Powder coating for automobile calipers as well as preparation method and application of powder coating

Abstract

The invention belongs to the technical field of powder coatings, and particularly relates to a powder coating for automobile calipers as well as a preparation method and application of the powder coating. The powder coating for the automobile calipers is prepared from the following raw materials: low-hydroxyl-value hydroxyl-terminated polyester resin, medium-hydroxyl-value hydroxyl-terminated polyester resin, an isocyanate curing agent, an accelerant and a breathable agent. The hydroxyl value of the hydroxyl-terminated polyester resin with the low hydroxyl value is 30-60mgKOH / g; the hydroxyl value of the hydroxyl-terminated polyester resin with the medium hydroxyl value is 75 to 190 mgKOH / g; the accelerant comprises a dibutyl tin laurate accelerant; the breathable agent comprises benzoin and breathable wax. The low-hydroxyl-value hydroxyl-terminated polyester resin and the medium-hydroxyl-value hydroxyl-terminated polyester resin are compounded, the benzoin and the breathable wax are compounded to serve as the breathable agent, and the accelerant of the specific type is combined, so that the powder coating has good water resistance, the problem of poor secondary adhesive force after the calipers are coated with water resistance can be effectively solved, and the service life of the calipers is prolonged. The corrosion resistance, high temperature resistance and high humidity resistance of the base material are obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of powder coating technology, and specifically relates to a powder coating for automotive calipers, its preparation method, and its application. Background Technology

[0002] As a crucial component of a car's braking system, automotive calipers are located inside the wheel hub, closely attached to the brake disc. During daily use, they generate high temperatures through friction with the brake disc, and are also exposed to temperature, humidity, and ultraviolet radiation. Therefore, automotive calipers not only require vibrant colors but also must be resistant to high temperatures and humidity, corrosion, and aging. Powder coatings used on the surface of automotive calipers also have even higher requirements in terms of water resistance, high temperature and humidity resistance, corrosion resistance, and aging resistance.

[0003] Traditional automotive calipers use cast iron as their base material. This type of base material has a high surface roughness and large porosity. Conventional primers cannot completely isolate moisture from the base material, allowing moisture to easily penetrate into the pores and corrode the internal metal of the caliper. This affects the adhesion between the base material and the surface coating, causing further corrosion of the metal base material, reducing the strength of the metal material, and severely impacting the caliper's service life. Furthermore, caliper powder coating is a single-layer powder application. Conventional primer systems such as epoxy polyester and polyester systems cannot fully meet aging requirements, and secondary adhesion after water resistance is poor, failing to effectively improve the base material's corrosion resistance and high-temperature and high-humidity resistance.

[0004] Therefore, it is of great significance to provide a powder coating with good water resistance that can effectively solve the problem of poor secondary adhesion after water-resistant coating of calipers and significantly improve the corrosion resistance, high temperature and high humidity resistance of the substrate. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a powder coating for automotive calipers, which has good water resistance, effectively solves the problem of poor secondary adhesion after water-resistant coating of calipers, and significantly improves the corrosion resistance and high temperature and humidity resistance of the substrate.

[0006] The inventive concept of this invention: The raw materials for preparing the powder coating of this invention include low-hydroxyl-value terminal hydroxyl polyester resin, medium-hydroxyl-value terminal hydroxyl polyester resin, isocyanate curing agent, accelerator, and breathable agent. The low-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 30-60 mgKOH / g; the medium-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 75-190 mgKOH / g; the accelerator includes dibutyltin laurylate accelerator; and the breathable agent includes benzoin and breathable wax.

[0007] This invention uses a blend of low-hydroxyl-value and medium-hydroxyl-value end-hydroxyl polyester resins, and a blend of benzoin and breathable wax as a breathable agent, combined with specific types of accelerators, to give the powder coating good water resistance. This effectively solves the problem of poor secondary adhesion after water resistance coating of calipers, and significantly improves the corrosion resistance, high temperature and high humidity resistance of the substrate.

[0008] Therefore, a first aspect of the present invention provides a powder coating for automotive calipers.

[0009] Specifically, the raw materials for preparing the powder coating for automotive calipers include low-hydroxyl-terminated polyester resin, medium-hydroxyl-terminated polyester resin, isocyanate curing agent, accelerator, and breathable agent; The low-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 30-60 mgKOH / g; the medium-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 75-190 mgKOH / g. The accelerator includes dibutyltin lauryl accelerators; The breathable agent includes benzoin and breathable wax.

[0010] Preferably, the low hydroxyl-terminated polyester resin has a hydroxyl value of 35-45 mg KOH / g.

[0011] Preferably, at 200°C, the viscosity of the low hydroxyl-terminated polyester resin is 3000-6000 mPa·s; more preferably, at 200°C, the viscosity of the low hydroxyl-terminated polyester resin is 3000-5000 mPa·s.

[0012] Preferably, the glass transition temperature of the low hydroxyl-terminated polyester resin is 56-60°C.

[0013] Preferably, the reactivity of the low hydroxyl-terminated polyester resin is 200-420s at 180°C; more preferably, the reactivity of the low hydroxyl-terminated polyester resin is 320-420s at 180°C.

[0014] Preferably, the hydroxyl value of the hydroxyl-terminated polyester resin is 80-140 mg KOH / g.

[0015] Preferably, at 200°C, the viscosity of the hydroxyl-terminated polyester resin with a medium hydroxyl value is 2000-8000 mPa·s; more preferably, at 200°C, the viscosity of the hydroxyl-terminated polyester resin with a medium hydroxyl value is 3000-6000 mPa·s.

[0016] Preferably, the glass transition temperature of the hydroxyl-terminated polyester resin is 58-60°C.

[0017] Preferably, the reactivity of the hydroxyl-terminated polyester resin with a medium hydroxyl value is 100-250 s at 180°C; more preferably, the reactivity of the hydroxyl-terminated polyester resin with a medium hydroxyl value is 120-200 s at 180°C.

[0018] Preferably, the isocyanate curing agent includes at least one of VESTAGON's curing agents B1530 and B1400.

[0019] Preferably, the mass ratio of benzoin to breathable wax in the breathable agent is 1:(2-5); more preferably, the mass ratio of benzoin to breathable wax in the breathable agent is 1:(3-4.5); even more preferably, the mass ratio of benzoin to breathable wax in the breathable agent is 1:3.

[0020] Preferably, the breathable wax includes at least one of polyethylene wax, polypropylene wax, and polyamide-modified wax.

[0021] Preferably, the raw materials for preparing the powder coating, by weight, include 35-55 parts of low hydroxyl-terminated polyester resin, 1.8-5.5 parts of medium hydroxyl-terminated polyester resin, 18-30 parts of isocyanate curing agent, 0.9-2.2 parts of accelerator, and 0.9-2.2 parts of breathable agent.

[0022] More preferably, by weight, the raw materials for preparing the powder coating include 40-50 parts of low-hydroxyl-terminated polyester resin, 2-5 parts of medium-hydroxyl-terminated polyester resin, 20-30 parts of isocyanate curing agent, 1-2 parts of accelerator, and 1-2 parts of breathable agent.

[0023] Preferably, the raw materials for preparing the powder coating also include at least one of leveling agent, gloss enhancer, pigment, and filler.

[0024] Preferably, the raw materials for preparing the powder coating further include leveling agents, gloss enhancers, pigments, and fillers; and by mass parts, the raw materials for preparing the powder coating include 35-55 parts of low hydroxyl-terminated polyester resin, 1.8-5.5 parts of medium hydroxyl-terminated polyester resin, 18-30 parts of isocyanate curing agent, 0.9-2.2 parts of accelerator, 0.9-2.2 parts of breathable agent, 0.9-2.2 parts of leveling agent, 0.5-1.1 parts of gloss enhancer, 2.7-5.5 parts of pigment, and 9-25 parts of filler.

[0025] More preferably, the raw materials for preparing the powder coating further include leveling agents, gloss enhancers, pigments, and fillers; and by mass parts, the raw materials for preparing the powder coating include 40-50 parts of low hydroxyl-terminated polyester resin, 2-5 parts of medium hydroxyl-terminated polyester resin, 20-30 parts of isocyanate curing agent, 1-2 parts of accelerator, 1-2 parts of breathable agent, 1-2 parts of leveling agent, 0.5-1 parts of gloss enhancer, 3-5 parts of pigment, and 10-25 parts of filler.

[0026] Preferably, the brightening agent comprises a copolymer of butyl acrylate and methyl methacrylate.

[0027] Preferably, the filler comprises at least one of precipitated barium sulfate, hard calcium carbonate, and kaolin.

[0028] Preferably, the pigment includes at least one of titanium dioxide, organic red, and iron oxide red.

[0029] A second aspect of the present invention provides a method for preparing the powder coating for automotive calipers described in the first aspect of the present invention.

[0030] Specifically, the preparation method of the powder coating for automotive calipers includes the following steps: The raw materials are mixed, melted and extruded, and then pulverized to obtain the powder coating.

[0031] Preferably, the process after melt extrusion further includes a tableting process.

[0032] Preferably, the pigment is first dispersed in a low-hydroxyl-value end-hydroxyl polyester resin to improve the pigment's wettability and dispersion effect.

[0033] Preferably, the pigment is dispersed in a coffee cup.

[0034] Preferably, the mixing is carried out in a stirring tank, where the solid components are uniformly mixed together and broken into smaller solid particles.

[0035] Preferably, the mixing time is 10-20 minutes.

[0036] Preferably, the melt extrusion is performed using a twin-screw extruder.

[0037] Preferably, the motor frequency for controlling the screw speed of the twin-screw extruder is 40-50Hz.

[0038] Preferably, the temperature of the melt extrusion is 90-120°C.

[0039] Preferably, the pulverization time is 5-15 minutes.

[0040] Preferably, the particle size after pulverization is 28-35 μm.

[0041] Preferably, the method for preparing the powder coating for automotive calipers includes the following steps: a. Pigment dispersion: The pigment is pre-dispersed in a low-hydroxyl-value end-hydroxyl polyester resin to improve the wettability and dispersion effect of the pigment. b. Mixing and crushing: uniformly mix the solid components together and crush them into smaller solid particles; c. Melt compounding: The uniformly mixed and crushed solid components are melt-extruded through a twin-screw extruder at high temperature, so that the solid components are more evenly dispersed in the molten state. d. Tableting and cooling: The molten components are pressed into tablets using rollers and cooled to room temperature; e. Crushing: The cooled flakes are crushed to the required particle size to obtain powder coating.

[0042] Preferably, depending on the requirements, metal powder and powder coating can be bonded to obtain powder coating with the desired appearance; then, it is sieved through a sieve of a specific mesh size to avoid the presence of particles in the product, and the product is obtained and packaged.

[0043] Preferably, the bonding time is 5-10 minutes.

[0044] Preferably, the mesh size of the sieve is 180-250 mesh.

[0045] A third aspect of the present invention provides an automotive caliper.

[0046] Specifically, the automotive caliper includes the powder coating described in the first aspect of this invention.

[0047] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) The present invention replaces the conventional polyester system and epoxy polyester system with a polyurethane system to obtain a powder coating product that can be applied to single-layer caliper coating. It can solve the problem of poor performance caused by conventional powder coating when applied to rough surfaces of calipers, and meet the performance requirements of caliper coating in terms of water resistance, high temperature and humidity resistance, corrosion resistance and aging resistance.

[0048] (2) This invention starts from the resin system, resin hydroxyl value screening and resin compounding, and production process, and works together to effectively solve the problem of poor secondary adhesion after water resistance coating of calipers, and greatly improves the corrosion resistance and high temperature and humidity resistance of caliper substrate.

[0049] (3) The caliper single-coat special powder coating of the present invention has the basic properties of conventional caliper powder coating, with good appearance and leveling, and excellent performance in copper accelerated acetic acid salt spray test (240h), neutral salt spray 500h, cyclic corrosion 720h, and water resistance 240h test. It has an effective protective effect on caliper substrates with high porosity, such as cast iron materials. Detailed Implementation

[0050] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0051] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0052] The information on the relevant raw material components in this embodiment of the invention is as follows: Low hydroxyl value end-hydroxyl polyester resin: NH-7803, hydroxyl value 35-45mgKOH / g, viscosity 3000-5000Pa·s / 200℃, glass transition temperature 57℃, reactivity 300-420s / 180℃, purchased from Qingtian Materials Technology Co., Ltd. Medium hydroxyl-terminated polyester resin: NH-7603, hydroxyl value 90-120mgKOH / g, viscosity 3000-6500Pa·s / 200℃, glass transition temperature 59℃, reactivity 110-210s / 180℃, purchased from Qingtian Materials Technology Co., Ltd. Isocyanate curing agent: B1530 isocyanate curing agent, purchased from VESTAGON; Leveling agent: MONENG-S1154, purchased from Dongguan Moneng Chemical Co., Ltd.; Accelerator: Dibutyltin lauryl accelerator, CAS No. 77-58-7, purchased from Shandong Yukang Chemical Co., Ltd.; Brightening agent: 701, a copolymer of butyl acrylate and methyl methacrylate, purchased from Guangzhou Shengqi Polymer Materials Technology Co., Ltd.; Breathable agents: Benzoin (benzoic acid ketone), purchased from Henan Wokas Biotechnology Co., Ltd.; Polyethylene wax, purchased from Dongguan Yuancheng New Materials Co., Ltd. Filler: Precipitated barium sulfate, purchased from Yingde Caihuan Nanotechnology Co., Ltd.; Pigments: Titanium dioxide, purchased from Guangdong Shuotian Titanium Industry Co., Ltd.; 3132 Organic Red, purchased from Dezhou Baotong Chemical Co., Ltd.

[0053] The raw material composition and dosage of the powder coating for automotive calipers in Examples 1-3 of this invention are shown in Table 1.

[0054] Table 1: Raw material components and dosages (parts by mass) of the powder coatings in Examples 1-3 of the present invention

[0055] Example 1 The raw material composition and dosage of the powder coating in Example 1 are shown in Table 1.

[0056] Example 1: The preparation method of powder coating is as follows: Titanium dioxide and 3132 organic red pigment were pre-dispersed in low hydroxyl value end hydroxyl polyester resin and dispersed evenly. Then, all raw material components were placed in a mixing tank and stirred for 12 minutes. After stirring evenly, a mixed raw material was obtained. The mixed raw materials are added to a twin-screw extruder for further mixing and extrusion. The temperature of zone I of the twin-screw extruder is 100℃, the temperature of zone II is 105℃, the motor frequency controlling the screw speed is 50Hz, and the roller cooling water temperature is 15℃. After extrusion, the material is pressed into sheets, cooled, pulverized in a pulverizer, sieved through a 200-mesh sieve, and packaged to obtain a powder coating for automotive calipers with a particle size D50 of 34μm.

[0057] Example 2 The raw material composition and dosage of the powder coating in Example 2 are shown in Table 1.

[0058] Example 2: The preparation method of the powder coating is the same as that in Example 1.

[0059] Example 3 The raw material composition and dosage of the powder coating in Example 3 are shown in Table 1.

[0060] Example 3 The preparation method of the powder coating is the same as that of Example 1.

[0061] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not add a hydroxyl-terminated polyester resin with a medium hydroxyl value; otherwise, it is the same as Example 1.

[0062] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses a high-hydroxyl-value end-hydroxyl polyester resin to replace the medium-hydroxyl-value end-hydroxyl polyester resin in Example 1 in equal amounts; otherwise, they are the same as in Example 1.

[0063] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 uses an imidazole accelerator to replace the accelerator in Example 1 in an equal amount; otherwise, they are the same as in Example 1.

[0064] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that Comparative Example 4 does not contain polyethylene wax; otherwise, they are the same as Example 1.

[0065] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that Comparative Example 5 replaces the internal extrusion method of polyethylene wax with external mixing. That is, Comparative Example 5 adds polyethylene wax during the pulverization process after cooling. Otherwise, it is the same as Example 1.

[0066] Performance testing The powder coatings prepared in Examples 1-3 and Comparative Examples 1-5 were applied to cast iron test specimens and cured at 180°C for 20 minutes to obtain a 100 μm thick powder coating. The cast iron test specimens underwent conventional phosphating treatment, which involved degreasing, followed by immersion in a phosphating solution for 1500 seconds, washing with water, surface conditioning, washing with water again, and drying. Performance testing was then conducted, and the test items and methods are as follows: Appearance leveling: visual inspection; Impact strength 50kg×cm: Tested according to GB / T1732-93; Copper-accelerated acetic acid salt spray test (CASS) 240h: Tested according to GB / T 10125-2008; Water resistance for 240 hours: Tested according to GB / T 1733-93; Secondary adhesion after water resistance: Tested according to GB / T 9286-2021; Neutral salt spray test for 500 hours: Tested according to GB / T 10125-2008; Cyclic corrosion test for 720 hours: Before the cyclic corrosion test, scribing should be performed according to ISO 2409 (one line), with a length of 3-5 cm; the test should consist of 30 cycles of cyclic corrosion testing, each cycle (24 hours) including: a) 4-hour neutral salt spray test, in accordance with ISO 9227 standard; b) 16h humid-hot climate storage test, with climate conditions in accordance with ISO 6270-2-CH(40±3)℃:100% air humidity; c) Place in natural indoor conditions (28°C) for 4 hours (including the cooling phase); recommended placement conditions can be found in the DIN50014-23 / 50-2 standard climate. A total of 30 test cycles were conducted; after the test, there was no blistering or metal substrate corrosion on the sample surface; the unilateral diffusion D ≤ 2.5 mm; Aging for 1000 hours: Tested according to GB / T 1865-2009.

[0067] The performance test results of the powder coatings in Examples 1-3 and Comparative Examples 1-5 are shown in Table 2.

[0068] Table 2: Performance test results of powder coatings in Examples 1-3 and Comparative Examples 1-5

[0069] As can be seen from Table 2, the powder coating for automotive calipers of the present invention has good appearance, water resistance, mechanical properties, secondary adhesion after water resistance, corrosion resistance, high temperature and high humidity resistance (cyclic corrosion), and aging resistance.

[0070] Example 2 powder coating increased the proportion of hydroxyl-terminated polyester resin with medium hydroxyl value, resulting in increased system viscosity. Under the same curing temperature, the leveling effect and appearance were somewhat reduced compared to Example 1.

[0071] Example 3: The powder coating increased the proportion of isocyanate curing agent, which improved the curing degree of the powder coating to a certain extent. However, under the same curing conditions, the coating may be over-cured, causing the coating to become brittle and reducing its flexibility and impact strength.

[0072] Comparative Example 1: Powder coating without the addition of medium-hydroxyl end-hydroxyl polyester resin resulted in excessively low system viscosity, significantly reduced coating anti-interference ability, and slight pinholes appearing in some areas of the appearance.

[0073] In Comparative Example 2, replacing the medium-hydroxyl-value terminal hydroxyl polyester resin with an equal amount of high-hydroxyl-value terminal hydroxyl polyester resin in the powder coating improved the coating density to some extent and resulted in good salt spray corrosion resistance. However, the introduction of high-hydroxyl-value resin into the compound increased the hydrophilicity of the hydroxyl groups, leading to a decrease in the coating's water resistance, reduced secondary adhesion after water exposure, and decreased cyclic corrosion resistance and aging resistance.

[0074] When the powder coating in Comparative Example 3 was replaced with an imidazole accelerator, the accelerator did not have a significant promoting effect, the cross-linking curing degree of the coating was insufficient, and the overall performance of the coating decreased significantly.

[0075] The powder coating in Comparative Example 4 did not contain the breathable agent polyethylene wax. The addition of benzoin alone could not guarantee that the porous substrate of cast iron was completely breathable, resulting in pinhole problems on the surface. Furthermore, the coating's water resistance, secondary adhesion after water exposure, corrosion resistance, and high temperature and humidity resistance were significantly reduced.

[0076] In Comparative Example 5, when the polyethylene wax was replaced by external mixing instead of internal extrusion, the dispersibility of the polyethylene wax in the powder coating decreased significantly, resulting in poor breathability. Pinholes appeared on the coating surface, and the appearance, water resistance, secondary adhesion after water treatment, corrosion resistance, and high temperature and humidity resistance of the coating decreased significantly.

[0077] In summary, this invention significantly improves the density of powder coatings by selecting a suitable polyurethane resin system, enhances anti-interference capabilities and improves leveling and pinhole phenomena by compounding low-hydroxyl and medium-hydroxyl polyester resins, and solves the problem of pinhole formation in porous cast iron substrates by using compounded breathable agents. Furthermore, by combining specific types of accelerators and other components and preparation processes, the powder coating exhibits excellent leveling, water resistance, corrosion resistance, and aging resistance. This effectively solves the problem of poor secondary adhesion after water-resistant coating of calipers, significantly improves the corrosion resistance and high-temperature and high-humidity resistance of the substrate, and meets the production requirements of calipers.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A powder coating, characterized in that, The raw materials for preparing the powder coating include low hydroxyl-terminated polyester resin, medium hydroxyl-terminated polyester resin, isocyanate curing agent, accelerator, and breathable agent. The low-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 30-60 mgKOH / g; the medium-hydroxyl-value terminal hydroxyl polyester resin has a hydroxyl value of 75-190 mgKOH / g. The accelerator includes dibutyltin lauryl accelerators; The breathable agent includes benzoin and breathable wax.

2. The powder coating according to claim 1, characterized in that, At 200°C, the viscosity of the low hydroxyl-terminated polyester resin is 3000-6000 mPa·s; And / or, the glass transition temperature of the low hydroxyl-terminated polyester resin is 56-60°C; And / or, at 180°C, the reactivity of the low hydroxyl-terminated polyester resin is 200-420 s.

3. The powder coating according to claim 1, characterized in that, At 200°C, the viscosity of the hydroxyl-terminated polyester resin with a medium hydroxyl value is 2000-8000 mPa·s; And / or, the glass transition temperature of the hydroxyl-terminated polyester resin is 58-60°C; And / or, at 180°C, the reactivity of the hydroxyl-terminated polyester resin is 100-250 s.

4. The powder coating according to claim 1, characterized in that, In the breathable agent, the mass ratio of benzoin to breathable wax is 1:(2-5); and / or, the breathable wax includes at least one of polyethylene wax, polypropylene wax, and polyamide modified wax.

5. The powder coating according to claim 1, characterized in that, The raw materials for preparing the powder coating, by weight, include 35-55 parts of low hydroxyl-terminated polyester resin, 1.8-5.5 parts of medium hydroxyl-terminated polyester resin, 18-30 parts of isocyanate curing agent, 0.9-2.2 parts of accelerator, and 0.9-2.2 parts of breathable agent.

6. The powder coating according to any one of claims 1-5, characterized in that, The raw materials for preparing the powder coating also include at least one of leveling agent, gloss enhancer, pigment, and filler.

7. The powder coating according to claim 6, characterized in that, The raw materials for preparing the powder coating also include leveling agents, gloss enhancers, pigments, and fillers; and by mass parts, the raw materials for preparing the powder coating include 35-55 parts of low hydroxyl-terminated polyester resin, 1.8-5.5 parts of medium hydroxyl-terminated polyester resin, 18-30 parts of isocyanate curing agent, 0.9-2.2 parts of accelerator, 0.9-2.2 parts of breathable agent, 0.9-2.2 parts of leveling agent, 0.5-1.1 parts of gloss enhancer, 2.7-5.5 parts of pigment, and 9-25 parts of filler.

8. The method for preparing powder coating according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: The raw materials are mixed, melted and extruded, and then pulverized to obtain the powder coating.

9. The preparation method according to claim 8, characterized in that, The temperature of the melt extrusion is 90-120℃; and / or the particle size of the pulverized material is 28-35μm.

10. A type of automotive caliper, characterized in that, Including the powder coating as described in any one of claims 1-7.

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