JPH0469621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyglycerin with little coloring.

Polyglycerin is used as a raw material for food emulsifiers, cosmetic moisturizers, plasticizers, surfactants, etc.

Conventionally, polyglycerin has been produced by recovering glycerin from distillation residue, dehydration condensation of glycerin, or direct synthesis from epichlorohydrin, but the polyglycerin produced by these methods is difficult to purify and is colored. The disadvantages were that the polymerization was severe and the degree of polymerization was distributed over a wide range.

In addition, in the method of addition polymerizing glycidol to glycerin, alkali hydroxide, amine, etc., which are ring-opening catalysts for epoxy groups, are generally used.
Polyglycerin produced by this method also had the drawbacks of being difficult to purify and being heavily colored.

Therefore, the present inventors conducted intensive studies to establish a method for producing polyglycerin that is less colored and easy to purify, and as a result, they completed the present invention.

The present invention is as follows. That is, (1) polyglycerol carboxylate is synthesized by adding glycidol in the number of moles corresponding to the degree of polymerization of the target product to the carboxylic acid represented by the following general formula (A), and then hydrolyzed and then desorbed. A method for producing polyglycerin, which is characterized by carrying out carboxylic acid.

R COOH...(A) Here, R represents hydrogen or an alkyl group having 1 to 5 carbon atoms.

(2) Claim 1, characterized in that the carboxylic acid of general formula (A) is one or more acids selected from formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and caproic acid. Addition reaction step (esterification) The amount of carboxylic acid to be used is determined by the ratio to glycidol depending on the degree of polymerization of the polyglycerin to be obtained. That is, to obtain n-mer polyglycerin, n moles of glycidol are required per mole of carboxylic acid.

The addition reaction is usually carried out by placing the galboxic acid in a reactor and adding glycidol little by little while stirring.

The reaction temperature is 80 to 110℃ until the amount of glycidol added is 1/2 of the specified amount, and then 110 to 230℃.
It is carried out at a temperature of preferably 120-140°C. If the reaction temperature is 110°C or higher in the first stage, the product polyglycerin will be severely colored, and if it is lower than 80°C, the reaction rate will be slow. If the reaction temperature in the latter stage is less than 110°C, diglycerin and the like will increase and the degree of polymerization will vary over a wide range, and if it exceeds 230°C, side reactions will occur due to decomposition of glycidol, which is not preferable.

At the end of the reaction, the conversion rate of glycidol is 99%.
Judgment will be made based on the above. Furthermore, the reaction rate can be further increased by adding an acid catalyst such as phosphoric acid as a catalyst.

Hydrolysis Step (Decarboxylic Acid) Hydrolysis is usually carried out by adding water to the polyglycerol carboxylate, hydrolyzing it, and then distilling water and carboxylic acid off under reduced pressure.

The amount of water added is 0.5 to 2.0 parts by weight based on the intermediate, and the reaction temperature is suitably 100 to 120°C and the time is about 3 to 5 hours.

Further, these reactions are preferably carried out under an inert gas such as nitrogen gas, and may be pressurized if necessary.

The product thus obtained can be easily purified by completely neutralizing the residual carboxylic acid with an alkali, dehydrating and precipitating, and then adsorbing the precipitate onto diatomaceous earth or the like to separate it. Monopolyglycerin has very little coloring,
It has a higher degree of polymerization suitable for the purpose. but,
Depending on the purpose, there is no need to purify the polyglycerin product if it does not cause any problem even if the polyglycerin carboxylic acid ester is mixed therein.

According to the present invention, based on carboxylic acid, the degree of polymerization of the target polyglycerin is determined by adding only glycidol, and by further passing through the intermediate polyglycerol carboxylate, harmful substances are removed. Can be erased.

Next, the present invention will be explained by giving examples, but the present invention is not limited to these.

Example 1 42 gr of acetic acid (0.7 mol) was placed in a 500 ml flask with a stirrer, the atmosphere was replaced with nitrogen gas, the temperature was raised to 90°C for 3 hours, and then the temperature was gradually raised to 130°C. 311 gr of glycidol (4.2 mol) was added dropwise for 2.5 hours, totaling 5.5 hours. The temperature was maintained for an additional 2 hours.

Then cool to 100℃ and add 170gr water,
After stirring for 3.5 hours and hydrolyzing, water and acetic acid were removed under reduced pressure, resulting in crude polyglycerin.
339gr was obtained, and its hue was almost colorless and transparent, with a Gardner value of 1 or less.

Next, take 200g of the above crude polyglycerin,
After adding 35 gr of 10% aqueous sodium hydroxide solution and stirring at 90°C for 1 hour, dehydration was performed at 20-5 Torr and 100-110°C. Cool to 90℃, add 0.16g of diatomaceous earth as an adsorbent, stir for 1 hour, and filter.
190 gr of purified polyglycerin was obtained. Its hue was almost colorless and transparent, with a Gardner value of 1 or less, a hydroxyl value of 966, and an average degree of polymerization of 6.

Comparative example: 9.2gr (1.0mol) in a 500ml flask with stirrer
of glycerin and 2.4 gr of 50% sodium hydroxide aqueous solution were replaced with nitrogen gas, heated and stirred at 90°C, and dehydrated under reduced pressure. Then, 115℃
The temperature was maintained at ~125°C, and 370 gr (5.0 mol) of glycidol was added dropwise over 3 hours. After maintaining the above temperature for an additional 2 hours, unreacted glycidol was removed under reduced pressure to obtain 456 gr of crude polyglycerin. Its hue was light brown and Gardner 8.

Next, 25 gr of 10% acetic acid aqueous solution was added to the above crude polyglycerin, heated to 80°C to 90°C and stirred for 1 hour, and then dehydrated at 10 to 5 Torr and 110°C to 120°C for 1 hour. Cool to 90℃, add 0.2g of diatomaceous earth as an adsorbent, stir for 1 hour, and filter to 334g.
Purified polyglycerin was obtained. The color was light brown, the Gardner value was 7, the hydroxyl value was 965, and the average degree of polymerization was 6.

Example 2 The reaction and purification were carried out in the same manner as in Example 1, except that 61.6 gr of butyric acid (0.7 mol) was used.

The hue of the obtained purified polyglycerin (190 gr) was almost colorless and transparent, with a Gardner value of 1 or less, a hydroxyl value of 964, and an average degree of polymerization of 6.

Claims (1)

[Claims] 1. Polyglycerol carboxylate is synthesized by adding glycidol in a number of moles corresponding to the degree of polymerization of the target product to the carboxylic acid represented by the following general formula (A), and then hydrolyzed. , a method for producing polyglycerin, characterized by carrying out decarboxylation. R COOH...(A) Here, R represents hydrogen or an alkyl group having 1 to 5 carbon atoms. 2. Claim 1, characterized in that the carboxylic acid of general formula (A) is one or more acids selected from formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and caproic acid. Method described.