DE2147131C3 - Process for the preparation of 4,4 '- (ethylenedioxy) bisbenzoic acid ester - Google Patents

Description

if necessary, the reaction rate obtained is too low. At temperatures above

product in a monocyclic aromatic of the upper limit is the formation of Ncbenreak-

Recrystallized hydrocarbon. causes the yield to be considerably reduced.

2. Method according to claim 1, thereby reducing.

indicates that the sodium or potassium If in the process of the invention the

carbonate carried out in amounts of 0.5 to 10 moles per mole of settlement under the best conditions

p-Hydroxybenzoic acid ester used. then the yield of EBB ester is

_# 3. The method according to claim 1 or 2, characterized 65 to 70% through the entire process. I characterized that the p- (2-chloroethoxy) - 20 The selectivity, based on the POB ester, reached I benzoic acid ester in an amount of more than more than 80%.

I 10 mol, based on the p-hydroxy used. As alkali metal carbonates are sodium carbonate and

ij benzoic acid ester, leads in the circuit. Potassium carbonate used. The amount used

I of the alkali carbonate lies in the range from 0.5 to 10 mol,

i as preferably 0.5 to 2.0 moles, per 1 mole of POB ester.

k The amount of EDC used is over 1 mole and

I preferably in the range from 1 to 2.0 mol per 1 mol

I 4,4 '- (ethylenedioxy) - bis - benzoic acid ester (EBB-POB ester.

I ester) has hitherto been prepared in such a way that it is expedient to use the one according to the invention

I the alkali salt of the parahydroxybenzoic acid ester 30 method to purify the EBB ester obtained since the

I (POB ester) in a polar solvent, e.g. B. crude crystals obtained from the reaction mixture

I in an alcohol, with an EthyJendihalogenid, the EBB ester is generally not sufficiently pure

I z. B. ethylene dichloride (EDC), converts. These are to be used as the starting material for the manufacture

I method, however, will serve the yield by secondary of high molecular weight polymers.

j reactions are significantly impaired. Such are z. B. 35 Corresponding studies have shown that

I the hydrolysis of the ester group of the POB ester and of the existing impurities the organic

I of the EBB ester and the formation of vinyl chloride see acidic substances the physical properties

ζ as a by-product related to the decomposition of EDC of the polymers obtained in the polymerization on

₍ f is attributed to. To affect the economic strongest adversely.

|. To carry out this process it is therefore necessary to 40 The presence and the amount of these acidic

£ - to suppress these side reactions. Substances can be obtained by titration in an organic

'f Corresponding studies have shown that solvents with alkali hydroxide using

S i the yields of the reaction can be largely determined by the type of thymol blue as an indicator.

^ depend on the alkali compound used. The presence of these acidic substances is generally

So z. B. the EBB ester only to a small extent as the number of moles of acidic groups in

Good, like 30%, obtained when the POB ester is expressed in 10 "g of EBB ester. More attempts have been made

an alcohol neutralized with an alkali hydroxide show that it is advantageous if the acid number of the

and then implemented with EDC. This low EBB ester below 1, preferably below 0.5,

, "J ζ yield is probably due to the fact that lies.

\ '\ k that in the neutralization of the POB ester with the 50 As examples of the known methods for purification

7'I |: Alkali hydroxide formed water the ester group in the supply of EBB ester can be called: The

'A t' the course of the reaction splits off. To avoid recrystallization in an alcoholic solution

I 'this disadvantage was already a process medium and the crystallization from an acetone

■ | £,; ^ applied in which an anhydrous solution water mixture, but with these methods must

%% Of an alkali compound of the POB ester used 55 extremely large amounts of solvents used

l · became, whereby these compounds become from the POB ester, since the solubility of the EBB ester is low

'· # I and a metal alcoholate. For example, the solubility of EBB dimethyl

: '&% -,' - '■ ' such a process is only 1.0 due to the esterification in methanol at 64 ° C. The solubility

fy ι "■ '.' ■ ^wendun 8 of the alkali metal is relatively expensive. is here and below in grams of dissolved substance /

The present invention is provided a process for example, 100 ml of solvent).

Production of 4,4 '- (Äthyiendioxyd) -bis-benzoic acid- These methods have therefore not only to

ester through implementation of p-hydroxybenzoic acid- reason of the necessary investment costs, but

ester with ethylene dichloride. also due to the high yield losses as

The method is characterized in that it has been proven disadvantageous. Another major disadvantage

"If" Vi ^conversion S ^{in the} presence of sodium 63 is that in these methods not the

or potassium carbonate, in which case the acidic substances mentioned are removed completely

p- (2-chloro- also formed as an intermediate product is possible.

athoxy) benzoic acid ester leads in the cycle and these disadvantages can be avoided according to the invention

be eliminated that monocyclic aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene are used as solvents for the recrystallization. The solubility of the EBB-ester in the above-mentioned aromatic hydrocarbons is greatly different very namely, at room temperature and at elevated temperature, So is the solubility of the EBB-Dimethyleau-rs in toluene at 11O ⁰ C 5.6, while it at 30 ° C, only Is 1.3. Therefore, by using these solvents, recrystallization can be carried out with a high yield. The recrystallization is preferably carried out in such a way that the solution has a concentration of 3 to 20 percent by weight at the elevated temperature.

The recrystallization effect that can be achieved by using these solvents is very great. As a result, even after a single recrystallization, the above-mentioned acid number attributable to acidic groups can be reduced to below 0.2.

Purification by recrystallization with these solvents is considered in connection with an EBB ester obtained by condensation of the POB ester with EDC. In contrast, the purification of an EBB ester obtained by autoxidation of 1,2- (paratolyloxy) -ethane and subsequent esterification of the oxidation product should not be considered here,
In the method of the invention should of course

the reaction rate and the selectivity in industrial implementation can be high, furthermore the product obtained should have an extremely high degree of purity and should only discolour slightly when heated, so that it can be used as output matena! for the production

ίο from high molecular weight objects such as fibers u, like., Can be used.

Investigations into the types of reaction show that some unexplained side reactions take place that therefore the selectivity at

If the conditions are right, the selectivity is sometimes not high enough for the longer the reaction time decreases and that it is necessary to achieve and maintain a high selectivity to work with short response times, Zur

To carry out the process of the invention economically, it is therefore necessary that the reaction rate is increased so that high conversions can be obtained even in short reaction times.

The table below shows the dependency

the selectivity of the reaction time
Response temperature of 200 ⁰ C.

at a

reaction time

EBB dimethyl ester (mmol)

CEB methyl ester (mmol)

Remaining POB methyl ester (mmol)
Ether selectivity (%) *).

15th
1.39
4.17
2.56

93.5

Composition of the feed:

POB methyl ester 10 mmol

EDC 16 mmol

Sodium carbonate 14 mmol

Methanol 60 mmol

2.29
3.24
1.33
79.0

*) Selectivity of the etherification =

(EBB dimethyl ester · 2) -l · CEB methyl ester
converted POB methyl ester

145
2.31
2.04
0
66.6

100 (mole / mole).

Investigations based on this have shown that if the reaction is carried out with circulation of the CEB ester as an intermediate product at a high concentration, then the reaction rate of the etherification increases, that the conversion is increased in a short reaction period, that side reactions are correspondingly suppressed, thereby increasing the selectivity is increased, and that thermal discoloration of the product obtained due to the presence of by-products is considerably reduced .

The curves in the diagram show the dependence of the etherification yield on the time in the case of using POB methyl ester and DEC as starting materials. In the diagram, curve 1 relates to the yield in the absence of CEB methyl ester, while curves 2 and 3 show the changes in yields with the addition of 30 and 60 mole percent of CEB methyl ester, respectively. The diagram thus shows that the addition of the CEB methyl ester has a positive influence and that this increases both the reaction rate and the conversion.
In the technical implementation of the invention

According to the process, it is expedient that essentially the same amount of the CEB ester after completion the reaction is taken from the reaction mixture, which in the initial charge was added, and then in the circuit

is performed. For this purpose, it is necessary that the total amount of the CEB ester formed and that of the same ester which is converted during the reaction are almost the same, so that the amount of the CEB ester at the time of loading

dispatch is practically the same as after the reaction, The conditions suitable for this purpose can easily be determined by selecting the loading material. ratios of the POB ester and EDC are obtained as starting materials.

If the amount of CEB ester that is circulated increases too much, then the Recovery costs and investment costs are too high, reducing the profitability of the

/ ahrens is affected. When the amount is too small the etherification reaction rate decreases. Regarding the relationships between the circulating amount of the CEB ester, the reaction rate, the reaction period and Research conducted on conversion has shown that the most appropriate range for circulating amount, based on the POB ester, 10 to 1000 mol percent, preferably 15 to 200 mol percent, is. jo

In the method of the invention, the circulation of the CEB ester take place by removing the ester from the reaction mixture after completion the reaction is taken out and that the ester isolated in this way is reused is fed. You can also proceed in such a way that you first remove the EBB ester from the reaction mixture separates and then circulates the Chö ester contained in the remaining mixture. In the latter If necessary, cleaning measures such. B. drainage and discoloration; execute. The invention is illustrated in the examples.

example 1

A 1 -! - autoclave was filled with 152 g of POB methyl ester, 150 g of methanol, 76 g of EDC and 74.2 g of sodium carbonate loaded. After the air was replaced with nitrogen, the reaction started Carried out for 3 hours at 180.degree. C. with thorough mixing. The gas chromatographic analysis of the The reaction mixture revealed that EBB dimethyl ester was formed in a yield of 73% and that there was 10% unreacted POB methyl ester. By filtering the reaction mixture, washing the precipitate with 70 g Methanol, washing the salt with water and drying the obtained white crystals were 107.2 g of EBB methyl ester were obtained. A 3.0 g sample of the EBB methyl ester «. was in 50 ml of a mixed solvent dissolved from methanol and chloroform (volume ratio 1: 9) and in the presence a 0.1% ethanolic solution of thymol blue with a '/ ,, "- n-methanolic solution of Titrated potassium hydroxide. The titration gave an acid value of 11.3. When recrystallizing the Crystals with 7 times excess by weight of toluene became crystals with an acid value of 0.13, a melting point of 157 to 159 C and a Harsen number of 40. When the recrystallization with 6.5 times the amount by weight of a XyIoI mixture followed, then crystals having an acid value of 0.23 were obtained.

In contrast, recrystallization with 100 times the amount of 95% ethanol Crystals with an acid value of 2.1.

Example 2

A 2-1 autoclave was charged with 365.1 g POB methyl ester, 222.4 g CEB methyl ester, 356.1 g sodium carbonate, 237.5 g EDC and 461.4 g methanol. The reaction mixture was ^{heated to 180 °} C. for 1 hour while stirring.

After the reaction, the reaction mixture was mixed with 500 ecm of methanol, filtered off and with Washed 400 and 200 ecm of methanol. The solid part separated by the filtration became out 1700 ecm of toluene recrystallized, giving 249.8 g of white EBB dimethyl ester of high purity would. In the released state, the E_, ter a Harsen number of 10. The filtrate was brought to pH 4 with concentrated hydrochloric acid set, with the toluene filtrate from the recrystallization combined and distilled. This produced 226.1 g of CEB methyl ester and 55.5 g of POB methyl ester obtained as fractions with 140 to 145 ° C / 3 mm Hg. The investigation of the distillation residue found that it contained 25.5 g of EBB dimethyl ester. The selectivity to the EBB dimethyl ester was found to be 81.9%.

Example 3

At 281.6 g one according to the example! 2 obtained mixture from POB methyl ester and CEB methyl ester were 309.6 g POB methyl ester, 237.5 g EDC, 356.1 g sodium carbonate and 461.4 g methanol were added. The implementation and the follow-up treatment was carried out as in Example 2. In this way, 280.1 g of a mixed fraction of CEB methyl ester were obtained and POB methyl ester (with 221.9 g CEB methyl ester and 59.7 g POB methyl ester). the Selectivity to EBB dimethyl ester was 79.5% determined.

Example 4

A 2-1 autoclave was charged with 365.2 g POB methyl ester, 262.2 g CEB methyl ester, 178.1 g sodium carbonate, 213.8 g EDC and 461.4 g methanol. ^{The reactants were heated to 180 °} C. for 30 minutes with stirring. Thereafter, the procedure of Example 2 was repeated, whereby 248.7 g of EBB dimethyl ester were obtained. The selectivity was 87.5%. In the dissolved state, the ester showed a Harsen number of 10.

Example 5

A 2-1 autoclave was charged with 394.8 g of POB ethyl ester, 262.8 g of ethyl para- (2-chloroethoxy) benzoate, 306.1 g of potassium carbonate, 185.3 g of EDC and 450 g of ethanol. The reactants were heated for 30 minutes under stirring to 18O ⁰ C. Following the procedure of Example 2, 278.3 g of EBB ethyl ester were obtained. The selectivity was 83.5%.

1 sheet of drawings

Claims (1)

1 2 the reaction product obtained is optionally recrystallized in a monocyclic aromatic hydrocarbon, 1. Process for the preparation of 4,4 '- (ethylene- In the process of the invention, good "} dioxy) bis-benzoic acid esters are obtained by reacting S results if a solvent p-Hydroxybenzoic acid ester with ethylene dichloride, especially an alcoholic solvent, r characterized by turning which is imstar.de during the ! the reaction in the presence of sodium or all of the POB ester is heated • Performs potassium carbonate, being given to dissolve the POB ester. The reaction temperatures if as an intermediate product formed p- (2-chloro-io extend from 100 to 23O ⁰ C. At temperatures ethoxy) benzoic acid ester in the cycle and below the lower limit is the reaction