Living physical preservative film and production system

Abstract

The invention discloses a living body physical preservative film and a production system, and relates to the technical field of preservative films. The preparation process comprises the following steps: S1, raw material pretreatment: S11, preparation of ZIF-8 coated SiO2 nanoparticles; s12, sulfonated carbon nano tube treatment; s2, master batch preparation: S21, premix preparation; pS and SEBS are added into a mixer and stirred, the S-CNT ethanol dispersion liquid is slowly sprayed in the process, stirring continues until ethanol is volatilized, ZIF-8 coated SiO2 is added, and the mixture is mixed and sieved. The preservative film allows nitrogen to slowly enter a package to maintain a high-nitrogen environment, and only allows a trace amount of oxygen to permeate, so that the lowest respiration requirement of fruits can be met, and decay caused by excessive oxygen is avoided; meanwhile, dynamic balance can be achieved, after the fruits breathe and consume oxygen, the film further inhibits oxygen supplementation, a low-oxygen-high-nitrogen stable state is formed, and manual intervention is not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of fresh-keeping films, and in particular to a living physical fresh-keeping film and a production system. Background Art

[0002] In the field of food preservation, especially for the storage of perishable fruits, maintaining a suitable atmospheric environment is key to extending shelf life and preserving food quality. Traditional preservation methods, such as refrigeration and modified atmosphere packaging (which adjusts the gas composition within the package, such as increasing nitrogen and reducing the oxygen ratio), can delay food spoilage to a certain extent, but they still have many limitations. For example, modified atmosphere packaging typically requires pre-filling with a specific ratio of gas and relies on highly sealed packaging materials to maintain the internal environment. This not only increases operational complexity and cost, but can also significantly reduce the preservation effect due to package damage or poor sealing.

[0003] Furthermore, even with modified atmosphere packaging, the ratio of gases within the package will change over time due to the fruit's respiration, leading to a gradual increase in oxygen content and accumulation of carbon dioxide, which in turn accelerates the aging and spoilage of the fruit. Therefore, developing a preservation technology that can automatically regulate gas exchange while maintaining a stable "low oxygen, high nitrogen" state over the long term has become a pressing issue in the food preservation field.

[0004] After searching, the Chinese patent application number CN202010538694.X discloses a process for preparing antibacterial wrapping cling film, which specifically involves an antibacterial wrapping cling film preparation device, including a device table, a clamping mechanism, a material return mechanism, a fixed-length adjustment mechanism, a slitting mechanism, an auxiliary guiding mechanism and an auxiliary blanking mechanism. The clamping machine includes a cylinder and three clamping assemblies arranged on the cylindrical surface of the cylinder. The fixed-length adjustment mechanism includes a handwheel screw, two scale guide rods with length scales and a gantry. The auxiliary guiding mechanism includes two clamping and guiding assemblies. The preparation process in the above patent has the following shortcomings: the prepared cling film has certain functionality, but does not have the ability to regulate gas exchange and cannot keep the fruit fresh for a long time. Summary of the Invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a living physical preservative film and a production system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A living physical cling film, the preparation process of which comprises the following steps:

[0008] S1: Raw material pretreatment, as follows:

[0009] S11: Preparation of ZIF-8@SiO2 nanoparticles;

[0010] S12: sulfonated carbon nanotube treatment;

[0011] S2: Masterbatch preparation, as follows:

[0012] S21: Premix preparation: PS and SEBS are added to the mixer and stirred. During the process, the S-CNT ethanol dispersion is slowly sprayed in. Stirring is continued until the ethanol evaporates. ZIF-8@SiO2 is added, mixed, and sieved;

[0013] S22: Twin-screw extrusion granulation; preheat to the set temperature, start the main machine, cut into pellets, water-cool, centrifuge dehydration, dehydration and drying;

[0014] S3: film blowing.

[0015] Preferably, the ZIF-8@SiO2 nanoparticles are prepared as follows:

[0016] S111: ZIF-8 activation: 50 g of ZIF-8 was placed in a vacuum oven and dehydrated at 120 °C for 2 h.

[0017] S112: SiO2 sol coating, the activated ZIF-8 was dispersed in 200 mL of ethanol and sonicated for 30 min;

[0018] S113: Add 10 mL of TEOS and 5 mL of aqueous ammonia, and stir at 45°C for 6 hours.

[0019] S114: Centrifugation, washing with ethanol three times, and drying at 80°C for 12 hours to obtain ZIF-8@SiO2.

[0020] Preferably, the sulfonated carbon nanotubes are treated as follows:

[0021] S121: Add 10 g of multi-walled carbon nanotubes to 100 mL of concentrated sulfuric acid and stir at 80°C for 4 hours;

[0022] S122: Slowly add 5 g of potassium permanganate and continue the reaction for 2 hours;

[0023] S123: After dilution, filter and wash with deionized water until the pH reaches 7 to obtain S-CNT;

[0024] S124: vacuum dried at 60°C for 24 hours, ground through a 200-mesh sieve;

[0025] S125: Ultrasonic dispersion in ethanol for 30 minutes before use.

[0026] Preferably: in the preparation of the premix, the specific formula includes:

[0027] 87 parts of PS particles, 6 parts of ZIF-8@SiO2, 5 parts of S-CNT dispersion, and 2 parts of SEBS;

[0028] Among them, the twin-screw extruder, the temperature of zone 1 is controlled at 160℃, the temperature of zone 2 is controlled at 180℃, the temperature of zone 3 is controlled at 195℃, the temperature of zone 4 is controlled at 185℃, the temperature of zone 5 is controlled at 190℃, and the die head temperature is controlled at 185℃;

[0029] The speed of the twin-screw extruder was controlled at 250 rpm, the feeding rate was controlled at 20 kg / h, the water cooling temperature was controlled at 12-18° C., and the mixture was dried at 50° C. for 4 hours after centrifugal dehydration.

[0030] Preferably, the film blowing molding specifically comprises the following steps:

[0031] S31: Heat to the set temperature and keep constant temperature for 1 hour; add masterbatch to the hopper and start slow feeding;

[0032] S32: When the melt flows out of the die head evenly, lead the film to the traction roller and slowly introduce compressed air to form a stable film bubble. Adjust the wind speed of the air ring to keep the frost line height 30 cm above the die head.

[0033] S33: Adjust the thickness to 25±2μm by adjusting the air pressure inside the bubble and the pulling speed;

[0034] S34: tension controlled at 20N, aging at 40℃ for 24 hours after winding;

[0035] Among them, the temperature of zone 1 is controlled at 170°C, the temperature of zone 2 is controlled at 185°C, the temperature of zone 3 is controlled at 195°C, and the temperature of the die head is controlled at 195°C.

[0036] Preferably, the mixer in S21 comprises:

[0037] A support frame is provided on which an outer cavity is fixed. An annular partition is installed on the inner side of the outer cavity through a bracket. The annular partition is concentrically arranged with the outer cavity, and an annular blanking cavity is formed between the annular partition and the outer cavity.

[0038] A mixing mechanism is installed in the annular partition and is used to stir and mix materials;

[0039] A top cover is fixed on the support frame and is located outside the top of the outer cavity;

[0040] A plurality of spray heads are installed on the outer cavity in a circumferential distribution, and the output end of the spray head is located in the blanking cavity; the other end of the spray head is connected to a liquid supply device through a delivery pipe, and the liquid supply device is used to deliver S-CNT ethanol dispersion and spray the liquid mist into the blanking cavity through the spray head;

[0041] The mixing mechanism comprises:

[0042] The rotating main shaft is provided with a mounting frame installed on the top of the top cover, and the rotating main shaft is rotatably mounted on the mounting frame, and the rotating main shaft is located at the center of the annular partition;

[0043] A connecting rod, the connecting rod is fixed to the side wall of the rotating main shaft;

[0044] The spiral trough is fixed to one end of the connecting rod. The two spiral troughs are arranged in a double spiral shape. The side of the spiral trough away from the rotating main shaft is an arc surface structure adapted to the inner wall of the annular partition. The top opening of the spiral trough faces the blanking cavity.

[0045] The hybrid drive unit is arranged on the mounting frame and is used to drive the rotating main shaft to rotate.

[0046] Preferably, the hybrid drive unit includes:

[0047] A hybrid drive motor, the hybrid drive motor is mounted on the mounting frame;

[0048] A hybrid drive gear, the shaft of which is in driving connection with the output end of the hybrid drive motor, a driven gear is mounted on the rotating main shaft, and the hybrid drive gear is meshed with the driven gear.

[0049] Preferably, a discharge cavity is fixed at the bottom of the outer cavity, the discharge cavity is annular in structure, an annular cavity is provided in the discharge cavity, a convex cover with an upward bulge in the middle is fixed at the center of the discharge cavity; a blocking component for blocking is provided in the annular cavity of the discharge cavity, and the blocking component includes:

[0050] Hydraulic cylinder, the hydraulic cylinder is installed on the support frame through a fixed frame;

[0051] The annular arc plate is fixed to the output end of the hydraulic cylinder and has an annular structure that matches the annular cavity. A guide rod is fixed to the bottom of the annular arc plate, and the guide rod penetrates and slides on the bottom inner wall of the discharge cavity.

[0052] The bottom of the outer cavity is an annular arc surface structure with a gradually decreasing inner diameter. The angle of the annular arc plate is adapted to the angle of the bottom of the outer cavity. When the annular arc plate moves to the top to seal the annular cavity, the bottom inner wall of the outer cavity, the top arc surface of the annular arc plate and the annular arc surface of the convex cover cooperate to form an annular supporting surface with a V-shaped cross section. The cross section of the spiral trough is a V-shaped structure adapted to the annular supporting surface.

[0053] There is a material leakage gap between the bottom of the annular partition and the annular supporting surface; and the bottom end point of the V-shaped cross section of the annular supporting surface is located on the side of the annular partition close to the rotating main shaft.

[0054] Preferably, a discharge port is provided on the inner side of the bottom of the discharge cavity, and a collection box is provided below the discharge cavity.

[0055] Preferably, an annular slide rail is fixed on the outside of the annular partition, an annular rotating plate is rotatably installed in the annular slide rail, the annular rotating plate is located directly above the blanking cavity, and evenly distributed sieve holes are provided on the annular rotating plate. An annular inner guide plate is fixed on the outside of the top of the annular partition, and an annular outer guide plate is fixed on the inside of the top cover, and the distance between the annular outer guide plate and the annular inner guide plate gradually decreases in the vertical downward direction; a rotation driving part for driving the annular rotating plate is installed on the outside of the outer cavity;

[0056] The rotation drive unit includes:

[0057] A rotation drive motor is installed outside the outer cavity through a motor seat;

[0058] The rotating drive gear, the shaft of the rotating drive gear is transmission-connected to the output end of the rotating drive motor, a strip-shaped opening adapted to the rotating drive gear is opened on the top cover, and circumferentially distributed convex teeth are fixed to the outer side of the annular rotating plate, and the rotating drive gear is engaged with the convex teeth through the strip-shaped opening.

[0059] The beneficial effects of the present invention are:

[0060] 1. The cling film of the present invention allows nitrogen to slowly enter the package, maintaining a high-nitrogen environment, while allowing only trace amounts of oxygen to penetrate. This not only meets the minimum respiratory needs of the fruit but also prevents spoilage caused by excessive oxygen. Furthermore, it achieves a dynamic balance: after the fruit consumes oxygen through respiration, the film further inhibits oxygen replenishment, forming a stable "low oxygen-high nitrogen" state without the need for human intervention.

[0061] 2. The cling film of the present invention does not require pre-filling with nitrogen. After packaging the fruit, the film automatically regulates gas exchange, eliminating the nitrogen filling step. The sealing requirements are relatively low. Even if there are tiny gaps in the packaging, the selective permeability of the film can still maintain the internal gas ratio as much as possible.

[0062] 3. The present invention is capable of sending the materials to be mixed into the annular baffle by setting a mixing mechanism, an outer cavity and an annular baffle. Based on the operation of the mixing drive part, the connecting rod and the spiral trough are driven to rotate, the connecting rod is used to stir the material, and the spiral trough is used to guide the material. When the material enters the spiral trough, based on the rotation of the spiral trough, the material is continuously guided to slide upward along the spiral trough; finally, it escapes from the top opening of the spiral trough and falls into the blanking cavity.

[0063] 4. The present invention provides a sealing component and an annular supporting surface formed by the cooperation of various structures. After the material falls through the blanking cavity, it can slide along the annular supporting surface, so that the material on the outside can slide back into the inside of the annular partition to achieve circulation mixing.

[0064] 5. The present invention sets a discharge port, which can control the annular arc plate to descend to the bottom of the annular cavity through the hydraulic cylinder when discharging is needed, thereby exposing the discharge port, and the material can be discharged from the discharge port through the annular cavity. Since the annular arc plate is an annular arc surface and the middle part of the convex cover is raised, it can better guide the material and make the material completely discharged.

[0065] 6. The present invention provides a ring-shaped rotating plate and other structures, which can be used to screen out possible foreign matter, while avoiding the material from falling in piles and affecting the contact effect with the liquid mist. Before the material passes through the sieve hole, based on the rotation of the ring-shaped rotating plate, the material can move to a certain extent on the ring-shaped rotating plate, promoting mixing; the inner ring guide plate and the outer ring guide plate can play a guiding role, allowing the material to pass through the sieve hole as much as possible, and the inner ring guide plate effectively shields the ring slide rail to avoid foreign matter from mixing into the ring slide rail. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a schematic diagram of the structure of each device in the production system of a living physical cling film proposed by the present invention;

[0067] Figure 2 This is a schematic structural diagram of various devices in a production system of a living physical cling film proposed by the present invention from another angle;

[0068] Figure 3 This is a structural diagram of a mixer in a production system of a living physical cling film proposed by the present invention;

[0069] Figure 4 This is a schematic structural diagram of a cross-section of a mixer in a production system of a living physical cling film proposed by the present invention;

[0070] Figure 5 This is a structural schematic diagram of a mixing machine in a production system of a living physical cling film proposed by the present invention with the top cover removed;

[0071] Figure 6 This is a cross-sectional plan view of a mixer in a production system of a living physical cling film proposed by the present invention with the top cover removed;

[0072] Figure 7 This is a schematic structural diagram of the cooperation between the spiral trough and the annular partition of the mixer in the production system of the living physical cling film proposed by the present invention;

[0073] Figure 8 This is a schematic structural diagram of the spiral trough and connecting rod of a mixer in a production system of a living physical cling film proposed by the present invention;

[0074] Figure 9This is a comparison of the appearance of strawberries in different packaging in the experiment of the present invention;

[0075] Figure 10 This is a comparison chart of the changes in respiration intensity of strawberries in different packages during storage in the experiment of the present invention;

[0076] Figure 11 This is a comparison chart of changes in strawberry hardness during storage in the experiment of the present invention;

[0077] Figure 12 This is a comparison chart of the changes in soluble solids of strawberries during storage in the experiment of the present invention;

[0078] Figure 13 This is a comparison chart of the changes in the malondialdehyde content of strawberries during storage in the experiment of the present invention.

[0079] In the figure: 1 support frame, 2 twin-screw extruder, 3 film blowing equipment, 4 mixing drive motor, 5 top cover, 6 rotation drive gear, 7 rotation drive motor, 8 hydraulic cylinder, 9 collection box, 10 conveying pipe, 11 mounting frame, 12 driven gear, 13 mixing drive gear, 14 fixed frame, 15 annular partition, 16 discharge port, 17 discharge cavity, 18 annular arc plate, 19 spiral trough, 20 spray head, 21 annular rotating plate, 22 annular outer guide plate, 23 annular inner guide plate, 24 rotating main shaft, 25 outer cavity, 26 convex teeth, 27 sieve hole, 28 motor base, 29 connecting rod, 30 convex cover, 31 guide rod, 32 annular slide rail. DETAILED DESCRIPTION

[0080] The technical solution of the present invention will be further described in detail below in conjunction with specific implementation methods.

[0081] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0082] Example 1:

[0083] A living physical preservative film, such as Figure 1-13 As shown, the preparation process includes the following steps:

[0084] S1: Raw material pretreatment, as follows:

[0085] S11: Preparation of ZIF-8@SiO2 nanoparticles;

[0086] S12: sulfonated carbon nanotube (S-CNT) treatment;

[0087] S2: Masterbatch preparation, as follows:

[0088] S21: Premix preparation: PS and SEBS are added to the mixer and stirred. During the process, the S-CNT ethanol dispersion is slowly sprayed in. Stirring is continued until the ethanol evaporates (the residual amount is ≤ 0.1%). ZIF-8@SiO2 is added, mixed, and sieved.

[0089] S22: Twin-screw extrusion granulation; preheat to the set temperature, start the main machine, cut into pellets, water-cool, centrifuge dehydration, dehydration and drying;

[0090] S3: film blowing.

[0091] The ZIF-8@SiO2 nanoparticles are prepared as follows:

[0092] S111: ZIF-8 activation: 50 g of ZIF-8 (Basolite Z1200) was placed in a vacuum oven and dehydrated at 120 °C for 2 h.

[0093] S112: SiO2 sol coating, the activated ZIF-8 was dispersed in 200 mL of ethanol and ultrasonicated for 30 min (power 300 W);

[0094] S113: Add 10 mL of TEOS (tetraethyl orthosilicate) and 5 mL of 28% ammonia water and stir at 45°C for 6 hours.

[0095] S114: Centrifugation, washing with ethanol three times, and drying at 80°C for 12 h yielded ZIF-8@SiO2 (SiO2 coating layer ≈ 5 nm).

[0096] The sulfonated carbon nanotube (S-CNT) treatment is specifically as follows:

[0097] S121: Add 10 g of multi-walled carbon nanotubes (diameter 10-20 nm) to 100 mL of concentrated sulfuric acid (98%) and stir at 80°C for 4 hours;

[0098] S122: Slowly add 5 g of potassium permanganate and continue the reaction for 2 hours;

[0099] S123: After dilution, filtration is performed and the pH is washed with deionized water to 7 to obtain S-CNT (sulfonic acid group density ≥ 2 mmol / g);

[0100] S124: vacuum dried at 60°C for 24 hours, ground through a 200-mesh sieve;

[0101] S125: Ultrasonic dispersion in ethanol for 30 minutes before use (concentration 5wt%).

[0102] Wherein, in the preparation of the premix, the specific formula includes:

[0103] 87 parts of PS particles, 6 parts of ZIF-8@SiO2, 5 parts of S-CNT dispersion (solid content 1 kg), 2 parts of SEBS;

[0104] Among them, the twin-screw extruder, the temperature of zone 1 is controlled at 160℃, the temperature of zone 2 is controlled at 180℃, the temperature of zone 3 is controlled at 195℃, the temperature of zone 4 is controlled at 185℃, the temperature of zone 5 is controlled at 190℃, and the die head temperature is controlled at 185℃;

[0105] The speed of the twin-screw extruder was controlled at 250 rpm, the feeding rate was controlled at 20 kg / h, the water cooling temperature was controlled at 12-18° C., and the mixture was dried at 50° C. for 4 hours after centrifugal dehydration.

[0106] The film blowing process specifically includes the following steps:

[0107] S31: Heat to the set temperature and keep constant temperature for 1 hour; add masterbatch to the hopper and start slow feeding (10kg / h);

[0108] S32: When the melt flows out of the die evenly, the film is led to the traction roller and compressed air (pressure 0.15 MPa) is slowly introduced to form a stable film bubble. The wind speed of the air ring is adjusted (inner wind 0.5 m / s, outer wind 0.8 m / s) to keep the frost line height 30 cm above the die;

[0109] S33: Adjust the thickness to 25 ± 2 μm by adjusting the air pressure in the bubble (0.12-0.18 MPa) and the pulling speed (12 m / min);

[0110] S34: tension controlled at 20N, aging at 40℃ for 24 hours after winding;

[0111] Among them, the temperature of zone 1 is controlled at 170°C, the temperature of zone 2 is controlled at 185°C, the temperature of zone 3 is controlled at 195°C, and the temperature of the die head is controlled at 195°C.

[0112] During the preparation of the cling film, samples were taken every 30 minutes, and the dispersion state of MOFs (agglomerated particles ≤ 1 μm) was observed by SEM. Three points were taken from each roll of film, and the O2 / N2 transmittance was tested according to ASTM D1434 (with an allowable deviation of ±10%).

[0113] Example 2:

[0114] A production system for a living physical cling film, such as Figure 1-8 Shown, including:

[0115] A mixer, a twin-screw extruder 2 and a film blowing device 3, wherein the mixer is the mixer in S21, and the mixer comprises:

[0116] The support frame 1 has an outer cavity 25 fixed on it. An annular partition 15 is installed on the inner side of the outer cavity 25 through a bracket. The annular partition 15 and the outer cavity 25 are concentrically arranged to form an annular blanking cavity between the annular partition 15 and the outer cavity 25.

[0117] A mixing mechanism is installed in the annular partition 15 and is used to stir and mix the materials;

[0118] The top cover 5 is fixed on the support frame 1 and is located outside the top of the outer cavity 25;

[0119] The spray head 20 is installed on the outer cavity 25 in a circumferential distribution. The output end of the spray head 20 is located in the blanking cavity. The other end of the spray head 20 is connected to the liquid supply device through the delivery pipe 10. The liquid supply device is used to deliver the S-CNT ethanol dispersion and spray the liquid mist into the blanking cavity through the spray head 20.

[0120] The mixing mechanism comprises:

[0121] The rotating main shaft 24 is provided with a mounting frame 11 on the top of the top cover 5. The rotating main shaft 24 is rotatably mounted on the mounting frame 11. The rotating main shaft 24 is located at the center of the annular partition 15.

[0122] A connecting rod 29, the connecting rod 29 being fixed to a side wall of the rotating main shaft 24;

[0123] The spiral trough 19 is fixed to one end of the connecting rod 29. The two spiral troughs 19 are arranged in a double spiral shape. The side of the spiral trough 19 away from the rotating main shaft 24 is an arc surface structure adapted to the inner wall of the annular partition 15. The top opening of the spiral trough 19 faces the blanking cavity.

[0124] A hybrid drive unit is provided on the mounting frame 11 and is used to drive the rotating main shaft 24 to rotate;

[0125] By providing the mixing mechanism, the outer cavity 25 and the annular partition 15, the material to be mixed can be fed into the annular partition 15. Based on the operation of the mixing drive unit, the connecting rod 29 and the spiral trough 19 are driven to rotate. The connecting rod 29 is used to stir the material, and the spiral trough 19 is used to guide the material. When the material enters the spiral trough 19, based on the rotation of the spiral trough 19, the material is continuously guided upward along the spiral trough 19; and finally, it escapes from the top opening of the spiral trough 19 and falls into the blanking cavity.

[0126] The liquid supply device works and sprays liquid mist, so that the material can contact with the liquid mist more fully, ensuring the mixing effect and avoiding insufficient contact due to material accumulation.

[0127] In order to facilitate the driving of the rotating main shaft 24, as shown in FIG. Figure 3 As shown, the hybrid drive unit includes:

[0128] The hybrid drive motor 4 is mounted on the mounting frame 11;

[0129] The hybrid drive gear 13 has a shaft drivingly connected to the output end of the hybrid drive motor 4 . The driven gear 12 is mounted on the rotating main shaft 24 . The hybrid drive gear 13 meshes with the driven gear 12 .

[0130] To facilitate the circulation mixing, Figure 4 、 Figure 6 As shown, a discharge cavity 17 is fixed at the bottom of the outer cavity 25. The discharge cavity 17 is an annular structure. An annular cavity is provided in the discharge cavity 17. A convex cover 30 with an upward bulge in the middle is fixed at the center of the discharge cavity 17. A blocking component for blocking is provided in the annular cavity of the discharge cavity 17. The blocking component includes:

[0131] Hydraulic cylinder 8, the hydraulic cylinder 8 is mounted on the support frame 1 through a fixing frame 14;

[0132] The annular arc plate 18 is fixed to the output end of the hydraulic cylinder 8 and has an annular structure that matches the annular cavity. A guide rod 31 is fixed to the bottom of the annular arc plate 18, and the guide rod 31 penetrates and slides on the bottom inner wall of the discharge cavity 17.

[0133] The bottom of the outer cavity 25 is an annular arc surface structure with a gradually decreasing inner diameter. The angle of the annular arc plate 18 is adapted to the angle of the bottom of the outer cavity 25. When the annular arc plate 18 moves to the top to seal the annular cavity, the bottom inner wall of the outer cavity 25, the top arc surface of the annular arc plate 18 and the annular arc surface of the convex cover 30 cooperate to form an annular supporting surface with a V-shaped cross section. The cross section of the spiral trough 19 is a V-shaped structure adapted to the annular supporting surface.

[0134] There is a gap between the bottom of the annular partition 15 and the annular supporting surface for material leakage; and the bottom end point of the V-shaped cross section of the annular supporting surface is located on the side of the annular partition 15 close to the rotating main shaft 24;

[0135] By setting up the annular supporting surface formed by the sealing component and various structures, the material can slide along the annular supporting surface after falling through the blanking cavity, so that the material on the outside can slide back into the inside of the annular partition 15 to achieve circulation mixing.

[0136] In order to facilitate the discharge of materials, such as Figure 4 、 Figure 6 As shown, a discharge port 16 is provided on the inner side of the bottom of the discharge cavity 17, and a collection box 9 is provided below the discharge cavity 17;

[0137] By setting up the discharge port 16, when discharging is required, the annular arc plate 18 can be controlled by the hydraulic cylinder 8 to descend to the bottom of the annular cavity, so that the discharge port 16 is exposed, and the material can be discharged from the discharge port 16 through the annular cavity. Since the annular arc plate 18 is an annular arc surface and the middle part of the convex cover 30 is raised, it can better guide the material and make the material completely discharged.

[0138] In order to improve the mixing effect and realize the screening function, such as Figure 4 、 Figure 5 As shown, an annular slide rail 32 is fixed to the outside of the annular partition 15, and an annular rotating plate 21 is rotatably installed in the annular slide rail 32. The annular rotating plate 21 is located directly above the blanking cavity. The annular rotating plate 21 is provided with evenly distributed sieve holes 27. An annular inner guide plate 23 is fixed to the outside of the top of the annular partition 15, and an annular outer guide plate 22 is fixed to the inside of the top cover 5. The distance between the annular outer guide plate 22 and the annular inner guide plate 23 gradually decreases in the vertical downward direction; a rotation driving portion for driving the annular rotating plate 21 is installed on the outside of the outer cavity 25;

[0139] By providing the annular rotating plate 21 and other structures, the annular rotating plate 21 can be used to screen out possible foreign matter, while preventing the material from falling in piles and affecting the contact effect with the liquid mist. In addition, before the material passes through the sieve holes 27, based on the rotation of the annular rotating plate 21, the material can move to a certain extent on the annular rotating plate 21, thereby promoting mixing. The annular inner guide plate 23 and the annular outer guide plate 22 can play a guiding role, allowing the material to pass through the sieve holes 27 as much as possible, and the annular inner guide plate 23 effectively shields the annular slide rail 32 to prevent foreign matter from mixing into the annular slide rail 32.

[0140] It is worth noting that there should be no large gap between the top surface of the annular rotating plate 21 and the annular inner guide plate 23 and the annular outer guide plate 22. In actual applications, one or more levers can be fixed between the annular inner guide plate 23 and the annular outer guide plate 22 to block the material to a certain extent during the rotation of the annular rotating plate 21, thereby preventing the material from continuing to rotate with the annular rotating plate 21 and promoting the screening of the material.

[0141] In order to facilitate the driving of the annular rotating plate 21 to rotate, as shown in FIG. Figure 5 As shown, the rotation drive unit includes:

[0142] The rotation drive motor 7 is mounted on the outside of the outer cavity 25 through the motor base 28;

[0143] The rotating drive gear 6 has a shaft that is in transmission connection with the output end of the rotating drive motor 7. The top cover 5 is provided with a strip-shaped opening adapted to the rotating drive gear 6. The outer side of the annular rotating plate 21 is fixed with circumferentially distributed protruding teeth 26. The rotating drive gear 6 is meshed with the protruding teeth 26 through the strip-shaped opening.

[0144] By providing a rotation driving portion, it is convenient to drive the annular rotating plate 21 to rotate, and the annular outer guide plate 22 can shield the protruding teeth 26 to prevent materials from contacting therewith.

[0145] test:

[0146] In order to prove the technical advantages of the preservative film of the present invention, the following experiments were performed:

[0147] Experimental purpose: To compare the quality changes of strawberries packaged with the plastic wrap of the present invention and two common PE plastic bags on the market at room temperature.

[0148] Fruit name: 99 strawberry;

[0149] Strawberry source: Yangchengzhai Strawberry Picking Garden, Sujiatun, Shenyang;

[0150] Test treatment:

[0151] Temperature: 3°C; Single package weight: 120±10g (6 strawberries)

[0152] Three groups of materials: the preservative film of the present invention (PSD), the Miaojie thick fresh-keeping bag (PE1), and the PE fruit and vegetable fresh-keeping bag (PE2);

[0153] Packaging method: Put the strawberries into a PP tray, then put them into plastic wrap / fresh-keeping bag and seal them quickly.

[0154] Test items:

[0155] 1. Appearance change; 2. Respiration strength; 3. Hardness change; 4. Soluble solids; 5. Malondialdehyde content; 6. Physical indicators of the film: thickness, oxygen permeability, carbon dioxide permeability, and water vapor permeability;

[0156] Testing instruments:

[0157] 1.VAC-VBS differential pressure gas permeability tester

[0158] 2. PARAMTSY-T1L / TSY-T1H Water Vapor Permeability Tester

[0159] 3. Checkpoint3 Portable Headspace Analyzer from Denmark

[0160] 4. CT3 Texture Analyzer

[0161] 5.H-1A Thickness Gauge

[0162] 6. Digital Brix Meter

[0163] Results and Analysis:

[0164] ①Appearance changes

[0165] Testing methods: 1. Test every 48 hours; 2. Take photos and visually observe changes in appearance; 3. Record changes in appearance through continuous photography.

[0166] Appearance analysis:

[0167] like Figure 7 As shown in the figure, compared with the PE1 and PE2 groups, the PSD packaging effectively maintained the color of the strawberries and showed no obvious symptoms such as rot black spots or water stains.

[0168] ②Respiratory intensity

[0169] Testing method: 1. Perform a measurement every 48 hours; 2. Place the strawberries in a 1L sealed container and calculate the respiration intensity by detecting the carbon dioxide production rate.

[0170] Respiratory intensity data analysis:

[0171] pass Figure 10 Analysis showed that the respiration rate of strawberries in all groups was inhibited under refrigerated conditions. The respiration rate of PSD group was higher than that of PE2 group and lower than that of PE1 group. This shows that PSD packaging can inhibit the respiration rate of strawberries and effectively delay the ripening and senescence of strawberries.

[0172] ③Hardness change

[0173] Testing method: 1. Test every 48 hours; 2. Use a CT3 texture analyzer to test the firmness of strawberries.

[0174] Hardness data analysis, such as Figure 11 As shown:

[0175] The maturity and quality of strawberry fruit during storage and preservation can be expressed by its hardness, which directly reflects the quality of the fruit. Compared with ordinary PE fresh-keeping bags, PSD film packaging has a higher hardness than all PE treatments, maintaining the firmness of the strawberries during storage.

[0176] ④ Changes in soluble solids

[0177] Testing method: 1. Perform a test every 48 hours. 2. Grind the strawberries, filter the juice with a filter cloth, and then use a digital sugar meter to test.

[0178] ⑤Soluble solids data analysis:

[0179] During storage, the nutrients in strawberry fruits will be consumed and the sweetness of the fruits will decrease, which can be reflected in the soluble solids content.

[0180] like Figure 12As shown in the figure, compared with ordinary PE fresh-keeping bag packaging, PSD film packaging effectively maintains the content of soluble solids, indicating that the ripening and aging of the fruit are better inhibited, which plays a better role in preserving the strawberries.

[0181] ⑥ Changes in malondialdehyde content

[0182] Detection method: 1. Perform the assay every 48 hours. 2. Homogenize 5 g of strawberry sample with 25 mL of 10% pre-cooled trichloroacetic acid (TCA), centrifuge at 10,000 × g for 10 min at 4°C, take 1 mL of the supernatant and mix it with 3 mL of 0.6% thiobarbituric acid (TBA), then heat in boiling water for 20 min. After cooling, measure the OD at 450 nm, 532 nm, and 600 nm.

[0183] Malondialdehyde data analysis:

[0184] Malondialdehyde is a product of membrane lipid peroxidation, and its content can reflect the degree of cell membrane lipid peroxidation and the degree of fruit aging. Figure 13 As shown in the results, the MDA content in the PSD group remained at the lowest throughout the storage period. This indicates that PSD packaging can effectively reduce the accumulation of MDA in strawberries, thereby alleviating the degree of membrane lipid peroxidation and delaying the aging of strawberries.

[0185] ⑦Film performance test (testing film thickness, oxygen permeability, carbon dioxide permeability)

[0186] Testing Method: 1. Use VAC-VBS differential pressure gas permeometer, PARAM TSY-T1L / TSY-T1H moisture permeability tester, and H-1A thickness gauge to test the gas permeability and water vapor permeability of the film. The details are as follows:

[0187] O2 / CO2 / water vapor transmission rate

[0188]

[0189] in conclusion:

[0190] Under refrigerated conditions, compared to traditional PE plastic wrap, PSD film can reduce strawberry respiration, slow the decline in soluble solids, maintain relatively high fruit firmness, preserve the strawberry color, inhibit the accumulation of malondialdehyde, and reduce the degree of membrane lipid peroxidation, thereby maintaining good strawberry quality. The research results show that PSD film is feasible for preserving strawberries.

[0191] The above description is only a preferred specific embodiment of the present invention. For parts that are not disclosed in detail, such as specific circuit connection methods or instrument models, those skilled in the art can use conventional technical means to implement them, so they are not described in detail.

Claims

1. A living physical preservative film, characterized in that: The preparation process includes the following steps: S1: Raw material pretreatment, as follows: S11: Preparation of ZIF-8@SiO2 nanoparticles; S12: sulfonated carbon nanotube treatment; S2: Masterbatch preparation, as follows: S21: Premix preparation: PS and SEBS are added to the mixer and stirred. During the process, the S-CNT ethanol dispersion is slowly sprayed in. Stirring is continued until the ethanol evaporates. ZIF-8@SiO2 is added, mixed, and sieved; S22: Twin-screw extrusion granulation; preheat to the set temperature, start the main machine, cut into pellets, water-cool, centrifuge dehydration, dehydration and drying; S3: film blowing.

2. A living physical preservative film according to claim 1, characterized in that: The ZIF-8@SiO2 nanoparticles are prepared as follows: S111: ZIF-8 activation: 50 g of ZIF-8 was placed in a vacuum oven and dehydrated at 120 °C for 2 h. S112: SiO2 sol coating, the activated ZIF-8 was dispersed in 200 mL of ethanol and sonicated for 30 min; S113: Add 10 mL of TEOS and 5 mL of aqueous ammonia, and stir at 45°C for 6 hours. S114: Centrifugation, washing with ethanol three times, and drying at 80°C for 12 hours to obtain ZIF-8@SiO2.

3. A living physical preservative film according to claim 2, characterized in that: The sulfonated carbon nanotube treatment is specifically as follows: S121: Add 10 g of multi-walled carbon nanotubes to 100 mL of concentrated sulfuric acid and stir at 80°C for 4 hours; S122: Slowly add 5 g of potassium permanganate and continue the reaction for 2 hours; S123: After dilution, filter and wash with deionized water until the pH reaches 7 to obtain S-CNT; S124: vacuum dried at 60°C for 24 hours, ground through a 200-mesh sieve; S125: Ultrasonic dispersion in ethanol for 30 minutes before use.

4. A living physical preservative film according to claim 1, characterized in that: In the preparation of the premix, the specific formula includes: 87 parts of PS particles, 6 parts of ZIF-8@SiO2, 5 parts of S-CNT dispersion, and 2 parts of SEBS; Among them, the twin-screw extruder, the temperature of zone 1 is controlled at 160℃, the temperature of zone 2 is controlled at 180℃, the temperature of zone 3 is controlled at 195℃, the temperature of zone 4 is controlled at 185℃, the temperature of zone 5 is controlled at 190℃, and the die head temperature is controlled at 185℃; The speed of the twin-screw extruder was controlled at 250 rpm, the feeding rate was controlled at 20 kg / h, the water cooling temperature was controlled at 12-18° C., and the mixture was dried at 50° C. for 4 hours after centrifugal dehydration.

5. A living physical preservative film according to claim 1, characterized in that: The blown film forming process specifically comprises the following steps: S31: Heat to the set temperature and keep constant temperature for 1 hour; add masterbatch to the hopper and start slow feeding; S32: When the melt flows out of the die head evenly, lead the film to the traction roller and slowly introduce compressed air to form a stable film bubble. Adjust the wind speed of the air ring to keep the frost line height 30 cm above the die head. S33: Adjust the thickness to 25±2μm by adjusting the air pressure inside the bubble and the pulling speed; S34: tension controlled at 20N, aging at 40℃ for 24 hours after winding; Among them, the temperature of zone 1 is controlled at 170°C, the temperature of zone 2 is controlled at 185°C, the temperature of zone 3 is controlled at 195°C, and the temperature of the die head is controlled at 195°C.

6. A living physical preservative film according to claim 1, characterized in that: The mixer in S21 includes: A support frame (1), an outer cavity (25) is fixed on the support frame (1), an annular partition (15) is installed on the inner side of the outer cavity (25) through a bracket, the annular partition (15) and the outer cavity (25) are concentrically arranged, and an annular blanking cavity is formed between the annular partition (15) and the outer cavity (25); A mixing mechanism, which is installed in the annular partition (15) and is used to stir and mix the materials; A top cover (5), the top cover (5) is fixed to the support frame (1), and the top cover (5) is located outside the top of the outer cavity (25); A spray head (20), wherein a plurality of spray heads (20) are installed on the outer cavity (25) in a circumferentially distributed manner, and an output end of the spray head (20) is located in the blanking cavity; the other end of the spray head (20) is connected to a liquid supply device through a delivery pipe (10), and the liquid supply device is used to deliver the S-CNT ethanol dispersion liquid, and spray the liquid mist into the blanking cavity through the spray head (20); The mixing mechanism comprises: A rotating main shaft (24) is provided on the top of the top cover (5) and a mounting frame (11) is mounted on the top of the top cover (5). The rotating main shaft (24) is rotatably mounted on the mounting frame (11). The rotating main shaft (24) is located at the center of the annular partition (15); A connecting rod (29), the connecting rod (29) being fixed to a side wall of the rotating main shaft (24); A spiral trough (19) is fixed to one end of the connecting rod (29), and the two spiral troughs (19) are arranged in a double spiral manner. The side of the spiral trough (19) away from the rotating main shaft (24) is an arc surface structure adapted to the inner wall of the annular partition (15); the top opening of the spiral trough (19) faces the blanking cavity; A hybrid drive unit is provided on the mounting frame (11) and is used to drive the rotating main shaft (24) to rotate.

7. A living physical preservative film according to claim 6, characterized in that: The hybrid drive unit includes: A hybrid drive motor (4), the hybrid drive motor (4) is mounted on a mounting frame (11); A hybrid drive gear (13) is connected to the output end of the hybrid drive motor (4) through a shaft thereof. A driven gear (12) is mounted on the rotating main shaft (24). The hybrid drive gear (13) is meshed with the driven gear (12).

8. A living physical preservative film according to claim 6, characterized in that: A discharge cavity (17) is fixed at the bottom of the outer cavity (25). The discharge cavity (17) is an annular structure. An annular cavity is provided in the discharge cavity (17). A convex cover (30) with an upwardly raised middle portion is fixed at the center of the discharge cavity (17). A blocking component for blocking is provided in the annular cavity of the discharge cavity (17). The blocking component comprises: A hydraulic cylinder (8), the hydraulic cylinder (8) is mounted on the support frame (1) via a fixing frame (14); An annular arc plate (18), the annular arc plate (18) is fixed to the output end of the hydraulic cylinder (8), and the annular arc plate (18) is an annular structure adapted to the annular cavity; a guide rod (31) is fixed to the bottom of the annular arc plate (18), and the guide rod (31) penetrates and slides on the bottom inner wall of the discharge cavity (17); The bottom of the outer cavity (25) is an annular arc surface structure with a gradually decreasing inner diameter. The angle of the annular arc plate (18) is adapted to the angle of the bottom of the outer cavity (25). When the annular arc plate (18) moves to the top to seal the annular cavity, the bottom inner wall of the outer cavity (25), the top arc surface of the annular arc plate (18) and the annular arc surface of the convex cover (30) cooperate to form an annular support surface with a V-shaped cross section. The cross section of the spiral trough (19) is a V-shaped structure adapted to the annular support surface. There is a material leakage gap between the bottom of the annular partition (15) and the annular supporting surface; and the bottom end point of the V-shaped cross section of the annular supporting surface is located on the side of the annular partition (15) close to the rotating main shaft (24).

9. A living physical preservative film according to claim 8, characterized in that: A discharge port (16) is provided on the inner side of the bottom of the discharge cavity (17), and a collection box (9) is provided below the discharge cavity (17).

10. The living physical preservative film according to claim 6, characterized in that: An annular slide rail (32) is fixed on the outside of the annular partition (15), and an annular rotating plate (21) is rotatably installed in the annular slide rail (32). The annular rotating plate (21) is located directly above the blanking cavity. The annular rotating plate (21) is provided with evenly distributed sieve holes (27). An annular inner guide plate (23) is fixed on the outside of the top of the annular partition (15), and an annular outer guide plate (22) is fixed on the inside of the top cover (5). The distance between the annular outer guide plate (22) and the annular inner guide plate (23) gradually decreases in the vertical downward direction; a rotation driving portion for driving the annular rotating plate (21) is installed on the outside of the outer cavity (25); The rotation drive unit includes: A rotation drive motor (7), the rotation drive motor (7) is mounted on the outside of the outer cavity (25) through a motor seat (28); A rotating drive gear (6) is connected to the shaft of the rotating drive gear (6) in a transmission connection with the output end of the rotating drive motor (7). A strip-shaped opening adapted to the rotating drive gear (6) is provided on the top cover (5). Convex teeth (26) distributed circumferentially are fixed to the outer side of the annular rotating plate (21). The rotating drive gear (6) is meshed with the convex teeth (26) through the strip-shaped opening.

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