Fresh fruit juice packaging film and preparation method thereof

Abstract

The invention belongs to the field of food packaging, and discloses a fresh fruit juice packaging film and a preparation method thereof, the fresh fruit juice packaging film comprises the following components by weight: 83.5%-84.5% of a polymer material, 9%-10% of an antibacterial agent, 0.5%-1% of an oxygen barrier, 0.3%-0.5% of a preservative, and 5.7%-6.7% of a function enhancer; the high polymer material is one or a combination of two of polyethylene (PE) and polypropylene (PP); according to the fresh fruit juice packaging film and the preparation method thereof, through innovative formula design and process optimization, the defects of an existing fresh fruit juice packaging film in the aspects of corrosion prevention, fresh keeping, processing performance and environmental protection are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of food packaging, in particular to a fresh juice packaging film and a preparation method thereof. Background Art

[0002] With growing consumer demand for healthy drinks, the fresh juice market continues to expand. However, fresh juice, rich in nutrients such as carbohydrates, proteins, and vitamins, is susceptible to spoilage due to microbial contamination, oxidation, and water loss. Traditional fresh juice packaging films, such as polyethylene (PE) and polypropylene (PP) films, while offering certain physical barrier properties, suffer from significant deficiencies in antimicrobial, oxygen barrier, and freshness preservation. On the one hand, ordinary packaging films lack effective antibacterial functions and are unable to inhibit the growth of harmful microorganisms such as Escherichia coli and Staphylococcus aureus, which makes fresh juice prone to microbial contamination during storage and transportation, shortening the shelf life of the product; on the other hand, their oxygen barrier properties are insufficient and cannot effectively isolate oxygen, causing the nutrients in the fresh juice to be oxidized and destroyed, affecting the taste and nutritional value; in addition, traditional packaging films have limited ability to retain moisture, which can easily cause fresh juice to lose moisture, resulting in a decline in product quality. To improve these problems, existing technologies attempt to add a single antibacterial agent or antioxidant to the packaging film. However, there are problems such as uneven dispersion of the additives and poor compatibility with the base material. It is impossible to achieve the synergistic optimization of multiple functions. In addition, the comprehensive performance of the packaging film is unstable, making it difficult to meet the needs of high-quality packaging of fresh fruit juice.

[0003] Therefore, the development of a fresh juice packaging film with high-efficiency antibacterial properties, good antioxidant preservation ability, excellent processing performance, safety and environmental protection is of great practical significance for promoting the development of the fresh juice industry, improving product quality and reducing food waste. Summary of the Invention

[0004] The purpose of the present invention is to provide a fresh juice packaging film and a preparation method thereof, which solves the deficiencies of existing fresh juice packaging films in terms of anti-corrosion and preservation, processing performance and environmental protection through innovative formula design and process optimization.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: The technical solution provided by the present invention is: a fresh juice packaging film, comprising the following components by weight percentage: 83.5%-84.5% of a polymer material, 9%-10% of an antibacterial agent, 0.5%-1% of an oxygen barrier agent, 0.3%-0.5% of a preservative, and 5.7%-6.7% of a functional enhancer; The polymer material is one or a combination of polyethylene (PE) and polypropylene (PP); The antibacterial agent comprises 2%-3% of nano-silver masterbatch, 10-20nm particle size, 1%-1.5% of nano-titanium dioxide masterbatch (anatase type, 20-50nm particle size), and 5.5%-6.5% of a natural antibacterial compound, wherein the natural antibacterial compound is a compound of chitosan and tea polyphenols in a weight ratio of 2:1-3:1, the chitosan deacetylation degree is ≥90%, and the tea polyphenols purity is ≥98%; The oxygen inhibitor is a composite system of vitamin E and phytic acid, with a weight ratio of 1:0.5-1:1; The preservative is a composite system of chitosan and phytic acid, with a weight ratio of 1:1-2:1; The functional enhancer includes 2%-3% of white carbon black, with a specific surface area of ≥150m² / g, 0.2%-0.3% of yeast inhibitor, wherein the yeast inhibitor is a 1:1 compound of potassium sorbate and sodium dehydroacetate, 3.5%-4.4% of antistatic masterbatch, and ethylene bisstearamide content of ≥20%.

[0006] Furthermore, the surface of the silica is modified with a silane coupling agent KH-570, and the amount of the modifier is 1%-3% of the weight of the silica.

[0007] Furthermore, the antistatic masterbatch and white carbon black form a network dispersion structure, and are mixed by a high-speed mixer at a rotation speed of 2000-3000 r / min to make the antistatic agent migration rate ≤5%.

[0008] A method for preparing a fresh juice packaging film comprises the following steps: S1: Surface modification of silica: Stir silica and silane coupling agent KH-570 at 80-100°C for 2-3 hours, then dry and set aside; S2: Pretreatment of natural antibacterial compound: Chitosan was dissolved in 1%-2% acetic acid solution, tea polyphenols were added and ultrasonically dispersed for 30 minutes to form a uniform aqueous phase, and then spray-dried to obtain composite masterbatch; S3: Multi-layer blending extrusion: Modified silica, antistatic masterbatch and polymer materials are first blended to form a base material layer, and then melt-blended with antimicrobial agent, antioxidant, preservative and yeast inhibitor through a twin-screw extruder (length-to-diameter ratio 32:1), with a screw temperature of 170-210°C and a speed of 180-220 r / min; S4: Gradient cooling film blowing: The film blank is blown into shape through a three-stage cooling air ring (temperatures are 60°C, 50°C, and 40°C, respectively), with a blowing ratio of 2-3:1 and a pulling speed of 10-15m / min; S5: UV-IR synergistic treatment: First perform UV curing (wavelength 254nm, power 100W / cm, irradiation time 20 seconds), then perform infrared heat treatment (temperature 70℃, time 40 minutes) to increase the crystallinity of the film to 35%-40%.

[0009] Furthermore, the thickness ratio of the substrate layer to the functional layer in S3 is 7:3, the substrate layer contains 80%-85% of the total polymer material, all white carbon black and antistatic masterbatch, and the functional layer contains all antibacterial agents, antioxidants, preservatives, yeast inhibitors and polymer materials accounting for 15%-20% of the total polymer material.

[0010] A fresh-keeping bag is prepared from the fresh-keeping film of the present invention.

[0011] The beneficial effects of this technical solution are: (1) Nano-silver masterbatch, nano-titanium dioxide masterbatch and natural antibacterial compound work synergistically. Nano-silver and nano-titanium dioxide destroy the cell membrane of microorganisms through contact, and the natural antibacterial compound (chitosan and tea polyphenols) inhibits microbial metabolism and antioxidant effects. The three complement each other, and the inhibition rate against Escherichia coli and Staphylococcus aureus is ≥99.8%, and the yeast inhibition rate is ≥98%, which effectively prevents fresh fruit juice from being contaminated and deteriorated by microorganisms.

[0012] (2) The antioxidant (vitamin E and phytic acid composite system) and the preservative (chitosan and phytic acid composite system) work synergistically. The antioxidant properties of vitamin E and chitosan are combined with the metal ion chelating ability of phytic acid to reduce the oxygen permeability to ≤30cm³ / (m²·24h·0.1MPa) and the water vapor permeability to ≤8g / (m²·24h), thereby inhibiting the oxidation and water loss of juice and maintaining the flavor and nutritional content of the juice.

[0013] (3) After being modified with a silane coupling agent, silica forms a stable network dispersion structure with the antistatic masterbatch, and the antistatic agent migration rate is ≤5%, ensuring that the antistatic performance of the packaging film is long-lasting; at the same time, the multi-layer blending extrusion and gradient cooling film blowing process make the components evenly dispersed, the film structure is dense, and the performance is stable.

[0014] (4) By rationally designing the proportions of each component and the preparation process, the packaging film has multiple functions such as antibacterial, oxygen barrier, freshness preservation, and antistatic. The surface resistivity is ≤10^9Ω, which avoids electrostatic adsorption of dust and adhesion, improves the user experience, and meets the high-quality packaging requirements of fresh juice. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a data sheet of Example 1 of a fresh juice packaging film proposed by the present invention; Figure 2 This is a data sheet for Example 2 of a fresh juice packaging film proposed by the present invention; Figure 3 This is a data sheet for Example 3 of a fresh juice packaging film proposed by the present invention; Figure 4 This is a data sheet for Example 4 of a fresh juice packaging film proposed by the present invention; Figure 5 This is a data sheet for Example 5 of a fresh juice packaging film proposed by the present invention; Figure 6 This is a data sheet for Example 6 of a fresh juice packaging film proposed by the present invention; Figure 7 This is a comparison table of the differences between various embodiments of a fresh juice packaging film proposed by the present invention; Figure 8 This is a comparison table of test data of an embodiment of a fresh juice packaging film proposed by the present invention; Figure 9 The following is a comparison table of data between the technical embodiment of the fresh juice packaging film proposed by the present invention and the prior art. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] The specific implementation process is as follows: Example 1: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a fresh juice packaging film preparation method, comprising the following steps: S1: Surface modification of silica: 20 g silica (specific surface area 150 m² / g) was weighed and placed in a reactor. 0.2 g silane coupling agent KH-570 was added. The mixture was stirred at 80°C and 200 r / min for 2 hours. After the reaction, the mixture was transferred to a vacuum drying oven and dried at 60°C for 12 hours to obtain modified silica for later use. S2: Pretreatment of the natural antibacterial compound: Weigh 10g of chitosan (90% deacetylation degree) and dissolve it in 500ml of 1% acetic acid solution, stirring until completely dissolved; add 5g of tea polyphenols (98% purity) and place it in an ultrasonic cleaner. Ultrasonic dispersion is carried out at a frequency of 40kHz for 30 minutes to form a uniform aqueous phase; the aqueous phase is transferred to a spray dryer with an inlet air temperature of 180℃ and an outlet air temperature of 80℃, and spray-dried to obtain a natural antibacterial composite masterbatch; S3: Multi-layer co-extrusion: 835 g of polyethylene (PE) was weighed as the polymer material, and the modified silica and 35 g of antistatic masterbatch (ethylene bisstearamide content 20%) were added thereto. The mixture was mixed in a high-speed mixer at 2000 rpm for 10 minutes to form a substrate layer mixture. Separately, 20 g of nano-silver masterbatch (particle size 10 nm), 10 g of nano-titanium dioxide masterbatch (anatase type, particle size 20 nm), and 55 g of natural antibacterial composite masterbatch were weighed as antibacterial agents. 5g of vitamin E and 5g of phytic acid were used as antioxidants; 3g of chitosan and 3g of phytic acid were used as preservatives; 2g of potassium sorbate and 2g of sodium dehydroacetate were used as yeast inhibitors; the antimicrobial agent, antioxidant, preservative, and yeast inhibitor were mixed with the remaining 165g of PE and fed into a twin-screw extruder (length-to-diameter ratio 32:1) together with the substrate layer mixture. The screw temperatures were set at 170°C, 180°C, 190°C, 200°C, and 210°C, respectively, and the speed was 180r / min for melt blending and extrusion. S4: Gradient cooling film blowing: The extruded film blank passes through a three-stage cooling air ring, with the first stage air ring temperature at 60°C, the second stage at 50°C, and the third stage at 40°C. The blowing ratio is 2:1, the pulling speed is 10m / min, and the film is blown into shape. S5: UV-IR synergistic treatment: The formed packaging film is first cured by UV radiation, using a wavelength of 254nm and a power of 100W / cm2 for 20 seconds, and then placed in an infrared heat treatment device at 70°C for 40 minutes to increase the film's crystallinity to 35%; In Example 1, 835g of polyethylene (PE) was used as the polymer material. By adding specific proportions of antimicrobial agents, oxygen inhibitors, preservatives, and functional enhancers, and coordinating with a comprehensive preparation process, the packaging film had significant beneficial effects. Among the antimicrobial agents, nanosilver masterbatch, nanotitanium dioxide masterbatch, and natural antimicrobial compound worked synergistically to achieve an inhibition rate of ≥99.8% against Escherichia coli and Staphylococcus aureus, and a yeast inhibition rate of ≥98%, effectively preventing fresh juice from being contaminated by microorganisms. The oxygen inhibitor (vitamin E and phytic acid composite system) and the preservative (chitosan and phytic acid composite system) worked synergistically to achieve an oxygen permeability as low as 28cm³ / (m²·24h·0.1MPa) and a water vapor permeability of 7.5g / (m²·24h), inhibiting juice oxidation and water loss. After being modified with 1% silane coupling agent KH-570, silica formed a network dispersed structure with 35g of antistatic masterbatch, with a surface resistivity of 8.5×10 8 Ω, good and stable antistatic performance; through multi-layer blending extrusion, gradient cooling film blowing and UV-infrared coordinated treatment process, the film crystallinity reaches 35%, the various components are evenly dispersed, the film structure is dense, and the comprehensive performance is excellent, meeting the high-quality packaging needs of fresh juice.

[0018] Example 2: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a fresh juice packaging film preparation method, comprising the following steps: S1: Surface modification of silica: Weigh 25g silica (specific surface area 160m² / g), add 0.5g silane coupling agent KH-570, and stir at 90℃ for 2.5 hours. After the reaction, dry in a vacuum drying oven at 65℃ for 10 hours to obtain modified silica. S2: Pretreatment of natural antibacterial compound: 12g chitosan (92% deacetylation) was dissolved in 600ml 1.5% acetic acid solution, 4g tea polyphenols (98% purity) were added, ultrasonically dispersed for 30 minutes, and spray dried (inlet air 185℃, outlet air 85℃) to prepare composite masterbatch; S3: Multi-layer blending extrusion: 840g of polypropylene (PP) was weighed and mixed with modified silica and 40g of antistatic masterbatch (ethylene bisstearamide content 22%) in a high-speed mixer at 2500r / min for 12 minutes to form a substrate layer; 25g of nano-silver masterbatch (particle size 15nm), 12g of nano-titanium dioxide masterbatch (anatase type, particle size 30nm), and 60g of natural antibacterial composite masterbatch were taken as antibacterial agents; 6g of vitamin E and 6g of phytic acid were taken as antioxidants; 3.5g of chitosan and 3.5g of phytic acid were taken as preservatives; 2.5g of potassium sorbate and 2.5g of sodium dehydroacetate were taken as yeast inhibitors; after mixing with the remaining 160g of PP, the mixture and the substrate layer were fed into a twin-screw extruder (length-to-diameter ratio 32:1) with the screw temperatures at 175℃, 185℃, 195℃, 205℃, and 210℃ and the speed at 200r / min for melt blending; S4: Gradient cooling film blowing: The film blank is blown into shape through three-stage cooling air ring (60℃, 50℃, 40℃), with a blowing ratio of 2.5:1 and a pulling speed of 12m / min; S5: UV-IR synergistic treatment: The packaging film is first irradiated with UV light at a wavelength of 254nm and a power of 100W / cm for 20 seconds, and then infrared treatment is performed at 70℃ for 40 minutes. The crystallinity of the film reaches 36%; In Example 2, 840g of polypropylene (PP) was used as the polymer material. The optimization of the formulation and process brought outstanding beneficial effects. The proportion of nanosilver masterbatch in the antibacterial agent was relatively increased, which enhanced the antibacterial ability. Nano-titanium dioxide masterbatch and natural antibacterial compound were combined to ensure efficient inhibition of microorganisms. White carbon black was modified with 2% of silane coupling agent KH-570 and 40g of antistatic masterbatch was used to form a more stable network dispersion structure, and the surface resistivity was reduced to 8.2×10 8Ω, and the antistatic performance is further improved; the synergistic effect of the oxygen barrier and preservative increases the oxygen permeability to 27cm³ / (m²·24h·0.1MPa) and the water vapor permeability to 7.2g / (m²·24h), effectively extending the shelf life of fresh juice; in terms of preparation technology, by adjusting parameters such as the twin-screw extruder temperature, blow-up ratio and traction speed, and through ultraviolet-infrared synergistic treatment, the film crystallinity is increased to 36%, improving the mechanical properties and stability of the packaging film. At the same time, it has excellent antibacterial, oxygen barrier, preservation and antistatic functions, providing high-quality packaging protection for fresh juice.

[0019] Example 3: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a preparation method of fresh juice packaging film, comprising the following steps: S1: Surface modification of silica: 30 g silica (specific surface area 170 m² / g) was weighed, 0.9 g silane coupling agent KH-570 was added, stirred at 100°C for 3 hours, and vacuum dried at 70°C for 8 hours to obtain modified silica; S2: Pretreatment of natural antibacterial compound: 15g chitosan (95% deacetylation) was dissolved in 750ml 2% acetic acid solution, 5g tea polyphenols (98% purity) were added and ultrasonically dispersed, and spray dried (inlet air 190℃, outlet air 90℃) to prepare composite masterbatch; S3: Multi-layer blending extrusion: 835g PE and 835g PP were mixed in a ratio of 1:1, and mixed with modified silica and 44g antistatic masterbatch (ethylene bisstearamide content 25%) at a high speed of 2800r / min for 15 minutes to form a substrate layer; 30g nano-silver masterbatch (particle size 20nm), 15g nano-titanium dioxide masterbatch (anatase type, particle size 50nm), and 65g natural antibacterial composite masterbatch were taken as antibacterial agents; 8g vitamin E and 8g phytic acid were used as antioxidants; 4g chitosan and 4g phytic acid were used as preservatives; 3g potassium sorbate and 3g sodium dehydroacetate were used as yeast inhibitors; and the mixture was put into a twin-screw extruder (length-to-diameter ratio 32:1) together with the remaining 165g mixed polymer materials, and melt blended at screw temperatures of 180℃, 185℃, 195℃, 205℃, and 210℃, and a speed of 220r / min; S4: Gradient cooling film blowing: The film blank is blown into shape through three-stage cooling air ring (60℃, 50℃, 40℃), with a blowing ratio of 3:1 and a pulling speed of 15m / min; S5: UV-IR synergistic treatment: The packaging film is irradiated with UV light at a wavelength of 254nm and a power of 100W / cm for 20 seconds, and then treated with infrared light at 70℃ for 40 minutes. The crystallinity of the film reaches 38%; Example 3 uses polyethylene (PE) and polypropylene (PP) mixed in a ratio of 1:1 as the polymer material, combined with a unique formula and process to achieve multiple beneficial effects; the proportion of nanosilver masterbatch in the antibacterial agent reaches 30%, which synergizes with other antibacterial ingredients to enhance the antibacterial performance and ensure that the fresh juice is protected from microbial invasion; 3% of the white carbon black modification amount and 44g of antistatic masterbatch make the antistatic agent have low migration rate and a surface resistivity of 8×10 8 Ω, with a long-lasting and stable antistatic effect; the optimized combination of oxygen inhibitors and preservatives reduces the oxygen permeability to 26cm³ / (m²·24h·0.1MPa) and the water vapor permeability to 7g / (m²·24h), effectively maintaining the freshness and nutritional content of the juice; during the preparation process, the temperature setting of the twin-screw extruder, a large blow-up ratio and traction speed, and UV-infrared synergistic treatment achieve a film crystallinity of 38%, which not only ensures the uniform dispersion of the packaging film components, but also improves the film's strength and barrier properties. The overall performance is excellent, meeting the packaging requirements for long-term storage and transportation of fresh juice.

[0020] Example 4: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a fresh juice packaging film preparation method, comprising the following steps: S1: Surface modification of silica: 22 g silica (specific surface area 155 m² / g) was weighed, 0.3 g silane coupling agent KH-570 was added, stirred at 85°C for 2 hours, and vacuum dried at 62°C for 11 hours to obtain modified silica; S2: Pretreatment of natural antibacterial compound: 11g chitosan (91% deacetylation) was dissolved in 550ml 1.2% acetic acid solution, and 3.7g tea polyphenols (98% purity) were added and ultrasonically dispersed. The mixture was then spray-dried (inlet air 182°C, outlet air 82°C) to prepare composite masterbatch. S3: Multi-layer blending extrusion: 842g PE was mixed with modified silica and 38g antistatic masterbatch (ethylene bisstearamide content 21%) at 2200r / min for 11 minutes to form a substrate layer; 22g nanosilver masterbatch (particle size 12nm), 11g nanotitanium dioxide masterbatch (anatase type, particle size 25nm), and 58g natural antibacterial composite masterbatch were taken as antibacterial agents; 5.5g vitamin E and 5.5g phytic acid were used as antioxidants; 3.2g chitosan and 3.2g phytic acid were used as preservatives; 2.2g potassium sorbate and 2.2g sodium dehydroacetate were used as yeast inhibitors; after mixing with the remaining 158g PE, the mixture was put into a twin-screw extruder (length-to-diameter ratio 32:1) and melt blended at screw temperatures of 172℃, 182℃, 192℃, 202℃, and 210℃, and a speed of 190r / min; S4: Gradient cooling film blowing: The film blank is blown into shape through three-stage cooling air ring (60℃, 50℃, 40℃), with a blow-up ratio of 2.2:1 and a pulling speed of 11m / min; S5: UV-IR synergistic treatment: The packaging film is irradiated with UV light at a wavelength of 254nm and a power of 100W / cm for 20 seconds, and then treated with infrared light at 70℃ for 40 minutes. The crystallinity of the film reaches 37%; In Example 4, 842g of polyethylene (PE) was used as the polymer material. The design of the formulation and process details gave the packaging film good performance. The reasonable ratio of the antibacterial agent allowed the nano-silver masterbatch, nano-titanium dioxide masterbatch and natural antibacterial compound to work together to achieve a high antibacterial effect. The 1.36% modified amount of white carbon black and 38g of antistatic masterbatch formed a stable network structure with a surface resistivity of 8.3×10 8 Ω, with reliable antistatic performance; the oxygen barrier and preservative work synergistically, with an oxygen permeability of 27.5cm³ / (m²·24h·0.1MPa) and a water vapor permeability of 7.3g / (m²·24h), effectively inhibiting juice oxidation and water loss; by controlling process parameters such as the twin-screw extruder speed, blow-up ratio, and traction speed, and through UV-infrared synergistic treatment, the film crystallinity reaches 37%, ensuring the quality stability of the packaging film. The film has excellent antibacterial, oxygen barrier, freshness-preserving, and antistatic properties, and can provide effective packaging protection for fresh juice.

[0021] Embodiment 5: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a fresh juice packaging film preparation method, comprising the following steps: S1: Surface modification of silica: 28 g silica (specific surface area 165 m² / g) was weighed, 0.7 g silane coupling agent KH-570 was added, stirred at 95°C for 2.8 hours, and vacuum dried at 68°C for 9 hours to obtain modified silica; S2: Pretreatment of natural antibacterial compound: 14g chitosan (94% deacetylation) was dissolved in 700ml 1.8% acetic acid solution, and 4.7g tea polyphenols (98% purity) were added and ultrasonically dispersed. The mixture was then spray-dried (inlet air 188°C, outlet air 88°C) to prepare composite masterbatch. S3: Multi-layer blending extrusion: 845g PP was mixed with modified silica and 42g antistatic masterbatch (ethylene bisstearamide content 23%) at 2700r / min for 13 minutes to form a substrate layer; 28g nanosilver masterbatch (particle size 18nm), 14g nanotitanium dioxide masterbatch (anatase type, particle size 40nm), and 63g natural antibacterial composite masterbatch were taken as antibacterial agents; 7g vitamin E and 7g phytic acid were used as antioxidants; 3.8g chitosan and 3.8g phytic acid were used as preservatives; 2.8g potassium sorbate and 2.8g sodium dehydroacetate were used as yeast inhibitors; after mixing with the remaining 155g PP, the mixture was put into a twin-screw extruder (length-to-diameter ratio 32:1) and melt blended at screw temperatures of 178℃, 188℃, 198℃, 208℃, and 210℃, and a speed of 210r / min; S4: Gradient cooling film blowing: The film blank is blown into shape through three-stage cooling air ring (60℃, 50℃, 40℃), with a blowing ratio of 2.8:1 and a pulling speed of 13m / min; S5: UV-IR synergistic treatment: The packaging film is first irradiated with UV light at a wavelength of 254nm and a power of 100W / cm for 20 seconds, and then infrared treatment is performed at 70℃ for 40 minutes. The crystallinity of the film reaches 39%; In Example 5, 845g of polypropylene (PP) was selected as the polymer material. The advantages of its formula and process were reflected in significant beneficial effects. The nanosilver masterbatch accounted for 28% of the antibacterial agent, and combined with other antibacterial ingredients, it had a significant inhibitory effect on microorganisms. The 2.5% white carbon black modification amount and 42g of antistatic masterbatch further optimized the antistatic performance, and the surface resistivity was 7.8×10 8 Ω, with strong and long-lasting antistatic ability; the synergistic combination of oxygen barrier and preservative reduces the oxygen permeability to 25.5cm³ / (m²·24h·0.1MPa) and the water vapor permeability to 6.8g / (m²·24h), greatly improving the oxygen barrier and preservation properties of the packaging film; in terms of preparation technology, the precise setting of the twin-screw extruder temperature, the specific blow-up ratio and traction speed, and the UV-infrared synergistic treatment enable the film to achieve a crystallinity of 39%, improving the density and mechanical strength of the packaging film. The film has excellent overall performance, can effectively extend the shelf life of fresh juice, and meet the market demand for high-quality fresh juice packaging.

[0022] Example 6: See also Figure 1-9 The present invention provides a typical ratio packaging film preparation scheme: a fresh juice packaging film preparation method, comprising the following steps: S1: Surface modification of silica: Weigh 24 g silica (specific surface area 158 m² / g), add 0.48 g silane coupling agent KH-570, and stir at 88°C for 2.2 hours. After the reaction, transfer the mixture to a vacuum drying oven and dry at 63°C for 11.5 hours to obtain modified silica for later use. S2: Pretreatment of the natural antibacterial compound: Weigh 13g of chitosan (93% deacetylation degree) and dissolve it in 650ml of 1.3% acetic acid solution, stirring until completely dissolved; add 4.3g of tea polyphenols (98% purity) and place it in an ultrasonic cleaner. Ultrasonic dispersion is carried out at a frequency of 40kHz for 30 minutes to form a uniform aqueous phase; the aqueous phase is transferred to a spray dryer with an inlet air temperature of 183°C and an outlet air temperature of 83°C, and spray-dried to obtain a natural antibacterial composite masterbatch; S3: Multi-layer co-extrusion: 838 g of polyethylene (PE) and 838 g of polypropylene (PP) were weighed and mixed as polymer materials, and the modified silica and 40.4 g of antistatic masterbatch (ethylene bisstearamide content 22%) were added thereto. The mixture was mixed in a high-speed mixer at 2400 r / min for 12 minutes to form a substrate layer mixture. 24 g of nano-silver masterbatch (particle size 14 nm), 12 g of nano-titanium dioxide masterbatch (anatase type, particle size 28 nm), and 62 g of natural antibacterial composite masterbatch were also weighed as antibacterial agents. 0.5g vitamin E and 7.5g phytic acid as antioxidants; 3.6g chitosan and 3.6g phytic acid as preservatives; 2.6g potassium sorbate and 2.6g sodium dehydroacetate as yeast inhibitors; the antimicrobial agent, antioxidant, preservative, and yeast inhibitor were mixed with the remaining 162g mixed polymer material and fed into a twin-screw extruder (length-to-diameter ratio 32:1) together with the substrate layer mixture. The screw temperatures were set to 173°C, 183°C, 193°C, 203°C, and 210°C, respectively, and the speed was 195r / min for melt blending and extrusion. S4: Gradient cooling film blowing: The extruded film blank passes through a three-stage cooling air ring, with the first stage air ring temperature at 60°C, the second stage at 50°C, and the third stage at 40°C. The blow-up ratio is 2.3:1, the pulling speed is 12m / min, and the film is blown into shape. S5: UV-IR synergistic treatment: The formed packaging film is first cured by UV radiation with a wavelength of 254nm and a power of 100W / cm for 20 seconds, and then placed in an infrared heat treatment device at 70°C for 40 minutes to increase the crystallinity of the film to 37.5%; Example 6 uses a polymer material mixed with polyethylene (PE) and polypropylene (PP) to achieve good packaging performance through a carefully designed formula and process. The scientific ratio of the antimicrobial agent ensures high inhibition of Escherichia coli, Staphylococcus aureus, and yeast. The 2% silica modification amount and 40.4g antistatic masterbatch form a stable antistatic network structure with a surface resistivity of 8.1×10 8Ω, with stable antistatic properties; the synergistic effect of oxygen barrier and preservatives achieves an oxygen permeability of 26.5cm³ / (m²·24h·0.1MPa) and a water vapor permeability of 7.1g / (m²·24h), effectively protecting fresh juice from oxidation and water loss; during the preparation process, by controlling the temperature, speed, blow-up ratio, and traction speed of the twin-screw extruder, combined with UV-infrared synergistic treatment, the film crystallinity reaches 37.5%, ensuring uniform distribution of the packaging film components and excellent physical properties. The film has excellent antibacterial, oxygen barrier, freshness-preserving, and antistatic properties, providing a reliable packaging solution for fresh juice.

[0023] See also Figure 1-9 By analyzing the performance data comparison table of each embodiment and the performance data comparison table of the embodiment and the prior art, combined with specific examples, the present technology has demonstrated significant progress in the field of fresh juice packaging film, as shown in the following: In each embodiment, a synergistic antibacterial system of nanosilver masterbatch, nanotitanium dioxide masterbatch and natural antibacterial compound is used. For example, in Examples 1-6, the antibacterial rate reaches ≥99.8%, and the yeast inhibition rate reaches ≥98%. This is due to the destructive effect of nanosilver and nanotitanium dioxide on microbial cell membranes, and the inhibition and antioxidant capacity of chitosan and tea polyphenols on microbial metabolism. In comparison, the antibacterial rate of the packaging film in the prior art is only 90%-95%, and the yeast inhibition rate is around 90%. The antibacterial system of this technology can more effectively inhibit the growth of harmful microorganisms such as Escherichia coli and Staphylococcus aureus, as well as yeast reproduction, greatly reducing the risk of fresh juice being contaminated and deteriorated by microorganisms and significantly extending the shelf life of the juice. According to the data from the examples, the oxygen permeability of the packaging film of this technology ranges from 25.5-28 cm³ / (m²·24h·0.1MPa), and the water vapor permeability ranges from 6.8-7.5 g / (m²·24h). Taking Example 3 as an example, the synergistic effect of the vitamin E and phytic acid composite oxygen barrier and the chitosan and phytic acid composite preservative effectively reduces the permeation of oxygen and water vapor, thereby reducing juice oxidation and water loss. In contrast, the oxygen permeability of the packaging film of the prior art is as high as 50-80 cm³ / (m²·24h·0.1MPa), and the water vapor permeability is 10-15 g / (m²·24h). This technology can better maintain the flavor, color, and nutritional content of fresh juice, meeting the strict packaging requirements of high-quality fresh juice. In each embodiment, a network dispersion structure is formed by surface modification of white carbon black and antistatic masterbatch, thereby achieving stable antistatic performance. For example, in Example 2, the amount of white carbon black modification is 2%, the amount of antistatic masterbatch is 40g, and the surface resistivity reaches 8.2×10 8 Ω, and the antistatic agent migration rate is ≤5%; in contrast, the existing technology, the packaging film has no stable antistatic effect, and the surface resistivity is usually >10 12Ω, antistatic agents are prone to migration and loss; this technology effectively solves the problems of packaging films adsorbing dust and easily sticking due to static electricity, and improves the convenience and hygiene of packaging films; This technology significantly improves the crystallinity of the film through processes such as ultraviolet-infrared synergistic treatment. In the examples, the film crystallinity ranges from 35% to 39%. For example, after treatment in Example 5, the crystallinity is increased to 39%, making the film structure denser and enhancing mechanical properties, while also helping to further improve barrier properties. However, the existing technology lacks a targeted process to improve film crystallinity, resulting in deficiencies in the strength and barrier properties of the packaging film. The packaging film of this technology is not a superposition of single functions, but rather a synergistic effect of various functional additives under reasonable formulation and process. As can be seen from the data in the examples, while having excellent antibacterial, oxygen barrier and fresh-keeping, and antistatic properties, various aspects of the performance cooperate with each other. For example, the antibacterial property creates a good microbial environment for oxygen barrier and fresh-keeping, and the stable antistatic property prevents the packaging process and product appearance from being affected by static electricity interference. The existing technology has a single function and it is difficult to achieve the synergy of multiple functions, and cannot meet the comprehensive needs of fresh juice packaging.

[0024] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A fresh juice packaging film, characterized in that: Calculated by weight percentage, it includes the following components: polymer material 83.5%-84.5%, antibacterial agent 9%-10%, antioxidant 0.5%-1%, preservative 0.3%-0.5%, functional enhancer 5.7%-6.7%; The polymer material is one or a combination of polyethylene (PE) and polypropylene (PP); The antibacterial agent comprises 2%-3% of nano-silver masterbatch, 1%-1.5% of nano-titanium dioxide masterbatch, and 5.5%-6.5% of a natural antibacterial compound, wherein the natural antibacterial compound is a compound of chitosan and tea polyphenols in a weight ratio of 2:1-3:1, the deacetylation degree of chitosan is ≥90%, and the purity of tea polyphenols is ≥98%; The oxygen inhibitor is a composite system of vitamin E and phytic acid, with a weight ratio of 1:0.5-1:1; The preservative is a composite system of chitosan and phytic acid, with a weight ratio of 1:1-2:1; The functional enhancer includes 2%-3% of white carbon black, with a specific surface area of ≥150m² / g, 0.2%-0.3% of yeast inhibitor, wherein the yeast inhibitor is a mixture of potassium sorbate and sodium dehydroacetate in a weight ratio of 1:1, 3.5%-4.4% of antistatic masterbatch, and ethylene bisstearamide content of ≥20%.

2. The fresh juice packaging film according to claim 1, characterized in that: The surface of the white carbon black is modified by a silane coupling agent KH-570, and the amount of the modifier used is 1%-3% of the weight of the white carbon black.

3. The fresh juice packaging film according to claim 1, characterized in that: The antistatic masterbatch and white carbon black form a network dispersion structure and are mixed by a high-speed mixer at a rotation speed of 2000-3000 r / min to make the antistatic agent migration rate ≤5%.

4. A method for preparing a fresh juice packaging film according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Surface modification of silica: Stir silica and silane coupling agent KH-570 at 80-100°C for 2-3 hours, then dry and set aside; S2: Pretreatment of natural antibacterial compound: Chitosan was dissolved in 1%-2% acetic acid solution, tea polyphenols were added and ultrasonically dispersed for 30 minutes to form a uniform aqueous phase, and then spray-dried to obtain composite masterbatch; S3: Multi-layer blending extrusion: Modified silica, antistatic masterbatch and polymer materials are first blended to form a base material layer, and then melt-blended with antimicrobial agent, antioxidant, preservative and yeast inhibitor through a twin-screw extruder (length-to-diameter ratio 32:1), with a screw temperature of 170-210°C and a speed of 180-220 r / min; S4: Gradient cooling film blowing: The film blank is blown into shape through a three-stage cooling air ring (temperatures are 60°C, 50°C, and 40°C, respectively), with a blowing ratio of 2-3:1 and a pulling speed of 10-15m / min; S5: UV-IR synergistic treatment: First perform UV curing (wavelength 254nm, power 100W / cm, irradiation time 20 seconds), then perform infrared heat treatment (temperature 70℃, time 40 minutes) to increase the crystallinity of the film to 35%-40%.

5. The preparation method according to claim 4, characterized in that The thickness ratio of the substrate layer to the functional layer in S3 is 7:

3. The substrate layer contains 80%-85% of the total polymer material, all white carbon black and antistatic masterbatch, and the functional layer contains all antibacterial agents, antioxidants, preservatives, yeast inhibitors and polymer materials accounting for 15%-20% of the total polymer material.

6. A fresh-keeping bag, made from the fresh-keeping film according to any one of claims 1 to 3.

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