Water-retaining and growth-promoting coated material suitable for obstacle soil and preparation method thereof

Abstract

The application discloses a water-retaining and growth-promoting type coated material suitable for obstacle soil and a preparation method thereof, and belongs to the technical field of fertilizers.The application takes polyaspartic acid as a core, and through water system synthesis technology (avoiding the use of organic solvents), the polyaspartic acid is compounded with carboxymethyl chitosan to construct a novel water-retaining and growth-promoting type material.The water-retaining and growth-promoting type coated material suitable for obstacle soil can still maintain high water absorption capacity in a high-temperature saline-alkali environment (60 DEG C, pH = 8.0), has no biological toxicity to crops, and has a soil degradation rate of 41.25% in 60 days, which can match the growth period of crops.Meanwhile, the combination of the water-retaining material and the fertilizer is realized through the coated material technology, and a water and fertilizer synergistic slow-release system is formed.Not only the problems of single performance and non-environmental protection in synthesis of traditional water-retaining materials are solved, but also the adaptability of the water-retaining and growth-promoting type coated material in a saline-alkali environment is verified through experiments, and an efficient and green solution is provided for soil improvement and agricultural sustainable development in arid and semi-arid areas.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fertilizers, and particularly relates to a water-retaining and growth-promoting type coating material suitable for obstacle soil and a preparation method thereof. BACKGROUND

[0002] Traditional water-retaining materials (such as polyacrylate) generally have problems such as single function, high environmental risk, and dependence on organic solvents in the synthesis process. For example, some materials have weak salt and alkali resistance, and their water absorption performance significantly decreases in saline soil; some materials are difficult to degrade, and long-term residual may easily destroy the soil microenvironment. Therefore, it is urgent to develop new water-retaining materials that have high water absorption performance, environmental friendliness, and multi-effect synergistic function.

[0003] Polyaspartic acid (PASP) as a natural source of polyamino acid water-retaining agent has been widely concerned due to its biodegradability, excellent water absorption capacity and plant growth promotion. Studies have shown that PASP can indirectly promote crop growth by regulating soil enzyme activity and nutrient release, for example, it can significantly increase the content of soil available phosphorus and ammonium nitrogen in cotton planting. However, PASP still has obvious limitations in practical application: first, its gel network strength is low, and its repeated water absorption capacity is insufficient, and its water retention performance decreases after long-term use; second, in saline-alkali environment, the water absorption rate of PASP decreases significantly; third, the traditional synthesis process often relies on organic solvents, which poses a risk of environmental pollution. These problems limit its large-scale application in arid and saline-alkali areas.

[0004] In view of the above problems, existing researches often enhance the performance by chemical modification or compounding with other polymer materials. For example, the introduction of polyacrylamide can improve the mechanical strength of the material, but often at the expense of environmental friendliness; some crosslinking strategies can improve salt tolerance, but complicate the synthesis process. In addition, existing water-retaining materials rarely have water-retaining, growth-promoting and slow-release functions, and there is a lack of systematic design for green synthesis process. SUMMARY

[0005] To solve the above technical problems, the application provides a water-retaining and growth-promoting type coating material suitable for obstacle soil and a preparation method thereof.

[0006] To achieve the above purpose, the application provides the following technical solutions.

[0007] One of the technical solutions of the application is as follows:

[0008] The application provides a water-retaining and growth-promoting type coating material suitable for obstacle soil, which is composed of a water-retaining and growth-promoting coating material, a coating liquid and a core material.

[0009] The water-retention and growth-promotion coating material is composed of the following raw materials in mass parts: 10-30 parts of a first organic polymer material, 6-24 parts of a second organic polymer material, 5-15 parts of a first crosslinking agent, 0.1-2.5 parts of a second crosslinking agent, and 1000-1500 parts of water, wherein the first organic polymer material is modified polyaspartic acid; and / or the second organic polymer material is carboxymethyl chitosan (molecular weight: 543.519 g / mol);

[0010] The coating liquid is composed of the following raw materials in mass parts: 80-120 parts of a water-soluble polymer and 1000-1500 parts of water;

[0011] The core material is selected from one of urea, ammonium chloride, ammonium sulfate, and compound fertilizer.

[0012] In the present application, the core material is selected from one of urea, ammonium chloride, ammonium sulfate, and compound fertilizer, which can provide precise water-retention and growth-promotion functions for different crops. For example, urea has a high nitrogen content (46%) and slow but long-lasting fertilizer effect, which is suitable for crops that need long-term nitrogen supply (such as corn and wheat); it is also suitable for alkaline soil improvement (neutralizing acidity). Ammonium chloride has a nitrogen content of about 25%, which belongs to quick-acting fertilizer and can release acidic substances, which is suitable for crops that like ammonium (such as rice and tobacco); it is also suitable for scenarios that require a decrease in soil pH value. Ammonium sulfate has a nitrogen content of about 21% and contains sulfur, with moderate fertilizer effect and long-lasting effect, which is suitable for crops that need sulfur supplementation (such as cruciferous plants); it is also suitable for acid soil improvement (providing sulfate).

[0013] Further, the mass ratio of the water-retention and growth-promotion coating material, the coating liquid, and the core material is (1.0-1.5):1:10, preferably 1.3:1:10.

[0014] Further, the preparation method of the water-retention and growth-promotion coating material comprises the following steps:

[0015] The first organic polymer material, the second organic polymer material, the first crosslinking agent, the second crosslinking agent, and water are accurately weighed in mass parts;

[0016] The first organic polymer material is dispersed in 250-500 parts of water in mass parts, and stirred until completely dissolved to obtain solution A1;

[0017] The second organic polymer material is dispersed in 750-1000 parts of water in mass parts, and stirred until completely dissolved to obtain solution A2;

[0018] The solution A1 is added dropwise into the solution A2 to obtain solution B;

[0019] adding the first crosslinking agent and the second crosslinking agent into the solution B, reacting at 35℃ for 2-4 hours to obtain a solution C;

[0020] adding anhydrous ethanol into the solution C, performing extraction and washing, and after drying and crushing, the water-retention and growth-promotion coated material is obtained.

[0021] Further,

[0022] The first crosslinking agent is a calcium chloride aqueous solution.

[0023] And / or, the second crosslinking agent is a glutaraldehyde aqueous solution.

[0024] Further, the concentration of the calcium chloride aqueous solution is 1wt%; and the concentration of the glutaraldehyde aqueous solution is 25wt%.

[0025] Further, the preparation method of the modified polyaspartic acid is as follows: mixing maleic anhydride and urea, adding water, reacting at 50℃ for 1 hour, and then polymerizing at 180℃ for 1 hour to obtain poly-succinimide; mixing high-molecular-weight organic amine and maleic anhydride, grinding, adding Ca(OH)2 and continuing to grind, adding water, and stirring uniformly to obtain a modifier; finally, dissolving the poly-succinimide in water, adding the modifier, and reacting at 30℃ for 10 hours to obtain the modified polyaspartic acid.

[0026] Further, in the preparation method of the modified polyaspartic acid, the mass ratio of the maleic anhydride to the urea is 1:1.1.

[0027] And / or, the mass ratio of the high-molecular-weight organic amine to the poly-succinimide is 1:1.

[0028] And / or, the high-molecular-weight organic amine is selected from ethylenediamine, propylenediamine, butylenediamine, pentanediamine or hexanediamine, preferably ethylenediamine.

[0029] Further, the preparation method of the coating liquid comprises the following steps:

[0030] Accurately weighing the water-soluble polymer and water according to the mass fraction;

[0031] Dispersing the water-soluble polymer in water, heating in a water bath to 90-100℃, and magnetically stirring until uniform to obtain the coating liquid.

[0032] Further, the water-soluble polymer is polyvinyl alcohol.

[0033] The present application constructs an amphiphilic water network skeleton by electrostatic-hydrogen bond assembly of modified polyaspartic acid and carboxymethyl chitosan; further utilizes Ca 2+The synergistic effect of ion cross-linking and glutaraldehyde covalent cross-linking forms a "rigidity-toughness" complementary structure, which resists charge shielding and improves water absorption space at high temperatures due to network relaxation. - / -N + R4) against charge shielding, and the polyvinyl alcohol adhesive layer anchors the coated powder through hydrogen bonds to achieve slow-release and water-retention linkage. The present application solves the contradiction between traditional materials, i.e., "resistant to salt but difficult to degrade, and water-retaining but lack of growth promotion". The water-retaining and growth-promoting coated material of the present application can realize the synergistic effect of water and fertilizer in saline-alkali / high-temperature areas.

[0034] The second technical solution of the present application is:

[0035] The present application also provides a preparation method of the above-mentioned water-retaining and growth-promoting coated material suitable for obstacle soil, comprising the following steps: placing the core material in a coating machine, preheating at 50-60 DEG C, spraying the coating liquid as the adhesive layer, and forming a uniform base (wet core material) by using its adhesion; then spraying the water-retaining coated material powder to the surface of the wet core material by using a powder gun, and realizing stable coating of the powder after curing of the adhesive to obtain the water-retaining and growth-promoting coated material suitable for obstacle soil.

[0036] Further, before placing the core material in the coating machine, the core material is pretreated: screening the core material particles to remove powder and impurities, and ensuring uniformity of the core material particles.

[0037] The third technical solution of the present application is:

[0038] The present application also provides the application of the above-mentioned water-retaining and growth-promoting coated material suitable for obstacle soil in water-retaining and growth-promoting of crops in obstacle soil.

[0039] For example, the obstacle soil is the soil in arid regions, semi-arid regions, high-temperature regions and saline-alkali land.

[0040] Compared with the prior art, the present application has the following advantages and technical effects:

[0041] The application takes polyaspartic acid as the core, and through water system synthesis technology (avoiding the use of organic solvents), the polyaspartic acid is compounded with carboxymethyl chitosan to construct a new water-retaining and growth-promoting material. Experiments show that the water-retaining and growth-promoting coated material suitable for obstacle soil can still maintain high water absorption capacity in a high-temperature saline-alkali environment (60 DEG C, pH = 8.0), and has no biological toxicity to crops, and the soil degradation rate is 41.25% in 60 days, which can match the growth period of crops. At the same time, the combination of water-retaining material and fertilizer is realized through the coated material technology to form a water and fertilizer synergistic slow-release system. This innovation not only solves the problem of single performance and non-environmental synthesis of traditional water-retaining materials, but also verifies its adaptability in saline-alkali environment through experiments, and provides an efficient and green solution for soil improvement and sustainable development of agriculture in arid and semi-arid areas. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application is not limited by the accompanying drawings. In the drawings:

[0043] Figure 1 The scanning electron microscope images of the modified polyaspartic acid, carboxymethyl chitosan, water-retaining and growth-promoting coated material and water-retaining and growth-promoting coated material suitable for obstacle soil in Example 4, wherein a is the modified polyaspartic acid (the magnification is 5.00k), b is the carboxymethyl chitosan (the magnification is 5.00k), c is the water-retaining and growth-promoting coated material (the magnification is 5.00k), and d is the water-retaining and growth-promoting coated material suitable for obstacle soil (the magnification is 50);

[0044] Figure 2 The actual photos of urea and the water-retaining and growth-promoting coated material suitable for obstacle soil in Example 4 (water-retaining and growth-promoting coated urea) and their water absorption in water;

[0045] Figure 3 The water absorption rates of the water-retaining and growth-promoting coated material in Example 3 in different environments, (a) is the water absorption rate under different temperatures, (b) is the water absorption rate under different pH values, and different lowercase letters represent significant differences, P < 0.05;

[0046] Figure 4 The biological toxicity and degradation rate of urea and the water-retaining and growth-promoting coated material suitable for obstacle soil in Example 4, (a) is the influence on the seed germination rate, (b) is the degradation rate in soil, and different lowercase letters represent significant differences, P < 0.05. DETAILED DESCRIPTION

[0047] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be merely illustrative in nature and are not to be considered as limiting the scope of the present application, and are understood to be within the scope of the present application, with some aspects, features and embodiments of the present application being described in more detail.

[0048] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter is also specifically included within the scope of the present application. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is also encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed within the scope of the present application.

[0049] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the content of the present specification will control.

[0050] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0051] With respect to the use of "comprising", "including", "containing", "having" and "ensing" and the like, these terms are used in the inclusive sense, and specify the presence of stated features or integers but do not preclude the presence or addition of one or more other features or integers.

[0052] The embodiment of the present application provides a water-retaining and growth-promoting type coated material suitable for obstacle soil, which is composed of a water-retaining and growth-promoting type coated material, a coating liquid and a core material;

[0053] The water-retaining and growth-promoting type coated material is composed of the following raw materials in mass fraction: 10-30 parts of a first organic polymer material, 6-24 parts of a second organic polymer material, 5-15 parts of a first crosslinking agent, 0.1-2.5 parts of a second crosslinking agent and 1000-1500 parts of water, wherein the first organic polymer material is modified polyaspartic acid; and the second organic polymer material is carboxymethyl chitosan (molecular weight: 543.519 g / mol).

[0054] The coating liquid is composed of the following raw materials in mass fraction: 80-120 parts of a water-soluble polymer and 1000-1500 parts of water.

[0055] The core material is selected from one of urea, ammonium chloride, ammonium sulfate and compound fertilizer.

[0056] In the present application, the core material is selected from one of urea, ammonium chloride, ammonium sulfate and compound fertilizer, which can provide precise water-retaining and growth-promoting functions for different crops. For example, urea has high nitrogen content (46%), slow but long-lasting fertilizer effect, and is suitable for crops that need long-term nitrogen supply (such as corn and wheat); it is also suitable for alkaline soil improvement (neutralizing acidity). Ammonium chloride has a nitrogen content of about 25%, belongs to quick-acting fertilizer, can release acidic substances, and is suitable for crops that like ammonium (such as rice and tobacco); it is also suitable for scenarios that require a decrease in soil pH value. Ammonium sulfate has a nitrogen content of about 21%, contains sulfur, has moderate fertilizer effect and long-lasting effect, and is suitable for crops that need sulfur supplementation (such as cruciferous crops); it is also suitable for acid soil improvement (providing sulfate).

[0057] In an embodiment of the present application, the mass ratio of the water-retaining and growth-promoting coating material, the coating liquid and the core material is (1.0-1.5):1:10, preferably 1.3:1:10.

[0058] In an embodiment of the present application, the preparation method of the water-retaining and growth-promoting coating material comprises the following steps:

[0059] The first organic high molecular material, the second organic high molecular material, the first crosslinking agent, the second crosslinking agent and water are accurately weighed by mass fraction;

[0060] The first organic high molecular material is dispersed in 250-500 parts of water by mass fraction, and is magnetically stirred at 35±2℃ until completely dissolved to obtain solution A1;

[0061] The second organic high molecular material is dispersed in 750-1000 parts of water by mass fraction, and is magnetically stirred at 35±2℃ until completely dissolved to obtain solution A2;

[0062] Solution A1 is added dropwise into solution A2 to obtain solution B;

[0063] The first crosslinking agent and the second crosslinking agent are added into solution B, and reacted at 35℃ for 2-4 hours to obtain solution C;

[0064] Solution C is added into anhydrous ethanol for washing, and after drying (drying in a 50℃ oven until constant weight) and crushing, the water-retaining and growth-promoting coating material is obtained by passing through a 40-mesh sieve.

[0065] In an embodiment of the present application, the second crosslinking agent is a glutaraldehyde aqueous solution. Preferably, the concentration of the calcium chloride aqueous solution is 1wt%; the concentration of the glutaraldehyde aqueous solution is 25wt%.

[0066] In the embodiment of the present application, the preparation method of the modified polyaspartic acid is as follows: maleic anhydride and urea are mixed in a mass ratio of 1:1.1, 6 times the total mass of the two is added with distilled water, after reacting at 50 DEG C for 1 hour, poly succinimide is prepared by polymerizing at 180 DEG C for 1 hour; high molecular weight organic amine and maleic anhydride are mixed in a mass ratio of 1:1, and are ground for 0.5 hours, after adding 0.5 parts of Ca(OH)2 solid, continue to grind for 1 hour, finally add 11 parts of distilled water, and stir uniformly to obtain a modifier; finally, the poly succinimide is dissolved in 10 parts of distilled water, 1 part of the modifier is added, and the reaction is carried out at 30 DEG C for 10 hours to obtain the modified polyaspartic acid. The high molecular weight organic amine is selected from ethylenediamine, propylenediamine, butylenediamine, pentanediamine or hexanediamine, and is preferably ethylenediamine.

[0067] In the embodiment of the present application, the preparation method of the film coating liquid comprises the following steps:

[0068] The water-soluble polymer and water are accurately weighed according to the mass fraction;

[0069] The water-soluble polymer is dispersed in water, heated to 90-100 DEG C in a water bath, and magnetically stirred until uniform to obtain the film coating liquid.

[0070] In the embodiment of the present application, the water-soluble polymer is polyvinyl alcohol.

[0071] The present application constructs an amphiphilic water network skeleton by electrostatic-hydrogen bond assembly of modified polyaspartic acid and carboxymethyl chitosan; further utilizes the synergistic effect of Ca 2+ ion crosslinking and glutaraldehyde covalent crosslinking to form a "rigidity-toughness" complementary structure, which resists charge shielding through endogenous ion pairs (-COO - / -N + R4) in a saline-alkali environment, and improves water absorption space at high temperatures due to network relaxation. At the same time, the polyvinyl alcohol adhesive layer anchors the film coating powder through hydrogen bonds to realize slow release-water retention linkage. The present application solves the contradiction between traditional materials that "resist salt but are difficult to degrade, and retain water but lack of growth promotion", and the water-retention and growth-promoting type film coating material of the present application can realize the synergistic effect of water and fertilizer in saline-alkali / high temperature areas.

[0072] The embodiment of the present application also provides a preparation method of the above-mentioned water-retention and growth-promoting type film coating material suitable for obstacle soil, comprising the following steps: placing the core material in a coating machine, preheating at 50-60 DEG C, spraying the film coating liquid as an adhesive layer, and forming a uniform base (wet core material) by using its adhesion; then spraying the water-retention film coating material powder to the surface of the wet core material by using a powder gun, and realizing stable coating of the powder after curing with the aid of the adhesive to obtain the water-retention and growth-promoting type film coating material suitable for obstacle soil.

[0073] In the embodiments of the present application, the core material is pretreated before being placed in the coating machine: screening the core material particles, removing powder and impurities, and ensuring uniformity of the core material particles.

[0074] The water-retaining and growth-promoting film material suitable for barrier soil provided by the embodiments of the present application can be used in barrier soil to retain water and promote growth of crops.

[0075] Illustratively, the barrier soil is soil in arid regions, semi-arid regions, high-temperature regions, and saline-alkali land.

[0076] Unless otherwise specified, the room temperature in the present application is 25±2℃.

[0077] The raw materials used in the embodiments of the present application are all commercially available.

[0078] The "parts" used in the embodiments of the present application are "mass parts" unless otherwise specified.

[0079] It should be noted that the details not described in the present application are all conventional operating means in the art and are not the focus of the present application.

[0080] The technical solutions of the present application are further described below through examples.

[0081] To verify the water absorption rate of the water-retaining and growth-promoting film material, the following test was conducted:

[0082] Example 1

[0083] The present embodiment provides a preparation method of a water-retaining and growth-promoting film material, and the steps are as follows:

[0084] (1.1) 20 parts (mass parts, the same below) of modified polyaspartic acid were dispersed in 250 parts of deionized water, and magnetic stirring was performed at 35℃ until complete dissolution to prepare a modified polyaspartic acid solution (solution A1);

[0085] (1.2) 12 parts of carboxymethyl chitosan (molecular weight 543.519 g / mol) were dispersed in 750 parts of deionized water, and magnetic stirring was performed at 35℃ until complete dissolution to prepare a carboxymethyl chitosan solution (solution A2);

[0086] (1.3) Solution A1 was added dropwise into solution A2, and mixed uniformly to prepare a mixed solution (solution B);

[0087] (1.4) 10 parts of 1wt% calcium chloride aqueous solution and 2 parts of 25wt% glutaraldehyde aqueous solution were sequentially added into solution B, and reacted in a 35℃ water bath for 4h to form a gel-like solution (solution C);

[0088] (1.5) The solution C is added to anhydrous ethanol for washing, dried in an oven at 50℃ to constant weight, and then crushed and sieved through a 40-mesh screen to obtain the water-retaining and growth-promoting type coated material 1.

[0089] The preparation method of the modified polyaspartic acid is as follows: maleic anhydride and urea are mixed in a mass ratio of 1:1.1, 6 times the total mass of the two is added with distilled water, and then the mixture is reacted at 50℃ for 1 hour, and then polymerized at 180℃ for 1 hour to obtain poly-succinimide; ethylenediamine and poly-succinimide are mixed in a mass ratio of 1:1, and then ground for 0.5 hours, 0.5 parts of Ca(OH)2 solid is added and then ground for 1 hour, and finally 11 parts of distilled water is added and stirred uniformly to obtain a modifier; finally, the poly-succinimide is dissolved in 10 parts of distilled water, the modifier is added, and the mixture is reacted at 30℃ for 10 hours to obtain the modified polyaspartic acid.

[0090] Example 2

[0091] The present example provides a preparation method of a water-retaining and growth-promoting type coated material, which is the same as that of Example 1, except that the mass fraction of the 25wt% glutaraldehyde aqueous solution is 1 part, and the water-retaining and growth-promoting type coated material prepared in the present example is denoted as water-retaining and growth-promoting type coated material 2.

[0092] Example 3

[0093] The present example provides a preparation method of a water-retaining and growth-promoting type coated material, which is the same as that of Example 1, except that the mass fraction of the 25wt% glutaraldehyde aqueous solution is 0.8 parts, and the water-retaining and growth-promoting type coated material prepared in the present example is denoted as water-retaining and growth-promoting type coated material 3.

[0094] The water absorption performance of the water-retaining and growth-promoting type coated materials prepared in Examples 1-3 is tested, and the specific method is as follows:

[0095] 0.5g of the dried water-retaining and growth-promoting type coated material is accurately weighed and placed in a 300-mesh tea bag, which is then tied tightly and immersed in a beaker containing 500mL of distilled water. The immersion position is 1 / 4 away from the mouth of the beaker, and the tea bag should not be in contact with the container wall. The tea bag is taken out at regular intervals, the surface is wiped dry, and the weight is measured and calculated to obtain the water absorption ratio.

[0096] The water absorption ratio of the water-retaining and growth-promoting type coated material is calculated according to formula (1):

[0097]

[0098] In formula (1), Q represents the water absorption ratio of the coated material, g / g;

[0099] m1 represents the total mass after water absorption, g;

[0100] m0 represents the dry mass before water absorption, g.

[0101] The water absorption ratio of the water-retention and growth-promotion coated material prepared in Examples 1-3 is shown in Table 1.

[0102] Table 1

[0103] Water-retention and growth-promoting coated material Water absorption ratio (g / g) Water-retention and growth-promoting coated material 1 17.98±0.48b Water-retention and growth-promoting coated material 2 16.36±0.47c Water-retention and growth-promoting coated material 3 19.63±0.27a

[0104] Note: Different lowercase letters represent significant differences, P < 0.05.

[0105] As can be seen from Table 1, the amount of crosslinking agent added will significantly affect the water absorption performance of the water-retention and growth-promotion coated material. As shown in Table 1,

[0106] The water-retention and growth-promotion coated material synthesized in Example 3 has the largest water absorption ratio; the core reason for the significant improvement in water absorption ratio when the amount of 25wt% glutaraldehyde aqueous solution added is 0.8 parts is the precise control of crosslinking density, and the essence is the balance optimization of "swelling space" and "structural stability" in the material network structure.

[0107] Example 4

[0108] The present embodiment provides a water-retention and growth-promotion coated material suitable for barrier soil, which is composed of a water-retention and growth-promotion coated material, a coating liquid and a core material. In the present embodiment, the core material is urea; the preparation method of the water-retention and growth-promotion coated material is as follows:

[0109] (1) 20 parts (mass fraction, the same below) of modified polyaspartic acid was dispersed in 250 parts of deionized water, and stirred by magnetic force at 35°C until completely dissolved to prepare a modified polyaspartic acid solution, denoted as solution A1;

[0110] (2) 12 parts of carboxymethyl chitosan (molecular weight 543.519 g / mol) was dispersed in 750 parts of deionized water, and stirred by magnetic force at 35°C until completely dissolved to prepare a carboxymethyl chitosan solution, denoted as solution A2;

[0111] (3) Solution A1 was added dropwise into solution A2 and mixed uniformly to prepare a mixed solution, denoted as solution B;

[0112] (4) 10 parts of 1wt% calcium chloride aqueous solution and 0.8 parts of 25wt% glutaraldehyde aqueous solution were sequentially added into solution B, and reacted in a 35°C water bath for 4h to form a gel-like solution, denoted as solution C;

[0113] (5) Anhydrous ethanol was added to solution C for washing, and dried to constant weight in a 50°C oven, then crushed and sieved through a 40 mesh sieve to obtain a water-retention and growth-promotion coated material.

[0114] The above-mentioned modified polyaspartic acid is prepared as follows: maleic anhydride and urea are mixed at a mass ratio of 1:1.1, and distilled water with a mass ratio of 6 times the total mass of the two is added. After reacting at 50°C for 1 hour, the mixture is polymerized at 180°C for 1 hour to obtain polysuccinimide. Subsequently, ethylenediamine and maleic anhydride are mixed in a mortar at a mass ratio of 1:1 and ground for 0.5 hours. 0.5 parts of Ca(OH)2 solid are added and grinding is continued for 1 hour. Finally, 11 parts of distilled water are added and stirred evenly to obtain a transparent liquid, which is the modifier. Finally, the obtained polysuccinimide is dissolved in 10 parts of distilled water, the aforementioned modifier is added, and the mixture is reacted at 30°C for 10 hours to obtain modified polyaspartic acid.

[0115] The above coating solution is prepared by dispersing 100 parts of polyvinyl alcohol in 1200 parts of deionized water, heating it in a water bath to 98°C, and stirring it magnetically until dissolved to prepare the coating solution.

[0116] The preparation method of the above-mentioned water-retaining and growth-promoting coating material suitable for obstacle soil is as follows: First, urea particles are sieved to remove powder and impurities, ensuring uniform particle size; then, 10 parts of uniform urea particles are placed in a coating machine and preheated at 60°C for 15 minutes until the surface is smooth, and 1 part of atomized coating liquid is sprayed in as a bonding layer to form a uniform substrate using its adhesion; then, 1.5 parts of water-retaining and growth-promoting coating material are sprayed onto the moist urea surface through a powder spray gun, and the powder is stably coated after curing with the help of the bonding layer. After drying, the water-retaining and growth-promoting coating material suitable for obstacle soil is obtained.

[0117] Figure 1 The images shown are scanning electron microscope (SEM) images of the modified polyaspartic acid, carboxymethyl chitosan, water-retaining and growth-promoting coating material, and water-retaining and growth-promoting coating material suitable for obstacle soils in this embodiment. It can be seen that the water-retaining and growth-promoting coating material synthesized in this embodiment (which is a modified polyaspartic acid / carboxymethyl chitosan type water-retaining and growth-promoting coating material) has more irregular pore structures inside than the raw materials modified polyaspartic acid and carboxymethyl chitosan, which helps to absorb and retain more water molecules.

[0118] Figure 2 The images show actual urea and the water-retaining and growth-promoting coating material (water-retaining and growth-promoting coated urea) suitable for obstacle soils in this embodiment, as well as their water absorption in water. Figure 1 d and Figure 2 It can be seen that the outer surface of the coated urea has a relatively clear coating material powder layer. The coating layer is dense and adheres tightly to the urea surface. When placed in water, it forms a strong water-retaining coating layer, which greatly slows down the hydrolysis rate of the internal urea and helps to release nutrients slowly.

[0119] Example 5

[0120] The embodiment provides a water-retention and growth-promotion type coated material suitable for obstacle soil, raw materials and a preparation method are the same as those in Embodiment 4, and the only difference is that butanediamine is used to replace ethylenediamine in preparation of modified polyaspartic acid, so that the mass ratio of butanediamine to maleic anhydride is 1:1.

[0121] Embodiment 6

[0122] The embodiment provides a water-retention and growth-promotion type coated material suitable for obstacle soil, raw materials and a preparation method are the same as those in Embodiment 4, and the only difference is that butanediamine is used to replace ethylenediamine in preparation of modified polyaspartic acid, so that the mass ratio of butanediamine to maleic anhydride is 1:1.

[0123] Embodiment 7

[0124] The embodiment provides a water-retention and growth-promotion type coated material suitable for obstacle soil, raw materials and a preparation method are the same as those in Embodiment 4, and the only difference is that butanediamine is used to replace ethylenediamine in preparation of modified polyaspartic acid, so that the mass ratio of butanediamine to maleic anhydride is 1:1.

[0125] The preparation method of the water-retention and growth-promotion type coated material is as follows:

[0126] (1) 30 parts of modified polyaspartic acid are dispersed in 500 parts of deionized water, and magnetic stirring is carried out at 35 DEG C until complete dissolution, so as to prepare a modified polyaspartic acid solution, which is recorded as solution A1;

[0127] (2) 6 parts of carboxymethyl chitosan (molecular weight is 543.519 g / mol) are dispersed in 1000 parts of deionized water, and magnetic stirring is carried out at 35 DEG C until complete dissolution, so as to prepare a carboxymethyl chitosan solution, which is recorded as solution A2;

[0128] (3) Solution A1 is added dropwise into solution A2, and is uniformly mixed, so as to prepare a mixed solution, which is recorded as solution B;

[0129] (4) 5 parts of 1wt% calcium chloride aqueous solution and 2.5 parts of 25wt% glutaraldehyde aqueous solution are sequentially added into solution B, and reaction is carried out in a 35 DEG C water bath for 4h, so as to form a gel-like solution, which is recorded as solution C;

[0130] (5) Anhydrous ethanol is added into solution C for washing, and drying is carried out in a 50 DEG C oven until constant weight, and then the water-retention and growth-promotion type coated material is obtained after crushing and passing through a 40-mesh sieve.

[0131] The preparation method of the modified polyaspartic acid is the same as that in Embodiment 4.

[0132] The preparation method of the coating liquid is as follows: 120 parts of polyvinyl alcohol are dispersed in 1500 parts of deionized water, and heating is carried out in a water bath to 98 DEG C, and magnetic stirring is carried out until dissolution, so as to prepare a coating liquid.

[0133] The preparation method of the water-retention and growth-promotion type coated material suitable for obstacle soil is the same as that in Embodiment 4.

[0134] Comparative Example 1

[0135] This comparative example provides a coating material, and the specific preparation method is as follows:

[0136] (1) 12 parts of carboxymethyl chitosan powder were dispersed in 750 parts of deionized water, and dissolved by magnetic stirring at 35°C to obtain solution A.

[0137] (2) 10 parts of 1wt% calcium chloride aqueous solution and 0.8 parts of 25wt% glutaraldehyde aqueous solution were sequentially added to solution A, and reacted in a 35°C water bath for 4h to form a gel (solution B).

[0138] (3) Solution B was washed with 80% (volume fraction) ethanol until neutral, and then vacuum dried at 60°C after suction filtration. After crushing and passing through a 40-mesh sieve, pure carboxymethyl chitosan coating material (finished product) was obtained.

[0139] The pure carboxymethyl chitosan coating material appeared to be coagulated during synthesis, and had a low water absorption ratio.

[0140] Comparative Example 2

[0141] This comparative example provides a coating material, and the specific preparation method is as follows:

[0142] (1) 20 parts of modified polyaspartic acid powder were dispersed in 250 parts of deionized water, and dissolved by magnetic stirring at 35°C until completely dissolved to obtain solution A.

[0143] (2) 10 parts of 1wt% calcium chloride aqueous solution and 0.8 parts of 25wt% glutaraldehyde aqueous solution were sequentially added to solution A, and reacted in a 35°C water bath for 4h to form a gel (solution B).

[0144] (3) Solution B was washed with anhydrous ethanol for 3 times, and dried to constant weight in a 50°C oven. After crushing and passing through a 100-mesh sieve, pure modified polyaspartic acid coating material (finished product) was obtained.

[0145] The preparation method of modified polyaspartic acid is the same as that of Example 4.

[0146] The pure modified polyaspartic acid coating material has no water retention capacity after extraction and drying.

[0147] The performance of the water-retaining and growth-promoting type coating material suitable for barrier soil prepared in Example 4 was tested, and the test method was as follows:

[0148] (1) Temperature sensitivity of the water-retaining and growth-promoting type coating material suitable for barrier soil

[0149] The tea bag method was used to determine the temperature sensitivity of the material. The beaker with tea bag was placed in a water bath at 30℃, 40℃, 50℃, and 60℃, respectively. The water absorption rate of the coated material was measured after being soaked in distilled water at 30-60℃ for 24h. Three parallel experiments were set for each temperature condition.

[0150] (2) pH sensitivity of the water-retaining and growth-promoting coated material suitable for impaired soil

[0151] The tea bag method was used to test the water absorption rate of the coated material in phosphate buffer solution with pH=3-8. Three parallel experiments were set for each pH condition.

[0152] (3) Biological toxicity detection of the water-retaining and growth-promoting coated material suitable for impaired soil

[0153] 50g of air-dried soil was accurately weighed in a culture dish, which was divided into experimental and control groups. In the experimental group, 1g of water-retaining and growth-promoting coated material was added to the soil. Ten seeds of Chinese cabbage were planted in each culture dish. The germination rate was measured after 7d. The difference between the experimental and control groups was compared to determine whether the water-retaining and growth-promoting coated material suitable for impaired soil had biological toxicity to plants.

[0154] (4) Degradation rate of the water-retaining and growth-promoting coated material suitable for impaired soil

[0155] 300g of soil with a water content of 30% was accurately weighed in a culture bottle and pre-cultured for 3d. 1g of dry coated material powder was accurately weighed and recorded as Q 原 The powder was placed in a tea bag and weighed, and recorded as Q 初 The tea bag was buried in the soil surface, and the room temperature was cultured. On the 30th day and 60th day, it was taken out and weighed, and recorded as Q i , and then the degradation rate QR(%) was calculated. The calculation method is shown in formula (2):

[0156]

[0157] Figure 3 The water absorption rate of the water-retaining and growth-promoting coated material suitable for impaired soil in different environments was shown. It was found that the water-retaining and growth-promoting coated material suitable for impaired soil had certain temperature and pH sensitivity. The water absorption rate was highest at 60℃ and pH=8.0, reaching 23.62g / g and 17.39g / g, respectively, indicating that it had good application prospects in hot and high-temperature areas and saline-alkali areas.

[0158] Figure 4The biotoxicity of the water-retention and growth-promoting type coated material suitable for impaired soil and the degradation rate thereof in soil are shown, and it can be seen that the water-retention and growth-promoting type coated material suitable for impaired soil has no biotoxicity and can further promote seed germination, and the germination rate is increased by 16.67%. Meanwhile, the water-retention and growth-promoting type coated material suitable for impaired soil synthesized in the embodiment 3 of the present application has good degradation performance in soil, and the 60-day degradation rate thereof can reach 41.25%. In comparison, the degradation rate of modified polyaspartic acid is 58.59-70.72% within 28 days, and the degradation of carboxymethyl chitosan in soil usually only needs 1-6 weeks. These materials all have the problem of too fast degradation rate, while the water-retention and growth-promoting type coated material suitable for impaired soil synthesized in the present application shows relatively slow degradation characteristics, and can better match the growth cycle of crops.

[0159] Taking the water-retention and growth-promoting type coated material suitable for impaired soil prepared in the embodiment 4 as an example, the influence of the water-retention and growth-promoting type coated material suitable for impaired soil of the present application on crop growth is verified, and the test method is as follows:

[0160] (1) Verification of growth-promoting function of water-retention and growth-promoting type coated urea

[0161] Taking Chinese cabbage (Jingcui 60 Chinese cabbage) as a model crop, a pot experiment is adopted, and three groups of blank group (CK), control group (T1) and experimental group (T2) are divided. Among them, CK does not apply fertilizer, T1 applies ordinary urea (purchased from Zhongyan Anhui Hong Sifang Fertilizer Co., Ltd.), and T2 applies the water-retention and growth-promoting type coated material suitable for impaired soil prepared in the embodiment 4, and the application amount is to ensure that the nitrogen content in the soil is 0.4 g N / kg. Four replicates are set up for each group, and 50 mL of water is poured every day. After growing for 14 days, the relative content of chlorophyll in plant leaves (SPAD value) and various indexes of root system are measured.

[0162] Table 2 shows the influence of different treatments on the photosynthetic rate and root growth of Chinese cabbage.

[0163] Table 2 shows the influence of different treatments on the photosynthetic rate and root growth of Chinese cabbage.

[0164]

[0165] Note: Different lowercase letters represent significant differences, P<0.05.

[0166] As can be seen from Table 2, the water-retaining and growth-promoting type of coated material suitable for obstacle soil is the most effective for promoting Chinese cabbage, wherein the relative chlorophyll content SPAD value is increased by 25.93% than that of the urea group, the total root length is increased by 18.76%, the root volume is increased by 2.31%, and the root surface area is increased by 10.77%. It is shown that the water-retaining and growth-promoting type of coated material suitable for obstacle soil has certain promoting effect on the photosynthesis and root growth of crops.

[0167] The water-retaining and growth-promoting type of coated material suitable for obstacle soil prepared in Examples 5-7 has no significant difference in performance from that of Example 4.

[0168] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A water-retaining and growth-promoting coating material suitable for obstacle soils, characterized in that, It consists of a water-retaining and growth-promoting coating material, a coating solution, and a core material; By weight, the water-retaining and growth-promoting coating material is composed of the following raw materials: 10-30 parts of a first organic polymer material, 6-24 parts of a second organic polymer material, 5-15 parts of a first crosslinking agent, 0.1-2.5 parts of a second crosslinking agent, and 1000-1500 parts of water. The first organic polymer material is modified polyaspartic acid; the second organic polymer material is carboxymethyl chitosan. The coating solution is composed of the following raw materials in parts by weight: 80-120 parts of water-soluble polymer and 1000-1500 parts of water; The core material is selected from one of urea, ammonium chloride, ammonium sulfate, and compound fertilizer; The mass ratio of the water-retaining and growth-promoting coating material, coating liquid, and core material is (1.0-1.5):1:10; The modified polyaspartic acid is prepared as follows: maleic anhydride and urea are mixed, water is added, and the mixture is reacted at 50°C for 1 hour, followed by polymerization at 180°C for 1 hour to obtain polysuccinimide; high molecular weight organic amine and maleic anhydride are mixed, ground, Ca(OH)2 is added, and grinding is continued, water is added, and the mixture is stirred evenly to obtain a modifier; finally, the polysuccinimide is dissolved in water, the modifier is added, and the mixture is reacted at 30°C for 10 hours to obtain the modified polyaspartic acid; The mass ratio of maleic anhydride to urea is 1:1.1; The mass ratio of the high molecular weight organic amine to polysuccinimide is 1:1; The high molecular weight organic amine is selected from ethylenediamine, propylenediamine, butylenediamine, pentanediamine, or hexamethylenediamine; The preparation method of the water-retaining and growth-promoting coating material includes the following steps: accurately weighing a first organic polymer material, a second organic polymer material, a first crosslinking agent, a second crosslinking agent, and water according to mass parts; dispersing the first organic polymer material in 250-500 parts of water by mass parts, stirring until completely dissolved to obtain solution A1; dispersing the second organic polymer material in 750-1000 parts of water by mass parts, stirring until completely dissolved to obtain solution A2; adding solution A1 dropwise into solution A2 to obtain solution B; adding the first crosslinking agent and the second crosslinking agent to solution B, reacting at 35°C for 2-4 hours to obtain solution C; adding anhydrous ethanol to solution C for extraction and washing, and obtaining the water-retaining and growth-promoting coating material after drying and pulverizing; The first crosslinking agent is an aqueous solution of calcium chloride, and the second crosslinking agent is an aqueous solution of glutaraldehyde; The preparation method of the coating solution includes the following steps: accurately weighing water-soluble polymer and water according to the mass fractions; dispersing the water-soluble polymer in water, heating in a water bath to 90-100℃, and magnetically stirring until uniform to obtain the coating solution; The water-soluble polymer is polyvinyl alcohol.

2. A method for preparing a water-retaining and growth-promoting coating material suitable for obstacle soils according to claim 1, characterized in that, Includes the following steps: The core material is placed in a coating machine and preheated at 50-60°C. A coating liquid is then sprayed on as an adhesive layer to obtain a moist core material. Subsequently, water-retaining coating material powder is sprayed onto the surface of the moist core material to obtain the water-retaining and growth-promoting coating material suitable for obstacle soils.

3. The application of a water-retaining and growth-promoting coating material as described in claim 1 for use in obstacle soils for crop water retention and growth promotion.

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