Cooking-resistant acrylic acid modified polyurethane resin emulsion for water-based plastic ink and preparation method of acrylic acid modified polyurethane resin emulsion

Abstract

The invention relates to the technical field of waterborne polyurethane resin emulsions, and provides an acrylate modified polyurethane resin emulsion for steaming-resistant waterborne plastic ink, waterborne gravure plastic ink prepared from the acrylate modified polyurethane resin emulsion provided by the invention is good in resolubility and excellent in anti-adhesion performance; the adhesive has good adhesion performance and steaming and boiling resistance to plastic (PE, BOPP, PVC, PET and the like) films, and the adhesive force is tested by a transparent adhesive tape and reaches zero level; and through a 100 DEG C boiling water / 60 min cooking test, the ink coating is complete, and is free of floating, whitening and bubbling. Meanwhile, the water-based plastic ink has good printability, and can be applied to the fields of packaging, printing and decoration of various (PE, BOPP, PVC, PET and the like) plastic films.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane resin preparation, and particularly relates to an acrylic acid-modified polyurethane resin emulsion for boiling-resistant water-based plastic ink and a preparation method thereof. Background Art

[0002] At present, traditional packaging plastic printing is mostly carried out using solvent-based inks. Plastic printing inks are mainly solvent-based inks, with highly volatile solvents such as toluene as the dispersion medium, and they account for almost more than 60% of the plastic ink weight. However, highly volatile solvents contain aromatic hydrocarbons, which are toxic and flammable. Excessive levels of organic solvents such as benzene are extremely harmful to the human body, and occupational health, safety and environmental protection issues are particularly prominent.

[0003] As the food packaging industry's demands for environmental protection, safety, and functionality continue to rise, stricter requirements are being placed on the environmental friendliness and safety of printed materials. In recent years, with the global emphasis on green production, water-based inks, which use water as a dispersion medium and have VOC content as low as below 5%, are more environmentally friendly during production and use. These inks comply with international standards such as EU REACH and FDA food contact materials, helping companies address evolving global environmental regulations and reduce environmental risks in the production process. Water-based plastic packaging inks are designed for printing on plastic substrates or films such as PE, BOPP, PVC, PET, and PP. They are generally composed of a binder, colorant, additives, and a dispersion medium.

[0004] Retort resistance is an essential core performance indicator for water-based plastic inks in the food packaging industry. From a food safety perspective, high-temperature retort is a necessary process for canned foods, meat, and other foods. Inadequate retort resistance can lead to ink shedding, migration, or chemical dissolution at high temperatures, posing a direct threat to consumer health. Inadequate retort resistance can damage the interfacial bonding between the ink and the plastic substrate, causing delamination of the ink layer, loss of pigment particles, and even the risk of chemical migration. For example, residual monomers, plasticizers, or heavy metals in the ink can penetrate into the contents through food simulants (such as water or acetic acid solution), directly threatening consumer health.

[0005] From a technical perspective, the boiling resistance of water-based inks depends on the crosslinking density and chemical stability of the resin system. For example, when using unmodified acrylic resin, water molecules easily penetrate the ink film at high temperatures, causing the resin to swell and the chain segments to move more rapidly, which in turn causes the colorant to separate from the binder. Summary of the Invention

[0006] To address the retort resistance deficiencies of existing water-based plastic inks, the present invention provides a retort-resistant acrylic-modified polyurethane resin emulsion for use in gravure water-based plastic inks and its preparation method. Applied to gravure water-based plastic inks, this emulsion exhibits excellent adhesion and retort resistance to plastic films (such as PE, BOPP, PVC, and PET), while also exhibiting excellent printability. This water-based plastic ink can be used in a variety of decorative packaging and printing applications on various plastic films, addressing the issues of poor adhesion and retort resistance of plastic inks to plastic substrates.

[0007] One of the technical solutions of the present invention is to provide an acrylic modified polyurethane resin emulsion for boiling-resistant water-based plastic ink, which is prepared from the following materials: 120.0-200.0 parts by weight of an acrylate oligomer polyol acetone solution, 50.0-100.0 parts by weight of a dimer acid-type polyester polyol, 60.0-90.0 parts by weight of a polyether polyol, 50.0-70.0 parts by weight of a diisocyanate, 5.0-15.0 parts by weight of a carboxyl-type hydrophilic chain extender, 0.3-0.6 parts by weight of an esterification reaction catalyst, 80.0-120.0 parts by weight of acetone, 10.0-15.0 parts by weight of a low-molecular-weight polyol chain extender, 5.0-15.0 parts by weight of triethylamine, 0.8-1.6 parts by weight of ethylenediamine, 500.0-600.0 parts by weight of deionized water, and 1.8-3.6 parts by weight of dihydrazide.

[0008] Furthermore, the acrylate oligomer polyol acetone solution is prepared from 18.0-25.0 parts by weight of tert-dodecyl mercaptan-S, 20.0-80.0 parts by weight of methyl methacrylate, 40.0-60.0 parts by weight of ethyl acrylate, 60.0-90.0 parts by weight of butyl acrylate, 50.0-110.0 parts by weight of vinyl neononanoate, 150.0-270.0 parts by weight of isobornyl acrylate, 15.0-25.0 parts by weight of hydroxyethyl acrylate, 20.0-35.0 parts by weight of diacetone acrylamide, 12.0-15.0 parts by weight of azobisisobutyronitrile, and 300.0-400.0 parts by weight of acetone solvent.

[0009] It is worth noting that the composition and preparation process of the acrylate oligomer polyol have a decisive influence on the comprehensive performance of the acrylate-modified polyurethane resin emulsion of the present invention. By introducing special acrylate monomers such as tertiary carbonate monomers such as vinyl neononanoate and isobornyl acrylate, the wetting and adhesion ability of the emulsion to the plastic substrate is significantly improved; at the same time, the high glass transition temperature hard monomer system formed by methyl methacrylate and the above two monomers synergistically enhances the rigidity and toughness of the emulsion, thereby improving the boiling resistance of the water-based plastic ink. In addition, acetone is selected as the preparation solvent for the acrylate oligomer polyol, which is consistent with the solvent used in the synthesis of the polyurethane resin emulsion, effectively avoiding the process compatibility problems caused by solvent differences and significantly improving the convenience of the synthesis process.

[0010] The formula of the present invention introduces a novel dimer acid-type polyester polyol. The unique long-chain hydrocarbon structure characteristics in the molecular structure of the dimer acid-type polyester polyol enable it to have excellent adhesion and anti-stick properties to plastic substrates. At the same time, it can give the ink coating excellent temperature resistance, mechanical strength and hydrolysis resistance, thereby improving the cooking resistance of the prepared water-based plastic.

[0011] Furthermore, the polyether polyol is one or a mixture of polypropylene glycol ether diol and polytetramethylene glycol ether diol; the number average molecular weight Mn of the polyether polyol is 1000-4000.

[0012] Furthermore, the diisocyanate is a mixture of one or more of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0013] Furthermore, the carboxyl type hydrophilic chain extender is one of dimethylol propionic acid and dimethylol butyric acid or a mixture of the two.

[0014] Furthermore, the esterification reaction catalyst is one of bismuth isooctanoate and bismuth neodecanoate, or a mixture of the two.

[0015] Furthermore, the low molecular weight polyol chain extender is one of 2-methyl-1,3-propanediol and 1,4-butanediol, or a mixture of the two.

[0016] Furthermore, the dihydrazide is one of adipic acid dihydrazide and malonic acid dihydrazide, or a mixture of the two; the ratio of the molar number of the hydrazide group in the dihydrazide to the molar number of the ketocarbonyl group of diacetone acrylamide in the acrylate oligomer polyol acetone solution is 0.4-2.0:1.0.

[0017] Further, the preparation of the acrylate oligomer polyol acetone solution has the following steps: Dissolve the formulated amount of tert-dodecyl mercaptan-S in acetone, stir and mix evenly to prepare a chain transfer agent solution.

[0018] The monomer raw materials such as methyl methacrylate, ethyl acrylate, butyl acrylate, vinyl neononanoate, isobornyl acrylate, hydroxyethyl acrylate and diacetone acrylamide in the formulated amount are dissolved in the solvent acetone, stirred and mixed evenly to prepare a raw material monomer mixed solution.

[0019] Dissolve the formulated amount of initiator azobisisobutyronitrile in solvent acetone, stir and mix evenly to prepare an initiator solution.

[0020] (2) Add the formulated amount of chain transfer agent solution to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, stir and heat, replace the air with nitrogen and protect, and keep warm for 20 minutes when the temperature rises to 56.0-60.0℃.

[0021] (3) Add 10% of the formulated raw monomer mixture solution and keep warm for 20 minutes. Add 80% of the formulated initiator solution and keep warm for 15 minutes. Start adding the remaining raw monomer mixture solution dropwise, maintaining a certain dropwise addition rate so that the remaining raw monomer mixture solution is added dropwise within 3.0 hours.

[0022] (4) After the addition is completed, add the remaining amount of initiator solution and maintain the temperature for 2.0 hours.

[0023] (5) After the heat preservation reaction is completed, samples are taken to test the solid content and viscosity. Depending on the test results, an appropriate amount of solvent acetone is added to adjust the solid content and viscosity. When the solid content is 55.0-65.0%, the hydroxyl content is 0.20%-0.50%, and the viscosity is 40.0-400.0 mPa·s / 25℃, the temperature is lowered and the material is discharged to obtain a light yellow transparent acrylate oligomer polyol acetone solution.

[0024] Among them, the above synthesis process steps are all carried out in a nitrogen protection atmosphere.

[0025] The second technical solution of the present invention is to provide a method for preparing the above-mentioned acrylic acid-modified polyurethane resin emulsion, which comprises the following steps: (1) Esterification reaction: Add the formulated amount of polyester polyol and polyether polyol to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, heat it to 100.0-105.0℃, keep it warm, reduce the pressure to -0.06~-0.08Mpa, remove water and dry for 1 hour; cool it to 50.0-55.0℃, add the formulated amount of acrylate oligomer polyol acetone solution, polyisocyanate, esterification reaction catalyst and solvent acetone, heat it to 58.0-62.0℃, keep it warm and react for 3.0-4.0 hours.

[0026] (2) Chain extension reaction: After the esterification reaction is completed, the temperature is lowered to 48.0-50.0°C, and a carboxyl-type hydrophilic chain extender, a low molecular weight chain extender, a neutralizer and a solvent acetone are added. The temperature is raised to 58.0-62.0°C and the reaction is kept warm for 4.0-5.0 hours.

[0027] (3) Emulsification and post-chain extension reaction: After the chain extension reaction is completed, cool to 35.0-38.0℃, adjust the agitator to 800-1000rpm, add deionized water for emulsification reaction, and add polyamine chain extender for chain extension reaction at the same time, and maintain high-speed stirring for 10.0-15.0 minutes.

[0028] (4) Desolventization: After the emulsification reaction is completed, the temperature is raised to 68.0-72.0℃, the pressure is reduced to -0.06~-0.08Mpa, and the solvent is removed for 2.5-4.0 hours. The solvent is collected and recovered; a sample is taken to test the residual solvent content. When the residual solvent content reaches the index requirement, the negative pressure is released and nitrogen is passed to normal pressure.

[0029] (5) Dispersing the crosslinking agent: After the solvent is removed, the temperature is lowered to 40.0-45.0°C, and an aqueous solution of dihydrazide is added and mixed and stirred for 20.0-30.0 minutes.

[0030] (6) Adjusting the solid content and viscosity of the emulsion: Take samples to test the solid content and viscosity. Depending on the test results, add appropriate amount of deionized water to adjust the solid content and viscosity. When the solid content is 33.0-37.0%, the pH value is 7.5-9.0, the rotational viscosity is 100.0-500 mPa·s / 25℃, and the emulsion particle size is 50.0-400.0nm, discharge and package to obtain a light yellow translucent or opaque acrylate modified polyurethane resin emulsion.

[0031] The present invention introduces diacetone acrylamide containing ketocarbonyl groups into an acetone solution of an acrylate oligomer polyol, and subsequently adds dihydrazide. The ketocarbonyl groups of the diacetone acrylamide can then undergo a ketohydrazide crosslinking and curing reaction with the hydrazide groups of the dihydrazide to produce a one-component, self-crosslinking water-based plastic ink. Because the ketohydrazide crosslinking reaction occurs during polymer film formation, after the system is dehydrated and under neutral or acidic conditions, the anionic polyurethane emulsion and the water-based ink prepared therefrom are generally in a weakly alkaline state. Therefore, the stability of the resin emulsion and ink system during storage can be ensured. During the drying and baking process of the water-based ink, the volatilization of the neutralizing agent during film formation of the resin polymer promotes crosslinking and curing of the ketohydrazide groups, resulting in a dense, crosslinked network coating formed on the ink coating. This significantly improves the water resistance and boiling resistance of the coating, achieving excellent overall performance.

[0032] The present invention is beneficial in that: The acrylate-modified polyurethane resin emulsion prepared by the preparation method provided herein comprises acrylic acid chemically modified and grafted onto polyurethane molecules. This emulsion exhibits both small particle size and strong stability. The emulsion can be mixed with pigment or dye pastes, various auxiliary agents, and the dispersion media of water and industrial alcohol. After stirring and grinding, the resulting water-based plastic gravure printing ink exhibits good solubility and excellent anti-stick properties. It also exhibits excellent adhesion to plastic film substrates (such as PE, BOPP, PVC, and PET), with adhesion reaching zero on transparent adhesive tape. It also exhibits excellent retort resistance, with a 60-minute retort test in 100°C boiling water demonstrating a complete ink coating with no blooming, whitening, or blistering. Furthermore, the water-based plastic ink exhibits excellent printability and is suitable for packaging, printing, and decorative applications on various plastic films (such as PE, BOPP, PVC, and PET). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the structural formula of methyl methacrylate.

[0034] Figure 2 It is the structural formula of vinyl neononanoate.

[0035] Figure 3 It is the structural formula of isobornyl acrylate. DETAILED DESCRIPTION

[0036] The following examples are used to further illustrate the present invention. Their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all references are by weight and weight percentage.

[0037] Unless otherwise specified, the raw materials used in the present invention are conventional commercial products; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0038] HDPOL-4420: Mn=2000, butanediol adipic acid type polyester polyol, Shanghai Huide Technology Co., Ltd. HDPOL-6620: Mn=2000, hexanediol adipate type polyester polyol, Shanghai Huide Technology Co., Ltd. Priplast™ 1900: Mn=2000, dimer acid-based polyester polyol, Cargill Investment (China) Co., Ltd. Priplast™ 1838: Mn=2000, dimer acid-based polyester polyol, Cargill Investment (China) Co., Ltd. PTMEG2000: Mn = 2000, polytetramethylene ether glycol, Hyosung Chemical (Jiaxing) Co., Ltd. PPG2000: Mn = 2000, polypropylene glycol, Hai'an Petrochemical Plant, Jiangsu Province; BCAT-E20: Bismuth neodecanoate type polyurethane catalyst, Guangzhou Yourun Synthetic Materials Co., Ltd.

[0039] The embodiments of the present invention are further described below with reference to a number of embodiments.

[0040] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0041] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0042] Table 1 shows examples of acrylate oligomer polyol acetone solutions, and Examples A to C are examples of the present invention.

[0043] Example A The formulation composition and experimental results of Example A are shown in Table 1 Example A, and the operating steps are as follows: (1) Dissolve the formulated amount of tert-dodecyl mercaptan-S in acetone, stir and mix evenly to prepare a chain transfer agent solution. Dissolve the formulated amount of monomer raw materials such as methyl methacrylate, ethyl acrylate, butyl acrylate, vinyl neononanoate, isobornyl acrylate, hydroxyethyl acrylate and diacetone acrylamide in the solvent acetone, stir and mix evenly to prepare a raw material monomer mixed solution. Dissolve the formulated amount of initiator azobisisobutyronitrile in the solvent acetone, stir and mix evenly to prepare an initiator solution.

[0044] (2) Add the formulated amount of chain transfer agent solution to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, stir and heat, replace the air with nitrogen and protect, and keep warm for 20 minutes when the temperature rises to 56.0-60.0℃.

[0045] (3) Add 10% of the formulated raw monomer mixture solution and keep warm for 20 minutes. Add 80% of the formulated initiator solution and keep warm for 15 minutes. Start adding the remaining raw monomer mixture solution dropwise, maintaining a certain dropwise addition rate so that all the remaining raw monomer mixture solution is added dropwise within 3.0 hours.

[0046] (4) After the addition is completed, add the remaining amount of initiator solution and maintain the temperature for 2.0 hours.

[0047] (5) After the heat preservation reaction is completed, samples are taken to test the solid content and viscosity. Depending on the test results, an appropriate amount of solvent acetone is added to adjust the solid content and viscosity. When the solid content and viscosity meet the index requirements, the temperature is lowered and the material is discharged to obtain a light yellow transparent acrylate oligomer polyol acetone solution.

[0048] Among them, the above synthesis process steps are all carried out in a nitrogen protection atmosphere.

[0049] Example B The formulation of Example B is shown in Table 1 Example B, and its operating steps are the same as those of Example A.

[0050] Example C The formulation of Example C is shown in Table 1 Example C, and its operating steps are the same as those of Example A.

[0051] Table 1 Examples of acrylate oligomer polyol acetone solutions Examples of Acrylate Modified Polyurethane Resin Emulsions Table 2 is the formula composition and implementation experimental results of the comparative example and embodiment of acrylate modified polyurethane resin emulsion, wherein the comparative example is a comparative example of acrylate modified polyurethane resin emulsion, which is a comparative example of the present invention, and Examples 1 to 9 are examples of the present invention.

[0052] Table 2 Acrylate modified polyurethane resin emulsion Table 2 Acrylate modified polyurethane resin emulsion Example 1 The formula composition and experimental results of Example 1 are shown in Table 2 Example 1, and the operating steps are as follows: (1) Esterification reaction: Add the formulated amount of polyester polyol and polyether polyol to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, heat it to 100.0-105.0℃, keep it warm, reduce the pressure to -0.06~-0.08Mpa, remove water and dry for 1 hour; cool it to 50.0-55.0℃, add the formulated amount of acrylate oligomer polyol acetone solution, polyisocyanate, esterification reaction catalyst and solvent acetone, heat it to 58.0-62.0℃, keep it warm and react for 3.0-4.0 hours.

[0053] (2) Chain extension reaction: After the esterification reaction is completed, the temperature is lowered to 48.0-50.0°C, and a carboxyl-type hydrophilic chain extender, a low molecular weight chain extender, a neutralizer and a solvent acetone are added. The temperature is raised to 58.0-62.0°C and the reaction is kept warm for 4.0-5.0 hours.

[0054] (3) Emulsification and post-chain extension reaction: After the chain extension reaction is completed, cool to 35.0-38.0℃, adjust the agitator to 800-1000rpm, add deionized water for emulsification reaction, and add polyamine chain extender for chain extension reaction at the same time, and maintain high-speed stirring for 10.0-15.0 minutes.

[0055] (4) Desolventization: After the emulsification reaction is completed, the temperature is raised to 68.0-72.0℃, the pressure is reduced to -0.06~-0.08Mpa, and the solvent is removed for 2.5-4.0 hours. The solvent is collected and recovered; a sample is taken to test the residual solvent content. When the residual solvent content reaches the index requirement, the negative pressure is released and nitrogen is passed to normal pressure.

[0056] (5) Dispersing the crosslinking agent: After the solvent is removed, the temperature is lowered to 40.0-45.0°C, and an aqueous solution of dihydrazide is added and mixed and stirred for 20.0-30.0 minutes.

[0057] (6) Adjusting the solid content and viscosity of the emulsion: Take samples to test the solid content and viscosity. Depending on the test results, add an appropriate amount of deionized water to adjust the solid content and viscosity. When the solid content and viscosity meet the index requirements, discharge and package the material to obtain a light yellow translucent or opaque acrylic modified polyurethane resin emulsion.

[0058] Example 2 The formula composition and experimental results of Example 2 are shown in Table 2 Example 2, and its operating steps are the same as those of Example 1.

[0059] Example 3 The formula composition and experimental results of Example 3 are shown in Table 2 Example 3, and the operating steps are the same as those of Example 1.

[0060] Example 4 The formula composition and experimental results of Example 4 are shown in Table 2 Example 4, and the operating steps are the same as those of Example 1.

[0061] Example 5 The formula composition and experimental results of Example 5 are shown in Table 2 Example 5, and its operating steps are the same as those of Example 1.

[0062] Example 6 The formula composition and experimental results of Example 6 are shown in Table 2 Example 6, and the operating steps are the same as those of Example 1.

[0063] Example 7 The formula composition and experimental results of Example 7 are shown in Table 2 Example 7, and the operating steps are the same as those of Example 1.

[0064] Example 8 The formula composition and experimental results of Example 8 are shown in Table 2 Example 8, and the operating steps are the same as those of Example 1.

[0065] Example 9 The formula composition and experimental results of Example 9 are shown in Table 2 Example 9, and the operating steps are the same as those of Example 1.

[0066] Comparative Example The formulation composition and experimental results of the comparative example are shown in Table 2. The operation steps are the same as those of Example 1.

[0067] The performance of the acrylate-modified polyurethane resin emulsion synthesized in the present invention is demonstrated by the properties of a water-based plastic gravure ink prepared from it. The components of the water-based plastic gravure ink are composed of the acrylate-modified polyurethane resin emulsion prepared in the present invention, a pigment paste, alcohol, water, and additives, including a leveling agent, a dispersant, a defoamer, a stabilizer, and a slip agent. The gravure water-based plastic ink is obtained by dispersion and filtration in a high-speed disperser or other equipment. The properties of the resulting water-based gravure plastic ink and the coating film are shown in Table 3.

[0068] Table 3 Water-based gravure plastic ink and coating properties Table 3 Water-based gravure plastic ink and coating properties The above examples demonstrate that the acrylate-modified polyurethane resin emulsion synthesized in the present invention, compared to the conventional polyurethane resin emulsion used in this example, produces a water-based plastic gravure printing ink with excellent solubility and anti-stick properties. It also exhibits excellent adhesion to plastic film substrates (such as PE, BOPP, PVC, and PET), with adhesion reaching zero in a cellophane tape test. It also exhibits excellent retort resistance, with the ink coating remaining intact after a 60-minute retort in 100°C boiling water test, exhibiting no blooming, whitening, or blistering. Furthermore, the water-based plastic ink exhibits excellent printability and is suitable for packaging, printing, and decorative applications on a variety of plastic films (such as PE, BOPP, PVC, and PET).

[0069] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the scope of protection of the present invention.

Claims

1. A boiling-resistant acrylic acid-modified polyurethane resin emulsion for water-based plastic ink, characterized by: The invention is prepared by using the following materials: 120.0-200.0 parts by weight of an acetone solution of an acrylate oligomer polyol, 50.0-100.0 parts by weight of a dimer acid-type polyester polyol, 60.0-90.0 parts by weight of a polyether polyol, 50.0-70.0 parts by weight of a diisocyanate, 5.0-15.0 parts by weight of a carboxyl-type hydrophilic chain extender, 0.3-0.6 parts by weight of an esterification reaction catalyst, 80.0-120.0 parts by weight of acetone, 10.0-15.0 parts by weight of a low-molecular-weight polyol chain extender, 5.0-15.0 parts by weight of triethylamine, 0.8-1.6 parts by weight of ethylenediamine, 500.0-600.0 parts by weight of deionized water, and 1.8-3.6 parts by weight of dihydrazide.

2. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The acrylate oligomer polyol acetone solution is prepared from 18.0-25.0 parts by weight of tert-dodecyl mercaptan-S, 20.0-80.0 parts by weight of methyl methacrylate, 40.0-60.0 parts by weight of ethyl acrylate, 60.0-90.0 parts by weight of butyl acrylate, 50.0-110.0 parts by weight of vinyl neononanoate, 150.0-270.0 parts by weight of isobornyl acrylate, 15.0-25.0 parts by weight of hydroxyethyl acrylate, 20.0-35.0 parts by weight of diacetone acrylamide, 12.0-15.0 parts by weight of azobisisobutyronitrile, and 300.0-400.0 parts by weight of acetone solvent.

3. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The polyether polyol is one of polypropylene glycol ether diol and polytetramethylene glycol ether diol or a mixture of the two; the number average molecular weight Mn of the polyether polyol is 1000-4000.

4. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The diisocyanate is a mixture of one or more of hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

5. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The carboxyl type hydrophilic chain extender is one of dimethylol propionic acid and dimethylol butyric acid or a mixture of the two.

6. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The esterification reaction catalyst is one of bismuth isooctanoate and bismuth neodecanoate, or a mixture of the two.

7. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The low molecular weight polyol chain extender is one of 2-methyl-1,3-propylene glycol and 1,4-butanediol or a mixture of the two.

8. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The dihydrazide is one of adipic acid dihydrazide and malonic acid dihydrazide, or a mixture of the two. In the acrylic acid-modified polyurethane resin emulsion for water-based plastic ink, the ratio of the molar number of the hydrazide group in the dihydrazide to the molar number of the ketocarbonyl group in the diacetone acrylamide is 0.4-2.0:1.

0.

9. The acrylic acid-modified polyurethane resin emulsion for water-based plastic ink according to claim 1, characterized in that: The preparation of acrylate oligomer polyol acetone solution has the following steps: (1) Dissolve the formulated amount of tert-dodecyl mercaptan-S in acetone, stir and mix uniformly to prepare a chain transfer agent solution; dissolve the formulated amount of monomer raw materials such as methyl methacrylate, ethyl acrylate, butyl acrylate, vinyl neononanoate, isobornyl acrylate, hydroxyethyl acrylate and diacetone acrylamide in the solvent acetone, stir and mix uniformly to prepare a raw material monomer mixed solution; dissolve the formulated amount of initiator azobisisobutyronitrile in the solvent acetone, stir and mix uniformly to prepare an initiator solution; (2) Add the formulated amount of chain transfer agent solution to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, stir and heat, replace the air with nitrogen and protect, and keep the temperature for 20 minutes when the temperature rises to 56.0-60.0℃; (3) Add 10% of the formula amount of the raw monomer mixed solution and keep it warm for 20 minutes; add 80% of the formula amount of the initiator solution and keep it warm for 15 minutes; start to drop the remaining raw monomer mixed solution and maintain a certain drop rate so that the remaining raw monomer mixed solution is added dropwise within 3.0 hours; (4) After the addition is completed, add the remaining amount of initiator solution and keep warm for 2.0 hours; (5) After the heat preservation reaction is completed, samples are taken to test the solid content and viscosity. Based on the test results, solvent acetone is added to adjust the solid content and viscosity. When the solid content is 55.0-65.0%, the hydroxyl content is 0.20%-0.50%, and the viscosity is 40.0-400.0 mPa·s / 25°C, the temperature is lowered and the material is discharged to obtain a light yellow transparent acrylate oligomer polyol acetone solution; Among them, the above synthesis process steps are all carried out in a nitrogen protection atmosphere.

10. A method for preparing the acrylic acid-modified polyurethane resin emulsion for flexible plastic ink according to claim 1, characterized in that: The following steps are involved: (1) Esterification reaction: Add the formulated amount of polyester polyol and polyether polyol to a 1000ml reactor equipped with a heating device, a stirrer and a distillation column, heat it to 100.0-105.0℃, keep it warm, reduce the pressure to -0.06~-0.08Mpa, remove water and dry for 1 hour; cool it to 50.0-55.0℃, add the formulated amount of acrylate oligomer polyol acetone solution, polyisocyanate, esterification reaction catalyst and solvent acetone, heat it to 58.0-62.0℃, keep it warm and react for 3.0-4.0 hours; (2) Chain extension reaction: After the esterification reaction is completed, the temperature is lowered to 48.0-50.0°C, and a carboxyl-type hydrophilic chain extender, a low molecular weight chain extender, a neutralizer and a solvent acetone are added. The temperature is raised to 58.0-62.0°C and the reaction is kept at this temperature for 4.0-5.0 hours. (3) Emulsification and post-chain extension reaction: After the chain extension reaction is completed, cool to 35.0-38.0℃, adjust the stirrer to 800-1000rpm, add deionized water for emulsification reaction, and add polyamine chain extender for chain extension reaction at the same time, and maintain high-speed stirring for 10.0-15.0 minutes; (4) Desolventization: After the emulsification reaction is completed, the temperature is raised to 68.0-72.0°C, the pressure is reduced to -0.06~-0.08Mpa, and the solvent is removed for 2.5-4.0 hours. The solvent is collected and recovered; a sample is taken to test the residual solvent content. When the residual solvent content reaches the index requirement, the negative pressure is released and nitrogen is passed to normal pressure; (5) Dispersing the crosslinking agent: After the solvent is removed, the temperature is lowered to 40.0-45.0°C, and an aqueous solution of dihydrazide is added and mixed and stirred for 20.0-30.0 minutes; (6) Adjusting the solid content and viscosity of the emulsion: Take samples to test the solid content and viscosity. Depending on the test results, add deionized water to adjust the solid content and viscosity. When the solid content is 33.0-37.0%, the pH value is 7.5-9.0, the rotational viscosity is 100.0-500 mPa·s / 25℃, and the emulsion particle size is 50.0-400.0nm, discharge and package to obtain a light yellow translucent or opaque acrylate modified polyurethane resin emulsion.

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