Composite coating for water purification equipment and preparation method thereof, electromagnetic valve containing the composite coating and water purifier

Abstract

The application provides a composite coating for a water purification device, a preparation method of the composite coating, an electromagnetic valve containing the composite coating and a water purifier. The composite coating comprises a bottom layer and a surface layer in direct contact with one surface of the bottom layer, the material of the bottom layer comprises an epoxy-amine based addition product; the material of the surface layer comprises nano-silicon dioxide and polyurethane modified fluorocarbon resin, and the particle size of the nano-silicon dioxide is 40-80 nm. The composite coating provided by the application can be applied to the water purification device, and can effectively reduce the blockage rate of the waste water ratio electromagnetic valve and the waste water pipeline.

Description

Technical Field

[0001] This invention specifically relates to a composite coating for water purification equipment and its preparation method, as well as an electromagnetic valve and a water purifier containing the same coating. Background Technology

[0002] Current nanofiltration and reverse osmosis water purifiers (excluding ultrafiltration) typically incorporate a wastewater ratio solenoid valve at the wastewater end to control the ratio of purified water to wastewater, ensuring the total dissolved solids (TDS) of the output water meets requirements. However, this can lead to higher TDS levels in the wastewater, which can cause scaling and blockage of the wastewater ratio solenoid valve, and even the wastewater pipes, ultimately affecting the normal operation of the water purifier.

[0003] For the wastewater ratio solenoid valve, in the normally closed state, only a specific small flow of wastewater is discharged for wastewater discharge during water production; in the energized state, it is fully open, and the wastewater flow is large for flushing; in order to achieve a specific wastewater flow, the wastewater ratio solenoid valve is equipped with a long pinhole, and different wastewater flow rates are achieved by assembling long pinholes with different diameters. Usually, the size of the pinhole is relatively small, typically less than 1.5mm in diameter and 15-24mm in length.

[0004] Current technology often employs the method of adding scale inhibitors before nanofiltration or reverse osmosis filter cartridges to interfere with the crystallization of metal ions such as calcium and magnesium in the water, thus inhibiting scale formation. The main component of scale inhibitors is phosphate, a food-grade additive. After filtration, the large molecular components of the scale inhibitor can be completely retained, ensuring the safety of the filtered water. However, users currently have misunderstandings about this substance and are reluctant to use water purifiers equipped with scale inhibitors, affecting the sales of water purifiers. Furthermore, scale inhibitors are consumed with use; if they are not replaced in time, their scale-inhibiting effect will be affected; if they are replaced in time, it will increase the user's operating costs.

[0005] Therefore, the search for a non-chemical scale inhibition method to delay scale buildup and blockage in wastewater solenoid valves and wastewater pipes, and extend the service life of water purifiers, has received widespread attention. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing water purifiers, such as the tendency for scale and blockage in the wastewater solenoid valve and wastewater pipeline. It provides a composite coating for water purification equipment, its preparation method, a solenoid valve containing the coating, and a water purifier. The composite coating provided by this invention, when applied to water purification equipment, can effectively reduce the blockage rate of the wastewater solenoid valve and wastewater pipeline.

[0007] This invention provides a composite coating for water purification equipment, comprising a base layer and a surface layer in direct contact with one surface of the base layer. The material of the base layer comprises an epoxy-amine addition product; the material of the surface layer comprises nano-silica and polyurethane-modified fluorocarbon resin, wherein the particle size of the nano-silica is 40-80 nm.

[0008] In this invention, the thickness of the underlying layer can be 0.5-0.8 μm. This thickness is sufficient to form a continuous and dense film layer. If it is too thick, the internal stress may increase due to curing shrinkage, which may reduce the adhesion.

[0009] In this invention, the epoxy-amine addition product is a cured product generated by an epoxy resin reacting with an aminosilane coupling agent and / or an amine curing agent in a ring-opening addition reaction, as commonly understood in the art, and may contain carbon-nitrogen bonds (CN), ether bonds (COC), and hydroxyl groups (-OH).

[0010] In this invention, the epoxy-amine addition product can be formed by reacting epoxy resin, silane coupling agent and first curing agent.

[0011] The epoxy resin can be any epoxy resin commonly used in the art, preferably a bisphenol A type epoxy resin. This epoxy resin exhibits good wettability and adhesion to metal substrates, and after curing, it has high hardness and low volume shrinkage, making it an ideal primer material.

[0012] The epoxy value of the epoxy resin can be 0.48-0.52 eq / 100g, for example 0.51 eq / 100g.

[0013] The epoxy resin has a viscosity of 8000-12000 mPa·s at 25°C, for example, 11500 mPa·s.

[0014] The silane coupling agent can be a conventionally used aminosilane coupling agent in the art, preferably an aminosilane coupling agent, such as γ-aminopropyltriethoxysilane (KH-550). This is because the molecular structure of the silane coupling agent consists of an alkoxy group at one end that can react with inorganic substances (long pinholes in metal materials) and an amino group at the other end that can react with organic substances (epoxy resin). It forms a "molecular bridge" between the metal substrate and the epoxy resin, greatly enhancing the chemical bonding. This can increase the adhesion to the metal substrate of the throttling needle to 15-18 MPa (compared to only 5-10 MPa for conventional coatings), ensuring the reliability of the coating system under long-term wastewater flushing and thermal cycling.

[0015] The purity of the silane coupling agent can be above 98%.

[0016] The mass of the silane coupling agent can be 3%-5% of the total mass of the silane coupling agent and epoxy resin, for example, 4%.

[0017] The first curing agent can be a substance commonly used in the art for curing epoxy resins, preferably an amine curing agent, such as polyetheramine or aliphatic amide amine epoxy curing agent.

[0018] The mass ratio of the first curing agent to the epoxy resin is (25-30):100, for example, 27:100.

[0019] In this invention, the thickness of the surface layer can be 0.8-1.2 μm. This thickness ensures complete coverage of the nano-rough structure without affecting the dimensional accuracy of the pores or causing cracking due to excessive thickness.

[0020] In this invention, the polyurethane-modified fluorocarbon resin can be a product formed by the addition polymerization reaction of hydroxyl groups (-OH) and isocyanate groups (-NCO) in fluorocarbon resins as commonly understood in the art, resulting in a cross-linked structure with urethane bonds (-NHCOO-).

[0021] In this invention, the polyurethane-modified fluorocarbon resin can be generated by reacting a fluorocarbon resin with a second curing agent. The reaction formula is R-NCO + R'-OH → R-NH-COO-R' (-NH-COO- is a urethane bond). Through this reaction, the fluorocarbon resin crosslinks from a linear structure into a three-dimensional network structure, which can impart excellent mechanical properties and chemical resistance to the coating.

[0022] The fluorocarbon resin can be a resin containing CF bonds commonly used in the art, such as FEVE-type fluorocarbon resin. Its CF bond energy is extremely high and its atomic polarizability is low, which significantly reduces the surface energy of the material and gives it excellent hydrophobic (hydrophobic and oleophobic) properties.

[0023] The fluorine content of the fluorocarbon resin may be ≥28%, for example, 30%.

[0024] The hydroxyl value of the fluorocarbon resin can be 50-60 mgKOH / g, for example, 55 mgKOH / g.

[0025] The mass ratio of the fluorocarbon resin to the nano-silica can be 100:(8-15), for example, 100:12.

[0026] The second curing agent may be an isocyanate and / or an aliphatic isocyanate, wherein the aliphatic isocyanate is preferably a hexamethylene diisocyanate trimer.

[0027] Preferably, the NCO content in the second curing agent is 15%-17%, for example 16.4%, where the percentage is the mass of the NCO groups relative to the mass of the second curing agent.

[0028] The mass ratio of the second curing agent to the fluorocarbon resin can be (12-15):100, for example, 13.5:100.

[0029] In this invention, the particle size of the nano-silica can be 40-60 nm, for example, 50 nm. The main purpose is to create microscopic roughness in the coating. Appropriate roughness can significantly amplify the hydrophobic effect, increasing the apparent contact angle from 110° on a smooth fluorocarbon surface to over 145°, achieving a superhydrophobic state.

[0030] In this invention, the specific surface area of ​​the nano-silica can be 180-220 m². 2 / g, for example 220 m 2 / g.

[0031] This invention provides a method for preparing a composite coating for water purification equipment. A bottom layer slurry is coated onto a substrate to be coated and cured for the first time to form a bottom layer. Then, a top layer slurry is coated on the surface of the bottom layer and cured for the second time to form a top layer, thus obtaining the composite coating. The bottom layer slurry comprises epoxy resin, silane coupling agent, first curing agent, and first solvent; the first curing temperature is 110℃-130℃; the silane coupling agent is an aminosilane coupling agent; the top layer slurry comprises fluorocarbon resin, nano-silica, second curing agent, and second solvent; the nano-silica has a particle size of 40-80nm; the second curing temperature is 170℃-190℃.

[0032] In this invention, the substrate to be coated can be a metallic material, such as stainless steel.

[0033] In this invention, the shape of the substrate to be coated can be adjusted according to application needs, for example, it can be in the form of a throttling needle or a sheet. In water purification equipment, the substrate to be coated can be a throttling needle. In this invention, the epoxy resin can be an epoxy resin conventionally used in the art, preferably a bisphenol A type epoxy resin.

[0034] In this invention, the epoxy value of the epoxy resin can be 0.48-0.52 eq / 100g, for example 0.51 eq / 100g.

[0035] In this invention, the viscosity of the epoxy resin at 25°C can be 8000-12000 mPa·s, for example 11500 mPa·s.

[0036] In this invention, the silane coupling agent can be an aminosilane coupling agent conventionally used in the art, preferably an aminosilane coupling agent, such as γ-aminopropyltriethoxysilane (KH-550).

[0037] In this invention, the purity of the silane coupling agent can be above 98%.

[0038] In this invention, the mass of the silane coupling agent can be 3%-5% of the total mass of the silane coupling agent and the epoxy resin.

[0039] In this invention, the first curing agent can be a substance commonly used in the art for curing epoxy resins, preferably an amine curing agent, such as polyetheramine or aliphatic amide amine epoxy curing agent.

[0040] In this invention, the mass ratio of the first curing agent to the epoxy resin is (25-30):100, for example, 27:100.

[0041] In this invention, the first solvent may be a substance conventionally used in the art, such as propylene glycol methyl ether acetate (PMA) and / or xylene.

[0042] In this invention, the amount of the first solvent can be adjusted to a viscosity that facilitates coating of the underlying slurry.

[0043] In this invention, the viscosity of the underlying slurry can be 110 cP - 130 cP, for example 120 cP.

[0044] In this invention, the fluorocarbon resin can be a resin containing CF bonds that is conventionally used in the art, such as FEVE type fluorocarbon resin.

[0045] In this invention, the fluorine content of the fluorocarbon resin can be ≥28%, for example 30%.

[0046] In this invention, the hydroxyl value of the fluorocarbon resin can be 50-60 mgKOH / g, for example 55 mgKOH / g.

[0047] In this invention, the particle size of the nano-silica can be 40-60 nm, for example 50 nm.

[0048] In this invention, the specific surface area of ​​the nano-silica can be 180-220 m². 2 / g, for example 220 m 2 / g.

[0049] In this invention, the mass ratio of the fluorocarbon resin to the nano-silica can be 100:(8-15), for example, 100:12.

[0050] In this invention, the second curing agent may be an isocyanate and / or an aliphatic isocyanate, wherein the aliphatic isocyanate is preferably a hexamethylene diisocyanate trimer.

[0051] Preferably, the NCO content in the second curing agent is 15%-17%, for example 16.4%, where the percentage is the mass of the NCO groups relative to the mass of the second curing agent.

[0052] In this invention, the mass ratio of the second curing agent to the fluorocarbon resin can be (12-15):100, for example, 13.5:100.

[0053] In this invention, the fluorocarbon resin and nano-silica are as described above.

[0054] In this invention, the second solvent may be a substance conventionally used in the art, such as one or more of xylene, butyl acetate, and propylene glycol methyl ether acetate.

[0055] In this invention, the amount of the second solvent can be adjusted to a viscosity that facilitates coating of the surface slurry.

[0056] In this invention, the viscosity of the surface slurry can be 75-85 cP, for example 80 cP.

[0057] In this invention, the surface slurry further includes a dispersant, which can be a substance that enables uniform dispersion of nano-silica, preferably a high-molecular-weight block copolymer, such as BYK series dispersants, such as BYK-163. The dispersant can achieve uniform dispersion of nano-silica through both anchoring group adsorption and steric hindrance. Specifically, the basic groups in the dispersant can be firmly adsorbed onto the surface of SiO2 particles through hydrogen bonds, acid-base interactions, or van der Waals forces; the side chains can form a steric hindrance layer, preventing SiO2 particles from approaching each other and agglomerating.

[0058] Preferably, the amount of the dispersant is 15%-20% of the mass of nano-silica.

[0059] In this invention, the coating method can be one or more of the methods commonly used in the art, such as spraying, dipping, and scraping.

[0060] In some specific implementations, the underlying slurry can be coated by dip coating. Dip coating is well-suited for complex-shaped cavities, small holes, and other structures, ensuring that the underlying material forms a uniform, seamless coverage on the inner wall of the throttling needle.

[0061] In some specific embodiments, the surface slurry can be applied by spraying. Spraying allows for precise control of coating thickness and uniformity. For small, elongated orifice structures, a specially designed micro-elongated nozzle is required.

[0062] In this invention, the first curing temperature can be 115℃-130℃, for example 120℃.

[0063] In this invention, the heating rate of the first curing process can be 1℃ / min-5℃ / min, for example, 3℃ / min.

[0064] In this invention, the first curing time can be 20 min to 40 min, for example, 30 min.

[0065] In some specific implementations, pre-curing is performed before the first curing.

[0066] The pre-curing temperature can be 60℃-90℃, for example 80℃.

[0067] The pre-curing heating rate can be 1℃ / min-3℃ / min, for example 2℃ / min.

[0068] The pre-curing time can be 5 min to 15 min, for example, 10 min.

[0069] In this invention, the second curing temperature can be 175℃-190℃, for example 180℃.

[0070] In this invention, the heating rate of the second curing process can be 1℃ / min-5℃ / min, for example, 3℃ / min.

[0071] In this invention, the second curing time can be 30-50 minutes, for example, 45 minutes.

[0072] The present invention also provides a solenoid valve comprising the composite coating as described above.

[0073] In this invention, the solenoid valve includes a throttling needle, which comprises a conical section and an equal-diameter section. The inlet of the equal-diameter section is connected to the outlet of the conical section. In the direction from the conical section to the equal-diameter section, the inner diameter of the conical section gradually decreases. The inlet diameter of the conical section is 20%-30% larger than the diameter of the equal-diameter section. The length of the conical section is 1.5-2 times the diameter of the equal-diameter section. The inner walls of both the conical section and the equal-diameter section are provided with the composite coating as described above.

[0074] In this invention, the surface roughness of the tapered segment can be below 2 μm.

[0075] In this invention, the aperture of the straight section can be less than 1.5 mm, preferably 1-1.5 mm.

[0076] In this invention, the length of the straight segment can be 15-24 mm.

[0077] The present invention also provides a water purifier that includes the solenoid valve as described above.

[0078] In this invention, the water inlet of the water purifier is located near the inlet of the conical section, and the outlet of the water purifier is located near the outlet of the constant diameter section.

[0079] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0080] The reagents and raw materials used in this invention are all commercially available.

[0081] The positive and progressive effects of this invention are as follows: The composite coating for water purification equipment provided by this invention, when applied to water purification equipment, results in a lower final clogging rate and a high anti-scaling effect; at the same time, it has a high bonding force with the substrate and a long service life. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of the throttling needle prepared in Example 2.

[0083] Figure 2 This is a schematic diagram of the structure of a solenoid valve containing the throttling needle obtained in Example 2.

[0084] Figure 3 This is a schematic diagram of the structure of a solenoid valve containing the throttling needle made in Comparative Example 8.

[0085] Reference numerals: 1-conical section; 2-equal diameter section; 3-water-saving valve; 4-wastewater interface; 5-electromagnetic coil; 6-reset spring; 7-guide rod; 8-valve body; 9-valve core; 10-diaphragm assembly. Detailed Implementation

[0086] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0087] The raw material information involved in the following examples and comparative examples is shown in Table 1 below: Table 1

[0088] Example 1

[0089] (1) Preparation of the bottom layer

[0090] By weight, 100 parts of bisphenol A epoxy resin, 4 parts of KH550, 27 parts of polyetheramine D-230 and propylene glycol methyl ether acetate were mixed to prepare the bottom layer slurry. The amount of propylene glycol methyl ether acetate was adjusted so that the viscosity of the bottom layer slurry was 120±10 cP. The substrate to be coated is immersed in the base slurry. After being removed, the temperature is raised from room temperature to 80°C at 2°C / min and held for 10 minutes to allow the solvent to evaporate slowly for pre-curing. Then, the temperature is raised to 120°C at 3°C / min and held for 30 minutes for curing to ensure complete cross-linking and form the base layer of the coating on the surface of the substrate to be coated. (2) Preparation of the surface layer A surface slurry was prepared by mixing 100 parts by weight of FEVE type fluorocarbon resin, 13.5 parts by weight of Desmodur N75, 12 parts by weight of oleophilic modified nano silica (average particle size of 50 nm), 2 parts by weight of BYK-163 polymer block copolymer dispersant and a mixed solvent (xylene and butyl acetate mixed in a mass ratio of 1:1). The amount of mixed solvent was adjusted to make the viscosity of the surface slurry 80±5 cP. The surface slurry was sprayed onto the base layer obtained in step (1), and then transferred to a curing oven. The temperature was increased from room temperature to 180°C at 3°C / min and kept at the temperature for 45 minutes to cure, thus obtaining a composite coating.

[0091] Comparative Example 1

[0092] Based on Example 1, KH550 in step (1) is adjusted to KH560, and other conditions are the same as in Example 1.

[0093] Comparative Example 2

[0094] Based on Example 1, step (1) does not add KH550 (i.e., no silane coupling agent is added to the bottom slurry), and other conditions are the same as in Example 1.

[0095] Comparative Example 3

[0096] Based on Example 1, the curing temperature of the bottom layer slurry in step (1) was adjusted to 100°C, and other conditions were the same as in Example 1.

[0097] Comparative Example 4

[0098] Based on Example 1, the curing temperature of the surface slurry in step (2) was adjusted to 160°C, and other conditions were the same as in Example 1.

[0099] Comparative Example 5

[0100] (1) Preparation of the bottom layer

[0101] By weight, 100 parts of bisphenol A epoxy resin, 4 parts of KH550, 27 parts of polyetheramine D-230 and propylene glycol methyl ether acetate were mixed to prepare the bottom layer slurry. The amount of propylene glycol methyl ether acetate was adjusted so that the viscosity of the bottom layer slurry was 120±10 cP. Immerse the substrate to be coated into the base slurry, and then let it stand at room temperature for only 2-3 minutes to allow the surface to level out, forming the base layer of the coating on the surface of the substrate to be coated. (2) Preparation of the surface layer A surface slurry was prepared by mixing 100 parts by weight of FEVE type fluorocarbon resin, 13.5 parts by weight of Desmodur N75, 12 parts by weight of oleophilic modified nano silica, 2 parts by weight of BYK-163 polymer block copolymer dispersant and a mixed solvent (xylene and butyl acetate mixed in a mass ratio of 1:1). The amount of mixed solvent was adjusted to make the viscosity of the surface slurry 80±5 cP. The surface slurry is sprayed onto the bottom layer obtained in step (1) and placed directly into a curing oven heated to 180°C. The oven is kept at the temperature for 45 minutes to cure, thus obtaining a composite coating.

[0102] Comparative Example 6

[0103] Based on Example 1, the particle size of the oleophilic nano silica was adjusted to 20 nm, while other conditions remained the same as in Example 1.

[0104] Comparative Example 7

[0105] Based on Example 1, the particle size of the oleophilic nano silica was adjusted to 100 nm, while other conditions remained the same as in Example 1.

[0106] Example 1

[0107] (1) Scale prevention rate of composite coating

[0108] Prepare a 50mm×25mm×2mm 304 stainless steel sheet, grind and clean it, and use it as the substrate to be coated; prepare the composite coating in the examples and comparative examples on its surface, and use it as the test piece of the experimental group; use the same 304 stainless steel sheet as the test piece of the blank group; record the initial weight of the experimental group and the blank group. A mixed solution of CaCl2 and NaHCO3 was prepared to simulate high hardness water, with the equivalent concentration of CaCO3 stabilized at 2000 ppm and pH = 8.0 ± 0.2. A scale prevention tester with constant temperature heating and circulation pump was used. The test piece was placed vertically in the flow tank of the scale prevention tester. The experimental parameters were set as follows: temperature: (60±2)°C; flow rate: (1.5±0.1) m / s (simulating the flow rate in the bypass hole); experimental period: 240 hours (10 days). After the experiment, remove the test piece, gently rinse it with deionized water, and then dry it. Soak it in 5% dilute hydrochloric acid until the scale is completely dissolved, dry it again, and weigh it. Calculate the scale weight per unit area (mg / cm²) based on the difference in mass of the test piece before and after the experiment, and then calculate the scale prevention rate using the following formula: Anti-scaling rate (%) = [(scaling weight per unit area of ​​blank group - scaling weight per unit area of ​​experimental group) / scaling weight per unit area of ​​blank group] × 100%, and the results are recorded in Table 2.

[0109] (2) Contact angle

[0110] Contact angle tracking measurement: Standard-sized coated samples and blank metal samples were prepared. They were immersed in concentrated hard water (TDS=2000ppm, mainly CaCO3 and MgSO4) at a constant temperature (60°C), and dynamic scaling was simulated by slow evaporation or a circulating pump. At days 0, 1, 3, 7, and 10, the samples were removed, gently rinsed with deionized water, and their water contact angles were measured (using the static seat drop method). The decay of hydrophobicity was observed, and the results are recorded in Table 2. Extremely low scale weight and slow contact angle decay indicate excellent scale inhibition performance of the coating.

[0111] Table 2

[0112] Example 2

[0113] Prepare a 50mm×25mm×2mm 304 stainless steel sheet, grind and clean it, and use it as the substrate to be coated; prepare the composite coating in the examples and comparative examples on its surface, and use it as the test piece in the experimental group; use the same 304 stainless steel sheet as the test piece in the blank group, and perform the following tests.

[0114] (1) Bonding strength test: Following the standard ASTM D4541, a portable adhesion tester was used. Aluminum dollies were adhered to the test piece using specialized adhesive. After removal, the pressure value (unit: MPa) was read. Five points were tested for each sample, and the average value was taken. The results are shown in Table 3.

[0115] (2) Surface energy test

[0116] The contact angles of the coating of the test piece with deionized water and diiodomethane were measured using a static contact angle meter. The surface energy (mN / m) was calculated using the Owens-Wendt-Rabel-Kaeble model, and the results are shown in Table 3.

[0117] Table 3

[0118] Note ①: Comparative Example 2 (without silane coupling agent) had extremely low adhesion between the bottom layer and the substrate, resulting in localized peeling of the coating during the sample processing required for surface energy testing. As a result, effective and stable contact angle data could not be obtained, and therefore the surface energy could not be measured.

[0119] Note ②: The " / " in the table indicates that surface energy testing was not performed on that group. This is because surface energy mainly reflects the surface function, and the differences in most comparative examples lie in the underlying layer or process, which have a limited impact on surface energy. Only the performance data of comparative example 1 was tested as typical data for KH-560; other comparative examples were not tested.

[0120] The composite coating provided by this invention has excellent scale inhibition effect and stable structure. After continuous water flow for 10 days, the scale weight per unit area is less than 1 mg / cm³. 2 The anti-scaling rate can reach over 90%, and the decrease in water contact angle compared to the initial state is also small. The adhesion between the composite coating and the substrate can reach over 15 MPa, and the surface energy is below 17 mN / m. This is due to the low adhesion and lotus effect of the composite coating. The extremely low surface energy significantly weakens the van der Waals forces and electrostatic attraction between dirt / particles and the coating, making it difficult for particles to be adsorbed and deposited. On the superhydrophobic surface, droplets form a very small contact area and easily roll away contaminants. Similarly, the actual contact area between dirt / particles in wastewater and the coating is also very small, making them easily carried away by the shear force of the wastewater.

[0121] The difference between Comparative Example 1 and Example 1 is that the silane coupling agent used in Comparative Example 1 is KH560. According to its effect data, the scale weight per unit area is about 7 times that of Example 1, the scale prevention rate and contact angle are also worse, and the adhesion to the substrate is much lower than that of Example 1. The surface energy is as high as 25.8mN / m, and solid particles are easily adsorbed or deposited on the surface of the coating, thus forming a blockage.

[0122] The difference between Comparative Example 2 and Example 1 is that no silane coupling agent was added. The resulting composite coating has a bonding strength of less than 5 MPa with the substrate, making it easy to peel off, which seriously affects its service life and significantly deteriorates its anti-scaling performance.

[0123] The difference between Comparative Example 3 and Example 1 is that the curing temperature of the bottom layer slurry is lower. The difference between Comparative Example 4 and Example 1 is that the curing temperature of the surface layer slurry is lower. Its scale weight per unit area is more than 3 times that of Example 1, and its scale prevention rate is also lower. Its adhesion to the substrate is only 11 MPa, which has a greater risk of peeling off and affects its service life.

[0124] The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 cured the bottom layer and the top layer in one step. The resulting coating surface has a large number of orange peel textures and a small number of bubbles. The adhesion strength is reduced to 8 MPa and there is interlayer peeling. Its scale weight per unit area is more than 8 times that of Example 1, and the scale prevention rate is only 63.2%. The performance is very poor and cannot meet the application requirements.

[0125] This is because the specific method of low-temperature curing of the bottom layer and high-temperature curing of the surface layer in this invention allows the bottom layer to form a stable support first, avoiding the huge internal stress caused by the different paces of solvent evaporation and cross-linking shrinkage when the two layers are cured at high temperature at the same time, which would lead to coating wrinkling, cracking or interlayer peeling.

[0126] The difference between Comparative Example 6, Comparative Example 7, and Example 1 lies in the different particle sizes of the oleophilic nano-silica, which has a significant impact on the scale inhibition effect and structural stability of the composite coating. When the particle size of the oleophilic nano-silica is 40-60 nm, it is more conducive to improving the scale inhibition performance of the composite coating.

[0127] Example 2

[0128] (1) Preparation of the bottom layer

[0129] By weight, 100 parts of bisphenol A epoxy resin, 4 parts of KH550, 27 parts of polyetheramine D-230 and propylene glycol methyl ether acetate were mixed to prepare the bottom layer slurry. The amount of propylene glycol methyl ether acetate was adjusted so that the viscosity of the bottom layer slurry was 120±10 cP. The throttling needle (which has a tapered section and a constant diameter section, with an inlet diameter of Φ1.9 mm, a tapered section length of 3.0 mm, and a surface roughness of Ra≤0.2μm, and a constant diameter section with an inlet diameter of Φ1.5 mm and a constant diameter section length of 15.0 mm) is immersed in the underlying slurry. After removal, the slurry on the outer wall of the throttling needle is removed. The temperature is raised from room temperature to 80°C at 2°C / min and held for 10 min to allow the solvent to evaporate slowly for pre-curing. Then, the temperature is raised to 120°C at 3°C / min and held for 30 min for curing to ensure complete cross-linking and form the underlying layer of the coating on the inner wall of the throttling needle. (2) Preparation of the surface layer A surface slurry was prepared by mixing 100 parts by weight of FEVE type fluorocarbon resin, 13.5 parts by weight of Desmodur N75, 12 parts by weight of oleophilic modified nano silica, 2 parts by weight of BYK-163 polymer block copolymer dispersant and a mixed solvent (xylene and butyl acetate mixed in a mass ratio of 1:1). The amount of mixed solvent was adjusted to make the viscosity of the surface slurry 80±5 cP. The surface slurry was sprayed onto the base layer obtained in step (1) using a micro-long fine nozzle, and then transferred to a curing oven. The temperature was increased from room temperature to 180°C at 3°C / min and kept at the temperature for 45 minutes to cure, thus obtaining a composite coating.

[0130] A schematic diagram of the throttling needle prepared in Example 2 is shown below. Figure 1 As shown, a schematic diagram of the solenoid valve containing the throttling needle is as follows. Figure 2 As shown. By Figure 1It can be seen that the throttling needle 3 includes a conical section 1 and a constant-diameter section 2, with the inlet of the constant-diameter section 2 connected to the outlet of the conical section 1. From Figure 2 It can be seen that the solenoid valve includes a water-saving valve 3, a wastewater interface 4, an electromagnetic coil 5, a return spring 6, a guide rod 7, a valve body 8, a valve core 9, and a diaphragm assembly 10.

[0131] Example 3

[0132] (1) Preparation of the bottom layer

[0133] By weight, 100 parts of bisphenol A epoxy resin, 4 parts of KH550, 27 parts of polyetheramine D-230 and propylene glycol methyl ether acetate were mixed to prepare the bottom layer slurry. The amount of propylene glycol methyl ether acetate was adjusted so that the viscosity of the bottom layer slurry was 120±10 cP. Immerse the throttling needle (the throttling needle has a constant diameter structure, an orifice diameter of Φ1.5mm, and a length of 18.0mm) into the bottom layer slurry. After removing it, remove the slurry from the outer wall of the throttling needle. Increase the temperature from room temperature to 80°C at 2°C / min and hold for 10min to allow the solvent to evaporate slowly for pre-curing. Then increase the temperature to 120°C at 3°C / min and hold for 30min for curing to ensure complete cross-linking and form the bottom layer of the coating on the inner wall of the throttling needle. (2) Preparation of the surface layer A surface slurry was prepared by mixing 100 parts by weight of FEVE type fluorocarbon resin, 13.5 parts by weight of Desmodur N75, 12 parts by weight of oleophilic modified nano silica, 2 parts by weight of BYK-163 polymer block copolymer dispersant and a mixed solvent (xylene and butyl acetate mixed in a mass ratio of 1:1). The amount of mixed solvent was adjusted to make the viscosity of the surface slurry 80±5 cP. The surface slurry was sprayed onto the base layer obtained in step (1) using a micro-long fine nozzle, and then transferred to a curing oven. The temperature was increased from room temperature to 180°C at 3°C / min and kept at the temperature for 45 minutes to cure, thus obtaining a composite coating.

[0134] Comparative Example 8

[0135] Prepare a slurry by mixing 100 parts epoxy resin, 30 parts curing agent, and 80 parts solvent. Immerse a throttling needle (which has a conical section and a constant diameter section, with an inlet diameter of Φ1.9 mm, a length of 3.0 mm, and a surface roughness of Ra≤0.2μm, and an inlet diameter of Φ1.5 mm and a length of 15.0 mm for the constant diameter section) into the slurry. Remove the needle and discard the slurry from its outer wall. Then, heat the slurry to 120°C at a rate of 3°C / min and hold for 30 min to cure the throttling needle, forming a coating on its inner wall.

[0136] A schematic diagram of the solenoid valve containing the throttling needle prepared in Comparative Example 8 is shown below. Figure 3 As shown. By Figure 3 It can be seen that the solenoid valve includes a water-saving valve 3, a wastewater interface 4, an electromagnetic coil 5, a return spring 6, a guide rod 7, a valve body 8, a valve core 9, and a diaphragm assembly 10.

[0137] Comparative Example 9

[0138] A throttling needle without any coating (the throttling needle has a constant diameter structure, an orifice diameter of Φ1.5mm, and a length of 18.0mm).

[0139] Example 3

[0140] Test method for the final blockage rate of solenoid valves: (1) The throttling needles containing composite coatings obtained in Examples 2, 3 and Comparative Examples 8, 9 were processed into simulated solenoid valve blocks with actual bypass small hole structure (standard hole diameter Φ1.0mm) and a length of 5mm.

[0141] (2) Simulate the structure of a water purifier and build a closed-loop circulation system, including a solution tank, a precision pump, a pressure sensor, a flow meter and a test valve block. Test conditions: solution TDS=1800ppm; temperature: 50℃; inlet pressure is constant at 0.3MPa; experimental period: 500 hours. (3) Blockage determination and calculation: Record the initial stable traffic Q0; record the real-time traffic Q every 24 hours. t The final congestion rate is calculated using the following formula: Final congestion rate = [(Q0-Q 500 [) / Q0]×100%; where Q 500 The flow rate is 500 hours.

[0142] After the experiment, the test valve block was dissected, and the deposits inside the orifice were visually observed and weighed. The results are shown in Table 4.

[0143] Table 4

[0144] When the composite coating provided by this invention is applied to a solenoid valve, it has good anti-clogging performance. After 500 hours of water immersion, its final clogging rate is only less than 40%.

[0145] The difference between Comparative Example 8 and Example 2 is that it is only a single-layer coating and does not include the surface layer in Example 3. Its surface energy is measured to be about 42.0 mN / m, which is much higher than that of the present invention, and its final blockage rate exceeds 60%, which cannot meet the application requirements.

[0146] The difference between Comparative Example 9 and Example 3 is that it does not contain a coating, but only a bare throttling needle, which eventually has a blockage rate of over 85%, completely blocking the flow and making it unusable.

[0147] Shear force tests were also conducted on Examples 2 and 3. The test method was to use a microparticle image velocimetry system or computational fluid dynamics software to compare and analyze the velocity gradient inside the orifice, especially near the wall, of the throttling needle with a conical structure and the throttling needle with a constant diameter structure at the same flow rate, thereby quantifying the increase in shear force. The results showed that the average shear stress generated near the orifice wall by the throttling needle with a conical structure in Example 3 was 18% higher than that of the throttling needle with a constant diameter structure.

[0148] The throttling needle in Example 2 has a conical section with a conical inlet. This smooth conical transition guides the wastewater to converge smoothly, significantly reducing flow separation and eddy currents, resulting in smoother streamlines. Furthermore, because the flow channel converges smoothly, the wastewater achieves a higher and more uniform velocity before entering the constant-diameter section. According to Newton's law of internal friction, the velocity gradient (shear rate) near the wall is greater, thus increasing the shear force (scouring force) exerted by the wastewater on the deposited particles by 15-20%. This increased shear force is sufficient to "wash away" particles that attempt to approach or weakly adhere to the material.

[0149] In Example 3, the inlet of the throttling needle is a sharp right angle. When wastewater enters the orifice, it suddenly contracts, creating flow separation and eddy zones downstream of the inlet edge. These eddies are low-energy regions with slow flow velocities, leading to the deposition of TDS particles at these locations.

[0150] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A composite coating for a water purification device, characterized in that, It includes a bottom layer and a surface layer in direct contact with one surface of the bottom layer. The material of the bottom layer includes an epoxy-amine addition product. The material of the surface layer includes nano-silica and polyurethane-modified fluorocarbon resin. The particle size of the nano-silica is 40-80 nm.

2. The composite coating for water purification equipment according to claim 1, characterized in that, The composite coating satisfies one or more of the following conditions: (1) The thickness of the bottom layer is 0.5-0.8 μm; (2) The epoxy-amine addition product is formed by the reaction of epoxy resin, silane coupling agent and first curing agent; (3) The thickness of the surface layer is 0.8-1.2 μm; (4) The polyurethane modified fluorocarbon resin is generated by reacting fluorocarbon resin and a second curing agent; (5) The particle size of the nano-silica is 40-60 nm, for example 50 nm; (6) The specific surface area of ​​the nano-silica is 180-220 m². 2 / g, for example 220 m 2 / g.

3. The composite coating for water purification equipment according to claim 2, characterized in that, The composite coating satisfies one or more of the following conditions: (1) The epoxy value of the epoxy resin is 0.48-0.52 eq / 100g, for example 0.51 eq / 100g; (2) The viscosity of the epoxy resin at 25°C is 8000-12000 mPa·s, for example 11500 mPa·s; (3) The silane coupling agent is an aminosilane coupling agent, such as γ-aminopropyltriethoxysilane; (4) The mass of the silane coupling agent is 3%-5% of the mass of the epoxy resin, for example, 4%; (5) The first curing agent is an amine curing agent, such as a polyetheramine or an aliphatic amide amine epoxy curing agent; (6) The mass ratio of the first curing agent to the epoxy resin is (25-30):100, for example 27:100; (7) The fluorocarbon resin is a FEVE type fluorocarbon resin; (8) The fluorine content of the fluorocarbon resin is ≥28%, for example 30%; (9) The hydroxyl value of the fluorocarbon resin is 50-60 mgKOH / g, for example 55 mgKOH / g; (10) The mass ratio of the fluorocarbon resin to the nano-silica is 100:(8-15), for example 100:12; (11) The second curing agent is an isocyanate and / or an aliphatic isocyanate, wherein the aliphatic isocyanate is preferably a hexamethylene diisocyanate trimer; The NCO content in the second curing agent is preferably 15%-17%, for example 16.4%, where the percentage is the mass of the NCO groups relative to the mass of the second curing agent. (12) The mass ratio of the second curing agent to the fluorocarbon resin is (12-15):100, for example 13.5:

100.

4. A method for preparing a composite coating for a water purification device, characterized in that, The bottom layer slurry is applied to the substrate to be coated and cured for the first time to form the bottom layer; then the top layer slurry is applied to the surface of the bottom layer and cured for the second time to form the top layer, thus obtaining the composite coating. The underlying slurry comprises epoxy resin, silane coupling agent, first curing agent, and first solvent; the first curing temperature is 110℃-130℃; the silane coupling agent is an aminosilane coupling agent. The surface slurry comprises fluorocarbon resin, nano-silica, a second curing agent, and a second solvent; the nano-silica has a particle size of 40-80 nm; and the second curing temperature is 170℃-190℃.

5. The method for preparing the composite coating for water purification equipment according to claim 4, characterized in that, The method for preparing the composite coating satisfies one or more of the following conditions: (1) The first curing agent is an amine curing agent, such as polyetheramine or aliphatic amide amine epoxy curing agent; (2) The mass ratio of the first curing agent to the epoxy resin is (25-30):100, for example 27:100; (3) The first solvent is propylene glycol methyl ether acetate and / or xylene; (4) The viscosity of the bottom slurry is 110 cP-130 cP, for example 120 cP; (5) The second solvent is one or more of xylene, butyl acetate and propylene glycol methyl ether acetate; (6) The second curing agent is an isocyanate and / or an aliphatic isocyanate, wherein the aliphatic isocyanate is preferably a hexamethylene diisocyanate trimer; The NCO content in the second curing agent is preferably 15%-17%, for example 16.4%, where the percentage is the mass of the NCO groups relative to the mass of the second curing agent. (7) The mass ratio of the second curing agent to the fluorocarbon resin is (12-15):100, for example 13.5:100; (8) The surface slurry also includes a dispersant, which is a polymer block copolymer dispersant, such as the BYK series dispersants produced by BYK Chemical. Preferably, the amount of the dispersant is 15%-20% of the mass of nano-silica; (9) The viscosity of the surface slurry is 75 cP - 85 cP, for example 80 cP.

6. The method for preparing the composite coating for water purification equipment according to claim 4, characterized in that, The method for preparing the composite coating satisfies one or more of the following conditions: (1) The coating method is one or more of spraying, dipping and scraping; preferably, the coating method of the bottom layer slurry is dipping; preferably, the coating method of the top layer slurry is spraying. (2) The first curing temperature is 115℃-130℃, for example 120℃; (3) The heating rate of the first curing is 1℃ / min-5℃ / min, for example 3℃ / min; (4) The first curing time is 20 min-40 min, for example 30 min; (5) Pre-curing is performed before the first curing; The pre-curing temperature is preferably 60℃-90℃, for example 80℃; The pre-curing heating rate is preferably 1℃ / min-3℃ / min, for example 2℃ / min; The pre-curing time is preferably 5 min to 15 min, for example 10 min; (6) The second curing temperature is 175℃-190℃, for example 180℃; (7) The heating rate of the second curing process is 1℃ / min-5℃ / min, for example 3℃ / min; (8) The second curing time is 30 min-50 min, for example 45 min.

7. The method for preparing the composite coating for water purification equipment according to claim 4, characterized in that, The method for preparing the composite coating satisfies one or more of the following conditions: (1) The epoxy value of the epoxy resin is 0.48-0.52 eq / 100g, for example 0.51 eq / 100g; (2) The viscosity of the epoxy resin at 25°C is 8000-12000 mPa·s, for example 11500 mPa·s; (3) The silane coupling agent is an aminosilane coupling agent, such as γ-aminopropyltriethoxysilane; (4) The mass of the silane coupling agent is 3%-5% of the total mass of the silane coupling agent and the epoxy resin, for example, 4%; (5) The fluorocarbon resin is a FEVE type fluorocarbon resin; (6) The fluorine content of the fluorocarbon resin is ≥28%, for example 30%; (7) The hydroxyl value of the fluorocarbon resin is 50-60 mgKOH / g, for example 55 mgKOH / g; (8) The particle size of the nano-silica is 40-60 nm, for example 50 nm; (9) The specific surface area of ​​the nano-silica is 180-220 m². 2 / g, for example 220 m 2 / g; (10) The mass ratio of the fluorocarbon resin to the nano silica is 100:(10-15), for example 100:

12.

8. A composite coating for a water purification device, characterized in that, It is prepared by the method for preparing a composite coating for a water purification device according to any one of claims 4-7.

9. A solenoid valve, characterized in that, It includes a composite coating for water purification equipment as described in any one of claims 1-3 and 8; Preferably, the solenoid valve includes a throttling needle, which comprises a conical section and an equal-diameter section, the inlet of the equal-diameter section being connected to the outlet of the conical section; in the direction from the conical section to the equal-diameter section, the inner diameter of the conical section gradually decreases; the inlet diameter of the conical section is 20%-30% larger than the diameter of the equal-diameter section; the length of the conical section is 1.5-2 times the diameter of the equal-diameter section; and the inner walls of both the conical section and the equal-diameter section are provided with a composite coating for water purification equipment as described in any one of claims 1-3 and 8.

10. A water purifier, characterized in that, It includes the solenoid valve as described in claim 9.

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