Photocuring water-based prime coat coating, preparation method and application

Abstract

The invention discloses a photocuring water-based prime coat coating and a preparation method thereof, and belongs to the technical field of medicine blister packaging. The coating is composed of 40 to 65% of a polycarbonate polyol emulsion with a hydroxyl value of 50 to 85 mg KOH / g, 1 to 6% of surface tannic acid chelating modified nano chitin whisker, 2 to 10% of a photoinitiator, 0.5 to 3% of tannic acid grafted graphene and a leveling agent. The preparation method comprises the steps of ultrasonic treatment chitin whisker modification, nitrogen protection dispersion, vacuum defoaming and the like. When the coating is applied to an aluminum foil base material, a base coating with high adhesive force, scratch resistance, antibacterial property and oxidation resistance can be formed through UV-LED curing under the low coating weight, and the printing requirement of medicine packaging is met while the flexibility of aluminum foil is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of water-based coatings, and in particular to a light-curable water-based primer coating and a preparation method thereof, as well as application of the coating on a blister packaging cover film. Background Art

[0002] Blister packaging (PTP) is commonly used for pharmaceuticals. The cavity formed between a rigid sheet and a cover film holds capsules, tablets, granules, and other pharmaceuticals. Rigid sheets typically include polyvinyl chloride, polyethylene terephthalate, polypropylene, and polyethylene. These sheets can optionally be coated with polyvinylidene chloride to form a barrier layer, thereby reducing oxygen and water vapor transmission rates and providing moisture-proof and antioxidant properties. For tablets that require light protection, a layer of cold-formed aluminum can be applied to the surface of the sheet, depending on the degree of light protection required.

[0003] The surface of the blister packaging cover film is typically printed with dosage and directions for administration. Direct printing on the cover film, often made of aluminum foil or polymer composite materials, can easily lead to insufficient ink adhesion. Existing technologies address this issue by applying a primer to the non-drug-contacting surface of the PTP cover film before printing. This creates polar groups or a rough microstructure, enhancing the mechanical anchoring and chemical bonding of the ink. Existing primers typically use acrylic, polyurethane, and nitrocellulose compositions, and a curing agent is also required during the primer application. To achieve good print quality, the film surface must maintain a stable coating weight of 0.7-1.6 gsm for optimal printability, resulting in high primer costs. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a primer for a blister packaging cover film to solve the problem of the prior art of sacrificing between printing quality and primer cost.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: A light-curable water-based primer coating is composed of the following components in percentage by mass: 40-65% polycarbonate polyol emulsion; 1-6% nano-chitin whiskers; 2-10% photoinitiator; 0.5-3% tannic acid-modified graphene; 0.1-1.5% leveling agent; and the balance is deionized water.

[0006] The polycarbonate polyol is preferably an aliphatic polycarbonate polyol and an alicyclic polycarbonate polyol, including but not limited to a polymer whose main chain contains a structure of an aliphatic polyol and an alicyclic polyol alternately connected with carbonate groups, such as 1,6-hexanediol, 1,4-butanediol, cyclohexanedimethanol, isosorbide, etc.

[0007] Furthermore, the polycarbonate polyol emulsion has a hydroxyl value of 50-85 mg KOH / g and a number average molecular weight of 8000-15000.

[0008] As an illustration, polycarbonate polyols can use 1,6-hexanediol (HDO) and dimethyl carbonate (DMC) condensation polymers and 1,4-butanediol (BDO) and cyclohexanedimethanol (CHDM) block copolymers as the resin matrix emulsion.

[0009] Chitosan is a linear polysaccharide formed by connecting N-acetylglucosamine through β-(1,4)-glycosidic bonds, and its molecular formula is (C8H 13 O5N) n The surface is rich in hydroxyl groups (-OH) and acetylamino groups (-NHCOCH3), and functional groups can be introduced through chemical modification. In the present invention, the diameter of the nano-chitosan whiskers is 20-80nm, and the aspect ratio is 500-1200.

[0010] Furthermore, the photoinitiator is composed of an α-hydroxyketone initiator and an acylphosphine oxide in a mass ratio of (2.5-4):1, and contains a visible light responsive titanocene derivative accounting for 0.5-2% of the total weight of the photoinitiator.

[0011] For clarification, a photoinitiator is a compound of two or more photoinitiators, achieving efficient curing through spectral complementarity. The function of the device is to achieve initiation by using different initiators to cover light sources of different wavelengths. Visible light-responsive titanocene derivatives respond in the visible light region to reduce the probability of free radicals on the coating surface being quenched by oxygen, thereby protecting the coating from bonding with the ink during printing.

[0012] Furthermore, the specific surface area of the tannic acid modified graphene is ≥500m 2 The surface grafting rate is 15-30%, and the grafting sites are located on the polyphenolic hydroxyl structures of tannic acid. The high specific surface area means more exposed carbon atoms and defect sites, providing ample grafting anchoring sites for tannic acid molecules.

[0013] The present invention also provides a method for preparing a light-curable water-based primer coating having at least any one of the above technical features, comprising the following steps: S1. Nano-chitosan whiskers and tannic acid-modified graphene are mixed and dispersed in a buffer solution to obtain a surface chelated modified complex.

[0014] S2. Add polycarbonate polyol emulsion to the composite and its aqueous phase system and disperse them evenly.

[0015] S3. Add a photoinitiator and a leveling agent to the aqueous phase system uniformly dispersed with the polycarbonate polyol and mix to form a finished coating.

[0016] Further, In S1, the mass ratio of nano-chitosan whiskers to tannic acid-modified graphene is 1:(0.1-0.3), the buffer solution pH is 4-6, and the mixing and dispersion is carried out by ultrasonic treatment for 30-60 minutes; In S2, the composite and the polycarbonate polyol emulsion are dispersed by high-speed stirring under a nitrogen atmosphere at a stirring rate of 6000-10000 rpm for 40-90 min, and the remaining tannic acid-modified graphene is mixed; In S3, vacuum degassing is performed during the mixing process until the bubble content is less than 0.1 vol%.

[0017] Further, The ultrasonic treatment conditions of S1 are: frequency 38-42 kHz, power density 0.5-1.5 W / cm 2 ; The dispersion temperature of S2 is 25-35°C; The S3 is further added with nano-silicon dioxide aerogel accounting for 0.01-0.1% by mass of the finished coating, with a particle size of 10-30 nm and a porosity of ≥95%.

[0018] The present invention further protects the application of a coating having at least any one of the above-mentioned technical features and / or a method thereof on a blister packaging cover film, wherein the application method comprises applying a primer coating on the surface of the non-drug contact side of the cover film aluminum foil substrate, and then curing the primer coating with a UV-LED light source.

[0019] Furthermore, the coating amount on the surface of the aluminum foil substrate is 0.08-0.35gsm, and the UV-LED light source is at a wavelength of 365-405nm and an intensity of 80-150mW / cm 2 Cure for 2-8 seconds.

[0020] The advantages and beneficial effects of the present invention are: 1. This invention utilizes a polycarbonate polyol emulsion as a matrix, providing excellent flexibility and adhesion to aluminum foil substrates, making it suitable for the repeated bending and flexing requirements of blister packaging. Nano-chitosan whiskers and tannic acid-modified graphene form a three-dimensional network structure, significantly enhancing the coating's hardness and scratch resistance. The photoinitiator operates at multiple wavelengths, achieving rapid curing and uniform cure depth.

[0021] 2. The polyphenolic hydroxyl grafting of tannic acid-modified graphene imparts antioxidant and antibacterial properties to the coating, making it suitable for the hygienic requirements of pharmaceutical packaging. This invention utilizes a water-based system, resulting in near-zero VOC emissions, meeting the environmental requirements of pharmaceutical packaging.

[0022] 3. The coating shown in the present invention can form a dense base coating at a relatively low coating amount, without affecting the flexibility of the aluminum foil, while meeting the high barrier (moisture-proof and light-proof) requirements of pharmaceuticals. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart for preparing the light-curing water-based primer coating of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a light-curing water-based primer coating, which adopts a polycarbonate polyol emulsion as a base resin, controls the cross-linking reaction rate by adjusting the hydroxyl density, ensures sufficient free radical cross-linking points in the light-curing stage, and avoids excessive viscosity of the system caused by excessive hydroxyl groups.

[0025] As a preferred embodiment, the number-average molecular weight of the polycarbonate polyol is between 8,000 and 15,000 to balance flexibility and mechanical strength. Within this range, an appropriate molecular weight distribution ensures both enhanced coating flexibility and the reactivity of the photocuring reaction. The present invention uses water as the dispersion medium to avoid organic solvent volatilization, meeting environmental requirements for pharmaceutical packaging. The polycarbonate polyol dispersed in the emulsion forms a continuous film upon curing, enhancing adhesion through hydrogen bonding between the hydroxyl groups and the aluminum oxide on the aluminum foil surface.

[0026] As further illustration, chitin whiskers with diameters ranging from 20-80nm and aspect ratios of 500-1200 form a nanoscale fiber network with a high specific surface area, enhancing the coating's scratch resistance through mechanical interlocking. Tannic acid chelation modification introduces polyphenolic hydroxyl groups onto the whisker surface, improving compatibility with aqueous emulsions. Furthermore, hydrogen bonding between the phenolic hydroxyl groups and polycarbonate polyols forms a three-dimensional crosslinked network, further enhancing hardness.

[0027] The polyphenol structure of tannic acid has antioxidant (scavenging free radicals) and antibacterial properties (destroying microbial cell membranes), which directly gives the coating antibacterial function and meets the hygiene requirements of pharmaceutical packaging.

[0028] As an illustration, the preparation method of tannic acid modified graphene can be prepared by mixing natural flake graphite with concentrated sulfuric acid and potassium permanganate in a mass ratio of 1:3:0.4 and reacting for 4 hours in an ice bath to generate graphite oxide. The graphite oxide is dispersed in deionized water, and sodium dodecylbenzene sulfonate accounting for 0.5% of the graphite mass is added. The graphite oxide is then heated at a frequency of 45kHz and a power density of 2W / cm 2 Ultrasonic peeling was performed under the same conditions for 90 minutes, and then a graphene oxide suspension with an average number of layers of 5±1 was obtained by centrifugation.

[0029] The concentration of the graphene oxide suspension was adjusted to 1.5 mg / mL, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were added. The molar ratio of EDC to the carboxyl group of graphene oxide was 5:1. The reaction was stirred at pH = 6.0 and 30°C for 2 hours to activate the carboxyl activity.

[0030] A 5wt% tannic acid solution was added to a mixture of graphene oxide and tannic acid in a mass ratio of 1:0.8. The mixture was reacted at 60°C under nitrogen at a pH of 8.5 (adjusted with ammonia). Tannic acid molecules were grafted onto the graphene surface via an esterification reaction, with the polyphenolic hydroxyl groups preferentially bonding with activated carboxyl groups. Unreacted hydroxyl groups were then adsorbed onto the graphene surface via π-π conjugation.

[0031] Ascorbic acid (2:1 mass ratio of graphene oxide to ascorbic acid) was then added, and the mixture was reduced in an 80°C water bath for 6 hours to restore the graphene's conjugated structure. The filtrate was filtered, washed, and centrifuged to remove unreacted material, and freeze-dried to obtain tannic acid-modified graphene as a black powder.

[0032] The present invention preferably uses photoinitiators, which include α-hydroxy ketones and acylphosphine oxides. The former initiates surface curing at short light wavelengths, while the latter promotes deep curing at long light wavelengths.

[0033] As a preferred embodiment, 0.5-2% of a visible light responsive titanocene derivative is added to the photoinitiator to expand the spectral response range of the initiator, reduce the oxygen inhibition effect, and improve the curing uniformity.

[0034] Tannic acid-modified graphene provides an ultra-thin sheet structure, which is grafted through the π-π conjugation of polyphenol hydroxyl groups with graphene to form a stable chemical bond and avoid graphene agglomeration.

[0035] The present invention also provides a method for preparing the aforementioned water-based coating. Step 1 utilizes ultrasonic cavitation to promote the penetration of tannic acid molecules onto the surface of chitin whiskers, where a chelation reaction (-OH groups bind to chitin amino groups) forms a stable modified layer. A buffer solution is used to adjust the ionization state of the tannic acid during the chelation reaction to optimize the efficiency of the chelation reaction. Step 2 utilizes stirring under a nitrogen atmosphere to prevent thermal oxidation of the chitin whiskers / graphene during the dispersion process and to suppress emulsion demulsification. Step 3 utilizes vacuum degassing to eliminate microporous defects in the coating material, improve its density, and thereby ensure good film flatness, facilitating surface printing.

[0036] As a preferred technical solution, in step 2, deionized water is added during stirring to control the temperature at 25-35° C. to avoid the glass transition of the polycarbonate polyol emulsion and maintain the stability of the emulsion.

[0037] As a preferred technical solution, in step 3, nano-silica aerogel with a particle size of 10-30 nm and a porosity of >95% is added to the coating during vacuum degassing. The nano-particle filling effect reduces the surface energy of the coating, improves leveling, and reduces shrinkage cavities.

[0038] The following embodiments are further described in conjunction with the accompanying drawings and examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0039] Example 1 A light-curing water-based primer coating comprises the following components by weight: Polycarbonate polyol emulsion (hydroxyl value 65mg KOH / g, number average molecular weight 12,000) 58%, nanochitin whiskers (diameter 50±10nm, aspect ratio 800) 3%, photoinitiator (Irgacure 184:TPO-L=3:1, containing 1% titanocene derivative SpeedCure 9385) 6%, tannic acid modified graphene (specific surface area 520m 2 / g, grafting rate 20%) 1.5%, leveling agent 0.8%, and the balance deionized water.

[0040] The preparation method of the water-based primer coating comprises the following steps: S1: Add 60% of the total water volume of deionized water to the reactor, add nano-chitosan whiskers, stir at 2000 rpm for 15 minutes to form a uniform suspension, adjust the pH of the aqueous phase in the reactor to 5.0 with citric acid buffer, add 25% of the mass of nano-chitosan whiskers to the tannic acid modified graphene and mix them in the reactor, and heat the mixture at 40 kHz, 1.0 W / cm 2 The complex was prepared by ultrasonic treatment for 40 min.

[0041] S2: The polycarbonate polyol emulsion was slowly added to the aqueous phase system, and the mixture in the reactor was stirred and dispersed at 6000 rpm under nitrogen protection for 60 minutes. During the stirring process, the remaining amount of tannic acid-modified graphene was added in two portions, and the system temperature was maintained at ≤35°C.

[0042] S3: Mix the photoinitiator, 0.05% nano-silica aerogel with a particle size of 20 nm and a porosity of 97%, the leveling agent and the remaining deionized water and add them to the system. At the same time, reduce the stirring rate to 4000 rpm and continue stirring for 30 minutes to evenly disperse the photoinitiator. Then, vacuum degassing (-0.095 MPa) is performed until the bubble content is less than 0.1 vol%.

[0043] Example 2 A light-curing water-based primer coating comprises the following components by weight: Polycarbonate polyol emulsion (hydroxyl value 75mg KOH / g, number average molecular weight 14,000) 62%, nanochitin whiskers (diameter 30±5nm, aspect ratio 1000) 4.5%, photoinitiator (Irgacure 184:TPO-L=3.5:1, containing 1.2% SpeedCure 9385) 8%, tannic acid modified graphene (specific surface area 550m 2 / g, grafting rate 25%) 2.2%, leveling agent 1.0%, and the balance deionized water.

[0044] The preparation method of the water-based primer coating comprises the following steps: S1: Add 60% of the total water volume of deionized water to the reactor, add nano-chitosan whiskers, and stir at 2500 rpm for 20 minutes to form a uniform suspension. Adjust the pH of the aqueous phase in the reactor to 5.5 with phosphate buffer. Add 30% of the weight of the nano-chitosan whiskers of tannic acid-modified graphene to the reactor and ultrasonicate at 45 kHz and 1.2 W / cm² for 50 minutes to obtain a composite.

[0045] S2: Add the polycarbonate polyol emulsion to the reactor in four separate additions (3-minute intervals between each addition). Stir and disperse the mixture at 8500 rpm under nitrogen for 70 minutes. Add the remaining tannic acid-modified graphene during stirring. Maintain the system temperature ≤ 30°C.

[0046] S3: Mix the photoinitiator, 0.08% nano-silica aerogel (particle size 15 nm, porosity 98%), leveling agent and the remaining deionized water and add them to the system. At the same time, reduce the stirring rate to 4500 rpm and continue stirring for 30 minutes to evenly disperse the photoinitiator. Then, vacuum degassing (-0.1 MPa) is performed until the bubble content is less than 0.1 vol%.

[0047] Example 3 A light-curing water-based primer coating comprises the following components by weight: Polycarbonate polyol emulsion (hydroxyl value 60mg KOH / g, number average molecular weight 10,000) 50%, nano-chitin whiskers (diameter 70±10nm, aspect ratio 600) 2.0%, photoinitiator (Irgacure 184:TPO-L=4:1, containing 1.8% SpeedCure9385) 10%, tannic acid modified graphene (specific surface area 480m 2 / g, grafting rate 18%), 0.8%, leveling agent 0.5%, and the balance deionized water.

[0048] The preparation method of the water-based primer coating comprises the following steps: S1: Add 60% of the total water volume of deionized water to the reactor, add nano-chitosan whiskers, and stir at 1800 rpm for 10 minutes to form a uniform suspension. Adjust the pH of the aqueous phase in the reactor to 4.8 with acetic acid-sodium acetate buffer, add tannic acid-modified graphene with a mass of 20% of the nano-chitosan whiskers to the reactor, and ultrasonicate at 38 kHz and 0.8 W / cm² for 35 minutes to obtain a composite.

[0049] S2: Add the polycarbonate polyol emulsion to the aqueous phase of the reactor all at once and stir at 7000 rpm under nitrogen for 50 minutes. Add the remaining tannic acid-modified graphene during stirring, maintaining the system temperature ≤35°C.

[0050] S3: Mix the photoinitiator, 0.03% nano-silica aerogel (particle size 25 nm, porosity 95%), leveling agent and the remaining deionized water and add them to the system. At the same time, reduce the stirring rate to 3500 rpm and continue stirring for 30 minutes to evenly disperse the photoinitiator. Then, vacuum degassing (-0.15 MPa) is performed until the bubble content is less than 0.1 vol%.

[0051] Example 4 A light-curing water-based primer coating comprises the following components by weight: Polycarbonate polyol emulsion (hydroxyl value 50mg KOH / g, number average molecular weight 8,000) 40%, nanochitin whiskers (diameter 20±5nm, aspect ratio 500) 1%, photoinitiator (Irgacure 184:TPO-L=2.5:1, containing 0.5% titanocene derivative SpeedCure 9385) 2%, tannic acid-modified graphene (specific surface area 500m² / g, grafting rate 15%) 0.5%, leveling agent 0.1%, and the balance is deionized water.

[0052] The preparation method of the water-based primer coating comprises the following steps: S1: Add 60% deionized water to a reactor, add nano-chitosan whiskers, and stir at 1500 rpm for 10 minutes to form a suspension. Adjust the pH to 4.0 with acetate buffer, add tannic acid-modified graphene with a mass of 10% of the nano-chitosan whiskers, and ultrasonicate at 38 kHz and 0.5 W / cm² for 30 minutes to prepare a composite.

[0053] S2: The polycarbonate polyol emulsion was added to the aqueous phase system in three portions, and the mixture was stirred and dispersed at 6000 rpm under nitrogen protection for 40 minutes. During the process, the remaining tannic acid-modified graphene was added in three portions, and the temperature was controlled at 25°C.

[0054] S3: Mix the photoinitiator, 0.01% nano-silica aerogel (particle size 10 nm, porosity 95%), leveling agent and the remaining deionized water and add them to the system. After stirring at 3000 rpm for 20 min, vacuum degassing (-0.09 MPa) was performed until the bubble content was less than 0.1 vol%.

[0055] Example 5 A light-curing water-based primer coating comprises the following components by weight: Polycarbonate polyol emulsion (hydroxyl value 85mg KOH / g, number average molecular weight 15,000) 65%, nanochitosan whiskers (diameter 80±10nm, aspect ratio 1200) 6%, photoinitiator (Irgacure 184:TPO-L=4:1, containing 2% SpeedCure 9385) 10%, tannic acid-modified graphene (specific surface area 600m² / g, grafting rate 30%) 3%, leveling agent 1.5%, and the balance is deionized water.

[0056] The preparation method of the water-based primer coating comprises the following steps: S1: Add 60% deionized water to a reactor, add nano-chitosan whiskers, and stir at 3000 rpm for 30 minutes to form a suspension. Adjust the pH to 6.0 with phosphate buffer. Add tannic acid-modified graphene with a mass of 30% of the nano-chitosan whiskers, and ultrasonicate at 42 kHz and 1.5 W / cm² for 60 minutes to prepare a composite.

[0057] S2: The polycarbonate polyol emulsion was slowly added to the aqueous phase system in 5 portions, and stirred and dispersed at 10,000 rpm under nitrogen protection for 20 minutes. During the process, the remaining tannic acid-modified graphene was added in 5 portions, and the temperature was controlled at 35°C.

[0058] S3: Mix the photoinitiator, 0.1% nano-silica aerogel (particle size 30 nm, porosity 98%), leveling agent and the remaining deionized water and add them to the system. After stirring at 5000 rpm for 40 min, vacuum degassing (-0.15 MPa) was performed until the bubble content was less than 0.1 vol%.

[0059] The present invention uses the primer coating prepared in the above examples as a blister packaging cover film. Each example is coated on the surface of an aluminum foil substrate to form a primer coating, which is then cured by a UV-LED light source. The coating amount is 0.08-0.35gsm, and the UV-LED light source is at a wavelength of 365-405nm and an intensity of 80-150mW / cm 2 The curing was carried out for 2-8 seconds. The preparation results are shown in Table 1: Table 1: Preparation Example Corresponding embodiment Coating weight, gsm Light source wavelength, nm <![CDATA[Light intensity, mW / cm 2 > 1 Example 1 0.08 365 80 2 Example 1 0.15 385 100 3 Example 2 0.22 395 120 4 Example 2 0.35 405 150 5 Example 3 0.12 375 90 6 Example 3 0.28 385 130 7 Example 4 0.10 365 85 8 Example 4 0.18 405 140 9 Example 5 0.25 395 110 10 Example 5 0.32 405 150 The curing effect of each of the above preparation examples was tested. The adhesion test was conducted using ASTM D3359, with a 1mm spacing cross-hatch method, and the test results were 0-5B (5B means no peeling). The pencil hardness was tested using ASTM D3363, with a Mitsubishi UNI pencil scratching the surface with a load of 750g at a 45° angle. The antibacterial rate test standard was JIS Z 2801, with an inoculum concentration of 1*10 6 CFU / mL, and the inhibition rate was calculated after incubation at 37°C for 24 h; the test results are shown in Table 2.

[0060] Table 2: The data in Table 2 show that the cracking rate of the primer coatings shown in the present invention increases at higher coating weights. However, their density is still superior to that of conventional acrylic primer coatings. All preparations exhibited a curing time of ≤8 seconds, and the coating weight was only 1 / 10 of that of the prior art. The curing time and coating cost are significantly lower than those of thermal curing processes.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A light-curing water-based primer coating, characterized in that: The invention is composed of the following components in percentage by weight: polycarbonate polyol emulsion, 40-65%; nano-chitin whiskers, 1-6%; photoinitiator, 2-10%; tannic acid modified graphene, 0.5-3%; leveling agent, 0.1-1.5%; and the balance is deionized water.

2. The light-curable water-based primer coating according to claim 1, characterized in that: The polycarbonate polyol emulsion has a hydroxyl value of 50-85 mg KOH / g and a number average molecular weight of 8000-15000.

3. The light-curable water-based primer coating according to claim 2, characterized in that: The diameter of the nano-chitosan whisker is 20-80 nm, and the aspect ratio is 500-1200.

4. The light-curable water-based primer coating according to claim 3, characterized in that: The photoinitiator is composed of an α-hydroxyketone initiator and an acylphosphine oxide in a mass ratio of (2.5-4):1, and contains a visible light responsive titanocene derivative accounting for 0.5-2% of the total weight of the photoinitiator.

5. The light-curable water-based primer coating according to claim 1, characterized in that: The specific surface area of the tannic acid modified graphene is ≥500m 2 / g, and the surface grafting rate is 15-30%, and the grafting point is the polyphenolic hydroxyl structure of tannic acid.

6. A method for preparing a light-curable water-based primer coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Mixing and dispersing nano-chitosan whiskers and tannic acid-modified graphene in a buffer solution to obtain a surface-chelated modified composite; S2. Adding a polycarbonate polyol emulsion to the composite and its aqueous phase system and dispersing it evenly; S3. Add a photoinitiator and a leveling agent to the aqueous phase system uniformly dispersed with the polycarbonate polyol and mix to form a finished coating.

7. The method for preparing a light-curable water-based primer coating according to claim 6, characterized in that: In S1, the mass ratio of nano-chitosan whiskers to tannic acid-modified graphene is 1:(0.1-0.3), the buffer solution pH is 4-6, and the mixing and dispersion is carried out by ultrasonic treatment for 30-60 minutes; In S2, the composite and the polycarbonate polyol emulsion are dispersed by high-speed stirring under a nitrogen atmosphere at a stirring rate of 6000-10000 rpm for 40-90 min, and the remaining tannic acid-modified graphene is mixed; In S3, vacuum degassing is performed during the mixing process until the bubble content is less than 0.1 vol%.

8. The method for preparing a light-curable water-based primer coating according to claim 7, characterized in that: The ultrasonic treatment conditions of S1 are: frequency 38-42 kHz, power density 0.5-1.5 W / cm 2 ; The dispersion temperature of S2 is 25-35°C; The S3 is further added with nano-silicon dioxide aerogel accounting for 0.01-0.1% by mass of the finished coating, with a particle size of 10-30 nm and a porosity of ≥95%.

9. A blister packaging cover film, characterized in that: The coating according to any one of claims 1 to 5 or the coating prepared by the method according to any one of claims 6 to 8 is coated on the surface of an aluminum foil substrate to form a primer layer, which is then cured by a UV-LED light source.

10. The blister packaging cover film according to claim 9, characterized in that The coating amount on the surface of the aluminum foil substrate is 0.08-0.35gsm, and the UV-LED light source is at a wavelength of 365-405nm and an intensity of 80-150mW / cm 2 Cure for 2-8 seconds.

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