DE2147131B2 - Process for the preparation of 4,4 '- (ethylenedioxy) bisbenzoic acid ester - Google Patents

Description

2. The 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 by 65 to 70% through the entire process,

characterized in that the p- (2-chloroethoxy) - 20 The selectivity, based on the POB ester, is achieved

benzoic acid esters in an amount greater than more than 80%.

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

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

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

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

The amount of the EDC used is over 1 mole, and preferably in the range of 1 to 2.0 moles per 1 mole

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

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

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

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

in an alcohol, with an ethylene dihalide, the EBB ester is generally not sufficiently pure

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

Process, however, will serve the yield by secondary of high molecular weight polymers,

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

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

of the EBB ester as well as the formation of vinyl chloride see acidic substances the physical properties

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

is due. To adversely affect economic thru-strongest,

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

Corresponding studies have shown that solvents with alkali hydroxide using

the yields of the reaction are strongly determined by the type of thymol blue as an indicator

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

booty, such as 30%, obtained when the POB ^{ester is expressed in 10 e} g of EBB ester. Have more attempts

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,

Yield is presumably due to the fact that lies.

the neutralization of the POB ester with the 50 As examples of the known methods for cleaning

Alkali hydroxide formed water the ester group in the supply of EBB ester can be called v / earth: The

The course of the reaction splits off. To avoid recrystallization in an alcoholic solution

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

applied in which an anhydrous solution water mixture. However, with these methods

an alkali compound of the POB ester is used 55 extremely large amounts of solvents are used

which compound will become the POB ester because the solubility of the EBB ester is low

and a metal alcoholate. For example, the solubility of EBB dimethyl

However, such a process is only 1.0 due to the esterification in methanol at 64 ° C. The solubility

Turning the alkali metal is relatively expensive. is here and below in grams of dissolved substance /

The invention relates to a method for 60 100 ml of solvent specified).

Production of 4,4 '- (ethylenedioxide) -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

one the reaction in the presence of sodium 65 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.

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

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 aromatic hydrocarbons mentioned is in fact very different at room temperature and at elevated temperature. Thus, the solubility of the EBB-Dimeihylesters is in toluene at 110 ⁰ C 5.6, while it is at 3O ⁰ C only 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 associated with a Considered EBB ester obtained by condensation of the POB ester with EDC. In contrast, the purification of an EBB ester, which is produced by autoxidation of l, 2- (paratolyloxy) -ethane and subsequent esterification of the oxidation product is not contemplated herein will.

In the process of the invention, the reaction rate and the selectivity should, of course, be taken into account be high in industrial implementation. Furthermore, the product obtained should have an extremely high purity own and only slightly discolored when heated, so that it can be used as a starting material for production

ίο from high molecular weight objects such as fibers and the 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. To the

economical implementation of the process of the invention, it is therefore necessary that the reaction rate is increased so that high conversions are obtained even in short reaction times can.

The table below shows the dependence of the selectivity on the reaction time at a reaction temperature of 200 ^° C.

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

60
2.29
3.24
1.33

79.0

*) Selectivity of the etherification =

(EBB dimethyl ester x 2) 4-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 occurs with circulation of the CEB ester takes place as an intermediate product with high concentration, then the reaction rate of the etherification increases, that the conversion is increased in a short reaction period, that side reactions are suppressed accordingly, whereby the selectivity is increased, and that a thermal discoloration of the product obtained due to the presence of by-products significant is decreased.

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

In the technical implementation of the In 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 recycled. For this purpose it is necessary that the total amount of the formed CEB ester and that of the same ester that during the Reaction is converted, is almost the same, so that the amount of CEB ester at the time of charging is practically the same as after the reaction. The conditions suitable for this purpose can easily by selecting the feed ratios of the POB ester and EDC as starting materials can be obtained.

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

driving is impaired. When the amount is too small. 19th
is, then the rate of reaction increases U e 1 «ρ 1 e I
Etherification off. With regard to the relationships between a 2-1 autoclave, with 365.1 g of POB methylene of the circulating amount of the CEB ester, the ester, 222.4 g of CEB methyl ester. 356.1 g of sodium reaction rate, reaction period and 5 carbonate, 237.5 g of EDC and 461.4 g of methanol for conversion studies carried out. The reaction mixture was allowed to stir for 1 hour while indicating the most suitable area for stirring to be heated to 180 ° C.

circulating amount, based on the POB ester, After the reaction, the reaction mixture was 10 to 1000 mol%, preferably 15 to 200 mol, mixed with 500 ecm of methanol, filtered off and mixed with percent, is. Washed 10 400 and 200 ecm of methanol. The through In the process of the invention, the circu- lation can be used to filter the separated solid part lation of the CEB ester take place in that the 1700 ecm of toluene recrystallizes, whereby 249.8 g Ester from the reaction mixture after completion of white EBB dimethyl ester with high purity earth Reaction is taken out and that it was held. In the dissolved state, the ester showed In this way, ester of reuse 15 isolated a Harsen number of 10. The filtrate was with is fed. You can also proceed in such a way that concentrated hydrochloric acid is brought to a pH of 4 the EBB ester is first adjusted from the reaction mixture, separated from the recrystalline with the toluene filtrate and then combined and distilled in the remaining mixture. Here were contained CEB ester can circulate. In the latter, 226.1 g of CEB methyl ester and 55.5 g of POB methyl case you can optionally cleaning measures, ore ester as fractions with 140 to 145 ° C / 3mm Hg. B. a drainage and discoloration persist. The investigation of the distillation recycling. The invention is shown in the examples obtained that this 25.5 g of EBB dimethyl ester purifies. contained. The selectivity to the EBB dimethyl ester

was found to be 81.9%.

Example »5 _D ■■, ■,

Example

A 1-liter autoclave was filled with 152 g of POB methyl ester, to 281.6 g of a Ge-150 obtained according to Example 2 g of methanol, 76 g of EDC and 74.2 g of a sodium mixture of POB methyl ester and CEB methyl ester carbonal loaded. After the air through stick were 309.6 g POB methyl ester, 237.5 g EDC, substance had been replaced, the reaction was 30 356.1 g of sodium carbonate and 461.4 g of methanol to-3 Hours at 180.degree. C. with thorough mixing. The implementation and the follow-up treatment guided. The gas chromatographic analysis of the was carried out as in Example 2. In this way, Reaction mixture revealed that the EBB dimethyl was 280.1 g of a mixed fraction of CEB methyl ester with a yield of 73% was formed ester and POB methyl ester (with 221.9 g CEB methyl and that 10% of unreacted POB methyl ester 35 esters and 59.7 g of POB methyl ester) are obtained. the were present. Filtration of the reaction selectivity to EBB dimethyl ester was found to be 79.5 ",, mixture, washing of the precipitate determined to be 70 g.

Methanol, washing the salt with water and B e '■' 14

Drying of the white crystals obtained were '"

107.2 g of EBB methyl ester were obtained. A 3.0 g sample of 40 A 2-1 autoclave was filled with 365.2 g of POB methyl

of the EBB methyl ester was dissolved in 50 ml of a mixed ester, 262.2 g of CEB methyl ester, 178.1 g of sodium

solvent made from methanol and chloroform (volcarbonate, 213.8 g EDC and 461.4 g methanol

lumen ratio 1: 9) and sends in the presence. The respondents were given 30 minutes

of a 0.1% ethanolic solution of Thymol · with stirring to 180 ^c C heated. After that, the

blue with a '/ öo-n-methanolic solution of 45 the procedure of Example 2 repeated, whereby

Titrated potassium hydroxide. The titration showed that 248.7 g of EBB dimethyl ester were obtained. the

Acid value of 11.3. At the time of recrystallization, the selectivity was 87.5%. In the dissolved state

Crystals with a 7-fold excess by weight, the ester showed a Harsen number of 10.
Toluene became crystals with an acid value of

0.13, a melting point of 157 to 159 ° C and a 50 B e 1 s ρ i e 1 5

Obtained Harsen's number of 40. When the recrystalline A 2-1 autoclave was filled with 394.8 g of POB ethyl

sation with 6.5 times the weight of a xylene ester, 262.8 g of ethyl para- (2-chloroethoxy) benzoate,

mixed, then crystals with a 306.1 g of potassium carbonate, 185.3 g of EDC and 450 g

Acid value obtained of 0.23. Charged with ethanol. The respondents were

In contrast, the recrystallization gave 55 heated to 180 ° C for 30 minutes with stirring. To

with 100 times the amount of 95% ethanol of the procedure of Example 2 were 278.3 g of EBB-

Crystals with an acid value of 2.1. Obtain ethyl ester. The selectivity was 83.5%.

1 sheet of drawings

Claims (1)

ι 2 if necessary, the reaction product obtained claims: 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 ester obtained by reacting 5 results if you use a solvent, p-Hydroxybenzoic acid ester with ethylene dichloride, in particular an alcoholic solvent, thereby characterized in that one turns which is capable of doing this, during the reaction in the presence of sodium or heaters, part or all of the POB ester Potassium carbonate carries out, being given to dissolve POB ester. The reaction temperatures if p- (2-chloro-io formed as an intermediate product extend from 100 to 230 "C. At temperatures ethoxy) benzoic acid ester leads in the circuit and below the lower limit is the reaction man possibly the reaction rate obtained is too low. At temperatures above product in a monocyclic aromatic of the upper limit is the formation of side reaction hydrocarbon recrystallized. effects that considerably reduce the yield