Water-based low-VOC environment-friendly black insulating paint and coating method thereof on surface of aluminum foil

Abstract

The invention discloses a water-based low-VOC environment-friendly black insulating coating and a coating method thereof on the surface of an aluminum foil, belongs to the technical field of environment-friendly coatings, and is suitable for insulation protection in the fields of electronic packaging, flexible circuit boards and the like. The paint has the characteristics of low volatile organic compounds (VOC), high insulativity, excellent adhesive force and rapid low-temperature curing: 1, zero benzene residue and low VOC: water is completely used as a solvent, benzene solvents are not detected, and the VOC content is less than or equal to 50g / L (the content of a traditional solvent type paint is greater than 500g / L); 2, high insulating property: through the synergistic effect of nano aluminum oxide and boron nitride, the dielectric strength of the coating is greater than or equal to 35kV / mm (only 15kV / mm-20kV / mm); and 3, low-temperature curing and high adhesive force: an aziridine cross-linking agent is added, curing is performed at 80-100 DEG C for 3 minutes, the adhesive force is greater than or equal to 98% (a cross-cut method), and the base material does not deform.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environment-friendly coatings, and particularly relates to a water-based low-VOC environment-friendly black insulating coating and a coating method thereof on the surface of aluminum foil. BACKGROUND

[0002] Traditional aluminum foil coatings mostly adopt solvent-based systems, which have problems such as high residual benzene solvents, excessive volatile organic compound (VOC) emissions (>150 g / L), and do not meet the requirements of environmental protection regulations.

[0003] In addition, when the existing coatings are coated on ultra-thin aluminum foil (thickness ≤20 µm), the substrate is often deformed due to insufficient adhesion, poor insulation performance, or the need for high-temperature curing (≥150℃). For example, the solvent residual amount of commercially available solvent-based aluminum foil coatings is generally >8 mg / m², and the dielectric strength after curing is less than 20 kV / mm.

[0004] In addition, a single filler system easily leads to poor coating uniformity, affects long-term stability, and is difficult to meet the insulation requirements of high-end fields such as new energy vehicle battery aluminum foil. SUMMARY

[0005] In view of the problems in the prior art, such as high residual benzene solvents, excessive VOC emissions (>150 g / L) of traditional aluminum foil coatings, and when the existing coatings are coated on ultra-thin aluminum foil (thickness ≤20 µm), the substrate is often deformed due to insufficient adhesion, poor insulation performance, or the need for high-temperature curing (≥150℃), leading to poor coating uniformity and affecting long-term stability, the present application provides a water-based low-VOC environment-friendly black insulating coating and a coating method thereof on the surface of aluminum foil, which is suitable for insulating protection in the fields of electronic packaging, flexible circuit boards, and has the characteristics of low volatile organic compounds (VOC), high insulation, excellent adhesion, and rapid low-temperature curing.

[0006] The object of the present application is achieved by the following technical solutions: A water-based low-VOC environment-friendly black insulating coating is prepared from the following mass percentage raw materials: A water-based resin system 30%-45%: made from water-based acrylic resin, water-based epoxy resin, and water-based polyurethane in a mass ratio of (12-18):(8-12):(5-8); Insulating filler 10%-20%: made from nano-aluminum oxide, boron nitride, and calcium silicate in a mass ratio of (5-8):(2-4):(3-5); Pigment 15%-25%: made from pigment carbon black and insulating carbon black in a mass ratio of 1:(1-2); Water-based environmentally friendly additives 3%-6%: including dispersants, defoamers, wetting and leveling agents, and thickeners, prepared in a mass ratio of (1-1.5):(0.5-1):(0.5-1):(0.5-1); the dispersant is selected from polycarboxylate salts; the defoamer is selected from organosilicon compounds; the wetting and leveling agent is selected from acetylenic diol derivatives; the thickener is selected from polyurethane associative types. Crosslinking agent 1%-3%: selected from aziridine; Deionized water: Balance; After the water-based low-VOC environmentally friendly black insulating coating is applied to the surface of aluminum foil, the surface resistivity of the water-based low-VOC environmentally friendly black insulating coating on the aluminum foil is ≥10. 12 Ω, dielectric strength ≥35kV / mm, VOC content ≤50g / L, coating adhesion ≥98% after curing (cross-cut test), and no deformation or oily odor release from the substrate; The water-based, low-VOC, environmentally friendly black insulating coating is applied to the surface of aluminum foil to form a coating. The resulting coating sample is then placed in a constant temperature and humidity test chamber (85℃ / 85% RH) to test the surface resistance, dielectric strength, and adhesion after 500h and 1000h, respectively. The surface resistance retention rate is ≥60% (500h) and ≥36.7% (1000h), and the dielectric strength retention rate is ≥84.2% (500h) and ≥73.7% (1000h). The coating has a uniform appearance, good adhesion, and is resistant to long-term high temperature and high humidity environments.

[0007] The above-mentioned method for coating an aluminum foil surface with a water-based, low-VOC, environmentally friendly black insulating coating includes the following steps: S1. Mix the aqueous resin system with deionized water and disperse at 1500 r / min for 10 min; S2. Add insulating filler and pigment, and grind to a fineness ≤10μm; S3. Add water-based environmentally friendly additives and adjust the viscosity to 25s-35s (copper cup #4). S4. After filtration, the coating is applied to the surface of aluminum foil, controlling the dry film thickness to be 3μm-5μm. It is then dried with hot air at 80℃-100℃ for 2-3 minutes. After curing, a water-based environmentally friendly insulating black aluminum foil is obtained. The surface resistivity of the water-based low-VOC environmentally friendly black insulating coating of the aforementioned water-based environmentally friendly insulating black aluminum foil is ≥10 Ω·cm. 12 Ω, dielectric strength ≥35kV / mm, VOC content ≤50g / L, coating adhesion ≥98% after curing (cross-cut test), and no deformation or oily odor release from the substrate.

[0008] Furthermore, the coating method described in S4 includes: bar coating, roller coating, comma blade coating, slot coating, etc.

[0009] Further, the water-based environmentally friendly insulating black aluminum foil in S4 has a thickness of 10-30 μm.

[0010] Compared with the prior art, the present application has the following beneficial effects: 1. The water-based low-VOC environmentally friendly black insulating coating is suitable for insulating protection in the fields of electronic packaging and flexible circuit boards, and has low volatile organic compounds (VOC), high insulation, excellent adhesion and rapid low-temperature curing characteristics.

[0011] 2. The water-based low-VOC environmentally friendly black insulating coating has: ① Zero benzene residue and low VOC: completely using water as a solvent, no benzene solvent is detected, and the VOC content is ≤50 g / L (traditional solvent-based coating > 500 g / L); ② High insulation performance: through the synergistic effect of nano-aluminum oxide and boron nitride, the dielectric strength of the coating is ≥35 kV / mm (the existing product is only 15-20 kV / mm); ③ Low-temperature curing and high adhesion: adding nitrogen propylene crosslinking agent, the coating can be completely cured at 80-100℃ hot air drying for 2-3 min (traditional curing requires 150℃ / 20 min), which saves energy by more than 40%, avoids high-temperature deformation of the aluminum foil, and the adhesion is ≥98% (crosshatch method), and the substrate is not deformed.

[0012] ④ Supports various methods such as wire bar, roller coating, comma doctor blade, and slot coating, and is suitable for 3-5 μm ultra-thin coating (substrate 10-30 μm aluminum foil), and has high mass production stability. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used together with embodiments of the present application to explain the present application, and do not constitute a limitation of the present application.

[0014] Figure 1 The process flow chart of the preparation method of the water-based low-VOC environmentally friendly black insulating coating is shown in the figure. Figure 2 The process flow chart of the coating method of the water-based low-VOC environmentally friendly black insulating coating is shown in the figure. Figure 3 The figure is an effect picture of the water-based low-VOC environmentally friendly black insulating coating prepared in Example 1 of the present application coated on the surface of an aluminum foil. DETAILED DESCRIPTION

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0017] Example 1: A water-based, low-VOC, environmentally friendly black insulating coating, such as Figure 1 As shown, it is made from the following raw materials by weight percentage: The composition consists of 15% waterborne acrylic resin, 10% waterborne epoxy resin, and 6% waterborne polyurethane, in a mass ratio of 15:10:6, totaling 31%. Insulating filler: 6% nano-alumina, 3% boron nitride, 4% calcium silicate, mass ratio 6:3:4, total 13%. Pigment: 10% pigment carbon black, 15% insulating carbon black, mass ratio 1:1.5, total 25%; Water-based environmentally friendly additives: 1.2% polycarboxylate dispersant, 0.75% silicone defoamer, 0.75% acetylation diol derivative wetting and leveling agent, 0.75% polyurethane associative thickener, 1% aziridine crosslinking agent, total 4.45%; Deionized water balance: 26.55%.

[0018] The above-mentioned method for coating an aluminum foil surface with a water-based, low-VOC, environmentally friendly black insulating coating is as follows: Figure 2 As shown, it includes the following steps: S1. Mix the aqueous resin system with deionized water and disperse at 1500 r / min for 10 min; S2. Add insulating filler and pigment, and grind to a fineness ≤10μm; S3. Add water-based environmentally friendly additives and adjust the viscosity to 30s for Cotton Cup #4. S4. After filtration, the film is coated onto 20μm aluminum foil using a comma-shaped scraper, with the dry film thickness controlled at 4μm. It is then dried with hot air at 90℃ for 2.5min.

[0019] Performance testing: Dielectric strength: 38kV / mm; Dielectric strength test specification: "GB / T 1408.1-2016"; Surface resistivity ≥1012 Ω; surface resistance tester Adhesion: 98% (crosshatch method); Adhesion test notes "crosshatch method (ASTM D3359) VOC content: 45g / L; Figure 3 is a water-based low-VOC environmentally friendly black insulating paint prepared in Example 1 after coating on the surface of aluminum foil. The results show that the substrate has no deformation and no oily odor release.

[0020] Example 2: A water-based low-VOC environmentally friendly black insulating paint is made of the following mass percentage raw materials: Water-based acrylic resin 18%, water-based epoxy resin 12%, water-based polyurethane 8%, mass ratio 18:12:8, total 38%; Insulating filler: nano-alumina 8%, boron nitride 4%, calcium silicate 5%, mass ratio 8:4:5, total 17%; Pigment: pigment carbon black 12%, insulating carbon black 13%, mass ratio 1:1.08, total 25%; Water-based environmental protection auxiliary agent: polycarboxylate dispersant 1.5%, silicone defoaming agent 1%, acetylenic diol derivative wetting and leveling agent 1%, polyurethane associated thickener 1%, aziridine crosslinking agent 3%, total 7.5%; Deionized water balance: 12.5%.

[0021] The coating method of the above-mentioned water-based low-VOC environmentally friendly black insulating paint on the surface of aluminum foil includes the following steps: S1, mix the water-based resin system with deionized water, disperse at 1500r / min for 10min; S2, add insulating filler and pigment, sand to fineness ≤10μm; S3, add water-based environmental protection auxiliary agent, adjust the viscosity to 25s of 4# cup coating; S4, after filtration, coat on 30μm aluminum foil through a slit, control the dry film thickness to 5μm, and dry at 100℃ hot air for 2min.

[0022] Performance test: Dielectric strength: 40kV / mm; Surface resistance ≥10 12 Ω; Adhesion: 99% (crosshatch method); VOC content: 48g / L; The substrate has no deformation and no oily odor release.

[0023] Example 3: An aqueous low VOC environmentally friendly black insulating paint is prepared from the following raw materials in mass percentage: Waterborne acrylic resin 14.4%, waterborne epoxy resin 9.6%, waterborne polyurethane 6%, mass ratio 12:8:5, total 30%; Insulating filler: nano-alumina 5%, boron nitride 2%, calcium silicate 3%, mass ratio 5:2:3, total 10%; Pigment: pigment carbon black 7.5%, insulating carbon black 7.5%, mass ratio 1:1, total 15%; Waterborne environmentally friendly additives: polycarboxylate dispersant 1.2%, silicone defoamer 0.6%, acetylenic diol derivative wetting and leveling agent 0.6%, polyurethane associated thickener 0.6%, aziridine crosslinking agent 2%, total 4%; Deionized water balance: 41%.

[0024] The above-mentioned aqueous low VOC environmentally friendly black insulating paint is coated on the surface of aluminum foil, which comprises the following steps: S1, mix the waterborne resin system with deionized water, disperse at 1500 r / min for 10 min; S2, add insulating filler and pigment, sand to fineness ≤10 μm; S3, add waterborne environmentally friendly additives, adjust the viscosity to 25 s for 4# cup coating; S4, after filtration, coat on 10 μm aluminum foil by wire bar and roller coating, control the dry film thickness to 3 μm, and dry at 80℃ hot air for 3 min.

[0025] Performance test: Dielectric strength: 35 kV / mm; Surface resistance ≥10 12 Ω; Adhesion: 99% (crosshatch method); VOC content: 48 g / L; The substrate is not deformed and no oily odor is released.

[0026] Comparative Example 1: Raw material ratio: no aziridine crosslinking agent is added, and the others are the same as Example 1.

[0027] Performance test: Curing temperature needs 150℃ / 20min, adhesion is only 75%, and the substrate is slightly deformed.

[0028] Comparative Example 2: Raw material ratio: nano-alumina (13%) is used to replace the insulating filler, and the others are the same as Example 1.

[0029] Performance test: Dielectric strength: 18 kV / mm, insulation performance is significantly reduced.

[0030] Surface resistance ≥ 10 12 Ω.

[0031] Comparative Example 3: The sample was prepared by using commercially available water-based insulation coating under the same process conditions, and the dielectric strength thereof was 20 kV / mm, the VOC content was 80 g / L, and the adhesion was 85%.

[0032] Performance test: aging test The coating obtained from Example 1 and Comparative Example 2 was coated on the surface of an aluminum foil, and the obtained coating sample was placed in a constant temperature and humidity test chamber (85℃ / 85% RH) to test the surface resistance, dielectric strength and adhesion after 500h and 1000h, respectively.

[0033] 1. Test conditions and index design Test environment: high temperature and high humidity conditions: 85℃ / 85% RH (relative humidity), continuous test for 500h and 1000h; 2. Test method and data summary

[0034] The results show that: The surface resistance retention rate of the coating of Example 1 to Example 3 was 60%-63.1% (500h), the surface resistance retention rate was 36.7%-39.2% (1000h), the dielectric strength retention rate was 84.2%-85.7% (500h), the dielectric strength retention rate was 73.7%-77.1% (1000h); the coating had uniform appearance, good adhesion, and good resistance to long-term high temperature and high humidity environment.

[0035] Comparative Example 1 did not add aziridine crosslinking agent, and the obtained coating needed to maintain a longer temperature drying film electrical performance to ensure, and its adhesion was much worse than the coating of the present application. After natural aging in a long-term high temperature environment, the stability was insufficient, and the natural aging of the coating led to further shrinkage and affected the deformation of the substrate.

[0036] Comparative Example 2 used a single filler, and the surface resistance retention rate of the obtained coating was <30% (500h / 1000h), and the dielectric strength retention rate was <70% (500h / 1000h). The insulation and stability were much worse than the coating of the present application.

[0037] Comparative Example 3 was a commercially available coating, and the surface resistance retention rate was also <30% (500h / 1000h), and the dielectric strength retention rate was <50% (500h / 1000h). The insulation and stability, as well as the adhesion, appearance and weather resistance of the coating, were much worse than the coating of the present application.

[0038] The above data prove that the water-based low-VOC environmentally friendly black insulating coating described in the application, through the water-based resin system, the compounding of the insulating filler, and the addition of the crosslinking agent, after being coated on the surface of the aluminum foil, the coating still meets the long-term reliability requirements of the electronic packaging field for insulation protection (such as the new energy automobile battery aluminum foil needs to withstand >10 years of damp heat cycle) in a harsh environment (85℃ / 85% RH).

[0039] The above has described various embodiments of the application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. An aqueous low VOC environmentally friendly black insulating paint, characterized by: The following raw materials are mixed in the following proportions by mass: Water-based resin system 30%-45%: made from water-based acrylic resin, water-based epoxy resin and water-based polyurethane in a mass ratio of (12-18):(8-12):(5-8); Insulating filler 10%-20%: made from nano-alumina, boron nitride and calcium silicate in a mass ratio of (5-8):(2-4):(3-5); Pigment 15%-25%: made from pigment carbon black and insulating carbon black in a mass ratio of 1:(1-2); Water-based environmentally friendly auxiliary agent 3%-6%: including dispersant, defoaming agent, wetting and leveling agent and thickening agent in a mass ratio of (1-1.5):(0.5-1):(0.5-1):(0.5-1); the dispersant is selected from polycarboxylate; the defoaming agent is selected from organosilicon; the wetting and leveling agent is selected from acetylenic diol derivative; the thickening agent is selected from polyurethane association type; Crosslinking agent 1%-3%: selected from aziridine; Deionized water: the rest; The water-based low-VOC environmentally-friendly black insulating paint has a surface resistance of the water-based low-VOC environmentally-friendly black insulating coating on the surface of the aluminum foil of ≥10 12 Ω, a dielectric strength of ≥35 kV / mm, a VOC content of ≤50 g / L, an adhesion of ≥98% after curing of the coating, a grid method, and no deformation and no oily odor release of the substrate; The water-based low-VOC environmentally friendly black insulating coating is coated on the surface of the aluminum foil to obtain a coating layer, and the obtained coating layer sample is placed in a constant temperature and humidity test box at 85°C / 85% RH, and the surface resistance, dielectric strength and adhesion after 500h and 1000h are tested respectively, the surface resistance retention rate of the coating layer is 500h≥60%, the surface resistance retention rate is 1000h≥36.7%, the dielectric strength retention rate is 500h≥84.2%, and the dielectric strength retention rate is 1000h≥73.7%; the coating layer has uniform appearance, good adhesion, and good resistance to long-term high temperature and high humidity environment.

2. The method for coating the surface of aluminum foil with the water-based low VOC environment-friendly black insulating paint of claim 1, characterized in that: The following steps are included: S1, mixing the water-based resin system with deionized water, dispersing at 1500r / min for 10min; S2, adding insulating filler and pigment, sanding to a fineness of ≤10μm; S3, adding water-based environmentally friendly auxiliary agent, adjusting the viscosity to 25s-35s of coating 4# cup; S4, after filtration, coating on the surface of aluminum foil, control the dry film thickness of 3-5 μm, hot air drying at 80-100 ℃ for 2-3 min, after curing to get water-based environmental protection insulation black aluminum foil, the water-based environmental protection insulation black aluminum foil of low VOC environmental protection black insulation coating surface resistance≥10 12 Ω, dielectric strength≥35 kV / mm, VOC content≤50 g / L, coating adhesion after curing≥98%, crosshatch method, and the substrate without deformation, no oily smell release.

3. The method for coating the surface of aluminum foil with the water-based low VOC environment-friendly black insulating paint of claim 2, characterized in that: The coating in S4 adopts the following coating methods: wire bar, roller coating, comma doctor blade coating and slot coating.

4. The method for coating the surface of aluminum foil with the water-based low VOC environment-friendly black insulating paint of claim 2, characterized in that: The water-based environmentally friendly insulating black aluminum foil in S4 has a thickness of 10μm-30μm.

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