JP7567526B2 - Method for producing polyalkylene ether glycol - Google Patents

Description

The present invention relates to a method for producing polyalkylene ether glycol, which is a raw material for polyurethane, polyurethane urea, polyester, etc.

Polyalkylene ether glycols, particularly polytetramethylene ether glycol (hereinafter sometimes abbreviated as "PTMG"), are used as polyester raw materials for thermosetting polyurethanes, thermoplastic polyurethanes, polyurethane ureas, thermoplastic elastomers, and the like.

A method for producing a polyalkylene ether glycol includes, for example, ring-opening polymerization of a cyclic ether in the presence of an acid catalyst and a carboxylic acid anhydride such as acetic anhydride to obtain a dicarboxylic acid ester of a polyalkylene ether glycol, and then subjecting the obtained diester to
The diester of polyalkylene ether glycol is converted into polyalkylene ether glycol by an alcoholysis reaction with an alkanol such as methanol, and the alkanol contained in the produced polyalkylene ether glycol is distilled off.
Patent Document 1 discloses a method for converting a diester of a polyalkylene ether glycol into a polyalkylene ether glycol by an alcoholysis reaction with an alkanol in the presence of a catalyst, in which the alkanol contained in the produced polyalkylene ether glycol is returned to the reaction system as a specific amount of water.

Patent Document 2 describes the use of a specific reactor for suppressing foaming in a process for producing polytetrahydrofuran having terminal hydroxyl groups by transesterification with an alcohol from acyloxy group-containing polytetrahydrofuran.

JP 2006-291189 A Japanese Patent Application Publication No. 11-158263

However, in the previously known methods, when removing alkanol from a mixture containing the polyalkylene ether glycol obtained by the alcoholysis reaction and the alkanol, the suppression of foaming was insufficient, and it was necessary to remove the alkanol in small amounts over a long period of time, or to use specific production equipment and remove the alkanol under specific production conditions while suppressing foaming.

The present invention has been made in view of the above problems, and provides a method for producing an alkanol-containing polyalkylene ether glycol by a simple operation from a mixture containing an alkanol and a polyalkylene ether glycol obtained by an alcoholysis reaction,
The object of the present invention is to provide a method for producing a polyalkylene ether glycol, which can efficiently remove alkanol while suppressing foaming.

As a result of investigations aimed at solving the above-mentioned problems, the present inventors have found that by adding a specific amount of a specific compound to a mixture containing a polyalkylene ether glycol obtained by an alcoholysis reaction and an alkanol, the occurrence of problems such as foaming can be suppressed and the alkanol can be efficiently removed from the mixture, which has led to the completion of the present invention.
The present invention has been achieved based on these findings, and is summarized in the following [1] to [4].

[1] A method for producing a polyalkylene ether glycol, comprising the steps of: subjecting a diester of a polyalkylene ether glycol to an alcoholysis reaction with an alkanol to obtain a mixture containing a polyalkylene ether glycol and an alkanol; and adding a compound to the mixture and removing the alkanol to obtain a crude alkylene ether glycol, wherein the solubility parameter SPa of the compound and the solubility parameter SP of the polyalkylene ether glycol are
and the absolute value of the difference between said compound and b is 12.9 or more, and the amount of said compound added is 3% by mass or more and 20% by mass or less based on the amount of polyalkylene ether glycol in the mixture.
[2] The method for producing a polyalkylene ether glycol according to [1], wherein the polyalkylene ether glycol is polytetramethylene ether glycol.
[3] The method for producing a polyalkylene ether glycol according to [1] or [2], wherein the alkanol is a C ₁ -C ₄ alkanol.
[4] The method for producing a polyalkylene ether glycol according to any one of [1] to 3, wherein the temperature for removing the alkanol is 60° C. or higher and 250° C. or lower.
[5] The concentration of polyalkylene ether glycol in the mixture is 30% by mass or more and 90% by mass or more.
5. The method for producing a polyalkylene ether glycol according to any one of [1] to [4], wherein the amount of the polyalkylene ether glycol is 0.01 to 0.25 wt % or less.
[6] The method for producing a polyalkylene ether glycol according to any one of [1] to [5], wherein the polyalkylene ether glycol has a number average molecular weight of 600 or more and 8,000 or less.

By carrying out the method for producing a polyalkylene ether glycol of the present invention, the occurrence of problems such as foaming can be suppressed and the alkanol can be efficiently removed from a mixture containing a polyalkylene ether glycol and an alkanol.

Schematic diagram of a glass heating type low boiling separation device used in the examples

The manufacturing method of the present invention will be described in detail below. The following description of the constituent elements is based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, the numerical ranges expressed using "to" are expressed as "to" and "to".
This means a range that includes the numbers written before and after as the lower and upper limits.

The polyalkylene ether glycol diester used in the production method of the present invention can be any conventionally known one.In addition, the polyalkylene ether glycol diester used in the present invention is preferably a polyalkylene ether glycol dicarboxylate, since it is easily dissolved in alkanol and the effect of the present invention is remarkable.Hereinafter, the polyalkylene ether glycol diester will be described using the polyalkylene ether glycol dicarboxylate as an example.

The method for producing the dicarboxylic acid ester of polyalkylene ether glycol may be any method as long as the dicarboxylic acid ester of polyalkylene ether glycol is produced. The dicarboxylic acid ester of polyalkylene ether glycol may be obtained, for example, by ring-opening polymerization of a cyclic ether in the presence of a carboxylic acid, a carboxylic anhydride, and an acid catalyst.

The polymerizability of the cyclic ether decreases when the number of carbon atoms in the ring constituting the cyclic ether is large. The number of carbon atoms in the ring constituting the cyclic ether is usually 2 to 10, and preferably 2 to 6. Specifically, the cyclic ether is a combination of one or more selected from cyclic ethers such as tetrahydrofuran (THF), ethylene oxide, propylene oxide, oxetane, tetrahydropyran, oxepane, 1,4-dioxane, and the like, and their derivatives. When two or more cyclic ethers are combined, even if one of them is difficult to polymerize, the polymerization is easy to proceed, which is preferable. Derivatives of these cyclic ethers include those in which the cyclic ethers are substituted with alkyl groups, aryl groups, acyl groups, halogen atoms, and the like. Here, the alkyl groups, aryl groups, acyl groups, and the like may further have a substituent. Examples of alkyl groups, aryl groups, acyl groups, and the like further having a substituent include alkoxy groups, aryloxy groups, acyloxy groups, arylalkyl groups, acylalkyl groups, alkoxyalkyl groups, acyloxyalkyl groups, aryloxyalkyl groups, and halogenated versions of these substituents. More specifically, the cyclic ether derivatives include 3-methyl-tetrahydrofuran, 2-methyl-tetrahydrofuran, 3-methyloxetane, 3,3-dimethyloxetane, 3-chloromethyl-3-ethyloxetane, and 3,3-bischloromethyloxetane.
Among these, tetrahydrofuran is preferred because it is easily polymerizable and has excellent physical properties when made into a polyurethane resin or the like.

The carboxylic acid used is an aliphatic or aromatic carboxylic acid. The number of carbon atoms in the carboxylic acid is usually 2 to 12, preferably 2 to 8. Specific examples of the carboxylic acid include:
Examples of suitable acids include acetic acid, propionic acid, butyric acid, maleic acid, succinic acid, phthalic acid, benzoic acid, etc. Among these, acetic acid, which has a small molecular weight, is preferably used because it is effective in controlling the molecular weight even in a small amount.

Examples of the carboxylic acid anhydride include the anhydrides of the above-mentioned carboxylic acids. The carboxylic acid anhydride may react with a trace amount of moisture in the reaction system, and part of it may become a carboxylic acid. Therefore, in order not to complicate the reaction system, it is preferable to use a carboxylic acid anhydride corresponding to the carboxylic acid used in the present invention. That is, it is particularly preferable to use acetic acid and acetic anhydride as the carboxylic acid and carboxylic acid anhydride used in the production of the diester of polyalkylene ether glycol.

The concentration of the carboxylic acid anhydride in the raw material solution varies depending on the molecular weight of the target polyalkylene ether glycol and the type of catalyst, but the lower limit is usually 0.1 mass%, preferably 0.5 mass%, and the upper limit is usually 30 mass%, preferably 15 mass%. The ratio (molar ratio) of the carboxylic acid to the carboxylic acid anhydride is usually 0 to 50.
As the acid catalyst, a solid acid catalyst such as activated clay, zeolite, a super strong acid ion exchange resin, a composite metal oxide, etc. is preferably used because it is easy to separate and remove after polymerization. The catalyst concentration in the reaction liquid is usually 0.1 to 20 mass % when the reaction is carried out in a suspension bed, for example.

The reactor used for producing the polyalkylene ether glycol diester may be any type of reactor as long as it can produce the polyalkylene ether glycol diester. As the reactor for producing the polyalkylene ether glycol diester, for example, a known type such as a fixed bed or a suspended bed can be used.
The reaction temperature may be appropriately set, but the lower limit is usually 10° C., preferably 30° C.
The upper limit is usually 80° C., preferably 50° C. If the reaction temperature is equal to or higher than the lower limit, the reaction rate is high, which is preferable, whereas if the reaction temperature is equal to or lower than the upper limit, the cyclic ether is unlikely to boil, which is preferable.

The reaction pressure may be appropriately selected within a range in which the reaction liquid maintains a liquid state. The reaction pressure is usually between normal pressure and 0.5 MPa, preferably between normal pressure and 0.3 MPa. If the pressure is high, the liquid state can be maintained at a higher temperature, but the construction cost will rise and the equilibrium conversion rate will decrease as the temperature increases. The reaction can also be carried out under reduced pressure. The reaction is usually carried out under an atmosphere that does not inhibit the reaction of the present invention, such as an inert gas such as nitrogen. The residence time of the reaction liquid in the reactor when the reaction is carried out continuously is determined by the activity and concentration of the catalyst. In the case of a continuous reaction, the residence time of the reaction liquid in the reactor is usually 0.5 hours to 15 hours, since a short residence time results in a low conversion rate, and a long residence time results in a close approach to the equilibrium conversion rate and a decrease in the apparent reaction rate.

The polymerization reaction liquid contains unreacted raw materials in addition to the desired polyalkylene ether glycol diester, and these are usually distilled off. The distillation of the unreacted raw materials is carried out as follows:
The distillation is usually carried out under normal pressure or reduced pressure. The cyclic ether, carboxylic acid and carboxylic acid anhydride distilled off may be purified as necessary and reused.
The polyalkylene ether glycol diester used in the present invention is, for example, TH
Dicarboxylic acid ester (PTME) of polytetramethylene ether glycol (PTMG) obtained by ring-opening polymerization of F is particularly preferred.

The mixture containing the polyalkylene ether glycol and the alkanol in the present invention is
It can be obtained by mixing a diester of a polyalkylene ether glycol with an alkanol and subjecting the mixture to an alcoholysis reaction in the presence of a catalyst for alcoholysis reaction (hereinafter sometimes referred to as "catalyst").
As the alkanol, _C1 - _C4 alkanols are preferred, and since the smaller the molecular weight, the greater the number of moles per the same mass, which is advantageous for the progress of the reaction, methanol, ethanol and propanol are preferred, methanol and ethanol are more preferred, and methanol is particularly preferred. The mass ratio of the alkanol to the diester of polyalkylene ether glycol in the raw material liquid is preferably 0.3 in the lower limit, more preferably 0.6, and is preferably 3.0 in the upper limit, more preferably 2.0. When the alkanol is equal to or greater than the lower limit, the reaction solution has a suitable viscosity and the reaction is likely to proceed smoothly. Also, when the alkanol is equal to or less than the upper limit, the scale of the apparatus is likely to be suitable, and excess alkanol is easily removed.

The catalyst is preferably an alkoxide of an alkali metal. Specific examples of the alkoxide of an alkali metal include sodium compounds such as sodium methoxide, sodium ethoxide, and sodium isopropoxide; and potassium compounds such as potassium methoxide, potassium ethoxide, and potassium isopropoxide. Of these, sodium compounds are preferred. In addition, sodium methoxide is particularly preferred, since the smaller the molecular weight, the cheaper the amount of the smaller the amount of the alkali metal alkoxide. The lower limit of the amount of the alkali metal alkoxide used relative to the reaction solution is
Usually 0.002% by mass, preferably 0.005% by mass, more preferably 0.01% by mass,
The upper limit is usually 0.1 mass%, preferably 0.03 mass%, and more preferably 0.02 mass%. When the amount of alkali metal alkoxide used is equal to or more than the lower limit, it is preferable in terms of the reaction rate, and when the amount is equal to or less than the upper limit, it is preferable in terms of easiness in removing the residual catalyst.

Specific examples of the method for supplying the raw materials and catalyst to the reactor include a method in which the raw materials and catalyst are placed in tanks, the liquids in the tanks are pumped to a mixing tank while controlling the flow rate, and the liquids are mixed in the mixing tank to be uniform, and then the liquids are subjected to the alcoholysis reaction. Since a small amount of the catalyst is usually used in a solid state, it is preferable to supply the catalyst as an alkanol solution. As the alkanol solution of the catalyst, it is convenient to use a commercially available methanol solution of sodium methoxide.

The type of reactor used in the alcoholysis reaction may be any type of reactor as long as polyalkylene ether glycol can be produced, and a plurality of reactors may be combined. At least one of the reactors used in the alcoholysis reaction is preferably equipped with a reboiler as a heat source. Specific examples of reactors for producing polyalkylene ether glycol include batch reaction tanks, continuous stirring tanks, tubular reactors, and reactive distillation columns. Among these, reactive distillation columns equipped with a heating device at the bottom of the tower are preferred because of their high efficiency. Therefore, it is preferred that at least a part of the alcoholysis reaction is carried out in a reactive distillation tank.

In addition, before the reactive distillation, the alcoholysis reaction may be partially carried out in a pre-stage reactor such as a tubular reactor or a continuous stirring tank, and then the alcoholysis reaction may be completed in the reactive distillation column. When a pre-stage reactor is used, the higher the conversion rate in the pre-stage reactor, the lower the load on the reactive distillation column, so it is preferable to carry out the reaction so that the transesterification rate is 85% or more of the equilibrium conversion rate. When a pre-stage reactor is used, the alkyl carboxylate by-produced here may be removed by a known method such as distillation, or it may not be removed. As the pre-stage reactor, a tubular reactor is preferably used because of its low construction cost. When the reaction is carried out in the pre-stage reactor, the higher the pressure, the higher the temperature can be raised to increase the reaction rate, but the higher the pressure, the higher the construction cost of the reactor. The pressure during the pre-stage reaction is usually 0.1 MPa, preferably 0.5 MPa, and the upper limit is usually 5 MPa, preferably 3 MPa. The temperature during the pre-stage reaction is usually 4 MPa, preferably 5 MPa, and the lower limit is usually 5 MPa.
The upper limit is usually 250° C., preferably 180° C. In the case of a tubular reactor, the residence time during the first stage reaction is usually 2 minutes, preferably 5 minutes.
The residence time during the first stage reaction is usually 60 minutes, and preferably 20 minutes.
In the case of a continuous stirring tank, the lower limit is usually 0.5 hours, preferably 1 hour, and the upper limit is usually 15 hours, preferably 10 hours. Heating during the first-stage reaction can be performed using known methods such as a jacket, an internal coil, or a heat exchanger. When a tubular reactor is used as the first-stage reactor, it is simple and preferable to supply the reaction liquid heated to the reaction temperature in a heat exchanger to a reactor insulated with a heat insulating material.

When using a reactive distillation column as a reactor, a commonly used reactive distillation column such as a packed column or a plate column equipped with a reflux device at the top and a reboiler at the bottom can be used. From the viewpoint of ensuring sufficient reaction time to proceed with the alcoholysis reaction, it is preferable to use a plate column equipped with a tray below the raw material supply stage of the reactive distillation column (recovery stage). As the type of tray, a bubble cap tray, a perforated plate tray, a valve tray, etc. are used. A bubble cap tray has a wide stable operation range, but is prone to high costs due to its complex structure. A perforated plate tray has a simple structure and small pressure loss, but has the disadvantage of a narrow stable operation range. For this reason, a bubble tray having both advantages is particularly suitable as the type of tray during the first-stage reaction. The upper side (concentration stage) of the reactive distillation column above the raw material supply stage is mainly a part where by-produced alkyl carboxylate and alkanol are separated by distillation, so it is sufficient to use a normal distillation equipment, and it does not necessarily have to be a plate tower, but may be a packed tower. The greater the number of theoretical plates in the distillation column, the easier it is to complete the reaction; however, construction costs increase accordingly. Therefore, it is preferable that the number of plates in the enrichment section be 1 to 10 and that in the stripping section be 5 to 40.

As the heating device at the bottom of the reactive distillation column, specifically, a known method such as a forced circulation reboiler or a natural circulation reboiler using a thermosiphon is used. Among these, a forced circulation reboiler is preferred because the viscosity of the reaction liquid increases due to evaporation of the alkanol in the reboiler.
The reaction pressure of the reactive distillation column may be appropriately selected within a range in which the reaction liquid remains liquid. The higher the reaction pressure, the faster the reaction rate can be increased by increasing the reaction temperature, and the more the foaming of the reaction liquid can be suppressed. On the other hand, in terms of the construction cost of the apparatus, the lower the reaction pressure is, the easier it is to reduce the construction cost. In particular, when a first-stage reactor is used, the reactive distillation column usually has a more complicated structure than the first-stage reactor, so that it is easier to reduce the construction cost by setting the reaction pressure lower in the reactive distillation column than in the first-stage reactor. In addition, setting the pressure of the reactive distillation column lower than that of the first-stage reactor is also preferable in that the alkyl carboxylate by-produced in the first-stage reactor can be flash evaporated when it is supplied to the reactive distillation column.
The reaction pressure of the reactive distillation column is usually normal pressure, preferably 0.2 MPa.
More preferably, it is 0.5 MPa, and the upper limit is usually 2.0 MPa, preferably 1.0 MPa.
It is better to have a.

The reaction temperature of the reactive distillation column may be appropriately set according to the reaction pressure. Specifically, for example, the lower limit of the column bottom temperature is usually 60° C., preferably 100° C., and the upper limit is
The reaction temperature is usually 180° C., preferably 160° C. If the reaction temperature is equal to or higher than the lower limit,
This is preferred because the reaction rate is high. In addition, if the reaction temperature is equal to or lower than the upper limit, the pressure required to maintain the temperature may be low, which is preferred in terms of reducing construction costs. The reaction temperature can be adjusted by adjusting the flow rate or temperature of the heat medium, which is the heat source of the reboiler.

The reaction is usually carried out in an atmosphere that does not inhibit the reaction of the present invention, such as an inert gas such as nitrogen.
When the reaction is carried out continuously, the residence time of the reaction liquid in the reactor is determined by the activity and concentration of the catalyst, etc. In the case of a continuous reaction, the residence time of the reaction liquid in the reactor is usually 10 to 30 minutes because the reaction is fast.
The reflux ratio during the reaction varies depending on the raw material composition and the number of stages of the distillation column, but is usually 0.5 to 20.
A reflux ratio of 1.0 to 10.0 is preferable. When the reflux ratio is equal to or less than the upper limit, the catalyst concentration in the liquid on the tray is high, and the reaction rate is high, which is preferable, and when the reflux ratio is equal to or more than the lower limit, the alkyl carboxylate is completely separated and the reaction is easily completed, which is preferable.

When the alcoholysis reaction of a polyalkylene ether glycol and an alkanol is carried out in a reactive distillation column, the alkanol and an alkyl carboxylate are distilled from the top of the reactive distillation column, and a mixture containing the polyalkylene ether glycol and the alkanol (hereinafter sometimes referred to as the "mixture") is discharged from the bottom of the column.

In order to obtain the desired polyalkylene ether glycol, it is necessary to remove the alkanol from the mixture to obtain a crude polyalkylene ether glycol.
The production method of the present invention includes a step of adding a compound to the mixture and removing alkanol from the mixture to obtain a crude polyalkylene ether glycol, the compound being a compound having an absolute value of the difference between the solubility parameter SPa of the compound and the solubility parameter SPb of the polyalkylene ether glycol contained in the mixture (hereinafter sometimes referred to as "difference in solubility parameters") of 12.9 or more, and the amount of the compound added is 3% by mass or more and 20% by mass or less with respect to the amount of the polyalkylene ether glycol in the mixture.
The difference in solubility parameters is preferably 13.0 or more, more preferably 13.1 or more, even more preferably 13.2 or more, and particularly preferably 13.3 or more. The upper limit of the difference in solubility parameters is preferably 15.0. When the difference in solubility parameters is within the above range, foaming can be suppressed and the alkanol can be efficiently removed.
The amount of the compound added is 3 to 100% based on the amount of polyalkylene ether glycol in the mixture.
It is preferably from 4% by mass to 16% by mass, more preferably from 5% by mass to 14% by mass, and more preferably from 6% by mass to 18% by mass.
When the amount of the compound added is within the above range, foaming can be suppressed and the alkanol can be efficiently removed.
The compound may be a single compound or a mixture of multiple compounds.

The solubility parameter of the polyalkylene ether glycol in the present invention (hereinafter referred to as "SP
The values are calculated based on "2. Fedor's Estimation Method" in "SP Value Basics, Applications and Calculation Methods" by Hideki Yamamoto, published by Johoki Corporation in 2005.
The SP value in the estimation method of the dor is (cohesive energy [J/mol])/(molecular volume [cm
³ /mol]) and is a useful physical property value that is mainly used to predict the solubility of a polymer in various solvents.
The SP value of the compound in the present invention is calculated by the method proposed by Fedors et al.
CIENCE, FEBRUARY, 1974, Vol. 14, No. 2, ROBERT
F. FEDORS. (pp. 147-154)". For example, toluene (SP value: 9.1), xylene (SP value: 9.1), ethyl acetate (SP value: 8.7
), butyl acetate (SP value: 8.7), cyclohexanone (SP value: 9.8), methyl ethyl ketone (SP value: 9.0), methyl isobutyl ketone (SP value: 8.7), N-methylpyrrolidone (SP value: 11.2), tetrahydrofuran (SP value: 9.1), isopropyl alcohol (SP value: 11.5), water (SP value: 23.4), etc.
Furthermore, when the compound is a mixture of multiple types, the following is described in the Journal of the Japan Packaging Society, Vol. 6, No. 6:
Based on "2.5 Calculation of Solubility Parameter (SP) Value" in (1997) (page 317),
It can be calculated based on various mole fractions.

The compound may be either solid or liquid, but is preferably liquid from the viewpoint of homogenization with the mixture.
Furthermore, although the compound is added to the mixture, it is preferably removed together with the alkanol in the step of removing the alkanol. In other words, it is preferable that the content of the compound in the obtained crude polyalkylene ether glycol is small.

The mixture obtained from the bottom of the reactive distillation column is sent to an alkanol removal facility after removing the catalyst, where a compound is added and the alkanol is removed. The alkanol removal facility may be a general light boiling removal facility, such as a distillation column or a stirring tank with a temperature-controlling jacket. The heating type light boiling separation device will be described below as the alkanol removal facility.
The compound may be added to the mixture before the mixture is sent to the heated light boiling separator or after the mixture is sent to the heated light boiling separator.

The removal of the alkanol may be carried out in a batch or continuous manner.
In the batch method, a desired amount of the mixture and a desired amount of the compound are charged into the heated low-boiling separation apparatus, and the pressure and heating temperature are appropriately set to vaporize the alkanol and distill it out from the heated low-boiling separation apparatus, thereby removing the alkanol from the mixture. If the pressure is too low, foaming is likely to occur, and if the pressure is too high, it becomes necessary to increase the heating temperature to vaporize the alkanol.
This may cause the polyalkylene ether glycol to deteriorate. Therefore, the pressure should be 0.00
The heating temperature depends on the pressure, but is preferably 60° C. or more and 250° C. or less, more preferably 60° C. or more and 210° C. or less, and more preferably 60° C. or more and 250° C. or less.
It is more preferable that the temperature is from 60° C. to 150° C., and more preferably from 60° C. to 180° C.
A heating temperature within the above range is particularly preferably 0° C. or higher and 120° C. or lower. If the heating temperature is within the above range, foaming can be suppressed, the alkanol can be efficiently removed, and deterioration of the polyalkylene ether glycol can be suppressed. The heating type low-boiling point separation device can be heated by a general method, for example, a temperature-controlling jacket coil, an internal coil, etc.

In the continuous type, the mixture and the compound are fed into the heated light boiling separator at desired flow rates, and the pressure and heating temperature are appropriately set to vaporize the alkanol and distill it out from the heated light boiling separator, thereby removing the alkanol from the mixture. When the heated light boiling separator is used alone, the removal of the alkanol is performed in the continuous type as in the batch type by appropriately setting the pressure and heating temperature, vaporizing the alkanol and distilling it out from the heated light boiling separator, thereby removing the alkanol from the mixture. If the pressure is too low, foaming is likely to occur, and if the pressure is too high, it becomes necessary to increase the heating temperature to vaporize the alkanol, which may cause deterioration of the polyalkylene ether glycol. Therefore, the pressure is set to be 0.005 MPa or more and 5 MPa or less.
Preferably, the pressure is 0.010 MPa or more and 4 MPa or less, more preferably 0.0150 MPa or more.
The heating temperature is preferably from 60° C. to 250° C., depending on the pressure.
The heating temperature is preferably 60° C. or lower, more preferably 60° C. or higher and 210° C. or lower, even more preferably 60° C. or higher and 180° C. or lower, particularly preferably 60° C. or higher and 150° C. or lower, and particularly preferably 60° C. or higher and 120° C. or lower. If the heating temperature is within the above range, foaming can be suppressed, the alkanol can be efficiently removed, and deterioration of the polyalkylene ether glycol can be suppressed. The heating type low boiling separation device can be heated by a general method, for example, a natural circulation type heat exchanger, a forced circulation type heat exchanger, a kettle type heat exchanger, etc.

The mixture comprises a polyalkylene ether glycol and an alkanol, with the preferred form of the polyalkylene ether glycol being PTMG since the preferred form of the diester of the polyalkylene ether glycol which is the precursor to the polyalkylene ether glycol is PTME.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, a small heating type low boiling separation device was used in the step of adding a compound to a mixture and removing alkanol to obtain a crude polyalkylene ether glycol in order to more clearly demonstrate the effects of the present invention.

<Example 1-1>
100 parts by weight of tetrahydrofuran, 5.5 parts by weight of acetic anhydride, and 0.07 parts by weight of acetic acid were reacted at 35° C. for 8 hours while stirring in the presence of 4.2 parts by weight of zirconia silica catalyst, and the catalyst was removed from the resulting reaction product by filtration, and then acetic anhydride and acetic acid were distilled off batchwise under reduced pressure of 10 torr or less. A small amount of nitrogen was further introduced under reduced pressure to remove volatiles, thereby obtaining PTME. The number average molecular weight measured by gel permeation chromatography was 2788, the acetic anhydride content was 10 ppm, and the acetic acid content was <10 ppm.
200 kg of the PTME and 460 kg of methanol containing 210 ppm of sodium methoxide were charged into a reactive distillation column, and a methanolysis reaction was carried out while successively distilling off methanol, etc., to obtain a reaction liquid. The reaction pressure was normal pressure, and the reaction temperature was 65° C.
The reaction solution was cooled and then mixed with a sulfonic acid type strongly acidic ion exchange resin (PK216LH manufactured by Mitsubishi Chemical Corporation) for 1 hour to remove the sodium ions dissolved in the reaction solution. The reaction solution after removing the sodium ions (hereinafter referred to as "mixture A") had a PTMG of 57.7.
% by mass, and methanol 42.3% by mass. The number average molecular weight of the PTMG measured by gel permeation chromatography was 2612, and the SP value was 9.2.
Mixed liquid A (760 g) was put into a glass heating type light boiling separator (hereinafter referred to as "light boiling separator") having an inner diameter of 100 mm shown in FIG. 1. Next, 31.6 g of water was added to mixed liquid A while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the measured static liquid level height was 109 mm. The rotation of the stirring blade 2 was resumed at a rotation speed of 150 rpm, and the inner temperature was raised to 68 ° C. by the jacket 1 at normal pressure, and nitrogen gas was introduced into the liquid inside the light boiling separator at 1000 ml / min by the nitrogen gas introduction part 3, while removing methanol. After the distillation of the distillate into the distillate container 6 started, the length from the upper surface of the liquid surface in the light boiling separator to the foamed upper surface was measured with a ruler one minute later, and it was 7 mm.
The SP value of the added compound, water, is 23.4.
The amount of water to be added relative to the amount of PTMG contained in the mixture can be calculated as follows.
31.6g ÷ (760g x 57.7% by mass) = 7.2% by mass
The results are summarized in Table 1.

<Comparative Example 1-1>
Mixture A (760 g) produced in the same manner as in Example 1-1 was charged into the light boiling separator in the same manner as in Example 1-1. The static liquid level measured after charging was 105 mm. Next, the stirring blade 2 was rotated at a rotation speed of 150 rpm, and the internal temperature was raised to 68 ° C. by the jacket 1 at normal pressure, and nitrogen gas was introduced into the liquid in the light boiling separator at 1000 ml / min by the nitrogen gas introduction part 3, while starting the removal of methanol. After 1 minute had elapsed since the distillation of the distillate into the distillate container 6 started, the length from the upper surface of the liquid surface in the light boiling separator to the foamed upper surface was measured with a ruler and found to be 28 mm, and the foamed upper surface had reached the vicinity of the lower end of the distillation tube 5.
The results are summarized in Table 1.

<Comparative Example 1-2>
Mixed liquid A (760 g) produced in the same manner as in Example 1-1 was charged into the light boiling separator in the same manner as in Example 1-1. Next, a mixture of 17.6 g of water and 14.0 g of tetrahydrofuran was added to mixed liquid A while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and found to be 109 mm. Next, the rotation speed was increased to 150 rpm, and the mixture was added to the light boiling separator.
The stirring blade 2 was rotated at 400° C., and the internal temperature was raised to 68° C. by the jacket 1 at normal pressure. At the same time, nitrogen gas was introduced into the liquid in the low boiling point separation apparatus at a rate of 1000 ml/min by the nitrogen gas introduction part 3, while starting the removal of methanol. After the distillation of the distillate into the distillate container 6 started,
After one minute had passed, the length from the top of the liquid surface in the light boiling separator to the top of the foam was measured with a ruler to be 40 mm, and the top of the foam had reached the inside of the distillation tube 5.
In addition, the compounds water (SP value: 23.4) and tetrahydrofuran (SP value: 9.1)
The SP value of the mixture can be calculated as follows:
First, calculate the total number of moles of the mixture as follows:
17.6g÷18.01528g/mol+14.0g÷72.11g/mol=1.
1711mol
The molar fraction of water and tetrahydrofuran is calculated from the total number of moles, and the molar fraction of water is 83.
The molar fraction of tetrahydrofuran is 16.6%. From the molar fraction, the SP value can be calculated using the following formula.
23.4 x 83.4% + 9.1 x 16.6% = 21.0
The results are summarized in Table 1.

<Example 2-1>
100 parts by weight of tetrahydrofuran, 5.5 parts by weight of acetic anhydride, and 0.07 parts by weight of acetic acid were reacted at 35° C. for 8 hours while stirring in the presence of 4.2 parts by weight of zirconia silica catalyst, and the catalyst was removed from the resulting reaction product by filtration, and then acetic anhydride and acetic acid were distilled off batchwise under reduced pressure of 10 torr or less. A small amount of nitrogen was further introduced under reduced pressure to remove volatiles, thereby obtaining PTME. The number average molecular weight measured by gel permeation chromatography was 2788, the acetic anhydride content was 10 ppm, and the acetic acid content was <10 ppm.
200 kg of the PTME and 440 kg of methanol containing 210 ppm of sodium methoxide were charged into a reactive distillation column, and a methanolysis reaction was carried out while successively distilling off methanol, etc., to obtain a reaction liquid. The reaction pressure was normal pressure, and the reaction temperature was 65° C.
The reaction solution was cooled and then mixed with a sulfonic acid type strongly acidic ion exchange resin (PK216LH manufactured by Mitsubishi Chemical Corporation) for 1 hour to remove the sodium ions dissolved in the reaction solution. The reaction solution after removing the sodium ions (hereinafter referred to as "mixture B") had a PTMG of 61.8.
% by mass, and methanol 38.2% by mass. The number average molecular weight of the PTMG measured by gel permeation chromatography was 2612, and the SP value was 9.2.
Mixed liquid B (760 g) was charged into the light boiling separator. Next, 28.7 g of water was added to mixed liquid B while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and found to be 109 mm.
The rotation of the separator was resumed, and the internal temperature was raised to 68° C. under normal pressure by the jacket 1, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler and found to be 7 mm.
The SP value of the compound water is 23.4.
The amount of water to be added relative to the amount of PTMG contained in the mixture can be calculated as follows.
28.7g ÷ (760g x 61.8% by mass) = 6.1% by mass
The results are summarized in Table 1.

<Comparative Example 2-1>
Mixture B (760 g) produced in the same manner as in Example 2-1 was charged into the low boiling separator in the same manner as in Example 2-1. The static liquid level after charging was 105 mm. Then, the rotation speed was increased to 150
The stirring blade 2 was rotated at 1000 rpm, the internal temperature was raised to 68° C. by the jacket 1 at normal pressure, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler to be 26 mm, and the upper surface of the foam had reached near the lower end of the distillation tube 5.
The results are summarized in Table 1.

<Comparative Example 2-2>
Mixed liquid B (760 g) produced in the same manner as in Example 2-1 was charged into the light boiling separator in the same manner as in Example 2-1. Next, a mixture of 17.4 g of water and 11.3 g of tetrahydrofuran was added to mixed liquid B while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and found to be 109 mm. Next, the rotation speed was increased to 150 rpm, and the mixture was added to the light boiling separator.
The stirring blade 2 was rotated at 400° C., and the internal temperature was raised to 68° C. by the jacket 1 at normal pressure. At the same time, nitrogen gas was introduced into the liquid in the low boiling point separation apparatus at a rate of 1000 ml/min by the nitrogen gas introduction part 3, while starting the removal of methanol. After the distillation of the distillate into the distillate container 6 started,
After one minute had passed, the length from the top of the liquid surface in the light boiling separator to the top of the foaming surface was measured with a ruler to be 26 mm, and the top of the foaming surface reached the vicinity of the lower end of the distillation tube 5. The SP value of the compound was calculated in the same manner as in Comparative Example 1-2 to be 21.4.
The results are summarized in Table 1.

<Example 3-1>
100 parts by weight of tetrahydrofuran, 5.5 parts by weight of acetic anhydride, and 0.07 parts by weight of acetic acid were reacted at 35° C. for 8 hours while stirring in the presence of 4.2 parts by weight of zirconia silica catalyst, and the catalyst was removed from the resulting reaction product by filtration, and then acetic anhydride and acetic acid were distilled off batchwise under reduced pressure of 10 torr or less. A small amount of nitrogen was further introduced under reduced pressure to remove volatiles, thereby obtaining PTME. The number average molecular weight measured by gel permeation chromatography was 2788, the acetic anhydride content was 10 ppm, and the acetic acid content was <10 ppm.
200 kg of the PTME and 420 kg of methanol containing 210 ppm of sodium methoxide were charged into a reactive distillation column, and a methanolysis reaction was carried out while successively distilling off methanol, etc., to obtain a reaction liquid. The reaction pressure was normal pressure, and the reaction temperature was 65° C.
The reaction solution was cooled and then mixed with a sulfonic acid type strongly acidic ion exchange resin (PK216LH manufactured by Mitsubishi Chemical Corporation) for 1 hour to remove sodium ions dissolved in the reaction solution. The reaction solution after removing the sodium ions (hereinafter referred to as "mixed solution C") had a PTMG of 66.1
% by mass, and methanol 33.9% by mass. The number average molecular weight of the PTMG measured by gel permeation chromatography was 2612, and the SP value was 9.2.
The mixed liquid C (760 g) was charged into the light boiling separator. Next, 34.2 g of water was added to the mixed liquid C while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and was 109 mm.
The rotation of the apparatus was resumed, and the internal temperature was raised to 69° C. under normal pressure by the jacket 1, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of the distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler and found to be 8 mm.
The SP value of the compound water is 23.4.
The amount of water to be added relative to the amount of PTMG contained in the mixture can be calculated as follows.
34.2g ÷ (760g x 66.1% by mass) = 6.8% by mass
The results are summarized in Table 1.

<Comparative Example 3-1>
Mixture C (760 g) produced in the same manner as in Example 3-1 was charged into the low boiling point separator in the same manner as in Example 3-1. The static liquid level after charging was 105 mm. Then, the rotation speed was increased to 150
The stirring blade 2 was rotated at 1000 rpm, the internal temperature was raised to 69° C. by the jacket 1 at normal pressure, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler and found to be 22 mm, and the upper surface of the foam had reached the vicinity of the lower end of the distillation tube 5.
The results are summarized in Table 1.

<Comparative Example 3-2>
Mixed liquid C (760 g) produced in the same manner as in Example 3-1 was charged into the light boiling separator in the same manner as in Example 3-1. Next, a mixture of 25.2 g of water and 9.0 g of tetrahydrofuran was added to mixed liquid C while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and found to be 110 mm. Next, the rotation speed was increased to 150 rpm, and the mixture was added to the light boiling separator in the same manner as in Example 3-1.
The stirring blade 2 was rotated under normal pressure, the internal temperature was raised to 69° C. by the jacket 1, and nitrogen gas was introduced into the liquid in the low boiling point separation apparatus at 1000 ml/min through the nitrogen gas introduction part 3, while removing methanol.
After 30 minutes had passed, the length from the top of the liquid surface in the light boiling separation apparatus to the top of the foaming surface was measured with a ruler to be 24 mm, and the top of the foaming surface reached the vicinity of the lower end of the distillation tube 5. The SP value of the compound was calculated in the same manner as in Comparative Example 1-2 to be 21.7.
The results are summarized in Table 1.

<Example 4-1>
100 parts by weight of tetrahydrofuran, 5.5 parts by weight of acetic anhydride, and 0.07 parts by weight of acetic acid were reacted at 35° C. for 8 hours while stirring in the presence of 4.2 parts by weight of zirconia silica catalyst, and the catalyst was removed from the resulting reaction product by filtration, and then acetic anhydride and acetic acid were distilled off batchwise under reduced pressure of 10 torr or less. A small amount of nitrogen was further introduced under reduced pressure to remove volatiles, thereby obtaining PTME. The number average molecular weight measured by gel permeation chromatography was 2788, the acetic anhydride content was 10 ppm, and the acetic acid content was <10 ppm.
200 kg of the PTME and 400 kg of methanol containing 210 ppm of sodium methoxide were charged into a reactive distillation column, and a methanolysis reaction was carried out while successively distilling off methanol, etc., to obtain a reaction liquid. The reaction pressure was normal pressure, and the reaction temperature was 65° C.
The reaction solution was cooled and then mixed with a sulfonic acid type strongly acidic ion exchange resin (PK216LH manufactured by Mitsubishi Chemical Corporation) for 1 hour to remove the sodium ions dissolved in the reaction solution. The reaction solution after removing the sodium ions (hereinafter referred to as "mixture D") had a PTMG of 70.4.
% by mass, and methanol was 29.6% by mass. The number average molecular weight of the PTMG measured by gel permeation chromatography was 2612, and the SP value was 9.2.
Mixed liquid D (760 g) was charged into the light boiling separator. Next, 24.6 g of water was added to mixed liquid D while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and was 108 mm.
The rotation of the separator was resumed, and the internal temperature was raised to 74° C. under normal pressure by the jacket 1, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler and found to be 13 mm.
The SP value of the compound water is 23.4.
The amount of water to be added relative to the amount of PTMG contained in the mixture can be calculated as follows.
24.6g ÷ (760g x 70.4% by mass) = 4.6% by mass
The results are summarized in Table 1.

<Comparative Example 4-1>
Mixture D (760 g) produced in the same manner as in Example 4-1 was charged into the low boiling point separator in the same manner as in Example 4-1. The static liquid level after charging was 105 mm. Then, the rotation speed was increased to 150
The stirring blade 2 was rotated at 1000 rpm, the internal temperature was raised to 74° C. by the jacket 1 at normal pressure, and removal of methanol was started while introducing nitrogen gas into the liquid in the light boiling separation apparatus at 1000 ml/min by the nitrogen gas inlet 3. One minute after the start of distillation of the distillate into the distillate container 6, the length from the upper surface of the liquid surface in the light boiling separation apparatus to the upper surface of the foam was measured with a ruler to be 23 mm, and the upper surface of the foam had reached near the lower end of the distillation tube 5.
The results are summarized in Table 1.

<Comparative Example 4-2>
Mixed liquid D (760 g) produced in the same manner as in Example 4-1 was charged into the light boiling separator in the same manner as in Example 4-1. Next, a mixture of 17.1 g of water and 7.5 g of tetrahydrofuran was added to mixed liquid D while rotating the stirring blade 2 at a rotation speed of 150 rpm. The rotation of the stirring blade 2 was stopped, and the static liquid level height was measured and found to be 108 mm. Next, the rotation speed was increased to 150 rpm, and the mixture was added to the light boiling separator in the same manner as in Example 4-1.
The stirring blade 2 was rotated under normal pressure, the internal temperature was raised to 74° C. by the jacket 1, and nitrogen gas was introduced into the liquid in the low boiling point separation apparatus at 1000 ml/min by the nitrogen gas introduction part 3, while removing methanol.
After 30 minutes had passed, the length from the top of the liquid surface in the light boiling separation apparatus to the top of the foam was measured with a ruler to be 26 mm, and the top of the foam reached the vicinity of the lower end of the distillation tube 5. The SP value of the compound was calculated in the same manner as in Comparative Example 1-2 to be 22.0.
The results are summarized in Table 1.

As is clear from Examples 1-1 to 4-1, it is possible to suppress foaming by adding a specific amount of a specific compound, and it is possible to efficiently remove alkanols such as methanol.

Reference Signs List 1 Jacket 2 Stirring blade 3 Nitrogen gas inlet 4 Distillation tube 5 Cooler 6 Distillate container 7 Cooling water 8 Pressure adjustment system

Claims (6)

A method for producing a polyalkylene ether glycol, comprising the steps of: subjecting a diester of a polyalkylene ether glycol to an alcoholysis reaction with an alkanol in the presence of an alkali metal alkoxide catalyst to obtain a mixture containing a polyalkylene ether glycol and an alkanol; removing the alkali metal alkoxide catalyst, and then adding water to the mixture and removing the alkanol to obtain a crude polyalkylene ether glycol,
an absolute value of a difference between a solubility parameter SPa of the water and a solubility parameter SPb of the polyalkylene ether glycol is 12.9 or more, and the amount of the water added is 3 mass % or more and 20 mass % or less with respect to the amount of the polyalkylene ether glycol in the mixture. The method for producing a polyalkylene ether glycol according to claim 1, wherein the polyalkylene ether glycol is polytetramethylene ether glycol. The method for producing a polyalkylene ether glycol according to claim 1 or 2, wherein the alkanol is a C ₁ -C ₄ alkanol. The method for producing a polyalkylene ether glycol according to any one of claims 1 to 3, wherein the temperature for removing the alkanol is 60°C or higher and 250°C or lower. The method for producing polyalkylene ether glycol according to any one of claims 1 to 4, wherein the concentration of polyalkylene ether glycol in the mixture is 30% by mass or more and 90% by mass or less. The method for producing a polyalkylene ether glycol according to any one of claims 1 to 5, wherein the number average molecular weight of the polyalkylene ether glycol is 600 or more and 8000 or less.

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