A decorative ink, its preparation method and application

Abstract

This invention relates to the field of inkjet ink technology, specifically to a decorative ink, its preparation method, and its application. By weight percentage, it comprises the following components: 35-40% fluorosilicone-modified polyurethane prepolymer, 15-25% inorganic pigment dispersion, 20-25% solvent, 2-4% crosslinking agent, 1-3% surfactant, 1-3% additives, and the balance being water. The solvent includes ester solvents and alcohol ether solvents, with a weight ratio of (1-3):1. This invention utilizes the combination of fluorosilicone-modified polyurethane and solvent to form an interfacial energy gradient structure, resulting in better dispersion of the inorganic pigment dispersion in the system, thus solving the internal stress problem existing in the application of inorganic inks to metal surfaces.

Description

Technical Field

[0001] This invention relates to the field of inkjet ink technology, specifically to a decorative ink, its preparation method, and its application. Background Technology

[0002] Metal substrates, due to their superior texture and durability, are widely used in automotive trim parts, building curtain walls, and other fields, with inkjet printing being the mainstream processing technology. Currently, most metal surface decorations use UV-cured inks, which, while offering fast curing speed and vibrant colors, have significant technical shortcomings: insufficient weather resistance, leading to fading and cracking with prolonged outdoor use; and high VOC content, failing to meet RoHS environmental standards, limiting their application in high-end fields. Inorganic inks, with their excellent weather resistance and environmental friendliness, have become an important alternative to UV inks. However, existing inorganic ink technologies face multiple bottlenecks: inorganic pigments have high density, making them prone to sedimentation and aggregation, resulting in poor ink storage stability and lighter color; simultaneously, inorganic inks have weak adhesion to metal substrates, especially at folded and irregularly shaped areas, where internal stress concentration can cause edge chipping and lifting. The industry often mitigates this through complex pigment modification processes, which are costly and have limited effectiveness.

[0003] The high-wear-resistant, high-gloss UV coating disclosed in Chinese invention patent CN116463050B uses fluorosilicone nano-modified polyurethane propylene resin and is designed only for PMMA / PC composite boards. Although it improves the coating hardness and stain resistance, it belongs to a UV curing solvent-based system and cannot be adapted to inkjet printing processes on metal substrates. It does not involve core technologies such as inorganic pigment dispersion, metal adhesion optimization, and folding edge chipping solutions.

[0004] In summary, there is currently a lack of water-based inorganic inkjet ink solutions suitable for metal surfaces, which cannot simultaneously address environmental friendliness, weather resistance, storage stability, and processing performance. There is an urgent need to develop new architectural and decorative inks to overcome existing technological bottlenecks. Summary of the Invention

[0005] The first aspect of the present invention provides a decorative ink, comprising, by weight percentage, the following components: 35-40% fluorosilicone modified polyurethane prepolymer, 15-25% inorganic pigment dispersion, 20-25% solvent, 2-4% crosslinking agent, 1-3% surfactant, 1-3% additives, and the balance being water.

[0006] The solvents include ester solvents and alcohol ether solvents (containing at least one of hydroxyl or ether bonds), and the weight ratio of the ester solvents to the alcohol ether solvents is (1-3):1.

[0007] Existing inorganic inks suffer from poor adhesion to metal substrates due to the high density of inorganic pigments, which tend to settle and agglomerate. Furthermore, they are prone to edge chipping and warping at folded or irregularly shaped areas due to stress concentration. The industry typically addresses this through complex pigment modification processes, which are costly and have limited effectiveness. This invention utilizes the synergistic effect of a fluorosilicone-modified polyurethane prepolymer and a specific ratio of ester-alcohol ether solvents to construct a continuous and gradient-changing interfacial energy field within the ink system. The low surface energy of the fluorosilicone segments and the high surface energy of the polyurethane backbone create a natural interfacial energy difference, which, combined with the gradient volatilization of the solvent during film formation... The increased dispersion rate allows the inorganic pigment particles, modified with silane coupling agents, to be uniformly dispersed in the resin matrix, avoiding the sedimentation and agglomeration of high-density inorganic pigments. Simultaneously, the flexible polytetrahydrofuran ether diol segments introduced into the fluorosilicone-modified polyurethane molecular chain form a soft-hard segment phase separation structure with the rigid isocyanate segments. When forming a film on a metal substrate, this structure effectively disperses internal stress through micro-deformation of the molecular chain, completely solving the problem of internal stress concentration in inorganic inks applied to metal surfaces. This significantly improves the coating's resistance to edge chipping and warping at folded and irregular metal surfaces.

[0008] Optionally, the weight ratio of the ester solvent to the alcohol ether solvent is (1-2):1.

[0009] The additives include at least one of leveling agents, defoamers, and dispersants.

[0010] Optionally, the additives include leveling agents, defoamers, and dispersants.

[0011] Optionally, the ester solvent includes at least one of propylene glycol methyl ether acetate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, butyl acetate, isoamyl acetate, and ethyl butyrate.

[0012] Optionally, the alcohol ether solvent includes at least one of ethanol, dipropylene glycol methyl ether, propylene glycol methyl ether, diethylene glycol butyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol methyl ether, tripropylene glycol methyl ether, and propylene glycol butyl ether.

[0013] Optionally, the dispersant is selected from at least one of the following brands: BYK-161, BYK-163, BYK-164, BYK-110, and BYK-180.

[0014] Optionally, the leveling agent is selected from at least one of the following brands: BYK-307, BYK-333, BYK-358, BYK-346, and BYK-355.

[0015] Optionally, the defoamer is selected from at least one of the following brands: BYK-022, BYK-024, BYK-025, BYK-028, and BYK-A530.

[0016] Optionally, the surfactant includes at least one of sodium dodecyl sulfate, sodium stearate, polyvinylpyrrolidone, and perfluorooctane sulfonate.

[0017] The crosslinking agent includes an aqueous blocked aliphatic isocyanate.

[0018] The aqueous blocked aliphatic isocyanate includes blocked HDI (hexamethylene diisocyanate) trimer or blocked IPDI (isophorone diisocyanate) trimer.

[0019] Optionally, the closed-cell HDI trimer is selected from at least one of the following grades: MODESTTY QT-3320, MODESTTY QT-3340, Bayhydur BL3175, Bayhydur BL 4265, WANNATE BL-1000, and WANNATE BL-2000.

[0020] Optionally, the closed-type IPDI trimer is selected from at least one of the following Covestro grades: Bayhydur BL5140 and Bayhydur BL5250.

[0021] The raw materials for preparing the fluorosilicone modified polyurethane prepolymer, by weight, include: 35-40 parts of polytetrahydrofuran ether diol, 25-28 parts of diisocyanate, 0.06-0.1 parts of catalyst, 5-8 parts of fluorinated diol, and 3-6 parts of dihydroxy-terminated polydimethylsiloxane.

[0022] The diisocyanate includes IPDI or HDI.

[0023] The catalyst includes at least one of dibutyltin dilaurate, stannous octanoate, dibutyltin diacetate, dioctyltin dilaurate, and dibutyltin octanoate.

[0024] The fluorinated diols include at least one of perfluoroalkyl diols, hexafluorobutylene glycol, octafluoropentane glycol, perfluorohexyl ethylene glycol, and fluorinated polyether diols.

[0025] The number average molecular weight of the perfluoroalkyl diol is 600-6000.

[0026] The number-average molecular weight of the dihydroxy-terminated polydimethylsiloxane is 300-4000.

[0027] Optionally, the number-average molecular weight of the dihydroxy-terminated polydimethylsiloxane is 300-2000.

[0028] The raw materials for preparing the inorganic pigment dispersion include: inorganic pigment, silane coupling agent and water, wherein the mass ratio of inorganic pigment to silane coupling agent is (20-50):(2-5).

[0029] Optionally, the mass ratio of the inorganic pigment to the silane coupling agent is 25:(2-5).

[0030] The solid content of the inorganic pigment dispersion is 16-30 wt%.

[0031] The silane coupling agent includes at least one of KH550, KH560, KH570, KH792, FD-7250, and A171.

[0032] The inorganic pigments include at least one of iron oxide red, chrome yellow, cobalt blue, titanium dioxide, iron oxide yellow, iron oxide black, ultramarine, phthalocyanine blue, phthalocyanine green, carbon black, and zinc oxide.

[0033] The preparation method of the fluorosilicone modified polyurethane prepolymer includes the following steps: adding polytetrahydrofuran ether diol, diisocyanate, and catalyst to a reaction vessel, carrying out a primary reaction under nitrogen protection, and adding fluorinated diol and dihydroxy-terminated polydimethylsiloxane for a secondary reaction to obtain the fluorosilicone modified polyurethane prepolymer.

[0034] The temperature of the first reaction is 75-85℃ and the time is 1-2 hours; the temperature of the second reaction is 70-75℃ and the time is 1-2 hours.

[0035] The method for preparing the inorganic pigment dispersion is as follows: Inorganic pigments are mixed with silane coupling agents and water is added to disperse them evenly to obtain an inorganic pigment dispersion.

[0036] The dispersion adopts a gradient dispersion, which includes: first dispersing at a speed of 500-4000 rpm for 0.5-2 hours, and then dispersing at a speed of 6000-12000 rpm for 0.2-1 hours.

[0037] The second aspect of the present invention provides a method for preparing decorative ink, comprising the following steps: mixing fluorosilicone modified polyurethane prepolymer, inorganic pigment dispersion, solvent, crosslinking agent, surfactant, additive and water uniformly, and filtering to obtain ink.

[0038] A third aspect of the present invention provides an application of a decorative ink for inkjet coating on metal surfaces, particularly inkjet coatings on aluminum plates.

[0039] Beneficial effects 1. The ink of this invention utilizes fluorosilicone-modified polyurethane in combination with a solvent to form an interfacial energy gradient structure, which improves the dispersion of inorganic pigments in the system. Fluorosilicone-modified polyurethane is prepared as the main resin through stepwise copolymerization of polytetrahydrofuran ether diol, diisocyanate, fluorinated diol, and dihydroxyl-terminated polydimethylsiloxane. The design of fluorosilicone-modified segments and flexible / rigid segments allows the ink film to effectively disperse stress through micro-deformation of the molecular chains, improving the coating's resistance to edge chipping at folded and irregular shapes. It exhibits excellent adhesion to metal substrates, and the coating possesses excellent flexibility and weather resistance, effectively solving the internal stress problem existing in the application of inorganic inks on metal surfaces.

[0040] 2. The ink prepared by this invention can control the ink droplet size to 10-15 pL during printing, resulting in smooth ink jetting without interruption or clogging; the ink has good storage stability and is suitable for industrial continuous printing.

[0041] 3. The curing process of this invention is simple and easy to operate, and the coating exhibits excellent reagent resistance. After curing, the coating is uniform and dense, suitable for long-term use on various substrates such as automotive metal and architectural decoration. The ink prepared by this invention has low VOCs and fully complies with RoHS environmental standards. Detailed Implementation

[0042] Example 1 A decorative ink, the components of which are shown in Table 1, wherein the formulation of the fluorosilicone-modified polyurethane prepolymer is shown in Table 2: Table 1

[0043] Table 2

[0044] Preparation method of fluorosilicone modified polyurethane prepolymer: Polytetrahydrofuran ether diol, diisocyanate and catalyst are added to a reaction vessel and reacted at 80°C for 1.5 h under nitrogen protection. Then, fluorinated diol and dihydroxy-terminated polydimethylsiloxane are added and reacted at 70°C for 2 h to obtain fluorosilicone modified polyurethane prepolymer.

[0045] The inorganic pigment dispersion consists of: inorganic pigment, silane coupling agent (KH560) and deionized water; the inorganic pigment is composed of cobalt blue (initial particle size of 8-10 μm, D90 < 0.8 μm after dispersion and grinding) and titanium dioxide (particle size of 150-200 nm).

[0046] Preparation method of inorganic pigment dispersion: Cobalt blue and titanium dioxide are mixed at a mass ratio of 10:0.3 to obtain an inorganic pigment compound. Then, the inorganic pigment compound is mixed with a silane coupling agent at a mass ratio of 25:2 and deionized water is added. The mixture is dispersed at 1000 rpm and 9000 rpm for 1.5 h and 0.5 h respectively to obtain an inorganic pigment dispersion with a solid content of 25 wt%.

[0047] A method for preparing a decorative ink comprises the following steps: mixing a fluorosilicone modified polyurethane prepolymer, an inorganic pigment dispersion, a solvent, a crosslinking agent, a surfactant, an additive, and deionized water; stirring and dispersing the mixture; and then filtering it through a 0.22-0.44 μm filter membrane to obtain the ink.

[0048] Example 2 The specific implementation method is the same as in Example 1, except that, by weight percentage, the components of the decorative ink are: 35% fluorosilicone modified polyurethane prepolymer, 25% inorganic pigment dispersion, 20% solvent, 4% crosslinking agent, 1% surfactant, 1% additives (0.4% leveling agent + 0.3% defoamer + 0.3% dispersant), and deionized water to make up the balance.

[0049] Example 3 The specific implementation method is the same as in Example 1, except that, by weight percentage, the components of the decorative ink are: 40% fluorosilicone modified polyurethane prepolymer, 15% inorganic pigment dispersion, 25% solvent, 2% crosslinking agent, 3% surfactant, 2% additives (0.8% leveling agent + 0.6% defoamer + 0.6% dispersant), and deionized water to make up the balance.

[0050] Example 4 The specific implementation method is the same as in Example 1, except that in the components of the inorganic pigment dispersion, the inorganic pigment is iron oxide red and the silane coupling agent is KH560; in the components of the decorative ink, the solvent is propylene glycol methyl ether acetate and dipropylene glycol methyl ether in a mass ratio of 1:1.

[0051] Example 5 The specific implementation method is the same as in Example 1, except that the inorganic pigment in the inorganic pigment dispersion is chrome yellow; the crosslinking agent in the decorative ink is added at 3.5 wt%, and the surfactant is sodium dodecyl sulfate.

[0052] Example 6 The specific implementation method is the same as in Example 1, except that the solvent in the decorative ink is a mixture of propylene glycol methyl ether acetate and ethanol in a mass ratio of 2:1, and the amount of crosslinking agent added is 2.5 wt%.

[0053] Example 7 The specific implementation method is the same as in Example 1, except that the amount of dihydroxy-terminated polydimethylsiloxane added to the fluorosilicone modified polyurethane prepolymer is 5 parts, and the amount of fluorinated diol added is 7 parts.

[0054] Comparative Example 1 The specific implementation method is the same as in Example 1; the difference is that the fluorosilicone modified polyurethane prepolymer is replaced with UV-curable resin, Dongguan Jingshang New Material Development Co., Ltd., model UV-1015.

[0055] Comparative Example 2 The specific implementation method is the same as in Example 1; the difference is that the fluorosilicone modified polyurethane prepolymer is replaced with a UV-curable resin, which was purchased from Jinan Mobe Chemical Co., Ltd., model WDS-8056.

[0056] Comparative Example 3 The specific implementation method is the same as in Example 1; the difference is that no silane coupling agent is added to the inorganic pigment dispersion.

[0057] Comparative Example 4 The specific implementation method is the same as in Example 1; the difference is that no crosslinking agent is added to the components of the decorative ink.

[0058] Comparative Example 5 The specific implementation method is the same as in Example 1; the difference is that, by weight percentage, the amount of fluorosilicone modified polyurethane prepolymer added to the decorative ink is modified to 30%, and the amount of inorganic pigment dispersion added is modified to 30%.

[0059] Comparative Example 6 The specific implementation method is the same as in Example 1; the difference is that, by weight percentage, the amount of crosslinking agent added in the decorative ink is modified to 6%, and the amount of surfactant added is modified to 5%.

[0060] Performance testing methods The inks prepared in the examples and comparative examples were subjected to performance tests. The test data of the examples are listed in Table 3, and the test data of the comparative examples are listed in Table 4.

[0061] 1. Perform the following physicochemical property tests: Viscosity test: tested using a rotational viscometer at a constant temperature of 25℃. Surface tension was tested using a BZY-1 fully automatic surface tension meter, using the platinum plate method. Record the stratification observed after standing at room temperature for 14 days.

[0062] 2. Using a piezoelectric printhead inkjet printer with a nozzle diameter of 40μm, the ink viscosity was adjusted to approximately 20cP, and the droplet size was controlled to approximately 12pL. After printing, the ink was left to stand at 60℃ for 18 minutes. Then, curing was performed at 85℃ for 10 minutes in the first stage and at 145℃ for 20 minutes in the second stage, resulting in a uniform inkjet coating of approximately 23μm thickness on the automotive metal trim substrate. The following tests were then conducted: 2.1 Adhesion Test: The adhesion test is judged according to the following standards: ISO Grade 0: The cut edges are completely smooth, with no peeling at the grid edges. ISO Grade 1: Small pieces peel at the intersections of the cuts, with actual damage not exceeding 5% within the grid area. ISO Grade 2: Peeling occurs at the cut edges and intersections, covering 5%-15% of the area. ISO Grade 3: Peeling occurs at the cut edges, large areas peel off entirely, and even some grids peel off entirely, with a peeled area of ​​15%-35%. ISO Grade 4: Large areas peel off at the cut edges, and some grids peel off completely, with a peeled area of ​​35%-65%.

[0063] 2.2 Bending resistance test: Fold the coated automotive metal trim substrate 180° and observe whether there is any edge chipping.

[0064] 2.3 Reagent Resistance Test: The evaluation and testing of the reagent resistance of printed matter and printing inks were conducted according to the national standard GB / T 18724-2024. A 5-level gray card rating system was adopted, with levels ranging from 1 (no change) to 5 (severe damage), as follows: Level 1: No obvious change (color, gloss, and ink adhesion are all normal); Level 2: Very slight change (such as slight fading or very shallow local marks, difficult to detect with the naked eye); Level 3: Slight change (visible fading, slight blurring, or slight local ink peeling); Level 4: Moderate change (obvious discoloration, partial ink peeling, or slight swelling of the substrate); Level 5: Severe change (large-area peeling, dissolution, exposure of the substrate, or severe discoloration).

[0065] Performance test data: Table 3 Performance test results of the embodiments

[0066] Table 4 Comparative Performance Test Results

Claims

1. A decorative ink, characterized in that, The product comprises the following components by weight percentage: 35-40% fluorosilicone modified polyurethane prepolymer, 15-25% inorganic pigment dispersion, 20-25% solvent, 2-4% crosslinking agent, 1-3% surfactant, 1-3% additives, and the balance being water; the solvent includes ester solvents and alcohol ether solvents, wherein the weight ratio of the ester solvent to the alcohol ether solvent is (1-3):

1.

2. The ink according to claim 1, characterized in that, The weight ratio of the ester solvent to the alcohol ether solvent is (1-2):

1.

3. The ink according to claim 2, characterized in that, The crosslinking agent includes an aqueous blocked aliphatic isocyanate.

4. The ink according to claim 1, characterized in that, The additives include at least one of leveling agents, defoamers, and dispersants.

5. The ink according to claim 1, characterized in that, The raw materials for preparing the inorganic pigment dispersion include: inorganic pigment, silane coupling agent and water; the mass ratio of the inorganic pigment to the silane coupling agent is (20-50):(2-5).

6. The ink according to claim 5, characterized in that, The raw materials for preparing the fluorosilicone modified polyurethane prepolymer, by weight, include: 35-40 parts of polytetrahydrofuran ether diol, 25-28 parts of diisocyanate, 0.06-0.1 parts of catalyst, 5-8 parts of fluorinated diol, and 3-6 parts of dihydroxy-terminated polydimethylsiloxane.

7. The ink according to claim 6, characterized in that, The preparation method of the fluorosilicone modified polyurethane prepolymer includes the following steps: adding polytetrahydrofuran ether diol, diisocyanate and catalyst into a reaction vessel, carrying out a primary reaction under nitrogen protection, and adding fluorinated diol and dihydroxy-terminated polydimethylsiloxane for a secondary reaction to obtain the fluorosilicone modified polyurethane prepolymer.

8. The ink according to claim 7, characterized in that, The temperature of the first reaction is 75-85℃ and the time is 1-2 hours; the temperature of the second reaction is 70-75℃ and the time is 1-2 hours.

9. A method for preparing the ink according to any one of claims 1-8, characterized in that, The process includes the following steps: mixing fluorosilicone modified polyurethane prepolymer, inorganic pigment dispersion, solvent, crosslinking agent, surfactant, additives and water evenly, and then filtering to obtain ink.

10. An application of the ink according to any one of claims 1-8, characterized in that, Inkjet coatings for metal surfaces.

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