A UV varnish with high adhesion for plastic substrates and its preparation method

Abstract

This invention discloses a high-adhesion UV varnish for plastic substrates and its preparation method, relating to the field of UV varnishes. The UV varnish is prepared from 6-10 wt% monofunctional UV monomers, 4-6 wt% trifunctional UV monomers, 15-20 wt% trifunctional flexible acrylic resin, 3-15 wt% active amines, 8-12 wt% photoinitiator, 0.1-0.5 wt% polyethylene wax, 1-1.5 wt% leveling agent, 0.1-0.3 wt% defoamer, 0.1-0.3 wt% polymerization inhibitor, and the balance being a hexafunctional modified acrylic resin. After photocatalytic curing, the UV varnish exhibits high adhesion to plastic substrates, resistance to yellowing, abrasion resistance, and resistance to soapy water. Furthermore, the UV varnish cures quickly; for printing with a varnish coating thickness of less than 3 μm, the curing energy is 40-70 mJ / cm². 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach over 85m / min, with good flexibility.

Description

Technical Field

[0001] This application relates to the field of UV varnishes, and in particular to a high-adhesion UV varnish for plastic substrates and a method for preparing the same. Background Technology

[0002] UV varnishes, as a highly efficient coating material, are widely used in toothpaste tube packaging printing, cosmetic tube packaging printing, pharmaceutical tube packaging printing, and other fields. They form a dense coating through a rapid curing reaction triggered by ultraviolet light irradiation, offering advantages such as high production efficiency and low volatile organic compound (VOC) emissions. However, with the increasingly stringent performance requirements of downstream applications, existing UV varnishes still face numerous technical bottlenecks.

[0003] For the curing of traditional UV varnishes, two or more mercury lamps with a power of 16KW-18KW are usually used to achieve one-time curing, with a minimum curing energy of 90mj / cm. 2 However, for printing on plastic substrates, excessively high energy can easily cause the plastic substrate to shrink and deform. Therefore, excessively high energy should not be used for curing varnishes on plastic substrates. Currently, traditional UV varnishes have a curing energy not exceeding 70 mJ / cm². 2 When cured in a single step under ideal conditions, the plastic substrate is less prone to shrinkage. However, the following problems exist: when the printing press speed exceeds 80 m / min, the varnish coating often suffers from insufficient curing efficiency, insufficient adhesion, poor resistance to yellowing, or poor resistance to soaping. Therefore, there is an urgent need to develop a new UV varnish formulation that can cure at a curing energy not exceeding 70 mJ / cm². 2 Under certain conditions, one-time curing is achieved, and the adhesion, yellowing resistance, and soap wash resistance of the UV varnish to the plastic substrate are ensured, even at printing speeds exceeding 80m / min. Summary of the Invention

[0004] To improve the curing energy of traditional UV varnishes, which does not exceed 70mJ / cm², 2 In high-speed printing scenarios (machine speed exceeding 80m / min) where one-time curing is performed under certain conditions, problems such as insufficient adhesion, poor resistance to yellowing, and poor resistance to soap water are prone to occur. This application provides a high-adhesion UV varnish for plastic substrates and its preparation method.

[0005] Firstly, the UV varnish provided in this application adopts the following technical solution:

[0006] A UV varnish is prepared from 6-10 wt% monofunctional UV monomer, 4-6 wt% trifunctional UV monomer, 15-20 wt% trifunctional flexible acrylic resin, 3-15 wt% active amine, 8-12 wt% photoinitiator, 0.1-0.5 wt% polyethylene wax, 1-1.5 wt% leveling agent, 0.1-0.3 wt% defoamer, 0.1-0.3 wt% polymerization inhibitor, and the balance being hexafunctional modified acrylic resin.

[0007] In this application, monofunctional UV monomers can improve the viscosity and fluidity of the UV varnish system; trifunctional UV monomers can accelerate the curing reaction speed of the UV varnish, increase the crosslinking density, and enhance the coating's abrasion resistance, yellowing resistance, and soap wash resistance; 3-functional flexible acrylic resins can impart flexibility to the coating, preventing cracking caused by substrate deformation; the high functionality of 6-functional modified acrylic resins can further improve the adhesion between the varnish coating and the substrate, and impart more beneficial abrasion resistance, yellowing resistance, and soap wash resistance to the coating; active amines mainly act as auxiliary photoinitiators to initiate curing and improve curing efficiency; polyethylene wax is used to improve the coating's abrasion resistance and lubricity; leveling agents can improve the coating's leveling properties, increase gloss, and reduce surface defects; defoamers are used to eliminate foam and prevent defects such as pinholes and pits from appearing in the coating; the main function of polymerization inhibitors is to prevent the UV varnish from undergoing self-polymerization during storage, thereby extending the product's shelf life and improving stability.

[0008] A UV varnish is prepared by combining monofunctional UV monomers, trifunctional UV monomers, trifunctional flexible acrylic resins, hexafunctional modified acrylic resins, active amines, photoinitiators, polyethylene wax, leveling agents, defoamers, and polymerization inhibitors in specific proportions. The resulting UV varnish, after photocatalytic curing, exhibits high adhesion to plastic substrates, resistance to yellowing, abrasion resistance, and resistance to soapy water. Furthermore, the UV varnish cures rapidly; for printing with a varnish coating thickness of less than 3 μm, the curing energy is 40-70 mJ / cm². 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach more than 85m / min. The resulting coating has high adhesion to the plastic substrate, is resistant to yellowing, resistant to soapy water, and has good flexibility.

[0009] In some specific embodiments, the monofunctional UV monomer is at least one selected from cyclotrimethylolpropane methyl acetal acrylate, hydroxyethyl acrylate, lauryl acrylate, isobornyl acrylate, and tetrahydrofuran acrylate.

[0010] In some specific embodiments, the trifunctional UV monomer is at least one of trimethylolpropane triacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, and ethoxylated trimethylolpropane triacrylate.

[0011] In some preferred embodiments, the monofunctional UV monomer is a composition of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate, wherein the weight ratio of cyclotrimethylolpropane methyl acetal acrylate to tetrahydrofuran acrylate is (7-8):(2-3).

[0012] In this application, the preferred monofunctional UV monomers are cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate in a weight ratio of (7-8):(2-3). This composition is beneficial for maintaining leveling properties while further improving the curing rate of the UV varnish. For printing with a varnish coating thickness of less than 3 μm, the curing energy is 60-65 mJ / cm. 2 Under suitable conditions, it can achieve one-time curing, and the printing speed can reach 90m / min. At the same time, the UV varnish has a low irritating odor and features high adhesion to plastic substrates, resistance to yellowing, abrasion resistance, and resistance to soapy water.

[0013] In some preferred embodiments, the trifunctional UV monomer is a composition of trimethylolpropane triacrylate and propoxyglycerol triacrylate, wherein the weight ratio of trimethylolpropane triacrylate to propoxyglycerol triacrylate is (3-4):1.

[0014] In this application, when the trifunctional UV monomer is selected from a composition of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate in a weight ratio of (7-8):(2-3), and the trifunctional UV monomer is selected from a composition of trimethylolpropane triacrylate and propoxyglycerol triacrylate in a weight ratio of (3-4):1, for printing with a varnish coating thickness of 3μm < varnish thickness ≤ 5μm, the curing energy is 68-70mj / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 85m / min. At the same time, the UV varnish has a low irritating odor and has the characteristics of high adhesion to plastic substrates, resistance to yellowing, wear resistance, soap water resistance, and is not prone to stress cracking.

[0015] In some preferred embodiments, the active amine accounts for 10-15 wt%.

[0016] In some preferred embodiments, the active amine is a composition of triethanolamine, alkyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone, wherein the weight ratio of triethanolamine, alkyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone is (1-2):(5-6):(2-4).

[0017] In this application, the amount of active amine is further preferably 10-15 wt%, and the weight ratio of triethanolamine, alkyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone is preferably (1-2):(5-6):(2-4). This composition is beneficial for promoting deep curing, and for printing with a varnish coating thickness of 3 μm < varnish coating thickness ≤ 5 μm, the curing energy is 60-65 mJ / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 90m / min. At the same time, the UV varnish has excellent adhesion to plastic substrates and is characterized by low odor, resistance to yellowing, wear resistance, resistance to soap water, and resistance to stress cracking.

[0018] In some specific embodiments, the photoinitiator is at least one of photoinitiator TPO, photoinitiator 819, and photoinitiator 184.

[0019] In some specific embodiments, the polymerization inhibitor is at least one of p-hydroxyanisole, 701 polymerization inhibitor, and N-nitroso-N-phenylhydroxylamine aluminum.

[0020] Secondly, the method for preparing a UV varnish provided in this application adopts the following technical solution:

[0021] A method for preparing a UV varnish includes the following steps:

[0022] Under light-protected conditions, monofunctional and trifunctional UV monomers are added to a reactor, along with a polymerization inhibitor. The mixture is stirred, dispersed, and heated to 65-70°C. Photoinitiator is then added and dissolved until the mixture is transparent and free of particulate matter. The mixture is then filtered to obtain a semi-finished photoinitiator product.

[0023] Under light-protected conditions, hexafunctional modified acrylic resin and trifunctional flexible acrylic resin were added sequentially to another reaction vessel, stirred and dispersed, and heated to 40-45℃. Defoamer, leveling agent and polyethylene wax were then added, and the mixture was stirred and dispersed for 30-40 minutes to obtain a resin mixture.

[0024] Under light-protected conditions, the photoinitiator semi-finished product is added to the resin mixture, and then active amine is added. The mixture is stirred and mixed evenly to obtain UV varnish.

[0025] In summary, this application includes at least the following beneficial technical effects:

[0026] (1) This application prepares a UV varnish by combining monofunctional UV monomers, trifunctional UV monomers, trifunctional flexible acrylic resins, hexafunctional modified acrylic resins, active amines, photoinitiators, polyethylene wax, leveling agents, defoamers, and polymerization inhibitors in specific proportions. The obtained UV varnish, after photocatalytic curing, has the characteristics of high adhesion to plastic substrates, resistance to yellowing, abrasion resistance, and resistance to soapy water. At the same time, the UV varnish cures quickly. For printing with a varnish coating thickness of less than 3 μm, the curing energy is 40-70 mJ / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach more than 85m / min. The resulting coating has high adhesion to the plastic substrate, is resistant to yellowing, resistant to soapy water, and has good flexibility.

[0027] (2) In this application, when the trifunctional UV monomer is selected from a composition of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate in a weight ratio of (7-8):(2-3), and the trifunctional UV monomer is selected from a composition of trimethylolpropane triacrylate and propoxyglycerol triacrylate in a weight ratio of (3-4):1, for printing with a varnish coating thickness of 3μm < varnish coating thickness ≤ 5μm, the curing energy is 68-70mj / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 85m / min. At the same time, the UV varnish has a low irritating odor and has the characteristics of high adhesion to plastic substrates, resistance to yellowing, wear resistance, soap water resistance, and is not prone to stress cracking.

[0028] (3) In this application, the amount of active amine is further preferably 10-15 wt%, and the weight ratio of triethanolamine, alkyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone is preferably (1-2):(5-6):(2-4). This composition is beneficial for promoting deep curing, and for printing with a varnish coating thickness of 3 μm < varnish coating thickness ≤ 5 μm, the curing energy is 60-65 mJ / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 90m / min. At the same time, the UV varnish has excellent adhesion to plastic substrates and is characterized by low odor, resistance to yellowing, wear resistance, resistance to soap water, and resistance to stress cracking. Attached Figure Description

[0029] Figure 1 This is a flowchart of the UV varnish preparation method of this application. Detailed Implementation

[0030] The following combines specific experiments and Figure 1 Further explanation of this application is provided.

[0031] Example

[0032]

Example 1

[0033] A UV varnish is prepared from 6 wt% monofunctional UV monomer, 6 wt% trifunctional UV monomer, 20 wt% trifunctional flexible acrylic resin, 3 wt% active amine, 12 wt% photoinitiator, 0.1 wt% polyethylene wax, 1.5 wt% leveling agent, 0.1 wt% defoamer, 0.1 wt% polymerization inhibitor and 51.2 wt% hexafunctional modified acrylic resin.

[0034] In this embodiment, the monofunctional UV monomer is cyclotrimethylolpropane methyl acetal acrylate.

[0035] The trifunctional UV monomer uses trimethylolpropane triacrylate;

[0036] The 3-functional flexible acrylic resin is Baojun Chemical's 3-functional modified polyester acrylate 6640.

[0037] The active amine used is methyl 4-dimethylaminobenzoate;

[0038] The photoinitiator used is TPO;

[0039] The polyethylene wax used is Luwax AF-30, a spherical high-density polyethylene micro powder wax.

[0040] The leveling agent used is BYK3510 leveling agent;

[0041] The defoamer used is BYK-088 defoamer;

[0042] The polymerization inhibitor used is p-hydroxyanisole;

[0043] The 6-functional modified acrylic resin uses Dinghao's 6-functional polyester acrylate UV resin DH-DT019.

[0044] Additionally, refer to Figure 1 The preparation method of UV varnish in this embodiment includes the following steps:

[0045] S1. Under light-protected conditions, add monofunctional UV monomers and trifunctional UV monomers to a reactor, add polymerization inhibitors, stir and disperse, and heat to 65°C. Continue to add photoinitiator to dissolve until transparent and free of particles, and filter to obtain photoinitiator semi-finished product.

[0046] S2. Under light-protected conditions, add the 6-functional modified acrylic resin and the 3-functional flexible acrylic resin to another reaction vessel in sequence, stir and disperse, and heat to 40°C. Continue to add defoamer, leveling agent and polyethylene wax, stir and disperse for 30 minutes to obtain resin mixture.

[0047] S3. Under light-protected conditions, add the photoinitiator semi-finished product to the resin mixture, then continue to add the active amine, stir and mix evenly to obtain UV varnish.

[0048]

Example 2

[0049] A UV varnish is prepared from 8.3 wt% monofunctional UV monomer, 5 wt% trifunctional UV monomer, 17 wt% trifunctional flexible acrylic resin, 13 wt% active amine, 10 wt% photoinitiator, 0.2 wt% polyethylene wax, 1.2 wt% leveling agent, 0.1 wt% defoamer, 0.2 wt% polymerization inhibitor and 45 wt% hexafunctional modified acrylic resin.

[0050] In this embodiment, the monofunctional UV monomer is a composition of cyclotrimethylolpropane methyl acetal acrylate and hydroxyethyl acrylate, with a weight ratio of cyclotrimethylolpropane methyl acetal acrylate to hydroxyethyl acrylate of 7.5:2.5.

[0051] The trifunctional UV monomer uses trimethylolpropane triacrylate;

[0052] The 3-functional flexible acrylic resin is Baojun Chemical's 3-functional modified polyester acrylate 6640.

[0053] The active amine used is methyl 4-dimethylaminobenzoate;

[0054] The photoinitiator used is TPO;

[0055] The polyethylene wax used is Luwax AF-30, a spherical high-density polyethylene micro powder wax.

[0056] The leveling agent used is BYK3510 leveling agent;

[0057] The defoamer used is BYK-088 defoamer;

[0058] The polymerization inhibitor used is p-hydroxyanisole;

[0059] The 6-functional modified acrylic resin uses Dinghao's 6-functional polyester acrylate UV resin DH-DT019.

[0060] Additionally, refer to Figure 1 The preparation method of UV varnish in this embodiment includes the following steps:

[0061] S1. Under light-protected conditions, add monofunctional UV monomers and trifunctional UV monomers to a reactor, add polymerization inhibitors, stir and disperse, and heat to 70°C. Continue to add photoinitiator to dissolve until transparent and free of particles, and filter to obtain photoinitiator semi-finished product.

[0062] S2. Under light-protected conditions, add the 6-functional modified acrylic resin and the 3-functional flexible acrylic resin to another reaction vessel in sequence, stir and disperse, and heat to 45°C. Continue to add defoamer, leveling agent and polyethylene wax, stir and disperse for 40 min to obtain resin mixture.

[0063] S3. Under light-protected conditions, add the photoinitiator semi-finished product to the resin mixture, then continue to add the active amine, stir and mix evenly to obtain UV varnish.

[0064]

Example 3

[0065] A UV varnish is prepared from 10 wt% monofunctional UV monomer, 4 wt% trifunctional UV monomer, 15 wt% trifunctional flexible acrylic resin, 15 wt% active amine, 8 wt% photoinitiator, 0.5 wt% polyethylene wax, 1 wt% leveling agent, 0.1 wt% defoamer, 0.3 wt% polymerization inhibitor and 46.1 wt% hexafunctional modified acrylic resin.

[0066] In this embodiment, the monofunctional UV monomer is a composition of cyclotrimethylolpropane methyl acetal acrylate and hydroxyethyl acrylate, with a weight ratio of cyclotrimethylolpropane methyl acetal acrylate to hydroxyethyl acrylate of 7.5:2.5.

[0067] The trifunctional UV monomer uses trimethylolpropane triacrylate;

[0068] The 3-functional flexible acrylic resin is Baojun Chemical's 3-functional modified polyester acrylate 6640.

[0069] The active amine used is ethyl 4-dimethylaminobenzoate;

[0070] The photoinitiator used is photoinitiator 819;

[0071] The polyethylene wax used is Luwax AF-30, a spherical high-density polyethylene micro powder wax.

[0072] The leveling agent used is BYK3510 leveling agent;

[0073] The defoamer used is BYK-088 defoamer;

[0074] The polymerization inhibitor used is p-hydroxyanisole;

[0075] The 6-functional modified acrylic resin uses Dinghao's 6-functional polyester acrylate UV resin DH-DT019.

[0076] Additionally, refer to Figure 1 The preparation method of UV varnish in this embodiment includes the following steps:

[0077] S1. Under light-protected conditions, add monofunctional UV monomers and trifunctional UV monomers to a reactor, add polymerization inhibitors, stir and disperse, and heat to 70°C. Continue to add photoinitiator to dissolve until transparent and free of particles, and filter to obtain photoinitiator semi-finished product.

[0078] S2. Under light-protected conditions, add the 6-functional modified acrylic resin and the 3-functional flexible acrylic resin to another reaction vessel in sequence, stir and disperse, and heat to 45°C. Continue to add defoamer, leveling agent and polyethylene wax, stir and disperse for 40 min to obtain resin mixture.

[0079] S3. Under light-protected conditions, add the photoinitiator semi-finished product to the resin mixture, then continue to add the active amine, stir and mix evenly to obtain UV varnish.

[0080]

Example 4

[0081] A UV varnish differs from [Example 2] in that the monofunctional UV monomer is selected differently. In this example, the monofunctional UV monomer is a composition of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate, with a weight ratio of 7.5:2.5.

[0082]

Example 5

[0083] A UV varnish differs from [Example 4] in that the trifunctional UV monomer is selected differently. In this example, the trifunctional UV monomer is a composition of trimethylolpropane triacrylate and propoxyglycerol triacrylate, with a weight ratio of 4:1.

[0084]

Example 6

[0085] A UV varnish differs from [Example 5] in that the trifunctional UV monomer is selected differently. In this example, the trifunctional UV monomer is a composition of trimethylolpropane triacrylate and propoxyglycerol triacrylate, with a weight ratio of 1:4.

[0086]

Example 7

[0087] A UV varnish differs from [Example 5] in that the active amine is selected differently. In this example, the active amine is a composition of triethanolamine, methyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone, with a weight ratio of 1.5:5.5:3.

[0088]

Example 8

[0089] A UV varnish differs from [Example 5] in that the active amine is selected differently. In this example, the active amine is a composition of triethanolamine, methyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone, with a weight ratio of 1:2:1.

[0090]

Example 9

[0091] A UV varnish, differing from [Example 7] in that: the amount of active amine is 8 wt%, and the amount of hexafunctional modified acrylic resin is 50 wt%.

[0092] Comparative Example

[0093] Comparative Example 1

[0094] A UV varnish differs from [Example 2] in that the proportions of the raw materials are different. In this comparative example, the UV varnish is prepared from 15 wt% monofunctional UV monomer, 10 wt% trifunctional UV monomer, 17 wt% trifunctional flexible acrylic resin, 13 wt% active amine, 10 wt% photoinitiator, 0.2 wt% polyethylene wax, 1.2 wt% leveling agent, 0.1 wt% defoamer, 0.2 wt% polymerization inhibitor, and the balance being 33.3 wt% hexafunctional modified acrylic resin.

[0095] Performance testing

[0096] 1. Printing speed: Using PE substrate as the substrate, a 7KW mercury lamp was used for one-time curing during the printing process. The maximum printing speed at which different UV varnishes achieved a complete, clear, and non-adhesive coating was recorded. When testing the printing speed of different UV varnishes, only the type or coating thickness of the UV varnish was changed, and the catalytic curing parameters remained unchanged.

[0097] 2. Adhesion: Ten samples of each type of UV varnish printed in the performance test (1) were randomly selected and the adhesion was tested by cross-cutting method in GB / T 13217.7-2023 "Ink Adhesion Test Method".

[0098] 3. Yellowing resistance: Five samples of each type of material printed with different UV varnishes were randomly selected from the performance test (1). The yellowing resistance test was carried out in accordance with GB / T 23983-2009. The exposure time was 168h. After the test, the color difference value was measured with a colorimeter and expressed as ΔE.

[0099] 4. Abrasion resistance: Five samples of different UV varnishes were randomly selected from the performance test (1) and abrasion resistance was tested according to GB / T 1768-2006 "Determination of abrasion resistance of paints and varnishes by rotating rubber wheel". The coating was recorded as worn through after the rubber wheel rotated 80 times.

[0100] 5. Soap water resistance: Prepare soap water with a mass concentration of 1%, randomly select 10 sample materials printed with different UV varnishes in performance test (1), put them into soap water with a mass concentration of 1%, soak for 1 hour, and observe whether the sample materials blister or fall off.

[0101] 6. Flexibility: Five samples of each type of UV varnish printed in the performance test (1) were randomly selected. They were then placed in an environment of 60°C for 30 minutes, cooled to room temperature, and then placed in an environment of -5°C for 30 minutes. After that, they were taken out and restored to room temperature. The above steps were repeated 10 times. The coating was then observed to see if there was any cracking. If there was no cracking, it means that the coating can relieve stress through deformation, which indirectly reflects that the coating has good flexibility.

[0102] Table 1

[0103]

[0104] Table 2

[0105]

[0106]

[0107] Table 3

[0108]

[0109] The difference between Comparative Example 1 and Example 2 lies in the different proportions of the raw materials. The proportions of the raw materials in Comparative Example 1 are not within the scope of this application. Based on the test results recorded in Tables 1-3, it can be seen that the printing speed and yellowing resistance of the UV varnish in Comparative Example 1 decreased. Therefore, the raw material proportions claimed in this application are preferred for UV varnish.

[0110] The difference between Example 4 and Example 2 lies in the selection of the monofunctional UV monomer. In Example 4, the monofunctional UV monomer is a composition in which the weight ratio of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate is in the range of (7-8):(2-3). In Example 2, the monofunctional UV monomer is cyclotrimethylolpropane methyl acetal acrylate. Based on the test results recorded in Tables 1-3, it can be seen that the preferred monofunctional UV monomer is a composition in which the weight ratio of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate is (7-8):(2-3). This composition is beneficial for further improving the curing rate of the UV varnish while maintaining leveling properties. For printing with a varnish coating thickness of less than 3 μm, the curing energy is 60-65 mJ / cm². 2 Under suitable conditions, it can achieve one-time curing, and the printing speed can reach 90m / min. Meanwhile, the UV varnish has the characteristics of high adhesion to plastic substrates, resistance to yellowing, abrasion resistance, and resistance to soapy water.

[0111] The difference between Examples 4-6 lies in the selection of trifunctional UV monomers. In Example 4, the trifunctional UV monomer is trimethylolpropane triacrylate; in Example 5, the trifunctional UV monomer is a composition in which the weight ratio of trimethylolpropane triacrylate and propoxyglycerol triacrylate is in the range of (3-4):1; and in Example 6, the trifunctional UV monomer is a composition in which the weight ratio of trimethylolpropane triacrylate and propoxyglycerol triacrylate is 1:4. Based on the test results recorded in Tables 1-3, it can be seen that when the trifunctional UV monomer is a composition in which the weight ratio of cyclotrimethylolpropane methyl acetal acrylate and tetrahydrofuran acrylate is in the range of (7-8):(2-3), and the trifunctional UV monomer is a composition in which the weight ratio of trimethylolpropane triacrylate and propoxyglycerol triacrylate is in the range of (3-4):1, for printing with a varnish coating thickness of less than 3 μm, the curing energy is 50-55 mJ / cm². 2 Under certain conditions, one-time curing can be achieved, with a printing speed of up to 95 m / min. For printing with a varnish coating thickness of 3 μm < varnish coating thickness ≤ 5 μm, the curing energy is 68-70 mJ / cm. 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 85m / min. At the same time, UV varnish has the characteristics of high adhesion to plastic substrate, yellowing resistance, wear resistance, and soap water resistance. Moreover, for varnish coatings with a thickness of more than 3μm, stress cracking is not likely to occur.

[0112] Examples 5 and 7-9, along with the results recorded in Tables 1-3, show that: the amount of active amine is preferably 10-15 wt%, and the weight ratio of triethanolamine, alkyl 4-dimethylaminobenzoate, and 4,4'-diethylaminobenzophenone is preferably in the range of (1-2):(5-6):(2-4). This promotes deep curing, and for printing with a varnish coating thickness of less than 3 μm, the curing energy is 40-45 mJ / cm. 2 Under these conditions, one-time curing can be achieved, with printing speeds up to 105 m / min. For printing with a varnish coating thickness of 3 μm < varnish coating thickness ≤ 5 μm, the curing energy is 60-65 mJ / cm². 2 Under certain conditions, it can achieve one-time curing, and the printing speed can reach 90m / min. At the same time, UV varnish has the characteristics of high adhesion to plastic substrates, resistance to yellowing, wear resistance, and resistance to soap water. Moreover, for varnish coatings with a thickness of more than 3μm, stress cracking is not likely to occur.

[0113] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A UV varnish characterized by: The UV oil is prepared from 6-10wt% single UV monomer, 4-6wt% three UV monomer, 15-20wt% three soft acrylic resin, 10-15wt% active amine, 8-12wt% photoinitiator, 0.1-0.5wt% polyethylene wax, 1-1.5wt% leveling agent, 0.1-0.3wt% defoamer, 0.1-0.3wt% polymerization inhibitor and the balance of 6 modified acrylic resin; The single UV monomer is a combination of cyclotrimethylopropane formal acrylate and tetrahydrofurfuryl acrylate, and the weight ratio of cyclotrimethylopropane formal acrylate to tetrahydrofurfuryl acrylate is (7-8):(2-3); The three UV monomer is a combination of trimethylolpropane triacrylate and propylene glyceryl triacrylate, and the weight ratio of trimethylolpropane triacrylate to propylene glyceryl triacrylate is (3-4):1; The active amine is a combination of triethanolamine, 4-dimethylamino benzoic acid alkyl ester and 4,4'-diethylaminobenzophenone, and the weight ratio of triethanolamine, 4-dimethylamino benzoic acid alkyl ester and 4,4'-diethylaminobenzophenone is (1-2):(5-6):(2-4).

2. The UV varnish according to claim 1, characterized in that: The photoinitiator is at least one of photoinitiator TPO, photoinitiator 819 and photoinitiator 184.

3. The UV varnish according to claim 1, wherein: The polymerization inhibitor is at least one of p-hydroxyanisole, 701 polymerization inhibitor and N-nitroso-N-phenylhydroxylamine aluminum.

4. A process for the preparation of a UV varnish according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The single UV monomer and the three UV monomer are added to a reaction kettle under light shielding conditions, the polymerization inhibitor is added, stirring and dispersion are carried out, and the temperature is raised to 65-70℃; the photoinitiator is continuously added to dissolve to be transparent and free of particles, and the photoinitiator semi-finished product is obtained by filtration; the 6 modified acrylic resin and the three soft acrylic resin are sequentially added to another reaction container under light shielding conditions, stirring and dispersion are carried out, and the temperature is raised to 40-45℃; the defoamer, the leveling agent and the polyethylene wax are continuously added, stirring and dispersion are carried out for 30-40min, and the resin mixture is obtained; the photoinitiator semi-finished product is added to the resin mixture under light shielding conditions, and then the active amine is continuously added, stirring and mixing are uniformly carried out, and the UV oil is obtained.

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