A method for preparing a coiled material powder coating for soilless planting pools and application thereof

Abstract

This invention relates to the field of powder coating technology, specifically to a method for preparing and applying a roll-type powder coating for hydroponic planting ponds. It addresses technical problems such as poor hydrolysis resistance and the release of harmful substances in existing coatings. The method involves pre-mixing high-hydrolysis-resistant polyester resin, curing agent, hydrolysis-resistant stabilizer, hydrolysis-resistant metal substrate adhesion promoter, pigment, precipitated barium sulfate, active silica powder, leveling agent, degassing agent, wetting and dispersing agent, and wax additives in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt mixing and extrusion. The resulting product is then tableted and cooled, pulverized, and finally finely ground in an ACM mill to obtain the roll-type powder coating. This roll-type powder coating meets the requirements of metal roll pre-coating processes, can withstand long-term immersion in hydroponic nutrient solutions and alkaline cleaning agents, and all components comply with food contact materials and drinking water hygiene standards, making it a safe, environmentally friendly, and durable special powder coating.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, specifically to a method for preparing and applying a roll powder coating for soilless planting ponds. Background Technology

[0002] With the development of modern agricultural technology, industrialized and intensive soilless cultivation is becoming increasingly popular. Its core equipment, the planting pool or cultivation trough, is typically made of pre-coated metal rolls through processes such as rolling, bending, and welding. The inner walls of these troughs need to be immersed in a hydroponic nutrient solution containing various inorganic salt ions such as nitrates, phosphates, potassium, calcium, and magnesium for extended periods. They also require regular cleaning and disinfection with alkaline solutions such as sodium hypochlorite and sodium hydroxide to inhibit the growth of algae and bacteria. Therefore, stringent requirements are placed on the protective coating for the inner walls.

[0003] Currently, the following methods are mainly used for the protection of the inner wall of such pools: (1) using ordinary liquid epoxy or polyurethane coatings, but harmful solvents may remain during the curing process, and there is a risk of coating softening, decreased adhesion and slow release of harmful substances after long-term immersion, which does not meet the requirements for food safety contact materials; (2) using conventional powder coatings, although there is no solvent problem, most general-purpose polyester / TGIC or epoxy / polyester systems are prone to hydrolysis and saponification reactions under long-term alkaline immersion and ion penetration, resulting in decreased coating gloss, blistering and peeling, and may release substances that affect plant growth or do not meet drinking water safety standards.

[0004] Therefore, the market urgently needs a special powder coating that can meet the requirements of metal coil pre-coating process, withstand long-term immersion in hydroponic nutrient solution and alkaline cleaning agent, and whose components meet the hygiene standards for food contact materials and drinking water. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing and applying a roll powder coating for soilless planting ponds.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, this application provides a method for preparing a roll-type powder coating for soilless planting ponds, comprising the following steps:

[0008] Step 1: Weigh out the following components by weight: 55-70 parts of high hydrolysis-resistant polyester resin, 4-7 parts of curing agent, 1-2.5 parts of hydrolysis-resistant stabilizer, 1.5-3 parts of hydrolysis-resistant metal substrate adhesion promoter, 8-15 parts of pigment, 10-12 parts of precipitated barium sulfate, 5-8 parts of activated silica powder, 0.5-1 part of leveling agent, 0.3-0.6 parts of degassing agent, 0.3-0.6 parts of wetting and dispersing agent, and 0.4-0.8 parts of wax additives.

[0009] Step 2: Add the high hydrolysis-resistant polyester resin, curing agent, hydrolysis-resistant stabilizer, hydrolysis-resistant metal substrate adhesion promoter, pigment, precipitated barium sulfate, activated silica powder, leveling agent, degassing agent, wetting and dispersing agent, and wax additives into a high-speed mixer and premix for 12-14 minutes at a speed of 1400-1500 r / min. Then add it to a twin-screw extruder and set the temperatures for each section: feeding section temperature 105℃, compression section temperature 115℃, and melting section temperature... The temperature is 125℃, the homogenization section temperature is 120℃, the screw speed is 300r / min, after melting and mixing, the mixture is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for preliminary pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverization speed set at 4500r / min and the classifying wheel speed at 12000r / min. After fine pulverization, the mixture is classified by a classifier, and powder with a particle size D50=35μm is collected to obtain the coil powder coating.

[0010] In a preferred embodiment of the present invention, the hydrolysis-resistant metal substrate adhesion promoter is prepared by the following steps:

[0011] Step a1: Add sepiolite and deionized water to a beaker, turn on mechanical stirring, and stir for 6-6.2 hours at a stirring rate of 750-800 r / min. During this period, use a strong magnet to attract the impurities back and forth at the bottom of the beaker 3 times every 1 hour. Stop mechanical stirring during attraction and continue stirring after the impurities settle. Then transfer to an ultrasonic cleaner and ultrasonically disperse for 40-42 minutes at a power of 450-500W and a frequency of 40kHz. Turn off the ultrasonic cleaner and let it stand for 8-10 hours. Pour off the upper two-thirds of the suspension, discard the bottom precipitate, filter the upper suspension with a Buchner funnel, collect the filter cake, wash it 4-5 times with distilled water, and then put it into a forced-air drying oven to dry to constant weight at a temperature of 75-80℃. Cool to room temperature to obtain purified and activated sepiolite.

[0012] Step a2: Add the purified and activated sepiolite and silicon tetrachloride solution to a beaker and stir magnetically for 30-33 min at a stirring rate of 450-500 r / min. Then transfer it to a three-necked flask equipped with a stirrer, thermometer and reflux condenser, and place it in a constant temperature water bath. Stir the reaction at a temperature of 70-75℃ and a stirring rate of 550-600 r / min for 8-8.2 h. After the reaction is completed, cool to room temperature, filter and collect the filter cake, wash with deionized water until the pH of the filtrate is neutral, place the filter cake in a vacuum drying oven and dry at a temperature of 55-60℃ for 24-26 h. After cooling, grind and pass through a 200-mesh standard sieve to obtain acid-modified sepiolite.

[0013] Step a3: Add γ-glycidoxypropyltrimethoxysilane, deionized water, and anhydrous ethanol to a beaker. Adjust the pH of the system to 9-10 with ammonia at 25-30℃ and a stirring rate of 280-300 r / min. Seal the beaker with plastic wrap and place it in a 35℃ constant temperature water bath. Stir magnetically for 30-32 min to obtain a silane hydrolysate. Add acid-modified sepiolite and the mixed solvent to the beaker and ultrasonically disperse at 280-300 W for 30-32 min to obtain a sepiolite dispersion. The silane hydrolysate was added dropwise to the sepiolite dispersion at a rate of 1 mL / min, and stirred for 10-12 min. The mixture was then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. The flask was placed in an 80°C water bath and refluxed for 5-5.2 h with a stirring rate of 450-500 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed 3-4 times with isopropanol, and then placed in a vacuum drying oven at 55-60°C for 12-13 h. After cooling, silane-modified sepiolite was obtained.

[0014] Step a4: Add polyethyleneimine, deionized water, and anhydrous ethanol to a beaker, place it in a 50℃ constant temperature water bath, and magnetically stir for 5-7 minutes at a stirring rate of 350-400 r / min to obtain a polyethyleneimine aqueous solution. Add silane-modified sepiolite and deionized water to the beaker, and ultrasonically disperse for 20-22 minutes at a power of 280-300 W to obtain a silane-modified sepiolite dispersion. Add the polyethyleneimine aqueous solution dropwise to the silane-modified sepiolite dispersion at a dropping rate of [missing information]. Stir at 0.5 mL / min for 10-12 min, then transfer to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. Place in a 60℃ constant temperature water bath and reflux for 4-4.2 h with a stirring rate of 450-500 r / min. After the reaction is complete, filter and collect the filter cake. Wash with distilled water 3-4 times, then place in a vacuum drying oven and dry at 55-60℃ for 12-13 h. After cooling, grind through a 100-mesh sieve to obtain modified sepiolite.

[0015] Step a5: Methylnadic anhydride, 1,4-butanediol, 1,6-hexanediol, and 1,10-decanediol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then p-toluenesulfonic acid was added, and nitrogen gas was introduced for protection. The mixture was stirred and reacted at 110-120℃ and a stirring rate of 350-400 r / min for 2-2.2 h. The temperature was then increased to 140-150℃ and reacted for another 2-2.2 h. Finally, the temperature was increased to 170-180℃ and reacted for another 2-2.2 h. After that, the mixture was distilled under reduced pressure at 80-85℃ and a pressure of 0.08-0.09 MPa and cooled to room temperature to obtain the methylnadic anhydride diacid compound.

[0016] Step a6: Add bisphenol A type epoxy resin and methyl nadic anhydride diacid compound to a beaker, turn on a high-speed shear emulsifier, and stir for 30-35 min at a temperature of 60-65℃ and a stirring rate of 1100-1200 r / min. Add polyethylene glycol diglycidyl ether and continue shear emulsification for 20-22 min. Then transfer to a three-necked flask and place it in an 85℃ constant temperature water bath. Add deionized water dropwise at a stirring rate of 350-400 r / min at a dropping rate of 1 mL / min and continue stirring for 30-32 min. Then distill under reduced pressure at a temperature of 80-85℃ and a pressure of 0.08-0.09 MPa. Add organosilicon defoamer and stir for 10-12 min. Filter the emulsion through a 200-mesh sieve to obtain modified waterborne epoxy resin.

[0017] Step a7: Add the modified sepiolite to anhydrous ethanol, transfer it to an ultrasonic disperser, and ultrasonically disperse it for 40-42 minutes at a power of 280-300W. Then transfer it to a vacuum drying oven and dry it at a temperature of 55-60℃ for 2-2.2 hours. Grind it with an agate mortar for 3-5 minutes and pass it through a 100-mesh sieve to obtain the pretreated modified sepiolite.

[0018] Step a8: Add the modified waterborne epoxy resin to a three-necked flask and place it in a constant temperature water bath at 50℃. Stir magnetically for 10-12 minutes at a stirring rate of 450-500 r / min. Then increase the stirring rate to 900-1000 r / min and add the pretreated modified sepiolite in three portions, with an interval of 5 minutes between each addition. Stir for 20-22 minutes each time. Then use a high-speed shear emulsifier to shear and disperse the resin for 20-22 minutes at a stirring rate of 1400-1500 r / min to obtain the reinforced modified epoxy resin.

[0019] Step a9: Add the phosphate ester adhesion promoter and the reinforced modified epoxy resin to a beaker, and magnetically stir for 15-17 minutes at a stirring rate of 750-800 r / min. Then transfer it to a high-speed mixer and mix for 15-17 minutes at a speed of 1100-1200 r / min. After high-speed mixing, cure at a temperature of 45-50℃ for 30-32 minutes to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0020] In a preferred embodiment of the present invention, the ratio of sepiolite to deionized water in step a1 is 30-32g: 1800-1900mL.

[0021] In a preferred embodiment of the present invention, the sepiolite in step a1 is 400 mesh.

[0022] In a preferred embodiment of the present invention, the ratio of purified and activated sepiolite to silicon tetrachloride solution in step a2 is 3-5g: 150-250mL.

[0023] In a preferred embodiment of the present invention, the concentration of the silicon tetrachloride solution in step a2 is 0.5 mol / L.

[0024] In a preferred embodiment of the present invention, the ratio of the amounts of γ-glycidyl etheroxypropyltrimethoxysilane, deionized water, anhydrous ethanol, acid-modified sepiolite, and mixed solvent in step a3 is 0.06-0.08 g : 0.06-0.08 mL : 0.7-0.9 mL : 2-2.6 g : 20-26 mL.

[0025] In a preferred embodiment of the present invention, the mixed solvent in step a3 is a solution of deionized water and anhydrous ethanol mixed in a volume ratio of 1:10.

[0026] In a preferred embodiment of the present invention, the mass fraction of the ammonia water in step a3 is 25%.

[0027] In a preferred embodiment of the present invention, the ratio of polyethyleneimine, deionized water, anhydrous ethanol, silane-modified sepiolite, and deionized water in step a4 is 0.3-0.5g: 10-16mL: 10-16mL: 1.5-2.5g: 30-50mL.

[0028] In a preferred embodiment of the present invention, the polyethyleneimine in step a4 is Aladdin Biochemical Technology, product number: P434400.

[0029] In a preferred embodiment of the present invention, the ratio of methylnadic anhydride, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol and p-toluenesulfonic acid in step a5 is 166-187g: 35-39g: 47-53g: 69-78g: 1.6-1.8g.

[0030] In a preferred embodiment of the present invention, the ratio of bisphenol A epoxy resin, methyl nadic anhydride diacid compound, polyethylene glycol diglycidyl ether, deionized water and organosilicon defoamer in step a6 is 60-84g: 40-56g: 2-2.8g: 120-168mL: 0.5-0.7g.

[0031] In a preferred embodiment of the present invention, the bisphenol A type epoxy resin in step a6 is NPEL-128; the silicone defoamer is silicone defoamer XP-104.

[0032] In a preferred embodiment of the present invention, the ratio of modified sepiolite to anhydrous ethanol in step a7 is 8.3-8.5g: 50-51mL.

[0033] In a preferred embodiment of the present invention, the ratio of modified waterborne epoxy resin to pretreated modified sepiolite in step a8 is 100-102g: 8.3-8.5g.

[0034] In a preferred embodiment of the present invention, the ratio of the phosphate ester adhesion promoter to the reinforced modified epoxy resin in step a9 is 0.8-1.6 mL: 100-110 g.

[0035] In a preferred embodiment of the present invention, the phosphate ester adhesion promoter in step a9 is model ADP-S479.

[0036] In a preferred embodiment of the present invention, the highly hydrolysis-resistant polyester resin is prepared by the following steps:

[0037] Isophthalic acid, adipic acid, neopentyl glycol, and cyclohexanediethanol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Tetrabutyl titanate and triphenyl phosphate were then added. Nitrogen gas was introduced for protection. The mixture was stirred at 25-30°C and a stirring rate of 180-200 rpm for 15-25 min. The temperature was then raised to 120-130°C, and the stirring rate was maintained at this temperature for 30-32 min. The temperature was then raised to 150-160°C, and the reaction was carried out for 2-2.2 h. The temperature was then increased to 180-190°C at a rate of 5°C / 10 min, and the reaction was carried out for 3-3.2 h. Continue heating to 200-210℃ and react for 2-2.2 hours. Then, maintain the temperature and start the vacuum system to increase the vacuum to 0.05 MPa and hold for 1.5-1.7 hours. Then, continue to increase the vacuum to 0.09-0.095 MPa and heat to 235℃. Control the stirring speed at 150 r / min and hold for 3-4 hours. Stop heating and keep nitrogen gas flowing through. After the system temperature drops below 100℃, transfer it to a stainless steel tray and allow it to cool naturally to room temperature. Then, place it in a forced-air drying oven and dry it at 75-80℃ for 2-2.2 hours. After that, pulverize it with a pulverizer to a particle size ≤5 mm to obtain a high hydrolysis resistant polyester resin.

[0038] In a preferred embodiment of the present invention, the ratio of isophthalic acid, adipic acid, neopentyl glycol, cyclohexanediol, tetrabutyl titanate, and triphenyl phosphate is 6.5-13.0 mol: 3.5-7.0 mol: 8.5-17.0 mol: 2-4 mol: 0.005-0.010 mol: 0.01-0.02 mol.

[0039] In a preferred embodiment of the present invention, the curing agent is a hydroxyalkylamide, model Primid® XL-552; the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P; the pigment is rutile titanium dioxide; the activated silica powder is model HY-GA-1; the leveling agent is model BYK-361N; the degassing agent is model BYK-054; the wetting and dispersing agent is model BYK-163; and the wax additive is polyethylene wax, model AC-6A.

[0040] Secondly, this application provides an application of a roll-type powder coating for soilless planting ponds in soilless planting ponds.

[0041] The beneficial effects of this invention are:

[0042] This invention discloses a method for preparing a roll-type powder coating for soilless planting ponds. The method involves pre-mixing a high-hydrolysis-resistant polyester resin, curing agent, hydrolysis-resistant stabilizer, hydrolysis-resistant metal substrate adhesion promoter, pigment, precipitated barium sulfate, activated silica powder, leveling agent, degassing agent, wetting and dispersing agent, and wax additives in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt mixing, extruded through a die, pressed into tablets using a tablet press, cooled to room temperature, and subsequently pre-pulverized in a pulverizer before being finely pulverized in an ACM mill to obtain the roll-type powder coating. The hydrolysis-resistant metal substrate adhesion promoter significantly improves the adhesion between the roll-type powder coating and the metal substrate, preventing peeling even after prolonged immersion in water. The high-hydrolysis-resistant polyester resin, with ester bonds as the main chain, utilizes the steric hindrance of neopentyl glycol and the cyclic structure of cyclohexanediol to synergistically resist hydrolysis, making it suitable for long-term immersion scenarios in soilless planting ponds. Its residual hydroxyl groups can efficiently crosslink with the curing agent, strengthening the coating's density, improving adhesion to metal substrates, inhibiting coating failure caused by water penetration, extending the coating's service life, and ensuring the coating's mechanical strength and application compatibility.

[0043] In the process of preparing coil powder coatings, a hydrolysis-resistant metal substrate adhesion promoter was first prepared. Firstly, sepiolite was physically purified and activated, then acid-modified, silane-modified, and polyethyleneimine-modified to obtain modified sepiolite. Next, a waterborne epoxy resin was modified with a methylnadic anhydride diacid compound to introduce hydrolysis-resistant segments and achieve waterborne properties, resulting in a modified waterborne epoxy resin. Then, the modified sepiolite was compounded with the modified waterborne epoxy resin to obtain a reinforced modified epoxy resin, which was then compounded with a phosphate ester adhesion promoter to finally obtain the hydrolysis-resistant metal substrate adhesion promoter.

[0044] Modified sepiolite: First, the sepiolite is impurity-removing process, simultaneously disrupting the van der Waals forces and hydrogen bonds between the sepiolite fibers, causing the aggregated fiber bundles to depolymerize and expose more surface active sites. Then, silicon tetrachloride hydrolyzes to produce hydrochloric acid, selectively etching and activating the sepiolite surface. The Si-OM (M = Mg, Al, etc.) bonds on the sepiolite surface break under the action of HCl, generating Si-OH active groups. Simultaneously, soluble impurities are removed, forming a porous and rough surface. The generation of numerous Si-OH active sites on the sepiolite surface provides a reaction basis for the subsequent condensation reaction of silane modification. The rough, porous structure increases the specific surface area, enhances the physical adsorption with the organic phase, removes easily hydrolyzable metal ion impurities, and reduces hydrolysis catalytic sites during subsequent use. Then, γ-glycidoxypropyltrimethoxysilane is hydrolyzed under alkaline conditions. The Si-OH groups on the sepiolite surface dehydrate and condense with the Si-OH groups generated from the silane hydrolysis, achieving a covalent bond connection between the sepiolite and the silane coupling agent. One end of the silane coupling agent is open to… Sepiolite is covalently linked via Si-O-Si bonds, with epoxy groups retained at the other end, providing active sites for subsequent reactions with organic polymers. The hydrophobic segments of the silane molecules reduce the hydrophilicity of the sepiolite surface, initially improving hydrolysis resistance and enhancing the compatibility of sepiolite with the organic phase, thus preventing agglomeration during the composite process. Subsequently, the amino / carboxyl groups of polyethyleneimine undergo a ring-opening addition reaction with the epoxy groups retained by γ-glycidoxypropyltrimethoxysilane, achieving the grafting of polyethyleneimine segments onto the sepiolite surface. Amines themselves possess excellent hydrolysis resistance, high temperature resistance, and mechanical strength. After grafting, they introduce a hydrolysis-resistant organic shell into sepiolite, inhibiting water molecules from penetrating to the interface between sepiolite and resin. The steric hindrance effect of branched polyethyleneimine can hinder the attack of water molecules on Si-O-Si bonds and ester bonds during the hydrolysis reaction, and work synergistically with hydrolysis-resistant stabilizers to improve overall hydrolysis resistance. The organic segments of polyethyleneimine have good compatibility with subsequent epoxy resins, further reducing the interfacial tension of the composite system and improving dispersion uniformity.

[0045] Modified waterborne epoxy resin: First, a methylnadic anhydride-based diacid compound is synthesized. The anhydride group of the methylnadic anhydride undergoes an esterification reaction with the hydroxyl group of a polyol to generate a carboxyl-containing diacid compound. The introduction of the long carbon chain of the polyol can improve the flexibility and hydrolysis resistance of the subsequent epoxy resin (the long carbon chain structure can alleviate stress concentration in the hydrolysis reaction). Then, the waterborne epoxy resin is modified with the methylnadic anhydride-based diacid. The carboxyl group of the diacid compound undergoes a ring-opening reaction with the epoxy group of the bisphenol A type epoxy resin. After the introduction of the carboxyl group, alkaline neutralization is used to... The carboxyl groups are converted into carboxylate salts, enabling the epoxy resin to be water-based. At the same time, the epoxy groups of polyethylene glycol diglycidyl ether react with the carboxyl / hydroxyl groups to form a dense cross-linked network. The long carbon chains of the diacid compound and the methyl nadic anhydride residues enhance the hydrolysis resistance and rigidity of the epoxy resin, avoiding the defects of conventional epoxy resins that are easily hydrolyzed. After the carboxyl groups are neutralized, water-based properties are achieved, resulting in excellent compatibility with the aqueous dispersion of sepiolite, which facilitates compounding. The cross-linking effect of polyethylene glycol diglycidyl ether makes the epoxy resin network denser, reduces water molecule penetration channels, and improves flexibility.

[0046] When pretreated modified sepiolite is mixed with modified waterborne epoxy resin, the polyethyleneimine segments and silane epoxy groups grafted on the sepiolite surface form hydrogen bonds, van der Waals forces, and even a small number of covalent bonds with the hydroxyl and carboxyl groups of the epoxy resin, achieving a tight bond at the inorganic-organic interface. The fibrous structure and high specific surface area of ​​sepiolite form a physical reinforcing skeleton in the epoxy resin, improving the mechanical strength (wear resistance, impact resistance) of the coating. At the same time, the fibrous structure can extend the water molecule penetration path, further improving hydrolysis resistance. High-speed shear dispersion ensures uniform dispersion of sepiolite, avoiding interface defects caused by agglomeration; the phosphorus ester adhesion promoter... The acid groups undergo a condensation reaction with the hydroxyl groups on the surface of the metal substrate to form stable MOP covalent bonds. At the same time, the organic segments of the phosphate ester interact with the epoxy and hydroxyl groups of the modified epoxy resin, tightly connecting the metal substrate and the coating and significantly improving adhesion. The polarity of the phosphate ester groups can adsorb a small amount of water molecules to form a bound water layer. Moreover, the phosphate ester groups themselves have excellent hydrolysis resistance and will not cause hydrolysis of themselves or the coating resin due to the adsorption of water molecules. Instead, they can form a water molecule barrier to prevent water molecules from penetrating to the metal-coating interface. Together with the hydrophobic shell of sepiolite and the dense network of epoxy resin, multiple hydrolysis-resistant protections are achieved.

[0047] A highly hydrolysis-resistant polyester resin was prepared during the preparation of coil powder coatings. Isophthalic acid and adipic acid were used as diacid monomers, and neopentyl glycol and cyclohexanediethanol were used as diol monomers. Under the catalysis of tetrabutyl titanate, the stabilization of triphenyl phosphate, and nitrogen protection, the resin was first mixed and dissolved at low temperature. Then, through a gradient heating process, the carboxyl groups of the diacids and the hydroxyl groups of the diols underwent esterification, dehydration to form ester bonds, and the formation of low molecular weight oligomers. Subsequently, by gradually increasing the vacuum and temperature, the oligomers underwent a condensation reaction, and the ester bonds were further linked to form high molecular weight oligomers. The polyester backbone is simultaneously degraded to remove residual water molecules and small alcohol molecules from the system, ultimately yielding a highly hydrolysis-resistant polyester resin. The generated ester bonds form the backbone of the resin. The quaternary carbon atoms of neopentyl glycol and the cyclic structure of cyclohexanediol provide steric hindrance, inhibiting the attack of water molecules on the ester bonds. The benzene ring structure of isophthalic acid enhances the rigidity of the backbone. The small amount of residual hydroxyl groups provides active sites for the subsequent crosslinking reaction with the hydroxyalkylamide curing agent. Triphenyl phosphate, by inhibiting the catalytic degradation of tetrabutyl titanate, synergistically improves the overall hydrolysis resistance of the resin. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] Example 1:

[0050] This embodiment describes a method for preparing a roll-type powder coating for soilless planting ponds, including the following steps:

[0051] Step s1: Add 30g of sepiolite (400 mesh) and 1800mL of deionized water to a beaker, turn on mechanical stirring, and stir for 6 hours at a stirring rate of 750r / min. During this period, use a strong magnet to attract the impurities back and forth at the bottom of the beaker 3 times every 1 hour. Stop mechanical stirring during attraction, and continue stirring after the impurities settle. Then transfer to an ultrasonic cleaner and ultrasonically disperse for 40 minutes at a power of 450W and a frequency of 40kHz. Turn off the ultrasonic cleaner and let stand for 8 hours. Pour off the upper two-thirds of the suspension, discard the bottom precipitate, filter the upper suspension with a Buchner funnel, collect the filter cake, wash it 4 times with distilled water, and then put it into a forced-air drying oven to dry to constant weight at a temperature of 75℃. Cool to room temperature to obtain purified and activated sepiolite.

[0052] Step s2: Add 3g of purified and activated sepiolite and 150mL of silicon tetrachloride solution (concentration of silicon tetrachloride solution is 0.5mol / L) to a beaker, and stir magnetically for 30min at a stirring rate of 450r / min. Then transfer to a three-necked flask equipped with a stirrer, thermometer and reflux condenser, place it in a constant temperature water bath, and stir the reaction at a temperature of 70℃ and a stirring rate of 550r / min for 8h. After the reaction is completed, cool to room temperature, filter and collect the filter cake, wash with deionized water until the pH of the filtrate is neutral, place the filter cake in a vacuum drying oven, dry at a temperature of 55℃ for 24h, cool and grind, and pass through a 200-mesh standard sieve to obtain acid-modified sepiolite.

[0053] Step s3: Add 0.06g of γ-glycidyl etheroxypropyltrimethoxysilane, 0.06mL of deionized water, and 0.7mL of anhydrous ethanol to a beaker. Under conditions of 25℃ and a stirring rate of 280r / min, adjust the pH of the system to 9 with 25% ammonia. Then seal the beaker with plastic wrap and place it in a 35℃ constant temperature water bath. Stir magnetically for 30min to obtain silane hydrolysate. Add 2g of acid-modified sepiolite and 20mL of mixed solvent (a solution of deionized water and anhydrous ethanol in a volume ratio of 1:10) to the beaker. The sepiolite dispersion was obtained by ultrasonic dispersion at 280W for 30 min. The silane hydrolysate was added dropwise to the sepiolite dispersion at a rate of 1 mL / min and stirred for 10 min. Then, it was transferred to a three-necked flask equipped with a stirrer, thermometer and reflux condenser and placed in an 80℃ constant temperature water bath. The mixture was refluxed at a stirring rate of 450 r / min for 5 h. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with isopropanol, and then placed in a vacuum drying oven at 55℃ for 12 h. After cooling, silane-modified sepiolite was obtained.

[0054] Step s4: Add 0.3g of polyethyleneimine (polyethyleneimine is from Aladdin Biochemical Technology, catalog number: P434400), 10mL of deionized water, and 10mL of anhydrous ethanol to a beaker, place it in a 50℃ constant temperature water bath, and magnetically stir for 5min at a stirring rate of 350r / min to obtain a polyethyleneimine aqueous solution. Add 1.5g of silane-modified sepiolite and 30mL of deionized water to the beaker, and ultrasonically disperse for 20min at a power of 280W to obtain a silane-modified sepiolite dispersion. Add polyethylene... An aqueous solution of enimine was added dropwise to a silane-modified sepiolite dispersion at a rate of 0.5 mL / min. The mixture was stirred for 10 min and then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. The flask was placed in a 60°C constant temperature water bath and refluxed for 4 h with a stirring rate of 450 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with distilled water, and then placed in a vacuum drying oven at 55°C for 12 h. After cooling, the cake was ground through a 100-mesh sieve to obtain modified sepiolite.

[0055] Step s5: 166g of methylnadic anhydride, 35g of 1,4-butanediol, 47g of 1,6-hexanediol, and 69g of 1,10-decanediol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. 1.6g of p-toluenesulfonic acid was then added, and nitrogen gas was introduced for protection. The mixture was stirred and reacted at 110℃ and a stirring rate of 350r / min for 2 hours. The temperature was then increased to 140℃ and reacted for 2 hours. Finally, the temperature was increased to 170℃ and reacted for 2 hours. After that, the mixture was distilled under reduced pressure at 80℃ and a pressure of 0.08MPa and cooled to room temperature to obtain the methylnadic anhydride diacid compound.

[0056] Step s6: Add 60g of bisphenol A type epoxy resin (the type of bisphenol A type epoxy resin is NPEL-128) and 40g of methyl nadic anhydride diacid compound to a beaker, turn on a high-speed shear emulsifier, and stir for 30min at 60℃ and a stirring rate of 1100r / min. Add 2g of polyethylene glycol diglycidyl ether and continue shear emulsification for 20min. Then transfer to a three-necked flask and place it in an 85℃ constant temperature water bath. Add 120mL of deionized water dropwise at a stirring rate of 1mL / min at 350r / min and continue stirring for 30min. Then distill under reduced pressure at 80℃ and 0.08MPa, add 0.5g of silicone defoamer (silicone defoamer is silicone defoamer XP-104), stir for 10min, and filter the emulsion through a 200-mesh sieve to obtain modified waterborne epoxy resin.

[0057] Step s7: Add 8.3g of modified sepiolite to 50mL of anhydrous ethanol, transfer to an ultrasonic disperser, and ultrasonically disperse for 40min at a power of 280W. Then transfer to a vacuum drying oven and dry at 55℃ for 2h. Grind with an agate mortar for 3min and pass through a 100-mesh sieve to obtain pretreated modified sepiolite.

[0058] Step s8: Add 100g of modified waterborne epoxy resin to a three-necked flask, place it in a constant temperature water bath at 50℃, and magnetically stir for 10min at a stirring rate of 450r / min. Then increase the stirring rate to 900r / min, add 8.3g of pretreated modified sepiolite in 3 portions, with an interval of 5min between each addition, and stir for 20min. Then use a high-speed shear emulsifier to shear and disperse for 20min at a stirring rate of 1400r / min to obtain the reinforced modified epoxy resin.

[0059] Step s9: Add 0.8 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter model is ADP-S479) and 100 g of reinforced modified epoxy resin to a beaker, and magnetically stir for 15 min at a stirring rate of 750 r / min. Then transfer it to a high-speed mixer and mix for 15 min at a speed of 1100 r / min. After high-speed mixing, cure at a temperature of 45℃ for 30 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0060] Step s10: Add 6.5 mol isophthalic acid, 3.5 mol adipic acid, 8.5 mol neopentyl glycol, and 2 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.005 mol tetrabutyl titanate and 0.01 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 25°C and 180 r / min for 15 min. Then raise the temperature to 120°C, maintain the stirring rate, and hold for 30 min. Then raise the temperature to 150°C and react for 2 h. After that, increase the stirring rate by 5°C / 10 min. The temperature was increased to 180℃ and reacted for 3 hours. The temperature was then increased to 200℃ and reacted for 2 hours. After that, the temperature was maintained and the vacuum system was started to increase the vacuum to 0.05MPa. The temperature was maintained for 1.5 hours. Then, the vacuum was increased to 0.09MPa and the temperature was increased to 235℃. The stirring speed was controlled at 150r / min and the temperature was maintained for 3 hours. The heating was stopped and nitrogen was kept flowing. After the system temperature dropped below 100℃, it was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 75℃ for 2 hours. After that, it was pulverized with a pulverizer to a particle size ≤5mm to obtain a high hydrolysis resistant polyester resin.

[0061] Step s11: Weigh out 55 parts by weight of high hydrolysis resistant polyester resin, 4 parts by weight of curing agent, 1 part by weight of hydrolysis resistant stabilizer, 1.5 parts by weight of hydrolysis resistant metal substrate adhesion promoter, 8 parts by weight of pigment, 10 parts by weight of precipitated barium sulfate, 5 parts by weight of activated silica powder, 0.5 parts by weight of leveling agent, 0.3 parts by weight of degassing agent, 0.3 parts by weight of wetting and dispersing agent, and 0.4 parts by weight of wax additives;

[0062] Step s12: Add the high hydrolysis-resistant polyester resin, curing agent (the curing agent is hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (the pigment is rutile titanium dioxide), precipitated barium sulfate, activated silica powder (activated silica powder, model HY-GA-1), leveling agent (leveling agent, model BYK-361N), degassing agent (degassing agent, model BYK-054), wetting and dispersing agent (wetting and dispersing agent, model BYK-163), and wax additives (wax additives are polyethylene wax, model AC-6A) into a high-speed mixer and premix for 12 minutes at a speed of 1400 r / min. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0063] Example 2:

[0064] This embodiment describes a method for preparing a roll-type powder coating for soilless planting ponds, including the following steps:

[0065] Step s1: Add 31g of sepiolite (400 mesh) and 1850mL of deionized water to a beaker, turn on mechanical stirring, and stir for 6.1h at a stirring rate of 770r / min. During this period, use a strong magnet to adsorb the bottom of the beaker 3 times every 1h. Stop mechanical stirring during adsorption, and continue stirring after the impurities settle. Then transfer to an ultrasonic cleaner and ultrasonically disperse for 41min at a power of 470W and a frequency of 40kHz. Turn off the ultrasonic cleaner and let stand for 9h. Pour off the upper two-thirds of the suspension, discard the bottom precipitate impurities, filter the upper suspension with a Buchner funnel, collect the filter cake, wash it 4 times with distilled water, and then put it into a forced-air drying oven to dry to constant weight at a temperature of 77℃. Cool to room temperature to obtain purified and activated sepiolite.

[0066] Step s2: Add 4g of purified and activated sepiolite and 200mL of silicon tetrachloride solution (concentration of silicon tetrachloride solution is 0.5mol / L) to a beaker. Stir magnetically for 31min at a stirring rate of 470r / min. Then transfer to a three-necked flask equipped with a stirrer, thermometer and reflux condenser. Place in a constant temperature water bath and stir for 8.1h at a temperature of 73℃ and a stirring rate of 570r / min. After the reaction is completed, cool to room temperature, filter and collect the filter cake. Wash with deionized water until the pH of the filtrate is neutral. Place the filter cake in a vacuum drying oven and dry at a temperature of 57℃ for 25h. After cooling, grind and pass through a 200-mesh standard sieve to obtain acid-modified sepiolite.

[0067] Step s3: Add 0.07g γ-glycidoxypropyltrimethoxysilane, 0.07mL deionized water, and 0.8mL anhydrous ethanol to a beaker. Under conditions of 27℃ and a stirring rate of 290r / min, adjust the pH of the system to 9 with 25% ammonia. Then seal the beaker with plastic wrap and place it in a 35℃ constant temperature water bath. Stir magnetically for 31min to obtain silane hydrolysate. Add 2.3g acid-modified sepiolite and 23mL mixed solvent (a solution of deionized water and anhydrous ethanol in a volume ratio of 1:10) to the beaker. The sepiolite dispersion was obtained by ultrasonic dispersion at 290W for 31 min. The silane hydrolysate was added dropwise to the sepiolite dispersion at a rate of 1 mL / min and stirred for 11 min. The mixture was then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser and placed in an 80℃ constant temperature water bath. The mixture was refluxed at a stirring rate of 470 r / min for 5.1 h. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with isopropanol, and then placed in a vacuum drying oven at 57℃ for 12.5 h. After cooling, silane-modified sepiolite was obtained.

[0068] Step s4: Add 0.4g of polyethyleneimine (polyethyleneimine is from Aladdin Biochemical Technology, catalog number: P434400), 13mL of deionized water, and 13mL of anhydrous ethanol to a beaker. Place the beaker in a 50℃ constant temperature water bath and magnetically stir for 6 minutes at a stirring rate of 370r / min to obtain a polyethyleneimine aqueous solution. Add 2g of silane-modified sepiolite and 40mL of deionized water to the beaker and ultrasonically disperse for 21 minutes at a power of 290W to obtain a silane-modified sepiolite dispersion. Add the polyethyleneimine... The aqueous solution was added dropwise to the silane-modified sepiolite dispersion at a rate of 0.5 mL / min, and stirred for 11 min. Then, it was transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser, and placed in a 60℃ constant temperature water bath. The reaction was carried out under reflux for 4.1 h with a stirring rate of 470 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with distilled water, and then placed in a vacuum drying oven at a temperature of 57℃ for 12.5 h. After cooling, it was ground through a 100-mesh sieve to obtain modified sepiolite.

[0069] Step s5: 176g of methylnadic anhydride, 37g of 1,4-butanediol, 50g of 1,6-hexanediol, and 73g of 1,10-decanediol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. 1.7g of p-toluenesulfonic acid was then added, and the mixture was purged with nitrogen for protection. The mixture was stirred at 115℃ and a stirring rate of 370r / min for 2.1h, then heated to 145℃ for 2.1h, and finally heated to 175℃ for 2.1h. After that, the mixture was distilled under reduced pressure at 83℃ and 0.08MPa, and cooled to room temperature to obtain the methylnadic anhydride diacid compound.

[0070] Step s6: Add 72g of bisphenol A type epoxy resin (the type of bisphenol A type epoxy resin is NPEL-128) and 48g of methyl nadic anhydride diacid compound to a beaker, turn on a high-speed shear emulsifier, and stir for 32min at a temperature of 63℃ and a stirring rate of 1150r / min. Add 2.4g of polyethylene glycol diglycidyl ether and continue shear emulsification for 21min. Then transfer to a three-necked flask and place it in an 85℃ constant temperature water bath. Add 144mL of deionized water dropwise at a stirring rate of 1mL / min at a stirring rate of 370r / min and continue stirring for 31min. Then distill under reduced pressure at a temperature of 82℃ and a pressure of 0.08MPa. Add 0.6g of silicone defoamer (silicone defoamer is silicone defoamer XP-104) and stir for 11min. Filter the emulsion through a 200-mesh sieve to obtain modified waterborne epoxy resin.

[0071] Step s7: Add 8.4g of modified sepiolite to 50.5mL of anhydrous ethanol, transfer to an ultrasonic disperser, and ultrasonically disperse for 41min at a power of 290W. Then transfer to a vacuum drying oven and dry at 57℃ for 2.1h. Grind with an agate mortar for 4min and pass through a 100-mesh sieve to obtain pretreated modified sepiolite.

[0072] Step s8: Add 101g of modified waterborne epoxy resin to a three-necked flask, place it in a constant temperature water bath at 50℃, and magnetically stir for 11min at a stirring rate of 470r / min. Then increase the stirring rate to 950r / min, add 8.4g of pretreated modified sepiolite in 3 portions, with an interval of 5min between each addition, and stir for 21min. Then use a high-speed shear emulsifier to shear and disperse for 21min at a stirring rate of 1450r / min to obtain the reinforced modified epoxy resin.

[0073] Step s9: Add 1.2 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter model is ADP-S479) and 105 g of reinforced modified epoxy resin to a beaker, and magnetically stir for 16 min at a stirring rate of 770 r / min. Then transfer to a high-speed mixer and mix for 16 min at a speed of 1150 r / min. After high-speed mixing, cure at a temperature of 47℃ for 31 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0074] Step s10: Add 9.7 mol isophthalic acid, 5.2 mol adipic acid, 12.7 mol neopentyl glycol, and 3 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.007 mol tetrabutyl titanate and 0.015 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 27°C and 190 r / min for 20 min. Then raise the temperature to 125°C, maintain the stirring rate, and hold for 31 min. Then raise the temperature to 155°C and react for 2.1 h. After that, increase the temperature by 5°C every 10 min. The temperature was rapidly increased to 185℃ and reacted for 3.1 h. The temperature was then increased to 205℃ and reacted for another 2.1 h. The temperature was then maintained while the vacuum system was activated, and the vacuum level was increased to 0.05 MPa. The temperature was maintained for 1.6 h, and then the vacuum level was increased to 0.093 MPa. The temperature was increased to 235℃, and the stirring speed was controlled at 150 r / min. The temperature was maintained for 3.5 h. Heating was then stopped, and nitrogen gas was continuously introduced. After the system temperature dropped below 100℃, the system was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 77℃ for 2.1 h. Finally, the system was pulverized to a particle size ≤ 5 mm to obtain a high hydrolysis resistant polyester resin.

[0075] Step s11: Weigh out the following components by weight: 62.5 parts of high hydrolysis resistant polyester resin, 5.5 parts of curing agent, 1.75 parts of hydrolysis resistant stabilizer, 2.25 parts of hydrolysis resistant metal substrate adhesion promoter, 11.5 parts of pigment, 11 parts of precipitated barium sulfate, 6.5 parts of activated silica powder, 0.7 parts of leveling agent, 0.45 parts of degassing agent, 0.45 parts of wetting and dispersing agent, and 0.6 parts of wax additives.

[0076] Step s12: Add the high hydrolysis-resistant polyester resin, curing agent (the curing agent is hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (the pigment is rutile titanium dioxide), precipitated barium sulfate, activated silica powder (activated silica powder, model HY-GA-1), leveling agent (leveling agent, model BYK-361N), degassing agent (degassing agent, model BYK-054), wetting and dispersing agent (wetting and dispersing agent, model BYK-163), and wax additives (wax additives are polyethylene wax, model AC-6A) into a high-speed mixer and premix for 13 minutes at a speed of 1450 r / min. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0077] Example 3:

[0078] This embodiment describes a method for preparing a roll-type powder coating for soilless planting ponds, including the following steps:

[0079] Step s1: Add 32g of sepiolite (400 mesh) and 1900mL of deionized water to a beaker, turn on mechanical stirring, and stir for 6.2h at a stirring rate of 800r / min. During this period, use a strong magnet to adsorb the bottom of the beaker 3 times every 1h. Stop mechanical stirring during adsorption, and continue stirring after the impurities settle. Then transfer to an ultrasonic cleaner and ultrasonically disperse for 42min at a power of 500W and a frequency of 40kHz. Turn off the ultrasonic cleaner and let stand for 10h. Pour off the upper two-thirds of the suspension, discard the bottom precipitate, filter the upper suspension with a Buchner funnel, collect the filter cake, wash it 5 times with distilled water, and then put it into a forced-air drying oven to dry to constant weight at a temperature of 80℃. Cool to room temperature to obtain purified and activated sepiolite.

[0080] Step s2: Add 5g of purified and activated sepiolite and 250mL of silicon tetrachloride solution (concentration of silicon tetrachloride solution is 0.5mol / L) to a beaker, and stir magnetically for 33min at a stirring rate of 500r / min. Then transfer it to a three-necked flask equipped with a stirrer, thermometer and reflux condenser, place it in a constant temperature water bath, and stir the reaction at a temperature of 75℃ and a stirring rate of 600r / min for 8.2h. After the reaction is completed, cool to room temperature, filter and collect the filter cake, wash with deionized water until the pH of the filtrate is neutral, place the filter cake in a vacuum drying oven, dry at a temperature of 60℃ for 26h, cool and grind, and pass through a 200-mesh standard sieve to obtain acid-modified sepiolite.

[0081] Step s3: Add 0.08g of γ-glycidoxypropyltrimethoxysilane, 0.08mL of deionized water, and 0.9mL of anhydrous ethanol to a beaker. Under conditions of 30℃ and a stirring rate of 300r / min, adjust the pH of the system to 10 with 25% ammonia solution. Then seal the beaker with plastic wrap and place it in a 35℃ constant temperature water bath. Stir magnetically for 32min to obtain silane hydrolysate. Add 2.6g of acid-modified sepiolite and 26mL of mixed solvent (a solution of deionized water and anhydrous ethanol in a volume ratio of 1:10) to the beaker. In a mixture of silane and isopropanol, the mixture was ultrasonically dispersed for 32 min at a power of 300 W to obtain a sepiolite dispersion. The hydrolysate of silane was added dropwise to the sepiolite dispersion at a drop rate of 1 mL / min and stirred for 12 min. The mixture was then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser and placed in an 80 °C constant temperature water bath. The mixture was refluxed for 5.2 h at a stirring rate of 500 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed four times with isopropanol, and then placed in a vacuum drying oven at a temperature of 60 °C for 13 h. After cooling, silane-modified sepiolite was obtained.

[0082] Step s4: Add 0.5g of polyethyleneimine (polyethyleneimine is from Aladdin Biochemical Technology, catalog number: P434400), 16mL of deionized water, and 16mL of anhydrous ethanol to a beaker. Place the beaker in a 50℃ constant temperature water bath and magnetically stir for 7 minutes at a stirring rate of 400r / min to obtain a polyethyleneimine aqueous solution. Add 2.5g of silane-modified sepiolite and 50mL of deionized water to the beaker and ultrasonically disperse for 22 minutes at a power of 300W to obtain a silane-modified sepiolite dispersion. Add the polyethyleneimine... An aqueous solution of imine was added dropwise to a silane-modified sepiolite dispersion at a rate of 0.5 mL / min. The mixture was stirred for 12 min and then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. The flask was placed in a 60°C constant temperature water bath and refluxed for 4.2 h with a stirring rate of 500 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed four times with distilled water, and then placed in a vacuum drying oven at 60°C for 13 h. After cooling, the cake was ground through a 100-mesh sieve to obtain modified sepiolite.

[0083] Step s5: 187g of methylnadic anhydride, 39g of 1,4-butanediol, 53g of 1,6-hexanediol, and 78g of 1,10-decanediol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. 1.8g of p-toluenesulfonic acid was then added, and the mixture was purged with nitrogen for protection. The mixture was stirred at 120°C and 400r / min for 2.2h, then heated to 150°C for 2.2h, and finally heated to 180°C for 2.2h. After that, the mixture was distilled under reduced pressure at 85°C and 0.09MPa, and cooled to room temperature to obtain the methylnadic anhydride diacid compound.

[0084] Step s6: Add 84g of bisphenol A type epoxy resin (the type of bisphenol A type epoxy resin is NPEL-128) and 56g of methyl nadic anhydride diacid compound to a beaker, turn on a high-speed shear emulsifier, and stir for 35min at 65℃ and a stirring rate of 1200r / min. Add 2.8g of polyethylene glycol diglycidyl ether and continue shear emulsification for 22min. Then transfer to a three-necked flask and place it in an 85℃ constant temperature water bath. Add 168mL of deionized water dropwise at a stirring rate of 1mL / min at 400r / min and continue stirring for 32min. Then distill under reduced pressure at 85℃ and 0.09MPa, add 0.7g of silicone defoamer (silicone defoamer is silicone defoamer XP-104), stir for 12min, and filter the emulsion through a 200-mesh sieve to obtain modified waterborne epoxy resin.

[0085] Step s7: Add 8.5g of modified sepiolite to 51mL of anhydrous ethanol, transfer to an ultrasonic disperser, and ultrasonically disperse for 42min at a power of 300W. Then transfer to a vacuum drying oven and dry at 60℃ for 2.2h. Grind with an agate mortar for 5min and pass through a 100-mesh sieve to obtain pretreated modified sepiolite.

[0086] Step s8: Add 102g of modified waterborne epoxy resin to a three-necked flask, place it in a constant temperature water bath at 50℃, and magnetically stir for 12min at a stirring rate of 500r / min. Then increase the stirring rate to 1000r / min, add 8.5g of pretreated modified sepiolite in 3 portions, with an interval of 5min between each addition, and stir for 22min. Then use a high-speed shear emulsifier to shear and disperse for 22min at a stirring rate of 1500r / min to obtain the reinforced modified epoxy resin.

[0087] Step s9: Add 1.6 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter model is ADP-S479) and 110 g of reinforced modified epoxy resin to a beaker, and magnetically stir for 17 min at a stirring rate of 800 r / min. Then transfer to a high-speed mixer and mix for 17 min at a speed of 1200 r / min. After high-speed mixing, cure at a temperature of 50℃ for 32 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0088] Step s10: Add 13.0 mol isophthalic acid, 7.0 mol adipic acid, 17.0 mol neopentyl glycol, and 4 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.010 mol tetrabutyl titanate and 0.02 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 30°C and 200 r / min for 25 min. Then raise the temperature to 130°C, maintain the stirring rate, and hold for 32 min. Then raise the temperature to 160°C and react for 2.2 h. After that, increase the temperature by 5°C / 10 min. The temperature was increased to 190℃ at a constant rate, and the reaction was carried out for 3.2 hours. The temperature was then increased to 210℃, and the reaction was carried out for another 2.2 hours. After that, the temperature was maintained and the vacuum system was started to increase the vacuum to 0.05MPa. The temperature was maintained for 1.7 hours. Then, the vacuum was increased to 0.095MPa, and the temperature was increased to 235℃. The stirring speed was controlled at 150r / min, and the temperature was maintained for 4 hours. Heating was then stopped, and nitrogen was kept flowing through the system. After the system temperature dropped below 100℃, it was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 80℃ for 2.2 hours. After that, it was pulverized with a pulverizer to a particle size ≤5mm to obtain a high hydrolysis resistant polyester resin.

[0089] Step s11: Weigh out 70 parts by weight of high hydrolysis resistant polyester resin, 7 parts by weight of curing agent, 2.5 parts by weight of hydrolysis resistant stabilizer, 3 parts by weight of hydrolysis resistant metal substrate adhesion promoter, 15 parts by weight of pigment, 12 parts by weight of precipitated barium sulfate, 8 parts by weight of activated silica powder, 1 part by weight of leveling agent, 0.6 parts by weight of degassing agent, 0.6 parts by weight of wetting and dispersing agent, and 0.8 parts by weight of wax additives;

[0090] Step s12: Add the high hydrolysis-resistant polyester resin, curing agent (the curing agent is hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (the pigment is rutile titanium dioxide), precipitated barium sulfate, activated silica powder (activated silica powder, model HY-GA-1), leveling agent (leveling agent, model BYK-361N), degassing agent (degassing agent, model BYK-054), wetting and dispersing agent (wetting and dispersing agent, model BYK-163), and wax additives (wax additives are polyethylene wax, model AC-6A) into a high-speed mixer and premix for 14 minutes at a speed of 1500 r / min. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0091] Comparative Example 1:

[0092] This comparative example illustrates a method for preparing a roll-type powder coating for soilless planting ponds, comprising the following steps:

[0093] Step s1: 166g of methylnadic anhydride, 35g of 1,4-butanediol, 47g of 1,6-hexanediol, and 69g of 1,10-decanediol were added to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. 1.6g of p-toluenesulfonic acid was then added, and nitrogen gas was introduced for protection. The mixture was stirred and reacted at 110℃ and a stirring rate of 350r / min for 2h. The temperature was then increased to 140℃ and reacted for 2h. Finally, the temperature was increased to 170℃ and reacted for 2h. After that, the mixture was distilled under reduced pressure at 80℃ and a pressure of 0.08MPa and cooled to room temperature to obtain the methylnadic anhydride diacid compound.

[0094] Step s2: Add 60g of bisphenol A type epoxy resin (the type of bisphenol A type epoxy resin is NPEL-128) and 40g of methyl nadic anhydride diacid compound to a beaker, turn on a high-speed shear emulsifier, and stir for 30min at 60℃ and a stirring rate of 1100r / min. Add 2g of polyethylene glycol diglycidyl ether and continue shear emulsification for 20min. Then transfer to a three-necked flask and place it in an 85℃ constant temperature water bath. Add 120mL of deionized water dropwise at a stirring rate of 1mL / min at 350r / min and continue stirring for 30min. Then distill under reduced pressure at 80℃ and 0.08MPa, add 0.5g of silicone defoamer (silicone defoamer is silicone defoamer XP-104), stir for 10min, and filter the emulsion through a 200-mesh sieve to obtain modified waterborne epoxy resin.

[0095] Step s3: Add 0.8 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter model is ADP-S479) and 100 g of modified waterborne epoxy resin to a beaker, and magnetically stir for 15 min at a stirring rate of 750 r / min. Then transfer to a high-speed mixer and mix for 15 min at a speed of 1100 r / min. After high-speed mixing, cure at a temperature of 45℃ for 30 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0096] Step s4: Add 6.5 mol isophthalic acid, 3.5 mol adipic acid, 8.5 mol neopentyl glycol, and 2 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.005 mol tetrabutyl titanate and 0.01 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 25°C and 180 r / min for 15 min. Then raise the temperature to 120°C, maintain the stirring rate, and hold for 30 min. Then raise the temperature to 150°C and react for 2 h. After that, increase the stirring rate by 5°C / 10 min. The temperature was increased to 180℃ and reacted for 3 hours. The temperature was then increased to 200℃ and reacted for 2 hours. After that, the temperature was maintained and the vacuum system was started to increase the vacuum to 0.05MPa. The temperature was maintained for 1.5 hours. Then, the vacuum was increased to 0.09MPa and the temperature was increased to 235℃. The stirring speed was controlled at 150r / min and the temperature was maintained for 3 hours. The heating was stopped and nitrogen was kept flowing. After the system temperature dropped below 100℃, it was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 75℃ for 2 hours. After that, it was pulverized with a pulverizer to a particle size ≤5mm to obtain a high hydrolysis resistant polyester resin.

[0097] Step s5: Weigh out 55 parts by weight of high hydrolysis resistant polyester resin, 4 parts by weight of curing agent, 1 part by weight of hydrolysis resistant stabilizer, 1.5 parts by weight of hydrolysis resistant metal substrate adhesion promoter, 8 parts by weight of pigment, 10 parts by weight of precipitated barium sulfate, 5 parts by weight of activated silica powder, 0.5 parts by weight of leveling agent, 0.3 parts by weight of degassing agent, 0.3 parts by weight of wetting and dispersing agent, and 0.4 parts by weight of wax additives;

[0098] Step s6: Add the high hydrolysis-resistant polyester resin, curing agent (the curing agent is hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (pigment is rutile titanium dioxide), precipitated barium sulfate, activated silica powder (activated silica powder model HY-GA-1), leveling agent (leveling agent model BYK-361N), degassing agent (degassing agent model BYK-054), wetting and dispersing agent (wetting and dispersing agent model BYK-163), and wax additives (wax additives are polyethylene wax, model AC-6A) into a high-speed mixer and premix for 12 minutes at a speed of 1400 r / min. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0099] Comparative Example 2:

[0100] This comparative example illustrates a method for preparing a roll-type powder coating for soilless planting ponds, comprising the following steps:

[0101] Step s1: Add 30g of sepiolite (400 mesh) and 1800mL of deionized water to a beaker, turn on mechanical stirring, and stir for 6 hours at a stirring rate of 750r / min. During this period, use a strong magnet to attract the impurities back and forth at the bottom of the beaker 3 times every 1 hour. Stop mechanical stirring during attraction, and continue stirring after the impurities settle. Then transfer to an ultrasonic cleaner and ultrasonically disperse for 40 minutes at a power of 450W and a frequency of 40kHz. Turn off the ultrasonic cleaner and let stand for 8 hours. Pour off the upper two-thirds of the suspension, discard the bottom precipitate, filter the upper suspension with a Buchner funnel, collect the filter cake, wash it 4 times with distilled water, and then put it into a forced-air drying oven to dry to constant weight at a temperature of 75℃. Cool to room temperature to obtain purified and activated sepiolite.

[0102] Step s2: Add 3g of purified and activated sepiolite and 150mL of silicon tetrachloride solution (concentration of silicon tetrachloride solution is 0.5mol / L) to a beaker, and stir magnetically for 30min at a stirring rate of 450r / min. Then transfer to a three-necked flask equipped with a stirrer, thermometer and reflux condenser, place it in a constant temperature water bath, and stir the reaction at a temperature of 70℃ and a stirring rate of 550r / min for 8h. After the reaction is completed, cool to room temperature, filter and collect the filter cake, wash with deionized water until the pH of the filtrate is neutral, place the filter cake in a vacuum drying oven, dry at a temperature of 55℃ for 24h, cool and grind, and pass through a 200-mesh standard sieve to obtain acid-modified sepiolite.

[0103] Step s3: Add 0.06g of γ-glycidyl etheroxypropyltrimethoxysilane, 0.06mL of deionized water, and 0.7mL of anhydrous ethanol to a beaker. Under conditions of 25℃ and a stirring rate of 280r / min, adjust the pH of the system to 9 with 25% ammonia. Then seal the beaker with plastic wrap and place it in a 35℃ constant temperature water bath. Stir magnetically for 30min to obtain silane hydrolysate. Add 2g of acid-modified sepiolite and 20mL of mixed solvent (a solution of deionized water and anhydrous ethanol in a volume ratio of 1:10) to the beaker. The sepiolite dispersion was obtained by ultrasonic dispersion at 280W for 30 min. The silane hydrolysate was added dropwise to the sepiolite dispersion at a rate of 1 mL / min and stirred for 10 min. Then, it was transferred to a three-necked flask equipped with a stirrer, thermometer and reflux condenser and placed in an 80℃ constant temperature water bath. The mixture was refluxed at a stirring rate of 450 r / min for 5 h. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with isopropanol, and then placed in a vacuum drying oven at 55℃ for 12 h. After cooling, silane-modified sepiolite was obtained.

[0104] Step s4: Add 0.3g of polyethyleneimine (polyethyleneimine is from Aladdin Biochemical Technology, catalog number: P434400), 10mL of deionized water, and 10mL of anhydrous ethanol to a beaker, place it in a 50℃ constant temperature water bath, and magnetically stir for 5min at a stirring rate of 350r / min to obtain a polyethyleneimine aqueous solution. Add 1.5g of silane-modified sepiolite and 30mL of deionized water to the beaker, and ultrasonically disperse for 20min at a power of 280W to obtain a silane-modified sepiolite dispersion. Add polyethylene... An aqueous solution of enimine was added dropwise to a silane-modified sepiolite dispersion at a rate of 0.5 mL / min. The mixture was stirred for 10 min and then transferred to a three-necked flask equipped with a stirrer, thermometer, and reflux condenser. The flask was placed in a 60°C constant temperature water bath and refluxed for 4 h with a stirring rate of 450 r / min. After the reaction was completed, the filter cake was collected by vacuum filtration, washed three times with distilled water, and then placed in a vacuum drying oven at 55°C for 12 h. After cooling, the cake was ground through a 100-mesh sieve to obtain modified sepiolite.

[0105] Step s5: Add 8.3g of modified sepiolite to 50mL of anhydrous ethanol, transfer to an ultrasonic disperser, and ultrasonically disperse for 40min at a power of 280W. Then transfer to a vacuum drying oven and dry at 55℃ for 2h. Grind with an agate mortar for 3min and pass through a 100-mesh sieve to obtain pretreated modified sepiolite.

[0106] Step s6: Add 100g of bisphenol A type epoxy resin (the type of bisphenol A type epoxy resin is NPEL-128) to a three-necked flask, place it in a constant temperature water bath at 50℃, and magnetically stir for 10min at a stirring speed of 450r / min. Then increase the stirring speed to 900r / min, add 8.3g of pretreated modified sepiolite in 3 portions, with an interval of 5min between each addition, and stir for 20min. Then use a high-speed shear emulsifier to shear and disperse for 20min at a stirring speed of 1400r / min to obtain the reinforced modified epoxy resin.

[0107] Step s7: Add 0.8 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter model is ADP-S479) and 100 g of reinforced modified epoxy resin to a beaker, and magnetically stir for 15 min at a stirring rate of 750 r / min. Then transfer to a high-speed mixer and mix for 15 min at a speed of 1100 r / min. After high-speed mixing, cure at a temperature of 45℃ for 30 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0108] Step s8: Add 6.5 mol isophthalic acid, 3.5 mol adipic acid, 8.5 mol neopentyl glycol, and 2 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.005 mol tetrabutyl titanate and 0.01 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 25°C and 180 r / min for 15 min. Then raise the temperature to 120°C, maintain the stirring rate, and hold for 30 min. Then raise the temperature to 150°C and react for 2 h. After that, increase the stirring rate by 5°C / 10 min. The temperature was increased to 180℃ and reacted for 3 hours. The temperature was then increased to 200℃ and reacted for 2 hours. After that, the temperature was maintained and the vacuum system was started to increase the vacuum to 0.05MPa. The temperature was maintained for 1.5 hours. Then, the vacuum was increased to 0.09MPa and the temperature was increased to 235℃. The stirring speed was controlled at 150r / min and the temperature was maintained for 3 hours. The heating was stopped and nitrogen was kept flowing. After the system temperature dropped below 100℃, it was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 75℃ for 2 hours. After that, it was pulverized with a pulverizer to a particle size ≤5mm to obtain a high hydrolysis resistant polyester resin.

[0109] Step s9: Weigh out 55 parts by weight of high hydrolysis resistant polyester resin, 4 parts by weight of curing agent, 1 part by weight of hydrolysis resistant stabilizer, 1.5 parts by weight of hydrolysis resistant metal substrate adhesion promoter, 8 parts by weight of pigment, 10 parts by weight of precipitated barium sulfate, 5 parts by weight of activated silica powder, 0.5 parts by weight of leveling agent, 0.3 parts by weight of degassing agent, 0.3 parts by weight of wetting and dispersing agent, and 0.4 parts by weight of wax additives;

[0110] Step s10: Add the high hydrolysis-resistant polyester resin, curing agent (the curing agent is hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (the hydrolysis-resistant stabilizer is a carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (pigment is rutile titanium dioxide), precipitated barium sulfate, activated silica powder (activated silica powder model HY-GA-1), leveling agent (leveling agent model BYK-361N), degassing agent (degassing agent model BYK-054), wetting and dispersing agent (wetting and dispersing agent model BYK-163), and wax additives (wax additives are polyethylene wax, model AC-6A) into a high-speed mixer and premix for 12 minutes at a speed of 1400 r / min. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0111] Comparative Example 3:

[0112] This comparative example illustrates a method for preparing a roll-type powder coating for soilless planting ponds, comprising the following steps:

[0113] Step s1: Add 0.8 mL of phosphate ester adhesion promoter (the phosphate ester adhesion promoter is model ADP-S479) and 100 g of bisphenol A epoxy resin (the bisphenol A epoxy resin is model NPEL-128) to a beaker, and stir magnetically for 15 min at a stirring rate of 750 r / min. Then transfer it to a high-speed mixer and mix at a speed of 1100 r / min for 15 min. After high-speed mixing, cure at a temperature of 45℃ for 30 min to obtain a hydrolysis-resistant metal substrate adhesion promoter.

[0114] Step s2: Add 6.5 mol isophthalic acid, 3.5 mol adipic acid, 8.5 mol neopentyl glycol, and 2 mol cyclohexanediethanol to a three-necked flask equipped with a stirrer, thermometer, gas delivery tube, and reflux condenser. Then add 0.005 mol tetrabutyl titanate and 0.01 mol triphenyl phosphate. Purge with nitrogen for protection and stir at 25°C and 180 r / min for 15 min. Then raise the temperature to 120°C, maintain the stirring rate, and hold for 30 min. Next, raise the temperature to 150°C and react for 2 h. Finally, increase the stirring rate by 5°C / 10 min. The temperature was increased to 180℃ and reacted for 3 hours. The temperature was then increased to 200℃ and reacted for 2 hours. After that, the temperature was maintained and the vacuum system was started to increase the vacuum to 0.05MPa. The temperature was maintained for 1.5 hours. Then, the vacuum was increased to 0.09MPa and the temperature was increased to 235℃. The stirring speed was controlled at 150r / min and the temperature was maintained for 3 hours. The heating was stopped and nitrogen was kept flowing. After the system temperature dropped below 100℃, it was transferred to a stainless steel tray and allowed to cool naturally to room temperature. Then, it was placed in a forced-air drying oven and dried at 75℃ for 2 hours. After that, it was pulverized with a pulverizer to a particle size ≤5mm to obtain a high hydrolysis resistant polyester resin.

[0115] Step s3: Weigh out 55 parts of high hydrolysis resistant polyester resin, 4 parts of curing agent, 1 part of hydrolysis resistant stabilizer, 1.5 parts of hydrolysis resistant metal substrate adhesion promoter, 8 parts of pigment, 10 parts of precipitated barium sulfate, 5 parts of active silica powder, 0.5 parts of leveling agent, 0.3 parts of degassing agent, 0.3 parts of wetting and dispersing agent, and 0.4 parts of wax additives according to the following weight proportions:

[0116] Step s4: Add the high hydrolysis-resistant polyester resin, curing agent (hydroxyalkylamide, model Primid® XL-552), hydrolysis-resistant stabilizer (carbodiimide compound, model Stabaxol P), hydrolysis-resistant metal substrate adhesion promoter, pigment (rutile titanium dioxide), precipitated barium sulfate, activated silica powder (HY-GA-1), leveling agent (BYK-361N), degassing agent (BYK-054), wetting and dispersing agent (BYK-163), and wax additive (polyethylene wax, model AC-6A) to a high-speed mixer and premix for 12 minutes at 1400 rpm. Then add the mixture to a twin-screw extruder. The extruder is set with the following temperatures: feeding section 105℃, compression section 115℃, melting section 125℃, homogenization section 120℃, and screw speed 300 r / min. After melting and mixing, the material is extruded through a die, pressed into tablets by a tablet press, cooled to room temperature, and then fed into a pulverizer for initial pulverization to a particle size ≤5mm. The coarse powder is then added to an ACM mill, with the pulverizing speed set at 4500 r / min and the classifying wheel speed at 12000 r / min. After fine pulverization, the powder is classified by a classifier, and powder with a particle size D50 = 35μm is collected to obtain the coil powder coating.

[0117] Performance testing: The coil powder coatings of Examples 1-3 and Comparative Examples 1-3 were tested according to the following methods;

[0118] Adhesion test on metal substrate: The test was conducted in accordance with GB / T 9286-1998 "Cross-cut test for paint and varnish film". A 1mm×1mm grid was drawn on the coating surface using a cross-cut tester, with 100 grids. 3M 610 tape was applied perpendicular to the grid surface, pressed firmly, and then quickly peeled off. This was repeated 3 times.

[0119] Hydrolysis resistance test: The powder coating was applied to the surface of Q235 steel substrate using an electrostatic spraying process and cured at 180℃ for 20 minutes. The coating thickness was controlled at 60μm. The sample size was 150mm×70mm×1.5mm, with 3 parallel samples per group. The samples were completely immersed in 25℃ deionized water, with the liquid level 20mm above the top of the sample. The samples were periodically removed, dried, and tested. Adhesion retention rate: According to GB / T 9286-1998, the 1mm grid cross-cut test was used. 3M 610 tape was applied and peeled off 3 times, and the percentage of remaining adhered area was calculated (the initial adhesion was grade 0, and the adhered area was 100%).

[0120] Impact strength test: The test was conducted in accordance with GB / T 1732-2020 "Determination of Impact Resistance of Coating Film". A falling ball impact tester was used, with an impact height of 50cm, an impact hammer mass of 1kg, and an impact head diameter of 12.7mm. The frontal impact was performed at the center of the sample, and 5 points were tested in each group.

[0121] Corrosion resistance test: The test was conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", using a salt spray test chamber, with a salt solution concentration of 5%, pH=6.5, and a fog deposition rate of 1-2 mL / (80 cm²). 2 (·h), temperature 35℃, continuous spraying for 500h.

[0122] Hot water resistance test: Immerse in 80℃ deionized water for 24 hours, and test the adhesion and appearance after cooling; Adhesion: After cooling to room temperature, test the adhesion level according to GB / T 9286-1998 "Cross-cut test of paint and varnish film" 1mm grid cross-cut method.

[0123] The test results are shown in the table below:

[0124]

[0125] Referring to the table above, based on the comparison between Examples 1-3 and Comparative Examples 1-3, it can be seen that through the synergistic effect of various modifications, combined with the hydrolysis-resistant adhesion promoter, the roll powder coating is suitable for use in scenarios such as long-term immersion and adhesion to metal substrates, fully meeting the requirements for use in soilless planting ponds.

[0126] Based on the comparison between Example 1 and Comparative Example 1, it can be seen that Comparative Example 1 lacks modified sepiolite, resulting in a moderate decrease in mechanical properties and hydrolysis resistance. However, since the epoxy resin is still hydrolysis-resistant modified, the corrosion resistance is not completely lost, indicating that the modified sepiolite mainly undertakes the functions of structural reinforcement and water molecule barrier.

[0127] Based on the comparison between Example 1 and Comparative Example 2, it can be seen that Comparative Example 2 lacks modified waterborne epoxy resin, resulting in a more significant decrease in hydrolysis resistance and corrosion resistance. The mechanical properties also decrease due to the insufficient stability of the resin itself, indicating that this modification is the core to improve the water resistance of the coating.

[0128] Based on the comparison between Example 1 and Comparative Example 3, it can be seen that Comparative Example 3 lacks modified sepiolite and modified waterborne epoxy resin, resulting in a cumulative decline in performance. The hydrolysis resistance retention rate is only 48%, the impact strength decreases, the adhesion drops to level 3, and the salt spray test completely fails. This indicates that there is a synergistic effect between modified sepiolite and methyl nadic anhydride diacid modification. The former strengthens the physical structure, while the latter optimizes the chemical water resistance. Only the combination of the two can achieve a leap in the overall performance of the coating.

[0129] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0130] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a powder coating for a soilless planting pond roll material, characterized in that, Includes the following steps: Step a1: Add sepiolite and deionized water to a beaker and stir. Then, disperse by ultrasonication, let stand, filter the upper suspension, wash, dry and cool to obtain purified and activated sepiolite. Step a2: Add purified and activated sepiolite and silicon tetrachloride solution to a beaker and stir magnetically. Then transfer to a three-necked flask and stir to react. Cool, filter, wash, dry, cool, grind, and sieve to obtain acid-modified sepiolite. Step a3: Add γ-glycidoxypropyltrimethoxysilane, deionized water and anhydrous ethanol to a beaker, adjust the pH, stir magnetically to obtain silane hydrolysate, ultrasonically disperse acid-modified sepiolite and mixed solvent to obtain sepiolite dispersion, add silane hydrolysate dropwise to sepiolite dispersion and stir, then transfer to a three-necked flask, reflux, filter, wash, dry and cool to obtain silane-modified sepiolite; Step a4: Polyethyleneimine, deionized water, and anhydrous ethanol are added to a beaker and magnetically stirred to obtain an aqueous solution of polyethyleneimine. Silane-modified sepiolite and deionized water are ultrasonically dispersed to obtain a silane-modified sepiolite dispersion. The aqueous solution of polyethyleneimine is added dropwise to the silane-modified sepiolite dispersion and stirred. Then, it is transferred to a three-necked flask, refluxed under condensation, filtered, washed, dried, cooled, ground, and sieved to obtain modified sepiolite. Step a5: Add methylnadic anhydride, 1,4-butanediol, 1,6-hexanediol and 1,10-decanediol to a three-necked flask, then add p-toluenesulfonic acid, stir the reaction, then heat the reaction, then distill under reduced pressure and cool to obtain the methylnadic anhydride dicarboxylic acid compound. Step a6: Add bisphenol A type epoxy resin and methyl nadic anhydride diacid compound to a beaker and stir to react. Add polyethylene glycol diglycidyl ether and continue shearing emulsification. Then add deionized water dropwise and continue stirring. Then distill under reduced pressure, add organosilicon defoamer, stir, filter, and obtain modified waterborne epoxy resin. Step a7: Add the modified sepiolite to anhydrous ethanol and ultrasonically disperse it, then dry, grind, and sieve to obtain pretreated modified sepiolite; Step a8: The modified waterborne epoxy resin is magnetically stirred to increase the stirring rate, pretreated modified sepiolite is added, stirred, and then sheared and dispersed to obtain the reinforced modified epoxy resin. Step a9: Add the phosphate ester adhesion promoter and the reinforced modified epoxy resin to a beaker and stir magnetically. Then transfer it to a high-speed mixer for mixing and maturation to obtain a hydrolysis-resistant metal substrate adhesion promoter. Step a10: Weigh out the following components by weight: 55-70 parts of high hydrolysis-resistant polyester resin, 4-7 parts of curing agent, 1-2.5 parts of hydrolysis-resistant stabilizer, 1.5-3 parts of hydrolysis-resistant metal substrate adhesion promoter, 8-15 parts of pigment, 10-12 parts of precipitated barium sulfate, 5-8 parts of activated silica powder, 0.5-1 part of leveling agent, 0.3-0.6 parts of degassing agent, 0.3-0.6 parts of wetting and dispersing agent, and 0.4-0.8 parts of wax additives. Step a11: Add high hydrolysis-resistant polyester resin, curing agent, hydrolysis-resistant stabilizer, hydrolysis-resistant metal substrate adhesion promoter, pigment, precipitated barium sulfate, active silica powder, leveling agent, degassing agent, wetting and dispersing agent, and wax additives to a high-speed mixer for premixing. Then add it to a twin-screw extruder for melt mixing and extrusion through a die. Press the extruder into tablets, cool them, and then put them into a pulverizer. Add them to an ACM mill for fine pulverization and then classify them through a classifier to collect the particle size and obtain the roll powder coating.

2. The method for preparing a roll-type powder coating for soilless planting ponds according to claim 1, characterized in that, In step a1, the ratio of sepiolite to deionized water is 30-32 g: 1800-1900 mL; in step a2, the ratio of purified and activated sepiolite to silicon tetrachloride solution is 3-5 g: 150-250 mL; in step a3, the ratio of γ-glycidyl etheroxypropyltrimethoxysilane, deionized water, anhydrous ethanol, acid-modified sepiolite, and mixed solvent is 0.06-0.08 g: 0.06 g. -0.08mL: 0.7-0.9mL: 2-2.6g: 20-26mL; the ratio of polyethyleneimine, deionized water, anhydrous ethanol, silane-modified sepiolite, and deionized water in step a4 is 0.3-0.5g: 10-16mL: 10-16mL: 1.5-2.5g: 30-50mL; the ratio of methylnadic anhydride, 1,4-butanediol, and 1,6-hexanediol in step a5 is... The ratio of 1,10-decanediol to p-toluenesulfonic acid is 166-187g:35-39g:47-53g:69-78g:1.6-1.8g; the ratio of bisphenol A epoxy resin, methylnadic anhydride diacid compound, polyethylene glycol diglycidyl ether, deionized water, and silicone defoamer in step a6 is 60-84g:40-56g:2-2.8g:120-168mL. The dosage of modified sepiolite in step a7 is 0.5-0.7g; the dosage ratio of modified sepiolite to anhydrous ethanol in step a7 is 8.3-8.5g: 50-51mL; the dosage ratio of modified waterborne epoxy resin to pretreated modified sepiolite in step a8 is 100-102g: 8.3-8.5g; the dosage ratio of phosphate ester adhesion promoter to reinforced modified epoxy resin in step a9 is 0.8-1.6mL: 100-110g.

3. The method for preparing a roll-type powder coating for soilless planting ponds according to claim 1, characterized in that, The sepiolite in step a1 is 400 mesh; the concentration of the silicon tetrachloride solution in step a2 is 0.5 mol / L; the mixed solvent in step a3 is a solution of deionized water and anhydrous ethanol mixed in a volume ratio of 1:

10.

4. The method for preparing a roll-type powder coating for soilless planting ponds according to claim 1, characterized in that, The highly hydrolysis-resistant polyester resin is prepared by the following steps: Isophthalic acid, adipic acid, neopentyl glycol, and cyclohexanediethanol were added to a three-necked flask, followed by the addition of tetrabutyl titanate and triphenyl phosphate. The mixture was stirred and reacted, then heated and allowed to react further. The vacuum was then increased, the mixture was kept at that temperature, cooled, dried, and finally pulverized to obtain a highly hydrolysis-resistant polyester resin.

5. The method for preparing a roll-type powder coating for soilless planting ponds according to claim 4, characterized in that, The ratio of isophthalic acid, adipic acid, neopentyl glycol, cyclohexanediol, tetrabutyl titanate, and triphenyl phosphate is 6.5-13.0 mol: 3.5-7.0 mol: 8.5-17.0 mol: 2-4 mol: 0.005-0.010 mol: 0.01-0.02 mol.

6. The method for preparing a roll-type powder coating for soilless planting ponds according to claim 1, characterized in that, The curing agent is a hydroxyalkylamide; the hydrolysis-resistant stabilizer is a carbodiimide compound; and the pigment is rutile titanium dioxide.

7. The application of a method for preparing a roll-type powder coating for soilless planting ponds as described in any one of claims 1-6 in soilless planting ponds.

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