JPS63176487A - Production of oxatetramethylene dicarboxylic acid - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the electrolytic oxidation of polytetrahydrofuran (
This invention relates to a novel method for producing poly)oxatetramethylene-dicarboxylic acid.

According to DE 2658714, (poly)oxatetramethylene-dicarboxylic acid is prepared from polytetrahydrofuran by oxidation with excess chromic anhydride in acetone in the presence of sulfuric acid and water. It is known as Shiuro. In this method, decomposition of the starting materials occurs during oxidation, so that reaction products with low molecular weights are obtained. Another drawback is the use of toxic chromic anhydride.

(Poly)oxatetramethylene dicarboxylic acid is a useful material for synthesizing thermoplastic polyetheramides or polyetheresters.

The object of the invention was to develop a method for producing (poly)oxatetramethylene dicarboxylic acid industrially easily and environmentally friendly.

The present invention solves this problem by converting polytetrahydrofuran represented by the general formula % (in which n has the meaning given below) into a polytetrahydrofuran using a redox catalyst that can be electrochemically regenerated in an alkaline aqueous medium. This is a method for producing (poly)oxatetramethylene dicarboxylic acid represented by the general formula % (1) (n means an integer from 0 to 20), which is characterized by electrolytic oxidation.

The method of the present invention is shown by the following reaction formula.

HWhat2CsHt-(OQHs) -0C3H? CH20
H+ 2H2O tenmMed0nee HOCcCsHy-(
OC2Hs) -0C3H? C0OH+ 8H+ mM
edRe.

n eo Med R8a An Od 13 M”dOX The electrochemically reproducible redox catalyst (also referred to as a redox mediator, for example) can be present in dissolved or suspended form in the electrolyte. It is particularly preferred that the redox catalyst is present as a layer fixed to the nickel oxide, for example an oxide of iron, silver, cobalt, nickel or copper, or a mixed oxide of nickel and cobalt, for example. , nickel oxide hydroxide) are particularly preferred.

It is known, for example, according to 7 Inthesis 1979, 513, that alcohols can be oxidized on an anode coated with nickel oxide hydroxide.

Tetrahedron 58.3299 (1982) describes that electrochemical oxidation of (poly)ethylene glycol on a nickel oxide hydroxide anode leads to a significant oxidative decomposition of the ether. That is, tetraethylene glycol is added under mild conditions (e.g. 3.13
mA/cm2 gradient electrode surface current density and a temperature of 5 °C), only up to 50% of the desired 3.6.9-t') oxaundecanoic acid consists, and the oxidation of the ether 3.6- of 16% due to decomposition
A product mixture is obtained containing thioxaoctanedioic acid and 6% of 6-oxabentanedioic acid.

Therefore, according to the method of the invention, (poly)oxatetramethylenedicarboxylic acids of formula 1 can be advantageously prepared by electrochemical oxidation of polytetrahydrofuran of formula
(e.g. due to molecular weight reduction), 20-40mA/at room temperature
d electrostatically industrial at the current density on the electrode surface;
All that was done to his advantage was unexpected.

According to the method of the invention, polytetrahydrofuran is prepared in an alkaline aqueous medium, preferably from 9 to 14, especially from 12 to 1
Electrolyze at a pH value of 4.

In order to adjust the pH value, the electrolyte may be supplemented with, for example, alkali metal and/or alkaline earth metal hydroxides, carbonates, hydrogen carbonates, phosphates, hydrogen phosphates or borates, preferably sodium or potassium. Add hydroxide and/or carbonate.

Since hydroxide ions are consumed in equimolar amounts to form dicarboxylic acids, the molar ratio of polytetrahydrofuran to alkali salt or alkaline earth salt is between 1:2.0 and 1:
It is 3.0. However, higher alkaline or alkaline earth concentrations can also be used.

Therefore, a suitable electrolytic solution may contain, for example, a polytetrahydrofuran content of 1 to 40% by weight, preferably 3 to 20% by weight.
is an alkaline aqueous solution of polytetrahydrofuran containing alkali or alkaline earth corresponding to the required molar ratio and desired conversion rate. In order to improve the solubility, especially in the case of high molecular weight polytetrahydrofuran, an inert organic solvent miscible with water can be added to this electrolyte. Suitable solvents include nitriles such as acetonitrile,
Ethers such as tetrahydrofuran or alcohols such as tertiary butanol.

Although the process of the invention does not require a special electrolytic cell, it is preferred to operate in an undivided flow cell. All common cathode materials are suitable as cathodes, such as those stable under electrolytic conditions, such as stainless steel, nickel, copper or noble metals, such as platinum. Particularly preferred cathode materials are steel and nickel.

The nickel oxide hydroxide is present in a thin layer on the anode material, such as carbon, steel or copper. This anode is, for example, J,
Appl, Electrochem, Volume 9, 707
(1979). However, a nickel oxide hydroxide layer on nickel as anode material is superior. For example, Tetrahedron Volume 68, 329
9 (1982), this nickel oxide hydroxide anode was prepared by preparing a nickel electrode in an aqueous solution containing 0.1N nickel sulfate, 0.1N sodium acetate, and 0.005N sodium hydroxide. 5[rIA/d and 1
mA/cII? It is produced by changing the polarity several times within a short time at a current density between

Electrolysis is preferably carried out using 8-10 F/mol polytetrahydrofuran. For example, the current density is 0.
5-6 A/dm2 electrode surface preferably 1-4 A/am
It is a two-electrode surface. The process according to the invention is carried out at temperatures up to 10° C. below the boiling point of the electrolyte used. It is particularly preferred to carry out the electrolysis at a temperature range of 20 to 70°C, particularly 20 to 40°C. Electrolysis can be carried out either discontinuously or continuously.

The work-up of the alkaline electrolysis effluent to isolate the (poly)oxatetramethylene dicarboxylic acid is carried out by conventional methods. For example, the electrolytic solution is adjusted to pH 1 to 2 using an inorganic acid such as hydrochloric acid or sulfuric acid, and the liberated (poly)oxatetramethylene dicarboxylic acid is extracted using a solvent such as an aliphatic ether. From this extract, by distilling off the solvent, (poly)oxatetramethylenedicarboxylic acid is isolated with a purity of 95% or more.

In an undivided electrolytic cell with an example guide steel and/or nickel electrode,
Perform electrolytic oxidation. During electrolysis, an electrolytic solution (the composition of which is shown in the examples) is pumped into the cell via a heat exchanger at a rate of 150 to 200 l/h.

To activate a nickel anode or a coated steel anode with a thin layer of nickel oxide hydroxide, the anode is treated with nickel sulfate (
■)0. IN, 1 m
Connect as anode and cathode alternately at a current density of A/cm2 (5-10 s).

After applying a charge of 0.5 Asec/cm2, the anode (covered with black fixed nickel ([I) oxide hydroxide) is washed with distilled water and used for electrolysis.

Example 1 In an electrolytic cell with a steel cathode and a nickel oxide hydroxide anode, polytetrahydrofuran 553 with a molecular weight of 250
．． y, an emulsion of 176 g of sodium hydroxide and 3000 g of water at a current density of 2 A/df [12 and 25
Electrolysis was carried out using 1 mole of 9F polytetrahydrofuran at a temperature of .degree.

The pH of the electrolyte was 13.7-12.8.

By extracting the alkaline electrolytic effluent with methyl tertiary butyl ether, polytetrahydrofuranf, 2
g was isolated. From this, the rate of change was calculated to be 98.0%. The electrolyte was acidified to pH 1 with sulfuric acid and extracted with methyl tertiary butyl ether. After removing the ether in vacuum, the purity was 953 or higher and the molecular weight was 304 (hydroxide value 0 and 574 m9KOH/i substance acid value). 638g of (poly)oxatetramethylenedicarboxylic acid (calculated from)
Obtained. The material yield was 79%.

Example 2 Same as Example 1 at 40°C temperature and 4A/
Electrolysis was carried out at a current density of dm2 to 95F1 molar polytetrahydrofuran. When the electrolytic effluent was finished in the same manner as in Example 1, polytetrahydrofuran was 6.7
I got it. The f conversion rate is 98%, and the molecular weight is 29 with high purity.
6 (poly)oxatetramethylenedicarboxylic acid power 34
6 g was obtained, and the yield was 86%.

Claims (1)

[Claims] 1. General formula HOCH_2C_3H_7(OC_4H_8)_n-O
General formula H, characterized in that polytetrahydrofuran represented by C_3H_7CH_2OH(II) (n has the meaning below) is electrolytically oxidized in an alkaline aqueous medium in the presence of an electrochemically reproducible redox catalyst.
OOCC_3H_7(OC_4H_8)_n-OC_3
A method for producing (poly)oxatetramethylene dicarboxylic acid represented by H_7COOH (I) (n means an integer of 0 to 20). 2. Process according to claim 1, characterized in that the electrochemically reproducible redox catalyst is present as a layer fixed on the anode. 3. The method according to claim 1 or 2, characterized in that a metal oxide is used as the electrochemically reproducible redox catalyst. 4. The method according to claim 1 or 2, characterized in that a metal oxide hydroxide is used as the electrochemically reproducible redox catalyst. 5. The method according to claim 1, 2 or 4, characterized in that NiOOH is used as the redox catalyst. 6. Any one of claims 1 to 5, characterized in that an alkaline aqueous electrolyte having a polytetrahydrofuran content of 1 to 40% by weight and a pH value of 9 to 14 is used. Method described. 7. The method according to any one of claims 1 to 6, characterized in that the electrolysis is carried out at a current density of 0.5 to 6 A/dm^2.