A polymer composite porous water-absorbing material and its preparation method

Abstract

The present invention provides a polymer composite porous water-absorbing material and a preparation method thereof, belonging to the field of soil moisture preservation and fertilizer enhancement. The preparation method of the polymer composite porous water-absorbing material provided by the present invention is as follows: First, a water-soluble urea-formaldehyde resin solution is pre-polymerized from formaldehyde and urea as raw materials through an acid-base catalyst, and a straw liquefaction mixture, an animal protein foaming agent, a silicone resin polyether emulsion, a superabsorbent resin aqueous solution, a modified chitin suspension, and a polyvinyl formal solution are added. A high-ratio foaming system is obtained by mechanical foaming, and an appropriate amount of phosphoric acid is added for curing and drying to obtain the polymer composite porous water-absorbing material. During the preparation of the porous water-absorbing material, chemical and physical high cross-linking of urea-formaldehyde resin, modified chitin, superabsorbent resin, silicone resin polyether, and polyvinyl formal is achieved, and the pore structure of the water-absorbing material is uniform and has a high porosity, with the advantages of a high water absorption ratio and strong repeated water absorption ability.

Description

Technical Field

[0001] The present invention belongs to the field of straw resource recycling, and specifically relates to a polymer composite porous water-absorbing material and a preparation method thereof. Background Art

[0002] Currently, superabsorbent materials are generally classified according to starch-based, synthetic resin-based, and cellulose-based.

[0003] Currently, the most widely used material is superabsorbent resin (SAPs), because it can absorb thousands of times its own weight of water and has good water absorption and retention ability, and is widely used in disposable sanitary products, industry, agriculture, gardening, food and medical supplies. However, superabsorbent resin is formed by graft copolymerization with acrylamide (Am) and acrylic acid (AA), etc., and most of these cross-linking agents are derived from non-renewable petroleum resources. The source of starch-based water-absorbing materials is relatively wide and the price is relatively low. It is a natural polyhydroxy substance, and generally, starch grafted acrylate and acrylamide are the main means, but there are also some deficiencies, such as being prone to rot and having poor water retention.

[0004] In addition, cellulose-based water-absorbing materials have the characteristics of rich sources, low price, renewable, biodegradable by microorganisms, safe and non-toxic, etc. However, the extraction and purification of cellulose raw materials also require a certain amount of energy consumption, and the preparation process is complex with a lot of intermediate waste, which is also not conducive to environmental protection.

[0005] Therefore, there is an urgent need to provide a preparation method of a polymer composite porous water-absorbing material with easily accessible raw materials, simple process, and environmental friendliness, which can realize resource recycling while preparing a moisturizing and fattening agent and endowing it with high water absorption and high water retention. Summary of the Invention

[0006] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a polymer composite porous water-absorbing material.

[0007] To solve the above problems, the technical solutions adopted by the present invention are as follows:

[0008] A preparation method of a polymer composite porous water-absorbing material includes the following steps:

[0009] Step 1: Place the formaldehyde solution in a reaction kettle equipped with a condenser, a stirring paddle and a thermometer, adjust the temperature to 50°C, and adjust the pH value to 8.5 with sodium hydroxide. Add the first batch of urea to the reaction kettle so that the molar ratio of formaldehyde to urea is 2.1, and react for 30 minutes;

[0010] Step 2: Add the second batch of urea to the reaction solution obtained in Step 1, adjust the molar ratio of formaldehyde to the total amount of urea added in two batches to 1.6, heat up to 90 °C, and react for 40 minutes;

[0011] Step 3: Adjust the pH of the reaction solution obtained in Step 2 to 5.0 with phosphoric acid. After the viscosity of the reaction solution reaches 0.25 - 0.40 Pa·s, adjust the pH value to 8.5 with sodium hydroxide, lower the temperature to 60 °C, then add the third batch of urea, adjust the final molar ratio of formaldehyde to urea to 1.4, and react for 10 minutes to obtain a water-soluble urea-formaldehyde resin prepolymer;

[0012] Step 4: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of urea and sodium hydroxide and stir evenly. Add a certain amount of chitin powder and disperse it in the reaction solution. Pre-cool to -18 °C and freeze for 48 hours. After thawing, obtain a clear and transparent aqueous solution. Add a certain amount of sodium chloroacetate, maintain the reaction solution at 15 °C, and react for 24 hours to obtain a modified chitin suspension;

[0013] Step 5: Add a certain amount of ethylene glycol and deionized water to the high-pressure reaction kettle, add a certain amount of corn straw powder and a certain amount of phosphoric acid catalyst and mix evenly. Under nitrogen protection, raise the temperature of the reaction solution to 170 °C, then react for 60 minutes, cool to obtain a straw liquefaction mixture. Subsequently, add and mix the chitin suspension obtained in Step 4 and the water-soluble urea-formaldehyde resin prepolymer obtained in Step 3 in sequence and mix evenly. After mixing evenly, add a certain amount of silicone resin polyether emulsion and mix evenly;

[0014] Step 6: Pour a certain amount of deionized water into the high-speed stirrer, add a certain amount of superabsorbent resin powder, and stir at high speed to mix evenly, so that the superabsorbent resin powder is evenly dispersed in the deionized water. Then add the reaction solution obtained in Step 5 and mix evenly;

[0015] Step 7: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of polyvinyl alcohol with the model number 17 - 99, heat up to 90 °C. After the polyvinyl alcohol is dissolved, add a certain amount of hydrochloric acid solution to adjust the pH value of the reaction solution to 2. Under stirring conditions, add an aqueous formaldehyde solution, heat up to 95 °C. When water separation appears in the reaction solution, immediately add an aqueous sodium hydroxide solution to adjust the pH value of the reaction solution to 7, and stir at high speed to finally obtain a polyvinyl formal solution. Then add the polyvinyl formal solution to the mixture in Step 6 and mix evenly;

[0016] Step 8: Pour a certain amount of deionized water into the high-speed stirrer, add a certain amount of foaming agent, and stir at high speed to mix evenly until the foam in the mixture no longer increases. Then add it to the mixture obtained in Step 7 and mix evenly;

[0017] Step 9: Mix the mixture obtained in Step 8 with a certain amount of phosphoric acid evenly, and adjust the pH value of the mixture to 5;

[0018] Step 10: Stir the liquid obtained in Step 9 and dry it at a certain temperature to obtain a foam water-absorbing material.

[0019] Further, the formaldehyde content of the formaldehyde solution in Step 1 is 37%.

[0020] Further, the suspension in Step 4 contains the following raw material components in parts by mass: 85 parts of water, 4 parts of urea, 11 parts of sodium hydroxide, 4 parts of chitin powder, and 2.5 parts of sodium chloroacetate.

[0021] Further, the ratio of ethylene glycol to water in the ethylene glycol aqueous solution in Step 5 is 3:1, the mass ratio of the ethylene glycol aqueous solution to the straw powder is 2:1, and the mass percentage of the phosphoric acid catalyst to the ethylene glycol aqueous solution is 1:10. When mixing, the mixture contains the following raw material components in parts by mass: 10 - 20 parts of straw liquefaction mixture, 11 - 22 parts of the modified chitin suspension prepared in Step 4, 25 - 35 parts of the water-soluble urea-formaldehyde resin prepolymer prepared in Step 3, and 2.5 parts of silicone resin polyether emulsion.

[0022] Further, the superabsorbent resin in Step 6 is a starch-acrylamide type superabsorbent resin, and the mass percentage of the superabsorbent resin aqueous dispersion is 0.25%.

[0023] Further, the solid content of the polyvinyl alcohol aqueous solution in Step 7 is 10%, and the content of formaldehyde is 2.5%.

[0024] Further, the foaming agent in Step 8 is an animal protein foaming agent, and the mass percentage of the foaming agent aqueous solution is 3%.

[0025] Further, the concentration of the phosphoric acid in Step 9 is 2 mol / L.

[0026] Further, the drying temperature in Step 10 is 40 - 45 °C, and the drying time is 20 - 30 h.

[0027] A polymer composite porous water-absorbing material is prepared by using any of the above-mentioned preparation methods.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The preparation method provided by the present invention has easily accessible raw materials, a simple process, can improve the performance of porous materials through various polymer composites, and no intermediate waste is generated during the preparation process, making it more environmentally friendly and capable of realizing resource recycling. Moreover, the porous water-absorbing material prepared by the preparation method of the present invention will decompose into substances that can provide nutrients for soil and plants after the water retention performance fails, so it also has a slow-release performance and has good application prospects. Description of the Drawings

[0030] Figure 1 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 1 of the present invention;

[0031] Figure 2 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 2 of the present invention;

[0032] Figure 3 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 3 of the present invention;

[0033] Figure 4 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 4 of the present invention;

[0034] Figure 5 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 5 of the present invention;

[0035] Figure 6 It is a scanning electron microscope image of the polymer composite porous water-absorbing material prepared by the preparation method of Example 6 of the present invention;

[0036] Figure 7 It is a water absorption rate curve graph obtained by performing a water absorption test on the polymer composite porous water-absorbing material prepared by the preparation method of Example 6 of the present invention;

[0037] Figure 8 It is a water retention rate curve graph obtained by performing a water retention test on the polymer composite porous water-absorbing material prepared by the preparation method of Example 6 of the present invention.

[0038] Figure 9 It is a repeated liquid absorption curve graph obtained by performing a water retention test on the polymer composite porous water-absorbing material prepared by the preparation method of Example 6 of the present invention. Detailed Embodiments

[0039] The present invention will be further described below in conjunction with specific embodiments.

[0040] The present invention mixes straw powder with ethylene glycol and phosphoric acid, and performs high-pressure liquefaction to obtain a partially liquefied straw fiber mixture.

[0041] In the present invention, the straw is obtained by subjecting straw raw materials to pretreatment.

[0042] In the present invention, the pretreatment preferably includes: sequentially washing the straw raw materials at room temperature, drying them in an oven at 80 °C for the first time, soaking them in deionized water at room temperature for 10 h, drying them in an oven at 80 °C for the second time, crushing, and ball milling.

[0043] In the present invention, the equipment for crushing is preferably a cell disruptor; there are no special limitations on the operation of the cell disruptor in the present invention, and the straw raw materials can be crushed by using the operation methods well-known to those skilled in the art.

[0044] In the present invention, the rotation speed of the ball milling is preferably 250 - 350 r / min, more preferably 300 r / min; the time for ball milling is 4 - 6 h, more preferably 5 h. By subjecting the straw raw materials to the above pretreatment, the size of the obtained straw can be made smaller, the contact area with the phosphoric acid solution during impregnation in the liquefying agent is larger, which is more conducive to fiber fibrillation and separation of cellulose; at the same time, the straw can be suspended in the mixed solution at a smaller particle size, so that the water-absorbing and water-retaining material can be prepared directly without filtration, no intermediate waste is generated during the preparation process, and resource recycling is more sufficient, and it is more environmentally friendly.

[0045] In the present invention, the particle size of the straw is 10 - 150 μm, preferably 20 - 130 μm, more preferably 50 - 100 μm, and most preferably 60 - 80 μm. By controlling the particle size of the straw within the above range, it is more conducive to the dissolution of cellulose and the generation of polyol substances, ensuring that the straw powder with a small particle size can be stably suspended in the suspension, which is more conducive to full contact with other components, thereby forming a water-absorbing and water-retaining material with a uniform and rich pore structure, more conducive to obtaining higher water absorption and water retention, and realizing the full recycling of straw.

[0046] By controlling the mass ratio of the straw to the liquefying agent solution within the above range in the present invention, it is more conducive to the fibrillation and dissolution of the fibers in the straw, thereby obtaining more polyol substances, and further effectively improving the water absorption and water retention of the straw-based water absorbent and water retainer.

[0047] In the present invention, the straw is preferably one or a mixture of two or more of corn straw, wheat straw, soybean straw, sorghum straw, sunflower straw, peanut straw, rice straw, cotton straw, and grass straw. By selecting the above types of straw, it is not only conducive to resource recycling but also can ensure that the straw contains richer cellulose.

[0048] In the present invention, the liquefying agent can be a polar solvent such as ethylene glycol, propylene glycol, polyethylene glycol, vinyl propionate, etc., and is preferably ethylene glycol.

[0049] In the present invention, the temperature of liquefaction is preferably 150 - 180°C, more preferably 165 - 175°C, and most preferably 170°C; the time of impregnation is preferably 40 - 90 min, more preferably 50 - 70 min, and most preferably 60 min. By controlling the temperature and time of impregnation liquefaction within the above ranges, the present invention can defibrate the pretreated straw under the action of heat and swell cellulose, and at the same time a large amount of polyol substances are generated by reaction.

[0050] By fully reacting the cellulose in the straw with the liquefying agent in the present invention, the cellulose combines with more active functional groups, which is more conducive to crosslinking with the product formed by the subsequent polycondensation reaction to form a rich three-dimensional network structure, obtaining a larger specific surface area, and thus having stronger water absorption and water retention properties.

[0051] In the present invention, the foaming agent is preferably a mixed solution of an animal protein foaming agent and deionized water.

[0052] In the present invention, the preparation method of the foaming agent is preferably to stir and foam the animal protein foaming agent and deionized water. There are no special limitations on the operation of the stirring and foaming in the present invention, and the foaming agent can be stirred until the foam is uniform and delicate by using the operation of stirring and foaming well-known to those skilled in the art.

[0053] In the present invention, the catalyst is preferably phosphoric acid, hydrochloric acid or sulfuric acid, and phosphoric acid is preferred. By selecting the catalyst of the above acidic substances in the present invention, the polycondensation reaction system can be in an acidic condition, which is more conducive to the full progress of the polycondensation reaction; at the same time, by selecting the catalyst of the above acidic types, it is beneficial for the water-absorbing and water-retaining material to be used in the soil, and the above types of catalysts can also slowly release substances beneficial to the soil after the water-absorbing material fails, which is more suitable for crops to absorb.

[0054] In the present invention, the pH value of the foam curing polycondensation reaction is preferably 2 - 6, and more preferably 5.0.

[0055] In the present invention, the method for regulating the pH is preferably to dropwise add the catalyst.

[0056] In the present invention, the temperature of drying is preferably 55 - 65°C, and more preferably 60°C; the time of drying is preferably 20 - 30 h, and more preferably 24 - 28 h. By controlling the temperature and time of curing and drying in the present invention, it is more conducive to the full crosslinking of urea-formaldehyde resin with other macromolecular substances, making the three-dimensional space network in the water-absorbing and water-retaining agent more complete and the pores more abundant, thereby effectively improving the water absorption and water retention effects of the polymer composite porous water-absorbing material.

[0057] In the present invention, after drying, baking is preferably further included; the temperature of the baking is preferably 70-80 °C, more preferably 80 °C; the present invention does not have special limitations on the baking time, and it is sufficient to reach the dry state at the baking temperature.

[0058] The preparation method provided by the present invention has easily accessible raw materials, a simple process, is more environmentally friendly, and can achieve resource recycling.

[0059] The present invention also provides a polymer composite porous water-absorbing material prepared by the preparation method described in the above technical solution.

[0060] The polymer composite porous water-absorbing material obtained by the preparation method provided by the present invention has excellent water absorption and water retention properties, and after the water retention property fails, it will decompose into substances that can provide nutrients for the soil and plants. Therefore, it also has a slow-release property and has good application prospects.

[0061] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0062] Example 1

[0063] A preparation method of a polymer composite porous water-absorbing material comprises the following steps:

[0064] Step 1: Place the formaldehyde solution in a reaction kettle equipped with a condenser, a stirring paddle, and a thermometer, adjust the temperature to 50 °C, and adjust the pH value to 8.5 with sodium hydroxide. Add the first batch of urea to the reaction kettle so that the molar ratio of formaldehyde to urea is 2.1, and react for 30 minutes. The concentration of the formaldehyde solution is 37%, a total of 70 parts are added, and 24 parts of the first batch of urea are added, so that the molar ratio of formaldehyde to urea (F / U1) is 2.1;

[0065] Step 2: Add the second batch of urea to the reaction solution obtained in Step 1, adjust the molar ratio of formaldehyde to the total amount of urea added in two batches to 1.6, raise the temperature to 90 °C, and react for 40 minutes. The amount of the second batch of urea added is 8 parts, and adjust F / (U1+U2) to 1.6;

[0066] Step 3: Adjust the pH of the reaction solution obtained in Step 2 to 5.0 with phosphoric acid. After the viscosity of the reaction solution reaches 0.25 - 0.40 Pa·s, adjust the pH value to 8.5 with sodium hydroxide, lower the temperature to 60°C, then add the third batch of urea, adjust the final molar ratio of formaldehyde to urea to 1.4, and react for 10 minutes to obtain a water-soluble urea-formaldehyde resin prepolymer. The amount of the third batch of urea added is 4.5 parts, and adjust the final F / (U1+U2+U3) to 1.4;

[0067] Step 4: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of urea and sodium hydroxide and stir evenly, add a certain amount of chitin powder and disperse it in the reaction solution, pre-cool to -18°C, freeze for 48 hours, and obtain a clear and transparent aqueous solution after thawing. Add a certain amount of sodium chloroacetate, maintain the reaction solution at 15°C, and react for 24 hours to obtain a modified chitin suspension. The amount of deionized water added is 85 parts, the amount of urea added is 4 parts, the amount of sodium hydroxide added is 11 parts, and the amount of chitin powder added is 4 parts;

[0068] Step 5: Add a certain amount of ethylene glycol and deionized water to the high-pressure reaction kettle, add a certain amount of corn straw powder and a certain amount of phosphoric acid catalyst and mix evenly. After the temperature of the reaction solution rises to 170°C under nitrogen protection, react for 60 minutes, cool to obtain a straw liquefaction mixture, and then add and mix the chitin suspension obtained in Step 4 and the water-soluble urea-formaldehyde resin prepolymer obtained in Step 3 in sequence and mix evenly. After mixing evenly, add a certain amount of silicone resin polyether emulsion and mix evenly. The amount of ethylene glycol added is 15 parts, the amount of deionized water added is 5 parts, the amount of corn straw powder added is 10 parts, the amount of phosphoric acid catalyst added is 1 part. The amount of the straw liquefaction mixture added during the mixing process is 10 parts, the amount of the modified chitin suspension added is 11 parts, the amount of the water-soluble urea-formaldehyde resin prepolymer added is 25 parts, and the amount of the silicone resin polyether emulsion added is 2.5 parts;

[0069] Step 6: Pour a certain amount of deionized water into a high-speed stirrer, add a certain amount of superabsorbent resin powder, and stir at high speed evenly to make the superabsorbent resin powder evenly dispersed in the deionized water. Then add the reaction solution obtained in Step 5 and mix evenly. The amount of deionized water added is 80 parts, the superabsorbent resin powder is a starch-acrylamide type superabsorbent resin, and the amount added is 0.2 parts;

[0070] Step 7: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of polyvinyl alcohol with the model number 17-99, heat up to 90 °C. After the polyvinyl alcohol is dissolved, add a certain amount of hydrochloric acid solution, adjust the pH value of the reaction solution to 2, add formaldehyde aqueous solution under stirring conditions, heat up to 95 °C. When water separation appears in the reaction solution, immediately add sodium hydroxide aqueous solution and adjust the pH value of the reaction solution to 7, and at the same time stir at high speed to finally obtain polyvinyl formal solution. Then add the polyvinyl formal solution to the mixture in Step 6 and mix evenly. Among them, the added amount of deionized water is 83 parts, the added amount of 17-99 polyvinyl alcohol is 10 parts, the formaldehyde aqueous solution is a formaldehyde aqueous solution with a concentration of 37%, and the added amount is 7 parts. When the obtained polyvinyl formal solution is added to the mixture in Step 6, the added amount of polyvinyl formal solution in the mixture is 10 parts;

[0071] Step 8: Pour a certain amount of deionized water into a high-speed stirrer, add a certain amount of foaming agent, and stir evenly at high speed until the foam in the mixture no longer increases, and then add it to the mixture obtained in Step 7 and mix evenly. Among them, the added amount of deionized water is 18 parts, and the foaming agent is animal protein foaming agent, and the added amount is 2 parts;

[0072] Step 9: Mix the mixture obtained in Step 8 evenly with a certain amount of phosphoric acid, and adjust the pH value of the mixture to 5. Among them, the concentration of phosphoric acid is 2 mol / L, and the added amount is 3 parts;

[0073] Step 10: Stir the liquid obtained in Step 9 and dry it at a certain temperature to obtain a foam water-absorbing material. Among them, the drying temperature is 40-45 °C, and the drying time is 20-30 hours.

[0074] Example 2

[0075] The preparation method of this example is basically the same as that of Example 1. The difference is that when mixing in Step 5, the added amount of water-soluble urea-formaldehyde resin prepolymer is 35 parts, the straw liquefaction mixture is 20 parts, the modified chitin suspension is 22 parts, and the polyvinyl formal solution is 20 parts, and a foam water-absorbing material is obtained through the subsequent same steps.

[0076] Example 3

[0077] The preparation method of this example is basically the same as that of Example 1. The difference is that when mixing in Step 5, the added amount of water-soluble urea-formaldehyde resin prepolymer is 30 parts, the straw liquefaction mixture is 15 parts, the modified chitin suspension is 16.5 parts, and the polyvinyl formal solution is 15 parts, and a foam water-absorbing material is obtained through the subsequent same steps.

[0078] Example 4

[0079] The preparation method of this example is basically the same as that of Example 1, except that in step eight, 27 parts of deionized water and 3 parts of foaming agent are added, and the foam absorbent material is obtained through the same subsequent steps.

[0080] Example 5

[0081] The preparation method of this example is basically the same as that of Example 2, except that in step eight, 27 parts of deionized water and 3 parts of foaming agent are added, and the foam absorbent material is obtained through the same subsequent steps.

[0082] Example 6

[0083] The preparation method of this example is basically the same as that of Example 3, except that in step eight, 27 parts of deionized water and 3 parts of foaming agent are added, and the foam absorbent material is obtained through the same subsequent steps.

[0084] The polymer composite porous absorbent materials prepared in Examples 1 - 6 were observed by scanning electron microscopy, and the SEM photos are as Figures 1 to 6 shown.

[0085] According to Figures 1 - 3 it can be seen that the structures of the polymer composite porous absorbent materials prepared in Examples 1 - 3 are relatively dense;

[0086] According to Figure 1 it can be seen that the straw liquefaction mixture and urea - formaldehyde prepolymer are too little, the system strength is low, the cell damage is serious, and the cell collapse phenomenon is more serious, affecting various properties of the polymer composite porous absorbent material;

[0087] According to Figure 2 it can be seen that the straw liquefaction mixture and urea - formaldehyde prepolymer are excessive, the structure of the polymer composite porous absorbent material is dense, the formation of holes is inhibited, there are fewer holes, which is not conducive to water absorption;

[0088] According to Figure 3 it can be seen that the network structure of the polymer composite porous absorbent material is relatively uniform, there are many holes and the shape and size of the holes are relatively uniform.

[0089] It can be seen that the porous structure of the polymer composite porous absorbent material prepared in Example 3 is the best.

[0090] According to 4 - 6, it can be seen that the network structures of the polymer composite porous absorbent materials prepared in Examples 4 - 6 are generally more delicate and compact than those of 1 - 3, the pore walls are complete, the hole sizes are uniformly moderate, and there are more connected holes;

[0091] It can be seen that the porous structure of the polymer composite porous absorbent material prepared in Example 6 is the best.

[0092] The high molecular composite porous water-absorbing materials prepared in Examples 1-6 were tested for water absorption rate by the natural filtration method; among them, the absorbed water was selected from deionized water, tap water, and 0.9 wt.% NaCl solution; the water absorption multiple represents the amount of absorbed water, denoted by the symbol W, with the unit of g / g, and the specific calculation formula is as follows:

[0093]

[0094] In the formula,

[0095] W: water absorption multiple, unit: g / g;

[0096] Wt: mass of the high molecular composite porous water-absorbing material after liquid absorption, unit: g;

[0097] Wd: mass of the high molecular composite porous water-absorbing material in the dry state, unit: g;

[0098] The test results are shown in Table 1 and Figure 7 the water absorption capacity as shown;

[0099]

[0100] Table 1

[0101] Among them, the multiple of deionized water absorption is denoted by W1, the multiple of tap water absorption is denoted by W2, and the multiple of 0.9 wt.% NaCl solution absorption is denoted by W3.

[0102] The high molecular composite porous water-absorbing materials after the water absorption rate test of the above Examples 1-6 were tested for water retention rate, and the test results are as Figure 7 shown.

[0103] From Table 1 and Figure 7 it can be seen that the water absorbent prepared in Examples 1-6 has a deionized water absorption ratio of 12.65-26.68 g / g, a tap water absorption ratio of 8.10-17.87 g / g, and a 0.9 wt.% NaCl solution absorption ratio of 7.15-13.56 g / g within 48 h. Among them, Example 6 has the best water absorption property.

[0104] Figure 8 It is the water retention rate curve obtained from the water retention test of the high molecular composite porous water-absorbing material prepared by the preparation method of Example 6.

[0105] Figure 9 It is the repeated liquid absorption curve obtained from the water retention test of the high molecular composite porous water-absorbing material prepared by the preparation method of Example 6.

[0106] From Figure 8It can be seen that the water retention time of the water absorbent and water retainer prepared in Example 6 can reach 25 days after absorbing deionized water, 23 days after absorbing tap water, and the water retention rate can reach 19 days after absorbing 0.9 wt.% NaCl solution.

[0107] It can be seen from Figure 9 that when the water absorbent and water retainer prepared in Example 6 is subjected to repeated water absorption tests, even when the number of repeated water absorption times reaches 10 times, the water absorption rate can still remain above 60%.

[0108] The results of the examples show that the polymer composite porous water absorbent material prepared by the preparation method provided by the present invention has a water absorption ratio of 26.68 g / g for deionized water, 17.87 g / g for tap water, and 13.56 g / g for 0.9 wt.% NaCl solution; the water retention time can reach 25 days after absorbing deionized water, 23 days after absorbing tap water, and the water retention rate can reach 19 days after absorbing 0.9% NaCl solution. And due to the complete three-dimensional space network in the water absorbent and water retainer material, the pores are more abundant. At the same time, due to the addition of the foaming agent, the specific surface area of the water absorbent and water retainer is further increased, thereby further improving the water absorption and water retention properties of the water absorbent and water retainer material, so that the polymer composite porous water absorbent material has a slow release function for various fertilizers such as nitrogen, phosphorus, and potassium.

[0109] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a polymer composite porous water-absorbing material, characterized in that It includes the following steps: Step 1: Place the formaldehyde solution in a reaction kettle equipped with a condenser, a stirring paddle and a thermometer, adjust the temperature to 50 °C, adjust the pH value to 8.5 with sodium hydroxide, add the first batch of urea to the reaction kettle, so that the molar ratio of formaldehyde to urea is 2.1, and react for 30 minutes; Step 2: Add the second batch of urea to the reaction solution obtained in Step 1, adjust the molar ratio of formaldehyde to the total amount of urea added in two batches to 1.6, raise the temperature to 90 °C, and react for 40 minutes; Step 3: Adjust the pH of the reaction solution obtained in Step 2 to 5.0 with phosphoric acid. When the viscosity of the reaction solution reaches 0.25 - 0.40 Pa·s, adjust the pH value to 8.5 with sodium hydroxide, lower the temperature to 60 °C, then add the third batch of urea, and adjust the final molar ratio of formaldehyde to urea to 1.4, and react for 10 minutes to obtain a water-soluble urea-formaldehyde resin prepolymer; Step 4: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of urea and sodium hydroxide and stir evenly, add a certain amount of chitin powder and disperse it in the reaction solution, pre-cool to -18 °C, freeze for 48 hours, thaw to obtain a clear and transparent aqueous solution, add a certain amount of sodium chloroacetate, maintain the reaction solution at 15 °C, and react for 24 hours to obtain a modified chitin suspension; Step 5: Add a certain amount of ethylene glycol and deionized water to a high-pressure reaction kettle, add a certain amount of corn straw powder and a certain amount of phosphoric acid catalyst and mix evenly. Under nitrogen protection, raise the temperature of the reaction solution to 170 °C, then react for 60 minutes, cool to obtain a straw liquefaction mixture, and then add and mix the chitin suspension obtained in Step 4 and the water-soluble urea-formaldehyde resin prepolymer obtained in Step 3 in sequence and mix evenly. After mixing evenly, add a certain amount of silicone resin polyether emulsion and mix evenly; Step 6: Pour a certain amount of deionized water into a high-speed stirrer, add a certain amount of superabsorbent resin powder, and stir at high speed evenly to make the superabsorbent resin powder evenly dispersed in deionized water, and then add the reaction solution obtained in Step 5 and mix evenly; Step 7: Pour a certain amount of deionized water into the reaction kettle, add a certain amount of polyvinyl alcohol with the model 17 - 99, raise the temperature to 90 °C. When the polyvinyl alcohol is dissolved, add a certain amount of hydrochloric acid solution, adjust the pH value of the reaction solution to 2, add an aqueous formaldehyde solution under stirring conditions, raise the temperature to 95 °C. When water separation appears in the reaction solution, immediately add an aqueous sodium hydroxide solution to adjust the pH value of the reaction solution to 7, and stir at high speed finally to obtain a polyvinyl formal solution, and then add the polyvinyl formal solution to the mixture in Step 6 and mix evenly; Step 8: Pour a certain amount of deionized water into a high-speed stirrer, add a certain amount of foaming agent, and stir at high speed evenly until the foam in the mixture no longer increases, and then add it to the mixture obtained in Step 7 and mix evenly; Step 9: Mix the mixture obtained in Step 8 evenly with a certain amount of phosphoric acid, and adjust the pH value of the mixture to 5; Step 10: Stir the liquid obtained in Step 9 and dry it at a certain temperature to obtain a foam water-absorbing material.

2. The preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, The formaldehyde content of the formaldehyde solution in Step 1 is 37%.

3. The preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, The suspension in the fourth step contains the following raw material components in parts by mass: 85 parts of water, 4 parts of urea, 11 parts of sodium hydroxide, 4 parts of chitin powder, and 2.5 parts of sodium chloroacetate.

4. The preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, In the fifth step, the ratio of ethylene glycol to water in the ethylene glycol aqueous solution is 3:1, the mass ratio of the ethylene glycol aqueous solution to the straw powder is 2:1, and the mass percentage of the phosphoric acid catalyst to the ethylene glycol aqueous solution is 1:

10. When mixing, the mixture contains the following raw material components in parts by mass: 10 - 20 parts of straw liquefied mixture, 11 - 22 parts of the modified chitin suspension prepared in the fourth step, 25 - 35 parts of the water-soluble urea-formaldehyde resin prepolymer prepared in the third step, and 2.5 parts of silicone resin polyether emulsion.

5. The preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, In the sixth step, the superabsorbent resin is a starch-acrylamide type superabsorbent resin, and the mass percentage of the superabsorbent resin aqueous dispersion is 0.25%.

6. The preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, In the seventh step, the solid content of the polyvinyl alcohol aqueous solution is 10%, and the content of formaldehyde is 2.5%.

7. A method for preparing a polymer composite porous water-absorbing material according to claim 1, characterized in that, In the eighth step, the foaming agent is an animal protein foaming agent, and the mass percentage of the foaming agent aqueous solution is 3%.

8. A preparation method of a polymer composite porous water-absorbing material according to claim 1, characterized in that, In the ninth step, the concentration of phosphoric acid is 2 mol / L.

9. The preparation method of a polymer composite porous water-absorbing material according to claim 1, wherein, In the tenth step, the drying temperature is 40 - 45 °C, and the drying time is 20 - 30 h.

10. A polymer composite porous water-absorbing material, characterized in that, The preparation is carried out using the preparation method described in any one of claims 1 - 9.

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