A water retaining agent and its preparation method

Abstract

The present invention provides a water retaining agent and a preparation method thereof. The preparation method at least includes the following steps: dissolving acrylic acid in a solvent, adding an alkaline solution and at least one nonionic monomer to the acrylic acid solution to obtain an intermediate solution; adding a crosslinking agent and an initiator to the intermediate solution; the initiator initiating a polymerization reaction between the acrylic acid and the nonionic monomer to obtain a gel; and drying, pulverizing and sieving the gel to obtain the water retaining agent. Through the water retaining agent and the preparation method thereof provided by the present invention, the salt tolerance and water absorption of the water retaining agent can be improved, and the preparation process is simple, efficient, safe and low in energy consumption.

Description

Technical Field

[0001] The present invention relates to the field of soil water retainers, and particularly to a water retainer and a preparation method thereof. Background Art

[0002] Most soil water retainers use acrylic acid as the main monomer. Although they have good water absorption performance, soil water retainers have problems such as being greatly affected by ionic strength and poor salt tolerance. The water absorption multiple of commercially available water retainers in 0.9wt% sodium chloride aqueous solution is generally lower than 40g / g, and soil water contains richer ions, so the water absorption rate of the water retainer in soil will be even lower. Therefore, in order to achieve a certain water absorption effect of the water retainer in soil, it is particularly important to improve the salt tolerance of the soil water retainer. Summary of the Invention

[0003] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a water retainer and a preparation method thereof, which can significantly improve the salt tolerance and water absorption of the water retainer, and the preparation process is simple, efficient, safe and has low energy consumption.

[0004] To solve the above technical problems, the present invention is realized through the following technical solutions.

[0005] The present invention provides a preparation method of a water retainer, which at least includes the following steps:

[0006] Dissolve acrylic acid in a solvent, and add an alkaline solution and at least one non-ionic monomer to the acrylic acid solution to obtain an intermediate solution;

[0007] Add a crosslinking agent and an initiator to the intermediate solution;

[0008] The initiator initiates the polymerization reaction of the acrylic acid and the non-ionic monomer to obtain a gel; and

[0009] Dry, crush and screen the gel to obtain a water retainer.

[0010] In one embodiment of the present invention, the non-ionic monomer includes at least one of methyl methacrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, acrylamide and 2-hydroxyethyl methacrylate.

[0011] In one embodiment of the present invention, the initiator includes a photoinitiator and a high-temperature initiator.

[0012] In one embodiment of the present invention, a salt-tolerant functional additive is further added to the intermediate solution.

[0013] In an embodiment of the present invention, the salt-tolerant functional aid includes at least one of inorganic phosphates, and the inorganic phosphates include sodium hypophosphite, calcium hypophosphite, ammonium hypophosphite, nickel hypophosphite, cobalt hypophosphite, and iron hypophosphite. The mass of the inorganic phosphate is 0.001%-0.1% of the total mass of the acrylic acid and the nonionic monomer.

[0014] In an embodiment of the present invention, the salt-tolerant functional aid includes a hydrophilic polymer material, and the hydrophilic polymer material includes at least one of 2,2,6,6-tetramethylpyridine-1-oxyl radical oxidized cellulose, carboxymethyl cellulose, carboxymethyl starch, hydroxyethyl cellulose, and carboxymethyl chitosan. The mass of the hydrophilic polymer material is 0.005%-5% of the total mass of the acrylic acid and the nonionic monomer.

[0015] In an embodiment of the present invention, the salt-tolerant functional aid includes a hydrophilic functional filler, and the hydrophilic functional filler at least includes water-absorbing resin particles. The mass of the hydrophilic functional filler is 0.01%-5% of the total mass of the acrylic acid and the nonionic monomer.

[0016] In an embodiment of the present invention, the preparation of the water-absorbing resin particles at least includes the following steps:

[0017] Adding an alkaline solution and at least one nonionic monomer to an acrylic acid solution to obtain an intermediate solution;

[0018] Adding a crosslinking agent and an initiator to the intermediate solution;

[0019] The initiator initiates the polymerization reaction of the acrylic acid and the nonionic monomer to obtain a gel;

[0020] Drying, pulverizing, and screening the gel to obtain water-retaining agent fine powder; and

[0021] Forming a coating on the surface of the water-retaining agent fine powder to obtain the water-absorbing resin particles.

[0022] In an embodiment of the present invention, the coating at least includes propylene glycol, ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and metal ions.

[0023] The present invention also provides a water-retaining agent obtained by using the preparation method described in any one of the above.

[0024] In summary, the present invention provides a water retaining agent and a preparation method thereof, which can significantly reduce the salt sensitivity of the water retaining agent, improve the salt tolerance and water absorption of the water retaining agent. Moreover, the preparation method of the water retaining agent provided by the present invention has the advantages of simple process, high production efficiency and safe process, and can also make full use of the reaction heat in the preparation process, effectively reduce the energy consumption in the preparation process, thereby reducing the preparation cost of the water retaining agent and being suitable for large-scale popularization and application.

[0025] Of course, it is not necessary to achieve all the above-mentioned advantages simultaneously when implementing any aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a schematic flow chart of the preparation method of the water retaining agent provided by the present invention.

[0028] Figure 2 For Figure 1 It is a schematic flow chart of the preparation method of the salt tolerance functional auxiliary agent in DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0030] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0031] The following further elaborates on the technical solutions of the present invention in conjunction with the embodiments and the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] Please refer to Figure 1As shown, the present invention provides a preparation method of a water retaining agent, which at least includes steps S11 - S14.

[0033] S11. Dissolve acrylic acid in a solvent, and add an alkaline solution and at least one non - ionic monomer to the acrylic acid solution to obtain an intermediate liquid.

[0034] S12. Add a cross - linker and an initiator to the intermediate liquid.

[0035] S13. The initiator initiates the polymerization reaction of acrylic acid and the non - ionic monomer to obtain a gel.

[0036] S14. Dry, crush and screen the gel to obtain the water retaining agent.

[0037] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S11, acrylic acid is dissolved in a solvent to obtain an acrylic acid solution. Among them, the solvent includes, for example, deionized water or pure water, etc. The mass of acrylic acid accounts for, for example, 25% - 35% in the acrylic acid solution. After acrylic acid is dissolved in the solvent, for example, the acrylic acid and the solvent also need to be homogenized to obtain a homogeneous acrylic acid solution. In this embodiment, the homogenization treatment is, for example, at least one of stirring and ultrasonic treatment, etc.

[0038] Please refer to Figure 1As shown, in an embodiment of the present invention, in step S11, after obtaining the acrylic acid solution, an alkaline solution and at least one non-ionic monomer are added to the acrylic acid solution to obtain an intermediate solution. Among them, the mass of the non-ionic monomer in the intermediate solution accounts for, for example, 5%-15%, the mass of the alkaline solution in the intermediate solution accounts for, for example, 5%-30%, and the total mass of the alkaline solution and the non-ionic monomer in the intermediate solution accounts for, for example, 20%-35%. The alkaline solution includes, for example, at least one of potassium hydroxide aqueous solution and sodium hydroxide aqueous solution, the concentration of the alkaline solution is, for example, 40wt%-50wt%, the alkaline solution neutralizes, for example, 70wt%-80wt% of the acrylic acid, the non-ionic monomer includes, for example, at least one of methyl methacrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, acrylamide, and 2-hydroxyethyl methacrylate, etc., and the temperature of the intermediate solution is, for example, 15°C-20°C. Moreover, in this embodiment, the alkaline solution and the non-ionic monomer are, for example, added to the acrylic acid solution successively. In the intermediate solution, the alkaline solution and acrylic acid release heat due to the neutralization reaction, and the non-ionic monomer dissolves with endothermic. By adding the alkaline solution and the non-ionic monomer to the acrylic acid solution simultaneously, the energy loss during the preparation of the intermediate solution can be saved, the temperature of the intermediate solution can be better controlled, and the subsequent polymerization reaction can be ensured to proceed smoothly. By adding the non-ionic monomer, the salt sensitivity of the water-retaining agent can be reduced, so that the salt tolerance of the water-retaining agent is significantly improved. Moreover, in this embodiment, for example, two non-ionic monomers are added to the acrylic acid solution, and the two non-ionic monomers are, for example, added to the acrylic acid solution simultaneously to form a ternary copolymerization system of acrylic acid-non-ionic monomer-non-ionic monomer. The ternary copolymerization system has better salt tolerance than the binary copolymerization system, thereby further improving the salt tolerance and water absorbency of the water-retaining agent.

[0039] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S12, after obtaining the intermediate solution, a crosslinking agent, an initiator, etc. are added to the intermediate solution. Among them, the crosslinking agent includes, for example, at least one of ethylene glycol, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polyethylene glycol diacrylate, and N,N'-methylenebisacrylamide, etc., and the mass of the crosslinking agent is, for example, 0.01%-1% of the total mass of the acrylic acid and the non-ionic monomer. By adding the crosslinking agent, strong chemical bonds with relatively high strength can be formed between the water-retaining agent and the soil, and the adhesiveness of the water-retaining agent can also be improved, which is convenient for the shaping of the water-retaining agent.

[0040] Please refer to Figure 1As shown, in an embodiment of the present invention, in step S12, the initiator includes, for example, a photoinitiator and a high-temperature initiator. Among them, the photoinitiator includes, for example, at least one of benzoin and its derivatives, benzil and its derivatives, acetophenone derivatives, α-hydroxy ketone derivatives, α-aminoalkyl acetophenone, and acylphosphine oxides, etc. The mass of the photoinitiator is, for example, 0.001%-1% of the total mass of acrylic acid and non-ionic monomers. The high-temperature initiator includes, for example, at least one of sodium persulfate, potassium persulfate, ammonium persulfate, 2,2'-azobisisobutyramidine dihydrochloride, 2,2'-azobis(2-methylpropylimid) dihydrochloride, etc. The mass of the high-temperature initiator is, for example, 0.01%-1% of the total mass of acrylic acid and non-ionic monomers.

[0041] Please refer to Figure 1 As shown, in another embodiment of the present invention, in step S12, a salt-tolerant functional additive is further added to the intermediate liquid. Among them, the salt-tolerant functional additive is, for example, a composite, and the salt-tolerant functional additive includes, for example, at least one of inorganic phosphates, hydrophilic polymer materials, and hydrophilic functional fillers, etc. By adding the salt-tolerant functional additive, the water retention agent can have better salt tolerance and gel strength. In this embodiment, the salt-tolerant functional additive includes, for example, inorganic phosphates, hydrophilic polymer materials, and hydrophilic functional fillers. Among them, the inorganic phosphate includes, for example, at least one of sodium hypophosphite, calcium hypophosphite, ammonium hypophosphite, nickel hypophosphite, cobalt hypophosphite, and iron hypophosphite, etc. The mass of the inorganic phosphate is, for example, 0.001%-0.1% of the total mass of acrylic acid and non-ionic monomers. The inorganic phosphate group can enable the water retention agent to form a better three-dimensional network structure during the reaction process. In this embodiment, the hydrophilic polymer material includes, for example, at least one of 2,2,6,6-tetramethylpyridine-1-oxyl oxidized cellulose, carboxymethyl cellulose, carboxymethyl starch, hydroxyethyl cellulose, and carboxymethyl chitosan, etc. The mass of the hydrophilic polymer material is, for example, 0.005%-5% of the total mass of acrylic acid and non-ionic monomers, and the hydrophilic polymer material has a high hydroxyl content. Since both the hydrophilic polymer material and the hydrophilic functional filler have hydrophilic groups, the salt tolerance and water absorption of the water retention agent can be improved.

[0042] Please refer to Figures 1 to 2 As shown, in an embodiment of the present invention, the hydrophilic functional filler at least includes water-absorbing resin particles, and the water-absorbing resin particles have a high degree of crosslinking. The mass of the hydrophilic functional filler is, for example, 0.01%-5% of the total mass of acrylic acid and non-ionic monomers. In this embodiment, the preparation steps of the water-absorbing resin particles, for example, include steps S121-S125, where steps S121-S124 are the same as steps S11-S14 and will not be elaborated here.

[0043] Please refer to Figures 1 to 2As shown, in an embodiment of the present invention, after obtaining the superabsorbent powder in step S124, in step S125, a coating is formed on the surface of the superabsorbent powder to obtain superabsorbent resin particles. By subjecting the screened superabsorbent powder to surface crosslinking treatment and then using it as a hydrophilic functional filler, on the one hand, the gel strength of the superabsorbent can be improved, and on the other hand, material loss can be reduced and the utilization rate of the superabsorbent powder can be increased. Among them, the mesh number of the superabsorbent powder is, for example, 100 mesh - 150 mesh, the coating is, for example, a composite, and the coating at least includes propylene glycol, ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, metal ions, etc. Among them, in the coating, propylene glycol accounts for, for example, 37% - 41%, ethylene glycol diglycidyl ether accounts for, for example, 9% - 13%, sorbitol polyglycidyl ether accounts for, for example, 26% - 30%, metal ions account for, for example, 19% - 23%, the metal ions include, for example, at least one of aluminum ions, etc., and the mass of the coating is, for example, 0.1% - 3% of the mass of the superabsorbent powder.

[0044] Please refer to Figures 1 to 2 As shown, in an embodiment of the present invention, in step S125, the method for forming a coating on the surface of the superabsorbent is, for example, at least one of spraying and soaking, etc. In this embodiment, the method for forming the coating is, for example, spraying. Specifically, a coating solution is prepared according to a preset ratio of propylene glycol, ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and metal ions, and then the coating solution is sprayed on the surface of the superabsorbent. After spraying, the superabsorbent with the sprayed solution is placed in an oven at a preset temperature for surface crosslinking treatment. Among them, the preset temperature is, for example, 100°C - 200°C.

[0045] Please refer to Figure 1As shown, in an embodiment of the present invention, after adding a crosslinking agent and an initiator, in step S13, the initiator initiates the polymerization reaction of acrylic acid and non-ionic monomers to obtain a gel. Specifically, the polymerization reaction includes the following steps. First, the photoinitiator initiates the photoinitiated polymerization reaction of acrylic acid and non-ionic monomers under light irradiation. After the reaction system reaches the preset reaction temperature, the light irradiation is stopped. Then, the high-temperature initiator initiates the continued high-temperature initiated polymerization reaction of acrylic acid and non-ionic monomers to obtain a gel. Among them, the light irradiation is, for example, UV ultraviolet light, the ultraviolet light is, for example, belt-type ultraviolet light, the ultraviolet light is, for example, long-wavelength ultraviolet light, the wavelength of the ultraviolet light is, for example, 300nm - 400nm, and the photoinitiated polymerization reaction of acrylic acid and non-ionic monomers can occur after irradiating for 40s - 60s. The preset reaction temperature is, for example, 50°C - 60°C, and the total time of the photoinitiated polymerization reaction and the high-temperature initiated polymerization reaction is, for example, 10min - 20min. By continuously carrying out the polymerization reaction in step S13, the time of the polymerization reaction can be shortened, the preparation process can be simplified, and the preparation efficiency of the water retaining agent can be improved. Moreover, through the rapid initiation of the polymerization reaction by the photoinitiator, after the polymerization reaction releases sufficient heat, the light irradiation is turned off, and the high-temperature initiator is used to continue to initiate the polymerization reaction. The two-step polymerization reaction makes full use of the reaction heat of the polymerization reaction without additional heat, can effectively reduce energy consumption, thereby reducing the cost of the preparation process, and is suitable for large-scale popularization and application. At the same time, the photoinitiated polymerization reaction can be completed under normal temperature and pressure without pressure equipment, so that the risk of the preparation process is extremely low.

[0046] Please refer to Figure 1 As shown, in an embodiment of the present invention, after obtaining the gel, in step S14, the gel is dried, crushed, and sieved to obtain a water retaining agent. Specifically, a gel-cutting aid is added to the gel during the crushing process to facilitate the shaping of the water retaining agent. Among them, the gel-cutting aid includes, for example, at least anhydrous sodium sulfite, etc., and the mass of the gel-cutting aid is, for example, 0.01% - 2% of the total mass of acrylic acid and non-ionic monomers.

[0047] Please refer to Figures 1 to 2 As shown, the present invention also provides a water retaining agent obtained by the above-mentioned preparation method of the water retaining agent. The water retaining agent provided by the present invention can reduce the salt sensitivity of the water retaining agent and improve the salt tolerance and water absorption of the water retaining agent by introducing non-ionic monomers and salt-tolerant functional aids during the preparation process.

[0048] The technical solutions of the present invention will be described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples and comparative examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples can be commercially purchased.

[0049] Example 1

[0050] Dissolve 200 g of acrylic acid in 424 g of deionized water, then add 276 g of 45 wt% potassium hydroxide aqueous solution, and carry out neutralization in an ice-water bath. Then add 100 g of acrylamide monomer to obtain an intermediate solution, and control the temperature of the intermediate solution to be 20 °C. Add 0.09 g of N,N-methylenebisacrylamide, 0.12 g of sodium persulfate, and 0.018 g of α-aminoalkylacetophenone to the intermediate solution to obtain a reaction solution. After deoxygenating the reaction solution for 3 min, pour it into a UV reaction tank, and turn on the ultraviolet lamp to initiate the polymerization reaction. When the reaction reaches 60 °C, turn off the ultraviolet lamp, and the high-temperature initiator continues to initiate the reaction. After reacting for 12 min, a water-retaining agent gel can be obtained. Crush the obtained water-retaining agent gel with an extruder, add 6 g of sodium sulfite solution during the crushing process, and screen the rubber particles by drying to obtain a water-retaining agent. The water-retaining agent is screened by mesh number into those with more than 150 meshes and those with 100 - 150 meshes. Among them, sodium sulfite is a 20 wt% solution.

[0051] Example 2

[0052] Mix 0.7 g of propylene glycol, 0.2 g of ethylene glycol diglycidyl ether, 0.375 g of aluminum sulfate, and 0.5 g of sorbitol polyol glycidyl ether to obtain a surface cross-linking solution. Spray the surface cross-linking solution onto the surface of the water-retaining agent with 100 - 150 meshes in Example 1, and then place the water-retaining agent in an oven at 150 °C for surface cross-linking treatment to obtain a hydrophilic functional filler. Among them, the mass of the water-retaining agent with 100 - 150 meshes is 100 g.

[0053] Place a beaker containing 50 mL of deionized water on a magnetic stirrer with a rotation speed of 300 rmp, slowly add 0.5 g of hydroxyethyl cellulose to the deionized water, and then add 0.5 g of the hydrophilic functional filler and 0.015 g of sodium hypophosphite to the above solution respectively, and stir evenly to obtain a salt-tolerant functional additive.

[0054] Dissolve 200 g of acrylic acid in 424 g of deionized water, then add 276 g of 45 wt% potassium hydroxide aqueous solution, and carry out neutralization in an ice-water bath. Then add 100 g of acrylamide monomer to obtain an intermediate solution, and control the temperature of the intermediate solution to be 20 °C. Add 0.09 g of N,N-methylenebisacrylamide, 0.12 g of sodium persulfate, 0.018 g of α-aminoalkylacetophenone, and 25 g of the salt-tolerant functional additive to the intermediate solution to obtain a reaction solution. After deoxygenating the reaction solution for 3 min, pour it into a UV reaction tank, and turn on the ultraviolet lamp to initiate the polymerization reaction. When the reaction reaches 60 °C, turn off the ultraviolet lamp, and the high-temperature initiator continues to initiate the reaction. After reacting for 12 min, a water-retaining agent gel can be obtained. Crush the obtained water-retaining agent gel with an extruder, add 6 g of sodium sulfite solution during the crushing process, and screen the rubber particles by drying to obtain a water-retaining agent. Among them, sodium sulfite is a 20 wt% solution.

[0055] Example 3

[0056] The difference between this example and Example 2 is that the mass of acrylic acid is 175 g. While adding 100 g of acrylamide monomer, 25 g of hydroxyethyl methacrylate monomer is also added, and the rest is the same.

[0057] Example 4

[0058] The difference between this example and Example 3 is that hydroxyethyl cellulose is not added during the preparation process of the salt-tolerant functional additive, and the rest is the same.

[0059] Example 5

[0060] The difference between this example and Example 3 is that hydrophilic functional fillers are not added during the preparation process of the salt-tolerant functional additive, and the rest is the same.

[0061] Example 6

[0062] The difference between this example and Example 3 is that sodium hypophosphite is not added during the preparation process of the salt-tolerant functional additive, and the rest is the same.

[0063] Comparative Example 1

[0064] Dissolve 200 g of acrylic acid in 424 g of deionized water, then add 276 g of 45 wt% potassium hydroxide aqueous solution, and carry out neutralization in an ice-water bath to obtain an intermediate solution, controlling the temperature of the intermediate solution at 20 °C. Add 0.09 g of N,N'-methylenebisacrylamide and 0.018 g of α-aminoalkylacetophenone to the intermediate solution to obtain a reaction solution. After deoxygenating the reaction solution for 3 min, pour it into a UV reaction tank and turn on the ultraviolet lamp to initiate the polymerization reaction. When the temperature no longer changes during the reaction, turn off the ultraviolet lamp to obtain a water-retaining agent gel. Crush the obtained water-retaining agent gel through an extruder, add 6 g of sodium sulfite solution during the crushing process, and the rubber particles are dried and screened to obtain a water-retaining agent. Among them, sodium sulfite is a 20 wt% solution.

[0065] The water-retaining agents prepared in Examples 1-6, Comparative Example 1, and commercially available water-retaining agents were tested. The test conditions were carried out according to the methods specified for water-retaining agents in the industry standard NY / T 886-2022 "Water-retaining Agents for Agriculture and Forestry", and the test results are shown in Table 1. Among them, the commercially available water-retaining agent was, for example, the HD204 model water-retaining agent of Jinan Huadi Industry and Trade Co., Ltd.

[0066] Table 1. Test results of Examples 1-6, Comparative Example 1, and commercially available water-retaining agents

[0067]

[0068] As can be seen from Table 1, the water absorption multiple and brine absorption multiple of the water retaining agents in Examples 2-6 are much higher than those of the water retaining agent in Example 1, the comparative examples, and the commercially available water retaining agents, indicating that the water retaining agents in Examples 2-6 have higher salt tolerance and water absorption. Therefore, for the preparation method of the water absorbent provided by the present invention, by introducing a non-ionic monomer and a salt-tolerant functional auxiliary into acrylic acid, the salt tolerance and water absorption of the water retaining agent can be improved. Moreover, for the preparation method provided by the present invention, through photoinitiated polymerization reaction and high-temperature initiated polymerization reaction, and by utilizing the exotherm of the polymerization reaction to complete the polymerization reaction, the energy consumption in the preparation process can be reduced, and the cost in the preparation process can be decreased.

[0069] In summary, the present invention provides a water retaining agent and a preparation method thereof. By introducing a non-ionic monomer and a salt-tolerant functional auxiliary into acrylic acid, the salt tolerance and water absorption of the water retaining agent can be improved. Moreover, for the preparation method provided by the present invention, the polymerization reaction is completed through two-step initiation of photoinitiation and high-temperature initiation, and by making full use of the exotherm of the polymerization reaction, the energy consumption in the preparation process can be saved, and the cost in the preparation process can be reduced, which is suitable for large-scale popularization and application. At the same time, the preparation method provided by the present invention has the advantages of simple, efficient, and safe process.

[0070] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation method of a water retaining agent, characterized in that, Comprising at least the following steps: Dissolve acrylic acid in a solvent, and add an alkaline solution and two non-ionic monomers to the acrylic acid solution to obtain an intermediate solution. The non-ionic monomers include two of methyl methacrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, acrylamide, and 2-hydroxyethyl methacrylate. The mass ratio of acrylic acid in the acrylic acid solution is 25%-35%, and the mass ratio of the non-ionic monomers in the intermediate solution is 5%-15%; Add a crosslinking agent, an initiator, and a salt-resistant functional aid to the intermediate solution. The salt-resistant functional aid includes inorganic phosphate, hydrophilic polymer material, and hydrophilic functional filler. The hydrophilic functional filler at least includes water-absorbing resin particles. The mass of the hydrophilic functional filler is 0.01%-5% of the total mass of acrylic acid and the non-ionic monomers. The inorganic phosphate includes sodium hypophosphite, calcium hypophosphite, ammonium hypophosphite, nickel hypophosphite, cobalt hypophosphite, and iron hypophosphite. The mass of the inorganic phosphate is 0.001%-0.1% of the total mass of acrylic acid and the non-ionic monomers. The hydrophilic polymer material includes 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized cellulose, carboxymethyl cellulose, carboxymethyl starch, hydroxyethyl cellulose, and carboxymethyl chitosan. The mass of the hydrophilic polymer material is 0.005%-5% of the total mass of acrylic acid and the non-ionic monomers; The initiator initiates the polymerization reaction of acrylic acid and the non-ionic monomers to obtain a gel; And Dry, crush, and screen the gel to obtain a water-retaining agent.

2. The preparation method according to claim 1, characterized in that, The initiator includes a photoinitiator and a high-temperature initiator.

3. The preparation method according to claim 1, wherein The preparation of the water-absorbing resin particles comprises at least the following steps: Add an alkaline solution and two non-ionic monomers to an acrylic acid solution to obtain an intermediate solution; Add a crosslinking agent and an initiator to the intermediate solution; The initiator initiates the polymerization reaction of acrylic acid and the non-ionic monomers to obtain a gel; Dry, crush, and screen the gel to obtain water-retaining agent micropowder; and Form a coating on the surface of the water-retaining agent micropowder to obtain the water-absorbing resin particles.

4. The preparation method according to claim 3, characterized in that, The coating at least includes propylene glycol, ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, and metal ions.

5. A water retaining agent, characterized in that, Obtained by using the preparation method according to any one of claims 1-4.

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