Polyether polyurethane emulsion for UV (ultraviolet) ink-jet digital printing as well as preparation method and application of polyether polyurethane emulsion

Abstract

The invention discloses a polyurethane emulsion for UV (ultraviolet) ink-jet digital printing as well as a preparation method and application of the polyurethane emulsion. The preparation method of the polyether type polyurethane emulsion comprises the following steps: adding polyether polyol, isocyanate, a catalyst and polyfunctional group acrylate into an organic solvent, mixing and uniformly stirring, heating to a first temperature, and stirring for reaction to obtain a polyether type polyurethane solution; and cooling to a second temperature, sequentially adding deionized water, adjusting the pH value, and uniformly mixing to obtain the water-based polyether polyurethane emulsion. The low-polarity polyether polyurethane is selected as a main body material, the polyfunctional group acrylate is introduced to increase the binding force between the ink and the main body, the compatibility among the components can be improved, the leveling property of the UV ink can be improved, a high-quality cured film layer can be formed without additionally adding a leveling agent, the internal stress during UV curing film forming is reduced, and the UV curing film forming quality is improved. Therefore, surface defects such as white points and pinholes caused by shrinkage of film holes in the UV curing process are avoided.

Description

A polyether-type polyurethane emulsion for UV inkjet digital printing, its preparation method and application Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a polyether-type polyurethane emulsion for UV inkjet digital printing, its preparation method, and its application. Background Technology

[0002] Breakthroughs in key label printing technologies, particularly in the areas of the Internet of Things, big data, and digitalization, are driving the industry's intelligent and personalized transformation. The application of digital technology in label printing improves efficiency, saves on plate-making and other processes, and enables customization to meet diverse needs.

[0003] UV inkjet printing is currently the most representative digital printing method. Compared with traditional flexographic printing, UV inkjet printing has more flexible, efficient, and customizable advantages. The number of UV inkjet printer manufacturers is also gradually increasing. The inkjet technology and types of UV inks used by different manufacturers vary greatly, resulting in different printing effects. Commonly used acrylic coatings and polyester polyurethane coatings have low compatibility and are difficult to meet the printing leveling requirements of most devices. Therefore, the universality of printing materials is a great challenge. It is necessary to develop coatings that can meet the needs of most UV inkjet manufacturers on the market, making it easier for users to select materials.

[0004] When using UV inkjet printing ink for label printing, the ink needs to have good adhesion to various label media, and the printed pattern needs to be accurate, especially the label pattern needs to be accurately printed during the rapid printing process. At the same time, the coating quality and stability are also required, and the surface of the printed product should be free of defects such as white spots and pinholes.

[0005] Waterborne polyurethane (WPU) is a class of polymeric synthetic materials with advantages such as wear resistance, corrosion resistance, good low-temperature flexibility, and fatigue resistance. It can be used as an adhesive in footwear, coatings, fabric coatings, and various packaging products. Using water as the dispersion medium, it is non-flammable, environmentally friendly, and has low irritation to the human body. Waterborne polyurethanes with polyether polyols and polyester polyols as the soft segments account for the vast majority of waterborne polyurethanes, and their excellent performance makes them widely used in inkjet printing.

[0006] However, the surface of polyurethane-based UV inkjet printed products currently has defects such as randomly distributed white spots and pinholes, which has always been one of the technical problems that need to be solved in UV inkjet printing coatings. Summary of the Invention

[0007] The main objective of this invention is to provide an aqueous polyether-type polyurethane emulsion for UV inkjet digital printing, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The present invention provides a method for preparing a polyether-type polyurethane emulsion for UV inkjet digital printing, comprising: adding polyether polyol, isocyanate, catalyst, and polyfunctional acrylate to an organic solvent, mixing and stirring evenly, heating to a first temperature and stirring to react, thereby obtaining a polyether-type polyurethane solution; then cooling to a second temperature, sequentially adding deionized water and adjusting the pH and mixing evenly, thereby obtaining an aqueous polyether-type polyurethane emulsion.

[0009] In some specific embodiments, the mass ratio of polyether polyol, isocyanate and polyfunctional acrylate is 40~50:30~45:4.

[0010] In some specific embodiments, the polyether polyol is polypropylene glycol or glycerol polyether.

[0011] In some specific embodiments, the number average molecular weight of the polyether polyol is 1000~3000.

[0012] In some specific embodiments, the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate.

[0013] In some specific embodiments, the catalyst is an organotin catalyst and / or a tertiary amine catalyst.

[0014] In some specific embodiments, the multifunctional acrylate is a trifunctional polyurethane acrylate or a trifunctional methacrylate phosphate.

[0015] Preferably, the multifunctional acrylate is any one of Uniclil R9107, FSP8006, and LuCure8296.

[0016] In some specific embodiments, the aliphatic diisocyanate is at least one selected from 1,6-hexanediisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0017] In some specific embodiments, the aromatic diisocyanate is 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or 4,4'-diphenylmethane diisocyanate.

[0018] In some specific embodiments, the catalyst is dibutyltin dilaurate and / or 1,4-diazabicyclo[2.2.2]octane.

[0019] In some specific embodiments, the first temperature is 60~80℃; the reaction time is 2~3h.

[0020] In some specific embodiments, the second temperature is 40~50°C.

[0021] In some specific embodiments, the organic solvent is acetone or butanone.

[0022] As a second objective of the invention, the present invention also provides a polyether-type polyurethane emulsion for UV inkjet digital printing, which is prepared by the preparation method described above.

[0023] As a third objective of the invention, the present invention also provides a polyurethane-type UV inkjet digital printing coating, which is prepared by a polyether-type polyurethane emulsion water prepared by any one of the preparation methods described in claims 1-7, or printed by a polyether-type polyurethane emulsion as described above.

[0024] Preferably, the coating thickness is 0.5~2μm.

[0025] In some specific embodiments, the preparation of the polyurethane-type UV inkjet digital printing coating includes: coating the polyether-type polyurethane emulsion onto the surface of the substrate using a microgravure coating method, and then drying it at 80-100°C for 20-40 seconds to obtain the polyurethane-type UV inkjet digital printing coating.

[0026] As a fourth objective of the invention, the present invention also provides a label that is printed on the surface of a substrate using a polyether-type polyurethane emulsion as described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention selects polyether-type polyurethane with low polarity as the main material of the emulsion, and introduces an appropriate amount of polyfunctional acrylate to increase the bonding force between the ink and the main body, while also improving the compatibility between components and increasing the leveling of UV ink. High-quality cured film can be obtained without the need to add additional leveling agent, and the internal stress during UV curing film formation is reduced, thereby avoiding surface defects such as white spots and pinholes caused by film pore shrinkage during UV curing.

[0028] 2. The polyether-type polyurethane emulsion provided by this invention has a simple composition, including only polyether polyol, isocyanate, catalyst, and polyfunctional acrylate. It has extremely strong stability in use, is compatible with existing UV inkjet printing equipment on the market, dries quickly, avoids printing failures, and avoids problems such as agglomeration and delamination caused by complex composition. It is also compatible with a variety of printers, which not only reduces production costs but also makes it suitable for large-scale promotion and application. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 is a photograph of the polyurethane UV inkjet digital printing coating provided in Embodiment 1 of the present invention.

[0031] Figure 2 is a cross-cut test photograph of the polyurethane UV inkjet digital printing coating provided in Embodiment 1 of the present invention.

[0032] Figure 3 is a photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 1 of the present invention.

[0033] Figure 4 is a cross-cut test photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 1 of the present invention.

[0034] Figure 5 is a photograph of the polyurethane-type UV inkjet digital printing coating provided in Comparative Example 6 of the present invention.

[0035] Figure 6 is a photograph of the polyurethane-type UV inkjet digital printing coating provided in Comparative Example 3 of the present invention.

[0036] Figure 7 is a photograph of the polyurethane-type UV inkjet digital printing coating provided in Comparative Example 4 of the present invention. Detailed Implementation

[0037] The invention will be more fully understood through the following detailed description, read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein. However, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0038] This invention provides a polyurethane-based UV inkjet digital printing coating, which comprises polyether polyol, isocyanate, catalyst, multifunctional acrylate, acetone, neutralizing agent, and deionized water.

[0039] By weight, the polyurethane-type UV inkjet digital printing coating comprises 40-50 parts of polyether polyol, 30-45 parts of isocyanate, 0.03-0.1 parts of catalyst, 2-6 parts of polyfunctional acrylate, 30-45 parts of acetone, 1-2 parts of neutralizer, and 70-90 parts of deionized water.

[0040] The present invention also provides a method for preparing the above-mentioned polyurethane-type UV inkjet digital printing coating, comprising the following steps: 1) mixing 40-50 parts of polyether polyol, 30-45 parts of isocyanate, 4-6 parts of chain extender, 0.03-0.1 parts of catalyst, 2-6 parts of polyfunctional acrylate, and 30-45 parts of acetone evenly, heating to 60-80℃ and stirring for 2-3 hours to obtain a polyether-type polyurethane solution; 2) cooling to 40-50℃, and sequentially adding 1-2 parts of neutralizer, 70-90 parts of deionized water, and 3-5 parts of tackifier to obtain an aqueous polyether-type polyurethane emulsion; 3) coating the aqueous polyether-type polyurethane emulsion obtained in step 2) onto the surface of the substrate film after corona treatment using a microgravure coating method, and then drying at 80-100℃ for 20-40 seconds to obtain a polyurethane-type UV inkjet digital printing coating; further, the thickness of the polyurethane-type UV inkjet digital printing coating in step 3) is 0.5-2 μm.

[0041] As one of the preferred embodiments, the number average molecular weight of the polyether polyol is 1000~3000.

[0042] Preferably, the isocyanate is either IPDI or HMDI.

[0043] Preferably, the catalyst is either DBTDL or DABCO.

[0044] Preferably, the multifunctional acrylate is any one of Uniclil R9107, FSP8006, and LuCure8296.

[0045] Preferably, the neutralizing agent is any one of triethylamine, sodium hydroxide, or ammonia.

[0046] Furthermore, the thickness of the polyurethane-type UV inkjet digital printing coating is 0.5~2.0μm.

[0047] The technical solution of the present invention will be described in detail below through specific embodiments.

[0048] Example 1

[0049] This embodiment provides a method for preparing a polyurethane-based UV inkjet digital printing coating. The specific steps include: 1. Mixing and stirring 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 4 parts of trifunctional phosphate methacrylate Uniclil R9107, and 40 parts of acetone until homogeneous. Heating and stirring at 70°C for 2.5 hours yields a polyether-based polyurethane solution; 2. Cooling to 45°C, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0-8.5, yields an aqueous polyether-based polyurethane emulsion; 3. Coating the above aqueous polyether-based polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, followed by drying at 90°C for 30 seconds to obtain a polyurethane-based UV inkjet digital printing coating with a thickness of 1 μm.

[0050] Example 2

[0051] 1. Mix 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate HMDI, 0.05 parts of catalyst DBTDL, 4 parts of trifunctional polyurethane resin LuCure8296, and 40 parts of acetone until homogeneous. Heat to 70℃ and stir for 2.5 hours to obtain a polyether polyurethane solution. 2. Cool to 45℃, add 80 parts of deionized water, and then add triethylamine to adjust the pH to 7.0~8.5 to obtain an aqueous polyether polyurethane emulsion. 3. Coat the above aqueous polyether polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, and then dry at 90℃ for 30 seconds to obtain a polyurethane UV inkjet digital printing coating with a coating thickness of 1μm.

[0052] Example 3

[0053] 1. Mix 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 4 parts of trifunctional polyurethane acrylate FSP8006, and 40 parts of acetone until homogeneous. Heat to 70℃ and stir for 2.5 hours to obtain a polyether polyurethane solution. 2. Cool to 45℃, add 80 parts of deionized water, and then add triethylamine to adjust the pH to 7.0~8.5 to obtain an aqueous polyether polyurethane emulsion. 3. Coat the above aqueous polyether polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, and then dry at 90℃ for 30 seconds to obtain a polyurethane UV inkjet digital printing coating with a thickness of 1 μm.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing a polyurethane-based UV inkjet digital printing coating. The specific steps include: 1. Mixing 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, and 40 parts of acetone until homogeneous, heating to 70℃ and stirring for 2.5 hours to obtain a polyether-based polyurethane solution; 2. Cooling to 45℃, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0~8.5 to obtain an aqueous polyether-based polyurethane emulsion; 3. Coating the above aqueous polyether-based polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, and then drying at 90℃ for 30 seconds to obtain a polyurethane-based UV inkjet digital printing coating; the coating thickness is 1 μm.

[0056] Comparative Example 2

[0057] This comparative example provides a method for preparing a polyurethane-type UV inkjet digital printing coating. The specific steps include: 1. Mixing and stirring 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 2 parts of trifunctional phosphate methacrylate Uniclil R9107, and 40 parts of acetone until homogeneous. Heating and stirring at 70°C for 2.5 hours yields a polyether-type polyurethane solution; 2. Cooling to 45°C, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0-8.5, yields an aqueous polyether-type polyurethane emulsion; 3. Coating the above aqueous polyether-type polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, followed by drying at 90°C for 30 seconds to obtain a polyurethane-type UV inkjet digital printing coating with a thickness of 1 μm.

[0058] Comparative Example 3

[0059] This comparative example provides a method for preparing a polyurethane-type UV inkjet digital printing coating. The specific steps include: 1. Mixing and stirring 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 6 parts of trifunctional phosphate methacrylate Uniclil R9107, and 40 parts of acetone until homogeneous. Heating and stirring at 70°C for 2.5 hours yields a polyether-type polyurethane solution; 2. Cooling to 45°C, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0-8.5, yields an aqueous polyether-type polyurethane emulsion; 3. Coating the above aqueous polyether-type polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, followed by drying at 90°C for 30 seconds to obtain a polyurethane-type UV inkjet digital printing coating with a thickness of 1 μm.

[0060] Comparative Example 4

[0061] This comparative example provides a method for preparing a polyurethane-based UV inkjet digital printing coating. The specific steps include: 1. Mixing 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 4 parts of hydroxyethyl methacrylate phosphate HEMAP, and 40 parts of acetone until homogeneous. Heating and stirring at 70°C for 2.5 hours yields a polyether-based polyurethane solution; 2. Cooling to 45°C, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0-8.5, yields an aqueous polyether-based polyurethane emulsion; 3. Coating the above aqueous polyether-based polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, followed by drying at 90°C for 30 seconds to obtain a polyurethane-based UV inkjet digital printing coating with a thickness of 1 μm.

[0062] Comparative Example 5

[0063] This comparative example provides a method for preparing a polyurethane-type UV inkjet digital printing coating. The specific steps include: 1. Mixing 45 parts of polyether polyol PPG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 4 parts of tripropylene glycol diacrylate, and 40 parts of acetone until homogeneous. Heating and stirring at 70°C for 2.5 hours yields a polyether-type polyurethane solution; 2. Cooling to 45°C, adding 80 parts of deionized water, and then adding triethylamine to adjust the pH to 7.0-8.5, yields an aqueous polyether-type polyurethane emulsion; 3. Coating the above aqueous polyether-type polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, followed by drying at 90°C for 30 seconds to obtain a polyurethane-type UV inkjet digital printing coating with a thickness of 1 μm.

[0064] Comparative Example 6

[0065] 1. Mix 45 parts of polyester polyol (polyethylene adipate) AA / EG-2000, 40 parts of isocyanate IPDI, 0.05 parts of catalyst DBTDL, 4 parts of trifunctional phosphate methacrylate Uniclil R9107, and 40 parts of acetone until homogeneous. Heat to 70℃ and stir for 2.5 hours to obtain a polyether-type polyurethane solution. 2. Cool to 45℃, add 80 parts of deionized water, and then add triethylamine to adjust the pH to 7.0~8.5 to obtain an aqueous polyether-type polyurethane emulsion. 3. Coat the above aqueous polyether-type polyurethane emulsion onto the surface of a corona-treated substrate film (PP) using a microgravure coating method, and then dry at 90℃ for 30 seconds to obtain a polyurethane-type UV inkjet digital printing coating with a coating thickness of 1μm.

[0066] The polyether-type polyurethane emulsions prepared in the above examples and comparative examples were printed using a SCREENTruepress Jet L350UV SAI series UV inkjet label printing system to obtain a series of label products.

[0067] Referring to Figure 1, which is a photograph of the polyurethane UV inkjet digital printing coating provided in Embodiment 1 of the present invention, the coating surface is smooth and flat without white spots or pinholes, and has good leveling properties and excellent color.

[0068] Referring to Figure 2, which shows the results of a cross-cut test on the polyurethane UV inkjet digital print coating provided in Example 1, as can be seen, the edges of the squares after the cross-cut test are completely smooth, with no coating peeling off, which meets the 5B standard of ISO 2409-2020.

[0069] Referring to Figure 3, which is a photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 1 of the present invention, the coating surface is smooth and flat, but there are obvious white spots and pinholes.

[0070] Referring to Figure 4, the results of the cross-cut test of the polyurethane UV inkjet digital printing coating provided in Comparative Example 1 are shown in the figure. After the grid is drawn, large areas of the edges of the squares are peeled off, and the peeling area is between 35% and 65% (1B).

[0071] Referring to Figure 5, which is a photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 6, as can be seen, the coating surface has poor leveling properties, is uneven, and has visible white spots and pinholes; obviously, the effect of using polyether polyol and multifunctional acrylate is significantly better than that of polyester polyol.

[0072] Referring to Figure 6, which shows a photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 3, and Figure 7, which shows a photograph of the polyurethane UV inkjet digital printing coating provided in Comparative Example 4, it can be seen that obvious white spots and pinholes are visible on the coating surface, indicating poor leveling. When the proportion of added multifunctional acrylate is too high, the leveling performance of the coating cannot meet the requirements, and defects such as white spots appear on the surface. When an equal amount of hydroxyethyl methacrylate phosphate is added as in Example 1, the leveling performance of the emulsion is significantly lower than that of the multifunctional acrylate. Furthermore, the surface of the polyether polyurethane obtained by using monofunctional acrylate has obvious white spots. This is because the high acid value and high proportion of polar groups of hydroxyethyl methacrylate directly lead to an increase in the surface energy of the coating prepared using it, thereby reducing the leveling performance of the emulsion and the adhesion to the surface material.

[0073] Referring to Tables 1 and 2, which show the performance comparison results of the coatings in the embodiments and comparative examples of the present invention, it can be seen from the results shown in the tables that the polyether-type acrylate emulsion generated by the trifunctional group and polyether polyol of the present invention has both leveling properties, high adhesion and good surface tension.

[0074] Table 1. Performance data of coatings obtained from the examples and comparative examples.

[0075] Table 2 Performance data of coatings obtained from the examples and comparative examples

[0076] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this document is not intended to limit the invention to the specific embodiments disclosed for carrying out the invention, but rather to include all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a polyether-type polyurethane emulsion for UV inkjet digital printing, characterized in that, include: Polyether polyol, isocyanate, catalyst, and multifunctional acrylate are added to an organic solvent, mixed and stirred until homogeneous. The mixture is then heated to a first temperature and stirred to carry out the reaction, resulting in a polyether polyurethane solution. The solution is then cooled to a second temperature, and deionized water is added sequentially to adjust the pH and mix until homogeneous, thus obtaining an aqueous polyether polyurethane emulsion.

2. The preparation method according to claim 1, characterized in that, The mass ratio of polyether polyol, isocyanate, and polyfunctional acrylate is 40~50:30~45:

4.

3. The preparation method according to claim 1, characterized in that, The polyether polyol is polypropylene glycol or glycerol polyether; and / or, the number average molecular weight of the polyether polyol is 1000~3000; and / or, the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate; and / or, the catalyst is an organotin catalyst and / or a tertiary amine catalyst.

4. The preparation method according to claim 3, characterized in that, The aliphatic diisocyanate is at least one selected from 1,6-hexanediisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; and / or, the aromatic diisocyanate is 2,4-toluenediisocyanate, 2,6-toluenediisocyanate, or 4,4'-diphenylmethane diisocyanate; and / or, the catalyst is dibutyltin dilaurate and / or 1,4-diazabicyclo[2.2.2]octane.

5. The preparation method according to claim 1, characterized in that, The multifunctional acrylate is a trifunctional polyurethane acrylate or a trifunctional methacrylate phosphate; preferably, the multifunctional acrylate is any one of Uniclil R9107, FSP8006, and LuCure8296.

6. The preparation method according to claim 1, characterized in that, The first temperature is 60~80℃; the reaction time is 2~3h; and / or, the second temperature is 40~50℃; and / or, the organic solvent is acetone or butanone.

7. A polyether-type polyurethane emulsion for UV inkjet digital printing, prepared by the preparation method according to any one of claims 1-6.

8. A polyurethane-type UV inkjet digital printing coating, prepared by the preparation method according to any one of claims 1-6, or printed by the polyether-type polyurethane emulsion according to claim 7; the coating thickness is 0.5~2μm.

9. The polyurethane-based UV inkjet digital printing coating according to claim 8, characterized in that, The process involves coating the polyether-type polyurethane emulsion onto the surface of a substrate using a microgravure coating method, and then drying it at 80–100°C for 20–40 seconds to obtain the polyurethane-type UV inkjet digital printing coating.

10. A label, obtained by printing a polyether-type polyurethane emulsion prepared by any one of the preparation methods of claims 1-6, or by printing a polyether-type polyurethane emulsion as described in claim 7 onto the surface of a substrate.

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