Plastic packaging material for food and preparation method thereof

Abstract

The invention discloses a plastic packaging material for food and a preparation method of the plastic packaging material. On one hand, the invention provides the plastic packaging material for the food, and the plastic packaging material is prepared from the following raw material components in parts by mass: 60 parts of HDPE (High-Density Polyethylene) resin, 40 to 50 parts of EVOH (Ethylene Vinyl Alcohol) resin, 24 to 32 parts of non-isocyanate polyurethane prepolymer and 6 to 10 parts of cinnamyl aldehyde grafted nano titanium dioxide; the non-isocyanate polyurethane prepolymer is prepared from the following raw material components in parts by mass: 60 to 68 parts of methyl 1, 6-hexamethylene dicarbamate, 6 to 8 parts of bio-based polyol, 10 to 16 parts of eugenol, 1 to 3 parts of ferric oxide and 2 to 4 parts of zinc acetate. On the other hand, the invention provides a preparation method of the plastic packaging material for food. The packaging material disclosed by the invention is excellent in high and low temperature resistance, excellent in solvent resistance and moisture resistance, excellent in oxygen barrier property, free of harmful substance precipitation and relatively excellent in antibacterial property.

Description

A food-grade plastic packaging material and its preparation method Technical Field

[0001] This application relates to the field of food packaging materials technology, and in particular to a plastic packaging material for food and its preparation method. Background Technology

[0002] Food packaging, as a crucial link in the food supply chain, serves as an effective barrier material to protect food from external contamination. With the continuous development of the modern food industry, fresh food products have become increasingly popular in recent years. These foods are processed from fresh ingredients in central kitchens, undergoing strict aseptic production combined with cold chain transportation, packaging technology, and various preservation techniques to achieve a certain shelf life for transportation and sales. However, as people increasingly value food safety, fresh food products have gradually abandoned the use of preservative chemical additives, placing higher demands on packaging technology. Safety, non-toxicity, and preservation are currently the high-end requirements for packaging materials for fresh food products.

[0003] The main factors leading to food spoilage are bacterial growth and oxidation. Although most fresh foods are produced using aseptic processes combined with high-temperature sterilization, bacterial contamination cannot be completely eliminated. Low-temperature cold chain transportation can, to some extent, slow bacterial growth and preserve freshness, but strict temperature control is difficult to maintain at retail outlets for fresh foods. Furthermore, oxygen from the air can penetrate food packaging, leading to oxidative spoilage. Therefore, packaging materials for fresh foods must possess excellent oxygen barrier properties, excellent low-temperature resistance, and excellent antibacterial properties. To meet the requirements of high-temperature sterilization and food safety, packaging materials for fresh foods also need excellent high-temperature resistance, solvent resistance, moisture resistance, and the ability to prevent the release of harmful substances. Furthermore, to further extend the shelf life of fresh foods, packaging materials should ideally also possess excellent antibacterial properties.

[0004] Currently available plastic packaging materials do not simultaneously meet all of the aforementioned performance requirements. Therefore, designing a packaging material that can simultaneously meet these performance requirements is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] In order to solve at least one of the above-mentioned technical problems, this application provides a food-grade plastic packaging material with excellent high and low temperature resistance, excellent solvent resistance and moisture resistance, excellent oxygen barrier properties, no harmful substance release, and excellent antibacterial properties.

[0006] On one hand, this application provides a plastic packaging material for food use, wherein the mass ratio of each raw material component of the plastic packaging material includes: 60 parts HDPE resin, 40-50 parts EVOH resin, 24-32 parts non-isocyanate polyurethane prepolymer, and 6-10 parts cinnamaldehyde-grafted nano-titanium dioxide; wherein the mass ratio of each raw material component of the non-isocyanate polyurethane prepolymer includes: 60-68 parts methyl 1,6-hexamethylenedicarbamate, 6-8 parts bio-based polyol, 10-16 parts eugenol, 1-3 parts ferric oxide, and 2-4 parts zinc acetate.

[0007] Optionally, the mass ratio of each raw material component in the plastic packaging material includes: 60 parts HDPE resin, 42-44 parts EVOH resin, 28-30 parts non-isocyanate polyurethane prepolymer, and 8-8.6 parts cinnamaldehyde-grafted nano-titanium dioxide.

[0008] Optionally, the mass ratio of each raw material component of the non-isocyanate polyurethane prepolymer includes: 62-64 parts of methyl 1,6-hexamethylenedicarbamate, 6.8-7.2 parts of bio-based polyol, 14-14.6 parts of eugenol, 1.8-2.4 parts of ferric oxide, and 2.8-3.2 parts of zinc acetate.

[0009] Optionally, the preparation of cinnamaldehyde-grafted nano-titanium dioxide includes the following steps: S1-a, accurately weighing KH550 and nano-titanium dioxide according to a mass ratio of KH550 to nano-titanium dioxide of 3.8:2~10; S1-b, dissolving KH550 in 75% ethanol solution to prepare a solution with a concentration of 2.5~3g / L, mixing thoroughly, heating to 60℃ for at least 60min, then adding nano-titanium dioxide, and ultrasonically reacting for at least 60min to obtain a reaction mixture; S1-c, accurately weighing cinnamaldehyde according to an addition ratio of 50~60mL of cinnamaldehyde per 1g of nano-titanium dioxide, adding it to the reaction mixture of step S1-b, continuing ultrasonic reaction for at least 60min, then stirring for at least 32h, filtering out the solid product, washing with alcohol, and vacuum drying at 40℃ to constant weight to obtain cinnamaldehyde-grafted nano-titanium dioxide.

[0010] Alternatively, the nano-titanium dioxide may be selected from fumed nano-titanium dioxide.

[0011] Optionally, the preparation of methyl 1,6-hexamethylenedicarbamate includes the following steps: Sa, accurately weigh dimethyl carbonate and 1,6-hexanediamine at a molar ratio of 6~6.2:1, add sodium methoxide accounting for 1.5% of the total mass of 1,6-hexanediamine, mix thoroughly, and prepare a reaction solution; Sb, heat the reaction solution prepared in step Sa to 92°C, reflux for 6 hours, cool, wash the reaction solution with 2 times the volume of 45°C warm water, filter out the solid product, and obtain crude methyl 1,6-hexamethylenedicarbamate; Sc, add anhydrous methanol to the crude methyl 1,6-hexamethylenedicarbamate obtained in step Sb until completely dissolved, obtain a solution, then add 5~6 times the volume of deionized water to the solution for recrystallization, filter out the crystals, dry, and obtain methyl 1,6-hexamethylenedicarbamate.

[0012] Further optionally, in step Sc, the drying is carried out by vacuum drying at 60°C to constant weight.

[0013] Optionally, the zinc acetate is selected from silica gel-supported zinc acetate.

[0014] Optionally, the preparation of the non-isocyanate polyurethane prepolymer includes the following steps: S2-a, thoroughly mixing each raw material component in the formulation to obtain a mixed reaction solution; S2-b, stirring the mixed reaction solution obtained in step S2-a at a temperature of 100~105℃ for more than 60 minutes under nitrogen protection, then raising the temperature to 160~165℃ and continuing the reaction for 1.5~2 hours, and after cooling, obtaining the non-isocyanate polyurethane prepolymer.

[0015] On the other hand, this application provides a method for preparing the above-mentioned food-grade plastic packaging material, including the following steps: S1, preparing cinnamaldehyde-grafted nano-titanium dioxide; S2, preparing a non-isocyanate polyurethane prepolymer; S3, accurately weighing HDPE resin, non-isocyanate polyurethane prepolymer and cinnamaldehyde-grafted nano-titanium dioxide according to the formula, adding them to a twin-screw extruder, and then melting, dispersing, extruding, cooling and pelletizing to obtain the food-grade plastic packaging material; the extrusion process parameters are as follows: the temperatures of the 6 temperature zones are 150~155℃, 155~160℃, 160~165℃, 165~170℃, 165~170℃, and 160~165℃ respectively.

[0016] In summary, the present invention includes at least one of the following beneficial technical effects: 1. This application uses a mixed resin of HDPE and EVOH as the main resin, and uses methyl 1,6-hexamethylenedicarbamate, bio-based polyol and eugenol to prepare a non-isocyanate polyurethane prepolymer grafted with eugenol. The packaging material is prepared by heat processing with the above raw materials and cinnamaldehyde-grafted nano-titanium dioxide. The resulting packaging material has a certain density of polyurethane crosslinking network grafted with eugenol and disperses cinnamaldehyde-grafted nano-titanium dioxide, which makes the packaging material have excellent high and low temperature resistance, excellent solvent resistance and moisture resistance, and excellent photothermal aging resistance.

[0017] 2. The packaging material of this application incorporates cinnamaldehyde-grafted nano-titanium dioxide and contains a polyurethane cross-linking network grafted with eugenol, thereby constructing a composite antibacterial system composed of cinnamaldehyde and eugenol. This gives the packaging material excellent antibacterial properties, and the aforementioned composite antibacterial system, based on a design of chemical grafting and physical mixing, exhibits extremely strong resistance to light and heat.

[0018] 3. The packaging material of this application has a simple raw material composition. The overall design adopts a polyurethane cross-linking network grafted with eugenol in HDPE resin. No plasticizers or chemical additives are added. No harmful substances are released during high-temperature cooking, and it fully meets all food safety requirements. Detailed Implementation

[0019] The present application will be further described in detail below with reference to the embodiments.

[0020] This application provides a plastic packaging material for food use. The raw material components of the plastic packaging material are formulated in the following proportions by weight: 60 parts HDPE resin, 40-50 parts EVOH resin, 24-32 parts non-isocyanate polyurethane prepolymer, and 6-10 parts cinnamaldehyde-grafted nano-titanium dioxide. The raw material components of the non-isocyanate polyurethane prepolymer are formulated in the following proportions by weight: 60-68 parts methyl 1,6-hexamethylenedicarbamate, 6-8 parts bio-based polyol, 10-16 parts eugenol, 2-4 parts a composite curing catalyst of quaternary ammonium salt and quaternary phosphate salt, and 0.1-0.15 parts zinc acetate.

[0021] The preparation method of the above-mentioned food-grade plastic packaging material includes the following steps: S1, preparing cinnamaldehyde-grafted nano-titanium dioxide; S2, preparing non-isocyanate polyurethane prepolymer; S3, accurately weighing HDPE resin, non-isocyanate polyurethane prepolymer and cinnamaldehyde-grafted nano-titanium dioxide according to the formula, adding them to a twin-screw extruder, and then melting, dispersing, extruding, cooling and pelletizing to obtain the food-grade plastic packaging material; the extrusion process parameters are as follows: the temperatures of the 6 temperature zones are 150~155℃, 155~160℃, 160~165℃, 165~170℃, 165~170℃, and 160~165℃ respectively.

[0022] Prior to this application, a wide variety of food-grade plastic packaging materials were prepared in the prior art, including PA, PP, PE, PET, and other food-grade plastics. Through composite technology, the resulting food-grade plastic packaging bags exhibit excellent performance in oxygen barrier properties, solvent resistance, and moisture resistance. PA material, in particular, possesses excellent strength and puncture resistance, strong chemical stability, excellent corrosion and solvent resistance, and outstanding high and low temperature resistance, making it an excellent high-end food packaging material. However, PA material lacks antibacterial properties, has insufficient resistance to light aging, and insufficient water barrier properties, limiting its application in the packaging of fresh foods. While other materials each have their advantages, they all have certain problems that make it difficult to meet the requirements of fresh food packaging.

[0023] The applicant designed this application, which uses HDPE resin and EVOH resin as mixed raw materials, and effectively solves the above-mentioned problems existing in the prior art by introducing a specific non-isocyanate polyurethane system and adding specific nanofillers.

[0024] The following are preparation examples and embodiments of this application.

[0025] The main raw materials used in the embodiments of this application are all commercially available.

[0026] Among them, HDPE resin, medical grade, was purchased from Dongguan Hongteng Plastic Raw Materials Co., Ltd.; EVOH resin, Rakure F104B from Japan, was purchased from Dongguan Chenxi Plastic Raw Materials Co., Ltd.; dimethyl carbonate, purity ≥ 99%, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; 1,6-hexanediamine, purity ≥ 99%, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; bio-based polyol, FH-3185, was purchased from Zhangjiagang Feihang Technology Co., Ltd.; silica-supported zinc acetate, loading rate 35%, customized, was purchased from Xi'an Qiyue Biotechnology Co., Ltd.; ferric oxide, purity ≥ 99%, was purchased from Langfang Qianyao Technology Co., Ltd.; eugenol, purity ≥ 99.5%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; fumed nano titanium dioxide, purity ≥ 99.9%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; KH550 was purchased from Hubei Changfu Chemical Co., Ltd.; cinnamaldehyde, purity ≥ 99%, was purchased from Hubei Qibu New Material Technology Co., Ltd.

[0027] The following is a preparation example of this application.

[0028] Preparation Example 1: The preparation of cinnamaldehyde-grafted nano-titanium dioxide in this preparation example includes the following steps: S1-a: Accurately weigh KH550 and nano-titanium dioxide according to a mass ratio of 3.8:10; S1-b: Dissolve KH550 in 75% ethanol solution to prepare a solution with a concentration of 3 g / L, mix thoroughly, heat to 60°C and react for 60 min, then add nano-titanium dioxide, and sonicate for 60 min to obtain a reaction mixture; S1-c: Accurately weigh cinnamaldehyde according to an addition ratio of 1 g nano-titanium dioxide to 60 mL cinnamaldehyde, add it to the reaction mixture of step S1-b, continue sonication for 60 min, then stir for 32 h, filter out the solid product, wash with alcohol, and vacuum dry at 40°C to constant weight to obtain cinnamaldehyde-grafted nano-titanium dioxide.

[0029] After testing the content of each component in the reaction solution, the grafting rate of cinnamaldehyde was calculated to be 2.06%.

[0030] Preparation Example 2: The preparation of cinnamaldehyde-grafted nano-titanium dioxide in this preparation example includes the following steps: S1-a: Accurately weigh KH550 and nano-titanium dioxide according to a mass ratio of KH550 to nano-titanium dioxide of 3.8:2; S1-b: Dissolve KH550 in 75% ethanol solution to prepare a solution with a concentration of 2.5 g / L, mix thoroughly, heat to 60°C and react for 60 min, then add gaseous nano-titanium dioxide, and sonicate for 60 min to obtain a reaction mixture; S1-c: Accurately weigh cinnamaldehyde according to an addition ratio of 1 g nano-titanium dioxide to 50 mL cinnamaldehyde, add it to the reaction mixture of step S1-b, continue sonication for 60 min, then stir for 32 h, filter out the solid product, wash with alcohol, and vacuum dry at 40°C to constant weight to obtain cinnamaldehyde-grafted nano-titanium dioxide.

[0031] After testing the content of each component in the reaction solution, the grafting rate of cinnamaldehyde was calculated to be 10.38%.

[0032] Preparation Example 3: The preparation of cinnamaldehyde-grafted nano-titanium dioxide in this preparation example includes the following steps: S1-a: Accurately weigh KH550 and nano-titanium dioxide according to a mass ratio of 3.8:5; S1-b: Dissolve KH550 in 75% ethanol solution to prepare a solution with a concentration of 2.8 g / L, mix thoroughly, heat to 60°C and react for 60 min, then add nano-titanium dioxide, and sonicate for 60 min to obtain a reaction mixture; S1-c: Accurately weigh cinnamaldehyde according to an addition ratio of 1 g nano-titanium dioxide to 56 mL cinnamaldehyde, add it to the reaction mixture of step S1-b, continue sonication for 60 min, then stir for 32 h, filter out the solid product, wash with alcohol, and vacuum dry at 40°C to constant weight to obtain cinnamaldehyde-grafted nano-titanium dioxide.

[0033] After testing the content of each component in the reaction solution, the grafting rate of cinnamaldehyde was calculated to be 5.06%.

[0034] Preparation Example 4: The preparation of methyl 1,6-hexamethylenedicarbamate in this preparation example includes the following steps: Sa, accurately weigh dimethyl carbonate and 1,6-hexanediamine in a molar ratio of 6:1, add sodium methoxide accounting for 1.5% of the total mass of 1,6-hexanediamine, mix thoroughly, and prepare a reaction solution; Sb, heat the reaction solution prepared in step Sa to 92°C, reflux for 6 hours, cool, wash the reaction solution with 2 times the volume of 45°C warm water, filter out the solid product, and obtain crude methyl 1,6-hexamethylenedicarbamate; Sc, add anhydrous methanol to the crude methyl 1,6-hexamethylenedicarbamate obtained in step Sb until completely dissolved, obtain a solution, then add 5 times the volume of deionized water to the solution for recrystallization, filter out the crystals, and dry under vacuum at 60°C to constant weight to obtain methyl 1,6-hexamethylenedicarbamate.

[0035] The purity was found to be 99.2% after testing.

[0036] Preparation Example 5: The preparation of methyl 1,6-hexamethylenedicarbamate in this preparation example includes the following steps: Sa, accurately weigh dimethyl carbonate and 1,6-hexanediamine at a molar ratio of 6.2:1, add sodium methoxide accounting for 1.5% of the total mass of 1,6-hexanediamine, mix thoroughly, and prepare a reaction solution; Sb, heat the reaction solution prepared in step Sa to 92°C, reflux for 6 hours, cool, wash the reaction solution with 2 times the volume of 45°C warm water, filter out the solid product, and obtain crude methyl 1,6-hexamethylenedicarbamate; Sc, add anhydrous methanol to the crude methyl 1,6-hexamethylenedicarbamate obtained in step Sb until completely dissolved, obtain a solution, then add 6 times the volume of deionized water to the solution for recrystallization, filter out the crystals, and dry under vacuum at 60°C to constant weight to obtain methyl 1,6-hexamethylenedicarbamate.

[0037] The purity was found to be 99.3% after testing.

[0038] Preparation Example 6: The preparation of the non-isocyanate polyurethane prepolymer in this preparation example includes the following steps: S2-a: The raw material components in the formulation are thoroughly mixed according to the following ratio: 68 parts of methyl 1,6-hexamethylenedicarbamate, 8 parts of bio-based polyol, 16 parts of eugenol, 1 part of ferric oxide, and 2 parts of zinc acetate loaded with silica gel to obtain a mixed reaction solution; S2-b: The mixed reaction solution obtained in step S2-a is stirred and reacted at 100°C for 60 min under nitrogen protection, and then the temperature is raised to 160°C and the reaction is continued for 1.5 h. After cooling, ferric oxide and zinc acetate are recovered by nanofiltration to obtain the non-isocyanate polyurethane prepolymer.

[0039] Methyl 1,6-hexamethylenedicarbamate prepared in Preparation Example 4 was selected.

[0040] Preparation Example 7: The preparation of the non-isocyanate polyurethane prepolymer in this preparation example includes the following steps: S2-a: The raw material components in the formulation are thoroughly mixed according to the following ratio: 60 parts of methyl 1,6-hexamethylenedicarbamate, 6 parts of bio-based polyol, 10 parts of eugenol, 3 parts of ferric oxide, and 4 parts of zinc acetate loaded with silica gel to obtain a mixed reaction solution; S2-b: The mixed reaction solution obtained in step S2-a is stirred and reacted at 105°C for 60 min under nitrogen protection, and then the temperature is raised to 165°C and the reaction is continued for 2 h. After cooling, ferric oxide and zinc acetate are recovered by nanofiltration to obtain the non-isocyanate polyurethane prepolymer.

[0041] Methyl 1,6-hexamethylenedicarbamate prepared in Preparation Example 4 was selected.

[0042] Preparation Example 8: The preparation of the non-isocyanate polyurethane prepolymer in this preparation example includes the following steps: S2-a: The raw material components in the formulation are thoroughly mixed according to the following ratio: 62 parts of methyl 1,6-hexamethylenedicarbamate, 6.8 parts of bio-based polyol, 14 parts of eugenol, 1.8 parts of ferric oxide, and 2.8 parts of zinc acetate loaded with silica gel to obtain a mixed reaction solution; S2-b: The mixed reaction solution obtained in step S2-a is stirred and reacted at 100°C for 60 min under nitrogen protection, and then the temperature is raised to 160°C and the reaction is continued for 1.6 h. After cooling, ferric oxide and zinc acetate are recovered by nanofiltration to obtain the non-isocyanate polyurethane prepolymer.

[0043] Methyl 1,6-hexamethylenedicarbamate prepared in Preparation Example 4 was selected.

[0044] Preparation Example 9: The preparation of the non-isocyanate polyurethane prepolymer in this preparation example includes the following steps: S2-a: The raw material components in the formulation are thoroughly mixed according to the following ratio: 64 parts of methyl 1,6-hexamethylenedicarbamate, 7.2 parts of bio-based polyol, 14.6 parts of eugenol, 2.4 parts of ferric oxide, and 3.2 parts of zinc acetate loaded with silica gel to obtain a mixed reaction solution; S2-b: The mixed reaction solution obtained in step S2-a is stirred and reacted at 100°C for 60 min under nitrogen protection, and then the temperature is raised to 160°C and the reaction is continued for 1.8 h. After cooling, ferric oxide and zinc acetate are recovered by nanofiltration to obtain the non-isocyanate polyurethane prepolymer.

[0045] Methyl 1,6-hexamethylenedicarbamate prepared in Preparation Example 4 was selected.

[0046] Preparation Example 10 differs from Preparation Example 9 in that methyl 1,6-hexamethylenedicarbamate prepared in Preparation Example 5 is used.

[0047] The following are embodiments of this application.

[0048] The method for preparing food-grade plastic packaging material according to this application includes the following steps: S1, selecting the corresponding cinnamaldehyde-grafted nano-titanium dioxide; S2, selecting the corresponding non-isocyanate polyurethane prepolymer; S3, accurately weighing HDPE resin, non-isocyanate polyurethane prepolymer and cinnamaldehyde-grafted nano-titanium dioxide according to the formula, adding them to a twin-screw extruder, and then melting, dispersing, extruding, cooling and pelletizing to obtain food-grade plastic packaging material; the extrusion process parameters are as follows: the temperatures of the 6 temperature zones are 155℃, 160℃, 165℃, 170℃, 170℃ and 165℃ respectively.

[0049] Example 1 The mass proportions of each raw material component in the plastic packaging material of this example include: 60 parts HDPE resin, 40 parts EVOH resin, 24 parts non-isocyanate polyurethane prepolymer, and 6 parts cinnamaldehyde-grafted nano titanium dioxide.

[0050] In this embodiment, we selected the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 1 and the non-isocyanate polyurethane prepolymer from Preparation Example 6.

[0051] Example 2 The mass proportions of each raw material component in the plastic packaging material of this example include: 60 parts HDPE resin, 50 parts EVOH resin, 32 parts non-isocyanate polyurethane prepolymer, and 10 parts cinnamaldehyde-grafted nano titanium dioxide.

[0052] In this embodiment, we selected the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 1 and the non-isocyanate polyurethane prepolymer from Preparation Example 6.

[0053] Example 3 The mass proportions of each raw material component in the plastic packaging material of this example include: 60 parts HDPE resin, 42 parts EVOH resin, 28 parts non-isocyanate polyurethane prepolymer, and 8 parts cinnamaldehyde-grafted nano titanium dioxide.

[0054] In this embodiment, we selected the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 1 and the non-isocyanate polyurethane prepolymer from Preparation Example 7.

[0055] Example 4 The mass proportions of each raw material component in the plastic packaging material of this example include: 60 parts HDPE resin, 44 parts EVOH resin, 30 parts non-isocyanate polyurethane prepolymer, and 8.6 parts cinnamaldehyde-grafted nano titanium dioxide.

[0056] In this embodiment, we selected the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 1 and the non-isocyanate polyurethane prepolymer from Preparation Example 8.

[0057] Example 5 differs from Example 4 in that the cinnamaldehyde-grafted nano-titanium dioxide from Example 2 and the non-isocyanate polyurethane prepolymer from Example 8 are selected in this example.

[0058] Example 6 The difference between this example and Example 4 is that this example uses the cinnamaldehyde-grafted nano-titanium dioxide from Example 3 and the non-isocyanate polyurethane prepolymer from Example 8.

[0059] Example 7 The difference between this example and Example 4 is that this example uses the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 2 and the non-isocyanate polyurethane prepolymer from Preparation Example 9.

[0060] Example 8 The difference between this example and Example 4 is that this example uses the cinnamaldehyde-grafted nano-titanium dioxide from Preparation Example 2 and the non-isocyanate polyurethane prepolymer from Preparation Example 10.

[0061] Comparative Example 1 uses PA66 antibacterial nylon masterbatch from Shanghai Songya Chemical Co., Ltd. as Comparative Example 1.

[0062] The difference between Comparative Example 2 and Example 8 is that cinnamaldehyde-grafted nano-titanium dioxide was replaced with an equal amount of gas-phase nano-titanium dioxide.

[0063] The difference between Comparative Example 3 and Example 8 is that an equal amount of HDPE resin was used to replace the non-isocyanate polyurethane prepolymer.

[0064] The properties of the products from Examples 1-8 and Comparative Examples 1-3 were tested. The products from Examples 1-8 and Comparative Examples 1-3 were used to prepare 0.2 mm thick films using a hot extrusion process. The tensile strength, high and low temperature resistance, solvent and moisture resistance, oxygen barrier properties, antibacterial properties, and photothermal aging resistance of the films were tested.

[0065] Tensile strength was tested according to the method described in GB / T 1040.1-2025; high and low temperature resistance was tested after treatment at -20℃ for 2 hours and boiling in deionized water at 100℃ for 2 hours, with TOC analyzer and ICP-MS used to analyze the water samples before and after boiling to detect the presence of precipitated impurities; solvent resistance was tested for leakage after holding salad oil for 24 hours and after immersion in salad oil for 24 hours, followed by washing and drying; moisture resistance was tested according to the method described in GB / T 1034-2008; oxygen barrier properties were tested according to the method described in GB / T 19789-2021; and antibacterial properties were tested according to QB / T The method described in GB / T 2591-2003 was used to test the antimicrobial rate against Staphylococcus aureus and Aspergillus; the photothermal aging resistance was tested by measuring the tensile strength, moisture resistance, oxygen barrier properties, and antimicrobial properties after aging treatment; aging parameters: 85℃ temperature, 100% humidity, UV intensity 0.45 W / m 2 Under these conditions, the treatment lasted for 30 days.

[0066] The results are shown in Tables 1 to 3 below.

[0067] Table 1 Performance test results of Examples 1-8 and Comparative Examples 1-3

[0068] Table 2 Performance test results of Examples 1-8 and Comparative Examples 1-3

[0069] Table 3. Aging performance test results of Examples 1-8 and Comparative Examples 1-3

[0070] As can be seen from the data in Tables 1 and 2, the plastic films prepared by the packaging materials in Examples 1-8 of this application have superior high and low temperature resistance compared with the plastic films prepared by the packaging materials in Comparative Example 1 of the prior art. Although their strength is not as good as that of the packaging materials in Comparative Example 1, their moisture absorption rate is significantly lower than that of the packaging materials in Comparative Example 1. Furthermore, their solvent resistance, oxygen barrier properties, and antibacterial properties are significantly better. It is evident that the packaging materials of this application have excellent performance in all aspects and are very suitable for the preservation packaging of fresh food.

[0071] By comparing the data from Examples 1 to 8 in Tables 1 and 2, it can be seen that the performance of the materials can be further improved after adjusting the raw material ratio. In addition, the antibacterial performance is further improved by using cinnamaldehyde-grafted nano-titanium dioxide with a higher grafting rate. Furthermore, the performance of the materials is further improved by using non-isocyanate polyurethane prepolymers with optimized ratios.

[0072] Comparing the data in Tables 1 and 2 between the examples and the comparative examples, it can be seen that the composite antibacterial system used in this application exhibits significantly better antibacterial performance against various food spoilage bacteria than the material in Comparative Example 1, which uses silver ion antibacterial agents. Furthermore, the polyurethane cross-linked network of this application can greatly improve the water-blocking performance and density of the material, giving it excellent moisture resistance, thereby effectively improving its high and low temperature resistance and oxygen barrier properties. In addition, the material system designed in this application possesses excellent resistance to photothermal aging, and no substances are released during high-temperature boiling, demonstrating extremely stable material performance and excellent safety.

[0073] A comparison of the antibacterial performance data in Tables 2 and 3 shows that the antibacterial performance of the packaging materials in Examples 1-8 of this application remained unchanged after long-term aging, while the antibacterial performance of the packaging materials in Comparative Examples 1-3 decreased. The applicant believes that the packaging material of this application has excellent resistance to photo-thermal aging, extremely low moisture absorption, and excellent oxygen barrier properties. Therefore, it can effectively prevent the antibacterial components from failing due to moisture and photo-thermal aging, and can ensure the long-term stability of antibacterial performance. In contrast, Comparative Example 1 uses a silver ion antibacterial system, and the packaging material has a high moisture absorption rate. After aging treatment, the packaging material will lose some of its antibacterial properties due to oxidation caused by moisture and photo-thermal aging, thus significantly reducing the antibacterial performance. The packaging material of Comparative Example 3 also has the same problem. Although it uses the cinnamaldehyde-grafted nano-titanium dioxide of this application, after aging, some of the cinnamaldehyde will decompose due to photo-thermal aging, thus losing its antibacterial properties. The packaging material of Comparative Example 2 has similar material properties to the embodiments of this application, except that it does not use cinnamaldehyde-grafted nano-titanium dioxide. Therefore, the antibacterial performance does not decrease significantly after aging treatment. The applicant believes that the slight difference in antibacterial performance is due to minor moisture absorption.

[0074] The applicant tested the packaging materials in accordance with relevant food safety regulations, and they fully comply with my country's relevant food safety regulations and are classified as food-grade materials.

[0075] The following is a migration experiment of the materials in this application.

[0076] The total migration of the materials from Examples 1 to 8 in four solvents—water, 4% acetic acid, ethanol, and n-hexane—was determined according to the method described in GB 31604.8-2016. The results are shown in Table 4 below.

[0077] Table 4. Sample Test Results

[0078] As can be seen from the results in Table 4, the packaging materials of Examples 1 to 8 of this application have excellent solvent migration resistance, and no harmful substances migrate to any of the four different solvents.

[0079] The following are the results of the long-term toxicity test for this application.

[0080] Seventy-two healthy adult rats were selected and divided into nine groups of eight rats each. There was one control group and eight sample groups.

[0081] The control group rats were fed and watered using laboratory standard feeding containers, while the eight sample groups were fed and watered using feeding containers made from the sample materials of Examples 1 to 8.

[0082] Rats were fed continuously for 3 months, and their weight changes were observed. Organ damage, blood routine and liver and kidney function indicators were tested every two weeks.

[0083] The test results are shown in Table 5 below.

[0084] Table 5. Long-term toxicity test results of Examples 1-8

[0085] As can be seen from the results in Table 5, the feeding containers prepared from the packaging materials of Examples 1 to 8 of this application showed no toxic effects on rats after long-term use, and there were no safety issues.

[0086] The following are the results of the acute toxicity test for this application.

[0087] Seventy-two healthy adult rats were selected and divided into nine groups of eight rats each. There was one control group and eight sample groups.

[0088] The materials from Examples 1 to 8 of this application were crushed into small pieces and fed to rats in sample groups 1 to 8 at a feeding dose of 5000 mg / kg, and acute toxicity reactions were monitored.

[0089] The test results are shown in Table 6 below.

[0090] Table 6. Acute toxicity test results of Examples 1-8

[0091] As can be seen from Table 6, the materials in Examples 1 to 8 of this application did not cause acute toxicity reactions when fed to rats, and fully meet the safety requirements for food packaging.

[0092] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A plastic packaging material for food, characterized in that, The mass proportions of the raw material components of the plastic packaging material include: 60 parts HDPE resin, 40-50 parts EVOH resin, 24-32 parts non-isocyanate polyurethane prepolymer, and 6-10 parts cinnamaldehyde-grafted nano-titanium dioxide; the mass proportions of the raw material components of the non-isocyanate polyurethane prepolymer include: 60-68 parts methyl 1,6-hexamethylenedicarbamate, 6-8 parts bio-based polyol, 10-16 parts eugenol, 1-3 parts ferric oxide, and 2-4 parts zinc acetate.

2. The food-grade plastic packaging material according to claim 1, characterized in that, The mass proportions of each raw material component in the plastic packaging material include: 60 parts HDPE resin, 42-44 parts EVOH resin, 28-30 parts non-isocyanate polyurethane prepolymer, and 8-8.6 parts cinnamaldehyde-grafted nano-titanium dioxide.

3. The food-grade plastic packaging material according to claim 1, characterized in that, The mass ratio of each raw material component in the non-isocyanate polyurethane prepolymer includes: 62-64 parts of methyl 1,6-hexamethylenedicarbamate, 6.8-7.2 parts of bio-based polyol, 14-14.6 parts of eugenol, 1.8-2.4 parts of ferric oxide, and 2.8-3.2 parts of zinc acetate.

4. The food-grade plastic packaging material according to claim 1, characterized in that, The preparation of cinnamaldehyde-grafted nano-titanium dioxide includes the following steps: S1-a, accurately weighing KH550 and nano-titanium dioxide according to a mass ratio of KH550 to nano-titanium dioxide of 3.8:2~10; S1-b, dissolving KH550 in 75% ethanol solution to prepare a solution with a concentration of 2.5~3g / L, mixing thoroughly, heating to 60℃ for at least 60min, then adding nano-titanium dioxide, and ultrasonically reacting for at least 60min to obtain a reaction mixture; S1-c, accurately weighing cinnamaldehyde according to an addition ratio of 50~60mL of cinnamaldehyde per 1g of nano-titanium dioxide, adding it to the reaction mixture of step S1-b, continuing ultrasonic reaction for at least 60min, then stirring for at least 32h, filtering out the solid product, washing with alcohol, and vacuum drying at 40℃ to constant weight to obtain cinnamaldehyde-grafted nano-titanium dioxide.

5. The food-grade plastic packaging material according to claim 4, characterized in that, The nano-titanium dioxide is selected from gas-phase nano-titanium dioxide.

6. The food-grade plastic packaging material according to claim 1, characterized in that, The preparation of methyl 1,6-hexamethylenedicarbamate includes the following steps: Sa, accurately weigh dimethyl carbonate and 1,6-hexanediamine at a molar ratio of 6~6.2:1, add sodium methoxide accounting for 1.5% of the total mass of 1,6-hexanediamine, mix thoroughly, and prepare a reaction solution; Sb, heat the reaction solution prepared in step Sa to 92℃, reflux for 6 hours, cool, wash the reaction solution with 2 times the volume of 45℃ warm water, filter out the solid product, and obtain crude methyl 1,6-hexamethylenedicarbamate; Sc, add anhydrous methanol to the crude methyl 1,6-hexamethylenedicarbamate obtained in step Sb until completely dissolved, obtain a solution, then add 5~6 times the volume of deionized water to the solution for recrystallization, filter out the crystals, dry, and obtain methyl 1,6-hexamethylenedicarbamate.

7. The food-grade plastic packaging material according to claim 6, characterized in that, In step Sc, the drying is carried out by vacuum drying at 60°C to constant weight.

8. The food-grade plastic packaging material according to claim 1, characterized in that, The zinc acetate used is silica-supported zinc acetate.

9. The food-grade plastic packaging material according to claim 1, characterized in that, The preparation of the non-isocyanate polyurethane prepolymer includes the following steps: S2-a, thoroughly mixing each raw material component in the formula amount to obtain a mixed reaction solution; S2-b, stirring the mixed reaction solution obtained in step S2-a at a temperature of 100~105℃ for more than 60 minutes under nitrogen protection, then raising the temperature to 160~165℃ and continuing the reaction for 1.5~2 hours, and after cooling, obtaining the non-isocyanate polyurethane prepolymer.

10. A method for preparing the food-grade plastic packaging material according to claim 1, characterized in that, Includes the following steps: S1. Prepare cinnamaldehyde-grafted nano-titanium dioxide; S2. Prepare non-isocyanate polyurethane prepolymer; S3. Accurately weigh HDPE resin, non-isocyanate polyurethane prepolymer, and cinnamaldehyde-grafted nano-titanium dioxide according to the formula, add them to a twin-screw extruder, and after melt dispersion, extrusion, cooling, and pelletizing, obtain food-grade plastic packaging material; The extrusion process parameters are as follows: the temperatures of the 6 temperature zones are 150~155℃, 155~160℃, 160~165℃, 165~170℃, 165~170℃, and 160~165℃ respectively.

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