A kind of impact-resistant bio-based coating material that can self-repair at room temperature and preparation method thereof

Abstract

The present invention discloses a kind of impact-resistant self-repairable bio-based coating material at room temperature and its preparation method, and belongs to the field of controlled release fertilizer production technology. The impact-resistant self-repairable bio-based coating material at room temperature of the present invention is made of the following raw materials in parts by weight: 20-100 parts of polyamine containing hydroxyl groups, 0.5-1 parts of surface synergist, and 1-15 parts of self-healing modified materials; the surface synergist is obtained by reacting urea carbonate, polycaprolactone and 2-methylbutanamide. The present invention constructs a reversible covalent network on the surface of the fertilizer, and the breaking and recombination of the reversible covalent bonds give the coating the characteristic of self-healing, solves the poor toughness and easy damage of bio-based slow-release fertilizers in production and application; the surface synergist is cross-linked into the reversible covalent network to increase the impact resistance and smoothness of the coating, which provides a good foundation for creating special fertilizers.

Description

Technical Field

[0001] The invention relates to the technical field of controlled-release fertilizer production, and in particular to an impact-resistant bio-based coating material capable of self-repairing at room temperature and a preparation method thereof. Background Art

[0002] With the advancement of science and technology, slow-release fertilizers have gradually replaced traditional chemical fertilizers. Controlled-release fertilizers are made by coating a layer of film on the surface of the fertilizer. Water enters the fertilizer through the micropores on the film, allowing nutrients to dissolve slowly, thereby improving nutrient utilization, reducing fertilizer usage, and controlling costs to a certain extent. However, the first generation of controlled-release fertilizer film materials are mostly petrochemical film materials, which are expensive and put pressure on the environment, which is not conducive to the green and sustainable development of the industry; bio-based film materials are the direction of industry modification and upgrading due to their low cost and degradability, but bio-based coated controlled-release fertilizers generally have the following problems:

[0003] (1) When preparing the coating liquid, the coating liquid contains some impurities that are easily soluble in water. When the fertilizer is soaked in water, the impurities on the membrane will dissolve with the water, making the holes on the membrane larger and releasing a large amount of nutrients inside the fertilizer;

[0004] (2) Bio-based film materials have poor toughness. During the coating process, the fertilizer particles keep rolling at a certain speed in the coating pan. During the solidification of the coating liquid, the collision and adhesion between the fertilizer particles and between the fertilizer particles and the coating pan can easily cause the film shell on the fertilizer surface to tear or break.

[0005] (3) During the transportation and use of fertilizers, due to the action of external forces, the collision between fertilizer particles and the collision between fertilizers and equipment will also cause damage to the surface membrane shell, reducing its controlled release ability.

[0006] In order to solve the above problems of bio-based coated controlled-release fertilizers, the relevant patent CN113336604A discloses a recyclable self-repairing elastic bio-based coating material and its preparation method. The coating material with self-repairing function is generated by using bio-based resin, dynamic modified material, and magnetic nanocellulose blending reaction. The principle is that dynamic covalent bonds and metal coordination bonds participate in the construction of dynamic covalent networks, and the movement of dynamic covalent bonds and metal coordination bonds enables it to have self-repairing function. Although it has the advantages of low cost and green environmental protection, the membrane material made of this material has an uneven surface, more impurities, and is easily soluble in water, causing the holes to become larger. The related patent CN113788711A discloses a self-repairing bio-based film, coated controlled-release fertilizer and preparation method. The biomass liquefied polyol is used as raw material and the self-repairing modified isocyanate is used as curing agent to prepare a biomass polyurethane film with self-repairing function. The principle is to graft the disulfide covalent bond compound into the molecular chain through the grafting modification of the molecular chain during the synthesis of biomass polyurethane. Although this grafting technology can give the material the function of self-repairing, the mobility of the covalent bond after grafting is poor, which inhibits its repair ability. The related patent CN109053949A discloses a graphene / polymer self-repairing material and a preparation method thereof. The principle is to form a reversible cross-linked network through a reversible Diels-Alder reaction (DA reaction) using functionalized graphene, functionalized polymer and cross-linking agent, so that the composite material has excellent self-repairing performance, but this cross-linked network is mainly formed by covalent cross-linking, and the cross-linking degree is low; and the production process is complicated, and the material needs to be kept at a temperature of 50~250℃ to be completely repaired, and it cannot be repaired at room temperature. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a bio-based coated controlled-release fertilizer that is impact-resistant and self-repairable at room temperature and a preparation method thereof. The temperature range of the self-repair of the present invention is 0-35°C. Under the condition of increased pressure and the attraction of the -CNO bond in the second component of the self-healing modified material, the electrons move, and the covalent bonds are converted into reversible covalent bonds. By constructing a reversible covalent network on the fertilizer surface, the breaking and reorganization of the reversible covalent bonds give the coating the characteristics of self-healing, solving the problem of poor toughness and easy damage in the production and application of bio-based slow-release fertilizers. Compared with grafted covalent bonds, reversible covalent bonds have better mobility, and can move faster when damaged at room temperature, break-reorganize to promote the repair of damaged areas; cross-linking the surface enhancer into the reversible covalent network increases the impact resistance and smoothness of the coating, providing a good foundation for creating special fertilizers. Compared with the dynamic covalent network of the above-mentioned patent, the reversible covalent network with the addition of the surface enhancer can fill the cross-linking pores generated by the cross-linking of the reversible covalent bonds and improve the cross-linking degree of the coating. The coating has good impact resistance and can withstand most external forces, protecting the fertilizer film shell and internal core.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] The first aspect of the present invention provides an impact-resistant bio-based coating material that can self-repair at room temperature, comprising the following raw materials in parts by weight:

[0010] 20-100 parts of polyamine containing hydroxyl group, 0.5-1 parts of surface enhancer, 1-15 parts of self-healing modified material;

[0011] The surface enhancer is obtained by reacting urea carbonate, polycaprolactone and 2-methylbutyramide;

[0012] The self-healing modified material is obtained by reacting a first component and a second component in a molar ratio of 1:(2-8); the first component is one or more of α-furoyl dioxime, di(octadecyl) disulfide, and di[(4-methoxyphenyl)methyl] diselenide; the second component is one or more of 2-thiophene isocyanate, 2-nitrophenyl isocyanate, and dicyclohexylmethane diisocyanate.

[0013] Preferably, the polyamine containing hydroxyl groups is obtained by reacting component A and component B in a mass ratio of (3-5): (7.0-7.5); the component A is one or more of walnut oil, cashew kernel oil, polytetramethylene glycol, coconut oil, and polyethylene glycol;

[0014] The B component is one or more of acrylamide, alanine and glycine.

[0015] More preferably, the reaction conditions of the polyamine containing hydroxyl groups are: mixing component A and component B, adding concentrated sulfuric acid or p-toluenesulfonic acid, and stirring at a speed of 300-500 rap / min for 5-6 hours.

[0016] Preferably, the reaction conditions of the surface enhancer are: adding urea carbonate and polycaprolactone to anhydrous ethanol, stirring at 35-55° C. for 20-40 minutes; then adding 2-methylbutanamide and stirring continuously until the solution changes color, adjusting the pH to 6.5-7.5, filtering, washing, and drying to prepare the surface enhancer.

[0017] More preferably, the ratio of the added amounts of urea carbonate, polycaprolactone and 2-methylbutyramide is 5 g: (2-4) ml: (8-12) ml.

[0018] Preferably, the reaction conditions of the self-healing modified material are: adding the first component and the second component into xylene, stirring continuously for 3-4 hours at 25-35° C., then ultrasonically oscillating for 20-40 minutes, and drying to remove excess xylene.

[0019] The second aspect of the present invention provides a method for preparing the above-mentioned impact-resistant bio-based coating material that can self-repair at room temperature, comprising the following steps:

[0020] The polyamine containing hydroxyl groups and the self-healing modified material are mixed in a solvent, and the mixture is continuously stirred under a nitrogen atmosphere to remove excess solvent to generate a prepolymer;

[0021] Add a surface enhancer to the generated prepolymer, stir evenly, then drop dibutyltin dilaurate, stir under ultrasonic vibration for 5-10 minutes, and then continue stirring under a nitrogen atmosphere until the mixed solution turns milky white, the reaction process gradually becomes stable, and the bubbles gradually disappear, thereby preparing an impact-resistant bio-based coating material that can self-repair at room temperature.

[0022] Preferably, the solvent is xylene or acetone.

[0023] The third aspect of the present invention provides the use of the above-mentioned impact-resistant bio-based coating material that can self-repair at room temperature in the preparation of controlled-release fertilizers.

[0024] The fourth aspect of the present invention provides a coated controlled-release fertilizer, comprising a fertilizer core, and an impact-resistant bio-based coating material that can self-repair at room temperature sprayed on the surface of the fertilizer core; the impact-resistant bio-based coating material that can self-repair at room temperature accounts for 3-5% of the weight of the fertilizer core.

[0025] A fifth aspect of the present invention provides a method for preparing the above-mentioned coated controlled-release fertilizer, comprising the following steps:

[0026] The impact-resistant bio-based coating material capable of self-repairing at room temperature is uniformly sprayed on the surface of the fertilizer core at a rotation speed of 20-25 rps at a pressure of 0.2-0.4 MPa, and cured at 25-35° C. for 5-10 minutes.

[0027] Beneficial effects of the present invention:

[0028] (1) The present invention solves the problem of poor toughness of bio-based slow-release fertilizers, improves the elasticity of fertilizer particles, provides a protective layer for fertilizer particles, and improves their damage resistance.

[0029] (2) The present invention improves the integrity of the membrane shell. During the production, transportation and use of fertilizers, the holes and cracks on the fertilizer membrane shell can be repaired at room temperature, thereby preventing a large amount of water from entering the fertilizer due to damage to the membrane shell, causing the nutrients to be released prematurely. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : Fourier infrared spectroscopy test results of the impact-resistant and room temperature self-repairing bio-based coating materials prepared in Examples 1-3 of the present invention.

[0031] Figure 2 : The surface and cross-sectional view of the polyurethane coating of the impact-resistant bio-based coating material capable of self-repairing at room temperature prepared in Example 1 of the present invention were observed under a scanning electron microscope (SEM).

[0032] Figure 3 : The impact-resistant bio-based coating material capable of self-repairing at room temperature prepared in Example 1 of the present invention was cut and the images before and after the polyurethane coating was repaired were observed under a scanning electron microscope (SEM).

[0033] Figure 4 : The results of tensile tests on the membrane shells formed by curing the impact-resistant bio-based coating materials that can self-repair at room temperature prepared in Examples 1-3 of the present invention.

[0034] Figure 5 : Nutrient release measurement results after collision of the coated controlled-release fertilizers prepared in Examples 4-6 of the present invention.

[0035] Figure 6 : Results of the self-repairing ability investigation at room temperature of the coated controlled-release fertilizers prepared in Examples 4-6 of the present invention.

[0036] Figure 7 : Nutrient release curves of the coated controlled-release fertilizers prepared in Examples 4-6 of the present invention. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0038] As mentioned above, existing bio-based coated fertilizers are mainly made of raw materials such as crop straw and discarded cardboard boxes, which are easy to obtain, inexpensive and have little pollution to the environment. However, the film materials made of these bio-based materials have poor toughness and are easily broken under the influence of external forces, which affects the controlled release efficiency of the fertilizer and the nutrient utilization rate.

[0039] In view of this, the present invention has developed an impact-resistant bio-based coating material that can self-repair at room temperature. By cross-linking reversible covalent bonds, strong hydrogen bonds, and surface enhancement modification materials to the surface coating of bio-based coated fertilizers, the bio-based coated fertilizers are given self-repairing properties, density, strength and toughness, etc., to ensure the integrity of the membrane shell, and solve the problem that the existing bio-based coated fertilizers cannot match the needs of crops due to shell damage, thereby achieving precise controlled release.

[0040] The impact-resistant bio-based coating material capable of self-healing at room temperature of the present invention is prepared by reacting a polyamine containing a hydroxyl group, a surface enhancer and a self-healing modified material. In one embodiment of the present invention, a method for preparing the impact-resistant bio-based coating material capable of self-healing at room temperature is provided, which is specifically as follows:

[0041] The polyamine containing hydroxyl groups and the self-healing modified material are mixed in a solvent, stirred continuously for 10 minutes under a nitrogen atmosphere, and the excess solvent is removed to generate a prepolymer; the solvent is xylene or acetone.

[0042] Add a surface enhancer to the generated prepolymer, stir evenly, then add 1 drop of dibutyltin dilaurate, place in an ultrasonic oscillator and stir at 25°C for 5 minutes, then continue stirring in a nitrogen atmosphere until the mixed solution turns milky white, the reaction process gradually becomes stable, and the bubbles gradually disappear, thereby preparing an impact-resistant bio-based coating material that can self-repair at room temperature.

[0043] The coating material of the present invention has excellent tensile properties, impact resistance and self-healing properties at room temperature. The mechanism of action of the coating material of the present invention is as follows: the first component and the second component in the self-healing modified material are dissolved in an organic solvent xylene solution, and the covalent bonds (oxime amine bonds, disulfide bonds, and diselenide bonds) in the first component are converted into free states. Under the condition of increased pressure and the attraction of -CNO bonds in the second component, electrons move, hydrogen bonds are converted into strong hydrogen bonds (tetrahydrogen bonds), and covalent bonds are converted into reversible covalent bonds (oxime amine bonds, disulfide bonds, and diselenide bonds) that are uniformly dispersed in the solution, and finally a viscous prepolymer product is generated. The prepolymer product reacts with a hydroxyl-containing polyamine and a surface enhancer in the organic solvent xylene, and the hydrogen bonds interweave the reversible covalent bonds (oxime amine bonds, disulfide bonds, and diselenide bonds) and the surface enhancer to generate a reversible covalent network with a high degree of cross-linking. Compared with ordinary covalent bonds and hydrogen bonds, free reversible covalent bonds and strong hydrogen bonds are more evenly dispersed in the network, and reversible covalent bonds and strong hydrogen bonds have good mobility. When damaged, they can move faster, break and reorganize to promote the repair of the damaged area; and the addition of surface enhancers, compared with ordinary covalent bond networks, can fill the cross-linking pores caused by cross-linking of reversible covalent bonds (oxime amine bonds, disulfide bonds, diselenide bonds), improve the cross-linking degree of the coating, and can greatly promote the energy dissipation of the coating surface, protecting the coating from damage.

[0044] In summary, in order to solve the problem that the existing bio-based coated fertilizers are prone to rupture or even breakage of fertilizer particles during long-term collisions, the present invention innovatively adds self-healing modified materials and surface enhancers to the coating materials, wherein the added surface enhancers can not only give the surface coating good impact resistance, but also improve the smoothness of the surface coating; the self-healing modified materials provide reversible covalent bonds (such as reversible oxime amine bonds, disulfide bonds, diselenide bonds) and strong hydrogen bonds (such as tetrahydrogen bonds). In the process of forming bio-based membrane materials, the self-healing modified materials and surface enhancers have a synergistic effect, and the surface enhancers are easily dispersed into the membrane materials, and together with the reversible covalent bonds and strong hydrogen bonds, a reversible covalent network is constructed, which significantly increases the toughness and damage resistance of the bio-based coating; by cross-linking the reversible covalent bonds and strong hydrogen bonds into the constructed reversible covalent network, the bio-based coating has the ability to self-repair after damage.

[0045] However, simply combining the hydroxyl-containing polyamine and the self-healing modifying material, or simply combining the hydroxyl-containing polyamine and the surfactant, cannot form an effective coating material. Therefore, the coating material formed by the hydroxyl-containing polyamine, the surfactant and the self-healing modifying material of the present invention is an organic whole and is inseparable.

[0046] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0047] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels. Among them:

[0048] Walnut oil, CAS No: 8024-09-7; Coconut oil, CAS No: 8001-31-8.

[0049] Example 1: Preparation of impact-resistant bio-based coating material that can self-repair at room temperature

[0050] (1) Walnut oil and polytetramethylene glycol were mixed in a molar ratio of 1:1 as component A; glycine was used as component B.

[0051] 3g of component A and 7.5g of component B were placed in a magnetic stirrer, 10ml of p-toluenesulfonic acid was added, and the mixture was stirred at a speed of 500rap / min for 5h. After the solution was uniform, the mixture was taken out to prepare a polyamine containing hydroxyl groups, which was stored in a vacuum environment.

[0052] (2) 5.71 g of the first component [dioctadecyl disulfide] and 5.24 g of the second component (4,4-dicyclohexylmethane diisocyanate) were placed in a reactor, 10 ml of xylene was added to dissolve them, and the mixture was stirred continuously at 35 °C for 3 h. The mixture was then placed in an ultrasonic oscillator and continuously shaken for 30 min. After being taken out, the mixture was placed in a vacuum drying oven at 75 °C and dried overnight to remove excess xylene, thereby preparing a self-healing modified material.

[0053] (3) Add 5 g of urea carbonate and 3 ml of polycaprolactone into a reaction bottle, inject 40 ml of anhydrous ethanol into the reaction bottle, stir at 50 °C for 30 min, add 10 ml of 2-methylbutanamide after mixing evenly, and continue stirring until the solution changes color. Adjust the pH to 7, filter out the precipitate in the solution, wash it with anhydrous ethanol, and dry it at room temperature to prepare a surface enhancer.

[0054] (4) 0.75 g of the self-healing modified material synthesized in step (2) and 5 g of the hydroxyl-containing polyamine prepared in step (1) were mixed in 10 ml of xylene solution, and stirred for 10 min under a nitrogen atmosphere. Excess xylene was removed to generate a prepolymer.

[0055] 0.25 g of the surface enhancer prepared in step (3) was added to the generated prepolymer, and after stirring evenly, 1 drop of dibutyltin dilaurate was added, and the mixture was placed in an ultrasonic oscillator and stirred at 25° C. for 5 minutes. Then, stirring was continued under a nitrogen atmosphere until the mixed solution turned milky white, and the reaction process gradually became stable and the bubbles gradually disappeared, thereby preparing an impact-resistant bio-based coating material that can self-repair at room temperature.

[0056] Example 2: Preparation of impact-resistant bio-based coating material that can self-repair at room temperature

[0057] (1) Coconut oil and polyethylene glycol were mixed in a molar ratio of 1:1 as component A; and alanine was used as component B.

[0058] Take 3g of component A and 7.12g of component B and place them in a magnetic stirrer, add 3ml of concentrated sulfuric acid, stir at a speed of 400rap / min for 5.5h, take out after the solution is uniform, and prepare polyamine containing hydroxyl groups, which is stored in a vacuum environment.

[0059] (2) 1.12 g of the first component (α-bifuroyl dioxime) and 6.56 g of the second component (2-nitrophenyl isocyanate) were placed in a reactor, 10 ml of xylene was added to dissolve them, and the mixture was stirred continuously at 30 °C for 3.5 h. The mixture was then placed in an ultrasonic oscillator and continuously shaken for 30 min. After being taken out, the mixture was placed in a vacuum drying oven at 75 °C and dried overnight to remove excess xylene, thereby preparing a self-healing modified material.

[0060] (3) Add 5 g of urea carbonate and 3 ml of polycaprolactone into a reaction bottle, inject 40 ml of anhydrous ethanol into the reaction bottle, stir at 50 °C for 30 min, add 10 ml of 2-methylbutanamide after mixing evenly, and continue stirring until the solution changes color. Adjust the pH to 7, filter out the precipitate in the solution, wash it with anhydrous ethanol, and dry it at room temperature to prepare a surface enhancer.

[0061] (4) 0.75 g of the self-healing modified material synthesized in step (2) and 5 g of the hydroxyl-containing polyamine prepared in step (1) were mixed in 10 ml of xylene solution, and stirred for 10 min under a nitrogen atmosphere. Excess xylene was removed to generate a prepolymer.

[0062] 0.25 g of the surface enhancer prepared in step (3) was added to the generated prepolymer, and after stirring evenly, 1 drop of dibutyltin dilaurate was added, and the mixture was placed in an ultrasonic oscillator and stirred at 25° C. for 5 minutes. Then, stirring was continued under a nitrogen atmosphere until the mixed solution turned milky white, and the reaction process gradually became stable and the bubbles gradually disappeared, thereby preparing an impact-resistant bio-based coating material that can self-repair at room temperature.

[0063] Example 3: Preparation of impact-resistant bio-based coating material that can self-repair at room temperature

[0064] (1) Coconut oil and polyethylene glycol were mixed in a molar ratio of 1:1 as component A; acrylamide was used as component B.

[0065] Take 5g of component A and 7.1g of component B and place them in a magnetic stirrer, add 10ml of concentrated sulfuric acid, stir at a speed of 300rap / min for 6h, take out after the solution is uniform, and prepare polyamine containing hydroxyl groups, which is stored in a vacuum environment.

[0066] (2) 4 g of the first component (bis(4-methoxyphenyl)methyl) diselenide) and 5 g of the second component (2-thiophene isocyanate) were placed in a reactor, 10 ml of acetone was added to dissolve them, and the mixture was stirred continuously at 25 °C for 4 h. The mixture was then placed in an ultrasonic oscillator and continuously shaken for 30 min. After being taken out, the mixture was placed in a vacuum drying oven at 75 °C and dried overnight to remove excess acetone, thereby preparing a self-healing modified material.

[0067] (3) Add 5 g of urea carbonate and 3 ml of polycaprolactone into a reaction bottle, inject 40 ml of anhydrous ethanol into the reaction bottle, stir at 50 °C for 30 min, add 10 ml of 2-methylbutanamide after mixing evenly, and continue stirring until the solution changes color. Adjust the pH to 7, filter out the precipitate in the solution, wash it with anhydrous ethanol, and dry it at room temperature to obtain a surface enhancer.

[0068] (4) 0.75 g of the self-healing modified material synthesized in step (2) and 5 g of the polyamine containing hydroxyl groups prepared in step (1) were mixed in 10 ml of acetone solution, and stirred continuously for 10 min under a nitrogen atmosphere, and excess acetone was removed to generate a prepolymer;

[0069] 0.25 g of the surface enhancer prepared in step (3) was added to the generated prepolymer, and after stirring evenly, 1 drop of dibutyltin dilaurate was added, and the mixture was placed in an ultrasonic oscillator and stirred at 25° C. for 5 min. Then, the mixture was stirred under a nitrogen atmosphere until the mixed solution turned milky white, and the reaction process gradually became stable and the bubbles gradually disappeared. Thus, an impact-resistant room temperature

[0070] Example 4: Preparation of coated controlled-release fertilizer

[0071] Take 1200g of polished urea granules and put them into a coating pan at 25°C. Keep the speed of the coating pan at 25rps. Use a spray gun to spray the impact-resistant self-repairable bio-based coating material prepared in Example 1 onto the surface of the rolling urea granules. Curing for 10 minutes, the spraying amount each time is 0.5% of the fertilizer mass, repeat the above spraying operation until the weight of the sprayed coating liquid accounts for 5% of the total weight of the urea granules. After stabilization, an impact-resistant coated controlled-release fertilizer with a controlled-release period of 64 days is obtained.

[0072] Example 5: Preparation of coated controlled-release fertilizer

[0073] Take 1200g of polished urea granules and put them into a coating pan at 30°C. Keep the speed of the coating pan at 25rps. Use a spray gun to spray the impact-resistant self-repairable bio-based coating material prepared in Example 2 onto the surface of the rolling urea granules. Curing for 10 minutes, the spraying amount each time is 0.5% of the fertilizer mass, repeat the above spraying operation until the weight of the sprayed coating liquid accounts for 4% of the total weight of the urea granules. After stabilization, a coated controlled-release fertilizer with a controlled-release period of 60 days is obtained.

[0074] Example 6: Preparation of coated controlled-release fertilizer

[0075] Take 1200g of polished urea granules and put them into a coating pan at 25°C. Keep the speed of the coating pan at 25rps. Use a spray gun to spray the impact-resistant and self-repairable bio-based coating material prepared in Example 3 onto the surface of the rolling urea granules. Curing for 10 minutes, the spraying amount each time is 0.5% of the fertilizer mass. Repeat the above spraying operation until the weight of the sprayed coating liquid accounts for 3% of the total weight of the urea granules. After stabilization, a coated controlled-release fertilizer with a controlled-release period of 42 days is obtained.

[0076] Comparative Example: Preparation of Conventional Bio-based Coated Fertilizer

[0077] (1) Take 2.5 g of soybean oil and 5 g of toluene diisocyanate and mix them evenly at room temperature. Stir continuously until the solution turns white, then stop stirring to prepare a bio-based coating solution.

[0078] (2) Take 1400g of polished urea granules and put them into a coating pan at 75℃. Keep the speed of the coating pan at 25rps. After preheating, use a spray gun to spray the bio-based coating liquid prepared in step (1) onto the surface of the rolling urea granules and cure for 15min. The spraying amount each time is 0.5% of the fertilizer mass. Repeat the above spraying operation until the weight of the sprayed coating liquid accounts for 5% of the total weight of the urea granules. After stabilization, conventional bio-based coated fertilizer is obtained.

[0079] Test Example 1: Performance evaluation of impact-resistant bio-based coating materials that can self-repair at room temperature

[0080] The impact-resistant bio-based coating material that can self-repair at room temperature prepared in Examples 1-3 was cured to form a membrane shell. The changes in the characteristic groups in the membrane shell were detected by Fourier transform infrared spectroscopy. The results were as follows: Figure 1 As shown, two characteristic peaks of polyurethane, NH group and C=O group, appeared, and -NCO group completely disappeared, indicating that the polyurethane coating had been formed.

[0081] The surface and cross section of the polyurethane coating formed by the coating material of Example 1 were observed using a scanning electron microscope (SEM). Figure 2 As shown in the figure, the addition of surface enhancer improves the cross-linking degree of polyurethane, making the surface and cross-section of the coating smoother and denser.

[0082] The film shell formed after the impact-resistant bio-based coating material capable of self-repairing at room temperature prepared in Example 1 was cured was cut and placed at room temperature. The film shell was observed using a scanning electron microscope (SEM) 5 minutes after cutting, 24 hours after cutting, and 48 hours after cutting. The results are as follows: Figure 3 As shown, within a period of time after the membrane shell is cut, there are obvious repair marks at the incision, and then the self-healing of the damaged area is promoted through the reorganization of strong hydrogen bonds and the movement of reversible covalent bonds. The results show that the coating material of the present invention has the ability of self-repair at room temperature.

[0083] The membrane shell formed by curing the impact-resistant bio-based coating material that can self-repair at room temperature prepared in Examples 1-3 was subjected to a tensile test using a universal testing machine, with a tensile rate of 50 mm / s; the membrane shell formed by curing the bio-based coating liquid in the comparative example was used as a control. Figure 4 As shown, the elongation rate of the coating material prepared by the present invention can be as high as 1000% without breaking. The results show that the self-repairing bio-based coating material prepared by the present invention has good tensile properties and elasticity.

[0084] Test Example 2: Performance evaluation of the coated controlled-release fertilizer prepared using the coating material of the present invention

[0085] 1. Impact resistance test:

[0086] 60 g of conventional bio-based coated fertilizer prepared in the comparative example, and coated controlled-release fertilizer prepared in Example 4, Example 5, and Example 6 were weighed into transparent plastic bottles, and 10 small steel balls with a diameter of 1.5 cm were placed therein, respectively. The bottles were placed in a shaker and shaken at a speed of 300 rap / min. Samples were taken at 20, 40, 60, and 80 minutes, and then immediately placed in water. The initial release rate of N was measured after 24 hours.

[0087] result Figure 5As shown, the initial release rate of N in Examples 4 to 6 fluctuates within a stable range (because these fertilizers may be mixed with bad grains, that is, the bad grains produced during the coating process, the number is very small), and the release rate fluctuation range is within 2%; the release rate of conventional bio-based coated fertilizers suddenly increased by 7% from stable. The results show that the impact resistance of the coated controlled-release fertilizer prepared by the present invention is significantly improved, and it can effectively resist the damage of the membrane shell caused by external forces during the transportation and use of the fertilizer, and improve the controlled-release ability.

[0088] 2. Investigation of self-healing ability at room temperature:

[0089] The conventional bio-based coated fertilizer prepared in the comparative example, and the coated controlled-release fertilizer prepared in Example 4, Example 5, and Example 6 were cut into three quarters of the whole particles with a cutter, left at room temperature for 1 hour for repair, and then placed in water after 1 hour, and an alkaline color developer was added dropwise; uncoated urea particles were used as blank controls.

[0090] After the fertilizer particles dissolve in water, the pH of the water will increase, making it alkaline. After phenolphthalein is added into the water, the cut fertilizer is placed in the water. The fertilizer without the repair effect dissolves quickly, causing the pH of the solution to rise rapidly. The faster the fertilizer dissolves, the more alkaline the solution is, and the darker the color is. On the contrary, the fertilizer with the repair effect is repaired after cutting, which delays the dissolution of the fertilizer, and the solution does not change color or becomes lighter.

[0091] The results are as follows Figure 6 As shown, the coated controlled-release fertilizers prepared in Examples 4-6 change color lightly or not; while the conventional bio-based coated controlled-release fertilizers appear dark. The results show that the conventional bio-based coated controlled-release fertilizers do not have self-repairing ability at room temperature, and nutrients are released quickly after cutting; while the coated controlled-release fertilizers prepared in the present invention have self-repairing ability at room temperature, can be repaired after cutting, and slow down the dissolution of nutrients.

[0092] 3. Nutrient release determination:

[0093] The nitrogen release rates of the coated controlled-release fertilizers prepared in Examples 4, 5 and 6 were determined according to the National Standard for Slow-Release Fertilizers GB / T 23348-2009 of the People's Republic of China.

[0094] The results are as follows Figure 7 As shown, the release period of the bio-based coated fertilizer in Example 4 is 64 days; the release period of the bio-based coated fertilizer in Example 5 is 60 days, and the release period of the bio-based coated fertilizer in Example 6 is 42 days.

[0095] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An impact-resistant bio-based coating material that can self-repair at room temperature, characterized in that: The invention comprises the following raw materials in parts by weight: 20-100 parts of polyamine containing hydroxyl group, 0.5-1 parts of surface enhancer, 1-15 parts of self-healing modified material; The surface enhancer is obtained by reacting urea carbonate, polycaprolactone and 2-methylbutyramide. The reaction conditions are as follows: adding urea carbonate and polycaprolactone to anhydrous ethanol, stirring at 35-55° C. for 20-40 minutes; then adding 2-methylbutyramide and stirring continuously until the solution changes color, adjusting the pH to 6.5-7.5, filtering, washing and drying to prepare the surface enhancer; the ratio of urea carbonate, polycaprolactone and 2-methylbutyramide added is 5g: (2-4) ml: (8-12) ml; The self-healing modified material is obtained by reacting a first component and a second component in a molar ratio of 1:(2-8); the first component is one or more of α-furoyl dioxime, di(octadecyl) disulfide, and di[(4-methoxyphenyl)methyl] diselenide; the second component is one or more of 2-thiophene isocyanate, 2-nitrophenyl isocyanate, and dicyclohexylmethane diisocyanate; The polyamine containing hydroxyl groups is obtained by reacting component A and component B in a mass ratio of (3-5): (7.0-7.5); the component A is one or more of walnut oil, cashew nut oil, polytetramethylene glycol, coconut oil, and polyethylene glycol; The B component is one or more of acrylamide, alanine and glycine; The impact-resistant bio-based coating material capable of self-repairing at room temperature is prepared by the following method: The polyamine containing hydroxyl groups and the self-healing modified material are mixed in a solvent, and the mixture is continuously stirred under a nitrogen atmosphere to remove excess solvent to generate a prepolymer; Add a surface enhancer to the generated prepolymer, stir evenly, then drop dibutyltin dilaurate, stir under ultrasonic vibration for 5-10 minutes, and then continue stirring under a nitrogen atmosphere until the mixed solution turns milky white, the reaction process gradually becomes stable, and the bubbles gradually disappear, thereby preparing an impact-resistant bio-based coating material that can self-repair at room temperature.

2. The impact-resistant bio-based coating material capable of self-repairing at room temperature according to claim 1, characterized in that: The reaction conditions of the polyamine containing hydroxyl groups are as follows: component A and component B are mixed, concentrated sulfuric acid or p-toluenesulfonic acid is added, and the mixture is stirred at a speed of 300-500 rap / min for 5-6 hours.

3. The impact-resistant bio-based coating material capable of self-repairing at room temperature according to claim 1, characterized in that: The reaction conditions of the self-healing modified material are as follows: adding the first component and the second component into xylene, stirring continuously for 3-4 hours at 25-35° C., ultrasonically oscillating for 20-40 minutes, and drying to remove excess xylene.

4. The impact-resistant bio-based coating material capable of self-repairing at room temperature according to claim 1, characterized in that: The solvent is xylene or acetone.

5. Use of the impact-resistant bio-based coating material capable of self-repairing at room temperature as claimed in any one of claims 1 to 4 in the preparation of controlled-release fertilizers.

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