Red light conversion agent and preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a red light conversion agent and a preparation method and application thereof, the red light conversion agent is changed into a complex, the center of the complex is europium, a first ligand is a maleic acid copolymer, and a second ligand is 1, 10-phenanthroline. The fluorescence excitation range of the red light conversion agent is 300 nm to 575 nm, and the fluorescence emission range of the red light conversion agent is 400 nm to 590 nm, 600 nm to 635 nm and 675 nm to 725 nm. The red light conversion agent disclosed by the invention is not easy to separate out from a resin matrix, has longer service life, has higher fluorescence quantum yield compared with a commercially available light conversion agent under the condition that the europium element content is close, and can be applied to the fields of agricultural light conversion films, solar cells and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to red light conversion agents, red light conversion powders, light conversion resins, their preparation methods and applications. Background Technology

[0002] my country is a major agricultural country, ranking among the world's top producers and consumers of agricultural films. With the development of modern agriculture, the demands for agricultural film performance are increasing, leading to the development of various functional films. The concept of light-converting film for agriculture was first proposed in 1983 by L. G. Lodkava and A. F. Lepaev of the Soviet Academy of Sciences, and it was recommended as "the most promising functional agricultural film" at the 1988 International Symposium on High Technology of Horticultural Facilities in Tokyo, Japan. Its basic principle is to increase light conversion function by adding light energy conversion agents to ordinary greenhouse films or materials such as polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyester, and ethylene-vinyl acetate copolymer, thereby improving the light transmission quality of the film and promoting photosynthesis in greenhouse crops. Field trials of light-converting film have shown that compared with ordinary films, using light-converting film can increase soil and greenhouse temperatures, promote early crop maturity, reduce crop disease indices, increase crop yields, and improve crop quality. Light conversion agents and light-converting films hold a very important position in the development of modern agricultural technology. Based on its light conversion requirements, the light conversion agent used in agricultural light conversion films should be a photoluminescent material with an excitation range of 280-350nm and / or 500-600nm and an emission range of 400-500nm and / or 600-700nm, and should have long-term stability matching the service life of the agricultural film and the highest possible light conversion efficiency.

[0003] Currently, the red light conversion agents used in agricultural films are mainly rare earth complexes. These agents primarily use rare earth ions as the central luminescent ions. The selection criterion for ligands is that their triplet energy levels must match the excited state energy levels of the rare earth ions. A coordination environment is formed through electrostatic interactions, hydrogen bonding, and intermolecular forces. Common rare earth organic complexes are mainly Eu... 3+ Complexes formed by ions with β-diketones and aromatic carboxylic acids (such as benzaldehyde and salicylic acid), especially those formed by rare earth elements and carboxylic acids, exhibit strong luminescent stability and high luminescence intensity. However, the inventors of this invention have discovered that when light-converting agents prepared using small organic molecule complexes are applied to resin-based agricultural films such as polyethylene, they are prone to precipitation from the resin due to the small size of the ligand molecules. Furthermore, given their wide applicability, cost control of red light-converting agents is crucial. Therefore, overcoming the tendency for red light-converting agents to precipitate, further improving the fluorescence intensity of the agent would be more beneficial for enhancing the light conversion effect of light-converting agricultural films and promoting their widespread application. Summary of the Invention

[0004] This invention addresses the problem of easy precipitation of red light-converting agents from rare earth organic complexes in existing technologies by providing a red light-converting agent, red light-converting powder, light-converting resin, its preparation method, and its application. The red light-converting agent of this invention is not easily precipitated from the resin matrix and has a longer service life. Moreover, compared with commercially available light-converting agents, the red light-converting agent of this invention has a higher fluorescence quantum yield at similar europium content.

[0005] The first aspect of the present invention is to provide a red light conversion agent, wherein the red light conversion agent is a complex, the center of the complex is europium, the first ligand is a maleic acid copolymer, and the second ligand is 1,10-phenanthroline.

[0006] According to the present invention, the center of the complex is an ion and the element is europium; that is, the central ion of the complex is a europium ion.

[0007] According to some preferred embodiments of the present invention, the molar ratio of europium, the carboxyl group in the first ligand, and the second ligand is 1:(0.5-5):(0.5-5), more preferably 1:(1-4):(1-4); and most preferably 1:(1-2):(2-3).

[0008] The preferred ratio of europium to the total amount of carboxyl groups in the first ligand and the second ligand is 1:4.

[0009] According to some preferred embodiments of the present invention, the fluorescence excitation range of the red light converting agent is 300 nm to 575 nm, and the fluorescence emission range is 400 nm to 590 nm, 600 nm to 635 nm, and 675 nm to 725 nm. Compared with commercially available converting agents, the red light converting agent of the present invention has a higher fluorescence quantum yield at a similar europium content.

[0010] According to some preferred embodiments of the present invention, the center is a trivalent europium ion.

[0011] According to some preferred embodiments of the present invention, the maleic acid copolymer is a hydrolysis product of maleic anhydride copolymer, preferably a hydrolysis product of maleic anhydride copolymer microspheres.

[0012] According to some more preferred embodiments of the present invention, the degree of hydrolysis of the anhydride group is 20% to 100%, with the total molar amount of anhydride in the maleic anhydride copolymer being 100%.

[0013] According to some preferred embodiments of the present invention, the maleic anhydride copolymer is a linear maleic anhydride copolymer and / or a crosslinked maleic anhydride copolymer. Preferably, the maleic anhydride copolymer can be maleic anhydride linear copolymer microspheres or maleic anhydride crosslinked copolymer microspheres.

[0014] According to some more preferred embodiments of the present invention, the diameter of the maleic anhydride copolymer microspheres is 0.2 to 5 micrometers, preferably 0.3 to 3 micrometers.

[0015] According to some preferred embodiments of the present invention, the maleic anhydride copolymer is a copolymer of maleic anhydride and one or more comonomers selected from those having isolated carbon-carbon double bonds with 2 to 30 carbon atoms.

[0016] Preferably, the maleic anhydride copolymer is a copolymer of maleic anhydride and one or more monomers selected from the following: butene, isobutene, cis-butadiene, pentene, isoprene, cyclopentadiene, dicyclopentadiene, hexene, hexadiene, cyclohexadiene, octene, octadiene, cyclooctadiene, styrene and its derivatives, vinyl acetate, vinyl alkyl ethers; most preferably, it is a maleic anhydride-butene copolymer.

[0017] For example, styrene and its derivatives include, but are not limited to, one or more of styrene, hyperbranched styrene, sulfonated styrene, and α-methylstyrene.

[0018] Preferably, the molar ratio of structural units derived from maleic anhydride to structural units derived from comonomers in the maleic anhydride copolymer is 1:99 to 99:1, more preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and most preferably a linear alternating maleic anhydride copolymer.

[0019] According to the present invention, maleic anhydride copolymer microspheres can be obtained from commercial products or can be made by existing methods. For example, the methods for making them can be found in CN114426617A and CN116262803A, including but not limited to the methods described in the embodiments of the present invention.

[0020] A second aspect of the present invention is to provide a method for preparing the red light conversion agent described in the first aspect, comprising:

[0021] A solution or dispersion containing maleic acid copolymer is mixed with europium salt solution to carry out a first reaction to obtain a first reaction mixture. Then, a solution containing 1,10-phenanthroline is mixed with the first reaction mixture to carry out a second reaction to obtain a mixture containing red light conversion agent. The solvent is removed to obtain the red light conversion agent.

[0022] According to some preferred embodiments of the present invention, the solvents used in the solutions or dispersions containing maleic acid copolymers, europium salt solutions, and solutions containing 1,10-phenanthroline are each non-aqueous solvents, which may be the same or different.

[0023] Preferably, the non-aqueous solvent is selected from at least one of methanol, ethanol, n-propanol, n-butanol, isopropanol, acetone, hexamethylphosphoric triamine, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, sulfolane, dioxane, hydroxypropionic acid, ethylamine, ethylenediamine, ethylene glycol, glycerol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol dimethyl ether, and 1,3-dioxane.

[0024] According to some preferred embodiments of the present invention, the preparation method further includes the step of preparing maleic anhydride copolymer by hydrolysis of preferred copolymer microspheres; preferably, the step of preparing maleic anhydride copolymer by hydrolysis includes: heating maleic anhydride copolymer in water to completely or partially dissolve or surface dissolve maleic anhydride copolymer, and then drying to obtain maleic anhydride copolymer.

[0025] The preferred selection of materials for the maleic anhydride copolymer is the same as that described in the first aspect, and will not be repeated here.

[0026] According to some preferred embodiments of the present invention, the molar ratio of europium in the europium salt, carboxyl group of maleic acid copolymer and 1,10-phenanthroline is 1:(0.5-5):(0.5-5), preferably 1:(1-4):(1-4); most preferably 1:(1-2):(2-3).

[0027] According to some preferred embodiments of the present invention, the europium salt is selected from trivalent europium salts, preferably at least one of europium chloride, europium sulfate, and europium nitrate.

[0028] According to some preferred embodiments of the present invention, the conditions for the first reaction include: a temperature of 15–65°C and / or a time of 0.1–24 h; and / or, the conditions for the second reaction include: a temperature of 15–65°C and / or a time of 0.1–24 h. Within the above temperature range, the reaction time can be appropriately shortened at higher temperatures and appropriately extended at lower temperatures, and so on, in combination and adjustment. This includes, but is not limited to, the reaction time and temperature conditions in the examples.

[0029] As an example, preferably, the preparation method of the red light conversion agent includes the following steps:

[0030] The maleic anhydride copolymer is added to sufficient water and heated until it is completely dissolved, partially dissolved, or surface dissolved, and then dried to obtain the maleic anhydride copolymer. A suitable non-aqueous solvent is selected to prepare a maleic anhydride copolymer solution.

[0031] Using the organic solvent described in step (1), prepare 1,10-phenanthroline solution and europium salt solution respectively, and heat and stir to completely dissolve the solid;

[0032] The maleic acid copolymer solution prepared in step (1) is slowly added to the europium salt solution prepared in step (2), and the mixture is stirred for a period of time to allow the reaction to proceed to completion.

[0033] The 1,10-phenanthroline ethanol solution prepared in step (2) is slowly added to the mixed solution obtained in step (3), and the mixture is heated to make the mixture homogeneous and react.

[0034] The mixed solution prepared in step (4) is dried to obtain the red light conversion agent solid.

[0035] A third aspect of the present invention is to provide a red light conversion powder, comprising a red light conversion agent and an optional carrier; wherein the red light conversion agent is the red light conversion agent described in the first aspect or the red light conversion agent obtained by the preparation method described in the second aspect.

[0036] According to some preferred embodiments of the present invention, the content of the red light-converting agent in the red light-converting powder is 0.1-100 wt%, and when no carrier is present, the content of the red light-converting agent in the red light-converting powder is 100 wt%. More preferably, the content of the red light-converting agent in the red light-converting powder is 10-75 wt%, and most preferably 25-50 wt%. Under the above-mentioned preferred content conditions, it is easier for the red light-converting powder to disperse in the resin, resulting in a more uniform light-converting resin.

[0037] According to some preferred embodiments of the present invention, the average particle size of the red light-converting powder ranges from 0.05 to 50 μm, preferably from 0.1 to 30 μm.

[0038] According to some preferred embodiments of the present invention, the carrier is an inorganic carrier and / or an organic carrier, preferably at least one of polyvinyl alcohol, ethylene-vinyl acetate copolymer, powdered rubber, silica, and calcium carbonate.

[0039] A fourth aspect of the present invention is to provide a method for preparing the red light-converting powder described in the third aspect, comprising:

[0040] The red light conversion agent is used to prepare the red light conversion powder, or the red light conversion powder is prepared by mixing raw materials including the red light conversion agent and the carrier.

[0041] Preferably,

[0042] The red light conversion agent is pulverized to obtain the red light conversion powder;

[0043] Alternatively, the mixed raw material containing the red light conversion agent and the carrier can be pulverized to obtain the red light conversion powder;

[0044] Alternatively, the red-light-converting powder can be prepared by spray drying of a solution or emulsion containing the red-light-converting agent and a carrier. This includes methods not described in the examples.

[0045] The fifth aspect of the present invention is to provide a light-converting resin comprising a thermoplastic resin and the red light-converting powder described in the third aspect or the red light-converting powder obtained by the preparation method described in the fourth aspect;

[0046] Preferably, the weight ratio of the red light-converting powder to the thermoplastic resin is (0.1–30):100, more preferably (0.5–20):100, and even more preferably (1–10):100; and / or,

[0047] Preferably, the thermoplastic resin is selected from at least one of the following resins: polyethylene, polyolefin elastomer, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl chloride, polystyrene, ethylene-tetrafluoroethylene copolymer, polypropylene, polyamide, polyoxymethylene, polymethyl methacrylate, polyphenylene ether, polysulfone, rubber, and polylactic acid.

[0048] A sixth aspect of the present invention is to provide a method for preparing the light-converting resin described in the fifth aspect, comprising melt-blending raw materials including the red light-converting powder and the thermoplastic resin.

[0049] As an example, the preparation method of the light-converting resin includes mixing the components, including the thermoplastic resin and the red light-converting powder, at the stated weight ratio until homogeneous, and then performing melt blending to obtain the light-converting resin. Specifically, the light-converting resin can be obtained by thoroughly mechanically mixing and stirring, followed by thermoplastic blending.

[0050] The method used in the preparation method of this invention for thermoplastic blending of components including thermoplastic resin and red light-converting powder is the usual melt blending method in rubber and plastic processing. The blending temperature, which is the usual processing temperature of thermoplastic resin, should be selected within a range that ensures the thermoplastic resin is completely melted without decomposing it.

[0051] In addition, depending on processing requirements, appropriate amounts of conventional thermoplastic resin processing additives can be added to the blended materials. During the blending process, the components, such as the red light-converting powder, can be simultaneously added to the melt blending equipment for melt blending via metering or other methods; alternatively, the components can be pre-mixed uniformly using general-purpose mixing equipment before being melt-blended in a rubber-plastic blending equipment.

[0052] The thermoplastic blending process described therein can be any thermoplastic melt blending process in the prior art, wherein preferably it is screw extrusion, internal mixing, open milling, or continuous mixing, and more preferably it is screw extrusion.

[0053] The rubber-plastic blending equipment used in the preparation method can be an open mill, internal mixer, single-screw extruder, twin-screw extruder, or torque rheometer, etc. The material mixing equipment is selected from existing mechanical mixing equipment such as high-speed mixers and kneaders.

[0054] The raw materials used in the preparation method may also contain commonly used additives in the plastics processing field, such as antioxidants, plasticizers, and other processing aids. The dosage of these commonly used additives is the conventional dosage, or it may be adjusted appropriately according to the actual requirements.

[0055] The seventh aspect of the present invention is to provide the application of the red light conversion agent described in the first aspect, or the red light conversion agent obtained by the preparation method described in the second aspect, or the red light conversion powder described in the third aspect, or the red light conversion powder obtained by the preparation method described in the fourth aspect, or the light conversion resin described in the fifth aspect, or the light conversion resin obtained by the preparation method described in the sixth aspect, in the fields of anti-counterfeiting materials, bioimaging, fluorescent dyes, light conversion films, solar cell sealants, and ultraviolet light absorbing materials.

[0056] The red light conversion agent of the present invention is not easily precipitated from the resin matrix and has a longer service life. Moreover, compared with commercially available conversion agents, the red light conversion agent of the present invention has a higher fluorescence quantum yield at a similar europium content. Attached Figure Description

[0057] Figure 1 The three-dimensional fluorescence spectrum of the red light converting agent prepared in Example 2;

[0058] Figure 2 The three-dimensional fluorescence spectrum of the red light converting agent prepared in Example 3;

[0059] Figure 3 The three-dimensional fluorescence spectrum of the red light converting agent prepared in Example 6;

[0060] Figure 4 Infrared spectra of the light-converting agents prepared for Comparative Example 1 (spectral line 1), Example 1 (spectral line 2), Example 2 (spectral line 3), Example 3 (spectral line 4), and Comparative Example 2 (spectral line 5).

[0061] Depend on Figure 4 It can be seen that in the red light conversion agents prepared in Comparative Example 1 and Examples 1-3, 625cm -1 The appearance of RE-O (rare earth-oxygen) stretching vibration peaks near the ion indicates that carboxylate ions have coordinated with rare earth ions; peaks of 1640–1690 cm⁻¹ were observed in Examples 1–3 and Comparative Example 2. -1The C=NH stretching vibration absorption peak shifted to the right and became stronger with increasing 1,10-phenanthroline content, indicating that rare earth ions coordinated with N in 1,10-phenanthroline. Examples 2 and 3 showed absorption peaks at 850 cm⁻¹. -1 and 720cm -1 The stretching vibration peaks observed should be attributed to the coordination of the secondary amine group in 1,10-phenanthroline with rare earth ions, which may explain the high quantum yield of the red light conversion agents prepared in Examples 2 and 3.

[0062] Using the same method, other examples also yielded complexes formed from maleic acid copolymers, 1,10-phenanthroline, and europium. Detailed Implementation

[0063] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0064] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0065] The experimental data in the examples were measured using the following instruments and methods:

[0066] (1) Observation of fluorescence phenomenon: The samples of the examples and comparative examples were placed in a dark room and the fluorescence phenomenon was observed under ultraviolet light irradiation. The power of the ultraviolet lamp was 24W and the wavelength of the ultraviolet light was 365nm.

[0067] (2) Fluorescence spectral data were analyzed and tested using a JY FL3 fluorescence spectrometer from Horiba Corporation, Japan. The resin sample was fixed on a solid sample holder, and the powder sample was spread on the fixed sample holder and compacted to ensure that the sample surface was smooth before testing. A 450W xenon lamp light source was used, with an excitation wavelength range of 250nm to 650nm and an emission spectrum range of 300nm to 1000nm. The emission spectrum was acquired using CCD mode.

[0068] Carboxyl equivalent of maleic acid copolymer: A fixed mass of maleic acid copolymer was used to prepare a 10 wt.% aqueous solution, which was then neutralized with sodium hydroxide aqueous solution. The molar amount of sodium hydroxide at pH≈7 was recorded as the carboxyl equivalent of maleic acid copolymer.

[0069] Test for whether red light conversion agent is easily precipitated in resin film: The light conversion film containing red light conversion agent is bonded together with a blank film without red light conversion agent. After two months, it is tested by visual inspection and ultraviolet light irradiation. If the blank film does not turn red and there is no red light under ultraviolet light, it is determined that no red light conversion agent migration is observed; if the blank film turns red and there is red light under ultraviolet light, it is determined that the red light conversion agent has migrated to the blank film, thus indicating that the red light conversion agent is easily precipitated from the light conversion film.

[0070] The maleic anhydride copolymer microspheres used in the examples were all self-made using existing methods, as described in CN114426617A and CN116262803A. The particle size can be controlled by reaction process parameters such as reaction time, monomer concentration, and reaction medium. The copolymer microspheres described in this invention are preferably monodisperse copolymer microspheres; the average particle size of the maleic anhydride copolymer microspheres in the following examples is 0.2–5 micrometers. Furthermore, the copolymers in the maleic anhydride copolymer microspheres in the following examples are all linear alternating copolymers.

[0071] Example 1

[0072] Weigh out maleic anhydride-butene linear alternating copolymer microspheres (average particle size 1.1 μm) and place them in a beaker. Add water to prepare a 10 wt.% suspension. Seal the beaker and place it in an oven. Heat at 70 °C for 4 hours. Dry the solution after the reaction to obtain a solid maleic anhydride-butene copolymer with 100% hydrolysis.

[0073] Prepare a 10 wt.% ethanol solution from maleic acid-butene copolymer solid by constant temperature heating and stirring until the solid is completely dissolved (at 50°C). Heat an EuCl3 ethanol solution at a constant temperature (50°C) and stir until completely dissolved. Prepare a 1,10-phenanthroline ethanol solution.

[0074] The prepared EuCl3 ethanol solution was slowly added to the maleic acid-butene copolymer ethanol solution. Some precipitate formed. The mixture was heated and stirred in a 50°C water bath until the precipitate was completely dissolved. Finally, the synergistic ligand 1,10-phenanthroline ethanol solution was added according to the specified ratio, and the mixture was heated and stirred at 50°C for 4 hours. The resulting solution was then placed in an oven and heated at 50°C until dry to obtain the red light conversion agent. The molar ratio of the three components (europium: carboxyl group in the maleic acid copolymer: 1,10-phenanthroline) was 1:3:1.

[0075] Comparative Example 1

[0076] The red light conversion agent was prepared according to the method of Example 1, except that 1,10-phenanthroline was not added, that is, the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) in the red light conversion agent was 1:4:0.

[0077] Examples 2-3

[0078] The steps are the same as in Example 1, except that the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) is controlled as shown in Table 1.

[0079] Comparative Example 2

[0080] The steps are the same as in Example 1, except that maleic acid copolymer is not added, i.e., the molar ratio of the three (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) is 1:0:4.

[0081] Example 4

[0082] Weigh out maleic anhydride-vinyl acetate copolymer microspheres (refer to Stabilizer-free dispersion copolymerization of maleic anhydride and vinyl acetate. I. Effects of principal factors on microspheres (J. Polym. Sci., Part A: Polym. Chem. 2005(43), 3760-3770. A novel facile method for the preparation of uniform, reactive maleic anhydride acetate copolymer micro-and nanospheres. Macromol. Rapid. Commun., 2004, 25, 1568-1574. (Preparation) Place the mixture in a beaker, add water to prepare a 10 wt.% suspension, seal the beaker, and place it in an oven. Heat at 70°C for 4 hours. Dry the reacted solution to obtain a solid maleic acid-vinyl acetate copolymer. Prepare a 10 wt.% ethanol solution from the solid maleic acid-vinyl acetate copolymer, heating and stirring at a constant temperature (50°C) until the solid is completely dissolved. Heat and stir an EuCl3 ethanol solution at a constant temperature until completely dissolved. Prepare a 1,10-phenanthroline ethanol solution, heating and stirring at 50°C until dissolved.

[0083] The prepared EuCl3 ethanol solution was slowly added to the maleic acid-vinyl acetate copolymer ethanol solution. Some precipitate formed. The mixture was heated and stirred in a 50°C water bath until the precipitate was completely dissolved. Finally, the co-ligand-1,10-phenanthroline ethanol solution was added according to the specified ratio, and the mixture was heated and stirred at 50°C for 4 hours. The resulting solution was then placed in an oven and heated at 50°C until dry to obtain the red light conversion agent. The molar ratio of the three components (europium: carboxyl group in the maleic acid copolymer: 1,10-phenanthroline) was controlled to be 1:3:1.

[0084] Comparative Example 3

[0085] The red light conversion agent was prepared according to the method in Example 4, except that 1,10-phenanthroline was not added, that is, the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) in the red light conversion agent was 1:4:0.

[0086] Examples 5-6

[0087] The steps are the same as in Example 4, except that the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) is controlled as shown in Table 1.

[0088] Example 7

[0089] Weigh maleic anhydride-styrene copolymer microspheres into a beaker, add water to prepare a 10 wt.% suspension, seal the beaker and place it in an oven, heating at 70°C for 4 hours. Dry the reacted solution to obtain maleic anhydride-styrene copolymer solid. Prepare a 10 wt.% ethanol solution from the maleic anhydride-styrene copolymer solid, heating and stirring at 50°C until the solid is completely dissolved. Heat and stir the EuCl3 ethanol solution at 50°C until completely dissolved. Prepare a 1,10-phenanthroline ethanol solution, heating and stirring at 50°C until dissolved. Slowly add the prepared EuCl3 ethanol solution to the maleic anhydride-styrene copolymer ethanol solution; some precipitate will form. Heat and stir in a 50°C water bath until the precipitate is completely dissolved. Finally, add the co-ligand-1,10-phenanthroline ethanol solution according to the ratio, heating and stirring at 50°C for 4 hours. Place the reacted solution in an oven and heat at 50°C until dry to obtain the red light conversion agent. The molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) is controlled to be 1:3:1.

[0090] Comparative Example 4

[0091] The red light conversion agent was prepared according to the method of Example 7, except that 1,10-phenanthroline was not added, that is, the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) in the red light conversion agent was 1:4:0.

[0092] Examples 8-9

[0093] The steps are the same as in Example 7, except that the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) is controlled as shown in Table 1.

[0094] Comparative Example 5

[0095] The steps are the same as in Example 7, except that maleic anhydride-styrene copolymer microspheres are not used, that is, the molar ratio of the three components (europium: carboxyl group in maleic acid copolymer: 1,10-phenanthroline) in the red light conversion agent is 1:0:4.

[0096] Comparative Example 6

[0097] The prepared EuCl3 ethanol solution was slowly added to the stearic acid ethanol solution. Some precipitate was formed. The mixture was heated and stirred in a 50°C constant temperature water bath until the precipitate was completely dissolved. Finally, the co-ligand-1,10-phenanthroline ethanol solution was added according to the ratio. The mixture was heated and stirred at 50°C for 4 hours. The resulting solution was placed in an oven and heated at 50°C until it was dried to obtain the red light conversion agent. The molar ratio of the three components (EuCl3: stearic acid: 1,10-phenanthroline) was controlled at 1:1:3.

[0098] Example 10

[0099] The red light conversion agent prepared in Example 2 was ball-milled for 1 hour to prepare red light conversion powder with a particle size of 3-50 μm.

[0100] Example 11

[0101] The red light conversion agent prepared in Example 6 was ball-milled for 1 hour to prepare red light conversion powder with a particle size of 3-50 μm.

[0102] Example 12

[0103] The red light conversion agent prepared in Example 9 was ball-milled for 1 hour to prepare red light conversion powder with a particle size of 3-50 μm.

[0104] Example 13

[0105] The ethanol solution of the red light conversion agent prepared in Example 2 was heated until a small amount of ethanol remained. It was then mixed with the emulsion of styrene-butadiene rubber (Sinopec Shanghai Gaoqiao Branch) and spray-dried (the specific spray-drying method is referred to patent CN200910176977.8). This process can prepare red light conversion powder that is supported and dispersed on powdered rubber. The mass ratio of red light conversion powder is controlled to be 25%, and the total mass of red light conversion powder and powdered rubber based on solid content is 100%. The conversion powder is hollow spherical with a particle size of 5-100 μm.

[0106] Example 14

[0107] The ethanol solution of the red light conversion agent prepared in Example 6 was heated until a small amount of ethanol remained. It was then mixed with the emulsion of styrene-butadiene rubber (Sinopec Shanghai Gaoqiao Branch) and spray-dried (for specific spray-drying methods, refer to patent CN200910176977.8) to prepare red light conversion powder loaded and dispersed in powder rubber. The mass ratio of red light conversion powder was controlled to be 40%, and the total mass of red light conversion powder and powder rubber based on solid content was 100%. The conversion powder was hollow spherical with a particle size of 5-100 μm.

[0108] Example 15

[0109] The ethanol solution of the red light conversion agent prepared in Example 9 was heated until only a small amount of ethanol remained. It was then mixed with the emulsion of styrene-butadiene rubber (Sinopec Shanghai Gaoqiao Branch) and spray-dried (for specific spray-drying methods, refer to patent CN200910176977.8) to prepare red light conversion powder loaded and dispersed in powder rubber. The mass ratio of red light conversion powder was controlled to be 50%, and the total mass of red light conversion powder and powder rubber based on solid content was 100%. The conversion powder was hollow spherical with a particle size of 5-100 μm.

[0110] Example 16

[0111] The red light-converting powder prepared in Example 13 was blended with LDPE granules, with the amount of red light-converting powder added to LDPE being 4%. Based on the mass of LDPE being 100%, the mixture was extruded and granulated using a twin-screw extruder and then hot-pressed into a film to prepare a light-converting resin and a light-converting film that can convert ultraviolet light into red light.

[0112] The prepared light-converting film was bonded together with a blank film without added light-converting agent, and after two months of storage, no migration of the light-converting agent was observed.

[0113] Example 17

[0114] The red light-converting powder prepared in Example 14 was blended with LDPE granules. The amount of red light-converting powder added to LDPE was 2.5%. Based on the mass of LDPE as 100%, the mixture was extruded and granulated by a twin-screw extruder and then hot-pressed into a film to prepare a light-converting resin and a light-converting film that can convert ultraviolet light into red light.

[0115] The prepared light-converting film was bonded together with a blank film without added light-converting agent, and after two months of storage, no migration of the light-converting agent was observed.

[0116] Example 18

[0117] The red light-converting powder prepared in Example 15 was blended with LDPE granules, with the amount of red light-converting powder added to LDPE being 2%. Based on the mass of LDPE being 100%, the mixture was extruded and granulated using a twin-screw extruder and then hot-pressed into a film to prepare a light-converting resin and a light-converting film that can convert ultraviolet light into red light.

[0118] The prepared light-converting film was bonded together with a blank film without added light-converting agent, and after two months of storage, no migration of the light-converting agent was observed.

[0119] Comparative Examples 7 and 8

[0120] Comparative Example 6 and commercially available light-converting agent were blended with LDPE granules, with the amount of red light-converting powder added to LDPE being 4%. The mixture was extruded and granulated using a twin-screw extruder with LDPE as 100% by mass, and then hot-pressed into a film to prepare a light-converting resin and a light-converting film that can convert ultraviolet light into red light.

[0121] The prepared light-converting film was bonded together with a blank film without added light-converting agent. After two months, red light-converting agent could be observed on the surface of the blank film, indicating that the small molecule doped light-converting agent would slowly migrate in the LDPE resin film.

[0122] It was verified that the red light conversion agent in Comparative Example 5 was also easily precipitated from the light conversion film.

[0123] Table 1

[0124]

[0125]

[0126] Table 2. Fluorescence quantum yield and europium content of red light converting agent and commercially available light converting agent in Examples 2, 3, 6, and 9.

[0127] Fluorescence quantum yield (%) Europium content (wt.%) Example 2 34.23 27.45 Example 3 25.20 25.99 Example 6 35.43 10.29 Example 9 20.06 34.69 Commercially available light conversion agents 16.38 27.40

[0128] The europium content was determined by energy-dispersive X-ray spectroscopy (EDS), with the total elemental mass of the red light-converting agent being 100 wt%.

[0129] As can be seen from the comparison between Examples 16-18 and Comparative Examples 7-8, the red light conversion agent of the present invention overcomes the problem that conventional organic small molecule complex red light conversion agents are easy to precipitate from the resin. The red light conversion agent of the present invention is not easy to precipitate from the resin matrix and has a longer service life.

[0130] Based on the above-mentioned technical effects, as can be seen from the comparison of Examples 1-9 and Comparative Examples 1-4, the present invention uses a complex of europium, maleic acid copolymer and 1,10-phenanthroline as a red light conversion agent, which has a higher fluorescence quantum yield.

[0131] As can be seen from the comparison of Examples 3, 6, and 9 with Comparative Example 6, under the same ratio of europium:carboxyl:1,10-phenanthroline, the red light conversion agent in the examples of the present invention has a higher fluorescence intensity, achieving unexpected technical effects.

[0132] As can be seen from the comparison between Example 2 and commercially available fluorescence converters, under similar europium content, the red fluorescence converter of the present invention has a higher fluorescence quantum yield. The present invention can obtain a red fluorescence converter with a high fluorescence quantum yield while minimizing the amount of europium added; thus achieving unexpected technical effects.

[0133] As can be seen from Examples 1-9, the ratio of the central ion europium to the first ligand being a maleic acid copolymer and the second ligand being 1,10-phenanthroline in this invention has a wide range. The specific ratio can be adjusted as needed to obtain red light conversion agents with different fluorescence quantum yields. Under the preferred ratio of this invention, the obtained red light conversion agent has a higher fluorescence quantum yield.

[0134] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0135] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0136] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0137] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0138] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0139] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A red light conversion agent, wherein the red light conversion agent is a complex, the center of the complex is europium, the first ligand is a maleic acid copolymer, and the second ligand is 1,10-phenanthroline.

2. The red light conversion agent according to claim 1, characterized in that: The molar ratio of europium, the carboxyl group in the first ligand, and the second ligand is 1:(0.5-5):(0.5-5), preferably 1:(1-4):(1-4); and / or, The red light conversion agent has a fluorescence excitation range of 300 nm to 575 nm and a fluorescence emission range of 400 nm to 590 nm, 600 nm to 635 nm, and 675 nm to 725 nm; and / or, The center is a trivalent europium ion.

3. The red light conversion agent according to claim 1, characterized in that: The maleic acid copolymer is a hydrolysis product of maleic anhydride copolymer; preferably, it is a product of maleic anhydride copolymer. The degree of hydrolysis of the anhydride groups is 20%–100%, with the total molar amount of anhydride in the maleic anhydride copolymer being 100%; and / or, Preferably, the maleic anhydride copolymer is a linear maleic anhydride copolymer and / or a crosslinked maleic anhydride copolymer; and / or, Preferably, the diameter of the microspheres of the maleic anhydride copolymer is 0.2 to 5 micrometers, more preferably 0.3 to 3 micrometers.

4. The red light conversion agent according to claim 3, characterized in that: The maleic anhydride copolymer is a copolymer of maleic anhydride and one or more comonomers selected from those having isolated carbon-carbon double bonds with 2 to 30 carbon atoms. Preferably, the maleic anhydride copolymer is a copolymer of maleic anhydride and one or more monomers selected from the following: butene, isobutene, maleic butadiene, pentene, isoprene, cyclopentadiene, dicyclopentadiene, hexene, hexadiene, cyclohexadiene, octene, octadiene, cyclooctadiene, styrene and its derivatives, vinyl acetate, vinyl alkyl ethers; and / or, Preferably, the molar ratio of structural units derived from maleic anhydride to structural units derived from comonomers in the maleic anhydride copolymer is 1:99 to 99:1, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:

30.

5. A method for preparing a red light conversion agent according to any one of claims 1-4, comprising: A solution or dispersion containing maleic acid copolymer is mixed with europium salt solution to carry out a first reaction to obtain a first reaction mixture. Then, a solution containing 1,10-phenanthroline is mixed with the first reaction mixture to carry out a second reaction to obtain a mixture containing red light conversion agent. The solvent is removed to obtain the red light conversion agent.

6. The preparation method according to claim 5, characterized in that: The solvents used in solutions or dispersions containing maleic acid copolymers, europium salt solutions, and solutions containing 1,10-phenanthroline are each non-aqueous solvents, and may be the same or different. Preferably, the non-aqueous solvent is selected from at least one of methanol, ethanol, n-propanol, n-butanol, isopropanol, acetone, hexamethylphosphoric triamine, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, sulfolane, dioxane, hydroxypropionic acid, ethylamine, ethylenediamine, ethylene glycol, glycerol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol dimethyl ether, and 1,3-dioxane.

7. The preparation method according to claim 5, characterized in that: The preparation method further includes a step of preparing maleic acid copolymer by hydrolysis of maleic anhydride copolymer; preferably, the step of preparing maleic acid copolymer by hydrolysis includes: The maleic anhydride copolymer is heated in water to completely or partially dissolve or surface dissolve the maleic anhydride copolymer, and then dried to obtain the maleic anhydride copolymer.

8. The preparation method according to any one of claims 5-7, characterized in that: The molar ratio of europium in the europium salt, the carboxyl group of the maleic acid copolymer, and 1,10-phenanthroline is 1:(0.5-5):(0.5-5), preferably 1:(1-4):(1-4); and / or, The europium salt is selected from trivalent europium salts, preferably at least one of europium chloride, europium sulfate, and europium nitrate; and / or, The conditions for the first reaction include a temperature of 15–65°C and / or a time of 0.1–24 h; and / or the conditions for the second reaction include a temperature of 15–65°C and / or a time of 0.1–24 h.

9. A red light conversion powder, comprising a red light conversion agent and an optional carrier; wherein the red light conversion agent is the red light conversion agent according to any one of claims 1-4 or the red light conversion agent obtained by the preparation method according to any one of claims 5-8; Preferably, the content of the red light conversion agent in the red light conversion powder is 0.1-100 wt%, more preferably 10-75 wt%.

10. The red light to light conversion powder according to claim 9, characterized in that: The average particle size of the red light-converting powder ranges from 0.05 to 50 μm, preferably from 0.1 to 30 μm; and / or, The carrier is an inorganic carrier and / or an organic carrier, preferably at least one of polyvinyl alcohol, ethylene-vinyl acetate copolymer, powdered rubber, silica, and calcium carbonate.

11. A method for preparing the red light-converting powder according to claim 9 or 10, comprising: The red light conversion agent is used to prepare the red light conversion powder, or the red light conversion powder is prepared by mixing raw materials including the red light conversion agent and the carrier. Preferably, The red light conversion agent is pulverized to obtain the red light conversion powder; Alternatively, the mixed raw material containing the red light conversion agent and the carrier can be pulverized to obtain the red light conversion powder; Alternatively, the red light-converting powder can be prepared by spray drying of a solution or emulsion containing the red light-converting agent and a carrier.

12. A light-converting resin comprising a thermoplastic resin and the red light-converting powder according to any one of claims 9 to 10 or the red light-converting powder obtained by the preparation method according to claim 11; Preferably, the weight ratio of the red light-converting powder to the thermoplastic resin is (0.1–30):100, more preferably (0.5–20):100, and even more preferably (1–10):100; and / or, Preferably, the thermoplastic resin is selected from at least one of the following resins: polyethylene, polyolefin elastomer, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl chloride, polystyrene, ethylene-tetrafluoroethylene copolymer, polypropylene, polyamide, polyoxymethylene, polymethyl methacrylate, polyphenylene ether, polysulfone, rubber, and polylactic acid.

13. A method for preparing the light-converting resin according to claim 12, comprising melt-blending raw materials including the red light-converting powder and thermoplastic resin.

14. The application of a red light conversion agent according to any one of claims 1 to 4, or a red light conversion agent obtained by the preparation method according to any one of claims 5 to 8, or a red light conversion powder according to any one of claims 9 to 10, or a red light conversion powder obtained by the preparation method according to claim 11, or a light conversion resin according to claim 12, or a light conversion resin obtained by the preparation method according to claim 13, in the fields of anti-counterfeiting materials, bioimaging, fluorescent dyes, light conversion films, solar cell sealants, and ultraviolet light absorbing materials.

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