A nano-metal powder bonding powder coating and its preparation method and application

Abstract

The invention discloses a nano-metal powder bonding powder coating and a preparation method and application thereof, belonging to the technical field of powder coatings. The raw material components include 50-75 parts of thermosetting resin, 5-20 parts of curing agent, 20-40 parts of inorganic filler, 2-10 parts of pigment, 1-10 parts of modified nano-metal powder pigment, and 0.5-2 parts of auxiliary agent. The preparation steps of the coating include stirring the thermosetting resin, curing agent, inorganic filler, pigment, and auxiliary agent to obtain a mixture; adding the mixture to an extruder, melt-extrude to obtain a flaky mixture; tableting the flaky mixture, cooling and crushing, grinding and screening to obtain a masterbatch; stirring and dispersing the modified nano-metal powder pigment and the masterbatch, and then sieving to obtain a nano-metal powder bonding powder coating. The nano-metal powder bonding powder coating provided by the invention overcomes the complexity and technical difficulties of the chemical modification of traditional metal pigments, solves the high requirements of the existing bonding metal powder production process for equipment, and can be applied in the field of regional architectural metal structure decoration.

Description

Technical Field

[0001] The invention belongs to the technical field of powder coatings, and in particular relates to a nano metal powder bonding powder coating and a preparation method and application thereof. Background Art

[0002] Among the many types of powder coatings, metal bonding powder coatings with excellent metallic feel, color retention, weather resistance, corrosion resistance and other properties have become a new product of decorative powder coatings in the building materials field. Through dry mixing or hot melt bonding during heat treatment, metal powders such as copper and gold powders, aluminum powders, and pearl powders are bound to the resin particles of the powder coating to form a uniformly dispersed powder coating. The sprayed coating has a bright metallic or pearlescent texture.

[0003] There are three main methods for preparing bonded metal powder: melt extrusion, dry mixing and thermal bonding. In the melt extrusion method, metal powder is added before extrusion and tableting, and then powder coating is obtained through extrusion, tableting, crushing and grinding. The metal powder will lose its gloss under the action of high temperature and shear force in the extruder, affecting the decorative effect of the final coating. In the dry mixing method, metal powder and powder coating particles are blended by traditional mechanical stirring. Due to the difference in conductivity between metal powder and powder particles, the powder coating prepared by this method will have uneven powder application during electrostatic spraying, resulting in local color difference, and the temperature rise caused by high-speed stirring will also cause oxidation of metal powder. The third method is the currently commonly used thermal bonding method. Through a dedicated thermal bonding equipment, metal powder and powder particles are stirred and mixed under nitrogen protection. The outer wall of the container has a heating layer injected with hot oil or hot water. When the container temperature is greater than the glass transition temperature (Tg) of the coating, the powder particles change from a glassy state to a viscoelastic state. The metal powder is bonded to the powder particles by thermal bonding to prepare a bonded metal powder coating with better gloss.

[0004] However, the bonding metal powder production process has high requirements for equipment. Since thermal bonding is the final step before crushing and screening in the bonding metal powder production process, the size of the bonding equipment also affects the production capacity of metal powder coatings. In order to develop new metal powder coatings, some researchers use more complex metal powder modification technology to improve the thermal stability of metal powders by chemical modification of the metal powder surface, and then prepare powder coatings by traditional melt extrusion methods. There are also other methods that use other physical coating modification methods to modify the metal powder surface, thereby eliminating the traditional bonding process and producing powder coating products through mechanical blending. However, these methods have environmental hazards, high energy consumption and poor coating metal effect. Nanomaterials can improve the corrosion resistance of coatings. Introducing nano metal powders into coatings can improve the metallic luster fullness of coatings. Then, the metal powder surface is organically coated and modified by low Tg polymers, so that nano metal powders can be bonded to resin particles through simple mechanical stirring. At present, there is a lack of technology to specifically improve the corrosion resistance of decorative coatings on the surface of metal structures in coastal high-salt, high-humidity and highly corrosive environments. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to propose a nano-metal powder bonding powder coating and its preparation method and application, which overcomes the complexity and technical difficulties of traditional metal pigment chemical modification, solves the high requirements of the existing bonding metal powder production process on equipment, and introduces nanotechnology into powder coating.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention is to provide a nano metal powder bonding powder coating, comprising the following raw materials in parts by weight: 50-75 parts of thermosetting resin, 5-20 parts of curing agent, 20-40 parts of inorganic filler, 2-10 parts of pigment, 1-10 parts of modified nano metal powder pigment, and 0.5-2 parts of additive.

[0008] In some embodiments, the modified nano-metal powder pigment is compounded by resin, nano-metal powder, and a cross-linking agent, and includes the following preparation steps:

[0009] (1) Add nano metal powder to the solution, disperse it by ultrasonic and then add resin and stir;

[0010] (2) adding tannic acid to deionized water to prepare an aqueous solution, then adding the aqueous solution to the mixed system of step (1), adding trihydroxyaminomethane solution after mixing, and continuing to stir;

[0011] (3) Filtering the mixed system in step (2) to obtain a filtered product after washing, and freeze-drying the filtered product to obtain a modified nano-metal powder pigment.

[0012] In some embodiments, the resin is a mixture of polyvinyl alcohol and polyethylene glycol in a weight ratio of 6-8:6-8; the mass ratio of the resin, nano-metal powder, tannic acid and trihydroxyaminomethane solution is 12-16:8-12:0.05-0.15:0.05-0.15.

[0013] In some embodiments, the nano metal powder is selected from at least one of aluminum silver powder, pearl powder, copper gold powder, and alumina; the solution is selected from at least one of deionized water, pure water, and distilled water; the stirring reaction time in step (2) is 6-12 hours; and the freeze-drying temperature in step (3) is -60 to -30°C.

[0014] In some embodiments, the thermosetting resin is selected from at least one of epoxy resin and fluorocarbon resin, the epoxy value of the epoxy resin is 0.1-0.18, and the hydroxyl value of the fluorocarbon resin is 44-48 mg (KOH) / g.

[0015] In some embodiments, the curing agent is selected from at least one of dicyandiamide curing agent and hydroxyalkylamide curing agent; the inorganic filler is selected from at least one of barium sulfate, silica powder, wollastonite, talc powder, and aluminum hydroxide, and the particle size is 1000-3000 mesh; the pigment is selected from at least one of high-color carbon black, iron red, phthalocyanine blue, organic yellow, and quinacridone violet.

[0016] In some embodiments, the auxiliary agent is a mixture of a curing accelerator, a leveling agent, benzoin, a defoamer, a wetting promoter, and a hyperdispersant, wherein the curing accelerator is imidazole and its modified substance, the leveling agent is an acrylic copolymer or an acrylate copolymer, the defoamer is a fine wax powder product, the wetting promoter is a high molecular weight copolymer containing a basic group, and the hyperdispersant is a coupling modifier with a highly active anchoring group.

[0017] It should be noted that the curing accelerator can be 2-methylimidazole, the leveling agent can be H98, WL588 (acrylic copolymer), Resiflow PV88 (inorganic silicone adsorbed acrylic acid), the defoamer can be CERAFLOUR-961, Hubei Laisi's defoamer 4430, the wetting promoter can be BYK-3492P, and the hyperdispersant can be modified fatty acid amide AS200, LD2180.

[0018] The second aspect of the present invention is to provide a method for preparing a nano metal powder bonding powder coating, comprising the following steps:

[0019] S1: stirring a thermosetting resin, a curing agent, an inorganic filler, a pigment, and an additive to obtain a mixture;

[0020] S2: adding the mixture into an extruder, and melt-extruding to obtain a sheet-like mixture;

[0021] S3: tabletting the flaky mixture, cooling and crushing it, grinding and screening it to obtain a masterbatch;

[0022] S4: The modified nano-metal powder pigment and the masterbatch prepared in S3 are stirred and dispersed, and then sieved to obtain a nano-metal powder bonding powder coating.

[0023] In some embodiments, the stirring time in S1 is 15-30 min; the extruder in S2 is set to a temperature of 85-110° C. in zone I and a temperature of 95-110° C. in zone II; the cooling temperature in S3 is 25-30° C., and the screening mesh is 60-250 mesh; the stirring speed in S4 is 1500-3000 r / min, the stirring time is 30-60 min, and the screening mesh is 60-250 mesh.

[0024] The third aspect of the present invention is to provide an application of nano metal powder bonding powder coating in the field of construction.

[0025] The present invention has the following beneficial effects:

[0026] 1. In the present invention, tannic acid, trihydroxyaminomethane and resin are used to prepare modified nano metal powder pigments. The polymer is grafted and coated on the surface of the metal powder by the self-polymerization reaction of tannic acid and trihydroxyaminomethane in an aqueous solution, and the super strong adhesion effect of the catechol functional group in the tannic acid molecule and the hydrogen bonding effect of the phenolic hydroxyl group are utilized. The coated polymer is prepared by mixing a high Tg polymer and a low Tg polymer layer on the surface of the metal powder with a temperature slightly higher than room temperature.

[0027] 2. The traditional bonding method is to heat up the powder particles to adhere to the metal powder. The present invention has made an improvement on this. The heat generated by high-speed stirring is used to soften the polymer on the surface of the modified nano-metal powder pigment particles to adhere to the powder coating particles. The appearance effect of the metal powder coating obtained by the ordinary bonding method can be achieved, and no special equipment is required to further reduce the production cost of the metal powder coating.

[0028] 3. The modified nano-metal powder pigment provided by the present invention can effectively avoid oxidation during long-term use, and its weather resistance is improved. Compared with the traditional dry mixing method, the improved reverse bonding method performs better in color uniformity and metallic gloss effect.

[0029] 4. The coating formula provided by the present invention selects fluorocarbon resin with excellent weather resistance and epoxy resin with excellent anti-corrosion performance, so that the powder coating has excellent weather resistance and anti-corrosion and other long-term use properties while having a good decorative appearance, and the service life of the coating and the substrate are greatly improved.

[0030] 5. The present invention develops a new type of room-temperature nano-metal powder bonding powder coating by modifying nano-metal powder pigments, which can further enhance the metal effect of the coating on the basis of energy conservation and emission reduction. The nano-metal powder bonding powder coating has excellent weather resistance and excellent corrosion resistance, super weather resistance and corrosion resistance, and can be widely used in the decoration of metal structures of buildings in coastal areas. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below. The embodiments described are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0032] Example 1

[0033] Preparation of modified nano metal powder

[0034] (1) Add 10 g of aluminum silver powder to a three-necked flask containing 100 g of deionized water at room temperature, and ultrasonically disperse for 25 min until the powder is uniformly dispersed and suspended. Then, add resin (8 g of PVA-1799 powder and 6 g of PEG-2000 powder) and stir.

[0035] (2) Add 0.1 g of tannic acid to 5 ml of deionized water to prepare an aqueous solution, then add the aqueous solution to the three-necked flask in step (1), mix and stir for 10 min, then add 0.1 ml of 1 M trishydroxyaminomethane solution dropwise to the three-necked flask, and continue stirring for 8 h;

[0036] (3) The mixed system of step (2) is filtered and washed with deionized water for several times to obtain a filtered product, which is freeze-dried at -40°C to obtain a modified nano-metal powder pigment.

[0037] A nano metal powder bonding powder coating comprises the following raw materials in parts by mass: 25 parts of HY903 epoxy resin (epoxy value is 0.14), 35 parts of LF710F fluorocarbon resin (hydroxyl value is 46 mg (KOH) / g), 12 parts of dicyandiamide curing agent, 10 parts of barium sulfate, 10 parts of talcum powder, 2 parts of phthalocyanine blue, 5 parts of the above-mentioned modified nano metal powder pigment, 0.3 parts of curing accelerator dimethylimidazole, 0.2 parts of benzoin, 0.2 parts of leveling agent Resiflow PV88, 0.2 parts of defoamer 4430, 0.6 parts of BYK-3492P wetting promoter, and 0.5 parts of AS200 super dispersant.

[0038] Preparation of modified nano-metal powder coatings

[0039] S1: Add thermosetting resin, curing agent, inorganic filler, pigment and additive into a high-speed disperser and stir for 20 minutes to obtain a mixture;

[0040] S2: adding the mixture into a twin-screw extruder, and melt-extruded to obtain a sheet-like mixture. The temperature of zone I of the extruder is set to 95°C, and the temperature of zone II is set to 105°C;

[0041] S3: tableting the flaky mixture, cooling and crushing it at 25°C, grinding it into powder and sieving it through a 160-mesh sieve to obtain a masterbatch;

[0042] S4: Add the modified nano metal powder pigment and the masterbatch prepared in S3 into a high-speed stirring pot, stir and disperse at a speed of 2500 r / min (high speed) for 45 minutes, and then sieve through 160 mesh to obtain a nano metal powder bonding powder coating.

[0043] Example 2

[0044] The preparation steps and other raw material components are consistent with those in Example 1, except that:

[0045] The raw material components include 15 parts of epoxy resin and 45 parts of fluorocarbon resin.

[0046] Example 3

[0047] The preparation steps and other raw material components are consistent with those in Example 1, except that:

[0048] The raw material components include 35 parts of epoxy resin and 25 parts of fluorocarbon resin.

[0049] Comparative Example 1

[0050] The preparation steps and other raw material components are consistent with those in Example 1, except that:

[0051] In step (1) of preparing modified nano-metal powder, the resin is 14 g of PVA-1799 powder.

[0052] Comparative Example 2

[0053] The preparation steps and other raw material components are consistent with those in Example 1, except that:

[0054] In step (1) of preparing the modified nano-metal powder, the resin is 14 g of PEG-2000 powder.

[0055] Comparative Example 3

[0056] A super weather-resistant anticorrosive powder coating without modified nano-metal powder, the preparation steps and other raw material components are consistent with those in Example 1, the only difference is:

[0057] The raw material components do not contain modified nano metal powder.

[0058] Comparative Example 4

[0059] A common bonding metal powder coating, the preparation steps and other raw material components are the same as those in Example 1, the only difference is:

[0060] The modified nano metal powder pigment in the raw material components is changed to metal powder.

[0061] Comparative Example 5

[0062] A dry-mixed metal powder coating, the preparation steps and other raw material components are the same as those in Example 1, the only difference is:

[0063] The modified nano metal powder pigment in the raw material components is changed to metal powder;

[0064] Step S4 in preparing the modified nano-metal powder coating is to add the metal powder and the masterbatch prepared in S3 into a high-speed stirring pot, stir and disperse at a speed of 2500r / min (high speed) for 45 minutes, and then sieve through 160 mesh to obtain a dry mixed metal powder coating.

[0065] Comparative test

[0066] The powder coatings prepared in Examples 1-3 and Comparative Examples 1-5 were electrostatically sprayed on treated aluminum plates (substrate thickness 1-1.5 mm), cured at 210° C. for 20 min, and the coating thickness was 300±50 μm. The coatings were then tested for appearance (visual inspection), dry adhesion (ISO2409), moisture and heat resistance (GB / T 1740), neutral salt spray resistance (GB / T 1771), weather resistance (GB / T 1865 method A) and other properties. The test results of the coating properties are shown in Tables 1 and 2.

[0067] Table 1 Performance test results of Examples 1-3 and Comparative Example 1

[0068]

[0069] Table 2 Comparative Examples 2-5 Performance Test Results

[0070]

[0071]

[0072] It can be seen from Table 1 and Table 2 that, compared with Comparative Example 1, the metallic gloss effect of the embodiments is better, indicating that the metal powder modified by the high Tg polymer has poor adhesion with the powder particles during the mechanical blending process, and the powder coating has a poor powder coating rate during the spraying process due to the difference in electrical conductivity and other reasons; compared with Comparative Example 2, the basic mechanical properties and weathering and corrosion resistance of the embodiments are better, indicating that the low Tg polymer modified nano-metal powder is easy to agglomerate and bond, resulting in easy agglomeration in the powder coating, and the coating has poor density and decorative properties. Comprehensive comparison, the better performance of the embodiments can indicate that the modified nano-metal powder in the embodiments can effectively bond to the base powder, thereby providing the coating with a good metallic decorative effect; Compared with Comparative Example 3, the metallic gloss effect of the embodiment is better, indicating that the modified nano-metal powder provided by the present invention can well improve the metal decorative effect; compared with Comparative Example 4, while achieving the same metal effect, the nano-metal powder bonding powder coating of Example 1 shows better weather resistance than the ordinary metal powder coating, indicating that the chemical modification improves the stability of the decorative effect of the metal powder during long-term service, and the coating achieves better long-term service performance using a simpler process; compared with Comparative Example 5, Example 1 shows better metallic gloss and weather resistance, indicating that the modified nano-metal powder can be well bonded to the base powder through mechanical blending, and the coating has a better metal effect.

[0073] In summary, the modified nano-metal powder coating prepared by the present invention has achieved good decorative performance, excellent weather resistance and anti-corrosion performance on the basis of improving the traditional metal powder coating production process, and is expected to be used in the decoration and corrosion protection of architectural metal structures in coastal areas with relatively harsh corrosive environments and aging environments.

[0074] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A nano metal powder bonding powder coating, characterized in that: The invention comprises the following raw materials in parts by weight: 50-75 parts of thermosetting resin, 5-20 parts of curing agent, 20-40 parts of inorganic filler, 2-10 parts of pigment, 1-10 parts of modified nano-metal powder pigment, and 0.5-2 parts of auxiliary agent; The pigment is selected from at least one of high-color carbon black, iron red, phthalocyanine blue, organic yellow, and quinacridone violet; the thermosetting resin is epoxy resin and fluorocarbon resin; the curing agent is dicyandiamide curing agent; The modified nano metal powder pigment is compounded by resin, nano metal powder, tannic acid and tris(hydroxymethyl)aminomethane solution, and comprises the following preparation steps: (1) Add nano-metal powder to the solution, disperse it ultrasonically, then add resin and stir; (2) adding tannic acid to deionized water to prepare an aqueous solution, then adding the aqueous solution to the mixed system of step (1), adding tris(hydroxymethyl)aminomethane solution after mixing, and continuing to stir; (3) filtering the mixed system in step (2), washing to obtain a filtered product, and freeze-drying the filtered product to obtain a modified nano-metal powder pigment; The resin in the modified nano-metal powder pigment is a mixture of polyvinyl alcohol and polyethylene glycol in a weight ratio of 6-8:6-8; the mass ratio of the resin, nano-metal powder, tannic acid and tris(hydroxymethyl)aminomethane solution in the modified nano-metal powder pigment is 12-16:8-12:0.05-0.15:0.05-0.

15.

2. The nano metal powder bonding powder coating according to claim 1, characterized in that: The nano metal powder is selected from at least one of aluminum silver powder, pearl powder, copper gold powder, and aluminum oxide; the solution is selected from at least one of deionized water, pure water, and distilled water; in the step (2), the stirring reaction time is 6-12 hours; in the step (3), the freeze-drying temperature is -60 to -30°C.

3. The nano metal powder bonding powder coating according to claim 1, characterized in that: The epoxy value of the epoxy resin is 0.1-0.18, and the hydroxyl value of the fluorocarbon resin is 44-48 mg(KOH) / g.

4. The nano metal powder bonding powder coating according to claim 1, characterized in that: The inorganic filler is selected from at least one of barium sulfate, silicon powder, wollastonite, talc powder and aluminum hydroxide, and has a particle size of 1000-3000 meshes.

5. The nano metal powder bonding powder coating according to claim 1, characterized in that: The auxiliary agent is a mixture of a curing accelerator, a leveling agent, benzoin, a defoamer, a wetting promoter, and a super dispersant, wherein the curing accelerator is imidazole and its modified substance, the leveling agent is an acrylic copolymer or an acrylate copolymer, the defoamer is a fine wax powder product, the wetting promoter is a high molecular weight copolymer containing a basic group, and the super dispersant is a coupling modifier with a highly active anchoring group.

6. A method for preparing the nano metal powder bonding powder coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: stirring the thermosetting resin, curing agent, inorganic filler, pigment and additive to obtain a mixture; S2: adding the mixture into an extruder, and melt-extruding to obtain a sheet-like mixture; S3: tabletting the flaky mixture, cooling and crushing it, grinding and screening it to obtain a masterbatch; S4: The modified nano-metal powder pigment and the masterbatch prepared in S3 are stirred and dispersed, and then sieved to obtain a nano-metal powder bonding powder coating.

7. The preparation method according to claim 6, characterized in that: In the S1, the stirring time is 15-30min; in the S2, the extruder is set to a temperature of 85-110°C in zone I and a temperature of 95-110°C in zone II; in the S3, the cooling temperature is 25-30°C, and the screening mesh is 60-250 mesh; in the S4, the stirring speed is 1500-3000 r / min, the stirring time is 30-60min, and the screening mesh is 60-250 mesh.

8. Use of the nano metal powder bonding powder coating according to any one of claims 1 to 5 in the field of construction.

Images