JPH11279128A - Production of 4,6-diaminoresorcinol or salt thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing high-purity 4,6-diamonoresorcinol in high yield from a 4,6-bis(substituted)phenylazoresorcinol. SOLUTION: This method for producing 4,6-aminoresorcinol or a salt thereof comprises the hydrogen reduction of a 4,6-bis(substituted)phenylazoresorcinol of the formula (R is a halogen, 1-5C alkyl, hydroxycarbonyl or 1-5C alkoxy; (n) is 0 or an integer of 1-5) in the presence of a metal catalyst; wherein the solvent to be used is an aliphatic nitrile compound (e.g. acetonitrile) or an organic solvent selected from the group consisting of aliphatic nitrile compounds, 3-5C aliphatic alcohols, dioxane and ethylene glycol monomethyl ether and the like, and the reduction is conducted also in the presence of a filter auxiliary (e.g. active carbon).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 4,6-diaminoresorcinol or a salt thereof. More specifically, the present invention relates to a method for producing 4,6-diaminoresorcinol or a salt thereof by reduction of 4,6-bis (substituted) phenylazoresorcinol.

[0002] 4,6-diaminoresorcinol is a monomer of polybenzoxazole, and this polybenzoxazole has high strength, high elastic modulus, heat resistance,
It is a polymer having excellent properties in chemical resistance (see Japanese Patent Application Laid-Open No. 61-501452 and Japanese Patent Application Laid-Open No. 2-229143).

[0003]

2. Description of the Related Art In general, 4,6-bisphenylazoresorcinol is reduced with hydrogen using a noble metal catalyst (JP-A-7-242604). JP-A-7-24260
According to publication 4, the reduction is carried out in a solvent under neutral conditions. It is described that water, lower alcohols, aromatic hydrocarbons, halo-substituted benzenes, halogenated aliphatic hydrocarbons, ethers and lower ketones are used alone or in combination as solvents. In addition, two methods are described for the post-treatment after the completion of the reduction reaction. One is to obtain 4,6-diaminoresorcinol by filtering through celite as it is under a nitrogen atmosphere, and then adding an acid to form an acid salt.
This is a method in which the catalyst and celite are separated by filtration, and then purified and isolated. The second is a method in which an acid is added to the reaction solution to form a salt, which is dissolved, and the catalyst is separated by filtration, followed by purification and isolation.

[0004] The former has the effect that the aniline generated in the reaction can be easily recovered and the purification step is simple, but the filterability is very poor. The loss of 4,6-diaminoresorcinol in the filtrate is large, and the yield is as poor as 60%, which is not an industrial method.

[0005] The latter has good stability in air and good operability since it is converted into a salt by adding an acid. In addition, the filterability is good,
No problem. However, there is also a disadvantage that separation and purification of by-produced aniline and 4,6-diaminoresorcinol are extremely complicated because of the acidic solution.

[0006]

SUMMARY OF THE INVENTION 4,6-Bis (substituted)
In the reduction of phenylazoresorcinol, two equivalents of an aniline derivative are by-produced in addition to 4,6-diaminoresorcinol. The biggest problem of a method for reducing 4,6-bis (substituted) phenylazoresorcinol is how to easily separate the aniline derivative with a small loss of the produced target product, 4,6-diaminoresorcinol.

The present inventors have conducted intensive studies and have found that 4,6-
The present inventors have found a method for industrially handling diaminoresorcinol free of charge and completed the present invention. That is, the reduction reaction of the 4,6-bisphenylazoresorcinol derivative was reduced with hydrogen in a selected solvent in the presence of a noble metal catalyst to obtain 4,6-diaminoresorcinol in high yield.

However, depending on the solvent, the filterability may be poor. At that time, if a filter aid such as activated carbon is added and reacted, the filterability is remarkably improved.

It is an object of the present invention to provide a method capable of easily obtaining 4,6-diaminoresorcinol with high yield from 4,6-bis (substituted) phenylazoresorcinol in high yield. Thereby, the recovery rate of the aniline derivative is also improved, which is economically advantageous.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found a method for solving the above-mentioned problems and completed the present invention. That is, the present invention relates to formula [1]

[0011]

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(Wherein R is a halogen atom, having 1 carbon atom)
Represents an alkyl group, a hydroxycarbonyl group or an alkoxy group having 1 to 5 carbon atoms, n represents an integer of 0 or 1 to 5, and two or more Rs may be the same or different from each other. Good. ) Is reduced by hydrogen in the presence of a metal catalyst to give 4,6-diaminoresorcinol or a salt thereof (the salt is an acid of 4,6-diaminoresorcinol) The present invention relates to a method for producing 4,6-diaminoresorcinol or a salt thereof, wherein an aliphatic nitrile compound is used as a solvent.

Further, the present invention provides a method for reducing 4,6-bis (substituted) phenylazoresorcinol represented by the above formula [1] by hydrogen in the presence of a metal catalyst and a solvent to obtain 4,6-diaminoresorcinol or In the reduction method for obtaining the salt, at least one organic solvent selected from aliphatic nitrile compounds, aliphatic alcohols having 3 to 5 carbon atoms, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and dioxane as a solvent And a method for producing 4,6-diaminoresorcinol or a salt thereof, wherein the reduction is carried out in the presence of a filter aid.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION 4,6-
Bis (substituted) phenylazoresorcinol is represented by the formula [2]

[0015]

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(Wherein R and n are defined the same as in formula [1]) by diazotizing a (substituted) aniline represented by the formula (1) to obtain a (substituted) benzenediazonium salt, and converting the diazonium salt to resorcinol And a coupling reaction. Specifically, in a mixture of a substituted aniline and 5 to 10 times by weight of water, under cooling, 2.
5 to 4 equivalents of an inorganic acid were added dropwise, and 1 to 3 of the (substituted) aniline dissolved in water in an amount of 1 to 3 times by weight was added to the mixture.
A 1.5-fold molar amount of sodium nitrite or potassium nitrite is added dropwise at a temperature of 10 ° C. or lower to obtain a (substituted) benzenediazonium salt. As inorganic acids, hydrochloric acid, hydrobromic acid,
At least one inorganic acid selected from sulfuric acid and phosphoric acid is used. Among these inorganic acids, hydrochloric acid is industrially and economically preferable.

Specifically, for example, aniline, 2-chloroaniline, 4-chloroaniline, 2,6-dichloroaniline, o-toluidine, m-toluidine, p-toluidine, anthranilic acid, o-anisidine, m-anisidine And p-anisidine and the like, and it is preferable to use any of these anilines. Economics,
Aniline is most preferred because of the stability of the compound.

The coupling reaction between the (substituted) benzenediazonium salt and resorcinol may be carried out by a known method, and the method of the present invention is disclosed in Japanese Patent Application Laid-Open No. 9-124575.

[0019]

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(Wherein R and n are defined as in formula [1], and X represents Cl, Br, OSO ₃ H or OPO ₃ H ₂ ). (Substituted) benzenediazonium salt represented by the formula: Or a solution of a (substituted) benzenediazonium salt represented by the formula [3] and a solution of an alkali metal or alkaline earth metal, which was filed in Japanese Patent Application Laid-Open No. 9-157239. A method is preferable in which an oxide solution or suspension is mixed to obtain an alkaline mixed solution, and the mixed solution is mixed with resorcinol and / or an alkali metal salt or an alkaline earth metal salt thereof and reacted.

As described above, 4,6-bis (substituted) phenylazoresorcinol, which is a raw material of the present invention, is obtained by reacting resorcinol with an alkaline (substituted) benzenediazonium salt, acidifying the mixture, and collecting by filtration and washing with water. Things. This may be used as it is, or may be used after drying. From the viewpoint of the yield of the reduction reaction, the incorporation of water increases the escape of 4,6-diaminoresorcinol into the filtrate, so that a dried product is preferred. Since the reaction mixture is used without purification, the purity of 4,6-bis (substituted) phenylazoresorcinol is around 80%, and 4-phenylazoresorcinol, 2,4,6-triphenylazoresorcinol and the like Some are unknown, but no major problems. A product obtained by recrystallizing this mixture with toluene or the like and purifying it can also be used with good results, but purification of 4,6-bisphenylazoresorcinol is very difficult because of its poor solubility.

Next, a method for hydrogen reduction of 4,6-bis (substituted) phenylazoresorcinol in the presence of a metal catalyst and a solvent will be described. As the solvent used for the reduction reaction, at least one kind of organic solvent selected from aliphatic nitrile compounds, aliphatic alcohols having 3 to 5 carbon atoms, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and dioxane Is used. methanol,
In ethanol, 4,6-diaminoresorcinol often escapes to the filtrate, which is economically problematic. Except for nitriles, the produced 4,6-diaminoresorcinol is very poor in filtration at the time of filtration, and there is a problem in industrial operation. At that time, if a filter aid is added during the reaction, the filterability is greatly improved. On the other hand, nitriles are preferable because they have good filterability and have little escape to the filtrate. Addition of a filter aid is effective for improving filterability even with nitriles.

Activated carbon, celite, activated clay and cellulose are used as the filter aid, and activated carbon is particularly preferred.

The amount of the filter aid is from 1 to 100% by weight based on 4,6-bis (substituted) phenylazoresorcinol, but may be large when the filterability is poor and small when the filterability is good. Preferably it is 5 to 30% by weight. The addition of a filter aid to the reaction system is effective not only for improving the filterability but also for shortening the reaction time. It will probably absorb the impurities in the feedstock and prevent catalyst degradation. In some cases, even if a filter aid is added after the completion of the reaction, an improvement in filterability is observed.

As the aliphatic nitrile compound, a compound having 2 carbon atoms
To 6 monocyano compounds are preferred. Specific examples include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, trimethylacetonitrile, hexanenitrile and 4-methylvaleronitrile. Particularly preferred are acetonitrile, propionitrile, butyronitrile, isobutyronitrile, and the like, which are quick and economically inexpensive.

More specifically, the reaction substrates are 4, 6
When bisphenylazoresorcinol is used,
The reaction yield of 6-diaminoresorcinol is 98-99%
The crystal yield of 4,6-diaminoresorcinol is 93
The aniline yield in crude crystals of 4,6-diaminoresorcinol is 1-2%, and high-purity 4,6-diaminoresorcinol is isolated as crystals in high yield. be able to. On the other hand, the filtrate contains almost the theoretical amount of aniline.

The amount of the solvent to be used is 1 to 50 times by weight, preferably 2 to 20 times by weight, based on 4,6-bis (substituted) phenylazoresorcinol.

The metal catalyst used in the present invention is at least one metal selected from copper and elements of Group VIII of the periodic table. As elements of Group 8 of the periodic table, platinum, palladium, ruthenium, rhodium, nickel, cobalt,
Iridium and the like. Of these metal catalysts, platinum and palladium are preferred, and 4,6-diaminoresorcinol can be obtained in a high yield in the present reaction, which is preferable.

Examples of the form of the catalyst include simple substances such as palladium black and platinum black, alloys such as Raney nickel and cobalt, metal salts such as palladium chloride and palladium acetate, metal oxides such as copper oxide and platinum oxide, copper acetylacetone and the like. Metal complexes such as acetylacetone palladium and metals with carriers supported on oxides such as carbon, silica, alumina, zirconia, titania and zeolite are exemplified. Among these, a metal with a carrier is particularly preferred for convenience of recovery and reuse, and palladium-carbon and platinum-carbon are preferred. In particular, platinum-carbon is palladium-
Higher activity than activated carbon is preferred.

Further, for the purpose of improving the activity and suppressing the deterioration due to the reaction and the acid treatment and the like, and enabling the reuse, a multi-component obtained by adding a second metal to a first metal such as platinum, palladium or ruthenium. Metal-based catalysts can also be used. As the second metal, rhenium, iridium, tin,
It is preferable to add one or more of antimony, germanium, indium and rhodium to the first metal in an amount of 2 to 50 atomic mol%.

Specifically, for example, 5% Pd / 1% Re-
C, 5% Pd / 2% In-C, 2% Pt / 0.5% Re
—C, 1% Pt / 0.2% Ge—C, and the like.

The amount of the catalyst used is 0.000 as a metal component with respect to 4,6-bis (substituted) phenylazoresorcinol.
It is preferably from 0.05 to 10% by weight, particularly preferably from 0.001 to 10% by weight.
Used in weight percent.

The hydrogen pressure is from normal pressure to 10000 kPa, preferably from normal pressure to 1000 kPa. The reaction temperature can be from -10 to 150 ° C, preferably from 0 to 150 ° C.
The temperature is more preferably from 100C to 10C.

In the reaction solution, 4,6-diaminoresorcinol is present as a solid. The removal method will be described. By filtering without contacting with air, 4,6-diaminoresorcinol can be obtained together with a catalyst and a filter aid. The aniline goes to the filtrate, but if the filterability is poor, the cake contains a large amount of liquid and the aniline is not sufficiently removed. Therefore, the aniline is washed with a small amount of a reaction solvent, a lower alcohol, or water.

When 4,6-diaminoresorcinol is free, both oxygen and temperature are unstable, so it is necessary to add an acid to form a salt. As the acid, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid and the like can be used, but hydrochloric acid is most industrially preferable. Add to twice or more moles hydrochloric acid aqueous solution and heat dissolve, or add two or more moles hydrochloric acid aqueous solution to funnel to dissolve or suspend, extract, and heat and dissolve. The insolubles are separated by filtration and, if necessary, activated carbon treatment. The activated carbon is separated by filtration, hydrochloric acid is added and the mixture is cooled, and the precipitated 4,6-diaminoresorcinol hydrochloride is collected by filtration. Activated carbon has a great effect on decolorization.

When dissolving 4,6-diaminoresorcinol using an aqueous hydrochloric acid solution, the amount of hydrochloric acid is 2 to 10 times the molar amount. However, if the amount of hydrochloric acid is large, the solubility decreases. Double molar is preferred. Water is used in an amount of 1 to 20 parts of 4,6-diaminoresorcinol, and preferably 3 to 10 parts in view of solubility and crystallization. The required amount of activated carbon varies depending on the color and purpose, but 0-10
0% by weight, preferably 5 to 30% by weight.

After the activated carbon treatment, concentrated hydrochloric acid is added to precipitate a solid by salting out. The hydrochloric acid to be added is preferably 4 to 20 times the molar amount of 4,6-diaminoresorcinol. Although it is economically affected by the amount of water, a molar amount of 4 to 8 times is preferable. Further, after filtration, drying is performed to obtain 4,6-diaminoresorcinol dihydrochloride.

4,6-Diaminoresorcinol dihydrochloride is also susceptible to oxidation, but the addition of stannous chloride has a resistance to oxidation. The reduction reaction can be performed continuously.

[0039]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Reference Example-1 In a mixed solution of 41 g of aniline, 98 g of 35% hydrochloric acid, and 100 g of water, 30 g of sodium nitrite was added to water 55 at 0 to 5 ° C.
The solution dissolved in g was added dropwise to synthesize an aqueous solution of benzenediazonium chloride. This aqueous solution of benzenediazonium chloride was added dropwise to a mixture of 55 g of sodium hydroxide and 110 g of water at 10 ° C. or lower.

This mixture was added to a mixture of 22 g of resorcinol, 24 g of sodium hydroxide and 22 g of water at 10 ° C.
For 40 minutes. After completion of the dropwise addition, the mixture was stirred at 10 ° C. for 3 hours. After the reaction, hydrochloric acid was added to the reaction mixture to make it acidic,
The precipitated solid was collected by filtration, washed with water, and dried to obtain 62 g of a dark red solid. The purity of 4,6-bisphenylazoresorcinol is 79.5% and contains about 5% of 2,4,6-triphenylazoresorcinol.

Example 1 4,6-bisphenylazoresorcinol (purity 79.
5%) 10.0 g (0.025 mol), 50 g of acetonitrile, and 2.0 g of 5% Pd-C were charged into a 100 ml Hastelloy autoclave, and the stirring speed was 600 while supplying hydrogen from the hydrogen accumulator at a constant pressure of 300 kPa.
The reaction was performed at 30 ° C. at rpm. With a reaction time of 2.5 hours,
The pressure reduction of the hydrogen accumulator stopped. So after stopping stirring,
After the temperature of the autoclave was returned to room temperature, the reaction product was taken out after purging with nitrogen. The slurry reaction product was separated into a cake and a filtrate by filtration under a nitrogen atmosphere. The filtration time was 20 minutes. The cake was washed with acetonitrile to obtain a wet product. Wet product and washing solution (mixture of washing solution and filtrate)
Was analyzed as a hydrochloride.

That is, 4,6 formed in the wet product and the washing solution
-The yields of diaminoresorcinol (DAR) and aniline were analyzed by liquid chromatography. Table 1 shows the results. The DAR yield in the wet product was 92.5%, the yield in the filtrate was 4.5%, and the total yield was 97%. The yield of aniline was 1.5% in wet products and 222.0% in the filtrate, and the total yield was 223.5%.

The reason why the aniline yield exceeds 200% is that 4-azoresorcinol and 2,4,6-triazoresorcinol contained as impurities in the raw material are hydrogenolyzed to release aniline. .

Comparative Example 1 A reduction reaction was carried out in the same manner as in Example 1 except that the solvent was changed to isopropanol. Filtration time is about 1
Since the process was not completed even if it took time, the subsequent processing was interrupted.

Example 2 4,6-bisphenylazoresorcinol (purity 79.
5%) 10.0 g (0.025 mol), 50 g of acetonitrile, 2.0 g of 5% Pd-C and 1.0 g of activated carbon were charged into a 100 ml Hastelloy autoclave, and hydrogen was supplied from the hydrogen accumulator at a constant pressure of 300 kPa. The reaction was carried out at 30 ° C. with a stirring speed of 600 rpm. At a reaction time of 2.5 hours, the pressure reduction of the hydrogen accumulator stopped.
Then, after stirring was stopped, the temperature of the autoclave was returned to room temperature, and the reaction product was taken out after nitrogen replacement. The slurry reaction product was separated into a cake and a filtrate by filtration under a nitrogen atmosphere.
The filtration time was 10 minutes. The cake was washed with acetonitrile to obtain a wet product. The analysis was performed in the same manner as in Example 1. The yield of DAR in the wet product was 93.1%, the yield in the filtrate was 4.9%, and the total yield was 98.0%. The yield of aniline was 1.5% in the crystals and 222.0% in the filtrate.
%, The total yield was 223.5%.

Examples 3 to 11 and Comparative Examples 2 to 6 The same reaction as in Example 2 was carried out except that acetonitrile was changed to another solvent. Table 1 shows the results. In addition, the filtration time was 30 minutes or less in all cases.

[0047]

[Table 1]

As shown in Table 1, by using acetonitrile, propionitrile and butyronitrile as the solvent for the reduction reaction, the aniline content was reduced as crystals, and D
High AR yield results were obtained. In the case of methanol or ethanol, the amount of 4,6-diaminoresorcinol dissolved in the filtrate is large, and the yield of 4,6-diaminoresorcinol obtained as crystals is low.

Example 12 4,6-bisphenylazoresorcinol (purity 79.
161 g (0.4 mol), acetonitrile 63
6 g, 5% Pd-C (5.09 g) and activated carbon (50% water-containing product) 38.2 g were charged into a 2 l SUS autoclave, and hydrogen was supplied from the hydrogen accumulator at a constant pressure of 3 kg / cm ² while stirring at 400 rpm, 30 rpm. The reaction was carried out at ℃. At a reaction time of 3 hours, the pressure reduction of the hydrogen accumulator stopped. Then, after stirring was stopped, the temperature of the autoclave was returned to room temperature, and the reaction product was taken out after nitrogen replacement. The slurry reaction product was separated into a cake and a filtrate by filtration. The cake was washed twice with 77 g and 230 g of acetonitrile.
158.6 g of a wet product, 704 g of a filtrate, and a washing solution were obtained.

After converting 4,6-diaminoresorcinol (DAR) and aniline formed in the cake, the filtrate and the washings into hydrochloride, the liquid was analyzed by liquid chromatography. As a result, the DAR yield in the cake was 93%. 0.8%, the aniline yield was 3.4%, and the DAR yield in the filtrate was 1.1.
%, The aniline yield was 203.1%. Furthermore,
The DAR yield in the washing solution was 0.1%, and the aniline yield was 6.5.
%Met.

Next, 67.4 g of this cake (DAR 0.1
6 mol), 35% hydrochloric acid water (34.4 g, 2.2 mol times), water 153 g and stannous chloride dihydrate 0.61.
g of the solution and dissolved at 60 ° C. for 1 hour. Subsequently, the catalyst and the activated carbon were separated by filtration. The catalyst and activated carbon were washed twice with 15.3 g and 30.7 g of 1% hydrochloric acid.

Activated carbon (50% water-containing product) (13.4 g) was added to the filtrate thus obtained, followed by stirring at 80 ° C. for 2 hours. Subsequently, after the activated carbon was separated by hot filtration, the filtrate was 35%
After adding 112 g of hydrochloric acid water and heating at 80 ° C. for 20 minutes, 10 g
Cooled to ° C. The precipitated crystals were separated by filtration, washed with 9.2 g of 20% aqueous hydrochloric acid, and dried under reduced pressure at 50 ° C. for 3 hours.
24.3 g of diaminoresorcinol dihydrochloride (purity 9
9.3%).

Examples 13 and 14 In Example 1, the catalyst was changed to 1.0 g of 1% Pt-C, 2% Pt-C
Except for changing to t / 0.5% Re-C, the same reaction and post-treatment operation were performed to obtain 9.83 g and 9.61 g of crystals (wet product), respectively. Table 2 shows the analysis results of the crystals and the filtrate.

[0054]

[Table 2]

[0055]

According to the present invention, an aliphatic nitrile compound is used as a reaction solvent, or an aliphatic nitrile compound, an aliphatic alcohol having 3 to 5 carbon atoms, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoamine is used as a reaction solvent. By using at least one organic solvent selected from ethyl ether and dioxane and further reducing in the presence of a filter aid, 4,6-diaminoresorcinol is produced in high yield, and the 4,6-diaminoresorcinol is obtained. Most of resorcinol can be separated as a slurry and thus can be collected by filtration at a high yield, and the by-produced aniline derivative can be separated as a filtrate at a high recovery rate. Thus, the solid (crude crystal) of 4,6-diaminoresorcinol isolated immediately after the reaction has a small content of the aniline derivative, so that the subsequent purification can be facilitated and the purification loss can be reduced. That is, high-purity 4,6-diaminoresorcinol can be easily obtained with a high purification yield.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C07B 61/00 300 B01J 23/64 104X (72) Inventor Hideo Suzuki 722-1, Tsuboi-cho, Funabashi-shi, Chiba Nissan Chemical Industrial Co., Ltd. (72) Isao Hashiba, Inventor 722-1, Tsuboi-cho, Funabashi-shi, Chiba Pref. Nissan Chemical Industry Co., Ltd.

Claims (8)

[Claims] [Claim 1] Formula [1] (Wherein, R represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxycarbonyl group or an alkoxy group having 1 to 5 carbon atoms, n represents an integer of 0 or 1 to 5, Two or more R's may be the same or different from each other.) 4,6-bis (substituted) phenylazoresorcinol is hydrogen-reduced in the presence of a metal catalyst and a solvent to give 4,6-diaminoresorcinol A method for producing 4,6-diaminoresorcinol or a salt thereof, wherein the method for obtaining a salt thereof comprises performing reduction using an aliphatic nitrile compound as a solvent. 2. Formula (1) (Wherein, R represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxycarbonyl group or an alkoxy group having 1 to 5 carbon atoms, n represents an integer of 0 or 1 to 5, Two or more R's may be the same or different from each other.) 4,6-bis (substituted) phenylazoresorcinol is hydrogen-reduced in the presence of a metal catalyst and a solvent to give 4,6-diaminoresorcinol Or in a reduction method for obtaining a salt thereof, at least one organic solvent selected from aliphatic nitrile compounds, aliphatic alcohols having 3 to 5 carbon atoms, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and dioxane as a solvent. Characterized in that the reduction is carried out using a solvent and further in the presence of a filter aid. Norezorushinoru or a salt thereof. 3. The method for producing 4,6-diaminoresorcinol or a salt thereof according to claim 1, wherein the aliphatic nitrile compound is a monocyano hydrocarbon compound having 2 to 6 carbon atoms. 4. The method for producing 4,6-diaminoresorcinol or a salt thereof according to claim 1 or 2, wherein the metal catalyst is at least one metal selected from copper and elements of Group VIII of the periodic table. 5. A method for producing 4,6-diaminoresorcinol or a salt thereof according to claim 1 or 2, wherein the metal catalyst is platinum. 6. The multi-element catalyst according to claim 1, wherein the metal catalyst is platinum, ruthenium or palladium, and at least one element selected from rhenium, indium, tin, antimony, germanium, iridium and rhodium is added. Of 4,6-diaminoresorcinol or a salt thereof. 7. The method for producing 4,6-diaminoresorcinol or a salt thereof according to claim 2, wherein the amount of the filter aid is 1 to 100% by weight based on 4,6-bis (substituted) phenylazoresorcinol. 8. The reduced reaction solution obtained by the method of claim 1 is cooled, and the precipitated solid is filtered under an inert atmosphere, and 4,6-bis (substituted) phenyl in the obtained solid is obtained. Hydrochloric acid more than twice the amount of azoresorcinol is added and dissolved by heating. If there is any insoluble matter, it is separated by filtration, concentrated hydrochloric acid is further added, and the precipitated solid is collected by filtration and dried. A method for producing 4,6-diaminoresorcinol or a salt thereof.