Nylon powder coating for metal surface coating and preparation method

Abstract

The invention discloses a nylon powder coating for metal surface coating and a preparation method thereof, and belongs to the technical field of polymer modification. The nylon powder coating is prepared from the following raw materials in parts by weight: 100 parts of nylon powder, 0-2 parts of toner, 0-1 part of antioxidant and 0.2-1 part of modified dispersant, the modified dispersing agent is a dispersing agent adsorbed with temperature-resistant lubricating oil. According to the nylon powder coating prepared by the invention, the dispersing agent adsorbed with the temperature-resistant lubricating oil is added into the nylon powder, so that the fluidity of the material is improved; and meanwhile, after being heated and melted, the coating is coated on the metal surface to form a special'island structure ', and then frosted textures are generated after cooling.

Description

Technical Field

[0001] The invention relates to the technical field of polymer modification, in particular to a nylon powder coating for coating metal surfaces to produce frosted textures and a preparation method thereof. Background Art

[0002] As a kind of thermoplastic powder coating, nylon powder coating has good wear resistance, heat resistance and corrosion resistance, and is widely used in pipeline transportation, home appliance protection, automobile interior and exterior decoration, industrial rollers, medical and health fields, such as dishwasher baskets, busbars, conveyor rollers, butterfly valve plates, metal buckles, spline shafts, etc. Usually, the metal parts are heated to 200-400℃, and then buried in nylon powder coating for adhesion coating; or the nylon powder coating is directly sprayed on the surface of the workpiece by electrostatic spraying, and then heated to melt and coat.

[0003] Objects that can be directly touched in certain specific scenes in daily life, such as lamp posts, fences, trolleys, stretchers, etc., usually require the coating to have a certain ornamental or surface roughness, that is, a certain texture needs to be designed to meet customized needs. Existing solutions are usually divided into two types: one is to add metal organic complexes, amide-modified special fluorinated polymers and other sand grain agent ingredients to nylon powder coatings, and through physical or chemical effects, after the powder coating melts, leveling and solidifies, the coating film forms a sand grain texture. However, this requires the nylon resin to be re-extruded and modified, and the changes in the physical and chemical properties of the raw materials brought about in this process may affect its subsequent use. The second is to add micro-powder wax such as modified polyethylene wax, through the Bernard vortex effect, a frost-like thin layer is formed on the surface of the coating after the film is cooled. However, due to the small molecular weight and low melting point of micro-powder wax, yellowing or sagging is very likely to occur during dipping or spraying. Summary of the invention

[0004] The invention provides a nylon powder coating for metal surface coating and a preparation method thereof. The powder coating can form a frosted texture coating on the metal surface after being heated and melted.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A nylon powder coating for metal surface coating, which is prepared from the following raw materials by weight: 100 parts of nylon powder, 0-2 parts of color powder, 0-1 part of antioxidant, and 0.2-1 part of modified dispersant;

[0007] The modified dispersant is a dispersant adsorbed with temperature-resistant lubricating oil.

[0008] In a further embodiment, the mass ratio of the temperature-resistant lubricating oil to the dispersant is (0.5-5):1.

[0009] In a further embodiment, the dispersant has a comprehensive oil absorption value higher than 50 g / 100 g and a particle size D50 less than 10 microns.

[0010] In a further embodiment, the dispersant is at least one of silicon dioxide, aluminum oxide, calcium carbonate, calcium oxide, silicon carbide, barium sulfate, talc, and kaolin.

[0011] In a further embodiment, the temperature-resistant lubricating oil contains at least one hydrophobic oil, and its chemical structure is polysiloxane with chain structure of different polymerization degree and its modified derivatives; its viscosity is lower than 1000cst at 25°C, and its boiling point or short-time thermal decomposition temperature is 200-400°C.

[0012] In a further embodiment, the nylon powder has a melt index of less than 50 g / 10 min at 230° C. / 2.16 kg and a particle size of 10-300 μm;

[0013] The toner has a comprehensive oil absorption value lower than 30 g / 100 g and a particle size D50 smaller than 10 microns.

[0014] In a further embodiment, the nylon powder is at least one of PA6, PA66, PA56, PA610, PA612, PA510, PA513, PA515, PA1012, PA1010, PA11, PA12, PA1212 and nylon elastomer;

[0015] The color powder is at least one of titanium dioxide, zinc sulfide, copper powder, iron oxide, carbon black, cobalt oxide and ultramarine.

[0016] In a further embodiment, the antioxidant is at least one of a hindered phenol antioxidant, a hindered amine antioxidant, and a phosphite antioxidant.

[0017] Another object of the present invention is to provide a method for preparing the above-mentioned nylon powder coating, which comprises the following steps:

[0018] S1. Adding the dispersant to the temperature-resistant lubricating oil and adsorbing it in an oven to obtain a modified dispersant;

[0019] S2. Add the modified dispersant, nylon powder, color powder and antioxidant into a high-speed mixer and stir continuously for 3-10 minutes at 600-1000 rpm to obtain nylon powder coating.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The nylon powder coating prepared by the present invention is prepared by adding a dispersant adsorbed with a heat-resistant lubricating oil to the nylon powder, heating and melting the dispersant, and then coating the nylon powder on the metal surface to form a frosted texture coating, thereby producing a frosted effect.

[0022] 2. The modified dispersant in the present invention is a dispersant adsorbed with heat-resistant lubricating oil. Since the dispersant has a small particle size, a large specific surface area, and a high comprehensive oil absorption value, the heat-resistant lubricating oil can be fully bridged and adsorbed onto the dispersant carrier and uniformly dispersed into the nylon powder under high mixing.

[0023] 3. After the powder coating is heated and melted, since the nylon resin is a phase with high surface tension and the heat-resistant lubricant is a phase with low surface tension, when the two liquids with different surface tensions come into contact, the heat-resistant lubricant gradually flows to the nylon phase and evaporates, and this process continues until the coating cools naturally in the air. And since the dispersant is dispersed on the surface of the nylon particles, the lubricant coated on the particles continues to migrate. When the coating cools naturally in the air, the area where the dispersant is located becomes a continuous phase, and the nylon resin becomes a dispersed phase. The surface coating forms a special "island structure", and then produces a frosted texture after cooling. DETAILED DESCRIPTION

[0024] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0025] Unless otherwise defined, the technical and scientific terms used in the following examples have the same meanings as those commonly understood by those skilled in the art of the present invention. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0026] The technical solution of the present invention is described in detail below through specific embodiments.

[0027] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0028] Nylon powder, commercially available nylon particles are selected and cooled to below -100°C in liquid nitrogen, and then ground into powder by mechanical crushing method, and then the powder with a particle size of 10-250μm is sieved with a suitable sieve, and the melt index is 15g / 10min under the conditions of 230°C / 2.16kg. Nylon particles are PA1012 or PA612 from Shandong Dongchen Ruisen.

[0029] Antioxidant: phosphite antioxidant, Irganox 168, BASF;

[0030] Toner 1: Cobalt Blue, K6310 PB28, BASF;

[0031] Toner 2: titanium dioxide, R103, DuPont;

[0032] Dispersant 1: fumed silica, Areosol A200, particle size D50 12 nm, Evonik;

[0033] Dispersant 2: fumed alumina, Alu C, particle size D50 13 nm, Evonik;

[0034] Dispersant 3: mica powder, Iriodin 6111, particle size D50 15 μm, Merck;

[0035] Temperature-resistant lubricant 1: dimethyl silicone oil, PMX-200, viscosity 100cst, Taoxi;

[0036] Temperature-resistant lubricant 2: dimethyl silicone oil, PMX-200, viscosity 350cst, Taoxi;

[0037] Temperature-resistant lubricant 3: α-olefin oil, PAO100, viscosity 1200cst, Chemtura.

[0038] Embodiment 1:

[0039] The preparation method of nylon powder coating comprises the following steps:

[0040] S1, adding 0.2 kg of dispersant 1 into 0.2 kg of temperature-resistant lubricating oil 1 for mixing, and then placing in an oven at 100° C. for adsorption for 1 hour to obtain a modified dispersant;

[0041] S2. Put 0.4 kg of modified dispersant, 100 kg of nylon powder PA1012, 0.1 kg of color powder 1, and 0.1 kg of antioxidant into a high-speed mixer, and stir continuously at 1000 rpm for 3 minutes to obtain a nylon powder coating.

[0042] Embodiment 2:

[0043] The preparation method of nylon powder coating comprises the following steps:

[0044] S1, adding 0.1 kg of dispersant 2 into 0.1 kg of temperature-resistant lubricating oil 1 for mixing, and then placing in an oven at 100° C. for adsorption for 1 hour to obtain a modified dispersant;

[0045] S2. Put 0.2 kg of modified dispersant, 100 kg of nylon powder PA612, 1 kg of color powder 2, and 1 kg of antioxidant into a high-speed mixer, and stir continuously at 600 rpm for 10 min to obtain nylon powder coating.

[0046] Embodiment 3:

[0047] The preparation method of nylon powder coating comprises the following steps:

[0048] S1, adding 0.5 kg of dispersant 1 into 0.5 kg of temperature-resistant lubricating oil 1 for mixing, and then placing in an oven at 120° C. for adsorption for 1 hour to obtain a modified dispersant;

[0049] S2. Put 1 kg of modified dispersant, 100 kg of nylon powder PA1012, 2 kg of color powder 1, and 0.1 kg of antioxidant into a high-speed mixer, and stir continuously at 900 rpm for 5 minutes to obtain a nylon powder coating.

[0050] Embodiment 4:

[0051] The preparation method of nylon powder coating comprises the following steps:

[0052] S1, adding 0.1 kg of dispersant 2 into 0.5 kg of temperature-resistant lubricating oil 2 for mixing, and then placing in an oven at 80° C. for adsorption for 2 h to obtain a modified dispersant;

[0053] S2. Add 0.6 kg of modified dispersant and 100 kg of nylon powder PA612 into a high-speed mixer and stir continuously at 800 rpm for 9 minutes to obtain nylon powder coating.

[0054] Comparative Example 1:

[0055] The same as embodiment 1, the only difference is that the temperature-resistant lubricating oil 1 is replaced by the temperature-resistant lubricating oil 3.

[0056] Comparative Example 2:

[0057] Same as Example 1, except that no heat-resistant lubricating oil is added.

[0058] Comparative Example 3:

[0059] Same as Example 1, except that the added amount of dispersant 1 is 0.8 kg.

[0060] Comparative Example 4:

[0061] The same as Example 1, the only difference is that dispersant 1 is changed to dispersant 3.

[0062] Comparative Example 5:

[0063] Same as Example 1, except that no dispersant was added.

[0064] Comparative Example 6:

[0065] The same as Example 1, except that the amount of dispersant 1 is 0.1 kg and the amount of temperature-resistant lubricating oil 1 is 0.9 kg.

[0066] The formulations of each example are shown in Table 1 below:

[0067] Table 1

[0068]

[0069] Put the prepared nylon powder coating into a container with a porous bottom plate, and introduce appropriate compressed air from the bottom of the container to keep the coating in a boiling (fluidized) state. Heat a 2mm thick metal sheet (rust and oil removal) to 300-400℃, then quickly immerse it in the powder for 3-10 seconds. After taking it out, record the appearance after dipping. According to the standard GB / T3505-2009, use a surface roughness meter to measure the roughness of the metal sheet surface. The test results are shown in Table 2.

[0070] Table 2

[0071]

[0072] Combined with Table 1-2 for analysis:

[0073] By comparing Example 1 and Comparative Examples 1-2, it can be seen that in Example 1, due to the addition of the modified dispersant adsorbed with the heat-resistant lubricating oil 1, the prepared nylon powder material has good fluidity and its surface is rough and frosted.

[0074] In Comparative Example 2, only dispersant 1 was used, and the prepared nylon powder material had good fluidity and a smooth surface of the dip coating. In Comparative Example 1, heat-resistant lubricating oil 3 was used to modify dispersant 1. Due to the high viscosity of heat-resistant lubricating oil 3, the prepared nylon powder material had poor fluidity and a smooth surface of the dip coating.

[0075] By comparing Example 1 and Comparative Example 3, it can be seen that in Comparative Example 3, due to the excessive amount of dispersant 1, the dispersant loaded on the surface of the nylon particles plays the role of "isolation protection", no particles are attached to the surface of the metal sheet, the powder does not melt, and no powder is formed during dipping.

[0076] Comparing Comparative Examples 4-5 and Example 1, it can be seen that dispersant 3 is used in Comparative Example 4. Due to the large particle size and low oil absorption value of dispersant 3, the heat-resistant lubricating oil 1 is dispersed and adsorbed on the nylon particles under the mixing treatment of the high-speed mixer, causing a "bridging" phenomenon, poor powder fluidity, uneven surface during dip molding, and a small amount of powder agglomerates. However, no dispersant was added in Comparative Example 5, which seriously affected its fluidity, and powder agglomerates accumulated during dip molding. In Example 1 of the present application, due to the addition of dispersant 1, the powder fluidity is good, and the dip molding surface is rough and frosted.

[0077] By comparing Comparative Example 6 and Example 1, it can be seen that in Comparative Example 6, due to the excessive amount of heat-resistant lubricating oil 1, the overall viscosity of the system is high, the powder fluidity is poor, and there is a serious bridging phenomenon, the dip-molded surface is uneven, and there are irregular powder agglomerations.

[0078] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A nylon powder coating for metal surface coating, characterized in that: The raw materials are prepared by weight: 100 parts of nylon powder, 0-2 parts of color powder, 0-1 parts of antioxidant, and 0.2-1 parts of modified dispersant; The modified dispersant is a dispersant adsorbed with temperature-resistant lubricating oil.

2. The nylon powder coating according to claim 1, characterized in that: The mass ratio of the temperature-resistant lubricating oil to the dispersant is (0.5-5):

1.

3. The nylon powder coating according to claim 1, characterized in that: The comprehensive oil absorption value of the dispersant is higher than 50g / 100g, and the particle size D50 is less than 10 microns.

4. The nylon powder coating according to claim 3, characterized in that: The dispersant is at least one of silicon dioxide, aluminum oxide, calcium carbonate, calcium oxide, silicon carbide, barium sulfate, talc, and kaolin.

5. The nylon powder coating according to claim 1, characterized in that: The temperature-resistant lubricating oil contains at least one hydrophobic oil, and its chemical structure is polyorganosiloxane with chain structure of different polymerization degrees and its modified derivatives; Its viscosity is less than 1000cst at 25°C, and its boiling point or short-time thermal decomposition temperature is 200-400°C.

6. The nylon powder coating according to claim 1, characterized in that: The nylon powder has a melt index of less than 50 g / 10 min at 230° C. / 2.16 kg and a particle size of 10-300 μm; The toner has a comprehensive oil absorption value lower than 30 g / 100 g and a particle size D50 smaller than 10 microns.

7. The nylon powder coating according to claim 6, characterized in that: The nylon powder is at least one of PA6, PA66, PA56, PA610, PA612, PA510, PA513, PA515, PA1012, PA1010, PA11, PA12, PA1212 and nylon elastomer; The color powder is at least one of titanium dioxide, zinc sulfide, copper powder, iron oxide, carbon black, cobalt oxide and ultramarine.

8. The nylon powder coating according to claim 1, characterized in that: The antioxidant is at least one of a hindered phenol antioxidant, a hindered amine antioxidant, and a phosphite antioxidant.

9. The method for preparing a nylon powder coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Adding the dispersant to the temperature-resistant lubricating oil and adsorbing it in an oven to obtain a modified dispersant; S2. Add the modified dispersant, nylon powder, color powder and antioxidant into a high-speed mixer and stir continuously for 3-10 minutes at 600-1000 rpm to obtain nylon powder coating.

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