Europium-doped hydrotalcite for enhancing PVC (polyvinyl chloride) light transmission as well as preparation method and application of europium-doped hydrotalcite

Abstract

The invention discloses europium-doped hydrotalcite for enhancing PVC (polyvinyl chloride) light transmission and a preparation method and application thereof, and belongs to the technical field of high polymer materials and inorganic nanomaterials. Trivalent europium (Eu < 3 + >) is doped into a lattice structure of LDHs (layered double hydroxides) through europium-doped coprecipitation, surface silanization and ultrasonic dispersion technologies; refractive index matching (1.50-1.53) is achieved, and light scattering is reduced. The particle size of the optimized hydrotalcite is controlled to be 50-150 nm, so that the light transmittance of the PVC composite film reaches 93% or above, and meanwhile, the PVC composite film has the characteristic of red fluorescence. Compared with the prior art, the material has the advantages that the transparency is improved, the heat-resistant stability and aging resistance of PVC are remarkably improved, the material is suitable for the fields of transparent films, daylighting panels, optical marks and the like, and the hydrotalcite nano material provided by the invention has the dual effects of refractive index matching and conversion from ultraviolet light to visible light; the light transmittance and the ageing resistance of the PVC material can be obviously improved at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and inorganic nanomaterials, and specifically relates to europium-doped hydrotalcite for enhancing the light transmittance of PVC, and a preparation method and application thereof. Background Art

[0002] Polyvinyl chloride (PVC) is a thermoplastic widely used in the construction, packaging and automotive industries. It is highly favored for its low cost and excellent processing performance. However, the light transmittance of traditional PVC materials is poor, especially after the addition of inorganic fillers (such as hydrotalcite), the light scattering phenomenon is aggravated, which limits its application in transparent films, skylights and other fields. Existing studies have mostly used methods such as particle size optimization and surface modification to improve transparency, but it is still difficult to break the limit of 85% transmittance. Hydrotalcite (Layered Double Hydroxides, LDHs), as a layered double hydroxy compound, is often used as a stabilizer for PVC due to its thermal stability and ion exchange capacity. Among them, magnesium aluminum hydrotalcite (MgAl-LDH) is the most widely used type of LDH with high thermal stability. However, the metal ions in the magnesium aluminum hydrotalcite layer are disordered and there are many surface hydroxyl defects, resulting in severe light scattering and a transmittance generally below 60%. Conventional hydrotalcite has the problem that the refractive index of the particles (about 1.55-1.60) does not completely match that of the PVC matrix (about 1.54), and it is easy to agglomerate, resulting in enhanced light scattering and decreased transmittance.

[0003] In the prior art, CN109721842A discloses a method for modifying hydrotalcite for thermal stabilization of PVC, but does not solve the problem of light transmittance; US20190106550A1 proposes a method for modifying PVC with nanofillers, but does not involve the optimization of optical properties. Rare earth elements have unique 4f electronic structure arrangements, large atomic magnetic moments, and strong spin-orbit coupling. Their rich optical, magnetic, and electrical properties are widely used in current scientific research. In recent years, they have gradually become the main doping elements in new materials. Among them, the f→f emission spectrum of europium (Eu3+) element has good monochromaticity and high intensity, which can repair lattice defects and reduce light absorption. Invention patent CN115109588A reports a rare earth-doped hydrotalcite nano-photofertilizer, which converts ultraviolet light into red light by doping trivalent europium ions into hydrotalcite, thereby improving crop light utilization.

[0004] However, existing research has mostly focused on europium-doped fluorescent materials, and has not yet seen its application in improving the transparency of hydrotalcite and in PVC composite materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a europium-doped hydrotalcite for enhancing the light transmittance of PVC, and a preparation method and application thereof in order to solve the above-mentioned problems.

[0006] The technical solution adopted by the present invention is as follows: a europium-doped hydrotalcite for enhancing the light transmittance of PVC, wherein the europium-doped hydrotalcite is a magnesium / aluminum / europium ternary hydrotalcite, and the molar ratio of Mg:Al:Eu is 2-4:1:0.01-0.1.

[0007] In a preferred embodiment, a method for preparing europium-doped hydrotalcite for enhancing the light transmittance of PVC comprises the following steps:

[0008] SA1: Prepare a mixed solution of Mg(NO3)2·6H2O, Al(NO3)3·9H2O and Eu(NO3)3·6H2O, adjust the pH to 9-11, and prepare Mg-Al-Eu hydrotalcite by coprecipitation;

[0009] SA2: hydrothermal reaction at 80-90°C for 2-4 hours to control the interlayer spacing of hydrotalcite;

[0010] SA3: Surface modification with methyltrimethoxysilane (MTMS) to adjust the particle size to 50-150 nm and enhance hydrophobicity;

[0011] SA4: Improve the particle uniformity through ultrasonic-high pressure homogenization dispersion method and vacuum dry to obtain the final product.

[0012] In a preferred embodiment, in step SA4, the drying step adopts a vacuum drying method with a vacuum degree of ≤0.1 MPa and a drying time of 6-12 hours.

[0013] In a preferred embodiment, a use of europium-doped hydrotalcite for enhancing the light transmittance of PVC is used to prepare highly transparent PVC packaging materials, optical marking films or medical films, thereby improving the light transmittance and aging resistance of PVC materials.

[0014] In a preferred embodiment, the application comprises the following steps:

[0015] S1: Mix hydrotalcite with titanate and silane coupling agents at a ratio of 1:0.3-0.5 and stir at high speed for 30 minutes to form a hydrophobic surface;

[0016] S2: Modified hydrotalcite, PVC resin and other auxiliary additives (MS resin, zinc stearate, epoxy plasticizer) were dry mixed in a high-speed rotary mixer for 20 minutes;

[0017] S3: melt mixing the mixture at a certain temperature using a two-roll mill for 10 minutes;

[0018] S4: The crushed flakes are cooled to room temperature, crushed into powder by a crusher, and the powder is injected into a calender to form PCV composite films and other products under a certain pressure.

[0019] In a preferred embodiment, in step S1, the coupling agent is diluted with an equal amount of toluene in a 1:1 solution and then sprayed on the surface of the hydrotalcite.

[0020] In a preferred embodiment, in step S3, the temperature of the double-roll mill should be controlled at 160-190° C. to prevent PVC from decomposing HCL due to high temperature.

[0021] In a preferred embodiment, in step S4, the compression molding pressure in the calender is 10-15 MPa, and the holding time is 5-10 minutes.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] In the present invention, trivalent europium (Eu 3 +) is doped into the lattice structure of hydrotalcite (LDHs), achieving refractive index matching (1.50-1.53) and reducing light scattering. The optimized hydrotalcite particle size is controlled at 50-150nm, resulting in a PVC composite film with a light transmittance exceeding 93% and red fluorescence. Compared to existing technologies, this material significantly improves the heat stability and aging resistance of PVC while increasing transparency, making it suitable for applications such as transparent films, skylights, and optical signage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process principle of the present invention;

[0025] Figure 2 This is a scanning electron microscope (SEM) image of the hydrotalcite obtained in Example 3 of the present invention;

[0026] Figure 3 2 is the XRD pattern of MgAlEu-LDHs with different Eu3+ doping amounts obtained in Example 3 of the present invention;

[0027] Figure 4 These are the excitation and emission spectra of MgAlEu-LDHs in Experimental Example 3 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Reference Figure 1-4 ,

[0030] Example 1: Preparation of Europium-doped Hydrotalcite Eu0.5%-LDHs:

[0031] Take Mg(NO3)2·6H2O (0.4 mol), Al(NO3)3·9H2O (0.1 mol) and Eu(NO3)3·6H2O (0.0025 mol) and dissolve them in 100 mL of deionized water (Mg:Al:Eu molar ratio is 4:1:0.025), add NaOH and Na2CO3 solution (0.5 mol / L), adjust the pH to 10, transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor, adjust the temperature to 80-90°C, and stir for 2 to 4 h. The mixture was cooled naturally to room temperature, centrifuged (8000 rpm, 10 minutes), washed with deionized water to a pH of 7, and vacuum-dried at 60°C for 12 hours to obtain white powdered Eu0.5%-MgAl-LDHs. 10 g of europium-doped Eu0.5%-MgAl-LDHs was dispersed in 50 mL of ethanol, 1.5 g of methyltrimethoxysilane was added, and the mixture was reacted at 60°C for 4 hours, washed, and dried. After ultrasonic treatment (300 W, 20 minutes) and high-pressure homogenization (100 MPa), particle size distribution analysis (laser particle size analyzer) revealed an average particle size of 80 nm, with a distribution range of 50-150 nm. This yielded europium-doped hydrotalcite Eu0.5%-LDHs.

[0032] Example 2: Preparation of europium-doped hydrotalcite Eu1%-LDHs.

[0033] Take Mg(NO3)2·6H2O (0.4 mol), Al(NO3)3·9H2O (0.1 mol) and Eu(NO3)3·6H2O (0.005 mol) and dissolve them in 100 mL of deionized water. Add NaOH and Na2CO3 solutions (0.5 mol / L) and adjust the pH to 10. Transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor, adjust the temperature to 80-90 °C, and stir for 2 to 4 h. The mixture was naturally cooled to room temperature, centrifuged (8000 rpm, 10 minutes), washed with deionized water to pH = 7, and vacuum dried at 60°C for 12 hours to obtain white powder Eu1%-MgAl-LDHs; 10 g of europium-doped Eu1%-MgAl-LDHs was dispersed in 50 mL of ethanol, 1.5 g of methyltrimethoxysilane was added, reacted at 60°C for 4 hours, washed and dried; under ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), after treatment with ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), the particle size distribution test (laser particle size analyzer) showed that the average particle size was 80 nm and the distribution range was 50-150 nm, thereby obtaining europium-doped hydrotalcite Eu1%-LDHs.

[0034] Example 3: Preparation of europium-doped hydrotalcite Eu1.5%-LDHs.

[0035] Take Mg(NO3)2·6H2O (0.4 mol), Al(NO3)3·9H2O (0.1 mol) and Eu(NO3)3·6H2O (0.0075 mol) and dissolve them in 100 mL of deionized water. Add NaOH and Na2CO3 solutions (0.5 mol / L), adjust the pH to 10, transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor, adjust the temperature to 80-90°C, and stir for 2 to 4 h. The mixture was naturally cooled to room temperature, centrifuged (8000 rpm, 10 minutes), washed with deionized water to pH = 7, and vacuum dried at 60°C for 12 hours to obtain white powdered Eu1.5%-MgAl-LDHs; 10 g of europium-doped Eu1.5%-MgAl-LDHs was dispersed in 50 mL of ethanol, 1.5 g of methyltrimethoxysilane was added, reacted at 60°C for 4 hours, washed and dried; under ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), after treatment with ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), the particle size distribution test (laser particle size analyzer) showed that the average particle size was 80 nm and the distribution range was 50-150 nm, thereby obtaining europium-doped hydrotalcite Eu1.5%-LDHs.

[0036] Example 4: Preparation of Europium-Doped Hydrotalcite Eu2%-LDHs. Mg(NO3)2·6H2O (0.4 mol), Al(NO3)3·9H2O (0.1 mol), and Eu(NO3)3·6H2O (0.0100 mol) were dissolved in 100 mL of deionized water. NaOH and Na2CO3 solutions (0.5 mol / L) were added, and the pH was adjusted to 10. The mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, the temperature was adjusted to 80-90°C, and the stirring time was 2 to 4 hours. The mixture was naturally cooled to room temperature, centrifuged (speed 8000 rpm, 10 minutes), washed with deionized water to pH = 7, and vacuum dried at 60°C for 12 hours to obtain white powder Eu2%-MgAl-LDHs; 10g of europium-doped Eu2%-MgAl-LDHs was dispersed in 50mL of ethanol, 1.5g of methyltrimethoxysilane was added, reacted at 60°C for 4 hours, washed and dried; under ultrasonic treatment (300W, 20min) and high-pressure homogenizer (100MPa), after treatment with ultrasonic treatment (300W, 20min) and high-pressure homogenizer (100MPa), the particle size distribution test (laser particle size analyzer) showed that the average particle size was 80nm and the distribution range was 50-150nm, thereby obtaining europium-doped hydrotalcite Eu2%-LDHs.

[0037] Example 5: Preparation of europium-doped hydrotalcite Eu2.5%-LDHs.

[0038] Take Mg(NO3)2·6H2O (0.4 mol), Al(NO3)3·9H2O (0.1 mol) and Eu(NO3)3·6H2O (0.0100 mol) and dissolve them in 100 mL of deionized water. Add NaOH and Na2CO3 solutions (0.5 mol / L), adjust the pH to 10, transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor, adjust the temperature to 80-90 °C, and stir for 2 to 4 h. The mixture was naturally cooled to room temperature, centrifuged (8000 rpm, 10 minutes), washed with deionized water to pH = 7, and vacuum dried at 60°C for 12 hours to obtain white powdered Eu2.5%-MgAl-LDHs; 10 g of europium-doped Eu2.5%-MgAl-LDHs was dispersed in 50 mL of ethanol, 1.5 g of methyltrimethoxysilane was added, reacted at 60°C for 4 hours, washed and dried; under ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), after treatment with ultrasonic treatment (300 W, 20 min) and high-pressure homogenizer (100 MPa), the particle size distribution test (laser particle size analyzer) showed that the average particle size was 80 nm and the distribution range was 50-150 nm, thereby obtaining europium-doped hydrotalcite Eu2.5%-LDHs.

[0039] Example 6: Preparation of Eu0-LDHs without Europium doping.

[0040] Take Mg(NO3)2·6H2O (0.4 mol) and Al(NO3)3·9H2O (0.1 mol) and dissolve them in 100 mL of deionized water, add NaOH and Na2CO3 solutions (0.5 mol / L), adjust the pH to 10, transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor, adjust the temperature to 80-90°C, and stir for 2 to 4 h. The mixture was naturally cooled to room temperature, centrifuged (8000 rpm, 10 minutes), washed with deionized water to pH = 7, and vacuum dried at 60°C for 12 hours to obtain white powder Eu0-MgAl-LDHs; 10g of europium-doped Eu0-MgAl-LDHs was dispersed in 50mL of ethanol, 1.5g of methyltrimethoxysilane was added, reacted at 60°C for 4 hours, washed and dried; europium-doped hydrotalcite Eu0-LDHs was obtained under ultrasonic treatment (300W, 20min) and high-pressure homogenizer (100MPa).

[0041] Example 7: Preparation of Eu-LDHs / PVC composite film.

[0042] Eu-LDHs doped with different europium contents were mixed with titanate and silane coupling agents at a ratio of 1:0.3-0.5 and stirred at high speed for 30 minutes to obtain the modified hydrotalcite. The modified hydrotalcite, PVC resin, and other auxiliary additives (MS resin, zinc stearate, epoxy plasticizer) were dry-mixed in a high-speed rotary mixer for 20 minutes. The mixture was melt-mixed at a certain temperature using a double-roll mill for 10 minutes. The crushed flakes were cooled to room temperature, crushed into powder using a crusher, and the powder was injected into a calender to form products such as PCV composite films under a certain pressure.

[0043] Comparative Example 1: Preparation of Eu0-LDHs / PVC composite film.

[0044] The modified hydrotalcite Eu0-LDHs was mixed with titanate and silane coupling agents at a ratio of 1:0.3-0.5 and stirred at high speed for 30 minutes to obtain the modified hydrotalcite; the modified hydrotalcite, PVC resin and other auxiliary additives (MS resin, zinc stearate, epoxy plasticizer) were dry-mixed in a high-speed rotary mixer for 20 minutes; the mixture was melt-mixed at a certain temperature for 10 minutes using a double-roll mill; the crushed flakes were cooled to room temperature, crushed into powder by a crusher, and the powder was injected into a calender to form PCV composite films and other products under a certain pressure.

[0045] Comparative Example 2: Commercially available calcium zinc stabilizer / PVC film.

[0046] The visible light transmittance (wavelength range 400-800nm) and ultraviolet light transmittance (wavelength range 200-400nm) of the film were tested using a WGW transmittance meter (ASTM D1003).

[0047] The initial thermal stability of the film was tested in a JZ401A thermal aging oven (180°C, 30 minutes). The test results of the film of the embodiment are shown in the following table:

[0048]

[0049] From the above experimental results, it can be seen that in the present invention, the crystal structure and light transmittance of highly transparent hydrotalcite are effectively improved by introducing the rare earth element europium Eu into the hydrotalcite. Europium doping significantly improves the transparency and structural stability of the hydrotalcite. Through europium doping co-precipitation, surface silanization and ultrasonic dispersion technology, trivalent europium (Eu3+) is doped into the lattice structure of the hydrotalcite (LDHs), achieving refractive index matching (1.50-1.53) and reducing light scattering. The optimized hydrotalcite particle size is controlled at 50-150nm, so that the light transmittance of the PVC composite film reaches more than 93%, and it also has red fluorescence characteristics. Compared with the existing technology, this material significantly improves the heat stability and anti-aging properties of PVC while improving transparency, and is suitable for transparent films, skylights and optical signs.

[0050] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0051] The above description is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A europium-doped hydrotalcite for enhancing the light transmittance of PVC, characterized in that: The europium-doped hydrotalcite is a magnesium / aluminum / europium ternary hydrotalcite, and the molar ratio of Mg:Al:Eu is 2-4:1:0.01-0.

1.

2. The method for preparing a europium-doped hydrotalcite for enhancing the light transmittance of PVC according to claim 1, wherein: The method comprises the following steps: SA1: Prepare a mixed solution of Mg(NO3)2·6H2O, Al(NO3)3·9H2O and Eu(NO3)3·6H2O, adjust the pH to 9-11, and prepare Mg-Al-Eu hydrotalcite by coprecipitation; SA2: hydrothermal reaction at 80-90°C for 2-4 hours to control the interlayer spacing of hydrotalcite; SA3: Surface modification with methyltrimethoxysilane to adjust the particle size to 50-150 nm and enhance hydrophobicity; SA4: The particle uniformity is improved by ultrasound-high pressure homogenization dispersion method, and the final product is obtained by vacuum drying.

3. The method for preparing a europium-doped hydrotalcite for enhancing the light transmittance of PVC according to claim 2, wherein: In step SA4, the drying step adopts a vacuum drying method with a vacuum degree of ≤0.1 MPa and a drying time of 6-12 hours.

4. An application of europium-doped hydrotalcite for enhancing the light transmittance of PVC, characterized in that: It is used to prepare highly transparent PVC packaging materials, optical marking films or medical films to improve the light transmittance and aging resistance of PVC materials.

5. The use of europium-doped hydrotalcite for enhancing the light transmittance of PVC as claimed in claim 4, characterized in that: The application comprises the following steps: S1: Mix hydrotalcite with titanate and silane coupling agents at a ratio of 1:0.3-0.5 and stir at high speed for 30 minutes to form a hydrophobic surface; S2: Modified hydrotalcite, PVC resin and other auxiliary additives (MS resin, zinc stearate, epoxy plasticizer) were dry mixed in a high-speed rotary mixer for 20 minutes; S3: melt mixing the mixture at a certain temperature using a two-roll mill for 10 minutes; S4: The crushed flakes are cooled to room temperature, crushed into powder by a crusher, and the powder is injected into a calender to form PCV composite films and other products under a certain pressure.

6. The use of europium-doped hydrotalcite for enhancing the light transmittance of PVC as claimed in claim 5, characterized in that: In the step S1, the coupling agent is diluted with an equal amount of toluene in a 1:1 ratio and then sprayed on the surface of the hydrotalcite.

7. The use of europium-doped hydrotalcite for enhancing the light transmittance of PVC as claimed in claim 5, characterized in that: In step S3, the temperature of the double-roll mill should be controlled at 160-190° C. to prevent PVC from decomposing HCL due to high temperature.

8. The use of europium-doped hydrotalcite for enhancing the light transmittance of PVC as claimed in claim 5, characterized in that: In step S4, the compression molding pressure in the calender is 10-15 MPa, and the holding time is 5-10 minutes.

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