Polyester-polyurethane composite coating as well as preparation method and application thereof

Abstract

The invention discloses a polyester-polyurethane composite coating as well as a preparation method and application thereof, and relates to the technical field of coatings. The polyester-polyurethane composite coating comprises polyester resin, hydroxy acrylic resin, a polyester resin curing agent, an acrylic resin curing agent, a texturing agent and an auxiliary agent, and the mass of the hydroxy acrylic resin is 5-20% of the mass of the polyester resin. The polyester-polyurethane composite coating provided by the invention is used as base powder of a vacuum plating process, a formed coating has an obvious grain effect, can be matched with metal powder to present an excellent silver flashing effect after vacuum plating, also has good flexibility, corrosion resistance, hardness and other properties, is suitable for the vacuum plating process, and has a good application prospect. The coating can be further matched with a vacuum electroplating process provided by the invention to achieve a better effect, and is suitable for vacuum electroplating surface coating of the hub.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a polyester-polyurethane composite coating and a preparation method and application thereof. Background Art

[0002] In recent years, powder coatings have been widely used in the wheel hub coating industry due to their high environmental protection, high utilization rate, low cost, excellent product appearance and product performance. In the normal coating production process, it is generally used in combination with base powder, mid-coat topcoat and transparent powder to ensure the appearance and performance of the product. The appearance of the mid-coat surface is directly related to the appearance of the wheel hub. At present, in the field of coating, the mid-coat surface is produced by spraying paint on the surface of the automobile wheel hub through air spraying and curing at high temperature. This coating process is affected by the environment, such as temperature and humidity, which will produce large fluctuations, resulting in uneven film thickness in different areas of the wheel hub, and the product appearance is greatly affected by the environment. In addition, a large amount of organic solvents will volatilize during the production process, resulting in waste paint, which is difficult to meet the requirements of environmental protection conditions and has certain production safety risks.

[0003] In order to solve the problems caused by the traditional paint spraying process, the vacuum plating process is used to form an electroplated layer with obvious metal decorative effects to replace the mid-coat topcoat formed by air spray paint, which is considered to be one of the most effective methods. However, the traditional base powder formula will have poor metal powder appearance, large texture, and uneven film thickness when combined with the vacuum plating process, making it difficult to form a silver flash effect with metal powder. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a polyester-polyurethane composite coating, which adjusts the glossiness of the base powder by combining the polyester system and the polyurethane system, improves the texture effect, and thus enhances the silver flash effect formed by combining the metal powder in the vacuum electroplating process.

[0005] The second aspect of the present invention is to provide a method for preparing a polyester-polyurethane composite coating.

[0006] The third aspect of the present invention is to provide an application of a polyester-polyurethane composite coating.

[0007] A fourth aspect of the present invention is to provide a vacuum electroplating process.

[0008] A fifth aspect of the present invention is to provide a wheel hub.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] The first aspect of the present invention provides a polyester-polyurethane composite coating, comprising polyester resin, hydroxy acrylic resin, polyester resin curing agent, acrylic resin curing agent, texture agent and auxiliary agent; the mass of the hydroxy acrylic resin is 5-20% of the mass of the polyester resin.

[0011] The polyester-polyurethane composite coating provided by the present invention is a coating that can be used in a PSC (physical vapor deposition silver coating) coating process, which includes a polyester resin and a hydroxy acrylic resin, wherein the hydroxyl group in the hydroxy acrylic resin reacts with an acrylic resin curing agent (such as an isocyanate curing agent) to form a polyurethane, so that the hydroxy acrylic resin and the acrylic resin curing agent constitute a polyurethane system, and by blending two systems with different reaction rates, a polyester system (polyester resin and its curing agent) and a polyurethane system, the compatibility structure between the two systems is changed, and the gloss level and texture size of the coating formed by the polyester-polyurethane composite coating are adjusted by using the reaction rate difference between the two systems and the corresponding resin percentage content. At the same time, a texture agent is added to the polyester-polyurethane composite coating to enhance the compatibility of the polyester system and the polyurethane system and improve the texture effect.

[0012] When the polyester-polyurethane composite coating of the present invention is used, the size of the texture of the coating can be adjusted by controlling the formula of the coating to match metal powders of different particle sizes to provide the required silver flash appearance, and the coating finally formed has good mechanical strength, corrosion resistance and aging resistance, and solves the problems of poor appearance effect and uneven film thickness when conventional leveling primer is used in combination with vacuum electroplating process.

[0013] Preferably, the mass content of the hydroxy acrylic resin is 5-10% or 10-20% of the mass of the polyester resin, and more preferably 5-10% or 15-20%.

[0014] Preferably, the polyester-polyurethane composite coating comprises the following components in parts by mass:

[0015] 80-100 parts of polyester resin,

[0016] 5 to 16 parts of hydroxy acrylic resin,

[0017] 4-10 parts of polyester resin curing agent,

[0018] 2 to 5 parts of acrylic resin curing agent,

[0019] 0.1-2 parts of texture agent,

[0020] 20 to 44 parts of additives.

[0021] Further preferably, the polyester-polyurethane composite coating comprises the following components in parts by mass:

[0022] 90-100 parts of polyester resin,

[0023] 6 to 15 parts of hydroxy acrylic resin,

[0024] 5-8 parts of polyester resin curing agent,

[0025] 2 to 4 parts of acrylic resin curing agent,

[0026] 0.2-1 part of texture agent,

[0027] 27 to 44 parts of additives.

[0028] More preferably, the hydroxy acrylic resin is 6 to 10 parts.

[0029] More preferably, the auxiliary agent is 28.5 to 43 parts.

[0030] Preferably, the auxiliary agent includes the following components by weight: 0.1-2 parts of a cross-linking accelerator, 20-35 parts of a filler, 0.1-2 parts of a breathable agent, 0.1-1.5 parts of a brightener, 0.1-1.5 parts of a hardener, and 0-2 parts of a pigment.

[0031] Further preferably, the auxiliary agent comprises the following components by mass: 1-2 parts of a cross-linking accelerator, 25-35 parts of a filler, 0.5-2 parts of a breathable agent, 0.2-1.5 parts of a brightener, 0.1-1.5 parts of a hardener, and 0-2 parts of a pigment.

[0032] More preferably, the auxiliary agent comprises the following components by mass fraction: 1-2 parts of cross-linking accelerator, 25-35 parts of filler, 0.5-1.5 parts of breathable agent, 0.5-1 part of brightener, 0.5-1 part of hardener, and 1-2 parts of pigment.

[0033] Further preferably, the texturing agent comprises an amide-modified polymer.

[0034] Further preferably, the cross-linking accelerator includes at least one of 2-phenylimidazoline and benzyltriethylammonium bromide.

[0035] Further preferably, the breathable agent includes at least one of benzoin and YPE.

[0036] Further preferably, the brightener comprises a copolymer of butyl acrylate and methyl methacrylate.

[0037] Further preferably, the hardener comprises a sand texture specific hardener.

[0038] More preferably, the polyester resin curing agent is TGIC.

[0039] More preferably, the acrylic resin curing agent is an isocyanate curing agent.

[0040] Preferably, the particle size of the polyester-polyurethane composite coating is 30-50 μm.

[0041] More preferably, the particle size of the polyester-polyurethane composite coating is 30-40 μm, more preferably 35-40 μm.

[0042] By adjusting the particle size range of the polyester-polyurethane composite coating, it is beneficial to improve the texture effect, and when applied to the vacuum electroplating process, it can be better matched with metal powder to form a silver flash effect.

[0043] The second aspect of the present invention provides a method for preparing the polyester-polyurethane composite coating according to the first aspect of the present invention, characterized in that it comprises the following steps:

[0044] The polyester resin, hydroxy acrylic resin, polyester resin curing agent, acrylic resin curing agent, texture agent and auxiliary agent are mixed, kneaded and tableted to obtain the polyester-polyurethane composite coating.

[0045] Preferably, the mixing is carried out in a twin-screw extruder.

[0046] Further preferably, the temperature of mixing zone I of the twin-screw extruder is 90-110°C; the temperature of mixing zone II is 100-120°C.

[0047] More preferably, the mixing rotor frequency of the twin-screw extruder is 30 to 50 Hz.

[0048] Preferably, the components further include a crushing step after mixing; the crushing time is 5 to 20 minutes.

[0049] Preferably, the tableting step further includes a crushing step; the crushing time is 10 to 20 minutes.

[0050] More preferably, the pulverizing step includes a cooling step, the cooling time is 30 to 60 minutes, and the cooling temperature is 20 to 30°C.

[0051] Preferably, the crushing step further includes a screening step, and the mesh size of the sieve is 180 to 250 meshes.

[0052] Preferably, the preparation method comprises the following steps:

[0053] The components are uniformly mixed, crushed, kneaded and then extruded, the extruded colloid material is extruded into sheets, crushed and cooled into powders of different particle sizes, and sieved to obtain the polyester-polyurethane composite coating.

[0054] The third aspect of the present invention provides an application of the polyester-polyurethane composite coating described in the first aspect of the present invention in a vacuum electroplating process.

[0055] Preferably, the polyester-polyurethane composite coating is used to prepare the base powder of the vacuum electroplating process, and metal powder is used for vacuum electroplating; the particle size of the metal powder after vacuum electroplating and curing is 10 to 40 μm.

[0056] In the present invention, the percentage content of the hydroxyl acrylic resin in the polyester-polyurethane composite coating, combined with different metal powder particle sizes, can form different silver flash effects. For example, in some embodiments of the present invention, when the hydroxyl acrylic resin content is controlled to be 5-10% of the polyester resin content, the coating texture formed is smaller and the gloss is higher. Further, when it is combined with a metal powder particle size of 10-20 μm, a fine silver flash appearance effect can be achieved; and when the hydroxyl acrylic resin content is 10-20% of the polyester resin content, the coating texture formed is larger and the gloss is lower. Correspondingly, when it is combined with a metal particle size of 20-40 μm, a coarse silver flash appearance effect can be achieved.

[0057] A fourth aspect of the present invention provides a vacuum plating process, comprising the following steps:

[0058] Providing a substrate, applying the polyester-polyurethane composite coating described in the first aspect of the present invention on the substrate, placing it in a vacuum plating chamber after curing, introducing an inert gas, adding metal powder, applying electricity to make the inert gas collide with the metal powder, and the metal powder forms a charged body adsorbed on the surface of the substrate, curing, and forming a coating;

[0059] The vacuum plating conditions satisfy at least one of the following a) to d):

[0060] a) Gas pressure is 0.2~0.5MPa;

[0061] b) Gas flow rate is 30-60cc / min;

[0062] c) The coating power is 10-20kW;

[0063] d) The vacuum plating time is 15 to 40 seconds.

[0064] The vacuum plating process of the present invention is a dry powder coating process, which uses physical vapor deposition silver coating to coat the substrate, so it is called PSC coating process.

[0065] The vacuum electroplating coating process of the present invention is different from the conventional vacuum electroplating process. It can directly cover the metal powder on the surface of the primer coating formed by the polyester-polyurethane composite coating and solidify it. The single-layer film thickness is only 10 to 50 μm. The conventional primer silver mixing process requires the metal powder to be bonded to the primer powder coating for spraying. The single-layer film thickness is generally 80 to 150 μm. The vacuum electroplating process of the present invention can greatly reduce the film thickness requirement while ensuring performance and appearance, and achieve energy conservation, emission reduction, and environmental protection requirements of green construction.

[0066] In addition, the traditional base powder combined with the vacuum plating process of the present invention will also have problems such as poor appearance effects. Therefore, the vacuum plating process of the present invention combined with the polyester-polyurethane composite coating provided by the present invention can exert better effects and enable the coating to achieve a more excellent silver flash effect.

[0067] Preferably, the substrate is a metal substrate, and more preferably a wheel hub.

[0068] Preferably, the gas pressure is 0.2-0.4 MPa.

[0069] Preferably, the gas flow rate is 40-50 cc / min.

[0070] Preferably, the coating power is 15-20 kW.

[0071] Preferably, the vacuum plating time is 20 to 30 seconds.

[0072] Preferably, the inert gas includes at least one of argon and nitrogen.

[0073] Preferably, a metal coating is formed after the vacuum plating, and the curing temperature of the metal coating is 180-220°C.

[0074] A fifth aspect of the present invention provides a wheel hub, comprising a coating formed by the polyester-polyurethane composite coating described in the first aspect of the present invention, or prepared by a preparation method including the vacuum electroplating process described in the fourth aspect of the present invention.

[0075] The polyester-polyurethane composite coating provided by the present invention has good physical and chemical properties, high impact strength, good flexibility, and high hardness, and can be used as a base powder. The coating formed after the vacuum electroplating process has excellent corrosion resistance and aging resistance, and passes the 240h CASS corrosion resistance test and the 1000h xenon lamp aging test. It has an excellent silver flash effect and is suitable for preparing a base powder for the wheel hub vacuum electroplating process. A base powder layer is formed on the surface of the wheel hub. When used in conjunction with the vacuum electroplating process provided by the present invention, a better metal coating can be formed, further improving the silver flash effect.

[0076] In addition, the vacuum electroplating process of the present invention is used in the surface coating of the wheel hub. In the production process of the middle coating surface, the solid metal powder nickel-chromium alloy is evenly coated on the surface of the wheel hub by vacuum electroplating. This ensures the uniformity of the wheel hub during the coating process, avoids uneven film thickness on the spokes or sides of the wheel hub due to structural problems, and greatly reduces product quality fluctuations caused by environmental factors, effectively improving product quality and stability.

[0077] Preferably, the wheel hub has a wheel size of 16 to 22 inches.

[0078] The polyester-polyurethane composite coating of the present invention has a wide range of applications and can be applied to complex wheel appearances.

[0079] Preferably, the wheel hub comprises an aluminum wheel hub.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] (1) The present invention provides a polyester-polyurethane composite coating, which changes the compatible structure of the two systems by blending a polyester system with a polyurethane system. At the same time, a polyester resin and a curing agent having a low reaction activity and a slow reaction rate are blended with a polyurethane resin system (i.e., a hydroxy acrylic resin and a curing agent) having a high reaction activity and a fast reaction rate. The obtained polyester-polyurethane composite powder coating has an appearance of fine or large textures and can be used as a base powder in a vacuum electroplating process. The formed coating has an obvious texture effect and can be combined with metal powder to present an excellent silver flash effect after vacuum electroplating. At the same time, it also has good flexibility, corrosion resistance, aging resistance, hardness and other properties. It is suitable for use as a base powder in a vacuum electroplating process and can be further combined with the vacuum electroplating process of physical deposition silver plating provided by the present invention to exert a better effect. It is suitable for vacuum electroplating surface coating of wheel hubs.

[0082] (2) The vacuum plating process provided by the present invention belongs to the PSC coating process. The metal powder is evenly spread on the surface of the substrate sprayed with polyester-polyurethane composite coating by the vacuum plating process in a physical deposition manner. Compared with the process of forming a middle coating surface by the traditional paint air spraying method, the problem that the construction appearance and construction effect of traditional paint are affected by temperature and humidity is solved. It is suitable for process applications with environmental interference and complex wheel shapes, can stabilize the appearance effects of products of different batches, has high production process value, and is particularly suitable for the surface coating production of wheel hubs. DETAILED DESCRIPTION

[0083] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0084] Some of the raw materials used in the following examples and comparative examples of the present invention are described as follows:

[0085] Metal powder: chromium-nickel alloy, Hunan Aoke New Material Technology Co., Ltd.

[0086] Inert gas: Argon, Guangzhou Xiangyu Chemical Gas Co., Ltd.

[0087] Polyester resin: NH8307 resin, Qingtian Material Technology Co., Ltd.

[0088] Hydroxylated acrylic resin: HE6552 resin, Guangdong Zhuohe New Materials Co., Ltd.

[0089] Polyester resin curing agent: TGIC, Taizhou Hongxing Chemical Co., Ltd.

[0090] Acrylic resin curing agent: B1530 isocyanate curing agent, VESTAGON.

[0091] Texture agent: SW301, Ningbo Nanhai Chemical Co., Ltd.

[0092] Cross-linking accelerator: CY168, Sino-French Chemical Co., Ltd.

[0093] Filler: BD-701 matte barium sulfate, Yichang Zhongtai New Materials Co., Ltd.

[0094] Breathing agent: Benzoin (benzoin), Dongguan Shanmu New Materials Co., Ltd.; YPE, Hubei Laisi Chemical New Materials Co., Ltd.

[0095] Brightener: 701, copolymer of butyl acrylate and methyl methacrylate, Yangzhou Yansheng Chemical Co., Ltd.

[0096] Sand texture special effect hardener: SA5066, Anhui Lu'an Jietongda New Materials Co., Ltd.

[0097] Pigment: Carbon black, Tianjin Yiborui Chemical Co., Ltd.

[0098] The following is a detailed description of the embodiments and comparative examples.

[0099] Example 1

[0100] A polyester-polyurethane composite coating, the formula of which is shown in Table 1 below.

[0101] Table 1: Polyester-polyurethane composite coating formulation of Example 1

[0102]

[0103]

[0104] The preparation method of the above-mentioned polyester-polyurethane composite coating is as follows: all components are mixed evenly, crushed for 10 minutes, and mixed using a twin-screw extruder, the temperature of zone I is 100°C, the temperature of zone II is 105°C, and the rotor frequency is 50HZ. The extruded sheet material is crushed and sieved with a 250-mesh sieve, cooled and packaged to obtain a polyester-polyurethane composite coating with a particle size D50=38μm.

[0105] Example 2

[0106] A polyester-polyurethane composite coating, the formula of which is shown in Table 2 below.

[0107] Table 2: Polyester-polyurethane composite coating formulation of Example 2

[0108] Components Mass NH8307 polyester resin 93 HE6552 Hydroxylated Acrylic Resin 15 TGIC curing agent 7 B1530 curing agent 3.75 Texturizing Agent 1 Crosslinking accelerator 1.5 Benzoin (benzoin) 0.5 701 0.8 YPE 0.5 Sand texture special effect hardener 0.5 Barium sulfate extinction 30 Carbon Black 1.5

[0109] The preparation method of the above-mentioned polyester-polyurethane composite coating is as follows: all components are mixed evenly, crushed for 10 minutes, and mixed using a twin-screw extruder, the temperature of zone I is 100°C, the temperature of zone II is 105°C, and the rotor frequency is 50HZ. The extruded sheet material is crushed and sieved with a 250-mesh sieve, cooled and packaged to obtain a polyester-polyurethane composite coating with a particle size D50=38μm.

[0110] Example 3

[0111] A polyester-polyurethane composite coating, the formula of which is shown in Table 3 below.

[0112] Table 3: Formulation of polyester-polyurethane composite coating of Example 3

[0113] Components Mass NH8307 polyester resin 93 HE6552 Hydroxylated Acrylic Resin 15 TGIC curing agent 7 B1530 curing agent 3.75 Texturizing Agent 0.2 Crosslinking accelerator 2 Benzoin (benzoin) 0.5 701 0.8 YPE 0.5 Sand texture special effect hardener 1 Barium sulfate extinction 30 Carbon Black 1.5

[0114] The preparation method of the above-mentioned polyester-polyurethane composite coating is as follows: all components are mixed evenly, crushed for 10 minutes, and mixed using a twin-screw extruder, the temperature of zone I is 100°C, the temperature of zone II is 105°C, and the rotor frequency is 50HZ. The extruded sheet material is crushed and sieved with a 250-mesh sieve, cooled and packaged to obtain a polyester-polyurethane composite coating with a particle size D50=38μm.

[0115] Example 4

[0116] A polyester-polyurethane composite coating is different from Example 1 in that the cross-linking accelerator in Example 1 is removed, and the remaining raw materials and preparation method are the same as Example 1.

[0117] Example 5

[0118] A polyester-polyurethane composite coating is different from Example 1 in that the defoaming agent YPE in Example 1 is removed, and the remaining raw materials and preparation method are the same as Example 1.

[0119] Example 6

[0120] A polyester-polyurethane composite coating is different from Example 1 in that the sand texture special effect hardener in Example 1 is removed and replaced with a common hardener polytetrafluoroethylene wax, and the remaining raw materials and preparation method are the same as Example 1.

[0121] Comparative Example 1

[0122] A powder coating, which is different from Example 1 in that the HE6552 hydroxy acrylic resin and the B1530 curing agent in Example 1 are removed, and the remaining raw materials and the preparation method are the same as those in Example 1.

[0123] Comparative Example 2

[0124] A powder coating, which is different from Example 1 in that the texture agent in Example 1 is removed, and the remaining raw materials and preparation method are the same as Example 1.

[0125] Application Examples

[0126] The coatings of the above-mentioned embodiments and comparative examples are electrostatically sprayed on the surface of the hub by high voltage, the curing temperature is 200℃ / 15min, the film thickness after curing is 80-100μm, the hub is transferred to a vacuum plating chamber, inert gas argon is injected under vacuum, the gas pressure is adjusted to 0.3MPa, the gas flow rate is 45cc / min, and chromium-nickel alloy powder with a chromium content of 70% is added, wherein the particle size of the chromium-nickel alloy powder used in Embodiment 1, Embodiment 3, and Comparative Examples 1 to 5 is 15μm, and the particle size of the chromium-nickel alloy powder used in Embodiment 2 is 30μm; turn on the coating equipment, adjust the coating power to 18kW, so that the chromium-nickel alloy powder forms a charged body and is uniformly adsorbed to the surface of the coating after curing of the conductive hub, and the electroplating time is controlled at 25s; after curing at 200℃ / 10min, a coating with a silver powder metal appearance effect is formed, and the film thickness of the metal coating is 30-40μm. Among them, due to the uneven appearance of the hub, the film thickness of the metal coating is a range value.

[0127] High-gloss acrylic transparent powder A-CL0306 is sprayed on the metal coating surface of the wheel hub by high-voltage electrostatic spraying. The curing temperature is 200℃ / 10min, and the film thickness after curing is 80-100μm.

[0128] The performance of the wheel hub coating after vacuum plating is tested as follows:

[0129] Coating appearance: The texture of the coatings formed by the coatings of the examples and comparative examples before vacuum plating was visually inspected.

[0130] Silver flash effect: Visually inspect the coating effect after vacuum plating curing.

[0131] Impact strength (50kg·cm -1 ): Tested in accordance with GB / T 1732-93.

[0132] Flexibility: Tested in accordance with GB / T 1731-93.

[0133] Hardness: Tested in accordance with GB / T 6739-2006.

[0134] CASS performance (240h): tested in accordance with ASTM B117-2009.

[0135] Water resistance (240h): Tested in accordance with GB / T 1733-93.

[0136] Neutral salt spray (1000h): Tested in accordance with GB / T 1771-2007.

[0137] Gravel impact: Tested in accordance with SAE-J400-2002.

[0138] Xenon lamp aging (1000h) gloss retention rate: Tested in accordance with GB / T 1865-2009.

[0139] The results are shown in Tables 4 and 5 below.

[0140] Table 4 Comparison of coating appearance and silver flash effect of the embodiment and the comparative example

[0141]

[0142]

[0143] Table 5 Comparison of the test results of the coating physicochemical properties of the embodiment and the comparative example

[0144]

[0145] Combining Table 4 and Table 5, we can see that:

[0146] Compared with comparative examples 1 to 2, examples 1 to 6 all have better texture effects and silver flash effects. Among them, the polyester-polyurethane composite coatings of examples 1 to 2 all have good appearance and performance. The hydroxyl acrylic resin used in example 1 accounts for 8.6% of the polyester resin ratio. The coating formed as a base powder has a small texture appearance, and the appearance is a fine silver flash effect when matched with metal powder; the hydroxyl acrylic resin used in example 2 accounts for 16.1% of the polyester resin ratio. The coating formed as a base powder has a large texture appearance, and the appearance is a coarse silver flash effect when matched with metal powder. At the same time, the mechanical properties and corrosion resistance of examples 1 and 2 meet the standards of powder coatings for wheel hubs. The polyurethane content in the system of example 2 is higher, and the corresponding aging resistance effect is better than that of example 1. Example 3 adjusts the content of texture agent, hardener and cross-linking accelerator. The sand texture appearance is not obvious when the texture agent content is reduced; the content of hardener and cross-linking accelerator is increased, the reaction is more sufficient, and the hardness and other properties are significantly improved.

[0147] Compared with Example 1, Example 4 removes the cross-linking promoter. Although the small grain effect and fine silver flash effect are retained, the coating is not completely cured under the same curing conditions, the mechanical properties and corrosion resistance are reduced to a certain extent, and the aging resistance is significantly reduced.

[0148] Compared with Example 1, Example 5 removes the defoaming agent YPE, and the texture effect and silver flash effect of the coating remain unchanged, but dense pinholes appear in the coating. This is because the gas generated by the volatilization of the blocked isocyanate cannot volatilize, resulting in the pinhole phenomenon on the surface.

[0149] In Example 6, the sand texture special effect hardener is replaced with a common hardener. Although it does not affect the appearance of the coating and the silver flash effect, the hardness of the coating decreases significantly.

[0150] In Comparative Example 1, the hydroxy acrylic resin and its curing agent are removed from the formula. Only the polyester resin system is present in the coating, and there is no polyester-polyurethane system blending and the compatible structure of the two. The appearance texture effect is not obvious, and the silver flash effect is not good.

[0151] In Comparative Example 2, the texture agent was removed, the polyester system and the polyurethane system had poor compatibility, and the appearance texture effect was not obvious.

[0152] In summary, the present invention changes the compatible structure of the two systems by blending the polyester system with the polyurethane system, and at the same time utilizes the polyester resin and its curing agent with low reaction activity and slow reaction rate to blend with the polyurethane resin system (i.e., hydroxy acrylic resin and its curing agent) with high reaction activation energy and fast reaction rate. The obtained polyester-polyurethane composite powder coating has an appearance of fine or large textures, can be used as a base powder in the vacuum electroplating process, and the formed coating has obvious texture effects. After vacuum electroplating, it can be combined with metal powder to present an excellent silver flash effect. At the same time, it also has good flexibility, corrosion resistance, hardness and other properties, is suitable for vacuum electroplating processes, and can be further combined with the vacuum electroplating process provided by the present invention to exert better effects, and is suitable for vacuum electroplating surface coating of wheel hubs.

[0153] In addition, due to the difference in reaction rates between the polyester system and the polyurethane system, the glossiness and grain size of the polyester-polyurethane composite coating can be adjusted by adjusting the percentage content of the polyester resin and the hydroxyl acrylic resin. The hydroxyl acrylic resin content of the polyester-polyurethane composite coating with fine grains is 5-10% of the polyester resin content, and the glossiness is relatively high, and the metal powder particle size corresponding to 10-20 μm can achieve a fine silver appearance effect; the hydroxyl acrylic resin content of the polyester-polyurethane composite coating with large grains is 10-20% of the polyester resin content, and the glossiness is relatively low, and the metal powder particle size corresponding to 20-40 μm can achieve a coarse silver appearance effect. At the same time, the polyester-polyurethane composite coating of the present invention can be further matched with a special texture agent to enhance the compatibility of the polyester system and the polyurethane system and improve the texture effect. The polyester-polyurethane composite coating finally obtained is used as a base powder for vacuum electroplating process, which is different from the conventional leveling base powder. It can form a fine silver and coarse silver appearance through grains of different sizes and metal powders of corresponding particle sizes, and has a wider range of applications.

[0154] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A polyester-polyurethane composite coating, characterized in that: The invention comprises polyester resin, hydroxy acrylic resin, polyester resin curing agent, acrylic resin curing agent, texture agent and auxiliary agent; the mass of the hydroxy acrylic resin is 5-20% of the mass of the polyester resin.

2. The polyester-polyurethane composite coating according to claim 1, characterized in that: By mass, it includes the following components: 80-100 parts of polyester resin, 5 to 16 parts of hydroxy acrylic resin, 4-10 parts of polyester resin curing agent, 2 to 5 parts of acrylic resin curing agent, 0.1-2 parts of texture agent, 20 to 44 parts of additives.

3. The polyester-polyurethane composite coating according to claim 1 or 2, characterized in that: The auxiliary agent comprises the following components by weight: 0.1 to 2 parts of a cross-linking accelerator, 20 to 35 parts of a filler, 0.1 to 2 parts of a breathable agent, 0.1 to 1.5 parts of a brightener, 0.1 to 1.5 parts of a hardener, and 0 to 2 parts of a pigment.

4. The polyester-polyurethane composite coating according to claim 3, characterized in that: The texturing agent comprises an amide-modified polymer; And / or, the cross-linking accelerator includes at least one of 2-phenylimidazoline and benzyltriethylammonium bromide; And / or, the breathable agent includes one or more of benzoin and polyether surfactant YPE; and / or, the brightener comprises a copolymer of butyl acrylate and methyl methacrylate; And / or, the hardener includes a sand texture special effect hardener.

5. The polyester-polyurethane composite coating according to claim 1, characterized in that: The particle size of the polyester-polyurethane composite coating is 30-50 μm.

6. A method for preparing the polyester-polyurethane composite coating according to any one of claims 1 to 5, characterized in that: The steps include: The polyester resin, hydroxy acrylic resin, polyester resin curing agent, acrylic resin curing agent, texture agent and auxiliary agent are mixed, kneaded and tableted to obtain the polyester-polyurethane composite coating.

7. Use of the polyester-polyurethane composite coating according to any one of claims 1 to 5 in a vacuum electroplating process.

8. The use according to claim 7, characterized in that: The polyester-polyurethane composite coating is used to prepare the base powder of the vacuum electroplating process, and metal powder is used for vacuum electroplating; the particle size of the metal powder after vacuum electroplating and curing is 10-40 μm.

9. A vacuum plating process, characterized in that: The following steps are involved: Providing a substrate, applying the polyester-polyurethane composite coating according to any one of claims 1 to 5 on the substrate, placing it in a vacuum plating chamber after curing, introducing an inert gas, adding metal powder, applying electricity to make the inert gas collide with the metal powder, and the metal powder forms a charged body adsorbed on the surface of the substrate, curing, and forming a coating; The vacuum plating conditions satisfy at least one of the following a) to d): a) Gas pressure is 0.2~0.5MPa; b) Gas flow rate is 30-60cc / min; c) The coating power is 10-20kW; d) The vacuum plating time is 15 to 40 seconds.

10. A wheel hub, characterized in that: A coating formed by the polyester-polyurethane composite coating according to any one of claims 1 to 5, or prepared by a preparation method including the vacuum electroplating process according to claim 9.

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