JPS591294B2 - Method for producing polyoxytetramethylene glycol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyoxytetramethylene glycol.

More specifically, the present invention relates to a method for producing polyoxytetramethylene glycol useful as a raw material for polyester from a lower fatty acid ester of polyoxytetramethylene glycol. It is well known that polyoxytetramethylene glycol is useful as a raw material for polyesters, particularly polyester elastomers. The method for producing polyoxytetramethylene glycol is as follows:
For example, a method is known in which a lower fatty acid ester of polyoxytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran is hydrolyzed using an alkali catalyst such as caustic soda (Industrial Chemistry Magazine, Vol. 61, p. 1347). , 1958, Japanese Patent Publication No. 47-3744, Japanese Patent Application Laid-open No. 10398-1982). However, this hydrolysis method not only requires a large amount of catalyst, but also has a poor yield of polyoxytetramethylene glycol. The production of ether elastomers had the drawback that the color tone of the resulting elastomers was unfavorable.

The present inventors have conducted intensive research on a method for obtaining polyoxytetramethylene glycol with good yield and excellent quality from such lower fatty acid esters of polyoxytetramethylene glycol, and as a result, they have arrived at the present invention.

That is, the present invention provides a method for transesterifying a lower fatty acid ester of polyoxytetramethylene glycol with a lower aliphatic alcohol to produce polyoxytetramethylene glycol. are the same or different carboxylic acid residues, aliphatic groups or aromatic groups, R7 to R9 are the same or different aliphatic groups or aromatic groups, RlO is an aliphatic group, and Rll is an aliphatic group Or it is an alkoxy group.

M is an alkali metal or an alkaline earth metal,
n is the valence of M. This is a method for producing polyoxytetramethylene glycol, characterized in that it is carried out at 50 to 300°C in the presence of at least one titanium compound selected from the following.

The polyoxytetramethylene glycol used in the present invention has an average molecular weight of 200 or more, preferably 200
-5000, particularly preferably 250-3000.

The lower fatty acid ester of polyoxytetramethylene glycol used in the present invention is, for example, an ester of the polyoxytetramethylene glycol and a fatty acid having 10 or less carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid.

Among these, particularly preferred are esters with acetic acid. Further, the lower aliphatic alcohol used in the present invention includes, for example, methanol, ethanol, isopropanol,
Alcohols having 10 or less carbon atoms, such as n-probanol, n-butanol, β-methoxyethanol, β-ethoxyethanol, and β-phenooxyethanol.

Among these, alcohols having 5 or less carbon atoms, particularly methanol, are preferred. In the present invention, the lower fatty acid ester of the polyoxytetramethylene glycol and the lower aliphatic alcohol are transesterified.

For example, when the acetate of polyoxytetramethylene glycol is transesterified with methanol, methyl acetate, which has a boiling point lower than that of the methanol, is produced, and the methyl acetate is distilled out of the reaction system. polyoxytetramethylene glycol can be obtained. In the transesterification reaction of the present invention, a specific catalyst, ie, a titanium compound represented by the above general formulas (a) to (h), is used. The aliphatic groups and aromatic groups in R1 to R9 in the general formulas (a) to (e) are substituted or unsubstituted, and specific examples include methyl, ethyl, propyl, butyl, hexyl, Examples include benzyl, cyclohexene, phenyl, p-tolyl, m-tolyl, 2,4-dimethylphenyl, and the like.

Examples of the carboxylic acid residues R1 to R5 in the general formulas (a) and (b) include lower fatty acid residues constituting the lower fatty acid esters described above. R1
-R6 when adjacent to each other may be bonded to each other to form a cyclic structure, for example, adjacent methyl groups and ethyl groups may be bonded to form a trimethylene group. The aliphatic group of RlO in the general formula (c)-{f) is substituted or unsubstituted, and is the same as the aliphatic group of R to R9.

Further, Rll is the same as R or O or is an alkoxy group, and examples of the alkoxy group include anolecooxy groups of lower aliphatic alcohols such as methoxy, ethoxy, propoxy and the like. M in the above general 2g) is NH4 or Li. Na. K, Mg. Ca,. is an alkali or alkaline earth metal such as Ba, and n is the above M
is the valence of

Preferred specific examples of such titanium compounds include the following. Compared to the titanium compound, conventionally known catalysts such as sodium and potassium catalysts are not preferred because they worsen the color tone of the resulting polyoxytetramethylene glycol.

In the present invention, in the transesterification reaction, lower aliphatic alcohol is used in an amount of at least 2 times the mole, preferably at least 2.2 times, particularly preferably at least 2.5 times, by mole, relative to the lower fatty acid ester of polyoxytetramethylene glycol. is used in an amount of not more than 50 times the mole, particularly preferably not more than 10 times the mole, and is carried out in the presence of a titanium compound.

The amount of the titanium compound may be 0.001 mol% or more, preferably 0.005 to 0.5 mol%, based on the lower fatty acid ester of polyoxytetramethylene glycol.
, particularly preferably 0.01 to 0.1 mol%. If the amount is too small, the effect of the present invention will be reduced accordingly, and if it is too large, the thermal stability of the elastomer obtained using polyoxytetramethylene glycol as a raw material will deteriorate, which is not preferable. Transesterification reaction is over 50'C3
It is carried out at temperatures of up to 00°C, preferably from 70 to 28'C, particularly preferably from 80 to 250'C.

If the reaction temperature is too low, the reaction rate will not be sufficient, and if it is too high, the elastomer obtained using polyoxytetramethylene glycol will become heavily colored, which is not preferable. Although the reaction can be carried out under conditions in which the lower aliphatic alcohol is supplied in the gas phase, it is preferable to choose conditions in which the lower aliphatic alcohol is present in the reaction system in liquid form, and if necessary, it can be carried out under pressure. can. Although the reaction time varies depending on the reaction temperature, it is preferably 1 hour or more, particularly 2 to 10 hours. The polyoxytetramethylene glycol obtained by the present invention has the advantage that it can be used as a raw material for polyester without special purification.
Polyoxytetramethylene glycol is industrially advantageously obtained from lower fatty acid esters of polyoxytetramethylene glycol.

Next, the method of the present invention will be explained with reference to Examples.

Note that parts in the examples mean parts by weight. Examples 1 to 2 Acetic anhydride and perchloric acid shown in Table 1 were mixed with 44.4 parts of tetrahydrofuran, and the mixture was heated to about 70% at room temperature (10 to 15°C).
Polymerization was carried out under stirring for a period of time under nitrogen gas.

Polymerization was terminated by adding a 2% aqueous sodium hydroxide solution to neutralize the catalyst. The obtained polymer was dissolved in ether, and then the ether layer was separated by washing with water, and the ether was distilled off to obtain a polymer. The molecular weight of the polymer was determined by decomposing a portion of the obtained polymer with an alcoholic solution of excess caustic potassium, and then back titrating with hydrochloric acid to quantify the amount of acetyl groups in the polymer.

The results are also shown in Table 1.

30 parts each of the polymer (acetic ester of polyoxytetramethylene glycol) obtained above and the amounts of methanol and titanium tetrabutoxide shown in Table 2 were charged into an autoclave equipped with a purification column, and then the system was heated to 25k9/cm with nitrogen gas. Pressurized to Cl7i and heated at 80~18'' for 5 hours.
The transesterification reaction was carried out by heating to 40°C.

During this time, methyl acetate produced by the transesterification reaction was distilled out together with methanol. Thereafter, the reaction system was returned to normal pressure and the internal temperature was lowered to 230°C to distill out unreacted methanol together with methyl acetate. The reaction results are shown in Table 2 along with the raw material charging conditions.

The yields of the polyoxytetramethylene glycols obtained were all 98% or higher, and the polyoxytetramethylene glycols were all white in color. Polyoxytetramethylene glycol produced as above 22.
Add 13.9 parts of dimethyl terephthalate and 9.7 parts of tetramethylene glycol to 7 parts to give 180 to 220 parts.
The methanol produced as a result of the reaction was distilled off by heating to .degree.

Subsequently, this reactant was transferred to a polymerization pot, and the reaction was carried out at 240°C under nitrogen gas at normal pressure, followed by polymerization for 30 minutes at the same temperature under reduced pressure of 15 mmHg, and further polymerization was carried out at 0.1 to 0.3
Polymerization was carried out for 230 minutes under reduced pressure of mmHg. The results obtained are shown in Table 3.

Examples 3 to 14 The same procedure as in Example 1 was carried out to prepare a polymer (
Acetate ester of polyoxytetramethylene glycol)
I got it.

13.6 parts of methanol and the catalyst shown in Table 4 were added to 30 parts of each of the obtained polymers, and a transesterification reaction was carried out in the same manner as in Example 1.

During this time, methyl acetate produced by the transesterification reaction was distilled out of the system together with methanol. Thereafter, the reaction system was returned to normal pressure and the internal temperature was raised to 23°C to distill out unreacted methanol together with methyl acetate. The results are shown in Table 4. From the above table, it can be seen that polyoxytetramethylene glycol can be obtained with a high transesterification rate.

Claims (1)

[Claims] 1. When producing polyoxytetramethylene glycol by transesterifying a lower fatty acid ester of polyoxytetramethylene glycol with a lower aliphatic alcohol, the transesterification reaction is carried out using the following formula ▲ mathematical formula, chemical formula in a catalytic amount. , tables, etc. ▼ (a) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (b) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (c)
▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (d) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (e) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (f) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ( g
) and TiO_2(h) [wherein R_1 to R_5 are the same or different carboxylic acid residues, aliphatic groups or aromatic groups, R_7 to R_9 are the same or different aliphatic groups or aromatic groups, and R_
1_0 is an aliphatic group, and R_1_1 is an aliphatic group or an alkoxy group. M is NH_4, an alkali metal or an alkaline earth metal, and n is the valence of M. ] A method for producing polyoxytetramethylene glycol, which is carried out at 50 to 300°C in the presence of at least one titanium compound selected from the following.