Ester cross-linked polyacrylic acid hydrogel uv protection material, preparation method and application thereof

Abstract

The present application relates to an ester cross-linked polyacrylic acid hydrogel ultraviolet protection material, a preparation method and application thereof, and belongs to the technical field of polymers. A phenolic phosphate ester compound T-P formed by compounding tannic acid and phytic acid is used as a physical cross-linking agent, hydrogen bonds are formed with polyacrylic acid (PAA), the material is gelled through an acid precipitation effect, and a hydrogel coating T-P-PAA with excellent ultraviolet protection effect and extreme environmental resistance is obtained. The phosphate groups and polyphenol structures in the phenolic phosphate ester compound T-P can absorb ultraviolet rays, and the hydrogen bond cross-linking structure in the T-P-PAA hydrogel can also effectively reduce the transmittance of ultraviolet rays.

Description

Technical Field

[0001] This invention relates to an ester-crosslinked polyacrylic acid hydrogel UV protection material, its preparation method, and its application, belonging to the field of polymer technology. Background Technology

[0002] The environmental aging of polymer materials is affected by factors such as temperature, humidity, ultraviolet radiation, ionizing radiation, chemical solvents, and physical stress. Because photochemical degradation requires relatively low activation energy, ultraviolet (UV) light can lead to the formation of free radicals in polymer materials, accelerating aging. Furthermore, UV radiation is harmful to human and animal skin. In particular, UVB with wavelengths of 290–320 nm is more likely to cause mutations and skin cancer than UVA with wavelengths of 320–400 nm. To limit the effects of UV radiation, researchers have designed various stabilizers (heat stabilizers, UV stabilizers, etc.) for use in polymers. However, in many cases, adding stabilizers to polymer materials can adversely affect the material's properties. Moreover, additives can leach out of the material over long-term use, leading to failure.

[0003] Hydrogel coatings have been widely used as an effective method of material protection due to their minimal impact on the properties of the material itself and their ability to form a stable homogeneous phase with functional additives. This is particularly relevant for applications such as high-temperature environmental protection, UV protection, and UV resistance. However, hydrogels contain a large amount of water, which can easily lead to dehydration in extremely dry environments or freezing and embrittlement at low temperatures. Therefore, it is necessary to develop a hydrogel UV protective coating that is resistant to freezing and embrittlement at low temperatures, does not easily dehydrate at high temperatures, and can operate stably without affecting the properties of the polymer material itself. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a cross-linked esterified polyacrylic acid hydrogel UV protection material, its preparation method, and its application. This invention uses a phenolic phosphate ester (TP) formed by the composite of tannic acid and phytic acid as a physical cross-linking agent, which forms hydrogen bonds with polyacrylic acid (PAA). The material gels through an acid precipitation effect, resulting in a hydrogel coating TP-PAA with excellent UV protection and resistance to extreme environments. The phosphate groups and polyphenol structure in the phenolic phosphate ester TP can absorb ultraviolet light, and the hydrogen-bonded cross-linking structure in the TP-PAA hydrogel can also effectively reduce the transmittance of ultraviolet light.

[0005] The antifreeze and moisturizing properties of the hydrogel are primarily determined by the interactions between water molecules and the polar groups of the surrounding chemical components. Hydrogen bonds dominate the interaction force between TP and water molecules. The interaction energy between TP and water is much higher than that between water molecules, indicating that the presence of phosphate polar groups enhances the interaction with water molecules. Furthermore, the nano-crosslinked network also restricts the internal migration of water molecules within the hydrogel, which also helps to suppress water evaporation. Therefore, this gel can remain stable in special environments.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A method for preparing a cross-linked esterified polyacrylic acid hydrogel UV protection material, the method comprising the following steps:

[0008] Polyphenolic phosphate esters are mixed with H2O at a mass ratio of 1:1 to 3 and stirred to dissolve, thus obtaining an aqueous solution of polyphenolic phosphate esters.

[0009] An aqueous solution of polyphenolic phosphoryl esters was added to an aqueous solution of polyacrylic acid, and the reaction was carried out at 60-80°C for 30-60 minutes. After the reaction was completed, a polyacrylic acid hydrogel UV protection material with cross-linked esters was obtained.

[0010] The structural formula of the polyphenolic phosphate ester is as follows:

[0011]

[0012] Among them, any one of the groups R1, R2, and R3 is The other two groups are -H;

[0013] The concentration of the polyacrylic acid aqueous solution is 20% to 30%, the molecular weight of the polyacrylic acid is 4000 to 6000, and the volume ratio of the polyphenol phosphate ester aqueous solution to the polyacrylic acid aqueous solution is 1:1 to 1.2.

[0014] Preferably, the polyphenolic phosphate ester is prepared by the following method, the method steps of which include:

[0015] (1) Under the protection of an inert gas, dicyandiamine, urea and phytic acid are dissolved in dimethyl sulfoxide (DMSO) in a mass ratio of 2-3:4-6:20. The mixture is stirred and mixed evenly at 90-130°C and dissolved at a stirring rate of 100-200 r / min to obtain a mixture.

[0016] (2) Under nitrogen atmosphere, tannic acid is added to the mixture, with a mass ratio of tannic acid to phytic acid of 1:1.5 to 2.5; the reaction is carried out at 90 to 130°C for 1 to 4 hours. After the reaction is completed, the mixture is centrifuged, washed, vacuum dried, and ground in a weakly polar organic solvent to obtain polyphenolic phosphate esters; more preferably, the weakly polar organic solvent is one or more of glycerol, ethyl acetate, diethyl ether, anhydrous ethanol, and anhydrous methanol.

[0017] Preferably, the polyacrylic acid aqueous solution is prepared by the following method, the method steps of which include:

[0018] After mixing acrylic acid and H2O in a mass ratio of 1:1 to 5, add 1 to 5% of the total mass of ammonium persulfate to dissolve the mixture, then heat to 60 to 80°C and stir for 2 to 4 hours.

[0019] More preferably, the stirring rate is 400-600 r / min.

[0020] A cross-linked esterified polyacrylic acid hydrogel UV protection material was prepared by the above method.

[0021] An application of the cross-linked esterified polyacrylic acid hydrogel UV protection material of the present invention, wherein the material is used as a UV protection coating.

[0022] Beneficial effects

[0023] This invention provides a cross-linked esterified polyacrylic acid hydrogel UV protection material. The material is rich in phosphate groups and phenolic hydroxyl groups, which can quench free radicals generated during UV irradiation and absorb UV light, thus providing excellent UV protection. Furthermore, the interaction energy between polyphenolic phosphate esters and water is much higher than that between water molecules. The presence of polar phosphate groups enhances the interaction with water molecules, and the nano-crosslinked network also restricts water molecule migration and inhibits water evaporation, achieving a long-lasting and stable protective effect.

[0024] This invention provides a method for preparing a cross-linked esterified polyacrylic acid hydrogel UV-protective material. The method uses H₂O as the reaction medium, where the strongly acidic phosphate groups in the polyphenolic phosphate ester precipitate the weakly acidic PAA from the aqueous solution, resulting in gelation. This yields a hydrogel material with PAA as the main network and TP providing hydrogen bonds.

[0025] This invention provides an application of a cross-linked esterified polyacrylic acid hydrogel UV protection material, which has excellent UV protection performance. Attached Figure Description

[0026] Figure 1 The results are obtained from cryo-scanning electron microscopy of the gel described in Example 1.

[0027] Figure 2 The results are the UV transmittance test results of the gels described in Examples 2-4.

[0028] Figure 3 The results are the DSC test results of the gel described in Example 1.

[0029] Figure 4 The results are the water loss test results of the gel described in Example 1 at room temperature.

[0030] Figure 5 The results are the dehydration test results of the gel described in Example 1 at 60°C. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1

[0033] 1. TP preparation:

[0034] (1) Dissolve 2.5g of dicyandiamine catalyst, 5g of urea, and 20g of TA in 200ml of DMSO, and then add the solution to a three-necked flask. Install a water separator and a condenser. Install the reaction apparatus in a constant temperature stirrer at a stirring rate of 100r / min, and stir the raw materials until they are mixed evenly and completely dissolved. The reaction temperature is 90℃.

[0035] (2) After TA is dissolved, 20 ml of 70% PA aqueous solution is added, and the reaction is carried out under nitrogen atmosphere for 2 h. The solution after reaction is poured into excess anhydrous ethanol to precipitate the product, and the solid is obtained after centrifugation.

[0036] (3) After washing the product in step (2) with solvent, centrifuge to separate the solid. Repeat this process three times to obtain the final solid product. Dry the solid product in a vacuum environment at 80°C and grind it to obtain polyphenol phosphate ester (TP) powder.

[0037] 2. PAA preparation:

[0038] (1) Using H2O as a solvent, mix acrylic acid and H2O in a mass ratio of 1:1 and add them to a glass bottle, then add 1% of the total mass of ammonium persulfate.

[0039] (2) After the ammonium persulfate is completely dissolved, the solution is heated to 60°C in a water bath and the magnetic stirring speed is 500r / min for 2 hours.

[0040] 3. Preparation of TP-PAA:

[0041] (1) TP and H2O were mixed at a mass ratio of 1:3 and stirred to dissolve, resulting in an aqueous solution of polyphenolic phosphate ester (TP).

[0042] (2) Add the TP aqueous solution to the PAA aqueous solution (PAA molecular weight is 5000), heat to 60℃ for 30 min, and the mass ratio of TP to PAA is 15:6; a cross-linked esterified polyacrylic acid hydrogel UV protection material is obtained. It is denoted as T-P5-PAA-1.

[0043] The structural formula of the polyphenolic phosphate ester is:

[0044]

[0045] Where R1 is R2 and R3 are -H.

[0046] Example 2

[0047] 1. TP preparation:

[0048] (1) Dissolve 2.5g of dicyandiamine catalyst, 5g of urea, and 20g of TA in DMSO, and then add the solution to a three-necked flask. Install a water separator and a condenser. Install the reaction apparatus in a constant temperature stirrer at a stirring rate of 100r / min to mix the raw materials evenly and completely dissolve them. The reaction temperature is 90℃.

[0049] (2) After TA is dissolved, 20 ml of 70% PA aqueous solution is added, and the reaction is carried out under nitrogen atmosphere for 2 h. The solution after reaction is poured into excess anhydrous ethanol to precipitate the product, and the solid is obtained after centrifugation.

[0050] (3) After washing the product in step (2) with solvent, centrifuge to separate the solid. Repeat this process three times to obtain the final solid product. Dry the product in a vacuum environment at 80°C and grind it to obtain polyphenol phosphate powder.

[0051] 2. PAA preparation:

[0052] (1) Using H2O as a solvent, mix acrylic acid and H2O in a 1:1 ratio and add them to a glass bottle, then add 1% of the total mass of ammonium persulfate.

[0053] (2) After the ammonium persulfate is completely dissolved, the solution is heated to 80°C in a water bath and stirred at a magnetic stirring rate of 500 r / min for 4 hours. This solution is denoted as T-P5-PAA-2.

[0054] 3. Preparation of TP-PAA:

[0055] (1) TP and H2O are mixed at a mass ratio of 1:1 and stirred to dissolve, thus obtaining an aqueous solution of TP.

[0056] (2) Add the TP aqueous solution to the PAA aqueous solution, heat to 80℃ for 60 min, and the mass ratio of TP to PAA is 5:6; a cross-linked esterified polyacrylic acid hydrogel UV protection material is obtained, denoted as T-P5-PAA-1.

[0057] Example 3

[0058] 1. TP preparation:

[0059] (1) Dissolve 2.5g of dicyandiamine catalyst, 5g of urea, and 20g of TA in 200ml of DMSO, and then add the solution to a three-necked flask. Install a water separator and a condenser. Install the reaction apparatus in a constant-temperature stirrer, using an inert gas such as nitrogen as a protective gas. The stirring speed is 100r / min. Stir the raw materials until they are mixed evenly and completely dissolved. The reaction temperature is 110℃.

[0060] (2) After TA is dissolved, add 20 ml of PA aqueous solution with a mass fraction of 70% and react for 2 h under nitrogen atmosphere. Pour the solution after reaction into excess anhydrous ethanol to precipitate the product. After centrifugation, obtain the solid.

[0061] (3) After washing the product in step (2) with solvent, centrifuge to separate the solid. Repeat this process three times to obtain the final solid product. Dry the product in a vacuum environment at 80°C and grind it to obtain polyphenol phosphate powder.

[0062] 2. PAA preparation:

[0063] (1) Using H2O as a solvent, mix acrylic acid and H2O in a 1:1 ratio and add them to a glass bottle, then add 1% of the total mass of ammonium persulfate.

[0064] (2) After the ammonium persulfate is completely dissolved, the solution is heated to 60°C in a water bath and the magnetic stirring speed is 500r / min for 2 hours.

[0065] 3. Preparation of TP-PAA:

[0066] (1) TP and H2O are mixed at a mass ratio of 1:1 and stirred to dissolve, thus obtaining an aqueous solution of TP.

[0067] (2) Add the TP aqueous solution to the PAA aqueous solution, heat to 80℃ for 30 min, and the mass ratio of TP to PAA is 10:6; a cross-linked esterified polyacrylic acid hydrogel UV protection material is obtained, denoted as T-P5-PAA-3.

[0068] Example 4

[0069] 1. TP preparation:

[0070] (1) Dissolve 2.5g of dicyandiamine catalyst, 5g of urea, and 20g of TA in DMSO, and then add the solution to a three-necked flask. Install a water separator and a condenser. Install the reaction apparatus in a constant temperature stirrer at a stirring rate of 100r / min to mix the raw materials evenly and completely dissolve them. The reaction temperature is 90℃.

[0071] (2) After TA is dissolved, 20 ml of 70% PA aqueous solution is added, and the reaction is carried out under nitrogen atmosphere for 2 h. The solution after reaction is poured into excess anhydrous ethanol to precipitate the product, and the solid is obtained after centrifugation.

[0072] (3) After washing the product in step (2) with solvent, centrifuge to separate the solid. Repeat this process three times to obtain the final solid product. Dry the product in a vacuum environment at 80°C and grind it to obtain polyphenol phosphate powder.

[0073] 2. PAA preparation:

[0074] (1) Using H2O as a solvent, mix acrylic acid and H2O in a ratio of 1:5 and add them to a glass bottle, then add 1% of the total mass of ammonium persulfate.

[0075] (2) After the ammonium persulfate is completely dissolved, the solution is heated to 60°C in a water bath and then stirred at a magnetic stirring rate of 500 r / min for 4 h.

[0076] 3. Preparation of TP-PAA:

[0077] (1) TP and H2O are mixed at a mass ratio of 1:1 and stirred to dissolve, thus obtaining an aqueous solution of TP.

[0078] (2) Add the TP aqueous solution to the PAA aqueous solution, with a TP to PAA mass ratio of 15:6; heat to 80℃ for 30 minutes to obtain a cross-linked esterified polyacrylic acid hydrogel UV protection material, denoted as T-P5-PAA-3.

[0079] Example 5

[0080] 1. TP preparation:

[0081] (1) Dissolve 2.5g of dicyandiamine catalyst, 5g of urea, and 20g of TA in DMSO, and then add the solution to a three-necked flask. Install a water separator and a condenser. Install the reaction apparatus in a constant temperature stirrer at a stirring rate of 100r / min to mix the raw materials evenly and completely dissolve them. The reaction temperature is 90℃.

[0082] (2) After TA is dissolved, 20 ml of 70% PA aqueous solution is added, and the reaction is carried out under nitrogen atmosphere for 2 h. The solution after reaction is poured into excess anhydrous ethanol to precipitate the product, and the solid is obtained after centrifugation.

[0083] (3) After washing the product in step (2) with solvent, centrifuge to separate the solid. Repeat this process three times to obtain the final solid product. Dry the product in a vacuum environment at 80°C and grind it to obtain polyphenol phosphate powder.

[0084] 2. PAA preparation:

[0085] (1) Using H2O as a solvent, mix acrylic acid and H2O in a ratio of 1:5 and add them to a glass bottle, then add 5% of the total mass of ammonium persulfate.

[0086] (2) After the ammonium persulfate is completely dissolved, the solution is heated to 80°C in a water bath and then stirred at a magnetic stirring rate of 500 r / min for 2 h.

[0087] 3. Preparation of TP-PAA:

[0088] (1) TP and H2O are mixed at a mass ratio of 1:1 and then stirred to dissolve.

[0089] (2) Add the solution from (1) to an aqueous PAA solution, heat to 80°C for 30 minutes, and the mass ratio of TP to PAA is 15:6; to obtain a cross-linked esterified polyacrylic acid hydrogel UV protection material.

[0090] The hydrogel UV protection material prepared in Example 3 was characterized by cryo-scanning electron microscopy (Cryo-SEM), and the results are as follows: Figure 1 As shown, TP-PAA exhibits a distinct three-dimensional gel network structure under cryo-electron microscopy. While ensuring the basic mechanical properties of the gel, the three-dimensional network structure can effectively lock in water and prevent the gel from drying and cracking.

[0091] The hydrogel UV-protective material was fabricated into a 10mm × 10mm × 2mm film, and its UV protection capability was tested. The UV transmittance of the hydrogel UV-protective materials prepared in Examples 2-4 was measured, with the transmittance measured in the wavelength range of 200–800 nm. The results are as follows: Figure 2 As shown, since the phosphate groups and polyphenol structures in TP can absorb ultraviolet light, the TP-PAA hydrogel film can effectively reduce the transmittance of ultraviolet light. Furthermore, with the increase of TP content, the ultraviolet light blocking ability is also significantly improved. It can almost completely block ultraviolet light in the wavelength range of 290-320nm, with a transmittance of less than 0.14%.

[0092] like Figure 3As shown, the differential scanning calorimetry (DSC) results indicate that the Tg of TP-PAA obtained in Example 1 is below -60°C, approximately 40°C lower than that of PAA; this demonstrates that TP-PAA can maintain the basic properties of an elastomer at extremely low temperatures and has a wider operating temperature range. The results for Examples 2-5 are similar to those for Example 1.

[0093] The hydrogel UV protection material obtained in Example 1 was placed at 25°C and relatively low humidity (30%) for 30 days (e.g., Figure 4 (as shown) and placed in a 60°C forced-air drying oven for 72 hours (e.g.) Figure 5 As shown in the figure, the total weight remained essentially stable, and the product retained its softness and rewetting properties, reflecting good moisture retention and environmental stability. The results of Examples 2-5 were similar to those of Example 1.

[0094] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A method for preparing an ester crosslinked polyacrylic acid hydrogel UV protective material, characterized by: The method steps comprise: The polyphenol phosphate ester is mixed with H2O in a mass ratio of 1:1-3, and stirred and dissolved to obtain a polyphenol phosphate ester aqueous solution; The polyphenol phosphate ester aqueous solution is added to the polyacrylic acid aqueous solution, and reacted at 60-80℃ for 30-60min, to obtain an ester cross-linked polyacrylic acid hydrogel UV protection material after the reaction is completed. The structure of the polyphenol phosphate ester is: ； wherein any one of R1, R2, R3is and the other two are -H; The concentration of the polyacrylic acid aqueous solution is 20%-30%, the molecular weight of the polyacrylic acid is 4000-6000, and the volume ratio of the polyphenol phosphate ester aqueous solution to the polyacrylic acid aqueous solution is 1:1-1.

2.

2. A method of preparing an ester crosslinked polyacrylic acid hydrogel UV protective material according to claim 1, characterized in that: The polyphenol phosphate ester is prepared by the following method, and the method steps comprise: (1) Under the protection of inert gas, dicyandiamide, urea and phytic acid are dissolved in dimethyl sulfoxide in a mass ratio of 2-3:4-6:20, stirred and mixed uniformly and dissolved at 90-130℃, and the stirring rate is 100-200r / min, to obtain a mixture; (2) Under the nitrogen environment, tannic acid is added to the mixture, and the mass ratio of tannic acid to phytic acid is 1:1.5-2.5; the mixture is reacted at 90-130℃ for 1-4h, and after the reaction is completed, the mixture is centrifuged, washed, vacuum dried, and ground in a weak polar organic solvent to obtain the polyphenol phosphate ester.

3. A method of preparing an ester crosslinked polyacrylic acid hydrogel UV protective material according to claim 2, characterized by: The weak polar organic solvent is one or more of glycerol, ethyl acetate, diethyl ether, anhydrous ethanol and anhydrous methanol.

4. A method of preparing an ester crosslinked polyacrylic acid hydrogel UV protective material according to claim 1, characterized by: The polyacrylic acid aqueous solution is prepared by the following method, and the method steps comprise: After the acrylic acid and H2O are mixed in a mass ratio of 1:1-5, 1-5% of the total mass of the solution of ammonium persulfate is added, dissolved, heated to 60-80℃, and stirred and reacted for 2-4h.

5. A method of preparing an ester crosslinked polyacrylic acid hydrogel UV protective material according to claim 4, characterized in that: The stirring rate is 400-600r / min.

6. An esterified crosslinked polyacrylic hydrogel UV protective material, characterized by: The material is prepared by the method of any one of claims 1-5.

7. Use of an esterified crosslinked polyacrylic hydrogel UV-protective material according to claim 6, characterized in that: The material is used as a UV protection coating.

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