Ultraviolet aging resistant polyvinyl chloride material and preparation method thereof

Abstract

The invention provides an anti-ultraviolet aging PVC (polyvinyl chloride) material and a preparation method thereof. The PVC material comprises a PVC base material and an ultraviolet shielding coating formed on the surface of the PVC base material, the ultraviolet shielding coating comprises metal polyphenol network modified mica nanosheets and a polymer carrier, and the mass ratio of the metal polyphenol network modified mica nanosheets to the polymer carrier is 1: 9-1: 1. The metal polyphenol network modified mica nanosheet comprises a mica nanosheet and a metal polyphenol network combined on the surface of the mica nanosheet through a hydrogen bond, and the metal polyphenol network is of a complex structure assembled by plant polyphenol and metal ions through chemical action between the plant polyphenol and the metal ions. The surface coating of the PVC material has absorbance greater than 1 at the wavelength of 200-400 nm of an ultraviolet visible absorption spectrum, or has transmittance less than 50% at the wavelength of 200-400 nm of an ultraviolet transmittance spectrum. The PVC material not only can resist aging caused by ultraviolet rays, but also can keep the intrinsic color and attractiveness of the PVC base material.

Description

Technical Field

[0001] The present invention relates to the technical field of new material development, and particularly relates to a polyvinyl chloride (PVC) material resistant to ultraviolet aging and a preparation method thereof. Background Art

[0002] The global awareness of ultraviolet protection has been continuously enhanced, and at the same time, the call for environmental protection has become increasingly high, which has promoted the continuous progress of research and development of related material technologies. Among many materials, PVC has attracted much attention due to its wide applications. However, when PVC is exposed to ultraviolet rays in the natural environment for a long time, it will undergo an aging process, resulting in a decline in its performance, manifested as problems such as reduced strength, color change, and structural damage, which directly affect the service life and safety of the material. Although there are various ultraviolet protection materials on the market, they often contain toxic components harmful to the environment and are difficult to degrade, thus imposing an additional burden on the ecological environment. While these materials provide ultraviolet protection, they also bring new environmental challenges. In addition, when existing ultraviolet shielding materials provide a certain degree of protection function, it is often difficult to balance transparency and ultraviolet shielding performance. Traditional ultraviolet protection materials usually achieve ultraviolet absorption and reflection by adding inorganic particles or organic compounds. Although these materials have a certain shielding effect, they often sacrifice the transparency of the material. Therefore, developing a PVC material that is both safe, environmentally friendly, and efficient, and can maintain its intrinsic color while maintaining ultraviolet resistance has become an urgent need of society. This is not only a challenge in the field of materials science but also an important direction for technological innovation. This new type of ultraviolet-resistant PVC material will be able to significantly extend the service life of PVC, improve its application potential in outdoor environments, and at the same time reduce the negative impact on the environment, achieving the goal of sustainable development. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a PVC material resistant to ultraviolet aging and a preparation method thereof. The PVC material provided by this application has excellent ultraviolet aging resistance and can also effectively scavenge free radicals generated by ultraviolet radiation. This method combines the ultraviolet shielding mechanisms of plant polyphenols and mica. On the basis of the ultraviolet shielding by mica flakes, the ultraviolet light irradiated on the mica surface will also be absorbed by the metal polyphenol network.

[0004] To this end, the present application provides the following aspects:

[0005] <1> . A PVC material resistant to ultraviolet aging, comprising a PVC substrate and an ultraviolet shielding coating formed on the surface of the PVC substrate, wherein the ultraviolet shielding coating comprises mica nanosheets modified with a metal polyphenol network and a polymer carrier, and the mass ratio of the mica nanosheets modified with the metal polyphenol network to the polymer carrier is 1:9-1:1, the mica nanosheets modified with the metal polyphenol network comprise mica nanosheets and a metal polyphenol network bonded to the surface of the mica nanosheets by hydrogen bonds, the metal polyphenol network is a complex structure assembled by chemical reactions between plant polyphenols and metal ions, and the thickness of the ultraviolet shielding coating ranges from 1 to 1000 μm.

[0006] <2> . according to <1> The PVC material, wherein the surface coating of the PVC material has an absorbance greater than 1 in the 200-400 nm band of the ultraviolet visible absorption spectrum, or has a transmittance lower than 50% in the 200-400 nm band of the ultraviolet transmittance spectrum.

[0007] <3> . The PVC material according to any of the above items, wherein the thickness of the mica nanosheets modified by the metal polyphenol network is in the range of 0.3-100 nm, and the sheet diameter is in the range of 50-10000 nm.

[0008] <4> . The PVC material according to any of the above, wherein the polymer carrier is selected from one or more of cellulose nanofibers, polyurethane and epoxy resin, and its molecular weight range is 10 3 -10 6 .

[0009] <5> . The PVC material according to any of the above items, wherein the plant polyphenols are selected from one or more of tannic acid and tea polyphenols.

[0010] <6> . The PVC material according to any of the preceding items, wherein the metal ion is selected from Cu 2+ , Fe 3+ ,Mg 2+ , Ca 2+ , Zn 2+ and Mn 2+ One or more of .

[0011] <7> . The PVC material according to any of the above items, wherein in the mica nanosheets modified with the metal polyphenol network, the molar ratio between the plant polyphenol and the metal ion is in the range of 1:3-4:1.

[0012] <8> . The PVC material according to any of the preceding items, wherein the modification amount of the metal polyphenol network accounts for 10%-50% of the mass of the mica nanosheets.

[0013] <9>. The PVC material according to any one of the preceding items, wherein the mica nanosheets are selected from one or more of phlogopite and muscovite.

[0014] <10>. A method for preparing the PVC material according to any one of <1> to <9>, the method comprising the following steps:

[0015] A) Providing a suspension of exfoliated mica nanosheets in water;

[0016] B) Adding plant polyphenols to the suspension of mica nanosheets, and the dosage is 10%-50% of the mass fraction of mica nanosheets, to obtain a mixture;

[0017] C) Adding metal ions to the mixture obtained in step B), and the molar ratio between the plant polyphenols and the metal ions is in the range of 1:3 - 4:1;

[0018] D) Adjusting the pH value of the mixture obtained in step C) to weakly alkaline to promote the complexation of plant polyphenols and metal ions, to obtain mica nanosheets modified with a metal polyphenol network;

[0019] E) Mixing the mica nanosheets modified with the metal polyphenol network obtained in step D) with a polymer carrier uniformly to obtain an aqueous coating,

[0020] F) Coating the aqueous coating on the surface of a PVC substrate and drying at a temperature of 20 - 80 °C to form an ultraviolet shielding coating as the surface coating of the PVC material.

[0021] For the anti-ultraviolet aging PVC material according to the present invention, the high-performance composite ultraviolet shielding coating of the mica nanosheets modified with a metal polyphenol network combines the ultraviolet shielding mechanisms of plant polyphenols and mica. Through the mica nanosheets modified with a metal polyphenol network, on the basis of the ultraviolet shielding of mica nanosheets, the ultraviolet shielding mechanism of plant polyphenols is combined. The ultraviolet light irradiated on the surface of the mica nanosheets will also be absorbed by the metal polyphenol network, and the presence of the metal polyphenol network causes an obvious red shift phenomenon in the absorption peak of the ultraviolet shielding coating on the surface of the PVC material in the ultraviolet-visible spectral region, further broadening the ultraviolet shielding ability of the PVC material. Description of the Drawings

[0022] Figure 1 It is a photograph of the aqueous dispersion of phlogopite nanosheets modified with a tannin manganese ion network prepared in Example 1 of the present invention. The obtained aqueous dispersion of phlogopite nanosheets modified with a tannin manganese ion network is a homogeneous, transparent light yellow dispersion;

[0023] Figure 2The micrograph of the mica nanosheets modified with tannin-manganese ion network prepared in Example 1 of the present invention observed under a field emission scanning electron microscope shows that the mica nanosheets modified with tannin-manganese ion network are of nanoscale;

[0024] Figure 3 The diameter distribution of the mica nanosheets prepared in Example 1 of the present invention obtained by dynamic light scattering test and Gaussian fitting shows that most of the sizes of the mica nanosheets modified with tannin-manganese ion network are in the range of 50-100 nm;

[0025] Figure 4 The ultraviolet absorption spectra of tannin, manganese chloride and tannin-manganese ion complex in Example 1 of the present invention show that the ultraviolet absorption spectrum is significantly red-shifted after the complexation of tannin and manganese ions, proving the formation of this complex structure;

[0026] Figure 5 The ultraviolet absorption spectra of the aqueous dispersions of mica nanosheets before and after the modification of tannin and tannin-manganese ion network prepared in Example 1 of the present invention show that the absorption of the mica nanosheets modified with tannin in the ultraviolet band is significantly enhanced, and the absorption of the mica nanosheets modified with tannin-manganese ion network in the ultraviolet band is further enhanced, and there is basically no change in absorbance in the visible light band, proving that the mica modified by this method can take into account the ultraviolet shielding performance and transparency;

[0027] Figure 6 The infrared spectra of tannin, mica nanosheets and mica nanosheets modified with tannin-manganese ion network prepared in Example 1 of the present invention prove the successful modification of tannin;

[0028] Figure 7 The X-ray photoelectron spectra of the mica nanosheets before and after the modification of tannin-manganese ion network prepared in Example 1 of the present invention also prove the successful modification of tannin;

[0029] Figure 8 The inductively coupled plasma emission spectra of the mica nanosheets before and after the modification of tannin-manganese ion network prepared in Example 1 of the present invention prove the successful complexation of tannin and Mn 2+ ;

[0030] Figure 9 The ultraviolet absorption spectrum of water of the mica nanosheets modified with tannin-iron ion network prepared in Example 2 of the present invention shows that the absorption of the mica nanosheets modified with tannin-iron ion network in the ultraviolet band is significantly enhanced, and there is basically no absorption in the visible light band;

[0031] Figure 10The UV absorption spectrum of the mica nanosheet water modified by the tea polyphenol manganese ion network prepared in Example 3 of the present invention is shown. It can be seen that the absorption of the mica nanosheet after being modified by the tea polyphenol manganese ion network is significantly enhanced in the UV band, and there is basically no absorption in the visible light band;

[0032] Figure 11 The UV absorption spectrum of the muscovite nanosheet aqueous dispersion modified by the tannin manganese ion network prepared in Example 4 of the present invention is shown. It can be seen that the absorption of the muscovite nanosheet after being modified by the tannin manganese ion network is significantly enhanced in the UV band, and there is basically no absorption in the visible light band;

[0033] Figure 12 The UV transmittance spectrum of the composite coating of mica modified by tannin manganese ion network and cellulose prepared in Example 1 of the present invention is shown. It can be seen that the transmittance of this coating in the UV band is very low, while a high transmittance is retained in the visible light band, taking into account both transparency and UV shielding;

[0034] Figure 13 The SEM of the mixed coating of mica modified by tannin manganese ion network and cellulose prepared in Example 1 of the present invention is shown. It can be seen that the nanosheets are evenly dispersed in the cellulose nanofibers;

[0035] Figure 14 The anti-ultraviolet aging PVC digital photo prepared in Example 1 of the present invention is shown. It can be seen that the introduction of the UV shielding coating basically does not change the color of the PVC;

[0036] Figure 15 The microscopic photo of the anti-ultraviolet aging PVC prepared in Example 1 of the present invention observed under a field emission scanning electron microscope is shown. It can be clearly seen the anti-UV coating on the surface of the PVC;

[0037] Figure 16 The comparison of the mechanical properties of the anti-ultraviolet aging PVC prepared in Example 1 of the present invention before and after UV aging is shown. It can be seen that the mechanical properties of the PVC after UV aging do not decrease significantly;

[0038] Figure 17 The comparison of the mechanical properties of the pure PVC without the anti-ultraviolet aging coating prepared in Example 1 of the present invention before and after UV aging is shown. It can be seen that the mechanical properties of the pure PVC after UV aging decrease significantly;

[0039] Figure 18 The test result of the adhesion strength between the PVC substrate and the UV shielding coating in the anti-ultraviolet aging PVC prepared in Example 1 of the present invention is shown. The test method follows the ASTM D3359 standard. It can be seen that there is good adhesion strength between the UV shielding coating and the PVC substrate;

[0040] Figure 19 Shown in the figure is the ultraviolet transmittance spectrum of the phlogopite and polyurethane composite coating modified with tannin manganese ions prepared in Example 5 of the present invention. It can be seen that the transmittance of this coating in the ultraviolet light band is also very low, while a very high transmittance is retained in the visible light band, taking into account both transparency and ultraviolet shielding. This indicates that the ultraviolet shielding effect of the present invention is not affected by the type of polymer carrier;

[0041] Figure 20 Shown in the figure is the ultraviolet transmittance spectrum of the unmodified phlogopite and cellulose nanofiber mixed coating prepared in Comparative Example 1. It can be seen that although this coating has a very high transmittance in the visible light band, its transmittance in the ultraviolet band is also very high, and its ultraviolet shielding performance is inferior to that of Example 1;

[0042] Figure 21 Shown in the figure is the ultraviolet absorption spectrum of the phlogopite dispersion modified with dopamine manganese ion complex prepared in Comparative Example 2. It can be seen that the absorption of the modified phlogopite nanosheets in the ultraviolet band is significantly enhanced, but the absorption in the visible light band is also enhanced to a certain extent. Therefore, it is impossible to take into account both ultraviolet shielding and transparency;

[0043] Figure 22 Shown in the figure is the ultraviolet transmittance spectrum of the phlogopite and cellulose nanofiber composite coating modified with dopamine manganese ion complex prepared in Comparative Example 2. It can be seen that the transmittance of this coating in the ultraviolet light band is very low, but its transmittance in the visible light band is also very low, further indicating that it is impossible to take into account both transparency and ultraviolet shielding. Detailed implementation mode

[0044] In view of the characteristics of PVC materials, mica nanosheets, plant polyphenols and polymer carriers themselves and the current situation of traditional ultraviolet protection materials, the present application provides an anti-ultraviolet aging PVC material and its preparation method.

[0045] On the one hand, the present application firstly provides a PVC material with anti-ultraviolet aging property, which is obtained by uniformly coating an ultraviolet shielding coating on the surface of traditional PVC and then drying. The PVC material comprises a PVC substrate and an ultraviolet shielding coating formed on the surface of the PVC substrate, wherein the ultraviolet shielding coating comprises mica nanosheets modified with metal polyphenol network and a polymer carrier, and the mass ratio of the mica nanosheets modified with metal polyphenol network to the polymer carrier is 1:9 - 1:1. The mica nanosheets modified with metal polyphenol network comprise mica nanosheets and a metal polyphenol network hydrogen-bonded to the surface of the mica nanosheets. The metal polyphenol network is a complex structure assembled by the chemical interaction between plant polyphenols and metal ions. The thickness range of the ultraviolet shielding coating is 1 - 1000 μm. The ultraviolet shielding coating exists as the surface coating of the PVC material or can exist in the form of wrapping all surfaces of the PVC substrate. It has an absorbance greater than 1 in the 200 - 400 nm band of the ultraviolet-visible absorption spectrum, or a transmittance lower than 50% in the 200 - 400 nm band of the ultraviolet transmittance spectrum.

[0046] In the PVC material with anti-ultraviolet aging property obtained in the present application, the ultraviolet shielding coating has an ultraviolet shielding effect at multiple scales. Among them, the mica nanosheets have a polarization effect and an interference effect due to their unique layered structure at the nanoscale, and can effectively block or scatter ultraviolet rays, thus showing excellent ultraviolet shielding performance; at the molecular scale, the plant polyphenols contain aromatic rings and conjugated double bond structures inside their molecules. These structural features enable the plant polyphenols to absorb ultraviolet rays in the 200 - 350 nm band and convert the absorbed ultraviolet energy into heat energy and release it. When the plant polyphenols form a complex with metal ions, due to the change of the chemical environment, the absorption peak in the ultraviolet-visible spectral region redshifts to 400 nm, further broadening the absorption range of ultraviolet rays (i.e., in the 200 - 400 nm region), enhancing the overall ultraviolet shielding ability, and at the same time having a certain transmittance in the visible light band, taking into account the transparency of the material.

[0047] In the present invention, the term "metal polyphenol network" means a complex structure assembled by the chemical interaction between plant polyphenols and metal ions.

[0048] In the present invention, the term "mica nanosheets" means nanosheets peeled from natural mica minerals.

[0049] In the present invention, the term "ultraviolet shielding" means having an absorbance greater than 1 in the 200 - 400 nm band of the ultraviolet-visible absorption spectrum, or a transmittance lower than 50% in the 200 - 400 nm band of the ultraviolet transmittance spectrum, so as to be able to block ultraviolet rays.

[0050] On the other hand, the present application also provides a method for preparing an anti-ultraviolet aging PVC material, comprising the following steps:

[0051] A) Provide a suspension of exfoliated mica nanosheets in water;

[0052] B) Add plant polyphenols to the suspension of the mica nanosheets, with the dosage being 10%-50% of the mass fraction of the mica nanosheets, to obtain a mixture;

[0053] C) Add metal ions to the mixture obtained in step B), and the molar ratio between the plant polyphenols and the metal ions is in the range of 1:3 - 4:1;

[0054] D) Adjust the pH value of the mixture obtained in step C) to weakly alkaline to promote the complexation of the plant polyphenols and the metal ions, to obtain mica nanosheets modified with a metal polyphenol network;

[0055] E) Mix the mica nanosheets modified with the metal polyphenol network obtained in step D) with a polymer carrier evenly to obtain an aqueous coating,

[0056] F) Coat the aqueous coating on the surface of the PVC substrate and dry to form an ultraviolet shielding coating.

[0057] As an example, step A) includes: uniformly dispersing mica raw materials in water, performing exfoliation treatment under the assistance of ultrasonic waves, and then centrifuging at a rotational speed of 2000 - 5000 r / min for 10 - 20 min, and taking the centrifuged supernatant to obtain a mica nanosheet suspension. The reason why mica flakes can be exfoliated by ultrasound is that the mica interlayer is K with balanced negative charges + , resulting in weak binding between mica layers and being easily exfoliated under external forces such as ultrasound. More specifically, the mica includes but is not limited to phlogopite, and can also be other mica such as muscovite.

[0058] Preferably, the mica raw materials are selected from one or more of phlogopite or muscovite.

[0059] Preferably, the plant polyphenols and the metal ions carry out a complexation reaction under conventional reaction conditions.

[0060] Preferably, the plant polyphenols are selected from one or more of tannic acid or tea polyphenols.

[0061] Preferably, the metal ions are selected from one or more of Cu 2+ , Fe 3+ , Mg 2+ , Ca 2+ , Zn 2+ or Mn 2+ in one or more.

[0062] Preferably, the buffer system for adjusting pH is selected from one of phosphate buffer (PBS), tris(hydroxymethyl)aminomethane-hydrochloric acid buffer (Tris-HCl), 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), or 3-(N-morpholino)propanesulfonic acid (MOPS).

[0063] Weakly alkaline pH means pH is in the range of 7.1 - 10.0, preferably in the range of 7.5 - 9.0, and more preferably in the range of 8.0 - 8.5.

[0064] Preferably, the polymer carrier is selected from one or more of cellulose nanofibers, polyurethanes, and epoxy resins. The selection criterion for the polymer carrier is hydrophilic polymers. For the polymer carrier of the present application, its molecular weight range is 10 3 -10 6 , preferably 10 4 -10 6 , more preferably 10 4 -10 5 .

[0065] For the mica nanosheets of the present application, its thickness range is 0.3 - 100 nm, preferably 0.6 - 10 nm, and more preferably 1 - 5 nm; the sheet diameter (i.e., diameter) range is 50 - 10,000 nm, preferably 60 - 800 nm, and more preferably 100 - 500 nm.

[0066] For the high-performance composite ultraviolet shielding coating of the metal polyphenol network modified mica nanosheets of the present application, its viscosity range is 10 - 10 9 mPa·s, preferably 10 2 -10 8 mPa·s, more preferably 10 3 -10 7 mPa·s; its thickness range is 1 - 1000 μm, preferably 10 - 500 μm, and more preferably 10 - 100 μm.

[0067] For the high-performance composite ultraviolet shielding coating of the metal polyphenol network modified mica nanosheets of the present application, the molar ratio between the plant polyphenol and the metal ion is in the range of 1:3 - 4:1, more preferably in the range of 1:2 - 3:1, and still more preferably in the range of 1:1 - 2:1. The modification amount of the metal polyphenol network accounts for 10% - 50% of the mass of the mica nanosheets, preferably 10% - 40%, and more preferably 10% - 30%.

[0068] For the high-performance composite ultraviolet shielding coating of the metal polyphenol network modified mica nanosheets of the present application, the mass ratio of the metal polyphenol network modified mica nanosheets to the polymer carrier is preferably in the range of 1:4 - 3:7.

[0069] During the process of forming the ultraviolet shielding coating on the PVC substrate, the drying temperature ranges from 20 to 80 °C, preferably from 40 to 80 °C, and more preferably from 50 to 60 °C. The drying temperature has a relatively significant impact on the anti-ultraviolet aging PVC material of the present application. When the temperature is too high, as a heat-sensitive material, chlorine atoms in the molecular chain of PVC are easily removed to generate hydrogen chloride gas, resulting in thermal degradation. This will change its chemical composition and molecular structure, make the internal structure of the material loose, enhance the ultraviolet penetrability, and at the same time, the small molecular substances generated by thermal degradation migrate to the surface, triggering a photochemical reaction under ultraviolet irradiation to accelerate aging, resulting in the material discoloring, becoming brittle, and the mechanical and optical properties deteriorating; while if the temperature is too low, the moisture in the PVC material is difficult to be completely removed, and they will form channels or voids inside the material, making ultraviolet rays more likely to scatter and refract, breaking chemical bonds, and the residual moisture is likely to trigger a hydrolysis reaction, and the active groups generated will undergo an oxidation reaction under the action of ultraviolet rays. In addition, the residual water will also affect the dispersibility of the coating, making it unable to fully play its role, and ultimately reducing the anti-ultraviolet aging performance of the material.

[0070] In the present invention, due to the synergistic effect of ultraviolet shielding of plant polyphenols and mica nanosheets at the molecular and nanoscale levels on the ultraviolet shielding coating of the prepared anti-ultraviolet aging PVC material, the nanosheets prepared by the present invention have extremely excellent ultraviolet shielding performance and at the same time have a very high visible light transmittance. Moreover, the plant polyphenols described in the present invention itself have antioxidant activity, can effectively scavenge free radicals generated by ultraviolet rays, protect macromolecules from oxidative damage by inhibiting the free radical chain reaction, and thus play a key role in the field of anti-ultraviolet materials. Therefore, the present application can provide an anti-ultraviolet aging PVC material, which is a new type of anti-ultraviolet PVC material, which will be able to significantly extend the service life of PVC, improve its application potential in outdoor environments, and at the same time reduce the negative impact on the environment. For example, according to the following examples, it can be seen from the comparison of the mechanical properties of the anti-ultraviolet aging PVC prepared according to the present application before and after ultraviolet aging that the mechanical properties of the PVC after ultraviolet aging do not decrease significantly. And from the comparison of the mechanical properties of the PVC substrate without the anti-ultraviolet coating before and after ultraviolet aging, it can be seen that after 10 days of ultraviolet aging, the elongation at break and the breaking strength of the PVC substrate decrease significantly. Therefore, it is expected that the present application will have good application prospects in industry.

[0071] Examples

[0072] To further understand the present invention, the anti-ultraviolet aging PVC material provided by the present invention will be described in detail below in conjunction with examples, and the protection scope of the present invention is not limited by the following examples.

[0073] All the reagents used in the following examples are commercially available reagents and are used directly without special treatment. In addition, the process of testing the ultraviolet absorption spectrum involved in this application is as follows: Dilute the total concentration of the prepared dispersion to 0.2 mg / mL, take 3 mL and place it in a cuvette, and use a SHIMADZU UV-2600 ultraviolet-visible spectrophotometer from Japan for testing. The process of testing the ultraviolet transmittance spectrum involved in this application is as follows: Take 1 mL of the coating with a concentration of 12 mg / mL, evenly apply it on a quartz sheet of 2.5×2.5 cm, wait for natural drying, and then use a SHIMADZU Solid 3700 DUV ultraviolet-visible near-infrared spectrophotometer from Japan for testing.

[0074] Example 1

[0075] A) Disperse the phlogopite raw material in water. Under the action of ultrasonic waves, exfoliate the phlogopite into phlogopite nanosheets, and then centrifuge at a speed of 3000 r / min for 10 min. Take the centrifuged supernatant to obtain a phlogopite nanosheet suspension;

[0076] B) Add tannic acid with a mass fraction of 16% of the phlogopite nanosheets to the phlogopite nanosheet suspension obtained in step A), and stir and mix evenly;

[0077] C) Add manganese chloride with a molar content close to that of tannic acid to the mixture of phlogopite nanosheets and tannic acid obtained in step B), and stir and mix evenly;

[0078] D) Adjust the pH of the mixture of phlogopite nanosheets, tannic acid, and manganese chloride obtained in step C) to 8.0 with a 2-(4-(2-Hydroxyethyl)piperazin-1-yl)ethanesulfonic acid (HEPES) buffer solution to complex tannic acid and manganese ions, and obtain an aqueous dispersion of phlogopite nanosheets modified with a tannin-manganese ion network;

[0079] E) Mix the modified mica obtained in step D) and cellulose nanofibers (the mass fraction ratio of mica to cellulose nanofibers is 3:7), and ultrasonically disperse for 2 min to make the modified mica and cellulose nanofibers fully and evenly mixed;

[0080] F) Uniformly coat the obtained composite on the surface of the PVC substrate and dry to form an ultraviolet shielding layer, and obtain the anti-ultraviolet aging PVC material described in this application.

[0081] Figure 1 This is a photograph of the aqueous dispersion of phlogopite nanosheets modified with a tannin-manganese ion network prepared in Example 1 of the present invention. The obtained aqueous dispersion of phlogopite nanosheets modified with a tannin-manganese ion network is a uniform, transparent, light yellow dispersion;

[0082] Figure 2This is a microscopic photograph of the mica nanosheets modified with tannin-manganese ion network prepared in Example 1 of the present invention observed under a field emission scanning electron microscope. It can be seen that the mica nanosheets modified with tannin-manganese ion network are of nanoscale;

[0083] Figure 3 This is the particle size distribution of the mica nanosheets prepared in Example 1 of the present invention obtained by dynamic light scattering test and Gaussian fitting. It can be seen that the sizes of the mica nanosheets modified with tannin-manganese ion network are mostly in the range of 50 - 100 nm;

[0084] Figure 4 This is the ultraviolet absorption spectrum of tannin, manganese chloride and tannin-manganese ion complex in Example 1 of the present invention. It can be seen that after the complexation of tannin and manganese ions, the ultraviolet absorption spectrum is significantly red-shifted, proving the formation of this complex structure.

[0085] Figure 5 This is the ultraviolet absorption spectrum of the aqueous dispersion of mica nanosheets before and after being modified with tannin and tannin-manganese ion network prepared in Example 1 of the present invention. It can be seen that the absorption of the mica nanosheets modified with tannin in the ultraviolet band is significantly enhanced, while the absorption of the mica nanosheets modified with tannin-manganese ion network in the ultraviolet band is further enhanced and there is also a red-shift, proving that tannin and manganese ions form a complex on the surface of the mica nanosheets, and there is basically no change in absorbance in the visible light band, preliminarily proving that the mica modified by this method can take into account ultraviolet shielding performance and transparency;

[0086] Figure 6 This is the infrared spectrum of tannin, mica nanosheets and mica nanosheets modified with tannin-manganese ion network prepared in Example 1 of the present invention. From the infrared spectrum of the modified mica, it can be seen that the absorption peak at 1734 cm -1 is the stretching vibration of the carbon-oxygen double bond of the ester group in tannin, and the absorption peak at 1189 cm -1 corresponds to the vibration of the carbon-oxygen single bond in tannin, and the absorption peak at 1650 - 1430 cm -1 corresponds to the skeletal vibration of the benzene ring in tannin. This proves the successful modification of tannin.

[0087] Figure 7 This is the X-ray photoelectron spectrum of the mica nanosheets before and after being modified with tannin-manganese ion network prepared in Example 1 of the present invention. It can be seen that the carbon element content of the mica nanosheets after modification increases significantly, which also proves the successful modification of tannin.

[0088] Figure 8 This is the inductively coupled plasma emission spectrum of the mica nanosheets before and after being modified with tannin-manganese ion network prepared in Example 1 of the present invention. It can be seen that the content of Mn 2+ in the mica nanosheets after modification increases significantly, proving that tannin and Mn2 + Successful complexation.

[0089] Figure 12 This is the ultraviolet transmittance spectrum of the mixed coating of mica and cellulose modified by tannin-manganese ion network prepared in Example 1 of the present invention. It can be seen that the transmittance of this coating in the ultraviolet band is very low, lower than 50%. At the same time, it retains a very high transmittance in the visible light band. The transmittance is higher than 60% in most visible light bands, taking into account both transparency and ultraviolet shielding. The low transmittance of the coating in the ultraviolet band endows the PVC material with the property of anti-ultraviolet aging, while the high transmittance in the visible light band can retain the intrinsic color of the PVC substrate.

[0090] Figure 13 This is the SEM of the mixed coating of mica and cellulose modified by tannin-manganese ion network prepared in Example 1 of the present invention. It can be seen that the mica nanosheets modified by tannin-manganese ion network are evenly dispersed in the cellulose nanofibers. This evenly dispersed structure ensures the uniform appearance color of PVC and the coating has good adhesion.

[0091] Figure 14 This is the digital photo of anti-ultraviolet aging PVC prepared in Example 1 of the present invention. It can be seen that the introduction of the ultraviolet shielding coating basically does not change the color of the PVC substrate.

[0092] Figure 15 This is the micrograph of anti-ultraviolet aging PVC prepared in Example 1 of the present invention observed under a field emission scanning electron microscope. It can be clearly seen the anti-ultraviolet coating on the surface of PVC.

[0093] Figure 16 This is the comparison of the mechanical properties of anti-ultraviolet aging PVC prepared in Example 1 of the present invention before and after ultraviolet aging. It can be seen that the mechanical properties of PVC after ultraviolet aging do not decrease significantly.

[0094] Figure 17 This is the comparison of the mechanical properties of the PVC substrate without anti-ultraviolet coating prepared in Example 1 of the present invention before and after ultraviolet aging. It can be seen that after 10 days of ultraviolet aging, the elongation at break and breaking strength of the PVC substrate decrease significantly.

[0095] Figure 18This is the test result of the adhesion strength between the PVC substrate and the ultraviolet shielding coating prepared in Example 1 of the present invention. The test method follows the ASTM D3359 standard. The coating is evenly applied on the washed substrate. After drying, it is vertically cut with a cross cutter to form a grid pattern. The wooden block is rotated 90 degrees and the cutting is repeated. The debris is gently brushed away along the diagonal with a soft brush. Tape is attached at the intersections and torn off after 60 seconds to observe the peeling situation. The result shows that the coating damage does not exceed 5%, indicating that there is good adhesion strength between the ultraviolet shielding coating and the PVC substrate.

[0096] Example 2

[0097] A) The phlogopite raw material is dispersed in water. Under the action of ultrasound, the phlogopite is exfoliated into phlogopite nanosheets, and then centrifuged at a speed of 3000 r / min for 10 min. The centrifuged supernatant is taken to obtain a phlogopite nanosheet suspension;

[0098] B) Tannic acid with a mass fraction of 16% of the phlogopite nanosheets is added to the phlogopite nanosheet suspension obtained in step A), and stirred and mixed evenly;

[0099] C) Ferric chloride with a molar content close to that of tannic acid is added to the mixed solution of phlogopite nanosheets and tannic acid obtained in step B), and stirred and mixed evenly;

[0100] D) The pH of the mixed solution of phlogopite nanosheets, tannic acid and ferric chloride obtained in step C) is adjusted to 8.0 with 2-(4-(2-hydroxyethyl)piperazin-1-yl)ethanesulfonic acid (HEPES) buffer solution to make tannic acid and iron ions complex.

[0101] E) The modified mica obtained in step D) and cellulose nanofibers are mixed (the mass fraction ratio of mica to cellulose nanofibers is 3:7), and ultrasonically dispersed for 2 min to make the modified mica and cellulose nanofibers fully and evenly mixed;

[0102] F) The obtained composite is evenly coated on the surface of the PVC substrate and dried to form an ultraviolet shielding layer.

[0103] Figure 9 This is the ultraviolet absorption spectrum of water of phlogopite nanosheets modified by tannic acid-iron ion network prepared in Example 2 of the present invention. It can be seen that the absorption of phlogopite nanosheets modified by tannic acid-iron ion network in the ultraviolet band is significantly enhanced, and there is basically no absorption in the visible light band, indicating that iron ions can also be used for the modification method of metal polyphenol network. And this strong absorption of phlogopite nanosheets modified by tannic acid-iron ion network in the ultraviolet light band and low absorption in the visible light band can also be used in the ultraviolet shielding coating, so that the PVC material has the performance of anti-ultraviolet aging while retaining the intrinsic color of the PVC substrate.

[0104] Example 3

[0105] A) Disperse phlogopite raw materials in water. Under the action of ultrasound, exfoliate phlogopite into phlogopite nanosheets, and then centrifuge at a speed of 3000 r / min for 10 min. Take the centrifuged supernatant to obtain a phlogopite nanosheet suspension;

[0106] B) Add tea polyphenols with a mass fraction of 16% of the phlogopite nanosheets to the phlogopite nanosheet suspension obtained in step A), and stir to mix evenly;

[0107] C) Add manganese chloride with a molar content close to that of tea polyphenols to the mixed solution of phlogopite nanosheets and tea polyphenols obtained in step B), and stir to mix evenly;

[0108] D) Adjust the pH of the mixed solution of phlogopite nanosheets, tea polyphenols and manganese chloride obtained in step C) to 8.0 with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution to chelate tea polyphenols and manganese ions.

[0109] E) Mix the modified mica obtained in step D) with cellulose nanofibers (the mass fraction ratio of mica to cellulose nanofibers is 3:7), and ultrasonically disperse for 2 min to make the modified mica and cellulose nanofibers fully and evenly mixed;

[0110] F) Uniformly coat the obtained composite on the surface of the PVC substrate and dry to form an ultraviolet shielding layer.

[0111] Figure 10 The ultraviolet absorption spectrum of water of phlogopite nanosheets modified by the tea polyphenol manganese ion network prepared in Example 3 of the present invention is shown. It can be seen that the absorption of the phlogopite nanosheets modified by the tea polyphenol manganese ion network is also significantly enhanced in the ultraviolet band, and there is basically no absorption in the visible light band, indicating that tea polyphenols can also be used in the modification method of metal polyphenol networks. And this strong absorption of the phlogopite nanosheets modified by the tea polyphenol manganese ion network in the ultraviolet light band and low absorption in the visible light band can also be used in ultraviolet shielding coatings, enabling the PVC material to have the performance of resisting ultraviolet aging while retaining the intrinsic color of the PVC substrate.

[0112] Example 4

[0113] A) Disperse muscovite raw materials in water. Under the action of ultrasound, exfoliate muscovite into muscovite nanosheets, and then centrifuge at a speed of 3000 r / min for 10 min. Take the centrifuged supernatant to obtain a muscovite nanosheet suspension;

[0114] B) Add tannic acid with a mass fraction of 16% of the muscovite nanosheets to the muscovite nanosheet suspension obtained in step A), and stir to mix evenly;

[0115] C) Add manganese chloride with a molar content close to that of tannic acid to the mixed solution of muscovite nanosheets and tannic acid obtained in step B), and stir to mix evenly;

[0116] D) Adjust the pH of the mixed solution of muscovite nanosheets, tannic acid and manganese chloride obtained in step C) to 8.0 with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution to complex tannic acid and manganese ions.

[0117] E) Mix the modified mica obtained in step D) with cellulose nanofibers (the mass fraction ratio of mica to cellulose nanofibers is 3:7), and ultrasonically disperse for 2 min to fully and uniformly mix the modified mica and cellulose nanofibers;

[0118] F) Uniformly coat the obtained composite on the surface of the PVC substrate and dry to form an ultraviolet shielding layer.

[0119] Figure 11 The ultraviolet absorption spectrum of the aqueous dispersion of muscovite nanosheets modified by tannin-manganese ion network prepared in Example 4 of the present invention is shown. It can be seen that the absorption of the muscovite nanosheets modified by tannin-manganese ion network in the ultraviolet band is significantly enhanced, and there is basically no absorption in the visible light band, indicating that the metal polyphenol modification method of the present invention is also applicable to muscovite. And this strong absorption of the muscovite nanosheets modified by tannin-manganese ion network in the ultraviolet light band and low absorption in the visible light band can also be used in the ultraviolet shielding coating, enabling the PVC material to have the performance of resisting ultraviolet aging while retaining the intrinsic color of the PVC substrate.

[0120] Example 5

[0121] A) Disperse phlogopite raw materials in water, and under the action of ultrasonic waves, exfoliate phlogopite into phlogopite nanosheets, then centrifuge at a speed of 3000 r / min for 10 min, and take the centrifugal supernatant to obtain a phlogopite nanosheet suspension;

[0122] B) Add tannic acid with a mass fraction of 16% of the phlogopite nanosheets to the phlogopite nanosheet suspension obtained in step A), and stir evenly;

[0123] C) Add manganese chloride with a molar content close to that of tannic acid to the mixed solution of phlogopite nanosheets and tannic acid obtained in step B), and stir evenly;

[0124] D) Adjust the pH of the mixed solution of phlogopite nanosheets, tannic acid and manganese chloride obtained in step C) to 8.0 with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution to complex tannic acid and manganese ions.

[0125] E) Mix the modified mica obtained in step D) with polyurethane (the mass fraction ratio of mica to polyurethane is 3:7), and ultrasonically disperse for 2 min to fully and uniformly mix the modified mica and polyurethane;

[0126] F) The obtained composite is evenly coated on the surface of the PVC substrate and dried to form an ultraviolet shielding layer.

[0127] Figure 19 This is the ultraviolet transmittance spectrum of the mixed coating of phlogopite modified by tannin manganese ion network and polyurethane prepared in Example 5 of the present invention. It can be seen that the transmittance of this coating in the ultraviolet light band is also very low, less than 50%, and at the same time, a very high transmittance is retained in the visible light band. The transmittance is higher than 60% in most of the visible light bands, taking into account both transparency and ultraviolet shielding. This indicates that the ultraviolet shielding effect of the present invention is not affected by the type of polymer carrier. And the low transmittance of this composite coating of phlogopite nanosheets modified by tannin manganese ion network and polyurethane in the ultraviolet light band and the high transmittance in the visible light band can also endow the PVC material with the property of anti-ultraviolet aging while retaining the intrinsic color of the PVC substrate.

[0128] Comparative Example 1

[0129] This comparative example is the same as Example 1, except that the phlogopite nanosheets in the coating used to coat the PVC substrate are not chemically modified by the metal polyphenol network, but commercially available phlogopite nanosheets are directly used. Although the ultraviolet shielding coating prepared by this method has a high visible light transmittance, it has poor ultraviolet barrier performance, further demonstrating the importance of the method of chemical modification of the metal polyphenol network for improving the ultraviolet shielding performance.

[0130] Figure 20 This is the ultraviolet transmittance spectrum of the unmodified phlogopite and cellulose nanofiber mixed coating prepared in Comparative Example 1. It can be seen that although this coating has a high transmittance in the visible light band, its transmittance in the ultraviolet band is also very high, and its ultraviolet shielding performance is inferior to that of Example 1.

[0131] Comparative Example 2

[0132] This comparative example is the same as Example 1, except that the phlogopite nanosheets in the coating used to coat the PVC substrate are chemically modified by dopamine manganese ion complex, which specifically includes the following steps:

[0133] A) The phlogopite raw material is dispersed in water. Under the action of ultrasonic waves, the phlogopite is exfoliated into phlogopite nanosheets, and then centrifuged at a speed of 3000 r / min for 10 min. The centrifuged supernatant is taken to obtain a phlogopite nanosheet suspension;

[0134] B) Add dopamine hydrochloride with a mass fraction of 16% of the phlogopite nanosheets to the phlogopite nanosheet suspension obtained in step A), and stir and mix evenly;

[0135] C) Add manganese chloride with a molar content close to that of dopamine to the mixture of phlogopite nanosheets and dopamine obtained in step B), and stir to mix evenly;

[0136] D) Adjust the pH of the mixture of phlogopite nanosheets, dopamine, and manganese ions obtained in step C) to 8.0 with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution, so that dopamine and manganese ions are complexed on the surface of phlogopite nanosheets;

[0137] E) Mix the dispersion of modified mica and cellulose nanofibers obtained in step D) (the mass ratio of mica to cellulose nanofibers is 3:7), and ultrasonically disperse for 2 min to make the modified mica and cellulose nanofibers fully and evenly mixed;

[0138] F) Uniformly coat the obtained composite on the surface of the PVC substrate and dry to form an ultraviolet shielding layer.

[0139] Figure 21 This is the ultraviolet absorption spectrum of the dopamine-manganese ion complex-modified phlogopite dispersion prepared in Comparative Example 2. It can be seen that the absorption of the modified phlogopite nanosheets in the ultraviolet band is significantly enhanced, but the absorption in the visible light band is also enhanced to a certain extent. Therefore, it is impossible to balance ultraviolet shielding and transparency;

[0140] Figure 22 This is the ultraviolet transmittance spectrum of the mixture coating of dopamine-manganese ion complex-modified phlogopite and cellulose nanofibers prepared in Comparative Example 2. It can be seen that the transmittance of this coating in the ultraviolet band is very low, lower than 50%, but the transmittance in the visible light band is also very low, lower than 60%, further indicating that it is impossible to balance transparency and ultraviolet shielding at the same time;

[0141] The above description of the disclosed embodiments is intended to enable those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the protection scope of the present invention will not be limited to these embodiments shown herein, but will be broadly interpreted by the appended claims.

Claims

1. A PVC material resistant to ultraviolet aging, comprising a PVC substrate and an ultraviolet shielding coating formed on the surface of the PVC substrate, wherein the ultraviolet shielding coating comprises mica nanosheets modified with a metal polyphenol network and a polymer carrier, and the mass ratio of the mica nanosheets modified with the metal polyphenol network to the polymer carrier is 1:9-1:1, the mica nanosheets modified with the metal polyphenol network comprise mica nanosheets and a metal polyphenol network bonded to the surface of the mica nanosheets by hydrogen bonds, the metal polyphenol network is a complex structure assembled by chemical reactions between plant polyphenols and metal ions, and the thickness of the ultraviolet shielding coating ranges from 1 to 1000 μm.

2. The PVC material according to claim 1, wherein: The surface coating of the PVC material has an absorbance greater than 1 in the 200-400 nm band of the ultraviolet-visible absorption spectrum, or has a transmittance lower than 50% in the 200-400 nm band of the ultraviolet transmittance spectrum.

3. The PVC material according to claim 1, wherein: The thickness of the mica nanosheet modified by the metal polyphenol network is in the range of 0.3-100 nm, and the sheet diameter is in the range of 50-10000 nm.

4. The PVC material according to claim 1, wherein The polymer carrier is selected from one or more of cellulose nanofibers, polyurethane and epoxy resin, and its molecular weight range is 10 3 -10 6 .

5. The PVC material according to claim 1, wherein: The plant polyphenols are selected from one or more of tannic acid and tea polyphenols.

6. The PVC material according to claim 1, wherein: The metal ion is selected from Cu 2+ , Fe 3+ ,Mg 2+ , Ca 2+ , Zn 2+ and Mn 2+ One or more of .

7. The PVC material according to claim 1, wherein in the metal polyphenol network-modified mica nanosheets, the molar ratio between the plant polyphenols and the metal ions is in the range of 1:3-4:

1.

8. The PVC material according to claim 1, wherein the modification amount of the metal polyphenol network accounts for 10%-50% of the mass of the mica nanosheets.

9. The PVC material according to claim 1, wherein: The mica nanosheets are selected from one or more of phlogopite and muscovite.

10. A method for preparing the PVC material according to any one of claims 1 to 9, the method comprising the following steps: A) providing a suspension of exfoliated mica nanosheets in water; B) adding plant polyphenols to the suspension of mica nanosheets in an amount of 10% to 50% of the mass fraction of the mica nanosheets to obtain a mixed solution; C) adding metal ions to the mixed solution obtained in step B), wherein the molar ratio between the plant polyphenols and the metal ions is in the range of 1:3-4:1; D) adjusting the pH value of the mixed solution obtained in step C) to be weakly alkaline to promote the complexation of plant polyphenols with metal ions, thereby obtaining mica nanosheets modified with a metal polyphenol network; E) uniformly mixing the metal polyphenol network-modified mica nanosheets obtained in step D) with a polymer carrier to obtain a water-based coating, F) coating the water-based coating on the surface of the PVC substrate and drying it at a temperature of 20-80° C. to form an ultraviolet shielding coating as a surface coating of the PVC material.

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