Coating material, preparation method and application in trace element coating for potassium chloride particles

Abstract

The invention relates to the technical field of fertilizers, and discloses a coating material, a preparation method and application of the coating material in a trace element coating for potassium chloride particles. The preparation method comprises the following steps: reacting isophorone diisocyanate with polycaprolactone diol, tartaric acid and dimethylglyoxime to prepare a polyurethane prepolymer, continuously reacting the polyurethane prepolymer with chitosan oligosaccharide Schiff base to obtain chitosan oligosaccharide modified polyurethane, and mixing the chitosan oligosaccharide modified polyurethane, a cross-linking agent, silane modified isocyanate and a trace element solution to obtain the coating material. The coating material is good in mechanical property, contains trace elements, has a controlled release effect on the potassium chloride granulated fertilizer, and can be applied to the potassium chloride granulated fertilizer as a trace element coating.

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 photolysis of water in photosynthesis and increase the osmotic pressure of cells. However, excessive or concentrated application of potassium chloride will cause excessive local ion concentration in the soil, thereby endangering plant health. In addition, since potassium chloride is a water-soluble fertilizer, it is easily 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, in which a coating agent is used to coat the granular potassium chloride fertilizer, 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 particles. The prepared coating material has good mechanical properties, contains trace elements, and has a controlled release effect on potassium chloride particle fertilizers. The coating material can be used as a trace element coating in potassium chloride particle 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 after the reaction is completed, 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 tri(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 is completed 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 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; when preparing the polyurethane prepolymer, the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 80-85°C for 1-1.5h; continuing the reaction conditions are: continuing the reaction in a nitrogen atmosphere at a temperature of 75-80°C for 6-7h; and re-reacting conditions are: reacting again in a nitrogen atmosphere at a temperature of 60-65°C for 1h; 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: reacting 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] The chitosan oligosaccharide is mixed with ethanol, swelled, salicylaldehyde is added, a regulator is added to adjust the pH value, reacted, and after the reaction is completed, filtered, washed, and dried to obtain the 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 salicylaldehyde 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.

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

[0017] Preferably, in the step (2), the molar ratio of tris(2-acryloxyethyl)isocyanurate, polyethylene glycol diacrylate and dopamine hydrochloride is 2:3:6, and the amount of dimethyl sulfoxide added is 2-3 times the sum of the mass of tris(2-acryloxyethyl)isocyanurate, polyethylene glycol diacrylate and dopamine hydrochloride; and the reaction conditions are: reacting in a light-proof 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, an equal volume of dichloromethane is added to the filtrate to mix and dissolve, and then 3-4 times the volume of the filtrate is added for precipitation by methyl tert-butyl ether, centrifugation is performed, and the centrifugal precipitate is taken and dried at 50-60° C. for 20-24 hours.

[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), mercaptopropyl trimethoxysilane and triethylamine are mixed and reacted to obtain silane-modified isocyanate after the reaction is completed;

[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: reacting 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, a 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 invention prepares an isocyanate-terminated polyurethane prepolymer by reacting isophorone diisocyanate with polycaprolactone diol, tartaric acid and dimethylglyoxime; wherein the polycaprolactone diol has certain degradability in a soil environment and is an environmentally friendly material, and the polycaprolactone diol is introduced into the polyurethane prepolymer as a degradable soft segment to improve the water resistance and mechanical properties of the polyurethane prepolymer; dimethylglyoxime reacts with an isocyanate group to form a dynamic covalent bond oxime urethane group, which can not only improve the mechanical properties of the polyurethane prepolymer, but also has a coordination effect with metal ions; the tartaric acid molecule contains two carboxyl groups, and the tartaric acid molecule is introduced into the polyurethane prepolymer, and the carboxyl group, as a hydrophilic group, can form a channel for water molecules to enter and exit, and has a complexing effect on metal ions, and synergistically optimizes the sustained release effect of the material with the oxime urethane group;

[0028] Chitosan oligosaccharide is a low polymer of chitosan. After reacting it with salicylaldehyde to form a Schiff base functionalization, chitosan oligosaccharide Schiff base is obtained, which is then further reacted with a polyurethane prepolymer to obtain chitosan oligosaccharide-modified polyurethane. On the one hand, the mechanical properties, hydrophobic properties and thermal stability of the polyurethane matrix are improved by increasing the degree of crosslinking. On the other hand, the introduction of biomass antioxidant material chitosan oligosaccharide and dynamic covalent Schiff base bonds with metal ion chelating ability can improve the mechanical properties of the polyurethane matrix and chelate the metal ions in the system, thereby improving the sustained release effect of the material.

[0029] The invention allows dopamine hydrochloride containing catechol groups to undergo Michael addition reaction with tri(2-acryloxyethyl)isocyanurate and polyethylene glycol diacrylate to form a hyperbranched crosslinking agent containing a catechol structure, and then uniformly mixes the hyperbranched crosslinking agent with chitosan oligosaccharide-modified polyurethane, silane-modified isocyanate and a metal ion solution to obtain a coating material. The crosslinking agent is rich in catechol groups, which can react with isocyanate groups in the system to form a crosslinking structure, thereby improving the crosslinking degree and hydrophobicity of the coating material. The catechol groups have excellent adhesion and metal ion chelating properties, thereby improving the adhesion of the coating material, making it difficult to fall off, and chelating metal ions in the system, thereby further improving the sustained release capacity of the material. The silane-modified isocyanate is prepared by nucleophilic reaction between IPDI trimer and mercaptopropyltrimethoxysilane, and introduces a hydrophobic group siloxane, thereby further improving the hydrophobicity of the coating material.

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

[0031] Figure 1 is a process flow chart for preparing coating materials in the present invention;

[0032] Figure 2 It is a bar graph of water absorption of samples 1-7 in the water resistance test of the present invention; DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment discloses a method for preparing 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, reacting again at 60° C. for 1 hour, and obtaining a polyurethane prepolymer with a solid content of 45wt% after the reaction;

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

[0039] Wherein, 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, salicylaldehyde was added, the mass ratio of chitosan oligosaccharide to salicylaldehyde was 10:0.8, 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6, reacted at 50°C for 4 hours, and after the reaction was completed, filtered, the filter cake was taken, ethanol and ether were added in an amount of 5 times the mass of the filter cake for washing, and dried at 40°C for 10 hours to obtain chitosan oligosaccharide Schiff base;

[0041] Step (2), tri(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, and then methyl tert-butyl ether in an amount three times the volume of the filtrate is added to precipitate, 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 sum of the 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, which is prepared by mixing ferric chloride and acetone;

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

[0046] IPDI trimer, mercaptopropyltrimethoxysilane and triethylamine were mixed and reacted in a nitrogen atmosphere at 75°C for 1.5 hours. After the reaction, silane-modified isocyanate was obtained. 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, reacting again at 60° C. for 1 hour, and obtaining a polyurethane prepolymer with a solid content of 45wt% after the reaction;

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

[0052] Wherein, 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, salicylaldehyde was added, the mass ratio of chitosan oligosaccharide to salicylaldehyde was 10:0.8, 0.1 mol / L sodium hydroxide aqueous solution was added to adjust the pH value to 6, reacted at 50°C for 4 hours, and after the reaction was completed, filtered, the filter cake was taken, ethanol and ether were added in an amount of 5 times the mass of the filter cake for washing, and dried at 40°C for 10 hours to obtain chitosan oligosaccharide Schiff base;

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

[0055] Among them, the preparation of the crosslinking agent is the same as that in Example 1; the metal ion solution is an acetone solution of 10 wt% metal ions, which is prepared by mixing copper chloride and acetone;

[0056] The silane modified isocyanate is prepared through the following steps:

[0057] Mix IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine, and react at 75 °C for 1.5 h in a nitrogen atmosphere. After the reaction is completed, silane modified isocyanate is obtained; the molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the addition amount of triethylamine is 1% of the sum of the masses of IPDI trimer and mercaptopropyltrimethoxysilane.

[0058] Example 3

[0059] This example discloses a preparation method of a coating material, including the following steps:

[0060] Step (1): Mix isophorone diisocyanate and polycaprolactone diol, heat up to 83 °C in a nitrogen atmosphere, add solvent acetone and catalyst dibutyltin dilaurate, react at 83 °C for 1.3 h. After the reaction is completed, add dimethylglyoxime and continue to react at 75 °C for 7 h. After the reaction is completed, add tartaric acid and react again at 60 °C for 1 h. After the reaction is completed, a polyurethane prepolymer with a solid content of 48 wt% is obtained;

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

[0062] Mix the polyurethane prepolymer and chitosan oligosaccharide Schiff base in a mass ratio of 30:7.3, react at 75 °C for 4.5 h in a nitrogen atmosphere. After the reaction is completed, rotary evaporate to remove the solvent acetone to obtain chitosan oligosaccharide modified polyurethane;

[0063] Among them, the chitosan oligosaccharide Schiff base is prepared through the following steps:

[0064] Mix chitosan oligosaccharide and ethanol at a mass ratio of 1:10, swell at 50 °C for 30 min, add salicylaldehyde, with the mass ratio of chitosan oligosaccharide to salicylaldehyde being 10:0.9, add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH value to 6, react at 55 °C for 3.5 h, after the reaction is completed, carry out suction filtration, take the filter cake, successively add ethanol and ether which are 5 times the mass of the filter cake for washing, and dry at 40 °C for 10 h to obtain chitosan oligosaccharide Schiff base;

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

[0066] Among them, the preparation of the crosslinking 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 zinc chloride and acetone;

[0067] The silane modified isocyanate is prepared through the following steps:

[0068] Mix IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine, react at 78 °C for 1.3 h in a nitrogen atmosphere, after the reaction is completed, obtain silane modified isocyanate; the molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the addition amount of triethylamine is 1.5% of the sum of the masses of IPDI trimer and mercaptopropyltrimethoxysilane.

[0069] Example 4

[0070] This example discloses a preparation method of a coating material, including the following steps:

[0071] Step (1): Mix isophorone diisocyanate and polycaprolactone diol, heat up to 85 °C in a nitrogen atmosphere, add solvent acetone and catalyst dibutyltin dilaurate, react at 85 °C for 1 h, after the reaction is completed, add dimethylglyoxime, continue to react at 80 °C for 6 h, after the reaction is completed, add tartaric acid, and react again at 65 °C for 1 h, after the reaction is completed, obtain a polyurethane prepolymer with a solid content of 50 wt%;

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

[0073] Mix the polyurethane prepolymer and chitosan oligosaccharide Schiff base at a mass ratio of 30:7.8, react at 80 °C for 4 h in a nitrogen atmosphere, after the reaction is completed, rotary evaporate to remove the solvent acetone to obtain chitosan oligosaccharide modified polyurethane;

[0074] Among them, the chitosan Schiff base is prepared through the following steps:

[0075] Mix chitosan and ethanol at a mass ratio of 1:15, swell at 60 °C for 20 min, add salicylaldehyde, with the mass ratio of chitosan to salicylaldehyde being 10:1, add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH value to 6, react at 55 °C for 3.5 h. After the reaction, perform suction filtration, take the filter cake, successively add ethanol and ether 5 times the mass of the filter cake for washing, and dry at 40 °C for 10 h to obtain the chitosan Schiff base;

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

[0077] Among them, the preparation of the crosslinking agent is the same as 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, and the mass ratio of ferric chloride to copper chloride is 1:1;

[0078] The silane-modified isocyanate is prepared through the following steps:

[0079] Mix IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine, react at 80 °C for 1 h in a nitrogen atmosphere. After the reaction, obtain the silane-modified isocyanate; the molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the addition amount of triethylamine is 2% of the sum of the masses of IPDI trimer and mercaptopropyltrimethoxysilane.

[0080] Example 5

[0081] This example discloses a preparation method of a coating material, including the following steps:

[0082] Step (1): Mix isophorone diisocyanate and polycaprolactone diol, heat up to 85 °C in a nitrogen atmosphere, add solvent acetone and catalyst dibutyltin dilaurate, react at 85 °C for 1 h. After the reaction, add dimethylglyoxime, continue to react at 80 °C for 6 h. After the reaction, add tartaric acid, and react again at 65 °C for 1 h. After the reaction, obtain a polyurethane prepolymer with a solid content of 50 wt%;

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

[0084] Mix the polyurethane prepolymer and chitosan Schiff base in a mass ratio of 30:8, react at 80 °C for 4 h in a nitrogen atmosphere. After the reaction, rotary evaporate to remove the solvent acetone to obtain chitosan-modified polyurethane;

[0085] Among them, the chitosan Schiff base is prepared by the following steps:

[0086] Mix chitosan and ethanol in a mass ratio of 1:15, swell at 60 °C for 20 min, add salicylaldehyde, the mass ratio of chitosan to salicylaldehyde is 10:1, add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH value to 6, react at 60 °C for 3 h. After the reaction, perform suction filtration, take the filter cake, successively add ethanol and ether 8 times the mass of the filter cake for washing, and dry at 50 °C for 8 h to obtain chitosan Schiff base;

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

[0088] Among them, the preparation of the crosslinking 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, and the mass ratio of ferric chloride to zinc chloride is 1:1;

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

[0090] Mix IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine, react at 80 °C for 1 h in a nitrogen atmosphere. After the reaction, obtain silane-modified isocyanate; the molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the addition amount of triethylamine is 2% of the sum of the masses of IPDI trimer and mercaptopropyltrimethoxysilane.

[0091] Comparative Example 1

[0092] This comparative example discloses a preparation method of a coating material, including the following steps:

[0093] Step (1): Mix isophorone diisocyanate and polycaprolactone diol, heat up to 80 °C in a nitrogen atmosphere, add the solvent acetone and the catalyst dibutyltin dilaurate, react at 80 °C for 1.5 h. After the reaction, add dimethylglyoxime, continue to react at 75 °C for 7 h. After the reaction, add tartaric acid, and react again at 60 °C for 1 h. After the reaction, obtain a polyurethane prepolymer with a solid content of 45 wt%;

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

[0095] Mix the polyurethane prepolymer and chitosan Schiff base in a mass ratio of 30:6.5, react at 70 °C for 5 h in a nitrogen atmosphere. After the reaction, rotary evaporate to remove the solvent acetone to obtain chitosan-modified polyurethane;

[0096] Among them, the chitosan Schiff base is prepared by the following steps:

[0097] Mix chitosan and ethanol in a mass ratio of 1:10, swell at 50 °C for 30 min, add salicylaldehyde, the mass ratio of chitosan to salicylaldehyde is 10:0.8, add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH value to 6, react at 50 °C for 4 h. After the reaction, filter by suction, take the filter cake, wash it successively with 5 times the mass of ethanol and ether of the filter cake, and dry it at 40 °C for 10 h to obtain chitosan Schiff base;

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

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

[0100] Comparative Example 2

[0101] This comparative example discloses a preparation method of a coating material, including the following steps:

[0102] Step (1), mix isophorone diisocyanate and polycaprolactone diol, heat up to 80 °C in a nitrogen atmosphere, add the solvent acetone and the catalyst dibutyltin dilaurate, and react at 80 °C for 5 h. After the reaction, obtain a polyurethane prepolymer with a solid content of 45 wt%;

[0103] Among them, the molar ratio of isophorone diisocyanate and polycaprolactone diol is 4:2.8; the addition amount of the catalyst dibutyltin dilaurate is 0.2% of the mass of polycaprolactone diol;

[0104] Mix the polyurethane prepolymer and chitosan in a mass ratio of 30:6.5, react at 70 °C for 5 h in a nitrogen atmosphere. After the reaction, rotary evaporate to remove the solvent acetone to obtain chitosan-modified polyurethane;

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

[0106] Among them, the preparation of the crosslinking agent is the same as that in Example 1; the metal ion solution is an acetone solution of 10 wt% metal ions, which is prepared by mixing ferric chloride and acetone;

[0107] The silane modified isocyanate is prepared through the following steps:

[0108] Mix IPDI trimer, mercaptopropyltrimethoxysilane, and triethylamine, and react at 75 °C for 1.5 h in a nitrogen atmosphere. After the reaction, silane modified isocyanate is obtained; the molar ratio of IPDI trimer to mercaptopropyltrimethoxysilane is 3:1; the addition amount of triethylamine is 1% of the sum of the masses of IPDI trimer and mercaptopropyltrimethoxysilane.

[0109] In the above examples and comparative examples:

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

[0111] Test Example

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

[0113] Take the coating materials prepared in Examples 1-5 and Comparative Examples 1-2, place them in a mold and cure at 80 °C for 3 h, and record them as Samples 1-7 respectively. Test the mechanical properties and water resistance of Samples 1-7, and the specific test results are shown in Table 1:

[0114] Table 1

[0115]

[0116]

[0117] The detection basis for the indicators in Table 1 is as follows: The impact strength is determined with reference to GB / T 1732-2020 "Determination of impact resistance of paint films"; The water resistance is expressed by the water absorption rate, and the water absorption rate is determined with reference to HGT3344-1985 "Determination of water absorption rate of paint films".

[0118] In Comparative Example 1, silane-modified isocyanate was not selected and no cross-linking agent was added, resulting in a decrease in the cross-linking degree of the coating material. Therefore, the mechanical properties and water resistance of Sample 6 prepared from 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 dosage of the coating material was 5wt% of the potassium chloride particles. After curing and cooling, Samples 1-7 were obtained respectively, and the sustained-release performance of Samples 1-7 was tested. The specific test results are shown in Table 2:

[0121] Table 2

[0122]

[0123]

[0124] The detection basis for the indicators in Table 2 is as follows: The nutrient release rate is determined with reference to GB / T23348-2009 "Slow-release fertilizers" at a temperature of 25°C.

[0125] It can be seen from the test results in Table 2 that the potassium chloride granular fertilizer prepared with the coating material prepared by the present invention has excellent sustained-release performance.

[0126] In Comparative Example 1, silane-modified isocyanate was not selected and no cross-linking agent was added, lacking catechol groups with adhesion properties and chelating effects, resulting in a decrease in the cross-linking degree of the coating material, a decrease in mechanical properties and water resistance. Sample 6 prepared from Comparative Example 1 is prone to surface damage during use, so the sustained-release performance is reduced;

[0127] When preparing the polyurethane prepolymer in Comparative Example 2, dimethylglyoxime and tartaric acid were not added, and chitosan was not modified, lacking oxime carbamate groups, carboxyl groups and Schiff base bonds with metal ion chelating ability. Although the water resistance was improved, the chelating ability for metal ions decreased. Therefore, the sustained-release performance of Sample 7 prepared from Comparative Example 2 decreased.

[0128] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended 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 after the reaction is completed, 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; Step (2), mixing tri(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; The chitosan oligosaccharide modified polyurethane, a crosslinking agent, a silane modified isocyanate and a metal ion solution are mixed to obtain a coating material.

2. The method for preparing a coating material according to claim 1, characterized in that: 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 added amount of the catalyst is 0.2-0.3% of the mass of the polycaprolactone diol.

3. The method for preparing a coating material according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: In the step (1), the chitosan oligosaccharide Schiff base comprises the following steps: The chitosan oligosaccharide is mixed with ethanol, swelled, salicylaldehyde is added, a regulator is added to adjust the pH value, reacted, and after the reaction is completed, filtered, washed, and dried to obtain the chitosan oligosaccharide Schiff base; The swelling conditions are: swelling at 50-60°C for 20-30 minutes; the mass ratio of chitosan oligosaccharide to salicylaldehyde 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 the step (2), the molar ratio of tri(2-acryloyloxyethyl)isocyanurate, polyethylene glycol diacrylate and dopamine hydrochloride is 2:3:6; and the reaction conditions are: reacting at 80° C. in a light-proof environment for 1-1.5 hours.

7. The method for preparing a coating material according to claim 1, characterized in that: 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 10wt% 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, characterized in that: In the step (2), the silane-modified isocyanate is prepared by the following steps: The IPDI trimer, mercaptopropyltrimethoxysilane and triethylamine are mixed and reacted to obtain silane-modified isocyanate after the reaction is completed; 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 as claimed in claim 9 in trace element coating of potassium chloride particles.

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