High adhesion retort resistant waterborne polyurethane ink and method of making

Abstract

The application belongs to the field of functional coatings, and particularly relates to a high-adhesion and steam-cooking-resistant water-based polyurethane ink and a preparation method thereof. The high-adhesion and steam-cooking-resistant water-based polyurethane ink comprises the following raw materials in parts by weight: water-based polyurethane binder 100 parts; pigment 20-40 parts; dispersing agent 1.0-3.0 parts; defoaming agent 0.1-0.5 parts; leveling agent 0.5-1.5 parts; deionized water 5-20 parts; wherein the water-based polyurethane binder is a composition of water-based polyurethane dispersion and ADH. The application solves the problems of insufficient adhesion of the existing water-based polyurethane ink to substrates such as PET, PVC and aluminum foil and easy peeling after steam cooking by molecular structure design of the water-based polyurethane binder and formula design.

Description

Technical Field

[0001] This invention belongs to the field of ink technology, specifically relating to a high-adhesion, retort-resistant waterborne polyurethane ink and its preparation method. Background Technology

[0002] Waterborne polyurethane inks, due to their low volatile organic compound (VOC) emissions, excellent environmental performance, good flexibility, and superior film-forming properties, have been widely used in food packaging, pharmaceutical packaging, daily chemical packaging, and composite flexible packaging in recent years. However, with the rapid development of high-temperature retort packaging, frozen food packaging, and high-barrier composite packaging, packaging materials not only need to have a good printed appearance but also require the ink layer to maintain excellent adhesion, water resistance, media resistance, and abrasion resistance under high-temperature retort conditions. In particular, packaging substrates with different polarities, such as PET, PVC, OPP, PE, metallized film, and aluminum foil, have significant differences in surface chemical composition, surface energy, and interfacial interaction modes. Traditional waterborne polyurethane inks struggle to achieve high adhesion performance on multiple substrates simultaneously. Therefore, high adhesion, retort resistance, and multi-substrate adaptability have become important development directions for high-end waterborne packaging inks.

[0003] Currently, to improve the water and boiling resistance of water-based polyurethane inks, existing technologies typically employ methods such as increasing the content of polyurethane hard segments, increasing the amount of crosslinking agent, introducing polycarbonate soft segments, or using a two-component crosslinking system to increase crosslinking density and film compactness. While these methods can improve resistance to media to some extent, they still have some shortcomings: increasing the proportion of hard segments or crosslinking density often reduces the flexibility of polyurethane molecular chains, increasing ink brittleness and affecting the bending and composite processing performance of flexible packaging films; and the crosslinking agent in a two-component system is prone to rapid reaction after mixing, leading to a shortened pot life, decreased storage stability, and increased application difficulty. Furthermore, some highly crosslinked systems, because the crosslinking reaction mainly occurs during the mixing stage, struggle to balance printing leveling and subsequent boiling resistance.

[0004] On the other hand, to improve the adhesion of inks on different substrates, existing technologies typically employ methods such as increasing resin polarity, adding coupling agents, and grafting hydroxyl or carboxyl functional groups to enhance interfacial interactions. However, relying solely on polar groups to form hydrogen bonds or van der Waals forces offers limited improvement in interfacial bonding between low surface energy polyolefin substrates and metallized films. Simultaneously, some small-molecule coupling agents are prone to migration, precipitation, or hydrolysis, leading to a significant decrease in interfacial bonding after prolonged immersion or high-temperature cooking, resulting in adhesion degradation. Furthermore, existing binders generally focus more on the resin's resistance to various media, while paying less attention to pigment wetting and dispersion properties. Different pigment systems often require re-adjustment of formulations, which can easily lead to pigment flocculation, storage sedimentation, decreased gloss, and hue shift, limiting the universal application of the same binder in various pigment systems.

[0005] Therefore, how to design the molecular structure of polyurethane to ensure good storage stability of waterborne polyurethane dispersions while also taking into account high adhesion performance to multiple substrates, good dispersibility of multiple pigments, excellent resistance to boiling and steaming, and avoiding the problems of short application period and insufficient performance in the later stage of traditional two-component systems, and to achieve good application performance in the early stage of film formation and post-curing characteristics that continuously improve crosslinking density after film formation, has become an important technical problem that urgently needs to be solved in the field of high-performance waterborne polyurethane ink binders. Summary of the Invention

[0006] The purpose of this invention is to address the problems of insufficient adhesion and easy detachment of existing waterborne polyurethane inks on substrates such as PET, PVC, and aluminum foil after boiling, and to provide a high-adhesion, boil-resistant waterborne polyurethane ink and its preparation method. Through structural design, catechol anchoring structures, microbranched structures, and AAEM ketone grafting structures are introduced into the polyurethane molecular chain, and a hydrazone crosslinking network is formed after ADH post-curing, effectively improving the ink's interfacial adhesion, water resistance, boiling resistance, alcohol resistance, and anti-blocking properties. To achieve the above objectives, the technical solution adopted by this invention to solve its technical problems is as follows: This invention provides a high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following raw materials in parts by weight: 100 parts of waterborne polyurethane binder; 20-40 parts pigment; Dispersant 1.0-3.0 parts; 0.1-0.5 parts of defoamer; Leveling agent 0.5-1.5 parts; 5-20 parts deionized water; The waterborne polyurethane binder is a composition of a waterborne polyurethane dispersion and ADH (adipic acid dihydrazide); and The aqueous polyurethane dispersion is a catechol-modified ketone-grafted anionic aqueous polyurethane dispersion. The ADH is used to form a hydrazone crosslinking network with the ketone graft structure in the aqueous polyurethane dispersion after film formation.

[0007] Furthermore, The molecular chain of the aqueous polyurethane dispersion contains a carboxylate hydrophilic structure, a polycarbonate soft segment, a polyester soft segment, a urea bond hard segment, a microbranched structure formed by triols, a catechol structure, and a ketone grafting structure.

[0008] Furthermore, The waterborne polyurethane binder has a solid content of 33±1%, a pH of 7.5-9.5, and an average particle size of 60-150nm.

[0009] Furthermore, The waterborne polyurethane binder includes the following preparation steps: S11, a diol, a carboxyl-containing diol, a triol and a diisocyanate are reacted to prepare a -NCO-terminated polyurethane prepolymer with a microbranched structure. The raw material proportions, based on the total hydroxyl content of the system, are as follows: -NCO / -OH molar ratio is 1.40-1.80:1; carboxyl diols account for 5-20 mol% of the total hydroxyl content; triols account for 0.5-2.0 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:0.60-1.00:0.20-0.50; S12, neutralize the -NCO-terminated polyurethane prepolymer; The degree of neutralization is 80-100%; S13, add an amino-containing catechol structure to the product of S12 to react with some isocyanate groups; The amount of the amino-containing catechol structure added is such that the amino / -NCO molar ratio is 0.05-0.15:1; S14, deionized water and diamine chain extender are simultaneously added dropwise to the product of S13 to complete the phase inversion dispersion and chain extension; The diamine is added in an amino / -NCO molar ratio of 1.05-1.15:1. S15, add a ketone functional monomer, and allow the α,β-unsaturated double bond in the ketone functional monomer to undergo an aza-Michael addition reaction with the primary amine and / or secondary amine to introduce a ketone graft structure, thereby obtaining an aqueous polyurethane dispersion; The amount of the ketone functional monomer added is such that the molar ratio of amino to unsaturated double bond is 1:0.7-1.0; S16, add ADH to obtain the water-based polyurethane ink binder; The ADH is added at a molar ratio of hydrazide to ketone of 0.5-1.0:1.

[0010] Furthermore, The diisocyanate is added by adding HDI and IPDI at a molar ratio of 1:1.0-3.0; and The amino-containing catechol has the structure of dopamine.

[0011] Furthermore, The ketone functional monomer is AAEM (ethyl acetoacetate methacrylate) or DAAM (diacetone acrylamide).

[0012] Furthermore, The pigment is one or more of the following: titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, azo pigment, quinacridone pigment, permanent red, permanent yellow, iron oxide pigment, aluminum powder pigment, and pearlescent pigment.

[0013] Another object of the present invention is to provide the above-mentioned high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following preparation steps: S21, mix waterborne polyurethane binder, dispersant and part of deionized water to obtain premixed liquid; S22, pigment is added to the premixed liquid, and high-speed dispersion and grinding are performed to obtain pigment slurry; S23, add defoamer, leveling agent and remaining deionized water to the pigment slurry, stir evenly, adjust viscosity and pH, and filter to obtain the high adhesion and boil-resistant waterborne polyurethane ink. During the grinding process, the slurry temperature is ≤40℃; the fineness of the ground pigment is ≤15μm; and the viscosity of the high-adhesion, boil-resistant waterborne polyurethane ink measured at 25℃ using a Forecast cup is 12-30s.

[0014] Another object of the present invention is to provide the application of the above-mentioned high-adhesion, retort-resistant waterborne polyurethane ink in the printing of food packaging films, pharmaceutical packaging films, daily chemical packaging films or composite flexible packaging, wherein the high-adhesion, retort-resistant waterborne polyurethane ink is used for surface printing on PET, PVC, OPP, PE, aluminum foil or metallized film substrates.

[0015] The present invention has the following beneficial effects: (1) This invention provides a high-adhesion, retort-resistant waterborne polyurethane ink. By introducing a catechol adhesion structure into the waterborne polyurethane dispersion, the binder can form hydrogen bonds, coordination adsorption and multi-point interface anchoring with the surfaces of PET, PVC, aluminum foil, aluminized film and inorganic pigments, thereby improving the initial adhesion of the ink to non-absorbent packaging substrates and the adhesion retention rate after retort.

[0016] (2) The present invention forms a microbranched structure in the polyurethane prepolymer by triol, which compensates for the chain growth termination effect caused by dopamine monoamine end capping, thereby improving the cohesive strength of the polyurethane molecular chain and the compactness of the film layer; at the same time, the polycarbonate soft segment and the urea bond hard segment synergistically improve the hydrolysis resistance, heat resistance and alcohol swelling resistance of the film layer, thereby improving the ink’s resistance to boiling, steaming, alcohol and anti-blocking properties.

[0017] (3) This invention directly grafts ketone groups onto the polyurethane chain and forms a hydrazone crosslinking network with ADH after film formation. This structure avoids the problems of initiator residue, monomer residue and phase separation in traditional free radical polymerization. While maintaining the flexibility and resolubility of waterborne polyurethane, it improves the resistance to humid heat, alcohol resistance and gloss retention after film formation.

[0018] (4) The waterborne polyurethane dispersion of the present invention has both a hydrophilic structure of carboxylate and a polar adsorption structure of catechol, which has good wetting, adsorption and dispersion stabilization effects on pigments, can reduce the risk of pigment agglomeration and sedimentation, and improve grinding efficiency, coloring uniformity and ink storage stability.

[0019] In summary, this invention, through the molecular structure design of "catechol interface anchoring - microbranching reinforcement - ketone grafting - ADH post-crosslinking" and combined with the optimization of the pigment dispersion system, achieves synergistic effects from four aspects: interface adhesion, film cohesion, post-curing resistance, and pigment dispersion stability. This results in a waterborne polyurethane ink with high adhesion, resistance to boiling, alcohol resistance, high gloss, and low VOC, suitable for food, pharmaceutical, and composite flexible packaging printing. Detailed Implementation

[0020] The present invention will be described in detail below with reference to the embodiments. However, it should be understood that the following embodiments are merely illustrative examples of the implementation of the present invention and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer, and the raw materials used in the following embodiments are all commercially available.

[0021] The purpose of this invention is to develop a high-adhesion, retort-resistant waterborne polyurethane ink. The approach is as follows: addressing the problems of insufficient adhesion to substrates such as PET, PVC, and aluminum foil, and easy detachment after retort in existing waterborne polyurethane inks, this invention focuses on the design of the polyurethane molecular chain structure and the construction of a post-curing crosslinking system. It designs a catechol-modified ketone-grafted anionic waterborne polyurethane binder that combines high adhesion, high dispersion, high resistance to media, and post-curing capability, and synergistically forms a continuous crosslinking system after film formation with ADH. The theoretical basis lies in the following: A dual-segment structure combining hydrolysis resistance, flexibility, and pigment wetting is constructed using polycarbonate and polyester soft segments. A trace amount of triol forms a microbranched polyurethane framework, improving dispersion stability and film density. Subsequently, the primary amino groups in dopamine react with the polyurethane chain to introduce a catechol-attached structure into the polyurethane molecular chain. Through hydrogen bonding, coordination, and π-π interactions between the catechol groups and different substrates, interfacial bonding is enhanced. Furthermore, AAEM (or DAAM) is grafted into the polyurethane chain via a aziramid addition reaction, introducing ketone functional sites. During ink film formation, it gradually forms a hydrazone bond network with ADH, achieving a continuous increase in crosslinking density over time. The synergistic effect of these molecular structures gives the ink excellent pigment dispersibility, multi-substrate adhesion, water resistance, boiling resistance, and solvent resistance, while maintaining good storage stability and application period, meeting the comprehensive performance requirements of high-end flexible packaging printing. Examples of this invention are as follows: This invention provides a high-adhesion, retort-resistant water-based polyurethane ink, comprising the following raw materials in parts by weight: 100 parts of waterborne polyurethane binder; 20-40 parts pigment; Dispersant 1.0-3.0 parts; 0.1-0.5 parts of defoamer; Leveling agent 0.5-1.5 parts; 5-20 parts deionized water; Wherein, the waterborne polyurethane binder is a composition of waterborne polyurethane dispersion and ADH; and The aqueous polyurethane dispersion is a catechol-modified ketone-grafted anionic aqueous polyurethane dispersion. The molecular chain of the aqueous polyurethane dispersion contains a carboxylate hydrophilic structure, a polycarbonate soft segment, a polyester soft segment, a urea bond hard segment, a microbranched structure formed by triol, a catechol attachment structure, and a ketone-grafted structure. The ADH is used to form a hydrazone crosslinking network with the ketone graft structure after film formation.

[0022] The waterborne polyurethane binder has a solid content of 33±1%, a pH of 7.5-9.5, and an average particle size of 60-150nm.

[0023] The waterborne polyurethane binder includes the following preparation steps: S11: Polycarbonate diol, polyester diol, 1,4-butanediol, carboxyl-containing diols and triols are added to a reactor equipped with a mechanical stirrer, thermometer, nitrogen inlet, condenser, and vacuum interface. The mixture is vacuum dehydrated for 1-2 hours at 100-120℃ and -0.08 to -0.095 MPa until the water content is controlled below 500 ppm. After dehydration, the system is cooled to 70-80℃, and diisocyanate and dibutyltin dilaurate are added. The mixture is then heated to 75-85℃ under nitrogen protection and reacted for 2-4 hours to obtain a -NCO-terminated polyurethane prepolymer with a microbranched structure.

[0024] The raw material proportions, based on the total hydroxyl content of the system, are as follows: -NCO / -OH molar ratio is 1.40-1.80:1; carboxyl diols account for 5-20 mol% of the total hydroxyl content; triols account for 0.5-2.0 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:0.60-1.00:0.20-0.50; The amount of dibutyltin dilaurate used is 0.05 wt% of the total mass of the reactants.

[0025] The carboxyl-containing diol can be DMPA (dimethylolpropionic acid) or DMBA (dimethylolbutyric acid); and DMPA is preferred.

[0026] The triol can be TMP (trimethylolpropane), or glycerol or trimethylolethane. TMP is used to form a slightly branched structure in the prepolymer stage to compensate for the chain growth termination effect caused by subsequent dopamine monoamine capping.

[0027] The weight-average molecular weight of the polycarbonate diol is preferably 1000-2000; specifically, Kuraray Polyol C-1090, C-2050, and C-2090 can be used; and in the following examples and comparative examples of the present invention, the polycarbonate diol is Kuraray Polyol C-1090 (weight-average molecular weight 2000).

[0028] The weight-average molecular weight of the polyester diol is preferably 1000-3000; it can be 1,4-butanediol adipic acid, neopentyl glycol adipic acid, polycaprolactone diol, etc.; and the polyester diol mentioned in the following examples and comparative examples of the present invention is 1,4-butanediol adipic acid, brand name HY-2022 (weight-average molecular weight 2000), purchased from Xuzhou Yihuiyang New Materials Co., Ltd.

[0029] The diisocyanate is prepared in a molar ratio of HDI to IPDI of 1:1.0-3.0.

[0030] Depending on the viscosity change, 10-25% acetone by mass of the prepolymer is added to the reaction system as a co-solvent, and then removed under reduced pressure.

[0031] S12, cool the -NCO-terminated polyurethane prepolymer obtained in S11 to 45-55℃, add a neutralizing agent to neutralize the carboxyl groups; keep the system anhydrous during the neutralization process and stir continuously for 20-40 minutes to fully convert the carboxyl groups into carboxylate structures, providing hydrophilic groups for subsequent water dispersion.

[0032] The degree of neutralization is 80-100%, preferably 90-100%.

[0033] The neutralizing agent can be triethylamine, AMP-95, or ammonia, preferably triethylamine.

[0034] After neutralization, instead of water dispersion, the process proceeds directly to step S13 to avoid hydrolysis of the -NCO group upon entering the aqueous phase, thereby improving the grafting efficiency of the subsequent catechin structure.

[0035] S13: Prepare a 5-15 wt% NMP solution containing amino-containing catechol structures. Adjust the pH to 6.8-7.5 with triethylamine. Slowly add the solution dropwise to the neutralized -NCO-terminated polyurethane prepolymer obtained in S12 under light-protected and nitrogen-protected conditions. Control the reaction temperature at 35-50℃ and the dropwise addition time at 15-40 min. After the dropwise addition is completed, continue stirring for 30-90 min to allow the primary amino groups in the amino-containing catechol structures to undergo an addition reaction with some isocyanate groups, forming a catechol-attached structure.

[0036] The amount of the amino-containing catechol structure added is such that the amino / -NCO molar ratio is 0.05-0.15:1.

[0037] The amino-containing catechol is preferably dopamine.

[0038] S14: The system obtained in S13 is slowly added to deionized water for phase inversion dispersion, and a diamine chain extender aqueous solution is added simultaneously to carry out chain extension reaction to obtain anionic aqueous polyurethane dispersion; wherein, the water dispersion temperature is controlled at 20-35℃, the dispersion speed is 1000-2000 r / min, and the water addition time is 20-40 min; then, a diamine chain extender aqueous solution with a mass concentration of 5-20 wt% is added dropwise over a time of 20-60 min, and after the addition is completed, the reaction continues for 30-90 min to allow the remaining isocyanate groups to undergo chain extension reaction with the diamine.

[0039] The diamine is added in an amino / -NCO molar ratio of 1.05-1.15:1.

[0040] The diamine chain extender may be one or more of EDA (ethylenediamine), IPDA (isophorone diamine), HDA (hexamethylenediamine), DETA (diethylenetriamine), and AEEA (aminoethyl ethanolamine), preferably EDA.

[0041] S15, the ketone functional monomer is added to the aqueous polyurethane dispersion containing amino reaction sites obtained in S14, and reacted at 40-60℃ for 2-4h, so that the α,β-unsaturated double bond in the ketone functional monomer undergoes aza-Michael addition reaction with the primary amino and / or secondary amino groups in the polyurethane molecular chain, thereby grafting the ketone group into the polyurethane molecular chain to obtain the aqueous polyurethane dispersion.

[0042] The amount of the ketone functional monomer is added at an amino / unsaturated double bond molar ratio of 1:0.7-1.0.

[0043] The ketone functional monomer is AAEM or DAAM.

[0044] When the ketone functional monomer is AAEM, AAEM is pre-emulsified with a small amount of deionized water, pH adjuster and nonionic emulsifying agent before addition. The pre-emulsification stirring speed is 800-1500 r / min and the time is 10-20 min. Then, it is added dropwise to the system at 40-55℃ and pH 8.0-8.8 for 20-60 min. After addition, the reaction is continued at the temperature for 2-3 h.

[0045] When the ketone functional monomer is DAAM, DAAM is prepared as a 30wt% aqueous solution.

[0046] S16: Dissolve ADH in deionized water to prepare a 5-15 wt% ADH aqueous solution. Add the solution to the dispersion obtained in S15 at 25-35℃, stir for 20-60 min, filter through a 100-200 mesh filter, and seal for storage to obtain the water-based polyurethane ink binder. The storage temperature is 5-35℃, and direct sunlight should be avoided.

[0047] The ADH is added at a molar ratio of hydrazide to ketone of 0.5-1.0:1.

[0048] The resulting waterborne polyurethane binder has a solid content of 33±1%, a pH of 7.5-9.5, and an average particle size of 60-150nm.

[0049] The above reaction steps S11-S15 of this invention are for the preparation of an aqueous polyurethane dispersion, wherein: the reaction proceeds in S11 and S13-S14 by -NCO titration; the amount of neutralizing agent added in S12 is determined by acid-base titration; and S15 is characterized by infrared spectroscopy (1611 cm⁻¹). -1 (-C=C- does not exist) Confirmation. The above S16 step of this invention is a blending operation of the aqueous polyurethane dispersion and ADH.

[0050] The pigment is one or more of the following: titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, azo pigment, quinacridone pigment, permanent red, permanent yellow, iron oxide pigment, aluminum powder pigment, and pearlescent pigment; the titanium dioxide can be one or more of Chemours Ti-Pure R-902+, LB Group BILLIONS BLR-699, and Ishihara R-930; the carbon black can be one or more of the Cabot MOGULL and Orion SPECIAL BLACK series; the water-based pigment paste can be LANXESS Levanyl or Levanox series.

[0051] The dispersant may be one or more of DISPERBYK-190, DISPERBYK-2012, and TEGO Dispers 750 W.

[0052] The defoamer may be one or more of BYK-024 and TEGO Foamex 810; The leveling agent may be one or more of BYK-346 and BYK-3455.

[0053] Another objective of this invention is to provide the above-mentioned high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following preparation steps: S21. Add waterborne polyurethane binder, dispersant and part of deionized water to a dispersion tank and stir at 500-800 r / min for 10-20 min at room temperature to obtain a premix.

[0054] S22: Under stirring conditions of 800-1200 r / min, add the pigment in batches to the premixed liquid obtained in S21, with an addition time of 15-30 min. After addition, increase the rotation speed to 1500-2500 r / min and disperse at high speed for 20-40 min to obtain a coarse dispersion slurry. Transfer the coarse dispersion slurry to a horizontal sand mill or basket mill for grinding. The preferred grinding media are 0.3-0.8 mm zirconia beads with a filling rate of 60-80%; the sand mill speed is 1800-3000 r / min, and the temperature is controlled by the cooling water jacket to keep the slurry temperature ≤40℃; the grinding time is 30-120 min. The grinding endpoint is controlled so that the pigment fineness is ≤15μm; for high-gloss gravure or flexographic printing inks, it is preferred to control D90 ≤5μm.

[0055] S23: Add defoamer, leveling agent, and remaining deionized water to the pigment slurry obtained in S22. Stir at 500-800 r / min for 10-30 min to adjust the viscosity and pH of the system. After filtration, the high-adhesion, retort-resistant waterborne polyurethane ink is obtained. The final ink has a pH of 7.5-9.0 and a viscosity of 12-30 s measured using a Ford cup at 25°C. The prepared ink is filtered through a 200-400 mesh filter, allowed to stand for degassing for 2-12 hours, and then filled. The preferred filling containers are light-proof plastic buckets or internally coated metal buckets, and the storage temperature is 5-35°C.

[0056] Another objective of this invention is to provide the application of the aforementioned high-adhesion, retort-resistant waterborne polyurethane ink in the printing of food packaging films, pharmaceutical packaging films, daily chemical packaging films, or composite flexible packaging. The high-adhesion, retort-resistant waterborne polyurethane ink is used for surface printing on PET, PVC, OPP, PE, aluminum foil, or metallized film substrates. The printing method can be gravure printing. Before printing, the substrate surface is preferably subjected to corona treatment or plasma treatment to achieve a surface tension of 38 mN / m or higher. The wet film thickness is 3-10 μm, and the dry film thickness is 0.8-3.0 μm. The drying temperature is 60-90℃, and the drying time is 10-60 s.

[0057] The working mechanism of the waterborne polyurethane binder of this invention: This invention employs a molecular structure design. First, polycarbonate soft segments, polyester soft segments, and a carboxylate hydrophilic structure are introduced into the polyurethane backbone. The polycarbonate soft segments impart excellent hydrolysis and cooking stability to the system, while the polyester soft segments enhance the wetting ability of pigments and packaging substrates. The carboxylate hydrophilic structure ensures the dispersion forms a uniform particle size and a stable aqueous system, working with the dispersant to promote uniform wetting and stable dispersion of different organic and inorganic pigments in the binder, thereby improving ink color strength, gloss, and printing stability. Second, the catechol structure introduced by dopamine can form a stable interfacial adsorption layer with different substrates such as PET, PVC, OPP, PE, aluminum foil, and metallized film through multiple interfacial interactions including hydrogen bonding, metal coordination, π-π interactions, and van der Waals forces, significantly improving adhesion and interfacial bonding stability under humid and hot environments. Third, the microbranched structure formed by trace amounts of triols improves the entanglement of polyurethane molecular chains and the film density, enhancing the mechanical strength and media resistance of the film while maintaining flexibility. Finally, a ketone structure is formed through AAEM (or DAAM) grafting, and hydrazone crosslinking gradually occurs with ADH during film formation and subsequent storage, constructing a post-cured three-dimensional network. This allows the crosslinking density to continuously increase over time, effectively restricting polyurethane chain segment movement and reducing the penetration of moisture, ethanol, and vapors. Simultaneously, it improves resistance to MEK wiping, boiling water, and retorting. The synergistic interaction of these structures achieves comprehensive properties such as high adhesion, high dispersion, high gloss, high retorting resistance, and high resistance to various media, meeting the long-term service stability requirements of food, pharmaceutical, and daily chemical flexible packaging inks.

[0058] To further understand the present invention, the following detailed description of a high-adhesion, boil-resistant waterborne polyurethane ink and its preparation method is provided in conjunction with embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0059] Example 1

[0060] A high-adhesion, retort-resistant waterborne polyurethane ink comprises the following raw materials in parts by weight: 100 parts of waterborne polyurethane binder; 30 parts titanium dioxide; Dispersant DISPERBYK-190 2.0 parts; 0.3 parts of defoamer BYK-024; Leveling agent BYK-346 0.8 parts; 12 portions of deionized water.

[0061] The waterborne polyurethane binder includes the following preparation steps: S11, polycarbonate diol, polyester diol, 1,4-butanediol, DMPA and TMP were added to a reactor equipped with a mechanical stirrer, thermometer, nitrogen inlet, condenser and vacuum interface. The system was vacuum dehydrated for 1.5 h at 110 °C and -0.08 to -0.095 MPa to control the water content of the system below 500 ppm. After dehydration, the system was cooled to 75 °C, and diisocyanate and dibutyltin dilaurate were added. The system was then heated to 80 °C and reacted for 3 h under nitrogen protection to obtain a -NCO-terminated polyurethane prepolymer with microbranched structure.

[0062] The raw material proportions, based on the total hydroxyl content of the system, show a -NCO / -OH molar ratio of 1.60:1; DMPA accounts for 12 mol% of the total hydroxyl content; and TMP accounts for 1.2 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:0.80:0.35; The amount of dibutyltin dilaurate used is 0.05 wt% of the total mass of the reactants.

[0063] The diisocyanate is prepared by a molar ratio of HDI to IPDI of 1:2.0.

[0064] S12, the -NCO-terminated polyurethane prepolymer obtained in S11 is cooled to 50°C, and triethylamine is added to neutralize the carboxyl groups; during the neutralization process, the system is kept anhydrous, and stirring is continued at 50°C for 30 min to fully convert the carboxyl groups into carboxylate structures.

[0065] The neutralization degree is 90%.

[0066] S13: Dopamine was prepared into a 10wt% NMP solution, and the pH was adjusted to 7.0 with triethylamine. Under light protection and nitrogen protection, it was slowly added dropwise to the neutralized -NCO-terminated polyurethane prepolymer obtained in S12. The reaction temperature was controlled at 40℃, and the addition time was 30 min. After the addition was completed, the mixture was stirred for another 60 min to allow the primary amino groups in dopamine to react with some of the isocyanate groups to form a catechol-attached structure.

[0067] The dopamine is added at an amino / -NCO molar ratio of 0.10:1.

[0068] S14: The system obtained in S13 was slowly added to deionized water for phase inversion dispersion. The water dispersion temperature was controlled at 25℃, the dispersion speed was 1500 r / min, and the water addition time was 30 min. After the water addition was completed, stirring was continued for 20 min. Then, a 10 wt% EDA aqueous solution was added dropwise at 30℃ for 45 min. After the addition was completed, the reaction was continued for 60 min to allow the remaining isocyanate groups to undergo chain extension reaction with EDA, thus obtaining an aqueous polyurethane dispersion containing amino reaction sites.

[0069] The EDA was added at an amino / -NCO molar ratio of 1.10:1.

[0070] S15, AAEM is added to the aqueous polyurethane dispersion containing amino reaction sites obtained in S14, and reacted at 50°C for 3 hours to allow the α,β-unsaturated double bonds in the ketone functional monomer to undergo a aziramidic addition reaction with the primary and / or secondary amino groups in the polyurethane molecular chain, thereby grafting the ketone group into the polyurethane molecular chain to obtain the aqueous polyurethane dispersion.

[0071] The AAEM was added at a molar ratio of amino to unsaturated double bond of 1:0.85.

[0072] S16: Dissolve ADH in deionized water to prepare a 10wt% ADH aqueous solution, add it to the dispersion obtained in S15 at 30℃, stir for 40 min, filter through a 100-200 mesh filter and seal for storage to obtain the water-based polyurethane ink binder; the storage temperature is 5-35℃, and direct sunlight should be avoided.

[0073] The ADH is added at a molar ratio of hydrazide to ketone of 0.75:1.

[0074] The resulting waterborne polyurethane binder had a solid content of 33.2%, a pH of 8.7, and an average particle size of 70-100 nm.

[0075] A high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following preparation steps: S21, add waterborne polyurethane binder, dispersant and part of deionized water into a dispersion tank, stir at 650 r / min for 15 min at room temperature to obtain a premixed solution.

[0076] In step S22, under stirring at 1000 r / min, the pigment is added in batches to the premixed liquid obtained in step S21 over a period of 25 min. After addition, the rotation speed is increased to 2000 r / min, and high-speed dispersion is carried out for 30 min to obtain a coarse dispersion slurry. The coarse dispersion slurry is then transferred to a horizontal sand mill for grinding. The grinding media consists of 0.5 mm zirconia beads with a filling rate of 70%; the sand mill speed is 2500 r / min, and the temperature is controlled by a cooling water jacket to keep the slurry temperature ≤40℃; the grinding time is 80 min. The grinding endpoint is controlled to have a pigment fineness ≤15 μm; for high-gloss gravure or flexographic printing inks, D90 is controlled to ≤5 μm.

[0077] S23: Add defoamer, leveling agent, and remaining deionized water to the pigment slurry obtained in S22. Stir at 650 r / min for 20 min to adjust the viscosity and pH of the system. After filtration, the high-adhesion, retort-resistant waterborne polyurethane ink is obtained. The final ink has a pH of 8.5 and a viscosity of 22s measured using a Ford cup at 25°C. The prepared ink is filtered through a 200-mesh filter, allowed to stand for 7 hours to defoam, and then filled. The preferred filling containers are light-proof plastic buckets or internally coated metal buckets, and the storage temperature is 5-35°C.

[0078] Example 2

[0079] A high-adhesion, retort-resistant waterborne polyurethane ink comprises the following raw materials in parts by weight: 100 parts of waterborne polyurethane binder; 20 parts carbon black; Dispersant DISPERBYK-190 1.0 part; Defoamer BYK-024 0.1 parts; Leveling agent BYK-346 0.5 parts; 5 parts deionized water.

[0080] The waterborne polyurethane binder includes the following preparation steps: S11, polycarbonate diol, polyester diol, 1,4-butanediol, DMPA and TMP were added to a reactor equipped with a mechanical stirrer, thermometer, nitrogen inlet, condenser and vacuum interface. The system was vacuum dehydrated for 1 hour at 120℃ and -0.08 to -0.095 MPa to control the water content of the system below 500 ppm. After dehydration, the system was cooled to 80℃, and diisocyanate and dibutyltin dilaurate were added. The system was then heated to 85℃ and reacted for 2 hours under nitrogen protection to obtain a -NCO-terminated polyurethane prepolymer with microbranched structure.

[0081] The raw material ratios, based on the total hydroxyl content of the system, show a -NCO / -OH molar ratio of 1.40:1; DMPA accounts for 20 mol% of the total hydroxyl content; TMP accounts for 0.5 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:0.60:0.50; The amount of dibutyltin dilaurate used is 0.05 wt% of the total mass of the reactants.

[0082] The diisocyanate is prepared by a molar ratio of HDI to IPDI of 1:3.0.

[0083] S12, the -NCO-terminated polyurethane prepolymer obtained in S11 is cooled to 55°C, and triethylamine is added to neutralize the carboxyl groups; during the neutralization process, the system is kept in an anhydrous state and stirred continuously for 20 minutes to fully convert the carboxyl groups into carboxylate structures.

[0084] The neutralization degree is 80%.

[0085] S13: Dopamine was prepared into a 5wt% NMP solution, and the pH was adjusted to 6.8 with triethylamine. The solution was then slowly added dropwise to the neutralized -NCO-terminated polyurethane prepolymer obtained in S12 under light-protected and nitrogen-protected conditions. The reaction temperature was controlled at 35℃, and the addition time was 15 min. After the addition was completed, the mixture was stirred for another 40 min to allow the primary amino groups in dopamine to undergo an addition reaction with some isocyanate groups, forming a catechol-attached structure.

[0086] The dopamine is added at an amino / -NCO molar ratio of 0.05:1.

[0087] S14: The system obtained in S13 was slowly added to deionized water for phase inversion dispersion. The dispersion temperature was controlled at 35℃, the dispersion speed at 2000 r / min, and the water addition time was 20 min. After the water addition was completed, stirring was continued for 30 min. Subsequently, 5 wt% EDA aqueous solution was added to carry out chain extension reaction. EDA was added dropwise at 40℃ for 20 min. After the addition was completed, the reaction was continued for 90 min to obtain an aqueous polyurethane dispersion containing amino reaction sites.

[0088] The EDA was added at an amino / -NCO molar ratio of 1.05:1.

[0089] S15, AAEM is added to the aqueous polyurethane dispersion containing amino reaction sites obtained in S14, and reacted at 60°C for 2 hours to allow the α,β-unsaturated double bonds in the ketone functional monomer to undergo aza-Michael addition reaction with the primary and / or secondary amino groups in the polyurethane molecular chain, thereby grafting the ketone group into the polyurethane molecular chain to obtain the aqueous polyurethane dispersion.

[0090] The amount of AAEM added is 1:0.7 molar ratio of amino to unsaturated double bond.

[0091] S16: Dissolve ADH in deionized water to prepare a 5wt% ADH aqueous solution, add it to the dispersion obtained in S15 at 35℃, stir for 20 minutes, filter through a 100-200 mesh filter and seal for storage to obtain the water-based polyurethane ink binder; the storage temperature is 5-35℃, and direct sunlight should be avoided.

[0092] The ADH is added at a molar ratio of hydrazide to ketone of 0.5:1.

[0093] The resulting waterborne polyurethane binder had a solid content of 32.8%, a pH of 8.3, and an average particle size of 60-80 nm.

[0094] A high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following preparation steps: S21, add waterborne polyurethane binder, dispersant and part of deionized water into a dispersion tank, stir at 800 r / min for 10 min at room temperature to obtain a premixed solution.

[0095] In step S22, under stirring at 1200 r / min, the pigment is added in batches to the premixed liquid obtained in step S21 over a period of 15 min. After addition, the rotation speed is increased to 2500 r / min, and high-speed dispersion is carried out for 20 min to obtain a coarse dispersion slurry. The coarse dispersion slurry is then transferred to a horizontal sand mill for grinding. The grinding media consists of 0.5 mm zirconia beads with a filling rate of 70%; the sand mill speed is 3000 r / min, and the temperature is controlled by a cooling water jacket to keep the slurry temperature ≤40℃; the grinding time is 30 min. The grinding endpoint is controlled to have a pigment fineness ≤15 μm; for high-gloss gravure or flexographic printing inks, D90 is controlled to be ≤5 μm.

[0096] S23: Add defoamer, leveling agent, and remaining deionized water to the pigment slurry obtained in S22. Stir at 800 rpm for 10 min to adjust the viscosity and pH of the system. After filtration, the high-adhesion, retort-resistant waterborne polyurethane ink is obtained. The final ink has a pH of 8.2 and a viscosity of 18s measured using a Ford cup at 25°C. The prepared ink is filtered through a 200-mesh filter, allowed to stand for 7 hours to remove bubbles, and then filled. The preferred filling containers are light-proof plastic drums or internally coated metal drums, and the storage temperature is 5-35°C.

[0097] Example 3

[0098] A high-adhesion, retort-resistant waterborne polyurethane ink comprises the following raw materials in parts by weight: 100 parts of waterborne polyurethane binder; 40 parts of titanium dioxide and phthalocyanine blue were mixed at a mass ratio of 5:3. Dispersant DISPERBYK-190 3.0 parts; Defoamer BYK-024 0.5 parts; Leveling agent BYK-346 1.5 parts; 20 parts deionized water.

[0099] The waterborne polyurethane binder includes the following preparation steps: S11, polycarbonate diol, polyester diol, 1,4-butanediol, DMPA and TMP were added to a reactor equipped with a mechanical stirrer, thermometer, nitrogen inlet, condenser and vacuum interface. The system was dehydrated under vacuum at 100℃ and -0.08 to -0.095 MPa for 2 hours to control the water content of the system below 500 ppm. After dehydration, the system was cooled to 70℃, and diisocyanate and dibutyltin dilaurate were added. The system was then heated to 75℃ and reacted for 4 hours under nitrogen protection to obtain a -NCO-terminated polyurethane prepolymer with microbranched structure.

[0100] The raw material proportions, based on the total hydroxyl content of the system, show that the -NCO / -OH molar ratio is 1.80:1; DMPA accounts for 5 mol% of the total hydroxyl content; and TMP accounts for 2.0 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:1.00:0.20; The amount of dibutyltin dilaurate used is 0.05 wt% of the total mass of the reactants.

[0101] The diisocyanate is prepared by a molar ratio of HDI to IPDI of 1:1.0.

[0102] S12, the -NCO-terminated polyurethane prepolymer obtained in S11 is cooled to 45°C, triethylamine is added to neutralize the carboxyl groups, and stirring is continued for 30 min under anhydrous conditions to fully convert the carboxyl groups into carboxylate structures.

[0103] The neutrality is 100%.

[0104] S13: Dopamine was prepared into a 15wt% NMP solution, and the pH was adjusted to 7.5 with triethylamine. Under light-protected and nitrogen-protected conditions, it was slowly added dropwise to the neutralized -NCO-terminated polyurethane prepolymer obtained in S12. The reaction temperature was controlled at 45℃, and the addition time was 40 min. After the addition was completed, the mixture was stirred for another 40 min to allow the primary amino group in dopamine to undergo an addition reaction with some isocyanate groups to form a catechol attached structure.

[0105] The dopamine is added at an amino / -NCO molar ratio of 0.15:1.

[0106] S14: The system obtained in S13 was slowly added to deionized water for phase inversion dispersion. The water dispersion temperature was controlled at 20℃, the dispersion speed was 1000 r / min, and the water addition time was 40 min. Then, a 20 wt% EDA aqueous solution was added dropwise at 25℃ for 60 min. After the addition was completed, the reaction continued for 30 min to allow the remaining isocyanate groups to undergo chain extension reaction with EDA, thus obtaining an aqueous polyurethane dispersion containing amino reaction sites.

[0107] The EDA was added at an amino / -NCO molar ratio of 1.15:1.

[0108] S15, AAEM is added to the aqueous polyurethane dispersion containing amino reaction sites obtained in S14, and reacted at 40°C for 4 hours, so that the α,β-unsaturated double bonds in the ketone functional monomer undergo a aziramidic addition reaction with the primary and / or secondary amino groups in the polyurethane molecular chain, thereby grafting the ketone group into the polyurethane molecular chain to obtain the aqueous polyurethane dispersion.

[0109] The amount of AAEM added is 1:1.0 in the molar ratio of amino to unsaturated double bond.

[0110] S16: Dissolve ADH in deionized water to prepare a 15wt% ADH aqueous solution. Add the solution to the dispersion obtained in S15 at 25°C, stir for 60 minutes, filter through a 100-200 mesh filter, and seal for storage to obtain the water-based polyurethane ink binder. The storage temperature is 5-35°C, and direct sunlight should be avoided.

[0111] The ADH is added at a molar ratio of hydrazide to ketone of 1.0:1.

[0112] The resulting waterborne polyurethane binder had a solid content of 33.5%, a pH of 9.0, and an average particle size of 120-150 nm.

[0113] A high-adhesion, retort-resistant waterborne polyurethane ink, comprising the following preparation steps: S21. Add waterborne polyurethane binder, dispersant and part of deionized water to a dispersion tank and stir at 500 r / min for 20 min at room temperature to obtain a premixed solution.

[0114] In step S22, under stirring at 800 rpm, the pigment is added in batches to the premixed solution obtained in step S21 over a period of 30 minutes. After addition, the rotation speed is increased to 1500 rpm, and high-speed dispersion is carried out for 40 minutes to obtain a coarse dispersion slurry. The coarse dispersion slurry is then transferred to a horizontal sand mill for grinding. The grinding media consists of 0.5 mm zirconia beads with a filling rate of 70%. The sand mill speed is 1800 rpm, and the temperature is controlled by a cooling water jacket to keep the slurry temperature ≤40℃. The grinding time is 120 minutes. The grinding endpoint is controlled to have a pigment fineness ≤15 μm; for high-gloss gravure or flexographic printing inks, D90 is controlled to ≤5 μm.

[0115] S23: Add defoamer, leveling agent, and remaining deionized water to the pigment slurry obtained in S22. Stir at 500 rpm for 30 min to adjust the viscosity and pH of the system. After filtration, the high-adhesion, retort-resistant waterborne polyurethane ink is obtained. The final ink has a pH of 8.8 and a viscosity of 28 s measured using a Ford cup at 25°C. The prepared ink is filtered through a 200-mesh filter, allowed to stand for 7 hours to defoam, and then filled. The preferred filling containers are light-proof plastic buckets or internally coated metal buckets, and the storage temperature is 5-35°C.

[0116] Example 4

[0117] Everything else is the same as in Example 1, except that: The pigment is composed of titanium dioxide and iron oxide added at a mass ratio of 1:2.

[0118] Example 5

[0119] Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, the -NCO / -OH molar ratio is 1.55:1 based on the total amount of hydroxyl groups in the system.

[0120] Example 6

[0121] Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, the -NCO / -OH molar ratio is 1.75:1 based on the total amount of hydroxyl groups in the system.

[0122] Example 7

[0123] Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, TMP accounts for 0.7 mol of the total hydroxyl content of the system.

[0124] Example 8

[0125] Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, TMP accounts for 1.5 mol of the total hydroxyl content of the system.

[0126] Example 9

[0127] Everything else is the same as in Example 1, except that: In step S15 of the preparation of the waterborne polyurethane binder, AAEM is added at a molar ratio of amino to unsaturated double bond of 1:0.75.

[0128] Example 10

[0129] Everything else is the same as in Example 1, except that: In step S15 of the preparation of the waterborne polyurethane binder, AAEM is added at a molar ratio of amino to unsaturated double bond of 1:0.95.

[0130] Example 11

[0131] Everything else is the same as in Example 1, except that: In step S15 of the preparation of the waterborne polyurethane binder, AAEM is replaced with DAAM.

[0132] The following proportions are all compared with specific embodiment 1: Comparative Example 1 Everything else is the same as in Example 1, except that: In step S13 of the preparation of the waterborne polyurethane binder, dopamine is replaced with p-hydroxyphenylethylamine; that is, the waterborne polyurethane dispersion does not contain a catechol structure.

[0133] Comparative Example 2 Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, based on the total amount of hydroxyl groups in the system, the diols are polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 0:1.80:0.35; that is, the waterborne polyurethane dispersion does not contain polycarbonate structure.

[0134] Comparative Example 3 Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, based on the total amount of hydroxyl groups in the system, the diols are polycarbonate diol, polyester diol, and 1,4-butanediol, which are added in a molar ratio of 1.80:0:0.35; that is, the waterborne polyurethane dispersion does not contain polyester structure.

[0135] Comparative Example 4 Everything else is the same as in Example 1, except that: In step S11 of the preparation of the waterborne polyurethane binder, TMP accounts for 0 mol% of the total hydroxyl content of the system; that is, the waterborne polyurethane dispersion does not contain triol structures.

[0136] Comparative Example 5 Everything else is the same as in Example 1, except that: In step S15 of the preparation of the waterborne polyurethane binder, AAEM is replaced with isooctyl methacrylate; that is, the waterborne polyurethane dispersion does not contain ketone grafted structures.

[0137] Comparative Example 6 Everything else is the same as in Example 1, except that: The preparation steps of the waterborne polyurethane binder did not include step S16; that is, the waterborne polyurethane binder does not contain ADH components.

[0138] The inks prepared in the above examples and comparative examples were gravure printed onto the surface of an aluminized film substrate (or PET film, PVC film, OPP film), with a dry film thickness of 2.0 ± 0.2 μm. The films were then placed in an 80°C oven for 40 seconds to obtain the ink products. The physical properties of the inks and their film products prepared in the examples and comparative examples of this invention were measured, and the results are shown in Table 1.

[0139] Table 1 Physical test performance of each embodiment

[0140] First, as can be seen from Examples 1-11 and Comparative Examples 1-6, the high-adhesion, retort-resistant waterborne polyurethane ink provided by the present invention exhibits excellent overall performance. Meanwhile, Example 1 maintained 5B adhesion when applied to aluminized film, PET film, PVC film, and OPP film, respectively, indicating that the binder material constructed by the present invention has strong multi-substrate versatility and can be applied to various packaging materials such as polar substrates, non-polar substrates, and metallized films. Examples 1-4, using different pigment systems such as titanium dioxide, carbon black, phthalocyanine blue, and iron oxide, all maintained high gloss, excellent storage stability, and mechanical properties, indicating that the binder material has good wetting, dispersion, and stabilizing capabilities for both inorganic and organic pigments.

[0141] Secondly, as can be seen from Example 1 and Comparative Example 1, after introducing dopamine to form a catechol adhesion structure, the adhesion increased from 3B to 5B, and the resistance to boiling water, steaming, and MEK was significantly improved. This indicates that the catechol groups can enhance the interfacial bonding between polyurethane and substrates such as PET, PVC, and metallized film through hydrogen bonds, coordination bonds, and π-π interactions, which is a key factor in obtaining high adhesion performance.

[0142] As can be seen from Example 1 and Comparative Examples 2-3, the polycarbonate soft segment imparts excellent hydrolysis and cooking resistance to the system, while the polyester soft segment improves the wetting ability of pigments and substrates. The two soft segments work together to form a continuous phase that combines flexibility and resistance to media. Therefore, the absence of either soft segment leads to a decrease in overall performance.

[0143] As can be seen from Example 1 and Comparative Example 4, the microbranched structure formed by trace amounts of triol improves the degree of molecular chain entanglement and film density, while also improving the storage stability of the dispersion and the integrity of the crosslinking network, which significantly contributes to the resistance to MEK and cooking.

[0144] As can be seen from Example 1 and Comparative Examples 5-6, the ketone graft structure formed by AAEM and the post-cured hydrazone network constructed by ADH are important factors in improving the resistance to boiling water, boiling, and solvents. As the hydrazone crosslinking continues after film formation, the crosslinking density of the film layer continues to increase, giving the coating both good initial film-forming performance and good later media resistance.

[0145] In summary, this invention, through the synergistic design of a catechol-attached structure, polycarbonate / polyester dual soft segments, a microbranched polyurethane structure, and an AAEM-ADH post-curing network, achieves multiple synergistic effects at the molecular structure level, including interfacial adhesion, pigment dispersion, film densification, and post-curing crosslinking. This not only endows the ink with excellent storage stability, gloss, resistance to boiling water, resistance to steaming, resistance to alcohol, and resistance to MEK, but also makes it compatible with various packaging substrates and various organic / inorganic pigment systems. It has good process adaptability, application versatility, and industrialization promotion value.

[0146] The testing method is as follows: (1) Storage stability: The prepared ink was sealed in a polyethylene bottle and stored in a constant temperature chamber at 50±2℃ for 7 days. Observe whether thickening, gelation, sedimentation, stratification, etc. occur. Among them: "no abnormality" means that the system does not stratify, settle, or gel after storage, and the viscosity change is ≤5%; "slight thickening" means that the viscosity increases by 5%-10% compared with the initial value, and can be restored to a uniform state after stirring at 300r / min for 5min, without affecting the printing process; while sedimentation (including slight sedimentation) indicates that the ink has a coarsening phenomenon and its stability is compromised.

[0147] (2) Gloss: The gloss was tested according to the method described in GB / T 9754-2007 and measured using a 60° gloss meter.

[0148] (3) Adhesion: Adhesion test shall be conducted in accordance with the method described in GB / T 9286-2021, using the cross-cut test.

[0149] (4) Water resistance: After boiling the ink film product in boiling water for 30 minutes, take it out, cool it to room temperature and then retest the adhesion.

[0150] (5) Adhesion resistance: The ink film product was placed in a high-pressure cooker and cooked at 121°C for 60 minutes. After being taken out and cooled to room temperature, the adhesion was retested.

[0151] (6) Alcohol resistance: The printed sample was completely immersed in 95 vol% anhydrous ethanol (or analytical grade ethanol) and soaked for 24 h at 25 ± 2 ℃. After taking it out, the surface ethanol was blotted dry with filter paper, and the paint film was observed after being placed at room temperature for 30 min. The adhesion was then retested.

[0152] (7) MEK wiping resistance: Refer to ASTM D5402. Wrap a 500 g weight in cotton cloth, dip it in MEK and wipe back and forth. One round trip is counted as one time until the bottom is exposed. Record the number of times.

[0153] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A high-adhesion, retort-resistant waterborne polyurethane ink, characterized in that, The ingredients include the following parts by weight: 100 parts of waterborne polyurethane binder; 20-40 parts pigment; Dispersant 1.0-3.0 parts; 0.1-0.5 parts of defoamer; Leveling agent 0.5-1.5 parts; 5-20 parts deionized water; Wherein, the waterborne polyurethane binder is a composition of waterborne polyurethane dispersion and ADH; and The aqueous polyurethane dispersion is a catechol-modified ketone-grafted anionic aqueous polyurethane dispersion. The ADH is used to form a hydrazone crosslinking network with the ketone graft structure in the aqueous polyurethane dispersion after film formation.

2. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 1, characterized in that, The molecular chain of the aqueous polyurethane dispersion contains a carboxylate hydrophilic structure, a polycarbonate soft segment, a polyester soft segment, a urea bond hard segment, a microbranched structure formed by triols, a catechol structure, and a ketone grafting structure.

3. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 1, characterized in that, The waterborne polyurethane binder has a solid content of 33±1%, a pH of 7.5-9.5, and an average particle size of 60-150nm.

4. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 1, characterized in that, The waterborne polyurethane binder includes the following preparation steps: S11, a diol, a carboxyl-containing diol, a triol and a diisocyanate are reacted to prepare a -NCO-terminated polyurethane prepolymer with a microbranched structure. The raw material proportions, based on the total hydroxyl content of the system, are as follows: -NCO / -OH molar ratio is 1.40-1.80:1; carboxyl diols account for 5-20 mol% of the total hydroxyl content; triols account for 0.5-2.0 mol% of the total hydroxyl content. The diol is polycarbonate diol, polyester diol, and 1,4-butanediol added in a molar ratio of 1:0.60-1.00:0.20-0.50; S12, neutralize the -NCO-terminated polyurethane prepolymer; The degree of neutralization is 80-100%; S13, add an amino-containing catechol structure to the product of S12 to react with some isocyanate groups; The amount of the amino-containing catechol structure added is such that the amino / -NCO molar ratio is 0.05-0.15:1; S14, deionized water and diamine chain extender are simultaneously added dropwise to the product of S13 to complete the phase inversion dispersion and chain extension; The diamine is added in an amino / -NCO molar ratio of 1.05-1.15:

1. S15, add a ketone functional monomer, and allow the α,β-unsaturated double bond in the ketone functional monomer to undergo an aza-Michael addition reaction with the primary amine and / or secondary amine to introduce a ketone graft structure, thereby obtaining an aqueous polyurethane dispersion; The amount of the ketone functional monomer added is such that the molar ratio of amino to unsaturated double bond is 1:0.7-1.0; S16, add ADH to obtain the water-based polyurethane ink binder; The ADH is added at a molar ratio of hydrazide to ketone of 0.5-1.0:

1.

5. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 4, characterized in that, The diisocyanate is added by adding HDI and IPDI at a molar ratio of 1:1.0-3.0; and The amino-containing catechol has the structure of dopamine.

6. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 4, characterized in that, The ketone functional monomer is AAEM or DAAM.

7. The high-adhesion, retort-resistant waterborne polyurethane ink according to claim 1, characterized in that, The pigment is one or more of the following: titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, azo pigment, quinacridone pigment, permanent red, permanent yellow, iron oxide pigment, aluminum powder pigment, and pearlescent pigment.

8. The high-adhesion, retort-resistant waterborne polyurethane ink according to any one of claims 1-7, characterized in that, The preparation steps include the following: S21, mix waterborne polyurethane binder, dispersant and part of deionized water to obtain premixed liquid; S22, pigment is added to the premixed liquid, and high-speed dispersion and grinding are performed to obtain pigment slurry; S23, add defoamer, leveling agent and remaining deionized water to the pigment slurry, stir evenly, adjust viscosity and pH, and filter to obtain the high adhesion and boil-resistant waterborne polyurethane ink. During the grinding process, the slurry temperature is ≤40℃; the fineness of the ground pigment is ≤15μm; and the viscosity of the high-adhesion, boil-resistant waterborne polyurethane ink measured at 25℃ using a Forecast cup is 12-30s.

9. The application of a high-adhesion, retort-resistant waterborne polyurethane ink according to any one of claims 1-7 in the printing of food packaging films, pharmaceutical packaging films, daily chemical packaging films, or composite flexible packaging, characterized in that, The high-adhesion, retort-resistant waterborne polyurethane ink is used for surface printing on PET, PVC, OPP, PE, aluminum foil, or aluminized film substrates.

Images