Diatomite modified composite high-water-absorption and rapid-water-absorption resin and preparation method thereof

Abstract

The invention relates to the technical field of functional polymer composite materials, and provides diatomite modified composite super absorbent and rapid absorbent resin and a preparation method thereof. The preparation raw materials of the diatomite modified composite high-water-absorption and rapid-water-absorption resin provided by the invention comprise acrylic acid, acrylamide, sodium hydroxide, N, N '-methylene bisacrylamide, ammonium persulfate and modified diatomite. The diatomite is modified by the silane coupling agent, the agglomeration problem of the diatomite is solved, the compatibility with organic monomers is improved, and the modified diatomite, acrylic acid and acrylamide are utilized to construct an organic-inorganic synergistic three-dimensional porous network structure, so that the resin has ultrahigh water absorption rate, rapid water absorption performance and good water retention stability. Meanwhile, the preparation method disclosed by the invention does not need nitrogen protection, has the advantages of simple process, controllable raw material cost and easiness in industrial mass production, and is suitable for multiple fields such as water-saving agriculture, soil moisturizing, landscaping and the like.

Description

Technical Field

[0001] This invention relates to the field of functional polymer composite materials technology, and in particular to a diatomaceous earth-modified composite superabsorbent and fast-absorbing resin and its preparation method. Background Technology

[0002] Superabsorbent polymers (SAPs), as a class of functional polymer materials with a three-dimensional network structure, can absorb hundreds or even thousands of times their own weight in water, exhibiting excellent water retention capacity. They have broad application prospects in fields such as agricultural water conservation, soil improvement, and landscaping. With the increasingly severe global water shortage problem, higher requirements are being placed on the water absorption performance, absorption rate, and application cost of superabsorbent polymers.

[0003] Traditional superabsorbent polymers are mostly prepared using monomers such as acrylic acid and acrylamide. Although they have a certain water absorption capacity, the water absorption rate is slow, and the inorganic fillers have poor compatibility with organic polymers, easily leading to agglomeration and unstable resin performance. While there have been attempts to combine superabsorbent polymers with inorganic fillers such as bentonite and attapulgite, most existing products have shown limited effectiveness in improving water absorption ratio and absorption rate.

[0004] Diatomaceous earth, as a natural siliceous mineral, possesses unique advantages such as a porous structure, large specific surface area, strong adsorption capacity, abundant reserves, and low cost, making it an ideal filler for composite absorbent materials. However, natural diatomaceous earth has poor compatibility with organic monomers, and direct addition easily leads to agglomeration, failing to fully utilize its porous structure to enhance water absorption performance. Summary of the Invention

[0005] In view of this, the present invention provides a diatomaceous earth-modified composite superabsorbent polymer and its preparation method. The present invention improves the dispersibility and compatibility of diatomaceous earth through modification treatment, and constructs a stable three-dimensional network by copolymerizing binary monomers, thus developing a composite superabsorbent polymer with both ultra-high absorbency and rapid water absorption performance, which has broad application prospects.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A diatomaceous earth-modified composite superabsorbent and fast-absorbing resin comprises the following raw materials in parts by weight: 5-8 parts acrylic acid, 3-6 parts acrylamide, 1.8-4 parts sodium hydroxide, 0.005-0.015 parts N,N'-methylenebisacrylamide, 0.03-0.10 parts ammonium persulfate, and 0.3-0.8 parts modified diatomaceous earth; The method for preparing the modified diatomaceous earth includes: acid leaching the diatomaceous earth to obtain pretreated diatomaceous earth; mixing the pretreated diatomaceous earth, a silane coupling agent, and a solvent to react and obtain the modified diatomaceous earth.

[0007] Preferably, the acid used in the acid leaching is hydrochloric acid; the concentration of the hydrochloric acid is 5-8 wt%.

[0008] Preferably, the acid leaching time is 2-3 hours.

[0009] Preferably, the silane coupling agent is KH-570; the mass of the silane coupling agent is 2-4% of the mass of the diatomaceous earth.

[0010] Preferably, the reaction temperature is 50~60℃, the time is 2~3 h, and the initial pH value is 3~4.

[0011] This invention also provides a method for preparing the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin described above, comprising the following steps: Water, acrylic acid, and modified diatomaceous earth are mixed to obtain solution A; Solution A and sodium hydroxide solution are mixed to obtain solution B; The solution B and acrylamide were mixed to obtain the precursor solution; The precursor solution, N,N'-methylenebisacrylamide, and ammonium persulfate were mixed and reacted to obtain the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin.

[0012] Preferably, the concentration of the sodium hydroxide solution is 30-50 wt%.

[0013] Preferably, the method for mixing sodium hydroxide solution and solution A includes: slowly adding sodium hydroxide solution dropwise to solution A under ice-water bath and stirring conditions to neutralize acrylic acid to a degree of neutralization of 65-85%, and continuing stirring for 8-12 minutes after the addition is complete to obtain solution B.

[0014] Preferably, the reaction temperature is 65~85℃, and the polymerization reaction time is based on continuing to keep warm for 1~3 hours after the gel is formed.

[0015] Preferably, after the reaction, the resulting gel product is further subjected to water washing, cutting, drying, pulverizing and sieving in sequence to obtain granular diatomaceous earth modified composite superabsorbent and fast-absorbing resin.

[0016] This invention provides a diatomaceous earth-modified composite superabsorbent polymer (DE-SAP), comprising the following raw materials in parts by weight: acrylic acid (AA) 5-8 parts, acrylamide (AM) 3-6 parts, sodium hydroxide 1.8-4 parts, N,N'-methylenebisacrylamide (MBA) 0.005-0.015 parts, ammonium persulfate (APS) 0.03-0.10 parts, and modified diatomaceous earth 0.3-0.8 parts. The preparation method of the modified diatomaceous earth includes: acid leaching of diatomaceous earth to obtain pretreated diatomaceous earth; mixing the pretreated diatomaceous earth, a silane coupling agent, and a solvent to react and obtain the modified diatomaceous earth. Compared with the prior art, this invention has the following significant advantages: (1) Significant synergistic effect of modified diatomaceous earth: This invention introduces unsaturated double bonds on the surface of diatomaceous earth through modification with silane coupling agents. The modified diatomaceous earth can undergo copolymerization with AA and AM monomers, effectively solving the problem of diatomaceous earth agglomeration, improving its compatibility with organic monomers, and achieving uniform dispersion of diatomaceous earth in the polymer network. Furthermore, the porous structure of the modified diatomaceous earth provides a rapid channel for water migration, while also enhancing the stability of the polymer network as a rigid framework.

[0017] (2) Excellent water absorption performance and fast water absorption rate: The present invention uses AA-AM binary monomer copolymerization to construct a stable three-dimensional network and utilizes the porous structure of modified diatomaceous earth to enhance the water absorption rate and water absorption ratio. The resulting water-absorbing resin has excellent water absorption performance and fast water absorption rate. The results of the examples show that the water-absorbing resin provided by the present invention has a water absorption ratio of 2276.28 g / g in deionized water, which is far superior to traditional binary monomer water-absorbing resins and commercially available products. In 0.9% NaCl solution, the water absorption ratio reaches 124.45 g / g, and in tap water, it reaches 372.22 g / g, showing good salt resistance and practical application adaptability. At the same time, the water absorption rate of the water-absorbing resin provided by the present invention is greatly improved. It reaches 62% of the equilibrium swelling value within 5 minutes and 99% within 45 minutes, which can quickly respond to water demand and solve the problem of slow water absorption of traditional products.

[0018] (3) Strong water retention stability: Under natural conditions at 25℃, the product can retain water for up to 216 hours after saturation and the water retention rate is still 40.48% after 72 hours, which is significantly better than commercially available products and can provide a stable water supply for soil or application scenarios for a long time.

[0019] This invention also provides a method for preparing the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin described above, comprising the following steps: mixing water, acrylic acid, and modified diatomaceous earth to obtain solution A; mixing solution A with sodium hydroxide solution to obtain solution B; mixing solution B with acrylamide to obtain a precursor solution; and reacting the precursor solution, N,N'-methylenebisacrylamide, and ammonium persulfate to obtain the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin. The preparation method provided by this invention is simple and the raw material cost is controllable. The polymerization process does not require nitrogen protection, simplifying production equipment and processes and shortening the process cycle. Using abundant and inexpensive diatomaceous earth as a filler, the binary monomer formulation avoids the use of expensive salt-resistant monomers, significantly reducing raw material costs and making it suitable for industrial mass production. Detailed Implementation

[0020] This invention provides a diatomaceous earth-modified composite superabsorbent and fast-absorbing resin, comprising the following raw materials in parts by weight: 5-8 parts acrylic acid, 3-6 parts acrylamide, 1.8-4 parts sodium hydroxide, 0.005-0.015 parts N,N'-methylenebisacrylamide, 0.03-0.10 parts ammonium persulfate, and 0.3-0.8 parts modified diatomaceous earth.

[0021] Unless otherwise specified, all raw materials used in the preparation of this invention are commercially available products.

[0022] The raw materials for preparing the diatomaceous earth modified composite superabsorbent and fast-absorbing resin provided by the present invention include 5 to 8 parts of acrylic acid, specifically 5, 6.5, 7 or 8 parts.

[0023] Based on the weight of the acrylic acid, the raw materials for preparing the diatomaceous earth modified composite superabsorbent and fast-absorbing resin provided by the present invention include 3 to 6 parts of acrylamide, specifically 3, 4.5, 5 or 6 parts.

[0024] Based on the weight parts of acrylic acid, the raw materials for preparing the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin provided by the present invention include 1.8 to 4 parts of sodium hydroxide, specifically 1.9, 2.7, 3.1, or 3.8 parts. In a specific embodiment of the present invention, the amount of sodium hydroxide is specifically determined to neutralize the acrylic acid to a degree of neutralization of 65 to 85% (i.e., the molar amount of sodium hydroxide is 65 to 85% of the molar amount of acrylic acid).

[0025] Based on the weight of the acrylic acid, the raw materials for preparing the diatomaceous earth modified composite superabsorbent and fast-absorbing resin provided by the present invention include 0.005 to 0.015 parts of N,N'-methylenebisacrylamide, specifically 0.005, 0.01, 0.012 or 0.015 parts; in the present invention, the N,N'-methylenebisacrylamide acts as a crosslinking agent.

[0026] Based on the weight of the acrylic acid, the raw materials for preparing the diatomaceous earth modified composite superabsorbent and fast-absorbing resin provided by the present invention include 0.03 to 0.10 parts of ammonium persulfate, specifically 0.03, 0.06, 0.07 or 0.1 parts; the ammonium persulfate is an initiator.

[0027] Based on the weight of the acrylic acid, the raw materials for preparing the diatomaceous earth modified composite superabsorbent and fast-absorbing resin provided by the present invention include 0.3 to 0.8 parts of modified diatomaceous earth, specifically 0.3, 0.5, 0.6 or 0.8 parts.

[0028] In this invention, the method for preparing the modified diatomaceous earth includes: acid leaching the diatomaceous earth to obtain pretreated diatomaceous earth; mixing the pretreated diatomaceous earth, a silane coupling agent, and a solvent to react and obtain the modified diatomaceous earth; preferably, the diatomaceous earth is used after sieving, and the sieve mesh number is 200 mesh. The acid used for acid leaching is preferably hydrochloric acid; the concentration of the hydrochloric acid is preferably 5-8 wt%, specifically 5 wt%, 6 wt%, 7 wt%, or 8 wt%; the leaching time is preferably 2-3 hours, specifically 2, 2.5, 2.8, or 3 hours; the leaching temperature is room temperature; after leaching, the diatomaceous earth is preferably washed with deionized water and then dried; the drying temperature is preferably 80°C; the silane coupling agent is preferably KH-570; the mass of the silane coupling agent is preferably 2-4% of the mass of the diatomaceous earth, specifically 2%, 3%, 3.5%, or 4%; the solvent is preferably an aqueous ethanol solution, the volume ratio of ethanol to water in the aqueous ethanol solution is preferably 1:2-3, and the ratio of silane coupling agent to solvent is preferably 2-4 g:50-100 mL, specifically 2-4 g:75 mL; the reaction temperature is preferably 50-60°C, specifically 50°C, 55°C, or 60°C, and the reaction time is preferably 2-3 hours, specifically 2, 2.5, or 3 hours. h, the initial pH value of the reaction is preferably 3-4, specifically 3, 3.5 or 4; the reaction is preferably carried out under stirring conditions. In a specific embodiment of the present invention, it is preferable to first dissolve the silane coupling agent in a solvent, adjust the pH value to 3-4, and then add pretreated diatomaceous earth to carry out the reaction; the reagent used to adjust the pH value is preferably dilute acetic acid.

[0029] After the reaction is completed, the reaction solution is preferably filtered, and the resulting solid product is dried, ground and sieved in sequence to obtain modified diatomaceous earth; the drying temperature is preferably 80°C; the mesh size of the sieve used for sieving is preferably 200 mesh, and the sieve residue is collected after sieving.

[0030] In this invention, the water-absorbing resin is prepared by aqueous solution polymerization, and the raw materials also include water; based on the weight parts of acrylic acid, the weight parts of water are preferably 18 to 45 parts, specifically 18, 24, 25 or 30 parts; specifically, the weight parts of water include water used to dilute acrylic acid and water used to dissolve sodium hydroxide; the water is specifically deionized water.

[0031] This invention also provides a method for preparing the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin described above, comprising the following steps: Water, acrylic acid, and modified diatomaceous earth are mixed to obtain solution A; The sodium hydroxide solution and solution A are mixed to obtain solution B; The solution B and acrylamide were mixed to obtain the precursor solution; The precursor solution, N,N'-methylenebisacrylamide, and ammonium persulfate were mixed and reacted to obtain the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin.

[0032] This invention involves mixing water, acrylic acid, and modified diatomaceous earth to obtain solution A. Preferably, a portion of water and acrylic acid are mixed to obtain an acrylic acid solution, and then modified diatomaceous earth is added. The mixture is magnetically stirred for 15-25 minutes to ensure uniform dispersion of the modified diatomaceous earth. When preparing the acrylic acid solution, the preferred ratio of water to acrylic acid is 5-8 g: 15-25 mL.

[0033] After obtaining solution A, the present invention mixes solution A with sodium hydroxide solution to obtain solution B. In the present invention, the concentration of the sodium hydroxide solution is preferably 30-50 wt%, specifically 35 wt%, 40 wt%, 45 wt%, or 50 wt%. The method of mixing the sodium hydroxide solution and solution A preferably includes: slowly adding sodium hydroxide solution dropwise to solution A under ice-water bath and stirring conditions, and continuing stirring for 8-12 minutes after the addition is complete, preferably for 10 minutes, to obtain solution B. The stirring is preferably magnetic stirring. The present invention uses sodium hydroxide to neutralize acrylic acid and controls the degree of neutralization of acrylic acid within the above-mentioned range, which can partially neutralize the acrylic acid monomer to -COONa. The -COO- on the polymer chain carries a negative charge, and the repulsion of like charges causes the network structure to expand, thereby providing sufficient space to accommodate water molecules.

[0034] After obtaining solution B, the present invention mixes solution B with acrylamide to obtain a precursor solution. Preferably, the present invention adds acrylamide to solution B and stirs for 10-15 minutes until completely dissolved to obtain the precursor solution.

[0035] After obtaining the precursor solution, the present invention mixes the precursor solution, N,N'-methylenebisacrylamide, and ammonium persulfate for reaction to obtain the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin. In the present invention, the reaction temperature is preferably 65~85℃, specifically 65℃, 75℃, or 85℃; the reaction time is based on the reaction continuing to be kept at the temperature for 1~3 h after the gel is formed; the reaction is specifically a copolymerization reaction. In a specific embodiment of the present invention, N,N'-methylenebisacrylamide and ammonium persulfate are preferably added to the precursor solution and stirred for 5~8 min until dissolved. Then, the reaction system is immediately placed in a water bath and reacted under water bath and stirring conditions until the system forms a gel that cannot be stirred. Then, the temperature is continued to be kept at the temperature for 1~3 h to obtain the gel product; the stirring speed is preferably 100~200 r / min, specifically 100, 120, 130, or 150 r / min.

[0036] In this invention, after the reaction, the process preferably further includes washing, cutting, drying, pulverizing and sieving the obtained gel product in sequence to obtain granular diatomaceous earth modified composite superabsorbent and fast-absorbing resin; the number of times the water is washed is preferably 3 to 4 times, and this invention removes unreacted monomers by washing; the drying temperature is preferably 60 to 80°C, and the mesh size of the sieve used for sieving is preferably 40 to 60 mesh.

[0037] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0038] Example 1 1. Preparation of modified diatomaceous earth: The diatomaceous earth was crushed and passed through a 200-mesh sieve. 100 g of the diatomaceous earth was soaked in a 5wt% hydrochloric acid solution for 2 hours, washed with deionized water until neutral, and dried at 80℃ to obtain pretreated diatomaceous earth. 2 g of silane coupling agent KH-570 was dissolved in 75 mL of ethanol aqueous solution (25 mL of ethanol and 50 mL of water), the pH was adjusted to 3, the pretreated diatomaceous earth was added, stirred at 50℃ for 2 hours, filtered, dried at 80℃, and ground through a 200-mesh sieve to obtain modified diatomaceous earth.

[0039] 2. Preparation of composite water-absorbing resin: (1) Take 5 g of acrylic acid and 15 mL of deionized water and mix them evenly. Add 0.3 g of modified diatomaceous earth and stir magnetically for 15 min to disperse it fully, so as to obtain solution A; (2) Under the conditions of ice water bath and magnetic stirring, slowly add sodium hydroxide solution with a concentration of 35wt% to solution A, adjust the neutralization degree of acrylic acid to 70%, and continue stirring for 8 min to obtain solution B; (3) Add 3 g of acrylamide to solution B and stir for 10 min until completely dissolved to obtain the precursor solution; (4) Add 0.005 g N,N'-methylenebisacrylamide and 0.03 g initiator ammonium persulfate to the precursor solution in sequence, stir for 5 min until completely dissolved, immediately place the reaction system in a 65℃ water bath, stir continuously at 100 r / min until the system forms a gel and cannot be stirred, keep warm for 2 h to obtain the gel product; (5) The obtained gel product is cut into pieces, washed with water 3 times, dried at 60°C, pulverized and passed through a 40-60 mesh sieve to obtain a granular resin product, which is denoted as DE-SAP 1.

[0040] Example 2 1. Preparation of modified diatomaceous earth: The diatomaceous earth was crushed and passed through a 200-mesh sieve. 100 g of the diatomaceous earth was soaked in a 6wt% hydrochloric acid solution for 2.5 h, washed with deionized water until neutral, and dried at 80℃ to obtain pretreated diatomaceous earth. 3 g of silane coupling agent KH-570 was dissolved in 75 mL of ethanol aqueous solution (25 mL of ethanol and 50 mL of water), the pH was adjusted to 3.5, the pretreated diatomaceous earth was added, and the mixture was stirred at 55℃ for 2.5 h. After filtration, the mixture was dried at 80℃ and ground through a 200-mesh sieve to obtain modified diatomaceous earth.

[0041] 2. Preparation of composite water-absorbing resin: (1) Take 6.5 g of acrylic acid and 20 mL of deionized water and mix them evenly. Add 0.5 g of modified diatomaceous earth and stir magnetically for 20 min to disperse it fully, so as to obtain solution A; (2) Under the conditions of ice water bath and magnetic stirring, slowly add sodium hydroxide solution with a concentration of 40wt% to solution A, adjust the neutralization degree of acrylic acid to 75%, and continue stirring for 10 min to obtain solution B; (3) Add 4.5 g of acrylamide to solution B and stir for 12 min until completely dissolved to obtain the precursor solution; (4) Add 0.01 g N,N'-methylenebisacrylamide and 0.06 g ammonium persulfate as initiator to the precursor solution in sequence, stir for 6 min until completely dissolved, immediately place the reaction system in a 75℃ water bath, stir continuously at 120 r / min until the system forms a gel and cannot be stirred, keep warm for 2.5 h to obtain the gel product; (5) Post-processing of the product: The obtained gel product is cut into pieces, washed with water 3 times, dried at 70°C, pulverized and passed through a 40-60 mesh sieve to obtain a granular resin product, which is denoted as DE-SAP 2.

[0042] Example 3 1. Preparation of modified diatomaceous earth: The diatomaceous earth was crushed and passed through a 200-mesh sieve. 100 g of the diatomaceous earth was soaked in an 8% hydrochloric acid solution for 3 hours, washed with deionized water until neutral, and dried at 80°C to obtain pretreated diatomaceous earth. 4 g of silane coupling agent KH-570 was dissolved in 75 mL of ethanol aqueous solution (25 mL of ethanol and 50 mL of water), the pH was adjusted to 4, the pretreated diatomaceous earth was added, stirred at 60°C for 3 hours, filtered, dried at 80°C, and ground through a 200-mesh sieve to obtain modified diatomaceous earth.

[0043] 2. Preparation of composite water-absorbing resin: (1) Take 8 g of acrylic acid and 25 mL of deionized water and mix them evenly. Add 0.8 g of modified diatomaceous earth and stir magnetically for 25 min to disperse it fully, so as to obtain solution A; (2) Under the conditions of ice water bath and magnetic stirring, slowly add 50wt% sodium hydroxide solution to solution A, adjust the neutralization degree of acrylic acid to 85%, and continue stirring for 12 min to obtain solution B; (3) Add 6 g of acrylamide to solution B and stir for 15 min until completely dissolved to obtain the precursor solution; (4) Add 0.015 g N,N'-methylenebisacrylamide and 0.10 g initiator ammonium persulfate to the precursor solution in sequence, stir for 8 min until completely dissolved, immediately place the reaction system in an 85℃ water bath, stir continuously at 150 r / min until the system forms a gel and cannot be stirred, keep warm for 2 h to obtain the composite gel; (5) Post-processing of the product: The obtained gel is cut into pieces, washed with water 3 times, dried at 80°C, pulverized and passed through a 40-60 mesh sieve to obtain a granular resin product, which is denoted as DE-SAP 3.

[0044] Example 4 1. Preparation of modified diatomaceous earth: The diatomaceous earth was crushed and passed through a 200-mesh sieve. 100 g of the diatomaceous earth was soaked in a 7% hydrochloric acid solution for 2.8 h, washed with deionized water until neutral, and dried at 80 °C to obtain pretreated diatomaceous earth. 3.5 g of silane coupling agent KH-570 was dissolved in 75 mL of ethanol aqueous solution (25 mL of ethanol and 50 mL of water), the pH was adjusted to 4, the pretreated diatomaceous earth was added, stirred at 60 °C for 3 h, filtered, dried at 80 °C, and ground through a 200-mesh sieve to obtain modified diatomaceous earth.

[0045] 2. Preparation of composite water-absorbing resin: (1) Take 7 g of acrylic acid and 22 mL of deionized water and mix them evenly. Add 0.6 g of modified diatomaceous earth and stir magnetically for 22 min to disperse it fully, so as to obtain solution A; (2) Under the conditions of ice water bath and magnetic stirring, slowly add sodium hydroxide solution with a concentration of 45wt% to solution A, adjust the neutralization degree of acrylic acid to 80%, and continue stirring for 11 min to obtain solution B; (3) Add 5 g of acrylamide to solution B and stir for 13 min until completely dissolved to obtain the precursor solution; (4) Add 0.012 g N,N'-methylenebisacrylamide and 0.07 g initiator ammonium persulfate to the precursor solution in sequence, stir for 7 min until completely dissolved, immediately place the reaction system in a 75℃ water bath, stir continuously at 130 r / min until the system forms a gel and cannot be stirred, keep warm for 2 h to obtain the composite gel; (1) Post-processing of the product: The obtained gel was cut into pieces, washed with water, dried at 80°C, crushed and sieved in sequence, and 40~60 mesh granular resin products were collected and recorded as DE-SAP 4.

[0046] Comparative Example 1 Compared with Example 2, Comparative Example 1 only did not add modified diatomaceous earth, while the other raw materials and preparation processes were the same, and the resin product SAP 1 was prepared.

[0047] Comparative Example 2 Comparative Example 2 was a commercially available starch-grafted acrylic superabsorbent polymer (brand name: Huashen, Shenzhen Huashen Chuangda Technology Co., Ltd.), which yielded product SAP 2.

[0048] Comparative Example 3 Comparative Example 3 was a commercially available attapulgite composite acrylic-acrylamide type water-absorbing resin (brand: Wote, Shengli Oilfield Chang'an Holding Group Co., Ltd.), which yielded product SAP 3.

[0049] Comparative Example 4 Comparative Example 4 was a commercially available acrylamide and potassium hydroxide copolymer water-absorbing resin (brand name: Linzhibao, Hebei Yida Agricultural Technology Co., Ltd.), which yielded product SAP 4.

[0050] Performance testing The resin products in the examples and comparative examples were subjected to comprehensive performance testing. The specific testing methods are as follows: (1) Water absorption ratio: Using the tea bag method (200 mesh nylon mesh bag), weigh 0.1g (accurate to 0.001g) of sample, seal it, and immerse it in excess deionized water, 0.9% NaCl solution, and tap water respectively. After reaching saturation, take it out, hang it for 10 min to drain the surface moisture, weigh it, and calculate the water absorption ratio according to formula (1): Water absorption ratio = (total mass after saturation - tea bag mass - dry sample mass) / dry sample mass (1).

[0051] (2) Water absorption rate: According to the above water absorption ratio test method, the sample was taken out and weighed at 5 min, 10 min, 15 min, 20 min, 25 min, 30 min and 45 min respectively, and the water absorption ratio at different time points was recorded. The proportion of the equilibrium swelling value was calculated.

[0052] (3) Water retention rate: 0.2 g (accurate to 0.001 g) of the saturated water-absorbing sample was placed in a constant temperature and humidity laboratory at 25℃, and weighed every 12 h. The water retention rate was calculated according to formula (2): Water retention rate = (mass of samples at different times - mass of dry sample) / (mass of saturated sample - mass of dry sample) × 100% (2).

[0053] The test results are shown in Tables 1-3: Table 1. Water absorption ratio (g / g) of different resin products

[0054] Table 2. Water absorption rate of different resin products (percentage reaching equilibrium swelling value, %)

[0055] Table 3. Water retention rate (%) of different resin products after deionization.

[0056] The above test results show that the diatomaceous earth-modified composite superabsorbent polymer (DE-SAP) prepared in Examples 1-4 of this invention has excellent comprehensive performance, high water absorption ratio, fast water absorption rate, and good water retention performance; among them, Example 2 has the best performance; specifically: (1) Example 2 has a water absorption ratio of 2276.28 g / g in deionized water, which is 1.5 times that of Comparative Example 1 (without modified diatomaceous earth) and 3.3 times that of Comparative Example 4, which has the best performance among commercially available products; in 0.9% NaCl solution, the water absorption ratio is 124.45 g / g, which is 1.47 times that of Comparative Example 1 and 1.82~3.09 times that of commercially available products; in tap water, the water absorption ratio is 372.22 g / g, which far exceeds all comparative example products, showing ultra-high water absorption ratio, good salt resistance and adaptability to practical application scenarios.

[0057] (2) Example 2 reached 62.01% of the equilibrium swelling value after absorbing water for 5 minutes, which is significantly higher than that of Comparative Example 1 (51.04%), Comparative Example 3 (45.66%) and Comparative Example 4 (42.61%). It can reach 99.96% of the equilibrium swelling value after 45 minutes. It can quickly respond to the water demand of arid environment or soil and solve the core difficulty of slow water absorption rate of traditional water-absorbing resin.

[0058] (3) Example 2 can retain water for up to 216 hours under natural conditions at 25°C, and the water retention rate is still 40.48% after 72 hours. In contrast, Comparative Example 1 can only retain water for 180 hours, and commercially available products (Comparative Examples 2, 3, and 4) lose all water within 96 hours. This proves that the three-dimensional network structure constructed by the copolymerization of modified diatomite and binary monomers in this invention significantly improves the water retention stability and can provide a continuous water supply for application scenarios for a long time.

[0059] In summary, this invention modifies diatomaceous earth using a silane coupling agent, fundamentally solving the problem of inorganic filler agglomeration. It utilizes modified diatomaceous earth copolymerized with binary monomers (AA-AM) to construct a synergistic three-dimensional porous network structure of "organic-inorganic" properties, enabling the product to possess ultra-high water absorption rate, rapid water absorption performance, and good water retention stability. Furthermore, this invention avoids the use of expensive salt-tolerant monomers, eliminates the need for nitrogen protection during preparation, simplifies the process, controls costs, and is suitable for industrial mass production. It is applicable to various fields such as water-saving agriculture, soil moisturizing, and landscaping.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A diatomaceous earth-modified composite superabsorbent and fast-absorbing resin, characterized in that, The preparation raw materials include the following parts by weight: 5-8 parts of acrylic acid, 3-6 parts of acrylamide, 1.8-4 parts of sodium hydroxide, 0.005-0.015 parts of N,N'-methylenebisacrylamide, 0.03-0.10 parts of ammonium persulfate, and 0.3-0.8 parts of modified diatomaceous earth; The method for preparing the modified diatomaceous earth includes: acid leaching the diatomaceous earth to obtain pretreated diatomaceous earth; mixing the pretreated diatomaceous earth, a silane coupling agent, and a solvent to react and obtain the modified diatomaceous earth.

2. The diatomaceous earth-modified composite superabsorbent and fast-absorbing resin according to claim 1, characterized in that, The acid used in the acid leaching is hydrochloric acid; the concentration of the hydrochloric acid is 5~8wt%.

3. The diatomaceous earth-modified composite superabsorbent and fast-absorbing resin according to claim 1, characterized in that, The acid leaching time is 2-3 hours.

4. The diatomaceous earth-modified composite superabsorbent and fast-absorbing resin according to claim 1, characterized in that, The silane coupling agent is KH-570; the mass of the silane coupling agent is 2-4% of the mass of the diatomaceous earth.

5. The diatomaceous earth-modified composite superabsorbent and fast-absorbing resin according to claim 1, characterized in that, The reaction was carried out at a temperature of 50-60°C for 2-3 hours, with an initial pH of 3-4.

6. The method for preparing the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin according to any one of claims 1 to 5, characterized in that, Includes the following steps: Water, acrylic acid, and modified diatomaceous earth are mixed to obtain solution A; Solution A and sodium hydroxide solution are mixed to obtain solution B; The solution B and acrylamide were mixed to obtain the precursor solution; The precursor solution, N,N'-methylenebisacrylamide, and ammonium persulfate were mixed and reacted to obtain the diatomaceous earth-modified composite superabsorbent and fast-absorbing resin.

7. The preparation method according to claim 6, characterized in that, The concentration of the sodium hydroxide solution is 30~50wt%.

8. The preparation method according to claim 6, characterized in that, The method for mixing sodium hydroxide solution and solution A includes: adding sodium hydroxide solution dropwise to solution A under ice-water bath and stirring conditions to neutralize acrylic acid to a degree of neutralization of 65-85%; and continuing to stir for 8-12 minutes after the addition is complete to obtain solution B.

9. The preparation method according to claim 6, characterized in that, The reaction temperature is 65~85℃, and the polymerization reaction time is determined by continuing to keep warm for 1~3 hours after the gel is formed.

10. The preparation method according to claim 6, characterized in that, After the reaction, the resulting gel product is sequentially washed with water, cut, dried, pulverized and sieved to obtain granular diatomaceous earth modified composite superabsorbent and fast-absorbing resin.

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