阅读说明：本技术 一种聚丙烯酸及其盐的制备方法 (Preparation method of polyacrylic acid and salt thereof ) 是由 陆久田 程终发 林胜涛 于 2020-07-28 设计创作，主要内容包括：本发明提供了一种聚丙烯酸(钠)的合成方法,在水溶液中,以过硫酸盐为引发剂和氧化剂,单质硫为还原剂和链转移剂,进行丙烯酸单体的聚合。本发明采用单质硫做还原剂和链转移剂,与过硫酸盐形成氧化还原引发体系,在二硫化碳的溶解作用下,缓慢进行反应,极大提高了引发剂过硫酸盐的有效使用率,降低所需引发剂用量,也降低了产品中的无机盐含量；单质硫的S<Sub>8</Sub>结构所形成硫自由基还起到链转移的作用,有效降低了聚合物分子量；过量硫可分离回用,整个反应过程简单且无三废产生,绿色环保。(The invention provides a method for synthesizing polyacrylic acid (sodium), which comprises the step of polymerizing acrylic acid monomers in aqueous solution by using persulfate as an initiator and an oxidant and elemental sulfur as a reducing agent and a chain transfer agent. The invention adopts elemental sulfur as a reducing agent and a chain transfer agent to form a redox initiation system with persulfate, and the redox initiation system slowly reacts under the dissolving action of carbon disulfide, thereby greatly improving the effective utilization rate of the persulfate as an initiator, reducing the required dosage of the initiator and reducing the content of inorganic salt in the product; s of elemental sulfur 8 The sulfur free radical formed by the structure also plays a role in chain transfer, so that the molecular weight of the polymer is effectively reduced; the excessive sulfur can be separated and recycled, the whole reaction process is simple, no three wastes are generated, and the method is green and environment-friendly.)

1. Adding pure water, carbon disulfide and sulfur powder into a reaction kettle, heating to 90-95 ℃ under stirring, dropwise adding an acrylic acid and persulfate aqueous solution, and keeping a reflux state in the kettle in the dropwise adding process;

(2) after the dripping is finished, continuously refluxing and preserving heat, and after the reaction is finished, cooling and diluting the saline water solution to obtain the polyacrylic acid water solution product.

2. The method according to claim 1, wherein the acrylic acid and the persulfate are each added dropwise in the form of an aqueous solution; the mass fraction of the acrylic acid aqueous solution is 60-70%; the mass fraction of the persulfate aqueous solution is 1-5%.

3. The method according to claim 1, wherein the persulfate is ammonium persulfate or sodium persulfate.

4. The method of claim 1, wherein the sulfur powder has a particle size of no greater than 5 microns.

5. The method according to claim 1, wherein the molar ratio n of the materials in step (1)_{Acrylic acid}:n_{Pure water}:n_Persulfates:n_{Carbon disulfide}1: 1-1.5: 0.005-0.01: 0.01-0.02.

6. The method according to claim 1, wherein the dropping time of the aqueous acrylic acid solution in the step (1) is 1 to 3 hours, the dropping time of the aqueous persulfate solution is 2 to 3 hours, and the aqueous acrylic acid solution is dropped after the dropping of the persulfate solution for 0.2 hour.

Technical Field

The invention relates to the technical field of fine chemicals, in particular to a method for synthesizing polyacrylic acid (sodium).

Background

Polyacrylic acid (sodium) [ PAA (S) ] is widely used as a dispersant for petroleum and mining industry, a synthetic detergent dispersant, and a scale inhibition dispersant which is used in a formula with other water treatment agents and is used in circulating cooling water systems of power plants, chemical plants, fertilizer plants, oil refineries, air conditioning systems and the like. Meanwhile, PAA (S) is used as a dispersant and can act on the soil, corrosion products and other amorphous substances. The product can also be compounded with a corrosion inhibitor to form a composite water stabilizer, so that the corrosion inhibition effect is enhanced. Polyacrylic acid (sodium) has wide application, and products with different molecular weights are used in various fields.

Polyacrylic acid (sodium) [ PAA (S) ] is widely used as a dispersant for petroleum and mining industry, a synthetic detergent dispersant, and a scale inhibition dispersant which is used in a formula with other water treatment agents and is used in circulating cooling water systems of power plants, chemical plants, fertilizer plants, oil refineries, air conditioning systems and the like. Meanwhile, PAA (S) is used as a dispersant and can act on the soil, corrosion products and other amorphous substances. The product can also be compounded with a corrosion inhibitor to form a composite water stabilizer, so that the corrosion inhibition effect is enhanced. Polyacrylic acid (sodium) has wide application, and products with different molecular weights are used in various fields.

At present, the synthesis of polyacrylic acid (sodium) is realized in industrial production, and the synthesis process of the polyacrylic acid (sodium) is gradually replaced by the aqueous phase for the organic phase. Lisanlan and the like propose that persulfate is used as an initiator, alcohol is used as a chain transfer agent, and a reducing agent such as sulfite is added to carry out polymerization reaction of acrylic monomers in an aqueous solution (synthesis and application of polyacrylic acid and acrylic copolymer, Guangdong chemical industry, 9 th 2005). Plum and the like propose to synthesize low molecular weight polyacrylic acid in an aqueous solution by using ammonium persulfate as an initiator and isopropanol as a telogen (synthesis of low molecular weight polyacrylic acid, chemical engineering management, 4 th year 2014). Patent CN105481676A mentions that persulfate or hydrogen peroxide is used as an initiator, and elemental silver is used as a catalyst to perform aqueous phase polymerization. Patent CN110894387A mentions the polymerization of acrylic acid monomers in aqueous solution with liquid alkali to control pH and adding ammonium persulfate and isopropanol. The aqueous phase polymerization process is safe and simple, and is the key point of the current research. The method also has certain defects that the use efficiency of the initiator persulfate is not high, and particularly when low-molecular-weight polyacrylic acid is synthesized, the use amount of the initiator is large, so that the production cost is improved, the product quality is influenced, and the salting-out phenomenon may occur in the later period.

Aiming at the problems, the invention provides a production process of polyacrylic acid (sodium), which can effectively improve the utilization rate of an initiator and improve the product quality (reduce the salt content).

Disclosure of Invention

The invention provides a method for synthesizing polyacrylic acid (sodium), which carries out the polymerization of acrylic acid monomers in aqueous solution by taking persulfate as an initiator and an oxidant and elemental sulfur as a reducing agent and a chain transfer agent, and mainly comprises the following steps:

(1) adding a certain amount of pure water, carbon disulfide and sulfur powder into a reaction kettle, heating to 90-95 ℃ under stirring, starting dropwise adding a certain amount of acrylic acid aqueous solution and persulfate aqueous solution according to a certain flow, and keeping a reflux state in the kettle in the dropwise adding process.

(2) After the dropwise addition is finished, continuously refluxing and preserving heat for 1h, and then cooling, filtering and diluting to obtain polyacrylic acid aqueous solution with the mass fraction of about 40% or cooling, filtering, adjusting alkali and diluting to obtain sodium polyacrylate aqueous solution with the mass fraction of about 40%.

Wherein the mass fraction of the acrylic acid aqueous solution in the step (1) is 50-70%; the persulfate can be ammonium persulfate, sodium persulfate and the like, and the mass fraction of the aqueous solution is 1-10%.

Wherein the grain diameter of the sulfur powder in the step (1) is required to be less than or equal to 5 mu m.

Wherein the molar ratio n of the materials in the step (1)_{(acrylic acid)}:n_{(pure water)}：n_(Sulfur):n_(persulfate):n_{(carbon disulfide)}Is 1 (1-1.5): (0.1-0.2): (0.005-0.01): (0.01-0.02).

Wherein the dropping time of the acrylic acid aqueous solution in the step (1) is 2 hours, the dropping time of the persulfate aqueous solution is 2.5 hours, and the dropping of acrylic acid is started after the dropping of the persulfate is started for 0.2 hour.

The beneficial effects of the invention are as follows:

the invention adopts elemental sulfur as a reducing agent and a chain transfer agent to form a redox initiation system with persulfate, and the redox initiation system slowly reacts under the dissolving action of carbon disulfide, thereby greatly improving the effective utilization rate of the persulfate as an initiator, reducing the required dosage of the initiator and reducing the content of inorganic salt in the product; s of elemental sulfur₈The sulfur free radicals formed by the structure also play a role in chain transfer,the molecular weight of the polymer is effectively reduced; the excessive sulfur can be separated and recycled, the whole reaction process is simple, no three wastes are generated, and the method 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.