JP2001002615A - Separation of dipentaerythritol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method enabling high purity dipentaerythritol where the content of pentaerythritol is small to be separated by a simple operation such as crystallization from an aqueous solution containing both pentaerythritol and dipentaerythritol and then heating dissolution without needlessly consuming energy e.g. in the addition, recovery, purification and the like of water. SOLUTION: In a method for separating dipentaerythritol from an aqueous solution containing both pentaerythritol and dipentaerythritol, this method is to subject the aqueous solution to stallization process to obtain a slurry containing crystallized pentaerythritol and dipentaerythritol and then to heat the slurry until the whole or almost whole quantity of pentaerythritol is dissolved, followed by subjecting the obtained slurry to solid-liquid separation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is widely used as a raw material for polyesters, polyethers, polyurethanes, alkyd resins and lubricating oils, and its acrylate is widely used as a raw material for high-density crosslinkers, inks, coatings and adhesives. The used dipentaerythritol (CAS N
o. 126-58-9, hereinafter abbreviated as DPN. )).

[0002]

2. Description of the Related Art DPN is first used in the reaction of synthesizing pentaerythritol (CAS No. 115-77-5, hereinafter abbreviated as PN), that is, alkali metal hydroxide or alkaline earth metal hydroxide. In the presence, by-products are produced when acetaldehyde and formaldehyde are reacted to form PN, and then formaldehyde is removed from the resulting reaction solution to give PN, DPN and alkali metal formate or alkaline earth. It is a general industrial manufacturing method to obtain an aqueous solution containing a metal-class formate as a main component, and to separate the aqueous solution from the aqueous solution by crystallization or extraction.

Among these, as a separation method utilizing crystallization, for example, US Pat. No. 282,066 discloses a method for separating PN and DPN from an aqueous solution containing PN and DPN having a weight ratio of PN / DPN of about 3 or more. First, under normal pressure conditions, at the boiling point of the aqueous solution, the DPN is concentrated to an upper limit concentration at which DPN is not substantially crystallized, and the crystallized crystals are solid-liquid separated at a high temperature near the concentration temperature. Is obtained, and then the solution obtained by separating the crystals is diluted with water to a concentration at which the PN is saturated at 60 to 70 ° C., and then the crystals are crystallized at 60 to 70 ° C. A technique has been disclosed in which a crystal mainly containing DPN is obtained by separation.

[0004] However, in the method described in the patent, after the crystals containing PN as a main component are separated, the solution is diluted with water. By adding water, energy is required to recover the water. Required. In addition, since it involves a solid-liquid separation operation near the boiling point temperature, the temperature decreases due to heat radiation and the like,
Precipitation and adhesion of crystals occur, making continuous operation for a long time difficult, and there is also a difficulty in operability.

On the other hand, JP-A-58-8028 discloses that
As a method for separating PN and DPN from an aqueous solution containing PN, DPN, etc. and having a PN / DPN weight ratio of 16 or less, an aqueous solution adjusted to a concentration range of not less than the solubility in water at the crystallization temperature of PN and not more than the supersolubility. From the crystallization temperature of 0 to 40 ° C, DPN or mostly DP
A technique of crystallizing and separating N crystals has been disclosed.

However, according to the method described in this patent, the obtained crystals contain 5 to 10% by weight of PN, so that they must be further purified by a method such as recrystallization, and the operation is complicated. Disadvantage.

[0007]

In the prior art, PN
When separating DPN from an aqueous solution containing
Since water is added during the separation process, there is a problem that energy is required to recover the water, and the obtained crystals contain PN, so that further purification is required. An object of the present invention is to efficiently separate DPN from an aqueous solution containing PN and DPN.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that when an aqueous solution containing PN and DPN is crystallized, the deposition rate of DPN is lower than that of PN. Paying attention to the fact that the solubility of DPN increases due to its slowness, and as a result, the amount of DPN recovered is reduced. When separating DPN from an aqueous solution containing PN and DPN, the aqueous solution is first crystallized. As a result, it was found that DPN and PN were once crystallized and then heated, whereby it was possible to selectively dissolve PN, thereby completing the present invention.

That is, the present invention provides a method for separating DPN from an aqueous solution containing PN and DPN, wherein the aqueous solution is crystallized to obtain a slurry containing the crystallized PN and DPN. Alternatively, this is a DPN separation method characterized by further performing solid-liquid separation on a slurry obtained by heating until almost the entire amount is dissolved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS PN and DPN used in the present invention
Is contained in an aqueous solution containing an alkali metal hydroxide such as sodium hydroxide or calcium hydroxide or an alkaline earth metal hydroxide in the presence of acetaldehyde and formaldehyde. PN and DPN obtained by removal
And an aqueous solution containing an alkali metal formate or an alkaline earth metal formate as a main component. Furthermore, this PN,
By a method such as crystallization or extraction from an aqueous solution containing DPN and an alkali metal formate or an alkaline earth formate as a main component, a part or a large amount of PN, DPN and an alkali metal formate or an alkaline earth formate is formed. An aqueous solution obtained after separating the parts may be used.
DPN is added to these aqueous solutions by the method of the present invention described later.
The mixture obtained by adding the aqueous solution after the separation as a recycle solution can be used as the aqueous solution.

At this time, impurities in these aqueous solutions include alkali metal formate or alkaline earth metal formate, bispentaerythritol monoformal, pentaerythritol monocyclic formal, and the like, and their presence affects solubility. However, there is no significant effect in practicing the present invention. However, in order to further enhance the effects of the present invention, the impurity concentration is preferably low.

Although the composition of the aqueous solution containing PN and DPN is not particularly limited, the PN weight-based concentration within a range operable under normal pressure or reduced pressure conditions is 5 to 5.
50%, more preferably 5 to 40%. When the PN concentration is lower than 5%, the crystallization temperature is lowered, and equipment such as a cooler is required. When the PN concentration is higher than 50%,
The crystallization temperature increases, and solid-liquid separation becomes difficult.

From these, the DPN concentration is set to a PN / DPN weight ratio of 1 to 16, preferably 1 to 12, from the viewpoint of solubility. As the PN / DPN ratio increases, the recovery rate of DPN decreases, and further, the PN / DPN
If the weight ratio is larger than 16, DPN cannot be separated.

In the present invention, first, an aqueous solution containing PN and DPN is crystallized, whereby the crystallized PN and DPN are crystallized.
To obtain a slurry containing Here, as the crystallization method, cooling crystallization for cooling by adiabatic evaporation under reduced pressure may be used, or cooling crystallization for external cooling using a crystallization tank with a jacket may be used. Further, concentrated crystallization for crystallizing while concentrating under normal pressure or reduced pressure conditions may be used.

The crystallization temperature may be a temperature at which DPN and PN are crystallized, but the crystallization may be performed at a temperature lower by 2 to 50 ° C. than a dissolution temperature of PN described later.

The crystallization time at these crystallization temperatures is 1
The reaction is performed for 5 minutes to 6 hours, preferably for 30 minutes to 3 hours. If the crystallization time is shortened, the crystallization of DPN is not sufficient,
The amount of recovered N decreases. If the crystallization time is lengthened, the volume of the crystallization tank increases, and DPN cannot be effectively separated.

Next, the slurry containing the crystallized PN and DPN obtained by crystallization is raised by 2 to 50 ° C. above the crystallization temperature of the aqueous solution containing PN and DPN, and the P
After dissolving all or almost all of N, solid-liquid separation is performed using a belt filter, centrifuge, etc.
A wet cake containing DPN as a main component is obtained.

Here, the so-called dissolution temperature for dissolving the whole or almost the entire PN in the slurry varies slightly depending on the type and concentration of impurities contained in the aqueous solution. Is about 70 ° C. when is 17% by weight.

The dissolution time is 1 minute to 6 hours, preferably 5 minutes to 2 hours. If the dissolution time is shortened, the dissolution of PN is not sufficient, and the PN content in the separated crystals increases. In addition, if the dissolution time is lengthened, the volume of the dissolution tank increases, which is not preferable.

The heating of the slurry containing the crystallized PN and DPN may be performed using a stirring tank equipped with a jacket or an internal coil, or may be performed using a heat exchanger.

The hydrated cake obtained by solid-liquid separation of the slurry obtained by dissolving all or almost all of the PN thus obtained may cause impurities to be mixed by rinsing with pure water. The adhesion of mother liquor can be prevented.

The wet cake obtained by the above operation is
A DPN product can be obtained by drying by a method generally used in industry.

In carrying out the method of the present invention,
The measurement may be performed using a batch type device or a continuous type device.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments.

Example 1 Concentration by weight of PN obtained during the PN manufacturing process 17.3
%, 1000 g of an aqueous solution having a PN / DPN weight ratio of 7.5,
Charge into a 1 L glass stirring tank and stir 90
The temperature was gradually cooled from 40 ° C. to 40 ° C., maintained for 1 hour, then raised to 70 ° C., and further maintained for 30 minutes. After filtering the whole amount of the obtained slurry under reduced pressure with a glass filter, the mixture was rinsed with 20 g of pure water at room temperature, and 10.3 g of a wet cake was obtained.
I got

The obtained wet cake was subjected to JIS K151
8 according to the method for measuring loss on drying of PN described in
After drying for 2 hours in a drier maintained at 8 ° C., the loss on drying was determined to be 46.8% by weight. Further, the crystals obtained by drying are subjected to ASTM D-2999.
Analysis by a silylation gas chromatography method based on the purity analysis method of PN described in -85 showed that the contents of PN and DPN were 1.1% and 9% by weight, respectively.
It was 4.9%.

Example 2 PN weight-based concentration obtained in the PN production process 17.3
%, 1000 g of an aqueous solution having a PN / DPN weight ratio of 7.5,
Charge into a 1 L glass stirring tank and stir 90
The temperature was gradually cooled from 40 ° C. to 40 ° C., maintained for 1 hour, then raised to 70 ° C., and further maintained for 5 minutes. After filtering the whole amount of the obtained slurry under reduced pressure using a glass filter, the resultant was rinsed with 20 g of pure water at room temperature to obtain 10.5 g of a wet cake.

The drying loss of the obtained water-containing cake was determined in Example 1.
When measured by the same method as in the above, 48.7% on a weight basis
Met. Further, the crystals obtained by drying were analyzed in the same manner as in Example 1. As a result, the contents of PN and DPN were 1.9% and 93.8% on a weight basis, respectively.

Example 3 Concentration by weight of PN obtained during the PN production process 17.6
%, An aqueous solution having a PN / DPN weight ratio of 7.4 at 90 ° C.
In a 1-liter complete mixing tank type crystallization tank equipped with a stirrer and a heat insulation jacket, set the average residence time to 1 hour,
The feed was continuous at a flow rate of 1 L per hour. The temperature in the crystallization tank is maintained by the medium of the jacket so as to be 40 ° C.

The slurry continuously pumped out of the crystallization tank is continuously fed to a complete mixing type dissolution tank equipped with a stirrer and a jacket for keeping warm. The volume of the dissolution tank was 500 mL so that the average residence time was 30 minutes. The temperature in the melting tank is maintained at 70 ° C. by the medium of the jacket.

Eight hours after starting the feed to the crystallization tank,
After the whole amount of the slurry in the dissolving tank was filtered under reduced pressure with a glass filter, rinsing with 10 g of pure water at room temperature was performed.
4.9 g of a water-containing cake was obtained. The loss on drying of the obtained water-containing cake was measured by the same method as in Example 1, and it was 48.1% by weight. Further, the crystals obtained by drying were analyzed by the same method as in Example 1.
The content of PN was 1.3% and 94.
2%.

Example 4 PN concentration by weight of 7.8% obtained in the PN production process,
An aqueous solution having a PN / DPN weight ratio of 11.0 was adjusted to 50 ° C., and was placed in a 1-liter complete mixing tank type crystallization tank equipped with a stirrer and a heat retaining jacket so that the average residence time was 1 hour. It was fed continuously at a flow rate of 1 L. The temperature in the crystallization tank is maintained at 10 ° C. by the medium of the jacket.

Then, the slurry continuously extracted from the crystallization tank by a pump is continuously fed to a complete mixing type dissolution tank equipped with a stirrer and a jacket for keeping heat. The capacity of the dissolution tank was 1 L so that the average residence time was 1 hour. The temperature in the melting tank is maintained at 30 ° C. by the medium of the jacket.

Eight hours after starting the feed to the crystallization tank,
After the whole amount of the slurry in the dissolving tank was filtered under reduced pressure with a glass filter, the solution was rinsed with 5 g of pure water at room temperature to obtain 0.9 g of a water-containing cake. When the loss on drying of the obtained water-containing cake was measured by the same method as in Example 1, it was 52.5% by weight. Further, the crystals obtained by drying were analyzed by the same method as in Example 1. As a result, PN and DPN were analyzed.
Are 1.4% and 94.7%, respectively, by weight.
Met.

Example 5 Concentration by weight of PN obtained in the PN production process of 38.5
%, An aqueous solution having a PN / DPN weight ratio of 10.4 was adjusted to 100 ° C., and a volume of 500 mL equipped with a stirrer and a heat retaining jacket
Was fed continuously at a flow rate of 1 L per hour so that the average residence time was 30 minutes. The temperature in the crystallization tank is maintained at 80 ° C. by the medium of the jacket.

Then, the slurry continuously extracted from the crystallization tank by a pump is continuously fed to a complete mixing type dissolution tank equipped with a stirrer and a jacket for keeping heat. The capacity of the dissolution tank was 1 L so that the average residence time was 1 hour. The temperature in the melting tank is maintained at 95 ° C. by the medium of the jacket.

Six hours after starting the feed to the crystallization tank,
The whole amount of the slurry in the dissolving tank was filtered by a pressure filter pre-heated to 95 ° C., and then rinsed with 10 g of pure water at normal temperature to obtain 2.3 g of a water-containing cake. The loss on drying of the obtained water-containing cake was measured by the same method as in Example 1, and it was 32.4% by weight. Further, the crystals obtained by drying were analyzed in the same manner as in Example 1, and the contents of PN and DPN were each 1.
1% and 94.4%.

Comparative Example 1 PN weight-based concentration obtained in the PN manufacturing process 17.3
%, 1000 g of an aqueous solution having a PN / DPN weight ratio of 7.5,
Charge into a 1 L glass stirring tank and stir 90
The temperature was gradually cooled from 40 ° C. to 40 ° C. and maintained for 1 hour. After filtering the whole amount of the obtained slurry under reduced pressure with a glass filter, the resultant was rinsed with 50 g of pure water at room temperature to obtain 70.8 g of a wet cake.

The drying loss of the obtained water-containing cake was measured in Example 1.
38.7% by weight based on the same method
Met. Further, the crystals obtained by drying were analyzed in the same manner as in Example 1. As a result, the contents of PN and DPN were 82.9% and 14.7% on a weight basis, respectively.

Comparative Example 2 PN weight-based concentration obtained in the PN production process 17.6
%, An aqueous solution having a PN / DPN weight ratio of 7.3 at 90 ° C.
The mixture was continuously fed at a flow rate of 1 L / hour to a complete mixing tank type crystallization tank having a capacity of 200 mL and equipped with a stirrer and a heat retaining jacket so that the average residence time was 12 minutes. The temperature in the crystallization tank is maintained by the medium of the jacket so as to be 40 ° C.

The slurry continuously pumped out of the crystallization tank is continuously fed to a complete mixing type dissolving tank equipped with a stirrer and a heat retaining jacket. The volume of the dissolution tank was 500 mL so that the average residence time was 30 minutes. The temperature in the melting tank is maintained at 70 ° C. by a medium in a jacket. Eight hours after the feed to the crystallization tank was started, the solution in the dissolution tank was confirmed to be transparent, and no crystals could be obtained because the average residence time was short.

[0042]

In obtaining dipentaerythritol,
After crystallization from an aqueous solution containing pentaerythritol and dipentaerythritol without adding unnecessary water during the production process, collecting the water, and further consuming unnecessary energy that also requires purification. It is possible to provide a method for separating dipentaerythritol having a low pentaerythritol content with high purity by a simple operation such as heating and dissolving, which is industrially superior.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsutomu Kajiguri 1-6-6 Takasago, Takaishi City, Osaka Prefecture Mitsui Chemicals, Inc. (72) Inventor Yoshiichi Uehara 1-6-6 Takasago, Takaishi City, Osaka Mitsui Chemicals, Inc. F term (reference) 4H006 AA02 AD15 AD17 BB31 BC50 BC51 BD82 FG40 FG90

Claims (3)

[Claims] 1. A method for separating dipentaerythritol from an aqueous solution containing pentaerythritol and dipentaerythritol, wherein the aqueous solution is crystallized to obtain a slurry containing crystallized pentaerythritol and dipentaerythritol, The total amount of pentaerythritol,
Alternatively, a method for separating dipentaerythritol, which further comprises solid-liquid separation of a slurry obtained by heating until almost the entire amount is dissolved. 2. An aqueous solution containing pentaerythritol and dipentaerythritol, wherein the weight-based concentration of pentaerythritol is 5 to 50% and pentaerythritol /
The method for separating dipentaerythritol according to claim 1, wherein the weight ratio of dipentaerythritol is 1 to 16. 3. The total amount of pentaerythritol, or
2. The dipentaerythritol according to claim 1, wherein the temperature for heating until almost the entire amount is dissolved is 2 to 50 ° C. higher than the crystallization temperature of the aqueous solution containing pentaerythritol and dipentaerythritol and is maintained for 1 minute to 2 hours. Separation method.