阅读说明：本技术 一种聚2-羟基丙烯酸的制备方法 (Preparation method of poly 2-hydroxy acrylic acid ) 是由 周响 程终发 申义驰 陆久田 于 2020-06-01 设计创作，主要内容包括：本发明公开了一种聚2-羟基丙烯酸钠的制备方法,以水为溶剂,用碱激发丙酮酸的烯醇式结构,在自由基条件下,聚合生成聚2-羟基丙烯酸钠。本发明为水相反应,利用丙酮酸烯醇式共振结构进行聚合反应,与传统工艺相比,避免了卤素及二卤代丙酸的使用,既降低原料成本,又提高了生产安全系数,同时无废酸产生,绿色环保。(The invention discloses a preparation method of poly-2-sodium hydroxy-acrylate, which takes water as a solvent, uses alkali to excite an enol structure of pyruvic acid, and polymerizes to generate the poly-2-sodium hydroxy-acrylate under the condition of free radicals. The invention is a water phase reaction, and utilizes the pyruvic acid enol resonance structure to carry out polymerization reaction, compared with the traditional process, the invention avoids the use of halogen and dihalogenated propionic acid, thereby not only reducing the cost of raw materials, but also improving the safety coefficient of production, and simultaneously, no waste acid is generated, and the invention is green and environment-friendly.)

1. The preparation method of the sodium poly-2-hydroxyacrylate is characterized by comprising the following steps:

(1) adding pyruvic acid into the reaction kettle, dropwise adding an aqueous solution of sodium hydroxide while stirring, and adjusting the pH of the mixed solution to 11-13;

(2) heating the reaction kettle to a reflux state, slowly dropwise adding aqueous hydrogen peroxide, keeping the reaction liquid in the reflux state in the dropwise adding process after dropwise adding is finished for 2-4 hours, and controlling the pH value to be within the range of 11-13;

(3) and after the dropwise addition, continuously preserving the heat for 0.5-1 h, then cooling to be less than or equal to 50 ℃, dropwise adding a certain amount of hydrogen peroxide degrading enzyme to decompose residual hydrogen peroxide, and diluting with pure water to obtain the poly-2-sodium hydroxy acrylate aqueous solution with the mass fraction of 25%.

2. The method according to claim 1, wherein the mass fraction of the sodium hydroxide aqueous solution in the step (1) is 35-45%; the molar ratio of the sodium hydroxide to the pyruvic acid is 0.8-1.2: 1.

3. The method according to claim 1, wherein the mass fraction of the aqueous hydrogen peroxide solution in step (2) is 25-35%, and the molar ratio of the amount of hydrogen peroxide to the amount of pyruvic acid is 0.2-1: 1.

4. The method according to claim 1, wherein the amount of the hydrogen peroxide degrading enzyme in the step (3) is 1 to 5% by mass of the total reaction system.

Technical Field

The invention relates to the technical field of fine chemicals, in particular to a preparation method of poly-2-sodium hydroxy-acrylate.

Background

Poly-a-hydroxyacrylates (PHA salts) represented by sodium poly-2-hydroxyacrylate are important industrial raw materials as hydrogen peroxide bleaching stabilizers for pulp, fibrous materials, builders, chelating agents, surfactants, and the like. It is prepared by reacting a polylactone compound corresponding to poly-alpha-hydroxyacrylic acid (PLAC) with a corresponding base material.

Japanese patent CN1260270C proposes a method for preparing an aqueous solution of poly-alpha-hydroxyacrylate. In particular, a polylactone compound of poly-alpha-hydroxy acrylic acid and alkali are subjected to hydrolysis reaction to generate a poly-alpha-hydroxy acrylic acid salt aqueous solution. The method does not involve monomer synthesis and cannot meet the requirement of industrial production. DE2061584 proposes a process for obtaining poly-alpha-hydroxyacrylic acids by polymerization of monomeric alpha-haloacrylic acids in the presence of organic solvents and free-radically active catalysts. The alpha-halogenated acrylic acid for polymerization by the method is difficult to exist in a pure form, and is usually reacted by using dihalopropionic acid, the dihalopropionic acid is expensive, and a large amount of halogen simple substances are consumed in the self-manufacturing process to generate a large amount of acid, so that the process risk coefficient is large, the environmental protection cost is high, and the method is not favorable for industrial popularization.

In order to overcome the defects of the problems, the invention provides a method for preparing a sodium poly-2-hydroxyacrylate aqueous solution by using acrylic acid as a monomer.

Disclosure of Invention

The invention provides a preparation method of poly-2-sodium hydroxy-acrylate, which mainly comprises the following steps:

(1) adding a certain amount of pyruvic acid into a reaction kettle, dropwise adding an aqueous solution of sodium hydroxide with the same molar weight as the pyruvic acid while stirring, and after neutralization reaction, continuously dropwise adding an aqueous solution of sodium hydroxide to adjust the pH value of the mixed solution to be within the range of 11-13;

(2) heating the reaction kettle to a reflux state, slowly dropwise adding a certain amount of aqueous hydrogen peroxide solution, after dropwise adding is completed for 2-4 hours, keeping the reaction solution in the reflux state in the dropwise adding process, and controlling the pH value to be within the range of 11-13;

(3) and after the dropwise addition, continuously preserving the heat for 0.5-1 h, then reducing the temperature to be less than or equal to 50 ℃, adjusting the pH of the system to be 6-8 by using hydrochloric acid, dropwise adding a certain amount of hydrogen peroxide degrading enzyme to decompose residual hydrogen peroxide, concentrating, recrystallizing and separating sodium chloride, and then diluting by using pure water to obtain a 25 mass percent sodium poly-2-hydroxyacrylate aqueous solution.

Wherein the mass fraction of the sodium hydroxide aqueous solution in the step (1) is 35-45%.

Wherein, the mass fraction of the aqueous solution of hydrogen peroxide in the step (2) is 25-35%, and the molar ratio of the amount of hydrogen peroxide to the amount of pyruvic acid is (0.2-1): 1, preferably (0.5-1): 1.

Wherein the dosage of the hydrogen peroxide degrading enzyme in the step (3) is 1-5 per mill of the total reaction system mass.

The relevant chemical reactions are:

。

the beneficial effects of the invention are as follows:

the invention is a water phase reaction, and utilizes the pyruvic acid enol resonance structure to carry out polymerization reaction, compared with the traditional process, the invention avoids the use of halogen and dihalogenated propionic acid, thereby not only reducing the cost of raw materials, but also improving the safety coefficient of production, and simultaneously, no waste acid is generated, and the invention is green and environment-friendly.

Detailed Description

The present invention is described in detail below by way of examples, which are intended to be illustrative only and not to be construed as limiting the scope of the invention, and one skilled in the art will be able to make variations within the scope of the invention based on the disclosure herein, in reagents, catalysts and reaction process conditions. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The pyruvic acid content is 98.0%; the mass fraction of the sodium hydroxide aqueous solution is 40.0 percent; the mass fraction of the aqueous solution is 25.0%.

Example 1

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, slowly dropwise adding 100g of sodium hydroxide aqueous solution for neutralization, controlling the temperature in the reaction kettle to be less than or equal to 50 ℃ in the neutralization reaction process, continuously dropwise adding the sodium hydroxide aqueous solution after neutralization, and adjusting the pH value of the system to be 11.2;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, dropwise adding 68g of aqueous hydrogen peroxide solution at a flow rate of 34g/h, controlling the pH value of the system to be 11-12 in the dropwise adding process through dropwise adding of the aqueous sodium hydroxide solution, and finishing the dropwise adding of the hydrogen peroxide after 2 hours;

step three: and continuously refluxing, reacting for 0.5h under heat preservation, cooling to 48 ℃, dropwise adding 60g of hydrochloric acid to adjust the pH value to 7.0, dropwise adding 2ml of hydrogen peroxide degrading enzyme, stirring and decomposing until no bubbles are generated, heating, concentrating and separating 28.0g of sodium chloride, and adding 280g of pure water to dilute to obtain 378.2g of poly 2-hydroxy sodium acrylate aqueous solution with the mass fraction of 25.9%.

Wherein, the conversion rate of pyruvic acid monomer is 88.5%, the chroma of the product is 17, and the average molecular weight is: 2145, viscosity 198, and chloride ion content 0.22%.

Example 2

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, slowly dropwise adding 100g of sodium hydroxide aqueous solution for neutralization, controlling the temperature in the reaction kettle to be less than or equal to 50 ℃ in the neutralization reaction process, continuously dropwise adding the sodium hydroxide aqueous solution after neutralization, and adjusting the pH value of the system to 12.5;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, dripping 136g of aqueous hydrogen peroxide solution at the flow rate of 34g/h, controlling the pH value of the system to be 12-13 by adding and dripping the aqueous sodium hydroxide solution in the dripping process, and finishing the dripping of the hydrogen peroxide after 4 h;

step three: and continuously carrying out reflux and heat preservation for reaction for 1 hour, then cooling to 47 ℃, dropwise adding 61g of hydrochloric acid to adjust the pH value to 6.8, dropwise adding 2ml of hydrogen peroxide degrading enzyme, stirring and decomposing until no bubbles are generated, heating, concentrating and separating 28.4g of sodium chloride, and adding 290g of pure water to dilute to obtain 389.0g of poly 2-sodium hydroxy acrylate aqueous solution with the mass fraction of 25.2%.

Wherein, the conversion rate of pyruvic acid monomer is 89.2%, the chroma of the product is 15, the average molecular weight is 2213, the viscosity is 205, and the content of chloride ion is 0.23%.

Comparative example 1

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, slowly dropwise adding 100g of sodium hydroxide aqueous solution for neutralization, controlling the temperature in the reaction kettle to be less than or equal to 50 ℃ in the neutralization reaction process, continuously dropwise adding the sodium hydroxide aqueous solution after neutralization, and adjusting the pH value of the system to 11.3;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, dropwise adding 34g of aqueous hydrogen peroxide solution at the flow rate of 17g/h, controlling the pH value of the system to be 11-12 in the dropwise adding process through dropwise adding of the aqueous sodium hydroxide solution, and finishing the dropwise adding of the hydrogen peroxide after 2 hours;

step three: and continuously carrying out reflux and heat preservation for reaction for 0.5h, then cooling to 47 ℃, dropwise adding 60g of hydrochloric acid to adjust the pH value to 6.9, dropwise adding 2ml of hydrogen peroxide degrading enzyme, stirring and decomposing until no bubbles are generated, heating, concentrating and separating 27.8g of sodium chloride, and adding 250g of pure water to dilute to obtain 348.9g of poly 2-hydroxy sodium acrylate aqueous solution with the mass fraction of 25.3%.

Wherein, the conversion rate of pyruvic acid monomer is 80.4%, the chroma of the product is 15, the average molecular weight is 1698, the viscosity is 175, and the content of chloride ion is 0.30%.

Comparative example 2

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, slowly dropwise adding 100g of sodium hydroxide aqueous solution for neutralization, controlling the temperature in the reaction kettle to be less than or equal to 50 ℃ in the neutralization reaction process, and controlling the pH value of a system after neutralization to be 8.6;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, dripping 68g of aqueous hydrogen peroxide solution according to the flow of 34g/h, gradually reducing the pH value of the system from 8.6 to 7.2 in the dripping process, and finishing the dripping of the hydrogen peroxide after 2 h;

step three: and continuously refluxing, reacting for 0.5h under heat preservation, cooling to 48 ℃, dropwise adding 1ml of hydrogen peroxide degrading enzyme, stirring and decomposing until no bubbles are generated, and obtaining 258g of poly 2-hydroxy sodium acrylate aqueous solution with the mass fraction of 11.8%.

Wherein, the conversion rate of pyruvic acid monomer is 27.5%, the chroma of the product is 13, the average molecular weight is 437, the viscosity is 67, and no chloride ion exists.

Comparative example 3

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, and slowly dropwise adding 10g of hydrochloric acid to obtain a system with a pH value of 1.0;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, dripping 136g of aqueous hydrogen peroxide solution at a flow rate of 34g/h, controlling the pH value of the system to be 1-3 by adding and dripping the aqueous sodium hydroxide solution in the dripping process, and finishing the dripping of the hydrogen peroxide after 4 h;

step three: and continuously carrying out reflux reaction for 0.5h under heat preservation, cooling to 46 ℃, dropwise adding 17g of sodium hydroxide to adjust the pH value to 6.6, dropwise adding 2ml of hydrogen peroxide degrading enzyme, stirring and decomposing until no bubbles are generated, heating, concentrating and separating 8.8g of sodium chloride, and adding 250g of pure water to dilute to obtain 337.5g of poly 2-hydroxy sodium acrylate aqueous solution with the mass fraction of 25.7%.

Wherein, the conversion rate of pyruvic acid monomer is 78.8%, the chroma of the product is 18, the average molecular weight is 4325, the viscosity is 785, and the content of chloride ion is 0.24%.

Comparative example 4

The method comprises the following steps: adding 90g of pyruvic acid into a glass reaction kettle, starting stirring, slowly dropwise adding 100g of sodium hydroxide aqueous solution for neutralization, controlling the temperature in the reaction kettle to be less than or equal to 50 ℃ in the neutralization reaction process, continuously dropwise adding the sodium hydroxide aqueous solution after neutralization, adjusting the pH value of the system to 11.2, and using ethanol as a tail gas absorption device;

step two: gradually heating the reaction kettle to 100 ℃ for reflux, adding azodiisobutyronitrile once every 10min according to the component of 5 g/time, adding 60g azodiisobutyronitrile in total, supplementing sodium hydroxide in the adding process to control the pH value of the system to be 11-12, and finishing the adding of the azodiisobutyronitrile after 2 hours;

step three: and (3) continuously refluxing and reacting under the heat preservation condition, then reducing the temperature to 48 ℃, dropwise adding 60g of hydrochloric acid to adjust the pH value to 7.0, heating, concentrating and separating 27.7g of sodium chloride, and adding 155g of pure water to dilute to obtain 209.7g of poly 2-sodium hydroxy acrylate aqueous solution with the mass fraction of 25.5%.

Wherein, the conversion rate of pyruvic acid monomer is 48.7%, the chroma of the product is 17, the average molecular weight is 217, and the viscosity is 52. The content of chloride ions is 0.55 percent.