JP2001011173A - Method for producing polytetramethylene ether glycol - Google Patents

Abstract

(57) [PROBLEMS] To produce PTMG by transesterifying PTME with a lower aliphatic alcohol in the presence of an alkali metal catalyst, without impairing the smooth progress of the transesterification reaction. Providing ways to reduce consumption. SOLUTION: In a method for producing polytetramethylene ether glycol by transesterifying a polytetramethylene ether glycol diacetate with a lower aliphatic alcohol in the presence of an alkali metal alkoxide or a hydroxide, a raw material polytetramethylene ether glycol is produced. The total concentration of acetic anhydride and acetic acid in the methylene ether glycol diacetate is 1000 ppm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing polytetramethylene ether glycol (hereinafter sometimes abbreviated as PTMG). Specifically, diacetate of PTMG (hereinafter sometimes abbreviated as PTME)
To transesterify with a lower aliphatic alcohol in the presence of an alkali metal catalyst to produce PTMG. PTMG is used as a soft segment of polyester resin, polyurethane resin and the like, processed into industrial products such as rolls, and elastic fibers for clothing such as shoe soles and spandex (registered trademark) and widely used in daily life. .

[0002]

2. Description of the Related Art PTMG is generally produced by reacting tetrahydrofuran (hereinafter sometimes abbreviated as THF) in the presence of a solid acid catalyst and a carboxylic anhydride such as acetic anhydride to obtain PTME. It is known to then transesterify this diester with a lower aliphatic alcohol such as methanol in the presence of a transesterification catalyst such as an oxide or hydroxide of an alkali metal or alkaline earth metal.

When the transesterification catalyst is an alkali metal oxide or hydroxide, the catalyst dissolves in the reaction solution and becomes a homogeneous phase, so that the reaction can be carried out quickly and advantageously.
Since it is a homogeneous phase, it is necessary to devise to remove the catalyst component from the generated PTMG. Since PTMG is used as a raw material such as polyurethane resin, the transesterification catalyst
It is not preferable to remain in G, and it is necessary to remove an alkali metal component contained in PTMG.

[0004] For this reason, for example, a method of adsorbing and removing an alkali metal by activated clay, which is employed in a post-treatment at the time of producing polyethylene glycol, can be considered. In this case, an acid treatment at the time of producing activated clay is considered. It is not preferable because the derived acid component elutes. As an alternative to this, a method in which the reaction solution after transesterification is treated with an acidic ion-exchange resin to adsorb and remove alkali metal ions remaining dissolved in the reaction solution is considered.

[0005]

However, in order for the transesterification reaction to proceed smoothly, a considerable amount of alkali metal catalyst is required. As a result, the alkali metal is adsorbed and removed from the reaction solution after transesterification. To do
There is a problem that a large amount of ion exchange resin is required. The present invention provides a method for producing PTMG by transesterifying PTME with a lower aliphatic alcohol in the presence of an alkoxide or hydroxide of an alkali metal, without inhibiting the transesterification reaction from proceeding smoothly. PT where usage can be reduced
An object is to provide a method for manufacturing MG.

[0006]

Means for Solving the Problems As a result of intensive studies in view of such circumstances, the present inventors have found that transesterification is achieved by reducing the total concentration of acetic anhydride and acetic acid contained as impurities in the raw material PTME. The amount of the transesterification catalyst can be reduced without impairing the smooth progress of the reaction, whereby the load of the post-treatment with the ion exchange resin can be reduced, and a high-quality P with few impurities can be obtained.
It has been found that TMG can be obtained, and the present invention has been completed.

That is, the gist of the present invention is to produce polytetramethylene ether glycol by transesterification of diacetate of polytetramethylene ether glycol with a lower aliphatic alcohol in the presence of an alkali metal alkoxide or hydroxide. A method for producing polytetramethylene ether glycol, wherein the total concentration of acetic anhydride and acetic acid in the diacetate of polytetramethylene ether glycol as a raw material is 1000 ppm or less. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The diacetate of PTMG used in the present invention is THF in the presence of a solid acid and acetic anhydride.
Is obtained by ring-opening polymerization of Activated clay,
Silica alumina, zirconia silica or the like is used. Regarding the molar ratio of acetic anhydride / THF, the target PTM
Depending on the molecular weight of G and the type of catalyst, it is usually 0.0
01 to 0.3. Acetic anhydride is used in an amount such that the concentration in the reaction solution is about 0.1 to 30% by weight, and the catalyst is used in an amount such that the concentration in the reaction solution is about 0.1 to 20% by weight.

As the reactor, a reactor equipped with a stirrer or a tubular reactor having an appropriate liquid rising speed is suitably used. The reaction is carried out at a reaction temperature of 20-60 ° C, preferably 30 ° C.
~ 50 ° C, reaction pressure is normal pressure or slightly pressurized (0 ~ 0.
2 MPa) is preferable, and the residence time of the reaction solution is determined by the activity and concentration of the catalyst, and is usually 2 to 15 hours.

[0010] The polymerization reaction solution thus obtained contains, in addition to the diacetate of the target PTMG, a diester of an oligomer of THF, unreacted raw materials, and the like. Therefore, usually, unreacted THF and acetic anhydride are used. Distill off under normal pressure or reduced pressure. The evaporated THF and acetic anhydride can be purified and reused if necessary. Regarding the composition of diacetate of crude PTMG after removing unreacted materials,
Usually 94 to 97% by weight of diacetate of PTMG, 2
Diesters of THF oligomers of about 10 to 10 mer
Wt%, acetic anhydride 1000-5000 ppm, acetic acid 10
It is 00-5000 ppm.

In the case of removing the diester of the THF oligomer, it is preferable to further separate the crude PTMG diester by distillation using a thin film evaporator or a molecular distillation apparatus. In this case, the distillation is 5 Torr (666.5 P
a) The reaction is carried out under the following high vacuum at a temperature of 250 to 350 ° C. or less, and usually, oligomers having a molecular weight of pentamer or less are separated as a distillate, and the distillate of PTMG in which the oligomer is reduced as a bottom liquid is obtained. An acetic ester is obtained. in this case,
The total concentration of acetic anhydride and acetic acid in the product is usually 100
It becomes 0 ppm or less.

In the present invention, as the diacetate of PTMG as a raw material, the total concentration of acetic anhydride and acetic acid is 10%.
It is necessary to use one having a concentration of 00 ppm or less. Therefore, the total concentration of acetic anhydride and acetic acid in the diacetate of crude PTMG after removing the unreacted substances is 10%.
There is no problem if it is less than 00 ppm, but if it exceeds this value, it will be further treated to remove the oligomer, separated by distillation using a thin film evaporator or molecular distillation apparatus, separated by blowing inert gas, etc. , The total concentration of acetic anhydride and acetic acid must be reduced.

The thus obtained PTME having a total concentration of acetic anhydride and acetic acid of 1000 ppm or less is mixed with a lower aliphatic alcohol and reacted in the presence of a transesterification catalyst to be converted to PTMG. Since the reaction rate of the transesterification reaction is proportional to the square of the alcohol concentration, the higher the alcohol content, the easier the process proceeds, and the transesterification reaction has an equilibrium, so that the carboxylic acid ester of the lower aliphatic alcohol produced is appropriately removed. It is preferred to do so. As the lower aliphatic alcohol used here, alcohols having 1 to 4 carbon atoms, particularly methanol, ethanol, propanol and the like are preferably used. The ratio of PTME to alcohol is preferably 1: 1 to 1: 3 by weight. If the amount of alcohol is small, the viscosity is high and the reaction is slow. On the other hand, if the amount is too large, the size of the apparatus becomes large, and the cost of removing excess alcohol is high. The starting alcohol may form an azeotrope with the by-produced carboxylic acid ester of the lower alcohol, and may be removed from the reaction system. Therefore, the starting alcohol may be appropriately supplied.

As the catalyst for the transesterification reaction of the present invention, an alkoxide or hydroxide of an alkali metal is used. Specific examples of the alkali metal include lithium, sodium, potassium, cesium, rubidium and the like. Of these, sodium and potassium are preferable. Specific examples of the alkoxide include, for example, methoxide, ethoxide, isopropoxide and the like. Specific examples of the alkali metal alkoxide or hydroxide include, for example, sodium methoxide, sodium ethoxide, sodium isopropoxide, potassium methoxide, potassium ethoxide, potassium isopropoxide, sodium hydroxide, potassium hydroxide And the like. Among them, sodium methoxide and sodium hydroxide are preferable. The amount of the alkali metal alkoxide or hydroxide is usually 0.005 to PTME.
-0.2% by weight, preferably 0.01-0.05% by weight
It is.

[0015] The transesterification reaction can be carried out under normal pressure or pressurized conditions, and the pressure is usually 0.1 to 2.0 MPa,
Preferably, 1 to 1.5 MPa is a suitable condition. The reaction temperature is preferably from 60 to 180 ° C., but the reaction is carried out under the pressure and temperature conditions under which the carboxylic acid ester of lower alcohol and the alcohol are azeotropic to remove the carboxylic acid ester by-produced.

The progress of the reaction is monitored by analyzing the PTME remaining in the reaction system by a conventional method such as chemical analysis or infrared analysis. When no more PTME is detected, stop the reaction and cool. A bottom fraction obtained by removing unreacted alcohol (usually methanol), carboxylic acid ester (usually methyl acetate) and the like from the reaction mixture obtained by the above transesterification reaction by distillation, and is usually a PTM.
It contains 30 to 60% by weight of G, 70 to 40% by weight of alcohol, and 0.003 to 0.1% of a transesterification catalyst. In addition, the water content is usually 0.05 to
0.2% by weight. If the PTMG concentration is too high, the viscosity becomes high, so that when the catalyst is removed by the ion exchange treatment, the catalyst cannot be sufficiently removed due to a decrease in the diffusion rate in the ion exchange resin. If the PTMG concentration is too low, the production efficiency will be reduced because the product efficiency will be reduced.

In the present invention, when the transesterified reaction solution is treated with an acidic ion exchange resin, the water content of the reaction solution is previously 0.5 to 10% by weight, preferably 1 to 5% by weight. It is preferable in that the load of the ion exchange treatment can be reduced. The treatment with the ion-exchange resin may be performed in any of a batch system and a flow system using a fixed bed apparatus with respect to the reaction solution, but the latter is simpler. The processing conditions are usually LHSV (liquid hourly space velocity) = 0.5 to 5 hr ^-1 and a temperature of 30 to 60 ° C., preferably LHSV = ^{1 to 3} hr ^-1 and a temperature of 40 to 50 ° C.
If the LHSV is lower than 0.5 hr ^-1 , it takes a long time to process, and if the LHSV exceeds 5 hr ^-1 , the exchange efficiency becomes poor. On the other hand, if the temperature is lower than 30 ° C., the exchange efficiency becomes poor, and if it exceeds 60 ° C., etherification and PTMG open polymerization occur, which is not preferable.

The acidic ion exchange resin is not particularly limited, but is preferably a strongly acidic ion exchange resin having a sulfonic acid group. Specific examples thereof include a cation exchange resin SK1B-H manufactured by Mitsubishi Chemical Corporation. SK110-
H, PK216-H, PK220-H and the like.
PTMG thus obtained is 1 pp as an alkali metal.
m or less and can be used as a product substantially free of a transesterification catalyst. According to the invention, the effective ion exchange capacity is almost equal to the theoretical ion exchange capacity. Therefore, it is possible to greatly reduce the amount of the ion exchange resin used. As a result, it is possible to reduce the load of the ion exchange treatment, thereby reducing the size of the ion exchange treatment equipment and extending the life. It is possible to obtain.

[0019]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples unless it exceeds the gist.

Example 1 Acetic anhydride and acetic acid were detected below the detection limit (2
PTME1 having a number average molecular weight of 2000
000 parts, 1000 parts of methanol and 0.2 parts of sodium methylate are mixed, the mixture is heated to the boiling point, and methyl acetate produced by a fractionation tower (14 theoretical plates) is distilled off as an azeotropic mixture with methanol for 5 hours. I let it. When the overhead temperature became equal to the boiling point of methanol, the mixture was cooled to 50 ° C. About 5 g of the reaction solution is collected, and the pressure is 4 to 5 kg / cm.
Blowing ² in nitrogen gas to evaporate the unreacted methanol and methyl acetate, by infrared analysis, it was analyzed. PTME remaining in the reaction system was below the carbonyl group 1μ equivalent / g. Next, the reaction solution was passed through a resin packed tower in which SK1B-H, a cation exchange resin manufactured by Mitsubishi Chemical Corporation, was replaced and washed with 5 times the volume of methanol. After passing through the solution at ^-1, methanol was distilled off from the solution after circulation to obtain PTMG. After incineration and acid dissolution of this PTMG, the sodium concentration was measured by atomic absorption spectroscopy. As a result, it was 0.1 ppm or less. In addition, as a result of analyzing residual ions by ion chromatography, 0.1 ppm of acetate ions and 0.1% of sulfate ions were analyzed.
ppm and chlorine ion were 0.1 ppm or less.

Example 2 1000 parts of PTME containing 30 ppm of acetic anhydride and 30 ppm of acetic acid and having a number average molecular weight of 2000, and 1000 parts of methanol
And 0.2 part of sodium methylate were mixed, the mixture was heated to the boiling point, and methyl acetate produced by a fractionating tower (14 theoretical plates) was distilled off as an azeotrope with methanol for 5 hours. When the overhead temperature became equal to the boiling point of methanol, the mixture was cooled to 50 ° C. When PTME remaining in the reaction system was analyzed by infrared analysis in the same manner as in Example 1, the result was 1 μeq / g or less of carbonyl groups. Then, the reaction solution was cation-exchange resin SK1 manufactured by Mitsubishi Chemical Corporation.
BH was passed through the resin packed tower, which was replaced and washed with 5 times the volume of methanol, at a flow rate of LHSV = 1 hr ^-1 from above the resin tower maintained at a temperature of 50 ° C., and methanol was removed from the liquid after the flow. It was distilled off to obtain PTMG. After incineration and acid dissolution of this PTMG, the sodium concentration was measured by atomic absorption spectrometry. As a result, it was 0.1 ppm or less. Further, as a result of analyzing residual ions by ion chromatography analysis, it was found that acetate ion was 0.5 ppm, sulfate ion was 0.1 ppm, and chloride ion was 0.1 ppm or less.

Example 3 500 parts of PTMG obtained in Example 2 and 125 parts of 4,4-diphenylmethane diisocyanate were reacted at 70 ° C. for 60 minutes to prepare a prepolymer of isocyanate at both ends. To this, 1120 parts of dimethylformamide was added and dissolved to form a homogeneous solution. The solution was cooled to 0 ° C., and a solution of 19 parts of 1,2-propylenediamine dissolved in 246 parts of dimethylformamide was added to carry out a chain extension reaction. 90% of the solution of 1,2-propylenediamine was added to reach 2500 poise at 25 ° C. At this point, 3 parts of monoethanolamine dissolved in 18 parts of dimethylformamide are added to eliminate the free isocyanate of the polymer solution, and then 3 parts of acetic anhydride dissolved in 18 parts of dimethylformamide are added to reduce the viscosity of the polymer solution. Stabilized. The obtained solid content is 32%, and the viscosity at 25 ° C. is 220.
A 0 poise polymer solution was obtained.

COMPARATIVE EXAMPLE 1 1000 parts of PTME having a number average molecular weight of 2,000 containing 2,000 ppm of acetic anhydride and 2,000 ppm of acetic acid, 1,000 parts of methanol and 0.5 part of sodium methylate were mixed, and the mixture was heated to the boiling point. The methyl acetate formed in step (d) was distilled off as an azeotrope with methanol. Even after 10 hours of reaction, the top temperature was not equal to the boiling point of methanol, at which point the reaction was stopped and cooled to 50 ° C. When PTME remaining in the reaction system was analyzed by infrared analysis in the same manner as in Example 1, the carbonyl group was found to be at least 20 μeq / g. Next, the reaction solution was subjected to cation exchange resin SK1 manufactured by Mitsubishi Chemical Corporation.
BH was passed through the resin-packed tower, which had been replaced and washed with 5 times the volume of methanol, at a flow rate of LHSV = 1 hr ^-1 from above the resin tower maintained at a temperature of 50 ° C., and after flowing, methanol was removed from the liquid. Was distilled off to obtain PTMG. After incineration and acid dissolution of this PTMG, the sodium concentration was measured by atomic absorption spectrometry. As a result, it was 0.1 ppm or less. Further, as a result of analyzing residual ions by ion chromatography analysis, it was found that acetate ions were 3.5 ppm, sulfate ions were 0.5 ppm, and chlorine ions were 1.7 ppm.

Comparative Example 2 500 parts of PTMG obtained in Comparative Example 1 and 125 parts of 4,4-diphenylmethane diisocyanate were reacted at 70 ° C. for 60 minutes to obtain a prepolymer of both ends isocyanate. To this, 1120 parts of dimethylformamide was added and dissolved to form a homogeneous solution. The solution was cooled to 0 ° C., and a solution of 19 parts of 1,2-propylenediamine dissolved in 246 parts of dimethylformamide was added to carry out a chain extension reaction. The viscosity at the time when 90% of the solution of 1,2-propylenediamine was added was as low as 1700 poise at 25 ° C.

[0025]

According to the present invention, when PTME is produced by transesterification of PTME with a lower aliphatic alcohol in the presence of an alkali metal catalyst, transesterification can be carried out without impairing the smooth progress of the transesterification reaction. The use amount of the catalyst can be reduced, whereby the load of the post-treatment with the ion exchange resin can be reduced, and high-quality PTMG with few impurities can be obtained.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C07B 61/00 300 C07B 61/00 300 (72) Inventor Hiroshi Takeo 1 Tohocho, Yokkaichi City, Mie Prefecture Mitsubishi Chemical Corporation Yokkaichi Office (72) Inventor Hidetoshi Tanaka 1 Tohocho, Yokkaichi City, Mie Prefecture Mitsubishi Chemical Corporation Yokkaichi Office F-term (reference) 4H006 AA02 AC41 AD32 BA02 BA29 BA32 BD10 GP01 GP10 4H039 CA60 CD10 CD90 4J005 AA08 BB01 BD02

Claims (3)

[Claims] 1. A process for producing polytetramethylene ether glycol by transesterifying a polytetramethylene ether glycol diacetate with a lower aliphatic alcohol in the presence of an alkali metal alkoxide or hydroxide. A method for producing polytetramethylene ether glycol, wherein the total concentration of acetic anhydride and acetic acid in the diacetate of tetramethylene ether glycol is 1000 ppm or less. 2. The polytetramethylene ether glycol according to claim 1, wherein the transesterified reaction solution is treated with an acidic ion exchange resin to remove alkali metal ions contained in the reaction solution. Production method. 3. The method for producing polytetramethylene ether glycol according to claim 1, wherein the acidic ion exchange resin is a strongly acidic ion exchange resin having a sulfonic acid group.