DE1281451B - Process for the preparation of p- (ª ‰ -oxyaethoxy) -benzoic acid - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07c

German class: 12 q- 29/01

Number: 1281451

File number: P 12 81 451.6-42 (P 32026)

Filing date: June 18, 1963

Opening day: October 31, 1968

The invention relates to a process for the preparation of p - (/ S-oxyethoxy) benzoic acid by Reaction of p-oxybenzoic acid with ethylene oxide or with ethylene chlorohydrin in an aqueous alkaline solution Solution at elevated temperature. The process is characterized in that the reaction is carried out at a pH of 9.0 to 11.5, optionally the mixture at a pH of 10.5 to 12 to temperatures> 70 ° C, partially> 80 ° C, heated and the p - (/ 3-oxyethoxy) benzoic acid in usually wins by adding acids.

Various processes are already known for producing this substance.

In Chemical Abstracts 52, 3355 d (1958), and 51, 17186 f (1967), manufacturing processes of p- (ß- oxyethoxy) -benzoic acid are described in which the methyl ester of p-oxybenzoic acid in the presence of Na as a catalyst with ethylene oxide implemented and the reaction product obtained is then saponified with sodium hydroxide solution.

In that described in U.S. Patent 2,471,023 Process is used for the production of p- (ß-oxyethoxy) benzoic acid the sodium salt of ethyl p-oxybenzoate with an alcoholic solution of ethylene chlorohydrin implemented and the reaction product obtained in this way is then subjected to hydrolysis.

Production takes place in the processes mentioned of the desired product in several stages, but there are already one-stage processes for production of p - (/ 3-oxyethoxy) benzoic acid known.

According to the method described in "Chemical Abstracts" 58, 8984f (1963) and 58, 12473 b (1963), p - (/? - -oxyethoxy) -benzoic acid is prepared by reacting oxybenzoic acid with ethylene chlorohydrin. In the first-mentioned process, a molar ratio of p - (/ S-oxyethoxy) benzoic acid to oxybenzoic acid of 1: 1.5 is used. In this case, be obtained at a good yield of 95% products having a temperature below 18O ⁰ C melting point.

Lowering the molar ratio to 1: 1 as in the second of the processes mentioned enables a pure product with a melting point of 179 ^° C. to be obtained, but reduces the yield to about 77% .Neither of the two processes is therefore suitable for the production of p- (/ 3-Oxyethoxy) -benzoic acid at the same time with high yield and very high purity, as it is necessary for the production of high polymer materials, suitable.

If the ethylene oxide or ethylene chlorohydrin content is increased to improve the yield, for example to about 2 moles per mole of p-oxybenzoic acid, a process for the preparation of
p - (/ 3-oxyethoxy) benzoic acid

Applicant:

Polyesterether Development Co., Ltd., Tokyo

Representative:

Dr.-Ing. E. Hoffmann

and Dipl.-Ing. W. Eitle, patent attorneys,

8000 Munich 8, Maria-Theresiastr. 6th

Named as inventor:

Keisuke Mihara, City of Saeki (Japan)

then the end products obtained become stronger due to the more pronounced side reactions contaminated.

It has now been shown that the reaction is influenced by the pH of the reaction mixture and progresses faster once the pH of the reaction mixture increases to a value above 8.0.

At the same time, however, the speed of the side reactions increases with increasing pH, and that The extent of the side reactions is influenced by the existing pH.

To explain the invention, reference is made to the diagram, which in various The conversion of the phenolic hydroxyl groups of p-oxybenzoic acid as a function of pH conditions of the ethylene oxide consumed.

The curves show the course of the reaction for a starting solution in which 20 mol of water per mol of p-oxybenzoic acid and 1.05 mol for the reaction according to curve A , 1.5 mol according to curves B, B ' and B and 1.5 mol according to curve C 2 moles of sodium hydroxide per mole of p-oxybenzoic acid are included.

Curve B ' describes the course of the reaction from point b when the pH of the reaction mixture is adjusted to 9.5 to 11.5, preferably 10.0 to 11.0, by adding an acidic substance. Curve B ″ shows the course of the reaction when the pH value of the reaction mixture is kept precisely at 10.5. In the course of the reaction shown in curve C, the pH value was kept in the range from 10 to 11 from the beginning.

From the diagram it can be seen that with a proportion of 1.05 mol NaOH (curve A), a large part of the ethylene oxide is trapped by side reactions

809 629/1457

because in the early stage of the reaction the pH of the reaction mixture is too low. If the pH value is increased by increasing the NaOH content (curve B), the ethylene oxide is not initially consumed so much in the side reactions, but point b of curve B shows that the conversion of the phenolic hydroxyl groups, caused by the incipient side reactions, decreases in comparison, so that with higher ethylene oxide even a poorer conversion than in case A is achieved.

The course of curves B ' and B ″ shows that the addition of an acidic substance, after the reaction has in part already progressed, can increase the conversion of the phenolic hydroxyl groups. The best results are then obtained according to curve C, if a large excess of alkali metal hydroxide was used at the beginning and the reaction can be used in the course of the reaction.

However, towards the end of the oxyethylation reaction, a mineral acid or p - (/? - oxyethoxy) benzoic acid should preferably be added to the reaction mixture, since otherwise the p-oxybenzoic acid would remain in the reaction mixture.
Instead of ethylene oxide, the oxyethylation

ethylene chlorohydrin can also be used. Here, the ethylene chlorohydrin is reacted with the alkali hydroxide converted into ethylene oxide and the chloride of the alkali metal concerned. The ethylene chlorohydrin can be in an excess

Amount are added, the proportion of ethylene chlorohydrin in the reaction mixture being greater must be the proportion of the alkali metal hydroxide released by the oxyethylation reaction. To one thereby caused decrease in pH

tion is taken to ensure that the pH does not prevent ao, one sets the reaction mixture during increases over the range 10-11. the reaction a basic substance, for example

The diagram shows that it is possible to decisively suppress the side reactions, if, on the one hand, one works with an excess of alkali at the beginning of the reaction and, on the other hand, takes care of it helps that the pH remains between 9 and 11.5 in the course of the reaction. With this approach, As the following Table 1 shows, a considerable increase in the yield or the purity of the

30th

p - (/ J-oxyethoxy) benzoic acid linked. Table 1

Constantly held p - (/ S-oxyethoxy) benzoic acid Melting point pH values of the yield ⁰ C Reaction mixture % 175 9.0 78 179 9.5 86 180 10.0 94 180 11.0 94 179 11.5 88 176 12.0 67

35

In one embodiment of the invention, the reaction is initiated with a solution which is 1 mol p-oxybenzoic acid, 1.1 to 2 moles of alkali metal hydroxide and 8 to 50 moles of water per mole of p-oxybenzoic acid contains.

Sodium hydroxide, too.

In the process according to the invention, the p-oxybenzoic acid can be replaced by a reaction product containing the potassium salt of p-oxybenzoic acid produced by the reaction of Potassium phenolate with carbon dioxide, the so-called Kolbe reaction, as described in "Ullmann", vol. 13, p. 92, is described.

In the invention the Oxyäthylierungsmittel can in an amount of 1.1 to 1.4 moles per mole of p-oxybenzoic acid may be used, and the reaction may be at a temperature in the range from 100 down to 6O ⁰ C, preferably at about 80 ° C to be executed. Water can be used in an amount of 8 to 50 moles, preferably less than 20 moles, per mole of p-oxybenzoic acid. The use of the oxyethylating agent in an amount of more than 1.4 mol is uneconomical. It is not advisable to use a reaction temperature below 60 ° C., since the reaction takes place too slowly at such a temperature. A reaction temperature of over 100 ° C., like the use of too large an amount of water, causes side reactions and adversely affects both the yield and the purity of the resulting p - (/? - oxyethoxy) benzoic acid.

Table 2 below shows the relationship between the amount of water used and the yield of p- (| 3-oxyethoxy) benzoic acid, if the reaction

By adding an acidic substance such as sulfuric acid, the pH of the reaction mixture per mole of p-oxybenzoic acid is then 1.3 moles of ethylene oxide Mixture to the range of 9.5 to 11.5, are preferably used.

10.0 to 11.0.

Instead of sulfuric acid, the pH value can also with hydrochloric acid, carbon dioxide, sulfur dioxide, p-oxybenzoic acid, p - (/? - oxyethoxy) -benzoic acid as well as with Mixtures of the same can be set.

When using p - (/? - oxyethoxy) benzoic acid The free sodium hydroxide formed during the reaction is used as a pH regulator by the formation of the sodium salt bound, causing the pH of the reaction mixture to drop. By adding p - (/? - oxyethoxy) benzoic acid a particularly pure end product can be obtained, as in this way the introduction foreign substances in the reaction mixture is avoided. The p-oxybenzoic acid, which is also suitable for acidification reacts as a dibasic acid with the sodium hydroxide to form the disodium salt, so that this acid also regulates the pH value

Table 2

Molar ratio p-G? -oxyethoxy) benzoic acid Melting point
° C H ₂ O: p-oxy
benzoic acid yield
% 179 50 87 180 30th 90 181 25th 91 181 20th 93 181 15th 95 181 8th 95

It has also been found that the contamination by the side reaction of ester formation is completely can be avoided if the reaction mixture after completion of the oxyethylation at a pH of over 10, preferably 10.5 to

12.0, at a temperature of about 70 ° C, preferably about 80 ⁰ C, heated.

Such a heat treatment causes the glycol ester produced in the side reaction to form p - (/ 3-oxyethoxy) benzoic acid and ethylene glycol is hydrolyzed.

The presence of the ester in the reaction mixture can be determined by the following test will:

95% ethanol and 1 ml η-hydrochloric acid are added to 0.1 g of the reaction mixture, followed by one drop a 10% iron (III) chloride solution (solution "A").

A 0.5 η solution of hydroxylamine hydrochloride is added to 0.1 g of the reaction mixture 95% ethanol and 0.2 ml 6N sodium hydroxide solution are added. After cooking and subsequent cooling 2 ml of η-hydrochloric acid and then 10% iron (III) chloride solution are added to the mixture (solution "B").

The appearance of a color of the solution in the shade of grape juice or light reddish violet or a color like the solution "A" is indicated with - \ --f- or -. The increase in the number of plus signs indicates the presence of a greater proportion of the ester compound in the reaction mixture.

After completion of the oxyethylation reaction, an acidic substance is added to the reaction mixture, such as sulfuric acid, hydrochloric acid, carbon dioxide or sulfur dioxide, added, whereupon the same is cooled, to precipitate the p- (ß-oxyethoxy) benzoic acid. In this case, the reaction mixture can previously with Water diluted and purified by separating the impurities or treating with active charcoal will.

The invention is to be explained with the aid of the following examples.

example 1

138 g of p-oxybenzoic acid were dissolved in a mixture of 70 g of sodium hydroxide and 250 g of water. The oxyethylation reaction was carried out by blowing ethylene oxide through the solution at a constant temperature of 80 ° C. As soon as the pH of the reaction mixture had risen to 11.0, it was lowered to 10.5 by adding sulfuric acid. After a total of 58 g of ethylene oxide had been bubbled through, 98% of the phenolic hydroxyl groups of p-oxybenzoic acid were oxyethylated, the pH being kept in the range from 10.5 to 11.0 during the reaction. The presence of ester compounds in the resulting reaction mixture was determined by means of the test described, whereby two pluses (++) were found. The reaction mixture was admixed with 200 g of water, the pH being adjusted to 11.0; this was followed by heating ^{to 90 ° C. for 30 minutes.} After the ester test had indicated a minus (-), the reaction mixture was treated with activated charcoal, treated with sulfuric acid until a pH of 2 was obtained, and then cooled ^{to 5 ° C. for crystallization.} The precipitated crystals were filtered off, washed with water and dissolved in boiling water, and the solution was filtered. To re-crystallization of p - (^ - Oxyäthoxy) benzoic acid, the filtrate was cooled to 5 ⁰ C. At a yield of 90% was obtained 164 g of p - (/? - Oxyäthoxy) benzoic acid having a melting point of 180 ⁰ C.

Example 2

100 g p-oxybenzoic acid was dissolved in a mixture of 43 g of sodium hydroxide and 200 g of water, followed by discontinued after heating the solution at 7O ⁰ C, the pH by addition of 50% sodium hydroxide solution to 11.0. The solution was in the course

72 g of ethylene chlorohydrin were slowly added over the course of one hour, the pH of the reaction mixture being kept at 10.5 + 0.2 by the slow addition of 50% sodium hydroxide solution during the reaction. After completion of the Äthylenchlorhydrinzugabe the reaction mixture was heated for 30 minutes at 90 ⁰ C and then filtered hot. The filtrate was treated with sulfuric acid and then cooled to 1O ⁰ C, whereby crystals separated from p- (.beta. Oxyäthoxy) benzoic acid. The crystals

ao were cleaned as in Example 1. There were 125 g of p - (/ 3-Oxyäthoxy) benzoic acid having a melting point of 18O ⁰ C at a yield of 95%.

Example 3

139 g p-oxybenzoic acid was dissolved in a mixture of 70 g of sodium hydroxide and 150 g of water, followed by adjusted by the addition of 50% sodium hydroxide solution igar to 11.0 after heating the solution at 75 ⁰ C the pH. Over the course of 2 hours

the solution was slowly added 105 g of ethylene chlorohydrin, wherein ig during the reaction by the slow addition of 50% sodium hydroxide ^{solution, he} pH of the reaction mixture during the first 40 minutes to 11.0, then for a further 40 minutes and finally 10.5 was held at 10.0 for the last 40 minutes. Then the reaction mixture was adjusted to a pH of 11.5 and heated for 1 hour with stirring to 85 ° C, was added followed by hydrochloric acid and the solution was cooled to 10 ⁰ C, the crystals of p- (.beta. Oxyäthoxy) - to precipitate benzoic acid. These were cleaned as in Example 1. In this g p 173 - (/ 3-Oxyäthoxy) benzoic acid having a melting point of 180 ⁰ C and in a yield of 95%.

Example 4

A reaction product suitable as starting material for p-oxybenzoic acid was obtained by reacting 13.2 kg of potassium phenate with carbon dioxide in an autoclave. After the carbon dioxide had been passed in, the reaction mixture was stirred ^{first at 180 °} C. and then at 220 ^{° C. for 2 hours.} The reaction product was dissolved in 25 l of water and purified by extracting the remaining phenol with benzene and by decolorizing with activated charcoal. The solution prepared in this way contained 8.3 kg of p-oxybenzoic acid. 3.4 kg of ethylene oxide were slowly added to the reaction product over the course of one hour, the pH of the reaction mixture being kept at 10 to 11 by blowing sulfur dioxide through it. Then the reaction mixture with stirring for 1 hour at 8O ⁰ C was heated, followed by sat added 50 1 of water and then filtered hot. After sulfur dioxide had been blown through the filtrate, it was ^{cooled to 10 °} C. in order to precipitate the solid substances. These were then dissolved at a temperature of 120 ⁰ C in 501 water. The solution was ^{cooled to 10 0} C for the purpose of renewed

Crystallization of the p - (/ J-Oxyäthoxy) benzoic acid, which in an amount of 10.2 kg having a melting point of 178 ⁰ C in 93% yield was obtained.

Example 5

138 kg of p-oxybenzoic acid were dissolved in a mixture of 75 kg of sodium hydroxide and 250 kg of water. The oxyethylation reaction was carried out by blowing 85 kg of ethylene oxide into the solution at 65 ° C., the pH of the reaction mixture being increased to 10.5+ by adding 110 kg of powdered p-oxybenzoic acid over the course of 2 hours 0.2 would be held. After completion of the p-Oxybenzoesäurezugabe more is were 13 kg ethylene oxide bubbled through the reaction mixture, the pH was maintained by addition of 50% igo "sulfuric acid to 10.5. After this blowing of Äthylenoxyds the reaction mixture was stirring for 1 hour at 80 ⁰ C. and then diluted with 1000 kg of water, whereupon with sulfuric acid the pH value would be adjusted to 3. The reaction mixture was ^{cooled to 10 °} C., whereby a precipitate was obtained, which was filtered off, washed with water, dissolved in 3000 kg of water and This was then recrystallized, giving 310 kg of pure p- (18-oxyethoxy) benzoic acid in crystal form.

Example 6

138 g of p-oxybenzoic acid were dissolved in a mixture of 80 g of sodium hydroxide and 300 g of water. 100 g of ethylene oxide, 125 g of p-oxybenzoic acid and 100 g of water were added in succession to the solution over the course of 3 hours at 75 ^{° C. with stirring, the pH of the reaction mixture being kept at 10.5 + 0.2.} The reaction mixture was then heated to 85 ° C. for 30 minutes, after which 2000 g of water and a mixture of 120 g of sulfuric acid and 500 g of water were added. The reaction mixture was cooled to 10 ° C, whereby a precipitate was obtained which

30th

35 was filtered off, washed with water, dissolved in 3000 g of water and then caused to crystallize. The yield of pQ? -Oxyäthoxy) benzoic acid was 95 ° / _0th

Claims (4)

Patent claims: 1. Process for the preparation of p - (/ S-oxyethoxy) benzoic acid by reacting p-oxybenzoic acid with ethylene oxide or with ethylene chlorohydrin in aqueous-alkaline solution at elevated temperature, characterized in that that the reaction is carried out at a pH of 9.0 to 11.5, if appropriate the mixture at a pH of 10.5 to 12 to temperatures> 70 ° C., preferably > 80 ° C, heated and the p - (/ S-oxyethoxy) benzoic acid wins in the usual way by adding acids. 2. The method according to claim 1, characterized in that the reaction _<# of p-oxybenzoic acid with ethylene oxide or ethylene chlorohydrin in a ratio of 1 mole of p-oxybenzoic acid to 1.1 to 1.4 moles of ethylene oxide or ethylene chlorohydrin is carried out. 3. The method according to claim 1 and 2, characterized in that in the implementation of p-Oxybenzoic acid with ethylene oxide the pH value from 9.0 to 11.5 by adding hydrochloric acid, Sulfuric acid, carbon dioxide, sulfur dioxide, p-benzoic acid, p - (/ 5-oxyethoxy) -benzoic acid or a mixture of these acids. 4. The method according to claim 1 to 3, characterized in that that the reaction is carried out with a water content of 8 to 50 moles per mole of p-oxybenzoic acid performs. Considered publications:
British Patent No. 719,706;
U.S. Patent No. 2,471,023;
Chemical Abstracts, 49, 15969d (1955); 51, 17186f (1957); 52, 3355d (1958); 58, 8984f, 12473b (1963). 1 sheet of drawings 809 629/1457 10.65 © Bundesdruckerei Berlin