JP5406643B2 - Method for producing metal salt of α-oxocarboxylic acid - Google Patents

Description

The present invention relates to a method for producing a metal salt of α-oxocarboxylic acid, particularly a metal salt of glyoxylic acid such as a calcium salt of glyoxylic acid, a copper salt of glyoxylic acid, or a zinc salt of glyoxylic acid .

  α-Oxocarboxylic acid salts, such as glyoxylates, are useful compounds as a crosslinking agent for acetoacetylated polyvinyl alcohol and a crosslinking agent for thermosetting resins. As a method for producing a salt of α-oxocarboxylic acid, for example, in Patent Document 1 (particularly Examples 1 to 4), a reaction solution obtained by hydrolyzing an α-oxocarboxylic acid ester is phase-separated into an aqueous phase and an organic phase. To obtain an aqueous solution containing α-oxocarboxylic acid and / or a salt thereof.

JP 2003-3000926 A

However, among α-oxocarboxylates, when an α-oxocarboxylic acid metal salt is to be produced using the above hydrolysis reaction, the α-oxocarboxylic acid metal salt has low solubility in water. Therefore, in order to dissolve the produced metal salt of α-oxocarboxylic acid in the aqueous phase, it is necessary to use a large amount of water as a reaction solution, and the apparatus used for the reaction becomes enormous and the production efficiency is low. It was a thing.
The present invention has been made in view of such circumstances, and an object of the present invention is to efficiently produce a metal salt of α-oxocarboxylic acid.

However, as a result of intensive studies in view of such circumstances, the present inventor has produced a metal salt of an α-oxocarboxylic acid with high production efficiency by mixing the α-oxocarboxylic acid and an aqueous medium using an acetic acid metal salt. And it was found that it was obtained in high yield.
That is, the present invention is a method for producing a metal salt of an α-oxocarboxylic acid having a step of mixing an α-oxocarboxylic acid and an acetic acid metal salt in an aqueous medium , wherein the α-oxocarboxylic acid is glyoxylic acid. In addition, the present invention relates to a method for producing a metal salt of α-oxocarboxylic acid, wherein the content of water in the aqueous medium is 80% by mass or more .

In the production method of the present invention, acetic acid is generated together with the metal salt of α-oxocarboxylic acid as the reaction proceeds. However, such acetic acid is easily collected by filtering the metal salt of α-oxocarboxylic acid after the reaction and drying it. Therefore, purification is easy and loss during purification can be suppressed. In addition, since the metal acetate used is highly soluble in water, it can be dissolved in a small amount of an aqueous medium, and the enlargement of the apparatus used for the reaction can be suppressed.
Therefore, when the production method of the present invention is used, a metal salt of α-oxocarboxylic acid can be obtained with high production efficiency and in a high yield.

Embodiments of the present invention will be described below.
The method of the present invention is a method for producing a metal salt (D) of α-oxocarboxylic acid, in which α-oxocarboxylic acid (A) and acetic acid metal salt (B) are mixed in an aqueous medium (C). Process. Hereinafter, the α-oxocarboxylic acid (A), the metal acetate (B), and the aqueous medium (C) will be described sequentially.

Examples of the α-oxocarboxylic acid (A) include glyoxylic acid, pyruvic acid, α-oxoglutaric acid and the like. In the present invention, glyoxylic acid is used. The α-oxocarboxylic acid can be prepared by a method such as hydrolysis of an α-oxocarboxylic acid ester.

  The α-oxocarboxylic acid (A) is usually prepared as an aqueous solution. The concentration of α-oxocarboxylic acid in the aqueous solution is usually 60% by mass or less, preferably 10 to 40% by mass, particularly preferably 20 to 30% by mass. If the concentration is too low, the product α-oxocarboxylic acid metal salt (D) becomes difficult to precipitate, resulting in a decrease in yield, and the amount of water with respect to the amount of product (D) increases and the volume increases. Since it becomes large, production efficiency tends to decrease. On the other hand, when the concentration is too high, the reaction solution is slurried due to the precipitation of the product (D), and stirring tends to be difficult, or it takes time for filtration.

  As a kind of metal element which comprises acetic acid metal salt (B), the metal element which forms a salt with acetic acid and can become a metal cation in an aqueous medium is used, specifically, an alkali metal element, an alkaline earth metal Element, transition metal element, metal element from group 12 to group 15, and the like, among these, alkaline earth metal element, group 12 metal, and transition metal element are preferable. Metal elements that can be valent cations are preferred.

  Examples of the alkaline earth metal element include beryllium, magnesium, calcium, barium, strontium, and the like. Among these, calcium is preferably used in terms of excellent productivity.

  Examples of the Group 12 element include zinc, cadmium, mercury, and the like. Among these, zinc is preferably used because it is excellent in productivity.

  Examples of the transition metal element include metal elements from Group 3 to Group 11, and among these, copper is preferably used in terms of excellent productivity.

  The acetic acid metal salt (B) may be either an anhydride or a hydrate.

  The metal acetate (B) is a solid such as a crystal or a powder, and when mixed with the α-oxocarboxylic acid (A), an aqueous solution is preferable from the viewpoint of work and yield. Acetic acid metal salts (B) such as alkaline earth metal salts, Group 12 element metal salts, and transition metal salts have high solubility in water. More specifically, for example, the solubility of calcium acetate (23 ° C. water) is 26.1% by mass. Therefore, the concentration of calcium acetate in the aqueous solution is preferably adjusted to 25% by mass or less, particularly 15 to 20% by mass. Moreover, since the solubility (23 degreeC water) of zinc acetate is 25.8 mass%, it is preferable to adjust the density | concentration of the zinc acetate in aqueous solution to 25 mass% or less, especially 15-20 mass%. Furthermore, since the solubility of copper acetate (23 ° C. water) was 6.6% by mass according to measurement by the present inventor, the concentration of copper acetate in the aqueous solution was 6% by mass or less, particularly 1 to 5%. It is preferable to adjust to mass%. Here, the solubility in water is a value calculated by (dissolved amount (g) × 100) / (water amount (g) + dissolved amount (g)).

On the other hand, metal hydroxides and metal carbonates have lower water solubility than the metal acetates (B). For example, the solubility of calcium hydroxide (23 ° C. water) is 0.2% by mass, the solubility of anhydrous zinc hydroxide (25 ° C. water) is 0.0012% by mass, and the solubility of anhydrous copper hydroxide (25 ° C. Water) is 0.00029% by mass (Reference: Chemical Handbook Basic Edition 3rd Edition, The Chemical Society of Japan, Maruzen Publishing).
When these hydroxides and carbonates (hereinafter referred to as hydroxides, etc.) are used, a large amount of water is required to completely dissolve these hydroxides, and the apparatus used for the reaction becomes enormous. This is inefficient in manufacturing.
Moreover, even if these hydroxides are completely dissolved using a large amount of water, the solubility of the product (D) in water is higher than the solubility of these hydroxides (for example, glyoxylic acid The solubility of calcium salt (23 ° C. water) is 0.7% by mass), and the product (D) hardly precipitates and is difficult to isolate and purify.
Further, when the reaction is carried out with insufficient dissolution of these hydroxides and the like, the unreacted (undissolved) hydroxide and the product (D) are both solid, so it is difficult to separate them. is there. Therefore, production efficiency and yield are reduced.

  The mixing molar ratio of α-oxocarboxylic acid (A) and acetic acid metal salt (B) is within a range including a theoretically calculated value, that is, the ionic valence of metal element constituting acetic acid metal salt / 1. Any range may be included. For example, when the ionic valence of the metal element constituting the metal acetate (B) is divalent, it may be in a range including a theoretically calculated value (2/1), preferably A / B = 1.5 / 1 to 2.5 / 1.

Aqueous medium (C) is mainly composed of water, the content of water in the aqueous medium (C) is 80 mass% or more, 90 mass% or more favorable preferred, 100 wt% Further preferred. However, in the present invention, an aqueous organic solvent such as acetone or alcohol may be included as long as the solubility of the raw materials and products is not affected. For example, when the α-oxocarboxylic acid (A) is prepared by hydrolysis of an α-oxocarboxylic acid ester, the aqueous medium (C) may contain an alcohol generated by hydrolysis of the ester. In particular, when producing a zinc salt of α-oxocarboxylic acid, an aqueous organic solvent such as acetone or alcohol is used in the aqueous medium (C) in order to improve the yield and shorten the drying time. It is preferable to add about 0.1 to 2 times the amount.

  When mixing the α-oxocarboxylic acid (A) and the metal acetate (B) in the aqueous medium (C), the aqueous solution of the metal acetate (B) is added to the aqueous solution of the α-oxocarboxylic acid (A). The mixing method is not limited, for example, an aqueous solution of α-oxocarboxylic acid (A) is added to the aqueous solution of metal acetate (B). The aqueous solution B) is preferably added dropwise.

  In the addition, it is preferable to add one aqueous solution dropwise while stirring the other aqueous solution. The time required for dropping varies depending on the metal type of the metal acetate (B) and cannot be generally specified. For example, when an aqueous solution of calcium acetate is dropped, it is usually 1 hour or more, preferably 1.5 hours. The dripping is performed over the above. When the time required for the dropping is too short, the stirring becomes insufficient, the product (D) including impurities is rapidly precipitated, and the purity of the product (D) tends to be lowered. After mixing both, the reaction is allowed to proceed in a stationary state or with stirring. Although the reaction time after mixing cannot be generally specified, for example, when the calcium salt (D) of α-oxocarboxylic acid is produced, the reaction is usually performed for 1 hour or longer, preferably about 2 hours.

  The reaction apparatus used for the reaction between the α-oxocarboxylic acid (A) and the metal acetate (B) is not particularly limited. For example, on a laboratory scale, there are two ports for inserting a thermometer and a dropping funnel. It can carry out using the reaction tube which has. The material of the reactor is not particularly limited, and examples include stainless steel (SUS) and glass. The stirring method is not particularly limited, and examples thereof include stirring using a three-one motor as a stirrer and a meniscus as a stirring blade. The stirring speed is usually 10 to 1000 rpm, preferably 100 to 500 rpm.

  The temperature at the time of performing the reaction is not particularly limited as long as it does not hinder the progress of the reaction, but if the temperature is too high, the solubility of the product (D) increases and the yield tends to decrease. Usually, the reaction is carried out at room temperature. Usually, the reaction is carried out under normal pressure.

  After the reaction is completed, the product (D) is isolated, purified and dried. When isolating the product (D), the product (D) obtained by filtration such as Nutsche filtration or centrifugal filtration is collected by filtration. When performing the filtration, the reaction solution may be cooled within a range that does not hinder. Since the product (D) collected by filtration contains acetic acid and impurities as by-products, it is preferable to wash the product (D) with water or hydrous alcohol. The washed product (D) is dried under normal pressure or reduced pressure. From the viewpoint of production efficiency, it is preferable to perform vacuum drying. Drying may be performed by any of stationary drying, conical drying, and nauter drying.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. Unless otherwise specified in the examples, “%” indicates a mass standard.

[Example 1: Method for producing calcium glyoxylate]
After adding 647 g of 25% aqueous glyoxylic acid solution (glyoxylic acid 162.1 g, 2.19 mol) to a 2 L two-necked reaction tube, 866 g of 20% aqueous calcium acetate solution (calcium acetate 173.2 g, 1.09 mol) was added at room temperature. The mixture was added dropwise over 1.5 hours with stirring, and stirred for 2 hours after completion of the addition. After filtering the reaction solution and collecting a white powder, the obtained powder was vacuum-dried at 50 ° C. for 3 hours to obtain 224 g of calcium glyoxylate white powder (1.01 mol, yield 92.5%, purity). 100%).
Stirring was performed at a stirring speed of about 300 rpm using a three-one motor as a stirrer and a meniscus as a stirring blade.

[Example 2: Method for producing copper glyoxylate]
After putting 203.2 g of 50% aqueous glyoxylic acid (glyoxylic acid 101.8 g, 1.37 mol) into a 3 L two-necked reaction tube, 2500 g of 5% aqueous copper acetate (125 g of copper acetate, 0.69 mol) was added at room temperature. The solution was added dropwise with stirring, and stirred for 2 hours after the completion of the addition. After filtering the reaction liquid and collecting the blue powder, the obtained powder was vacuum-dried at 50 ° C. for 4 hours to obtain 73.7 g (0.3 mol, yield 43.4%) of a blue powder of copper glyoxylate. , 100% purity).
In addition, stirring was performed at a stirring speed of about 300 rpm using a three-one motor as a stirrer and a meniscus as a stirring blade.

[Example 3: Method for producing zinc glyoxylate]
285 g of water and zinc acetate (75 g, 0.34 mol) were added to a 1 L two-necked reaction tube, and a 20% aqueous zinc acetate solution was prepared at room temperature with stirring. To this, 100 g of 50% aqueous glyoxylic acid solution (glyoxylic acid 50.1 g, 0.68 mol) was added and stirred for 1 hour after completion of the dropwise addition. Further, 460 g of acetone was added, and the mixture was stirred for 6 hours after completion of the dropwise addition. After filtering the reaction liquid and collecting a white powder, the obtained powder was vacuum-dried at 50 ° C. for 3 hours to obtain 58.1 g (0.24 mol, yield 69.0%) of a white powder of zinc glyoxylate. , 100% purity).
Stirring was performed at a stirring speed of about 300 rpm using a three-one motor as a stirrer and a meniscus as a stirring blade.

[Comparative Example 1]
In this comparative example, a calcium hydroxide aqueous solution close to saturation was used instead of the calcium acetate aqueous solution. Specifically, after putting 40 g of 25% aqueous glyoxylic acid (glyoxylic acid 10 g, 0.14 mol) into a 3 L two-necked reaction tube, 0.2% aqueous calcium hydroxide (calcium hydroxide 5.01 g, 0.04 g,. (07 mol) 2501.7 g was added dropwise over 1.5 hours at room temperature with stirring, and the mixture was stirred for 2 hours after completion of the addition. After filtering the reaction solution and collecting a white powder, the obtained powder was vacuum-dried at 50 ° C. for 3 hours to obtain 8.12 g of white powder of calcium glyoxylate (0.04 mol, yield 57.1%). , Purity 100%).

  Since the calcium hydroxide used in this comparative example has low solubility in water, the volume of the reaction liquid with respect to 1 mol of glyoxylic acid as a raw material becomes enormous (about 26 times that of Example 1). Therefore, not only the reaction tube larger than the reaction tube of Example 1 had to be used, but also the product calcium glyoxylate was difficult to precipitate, and the yield decreased.

[Comparative Example 2]
In this comparative example, an aqueous calcium hydroxide solution having the same concentration as in comparative example 1 was used, and the amount of the aqueous medium (water) in the reaction solution was set to the same amount as in example 1. Specifically, after putting 647 g of 25% aqueous glyoxylic acid (glyoxylic acid 162.1 g, 2.19 mol) in a 2 L two-necked reaction tube, 0.2% aqueous calcium hydroxide (1.73 g calcium hydroxide, 0.02 mol) 866 g was added dropwise over 1.5 hours at room temperature with stirring, and stirred for 2 hours after completion of the addition, but a white solution containing calcium glyoxylate powder was not obtained.

  In this comparative example, the amount of the reaction solution is the same as in Example 1, but the molar concentration of calcium hydroxide in the reaction solution is low (about 0.02 times the molar concentration of calcium acetate in Example 1). The product was not obtained to the extent that the saturation concentration of the product calcium glyoxylate was exceeded.

[Comparative Example 3]
In Example 2, assuming that a copper hydroxide aqueous solution close to saturation is used instead of the copper acetate aqueous solution, the mass of anhydrous copper hydroxide contained in 1 L of the saturated aqueous solution at 25 ° C. is 0.0029 g ( Reference: Chemical Handbook Basic Edition, revised 3rd edition, The Chemical Society of Japan, Maruzen Publishing), the concentration of copper hydroxide in the saturated aqueous solution is 0.00029%. If an aqueous copper hydroxide solution close to saturation is used, the capacity of the 0.00029% aqueous copper hydroxide solution required for the reaction with 1 mol of glyoxylic acid as a raw material becomes enormous, and compared with the 5% aqueous copper acetate solution of Example 2. Thus, the amount of the 0.00029% copper hydroxide aqueous solution is about 93 times. Therefore, a reaction tube larger than the reaction tube of Example 2 must be used, and the production efficiency is lowered.

[Comparative Example 4]
In this comparative example, an aqueous copper hydroxide solution having the same concentration as in comparative example 3 was used, and the amount of the aqueous medium (water) in the reaction solution was set to the same amount as in example 2. In this comparative example, the amount of the reaction solution is the same as in Example 2, but the molar concentration of copper hydroxide in the reaction solution is low (about 0.01 times the molar concentration of copper acetate in Example 2). The product was not obtained to the extent that the saturation concentration of the product copper glyoxylate was exceeded.

[Comparative Example 5]
In Example 3, assuming that a zinc hydroxide aqueous solution close to saturation was used instead of the zinc acetate aqueous solution, the mass of anhydrous zinc hydroxide contained in 1 L of the saturated aqueous solution at a temperature of 25 ° C. was 0.012 g ( Reference: Chemical Handbook Basic Edition, revised 3rd edition, The Chemical Society of Japan, Maruzen Publishing), the concentration of zinc hydroxide in saturated aqueous solution is 0.0012%. If a nearly saturated zinc hydroxide aqueous solution is used, the capacity of the 0.0012% zinc hydroxide aqueous solution required for the reaction with 1 mol of glyoxylic acid as a raw material becomes enormous, and compared with the 20% zinc acetate aqueous solution of Example 3. Thus, the amount of 0.0012% zinc hydroxide aqueous solution is about 78 times. Therefore, a reaction tube larger than the reaction tube of Example 3 must be used, and the production efficiency is lowered.

[Comparative Example 6]
In this comparative example, a zinc hydroxide aqueous solution having the same concentration as in comparative example 5 was used, and the amount of the aqueous medium (water) in the reaction solution was set to the same amount as in example 3. In this comparative example, the amount of the reaction solution is the same as in Example 3, but the molar concentration of zinc hydroxide in the reaction solution is low (about 0.01 times the molar concentration of zinc acetate in Example 3). The product was not obtained to the extent that the saturation concentration of the product zinc glyoxylate was exceeded.

In the production method of the present invention, acetic acid is generated together with the metal salt of α-oxocarboxylic acid as the reaction proceeds. However, such acetic acid is easily collected by filtering the metal salt of α-oxocarboxylic acid after the reaction and drying it. Therefore, purification is easy and loss during purification can be suppressed. In addition, since the metal acetate used is highly soluble in water, it can be dissolved in a small amount of an aqueous medium, and the enlargement of the apparatus used for the reaction can be suppressed.
Therefore, when the production method of the present invention is used, a metal salt of α-oxocarboxylic acid can be obtained with high production efficiency and in a high yield. That is, the method for producing a metal salt of α-oxocarboxylic acid of the present invention is an industrially very useful production method.

  Furthermore, the metal salt of α-oxocarboxylic acid obtained by the production method of the present invention can be effectively used as a crosslinking agent for acetoacetylated polyvinyl alcohol and a crosslinking agent for thermosetting resins.

Claims (5)

A method for producing a metal salt of an α-oxocarboxylic acid, comprising a step of mixing an α-oxocarboxylic acid and an acetic acid metal salt in an aqueous medium ,
A method for producing a metal salt of an α-oxocarboxylic acid, wherein the α-oxocarboxylic acid is glyoxylic acid, and the content of water in the aqueous medium is 80% by mass or more . The metal element is an alkali earth metal element constituting the metal acetate, Group 12 elements, or method for producing a metal salt according to claim 1 wherein the α- oxo carboxylic acid, which is a transition metal element. The method for producing a metal salt of α-oxocarboxylic acid according to claim 2 , wherein the alkaline earth metal element is calcium. The method for producing a metal salt of α-oxocarboxylic acid according to claim 2 , wherein the Group 12 element is zinc. The method for producing a metal salt of α-oxocarboxylic acid according to claim 2 , wherein the transition metal element is copper.