Non-ionic polymer and application thereof in soil improvement

Abstract

The invention provides a nonionic polymer and application thereof in soil improvement, and belongs to the technical field of soil improvement. The preparation method comprises the following steps: controlling reaction conditions, taking an acrylamide monomer as a raw material, and taking a mixture of polyethylene glycol and sodium tripolyphosphate as a dispersing agent, so as to prepare the nonionic polyacrylamide. The non-ionic polyacrylamide prepared by the method provided by the invention is relatively thorough in reaction, few acrylamide monomers are remained in the product, and the obtained colloid product has the characteristics of high intrinsic viscosity and low apparent viscosity; when the polymer is applied to a soil conditioner, the water content and the water retention rate of soil can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of soil improvement, and in particular relates to a nonionic polymer and an application thereof in soil improvement. Background Art

[0002] With the continuous development of society, soil resources are seriously insufficient, and due to some unreasonable utilization, such as large-scale unreasonable application of fertilizers, excessive spraying of pesticides, over-grazing, etc., the soil has been seriously degraded. The main manifestations are soil compaction and hardening, erosion, salinization, acidification, element imbalance, chemical pollution, organic matter loss and degradation of flora and fauna. The result of soil degradation is reduced soil productivity, reduced crop quality, and even enrichment of toxic elements. Therefore, how to maintain soil quality, improve acid-base soil, eliminate soil toxicity, and reduce the spread of soil-borne diseases has become the focus of people's attention.

[0003] The application of soil conditioners is one of the important measures to repair degraded soil. Soil conditioners can effectively improve the physical and chemical properties of soil and soil nutrient status, and have a positive effect on soil microorganisms, thereby improving the productivity of degraded soil. Soil properties include soil results, soil water content, soil temperature, soil enzyme activity, soil microbial population, soil aeration conditions, soil solution concentration, and soil hydrogen ion concentration. Different types of soil conditioners have different mechanisms of action on the soil, but they all effectively improve the physical structure of the soil, reduce soil bulk density, increase soil water content, change soil chemical properties, increase soil microbial activity, increase enzyme activity, increase soil trace element content, and adjust some or all of the soil water, fertilizer, air, and heat conditions to ultimately achieve the purpose of improving soil fertility.

[0004] Soil conditioners can be divided into natural conditioners, artificial synthetic conditioners, natural-synthetic copolymer conditioners and biological conditioners according to the source of raw materials.

[0005] Chinese patent CN117624465A discloses a preparation method and application of a soil conditioner, wherein triphenylsulfonate-based acrylamide is used as a functional monomer, and a bisallyl crosslinking agent is used as a novel crosslinking agent, and crosslinking polymerization is performed with acrylamide to obtain a soil conditioner containing hydrophilic sulfonate, quaternary ammonium salt, hydroxyl, and ether bond, which significantly improves the water absorption rate of the soil conditioner, and contains a salt-resistant sulfonate structure, so that the soil conditioner has good salt resistance and salt water absorption rate, and can be well applied to water absorption and water retention and improvement of inorganic salt-containing soil. The sulfonate anions contained in the soil conditioner interact electrostatically with the quaternary ammonium salt cations, forming a crosslinked network with a stable structure in the soil conditioner, making it difficult for water to flow out, so that the soil conditioner exhibits good soil water retention performance.

[0006] Chinese patent CN 115772267A discloses a soil conditioner and its preparation method. The raw materials for preparing the soil conditioner include SL, PVA, and quaternary ammonium salt. First, the amphoteric monomer ASL is synthesized by graft copolymerization of SL and quaternary ammonium salt; then ASL and PVA are cross-linked to prepare ASL / PVA copolymer emulsion. This invention uses lignin sulfonate as a raw material, and then amination modification is carried out and then cross-linked copolymerized with polyvinyl alcohol to prepare a zwitterionic emulsion, synthesizing a new type of soil conditioner, which can improve the soil's wind erosion resistance, water retention and salt resistance, has a certain protective effect on plant growth, and can improve the physical and chemical properties and nutrients of sandy high-salt soil. It is environmentally friendly and degradable, has a long action time and is more resistant to degradation.

[0007] However, the existing soil conditioners have little effect on the adsorption and release of fertilizers in the soil, and the increase in soil moisture content. Therefore, it is necessary to develop a non-ionic polymer that can effectively adsorb and release fertilizers and increase soil moisture content, and its application in soil improvement. Summary of the invention

[0008] Based on the deficiencies in the prior art, the present invention aims to provide a nonionic polymer, which is a nonionic polyacrylamide. The present invention controls the reaction conditions, uses acrylamide monomer as a raw material, and uses a mixture of polyethylene glycol and sodium tripolyphosphate as a dispersant to prepare a nonionic polyacrylamide. The nonionic polyacrylamide prepared by the method provided in the present invention reacts more thoroughly, and less residual acrylamide monomer is contained in the product. The obtained colloidal product has the characteristics of high intrinsic viscosity and low apparent viscosity. The use of the polymer in a soil conditioner can improve the soil moisture content and water retention rate.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A nonionic polymer, wherein the nonionic polymer is nonionic polyacrylamide.

[0011] Prepared as follows:

[0012] (1) Mixing monomers, dispersants and water, adjusting the pH value to 6-7, stirring and dissolving under nitrogen protection to obtain a polymerization reaction solution;

[0013] (2) adding an initiator to the polymerization reaction solution under nitrogen protection, and continuing the reaction until completion to obtain a colloidal product;

[0014] (3) The colloidal product is cut into granules, dried, ground and pulverized to obtain the nonionic polyacrylamide.

[0015] The monomer described in step (1) is acrylamide.

[0016] The dispersant described in step (1) is a mixture of polyethylene glycol and sodium tripolyphosphate;

[0017] Preferably, the dispersant is a mixture of polyethylene glycol 400 and sodium tripolyphosphate;

[0018] More preferably, the mass ratio of polyethylene glycol 400 to sodium tripolyphosphate is 3-5:1; preferably 4:1.

[0019] In the polymerization reaction liquid system, the mass fraction of the monomer is 18-22%, preferably 19-21%, and more preferably 20%.

[0020] In the polymerization reaction liquid system, the mass fraction of the dispersant is 15-20%, preferably 16-18%, and more preferably 18%.

[0021] The pH value was adjusted with potassium dihydrogen phosphate-sodium hydroxide buffer solution.

[0022] The initiator described in step (2) is a redox initiation system composed of ammonium persulfate and sodium bisulfite.

[0023] In the polymerization reaction liquid system, the mass fraction of the initiator is 0.05-0.10%, preferably 0.06-0.08%, and more preferably 0.07%.

[0024] In the polymerization reaction liquid system, the reaction temperature is 25-35°C, preferably 32°C.

[0025] In the polymerization reaction liquid system, the reaction time is 4-8 hours, preferably 5-7 hours, and more preferably 6 hours.

[0026] The intrinsic viscosity of the nonionic polyacrylamide prepared by the above method is 100-150mL·g -1 ; The apparent viscosity is 200-300mPa·s.

[0027] The present invention also provides the use of the nonionic polymer in preparing a soil conditioner.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention makes the reaction more thorough by reasonably controlling the reaction temperature and time, as well as the addition amount of various raw materials. The reaction conversion rate is relatively high, the residual acrylamide monomer in the product is less, and the obtained product has high stability.

[0030] (2) During the implementation of the present invention, it was unexpectedly found that the use of a mixture of polyethylene glycol 400 and sodium tripolyphosphate as a dispersant can make the obtained colloidal product have the characteristics of high intrinsic viscosity and low apparent viscosity, and is suitable for use as a soil conditioner;

[0031] (3) The nonionic polyacrylamide of the present invention is prepared into a soil conditioner to increase the soil moisture content and water retention rate. DETAILED DESCRIPTION

[0032] Example 1 A method for preparing a nonionic polymer

[0033] The nonionic polymer is nonionic polyacrylamide.

[0034] Prepared as follows:

[0035] (1) 18% acrylamide, 15% dispersant and water are mixed, the pH value is adjusted to 6, and the mixture is stirred and dissolved under nitrogen protection to obtain a polymerization reaction liquid;

[0036] (2) adding 0.05% ammonium persulfate and sodium bisulfite to the polymerization reaction solution under nitrogen protection, and continuing the reaction at 25° C. for 8 hours to obtain a colloidal product;

[0037] (3) The colloidal product is cut into granules, dried, ground and pulverized to obtain the nonionic polyacrylamide.

[0038] The dispersant is a mixture of polyethylene glycol 400 and sodium tripolyphosphate; the mass ratio is 3:1.

[0039] Example 2 A method for preparing a nonionic polymer

[0040] The nonionic polymer is nonionic polyacrylamide.

[0041] Prepared as follows:

[0042] (1) 22% acrylamide, 20% dispersant and water are mixed, the pH value is adjusted to 7, and the mixture is stirred and dissolved under nitrogen protection to obtain a polymerization reaction liquid;

[0043] (2) adding 0.1% ammonium persulfate and sodium bisulfite to the polymerization reaction solution under nitrogen protection, and continuing the reaction at 35° C. for 5 h to obtain a colloidal product;

[0044] (3) The colloidal product is cut into granules, dried, ground and pulverized to obtain the nonionic polyacrylamide.

[0045] The dispersant is a mixture of polyethylene glycol 400 and sodium tripolyphosphate; the mass ratio is 5:1.

[0046] Example 3 A method for preparing a nonionic polymer

[0047] The nonionic polymer is nonionic polyacrylamide.

[0048] Prepared as follows:

[0049] (1) 20% acrylamide, 18% dispersant and water are mixed, the pH value is adjusted to 6.5, and the mixture is stirred and dissolved under nitrogen protection to obtain a polymerization reaction liquid;

[0050] (2) adding 0.07% ammonium persulfate and sodium bisulfite to the polymerization reaction solution under nitrogen protection, and continuing the reaction at 32° C. for 6 hours to obtain a colloidal product;

[0051] (3) The colloidal product is cut into granules, dried, ground and pulverized to obtain the nonionic polyacrylamide.

[0052] The dispersant is a mixture of polyethylene glycol 400 and sodium tripolyphosphate; the mass ratio is 4:1.

[0053] Comparative Example 1

[0054] The difference from Example 3 is that the dispersant is only polyethylene glycol 400, and the rest is the same as Example 3.

[0055] Comparative Example 2

[0056] The difference from Example 3 is that the dispersant is only sodium tripolyphosphate, and the rest is the same as Example 3.

[0057] Comparative Example 3

[0058] The difference from Example 3 is that the mass ratio of polyethylene glycol 400 to sodium tripolyphosphate is 2:1, and the rest is the same as Example 3.

[0059] Performance Test:

[0060] 1. Viscosity and molecular weight test

[0061] The colloidal products obtained in step (2) of the above Examples 1-3 and Comparative Examples 1-2 were subjected to viscosity testing.

[0062] Determination of intrinsic viscosity: at 30°C, use a non-dilution Ubbelohde viscometer in accordance with GB12005.1-89.

[0063] Apparent viscosity: Use NDJ-52 rotational viscometer at 25℃.

[0064] Molecular weight: Measured by dilute solution viscosity method.

[0065] The test results are shown in Table 1 below.

[0066] Table 1

[0067] <![CDATA[Intrinsic viscosity [η] / (mL·g -1 )]]> Apparent viscosity / (mPa·s) Molecular weight Example 1 100 225 <![CDATA[1820×10 4 ]]> Example 2 138 233 <![CDATA[1940×10 4 ]]> Example 3 146 242 <![CDATA[2080×10 4 ]]> Comparative Example 1 82 174 <![CDATA[1570×10 4 ]]> Comparative Example 2 - - - Comparative Example 3 95 152 <![CDATA[1650×10 4 ]]>

[0068] Note: “-” indicates that no relevant test was performed.

[0069] According to the test results in Table 1 above, the intrinsic viscosity of the polyacrylamide prepared by the present invention is 100-150 mL·g -1 , the apparent viscosity is 200-300mPa·s. In Comparative Example 1, only polyethylene glycol is used, and the intrinsic viscosity and apparent viscosity of the obtained polyacrylamide are significantly reduced, which is not conducive to its use in soil conditioners; in Comparative Example 2, only sodium tripolyphosphate is used as a dispersant, and a uniform and stable emulsion cannot be obtained, so no subsequent detection is performed; in Comparative Example 3, changing the mass ratio of polyethylene glycol 400 and sodium tripolyphosphate will also affect the formation of the final product, and the intrinsic viscosity and apparent viscosity of the obtained product, as well as the molecular weight, are reduced to a certain extent, and according to the molecular weight test results, it can be seen that the molecular weight of the polyacrylamide prepared by the present invention is moderately between 18 million and 20 million, which can better adsorb and release fertilizers and increase soil water content.

[0070] 2. Detection of residual acrylamide monomer content

[0071] The detection was carried out according to the method described in the prior art "Detection of residual acrylamide monomer in hydrophobic polymer by high performance liquid chromatography". The detection results are shown in Table 2 below.

[0072] Table 2

[0073]

[0074]

[0075] Note: “-” indicates that no relevant test was performed.

[0076] According to the test results in Table 2 above, the residual acrylamide monomer content in the polyacrylamide prepared by the present invention is less than 0.05%, indicating that the product conversion rate of the preparation method provided by the present invention is high and the content of each raw material is appropriate. In Comparative Example 1, only polyethylene glycol was used, and the residual acrylamide monomer content in the obtained polyacrylamide was 0.08%, indicating that the reaction was not thorough; in Comparative Example 2, only sodium tripolyphosphate was used as a dispersant to fail to obtain a uniform and stable emulsion, so no subsequent testing was performed; in Comparative Example 3, changing the mass ratio of polyethylene glycol 400 and sodium tripolyphosphate also affects the formation of the final product, and the residual acrylamide monomer content of the obtained product increases to a certain extent.

[0077] 3. Water absorption and water retention rate testing

[0078] 3.1. Dry and weigh the prepared polyacrylamide sample, recorded as m, soak it in water for 24 hours, take it out and use filter paper to absorb the residual moisture on the surface, weigh it and record it as m1, and calculate the water absorption rate Q, Q = (m1-m) / m.

[0079] 3.2. Add the prepared polyacrylamide sample into water to prepare a polyacrylamide solution with a mass fraction of 2%. Dry the natural soil, grind and sieve it, and weigh it, recorded as m1. Mix the polyacrylamide solution at a concentration of 2 kg / m 2 The amount of polyacrylamide solution was sprayed on the soil surface, and the mass of water in the polyacrylamide solution was recorded as m2. It was left to stand for 7 days. The experimental temperature was 25℃ and the relative humidity was 65%. Then the total mass of the soil was measured, m3. The soil water retention rate W was calculated, W = (m4 / m2) × 100%, where m4 is the weight of the remaining water in the soil, m4 = m3-m1.

[0080] The test results are shown in Table 3 below.

[0081] Table 3

[0082] Water absorption % Water retention rate% Example 1 984.6％ 75.2％ Example 2 975.8％ 80.6％ Example 3 995.3％ 89.4％ Comparative Example 1 642.7％ 69.7％ Comparative Example 3 713.7％ 70.4％

[0083] According to the test results in Table 3 above, the polyacrylamide prepared by the present invention has better water retention and water absorption, the water absorption rate can reach more than 950%, and the water retention rate can reach more than 75%; while in Comparative Example 1, the dispersant only uses polyethylene glycol 400, and the water absorption rate and water retention rate of the obtained polyacrylamide are significantly reduced. In Comparative Example 3, the mass ratio of polyethylene glycol 400 and sodium tripolyphosphate is changed, and the water absorption rate and water retention rate of the obtained polyacrylamide are reduced to a certain extent compared with the embodiment.

[0084] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered as the protection scope of the present invention.

Claims

1. A nonionic polymer, characterized in that: The nonionic polymer is nonionic polyacrylamide; The nonionic polyacrylamide is prepared according to the following method: (1) Mixing monomers, dispersants and water, adjusting the pH value to 6-7, stirring and dissolving under nitrogen protection to obtain a polymerization reaction solution; (2) adding an initiator to the polymerization reaction solution under nitrogen protection, and continuing the reaction until completion to obtain a colloidal product; (3) cutting the colloidal product into granules, drying, grinding and pulverizing to obtain the nonionic polyacrylamide; The dispersant described in step (1) is a mixture of polyethylene glycol and sodium tripolyphosphate.

2. The nonionic polymer according to claim 1, characterized in that: The dispersant is a mixture of polyethylene glycol 400 and sodium tripolyphosphate.

3. The nonionic polymer according to claim 1, characterized in that: The mass ratio of polyethylene glycol 400 to sodium tripolyphosphate is 3-5:

1.

4. The nonionic polymer according to claim 5, characterized in that: The mass ratio of polyethylene glycol 400 to sodium tripolyphosphate is 4:

1.

5. The nonionic polymer according to claim 1, characterized in that: In the polymerization reaction liquid system, the mass fraction of the monomer is 18-22%.

6. The nonionic polymer according to claim 1, characterized in that: In the polymerization reaction liquid system, the mass fraction of the dispersant is 15-20%.

7. The nonionic polymer according to claim 1, characterized in that: The initiator in step (2) is a redox initiation system composed of ammonium persulfate and sodium bisulfite; in the polymerization reaction liquid system, the mass fraction of the initiator is 0.05-0.10%.

8. The nonionic polymer according to claim 1, characterized in that: In the polymerization reaction liquid system, the reaction temperature is 25-35° C.; the reaction time is 4-8 hours.

9. The nonionic polymer according to claim 1, characterized in that: The intrinsic viscosity of the nonionic polyacrylamide is 100-150 mL·g -1 ; The apparent viscosity is 200-300mPa·s.

10. Use of the nonionic polymer according to any one of claims 1 to 9 in the preparation of a soil conditioner.

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