Waterborne polyurethane transfer coating for anti-counterfeit label and preparation method of waterborne polyurethane transfer coating

Abstract

The invention discloses a waterborne polyurethane transfer coating for an anti-counterfeit label and a preparation method of the waterborne polyurethane transfer coating, belongs to the technical field of coating preparation, and is used for solving the technical problem that the adhesive force and the corrosion resistance of a transfer coating in the prior art need to be further improved. The modified transfer coating comprises the following raw materials in parts by weight: 30-50 parts of composite polyurethane, 5-10 parts of composite filler, 5-6 parts of a modified curing agent, 45-60 parts of a mixed solvent and 5-9 parts of an auxiliary additive, and the modified transfer coating is obtained by preparing waterborne polyurethane with multiple hydrophilic groups, the modified curing agent with protected groups and the composite filler, mixing the three with auxiliary materials and sieving. In the curing process, the silicon dioxide component in the composite filler promotes microwave heating, so that the modified curing agent removes the protective groups, the coating is cured, the anti-counterfeit label is difficult to fall off after being corroded by liquid, and the anti-counterfeit performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coating preparation, and particularly relates to an aqueous polyurethane transfer coating for anti-counterfeiting labels and a preparation method thereof. Background Art

[0002] Aqueous polyurethane transfer coatings perform excellently in terms of abrasion resistance and corrosion resistance, becoming the preferred materials for applications in many industries. The corrosion resistance of aqueous polyurethane coatings is also one of their important characteristics, capable of providing good protection under different environmental conditions, especially in harsh conditions such as humidity and salt spray. Due to the special molecular structure of aqueous polyurethane, it has strong waterproof, oil-proof, and chemical corrosion resistance capabilities, effectively resisting the erosion of the external environment on the substrate and preventing rust and degradation. Therefore, aqueous polyurethane transfer coatings not only meet environmental protection requirements but also exhibit strong advantages in adhesion and corrosion resistance performance, improving the anti-counterfeiting performance of anti-counterfeiting labels.

[0003] For example, in the prior art CN106589310B discloses an aqueous polyurethane emulsion for temperature-resistant transfer coatings and a preparation method thereof, which consists of the following substances in weight components: oligomeric polyol 6 - 14%, diisocyanate 10 - 14.2%, hydrophilic chain extender 1.2 - 1.6%, crosslinking agent 1.5 - 3%, acetone 16 - 18%, NMP 2 - 4%, amine chain extender 4.0 - 4.5%, catalyst 0.006 - 0.010%, ice pure water 43.69 - 51.49%, neutralizing agent 0.8 - 1.2%. By using main raw materials such as oligomeric polyol, diisocyanate, hydrophilic chain extender, crosslinking agent, and amine chain extender, and adopting a two-step prepolymer method, without increasing the cost of raw materials, an aqueous polyurethane emulsion for temperature-resistant transfer coatings with good transferability and temperature resistance is provided.

[0004] However, in the above invention, after curing with an amine curing agent during the preparation of the polyurethane material, an aqueous polyurethane emulsion is obtained. However, after using an ammonia chain extender for chain extension during the preparation of polyurethane, the high reactivity of the amine chain extender and isocyanate will cause excessive consumption of free isocyanate groups in the prepolymer. In the subsequent curing stage, due to insufficient active groups, it is difficult to achieve sufficient crosslinking, resulting in poor curing effect of the coating, poor adhesion and corrosion resistance of the coating, and thus the anti-counterfeiting label is prone to falling off after liquid corrosion, reducing the anti-counterfeiting performance of the anti-counterfeiting label. Summary of the Invention

[0005] The purpose of the present invention is to provide an aqueous polyurethane transfer coating for anti-counterfeiting labels and a preparation method thereof, aiming to solve the technical problem that the adhesion and corrosion resistance of the transfer coating in the prior art need to be further improved.

[0006] The object of the present invention can be achieved by the following technical solutions: An aqueous polyurethane transfer coating for anti-counterfeiting labels, comprising the following raw materials by weight: 30-50 parts of composite polyurethane, 5-10 parts of composite filler, 45-60 parts of mixed solvent, and 5-9 parts of auxiliary additive;

[0007] Among them, the mixed solvent is obtained by mixing deionized water and ethanol in a weight ratio of 2:1, and the auxiliary additive comprises the following raw materials by weight: 1-2 parts of polydimethylsiloxane, 1-2 parts of phenyltrimethoxysilane, and 2-3 parts of 2,2'-azobis(2-methylbutyronitrile).

[0008] Furthermore, the preparation method of the composite polyurethane comprises the following steps:

[0009] A1. Add polyethylene glycol, hydroxyl-terminated methyl vinyl silicone oil, N,N-dimethylformamide, and dibutyltin dilaurate into a reaction kettle and stir. Raise the temperature of the reaction kettle to 50-60°C, and dropwise add a 4,4'-diisocyanatodicyclohexylmethane solution into the reaction kettle. Keep the reaction at a constant temperature for 40-60 min, and perform post-treatment to obtain modified polyurethane;

[0010] A2. Add the modified polyurethane, acrylic acid, vinylamine, and N,N-dimethylformamide into the reaction kettle. Raise the temperature of the reaction kettle to 60-80°C, keep stirring at a constant temperature for 15-20 min, then add azobisisobutyronitrile into the reaction kettle. Keep the reaction at a constant temperature for 2-4 h, then add a capping agent into the reaction kettle, and keep the reaction at a constant temperature for 30-40 min. Perform post-treatment to obtain the composite polyurethane.

[0011] The reaction equation for preparing the composite polyurethane is:

[0012]

[0013] In the formula: "*" represents the active connection site of the organic chain segment.

[0014] The reaction principle for preparing the composite polyurethane is as follows: Under the promotion of a catalyst and high temperature, the hydroxyl groups on polyethylene glycol and hydroxyl-terminated methyl vinyl silicone oil react with the isocyanate groups on 4,4'-diisocyanatodicyclohexylmethane to form a long-chain polyurethane structure embedded with siloxane segments and polyethylene glycol. After post-treatment hydrolysis, a modified polyurethane structure capped with amino groups is formed at the end. Finally, under the catalysis of a radical initiator, the double bonds on the siloxane segments react with the double bonds on acrylic acid and vinylamine through radical addition reactions, introducing amino and carboxyl groups into the long-chain structure, and finally obtaining the composite polyurethane.

[0015] Further, in step A1, the dosage ratio of polyethylene glycol, hydroxyl-terminated methyl vinyl silicone oil, N,N-dimethylformamide, dibutyltin dilaurate and 4,4'-dicyclohexylmethane diisocyanate solution is 6-8 g: 2-3 g: 40-45 mL: 0.3-0.5 g: 10-12 mL. Among them, the 4,4'-dicyclohexylmethane diisocyanate solution is obtained by mixing 4,4'-dicyclohexylmethane and N,N-dimethylformamide according to the dosage ratio of 2-3 g: 10-12 mL; the post-treatment includes: after the reaction is completed, purified water is added to the reaction kettle, the temperature of the reaction kettle is raised to 120-140 °C, and vacuum distillation is carried out until no liquid is collected, to obtain the modified polyurethane;

[0016] Further, in step A2, the dosage ratio of the modified polyurethane, acrylic acid, vinylamine, N,N-dimethylformamide, azobisisobutyronitrile and the capping agent is 8-10 g: 2-3 g: 1-2 g: 40-50 mL: 0.2-0.4 g: 10-12 mL. Among them, the capping agent is 3-mercapto-1-propanesulfonic acid sodium salt. The post-treatment includes: after the reaction is completed, after the reaction kettle is cooled to room temperature, the reaction solution is added into a rotary evaporator with a water bath temperature of 80-100 °C, and vacuum distillation is carried out until no liquid is collected, to obtain the composite polyurethane.

[0017] Further, the preparation method of the modified curing agent is: adding vinyl isocyanate, dimethylallylamine and N,N-dimethylformamide into the reaction kettle, raising the temperature of the reaction kettle to 60-80 °C, keeping warm and stirring for 10-15 min, then adding azobisisobutyronitrile into the reaction kettle, keeping warm and reacting for 2-4 h, then adding methyl ethyl ketoxime and dibutyltin dilaurate into the reaction kettle, keeping warm and stirring for 20-30 min, and obtaining the modified curing agent through post-treatment.

[0018] The reaction equation for preparing the composite polyurethane is:

[0019]

[0020] The reaction principle for preparing the composite polyurethane is: under the promotion of a radical initiator, the double bonds on vinyl isocyanate and dimethylallylamine undergo a radical addition reaction to form a long-chain structure, and through the reaction of methyl ethyl ketoxime with isocyanate groups, a protective structure is formed, and finally the

[0021] Further, the dosage ratio of vinyl isocyanate, dimethylallylamine, N,N-dimethylformamide, azobisisobutyronitrile, methyl ethyl ketoxime and dibutyltin dilaurate is 3.4 - 3.5 g : 4.2 - 4.3 g : 40 - 45 mL : 0.3 - 0.5 g : 4.3 - 4.4 g : 0.3 - 0.5 g. The post-treatment includes: after the reaction is completed, after the reaction kettle is cooled to room temperature, the reaction solution is added into a rotary evaporator with a water bath temperature of 80 - 100 °C, and vacuum distilled until no liquid is collected, to obtain the modified curing agent.

[0022] Further, the preparation method of the composite filler includes the following steps:

[0023] B1. Add tetra-isopropyl titanate, tetraethyl orthosilicate and absolute ethanol into a reaction kettle and stir. After stirring at room temperature for 15 - 20 min, continue to dropwise add deionized water. After the temperature of the reaction kettle rises to 50 - 60 °C, use saturated sodium hydroxide solution to adjust the pH of the system to 8 - 10, and keep warm for 3 - 4 h to obtain a composite gel.

[0024] B2. Transfer the composite gel to a tubular furnace for calcination to obtain the modified filler.

[0025] B3. Add the modified filler, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and absolute ethanol into a reaction kettle. Raise the temperature of the reaction kettle to 40 - 60 °C and keep the reaction warm for 30 - 40 min. After post-treatment, obtain the composite filler.

[0026] The reaction principle for preparing the composite filler is: tetra-isopropyl titanate and tetraethyl orthosilicate hydrolyze to form a gel-like structure. After high-temperature calcination and steam activation, the modified filler is obtained. Finally, the active hydroxyl group structure on the modified filler undergoes a ring-opening reaction with 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and finally the composite filler is prepared.

[0027] Further, in step B1, the dosage ratio of tetra-isopropyl titanate, tetraethyl orthosilicate, absolute ethanol and deionized water is 3 - 5 g : 5 - 6 g : 30 - 40 mL : 10 - 15 mL.

[0028] Further, in step B2, the calcination operation includes: transfer the composite gel to a tubular furnace, after introducing nitrogen for protection, the tubular furnace is heated at a heating rate of 5 - 6 °C / min to 500 - 600 °C, keep warm for 3 - 4 h, the tubular furnace is naturally cooled to 200 - 300 °C, disconnect the nitrogen, and introduce steam at a rate of 60 - 80 sccm, keep warm for 2 - 3 h, and then naturally cool to obtain the modified filler.

[0029] Further, in step B3, the dosage ratio of the modified filler, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine, and absolute ethanol is 8-10 g: 1-2 g: 0.3-0.5 g: 40-48 mL. The post-treatment includes: after the reaction is completed, when the temperature of the reaction kettle drops to room temperature, filter the reaction solution to collect the filter cake. After washing the filter cake 3-5 times with ethanol and deionized water, transfer the filter cake to a drying oven at 60-80 °C for vacuum drying until the filter cake reaches a constant weight, obtaining the composite filler.

[0030] The present invention also provides a preparation method of an aqueous polyurethane transfer coating for anti-counterfeiting labels: adding composite polyurethane, composite filler, modified curing agent, mixed solvent, polydimethylsiloxane, phenyltrimethoxysilane, and azodiisooctylonitrile into a stirring kettle, mixing evenly, and then passing through an 80-100 mesh sieve to obtain the modified transfer coating.

[0031] Further, the curing process of the modified transfer coating is as follows: after the coating is impregnated, put the mold into a microwave generator. The power of the microwave generator is 5-8 kW, the power density is 2-4 W / cm 3 , the microwave frequency is 2.4-2.5 GHz, and heat at a temperature of 100-120 °C until no solvent is extracted, and then continue to heat for 3-5 min to obtain a cured coating.

[0032] The curing principle of the modified transfer coating is as follows: the titanium dioxide component of the composite filler promotes the microwave heating process. At high temperature, the methyl ethyl ketoxime group on the modified curing agent is removed, and the isocyanate group on the modified curing agent is exposed to crosslink with the amino group in the composite polyurethane. Moreover, the removed methyl ethyl ketoxime group undergoes a radical addition reaction to form a long-chain structure. The hydroxyl group on the structure dehydrates with the silanol group to further crosslink with the material, finally curing the coating.

[0033] The present invention has the following beneficial effects:

[0034] 1. In the present invention, a molecular network structure with alternating soft and hard segments is formed by the combination of silicone oil segments and ethylene glycol segments. The flexibility of the silicone oil can absorb the energy during the friction process, while the regular arrangement of the polyurethane hard segments and ethylene glycol enhances the rigidity of the material to jointly resist wear. At the same time, the dynamic ionic bonds formed by the sulfonic acid groups and amino groups introduced into the material can preferentially break and recombine when stressed, achieving energy dissipation and local self-repair to avoid damage to the overall structure. The nanoparticles and silane coupling agents in the composite filler enhance the surface hardness of the coating, reduce friction loss through chemical bonding with the substrate, and active groups such as amino groups and epoxy groups can form strong interactions such as hydrogen bonds and covalent bonds with the substrate surface to ensure the tight connection between the coating and the substrate. The hydrophilic-hydrophobic segments of the coating drive the molecules to penetrate into the micropores of the substrate through wetting differences during coating, forming a physical anchoring effect. The cross-linking reaction between the modified curing agent and the polyurethane chain constructs a three-dimensional network structure, further enhancing the cohesive strength and interfacial bonding force of the coating.

[0035] 2. In the present invention, a low-porosity coating is formed by the close arrangement of silicone oil and polyurethane, effectively blocking the penetration of moisture and corrosive substances. The composite filler is tightly combined with the substrate through surface chemical modification, filling microscopic defects and extending the diffusion path of corrosive media. The amino groups in the coating react with the substrate material to form a stable protective layer, while the sulfonic acid groups repel erosive ions through electrostatic action, reducing the risk of metal contact. The existence of dynamic chemical bonds enables the coating to self-repair small cracks when locally damaged, maintaining the continuity of protection. At the same time, the organic titanium component inhibits the electrochemical corrosion reaction of the metal by adjusting the electronic properties of the coating, and the active groups in the siloxane can also neutralize acidic substances to maintain a stable interfacial environment. These mechanisms work together to comprehensively improve the corrosion resistance from physical barrier, chemical protection to dynamic repair.

[0036] 3. In the present invention, a low-porosity coating is formed by the close arrangement of silicone oil and polyurethane, effectively blocking the penetration of moisture and corrosive substances. The composite filler is tightly combined with the substrate through surface chemical modification, filling microscopic defects and extending the diffusion path of corrosive media. The amino groups in the coating react with the substrate material to form a stable protective layer, while the sulfonic acid groups repel erosive ions through electrostatic action, reducing the risk of metal contact. The existence of dynamic chemical bonds enables the coating to self-repair small cracks when locally damaged, maintaining the continuity of protection. At the same time, the organic titanium component inhibits the electrochemical corrosion reaction of the metal by adjusting the electronic properties of the coating, and the active groups in the siloxane can also neutralize acidic substances to maintain a stable interfacial environment. These mechanisms work together to comprehensively improve the corrosion resistance from physical barrier, chemical protection to dynamic repair. Detailed implementation manners

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0038] The hydroxyl-terminated methyl vinyl silicone oil used in the present invention is purchased from Anhui Mingyi Silicon Industry Co., Ltd., and the product number is MY1203V;

[0039] The polyethylene glycol used in the present invention is purchased from Xingtai Xinlanxing Technology Co., Ltd., and the product number is PEG2000;

[0040] The phenyltrimethoxysilane used in the present invention is purchased from Nanjing Nengde New Material Technology Co., Ltd., and the model is SCA-P61M;

[0041] The polydimethylsiloxane used in the present invention is purchased from Shanghai Titan Technology Co., Ltd., and the product number is 89315E.

[0042] Example 1

[0043] This example provides a preparation method of a composite polyurethane for preparing an aqueous polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0044] Step ①, prepare modified polyurethane

[0045] Weigh: 20.0 g of 4,4-diisocyanatodicyclohexylmethane and 100.0 mL of N,N-dimethylformamide are mixed to obtain a 4,4-diisocyanatodicyclohexylmethane solution;

[0046] Weigh: 60.0 g of polyethylene glycol, 20.0 g of hydroxyl-terminated methyl vinyl silicone oil, 400.0 mL of N,N-dimethylformamide and 3.0 g of dibutyltin dilaurate are added to a reaction kettle and stirred. The temperature of the reaction kettle is raised to 50 °C, and 100.0 mL of 4,4-diisocyanatodicyclohexylmethane solution is added dropwise to the reaction kettle. After holding the reaction for 40 - 60 min, after the reaction is completed, purified water is added to the reaction kettle, and the temperature of the reaction kettle is raised to 120 °C, and vacuum distillation is carried out until no liquid is collected, to obtain modified polyurethane.

[0047] Step ②, prepare composite polyurethane

[0048] Weigh: 80.0 g of modified polyurethane, 20.0 g of acrylic acid, 10.0 g of ethyleneamine, and 400.0 mL of N,N-dimethylformamide and add them to a reaction kettle. Raise the temperature of the reaction kettle to 60 °C. After heat preservation and stirring for 15 min, add 2.0 g of azobisisobutyronitrile to the reaction kettle. After heat preservation and reaction for 2 h, add 5.0 mL of 3-mercapto-1-propanesulfonic acid to the reaction kettle. After heat preservation and reaction for 30 min, after the reaction is completed, cool the reaction kettle to room temperature, and then add the reaction solution to a rotary evaporator with a water bath temperature of 80 °C, and perform vacuum distillation until no liquid is collected to obtain the composite polyurethane.

[0049] Example 2

[0050] This example provides a method for preparing a composite polyurethane for use in a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0051] Step ①, prepare modified polyurethane

[0052] Weigh: Mix 30.0 g of 4,4'-diisocyanatodicyclohexylmethane and 120.0 mL of N,N-dimethylformamide to obtain a 4,4'-diisocyanatodicyclohexylmethane solution;

[0053] Weigh: Add 80.0 g of polyethylene glycol, 30.0 g of hydroxy-terminated methyl vinyl silicone oil, 450.0 mL of N,N-dimethylformamide, and 5.0 g of dibutyltin dilaurate to a reaction kettle and stir. Raise the temperature of the reaction kettle to 60 °C. Dropwise add 120.0 mL of the 4,4'-diisocyanatodicyclohexylmethane solution to the reaction kettle. After heat preservation and reaction for 60 min, after the reaction is completed, add purified water to the reaction kettle. Raise the temperature of the reaction kettle to 140 °C, and perform vacuum distillation until no liquid is collected to obtain the modified polyurethane.

[0054] Step ②, prepare composite polyurethane

[0055] Weigh: Add 100.0 g of modified polyurethane, 30.0 g of acrylic acid, 20.0 g of ethyleneamine, and 500.0 mL of N,N-dimethylformamide to a reaction kettle. Raise the temperature of the reaction kettle to 80 °C. After heat preservation and stirring for 20 min, add 4.0 g of azobisisobutyronitrile to the reaction kettle. After heat preservation and reaction for 4 h, add 8.0 mL of 3-mercapto-1-propanesulfonic acid to the reaction kettle. After heat preservation and reaction for 40 min, after the reaction is completed, cool the reaction kettle to room temperature, and then add the reaction solution to a rotary evaporator with a water bath temperature of 100 °C, and perform vacuum distillation until no liquid is collected to obtain the composite polyurethane.

[0056] Example 3

[0057] This example provides a method for preparing a composite polyurethane for use in a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0058] Step ①: Prepare modified polyurethane

[0059] Weigh: 25.0 g of 4,4 - diisocyanate dicyclohexylmethane and 120.0 mL of N,N - dimethylformamide are mixed to obtain a 4,4 - diisocyanate dicyclohexylmethane solution;

[0060] Weigh: 72.0 g of polyethylene glycol, 24.0 g of hydroxyl - terminated methyl vinyl silicone oil, 420.0 mL of N,N - dimethylformamide and 4.0 g of dibutyltin dilaurate are added to a reaction kettle and stirred. The temperature of the reaction kettle is raised to 54 °C, and 120.0 mL of the 4,4 - diisocyanate dicyclohexylmethane solution is added dropwise to the reaction kettle. After holding the reaction for 60 min, purified water is added to the reaction kettle, the temperature of the reaction kettle is raised to 140 °C, and vacuum distillation is carried out until no liquid is collected, obtaining modified polyurethane.

[0061] Step ②: Prepare composite polyurethane

[0062] Weigh: 96.0 g of modified polyurethane, 24.0 g of acrylic acid, 16.0 g of ethyleneamine and 480.0 mL of N,N - dimethylformamide are added to a reaction kettle. The temperature of the reaction kettle is raised to 70 °C, and after holding and stirring for 18 min, 3.6 g of azobisisobutyronitrile is added to the reaction kettle. After holding the reaction for 3 h, 6.0 mL of 3 - mercapto - 1 - propanesulfonic acid is added to the reaction kettle, and the reaction is held for 36 min. After the reaction is completed, the reaction kettle is cooled to room temperature, and the reaction solution is added to a rotary evaporator with a water bath temperature of 100 °C, and vacuum distillation is carried out until no liquid is collected, obtaining composite polyurethane.

[0063] Example 4

[0064] This example provides a preparation method of a composite filler for a water - based polyurethane transfer coating for anti - counterfeiting labels, including the following steps:

[0065] Step Ⅰ: Prepare composite gel

[0066] Weigh: 30.0 g of tetra - isopropyl titanate, 50.0 g of tetraethyl orthosilicate and 300.0 mL of absolute ethanol are added to a reaction kettle and stirred. After stirring at room temperature for 18 min, 100.0 mL of deionized water is continuously added dropwise. After the temperature of the reaction kettle is raised to 50 °C, the pH of the system is adjusted to 8 using saturated sodium hydroxide solution, and after holding for 3 h, composite gel is obtained.

[0067] Step Ⅱ: Prepare modified filler

[0068] Transfer 100.0 g of the composite gel into a tube furnace. After introducing nitrogen for protection, the tube furnace is heated to 500 °C at a heating rate of 5 °C / min, held for 3 h, naturally cooled to 200 °C, the nitrogen is disconnected, and water vapor is introduced at a rate of 60 sccm. After holding for 2 h, it is naturally cooled to obtain the modified filler.

[0069] Step III: Prepare the composite filler

[0070] Weigh: 80.0 g of the modified filler, 10.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3.0 g of triethylamine and 400.0 mL of absolute ethanol are added to a reaction kettle. The temperature of the reaction kettle is raised to 40 °C and held for 30 min. After the reaction is completed, when the temperature of the reaction kettle drops to room temperature, the reaction solution is filtered to collect the filter cake. After washing 3 times with ethanol and deionized water, the filter cake is transferred to a drying oven at 60 °C and vacuum dried until the filter cake reaches a constant weight to obtain the composite filler.

[0071] Example 5

[0072] This example provides a preparation method of a composite filler for a waterborne polyurethane transfer coating used for anti-counterfeiting labels, including the following steps:

[0073] Step I: Prepare the composite gel

[0074] Weigh: 50.0 g of tetra-isopropyl titanate, 60.0 g of tetraethyl orthosilicate and 400.0 mL of absolute ethanol are added to a reaction kettle and stirred. After stirring at room temperature for 20 min, 150.0 mL of deionized water is continuously added dropwise. After the temperature of the reaction kettle is raised to 60 °C, the pH of the system is adjusted to 10 using saturated sodium hydroxide solution. After holding for 4 h, the composite gel is obtained.

[0075] Step II: Prepare the modified filler

[0076] Transfer 120.0 g of the composite gel into a tube furnace. After introducing nitrogen for protection, the tube furnace is heated to 600 °C at a heating rate of 6 °C / min, held for 4 h, naturally cooled to 300 °C, the nitrogen is disconnected, and water vapor is introduced at a rate of 80 sccm. After holding for 3 h, it is naturally cooled to obtain the modified filler

[0077] Step III: Prepare the composite filler

[0078] Weigh: 100.0 g of modified filler, 20.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 5.0 g of triethylamine and 480.0 mL of absolute ethanol are added to the reaction kettle. The temperature of the reaction kettle is raised to 60 °C, and the reaction is carried out under insulation for 40 min. After the reaction is completed, when the temperature of the reaction kettle drops to room temperature, the reaction solution is filtered by suction to collect the filter cake. After washing 5 times with ethanol and deionized water, the filter cake is transferred to a drying oven at 80 °C and vacuum dried until the filter cake reaches a constant weight to obtain the composite filler.

[0079] Example 6

[0080] This example provides a preparation method of a composite filler for a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0081] Step I. Preparation of composite gel

[0082] Weigh: 50.0 g of tetra-isopropyl titanate, 50.0 g of tetraethyl orthosilicate and 360.0 mL of absolute ethanol are added to the reaction kettle and stirred. After stirring at room temperature for 18 min, 120.0 mL of deionized water is continuously added dropwise. After the temperature of the reaction kettle is raised to 54 °C, the pH of the system is adjusted to 9 using saturated sodium hydroxide solution. After heat preservation for 4 h, the composite gel is obtained.

[0083] Step II. Preparation of modified filler

[0084] Transfer 110.0 g of the composite gel to a tubular furnace. After purging with nitrogen, the tubular furnace is heated to 600 °C at a heating rate of 5 °C / min and heat-treated for 4 h. The tubular furnace is naturally cooled to 280 °C, the nitrogen is disconnected, and water vapor is introduced at a rate of 70 sccm. After heat preservation for 3 h, it is naturally cooled to obtain the modified filler

[0085] Step III. Preparation of composite filler

[0086] Weigh: 90.0 g of modified filler, 16.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 4.0 g of triethylamine and 420.0 mL of absolute ethanol are added to the reaction kettle. The temperature of the reaction kettle is raised to 50 °C, and the reaction is carried out under insulation for 36 min. After the reaction is completed, when the temperature of the reaction kettle drops to room temperature, the reaction solution is filtered by suction to collect the filter cake. After washing 4 times with ethanol and deionized water, the filter cake is transferred to a drying oven at 70 °C and vacuum dried until the filter cake reaches a constant weight to obtain the composite filler.

[0087] Example 7

[0088] This example provides a preparation method of a modified curing agent for a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0089] Weigh: 34.0 g of vinyl isocyanate, 42.0 g of dimethylallylamine and 400.0 mL of N,N-dimethylformamide and add them to a reaction kettle. Raise the temperature of the reaction kettle to 60 °C. After keeping the temperature and stirring for 10 min, add 3.0 g of azobisisobutyronitrile to the reaction kettle. After reacting under constant temperature for 2 h, add 43.0 g of methyl ethyl ketoxime and 3.0 g of dibutyltin dilaurate to the reaction kettle. Keep the temperature and stir for 20 min. After the reaction is completed, cool the reaction kettle to room temperature, then add the reaction solution to a rotary evaporator with a water bath temperature of 80 °C, and carry out vacuum distillation until no liquid is collected to obtain a modified curing agent.

[0090] Example 8

[0091] This example provides a preparation method of a modified curing agent for a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0092] Weigh: 35.0 g of vinyl isocyanate, 43.0 g of dimethylallylamine and 450.0 mL of N,N-dimethylformamide and add them to a reaction kettle. Raise the temperature of the reaction kettle to 80 °C. After keeping the temperature and stirring for 15 min, add 5.0 g of azobisisobutyronitrile to the reaction kettle. After reacting under constant temperature for 4 h, add 44.0 g of methyl ethyl ketoxime and 5.0 g of dibutyltin dilaurate to the reaction kettle. Keep the temperature and stir for 30 min. After the reaction is completed, cool the reaction kettle to room temperature, then add the reaction solution to a rotary evaporator with a water bath temperature of 100 °C, and carry out vacuum distillation until no liquid is collected to obtain a modified curing agent.

[0093] Example 9

[0094] This example provides a preparation method of a modified curing agent for a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0095] Weigh: 35.0 g of vinyl isocyanate, 42.0 g of dimethylallylamine and 420.0 mL of N,N-dimethylformamide and add them to a reaction kettle. Raise the temperature of the reaction kettle to 70 °C. After keeping the temperature and stirring for 12 min, add 4.0 g of azobisisobutyronitrile to the reaction kettle. After reacting under constant temperature for 3 h, add 44.0 g of methyl ethyl ketoxime and 4.0 g of dibutyltin dilaurate to the reaction kettle. Keep the temperature and stir for 25 min. After the reaction is completed, cool the reaction kettle to room temperature, then add the reaction solution to a rotary evaporator with a water bath temperature of 90 °C, and carry out vacuum distillation until no liquid is collected to obtain a modified curing agent.

[0096] Example 10

[0097] This example provides a preparation method of a waterborne polyurethane transfer coating for anti-counterfeiting labels, including the following steps:

[0098] Weigh: Mix 40 parts of deionized water and 20 parts of ethanol to obtain a mixed solvent;

[0099] Weigh: 30 parts of the composite polyurethane prepared in Example 1, 5 parts of the composite filler prepared in Example 4, 5 parts of the modified curing agent prepared in Example 7, 45 parts of the mixed solvent, 1 part of polydimethylsiloxane, 1 part of phenyltrimethoxysilane, and 2 parts of azodiisooctanenitrile, add them to a stirring kettle. After mixing evenly, pass through an 80 - 100 mesh sieve to obtain the modified transfer coating.

[0100] Example 11

[0101] This example provides a preparation method of an aqueous polyurethane transfer coating for anti - counterfeiting labels, including the following steps:

[0102] Weigh: Mix 40 parts of deionized water and 20 parts of ethanol to obtain a mixed solvent;

[0103] Weigh: 50 parts of the composite polyurethane prepared in Example 2, 10 parts of the composite filler prepared in Example 5, 6 parts of the modified curing agent prepared in Example 8, 60 parts of the mixed solvent, 2 parts of polydimethylsiloxane, 2 parts of phenyltrimethoxysilane, and 3 parts of azodiisooctanenitrile, add them to a stirring kettle. After mixing evenly, pass through an 80 - 100 mesh sieve to obtain the modified transfer coating.

[0104] Example 12

[0105] This example provides a preparation method of an aqueous polyurethane transfer coating for anti - counterfeiting labels, including the following steps:

[0106] Weigh: Mix 40 parts of deionized water and 20 parts of ethanol to obtain a mixed solvent;

[0107] Weigh: 40 parts of the composite polyurethane prepared in Example 3, 8 parts of the composite filler prepared in Example 6, 6 parts of the modified curing agent prepared in Example 9, 54 parts of the mixed solvent, 2 parts of polydimethylsiloxane, 2 parts of phenyltrimethoxysilane, and 3 parts of azodiisooctanenitrile, add them to a stirring kettle. After mixing evenly, pass through an 80 - 100 mesh sieve to obtain the modified transfer coating.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 12 is that in the preparation of the composite polyurethane used in this comparative example, step ② is cancelled, and the modified polyurethane prepared in step ① is used to replace the composite polyurethane in equal amount.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 12 is that in step ① of the preparation process of the composite polyurethane used in this comparative example, the use of hydroxyl - terminated methyl vinyl silicone oil is cancelled, and step ② is cancelled.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 12 is that in the preparation of the composite filler used in this comparative example, step III is cancelled, and the modified filler prepared in step II is used to replace the composite filler in equal amount.

[0114] Performance test:

[0115] Referring to the standard GB / T 31586.2-2015 "Evaluation and acceptance criteria for the adhesion / cohesion (failure strength) of protective coating systems for the corrosion protection of steel structures - Part 2: Cross-cut test and cross-hatch test", the adhesion grade of the cured modified transfer coatings prepared in Examples 10-12 and Comparative Examples 1-3 was tested;

[0116] Referring to the standard YY / T 0988.15-2016 "Surgical implants - Coatings - Part 15: Test method for wear resistance of metallic thermal spray coatings", the mass loss after 100 cycles of wear of the cured modified transfer coatings prepared in Examples 10-12 and Comparative Examples 1-3 was tested;

[0117] Referring to the standard JB / T 6073-1992 "Metallic coatings - Laboratory immersion corrosion test", the corrosion resistance of the cured modified transfer coatings prepared in Examples 10-12 and Comparative Examples 1-3 was tested;

[0118] Referring to the standard GB / T 23987-2009 "Paints and varnishes - Exposure to artificial weathering of coatings - Exposure to fluorescent UV and water", the cured coatings of the modified transfer coatings prepared in Examples 10-12 and Comparative Examples 1-3 were subjected to ultraviolet corrosion, and the adhesion grade, wear resistance and corrosion resistance of the coatings were tested for the second time to obtain the performance data of the coatings after ultraviolet aging. The specific data are shown in Table 1.

[0119] Table 1 - Performance test data table of each specimen

[0120]

[0121]

[0122] Data analysis:

[0123] By comparing and analyzing the data in Table 1 above, it can be found that the adhesion grade of the modified transfer coating prepared by the present invention is grade 0, the mass loss is 4.2 mg, the corrosion rate is 0.19%, and after ultraviolet aging, the adhesion grade is still grade 0, the mass loss is 4.4, and the corrosion rate is 0.21%. All the data are better than those of the comparative examples;

[0124] In the present invention, a molecular network structure with alternating hard and soft segments is formed by the combination of silicone oil segments and ethylene glycol segments. The flexibility of the silicone oil can absorb the energy during the friction process, while the regular arrangement of the polyurethane hard segments and ethylene glycol enhances the rigidity of the material, jointly resisting wear. At the same time, the dynamic ionic bonds formed by the sulfonic acid groups and amino groups introduced into the material can preferentially break and recombine when stressed, achieving energy dissipation and local self-repair, and avoiding the destruction of the overall structure. The nanoparticles and silane coupling agents in the composite filler enhance the surface hardness of the coating, and reduce the friction loss through chemical bonding with the substrate. Moreover, active groups such as amino groups and epoxy groups can form strong interactions such as hydrogen bonds and covalent bonds with the surface of the substrate, ensuring the tight connection between the coating and the substrate. The hydrophilic-hydrophobic segments of the coating drive the molecules to penetrate into the micropores of the substrate through wetting differences during coating, forming a physical anchoring effect. The cross-linking reaction between the modified curing agent and the polyurethane chain constructs a three-dimensional network structure, further enhancing the cohesive strength and interfacial bonding force of the coating;

[0125] In the present invention, a low-porosity coating is formed by the close arrangement of silicone oil and polyurethane, effectively blocking the penetration of moisture and corrosive substances. The composite filler is tightly combined with the substrate through surface chemical modification, filling the microscopic defects and extending the diffusion path of the corrosive medium. The amino groups in the coating react with the substrate material to generate a stable protective layer, while the sulfonic acid groups repel the erosive ions through electrostatic action, reducing the risk of metal contact. The existence of dynamic chemical bonds enables the coating to self-repair tiny cracks when locally damaged, maintaining the protection continuity. At the same time, the organic titanium component inhibits the electrochemical corrosion reaction of the metal by adjusting the electronic properties of the coating, and the active groups in the siloxane can also neutralize acidic substances, keeping the interface environment stable. These mechanisms work together to comprehensively improve the anti-corrosion performance from physical barrier, chemical protection to dynamic repair;

[0126] In the present invention, a dense coating is formed by the close structure of silicone oil and polyurethane, reducing the ultraviolet penetration. The titanium-based component in the composite filler can absorb and disperse ultraviolet rays, reducing their destructive energy. A stable network is formed inside the coating through cross-linking reactions, and the amino groups and carboxyl groups enhance the intermolecular binding force, reducing the chemical bond breakage caused by ultraviolet rays. The introduced sulfonic acid groups can neutralize the harmful free radicals generated by ultraviolet rays, delaying the oxidation and decomposition of the material. When the dynamic chemical bonds in the coating are locally damaged by ultraviolet rays, they repair the tiny cracks through reversible recombination, preventing the expansion of defects. In addition, the chemical bonding between the amino groups and the substrate reduces the secondary damage to the coating caused by light reflection, and the titanium component inhibits the photochemical reaction by adjusting the electronic behavior. These mechanisms work together to improve the anti-aging performance from blocking ultraviolet rays, stabilizing the material structure to actively repairing damage;

[0127] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments only. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A water-based polyurethane transfer coating for anti-counterfeiting labels, characterized in that: The raw material composition comprises the following parts by weight: 30-50 parts of composite polyurethane, 5-10 parts of composite filler, 5-6 parts of modified curing agent, 45-60 parts of mixed solvent and 5-9 parts of auxiliary additives; The mixed solvent is obtained by mixing deionized water and ethanol in a weight ratio of 2:1, and the auxiliary additives include the following raw materials in parts by weight: 1-2 parts of polydimethylsiloxane, 1-2 parts of phenyltrimethoxysilane and 2-3 parts of azobisisoheptonitrile.

2. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 1, characterized in that: The preparation method of the composite polyurethane comprises the following steps: A1. Add polyethylene glycol, hydroxyl-terminated methyl vinyl silicone oil, N,N-dimethylformamide and dibutyltin dilaurate into a reaction kettle and stir. The temperature of the reaction kettle is raised to 50-60° C., and 4,4-diisocyanate dicyclohexylmethane solution is added dropwise into the reaction kettle. The reaction is kept warm for 40-60 minutes, and modified polyurethane is obtained by post-treatment. A2. Add modified polyurethane, acrylic acid, ethyleneamine and N,N-dimethylformamide into a reactor, raise the temperature of the reactor to 60-80°C, keep warm and stir for 15-20 minutes, add azobisisobutyronitrile into the reactor, keep warm and react for 2-4 hours, add a capping agent into the reactor, keep warm and react for 30-40 minutes, and perform post-treatment to obtain a composite polyurethane.

3. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 2, characterized in that: In step A1, the dosage ratio of polyethylene glycol, hydroxyl-terminated methyl vinyl silicone oil, N,N-dimethylformamide, dibutyltin dilaurate and 4,4-diisocyanate dicyclohexylmethane solution is 6-8g:2-3g:40-45mL:0.3-0.5g:10-12mL, wherein the 4,4-diisocyanate dicyclohexylmethane solution is obtained by mixing 4,4-diisocyanate dicyclohexylmethane and N,N-dimethylformamide at a dosage ratio of 2-3g:10-12mL.

4. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 2, characterized in that: In step A2, the modified polyurethane, acrylic acid, ethyleneamine, N,N-dimethylformamide, azobisisobutyronitrile and end-capping agent are used in an amount ratio of 8-10 g: 2-3 g: 1-2 g: 40-50 mL: 0.2-0.4 g: 0.5-0.8 mL, wherein the end-capping agent is sodium 3-mercapto-1-propanesulfonate.

5. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 1, characterized in that: The preparation method of the modified curing agent is as follows: vinyl isocyanate, dimethylallylamine and N,N-dimethylformamide are added to a reaction kettle, the temperature of the reaction kettle is increased to 60-80°C, and after being kept warm and stirred for 10-15 minutes, azobisisobutyronitrile is added to the reaction kettle, and after being kept warm and reacted for 2-4 hours, methyl ethyl ketone oxime and dibutyltin dilaurate are added to the reaction kettle, and the reaction kettle is kept warm and stirred for 20-30 minutes, and the modified curing agent is obtained by post-treatment.

6. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 5, characterized in that: The usage ratio of vinyl isocyanate, dimethylallylamine, N,N-dimethylformamide, azobisisobutyronitrile, methyl ethyl ketone oxime and dibutyltin dilaurate is 3.4-3.5g:4.2-4.3g:40-45mL:0.3-0.5g:4.3-4.4g:0.3-0.5g.

7. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 1, characterized in that: The preparation method of the composite filler comprises the following steps: B1. Tetraisopropyl titanate, tetraethyl silicate and anhydrous ethanol were added to a reaction kettle and stirred. After stirring at room temperature for 15-20 minutes, deionized water was continued to be added dropwise. After the temperature of the reaction kettle was raised to 50-60° C., a saturated sodium hydroxide solution was used to adjust the pH of the system to 8-10. After keeping the temperature for 3-4 hours, a composite gel was obtained. B2, transferring the composite gel to a tubular furnace for calcination to obtain a modified filler; B3. Add the modified filler, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol into the reactor, increase the temperature of the reactor to 40-60°C, keep the temperature for 30-40 minutes, and obtain the composite filler through post-treatment.

8. The water-based polyurethane transfer coating for anti-counterfeiting labels according to claim 7, characterized in that: In step B1, the dosage ratio of tetraisopropyl titanate, tetraethyl silicate, anhydrous ethanol and deionized water is 3-5g:5-6g:30-40mL:10-15mL; in step B2, the calcination operation includes: transferring the composite gel to a tubular furnace, introducing nitrogen protection, heating the tubular furnace to 500-600°C at a heating rate of 5-6°C / min, and heat preservation for 3-4h, and naturally cooling the tubular furnace to 200-300°C, disconnecting the nitrogen, and introducing water vapor at a rate of 60-80sccm, heat preservation for 2-3h, and naturally cooling to obtain a modified filler; in step C3, the dosage ratio of the modified filler, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, triethylamine and anhydrous ethanol is 8-10g:1-2g:0.3-0.5g:40-48mL.

9. A method for preparing a water-based polyurethane transfer coating for an anti-counterfeiting label according to any one of claims 1 to 8, characterized in that: The composite polyurethane, composite filler, mixed solvent, polydimethylsiloxane, phenyltrimethoxysilane and azobisisoheptanenitrile are added into a stirring kettle, mixed evenly, and then passed through a 80-100 mesh sieve to obtain a modified transfer coating.

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