High-adhesion water-based ink applied to PET (polyethylene terephthalate) film printing and preparation method of high-adhesion water-based ink

Abstract

The invention relates to the technical field of water-based ink, in particular to high-adhesion water-based ink applied to PET film printing and a preparation method of the high-adhesion water-based ink. The preparation method of the high-adhesion water-based ink applied to PET film printing comprises the following steps: S1, preparing water-based basic ink; s210, preparation of a polyurethane prepolymer; s220, preparation of a pre-emulsified acrylate monomer: mixing methyl methacrylate, butyl acrylate, hydroxyethyl acrylate and epoxy resin, adding an emulsifier, deionized water and an antioxidant, and pre-emulsifying for 0.5-1 hour to form the pre-emulsified acrylate monomer; s230, preparation of a composite emulsion; s3, preparing the water-based ink; according to the high-adhesion water-based ink applied to PET film printing disclosed by the invention, the isocyanate-terminated polyurethane prepolymer is copolymerized with the acrylate monomer and the epoxy resin to form an interpenetrating network structure; the water-based ink can directly form strong combination on the PET surface, and the adhesive force of the ink is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of water-based inks, in particular to a water-based ink with high adhesion for PET film printing and a preparation method thereof. Background Art

[0002] PET film is widely used in various packaging and industrial applications, especially in food, electronic products and pharmaceutical packaging. Due to its excellent physical properties, such as heat resistance, chemical resistance and high transparency, PET film has become the material of choice for many applications. However, how to ensure that the ink can be firmly attached to the surface of the PET film and not easily fall off or delaminate is a key issue that needs to be solved during the printing process.

[0003] At present, lipophilic inks are mainly used for printing on PET film as the substrate, and their solvents are usually ethyl acetate or toluene. The advantages of lipophilic inks over water-based inks are mainly reflected in the following aspects: Strong adhesion: Fat-soluble ink can form strong adhesion on the surface of PET film. Since the surface of PET film itself is relatively smooth and less hydrophilic, fat-soluble ink can provide better adhesion effect through the volatilization of solvent and the interaction of ink components; High composite fastness: The high composite fastness of fat-soluble ink makes it more stable during the composite process and less prone to delamination or stratification; Not easy to de-ink: Due to its chemical properties, fat-soluble inks are difficult to fall off from the surface, which is very necessary for some high-demand applications (such as food and pharmaceutical packaging) to ensure that the product will not be contaminated during transportation and storage.

[0004] Many countries and regions are promoting the reduction of the use of hazardous substances, especially solvent-based inks that may have a negative impact on the environment and human health. The solvents commonly used in fat-soluble inks, such as toluene and xylene, are more harmful to the environment and human body, especially the emission of volatile organic compounds (VOCs), which may affect air quality and worker health. Therefore, as environmental regulations are gradually strengthened, water-based inks have become one of the alternatives.

[0005] Water-based ink is an ink that uses water as a solvent. Compared with traditional solvent-based inks, water-based inks are more environmentally friendly, have extremely low VOC emissions, and meet modern environmental protection requirements. Therefore, many companies have begun to try to use water-based inks to replace traditional solvent-based inks, especially in some fields with strict environmental protection requirements. However, water-based inks still face some challenges in printing and laminating effects: (1) Poor adhesion: Due to the low surface energy of PET film, water-based ink is slightly worse than fat-soluble ink in terms of adhesion, which results in the adhesion of the printed layer being worse than that of fat-soluble ink and easy to peel off; (2) Insufficient composite fastness: The composite fastness of water-based inks is often not as good as that of fat-soluble inks, which will lead to delamination problems between composite materials and affect the performance and appearance of the final product; (3) Slow drying speed: Water-based inks usually take longer to dry completely, which increases production cycle and equipment costs. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a water-based ink with high adhesion to a PET substrate and a preparation method thereof. The preparation method of the water-based ink with high adhesion applied to PET film printing comprises the following steps: Preparation of S1 water-based base ink: The pigment is mixed with ethanol and ground to obtain a base ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: placing the polyol into a stirred reactor, heating it to 100-120° C., stirring it, and evacuating it to remove moisture; S212: lowering the temperature to 60-70° C., stirring and mixing the isocyanate and the polyol, adding a catalyst and a chain extender, and reacting for 2-3 hours to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: Methyl methacrylate, butyl acrylate, hydroxyethyl acrylate and epoxy resin are mixed, and emulsifier, deionized water and antioxidant are added, and pre-emulsified for 0.5-1h to form pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: Mix the polyurethane prepolymer and the pre-emulsified acrylate monomer with deionized water and acetonitrile, raise the temperature to 70-80°C, add the initiator dropwise, and complete the addition within 3 hours, then raise the temperature to 85-90°C, add the crosslinking agent, and react for 2-3 hours to ensure complete reaction; S232: cooling to 40° C., adding a neutralizer for neutralization, and then adding a pH adjuster to adjust the pH value to 8-9, filtering, adding an adhesion promoter, and stirring and mixing to obtain a water-soluble acrylic acid-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: The water-based basic ink prepared in step S1 is mixed with the connecting material prepared in step S2 to obtain a water-based ink.

[0007] Furthermore, the polyol described in step S211 is polyether polyol and / or polyester polyol, and the isocyanate described in step S212 is isophorone diisocyanate or diphenylmethane diisocyanate.

[0008] Further, the catalyst is an organic tin catalyst, and the amount used is 0.3-0.8% of the total mass of isocyanate and polyol; The chain extender includes a hydrophilic chain extender and a small molecule chain extender, and the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid; The small molecule chain extender is one or more of neopentyl glycol, methyl propylene glycol, ethylenediamine, and diethylenetriamine.

[0009] Further, the amount of the hydrophilic chain extender is 3-8% of the total mass of the isocyanate and the polyol; The dosage of the small molecule chain extender is 1-3% of the total mass of the isocyanate and the polyol.

[0010] Furthermore, 5. the mass ratio of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate in step S221 is (3-5): (4-6): 1; The epoxy resin is 3-8% of the total mass of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate; The emulsifier is sulfobetaine and 2-pyridylthiourea, and the amount used is 3-8% of the total mass of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate.

[0011] Furthermore, the mass ratio of the sulfobetaine to 2-pyridylthiourea is 1:(1-1.5).

[0012] Further, in step S231, the mass ratio of the polyurethane prepolymer to the pre-emulsified acrylate monomer is 1:(2-3); The initiator is ammonium persulfate, and the amount used is 0.5-0.8% of the mass of the pre-emulsified acrylate monomer; The crosslinking agents are hydroxypropyl methacrylate and tetraethylene glycol dimethacrylate, and the amount used is 2-5% of the mass of the pre-emulsified acrylate monomer.

[0013] Furthermore, in step S231, the mass ratio of hydroxypropyl methacrylate to tetraethylene glycol dimethacrylate is 1:(1-1.5).

[0014] Furthermore, the neutralizing agent in step S232 is triethylamine, and the amount used is 2-7% of the total mass of the polyurethane prepolymer and the pre-emulsified acrylate monomer; The adhesion promoter is one or more of phosphate acrylate, titanate coupling agent, and phenoxydimethylsilane compound; The amount of the adhesion promoter is 0.5-1% of the total mass of the polyurethane prepolymer and the pre-emulsified acrylate monomer.

[0015] In addition, the present invention also provides a water-based ink with high adhesion for PET film printing, which is prepared by the above preparation method.

[0016] Beneficial technical effects (1) The water-based ink with high adhesion for printing on PET film of the present invention first prepares a polyurethane prepolymer terminated with an isocyanate group, and then copolymerizes with an acrylate monomer and an epoxy resin to form an interpenetrating network structure; the polyurethane chain segment provides flexibility and water resistance, the acrylate imparts hardness and quick drying, and the epoxy resin enhances chemical bonding through the reaction of epoxy groups with hydroxyl groups on the surface of PET, so that the water-based ink can directly form a strong bond on the PET surface, significantly improving the adhesion of the ink; (2) In the pre-emulsified acrylate monomer stage, epoxy resin and acrylate monomer are copolymerized, and the epoxy groups undergo a ring-opening reaction with the ester groups on the PET surface under alkaline conditions to form a stable ether bond covalent connection; the epoxy resin participates in the reaction in the emulsion copolymerization stage, rather than the physical blending of the traditional process, to ensure that the epoxy groups are evenly distributed on the surface of the latex particles and directly contact the PET interface, thereby improving the adhesion of the ink; (3) The preparation of acrylate monomers uses a compound of methyl methacrylate, butyl acrylate, and hydroxyethyl acrylate. The hydroxyl group of hydroxyethyl acrylate can form hydrogen bonds with the PET substrate to enhance adhesion. Secondly, the hydroxyl group of hydroxyethyl acrylate may participate in the cross-linking reaction during the emulsion polymerization process, thereby increasing the cohesive strength of the resin and thus improving adhesion; (4) The present invention adopts a hydrophilic chain extender to introduce carboxyl groups into the polyurethane prepolymer, thereby adjusting the chain segment structure to improve the hydrophilicity and fluidity of the ink, which helps to improve the wettability and dispersibility of the ink in the aqueous system; the use of a small molecule chain extender helps to enhance the degree of crosslinking, so that the hardness and wear resistance of the ink are further enhanced; (5) The emulsifier is a compound of sulfobetaine (zwitterionic type) and 2-pyridylthiourea (reactive type), which further improves the dispersibility of pigments in water-based inks compared to the traditional SDS / OP-10 system. Sulfobetaine forms a directional adsorption layer at the ink-PET interface, reducing the interfacial tension, making it easier for the resin to spread and fill the surface defects of PET. 2-Pyridylthiourea is partially connected to the polymer chain during the polymerization process, avoiding the weak interface boundary layer caused by the migration of traditional emulsifiers. (6) Hydroxypropyl methacrylate and tetraethylene glycol dimethacrylate are used together to form a three-dimensional cross-linked network through free radical polymerization, which reduces the shrinkage internal stress during the film formation process. At the same time, the hydroxyl group of hydroxypropyl methacrylate forms hydrogen bonds with the PET surface to assist adhesion. DETAILED DESCRIPTION

[0017] The sources of the raw materials used in the examples and comparative examples of the present invention are as follows: PTMEG - 1000: Polytetrahydrofuran, with a molecular weight of 1000, hydroxyl value of 110 mg KOH / g, manufacturer: Mitsubishi Chemical Corporation, Japan; POL - 456: Polypropylene adipate, with a molecular weight of 2000, hydroxyl value of 56 mg KOH / g, manufacturer: Qingdao Xinyutian Chemical Co., Ltd.; MDI - 50: Diphenylmethane diisocyanate, manufacturer: Wanhua Chemical (Group) Co., Ltd., Yantai; IPID: Isophorone diisocyanate, manufacturer: Bayer AG, Germany; T - 12; Dibutyltin dilaurate, manufacturer: Air Products and Chemicals, Inc., USA; DMPA: 2,2 - Dimethylolpropionic acid, manufacturer: Shandong Saimeike Chemical Co., Ltd.; DMBA: 2,2 - Dimethylolbutyric acid, manufacturer: Shandong Saimeike Chemical Co., Ltd.; Neopentyl glycol: manufacturer: Zibo Anhao Chemical Co., Ltd.; Methylpropanediol: manufacturer: Shandong Qiyi Chemical Technology Co., Ltd.; Ethylenediamine: manufacturer: Jinan Liyang Chemical Co., Ltd.; MMA: Methyl methacrylate, manufacturer: Shandong Feihong New Materials Co., Ltd.; BA: Butyl acrylate, manufacturer: Shandong Feihong New Materials Co., Ltd.; HEMA: 2 - Hydroxyethyl acrylate, manufacturer: Shandong Feihong New Materials Co., Ltd.; E - 44: Epoxy resin, manufacturer: Jinan Haiyuxing Chemical Co., Ltd. Dodecyl ethoxysulfobetaine: manufacturer: Shandong Chuangli New Materials Co., Ltd.; 2 - Pyridylthiourea: manufacturer: Shanghai Yuanye Bio - Technology Co., Ltd.; Hydroquinone: manufacturer: Shanghai Yuanye Bio - Technology Co., Ltd.; Ammonium persulfate: manufacturer: Shandong Youwei Chemical Co., Ltd.; HPMA: Hydroxypropyl methacrylate, manufacturer: Shandong Hengqiang Chemical Co., Ltd Tetraethylene glycol dimethacrylate: manufacturer: Guangzhou Kangyang Chemical Co., Ltd.; Triethylamine: manufacturer: Shandong Feihong New Materials Co., Ltd.; Phosphate acrylate: manufacturer: Jining Fangyu Chemical Co., Ltd.; Titanate coupling agent: manufacturer: Jinan Rongzheng Chemical Co., Ltd.; Methylphenyldiethoxysilane: manufacturer: Hubei Chengfeng Chemical Co., Ltd.; SDS: Sodium dodecyl sulfate, manufacturer: Guangdong Guanghua Sci - Tech Co., Ltd.; OP-10: Manufacturer: Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0018] Example 1

[0019] Preparation of S1 water-based base ink: 60 g of carbon black and 32 g of ethanol were added into a dispersion container, dispersed at a speed of 1000 rpm for 60 min, then the speed was increased to 3000 rpm, dispersed and ground for 4 h, and then allowed to stand for 30 min to obtain a basic ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: Put 50g of PTMEG-1000 and 30g of POL-456 into a three-necked flask, stir and mix, heat to 100-120°C, stir and vacuum for 1-1.5h to remove moisture; S212: lower the temperature to 60-70°C, add 20g of MDI-50 to the polyol, stir and mix, add 0.4g of catalyst T-12, 4g of hydrophilic chain extender DMBA, and 2g of small molecule chain extender ethylenediamine, and react for 2-3h to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: 30g MMA, 50g BA, 10g HEMA and 4.5g E-44 were mixed and stirred uniformly, and then the temperature was raised to 80°C, 0.9g dodecylethoxy sulfobetaine, 0.9g 2-pyridylthiourea, 100g deionized water and 1.5g hydroquinone were added, and pre-emulsified for 0.5-1h to form pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: 12 g of the polyurethane prepolymer prepared in step S212 and 28 g of the pre-emulsified acrylate monomer prepared in step S221 are mixed with 166 g of deionized water and 12 g of acetonitrile, the mixture is heated to 80° C., 4.6 g of a 3% aqueous solution of ammonium persulfate is added dropwise within 3 hours, and the mixture is heated to 85-90° C., 0.24 g of HPMA and 0.34 g of tetraethylene glycol dimethacrylate are added, and the mixture is reacted for 2-3 hours to ensure that the reaction is complete; S232: Cooling to 40°C, adding 1.2g of triethylamine for neutralization, then adding ammonia water to adjust the pH value to 8, filtering, adding 0.2g of phosphate acrylate, stirring and mixing evenly to obtain a water-soluble acrylic-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: 46 g of the aqueous base ink prepared in step S1 and 154 g of the connecting material prepared in step S232 were mixed uniformly at a rotation speed of 1000 rpm to obtain an aqueous ink.

[0020] Example 2

[0021] Preparation of S1 water-based base ink: 60 g of carbon black and 32 g of ethanol were added into a dispersion container, dispersed at a speed of 1000 rpm for 60 min, then the speed was increased to 3000 rpm, dispersed and ground for 4 h, and then allowed to stand for 30 min to obtain a basic ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: Put 20g of PTMEG-1000 and 50g of POL-456 into a three-necked flask, stir and mix, heat to 100-120°C, stir and vacuum for 1-1.5h to remove moisture; S212: lower the temperature to 60-70°C, add 16g of MDI-50 to the polyol, stir and mix, add 0.6g of catalyst T-12, 3g of hydrophilic chain extender DMPA, 0.85g of small molecule chain extender ethylenediamine, and 1g of methyl propylene glycol, and react for 2-3h to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: 40g MMA, 50g BA, 10g HEMA and 6g E-44 were mixed and stirred uniformly, and then the temperature was raised to 80°C, and 2g dodecylethoxy sulfobetaine, 3g 2-pyridylthiourea, 100g deionized water, 7.5g acetonitrile and 1.5g hydroquinone were added, and pre-emulsified for 0.5-1h to form a pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: 12 g of the polyurethane prepolymer prepared in step S212 and 36 g of the pre-emulsified acrylate monomer prepared in step S221 are mixed with 165 g of deionized water and 16 g of acetonitrile, the mixture is heated to 80° C., 9.6 g of a 3% aqueous solution of ammonium persulfate is added dropwise within 3 hours, and the mixture is heated to 85-90° C., 0.72 g of HPMA and 0.72 g of tetraethylene glycol dimethacrylate are added, and the mixture is reacted for 2-3 hours to ensure that the reaction is complete; S232: Cooling to 40°C, adding 2g of triethylamine for neutralization, then adding ammonia water to adjust the pH value to 8.5, filtering, adding 0.38g of titanate coupling agent, stirring and mixing evenly to obtain a water-soluble acrylic-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: 55 g of the aqueous base ink prepared in step S1 and 145 g of the connecting material prepared in step S232 were mixed uniformly at a rotation speed of 1000 rpm to obtain an aqueous ink.

[0022] Example 3

[0023] Preparation of S1 water-based base ink: 60 g of carbon black and 32 g of ethanol were added into a dispersion container, dispersed at a speed of 1000 rpm for 60 min, then the speed was increased to 3000 rpm, dispersed and ground for 4 h, and then allowed to stand for 30 min to obtain a basic ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: Put 10g PTMEG-1000 and 70g POL-456 into a three-necked flask, stir and mix, heat to 100-120°C, stir and vacuum for 1-1.5h to remove moisture; S212: lowering the temperature to 60-70° C., adding 15 g IPDI to the polyol and stirring to mix, adding 0.7 g catalyst T-12, 7 g hydrophilic chain extender DMPA, and 1 g small molecule chain extender ethylenediamine, and reacting for 2-3 h to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: 40g MMA, 60g BA, 10g HEMA and 8g E-44 were mixed and stirred evenly, and then the temperature was raised to 80°C, 0.9g dodecylethoxy sulfobetaine, 1.35g 2-pyridylthiourea, 120g deionized water and 1.5g hydroquinone were added, and pre-emulsified for 0.5-1h to form pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: 12 g of the polyurethane prepolymer prepared in step S212 and 24 g of the pre-emulsified acrylate monomer prepared in step S221 are mixed with 168 g of deionized water and 12 g of acetonitrile, the mixture is heated to 80° C., 4.8 g of a 3% aqueous solution of ammonium persulfate is added dropwise within 3 hours, and the mixture is heated to 85-90° C., 0.48 g of HPMA and 0.72 g of tetraethylene glycol dimethacrylate are added, and the mixture is reacted for 2-3 hours to ensure that the reaction is complete; S232: Cooling to 40°C, adding 2.2g of triethylamine for neutralization, then adding ammonia water to adjust the pH value to 9, filtering, adding 0.28g of phosphate acrylate, stirring and mixing evenly to obtain a water-soluble acrylic-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: 50 g of the water-based base ink prepared in step S1 and 150 g of the connecting material prepared in step S232 were mixed uniformly at a rotation speed of 1000 rpm to obtain a water-based ink.

[0024] Example 4

[0025] Preparation of S1 water-based base ink: 60 g of carbon black and 32 g of ethanol were added into a dispersion container, dispersed at a speed of 1000 rpm for 60 min, then the speed was increased to 3000 rpm, dispersed and ground for 4 h, and then allowed to stand for 30 min to obtain a basic ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: Put 100g of POL-456 into a three-necked flask and stir and mix, heat to 100-120°C, stir and evacuate for 1-1.5h to remove moisture; S212: lowering the temperature to 60-70° C., adding 18 g of IPID to the polyol and stirring to mix, adding 0.7 g of catalyst T-12, 8 g of hydrophilic chain extender DMPA, 1 g of small molecule chain extender ethylenediamine, and 1 g of neopentyl glycol, and reacting for 2-3 h to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: 40g MMA, 50g BA, 10g HEMA and 8g E-44 were mixed and stirred uniformly, and then the temperature was raised to 80°C, and 2g dodecylethoxy sulfobetaine, 2g 2-pyridylthiourea, 100g deionized water, 7.5g acetonitrile and 1.5g hydroquinone were added, and pre-emulsified for 0.5-1h to form pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: 12 g of the polyurethane prepolymer prepared in step S212 and 30 g of the pre-emulsified acrylate monomer prepared in step S221 are mixed with 165 g of deionized water and 12 g of acetonitrile, the mixture is heated to 80° C., 5.25 g of a 3% aqueous solution of ammonium persulfate is added dropwise within 3 h, and the mixture is heated to 85-90° C., 0.4 g of HPMA and 0.5 g of tetraethylene glycol dimethacrylate are added, and the mixture is reacted for 2-3 h to ensure that the reaction is complete; S232: Cooling to 40°C, adding 0.9g of triethylamine for neutralization, then adding ammonia water to adjust the pH value to 8.4, filtering, adding 0.125g of phosphate acrylate and 0.175g of methylphenyldiethoxysilane, stirring and mixing evenly to obtain a water-soluble acrylic-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: 50 g of the water-based base ink prepared in step S1 and 150 g of the connecting material prepared in step S232 were mixed uniformly at a rotation speed of 1000 rpm to obtain a water-based ink.

[0026] Comparative Example 1

[0027] The difference between this comparative example and Example 2 is that the preparation of the S230 composite emulsion is different, and the specific steps are as follows: S231: 24 g of the polyurethane prepolymer prepared in step S212 and 24 g of the pre-emulsified acrylate monomer prepared in step S221 are mixed with 165 g of deionized water and 16 g of acetonitrile, the mixture is heated to 80° C., 6.4 g of a 3% aqueous solution of ammonium persulfate is added dropwise within 3 hours, and the mixture is heated to 85-90° C., 0.48 g of HPMA and 0.48 g of tetraethylene glycol dimethacrylate are added, and the mixture is reacted for 2-3 hours to ensure that the reaction is complete; S232: Cool down to 40°C, add 2g of triethylamine for neutralization, then add ammonia water to adjust the pH value to 8.5, add 0.38g of titanate coupling agent after filtering, stir and mix evenly to obtain a water-soluble acrylic-epoxy resin-polyurethane composite emulsion, i.e., a connecting material.

[0028] Comparative Example 2

[0029] The difference between this comparative example and Example 2 is that in step S221, epoxy resin E-44 is not added.

[0030] Comparative Example 3

[0031] The difference between this comparative example and Example 2 is that in step S221, the amount of epoxy resin E-44 used is 15 g.

[0032] Comparative Example 4

[0033] The difference between this comparative example and Example 2 is that in step S221, no dodecylethoxysulfobetaine is added, and an equal amount of 2-pyridylthiourea is used instead.

[0034] Comparative Example 5

[0035] The difference between this comparative example and Example 2 is that in step S221, 2-pyridylthiourea is not added, and an equal amount of dodecylethoxysulfobetaine is used instead.

[0036] Comparative Example 6

[0037] The difference between this comparative example and Example 2 is that in step S221, an SDS / OP-10 system emulsification system is used instead of dodecylethoxysulfobetaine and 2-pyridylthiourea, the amount of OP-10 used is 3 g, and the amount of SDS used is 2 g.

[0038] Comparative Example 7

[0039] The difference between this comparative example and Example 2 is that in step S221, the amount of dodecylethoxysulfobetaine used is 3 g, and the amount of 2-pyridylthiourea used is 2 g.

[0040] Comparative Example 8

[0041] The difference between this comparative example and Example 2 is that in step S231, HPMA is not added, and an equal amount of tetraethylene glycol dimethacrylate is used instead.

[0042] Comparative Example 9

[0043] The difference between this comparative example and Example 2 is that in step S231, tetraethylene glycol dimethacrylate is not added, and an equal amount of HPMA is used instead.

[0044] Comparative Example 10

[0045] The difference between this comparative example and Example 2 is that in step S212, small molecule chain extenders ethylenediamine and neopentyl glycol are not added, and an equal amount of hydrophilic chain extender DMPA is used instead.

[0046] Comparative Example 11

[0047] The difference between this comparative example and Example 2 is that the pre-emulsified acrylate monomer is replaced by a dissolved solution of acrylic resin Soluryl-60L produced by Hanwha of South Korea.

[0048] Preparation of acrylic resin Soluryl-60L solution: 100 g of solid acrylic resin Soluryl-60L was added to 100 g of deionized water, and after heating to 70°C, 7 g of 25% ammonia water was slowly added, and stirred at 75-80°C for 2 hours to obtain a dissolved acrylic resin Soluryl-60L.

[0049] Comparative Example 12

[0050] The difference between this comparative example and Example 2 is that HEMA is not used in step S221, but an equal amount of BA is used instead.

[0051] (1) Ink adhesion test Preparation of ink layer: The ink prepared in each embodiment and comparative example was subjected to gravure printing, wherein the plastic gravure electroplate had 90 lines, a depth of 25-30 μm, a bellows length of 2.5 m, a bellows wind speed of 30-35 m / s, and was printed on the PET film at a speed of 600 m / min.

[0052] According to GB / T13217.7-2023, the disc peeling method is used to test. The tape is pasted on the ink printed surface, rolled back and forth on the tape roller for 3 times, and then the sample is immediately clamped on the A disc. The exposed tape is fixed on the B disc, and then the machine is turned on. The A disc rotates at a speed of 0.6m / s to peel off the tape.

[0053] Use a 20mm wide translucent millimeter grid paper to cover the uncovered part, count the number of grids occupied by the ink layer and the number of grids occupied by the peeled ink layer, and calculate according to the following formula: ; A is the ink adhesion force, where A 1 is the number of grids of the remaining ink layer on the substrate after peeling off the tape, and A 2 is the number of grids of the peeled-off ink layer.

[0054] The test results of the ink adhesion force prepared in Examples 1-4 and Comparative Examples 1-12 are shown in Table 1.

[0055] Table 1: Adhesion fastness (%) Example 1 99.4 Example 2 99.6 Example 3 99.3 Example 4 99.4 Comparative Example 1 97.2 Comparative Example 2 97.7 Comparative Example 3 98.3 Comparative Example 4 97.1 Comparative Example 5 97.0 Comparative Example 6 97.4 Comparative Example 7 97.3 Comparative Example 8 96.8 Comparative Example 9 96.6 Comparative Example 10 95.9 Comparative Example 11 92.2 Comparative Example 11 91.5 (2) Ink resistance to ethanol, alkali, acid, and water Put a small amount of the ink prepared in each example and comparative example on the upper middle of the scraping paper with a palette knife, hold the scraping knife and scrape it forcefully from top to bottom on the scraping sample to form a uniform scraping sample, and then let it stand at room temperature and dry for 24 h; Cut a small piece of the colored part of the dried scraping sample and soak it in each test tube of acid, alkali, alcohol, and water with a specified concentration respectively; After soaking for 24 h, take out the scraping sample with tweezers and compare it with the non-soaked scraping sample to check the color change of the scraping sample, and evaluate the levels of the inspected ink's resistance to acid, alkali, alcohol, and water according to Table 2.

[0056] Table 2: level Scrape discoloration 1 Severe discoloration 2 Obvious discoloration 3 Slightly discolored 4 Basically no discoloration 5 No color change The test results are shown in Table 3.

[0057] Table 3 Ethanol resistance, alkali resistance, acid resistance, water resistance Example 1 Level 5 Example 2 Level 5 Example 3 Level 5 Example 4 Level 5 Comparative Example 1 Level 5 Comparative Example 2 Level 3 Comparative Example 3 Level 4 Comparative Example 4 Level 3 Comparative Example 5 Level 3 Comparative Example 6 Level 4 Comparative Example 7 Level 4 Comparative Example 8 Level 3 Comparative Example 9 Level 3 Comparative Example 10 Level 3 Comparative Example 11 Level 3 Comparative Example 12 Level 3 According to the above test results, it can be obtained that the water-based ink with high adhesion degree applied to PET film printing in the present invention has a relatively high adhesion fastness to the PET film and strong resistance to ethanol, alkali, acid, and water.

[0058] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the relevant art can understand and utilize the present invention well.

Claims

1. A method for preparing a water-based ink with high adhesion for printing on PET film, characterized in that: The following steps are involved: Preparation of S1 water-based base ink: The pigment is mixed with ethanol and ground to obtain a base ink; Preparation of S2 connecting material: Preparation of S210 polyurethane prepolymer S211: placing the polyol into a stirred reactor, heating it to 100-120° C., stirring it, and evacuating it to remove moisture; S212: lowering the temperature to 60-70° C., stirring and mixing the isocyanate and the polyol, adding a catalyst and a chain extender, and reacting for 2-3 hours to prepare an isocyanate-terminated polyurethane prepolymer; Preparation of S220 pre-emulsified acrylate monomer S221: Methyl methacrylate, butyl acrylate, hydroxyethyl acrylate and epoxy resin are mixed, and emulsifier, deionized water and antioxidant are added, and pre-emulsified for 0.5-1h to form pre-emulsified acrylate monomer; Preparation of S230 composite emulsion S231: Mix the polyurethane prepolymer and the pre-emulsified acrylate monomer with deionized water and acetonitrile, raise the temperature to 70-80°C, add the initiator dropwise, and complete the addition within 3 hours, then raise the temperature to 85-90°C, add the crosslinking agent, and react for 2-3 hours to ensure complete reaction; S232: cooling to 40° C., adding a neutralizer for neutralization, and then adding a pH adjuster to adjust the pH value to 8-9, filtering, adding an adhesion promoter, and stirring and mixing to obtain a water-soluble acrylic acid-epoxy resin-polyurethane composite emulsion, i.e., a connecting material; Preparation of S3 water-based ink: The water-based basic ink prepared in step S1 is mixed with the connecting material prepared in step S2 to obtain a water-based ink.

2. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 1, characterized in that: The polyol described in step S211 is polyether polyol and / or polyester polyol, and the isocyanate described in step S212 is isophorone diisocyanate or diphenylmethane diisocyanate.

3. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 2, characterized in that: The catalyst is an organic tin catalyst, and the amount used is 0.3-0.8% of the total mass of isocyanate and polyol; The chain extender includes a hydrophilic chain extender and a small molecule chain extender, and the hydrophilic chain extender is dimethylol propionic acid or dimethylol butyric acid; The small molecule chain extender is one or more of neopentyl glycol, methyl propylene glycol, ethylenediamine, and diethylenetriamine.

4. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 3, characterized in that: The amount of the hydrophilic chain extender is 3-8% of the total mass of isocyanate and polyol; The amount of the small molecule chain extender is 1-3% of the total mass of the isocyanate and the polyol.

5. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 1, characterized in that: The mass ratio of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate in step S221 is (3-5): (4-6): 1; The epoxy resin is 3-8% of the total mass of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate; The emulsifier is sulfobetaine and 2-pyridylthiourea, and the amount used is 3-8% of the total mass of methyl methacrylate, butyl acrylate and hydroxyethyl acrylate.

6. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 5, characterized in that: The mass ratio of the sulfobetaine to 2-pyridylthiourea is 1:(1-1.5).

7. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 1, characterized in that: In step S231, the mass ratio of the polyurethane prepolymer to the pre-emulsified acrylate monomer is 1:(2-3); The initiator is ammonium persulfate, and the amount used is 0.5-0.8% of the mass of the pre-emulsified acrylate monomer; The crosslinking agents are hydroxypropyl methacrylate and tetraethylene glycol dimethacrylate, and the amount used is 2-5% of the mass of the pre-emulsified acrylate monomer.

8. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 7, characterized in that: In step S231, the mass ratio of hydroxypropyl methacrylate to tetraethylene glycol dimethacrylate is 1:(1-1.5).

9. The method for preparing a water-based ink having high adhesion for printing on PET film according to claim 8, characterized in that: The neutralizing agent in step S232 is triethylamine, and the amount used is 2-7% of the total mass of the polyurethane prepolymer and the pre-emulsified acrylate monomer; The adhesion promoter is one or more of phosphate acrylate, titanate coupling agent, and phenoxydimethylsilane compound; The amount of the adhesion promoter is 0.5-1% of the total mass of the polyurethane prepolymer and the pre-emulsified acrylate monomer.

10. A water-based ink with high adhesion applied to PET film printing, characterized in that: The ink is prepared according to the method for preparing a water-based ink with high adhesion for printing on PET film according to any one of claims 1 to 9.