Organic / inorganic composite structure uv shielding agent and method for preparing the same

Abstract

The application discloses a preparation method of an organic / inorganic composite structure ultraviolet shielding agent and belongs to the technical field of material application. 2+ 2+ 3+ ‑ 2‑ The inorganic functional hydrotalcite-like material has a wide application prospect, a main body of the structure is a metal double hydroxide layered structure (LDHs) formed by metal salts in an alkaline environment, has an ultraviolet protection function and does not decompose under ultraviolet irradiation. In order to improve the characteristics of easy agglomeration of the inorganic functional hydrotalcite-like material in a polymer material, surface modification is conducted on the inorganic functional hydrotalcite-like material by using 3-aminopropyl triethoxysilane (KH550) and pyromellitic dianhydride (PMDA), the steric hindrance between particles is increased, the inorganic functional hydrotalcite-like material is not prone to agglomeration due to the structure, meanwhile, Si-O bonds and benzene ring conjugated structures with ultraviolet shielding performance are introduced, and the organic / inorganic composite structure strong ultraviolet shielding agent with good dispersibility in a polymer matrix and not prone to migration loss is obtained.​​​​

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer material application, and particularly relates to a preparation method of an organic / inorganic composite structure ultraviolet shielding agent. BACKGROUND

[0002] Inorganic ultraviolet shielding agent, often called ultraviolet reflecting agent, is some nanometer metal oxide material, which mainly reflects or refracts ultraviolet light to shield ultraviolet.

[0003] Organic ultraviolet shielding agent, similar in principle to dye absorption of visible light, is called ultraviolet absorbing agent, which uses the energy of internal electron to absorb photons to cause energy level transition, but in the process of electron transition, due to the quantization of energy level, the molecule can only absorb specific wavelength energy to produce molecular absorption spectrum, and the spectrum of ultraviolet light is just in the molecular absorption spectrum, so this kind of substance has the ability of ultraviolet absorption.

[0004] Zn 2+ , Mg 2+ , Al 3+ and OH - , CO3 2- anions generate layered structure three-metal hydroxides with ultraviolet shielding capacity under alkaline conditions, which are inorganic functional hydrotalcite-like materials with wide application prospect and have excellent ultraviolet shielding performance. The substance usually has a double-layer structure, and the main structure is a double hydroxide of two metal salts formed in an alkaline environment, so it is also called layered double hydroxide (LDHs). LDHs do not decompose under ultraviolet irradiation, are stable in neutral environment, are suitable for ultraviolet protection function, but are easy to agglomerate in polymer materials.

[0005] Organic ultraviolet shielding agent mainly absorbs ultraviolet light, and inorganic ultraviolet shielding agent mainly refracts and reflects ultraviolet light. Both of them have advantages and disadvantages in production and use. Organic ultraviolet absorbing agent has conjugated π electron system, and the ultraviolet shielding agent derived from the main material has a strong absorption capacity for a certain band of ultraviolet light, but such organic molecules are easy to be photodegraded, migrated and lost, which makes the effective time of organic ultraviolet shielding agent not long. SUMMARY

[0006] In view of the defects and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of an organic / inorganic composite structure ultraviolet shielding agent, which coats the surface of hydrotalcite by grafting coupling agent to increase the steric hindrance between particles to weaken the agglomeration, so that the organic / inorganic composite structure ultraviolet shielding agent is not easy to agglomerate due to the structure, and has good dispersibility and is not easy to migrate and lose in the polymer matrix.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] 1. A method for preparing an organic / inorganic composite structure ultraviolet shielding agent, characterized by comprising the following synthesis steps:

[0009] (1) Three equal volumes of soluble magnesium salt, zinc salt and aluminum salt (hydrochloride or nitrate) aqueous solution (denoted as solutions A, B and C, respectively), sodium hydroxide solution (NaOH, denoted as solution D) and sodium carbonate solution (Na2CO3, denoted as solution E).

[0010] The above five solutions are simultaneously added to a reactor, and under the condition of continuous stirring, 80 ℃ reaction for 8 h, centrifugation, washing, drying, to obtain Zn-Mg-Al-LDH.

[0011] (2) Dissolve Zn-Mg-Al-LDH in anhydrous ethanol and ultrasonically disperse, add γ-aminopropyl triethoxysilane (KH550) and reflux at 80 ℃ for 6 h under stirring conditions, centrifuge, wash, dry, to obtain Zn-Mg-Al-LDH@SiO2-NH2.

[0012] (3) Dissolve Zn-Mg-Al-LDH@SiO2-NH2 in N,N-dimethylformamide (DMF), ultrasonically disperse uniformly, drop the PMDA DMF solution into the above solution under constant stirring, and then stir for 1 h, centrifuge, wash, dry, to obtain Zn-Mg-Al-LDH@SiO2-NH2-PMDA.

[0013] As a preferred, the experimental water is self-made deionized water.

[0014] As a preferred, the concentration of Mg 2+ , Zn 2+ , Al 3+ in step (1) is 0.4 mol / L, and the volume ratio of each salt solution to D and E solution is 1:1.5:1.5.

[0015] As a preferred, the concentration of NaOH solution in step (1) is 2.4 mol / L, and the concentration of Na2CO3 solution is 0.4 mol / L.

[0016] As a preferred, the mass ratio of Zn-Mg-Al-LDH and KH550 in step (2) is 1 g:1 g, and the mass-volume ratio of Zn-Mg-Al-LDH and anhydrous ethanol is 1 g:(120-150) mL.

[0017] As preferred, the mass ratio of Zn-Mg-Al-LDH@SiO2-NH2 and PMDA in step (3) = 1 g: (3 ~ 5) g, the mass-volume ratio of Zn-Mg-Al-LDH@SiO2-NH2 and DMF = 1 g: 50 mL, and the mass-volume ratio of PMDA and DMF = 1 g: 10 mL.

[0018] As preferred, the washing agent in step (1) is deionized water, and the washing agent in steps (2) and (3) is an aqueous ethanol solution with a volume ratio of 1:1.

[0019] As preferred, the drying temperature in steps (1), (2) and (3) is 60 ~ 80 ℃.

[0020] The present application has simple steps and strong operability, and the prepared organic / inorganic composite structure ultraviolet shielding agent has good dispersibility, stability, excellent ultraviolet shielding performance and environmental protection in a polymer matrix, and can be used as an ultraviolet shielding additive in a polymer material for outdoor or some special sites. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The infrared spectrograms of S1, M1 and SL1 prepared in Example One.

[0022] Figure 2 The X-ray diffraction patterns (XRD) of S1, M1 and SL1 prepared in Example Four.

[0023] Figure 3 The degradation change curves of Rhodamine B (RhB) solution under ultraviolet irradiation under the protection of PVC and PVC composite films containing S1, M1, SL1, SL2 and SL3 with a content of 2%.

[0024] Figure 4 The degradation change curves of Rhodamine solution under ultraviolet irradiation under the protection of PVC composite films with different contents of SL1.

[0025] Figure 5 The ultraviolet transmission spectra of PVC and its composite films. DETAILED DESCRIPTION

[0026] The present application will be further described below in combination with examples, but is not limited thereto.

[0027] It should be noted that the materials involved in the examples of the present application are all known and commonly used, and can be purchased regularly, unless otherwise specified.

[0028] Example One

[0029] 0.8132 g, 0.5453 g, 0.5336 g of MgCl2·6H2O, anhydrous ZnCl2 and anhydrous AlCl3 were weighed into 10.0 mL of deionized water respectively, and stirred to completely dissolve to prepare three kinds of salt solutions.

[0030] 1.440 g of NaOH and 0.6360 g of Na2CO3 were weighed into deionized water respectively to prepare 15.0 mL of two kinds of base solutions.

[0031] The above three kinds of salt solutions and two kinds of base solutions were poured into two flasks at the same time, stirred uniformly, heated to 80 °C, and reacted for 8 h under continuous stirring. After centrifugation, washing with deionized water until the supernatant pH≈7, and drying at 80 °C for 6 h, Zn-Mg-Al-LDHs (denoted as S1) were obtained.

[0032] 0.6 g of Zn-Mg-Al-LDH was ultrasonically dispersed in 80 mL of anhydrous ethanol for 0.5 h, and then 0.6 g of KH550 was added to the dispersion. The mixture was continuously refluxed at 80 °C for 6 h, centrifuged, washed with 1:1 ethanol-water solution, and dried at 80 °C for 12 h to obtain Zn-Mg-Al-LDHs@SiO2-NH2 (denoted as M1).

[0033] 0.4 g of M1 was dissolved in 20 mL of N,N-dimethylformamide (DMF), and then 1.2 g of PMDA was dissolved in 12 mL of DMF and added dropwise to the above M1 solution. After the addition of PMDA solution was completed, the reaction was completed after stirring for 1 h, and the mixture was centrifuged. The product was washed with 1:1 ethanol-water solution and dried at 80 °C for 12 h to obtain Zn-Mg-Al-LDH@SiO2-NH2-PMDA (denoted as product SL1).

[0034] Example Two

[0035] 0.4 g of M1 was dissolved in 20 mL of N,N-dimethylformamide (DMF), and then 1.6 g of PMDA was dissolved in 16 mL of DMF and added dropwise to the above M1 solution. After the addition of PMDA solution was completed, the reaction was completed after stirring for 1 h, and the mixture was centrifuged. The product was washed with 1:1 ethanol-water solution and dried at 80 °C for 12 h to obtain Zn-Mg-Al-LDH@SiO2-NH2-PMDA (denoted as product SL2).

[0036] 0.4 g M1 was dissolved in 20 mL of N,N-dimethylformamide (DMF), and 2 g of PMDA was dissolved in 20 mL of DMF, which was added dropwise to the above M1 solution. After the PMDA solution was added, the reaction was completed after stirring for 1 h, and centrifugation was performed. Washing with 1:1 ethanol water solution and drying at 80 °C for 12 h, Zn-Mg-Al-LDH@SiO2-NH2-PMDA (denoted as product SL3) was obtained.

[0037] Example Three

[0038] Preparation of composite film (taking PVC as an example)

[0039] The weighed nanoparticles were washed with a small amount of acetone under ultrasonic stirring and centrifuged for subsequent use.

[0040] 0.8 g of PVC powder was slowly added to 10 mL of DMF under stirring, and the mixture was stirred and dispersed uniformly.

[0041] A specified amount of nanoparticles was dissolved in 10 mL of DMF and ultrasonically dispersed uniformly, and then added to the above PVC solution. After stirring for 2 h and ultrasonic treatment for 0.5 h, a dispersion liquid was obtained.

[0042] After degassing treatment, the film-forming solution was cast on a flat plate, and the film was formed by standing in the air and vacuum drying to constant weight. After peeling, a UV shielding film was obtained, with a thickness of about 50 µm.

[0043] 0.8 g of PVC powder was slowly added to 20 mL of DMF, and the mixture was stirred and dispersed uniformly. Using the same method, a pure PVC film without nanoparticles was prepared for comparison of UV shielding performance.

[0044] Study on the UV shielding performance of PVC composite film

[0045] 50 mL of RhB solution (10 -5 M) and 50 mg of UV light catalyst TiO2 were mixed in a beaker and stirred magnetically for 30 min in the dark to reach adsorption equilibrium.

[0046] The PVC composite film to be tested was used as a UV shielding film to cover the beaker mouth, and a UV lamp (20 W, 365 nm wavelength) was vertically irradiated above the RhB solution. The solution was magnetically stirred and UV irradiated at room temperature, and 4 mL of the solution was taken from the beaker and centrifuged at 40, 80, 120, 160, and 200 min, respectively, to take the supernatant for absorbance test. The absorbance at 554 nm was recorded; after the test was completed, the solution was recovered and dispersed uniformly by centrifugation, and then poured back into the beaker for the next irradiation period (the following tests were the same).

[0047] The UV shielding ability of the UV shielding film was tested by (At The change of A0 value was compared, A0 and A t A0 and A554 represent the absorbance of RhB solution at 554 nm under original and UV irradiation with film protection, respectively.

[0048] The light degradation curve of PVC composite film prepared by the products of examples one, two and three shows that the UV shielding effect of Zn-Mg-Al-LDH@SiO2-NH2-PMDA is the best under the same conditions.

[0049] The above research results show that the hydroxyl groups on the surface of KH550 and Zn-Mg-Al-LDH are bonded by dehydration reaction, and the amino groups on the surface of the reactant are bonded with PMDA, so that Zn-Mg-Al-LDH is not easy to cause agglomeration due to the structure, and an organic / inorganic composite structure UV shielding agent with good dispersibility in the polymer matrix and not easy to cause organic small molecule migration loss is obtained.

Claims

1. A method for preparing an organic / inorganic composite ultraviolet shielding agent, characterized in that, The synthesis steps include the following: (1) Three equal volumes of soluble magnesium salt, zinc salt and aluminum salt aqueous solutions (referred to as solutions A, B and C respectively), sodium hydroxide solution (NaOH, referred to as solution D) and sodium carbonate solution (Na2CO3, referred to as solution E) were added to the reactor at the same time. The reactor was reacted at 80 °C for 8 h under continuous stirring. After centrifugation, washing and drying, Zn-Mg-Al-LDH was obtained. (2) Zn-Mg-Al-LDH was dissolved in anhydrous ethanol and ultrasonically dispersed. γ-aminopropyltriethoxysilane (KH550) was added and refluxed at 80 °C for 6 h under stirring. After centrifugation, washing, and drying, Zn-Mg-Al-LDH@SiO2-NH2 was obtained. (3) Zn-Mg-Al-LDH@SiO2-NH2 was dissolved in N,N-dimethylformamide (DMF), ultrasonically dispersed evenly, and then a DMF solution of pyromellitic dianhydride (PMDA) was added dropwise to the above solution while continuously stirring. The reaction was stirred for 1 h, centrifuged, washed, and dried to obtain Zn-Mg-Al-LDH@SiO2-NH2-PMDA.

2. The method for preparing an organic / inorganic composite ultraviolet shielding agent according to claim 1, characterized in that, In step (1) Mg 2+ Zn 2+ Al 3+ The concentrations of all solutions were 0.4 mol / L, and the volume ratios of each salt solution to solutions D and E were 1:1.5:1.

5. The concentration of the NaOH solution was 2.4 mol / L, and the concentration of the Na2CO3 solution was 0.4 mol / L.

3. The method for preparing an organic / inorganic composite ultraviolet shielding agent according to claim 1, characterized in that, In step (2), the mass ratio of Zn-Mg-Al-LDH to KH550 is 1 g: 1 g, and the mass-volume ratio of Zn-Mg-Al-LDH to anhydrous ethanol is 1 g: (120~150) mL.

4. The method for preparing an organic / inorganic composite ultraviolet shielding agent according to claim 1, characterized in that, In step (3), the mass ratio of Zn-Mg-Al-LDH@SiO2-NH2 to pyromellitic dianhydride is 1 g: (3 ~ 5) g, the mass-volume ratio of Zn-Mg-Al-LDH@SiO2-NH2 to DMF is 1 g: 50 mL, and the mass-volume ratio of PMDA to DMF is 1 g: 10 mL.

5. The method for preparing an organic / inorganic composite ultraviolet shielding agent according to claim 1, characterized in that, In step (1), the detergent is deionized water, and in steps (2) and (3), the detergent is an aqueous solution of ethanol with a volume ratio of 1:

1.

6. The method for preparing an organic / inorganic composite ultraviolet shielding agent according to claim 1, characterized in that, The drying temperature described in steps (1), (2) and (3) is 60–80 °C.

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