JP2007070339A - Method for producing high-purity hydroxypivalaldehyde and/or its dimer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous method for efficiently producing high-purity HPA and/or its dimer in a simple process. <P>SOLUTION: The method for obtaining high-purity hydroxypivalaldehyde and/or its dimer by reacting isobutylaldehyde and formaldehyde in the presence of a basic catalyst, adding a diluent to an aqueous solution obtained by distillating off low-boiling components including unreacted isobutylaldehyde, crystallizing hydroxypivalaldehyde and/or its dimer by cooling the aqueous solution, separating a solid from the aqueous solution and washing the solid with an organic solvent and/or water, is characterized by diluting the aqueous solution containing the hydroxypivalaldehyde and/or its dimer which is obtained by distillating off the low-boiling components with the diluent and a basic compound so that the concentration of the hydroxypivalaldehyde and/or its dimer is 5 to 23% by mass, the concentration of the formaldehyde is 0.2 to 2.5% by mass and that the pH is not lower than 5.0, and crystallizing in the temperature range of 20 to 45°C followed by solid/liquid separation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing hydroxypivalaldehyde and / or a dimer thereof by reacting isobutyraldehyde and formaldehyde, and more specifically, by crystallizing and separating hydroxypivalaldehyde and / or its dimer from a reaction solution. The present invention relates to a method for efficiently producing high-purity hydroxypivalaldehyde and / or a dimer thereof by a simple process.

In general, hydroxypivalaldehyde (3-hydroxy-2,2-dimethylpropanal, hereinafter referred to as HPA) is synthesized by subjecting isobutyraldehyde and formaldehyde to an aldol condensation reaction in the presence of a basic catalyst. Although the aldol condensation reaction proceeds under both acidic and basic conditions, HPA has a carbonyl group and a hydroxyl group in one molecule, and therefore, under acidic conditions, condensation from a dimer to a tetramer occurs. As a result, the reaction is carried out under basic conditions as described above (Patent Documents 1 and 2).
After completion of the reaction, an aqueous solution containing HPA is obtained by distilling off low-boiling components such as unreacted isobutyraldehyde and formaldehyde. HPA is often used as an intermediate for synthesizing organic compounds such as neopentyl glycol and spiro glycol, and this reaction product solution is often used in the next step without purification (Patent Documents 3 to 4).

  Note that HPA has an equilibrium relationship between a monomer and a dimer represented by the formula (1) (Non-patent Document 1), and HPA obtained as a crystal upon crystallization purification is a dimer. Patent Document 3 discloses that this dimer exhibits reactivity equivalent to that of a monomer.

In addition, methods for obtaining high-purity HPA by adding water to the above-described aqueous solution containing HPA, diluting and purifying by crystallization and solid-liquid separation are disclosed (Patent Documents 5 to 6).
That is, in Patent Document 5, the total concentration of HPA and / or its dimer after adding water to the aldol condensation reaction liquid and distilling off isobutyraldehyde is adjusted to be in the range of 23 to 30% by mass. Crystallization takes place. However, when crystallized by cooling to 15 to 20 ° C. at such a high concentration, a very high viscosity slurry is obtained or the fluidity is lost, so that it is difficult to handle industrially. Have. Furthermore, in Patent Document 5, since a large amount of HPA and / or its dimer remains in the liquid obtained by solid-liquid separation of the slurry, extraction with isobutyraldehyde is performed and the organic layer is circulated to the low boiling distillation step. Thus, HPA and / or its dimer is recovered, and isobutyraldehyde dissolved in the aqueous layer is also recovered by distillation. However, a large amount of isobutyraldehyde is distilled, which is disadvantageous in terms of energy.

  Further, in Patent Document 6, a part of the filtrate and washing liquid obtained in the solid-liquid separation and washing steps are circulated to the aldol condensation reactor and the distillation tower, and the remainder is subjected to deamination treatment to add water for crystallization and Although it is used for washing water, formic acid produced as a by-product during aldol condensation accumulates by circulation, and the pH value of the crystallizing solution decreases, so that HPA and / or its dimer is difficult to precipitate. Have. Even in the method of Patent Document 6, since a large amount of liquid is circulated in the distillation process, the load in distillation is high and the energy is disadvantageous. The ion exchange resin used for the deamination treatment needs to be regenerated and the process is complicated. And so on.

JP 7-215904 A JP 2000-26356 A JP-A-1-299239 JP 2005-29563 A JP 51-68514 A Japanese Examined Patent Publication No. 6-29206 Journal of the Chemical Society, Perkin Transactions II, 3, 189-192 (1978)

  The object of the present invention is to solve the problem in crystallization purification by adding water to the above aqueous solution containing HPA and diluting it. The high-purity HPA and / or dimer thereof can be efficiently and industrially produced by a simple process. It is another object of the present invention to provide a method for producing the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained an aqueous solution containing HPA and / or a dimer thereof obtained by distilling off a low-boiling component from a reaction mixture of isobutyraldehyde and formaldehyde. By adjusting the pH value of HPA and maintaining crystallization of HPA and / or its dimer and formaldehyde in appropriate ranges, it is easy to handle industrially and high purity HPA and / or its dimer. The inventors have found that the monomer can be obtained in high yield, and have reached the present invention.
That is, the present invention provides the following high-purity hydroxypivalaldehyde and / or a method for producing the dimer thereof.
1. A diluent is added to an aqueous solution obtained by reacting isobutyraldehyde and formaldehyde in the presence of a basic catalyst, and a low-boiling component containing unreacted isobutyraldehyde is distilled off, and cooled to hydroxypivalaldehyde and / or The dimer is crystallized and separated into solid and liquid, and this is further washed with an organic solvent and / or water to obtain high-purity hydroxypivalaldehyde and / or dimer thereof. Into the aqueous solution containing hydroxypivalaldehyde and / or its dimer obtained by adding a diluent and a basic compound, the concentration of hydroxypivalaldehyde and / or its dimer is 5 to 23% by mass, Crystallization in a temperature range of 20 to 45 ° C. after dilution so that the formaldehyde concentration is 0.2 to 2.5 mass% and the pH value is 5.0 or more, High-purity hydroxypivalaldehyde and / or methods of making dimer characterized by solid-liquid separation to wash the crystals of hydroxypivalaldehyde and / or dimer Ide.
2. The method for producing high-purity hydroxypivalaldehyde and / or a dimer thereof according to 1 above, wherein a separation liquid and / or a washing liquid obtained by solid-liquid separation is used as a diluent.
3. 2. The method for producing high purity hydroxypivalaldehyde and / or a dimer thereof according to 2 above, wherein the use of the separated liquid as a diluent is repeated twice or more.
4). The method for producing a high-purity hydroxypivalaldehyde and / or dimer thereof according to any one of the above 1 to 3, wherein the crystallization temperature is in the range of 20 to 45 ° C.
5. The method for producing a high-purity hydroxypivalaldehyde and / or dimer thereof according to any one of the above 1 to 4, wherein the viscosity of the crystal slurry obtained by crystallization is 500 mPa · s or less.

In the production method of the present invention, complicated operations such as handling a high-viscosity slurry and regeneration of an ion exchange resin are not required, and it is a simple process and is advantageous in terms of energy, and has high purity HPA and / or Alternatively, the dimer thereof can be obtained in high yield, and intermediate synthesis of organic compounds such as neopentyl glycol, 2,2-dimethyl-1,3-propanediol hydroxypivalic acid monoester, hydroxypivalic acid, spiroglycol, etc. As a body, it can be used industrially advantageously.
In addition, in the production method of the present invention, the yield of HPA and / or its dimer is improved and the wastewater treatment load is reduced by repeatedly using a separation liquid obtained by solid-liquid separation as a diluent. Further industrial advantages.

The present invention relates to an improved process for crystallizing an aqueous solution containing HPA and its dimer (hereinafter referred to as a crude HPA aqueous solution) obtained by distilling off low-boiling components from a reaction product solution of isobutyraldehyde and formaldehyde. Is.
In the present invention, the crude HPA aqueous solution used as a crystallization raw material is subjected to aldol condensation of isobutyraldehyde and formaldehyde in the presence of a basic catalyst, and then from the aldol condensation reaction product liquid, low boiling points such as unreacted isobutyraldehyde and formaldehyde. It is obtained by distilling off the components.
Formaldehyde or an aqueous formaldehyde solution (formalin) is used as the formaldehyde used for producing the crude HPA aqueous solution. However, the aldol condensation reaction of isobutyraldehyde and formaldehyde to which a basic catalyst is added is extremely susceptible to the water concentration of the reaction system, and if the isobutyraldehyde or formaldehyde concentration is dilute, the reaction rate becomes slow and a constant yield is obtained. Therefore, it is preferable that the formaldehyde concentration of formalin is as high as possible. The raw material formalin is preferably one having a formaldehyde concentration of 37% by mass or more and containing no methanol or having as little methanol as possible.
The commercially available isobutyraldehyde used for producing the crude HPA aqueous solution can be used, but it is preferable that the content of n-butyraldehyde is as low as possible and the organic substance purity is 99% or more.

In the present invention, the aldol condensation reaction of isobutyraldehyde and formaldehyde may be either a batch type or a continuous type, and a method of performing atmospheric pressure or pressurization under air shutoff or in a nitrogen stream is preferable. In the case of a batch system, there is no particular limitation on the supply method of isobutyraldehyde, formaldehyde or formalin and catalyst. However, if isobutyraldehyde or formaldehyde or formalin is brought into contact with a basic catalyst in advance, the aldol condensation reaction between isobutyraldehyde or formaldehyde is performed. Alternatively, since a Kanitz allo reaction may occur and the yield of HPA and / or its dimer may be reduced, a method of supplying a basic catalyst to a mixture of isobutyraldehyde and formaldehyde or formalin is preferable.
Also in the case of a continuous system, there is no particular limitation on the method for supplying isobutyraldehyde, formaldehyde or formalin and the catalyst, but it is preferably carried out by a multistage system of about 2 to 4 stages in order to improve the reaction efficiency.
The molar equivalent of isobutyraldehyde with respect to formaldehyde is usually in the range of 0.8 to 1.6, preferably 0.9 to 1.4. In the case of a batch system, the reaction becomes heterogeneous for several minutes from the start of the reaction, but changes to a homogeneous reaction as HPA and / or its dimer are produced. The reaction temperature is usually 40 to 98 ° C, preferably 80 to 95 ° C under normal pressure. Under normal pressure, it temporarily stops at the reflux point of isobutyraldehyde, which is about 62 to 65 ° C., but gradually increases with the production of HPA and / or its dimer (consumption of isobutyraldehyde), and finally it is usually 80 ° C. Control above. The reaction is completed by holding at about 80 to 95 ° C. for about 0.05 to 2 hours. In the case of a continuous system, the reaction proceeds in a homogeneous system. The reaction temperature is usually 50 to 98 ° C., preferably 70 to 95 ° C., and the residence time is about 0.1 to 5 hours, preferably 0.3 to 3 hours. The reaction temperature can be controlled by heating / cooling with a jacket or a coil provided in the reactor, cooling by circulating the reaction liquid to an external heat exchanger, and heat removal by refluxing with a low boiling point. .

  Examples of the basic catalyst used in the aldol condensation reaction include inorganic bases such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, and organic bases such as tertiary amine and pyridine. Use of a tertiary amine causes HPA and / or its dimer to combine with a cannitz allo reaction with unreacted formaldehyde to reduce the yield, and if the basicity is too weak, the reaction becomes slow. Is preferred. Examples of the tertiary amine include trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triisobutylamine, N-methylpiperidine, N-ethylpiperidine, N-ethylpiperidine, N-methylmorpholine, N- Examples thereof include ethylmorpholine, N-methylpyrrolidine, N-ethylpyrrolidine and the like, preferably trimethylamine, triethylamine and a mixture thereof which can be obtained at low cost, and more preferably triethylamine. Although the preferable addition amount of a basic catalyst changes naturally also with the kind, it is 0.001-0.5 normally by molar equivalent with respect to isobutyraldehyde, Preferably it is 0.01-0.2.

  After such an aldol condensation reaction, HPA and / or its dimer are obtained by distilling off a low boiling fraction mainly composed of unreacted isobutyraldehyde, formaldehyde, or methanol contained as an impurity in formalin. An aqueous solution (crude HPA aqueous solution) containing the body and water is obtained. Since the alteration of HPA and / or its dimer accelerates as the temperature increases, the distillation of the low boiling fraction is such that the top temperature is about 40 to 80 ° C., which does not hinder the recovery of unreacted isobutyraldehyde, etc. It is preferable to carry out at a reduced pressure of about ~ 95 kPa. The distillation method may be either a batch type or a continuous type. In order to promote the removal of the low boiling fraction, water may be added and then distilled.

The aqueous solution (crude HPA aqueous solution) containing HPA and / or its dimer thus obtained is diluted by adding a diluent. As a diluent, either (a) diluted water, (b) a separated liquid produced during solid-liquid separation, or (c) a washing liquid obtained by washing the crystals of HPA and / or its dimer with water, or Add them in appropriate combinations and dilute. The total concentration of HPA and / or its dimer in the aqueous solution after dilution is adjusted to 5 to 23% by mass. Preferably, it adjusts so that it may become 15-22 mass%. By setting it as such a range, HPA and / or its dimer can be obtained with high production efficiency and industrially stably. By setting the total concentration of HPA and / or its dimer in the diluted solution to 5% by mass or more, HPA and / or its dimer does not precipitate at all, or even if it precipitates, it corresponds to the crystallization tank capacity. Since the production amount is not significantly reduced, it is preferable for industrial operation.
Since (b) the liquid obtained by solid-liquid separation and (c) the washing liquid contain a large amount of HPA and / or its dimer, diluting water is also used to reduce the amount of drainage and improve the recovery rate. Instead of the above, it is preferable to use a separation liquid obtained by solid-liquid separation or a washing liquid obtained when obtaining high-purity HPA and / or a dimer thereof.
The separation liquid in solid-liquid separation can be used repeatedly as dilution water two or more times. When the number of repeated uses increases, a high recovery rate and low drainage load of HPA and / or its dimer can be maintained. In addition, the separation liquid in solid-liquid separation can be used repeatedly as dilution water, so that the amount of basic compounds described below can be reduced and the wastewater treatment load is reduced. Is advantageous.

  In the present invention, a basic compound is added to a crude HPA aqueous solution to which a diluent has been added to adjust the pH value. The basic compound is not particularly limited, but is preferably the same as the basic catalyst used in the aldol condensation reaction, more preferably organic amines used as the basic catalyst, and particularly preferably a tertiary amine. The pH value is adjusted to be 5.0 or more, preferably 6.0 or more. When the pH value is 5.0 or more, the crystallization rate of HPA and / or its dimer is not significantly reduced, which is advantageous in industrial operation. As described above, when using a separation liquid or washing water generated during solid-liquid separation as a diluent, since the basic compound is contained in the separation liquid or washing water, the amount of the basic compound to be added is used. Can be reduced.

Moreover, in this invention, a diluent is added and it adjusts so that the formaldehyde density | concentration in crude HPA aqueous solution may be 0.2-2.5 mass%. Formaldehyde has the property of inhibiting the crystallization of HPA and / or its dimer, and a large increase in formaldehyde significantly reduces the crystallization rate of HPA and / or its dimer, so the formaldehyde concentration is 0. It adjusts so that it may become 2-2.5 mass%, Preferably it is 0.2-2 mass%. By adjusting the formaldehyde concentration to 2.5% by mass or less, the crystallization amount and crystallization rate of HPA and / or its dimer are not significantly reduced even when the pH is adjusted to 5.0 or more. It is advantageous in industrial operation. When the separated liquid obtained by solid-liquid separation using a crude HPA aqueous solution with high formaldehyde concentration is used repeatedly instead of diluting water, the unreacted formaldehyde concentration should not exceed 2.5 mass%. .
When the formaldehyde concentration is lower than 0.2% by mass, no particular inconvenience occurs in the crystallization operation of HPA and / or its dimer itself. However, as a method for reducing the formaldehyde concentration to less than 0.2% by mass, there is a method in which isobutyraldehyde is excessively used in the aldol condensation reaction to increase the conversion rate of formaldehyde. The dimer yield is reduced, which is disadvantageous for industrial operation. As another method for reducing the formaldehyde concentration to less than 0.2% by mass, there is a method in which the distillation temperature is increased in the low boiling point distillation after the aldol condensation reaction to increase the formaldehyde removal rate. HPA and / or its dimer Is also industrially disadvantageous because it alters the formation of hydroxypivalic acid neopentyl glycol monoester and reduces the yield of HPA and / or its dimer.

  The crystallization temperature is preferably in the range of 20 to 45 ° C, more preferably in the range of 28 to 43 ° C. By adjusting to this temperature range, HPA and / or its dimer can be precipitated stably and with a high recovery rate. By setting the crystallization temperature to 20 ° C. or higher, the slurry becomes highly viscous or loses its fluidity, and an excessively large utility is not required for cooling, which is advantageous for industrial operation. It is. By setting the crystallization temperature to 45 ° C. or lower, HPA and / or a dimer thereof are precipitated in an appropriate amount, which is extremely advantageous in industrial operation.

In order to crystallize while maintaining the fluidity of the slurry, the crystallization is preferably terminated when the slurry viscosity at the slurry temperature is 500 mPa · s or less, and more preferably 300 mPa · s or less. Therefore, it is advantageous in the solid-liquid separation operation that the slurry viscosity is 500 mPa · s or less. There is no particular limitation on the apparatus used for solid-liquid separation, but it is preferable to use a basket-type centrifuge that can efficiently wash crystals.
The separated crystals of HPA and / or its dimer are washed with an organic solvent and / or water to obtain high-purity HPA and / or its dimer. The organic solvent and / or water is preferably used in an amount of about 0.2 to 5 times by mass with respect to the separated HPA and / or dimer crystals thereof.
For the washing, an organic solvent and / or water can be used, but water is preferred. When water is used, the washing liquid after washing the crystals can be used as a diluent for the crude HPA aqueous solution as described above. When the organic solvent is used, the type of the organic solvent to be used is not particularly limited, but alcohols and ketones that are polar solvents are preferable from the viewpoint of high cleaning effect. Of these, methanol, ethanol, propanol and acetone that are miscible with water are preferred. There is no particular limitation on the mixing ratio of the organic solvent and water.

Next, the present invention will be described more specifically. However, the present invention is not limited to this. In the following examples, the composition analysis of the crude HPA aqueous solution was performed by gas chromatography.
<Measurement method of slurry viscosity>
The measurement was performed at the crystallization temperature using a B-type viscometer (model BM, manufactured by Tokyo Keiki Seisakusho Co., Ltd.).
<Measurement method of gas chromatography>
For gas chromatography analysis of HPA and / or its dimer, a capillary column (Agilent Technologies DB-1 equivalent) was used to prepare an acetone solution for analysis. HPA and / or its dimer are evaluated together as HPA.

Reference example 1
While stirring 199.5 parts of isobutyraldehyde (grade 1 manufactured by Wako Pure Chemical Industries) and 225 parts by mass of 40% by weight formalin (produced by Mitsubishi Gas Chemical), 9.9 parts by mass of triethylamine (special grade manufactured by Wako Pure Chemical Industries) was added as a catalyst. The aldol condensation reaction was performed. The reaction solution was distilled at 70 to 80 ° C. under a pressure of 40 kPa to remove low-boiling components such as unreacted isobutyraldehyde and triethylamine to obtain 425 parts by mass of a crude HPA aqueous solution. As a result of analyzing the composition of the crude HPA aqueous solution, HPA 62.1% by mass, neopentyl glycol 1.53% by mass, formaldehyde 1.60% by mass, triethylamine 1.30% by mass, formic acid 0.41% by mass, hydroxypivalic acid Neopentyl glycol monoester was 0.95 mass%, water was 28.5 mass%, and the others were 3.65 mass%.

Example 1
623 parts by mass of diluted water was added to 210 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 to make the concentration of HPA and / or its dimer 16.5% by mass. Further, 0.5 parts by mass of triethylamine was added as a pH adjuster to adjust the pH value to 6.2. At this time, the formaldehyde concentration was 0.40% by mass. While stirring this solution, it was cooled to 40 ° C and crystallized at 39-40 ° C. After 90 minutes, crystallization was complete. The slurry viscosity at this time was 85 mPa · s. Thereafter, solid-liquid separation was performed using a centrifuge, and crystals (HPA and its dimer) were washed using 80 parts by mass of washing water. As a result, 780 parts by mass of the separated liquid was recovered to obtain 75 parts of wet crystals. This wet crystal was dried at 30 ° C. under a nitrogen stream to obtain 58.2 parts by mass of HPA and / or its dimer (dry crystal). The recovery rate of HPA and / or its dimer in the crude HPA aqueous solution was 44.1% by mass, and when this dry crystal was analyzed by gas chromatography, the purity of HPA and / or its dimer was 98. 8% (see Table 1). In addition, HPA in a table | surface shows "HPA and / or its dimer."

Example 2
110 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 and 740 parts by mass of the separation liquid obtained by solid-liquid separation in Example 1 were charged as diluents, and the concentration of HPA and / or its dimer was adjusted. The content was 17.8% by mass. Further, 0.2 parts by mass of triethylamine was added to adjust the pH to 6.2. The formaldehyde concentration at this time was 0.58 mass%. Crystallization was carried out in the same manner as in Example 1, and after 80 minutes, crystallization was completed. The slurry viscosity at this time was 125 mP · s. In the same manner as in Example 1, solid-liquid separation, washing, and drying were performed using a centrifuge to obtain 57.5 parts of dried crystals (HPA and / or its dimer) and 783 parts by mass of a separated liquid. The recovery rate of HPA and / or its dimer in the newly added crude HPA aqueous solution was 83.2% by mass, which was analyzed by gas chromatography. The purity of HPA and / or its dimer was 98. 0.8% (see Table 1).

Examples 3-19
Using 110 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 and the separated liquid obtained by solid-liquid separation in Example 2, an aqueous solution containing HPA and / or its dimer is obtained in the same manner as in Example 2. Then, the pH value was adjusted to 6.2, and the same crystallization operation was performed. Next, using the separated liquid obtained by solid-liquid separation, an aqueous solution containing HPA and / or its dimer is similarly obtained, the pH value is adjusted to 6.2 to 6.3, and the same crystallization operation is performed. This was repeated a total of 17 times. PH, HPA and / or its dimer concentration, formaldehyde concentration, crystallization time, slurry viscosity, recovery rate and purity for HPA and / or its dimer in newly added crude HPA aqueous solution at each operation Is shown in Table 1.

Comparative Example 1
Crystallization was carried out in the same manner as in Example 1 except that triethylamine was not added and the pH was not adjusted. The pH value was 4.5. After 90 minutes, crystallization was complete. The slurry viscosity was 100 mPa · s. Solid-liquid separation and drying were performed to obtain 804 parts by mass of the filtrate and 40.8 parts by mass of HPA and / or its dimer. The recovery rate with respect to HPA and / or its dimer was 31.8 mass%, and this was analyzed by gas chromatography. As a result, the purity was 98.8%. (See Table 2)

Comparative Example 2
110 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 and 740 parts by mass of the filtrate collected in Comparative Example 1 were charged, so that the HPA concentration was 17.7% by mass. Crystallization was carried out in the same manner without adding triethylamine and adjusting the pH value to 4.4. After 90 minutes, crystallization was complete. The slurry viscosity was 98 mPa · s. Solid-liquid separation and drying were performed to obtain 36.2 parts by mass of HPA and / or its dimer. The recovery rate with respect to HPA and / or its dimer was 53.0 mass%, and this was analyzed by gas chromatography. As a result, the purity was 98.8%.

Comparative Examples 3-12
Using 110 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 and the collected filtrate, the same crystallization operation as in Comparative Example 2 was repeated 11 times. PH, HPA and / or its dimer concentration, formaldehyde concentration, crystallization time, slurry viscosity, recovery rate and purity for HPA and / or its dimer in newly added crude HPA aqueous solution at each operation Is shown in Table 2.

  In Table 2, when crystallization is repeated without adjusting the pH, the pH value gradually decreases, and the recovery rate for HPA and / or its dimer decreases with decreasing pH value, and the purity also decreases. is doing. On the other hand, it can be seen from Table 1 that the crystallization after the pH adjustment according to the present invention maintains the purity and the recovery rate at a high level even if the crystallization is repeated.

Comparative Example 13
Crystallization in the same manner as in Example 1 except that 312 parts by mass of water was added to 210 parts by mass of the crude HPA aqueous solution obtained in Reference Example 1 to obtain a concentration of 25.0% by mass of HPA and / or its dimer. However, after 70 minutes from the start of crystallization, the slurry viscosity increased to 1000 mPa · s or more, the fluidity was lost, and the crystallization operation could not be continued.

Comparative Example 14
The crystallization was performed in the same manner as in Example 1 except that the crystallization temperature was 50 ° C. However, no slurry was obtained even 180 minutes after the start of crystallization, and the solution remained a clear solution.

Reference example 2
While stirring 199.5 parts by mass of isobutyraldehyde and 300 parts by mass of 40% by mass of formalin, 9.9 parts by mass of triethylamine was added as a catalyst to perform an aldol condensation reaction. The reaction solution was distilled at 70 ° C. under a pressure of 40 kPa to remove low-boiling components such as unreacted isobutyraldehyde and triethylamine to obtain 480 parts by mass of a crude HPA aqueous solution. As a result of analyzing the composition of the crude HPA aqueous solution, HPA 56.0% by mass, neopentyl glycol 1.50% by mass, formaldehyde 7.50% by mass, triethylamine 0.95% by mass, formic acid 2.05% by mass, hydroxypivalic acid Neopentyl glycol monoester was 0.85% by mass, water was 28.0% by mass, and others were 3.15% by mass.

Example 20
503 parts by mass of water was added to 210 parts of the crude HPA aqueous solution obtained in Reference Example 2 to adjust the concentration of HPA and / or its dimer to 16.5% by mass. Furthermore, 1.5 parts by mass of triethylamine was added as a pH adjuster to adjust the pH value to 6.1. At this time, the formaldehyde concentration was 2.21% by mass. While stirring this solution, it was cooled to 40 ° C and crystallized at 39-40 ° C. After 90 minutes, crystallization was complete. The slurry viscosity at this time was 140 mPa · s. Thereafter, solid-liquid separation was performed using a centrifuge. At this time, 80 parts of water was used for washing the crystals (HPA and its dimer). As a result, 748 parts by mass of the filtrate was recovered to obtain 61 parts of wet crystals. The wet crystals were dried at 30 ° C. under a nitrogen stream to obtain 47 parts of HPA and / or its dimer. The recovery rate with respect to HPA and / or its dimer was 40.0 mass%, and this was analyzed by gas chromatography. As a result, the purity was 98.6%.

Comparative Example 15
110 parts by mass of the crude HPA aqueous solution obtained in Reference Example 2 and 740 parts by mass of the filtrate collected in Example 20 were charged, and the HPA concentration was set to 18.0% by mass. Furthermore, 1.5 parts by mass of triethylamine was added as a pH adjuster to adjust the pH value to 6.1. The formaldehyde concentration at this time was 2.89% by mass. Crystallization was carried out in the same manner as in Example 20. The slurry viscosity was 70 mPa · s. Solid-liquid separation and drying were performed to obtain 25 parts by mass of HPA and / or a dimer thereof. The recovery rate with respect to HPA and / or its dimer was 40.5 mass%, and this was analyzed by gas chromatography. As a result, the purity was 97.8%.

Reference example 3
After performing the aldol condensation reaction in the same manner as in Reference Example 1, the reaction solution was distilled at 100 to 105 ° C. and normal pressure to remove low-boiling components such as unreacted isobutyraldehyde and triethylamine, and 425 parts of a crude HPA aqueous solution was obtained. Obtained. As a result of analyzing the composition of the crude HPA aqueous solution, HPA 50.1 mass%, neopentyl glycol 6.53 mass%, formaldehyde 0.37 mass%, triethylamine 1.54 mass%, formic acid 1.81 mass%, hydroxypivalic acid They were 7.50 mass% neopentyl glycol monoester, 28.5 mass% water, and 3.77 mass% other.

Comparative Example 16
428 parts by mass of water was added to 210 parts by mass of the crude HPA aqueous solution obtained in Reference Example 3 to adjust the concentration of HPA and / or its dimer to 16.5% by mass. Furthermore, 1.3 parts by mass of triethylamine was added as a pH adjuster to adjust the pH value to 6.1. At this time, the formaldehyde concentration was 0.12% by mass. While stirring this solution, it was cooled to 40 ° C and crystallized at 39-40 ° C. After 90 minutes, crystallization was complete. The slurry viscosity at this time was 50 mPa · s. Thereafter, solid-liquid separation was performed using a centrifuge. At this time, 80 parts by mass of water was used for washing the crystals (HPA and its dimer). As a result, 763 parts of the filtrate was recovered to obtain 45 parts of wet crystals. This wet crystal was dried at 30 ° C. under a nitrogen stream to obtain 33.3 parts by mass of HPA and / or its dimer. The recovery rate with respect to HPA and / or its dimer was 31.7 mass%.

Claims (4)

  In the presence of a basic catalyst, isobutyraldehyde and formaldehyde are reacted, and a low-boiling component containing unreacted isobutyraldehyde is distilled off. A diluent is added to the aqueous solution and cooled to obtain hydroxypivalaldehyde and / or The dimer is crystallized and separated into solid and liquid, and this is further washed with an organic solvent and / or water to obtain high-purity hydroxypivalaldehyde and / or dimer thereof. Into the aqueous solution containing hydroxypivalaldehyde and / or its dimer obtained by adding a diluent and a basic compound, the concentration of hydroxypivalaldehyde and / or its dimer is 5 to 23% by mass, Crystallization in a temperature range of 20 to 45 ° C. after dilution so that the formaldehyde concentration is 0.2 to 2.5 mass% and the pH value is 5.0 or more, High-purity hydroxypivalaldehyde and / or methods of making dimer characterized by solid-liquid separation to wash the crystals of hydroxypivalaldehyde and / or dimer Ide.   The method for producing high-purity hydroxypivalaldehyde and / or a dimer thereof according to claim 1, wherein a separation liquid and / or a washing liquid obtained by solid-liquid separation is used as a diluent.   The method for producing high-purity hydroxypivalaldehyde and / or a dimer thereof according to claim 2, wherein the use of a separated liquid obtained by solid-liquid separation as a diluent is repeated twice or more.   The method for producing a high-purity hydroxypivalaldehyde and / or dimer thereof according to any one of claims 1 to 3, wherein the viscosity of the crystal slurry obtained by crystallization is 500 mPa · s or less.