A kind of fluorescent waterborne polyurethane modified by carbon quantum dots and preparation method thereof

Abstract

The present invention provides a fluorescent waterborne polyurethane modified with carbon quantum dots and a preparation method thereof, wherein the fluorescent waterborne polyurethane is composed of the following raw materials: polyisocyanate, polyol, carbon quantum dots, hydrophilic chain extender, neutralizer, post-chain extender, and water. The carbon quantum dots added in the present invention have solid-state luminescence properties, and are distributed in the main segment structure of the polyurethane in the form of blocks as fluorescent centers with polyetheramine as a connecting structure. The fluorescent waterborne polyurethane of the present invention has multicolor luminescence ability and excellent friction color fastness performance, and has a more excellent anti-counterfeiting effect.

Description

Technical Field

[0001] The invention relates to the technical field of waterborne polyurethane polymer structure design and synthesis, and in particular to a carbon quantum dot-modified fluorescent waterborne polyurethane and a preparation method thereof. Background Art

[0002] As the copyright awareness of the society continues to increase, higher requirements are also put forward for the anti-counterfeiting technology of products. Existing anti-counterfeiting methods include pressure-sensitive, heat-sensitive, photosensitive anti-counterfeiting and other methods, which change the physical properties of anti-counterfeiting materials through different stimulus responses to achieve the effect of anti-counterfeiting marks. Among them, fluorescent anti-counterfeiting is a simple and effective photosensitive anti-counterfeiting method.

[0003] Patent CN103102675A provides a method for preparing fluorescent polyurethane resin, which uses a complex of the expensive rare earth element europium as a fluorescent luminescent center and can only emit monochromatic fluorescence. However, ordinary monochromatic fluorescent anti-counterfeiting has the disadvantages of being easy to crack, unstable fluorescent materials, and short lifespan, which can no longer meet market needs. Therefore, it is necessary to develop a more stable, reliable, and difficult-to-crack fluorescent anti-counterfeiting method.

[0004] In many fields, the conversion of polyurethane to water is an irresistible trend. Waterborne polyurethane is often used as a surface coating for clothing, bags, decorations, etc., as a surface coating or printing ink. Therefore, fluorescent waterborne polyurethane can be used to make anti-counterfeiting labels and creative designs. The preparation and application of waterborne polyurethane materials are very mature. The key to the preparation of fluorescent waterborne polyurethane lies in the preparation method of fluorescent materials and how to stably and firmly combine fluorescent materials with polyurethane. Patent CN200510112138.1 provides a screen-printed fluorescent coating for color conversion and a preparation method thereof, which directly blends fluorescent dyes with high molecular polymers, but the fluorescent resin dye prepared by this method is not firmly combined with the polymer, is easy to decolorize, and is not resistant to solvent washing.

[0005] Patent CN110330622A discloses a fluorescent waterborne polyurethane and its preparation method, which first mixes fluorescein with diisocyanate, then performs prepolymerization and chain extension to obtain a yellow-green fluorescent waterborne polyurethane. However, the polyurethane can only emit a single fluorescence, has no fluorescence regulation capability, has poor color fastness, and has high biological toxicity of fluorescein, which places higher protection requirements on operators.

[0006] Carbon quantum dots are a new type of low-toxic or even non-toxic nano fluorescent material. They are mainly composed of C elements, have a carbon core of 1-20nm and are modified with rich organic functional groups on the surface. They can be excited by light and generally have spherical or quasi-spherical particles with multi-color fluorescence emission. Because their surface is easy to modify with amino, hydroxyl and other functional groups, they can be grafted onto the polyurethane polymer chain or used as the chain extension center of the polyurethane polymer during the prepolymerization or chain extension process of waterborne polyurethane, forming a structure in which carbon quantum dots are monodispersed in the polyurethane polymer.

[0007] Carbon quantum dots also have unique excitation wavelength-dependent fluorescence emission properties. They can generally be excited by light of different wavelengths and emit light of different wavelengths. This is different from traditional monochromatic fluorescent materials. This is due to the fact that carbon quantum dots have multiple types of fluorescent active centers that can respond to light excitation of different wavelengths. In addition, carbon quantum dots with different particle sizes and modified with different functional groups have different optical properties. Therefore, this special property makes carbon quantum dots have a more reliable anti-counterfeiting function.

[0008] However, carbon quantum dots usually do not have the property of solid-state luminescence and can only have the ability to emit fluorescence when they are in a monodisperse state. This property is called "concentration quenching phenomenon", which limits the luminescence efficiency and maximum luminescence intensity of carbon quantum dots in polymers. Summary of the invention

[0009] In order to obtain fluorescent waterborne polyurethane with stronger luminescence ability, it is necessary to prepare carbon quantum dots that are not quenched by concentration. The object of the present invention is to provide a fluorescent waterborne polyurethane modified with carbon quantum dots that are not quenched by concentration, which has the property of multicolor fluorescence emission and excellent resistance to water washing and alcohol washing.

[0010] Another object of the present invention is to provide a method for preparing the fluorescent waterborne polyurethane modified with carbon quantum dots which is not quenched by concentration.

[0011] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

[0012] A carbon quantum dot-modified fluorescent waterborne polyurethane, wherein the fluorescent waterborne polyurethane is prepared from the following raw materials:

[0013] (a) polyisocyanates;

[0014] (b) polyols;

[0015] (c) carbon quantum dots;

[0016] (d) a hydrophilic chain extender;

[0017] (e) neutralizing agent;

[0018] (f) post-chain extender;

[0019] (g) Water.

[0020] In a specific embodiment, the fluorescent waterborne polyurethane is prepared from the following raw materials in parts by weight:

[0021] (a) polyisocyanate, 5-15 parts, preferably 6-9 parts;

[0022] (b) polyol, 15-30 parts, preferably 18-24 parts;

[0023] (c) carbon quantum dots, 0.1-0.9 parts, preferably 0.15-0.5 parts;

[0024] (d) hydrophilic chain extender, 0.3-1.5 parts, preferably 0.5-1 parts;

[0025] (e) neutralizing agent, 0.3-1.5 parts, preferably 0.5-1 parts;

[0026] (f) post-chain extender, 0.1-1 part, preferably 0.2-0.5 part;

[0027] (g) Water: 50-80 parts, preferably 60-70 parts.

[0028] In a specific embodiment, the carbon quantum dots are solid powders with a particle size of 1 to 20 nm and a number average molecular weight of 2000 to 10000.

[0029] In a specific embodiment, the carbon quantum dots are prepared from a carbon source, ethylenediamine and polyetheramine, wherein by mass percentage, the carbon source accounts for 70% to 90%, ethylenediamine accounts for 5% to 20%, and polyetheramine accounts for 5% to 10%.

[0030] In a specific embodiment, the carbon source structure is as shown in formula (I); preferably, the carbon source is prepared by reacting 4,4'-dicyanomethyltriphenylamine with 4,4'-dialdehydetetraphenylethylene or its derivatives.

[0031]

[0032] In a specific embodiment, the molecular weight of the polyetheramine is 500-4000, preferably 600-1000.

[0033] In a specific embodiment, the method for preparing carbon quantum dots comprises the following steps:

[0034] 1) Solid phase reaction: dissolve the carbon source in tetrahydrofuran, then quickly add sodium methoxide to it, remove the tetrahydrofuran by vacuum distillation after evenly dispersing, quickly transfer the powder to a reactor, add ethylenediamine, and place in an oven at 180-240°C to react for 4-12 hours;

[0035] 2) Solvothermal reaction: The powder obtained by the solid phase reaction is dissolved in tetrahydrofuran, and then polyetheramine is added thereto, and the mixture is placed in an oven at 180-240°C for reaction for 4-12 hours;

[0036] 3) Purification: Use hydrochloric acid to adjust the pH of the solvent hot reaction mixture to neutral, dissolve the mixture in water, centrifuge and filter the supernatant, then purify by column chromatography or dialysis, and finally freeze-dry the dialyzate to obtain carbon quantum dot powder.

[0037] In a specific embodiment, in step 3), the speed of the centrifuge is 10000-20000 rpm, and the pore size of the filter membrane used for filtration is 0.2 μm; preferably, the solvent used for column chromatography purification is one or more of methanol, dichloromethane, n-hexane, and toluene, and the silica gel is 100 mesh to 300 mesh; the molecular weight of the dialysis bag used for dialysis purification is 2000-10000, and the dialysate is one or more of water, ethanol, and toluene; preferably, the volume of the dialysate should be 30-100 times the volume of the dialysate to be dialyzed, and stirring is performed during dialysis, and the rotor speed is 200-800 rpm; more preferably, the dialysate is replaced every 8-12 hours, and a total of 3-5 times.

[0038] In a specific embodiment, the fluorescent waterborne polyurethane can emit solid-state light in multiple colors, and has an excitation wavelength-dependent fluorescence emission capability, with an excitation wavelength range of 200-500 nm and a fluorescence emission range of 300-800 nm.

[0039] On the other hand, the preparation method of the aforementioned fluorescent waterborne polyurethane comprises the following steps:

[0040] a) Place polyisocyanate in a three-necked flask, add polyol, hydrophilic chain extender and appropriate amount of catalyst, disperse evenly, heat to 70-90°C, continue stirring, and keep stirring for 2-4 hours;

[0041] b) adding carbon quantum dots thereto and reacting at 60-80° C. for 2 h;

[0042] c) cooling to 5-35° C., adding acetone, and then adding water for dispersion, adding a neutralizer after dispersion, adding a post-chain extender after neutralization, removing the acetone by vacuum distillation, and obtaining a fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0043] A carbon quantum dot-modified fluorescent waterborne polyurethane is prepared from the following raw materials in parts by weight. Compared with the prior art, the beneficial effects of the present invention are:

[0044] The method for preparing fluorescent waterborne polyurethane modified with carbon quantum dots of the present invention can prepare waterborne fluorescent polyurethane with multicolor luminescence ability, and has a more excellent anti-counterfeiting effect. The present invention innovatively uses 4,4'-dicyanomethyl triphenylamine and 4,4'-dialdehyde tetraphenylethylene derivatives as non-coplanar DA-D' structures, and the prepared carbon quantum dots break the concentration quenching limitation, so that the quantum dot-modified polyurethane has a stronger luminescence intensity.

[0045] The preparation method of the present invention can introduce hydroxyl groups and amino groups on the surface of carbon quantum dots. In particular, it also innovatively introduces polyetheramine chain molecules to increase the surface amino activity and chain segment length, reduce steric hindrance, and enable it to be tightly combined with polyurethane molecules, thereby enhancing its stability and color fastness. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The figure is a schematic diagram of the chemical reaction structure for preparing fluorescent waterborne polyurethane according to the present invention.

[0047] Figure 2 This is a transmission electron microscope photo of the carbon quantum dots prepared in the present invention, and the inset is a single magnified photo.

[0048] Figure 3 This is a normalized fluorescence spectrum of the carbon quantum dots prepared in the present invention.

[0049] Figure 4 The present invention provides a preparation route for the aldehyde triphenylamine and its derivatives used in the present invention.

[0050] Figure 5 This is a schematic diagram of the reaction principle for preparing carbon quantum dots in the present invention.

[0051] Figure 6 The present invention is a schematic diagram of the process of preparing fluorescent waterborne polyurethane. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] like Figure 6As shown, the preparation process of the fluorescent waterborne polyurethane of the present invention is as follows: polyisocyanate is placed in a three-necked flask, polyol, hydrophilic chain extender, and catalyst are added in a metered manner, and the temperature is raised to 70-90°C after uniform dispersion, and stirring is continued for 2-4 hours; carbon quantum dots are then added thereto, and the reaction is carried out at 60-80°C for 2 hours to obtain a prepolymer. Acetone is added after cooling to 5-35°C, and water is added for dispersion, a neutralizer is added for neutralization, a post-chain extender is added after neutralization, acetone is removed by reduced pressure distillation, and fluorescent waterborne polyurethane modified with carbon quantum dots is obtained after aging.

[0054] The reaction principle of the above preparation steps is as follows Figure 1 As shown in the figure, fluorescent waterborne polyurethane is mainly obtained by the reaction of polyisocyanate, polyol and carbon quantum dots. Among them, waterborne polyurethane has more hydrophilic groups, which can produce hydrogen bonds, electrostatic attraction and other intermolecular forces with amino, carboxyl and other functional groups on the surface of carbon quantum dots, and combine the two in various ways such as chemical bonds. In particular, the introduction of polyetheramine terminal amino chain structure on the surface of carbon quantum dots can more effectively graft carbon quantum dots as chain extension centers into polyurethane molecules. Therefore, through the chemical bonding, intermolecular forces and spatial confinement of carbon quantum dots and polyurethane molecules, monodisperse carbon quantum dot waterborne polyurethane dispersions can be better prepared, such as Figure 2 As shown, the water-based polyurethane has strong resistance to solvent washing.

[0055] The fluorescent waterborne polyurethane in the present invention has an excitation wavelength-dependent fluorescence emission capability, the excitation wavelength range is 200-500nm, and the fluorescence emission range is 300-800nm. Figure 3 As shown. As the excitation wavelength changes, the fluorescence emission wavelength also changes, that is, multiple colors of fluorescence.

[0056] Wherein, the fluorescent waterborne polyurethane is prepared from the following raw materials in parts by weight:

[0057] (a) polyisocyanate, 5-15 parts, preferably 6-9 parts;

[0058] (b) polyol, 15-30 parts, preferably 18-24 parts;

[0059] (c) carbon quantum dots, 0.1-0.9 parts, preferably 0.15-0.5 parts;

[0060] (d) hydrophilic chain extender, 0.3-1.5 parts, preferably 0.5-1 parts;

[0061] (e) neutralizing agent, 0.3-1.5 parts, preferably 0.5-1 parts;

[0062] (f) post-chain extender, 0.1-1 part, preferably 0.2-0.5 part;

[0063] (g) Water, 50-80 parts, preferably 60-70 parts.

[0064] In the present invention, the polyisocyanate is selected from one or more of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate, preferably isophorone diisocyanate.

[0065] The polyol is one or more of polyether polyol or polyester polyol, and has a number average molecular weight of 1000 to 3000, and is preferably polybutylene adipate diol with a number average molecular weight of 2000.

[0066] The hydrophilic chain extender is one or more of dimethylol propionic acid, sodium ethylenediamine sulfonate, ethylenediamine, and methyldiethanolamine, preferably dimethylol propionic acid.

[0067] The neutralizing agent is triethylamine or dimethylethanolamine, preferably triethylamine.

[0068] The post-chain extender is a small molecule diamine, such as one or more of ethylenediamine, isophoronediamine, and diethanolamine, preferably ethylenediamine.

[0069] In the present invention, the carbon quantum dots are solid powders with a particle size of 1 to 20 nm and a molecular weight of 2000 to 10000. Specifically, the carbon quantum dots have one or more of amino groups and hydroxyl groups on their surface, and the amino content is 5-10 wt% and the hydroxyl content is 5-15 wt% by weight.

[0070] In the present invention, the carbon quantum dots are prepared from a carbon source and a dopant. Preferably, the carbon source is a molecule described in structural formula (I); and the dopant is ethylenediamine or polyetheramine.

[0071]

[0072] The carbon source molecules used are prepared from 4,4'-dicyanomethyl triphenylamine and 4,4'-dialdehyde tetraphenylethylene, such as Figure 4 As shown. Specifically, the synthesis method is: 4,4'-dicyanomethyl triphenylamine and 4,4'-dialdehyde tetraphenylene are dissolved in anhydrous ethanol and anhydrous tetrahydrofuran at a molar ratio of 1:1, 0.05%-0.1% sodium methoxide is quickly added thereto as a base catalyst, and heated under reflux and stirred for 24 hours under a nitrogen atmosphere. The mixture is cooled to room temperature, poured into water, extracted with dichloromethane, the solvent is removed by reduced pressure distillation, and the mixture is purified by column chromatography after drying.

[0073] The precursor of the carbon source molecule used in the present invention, 4,4'-dicyanomethyl triphenylamine, is prepared from triphenylamine. The synthesis method is, for example:

[0074] 1) In an ice bath, drop phosphorus oxychloride into dry N,N-dimethylformamide, and then stir at room temperature for 1-2 hours. Then drop a 1,2-dichloroethane solution of triphenylamine into the above phosphorus oxychloride / N,N-dimethylformamide system in an ice bath, heat to 90°C, monitor the reaction by TLC, and then cool to room temperature. Pour the mixture into water, extract with dichloromethane, remove the solvent by vacuum distillation, dry, and purify by column chromatography to obtain 4,4'-dialdehyde triphenylamine.

[0075] 2) Under nitrogen atmosphere, keep the temperature at -40°C, slowly add p-toluenesulfonylmethyl isocyanide to the tetrahydrofuran solution of potassium tert-butoxide, then slowly add the tetrahydrofuran solution of 4,4'-dialdehyde triphenylamine, and stir for 45 minutes. Then add methanol, heat the mixed system to 80°C, and react for 20 minutes. Cool to room temperature, remove the solvent by vacuum distillation, add acetic acid aqueous solution, extract with dichloromethane, remove the solvent by vacuum distillation, dry, and purify by column chromatography to obtain 4,4'-dicyanomethyl triphenylamine.

[0076] The precursor of the carbon source molecule used in the present invention, 4,4'-dialdehyde tetraphenylethylene, is prepared from tetraphenylethylene. The synthesis method is as follows: in an ice bath, phosphorus oxychloride is dripped into dry N,N-dimethylformamide, and then stirred at room temperature for 1-2 hours. Then, in an ice bath, a 1,2-dichloroethane solution of tetraphenylethylene is dripped into the above phosphorus oxychloride / N,N-dimethylformamide system, the temperature is raised to 90°C, and the reaction is monitored by TLC and then cooled to room temperature after completion. The mixture is poured into water, extracted with dichloromethane, the solvent is removed by vacuum distillation, and the mixture is dried and purified by column chromatography to obtain 4,4'-dialdehyde tetraphenylethylene.

[0077] In the present invention, Figure 5 As shown, the method for preparing carbon quantum dots is a two-step method:

[0078] 1) Solid phase reaction: The carbon source prepared above is dissolved in anhydrous tetrahydrofuran, and then 0.05%-0.1% sodium methoxide is quickly added thereto. After uniform dispersion, the tetrahydrofuran is removed by vacuum distillation; the powder is quickly transferred to a reaction vessel, and then 5%-15% ethylenediamine is added, and the reaction is carried out in an oven at 200°C for 4-12 hours.

[0079] 2) Solvothermal reaction: The powder obtained by the solid phase reaction is dissolved in tetrahydrofuran, the pH is adjusted to neutral using nitric acid, polyetheramine is added thereto, and the mixture is placed in an oven at 200°C for reaction for 4-12 hours; the mixture is dissolved in water, the supernatant is filtered by centrifugation, and then dialyzed for purification, and the dialyzate is freeze-dried to obtain carbon quantum dot powder.

[0080] The molecular weight distribution of the polyetheramine used in the preparation of carbon quantum dots in the present invention is 500-4000, including but not limited to 500, 1000, 1500, 2000, 2500, 3000, 3500, and 4000.

[0081] When purifying carbon quantum dots, the centrifuge speed is 10000-20000rpm, such as 10000rpm, 15000rpm, 20000rpm, etc., and the pore size of the filter membrane used for filtration is 0.2μm. The solvent used for column chromatography purification is one or more of methanol, dichloromethane, n-hexane, and toluene, and the silica gel is 100 mesh-300 mesh. The molecular weight of the dialysis bag used for dialysis purification is 2000-10000, and the dialysate is one or more of water, ethanol, and toluene. The volume of the dialysate should be 30-100 times the volume of the dialysate to be dialyzed, and it should be stirred during dialysis. The rotor speed is 200-800rpm. Replace the dialysate every 8-12 hours, and replace it 3-5 times in total.

[0082] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0083] The main raw materials used in the following examples are from the following sources:

[0084]

[0085]

[0086] The main detection methods involved in the embodiment are as follows:

[0087] Test items Test Method Maximum fluorescence intensity Agilent Cary Eclipse fluorescence spectrometer, excitation at 500 nm Alcohol resistant Color fastness tester, 75% ethanol, load 1kg, level 3

[0088] Preparation example:

[0089] See also Figure 4 , provides a method for preparing a carbon source, comprising the following steps:

[0090] 1) In an ice bath, drop 17 mL of phosphorus oxychloride into 35 mL of dry N, N-dimethylformamide, and then stir at room temperature for 1-2 hours. Then drop 20 g of triphenylamine in 1,2-dichloroethane into the above phosphorus oxychloride / N, N-dimethylformamide system in an ice bath, heat to 90°C, monitor the reaction by TLC, and then cool to room temperature. Pour the mixture into water, extract with dichloromethane, remove the solvent by vacuum distillation, dry, and purify by column chromatography to obtain 4,4'-dialdehyde triphenylamine.

[0091] 2) Under nitrogen atmosphere, keep the temperature at -40°C, slowly drop 2.15g of p-toluenesulfonylmethyl isocyanide into a tetrahydrofuran solution (50mL) of 2.55g of potassium tert-butoxide, then slowly drop 17mL of a tetrahydrofuran solution containing 2.6g of 4,4'-dialdehyde triphenylamine, and stir for 45min. Then add 50mL of methanol, heat the mixture to 80°C, and react for 20min. Cool to room temperature, remove the solvent by vacuum distillation, add 10mL of acetic acid aqueous solution, extract with dichloromethane, remove the solvent by vacuum distillation, dry, and purify by column chromatography to obtain 4,4'-dicyanomethyl triphenylamine.

[0092] 3) In an ice bath, drop 17 mL of phosphorus oxychloride into 35 mL of dry N, N-dimethylformamide, and stir at room temperature for 1-2 hours. Then drop 20 g of tetraphenylethylene in 1,2-dichloroethane into the above phosphorus oxychloride / N, N-dimethylformamide system in an ice bath, heat to 90°C, monitor the reaction by TLC, and cool to room temperature. Pour the mixture into water, extract with dichloromethane, remove the solvent by vacuum distillation, dry, and purify by column chromatography to obtain 4,4'-dialdehyde tetraphenylethylene.

[0093] 4) Dissolve 1g of 4,4'-dicyanomethyl triphenylamine and 1g of 4,4'-dialdehyde tetraphenylene in 20mL of anhydrous ethanol and anhydrous tetrahydrofuran (v:v=1:1), quickly add 0.05g of sodium methoxide as a base catalyst, heat under reflux and stir for 24h under nitrogen atmosphere. Cool the mixture to room temperature, pour into water, extract with dichloromethane, remove the solvent by vacuum distillation, dry and purify by column chromatography.

[0094] Embodiment 1:

[0095] See also Figure 1 , a method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0096] Please read first Figure 5 , weigh 2g of the carbon source of the preparation example and dissolve it in 10mL of dry tetrahydrofuran, then quickly add 0.05g of sodium methoxide to it, disperse it evenly, and then remove the tetrahydrofuran by vacuum distillation. Quickly transfer the powder to the reactor, add 0.2g of ethylenediamine, and place it in a 200℃ oven to react for 8h.

[0097] The powder obtained by the solid phase reaction was dissolved in 10 mL of tetrahydrofuran, and the pH was adjusted to neutral (pH = 7) using nitric acid. Then 0.4 g of PEA-D2000 was added and placed in a 200 ° C oven for 6 h. The mixture was dissolved in water, centrifuged, the supernatant was filtered, and then dialyzed for purification. The dialyzate was freeze-dried to obtain a solid powder, which was recorded as CDs1. The electron microscope photo of the carbon quantum dots is shown in FIG. Figure 2 As shown, the particles are 5 nm spherical in shape.

[0098] See also Figure 6 , put 6g of isophorone diisocyanate in a three-necked flask, add 18g of PBA2000, 0.5g of ethylenediamine, 0.5g of 2,2-dihydroxymethylpropionic acid, and 0.1g of an organic tin catalyst (the same below), disperse evenly, heat to 80°C, continue stirring, and maintain for 3h. Then add 0.2g of CDs1 and react at 80°C for 2h. Cool to 25°C, add 10mL of acetone, and then add 60mL of water for dispersion. After dispersion, add 0.5g of triethylamine for neutralization. After neutralization, add 0.2g of ethylenediamine, remove the acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging. The fluorescence spectrum is as follows Figure 3 shown.

[0099] Comparative Example 1:

[0100] A method for preparing carbon quantum dots of a conventional citric acid system and fluorescent waterborne polyurethane modified with carbon quantum dots is provided as a comparative example, comprising the following steps:

[0101] Take 1g of citric acid and 1g of urea and dissolve them in 50mL of water, add 0.2g of ethylenediamine, transfer to a polytetrafluoroethylene liner, and seal it in a reactor. Place the reactor in a preheated 200℃ oven for hydrothermal reaction for 8h. After the reaction is completed, take it out and cool it naturally at room temperature. After cooling, adjust the pH to neutral, add 0.4g of PEA-D2000, seal it in a reactor, and continue to react at 200℃ for 6h. Take the reaction solution and filter it under pressure with a 0.2μm aqueous phase filter membrane, and centrifuge the clear liquid (10000r / min, 10min). Take the centrifugal supernatant and place it in a dialysis bag with Mw=2000 for 24h (change the dialysis water every 8h, for a total of 3 times). The dialyzed solution was freeze-dried to obtain a brown powder, recorded as CDs2.

[0102] See also Figure 6 , put 6g of isophorone diisocyanate in a three-necked flask, add 18g of PBA2000, 0.5g of ethylenediamine, 0.5g of 2,2-dimethylolpropionic acid, and 0.1g of catalyst, disperse evenly, heat to 80°C, stir continuously, and keep for 3h. Then add 0.2g of CDs2 and react at 80°C for 2h. Cool to 25°C, add 10mL of acetone, and then add 60mL of water for dispersion. After dispersion, add 0.5g of triethylamine for neutralization. After neutralization, add 0.2g of ethylenediamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0103] Comparative Example 2:

[0104] Provided is a method for preparing carbon quantum dots without polyetheramine modification and fluorescent waterborne polyurethane modified with carbon quantum dots, as a comparative example, comprising the following steps:

[0105] Please read first Figure 5 , weigh 2g of the carbon source of the preparation example and dissolve it in 10mL of dry tetrahydrofuran, then quickly add 0.05g of sodium methoxide to it, disperse it evenly, and then remove the tetrahydrofuran by vacuum distillation. Quickly transfer the powder to the reactor, add 0.2g of ethylenediamine, and place it in a 200℃ oven to react for 8h.

[0106] The powder obtained by the solid phase reaction was dissolved in 10 mL of tetrahydrofuran, the pH was adjusted to neutral with nitric acid, the mixture was dissolved in water, the supernatant was filtered by centrifugation, and then dialyzed for purification. The dialyzate was freeze-dried to obtain a solid powder, which was recorded as CDs3.

[0107] See also Figure 6 , put 6g of isophorone diisocyanate in a three-necked flask, add 18g of PBA2000, 0.5g of ethylenediamine, 0.5g of 2,2-dimethylolpropionic acid, and 0.1g of catalyst, disperse evenly, heat to 80°C, stir continuously, and keep for 3h. Then add 0.2g of CDs3 and react at 80°C for 2h. Cool to 25°C, add 10mL of acetone, and then add 60mL of water for dispersion. After dispersion, add 0.5g of triethylamine for neutralization. After neutralization, add 0.2g of ethylenediamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0108] Embodiment 2:

[0109] A method for preparing fluorescent waterborne polyurethane modified with excess carbon quantum dots is provided, comprising the following steps:

[0110] Please refer to Example 1, Preparation of CDs1.

[0111] See also Figure 6 , put 6g of isophorone diisocyanate in a three-necked flask, add 18g of PBA2000, 0.5g of ethylenediamine, 0.5g of 2,2-dimethylolpropionic acid, and 0.1g of catalyst, disperse evenly, heat to 80°C, stir continuously, and maintain for 3h. Then add 0.9g of CDs1 and react at 80°C for 2h. Cool to 25°C, add 10mL of acetone, and then add 60mL of water for dispersion. After dispersion, add 0.5g of triethylamine for neutralization. After neutralization, add 0.2g of ethylenediamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0112] Comparative Example 3:

[0113] Provided is a method for preparing carbon quantum dots and carbon quantum dot-modified fluorescent waterborne polyurethane in an excess conventional citric acid system, as a comparative example, comprising the following steps:

[0114] Please refer to Comparative Example 1 to prepare CDs2.

[0115] See also Figure 6 , put 6g of isophorone diisocyanate in a three-necked flask, add 18g of PBA2000, 0.5g of ethylenediamine, 0.5g of 2,2-dimethylolpropionic acid, and 0.1g of catalyst, disperse evenly, heat to 80°C, stir continuously, and keep for 3h. Then add 0.9g of CDs2 and react at 80°C for 2h. Cool to 25°C, add 10mL of acetone, and then add 60mL of water for dispersion. After dispersion, add 0.5g of triethylamine for neutralization. After neutralization, add 0.2g of ethylenediamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0116] Embodiment 3:

[0117] A method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0118] Please read first Figure 5 , weigh 2g of the carbon source in the preparation example and dissolve it in 10mL of dry tetrahydrofuran, then quickly add 0.05g of sodium methoxide to it, disperse it evenly and remove the tetrahydrofuran by vacuum distillation. Quickly transfer the powder to the reactor, add 0.2g of ethylenediamine, and place it in an oven at 180℃ for 12h.

[0119] The powder obtained by the solid phase reaction was dissolved in 10 mL of tetrahydrofuran, the pH was adjusted to neutral with nitric acid, and 0.2 g of PEA-D500 was added thereto, and the mixture was placed in an oven at 180°C for 9 h. The mixture was dissolved in water, the supernatant was filtered by centrifugation, and then purified by dialysis. The dialysate was freeze-dried to obtain a solid powder, which was recorded as CDs4.

[0120] See also Figure 6 , put 9g hexamethylene diisocyanate in a three-necked flask, add 15g PBA1000, 0.8g diethanolamine, 1.0g 2,2-dihydroxymethyl propionic acid, 0.2g catalyst, disperse evenly and heat to 70℃, keep stirring and keep for 3h. Then add 0.1g CDs4 and react at 70℃ for 3h. Cool to 25℃ and add 15mL acetone, then add 80mL water for dispersion, add 1.0g dimethylethanolamine for neutralization after dispersion, add 0.1g isophorone diamine after neutralization, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0121] Embodiment 4:

[0122] A method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0123] Please read first Figure 5, weigh 2g of the carbon source of the preparation example and dissolve it in 10mL of dry tetrahydrofuran, then quickly add 0.05g of sodium methoxide to it, disperse it evenly and remove the tetrahydrofuran by vacuum distillation. Quickly transfer the powder to the reactor, add 0.2g of ethylenediamine, and place it in a 240℃ oven to react for 4h.

[0124] The powder obtained by the solid phase reaction was dissolved in 10 mL of tetrahydrofuran, the pH was adjusted to neutral with nitric acid, and 0.8 g of PEA-D4000 was added thereto, and the mixture was placed in an oven at 240°C for 3 h. The mixture was dissolved in water, the supernatant was filtered by centrifugation, and then purified by dialysis. The dialyzate was freeze-dried to obtain a solid powder, which was recorded as CDs5.

[0125] See also Figure 6 , 8g of diphenylmethane diisocyanate was placed in a three-necked flask, 20g of PBA3000, 0.8g of ethylenediamine, 1.2g of 2,2-dimethylolpropionic acid, and 0.15g of catalyst were added, and the temperature was raised to 90°C after uniform dispersion, and stirring was continued for 2h. Then 0.5g of CDs5 was added thereto, and the reaction was carried out at 90°C for 2h. The temperature was lowered to 25°C, 12mL of acetone was added, and 70mL of water was added for dispersion, and 0.3g of dimethylethanolamine was added for neutralization after dispersion, and 0.8g of diethanolamine was added after neutralization, and the acetone was removed by vacuum distillation, and the fluorescent waterborne polyurethane modified with carbon quantum dots was obtained after aging.

[0126] Embodiment 5:

[0127] A method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0128] Please refer to Example 1, Preparation of CDs1.

[0129] See also Figure 6 , put 15g of isophorone diisocyanate in a three-necked flask, add 30g of PBA2000, 1.0g of ethylenediamine, 1.5g of 2,2-dimethylolpropionic acid, and 0.2g of catalyst, disperse evenly, heat to 80°C, stir continuously, and keep for 3h. Then add 0.2g of CDs1 and react at 80°C for 2h. Cool to 25°C, add 15mL of acetone, and then add 80mL of water for dispersion. After dispersion, add 1.5g of dimethylethanolamine for neutralization. After neutralization, add 0.8g of isophorone diamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0130] Embodiment 6:

[0131] A method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0132] Please refer to Example 3, Preparation of CDs4.

[0133] See also Figure 6 , put 5g toluene diisocyanate in a three-necked flask, add 16g PBA2000, 0.1g ethylenediamine, 0.4g 2,2-dimethylol propionic acid, 0.05g catalyst, disperse evenly and heat to 70℃, keep stirring and keep for 3h. Then add 0.1g CDs4 and react at 70℃ for 3h. Cool down to 25℃ and add 5mL acetone, then add 50mL water for dispersion, add 0.3g triethylamine for neutralization after dispersion, add 0.5g ethylenediamine after neutralization, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0134] Embodiment 7:

[0135] A method for preparing a carbon quantum dot-modified fluorescent waterborne polyurethane is provided, comprising the following steps:

[0136] Please refer to Example 4, Preparation of CDs5.

[0137] See also Figure 6 , put 5g of isophorone diisocyanate in a three-necked flask, add 15g of PBA2000, 0.15g of ethylenediamine, 0.3g of 2,2-dimethylolpropionic acid, and 0.05g of catalyst, disperse evenly, heat to 90°C, stir continuously, and keep for 2h. Then add 0.5g of CDs5 and react at 90°C for 2h. Cool to 25°C, add 5mL of acetone, and then add 50mL of water for dispersion. After dispersion, add 1.5g of triethylamine for neutralization. After neutralization, add 0.5g of diethanolamine, remove acetone by vacuum distillation, and obtain fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

[0138] The performance test results of the fluorescent waterborne polyurethane modified with carbon quantum dots obtained in the examples and comparative examples are as follows:

[0139]

[0140]

[0141] The comparison results of Example 1 and Comparative Example 1 show that the fluorescent waterborne polyurethane modified with carbon quantum dots designed by the present invention has better fluorescence intensity and alcohol rubbing color fastness than the fluorescent waterborne polyurethane prepared from conventional carbon sources. The comparison results of Example 1 and Comparative Example 2 show that the polyetheramine structure introduced on the surface of carbon quantum dots by the present invention can effectively increase the alcohol rubbing color fastness. The comparison results of Example 2 and Comparative Example 3 show that the carbon quantum dots designed by the present invention can still maintain a high fluorescence intensity and good alcohol rubbing color fastness when in excess, while the fluorescence intensity and alcohol rubbing color fastness of the quantum dots prepared from conventional carbon sources are greatly weakened when in excess.

[0142] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A fluorescent waterborne polyurethane modified with carbon quantum dots, characterized in that: The fluorescent waterborne polyurethane is prepared from the following raw materials: (a) polyisocyanates; (b) polyols; (c) carbon quantum dots; (d) a hydrophilic chain extender; (e) neutralizing agent; (f) post-chain extender; (g) water; The carbon quantum dots are prepared from a carbon source, ethylenediamine and polyetheramine, wherein by mass percentage, the carbon source accounts for 70% to 90%, the ethylenediamine accounts for 5% to 20%, and the polyetheramine accounts for 5% to 10%.

2. The fluorescent waterborne polyurethane according to claim 1, characterized in that: The fluorescent waterborne polyurethane is prepared from the following raw materials in parts by weight: (a) polyisocyanate, 5-15 parts; (b) polyol, 15-30 parts; (c) carbon quantum dots, 0.1-0.9 parts; (d) hydrophilic chain extender, 0.3-1.5 parts; (e) neutralizing agent, 0.3-1.5 parts; (f) post-chain extender, 0.1-1 part; (g) Water, 50-80 parts.

3. The fluorescent waterborne polyurethane according to claim 2, characterized in that: The fluorescent waterborne polyurethane is prepared from the following raw materials in parts by weight: (a) polyisocyanate, 6 to 9 parts; (b) polyol, 18 to 24 parts; (c) carbon quantum dots, 0.15 to 0.5 parts; (d) hydrophilic chain extender, 0.5-1 part; (e) neutralizing agent, 0.5 to 1 part; (f) post-chain extender, 0.2-0.5 parts; (g) Water, 60-70 parts.

4. The fluorescent waterborne polyurethane according to any one of claims 1 to 3, characterized in that: The carbon quantum dots are solid powders with a particle size of 1 to 20 nm and a number average molecular weight of 2,000 to 10,000.

5. The fluorescent waterborne polyurethane according to any one of claims 1 to 3, characterized in that: The carbon source structure is shown in formula (I); 6. The fluorescent waterborne polyurethane according to claim 5, characterized in that: The carbon source is prepared by reacting 4,4'-dicyanomethyl triphenylamine with 4,4'-dialdehyde tetraphenylethylene or a derivative thereof.

7. The fluorescent waterborne polyurethane according to any one of claims 1 to 3, characterized in that: The molecular weight of the polyetheramine is 500-3000.

8. The fluorescent waterborne polyurethane according to claim 7, characterized in that: The molecular weight of the polyetheramine is 600-1000.

9. The fluorescent waterborne polyurethane according to any one of claims 1 to 3, characterized in that: The method for preparing carbon quantum dots comprises the following steps: 1) Solid phase reaction: dissolve the carbon source in tetrahydrofuran, then quickly add sodium methoxide thereto, disperse evenly, and remove the tetrahydrofuran by vacuum distillation. Quickly transfer the powder to a reactor, add ethylenediamine, and place in an oven at 100-300°C for reaction for 4-12 hours; 2) Solvothermal reaction: The powder obtained by the solid phase reaction is dissolved in tetrahydrofuran, and then polyetheramine is added thereto, and the mixture is placed in an oven at 100-300°C for reaction for 4-12 hours; 3) Purification: Use hydrochloric acid to adjust the pH of the solvent hot reaction mixture to neutral, dissolve the mixture in water, centrifuge and filter the supernatant, then purify by column chromatography or dialysis, and finally freeze-dry the dialyzate to obtain carbon quantum dot powder.

10. The fluorescent waterborne polyurethane according to claim 9, characterized in that: In step 3), the speed of the centrifuge is 10000-20000 rpm, and the pore size of the filter membrane used for filtration is 0.2 μm.

11. The fluorescent waterborne polyurethane according to claim 10, characterized in that: In step 3), the solvent used for column chromatography purification is one or more of methanol, dichloromethane, n-hexane, and toluene, and the silica gel is 100-300 mesh; the molecular weight of the dialysis bag used for dialysis purification is 2000-10000, and the dialysate is one or more of water, ethanol, and toluene.

12. The fluorescent waterborne polyurethane according to claim 11, characterized in that: The dialysate volume should be 30 to 100 times the volume of the dialysate to be dialyzed, and it should be stirred during dialysis with a rotor speed of 200 to 800 rpm.

13. The fluorescent waterborne polyurethane according to claim 12, characterized in that: The dialysate was replaced every 8 to 12 hours, for a total of 3 to 5 times.

14. The fluorescent waterborne polyurethane according to any one of claims 1 to 3, characterized in that: The fluorescent waterborne polyurethane can emit light in a solid state as fluorescence of various colors, and has a fluorescence emission capability that depends on the excitation wavelength. The excitation wavelength range is 200-500nm, and the fluorescence emission range is 300-800nm.

15. The method for preparing the fluorescent waterborne polyurethane according to any one of claims 1 to 14, characterized in that: The following steps are involved: a) Place polyisocyanate in a three-necked flask, add polyol, hydrophilic chain extender and appropriate amount of catalyst, disperse evenly, heat to 70-90°C, continue stirring, and keep for 2-4 hours; b) adding carbon quantum dots thereto and reacting at 60-80° C. for 2 h; c) cooling to 5-35° C., adding acetone, and then adding water for dispersion, adding a neutralizer after dispersion, adding a post-chain extender after neutralization, removing the acetone by vacuum distillation, and obtaining a fluorescent waterborne polyurethane modified with carbon quantum dots after aging.

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