Bottle cap coating process and bottle cap

Abstract

The invention relates to the field of film plating, and discloses a bottle cap film plating process and a bottle cap. According to the bottle cap film plating process, firstly, surface dirt is removed, and the influence of impurities attached to a coating is eliminated; then an adhesive force improving treatment agent is sprayed and dried, and the problem that the adhesive force of the primer is poor is solved by constructing a stable transition layer of the coating and the base material; after primer spraying, heating leveling and ultraviolet curing are carried out, MPPE injection molding internal stress is adapted, coating defects are avoided, and meanwhile a flat substrate is formed; vacuum aluminum plating is adopted to isolate light to protect wine, so that the problem of insufficient light shielding of a conventional coating is solved; and finally, after finish paint is sprayed, heating leveling and ultraviolet curing are conducted, a coating film layer is protected against abrasion and oxidation, the appearance and durability are both considered, and the effects that the coating is firm and stable in performance are finally achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating, in particular to a bottle cap coating process and bottle cap. BACKGROUND

[0002] ABS (acrylonitrile (A), butadiene (B), styrene (S) terpolymer) has become a commonly used material for bottle cap injection molding and coating process due to its excellent processing performance and basic use characteristics: it has good flexibility, with a breaking elongation of 16% to 30%, which can meet the toughness requirements of bottle cap opening and closing, and avoid brittle fracture caused by excessive rigidity; more importantly, ABS has good melt flowability, can easily fill the mold cavity, is suitable for large-scale injection molding production, and its surface is easy to paint and electroplate, so that appearance decoration and basic anti-counterfeiting can be achieved through coating process.

[0003] However, the shortcomings of ABS are also obvious: the mechanical properties are weak, and the temperature resistance is insufficient, which limits the strength of the bottle cap made of ABS and makes it easy to be artificially disassembled or damaged. In view of the above problems, the characteristics of modified polyphenyl ether (MPPE) are complementary, which has high rigidity, excellent dimensional stability, and outstanding heat distortion temperature, so that the strength and structural stability of the wine bottle cap made of MPPE are greatly improved, which can effectively resist artificial damage and enhance the anti-counterfeiting ability from the physical level.

[0004] However, MPPE also faces significant process problems in bottle cap applications, mainly due to its high melt viscosity, which makes its flowability poor during injection molding, increasing the molding difficulty and causing the surface of the molded bottle cap to be abnormally smooth. In addition, the close molecular arrangement makes the surface polarity very low, lacking the necessary anchoring points for painting and electroplating. Moreover, the strong chemical inertness of MPPE itself further enhances the surface inertness during injection molding, making it difficult to form effective bonding with the coating material. Therefore, whether it is conventional painting or electroplating process, problems such as coating peeling and uneven coating are likely to occur, making it difficult to achieve appearance decoration and coating anti-counterfeiting process for bottle caps.

[0005] Therefore, the existing technology needs to be improved and enhanced. SUMMARY

[0006] In view of the shortcomings of the existing technology, the purpose of the present application is to provide a bottle cap coating process and bottle cap, aiming to solve the problem of MPPE bottle cap coating.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions: A bottle cap coating process, comprising the following steps: S1. removing dirt on the surface of the bottle cap; S2. spraying a primer adhesion enhancer on the surface of the bottle cap, and forming an adhesion enhancement layer after drying; S3. Spraying a primer on the surface of the adhesion promoting layer, and after heating to make the primer flow flat, forming a primer layer by ultraviolet curing; S4. Plating an aluminum film on the surface of the bottle cap in a vacuum environment to form a plating film layer; S5. Spraying a topcoat on the surface of the plating film layer, and after heating to make the topcoat flow flat, forming a topcoat layer by ultraviolet curing.

[0008] The bottle cap plating film process, wherein the specific operation of removing dirt from the surface of the bottle cap in step S1 is: wiping the surface of the bottle cap with 95° alcohol; and then electrostatically cleaning the bottle cap.

[0009] The bottle cap plating film process, wherein the primer adhesion promoting agent of step S2 comprises the following components by weight: 5-15 parts of acrylic resin, 30-50 parts of butyl acetate, and 30-50 parts of ethyl acetate; and the primer adhesion promoting agent is dried at a temperature of 45-60°C.

[0010] The bottle cap plating film process, wherein the primer in step S3 comprises the following components by weight: 15-30 parts of polyurethane acrylic resin, 15-30 parts of active monomer, 1-5 parts of photoinitiator, 20-30 parts of diacetone alcohol, and 20-30 parts of isopropyl alcohol; and the primer is surface flow flat at a temperature of 45-55°C.

[0011] The bottle cap plating film process, wherein the line speed when spraying the primer is ≥12 m / min; and the energy of the ultraviolet light when ultraviolet curing the primer is 600-650 mj / cm 2 .

[0012] The bottle cap plating film process, wherein the thickness of the plating film layer in step S4 is 10-15 μm.

[0013] The bottle cap plating film process, wherein electrostatic cleaning of the plating film layer is additionally required between step S4 and step S5, and the bottle cap after electrostatic cleaning is baked at a temperature of 45-60°C for haze removal treatment.

[0014] The bottle cap plating film process, wherein the topcoat of step S5 comprises the following components by weight: 30-45 parts of ethyl acetate, 20-35 parts of butyl acetate, 20-30 parts of trimethylolpropane triacrylate, and 10-15 parts of epoxy resin; and the topcoat is surface flow flat at a temperature of 45-55°C.

[0015] The bottle cap plating film process, wherein the energy of the ultraviolet light when ultraviolet curing the topcoat is 650-720 mj / cm 2 .

[0016] A bottle cap is made by the bottle cap coating process described above; the bottle cap comprises an MPPE bottle cap body, and an adhesion promotion layer, a primer layer, a coating layer, and a topcoat layer arranged in sequence from the inside to the outside on the surface of the MPPE bottle cap body.

[0017] Advantages: The application provides a bottle cap coating process and a bottle cap, the bottle cap coating process first eliminates the influence of pollutants through physical cleaning to create clean conditions for the direct contact of the coating and the substrate. Secondly, the primer adhesion promotion treatment agent is sprayed and dried, which is the key to solving the surface inertness of the MPPE. The MPPE has low surface energy and weak polarity, and the conventional coating is difficult to adhere. However, the adhesion promotion treatment agent can form a stable combination with the surface of the MPPE through a specific action, and can build a stable transition layer between the coating and the substrate. At the same time, a dense layer is formed after drying, which solves the problem of poor adhesion of the coating caused by the inertness of the substrate and lays a foundation for the subsequent adhesion of the primer. Then, the primer is sprayed, heated, leveled, and ultraviolet cured to further strengthen the stability of the coating. After injection molding, the MPPE is prone to have internal stress differences. If the primer is directly cured, appearance defects may occur due to stress release. Heating and leveling can make the primer spread fully and eliminate bubbles, adapt to the stress distribution of the substrate, and quickly form a high-strength primer layer through ultraviolet curing. This not only avoids the interface damage caused by excessive penetration of solvents, but also provides a smooth and wear-resistant substrate for subsequent aluminum plating, solving the problem that the coating is prone to defects due to the stress of the substrate. Then, vacuum aluminum plating forms a uniform and dense aluminum film layer to effectively block light according to the requirement of light protection of wine. At the same time, the metallic properties of the aluminum film also add color to the appearance. Finally, the topcoat is sprayed, heated, leveled, and ultraviolet cured. The coating layer is prone to wear and tear and corrosion by moisture. The topcoat ensures the surface to be smooth through heating and leveling, and forms a high-weather-resistant and scratch-resistant protective layer through ultraviolet curing, solving the problems of wear and tear and oxidation of the coating layer. At the same time, the topcoat takes into account the decoration and durability, and finally realizes the comprehensive effect of firm coating, stable performance, and standard appearance. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The adhesion test results of the bottle caps prepared in Example 1 and Example 2 are shown in the schematic diagram.

[0019] Figure 2 The adhesion test results of the bottle caps prepared in Comparative Example 1 and Comparative Example 2 are shown in the schematic diagram.

[0020] Figure 3 The schematic diagram of the bottle cap prepared in Example 1 is shown in Figure 1 .

[0021] Figure 4 The schematic diagram of the bottle cap prepared in Example 1 is shown in Figure 2 .

[0022] Figure 5 The schematic diagram of the bottle cap prepared in Comparative Example 3 is shown in DETAILED DESCRIPTION

[0023] The present application provides a bottle cap film plating process and a bottle cap. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the protection scope of the present application.

[0024] The present application provides a bottle cap film plating process, comprising the following steps: (1) The surface of the bottle cap is wiped with 95° alcohol. The alcohol has both fat solubility and volatility. It can not only efficiently dissolve and remove oily contaminants such as mold release agent and processing oil film remaining in the injection molding process, but also quickly volatilize without leaving water stains or residues. At the same time, it can also simultaneously remove dust particles attached to the surface of the bottle cap. Then, the floating dust on the surface of the bottle cap is removed by an electrostatic dust removal gun. The electrostatic dust removal is a secondary cleaning. By means of the adsorption force generated by high voltage electrostatic, fine floating dust, fibers and other light impurities that may remain after alcohol wiping can be removed. In particular, it can eliminate static electricity generated on the surface of the bottle cap due to friction, avoiding the re-attachment of dust due to static electricity in subsequent processes. Through the above double pretreatment, the interference of the initial contaminants on the surface of the MPPE bottle cap on the adhesion of the coating is solved, ensuring that the adhesion promoter, primer and other subsequent spraying can directly contact the clean substrate surface, laying a key foundation for forming a uniform and firm coating.

[0025] (2) A primer adhesion promoter is sprayed on the surface of the bottle cap, and dried in an oven at a temperature of 45-60°C to form an adhesion promotion layer. Specifically, the primer adhesion promoter comprises the following components: 5-15 parts of acrylic resin, 30-50 parts of butyl acetate, and 30-50 parts of ethyl acetate. After spraying the above primer adhesion promoter, the butyl acetate and ethyl acetate therein act as solvents, which can further dissolve and remove a small amount of oil stains that may remain after pretreatment. At the same time, by means of the penetration of the solvents, the acrylic resin is more evenly spread on the surface of the bottle cap. Subsequently, drying is carried out in an oven at a temperature of 45-60°C. After the solvents volatilize, the acrylic resin forms intermolecular forces with the surface of the MPPE by virtue of its own polar groups such as carboxyl and hydroxyl groups, thereby constructing an active transition layer on the originally inert substrate surface. The adhesion promotion layer not only strengthens the surface cleanliness through secondary oil removal, but more importantly, through the polar properties of the acrylic resin, it makes up for the lack of surface polarity of the MPPE, providing a good adhesion substrate for the subsequent primer and greatly improving the interfacial bonding force between the primer and the substrate, thereby fundamentally solving the problem of poor coating adhesion caused by the inert surface of the MPPE.

[0026] (3) The primer is sprayed on the surface of the adhesion promotion layer. It is noted that the line speed of spraying the primer is ≥ 12 m / min. For the MPPE bottle cap, due to the high melt viscosity and uneven cooling rate during the injection molding process, stress differences are easily formed inside, which leads to slight differences in the molecular arrangement density and microscopic pores in different areas of the surface. Therefore, when the line speed of spraying the primer is lower than 12 m / min, the residence time of the primer on the surface of the bottle cap is prolonged, and solvents such as diacetone alcohol and isopropyl alcohol will excessively penetrate into the stress concentration area of the MPPE surface. The intermolecular force of this area is relatively weak, which is easy to be swelled by the solvent, and the resin component in the primer will penetrate into the surface layer of the substrate along with the solvent. When the solvent evaporates and the primer solidifies, the substrate and the coating in the swelled area will have different shrinkage rates, and irregular wrinkles will be formed on the surface, i.e. the primer will bite the surface. When the line speed is ≥ 12 m / min, the adhesion amount of the primer on the surface is uniform and the residence time is short, the penetration depth of the solvent is controllable, and only a moderate infiltration is formed on the surface layer, which will not damage the stability of the substrate interface and keep the surface of the bottle cap bright and smooth.

[0027] Subsequently, the bottle cap is placed in an oven with a temperature of 45-55°C for paint surface leveling. After leveling, the bottle cap is subjected to ultraviolet drying and curing, and the energy of the ultraviolet light is 600-650 mj / cm 2 , to form a primer layer.

[0028] Specifically, the primer includes the following components: 15-30 parts of polyurethane acrylic resin, 15-30 parts of active monomer (optionally multi-functional acrylate such as trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), tripropylene glycol diacrylate (TPGDA) and the like), 1-5 parts of photoinitiator (optionally free radical initiator such as 1-hydroxycyclohexyl phenyl ketone (184), 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide (TPO), 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) and the like), 20-30 parts of diacetone alcohol, and 20-30 parts of isopropyl alcohol. In the primer formulation, the 15-30 parts of polyurethane acrylic resin can form chemical and physical bonding with the acrylic resin of the underlying adhesion promoting layer due to certain flexibility and polarity, the 15-30 parts of active monomer adjusts the viscosity of the system and participates in the curing reaction, the 1-5 parts of photoinitiator initiates crosslinking under the action of ultraviolet light, and the mixed solvent composed of 20-30 parts of diacetone alcohol and 20-30 parts of isopropyl alcohol is volatilized by gradient, and is combined with the leveling treatment at 45-55°C to ensure uniform spreading of the paint, and to eliminate bubbles and pinholes. When the leveling temperature is too low, the solvents such as diacetone alcohol and isopropyl alcohol in the primer volatilize slowly, and the paint is difficult to spread fully on the surface, and is prone to leave bubbles, pinholes or sagging marks; if the leveling temperature is too high, the solvents volatilize quickly, and the paint is already surface dried before it is fully leveled, forming orange peel, shrinkage and other surface defects. For the MPPE bottle cap with smooth surface and low polarity, only at the appropriate temperature, the paint can uniformly cover the substrate with the help of the flowability of the solvent, and the resin molecules are orderly arranged through slow volatilization to form a smooth and dense coating, providing a continuous adhesion interface for subsequent plating.

[0029] Finally, 600-650 mj / cm 2 The primer layer cured by ultraviolet energy not only can further seal the micro defects on the surface of MPPE, but also can provide a smooth and dense adhesion interface for subsequent vacuum aluminum plating, and can buffer the stress of the substrate by its own mechanical properties to avoid cracking of the subsequent plating layer due to small deformation of the substrate. It is the key functional layer connecting the underlying adhesion promoting layer and the upper plating layer. When the energy is insufficient, the photoinitiator cannot be completely decomposed, and the crosslinking reaction of polyurethane acrylic resin and active monomer is not complete, resulting in insufficient hardness and poor solvent resistance of the primer layer, which is easily eroded during subsequent aluminum plating or spray finishing. If the energy is too high, the coating will be over-crosslinked, resulting in internal stress, and combined with the internal stress of MPPE formed by injection molding, it may cause the primer layer to crack or peel off from the underlying adhesion promoting layer. The above energy range can ensure that the primer forms a three-dimensional network structure with moderate crosslinking in a short time, which not only has enough mechanical strength to support the subsequent process, but also has certain flexibility to buffer the stress of the substrate, finally realizing the stability and reliability of the coating performance.

[0030] (4) The surface of the bottle cap is plated with aluminum film in a vacuum environment to form a plating layer with a thickness of 10-15 μm for enhancing light resistance. The vacuum environment can eliminate the interference of air impurities on the deposition of aluminum atoms, ensure that the aluminum film is evenly covered on the surface of the primer layer, and avoid oxidation or pinhole of the plating layer caused by oxygen and dust in the air; and aluminum itself has extremely high light resistance, the metal film layer formed can effectively block ultraviolet rays, visible light and other light from penetrating, prevent the oxidation and deterioration of the wine liquid in the bottle caused by light, and protect the stability of the wine flavor. In addition, the dense aluminum film can also provide a smooth surface with certain adhesion for subsequent spraying of the topcoat, avoid the penetration problem that may occur when the topcoat directly contacts the primer layer, and at the same time give the bottle cap a metallic appearance and texture, improving the visual level of the product.

[0031] The above thickness range can not only ensure sufficient light resistance and plating firmness, but also control the process cost and avoid quality problems caused by improper thickness. When the thickness of the plating layer is less than 10 μm, the aluminum film is prone to local ultra-thin or pinhole, resulting in an increase in light transmittance and failure to achieve the ideal light resistance effect, and the mechanical strength of the thin plating layer is insufficient and is prone to wear and tear during subsequent processing or use; when the thickness of the plating layer exceeds 15 μm, on the one hand, it will increase the consumption of aluminum material and the vacuum plating time, and increase the production cost, and on the other hand, the internal stress of the over-thick aluminum film layer will increase, and the bonding force with the primer layer will decrease, which may cause cracking and warping during subsequent leveling and curing due to thermal expansion and contraction, thereby affecting the overall stability of the coating.

[0032] (5) The bottle cap is stored in the workshop environment for a long time, and dust is deposited on its surface; in addition, the humidity in the air may form a fine water film on the plating layer during long-term storage. If the above pollutants are not removed, it will cause defects such as shrinkage, pinholes or uneven coating of the topcoat during spraying, so the bottle cap product needs to be electrostatically dusted before spraying the topcoat to avoid the embedding of particulate matter into the topcoat layer affecting the flatness. The bottle cap after electrostatic dusting also needs to be baked at a temperature of 45-60 ℃ for defogging treatment, which can evaporate the surface water film through moderate heating, and at the same time, the aluminum film layer or the bottom coating will not be deformed due to excessive temperature, ensuring that the substrate is in a dry state. The above treatment can eliminate secondary pollution introduced during storage, allowing the topcoat to adhere uniformly and form a good bond with the aluminum film layer, laying a foundation for the density and gloss of the final coating.

[0033] In addition, the temperature range for defogging is the key to balancing the water evaporation efficiency and material stability. When the temperature is lower than 45 ℃, the water film evaporates slowly and it is difficult to completely remove the moisture, and the residual trace of moisture will form bubbles or pinholes after the topcoat is cured; when the temperature is higher than 60 ℃, although the water evaporates faster, it may cause stress between the plating layer and the primer layer due to the difference in thermal expansion, especially for MPPE which is a rigid material, excessive heating may exacerbate the release of internal stress of the substrate, causing micro-cracks in the coating.

[0034] (6) Spraying a topcoat on the surface of the coating layer, and performing leveling at a temperature of 45-55℃. The bottle cap after leveling enters ultraviolet drying and curing, and the energy of the ultraviolet light is 650-720 mj / cm 2 . A topcoat layer is formed. Specifically, the topcoat includes the following components: 30-45 parts of ethyl acetate, 20-35 parts of butyl acetate, 20-30 parts of trimethylolpropane triacrylate (TMPTA), and 10-15 parts of epoxy resin. After spraying the above topcoat, the leveling treatment at 45-55℃ enables the mixed solvent to volatilize by gradient, so that the paint fully spreads and fills the fine concave-convex surface of the aluminum film layer, forming a smooth and flat coating base; then, through ultraviolet curing at 650-720 mj / cm 2 , the TMPTA as a multifunctional monomer can cross-link with the epoxy resin to form a high-density three-dimensional network structure, giving the topcoat layer excellent wear resistance, scratch resistance and chemical corrosion resistance. The topcoat layer not only physically isolates the water vapor and pollutants in the external environment from corroding the aluminum film layer, preventing the aluminum film from oxidizing and discoloring, but also realizes different gloss and texture, improving the appearance and decoration of the bottle cap; at the same time, the mechanical properties after curing can form synergy with the bottom structure, further enhancing the impact resistance and adhesion of the overall coating, ensuring that the bottle cap maintains a perfect appearance and stable function during transportation and use, and finally realizes protection, decoration and durability.

[0035] From the formula, the ratio of 30-45 parts of ethyl acetate and 20-35 parts of butyl acetate mixed solvent is to realize the gradient volatilization effect of fast drying and medium speed drying, and the ethyl acetate quickly drives the paint to spread initially, avoiding sagging, and the butyl acetate delays the volatilization of the deep layer solvent, providing sufficient time for the paint to fill the fine concave-convex of the aluminum film layer. If the ratio is unbalanced, it is easy to cause bubbles to remain due to slow solvent volatilization, or to form orange peel due to fast volatilization; the ratio of 20-30 parts of TMPTA and 10-15 parts of epoxy resin is the key to balance the cross-linking density and flexibility, and insufficient TMPTA will result in insufficient hardness and wear resistance of the topcoat, and excessive TMPTA will easily crack, and too low a proportion of epoxy resin will reduce chemical resistance, and too high a proportion will increase the risk of rigid stacking.

[0036] The leveling temperature is limited to 45-55℃, which balances the solvent volatilization efficiency and the stability of the coating layer. If the temperature is too low, the solvent volatilizes slowly, and the paint cannot fully spread, leaving pinholes; if the temperature is too high, the surface solvent quickly dries, forming shrinkage holes, and the aluminum film and the primer may also have decreased adhesion due to thermal expansion differences. The ultraviolet curing energy is set to 650-720 mj / cm 2, which is higher than the primer energy to adapt to the more complex cross-linking requirements of the topcoat, and insufficient energy will lead to incomplete cross-linking of TMPTA and epoxy resin, poor solvent resistance and adhesion of the topcoat; and too high energy will cause excessive cross-linking, preventing the topcoat layer from cracking due to the superimposed internal stress of the MPPE substrate and the stress of the aluminum film layer, so that the topcoat layer can form a smooth and smooth decorative surface and also serve as a protective barrier to prevent water vapor and pollutants.

[0037] The application also provides a bottle cap, which comprises an MPPE bottle cap body, and an adhesion improvement layer, a primer layer, a plating layer and a topcoat layer arranged in sequence from the inside to the outside on the surface of the MPPE bottle cap body. Figure 4 As can be seen, the bottle cap is made of MPPE material (the bottle cap made of ABS material is milky white). First, the MPPE bottle cap body has the characteristics of high rigidity, good dimensional stability and high heat distortion temperature, which fundamentally resists artificial disassembly or damage, greatly improves the physical anti-counterfeiting capability, and makes up for the shortcomings of the traditional ABS bottle cap in mechanical properties and temperature resistance; second, the coating structure from the inside to the outside solves the problem of MPPE surface inertness layer by layer, the adhesion improvement layer introduces polar groups through acrylic resin to build chemical anchor points for subsequent coatings, and improves the problem of poor coating adhesion caused by low surface energy of MPPE; the primer layer forms a smooth and dense transition layer through precise process control (line speed, leveling temperature and curing energy), which avoids the bottom biting defect and provides a stable adhesion substrate for the plating layer; the vacuum aluminum plating layer (10-15 μm) efficiently blocks light to prevent the oxidation and deterioration of the wine in the bottle due to light, and its metallic luster enhances the appearance; the outermost topcoat layer is cross-linked by TMPTA and epoxy resin, which gives the bottle cap excellent wear resistance and chemical resistance, protects the plating layer from oxidation and wear, and improves the product grade through a smooth and glossy surface. The overall structure not only fully utilizes the high performance advantages of MPPE material (anti-damage, dimensional stability), but also breaks through the process bottleneck of difficult plating, and finally realizes the characteristics of high anti-counterfeiting, strong protection and excellent decoration, effectively prevents fake wine problems, and ensures the appearance and functional stability of the bottle cap during long-term use.

[0038] In order to further illustrate the bottle cap plating process and bottle cap provided by the application, the following examples and comparative examples are provided.

[0039] Example 1 A bottle cap plating process, comprising the following steps: 1. Wipe the surface of the bottle cap with 95° alcohol, and then remove the dust on the surface of the bottle cap with an electrostatic dust gun.

[0040] 2. A primer adhesion promoting treatment agent is sprayed on the surface of the cap, and dried in an oven at a temperature of 55°C to form an adhesion promoting layer. Specifically, the primer adhesion promoting treatment agent includes the following components: 8 parts of an acrylic resin, 40 parts of butyl acetate, and 35 parts of ethyl acetate.

[0041] 3. A primer is sprayed on the surface of the adhesion promoting layer, and the primer is sprayed at a line speed of 14 m / min. Subsequently, the cap is placed in an oven at a temperature of 50°C to perform a paint leveling. The leveled cap is subjected to UV drying and curing, and the energy of the UV light is 630 mj / cm 2 , to form a primer layer. Specifically, the primer includes the following components: 20 parts of a polyurethane acrylic resin, 22 parts of a reactive monomer, 2 parts of a photoinitiator, 28 parts of diacetone alcohol, and 22 parts of isopropyl alcohol.

[0042] 4. An aluminum film is plated on the surface of the cap in a vacuum environment to form a plating layer with a thickness of 13 μm.

[0043] 5. The cap is subjected to electrostatic dust removal. Then, the cap is subjected to a haze removal treatment at a temperature of 58°C.

[0044] 6. A topcoat is sprayed on the surface of the plating layer, and the paint is leveled at a temperature of 48°C. The leveled cap is subjected to UV drying and curing, and the energy of the UV light is 690 mj / cm 2 , to form a topcoat layer. Specifically, the topcoat includes the following components: 38 parts of ethyl acetate, 25 parts of butyl acetate, 26 parts of trimethylolpropane triacrylate, and 12 parts of an epoxy resin.

[0045] Example 2 A cap plating process includes the following steps: 1. The surface of the cap is wiped with 95° alcohol, and then the cap is subjected to electrostatic dust removal.

[0046] 2. A primer adhesion promoting treatment agent is sprayed on the surface of the cap, and dried in an oven at a temperature of 45°C to form an adhesion promoting layer. Specifically, the primer adhesion promoting treatment agent includes the following components: 15 parts of an acrylic resin, 32 parts of butyl acetate, and 48 parts of ethyl acetate.

[0047] 3. A primer is sprayed on the surface of the adhesion promoting layer, and the primer is sprayed at a line speed of 12 m / min. Subsequently, the cap is placed in an oven at a temperature of 55°C to perform a paint leveling. The leveled cap is subjected to UV drying and curing, and the energy of the UV light is 600 mj / cm 2 , to form a primer layer. Specifically, the primer includes the following components: 15 parts of a polyurethane acrylic resin, 18 parts of a reactive monomer, 4 parts of a photoinitiator, 22 parts of diacetone alcohol, and 29 parts of isopropyl alcohol.

[0048] 4. The surface of the bottle cap is plated with aluminum film under vacuum environment to form a plating layer with a thickness of 10 μm.

[0049] 5. The bottle cap is electrostatically dedusted. Then the bottle cap is baked at a temperature of 45°C for haze removal treatment.

[0050] 6. The surface of the plating layer is sprayed with topcoat, and topcoat leveling is performed at a temperature of 55°C. The leveled bottle cap is subjected to ultraviolet drying and curing, and a topcoat layer is formed with an ultraviolet light energy of 720 mj / cm 2 . Specifically, the topcoat includes the following components: 45 parts of ethyl acetate, 30 parts of butyl acetate, 20 parts of trimethylolpropane triacrylate, and 15 parts of epoxy resin.

[0051] Example 3 A bottle cap plating process includes the following steps: 1. The surface of the bottle cap is wiped with 95° alcohol, and then the bottle cap surface is dedusted with an electrostatic dedusting gun.

[0052] 2. The surface of the bottle cap is sprayed with a primer adhesion enhancer, and drying is performed in an oven at a temperature of 60°C to form an adhesion enhancement layer. Specifically, the primer adhesion enhancer includes the following components: 5 parts of acrylic resin, 48 parts of butyl acetate, and 30 parts of ethyl acetate.

[0053] 3. The surface of the adhesion enhancement layer is sprayed with primer, and the line speed during spraying of the primer is 16 m / min. Subsequently, the bottle cap is placed in an oven at a temperature of 45°C for paint leveling. The leveled bottle cap is subjected to ultraviolet drying and curing, and a primer layer is formed with an ultraviolet light energy of 650 mj / cm 2 . Specifically, the primer includes the following components: 30 parts of polyurethane acrylic resin, 25 parts of active monomer, 1 part of photoinitiator, 30 parts of diacetone alcohol, and 20 parts of isopropyl alcohol.

[0054] 4. The surface of the bottle cap is plated with aluminum film under vacuum environment to form a plating layer with a thickness of 15 μm.

[0055] 5. The bottle cap is electrostatically dedusted. Then the bottle cap is baked at a temperature of 52°C for haze removal treatment.

[0056] 6. The surface of the plating layer is sprayed with topcoat, and topcoat leveling is performed at a temperature of 45°C. The leveled bottle cap is subjected to ultraviolet drying and curing, and a topcoat layer is formed with an ultraviolet light energy of 650 mj / cm 2 . Specifically, the topcoat includes the following components: 30 parts of ethyl acetate, 35 parts of butyl acetate, 30 parts of trimethylolpropane triacrylate, and 10 parts of epoxy resin.

[0057] Comparative Example 1 The coating process of Comparative Example 1 is basically the same as that of Example 1, except that the primer adhesion promoting treatment agent of Comparative Example 1 comprises the following components: 3 parts of acrylic resin, 55 parts of butyl acetate, and 42 parts of ethyl acetate.

[0058] Comparative Example 2 The coating process of Comparative Example 2 is basically the same as that of Example 1, except that the primer adhesion promoting treatment agent of Comparative Example 2 comprises the following components: 18 parts of acrylic resin, 28 parts of butyl acetate, and 54 parts of ethyl acetate.

[0059] Comparative Example 3 The coating process of Comparative Example 3 is basically the same as that of Example 1, except that the line speed is 10 m / min when the primer is sprayed in Comparative Example 3.

[0060] Performance Test: 1. The adhesion was determined according to the paint film grid method (GB / T 9286-1998), wherein the adhesion of Example 1 ( Figure 1 left) and Example 2 ( Figure 1 right) were both 5B, and the adhesion of Comparative Example 1 was 2B ( Figure 2 left). The reason is that the amount of polar groups such as carboxyl and hydroxyl groups is insufficient due to only 3 parts of acrylic resin, resulting in weak intermolecular forces with the surface of MPPE, and unable to form effective chemical anchor points; at the same time, 55 parts of butyl acetate as a medium speed solvent, excessive amount will delay the drying speed, and the molecules of acrylic resin cannot be quickly and orderly arranged when drying in the 55°C oven, but instead, local aggregation occurs due to long time uncured, resulting in small pores in the adhesion promoting layer and loose combination with the surface of MPPE. The adhesion of Comparative Example 2 was 3B ( Figure 2 right). The reason is that the excessive resin leads to abnormal increase in system viscosity due to 18 parts of acrylic resin, which increases the spreading difficulty of resin on the surface of MPPE when spraying, and easily forms local thick film; the fast-drying solvent ratio is too high due to 28 parts of butyl acetate and 54 parts of ethyl acetate, and the surface layer solvent volatilizes quickly during the drying process, while the internal resin has not completely leveled, resulting in a decrease in the density of the adhesion promoting layer, so although the total amount of acrylic resin in Comparative Example 2 is high and the polar groups are sufficient, the defects in the coating structure weaken the adhesion with the primer.

[0061] 2. From Figure 3 and Figure 5It can be seen that the line speed of Example 1 is high, and the solvent does not penetrate to the stress weak area of the MPPE; at the same time, after the resin component spreads rapidly, it is uniformly solidified with the solvent gradient volatilization, and the surface is free of wrinkles, finally presenting a bright and smooth appearance. The line speed of Comparative Example 3 is reduced, the residence time of the primer on the surface of the bottle cap is prolonged, the solvent penetrates to the stress weak area of the MPPE, the primer resin penetrates into the surface layer of the substrate with the solvent, and the difference in shrinkage rate between the substrate and the coating in the swelling area is significant when the solvent volatilizes and the primer solidifies, finally forming irregular wrinkle marks on the surface (i.e. "biting bottom").

[0062] It can be understood that, for those skilled in the art, equivalent replacements or changes can be made according to the technical solutions and inventive concepts of the present application, and all such changes or replacements shall fall within the protection scope of the present application.

Claims

1. A bottle cap coating process, characterized in that, Includes the following steps: S1. Remove dirt from the surface of the bottle cap; S2. Spray a primer adhesion enhancer onto the surface of the bottle cap, and after drying, form an adhesion enhancer layer; S3. Spray primer onto the surface of the adhesion enhancement layer, heat to level the primer, and then cure with ultraviolet light to form a primer layer; S4. Apply an aluminum film to the surface of the bottle cap in a vacuum environment to form a coating layer; S5. Spray a topcoat onto the surface of the coating layer, heat it to level the topcoat, and then cure it with ultraviolet light to form a topcoat layer.

2. The bottle cap coating process according to claim 1, characterized in that, The specific steps for removing dirt from the bottle cap surface in step S1 are as follows: wipe the bottle cap surface with 95° alcohol; then perform electrostatic dust removal on the bottle cap.

3. The bottle cap coating process according to claim 1, characterized in that, The primer adhesion enhancer in step S2 comprises the following components by weight: 5-15 parts acrylic resin, 30-50 parts butyl acetate, and 30-50 parts ethyl acetate; the primer adhesion enhancer is dried at a temperature of 45-60°C.

4. The bottle cap coating process according to claim 1, characterized in that, The primer in step S3 comprises the following components by weight: 15-30 parts polyurethane acrylic resin, 15-30 parts reactive monomer, 1-5 parts photoinitiator, 20-30 parts diacetone alcohol, and 20-30 parts isopropanol; the primer is leveled at a temperature of 45-55°C.

5. The bottle cap coating process according to claim 4, characterized in that, The linear velocity during spraying of the primer is ≥12 m / min; the energy of the ultraviolet light during UV curing of the primer is 600–650 mJ / cm. 2 .

6. The bottle cap coating process according to claim 1, characterized in that, In step S4, the thickness of the coating layer is 10–15 μm.

7. The bottle cap coating process according to claim 1, characterized in that, Between steps S4 and S5, electrostatic dust removal is required on the coating layer, and the bottle cap after electrostatic dust removal is baked at a temperature of 45-60°C to remove fog.

8. The bottle cap coating process according to claim 1, characterized in that, The topcoat in step S5, calculated by weight, comprises the following components: 30-45 parts ethyl acetate, 20-35 parts butyl acetate, 20-30 parts trimethylolpropane triacrylate, and 10-15 parts epoxy resin; the topcoat is leveled at a temperature of 45-55°C.

9. The bottle cap coating process according to claim 8, characterized in that, The energy of the ultraviolet light used to cure the topcoat is 650–720 mJ / cm. 2 .

10. A bottle cap, characterized in that, The bottle cap is made by the bottle cap coating process described in any one of claims 1-9; the bottle cap includes an MPPE bottle cap body, and an adhesion enhancement layer, a primer layer, a coating layer, and a topcoat layer sequentially disposed on the surface of the MPPE bottle cap body from the inside to the outside.

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