Tough double-wavelength fluorescent security paper and preparation method and application thereof

Abstract

The application discloses strong and tough double-wavelength fluorescent anti-fake paper as well as a preparation method and application thereof, belongs to the field of nanofiber and rare earth functional materials, and utilizes multi-element composite aramid nanofiber and lanthanide metal organic framework to prepare the strong and tough double-wavelength fluorescent anti-fake paper through a wet papermaking process, so that the production process is simple and feasible, and problems such as poor paper evenness, poor interface combination, low mechanical strength and single fluorescent anti-fake performance of cellulose-based anti-fake paper caused by doping fluorescent fiber are avoided; the prepared anti-fake paper has the characteristics of high mechanical strength, high evenness and double-wavelength emission light switch, can effectively improve the durability and safety of the anti-fake paper, is suitable for senior fluorescent anti-fake under naked eye vision, and can be applied to securities paper, banknote paper and other special paper needing anti-fake technology in the papermaking industry, so that the application of high-performance nanofiber in the field of special paper is expanded.

Description

Technical Field

[0001] The present invention belongs to the field of nanofibers and rare earth functional materials, and in particular relates to a strong and tough dual-wavelength fluorescent anti-counterfeiting paper and a preparation method and application thereof. Background Art

[0002] Currently, fluorescent security paper is a commonly used anti-counterfeiting material. Its ease of use and easy identification make it widely used in banknotes, securities, certificates, and anti-counterfeiting packaging. However, traditional fluorescent security paper is made from plant fibers. Due to the inherent properties of plant fibers, cellulose-based paper often suffers from poor thermal stability, insufficient flexibility, and low folding resistance. Furthermore, most existing security papers are produced by adding functionally modified synthetic fibers during the papermaking process. These synthetic fibers are primarily composed of a mixture of fluorescent powder and polymers, such as polypropylene, polyethylene, and polyester. Due to the long length of these synthetic fibers, they are difficult to disperse in water. Therefore, they easily flocculate and clump during the papermaking process, hindering the dispersion of the plant fibers in water and resulting in poor paper uniformity. Most synthetic fibers have a smooth surface and a low degree of fibrillation, which results in poor fiber entanglement and reduced paper strength. Furthermore, traditional single-mode luminescent materials can only produce a single color of light under a single excitation mode, making them easily replicable and difficult to meet effective anti-counterfeiting requirements. Therefore, there is an urgent need to develop high-performance plant fiber-based fluorescent anti-counterfeiting paper with excellent mechanical strength, uniformity and multi-mode luminescence to improve product quality and meet the requirements of high-end applications. Summary of the Invention

[0003] The present invention aims to provide a strong and resilient dual-wavelength fluorescent anti-counterfeiting paper, its preparation method, and its application, to overcome the problems of poor uniformity, low mechanical strength, and limited anti-counterfeiting properties of conventional anti-counterfeiting paper. This paper, based on plant fibers, employs multi-component composite aramid nanofibers and a lanthanide metal-organic framework to produce a strong and resilient dual-wavelength fluorescent anti-counterfeiting paper. The papermaking industry has the potential to apply this technology to specialty papers requiring anti-counterfeiting technology, such as security paper and banknote paper.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper comprises the following steps:

[0006] S1: fiber slurry preparation; dispersing aramid nanofibers and plant fibers in water, and obtaining an aramid nanofiber / plant fiber mixed slurry by stirring and dispersing;

[0007] S2: in situ deposition; adding a lanthanide metal nitrate to the aramid nanofiber / plant fiber mixed slurry, adding an ethanol solution of pyromellitic acid after stirring to react, and in situ depositing a lanthanide metal organic framework on the fiber surface of the aramid nanofiber / plant fiber mixed slurry, finally obtaining an aramid nanofiber / plant fiber mixed slurry after in situ deposition;

[0008] S3: wet forming; filtering the in-situ deposited aramid nanofiber / plant fiber mixed slurry, pressing and drying it to obtain a strong and tough dual-wavelength fluorescent anti-counterfeiting paper.

[0009] Furthermore, in S1, a total of 2 g or 3 g of the aramid nanofiber and the plant fiber are added to every 150 mL of water, and the mass ratio of the aramid nanofiber to the plant fiber is (2-10): (90-98).

[0010] Furthermore, in S1, the mass concentration of the aramid nanofiber / plant fiber mixed slurry is 1% to 2%.

[0011] Furthermore, in S2, the lanthanide metal nitrate is Eu(NO3)3.6H2O.

[0012] Furthermore, in S2, the molar ratio of the lanthanide metal nitrate to the pyromellitic acid is 1:2, and each 50 mL of ethanol solution contains 2 mmol to 6 mmol of pyromellitic acid.

[0013] Furthermore, in S2, the stirring time is 0.5h to 1h, the reaction time is 3h to 5h, and the reaction temperature is 35°C to 40°C.

[0014] Furthermore, in S3, the pressing pressure is 0.4 MPa and the pressing time is 3 min to 5 min.

[0015] Furthermore, in S3, the vacuum pressure of the drying is -0.1 MPa, the temperature is 85°C to 105°C, and the time is 5 minutes to 8 minutes.

[0016] A strong and tough dual-wavelength fluorescent anti-counterfeiting paper is obtained by adopting the above-mentioned preparation method of the strong and tough dual-wavelength fluorescent anti-counterfeiting paper.

[0017] The invention discloses an application of strong and tough dual-wavelength fluorescent anti-counterfeiting paper in banknotes, securities, certificates and anti-counterfeiting packaging materials.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper. Utilizing aramid nanofibers with a unique nanoscale structure, high strength and modulus, high specific surface area, high aspect ratio, excellent temperature resistance, and wet strength as cellulose reinforcement, the method overcomes the shortcomings of traditional anti-counterfeiting paper, such as hygroscopicity, poor thermal stability, and aging. The present invention not only significantly improves the mechanical strength of anti-counterfeiting paper but also solves the problem of poor paper uniformity caused by traditional fluorescent synthetic fibers, thus offering broad application prospects. The present invention in situ deposits a lanthanide metal-organic framework on the fiber surface of an aramid nanofiber / plant fiber mixed slurry. The bridging and filling effects of the aramid nanofibers facilitate fiber entanglement and fill the interfiber pores. The film-like coating structure formed on the fiber surface also facilitates the adhesion of the lanthanide metal-organic framework, thereby enhancing the stability of the material.

[0020] The present invention provides a strong and tough dual-wavelength fluorescent anti-counterfeiting paper, which is prepared by multi-component composite aramid nanofibers and lanthanide metal organic frameworks. The composite paper has high mechanical strength, high forming uniformity and optical switching characteristics of dual-wavelength emission, overcoming the shortcomings of traditional anti-counterfeiting paper based on fluorescent fibers, such as low mechanical strength, poor uniformity and single fluorescent anti-counterfeiting performance, and has broad application prospects.

[0021] The present invention provides an application for strong and tough dual-wavelength fluorescent anti-counterfeiting paper. This fluorescent anti-counterfeiting paper is a composite paper made from multi-component composite aramid nanofibers and a lanthanide metal-organic framework. This composite paper can act as a photoelectric switch, switching the color of light emitted at different wavelengths (red light emission at an excitation wavelength of 254nm and green light emission at 365nm). The prepared composite specialty paper exhibits the optical switching properties of dual-wavelength emission, making it suitable for advanced fluorescent anti-counterfeiting under naked-eye vision. It can be applied to specialty papers requiring anti-counterfeiting technology in the papermaking industry, such as security paper, banknote paper, documents, and anti-counterfeiting packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 This is the SEM image of the fluorescent anti-counterfeiting paper of Example 5 of the present invention.

[0024] Figure 2 This is a photoluminescence image of the fluorescent anti-counterfeiting paper according to Example 5 of the present invention. DETAILED DESCRIPTION

[0025] The content of the present invention is described in further detail below:

[0026] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper comprises the following steps:

[0027] Step 1: Disperse aramid nanofibers and plant fibers in water and obtain an aramid nanofiber / plant fiber aqueous dispersion by sufficient dispersing. The aramid nanofibers are colloidal para-aramid nanofibers with a diameter of 56±10 nm. The plant fibers are made from either a needlewood pulp board or a cotton pulp board. After refining and dilution and dispersion in a pulping machine, a slurry with a beating degree of 50°SR to 60°SR is obtained; the mass concentration of the diluted slurry dispersion is 1% to 2%. The mass ratio of the aramid nanofibers to the plant fibers is (2-10):(90-98).

[0028] Step 2: Add lanthanide metal nitrate to the dispersion of step 1, continue to add ethanol solution of pyromellitic acid (H4BTC), and continue stirring to in situ deposit lanthanide metal organic framework on the fiber surface. The lanthanide metal nitrate is Eu(NO3)3.6H2O, stir for 0.5h~1h, and allow Eu to 3+ The ions are evenly distributed in the suspension. The molar ratio of Eu(NO3)3.6H2O to H4BTC is always 1:2. An ethanol solution of pyromellitic acid (H4BTC) is added to the suspension and allowed to react for 3 to 5 hours. The dispersion is reacted at 35°C to 40°C. After completion of the reaction, the final product is thoroughly rinsed with 1L of deionized water to remove any unreacted reagents.

[0029] Step 3: Pour the slurry dispersed in Step 2 into the forming barrel of the sheeting machine. After filtering the water, filter it on a forming screen and form it. Then, press and dry it to obtain strong and tough dual-wavelength fluorescent anti-counterfeiting paper. When pressing the wet paper web, the pressure is 0.4MPa and the time is 3-5 minutes. The vacuum pressure during drying is -0.1MPa, the temperature is 85-105℃, and the drying time is 5-8 minutes.

[0030] Below in conjunction with embodiment, the present invention is described in further detail, it should be noted that, when not conflicting, the raw material ratios in the embodiment in the present application and the embodiment can be combined with each other. All technical terms adopted in the present invention are identical with the commonly understood implication of those skilled in the art of the application. The term used in the present invention is only to describe specific embodiments, and is not intended to limit the exemplary embodiments according to the present invention.

[0031] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper is disclosed. The method uses softwood fiber or cotton fiber as a substrate, and wet-laid papermaking using a multi-component composite of aramid nanofibers and a lanthanide metal-organic framework. The mass ratio of aramid nanofiber to cellulose fiber is (2-10):(90-98). The raw materials are then slurried, in-situ deposited, and wet-laid to form a strong and tough dual-wavelength fluorescent anti-counterfeiting paper.

[0032] A method for preparing a strong and tough dual-wavelength fluorescent security paper, comprising the following steps:

[0033] (1) Fiber pulp preparation: a certain amount of aramid nanofiber and plant fiber is dispersed in water, wherein the mass ratio of aramid nanofiber is between 2 and 10 parts, and the mass ratio of plant fiber is between 90 and 98 parts; after stirring and dispersing for 5000r-10000r, a mixed pulp of aramid nanofiber / plant fiber with a mass concentration of 1%-2% is obtained.

[0034] (2) In-situ deposition: Eu(NO3)3.6H2O is added to the pulp prepared in (1) and stirred for 0.5h-1h, so that Eu 3+ ions are uniformly distributed in the suspension. An ethanol solution of benzene-1, 2, 4, 5-tetracarboxylic acid (H4BTC) is added to the suspension and reacted for 3h-5h at a reaction temperature of 35°C-40°C. The molar ratio of Eu(NO3)3.6H2O to H4BTC is always 1:2. After the reaction is completed, the final product is washed thoroughly with 1L deionized water to remove the reagents that do not participate in the reaction.

[0035] (3) Wet forming: the pulp dispersed well in (2) is poured into the forming barrel of a sheet former, filtered and formed on a 200-mesh screen, then placed in a press for 3min-5min under a pressure of 0.4MPa, and then placed in a vacuum dryer for drying treatment, with a vacuum pressure of -0.1MPa, a temperature of 85°C-105°C, and a drying time of 5min-8min, to obtain a strong and tough dual-wavelength fluorescent security paper, which is a multi-element composite fluorescent security paper.

[0036] Example 1

[0037] A method for preparing a strong and tough dual-wavelength fluorescent security paper, which uses coniferous wood fiber as a substrate and multi-element composite aramid nanofiber and lanthanide metal organic framework to perform wet papermaking, wherein the mass ratio of aramid nanofiber to coniferous wood fiber is 2:98. The raw materials are processed through fiber pulp preparation, in-situ deposition, and wet forming to obtain a strong and tough dual-wavelength fluorescent security paper.

[0038] A strong and tough dual-wavelength fluorescent security paper and a method for preparing the same, comprising the following steps:

[0039] (1) Fiber pulp preparation: a certain amount of aramid nanofiber and coniferous wood fiber is dispersed in 150ml water, wherein the mass of aramid nanofiber is 0.04g and the mass of coniferous wood fiber is 1.96g; after stirring and dispersing for 5000r-10000r, a mixed pulp of aramid nanofiber / coniferous wood fiber with a mass concentration of 1.3% is obtained.

[0040] (2) In-situ deposition: Add 1 mmol (0.446 g) of Eu(NO3)3.6H2O to the slurry prepared in step (1) and stir for 1 h to allow Eu to 3+ The ions are evenly distributed throughout the suspension. Add 50 ml of an ethanol solution containing 2 mmol (0.50 g) of pyromellitic acid (H4BTC) to the suspension and allow the reaction to proceed for 4 hours at 40°C. After the reaction, thoroughly rinse the final product with 1 L of deionized water to remove any unreacted reagents.

[0041] (3) Wet forming: Pour the slurry stirred and dispersed in step (2) into the forming barrel of the sheet making machine, filter the water and form it on a 200-mesh screen, put it into a press and press it at a pressure of 0.4 MPa for 3 minutes, then put it into a vacuum dryer for drying at a vacuum pressure of -0.1 MPa, a temperature of 85°C, and a drying time of 6 minutes to obtain a multi-component composite fluorescent anti-counterfeiting paper.

[0042] Example 2

[0043] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper is described. Using cotton fiber as a substrate, a multi-component composite of aramid nanofibers and a lanthanide metal-organic framework is wet-laid to form paper. The mass ratio of aramid nanofiber to cotton fiber is 3:97. The raw materials are then slurried, in-situ deposited, and wet-laid to form the paper.

[0044] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper comprises the following steps:

[0045] (1) Fiber slurry preparation: a certain mass of aramid nanofiber and cotton fiber is dispersed in 150 ml of water, wherein the mass of aramid nanofiber is 0.06 g and the mass of cotton fiber is 1.94 g; after stirring and dispersing for 5000 r to 10000 r, an aramid nanofiber / cotton fiber mixed slurry with a mass concentration of 1.3% is obtained.

[0046] (2) In-situ deposition: Add 3 mmol (1.338 g) of Eu(NO3)3.6H2O to the slurry prepared in step (1) and stir for 1 h to allow Eu to 3+ The ions are evenly distributed in the suspension. Add 50 ml of an ethanol solution containing 6 mmol (1.50 g) of pyromellitic acid (H4BTC) to the suspension and allow the reaction to proceed for 3 hours at 35°C. After the reaction, thoroughly rinse the final product with 1 L of deionized water to remove any unreacted reagents.

[0047] (3) Wet forming: the well-stirred slurry in step (2) was poured into the forming barrel of the sheet former, filtered and formed on a 200-mesh screen, placed in a press using a pressure of 0.4 MPa for 3 min, and then placed in a vacuum dryer for drying treatment, with a vacuum pressure of -0.1 MPa, a temperature of 105°C, and a drying time of 8 min, to obtain the multi-component composite fluorescent security paper.

[0048] Example 3

[0049] A kind of strong and tough dual-wavelength fluorescent security paper is prepared, a kind of strong and tough dual-wavelength fluorescent security paper is prepared method, with cotton fiber as substrate, multi-component composite aramid nanofiber and lanthanide metal organic framework are wet papermaking, wherein the mass ratio of aramid nanofiber and cotton fiber is 5:95. Raw materials are obtained by fiber slurry preparation, in-situ deposition and wet forming, etc. A kind of strong and tough dual-wavelength fluorescent security paper.

[0050] A kind of strong and tough dual-wavelength fluorescent security paper is prepared method, comprising the following steps:

[0051] (1) Fiber slurry preparation: a certain mass of aramid nanofiber and cotton fiber are dispersed in 150 ml of water, wherein the mass of aramid nanofiber is 0.15 g and the mass of cotton fiber is 2.85 g; after stirring and dispersing for 5000 r to 10000 r, a mixed slurry of aramid nanofiber / cotton fiber with a mass concentration of 2% is obtained.

[0052] (2) In-situ deposition: 2.5 mmol (1.115 g) of Eu(NO3)3.6H2O is added to the slurry prepared in step (1) and stirred for 1 h, so that Eu 3+ ions are uniformly distributed in the suspension. 50 ml of an ethanol solution containing 5 mmol (1.25 g) of benzene-1,4-dicarboxylic acid (H4BTC) is added to the suspension and reacted for 5 h at a reaction temperature of 40°C. After the reaction is completed, the final product is washed thoroughly with 1 L of deionized water to remove the reagents that do not participate in the reaction.

[0053] (3) Wet forming: the well-stirred slurry in step (2) was poured into the forming barrel of the sheet former, filtered and formed on a 200-mesh screen, placed in a press using a pressure of 0.4 MPa for 3 min, and then placed in a vacuum dryer for drying treatment, with a vacuum pressure of -0.1 MPa, a temperature of 105°C, and a drying time of 8 min, to obtain the multi-component composite fluorescent security paper.

[0054] Example 4

[0055] A kind of preparation of strong toughness dual-wavelength fluorescent security paper, a kind of preparation method of strong toughness dual-wavelength fluorescent security paper, with cotton fiber as substrate, multiple composite aramid nanofiber and lanthanide metal organic framework are wet papermaking, wherein the mass ratio of aramid nanofiber and cotton fiber is 7:93.Raw materials are obtained by fiber pulp mixing, in-situ deposition and wet forming etc.

[0056] A kind of preparation method of strong toughness dual-wavelength fluorescent security paper, comprising the following steps:

[0057] (1) fiber pulp mixing: a certain mass of aramid nanofiber and cotton fiber are dispersed in 100ml water, wherein the mass of aramid nanofiber is 0.14g, and the mass of cotton fiber is 1.86g;After stirring and dispersing 5000r-10000r, aramid nanofiber / cotton fiber mixed slurry with a mass concentration of 2% is obtained.

[0058] (2) in-situ deposition: 1mmol (0.446g) of Eu (NO3) 3.6H2O is added to the slurry prepared in step (1) and stirred for 1h, so that Eu 3+ Ions are uniformly distributed in the suspension. 50ml of ethanol solution containing 2mmol (0.50g) of benzene-1, 4-tetracarboxylic acid (H4BTC) is added to the suspension and reacted for 4h at a reaction temperature of 35℃. After the reaction is completed, the final product is washed thoroughly with 1L of deionized water to remove the reagents that do not participate in the reaction.

[0059] (3) wet forming: the slurry dispersed in step (2) is poured into the forming barrel of the sheet former, filtered and formed on a 200 mesh screen, then placed in a press for 4min using a pressure of 0.4MPa, and then placed in a vacuum dryer for drying treatment, with a vacuum pressure of-0.1MPa and a temperature of 105℃, and a drying time of 8min, to obtain a multiple composite fluorescent security paper.

[0060] Example 5

[0061] A kind of preparation of strong toughness dual-wavelength fluorescent security paper, a kind of preparation method of strong toughness dual-wavelength fluorescent security paper, with cotton fiber as substrate, multiple composite aramid nanofiber and lanthanide metal organic framework are wet papermaking, wherein the mass ratio of aramid nanofiber and cotton fiber is 7:93.Raw materials are obtained by fiber pulp mixing, in-situ deposition and wet forming etc.

[0062] A kind of preparation method of strong toughness dual-wavelength fluorescent security paper, comprising the following steps:

[0063] (1) Fiber slurry preparation: a certain mass of aramid nanofiber and cotton fiber is dispersed in 150 ml of water, wherein the mass of aramid nanofiber is 0.14 g and the mass of cotton fiber is 1.86 g; after stirring and dispersing for 5000 r to 10000 r, an aramid nanofiber / cotton fiber mixed slurry with a mass concentration of 1.3% is obtained.

[0064] (2) In-situ deposition: Add 2.5 mmol (1.115 g) of Eu(NO3)3.6H2O to the slurry prepared in step (1) and stir for 1 h to allow Eu to 3+ The ions are evenly distributed throughout the suspension. Add 50 ml of an ethanol solution containing 5 mmol (1.25 g) of pyromellitic acid (H4BTC) to the suspension and allow the reaction to proceed for 4 hours at 35°C. After the reaction, thoroughly rinse the final product with 1 L of deionized water to remove any unreacted reagents.

[0065] (3) Wet forming: Pour the slurry stirred and dispersed in step (2) into the forming barrel of the sheet making machine, filter the water and form it on a 200-mesh screen, put it into a press and press it at a pressure of 0.4 MPa for 4 minutes, and then put it into a vacuum dryer for drying at a vacuum pressure of -0.1 MPa, a temperature of 105°C, and a drying time of 8 minutes to obtain a multi-component composite fluorescent anti-counterfeiting paper.

[0066] Example 6

[0067] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper is described. Using cotton fiber as a substrate, a multi-component composite of aramid nanofibers and a lanthanide metal-organic framework is wet-laid to form paper. The mass ratio of aramid nanofiber to cotton fiber is 10:90. The raw materials are then slurried, in-situ deposited, and wet-laid to form the paper.

[0068] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper comprises the following steps:

[0069] (1) Fiber slurry preparation: a certain mass of aramid nanofiber and cotton fiber was dispersed in 200 ml of water, wherein the mass of aramid nanofiber was 0.2 g and the mass of cotton fiber was 1.8 g; after stirring and dispersing for 5000 r to 10000 r, an aramid nanofiber / cotton fiber mixed slurry with a mass concentration of 1% was obtained.

[0070] (2) In-situ deposition: Add 2.5 mmol (1.115 g) of Eu(NO3)3.6H2O to the slurry prepared in step (1) and stir for 0.5 h to make Eu 3+The ions are evenly distributed throughout the suspension. A 50 mL ethanol solution containing 5 mmol (1.25 g) of pyromellitic acid (H4BTC) was added to the suspension and allowed to react for 5 hours at 37°C. After the reaction, the final product was thoroughly rinsed with 1 L of deionized water to remove any unreacted reagents.

[0071] (3) Wet forming: Pour the slurry stirred and dispersed in step (2) into the forming barrel of the sheet making machine, filter the water and form it on a 200-mesh screen, put it into a press and press it at a pressure of 0.4 MPa for 4 minutes, and then put it into a vacuum dryer for drying at a vacuum pressure of -0.1 MPa, a temperature of 100°C, and a drying time of 8 minutes to obtain a multi-component composite fluorescent anti-counterfeiting paper.

[0072] Example 7

[0073] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper is described. Using cotton fiber as a substrate, a multi-component composite of aramid nanofibers and a lanthanide metal-organic framework is wet-laid to form paper. The mass ratio of aramid nanofiber to cotton fiber is 4:96. The raw materials are then slurried, in-situ deposited, and wet-laid to form the paper.

[0074] A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper comprises the following steps:

[0075] (1) Fiber slurry preparation: a certain mass of aramid nanofiber and cotton fiber was dispersed in 150 ml of water, wherein the mass of aramid nanofiber was 0.08 g and the mass of cotton fiber was 1.92 g; after stirring and dispersing for 5000 to 10000 hours, an aramid nanofiber / cotton fiber mixed slurry with a mass concentration of 1.3% was obtained.

[0076] (2) In-situ deposition: Add 2.5 mmol (1.115 g) of Eu(NO3)3.6H2O to the slurry prepared in step (1) and stir for 0.8 h to make Eu 3+ The ions are evenly distributed throughout the suspension. A 50 mL ethanol solution containing 5 mmol (1.25 g) of pyromellitic acid (H4BTC) was added to the suspension and allowed to react for 5 hours at 38°C. After the reaction, the final product was thoroughly rinsed with 1 L of deionized water to remove any unreacted reagents.

[0077] (3) Wet forming: Pour the slurry stirred and dispersed in step (2) into the forming barrel of the sheet making machine, filter the water and form it on a 200-mesh screen, put it into a press and press it at a pressure of 0.4 MPa for 5 minutes, and then put it into a vacuum dryer for drying at a vacuum pressure of -0.1 MPa, a temperature of 100°C, and a drying time of 8 minutes to obtain a multi-component composite fluorescent anti-counterfeiting paper.

[0078] The dual-wavelength fluorescent security paper prepared in Example 5 of the present application was detected and characterized, and some indexes thereof were as follows: tensile index: 63.72 N.m 2 .g -1 uniformity index: 117, folding endurance: 1856 times. Figure 1 As shown in the SEM characterization of the fluorescent security paper prepared in Example 5, the introduction of ANF helps to entangle the fibers and fill the pores between the fibers, and the film-like coating structure helps to adhere Eu-MOF, thereby improving the uniformity of the paper. Figure 2 As shown in the SEM characterization of the fluorescent security paper prepared in Example 5, the introduction of ANF helps to entangle the fibers and fill the pores between the fibers, and the film-like coating structure helps to adhere Eu-MOF, thereby improving the uniformity of the paper.

[0079] The present application adopts new process and new method to develop and produce a kind of strong dual-wavelength fluorescent security paper with high mechanical strength, high forming uniformity and dual-wavelength emission light switch characteristics, the composite fluorescent security paper can act as a photoelectric switch, and the color of the light can be switched under different wavelengths (when the excitation wavelength is 254 nm, red light emission is presented, and when the excitation wavelength is 365 nm, green light emission is presented), which is suitable for naked eye vision under high-grade fluorescent security paper, and can be applied to security paper, banknote paper, certificate and anti-counterfeiting packaging materials in paper industry, etc. The special paper needs anti-counterfeiting technology to overcome the shortcomings of traditional anti-counterfeiting paper based on fluorescent fiber, such as low mechanical strength, poor uniformity, single fluorescent anti-counterfeiting performance, etc., and has wide application prospect.

[0080] The above-described embodiments are only preferred technical solutions of the present application, and should not be regarded as limiting the present application. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The protection scope of the present application should be based on the technical solutions recited in the claims, including the equivalent replacement solutions of the technical features recited in the claims. That is, within this range, equivalent replacement improvements are also within the protection scope of the present application.

Claims

1. A method for preparing strong and tough dual-wavelength fluorescent anti-counterfeiting paper, characterized in that: The following steps are involved: S1: fiber slurry preparation; dispersing aramid nanofibers and plant fibers in water, and obtaining an aramid nanofiber / plant fiber mixed slurry by stirring and dispersing; S2: in situ deposition; adding a lanthanide metal nitrate to the aramid nanofiber / plant fiber mixed slurry, adding an ethanol solution of pyromellitic acid after stirring to react, and in situ depositing a lanthanide metal organic framework on the fiber surface of the aramid nanofiber / plant fiber mixed slurry, finally obtaining an aramid nanofiber / plant fiber mixed slurry after in situ deposition; S3: wet forming; filtering, pressing and drying the aramid nanofiber / plant fiber mixed slurry after the in-situ deposition to obtain a strong and tough dual-wavelength fluorescent anti-counterfeiting paper; In S2, the molar ratio of the lanthanide metal nitrate to the pyromellitic acid is 1:2, and each 50 mL of ethanol solution contains 2 mmol to 6 mmol of pyromellitic acid; In S2, the stirring time is 0.5h~1h, the reaction time is 3h~5h, and the reaction temperature is 35°C~40°C; In S2, the lanthanide metal nitrate is Eu(NO3)3.6H2O.

2. The method for preparing a strong and tough dual-wavelength fluorescent anti-counterfeiting paper according to claim 1, characterized in that: In S1, a total of 2 g or 3 g of the aramid nanofiber and the plant fiber are added to every 150 mL of water, and the mass ratio of the aramid nanofiber to the plant fiber is (2-10): (90-98).

3. The method for preparing a strong and tough dual-wavelength fluorescent anti-counterfeiting paper according to claim 1, characterized in that: In S1, the mass concentration of the aramid nanofiber / plant fiber mixed slurry is 1% to 2%.

4. The method for preparing a strong and tough dual-wavelength fluorescent anti-counterfeiting paper according to claim 1, characterized in that: In S3, the pressing pressure is 0.4 MPa and the pressing time is 3 min to 5 min.

5. The method for preparing a strong and tough dual-wavelength fluorescent anti-counterfeiting paper according to claim 1, characterized in that: In S3, the vacuum pressure of the drying is -0.1 MPa, the temperature is 85°C to 105°C, and the time is 5 minutes to 8 minutes.

6. A strong and tough dual-wavelength fluorescent anti-counterfeiting paper, characterized in that: The strong and tough dual-wavelength fluorescent anti-counterfeiting paper is obtained by the preparation method of any one of claims 1 to 5.

7. Use of the strong and tough dual-wavelength fluorescent anti-counterfeiting paper according to claim 6 in banknotes, securities, certificates and anti-counterfeiting packaging materials.

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