CN111265414B

CN111265414B - Kaolinite loaded nano ZnO composite anti-ultraviolet agent and preparation method thereof

Info

Publication number: CN111265414B
Application number: CN201911075986.8A
Authority: CN
Inventors: 汪灵; 梁唯丛; 董秋冶
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2019-11-06
Filing date: 2019-11-06
Publication date: 2022-08-05
Anticipated expiration: 2039-11-06
Also published as: CN111265414A

Abstract

The invention relates to a kaolinite loaded nano ZnO composite uvioresistant agent and a preparation method thereof, wherein natural sheet mineral kaolinite is used as a carrier mineral raw material, a room-temperature solid-phase synthesis method is adopted, and step 1, a mixed material is weighed and ground according to the mass ratio of zinc sulfate heptahydrate to kaolinite mineral raw material of 2-5: 1 to prepare a zinc sulfate heptahydrate-kaolinite mixture; 2, weighing and grinding the mixed material according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate of 1-2: 1 to prepare a precursor zinc oxalate-kaolinite mixture; 3, removing impurities in the precursor zinc oxalate-kaolinite mixture by centrifugal washing by using a centrifugal washing device; 4, drying the materials by adopting a drying device at the drying temperature of 105 ℃ for 3-6 h; and 5, roasting the load drying material by adopting a roasting device, wherein the heating rate is 10-15 ℃/min, the roasting temperature is 400-550 ℃, and the heat preservation is carried out for 2-4 h, so as to obtain the kaolinite load nano ZnO composite uvioresistant agent. The method has the advantages of obvious effect, good safety, simple process, easy popularization and application, wide application and remarkable social and economic benefits.

Description

Kaolinite loaded nano ZnO composite anti-ultraviolet agent and preparation method thereof

1. Field of the invention

The invention relates to a kaolinite loaded nano ZnO composite uvioresistant agent and a preparation method thereof.

2. Background of the invention

2.1 ultraviolet concept

Ultraviolet (UV) is an electromagnetic wave having a wavelength of 200nm to 400 nm. The ultraviolet rays in the sunlight can be divided into three sections of long-wave ultraviolet ray UVA (320-400 nm), medium-wave ultraviolet ray UVB (280-320 nm) and short-wave ultraviolet ray UVC (200-280 nm) according to the wavelength. Proper sunlight irradiation can increase oxygen content of organism cells, reduce blood sugar and cholesterol content, and enhance human vitality. However, when the sun is excessively exposed for a long time, various skin diseases such as sunburn, freckle, acne and the like are easily induced and aggravated, and internal organs of the body are damaged in severe cases. The basic characteristics of the uv segments are now collated as shown in table 1.

TABLE 1 classification and characterization of UV

The short wave ultraviolet UVC is absorbed by the ozone layer, cannot reach the ground and has no effect on human bodies. The energy of the medium-wave ultraviolet UVB is highest, and the great part of the energy is absorbed by the skin dermis to cause the dermal blood vessels to expand and present the symptoms of red swelling, blisters and the like. If the skin is subjected to UVB irradiation for a long time, the skin can generate erythema, inflammation and skin aging, and skin cancer can be seriously caused. In daily life, 95% or more of ultraviolet rays which the skin comes into contact with are UVA, the penetration force is strong, the skin is photo-aged, skin cancer is caused, and UVA attracts people gradually in recent years.

Ultraviolet rays not only cause harm to human bodies, but also have certain damage and aging effects on coatings, plastics, printing ink and other high polymer materials, so that the high polymer materials have the phenomena of light loss, fading, yellowing, cracking, peeling, embrittlement, pulverization, strength reduction, delamination and the like. Even indoor light and sunlight transmitted through a glass window can degrade some materials.

Therefore, ultraviolet rays have considerable harm to human health, high polymer materials and the like, so that the research and application of the ultraviolet resistant agent or the ultraviolet shielding material have very important practical significance.

2.2 research and State of the Art ultraviolet Shielding materials

Since the discovery of the hazards of ultraviolet light by humans, some means have been taken to shield ultraviolet light. Ultraviolet shielding materials for human skin protection are mainly of two types: one category is ultraviolet resistant textiles including sun protection clothing, sun protection hats, sun protection gloves, and sun protection umbrellas, among others. The ultraviolet resistant coating is a sunscreen skin care product or a cosmetic mainly used in daily life, and is prepared into a paste or liquid semi-liquid product by mutually matching ultraviolet resistant sunscreens (organic or inorganic) or compounding the ultraviolet resistant sunscreens with other components. The ultraviolet shielding material for protecting the high polymer material is mainly a filler with an ultraviolet shielding function, but the research on the aspect is relatively weak.

The anti-ultraviolet agent in skin care products or cosmetics means a substance which can effectively absorb or scatter solar radiation, can reduce damage to the skin, and can effectively absorb or scatter long-wave ultraviolet rays (UVA) and medium-wave ultraviolet rays (UVB) in sunlight. They can be divided into physical and chemical sunscreens by their protective mechanism of action, also commonly referred to as inorganic and organic sunscreens, respectively.

Chemical sunscreens (organic sunscreens), also known as uv absorbers, are primarily organic compounds which absorb harmful uv radiation. Among them, tert-butyl methoxydibenzoylmethane is the most representative UVA segment ultraviolet absorbent in the current sunscreen cosmetics, and isooctyl methoxycinnamate is the most widely used UVB segment ultraviolet absorbent in the current sunscreen cosmetics. However, organic sunscreens often require strict precautions in terms of heat resistance, stability, ultraviolet absorption range, toxicity, etc., which act only in a single wavelength band (UVA or UVB), and which may also decompose and lose the sunscreen effect under the action of light, with a short period of effectiveness. In contrast, inorganic sunscreens (physical sunscreens) are more stable and safer, and they achieve the goal of sunscreening by primarily scattering ultraviolet light while absorbing ultraviolet light in small amounts. Inorganic sunscreens are increasingly widely used due to their advantages of high efficiency, safety, durability, etc.

Current inorganic sunscreens (physical sunscreens) are predominantly TiO ₂ And ZnO, both of which are semiconductor materials, TiO ₂ Mainly aiming at UVB protection, ZnO mainly shields UVA. But the sun-screening and ultraviolet screening effects of the two are closely related to the particle size or nanometer effect of the two. The results of the previous study show that when both are nanoparticles, i.e. TiO ₂ When the particle size is 30-50 nm (grandma et al, 1998) and the particle size of ZnO is 10-35 nm, the nano effect is prominent, and the sunscreen ultraviolet shielding effect is excellent (YaoOer et al, 2003).

Nanometer ZnO is used as a widely used physical sun-screening agent, the principle of shielding ultraviolet rays is to absorb and scatter the ultraviolet rays, and the nanometer ZnO has the characteristics of small particle size, large specific surface area, good stability, small irritation and the like; in addition to good ultraviolet shielding performance, the antibacterial ultraviolet shielding material also has the advantages of safety, stability, heat resistance, certain antibacterial property and the like, so the antibacterial ultraviolet shielding material is widely applied to the field of sunscreen skin care products or cosmetics in recent years.

However, as the nano ZnO has the characteristics of weak polarity and tiny nano particles and high surface energy, the nano particles are in a thermodynamic unstable state and tend to agglomerate, thereby limiting the exertion of the nano effect and the ultraviolet shielding effect. In addition, in the process of manufacturing skin care products or cosmetics, nano ZnO particles are difficult to disperse to the original particle size, the ultraviolet absorption effect in the UVA, UVB, and UVC bands is reduced, the transparency and ultraviolet shielding performance thereof cannot be sufficiently exhibited, and the effect as a sunscreen agent in practical use is not good. In summary, as an inorganic sunscreen agent, the nano ZnO has the following main problems:

(1) agglomeration problem: the nano ZnO has high surface energy, and the particles tend to agglomerate.

(2) The problem of delamination: the density of the emulsifier in the sunscreen product is about 0.96-1.1g/cm ³ And the density of the nano ZnO is about 5.6g/cm ³ Therefore, when the nano ZnO with high density is mixed into the emulsifier, the nano ZnO is easy to precipitate, and the delamination phenomenon is generated. The layering phenomenon greatly limits the use efficiency of the nano ZnO material, and the nano ZnO material cannot be directly mixed with common cosmetics for use. If the dispersion is used alone, the dispersion and the dispersion can be separated into layers, and the dispersion must be shaken well before being used. This not only causes inconvenience to the user but also increases the use cost.

(3) Health problems are as follows: the nanometer ZnO in the sunscreen product is easy to gather at the horny layer of the skin of a human body, the opening of the sebaceous gland of hair follicle and the wrinkle, and the size of the facial pore of the human body is generally 20 mu m, so the nanometer ZnO is easy to block the skin pore after long-term use, is not beneficial to the secretion of sweat and is easy to cause skin infection. Furthermore, trace amounts of zinc may also be absorbed through the skin into the blood, which is very detrimental to human health, especially in sunburn and skin-damaged patients.

(4) The aesthetic problem is that: due to the aggregation of the nano ZnO, the phenomenon of unnatural whitening can be generated when the nano ZnO is smeared on the skin, and the aesthetic effect is influenced.

(5) Environmental problems: zn ²⁺ The dissolution and the generation of active oxygen may have certain influence on the environment and the ecosystem and are not easy to recycle.

(6) The price problem is as follows: because the nano ZnO can not be directly mixed with common cosmetics for use, in order to overcome the layering phenomenon of dispersion liquid when the nano ZnO is used alone, a small-sized special container and a device are needed in actual use, the production and use cost of physical sun-proof products is greatly increased, the market condition of the products is generally higher, and the using amount of the products is limited.

2.3 Current State of the Art for the preparation of Nano ZnO

The preparation method of nano ZnO mainly comprises three types, namely a liquid phase method, a solid phase method and a gas phase method according to different states of raw materials and preparation processes. Among them, the gas phase method is not suitable for wide application due to the disadvantages of harsh reaction conditions, high production cost, low product purity, etc. At present, the liquid phase method and the solid phase method are mainly adopted for preparing the nano ZnO, and the main advantages and disadvantages are shown in the table 2.

TABLE 2 advantages and disadvantages of the main preparation method of nano ZnO

2.4 research technical status of mineral-loaded nano ZnO composite uvioresistant agent

The problems of nano ZnO agglomeration, delamination and the like are solved, and the method can be started from two aspects: firstly, a certain preparation method is adopted to modify nano ZnO, regulate and control the shape of the nano ZnO and the like; firstly, the mineral is used as a carrier to load nano ZnO. The leading research progress of the predecessors was as follows:

US 6086666 discloses a method for preparing a flaky mineral loaded nano ZnO anti-ultraviolet material by a hydrolysis precipitation method, which is characterized in that a zinc source and a precipitator are added into an aqueous solution of minerals at a certain reaction temperature for reaction, and after a certain time, the mixture is filtered, dried and calcined to obtain the anti-ultraviolet composite material, wherein the flaky 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, which is characterized in that in an aqueous solution system, calcium hydroxide or calcium oxide is added into a mixed system of sericite powder and zinc sulfate solution to directly obtain the nano ZnO-coated sericite powder composite material. The obtained composite material has good dispersibility in an organic solvent, and has excellent uvioresistant performance and antibacterial and deodorant performance.

Gongmeizhuo, Zhengshuilin, etc. (2017) mention that the hydrolytic precipitation method is adopted to coat nano ZnO on the surface of calcined kaolin to prepare the nano ZnO/calcined kaolin composite anti-ultraviolet powder material, and the composite powder material has good anti-ultraviolet performance under the proper preparation conditions, namely, the coating amount is 8%, the reaction temperature is 90 ℃, the modification time is 10min, the pulp concentration is 10:1, and the calcination temperature is 400 ℃.

From the above description, the preparation method adopted in the prior art for the mineral-supported nano ZnO is mainly a liquid phase method. According to the search of the inventor, no technical result report of preparing the kaolinite loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method exists at present.

3. Summary of the invention

The invention aims to prepare a composite ultraviolet resistant agent or an ultraviolet shielding material by taking natural flaky mineral kaolinite with a layered structure as a raw material and loading nano ZnO, so as to overcome the problems of easy agglomeration, easy delamination, poor dispersibility and the like of the existing nano ZnO, improve the sun-proof and ultraviolet shielding performances, improve the aesthetic effect, prevent the whitening phenomenon, improve the use efficiency and reduce the use cost. To achieve the above object, the following technical problems must be solved:

(1) selection of carrier mineral raw materials: the layered structure silicate minerals are of various types, and the selection conditions are as follows: has a layered structure and two-dimensional habit crystals, and mineral crystals are mainly in a fine scale shape, are non-toxic and harmless, and have rich mineral raw materials.

(2) Selecting a preparation method of nano ZnO: as shown in Table 2, several methods of the present invention have advantages and disadvantages, and the selection conditions of the preparation method of the present invention are: no toxicity and harm, convenience and feasibility and good effect.

(3) The preparation process of the room temperature solid phase synthesis method of nano ZnO comprises the following steps: on the basis of the work in the step (2), the process conditions for preparing the nano ZnO by the room-temperature solid-phase synthesis method are further determined by experiments.

(4) The preparation process of the kaolinite loaded nano ZnO composite uvioresistant agent comprises the following steps: on the basis of the work in the step (3), the process conditions for preparing the kaolinite loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method are further determined through experiments.

The specific technical scheme is as follows:

3.1 selection of Carrier mineral raw materials

Kaolinite is a 1:1 type dioctahedral lamellar structure aluminosilicate mineral with a crystal chemical formula of Al ₄ [Si ₄ O ₁₀ ](OH) ₈ Theoretical chemical composition is Al ₂ O ₃ 41.2％，SiO ₂ 48.0% and H ₂ And (4) O10.8%. The kaolinite is a triclinic system, and the crystal structure of the kaolinite is formed by a layer of SiO4]Tetrahedron and a layer of [ AlO ₆ ]Octahedron structure, with a typical 1:1 layered structure. Restricted by a crystal layer-shaped structure, kaolinite generally takes the shape of scales, books, pseudo hexagonal plates and the like; the kaolinite has stable chemical property, is non-toxic and harmless, and meets the requirement of serving as a nano ZnO carrier mineral. It should be noted that the crystal structure of kaolinite is similar to that of dickite, but is different from that of dickite in terms of homogeneity, multiple image variants, geological causes, occurrence and the like, and is therefore different mineral species.

Fig. 1 is an X-ray powder diffraction pattern (XRD) of the kaolinite sample used in the present invention, and it can be seen that the diffraction peak of the kaolinite is relatively sharp, which indicates that the crystal structure of the raw material kaolinite is complete, the crystalline state is good, and is substantially consistent with the kaolinite standard card (PDF: 14-0164), and the characteristic diffraction peak is:

clearly distinct from dickite. In summary, the kaolinite used in the invention is pure, but a quartz diffraction peak appears on an XRD spectrogram, which indicates that the kaolinite also contains a small amount or trace of quartz minerals and the like.

Table 3 shows the results of X-ray fluorescence spectrum (XRF) detection of chemical components of the kaolinite sample used in the present invention, and it can be seen that the kaolinite sample has chemical components with weight percentage (%) close to the theoretical components, and has very low contents of other impurity components, and contains no toxic and harmful impurity components for human body. And the XRD analysis result is combined, so that the experimental sample is relatively pure, belongs to the kaolinite single mineral aggregate and meets the selection condition of the carrier mineral raw material.

TABLE 3X-ray fluorescence Spectroscopy (XRF) measurements of the chemical composition of kaolinite samples (in weight percent,%)

Substance(s)	SiO ₂	Al ₂ O ₃	Fe ₂ O ₃	TiO ₂	CaO	MgO	K ₂ O	Na ₂ O	MnO	P ₂ O ₅	SO ₃	H ₂ O
													Content (wt.)	44.21	35.76	0.89	0.46	0.02	0.16	0.87	1.01	—	0.8	0.62	15.17

3.2 selection of preparation method of Nano ZnO

According to related documents, the five methods shown in table 2 are adopted in the invention, the nano ZnO is respectively prepared under the optimized conditions, and the ultraviolet-visible light spectrophotometer is adopted to further detect and analyze the ultraviolet shielding performance of the nano ZnO, and the result is shown in fig. 2.

According to the purpose and requirement of the invention, the ultraviolet resistant agent or the ultraviolet shielding material not only ensures higher absorbance of the ultraviolet region, but also ensures high transmittance of the visible region. As can be seen from FIG. 2, the industrial ZnO particles are coarse, and the UV shielding performance is poor, which is not satisfactory. The standard for distinguishing the ultraviolet resistance of domestic products at present is divided into the following parts according to the ultraviolet shielding rate: class a, the ultraviolet shielding rate is more than 90 percent; b level, ultraviolet shielding rate is 80-90%; c level, and the ultraviolet shielding rate is 50-80%. The ultraviolet resistant agent or ultraviolet shielding material should be selected from a class a as appropriate. As shown in figure 2, the ultraviolet screening rate of the nano ZnO prepared by the room temperature solid phase synthesis method is more than 90 percent, belongs to a grade and meets the requirement of the invention.

Room temperature solid phase synthesis method preparation process of 3.3 nano ZnO

The invention further determines the technological conditions for preparing the nano ZnO by the room temperature solid phase synthesis method through experiments, and the technological conditions are as follows:

(1) preparing a precursor zinc oxalate: weighing zinc sulfate heptahydrate (ZnSO) according to the molar ratio of 1-2: 1 ₄ ·7H ₂ O) and sodium oxalate (Na) ₂ C ₂ O ₄ ) And further grinding and mixing for 30-40 min to obtain a precursor zinc oxalate (ZnC) ₂ O ₄ ·2H ₂ O)；

(2) Washing to remove impurities: carrying out centrifugal washing on the precursor zinc oxalate by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

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

(4) roasting synthesis: heating the dried precursor zinc oxalate to 400-550 ℃ by adopting a roasting device in an air environment at the heating rate of 10-15 ℃/min, and preserving the heat for 2-4 h to obtain the nano ZnO.

FIG. 3 is the X-ray powder diffraction pattern of nano ZnO prepared by room temperature solid phase synthesis, and it can be seen that three standard strong peaks with sharp peak shape and high intensity appear in the range of 30-40 degree diffraction angle, namely

This is essentially coincident with the nano ZnO standard PDF card (36-1451). Considering that the characteristic peaks appearing in the whole angle diffraction range are relatively sharp, the nano ZnO sample has a relatively good crystal form and relatively complete crystallization. Meanwhile, no miscellaneous peak which can not correspond to the standard card appears in the diffraction pattern, which indicates that the purity of the sample is higher.

FIG. 4 is a scanning electron microscope analysis photo of nano ZnO prepared by room temperature solid phase synthesis, which shows that the nano ZnO powder crystal grain is spherical or quasi-spherical, has the characteristics of nano particles, the particle size is 30 nm-50 nm, but the agglomeration phenomenon is more obvious.

3.4 preparation process of kaolinite loaded nano ZnO composite uvioresistant agent

On the basis of the work, the process conditions for preparing the kaolinite loaded nano ZnO composite uvioresistant agent by adopting a room-temperature solid-phase synthesis method are further determined by experiments, and specifically comprise the following steps:

(1) preparing a zinc sulfate heptahydrate-kaolinite mixture: zinc sulfate heptahydrate (ZnSO) ₄ ·7H ₂ O) and kaolinite mineral raw material in a mass ratio of 2-5: 1, respectively weighing a certain mass of zinc sulfate heptahydrate and kaolinite mineral raw material powder, and further grinding and mixing for 30-40 min to obtain a zinc sulfate heptahydrate-kaolinite mixture;

(2) preparing a precursor zinc oxalate-kaolinite mixture: weighing a certain mass of sodium oxalate (Na) according to the molar ratio of zinc sulfate heptahydrate to sodium oxalate of 1-2: 1 ₂ C ₂ O ₄ ) Adding the mixture into a zinc sulfate heptahydrate-kaolinite mixture, and continuously grinding for 50-60 min to obtain a precursor zinc oxalate (ZnC) ₂ O ₄ ·2H ₂ O) -kaolinite mixtures;

(3) washing to remove impurities: carrying out centrifugal washing on the precursor zinc oxalate-kaolinite mixture by adopting a centrifugal washing device, washing with distilled water twice, and washing with absolute ethyl alcohol twice to remove impurities;

(4) drying the materials: transferring the washed and impurity-removed precursor zinc oxalate-kaolinite 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 oxalate-kaolinite mixture to 400-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in an air environment, and preserving the heat for 2-4 h to obtain the kaolinite loaded nano ZnO composite anti-ultraviolet agent.

3.5 technical advantages

(1) The effect is obvious. The kaolinite-loaded nano ZnO composite uvioresistant agent is prepared by taking kaolinite as a carrier and adopting a room-temperature solid-phase synthesis method, and the composite material has better uvioresistant performance or ultraviolet shielding performance than nano ZnO prepared independently, has better dispersibility in a solvent, has higher transmittance on visible light, and solves the problems of agglomeration, layering, attractiveness and the like of the nano ZnO.

(2) The safety is good. The kaolinite used in the invention is a natural mineral, and is nontoxic and pollution-free. The raw material reagents used in the process of preparing the nano ZnO are nontoxic, safe and reliable.

(3) The process is simple. The room temperature solid phase synthesis method used by the invention has simple operation and convenient work.

(4) Easy popularization and application. The invention has simple process, convenient operation and easy learning, mastering, popularization and application.

(5) Has wide application and remarkable economic and social benefits.

With the recognition of the harm of ultraviolet rays to human bodies, ultraviolet resistant materials are receiving more and more attention, and especially, compared with chemical ultraviolet resistant agents, physical ultraviolet resistant agents are safer and more stable. The kaolinite loaded nano ZnO composite uvioresistant agent prepared by the invention better solves the technical problems of agglomeration of the current nano ZnO and the like, has important significance for the development of the uvioresistant material industry, and has wide application prospect and obvious economic and social benefits.

4. Description of the drawings

FIG. 1: the X-ray powder crystal diffraction spectrogram of the kaolinite sample adopted by the invention.

FIG. 2: the ultraviolet shielding performance (Abs-absorbance and T-ultraviolet shielding rate) of the nano ZnO prepared by different methods.

FIG. 3: x-ray powder diffraction spectrum of nano ZnO prepared by room temperature solid phase synthesis.

FIG. 4: scanning electron microscope analysis photo of nano ZnO prepared by room temperature solid phase synthesis method.

FIG. 5: and X-ray powder crystal diffraction spectra of kaolinite, nano ZnO and kaolinite-loaded nano ZnO composite uvioresistant agent.

FIG. 6: scanning electron microscope analysis photos of the kaolinite (a) and the kaolinite loaded nano ZnO uvioresistant agent (b).

FIG. 7: ultraviolet-visible light spectrum contrast diagrams (Abs-absorbance and T-ultraviolet shielding rate) of kaolinite, industrial ZnO, nano ZnO and kaolinite-loaded nano ZnO composite ultraviolet-resistant agent.

5. Detailed description of the preferred embodiments

Example 1: kaolinite loaded nano ZnO composite anti-ultraviolet agent and preparation method thereof

The kaolinite-loaded nano ZnO composite uvioresistant agent is prepared by a room-temperature solid-phase synthesis method, wherein natural flaky mineral kaolinite is used as a carrier mineral raw material, the kaolinite is relatively pure (figure 1), crystals are in irregular scaly shapes, the scale sizes are 0.5-2 mu m (figure 6a), the chemical components of the kaolinite are shown in table 3, and the preparation process comprises the following 5 steps:

(3) washing to remove impurities: adopting a centrifugal washing device to centrifugally wash a precursor zinc oxalate-kaolinite mixture, washing with distilled water twice, washing with absolute ethyl alcohol twice and removing impurities;

The detection result shows that the kaolinite loaded nano ZnO composite uvioresistant agent obtained by the method of the embodiment has the following characteristics:

(1) fig. 5 is an X-ray powder diffraction pattern of kaolinite, nano ZnO and kaolinite-supported nano ZnO composite anti-ultraviolet agent, and it can be seen that, compared with kaolinite and nano ZnO, the diffraction peak intensity of kaolinite in the XRD pattern of the kaolinite-supported nano ZnO composite anti-ultraviolet agent is very weak, which indicates that structural water in kaolinite is partially removed after calcination at 500 ℃, and the crystal structure is destroyed. No new peak is generated, which indicates that the two systems are physically compounded.

(2) Fig. 6 is a Scanning Electron Microscope (SEM) photograph of the kaolinite (a) and the kaolinite-supported nano ZnO uvioresistant agent (b), and it can be seen that the kaolinite flakes are supported with nano ZnO particles on the surface, have uniform particle size distribution, are spherical, have a size of about 30nm to 50nm, and significantly improve the agglomeration phenomenon.

(3) Fig. 7 is a comparison graph of ultraviolet-visible light spectra of kaolinite, industrial ZnO, nano ZnO, kaolinite-loaded nano ZnO composite anti-ultraviolet agent, and it can be seen that: first, kaolinite and industrial ZnO both have poor uv resistance and do not meet the performance requirements of uv resistance agents. Secondly, compared with industrial ZnO, the absorbance of the nano ZnO in an ultraviolet region is obviously increased, the ultraviolet resistance is excellent, the ultraviolet shielding rate can reach 95%, the transmittance in a visible light region is lower, and the whiteness is lower than that of the industrial ZnO. Thirdly, compared with nano ZnO, the absorbance of the kaolinite loaded nano ZnO ultraviolet resistant agent in an ultraviolet region is further improved, the ultraviolet shielding rate is close to 99 percent, which shows that the ultraviolet resistant performance is excellent, the transmittance of the kaolinite loaded nano ZnO ultraviolet resistant agent to visible light is also superior to that of the prepared nano ZnO, and the transparency of the kaolinite loaded nano ZnO ultraviolet resistant agent is good.

The detection results show that the kaolinite loaded nano ZnO composite anti-ultraviolet agent obtained by the embodiment of the invention can overcome the technical problems of easy agglomeration of the existing nano ZnO and the like, obviously improves the performance of the anti-ultraviolet or ultraviolet shielding material of the nano ZnO, and has good market prospect and social and economic benefits.

A fund project: the work subsidies national science fund projects (41972039, 41572038) and scientific research projects (16TD0011) funded by the university and development hall in Sichuan.

Claims

1. The kaolinite loaded nano ZnO composite uvioresistant agent is prepared by taking natural flaky mineral kaolinite as a carrier mineral raw material and adopting a room temperature solid phase synthesis method, and is characterized in that:

(5) roasting and loading: heating the dried precursor zinc oxalate-kaolinite mixture to 400-550 ℃ by adopting a roasting device at the heating rate of 10-15 ℃/min in an air environment, and preserving the heat for 2-4 h to obtain the kaolinite loaded nano ZnO composite uvioresistant agent;

the kaolinite is a 1:1 type dioctahedral layered structure aluminosilicate mineral with a crystal chemical formula of Al4[ Si4O10 ]](OH)8, the characteristic peak of the X-ray powder diffraction analysis is