JPH0477751B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying dibenzylidene sorbitols (hereinafter referred to as DBS) represented by the following general formula, and more specifically to a purification method using a fluid in a subcritical or supercritical state. (In the formula, R represents an alkyl group, an alkoxy group, a halide atom, or a nitro group, m and n each represent an integer of 0 to 5, and p represents an integer of 0 to 1.) It is a useful compound that is used in many other fields, such as solidifying, gelling, and thickening organic liquids, as a nucleating agent for various polymers, and for recovering organic substances. DBSs are generally produced by condensation of polyhydric alcohols and aromatic aldehydes, and the production method has been published in various patents and literature. These manufacturing methods yield products with sufficient purity for practical use and have already been commercialized, but depending on the application, DBS
The purity, odor, etc. of the product are greatly affected, and the commercial value may not be satisfied. For example, structural isomers other than 1,3:2,4 in the general formula (1,
2:3, 4, etc.) or trace amounts of aromatic aldehydes remaining, which requires extreme purification to completely remove them. As an example, washing methods and recrystallization methods using organic solvents have been proposed, but the purification itself is not perfect, there are problems with the danger of using organic solvents, and there are problems such as the need for a drying process after treatment, etc. This is not something to be satisfied with. Therefore, the present inventors have conducted repeated research with the aim of industrially advantageously obtaining high-purity DBS, and have utilized the characteristics of subcritical or supercritical fluids to reduce impurities in DBS. It was discovered that highly purified DBS can be obtained by using it as an extraction solvent, and the present invention was achieved. Furthermore, the present invention was completed by studying the extraction process, the type of extractant, the conditions for separating the extract, etc. That is, an object of the present invention is to provide an industrially advantageous method for purifying DBS, and its gist is an extraction purification method characterized by using a fluid in a subcritical or supercritical state as an extraction solvent. . A method of separating organic compounds from a mixture containing them using a fluid in a subcritical or supercritical state is known, for example, as described in Japanese Patent Publication No. 10539/1982, but a method of extracting impurities from DBSs is well known. is not yet known. A fluid in a subcritical or supercritical state is a fluid in a state near or exceeding critical temperature and pressure. For example, ethylene (9.9℃,
50.5atm), ammonia (132.3℃, 111.3atm), and carbon dioxide (31.0℃, 72.9atm), which are near or above the critical state and have a density close to that of a liquid due to large diffusion close to a gaseous body. It is a fluid with a coefficient. Because of this physical property, various compounds can be extracted quickly and efficiently in large quantities, and the extractant can be easily separated. In the present invention, any of the above-mentioned fluids in the subcritical or supercritical state can generally be used, but they must be harmless and inert, can be processed at relatively low temperatures, and are easy to handle and operate. Carbon dioxide (CO ₂ ) is widely used as an extraction agent because it has many advantages such as being economically advantageous. Furthermore, types of DBS,
The optimum temperature and pressure conditions should be selected depending on the type and amount of impurities contained therein. Also
Appropriate amounts of various entrainers such as lower alcohols, aromatic hydrocarbons, cyclic ethers, and aliphatic ketones, which are conventionally used as organic solvents for refining DBS, are blended to produce a fluid in the subcritical or supercritical state. When used simultaneously, more efficient and selective extraction and purification can be achieved due to the synergistic effect compared to when used alone. Examples of these organic solvents include methanol, ethanol, isopropyl alcohol, n-butanol, isobutanol, benzene, toluene, xylene, tetrahydrofuran, telohydropyran, dioxane, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl n- Targets include amyl ketone, etc.
Select the appropriate amount depending on the type and purpose of DBS and use. Embodiments of the present invention will be described below based on a flow sheet. In Fig. 1, CO ₂ from cylinder 1 to compressor 2
The CO ₂ compressed to a predetermined pressure using a heat exchanger 3 is set at a predetermined extraction temperature and brought into a subcritical or supercritical state and introduced into an extraction and purification column 4 . The extraction and purification tower 4 is filled with raw material DBS, and the CO ₂ phase from which impurities have been extracted is reduced in pressure through a pressure reducing valve 5 and led to a separator 6 to separate the extract from the CO ₂ . The CO ₂ separated from the extract is cooled and liquefied in a condenser 7 and recycled via a compressor 2. In addition, when blending the entrainer, the entrainer is mixed with the raw material in advance and packed into the extraction and purification tower 4, or a predetermined amount is sent from the entrainer holder 8 to the heat exchanger 3 using the pump 9. In the above process, the pressure of CO ₂ in the extraction and purification column is 50 to 500 Kg/cm ² , preferably 60 to 300 Kg/cm ² ,
It is necessary to maintain the temperature in the range of 25 to 100°C, preferably 30 to 70°C for extraction. If the temperature is too low, the CO ₂ becomes liquefied, resulting in poor contact efficiency with DBS, and energy is required to separate the extract from the extractant. On the other hand, if the pressure and temperature are too high, the cost of the equipment will increase and there may be problems with economic efficiency. In addition to the above-mentioned reduced pressure method, the extract and the extractant may be separated by a temperature change method. In addition, if organic solvents are used together, the raw materials
There are two methods: one is to charge the extraction agent together with DBS into the extraction and purification tower and then feed the extractant, and the other is to mix it with the extractant in advance and feed it. Although high-quality DBS can be obtained by the method of the present invention, the following superior effects can be achieved compared to conventional methods. (1) Organic solvent extraction can extract and remove components that are difficult to extract, making it possible to obtain extremely high-quality DBS. (2) Since it is possible to selectively extract only impurity components, the product
DBS has a high recovery rate and is economical. (3) The use of subcritical or commercially critical fluids eliminates the need for drying the product, and the separation of the raffinate phase and extractant is complete, eliminating the possibility of residual solvent as in the case of extraction with organic solvents. It can be used in the pharmaceutical and food fields without any concerns. (4) Impurity components can be extracted selectively and efficiently by selecting pressure and temperature conditions and blending additives. (5) If CO ₂ is used as an extractant, the DBS will not undergo any changes and can be completely handled since it is operated under mild temperature conditions and in an inert atmosphere. EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. Example 1 2 kg of 1,3:2,4-dimethylbenzylidene sorbitol with a purity of 99% was packed into an extraction and purification column with an internal capacity of 5, and the extraction temperature was adjusted according to the process shown in Figure 1.
Extract and purify using _CO2 at 43℃ and pressure 200Kg/ ^cm2 ,
The extract was separated at room temperature and atmospheric pressure to obtain about 20 g of extract and 1980 g of extracted residue. When the extract and extraction residue were analyzed, the extraction residue was powder and the purity was
It was 99.9% 1,3:2,4-dimethylbenzylidene sorbitol. Extracts are liquid substances;
It was an isomer mixture of dimethylbenzylidene sorbitol and trimethylbenzylidene sorbitol. Example 2 The same 1,3:2,4-dimethylbenzylidene sorbitol used in Example 1 (2 kg) mixed with about 2 kg of methanol was used as the raw material, and the extraction temperature was 43°C and the pressure was 200 kg/min using the same process as in Example 1. ^cm2
Extract and purify using CO ₂ and separate the extract from the extraction solvent under atmospheric pressure. Approximately 80 g of extract and 1900
g of the extraction residue was obtained. When the extract and the extraction residue were analyzed, the purity of the extraction residue powder was 100.0%. The extract was solid and contained 25% 1,3:2,4-dimethylbenzylidene sorbitol, the rest being an isomeric mixture of monomethylbenzylidene sorbitol, dimethylbenzylidene sorbitol, and trimethylbenzylidene sorbitol. Example 3 Using 2 kg of 13:2,4-diethylbenzylidene sorbitol with a purity of 98% as a raw material, extraction temperature was 41°C and methanol was added at 5 to 10% by the process shown in Figure 1.
Extraction and purification was performed using CO ₂ containing % by weight at a pressure of 220 to 230 kg/cm ² , and the extract was separated from the extraction solvent under atmospheric pressure to obtain about 80 g of extract and 1900 g of extraction residue. When the extract and extraction residue were analyzed, the extraction residue was found to be a powder with a purity of 100.0%. The extract was solid and contained approximately 50% 1,3:2,4-diethylbenzylidene sorbitol, the rest being an isomeric mixture of monoethylbenzylidene sorbitols, diethylbenzylidene sorbitols, and triethylbenzylidene sorbitols. . (Odor determination) Examples 1 to 200ml mayonnaise bottles as samples
Add 20g of the extraction residue obtained in step 3 and seal the container. 100℃×2
After heating for a certain period of time, remove the stopper and use your sense of smell to determine the presence or absence of the odor. The obtained results are listed in Table 1, and for comparison, the results of odor determination using the unpurified sample as a sample according to the above method are also shown.

[Table] As is clear from Table 1, the extraction residues obtained in Examples 1 to 3 are all odorless, and the strong odor before extraction and purification has been removed.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A purification method characterized by treating dibenzylidene sorbitol represented by the following general formula with a fluid in a subcritical or supercritical state. (In the formula, R represents an alkyl group, an alkoxy group, a halogen atom, or a nitro group, m and n each represent an integer of 0 to 5, and p represents an integer of 0 to 1.) 2 A fluid in a subcritical or supercritical state 2. The method according to claim 1, wherein the carbon dioxide is carbon dioxide. 3 Fluid in subcritical or supercritical state has a pressure of 60~
3. The method according to claim 2, wherein the carbon dioxide is 300 Kg/cm ² and a temperature of 25 to 70°C. 4. The method according to claim 2 or 3, wherein carbon dioxide is mixed with at least one organic solvent selected from the group consisting of lower alcohols, aromatic hydrocarbons, cyclic ethers, and aliphatic ketones. 5. The method according to claim 4, wherein the organic solvent is methanol.