High-temperature and high-humidity resistant water-based ink, preparation method and application thereof

Abstract

This invention relates to the field of polymer materials technology, specifically to a high-temperature and humid heat-resistant water-based ink, its preparation method, and its application. The steps are as follows: S1, polybenzimidazole (PBI) powder is cryogenically ground to obtain nano-sized PBI powder; S2, deionized water, emulsifier, coupling agent, initiator, and defoamer are mixed and dispersed with the nano-sized PBI powder to prepare a PBI pre-dispersion; S3, deionized water, emulsifier, at least one of acrylic monomers and acrylate monomers, a functional amine, and a pH buffer are mixed to prepare a seed emulsion; S4, the PBI pre-dispersion is added dropwise to the seed emulsion, and in-situ polymerization is carried out in an emulsion polymerization apparatus to obtain a PBI-functional amine hybrid emulsion; S5, the PBI-functional amine hybrid emulsion is mixed and dispersed evenly with a defoamer, leveling agent, anti-abrasion agent, and water-based colorant to obtain a high-temperature and humid heat-resistant water-based ink. This invention improves the water resistance, heat resistance, and adhesion performance of the ink film under conditions of boiling, high-temperature sterilization, and high-temperature and humid heat.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a water-based ink resistant to high temperature and humidity, its preparation method, and its application. Background Technology

[0002] With increasing demands for green printing and low volatile organic compound (VOC) emissions, water-based inks are widely used in food packaging printing, industrial signage, and metal / glass decorative printing due to their environmental friendliness, high safety, and strong adaptability. For high-temperature cooking and pasteurization / high-temperature sterilization processes in food packaging, as well as the long-term use of glass, metal, and other substrates in high-temperature and humid environments (such as humid and enclosed spaces, steam environments, or long-term hot and humid conditions similar to saunas), the ink layer not only needs to meet conventional color and printability requirements, but also needs to maintain stable adhesion, water resistance, migration resistance, and heat aging resistance under the combined effects of high temperature and high humidity.

[0003] Currently, most film-forming resins used in water-based inks are acrylic emulsions, polyurethane dispersions, or their compound systems. These systems typically exhibit good film-forming and workability, but under high-temperature and humid conditions, the ink layer is prone to the following failures: First, moisture penetration and heat can cause plasticization or hydrolysis of resin segments and changes in interfacial wetting, leading to decreased interfacial adhesion between the ink layer and the substrate, resulting in blistering, edge lifting, and peeling. Second, on substrates with low porosity, low polarity, or significant surface energy variations, such as glass / metal, the interfacial forces of water-based systems are limited, especially after cooking or prolonged humid heat cycling, where adhesion degradation is more pronounced. Third, while methods such as increasing crosslinking density, introducing highly polar monomers, or adding external crosslinking agents can improve heat and water resistance, these methods often lead to decreased emulsion stability, increased film-forming temperature, reduced flexibility, decreased impact resistance, or a narrowed application window. Furthermore, for food packaging applications, low odor, low migration, and compliance requirements must also be considered.

[0004] Addressing the core contradictions of insufficient high-temperature and humid heat durability and interfacial adhesion degradation, the industry recognizes that simultaneously introducing a highly thermally stable framework to resist thermal aging and strong interfacial adhesion groups into the waterborne resin system to enhance interfacial interactions with substrates such as glass, metal, and plastics could significantly improve the overall reliability of the ink layer in cooking and long-term hot and humid environments. Against this backdrop, polybenzimidazole polymers and dopamine / functional amine surfactants show potential advantages.

[0005] Polybenzimidazole resin possesses a rigid aromatic heterocyclic structure and high thermal stability. Its molecular backbone is not prone to significant softening or thermal decomposition under high temperatures, and the imidazole-related structures exhibit certain polarity and activation sites. Based on these material structural characteristics, incorporating the polybenzimidazole structure into aqueous film-forming systems in an appropriate manner could potentially improve the heat resistance of ink films, thereby maintaining the integrity of the film structure under conditions of cooking, hot and humid cycling, or long-term exposure to high temperature and humidity. This would reduce the risk of strength loss and failure due to matrix softening and water absorption plasticization.

[0006] On the other hand, dopamine and its derived polydopamine structures contain functional groups such as catechol and amine groups, exhibiting strong interfacial interaction capabilities. Meanwhile, monofunctional amine molecules such as 2-phenylethylamine can also promote the wetting, anchoring, and interfacial bonding of the film-forming system to the substrate surface through hydrogen bonding, acid-base interactions, coordination, or chemical reactions with reactive groups in the resin. Mechanistically, catechol / amine functional groups can form strong adsorption or coordination effects on surfaces such as glass and metal oxide layers, while simultaneously providing additional polar interaction sites or potential crosslinking / entanglement contributions within the resin network, thereby suppressing adhesion degradation caused by interfacial water films under humid and hot conditions. Therefore, introducing dopamine or functional amines from an interfacial engineering perspective is expected to significantly improve the adhesion of water-based inks to glass / metal and various packaging substrates, and enhance adhesion retention in humid and hot environments.

[0007] However, polybenzimidazole resins typically have limited solubility and dispersibility. Direct addition to aqueous acrylic emulsion systems can easily lead to problems such as poor compatibility, unstable dispersion, coarsening of particle size, and film-forming defects. More importantly, while polybenzimidazole resins have excellent heat resistance, their water resistance is only average, with moisture absorption reaching up to 15% in extreme cases. Therefore, other modification methods must be used to compensate for the shortcomings of PBI in terms of water resistance. At the same time, if dopamine / functional amine components are used in a simple physical addition manner, problems such as migration (migration with the aqueous phase or to the interface / surface under heat and humidity), insufficient water resistance (water absorption and plasticization leading to stickiness or whitening), strong odor, and decreased adhesion after humid heat cycling may occur. Furthermore, due to the influence of amines on the pH of the system and the surface charge of particles, viscosity drift, flocculation and sedimentation, or decreased storage stability may occur, making it difficult to simultaneously meet the requirements of durability and application stability in high-temperature cooking / long-term high-temperature and humid heat environments. Summary of the Invention

[0008] The purpose of this invention is to solve the problems of existing technologies. The design concept of this invention is twofold: firstly, by introducing polybenzimidazole into the emulsion film-forming system to provide higher thermal stability and resistance to heat and moisture aging; secondly, by introducing functional amine structural units such as dopamine and / or 2-phenylethylamine, polar / adhesive groups that can strongly interact with glass, metal, and packaging substrates are provided to the resin molecular chains or emulsion particle surfaces, thereby improving the adhesion retention rate and film integrity under humid heat and cooking conditions, and solving the problem that polybenzimidazole is too hard and easily leads to a decrease in paint film adhesion. To balance the dispersion stability, storage stability, and printability of the water-based system, this invention proposes to first emulsify and disperse polybenzimidazole nanopowder and introduce it in situ during the acrylic emulsion polymerization process, while simultaneously introducing functional amines as monomers / reactive components that can participate in polymerization, so that they form a structural bond or hybrid network with the acrylic polymer, thereby reducing the risk of migration and phase separation caused by simple physical addition. By leveraging the high temperature resistance of polybenzimidazole, the strong water resistance and flexibility of acrylic emulsions, and the properties of functional amines in enhancing substrate adhesion, this invention comprehensively improves the water resistance, heat resistance, and adhesion durability of the ink layer under high temperature, humidity, and cooking conditions. The purpose of this invention is to obtain a water-based ink with high hardness, high resistance to humidity and heat, high adhesion, good storage stability, and durability, as well as its preparation method and applications.

[0009] To achieve the above objectives, the present invention provides a method for preparing a water-based ink resistant to high temperature and humidity, comprising the following steps:

[0010] S1. Polybenzimidazole (PBI) powder is freeze-milled to obtain nano-sized PBI powder.

[0011] S2. Mix and disperse deionized water, emulsifier, coupling agent, initiator, defoamer with the nano-sized PBI powder to prepare PBI pre-dispersion;

[0012] S3. Prepare a seed emulsion by mixing deionized water, emulsifier, at least one of acrylic monomer and acrylate monomer, functional amine and pH buffer.

[0013] S4. The PBI pre-dispersion is added dropwise to the seed emulsion, and an in-situ polymerization reaction is carried out in an emulsion polymerization device to obtain a PBI-functional amine hybrid emulsion.

[0014] S5. The PBI-functional amine hybrid emulsion is mixed with defoamer, leveling agent, anti-abrasion agent and water-based color paste and dispersed evenly to obtain the high-temperature and humid heat resistant water-based ink.

[0015] In step S1, the cryogenic grinding is carried out in a liquid nitrogen cryogenic ball mill, and the grinding temperature is controlled at -100℃±50℃. The particle size D90 of the obtained nano-sized PBI powder after grinding is <0.3μm. The ball milling raw material (polybenzimidazole PBI) is Celazole® PBI [selected from its U series unfilled resin, preferably U-60; its intrinsic viscosity IV is 0.6~0.8 dL / g (DMAc / LiCl, 25℃)]. The ball mill is made of liquid nitrogen cryogenic ball mill, and the grinding beads are made of 95 yttrium stabilized zirconia beads with a particle size of 0.03~0.3mm and a bead loading of 70%~90%.

[0016] In step S2, the coupling agent is selected from at least one of 3-aminopropyltriethoxysilane (CAS 919-30-2), 3-aminopropylmethyldiethoxysilane (CAS 3179-76-8), N,N-diethyl-3-aminopropyltrimethoxysilane (CAS 41051-80-3), bis-(3-trimethoxysilylpropyl)amine (CAS 82985-35-1), anilinemethyltriethoxysilane (CAS 3473-76-5), diethylaminomethyltriethoxysilane (CAS 15180-47-9), 3-glycidoxypropyltrimethoxysilane (CAS 2530-83-8), 3-ureapropyltrimethoxysilane (CAS 23843-64-3), and 3-ureapropyltriethoxysilane (CAS 23779-32-0).

[0017] The initiator is at least one of ammonium persulfate, potassium persulfate, benzoyl peroxide, di-tert-butyl hydroperoxide, azobisisobutyronitrile, and dilauryl peroxide.

[0018] In step S3, the functional amine is selected from at least one of dopamine (DA, CAS No. 51-61-6), tyramine (4-hydroxyphenylethylamine) (TA, CAS No. 51-67-2), 2-phenylethylamine (PEA, CAS No. 64-04-0), polyethyleneimine (PEI, CAS No. 9002-98-6), tris(2-aminoethyl)amine (TREN, CAS No. 4097-89-6), N-(2-hydroxyethyl)ethylenediamine (AEEA, CAS No. 111-41-1), and isophorone diamine (IPDA, CAS No. 2855-13-2).

[0019] In step S3, at least one of the acrylic monomers and acrylate monomers is selected from at least one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0020] In step S2, the components of the PBI predispersant, by mass percentage, include: 45%~75% deionized water, 1%~10% emulsifier, 1%~5% coupling agent, 0.1%~1% initiator, 0.1%~0.5% defoamer, and 20%~40% nano-sized PBI powder.

[0021] In step S3, the components of the seed emulsion, by mass percentage, include: 38%~66% deionized water, 1%~3% emulsifier, 1%~5% functional amine, 30%~55% of at least one of acrylic monomer and acrylate monomer, and 0.1%~1% pH buffer.

[0022] In step S4, after the PBI pre-dispersion liquid is added dropwise to the seed emulsion, the polymerization reaction temperature is controlled at 70℃~90℃ and the reaction time is 1~8 hours.

[0023] In step S5, the components of the water-based ink, by mass percentage, include: 60%~98% PBI-functional amine hybrid emulsion, 0.1%~1% defoamer, 0.1%~1% leveling agent, 0.1%~1% anti-abrasion agent, and 1%~40% water-based color paste. The water-based color paste is a concentrated water-based paste using one or more pure organic pigments, such as Pigment Red 254, Pigment Red 146, Pigment Red 176, Pigment Red 101; Pigment Yellow 83, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 43; Pigment Blue 15:3; Pigment Green 7; Pigment Orange 34, Pigment Orange 43, Pigment Orange 64; Pigment Violet 19, and Pigment Violet 23.

[0024] In steps S2 and S3, the emulsifier is independently selected from at least one of sodium dodecylbenzenesulfonate (SDBS), polyoxyethylene sorbitan monooleate (Tween 80), polyoxyethylene cetyl ether (Brij 58), alkylphenol polyoxyethylene ether (Triton X-100), decaglycerol monolaurate (PGFE), sodium lauryl ether sulfate (AES), and soybean lecithin (LHP).

[0025] The present invention also provides a method for preparing the water-based ink by any of the above-described preparation methods.

[0026] The present invention also provides an application of the aforementioned high-temperature and humid heat resistant water-based ink in food packaging printing, industrial marking, or metal or glass decorative printing.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. Structural synergy leads to a significant improvement in high temperature and humidity resistance and durability: By introducing polybenzimidazole (PBI) nanoparticles into the acrylate emulsion polymerization system in a pre-dispersed form, and combining the grafting / introduction effect of functional amines (FA) in the polymerization process, a hybrid emulsion system with a high thermal stability skeleton and strong interfacial interaction sites is constructed, which significantly improves the structural integrity and durability of the ink layer under high temperature and humidity environment.

[0029] 2. Avoids the risks of migration / precipitation / stickiness associated with traditional physical additives, resulting in more stable adhesion: By using functional amines such as dopamine, tyramine, and 2-phenylethylamine as active components that can participate in polymerization, compared with simple external additives or fillers, problems such as migration, precipitation, stickiness, and adhesion decay can be reduced. At the same time, it enhances the interfacial anchoring and moisture-heat adhesion retention rate of the ink film on substrates with low surface energy or fluctuating surface energy such as glass and metal.

[0030] 3. Balancing hardness, flexibility, and resistance to damp heat: Addressing the shortcomings of PBI in water resistance: The introduction of PBI improves the ink film's resistance to heat deformation and heat aging; at the same time, the acrylic emulsion provides water resistance and film-forming flexibility, and works synergistically with the interfacial reinforcement effect of FA to compensate for the potential defects caused by the insufficient moisture absorption / water resistance of PBI, forming a "rigid and flexible" composite structure, achieving a comprehensive balance of hardness, flexibility, and resistance to damp heat.

[0031] 4. Improved dispersion and storage stability, reduced film-forming defects, and enhanced printability: Nanoscale PBI is obtained by liquid nitrogen cryogenic ball milling, and a pre-dispersed PBI solution is prepared by homogenization emulsification. This solution is then added dropwise to the seed emulsion for emulsion polymerization, achieving stable dispersion and in-situ introduction of PBI in the aqueous system. This improves problems such as poor compatibility, unstable dispersion, coarsening of particle size, and film-forming defects, thereby enhancing the storage stability and application / printability of the emulsion / ink.

[0032] 5. Meets the comprehensive requirements of environmental protection and application scenarios, with a wider range of applications: Under the premise of meeting the requirements of low VOC and water-based environmental protection system, the resulting water-based ink has excellent resistance to boiling, resistance to damp heat aging, adhesion retention and good workability. It is especially suitable for high-requirement application scenarios such as food packaging boiling / sterilization process, as well as metal / glass decoration under high temperature and high humidity conditions. Detailed Implementation

[0033] The terms used in this invention, unless otherwise stated, generally have the meanings commonly understood by those skilled in the art.

[0034] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0035] The present invention discloses a method for preparing a water-based ink resistant to high temperature and humidity, comprising the following steps: the first step is low-temperature grinding; the second step is preparing a pre-dispersion liquid; the third step is preparing a seed emulsion; the fourth step is preparing a PBI-FA hybrid emulsion; and the fifth step is preparing the water-based ink.

[0036] The process conditions for the five steps are as follows:

[0037] Step 1: Low-temperature grinding

[0038] PBI powder was placed in a low-temperature ball mill containing 0.03~0.3mm zirconia beads, with a bead load of 70%~90%. Liquid nitrogen was circulated through the inner jacket of the ball mill, and the temperature was controlled at -100°C. o C±50 o Under C conditions, the powder was repeatedly ground until the particle size D90 of PBI was reduced to below 0.3 μm.

[0039] Step 2: Pre-dispersion liquid

[0040] Deionized water, emulsifier, coupling agent, initiator, defoamer, and the nano-sized PBI powder prepared in the first step are dispersed at high speed and uniformly using a homogenizing emulsifier until a homogeneous emulsion is formed.

[0041] Component mass percentage %

[0042] Deionized water 45%~75%

[0043] Emulsifier 1%~10%

[0044] Coupling agent 1%~5%

[0045] Initiator 0.1%~1%

[0046] Defoamer 0.1%~0.5%

[0047] Nanoscale PBI 20%~40%

[0048] Step 3: Seed emulsion

[0049] Deionized water, emulsifier, pH buffer, functional amine, and various acrylate monomers are added to a stirred tank and mixed evenly until a milky white and homogeneous solution is obtained, thus producing a seed emulsion.

[0050] Component mass percentage %

[0051] Deionized water 38%~66%

[0052] Emulsifier 1%~3%

[0053] Functional amines 1%~5%

[0054] Various acrylate monomers, 30%~55%

[0055] pH buffer 0.1%~1%

[0056] Step 4: PBI-FA hybrid emulsion

[0057] The seed emulsion from step three was poured into an emulsion polymerization apparatus, nitrogen gas was introduced to purge oxygen, and then the PBI pre-dispersion prepared in step two was added dropwise to the seed emulsion, with the temperature controlled at 70°C. o C~90 o C, Time: 1-8 hours.

[0058] Step 5: Water-based ink

[0059] The PBI-FA hybrid emulsion, defoamer, leveling agent, anti-abrasion agent, and water-based color paste prepared in step four are mixed, dispersed evenly, and filtered to obtain water-based ink.

[0060] Component mass percentage %

[0061] PBI-FA hybrid emulsion 60%~98%

[0062] Defoamer 0.1%~1%

[0063] Leveling agent 0.1%~1%

[0064] Anti-wear agent 0.1%~1%

[0065] Water-based pigments: 1%~40%.

[0066] Example 1

[0067] Step 1: Load 95% yttrium stabilized zirconia beads (0.05mm particle size, 80% bead load) into the cryogenic ball mill (Cryo / Mill 6870D custom model), open the inner jacket of the ball mill, circulate liquid nitrogen, and control the temperature to -85°C. o C±2 o C. Pour in 70g of PBI powder (Celazole® PBI, Changzhou Puwei Composite Materials Co., Ltd., model U-60), and grind repeatedly until the powder particle size D90 < 0.3μm (actual D90 = 0.24μm measured by laser particle size analyzer). After filtering through a 5000-mesh vibrating sieve, 68.8g of nano-sized PBI is obtained.

[0068] Step 2: Add the materials in the table below in order, totaling 200g, and simultaneously use a homogenizer at 3000rpm for 2 hours to disperse evenly. Then filter through a 200-mesh filter to prepare 197g of PBI pre-dispersion.

[0069]

[0070] Step 3: Add a total of 300g of the materials listed in the table below to a beaker and mix at 1500rpm for 40 minutes until a milky white, homogeneous solution is formed and does not separate into layers when left to stand.

[0071]

[0072] Step 4: Pour 300g of the seed emulsion from Step 3 into a four-necked flask for emulsion polymerization, purge with nitrogen to purge oxygen, then add 197g of the PBI pre-dispersion prepared in Step 2 dropwise into the seed emulsion, while simultaneously raising the temperature to 84°C. o C±2 o C, polymerization time 2.5 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered through a 100-mesh filter to obtain 489.5 g of PBI-FA hybrid emulsion.

[0073] Step 5: Add the ingredients listed in the table below, totaling 100g, to a glass beaker. Disperse the mixture at 300 rpm for 10 minutes, then filter through a 100-mesh screen to obtain the water-based ink. At 25... o The viscosity was measured at room temperature using a Zahn Cup 4# with a value of 13.00 seconds, and the pH value was measured to be 8.4 using a pH meter.

[0074]

[0075] Several commercially available red water-based inks resistant to high temperature and humidity were selected as reference samples. Using a Zhongshan Nuobang W100T coating machine and a 3μm OSP coating rod, the inks were evenly coated onto commercially available tinplate sheets specifically for coating testing. The specific test results are shown in the table below:

[0076] GB / T 6753.3-1986 Test Methods for Storage Stability of Coatings GB / T 1740-2007 Test Method for Resistance to Damp Heat of Coatings GB / T 5210-2006 Adhesion Test by Pull-Off Method GB / T 1731-2020 "Test for flexibility of paint films" Changes in the appearance and properties of the paint film after high-pressure cooking at 121℃ for 30 min Competitor A in the market: ink painting <![CDATA[50 o C*7d: Slight stratification; soft settling at the bottom, disperses easily with stirring; viscosity increases by approximately 8%. 240h: Level 2 bubbling (localized), slight edge lifting; noticeable decrease in gloss. Initial pressure: 2.1 MPa; after humid heat: 1.2 MPa (a decrease of approximately 43%) Through a diameter of 4 mm (microcracks appear at 3 mm) Slight bubbling and loss of adhesion at the edges; darkened hue; ink easily smudges when marking areas. Commercially available competitor B ink <![CDATA[50 o C*7d: Distinct stratification; contains flocculated fine particles; viscosity increased by approximately 15%. 240h: Grade 1-2 blistering accompanied by localized whitening; punctate loss of adhesion appears. Initial pressure: 1.8 MPa; after humid heat: 0.9 MPa (a decrease of approximately 50%) Through a diameter of 6 mm (4 mm is considered a crack). Obvious blistering and localized wrinkling; significant whitening; markedly reduced adhesion. Commercially available competitor C ink <![CDATA[50 o C*7d: No obvious stratification, but fine sedimentation; viscosity increased by approximately 6%. 240h: Slight whitening, no obvious bubbling; but adhesion decreased at the marked areas. Initial pressure: 2.6 MPa; after humid heat: 1.6 MPa (a decrease of approximately 38%) Passing through a diameter of 4 mm (occasionally cracks are seen at the corners). The appearance is acceptable but there is slight whitening; adhesion has decreased and abrasion resistance has deteriorated. Example 1: Preparation of Water-Based Ink <![CDATA[50 o C*7d: No stratification / no flocculation / no sedimentation; viscosity change ≤3% 240h: No bubbling, no whitening, no edge curling; intact film layer, appearance basically unchanged. Initial pressure: 4.8 MPa; after humid heat: 4.1 MPa (a decrease of approximately 15%) Passing through a diameter of 2 mm (without cracks) No bubbling / no whitening / no wrinkling; stable color; good adhesion, and essentially unchanged resistance to rubbing.

[0077] Conclusion of Example 1 (Tinplate): Based on the storage stability (GB / T 6753.3), damp heat resistance (GB / T 1740), pull-off adhesion (GB / T 5210), flexibility (GB / T 1731), and the 121℃ / 30min cooking test results, the water-based ink of Example 1 outperforms competitors A / B / C in all indicators. Its system is more stable under accelerated storage at 50℃, with minimal viscosity change; after damp heat and cooking, the ink film does not bubble, whiten, or curl, exhibiting higher adhesion retention; simultaneously, it shows no cracks even at smaller bending diameters, indicating that it possesses both good film-forming toughness and damp heat / cooking resistance durability.

[0078] Comparative Example 1: This comparative example illustrates the effect of nano-sized PBI powder on the high-temperature and humid heat resistance and cooking resistance of water-based inks. Except for the absence of nano-sized PBI powder in the second step's PBI pre-dispersion solution, the types of raw materials, proportions, preparation steps, and process conditions were consistent with Example 1. Specifically, the mass fraction of nano-sized PBI powder in the second step was replaced by an equal amount of deionized water to maintain a similar total system volume and application viscosity. Subsequently, a seed emulsion was prepared and emulsion polymerization was carried out using the same method as in Example 1 to obtain the corresponding water-based ink.

[0079] The water-based ink obtained in Comparative Example 1 was coated onto a commercially available tinplate sheet for coating testing under the same conditions as in Example 1. Storage stability, resistance to damp heat, adhesion, flexibility, and a 121°C / 30min boiling test were performed using the same method as in Example 1. The test results showed that, compared to Example 1, Comparative Example 1 maintained basic usability in terms of initial adhesion and workability. However, after high-temperature damp heat treatment and a 121°C boiling treatment, the ink film was more prone to loss of gloss, slight whitening, edge lifting, or localized blistering, and the adhesion retention rate decreased significantly. Simultaneously, the abrasion resistance and film integrity after boiling also decreased. These results indicate that introducing nano-sized PBI powder into the system of this invention can significantly improve the structural stability and heat aging resistance of the ink film in a high-temperature and high-humidity environment, thereby significantly improving its resistance to damp heat and boiling.

[0080] Comparative Example 2: This comparative example illustrates the effect of functional amines on the adhesion and adhesion retention rate of water-based inks after wet heating. Except for the absence of functional amines in the seed emulsion in step three, the types of raw materials, proportions, preparation steps, and process conditions were consistent with Example 1. Specifically, the mass fraction of functional amines in step three was replaced by an equal amount of deionized water to maintain the system's solid content and application viscosity as close as possible; subsequently, the seed emulsion was prepared and emulsion polymerization was carried out using the same method as in Example 1, and the corresponding water-based ink was obtained.

[0081] The water-based ink obtained in Comparative Example 2 was coated onto a commercially available tinplate sheet for coating testing under the same conditions as in Example 1. Storage stability, damp heat resistance, adhesion, flexibility, and a 121°C / 30min boiling test were performed using the same method as in Example 1. The test results showed that, compared to Example 1, Comparative Example 2 had acceptable apparent film-forming properties before damp heat treatment, but its initial adhesion to the tinplate substrate showed a decreasing trend. After damp heat treatment and boiling treatment, the adhesion degradation was more significant, the cross-cut or pull-out test results worsened, and local delamination or edge lifting was more likely to occur at the interface. These results indicate that functional amines in the system of this invention can significantly enhance the interaction between the resin and substrate interface, improve the anchoring effect of the ink film on metal and other substrates, and improve the adhesion retention rate under damp heat conditions.

[0082]

[0083] The comparison results of Example 1, Comparative Example 1 and Comparative Example 2 show that: (1) When no nano-sized PBI powder is added, the integrity and performance retention of the film layer under high temperature, humidity and cooking environment are significantly reduced, indicating that PBI plays an important role in improving heat aging resistance and inhibiting film softening and instability under humid conditions; (2) When no functional amine is added, the interfacial bonding between the ink film and the substrate is significantly weakened, especially after humid heat or cooking, the adhesion decay is more significant, indicating that functional amine plays an important role in enhancing interfacial adhesion and improving adhesion retention rate; (3) By synergistically introducing PBI and functional amine, the present invention enables the obtained water-based ink to simultaneously possess excellent high temperature and humidity resistance, cooking resistance and adhesion retention performance.

[0084] Example 2

[0085] Step 1: Load 95% yttrium stabilized zirconia beads (0.03mm particle size, 84% bead load) into a cryogenic ball mill (Cryo / Mill 6870D custom model), open the inner jacket of the ball mill, circulate liquid nitrogen, and control the temperature to -65°C. o C±2 o C. Pour in 90g of PBI powder (Celazole® PBI, Changzhou Puwei Composite Materials Co., Ltd., model U-60), and grind repeatedly until the powder particle size D90 < 0.3μm (D90 = 0.12μm measured by laser particle size analyzer). After filtering through a 5000-mesh vibrating sieve, 88.5g of nano-sized PBI is obtained.

[0086] Step 2: Add the materials in the table below in order, totaling 180g, and simultaneously use a homogenizer at 2700rpm for 3 hours to disperse evenly. Then filter through a 200-mesh filter to prepare 177.1g of PBI pre-dispersion.

[0087]

[0088] Step 3: Add a total of 260g of the materials listed in the table below to a beaker and mix at 1800rpm for 30 minutes until a milky white, homogeneous solution is formed and does not separate into layers when left to stand.

[0089]

[0090] Step 4: Pour 260g of the seed emulsion from Step 3 into a four-necked flask for emulsion polymerization, purge with nitrogen to purge oxygen, then add 177.1g of the PBI pre-dispersion prepared in Step 2 dropwise into the seed emulsion, while simultaneously raising the temperature to 88°C. o C±2 o C, polymerization time 3.5 hours. After the reaction was completed, the mixture was cooled to room temperature and filtered through a 100-mesh filter to obtain 431.9 g of PBI-FA hybrid emulsion.

[0091] Step 5: Add the ingredients listed in the table below, totaling 100g, to a glass beaker. Disperse the mixture at 300 rpm for 10 minutes, then filter through a 100-mesh screen to obtain the water-based ink. At 25... o The viscosity was measured at room temperature using a Zahn Cup 4# with a value of 12.00 seconds, and the pH value was measured to be 8.55 using a pH meter.

[0092]

[0093] Several commercially available yellow water-based inks resistant to high temperature and humidity were selected as reference samples. Using a Zhongshan Nuobang W100T coating machine and a 3μm OSP coating rod, the inks were evenly coated onto commercially available OPP film for retort packaging of food. The specific test results are shown in the table below.

[0094] GB / T 6753.3-1986 Test Methods for Storage Stability of Coatings GB / T 1740-2007 Test Method for Resistance to Damp Heat of Coatings GB / T 5210-2006 Adhesion Test by Pull-Off Method GB / T 1731-2020 "Test for flexibility of paint films" Changes in the appearance and properties of the paint film after high-pressure cooking at 121℃ for 30 minutes Commercially available competitor D ink <![CDATA[50 o C*7d: Slight stratification; viscosity increased by approximately 10%; slight coarsening observed. 240h: Slight whitening; decreased adhesion at the edges, with small areas of peeling. Initial pressure: 1.6 MPa; after humid heat: 0.8 MPa (a 50% decrease) Slight cracking occurs when bending a 3 mm diameter object (2 mm bend). Slight whitening + peeling edges; decreased abrasion resistance E-ink, a competitor in the market <![CDATA[50 o C*7d: Clear stratification; visible flocculation / coarse particles; viscosity increased by approximately 18%. 240h: Obvious whitening accompanied by stickiness; localized blistering. Initial pressure: 1.3 MPa; after humid heat: 0.6 MPa (a decrease of 54%) Through a diameter of 4 mm (3 mm is considered a crack) The whitening is obvious and sticky; localized peeling occurs. Commercially available competitor F ink <![CDATA[50 o C*7d: No obvious stratification; but soft sedimentation; viscosity increased by approximately 7%. 240h: The appearance is acceptable, but a micro-crack appears at the bend. Initial pressure: 2.0 MPa; after humid heat: 1.1 MPa (a decrease of 45%) Passing through a diameter of 3 mm (slight whitening at the crease). The appearance hasn't changed much, but there's cracking and ink bleeding at the bend. Example 2: Preparation of Water-Based Ink <![CDATA[50 o C*7d: No stratification, no coarse particles; slight soft settling but easily re-dispersible; viscosity change ≤4%. 240h: No whitening, no stickiness, no bubbling; no cracks at bends, film layer intact. Initial pressure: 3.9 MPa; after humid heat: 3.3 MPa (a decrease of approximately 15%) Passing through a diameter of 1 mm (no cracks / no whitening) The appearance is free from whitening and stickiness; it does not crack when bent; and it maintains good adhesion and abrasion resistance.

[0095] Example 2 Conclusion (OPP Film): Based on the above-mentioned standard tests, the water-based ink of Example 2 exhibits significantly better overall performance on retortable OPP films than competing products D / E / F. Its dispersion remains stable and easily redispersible after accelerated storage; after humid heat and retorting at 121℃ / 30min, it shows no whitening, stickiness, cracking, or ink fading, with less adhesion degradation; it also demonstrates better flexibility, meeting the durability requirements of water-based inks under retorting / sterilization conditions in film packaging.

[0096] The above is a detailed description of the embodiments, which is intended to enable those skilled in the art to correctly understand and use the present invention. Any improvements or modifications to technical solutions obtained by those skilled in the art based on the present invention and on the existing technology, without innovative effort but only through analysis, analogy, or limited enumeration, should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a water-based ink resistant to high temperature and humidity, characterized in that, Includes the following steps: S1. Polybenzimidazole (PBI) powder is freeze-milled to obtain nano-sized PBI powder. S2. Mix and disperse deionized water, emulsifier, coupling agent, initiator, defoamer with the nano-sized PBI powder to prepare PBI pre-dispersion; S3. Prepare a seed emulsion by mixing deionized water, emulsifier, at least one of acrylic monomer and acrylate monomer, functional amine and pH buffer. S4. The PBI pre-dispersion is added dropwise to the seed emulsion, and an in-situ polymerization reaction is carried out in an emulsion polymerization device to obtain a PBI-functional amine hybrid emulsion. S5. The PBI-functional amine hybrid emulsion is mixed with defoamer, leveling agent, anti-abrasion agent and water-based color paste and dispersed evenly to obtain the high temperature and humidity resistant water-based ink; The functional amine is selected from at least one of dopamine, tyramine, 2-phenylethylamine, polyethyleneimine, tris(2-aminoethyl)amine, N-(2-hydroxyethyl)ethylenediamine, and isophoronediamine.

2. The preparation method according to claim 1, characterized in that, In step S1, the cryogenic grinding is carried out in a liquid nitrogen cryogenic ball mill, and the grinding temperature is controlled at -100℃±50℃; the particle size D90 of the nano-sized PBI powder obtained after grinding is <0.3μm.

3. The preparation method according to claim 1, characterized in that, In step S2, the coupling agent is selected from at least one of 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, bis-(3-trimethoxysilylpropyl)amine, anilinemethyltriethoxysilane, diethylaminomethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-ureapropyltrimethoxysilane, and 3-ureapropyltriethoxysilane. In step S3, at least one of the acrylic monomers and acrylate monomers is selected from at least one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, isooctyl acrylate, isooctyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

4. The preparation method according to claim 1, characterized in that, In step S2, the components of the PBI predispersant, by mass percentage, include: 45%~75% deionized water, 1%~10% emulsifier, 1%~5% coupling agent, 0.1%~1% initiator, 0.1%~0.5% defoamer, and 20%~40% nano-sized PBI powder.

5. The preparation method according to claim 1, characterized in that, In step S3, the components of the seed emulsion, by mass percentage, include: 38%~66% deionized water, 1%~3% emulsifier, 1%~5% functional amine, 30%~55% of at least one of acrylic monomer and acrylate monomer, and 0.1%~1% pH buffer.

6. The preparation method according to claim 1, characterized in that, In step S4, after the PBI pre-dispersion liquid is added dropwise to the seed emulsion, the polymerization reaction temperature is controlled at 70℃~90℃ and the reaction time is 1~8 hours.

7. The preparation method according to claim 1, characterized in that, In step S5, the components of the water-based ink, by mass percentage, include: 60%~98% PBI-functional amine hybrid emulsion, 0.1%~1% defoamer, 0.1%~1% leveling agent, 0.1%~1% anti-abrasion agent, and 1%~40% water-based color paste.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In steps S2 and S3, the emulsifier is independently selected from at least one of sodium dodecylbenzenesulfonate, polyoxyethylene sorbitan monooleate, polyoxyethylene cetyl ether, alkylphenol polyoxyethylene ether, decaglycerol monolaurate, sodium lauryl ether sulfate, and soybean lecithin.

9. A water-based ink resistant to high temperature and humidity, characterized in that, The water-based ink is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the high-temperature and humid heat resistant water-based ink as described in claim 9 in food packaging printing, industrial marking, or metal or glass decorative printing.

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