Packaging box high gloss quick-drying printing ink and preparation method thereof

Abstract

The application discloses a kind of packing box high gloss quick-drying printing ink and preparation method thereof, belong to novel ink technical field, comprising: preparation composite resin, preparation modified filler, final mix compound.This application is prepared by specific proportion of epoxy acrylate, polyurethane acrylate and castor oil base polyurethane prepolymer composite resin, both ensure that ink layer reaches the hardness that meets the wear resistance demand on copperplate paper, PET film, aluminum foil composite paper and other commonly used substrates, can resist friction, scratching and other physical damage in logistics transportation, while giving ink layer good elongation at break, avoid the phenomenon of ink layer microcrack, through cracking or peeling in die cutting folding, hot pressing forming, edge curling and other post-processing links, while guaranteeing the moisture-proof, stain-proof protection function of substrate.

Description

Technical Field

[0001] This invention relates to the field of novel ink technology, specifically to a high-gloss, fast-drying printing ink for packaging boxes and its preparation method. Background Technology

[0002] As a dual carrier of product protection and brand display, packaging boxes have rigid requirements for the hardness of the ink layer. During logistics transportation and end-user use, the surface of the packaging box is easily subjected to physical actions such as friction and scratches. A high-hardness ink layer can effectively resist such damage and maintain the integrity of the printed pattern. Therefore, existing technologies often improve the hardness of the ink layer by optimizing the resin system and curing process. For example, Chinese patent CN119101396B discloses a high-gloss environmentally friendly UV-curable luminous ink and its preparation method, which can achieve a hardness of 5H, meeting the basic wear resistance requirements.

[0003] However, increased ink layer hardness is often accompanied by decreased flexibility. In the post-processing of packaging boxes, whether it's die-cutting and folding of paper boxes, thermoforming of plastic boxes, or edge curling of metal boxes, the ink layer must withstand continuous mechanical stress and deformation. When the stress exceeds the elongation at break threshold of the ink layer, micro-cracks are easily generated on the surface. In severe cases, through-cracks along the fold lines or ink layer peeling may occur. This defect not only damages the visual aesthetics of the packaging box but may also lead to exposure of the substrate, reducing its protective functions such as moisture resistance and stain resistance. Especially in high-end packaging fields such as food and gifts, such problems directly affect the product's market competitiveness.

[0004] High gloss is an important indicator for improving the visual quality of packaging boxes. Its essence depends on the microscopic smoothness of the surface after the ink is cured and the optical stability of the resin and pigment. In the actual life cycle of the packaging box, environmental factors such as light and humidity will continue to reduce the gloss of the ink layer.

[0005] Based on this, the present invention designs a high-gloss, fast-drying printing ink for packaging boxes and its preparation method to solve the above problems. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing a high-gloss, fast-drying printing ink for packaging boxes, comprising the following steps:

[0007] S1. Preparation of composite resin: Add 32-40 parts by weight of epoxy acrylate, 18-28 parts by weight of polyurethane acrylate and 12-20 parts by weight of castor oil-based polyurethane prepolymer to the reaction vessel, heat up, add the catalyst dibutyltin dilaurate, stir and react to obtain composite resin.

[0008] S2. Preparation of modified filler: 14-16 parts by weight of nano silica, 5-8 parts by weight of polydimethylsiloxane and silane coupling agent are added to a dispersion tank and sheared at high speed to form a dispersion. 10-20% by weight of methyl methacrylate, 2-5% by weight of trimethylolpropane triacrylate, 0.5-1.5% by weight of azobisisobutyronitrile and 0.01-0.03% by weight of hydroquinone are added to the dispersion and ultrasonically dispersed to form an emulsion. The emulsion is heated and stirred, sodium chloride is added to break the emulsion, centrifuged, and the supernatant is discarded to obtain the modified filler.

[0009] S3. Compounding: The composite resin obtained in S1 is naturally cooled and kept warm. 4-8 parts by weight of N-vinylpyrrolidone are added and stirred. 5-9 parts by weight of premixed and preheated additives and preheated composite photoinitiator are added and stirred. Heating is stopped and the mixture is naturally cooled. Pigment is added and stirred to obtain the precursor.

[0010] S4. Final mixing: After the precursor is cooled naturally, stir it and add the modified filler prepared in S2 in 3-4 batches. After each addition of the modified filler, raise the temperature. After all the filler has been added, continue stirring to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0011] Furthermore, S1 specifically involves adding 32-40 parts by weight of epoxy acrylate, 18-28 parts by weight of polyurethane acrylate, and 12-20 parts by weight of castor oil-based polyurethane prepolymer to a reactor, heating to 80-90°C, adding 0.1-0.5 parts by weight of dibutyltin dilaurate catalyst, and stirring at 600-800 rpm for 2-3 hours to obtain the composite resin.

[0012] Furthermore, S2 specifically involves adding 14-16 parts by weight of nano-silica, 5-8 parts by weight of polydimethylsiloxane, and 0.4-0.8 parts by weight of silane coupling agent KH550 to a dispersion tank, and shearing at 2000-3000 rpm for 10-15 minutes to form a dispersion. Then, adding 10-20% by weight of methyl methacrylate, 2-5% by weight of trimethylolpropane triacrylate, 0.5-1.5% by weight of azobisisobutyronitrile, and 0.01-0.03% by weight of hydroquinone to the dispersion, and ultrasonically dispersing at 200-400W for 10-20 minutes to form an emulsion. The emulsion is then heated to 60-70℃ and stirred at 200-300 rpm for 4-6 hours. Sodium chloride (5-8% by weight of the emulsion) is added to break the emulsion, followed by centrifugation. The supernatant is discarded to obtain the modified filler.

[0013] Furthermore, S3 specifically involves: naturally cooling the composite resin obtained in S1 to 50-62℃ and maintaining the temperature, adding 4-8 parts by weight of N-vinylpyrrolidone, stirring at 200-300 rpm for 10-15 minutes, adding 5-9 parts by weight of premixed additives preheated to 48-56℃ and composite photoinitiator preheated to 45-52℃, stirring at 600-800 rpm for 25-35 minutes, stopping heating, naturally cooling to 32-38℃, adding 12-15 parts by weight of pigment, and stirring at 300-500 rpm for 15-20 minutes to obtain the precursor.

[0014] Furthermore, the additives include ultraviolet absorbers, defoamers, and leveling agents in a mass ratio of 1.2-1.5:0.2-0.7:0.2-0.5.

[0015] Furthermore, the composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 2-5:1-3:0.8-1.5:0.3-0.7.

[0016] Furthermore, S4 specifically involves: after the precursor is naturally cooled to 25-30℃, stirring at 500-700rpm for 5-10min, adding the modified filler prepared by S2 in 3-4 portions, with an interval of 3-5min between each addition, raising the temperature by 4-6℃ after each addition, and continuing to stir at 500-700rpm for 8-12min after all the filler has been added, to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0017] A high-gloss, fast-drying printing ink for packaging boxes prepared according to the preparation method described above.

[0018] Compared with the prior art, the beneficial effects of this invention are as follows:

[0019] 1. This invention prepares a composite resin by using a specific ratio of epoxy acrylate, polyurethane acrylate and castor oil-based polyurethane prepolymer. This ensures that the ink layer achieves the required hardness for wear resistance on common substrates such as coated paper, PET film, and aluminum foil composite paper, resisting physical damage such as friction and scratches during logistics and transportation. At the same time, it gives the ink layer good elongation at break, preventing micro-cracks, through-cracks or peeling of the ink layer during post-processing stages such as die-cutting, folding, thermoforming, and edge curling of the packaging box. It also ensures the moisture-proof and stain-proof protection of the substrate.

[0020] 2. This invention possesses high gloss and excellent anti-aging and gloss retention capabilities, enhancing the visual texture and durability of packaging boxes. The modified nano-silica filler, processed through high-speed shearing, ultrasonic dispersion, and demulsification, can be uniformly dispersed in the ink. Combined with composite resin, it provides the ink with high initial gloss, enhancing the brand display effect of the packaging box. A specific proportion of additives can resist the attenuation of ink layer gloss caused by environmental factors such as light, high temperature, and high humidity, allowing the ink to maintain a high gloss retention rate during long-term use, thus maintaining the visual aesthetics of the packaging box. It is suitable for fields such as food and gifts where high packaging texture is required.

[0021] 3. This invention is compatible with a variety of packaging box substrates, broadening the application range of the ink. The ink can stably exhibit high gloss, high hardness, good flexibility and anti-aging properties on packaging box substrates of different materials such as coated paper, PET film, and aluminum foil composite paper. It has good interfacial bonding ability with various substrates, and there is no need to adjust the core formula for different substrates. It can meet the printing needs of various types of packaging boxes such as paper, plastic and metal composite, improving the practicality and applicability of the ink. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0023] Figure 1 Infrared spectra of the composite resin, modified filler, precursor, and finally high-gloss fast-drying printing ink for packaging boxes prepared in Example 3 of the present invention.

[0024] Figure 2 Thermogravimetric analysis curve of the high-gloss fast-drying printing ink for packaging boxes prepared in Example 3 of the present invention;

[0025] Figure 3 This is a photograph of the high-gloss, fast-drying printing ink for packaging boxes produced according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1: This example provides a method for preparing a high-gloss, fast-drying printing ink for packaging boxes, including the following steps:

[0028] S1. Preparation of composite resin;

[0029] 32 parts by weight of epoxy acrylate, 18 parts by weight of polyurethane acrylate and 12 parts by weight of castor oil-based polyurethane prepolymer were added to the reactor, the temperature was raised to 80°C, 0.1 parts by weight of dibutyltin dilaurate catalyst was added, and the mixture was stirred at 600 rpm for 2 hours to obtain the composite resin.

[0030] S2. Preparation of modified fillers;

[0031] 14 parts by weight of nano-silica, 5 parts by weight of polydimethylsiloxane and 0.4 parts by weight of silane coupling agent KH550 were added to a dispersion tank and sheared at 2000 rpm for 10 min to form a dispersion. 10% by weight of methyl methacrylate, 2% by weight of trimethylolpropane triacrylate, 0.5% by weight of azobisisobutyronitrile and 0.01% by weight of hydroquinone were added to the dispersion and ultrasonically dispersed at 200 W for 10 min to form an emulsion. The emulsion was heated to 60℃ and stirred at 200 rpm for 4 h. Sodium chloride (salting-out method) was added at 5% by weight of the emulsion to break the emulsion. The mixture was centrifuged and the supernatant was discarded to obtain the modified filler.

[0032] S3. Compound preparation;

[0033] The composite resin obtained from S1 was naturally cooled to 50°C and kept at that temperature. 4 parts by weight of N-vinylpyrrolidone were added, and the mixture was stirred at 200 rpm for 10 min. 5 parts by weight of premixed and preheated additives to 48°C and composite photoinitiator preheated to 45°C were added. The mixture was stirred at 600 rpm for 25 min, heating was stopped, and the mixture was naturally cooled to 32°C. 12 parts by weight of pigment were added, and the mixture was stirred at 300 rpm for 15 min to obtain the precursor.

[0034] The additives include UV-6603 (ultraviolet absorber), RH-9200 (defoamer), and BYK-333 (leveling agent) in a mass ratio of 1.2:0.2:0.2.

[0035] The composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 2:1:0.8:0.3.

[0036] S4. Final Mixing;

[0037] After the precursor is naturally cooled to 25°C, it is stirred at 500 rpm for 5 minutes. The modified filler prepared by S2 is added in three batches, with a 3-minute interval between each addition. The temperature is increased by 4°C after each addition of the modified filler. After all the filler is added, it is stirred at 500 rpm for 8 minutes to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0038] Example 2: This example provides a method for preparing a high-gloss, fast-drying printing ink for packaging boxes, including the following steps:

[0039] S1. Preparation of composite resin;

[0040] 40 parts by weight of epoxy acrylate, 28 parts by weight of polyurethane acrylate and 20 parts by weight of castor oil-based polyurethane prepolymer were added to the reactor, the temperature was raised to 90°C, 0.5 parts by weight of catalyst dibutyltin dilaurate were added, and the mixture was stirred at 800 rpm for 3 hours to obtain the composite resin.

[0041] S2. Preparation of modified fillers;

[0042] 16 parts by weight of nano-silica, 8 parts by weight of polydimethylsiloxane and 0.8 parts by weight of silane coupling agent KH550 were added to a dispersion tank and sheared at 3000 rpm for 15 min to form a dispersion. 20% by weight of methyl methacrylate, 5% by weight of trimethylolpropane triacrylate, 1.5% by weight of azobisisobutyronitrile and 0.03% by weight of hydroquinone were added to the dispersion and ultrasonically dispersed at 400 W for 20 min to form an emulsion. The emulsion was heated to 70℃ and stirred at 300 rpm for 6 h. 8% by weight of sodium chloride (salting-out method) was added to break the emulsion. The mixture was centrifuged and the supernatant was discarded to obtain the modified filler.

[0043] S3. Compound preparation;

[0044] The composite resin obtained from S1 was naturally cooled to 62°C and kept at that temperature. 8 parts by weight of N-vinylpyrrolidone were added, and the mixture was stirred at 300 rpm for 15 min. 9 parts by weight of premixed additives preheated to 56°C and composite photoinitiator preheated to 52°C were added. The mixture was stirred at 800 rpm for 35 min, heating was stopped, and the mixture was naturally cooled to 38°C. 15 parts by weight of pigment were added, and the mixture was stirred at 500 rpm for 20 min to obtain the precursor.

[0045] The additives include UV-6603 (ultraviolet absorber), RH-9200 (defoamer), and BYK-333 (leveling agent) in a mass ratio of 1.5:0.7:0.5.

[0046] The composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 5:3:1.5:0.7.

[0047] S4. Final Mixing;

[0048] After the precursor is naturally cooled to 30°C, it is stirred at 700 rpm for 10 minutes. The modified filler prepared by S2 is added in 4 batches, with an interval of 5 minutes between each addition. The temperature is increased by 6°C after each addition of the modified filler. After all the filler is added, it is stirred at 700 rpm for 12 minutes to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0049] Example 3: This example provides a method for preparing a high-gloss, fast-drying printing ink for packaging boxes, including the following steps:

[0050] S1. Preparation of composite resin;

[0051] 35 parts by weight of epoxy acrylate, 21 parts by weight of polyurethane acrylate and 17 parts by weight of castor oil-based polyurethane prepolymer were added to the reactor, the temperature was raised to 88°C, 0.4 parts by weight of dibutyltin dilaurate catalyst was added, and the mixture was stirred at 600 rpm for 3 hours to obtain the composite resin.

[0052] S2. Preparation of modified fillers;

[0053] 15.2 parts by weight of nano-silica, 6.7 parts by weight of polydimethylsiloxane and 0.5 parts by weight of silane coupling agent KH550 were added to a dispersion tank and sheared at 2000 rpm for 12 min to form a dispersion. 14% by weight of methyl methacrylate, 3% by weight of trimethylolpropane triacrylate, 1.1% by weight of azobisisobutyronitrile and 0.02% by weight of hydroquinone were added to the dispersion and ultrasonically dispersed at 200 W for 15 min to form an emulsion. The emulsion was heated to 66℃ and stirred at 240 rpm for 5 h. Sodium chloride (salting-out method) was added at 6% by weight of the emulsion to break the emulsion. The mixture was centrifuged and the supernatant was discarded to obtain the modified filler.

[0054] S3. Compound preparation;

[0055] The composite resin obtained from S1 was naturally cooled to 57°C and kept at that temperature. 7 parts by weight of N-vinylpyrrolidone were added, and the mixture was stirred at 270 rpm for 13 min. 8 parts by weight of premixed and preheated additives to 52°C and composite photoinitiator preheated to 48°C were added. The mixture was stirred at 720 rpm for 30 min, heating was stopped, and the mixture was naturally cooled to 35°C. 14 parts by weight of pigment were added, and the mixture was stirred at 450 rpm for 17 min to obtain the precursor.

[0056] The additives include UV-6603 (ultraviolet absorber), RH-9200 (defoamer), and BYK-333 (leveling agent) in a mass ratio of 1.3:0.5:0.3.

[0057] The composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 3:2:1:0.5.

[0058] S4. Final Mixing;

[0059] After the precursor is naturally cooled to 27°C, it is stirred at 640 rpm for 8 minutes. The modified filler prepared by S2 is added in 4 batches, with an interval of 5 minutes between each addition. The temperature is increased by 5°C after each addition of the modified filler. After all the filler is added, it is stirred at 640 rpm for 10 minutes to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0060] Example 4: This example provides a method for preparing a high-gloss, fast-drying printing ink for packaging boxes, including the following steps:

[0061] S1. Preparation of composite resin;

[0062] 38 parts by weight of epoxy acrylate, 24 parts by weight of polyurethane acrylate and 14 parts by weight of castor oil-based polyurethane prepolymer were added to the reactor, the temperature was raised to 84°C, 0.3 parts by weight of dibutyltin dilaurate catalyst was added, and the mixture was stirred at 740 rpm for 3 hours to obtain the composite resin.

[0063] S2. Preparation of modified fillers;

[0064] 14 parts by weight of nano-silica, 7 parts by weight of polydimethylsiloxane and 0.6 parts by weight of silane coupling agent KH550 were added to a dispersion tank and sheared at 3000 rpm for 12 min to form a dispersion. 18% by weight of methyl methacrylate, 4% by weight of trimethylolpropane triacrylate, 0.8% by weight of azobisisobutyronitrile and 0.03% by weight of hydroquinone were added to the dispersion and ultrasonically dispersed at 360 W for 17 min to form an emulsion. The emulsion was heated to 64 °C and stirred at 270 rpm for 5 h. Sodium chloride (salting-out method) was added at 5% by weight of the emulsion to break the emulsion. The mixture was centrifuged and the supernatant was discarded to obtain the modified filler.

[0065] S3. Compound preparation;

[0066] The composite resin obtained from S1 was naturally cooled to 60°C and kept at that temperature. 5 parts by weight of N-vinylpyrrolidone were added, and the mixture was stirred at 300 rpm for 15 min. 7 parts by weight of premixed and preheated additives to 50°C and composite photoinitiator preheated to 45-52°C were added. The mixture was stirred at 760 rpm for 30 min, heating was stopped, and the mixture was naturally cooled to 30°C. 12 parts by weight of pigment were added, and the mixture was stirred at 440 rpm for 18 min to obtain the precursor.

[0067] The additives include UV-6603 (ultraviolet absorber), RH-9200 (defoamer), and BYK-333 (leveling agent) in a mass ratio of 1.2:0.5:0.2.

[0068] The composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 3:2:1:0.7.

[0069] S4. Final Mixing;

[0070] After the precursor is naturally cooled to 30°C, it is stirred at 650 rpm for 8 minutes. The modified filler prepared by S2 is added in 3 batches, with an interval of 3 minutes between each addition. The temperature is increased by 4°C after each addition of the modified filler. After all the filler is added, it is stirred at 680 rpm for 12 minutes to obtain the high-gloss fast-drying printing ink for packaging boxes.

[0071] It should be noted that the pigments described in Examples 1-4 above include Clariant PV Fast Blue BG, Clariant Permanent Yellow PG, and Clariant BNP Red.

[0072] The epoxy acrylate is produced by Guangzhou Shanghe Chemical Technology Co., Ltd., CAS number 71281-65-7;

[0073] The polyurethane acrylate is produced by Jiangsu Pules Biotechnology Co., Ltd., and the product name is difunctional aliphatic polyurethane acrylate.

[0074] The preparation method of the castor oil-based polyurethane prepolymer refers to Zhou Bing. Structural Design and Performance Study of Dual-Cure Castor Oil-Based Polyurethane Prepolymer [D]. Fuzhou University, 2023. DOI:10.27022 / d.cnki.gfzhu.2023.002272. Specifically:

[0075] Castor oil and PTMEG were vacuum dehydrated at 120°C for 2 hours. 18 parts by weight of castor oil, 5 parts by weight of PTMEG, 16 parts by weight of IPDI, 5 parts by weight of catalyst (organic bismuth MB20), and 7 parts by weight of THFA were added sequentially to a 250 mL three-necked flask. The mixture was heated in an oil bath at 80°C for 3 hours. After cooling to 60°C, 7 parts by weight of HEMA were added and reacted for 3 hours to obtain castor oil-based polyurethane prepolymer.

[0076] Comparative Example 1: The difference between this comparative example and Example 4 is that in S1, the composite resin does not contain castor oil-based polyurethane prepolymer.

[0077] Comparative Example 2: The difference between this comparative example and Example 4 is that in S2, demulsification was not performed, and the emulsion was directly used as the modified filler.

[0078] Comparative Example 3: The difference between this comparative example and Example 4 is that the mass ratio of the ultraviolet absorber, defoamer and leveling agent in the additives is 0.5:1.8:0.2.

[0079] Comparative Example 4: The difference between this comparative example and Example 4 is that the composite resin does not contain castor oil-based polyurethane prepolymer; demulsification was not performed, and the emulsion was directly selected as the modified filler; the mass ratio of ultraviolet absorber, defoamer and leveling agent in the additives is 0.5:1.8:0.2.

[0080] Experimental Example 1: Figure 1 As shown in the final ink curve, the core functional group peak of the modified filler is completely integrated with the precursor peak, without peak splitting or abnormal shift, proving that the filler and precursor have good compatibility. The Si-O-Si stretching peak of the modified filler forms an ultra-wide and strong peak with the COC stretching peak of the precursor, and the peak shape is smooth without splitting, proving that the nano silica has not agglomerated (if agglomerated, there will be Si-O peak splitting or a sudden drop in peak height), and is completely integrated into the ink matrix.

[0081] The Si-CH3 stretching peak of the modified filler superimposed with the alkyl CH peak of the precursor to form a broad peak with a significant increase in peak intensity, proving that the organic phase of the modified filler is compatible with the alkyl structure of the resin and there is no phase separation.

[0082] In the final ink, the peaks of the pyrrolidone C=O, benzene ring, and ester group C=O of the precursor are still clearly visible, proving that the final mixing process did not destroy the precursor components.

[0083] like Figure 2 As shown, low-boiling-point small molecules volatilize in the 50-150℃ range, resulting in a weight loss of 2.04%.

[0084] The photoinitiator and additives decomposed at 150-300℃, resulting in a weight loss of 8.23%; the composite resin and modified filler decomposed at 300-450℃, resulting in a weight loss of 39.97%; the residual carbides oxidized and burned at 450-600℃, resulting in a weight loss of 11.05%; and at 600℃, the ink residue was 38.71%, proving that the ink prepared by this invention has better thermal stability.

[0085] Experimental Example 2: Gloss Detection;

[0086] Curing: Three commonly used packaging box substrates are selected, 300g / m³ 2 Coated paper, 0.1mm thick PET film, 0.02mm thick aluminum foil composite paper;

[0087] Lay the substrate flat on a glass table and secure the four corners with tape. Take 10g of the ink prepared in the embodiments and comparative examples of this invention and pour it onto one end of the substrate. Hold the brush and spread it evenly to the other end at a speed of 5cm / s (coating area 10cm×15cm). Immediately after coating, pick up the substrate (interval ≤10s). Place the coated substrate (coating side up) at the inlet of the UV curing machine (power density 100W / cm, lamp distance 18cm). The substrate passes through the UV lamp irradiation area with the conveyor belt. After being taken out from the outlet, place it in a dust-free tray. Place the cured substrate in a 25℃ room temperature environment and let it stand for 20 minutes without touching the surface of the ink layer. The conveyor belt speed is 4m / min, and curing is achieved within 3s.

[0088] Aging: A xenon lamp (filtering visible light and retaining the 300-400nm ultraviolet band, simulating the key wavelength in sunlight that causes gloss decay) was selected, with an irradiance of 0.51W / (m²). 2 •nm) (340nm band), temperature 60±2℃ (simulating high outdoor temperature environment in summer to accelerate the decay of gloss by light), relative humidity 90±5%, aging time 72h;

[0089] The ink gloss (GU) at 60° before and after aging was tested according to GB / T 13217.2-2024, and the results are shown in Table 1.

[0090] Experiment Example 3: Mechanical Property Testing;

[0091] The hardness of the ink was tested according to GB / T 6739-2022;

[0092] The elongation at break (%) of the ink in its bonded state with the substrate was measured according to GB / T 16777-2008, and the results are shown in Table 2.

[0093] Table 1:

[0094]

[0095] As shown in Table 1, the high-gloss, fast-drying printing ink for packaging boxes prepared by this invention can stably impart high initial gloss to the ink and is suitable for coating requirements of different packaging box substrates.

[0096] Examples 1-4, after undergoing accelerated aging in a simulated sunlight ultraviolet band and high temperature and humidity environment, showed only a slight decrease in gloss and a retention rate generally above 98.4%. This indicates that the specific proportion of additives in this invention can effectively resist the damage of ultraviolet light to the optical stability of the ink layer. At the same time, the synergistic effect of the composite resin and the modified filler reduces gloss decay.

[0097] Comparative Example 1, lacking castor oil-based polyurethane prepolymer in its composite resin, exhibited a significantly lower gloss retention rate on aluminum foil composite paper compared to the Example. Comparative Example 3, with its proportions of UV absorber, defoamer, and leveling agent deviating from the range set in this invention, saw its gloss retention rate plummet to approximately 95% after aging, highlighting the crucial role of additive formulation in the ink's anti-aging and gloss retention performance. Comparative Example 4, simultaneously lacking castor oil-based polyurethane prepolymer, failing to demulsify the modified filler, and having an inappropriate additive ratio, had the lowest initial gloss and gloss retention rates after aging among all tested samples. This further confirms that the synergistic effect of the composite resin formulation, modified filler treatment process, and additive formulation in this invention is the core guarantee for achieving high gloss and excellent anti-aging and gloss retention performance of the ink.

[0098] Table 2:

[0099]

[0100] As shown in Table 2, the hardness of the embodiments and comparative examples on three commonly used substrates is highly consistent, which meets the rigid requirements of the packaging box in logistics transportation (anti-friction and scratch) and end use (anti-daily touch damage). This shows that the present invention does not compromise on the hardness in order to take into account the flexibility.

[0101] While maintaining high hardness, it also maintains excellent elongation at break. This indicator directly corresponds to the core requirements of post-processing scenarios for packaging boxes (die-cutting and folding of paper boxes, thermoforming of plastic boxes, and edge curling of metal boxes), meaning that the ink layer must withstand continuous mechanical stress and deformation without breaking.

[0102] Comparative Examples 1-3, due to the absence of castor oil-based polyurethane prepolymer in the composite resin, the deviation of the proportion of additives (UV absorber, defoamer, leveling agent) from the range set by this invention, and the failure to demulsify, showed varying degrees of reduction in elongation at break compared to the examples.

[0103] Comparative Example 4 exhibits three major defects: lack of castor oil-based polyurethane prepolymer, failure to demulsify, and incorrect additive ratio. Its elongation at break is far lower than that of the Example. This indicates that the mechanical performance advantage of the present invention is not due to a single factor, but rather the result of the synergy of various processes. The absence of any step or deviation from any parameter will lead to varying degrees of reduction in flexibility.

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-gloss, fast-drying printing ink for packaging boxes, characterized in that, Includes the following steps: S1. Preparation of composite resin: Add 32-40 parts by weight of epoxy acrylate, 18-28 parts by weight of polyurethane acrylate and 12-20 parts by weight of castor oil-based polyurethane prepolymer to the reaction vessel, heat up, add the catalyst dibutyltin dilaurate, stir and react to obtain composite resin. The specific preparation method of the castor oil-based polyurethane prepolymer is as follows: castor oil and PTMEG are vacuum dehydrated at 120°C for 2 hours. 18 parts by weight of castor oil, 5 parts by weight of PTMEG, 16 parts by weight of IPDI, 5 parts by weight of catalyst and 7 parts by weight of THFA are added sequentially to a 250 mL three-necked flask. The mixture is heated in an oil bath at 80°C for 3 hours. After cooling to 60°C, 7 parts by weight of HEMA are added and reacted for 3 hours to obtain the castor oil-based polyurethane prepolymer. S2. Preparation of modified filler: 14-16 parts by weight of nano silica, 5-8 parts by weight of polydimethylsiloxane and 0.4-0.8 parts by weight of silane coupling agent are added to a dispersion tank and sheared at high speed to form a dispersion. 10-20% by weight of methyl methacrylate, 2-5% by weight of trimethylolpropane triacrylate, 0.5-1.5% by weight of azobisisobutyronitrile and 0.01-0.03% by weight of hydroquinone are added to the dispersion and ultrasonically dispersed to form an emulsion. The emulsion is heated and stirred, sodium chloride is added to break the emulsion, centrifuged, and the supernatant is discarded to obtain the modified filler. S3. Compounding: The composite resin obtained in S1 is naturally cooled and kept at a certain temperature. 4-8 parts by weight of N-vinylpyrrolidone are added and stirred. 5-9 parts by weight of premixed and preheated additives and preheated composite photoinitiator are added and stirred. Heating is stopped, and the mixture is allowed to cool naturally. Pigment is added and stirred to obtain the precursor. The additives include ultraviolet absorbers, defoamers, and leveling agents in a mass ratio of 1.2-1.5:0.2-0.7:0.2-0.

5. S4. Final mixing: After the precursor is cooled naturally, stir it and add the modified filler prepared in S2 in 3-4 batches. After each addition of the modified filler, raise the temperature. After all the filler has been added, continue stirring to obtain the high-gloss fast-drying printing ink for packaging boxes.

2. The method for preparing high-gloss, fast-drying printing ink for packaging boxes according to claim 1, characterized in that, S1 specifically involves adding 32-40 parts by weight of epoxy acrylate, 18-28 parts by weight of polyurethane acrylate, and 12-20 parts by weight of castor oil-based polyurethane prepolymer to a reactor, heating to 80-90℃, adding 0.1-0.5 parts by weight of dibutyltin dilaurate catalyst, and stirring at 600-800 rpm for 2-3 hours to obtain the composite resin.

3. The method for preparing high-gloss, fast-drying printing ink for packaging boxes according to claim 1, characterized in that, S2 is specifically as follows: 14-16 parts by weight of nano-silica, 5-8 parts by weight of polydimethylsiloxane, and 0.4-0.8 parts by weight of silane coupling agent KH550 are added to a dispersion tank and sheared at 2000-3000 rpm for 10-15 min to form a dispersion. 10-20% by weight of methyl methacrylate, 2-5% by weight of trimethylolpropane triacrylate, 0.5-1.5% by weight of azobisisobutyronitrile, and 0.01-0.03% by weight of hydroquinone are added to the dispersion and ultrasonically dispersed at 200-400W for 10-20 min to form an emulsion. The emulsion is heated to 60-70℃ and stirred at 200-300 rpm for 4-6 h. Sodium chloride (5-8% by weight of the emulsion) is added to break the emulsion. The mixture is centrifuged, and the supernatant is discarded to obtain the modified filler.

4. The method for preparing high-gloss, fast-drying printing ink for packaging boxes according to claim 1, characterized in that, S3 is specifically as follows: The composite resin obtained in S1 is naturally cooled to 50-62℃ and kept at that temperature. 4-8 parts by weight of N-vinylpyrrolidone are added, and the mixture is stirred at 200-300 rpm for 10-15 minutes. 5-9 parts by weight of premixed additives preheated to 48-56℃ and composite photoinitiators preheated to 45-52℃ are added. The mixture is stirred at 600-800 rpm for 25-35 minutes. Heating is stopped, and the mixture is naturally cooled to 32-38℃. 12-15 parts by weight of pigment are added, and the mixture is stirred at 300-500 rpm for 15-20 minutes to obtain the precursor.

5. The method for preparing high-gloss, fast-drying printing ink for packaging boxes according to claim 4, characterized in that, The composite photoinitiator is obtained by compounding 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, benzophenone, triethanolamine and triarylthionium salt in a mass ratio of 2-5:1-3:0.8-1.5:0.3-0.

7.

6. The method for preparing high-gloss, fast-drying printing ink for packaging boxes according to claim 1, characterized in that, S4 is specifically prepared as follows: After the precursor is naturally cooled to 25-30℃, it is stirred at 500-700rpm for 5-10min. The modified filler prepared by S2 is added in 3-4 batches, with an interval of 3-5min between each addition. After each addition of the modified filler, the temperature is increased by 4-6℃. After all the filler is added, it is stirred at 500-700rpm for 8-12min to obtain high-gloss fast-drying printing ink for packaging boxes.

7. A high-gloss, fast-drying printing ink for packaging boxes prepared by the preparation method according to any one of claims 1-6.

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