阅读说明：本技术 一种常温溶胶凝胶过程制备紫外屏蔽核壳纳米微球的简易可控方法 (Simple and controllable method for preparing ultraviolet shielding core-shell nano microspheres in normal-temperature sol-gel process ) 是由 胡金刚 任俊达 吴雪宁 吴婕 杨琪 于 2021-10-18 设计创作，主要内容包括：本发明涉及一种常温溶胶凝胶过程制备紫外屏蔽核壳纳米微球的简易可控方法,该纳米微球是以钛酸四丁酯和硅氧化合物为混合前驱体,在三氟乙酸的氛围中通过常温溶胶凝胶过程即可得到,其内核为纳米二氧化钛,大小在50～90nm,壳层为硅氧硅缩聚物,壳层厚度在10～30nm。由于硅氧硅缩聚物较高的光透过性,制备的该核壳纳米微球在具有较强的紫外屏蔽作用的同时又有较好的光透过性。此外,该核壳微球的色泽呈现无色并在有机溶剂中具有很好的分散性,因而可广泛应用于光学膜领域,特别是应用在有机玻璃中能屏蔽紫外辐射的带来的危害。(The invention relates to a simple and controllable method for preparing ultraviolet shielding core-shell nano microspheres in a normal-temperature sol-gel process, wherein the nano microspheres are obtained by taking tetrabutyl titanate and a silica compound as a mixed precursor through the normal-temperature sol-gel process in the atmosphere of trifluoroacetic acid, the inner core of the nano microspheres is nano titanium dioxide, the size of the nano titanium dioxide is 50-90 nm, the shell layer of the nano titanium dioxide is a silica-silica polycondensate, and the thickness of the shell layer is 10-30 nm. Because of the higher light transmission of the silicon-oxygen-silicon polycondensate, the prepared core-shell nano-microsphere has stronger ultraviolet shielding effect and better light transmission. In addition, the core-shell microsphere is colorless in color and has good dispersibility in an organic solvent, so that the core-shell microsphere can be widely applied to the field of optical films, and particularly can be applied to organic glass to shield the harm caused by ultraviolet radiation.)

1. A simple and controllable method for preparing ultraviolet shielding core-shell nano-microspheres in a normal-temperature sol-gel process is characterized in that the nano-microspheres take tetrabutyl titanate and a silica compound as mixed precursors, and core-shell nano-spheres of silica-silica polycondensate wrapped on nano titanium dioxide can be obtained in a trifluoroacetic acid atmosphere through the normal-temperature sol-gel process.

2. The simple and controllable method for preparing the ultraviolet shielding core-shell nano-microspheres according to the claim 1 in the normal temperature sol-gel process is characterized in that the preparation method comprises the following steps:

a) mixing tetrabutyl titanate and a siloxane compound according to a molar ratio of 1: 2-4: 1, adding the mixture into a reaction kettle, stirring, slowly dripping the mixture into the mixture according to a molar ratio of the sum of trifluoroacetic acid and the mixture substances of 4: 1-5: 1, stirring and reacting for 4-8 hours, and standing for 1 d to obtain the core-shell nano-microsphere;

b) and b) taking the mass of the core-shell nano microspheres obtained in the step a) as the mass ratio of the core-shell nano microspheres to the polymer resin as 1: 10-1: 100, uniformly stirring, and pouring and forming to obtain the ultraviolet shielding composite material.

3. The simple and controllable method for preparing ultraviolet shielding core-shell nano-microspheres according to claim 2, characterized in that the siloxane compound in step a) of the preparation method is one or more of vinyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, vinyltris (beta-methoxyethoxy) silane, and tetraethyl silicate.

4. The simple and controllable method for preparing ultraviolet shielding core-shell nano-microspheres according to claim 2, characterized in that the polymer resin in step b) of the preparation method is one of methyl methacrylate, urethane acrylate, epoxy acrylic resin and phenolic resin.

Technical Field

The invention relates to a simple and controllable method for preparing ultraviolet shielding core-shell nano microspheres in a normal-temperature sol-gel process, belongs to the technical field of functional materials, and can be applied to ultraviolet shielding materials with high requirements on light transmittance.

Background

Radiation has great harm to human body, radiation pollution not only can affect the circulatory system, immunity, reproduction and metabolic functions of human body, but also can seriously induce cancer and accelerate the proliferation of cancer cells of human body. The main harm brought by radiation is from short-wave radiation, and invisible short waves such as X rays, gamma rays, ultraviolet rays and the like bring inevitable influence on daily life and work of people. At present, organic plastics are widely applied by people due to the characteristics of light weight and excellent quality, and the aging problem caused by the organic plastics is not well solved all the time, such as the aging of the outer layers of optical cables and electric wires, the radiation of CT rooms in hospitals, the poor ultraviolet shielding effect of organic glass and the like. Therefore, the research on a simple and controllable method for preparing the ultraviolet shielding composite material is of great significance.

The nanometer titanium dioxide is powder with stable chemical and physical properties, has higher refractive index, smaller granularity and excellent ultraviolet shielding effect, and is widely applied to the manufacturing fields of synthetic resin, chemical fiber, rubber, paint, cosmetics, paper, ceramics and the like. The nano titanium dioxide has small granularity and large specific surface area, so the nano titanium dioxide is easy to agglomerate in the preparation, post-treatment and application processes. However, in the industrial fields of material molding, paint preparation and the like, the product performance depends on the dispersion degree of the nano titanium dioxide to a great extent. The strong polarity of the titanium dioxide and the micronization of the particles make the titanium dioxide difficult to disperse in a nonpolar medium and easy to agglomerate in a polar medium, and directly influence the exertion of the excellent performance of the titanium dioxide. Therefore, improving the dispersibility of titanium dioxide in resins is of particular interest for broadening its applications in the plastics field and for enhancing the properties of materials. In addition, the addition of titanium dioxide in a large amount can seriously reduce the visible over-transmittance of the material, so that the improvement of the light transmittance is the key point of many scientific researches. At present, there are no reports of preparing microspheres with multilayer structures by using a sol-gel method. For example, patent CN101274246 discloses a sol-gel method for preparing silica/titania hollow microspheres, which uses cationic polystyrene microspheres (PS) as a template, ethyl silicate and butyl titanate as raw materials, diluted ammonia water as a PH regulator, and performs a sol-gel reaction at 70-80 ℃ to obtain multilayer organic-inorganic hybrid composite microspheres. Patent CN1824382 discloses a method for preparing titanium dioxide hollow microspheres, which comprises the steps of firstly, fully and uniformly mixing titanium dioxide sol and cation exchange resin, then carrying out suction filtration, drying at 70-90 ℃ for 8-16 hours, and finally calcining to obtain the titanium dioxide hollow microspheres. Similar patents exist, but the common points are that the multilayer microspheres can be obtained by high temperature, and some microspheres can be prepared even in the presence of a template. The preparation of the internal and external double-layer core-shell microspheres by a sol-gel method at normal temperature is not reported in documents.

The ultraviolet shielding core-shell nano-microspheres are prepared by using a simple normal-temperature sol-gel process and excellent visible light transmittance of siloxane, and the prepared nano-microspheres not only have a good dispersing effect in resin, but also have short-wave radiation resistance and excellent thermal stability, can be widely applied to the field of plastics, and can be used in optical materials with high requirements on light transmittance. The microsphere is simple in preparation method, has a large potential application value, is low in cost, and is green, environment-friendly and simple in preparation process.

Disclosure of Invention

The invention aims to provide a simple and controllable method for preparing ultraviolet shielding core-shell nano microspheres in a normal-temperature sol-gel process, wherein the nano microspheres are obtained by taking tetrabutyl titanate and a silica compound as a mixed precursor through the normal-temperature sol-gel process in the atmosphere of trifluoroacetic acid, the inner core of the nano microspheres is nano titanium dioxide, the size of the nano titanium dioxide is 50-90 nm, the shell layer of the nano titanium dioxide is a silica-silica polycondensate, and the thickness of the shell layer is 10-30 nm.

The invention prepares the core-shell nano-microsphere with ultraviolet shielding through a simple process of normal-temperature sol-gel, the nano-microsphere takes tetrabutyl titanate and siloxane compound as a mixed precursor, the reaction is carried out in the atmosphere of trifluoroacetic acid, and the core-shell nano-sphere of silica-silica polycondensate wrapped on nano titanium dioxide can be obtained by carrying out the sol-gel process at normal temperature by utilizing the strong moisture absorption characteristic of the trifluoroacetic acid.

A simple and controllable method for preparing ultraviolet shielding core-shell nano microspheres in a normal-temperature sol-gel process comprises the following steps:

a) and mixing tetrabutyl titanate and a siloxane compound according to a molar ratio of 1: 2-4: 1, adding into a reaction kettle, stirring, slowly dripping into the mixture according to a molar ratio of the sum of the trifluoroacetic acid and the mixture substances of 4: 1-5: 1, stirring for reacting for 4-8 h, and standing for 1 d to obtain the core-shell nano-microsphere.

b) And b) taking the mass of the core-shell nano microspheres obtained in the step a) as the mass ratio of the core-shell nano microspheres to the polymer resin as 1: 10-1: 100, uniformly stirring, and pouring and forming to obtain the ultraviolet shielding composite material.

The simple and controllable method for preparing the ultraviolet shielding core-shell nano-microsphere in the normal-temperature sol-gel process comprises the following steps that a) the siloxane compound is one or more of vinyl trimethoxy silane, gamma-methacryloxypropyl trimethoxy silane, vinyl tri (beta-methoxyethoxy) silane and tetraethyl silicate; the polymer resin in the step b) is one of methyl methacrylate, urethane acrylate, epoxy acrylic resin and phenolic resin.

Has the advantages that: the core-shell structure nano-microsphere has a plurality of unique properties due to the unique double-layer structure, and the invention adopts a simple normal-temperature sol-gel method to prepare the core-shell structure nano-microsphere with the core of nano titanium dioxide and the shell of silicon-oxygen-silicon polycondensate. The strong moisture absorption characteristic of trifluoroacetic acid is a determining factor for realizing the formation of the nano microspheres by normal-temperature sol-gel, a core layer is formed due to the high reaction speed of tetrabutyl titanate, the trifluoroacetic acid and water molecules in air, and a core-shell double-layer structure is formed due to the difference of the reaction rates of the two mixtures. The prepared nano-microsphere has the excellent characteristics of an internal compound and an external compound, and the preparation process is green, environment-friendly and simple, so that the nano-microsphere has important significance in enhancing the performance of the material and widening the application thereof, and has wide application value in the fields of multifunctional materials, optics and the like.

The invention has the characteristics that: (1) the core-shell type nanometer microsphere has stronger ultraviolet absorption performance and obvious shielding effect on short-wave radiation.

(2) The prepared core-shell type nano-microsphere has good dispersion performance, and can not be agglomerated when being used for thermosetting molding or UV curing molding.

(3) The hybrid microsphere has better thermal stability.

Detailed Description

Example 1:

respectively adding 0.02 mol of tetrabutyl titanate and 0.04 mol of tetraethyl silicate into a reaction kettle, stirring, slowly dripping 0.24 mol of trifluoroacetic acid into the mixed liquid for 1 hour, then stirring for reacting for 6 hours, and standing for 1 day to obtain the 110 nm core-shell nano-microsphere with the shell thickness of 20 nm. Next, 2 g of the prepared microspheres were taken out and added to 20 g of methacrylic resin, stirred at 80 ℃ for half an hour, and poured into a mold so that the film thickness was 10 μm. And cooling to room temperature, wherein the visible light transmittance of the film is 94% by a haze meter, the haze is 73%, and the ultraviolet transmittance is 12% by an ultraviolet spectrometer, so that the film can be used as a high-transmittance diffusion film.

Example 2:

respectively adding 0.06 mol of tetrabutyl titanate and 0.02 mol of tetraethyl silicate into a reaction kettle, stirring, slowly dripping 0.32mol of trifluoroacetic acid into the mixed liquid for 1 hour, then stirring for reaction for 5 hours, and standing for 1 day to obtain the 100 nm core-shell nano-microspheres with the shell thickness of 10 nm. Next, 2 g of the prepared microspheres were taken out and added to 20 g of methacrylic resin, stirred at 80 ℃ for half an hour, and poured into a mold so that the film thickness was 10 μm. And cooling to room temperature, wherein the visible transmittance of the film is 91% by a haze meter, the haze is 75%, and the ultraviolet transmittance is 7% by an ultraviolet spectrometer, so that the film can be used as a high-transmittance diffusion film.

Example 3:

respectively adding 0.03 mol of tetrabutyl titanate and 0.06 mol of vinyltrimethoxysilane into the reaction kettle, stirring, slowly dripping 0.42mol of trifluoroacetic acid into the mixed liquid for 1 hour, then stirring for reacting for 6 hours, and standing for 1 day to obtain the 115 nm core-shell nano microsphere with the shell thickness of 22 nm. Next, 2 g of the prepared microspheres were taken out and added to 20 g of methacrylic resin, stirred at 80 ℃ for half an hour, and poured into a mold so that the film thickness was 10 μm. And cooling to room temperature, wherein the visible transmittance of the film is 95% and the haze is 69% as measured by a haze meter, and the ultraviolet transmittance is 10% as measured by an ultraviolet spectrometer, so that the film can be used as a high-transmittance diffusion film.

Example 4:

respectively adding 0.09 mol of tetrabutyl titanate and 0.03 mol of vinyltrimethoxysilane into a reaction kettle, stirring, slowly dripping 0.55mol of trifluoroacetic acid into the mixed liquid for 1 hour, then stirring for reaction for 5 hours, and standing for 1 day to obtain the 95 nm core-shell nano microsphere with the shell thickness of 10 nm. 2 g of the microspheres prepared were subsequently taken and added to 20 g of urethane acrylate, stirred at 80 ℃ for half an hour and poured into a mold to give a film thickness of 10 μm. And cooling to room temperature, wherein the visible transmittance of the film is 92% and the haze is 72% as measured by a haze meter, and the ultraviolet transmittance is 8% as measured by an ultraviolet spectrometer, so that the film can be used as a high-transmittance diffusion film.