JP4180525B2 - Low hue polyvalent carboxylic acid mixture and process for producing the same - Google Patents

Description

  The present invention relates to a low hue polyvalent carboxylic acid mixture and a method for producing the same. More specifically, the present invention relates to a polyvalent carboxylic acid mixture in which the content of 1,3,6-hexanetricarboxylic acid is 80% by mass or more, and 5.00 g of the polyvalent carboxylic acid mixture is added to 5.0 mL. The lightness index L value of the solution dissolved in dimethylformamide is 98 or more, the a value of the chromaticity index is -2.0 to 2.0, the b value is -2.0 to 3.0, and the polyvalent carboxylic acid A low-color polyvalent carboxylic acid mixture characterized in that the acid mixture contains 10 mass ppm to 5,000 mass ppm of an inorganic salt, and a polyvalent carboxylic acid containing 1,3,6-hexanetricarboxylic acid A method for producing a mixture, comprising (1) alkaline hydrolysis of a nitrile mixture mainly composed of 1,3,6-tricyanohexane to obtain an aqueous solution of the hydrolysis mixture, (2) pH of the aqueous solution After adjusting to the range of 3 to 13 to obtain an aqueous solution containing a mixture of polyvalent carboxylates, and subsequently treating with a solid adsorbent, (3) the polyvalent amount in the aqueous solution treated in step (2) A step of converting a mixture of carboxylates into a polyvalent carboxylic acid using an acid, thereby obtaining an aqueous solution containing the polyvalent carboxylic acid mixture; (4) a polyvalent containing an inorganic salt obtained in step (3); And a step of recovering the polyvalent carboxylic acid mixture from an aqueous solution of the carboxylic acid mixture by crystallization, and further comprising two or more in the molecule. A curable composition comprising a compound (a) having an epoxy group and a curing agent (b) containing the low-color polyvalent carboxylic acid mixture.

Since 1,3,6-hexanetricarboxylic acid is aliphatic and trifunctional, when used as a curing agent for a coating containing an epoxy group, as disclosed in Patent Document 1, the weather resistance, and A coating film having excellent scratch resistance and the like can be provided.
The curing reaction between the epoxy group and the carboxylic acid group is usually performed by heating to 120 to 180 ° C. in the air. For this reason, in order to obtain a low-color coating film, the thermal stability in the air is required. An excellent 1,3,6-hexanetricarboxylic acid mixture has been demanded, and 1,3,6-hexanetricarboxylic acid obtained by a known method has insufficient thermal stability.
In addition, 1,3,6-hexanetricarboxylic acid is mainly obtained by hydrolyzing 1,3,6-tricyanohexane. Conventionally, in order to obtain 1,3,6-hexanetricarboxylic acid having a low hue, Only a manufacturing method requiring a long process, a complicated process, or special equipment is disclosed.

For example, in Patent Document 2, 1,3,6-tricyanohexane is hydrolyzed with sodium hydroxide, then carboxylated with concentrated sulfuric acid, and the reaction mixture is completely dried, and the resulting residue is extracted with acetate. Later, crude 1,3,6-hexanetricarboxylic acid is obtained by distilling off the acetic ester, and 1,3,6-hexanetricarboxylic acid having a low hue is obtained by repeating crystallization.
In this case, a method of extracting the carboxylic acid with a solvent is used for the purpose of separating the inorganic salt and 1,3,6-hexanetricarboxylic acid. In the crystallization method, an extraction method is used because the separation efficiency between the carboxylic acid and the inorganic salt is insufficient. However, this method is not an advantageous method for using a large amount of the extraction solvent, and has a problem that the solvent remains in the product.

In Patent Document 3, 1,3,6-tricyanohexane is hydrolyzed with sodium hydroxide and then decolorized, followed by carboxylic acid sodium salt carboxylation by electrodialysis or ion exchange resin. Oxidation treatment is performed, and further crystallization is performed to obtain 1,3,6-hexanetricarboxylic acid having a low hue.
In this case, a step of carboxylic oxidation of the carboxylic acid sodium salt before crystallization is necessary, and there are disadvantages that a special facility is required and the number of steps is complicated.
International Publication No. WO02 / 066536 German Patent Application Publication No. 19367428 International Publication No. WO03 / 055836

  An object of the present invention is to provide a low-color polyvalent carboxylic acid mixture excellent in thermal stability under air, to provide a production method thereof, and to a compound having two or more epoxies in the molecule and the present invention. It is to provide a curable composition including a curing agent containing the polyvalent carboxylic acid mixture of the invention.

  As a result of intensive studies on a polyvalent carboxylic acid mixture containing 1,3,6-hexanetricarboxylic acid as a main component, the present inventors added an acid to a solution of the polyvalent carboxylate mixture to carry out carboxyl oxidation. A method for producing 1,3,6-hexanetricarboxylic acid selectively and crystallizing and recovering in a high yield while suppressing the precipitation of the inorganic salt during crystallization despite the presence of the produced inorganic salt Furthermore, the polyvalent carboxylic acid mixture containing a trace amount of inorganic salt obtained in this way was found to have improved thermal stability in air as compared with the conventional polyvalent carboxylic acid mixture. The present invention has been completed.

That is, the present invention is as follows.
(1) A polyvalent carboxylic acid mixture containing a polyvalent carboxylic acid having an amount of 1,3,6-hexanetricarboxylic acid of 80% by mass or more and an inorganic salt , wherein the polyvalent carboxylic acid mixture A solution in which 00 g is dissolved in 5.0 mL of dimethylformamide has a lightness index L value of 98 or more, a value of a chromomatics index of -2.0 to 2.0, and a b value of -2.0 to 3.0. And the polyvalent carboxylic acid mixture contains 10 mass ppm to 5,000 mass ppm of an inorganic salt.
(2) The low-hue polyvalent carboxylic acid mixture as described in 1 above, wherein the inorganic salt is NaCl.

(3) A method for producing a polyvalent carboxylic acid mixture containing the 1,3,6-hexanetricarboxylic acid according to (1) or (2 ) above and an inorganic salt ,
[1] A step of obtaining an aqueous solution of a hydrolysis mixture by alkaline hydrolysis of a nitrile mixture mainly composed of 1,3,6-tricyanohexane,
[2] A step of adjusting the pH of the aqueous solution to a range of 3 to 13, obtaining an aqueous solution containing a mixture of polyvalent carboxylates, and then treating with a solid adsorbent;
[3] A step of converting the mixture of the polyvalent carboxylates in the aqueous solution treated in the step [2] into polyvalent carboxylic acids using an acid, thereby obtaining an aqueous solution containing the polyvalent carboxylic acid mixture,
[4] A step of recovering the polyvalent carboxylic acid mixture from the aqueous solution of the polyvalent carboxylic acid mixture containing the inorganic salt obtained in the step [3] by crystallization. Method for producing an acid mixture.

(4) The above (3), wherein the alkali used for the alkali hydrolysis in the step [1] is sodium hydroxide, and the acid used for the conversion to the polyvalent carboxylic acid in the step [3] is hydrochloric acid. A process for producing the low-hue polyvalent carboxylic acid mixture as described.
(5) Use of the low-hue polyvalent carboxylic acid mixture according to (1) or (2) as a curing agent to be added to a compound having two or more epoxy groups in the molecule. is there.

Hereinafter, the present invention will be described in detail.
In the polyvalent carboxylic acid mixture of the present invention, the content of 1,3,6-hexanetricarboxylic acid (4-carboxy-1,8-octanedioic acid) is 80% by mass or more. In the polyvalent carboxylic acid mixture of the present invention, for the content of polyvalent carboxylic acid components other than 1,3,6-hexanetricarboxylic acid, if the total is less than 20% by mass, There is no particular limitation. In the present invention, the polyvalent carboxylic acid means an aliphatic carboxylic acid having 2 to 4 carboxyl groups in the molecule and having a molecular weight of 400 or less. Specific examples of the polyvalent carboxylic acid other than 1,3,6-tricarboxylic acid include adipic acid, 3-carboxymethyl-1,5-pentanedicarboxylic acid and the like.

  The composition of the polyvalent carboxylic acid mixture of the present invention is not particularly limited as long as the content of 1,3,6-hexanetricarboxylic acid is 80% by mass or more. When adjusting the coating material, the polyvalent carboxylic acid mixture is dissolved in a solvent at about 50 ° C. to about 130 ° C. or melt kneaded with a resin having a reactive functional group at about 90 ° C. to about 130 ° C. In consideration of the case and the case of dissolving in water, the content of 1,3,6-hexanetricarboxylic acid is 80% by mass or more, the content of adipic acid is 5% by mass or less, 3-carboxymethyl-1,5- It is preferable that the content rate of pentanedicarboxylic acid is 10 mass% or less. More preferably, the polycarboxylic acid mixture of the present invention has a 1,3,6-hexanetricarboxylic acid content of 95% by mass or more, an adipic acid content of 1% by mass or less, 3-carboxymethyl-1, The content of 5-pentanedicarboxylic acid is 4% by mass or less. Most preferably, the polycarboxylic acid mixture of the present invention has a content of 1,3,6-hexanetricarboxylic acid of 98% by mass or more.

In the polyvalent carboxylic acid mixture of the present invention, when the content of 1,3,6-hexanetricarboxylic acid is less than 80% by mass, the characteristics inherent to 1,3,6-hexanetricarboxylic acid are various in various applications. There is a tendency not to express. For example, when the content of 1,3,6-hexanetricarboxylic acid is less than 80% by mass and the amount of polycarboxylic acid having relatively low water solubility such as adipic acid is 10% by mass or more, Carboxylic acid mixtures tend not to dissolve uniformly in aqueous media such as water.
The content of each polycarboxylic acid such as 1,3,6-hexanetricarboxylic acid in the polycarboxylic acid mixture is determined from the peak area measured by the RI detector using liquid chromatography.

The polyvalent carboxylic acid mixture of the present invention contains 10 mass ppm to 5,000 mass ppm of an inorganic salt. Surprisingly, the thermal stability is improved by containing an inorganic salt. Preferably they are 10 mass ppm-3,000 mass ppm, More preferably, they are 10 mass ppm-1,500 mass ppm. When the content of the inorganic salt in the polyvalent carboxylic acid mixture is less than 10 ppm by mass, the effect of improving the thermal stability is not observed. When the content exceeds 5,000 ppm by mass, for example, when used in a paint, the coating is inorganic. Salt elution occurs, pinholes and depressions occur in the coating film, and the physical properties of the coating film deteriorate and the coating film becomes dirty over time.
The inorganic salt of the present invention is a compound which is generated in a form in which a cation and an anion neutralize electric charge and does not contain carbon. However, carbonates containing metal elements are also included.

The content of the inorganic salt is measured by ion chromatography, and can be controlled by the production method described below, for example, by the number of crystallizations. It is also preferable to add an inorganic salt to the obtained 1,3,6-hexanetricarboxylic acid. The addition method may be dry blending, or it is preferable to dissolve an inorganic salt in a solvent in advance and add it to a crystal or solution of 1,3,6-hexanetricarboxylic acid before drying.
The polycarboxylic acid mixture of the present invention preferably contains no organic solvent. When an organic solvent is included, a solvent-free paint such as a thermosetting powder paint using a curable main agent such as an acrylic resin containing an epoxy group and a polyvalent carboxylic acid mixture as a hardener is prepared. In such a case, it is not preferable because a solvent-free paint cannot be obtained.

The low hue polyvalent carboxylic acid mixture of the present invention is characterized by its hue. That is, a lightness index L value measured at 25 ° C. of a solution obtained by dissolving 1.00 g of the polyvalent carboxylic acid mixture of the present invention in 5.0 mL of dimethylformamide was 98 or more, and the a value of the chromaticness index was −2.0. -2.0, b value is -2.0-3.0.
The L value, a value, and b value used in the present invention are determined according to the method of JIS standard Z8722. That is, based on the tristimulus values X, Y, Z values in the XYZ system measured by the transmission method in the wavelength range of 380 to 780 nm using the standard light C by a spectrophotometer, the values specified in JIS standard Z8730 Calculated by the Hunter's color difference formula shown in the formula. The L value is the brightness index in the Hunter's color difference formula, and the a value and the b value are called the chromaticness index in the Hunter's 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 the formula, X, Y, and Z are tristimulus values in the XYZ system)

  Generally, the lightness index L value has an upper limit of 100, and as the numerical value increases, the whiteness increases in the hue of the substance to be measured, and as the numerical value decreases, the blackness increases. To do. The a value which is a chromaticness index means that when the numerical value is negative with respect to 0, the greenness increases in the hue of the substance to be measured, and when the numerical value is positive, the redness increases. The b value as a chromaticness index means that when the numerical value is negative, the blueness increases in the hue of the substance to be measured, and when the numerical value is positive, the yellowness increases. The closer the L value is to 100, the lower the hue is as the a and b values are 0.

The polyvalent carboxylic acid mixture of the present invention has a lightness index L value of 98 or more, preferably 99 or more, more preferably 99.5 or more. The a value is -2.0 to 2.0, preferably -1.0 to 1.0. The b value is in the range of -2.0 to 3.0, preferably -1.0 to 1.0, more preferably -0.5 to 0.5.
When the L value, the a value, and the b value are out of the above ranges, for example, when used in a paint, the coating tends to exhibit a color such as yellow or gray. In addition, when the L value, a value, and b value are out of the above ranges, the thermal stability of the polycarboxylic acid mixture itself is low, and the coloration (increase in b value) when heat-treated in air is remarkable. Become. Therefore, when such a polyvalent carboxylic acid mixture is used in a coating that is cured by heating, it tends to cause discoloration such as yellowing during curing.

  The thermal stability of the low-hue polycarboxylic acid mixture in the present invention is the change in the b value, which is the chromaticness index after heat treatment at 160 ° C. for 24 hours in air (acceleration test) (this is represented by Δb below). )), The thermal stability can be evaluated. The Δb value of the low hue polyvalent carboxylic acid of the present invention is usually 20 or less, preferably 18 or less. When the Δb value exceeds 20 in a heat treatment test at 160 ° C. for 24 hours, it is not preferable because the coating film containing a polyvalent carboxylic acid as a curing agent is colored to the extent that it can be visually observed during film formation.

  Next, a polycarboxylic acid mixture in which the content of 1,3,6-hexanetricarboxylic acid is 80% by mass or more, and 1.00 g of the polyvalent carboxylic acid mixture was dissolved in 5.0 mL of dimethylformamide. The lightness index L value of the solution is 98 or more, the a value of the chromaticity index is -2.0 to 2.0, the b value is -2.0 to 3.0, and the polyvalent carboxylic acid mixture is an inorganic salt A method for producing a low-hue polyvalent carboxylic acid mixture characterized by containing 10 mass ppm to 5,000 mass ppm.

  The method for producing a low-hue polyvalent carboxylic acid mixture of the present invention is a method for producing a polyvalent carboxylic acid containing 1,3,6-hexanetricarboxylic acid, which comprises (1) 1,3,6-tricyano. A step of obtaining an aqueous solution of the hydrolysis mixture by alkaline hydrolysis of a nitrile mixture containing hexane as a main component; (2) an aqueous solution containing a mixture of polyvalent carboxylates by adjusting the pH of the aqueous solution to a range of 3 to 13; And (3) converting the mixture of polyvalent carboxylates in the aqueous solution treated in step (2) into polyvalent carboxylic acids using an acid, A step of obtaining an aqueous solution containing the polyvalent carboxylic acid mixture by (4), a step of recovering the polyvalent carboxylic acid mixture by crystallization from an aqueous solution of the polyvalent carboxylic acid mixture containing the inorganic salt obtained in step (3), To include A polycarboxylic acid production method according to symptoms.

Next, process (1) is demonstrated.
In step (1), a nitrile mixture mainly composed of 1,3,6-tricyanohexane is hydrolyzed to obtain an aqueous solution of the hydrolysis reaction mixture.
1,3,6-tricyanohexane may be obtained as a by-product in the process of producing adiponitrile by the electrolytic dimerization reaction of acrylonitrile, or may be obtained by reacting acrylonitrile with adiponitrile. preferable. Usually, the nitrile mixture is highly colored.
In the electrolytic dimerization reaction of acrylonitrile, it is reported that a trinitrile compound and a high molecular weight compound which cannot be ignored are obtained, Journal of Organic Chemistry (J. Org. Chem.), 30 (5) 1351 ( 1965).

Generally, the trinitrile compound by-produced in the electrolytic dimerization reaction of acrylonitrile is mainly 1,3,6-tricyanohexane, and in addition, 3-cyanomethyl which is an isomer of 1,3,6-tricyanohexane. A small amount of -1,5, -dicyanopentane and the like is also produced.
From the above reaction mixture, for example, by removing a low-boiling component such as acrylonitrile and adiponitrile with respect to the trinitrile component and, if necessary, a high molecular weight product of acrylonitrile by distillation under reduced pressure, 1,3,6-tricia is obtained. The above nitrile mixture containing nohexane as a main component is obtained. In this nitrile mixture, a low boiling point component that has not been removed by the above operation may remain together with a high boiling point component.

  The total content of 1,3,6-tricyanohexane and 3-cyanomethyl-1,5-dicyanopentane in the nitrile mixture is preferably 80% by mass or more, more preferably 90% by mass or more. When the total content is less than 80% by mass, the above-mentioned low-boiling component, high molecular weight acrylonitrile, and coloring components that are difficult to measure are included in an amount exceeding 20% by mass in total. There is a possibility that the purity of the polyvalent carboxylic acid mixture obtained may be reduced and coloring may be caused. Furthermore, in order to improve the purity, it is necessary to go through various purification steps as a subsequent step, and as a result, the yield of the polyvalent carboxylic acid mixture tends to decrease and the production efficiency tends to decrease.

In the present invention, regarding the 1,3,6-tricyanohexane content of the nitrile mixture, 1,3,6-hexane in a mixture of polyvalent carboxylic acids or salts thereof obtained by hydrolysis of the nitrile mixture. It is preferable that 1,3,6-tricyanohexane is contained so that the content of tricarboxylic acid or a salt thereof is 80% by mass or more. The content of 1,3,6-tricyanohexane in the colored nitrile mixture is usually 80% by mass or more.
The nitrile mixture usually contains 3-cyanomethyl-1,5-dicyanopentane in the range of 0.01 to 10% by mass. In the present invention, for example, when 1,3,6-hexanetricarboxylic acid is obtained with a high purity of 97% by mass or more and a high yield of 70% or more in the crystallization step, 3-cyanomethyl-1 The content of 1,5-dicyanopentane is preferably 0.01 to 5% by mass, more preferably 0.01 to 3% by mass.

The trinitrile mixture used as a raw material of the mixture mainly composed of 1,3,6-hexanetricarboxylic acid of the present invention preferably has an adiponitrile content of 10% by mass or less, and a trinitrile compound content of 80% by mass. It is preferable that it is the above high purity trinitrile mixture.
The polycarboxylic acid mixture having a 1,3,6-hexanetricarboxylic acid content of 80% by mass or more according to the present invention is obtained by hydrolyzing the above trinitrile mixture in the presence of an alkali.

Next, the alkaline hydrolysis of the present invention will be described.
The alkali used for the hydrolysis is a compound that exhibits alkalinity in an aqueous solution, and examples thereof include alkali metal compounds, alkaline earth metal compounds, and nitrogen compounds.
Examples of the alkali metal compound include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate. Alkali metal carbonates such as lithium bicarbonate, sodium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, etc., lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, Alkali metal bicarbonate such as cesium bicarbonate, potassium butoxide, potassium ethoxide, potassium methoxide, sodium butoxide, sodium ethoxide, sodium methoxide, lithium butoxide, lithium ethoxide, lithium methoxide, etc. And alkali metal alkoxides.

  Alkaline earth metal compounds include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, radium hydroxide and other alkaline earth metal hydroxides, beryllium carbonate, magnesium carbonate, calcium carbonate Alkaline earth metal carbonates such as strontium carbonate, barium carbonate, radium carbonate, alkaline earth metal carbonates such as beryllium bicarbonate, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate, barium bicarbonate, rubidium bicarbonate And alkaline earth metal bicarbonates such as bicarbonate rim, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate, barium bicarbonate, and radium bicarbonate.

Examples of nitrogen compounds include ammonia and various amine compounds.
These alkalis may be used alone or in combination of two or more.
Particularly preferred is sodium hydroxide.
The solvent for the hydrolysis is preferably water alone or a mixed solvent of water and a solvent miscible with water. The mixing ratio of the water-miscible solvent and water in the mixed solvent is preferably 1/99 to 99/1 in terms of mass%. More preferable water-miscible solvents include alcohols such as methanol, ethanol and propanol, ketones such as acetone, methyl ethyl ketone and diethyl ketone, esters such as methyl formate, methyl acetate and ethyl acetate, ethyl ether, isopropyl ether, And ethers such as tetrahydrofuran and ethylene glycol monomethyl ether.

In the present invention, the concentration of the aqueous alkali solution when alkali is used in the aqueous medium for hydrolysis is usually preferably in the range of 1 to 50% by mass. This is because within this range, the reaction rate is high and the solubility of 1,3,6-tricyanohexane in water, which is the reaction field, can be sufficiently maintained.
The equivalent ratio of 1,3,6-tricyanohexane and alkali is theoretically 1 equivalent or more as a base with respect to the nitrile group, but is usually 1 to 3 for the purpose of obtaining a sufficient reaction rate. It is 0.0 equivalent, Preferably it is the range of 1.1-2.0 equivalent. When the amount exceeds 3.0 equivalents, excess alkali remains in the reaction system, and a large amount of salt as a by-product is generated in order to remove the alkali, making separation and purification complicated.

The concentration of the nitrile mixture in the hydrolysis solution during the hydrolysis is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and still more preferably 15 to 25% by mass. Within this range, the reaction rate is high and the possibility of side reactions such as decomposition is low.
The reaction temperature is usually in the range of 50 to 374 ° C, preferably 80 to 250 ° C. Within this range, the reaction rate is high and the possibility of side reactions such as decomposition is low.
The reaction time is usually preferably in the range of 0.1 to 200 hours. The total reaction time of the trinitrile raw material and the intermediate having an amide group intermediate obtained by hydration of the nitrile group or nitrile group is preferably 5% by mass or less based on the trinitrile raw material initially present. It is preferable to carry out the reaction until it becomes 1% by mass or less.

There is no restriction | limiting in particular in the pressure at the time of reaction, You may implement reaction under pressurization, atmospheric pressure, and also under pressure reduction.
The atmosphere during the reaction is preferably one that does not cause side reactions, for example, in the presence of an inert gas such as nitrogen or in the air. For example, when the hydrolysis is performed under atmospheric pressure or reduced pressure, the reaction vessel has a cooling device for returning evaporated water to the system, or the liquid phase is a gas such as nitrogen gas or air. An apparatus having an apparatus for bubbling and expelling dissolved ammonia out of the system is preferable. In the case of carrying out under a pressurized condition, it is desirable that the apparatus is equipped with a device that can escape by-produced ammonia out of the system.

After the reaction, the ammonia remaining in the solution is bubbled with a gas such as nitrogen gas or air under normal pressure, or the dissolved ammonia is expelled out of the system under reduced pressure to make the ammonia in the solution as much as possible. It is preferable to reduce the amount because impurities nitrogen compounds can be reduced in the product. The temperature for removing ammonia is preferably not higher than the boiling point of the liquid phase solvent.
In the present invention, the hydrolysis may be carried out in a one-step reaction. For example, when an amide compound is present as an intermediate in the reaction system after hydrolysis with an alkali, another alkali is subsequently used. Hydrolysis may be performed. Moreover, you may carry out by providing separately the process of performing hydrolysis, and the process of removing ammonia in a system with a distillation tower etc.

Next, process (2) is demonstrated.
In the present invention, the pH of the aqueous solution of the hydrolysis reaction mixture obtained by the hydrolysis in the step (1) (a mixture composed of a polyvalent carboxylic acid or a salt thereof) is adjusted to a range of 3 to 13 to adjust the pH. An aqueous solution containing a mixture of carboxylates (a small amount of a mixture of polyvalent carboxylic acids may coexist in this mixture) is obtained, and the aqueous solution is treated with a solid adsorbent in step (2). That is, since the aqueous solution of the hydrolysis reaction mixture is usually markedly colored, it is decolorized by treatment with a solid adsorbent.
The pH of the aqueous solution containing the polyvalent carboxylic acid mixture when the hydrolyzed solution is treated with the solid adsorbent is extremely important. The solution after alkaline hydrolysis usually exceeds pH 13, and even if it is treated with a solid adsorbent in this state, a low-color polyvalent carboxylic acid mixture cannot be obtained and the decolorization efficiency tends to decrease. is there. Therefore, it is extremely important to adjust the pH to the range of 3 to 13 and treat with the solid adsorbent.

The pH of the reaction solution during treatment with the solid adsorbent is preferably adjusted to a range of 4 to 11, more preferably a range of 5 to 9. There is a tendency for the adsorption efficiency to be maximized near neutrality.
As a method for adjusting pH, for example, a method of adding an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, an organic acid such as acetic acid or 1,3,6-hexanetricarboxylic acid, or a method of contacting with various ion exchange resins A method using electrodialysis is preferred.
Particularly preferred is a method of adding hydrochloric acid.

  The solid adsorbent refers to a substance that has no fluidity at 25 ° C. and the temperature at which the treatment is performed, maintains a solid shape, and has an interface that causes positive adsorption. Specifically, oxides and hydroxides of aluminum, iron, titanium, silicon, tin, etc., activated carbon, bentonite, activated clay, diatomaceous earth, zeolites, hydrotalcites, cation exchange resins, anion exchange resins Etc. Examples of the oxides and hydroxides of aluminum, iron, titanium, silicon, tin and the like include activated alumina, silica gel, titanium oxide, and the like. In the present invention, activated carbon is preferred because it tends to have high decolorization efficiency.

Activated carbon further has different decolorization efficiency depending on the derived raw material. As the derived raw material, wood, coal and coconut shell are good, preferably wood and coal, and more preferably activated carbon derived from wood.
These solid adsorbents may be used alone, or two or more kinds may be mixed and used simultaneously or separately. Moreover, various well-known things can be used for the shape, particle size, etc. of these solid adsorbents.
The contact time with the solid adsorbent is usually preferably 10 seconds to 10 hours, more preferably 1 minute to 5 hours, and even more preferably 5 minutes to 2 hours. Within this range, the decoloring effect is sufficient and the production efficiency is good.

The amount of the solid adsorbent used is usually preferably in the range of 0.01 to 100 parts by mass, more preferably in the range of 0.1 to 80 parts by mass with respect to 100 parts by mass of the polyvalent carboxylic acid mixture. More preferably, it is the range of 0.1-50 mass parts. If it is this range, sufficient decoloring effect will be acquired and the fall of the yield of the polyhydric carboxylic acid mixture by adsorption | suction can be suppressed.
Generally, the solid adsorbent is adsorbed on a solution containing a polyvalent carboxylic acid mixture and stirred, or the solid adsorbent is packed in a column and the solution is passed through. Various methods can be used.

The concentration of the polyvalent carboxylic acid mixture or the salt thereof in the aqueous solution during the treatment with the solid adsorbent is usually preferably 0.1 to 50% by mass, more preferably 1 to 40% by mass, and still more preferably 5 to 35%. It is the range of mass%. If the amount is less than 0.1% by mass, the amount of the treatment liquid increases, so that it is difficult to recover from the solution, and the yield decreases. In the range exceeding 50% by mass, a mixture comprising a polyvalent carboxylic acid and a salt thereof is deposited, and the adsorption of the colored material by the solid adsorbent becomes insufficient.
The treatment temperature with the solid adsorbent is a temperature range in which the solution of the mixture comprising the polyvalent carboxylic acid or a salt thereof does not solidify or further decompose. For example, activated carbon is used as the solid adsorbent and water is used as the aqueous medium. When used, the temperature range is usually from the lowest temperature at which solidification does not occur to 100 ° C. Preferably, it is the range of the minimum temperature which does not solidify-50 degreeC.
Any known method can be used as a method for separating and removing the used solid adsorbent after the treatment using the solid adsorbent described above, and a known general method such as a filtration method is performed. be able to.

Next, process (3) is demonstrated.
In the present invention, the mixture of the polyvalent carboxylates in the aqueous solution treated in the step (2) is converted into the polyvalent carboxylic acid using an acid in the step (3), thereby the polyvalent carboxylic acid mixture. And an aqueous solution containing an inorganic salt.
The pH of the solution containing the polyvalent carboxylic acid mixture or salt thereof in the step (3) depends on the concentration of the polyvalent carboxylic acid contained in the solution, but is usually adjusted to a pH of less than 4. Preferably it is less than 3, more preferably less than 2, most preferably less than 1.5.
The acid used for the carboxyl oxidation in the step (3) is an inorganic acid. In general, inorganic acids are preferred because they have high acid strength and tend to increase the yield of free carboxylic acid. Examples of the inorganic acid used include sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and the like, preferably hydrochloric acid. These acids may be used alone or in combination of two or more or separately added.
Particularly preferred is hydrochloric acid.

Generally, when recovering a crystalline carboxylic acid compound by crystallization from an aqueous solution of an inorganic salt and a crystalline carboxylic acid compound, the inorganic salt and the carboxylic acid compound are co-precipitated to selectively obtain the carboxylic acid compound. However, sodium chloride is less dependent on temperature than other inorganic salts, and its solubility is high and its solubility is high. Since the recovery efficiency of 1,6-hexanetricarboxylic acid is increased, hydrolysis is performed using sodium hydroxide in step (1), pH is adjusted using hydrochloric acid in step (2), and in step (3) Most preferred is the conversion to carboxylic acid using hydrochloric acid.
Although the process is complicated, the solution treated with the solid adsorbent is treated with various cation exchange resins, treated with other methods such as an electrodialyzer, and then treated with acid, or added with an inorganic acid. Then, it may be converted into a polyvalent carboxylic acid in combination with various ion exchange resins or other methods such as electrodialysis.
The temperature at which the acid is added is preferably in a range where no side reaction occurs, and is usually in the range of 0 ° C to 100 ° C, more preferably in the range of 0 ° C to 60 ° C.

  Regarding the method for recovering the polyvalent carboxylic acid mixture in high yield from the aqueous solution of the polyvalent carboxylic acid mixture containing the inorganic salt obtained in the step (3), the conventionally disclosed methods include: The mixed solution is once dried and extracted with an organic solvent such as acetone, ethyl acetate, ethylene glycol dimethyl ether, tert-butyl methyl ether using a known method such as stirring or Soxhlet, and then the solvent is removed. And the like to obtain a polyvalent carboxylic acid mixture. This method requires a large amount of extraction solvent, and requires a purification step by crystallization after distilling the extraction solvent from the obtained extract to dryness. Have the problem of being bad.

According to the present invention, as described in the following step (4), it was found that the separation of the carboxylic acid and the inorganic salt is efficiently performed.
Next, process (4) is demonstrated.
The temperature at which crystallization is carried out can be carried out as long as it is not less than the minimum temperature at which the solution does not solidify, but is usually in the range from the minimum temperature at which the solution does not solidify to 30 ° C., preferably the minimum at which solidification does not occur. The temperature is in the range of 10 ° C, more preferably in the range of 5 ° C from the lowest temperature at which solidification does not occur.
Regarding the presence or absence of agitation when crystallization is performed, the crystallization operation while stirring can stabilize the particle size of the polyvalent carboxylic acid crystal obtained and can suppress crystal precipitation on the wall surface. It is preferable at such points.

Prior to crystallization, the solution concentration of the inorganic salt and polyvalent carboxylic acid mixture may be adjusted. Concentration and dilution are not limited as long as crystals are precipitated and the crystals can be separated.
When crystallization is performed, it is also possible to add a seed crystal to shorten the time for starting the crystal.
Crystals generated by crystallization can be recovered by filtration. As the filtration method, it is preferable to use a general method such as pressure filtration, vacuum filtration, centrifugal separation, and pressing. When filtration is performed, the adhesion of the mother liquor leads to the inclusion of the inorganic salt in the polyvalent carboxylic acid mixture after the crystallization product is dried. Therefore, it is preferable to perform filtration by a filtration method that can control the amount of adhesion of the mother liquor.
The crystallization step is usually a method in which the polyvalent carboxylic acid mixture is recovered by a general method such as extraction and then purified by crystallization as a separate step. In the analyzing step, the polyvalent carboxylic acid mixture is selectively recovered from the aqueous solution in which the inorganic salt and the polyvalent carboxylic acid mixture coexist, and at the same time, the purity of 1,3,6-hexanetricarboxylic acid in the polyvalent carboxylic acid mixture It is a manufacturing method with high production efficiency because the process can be simplified.

The content of the inorganic salt of the present invention can be adjusted by the number of crystallizations. Usually, the crystal of tricarboxylic acid obtained in step (4) contains an inorganic salt at about 5,000 to 30,000 mass ppm, and the content is about 200 to 3, by recrystallization. It becomes 000 mass ppm, and the content rate becomes about 10-300 mass ppm by performing crystallization further.
Further, the content of the inorganic salt can be reduced and adjusted by washing the crystal obtained by crystallization with a solvent. It is preferable to adjust the content of the inorganic salt by combining crystallization and solvent washing.
As the solvent, methyl acetate, ethyl acetate, and methyl isobutyl ketone are preferable, and as a washing method, for example, after separating the crystals by pressure filtration or centrifugation, the crystals are dispersed in an organic solvent such as ethyl acetate, and then again. It is possible to separate the crystals by filtration or to wash the crystals by a method such as replacing the mother liquor with the solvent after the crystals are separated. When washing, it is preferable to wash the crystals without drying the crystals, and the washing temperature is preferably controlled at a temperature at which the crystals are hardly dissolved.

The polyvalent carboxylic acid mixture of the present invention can be suitably used as a curing agent for a compound having two or more epoxy groups in the molecule. That is, in this invention, the curable composition containing the hardening | curing agent (b) containing the compound (a) which has 2 or more epoxy in a molecule | numerator, and the low hue polyhydric carboxylic acid mixture of this invention is provided. Is done.
The curable composition of the present invention has a high curing rate, is excellent in physical and mechanical properties of the resulting cured product, and can reduce discoloration of the cured product during heat curing.
In the present invention, the curing agent (b) means a compound capable of reacting with an epoxy group to form a crosslinked structure, and specifically, the polyvalent carboxylic acid mixture of the present invention may be used alone, You may use with another hardening | curing agent and a mixture. Other curing agents other than the polyvalent carboxylic acid mixture of the present invention include carboxylic acid compounds, acid anhydrides, amine compounds, and the like.

Examples of the carboxylic acid compound include aliphatic, aromatic, and alicyclic carboxylic acids containing two or more carboxyl groups in the molecule, and specifically include suberic acid, sebacic acid, azelaic acid, decanedicarboxylic acid. Acid, cyclohexanedicarboxylic acid, isophthalic acid, trimellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 1,2,4-butanetricarboxylic acid, a copolymer containing acrylic acid or methacrylic acid, acid-terminated polyester resin, Examples include acid-terminated polyamide resins.
Examples of the acid anhydride include maleic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, and the like.

As the amine compound, a compound having one or more amino groups in the molecule can be used, and examples thereof include ethylenediamine, diethylenetetralin, triethylenetetramine, and hexamethylenediamine.
In the curing agent (b) used in the curable composition of the present invention, the content of the polycarboxylic acid mixture of the present invention is preferably 10% by mass or more for the purpose of improving the crosslinking density of the resulting cured product. More preferably, it is 50 mass% or more.
Further, in the low hue polyvalent carboxylic acid mixture of the present invention used in the curable composition, the 1,3,6-hexanetricarboxylic acid contained is preferably 90% by mass or more, more preferably 95% by mass, particularly Preferably it is 98 mass% or more.

Hereinafter, the epoxy compound (a) used in the curable composition of the present invention will be described.
The epoxy group means a three-membered ring structure composed of carbon-carbon-oxygen. The carbon-carbon part may be a part of a linear or branched carbon structure, or may be a part of a carbon hydrogen structure in which a cyclic structure such as a 5-membered ring or a 6-membered ring is formed. These carbon-hydrogen structures may be bonded to a functional group such as a halogen such as fluorine, chlorine or bromine, or a hydroxyl group. Furthermore, an alkyl group such as a methyl group or a halogen may be bonded to the carbon atom forming the epoxy group. Examples of these epoxy groups include glycidyl groups and alicyclic epoxy groups, with glycidyl groups being preferred.

The epoxy group compound (a) is not particularly limited as long as it has two or more epoxy groups in the molecule. The molecular weight of the epoxy group compound (a) is not particularly limited, and may be any of a low molecular weight compound having a number average molecular weight of less than 1,000 and a high molecular weight compound having a molecular weight of 1,000 or more, and further a molecular weight distribution. It may be a polymer having
Examples of the epoxy compound (a) used in the curable composition of the present invention include a compound having an epoxy group such as a glycidyl group via an ether bond or an ester bond, a compound having an epoxy group via a nitrogen atom, an epoxy And group-containing polymers. These epoxy compounds (a) may be used alone or in a mixture of two or more depending on various uses and desired physical properties.

  Examples of the epoxy compound having a glycidyl group via an ether bond include ethylene glycol diglycidyl ether, propanediol diglycidyl ether, butanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, and diglycidyl ether derived from hydroquinone. And diglycidyl ether derived from bisphenol A, diglycidyl ether derived from tetramethyldihydroxybiphenyl, glycidyl ether compounds derived from phenol novolac resin and cresol novolac resin, and halogen compounds thereof. Among these, diglycidyl ether derived from bisphenol A can be used in a wide variety of applications in liquid or solid form depending on the molecular weight, and is generally easily available as “bisphenol A type epoxy resin”. Yes, it can be used suitably.

  Low molecular weight compounds having glycidyl groups via ester bonds include diglycidyl phthalate, diglycidyl maleate, diglycidyl terephthalate, diglycidyl isophthalate, diglycidyl naphthalenedicarboxylate, diglycidyl biphenyldicarboxylate, diglycidyl succinate, diglycidyl fumarate, glutar Diglycidyl acid, diglycidyl adipate, diglycidyl suberate, diglycidyl sebacate, diglycidyl decanedicarboxylate, diglycidyl cyclohexanedicarboxylate, triglycidyl trimellitic acid, glycidyl esters derived from dimer acid, and halides and oligomers thereof It is done. Compounds with glycidyl group bonded to nitrogen atom include triglycidyl isocyanurate, tetraglycidyldiaminodiphenylmethane, triglycidyldiaminophenol, glycidylaniline, diglycidyltoluidine, tetraglycidylmetaxylenediamine, tetraglycidylhexamethylenediamine, tetraglycidylbis Examples thereof include aminomethylcyclohexane, glycidyl compounds derived from hydantoin compounds, and halides and oligomers thereof. Examples of the alicyclic epoxy compound include bis (3,4-epoxycyclohexyl) adipate, bis (3,4-epoxycyclohexyl) terephthalate, 3,4-epoxycyclohexyl-3,4-epoxycyclohexanecarboxylate, 3,4- Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) oxalate, bis (3,4-epoxy-6-methylcyclohexyl) adipate, bis (3,4-epoxycyclohexylmethyl) Examples include pimelate and vinylcyclohexene dioxide.

Examples of the epoxy group-containing polymer include a polymer having an epoxy group such as a glycidyl group in the terminal, side chain, or branched chain, and having a weight average molecular weight of 800 to 5,000,000. Examples thereof include a resin having a polyester skeleton, a resin having a polyamide skeleton, and a homopolymer or copolymer of a monomer having a polysynthetic unsaturated double bond.
When the curable composition of the present invention is used, for example, in coating applications, the above-mentioned epoxy group-containing polymer can be suitably used, and among them, a homopolymer or copolymer of monomers having a polymerizable unsaturated double bond. A coalescence can be used suitably. This polymer is one or two or more kinds of monomers having an epoxy group, or a copolymer of a monomer having an epoxy group and a monomer having no epoxy group.

  Examples of the monomer having a polymerizable unsaturated double bond and an epoxy group at the same time include, for example, glycidyl ester or methyl glycidyl ester of (meth) acrylic acid such as glycidyl (meth) acrylate and β-methylglycidyl (meth) acrylate. And glycidyl ether and methyl glycidyl ether of allyl alcohol, N-glycidyl acrylic acid amide, glycidyl vinyl sulfonate and the like. In the present invention, (meth) acrylic acid means acrylic acid or methacrylic acid.

  Examples of the monomer having a polymerizable unsaturated double bond and having no epoxy group and capable of being copolymerized with the monomer having the epoxy group include, for example, (meth) acrylic acid esters and hydroxyl groups. Examples thereof include acrylic monomers such as (meth) acrylic acid esters and other monomers. Examples of esters of (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, ( Isobutyl acrylate, tert-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylic acid 2-ethyloctyl, benzyl (meth) acrylate, dodecyl (meth) acrylate, phenyl (meth) acrylate, stearyl (meth) acrylate, and the like. Examples of the (meth) acrylic acid ester having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxycyclohexyl (meth) acrylate. Other monomers that can be copolymerized with a monomer having an epoxy group include hydrocarbons such as styrene, α-methylstyrene, vinyltoluene, nitriles such as acrylonitrile and methacrylonitrile, acrylamide, methacrylamide, Amides such as methylolacrylamide, esters such as dialkyl esters of fumaric acid and dialkyl esters of itaconic acid, vinyl oxazolines, vinyl acetate, vinyl propionate, lauryl vinyl ether, halogen-containing vinyl monomers, silicon-containing vinyl monomers It is done.

In the curable composition of the invention, as the epoxy compound (a), the glycidyl group-containing acrylic resin is excellent in durability such as weather resistance and abrasion resistance of the resulting cured product, and is particularly used in the field of paints used outdoors. Can be preferably used. In the present invention, the “glycidyl group-containing acrylic resin” means an acrylic resin containing a glycidyl group. Glycidyl group-containing acrylic resins such as methyl methacrylate and copolymers based on glycidyl methacrylate, and copolymers based on methyl methacrylate, glycidyl methacrylate, and styrene can be particularly preferably used. .
The glycidyl group-containing polymer has a number average molecular weight in the range of 1,000 to 1,000,000, preferably 1,000 to 30,000, depending on the resin composition, for example, when used for coatings. More preferably, the range is 1,500 to 20,000. If it is this range, the performance of a cured coating film is good, and when creating a coating material using a solvent, possibility that a viscosity will become high too much can be avoided.

The number average molecular weight is measured by gel permeation chromatography (GPC) using polystyrene as a standard substance, and is a relative value with respect to the standard substance.
The epoxy equivalent of the epoxy compound (a) used in the present invention is usually preferably in the range of 85 to 10,000 g / equivalent. For example, an epoxy compound composed of glycidyl ether derived from bisphenol A is generally in the range of 180 to 5,000 g / equivalent. Moreover, the epoxy equivalent of the glycidyl group containing acrylic resin used by this invention is the range of 200-5,000 g / equivalent normally, Most preferably, it is the range of 300-2,500 g / equivalent.

In the curable composition of the present invention, the compounding ratio of the epoxy compound (a) and the curing agent (b) described above is such that the curing agent (b) which can react with the epoxy group with respect to the epoxy group of the epoxy compound (a). ) Is preferably used in an amount of 0.5 to 3 equivalents, particularly preferably in the range of 0.7 to 1.5 equivalents. Within this equivalence ratio range, the gel fraction of the resulting cured product is sufficient and the mechanical properties are also satisfied.
The curable composition of the present invention is obtained by mixing the curing agent (b) and the epoxy compound (a). For example, the curing agent (b) and the epoxy compound (a) are heated at room temperature or heated. Produced by a method of kneading in a state, a method of dispersing or dissolving both in water or an organic solvent, and a method of removing the water or organic solvent used after dispersing or dissolving both in water or an organic solvent it can.

Further, the curing agent (b) to be used may be a mixture of the polyvalent carboxylic acid mixture of the present invention and other curing agent in advance, or the polyvalent carboxylic acid mixture and the other curing agent may be separately epoxied. You may mix with a compound.
The curable composition of the present invention includes a curing accelerator, a reactive diluent, a filler and a reinforcing agent, an antimony trioxide, a halogenated compound, a flame retardant such as aluminum hydroxide, a dye and a pigment according to various uses. Coloring agents, mold release agents and flow control agents, plasticizers, antioxidants, heat stabilizers, UV absorbers, light stabilizers, antifoaming agents, leveling agents, titanium dioxide, solvents, etc. can be added. The application amount can be arbitrarily applied within a range not impairing the effects of the present invention. As a method of blending these additives, a conventional blending method can be applied.

  Examples of the curing accelerator include imidazoles such as 2-ethyl-4-methylimidazole, 2-methylimidazole, and 1-benzyl-2-methylimidazole, dimethylcyclohexylamine, benzyldimethylamine, and tris (diaminomethyl) phenol. Tertiary amines, diazabicycloalkenes such as 1,8-diazabicyclo (5,4,0) undecene-7 and salts thereof, organometallic compounds such as zinc octylate, tin octylate and aluminum acetylacetone complex, Organophosphorus compounds such as triphenylphosphine and triphenyl phosphite, boron trifluoride, boron trifluoride diethyl ether complex, boron trifluoride piperidine complex, boron compounds such as triphenylporate, zinc chloride, chloride Metal halogen such as stannic Compounds, quaternary ammonium compounds, alkali metal alcoholates such as sodium alcoholate of 2,4-dihydroxy-3-hydroxymethylpentane, anacardic acid and its salts, phenols such as cardol, cardanol, phenol, cresol, etc. Can be mentioned.

Examples of the reactive diluent include butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, and glycidyl methacrylate.
Examples of fillers and reinforcing agents include coal tar, woven fabric, glass fiber, asbestos fiber, carbon fiber, boron fiber, aromatic polyamide fiber, mineral silicate, mica, quartz powder, aluminum hydroxide, bentonite, kaolin, and silicate aerogel. And metal powders such as aluminum powder and iron.
Examples of the release agent and flow control agent include silicone, aerosil, colloidal hydrous aluminum silicate, wax, stearate, calcium carbonate, talc and the like.

Examples of plasticizers include pine oil, low-viscosity liquid polymer, rubbery material, tar, polysulfide, urethane prepolymer, polyol, diethyl phthalate, dibutyl phthalate, polymer of epicudrhydrin, dioctyl phthalate, dioctyl adipate, tri Examples include cresyl phosphate.
Examples of the ultraviolet absorber include “Tinubin (trade name)” (manufactured by Ciba Specialty Chemicals, Switzerland). Examples of sterically hindered amine light stabilizers and phenolic antioxidants include “Tinuvin 144 (trade name)”, “Irganox 1010 (trade name)” or “Irgaphos P-EPQ (trade name)” (whichever Ciba Specialty Chemicals Co., Ltd.). As a method of blending these additives, a conventional blending method can be applied.

As pigments, azo pigments, copper phthalocyanine pigments, basic dye lakes, acid dye lakes, mordant dye pigments, construction dye pigments, quinacridone pigments, dioxazine pigments, carbon black, chromate, ferrocyan compounds, Examples include extender pigments such as titanium oxide, selenium sulfide compound, silicate, carbonate, phosphate, metal powder, gypsum, alumina white, clay, silica, talc, calcium silicate, and magnesium carbonate.
Other additives include dryers such as cobalt naphthenate, anti-skinning agents such as methoxyphenol and cyclohexaneoxime, thickeners such as highly polymerized linseed oil, organic bentonite and silica, side-effect inhibitors such as benzoin, and flow control. An agent etc. can be used conveniently.

The curable composition of the present invention can be cured by energy such as heat and ultraviolet rays. For example, when cured by heating, it is usually room temperature to 250 ° C., desirably 80 to 200 ° C., more desirably 80 to 160. Curing can be performed in the range of ° C. The curing time largely depends on the composition, but is usually in the range of several seconds to 200 hours.
The curable composition of the present invention can be suitably used for paints, electrical insulating materials, adhesives, matrix resins for composite materials, adhesives, sealing agents, and the like. When the curable composition of the present invention is used for an electrical insulating material, specifically, it can be used as a casting molding agent, a semiconductor sealing agent, an insulating paint, and a laminate.

The curable crude composition of the present invention can be particularly preferably used as a paint, and in particular, can be used in the form of powder paint, water-dispersed slurry paint, water-based paint, emulsion paint, and solvent-based paint. For example, when the epoxy compound (a) is a glycidyl group-containing acrylic resin, the curing rate is fast and the durability such as weather resistance is excellent. It can be preferably used as a top coat for machines, road materials and automobiles.
The resulting coating has excellent durability such as weather resistance, and can be used as protective material for metal, concrete, wood, plastic materials, cans, automobiles, road materials (guardrails, etc.), exterior wall materials for houses, exteriors, It can be suitably used for ships or construction materials.

Hereinafter, the present invention will be described specifically by way of examples.
The measuring method used in the present invention is as follows.
[Measurement method of trinitrile]
The purity of the trinitrile mixture is determined by measurement by gas chromatography and measurement by gel permeation chromatography (hereinafter referred to as GPC). The content of the high molecular weight polymer of tetramer or higher of acrylonitrile contained in the trinitrile mixture is determined by GPC. The hue is obtained from UV measurement by a transmission method. Each measurement is performed with the following apparatus and conditions.

<Gas chromatography measurement method>
Equipment: GC-14B manufactured by Shimadzu Corporation
Column: GL Science Inc. Capillary column
TC-1 (0.25 mm ID, length 30 m)
Carrier gas: He
Detection: FID
Column temperature condition: 120 ° C. to 200 ° C. at 20 ° C./min,
After holding for 5 minutes, the temperature was raised to 250 ° C. at 10 ° C./min and held for 10 minutes.
Sample dissolution solvent: acetone

<GPC measurement method>
Analysis is performed by dissolving 2.0 mg of each compound with 2.0 g of tetrahydrofuran, filtering through a 0.5 μm filter, and developing and detecting under the following conditions.
Measuring device: HLC-8120GPC manufactured by Tosoh Corporation
Detector: RI
Developing solution: Tetrahydrofuran Developing solution flow rate: 1.0 mL / min
Column: One TSKgel (trademark) GMH _HR- N manufactured by Tosoh Corporation and two G1000H _XL installed in series Column temperature: 40 ° C

<Method of measuring hue>
Dissolve 0.400 g of the trinitrile mixture in 4.0 mL of diethylene glycol ether measured with a whole pipette, perform UV measurement by the following transmission method, and obtain the L value, a value, and b according to Hunter's equation from the tristimulus values obtained. Find the value.
Lightness index: 100 (white) <L value <0 (black)
Chromanetics index a value: + (red) ← 0 →-(green)
Chromanetics index b value: + (yellow) ← 0 →-(blue)
Measuring device: UV2500PC manufactured by Shimadzu Corporation
Sample cell: Quartz, outer dimensions 12.4 mm × 12.4 mm × height 45 mm,
Optical path length 10.0mm
Diethylene glycol dimethyl ether: Wako Pure Chemicals special grade reagent Measurement temperature: 25 ± 2 ° C
Wavelength range: 380 to 780 nm
Wavelength feed rate: Low speed range (140 nm / min)

[Measurement method of hexanetricarboxylic acid]
The content of 1,3,6-hexanetricarboxylic acid is determined by measurement by high performance liquid chromatography (hereinafter referred to as LC). The hue is obtained from UV measurement by a transmission method. Each measurement is performed with the following apparatus and conditions.

<Method of measuring hue>
After 1.00 g of the polyvalent carboxylic acid mixture is made up to 5.0 mL with dimethylformamide and dissolved, UV measurement is performed by the transmission method described below. The L value, a value, and b value are obtained from the obtained tristimulus values according to Hunter's equation.
Lightness index: 100 (white) <L value <0 (black)
Chromanetics index a Value: + (red) ← 0 →-(green)
Chromanetics index b value: + (yellow) ← 0 →-(blue)
The thermal stability was evaluated by the Δb value, which is the increase in the chromatic index b value after heating at 160 ° C. for 24 hours in air. The smaller this value, the better the thermal stability.
Measuring device: UV2500PC manufactured by Shimadzu Corporation
Sample cell: Quartz, outer dimensions 12.4 mm x 12.4 mm x height 45 mm,
Optical path length 10.0mm
Distilled water: Wako Pure Chemical Industries, Ltd.
Measurement temperature: 25 ± 2 ° C
Wavelength range: 380 to 780 nm
Wavelength feed rate: Low speed range (140 nm / min)

<LC measurement>
0.020 g of the polyvalent carboxylic acid mixture is dissolved in 2.0 mL of distilled water, and the measurement is performed by the following method.
Apparatus: LC-10A manufactured by Shimadzu Corporation
Column: One SCR-101H manufactured by Shimadzu Corporation Detector: RI
Developing solution: pH 2.2 to 2.4 with perchloric acid (pH at 25 ° C.)
Column temperature: 40 ° C
Developing solution flow rate: 1.0 mL / min
Perchloric acid: Wako Pure Chemical Industries, Ltd. 60% concentration (for precision analysis)

<Na amount measurement method>
The polyvalent carboxylic acid mixture was dissolved in distilled water and measured by ion chromatography using a cation exchange resin packed column to measure the amount of Na in the solution. An aqueous NaOH solution with a known amount of Na was measured in advance to prepare a calibration curve, and the amount of Na in the polyvalent carboxylic acid mixture was calculated from the calibration curve.
Measuring device: 8020 series manufactured by Tosoh Corp. Detector: CM-8020 conductivity meter manufactured by Tosoh Corp. Developing solution: 2 mmol / L nitric acid aqueous solution Column: IC-Cation (4.6 mm (ID) x 50 mm (L) manufactured by Tosoh Corp. )
Column temperature: 40 ° C
Flow rate: 0.5 mL / min
Sample injection volume: 10 μL

<Cl content measurement method>
The polyvalent carboxylic acid mixture was dissolved in distilled water and measured by ion chromatography using a column packed with an anion exchange resin to measure the amount of Cl in the solution. A NaCl aqueous solution with a known amount of Cl was measured to prepare a calibration curve, and the amount of Cl in the polyvalent carboxylic acid mixture was calculated from the calibration curve.
Measuring apparatus: 8020 series manufactured by Tosoh Corporation Detector: CM-8020 conductivity meter manufactured by Tosoh Corporation Developing solution: 5-500 mM NaOH aqueous solution gradient Column: IonPacAS11 (2 mm x 250 mm) manufactured by Nippon Dionex
Column temperature: 40 ° C
Flow rate: 0.5 mL / min
Sample injection volume: 10 μL

[Method of measuring epoxy equivalent of acrylic copolymer having epoxy group]
A 100 mL Erlenmeyer flask was accurately weighed 0.1 to 1.0 g of the sample (dried product), and a stir bar was added. Subsequently, 50 mL of n-propyl alcohol, 4 mL of benzyl alcohol, and 3 mL of 0.04% bromothymol blue indicator were added, a reflux condenser was attached, and the mixture was refluxed with stirring on a stirrer with a hot plate. Further, under reflux, 3.0 g of potassium iodide was dissolved in 10 mL of water and added (blue color).
The solution was titrated with 1N or 0.2N hydrochloric acid under reflux, and when the yellow color was maintained for 30 seconds, the epoxy equivalent was determined by the following formula.
Epoxy equivalent (g / eq) = sample weight (g) × 1000 / (hydrochloric acid normality (N) × drop measurement (ml))

[Method for evaluating cured coating film of thermosetting paint]
<Smoothness and gloss of coating film>
The surface of the coating film was evaluated with the naked eye, and a good one was marked with ◯, a slightly inferior one with Δ, and a defect with x.
<Ericsen value measurement method>
After the coated plate is placed in a constant temperature and humidity chamber (20 ° C, 75% RH) for 1 hour, the coated film is attached to the Eriksen tester with the coating plate facing outwards, and a punch with a radius of curvature of 10 mm is defined from the back side of the test plate. Extrude at a speed of 0.1 mm per second for as much distance as possible with as much speed as possible. Immediately after extruding whether the protruding coating film had cracks or peeling, it was examined with the naked eye and expressed as the maximum number of mm when there was no abnormality in the coating film.

<Pencil hardness measurement method>
The test was conducted according to the pencil scratch value tester method of JIS K5400.
<Adhesion measurement method>
The adhesion state of the coating film was visually observed by a cross-cut tape method according to JIS standard K5400. Actually, 100 squares of 1 mm × 1 mm were prepared with a cutter knife for the coating film, and “the number of squares not peeled off with the tape / 100 squares” was used as the evaluation result.

[Production Example 1]
Electrolytic dimerization reaction was carried out according to Japanese Patent Application Publication No. 61-21316. In the single electrolytic cell, a lead alloy having an energization surface of 1 cm × 90 cm was used as a cathode, carbon steel having the same energization surface was used as an anode, and the anode and the cathode were kept at an interval of 2 mm. The electrolytic solution forms an emulsion with 10 parts by volume of an oil phase and 90 parts by volume of an aqueous phase, and the composition of the aqueous phase is 2.0% by mass of acrylonitrile, 10% by mass of K ₂ HPO ₄ , and K ₂ B ₄ O. _{7 An} aqueous solution containing 3% by mass, 0.3% by mass of ethyltributylammonium ethyl sulfate, and some adiponitrile, propionitrile, and 1,3,6-tricyanohexane. The pH was adjusted to 8 with phosphoric acid. did. The oil phase was in equilibrium with the aqueous phase, and its composition was 28% by mass of acrylonitrile and 62% by mass of adiponitrile.

This emulsion was circulated and supplied to a single electrolytic cell so that the linear velocity was 1 m / sec on the electrolysis surface, and electrolysis was performed at a current density of 20 A / dm ² and 50 ° C. Simultaneously with the start of electrolysis, the aqueous phase of the emulsion sent from the electrolyte tank to the oil / water separator was iminodiacetic acid type chelate resin (Lewatit TP207 (trademark) K ⁺ type, kept at 50 ° C.). The treatment was started at a rate of 6 CC / AH at 200 CC and circulated to the electrolyte tank.
At the same time, the oil phase was continuously extracted, acrylonitrile and water were continuously added so as to maintain the electrolyte solution composition, and ethyltributylammonium ethylsulfuric acid extracted after being dissolved in the oil phase was added as needed.

As a result of conducting electrolysis for 2000 hours in this way, the initial electrolysis voltage was stable at 3.9 V, the hydrogen contained in the generated gas was 0.16 vol% at the end of electrolysis, and the consumption rate of the cathode was 0.8. The anode consumption rate was 21 mg / AH, 0.23 mg / AH, and there was no uneven anode corrosion. The yield of adiponitrile based on the consumed acrylonitrile was 90%, and the yield of 1,3,6-tricyanohexane was 7.5%.
Next, the oil phase obtained by the above electrolysis was collected, subjected to water extraction treatment, acrylonitrile, propionitrile and water were distilled off, and then adiponitrile was removed by vacuum distillation. The adiponitrile in this residue was 11.5% by mass.

The removal of adiponitrile from this residual liquid was carried out by batch distillation of a fraction containing adiponitrile as a main component using a vacuum-coated distillation column having a diameter of 32 mmφ and 5 actual stages, and a top temperature of 120 mm at a vacuum of 2.0 mmHg. The distillation residue (A) was obtained by carrying out the first distill cut of the fraction to -210 degreeC.
This distillation residue (A) is composed of 4.0% by mass of adiponitrile, 84.5% by mass of 1,3,6-tricyanohexane, 5.0% by mass of 3-cyanomethyl-1,5-dicyanopentane, and a high molecular weight product. It was a trinitrile mixture (B) mainly composed of 6.5% by mass of a trinitrile compound.

Isolation of trinitriles mixture from the distillation residue (A), molecular distillation apparatus for Smith type laboratory (Shinko Pfaudler Co., type 2, heating area 0.032 ^2, glass) was used. The operation was performed at a vacuum degree of 0.2 mmHg, an outer wall surface heating temperature of 230 ° C., and a distillation residue (A) supply rate of 2 g / min. The supply amount was 2000 g, the distillate amount was 1480 g, and the distillation residue was 500 g. The distillate is a yellow trinitrile mixture having a composition of 93.1% by weight of 1,3,6-tricyanohexane, 5.7% by weight of 3-cyanomethyl-1,5-dicyanopentane, and 1.2% by weight of adiponitrile. (C).
As a result of measuring the hue of the trinitrile mixture (C) obtained above, the L value was 98.2, the a value was -0.57, and the b value was 1.80.
As 1,3,6-tricyanohexane used in the following Examples and Comparative Examples, a trinitrile mixture (C) obtained by repeatedly performing the same operation as described above was used.

161 g (1.0 mol) of the trinitrile mixture (C) obtained in Production Example 1 was added to 780 g of a 20% aqueous sodium hydroxide solution (3 mol) in a four-necked flask with a stirrer having an internal volume of 1 liter equipped with a reflux condenser. .9 mol) and hydrolyzed by heating under reflux for 24 hours. It cooled to room temperature and obtained 893g of hydrolysis reaction liquid (D).
893 g of the hydrolysis reaction solution (D) was cooled with ice water to adjust the pH to 7.0 with 36% HCl so that the solution temperature did not exceed 20 ° C., and 987 g of a neutralization reaction solution (E) was obtained. Next, 28.2 g of activated carbon (Shirakaba A-2 (trademark), manufactured by Takeda Pharmaceutical Company Limited) was added to the neutralization reaction solution (E), and the mixture was stirred at room temperature for 1 hour. The activated carbon was removed by filtration to obtain 986 g of a transparent decolorization reaction solution (F). When the activated carbon was filtered, the activated carbon was washed with 30 g of distilled water in order to replace the liquid in the activated carbon. Next, 36% hydrochloric acid is added while cooling with ice water so that the liquid temperature does not exceed 20 ° C., and the pH is lowered to pH 1 below the inflection point of pH at which the carboxylate is carboxylated, and 1262 g of the carboxylated solution (G) is obtained. Obtained.

  1262 g of the obtained carboxylated solution (G) was charged into a 1.7 L crystallization tank with a refrigerant circulation jacket, and the internal temperature was lowered to −3 ° C. while stirring with a Teflon (registered trademark) -coated stirring blade. Was precipitated. The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 20 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 10%. After preliminary drying at 25 ° C. for 5 hours with a vacuum dryer, 178 g of polyvalent carboxylic acid mixture crystals (H) for the first crystallization were obtained by continuing drying at 40 ° C. for 20 hours (yield: 81.81). 7%).

  When the obtained polyvalent carboxylic acid mixture (H) was measured by liquid chromatography, 1,3,6-hexanetricarboxylic acid detected within a retention time of 10.00 to 11.20 min with respect to the entire area in RI detection And the total area of other polycarboxylic acid peaks was 98.6%. When the amount of Na and Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 6,880 ppm, the amount of Cl was 10,850 ppm, and the total inorganic salt content was 17,730 ppm. there were. When the hue was measured, the L value was 99.74, the a value was -0.08, and the b value was 0.50. When the thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 19.8. The hue was low and the thermal stability was excellent.

Subsequently, 175 g of the polycarboxylic acid mixture (H) was charged into a 1.0 L crystallization tank with a refrigerant circulation jacket, 372 g of distilled water was added, and the internal temperature was 40 ° C. while stirring with a Teflon (registered trademark) coated stirring blade. Dissolution was performed. After becoming uniform, the internal temperature was lowered to −2 ° C. to precipitate crystals while stirring for 5 hours.
The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 20 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 8%. After preliminary drying at 25 ° C. for 5 hours by a vacuum dryer, 130 g of polyvalent carboxylic acid mixture crystals (I) for the second crystallization were obtained by continuing drying at 40 ° C. for 20 hours (yield 74. 3%).

  When the obtained polycarboxylic acid mixture (I) was measured by liquid chromatography, the total area of 1,3,6-hexanetricarboxylic acid and other polycarboxylic acid peaks was 99.7%. When the amount of Na and Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 290 ppm, the amount of Cl was 450 ppm, and the total content of inorganic salt was 740 ppm. When the hue was measured, the L value was 99.70, the a value was 0.02, and the b value was 0.19. When the thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 16.5. The hue was low and the thermal stability was excellent.

A hydrolyzed liquid (D) was produced in the same manner as in Example 1, and a polyvalent carboxylic acid mixture crystal was obtained in the same manner as in Example 1 except that the pH during the activated carbon treatment was 13.
The yield of the polyvalent carboxylic acid mixture crystal (J) in the first crystallization is 177 g (yield: 81.2%). When measured by liquid chromatography, 1,3,6-hexanetricarboxylic acid and other The total area of the polyvalent carboxylic acid peak was 98.6%. When the amount of Na and Cl were quantified by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 7,160 ppm, the amount of Cl was 11,830 ppm, and the total inorganic salt content was 18,990 ppm. there were. The hue L value was 99.68, the a value was -0.08, and the b value was 0.72, indicating a low hue.

  The yield of the polyvalent carboxylic acid mixture crystal (K) in the second crystallization was 128 g (yield 72.3%), which was measured by liquid chromatography and found to be 1,3,6-hexanetricarboxylic acid and other crystals. The total area of the polyvalent carboxylic acid peak was 99.7%. When the amount of Na and the amount of Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 300 ppm, the amount of Cl was 460 ppm, and the total content of inorganic salts was 760 ppm. The hue L value was 99.62, the a value was -0.02, and the b value was 0.38. Furthermore, when a thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 18.4. The hue was low and the thermal stability was excellent.

A hydrolyzed liquid (D) was prepared in the same manner as in Example 1, and the first crystallization of the polyvalent carboxylic acid mixture crystallized in the same manner as in Example 1 except that the pH during the activated carbon treatment was set to 3. And the second crystallization of polyvalent carboxylic acid mixture crystals was obtained.
The yield of the polyvalent carboxylic acid mixture crystal (L) in the first crystallization was 169 g (yield 77.5%). When measured by liquid chromatography, 1,3,6-hexanetricarboxylic acid and other The total area of the polyvalent carboxylic acid peak was 98.5%. When the amount of Na and Cl were quantified by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 7,030 ppm, the amount of Cl was 10,760 ppm, and the total inorganic salt content was 17,790 ppm. there were. The L value of the hue was 99.70, the a value was -0.09, and the b value was 0.59.

  The yield of the polyvalent carboxylic acid mixture crystal (M) in the second crystallization was 123 g (72.8%), and it was determined by liquid chromatography to be 1,3,6-hexanetricarboxylic acid and other polyvalent carboxylic acids. The total area of the carboxylic acid peak was 99.6%. When the amount of Na and the amount of Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 290 ppm, the amount of Cl was 460 ppm, and the total inorganic salt content was 750 ppm. The L value of the hue was 99.68, the a value was -0.01, the b value was 0.26, and a thermal stability test was further conducted at 160 ° C. for 24 hours. The Δb value was 17.7. . The hue was low and the thermal stability was excellent.

1260 g of the carboxylic acid solution (G) was prepared in the same manner as in Example 1, and the obtained carboxylic acid solution (G) was charged into a 1.7 L crystallization tank with a refrigerant circulation jacket, and a Teflon (registered trademark) coated stirring blade The internal temperature was lowered to −3 ° C. while stirring for 1 hour to precipitate crystals while stirring for 16 hours. The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 10 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 14%.
The crystals were dispersed in ethyl acetate cooled to −2 ° C. in an undried state, and filtered through a PTFE filter having a pore size of 1 μm. The crystals were preliminarily dried at 20 ° C. for 3 hours under vacuum, and then dried at 40 ° C. for 24 hours. Vacuum drying was performed for hours. The weight change at the end of drying was 0.001 g / hr or less.

  The yield of the obtained first crystallized polycarboxylic acid mixture crystal (N) was 172 g (yield: 78.9%). When measured by liquid chromatography, 1,3,6-hexanetricarboxylic acid and The total area of other polycarboxylic acid peaks was 99.1%. When the amount of Na and Cl were quantified by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 65 ppm, the amount of Cl was 100 ppm, and the total content of inorganic salt was 165 ppm. The L value of the hue was 99.85, the a value was -0.01, and the b value was 0.23.

  In the second crystallization, 168 g of the polyvalent carboxylic acid mixture (N) was charged into a 1.0 L crystallization tank with a refrigerant circulation jacket, 357 g of distilled water was added, and the internal temperature was adjusted to 40 with stirring with a Teflon (registered trademark) coated stirring blade. Dissolution was performed at ° C. After becoming uniform, the internal temperature was lowered to −2 ° C. to precipitate crystals while stirring for 5 hours. The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 20 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 7%. Preliminary drying was performed at 25 ° C. for 5 hours with a vacuum dryer, and then continued drying at 40 ° C. for 20 hours to obtain 126 g of polyvalent carboxylic acid mixture crystals (O) for the second crystallization (yield: 75. 0%).

  When the obtained polyvalent carboxylic acid mixture (O) was measured by liquid chromatography, the total area of 1,3,6-hexanetricarboxylic acid and other polyvalent carboxylic acid peaks was 99.9%. When the amount of Na and Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 4.5 ppm, the amount of Cl was 7.0 ppm, and the total content of inorganic salt was 11.5 ppm. there were. The L value of the hue was 99.93, the a value was 0.00, and the b value was 0.06. Further, when a thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 15.2. The hue was low and the thermal stability was excellent.

[Comparative Example 1]
In the same manner as in Example 1, 1262 g of a pH 1 carboxylated solution (G) was obtained. Next, the carboxylated solution (G) was transferred to a 1 L eggplant flask, and water was removed in several portions by a rotary evaporator at about 90 ° C. under reduced pressure, and concentrated. The residue was taken out into a vat and dried at 50 ° C. under reduced pressure until water was completely removed. Next, the residue was transferred to a 10 L container, 4500 ml of tert-butyl methyl ether was added, and the mixture was stirred for 1 hour. After extraction with a solvent, the salt was removed by filtration. 50 g anhydrous magnesium sulfate was added to the filtrate and stirred for 1 hour to dry the extract. The precipitate was removed by filtration, and the solvent was evaporated from the filtrate at 50 ° C. under a reduced pressure using a rotary evaporator. The concentrated residue was dried under reduced pressure at 40 ° C. to obtain 202 g of a polycarboxylic acid mixture (P).

  Charge 202 g of polycarboxylic acid mixture (P) into a 1.7 L crystallization tank with a refrigerant circulation jacket, add 606 g of distilled water, and dissolve at an internal temperature of 40 ° C. while stirring with a Teflon (registered trademark) coated stirring blade. It was. After becoming uniform, the internal temperature was lowered to −3 ° C. to precipitate crystals while stirring for 16 hours. The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 20 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 8%. After preliminary drying at 25 ° C. for 5 hours with a vacuum dryer, drying was continued at 40 ° C. for 20 hours to obtain 129 g of polyvalent carboxylic acid mixture crystals (Q) for the first crystallization. The process was complicated and the yield was as low as 59.2%.

When the obtained polyvalent carboxylic acid mixture (Q) was measured by liquid chromatography, the total area of 1,3,6-hexanetricarboxylic acid and other polyvalent carboxylic acid peaks was 99.5%. When the amount of Na and Cl were measured by ion chromatography, the amount of Na in the polyvalent carboxylic acid mixture was 3.0 ppm, the amount of Cl was 4.6 ppm, and the total inorganic salt content was 7.6 ppm. there were. The L value of the hue was 99.78, the a value was -0.07, and the b value was 0.33.
When the thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 30.6. The thermal stability was insufficient.

  Subsequently, 126 g of the polyvalent carboxylic acid mixture (Q) was charged into a 1.0 L crystallization tank with a refrigerant circulation jacket, 268 g of distilled water was added, and the internal temperature was 40 ° C. while stirring with a Teflon (registered trademark) coated stirring blade. Dissolution was performed. After becoming uniform, the internal temperature was lowered to −2 ° C. to precipitate crystals while stirring for 5 hours. The precipitated crystals were filtered with a PTFE filter having a pore size of 1 μm, put into a 200 mesh filter cloth, and centrifuged at 5,000 rpm for 20 minutes with a basket size 130Φ centrifuge to obtain crystals. At this time, the water content was 8%. After preliminary drying at 25 ° C. for 5 hours by a vacuum dryer, 94 g of polyvalent carboxylic acid mixture crystals (R) for the second crystallization was obtained by continuing drying at 40 ° C. for 20 hours (yield 74. 6%).

  When the obtained polyvalent carboxylic acid mixture (R) was measured by liquid chromatography, the total area of 1,3,6-hexanetricarboxylic acid and other polyvalent carboxylic acid peaks was 99.9%. When the amount of Na and Cl were measured by ion chromatography, Na and Cl were not detected in the polyvalent carboxylic acid mixture. The L value of the hue was 99.81, the a value was -0.09, and the b value was 0.12. Furthermore, when a thermal stability test was conducted at 160 ° C. for 24 hours, the Δb value was 25.5. The thermal stability was insufficient.

A monomer and a polymerization initiator comprising 20 parts by weight of methyl methacrylate, 10 parts by weight of n-butyl acrylate, 55 parts by weight of glycidyl methacrylate, 15 parts by weight of styrene, and 8.4 parts by weight of azobisisobutyronitrile. The mixture was dropped into 100 parts by weight of toluene at 110 ° C. over about 30 minutes, and polymerized for 5 hours from the end of dropping while maintaining the internal temperature at 110 ° C. The resulting solution was reduced in pressure to remove the solvent, and an epoxy group-containing polymer having a number average molecular weight of 3,580 and an epoxy equivalent of 241 g / equivalent was obtained.
The first and second crystallization products obtained in Example 1 were blended at a weight ratio of 1: 4 and used as a curing agent. The content of inorganic salt was 4,100 ppm. 232 g of 1,3,6-hexanetricarboxylic acid was added to a 3 L dissolution tank with a cooling jacket containing 1000 g of acetone while stirring the acetone with a propeller type stirring blade, and stirred for 3 hours.

Next, 770 g of an epoxy group-containing polymer was added at a speed within a range where stirring is possible while stirring, and stirring was further performed for 3 hours to dissolve the polymer. Water was circulated through the cooling jacket so that the solution temperature did not exceed 30 ° C. during dissolution.
The obtained paint was applied with a spray gun so that the thickness of the coating film after baking on the SPCC steel sheet was about 70 μm. The obtained coated object was air-dried at 30 ° C. for 20 hours and then baked at 140 ° C. for 30 minutes. The smoothness and gloss of the obtained coating film were good, the adhesiveness was 100/100, the Erichsen value was 8 mm, and the pencil hardness was 2H. Even when the obtained coating film was allowed to stand in a thermostatic bath at 60 ° C. and 95% humidity for 14 days, the smoothness and gloss of the coating film were not visually changed, and generation of rust and the like was not observed.

[Comparative Example 2]
The same procedure as in Example 5 was performed except that the same weight blend of the first crystallization product and the second crystallization product in Example 1 was used as 1,3,6-hexanetricarboxylic acid. The content of inorganic salt was 9,200 ppm.
As a result, the smoothness and gloss of the coating film after 30 minutes at 140 ° C. were good, the adhesion was 100/100, the Erichsen value was 6 mm, and the pencil hardness was 2H. The resulting coating film was allowed to stand for 14 days in a thermostatic bath at 60 ° C. and a humidity of 95%. The smoothness of the coating film was ◯, but the gloss was △ and depressions were observed on the coating film surface.

  Provided is a low-color polyvalent carboxylic acid mixture mainly composed of a low-color 1,3,6-hexanetricarboxylic acid, which is reduced in coloration to a high level that can be used for automobile paints and has excellent thermal stability. .

Claims (5)

A polyvalent carboxylic acid mixture containing a polyvalent carboxylic acid having a content of 1,3,6-hexanetricarboxylic acid of 80% by mass or more and an inorganic salt , wherein 1.00 g of the polyvalent carboxylic acid mixture is added to 5 A solution in 0.0 mL of dimethylformamide has a lightness index L value of 98 or more, a value of chromanetic index of -2.0 to 2.0, b value of -2.0 to 3.0, and A low color polyvalent carboxylic acid mixture, wherein the polyvalent carboxylic acid mixture contains 10 mass ppm to 5,000 mass ppm of an inorganic salt. 2. The low hue polyvalent carboxylic acid mixture according to claim 1, wherein the inorganic salt is NaCl. A method for producing a polyvalent carboxylic acid mixture containing the 1,3,6-hexanetricarboxylic acid according to claim 1 or 2 and an inorganic salt ,
(1) A step of obtaining an aqueous solution of the hydrolysis mixture by alkaline hydrolysis of a nitrile mixture containing 1,3,6-tricyanohexane as a main component,
(2) adjusting the pH of the aqueous solution to a range of 3 to 13, obtaining an aqueous solution containing a mixture of polyvalent carboxylates, and then treating with a solid adsorbent;
(3) converting the mixture of polyvalent carboxylates in the aqueous solution treated in step (2) into polyvalent carboxylic acids using an acid, thereby obtaining an aqueous solution containing the polyvalent carboxylic acid mixture;
(4) a step of recovering the polyvalent carboxylic acid mixture by crystallization from an aqueous solution of the polyvalent carboxylic acid mixture containing the inorganic salt obtained in the step (3), Method for producing an acid mixture. The low alkali according to claim 3 , wherein the alkali used for the alkali hydrolysis in the step (1) is sodium hydroxide and the acid used for the conversion to the polyvalent carboxylic acid in the step (3) is hydrochloric acid. A method for producing a hue polycarboxylic acid mixture. Use of the low-hue polyvalent carboxylic acid mixture according to claim 1 or 2 as a curing agent added to a compound having two or more epoxy groups in the molecule.