Preparation method of small-particle-size narrow-distribution double-group anion exchange resin

Abstract

The invention provides a preparation method of small-particle-size narrow-distribution double-group anion exchange resin. The preparation method comprises the following steps: respectively preparing an oil-phase mixed solution and a water-phase mixed solution; carrying out heating reaction on the two materials under a magnetic stirring condition to obtain superfine resin white balls; the superfine resin white balls are prepared into chloromethylated superfine resin white balls, then primary amination treatment is carried out, quaternary amine groups are grafted, and the double-group superfine anion exchange resin is obtained. The small-particle-size narrow-distribution double-group anion exchange resin of which the effective particle size is less than 50 microns and the uniformity coefficient is less than 1.5 is prepared through the synergistic dispersion effect of the polyvinyl alcohol and the sodium hexametaphosphate and the uniform shearing effect of magnetic stirring.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of synthesis of ion exchange resin, more particularly to a preparation method of small particle size and narrow distribution double-group anion exchange resin. BACKGROUND

[0002] For anion exchange resin, the smaller the particle size of the resin, the larger the specific surface area, the more active exchange groups exposed on the surface, and the higher the probability of contact with target ions; at the same time, due to the smaller particle size, the diffusion path of ions inside the resin is shorter, and the adsorption process can be completed quickly. The narrower the particle size distribution, the more uniform the functional groups of small particle size resin, and the faster the regeneration agent can penetrate into the particle interior, avoiding the common problem of incomplete regeneration of large particle resin, effectively improving the regeneration efficiency and reducing the consumption of regeneration agent.

[0003] The core value of small particle size and narrow particle size distribution anion exchange resin lies in both improving mass transfer and adsorption efficiency through small particle size and ensuring functional group consistency through narrow distribution, making it an irreplaceable material in high-end water treatment (such as ultrapure water, nuclear waste water), precise separation, ion adsorption in extreme environments, etc.

[0004] Patent CN117069883A discloses a preparation method of small particle size and narrow distribution double-group anion exchange resin and its application in alkali-activated heavy-duty coating. By configuring an oil phase and a water phase mixed solution, an ultrafine resin white ball is obtained through heating reaction, and then chloromethylation, primary amination treatment and grafting of quaternary amine groups are carried out to obtain a double-group ultrafine anion exchange resin. By controlling the mass ratio of styrene, divinylbenzene, etc. in the oil phase, the mass ratio of gelatin, sodium polyphosphate and water in the water phase, and the stirring speed during the reaction, an anion exchange resin with small particle size and narrow distribution is obtained, which carries primary amine groups and quaternary amine groups, can simultaneously replace multiple external anions, and can be used as one of the raw materials to prepare alkali-activated heavy-duty coating with low shrinkage and high flexibility by combining with fly ash, slag and other raw materials. The coating has the advantages of low shrinkage, high flexibility and high corrosion resistance, and can prolong the service life of marine structures, which has important significance and application value in the field of marine engineering.

[0005] The smaller the particle size, the higher the surface charge density, and the more likely to occur irreversible agglomeration, resulting in a wider apparent particle size distribution. Therefore, the uniformity control of small particle size particles requires higher requirements for preparation equipment and separation means, and therefore there is an urgent need for a preparation method of double-group anion exchange resin carrying primary amine groups and quaternary amine groups with small particle size and narrow particle size distribution. SUMMARY

[0006] The present application provides a preparation method of small particle size and narrow distribution double-group anion exchange resin.

[0007] To achieve the technical purpose of the present application, the present application adopts the following technical solutions: a preparation method of small-particle-size narrow-distribution double-group anion exchange resin, comprising the following steps: (1) mixing styrene, divinylbenzene, liquid paraffin and dibenzoyl peroxide in proportion to obtain an oil phase mixed solution; adding polyvinyl alcohol and sodium hexametaphosphate in water in proportion, mixing uniformly at 50-60°C to obtain an aqueous phase mixed solution; (2) adding the oil phase mixed solution into the aqueous phase mixed solution, heating at 80-90°C under the condition of magnetic stirring at 600-1000 rpm for 6-8 h, washing the reaction product with deionized water until neutral, and filtering to obtain superfine resin white balls; (3) swelling the superfine resin white balls in step (2) and then putting them into chloromethyl ether, adding tin tetrachloride four times at intervals of 20-40 min, reacting at 30-40°C and 300-500 rpm for 8-10 h, and then filtering, washing and drying to obtain chloromethylated superfine resin white balls; (4) swelling the chloromethylated superfine resin white balls obtained in step (3) again, adding hexamethylenetetramine, reacting at 40-50°C and 300-500 rpm for 7-9 h, washing with anhydrous ethanol, filtering, and then treating with 36-38% mass fraction concentrated hydrochloric acid and washing with deionized water until neutral to obtain primary amine superfine resin; (5) adding the primary amine superfine resin obtained in step (4) into 60-69% mass fraction 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution, adjusting the pH to 10-12 using NaOH solid, and reacting at 20-30°C and 300-500 rpm for 15-20 h; then soaking in 1-2 mol / L NaCl solution, filtering and washing with deionized water to obtain double-group superfine anion exchange resin.

[0008] Preferably, in step (1), the mass ratio of styrene, divinylbenzene, liquid paraffin and dibenzoyl peroxide is 1:(0.14-0.16):(0.55-0.6):(0.02-0.024). Since small-particle-size resin needs higher crosslinking degree to balance mechanical strength and chemical stability, thereby maintaining long-term performance in practical application, a higher content of divinylbenzene is added in the present application.

[0009] Preferably, the liquid paraffin is C10-C18 liquid paraffin; it has suitable viscosity and boiling point, can better play a pore-forming role in the polymerization process, and can be easily removed by solvent extraction and the like subsequently.

[0010] Preferably, in the step (1), the mass ratio of sodium hexametaphosphate, polyvinyl alcohol and water is 1:(2-4):(50-70). Further, the molecular weight of polyvinyl alcohol is between 400-1000.

[0011] Preferably, in the step (2), the mass ratio of the oil phase mixed solution and the water phase mixed solution is 1:(8-10).

[0012] Preferably, in the step (3), the swelling treatment adopts dichloromethane solvent, the mass ratio of the ultra-fine resin white ball and dichloromethane is 1:(3-4), the swelling treatment time is 4-6h; the mass ratio of the ultra-fine resin white ball (the weight before swelling treatment), chloromethyl ether and tin tetrachloride is 1:(6-8):(0.6-1.2), the cleaning adopts the way of alternating cleaning 2-4 times with anhydrous ethanol and deionized water, and vacuum drying at 50-60℃ for 12-14h. Since chloromethyl methyl ether has toxicity and certain carcinogenicity, the present application selects chloromethyl ethyl ether to replace it.

[0013] Preferably, in the step (4), the swelling treatment adopts a mixed solution of anhydrous ethanol and chloroform, the mass ratio of the chloromethylated ultra-fine resin white ball (the weight before swelling treatment), anhydrous ethanol and chloroform is 1:(0.1-0.12):(10-12), and the swelling treatment time is 5-7h; the mass ratio of hexamethylenetetramine and the chloromethylated ultra-fine resin white ball (the weight before swelling treatment) is (1-1.2):1. Preferably, in the step (4), the mass fraction of concentrated hydrochloric acid is 37%.

[0014] Preferably, in the step (5), the mass ratio of the primary amine ultra-fine resin and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution is 1:(10-12), and the mass fraction of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution is 69%.

[0015] In order to make the prepared anion exchange resin have the characteristics of small particle size and narrow particle size uniform distribution, the present application adopts the mixed mode of organic polymer dispersant + inorganic dispersant for dispersion. The polyvinyl alcohol is an organic polymer dispersant, which can be adsorbed on the particle surface through the hydroxyl group in the molecular chain to form a steric hindrance effect, and at the same time, a protective film can be formed on the droplet surface to slow down the monomer diffusion rate and avoid excessive growth of the particles. Sodium hexametaphosphate as an inorganic phosphate salt, through dissociation, negative ions are adsorbed on the surface of the resin particles to form electrostatic repulsion, preventing the particles from agglomerating due to Brownian motion or collision caused by stirring; at the same time, the cyclic structure itself has a certain space volume, and the adsorption layer formed can hinder the particles from approaching, thereby enhancing the dispersion capacity of the monomer droplets.

[0016] Generally speaking, higher stirring speed is beneficial to the formation of smaller oil droplets, but it will affect the uniformity of the oil droplet size. In the present application, the stability of the oil droplets is increased by regulating the dispersing agent, so that the uniformity of the particle size distribution can be ensured under high-speed stirring conditions.

[0017] Meanwhile, the stirring method of step (2) is optimized in the present application, and magnetic stirring is adopted instead of the traditional mechanical stirring. Compared with the traditional mechanical stirring, the core advantage lies in the more precise control of the uniformity of droplet dispersion and the stability of the system. The magnetic stirring drives the stirrer to rotate through the magnetic field, and there is no rigid connection between the mechanical transmission shaft and the stirring paddle, so the speed fluctuation is very small. The stirrer has a small volume, and the flow field formed in the container is closer to the axial uniform flow, so the shear force is more uniformly distributed in the reaction system. This uniform shear can make the monomer droplets receive similar forces in the whole system, forming small droplets with uniform size. This stability can ensure that the monomer droplets receive uniform forces during the shearing process, which is crucial for the formation of small-particle-size and narrow-distribution resins. This method is particularly suitable for laboratory-scale or medium-viscosity system suspension polymerization. The magnetic stirrer can provide a relatively uniform and stable shear field under this condition, which is beneficial to the formation of small-particle-size and narrow-distribution resins. Since steps (3)-(5) do not involve the formation of small-particle-size and narrow-distribution resins, the stirring method in other steps does not need to be limited, and magnetic stirring, mechanical stirring or other conventional stirring methods can be used as long as the speed is controlled within 300-500 rpm to achieve the purpose of the present application.

[0018] Compared with the prior art, the present application has the following technical advantages: (1) The present application further optimizes the dispersion system through the synergistic effect of polyvinyl alcohol and sodium hexametaphosphate, which not only limits the coalescence and diffusion of monomer droplets, but also prevents the agglomeration of the particles that have been formed, thereby preparing anion exchange resins with an effective particle size of 50 μm or less and a uniformity coefficient of 1.5 or less.

[0019] (2) The present application uses magnetic stirring in the step of white ball suspension polymerization. Compared with the traditional mechanical stirring, the monomer droplets can receive uniform forces during the shearing process, which is more conducive to the formation of small droplets with uniform size, and further optimizes the particle size uniformity of the obtained anion exchange resins. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be further described below through specific embodiments. Those skilled in the art should know that the embodiments are only used to help understand the technical content and technical effects of the present application, and should not be regarded as a limitation of the present application. The raw materials used in the present embodiments and comparative examples are all conventional commercially available products.

[0021] Three embodiments and three comparative examples of the present application are carried out.

[0022] Examples 1-3 The main raw material ratio (each ratio is mass ratio) and part of the process parameters involved in the preparation of small particle size and narrow distribution of double group anion exchange resin in examples 1-3 are shown in Table 1.

[0023] ; Example 1-3 A method for preparing a small particle size and narrow distribution of double group anion exchange resin, comprising the following steps: (1) mixing styrene, divinylbenzene, liquid paraffin and dibenzoyl peroxide in proportion to obtain an oil phase mixed solution; adding polyvinyl alcohol and sodium hexametaphosphate into water in proportion, mixing uniformly at 60℃ to obtain an aqueous phase mixed solution; (2) adding the oil phase mixed solution into the aqueous phase mixed solution, heating at 85℃ under magnetic stirring for 7h, washing the reaction product with deionized water until neutral, and filtering to obtain ultrafine resin white balls; (3) placing the ultrafine resin white balls in step (2) for swelling treatment for 5h, then putting them into chloromethyl ether, adding tin tetrachloride four times at intervals of 30min, reacting at 30℃ and 400rpm for 10h, filtering, washing with anhydrous ethanol and deionized water alternately for 3 times, and placing in a vacuum dryer at 60℃ for 14h to obtain chloromethylated ultrafine resin white balls; (4) placing the chloromethylated ultrafine resin white balls obtained in step (3) for swelling treatment for 5h again, adding hexamethylenetetramine, reacting at 45℃ and 350rpm for 8h, washing with anhydrous ethanol, filtering, then treating with 37% mass fraction of concentrated hydrochloric acid for 3h, and washing with deionized water until neutral to obtain primary amine ultrafine resin; (5) adding the primary amine ultrafine resin obtained in step (4) into 69% mass fraction of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride solution, adjusting the pH value to 11 with NaOH solid, reacting at 25℃ and 450rpm for 18h; soaking with 1mol / L NaCl solution, filtering and washing with deionized water to obtain double group ultrafine anion exchange resin.

[0024] Comparative Example 1

[0025] The difference from Example 1 is that gelatin and sodium polyphosphate are selected as dispersants, and the mass ratio of sodium polyphosphate: gelatin: water is 1:3:60.

[0026] Comparative Example 2

[0027] The difference from Example 2 is that pitched paddle stirring is selected instead of magnetic stirring in step (2), and the stirring rate remains unchanged.

[0028] Comparative Example 3

[0029] Different from example 1 is that the ratio of sodium hexametaphosphate: polyvinyl alcohol: water is 3:1:60.

[0030] The following tests were performed on the anion exchange resins obtained in examples 1-3 and comparative examples 1-3: The effective particle size, average particle size and uniformity coefficient were determined according to GB / T 5758-2023.

[0031] The ion exchange resins in examples 1-3 and comparative examples 1-3 were converted into hydroxyl type, and the total exchange capacity, strong basic group exchange capacity and weak basic group exchange capacity were determined according to GB / T 5760-2000.

[0032] ; From the test results, the anion exchange resins obtained in examples 1-3 have smaller effective particle size and average particle size, higher resin uniformity, more sufficient chloromethylation, amination and quaternary amine group grafting, and higher exchange capacity compared to comparative examples 1-3.

[0033] From the comparison of examples and comparative example 1, since gelatin is selected instead of polyvinyl alcohol as a dispersant in comparative example 1, the adsorption layer thickness is uneven due to the too wide molecular weight distribution of gelatin, the electrostatic repulsion of sodium polyphosphate is weaker than that of sodium hexametaphosphate and the structure is unstable, which ultimately leads to uneven particle size distribution, thereby affecting the exchange capacity performance.

[0034] From the comparison of examples and comparative example 2, mechanical stirring method is difficult to provide sufficient and uniform shear force compared to magnetic stirring, which leads to wide size distribution of oil phase droplets and uneven local crosslinking degree, thereby affecting the exchange capacity performance.

[0035] From the comparison of examples and comparative example 3, when the amount of sodium hexametaphosphate is too high, the electrolyte concentration in the system increases significantly, which compresses the double electric layer on the surface of the resin particles, weakens the electrostatic stabilization effect, leads to certain particle agglomeration, and too little amount of polyvinyl alcohol will lead to insufficient adsorption layer thickness, thereby affecting the particle size distribution and exchange capacity performance.

[0036] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments, combination of part of the constituent elements in the embodiments to construct other ways can also be included in the scope of the present application.

Claims

1. A method for preparing a small-particle-size, narrow-distribution bifunctional anion exchange resin, characterized in that, Includes the following steps: (1) Styrene, divinylbenzene, liquid paraffin and benzoyl peroxide are mixed in proportion to obtain an oil phase mixed solution; polyvinyl alcohol and sodium hexametaphosphate are added to water in proportion and mixed at 50-60℃ to obtain an aqueous phase mixed solution; (2) Add the oil phase mixture to the aqueous phase mixture, and heat the mixture at 80-90°C for 6-8 hours under magnetic stirring at 600-1000 rpm. Wash the reaction product with deionized water until neutral and filter to obtain ultrafine resin white balls. (3) The ultrafine resin white balls in step (2) were allowed to swell and then put into chloromethyl ethyl ether. Tin tetrachloride was added in four portions every 20-40 min. The reaction was carried out at 30-40℃ and 300-500 rpm for 8-10 h. After filtration, washing and drying, chloromethylated ultrafine resin white balls were obtained. (4) The chloromethylated ultrafine resin white balls obtained in step (3) were allowed to stand and swell again, and hexamethylenetetramine was added. The reaction was carried out at 40-50℃ and 300-500rpm for 7-9h. After washing with anhydrous ethanol and filtering, the mixture was treated with 36-38% hydrochloric acid and washed with deionized water until neutral to obtain primary amination ultrafine resin. (5) Add the primary amination ultrafine resin obtained in step (4) to a 60-69% mass fraction of 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution, adjust the pH to 10-12 with NaOH solid, and react at 20-30℃ and 300-500rpm for 15-20h; after soaking in 1-2mol / L NaCl solution for transformation, filter and wash with deionized water to obtain the bifunctional ultrafine anion exchange resin.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of styrene, divinylbenzene, liquid paraffin and benzoyl peroxide is 1:(0.14~0.16):(0.55~0.6):(0.02~0.024); the liquid paraffin is C10-C18 liquid paraffin.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of sodium hexametaphosphate, polyvinyl alcohol and water is 1:(2-4):(50-70).

4. The preparation method according to claim 3, characterized in that, The molecular weight of polyvinyl alcohol is between 400 and 1000.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the oil phase mixture to the water phase mixture is 1:(8-10).

6. The preparation method according to claim 1, characterized in that, In step (3), dichloromethane solvent is used for swelling treatment, the mass ratio of ultrafine resin white balls to dichloromethane is 1:(3-4), and the swelling treatment time is 4-6h; the mass ratio of ultrafine resin white balls (weight without swelling treatment), chloromethyl ethyl ether, and tin tetrachloride is 1:(6-8):(0.6-1.2), and the cleaning is performed by alternating cleaning with anhydrous ethanol and deionized water 2-4 times, and then vacuum drying at 50-60℃ for 12-14h.

7. The preparation method according to claim 1, characterized in that, In step (4), the swelling treatment uses a mixed solution of anhydrous ethanol and chloroform. The mass ratio of chloromethylated ultrafine resin white balls (weight of unswelled), anhydrous ethanol and chloroform is 1:(0.1-0.12):(10-12), and the swelling treatment time is 5-7h. The mass ratio of hexamethylenetetramine to chloromethylated ultrafine resin white balls (weight of unswelled) is (1-1.2):

1.

8. The preparation method according to claim 1, characterized in that, In step (4), the mass fraction of concentrated hydrochloric acid is 37%.

9. The preparation method according to claim 1, characterized in that, In step (5), the mass ratio of the primary amination ultrafine resin to the aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:(10-12).