A masking coating for shrinking the surface of a film printed coating and a method for its preparation

Abstract

The present application belongs to the technical field of polyester shrink film, and particularly relates to a kind of masking coating for the surface of shrink film printing coating and a preparation method thereof.PET heat shrink film obtained by setting an ink printing layer on one side of the shrink film first, and then setting an aluminum plating layer on the surface of the ink printing layer, has low light transmittance, high haze, and dull pattern color.Based on the above problems, the present application provides a kind of masking coating for the surface of shrink film printing coating, the cured coating of which has high transparency, does not affect the light transmittance and haze of the shrink film, and the pattern of the ink printing layer can be better presented, the pattern color is closer to the original color of the printed pattern, and has better decorative effect.The transparent coating formed after curing of the masking coating is arranged between the ink printing layer and the aluminum plating layer, which on the one hand forms a shielding and protective effect on the ink printing layer, and on the other hand enhances the adhesion between the aluminum plating layer on the surface of the shrink film and the shrink film.

Description

Technical Field

[0001] This invention belongs to the field of polyester shrink film technology, specifically relating to a masking coating for the surface of a shrink film printing coating and its preparation method. Background Technology

[0002] PET heat shrink film is a new type of heat shrink packaging material. It is easy to recycle, non-toxic, odorless, has good mechanical properties, and is particularly environmentally friendly. In developed countries, it has become an ideal alternative to polyvinyl chloride (PVC) heat shrink film. To enable PET shrink film packaging materials to have decorative and barrier protective functions, a printing ink layer and an aluminum plating layer need to be applied to the surface of the shrink film.

[0003] Currently, PET heat-shrinkable composite films with decorative and barrier functions are usually made by laminating an aluminized base film (with an aluminized layer on the surface of the shrink film) and a printed top film (with an ink printing layer on the surface of the shrink film) with a composite adhesive. This process is relatively complex and costly.

[0004] Alternatively, a process can be used where an ink printing layer is placed on one side of the shrink film and an aluminum plating layer is placed on the other side. However, the ink printing layer exposed on the surface of the shrink film obtained by this method is not scratch-resistant, and a varnish protective layer needs to be placed on the surface of the ink printing layer. Due to the special material of the varnish layer, this solution will significantly increase the probability of warping or poor adhesion at the bonding joint of the shrink film.

[0005] Alternatively, an ink printing layer can be first applied to one side of the shrink film, followed by an aluminum plating layer. For example, Chinese Utility Model Patent CN206697136U discloses a hot-stamping shrink sleeve label. While this method solves the problem of the ink printing layer being easily scratched, the resulting heat shrink film has low light transmittance, high haze, and dull colors, making it prone to distortion. This is likely because the ink printing layer has a certain thickness, resulting in microscopic pits and unevenness. This surface unevenness prevents the aluminum plating layer from forming a uniform and continuous reflective surface. When light shines on such an aluminum plating layer, the reflection direction becomes chaotic, reducing the proportion of specular reflection and thus lowering the overall gloss of the heat shrink film, making the overall pattern color dull and distorted. In addition, aluminum atoms in the vacuum metallization process can easily penetrate into the pigments in the ink printing layer. The penetration and filling effect affects the light absorption and scattering characteristics of the pigment particles in the ink printing layer, which can easily cause changes and distortions in the color of the printed pattern. Summary of the Invention

[0006] The existing technology has the following problems: PET heat shrink film obtained by first setting an ink printing layer on one side of the shrink film and then setting an aluminum plating layer on the surface of the ink printing layer has dull colors, is prone to distortion, and has poor decorative effect. To address these problems, this invention provides a masking coating for the surface of the printed coating of shrink film. By weight, it is obtained by seed emulsion polymerization of 30-35 parts acrylate soft monomer, 60-70 parts hard monomer, 1-3 parts acrylate crosslinking monomer, 2-4 parts acrylic monomer, 3-8 parts silane coupling agent containing double bonds, 2-3 parts emulsifier, 0.5-1 part initiator, 0.5-0.8 parts neutralizer, 400-450 parts water, 0.2-1 part reducing agent, 0.5-1 part wetting agent, 0.05-0.5 parts defoamer, and 10-15 parts cosolvent.

[0007] Specifically, the acrylate soft monomer includes one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate.

[0008] Specifically, the hard monomer includes one or more of methyl methacrylate, styrene, ethyl methacrylate, isopropyl methacrylate, and butyl methacrylate.

[0009] Specifically, the acrylate crosslinking monomer includes one or more of TPGDA, TMPTA, EGDMA, HDDA, and PETA.

[0010] Specifically, the acrylic monomer includes one or more of acrylic acid, methacrylic acid, and maleic acid.

[0011] Specifically, the silane coupling agent containing double bonds includes one or more of KH-570, TMPSM, A-171, and A-151, with KH570 being preferred.

[0012] Specifically, the emulsifier includes one or more of sodium alkyl polyoxyethylene ether sulfate, sodium alkyl sulfonate, sodium alkyl sulfate, alkyl ether sulfate, alkyl aryl sulfonate, alkyl ethoxy phosphate, alkyl polyoxyethylene ether, and allyl polyoxyethylene ether sulfate. It is more preferable to use SR-10 emulsifier and DES-30 emulsifier in a weight ratio of 1:2 as the emulsifier in the reaction system.

[0013] Specifically, the initiator is a persulfate, preferably ammonium persulfate or potassium persulfate.

[0014] Specifically, the neutralizing agent includes one or more of triethylamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, and ammonia, with dimethylethanolamine being preferred.

[0015] Specifically, the co-solvent includes one or more of ethanol, isopropanol, n-propanol, and ethylene glycol methyl ether, with isopropanol being preferred.

[0016] Specifically, the reducing agent is a sodium salt of an organic sulfinic acid derivative, including one or more of disodium hydroxyacetate sulfinate, sodium benzene sulfinate, and sodium methyl sulfinate.

[0017] Specifically, the wetting agent is an acetylenic diol wetting agent or an organosilicon wetting agent, preferably an acetylenic diol wetting agent, such as Superwet-320.

[0018] Specifically, the defoamer is a mineral oil-based defoamer or an organosilicon-based defoamer, preferably a mineral oil-based defoamer, such as BASF A10.

[0019] Specifically, the preparation method of the masking coating for the surface of a shrink film printing coating includes the following steps:

[0020] S1. Mix 2 / 5 of the formula amount of deionized water and 4 / 5 of the formula amount of emulsifier evenly, then add the total amount of acrylate soft monomer, hard monomer, acrylic monomer, silane coupling agent containing double bonds, acrylate crosslinking monomer and 1 / 3-1 / 2 of the formula amount of neutralizer, stir evenly to obtain a mixture, and take 5-10% of the total mass of the mixture as seed emulsion.

[0021] S2. Dissolve the initiator of the specified amount in 1 / 20 of the specified amount in deionized water to obtain an initiator solution;

[0022] Add 1 / 2 of the total mass of initiator solution to the remaining mixture, mix well to obtain a pre-emulsion;

[0023] Add the amount of reducing agent in the formula to 1 / 20 of the amount of deionized water to obtain the reducing agent solution;

[0024] S3. At room temperature, add the remaining amount of deionized water and emulsifier to the reaction vessel and mix well. Then raise the temperature of the reaction system to 78-80℃, add the seed emulsion, and then add all the remaining initiator solution. Stir the reaction at a constant temperature for 0.5-1h, then start to continuously add the pre-emulsion, and complete the addition within 3.5-4h. Stir the reaction at a constant temperature for 1-1.5h, and the reaction ends.

[0025] S4. After the reaction in step (3) is completed, the reaction temperature is lowered to 60-65℃, and the reducing agent solution is continuously added dropwise within 1 hour. Then, the reaction is stirred at a constant temperature for 0.5-1 hour. After that, the temperature of the reaction system is lowered to room temperature. Then, the remaining amount of neutralizing agent, wetting agent, and defoamer are added to the reaction system in sequence. The mixture is stirred thoroughly and dispersed evenly. Finally, the amount of cosolvent is added and stirred evenly. The mixture is then filtered through a 200-240 mesh screen to obtain a masking coating with an average particle size range of 50-150nm.

[0026] The present invention has the following beneficial effects:

[0027] (1) The present invention uses seed emulsion polymerization to obtain a masking coating for the surface of the printed coating of shrink film. The transparent coating formed after the coating is cured is placed between the ink printing layer and the aluminum plating layer. On the one hand, it provides a masking protection effect for the ink printing layer, and on the other hand, it enhances the adhesion between the aluminum plating layer and the shrink film on the surface of the shrink film.

[0028] (2) The masking coating obtained by the present invention has high transparency and will not affect the light transmittance and haze of the shrink film. The pattern of the ink printing layer can be better presented and the pattern color is closer to the original color of the printed pattern, which has a better decorative effect.

[0029] (3) By selecting the type of co-solvent, the present invention enables the obtained masking coating to dry quickly at a low temperature of about 70°C, which does not easily affect the shrinkage rate of the shrink film. The shrinkage rate of the obtained shrink composite film is less than 0.1% in both the horizontal and vertical directions.

[0030] (4) The masking coating obtained by the present invention contains silane coupling agent modified acrylate, which effectively overcomes the inherent defects of hot stickiness and cold brittleness of acrylate coatings.

[0031] (5) The masking coating can dry quickly at a lower temperature and is not easy to stick together when rolled up. It has high cohesive strength, thus ensuring the integrity, adhesion, surface quality and hydrophobicity of the masking coating, and further ensuring the gloss and adhesion of the aluminum-plated surface.

[0032] (6) The water-based masking coating obtained by the present invention has good interfacial compatibility with the ink printing layer. This is because the masking coating obtained by the present invention contains preferred co-solvent components. The co-solvent is more volatile during the coating process, which is more conducive to forming a uniform and dense coating film, reducing the surface tension of the masking coating, and enhancing the wettability and contact between the masking coating and the ink printing layer, thereby helping to improve the interfacial compatibility between the two.

[0033] On the other hand, the latex particle molecular structure of the masking coating obtained by the present invention contains a silane coupling agent modified segment. The silane coupling agent is introduced into the latex particle molecular structure through a double bond at one end, and chemically bonds and physically adsorbs with the polar functional groups in the ink printing layer through the siloxane chain segment at the other end, forming certain chemical bonds and hydrogen bonds. This results in a strong chemical bonding anchoring effect or physical force anchoring effect between the masking coating and the ink printing layer, thereby improving the interfacial compatibility between the masking coating and the ink printing layer. In addition, the water-based masking coating does not corrode the ink printing layer, effectively masking and protecting the ink printing layer while also having high light transmittance and low haze. Detailed implementation method:

[0034] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0035] The silane coupling agent containing double bonds in the following embodiments of the present invention can be one or more of KH-570, TMPSM, A-171, and A-151, with KH570 being preferred.

[0036] In the following embodiments of the present invention, the emulsifier may be one or more of sodium alkyl polyoxyethylene ether sulfate, sodium alkyl sulfonate, sodium alkyl sulfate, alkyl ether sulfate, alkyl aryl sulfonate, alkyl ethoxy phosphate, alkyl polyoxyethylene ether, and allyl polyoxyethylene ether sulfate. It is more preferable to use SR-10 emulsifier and DES-30 emulsifier in a weight ratio of 1:2 as the emulsifier for the reaction system.

[0037] The initiator in the following embodiments of the present invention can be a persulfate, preferably ammonium persulfate or potassium persulfate.

[0038] The neutralizing agent in the following embodiments of the present invention may be one or more of triethylamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, and ammonia, with dimethylethanolamine being preferred.

[0039] The co-solvent in the following embodiments of the present invention may be one or more of ethanol, isopropanol, n-propanol, and ethylene glycol methyl ether, with isopropanol being preferred.

[0040] The wetting agent in the following embodiments of the present invention may be an acetylenic diol wetting agent or an organosilicon wetting agent, preferably an acetylenic diol wetting agent, such as Superwet-320.

[0041] The defoamer in the following embodiments of the present invention can be a mineral oil defoamer or an organosilicon defoamer, preferably a mineral oil defoamer, such as BASF A10.

[0042] The masking coatings in the following embodiments of the present invention are all prepared according to the following steps:

[0043] S1. Mix 2 / 5 of the formula amount of deionized water and 4 / 5 of the formula amount of emulsifier evenly, then add the full amount of the formula amount of acrylate soft monomer, hard monomer, acrylic monomer, silane coupling agent containing double bond, acrylate crosslinking monomer and 1 / 3 of the formula amount of neutralizer, stir evenly to obtain a mixture, and take 5% of the total mass of the mixture as seed emulsion.

[0044] S2. Dissolve the initiator of the specified amount in 1 / 20 of the specified amount in deionized water to obtain an initiator solution;

[0045] Add 1 / 2 of the total mass of initiator solution to the remaining mixture, mix well to obtain a pre-emulsion;

[0046] Add the amount of reducing agent in the formula to 1 / 20 of the amount of deionized water to obtain the reducing agent solution;

[0047] S3. At room temperature, add the remaining amount of deionized water and emulsifier to the reaction vessel and mix well. Then raise the temperature of the reaction system to 80°C, add the seed emulsion, and then add all the remaining initiator solution. Stir the reaction at a constant temperature for 0.5 hours, then start to add the pre-emulsion dropwise continuously, and complete the dropwise addition within 3.5 hours. Stir the reaction at a constant temperature for 1 hour, and the reaction ends.

[0048] S4. After the reaction in step (3) is completed, the reaction temperature is lowered to 60°C, and the reducing agent solution is continuously added dropwise within 1 hour. Then, the reaction is stirred at a constant temperature of 65°C for 0.5 hours. After that, the temperature of the reaction system is lowered to room temperature. Then, the remaining amount of neutralizing agent, wetting agent, and defoamer are added to the reaction system in sequence, stirred thoroughly and dispersed evenly. Finally, the amount of cosolvent is added, stirred evenly, and filtered through a 200-mesh filter to obtain the final product.

[0049] Example 1

[0050] A masking coating for use on the surface of a shrink film printing coating has the following components by weight:

[0051] 35 parts of isooctyl acrylate;

[0052] 65 parts of methyl methacrylate;

[0053] 3 servings of TPGDA;

[0054] 4 parts methacrylic acid;

[0055] KH-570 3 copies;

[0056] 3 parts emulsifier;

[0057] 0.5 parts potassium persulfate;

[0058] 0.8 parts of dimethylethanolamine;

[0059] 400 parts of deionized water;

[0060] 0.1 parts of reducing agent FF6M;

[0061] 0.5 parts of wetting agent Superwet-320;

[0062] BASF A-10 defoamer, 0.5 parts;

[0063] 12 parts isopropanol;

[0064] The emulsifier is a mixture of emulsifier SR-10 and emulsifier DES-30 in a weight ratio of 1:2.

[0065] Example 2

[0066] A masking coating for use on the surface of a shrink film printing coating has the following components by weight:

[0067] 32 parts of isooctyl acrylate;

[0068] 70 parts styrene;

[0069] 2 servings of TMPTA;

[0070] 3 parts methacrylic acid;

[0071] KH-570 4 copies;

[0072] 3 parts emulsifier;

[0073] 1 part ammonium persulfate;

[0074] 0.6 parts of dimethylethanolamine;

[0075] 450 portions of deionized water;

[0076] 0.2 parts of reducing agent FF6M;

[0077] 0.5 parts of wetting agent Superwet-320;

[0078] 0.1 parts of defoamer WBA;

[0079] 13 parts of isopropanol.

[0080] The emulsifier is a mixture of emulsifier SR-10 and emulsifier DES-30 in a weight ratio of 1:2.

[0081] Example 3

[0082] A masking coating for use on the surface of a shrink film printing coating has the following components by weight:

[0083] 30 parts of isooctyl acrylate;

[0084] 65 parts of hard monomer;

[0085] EGDMA 1 dose;

[0086] 2 parts acrylic acid;

[0087] A-171 (8 copies);

[0088] 3 parts emulsifier;

[0089] Ammonium persulfate 0.8 parts;

[0090] 0.5 parts of dimethylethanolamine;

[0091] 420 portions of deionized water;

[0092] 1 part of reducing agent FF6M;

[0093] 0.5 parts of wetting agent Superwet-320;

[0094] BASF A10 defoamer, 0.1 parts;

[0095] 15 parts of isopropanol.

[0096] The hard monomer is a mixture of styrene and methyl methacrylate in a weight ratio of 35:30; the emulsifier is a mixture of emulsifier SR-10 and emulsifier DES-30 in a weight ratio of 1:2.

[0097] Example 4

[0098] A masking coating for the surface of a shrink film printing coating has the following composition by weight: 35 parts of acrylate soft monomer;

[0099] 60 parts of methyl methacrylate;

[0100] 3 copies of HDDA;

[0101] 2.5 parts methacrylic acid;

[0102] A-151, 6 copies;

[0103] 2 parts emulsifier;

[0104] 0.6 parts potassium persulfate;

[0105] 0.5 parts of dimethylethanolamine;

[0106] 400 parts of deionized water;

[0107] 0.8 parts of reducing agent FF6M;

[0108] 1 part of wetting agent Superwet-320;

[0109] BASF A10 defoamer 0.05 parts;

[0110] 10 parts isopropanol.

[0111] The emulsifier is a mixture of emulsifier SR-10 and emulsifier DES-30 in a weight ratio of 1:2.

[0112] The acrylate soft monomer is composed of isooctyl acrylate and butyl acrylate in a weight ratio of 25:10.

[0113] Example 5 is the same as Example 1, except that the emulsifier in Example 5 is a mixture of emulsifier SR-10 and emulsifier DS-10 in a weight ratio of 1:2, which replaces the emulsifier composition in Example 1.

[0114] Example 6 is the same as Example 1, except that the emulsifier in Example 6 is a mixture of SR-10 emulsifier and DES-30 emulsifier in a weight ratio of 2:1.

[0115] Example 7 is the same as Example 1, except that in Example 7, triethylamine is used in place of dimethylethanolamine in Example 1 in equal parts by weight.

[0116] Example 8 is the same as Example 1, except that in Example 8, ammonia water of equal weight is used instead of dimethylethanolamine in Example 1.

[0117] Example 9 is the same as Example 1, except that in Example 9, ethylene glycol methyl ether is used in place of isopropanol in Example 1 in the same weight proportions.

[0118] Example 10 is the same as Example 1, except that in Example 10, n-propanol is used instead of isopropanol in Example 1 in the same weight proportions.

[0119] Example 11 is the same as Example 1, except that in Example 11, ethanol is used in place of isopropanol in Example 1 in the same weight proportions.

[0120] Comparative Example 1 is the same as Example 1, except that the co-solvent used in the preparation of the masking coating in Comparative Example 1 is acetone.

[0121] Comparative Example 2 is the same as Example 1, except that the amount of seed emulsion added during the preparation of the masking coating in Comparative Example 2 is too small. In step S1, 3% of the total mass of the mixed solution is used as the seed emulsion.

[0122] Comparative Example 3 is the same as Example 1, except that the silane coupling agent used in the preparation of the masking coating in Comparative Example 3 is KH550.

[0123] Comparative Example 4 is the same as Example 1, except that in the preparation process of the masking coating in Comparative Example 4, too much seed emulsion is added. In step S1, 15% of the total mass of the mixed solution is used as the seed emulsion.

[0124] Performance testing

[0125] A 5μm thick ink printing layer was obtained by printing on the surface of a 50μm thick PET shrink film. Then, a masking coating obtained in Examples 1-11 of this invention was coated onto the surface of the ink printing layer, and baked and cured at 70°C to obtain a 2μm thick masking coating. Next, a 0.5μm thick aluminum plating layer was deposited on the surface of the masking coating under high vacuum (both examples and comparative examples were vacuum-plated under the same conditions). The resulting composite shrink film was then subjected to relevant performance tests, and the specific test results are shown in Table 1 and Table 1 (continued). The PET shrink film used was made from Yizheng Chemical Fiber PET BG80 polyester chips, with a longitudinal shrinkage rate of 28%-29% and a transverse shrinkage rate of 1%. The ink printing layer coating was white Bauhinia variegata 120D-102 screen printing white ink.

[0126] (1) Adhesion strength of the masking coating, i.e., the adhesion strength between the masking coating and the ink printing layer: determined according to GB / T 9286-1998 "Cross-cut test of paint and varnish film".

[0127] (2) Anti-adhesion of the masking coating: The adhesion was measured in accordance with GB / T39935-2021 "Determination of anti-adhesion of plastic film and sheet" and the adhesion was observed.

[0128] (3) Adhesion strength of the aluminum plating layer, i.e., the adhesion strength between the aluminum plating layer and the masking coating: Apply 3M 600 standard pressure-sensitive tape to the aluminum layer of the aluminum plating film, and press it with a standard roller to ensure close contact with the aluminum layer. Quickly peel off the tape, and observe and record whether the aluminum layer is peeled off or transferred along with the tape. The adhesion strength of the aluminum plating layer is judged based on the area of ​​the aluminum layer remaining on the aluminum plating film after peeling.

[0129] (4) Light transmittance and haze of the masking coating: The light transmittance and haze of the masking coating shall be determined in accordance with GB / T2410-2008 "Determination of light transmittance and haze of transparent plastic".

[0130] (6) Shrinkage rate of composite shrink film: determined in accordance with GB / T 12027-2004 "Test method for dimensional change rate of plastic film and sheet under heating".

[0131] (7) Gloss of the masking coating: The gloss was determined in accordance with GB / T 9754-2007 "Determination of 20°, 60° and 85° specular gloss of paint films without metallic pigments".

[0132] The masking coating obtained in Comparative Example 1 used acetone as a co-solvent. Acetone has a low boiling point; when it evaporates rapidly, the surface of the masking coating dries too quickly while the underlying layer hasn't fully evaporated, resulting in an internally wet, externally dry state. The moisture remaining inside the masking coating is forced to rise to the surface because it cannot escape smoothly, causing the surface to appear white and hazy. Simultaneously, the masking coating is not completely dry and is prone to slight adhesion. This phenomenon is consistent with the test data in Table 1.

[0133] The masking coating obtained in Comparative Example 2 had a larger latex particle size, resulting in poor film-forming properties. After coating, the coating turned white and had excessive haze, affecting the appearance of the finished product. This phenomenon is consistent with the test data in Table 1.

[0134] In the preparation of the masking coating obtained in Comparative Example 3, KH550 was used to modify the acrylic resin. Since KH550 does not possess direct reactivity with acrylate monomers, it cannot be introduced into the molecular chain structure of the acrylic resin through chemical bonds. Instead, it exists in a free form within the coating. This not only fails to significantly improve the temperature resistance of the masking coating and its adhesion to the printed and aluminized layers, but also leads to insufficient cross-linking within the masking coating, ultimately resulting in a decrease in the mechanical properties and an increase in surface tack. This phenomenon is consistent with the test data in Table 1.

[0135] In Comparative Example 4, the excessive seed emulsion during the preparation of the masking coating led to an excessively rapid and uneven emulsion polymerization reaction, resulting in a large number of tiny aggregated particles. This increased the amount of slag produced by the masking coating, which was difficult to remove using conventional filtration. Consequently, microscopic defects formed during the curing of the masking coating, reducing its gloss and affecting its appearance and performance. This phenomenon is consistent with the test data in Table 1.

[0136] Table 1

[0137]

[0138] Continued from Table 1

[0139]

[0140] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A masking coating for the surface of a shrink film printing coating, characterized in that, By weight, it is obtained by seed emulsion polymerization of 30-35 parts soft acrylate monomer, 60-70 parts hard monomer, 1-3 parts crosslinking acrylate monomer, 2-4 parts acrylic monomer, 3-8 parts silane coupling agent containing double bonds, 2-3 parts emulsifier, 0.5-1 part initiator, 0.5-0.8 parts neutralizer, 400-450 parts deionized water, 0.2-1 part reducing agent, 0.5-1 part wetting agent, 0.05-0.5 parts defoamer, and 10-15 parts cosolvent. The silane coupling agent containing double bonds includes one or more of KH-570, TMPSM, A-171, and A-151; The co-solvent includes one or more of ethanol, isopropanol, n-propanol, and ethylene glycol methyl ether; The masking coating for the surface of a shrink film printing coating is prepared by the following steps: S1. Mix 2 / 5 of the formula amount of deionized water and 4 / 5 of the formula amount of emulsifier evenly. Then add the full amount of the formula amount of acrylate soft monomer, hard monomer, acrylic monomer, silane coupling agent containing double bond, acrylate crosslinking monomer and 1 / 3-1 / 2 of the formula amount of neutralizer. After mixing evenly, a mixture is obtained. Take 5-10% of the total mass of the mixture as seed emulsion. S2, dissolve the initiator of the prescribed amount in 1 / 20 of the prescribed amount in deionized water to obtain an initiator solution; Add 1 / 2 of the total mass of initiator solution to the remaining mixture, mix well to obtain a pre-emulsion; Add the amount of reducing agent in the formula to 1 / 20 of the amount of deionized water to obtain the reducing agent solution; S3, at room temperature, add the remaining amount of deionized water and emulsifier to the reaction vessel and mix well. Then raise the temperature of the reaction system to 78-80℃, add the seed emulsion, and then add all the remaining initiator solution. After stirring at a constant temperature for 0.5-1h, start to continuously add the pre-emulsion, and complete the addition within 3.5-4h. Stir at a constant temperature for 1-1.5h, and the reaction ends. S4. After the reaction in step (3) is completed, the reaction temperature is lowered to 60-65℃, and the reducing agent solution is continuously added dropwise within 1 hour. Then, the reaction is stirred at a constant temperature for 0.5-1 hour. After that, the temperature of the reaction system is lowered to room temperature. Then, the remaining amount of neutralizing agent, wetting agent, and defoamer are added to the reaction system in sequence. The mixture is stirred thoroughly and dispersed evenly. Finally, the amount of cosolvent is added. After stirring evenly, the mixture is filtered to obtain the masking coating with the required particle size.

2. The masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The acrylate soft monomers include one or more of ethyl acrylate, butyl acrylate, and isooctyl acrylate.

3. The masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The hard monomers include one or more of methyl methacrylate, styrene, ethyl methacrylate, isopropyl methacrylate, and butyl methacrylate.

4. The masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The acrylate crosslinking monomers include one or more of TPGDA, TMPTA, EGDMA, HDDA, and PETA.

5. A masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The acrylic monomer includes one or both of acrylic acid and methacrylic acid.

6. A masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The emulsifier is a mixture of emulsifier SR-10 and emulsifier DES-30 in a weight ratio of 1:

2.

7. A masking coating for the surface of a shrink film printing coating according to claim 1, characterized in that, The neutralizing agent includes one or more of triethylamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, and ammonia.

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