JPH04173765A - Production of 1,3-phenylenedioxydiacetic acid - Google Patents

Abstract

PURPOSE:To produce the title compound hardly containing coloring impurities in high yield by reacting resorcinol with monochloroacetic acid in the presence of an antioxidant in the system. CONSTITUTION:In reacting resorcinol with monocloroacetic acid in an alkali aqueous solution, the reaction is carried out in the presence of an antioxidant (especially sulfur-based an phosphorus-based antioxidant and the amount thereof used is preferably 0.1-1wt.% based on resorcinol) to give high-purity 1,3- phenylenedioxydiacetic acid in high yield. When a polymer is produced by using the objective compound as the raw materials, the polymer has high transmittance.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to 1,3-phenylenedioxydiacetic acid (hereinafter referred to as 1
．． 3-PDDA).

[Prior Art] 1.3- PDDA is an aromatic dicarboxylic acid that can be used as a monomer for producing polymers such as polyester and polyamide, and is an industrially useful compound. 1.
Several methods have been known for the synthesis of 3-PDDA, but the applicant has developed a method for synthesizing 3-PDDA by reacting resorcin and monochloroacetic acid under specific conditions.
They discovered a method for recovering 1.3-PDDA in high yield and filed a patent application (Japanese Patent Application No. 343981/1999).

However, according to this method, since resorcinol and monochloroacetic acid are reacted in an alkaline aqueous solution, the resulting 1,3-PDDA is produced as a dialkali salt, so this is acidified to crystallize 1,3-PDDA. However, the crystals recovered here tend to be slightly colored due to the influence of trace impurities. These colored crystals are difficult to purify even by recrystallization with water.

When producing a polymer using colored 1,3-PDDA crystals, it is difficult to obtain a polymer with high transmittance, so it is desirable that the degree of coloring of the 1,3-PDDA crystals be as small as possible.

[Problems to be Solved by the Invention and Means for Solving the Problems] In view of the above-mentioned circumstances, the present inventors have developed a method for producing 1,3-PDDA from resorcinol and monochloroacetic acid with high purity and low degree of coloring. As a result of various studies on methods for obtaining crystals, we found that the presence of an antioxidant during the reaction between resorcinol and monochloroacetic acid improves the degree of coloration of the 1,3-PDDA crystals ultimately recovered. Heading, the invention was completed.

That is, the gist of the present invention is to react resorcin and monochloroacetic acid in an alkaline aqueous solution, and to react with 1.3-PD
A method for producing 1,3-PDDA is characterized in that an antioxidant is present in the reaction system when producing DA.

The present invention will be explained in detail below.

In the present invention, resorcinol and monochloroacetic acid are reacted in an alkaline aqueous solution, and the alkaline aqueous solution usually includes alkali hydroxides such as sodium hydroxide and potassium hydroxide, and alkali carbonates such as sodium carbonate and potassium carbonate.

Further, it is desirable to maintain the pH within the reaction system in the range of usually 7.5 to 12, preferably 8 to 11. That is, as hydrochloric acid is produced as a by-product as the reaction progresses, the pH within the reaction system tends to gradually decrease, but in the present invention it is preferable to maintain the inside of the reaction system alkaline at all times. The amount of monochloroacetic acid to be used is 2 times or more, preferably 2.1 to 3 times, by mole relative to resorcinol. If this amount is too small, the amount of phenol 3-oxyacetate, which is an intermediate, produced will increase, which is not preferable. . Note that the concentration of resorcin in the alkaline aqueous solution is usually 10 to 50% by weight.

, The reaction temperature in the present invention is usually 40°C to 100°C.
°C, preferably 50 °C to 95 °C. If the reaction temperature is too low, the reaction rate is slow and the desired product cannot be obtained satisfactorily, whereas if the reaction temperature is too high, by-products will be produced, which is not preferable. In addition, the reaction time varies depending on the reaction temperature and reaction method, but usually 0.5
~10 hours, preferably about 1 to 7 hours.

In carrying out the reaction of the present invention, for example, a method may be used in which an aqueous alkali solution containing resorcinol is used as a bed solution, and an aqueous alkali solution is added to the solution, and monochloroacetic acid is supplied while maintaining the pH in the reaction system at a desired value. desirable. In this case, the supply of monochloroacetic acid may be continuous or intermittent, but if the supply rate is too high, decomposition of monochloroacetic acid will occur, so usually the unreacted monochloroacetic acid supplied into the reaction system is The concentration is adjusted to 10% by weight or less. The supply time at this time varies depending on the reaction conditions, etc., but is usually about 1 to 10 hours. Note that resorcin exists as a dialkali salt in an alkaline aqueous solution, and 1,3-PDDA produced by the reaction also becomes a dialkali salt.

In the present invention, it is an essential requirement that an antioxidant be present during the above-mentioned reaction. In short, the presence of an antioxidant in the reaction system attempts to suppress the production of trace impurities that cause coloring. Examples of antioxidants that can be used in the present invention include:
Sulfur-based antioxidants such as sodium sulfite, sodium hyposulfite, and sodium hydrogen sulfite; phosphorus-based antioxidants such as sodium phosphite and sodium hydrogen phosphite;
Examples include amine antioxidants such as hydroxyamine, phenolic antioxidants, and sulfur-based and phosphorus-based antioxidants are particularly preferred.

The amount of antioxidant used is usually 0 for resorcinol.
．． 01 to 5% by weight, preferably 0.1 to 1% by weight, and if it is too small, the final 1,3-P
Coloring of DDA crystals cannot be sufficiently suppressed. In the present invention, it is more effective to replace the gas phase in the reactor with N2 gas.

After the reaction, the mixture is acidified according to a conventional method to precipitate the desired 1,3 + PDDA crystals, but this operation is usually done by adding an aqueous solution of hydrochloric acid or sulfuric acid to the reaction mixture to adjust the pH of the mixture to 3. This can be carried out by making the following adjustments. Note that depending on the concentration of resorcinol in the above reaction, 1.3-
In some cases, dialkali salt crystals of PDDA are precipitated, but even in such cases, 1,3-PDDA crystals can be obtained by adding an acid to the reaction mixture and acidifying it in the same way. Then, the precipitated 1,3-PDDA
The crystals are separated from the mixture and then optionally recovered after water recrystallization and/or water washing.

[Examples] Hereinafter, the present invention will be explained in detail according to Examples, but the present invention is not limited in any way by the following Examples.

Example 1 [Etherification reaction] 165.2 g of resorcinol (1,50 mo
1) and 125 ml of an aqueous solution in which 0.735 g of sodium sulfite was dissolved were added, and hot water was poured into the jacket while stirring under a nitrogen atmosphere, and the internal temperature was raised to 50°C to dissolve the crystals. Next, at the same temperature, a 47% caustic soda aqueous solution was added using a pump, and the pH in the system was controlled to 8.2, while the temperature was increased to 95°.
The temperature was raised to C. to prepare an aqueous solution containing the sodium salt of resorcinol. Next, at 95°C, 47% caustic soda aqueous solution was added using a pump, and while controlling the pH to 8.2, 605.8 g of monochloroacetic acid aqueous solution (monochloroacetic acid 3
78.9 g (4,00 mol)) was added dropwise using the same pump for 5 hours. Further, at the same temperature for 2 hours, the pH was adjusted to 8.2.
The reaction continued while being controlled. Crystals precipitated in the reaction system during the monochloroacetic acid supply process, resulting in a slurry state.

[Acid precipitation] Add 50% of demineralized water to the slurry obtained in the etherification reaction.
After adding 0 ml, the internal temperature was raised to 90°C, 833 g of 30% sulfuric acid was added, and stirring was continued at the same temperature for 30 minutes.

Next, run cold water through the jacket and cool it down to 20°C.
Small centrifuge (manufactured by Kokusan Centrifuge Co., Ltd., H+)
The crystals were separated using a furnace (Model 110) and washed by sprinkling with 10,100 O of demineralized water.

[Recrystallization] Crystals obtained by acid precipitation and demineralized water 13 were placed in a 2E 4-hole flask (manufactured by Pyrex) equipped with a cooling tube, a thermometer, and a stirrer.
When 00ml of the system was charged and the internal temperature was raised to 100°C, the inside of the system became uniform. Stop heating and reduce internal temperature to 40°C
After the temperature was lowered and maintained for 1 hour, the crystals were separated in a small centrifuge and washed with 500 ml of demineralized water. The obtained crystals were vacuum dried at 90°C to obtain 283.2g of 1.3+PDDA.

5 g of this crystal was dissolved in 25 ml of 2N caustic soda aqueous solution, and the volume was made up to 50 ml with demineralized water.
The transmittance was measured.

The results are shown in Table-1.

Examples 2 and 3 The same procedure as in Example 1 was performed except that 0.735 g of each of the antioxidants listed in Table 1 was used in place of the sodium sulfite in Example 1. The transmittance of the obtained 1,3-PDDA is shown in Table 1.

Comparative Example The same procedure as in Example 1 was carried out except that the sodium sulfite used in Example 1 was not used. Obtained 1,3-PDD
The transmittance of A is shown in Table 1.

Table 1 [Effects of the invention] According to the method of the present invention, 1, which is useful as a raw material for polymers,
Since 3-phenylenedioxydiacetic acid can be produced in high yield and almost free of coloring impurities, when a polymer is produced using this, a polymer having high transmittance can be obtained.

Claims (1)

[Claims] (1) 1,3-phenylene diacetic acid is produced by reacting resorcinol and monochloroacetic acid in an alkaline aqueous solution to produce 1,3-phenylene dioxydiacetic acid, in which an antioxidant is present in the reaction system. Production method of oxydiacetic acid.