JPH06135897A - Production of alkyl-beta-@(3754/24)3,5-dialkyl-4-hydroxyphenyl) propionate - Google Patents

Abstract

PURPOSE:To obtain the subject compound free from coloring, useful as an antioxidant by subjecting a (3,5-dialkyl-4-hydroxyphenyl)propionic acid lower alkyl ester to ester exchange in the presence of an alkali metal hydroxide. CONSTITUTION:A 2,6-dialkylphenol and potassium hydroxide are heated to 90 deg.C while stirring, the system is made into a state of reduced pressure and retained for 30 minutes to distill away formed water. Methyl acrylate is dripped to the system under normal pressure at 130 deg.C and reacted for two hours to give a (3,5-dialkyl-4-hydroxyphenyl)propionic acid lower alkyl ester. Then this compound is subjected to transesterification with a higher alcohol such as n- octadecyl alcohol in the presence of an alkaline (earth) metal hydroxide or carbonate to give the objective alkyl-3-(3,5-dialkyl-4-hydroxyphenyl)-propionate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to alkyl-β- which is widely used as an antioxidant for polyolefins and the like.
It relates to a method for producing (3,5-dialkyl-4-hydroxyphenyl) propionate.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of transesterifying an alkyl-β- (3,5-dialkyl-4-hydroxyphenyl) propionate substituted with a lower alkyl group and a higher alcohol in the presence of a catalyst. For example, JP-A-1-316346 discloses a method using an organic tin compound as a catalyst.

[0003]

However, the method of using the above-mentioned organotin compound as a catalyst causes coloration of the product, and the separation of the catalyst is difficult. To separate, the catalyst is decomposed with oxalic acid, etc. A complicated process of extraction was required, and the reaction time was long.

The problem to be solved by the present invention is that alkyl-β- (3,5-dialkyl-4-) which makes it easy to separate the catalyst after the reaction, does not cause coloring of the product, and shortens the reaction time. It is to provide a method for producing (hydroxyphenyl) propionate.

[0005]

As a result of intensive studies, the present inventors have found that (3,5-dialkyl-4-hydroxyphenyl) propionic acid lower alkyl ester, higher alcohol, alkali metal or alkaline earth metal. It has been found that the above problems can be solved by carrying out a transesterification reaction in the presence of a hydroxide of a group metal or a carbonate (A) of an alkali metal or an alkaline earth metal, and completed the present invention.

That is, the present invention provides (3,5-dialkyl-
Transesterification of a lower alkyl ester of 4-hydroxyphenyl) propionic acid with a higher alcohol in the presence of an alkali metal or alkaline earth metal hydroxide or an alkali metal or alkaline earth metal carbonate (A). Alkyl-β- (3,5
-Dialkyl-4-hydroxyphenyl) -propionate.

(3,5-Dialkyl-4) used in the present invention
The lower alkyl ester of -hydroxyphenyl) propionic acid is not particularly limited, but is not particularly limited, and examples thereof include those represented by the following general formula (1).

[0008]

[Chemical 1]

(Wherein R 1 represents a branched alkyl group having 3 or 4 carbon atoms, and R 2 represents a linear or branched alkyl group having 1 to 4 carbon atoms).

Specific examples thereof include methyl-β- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate, ethyl-β- (3,5-di-t-butyl-4)
-Hydroxyphenyl) propionate, n-propyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, i-propyl-β- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate, n-butyl-β- (3,5-di-t-butyl-4)
-Hydroxyphenyl) propionate, t-butyl-
β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, methyl-β- (3,5-di-i-
Propyl-4-hydroxyphenyl) propionate,
Ethyl-β- (3,5-di-i-propyl-4-hydroxyphenyl) propionate, methyl-β- (3,5
-Di-sec-butyl-4-hydroxyphenyl) propionate, ethyl-β- (3,5-di-sec-butyl-4-hydroxyphenyl) propionate and the like, among which methyl-β- (3,5- Di-t-butyl-
4-Hydroxyphenyl) propionate is preferable because of its excellent yield and the usefulness of the final purified product obtained as an antioxidant.

The method for producing such a lower alkyl ester of (3,5-dialkyl-4-hydroxyphenyl) propionic acid is not particularly limited, but the one obtained by the following method is prepared from the raw materials. This is preferable because it enables a consistent manufacturing method.

That is, first, a 2,6-dialkylphenol and an alkyl acrylate are reacted in the presence of a basic catalyst (B). Examples of the 2,6-dialkylphenol used here include a branched alkyl group having 3 or 4 carbon atoms (i-propyl group, sec-butyl group, t-butyl group, etc.) as the alkyl group of 2,6-dialkylphenol. )
And two alkyl groups in one molecule may be the same or different, but especially 2,6-di-t
-Butylphenol is preferred because of its excellent yield and the usefulness of the final purified product obtained as an antioxidant.

Examples of the alkyl acrylate used include those having a linear or branched alkyl group (methyl group, ethyl group, propyl group, butyl group, etc.). The basic compound (B) described above is not particularly limited, but examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, Examples thereof include hydroxides of alkali metals or alkaline earth metals such as calcium carbonate and barium carbonate, carbonates of alkali metals or alkaline earth metals, or alcoholates of alkali metals such as sodium methoxide and potassium t-butoxide. Of these, hydroxides of alkali metals or alkaline earth metals or carbonates of alkali metals or alkaline earth metals are preferable from the viewpoint of high yield, and potassium hydroxide is preferable from the viewpoint of even higher yield.

The reaction conditions for this reaction are not particularly limited. For example, 2,6-dialkylphenol 1 and 2,6-dialkylphenol 1 and 2,6-dialkylphenol 1
The basic catalyst (B) is 0.001 to 0.1 per mol.
A method may be mentioned in which the reaction is carried out in a molar range to remove the produced water, and then the alkyl acrylate is reacted in a range of more than 1 mol per 1 mol of 2,6-dialkylphenol.

Among them, the 2,6-dialkylphenol and the basic catalyst (B) are mixed with the basic catalyst (B) in an amount of 0.015 to 0.05 per mol of the 2,6-dialkylphenol.
5 mol, more preferably 0.015 to 0.03
After reacting in a molar range and removing the produced water, the alkyl acrylate was added to 2,6-dialkylphenol 1
A method of continuously supplying and reacting in the range of 1.0 to 1.5 moles relative to the moles is to adjust the purity of the lower alkyl ester of (3,5-dialkyl-4-hydroxyphenyl) propionic acid in the reaction solution. It is preferable because a high reaction solution can be obtained and the time spent for the reaction is shortened.

In the process for producing the reaction solution,
Examples of the method for removing the generated water include a method of removing the generated water by azeotropic distillation in the presence of an organic solvent in the reaction system, and a method of distilling the generated water under reduced pressure in the system. Then, the method is preferable because it is troublesome to add water to the system sequentially. The method of (1) specifically includes a method of stirring under a reduced pressure of 20 to 50 mmHg at 90 to 100 ° C. and excluding generated water out of the system.

The alkyl acrylate may be continuously supplied for 1 to 5 hours, preferably 2 to 4 hours, from the viewpoints of suppressing by-products and safety in production.
The reaction time varies depending on the molar ratio of the raw materials, the type of catalyst, the reaction temperature and the like, but generally the reaction is completed in 4 to 8 hours including the dropping time of the acrylic acrylate.

The reaction temperature is selected from the range of room temperature to about 200 ° C., but is 1 to accelerate the reaction.
The range of 00 to 150 ° C is preferable.

In the present invention, when a lower alkyl ester of (3,5-dialkyl-4-hydroxyphenyl) propionic acid (hereinafter abbreviated as "propionic ester") is produced by the above method, The reaction liquid containing the propionic ester does not need to be purified and can be directly used in the production method of the present invention.
That is, the reaction liquid naturally contains the basic compound (B) used as a catalyst for the reaction between the 2,6-dialkylphenol and the alkyl acrylate, but the basic compound (B) is neutralized. The transesterification reaction in the next step can be carried out without performing the above procedure and without isolating and purifying the propionic acid ester.

Next, the higher alcohol which undergoes the transesterification reaction with the above-mentioned propionic ester is not particularly limited, but it is a saturated or unsaturated higher alcohol such as n-dodecyl alcohol, n.
-Tetradecyl alcohol, n-hexadecyl alcohol, n-octadecyl alcohol, oleyl alcohol, etc. are mentioned. Among them, n-octadecyl alcohol is particularly preferable because of its industrial utility.

The alkali metal or alkaline earth metal hydroxide or alkali metal or alkaline earth metal carbonate (A) (hereinafter referred to as the alkali catalyst (A)) used in the transesterification reaction is, for example, water. Examples thereof include lithium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, calcium carbonate and barium carbonate. Among them, hydroxide is preferred in terms of high yield. Lithium hydroxide is particularly preferable because its yield is remarkably excellent.

In the transesterification reaction, the proportion of the propionic acid ester and the higher alcohol used is usually in the range where the amount of the higher alcohol used and the amount of the propionic acid ester are in the stoichiometric amount, or the stoichiometry of the higher alcohol. Although the amount of the propionic acid ester in the reaction solution is an excessive amount than the amount, in the purification of the product after the reaction such as recrystallization, the unreacted propionic acid ester can be less mixed. A preferred range is 1.5 to 1.0 mol of propionic ester with respect to 1 mol of higher alcohol.

The amount of the alkali catalyst (A) used in this transesterification reaction is usually in the range of 0.01 to 0.5 mol of the alkali catalyst (A) with respect to 1 mol of the higher alcohol as a raw material. From the standpoint that the reaction can proceed faster, the alkali catalyst is less than 0.1 mol per mol of the higher alcohol.
The range of 05 to 0.3 is preferable.

When the reaction solution obtained by the above-mentioned production method is used as the proponate ester, even when the same compound as the basic catalyst (B) is used as the alkali catalyst (A), the alkali The residual amount of the basic catalyst (B) is not included in the amount of the catalyst (A) used.

The transesterification reaction carried out in the present invention is an equilibrium reaction, and the reaction proceeds easily by taking out the produced alcohol out of the system. Therefore, the reaction temperature is a temperature above the boiling point of the alcohol produced, 100
The range of ˜300 ° C. is preferred.

The reaction may be carried out under atmospheric pressure, but it is preferably carried out at a relatively low temperature and under reduced pressure in order to facilitate the distillation of alcohol and to suppress the occurrence of side reactions. Specifically, it is 100-at 20-100 mmHg.
The range of 200 ° C. is included.

The time required for the reaction varies depending on the reaction temperature, the amount of the catalyst and the like, but it is usually 1 to 3 hours, which is a very short time. The reaction solvent does not have to be particularly used, but if necessary, the reaction may be carried out using a polar solvent having a high boiling point such as dimethylformamide, dimethylsulfoxide and sulfolane.

After the reaction has ended, the product can be separated very easily from the alkali catalyst (A) by filtration.
Further, the product is then purified by recrystallization to obtain a product. In the present invention, this recrystallization can be extremely easily performed.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 107 g (0.52) of 2,6-di-t-butylphenol
Mol) and 0.84 g (0.015 mol) of potassium hydroxide in a 500 ml flask, heated to 90 ° C. with stirring, and the system is kept under reduced pressure of 30 to 50 mmHg for 30 minutes to generate water. It was distilled out of the system. Then, at 130 ° C. under normal pressure, 54 g of methyl acrylate (0.6 g
(3 mol) was added dropwise over 2 hours, and the mixture was further reacted at the same temperature for 2 hours with stirring to cause reaction.
A reaction solution containing -butyl-4-hydroxyphenyl) propionate (0.50 mol) was obtained.

138 g (0.5 mol) of n-octadecyl alcohol and 0.37 of lithium hydroxide were added to the reaction solution.
g (0.135 mol) was added, the mixture was heated to 160 ° C. with stirring, the system was kept under reduced pressure of 20 to 30 mmHg for 1 hour, water and generated methanol were distilled off, and stirring was continued for 2 hours. It was made to react.

After cooling to 100 ° C., the catalyst is separated by filtration to separate lithium hydroxide, and n-octadecyl-β- (3,
293 g of a reaction solution containing 5-di-t-butyl-4-hydroxyphenyl) propionate was obtained. Here, the catalyst lithium hydroxide could be completely filtered off by this single filtration.

As a result of analysis by liquid chromatography, n-octadecyl-β- (3,5-di-
It contained 252 g of t-butyl-4-hydroxyphenyl) propionate and had a production rate of 95.0 mol% with respect to octadecyl alcohol. Further, the obtained product was colorless.

Next, recrystallization was carried out by using 95% isopropyl alcohol (a mixed solution of 95 parts by weight of isopropyl alcohol and 5 parts by weight of water) in an amount twice the weight of the product. The yield in the recrystallization process is 9
It was 4.5 mol%, and the yield in all steps was 89.8 mol%.

Example 2 146 g (0.5 mol) of methyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate
135 g (0.5 mol) of n-octadecyl alcohol was placed in a 500 ml flask and dissolved by heating at 70 ° C under stirring, and then 0.36 (0.015 mol) of lithium hydroxide was added and heated to 160 ° C. Methanol generated under reduced pressure of 50 mmHg in the system was distilled out of the system to continue reaction for 2 hours while stirring.

The reaction solution was cooled to 100 ° C. and then filtered to separate lithium hydroxide as a catalyst, and n-octadecyl-β
267 g of a reaction liquid containing-(3,5-di-t-butyl-4-hydroxyphenyl) propionate was obtained. Here, the catalyst lithium hydroxide could be completely filtered off by this single filtration.

As a result of analysis by liquid chromatography, n-octadecyl-β- (3,5-di-
It contained 252 g of t-butyl-4-hydroxyphenyl) propionate and had a production rate of 95.0 mol% with respect to octadecyl alcohol. Further, the obtained product was colorless.

Then, in the same manner as in Example 1, recrystallization was performed using twice the weight of the product, 95% isopropyl alcohol (a mixed solution of 95 parts by weight of isopropyl alcohol and 5 parts by weight of water). The yield of the obtained purified product in the recrystallization step was 95.0 mol%, and the yield in all the steps was 90.3 mol%.

Example 3 In the method of Example 1, the same reaction was carried out by using 94 g (0.5 mol) of n-dodecanol instead of n-octadecyl alcohol, followed by filtration to separate lithium hydroxide as a catalyst. Then, 226 g of a reaction solution containing n-dodecyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate was obtained. Further, the catalyst lithium hydroxide could be completely separated by one filtration.

As a result of analysis by liquid chromatography, n-dodecyl-β- (3,5-di-t-in the product.
Butyl-4-hydroxyphenyl) propionate 20
Contains 8 g, 9 for dodecyl alcohol
It was 3.0 mol%. Further, the obtained product was colorless.

Then, in the same manner as in Example 1, recrystallization was performed by using 95% isopropyl alcohol (a mixed solution of 95 parts by weight of isopropyl alcohol and 5 parts by weight of water) in an amount twice the weight of the product. The yield of the obtained purified product in the recrystallization step was 96.5 mol% and the yield in all the steps was 89.7 mol%.

Example 4 The reaction was carried out in the same manner as in Example 1 except that the same molar number of calcium hydroxide was used instead of lithium hydroxide, and after completion of the reaction, it was filtered and n-octadecyl-β- (3. 5-
A product containing di-t-butyl-4-hydroxyphenyl) propionate was obtained. The calcium hydroxide used as a catalyst could be completely filtered off by one filtration, and the obtained product was colorless.

Example 5 The reaction was carried out in the same manner as in Example 1 except that the same molar number of lithium carbonate was used instead of lithium hydroxide, and after completion of the reaction, it was filtered and n-octadecyl-β- (3,5 -Ge-t
A product containing -butyl-4-hydroxyphenyl) propionate was obtained. The lithium carbonate used as a catalyst could be completely separated by one filtration, and the obtained product was colorless.

Example 6 The reaction was performed in the same manner as in Example 1 except that the same molar number of calcium carbonate was used instead of lithium hydroxide.
After the completion, it was filtered and n-octadecyl-β- (3,5-di-
A product containing t-butyl-4-hydroxyphenyl) propionate was obtained. The calcium carbonate used as a catalyst could be completely separated by one filtration, and the obtained product was colorless.

Comparative Example 1 210 g (0.72 mol) of methyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 150 g of n-octadecyl alcohol (0.55)
Mol) and 0.1 g of monobutyltin triuretate to 500
Place in a ml flask and at 185-190 ° C for 1 hour, 2
It heated under reduced pressure of 0 mmHg, and the methanol produced | generated was distilled off. Continue to 185-1 under reduced pressure of 3 to 1 mmHg.
After heating at 90 ° C. for 7 hours and further distilling off methanol, the pressure was returned to normal pressure to complete the reaction.

As a result of analysis by liquid chromatography, n-octadecyl-β- (3,5-di-
It contained 271.3 g of t-butyl-4-hydroxyphenyl) propionate and was 92.0 mol% based on octadecyl alcohol. The obtained product was almost black.

Then, in the same manner as in Example 1, recrystallization was performed using twice the weight of the product, 95% isopropyl alcohol (a mixed solution of 95 parts by weight of isopropyl alcohol and 5 parts by weight of water). It was carried out, but the obtained purified product contained tin ions corresponding to 0.01 g of monobutyltin triureate. Therefore, the purified product was further treated with oxalic acid to separate monobutyltin triureate. The yield of the obtained purified product in the recrystallization step was 90.5 mol%, and the yield in all the steps was 83.3 mol%.

[0048]

EFFECTS OF THE INVENTION According to the present invention, alkyl-β- (3,3) which does not cause coloration of the product, facilitates separation of the catalyst, easily produces the product, and has a short reaction time.
A method for producing 5-dialkyl-4-hydroxyphenyl) propionate can be provided.

Claims (7)

[Claims] 1. A lower alkyl ester of (3,5-dialkyl-4-hydroxyphenyl) propionic acid and a higher alcohol are mixed with an alkali metal or alkaline earth metal hydroxide or an alkali metal or alkaline earth metal hydroxide. Alkyl-3- (3,5-dialkyl-, characterized by transesterification in the presence of carbonate (A)
Preparation of 4-hydroxyphenyl) -propionate. 2. A lower alkyl ester of (3,5-dialkyl-4-hydroxyphenyl) propionate is
The method according to claim 1, wherein the 2,6-dialkylphenol and the alkyl acrylate substituted with a lower alkyl group are reacted in the presence of a basic catalyst (B). 3. An alkyl acrylate substituted with a lower alkyl group is an acrylic acrylate substituted with a lower alkyl group having 1 to 4 carbon atoms, and the higher alcohol is a higher alcohol having 12 to 24 carbon atoms. The manufacturing method according to claim 2. 4. The alkali metal or alkaline earth metal hydroxide or alkali metal or alkaline earth metal carbonate (A) is a lithium compound.
The production method according to 3 or 4. 5. The basic catalyst (B) is a hydroxide of an alkali metal or an alkaline earth metal or a carbonate of an alkali metal or an alkaline earth metal.
Alternatively, the production method described in 4. 6. The alkali metal or alkaline earth metal hydroxide or alkali metal or alkaline earth metal carbonate (A) is lithium hydroxide, and the basic catalyst (B) is potassium hydroxide. The method according to claim 2, 3 or 5, wherein 7. A 2,6-dialkylphenol is 2,6
The process according to claim 3, which is -di-t-butylphenol and the higher alcohol is n-octadecyl alcohol.