A rupture-resistant foam protective film for packaging and transportation and its preparation method

Abstract

This invention belongs to the field of polymer materials technology and discloses a rupture-resistant foam protective film for packaging and transportation and its preparation method. The rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, and a PS layer laminated onto the surface of the modified EVA layer. The adhesion layer is a water-based acrylic ester modified polyurethane emulsion. The modified EVA layer includes the following raw materials: EVA resin, hydrogenated petroleum resin, MAH-g-EVA, modified nano zinc oxide, microcrystalline wax, and antioxidant 168. The modified EVA layer of the rupture-resistant foam protective film for packaging and transportation of this invention adds modified nano zinc oxide. The modified nano zinc oxide is formed by covalently grafting ultraviolet absorbers onto the surface of nano zinc oxide through a mercapto-olefin click reaction after surface thiolation. This provides structural stability and, moreover, the synergistic mechanism of ultraviolet shielding and absorption improves the material's ultraviolet resistance.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a rupture-resistant foam protective film for packaging and transportation and its preparation method. Background Technology

[0002] EPS foam (expanded polystyrene) is commonly used for edge and corner protection of large household appliances to prevent damage from shaking and impacts during transportation. EPS foam has the advantages of low density and good cushioning, making it widely used in protective packaging during transport. However, EPS foam has disadvantages such as insufficient mechanical strength, susceptibility to bursting under pressure, poor UV resistance, easy embrittlement, and the generation of fine powder that can be easily inhaled. Currently, a protective film is usually adhered to the surface of EPS foam to increase its mechanical strength, improve UV resistance, and reduce microparticle splashing.

[0003] Existing EPS foam protective films include a PET substrate and an EVA hot melt adhesive layer. For example, Chinese invention patent CN118027834B discloses an anti-UV card protector and its preparation process, which includes a modified polyethylene terephthalate substrate (PET), polyethylene and ethylene-vinyl acetate copolymer adhesive (EVA). By modifying the film substrate of the card protector, and grafting hydroxyl-containing copolyester after modifying nano-titanium dioxide with isocyanate, the compatibility with the substrate is improved, so that the prepared card protector substrate has good anti-UV properties, thereby improving the anti-UV capability of the card protector.

[0004] The aforementioned patents merely graft polyester onto the surface of nano-titanium dioxide to improve its dispersibility. They mainly utilize the absorption and scattering of ultraviolet light by nano-titanium dioxide itself to create a shielding effect against ultraviolet light, thereby improving the material's UV resistance. Therefore, the improvement in the material's UV aging resistance is limited. Furthermore, the aforementioned patents only modify the PET substrate, while the EVA adhesive layer is not modified for aging resistance. With prolonged use, there is a risk of delamination as the EVA layer ages due to UV radiation. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a rupture-resistant foam protective film for packaging and transportation and its preparation method. Modified nano zinc oxide is added to the modified EVA layer of the rupture-resistant foam protective film for packaging and transportation. The modified nano zinc oxide is formed by covalently grafting ultraviolet absorbers onto the surface of nano zinc oxide through a mercapto-alkene click reaction. On the one hand, it has the advantage of structural stability, and on the other hand, the synergistic mechanism of ultraviolet shielding and absorption can improve the ultraviolet resistance of the material.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, the adhesion layer being a water-based acrylic modified polyurethane emulsion, and the modified EVA layer comprising the following raw materials in parts by weight: 60-70 parts EVA resin, 20-30 parts hydrogenated petroleum resin, 4-6 parts MAH-g-EVA, 3-5 parts modified nano zinc oxide, 4-6 parts microcrystalline wax, and 0.5-1.5 parts antioxidant 168;

[0008] The modified nano-zinc oxide is a nano-zinc oxide surface thiolized and then covalently grafted with an ultraviolet absorber via a thiol-alkene click reaction. The ultraviolet absorber is an ultraviolet absorber possessing both benzotriazole and triazine structures, and its molecular formula is as follows:

[0009] .

[0010] Preferably, the waterborne acrylate-modified polyurethane emulsion is obtained by mixing acrylate monomers with polyurethane emulsion and then adding ammonium persulfate to initiate a polymerization reaction.

[0011] Preferably, the method for preparing the ultraviolet absorber includes the following steps:

[0012] (1) Add 2-(2-hydroxy-5-methylphenyl)benzotriazole and 1,4-dioxane to a three-necked flask, heat to 80°C and stir to dissolve. Then slowly add selenium dioxide in batches and reflux at 100°C for 6-10 hours. After the reaction is complete, filter while hot to remove the black selenium precipitate. Concentrate the filtrate under reduced pressure to 1 / 3 of the original volume. Add ice water to precipitate the yellow solid and filter. Wash the filter cake with methanol 3-5 times and dry under vacuum to obtain intermediate A.

[0013] (2) Cyanuryl chloride was dissolved in anhydrous tetrahydrofuran under ice bath, and then allyl alcohol and triethylamine were added dropwise. The temperature was kept <5℃. After adding the solution, the temperature was raised to room temperature and reacted for 3~5h. The triethylamine hydrochloride was removed by filtration. The filtrate was concentrated to obtain intermediate B. Intermediate B was added to an autoclave, and 25wt% ammonia water was added. The reaction was carried out at 80℃ for 10~12h. After cooling, the mixture was filtered. The filter cake was washed with water 3~5 times and dried under vacuum to obtain intermediate C.

[0014] (3) Under nitrogen protection, intermediate A and intermediate C were added to anhydrous ethanol, followed by p-toluenesulfonic acid and molecular sieve. The mixture was heated to 78°C and refluxed for 20-24 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered to remove the molecular sieve, and the filtrate was dropped into ice water to precipitate a yellow precipitate. The filtrate was then filtered, and the filter cake was washed 3-5 times with cold water, ethanol, and n-hexane. The precipitate was purified by silica gel column chromatography to obtain the ultraviolet absorber.

[0015] Preferably, in step (1), the molar ratio of 2-(2-hydroxy-5-methylphenyl)benzotriazole and selenium dioxide is 1:1.

[0016] Preferably, in step (2), the molar ratio of cyanuric chloride, allyl alcohol and triethylamine is 1:2:2, and the solid-liquid ratio of intermediate B and ammonia is 1g:5mL.

[0017] Preferably, in step (3), the molar ratio of intermediate A to intermediate C is 2:1, and the mass of p-toluenesulfonic acid added is 2 to 4% of the total mass of intermediate A and intermediate C.

[0018] Preferably, the preparation method of modified nano zinc oxide includes the following steps:

[0019] A. Place nano zinc oxide in a round-bottom flask, add 0.1M HNO3 aqueous solution, sonicate for 20~40min, stir and reflux at 80℃ for 4~8h, after the reaction is complete, centrifuge and separate, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain pretreated nano zinc oxide.

[0020] B. Disperse the pretreated nano zinc oxide in anhydrous ethanol, then add the nano zinc oxide dispersion to a three-necked flask, and slowly add 3-mercaptopropyltrimethoxysilane dropwise under nitrogen protection. React at 80°C for 8-12 hours. After the reaction is complete, centrifuge and wash with ethanol and acetone 3-5 times each. Dry under vacuum at 60°C to obtain mercapto-modified nano zinc oxide.

[0021] C. Add N,N-dimethylformamide and mercapto-modified nano-zinc oxide to a quartz reactor, ultrasonically disperse for 20-40 min, add ultraviolet absorber and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone, stir for 1-3 h under light-protected conditions to ensure thorough mixing, purge with nitrogen to remove oxygen, and then irradiate with UV light for 1-2 h. After the reaction is complete, transfer to a dialysis bag, dialyze with deionized water for 72 h to remove unreacted ultraviolet absorber, and freeze-dry to obtain the modified nano-zinc oxide.

[0022] Preferably, the mass ratio of pretreated nano-zinc oxide to 3-mercaptopropyltrimethoxysilane is 10~20:1.

[0023] Preferably, the mass ratio of thiolized nano zinc oxide to ultraviolet absorber is 2:1.

[0024] A method for preparing a rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0025] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 160~170℃. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140℃, add modified nano zinc oxide and antioxidant. Stir for 20~40 minutes to ensure uniform dispersion and obtain modified EVA layer material.

[0026] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature range of 50~120℃.

[0027] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0028] The beneficial effects of this invention are:

[0029] The BOPET film of this invention, used for packaging and transportation, is modified with an adhesion layer and an EVA layer. This ensures the adhesion of the modified EVA layer to the BOPET film under conditions of high and low temperatures and high humidity. The modified EVA layer is modified by adding hydrogenated petroleum resin, MAH-g-EVA, modified nano zinc oxide, microcrystalline wax, and antioxidant 168, which effectively improves the overall performance of the protective film. The addition of a PS layer increases the adhesion to PS foam board and reduces the shrinkage of the bonding surface under different climatic conditions, ensuring the long-term stability of the adhesion between (BOPET+EVA+PS) and PS foam board.

[0030] This invention modifies nano-zinc oxide by covalently grafting a UV absorber onto the surface of nano-zinc oxide via a thiol-alkene click reaction. The UV absorber possesses both benzotriazole and triazine structures. On one hand, it offers structural stability advantages. Covalent grafting prevents the migration of small molecule UV absorber auxiliaries, while the grafted layer also inhibits the aggregation of nano-zinc oxide, ensuring uniform dispersion within the EVA matrix. The allyl groups of the UV absorber form physical entanglements with the EVA chains, reducing stress concentration. On the other hand, the synergistic mechanism of UV shielding and absorption improves the material's UV resistance. Nano-zinc oxide can scatter / reflect UV light, especially wavelengths from 280 to 400 nm, while the benzotriazole structure of the UV absorber absorbs light from 300 to 350 nm, and the triazine structure absorbs light from 350 to 400 nm, achieving full-band coverage. The excited-state UV absorber transfers energy to the conduction band of zinc oxide via covalent bonds, preventing energy accumulation that could lead to molecular chain breakage.

[0031] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The infrared spectrum of the ultraviolet absorber prepared in Example 1 of this invention;

[0034] Figure 2 The thermogravimetric analysis curves before and after modification with nano zinc oxide in Example 2 of this invention are shown. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] An ultraviolet absorber having a hybrid structure of benzotriazole and triazine, with the following molecular formula:

[0038] ;

[0039] The above-mentioned method for preparing ultraviolet absorbers includes the following steps:

[0040] (1) Add 23.4g of 2-(2-hydroxy-5-methylphenyl)benzotriazole and 200mL of 1,4-dioxane to a 500mL three-necked flask, heat to 80℃ and stir to dissolve. Then slowly add 11.1g of selenium dioxide in batches, heat to 100℃ and reflux for 8h. After the reaction is complete, filter while hot to remove the black selenium precipitate. Concentrate the filtrate under reduced pressure to 1 / 3 of the original volume, add 200mL of ice water to precipitate the yellow solid, filter, wash the filter cake with 50mL of methanol 3-5 times, and dry under vacuum to obtain intermediate A.

[0041] (2) Dissolve 8.4g of cyanuric chloride in 150mL of anhydrous tetrahydrofuran under ice bath, then add 11.6g of allyl alcohol and 20.2g of triethylamine dropwise, keep the temperature <5℃, and react at room temperature for 4h. Filter to remove triethylamine hydrochloride, concentrate the filtrate to obtain intermediate B, add 19.8g of intermediate B to a high pressure vessel, add 100mL of 25wt% ammonia water, react at 80℃ for 10~12h, cool and filter, wash the filter cake with water 3~5 times, and vacuum dry to obtain intermediate C;

[0042] (3) Under nitrogen protection, 12.8 g of intermediate A and 4.2 g of intermediate C were added to anhydrous ethanol, followed by 0.5 g of p-toluenesulfonic acid and 10 g of molecular sieve. The mixture was heated to 78 °C and refluxed for 24 h. After the reaction was completed, the mixture was cooled to room temperature and filtered to remove the molecular sieve. The filtrate was added dropwise to 500 mL of ice water to precipitate a yellow precipitate. The precipitate was then filtered and washed with cold water, ethanol, and n-hexane 3 to 5 times in sequence. The precipitate was purified by silica gel column chromatography to obtain the ultraviolet absorber.

[0043] The ultraviolet absorber prepared in Example 1 was subjected to infrared spectroscopy analysis, and the resulting infrared spectrum is shown below. Figure 1 As shown, from Figure 1 It can be seen from 3450cm -1 The peak at 3150 cm⁻¹ represents the stretching vibration of the NH group. -1 The peak at 1550–1600 cm⁻¹ represents the stretching vibration of the phenolic hydroxyl group (-OH). -1 The peak at 1350-1250 cm⁻¹ is a strong and concentrated C=N stretching peak of the triazine ring, while the peak at 1350-1250 cm⁻¹ is a strong and concentrated peak of the triazine ring. -1 The presence of a strong CN / NN stretching vibration peak at 2900 cm⁻¹ indicates the presence of a triazole ring in the molecular structure. The peak at 2900 cm⁻¹ corresponds to the =CH stretching vibration, while the peak at 993 cm⁻¹ is also present. -1 and 909 cm -1 The out-of-plane bending peak at =CH2 indicates the presence of terminal olefins, demonstrating the successful synthesis of an ultraviolet absorber possessing both benzotriazole and triazine structures.

[0044] Example 2

[0045] A modified nano-zinc oxide, specifically an ultraviolet absorber prepared in Example 1 by covalent grafting of thiol-alkene click reaction onto the surface of nano-zinc oxide, comprises the following steps:

[0046] A. Place 10g of nano zinc oxide in a round-bottom flask, add 200mL of 0.1M HNO3 aqueous solution, sonicate for 30min, stir and reflux at 80℃ for 6h, after the reaction is complete, centrifuge and separate, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain pretreated nano zinc oxide.

[0047] B. Disperse 10g of pretreated nano zinc oxide in 200mL of anhydrous ethanol, then add the nano zinc oxide dispersion to a three-necked flask, and slowly add 1.5g of 3-mercaptopropyltrimethoxysilane under nitrogen protection. React at 80℃ for 10h. After the reaction is complete, centrifuge and wash with ethanol and acetone 3-5 times each. Dry under vacuum at 60℃ to obtain mercapto-treated nano zinc oxide.

[0048] C. Add 80 mL of N,N-dimethylformamide and 5 g of mercapto-modified nano-zinc oxide to a quartz reactor, and ultrasonically disperse for 20-40 min. Add 2.5 g of ultraviolet absorber and 0.15 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone, and stir for 2 h under light-protected conditions to ensure thorough mixing. After purging with nitrogen to remove oxygen, irradiate with UV light for 1.5 h. After the reaction is complete, transfer to a dialysis bag and dialyze with deionized water for 72 h to remove unreacted ultraviolet absorber. Freeze-dry to obtain the modified nano-zinc oxide.

[0049] Thermogravimetric analysis (TGA) was performed on the nano-zinc oxide before and after modification in Example 2. The TGA curves of nano-zinc oxide and modified nano-zinc oxide are shown below. Figure 2 As shown, by Figure 2 It can be seen that nano zinc oxide loses about 5.7% of its weight in the temperature range of 25~150℃ due to the desorption of adsorbed water, and reaches equilibrium after 200℃; modified nano zinc oxide loses about 2.1% of its weight in the temperature range of 25-150℃ due to the desorption of adsorbed water, about 5.3% of its weight in the temperature range of 150~300℃ due to the volatilization of residual solvent, about 23.1% of its weight in the temperature range of 300~500℃ due to the decomposition of organic matter, and about 1.2% of its weight in the temperature range of 500~800℃ due to the combustion of residual carbon. It can be seen that nano zinc oxide successfully grafted the ultraviolet absorber, and the grafting rate is about 23%.

[0050] Example 3

[0051] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, and the adhesion layer being a water-based acrylate-modified polyurethane emulsion. The modified EVA layer comprises the following raw materials in parts by weight: 60 parts EVA resin, 30 parts hydrogenated petroleum resin, 4 parts MAH-g-EVA, 5 parts modified nano zinc oxide, 4 parts microcrystalline wax, and 1.5 parts antioxidant 168; the modified nano zinc oxide is prepared in Example 2.

[0052] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0053] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 160°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add modified nano zinc oxide and antioxidant. Stir for 40 minutes to ensure uniform dispersion and obtain modified EVA layer material.

[0054] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 50°C.

[0055] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0056] Example 4

[0057] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, and the adhesion layer being a water-based acrylate-modified polyurethane emulsion. The modified EVA layer comprises the following raw materials in parts by weight: 70 parts EVA resin, 20 parts hydrogenated petroleum resin, 6 parts MAH-g-EVA, 3 parts modified nano zinc oxide, 6 parts microcrystalline wax, and 0.5 parts antioxidant 168; the modified nano zinc oxide is prepared in Example 2.

[0058] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0059] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 170°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add modified nano zinc oxide and antioxidant. Stir for 20 minutes to ensure uniform dispersion and obtain modified EVA layer material.

[0060] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 120℃.

[0061] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0062] Example 5

[0063] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, and the adhesion layer being a water-based acrylate-modified polyurethane emulsion. The modified EVA layer comprises the following raw materials in parts by weight: 65 parts EVA resin, 25 parts hydrogenated petroleum resin, 5 parts MAH-g-EVA, 4 parts modified nano zinc oxide, 5 parts microcrystalline wax, and 1 part antioxidant 168; the modified nano zinc oxide is prepared in Example 2.

[0064] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0065] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 165°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add modified nano zinc oxide and antioxidant. Stir for 30 minutes to ensure uniform dispersion and obtain modified EVA layer material.

[0066] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 80°C.

[0067] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0068] Comparative Example 1

[0069] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, the adhesion layer being a water-based acrylate-modified polyurethane emulsion, and the modified EVA layer comprising the following raw materials in parts by weight: 65 parts EVA resin, 25 parts hydrogenated petroleum resin, 5 parts MAH-g-EVA, 4 parts nano zinc oxide, 5 parts microcrystalline wax, and 1 part antioxidant 168.

[0070] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0071] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 165°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add nano zinc oxide and antioxidant. Stir for 30 minutes to ensure uniform dispersion and obtain modified EVA layer material.

[0072] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 80°C.

[0073] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0074] Comparative Example 2

[0075] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, and the adhesion layer being a water-based acrylate-modified polyurethane emulsion. The modified EVA layer comprises the following raw materials in parts by weight: 65 parts EVA resin, 25 parts hydrogenated petroleum resin, 5 parts MAH-g-EVA, 4 parts UV absorber, 5 parts microcrystalline wax, and 1 part antioxidant 168; the UV absorber is prepared in Example 1.

[0076] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0077] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 165°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add UV absorber and antioxidant and stir for 30 minutes to ensure uniform dispersion to obtain modified EVA layer material.

[0078] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 80°C.

[0079] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0080] Comparative Example 3

[0081] A rupture-resistant foam protective film for packaging and transportation includes a BOPET film, an adhesion layer coated on one side of the BOPET film, a modified EVA layer laminated onto the surface of the adhesion layer, a PS layer laminated onto the surface of the modified EVA layer, the adhesion layer being a water-based acrylic modified polyurethane emulsion, and the modified EVA layer comprising the following raw materials in parts by weight: 65 parts EVA resin, 25 parts hydrogenated petroleum resin, 5 parts MAH-g-EVA, 5 parts microcrystalline wax, and 1 part antioxidant 168.

[0082] The method for preparing the above-mentioned rupture-resistant foam protective film for packaging and transportation includes the following steps:

[0083] S1. Add EVA resin and petroleum resin to a mixer and melt mix at 165°C. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140°C, add antioxidant and stir for 30 minutes to ensure uniform dispersion to obtain modified EVA layer material.

[0084] S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature of 80°C.

[0085] S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

[0086] Performance testing

[0087] The modified EVA layer materials prepared in Examples 3-5 and Comparative Examples 1-3 were mixed in an internal mixer and then pressed into 1 mm thick films using a flat vulcanizing machine (170℃ / 10MPa). These films were then cut into 100×50 mm standard samples and placed in an environment of 23±2℃ and 50±5%RH for 48 hours to eliminate internal stress. Afterward, ultraviolet aging tests were conducted according to GB / T 16422.3-2014 using a QUV ultraviolet aging test chamber with 340 nm UVA and an irradiation intensity of 0.76 W / m². 2 The testing cycle was 8 hours of light exposure (60℃) + 4 hours of condensation (50℃). Three parallel samples were taken every 120 hours to test the performance. The test intervals were 0h, 120h, 240h, 500h, 750h, and 1000h. The yellowing index (ΔYI) was measured using a colorimeter (ASTM D2244), and the tensile strength was tested using a universal testing machine (GB / T 1040.3). The results are shown in Tables 1 and 2 below.

[0088] Table 1 Yellowing Index of Bursting-Proof Foam Protective Film for Packaging and Transportation

[0089]

[0090] Table 2 Tensile Strength Retention Rate of Bursting-Proof Foam Protective Film for Packaging and Transportation

[0091]

[0092] As shown in Table 1, the ΔYI (+2.9) in Examples 3-5 is significantly lower than that of using nano-zinc oxide or the UV absorber alone, proving that the synergistic effect of the UV absorber absorbing UV light and the scattering of nano-zinc oxide effectively blocks the formation of chromophores. Comparative Example 1 showed acceptable performance in the initial stage (<500h), demonstrating the UV shielding effect of nano-zinc oxide. As shown in Table 2, the tensile strength retention rate in Examples 3-5 is much higher than that in Comparative Examples 1 and 2, indicating that covalent grafting protects the EVA main chain from photo-oxidative breakage. The modified nano-zinc oxide of this invention grafts and copolymerizes the UV absorber with nano-zinc oxide, which has the advantage of structural stability. Covalent grafting prevents the migration of small molecule additives in the UV absorber, while the grafted layer also prevents the agglomeration of nano-zinc oxide, ensuring uniform dispersion of nano-zinc oxide in the EVA matrix. Simultaneously, the allyl groups of the UV absorber form physical entanglements with the EVA chains, reducing stress concentration. On the other hand, the synergistic mechanism of UV shielding and absorption can improve the UV resistance of materials. Nano zinc oxide can scatter / reflect UV light, especially UV light with wavelengths of 280~400nm, while the benzotriazole structure of the UV absorber absorbs 300~350nm and the triazine structure absorbs 350~400nm, achieving full-band coverage. At the same time, the excited-state UV absorber transfers energy to the conduction band of zinc oxide through covalent bonds, avoiding energy accumulation that could lead to molecular chain breakage.

[0093] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0094] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A break-resistant foam protective film for packaging and shipping, characterized by, The invention includes a BOPET film, wherein an adhesion layer is coated on one side of the BOPET film, a modified EVA layer is laminated onto the surface of the adhesion layer, a PS layer is laminated onto the surface of the modified EVA layer, the adhesion layer is a water-based acrylate-modified polyurethane emulsion, and the modified EVA layer comprises the following raw materials in parts by weight: 60-70 parts of EVA resin, 20-30 parts of hydrogenated petroleum resin, 4-6 parts of MAH-g-EVA, 3-5 parts of modified nano zinc oxide, 4-6 parts of microcrystalline wax, and 0.5-1.5 parts of antioxidant 168. The modified nano-zinc oxide is a nano-zinc oxide surface thiolized and then covalently grafted with an ultraviolet absorber via a thiol-alkene click reaction. The ultraviolet absorber is an ultraviolet absorber possessing both benzotriazole and triazine hybrid structures, and its molecular formula is as follows: 。 2. The break resistant foam protective film for packaging and shipping according to claim 1, characterized by, The waterborne acrylate-modified polyurethane emulsion is obtained by mixing acrylate monomers with polyurethane emulsion and then adding ammonium persulfate to initiate a polymerization reaction.

3. The break resistant foam protective film for packaging and shipping of claim 1, wherein, The method for preparing the ultraviolet absorber includes the following steps: (1) Add 2-(2-hydroxy-5-methylphenyl)benzotriazole and 1,4-dioxane to a three-necked flask, heat to 80°C and stir to dissolve. Then slowly add selenium dioxide in batches and reflux at 100°C for 6-10 hours. After the reaction is complete, filter while hot to remove the black selenium precipitate. Concentrate the filtrate under reduced pressure to 1 / 3 of the original volume. Add ice water to precipitate the yellow solid and filter. Wash the filter cake with methanol 3-5 times and dry under vacuum to obtain intermediate A. (2) Cyanuryl chloride was dissolved in anhydrous tetrahydrofuran under ice bath, and then allyl alcohol and triethylamine were added dropwise. The temperature was kept <5℃. After adding the solution, the temperature was raised to room temperature and reacted for 3~5h. The triethylamine hydrochloride was removed by filtration. The filtrate was concentrated to obtain intermediate B. Intermediate B was added to an autoclave, and 25wt% ammonia water was added. The reaction was carried out at 80℃ for 10~12h. After cooling, the mixture was filtered. The filter cake was washed with water 3~5 times and dried under vacuum to obtain intermediate C. (3) Under nitrogen protection, intermediate A and intermediate C were added to anhydrous ethanol, followed by p-toluenesulfonic acid and molecular sieve. The mixture was heated to 78°C and refluxed for 20-24 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered to remove the molecular sieve, and the filtrate was dropped into ice water to precipitate a yellow precipitate. The filtrate was then filtered, and the filter cake was washed 3-5 times with cold water, ethanol, and n-hexane. The precipitate was purified by silica gel column chromatography to obtain the ultraviolet absorber.

4. The rupture-resistant foam protective film for packaging and transportation according to claim 3, characterized in that, In step (1), the molar ratio of 2-(2-hydroxy-5-methylphenyl)benzotriazole and selenium dioxide is 1:

1.

5. The rupture-resistant foam protective film for packaging and transportation according to claim 3, characterized in that, In step (2), the molar ratio of cyanuric chloride, allyl alcohol and triethylamine is 1:2:2, and the solid-liquid ratio of intermediate B and ammonia is 1g:5mL.

6. The rupture-resistant foam protective film for packaging and transportation according to claim 3, characterized in that, In step (3), the molar ratio of intermediate A to intermediate C is 2:1, and the mass of p-toluenesulfonic acid added is 2 to 4% of the total mass of intermediate A and intermediate C.

7. The rupture-resistant foam protective film for packaging and transportation according to claim 1, characterized in that, The preparation method of the modified nano zinc oxide includes the following steps: A. Place nano zinc oxide in a round-bottom flask, add 0.1M HNO3 aqueous solution, sonicate for 20~40min, stir and reflux at 80℃ for 4~8h, after the reaction is complete, centrifuge and separate, wash with deionized water until neutral, and vacuum dry at 60℃ to obtain pretreated nano zinc oxide. B. Disperse the pretreated nano zinc oxide in anhydrous ethanol, then add the nano zinc oxide dispersion to a three-necked flask, and slowly add 3-mercaptopropyltrimethoxysilane dropwise under nitrogen protection. React at 80°C for 8-12 hours. After the reaction is complete, centrifuge and wash with ethanol and acetone 3-5 times each. Dry under vacuum at 60°C to obtain mercapto-modified nano zinc oxide. C. Add N,N-dimethylformamide and mercapto-modified nano-zinc oxide to a quartz reactor, ultrasonically disperse for 20-40 min, add ultraviolet absorber and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone, stir for 1-3 h under light-protected conditions to ensure thorough mixing, purge with nitrogen to remove oxygen, and then irradiate with UV light for 1-2 h. After the reaction is complete, transfer to a dialysis bag, dialyze with deionized water for 72 h to remove unreacted ultraviolet absorber, and freeze-dry to obtain the modified nano-zinc oxide.

8. The rupture-resistant foam protective film for packaging and transportation according to claim 7, characterized in that, The mass ratio of the pretreated nano-zinc oxide to 3-mercaptopropyltrimethoxysilane is 10~20:

1.

9. The rupture-resistant foam protective film for packaging and transportation according to claim 7, characterized in that, The mass ratio of the thiolized nano zinc oxide to the ultraviolet absorber is 2:

1.

10. A method for preparing a rupture-resistant foam protective film for packaging and transportation as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Add EVA resin and hydrogenated petroleum resin to a mixer and melt mix at 160~170℃. Then add MAH-g-EVA and microcrystalline wax and continue mixing. After cooling to 140℃, add modified nano zinc oxide and antioxidant. Stir for 20~40 minutes to ensure uniform dispersion and obtain modified EVA layer material. S2. First, an adhesion layer is applied to one side of the BOPET film by dip coating, and then dried in a suspension oven at a controlled temperature range of 50~120℃. S3. The modified EVA layer is laminated onto the surface of the adhesion layer through the first extruder, and the PS layer is laminated onto the modified EVA layer through the second extruder to obtain a rupture-resistant foam protective film for packaging and transportation.

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