A non-stick UV coating and its preparation method and application

Abstract

The present invention discloses a non-stick UV coating and its preparation method and application. The raw materials for its preparation include: 7 to 15 parts of thermoplastic acrylic resin; 8 to 15 parts of organic-inorganic hybrid polyurethane resin; 8 to 15 parts of fluorine-modified polyurethane; 3 to 5 parts of high-functional monomer; 2 to 5 parts of photoinitiator; 0.5 to 1 part of anti-fingerprint additive; and 45 to 55 parts of diluent; the organic-inorganic hybrid polyurethane resin has a functionality of 9 to 15; and the fluorine-modified polyurethane has a functionality of 2-5. Using the coating provided by the present invention, in conjunction with the easy-to-peel coating described in patent CN116478585A, the CNC machine frame rear edge touch-up process in the NCVM process can be well realized. The front flying paint part is extremely easy to peel off without residue. In the actual mass production process, the timeliness problem of paint stripping under the original scheme is improved, and the poor scratch resistance and dirt resistance of the vacuum coating topcoat are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular relates to a non-stick UV coating and a preparation method and application thereof. Background Art

[0002] The invention patent application with patent publication number: CN116478585A proposes a new process to solve the defect of paint accumulation on the edge of the middle frame workpiece, namely: after completing the vacuum coating process on the middle frame workpiece of PC material and spraying the vacuum coating topcoat, the paint accumulation parts on the edges of the workpiece are removed by CNC process, and the edges of the material are chamfered to obtain a middle frame with no edge accumulation. Then, the whole is coated (touch-up paint) with an easy-to-peel two-component paint. After drying, the coated coating (touch-up paint coating) is physically peeled off (peeled off). The coated coating on the chamfered part of the material exposed by the edge CNC process has good adhesion and is retained during the peeling process, thereby obtaining a middle frame with no edge accumulation and a complete coating, so that the front and side of the workpiece can maintain a consistent decorative effect.

[0003] The easily peelable two-component coating is one of the key coatings developed by the applicant specifically for this process. This process has been successfully applied to a certain mobile phone terminal. During the actual mass production process, some defects were found, specifically:

[0004] 1. The coating can be peeled off for a short time. If the product is left for more than 96 hours after touch-up, the touch-up coating will gradually solidify at room temperature, resulting in residue on the vacuum-plated topcoat when peeling, which reduces the peelability.

[0005] 2. The scratch resistance of the vacuum coating after the product is stripped is not ideal, and scratches are easily caused during the cleaning and transportation process;

[0006] 3. After the product is stripped of paint, the vacuum coating topcoat has poor anti-fouling ability and fingerprints are difficult to clean.

[0007] For this reason, another key coating in this process, namely the vacuum coating topcoat, was re-optimized and designed to obtain the non-stick UV coating of the present invention. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology. The present invention provides a non-stick UV coating that is scratch-resistant and has good peelability and timeliness, as well as its preparation method and application, which is used in conjunction with the easy-to-peel two-component coating of CN116478585A.

[0009] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0010] A non-stick UV coating, wherein the raw materials for preparing the non-stick UV coating include, by weight:

[0011]

[0012]

[0013] The organic-inorganic hybrid polyurethane resin has a functionality of 9 to 15;

[0014] The functionality of the fluorine-modified polyurethane is 2-5.

[0015] As a further improvement, the raw materials for preparation further include 0.2 to 0.5 parts of a leveling agent.

[0016] As a further improvement, the organic-inorganic hybrid polyurethane resin is nano-SiO2 hybrid polyurethane, with a weight portion of 12 to 15 parts.

[0017] As a further improvement, the organic-inorganic hybrid polyurethane resin is selected from one or both of 601X-35 of Changxing Chemical and GN8006 of Hunan Unico Chemical; and / or

[0018] The fluorine-modified polyurethane is selected from DSP-670F of Zhongshan Jieshida; and / or

[0019] The high-functional monomer is DPHA.

[0020] As a further improvement, the anti-fingerprint auxiliary agent is a fluorine-containing acrylate compound.

[0021] As a further improvement, the anti-fingerprint auxiliary agent is selected from DSP-730F produced by Zhongshan Jieshida Company.

[0022] The present invention also provides a method for preparing the non-stick UV coating, comprising the following steps:

[0023] S1. The photoinitiator is mixed with the first portion of the diluent to obtain a system 1;

[0024] S2. The thermoplastic acrylic resin, organic-inorganic hybrid polyurethane resin, fluorine-modified polyurethane, high-functional monomer is preheated and then mixed with the second portion of the diluent to obtain system 2;

[0025] S3. Add system 1 to system 2 and mix;

[0026] S4. Add the leveling agent, anti-fingerprint additive and the remaining diluent to the system obtained in step S3 and mix them to obtain the non-stick UV coating.

[0027] The present invention also provides an application of the non-stick UV coating in preparing an electronic product housing, wherein the electronic product housing is a mobile phone middle frame.

[0028] As a further improvement, the application includes:

[0029] After the mobile phone middle frame workpiece completes the vacuum coating process, the paint accumulation on the edges of the workpiece is removed by CNC process, and the edges of the material are chamfered to obtain a middle frame without edge accumulation; the vacuum coating topcoat in the vacuum coating process is the non-stick UV coating according to any one of claims 1 to 5;

[0030] The whole portion is coated with an easy-to-peel coating and dried, the coating covering the vacuum coating topcoat and the exposed material at the chamfered portion; the main components of the easy-to-peel coating include the following components in parts by weight: 65-75 parts of thermoplastic acrylic resin; 5-10 parts of polyester resin; 4-6 parts of aluminum silver paste; and 15-25 parts of diluent; the polyester resin is a saturated polyester with a hydroxyl content of 8-12 wt%;

[0031] Spraying protective topcoat;

[0032] The coating layer applied on the vacuum-plated topcoat is peeled off physically, and the coating layer on the chamfered portion is not peeled off but retained, thereby obtaining a mobile phone middle frame without edge accumulation and covered with a complete coating layer.

[0033] When the present invention is used, a vacuum coating is first performed on a PC material. The topcoat of the vacuum coating process is the non-stick UV coating of the present invention. The CNC process removes the paint accumulated on the edge, forming a chamfer at the edge of the material, and the material is exposed at the chamfer. The two-component coating of CN116478585A is then applied to form an overall coating, covering the vacuum coating topcoat and the exposed material at the chamfer. The two-component coating on the front side is physically peeled off from the vacuum coating topcoat. The vacuum coating topcoat on the front side is dense, smooth and non-sticky, so the coating on it is easy to peel off, while the two-component coating at the chamfer is retained, ultimately forming a filler effect at the chamfer.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The main resin of the present invention adopts high-functionality organic-inorganic hybrid polyurethane resin, and the crosslinking degree and hardness of the paint film are greatly improved compared with conventional vacuum coating topcoat. The nano-inorganic components (such as SiO2) in the resin greatly optimize the surface scratch resistance.

[0036] Another component in the present invention is a relatively low-functionality fluorine-modified polyurethane resin, which effectively adjusts the toughness of the overall paint film and greatly reduces the surface tension of the paint film, making it difficult for the two-component coating of the filler to wet well on the surface of the vacuum plating topcoat, resulting in poor adhesion and making the filler coating easier to peel off.

[0037] The combination of fluorine-modified polyurethane and organic-inorganic hybrid polyurethane enhances both anti-fouling properties and the peelability of the overlying two-component coating. Furthermore, the addition of an anti-fingerprint additive improves the surface slip of the vacuum-plated topcoat, making the filler coating easier to peel. These multiple benefits ensure the long-lasting peelability of the two-component coating.

[0038] Therefore, the use of the coating provided by the present invention, in combination with the easy-to-peel coating described in patent CN116478585A, can well realize the CNC rear edge touch-up process of the frame in the NCVM process. There is no need to design a spray blocking fixture, and the front flying paint part is extremely easy to peel off without residue. In the actual mass production process, the long-term effectiveness problem of paint peeling under the original scheme is improved, and the poor scratch resistance and dirt resistance of the vacuum coating topcoat are improved, so that the new plastic parts coating process proposed by the present invention can be smoothly implemented in mass production, giving the product high added value. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0041] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0042] In some embodiments of the present invention, the non-stick UV coating of the present invention is prepared from raw materials including, by weight:

[0043]

[0044] In some preferred embodiments of the present invention, the thermoplastic acrylic resin has a glass transition temperature (TG) of 80-95°C and can be selected from one or more of DIC 56-1155 and Bolier MB107. This acrylic resin has excellent compatibility with UV resins. When added in an amount of 7-15 parts by weight, it improves workability and hiding power without affecting surface leveling, while also reducing cure shrinkage and cost of the paint film.

[0045] In some preferred embodiments of the present invention, the organic-inorganic hybrid polyurethane resin is a nano-SiO2 hybrid polyurethane having a viscosity of 1000-2000 mPa.s and a functionality of 9-15, for example, 9 or 15. Specifically, it can be selected from one or more of Changxing Chemical's 601X-35 and Hunan Unico Chemical's GN8006. In some preferred embodiments of the present invention, the organic-inorganic hybrid polyurethane resin is present in an amount of 12-15 parts by weight. At this weight, the cured paint film exhibits a high surface hardness, significantly improving the scratch resistance of the vacuum coating topcoat. A reduced addition can negatively impact the scratch resistance.

[0046] In some preferred embodiments of the present invention, the fluorine-modified polyurethane, characterized by its stain resistance and ease of cleaning, has a functionality of 2-5 and can be specifically selected from Zhongshan Jieshida's DSP-670F. When this relatively low-functionality fluorine-modified polyurethane is combined with the aforementioned high-functionality organic-inorganic hybrid polyurethane at an addition level of 8-15 parts by weight, it effectively adjusts the coating's toughness, preventing cracking during CNC processing. It also imparts ultra-low surface tension, enhancing stain resistance and the peelability of the overlying two-component coating.

[0047] In some preferred embodiments of the present invention, the high-functional monomer is DPHA, specifically selected from Sartomer SR399. This high-functional monomer effectively dilutes the system, promoting integration between components. Its high reactivity also mitigates oxygen inhibition, increasing the curing conversion rate of the paint film surface and improving the scratch resistance of the paint film surface.

[0048] In some preferred embodiments of the present invention, the photoinitiator is at least one of 1-hydroxycyclohexyl phenyl ketone and benzophenone.

[0049] In some preferred embodiments of the present invention, the diluent is at least one of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate and diacetone alcohol. In some preferred embodiments of the present invention, the diluent composition is, by weight:

[0050]

[0051] The diluent needs to have a volatilization gradient. Too fast or too slow will cause paint film defects. The combination of the above diluents ensures that the volatilization will not be too fast or too slow.

[0052] In some embodiments of the present invention, the leveling agent is an acrylate or polyether-modified polydimethylsiloxane, specifically a leveling agent purchased from BYK, Germany, model BYK 371. The leveling agent can reduce the surface tension of the UV-resistant coating and prevent craters and oil pits.

[0053] In some embodiments of the present invention, the anti-fingerprint agent is a fluorinated acrylate compound, specifically DSP-730F, a product from Zhongshan Jieshida Co., Ltd. This anti-fingerprint agent can participate in UV cross-linking reactions, long-term accumulation on the surface of the UV coating, imparting anti-fouling and easy-to-clean properties to the coating while also improving peeling performance.

[0054] The present invention improves the hardness and cross-linking density of the coating surface through the application of organic-inorganic hybrid resin, thereby solving the problem of poor scratch resistance of the topcoat; through the application of organic fluorine-modified resin and additives, the tension of the topcoat surface is greatly reduced, so that the touch-up paint coating cannot form effective adhesion thereon, and the easy peeling property of the touch-up paint coating has long-term effectiveness. At the same time, because the vacuum plating topcoat has the characteristics of oleophobic and hydrophobicity, the dirt resistance is also improved, which completely solves the shortcomings exposed in the touch-up paint process of the rear edge of the CNC frame in the NCVM process.

[0055] According to another aspect of the present invention, a method for preparing the UV-resistant coating is provided, comprising the following steps:

[0056] S1. The photoinitiator is mixed with the first portion of the diluent to obtain a system 1 for standby use;

[0057] S2. The thermoplastic acrylic resin, organic-inorganic hybrid polyurethane resin, fluorine-modified polyurethane, high-functional monomer is preheated and then mixed with the second portion of the diluent to obtain system 2;

[0058] S3. The system 1 is added to the system 2 and mixed;

[0059] S4. Add the leveling agent, anti-fingerprint agent and the remaining diluent to the system obtained in step S3 and mix to obtain the coating.

[0060] In some embodiments of the present invention, in step S1, the mass ratio of the total weight of the photoinitiator to the first portion of the diluent is approximately 1:3.

[0061] In some embodiments of the present invention, in step S1, the mixing includes at least one of soaking and stirring, and specifically, the mixture may be soaked for about 20 minutes and then stirred for 10 to 15 minutes.

[0062] In some embodiments of the present invention, in step S2, the mixing temperature is 40-50° C., the mixing is performed by stirring, wherein the stirring speed is 1000±50 rpm, and the mixing time is 25-30 min.

[0063] In some preferred embodiments of the present invention, step S2 further includes preheating the UV type resin separately before the mixing.

[0064] In some embodiments of the present invention, the preheating temperature is 60-70° C. and the preheating time is 3-4 hours.

[0065] In some embodiments of the present invention, in step S2, the second portion of diluent accounts for 1 / 4 to 1 / 3 of the total mass of the diluent.

[0066] In some embodiments of the present invention, in step S3, the mixing is performed by stirring, wherein the rotation speed is 500 to 600 rpm and the mixing time is 25 to 30 minutes.

[0067] In some embodiments of the present invention, in step S4, the mixing is performed by stirring, wherein the rotation speed is 500 to 600 rpm and the mixing time is 15 to 20 minutes.

[0068] According to another aspect of the present invention, the use of the aforementioned UV-resistant coating in the manufacture of electronic products (including consumer electronics products, such as mobile phones), particularly in the manufacture of electronic product casings (e.g., mobile phone midframes), is proposed. The mobile phone midframe is made of polycarbonate. This addresses the problem of paint buildup on the edges of the midframe, which can lead to defects in mass production.

[0069] In some embodiments of the present invention, the use of the non-stick UV coating in the preparation of electronic products comprises the following steps:

[0070] D1. Spray Primer on the surface of the electronic product and level it;

[0071] D2. Spray vacuum coating primer (PVD primer) on the Primer surface after leveling and dry;

[0072] D3 vacuum coating process is performed on the vacuum coating primer after drying;

[0073] D4 spray the vacuum coating primer surface after coating vacuum coating paint, and dry;

[0074] D5. Spray the non-stick UV coating (vacuum coating topcoat) of the present invention onto the dried vacuum coating midcoat and dry it;

[0075] D6. The workpiece undergoes CNC processing to remove 2-3mm of paint accumulation on the edge and form a 45-50° chamfer;

[0076] D7. After cleaning the workpiece, spray the two-component coating described in the invention CN116478585A and dry it;

[0077] D8. Spray protective topcoat and let it dry;

[0078] D9. Physically peel off the front coating (using adhesive tape).

[0079] In some embodiments of the present invention, in step D1, the main components of the primer include, by weight: 8-15 parts solvent-based modified polyurethane acrylate; 5-15 parts thermoplastic acrylic resin; 10-30 parts polycarbonate modified polyurethane acrylate; 1-2 parts 184 photoinitiator; 0.5-1 part TPO photoinitiator; 0.05-0.1 part leveling agent; 3-10 parts polyethylene wax slurry; 1-3 parts modified silica; and 40-60 parts diluent. In some embodiments of the present invention, the primer model is Matsui PAP30737A. In some embodiments of the present invention, in step D1, the primer has a paint film thickness of 15-25 μm.

[0080] In some embodiments of the present invention, in step D1, the leveling is specifically carried out at a temperature range of 50 to 60° C. for 5 to 8 minutes.

[0081] In some embodiments of the present invention, in step D2, the main components of the vacuum coating primer include, by weight: 15-30 parts difunctional urethane acrylate resin; 5-10 parts trifunctional urethane acrylate resin; 5-15 parts reactive monomer; 3-10 parts modified epoxy resin; 3-4 parts photoinitiator; 0.2-0.8 parts leveling agent; and 35-45 parts mixed solvent. In some embodiments of the present invention, the vacuum coating primer is model number Matsui SP110-10002. In some embodiments of the present invention, the vacuum coating primer has a film thickness of 22-28 μm.

[0082] In some embodiments of the present invention, in step D2, the drying includes leveling and curing. Preferably, the leveling is performed at a temperature range of 50 to 60°C for 5 to 8 minutes; the curing is performed at a temperature range of 600 to 800 mJ / cm 2 Curing under high energy UV light.

[0083] In some preferred embodiments of the present invention, in step D3, the vacuum coating is performed using indium as the coating material.

[0084] In some embodiments of the present invention, in step D4, the main components of the vacuum coating intermediate, by weight, include: 3-5 parts difunctional polyurethane acrylate resin; 15-35 parts difunctional solvent-based polyurethane acrylate resin; 3-5 parts reactive monomer; 1-3 parts hexafunctional solvent-based polyurethane acrylate resin; 3-4 parts photoinitiator; 0.2-0.5 parts leveling agent; 0.5-1 parts special additives; and 55-65 parts mixed solvent. In some preferred embodiments of the present invention, the vacuum coating intermediate is model number Matsui SP120-20005. In some embodiments of the present invention, the vacuum coating intermediate has a coating thickness of 6-8 μm.

[0085] In some embodiments of the present invention, in step D4, the drying includes leveling and curing. Preferably, the leveling is leveling at a temperature range of 60-65°C for 5-8 minutes; the curing is at a temperature range of 300-500 mJ / cm 2 Curing under high energy UV light.

[0086] In some embodiments of the present invention, in step D5, the vacuum coating topcoat has a paint film thickness of 20 to 25 μm.

[0087] In some embodiments of the present invention, in step D5, the drying is performed by first leveling at 60-70°C for 5-8 minutes, and then at 1000-1200 mJ / cm 2 Curing under high energy UV light.

[0088] In some embodiments of the present invention, in step D7, the two-component coating comprises the following components, by weight: 65-75 parts of a thermoplastic acrylic resin; 5-10 parts (preferably 5-8 parts) of a polyester resin; 4-6 parts of an aluminum paste; and 15-25 parts of a diluent, wherein the polyester resin is a saturated polyester having a hydroxyl content of 8-12 wt%. In some specific embodiments, the polyester resin has a viscosity of 2000-3000 mPa.s, and the thermoplastic acrylic resin has a TG point of 45-65°C. In some specific embodiments, the raw materials further comprise 0.05-0.1 parts of a leveling agent. In some specific embodiments, the diluent is at least one of ethyl acetate, butyl acetate, butanone, or diacetone alcohol.

[0089] In some embodiments of the present invention, in step D7, a curing agent is added at 3-5 wt% by weight of the coating and a diluent is added at 100-150 wt% by weight of the coating. In some preferred embodiments of the present invention, the diluent comprises, by weight, 20-30 parts of ethyl acetate; 40-50 parts of butyl acetate; and 20-30 parts of butanone. In some embodiments of the present invention, the diluent is GW333A. In some preferred embodiments of the present invention, the curing agent is an isocyanate curing agent. In some embodiments of the present invention, the curing agent is Bayer N-3390.

[0090] In some embodiments of the present invention, in step D7, the two-component coating has a paint film thickness of 8 to 12 μm.

[0091] In some embodiments of the present invention, the drying step D7 is performed by baking at 70-75°C for 12-15 minutes. The baking time in D7 is too short, so the curing agent does not react completely, and the paint film strength is not high. Therefore, an additional baking operation is required after the stripping step to ensure complete reaction and curing.

[0092] In some embodiments of the present invention, in step D8, the main components of the protective topcoat include, by weight: 10-15 parts difunctional polyurethane acrylate resin; 20-30 parts solvent-based polyurethane acrylate; 5-10 parts trifunctional polyurethane acrylate resin; 10-15 parts hexafunctional polyurethane acrylate resin; 5-10 parts monomer; 3-4 parts initiator; 0.2-0.8 parts leveling agent; and 35-45 parts mixed solvent. In some embodiments of the present invention, the protective topcoat is Matsui ET370-50000. In some embodiments of the present invention, the protective topcoat has a film thickness of 20-25 μm.

[0093] In some embodiments of the present invention, in step D8, the drying is specifically performed by first leveling at 60-70°C for 5-8 minutes, and then at 1000-1200 mJ / cm 2 Curing under high energy UV light.

[0094] In some embodiments of the present invention, in step D9, the physical stripping of the front coating is specifically performed by sticking special adhesive tape on the surface of the sprayed workpiece and directly pulling it up to strip off the overcoated coating (two-component coating plus protective topcoat coating).

[0095] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0096] Unless otherwise specified, the reagents used in the specific examples are shown in Table 1.

[0097] Table 1 Information on reagents used in the examples

[0098]

[0099] Example 1

[0100] This embodiment prepares a non-stick UV coating, and the specific process includes the following steps:

[0101] S1. The photoinitiator and the first part of the diluent (mass ratio 1: 3) were mixed (soaked for about 20 minutes, then stirred for 10 to 15 minutes) to obtain a system 1 for standby use;

[0102] S2. The thermoplastic acrylic resin, the organic-inorganic hybrid polyurethane resin, the fluorine-modified polyurethane, and the high-functional monomer are preheated and then mixed with the second portion of the diluent, which accounts for 1 / 3 of the total mass of the diluent (stirring speed is 1000 ± 50 rpm, stirring time is 25 to 30 min, and temperature is controlled at 40 to 50 ° C), to obtain system 2;

[0103] S3. Add the system 1 to the system 2 and mix (stirring speed is 500-600 rpm, time is 25-30 min);

[0104] S4. Add the leveling agent, anti-fingerprint agent, and remaining diluent to the system obtained in step S3 and mix (stirring at 500-600 rpm for 15-20 minutes) to obtain the coating. Stir thoroughly before use, filter through a 400-mesh filter cloth, and then spray. The raw materials used in this example are shown in Table 2.

[0105] Examples 2 to 6 respectively prepared a non-stick UV coating, which differs from Example 1 in that the composition of the raw materials used in the preparation is different. The specific composition is shown in Table 2.

[0106] Table 2 Composition of raw materials used in Examples 1 to 6 (parts by weight)

[0107]

[0108] In Examples 1 to 6, some parameters are range values. It has been verified that the same results can be achieved within the above ranges. Controlling the preparation process according to the range parameters does not affect the quality of the obtained product.

[0109] Comparative Example 1

[0110] This comparative example prepares a UV coating, which differs from Example 6 in that:

[0111] In this comparative example, 15 parts by weight of a common 9-functionality polyurethane acrylic resin (trade name Changxing Chemical 6195-100) is used to replace 15 parts by weight of the organic-inorganic hybrid polyurethane resin in Example 6.

[0112] Comparative Example 2

[0113] This comparative example prepares a UV coating, which differs from Example 6 in that:

[0114] In this comparative example, 10 parts by weight of a common trifunctional polyurethane acrylic resin (trade name: Sadomar CN989) is used to replace 10 parts by weight of the fluorine-modified polyurethane in Example 6.

[0115] Comparative Example 3

[0116] This comparative example prepares a UV coating, which differs from Example 6 in that:

[0117] In this comparative example, 0.7 parts by weight of the anti-fingerprint agent in Example 6 was replaced with 0.7 parts by weight of polyether-modified polydimethylsiloxane (trade name BYK333).

[0118] Comparative Example 4

[0119] This comparative example prepares a UV coating, which differs from Example 6 in that:

[0120] In this comparative example, the high-functional monomer in Example 6 was not added.

[0121] Application Examples

[0122] In this application example, the UV coatings obtained in Examples 1 to 6 and Comparative Examples 1 to 3 are applied to the surface of the middle frame of a smartphone by overlapping spraying, specifically comprising the following steps:

[0123] D1. Spray Primer onto the mobile phone midframe substrate (PC material) to a coating thickness of 20 μm and level it at 55°C for 6 minutes.

[0124] D2. Spray vacuum coating primer (PVD primer) on the surface of the Primer paint film obtained in step D1, with a coating film thickness of 28 μm, and level it at 55 ° C for 6 minutes, at 700 ~ 900 mJ / cm 2 Solidification under the energy of

[0125] D3. Vacuum coating process is performed on the cured primer. The coating material is indium, and the coating thickness is about 20 to 40 nanometers.

[0126] D4. Spray vacuum coating intermediate paint (PVD intermediate paint) on the coating layer with a coating film thickness of 7μm. After leveling at 65℃ for 6min, spray at 400~600mJ / cm 2 Solidification under the energy of

[0127] D5. The UV coatings obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were sprayed on the surface of the vacuum coating, with a coating thickness of 25 μm. After leveling at 65°C for 6 minutes, the UV coatings were sprayed on the surface of the vacuum coating. The ... coating thickness was 25 μm. After leveling at 65°C for 6 minutes, the UV coatings were sprayed on the surface of the 2 Solidification under the energy of

[0128] D6. The workpiece is taken off the production line for CNC processing to remove the 1-2mm paint accumulation on the edge of the workpiece;

[0129] D7. Spraying a two-component coating prepared in Example 6 of the invention patent application disclosed in publication number CN116478585A on a CNC workpiece (5 wt% curing agent N-3390, 150 wt% dilution was added before spraying), the coating film thickness was 10 μm, and leveling was performed at 75 ° C for 12 min;

[0130] D8. Spray protective topcoat, coating film thickness 25μm, leveling at 65℃ for 6min, at 1000-1200mJ / cm 2 Solidification under the energy of

[0131] D9. Peel off the two-component coating plus protective topcoat on the front. The two-component coating plus protective topcoat on the side of the workpiece is adhered to the material and is not peeled off, resulting in a high-quality, high-leveling metal-effect mobile phone middle frame with no edge accumulation.

[0132] Test example

[0133] This test example tests the peelability of the paint film on the smartphone middle frame obtained in the application example and the comparative example, the anti-scratch effect and anti-fouling performance of the workpiece after peeling. The specific results are shown in Table 3.

[0134] Peelability refers to whether there is any residual two-component paint coating on the PVD topcoat after peeling off the topcoat with special adhesive tape (adhesion 3.9-5N / 10mm).

[0135] The peelability is measured by the length of time the workpiece is placed in a natural environment after step D8 in the above application example. Good peelability is achieved when no residue remains on the PVD topcoat surface after peeling it off with special adhesive tape (adhesion 3.9-5N / 10mm).

[0136] The anti-scratch effect is measured by the steel wool test. The test method is: use Japanese bonstar #0000 steel wool, load 500gf, and grind 50 circles on the peeled workpiece surface. The surface scratch level 0 to 2 is qualified.

[0137] The anti-fouling performance test method is as follows: draw a 3cm long straight line on the peeled workpiece with a ZEBRA MO-150-MC (red) marker, store it in a 55℃, 95% RH environment for 2 hours, and wipe it with a concentration of ≥99.5%. If the surface is clean as before and there is no ink residue, it is judged as OK, otherwise it is judged as NG.

[0138] The smartphone middle frame is numbered according to the embodiment from which the non-stick UV coating used therein is obtained. For example, if the non-stick UV coating used in the smartphone middle frame is from embodiment 1, the smartphone middle frame is numbered as embodiment 1.

[0139] Table 3 Performance results of mobile phone midframe obtained from application examples

[0140]

[0141] The results in Table 3 illustrate that the paint films obtained in Examples 1 to 6 are beneficial in extending the peelability, greatly improving the convenience in actual production, and at the same time improving the scratch resistance and anti-fouling performance of the finished workpiece, which is helpful in improving the yield rate; the reason why the scratch resistance of Examples 1 to 2 is relatively poor is due to the insufficient content of the organic-inorganic hybrid resin.

[0142] Compared with Example 6, Comparative Example 1 uses a common 9-functional polyurethane acrylic resin (trade name Changxing Chemical 6195-100) instead of the organic-inorganic hybrid resin in Example 6, which reduces the density of the vacuum plating topcoat surface and increases the surface tension. The two-component coating thereon has a certain adhesion after being completely dried, which affects the peelability and timeliness, and the dirt resistance is also deteriorated.

[0143] Compared with Example 6, Comparative Example 2 uses ordinary trifunctional polyurethane acrylate (trade name Sadomar CN989) to replace the fluorine-modified polyurethane in Example 6, which reduces the smoothness of the vacuum plating topcoat, increases the surface tension, affects the peelability and timeliness, and deteriorates the dirt resistance.

[0144] Compared with Example 6, Comparative Example 3 uses a conventional polyether-modified polydimethylsiloxane additive (trade name BYK333) to replace the reactive fluorine-containing anti-fingerprint additive in Example 6, which reduces the smoothness of the vacuum plating topcoat. At the same time, the non-reactive additive has poor anti-migration properties, which has a negative impact on the peeling timeliness and dirt resistance.

[0145] Compared with Example 6, Comparative Example 4 eliminates the high-functional monomer component, which reduces the overall reaction rate of the system, reduces the double bond conversion rate, and affects the surface density. Therefore, the steel wool resistance is slightly lower than that of Example 6.

[0146] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A UV-resistant coating, characterized in that: The raw materials for preparing the non-stick UV coating include, by weight: 7-15 parts of thermoplastic acrylic resin; 8-15 parts of organic-inorganic hybrid polyurethane resin; 8-15 parts of fluorine-modified polyurethane; 3~5 parts of high-ranking monomer; 2~5 parts of photoinitiator; 0.5~1 part of anti-fingerprint agent; and 45~55 parts of diluent; The organic-inorganic hybrid polyurethane resin is a nano-SiO2 hybrid polyurethane with a functionality of 9 to 15; The functionality of the fluorine-modified polyurethane is 2-5; The anti-fingerprint auxiliary agent is a fluorine-containing acrylate compound; The non-stick UV coating is used as a vacuum coating topcoat, on which an easy-to-peel coating is coated, and the coating formed by the easy-to-peel coating is peeled off from the vacuum coating topcoat; The main components of the easy-to-peel coating include the following components in parts by weight: 65-75 parts of thermoplastic acrylic resin; 5-10 parts of polyester resin; 4-6 parts of aluminum silver paste; and 15-25 parts of diluent. The polyester resin is a saturated polyester with a hydroxyl content of 8-12 wt%.

2. The non-stick UV coating according to claim 1, characterized in that: The preparation raw materials also include 0.2 to 0.5 parts of a leveling agent.

3. The UV-resistant coating according to claim 1 or 2, wherein: The weight portion of the organic-inorganic hybrid polyurethane resin is 12 to 15 parts.

4. The UV-resistant coating according to claim 1 or 2, wherein: The organic-inorganic hybrid polyurethane resin is selected from one or both of 601X-35 of Changxing Chemical and GN8006 of Hunan Unico Chemical; and / or The fluorine-modified polyurethane is selected from DSP-670F of Zhongshan Jieshida; and / or The high-functional monomer is DPHA.

5. The non-stick UV coating according to claim 1, characterized in that: The anti-fingerprint auxiliary agent is selected from DSP-730F produced by Zhongshan Jieshida Company.

6. A method for preparing a non-stick UV coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. The photoinitiator is mixed with the first portion of the diluent to obtain a system 1; S2. The thermoplastic acrylic resin, organic-inorganic hybrid polyurethane resin, fluorine-modified polyurethane, high-functional monomer is preheated and then mixed with the second portion of the diluent to obtain system 2; S3. Add system 1 to system 2 and mix; S4. Add the leveling agent, anti-fingerprint additive and the remaining diluent to the system obtained in step S3 and mix them to obtain the non-stick UV coating.

7. Use of the non-stick UV coating according to any one of claims 1 to 5 in preparing electronic product housings.

8. The use according to claim 7, characterized in that The electronic product shell is a mobile phone middle frame.

9. The use according to claim 7, characterized in that The applications include: After the mobile phone middle frame workpiece completes the vacuum coating process, the paint accumulation on the edges of the workpiece is removed by CNC processing, and the edges of the material are chamfered to obtain a middle frame without edge accumulation; the vacuum coating topcoat in the vacuum coating process is the non-stick UV coating according to any one of claims 1 to 5; The whole part is coated with the easy-to-peel coating and dried, and the coating covers the vacuum coating topcoat and the exposed material at the chamfered part; Spraying protective topcoat; The coating layer applied on the vacuum-plated topcoat is peeled off physically, and the coating layer on the chamfered portion is not peeled off but retained, thereby obtaining a mobile phone middle frame without edge accumulation and covered with a complete coating layer.

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