CN110876689A - A kind of calcined kaolin supported nano-ZnO composite anti-ultraviolet agent and preparation technology thereof - Google Patents

Abstract

The invention relates to a calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent and a preparation technology thereof. The flaky mineral calcined kaolin is used as a carrier mineral raw material, and a direct precipitation method is adopted. The first step is to weigh zinc nitrate hexahydrate in a mass ratio of 4:1. and calcined kaolin mineral raw material powder, stir and mix in distilled water to obtain zinc nitrate hexahydrate-calcined kaolin mixed liquid; secondly, weigh sodium carbonate according to the molar ratio of zinc nitrate hexahydrate and sodium carbonate 1:1.5～3.5, dissolve in distilled water and add In the pre-mixed liquid, the precursor zinc carbonate-calcined kaolin mixed liquid is obtained by stirring; the third is centrifugal washing to remove impurities in the mixed liquid to obtain the precursor zinc carbonate-calcined kaolin mixture; the fourth is drying the mixture, the temperature is 105 ° C, and the time 3h～6h; No. 5 is drying the material before roasting, the heating rate is 10℃～15℃/min, the roasting temperature is 350℃～550℃, and the temperature is kept for 1h～3h to obtain the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent. The effect is obvious, the safety is good, the process is simple, the popularization and application are easy, the use is wide, and the social and economic benefits are remarkable.

Description

A kind of calcined kaolin supported nano-ZnO composite anti-ultraviolet agent and preparation technology thereof

1. Technical field

The invention relates to a calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent and a preparation technology thereof. A direct precipitation method is adopted to coat nano-ZnO on the surface of flaky mineral calcined kaolin to obtain a calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent, which is suitable for use in UV-resistant materials or UV-shielding materials.

2. Background technology

2.1 UV Concept

Ultraviolet (Ultraviolet, UV for short) is an electromagnetic wave with a wavelength of 200 nm to 400 nm. Ultraviolet rays in sunlight can be divided into long-wave ultraviolet UVA (320-400nm), medium-wave ultraviolet UVB (280-320nm) and short-wave ultraviolet UVC (200-280nm) according to different wavelengths. Appropriate sunlight exposure can increase the oxygen content of the body's cells, reduce blood sugar and cholesterol levels, and enhance human vitality. However, excessive exposure to the sun for a long time can easily induce and aggravate various skin diseases, such as sunburn, freckles, acne, etc., and even damage the internal organs of the body in severe cases. Now the basic characteristics of each section of UV are sorted as shown in Table 1.

Table 1 Classification and characteristics of ultraviolet rays

Short-wave ultraviolet UVC is absorbed by the ozone layer, cannot reach the ground, and has no effect on the human body. UVB has the highest energy, and most of it is absorbed by the dermis of the skin, causing dermal blood vessels to dilate, showing symptoms such as redness, swelling, and blisters. Long-term exposure to UVB radiation can cause skin erythema, inflammation, skin aging, and even skin cancer in severe cases. In daily life, more than 95% of the ultraviolet rays that the skin comes into contact with are UVA, which has strong penetrating power and can cause skin photoaging and skin cancer. In recent years, UVA has gradually attracted people's attention.

Ultraviolet rays not only harm the human body, but also have certain damage and aging effects on coatings, plastics, inks and other polymer materials, causing the polymer materials to lose light, fade, yellow, crack, peel, embrittlement, powder densification, strength reduction and delamination. Even indoor light and sunlight transmitted through glass windows can degrade some materials.

Therefore, the research and application of anti-ultraviolet agents or ultraviolet shielding materials has important practical significance.

2.2 Research and technical status of UV shielding materials

Since the harm of ultraviolet rays was discovered by humans, people have begun to take certain measures to shield ultraviolet rays. There are two main types of UV shielding materials for human skin protection: one is anti-UV textiles, including sunscreen clothing, sunscreen hats, sunscreen gloves, and sunscreen umbrellas. One is anti-ultraviolet coating agent, which is mainly sunscreen skin care products or cosmetics used in daily life. It uses anti-ultraviolet sunscreen agent (organic or inorganic) to cooperate with each other or compound with other ingredients to make paste or liquid. Semi-liquid products. The UV shielding materials used for the protection of polymer materials are mainly fillers with UV shielding function, but the research in this area is still relatively weak.

Anti-ultraviolet agents in skin care products or cosmetics refer to substances that can effectively absorb or scatter solar radiation and reduce damage to the skin. It can effectively absorb or scatter long-wave ultraviolet (UVA) and medium-wave ultraviolet (UVB) in sunlight. ). According to their protective mechanism, they can be divided into physical sunscreens and chemical sunscreens, which are usually called inorganic sunscreens and organic sunscreens respectively.

Chemical sunscreens (organic sunscreens), also known as UV absorbers, mainly refer to organic compounds that can absorb harmful UV radiation. Among them, tert-butyl methoxydibenzoylmethane is the most representative UVA ultraviolet absorber in the current sunscreen cosmetics, and isooctyl methoxycinnamate is the most widely used UVB ultraviolet absorber in the current sunscreen cosmetics. However, organic sunscreens often need to be strictly controlled in terms of heat resistance, stability, UV absorption range, toxic side effects, etc. They only work in a single wavelength band (UVA or UVB), and may decompose and destroy under the action of light. The sunscreen effect is lost, and the effective time is short. In contrast, inorganic sunscreens (physical sunscreens) are more stable and safer. They mainly scatter UV rays while absorbing a small amount of UV rays to achieve the purpose of sun protection. Due to the advantages of high efficiency, safety and durability, inorganic sunscreens are more and more widely used.

The current inorganic sunscreens (physical sunscreens) are mainly _TiO2 and ZnO, both of which are semiconductor materials, _TiO2 is mainly for UVB protection, and ZnO is mainly for UVA protection. However, the sunscreen and UV shielding effects of both are closely related to their particle size or nano-effect. The previous research results show that when the two are nanoparticles, that is, when the particle size of TiO ₂ is 30-50 nm (Zu Yong et al., 1998) and the particle size of ZnO is 10-35 nm, it exhibits outstanding nano-effect and has excellent performance. UV shielding effect of sunscreen (Yao Chao et al., 2003).

Nano ZnO is a widely used physical sunscreen agent. Its principle of shielding ultraviolet rays is to absorb and scatter ultraviolet rays. Due to its small particle size, large specific surface area, good stability, and low irritation, it has good UV shielding performance. It also has the advantages of safety, stability, heat resistance and certain antibacterial properties, so it has been widely used in the field of sunscreen skin care products or cosmetics in recent years.

However, due to the weak polarity and very small nanoparticles, nano-ZnO has high surface energy, which makes the nanoparticles in a thermodynamically unstable state and tends to agglomerate, thus limiting the exertion of its nano-effect and UV-shielding effect. In addition, in the manufacturing process of skin care products or cosmetics, nano-ZnO particles are difficult to disperse to the original particle size, the ultraviolet absorption effect in UVA, UVB and UVC bands is reduced, and its transparency and ultraviolet shielding properties cannot be fully exerted. Sunscreens are not as effective. To sum up, as an inorganic sunscreen agent, nano-ZnO still has the following main problems:

(1) Agglomeration problem: The surface energy of nano-ZnO is high, and the particles tend to agglomerate.

(2) Delamination problem: the emulsifier density of sunscreen products is about 0.96-1.1g/cm ³ , while the density of nano-ZnO is about 5.6g/cm ³ , so when high-density nano-ZnO is incorporated into the emulsifier, it is very difficult to It is easy to precipitate and cause stratification. This layering phenomenon greatly limits the use efficiency of nano-ZnO materials and cannot be directly mixed with ordinary cosmetics. If it is used alone, it will also produce layering phenomenon with the dispersion, and it must be shaken well before use. This not only brings inconvenience to the user, but also increases the use cost.

(3) Health problems: Nano-ZnO in sunscreen products is easy to accumulate in the stratum corneum of the human skin, the openings of the hair follicles and sebaceous glands and the wrinkles. Since the size of human facial pores is generally 20 μm, excessive use is easy to block skin pores, which is not conducive to sweating. secretion, which can easily cause skin infections. Moreover, trace amounts of zinc may also be absorbed through the skin into the bloodstream, which is very detrimental to human health, especially for sunburned and damaged skin patients.

(4) Aesthetic problems: Due to the agglomeration effect of nano-ZnO, it may cause unnatural whitening when smeared on the skin, which affects the aesthetic effect.

(5) Environmental issues: the dissolution of Zn ²⁺ and the generation of reactive oxygen species may have a certain impact on the environment and ecosystem, and it is not easy to recycle.

(6) Price problem: Since nano-ZnO cannot be directly mixed with ordinary cosmetics, in order to overcome the phenomenon of delamination of the dispersion when used alone, small and special containers and devices must be used in actual use, which greatly increases the production and cost of physical sunscreen products. The cost of use makes the market price of such products generally high, which limits its usage.

2.3 Status of preparation technology of nano-ZnO

According to the state of the raw materials and the preparation process, the preparation methods of nano-ZnO mainly include three types: liquid phase method, solid phase method and gas phase method. Among them, the gas phase method is not suitable for wide application due to the disadvantages of harsh reaction conditions, high production cost and low product purity. At present, the preparation of nano-ZnO mainly adopts liquid phase method and solid phase method. The main advantages and disadvantages are shown in Table 2.

Table 2 The advantages and disadvantages of the main preparation methods of nano-ZnO

2.4 Research status of mineral-loaded nano-ZnO composite anti-ultraviolet agent

To solve the problems of nano-ZnO agglomeration and delamination, we can start from two aspects: one is to use a certain preparation method to modify nano-ZnO and control the morphology of nano-ZnO; the other is to use minerals as a carrier to support nano-ZnO . The main research progress of the predecessors is as follows:

US 6086666 discloses a method for preparing flaky mineral-loaded nano-ZnO anti-ultraviolet material by hydrolysis and precipitation, which is characterized in that at a certain reaction temperature, zinc source and precipitant are added to the mineral water solution for reaction, and after a certain time, filtration is carried out After drying and calcining, an anti-ultraviolet composite material is obtained, wherein the flake material can be muscovite, sericite, talc and kaolinite.

CN 104017393A discloses a method for preparing nano-ZnO-coated sericite powder composite material by direct precipitation method, which is characterized in that in an aqueous solution system, calcium hydroxide or calcium oxide is added to the mixed system of sericite powder and zinc sulfate solution , and directly obtain nano-ZnO-coated sericite powder composites. The obtained composite material has good dispersibility in organic solvents, as well as excellent anti-ultraviolet performance and antibacterial and deodorizing performance.

Gong Zhaozhuo, Zheng Shuilin et al. (2017) mentioned that nano-ZnO was coated on the surface of calcined kaolin by hydrolysis precipitation method to prepare nano-ZnO/calcined kaolin composite anti-ultraviolet powder material. Under suitable preparation conditions, the coating amount was 8%, and the reaction When the temperature is 90℃, the modification time is 10min, the pulp concentration is 10:1, and the calcination temperature is 400℃, the composite powder material has good anti-ultraviolet performance.

From the above introduction, it can be seen that the current preparation method of mineral-loaded nano-ZnO anti-UV agent is mainly the hydrolysis precipitation method in the liquid phase method. Among them, Wan Bin et al. (2014) used the direct precipitation method to prepare nano-ZnO-coated sericite powder composite Material. However, according to the search of the inventor, there is no report on the technical achievement of preparing the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent by the direct precipitation method.

3. Technical solutions

The purpose of the present invention is to prepare a kind of composite anti-ultraviolet agent or ultraviolet shielding material by loading nano-ZnO with flaky mineral calcined kaolin with layered structure as raw material, so as to overcome the easy agglomeration, delamination, etc. of existing nano-ZnO. Poor dispersion and other problems, improve the performance of sunscreen and UV shielding, improve the aesthetic effect, prevent the phenomenon of whitening, improve the use efficiency and reduce the use cost. In order to achieve the above goals, the following technical problems must be solved:

(1) Selection of carrier mineral raw materials: There are many types of layered silicate minerals. The selection conditions are: layered structure and two-dimensional habit crystals. The mineral crystals are mainly small scale-like, non-toxic and harmless. relatively abundant.

(2) Selection of nano-ZnO preparation method: as shown in Table 2, several current methods have their own advantages and disadvantages. The selection conditions of the preparation method of the present invention are: non-toxic and harmless, convenient and feasible, and good in effect.

(3) Preparation process of nano-ZnO by direct precipitation method: On the basis of the work of (2), further experiments were carried out to determine the technological conditions of direct precipitation method to prepare nano-ZnO.

(4) Preparation process of calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent: On the basis of the work of (3), further experiments were carried out to determine the technological conditions for preparing calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent by direct precipitation method.

The specific technical solutions are as follows:

3.1 Selection of carrier mineral raw materials

Kaolinite is a 1:1 dioctahedral layered aluminosilicate mineral with a crystal chemical formula of Al ₄ [Si ₄ O ₁₀ ](OH) ₈ . Kaolinite is a triclinic system, and its crystal structure consists of a layer of [SiO ₄ ] tetrahedron and a layer of [AlO ₆ ] octahedron, with a typical 1:1 layered structure. Restricted by the layered structure of crystals, kaolinite is generally scaly, book-shaped or pseudo-hexagonal.

Calcined kaolin is a dehydrated kaolin prepared by calcining kaolin at high temperature. Its main phase is dehydrated kaolinite, also known as metakaolinite. Metakaolinite removes the structural water in the mineral crystal structure, and the theoretical chemical composition is Al ₂ O ₃ 45.9%, SiO ₂ 54.1%. The microscopic features of metakaolinite are basically the same as kaolinite, and it still maintains the shape of small scales, book-like or pseudo-hexagonal flakes, etc., and is non-toxic and harmless, and has stable chemical properties, which meets the requirements of nano-ZnO carrier minerals.

Fig. 1 is the X-ray powder crystal diffractogram (XRD) of the calcined kaolin sample adopted in the present invention, it can be seen that the diffraction peak of this calcined kaolin is steamed bread peak, it is explained that the raw material calcined kaolin is amorphous material, contains a small amount of quartz simultaneously and other minerals, whose characteristic diffraction peaks are

Table 3 is the X-ray fluorescence spectrum (XRF) detection result of the chemical composition of the calcined kaolin sample adopted in the present invention, it can be seen that the weight percentage (%) of the chemical composition of the calcined kaolin sample is relatively close to its theoretical composition, and other impurity components The content is very low and does not contain toxic and harmful impurities to the human body. Combined with the XRD analysis results, it shows that the experimental sample is relatively pure, belongs to the single mineral aggregate of calcined kaolin, and meets the selection conditions of carrier mineral raw materials.

Table 3 X-ray fluorescence spectrum (XRF) detection results of chemical components of calcined kaolin samples (unit is weight percentage, %)

substance SiO₂ Al₂O₃ Fe₂O₃ TiO₂ CaO MgO K₂O Na₂O MnO P₂O₅ SO₃ H₂O content 56.35 41.62 0.30 0.77 0.10 0.08 0.28 0.97 — 0.27 — —

3.2 Selection of the preparation method of nano-ZnO

According to the relevant literature, the present invention adopts the five methods shown in Table 2, respectively prepares nano-ZnO under its optimized conditions, and further detects and analyzes their ultraviolet shielding properties by using an ultraviolet-visible spectrophotometer. The results are shown in Figure 2. Show.

According to the purpose and requirements of the present invention, the anti-ultraviolet agent or the ultraviolet shielding material should ensure high absorbance in the ultraviolet region and high transmittance in the visible light region. It can be seen from Figure 2 that due to the coarse particles of industrial ZnO, the UV shielding performance is poor and does not meet the requirements. At present, the standard for distinguishing the anti-ultraviolet effect of domestic products is divided into: a grade, the ultraviolet shielding rate is more than 90%; b grade, the ultraviolet shielding rate is 80%~90%; c grade, the ultraviolet shielding rate is 50%~ 80%. Anti-ultraviolet agent or ultraviolet shielding material should generally be selected as grade a. As shown in FIG. 2 , because the ultraviolet shielding rate of the nano-ZnO prepared by the direct precipitation method is greater than 90%, it belongs to the class a, which meets the requirements of the present invention.

3.3 Preparation process of nano-ZnO by direct precipitation

The present invention further experiments to determine the process conditions for preparing nano-ZnO by direct precipitation method, the details are as follows:

(1) Preparation of precursor zinc carbonate liquid: Weigh a certain mass of zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O) and sodium carbonate ( Na ₂ CO ₃ ), respectively dissolved in a certain amount of distilled water, and the aqueous solution of zinc nitrate hexahydrate was magnetically stirred for 10 minutes, then the aqueous sodium carbonate solution was added to the aqueous solution of zinc nitrate hexahydrate, and the magnetic stirring was continued for 30 to 40 minutes to obtain the precursor Zinc carbonate liquid;

(2) washing and removing impurities: using a centrifugal washing device, the precursor zinc carbonate liquid is subjected to centrifugal washing, two times of distilled water washing, and two times of absolute ethanol washing to remove impurities to obtain the precursor zinc carbonate material;

(3) Drying material: move the precursor zinc carbonate material after washing and removing impurities into a drying device, the drying temperature is 105°C, and the drying time is 3h to 6h;

(4) Roasting synthesis: using a roasting device, in an air environment, at a heating rate of 10°C to 15°C/min, the dried precursor zinc carbonate material is heated to 350°C to 550°C, and kept for 1h to 3h, that is, Obtained nano-ZnO powder.

这与纳米ZnO标准PDF卡片(36-1451)是完全重合的。考虑到整个角度衍射范围内出现的特征峰都较为尖锐，说明本纳米ZnO样品的晶型较好，结晶较为完整。同时，衍射图谱中未出现与标准卡片无法对应的杂峰，说明样品的纯度较高。Figure 3 is the X-ray powder crystal diffraction pattern of the nano-ZnO prepared by the direct precipitation method. It can be seen that three standard strong peaks with sharp peak shape and high intensity appear in the range of 30°～40° diffraction angle, namely

This completely coincides with the nano-ZnO standard PDF card (36-1451). Considering that the characteristic peaks appearing in the entire angular diffraction range are relatively sharp, it shows that the crystal form of the nano-ZnO sample is better and the crystallization is relatively complete. At the same time, there are no impurity peaks that cannot correspond to the standard card in the diffraction pattern, indicating that the purity of the sample is high.

Figure 4 is a photo of the SEM analysis of the nano-ZnO prepared by the direct precipitation method. It can be seen that the nano-ZnO powder grains are spherical or quasi-spherical, with the characteristics of nano-particles, and the particle size is 30nm-50nm, but there is obvious agglomeration Phenomenon.

3.4 Preparation process of calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent

On the basis of the above work, further experiments were carried out to determine the process conditions for preparing calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent by direct precipitation method, as follows:

(1) Preparation of zinc nitrate hexahydrate-calcined kaolin mixed liquid: Weigh a certain mass of zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O) and calcined kaolin mineral raw material powder at a mass ratio of 4:1, respectively. Dissolve zinc nitrate hexahydrate in a certain amount of distilled water, stir magnetically for 10 minutes, then add calcined kaolin powder into it, and stir magnetically for 30 minutes to obtain zinc nitrate hexahydrate-calcined kaolin mixed liquid;

(2) Preparation of precursor zinc carbonate-calcined kaolin mixed liquid: Weigh a certain mass of sodium carbonate (Na ₂ CO ₃ ) according to the molar ratio of zinc nitrate hexahydrate and sodium carbonate of 1:1.5 to 3.5, and dissolve it in a certain amount of distilled water first. In the process, the sodium carbonate aqueous solution is added to the zinc nitrate hexahydrate-calcined kaolin mixed liquid, and the magnetic stirring is continued for 30min-40min to obtain the precursor zinc carbonate (ZnCO ₃ )-calcined kaolin mixed liquid;

(3) washing and removing impurities: adopt centrifugal washing device, centrifugal washing precursor zinc carbonate-calcined kaolin mixed liquid, twice distilled water washing, twice absolute ethanol washing, remove impurities, obtain precursor zinc carbonate-calcined kaolin mixture;

(4) Drying materials: move the precursor zinc carbonate-calcined kaolin mixture after washing and removing impurities into a drying device, the drying temperature is 105°C, and the drying time is 3h-6h;

(5) Roasting load: Using a roasting device, in an air environment, the dried precursor zinc carbonate-calcined kaolin mixture is heated to 350°C～550°C at a heating rate of 10°C～15°C/min, and kept for 1h～ 3h, the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent was obtained.

4. Technical advantages

(1) The effect is obvious. The invention uses calcined kaolin as a carrier and adopts a direct precipitation method to prepare a calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent. It has better dispersibility and higher transmittance to visible light, which solves the problems of agglomeration, delamination and aesthetics of nano-ZnO.

(2) Good safety. The calcined kaolin used in the present invention is calcined from kaolinite minerals, and is non-toxic and non-polluting. The raw materials and reagents used in the preparation of nano-ZnO are also non-toxic, safe and reliable.

(3) The process is simple. The direct precipitation method used in the present invention is simple to operate and convenient to work.

(4) It is easy to promote and apply. The invention has the advantages of simple process, convenient operation, easy learning, mastering, popularization and application.

(5) Wide range of uses and significant economic and social benefits. As people gradually realize the harm of ultraviolet rays to the human body, anti-ultraviolet materials have attracted more and more attention, especially compared with chemical anti-ultraviolet agents, physical anti-ultraviolet agents are safer and more stable. The calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent prepared by the invention better solves the current technical problems such as agglomeration of nano-ZnO, has great significance for the development of anti-ultraviolet material industry, and has broad application prospects and significant economic and social benefits.

5. Description of drawings

Figure 1: X-ray powder crystal diffraction spectrum of the calcined kaolin sample used in the present invention.

Figure 2: UV shielding properties (Abs-absorbance, T-UV shielding ratio) of nano-ZnO prepared by different methods.

Figure 3: X-ray powder crystal diffraction pattern of nano-ZnO prepared by direct precipitation method.

Figure 4: Scanning electron microscope analysis photo of nano-ZnO prepared by direct precipitation method.

Figure 5: X-ray powder crystal diffraction patterns of calcined kaolin, nano-ZnO and calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent.

Figure 6: Scanning electron microscope analysis photographs of calcined kaolin (a) and calcined kaolin-supported nano-ZnO anti-UV agent (b).

Figure 7: UV-Vis spectrum comparison chart (Abs-absorbance, T-UV shielding ratio) of calcined kaolin, industrial ZnO, nano-ZnO, and calcined kaolin-supported nano-ZnO composite anti-UV agent.

6. Specific implementation

Example 1: A kind of calcined kaolin supported nano-ZnO composite anti-ultraviolet agent and its preparation technology

Calcined kaolin was used as the carrier mineral raw material. The calcined kaolin was relatively pure (Fig. 1), and the crystals were irregular scales with scales ranging from 0.5 μm to 2 μm (Fig. 6a). Its chemical composition is shown in Table 3. The calcined kaolin supported nano-ZnO composite anti-ultraviolet agent is prepared by the direct precipitation method, and the preparation process is carried out according to the following 5 steps:

(1) Preparation of zinc nitrate hexahydrate-calcined kaolin mixed liquid: Weigh a certain mass of zinc nitrate hexahydrate (Zn(NO ₃ ) ₂ ·6H ₂ O) and calcined kaolin mineral raw material powder at a mass ratio of 4:1, respectively. Dissolve zinc nitrate hexahydrate in a certain amount of distilled water, stir magnetically for 10 minutes, then add calcined kaolin powder into it, and stir magnetically for 30 minutes to obtain zinc nitrate hexahydrate-calcined kaolin mixed liquid;

(2) Preparation of precursor zinc carbonate-calcined kaolin mixed liquid: Weigh a certain mass of sodium carbonate (Na ₂ CO ₃ ) according to the molar ratio of zinc nitrate hexahydrate and sodium carbonate of 1:1.5 to 3.5, and dissolve it in a certain amount of distilled water first. In the process, the sodium carbonate aqueous solution is added to the zinc nitrate hexahydrate-calcined kaolin mixed liquid, and the magnetic stirring is continued for 30min-40min to obtain the precursor zinc carbonate (ZnCO ₃ )-calcined kaolin mixed liquid;

(3) washing and removing impurities: adopt centrifugal washing device, centrifugal washing precursor zinc carbonate-calcined kaolin mixed liquid, twice distilled water washing, twice absolute ethanol washing, remove impurities, obtain precursor zinc carbonate-calcined kaolin mixture;

(4) Drying materials: move the precursor zinc carbonate-calcined kaolin mixture after washing and removing impurities into a drying device, the drying temperature is 105°C, and the drying time is 3h-6h;

(5) Roasting load: Using a roasting device, in an air environment, the dried precursor zinc carbonate-calcined kaolin mixture is heated to 350°C～550°C at a heating rate of 10°C～15°C/min, and kept for 1h～ 3h, the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent was obtained.

The detection results show that the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent obtained by the method of this example has the following characteristics:

(1) Fig. 5 is the X-ray powder crystal diffraction pattern of calcined kaolin, nano-ZnO and calcined kaolin-loaded nano-ZnO composite anti-ultraviolet agent, because the calcined kaolin is an amorphous material, its XRD pattern is a steamed bread peak, and the diffraction intensity is very weak, So there are no obvious peaks in the spectrum.

(2) Figure 6 is a scanning electron microscope (SEM) photo of calcined kaolin (a) and calcined kaolin-supported nano-ZnO anti-ultraviolet agent (b). Uniform, spherical, and the size is about 30nm to 50nm, which obviously improves the agglomeration phenomenon.

(3) Fig. 7 is a UV-Vis spectrum comparison diagram of calcined kaolin, industrial ZnO, nano-ZnO, and calcined kaolin-loaded nano-ZnO composite anti-ultraviolet agent. It can be seen that: first, the anti-ultraviolet properties of calcined kaolin and industrial ZnO are relatively high. Poor, does not meet the performance requirements of anti-ultraviolet agent. Second, compared with industrial ZnO, nano-ZnO has a significant increase in absorbance in the ultraviolet region, excellent anti-ultraviolet performance, and the ultraviolet shielding rate can reach 95%. Third, compared with nano-ZnO, the absorbance of calcined kaolin-supported nano-ZnO anti-ultraviolet agent in the ultraviolet region is further improved, and the ultraviolet shielding rate is close to 99%, indicating that its anti-ultraviolet performance is excellent, and the transmittance of visible light is also better than The prepared nano-ZnO shows good transparency.

The above detection results show that the calcined kaolin-supported nano-ZnO composite anti-ultraviolet agent obtained in the embodiment of the present invention can overcome the technical problems such as easy agglomeration of the existing nano-ZnO, significantly improve the anti-ultraviolet or ultraviolet-shielding material performance of the nano-ZnO, and has a good market. Prospects and socioeconomic benefits.

Funding project: This work is funded by the National Natural Science Foundation of China (41972039, 41572038) and the Sichuan Provincial Department of Education-funded scientific research project (16TD0011).

Claims (1)

1. A calcined kaolin loaded nano ZnO composite anti-ultraviolet agent and a preparation technology thereof are disclosed, wherein a flake mineral calcined kaolin is used as a carrier mineral raw material, and a direct precipitation method is adopted to prepare the calcined kaolin loaded nano ZnO composite anti-ultraviolet agent, which is characterized in that:

(1) preparing a zinc nitrate hexahydrate-calcined kaolin mixed liquid: respectively weighing zinc nitrate hexahydrate (Zn (NO) with a certain mass ratio of 4:1₃)₂·6H₂O) and calcined kaolin mineral raw material powder, dissolving zinc nitrate hexahydrate in a certain amount of distilled water, magnetically stirring for 10min, adding calcined kaolin powder into the solution, and magnetically stirring for 30min to obtain a zinc nitrate hexahydrate-calcined kaolin mixed liquid;

(2) preparing a precursor zinc carbonate-calcined kaolin mixed liquid: weighing a certain mass of sodium carbonate (Na) according to the molar ratio of zinc nitrate hexahydrate to sodium carbonate of 1: 1.5-3.5₂CO₃) Dissolving the mixture in a certain amount of distilled water, adding a sodium carbonate aqueous solution into a zinc nitrate hexahydrate-calcined kaolin mixed liquid, and continuously magnetically stirring for 30-40 min to obtain a precursor zinc carbonate (ZnCO)₃) -calcined kaolin clay mixing liquid;

(3) washing to remove impurities: centrifugally washing a precursor zinc carbonate-calcined kaolin mixed liquid by using a centrifugal washing device, washing with distilled water twice, washing with absolute ethyl alcohol twice, and removing impurities to obtain a precursor zinc carbonate-calcined kaolin mixture;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc carbonate-calcined kaolin mixture into a drying device, wherein the drying temperature is 105 ℃, and the drying time is 3-6 h;

(5) roasting and loading: heating the dried precursor zinc carbonate-calcined kaolin mixture to 350-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in an air environment, and preserving the heat for 1-3 h to obtain the calcined kaolin loaded nano ZnO composite anti-ultraviolet agent.

The calcined kaolin is dehydrated kaolin prepared by taking kaolin as a raw material through high-temperature calcination, and the main phase of the calcined kaolin is dehydrated kaolinite, namely metakaolinite; the metakaolin has Al as theoretical chemical component₂O₃45.9％，SiO₂54.1 percent, the phase characteristic of the crystal is an amorphous phase, and the X-ray powder crystal diffraction spectrum of the crystal is a dispersed steamed bun peak.

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