Vacuum aluminizing water-based coating liquid for paper printing as well as preparation method and application of vacuum aluminizing water-based coating liquid

Abstract

The invention discloses a vacuum aluminizing water-based coating liquid for paper printing. The coating liquid comprises a low-Tg / high-hardness water-based acrylic emulsion and a polycarbonate type and / or acrylic acid modified water-based polyurethane dispersion which are used as film-forming materials, and is matched with substances such as a water-based auxiliary agent, a film-forming auxiliary agent, a wax emulsion and water. The low-Tg / high-hardness water-based acrylic emulsion is a styrene-acrylic emulsion with a core-shell structure, which is synthesized by adopting alkali-soluble acrylate solid resin under specific selection as a reactive macromolecular rheology control emulsifier and adopting a seeded emulsion polymerization method. The coating liquid disclosed by the invention has excellent rheological property, excellent sealing property and film-forming property, ultrahigh aluminizing gloss and wear resistance, excellent anti-sticking and anti-light-reversing property, chemical resistance, redissolving property, printing adaptability and environmental protection property, and is suitable for various printing and coating modes; the printing ink is especially suitable for the printing industries of tobacco, wine and the like which have extremely strict requirements on printing speed, drying speed, wear resistance, sticking resistance and aluminized appearance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material preparation, and specifically relates to a vacuum aluminum plating water-based coating liquid for paper printing, a preparation method and an application thereof. Background Art

[0002] At present, with the enhancement of environmental awareness in countries around the world and the implementation of various laws and regulations, green production, green packaging, green consumption and circular economy have become the pursuit of various industries and enterprises. At present, these green concepts are being implemented in the printing and packaging industries, and packaging lightweight, reduced, single material, aluminum removal / aluminum reduction, PVDC removal, PVC removal, recyclable, recyclable and degradable are gradually being respected and welcomed by the industry.

[0003] It is difficult for paper-based packaging to meet the barrier properties (oxygen barrier, water barrier, moisture barrier) required in the food packaging application process. The current common method is to laminate the paper base with aluminum foil to make it have barrier properties. According to different production processes, it can be divided into three types, namely aluminum foil composite paper, vacuum aluminum-plated paper, and transfer aluminum-plated paper. Compared with aluminum foil composite paper, aluminized paper has the properties of cost reduction and energy conservation and environmental protection, which is more in line with the development trend of the packaging paper industry. It has become a major trend in the fields of labels, tobacco and alcohol labels, food, daily chemicals, gift box packaging, etc.

[0004] With the development of the industry, social needs and technology, vacuum aluminum plating has stable and reliable printing performance, good moisture-proof and moisturizing properties, uses less aluminum, and is biodegradable and recyclable. It is increasingly favored by the printing and packaging industry and has a wider range of applications.

[0005] The direct aluminizing process is to apply a special primer coating on the surface of the direct-plated paper, and then vacuum-plated aluminum to deposit and arrange aluminum molecules on the surface of the paper to form aluminized paper. For the direct aluminizing process, in order to improve the problem of rough paper surface and uneven aluminum effect, it is necessary to super-calender the direct-plated paper and / or pre-treat the surface of the direct-plated paper by coating the primer varnish to fill the micropores or fiber structure on the surface of the paper.

[0006] It should be emphasized that the direct-plated paper currently used is basically imported special paper. Ordinary paper that has not been overpressured has a rough and loose surface fiber structure. Conventional direct-plated primer resin has poor surface film formation, strong permeability, and good leveling. The aluminum-plated surface will lose gloss and become gray, and it is impossible to obtain good aluminum-plating effect and durability.

[0007] At present, the pretreatment coating primer is mainly solvent-based paint or mixed with various water-based resin types. Solvent-based paint has the characteristics of volatility, flammability and explosion, irritation to the human respiratory tract and eyes, and physical discomfort to construction workers, and is not recommended in terms of environmental protection and safety. Conventional water-based resins have advantages in safety, environmental protection and green production, but their primers have the characteristics of poor permeability, compatibility, resistance, and poor aluminum plating effect. Therefore, the industry is seeking and developing environmentally friendly, aluminum-plated, and resistant pretreatment water-based primers.

[0008] Patent CN 103410047 A discloses "a water-soluble varnish for coating the surface of aluminum-plated lining paper for cigarettes". This patent solves the problems of wear resistance, abrasion resistance, folding resistance and surface flatness of the lining paper for cigarette packages to a certain extent, but there are the following problems: the selected resin is a mixture of water-soluble styrene-acrylic acid copolymer and water-soluble butyl acrylate-styrene copolymer, which has compatibility problems, and a large amount of ethanol is used as a co-solvent, which is neither economical nor environmentally friendly. The gloss, chemical resistance, anti-adhesion and other properties of the upper line are not mentioned.

[0009] Patent CN 103866607 A discloses "a high-strength direct aluminum-plated water-based primer and its preparation method and application". This patent solves the sealing, flexibility, high metallic texture and other properties of aluminum-plated paper, but it requires different types of resins (polyurethane, acrylic, polyester, etc.) combined with cross-linking agents (amino resin, isocyanate curing agent, aziridine, carbodiimide, etc.), needs to be prepared on the spot, has incompatibility problems, and requires a long time of maturation after pre-treatment of the primer before aluminum plating, which is too inefficient for common printing and coating.

[0010] Patent CN 110167993 A discloses "emulsion particles, emulsion containing the same and method for preparing the emulsion". This patent adopts a core-shell four-layer structure from the technical route, and synergistically improves the film performance and durability that are difficult to achieve in the existing technology through different glass transition temperatures, but does not mention the gloss, adhesion, chemical resistance and printing adaptability of direct-plated paper.

[0011] Patent CN 105568758 A discloses "a water-based direct-plating primer coating for ordinary transfer paper and its preparation method". The invention uses polyvinyl alcohol to coat a large amount of silica sol, and forms a network structure by cross-linking polyvinyl alcohol and boric acid, and fills the silica sol to achieve the purpose of sealing the non-coated base paper. Boric acid can only cross-link with polyvinyl alcohol when dried at high temperature, so that the product does not need to be made into a two-component product; by adding acrylic acid, a higher aluminum plating brightness is achieved. Ordinary non-coated base paper can be used for direct aluminum-plated lining paper products to achieve the purpose of reducing costs.

[0012] The present invention aims to solve the above-mentioned problems and develops a water-based primer resin that can be used for vacuum aluminum plating on ordinary direct-plated paper. The water-based primer resin has excellent sealing and film-forming properties, ultra-high aluminum plating gloss, excellent anti-sticking, wear resistance, printing adaptability and environmental protection, and can obtain the same direct plating effect as direct-plated super calendered paper. Summary of the invention

[0013] In view of this, in view of the industry difficulties encountered in the process of circular economy and future development trend of paper-based packaging (de-aluminization / reduction of aluminum, recyclable and recyclable, and degradable), the purpose of the present invention is to provide a vacuum aluminum plating water-based coating liquid for paper printing. It only needs to apply the coating liquid of the present invention on the paper material that has not been super-calendered to obtain the direct plating effect and durability equivalent to direct-plated super-calendered paper. It is easy to use and simple to construct. The coating liquid of the present invention has excellent sealing and film-forming properties, ultra-high aluminum plating gloss, excellent anti-sticking, wear resistance, solubility, printing adaptability and environmental protection, and can obtain the direct plating effect equivalent to direct-plated super-calendered paper, which can effectively accelerate the water conversion process and the industry's "low-carbon" green development and other characteristics.

[0014] In order to achieve the above invention object, the technical solution of the present invention is as follows:

[0015] A vacuum aluminum plating water-based coating liquid for paper printing, comprising the following raw materials in percentage by weight:

[0016] Aqueous acrylic emulsion 50-75%, preferably 55-70%,

[0017] Aqueous polyurethane dispersion 5-20%, preferably 5-15%,

[0018] Deionized water 10-30%, preferably 10-25%,

[0019] Wax emulsion 2-5%, preferably 2.5-4.5%,

[0020] Defoaming agent 0.1-0.5%, preferably 0.2-0.4%,

[0021] Wetting agent 0.5-1.5%, preferably 0.5-1.0%,

[0022] Film-forming aid 0-3%, preferably 0-2%,

[0023] The quick-drying solvent is 7-25%, preferably 10-20%.

[0024] In the present invention, the aqueous acrylic emulsion is an aqueous acrylic emulsion with a core-shell structure, with an acid value of 20 to 70 mgKOH / g and a solid content of 40 to 50 wt %; preferably, the inner core glass transition temperature Tg is -30 to 20°C (e.g., -25°C, -20°C, -15°C, 5°C, 15°C, etc.), the outer shell glass transition temperature Tg is 85 to 120°C (e.g., 90°C, 95°C, 100°C, 110°C, 115°C, etc.), the core / shell mass ratio is 50 / 50 to 70 / 30, and the particle size range is 50 to 80 nm;

[0025] As a preferred embodiment, the aqueous acrylic emulsion of the present invention is a styrene-acrylic emulsion with a core-shell structure synthesized by seed emulsion polymerization using a specifically selected alkali-soluble acrylic solid resin as a reactive macromolecular rheology control emulsifier. Wherein, the specifically selected alkali-soluble acrylic solid resin is a styrene-acrylic resin and / or a maleic anhydride-modified styrene-acrylic resin having an acid value of 200 to 300 mg KOH / g, a molecular weight Mw of 7500 to 16000 g / mol, a molecular weight distribution PDI of 1.4 to 2.0, and a glass transition temperature Tg of 80 to 120°C;

[0026] The present invention uses alkali-soluble acrylic resin as a rheology control emulsifier during the emulsion polymerization of the shell layer and the core layer, and the polymerization reaction stability is better, the storage stability is good, and the rheology of the emulsion is close to that of a Newtonian fluid, so that after being coated with the coating liquid, it can quickly flow and wet on the substrate and fill each fiber of the paper. The resin has a large number of carboxyl groups that can combine with the paper fibers to form hydrogen bonds; in addition, the emulsion has a narrow particle size distribution and a small particle size, and the two work together to obtain a direct plating effect (high gloss and good transparency) equivalent to that of direct-plated super-calendered paper; because the emulsion has a core-shell structure and a high content of carboxyl groups, the coating liquid can have a fast drying speed and hardness establishment while ensuring a low film-forming temperature, and can perfectly balance the contradiction between film-forming and anti-sticking in a conventional acrylic resin system; because the system contains a large number of carboxyl groups and has good film-forming properties, it can improve excellent re-solubility and resistance;

[0027] As some specific embodiments, the aqueous acrylic emulsion comprises Wanhua Chemical's 0836, 0837, One or more of 0857.

[0028] In the present invention, the aqueous polyurethane dispersion is an anionic polycarbonate polyurethane and / or an acrylic modified polyurethane dispersion, with a particle size range of 50 to 80 nm, a minimum film forming temperature MFFT of 20 to 70° C., a solid content of 30 to 45%, preferably, an elongation at break of 150 to 450% (e.g., 200%, 250%, 300%, 350%, 400%, etc.), and a 100% modulus of 6 to 12 MPa. The polyurethane dispersion meeting the above conditions has a small particle size, a narrow particle size distribution, and is hard and tough, has good compatibility with acrylic emulsion, and has a rheological curve similar to that of a Newtonian fluid, especially low viscosity under low shear, and no obvious viscosity drop under high shear, which is helpful for the transferability of the coating liquid during the coating process, increases the coating amount of the substrate, and thus improves the coating quality and durability.

[0029] As some specific embodiments, the aqueous polyurethane dispersion comprises Wanhua Chemical's 3920, 0301A, One or more of 6112.

[0030] In the present invention, the wax emulsion is one or more of nonionic polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, and carnauba wax, preferably one or more of polyethylene wax and polypropylene wax, and most preferably one or more of BASF's WAX 26, WAX35, WENGKAIER E801, and E340.

[0031] In the present invention, the defoaming agent is one or more of Tego825 and Tego 1488.

[0032] In the present invention, the wetting agent is one or more of Tego KL245 and Hydropalat WE 3650.

[0033] In the present invention, the film-forming aid is one or more of diethylene glycol methyl ether DPM and ethylene glycol methyl ether PM.

[0034] In the present invention, the quick-drying solvent is one or more of ethanol, isopropanol and isobutanol.

[0035] Another aspect of the present invention provides a method for preparing the vacuum aluminum plating aqueous coating liquid for paper printing, comprising the following steps:

[0036] (1) Deionized water, wax emulsion, film-forming aid, and quick-drying solvent are stirred and mixed at a speed of 500 to 800 r / min, and after premixing, water-based acrylic emulsion and water-based polyurethane dispersion are added, and stirred at a speed of 500 to 800 r / min for 30 to 45 minutes;

[0037] (2) Add a defoaming agent and a wetting agent to the mixture in the above step (1), and stir at a speed of 800 to 1000 r / min for 30 to 45 minutes to obtain a vacuum aluminum plating aqueous coating liquid for paper printing.

[0038] The coating liquid prepared by the present invention has a Zion-3 cup viscosity of 13 to 18 seconds;

[0039] In the present invention, the coating liquid is coated at a high line speed by a gravure printing machine, the dry film coating amount is 2-4 gsm, and vacuum aluminum is plated after baking at 80-120° C. for 10 seconds, the aluminum plating thickness is 30-50 nm, and the final performance is tested.

[0040] The vacuum aluminum plating water-based coating liquid for paper printing of the present invention can obtain high gloss, good aluminum plating effect, wear resistance, anti-adhesion, chemical resistance, solubility, printing adaptability (foaming, knife line, etc.), and environmental protection for the final product. It is suitable for various printing and coating methods, and is particularly suitable for the tobacco and alcohol printing industries that have extremely strict requirements on printing speed, drying speed, wear resistance and anti-adhesion, and aluminum plating appearance.

[0041] The present invention provides a vacuum aluminum plating water-based coating liquid for paper printing, which has the following characteristics:

[0042] Beneficial effects:

[0043] (1) The coating liquid of the present invention mainly uses water as a dispersion medium, and has an extremely low solvent content. Compared with solvent-based coating liquids, the solvent content is reduced by more than 90%; it does not contain benzene solvents, formaldehyde, heavy metals, halogenated hydrocarbons, or alkylphenol polyoxyethylene ether (APEO), and is safe and environmentally friendly. It can not only reduce the environmental emission tax and fee expenditure of enterprises, but also greatly reduce the impact on the environment and harm to the human body, truly realizing the development concept of green, safe, and environmentally friendly.

[0044] (2) Using a specifically selected alkali-soluble acrylic solid resin as a reactive macromolecular rheology control emulsifier, a seed emulsion polymerization method is used to synthesize a core-shell structured styrene acrylic emulsion. The polymerization reaction has better stability and the emulsion rheology is close to that of a Newtonian fluid. After the coating liquid is applied, it can quickly flow on the substrate to wet and fill each fiber of the paper. The resin contains a large number of carboxyl groups that can combine with the paper fibers to form hydrogen bonds. In addition, the emulsion has a narrow particle size distribution and a small particle size. The two work together to obtain a direct plating effect (high gloss and good transparency) equivalent to that of direct-plated super-calendered paper. Because the emulsion has a core-shell structure and a high content of carboxyl groups, it can perfectly balance the contradiction between film formation and anti-sticking in conventional acrylic resin systems.

[0045] (3) The selected polyurethane dispersion has a small particle size and a narrow particle size distribution. It is hard and tough, has good compatibility with acrylic emulsion, and has a rheological curve similar to that of a Newtonian fluid. In particular, it has low viscosity under low shear and does not drop significantly under high shear. This helps to facilitate the transferability of the coating liquid during the coating process and increase the coating amount on the substrate. Under the premise of ensuring the performance requirements such as anti-adhesion and gloss, the coating quality and performance are further improved.

[0046] (4) The coating liquid obtained by the structural design and specific combination of low Tg / high hardness water-based acrylic emulsion and polyurethane dispersion has high gloss and transmittance, good aluminum plating effect, wear resistance, anti-adhesion, chemical resistance, solubility, printing adaptability (foaming, knife line, etc.), heat resistance, and environmental protection, and obtains the same direct plating effect as direct-plated super calendered paper (high gloss and good transmittance). DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and all other embodiments obtained based on the overall concept of the embodiments in the present invention without creative inventions belong to the protection scope of the present invention.

[0048] Gloss: Use a five-angle gloss meter placed on the surface of the aluminum-plated paint film to measure the aluminum-plated gloss, ≥680°.

[0049] Flash index Fi: Use a five-angle gloss meter to test the whiteness of the paint film at various angles, Fi = [2.69 (L15-L110) 1.11 / (L45) 0.85 ], the larger Fi is, the better.

[0050] Water resistance: Use a cotton swab dipped in deionized water to wipe the paint film and see how many times the paint film is damaged, ≥15 times.

[0051] Alcohol resistance: Use a cotton swab dipped in 80% ethanol to wipe the paint film and see how many times the paint film is damaged, ≥5 times.

[0052] Abrasion resistance: Place the dried primer on an abrasion resistance instrument, test it 50 times at 4 pounds of pressure and 85 rpm to see how the paint film wears. Rating and scoring are performed from 1 to 5 (5 is the best and 1 is the worst) based on the degree of wear.

[0053] Anti-adhesion: Place the paint film in an oven at 50°C and 80% humidity, 10kg / cm 2 Press down for 24 hours, observe the adhesion of "coating-coating, coating-substrate", and rate it from 1 to 5 (5 is the best, 1 is the worst) according to the degree of damage.

[0054] Anti-glare: Place the paint film in an oven at 50°C and 80% humidity, 10kg / cm 2 Press down for 24h / 48h, observe the adhesion of "coating-coating, coating-substrate" and gloss change, and rate and score from 1-5 (5 is the best, 1 is the worst) according to the degree of damage and change.

[0055] Resolubility: Drop a drop of the same coating liquid on the dry film, start timing, and then wipe off the ink drop with a dry paper towel after 5 seconds. If there is dried ink that is not completely removed, extend the contact time of the paper towel and the dry film in a gradient of 5 seconds until the ink is completely removed, and record the time used, seconds.

[0056] Alcohol impregnation: prepare 80% ethanol and mix it in the ratio of ethanol: emulsion = 0.2-1:1 to see whether the mixed emulsion breaks, produces slag, cokes, and whether the fineness increases.

[0057] Heat resistance: Use heat sealer to test, set pressure to 300kPa, test temperature 130-180℃, pressing time 1s, change the set temperature to observe whether there is embossing or gloss change on the surface, ≥150℃.

[0058] Folding resistance: Use a paper folding machine to fold the paper 180 degrees and then restore it to its original shape to see if the paint film has any cracks, damage or collapse. If there is no problem with the appearance, it is considered 1 time, ≥ 3 times.

[0059] Printing adaptability: Coat the primer mixture on a paper coating machine at a coating speed of 200-800 m / min to see if there are defects such as shrinkage cavities, exposed coating, and knife lines on the substrate surface.

[0060] Foaming and foam stability: Place the coating liquid in an oscillator and shake it continuously for more than 3 hours. Then take it out and observe the foaming level of the emulsion and place it in a measuring cylinder. Observe the defoaming strength of the ink every 0.5 hours, and rate and score from 1 to 5 (5 is the best, 1 is the worst) based on the foaming and defoaming levels.

[0061] Skinning: Weigh the same mass of emulsion and place it in a constant temperature and humidity room with an open mouth. Test the mass decline rate of the emulsion and the skinning rate on the surface of the emulsion for 24 hours.

[0062] Related raw material information:

[0063] 0836: core Tg = 17 ° C, shell Tg = 120 ° C, core-shell ratio 50 / 50 ~ 70 / 30, particle size 68 ± 5nm, acid value 67mgKOH / g, solid content 40%;

[0064] 0837: core Tg = -17 ° C, shell Tg = 110 ° C, core-shell ratio is 50 / 50 to 70 / 30, acid value is 55 mgKOH / g, particle size is 75nm, solid content is 44%;

[0065] 0857: core Tg = -15°C, shell Tg = 100°C, core-shell ratio 50 / 50~70 / 30, particle size 55±3nm, acid value 25mgKOH / g, solid content 42%.

[0066] 3920: particle size 65nm, solid content: 33%, elongation at break: 400%, 100% modulus: 6.5MPa, MFFT: 23℃

[0067] 0301A: Particle size: 78nm, solid content: 40%, elongation at break: 160-190%, 100% modulus: 7-9MPa, MFFT: 65℃

[0068] 6112: particle size 55nm, solid content: 31%, elongation at break: 165%, 100% modulus: 11MPa, MFFT: 35℃.

[0069] Examples 1 to 5

[0070] The weight parts of the raw materials of Examples 1 to 5 are shown in Table 1 below, and the specific components are shown in Table 2 below:

[0071] Table 1

[0072]

[0073] Table 2

[0074]

[0075]

[0076] According to the formulas provided in Examples 1 to 5, the method for preparing the coating solution of this embodiment comprises the following steps:

[0077] (1) Deionized water, wax emulsion, film-forming aid, and quick-drying solvent are stirred at a speed of 500 to 800 r / min for 30 minutes, and after premixing, water-based acrylic emulsion and water-based polyurethane dispersion are added, and stirred at a speed of 500 to 800 r / min for 30 minutes;

[0078] (2) adding a defoaming agent and a wetting agent to the mixture in the above step (1), stirring at a speed of 800 to 1000 r / min for 30 min to obtain a coating solution;

[0079] (3) The coating liquid is coated at a high line speed by a gravure printing machine, and the dry film coating amount is 2 to 4 gsm. After baking at 100° C. for 10 seconds, vacuum aluminum plating is performed, and the aluminum plating thickness is 20 to 30 nm. The final performance is tested.

[0080] Comparative Example 1

[0081] No water-based acrylic emulsion is used 0836, and the rest is the same as in Example 1.

[0082] Comparative Example 2

[0083] No waterborne polyurethane dispersions are used 6112, and the rest is the same as in Example 2.

[0084] Comparative Example 3

[0085] The aqueous acrylic emulsion in Example 4 was treated with BASF PDX-7339 (Sc=43%, AC=76, MFFT=22°C) was replaced by an equal amount 0837, the rest remains unchanged.

[0086] Comparative Example 4

[0087] The aqueous polyurethane dispersion in Example 2 was treated with Covestro's R3986 (Sc=31%, 100% modulus=10.5-12MPa, elongation at break 150-170%, minimum film forming temperature MFFT=6°C) replaced in equal amounts 6112, the rest remain unchanged.

[0088] The coating liquid in each embodiment / comparative example was tested for performance, and the results are shown in Table 3.

[0089] Table 3 Performance test results of vacuum aluminum plating water-based coating liquid for paper printing

[0090]

[0091] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A coating liquid, characterized in that: It includes the following raw materials in weight percentage:

2. The coating solution according to claim 1, characterized in that The aqueous acrylic emulsion is an aqueous acrylic emulsion with a core-shell structure, with an acid value of 20-70 mgKOH / g and a solid content of 40-50 wt %. Preferably, the core / shell ratio of the aqueous acrylic emulsion is 50 / 50-70 / 30, and the particle size range is 50-80 nm. Preferably, the inner core glass transition temperature Tg is -30-20° C., and the outer shell glass transition temperature Tg is 85-120° C.

3. The coating solution according to any one of claims 1 to 2, characterized in that: The aqueous acrylic emulsion is a styrene-acrylic emulsion with a core-shell structure synthesized by seed emulsion polymerization using a specifically selected alkali-soluble acrylic solid resin as a reactive macromolecular rheology control emulsifier; wherein the specifically selected alkali-soluble acrylic solid resin is a styrene-acrylic resin and / or a maleic anhydride-modified styrene-acrylic resin having an acid value of 200 to 300 mg KOH / g, a molecular weight Mw of 7500 to 16000 g / mol, a molecular weight distribution PDI of 1.4 to 2.0, and a glass transition temperature Tg of 80 to 120°C.

4. The coating solution according to any one of claims 1 to 3, characterized in that: The aqueous acrylic emulsion comprises Wanhua Chemical's 0836, 0837, One or more of 0857.

5. The coating solution according to any one of claims 1 to 4, characterized in that: The aqueous polyurethane dispersion is an anionic polycarbonate polyurethane and / or acrylic modified polyurethane dispersion, with a solid content of 30-45% and a minimum film forming temperature MFFT of 20-70°C; preferably, its particle size range is 50-80nm, the elongation at break is 150-450%, and the 100% modulus is 6-12Mpa.

6. The coating solution according to claim 1 or 5, characterized in that The aqueous polyurethane dispersion comprises Wanhua Chemical's 3920, 0301A, One or more of 6112.

7. The coating solution according to claim 1, wherein The wax emulsion is one or more of nonionic polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, and carnauba wax, preferably one or more of polyethylene wax and polypropylene wax, and most preferably one or more of BASF's WAX 26, WAX35, Wong Kaier E801, and E340.

8. The coating solution according to claim 1, wherein The defoaming agent is one or more of Tego825, Tego 1488, and / or The wetting agent is one or more of Tego KL245, Hydropalat WE 3650, and / or The film-forming aid is one or more of diethylene glycol methyl ether DPM, ethylene glycol methyl ether PM, and / or The quick-drying solvent is one or more of ethanol, isopropanol and isobutanol.

9. A method for preparing the coating solution according to any one of claims 1 to 8, comprising the following steps: (1) mixing deionized water, wax emulsion, film-forming aid, and quick-drying solvent, adding water-based acrylic emulsion and water-based polyurethane dispersion after premixing, and stirring; (2) Add a defoaming agent and a wetting agent to the mixture in step (1), and stir to obtain a coating solution.

10. Use of the coating liquid according to any one of claims 1 to 8 in the printing industry.

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