JPH06210104A - Refining method of polyoxytetramethylene glycol - Google Patents

Abstract

PURPOSE:To improve hue of a polyoxytetramethylene glycol product by removing the catalyst component used for the production reaction of polyoxytetramethylene glycol by alkolysis of carboxylic acid ester of polyoxytetramethylene glycol. CONSTITUTION:The reaction raw liquid of polyoxytetramethylene glycol produced by alkolysis of carboxylic acid ester of polyoxytetramethylene glycol in the presence of an alkali catalyst is treated with activated carbon so as to improve the hue of a polyoxytetramethylene glycol product. In this refining method, the catalyst component used for the production reaction of polyoxytetramethylene glycol by alkolysis of carboxylic acid ester of polyoxytetramethylene glycol can easily be removed and the hue of polyoxytetramethylene glycol product is significantly improved.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a polyoxytetramethylene glycol carboxylic acid ester (hereinafter referred to as PTMGAC).
Is abbreviated) as crude polyoxytetramethylene glycol produced by alcoholysis in the presence of an alkali catalyst (hereinafter,
The present invention relates to a method for improving the hue of a product polyoxytetramethylene glycol by treating a reaction crude liquid (abbreviated as PTMG) with activated carbon.

[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 field of elastomers, 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.

[0004] In recent years, alcoholysis is becoming the mainstream because of less coloring of products and less drainage load as compared with hydrolysis.

Alcoholsis is a method of producing PTMG using aliphatic alcohol such as methanol while removing the by-produced carboxylic acid ester by azeotropic distillation with alcohol by means of reactive distillation (Japanese Patent Publication No. 61-61). -11969 etc.). The catalyst separation method of this method is often carried out by filtration separation or water washing, but a trace amount of the catalyst remains in the product PTMG and the hue deteriorates.

[0006]

[Problems to be solved by the invention] PTMG produced by alcoholysis of PTGAC in the presence of an alkali catalyst
Although the hue is improved over the conventional hydrolysis method, it is not good.

[0007]

OBJECTS OF THE INVENTION The object of the present invention is to provide P
It is to develop a method for improving the hue of the product PTMG by removing the catalyst component used in the production reaction of PTMG from TMGAC.

[0008]

Means for Solving the Problems That is, the present invention provides a method of treating a crude polyoxytetramethylene glycol reaction liquid prepared by alcoholysis of a polyoxytetramethylene glycol carboxylic acid ester in the presence of an alkali catalyst with activated carbon. The method for purifying polyoxytetramethylene glycol is characterized in that it improves the hue of the product polyoxytetramethylene glycol.

PTMGAC produced by cationic polymerization
Is PTMG by alcoholysis in the presence of an alkali catalyst.
Is converted to.

The reaction proceeds according to the following reaction formula.

[0011] In the above reaction formula, R ¹ is a linear alkyl group, and n represents 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 separability 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. In addition, since this catalyst reacts with carbon dioxide in the air to form a carbonate during storage, or reacts with moisture in the air to form a hydroxide, the catalytic activity tends to decrease, 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.

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

When an alkali metal or alkaline earth metal alcoholate is used as the alcoholysis catalyst, the catalyst concentration varies depending on the type of the catalyst.
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.

The reaction temperature for alcoholysis is not particularly limited, but 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 method 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 system 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, when 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 are stacked. 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 the, etc., it is usually carried out in the range of 0.5 to 10 hours. If the reaction time is too long, the hue of PTMG in the final product will be poor, or the reaction will have ended, but it will have an extra residence time.
There is no merit because the amount of PTMG produced will fall. Conversely, if the reaction time becomes too short, PTMGA
This is not preferable because the PTMG production reaction by the alcoholysis of C is not completed.

The ester residue in PTMG is PT
It is necessary to complete the reaction for producing PTMG from PTGAC because it deteriorates the product quality of polyurethane produced from MG.

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

Also, 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 alkali 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 alkali catalyst used is small. That is, P used as a raw material
As a measure of the acid content of TMGAC, JIS K0070-
The acid value is preferably about 10 mgKOH / g or less by the measuring method of 1966.

As the raw material alcohol, it is preferable to use a product having a purity higher than that usually used in industry. Further, it is preferable to use a product having a purity of the alkaline earth metal oxide catalyst to be used which is higher than the purity usually used industrially.

In the presence of an alkaline earth metal oxide catalyst, P
When there is an insoluble catalyst in the reaction crude liquid from the bottoms of the distillation column produced by the alcoholysis of TMGAC, most of the catalyst is usually separated and removed by filtration or centrifugation. However, a slightly dissolved catalyst still remains in the reaction crude liquid.

When an alkali metal or alkaline earth metal alcoholate is used as a catalyst for alcoholysis, the reaction crude liquid is usually homogeneous and therefore cannot be separated by filtration or centrifugation.

Next, the unreacted alcohol is recovered and recycled. The reaction crude liquid in which the alkali catalyst remains is treated as it is by the flash operation, and the crude P discharged from the bottom is discharged.
The coloration of TMG is extremely poor.

Therefore, when the present inventors examined the cause of coloration during the flash operation, it became clear that the alkaline catalyst remaining in the reaction crude liquid was the cause of coloration.
The inventors have found that the treatment with activated carbon is effective for removing the alkaline catalyst remaining in the reaction crude liquid, and have reached the present invention.

The temperature of the activated carbon treatment is usually in the range of 0 to 100 ° C, more preferably 20 to 70 ° C.

Further, the activated carbon treatment may be carried out by a batch treatment or a continuous treatment. Specifically, in the case of batch treatment, a PTMG reaction crude liquid and fine powdery or granular activated carbon are charged in a jacketed reactor equipped with a stirrer and stirred for several hours. The activated carbon concentration and treatment time are appropriately selected, but the activated carbon concentration is usually 1 to
It is carried out in the range of 30 wt% and the processing time is 0.5 to 10
It is carried out within a range of time. In the case of batch treatment, activated carbon is filtered after the treatment to separate from the PTMG reaction crude liquid. When it is carried out by continuous treatment, it is a method in which granular or expanded activated carbon is packed in a jacketed packed column and brought into contact with the PTMG reaction crude liquid in a fixed bed system. The contact time at this time is
It is usually carried out in the range of 0.5 to 10 hours.

In the case of industrial implementation, it is preferable to use the continuous method, which does not require a step of separating the activated carbon used for the treatment and has a low equipment cost. Specific examples of the activated carbon to be used include granular white heron siri produced by Takeda Pharmaceutical Co., Ltd. -, Carborafine and the like, CAL, CPG, SGL and the like manufactured by Toyo Calgon, and DIAHOPE SERIES manufactured by Mitsubishi Kasei.

The PTMG reaction crude liquid after the treatment with activated carbon is
After separating the activated carbon, it is flashed 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 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.

The crude PTMG discharged from the bottom of the thin film evaporator contains an oligomer component, so that a washing operation may be carried out to remove the oligomer component. However, when the washing operation is performed, a flush operation for removing water from PTMG is further required.

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.

[0040]

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, 800 g of the reaction crude liquid and 80 g of granular Shirasagi C2C manufactured by Takeda Pharmaceutical Co., Ltd. were placed in a 1-liter jacketed flask equipped with a stirrer and stirred at room temperature for 1 hour. After filtering off the activated carbon, the filtrate was poured into an evaporator and the low boiling point was flushed while leaking nitrogen. By flashing, 410 g of PTMG having a number average molecular weight of 1500 of APHA20 was obtained.

[0042]

[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 the reaction is complete, the reaction liquid is cooled and the reaction crude liquid is evaporated.
A low boiling point was flushed with nitrogen while leaking. By flashing, 411 g of PTMG having a number average molecular weight of 1500 of APHA150 was obtained.

In Comparative Example 1, when the activated carbon treatment was not performed, the hue (APHA) of the product PTMG was 2 as compared with Example 1.
It shows that it is significantly deteriorated from 0 to 150.

[0045]

According to the method of the present invention, the catalyst component used in the reaction for producing PTMG from PTMGAC by alcoholysis can be easily removed, and the hue of the product PTMG is remarkably improved.

Claims (4)

[Claims] 1. A polyoxytetramethylene glycol reaction crude liquid produced by alcoholysis of a polyoxytetramethylene glycol carboxylate ester in the presence of an alkali catalyst is treated with activated carbon to give a product polyoxytetramethylene glycol. A method for purifying polyoxytetramethylene glycol, characterized by improving hue. 2. The method for purifying polyoxytetramethylene glycol according to claim 1, wherein the polyoxytetramethylene glycol carboxylic acid ester is polyoxytetramethylene glycol acetic acid ester. 3. The method for purifying polyoxytetramethylene glycol according to claim 1, wherein the alkali catalyst is sodium methylate. 4. The method for purifying polyoxytetramethylene glycol according to claim 1, wherein the alcohol used for alcoholysis is methanol.