UV gloss oil for laser as well as preparation method and application of UV gloss oil

Abstract

The invention belongs to the technical field of UV gloss oil, and particularly relates to UV gloss oil for laser as well as a preparation method and application of the UV gloss oil. The UV gloss oil for laser comprises the following components in percentage by mass: 40%-50% of a polar monomer, 15%-30% of a diluting monomer, 5%-15% of blended resin, 8%-13% of a photoinitiator, 0.15%-0.3% of a thixotropic agent, 0.1%-0.2% of a wetting agent, 0.1%-0.3% of a flatting agent, 0.05%-0.1% of a defoaming agent, 0.05%-0.1% of an antioxidant and 0.3%-1% of an adhesion promoter. When the UV gloss oil is used, the process film covering step can be omitted, the production efficiency is improved, the production cost is reduced, the high-gloss effect equal to that of the film covering process is achieved, and meanwhile the laser powder can be endowed with high surface energy and high-gloss effects.

Description

Technical Field

[0001] This invention belongs to the field of UV varnish technology, specifically relating to a UV varnish for lasers, its preparation method, and its application. Background Technology

[0002] Laser UV varnish is a special functional coating specifically designed for the surface treatment of laser printing or laser packaging materials. It belongs to the category of ultraviolet (UV) curing inks / coatings. It is widely used in the packaging printing of high-end tobacco and alcohol products, cosmetics, gift boxes, labels, etc., to enhance the product's appearance and texture, and, combined with laser effects, achieve special visual anti-counterfeiting and decorative functions.

[0003] Most UV varnishes are made from esters synthesized from acrylic acid, epoxy, polyester, and polyurethane. Besides double bonds, their main functional groups are ester groups, which are less polar than hydroxyl and carboxyl groups. Therefore, their surface energy after curing is typically low, with a surface dyne value of only 36-40. Without the use of relatively highly polar photoinitiators such as alpha ketones and other highly polar additives, the surface dyne value after curing can be even lower. When made into laser powder, the surface tension of conventional UV monomers reaches 30-40. The surface tension of the monomers is not significantly different from the surface energy of the UV coating, resulting in slower wetting of the laser powder when added to UV decorative coatings. This necessitates the addition of more wetting agents to the decorative coating to reduce surface tension and achieve better wetting. Furthermore, after physical mixing, laser powder is larger and heavier than other powder materials such as matte powder and pigment powder, making it prone to settling and stratifying after prolonged storage.

[0004] After UV varnish is cured, the surface needs to be used for aluminum plating to achieve a laser effect. However, compared to water-based or oil-based coatings, the surface density of UV varnish after curing is denser, which is less favorable for aluminum plating adhesion. In addition, the low surface tension after curing means that even if sufficient corona treatment is performed to temporarily increase the surface tension to 46-52, although it can improve the adhesion to aluminum plating in the short term, the surface tension will decrease significantly after aging, and the adhesion to aluminum plating will also decrease significantly.

[0005] Laser UV varnishes need to achieve high gloss after curing. However, conventional UV varnishes struggle to achieve good leveling during application and also fail to achieve high gloss after curing. To address this issue, a release film is applied and laminated after the UV varnish is applied. The smooth surface of the film allows the cured UV coating to also achieve high gloss. This process not only wastes a significant amount of release film but also adds an extra lamination step, greatly reducing production efficiency. Furthermore, most UV resins have a higher molecular weight (Mw=750-3000) and viscosity than UV monomers (Mw=150-500). If the resin is modified with polar functional groups such as hydroxyl or isocyanate, the increased polarity also significantly increases the viscosity, resulting in much poorer leveling and flowability compared to polar monomers.

[0006] In response to the series of problems existing in the actual production of the aforementioned UV varnishes, in order to eliminate the coating step in the process, improve production efficiency, reduce production costs, and achieve the same high gloss effect as the coating process, there is an urgent need for a self-leveling UV varnish that can impart high surface energy, high gloss, and easy application to laser powder. Summary of the Invention

[0007] The purpose of this invention is to provide a UV varnish for lasers, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a UV varnish for lasers, comprising the following components by mass percentage: 40-50% polar monomer, 15-30% diluent monomer, 5-15% blending resin, 8-13% photoinitiator, 0.15-0.3% thixotropic agent, 0.1-0.2% wetting agent, 0.1-0.3% leveling agent, 0.05-0.1% defoamer, 0.05-0.1% antioxidant, and 0.3-1% adhesion promoter.

[0009] Preferably, the polar monomer includes trifunctional acrylate monomers and long-chain unsaturated fatty alcohols.

[0010] Preferably, the trifunctional acrylate monomer is pentaerythritol triacrylate (PET3A).

[0011] Preferably, the polar monomer comprises a trifunctional acrylate monomer and a long-chain unsaturated fatty alcohol in a mass ratio of (2-4):1.

[0012] The polar monomer selected in this invention is pentaerythritol triacrylate (Mw=298) as the main component of the UV varnish. This provides higher polarity and surface tension to the surface after UV curing, ensuring good adhesion to aluminum plating while saving energy consumption in corona treatment. Simultaneously, it ensures high fluidity, achieving a rapid mirror-like leveling effect. However, simply using the aforementioned polar monomer as the main component of the UV varnish cannot simultaneously achieve rapid self-leveling and a significant increase in surface energy. The inventors further improved the rapid self-leveling and surface energy of the UV varnish by adding long-chain unsaturated fatty alcohols, while also improving storage stability and resistance to yellowing.

[0013] Preferably, the long-chain unsaturated fatty alcohol includes at least one of 8-nonen-1-ol and 9-decen-1-ol.

[0014] The long-chain unsaturated fatty alcohols of this invention include at least one of 8-nonen-1-ol and 9-decen-1-ol, which can better help reduce the hardness and brittleness caused by the large amount of PET3A in the system and increase flexibility. The molecular weights of 8-nonen-1-ol and 9-decen-1-ol ensure the flexibility of the system of this invention, while reducing the occurrence of side reactions such as pinacol rearrangement and avoiding the release of large amounts of heat during photocuring.

[0015] Preferably, the blending resin is selected from at least one of polyester acrylate and aliphatic polyurethane acrylate.

[0016] Preferably, the molecular weight (Mw) of the blended resin is 4000-7200.

[0017] Preferably, the molecular weight (Mw) of the polyester acrylate is 4800-7200; the molecular weight (Mw) of the aliphatic polyurethane acrylate is 4000-6000.

[0018] Preferably, the molecular weight of polyester acrylate is Mw=6000; the molecular weight of aliphatic polyurethane acrylate is Mw=5000.

[0019] Preferably, the polyester acrylate is EBECRIL 885; the aliphatic polyurethane acrylate is EBECRIL 230.

[0020] Preferably, the mass ratio of EBECRIL 885 to EBECRIL 230 is in the range of 0-2:0-2.

[0021] More preferably, the mass ratio of EBECRRYL 885 to EBECRRYL 230 is 1:0, 1:1, 2:1, 1:2, or 0:1. More preferably, the mass ratio of EBECRRYL 885 to EBECRRYL 230 is 1:1.

[0022] This invention improves the film breakage phenomenon during the aluminum plating process by adding a blending resin, and at the same time avoids further crushing during the cutting and transportation process.

[0023] Preferably, the diluent monomer is selected from difunctional acrylate monomers.

[0024] Preferably, the difunctional acrylate monomer includes at least one of dipropylene glycol diacrylate (DPGDA) and tripropylene glycol diacrylate (TPGDA).

[0025] More preferably, the difunctional acrylate monomer comprises (1-2): 1 of dipropylene glycol diacrylate (DPGDA) and tripropylene glycol diacrylate (TPGDA).

[0026] The diluent monomer used in this invention is a difunctional acrylate monomer, which has a lower irritating odor and can improve the application performance of UV varnishes. In particular, the overall performance of the UV varnish is even better when it is blended with TPGDA and DPGDA in a specific ratio.

[0027] Preferably, the photoinitiator includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), methyl benzoylformate (MBF), 4-chlorobenzophenone (CBP), 4-phenylbenzophenone (PBZ), and a co-initiator.

[0028] Preferably, the co-initiator is an amine co-initiator.

[0029] Preferably, the amine co-initiator is selected from yellowing-resistant active amines, specifically Hengzhiguang A113.

[0030] Preferably, the photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, methyl benzoylformate, 4-chlorobenzophenone, 4-phenylbenzophenone, and an amine co-initiator in a mass ratio of (1-3):(1-3):(0.5-1.5):(0.5-1.5):(5-8).

[0031] The main considerations for selecting photoinitiators include: reaction rate, polarity, odor, oxygen barrier properties, yellowing resistance, solubility, adhesion, and dyne value of the cured surface. In terms of dosage, several factors are added to the considerations of photocuring surface drying, aging yellowing, and the dyne value of the aged surface. The system of this invention, using a specific ratio of photoinitiators, can improve both the reaction rate and curing yield, while also exhibiting good yellowing resistance, thus achieving a comprehensive advantage in terms of both cost and performance.

[0032] Preferably, the adhesion promoter is a silane coupling agent.

[0033] Preferably, the adhesion promoter is 3-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) or 3-isocyanate-propyltrimethoxysilane.

[0034] This invention promotes adhesion to the aluminum-plated layer by adding an appropriate amount of KH560 adhesion promoter, which reacts with moisture in the environment. Analysis suggests that after conventional UV curing, a small amount of photoinitiator remains, which reacts further during storage, causing a decrease in surface energy over time and consequently reducing the adhesion between the aluminum-plated layer and the UV layer. This invention cannot use silane coupling agents 550 or 570, as they lack active functional groups to participate in the hygrothermal curing process during aging and cannot improve aging performance.

[0035] Preferably, the thixotropic agent is selected from at least one of Evonik AEROSIL 200 ZNJ and Evonik AEROSIL E972.

[0036] Because the coating is thin and mostly composed of monomers, the molecular gaps are relatively large at the microscopic level, making it more susceptible to oxygen inhibition. Therefore, a large amount of photoinitiators and co-initiators are needed to achieve surface drying. The viscosity of UV coatings fluctuates greatly due to the influence of ambient temperature. When the ambient temperature is high, the viscosity is too low, which can easily lead to sagging. Therefore, a certain amount of easily dispersible silica is added to increase the thixotropy of the coating. However, adding too much will seriously affect the leveling and flowability of the coating.

[0037] Preferably, the antioxidant is butylated hydroxytoluene (BHT).

[0038] Because the light curing lamp used is a mercury lamp, there is a side reaction at a wavelength of 240nm where oxygen is converted into ozone, which has a stronger oxidizing effect. In addition, the large amount of heat generated during the light curing process will form two side reactions that cause yellowing: photo-oxidation and thermal oxidation. This problem is usually solved by adding an appropriate amount of antioxidant. The mechanism of action of antioxidant is to compete for free radicals. It not only competes for oxygen free radicals, but also for active free radicals after the photoinitiator is cracked. This will reduce the efficiency of the photoinitiator and lead to insufficient curing. However, if the amount added is too small, it will not be able to play a role in preventing oxidative yellowing. Therefore, it is necessary to strictly control the amount of antioxidant added.

[0039] Preferably, the wetting agent is selected from at least one of polyether-modified siloxane and modified acrylate.

[0040] Preferably, the wetting agent is selected from BYK-3565 and BYK-379 from BYK Chemical.

[0041] Preferably, the wetting agent comprises polyether-modified siloxane and modified acrylate in a mass ratio of 2:1 to 1:1.

[0042] Due to the relatively high monomer content, the self-leveling coating exhibits a larger shrinkage rate compared to the resin. Adding an appropriate amount of fumed silica can effectively reduce the coating's shrinkage rate. Experiments have shown that a mixture of polyether-modified siloxane and modified acrylate wetting agents is more effective in improving the wetting properties of UV varnishes than using either alone, thus enhancing adhesion to PET chemical films. Polyether-modified siloxane has better wetting properties than modified acrylate, while modified acrylate offers relatively higher flexibility, thus improving toughness. Therefore, the recommended ratio is 2:1 to 1:1, with 1:1 being the preferred ratio.

[0043] Preferably, the leveling agent is selected from polyacrylates.

[0044] Preferably, the leveling agent is Shanghai Ziyi Chemical ZY-1358 or BYK Chemical BYK-361N.

[0045] Preferably, the defoamer is a polyacrylate defoamer.

[0046] Preferably, the defoamer is Evonik TEGO AIREX 923 or BYK LP D 25665.

[0047] Considering surface polarity and surface energy, polyacrylates are selected for leveling agents and defoamers, rather than silicones or polyolefins, which would reduce surface energy. The amount added is adjusted accordingly based on the amount of resin.

[0048] This invention provides a method for preparing the aforementioned UV varnish for lasers, comprising the following steps: (1) Weigh the polar monomer and diluent monomer and pour them into a stainless steel reactor with circulating water. Start low-speed stirring to obtain a mixed solution; (2) Pour the defoamer and wetting agent into the mixed solution, and then pour in the thixotropic agent until all the powder is wetted by the solution and does not float on the surface of the solution; (3) Pour in the photoinitiator and antioxidant, start the water circulation and heat to 35-50℃ until completely dissolved; (4) Pour in the remaining components until the fluid is turbulent and uniform; (5) Turn off the stirring and water circulation heating, take a sample and test it; (6) After the inspection is qualified, start the water circulation cooling until the liquid temperature is below 35℃, install a filter screen at the end of the discharge pipe for filtration and put it into the barrel.

[0049] This invention provides a method for preparing the aforementioned UV varnish for lasers: (1) Weigh out the required thixotropic agent and pour it into the circulating water stainless steel kettle; (2) Pour the polar monomer, defoamer, and wetting agent into the stainless steel reactor of circulating water, and start slow stirring until all the thixotropic agent is below the liquid surface; (3) Pour the remaining raw materials into the mixture and start the water circulation to heat to 35-50℃; (4) Turn off the water circulation heating and stirring, and take a sample for testing; (5) After the inspection is qualified, start the water circulation to cool down, install the filter screen at the outlet of the discharge pipe and discharge the material into the barrel.

[0050] The third aspect of the present invention provides the application of the aforementioned UV varnish for laser printing in laser printing or laser packaging materials.

[0051] The UV varnish of this invention is suitable for preparation using two processes. The first process offers high controllability and significantly avoids problems such as poor shear dispersion of gaseous silicon and incomplete dissolution caused by the settling of solid photoinitiators. The second process reduces the number of steps and greatly improves preparation efficiency. Products prepared using either process exhibit excellent performance. Therefore, the UV varnish can be prepared using a specific method to meet different needs.

[0052] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: (1) The UV varnish for lasers provided by this invention can effectively eliminate the coating step required in traditional processes in practical applications, significantly simplifying the production process. Through optimized formulation design, this varnish has excellent leveling and rapid curing performance. Under ultraviolet light irradiation, it can quickly crosslink and cure to form a dense and smooth surface coating, achieving a high gloss effect comparable to or even better than traditional coating processes; (2) The UV varnish provided by this invention has excellent storage stability and aging resistance, and is not prone to delamination or deterioration during long-term storage. While giving the laser powder good surface wettability and adhesion, it can also significantly improve its surface energy and optical performance, so that the final product presents a brighter, more uniform and longer-lasting metallic luster. The UV varnish of this invention not only meets the dual requirements of aesthetics and functionality in high-end packaging, anti-counterfeiting labels, decorative materials and other fields, but also further expands its application prospects in fine printing and special decoration fields; (3) All four application paths of the UV varnish of the present invention are qualified and superior to commercially available products. Due to its high surface dyne value and polarity, the UV varnish of the present invention is suitable for use as a base or intermediate layer coating. Since the laser powder is dispersed in the subsequent decorative coating, it can also be applied to the outer layer. If it is not used with UV laser powder, it can also be used for molding coatings, i.e., application path one, which does not require further cutting. It has a wide range of uses and broad market prospects and application value. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the preparation process one; Figure 2 This is a schematic diagram of the preparation process two; Figure 3 This is a process flow diagram for downstream applications of laser varnish. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] The present invention provides a UV varnish for lasers, comprising the following components by mass percentage, as detailed in Table 1.

[0056]

[0057] Please see Figure 1 The present invention provides a method for preparing the aforementioned UV varnish for lasers, comprising the following steps: (1) Weigh the polar monomer and diluent monomer and pour them into a stainless steel reactor with circulating water. Start low-speed stirring to obtain a mixed solution; (2) Pour the defoamer and wetting agent into the mixed solution, and then pour in the thixotropic agent until all the powder is wetted by the solution and does not float on the surface of the solution; (3) Pour in the photoinitiator and antioxidant, start the water circulation and heat to 35-50℃ until completely dissolved; (4) Pour in the remaining components until the fluid is turbulent and uniform; (5) Turn off the stirring and water circulation heating, take a sample and test it; (6) After the inspection is qualified, start the water circulation cooling until the liquid temperature is below 35℃, install a filter screen at the end of the discharge pipe for filtration and put it into the barrel.

[0058] Please see Figure 2 The present invention provides a method for preparing the aforementioned UV varnish for lasers: (1) Weigh out the required thixotropic agent and pour it into the circulating water stainless steel kettle; (2) Pour the polar monomer, defoamer, and wetting agent into the stainless steel reactor of circulating water, and start slow stirring until all the thixotropic agent is below the liquid surface; (3) Pour the remaining raw materials into the mixture and start the water circulation to heat to 35-50℃; (4) Turn off the water circulation heating and stirring, and take a sample for testing; (5) After the inspection is qualified, start the water circulation to cool down, install the filter screen at the outlet of the discharge pipe and discharge the material into the barrel.

[0059] Examples 1-5 A UV varnish for lasers comprises the following components by mass percentage, as detailed in Table 2.

[0060]

[0061]

[0062] The above-mentioned UV varnish for lasers and its preparation method include the following steps: (1) Weigh all the monomers and pour them into the circulating water stainless steel kettle. Start the low-speed stirring at a speed of 200 r / min. (2) Weigh the required defoamer and wetting agent and pour them into the solution of step (1). Slowly pour the thixotropic agent powder into the solution until all the powder is wetted by the solution and does not float on the surface of the solution. Start high-speed stirring at a speed of 2500 r / min for 50 minutes to obtain a mixed solution. (3) Reduce the rotation speed to about 400 r / min, pour in the required photoinitiator and antioxidant, start the water circulation and heat to 40°C, increase the rotation speed to 900 r / min until completely dissolved; (4) Reduce the rotation speed to about 400 r / min, pour in the required amount of resin, leveling agent, adhesion promoter and amine co-initiator, increase the rotation speed to 900 r / min, stir for about 40 minutes until the fluid is turbulent and uniform; (5) Turn off the stirring and water circulation heating, take a sample and test it; (6) After the inspection is qualified, start the water circulation cooling until the liquid temperature is below 35℃, install a filter screen at the end of the discharge pipe for filtration and put it into the barrel.

[0063] Comparative Examples 1-7 The difference between Comparative Examples 1-7 and Example 3 is the different formulations. See Table 3 for details.

[0064]

[0065]

[0066] Performance testing: I. Intermediate product testing: (1) Evaluation of the dispersion effect of thixotropic agent and defoamer: Take 300mL of the mixed solution after high-speed shearing in step (2), place it in a colorless transparent glass cup, perform ultrasonic rapid foam breaking, irradiate with a flashlight, and observe whether there are obvious large particles suspended; then scrape with a 60μ wire rod and observe whether there are obvious particles and whether there are obvious shrinkage pores. II. Inspection before finished product discharge: (1) Appearance: The solution is a uniform yellow slightly turbid liquid with no obvious large particles suspended; (2) Viscosity: Take about 300mL of UV varnish, cool it down and keep it at 30±1℃, put it in a rotor and test it with a rotational viscometer. Repeat the test three times and take the average value. The viscosity should be 20-50mpas; (3) Coating inspection: Use a 20μ coating rod, take an appropriate amount of varnish and place it on a corona-treated PET film for coating. There should be no obvious particles, bubbles or pinholes; (4) Odor detection: There should be no obvious unpleasant odor at room temperature; (5) Leveling test: Take an appropriate amount of varnish and use a coating leveling instrument LPQ-1 to test it. The time required for the leveling grade to be 10 should be less than 5s. III. Supplementary inspection before shipment of finished products: (1) Accelerated aging test: Take 250mL of varnish and place it in a black light-proof bottle. Place it in a 70℃ oven for three days. After aging, the appearance color and viscosity should not change significantly compared with before aging. (2) Environmental protection test: It meets the tobacco packaging test standard "YC / T-207-2014 Determination of solvent residue in tobacco paper by headspace gas chromatography-mass spectrometry". Toluene, formaldehyde and other substances do not exceed the standard. After testing, all the above tests of the laser UV varnish prepared in Examples 1-5 are qualified. The laser UV varnishes of Comparative Example 1 and Comparative Example 2 failed the inspection before the finished product was released. In Comparative Example 1, only PET3A was used and no 8-nonen-1-ol was added. The leveling properties of the construction were poor. Before curing, it was impossible to achieve a mirror level state. At a faster speed, the anilox roller texture was still present after curing, which affected the surface smoothness and gloss. In Comparative Example 2, when the ratio of resin one to resin two was 5%, the proportion of long-chain alcohol was too high, resulting in a significant decrease in viscosity. When the ambient temperature exceeded 30°C, sagging easily occurred during the coating process. All tests for the laser UV varnishes in Comparative Examples 3-7 were passed. The application performance of the laser UV varnishes in Examples 1-5 and Comparative Examples 3-7 was then tested. IV. Application Performance Testing: Application tests were conducted on the UV varnishes used in Examples 1-5 and Comparative Examples 3-7, as well as a conventional UV varnish (commercially available UV laser varnish 1103TF). Application paths are shown below. Figure 3 Conventional UV varnish is applied according to application path three. Key parameters for the application process are shown in Table 4.

[0067]

[0068] Detection method: (1) Surface energy measurement: Draw a line on the surface of the UV-cured coating with a dyne pen. If it does not shrink in 3-5 seconds, gradually increase or decrease the dyne value for testing. When the dyne pen test is qualified, the next dyne pen test will shrink. This dyne pen test represents the surface tension measurement value. Perform three parallel tests. (2) Surface energy test after accelerated photoaging: Under a 3kV mercury lamp and a vehicle speed of 20m / min, an A4-sized film was subjected to 20 machine curing cycles and the surface energy was measured according to the surface energy test method. (3) Corrosion resistance: Dilute concentrated hydrochloric acid in water to 5%, use a dropper to take a small amount of dilute acid solution and drop it onto the cured surface, let it stand for 15-30 seconds, then wipe it clean and observe whether there is any change in appearance. If there is no obvious change, it is qualified; if other phenomena such as fogging occur, it is unqualified. (4) Gloss: Use a colorimeter to test the Lab values ​​of 3-5 points on the cured surface, and calculate the average value of the L values; (5) Aluminum plating adhesion 1: Press the aluminum plating surface or UV layer tightly with polar bear tape. If the aluminum plating layer and UV layer do not separate, it is qualified; otherwise, it is unqualified. (6) Aluminum plating fastness 2: Apply water-based adhesive to the cardboard to form a composite UV and aluminum plating coating, peel off the PET release film, and then press the UV and aluminum plating coating tightly with polar bear tape. If the aluminum plating layer and the UV layer do not separate, it is qualified; otherwise, it is unqualified. (7) Adhesion to PET chemical film: Press the UV layer tightly with polar bear tape. If the PET and UV layers do not separate, it is qualified; otherwise, it is unqualified. (8) Firmness to PET release film: Press the aluminized surface or UV layer tightly with polar bear tape. If the UV layer can be easily separated from the PET release film, it is considered qualified. If there is any residue, it is unqualified. (9) Storage stability test: According to GB / T33327-2016 Evaluation of storage stability of UV curable coatings, the above laser powder was placed in a conventional UV coating and placed in a 50℃ oven for 7 consecutive days for continuous testing. The settling of the laser powder was observed every day and the number of days of settling was recorded. (10) Accelerated yellowing test: Under a 3kV mercury lamp and a vehicle speed of 20m / min, apply an appropriate amount of varnish to white cardstock and cure it 20 times. If the color does not darken significantly and yellows, it is qualified; otherwise, it is unqualified.

[0069] The construction results of Example 3 are shown in Table 5.

[0070]

[0071] It should be noted that in the table above, " / " indicates that no test was performed, fastness test 1 is the test method for composite coatings, and fastness test 2 is the test method for transfer coatings.

[0072] Testing showed that the surface energy of the UV varnishes prepared in Examples 1-5 was greater than or equal to 50, and the surface energy after accelerated photoaging was greater than or equal to 46. The surface energy and gloss were superior to conventional products. All four application paths were qualified. The aluminum plating fastness was high, the corrosion resistance was qualified, the bonding strength with PET was high, and the storage stability and yellowing resistance were good.

[0073] Testing revealed that in Comparative Example 3, the types of monomers 4 and 5 were replaced. HDDA exhibited significantly worse antioxidant inhibition during curing compared to DPGDA, resulting in a poorer degree of curing and surface drying. The surface dyne value and viscosity also deteriorated. Under construction path 3, the aluminum plating adhesion was unqualified, and the surface drying was insufficient. All four construction paths resulted in some adhesion between the coils after winding.

[0074] In Comparative Example 4, the amount of monomer 4 was significantly increased, and when the ambient temperature during construction was above approximately 35°C, sagging occurred during coating.

[0075] Replacing monomer one in Comparative Example 5 will cause the aluminum plating adhesion in construction processes one, two, and three to fail the test in both processes one and two.

[0076] In Comparative Example 6, replacing monomer two narrows the construction environment temperature range, making it unsuitable for practical applications.

[0077] In Comparative Example 7, replacing EBECRRYL 885 with EBECRRYL 884 and EBECRRYL 230 with EBECRRYL 4512 resulted in incomplete filling during molding in the first construction path, leading to incomplete patterns. Filling with low molecular weight resin could improve the situation to some extent, but it was difficult to completely solve the problem.

[0078] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A UV varnish for laser engraving, characterized in that, It includes the following components by weight percentage: 40-50% polar monomer, 15-30% diluent monomer, 5-15% blended resin, 8-13% photoinitiator, 0.15-0.3% thixotropic agent, 0.1-0.2% wetting agent, 0.1-0.3% leveling agent, 0.05-0.1% defoamer, 0.05-0.1% antioxidant, and 0.3-1% adhesion promoter.

2. The UV varnish for laser engraving according to claim 1, characterized in that, The polar monomers are selected from trifunctional acrylate monomers and long-chain unsaturated fatty alcohols.

3. The UV varnish for laser engraving according to claim 2, characterized in that, The polar monomers comprise trifunctional acrylate monomers and long-chain unsaturated fatty alcohols in a mass ratio of (2-4):

1.

4. The UV varnish for laser engraving according to claim 3, characterized in that, The blending resin is selected from at least one of polyester acrylate and aliphatic polyurethane acrylate; the diluting monomer is selected from difunctional acrylate monomer.

5. The UV varnish for laser engraving according to claim 4, characterized in that, The molecular weight (Mw) of the blended resin is 4000-7200.

6. The UV varnish for laser engraving according to claim 5, characterized in that, The long-chain unsaturated fatty alcohol is selected from at least one of 8-nonen-1-ol and 9-decen-1-ol; the difunctional acrylate monomer includes at least one of dipropylene glycol diacrylate and tripropylene glycol diacrylate.

7. The UV varnish for laser engraving according to claim 1, characterized in that, The photoinitiator includes 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, methyl benzoylformate, 4-chlorobenzophenone, 4-phenylbenzophenone, and a co-initiator.

8. A method for preparing a UV varnish for lasers according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Weigh the polar monomer and diluent monomer and pour them into a stainless steel circulating water reactor. Stir to obtain a mixed solution; (2) Pour the defoamer and wetting agent into the mixed solution, and then pour in the thixotropic agent until all the powder is wetted by the solution and does not float on the surface of the solution; (3) Continue to add the photoinitiator and antioxidant, and heat until completely dissolved; (4) Pour in the remaining components until the fluid is turbulent and uniform; (5) Turn off the stirring and water circulation heating, take a sample and test it; (6) After passing the inspection, start the water circulation cooling, install a filter screen at the end of the discharge pipe for filtration and pack into a barrel.

9. A method for preparing a UV varnish for lasers according to any one of claims 1-7, characterized in that: (1) Weigh out the thixotropic agent and pour it into the stainless steel reactor containing circulating water; (2) Pour the polar monomer, defoamer, and wetting agent into the stainless steel reactor of circulating water and stir until all the thixotropic agent is below the liquid surface to obtain a mixture; (3) Pour all remaining raw materials into the mixture and start water circulation heating; (4) Turn off the water circulation heating and stirring, and take a sample for testing; (5) After the inspection is qualified, start the water circulation to cool down, install the filter screen at the outlet of the discharge pipe and discharge the material into the barrel.

10. The use of a UV varnish for laser printing according to any one of claims 1-7 in laser printing or laser packaging materials.

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