CN110817934A - A kind of pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent and preparation technology thereof - Google Patents

Abstract

The invention relates to a pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent and a preparation technology thereof. The natural flaky mineral pyrophyllite is used as a carrier mineral raw material, and a direct precipitation method is adopted. Water zinc nitrate and pyrophyllite mineral raw material powder are stirred and mixed in distilled water to obtain a mixed liquid of zinc nitrate hexahydrate-pyrophyllite; the second is to weigh sodium carbonate according to the molar ratio of zinc nitrate hexahydrate and sodium carbonate 1:1.5～3.5, After being dissolved in distilled water, it is added to the pre-mixed liquid, and stirred to obtain a precursor zinc carbonate-pyrophyllite mixed liquid; the third step is to centrifugally wash and remove impurities in the mixed liquid to obtain a precursor zinc carbonate-pyrophyllite mixture; the fourth step is to dry Mixture, temperature 105 ℃, time 3h ~ 6h; the fifth is to dry the material before roasting, heating rate 10 ℃ ~ 15 ℃ /min, roasting temperature 350 ℃ ~ 550 ℃, heat preservation for 1h ~ 3h, to obtain pyrophyllite-loaded nanometer 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 pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent and preparation technology thereof

1. Technical field

The invention relates to a pyrophyllite-loaded 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 natural flaky mineral pyrophyllite to obtain a pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent. It is suitable for the field of anti-ultraviolet materials or ultraviolet 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 body 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. In severe cases, it will damage the internal organs of the body. The basic characteristics of each section of ultraviolet light are listed 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 have 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-butylmethoxydibenzoylmethane is the most representative UVA ultraviolet absorber in sunscreen cosmetics, and isooctyl methoxycinnamate is the most widely used UVB ultraviolet absorber in sunscreen cosmetics. However, organic sunscreens often need to be strictly controlled in terms of heat resistance, stability, UV absorption range, toxic and side effects, etc. It only works 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 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. Because of 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 characteristics of weak polarity and very small nanoparticles, nano-ZnO has a high surface energy, which makes the nanoparticles in a thermodynamically unstable state and tends to agglomerate, thus limiting 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. Furthermore, trace amounts of zinc may also be absorbed through the skin and enter 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 predecessors is as follows:

US 6086666 discloses a method for preparing sheet-like 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 technical achievement report on the preparation of pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent by direct precipitation method at present.

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 natural flaky mineral pyrophyllite with layered structure as raw material, so as to overcome the easy agglomeration and separation of existing nano-ZnO. layer, 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 pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent: On the basis of the work of (3), further experiments were conducted to determine the technological conditions for preparing pyrophyllite-loaded 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

Pyrophyllite is a 2:1 dioctahedral layered aluminosilicate mineral with a crystal chemical formula of Al ₂ [Si ₄ O ₁₀ ](OH) ₂ and a theoretical chemical composition of Al ₂ O ₃ 28.3%. _SiO2 66.7% and _H2O 5.0%. Pyrophyllite is monoclinic or triclinic, and its crystal structure consists of two layers of [SiO ₄ ] tetrahedron and one layer of [AlO ₆ ] octahedron, with a typical 2:1 layered structure. Restricted by the layered structure of the crystal, pyrophyllite is generally scaly, fine in texture, waxy luster, slippery, non-toxic and harmless, and has stable chemical properties, which meets the requirements of nano-ZnO carrier minerals.

而且， 在XRD谱图上几乎没有杂质峰出现，说明叶蜡石样品纯度很高。Fig. 1 is the X-ray powder crystal diffractogram (XRD) of the pyrophyllite sample adopted by the present invention, it can be seen that the diffraction peak of this pyrophyllite is sharper, illustrating that the raw material pyrophyllite crystal structure is complete, and the crystalline state is good, and The pyrophyllite standard card (PDF: 46-1308) is basically the same, and its characteristic diffraction peaks are:

Moreover, there are almost no impurity peaks in the XRD pattern, indicating that the pyrophyllite sample is of high purity.

Table 3 is the X-ray fluorescence spectrum (XRF) detection result of the chemical composition of the pyrophyllite sample used in the present invention, it can be seen that the weight percentage (%) of the chemical composition of the pyrophyllite sample is relatively close to its theoretical composition, and other The content of impurities is very low, and it 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 pyrophyllite single mineral aggregate, and meets the selection conditions of carrier mineral raw materials.

Table 3 X-ray fluorescence spectrometry (XRF) detection results of chemical constituents of pyrophyllite samples (unit is weight percentage, %)

substance SiO₂ Al₂O₃ Fe₂O₃ TiO₂ CaO MgO K₂O Na₂O MnO P₂O₅ SO₃ H₂O content 67.96 26.73 0.07 0.24 0.09 — 0.08 0.21 — 0.09 0.06 4.49

It should be pointed out that the pyrophyllite mineral raw materials of the present invention may contain a small or trace amount of quartz, dickite, kaolinite, sericite and the like. According to the useful chemical composition Al ₂ O ₃ and the content of impurities, the ore types of pyrophyllite mineral raw materials are divided into three types: high alumina pyrophyllite (Al ₂ O ₃ >25%), medium alumina pyrophyllite (Al ₂ O ₃ >18%) and low aluminum pyrophyllite (Al ₂ O ₃ <18%); or divided into three grades, namely: glass fiber grade, ceramic grade and filler grade.

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 not only ensure a high absorbance in the ultraviolet region, but also have a 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 agents or ultraviolet shielding materials should generally be selected as grade a. As shown in Figure 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: adopt centrifugal washing device, the precursor zinc carbonate liquid is carried out centrifugal washing, twice distilled water wash, twice dehydrated alcohol wash, remove impurity, obtain 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-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)是基本重合的。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 nano-ZnO prepared by 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 basically 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 pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent

On the basis of the above work, further experiments determine the process conditions for preparing pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent by direct precipitation method, the details are as follows:

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

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

(3) washing and removing impurities: using centrifugal washing device, centrifugal washing precursor zinc carbonate-pyrophyllite mixed liquid, twice distilled water washing, twice absolute ethanol washing, removing impurities, obtaining precursor zinc carbonate-pyrophyllite mixture ;

(4) drying material: the precursor zinc carbonate-pyrophyllite mixture after washing and removing impurities is moved 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, at a heating rate of 10°C to 15°C/min, the dried precursor zinc carbonate-pyrophyllite mixture is heated to 350°C to 550°C, and kept for 1 hour. ~3h, the pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent is obtained.

4. Technical advantages

(1) The effect is obvious. The invention uses pyrophyllite as a carrier and adopts a direct precipitation method to prepare a pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent, and the composite material has better anti-ultraviolet performance or ultraviolet shielding performance than the separately prepared nano-ZnO, It has better dispersibility in solvent and higher transmittance to visible light, which solves the problems of agglomeration, delamination and aesthetics of nano-ZnO.

(2) Good safety. The pyrophyllite used in the present invention is a natural mineral, 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 pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent prepared by the invention better solves the technical problems such as the agglomeration of the current nano-ZnO, is of great significance to the development of the anti-ultraviolet material industry, and has broad application prospects and significant economic and social benefits.

5. Description of drawings

Fig. 1: The X-ray powder crystal diffraction spectrum of the pyrophyllite sample adopted 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 pyrophyllite, nano-ZnO and pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent.

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

Figure 7: UV-Vis spectrum comparison (Abs-absorbance, T-UV shielding rate) of pyrophyllite, industrial ZnO, nano-ZnO, and pyrophyllite-loaded nano-ZnO composite anti-UV agent.

6. Specific implementation

Example 1: A kind of pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent and its preparation technology

The natural flaky mineral pyrophyllite is used as the carrier mineral material. The pyrophyllite mineral material is a single mineral aggregate of pyrophyllite (Fig. 1), and the crystals are irregular scales with scales ranging from 2 μm to 5 μm (Fig. 6a). , its chemical composition is shown in table 3, adopts the direct precipitation method to prepare pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent, and its preparation process is carried out according to the following 5 steps:

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

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

(3) washing and removing impurities: using centrifugal washing device, centrifugal washing precursor zinc carbonate-pyrophyllite mixed liquid, twice distilled water washing, twice absolute ethanol washing, removing impurities, obtaining precursor zinc carbonate-pyrophyllite mixture ;

(4) drying material: the precursor zinc carbonate-pyrophyllite mixture after washing and removing impurities is moved 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, at a heating rate of 10°C to 15°C/min, the dried precursor zinc carbonate-pyrophyllite mixture is heated to 350°C to 550°C, and kept for 1 hour. ~3h, the pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent is obtained.

The detection result shows that the pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent obtained by the method of this example has the following characteristics:

(1) Figure 5 is the X-ray powder crystal diffraction pattern of pyrophyllite, nano-ZnO and pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent. It can be seen that compared with pyrophyllite and nano-ZnO, pyrophyllite-loaded nano-ZnO The characteristic peaks of pyrophyllite and nano-ZnO can be seen in the XRD pattern of the composite anti-ultraviolet agent. Since no new peaks are seen, the two are physically complex.

(2) Figure 6 is a scanning electron microscope (SEM) photo of pyrophyllite (a) and pyrophyllite-loaded nano-ZnO anti-ultraviolet agent (b). It can be seen that the surface of pyrophyllite scales is loaded with nano-ZnO particles, The particle size distribution is relatively uniform, spherical, and the size is about 30nm to 50nm, which obviously improves the agglomeration phenomenon.

(3) Fig. 7 is the UV-Vis spectrum comparison chart of pyrophyllite, industrial ZnO, nano-ZnO, pyrophyllite-loaded nano-ZnO composite anti-ultraviolet agent, it can be seen that: first, the anti-ultraviolet performance of pyrophyllite and industrial ZnO All are poor and do not meet the performance requirements of anti-ultraviolet agents. Second, compared with industrial ZnO, nano-ZnO has an obvious 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 pyrophyllite-loaded 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 excellent. For the prepared nano-ZnO, it shows that its transparency is good.

The above detection results show that the pyrophyllite-loaded 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, obviously improve the anti-ultraviolet or ultraviolet-shielding material performance of the nano-ZnO, and has 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 pyrophyllite loaded nano ZnO composite uvioresistant agent and a preparation technology thereof are disclosed, natural flaky mineral pyrophyllite is used as a carrier mineral raw material, and a direct precipitation method is adopted to prepare the pyrophyllite loaded nano ZnO composite uvioresistant agent, which is characterized in that:

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

(2) preparing a precursor zinc carbonate-pyrophyllite 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-pyrophyllite mixed liquid, and continuously magnetically stirring for 30-40 min to obtain a precursor zinc carbonate (ZnCO)₃) -pyrophyllite mixing liquid;

(3) washing to remove impurities: centrifugally washing a precursor zinc carbonate-pyrophyllite 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-pyrophyllite mixture;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc carbonate-pyrophyllite 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-pyrophyllite mixture to 350-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in the air environment, and preserving the heat for 1-3 h to obtain the pyrophyllite loaded nano ZnO composite anti-ultraviolet agent.

The pyrophyllite is 2:1 type dioctahedral layered structure aluminosilicate mineral with a crystal chemical formula of Al₂[Si₄O₁₀](OH)₂Identification of X-ray powder diffraction analysisThe definite characteristic peak is

The pyrophyllite mineral raw material can contain a small amount or trace amount of quartz, dickite, kaolinite, sericite and the like.

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