Fluorescent copolymer microsphere as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, in particular to a fluorescent copolymer microsphere as well as a preparation method and application thereof. A copolymer of the fluorescent copolymer microsphere is a linear copolymer and contains a structural unit containing at least one group selected from a maleic amide group and a maleimide group; the fluorescent copolymer microspheres are at least one of microspheres obtained in the following mode: carrying out spray drying on a solution of a polymer containing a maleic amide group to obtain maleic amidated copolymer microspheres; or the preparation method further comprises the step of heating and imidizing the maleimide copolymer microspheres, so as to obtain the maleimide copolymer microspheres. The fluorescent copolymer microsphere provided by the invention has better fluorescence property and adjustable particle size, and is very suitable for being used as a fluorescent auxiliary agent of downstream products.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to fluorescent copolymer microspheres, a preparation method thereof, and applications thereof. Background Art

[0002] Maleic anhydride, as a common monomer, can be copolymerized with a variety of monomers, but due to the presence of anhydride reactive groups in the copolymer, its heat resistance and weather resistance are undesirable. The performance of maleic anhydride copolymers has more superior performance than maleic anhydride copolymers, and the imidized ring is very stable, and its application is more extensive. Usually, maleic anhydride copolymers need to synthesize N-hydrocarbon-substituted maleamide / imide monomers first, and then copolymerize with other monomers. The steps are relatively loaded down with trivial details, and the purification of monomers is difficult. However, the maleic anhydride copolymer amidation / imidization modification method is simpler and more feasible.

[0003] Li Benqiang et al. (Study on the preparation of SMI by imidization and its heat-resistant modification of ABS [J]. Plastics Industry, 2016, 44(12): 23-27.) used styrene-maleic anhydride copolymer (SMA) and aniline as raw materials and synthesized styrene-N-phenylmaleimide copolymer (SMI) by imidization. The prepared SMI was melt-blended with ABS resin in a certain proportion and it was found that SMI could effectively improve the heat resistance of ABS resin and maintain good mechanical properties. However, the article did not mention the fluorescence properties and morphology of SMI. Patent CN112574336B aminates maleic anhydride copolymer microspheres in an atmosphere of aminating gas to obtain maleamic acid copolymer microspheres, and then heats them to obtain microspherical maleimide copolymers, but the patent did not mention the fluorescence properties. Patent RU2513100C2 utilizes a mixed reaction of styrene-maleic anhydride copolymer and an alkylamine solution, and then obtains a maleimide copolymer at 310-340°C. The application effect in resins such as ABS, AES, and ASA is studied. However, this patent does not involve the fluorescence properties and morphology of the maleimide copolymer.

[0004] Fluorescence refers to a phenomenon known as photoluminescence. After receiving energy from high-energy (short-wavelength) photons, fluorescent materials dissipate some of this energy as heat, while converting the remaining energy into low-energy (long-wavelength) photons, generating fluorescence. Fluorescent materials have a wide range of applications in biology, medicine, chemistry, physics, and engineering. They can be used not only to study and monitor biomolecules and environmental parameters, but also in advertising, safety signs, and artwork. To date, there are few reports of maleimide copolymers that are both fluorescent and microspherical. Therefore, the development of fluorescent maleimide / imidized copolymer microspheres, their preparation methods, and their applications are of great practical significance. Summary of the Invention

[0005] The inventors of the present invention have found through research that the copolymer microspheres with fluorescent properties can be obtained by ammoniation with ammonia using linear alternating maleic anhydride copolymer microspheres, or further heat treatment imidization. However, the fluorescence intensity of the copolymer microspheres obtained is low, and, subject to the morphology of the upstream linear alternating maleic anhydride copolymer microspheres, it is difficult to obtain microspheres with larger particle diameters. The above two factors limit its scope of application. The inventors of the present invention have unexpectedly found that new fluorescent copolymer microspheres can be obtained using the method of the present invention, which not only can significantly improve the fluorescent properties of the copolymer microspheres, but also the particle diameter of the copolymer microspheres is adjustable, and microspheres with smaller particle diameters can be obtained as needed, or microspheres with larger particle diameters can be obtained. Specifically, the purpose of this invention is to provide a kind of fluorescent copolymer microspheres and preparation method and application thereof, as mentioned above, the fluorescent copolymer microspheres of the present invention have better fluorescent properties and adjustable particle diameter, and are very suitable as fluorescent auxiliary agents for downstream products.

[0006] The first aspect of the present invention is to provide fluorescent copolymer microspheres, wherein the copolymer is a linear copolymer containing a structural unit containing at least one group selected from maleamide groups and maleimide groups;

[0007] The fluorescent copolymer microspheres are at least one of the microspheres obtained in the following ways:

[0008] The maleimide group-containing polymer solution is spray-dried to obtain maleimide copolymer microspheres; or the maleimide copolymer microspheres are further heated for imidization to obtain maleimide copolymer microspheres.

[0009] As mentioned above, under the same test conditions, the fluorescent copolymer microspheres of the present invention have a higher fluorescence intensity than the same type of fluorescent copolymer microspheres prepared by using the same raw materials and ammonia. Since there is a deviation in the fluorescence intensity of the same sample detected by different equipment or under different experimental conditions, as an example, the equipment and method of the present invention are used to analyze and test the sample using a JY FL3 fluorescence spectrometer from Horiba, Japan, using a 450W xenon lamp light source, an excitation wavelength range of 250 to 650nm, and an emission spectrum range of 300 to 1000nm. Under the same equipment and detection conditions, the fluorescent copolymer microspheres of the present invention (such as Example 1) and the same type of fluorescent copolymer microspheres prepared by using the same raw materials and ammonia (Comparative Example 2) are detected. The maleimide copolymer microspheres of the present invention have a maximum emission intensity of 47,000 counts at 380nm excitation light, and the maleimide copolymer microspheres have a maximum emission intensity of 65,000 counts at 380nm excitation light. The maximum emission intensity of the same type of fluorescent copolymer microspheres prepared by using the same raw materials and ammonia at 380nm excitation light is less than 17,000 counts. Not only that, the fluorescence performance of the copolymer microspheres of the present invention is also higher than that of the sheet product obtained under the same preparation conditions. It can be seen that the present invention has achieved expected different technical effects from multiple aspects.

[0010] After research, it was found that the fluorescent properties of maleimidized copolymer microspheres obtained from the same raw materials are better than those of maleamidated copolymer microspheres. Therefore, it is further preferred that the fluorescent copolymer microspheres of the present invention are maleimidized copolymer microspheres.

[0011] According to some preferred embodiments of the present invention, the fluorescent copolymer microspheres have a fluorescence emission range of 400-600 nm when the excitation light range is 320-500 nm. Preferably, the strongest fluorescence emission range is 450-500 nm, exhibiting blue-green fluorescence, which is beneficial for its application as a fluorescent material.

[0012] The strongest fluorescence emission interval refers to a fluorescence emission interval in the fluorescence spectrum where the emission peak intensity is 60% or more of the strongest emission peak intensity.

[0013] As previously mentioned, the particle size of the copolymer microspheres of the present invention is adjustable, and smaller or larger particle size microspheres can be obtained by adjusting the spray drying parameters or the concentration and viscosity of the polymer solution as needed. According to some preferred embodiments of the present invention, the fluorescent copolymer microspheres are spherical or quasi-spherical in shape, preferably with a particle size range of 0.8-30 μm, more preferably 1-20 μm, for example, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 10 μm, 15 μm, 20 μm, and any two values ​​or any interval between any two values.

[0014] According to some preferred embodiments of the present invention, when the fluorescent copolymer microspheres are maleimidized copolymer microspheres, the total molar proportion of structural units containing maleimide groups in the maleimidized copolymer is greater than 10%, and is between 10% and 100%, preferably between 10% and 70%, more preferably between 10% and 60%, and most preferably between 20% and 55%, based on the total molar amount of maleic anhydride groups and maleic anhydride-derived groups contained in the maleimidized copolymer as 100%. Studies have shown that the degree of imidization in the maleimidized copolymer microspheres obtained using the method of the present invention is lower than that of maleimidized copolymer microspheres obtained by amination with ammonia and then imidization.

[0015] According to the present invention, the maleic anhydride derivative group refers to one or more of a maleamide group, a maleic acid group, a maleimide group, and a maleamide group.

[0016] According to some preferred embodiments of the present invention, the number average molecular weight of the linear copolymer is less than 30,000 g / mol, preferably less than 25,000 g / mol.

[0017] The copolymer raw materials in the present invention can be selected according to the following materials, for example, the copolymer raw materials can obtain a solution of a polymer containing maleamide groups in ammonia water, and then carry out subsequent preparation steps. The inventors of the present invention have found that when a copolymer containing maleic anhydride and its derivative groups, such as a polymer raw material containing at least one of the structural units of maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups, is dissolved in ammonia water, a polymer aqueous solution can be obtained. According to some preferred embodiments of the present invention, the linear copolymer is derived from one or more copolymer raw materials containing maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups; preferably, the copolymer raw material is a copolymer of one or more polymerization monomers containing maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups and a monomer containing isolated carbon-carbon double bonds.

[0018] The maleic anhydride group refers to The maleimide group refers to Maleic acid and ammonium salt groups, maleamic acid and ammonium salt groups refer to Wherein M is the same or different and each is hydroxyl, amino or ammonium (-ONH4).

[0019] According to the invention, the polymers are carbon chain polymers in which the heteroatoms O and N are present in side groups.

[0020] The inventors of the present invention have also found that when maleic anhydride cross-linked alternating copolymers are used to replace the raw materials in the existing embodiments, it is difficult to form a uniform and transparent solution when mixed with ammonia water, and it is not suitable for preparing microspheres by spray drying. Therefore, more preferably, the copolymer raw material is a maleic anhydride linear copolymer. The inventors of the present invention have also found that when the content of maleic anhydride-derived structural units in the linear copolymer is low (such as commercially available styrene-maleic anhydride copolymers, the anhydride content is 8%-42%, based on the total content of all structural units as 100%), it is difficult to form a uniform and transparent solution with ammonia water, and it is not suitable for preparing microspheres by spray drying. Preferably, the content of maleic anhydride-derived structural units in the maleic anhydride linear copolymer is above 45%, based on the total content of all structural units as 100%. In this preferred embodiment, the maleic anhydride linear copolymer can form a uniform and transparent solution with ammonia water, and can be combined with spray drying to prepare microspheres. Further more preferably, at least one of the maleic anhydride linear alternating copolymers. More preferably, it is a linear alternating copolymer of maleic anhydride obtained by combining structural unit A provided by maleic anhydride and structural unit B provided by monomer M; the monomer M is selected from monomers containing isolated carbon-carbon double bonds, preferably at least one of vinyl acetate, C4 olefins, C4 fractions, C5 olefins, C5 fractions, C8 olefins, C8 fractions, C9 olefins, and C9 fractions, more preferably at least one of vinyl acetate, styrene, α-methylstyrene, C4 olefins, C4 fractions, C5 olefins, and C5 fractions.

[0021] The C4 olefins, C5 olefins, C8 olefins, and C9 olefins refer to olefins or mixed olefins containing 4, 5, 8, or 9 carbon atoms, respectively. For example, the C4 olefins may be a mixture of one or more olefins containing 4 carbon atoms; the C5 olefins may be a mixture of one or more olefins containing 5 carbon atoms; the C8 olefins may be a mixture of one or more olefins containing 8 carbon atoms; and the C9 olefins may be a mixture of one or more olefins containing 9 carbon atoms.

[0022] The C4 fraction and C5 fraction are selected from the C4 or C5 fractions of the oil refining or ethylene industry, preferably the C4 or C5 fractions obtained from ethylene cracking in the petrochemical industry; the C8 fraction and C9 fraction are selected from the steam cracking ethylene production process, naphtha platinum reforming process and coal tar in the petrochemical industry.

[0023] According to some more preferred embodiments of the present invention, the method for preparing the copolymer microspheres comprises:

[0024] reacting a copolymer raw material containing at least one of the structural units of maleic anhydride, maleimide, maleic acid and ammonium salt, or maleamic acid and ammonium salt groups with aqueous ammonia in a sealed environment to obtain a solution containing a polymer containing maleamide groups, and spray-drying the solution to obtain maleamidated copolymer microspheres; or

[0025] The method further comprises heating the maleimide copolymer microspheres to obtain maleimide copolymer microspheres.

[0026] The second aspect of the present invention is to provide a method for preparing the fluorescent copolymer microspheres described in the first aspect, comprising:

[0027] A copolymer raw material containing at least one of the structural units of maleic anhydride, maleimide, maleic acid and ammonium salt, or maleamic acid and ammonium salt groups is subjected to an amidation reaction with aqueous ammonia in a sealed environment to obtain a solution containing a polymer containing maleamide groups, and the solution is spray-dried to obtain maleamidated copolymer microspheres;

[0028] Alternatively, the maleimide copolymer microspheres are further subjected to heat treatment to obtain maleimide copolymer microspheres;

[0029] Wherein, the copolymer raw material is a linear copolymer.

[0030] According to some preferred embodiments of the present invention, the viscosity of the solution containing the maleimide-containing polymer is less than 100 mPa·s, preferably less than 80 mPa·s, and more preferably less than 50 mPa·s. Under the preferred solution viscosity of the present invention, the resulting microspheres have a more regular morphology.

[0031] The viscosity of the solution containing the maleimide group-containing polymer is related to the selection of the copolymer raw materials and the feeding of the raw materials.

[0032] According to some more preferred embodiments of the present invention, the molar ratio of the copolymer raw material, calculated as anhydride groups, to the ammonia solution, calculated as NH3, is 1:(0.1-10), preferably 1:(0.1-5), and more preferably 1:(0.1-2). The reaction is an amidation reaction between the anhydride groups in the maleic anhydride copolymer and the ammonia solution.

[0033] The ammonia water is selected from ammonia water of various concentrations in the prior art.

[0034] According to some more preferred embodiments of the present invention, the copolymer raw material accounts for 0.1%-10% of the total weight of the reaction mixture, preferably 0.1%-8%.

[0035] According to some more preferred embodiments of the present invention, the number average molecular weight of the copolymer raw material is less than 30,000 g / mol, preferably less than 25,000 g / mol. Under the preferred molecular weight conditions of the present invention, the obtained microspheres have a more regular morphology.

[0036] As an example, according to a more preferred technical solution of the present invention, a linear maleic anhydride copolymer is used as a matrix, and after amidation, a microspherical copolymer with fluorescent properties is prepared by controlling the viscosity and concentration of the solution, the molecular weight of the linear maleic anhydride copolymer used, and the molding method conditions, or further imidization is performed to obtain a microspherical copolymer with better fluorescent properties, and the resulting microspheres have a more regular morphology.

[0037] In the present invention, there is no particular requirement for the temperature and time of amidation in aqueous ammonia. As long as a solution containing a polymer containing maleic amide groups is obtained, preferably a transparent solution is formed, the next step can be carried out.

[0038] According to some preferred embodiments of the present invention, the copolymer raw material is a copolymer of a monomer containing one or more of maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups and a monomer containing an isolated carbon-carbon double bond;

[0039] More preferably, the copolymer raw material is a linear copolymer of maleic anhydride, preferably, the content of maleic anhydride-derived structural units in the linear copolymer of maleic anhydride is more than 45%, based on the total content of all structural units as 100%; further more preferably, it is at least one of a linear alternating copolymer of maleic anhydride, and even more preferably a linear alternating copolymer of maleic anhydride obtained by structural unit A provided by maleic anhydride and structural unit B provided by monomer M; the monomer M is selected from monomers containing isolated carbon-carbon double bonds, preferably at least one of vinyl acetate, C4 olefins, C4 fractions, C5 olefins, C5 fractions, C8 olefins, C8 fractions, C9 olefins, and C9 fractions; preferably at least one of vinyl acetate, styrene, α-methylstyrene, C4 olefins, C4 fractions, C5 olefins, and C5 fractions.

[0040] According to some preferred embodiments of the present invention, the spray drying conditions include: an air inlet temperature of 150°C-200°C, preferably 155°C-180°C; and / or an air outlet temperature of 60°C-100°C, preferably 70-95°C.

[0041] According to some preferred embodiments of the present invention, the conditions for the heat treatment include: a heat treatment temperature of 100°C-250°C, preferably 150°C-200°C, and / or a heat treatment time of 5min-60min, preferably 10min-30min.

[0042] In the preparation of fluorescent copolymer microspheres of the present invention, using the preferred number-average molecular weight, solution concentration, solution viscosity, and molding conditions of the maleic anhydride copolymer of the present invention, spherical or quasi-spherical modified products can be obtained with more regular morphology. When the number-average molecular weight, solution concentration, and solution viscosity of the maleic anhydride copolymer are not within the above-mentioned preferred conditions, although spherical or quasi-spherical fluorescent microspheres can be prepared, due to the close entanglement of the molecular chains in the solution, problems such as slow solution drying speed and wall hanging or product stringing and adhesion are likely to occur during the spray drying process. Within the preferred scope of the present invention, the entanglement concentration of the polymer molecular chains is suitable, and relatively more uniform particles can be formed during the spray drying process.

[0043] The third aspect of the present invention is to provide a use of the fluorescent copolymer microspheres described in the first aspect or the fluorescent copolymer microspheres obtained by the preparation method described in the second aspect as a fluorescent agent, an anti-ultraviolet agent, or a heat-resistant modifier.

[0044] As mentioned above, the fluorescent copolymer microspheres of the present invention have higher fluorescence intensity, a wide particle size range, and are more adjustable, and are very suitable for use as fluorescent agents for downstream products.

[0045] The fluorescent copolymer microspheres of the present invention can convert part of ultraviolet light into blue-green light, and thus can be used as an anti-ultraviolet agent.

[0046] The imide / amide groups in the fluorescent copolymer microspheres of the present invention can react with some resins such as PC and ABS, and can also serve as heat-resistant modifiers.

[0047] The inventors of this application discovered that, after reacting linear copolymers of maleic anhydride with ammonia, a solution of polymers containing maleimide groups can be obtained. This solution can then be spray-dried or combined with subsequent steps to produce fluorescent copolymer microspheres. Furthermore, compared to the prior art methods of preparing maleimide / imidized copolymers using gas amidation and subsequent imidization, the fluorescent copolymer microspheres of the present invention exhibit stronger fluorescence properties, achieving unexpected technical benefits. This may be because the present invention dissolves the linear copolymers of maleic anhydride in ammonia. In a solution environment, the polymer molecular chains can move relatively freely, and the amidated groups can act as non-conjugated fluorescent groups, which aggregate during the drying process, resulting in maleimide copolymer microspheres with higher fluorescence intensity. In contrast, products produced using gas amidation, because the polymer molecular chains are always in a fixed state, have fluorescence properties that are difficult to achieve compared to those produced using solution methods.

[0048] The main advantages of the present invention are:

[0049] (1) The raw materials of the maleic anhydride copolymer are readily available and the production process is mature;

[0050] (2) The preparation process of the fluorescent copolymer microspheres is industrially mature spray drying and heating treatment, which is easy to scale up and promote industrially;

[0051] The fluorescent copolymer microspheres can be evenly dispersed in resins, solutions, etc., and their fluorescent properties can provide them with a certain anti-counterfeiting effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is the SEM of the fluorescent maleamidated copolymer microspheres prepared in Example 1;

[0053] Figure 2 This is the fluorescence spectrum of the fluorescent maleamidated copolymer microspheres prepared in Example 1;

[0054] Figure 3 This is the SEM image of the fluorescent maleimidized copolymer microspheres prepared in Example 1;

[0055] Figure 4 This is the fluorescence spectrum of the fluorescent maleimidized copolymer microspheres prepared in Example 1;

[0056] Figure 5 This is the SEM of the fluorescent maleamidated copolymer prepared in Comparative Example 1;

[0057] Figure 6 This is the fluorescence spectrum of the fluorescent maleamidated copolymer prepared in Comparative Example 1;

[0058] Figure 7 This is the SEM of the fluorescent maleimidized copolymer prepared in Comparative Example 1;

[0059] Figure 8 This is the fluorescence spectrum of the fluorescent maleimidized copolymer prepared in Comparative Example 1;

[0060] Figure 9 This is the SEM of the fluorescent maleamidated copolymer prepared in Comparative Example 2;

[0061] Figure 10 This is the fluorescence spectrum of the fluorescent maleamidated copolymer prepared in Comparative Example 2;

[0062] Figure 11 This is the SEM of the fluorescent maleimidized copolymer prepared in Comparative Example 2;

[0063] Figure 12 This is the fluorescence spectrum of the fluorescent maleimidized copolymer prepared in Comparative Example 2;

[0064] Figure 13 This is the SEM of the fluorescent maleamidated copolymer prepared in Example 2;

[0065] Figure 14 This is the fluorescence spectrum of the fluorescent maleamidated copolymer prepared in Example 2;

[0066] Figure 15 This is the fluorescence spectrum of the fluorescent maleimidized copolymer prepared in Example 2;

[0067] Figure 16 This is the SEM of the fluorescent maleamidated copolymer prepared in Example 5. DETAILED DESCRIPTION

[0068] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0069] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0070] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0071] 1. The raw materials in the embodiments and comparative examples include:

[0072] Maleic anhydride, styrene, isoamyl acetate, azobisisobutyronitrile, and sodium hydroxide were purchased from Inokai and were of analytical grade; mixed C4 (C4 fraction) was from Zhenhai Refining and Chemical.

[0073] The maleic anhydride-styrene linear alternating copolymer (MSL) used in the examples was prepared according to the method described in the publication A new family of thermoplastic photoluminescence polymers. The main preparation conditions and parameters included a 1:1 molar ratio of maleic anhydride to styrene as the reaction monomers, isoamyl acetate as the medium, and azobisisobutyronitrile as the initiator. The molecular weight was adjusted by adjusting the reaction concentration, temperature, and time.

[0074] The maleic anhydride-C4 linear alternating copolymer (MC4L) used in the embodiment was prepared according to the preparation method described in Example 1 of the Chinese patent publication number CN107722177A. The main preparation conditions and parameters were as follows: the reaction monomers were maleic anhydride (20 kg) and mixed C4 (C4 fraction) A (14 kg), the medium was isoamyl acetate (100 L), and the initiator was azobisisobutyronitrile (2.4 kg). The composition (weight percentage) of the mixed C4 A was: 1,2-butadiene, 8.92%; 1,3-butadiene, 14.14%; 1-butene, 8.38%; trans-2-butene, 5.84%; cis-2-butene, 31.7%; vinyl acetylene, 10.99%; isobutane, 1.3%; isobutylene, 12.78%; n-butane, 2.58%, and others, 3.37%.

[0075] 2. The experimental data of the embodiments and comparative examples were measured using the following method:

[0076] (1) Solution viscosity: Fangrui NDJ-5S, 2# rotor, speed 60RPM.

[0077] (2) Scanning electron microscopy (SEM): The sample was glued on a conductive adhesive, gold-sprayed, and then observed using a COXEM EM-30 scanning electron microscope.

[0078] (3) Fluorescence performance test: The samples were analyzed and tested using a JY FL3 fluorescence spectrometer from Horiba, Japan, using a 450W xenon lamp as the light source, with an excitation wavelength range of 250 to 650 nm and an emission spectrum range of 300 to 1000 nm.

[0079] (4) Maleimidation rate: The ratio of maleimide to maleic anhydride (maleic anhydride in the polymer raw material is equal to the total amount of maleic anhydride + maleimide in the maleimidated copolymer) is calculated by integrating the area of ​​hydrogen on the NH of maleimide using nuclear magnetic resonance hydrogen spectrum and maleic anhydride comonomer as the internal standard, i.e., the maleimidation rate.

[0080] Unless otherwise specified, in the following examples and comparative examples, the reaction temperature for amidation to obtain a uniform solution is 80° C., and the reaction is carried out in a closed condition.

[0081] Example 1:

[0082] 15g of MSL (homemade, number-average molecular weight 23,800g / mol) was added to 23.17g of 25% ammonia solution and 261.8g of deionized water. The molar ratio of MSL (calculated as anhydride groups) to ammonia (calculated as NH3) was approximately 1:2. After a homogeneous solution (viscosity 33.5mPa·s) was formed, it was spray-dried at an inlet temperature of 175°C and an outlet temperature of 75°C. The resulting powder was collected as fluorescent maleamidated copolymer microspheres.

[0083] Its SEM photos are as follows Figure 1 As shown, it can be seen that the product particle size is between 1-15 μm; its fluorescence spectrum is as follows Figure 2 As shown, it can be seen that when the excitation light is between 300-500nm, the emission light range is 400-600nm, and the strongest emission area is 450-500nm.

[0084] The fluorescent maleimide copolymer microspheres were heated at 180°C for 30 min to obtain fluorescent maleimide copolymer microspheres. The SEM images are shown in FIG. Figure 3 As shown in the figure, the morphology of the product is almost unchanged before and after the heating treatment, and the particle size of the product is between 1-15 μm; its fluorescence spectrum is shown in the figure. Figure 4 As shown, it can be seen that compared with the above fluorescent maleimidated copolymer microspheres, the fluorescent maleimidated copolymer microspheres after heat treatment have stronger fluorescence intensity. When the excitation light is between 320-500nm, the emission light range is 400-600nm, and the strongest emission region is 450-500nm.

[0085] The strongest emission intensity of the maleamidated / imidated copolymer obtained in this example under 380 nm excitation light is shown in Table 1.

[0086] Comparative Example 1:

[0087] 15g of MSL (homemade, number-average molecular weight 23800g / mol) was added to 23.17g of 25% ammonia solution and 261.8g of deionized water. The molar ratio of MSL (calculated as anhydride groups) to ammonia (calculated as NH3) was approximately 1:2. After a uniform solution was formed, it was dried in an 80°C forced air oven to obtain a fluorescent maleamidated copolymer. Its SEM photograph is shown below. Figure 5 As shown, the product is a large piece of hundreds of microns; its fluorescence spectrum is as follows Figure 6 As shown, it can be seen that when the excitation light is between 320-450nm, the emission light range is 400-600nm, and the strongest emission area is 450-500nm.

[0088] The fluorescent maleimide copolymer was heated at 180°C for 30 min to obtain a fluorescent maleimide copolymer. Figure 7 As shown in Figure 2, the morphology of the product is almost unchanged before and after the heating treatment, and the particle size of the product is still hundreds of microns (large flakes); its fluorescence spectrum is shown in Figure 2. Figure 8 As shown, the fluorescent maleimidized copolymer after heat treatment exhibits a stronger fluorescence intensity than the aforementioned fluorescent maleimidized copolymer. When the excitation light is between 320-500 nm, the emission range is 400-600 nm, with the strongest emission region being 450-500 nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this comparative example when excited at 380 nm is shown in Table 1.

[0089] Comparative Example 2:

[0090] 15g of MSL (homemade, number average molecular weight 23800g / mol) was placed in a three-necked flask and ammonia was continuously introduced. After the reaction was completed (heat was released during the reaction, and the reaction was considered complete when the temperature of the three-necked flask returned to room temperature), fluorescent maleimide copolymer microspheres were obtained. The SEM photo of the microspheres is shown below. Figure 9 As shown, it can be seen that the product is a microsphere of about 1 μm, which has the same morphology as before the reaction; its fluorescence spectrum is shown in Figure 10 As shown, it can be seen that when the excitation light is between 350-450nm, the emission light range is 400-550nm, and the strongest emission area is 450-500nm.

[0091] The fluorescent maleimide copolymer microspheres were heated at 180°C for 30 min to obtain fluorescent maleimide copolymer microspheres. The SEM images are shown in FIG. Figure 11 As shown in Figure 2, the morphology of the product is almost unchanged before and after the heating treatment, and the particle size of the product is still about 1 μm; its fluorescence spectrum is shown in Figure 2. Figure 12 As shown in the figure, compared to the fluorescent maleimidized copolymer microspheres described above, the fluorescent maleimidized copolymer microspheres after heat treatment have a stronger fluorescence intensity. When the excitation light is between 320-500nm, the emission range is 400-600nm, with the strongest emission region being 450-500nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this comparative example when excited at 380nm is shown in Table 1.

[0092] By comparison, it can be seen that the fluorescence intensity obtained in Example is higher, significantly higher than that in Comparative Example 2. The reason may be that in Comparative Example 2, MSL solid is reacted with ammonia, and the MSL molecular chain is basically fixed, while a polymer solution is obtained in Example, and the polymer can move more freely in the solution. During the drying process, the fluorescent groups re-aggregate, and the fluorescence intensity of the product is higher. It can be seen that the present invention has achieved unexpected technical effects.

[0093] Example 2:

[0094] 15g of MSL (homemade, number average molecular weight 19800g / mol) was added to 11.5g of ammonia solution (concentration 25%) and 273.5g of deionized water. The molar ratio of MSL (calculated as anhydride groups) to ammonia solution (calculated as NH3) was approximately 1:1. After a uniform solution (viscosity 36.5mPa·s) was formed, it was spray-dried at an inlet temperature of 175°C and an outlet temperature of 75°C. The resulting powder was collected as fluorescent maleamidated copolymer microspheres. Its SEM photograph is shown below. Figure 13 As shown, it can be seen that the product particle size is between 1-15 μm; its fluorescence spectrum is as follows Figure 14 As shown, it can be seen that when the excitation light is between 300-500nm, the emission light range is 400-600nm, and the strongest emission area is 450-500nm.

[0095] The fluorescent maleimide copolymer microspheres were heated at 180°C for 30 min to obtain fluorescent maleimide copolymer microspheres. The SEM images showed that the morphology of the microspheres was almost unchanged before and after the heating treatment, and the particle size of the product was between 1 and 15 μm. The fluorescence spectrum was as shown in FIG. Figure 15 As shown, the fluorescent maleimidized copolymer microspheres after heat treatment exhibited stronger fluorescence intensity than the aforementioned fluorescent maleimidized copolymer microspheres. When the excitation light was between 320 and 500 nm, the emission range was 400 to 600 nm, with the strongest emission occurring between 450 and 500 nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this example, when excited at 380 nm, is shown in Table 1.

[0096] Example 3:

[0097] 10g of MSL (homemade, number-average molecular weight 19,800g / mol) was added to 3.68g of 25% ammonia solution and 186.32g of deionized water. The molar ratio of MSL (calculated as anhydride groups) to ammonia (calculated as NH3) was approximately 1:0.5. Once a homogeneous solution (viscosity 39mPa·s) was formed, it was spray-dried at an inlet temperature of 175°C and an outlet temperature of 75°C. The resulting powder was collected to form fluorescent maleamidated copolymer microspheres. The particle size ranged from 1 to 15μm. In the fluorescence spectrum, when the excitation wavelength was between 300 and 500nm, the emission range was 400-600nm, with the strongest emission occurring between 450 and 500nm.

[0098] The fluorescent maleimidized copolymer microspheres were heated at 180°C for 30 minutes to obtain fluorescent maleimidized copolymer microspheres. The particle size and morphology of the microspheres remained almost unchanged before and after the heat treatment, and the product particle size ranged from 1 to 15 μm. In the fluorescence spectrum, the fluorescent maleimidized copolymer microspheres after heat treatment exhibited stronger fluorescence intensity than the fluorescent maleimidized copolymer microspheres described above. When the excitation light was between 320 and 500 nm, the emission light ranged from 400 to 600 nm, with the strongest emission region being between 450 and 500 nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this example when excited at 380 nm is shown in Table 1.

[0099] Example 4:

[0100] 10g of MC4L (homemade, number-average molecular weight 19,800g / mol) was added to 10g of 25% ammonia solution and 180g of deionized water. The molar ratio of MC4L (calculated as anhydride groups) to ammonia (calculated as NH3) was approximately 1:2.3. After a homogeneous solution (viscosity 29.5mPa·s) was formed, it was spray-dried at an inlet temperature of 175°C and an outlet temperature of 75°C. The resulting powder was collected to form fluorescent maleamidated copolymer microspheres. The particle size ranged from 1 to 15μm. In the fluorescence spectrum, when the excitation wavelength was between 300 and 500nm, the emission range was 400-600nm, with the strongest emission occurring between 450 and 500nm.

[0101] The fluorescent maleimidized copolymer microspheres were heated at 180°C for 30 minutes to obtain fluorescent maleimidized copolymer microspheres. The particle size and morphology of the microspheres remained almost unchanged before and after the heat treatment, and the product particle size ranged from 1 to 15 μm. In the fluorescence spectrum, the fluorescent maleimidized copolymer microspheres after heat treatment exhibited stronger fluorescence intensity than the fluorescent maleimidized copolymer microspheres described above. When the excitation light was between 320 and 500 nm, the emission light ranged from 400 to 600 nm, with the strongest emission region being between 450 and 500 nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this example when excited at 380 nm is shown in Table 1.

[0102] Example 5:

[0103] 15g of MSL (homemade, number average molecular weight 23800g / mol) was added to 23.17g of ammonia solution (concentration 25%) and 111.83g of deionized water. The molar ratio of MSL (calculated as anhydride groups) to ammonia solution (calculated as NH3) was approximately 1:2. After a uniform solution (viscosity 109.5mPa·s) was formed, it was spray-dried with an inlet temperature of 175°C and an outlet temperature of 75°C. The collected product was fluorescent maleamidated copolymer microspheres. Its SEM photograph is shown below. Figure 16As shown, it can be seen that the product has a large number of filaments with a particle size of more than 20μm, and the product drawing phenomenon can be clearly seen during the spray drying process; in the fluorescence spectrum, when the excitation light is between 300-500nm, the emission light range is 400-600nm, and the strongest emission area is 450-500nm.

[0104] The fluorescent maleimidized copolymer microspheres were heated at 180°C for 30 minutes to obtain fluorescent maleimidized copolymer microspheres. The morphology remained almost unchanged before and after the heat treatment, and the product still contained a large number of filaments with a particle size exceeding 20 μm. In the fluorescence spectrum, the fluorescent maleimidized copolymer microspheres after heat treatment had a stronger fluorescence intensity than the fluorescent maleimidized copolymer microspheres. When the excitation light was between 320 and 500 nm, the emission light ranged from 400 to 600 nm, with the strongest emission region being 450 to 500 nm. The strongest emission intensity of the maleimidized / imidized copolymer obtained in this example when excited at 380 nm is shown in Table 1.

[0105] Test example

[0106] After testing, the maleimide rates of the maleimide copolymers obtained in Examples 1-5 and Comparative Examples 1-2 are as follows: the maleimide rate of the maleimide copolymer obtained in Example 3 is in the range of 36%-40%, and the maleimide rates of Example 1, Comparative Example 1 and Example 5 are all in the range of 45%-51%; the maleimide rate of the maleimide copolymer obtained in Example 2 is in the range of 42%-45%, the maleimide rate of the maleimide copolymer obtained in Example 4 is in the range of 50%-54%, and the maleimide rate of the maleimide copolymer obtained in Comparative Example 2 is as high as 99%.

[0107] Table 1 The strongest emission intensity of maleamidated / imidated copolymers under 380 nm excitation light

[0108] serial number Maleamidated copolymer counts Maleimidized copolymer counts Example 1 47470 65188 Comparative Example 1 44294 62011 Comparative Example 2 14105 16623 Example 2 44941 62376 Example 3 41964 60552 Example 4 47611 66458 Example 5 42058 63682

[0109] From the results of Example 1, Comparative Example 1, and Comparative Example 2 in Table 1, it can be seen that, compared with the drying method, the fluorescent maleimide / imidized copolymer microspheres of the present invention have a particle size of 1-15 μm, making them more uniformly dispersed in the resin; compared with the microspheres obtained by the gas amidation method, the fluorescent maleimide / imidized copolymer microspheres of the present invention have a higher fluorescence intensity.

[0110] By comparing the maleimide copolymer microspheres and the maleimidide copolymer microspheres obtained in the same example, it can be seen that the maleimidide copolymer microspheres have stronger fluorescence properties.

[0111] As can be seen from Example 5, when the solution viscosity is high, although spherical or quasi-spherical fluorescent microspheres can be prepared by spray drying, problems such as product adhesion and stringing are prone to occur. Under the preferred solution viscosity of the present invention (such as Example 1), the obtained microspheres have a more regular morphology.

[0112] Furthermore, during the experiment, it was found that when maleic anhydride cross-linked alternating copolymer was used to replace the raw materials in the existing embodiment, it was difficult to form a uniform and transparent solution when mixed with ammonia water, and was not suitable for preparing microspheres by spray drying.

[0113] The present invention preferably uses a linear copolymer formed by polymerization of maleic anhydride and a comonomer as a raw material. When the linear copolymer contains a low content of maleic anhydride-derived structural units (for example, commercially available styrene-maleic anhydride copolymers have an anhydride content of 8-42%, based on the total content of all structural units as 100%), it is difficult to form a uniform, transparent solution with aqueous ammonia, making it unsuitable for preparing microspheres by spray drying. However, when the maleic anhydride-derived structural unit content in the linear copolymer is 45% or more, it can form a uniform, transparent solution with aqueous ammonia, and can be used in conjunction with spray drying to prepare microspheres.

[0114] If the molecular weight of the linear alternating maleic anhydride copolymer used exceeds the preferred range of the present invention, although spherical or quasi-spherical fluorescent microspheres can be prepared, stringing is likely to occur. Under the preferred molecular weight of the present invention, the obtained microspheres have a more regular morphology.

[0115] In summary, the method of the present invention can be used to prepare maleated amidated / imidized copolymer microspheres with fluorescent properties. According to the preferred conditions of the present invention, maleated amidated / imidized copolymer microspheres with better fluorescent properties and more regular shapes can be prepared.

[0116] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0117] The endpoints and any values ​​of the ranges disclosed in this application document are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

Claims

1. A fluorescent copolymer microsphere, wherein the copolymer is a linear copolymer containing a structural unit containing at least one group selected from maleamide group and maleimide group; The fluorescent copolymer microspheres are at least one of the microspheres obtained in the following ways: The maleimide group-containing polymer solution is spray-dried to obtain maleimide copolymer microspheres; or the maleimide copolymer microspheres are further heated for imidization to obtain maleimide copolymer microspheres.

2. The fluorescent copolymer microspheres according to claim 1, characterized in that: The fluorescence emission range of the fluorescent copolymer microspheres is 400-600 nm when the excitation light range is 320-500 nm, and preferably, the strongest fluorescence emission range is 450-500 nm; and / or, The fluorescent copolymer microspheres are spherical or quasi-spherical in shape, and preferably have a particle size ranging from 0.8 to 30 μm, more preferably from 1 to 20 μm.

3. The fluorescent copolymer microspheres according to claim 1, characterized in that: When the fluorescent copolymer microspheres are maleimidized copolymer microspheres, the total molar ratio of structural units containing maleimide groups in the maleimidized copolymer is 10%-100%, preferably 10%-70%, more preferably 10%-60%, and most preferably 20%-55%, based on the total molar amount of maleic anhydride groups and maleic anhydride derivative groups contained in the maleimidized copolymer being 100%.

4. The fluorescent copolymer microspheres according to claim 1, characterized in that: The number average molecular weight of the linear copolymer is less than 30,000 g / mol, preferably less than 25,000 g / mol; and / or, The linear copolymer is derived from a copolymer raw material containing one or more of the structural units selected from maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups; preferably, the copolymer raw material is a copolymer of a polymerized monomer containing one or more of the structural units selected from maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups and a monomer containing an isolated carbon-carbon double bond; more preferably, The copolymer raw material is a linear copolymer of maleic anhydride, further more preferably at least one of a linear alternating copolymer of maleic anhydride, and even more preferably a linear alternating copolymer of maleic anhydride obtained by jointly producing structural unit A provided by maleic anhydride and structural unit B provided by monomer M; the monomer M is selected from monomers containing isolated carbon-carbon double bonds, preferably at least one of vinyl acetate, C4 olefins, C4 fractions, C5 olefins, C5 fractions, C8 olefins, C8 fractions, C9 olefins, and C9 fractions, more preferably at least one of vinyl acetate, styrene, α-methylstyrene, C4 olefins, C4 fractions, C5 olefins, and C5 fractions.

5. The fluorescent copolymer microspheres according to any one of claims 1 to 4, characterized in that: The preparation method of the copolymer microspheres comprises: reacting a copolymer raw material containing at least one of the structural units of maleic anhydride, maleimide, maleic acid and ammonium salt, or maleamic acid and ammonium salt groups with aqueous ammonia in a sealed environment to obtain a solution containing a polymer containing maleamide groups, and spray-drying the solution to obtain maleamidated copolymer microspheres; or The method further comprises heating the maleimide copolymer microspheres to obtain maleimide copolymer microspheres.

6. A method for preparing the fluorescent copolymer microspheres according to any one of claims 1 to 5, comprising: A copolymer raw material containing at least one of the structural units of maleic anhydride, maleimide, maleic acid and ammonium salt, or maleamic acid and ammonium salt groups is subjected to an amidation reaction with aqueous ammonia in a sealed environment to obtain a solution containing a polymer containing maleamide groups, and the solution is spray-dried to obtain maleamidated copolymer microspheres; Alternatively, the maleimide copolymer microspheres are further subjected to heat treatment to obtain maleimide copolymer microspheres; Wherein, the copolymer raw material is a linear copolymer.

7. The preparation method according to claim 6, characterized in that: The viscosity of the solution containing the polymer containing maleamide groups is less than 100 mPa·s, preferably less than 80 mPa·s, more preferably less than 50 mPa·s; preferably: The molar ratio of the copolymer raw material calculated as anhydride groups to the ammonia water calculated as NH3 is 1:(0.1-10), preferably 1:(0.1-5), more preferably 1:(0.1-2); and / or, The copolymer raw material accounts for 0.1%-10% of the total weight of the reaction mixture, preferably 0.1%-8%; and / or, The number average molecular weight of the copolymer raw material is less than 30,000 g / mol, preferably less than 25,000 g / mol.

8. The preparation method according to claim 6, characterized in that: The copolymer raw material is a copolymer of one or more polymerizable monomers containing maleic anhydride, maleimide, maleic acid and ammonium salt, maleamic acid and ammonium salt groups and a monomer containing an isolated carbon-carbon double bond; more preferably, The copolymer raw material is a maleic anhydride linear copolymer, further more preferably at least one of maleic anhydride linear alternating copolymers, and even more preferably a maleic anhydride linear alternating copolymer obtained by jointly providing structural unit A provided by maleic anhydride and structural unit B provided by monomer M; the monomer M is selected from monomers containing isolated carbon-carbon double bonds, preferably at least one of vinyl acetate, C4 olefins, C4 fractions, C5 olefins, C5 fractions, C8 olefins, C8 fractions, C9 olefins, and C9 fractions, more preferably at least one of vinyl acetate, styrene, α-methylstyrene, C4 olefins, C4 fractions, C5 olefins, and C5 fractions.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The spray drying conditions include: an air inlet temperature of 150°C-200°C, preferably 155°C-180°C; and / or an air outlet temperature of 60°C-100°C, preferably 70-95°C; And / or, the conditions of the heat treatment include: the heat treatment temperature is 100°C-250°C, preferably 150°C-200°C, and / or, the heat treatment time is 5-60 minutes, preferably 10-30 minutes.

10. Use of the fluorescent copolymer microspheres according to any one of claims 1 to 5 or the fluorescent copolymer microspheres obtained by the preparation method according to any one of claims 6 to 9 as a fluorescent agent, an anti-ultraviolet agent, or a heat-resistant modifier.

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