A kind of water-based polyurethane fluorescent ink and preparation method thereof

Abstract

The present invention relates to the technical field of inks, and discloses a water-based polyurethane fluorescent ink and a preparation method thereof. The water-based polyurethane fluorescent ink comprises the following components by weight: 40-50 parts of water-based polyurethane resin, 20-35 parts of fluorescent pearlescent pigment, 2-3 parts of defoamer, 0.5-2 parts of thickener, and 20-30 parts of deionized water. The ink preparation method comprises first adding water-based polyurethane resin, defoamer and water into a stirring tank and mixing them evenly to obtain an ink premix, then adding fluorescent pearlescent pigment and thickener into the premix, and continuing to stir and mix evenly to obtain an ink premix. The fluorescent pearlescent pigment in the water-based polyurethane fluorescent ink of the present invention can be evenly dispersed in the ink, and has a good fluorescent effect.

Description

Technical Field

[0001] The invention relates to the technical field of inks, and in particular to a water-based polyurethane fluorescent ink and a preparation method thereof. Background Art

[0002] Fluorescent ink is one of the most widely used inks in anti-counterfeiting packaging printing, and one of its main ingredients is fluorescent pigment. Fluorescent pigment is a functional luminescent pigment. The difference from general pigments is that when exposed to external light, including ultraviolet light, it can absorb a certain form of energy and excite photons, releasing the absorbed energy in the form of low visible light, thereby producing fluorescence phenomena of different hues. Different colors of light combine to form extremely bright colors, and when the light stops shining, the luminescence phenomenon disappears, so it is called fluorescent pigment. Fluorescent pigments are mixed with polymer resin binders, solvents and additives, and ground to produce fluorescent ink. This ink, which is invisible to the naked eye, only glows under ultraviolet or infrared light. It is precisely because of its convertible and hidden characteristics and the fact that it cannot be accurately reproduced on a color copier that this ink is widely used in the special printing industry.

[0003] Chinese Patent Publication No. CN104559452 discloses a method for preparing pearlescent ink for printing, which uses a liquid phase deposition method to double-coat titanium dioxide and praseodymium-doped calcium hydroxide on the surface of a mica substrate, and generates a praseodymium-doped calcium titanate fluorescent layer between the two layers after high-temperature calcination to obtain a pearlescent pigment, and then the pearlescent pigment is mixed evenly with an ultraviolet absorber, a light stabilizer, a defoamer, etc. to obtain a fluorescent ink. For example, Chinese Patent Publication No. CN104449030 discloses a solvent-based gravure pearlescent ink and a preparation method thereof, and the ink components include pearlescent pigments, solid resins, ethyl acetate, ethanol, isopropanol, n-propyl acetate, propylene glycol butyl ether, and composite additives, and the composite additives include dispersants, wetting agents, color extenders, and leveling agents. The above combination is mixed to obtain a gravure pearlescent ink. The problem existing in the above fluorescent ink technical solution is that the pearlescent pigment added to the ink is difficult to disperse evenly, and the pearlescent pigment forms agglomerations locally in the ink, affecting the fluorescent effect of the ink. Summary of the invention

[0004] The present invention is to overcome the above problems of the prior art and provide a water-based polyurethane fluorescent ink. The fluorescent pearlescent pigment in the water-based polyurethane fluorescent ink of the present invention can be evenly dispersed in the ink and has a good fluorescent effect.

[0005] The invention also provides a method for preparing the water-based polyurethane fluorescent ink.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] Aqueous polyurethane fluorescent ink comprises the following components in parts by weight:

[0008] 40-50 parts of waterborne polyurethane resin,

[0009] Fluorescent pearlescent pigment 20-35 parts,

[0010] 2-3 parts of defoaming agent,

[0011] Thickener 0.5-2 parts,

[0012] 20-30 parts of deionized water.

[0013] Preferably, the defoaming agent is at least one of polyethylene glycol, polypropylene glycol and polyethylene oxide.

[0014] Preferably, the thickener is at least one of sodium alginate, sodium carboxymethyl cellulose and sodium carboxymethyl starch.

[0015] Preferably, the preparation method of the fluorescent pearlescent pigment comprises the following steps:

[0016] (1) Using fluorphlogopite as raw material, coating the surface of fluorphlogopite with a titanium dioxide layer to obtain mica titanium pearlescent particles;

[0017] (2) mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate, and calcining to obtain praseodymium-doped mica titanium pearlescent particles;

[0018] (3) γ-glycidyloxypropyltrimethoxysilane is grafted onto the surface of praseodymium-doped mica titanium pearlescent particles to obtain fluorescent pearlescent pigments.

[0019] The present invention first coats a titanium dioxide layer on the surface of fluorphlogopite, decomposes calcium nitrate and praseodymium nitrate to generate calcium oxide and praseodymium oxide respectively, and reacts the titanium dioxide on the surface of the fluorphlogopite with the calcium oxide and praseodymium oxide to generate a praseodymium-doped calcium carbonate layer with a fluorescent effect. Meanwhile, the titanium dioxide layer can prevent impurity ions in the mica from entering the fluorescent layer and affecting the fluorescent effect.

[0020] However, when praseodymium-doped mica titanium pearlescent particles with fluorescent effect are mixed into ink, there is a problem that the inorganic praseodymium-doped mica titanium pearlescent particles are easily agglomerated in the aqueous polyurethane ink, affecting the fluorescent effect of the ink. Therefore, the present invention modifies the praseodymium-doped mica titanium pearlescent particles, grafts γ-glycidyloxypropyltrimethoxysilane on the surface of the praseodymium-doped mica titanium pearlescent particles, and makes the surface of the mica titanium pearlescent particles organic, thereby preventing the agglomeration of the praseodymium-doped mica titanium pearlescent particles and improving the fluorescent effect of the ink.

[0021] Preferably, in step (2), the calcination temperature is 600-900° C. and the calcination time is 2-4 hours.

[0022] Preferably, in step (3), the mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is 1:(0.15-0.48).

[0023] The present invention determines through a large number of experiments that the mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is lower than 1:0.15. When the mass ratio of the two is higher than 1:0.15, the grafting amount of γ-glycidyloxypropyltrimethoxysilane on the surface of the praseodymium-doped mica titanium pearlescent particles is too low, and the praseodymium-doped mica titanium pearlescent particles cannot be evenly dispersed in the ink.

[0024] The latest research by the present invention team found that although a certain amount of γ-glycidyloxypropyl trimethoxysilane can improve the dispersion performance of praseodymium-doped mica titanium pearlescent particles in ink, γ-glycidyloxypropyl trimethoxysilane also has a negative impact on the fluorescence effect of the praseodymium-doped mica titanium pearlescent particles themselves. This is because γ-glycidyloxypropyl trimethoxysilane is grafted on the surface of the praseodymium-doped mica titanium pearlescent particles, covering and shielding the fluorescence of the praseodymium-doped calcium carbonate layer on the surface of the praseodymium-doped mica titanium pearlescent particles. The present invention has found that when the mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is higher than 1:0.48, the fluorescence shielding effect of γ-glycidyloxypropyltrimethoxysilane on the praseodymium-doped calcium carbonate layer is weak, which can overcome the fluorescence covering and shielding effect of γ-glycidyloxypropyltrimethoxysilane on the praseodymium-doped calcium carbonate layer. Therefore, the present invention strictly controls the mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane to be higher than 1:0.48.

[0025] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0026] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly to obtain ink premix; add fluorescent pearlescent pigment and thickener into the premix, continue to stir and mix evenly to obtain ink. The present invention has the following beneficial effects:

[0027] (1) The present invention first coats a titanium dioxide layer on the surface of fluorphlogopite, decomposes calcium nitrate and praseodymium nitrate to generate calcium oxide and praseodymium oxide respectively, and reacts the titanium dioxide on the surface of fluorphlogopite with calcium oxide and praseodymium oxide to generate a praseodymium-doped calcium carbonate layer with a fluorescent effect. At the same time, the titanium dioxide layer can prevent impurity ions in the mica from entering the fluorescent layer and affecting the fluorescent effect.

[0028] (2) modifying the praseodymium-doped mica titanium pearlescent particles by grafting γ-glycidyloxypropyltrimethoxysilane on the surface of the praseodymium-doped mica titanium pearlescent particles to make the surface of the mica titanium pearlescent particles organic, thereby preventing the aggregation of the praseodymium-doped mica titanium pearlescent particles and improving the fluorescence effect of the ink;

[0029] (3) The mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is controlled to be higher than 1:0.48. The fluorescence shielding effect of γ-glycidyloxypropyltrimethoxysilane on the praseodymium-doped calcium carbonate layer is weak, which can overcome the fluorescence covering and shielding effect of γ-glycidyloxypropyltrimethoxysilane on the praseodymium-doped calcium carbonate layer. DETAILED DESCRIPTION

[0030] Unless otherwise specified, the raw materials and equipment used in the specific embodiments of the present invention can be purchased from the market or are commonly used in the art. The methods in the embodiments are all conventional methods in the art unless otherwise specified.

[0031] Example 1

[0032] Preparation of fluorescent pearlescent pigments:

[0033] (1) adding fluorphlogopite to deionized water to prepare a suspension with a mass concentration of 8%, adjusting the pH to 2.5, heating to 75° C., stirring evenly, then adding 2 mol / L titanium tetrachloride solution, and at the same time dropping 1 mol / L sodium hydroxide solution to keep the pH value of the reaction system stable, the mass ratio of fluorphlogopite to titanium tetrachloride is 1:0.5, stirring and reacting for 50 minutes, filtering, washing, and drying to obtain mica titanium pearlescent particles;

[0034] (2) Mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate in a mass ratio of 1:0.2:0.05, adding the mixture into anhydrous ethanol in a mass volume ratio of 1 g / 50 mL, stirring and mixing evenly, heating to 100° C., and maintaining for 30 min to obtain a precursor;

[0035] The precursor was placed in a muffle furnace and calcined at 800°C for 3 hours to obtain praseodymium-doped mica titanium pearlescent particles;

[0036] (3) ethanol and water were mixed in a volume ratio of 1:0.3 to form a mixed solution, γ-glycidyloxypropyltrimethoxysilane was added to the mixed solution in a mass ratio of 1:15, the pH was adjusted to 5, and the reaction was stirred for 50 minutes to obtain a hydrolyzate;

[0037] The praseodymium-doped mica titanium pearlescent particles were added to the above hydrolyzate, the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane was controlled to be 1:0.15, the reaction was stirred for 2 hours, and the fluorescent pearlescent pigment was obtained through centrifugal separation, washing and drying.

[0038] A water-based polyurethane fluorescent ink comprises the following components in parts by weight:

[0039] 45 parts of waterborne polyurethane resin,

[0040] 30 parts of fluorescent pearlescent pigment,

[0041] Defoaming agent: 2.5 parts of ethylene glycol,

[0042] Thickener: 1 part sodium alginate,

[0043] 25 parts of deionized water.

[0044] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0045] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly at 1000 r / min to obtain ink premix;

[0046] Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

[0047] Comparative Example 1

[0048] The difference between Comparative Example 1 and Example 1 is that step (3) is missing in the preparation process of the fluorescent pearlescent pigment, and the praseodymium-doped mica titanium pearlescent particles prepared in step (2) are directly added to the ink as the fluorescent pearlescent pigment.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 1 is that the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is 1:0.14.

[0051] Performance Testing

[0052] The ink was placed on filter paper and a sample strip with a thickness of 15 μm was prepared using a wet film preparation apparatus.

[0053] At room temperature and pressure, a fluorescence spectrophotometer was used to test the excitation spectrum of the sample. The gap of the excitation unit was 3 mm, the gap of the emission unit was 5 mm, and a 500 nm filter was added. The measurement range was 230-400 nm for the excitation spectrum.

[0054] The above test results are shown in Table 1:

[0055] Table 1

[0056]

[0057] Example 2

[0058] Preparation of fluorescent pearlescent pigments:

[0059] (1) adding fluorphlogopite to deionized water to prepare a suspension with a mass concentration of 8%, adjusting the pH to 2.5, heating to 75° C., stirring evenly, then adding 2 mol / L titanium tetrachloride solution, and at the same time dropping 1 mol / L sodium hydroxide solution to keep the pH value of the reaction system stable, the mass ratio of fluorphlogopite to titanium tetrachloride is 1:0.5, stirring and reacting for 50 minutes, filtering, washing, and drying to obtain mica titanium pearlescent particles;

[0060] (2) Mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate in a mass ratio of 1:0.2:0.05, adding the mixture into anhydrous ethanol in a mass volume ratio of 1 g / 50 mL, stirring and mixing evenly, heating to 100° C., and maintaining for 30 min to obtain a precursor;

[0061] The precursor was placed in a muffle furnace and calcined at 800°C for 3 hours to obtain praseodymium-doped mica titanium pearlescent particles;

[0062] (3) ethanol and water were mixed in a volume ratio of 1:0.3 to form a mixed solution, γ-glycidyloxypropyltrimethoxysilane was added to the mixed solution in a mass ratio of 1:15, the pH was adjusted to 5, and the reaction was stirred for 50 minutes to obtain a hydrolyzate;

[0063] The praseodymium-doped mica titanium pearlescent particles were added to the above hydrolyzate, the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane was controlled to be 1:0.48, the reaction was stirred for 2 hours, and the fluorescent pearlescent pigment was obtained through centrifugal separation, washing and drying.

[0064] A water-based polyurethane fluorescent ink comprises the following components in parts by weight:

[0065] 40-50 parts of waterborne polyurethane resin,

[0066] Fluorescent pearlescent pigment 20-35 parts,

[0067] Defoaming agent (ethylene glycol, polypropylene glycol, polyethylene oxide) 2-3 parts,

[0068] Thickener (sodium alginate, sodium carboxymethyl cellulose, sodium carboxymethyl starch) 0.5-2 parts, deionized water 20-30 parts.

[0069] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0070] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly at 1000 r / min to obtain ink premix;

[0071] Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

[0072] Comparative Example 3

[0073] The difference between Comparative Example 3 and Example 2 is that the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is 1:0.49.

[0074] Performance Testing

[0075] The ink was placed on filter paper and a sample strip with a thickness of 15 μm was prepared using a wet film preparation apparatus.

[0076] At room temperature and pressure, a fluorescence spectrophotometer was used to test the excitation spectrum of the sample. The gap of the excitation unit was 3 mm, the gap of the emission unit was 5 mm, and a 500 nm filter was added. The measurement range was 230-400 nm for the excitation spectrum.

[0077] The above test results are shown in Table 2:

[0078] Table 2

[0079]

[0080] Example 3

[0081] Preparation of fluorescent pearlescent pigments:

[0082] (1) adding fluorphlogopite to deionized water to prepare a suspension with a mass concentration of 8%, adjusting the pH to 2.5, heating to 75° C., stirring evenly, then adding 2 mol / L titanium tetrachloride solution, and at the same time dropping 1 mol / L sodium hydroxide solution to keep the pH value of the reaction system stable, the mass ratio of fluorphlogopite to titanium tetrachloride is 1:0.5, stirring and reacting for 50 minutes, filtering, washing, and drying to obtain mica titanium pearlescent particles;

[0083] (2) Mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate in a mass ratio of 1:0.2:0.05, adding the mixture into anhydrous ethanol in a mass volume ratio of 1 g / 50 mL, stirring and mixing evenly, heating to 100° C., and maintaining for 30 min to obtain a precursor;

[0084] The precursor was placed in a muffle furnace and calcined at 900°C for 2 hours to obtain praseodymium-doped mica titanium pearlescent particles;

[0085] (3) ethanol and water were mixed in a volume ratio of 1:0.3 to form a mixed solution, γ-glycidyloxypropyltrimethoxysilane was added to the mixed solution in a mass ratio of 1:15, the pH was adjusted to 5, and the reaction was stirred for 50 minutes to obtain a hydrolyzate;

[0086] The praseodymium-doped mica titanium pearlescent particles were added to the above hydrolyzate, the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane was controlled to be 1:0.3, the reaction was stirred for 2 hours, and the fluorescent pearlescent pigment was obtained through centrifugal separation, washing and drying.

[0087] A water-based polyurethane fluorescent ink comprises the following components in parts by weight:

[0088] 50 parts of waterborne polyurethane resin,

[0089] 35 parts of fluorescent pearlescent pigment,

[0090] Defoaming agent: 3 parts of polypropylene glycol,

[0091] Thickener: 2 parts sodium carboxymethyl cellulose,

[0092] 30 parts of deionized water.

[0093] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0094] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly at 1000 r / min to obtain ink premix;

[0095] Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

[0096] Example 4

[0097] Preparation of fluorescent pearlescent pigments:

[0098] (1) adding fluorphlogopite to deionized water to prepare a suspension with a mass concentration of 8%, adjusting the pH to 2.5, heating to 75° C., stirring evenly, then adding 2 mol / L titanium tetrachloride solution, and at the same time dropping 1 mol / L sodium hydroxide solution to keep the pH value of the reaction system stable, the mass ratio of fluorphlogopite to titanium tetrachloride is 1:0.5, stirring and reacting for 50 minutes, filtering, washing, and drying to obtain mica titanium pearlescent particles;

[0099] (2) Mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate in a mass ratio of 1:0.2:0.05, adding the mixture into anhydrous ethanol in a mass volume ratio of 1 g / 50 mL, stirring and mixing evenly, heating to 100° C., and maintaining for 30 min to obtain a precursor;

[0100] The precursor was placed in a muffle furnace and calcined at 600°C for 4 hours to obtain praseodymium-doped mica titanium pearlescent particles;

[0101] (3) ethanol and water were mixed in a volume ratio of 1:0.3 to form a mixed solution, γ-glycidyloxypropyltrimethoxysilane was added to the mixed solution in a mass ratio of 1:15, the pH was adjusted to 5, and the reaction was stirred for 50 minutes to obtain a hydrolyzate;

[0102] The praseodymium-doped mica titanium pearlescent particles were added to the above hydrolyzate, the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane was controlled to be 1:0.3, the reaction was stirred for 2 hours, and the fluorescent pearlescent pigment was obtained through centrifugal separation, washing and drying.

[0103] A water-based polyurethane fluorescent ink comprises the following components in parts by weight:

[0104] 40 parts of waterborne polyurethane resin,

[0105] 20 parts of fluorescent pearlescent pigment,

[0106] Defoamer: 2 parts of polyethylene oxide, thickener: 0.5 parts of sodium carboxymethyl starch,

[0107] 20 parts of deionized water.

[0108] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0109] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly at 1000 r / min to obtain ink premix;

[0110] Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

[0111] Example 5

[0112] Preparation of fluorescent pearlescent pigments:

[0113] (1) adding fluorphlogopite to deionized water to prepare a suspension with a mass concentration of 8%, adjusting the pH to 2.5, heating to 75° C., stirring evenly, then adding 2 mol / L titanium tetrachloride solution, and at the same time dropping 1 mol / L sodium hydroxide solution to keep the pH value of the reaction system stable, the mass ratio of fluorphlogopite to titanium tetrachloride is 1:0.5, stirring and reacting for 50 minutes, filtering, washing, and drying to obtain mica titanium pearlescent particles;

[0114] (2) Mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate in a mass ratio of 1:0.2:0.05, adding the mixture into anhydrous ethanol in a mass volume ratio of 1 g / 50 mL, stirring and mixing evenly, heating to 100° C., and maintaining for 30 min to obtain a precursor;

[0115] The precursor was placed in a muffle furnace and calcined at 700°C for 3 hours to obtain praseodymium-doped mica titanium pearlescent particles;

[0116] (3) ethanol and water were mixed in a volume ratio of 1:0.3 to form a mixed solution, γ-glycidyloxypropyltrimethoxysilane was added to the mixed solution in a mass ratio of 1:15, the pH was adjusted to 5, and the reaction was stirred for 50 minutes to obtain a hydrolyzate;

[0117] The praseodymium-doped mica titanium pearlescent particles were added to the above hydrolyzate, the mass ratio of the praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane was controlled to be 1:0.4, the reaction was stirred for 2 hours, and the fluorescent pearlescent pigment was obtained through centrifugal separation, washing and drying.

[0118] A water-based polyurethane fluorescent ink comprises the following components in parts by weight:

[0119] 45 parts of waterborne polyurethane resin,

[0120] 30 parts of fluorescent pearlescent pigment,

[0121] Defoaming agent: 2.5 parts of polypropylene glycol,

[0122] Thickener: 1 part sodium carboxymethyl cellulose,

[0123] 25 parts of deionized water.

[0124] A method for preparing a water-based polyurethane fluorescent ink comprises the following steps:

[0125] Add waterborne polyurethane resin, defoamer and water into a stirring kettle and mix them evenly at 1000 r / min to obtain ink premix;

[0126] Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

[0127] Performance Testing

[0128] The ink was placed on filter paper and a sample strip with a thickness of 15 μm was prepared using a wet film preparation apparatus.

[0129] At room temperature and pressure, a fluorescence spectrophotometer was used to test the excitation spectrum of the sample. The gap of the excitation unit was 3 mm, the gap of the emission unit was 5 mm, and a 500 nm filter was added. The measurement range was 230-400 nm for the excitation spectrum.

[0130] The above test results are shown in Table 3:

[0131] Table 3

[0132]

[0133] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A water-based polyurethane fluorescent ink, characterized in that: It comprises the following components by weight: 40-50 parts of waterborne polyurethane resin, Fluorescent pearlescent pigment 20-35 parts, 2-3 parts of defoaming agent, Thickener 0.5-2 parts, 20-30 parts of deionized water; The preparation method of the fluorescent pearlescent pigment comprises the following steps: (1) Using fluorphlogopite as raw material, coating the surface of fluorphlogopite with a titanium dioxide layer to obtain mica titanium pearlescent particles; (2) mixing mica titanium pearlescent particles, calcium nitrate and praseodymium nitrate, and calcining to obtain praseodymium-doped mica titanium pearlescent particles; (3) γ-glycidyloxypropyltrimethoxysilane is grafted onto the surface of praseodymium-doped mica titanium pearlescent particles, and the mass ratio of praseodymium-doped mica titanium pearlescent particles to γ-glycidyloxypropyltrimethoxysilane is 1:(0.15-0.48) to obtain a fluorescent pearlescent pigment.

2. The aqueous polyurethane fluorescent ink according to claim 1, characterized in that: The defoaming agent is selected from at least one of polyethylene glycol and polypropylene glycol.

3. The water-based polyurethane fluorescent ink according to claim 1, characterized in that: The thickener is selected from at least one of sodium alginate, sodium carboxymethyl cellulose and sodium carboxymethyl starch.

4. The water-based polyurethane fluorescent ink according to claim 1, characterized in that: In the step (2), the calcination temperature is 600-900° C. and the calcination time is 2-4 hours.

5. A method for preparing the water-based polyurethane fluorescent ink according to any one of claims 1 to 4, characterized in that: The following steps are involved: Adding waterborne polyurethane resin, defoamer and water into a stirring kettle and mixing them evenly to obtain ink premix; Add fluorescent pearlescent pigment and thickener to the premix, continue stirring and mixing evenly to obtain the product.

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