JPH03135931A - Method for distilling and isolating oligoethylene glycols - Google Patents

Abstract

PURPOSE:To obtain the subject high-purity substance of good hue without scorch smell by rectifying a mixture of oligoethylene glycols and a mixture of chain or alicyclic saturated hydrocarbons using a rectifying column and carrying out phase separation of the resultant mixed distillate. CONSTITUTION:A mixture of oligoethylene glycols (OEG) and a mixture of 14-20C chain or alicyclic saturated hydrocarbons expressed by formula I (m is a positive number of >3) are placed in a still having a rectifying column and a reflex device and preferably rectified at 100-200 deg.C under about 5-20 mmHg vacuum degree and both of the simultaneously vaporized components are then reflexed at a desired reflux ratio to afford a high-quality compound expressed by formula II (n is 4, 5 or 6) of desired purity. It is essential that the compounds expressed by formula I will not mutually dissolve in the OEG and the boiling point thereof is remarkably higher than that of the OEG. The compound expressed by formula II is useful as a raw material for unsaturated polyesters, polyurethanes, etc.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is useful as a raw material for unsaturated polyesters or polyurethanes, etc., and is useful for materials containing 4.5 or 4.5 This invention relates to a method for distilling and isolating high quality oligoethylene glycols.

“Prior art” Oligoethylene glycols with a low degree of polycondensation (hereinafter referred to as OE
Abbreviated as G. ) Even if an attempt is made to obtain each isolated component from a mixture of Even if obtained by
The only quality products that could be obtained were those that contained thermal decomposition products or were colored and had a burnt odor.

Even if an attempt is made to achieve the above objective by lowering the apparent boiling point by rectifying OEG, which is the raw material, by coexisting with a second component that is mutually soluble with OEG, the objective of lowering the boiling point is not achieved with this method. However, since the distilled components mix with each other to form a homogeneous solution, the purpose of isolating glycols cannot be fully achieved.

"Problem to be Solved by the Invention" If components that do not dissolve in each other in the liquid phase and gas phase coexist in the above OEG mixture, the partial pressure occupied by OEG during distillation will become part of the pressure in the distillation apparatus. Therefore, it is expected that substantially the same result as distilling OEG at a higher degree of vacuum will be obtained, and the present inventors have already filed an application as a new invention based on the results of their study. .

In this application, the OEGs to be distilled are of high quality without any coloration or so-called burnt odor, but they are OEG mixtures in which the number of oxyethylene groups is within a specific range, for example, In cases where pentaethylene glycol alone is required, this method is still technically insufficient.

That is, the problem to be solved by the method of the present invention is how to easily obtain a single compound of high molecular weight ethylene glycols, which is difficult to obtain by known methods.

For the reasons mentioned above, the present inventors continued their studies and found that even if a rectification operation is added during the above-mentioned special distillation, it will not be possible to solve the problem based on the conventional knowledge regarding the vapor-liquid equilibrium relationship. discovered an unthinkable fact and arrived at the present invention.

That is, the present invention provides a mixture of oligoethylene glycols represented by the following general formula [1] and HO(CH2CH2)mOH---[1] where m represents a positive number exceeding 3. A mixture of linear or alicyclic saturated hydrocarbons having 14 to 20 carbon atoms is subjected to a rectification operation using a rectification column, and the resulting mixed distillate is subjected to phase separation. This is a distillation method for isolating oligoethylene glycols.

HO(CH2CH2)nOH-----[2] where n is 4, 5 or 6. J As mentioned above, a rectification operation is essential to carrying out the method of the present invention, and for this purpose, the distillation apparatus must be equipped with a rectification column and a reflux apparatus.

(Here, the rectification operation and the rectification column are defined, for example, as described in "Chemistry Dictionary" (Kyoritsu Shuppansha, 1971 edition, pages 282-283).) The number of plates in the rectification column should be determined depending on the operating conditions, the raw materials used, and the purity of the components to be obtained, but the preferred number of theoretical plates is 3 to 20.

The OEG used in the method of the present invention before distillation may be any mixture as long as m in the formula [11] exceeds 3, but if m is too large, the distillation operation temperature will become too high and the Therefore, OEG mixtures with m between 3 and 8 should be used as raw materials.

Furthermore, if m is 3 or less, it is not necessary to use the method of the present invention since it can be obtained by a well-known method commonly used in industry without using the method of the present invention.

The other raw material used in the method of the present invention is a specific hydrocarbon, which must be substantially insoluble with OEG before and after the distillation, and must have a boiling point lower than that of the OEG to be obtained. It is essential that the value is not extremely high. Hydrocarbons that meet these conditions have a carbon number of 1
Saturated chain or saturated alicyclic hydrocarbons having 2 to 30 carbon atoms are preferred, and the above hydrocarbons having 14 to 20 carbon atoms are particularly preferred.

These hydrocarbons include chain hydrocarbons such as tetradecane, pentadecane, hexadecane, heptadecane, octadecane, lanadecane, and eicosane, and alicyclic hydrocarbons such as octylcyclohexane, undecylcyclohexane, dodecylcyclohexane, and decylcyclooctane. I can give an example. These can be used alone or in a mixture of two or more.

The OEGs having an average repeating unit number of oxyethylene groups exceeding 3 to be used in the method of the present invention may be any OEGs as long as the average molecular weight exceeds the molecular weight of triethylene glycol, that is, 150; When the molecular weight becomes larger, even if the above-mentioned hydrocarbons are used for distillation, there is very little risk of OEGs being distilled out in parallel. Therefore, OEGs having an average molecular weight of less than 500 are preferably used.

These OEGs include relatively low molecular weight portions of polyethylene glycol, distillation residues containing tetraethylene glycol or pentaethylene glycol, which are by-products during the production of ethylene glycols, and polyethylene terephthalate using ethylene glycol. Examples include residual components during distillation recovery for reuse of ethylene glycol recovered during the production of ethylene glycol.

Next, an embodiment of the method of the present invention will be described using a batch operation as an example.

If the raw materials OEG and hydrocarbons are put into a distillation vessel equipped with a rectification column and a reflux device and heated at the desired degree of vacuum, OEG and hydrocarbons will vaporize at the same time. The OEG isolated component and hydrocarbon gas of desired purity are obtained by refluxing at a desired reflux ratio through the OEG, and by cooling this, it is possible to obtain a high quality target isolated component without coloration or burnt depth. can.

The degree of vacuum at the time of distillation varies depending on the average molecular weight of the raw material OEG used and the type of hydrocarbons coexisting, but preferably it should be distilled at a pressure of about 5-20 mmHG, and at this degree of vacuum, the distillation temperature The temperature is about 100-200°C. Naturally, it is also possible to carry out the process of the invention continuously.

These liquids obtained by liquefaction do not dissolve in each other and separate into two phases, so by phase-separating them using a known method, the desired OEG isolated component and hydrocarbons can be separated. It goes without saying that the separated hydrocarbons can be recycled and used again in the distillation system.

The solubility of the hydrocarbons in the obtained OEG is extremely low, and therefore it is not necessarily necessary to carry out purification operations such as washing. However, depending on the intended use of the obtained OEG, known methods such as activated clay or may be purified by adsorption treatment using an adsorbent such as activated carbon, or by extracting trace amounts of the hydrocarbons with low boiling point hydrocarbons such as n-hexane.

Although the method of the present invention is a method for obtaining high-quality, high-boiling point ethylene glycols alone, which are extremely difficult to obtain using known separation methods, it is a matter of course that the method of the present invention can be applied to the rectification of hydrocarbons.

"Example" The method of the present invention will be explained in more detail below by giving Examples and Comparative Examples.

In the following description, 2 indicates weight % unless otherwise specified.

Example 1 15L of triethylene glycol was added to an IQ distiller equipped with a 30aa long Widma rectifier, a reflux device, and a liquid-liquid separator.
500 g of a brown-colored oligoethylene glycol mixture consisting of 16% tetraethylene glycol and 9% high-boiling glycols higher than pentaethylene glycol and 80 g of heptadecane with a purity of 98% were added.

The distiller was heated to a reduced pressure of 9 to 10 μmHg, and when the temperature in the system reached 138 to 142° C., distillation started, and the reflux ratio was set to 0.5, and a distillate of 74 K was obtained by cooling. The composition of this distillate was 95% triethylene glycol and 5z tetraethylene glycol.

Thereafter, 9-10 ml (154-156°C)
345 g of pure tetraethylene glycol was obtained under the conditions of g and reflux ratio of 1.0.

During the above distillation, the heptadecane distilled in parallel was returned to the distiller via a liquid-liquid separator.

The purity of the obtained tetraethylene glycol was 99.2%
The hue was below IO as expressed by ^PHA (hue display method based on the American Public Health Association). Also, there is no burnt smell.

It wasn't bad.

Example 2 A distillation apparatus similar to Example 1 except that a rectification column filled with a glass Utschig ring was used, and high molecular weight glycols higher than 18% tetraethylene glycol, pentaethylene glycol 72z, and hexaethylene glycol were used! 500 g of a brown oligoethylene glycol mixture containing 39% octadecane, nona.

First, 89 g of tetraethylene glycol with a purity of 94% was obtained under the conditions of 151-160°C, 5-6 mm1 (and reflux ratio 0.5), and then 160-164°C,
5.5-6.6++uaHg.

321 g of pentaethylene glycol with a purity of 99.0% was obtained under the conditions of a reflux ratio of 1.0. Its hue was 15 on the APHA scale.

During the above rectification, hydrocarbons distilled out in parallel were separated in a liquid-liquid separator and returned to the distiller.

Example 3 A brown oligoethylene glycol mixture consisting of 35% pentaethylene glycol, 57% hexaethylene glycol, and 8% high molecular weight glycols higher than octaethylene glycol and 80 g of eicosane were placed in a distillation apparatus similar to that described in Example 2. A rectification similar to that described in Example 2 was carried out.

First, 174-177℃, 6mmHg and reflux ratio 1.0
Under the following conditions, 158 g of pentaethylene glycol with a purity of 98% and a hue of API (A designation of 15) was obtained.
~! 222 g of hexaethylene glycol with a purity of 98.chi. was obtained under the conditions of 85 DEG C., 7 to 8 mat (g) and a reflux ratio of 1.0.The hue was 20 or less in APHA.

Example 4 Triethylene glycol 1 was added to the same distillation apparatus as Example 1.
5x, a brown-colored oligoethylene glycol mixture 500 consisting of 76% tetraethylene glycol and 9% high molecular weight glycols higher than pentaethylene glycol.
g and 80 g of a saturated alicyclic hydrocarbon mixture consisting of 40% decylcyclohexane, 30% undecylcyclohexane and 30% dodecylcyclohexane were added, and rectification was carried out in the same manner as described in Example 2.

After distilling 74 g of triethylene glycol with a purity of 95% under the conditions of +20-128°C and a 9-10m9-1O reflux ratio of 0.5, it was subsequently heated to +32-137°C,! 11-1
011-1O and a reflux ratio of 1.0, 342 g of tetraethylene glycol with a purity of 99.3L and a hue of less than 1O as indicated by APIIA was obtained.

Comparative Example 1 When the method described in Example 1 was repeated without adding any hydrocarbons, no glycols including triethylene glycol were distilled out.

Furthermore, when the temperature was raised at the same degree of vacuum, triethylene glycol distilled out when the temperature exceeded 160°C, but glycols higher than tetraethylene glycol could not be distilled out at the same temperature, and only after reaching 200°C or higher. Tetraethylene glycol began to distill out.

The purity of the obtained tetraethylene glycol was 95%, but the hue was 150 or more according to APIIA, and it had a significant burnt odor.

"Effect of the invention J By using the method of the present invention, tetraethylene glycol, pentaethylene glycol, or hexaethylene glycol with high purity, good color, and no burnt odor, which could not be obtained by any known method, can be obtained. can be obtained.

Claims (1)

[Claims] 1. A mixture of oligoethylene glycols represented by the following general formula [1] and HO(CH_2CH_2)_mOH---[1] "Here, m is a positive number exceeding 3. The following general formula is characterized in that a mixture of linear or alicyclic saturated hydrocarbons having 14 to 20 carbon atoms is subjected to a rectification operation using a rectification column, and the resulting mixed distillate is subjected to phase separation. [2]
Distillation isolation method for oligoethylene glycols shown in . HO(CH_2CH_2)_nOH---[2] "Here, n is 4, 5 or 6."