JP3384420B2 - Method for producing polyaspartate - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing an amino acid-based polymer, polyaspartate. The polyaspartic acid salt, which is the object compound of the present invention, is a water-soluble polymer, and is effective in cosmetics, foods, medicines and agrochemicals, papermaking, paints, leather, films, emulsifiers, etc., and has industrially important properties. It is a very useful polymer that has various uses. 2. Description of the Related Art Various polyamino acids have been synthesized and used in various fields. As a method for producing a polyamino acid, a method based on polymerization of N-carboxy-α-amino acid anhydride (NCA) is simple and generally used.
Since phosgene is used in the production of NCA, it is extremely difficult to handle and has not developed much. On the other hand, it is known that polyaspartic acid can be easily produced by heating aspartic acid to produce polysuccinimide and hydrolyzing it. Japanese Patent Application Laid-Open No. 5-506615 discloses the production of lipoliskcinimide by directly heating a container filled with aspartic acid. However, in this method, it is difficult to heat uniformly, and in order to complete the reaction, it is necessary to lengthen the reaction time or to heat at 230 ° C. or more, which is a disadvantage that a side reaction easily occurs. was there. In European Patent Publication No. 0 578 449, after aspartic acid is heated in polyethylene glycol at 200 ° C. for 15 hours, the produced polysuccinimide is hydrolyzed to produce a polyaspartic acid salt. It was difficult to remove the solvent from the product due to its water solubility. [0004] An object of the present invention is to provide a simple and efficient production method capable of producing polyaspartic acid having few impurities such as by-products and solvents. The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that polyisuccinimide can be efficiently prepared by performing a reaction using a water-insoluble solvent. The present inventors have found that the water-insoluble solvent can be almost completely removed from the product by separation and subsequent treatment with an inorganic or organic powder, and the present invention has been completed based on this finding. That is, the present invention provides the following steps (1) to
(4) A method for producing a polyaspartate, characterized by performing (4). (1) Step of heating aspartic acid in a water-insoluble solvent to form polysuccinimide (2) Step of adding an aqueous alkali solution to hydrolyze to form polyaspartate (3) Step of converting the aqueous layer of polyaspartate to water-insoluble Step of separating from the solvent layer (4) Step of treating the aqueous solution of polyaspartate with an inorganic or organic powder The water-insoluble solvent used in the present invention separates when mixed with water. And the boiling point is 200 ° C
Any of the above may be used, and preferred is n-
Saturated hydrocarbon compounds such as paraffin and liquid paraffin,
Among silicone oils, fluorine oils, etc., 200
° C, preferably 230 ° C or higher, and has a viscosity at 25 ° C of 100 cP or lower, preferably 20 cP or lower.
Solvents below cP are desirable. If the viscosity of the solvent is high, water generated in the reaction cannot be easily distilled off. Two or more solvents may be used as a mixture. The reaction temperature is 200 ° C
~ 230 ° C is desirable. When the reaction temperature is 200 ° C. or less,
The reaction is slow and the reaction efficiency is poor. At 230 ° C or higher,
Although the reaction is completed in a short time, the resulting polyaspartate is colored due to a side reaction. [0008] Examples of the aqueous alkali solution used for the hydrolysis of polysuccinimide include aqueous solutions of sodium hydroxide, potassium hydroxide and basic organic amines. The hydrolysis is usually performed at 5 ° C to 75 ° C. The aqueous solution of polyaspartate thus obtained is separated from a water-insoluble solvent by a commonly used separation method. The separated polyaspartate aqueous solution still contains a small amount of impurities such as a water-insoluble solvent, but by treating with an inorganic or organic powder,
It can be almost completely removed. As inorganic powder,
Celite, activated clay, acid clay, synthetic zeolite, silica, alumina and the like can be mentioned. As the organic powder, activated carbon, cellulose powder, ion exchange resin, adsorption resin, chelate resin and the like can be mentioned. The treatment is more preferably performed using both inorganic powder and organic powder. In addition, as a treatment method, an inorganic or organic powder is added to an aqueous solution of polyaspartate and agitated, and the aqueous solution of polyaspartate is passed through a column filled with inorganic or organic powder, and both are used by a commonly used method. What is necessary is just to make contact. The present invention will be described in detail with reference to the following examples. Example 1 A 1-liter four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer was purged with nitrogen.
133 g of aspartic acid and n-paraffin (H) 2
00g (manufactured by Nippon Petroleum, boiling point: 244 to 262 ° C, viscosity: 2.
20 cP) was added. This was reacted at 220 ° C. for 4 hours, cooled to 50 ° C., 286 g of 14% aqueous sodium hydroxide solution was added, and the mixture was stirred for 1 hour. The reaction mixture was separated into an aqueous layer and an organic layer, and the aqueous layer was taken out. The resulting water layer is
It was cloudy due to residual n-paraffin. The aqueous layer was treated with celite and activated carbon to obtain an aqueous solution of sodium polyaspartate. This aqueous layer was transparent. It was confirmed by GPC and 13 C-NMR that aspartic acid had reacted 100%. The molecular weight of the produced polyaspartate is Mw = 24000, Mw / Mn
= 1.5. In addition, a 2% aqueous solution of sodium polyaspartate (pH = 7) was prepared, and the UV transmittance was measured. The result is shown in FIG. Comparative Example 1 After a 1-liter flask equipped with a stirrer was purged with nitrogen, 133 g of L-aspartic acid was added thereto. This was reacted at 245 ° C. for 4 hours, then cooled to 50 ° C., 286 g of 14% aqueous sodium hydroxide solution was added, and the mixture was stirred for 1 hour. Further, a 2% aqueous solution of sodium polyaspartate (pH = 7) was prepared from the obtained aqueous solution, and the UV transmittance was measured (FIG. 1). As a result of GPC measurement, the molecular weight and molecular weight distribution of polyaspartic acid were almost the same as those in Example 1. Comparative Example 2 An aqueous solution of sodium polyaspartate was prepared in the same manner as in Example 1 except that the reaction temperature was 200 ° C. G
As a result of PC measurement, 50% or more of unreacted aspartic acid remained. The molecular weight of polyaspartic acid was almost the same as in Example 1. According to the present invention, it has become possible to efficiently produce polyaspartate containing less impurities.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the transmittance of a 2% aqueous solution of sodium polyaspartate.

Claims (1)

(57) [Claims] (1) A method for producing a polyaspartate, which comprises performing the following steps (1) to (4). (1) Step of heating aspartic acid in a water-insoluble solvent to form polysuccinimide (2) Step of adding an aqueous alkali solution to hydrolyze to form polyaspartate (3) Step of converting the aqueous layer of polyaspartate to water-insoluble Step of separating from solvent layer (4) Step of treating polyaspartate aqueous solution with inorganic or organic powder