposes are transferred from the intermediate chamber to the cathode chamber, and highly purified quaternary phosphonium hydroxide is transferred in the cathode chamber. Oxide can be obtained.

The concentration of the quaternary phosphonium salt supplied to the intermediate chamber may be set under the same conditions as in the case where one cation exchange membrane is used.

Next, the acidic electrolyte used in the solution supplied to the anode chamber should be one that is less likely to corrode or deteriorate the materials that make up the anode chamber, and that does not generate corrosive or toxic gases. For example, sulfuric acid, phosphorus, etc. Examples include dilute aqueous solutions such as dilute aqueous solutions, and aqueous solutions of organic acids such as formic acid, oxalic acid, and tartaric acid. These acidic electrolytes do not need to be used in high concentrations and have a conductivity necessary for electrolysis, e.g. 5 to 300 m5, preferably lO to
A concentration of 200 layers S is sufficient. Expressing these concentrations in concrete numbers, for sulfuric acid it is 1.0~
10. OwL%, and for oxalic acid it is 2.0 to 10 wt%.

Further, pure water is supplied to the cathode chamber, but since it is difficult to cause electrolysis with pure water alone at the beginning of operation, electrolysis is performed after adding a small amount of quaternary phosphonium hydroxide in the same manner as described above. In this way, by electrolyzing two or more cation exchange membranes as a diaphragm, we can efficiently produce high-purity quaternary phosphonium hydroxide by removing the negative effects of IX corrosive gas on the electrodes and preventing back diffusion. I can do something.

However, since providing more diaphragms than necessary leads to a decrease in current efficiency, it is often sufficient to use up to five exchange membranes. Incidentally, in direct current electrolysis, conditions such as temperature, current density, voltage, etc. may be carried out under the same conditions as in the method using one of the above-mentioned cation exchange membranes.

Further, the method of supplying each aqueous solution to the anode chamber, intermediate chamber, and cathode chamber can be implemented by any of a circulation type, continuous type, and semi-continuous type. The residence time of each aqueous solution in each chamber is 1 to 60 seconds, preferably 1 to IO seconds.

[Function] The method for producing quaternary phosphonium hydroxide of the present invention involves supplying a quaternary phosphonium salt aqueous solution to an anode chamber partitioned by a cation exchange membrane and water to a cathode chamber, and applying a direct current between the two electrodes. By applying electricity, only the quaternary phosphonium cations selectively permeate through the cation exchange membrane from the anode to the cathode, so that a highly purified quaternary phosphonium hydroxide corresponding to the cathode chamber can be obtained.

In addition, an acidic electrolyte is supplied to the anode chamber of an electrolytic cell separated by two or more cation exchange membranes, water is supplied to the cathode, and a quaternary phosphonium salt is supplied to the intermediate chamber, so that a direct current of 1! When the flow is passed through, the selective permeation effect of the cation exchange membrane causes the concentration of halogen ions contained as the main component or impurity of the quaternary phosphonium salt, the generation of gases such as nitrogen oxides, and the opposite effect. No diffusion occurs, and quaternary phosphonium hydroxide can be selectively obtained in high purity in the cathode chamber.

[Example] Hereinafter, an example will be shown and the present invention will be explained more specifically. Example 1 An ion exchange membrane was coated with Nafion: 124
The electrolytic cell is divided into an anode chamber and a cathode chamber using a fluororesin cation exchange membrane (manufactured by DuPont).The anode is a titanium plate coated with platinum, and the cathode is a stainless steel (5115).
304) A plate was used.

Next, 10% of a 12.94 wt% tetraethylphosphonium bromide aqueous solution was placed in the anode chamber of the electrolytic cell. [1 kg] and 4.0 kg of 0.23 wt% tetraethylphosphonium hydroxide aqueous solution were supplied to the cathode chamber, and a DC voltage of 10-15 V was applied between the anode and cathode at room temperature to perform electrolysis for 24 hours. As a result, 6.62W was applied to the cathode chamber.
A t% aqueous solution of tetraethylphosphonium hydroxide was obtained. The amount of current flowing at this time was 3.1 F'''I? The current efficiency was 72.3%.

As a result of analyzing the impurities in the tetraethylphosphonium hydroxide aqueous solution obtained here, it was found that Na≦0. O5p
pm, ≦0.0]ppm, Fe=0.0
1ppm, Ni≦0.02p1)-, Cr≦0.
01ppm, Cu≦0. O2ppm, Ba
=0.014 ppm, Pb≦0.05pp, T
i=0.012p9 layer, C1)=0.2ppm,
Br=1O, 5ppm, SO4≦0. The purity was extremely high at 1ppm.

Example 2 6.13 as a quaternary phosphonium salt supplied to the anode chamber
wt% tetraethylphosphonium bromide aqueous solution 1
Electrolysis was carried out under the same conditions as in Example 1 except that 0.0 kg was used, and as a result, 6.15 wt % of tetraethylphosphonium hydroxide was obtained in the cathode chamber. The amount of current applied at this time was 3.2 F, and the current efficiency was 63.7%.

As a result of analyzing the impurities in the obtained tetraethylphosphonium hydroxide aqueous solution, Na≦0.05p1)-
IK≦0.01ppm, Fe=0. O2p
pm, Ni≦0.01ppm.

Cr≦0. O2ppm, Cu≦0. O2ppm,
Ba=0.01ppm, Pb≦0.05p
p(Ti≦00-01pp, C1) ≦0.1pp(
Br≦0.11) I) Proverb, S04≦0. An extremely high purity product was obtained with lpp■.

Example 3 7.4 as a quaternary phosphonium salt supplied to the anode chamber
8.0 kg of wt% trimethylpropylphosphonium iodite aqueous solution, and 0.27 wL% trimethylpropylphosphonium hydroxide aqueous solution 4.0 kg in the cathode chamber.
Electrolysis was carried out under the same conditions as in Example 1 except that 5 kg was used, and as a result, 4.9 kg of a 6.06 wt % trimethylpropylphosphonium hydroxide aqueous solution was obtained in the cathode chamber. At this time, the current flow was 3.1F and the current efficiency was 67.
It was 5%.

As a result of analyzing the impurities in the obtained aqueous solution of trimethylpro and phosphonium hydrogen oxide, it was found that Ha≦0. O5p
pm, K≦0.01ppm, Fe=0.01p
p(Xi≦0.01pp(Cr≦0.O2ppm,
Cu≦0. O2ppm, Ba=0.01ppm
, Pb≦0. O5ppm, Ti≦0.01p
pm, Cj'≦0, lppm, Br≦0. lppm
, I≦0.191)l, SO4≦0. lppm
It was found to be of extremely high purity.

Example 4 3.60 as quaternary phosphonium salt supplied to the anode chamber
Electrolysis was carried out under the same conditions as in Example 1, except that 10.0 kg of wt% tetraethylphosphonium hydroxide aqueous solution was used. As a result, 5.84wt% was added to the cathode chamber.
of tetraethylphosphonium hydroxide was obtained. The amount of current applied at this time was 2.8F, and the current efficiency was 75.1%.

The analysis results of impurities in the tetraethylphosphonium hydroxide aqueous solution before and after electrolysis are as shown in Table 1 below.

Table ” (ppm) Example 5 Nafion 324 ion exchange membrane
(manufactured by DuPont, fluororesin cation exchange membrane) The electrolytic cell is divided into an anode chamber, an intermediate chamber and a cathode chamber using two sheets,
A titanium plate coated with platinum was used as the anode, and a stainless steel (SO3304) plate was used as the cathode. After thoroughly washing both chambers with pure water, add 3.93 kg of 19 wt% sulfuric acid to the anode chamber, 14.94 kg of 5.11 wt% tetraethylphosphonium bromide to the intermediate chamber, and 0.74 wt% sulfuric acid to the cathode chamber. 4.34 kg of an aqueous solution of tetraethylphosphonium hydroxide was supplied, and a DC voltage of 15 to 20 V was applied between the anode and the cathode at room temperature.
As a result of electrolysis for 4 hours, 8.88wt was found in the cathode chamber.
% tetraethylphosphonium hydroxide aqueous solution 4
．． Obtained 80 kg. The amount of current applied at this time was 3.52F, and the current efficiency was 68.0%.

As a result of analyzing the impurities in the tetraethylphosphonium hydroxide aqueous solution obtained here, it was found that Na≦0. O5p
pm, K≦0.01ppm, Fe≦0.01
ppm, Ni≦0, O2ppm, Cr≦0.
01ppm, Cu≦0. O2ppm, Ba≦0
, O2ppm, Pb≦0. O5ppm, T
i≦0.01ppm, C1'≦0.29p■, 8
"It was of extremely high purity with ≦0.2 ppm, 5o4==i, spp■.

Example 6 In the same apparatus as Example 5, 4.34 wt% was added to the anode chamber.
4.20 kg of oxalic acid aqueous solution, 10.1 wt in the middle chamber
% tetraethylphosphonium bromide 8.50kg
, 4.50 kg of 0.69 wt% tetraethylphosphonium hydroxide was supplied to the cathode chamber, and 15 to 2
As a result of applying a DC voltage of 0 V and carrying out electrolysis for 24 hours, 4.76 kg of a 7.60 wt% tetraethylphosphonium hydroxide aqueous solution was obtained in the cathode chamber. The amount of current applied at this time was 2.83F, and the current efficiency was 71%.

As a result of analyzing the impurities in the tetraethylphosphonium hydroxide aqueous solution obtained here, it was found that Na≦0. O5p
pm, K≦0.01pp (Fe≦0.01ppm,
Ni≦0, O2ppm, Cr≦0.01p
pm, Cu≦0. O2ppm, Ba≦0,
O2ppm, Pb≦0. O5ppm, Ti
≦0.0191) Otori, C1)≦0.2ppm,
It was of extremely high purity with a pH of Dr≦0.2ppm, SO4<0.21).

Example 7 In the same apparatus as Example 5, 3.96 wt% was added to the anode chamber.
4.00 kg of aqueous solution of oxalic acid, 6.8 wt in the middle chamber
% tetraethylphosphonium hydroxide 10.0
In addition, 4.20 kg of a 0.58 wt% aqueous solution of tetraethylphosphonium hydroxide was supplied to the cathode chamber, and 15 to 20 V of direct current was applied to perform electrolysis for 24 hours. As a result, 8.30 wt. % tetraethylphosphonium hydroxide aqueous solution 4.40kg
I got it. The amount of current flowing at this time was 1.79F, and the current efficiency was 7
It was 4.5%.

The analysis results of impurities in the tetraethylphosphonium hydroxide aqueous solution before and after electrolysis are as shown in Table 2 below.

Example 8 In the same apparatus as in Example 5, 4. o5at%
4-Okg of oxalic acid aqueous solution, 12.3 wt% in the middle chamber
triethylmethylphosphonium iodite 8.10k
g, and 4.00 kg of 0.45 wt% triethylmethylphosphonium hydroxide was supplied to the cathode chamber.
Electrolysis was carried out for 24 hours by applying a DC voltage of 5 to 20 V. As a result, 4.45 kg of 8.92 wt % triethylmethylphosphonium hydroxide was obtained in 9 cathode chambers. The amount of current applied at this time was 3.25F, and the current efficiency was 77.6%.

As a result of analyzing the impurities in the triethylmethylphosphonium hydroxide aqueous solution obtained here, it was found that Na≦0.
O5ppm, ≦0.01ppm, Fe≦0.0
1ppm.

Ni≦0. O2ppm, Cr≦0.01ppm,
Cu≦0. O2ppm, Ba≦(1, (1
2ppm, Pb≦0. O5ppm, Ti≦
0. (llppm, C1';;0.2ppm,
Br≦0.2ppm, I≦0.2pp(SO4
The purity was ≦0.2 ppm, indicating extremely high purity.

[Effects of the Invention] As explained above, according to the production method of the present invention, a quaternary phosphonium salt aqueous solution is subjected to DC electrolysis in an electrolytic cell using a cationic exchange membrane as a diaphragm, thereby producing high purity. of quaternary phosphonium hydroxide can be obtained in high yield.

In addition, because the target product quaternary phosphonium hydroxide produced by the method of the present invention is of high purity, the polymerization catalyst 1
M, an intermediate raw material used in the production of quaternary phosphonium salts for capacitor electrolysis, a curing catalyst for epoxy resins with excellent electrical properties that are widely used in the sealing and impregnation of electronic components such as semiconductor devices and electronic devices. It is useful as a raw material, etc., and the industrial value of the present invention is extremely high.

Applicant: Nippon Chemical Industry Co., Ltd. Agent: Hiroshi Watari Hebe

Claims (6)

[Claims] (1) In an electrolytic cell using one or more cation exchange membranes as a diaphragm, the following general formula ▲Mathematical formula, chemical formula, table, etc.▼ (In the formula, R_1, R_2, R_3 and R_4 have 1 carbon atom ~8 alkyl group, aryl group, aralkyl group, or at least one group thereof is substituted with a hydroxyl group or an alkoxyl group, and X^■ represents an anion) Quaternary phosphonium represented by A method for producing quaternary phosphonium hydroxide, which comprises obtaining quaternary phosphonium hydroxide from a cathode chamber by direct current electrolysis of a salt aqueous solution. (2) In the method for producing quaternary phosphonium hydroxide according to claim 1, an aqueous quaternary phosphonium salt solution is supplied to an anode chamber partitioned by one cation exchange membrane, and water is supplied to a cathode chamber, and both electrodes are A method for producing quaternary phosphonium hydroxide, which comprises passing a direct current between the two. (3) In the method for producing quaternary phosphonium hydroxide according to claim 1, an acidic electrolyte is placed in an anode chamber partitioned by two or more cation exchange membranes, water is placed in a cathode chamber, and quaternary phosphonium hydroxide is placed in an intermediate chamber. A method for producing quaternary phosphonium hydroxide, which comprises supplying an aqueous salt solution and passing a direct current between the two electrodes. (4) The quaternary phosphonium salt aqueous solution according to claim 1, 2 or 3, wherein the DC electrolysis of the quaternary phosphonium salt aqueous solution is carried out at a temperature of 50° C. or lower, a current density of 1 to 50 A/dm^2, and a voltage of 1 to 50 V. Method for producing phosphonium hydroxide. (5) The supply concentration of the quaternary phosphonium salt aqueous solution is 2 to 5
5. The method for producing quaternary phosphonium hydroxide according to any one of claims 1 to 4, wherein the content is 0 wt%. (6) The method for producing quaternary phosphonium hydroxide according to any one of claims 1 to 5, wherein the aqueous quaternary phosphonium salt solution is an aqueous solution of tetraethylphosphonium bromide.