A method for preparing an anti-aging polypropylene composite

Abstract

This invention discloses an anti-aging PP composite material and its preparation method, belonging to the field of polymer composite material technology. The anti-aging PP composite material is prepared by adding a composite anti-aging agent BP-4@LDH-DAO to PP. The composite anti-aging agent is based on hydrotalcite (LDH), modified by intercalation with the ultraviolet absorber BP-4, and then surface-grafted with the silanized antioxidant KH-560-DAO. This invention, by adding a small amount of composite anti-aging agent to polypropylene, can effectively enhance the PP material's resistance to ultraviolet radiation, heat and oxygen aging, and oxygen barrier properties, preparing a high-performance PP composite material. Its comprehensive anti-aging performance is superior to antioxidant 1010, and its synergistic effect with antioxidant 168 is even better, showing potential application value.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material technology, specifically relating to a polypropylene composite material with excellent resistance to ultraviolet radiation, resistance to thermo-oxidative aging and oxygen barrier properties, and its preparation method. Background Technology

[0002] Polypropylene (PP), as a general-purpose plastic, is widely used in construction, automotive, and electronics industries due to its low density, good processability, and low cost. However, the carbon chains in the PP molecular structure are highly sensitive to light, heat, and oxygen, making it prone to aging and degradation under outdoor use or high-temperature environments. This leads to discoloration, brittleness, a sharp decline in mechanical properties, and a significantly shortened service life. To inhibit these aging processes, small-molecule antioxidants and light stabilizers are typically added to PP. However, these small-molecule additives are easily lost through migration and volatilization from the polymer matrix, resulting in insufficient long-term stability.

[0003] Layered bimetallic hydroxides (LDHs), as anionic layered materials, are used as carriers to load various functional molecules due to their tunable interlayer anion composition, abundant surface hydroxyl groups, and other advantages, aiming to solve the migration problem of small molecules. Existing technologies have involved intercalating antioxidants or UV absorbers into the LDH interlayer. However, this method suffers from low loading rates and limited molecular activity after intercalation modification. In particular, pure LDH has limited absorption capacity for UV light in the 280-400 nm wavelength range and lacks the ability to actively capture free radicals, failing to fully meet the long-term anti-aging requirements of polypropylene under harsh environments. Furthermore, the abundant hydroxyl groups on the LDH surface result in strong hydrophilicity and poor compatibility with non-polar polypropylene, leading to easy agglomeration during melt blending and affecting the mechanical properties of the composite material. Therefore, developing a novel composite material system based on LDH that can simultaneously and efficiently resist UV and thermo-oxidative aging, while exhibiting good compatibility with the polypropylene matrix and minimal migration is a pressing technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a PP composite material with resistance to ultraviolet radiation and thermo-oxidative aging, as well as good oxygen barrier properties, and its preparation method. This composite material, through the addition of the organic-inorganic composite anti-aging agent BP-4@LDH-DAO, achieves multifunctional synergy of ultraviolet light shielding, free radical scavenging, and oxygen barrier properties, significantly improving the weather resistance of polypropylene and giving it excellent processing performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An anti-aging PP composite material, the raw materials of which include: 100 parts of polypropylene (PP) and 0.5-2.0 parts of composite anti-aging agent BP-4@LDH-DAO.

[0006] Furthermore, the raw materials used also include antioxidant 168.

[0007] Furthermore, the preparation of the composite anti-aging agent BP-4@LDH-DAO includes the following steps: 1) Preparation of intercalated layered double hydroxide (LDH) as an ultraviolet absorber: Zinc nitrate hexahydrate and aluminum nitrate nonahydrate were dissolved in a mixed solution of deionized water and ethanol in a volume ratio of 2:1 to form solution A; NaOH and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4) were dissolved in a mixed solution of deionized water and ethanol in a volume ratio of 1:1 to form solution B; then, under a nitrogen atmosphere at 70°C, solution B was slowly added dropwise to solution A while stirring vigorously. After the addition was complete, the mixture was transferred to a hydrothermal reactor and aged at 110°C for 24 hours. After centrifugation, a yellow solid powder was obtained. After washing several times with deionized water and ethanol, it was dried at 60°C for 12 hours to obtain intercalated layered double hydroxide (BP-4@LDH) as an ultraviolet absorber. 2) Preparation of silanized antioxidant: 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (AO), γ-glycidoxypropyltrimethoxysilane (KH-560) and triphenylphosphine were dissolved in DMF, and then stirred at 125 °C and 500 rpm for 48 h under nitrogen protection. After the reaction was completed, the mixture was cooled in an ice bath, and triethylamine was added. Then, a DMF solution of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride (AO-Cl) was slowly added dropwise. After stirring and mixing, the mixture was reacted at 45 °C for 12 h. The resulting mixture was extracted, centrifuged, and freeze-dried to obtain the silanized antioxidant (KH-560-DAO). 3) Preparation of composite anti-aging agent: BP-4@LDH obtained in step 1) was dispersed in a mixed solution of ethanol and water with a volume ratio of 4:1, and ultrasonically treated for 30 minutes. Then, KH-560-DAO obtained in step 2) was slowly added, and the mixture was stirred and refluxed at 80°C under a nitrogen atmosphere for 24 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and freeze-dried to obtain the final product.

[0008] Furthermore, the mass ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate, NaOH, and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid used in step 1) is 2.97:1.875:1.4:3.08.

[0009] Furthermore, in step 2), the ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, γ-glycidoxypropyltrimethoxysilane, triphenylphosphine, triethylamine, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride is 1.4 g:1.18 g:2 mg:1 mL:1.48 g.

[0010] Furthermore, in step 3), the mass ratio of BP-4@LDH to KH-560-DAO used is 9:1.

[0011] Furthermore, the preparation of the anti-aging PP composite material includes the following steps: a) After mixing PP and composite anti-aging agent BP-4@LDH-DAO evenly in a high-speed mixer, vacuum dry at 60℃ for 6h; b) The dried material is extruded and granulated to obtain masterbatch, which is then dried and injection molded to obtain the anti-aging PP composite material.

[0012] Furthermore, the high-speed mixer described in step a) has a rotation speed of 300 r / min and a temperature of 60°C.

[0013] Furthermore, the extrusion granulation described in step b) is carried out in five stages, with the following parameters: first stage 165℃ / 30s, second stage 180℃ / 45s, third stage 185℃ / 30s, fourth stage 185℃ / 20s, and fifth stage 180℃ / 15s; the screw speed is 10 r / min.

[0014] Furthermore, the drying temperature described in step b) is 60°C, and the time is 1 hour.

[0015] Furthermore, the injection molding described in step b) is performed in a micro injection molding machine, under conditions of 220°C and 0.3~0.5Mpa, for 10 seconds of pressing and 5 seconds of holding pressure (mold temperature 60°C).

[0016] The beneficial effects of this invention are as follows:

[0017] (1) Synergistic anti-aging: The BP-4@LDH-DAO designed in this invention has three functions: ultraviolet light shielding, free radical scavenging and oxygen blocking. The three functions work together effectively to significantly enhance the weather resistance of PP / BP-4@LDH-DAO. Its comprehensive anti-aging performance is better than that of antioxidant 1010, and its synergistic effect with antioxidant 168 is even better, which has potential application value.

[0018] (2) Excellent anti-extraction properties: The silanized antioxidant KH-560-DAO is firmly grafted onto the surface of BP-4@LDH, which greatly avoids the migration and volatilization loss of antioxidant components during use, and ensures the long-term stable anti-aging properties of the composite material.

[0019] (3) Significantly improved compatibility: The silanized antioxidant KH-560-DAO is grafted onto the hydrophilic BP-4@LDH surface, replacing the original hydrophilic hydroxyl groups on the LDH surface. This effectively improves the compatibility between BP-4@LDH and the non-polar PP matrix, making it more uniformly dispersed in the matrix. This avoids the decrease in mechanical properties caused by filler agglomeration. At the same time, it can give full play to the oxygen barrier effect of inorganic layered LDH, further enhancing the thermal oxidation stability of PP composite materials. Attached Figure Description

[0020] Figure 1 The FTIR spectrum of the composite anti-aging agent BP-4@LDH-DAO prepared in Example 1 is shown in the figure. (2958 cm⁻¹) -1 2870 cm -1 The peak at 1733 cm⁻¹ represents the characteristic absorption peaks of the antisymmetric and symmetric stretching vibrations of the -CH₂ and -CH₃ groups generated by grafting antioxidant KH-560-DAO onto the surface of BP-4@LDH-DAO. -1 The peak at this location is a characteristic absorption peak of the ester, which proves the successful synthesis of BP-4@LDH-DAO.

[0021] Figure 2 The image shows a SEM image of the composite anti-aging agent BP-4@LDH-DAO prepared in Example 1.

[0022] Figure 3 The image shows a TEM image of the composite anti-aging agent BP-4@LDH-DAO prepared in Example 1. As can be seen from the image, the average interplanar spacing of the (003) crystal planes of BP-4@LDH-DAO is 2.23 nm, indicating that BP-4 has successfully entered the LDH interlayer.

[0023] Figure 4 The image shows a STEM image of the composite anti-aging agent BP-4@LDH-DAO prepared in Example 1.

[0024] Figure 5 The thermogravimetric analysis (TGA) curves of the composite anti-aging agent BP-4@LDH-DAO are shown in the figure. As can be seen from the figure, the mass retention rates of BP-4@LDH and BP-4@LDH-DAO at 800℃ are 63.15% and 55.23%, respectively, indicating that the loading of the surface antioxidant KH-560-DAO of BP-4@LDH-DAO is approximately 8 wt%.

[0025] Figure 6 The image shows a SEM image of the surface of the PP / BP-4@LDH-DAO composite material prepared in Example 3.

[0026] Figure 7The images show cross-sectional SEM images and EDS distribution information of Zn in the PP / BP-4@LDH-DAO composite material prepared in Example 3. As can be seen from the images, BP-4@LDH-DAO is uniformly distributed in the PP matrix.

[0027] Figure 8 The image shows the UV-Vis spectrum of the PP / BP-4@LDH-DAO composite film prepared in Example 3. As can be seen from the figure, PP / BP-4@LDH-DAO exhibits good ultraviolet absorption performance in the UV-A (320-400 nm) and UV-B (280-320 nm) bands of ultraviolet light.

[0028] Figure 9 The thermogravimetric curves of the PP / BP-4@LDH-DAO composite material prepared in Example 3 in air atmosphere and the temperature corresponding to 50% weight loss are shown in the figure. As can be seen from the figure, the thermal decomposition temperature of PP / BP-4@LDH-DAO (T...) 50% The temperature was 343.22°C, which is significantly higher than that of pure PP, indicating that the highly efficient silanized antioxidant in BP-4@LDH-DAO and BP-4@LDH have good synergistic properties. Detailed Implementation

[0029] An anti-aging PP composite material, the preparation of which includes the following steps: a) By weight, add 100 parts of PP and 0.5-2.0 parts of composite anti-aging agent BP-4@LDH-DAO into a high-speed mixer, mix evenly at 60℃ and 300 r / min, and then vacuum dry at 60℃ for 6h. b) The dried material is added to a twin-screw extruder, the screw speed is set to 10 r / min, and the masterbatch is obtained by five-stage extrusion granulation (first stage 165℃ / 30s, second stage 180℃ / 45s, third stage 185℃ / 30s, fourth stage 185℃ / 20s, fifth stage 180℃ / 15s); c) Place the obtained masterbatch in a drying oven and dry it at 60°C for 1 hour. Then add it to an injection molding machine and press it at 220°C and 0.3~0.5 MPa for 10 seconds and hold it for 5 seconds (mold temperature 60°C) to obtain the anti-aging PP composite material.

[0030] The preparation of the composite anti-aging agent BP-4@LDH-DAO includes the following steps: 1) Preparation of intercalated hydrotalcite as an ultraviolet absorber: Zinc nitrate hexahydrate and aluminum nitrate nonahydrate were dissolved in a mixed solution of deionized water and ethanol (2:1, v / v) to form solution A; NaOH and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (BP-4) were dissolved in a mixed solution of deionized water and ethanol (1:1, v / v) to form solution B; then solution A was placed in a three-necked flask, and solution B was slowly added dropwise to solution A at 70°C under a nitrogen atmosphere, while vigorous stirring. After stirring and dripping, the mixture was transferred to a hydrothermal reactor and aged at 110℃ for 24 hours. After centrifugation, a yellow solid powder was obtained. This powder was washed several times with deionized water and ethanol, and then dried in a vacuum oven at 60℃ for 12 hours to obtain the ultraviolet absorber intercalated hydrotalcite (BP-4@LDH). The mass ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate, NaOH, and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid used was 2.97:1.875:1.4:3.08. 2) Preparation of silanized antioxidant: 1.4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (AO), 1.18 g of γ-glycidoxypropyltrimethoxysilane (KH-560) and 2 mg of triphenylphosphine were dissolved in 100 mL of DMF, and then placed in a three-necked flask. Under nitrogen protection, the mixture was stirred at 125 °C and 500 rpm for 48 h. After the reaction was completed, the mixture was cooled in an ice bath, and 1 mL of triethylamine was added. Then, a DMF solution containing 1.48 g of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride (AO-Cl) was slowly added dropwise. After stirring and mixing, the mixture was reacted at 45 °C for 12 h. The resulting mixture was extracted, centrifuged, and freeze-dried to obtain the silanized antioxidant (KH-560-DAO). 3) Preparation of composite anti-aging agent: BP-4@LDH obtained in step 1) was dispersed in a mixed solution of ethanol and water (4:1, v / v), and ultrasonically treated for 30 minutes. Then, KH-560-DAO obtained in step 2) was slowly added, and the mixture was stirred and refluxed at 80°C under a nitrogen atmosphere for 24 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and freeze-dried to obtain the final product. The mass ratio of BP-4@LDH to KH-560-DAO used was 9:1.

[0031] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto. Example 1

[0032] The specific steps of the preparation method of an anti-aging PP composite material are as follows: 1) Preparation of the composite anti-aging agent BP-4@LDH-DAO: a) Preparation of intercalated layered double hydroxide (LDH) as an ultraviolet absorber: 2.97 g zinc nitrate hexahydrate and 1.875 g aluminum nitrate nonahydrate were dissolved in 90 ml of a mixed solution of deionized water and ethanol (2:1, v / v) to form solution A; 1.4 g NaOH and 3.08 g BP-4 were dissolved in 80 ml of a mixed solution of deionized water and ethanol (1:1, v / v) to form solution B; solution A was placed in a three-necked flask, and solution B was slowly added dropwise to the flask at 70 °C under a nitrogen atmosphere while stirring vigorously. After the addition was complete, the mixture was transferred to a hydrothermal reactor and aged in an oven at 110 °C for 24 h. After centrifugation, a yellow solid powder was obtained, which was washed several times with deionized water and ethanol, and then dried in a vacuum oven at 60 °C for 12 h to obtain the intercalated layered double hydroxide as an ultraviolet absorber, denoted as BP-4@LDH; b) Preparation of silanized antioxidant: 1.4 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (AO), 1.18 g of KH-560 and 2 mg of triphenylphosphine were dissolved in 100 mL of DMF and placed in a 250 mL three-necked flask. Nitrogen gas was introduced for protection, and the mixture was heated to 125 °C and stirred at 500 rpm for 48 h. After the reaction was completed, the solution was cooled in an ice bath, and 1 mL of triethylamine was added. 1.48 g of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride (AO-Cl) was dissolved in 20 mL of DMF and then slowly added dropwise to the above flask. After the addition was completed, the temperature was raised to 45 °C and the reaction was carried out for 12 h. The mixture was then extracted once with deionized water at 5 °C, centrifuged, and freeze-dried to obtain the silanized antioxidant, denoted as KH-560-DAO. c) Preparation of composite anti-aging agent: 1.8g of BP-4@LDH obtained in step a) was dispersed in a mixed solution of ethanol and water (4:1, v / v), and sonicated for 30 minutes. Then, 0.2g of KH-560-DAO obtained in step b) was slowly added, and the mixture was stirred and refluxed at 80℃ under a nitrogen atmosphere for 24h. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and freeze-dried to obtain the final product BP-4@LDH-DAO.

[0033] 2) Mix 0.5 parts by weight of BP-4@LDH-DAO and 100 parts by weight of PP in a high-speed mixer at a speed of 300 r / min and a temperature of 60℃, and then vacuum dry at 60℃ for 6 hours.

[0034] 3) Add the dried material to a twin-screw extruder. The extrusion parameters of the twin-screw extruder are: first stage 165℃ / 30s, second stage 180℃ / 45s, third stage 185℃ / 30s, fourth stage 185℃ / 20s, and fifth stage 180℃ / 15s; the screw speed is 10 r / min; and obtain mixed masterbatch by extrusion granulation.

[0035] 4) The obtained mixed masterbatch was dried in an oven at 60℃ for 1 hour, and then injection molded in a micro injection molding machine at 220℃ and 0.3~0.5Mpa for 10 seconds and held for 5 seconds (mold temperature 60℃) to obtain PP / BP-4@LDH-DAO composite material.

[0036] 5) Simultaneously, the obtained mixed masterbatch was dried in an oven at 60°C for 1 hour, and then hot-pressed for 5 minutes at 185°C and 15MPa pressure using a flat vulcanizing machine to obtain a PP / BP-4@LDH-DAO composite film with a thickness of approximately 100μm. Example 2

[0037] In step 2), 1.0 parts by weight of BP-4@LDH-DAO and 100 parts by weight of PP are mixed evenly in a high-speed mixer. Other operations are the same as in Example 1 to obtain the PP / BP-4@LDH-DAO composite material and its film. Example 3

[0038] In step 2), 1.5 parts by weight of BP-4@LDH-DAO and 100 parts by weight of PP are mixed evenly in a high-speed mixer. Other operations are the same as in Example 1 to obtain the PP / BP-4@LDH-DAO composite material and its film. Example 4

[0039] In step 2), 2.0 parts by weight of BP-4@LDH-DAO and 100 parts by weight of PP are mixed evenly in a high-speed mixer. Other operations are the same as in Example 1 to obtain the PP / BP-4@LDH-DAO composite material and its film. Example 5

[0040] In step 2), 1.5 parts by weight of BP-4@LDH-DAO, 0.12 parts by weight of antioxidant 168 and 100 parts by weight of PP are mixed evenly in a high-speed mixer. Other operations are the same as in Example 1 to obtain PP / BP-4@LDH-DAO composite material and its film.

[0041] Comparative Example 1 1) Add the dried PP to a twin-screw extruder. The extrusion parameters of the twin-screw extruder are: first stage 165℃ / 30s, second stage 180℃ / 45s, third stage 185℃ / 30s, fourth stage 185℃ / 20s, fifth stage 180℃ / 15s; the screw speed is 10 r / min; PP masterbatch is obtained by extrusion granulation.

[0042] 2) The obtained PP masterbatch is dried in an oven at 60℃ for 1 hour, and then injection molded in a micro injection molding machine at 220℃ and pressure of 0.3~0.5Mpa for 10 seconds and holding pressure for 5 seconds (mold temperature 60℃) to obtain pure PP material.

[0043] 3) Simultaneously, the obtained PP masterbatch was dried in an oven at 60°C for 1 hour, and then hot-pressed for 5 minutes at 185°C and 15MPa pressure using a flat vulcanizing machine to obtain a pure PP film with a thickness of approximately 100μm.

[0044] Comparative Example 2 1) Preparation of hydrotalcite: Take 2.97g zinc nitrate hexahydrate and 1.875g aluminum nitrate nonahydrate, dissolve them in 90ml of a mixed solution of deionized water and ethanol (2:1, v / v) to form solution A; transfer solution A to a hydrothermal reactor and age it in an oven at 110℃ for 24h. After centrifugation, obtain solid powder, wash it several times with deionized water and ethanol, and then dry it in a vacuum oven at 60℃ for 12h to obtain hydrotalcite, denoted as LDH; 2) Prepare silanized antioxidant KH-560-DAO according to step b) of Example 1.

[0045] 3) Mix 1.25 parts by weight of LDH, 0.13 parts by weight of BP-4, 0.12 parts by weight of KH-560-DAO and 100 parts by weight of PP in a high-speed mixer until homogeneous. Other operations are the same as in Example 1 to obtain the PP / BP-4 / LDH-DAO composite material and its film.

[0046] Comparative Example 3 1) Prepare the ultraviolet light absorber intercalated hydrotalcite BP-4@LDH and the silanized antioxidant KH-560-DAO according to steps a) and b) of Example 1, respectively.

[0047] 2) Mix 1.38 parts by weight of BP-4@LDH, 0.12 parts by weight of KH-560-DAO and 100 parts by weight of PP in a high-speed mixer until homogeneous. Other operations are the same as in Example 1 to obtain PP / BP-4@LDH / DAO composite material and its film.

[0048] Comparative Example 4 To compare the effects of KH-560-DAO, an antioxidant of the same phenolic class was used as a substitute for antioxidant 1010. The specific procedures are as follows: 1) Prepare the ultraviolet light absorber intercalated hydrotalcite BP-4@LDH according to step a) of Example 1.

[0049] 2) Mix 1.38 parts by weight of BP-4@LDH, 0.12 parts by weight of antioxidant 1010 and 100 parts by weight of PP in a high-speed mixer until homogeneous. Other operations are the same as in Example 1 to obtain PP / BP-4@LDH composite material and its film.

[0050] Performance testing 1. Mechanical properties and UV radiation resistance testing The materials were subjected to accelerated UV aging tests using an ultraviolet (UV) aging chamber with an irradiance of 0.5 W / (m²) at 340 nm. 2 ·nm), relative humidity: 60%, blackboard temperature: 65°C, aging time: 400h.

[0051] The impact properties of the material before and after UV aging were tested using an electronic simply supported beam impact testing machine, and the testing standard was in accordance with GB / T 1043.1-2019. The test results are shown in Table 1.

[0052] Table 1

[0053] As shown in Table 1, the initial impact strength of the PP composite materials obtained in Examples 1-4 slightly decreased with increasing addition of the composite anti-aging agent BP-4@LDH-DAO, but the performance retention rate after UV aging showed an upward trend. Considering mechanical properties, anti-aging properties, and cost, the PP composite material prepared by adding 1.5 parts of the composite anti-aging agent BP-4@LDH-DAO in Example 3 exhibited the best overall performance. Furthermore, a comparison of the data from Examples 3 and 5 shows that further addition of antioxidant 168 can achieve even better results.

[0054] Furthermore, a comparison of the data from Example 3 with Comparative Examples 2-3 shows that after intercalating LDH with BP-4 and then surface-modifying BP-4@LDH with the silanized antioxidant KH-560-DAO, the UV shielding effect of LDH and its dispersibility in PP can be enhanced, thereby improving the UV shielding performance of the PP composite material. Therefore, Example 3 exhibits higher initial impact strength and higher performance retention after UV aging. A comparison of the data from Comparative Examples 3 and 4 reveals that the silanized antioxidant KH-560-DAO synthesized using this method achieves better results than antioxidant 1010.

[0055] 2. Oxygen barrier performance and resistance to thermo-oxidative aging tests The oxygen transmission rate (OTR) of the composite film (0.1 mm thick) was measured using a gas transmission rate tester (BSG-11, Lab Stone, China) at 23°C and 0% relative humidity, in accordance with ASTM D3985-17.

[0056] The compressed film was cut into 2cm × 2cm samples and subjected to thermal oxidation aging tests in a forced-ventilation accelerated thermal oxidation aging chamber, i.e., aged for 300 hours at 110°C. Fourier transform infrared (FTIR) spectra of the aged composite film were recorded using a Thermo Fisher (USA) spectrometer. The carbonyl index of the samples was determined through 1725 cm⁻¹. -1 The C=O peak area at 1376 cm⁻¹ is similar to that at 1376 cm⁻ -1 The calculation is based on the ratio of the CH3 peak area, and the formula is as follows: , The test results are shown in Table 2.

[0057] Table 2

[0058] As shown in Table 2, the test results of Examples 1-4 indicate that the oxygen permeability of the composite material first decreases and then increases with the increase of the amount of composite anti-aging agent BP-4@LDH-DAO added, with Example 3 showing the lowest oxygen permeability. Simultaneously, the increase in carbonyl index after aging is also at a low level. Furthermore, a comparison of the data from Example 3 and the comparative examples shows that BP-4@LDH without surface modification by the silanized antioxidant KH-560-DAO tends to aggregate in the PP matrix, failing to exert its gas barrier effect. However, after modification with the silanized antioxidant KH-560-DAO, the dispersion of BP-4@LDH in PP is enhanced, resulting in samples with good gas barrier performance and free radical scavenging effect.

[0059] 3. Extraction resistance test Dichloromethane was used as the extraction solvent, and the composite film was extracted at 45°C for 24 h. After washing and drying, the oxidation induction time (OIT) of the material was measured using a differential scanning calorimeter (DSC) (Mettler-Toledo) according to the standard (ISO 11357-6:2008) (OIT values ​​were calculated using the tangent method). The results are shown in Table 3.

[0060] Table 3

[0061] As shown in Table 3, compared with the comparative example, the sample obtained in Example 3 had a longer oxidation induction time after extraction, indicating that it had higher thermal oxidation stability. Furthermore, since the silanized antioxidant KH-560-DAO was stably grafted onto the BP-4@LDH surface, the loss of antioxidant components was avoided, thus resulting in better anti-extraction ability.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An anti-aging PP composite material, characterized in that, By weight, the raw materials used include: 100 parts PP and 0.5-2.0 parts composite anti-aging agent BP-4@LDH-DAO.

2. The anti-aging PP composite material according to claim 1, characterized in that, The raw materials used also include antioxidant 168.

3. The anti-aging PP composite material according to claim 1, characterized in that, The preparation of the composite anti-aging agent BP-4@LDH-DAO includes the following steps: 1) Preparation of intercalated layered double hydroxide (LDH) as an ultraviolet absorber: Zinc nitrate hexahydrate and aluminum nitrate nonahydrate were dissolved in a mixed solution of deionized water and ethanol in a volume ratio of 2:1 to form solution A; NaOH and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid were dissolved in a mixed solution of deionized water and ethanol in a volume ratio of 1:1 to form solution B; then, under a nitrogen atmosphere at 70°C, solution B was slowly added dropwise to solution A while stirring vigorously. After the addition was complete, the mixture was transferred to a hydrothermal reactor and aged at 110°C for 24 hours. After centrifugation, a yellow solid powder was obtained. The powder was washed several times with deionized water and ethanol and then dried to obtain intercalated layered double hydroxide BP-4@LDH as an ultraviolet absorber. 2) Preparation of silanized antioxidant: 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, γ-glycidoxypropyltrimethoxysilane and triphenylphosphine were dissolved in DMF, and then stirred at 125 °C and 500 rpm for 48 h under nitrogen protection. After the reaction was completed, the mixture was cooled in an ice bath and triethylamine was added. Then, a DMF solution of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride was slowly added dropwise. After stirring and mixing, the mixture was reacted at 45 °C for 12 h. The resulting mixture was extracted, centrifuged and freeze-dried to obtain the silanized antioxidant KH-560-DAO. 3) Preparation of composite anti-aging agent: The ultraviolet light absorber intercalated hydrotalcite BP-4@LDH obtained in step 1) was dispersed in a mixed solution of ethanol and water with a volume ratio of 4:1, and ultrasonically treated for 30 minutes. Then, the silanized antioxidant KH-560-DAO obtained in step 2) was slowly added, and the mixture was stirred and refluxed at 80°C under a nitrogen atmosphere for 24 hours. After the reaction was completed, the mixture was washed three times with anhydrous ethanol and freeze-dried to obtain the final product.

4. The anti-aging PP composite material according to claim 3, characterized in that, The mass ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate, NaOH, and 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid used in step 1) is 2.97:1.875:1.4:3.

08.

5. The anti-aging PP composite material according to claim 3, characterized in that, In step 2), the ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, γ-glycidoxypropyltrimethoxysilane, triphenylphosphine, triethylamine, and 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride is 1.4 g:1.18 g:2 mg:1 mL:1.48 g.

6. The anti-aging PP composite material according to claim 3, characterized in that, The mass ratio of BP-4@LDH to KH-560-DAO used in step 3) is 9:

1.

7. The anti-aging PP composite material according to claim 1, characterized in that, The preparation of the anti-aging PP composite material includes the following steps: a) After mixing PP and composite anti-aging agent BP-4@LDH-DAO evenly in a high-speed mixer, vacuum dry at 60℃ for 6h; b) The dried material is extruded and granulated to obtain masterbatch, which is then dried and injection molded to obtain the anti-aging PP composite material.

8. The anti-aging PP composite material according to claim 7, characterized in that, The high-speed mixer described in step a) has a rotation speed of 300 r / min and a temperature of 60℃.

9. The anti-aging PP composite material according to claim 7, characterized in that, The extrusion granulation described in step b) is carried out in five stages, with the following parameters: first stage 165℃ / 30s, second stage 180℃ / 45s, third stage 185℃ / 30s, fourth stage 185℃ / 20s, and fifth stage 180℃ / 15s; the screw speed is 10 r / min.

10. The anti-aging PP composite material according to claim 7, characterized in that, The injection molding described in step b) is performed by pressing for 10 seconds and holding for 5 seconds at 220°C and a pressure of 0.3~0.5 MPa.

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