JP2003192630A - Method for producing 1,3,6-hexanetricarboxylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing 1,3,6-hexanetricarboxylic acid and/or its salt with reduced discoloration from 1,3,6-tricyanohexane obtained by an electrolytic reducing reaction of acrylonitrile according to simple and industrial treating procedures. <P>SOLUTION: This method for producing the 1,3,6-hexanetricarboxylic acid and/or its salt is carried out as follows. A trinitrile mixture consisting essentially of the 1,3,6-tricyanohexane is separated from an electrolyte consisting essentially of adiponitrile and obtained by the electrolytic reducing reaction of the acrylonitrile. The 1,3,6-tricyanohexane in the mixture is hydrolyzed to provide a tricarboxylic acid or its salt or both which are then treated with an oxidizing agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the production of adiponitrile by the electrolytic reduction reaction of acrylonitrile,
The present invention relates to a method for producing 1,3,6-hexanetricarboxylic acid by hydrolyzing 1,3,6-tricyanohexane obtained as a by-product. More specifically, 1,3,6-hexanetricarboxylic acid and / or a salt thereof having a low hue, high purity and high heat stability, which can be suitably used as a builder in paint applications, detergents, cleaning agents and as a water stain inhibitor. Manufacturing method.

[0002]

2. Description of the Related Art 1,3,6-Tricyanohexane is
Aminomethyl-1,8-diaminooctane and 1,3,6
-Useful as a raw material for hexanetricarboxylic acid. Among them, 1,3,6-hexanetricarboxylic acid is water-soluble and has good biodegradability, so that it has been proposed to be applied to various uses. For example, it has been proposed that 1,3,6-hexanetricarboxylic acid or a salt thereof can be suitably used as a detergent preparation, a chain lubricant, etc. (German Patent Application Publication No. 19637428).

Further, JP-A-4-342748 discloses that 1,3,6-hexanetricarboxylic acid can be suitably used as a plasticizer for halogen-containing resins having excellent cold resistance by esterification with higher alcohol. Proposed. With the development of 1,3,6-tricyanohexane for these applications, it is desired that the esterified products with 1,3,6-hexanetricarboxylic acid and higher alcohols have a low hue without coloring. There is.

For example, when 1,3,6-hexanetricarboxylic acid is colored, its esterified product also tends to be markedly colored, and in the case of a derivative having a high boiling point such as an esterified product with a higher alcohol. Is difficult to purify by distillation. As a method for producing 1,3,6-hexanetricarboxylic acid, various methods have hitherto been known, and generally, 1,3,6-tricyanohexane obtained by an electrolytic reduction reaction of acrylonitrile is used as a raw material, The method of producing by hydrolysis is well known.

1,3,6 obtained in electrolytic reduction reaction
-For the purpose of increasing the purity of 1,3,6-tricyanohexane in a trinitrile mixture containing tricyanohexane, for example, when distillation purification is performed, it is usually markedly colored, and yellow or black Presents. For example, in JP-A-62-270550, 1,3,6-tricyanohexane is purified by molecular distillation, but the purified product is a yellow liquid having a Hazen value of 400 or more. 1,3,6-hexanetricarboxylic acid obtained by hydrolysis using a trinitrile mixture containing 1,3,6-tricyanohexane as a main component that exhibits such coloring is
Similarly, it is yellowish brown or reddish brown, and is markedly colored. Furthermore, the 1,3,6-hexanetricarboxylic acid colored in this way further increases the degree of coloring when heated to 80 ° C. or higher, resulting in a color difference (Δ) before and after heating.
E) tends to greatly exceed 1, and the thermal stability is low.

[0006] For example, German Patent Application Publication No. 196374.
No. 28, a beige color formed by heating tricyanohexane obtained by electrolytic reduction reaction of acrylonitrile under reflux with 20% caustic soda, cooling and then carboxylic oxidation with concentrated sulfuric acid, and completely drying the obtained reaction mixture. A method for producing colorless to pale yellow 1,3,6-hexanetricarboxylic acid by extracting the residue of the above with acetic ester using a Soxlet extractor and removing the acetic ester under reduced pressure is disclosed. ing.

As a purification method, Soxle
tt) In addition to the method using an extractor, the reaction mixture is extracted three times with tert-butyl methyl ether, the extract is dried over magnesium sulfate, the solvent is distilled off, and the residue is mixed with acetone and cyclohexane. Introduced into, and collecting the crystals generated by cooling by filtration,
A colorless to pale yellow 1,3,6-hexanetricarboxylic acid is obtained. Furthermore, tricyanohexane was mixed with concentrated sulfuric acid with crushed ice pieces, and the aqueous mixture obtained by hydrolysis at 140 ° C. was extracted three times with tert-butyl methyl ester, and the ether mixture was dried over magnesium sulfate, and then the solvent was added. Is distilled to produce 1,3,6-hexanetricarboxylic acid from colorless to pale yellow.

The purity of 1,3,6-hexanetricarboxylic acid obtained by these disclosed methods largely depends on the content of 1,3,6-tricyanohexane in the raw material, and the purity is usually It is 95% or less. Furthermore, in any of the methods disclosed above,
The lightness index L value of 3,6-hexanetricarboxylic acid is 9
Less than 8, b value of chromaticness index is 3 or more, 80
It has one or more properties such as a color difference (ΔE) of 2 or more when left at 18 ° C for 18 hours, and it is colored or has low thermal stability and is colored by heating 1,3,6- Only hexanetricarboxylic acid can be obtained.

Further, German Patent Application Publication No. 196374
The methods disclosed in Japanese Patent No. 28 are not industrially advantageous methods because they use a large amount of extraction solvent. In addition, as a method for producing 1,3,6-hexanetricarboxylic acid, Houben-Weyl VIII, p. 6
No. 97,539, first a pinner (Pinne
r) the tricarboxylic acid ester is prepared from the nitrile via the trisimino ester based on the reaction, and then
It is also possible to produce 1,3,6-hexanetricarboxylic acid by hydrolysis.

However, in the Pinner reaction, when producing an iminoester from a nitrile and an alcohol, it is necessary to control the water content enough to improve the yield, such as using dry hydrochloric acid gas. Furthermore, a manufacturing process involving a chemical reaction is long, such as using corrosive hydrochloric acid gas, a step of hydrolyzing an iminoester to an ester and a step of hydrolyzing an ester to a carboxylic acid, and industrially, Requires a great deal of equipment.

[0011]

The object of the present invention is to obtain 1,3,3 obtained in the electrolytic reduction reaction of acrylonitrile.
1,3,6-hexanetricarboxylic acid having high purity, low hue, and excellent thermal stability, which is purified from 6-tricyanohexane by a simple and industrial treatment operation and / or
Alternatively, it is to provide a method for producing a salt thereof. A further object of the present invention is to provide 1,3,6-hexanetricarboxylic acid and / or a salt thereof having a high purity, a low hue, and a high thermal stability in which the hue change due to heat is reduced. .

[0012]

In order to solve the above-mentioned problems, the present inventors hydrolyzed 1,3,6-tricyanohexane obtained by the electrolytic reduction reaction of acrylonitrile, and obtained 1, As for the method for purifying 3,6-hexanetricarboxylic acid, earnest studies were conducted. as a result,
The inventors have found that the hue can be remarkably improved by treating 1,3,6-hexanetricarboxylic acid or a salt thereof obtained by electrolytic reduction reaction and hydrolysis of acrylonitrile with an oxidizing agent, and have completed the present invention.

That is, the present invention is as follows. [1] At least low-boiling components relative to the trinitrile component contained in the electrolytic solution are removed from the electrolytic solution containing adiponitrile as a main component obtained by the electrolytic reduction reaction of acrylonitrile to obtain 1,3,6-tricyano. A trinitrile mixture containing hexane as a main component was separated, and 1,3,6-tricyanohexane in the trinitrile mixture was hydrolyzed to obtain 1,3,6-hexanetricarboxylic acid and / or a salt thereof and a solvent. A method for producing 1,3,6-hexanetricarboxylic acid and / or a salt thereof, which comprises treating the resulting solution with an oxidizing agent. [2] 1, 3, 6 according to [1], wherein the oxidant is ozone
-A method for producing hexanetricarboxylic acid and / or a salt thereof. [3] 1,3,6-hexanetricarboxylic acid and / or a salt thereof obtained by the method described in [1] or [2].

The present invention will be described in detail below. The electrolytic reduction reaction of acrylonitrile used in the present invention is generally an industrial method for producing adiponitrile, and the reaction solution obtained at this time is an organic compound having one or more nitrile groups in the molecule. There are various types of nitrile compounds. As the nitrile compound, for example, the main component is
Adiponitrile and unreacted acrylonitrile which are the main products of the electrolytic reduction reaction, by-products are by-products of the electrolytic reduction reaction, propionitrile, α-methylglutaronitrile, hydroxypropionitrile, succinonitrile,
Examples thereof include acrylonitrile trimers such as 1,3,6-tricyanohexane, 3-cyanomethyl-1,5-dicyanopentane, and high molecular weight polymers having acrylonitrile tetramers or more.

In the electrolytic reduction reaction of acrylonitrile, it is possible to obtain a non-negligible amount of an acrylonitrile trimer containing 1,3,6-tricyanohexane as a main component and a high molecular weight tetramer or higher. , Journal of
Organic Chemistry (J. Org. Che
m. ), 30 (5) 1351 (1965). Generally, an acrylonitrile trimer produced by an electrolytic reduction reaction of acrylonitrile has a main component of 1, 3, 6
-Tricyanohexane, 3 as the other isomer
-Cyanomethyl-1,5-dicyanopentane and the like are contained.

The term "trinitrile mixture" as used in the present invention means a mixture of the above-mentioned nitrile compounds containing 80% by mass or more of acrylonitrile trimer produced by the electrolytic reduction reaction of acrylonitrile. The trinitrile mixture is an electrolytic solution containing a nitrile compound containing adiponitrile as a main component obtained by electrolytic reduction reaction, for example, by distillation under reduced pressure, acrylonitrile or adiponitrile which is a low boiling point component for trinitrile, and the like, if necessary. It is possible to obtain a high boiling point component by removing a tetramer or higher polymer of acrylonitrile. Needless to say, a component having a low boiling point relative to the trinitrile component, which cannot be completely removed by the low boiling point removal, may remain in the liquid from which the low boiling point component has been removed.

The trinitrile mixture thus obtained contains 1,3,6-tricyanohexane in an amount of preferably 80% by mass or more, more preferably 85% by mass or more. 1, in the trinitrile mixture
When the content of 3,6-tricyanohexane is less than 80% by mass, the low-boiling point component described above, the high-boiling point component composed of a high molecular weight polymer of tetramer or more of acrylonitrile, and further in an amount that is difficult to quantify. Since a large amount of a coloring component is contained, the efficiency of decolorization due to the treatment with the oxidizing agent of the present invention after the hydrolysis reaction tends to decrease, or the treatment tends to take a long time.

The trinitrile mixture used in the present invention usually contains 3-cyanomethyl 1,5-dicyanopentane in the range of 0.01 to 10% by mass. In the present invention, the range is not limited, but when 1,3,6-hexanetricarboxylic acid is obtained with high purity and high yield, the content is preferably 0.01 to 5% by mass, It is preferably 0.01 to 3% by mass. The electrolytic reduction reaction of acrylonitrile will be described below.

The electrolytic reduction reaction of acrylonitrile is obtained by using a so-called diaphragm electrolyzer, which is made of acrylonitrile as a raw material and comprises a cathode chamber and an anode chamber in which a pair of cathode and anode are partitioned by a cation exchange membrane. It can also be obtained by using a single electrolytic cell without an ion exchange membrane. These electrolysis methods are disclosed, for example, in Japanese Patent Publication No. 45-24128, Japanese Patent Laid-Open No. 59-59888, and Japanese Patent Laid-Open No. 59-185788.
It is disclosed in Japanese Patent Publication No.

For example, electrolysis using a diaphragm electrolyzer is carried out as follows. Generally, a cathode having a high hydrogen overvoltage can be used as the cathode, and for example, lead, cadmium or an alloy containing these as the main components is preferably used. The anode is
A material having a high corrosion resistance such as lead, a lead alloy, or platinum is preferable, and lead or a lead alloy is preferably used. A cation exchange membrane is generally used as the diaphragm, and a sulfuric acid aqueous solution is used as the anolyte. During the reaction, the catholyte contains acrylonitrile, adiponitrile, trinitrile compounds, other by-products,
The emulsion is composed of water and a conductive supporting salt and is either an emulsion separated into an oil phase and an aqueous phase, or a uniform solution due to an excess of acrylonitrile.

The conductive support salt is represented by the following general formula ^{[NR 1 R 2 R 3 R} 4] + X - ( ^{wherein, R 1, R 2, R} 3 is an alkyl group having 1 to 5 carbon atoms,
R ⁴ is an alkyl group having 1 to 16 carbon atoms, X ⁻ is sulfuric acid, carbonic acid,
An anion such as alkylsulfuric acid or phosphoric acid, or a residue of an organic acid or an organic polyvalent acid) is preferably used.

The pH of the catholyte is usually in the range of 5-12. The electrolytic solution temperature in the battery case during the electrolytic reduction reaction is usually in the range of 40 to 60 ° C., and the current density is usually in the range of 5 to 50 amperes per 1 dm ² of the cathode surface. The distance between the cathode and the anode is usually 1 via a diaphragm.
˜20 mm, and the catholyte and anolyte are each passed through at a linear velocity of usually 0.1 to 10.0 m / sec.

When carrying out the electrolytic reduction reaction of acrylonitrile using a single electrolytic cell without an ion-exchange membrane as a diaphragm, lead, cadmium, mercury or an alloy containing at least one of these is preferably used as the cathode. As the anode, iron, nickel, or an alloy thereof is used. The electrolytic solution contains an alkali metal salt, the above quaternary ammonium salt and water as main components, and during the reaction, acrylonitrile, adiponitrile, trinitrile compounds and other by-products are present in an emulsion or uniformly dissolved state. . Examples of the cation of the alkali metal salt include lithium, sodium, potassium, rubidium, and the like, and the anion is an inorganic salt of phosphoric acid, boric acid, carbonic acid, sulfuric acid, or the residue of a polyvalent acid.

There is no limitation on the method for obtaining the trinitrile mixture from the electrolytic solution after completion of the reaction, and a general extraction method, distillation method or a combination thereof is used. That is, when the electrolytic solution after the electrolytic reduction reaction is an emulsion of oil-water, the low boiling point components such as unreacted acrylonitrile and by-product propionitrile are distilled off, and then the emulsion is broken to obtain two layers of oil-water. To separate. Inorganic substances and 4 in the water layer
The primary ammonium salt is distributed, and some water, low-boiling components, adiponitrile, trinitrile compounds, and other high-boiling components are distributed to the oil layer.

On the other hand, when the electrolytic solution after completion of the electrolytic reduction reaction is a uniform solution, for example, water and a non-aqueous organic solvent such as methylene chloride are added to the aqueous layer to form an inorganic salt or a quaternary ammonium salt. Is extracted, and the nitrile compound and the high boiling point component are extracted into the oil layer. In each case, a low-boiling-point component such as adiponitrile is removed from the low-boiling-point component with respect to the trinitrile component by, for example, a general distillation method to obtain a high-boiling-point component residue containing the trinitrile mixture. As described above, the high-boiling-point component residue containing the trinitrile component contains high-boiling substances of acrylonitrile tetramer or higher, including low-boiling-point components such as adiponitrile that were not removed by the low-boiling-point component removing operation. Be done.

In the present invention, in the composition of the high boiling residue, when the trinitrile mixture is less than 80% by mass, for example, a low boiling point component such as adiponitrile that has not been removed and a high boiling point component as necessary are added. Further distillation may be carried out once or more for the purpose of removal, and as a result, a trinitrile mixture having a trinitrile compound content of 80% by mass or more may be obtained. As a further distillation method, for example, a molecular distillation method or a thin film distillation method described in JP-A-62-270550 can be preferably used. In addition, if necessary, for the purpose of adjusting the content of the trinitrile compound to 80% by mass or more, the high boiling residue is extracted with a solvent that selectively dissolves the trinitrile compound, and then extracted in a subsequent step. The trinitrile mixture may be obtained by removing the solvent.

The 1,3,6-hexanetricarboxylic acid of the present invention is obtained by hydrolyzing the above-described trinitrile mixture with an alkali or an acid in the presence of water or alcohol. Next, the hydrolysis used in the present invention will be described. The above-mentioned alkali used for hydrolysis is a compound that exhibits alkalinity in an aqueous solution, and examples thereof include an alkali metal compound, an alkaline earth metal compound, and a nitrogen compound.

Examples of the alkali metal compound include:
Lithium hydroxide, sodium hydroxide, potassium hydroxide,
Alkali metal hydroxides such as rubidium hydroxide and cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, alkali metal carbonates such as rubidium carbonate and cesium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, hydrogen carbonate Alkali metal bicarbonates such as rubidium and cesium hydrogen carbonate, lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, alkali metal bicarbonates such as cesium bicarbonate, potassium butoxide, potassium ethoxide, potassium methoxide ,
Examples thereof include alkali metal alkoxides such as sodium butoxide, sodium ethoxide, sodium methoxide, lithium butoxide, lithium ethoxide, and lithium methoxide.

Examples of the alkaline earth metal compound include alkaline earth metal hydroxides such as beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide and radium hydroxide, beryllium carbonate and magnesium carbonate. , Alkaline earth metal carbonates such as calcium carbonate, strontium carbonate, barium carbonate and radium carbonate, beryllium hydrogen carbonate, magnesium hydrogen carbonate, calcium hydrogen carbonate, strontium hydrogen carbonate,
Alkaline earth metal bicarbonates such as barium hydrogen carbonate and rubidium hydrogen carbonate, beryllium bicarbonate, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate, barium bicarbonate, alkaline earth metal bicarbonates such as radium bicarbonate, etc. Is mentioned. Further, examples of the nitrogen compound include ammonia and various amine compounds.

These alkalis may be used alone,
Moreover, you may use 2 or more types. The acid used for the hydrolysis is a compound showing acidity in an aqueous solution, and examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, and various carboxylic acids and sulfonic acid organic acids. The concentration of the aqueous alkali solution when the alkali is used as an aqueous solution for hydrolysis is not limited in the present invention, but is usually in the range of 1.0 to 50 mass%. For example, when hydrolyzing at atmospheric pressure using sodium hydroxide as an alkali, it is usually 2.0
-40.0 mass%, preferably 10.0-30.0 mass%. If the concentration is less than 2.0% by mass, the reaction rate is slow, and if it exceeds 40.0% by mass, 1,3,6-
The solubility of tricyanohexane in water, which is a reaction field, becomes extremely low, and the hydrolysis rate tends to be remarkably reduced.

The equivalent ratio of 1,3,6-tricyanohexane and alkali is theoretically 1.00 equivalent or more as a base with respect to the nitrile group, but is preferable for the purpose of obtaining a sufficient reaction rate. Is in the range of 1.01 to 3.00 equivalents, and more preferably 1.03 to 2.00 equivalents. 3.00
When the amount exceeds the equivalent, a large amount of excess alkali remains in the reaction system, and a large amount of salt is produced as a by-product to remove the alkali. On the other hand, when hydrolyzing with an acid,
The concentration varies depending on the type of acid, but is usually 1 to 98.
It is in the mass% range. For example, in the case of hydrochloric acid, usually 2 to
It is in the range of 37% by mass, preferably 20 to 37% by mass. If the concentration is less than 2.0% by mass, the reaction rate tends to be slow, and if it exceeds 37% by mass, it is industrially difficult to obtain. In the case of sulfuric acid, it is usually in the range of 2 to 75% by mass, preferably 20 to 60% by mass. If it is less than 2% by mass, the reaction rate tends to be slow, and if it exceeds 75% by mass, an excessive amount of sulfuric acid is required to secure the amount of water required for hydrolysis.

The equivalent ratio of 1,3,6-tricyanohexane and acid is usually 1.
It is in the range of 01 to 5.0 equivalents, preferably 1.05 to 3.0 equivalents. When the equivalent ratio is less than 1.01, the reaction rate becomes slow and the reaction time becomes long. When it exceeds 5.0 equivalents, a large amount of excess acid used remains in the reaction system, and a large amount of salt is produced as a by-product to remove the acid. The reaction temperature is usually 50 to 250 for both alkali and acid.
C., preferably 80 to 140.degree. If the reaction temperature is less than 50 ° C, the reaction rate is slow, and if it exceeds 250 ° C, side reactions such as decomposition tend to occur simultaneously.

The reaction time is usually in the range of 1 to 200 hours. The pressure during the reaction is not limited, and the reaction may be performed under pressure, atmospheric pressure, or reduced pressure. The atmosphere during the reaction is not limited as long as it does not cause side reactions, and may be in the presence of an inert gas such as nitrogen or in the air.
Further, for example, when performing hydrolysis under atmospheric pressure, the reaction vessel has a cooling device for returning evaporated water into the system, or the liquid phase is bubbled with a gas such as nitrogen gas or air. However, it may have a device for expelling the dissolved ammonia out of the system. When it is carried out under a pressurized condition, it is desirable that the device is equipped with a device that allows the by-produced ammonia to escape to the outside of the system.

In the present invention, the hydrolysis may be carried out in a one-step reaction. For example, after hydrolysis with an alkali,
When an amide compound is present as an intermediate in the reaction system, it may be subsequently hydrolyzed using another alkali or acid. A feature of the present invention is to treat a solution of 1,3,6-hexanetricarboxylic acid and / or a salt thereof obtained by hydrolysis and a solvent with an oxidizing agent. The salt of 1,3,6-hexanetricarboxylic acid is
1,3,6-hexanetricarboxylic acid and sodium,
A salt with a metal ion such as an alkali metal such as potassium or an alkaline earth metal, an ammonium salt such as ammonia, or an amine salt with an amine compound.

As the solvent, below the boiling point of the solvent,
An inorganic substance or an organic substance which dissolves 1,3,6-hexanetricarboxylic acid and / or a salt thereof in an amount of 3% by mass or more and which is not chemically deteriorated by the oxidizing agent used can be preferably used. Among them, when water is used as the solvent, the solubility in 1,3,6-hexanetricarboxylic acid or its salt is high,
The hue tends to be remarkably improved, which is preferable. Further, in the present invention, after the hydrolysis, 1,3,6-hexanetricarboxylic acid and / or its salt is separated by performing drying or the like, dissolved again in a desired solvent, and treated with an oxidizing agent. Alternatively, the reaction liquid after hydrolysis may be directly treated with an oxidizing agent.

The oxidant used in the present invention is a compound which generally gives oxygen to an organic substance, a compound which deprives hydrogen of it, or a compound which increases the positive oxidation number. Specifically, permanganic acid and its salts such as potassium permanganate, chromic acid and its salts such as potassium chromate, nitric acid, copper nitrate, nitric acid and its salts such as ammonium nitrate, halogen such as chlorine,
Peracids such as peracetic acid and perbenzoic acid, and salts thereof, fuming sulfuric acid, sulfuric acids such as sulfurous acid and salts thereof, oxygen acids such as sodium hypochlorite and salts thereof, metal salts such as copper acetate and bismuth acetate, and dioxide. Metal oxides such as manganese, hydrogen peroxide, t-
Examples include peroxides such as butyl hydrobaroxide, oxygens such as air, oxygen and ozone.
One kind or two or more kinds may be used in separate steps or simultaneously.

The oxidizing agent used in the present invention is preferably one which has a high decolorizing efficiency after being treated with the oxidizing agent and can be easily removed from the trinitrile mixture after the treatment. As such an oxidizing agent, ozone is particularly preferable. preferable. In the present invention, the treatment with the oxidizing agent is achieved by directly contacting the oxidizing agent with the trinitrile mixture. Specifically, when the oxidizing agent used is a solid and is not dissolved in a solution consisting of 1,3,6-hexanetricarboxylic acid and / or its salt and a solvent, the oxidizing agent is added to the solution, For example, a method of dispersing by stirring or a method of filling a column with an oxidant and passing a solution is used. When the oxidizing agent used is a gas such as ozone,
It may be blown directly into the trinitrile mixture.

The amount of oxidizing agent used is 1,3,6-
There is no limitation as long as the coloration of hexanetricarboxylic acid and / or its salt can be significantly reduced, and usually 0.001-1 oxidizer per 100 parts by mass of the trinitrile mixture.
It is in the range of 00 parts by mass. There is no limitation on the time for the treatment with the oxidizing agent, and it is usually in the range of 1 minute to 500 hours. The temperature when treating with an oxidizing agent is also usually -20 ° C.
˜250 ° C., preferably 0 ° C. to 150 ° C., more preferably 10 ° C. to 100 ° C. When the temperature is high, particularly when it exceeds 250 ° C., 1,3,6-hexanetricarboxylic acid and / or its salt itself is decomposed, or the coloring component contained therein is modified, so that it tends to be further colored.
When the temperature is low, particularly below -20 ° C, the viscosity of the solution becomes high, or 1,3,6-hexanetricarboxylic acid and / or its salt precipitates, which tends to prolong the treatment time with the oxidizing agent. is there.

When the treatment with the oxidizing agent is carried out, the atmosphere and the pressure are not limited, and the treatment may be carried out under atmospheric pressure or high pressure by an inert gas such as air or nitrogen, or under reduced pressure. After the treatment with the oxidizing agent described above, the method of separating and removing the oxidizing agent and the solvent used is not limited, and by performing a known general method such as a filtration method, a drying method, or a reduced pressure method, It is possible to obtain 1,3,6-hexanetricarboxylic acid or a salt thereof with reduced coloration.

In the present invention, after treatment with an oxidizing agent, further purification treatment with a solid adsorbent such as activated carbon, activated alumina or ion exchange resin may be performed. Furthermore, after the treatment with an oxidizing agent, a crystallization operation may be performed for the purpose of increasing the purity of 1,3,6-hexanetricarboxylic acid and / or its salt. For example, after the treatment with an oxidizing agent, the solution is cooled using an appropriate method according to the magnitude of the change in solubility with temperature as a method of changing the concentration, and 1,3,6-hexanetricarboxylic acid and / Or the salt can be precipitated. As a method of changing the concentration, a supersaturated solution is prepared by distilling off the solvent from the solution by heating and evaporative concentration,
A precipitate of 1,3,6-hexanetricarboxylic acid and / or its salt may be obtained.

The solvent used for crystallization is preferably a solvent capable of dissolving 1,3,6-hexanetricarboxylic acid and / or a salt thereof in an amount of 3% by mass or more at a temperature not higher than the boiling point of the solvent. The solvent used during the treatment with the oxidizing agent may be used as it is. Above all, it is preferable to use water, an ether compound, an ester compound, or a ketone compound as a solvent because not only the purity is improved but also the hue is significantly improved. In addition, the solvent used during the treatment with the oxidizing agent may be used as it is.

Examples of the above ether compounds include dialkyl ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and tert-butyl methyl ether, and cyclic ethers such as tetrahydrofuran and 1,4-dioxane. As the above ester compound, dimethyl carbonate,
Examples thereof include carbonic acid esters such as diethyl carbonate, and aliphatic or aromatic alkyl esters such as ethyl acetate, methyl acetate and methyl benzoate. Examples of the above-mentioned ketone compounds include methyl ethyl ketone, methyl isobutyl ketone, and acetone. These solvents may be used alone or as a mixed solvent of two or more kinds.

In crystallization, water, dimethyl carbonate, ter
Since the solubility of 1,3,6-hexanetricarboxylic acid in a solvent such as t-butyl methyl ether, acetone, or tetrahydrofuran is 10% by mass or more at 25 ° C, a crystallization operation can be efficiently performed with a small amount of solvent. It is possible. Among them, water has an extremely high solubility in 1,3,6-hexanetricarboxylic acid and / or its salt at high temperature, and can be crystallized in a small amount. With respect to 3,6-hexanetricarboxylic acid and its salt, it has sufficient temperature dependence of solubility for performing crystallization operation, and the thermal stability of the obtained 1,3,6-hexanetricarboxylic acid and its salt is high. It is more preferable because it remarkably improves.

In the step of crystallizing 1,3,6-hexanetricarboxylic acid and / or its salt of the present invention, the solution may be agitated or left standing to precipitate a solid. Good. In the agitated state, the generation of crystal nuclei is promoted, and the crystallization speed tends to be improved. When performing in a stationary state, the crystallization rate tends to decrease as compared with the case where stirring is performed, but 1,3,6-hexanetricarboxylic acid and / or a salt thereof whose coloring is further reduced is used. Tends to get. Further, in the crystallization step, for example, 1,3,6-hexanetricarboxylic acid serving as a crystal nucleus and / or
Alternatively, it is possible to introduce seed crystals of its salt.

In the crystallization step, in order to prepare a uniform solution, it is possible to heat within a range not higher than the boiling point of the solvent used. During the crystallization operation, the solution can be cooled in a range where the solution does not solidify. For example, when 1,3,6-hexanetricarboxylic acid and / or its salt is crystallized using water as a solvent, the temperature for adjusting a uniform solution is not limited, but is usually 20 to 100 ° C. ,
The temperature for precipitating crystals is in the range of -10 to 50 ° C.

In the crystallization step, 1,3,6-precipitated
The method for filtering hexanetricarboxylic acid and / or its salt is not limited, and a suction filtration method using various filters, a pressure filtration method, a method using a centrifuge or the like can be used. When 1,3,6-hexanetricarboxylic acid is crystallized in a salt state, as a post-process, for example,
1,3,6-hexanetricarboxylic acid can be converted into a carboxylic acid by a cation exchange resin or a method of acidifying a solution with an inorganic acid such as sulfuric acid or hydrochloric acid, and then separating the generated inorganic salt. Obtainable.

The hue of the 1,3,6-hexanetricarboxylic acid and / or salt thereof obtained according to the present invention is remarkably improved. Preferably, water is used as a standard substance and an aqueous solution having a concentration of 0.1 g / ml is used. The lightness index L value measured at 25 ° C. is 98 or more, the a value of the chromaticness index is −2.0 to 2.0, and the b value is −2.0 to 3.0. The 1,3,6-hexanetricarboxylic acid and / or salt thereof obtained by the present invention has excellent thermal stability,
For example, color difference (ΔE) before and after holding at 80 ℃ for 18 hours
Is usually 2 or less.

The L value, the a value, and the b value are the JIS standard Z87.
According to the method of No. 22, the standard stimulus C is used with a spectrophotometer, and the tristimulus values X, Y, and Z values in the XYZ system are obtained by the transmission method in the wavelength range of 380 to 780 nm. Based on this value, specified by JIS standard Z8730,
The L value, the a value, and the b value are calculated by the Hunter color difference formula shown below. The L value is called the lightness index in the Hunter color difference formula, and the a and b values are called the chromaticness index in the Hunter color difference formula.

L = 10Y ^0.5 a = 17.5 (1.02X−Y) / Y ^0.5 b = 7.0 (Y−0.847Z) / Y ^{0.5 In} general, the upper limit of the lightness index L value is 100, It means that the hue of the substance to be measured increases the whiteness as the value increases and the blackness as the value decreases. The value a, which is a chromaticness index, is based on 0, and when the value becomes negative, the hue of the substance to be measured increases greenness, and when it becomes positive, it means that redness increases.
The b value, which is a chromaticness index, is based on 0, and when the numerical value is negative, it means that the hue of the substance to be measured is blue, and when it is positive, it is yellow.

That is, the low hue in the present invention means that the L value is close to 100 and the a value and the b value are close to 0. The color difference (ΔE) means, for example, from the above L, a, and b values obtained for 1,3,6-hexanetricarboxylic acid and / or a salt thereof before and after heat treatment, according to the following formula. It is a required value, and the closer it is to 0, the higher the thermal stability.

ΔE = √ (ΔL) ² + (Δa) ² + (Δb) ² (where ΔL value is the difference in lightness index L value before and after heat treatment,
The Δa value is the difference between the chromaticness index a values before and after the heat treatment, and the Δb value is the chromaticness index b before and after the heat treatment.
Represents the difference in value. ) The L value of 1,3,6-hexanetricarboxylic acid and / or its salt obtained in the present invention is preferably 98.0.
It is 0 or more, more preferably 99.00 or more, and most preferably 99.55 or more. Its a value is -2.0 to 2.0
, The range of -1.0 to 1.0 is preferable, and
The range of 0.5 to 0.5 is more preferable. The b value is in the range of -2.0 to 3.0, preferably in the range of -1.0 to 2.0, and more preferably in the range of -0.5 to 0.5.

In the present invention, 1,3,6-hexanetricarboxylic acid and / or its salt having extremely high thermal stability preferably has a ΔE value of 1.0 or less,
The following is more preferable. When the L value, a value and b value of 1,3,6-hexanetricarboxylic acid and / or its salt deviate from the above-mentioned preferable range, the coloration of tricarboxylic acid can be clearly confirmed by the naked eye, and The resulting product tends to exhibit a similar color when used in applications.

[0053]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples. The measuring method used in the present invention is as follows. [Measurement method of trinitrile] The purity of the trinitrile mixture is measured by gas chromatography and gel permeation chromatography (hereinafter, GP) by the following method.
C). The content ratio of the tetramer or higher polymer of acrylonitrile contained in the trinitrile mixture is determined by GPC. The hue is determined by UV measurement by the transmission method.

Each measurement is carried out under the following equipment and conditions. Gas chromatography measurement: Apparatus: Shimadzu Corporation GC-14B Column: GL Science Inc. Capillary column TC-1 (0.25 mmI.D., length 30 m) Carrier gas: He Detection: FID Column temperature condition: 200 from 120 ° C. to 20 ° C./min
After raising the temperature to ℃ and holding for 5 minutes, 2 at 10 ℃ / min
Sample dissolution solvent heated to 50 ° C. and held for 10 minutes: Acetone GPC measurement: 2.0 mg of each compound is dissolved in 2.0 g of tetrahydrofuran, filtered through a 0.5 μm filter, and developed and detected under the following conditions Analyze according to.

Measuring device: HLC-812 manufactured by Tosoh Corporation
0GPC detector: RI developing solution: Tetrahydrofuran developing solution flow rate: 1.0 ml / min Column: TSKgel (registered trademark) G manufactured by Tosoh Corporation
1 MH _HR- N and 2 G1000H _XL are installed in series Column temperature: 40 ° C. Method for measuring color of trinitrile: 0.40 g of trinitrile mixture is dissolved in 4 ml of diethylene glycol ether quantified with a Hall pipette,
UV measurement is performed by the following transmission method, and the L value, a value, and b value are obtained from the obtained tristimulus values according to the Hunter equation.

Measuring device: UV250 manufactured by Shimadzu Corporation
0PC sample cell: made of quartz, outer dimensions 12.4 mm x 12.4 m
m × height 45 mm, optical path length 10.0 mm diethylene glycol dimethyl ether: manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent measurement temperature: 25 ± 2 ° C. wavelength range: 380 to 780 nm wavelength feed rate: low speed range (about 140 nm / min) [ Method for Measuring Hexanetricarboxylic Acid] The purity of hexanetricarboxylic acid is determined by measurement by high performance liquid chromatography (hereinafter referred to as LC) by the following method. The hue is determined by UV measurement by the transmission method.

Each measurement is performed with the following equipment and conditions. LC measurement: Device: LC-10A manufactured by Tosoh Corp. Column: One SCR-101H manufactured by Shimadzu Corporation Detector: RI and UV (wavelength 210 nm) Developer: Perchloric acid pH 2.2-2. Range of 4 (25 ℃
PH in column) Column temperature: 40 ° C. Flow rate of developing solution: 1.0 ml / min Perchloric acid: Wako Pure Chemical Industries, Ltd. (60% concentration, for precision analysis) Measurement of hue of 1,3,6-hexanetricarboxylic acid Law:
Dissolve 0.40 g of tricarboxylic acid in 4 ml of di-distilled water determined by a whole pipette, and add U by the permeation method described below.
The V value is measured, and the L value, the a value, and the b value are obtained from the obtained tristimulus values according to the Hunter equation. Measuring device: UV2500PC made by Shimadzu Corporation Sample cell: made of quartz, external dimensions 12.4 mm x 12.4 m
m × height 45 mm, optical path length 10.0 mm Distilled water: manufactured by Wako Pure Chemical Industries, Ltd. Measurement temperature: 25 ± 2 ° C. Wavelength range: 380-780 nm Wavelength feed rate: Low speed range (about 140 nm / min)

[0058]

Example 1 Purification of 1,3,6-tricyanohexane A single electrolytic cell is a lead alloy with a current-carrying surface of 1 cm x 90 cm
As a cathode and carbon steel with the same current-carrying surface as an anode
The anode and cathode were kept at a distance of 2 mm. The electrolyte is 10
An emulsion is formed with 90 parts by weight of an oil phase and 90 parts by weight of an aqueous phase.
The composition of the water phase is about 2.0 mass of acrylonitrile.
%, K₂HPO_FourAbout 10% by mass, K₂B_FourO ₇About 3% by mass,
Ethyl tributyl ammonium ethyl sulfate 0.3 mass
%, And some adiponitrile, propionitrile and
An aqueous solution containing 1,3,6-tricyanohexane
The pH was adjusted to about 8 with phosphoric acid. Oil phase dissolves with water phase
It is in equilibrium and its composition is about 28 acrylonitrile.
% By mass, and about 62% by mass in adiponitrile.

This emulsion was subjected to a linear velocity of 1 m / s on the electrolytic surface.
Circulate and supply to a single electrolyzer to achieve ec, current density 2
Electrolysis was performed at 0 A / dm ² and 50 ° C. Simultaneously with the start of electrolysis, the aqueous phase of the emulsion sent from the electrolytic solution tank to the oil-water separator is kept at about 50 ° C. in the iminodiacetic acid type chelate resin (Lewatit ™ TP20).
7, Bayer Co., Ltd.) K ⁺ type 200CC 6CC / A
The treatment was started at the rate of H and circulated in the electrolytic solution tank.

At the same time, the oil phase was continuously withdrawn, acrylonitrile and water were continuously added so as to maintain the composition of the electrolytic solution, and ethyltributylammonium ethylsulfuric acid dissolved in the oil phase and withdrawn was added at any time. As a result of performing electrolysis for 2000 hours in this manner, the initial electrolysis voltage was 3.
Stable at 9 V, hydrogen contained in the generated gas was 0.16 vol% at the end of electrolysis, and the consumption rate of the cathode was 0.21 m.
g / AH, the consumption rate of the anode was 0.23 mg / AH, and there was no uneven anode corrosion product. 90% yield of adiponitrile based on consumed acrylonitrile,
The yield of 1,3,6-tricyanohexane was 7.5%.

Next, the oil phases obtained by the above electrolysis were collected and subjected to a water extraction treatment to remove acrylonitrile, propionitrile and water by distillation, and then to remove adiponitrile by vacuum distillation. The adiponitrile in this residual is 1
It was 1.5% by mass. The removal of adiponitrile from the residual liquid was carried out by batch distillation of a fraction containing adiponitrile as a main component using a vacuum jacketed distillation column having a diameter of 32 mmφ and an actual number of stages of 5 and the column top temperature at a vacuum degree of 2.0 mmHg. 12
The distillation residue (A) was obtained by first distilling the fraction from 0 to 210 ° C.

The distillation residue (A) was obtained by adding 4.0% by mass of adiponitrile and 84.% of 1,3,6-tricyanohexane.
It was a trinitrile mixture (B) containing 5% by mass, 5.0% by mass of 3-cyanomethyl-1,5-dicyanopentane and 6.5% by mass of a high molecular weight substance as a main component of a trinitrile compound. Isolation of the trinitrile mixture from this distillation residue (A) was carried out by Smith-type laboratory molecular distillation apparatus (Shinko Faudler Co., Ltd. type 2, electric heating area 0.032).
m ² , made of glass). Vacuum degree 0.1mmH
g, an outer wall surface heating temperature of 180 ° C., and a distillation residue (A) supply rate of 2 g / min. Supply amount 2000g,
The distillation amount was 1150 g, and the distillation residue was 900 g. The distillate is a yellow trinitrile mixture having a composition of 93.3% by mass of 1,3,6-tricyanohexane, 5.8% by mass of 3-cyanomethyl-1,5-dicyanopentane, and 0.9% by mass of adiponitrile. It was (C).

Trinitrile mixture (C) obtained above
As a result of measuring the hue, the L value was 98.2 and the a value was -1.
18, the b value was 3.68. The Hazen value of the trinitrile mixture was 400. A 300 ml eggplant-shaped flask was charged with 100 g of the trinitrile mixture (C) obtained above and 80 g of 30% hydrogen peroxide solution,
The treatment was carried out by stirring vigorously at room temperature for 100 hours. The liquid was an oil-water two-phase system. After stirring, the oil phase is separated,
The oil phase was dried over anhydrous magnesium sulfate. As a result of measuring the composition of the oil phase, there was no change from the used trinitrile mixture (C), and as a result of measuring the hue, the L value was 99.8, a.
Value is -0.20, b value is 0.11, Hazen value is 100.
It was below. This oil phase was a low hue trinitrile mixture that was almost colorless and transparent in appearance.

Preparation of Hydrolysis Reaction Solution In a 1 L glass four-necked flask equipped with a reflux condenser, 161.2 g of a mixture containing 1,3,6-tricyanohexane purified by the method of Example 1 as a main component. (1.
0 mol), 20% aqueous sodium hydroxide solution 780.0
g (3.9 mol) and a Teflon (registered trademark) -coated rotor were added, the mixture was heated to 110 ° C. using an oil bath, and reacted for 24 hours while stirring with a magnetic stirrer. Then, the reaction liquid was cooled to room temperature.

Treatment with Oxidizing Agent A 36% aqueous hydrochloric acid solution was added to the reaction solution obtained by the above hydrolysis to adjust the pH of the reaction solution to 1.2. Then, water and hydrochloric acid were removed by evaporation to obtain a light brown residue. Furthermore, extraction operation was performed on the solid by using 3 liters of dried t-butyl methyl ether to obtain t-
By removing butyl methyl ether, 212.1 g of a light brown solid (A) was obtained. LC measurement results,
The purity of 1,3,6-tricarboxylic acid was 92% by mass.

30.0 g of the obtained 1,3,6-hexanetricarboxylic acid was dissolved in 70.0 g of distilled water to prepare a uniform solution, and an ozone generator (manufactured by Nippon Ozone Co., Ltd., ON-
1-2 type), air having an ozone concentration of about 10 g / Nm ³ was blown at a flow rate of 30 Nl / hr for 5 hours in a temperature range of 25 ° C to 30 ° C while stirring the solution. The obtained aqueous solution was evaporated and further vacuum dried at 30 ° C. for 12 hours. As a result of analysis by LC, 1, 3,
There was no change in the purity of 6-tricarboxylic acid. As a result of measuring hue, L value is 99.86, a value is -0.66, b
The value was 1.62.

[0067]

Example 2 Example 1 was repeated except that 20.0 g of the light brown solid (A) obtained in Example 1 was dissolved in 80.0 g of distilled water and the treatment with ozone was carried out for 12 hours. By the same operation, 1,3,6-hexanetricarboxylic acid was obtained. As a result of LC analysis, there was no change in purity. As a result of measuring the hue, the L value was 99.8.
9, the a value was -0.43, and the b value was 0.87, and the hue was remarkably improved.

[0068]

Example 3 30.0 g of 1,3,6-hexanetricarboxylic acid obtained in Example 1 was dissolved in 30.0 g of distilled water, and this aqueous solution was gradually cooled using a thermostatic bath, and finally Crystallization was performed by cooling with stirring to 3 to 10 ° C. The resulting precipitate was separated by suction filtration using a membrane filter to obtain 17.8 g of 1,3,6-hexanetricarboxylic acid.

As a result of analysis by LC, the purity of 1,3,6-hexanetricarboxylic acid was 99.3%. As a result of measuring the hue, the L value is 99.99, the a value is 0.00,
The b value was -0.16. The obtained 1,3,6-hexanetricarboxylic acid was heat-treated in air at 80 ° C. for 18 hours, and the color difference (ΔE) before and after the treatment was measured. As a result, ΔE was 0.6, which was excellent. It had thermal stability.

[0070]

Comparative Example 1 Light brown solid (A) obtained in Example 1
As a result of measuring the hue of, the L value is 96.93 and the a value is 4.
The values of 15 and b were 8.25.

[0071]

Comparative Example 2 A 1 L glass four-necked flask equipped with a reflux condenser was charged with 1,3,6-tricyanohexane 20.
0 g (0.124 mol), 20% aqueous sodium hydroxide solution 130.0 g (0.707 mol), and a Teflon (registered trademark) -coated rotor were added, and the mixture was heated to reflux with stirring using a magnetic stirrer for 5 hours. It was made to react. After cooling the obtained reaction mixture, 68.7 g (0.70 mol) of concentrated sulfuric acid was added dropwise while cooling with ice. In this case, the temperature of the reaction mixture did not exceed 20 ° C. The reaction mixture was then washed three times, each with te.
It was extracted with 50 ml of rt-butyl methyl ether and the ether extract was dried over magnesium sulfate.

After distilling off the solvent using an evaporator, the residue was mixed with 35 ml of acetone and 50 m of cyclohexane.
It was introduced into 1 l of the mixed solvent with stirring, cooled, and the resulting precipitate was suction-filtered using a membrane filter. As a powder having a pale yellow to white hue, 19.6 g (yield 72.7%) of 1,3,6-hexanetricarboxylic acid was obtained. As a result of LC measurement, the purity was 92.9%.
As a result of measuring the hue, the L value is 96.70 and the a value is 1.7.
6 and b value were 4.07. Further, heat treatment was carried out in air at 80 ° C. for 18 hours, and the color difference before and after the treatment was measured. As a result, ΔE was 4.62.

[0073]

EFFECTS OF THE INVENTION According to the present invention, 1,3,6-hexanetricarboxylic acid and / or its purified high purity, low hue and excellent thermal stability, which are purified by a simple and industrial operation treatment, Salts can be produced. The obtained compound can be suitably used particularly as a composition such as a paint and as a raw material for various derivatives.

Claims (3)

[Claims] 1. A low boiling point component with respect to a trinitrile component contained in an electrolytic solution is removed from an electrolytic solution containing adiponitrile as a main component, which is obtained by an electrolytic reduction reaction of acrylonitrile, to obtain 1,3,6- A trinitrile mixture containing tricyanohexane as a main component was separated, and 1,3,6-tricyanohexane in the trinitrile mixture was hydrolyzed to obtain 1,3,6-hexanetricarboxylic acid and / or a salt thereof. A method for producing 1,3,6-hexanetricarboxylic acid and / or a salt thereof, which comprises treating a solution containing a solvent with an oxidizing agent. 2. The method for producing 1,3,6-hexanetricarboxylic acid and / or a salt thereof according to claim 1, wherein the oxidizing agent is ozone. 3. A 1,3,6-hexanetricarboxylic acid and / or a salt thereof obtained by the method according to claim 1.