High-temperature-resistant baking varnish for automobile hubs and preparation process of high-temperature-

Abstract

The invention discloses high-temperature-resistant stoving varnish for automobile hubs and a preparation process of the high-temperature-resistant stoving varnish. The stoving varnish is prepared from the following components in parts by weight: 30-50 parts of epoxy modified organic silicon resin, 15-25 parts of high-temperature-resistant pigment, 10-20 parts of high-temperature-resistant filler, 1-3 parts of an adhesion promoter, 0.5-1.5 parts of a flatting agent, 0.3-1.0 part of a defoaming agent, 1-2 parts of an ultraviolet light absorber, 0.5-1.5 parts of a light stabilizer, 10-20 parts of a curing agent and 20-30 parts of an organic solvent. The manufacturing process comprises the steps of premixing, grinding and dispersing, paint mixing, filtering and the like, and curing and film forming are carried out under a proper baking condition. The baking varnish has adhesive force, high temperature resistance, corrosion resistance and weather resistance, and is suitable for coating of automobile hubs with high performance requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wheel hub coating and painting process, in particular to a high-temperature-resistant baking paint for automobile wheel hub and a manufacturing process thereof. BACKGROUND

[0002] With the improvement of appearance and long-term durability of high-end vehicles, the wheel hub coating needs to maintain integrity and gloss under harsh conditions such as high-temperature cleaning, high-temperature conduction of brakes, splashing salt spray and ultraviolet radiation. The traditional organic baking paint is prone to yellowing, powdering or adhesion reduction at high temperature, and the pure organic silicon system has deficiencies in mechanical properties or adhesion.

[0003] Therefore, a product is needed, which is based on epoxy-modified silicone resin, compounded with high-temperature-resistant pigments and fillers, and cooperated with functional additives, can improve adhesion and comprehensive weather resistance while meeting heat resistance, and is suitable for high-end automobile wheel hub coating. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the problems in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art, provide a high-temperature-resistant baking paint for automobile wheel hub and a manufacturing process thereof, a baking paint formula for automobile wheel hub with excellent adhesion, high-temperature resistance (able to withstand more than 200℃), corrosion resistance and weather resistance, and an industrialized manufacturing process thereof, while ensuring that the components in the formula are compatible with each other, have good construction performance, and are suitable for conventional wheel hub spraying and baking processes.

[0007] To solve the above technical problems, a high-temperature-resistant baking paint for automobile wheel hub is provided, which comprises, by weight: epoxy-modified silicone resin 30-50 parts, high-temperature-resistant pigment 15-25 parts, high-temperature-resistant filler 10-20 parts, adhesion promoter 1-3 parts, leveling agent 0.5-1.5 parts, defoaming agent 0.3-1.0 parts, ultraviolet absorber 1-2 parts, light stabilizer 0.5-1.5 parts, curing agent 10-20 parts and organic solvent 20-30 parts.

[0008] The present application also provides a manufacturing process for the baking paint, which is carried out according to the following steps: Pre-mixing: the epoxy-modified silicone resin is preliminarily mixed with high-temperature-resistant pigments and fillers, and then an adhesion promoter, a leveling agent, a defoaming agent, an ultraviolet absorber and a light stabilizer are added and uniformly stirred to obtain a pre-dispersed paint paste; Grinding and dispersing: the pre-dispersed paint paste is subjected to grinding and dispersing treatment until the pigments / fillers are uniformly dispersed and reach a suitable dispersion fineness for spraying; Paint adjustment: a curing agent and an organic solvent are added to adjust the viscosity and solid content of the paint to meet the requirements of spraying construction, and degassing treatment is performed if necessary; Filtering: filtering is performed with a suitable filter screen (the filter screen size is selected according to the requirements of the spray gun) to ensure that no obvious impurities block the spray gun during spraying; Application and baking: the paint is sprayed on the surface-treated wheel hub substrate, and baking and curing are performed according to the process parameters to obtain a dense baked paint film.

[0009] Preferably, the epoxy-modified silicone resin serves as a base material and has heat resistance and film-forming ability; the high-temperature-resistant pigments and fillers form a structure for heat insulation, coloring and enhancing the stability of the film layer; the adhesion promoter improves the chemical or physical adhesion to the metal substrate; the leveling agent and the defoaming agent ensure surface flatness and construction stability; the ultraviolet absorber and the light stabilizer improve weather resistance; the curing agent crosslinks with the epoxy groups to form a cured network; and the organic solvent is used to adjust the construction viscosity and dilution performance.

[0010] The present application has the following advantages: by using the epoxy-modified silicone resin as a base material and reasonably matching with functional additives, the baked paint film obtained has good adhesion and gloss under high-temperature working conditions, is resistant to high temperature (can withstand short-term exposure to about 200-250℃ without obvious chalking or discoloration), corrosion and weathering; at the same time, the formulation has good construction performance and is suitable for conventional spraying and baking processes, meeting the comprehensive requirements of high-end automobile wheels for appearance and long-term durability. DETAILED DESCRIPTION

[0011] In order to make the above-mentioned objects, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the description examples.

[0012] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from the description, and those skilled in the art can make similar generalizations without departing from the scope of the present application, therefore the present application is not limited to the specific examples disclosed below.

[0013] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0014] Raw material description: Epoxy-modified silicone resin: silicone polymers with epoxy groups introduced into the chain ends or side chains, possessing the heat-resistant backbone of the silicone backbone and the crosslinking function of the epoxy groups; High-temperature resistant pigments: Inorganic pigments or ceramic colorants suitable for high-temperature baking, used to provide color and heat resistance; High-temperature resistant fillers: ceramic powder or high-melting-point inorganic powder, used to improve thermal stability and mechanical strength; Adhesion promoters: mainly silane coupling agents, which can form chemical or physical bridging on the metal surface of the substrate; Leveling agents, defoamers, UV absorbers, and light stabilizers: commonly used industrial additives, used to improve surface smoothness, eliminate bubbles, and enhance weather resistance, respectively. Curing agent: A curing system that can cross-link and cure with epoxy groups; Organic solvents: commonly used paint thinners, used to adjust the viscosity during application.

[0015] Example 1 This embodiment provides a high-temperature resistant paint for automobile wheel hubs and its manufacturing process. Specifically, the formula (by weight) is as follows: 40 parts epoxy modified silicone resin, 20 parts high-temperature resistant pigment, 15 parts high-temperature resistant filler (ceramic powder), 2 parts adhesion promoter (silane coupling agent), 1 part leveling agent, 0.5 parts defoamer, 1.5 parts ultraviolet absorber, 1 part light stabilizer, 15 parts curing agent, and 20 parts organic solvent.

[0016] Manufacturing process: Premixing: Place the epoxy-modified silicone resin in a clean container and stir at a medium speed. Slowly add 20 parts of high-temperature resistant pigment and 15 parts of high-temperature resistant filler, and keep stirring to fully wet the pigment and filler with the resin and form a paste. Then add 2 parts adhesion promoter, 1 part leveling agent, 0.5 parts defoamer, 1.5 parts ultraviolet absorber and 1 part light stabilizer, and continue stirring for about 10 to 20 minutes until the surface of the mixture is uniform and there are no obvious lumps.

[0017] Grinding and dispersing: Grind and disperse the pre-dispersed paint paste to ensure that the pigments and fillers are evenly dispersed. The grinding time can be adjusted according to the equipment and batch size (example operation time is about 30 to 90 minutes) until the paint paste appears uniform and fine when visually observed. During the grinding process, maintain temperature control to avoid overheating and affecting the stability of the components.

[0018] Paint mixing: Add 15 parts of hardener and 20 parts of organic solvent to the ground and dispersed paint paste, stir evenly until the overall viscosity and solid content meet the requirements of spraying construction. If necessary, let it stand for a while to allow the air bubbles to rise and remove the mixed air by vacuum degassing or low-speed stirring.

[0019] Filtration: Use an appropriate filtration device to filter the paint to remove larger particles or undispersed clumps and ensure that the spray gun does not become clogged.

[0020] Application and baking: After the wheel hub substrate undergoes conventional surface treatment (degreasing, rust removal, phosphating or conversion coating treatment, etc.), the prepared paint liquid is evenly applied using conventional spraying methods. After initial drying, it is placed in an oven and baked at 200℃ for 30 minutes to cure. After cooling, a dense paint film is obtained.

[0021] Tests and Results: Adhesion: Tested using the cross-hatching method, grade 0 (no grid lines detached); High temperature resistance: When the coating is exposed to 220°C for a short period of time (e.g., 2 hours), no obvious chalking or large-area discoloration is observed on the surface; Weather resistance: Under accelerated light and temperature and humidity cycling, the surface shows no obvious cracking or significant loss of gloss; Surface characteristics: The paint film hardness, gloss and feel meet the requirements of wheel appearance, and the surface is smooth and free of obvious bubbles.

[0022] Furthermore, this embodiment uses epoxy-modified silicone resin as the base material. The epoxy groups can form a three-dimensional cross-linked network in the presence of the curing agent, providing mechanical strength and film integrity. The silicone skeleton provides a thermally stable substrate, and the high-temperature resistant pigments and ceramic fillers form a heat-insulating and reinforcing structure, reducing the impact of high-temperature effects on the organic components. The silane coupling agent enhances the bond between the resin and the metal substrate, thereby improving the adhesion stability of the coating film under thermal cycling and mechanical loads.

[0023] Example 2 This embodiment provides a high-temperature resistant paint for automotive wheel hubs and its manufacturing process.

[0024] Specifically, the formula (by weight) is as follows: epoxy modified silicone resin: 45 parts, high-temperature resistant pigment: 18 parts, high-temperature resistant filler (ceramic powder) 12 parts, adhesion promoter (silane coupling agent) 2 parts, leveling agent 1.2 parts, defoamer 0.6 parts, ultraviolet absorber 2 parts, light stabilizer 1.2 parts, curing agent 12 parts, and organic solvent 18 parts. The manufacturing process is as follows: The premixing steps are the same as in Example 1, but care should be taken to ensure that the UV absorber and light stabilizer are fully and evenly dispersed with the resin when they are added.

[0025] The grinding and dispersion stage should be extended appropriately to ensure that the fillers and pigments maintain good dispersibility even under high resin loads.

[0026] During the paint mixing stage, hardeners and solvents are added to control the viscosity and facilitate film spraying, aiming to obtain a thinner and more uniform coating.

[0027] The filtration, spraying and baking steps are the same as in Example 1. The baking temperature can be in the range of 180-200℃, and the baking time can be adjusted according to the activity of the curing agent and the film thickness.

[0028] Tests and Results: Weather resistance: After undergoing accelerated light exposure and salt spray combined aging tests, the color and gloss are well maintained; Corrosion resistance: Under salt spray conditions, the film does not show obvious blistering or large-area desorption, exhibiting good barrier performance; Adhesion: The cross-cut test shows a rating of 0 to 1, which meets the requirements for wheel hub applications.

[0029] Furthermore, increasing the proportion of epoxy-modified silicone resin and the amount of ultraviolet absorber / light stabilizer can delay the photochemical degradation process under long-term exposure of the film, thereby maintaining color and gloss; slightly reducing the amount of filler helps to improve the density and adhesion continuity of the coating; in terms of process, emphasis is placed on dispersion uniformity and film control to take into account both appearance and durability requirements.

[0030] Example 3 This embodiment provides a high-temperature resistant paint for automotive wheel hubs and its manufacturing process.

[0031] Formula (by weight): Epoxy modified silicone resin: 35 parts, High-temperature resistant pigment: 22 parts, High-temperature resistant filler (ceramic powder) 18 parts, Adhesion promoter (silane coupling agent) 1.5 parts, Leveling agent 0.8 parts, Defoamer 0.4 parts, Ultraviolet absorber 1 part, Light stabilizer 0.8 parts, Curing agent 12 parts, Organic solvent 18 parts; Manufacturing process: During premixing, special care should be taken to gradually disperse the filler into the resin to avoid agglomeration; The grinding and dispersion stage is controlled at a moderate intensity to obtain a paint paste that balances dispersibility and particle size distribution. By appropriately selecting the solvent ratio during the paint mixing stage, a viscosity suitable for spraying can be obtained, thereby improving the adaptability of on-site construction. After filtration, spray and bake at 200℃ for about 25 to 35 minutes to cure.

[0032] Tests and Results: Abrasion resistance: The surface hardness and abrasion resistance of the paint film are improved, making it suitable for wheel hubs in environments with frequent friction. Adhesion and high temperature resistance: Maintains good stability under normal testing conditions; Workability: Smooth spraying, low sagging, and uniform film formation.

[0033] Furthermore, increasing the filler ratio and pigment amount can improve wear resistance and hiding power, but excessive filler amount may affect film formation and adhesion. Therefore, good workability and durability can be obtained at the same time by balancing the ratio of filler to resin and optimizing the dispersion process.

[0034] Comparative Example 1 The formulation was adjusted from Example 1, except that the adhesion promoter was changed from 2 parts to 0 parts, while the rest of the formulation remained unchanged. The process and application conditions were the same as in Example 1.

[0035] After the same baking and heat cycling treatment, the adhesion between the paint film and the metal substrate decreased, and small areas of peeling occurred in the cross-cut adhesion test; the lack of silane coupling agent resulted in weak interfacial bonding between the resin and the metal, which was more likely to manifest as peeling or cracking along the interface, especially at high temperature or heat cycling.

[0036] Comparative Example 2 The formula was adjusted from Example 2, removing the ultraviolet absorber and light stabilizer, while the rest of the formula and process remained unchanged.

[0037] After accelerated light aging, the paint film shows color changes and reduced gloss.

[0038] Therefore, it can be concluded that ultraviolet absorbers and light stabilizers have a protective effect against external photochemical degradation, and their absence will reduce long-term weather resistance.

[0039] In summary, the epoxy-modified silicone resin system combines the advantages of both epoxy groups and silicone backbone, providing a high-temperature stable Si–O bond structure and enabling the construction of a cross-linking network between epoxy groups and curing agents to achieve the desired mechanical properties and film integrity.

[0040] High-temperature resistant pigments and ceramic fillers reduce the damage to organic components caused by heat conduction by forming a thermal shield and inorganic framework, thereby improving color and structural stability at high temperatures. Silane coupling agents, as interfacial bridges, can improve the chemical bonding between resin and metal substrates, thus enhancing adhesion stability under high temperatures and mechanical stress.

[0041] UV absorbers and light stabilizers slow down the photochemical aging process of the paint film by absorbing and dissipating harmful UV energy and inhibiting free radical chain reactions. Leveling agents and defoamers provide necessary surface tension adjustment and bubble control for application and film formation, ensuring a smooth appearance.

[0042] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-temperature resistant paint for automotive wheel hubs, characterized in that: By weight, it comprises: 30-50 parts epoxy-modified silicone resin, 15-25 parts high-temperature resistant pigment, 10-20 parts high-temperature resistant filler, 1-3 parts adhesion promoter, 0.5-1.5 parts leveling agent, 0.3-1.0 parts defoamer, 1-2 parts ultraviolet absorber, 0.5-1.5 parts light stabilizer, 10-20 parts curing agent, and 20-30 parts organic solvent.

2. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: The epoxy-modified silicone resin contains epoxy groups, and the adhesion promoter is a silane coupling agent, with an amount of 1 to 3 parts.

3. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: The high-temperature resistant filler is selected from ceramic powder or inorganic filler with ceramic powder as the main component, and the filler dosage is 10 to 20 parts.

4. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: The curing agent is a curing agent that undergoes a cross-linking reaction with epoxy groups, and the amount of curing agent used is 10 to 20 parts.

5. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: The amount of ultraviolet absorber is 1 to 2 parts, the amount of light stabilizer is 0.5 to 1.5 parts, the amount of leveling agent is 0.5 to 1.5 parts, and the amount of defoamer is 0.3 to 1.0 parts.

6. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: 20-30 parts of organic solvent are common organic diluents, either single or mixed, used to adjust the spraying viscosity and solid content.

7. The manufacturing process of a high-temperature resistant paint for automobile wheel hubs as described in any one of claims 1-6, characterized in that: Includes the following steps: A. Premixing: Epoxy modified silicone resin, high-temperature resistant pigments, high-temperature resistant fillers, adhesion promoters, leveling agents, defoamers, ultraviolet absorbers and light stabilizers are mixed evenly to obtain a pre-dispersed paint paste; B. Grinding and dispersing: Grind and disperse the pre-dispersed paint paste until the pigments and fillers reach the dispersion fineness suitable for spraying; C. Paint mixing: Add hardener and organic solvent and stir until homogeneous; degas if necessary. D. Filtration: Filtration using a suitable filtration device to obtain a sprayable paint solution.

8. The manufacturing process of a high-temperature resistant paint for automotive wheel hubs as described in claim 7, characterized in that: During the grinding and dispersing step, continue stirring or grinding until the paint is uniform. The grinding time or grinding energy is determined according to the actual equipment capacity to obtain a stable dispersion state.

9. The manufacturing process of a high-temperature resistant paint for automobile wheel hubs as described in claim 7, characterized in that: The filtered paint is sprayed onto the surface of the metal wheel hub substrate that has been cleaned or pretreated, and cured under industrial baking conditions. The baking temperature is preferably in the range of 160 to 220°C, and the baking time is determined according to the substrate and curing agent system to obtain a dense paint film.

10. The high-temperature resistant paint for automotive wheel hubs as described in claim 1, characterized in that: This paint is suitable for high-end automotive wheel rims to meet the durability requirements of the rims under conditions such as high temperature, salt spray and sunlight exposure.