JPH06211979A - Method for purifying polyoxytetramethylene glycol - Google Patents

Abstract

PURPOSE:To overcome the problem of poor separability of a water layer from an org. layer after washing with water in the process for removing the catalysts and oligomers used for reaction from crude polyoxytetramethylene glycol and to thereby purify the crude polyoxytetramethylene glycol efficiently. CONSTITUTION:Crude polyoxytetramethylene glycol produced by decomposing a polyoxytetramethylene glycol carboxylate in the presence of an alkali catalyst is washed with water and subjected to the liq. separation step using a centrifugal separator. Thus, difficulties in liq. separation after washing with water of crude polyoxytetramethylene glycol contg. catalysts and oligomers is overcome, and the purification without using an org. solvent in the washing step becomes possible.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a polyoxytetramethylene glycol carboxylic acid ester (hereinafter referred to as PTMGAC).
(Hereinafter abbreviated) is decomposed and produced in the presence of an alkali catalyst, and crude polyoxytetramethylene glycol (hereinafter abbreviated as PTMG) is purified by washing with water.

[0002]

2. Description of the Related Art PTMG is a polyurethane or polyester used for spandex, elastomer, artificial leather, etc.
It is an industrially useful polymer used for the main raw materials of teresters and polyether (ester) amides, surfactants, pressure fluids, etc., and in recent years mainly in the elastomer field, engineering materials, medical polymer materials Has been especially noticed as.

PTMGAC after manufacturing PTMGAC
PTMG is usually produced by hydrolysis or alcoholysis in the presence of an alkali catalyst.

Hydrolysis in the presence of an alkali catalyst is usually carried out in the presence of an aliphatic alcohol such as butanol at about 100 ° C. for several hours, and after repeated washing with water, the aliphatic alcohol such as butanol is flushed. To obtain PTMG, but the liquid separation after this washing operation is very poor (Japanese Patent Publication No. 63-757).
1st grade).

For alcoholysis, an aliphatic alcohol such as methanol is used, and by-product carboxylic acid ester is removed by azeotropy with alcohol by reactive distillation to obtain PTM.
This is a method for producing G (Japanese Patent Publication No. 61-11969).
etc). The catalyst separation method of this method is often performed by filtration separation, but since a trace amount of the catalyst often remains in the product PTMG, a water washing operation is often performed, and the liquid separation property after this water washing operation is performed. Is also very bad.

[0006]

The crude PTMG prepared by decomposing PTGAC in the presence of an alkali catalyst has very poor liquid separation properties after washing.

[0007]

OBJECT OF THE INVENTION The object of the present invention is to determine the liquid separation property between the organic layer and the aqueous layer after the washing operation for removing the catalyst or oligomer from the crude PTMG containing the catalyst or oligomer used in the reaction. It is to develop a method for improving badness and efficiently purifying PTMG.

[0008]

That is, according to the present invention, "a crude polyoxytetramethylene glycol produced by decomposing a polyoxytetramethylene glycol carboxylic acid ester in the presence of an alkali catalyst is purified by washing with water. ,
The subsequent liquid separation operation is carried out by a centrifugal separation operation. ”A method for purifying polyoxytetramethylene glycol.

PTMGAC produced by cationic polymerization
Usually produces a PTMG by converting the terminal ester group into a hydroxyl group by hydrolysis or alcoholysis.

First, the terminal ester group is hydrolyzed to PT
A case of manufacturing MG will be described. Alkaline hydrolysis is usually the addition of an aqueous alkaline solution in the presence of an organic solvent,
It is a method of heating to change the terminal ester group to a hydroxyl group,
Proceed according to reaction formula (1) In the above reaction formula, R ¹ is a linear alkyl group, and n represents the degree of polymerization.

However, since the reaction is usually carried out in an aqueous solution of an alkali metal or alkaline earth metal hydroxide, the produced aliphatic carboxylic acid is converted to an alkali metal or alkaline earth metal aliphatic carboxylic acid salt. There is.

The organic solvent used in the present invention includes aromatic hydrocarbons such as benzene, toluene and xylene, which have been conventionally used for hydrolysis of terminal ester groups, and n.
Compounds that are separated from water such as aliphatic alcohols such as butanol and aliphatic ethers such as di-isopropyl ether are used.

As the alkali used in the present invention, hydroxides of alkali metals and alkaline earth metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide are used. These alkali metal and alkaline earth metal hydroxides are usually used as an aqueous solution. The concentration of this aqueous solution is usually 1 to 50% by weight.
The amount of the alkali metal and alkaline earth metal hydroxide aqueous solution added varies depending on the weight of water to PTMGAC used, but the weight of water to PTMGAC is usually 0.1 to 10 times, and PTMGAC and water are added. And the total alkali concentration is 0.01 to 4
It is used in the range of 0% by weight. The alkali hydrolysis temperature is usually 50 to 150 ° C., though it varies depending on the alkali concentration and the type of alkali used.

The alkali hydrolysis time is usually in the range of 0.1 to 20 hours, though it varies depending on the alkali concentration, the type of alkali used and the hydrolysis temperature.

After the completion of alkaline hydrolysis, if the organic layer and the aqueous layer are separated by natural separation, it takes a long time because the liquid separation property is very poor. Therefore, the reaction crude liquid containing water is centrifuged to separate the organic layer and the aqueous layer in a short time, and then the lower aqueous layer side is separated.

After that, water is added again to the upper organic layer side and the mixture is stirred, and then centrifuged to separate into an organic layer and an aqueous layer. The water added at this time is used in the range of 0.1 to 10 times by weight the weight of the upper organic layer.

The same operation is repeated 1 to 10 times, the last remaining organic layer is recovered, and the organic solvent and water are evaporated by using an evaporator having a short residence time such as a thin film evaporator to obtain the product P.
Get TMG. Further, since the organic solvent is slightly dissolved in the water layer of each operation, it is preferable to recover and recycle and reuse.

The centrifugation and washing operation as described above is carried out by using a device such as a continuous centrifugal extractor for continuously mixing the reaction crude liquid and water to continuously separate the organic layer and the aqueous layer. Is also good. Next, the PTMGAC produced by cationic polymerization was subjected to PTMGAC in the presence of an alkali catalyst by means of alcoholysis, which is a method with less coloring compared to conventional alkali hydrolysis.
A method of manufacturing G will be described.

The reaction proceeds according to the following reaction formula (2).

[0020] In the reaction formula, R ² and R ³ are linear alkyl groups, and n indicates the degree of polymerization.

The alcohol used in this reaction is methanol.
Aliphatic alcohols such as alcohol, ethanol, butanol, etc. are used. Among them, methanol has a price point, a reactivity point, and a separation property between the ester formed by the reaction and the raw material alcohol. Most preferred from the point. As the alkali catalyst used in this reaction, an alkaline earth metal oxide, an alkali metal, or an alkaline earth metal alcoholate is used.

As the alkaline earth metal oxide, magnesium oxide, calcium oxide, strontium oxide and barium oxide are used, and of these, calcium oxide is most preferable.

Further, during storage, this catalyst reacts with carbon dioxide gas in the air to form a carbonate, or reacts with moisture in the air to form a hydroxide, which lowers the catalytic activity. Since it is easy to use, it is preferable to use one that has been fired at 300 to 800 ° C. for several hours in a firing furnace before use. Furthermore, more preferably, the alkaline earth metal oxide is generally different depending on the kind of the metal, but the alkaline earth metal oxide prepared from the alkaline earth metal carbonate is prepared from the alkaline earth metal hydroxide. Since the alkaline earth metal oxide is more active than the alkaline earth metal oxide, it is preferable to prepare the alkaline earth metal oxide from the alkaline earth metal carbonate.

The catalyst is usually used in the form of powder, but it may be used in the form of tablets, and may be appropriately selected depending on the reaction system and the method of separating the catalyst.

The amount of the catalyst used is usually 0.1 to 10 wt%, more preferably 0.5 to 3 w in terms of the catalyst concentration in the crude reaction liquid.
Used at a catalyst concentration of t%. When the catalyst is a powder, the contact surface area per unit weight of the catalyst with the reaction crude liquid is large, so the catalyst concentration may be low, but in the case of a tablet-molded catalyst, the contact surface area per unit weight of the catalyst is small, so the catalyst concentration. Is preferably higher.

Further, since the catalyst in the reactor has a low contact efficiency with the reaction crude liquid, particularly in the case of a tablet-molded catalyst, it is better to stir the reactor with a stirrer capable of forcibly stirring. It is more preferable because the time can be shortened.

When an alkali metal or alkaline earth metal alcoholate is used as a catalyst for alcoholysis, the catalyst concentration varies depending on the kind of the catalyst, but
It is used in the range of 01 to 3 wt%. Moreover, it is usually used in the form of an alcohol solution in terms of easy handling.

Although the reaction temperature for alcoholysis is not particularly limited, it is usually carried out at a temperature of 30 to 120 ° C. under normal pressure. If the reaction temperature is higher than 120 ° C. under atmospheric pressure, the hue of the final product will be deteriorated, so that the hue of the final product will deteriorate.
In such a case, it is preferable to carry out the reaction under reduced pressure so that the reaction temperature of the distillation column is 120 ° C.

On the contrary, if the reaction temperature is too low, it takes too much time until the reaction is completed, which is not preferable. Further, when alcohol having a low boiling point such as methanol or ethanol is used, the reaction temperature in the distillation column kettle is increased to such an extent that the coloration of the final product is not aggravated, and the time until the reaction is completed. The reaction may be carried out under pressure in order to shorten the reaction time.
However, in consideration of the equipment cost and the ease of operation and management, it is usually necessary to carry out the reaction under normal pressure so that the temperature of the reactor is such that the coloration of the final product is less likely to occur and the reaction rate is rather fast. It is preferred to react with

The alcoholysis may be carried out in a batch system or in a continuous system, but it is necessary to select the production system in consideration of the production amount of PTMG, equipment cost and the like. When PTMG is produced on a large scale or in a state where there are few plant switching operations due to changes in the number average molecular weight, a continuous method is preferable, although the equipment cost is high but more efficient production is possible, but on the contrary, on a small scale. In the case where PTMG is produced in a state where there are many plant switching operations associated with changes in the number average molecular weight, the equipment cost is low and a batch method suitable for switching operations is preferable.

When the batch system is used, the catalyst, PTMGAC and alcohol are placed in a kettle of a batch distillation column equipped with a reflux device.
After carrying out reactive distillation by pouring in the reactor and distilling the carboxylic acid ester generated in the kettle azeotropically with the alcohol, the reaction is carried out until the column top temperature reaches the boiling point of the alcohol to complete the alcoholysis. Let In case of continuous process, catalyst, PT
MGAC and alcohol were continuously charged to a continuous distillation column so that a residence time was set so that the reaction was completed, and the carboxylic acid ester produced from the top of the continuous distillation column was converted into an azeotropic mixture with the raw material alcohol. The unreacted alcohol, the formed PTMG and the catalyst are continuously withdrawn from the kettle.

However, the continuous distillation method cannot be carried out in the case of a suspension in which the catalyst is difficult to dissolve. Therefore, when an alkaline earth metal oxide is used as the alkali catalyst, the catalyst is hardly dissolved, and therefore the batch reaction is performed in most cases. On the contrary, when an alkali metal or alkaline earth metal alcoholate is used, the catalyst is easily dissolved, so that it can be carried out in a batch reaction or a continuous reaction.

PTM by Alcoholsis of PTMGAC
The production of G differs depending on the type of distillation column, the packing material of the distillation column and the distillation system (continuous distillation and batch distillation), but it is preferable to use a distillation column having 20 to 100 theoretical plates. When a distillation column having a low theoretical plate number is used, it becomes difficult to separate the azeotrope of the raw material alcohol and the produced carboxylic acid ester from the raw material alcohol, and the normal raw material alcohol and the produced carboxylic acid ester are usually separated from each other. Since the boiling mixture is incinerated, if the azeotropic mixture of the raw material alcohol and the produced carboxylic acid ester and the raw material alcohol are poorly separated, the amount of the raw material alcohol used increases, which is not preferable.

On the contrary, if a distillation column having a high theoretical plate number is used, an azeotropic mixture of the raw material alcohol and the produced carboxylic acid ester and more stages than necessary for separating the raw material alcohol will be loaded. Therefore, not only is the equipment cost high, but also the energy cost for operating the distillation column is high, which is not preferable.

The reaction time (residence time) of alcoholysis is
Catalyst concentration, reaction temperature and raw material alcohol and PTMGAC
Although it is determined by the molar ratio of 1), etc., it is usually carried out for 1 to 10 hours. If the reaction time is too long, P of the final product
Despite the poor hue of TMG and the end of the reaction, it will have an extra residence time.
There is no merit because the MG production amount will decrease.

On the contrary, if the reaction time becomes too short, PT
This is not preferable because the PTMG production reaction by the alcoholysis of MGAC is not completed. Moreover, the ester residue in PTMG deteriorates the product quality of the polyurethane produced from PTMG, and therefore the reaction for producing PTMG from PTMGAC must be completed.

The molar ratio of PTMGAC to alcohol used for alcoholysis varies depending on the number average molecular weight and dispersity of PTMGAC, but the molar ratio of alcohol to PTMGAC is usually selected from the range of 3 to 100.
Here, if the molar ratio of alcohol to PTMGAC is too low, alcoholysis becomes very slow, the reaction time becomes long, and the reaction may not be completed, which is not preferable.

On the contrary, if the molar ratio of alcohol to PTMGAC is too high, the energy cost required for the alcoholysis and the amount of the alcohol flushed after the alcoholysis increase, which increases the energy cost, which is not preferable. .

Further, PTMGAC used as a raw material
As the impurities of PTMGAC, PTMGAC produced by cationic polymerization using an acid anhydride as a cocatalyst is usually used in the presence of a strong acid catalyst.
Acid substances such as acid anhydrides and carboxylic acids may be mixed in the product, but acid anhydrides and carboxylic acids, etc.
Since the basic catalyst in the PTMG production step by alcoholysis of 1 is poisoned, it is preferable that the amount of acid in PTMGAC used as a raw material is small because the amount of the basic catalyst used can be small. That is, PTM used as a raw material
JIS K0070-19 is a standard for the acid content of GAC.
According to the measuring method of 66, the acid value is preferably about 10 mgKOH / g or less.

As the raw material alcohol, it is preferable to use a product having a purity higher than that usually used in industry. Furthermore, the purity of the alkaline earth metal oxide catalyst or the alkali metal or alkaline earth metal alcohol used is also
It is preferable to use a product having a purity higher than that usually used in industry.

In the presence of an alkaline earth metal oxide catalyst, P
If there is an insoluble catalyst in the reaction crude liquid from the bottoms of the distillation column produced by the alcoholysis of TMGAC, the catalyst is usually separated and removed by filtration separation or centrifugation, and the unreacted alcohol is recovered and recycled. Therefore, flashing is performed using a flash device such as a thin film evaporator having a short residence time. If the residence time at this time is too long, it will be one of the causes of deterioration of the hue of the final product, which is not preferable.

Further, as the heat source, water vapor is generally used industrially because it has a large latent heat of vaporization and a small temperature difference between the transmission surface and the liquid film. The operating pressure during flashing may be atmospheric pressure, but it is usually performed under reduced pressure to lower the temperature of the evaporation surface so that coloring is unlikely to occur.

Since the crude PTMG discharged from the bottom of the thin film evaporator contains the catalyst components dissolved in the reaction crude liquid, water and crude PTG were removed in order to remove these catalyst components and oligomers.
Charge TMG in a stirring tank and stir for several hours while heating. When the upper PTMG layer and the lower aqueous layer are naturally separated after completion of the stirring and washing, it takes a long time because the liquid separation property is very poor. After liquid separation with a centrifugal separator, the water layer and the PTMG layer are separated, the lower water layer side is separated and removed, and then the same operation is repeated several times. Then, the product PTMG is obtained by flushing water from the finally obtained PTMG layer.

The amount of water charged at this time is 0.1 to 10 times by weight, preferably 0.5 to 10 times the weight of the crude PTMG.
It is used in a range of 3 times by weight.

The washing temperature is slightly different depending on the molecular weight of PTMG, but a temperature slightly higher than the temperature at which PTMG has fluidity is preferable. Specifically, it is washed in the range of 30 to 100 ° C. If the washing temperature is higher than 100 ° C., it will be one of the causes of coloring of the product PTMG depending on the washing time, which is not preferable.

The washing time should be appropriately selected depending on the amount of water used and the washing temperature, but generally 0.2
It is selected within a range of up to 5 hours.

As in the case of alkali hydrolysis, this washing step is an apparatus such as a continuous centrifugal extractor for continuously mixing the reaction crude liquid and water to continuously separate the organic layer and the aqueous layer. May be used.

Further, it is not necessary to use an organic solvent other than water as a cleaning solvent, but since water and PTMG are difficult to mix with each other, in order to improve the cleaning efficiency in the cleaning step, during the alkaline hydrolysis reaction described above, The organic solvent used may be used.

There is no particular limitation on the size and the number of rotations of the rotor, that is, the size of G to be added when the centrifugal separation operation is performed. It may be arbitrarily selected in consideration of the size of the apparatus and the economical efficiency of the equipment according to the processing capacity and the separation characteristics.

The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples.

[0051]

Example 1 A 40 mmφ 40-stage Oldershaw batch distillation column equipped with a stirrer and a 1-liter glass flask was used, and 640 g of methanol was added to the flask, 200 g of PTMGAC having a number average molecular weight of 1200 and 4 g of calcium oxide.
The mixture was heated to boiling by pouring in, and the produced methyl acetate was azeotroped with methanol (19 wt%) (boiling point 54
The reaction was carried out for 5 hours while distilling it out as (° C.).

After completion of the reaction, the mixture was cooled, and the insoluble calcium oxide in the flask was separated by filtration, and the low boiling point was flushed with an evaporator while nitrogen was being leaked.

Then, the crude PTM obtained by flashing
G184 g was charged into a jacketed reactor equipped with a stirrer, and 184 g of water was further charged, and 0.5 g at 70 ° C.
Stir for hours. Pour the liquid in the reactor into the centrifuge,
When it was rotated at 3500 rpm for about 15 minutes, the upper layer P
The TMG layer and the lower aqueous layer were separated.

The lower aqueous layer was withdrawn, the upper PTMG layer was recovered, and the washing and centrifuging operations were repeated 5 times in total as in the above. Finally, the lower aqueous layer is removed and the upper P layer is removed.
PTMG1 having a number average molecular weight of 1550 was obtained by flushing water with an evaporator while leaking nitrogen to the TMG layer.
72 g were obtained.

[0055]

Example 2 A 40 mmφ 40-stage Oldershaw batch distillation column equipped with a stirrer and a 1-liter glass flask was used, and 450 g of MeOH and 1 of the number average molecular weight were used in the flask.
580 PTMGAC (450 g) and 28% sodium methylate methanol solution (0.7 g) were added to the mixture, and the mixture was heated to the boil to form methyl acetate (19 wt.
%) And the reaction was carried out for 5 hours while distilling it out as an azeotropic mixture (boiling point 54 ° C.).

After the reaction is completed, the reaction liquid is cooled and the reaction crude liquid is evaporated.
A low boiling point was flushed with nitrogen while leaking.

Then, the crude PTM obtained by flashing
G425 g was charged into a jacketed reactor equipped with a stirrer, 425 g of water was further charged, and 0.5 g at 70 ° C.
Stir for hours. Pour the liquid in the reactor into the centrifuge,
When it was rotated at 3500 rpm for about 15 minutes, the upper layer P
The TMG layer and the lower aqueous layer were separated.

The lower aqueous layer was withdrawn, the upper PTMG layer was recovered, and the washing and centrifuging operations were repeated 5 times in total as in the above. Finally, the lower aqueous layer is removed and the upper P layer is removed.
PTMG3 having a number average molecular weight of 2040 was obtained by flushing water with an evaporator while leaking nitrogen to the TMG layer.
93 g were obtained.

[0059]

[Comparative Example 1] A 40 mmφ 40-stage Oldershaw batch distillation column equipped with a stirrer and a 1-liter glass flask was used, and 450 g of methanol, 450 g of PTMGAC having a number average molecular weight of 1580, and sodium methyla were used in the flask.
The reaction mixture was heated for 5 hours while boiling 0.7 g of the mixture and boiling the mixture to distill the produced methyl acetate as an azeotrope (boiling point 54 ° C.) with methanol (19 wt%). After completion of the reaction, the mixture was cooled, the reaction crude liquid was poured into an evaporator, and low boiling components were flushed while leaking nitrogen.

Then, the crude PTM obtained by flashing
G425 g was charged into a jacketed reactor equipped with a stirrer, 425 g of water was further charged, and 0.5 g at 70 ° C.
Stir for hours. After that, when stirring was stopped and left for a whole day and night, a layer that appeared to be a slight water layer appeared in the lower layer,
It was impossible to separate the lower aqueous layer from the upper PTMG layer because it was cloudy and the interface was not clear.

In Comparative Example 1, since the liquid separation operation after washing the crude PTMG with water is not performed by the centrifugal separation operation and the natural liquid separation is attempted, the liquid separation property is extremely poor. Therefore, the upper PTMG layer and the lower layer are separated. It shows that the water layer of can not be separated.

[0062]

According to the method of the present invention, a catalyst or an oligomer can be obtained.
The poor separation property of the crude PTMG containing water after washing was overcome, and the crude PTMG was removed without using an organic solvent other than water in the washing step.
Has become possible.

Claims (2)

[Claims] 1. A crude polyoxytetramethylene glycol produced by decomposing a polyoxytetramethylene glycol carboxylic acid ester in the presence of an alkali catalyst is purified by washing with water, and a liquid separation operation thereafter is performed by centrifugation. A method for purifying polyoxytetramethylene glycol, characterized in that 2. The method for purifying polyoxytetramethylene glycol according to claim 1, wherein the polyoxytetramethylene glycol carboxylic acid ester is polyoxytetramethylene glycol acetic acid ester.