Process for preparing uv-inkjet ink, battery case insulating inkjet coating and application thereof

Abstract

The application relates to the technical field of photocuring ink, in particular to a UV inkjet ink and a preparation method and application of a battery shell insulating inkjet coating. The UV inkjet ink comprises the following components in parts by weight: 20-50 parts of acrylic acid modified glycidyl amine type epoxy resin, 0.5-5 parts of adhesion promoter, 40-70 parts of active diluent, 2-8 parts of photoinitiator, 1-10 parts of thermal curing agent and 0.1-3 parts of auxiliary agent. The acrylic acid modified glycidyl amine type epoxy resin is used as a base resin and cooperates with the adhesion promoter and other auxiliary agents, and can be used for forming the battery shell inkjet coating, so that the coating has high adhesion, high insulation voltage resistance and electrolyte resistance.

Description

Technical Field

[0001] This invention relates to the field of photocurable coating technology, specifically to the preparation and application of UV inkjet inks and insulating inkjet coatings for battery casings. Background Technology

[0002] As new energy vehicles accelerate their upgrade towards 800V high-voltage fast charging and CTP module-less assembly, the insulation and protection performance of power battery cell casings faces more stringent requirements. Currently, the industry generally uses polyethylene terephthalate (PET) blue film to coat the metal casing of the battery cell for insulation protection, but this solution has many inherent defects: insufficient adhesion between the blue film and the metal casing, making it prone to scratches, damage, wrinkles, and bubbles during use, and easily forming exposed dead corners at the edges and corners of the casing; limited insulation withstand voltage capability, unable to meet the insulation reliability requirements of high-voltage platforms; the blue film itself does not have flame retardancy, posing a safety hazard of combustion spread in thermal runaway scenarios; at the same time, the coating process is long and has low production efficiency, the coating thickness is fixed and cannot be flexibly adjusted, and the adaptability to various scenarios is poor.

[0003] To replace traditional PET blue film, UV-cured insulating coating technology has gradually become a research hotspot in the industry. Chinese invention patent application CN119350922A discloses a UV-cured inkjet printing ink for blue film on power batteries, using acrylate resins combined with UV-curable monomers to solve the problem of edge sealing of the battery cell casing through inkjet printing. However, its base resin is mostly general-purpose acrylate, lacking active sites that can participate in secondary cross-linking. After curing, the cross-linking density of the coating is insufficient, and its insulation, voltage resistance, and electrolyte resistance performance cannot meet the long-term use requirements of high-voltage fast charging and CTP structures.

[0004] Therefore, developing a battery casing inkjet coating system that requires no complex surface pretreatment, has high adhesion, high insulation and voltage resistance, and electrolyte resistance, while simplifying the production process and improving production cycle time, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The first aspect of the present invention provides a UV inkjet ink, comprising the following components by weight: 20-50 parts of acrylic-modified epoxy resin, 0.5-5 parts of adhesion promoter, 40-70 parts of reactive diluent, 2-8 parts of photoinitiator, 1-10 parts of thermosetting agent, and 0.1-3 parts of additives; wherein the acrylic-modified epoxy resin is an acrylic-modified glycidylamine type epoxy resin.

[0006] In existing technologies, conventional UV-cured insulating coatings mostly use general-purpose acrylic resin systems, which lack active reaction sites that can participate in secondary crosslinking. Furthermore, the ink viscosity is not well-suited to high-precision inkjet processes, making it difficult to construct a highly dense crosslinked network while ensuring coating accuracy. Acrylic-modified glycidylamine epoxy resin serves as the base resin. Its molecular chain contains both acrylate double bonds that can participate in UV free radical polymerization and epoxy active groups that can undergo thermal ring-opening reactions. During the UV curing stage, the acrylate double bonds rapidly polymerize under the action of photoinitiators to form a preliminary cross-linked network, achieving surface drying and setting of the coating. In the subsequent thermal curing stage, the epoxy groups in the resin react with amine curing agents, silane accelerators, etc., to further form a dense three-dimensional cross-linked structure, effectively improving the coating's insulation, voltage resistance, and electrolyte barrier properties. The amine structure of the acrylic-modified glycidylamine epoxy resin also has a certain polarity matching and anchoring force with the aluminum surface of the battery casing, further promoting adhesion and improving overall performance. It is suitable for inkjet coating systems for battery casings that can achieve high adhesion, high insulation, voltage resistance, and electrolyte resistance without complex surface pretreatment, while simplifying production processes and increasing production cycle time.

[0007] The weight ratio of the acrylic-modified glycidylamine epoxy resin, adhesion promoter, and reactive diluent is 25:(2~4):(40~50). This invention's UV inkjet ink, obtained through a specific combination, can form a continuous and consistent coating layer on both the flat and corner areas of the battery casing. This avoids printhead clogging and uneven coating caused by excessively high viscosity, or sagging and uncontrolled thickness caused by excessively low viscosity. Through synergistic combination, the final formed coating possesses excellent interfacial adhesion, high insulation and voltage resistance, and electrolyte stability.

[0008] Optionally, the acrylic-modified glycidylamine epoxy resin is selected from at least one of acrylic-modified TGDDM, acrylic-modified TGPAP, acrylic-modified TGMAP, and acrylic-modified hydantoin epoxy resin, wherein the hydantoin epoxy resin is also a glycidylamine epoxy resin and is aliphatic, containing a five-membered nitrogen-containing heterocycle. A conventional preparation method involves the reaction of glycidylamine epoxy resin with acrylic acid (AA) via an epoxy-carboxyl ring-opening addition reaction. Correspondingly, it can be the reaction product between TGDDM (tetraglycidyldiaminodiphenylmethane), TGPAP (triglycidylp-aminophenol), and TGMAP (triglycidylm-aminophenol) multifunctional epoxy resins, hydantoin epoxy resin, and acrylic acid. Specific examples in some embodiments can be found in Qian Jianhua et al.'s article "Synthesis and Structural Characterization of Multifunctional Terminal Vinyl Ester-Based Epoxy Resins" published in *Polymer Materials Science and Engineering*, 2019, Vol. 11, by controlling N, N, A polyfunctional vinyl-terminated epoxy resin (MVE-EP), namely acrylic acid-modified glycidylamine epoxy resin (acrylic acid-modified TGDDM), is synthesized by using N′,N′-tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) and acrylic acid (AA) in a molar ratio of n(AA) / n(TGDDM) = 2:1. Correspondingly, acrylic acid-modified TGPAP, acrylic acid-modified TGMAP, etc., can also be synthesized. In some embodiments, the acrylic acid-modified hydantoin epoxy resin can be selected from Hongming Chemical Reagents RHYA series acrylic acid-modified hydantoin epoxy resin RHYA-500, etc.

[0009] Optionally, the acrylic-modified glycidylamine epoxy resin includes any one of acrylic-modified TGDDM, acrylic-modified TGPAP, and acrylic-modified TGMAP, which is combined with acrylic-modified hydantoin epoxy resin in a weight ratio of (2~4):1.

[0010] The adhesion promoters include epoxy silanes and amino silanes.

[0011] The mass ratio of the epoxy silane to the amino silane is 1:(0.5~2).

[0012] Optionally, the mass ratio of the epoxy silane to the amino silane is 1:(1~2).

[0013] Optionally, the epoxy silane includes at least one of γ-glycidyl ether propoxytrimethoxysilane (KH-560), γ-glycidyl ether propyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KH-566), γ-glycidyl ether propylmethyldiethoxysilane (KH-561), and 3-glycidyl ether propylmethyldiethoxysilane.

[0014] Optionally, the aminosilane includes at least one of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-540), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602), and N-phenyl-γ-aminopropyltrimethoxysilane.

[0015] The thermosetting agent is an amine curing agent. Optionally, the amine curing agent is selected from one or two of polyetheramine D-230, isophorone diamine (IPDA), polyetheramine D-400, 4,4'-diaminodicyclohexylmethane (PACM-20), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), m-phenylenediamine (MXDA), N-aminoethylpiperazine (N-AEP), and trifunctional polyetheramine T-403.

[0016] Optionally, the reactive diluent includes at least one of isobornyl acrylate (IBOA), tetrahydrofuran acrylate (THFA), 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), hydroxyethyl acrylate (HEA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate (NPGDA), pentaerythritol triacrylate (PETA), and ethoxylated trimethylolpropane triacrylate (EO-TMPTA). Optionally, the reactive diluent includes isobornyl acrylate, tetrahydrofuran acrylate, and 1,6-hexanediol diacrylate in a weight ratio of 1:(1~2):(2~4).

[0017] The photoinitiator includes a radical photoinitiator. Optionally, the radical photoinitiator includes two or more of the following: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 1-hydroxycyclohexylphenyl ketone (184), 2-hydroxy-2-methyl-1-phenylpropanone (1173), ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone (907), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (369), and benzophenone (BP).

[0018] The additives include leveling agents and defoamers.

[0019] The leveling agent is selected from silicone or polyacrylate leveling agents. Optionally, the leveling agent includes at least one of BYK-333, TegoGlide410, BYK-306, BYK-346, Tego Glide100, Tego Flow300, Efka 3777, and Dow Corning DC-57.

[0020] The defoamer is selected from silicone-based defoamers. Optionally, the defoamer includes at least one of BYK-501, TegoAirex900, BYK-055, BYK-066N, Tego Airex920, Tego Foamex810, Efka 2022, and Deqian 6500.

[0021] The second aspect of the present invention provides a method for preparing an insulating inkjet coating for a battery casing. The method uses the UV inkjet ink to form an insulating coating on the surface of a battery metal casing by inkjet printing. The method includes the following steps: cleaning and pre-treating the battery metal casing to be printed and determining the printing area; using UV ink to perform inkjet printing in the printing area; and after printing, performing UV curing and thermal curing treatments in sequence to form an insulating inkjet coating.

[0022] Optional, the following steps may be included: S1, Cleaning and pre-treatment of the metal casing of the battery to be printed; S2, uses a CCD vision recognition system to photograph and extract the outline of the battery casing to determine the area to be printed; S3 controls the inkjet printhead to spray UV ink onto the area to be printed. The ink is first cured by UV light and then sent to the drying tunnel for heat curing to form a fully cured insulating coating with high cross-linking density.

[0023] The UV curing wavelength is 365~405nm, and the UV curing irradiation energy is 500~3000mJ / cm². 2 The UV curing time is 2~10s.

[0024] Optionally, the temperature for heat curing is 120~150 ℃ and the time is 20~30 min.

[0025] The battery's metal casing is an aluminum casing for new energy batteries.

[0026] The thickness of the insulating coating is 30~200μm.

[0027] The area to be printed includes the front surface, sides, and edge of the end cap of the battery casing.

[0028] Thirdly, the present invention provides a new energy battery, which includes a battery body and a battery casing insulating inkjet coating formed on the outer surface of the battery body. The battery casing insulating inkjet coating is formed by inkjet printing as described above or prepared by the aforementioned preparation method to obtain an inkjet printed coating.

[0029] Beneficial effects: 1. Using acrylic-modified glycidylamine epoxy resin as the base resin, combined with reactive diluent, curing agent, and adhesion promoter, it can be used to form an inkjet coating for battery casing. This coating has high adhesion, high insulation and voltage resistance, and electrolyte resistance. The resulting UV inkjet ink can ensure the crosslinking density and insulation and voltage resistance of the coating while avoiding increased coating brittleness, thus balancing interfacial adhesion and overall coating toughness.

[0030] 2. Using a blend of epoxy-based and amino-based silanes as adhesion promoters can synergistically enhance the adhesion strength of the coating on the aluminum shell surface through the dual effects of covalent bonding between the epoxy groups and the resin system, and coordination bonding between the amino groups and the surface of the aluminum shell. Maintaining a mass ratio of epoxy-based to amino-based silanes of 1:(0.5~2) ensures optimal balance in interfacial bonding, avoiding both the decrease in coating insulation performance caused by excessive amino-based silanes and the adhesion degradation caused by insufficient epoxy-based silanes.

[0031] 3. By compounding acrylic-modified glycidylamine epoxy resin, adhesion promoter and reactive diluent in a weight ratio of 25:(2~4):(40~50), the resin matrix, interface promoter and viscosity control can form a synergistic effect, simultaneously ensuring the cross-linking density of the coating, the interface adhesion and inkjet process compatibility, and improving the overall performance. It is particularly suitable for inkjet coating of battery casing insulation and its preparation method, and is also suitable for cost reduction needs such as simplifying production process and increasing production cycle. Detailed Implementation

[0032] Example 1 A UV inkjet ink, by weight, comprises: Acrylic modified epoxy resin: 25 parts, specifically a mixture of acrylic modified TGDDM and acrylic modified hydantoin epoxy resin in a weight ratio of 2.8:1; Adhesion promoter: 2 parts, specifically KH-560 and KH-550 compounded in a weight ratio of 1:1.2; Reactive diluent: 47 parts, specifically composed of isobornyl acrylate, tetrahydrofuran acrylate, and 1,6-hexanediol diacrylate in a weight ratio of 1:2:3; Photoinitiator: 3 parts, specifically a mixture of 1 part TPO initiator and 2 parts 184 initiator; Thermosetting agent: 4 parts, specifically polyetheramine D-230; Additives (leveling agent and defoamer): 2 parts, specifically 1.5 parts leveling agent is BYK-333; 0.5 parts defoamer is BYK-501.

[0033] The preparation method of the UV inkjet ink is as follows: all components are mixed evenly in the dark.

[0034] A method for preparing an insulating inkjet coating for a battery casing, which is formed by inkjet printing using UV ink, includes the following steps: cleaning and pre-treating the battery metal casing to be printed and determining the printing area; using UV ink to perform inkjet printing in the printing area; and after printing, performing UV curing and thermal curing treatments in sequence to form an insulating inkjet coating.

[0035] Optional, the following steps may be included: S1, Cleaning and pre-treatment of the metal casing of the battery to be printed; S2, uses a CCD vision recognition system to photograph and extract the outline of the battery casing to determine the area to be printed; S3 controls the inkjet printhead to spray UV ink onto the area to be printed. The ink is first cured by UV light and then sent to the drying tunnel for heat curing to form a fully cured insulating coating with high cross-linking density.

[0036] A new energy battery includes a battery body and an insulating inkjet coating formed on the outer surface of the battery body.

[0037] Example 2 The specific implementation method is the same as in Example 1; the difference is that 25 parts of acrylic modified epoxy resin, 4 parts of adhesion promoter (KH-566 and KH-540 are compounded in a weight ratio of 1:1.6), 50 parts of reactive diluent, 5 parts of photoinitiator, 6 parts of thermosetting agent (PACM-20), and 3 parts of additives are used.

[0038] Example 3 The specific implementation method is the same as in Example 1; the difference is that 25 parts of acrylic modified epoxy resin (acrylic modified TGPAP and acrylic modified hydantoin epoxy resin are combined in a weight ratio of 2.2:1), 2 parts of adhesion promoter (KH-566 and KH-540 are compounded in a weight ratio of 1:0.8), 43 parts of reactive diluent, 6 parts of photoinitiator, 2 parts of thermosetting agent, and 0.3 parts of additives are used.

[0039] Example 4 The specific implementation method is the same as in Example 1, except that 30 parts of acrylic modified epoxy resin (acrylic modified TGDDM and acrylic modified hydantoin epoxy resin in a weight ratio of 3.6:1), 4 parts of adhesion promoter (KH-561 and KH-792 in a weight ratio of 1:1.8), and 60 parts of reactive diluent are prepared in the following weight ratios: isoborneol acrylate, tetrahydrofuran acrylate, and 1,6-hexanediol diacrylate.

[0040] Example 5 The specific implementation method is the same as in Example 1, except that 40 parts of acrylic modified epoxy resin (acrylic modified TGDDM and acrylic modified hydantoin epoxy resin in a weight ratio of 2.2:1), 5 parts of adhesion promoter (KH-566 and KH-540 in a weight ratio of 1:1.8), and 70 parts of reactive diluent are prepared in the following weight ratios: isoborneol acrylate, tetrahydrofuran acrylate, and 1,6-hexanediol diacrylate.

[0041] Comparative Example 1 The specific implementation method is the same as in Example 1; the difference is that the acrylic modified epoxy resin is replaced by acrylic modified glycidylamine type epoxy resin A102 from Guangzhou Xieyu New Materials.

[0042] Comparative Example 2 The specific implementation method is the same as in Example 1; the difference is that acrylic modified TGDDM and acrylic modified hydantoin epoxy resin are combined in a weight ratio of 6:1.

[0043] Comparative Example 3 The specific implementation method is the same as in Example 1; the difference is that 25 parts of acrylic modified epoxy resin, 8 parts of adhesion promoter, and 80 parts of reactive diluent are used.

[0044] Comparative Example 4 The specific implementation method is the same as in Example 1; the difference is that the mass ratio of epoxy silane to amino silane in the adhesion promoter is 1:0.01.

[0045] Comparative Example 5 The specific implementation method is the same as in Example 1; the difference is that the mass ratio of epoxy silane to amino silane in the adhesion promoter is 1:3.

[0046] Comparative Example 6 The specific implementation method is the same as in Example 1; the difference is that the proportions of the acrylic modified epoxy resin, adhesion promoter and reactive diluent are 50 parts, 1 part and 45 parts, respectively.

[0047] Performance testing methods The coatings prepared in the Examples and Comparative Examples were subjected to the following performance tests, and the test data are listed in Table 1.

[0048] Adhesion test: The test is carried out in accordance with GB / T 9286-1998 "Paints and varnishes - Cross-cut test for films". A cross-cut tool is used to scribe a grid array (10×10 grids) with a spacing of 1 mm on the surface of the coating, then a 3M tape is applied and quickly peeled off, the peeling of the coating is observed, and the adhesion level is evaluated according to the standard (Level 0 is the best, Level 5 is the worst). When the adhesion level is higher than Level 2, it is evaluated as qualified.

[0049] Insulation performance test: The test is carried out in accordance with GB / T 1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials". The three-electrode method is adopted, the test voltage is 1000V DC, the test duration is 1 minute, and the surface resistivity of the coating is recorded. When the surface resistivity of the coating is >1×10 13 , it is evaluated as qualified.

[0050] Electrolyte corrosion resistance test: 0.1 mL of electrolyte (1 mol / L LiPF6 / EC+DMC (volume ratio 1:1)) is dropped on the surface of the coating sample, and the sample is placed at a constant temperature of 85°C for 2 hours. After taking out, the change of the surface state of the coating is observed, and if no abnormality is found, it is evaluated as qualified.

[0051] Performance test data: Table 1

[0052] It can be seen from the test results in Table 1 that Comparative Example 1 uses an acrylic modified epoxy resin with no amino group in the branched chain, Comparative Example 2 uses too little acrylic modified hydantoin epoxy resin, Comparative Example 3 uses a relatively excessive amount of adhesion promoter and diluent, Comparative Example 4 uses too little aminosilane, Comparative Example 5 uses too little epoxy silane, and Comparative Example 6 uses a relatively insufficient amount of adhesion promoter and diluent. After comparison of the test results, the performances in multiple aspects such as adhesion, insulation property and electrolyte resistance are all unqualified. The UV ink obtained by the combination and material selection in the Examples of the present invention has excellent overall comprehensive performance.

[0053] The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope disclosed in the present application, and these modifications or substitutions shall all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A UV inkjet ink, characterized in that, By weight, it comprises the following components: 20-50 parts of acrylic-modified epoxy resin, 0.5-5 parts of adhesion promoter, 40-70 parts of reactive diluent, 2-8 parts of photoinitiator, 1-10 parts of thermosetting agent, and 0.1-3 parts of additives; wherein the acrylic-modified epoxy resin includes acrylic-modified glycidylamine type epoxy resin.

2. The ink according to claim 1, characterized in that, The acrylic-modified glycidylamine type epoxy resin includes any one of acrylic-modified TGDDM, acrylic-modified TGPAP, and acrylic-modified TGMAP, which is combined with acrylic-modified hydantoin epoxy resin in a weight ratio of (2~4):

1.

3. The ink according to claim 1, characterized in that, The adhesion promoter comprises epoxy silane and amino silane; and / or the weight ratio of the epoxy silane and amino silane is 1:(0.5~2).

4. The ink according to claim 1, characterized in that, The reactive diluent includes isobornyl acrylate, tetrahydrofuran acrylate, and 1,6-hexanediol diacrylate, with a weight ratio of 1:(1~2):(2~4).

5. The ink according to claim 1, characterized in that, The thermosetting agent is an amine-based curing agent.

6. The ink according to claim 1, characterized in that, The additives include leveling agents and defoamers.

7. The ink according to claim 1, characterized in that, The weight ratio of the acrylic-modified glycidylamine epoxy resin, adhesion promoter, and reactive diluent is 25:(2~4):(40~50).

8. A method for preparing an insulating inkjet coating for a battery casing, characterized in that, Using the UV inkjet ink described in any one of claims 1 to 7, an insulating coating is formed on the surface of a battery metal casing by inkjet printing, comprising the following steps: cleaning and pre-treating the battery metal casing to be printed and determining the printing area; using UV ink to perform inkjet printing in the printing area; and after printing, sequentially undergoing UV curing and thermal curing treatments to form an insulating inkjet coating.

9. The preparation method according to claim 8, characterized in that, The UV curing wavelength is 365~405nm, and the irradiation energy is 500~3000mJ / cm². 2 The time is 2~10s; and / or the temperature for heat curing is 120~150℃ and the time is 20~30 min.

10. A new energy battery, characterized in that, The battery includes a battery body and a battery housing insulating inkjet coating formed on the outer surface of the battery body. The battery housing insulating inkjet coating is formed by inkjet printing as described in claims 1-7 or prepared by the preparation method as described in claim 8.

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