A coating material, a method of preparation and use in a trace element coating for potassium chloride particles

Abstract

The application relates to the technical field of fertilizers, and discloses a coating material, a preparation method and application in a trace element coating for potassium chloride particles. The preparation method comprises the following steps: preparing a polyurethane prepolymer by reacting isophorone diisocyanate with polycaprolactone diol, tartaric acid and butanedione oxime; continuously reacting the polyurethane prepolymer with chitosan oligosaccharide Schiff base to obtain chitosan oligosaccharide modified polyurethane; and mixing the chitosan oligosaccharide modified polyurethane, a crosslinking agent, silane modified isocyanate and a trace element solution to obtain the coating material. The coating material has good mechanical properties, contains trace elements, has a controlled release effect on potassium chloride particle fertilizers, and can be applied as a trace element coating in potassium chloride particle fertilizers.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a coating material, a preparation method and application of the coating material in trace element coatings for potassium chloride particles. Background Art

[0002] Potassium and chlorine are essential nutrients for crop growth. Potassium can promote photosynthesis, accelerate the synthesis and transportation of organic matter, and thus promote the formation of yield. Chlorine can participate in the water photolysis reaction in photosynthesis and increase the osmotic pressure of cells. However, excessive or concentrated application of potassium chloride will cause the local ion concentration in the soil to be too high, thereby endangering plant health. In addition, since potassium chloride is a water-soluble fertilizer, it is easy to be lost after fertilization, so it is necessary to improve the utilization rate of potassium chloride fertilizer to reduce pollution to the environment.

[0003] Existing technologies, such as Chinese patent application CN102690142A, disclose a method for producing slow-release granular potassium chloride fertilizer. The granular potassium chloride fertilizer is coated with a coating agent, which has slow-release properties and high strength. However, the water resistance of the coating material and its complexing effect on metal ions need to be improved. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a coating material, a preparation method and an application in a trace element coating for potassium chloride granules. The prepared coating material has good mechanical properties, contains trace elements, and has a controlled release effect on potassium chloride granular fertilizers. The coating material can be used as a trace element coating in potassium chloride granular fertilizers.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a coating material comprises the following steps:

[0007] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, adding a solvent and a catalyst, reacting, adding dimethylglyoxime after the reaction is completed, continuing the reaction, adding tartaric acid, reacting again, and obtaining a polyurethane prepolymer after the reaction is completed;

[0008] The polyurethane prepolymer and the chitosan oligosaccharide Schiff base are mixed and reacted, and after the reaction is completed, the solvent acetone is removed by rotary evaporation to obtain the chitosan oligosaccharide modified polyurethane;

[0009] Step (2), mixing tris(2-acryloyloxyethyl)isocyanurate, polyethylene glycol diacrylate, dopamine hydrochloride, and dimethyl sulfoxide, adding a regulator to adjust the pH value, reacting, and purifying after the reaction to obtain a cross-linking agent;

[0010] The chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate and a metal ion solution are mixed to obtain a coating material.

[0011] Preferably, in step (1), the molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime, and tartaric acid is 4:1-1.2:0.8-1:0.8-1; the catalyst is dibutyltin dilaurate, and the amount of the catalyst added is 0.2-0.3% of the mass of the polycaprolactone diol; when preparing the polyurethane prepolymer, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 80-85°C for 1-1.5 hours; continuing the reaction conditions are: continuing the reaction in a nitrogen atmosphere at a temperature of 75-80°C for 6-7 hours; and re-reacting conditions are: reacting again in a nitrogen atmosphere at a temperature of 60-65°C for 1 hour; and the solid content of the polyurethane prepolymer is 45-50wt%.

[0012] Preferably, in step (1), the mass ratio of polyurethane prepolymer to chitosan oligosaccharide Schiff base is 30:6.5-8; when preparing chitosan oligosaccharide modified polyurethane, the reaction conditions are: reaction in a nitrogen atmosphere at a temperature of 70-80° C. for 4-5 hours.

[0013] Preferably, in step (1), the chitosan oligosaccharide Schiff base comprises the following steps:

[0014] Chitosan oligosaccharide is mixed with ethanol, swelled, salicylaldehyde is added, a regulator is added to adjust the pH value, reacted, filtered, washed, and dried to obtain chitosan oligosaccharide Schiff base;

[0015] The swelling conditions are: swelling at 50-60°C for 20-30 minutes; the mass ratio of chitosan oligosaccharide to salicylic aldehyde is 10:0.8-1; and the reaction conditions are: reaction at pH 6 and 50-60°C for 3-4 hours.

[0016] Furthermore, the regulator is a 0.1 mol / L sodium hydroxide aqueous solution.

[0017] Preferably, in step (2), the molar ratio of tris(2-acryloyloxyethyl) isocyanurate, polyethylene glycol diacrylate, and dopamine hydrochloride is 2:3:6, and the amount of dimethyl sulfoxide added is 2-3 times the total mass of tris(2-acryloyloxyethyl) isocyanurate, polyethylene glycol diacrylate, and dopamine hydrochloride; and the reaction conditions are: reacting in a dark environment at a temperature of 80°C for 1-1.5h.

[0018] Preferably, the modifier comprises triethylamine.

[0019] Preferably, the purification operation is as follows: after the reaction is completed, suction filtration is performed, the filtrate is taken, and a volume of dichloromethane equal to the filtrate is added to mix and dissolve, and then methyl tert-butyl ether with a volume 3-4 times the volume of the filtrate is added for precipitation, centrifugation is performed, and the centrifugal precipitate is taken and dried at 50-60°C for 20-24h.

[0020] Preferably, in step (2), the mass ratio of chitosan oligosaccharide modified polyurethane, crosslinking agent, silane modified isocyanate, and metal ion solution is 100:10-15:8-10:6; the metal ion solution is an acetone solution containing 10 wt% of metal ions, and the metal ions include one or more of iron, copper, and zinc.

[0021] Preferably, in step (2), the silane-modified isocyanate is prepared by the following steps:

[0022] IPDI trimer (isophorone diisocyanate trimer), mercaptopropyltrimethoxysilane, and triethylamine are mixed and reacted to obtain silane-modified isocyanate;

[0023] The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the amount of triethylamine added is 1-2% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane; and the reaction conditions are: reaction in a nitrogen atmosphere at a temperature of 75-80° C. for 1-1.5 hours.

[0024] Preferably, a coating material is prepared using the coating material preparation method as described above.

[0025] Preferably, the coating material as described above is used in a trace element coating of potassium chloride particles.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention prepares an isocyanate-terminated polyurethane prepolymer by reacting isophorone diisocyanate with polycaprolactone diol, tartaric acid, and dimethylglyoxime. The polycaprolactone diol has a certain degree of degradability in a soil environment and is an environmentally friendly material. Introducing the polycaprolactone diol as a degradable soft segment into the polyurethane prepolymer can improve the water resistance and mechanical properties of the polyurethane prepolymer. Dimethylglyoxime reacts with the isocyanate group to form a dynamic covalent bond oxime urethane group, which not only improves the mechanical properties of the polyurethane prepolymer but also has a coordination effect with metal ions. Tartaric acid molecules contain two carboxyl groups. When introduced into the polyurethane prepolymer, the carboxyl groups, as hydrophilic groups, can form channels for water molecules to enter and exit, and have a complexing effect on metal ions. The carboxyl groups, in combination with the oxime urethane groups, synergistically optimize the sustained-release effect of the material.

[0028] Chitosan oligosaccharide is an oligomer of chitosan, which is functionalized with salicylaldehyde to obtain chitosan oligosaccharide Schiff base, and then the chitosan oligosaccharide Schiff base is further reacted with polyurethane prepolymer to obtain chitosan oligosaccharide modified polyurethane, which improves the mechanical properties, hydrophobic properties and thermal stability of the polyurethane matrix by increasing the crosslinking degree, and introduces biomass antioxidant material chitosan oligosaccharide and dynamic covalent Schiff base bond with metal ion chelating ability, which can improve the mechanical properties of the polyurethane matrix, and chelate the metal ions in the system, thereby improving the slow-release effect of the material.

[0029] The present application is prepared by Michael addition reaction of dopamine hydrochloride containing o-diphenol group with tris(2-acryloyloxyethyl) isocyanurate and polyethylene glycol diacrylate to form hyperbranched crosslinking agent containing o-diphenol structure, which is mixed uniformly with chitosan oligosaccharide modified polyurethane, silane modified isocyanate and metal ion solution to obtain a coating material; wherein the crosslinking agent is rich in o-diphenol groups, which can not only react with isocyanate groups in the system to form crosslinking structure, but also improve the crosslinking degree and hydrophobicity of the coating material, and the o-diphenol group has excellent adhesion and metal ion chelating properties, which can improve the adhesion of the coating material and prevent it from falling off, and the metal ions in the chelating system further improve the slow-release ability of the material; the silane modified isocyanate is prepared by nucleophilic reaction of IPDI trimer and mercaptopropyl trimethoxysilane, and the hydrophobic group siloxane is introduced to further improve the hydrophobicity of the coating material.

[0030] When the coating material prepared by the present application is applied to the trace element coating of potassium chloride particles, a film structure with controllable thickness is formed on the surface of the potassium chloride particles by solidification, realizing the slow release of potassium fertilizer and trace elements. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is the process flow chart for preparing the coating material in the present application;

[0032] Figure 2 is the water absorption rate column chart of samples 1-7 in the water resistance test of the present application; DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application, obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments, based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0034] Example 1

[0035] The present embodiment discloses a preparation method of a coating material, comprising the following steps:

[0036] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 80°C in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 80°C for 1.5 hours, adding dimethylglyoxime after the reaction, continuing to react at 75°C for 7 hours, adding tartaric acid after the reaction, and reacting again at 60°C for 1 hour, after the reaction, obtaining a polyurethane prepolymer with a solid content of 45wt%;

[0037] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1:0.8:1; the amount of catalyst dibutyltin dilaurate added is 0.2% of the mass of polycaprolactone diol;

[0038] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:6.5, and reacted at 70°C in a nitrogen atmosphere for 5 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0039] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0040] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:10, swelled at 50°C for 30 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:0.8. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 50°C for 4 hours. After the reaction was completed, the filter cake was filtered and washed with ethanol and ether 5 times the mass of the filter cake, and dried at 40°C for 10 hours to obtain a chitosan oligosaccharide Schiff base.

[0041] Step (2), tris(2-acryloyloxyethyl)isocyanurate, polyethylene glycol diacrylate, dopamine hydrochloride, and dimethyl sulfoxide are mixed, triethylamine is added to adjust the pH value to 8, and the mixture is reacted at 80°C in a dark environment for 1 hour. After the reaction is completed, the mixture is filtered, the filtrate is taken, and an equal volume of dichloromethane is added to the filtrate to mix and dissolve the mixture. Then, methyl tert-butyl ether (3 times the volume of the filtrate) is added to precipitate the mixture, and the mixture is centrifuged. The centrifuged precipitate is taken and dried at 50°C for 24 hours to obtain a cross-linking agent;

[0042] The molar ratio of tris(2-acryloyloxyethyl) isocyanurate, polyethylene glycol diacrylate, and dopamine hydrochloride is 2:3:6, and the amount of dimethyl sulfoxide added is twice the total mass of tris(2-acryloyloxyethyl) isocyanurate, polyethylene glycol diacrylate, and dopamine hydrochloride;

[0043] The chitosan oligosaccharide modified polyurethane, the crosslinking agent, the silane modified isocyanate, and the metal ion solution are mixed in a mass ratio of 100:10:8:6 to obtain a coating material;

[0044] The metal ion solution is a 10 wt% metal ion acetone solution prepared by mixing ferric chloride and acetone;

[0045] Silane-modified isocyanate is prepared by the following steps:

[0046] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted at 75°C in a nitrogen atmosphere for 1.5 hours to obtain silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 1% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0047] Example 2

[0048] This embodiment discloses a method for preparing a coating material, comprising the following steps:

[0049] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 80°C in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 80°C for 1.5 hours, adding dimethylglyoxime after the reaction, continuing to react at 75°C for 7 hours, adding tartaric acid after the reaction, and reacting again at 60°C for 1 hour, after the reaction, obtaining a polyurethane prepolymer with a solid content of 45wt%;

[0050] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1.5:0.85:0.95; the amount of catalyst dibutyltin dilaurate added is 0.2% of the mass of polycaprolactone diol;

[0051] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:6.8, and reacted at 70°C in a nitrogen atmosphere for 5 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0052] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0053] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:10, swelled at 50°C for 30 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:0.8. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 50°C for 4 hours. After the reaction was completed, the filter cake was filtered and washed with ethanol and ether 5 times the mass of the filter cake, and dried at 40°C for 10 hours to obtain a chitosan oligosaccharide Schiff base.

[0054] Step (2), mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution in a mass ratio of 100:11:8.5:6 to obtain a coating material;

[0055] The preparation of the cross-linking agent is the same as that in Example 1; the metal ion solution is a 10 wt% metal ion acetone solution prepared by mixing copper chloride and acetone;

[0056] Silane-modified isocyanate is prepared by the following steps:

[0057] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted at 75°C in a nitrogen atmosphere for 1.5 hours to obtain silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 1% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0058] Example 3

[0059] This embodiment discloses a method for preparing a coating material, comprising the following steps:

[0060] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 83° C. in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 83° C. for 1.3 hours, adding dimethylglyoxime after the reaction, continuing to react at 75° C. for 7 hours, adding tartaric acid after the reaction, and reacting again at 60° C. for 1 hour, obtaining a polyurethane prepolymer with a solid content of 48 wt% after the reaction;

[0061] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1.1:0.9:0.9; the amount of catalyst dibutyltin dilaurate added is 0.2% of the mass of polycaprolactone diol;

[0062] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:7.3, and reacted at 75°C in a nitrogen atmosphere for 4.5 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0063] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0064] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:10, swelled at 50°C for 30 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:0.9. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 55°C for 3.5 hours. After the reaction was completed, the mixture was filtered and the filter cake was taken. The mixture was washed with ethanol and ether in an amount 5 times the mass of the filter cake, and dried at 40°C for 10 hours to obtain a chitosan oligosaccharide Schiff base.

[0065] Step (2), mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution in a mass ratio of 100:13:9:6 to obtain a coating material;

[0066] The preparation of the cross-linking agent is the same as that in Example 1; the metal ion solution is a 10 wt % metal ion acetone solution prepared by mixing zinc chloride and acetone;

[0067] Silane-modified isocyanate is prepared by the following steps:

[0068] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted in a nitrogen atmosphere at 78°C for 1.3 hours to obtain silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 1.5% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0069] Example 4

[0070] This embodiment discloses a method for preparing a coating material, comprising the following steps:

[0071] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 85°C in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 85°C for 1 hour, adding dimethylglyoxime after the reaction, continuing to react at 80°C for 6 hours, adding tartaric acid after the reaction, and reacting again at 65°C for 1 hour, after the reaction, obtaining a polyurethane prepolymer with a solid content of 50wt%;

[0072] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1.15:0.95:0.85; the amount of catalyst dibutyltin dilaurate added is 0.3% of the mass of polycaprolactone diol;

[0073] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:7.8, and reacted at 80°C in a nitrogen atmosphere for 4 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0074] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0075] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:15, swelled at 60°C for 20 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:1. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 55°C for 3.5 hours. After the reaction was completed, the filter cake was filtered and washed with ethanol and ether 5 times the mass of the filter cake, and dried at 40°C for 10 hours to obtain a chitosan oligosaccharide Schiff base.

[0076] Step (2), mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution in a mass ratio of 100:14:9.5:6 to obtain a coating material;

[0077] The preparation of the cross-linking agent is the same as that in Example 1; the metal ion solution is a 10 wt% metal ion acetone solution, which is prepared by mixing ferric chloride, copper chloride and acetone, with the mass ratio of ferric chloride to copper chloride being 1:1;

[0078] Silane-modified isocyanate is prepared by the following steps:

[0079] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted at 80°C in a nitrogen atmosphere for 1 hour to obtain a silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 2% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0080] Example 5

[0081] This embodiment discloses a method for preparing a coating material, comprising the following steps:

[0082] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 85°C in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 85°C for 1 hour, adding dimethylglyoxime after the reaction, continuing to react at 80°C for 6 hours, adding tartaric acid after the reaction, and reacting again at 65°C for 1 hour, after the reaction, obtaining a polyurethane prepolymer with a solid content of 50wt%;

[0083] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1.2:1:0.8; the amount of catalyst dibutyltin dilaurate added is 0.3% of the mass of polycaprolactone diol;

[0084] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:8, and reacted at 80°C for 4 hours in a nitrogen atmosphere. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0085] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0086] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:15, swelled at 60°C for 20 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:1. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 60°C for 3 hours. After the reaction was completed, the filter cake was filtered and washed with ethanol and ether in an amount 8 times the mass of the filter cake. The mixture was dried at 50°C for 8 hours to obtain a chitosan oligosaccharide Schiff base.

[0087] Step (2), mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution in a mass ratio of 100:15:10:6 to obtain a coating material;

[0088] The preparation of the cross-linking agent is the same as that in Example 1; the metal ion solution is a 10 wt % metal ion acetone solution, which is prepared by mixing ferric chloride, zinc chloride and acetone, with the mass ratio of ferric chloride to zinc chloride being 1:1;

[0089] Silane-modified isocyanate is prepared by the following steps:

[0090] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted at 80°C in a nitrogen atmosphere for 1 hour to obtain a silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 2% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0091] Comparative Example 1

[0092] This comparative example discloses a method for preparing a coating material, comprising the following steps:

[0093] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 80°C in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 80°C for 1.5 hours, adding dimethylglyoxime after the reaction, continuing to react at 75°C for 7 hours, adding tartaric acid after the reaction, and reacting again at 60°C for 1 hour, after the reaction, obtaining a polyurethane prepolymer with a solid content of 45wt%;

[0094] The molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1:0.8:1; the amount of catalyst dibutyltin dilaurate added is 0.2% of the mass of polycaprolactone diol;

[0095] The polyurethane prepolymer and chitosan oligosaccharide Schiff base were mixed in a mass ratio of 30:6.5, and reacted at 70°C in a nitrogen atmosphere for 5 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide modified polyurethane;

[0096] The chitosan oligosaccharide Schiff base is prepared by the following steps:

[0097] Chitosan oligosaccharide and ethanol were mixed in a mass ratio of 1:10, swelled at 50°C for 30 minutes, salicylic aldehyde was added, and the mass ratio of chitosan oligosaccharide to salicylic aldehyde was 10:0.8. A 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6. The mixture was reacted at 50°C for 4 hours. After the reaction was completed, the filter cake was filtered and washed with ethanol and ether 5 times the mass of the filter cake, and dried at 40°C for 10 hours to obtain a chitosan oligosaccharide Schiff base.

[0098] Step (2), mixing chitosan oligosaccharide modified polyurethane, IPDI trimer, and metal ion solution in a mass ratio of 110:8:6 to obtain a coating material;

[0099] The metal ion solution is an acetone solution containing 10 wt% of metal ions, which is prepared by mixing ferric chloride and acetone.

[0100] Comparative Example 2

[0101] This comparative example discloses a method for preparing a coating material, comprising the following steps:

[0102] Step (1), mixing isophorone diisocyanate and polycaprolactone diol, heating to 80° C. in a nitrogen atmosphere, adding solvent acetone and catalyst dibutyltin dilaurate, reacting at 80° C. for 5 hours, and obtaining a polyurethane prepolymer with a solid content of 45 wt% after the reaction is completed;

[0103] The molar ratio of isophorone diisocyanate to polycaprolactone diol is 4:2.8; the amount of catalyst dibutyltin dilaurate added is 0.2% of the mass of polycaprolactone diol;

[0104] The polyurethane prepolymer and chitosan oligosaccharide were mixed in a mass ratio of 30:6.5, and reacted at 70°C in a nitrogen atmosphere for 5 hours. After the reaction, the solvent acetone was removed by rotary evaporation to obtain chitosan oligosaccharide-modified polyurethane;

[0105] Step (2), mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution in a mass ratio of 100:10:8:6 to obtain a coating material;

[0106] The preparation of the cross-linking agent is the same as that in Example 1; the metal ion solution is a 10 wt % metal ion acetone solution prepared by mixing ferric chloride and acetone;

[0107] Silane-modified isocyanate is prepared by the following steps:

[0108] IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine were mixed and reacted at 75°C in a nitrogen atmosphere for 1.5 hours to obtain silane-modified isocyanate. The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane was 3:1. The amount of triethylamine added was 1% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane.

[0109] In the above embodiments and comparative examples:

[0110] Polycaprolactone diol was obtained from Juren Chemical New Materials Technology Co., Ltd., product name PCL2053, Mw=530; tartaric acid was obtained from Leyan Reagent, CAS number: 133-37-9; dimethylglyoxime was obtained from Aladdin Biochemical Technology Co., Ltd., CAS number: 95-45-4; chitosan oligosaccharide was obtained from Wuhan Jiangxin Biotechnology Co., Ltd., with a degree of deacetylation of 90% and a relative molecular mass of ≤5000; salicylaldehyde was obtained from Aladdin Biochemical Technology Co., Ltd., CAS number: 90-02-8; tris(2-acryloyloxyethyl) isocyanurate was obtained from MacLean Biochemical Technology Co., Ltd., CAS number: 40220-08-4; polyethylene glycol diacrylate was obtained from Aladdin Biochemical Technology Co., Ltd., with an average molecular weight of 400; dopamine hydrochloride was obtained from MacLean Biochemical Technology Co., Ltd., CAS number: 62-31-7; IPDI trimer was Evonik IPDI trimer Vestanat T1890E, the solvent was n-butyl acetate, and the solid content was 70%.

[0111] Test example

[0112] (1) Mechanical properties and water resistance test

[0113] The coating materials prepared in Examples 1-5 and Comparative Examples 1-2 were placed in a mold and cured at 80° C. for 3 hours, respectively designated as Samples 1-7. The mechanical properties and water resistance of Samples 1-7 were tested. The specific test results are shown in Table 1:

[0114] Table 1

[0115]

[0116]

[0117] The testing of the indicators in Table 1 is based on the following standards: impact strength is measured with reference to GB / T 1732-2020 "Determination of impact resistance of paint films"; water resistance is expressed by water absorption, which is measured with reference to HGT3344-1985 "Determination of water absorption of paint films".

[0118] Comparative Example 1 did not use silane-modified isocyanate and did not add a crosslinking agent, so the crosslinking degree of the coating material decreased. Therefore, the mechanical properties and water resistance of Sample 6 prepared in Comparative Example 2 decreased.

[0119] (2) Sustained release performance test

[0120] The coating materials prepared in Examples 1-5 and Comparative Examples 1-2 were used to coat potassium chloride spherical particles. The amount of coating material used was 5 wt % of the potassium chloride particles. After solidification and cooling, samples 1-7 were obtained. The sustained-release properties of samples 1-7 were tested. The specific test results are shown in Table 2:

[0121] Table 2

[0122]

[0123]

[0124] The testing of the indicators in Table 2 is based on the following standards: the nutrient release rate is measured with reference to GB / T23348-2009 "Slow-release fertilizers" and the temperature is 25°C.

[0125] According to the test results in Table 2, it can be seen that the potassium chloride granular fertilizer prepared by using the coating material prepared by the present invention has excellent slow-release performance.

[0126] In Comparative Example 1, no silane-modified isocyanate was used, no crosslinking agent was added, and the lack of catechol groups with adhesion and chelation properties resulted in a decreased degree of crosslinking of the coating material, reduced mechanical properties, and water resistance. Sample 6 prepared in Comparative Example 1 was prone to surface damage during use, resulting in reduced sustained-release performance.

[0127] In Comparative Example 2, no dimethylglyoxime and tartaric acid were added when preparing the polyurethane prepolymer, and the chitosan oligosaccharide was not modified. It lacked oxime urethane groups, carboxyl groups and Schiff base bonds with metal ion chelating ability. Although the water resistance was improved, the chelating ability for metal ions was reduced, so the sustained-release performance of Sample 7 prepared by Comparative Example 2 was reduced.

[0128] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing a coating material, characterized in that: The following steps are involved: Step (1), mixing isophorone diisocyanate and polycaprolactone diol, adding a solvent and a catalyst, reacting, adding dimethylglyoxime after the reaction is completed, continuing the reaction, adding tartaric acid, reacting again, and obtaining a polyurethane prepolymer after the reaction is completed; The polyurethane prepolymer and the chitosan oligosaccharide Schiff base are mixed and reacted, and after the reaction is completed, the solvent acetone is removed by rotary evaporation to obtain the chitosan oligosaccharide modified polyurethane; The chitosan oligosaccharide Schiff base is prepared by the following steps: Chitosan oligosaccharide is mixed with ethanol, swelled, salicylaldehyde is added, a regulator is added to adjust the pH value, reacted, filtered, washed, and dried to obtain chitosan oligosaccharide Schiff base; Step (2), mixing tris(2-acryloyloxyethyl)isocyanurate, polyethylene glycol diacrylate, dopamine hydrochloride, and dimethyl sulfoxide, adjusting the pH value, reacting, and purifying after the reaction to obtain a cross-linking agent; mixing chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate, and a metal ion solution to obtain a coating material; Wherein, the silane-modified isocyanate is prepared by the following steps: IPDI trimer, mercaptopropyltrimethoxysilane and triethylamine are mixed and reacted to obtain silane-modified isocyanate after the reaction is completed.

2. The method for preparing a coating material according to claim 1, wherein: In the step (1), the molar ratio of isophorone diisocyanate, polycaprolactone diol, dimethylglyoxime and tartaric acid is 4:1-1.2:0.8-1:0.8-1; the catalyst is dibutyltin dilaurate, and the amount of the catalyst added is 0.2-0.3% of the mass of the polycaprolactone diol.

3. The method for preparing a coating material according to claim 1, wherein: In the step (1), when preparing the polyurethane prepolymer, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 80-85°C for 1-1.5 hours; continuing the reaction conditions are: continuing the reaction in a nitrogen atmosphere at a temperature of 75-80°C for 6-7 hours; and re-reacting conditions are: reacting again in a nitrogen atmosphere at a temperature of 60-65°C for 1 hour; and the solid content of the polyurethane prepolymer is 45-50wt%.

4. The method for preparing a coating material according to claim 1, wherein: In the step (1), the mass ratio of the polyurethane prepolymer to the chitosan oligosaccharide Schiff base is 30:6.5-8; when preparing the chitosan oligosaccharide modified polyurethane, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 70-80° C. for 4-5 hours.

5. The method for preparing a coating material according to claim 1, wherein: When preparing chitosan oligosaccharide Schiff base in step (1): The swelling conditions are: swelling at 50-60°C for 20-30 minutes; the mass ratio of chitosan oligosaccharide to salicylic aldehyde is 10:0.8-1; and the reaction conditions are: reacting at a pH value of 6 and a temperature of 50-60°C for 3-4 hours.

6. The method for preparing a coating material according to claim 1, characterized in that: In step (2), the molar ratio of tris(2-acryloyloxyethyl)isocyanurate, polyethylene glycol diacrylate, and dopamine hydrochloride is 2:3:6; and the reaction conditions are: reacting in a dark environment at a temperature of 80° C. for 1-1.5 hours.

7. The method for preparing a coating material according to claim 1, wherein: In the step (2), the mass ratio of chitosan oligosaccharide modified polyurethane, crosslinking agent, silane modified isocyanate, and metal ion solution is 100:10-15:8-10:6; the metal ion solution is an acetone solution containing 10 wt% of metal ions, and the metal ions include one or more of iron, copper, and zinc.

8. The method for preparing a coating material according to claim 1, wherein: When preparing silane-modified isocyanate in step (2): The molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the amount of triethylamine added is 1-2% of the total mass of IPDI trimer and mercaptopropyltrimethoxysilane; and the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 75-80° C. for 1-1.5 hours.

9. A coating material prepared by the method for preparing a coating material according to any one of claims 1 to 8.

10. Use of the coating material according to claim 9 in trace element coating of potassium chloride particles.

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