A thermosetting powder coating material, its preparation method and application

Abstract

This invention relates to the field of powder coating technology, and more particularly to a thermosetting powder coating, its preparation method, and its application. The aforementioned thermosetting powder coating comprises, by weight, the following raw materials: 80-120 parts epoxy resin, 20-40 parts polyester resin, 1-5 parts triglycidyl isocyanate, 1-2 parts leveling agent, 1-2 parts gloss enhancer, 1-2 parts benzoin, 1-5 parts wax powder, 5-15 parts calcium carbonate, 1-3 parts organic pigment, 1-2 parts titanium dioxide, 1-2 parts texture agent, 1-2 parts orange peel agent, 1-2 parts amino-terminated polyamide amine, 1-3 parts aqueous silane coupling agent, 5-15 parts sodium sulfate aqueous solution, and 10-30 parts barium chloride aqueous solution. The coating obtained by this invention not only has good toughness and impact resistance, but also strong adhesion to the pipe body, ensuring a firm bond to the pipe material with first-class adhesion; furthermore, it exhibits excellent high-temperature resistance, enabling long-term use in high-temperature water environments, and excellent resistance to damp heat.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and in particular to a thermosetting plastic powder coating, its preparation method and application. Background Technology

[0002] Existing pipelines are mostly made of metal pipes, which have high pressure resistance and flexible connection methods. Heating pipelines are in a complex environment of high temperature and high humidity for a long time, which makes them prone to metal corrosion, reducing the strength, plasticity, toughness and other mechanical properties of the heating pipelines. Therefore, it is necessary to coat the surface of the metal pipes with a coating to prevent corrosion and improve wear resistance.

[0003] However, the adhesion between the coating and the substrate is relatively weak, and it cannot effectively bond with the metal pipe to form a whole. During use, it is prone to peeling off from the metal pipe, causing delamination. Currently, powder coatings are commonly used to spray the surface of metal pipes, but high temperature and high humidity environments place higher demands on the performance of the coating. The coating must be able to withstand high temperature and high humidity environments for a long time without peeling, falling off, or deforming. It must also have sufficient toughness and ductility to ensure that its adhesion to the metal is not affected during high and low temperature alternation. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a thermosetting plastic powder coating, its preparation method, and its application.

[0005] A thermosetting powder coating, the raw materials of which, by weight, include: 80-120 parts epoxy resin, 20-40 parts polyester resin, 1-5 parts triglycidyl isocyanate, 1-2 parts leveling agent, 1-2 parts gloss enhancer, 1-2 parts benzoin, 1-5 parts wax powder, 5-15 parts calcium carbonate, 1-3 parts organic pigment, 1-2 parts titanium dioxide, 1-2 parts texture agent, 1-2 parts orange peel agent, 1-2 parts amino-terminated polyamide amine, 1-3 parts water-based silane coupling agent, 5-15 parts sodium sulfate aqueous solution, and 10-30 parts barium chloride aqueous solution.

[0006] Epoxy resin, as a major component of coatings, can improve the hardness and adhesion of coatings. The epoxy groups in epoxy resin molecules can react with the active hydroxyl or amine groups in the coating to form strong chemical bonds, thereby improving the wear resistance, hardness, and adhesion of the coating film. The stable chemical structure of epoxy resin can protect pigments and other components in the coating from corrosion and oxidation; adding epoxy resin to coatings can improve their corrosion resistance, thus extending the service life of the coating. The relatively long molecular chains and high degree of cross-linking of epoxy resin can form a denser coating film structure, increasing the gloss and flowability of the coating.

[0007] The combination of epoxy resin and polyester resin can be used to make outdoor products. Polyester resin can be used as a coating on metal surfaces to improve the corrosion resistance and wear resistance of metals, as well as their impact resistance and tensile strength.

[0008] Triglycidyl isocyanate (TGIC) is used as a powder coating curing agent, and can also be used in the manufacture of electrical insulation materials, laminates, printed circuits, various tool adhesives, and plastic stabilizers.

[0009] Leveling agents: The main cause of pinholes on the coating surface is an imbalance of surface tension, while leveling agents can adjust the surface tension of the coating and reduce the formation of pinholes.

[0010] Gloss enhancers: A type of coating additive that reduces the surface roughness of the paint film and increases its gloss.

[0011] Benzoin is an effective powder defoamer that eliminates air bubbles in molten powder coatings, thus eliminating the main factor that forms pinhole defects in the coating film. It is used in almost all types of powder coatings.

[0012] Wax powder is a special polymer material with wax properties. It has a relatively small particle size and mainly plays a role in scratch resistance, wear resistance, non-sticking and hardening. It also has lubricating properties and plays a significant role in the uniform dispersion of fillers, resins and additives.

[0013] Barium sulfate is used as an extender pigment in coatings to improve coating thickness, abrasion resistance, water resistance, heat resistance, surface hardness, and impact resistance.

[0014] Calcium carbonate is a commonly used filler in coatings, possessing excellent filling properties. It can fill voids and capillaries in coatings, improving the gloss and smoothness of the film. Simultaneously, calcium carbonate can reduce coating shrinkage and address issues such as film cracking and warping. Calcium carbonate also exhibits excellent thickening properties; its particle size and surface hydrophobicity can be controlled through surface modification methods, thereby improving the viscosity, rheological properties, and other characteristics of coatings.

[0015] Organic pigments, available in a variety of colors, easy to process, light and heat resistant, and environmentally friendly.

[0016] Textured powder coatings utilize differences in surface tension or compatibility with the molten coating, or influence the coating's melt viscosity and curing speed, to achieve effects such as physical separation, matte finish, sandblasting, and increased hardness. By adjusting the dosage and combining it with materials such as organobentonite, fine and uniform textured powders, as well as mottled powders or fine orange-textured powders, can be produced.

[0017] Orange peel agent is an additive that enhances the surface finish of a coating and creates a beautiful texture.

[0018] Preferably, the concentration of sodium sulfate aqueous solution is 1-2 mol / L, and the concentration of barium chloride aqueous solution is 0.1-1 mol / L.

[0019] Preferably, the generation of the terminal amino polyamide amine is 2.0-4.0.

[0020] Preferably, the aqueous silane coupling agent is silane coupling agent KH460.

[0021] Preferably, the wax powder is at least one of polyethylene wax, polytetrafluoroethylene wax, and polyamide wax.

[0022] Preferably, the organic pigment is at least one of Permanent Orange RN, Permanent Orange HSL, Permanent Violet RL, Golden Red, Benzidine Yellow G, Pigment Yellow 2GLT, Phthalocyanine Blue, and Phthalocyanine Violet.

[0023] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0024] S1. Add terminal amino polyamide amine and ethanol to sodium sulfate aqueous solution and mix evenly to obtain solution A; mix aqueous silane coupling agent with barium chloride aqueous solution evenly to obtain solution B; in membrane dispersion microreactor, solution A and solution B are mixed after passing through a microporous membrane with a micropore equivalent diameter of 1-3 μm, stand at 40-60℃ for 1-2 h, sonicate for 10-30 min, centrifuge, wash, vacuum dry, and pulverize to obtain pre-prepared material;

[0025] S2. Mix epoxy resin and polyester resin evenly, extrude and granulate at 150-160℃, add pre-made material and mix evenly, freeze and keep warm for 15-20 minutes, grind at ultra-low temperature and sieve, add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, wax powder, calcium carbonate, organic pigment, titanium dioxide, sanding agent and orange peel agent to mix, grind and pass through a 2500 mesh sieve.

[0026] Preferably, in S1, the flow rates of liquid A and liquid B through the microporous membrane are 5-10 mL / min.

[0027] Preferably, in S1, the ultrasonic frequency is 5-12 kHz.

[0028] The above-mentioned thermosetting plastic powder coating is applied to the surface of the metal pipe by spraying it onto the surface and heating it to 160-180℃ for 1-2 hours. Beneficial effects

[0029] Amino-terminated polyamides have unique structures and properties, exhibiting good symmetry and highly branched structures. Hydrogen bonds between amide groups or carboxyl groups within their molecules interact, enabling amino-terminated polyamides to form stable micelles in water, thus exhibiting the characteristics of surfactants.

[0030] This invention combines amino-terminated polyamide-amine with sodium sulfate, and then rapidly mixes it with barium chloride. This allows the amino-terminated polyamide-amine to be uniformly bonded to the surface of barium sulfate, which can significantly improve the wear resistance and heat resistance of the coating, enhance the surface impact resistance, and can also be combined with epoxy resin and polyester resin. After curing, it can significantly enhance the adhesion strength between the coating and the metal pipe.

[0031] The coating obtained by this invention has a smooth surface and effectively isolates the corrosive medium from contact with the metal pipe, thus protecting the pipe well. Barium sulfate has good affinity with epoxy resin. After curing, it forms a three-dimensional network polymer structure with polyester resin, thereby significantly improving the wear resistance and adhesion of the coating, and exhibiting excellent corrosion resistance, especially excellent high-temperature wear resistance.

[0032] The coating obtained by this invention not only has good toughness and impact resistance, but also has strong adhesion to the pipe body, making it firmly bonded to the pipe with first-class adhesion; at the same time, the coating thickness is adjustable, ranging from tens of micrometers to several millimeters, and it has excellent high-temperature resistance, can be used for a long time in high-temperature water environments, and has excellent resistance to damp heat.

[0033] This invention contains no organic solvents, produces no VOC harmful gases during preparation and application, and has a simple production process, is easy to use, and is inexpensive. Attached Figure Description

[0034] Figure 1 This is a comparison diagram of the corrosion resistance potential of steel samples coated with the thermosetting plastic powder coatings obtained in Example 5 and Comparative Examples 1-2.

[0035] Figure 2 This is a comparison chart of the adhesion strength of coatings made using the thermosetting plastic powder coatings obtained in Example 5 and Comparative Examples 1-2.

[0036] Figure 3 The graph shows a comparison of the mortar abrasion rates of coatings made using the thermosetting plastic powder coatings obtained in Example 5 and Comparative Examples 1-2. Detailed Implementation

[0037] The present invention will be further explained below with reference to specific embodiments.

[0038] The epoxy resin described below is from Sinopec, brand name E-12; the polyester resin described below is from Shenjian Co., Ltd., brand name SJ42-T; the leveling agent described below is from Suzhou Qihang, model name Sl-88; the gloss enhancer described below is from Suzhou Qihang, model name Sl-701; the orange peel texture agent described below is from Suzhou Qihang, model name CAB; the sanding texture agent described below is from Shanghai Shuangshi, model name 207E; the titanium dioxide described below is from Yiyan, brand name R-5188; and all the organic pigments described below are from Baihehua. Example 1

[0039] A thermosetting powder coating comprises the following raw materials: 800g epoxy resin, 200g polyester resin, 10g triglycidyl isocyanate, 10g leveling agent, 10g gloss enhancer, 10g benzoin, 10g polytetrafluoroethylene wax, 50g calcium carbonate, 10g organic pigment, 10g titanium dioxide, 10g texture agent, 10g orange peel agent, 10g 2.0 generation amino-terminated polyamide amine, 10g silane coupling agent KH460, 50g sodium sulfate aqueous solution with a concentration of 1mol / L, and 100g barium chloride aqueous solution with a concentration of 0.1mol / L.

[0040] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0041] S1. Add amino-terminated polyamide amine and 50g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B;

[0042] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 5 mL / min and mixed with solution B, which was also passed through the microporous membrane at a flow rate of 5 mL / min. The equivalent diameter of the micropores in the microporous membrane was 1 μm. The mixture was allowed to stand at 40 °C for 1 h, then sonicated for 10 min at a sonic frequency of 5 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0043] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 150℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture in a cooling tank containing liquid nitrogen and keep it warm for 15 minutes. Grind it using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polytetrafluoroethylene wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve. Example 2

[0044] A thermosetting powder coating comprises the following raw materials: 1200g epoxy resin, 400g polyester resin, 50g triglycidyl isocyanate, 20g leveling agent, 20g gloss enhancer, 20g benzoin, 50g polyamide wax, 150g calcium carbonate, 30g organic pigment, 20g titanium dioxide, 20g texture agent, 20g orange peel agent, 20g 4.0 generation terminal amino polyamide amine, 30g silane coupling agent KH460, 150g sodium sulfate aqueous solution with a concentration of 2mol / L, and 300g barium chloride aqueous solution with a concentration of 1mol / L.

[0045] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0046] S1. Add amino-terminated polyamide amine and 150g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B;

[0047] In a membrane dispersion microreactor, solution A flows through a microporous membrane at a flow rate of 10 mL / min and is mixed with solution B, which also flows through the microporous membrane at a flow rate of 10 mL / min. The equivalent diameter of the micropores in the microporous membrane is 3 μm. The mixture is allowed to stand at 60 °C for 2 h, then sonicated for 30 min at a sonic frequency of 12 kHz. After centrifugation, the mixture is washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0048] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 160℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture in a cooling tank containing liquid nitrogen and keep it warm for 20 minutes. Grind it using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyamide wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve. Example 3

[0049] A thermosetting powder coating comprises the following raw materials: 900g epoxy resin, 350g polyester resin, 20g triglycidyl isocyanate, 17g leveling agent, 12g gloss enhancer, 17g benzoin, 20g polyethylene wax, 120g calcium carbonate, 15g organic pigment, 17g titanium dioxide, 12g texture agent, 17g orange peel texture agent, 18g 3.5-generation amino-terminated polyamide amine, 15g silane coupling agent KH460, 80g sodium sulfate aqueous solution with a concentration of 1.8mol / L, and 150g barium chloride aqueous solution with a concentration of 0.7mol / L.

[0050] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0051] S1. Add amino-terminated polyamide amine and 120g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B;

[0052] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 7 mL / min and mixed with solution B, which was passed through the microporous membrane at a flow rate of 9 mL / min. The equivalent diameter of the micropores in the microporous membrane was 1.5 μm. The mixture was allowed to stand at 55 °C for 80 min, then sonicated for 25 min at a sonic frequency of 6 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0053] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 158℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture into a cooling tank containing liquid nitrogen and keep it at a temperature of 16 minutes. Grind the mixture using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyethylene wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve. Example 4

[0054] A thermosetting powder coating comprises the following raw materials: 1100g epoxy resin, 250g polyester resin, 40g triglycidyl isocyanate, 13g leveling agent, 18g gloss enhancer, 13g benzoin, 40g polyethylene wax, 80g calcium carbonate, 25g organic pigment, 13g titanium dioxide, 18g texture agent, 13g orange peel agent, 12g 2.5-generation amino-terminated polyamide amine, 25g silane coupling agent KH460, 120g sodium sulfate aqueous solution with a concentration of 1.2mol / L, and 250g barium chloride aqueous solution with a concentration of 0.3mol / L.

[0055] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0056] S1. Add amino-terminated polyamide amine and 80g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B.

[0057] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 9 mL / min and mixed with solution B, which was passed through the microporous membrane at a flow rate of 7 mL / min. The equivalent diameter of the micropores in the microporous membrane was 2.5 μm. The mixture was allowed to stand at 45 °C for 100 min, then sonicated for 15 min at a sonic frequency of 10 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0058] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 152℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture into a cooling tank containing liquid nitrogen and keep it at a temperature of 19 minutes. Grind the mixture using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyethylene wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve. Example 5

[0059] A thermosetting powder coating comprises the following raw materials: 1000g epoxy resin, 300g polyester resin, 30g triglycidyl isocyanate, 15g leveling agent, 15g gloss enhancer, 15g benzoin, 30g polyethylene wax, 100g calcium carbonate, 20g organic pigment, 15g titanium dioxide, 15g texture agent, 15g orange peel agent, 15g 3.0 generation amino-terminated polyamide amine, 20g silane coupling agent KH460, 100g sodium sulfate aqueous solution with a concentration of 1.5mol / L, and 200g barium chloride aqueous solution with a concentration of 0.5mol / L.

[0060] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0061] S1. Add amino-terminated polyamide amine and 100g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B.

[0062] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 8 mL / min and mixed with solution B, which was also passed through the microporous membrane at a flow rate of 8 mL / min. The equivalent diameter of the micropores in the microporous membrane was 2.0 μm. The mixture was allowed to stand at 50 °C for 90 min, then sonicated for 20 min at a sonic frequency of 9 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0063] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 155℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture into a cooling tank containing liquid nitrogen and keep it at a temperature for 18 minutes. Grind the mixture using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyethylene wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve.

[0064] Comparative Example 1

[0065] A thermosetting powder coating comprises the following raw materials: 1000g epoxy resin, 300g polyester resin, 30g triglycidyl isocyanate, 15g leveling agent, 15g gloss enhancer, 15g benzoin, 30g polyethylene wax, 100g calcium carbonate, 20g organic pigment, 15g titanium dioxide, 15g texture agent, 15g orange peel agent, 15g sodium stearate, 20g silane coupling agent KH460, 100g sodium sulfate aqueous solution with a concentration of 1.5mol / L, and 200g barium chloride aqueous solution with a concentration of 0.5mol / L.

[0066] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0067] S1. Add sodium stearate and 100g of ethanol to an aqueous sodium sulfate solution and mix well to obtain solution A; mix silane coupling agent KH460 with an aqueous barium chloride solution to obtain solution B;

[0068] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 8 mL / min and mixed with solution B, which was also passed through the microporous membrane at a flow rate of 8 mL / min. The equivalent diameter of the micropores in the microporous membrane was 2.0 μm. The mixture was allowed to stand at 50 °C for 90 min, then sonicated for 20 min at a sonic frequency of 9 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0069] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 155℃ twin-screw extruder. Add the pre-made material and mix evenly. Place the mixture into a cooling tank containing liquid nitrogen and keep it at a temperature for 18 minutes. Grind the mixture using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyethylene wax, calcium carbonate, organic pigment, titanium dioxide, sanding agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve.

[0070] Comparative Example 2

[0071] A thermosetting powder coating comprises the following raw materials: 1000g epoxy resin, 300g polyester resin, 30g triglycidyl isocyanate, 15g leveling agent, 15g gloss enhancer, 15g benzoin, 30g polyethylene wax, 100g calcium carbonate, 20g organic pigment, 15g titanium dioxide, 15g texture agent, 15g orange peel agent, 15g 3.0 generation amino-terminated polyamide amine, 20g silane coupling agent KH460, 100g sodium sulfate aqueous solution with a concentration of 1.5mol / L, and 200g barium chloride aqueous solution with a concentration of 0.5mol / L.

[0072] The preparation method of the above-mentioned thermosetting powder coating includes the following steps:

[0073] S1. Add 100g of ethanol to sodium sulfate aqueous solution and mix well to obtain solution A; mix silane coupling agent KH460 with barium chloride aqueous solution to obtain solution B.

[0074] In a membrane dispersion microreactor, solution A was passed through a microporous membrane at a flow rate of 8 mL / min and mixed with solution B, which was also passed through the microporous membrane at a flow rate of 8 mL / min. The equivalent diameter of the micropores in the microporous membrane was 2.0 μm. The mixture was allowed to stand at 50 °C for 90 min, then sonicated for 20 min at a sonic frequency of 9 kHz. After centrifugation, the mixture was washed with deionized water, vacuum dried, and pulverized to obtain the pre-prepared material.

[0075] S2. Mix epoxy resin and polyester resin evenly, then granulate them after passing them through a 155℃ twin-screw extruder. Add pre-made materials and terminal amino polyamide amine and mix evenly. Place the mixture in a cooling tank containing liquid nitrogen and keep it at a temperature of 18 minutes. Grind the mixture using an ultra-low temperature grinding process and pass it through a 60-mesh sieve. Add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, polyethylene wax, calcium carbonate, organic pigment, titanium dioxide, texture agent, and orange peel agent to the mixture and grind it through a 2500-mesh sieve.

[0076] Q235 carbon steel plate (80mm×40mm×3mm) was used. Then, the surface rust and oil were removed, the plate was sanded, and the plate was cleaned to obtain the sample steel. The thermosetting plastic powder coatings obtained in Example 5 and Comparative Examples 1-2 were sprayed onto the surface of the sample steel and cured at 170℃ for 90 minutes.

[0077] The Tafel polarization curves of the treated steel samples were tested using an electrochemical workstation. The corrosive medium was a 3% sodium chloride aqueous solution. A platinum electrode was used as the auxiliary electrode, a saturated calomel electrode was used as the reference electrode, and the treated steel samples were used as the working electrode.

[0078] The test parameters are as follows: initial potential is -1.20V, termination potential is -0.00V, scan speed is 0.005 V / s, waiting time is 0s, current polarization mode is reduction, and frequency is 50Hz.

[0079] The results are as follows Figure 1 As shown, the steel sample coated with the thermosetting powder coating obtained in Example 5 has the highest corrosion resistance potential, which is better than that of Comparative Examples 1-2 (P<0.05).

[0080] A PTC water boiling test chamber was used to simulate the high-temperature environment of the heating pipeline, and a water boiling test was conducted on the above-mentioned sprayed and cured steel samples (test period was 7 days). The above-mentioned sprayed and cured steel samples were immersed in 5% hydrochloric acid and 5% sodium hydroxide solutions for 48 hours, respectively. The results are shown in Table 1.

[0081] Example 5 Comparative Example 1 Comparative Example 2 Boiling experiment The coating surface is smooth and intact, without bubbles or peeling. The coating surface is incomplete and rough, with bubbles and peeling. The coating surface is intact but not smooth, with bubbles that have not yet been peeled off. 5% hydrochloric acid The coating surface is smooth and intact, without bubbles or peeling. The coating surface is intact but not smooth, with bubbles that have not yet been peeled off. The coating surface is smooth and intact, without bubbles or peeling. 5% sodium hydroxide solution The coating surface is smooth and intact, without bubbles or peeling. The coating surface is intact but not smooth, with bubbles that have not yet been peeled off. The coating surface is smooth and intact, without bubbles or peeling.

[0082] As can be seen from Table 1, the coating made by using the thermosetting plastic powder coating obtained in Example 5 has the strongest adhesion, the best heat resistance and damp heat resistance, and better acid and alkali corrosion resistance.

[0083] The adhesion of the thermosetting powder coatings obtained in Example 5 and Comparative Examples 1-2 after spraying and curing was tested in accordance with GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test".

[0084] The thermosetting plastic powder coatings obtained in Example 5 and Comparative Examples 1-2 were sprayed onto the surface of the steel pipe. After curing, the mortar abrasion test was carried out in accordance with the test method of mortar abrasion rate in CJ / T237-2019 "Construction Sand". The mortar abrasion rate was tested at 23±3℃ and 60±3℃ respectively.

[0085] like Figure 2 and Figure 3 As shown, the coating made with the thermosetting plastic powder coating obtained in Example 5 has the highest adhesion and the lowest mortar abrasion rate, which is better than Comparative Examples 1-2 (P<0.05).

[0086] The applicant believes that this is because the present invention combines terminal amino polyamide-amine with sodium sulfate and then rapidly mixes it with barium chloride, which can uniformly bind terminal amino polyamide-amine on the surface of barium sulfate. This can significantly improve the wear resistance and heat resistance of the coating, enhance the surface impact resistance, and can also be combined with epoxy resin and polyester resin. After curing, it can significantly enhance the bonding strength between the coating and the metal pipe.

[0087] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A thermosetting powder coating characterized in that, The raw materials, by weight, include: 80-120 parts epoxy resin, 20-40 parts polyester resin, 1-5 parts triglycidyl isocyanate, 1-2 parts leveling agent, 1-2 parts gloss enhancer, 1-2 parts benzoin, 1-5 parts wax powder, 5-15 parts calcium carbonate, 1-3 parts organic pigment, 1-2 parts titanium dioxide, 1-2 parts sanding agent, 1-2 parts orange peel agent, 1-2 parts amino-terminated polyamide amine, 1-3 parts water-based silane coupling agent, 5-15 parts sodium sulfate aqueous solution, and 10-30 parts barium chloride aqueous solution. The pre-prepared material is prepared by the following steps using terminal amino-terminated polyamide amine, aqueous silane coupling agent, sodium sulfate aqueous solution, and barium chloride aqueous solution: terminal amino-terminated polyamide amine and ethanol are added to sodium sulfate aqueous solution and mixed evenly to obtain solution A; aqueous silane coupling agent and barium chloride aqueous solution are mixed evenly to obtain solution B; in a membrane dispersion microreactor, solution A and solution B are mixed after passing through a microporous membrane with a micropore equivalent diameter of 1-3 μm, and the mixture is allowed to stand at 40-60℃ for 1-2 h, ultrasonically treated for 10-30 min, centrifuged, washed, vacuum dried, and pulverized to obtain the pre-prepared material.

2. The thermosetting powder coating according to claim 1, characterized in that, The concentration of sodium sulfate aqueous solution is 1-2 mol / L, and the concentration of barium chloride aqueous solution is 0.1-1 mol / L.

3. The thermosetting powder coating according to claim 1, characterized in that, The generation of terminal amino-terminated polyamide amines is 2.0-4.

0.

4. The thermosetting powder coating according to claim 1, characterized in that, The aqueous silane coupling agent is silane coupling agent KH460.

5. The thermosetting powder coating according to claim 1, characterized in that, The wax powder is at least one of polyethylene wax, polytetrafluoroethylene wax, and polyamide wax.

6. The thermosetting powder coating according to claim 1, characterized in that, The organic pigment is at least one of Permanent Orange RN, Permanent Orange HSL, Permanent Violet RL, Golden Red, Benzidine Yellow G, Pigment Yellow 2GLT, Phthalocyanine Blue, and Phthalocyanine Violet.

7. A method for preparing a thermosetting powder coating as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Add terminal amino polyamide amine and ethanol to sodium sulfate aqueous solution and mix evenly to obtain solution A; mix aqueous silane coupling agent with barium chloride aqueous solution evenly to obtain solution B; in membrane dispersion microreactor, solution A and solution B are mixed after passing through a microporous membrane with a micropore equivalent diameter of 1-3 μm, stand at 40-60℃ for 1-2 h, sonicate for 10-30 min, centrifuge, wash, vacuum dry, and pulverize to obtain pre-prepared material; S2. Mix epoxy resin and polyester resin evenly, extrude and granulate at 150-160℃, add pre-made material and mix evenly, freeze and keep warm for 15-20 minutes, grind at ultra-low temperature and sieve, add triglycidyl isocyanate, leveling agent, brightening agent, benzoin, wax powder, calcium carbonate, organic pigment, titanium dioxide, sanding agent and orange peel agent to mix, grind and pass through a 2500 mesh sieve.

8. The method for preparing the thermosetting powder coating according to claim 7, characterized in that, In S1, the flow rates of solutions A and B through the microporous membrane are 5-10 mL / min.

9. The method for preparing the thermosetting powder coating according to claim 7, characterized in that, In S1, the ultrasonic frequency is 5-12kHz.

10. A method of using a thermosetting powder coating as described in any one of claims 1-6, characterized in that, The thermosetting plastic powder coating as described in any one of claims 1-6 is sprayed onto the surface of the metal pipe and cured at 160-180°C for 1-2 hours.

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