Production process of antifogging, mildew-proof and antibacterial plastic preservative film

Abstract

The invention discloses a production process of an anti-fog, mildew-proof and antibacterial plastic preservative film, and relates to the technical field of high polymer material processing. The preparation method comprises the following steps: S1, preparing matrix resin; s2, compounding functional raw materials; s3.1, preparing an anti-fog melt; s3.2, preparing a raw material gradient distribution blending melt; s4, performing multi-layer co-extrusion film blowing molding; and S5, plasma surface modification. According to the production process of the anti-fogging, mildew-proof and antibacterial plastic preservative film, the technical contradiction that the anti-fogging performance and the antibacterial performance of a traditional preservative film are difficult to coexist is solved; no solvent is added in the whole process, and the highest safety standard of food contact materials is met; according to the five-layer co-extrusion film blowing unit disclosed by the invention, the air ring and the mold core can be conveniently and quickly mounted and dismounted, the maintenance operation is convenient, and the production efficiency and the product quality are favorably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material processing, and particularly to a production process of an anti-fog, anti-mildew and antibacterial plastic food wrap. Background Art

[0002] With the rapid development of the fresh food cold chain logistics and the ready-to-eat food market, consumers' functional requirements for food wrap have been upgraded from basic physical barrier to comprehensive protection requirements of anti-fog visualization and antibacterial and anti-mildew integration. The market share of multi-functional food wrap has been increasing year by year, but the existing products still have significant defects in long-term anti-fog, broad-spectrum antibacterial and processing stability, which restricts their application expansion in the high-end fresh food packaging field.

[0003] The existing anti-fog, anti-mildew and antibacterial food wrap mainly adopts a processing method of directly blending functional additives with base resin. For example, glycerol monostearate anti-fog agent and silver-loaded inorganic antibacterial agent are simultaneously added to polyethylene melt for blown film forming. However, due to the compatibility difference between the high-polarity characteristic of the anti-fog agent and the polyethylene matrix, obvious surface migration phenomenon of the additives will occur during the use of the film. Experimental research shows that after such a film contacts with water-containing food materials for 48 hours, the loss rate of the surface anti-fog agent can reach more than 40%. At the same time, the internal antibacterial agent is difficult to effectively act on the food contact interface because it is wrapped by the resin, and the inhibition rate against common spoilage bacteria is less than 75%.

[0004] To improve the surface performance, some enterprises have tried to add an anti-fog coating or an antibacterial agent spraying process after film forming. Although such secondary processing processes can temporarily increase the surface functional concentration, the interfacial bonding force between the coating and the substrate is weak and is easy to fall off after mechanical friction or condensate water scouring. According to the ASTM D3359 standard test, the cross-cut adhesion of a typical coated food wrap is only grade 2, and the solvent-based coating process will introduce the risk of VOCs residue, which does not meet the food contact material safety specification (GB9685-2016). And the anti-fog function requires hydrophilic components to be enriched on the film surface to reduce the haze, while the antibacterial and anti-mildew components need to form a sustained release system inside the substrate to avoid rapid loss. The traditional homogeneous blending process cannot reconcile this contradiction, resulting in the common problem of efficiency imbalance of "anti-fog without antibacterial" or "antibacterial easy to fail" in existing products.

[0005] In addition, during the film blowing production process, a certain amount of melt will remain inside the die head of the film blowing machine. These residual materials will solidify after cooling. If they are not removed in time, they will affect the quality of the next product produced and may even cause the die head to be blocked. By disassembling the die head, these residual materials can be completely removed to ensure the cleanliness and smoothness of the die head. The parts inside the die head may be worn or damaged after long-term use. It is necessary to carefully check these parts regularly to promptly detect and repair worn or damaged parts to extend the service life and ensure production quality. Under normal operation, the parts inside the die head also need to be lubricated regularly to reduce wear and friction. However, the existing film blowing machine equipment has the problem of inconvenient disassembly and installation of the die head, which brings difficulties to production maintenance, thereby reducing production efficiency and product quality.

[0006] To break through the above-mentioned technical bottlenecks, it is urgently necessary to collaboratively tackle the problems from two dimensions: material distribution regulation and special processing equipment innovation, and develop a cling film preparation system that can achieve precise positioning of functional components, synergistic enhancement of surface-bulk properties, and is feasible for industrial production. Summary of the invention

[0007] The purpose of the present invention is to solve the problems of unbalanced distribution of functional components, short-term surface modification effect and insufficient controllability of production process in the background technology. The primary purpose of the present invention is to provide a production process for anti-fog, anti-mildew and antibacterial plastic cling film, and to achieve multifunctional, long-term and stable integration through the collaborative innovation of raw material system design, gradient distribution process and surface modification technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a production process of anti-fog, anti-mildew and anti-bacterial plastic cling film, comprising the following steps: S1. Prepare a matrix resin: put 55-75wt% of a low-density polyethylene having a melt index of 2-5g / 10min and 25-45wt% of a linear low-density polyethylene having a density of 0.915-0.925g / cm³ into a high-speed mixer, and premix for 5-10min at 60-80°C to form a matrix resin blend; S2, compounding of functional raw materials: to the base resin blend prepared in the above step S1, add the following weight percentages of masterbatch and additives in sequence according to the total weight percentage of the final mixture: 3-5% of anti-fog functional masterbatch, 3-6% of antibacterial and mildew-proof composite masterbatch, and 0.6-1.3% of processing aid; mix well and stir at a low speed under nitrogen protection to obtain a functional raw material mixture; S3.1, anti-fog melt preparation: add 3-5% by weight of anti-fog masterbatch to the base resin blend prepared in step S1 above, mix at 50-60°C for 10 min, and obtain an anti-fog melt after the anti-fog agent is evenly dispersed; S3.2. Preparation of the raw material gradient distribution blend melt: Input the functional raw material mixture prepared in the above step S2 into the gradient distribution mixing system. After performing primary dynamic shearing and secondary laminar flow guiding blending in sequence, output a composite melt with a core layer antibacterial and mold-proof - surface anti-fog gradient structure; S4. Multi-layer co-extrusion blown film forming: Inject the matrix resin blend prepared in step S1 into the second and fourth layer flow channels respectively, inject the anti-fog melt prepared in step S3.1 into the first and fifth layer flow channels respectively, and inject the composite melt with a core layer antibacterial and mold-proof - surface anti-fog gradient structure prepared in step S3.2 into the third layer flow channel, and perform blown film forming to prepare a base film; S5. Plasma surface modification: Introduce the base film prepared in the above step S4 through traction into the atmospheric pressure dielectric barrier discharge plasma region for plasma surface modification to obtain an anti-fog, mold-proof, and antibacterial plastic fresh-keeping film, and then obtain the finished product after winding and cutting.

[0009] As a further scheme of the present invention: The anti-fog functional masterbatch described in step S2 is a masterbatch prepared by compounding glycerol monostearate and polyoxyethylene sorbitan monooleate in a mass ratio of 1:(1 - 2) and then granulating through a twin-screw granulator, with a particle size of 2 - 3 mm; The antibacterial and mold-proof composite masterbatch is prepared by dry-blending silver-loaded zeolite, nano-zinc oxide, organosilicon quaternary ammonium salt, and linear low-density polyethylene carrier resin in a mass ratio of 2:1:1:4, and then melt-coating through an enclosed mixer at 120 - 140 °C; The processing aid is a powder obtained by uniformly mixing erucic acid amide and antioxidant 1010 in a mass ratio of (4 - 5):1; The silver-loaded zeolite has a particle size of 50 - 100 nm, a silver ion loading amount of ≥2.5 wt%, and the nano-zinc oxide has a particle size of 20 - 50 nm.

[0010] As a further scheme of the present invention: In step S4, the melt distribution thickness ratio is: the first layer: the second layer: the third layer: the fourth layer: the fifth layer = 0.8:1.2:1.5:1.2:0.8, where the first layer is the air contact surface, the fifth layer is the food contact surface, and the third layer is the core layer; the die head temperature is 160 - 190 °C, perform blown film forming according to a blow-up ratio of (2.0 - 2.5):1, and the traction speed is 15 - 25 m / min to obtain a base film with a thickness of 20 - 50 μm.

[0011] As a further scheme of the present invention: The processing parameters of the plasma surface modification described in step S5 are: power density 0.8 - 1.0 W / cm 2 , electrode spacing 2 - 3 mm, argon gas flow rate 10 - 15 L / min, film running speed 15 - 25 m / min; surface etching: Plasma bombardment forms pores with a pore size of 50 - 200 nm and a density on the surface The microporous structure is [X] pieces / cm², the AFM roughness Ra = 120 - 150 nm, the surface contact angle is reduced to less than 35°, and the anti-fogging aging time is ≥ 72 hours.

[0012] As a further solution of the present invention: Step S4 is carried out in a five-layer co-extrusion blown film unit, which includes a mounting frame and a blown film die head. Five flow channels are arranged in the blown film die head; an extruder is arranged on one side of the blown film die head, and the output end of the extruder is connected to the feeding end of one of the flow channels in the blown film die head. A bubble stabilizing frame is fixedly connected above the blown film die head on the mounting frame, a herringbone flattening row is installed above the bubble stabilizing frame on the mounting frame, a traction and winding machine is arranged on one side of the mounting frame, an air ring is arranged above the blown film die head, a die core is installed at the top of the blown film die head, the air ring is installed through an installation mechanism, and the die core is installed at the top of the blown film die head through a connection mechanism.

[0013] As a further solution of the present invention: The installation mechanism includes a positioning ring, which is arranged at the top of the blown film die head. Positioning columns are symmetrically and fixedly installed on both sides of the positioning ring. An installation ring is fixedly connected to the bottom end of the air ring. Vertical grooves are symmetrically opened at the bottom end of the inner wall of the installation ring. A rotating ring is rotatably connected to the outer wall of the installation ring. A bevel gear is rotatably connected to the inner wall of the installation ring inside the installation ring. One end of the bevel gear is fixedly connected to a lead screw. A positioning frame is connected to the outer wall of the lead screw. The positioning frame is slidably connected to the inside of the installation ring. One end of the positioning frame extends to the inner wall of the vertical groove. A card slot is opened on the outer wall of the rotating ring. A clamping block is rotatably connected to the outer wall of the installation ring above the rotating ring. A counterweight block is fixedly connected to the outer wall of the clamping block.

[0014] As a further solution of the present invention: The connection mechanism includes a threaded column, which is fixedly connected to the bottom end of the die core. A threaded groove for the connection of the threaded column is opened inside the blown film die head. First threaded holes are symmetrically opened at the top end of the die core. Second threaded holes are symmetrically opened on the outer wall of the positioning ring. One end of the positioning column is fixedly connected to a threaded rod. A round hole is opened on the outer wall of the positioning column. Connection grooves are symmetrically opened at the top end of the blown film die head. Fixed grooves are symmetrically opened on the inner wall of the connection grooves. Connection blocks are symmetrically and fixedly connected to the bottom end of the positioning ring. Fixing blocks are symmetrically and slidably connected to the inside of the connection blocks. One end of the fixing block is rotatably connected to a connecting rod. One end of the connecting rod is rotatably connected to a displacement frame. The displacement frame is slidably connected to the inside of the positioning ring and the connection block. A spring is connected between the displacement frame and the positioning ring. An extrusion rod is slidably connected to one side of the displacement frame inside the positioning ring. The extrusion rod extends into the inner cavity of the second threaded hole.

[0015] As a further solution of the present invention: the inner wall of the mounting ring is attached to the outer wall of the die head of the blown film machine, and the inner wall of the vertical groove is attached to the outer wall of the positioning post.

[0016] As a further solution of the present invention: the inner wall of the rotating ring is provided with a toothed groove, the toothed groove meshes with the bevel gear, a connecting hole is opened on the outer wall of the positioning frame, the inner wall of the connecting hole is provided with a thread matching the lead screw, and the inner wall of the clamping groove is attached to the outer wall of the clamping block.

[0017] As a further solution of the present invention: the threaded post matches the threaded groove, the inner wall of the connecting groove is attached to the outer wall of the connecting block, the inner wall of the fixing groove is attached to the outer wall of the fixing block, one side of the displacement frame is provided with an inclined surface, the extrusion rod contacts the inclined surface, and both the second threaded hole and the first threaded hole match the threaded rod.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. The anti-fogging, anti-mildew and antibacterial plastic fresh-keeping film production process of the present invention solves the technical contradiction that it is difficult to coexist the anti-fogging and antibacterial properties of traditional fresh-keeping films through the precise compounding of LDPE / LLDPE matrix resin and functional masterbatch, combined with the gradient distribution process. The anti-fogging functional masterbatch reduces the surface energy through polarity synergy, makes the contact angle drop to ≤35°, and realizes long-term anti-fogging for 72h through plasma micropore anchoring; the antibacterial and anti-mildew composite masterbatch uses the synergistic mechanism of metal ion slow release and organic bacteriostasis, and the antibacterial rate against Escherichia coli is >99%, and the mildew-proof grade reaches level 0 (ASTM G21, 28 days). The two are gradiently isolated through the core layer - surface layer to avoid component interference, and the performance stability is improved by more than 2 times compared with the traditional blending process. The anti-fogging, anti-mildew and antibacterial plastic fresh-keeping film production process of the present invention has no solvent addition in the whole process and meets the highest safety standards for food contact materials.

[0019] 2. The anti-fogging, anti-mildew and antibacterial plastic fresh-keeping film production process of the present invention is based on the five-layer co-extrusion blown film process. The high-concentration anti-fogging melt prepared by S3a is specifically used for the outer layer. At the same time, the gradient mixing prepared by S3.2 drives the anti-fogging agent in the composite melt to migrate to the surface layer and the antibacterial agent to enrich in the core layer (the surface concentration ratio ≥70%). The two work together to achieve spatial isolation of the anti-fogging - antibacterial function; plasma treatment forms micropores with a pore diameter of 50 - 200nm on the surface layer, anchors the anti-fogging agent through capillary action and ester bond chemical bonding, the contact angle drops below 35° and the rise within 72h is ≤10%, and the symmetric structure makes the heat shrinkage balanced.

[0020] 3. In conjunction with the improved production process, the present invention is also designed to match a five-layer co-extrusion film blowing machine unit, which is equipped with an installation mechanism and a connecting mechanism, and the card block is rotated to move out of the card slot, and then the rotating ring is rotated to drive the positioning frame to move, and the positioning frame moves out of the vertical slot, canceling the fixation of the installation ring, and the air ring can be disassembled at this time; when the mold core is disassembled, the positioning column is removed, and at this time the fixed block moves out of the fixed slot, canceling the fixation of the positioning ring, and the positioning ring is moved out from the top of the film blowing machine die head. After completion, the positioning column is installed on the first threaded hole, and then the mold core can be driven to rotate by moving the first threaded hole, and the threaded column is rotated out of the threaded groove, and the mold core is disassembled. At the same time, the hook of the crane can pass through the circular hole on the positioning column to lift the positioning column and the mold core, and the mold core is moved, which is convenient for rapid installation and disassembly of the air ring and the mold core, convenient for maintenance operations, and helpful for improving production efficiency and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the five-layer co-extrusion film blowing unit of the present invention; Figure 2 It is a structural schematic diagram of the air ring of the five-layer co-extrusion film blowing unit of the present invention; Figure 3 This is a schematic diagram of the installation of the air ring of the five-layer co-extrusion film blowing unit of the present invention; Figure 4 This is a schematic diagram of the internal structure of the mounting ring of the five-layer co-extrusion film blowing unit of the present invention; Figure 5 The five-layer co-extrusion film blowing machine unit of the present invention Figure 4 The enlarged view of point A in the middle; Figure 6 It is a schematic diagram of the installation of the mold core of the five-layer co-extrusion film blowing unit of the present invention; Figure 7 The five-layer co-extrusion film blowing machine unit of the present invention Figure 6 The enlarged view of point B in the middle; Figure 8 The five-layer co-extrusion film blowing machine unit of the present invention Figure 6 Enlarged view of point C in the middle; Figure 9 This is a schematic diagram of the installation of the positioning columns of the five-layer co-extrusion film blowing unit of the present invention.

[0022] In the figure: 1, mounting frame; 2, film blowing die head; 3, extruder; 4, bubble stabilizing frame; 5, herringbone flattening row; 6, traction and winding machine; 7, air ring; 8, installation mechanism; 801, positioning ring; 802, positioning column; 803, installation ring; 804, vertical groove; 805, rotating ring; 806, bevel gear; 807, lead screw; 808, positioning frame; 809, card slot; 810, card block; 811, counterweight block; 9, connecting mechanism; 901, threaded column; 902, threaded groove; 903, first threaded hole; 904, second threaded hole; 905, threaded rod; 906, round hole; 907, connecting groove; 908, fixing groove; 909, connecting block; 910, fixing block; 911, connecting rod; 912, displacement frame; 913, spring; 914, extrusion rod; 10, die core. Detailed implementation manner

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection", "setting" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations. The embodiments of the present invention will be described below according to the overall structure of the present invention. Embodiment 1

[0025] Please refer to Figures 1 to 9 , in the embodiment of the present invention, a production process of an anti-fog, anti-mildew and antibacterial plastic fresh-keeping film includes the following steps: S1. Prepare the matrix resin: 55 wt% of low-density polyethylene with a melt index of 3.5 g / 10 min and 45 wt% of linear low-density polyethylene with a density of 0.920 g / cm³ were put into a high-speed mixer and premixed at 70 °C for 8 min to form a matrix resin blend.

[0026] S2. Functional raw material compounding: 4 wt% of an anti-fog functional masterbatch, 4.5 wt% of an antibacterial and mildew-proof composite masterbatch, and 1.0 wt% of a processing aid were added to the matrix resin blend, and it was stirred slowly at 55 °C for 18 min under nitrogen protection; The anti-fog functional masterbatch was compounded from glycerol monostearate and polyoxyethylene sorbitan monooleate at a mass ratio of 1:1.5 and made into masterbatch with a particle size of 2.5 mm by twin-screw granulation; The antibacterial and mildew-proof composite masterbatch was made by melt coating silver-loaded zeolite (particle size 80 nm, silver ion loading 2.8 wt%), nano-zinc oxide (particle size 30 nm), organosilicon quaternary ammonium salt and LLDPE at a mass ratio of 2:1:1:4 at 130 °C; The processing aid is a powder mixture of erucic acid amide and antioxidant 1010 at a ratio of 4.5:1.

[0027] S3.1. Anti-fog melt preparation: 4% by weight of an anti-fog masterbatch was added to the matrix resin blend and mixed at 55 °C for 10 min to obtain an anti-fog melt after ensuring uniform dispersion of the anti-fog agent.

[0028] S3.2. Gradient distribution blending of raw materials: The functional raw material mixture was put into a gradient distribution mixing system and subjected to primary dynamic shear (melt mixing at 80 °C and shear rate conditions) and secondary laminar flow guiding blending (maintained for 12 s in a laminar flow field at 110 °C and Reynolds number ≤ 50), and a composite melt with a core-layer antibacterial and mildew-proof - surface-layer anti-fog gradient structure was output, with SEM interface clarity of 92%.

[0029] S4. Multi-layer co-extrusion blown film forming: The matrix resin blend was respectively injected into the second and fourth layer runners, the anti-fog melt was respectively injected into the first and fifth layer runners, and the composite melt with a core-layer antibacterial and mildew-proof - surface-layer anti-fog gradient structure was injected into the third layer runner. During blown film forming, the melt distribution thickness ratio was: first layer: second layer: third layer: fourth layer: fifth layer = 0.8:1.2:1.5:1.2:0.8. The die head temperature was controlled at 180 °C, the blow-up ratio was 2.3:1, and the traction speed was 20 m / min, and finally a base film with a thickness in the range of 20 - 50 μm was obtained. The surface contact angle of the obtained base film was 68° (testing method same as GB / T30693-2014).

[0030] S5. Plasma surface modification: The base film is treated by atmospheric pressure dielectric barrier discharge plasma (power density 0.9 kW / m, electrode spacing 2.5 mm, argon 12 L / min, running speed 22 m / min), and micropores with a pore diameter of 100 nm and a density of per cm² are formed on the surface, and the AFM roughness Ra = 135 nm; the contact angle drops from 68° to 32° and remains for 78 h, obtaining the anti-fogging, anti-mildew and antibacterial plastic fresh-keeping film of the present invention.

[0031] Please refer specifically to Figures 3 to 5 , step S4 is carried out in a five-layer co-extrusion blown film unit. The five-layer co-extrusion blown film unit includes a mounting frame 1 and a blown film die head 2. Five concentric annular distribution channels are arranged in the blown film die head 2; five extruders 3 are correspondingly arranged on one side of the blown film die head 2, and the output ends of the respective extruders 3 are respectively communicated with the feed ends of one distribution channel in the blown film die head 2.

[0032] A bubble stabilizing frame 4 is fixedly connected above the blown film die head 2 on the mounting frame 1. A herringbone flattening row 5 is installed above the bubble stabilizing frame 4 on the mounting frame 1. A traction winding machine 6 is arranged on one side of the mounting frame 1. The atmospheric pressure dielectric barrier discharge plasma area is arranged between the mounting frame and the traction winding machine 6. An air ring 7 is arranged above the blown film die head 2. A die core 10 is installed at the top of the blown film die head 2. The opposite surface between the blown film die head 2 and the die core 10 is in an inverted conical funnel shape and forms an annular material collecting channel therebetween. The upper discharge ports of the respective distribution channels are respectively oriented towards the die core 10 and are communicated with the annular material collecting channel.

[0033] In this embodiment: a matrix resin blend, an anti-fogging melt and a composite melt with a core layer antibacterial and mildew-proof - surface layer anti-fogging gradient structure are respectively placed in each extruder. Among them, the matrix resin blend is respectively injected into the distribution channels of the second layer and the fourth layer, the anti-fogging melt is respectively injected into the distribution channels of the first layer and the fifth layer, and the composite melt with a core layer antibacterial and mildew-proof - surface layer anti-fogging gradient structure is injected into the distribution channel of the third layer. The materials in each layer of the distribution channels are collected layer by layer from the annular material collecting channel to form an anti-fogging, anti-mildew and antibacterial plastic fresh-keeping film with a multi-layer functional structure.

[0034] The air ring 7 is installed through the installation mechanism 8, and the die core 10 is installed at the top of the die head 2 of the blown film machine through the connection mechanism 9. The installation mechanism 8 includes a positioning ring 801, which is arranged at the top of the die head 2 of the blown film machine. Symmetrically fixed on both sides of the positioning ring 801 are positioning columns 802. The bottom end of the air ring 7 is fixedly connected with an installation ring 803. Symmetrically opened at the bottom end of the inner wall of the installation ring 803 are vertical grooves 804. The outer wall of the installation ring 803 is rotatably connected with a rotating ring 805. Inside the installation ring 803 and on the inner wall of the rotating ring 805 is rotatably connected a bevel gear 806. One end of the bevel gear 806 is fixedly connected with a lead screw 807. Connected to the outer wall of the lead screw 807 is a positioning frame 808, which is slidably connected inside the installation ring 803. One end of the positioning frame 808 extends to the inner wall of the vertical groove 804. Opened on the outer wall of the rotating ring 805 is a card slot 809. Rotatably connected above the rotating ring 805 on the outer wall of the installation ring 803 is a clamping block 810. Fixedly connected to the outer wall of the clamping block 810 is a counterweight 811.

[0035] In this embodiment: When installing the air ring 7, place the air ring 7 on the top of the positioning ring 801. At this time, the installation ring 803 is sleeved on the outer walls of the positioning ring 801 and the die head 2 of the blown film machine, and the positioning columns 802 slide into the inner walls of the vertical grooves 804. After completion, rotate the rotating ring 805. The rotation of the rotating ring 805 drives the bevel gear 806 to rotate. The rotation of the bevel gear 806 drives the lead screw 807 to rotate. The rotation of the lead screw 807 drives the positioning frame 808 to displace. The displacement of the positioning frame 808 inserts into the vertical groove 804 and contacts the bottom end of the positioning column 802, fixing the positioning column 802 in the vertical groove 804, thereby fixing the installation ring 803 and further fixing the air ring 7. Then rotate the clamping block 810, and the clamping block 810 rotates and engages into the card slot 809 to fix the rotating ring 805.

[0036] When disassembling the air ring 7, rotate the clamping block 810 to move out of the card slot 809. Then rotate the rotating ring 805 to drive the positioning frame 808 to displace. The displacement of the positioning frame 808 out of the vertical groove 804 cancels the fixation of the installation ring 803. At this time, the air ring 7 can be disassembled, facilitating the quick installation and disassembly of the air ring 7 when maintenance is required.

[0037] Please refer specifically to Figures 6 to 9, the connecting mechanism 9 includes a threaded post 901, the threaded post 901 is fixedly connected to the bottom end of the die core 10, a threaded groove 902 for the threaded post 901 to connect and enter is provided inside the blown film machine die head 2, first threaded holes 903 are symmetrically provided at the top end of the die core 10, second threaded holes 904 are symmetrically provided on the outer wall of the positioning ring 801, one end of the positioning post 802 is fixedly connected with a threaded rod 905, a circular hole 906 is provided on the outer wall of the positioning post 802, connecting grooves 907 are symmetrically provided at the top end of the blown film machine die head 2, fixing grooves 908 are symmetrically provided on the inner wall of the connecting grooves 907, connecting blocks 909 are symmetrically and fixedly connected to the bottom end of the positioning ring 801, fixing blocks 910 are symmetrically and slidably connected inside the connecting blocks 909, one end of the fixing block 910 is rotatably connected with a connecting rod 911, one end of the connecting rod 911 is rotatably connected with a displacement frame 912, the displacement frame 912 is slidably connected inside the positioning ring 801 and the connecting block 909, a spring 913 is connected between the displacement frame 912 and the positioning ring 801, an extrusion rod 914 is slidably connected inside the positioning ring 801 on one side of the displacement frame 912, and the extrusion rod 914 extends into the inner cavity of the second threaded hole 904.

[0038] In this embodiment: When installing the die core 10, place the die core 10 on the top end of the blown film machine die head 2, connect the threaded post 901 into the threaded groove 902 to fix the die core 10. Then, sleeve the positioning ring 801 on the top of the die core 10 and at the top end of the blown film machine die head 2. At this time, the connecting block 909 is inserted into the connecting groove 907. After completion, connect the threaded rod 905 into the second threaded hole 904 to install the positioning post 802. The displacement of the threaded rod 905 contacts the extrusion rod 914, pushing the extrusion rod 914 to displace. The displacement of the extrusion rod 914 pushes the displacement frame 912 to displace, squeezing the spring 913. The displacement of the displacement frame 912 drives the fixing block 910 to displace through the connecting rod 911, and the displacement of the fixing block 910 is inserted into the fixing groove 908 to fix the positioning ring 801.

[0039] When disassembling the mold core 10, rotate the threaded rod 905 out of the second threaded hole 904 and remove the positioning post 802. At this time, the displacement frame 912 is reset under the elastic force of the spring 913, and the fixed block 910 is displaced out of the fixed groove 908, canceling the fixation of the positioning ring 801. Move the positioning ring 801 out of the top of the blown film machine die head 2. After completion, connect the threaded rod 905 into the first threaded hole 903, install the removed positioning post 802 onto the first threaded hole 903. Then, the mold core 10 can be rotated by moving the first threaded hole 903, and the threaded post 901 is rotated out of the threaded groove 902 to disassemble the mold core 10. At the same time, the hook of the crane can pass through the round hole 906 on the positioning post 802 to lift the positioning post 802 and the mold core 10, and move the mold core 10, which is convenient for the quick installation and disassembly of the mold core 10.

[0040] Please refer particularly to Figures 3 to 5 , the inner wall of the mounting ring 803 fits with the outer wall of the blown film machine die head 2, and the inner wall of the vertical groove 804 fits with the outer wall of the positioning post 802.

[0041] In this embodiment: Place the air ring 7 on the top of the positioning ring 801. At this time, the mounting ring 803 is sleeved on the outer walls of the positioning ring 801 and the blown film machine die head 2, and the positioning post 802 slides into the inner wall of the vertical groove 804.

[0042] Please refer particularly to Figures 3 to 5 , the inner wall of the rotating ring 805 is provided with a tooth groove, the tooth groove meshes with the bevel gear 806, the outer wall of the positioning frame 808 is provided with a connection hole, the inner wall of the connection hole is provided with a thread matching the lead screw 807, and the inner wall of the card slot 809 fits with the outer wall of the card block 810.

[0043] In this embodiment: Rotate the rotating ring 805. The rotation of the rotating ring 805 drives the bevel gear 806 to rotate. The rotation of the bevel gear 806 drives the lead screw 807 to rotate. The rotation of the lead screw 807 drives the positioning frame 808 to be displaced. The positioning frame 808 is displaced and inserted into the vertical groove 804 to contact the bottom end of the positioning post 802, fixing the positioning post 802 in the vertical groove 804.

[0044] Please refer particularly to Figures 6 to 9 , the threaded post 901 matches the threaded groove 902, the inner wall of the connection groove 907 fits with the outer wall of the connection block 909, the inner wall of the fixed groove 908 fits with the outer wall of the fixed block 910, one side of the displacement frame 912 is provided with an inclined surface, the extrusion rod 914 contacts the inclined surface, and both the second threaded hole 904 and the first threaded hole 903 match the threaded rod 905.

[0045] In this embodiment: The positioning ring 801 is sleeved on the top of the die core 10 and located at the top of the die head 2 of the blown film machine. At this time, the connecting block 909 is inserted into the connecting groove 907. After completion, the threaded rod 905 is connected into the second threaded hole 904 to install the positioning column 802. The displacement of the threaded rod 905 contacts the extrusion rod 914, pushing the extrusion rod 914 to displace. The displacement of the extrusion rod 914 pushes the displacement frame 912 to displace, squeezing the spring 913. The displacement of the displacement frame 912 drives the fixed block 910 to displace through the connecting rod 911. The displacement of the fixed block 910 is inserted into the fixed groove 908 to fix the positioning ring 801. Embodiment 2

[0046] A production process of anti-fog, anti-mildew and antibacterial plastic fresh-keeping film includes the following steps: S1. Preparation of matrix resin: 65 wt% of low-density polyethylene with a melt index of 4.0 g / 10 min and 35 wt% of linear low-density polyethylene with a density of 0.918 g / cm³ are premixed at 75 °C for 6 min.

[0047] S2. Compound of functional raw materials: Add 3.5 wt% of anti-fog masterbatch (glyceryl monostearate: polyoxyethylene sorbitan monooleate = 1:2, particle size 2.2 mm), 5.5 wt% of anti-mildew and antibacterial composite masterbatch (silver-loaded zeolite particle size 60 nm / silver loading 3.0 wt%, nano-ZnO particle size 40 nm), and 0.8 wt% of processing aids (erucic acid amide: antioxidant 1010 = 4.2:1), and stir at low speed at 58 °C for 16 min.

[0048] S3.1 Preparation of anti-fog melt: Add 3.5% of anti-fog masterbatch to the matrix resin blend and mix at 55 °C for 12 min1.

[0049] S3.2 Gradient distribution blending of raw materials: Put the functional raw material mixture into the gradient distribution mixing system, and perform primary dynamic shear (melt mixing at 90 °C and shear rate conditions) and secondary laminar flow guiding blending (maintain for 10 s in a laminar flow field at 100 °C and Reynolds number ≤ 50) in sequence, and output a composite melt with a core layer of anti-mildew and antibacterial - surface layer of anti-fog gradient structure, and the SEM interface clarity is 93%.

[0050] S4. Multi-layer co-extrusion blown film forming: The matrix resin blend is respectively injected into the second-layer and fourth-layer runner channels, the anti-fog melt is respectively injected into the first-layer and fifth-layer runner channels, and the composite melt with a core-layer antibacterial and antifungal - surface-layer anti-fog gradient structure is injected into the third-layer runner channel, and then blown film molding is carried out to prepare the base film; the melt distribution thickness ratio is: first layer: second layer: third layer: fourth layer: fifth layer = 0.8:1.2:1.5:1.2:0.8; The die head temperature is 160 °C, blown film molding is carried out according to a blow-up ratio of 2:1, the traction speed is 15 m / min, and a base film with a thickness of 20 - 50 μm is obtained, and the thickness deviation ≤ ±3%.

[0051] S5. Plasma surface modification: Plasma treatment (power density 0.85 kW / m, electrode spacing 2.2 mm, argon 14 L / min), the surface micropore density per cm², the contact angle of 30° is maintained for 80 h, and the anti-fog, anti-mildew and antibacterial plastic food wrap of the present invention is obtained.

[0052] The five-layer co-extrusion blown film unit used in the preparation process is the same as that in Example 1 and will not be elaborated here. Example 3

[0053] A production process of an anti-fog, anti-mildew and antibacterial plastic food wrap, comprising the following steps: S1. Preparation of matrix resin: 75 wt% of low-density polyethylene with a melt index of 2.8 g / 10 min and 25 wt% of linear low-density polyethylene with a density of 0.922 g / cm³ are premixed at 65 °C for 9 min.

[0054] S2. Compound of functional raw materials: Add 4.8 wt% of anti-fog masterbatch (monostearin: polysorbate 80 = 1:1, particle size 2.8 mm), 3.8 wt% of antibacterial and antifungal composite masterbatch (silver-loaded zeolite particle size 90 nm / silver loading 2.6 wt%, nano-ZnO particle size 25 nm), 1.2 wt% of processing aids (erucamide: antioxidant 1010 = 4.8:1), and stir at low speed for 18 min.

[0055] S3.1. Preparation of anti-fog melt: Add 3 - 5% of anti-fog masterbatch to the matrix resin blend, mix at 50 - 60 °C for 10 min, and prepare the anti-fog melt after ensuring that the anti-fog agent is evenly dispersed.

[0056] S3.2. Gradient distribution blending of raw materials: Put the functional raw material mixture into the gradient distribution mixing system, and carry out primary dynamic shear in turn (at 100 °C, shear rate Under the condition of melt blending) and secondary laminar flow guiding blending (maintaining for 15 s in a laminar flow field at 120 °C and a Reynolds number ≤ 50), a composite melt with a core-layer antibacterial and mildew-proof - surface anti-fog gradient structure is output, and the SEM interface clarity is 93%.

[0057] S4. Multi-layer co-extrusion blown film forming: Inject the matrix resin blend into the second and fourth layer runners respectively, inject the anti-fog melt into the first and fifth layer runners respectively, and inject the composite melt with a core-layer antibacterial and mildew-proof - surface anti-fog gradient structure into the third layer runner, and perform blown film forming to prepare the base film; the melt distribution thickness ratio is: the first layer: the second layer: the third layer: the fourth layer: the fifth layer = 0.8:1.2:1.5:1.2:0.8; the die head temperature is 160 - 190 °C, perform blown film forming according to a blow-up ratio of (2.0 - 2.5):1, and the traction speed is 15 - 25 m / min to obtain a base film with a thickness of 20 - 50 μm, and the thickness deviation ≤ ±3%.

[0058] S5. Plasma surface modification: Plasma treatment (power density 1.0 kW / m, electrode spacing 2.8 mm, argon 11 L / min), the surface micropore density pieces / cm², the contact angle is 33° and is maintained for 75 h to obtain the anti-fog, mildew-proof and antibacterial plastic fresh-keeping film of the present invention.

[0059] The five-layer co-extrusion blown film unit used in the preparation process is the same as that in Example 1, and will not be elaborated here.

[0060] Comparative Example 1 Cancel the gradient mixing In step S3.2, cancel the secondary laminar flow guiding, and only perform primary dynamic shear (90 °C, shear rate ). The remaining steps are the same as those in Example 1.

[0061] Comparative Example 2 Without plasma treatment Only do not use the plasma surface modification step in step S5, and the remaining steps are the same as those in Example 1.

[0062] Comparative Example 3 Unbalanced layer thickness ratio In step S4, change the melt distribution layer thickness ratio to the first layer: the second layer: the third layer: the fourth layer: the fifth layer = 1:1:1:1:1, and the remaining steps are the same as those in Example 1.

[0063] Performance test Cut standard specimens from the anti-fog, mildew-proof and antibacterial fresh-keeping film base films (thickness 20 - 50 μm) prepared in Examples 1 - 3 and Comparative Examples 1 - 3, and conduct the following tests: I. Functional component distribution test 1. Anti-fog agent migration rate and surface proportion Method: SEM-EDS surface scanning (Hitachi SU8010, acceleration voltage 15 kV), collecting element distribution maps along the film cross-section (C / O elements characterize the anti-fog agent). Calculation: Mobility = (O atom concentration in the surface layer / O atom concentration in the whole cross-section) × 100%; Surface proportion = proportion of O atom concentration within 1 μm of the surface layer.

[0064] 2. Mobility of the antibacterial agent core layer Method: SEM-EDS line scanning (Ag / Zn elements characterize the antibacterial agent), taking points every 0.5 μm from the surface layer to the core. Calculation: Core layer mobility = (Ag + Zn atom concentration in the 10-μm region of the core / concentration in the whole cross-section) × 100%.

[0065] II. Surface performance testing 3. Contact angle and anti-fogging aging Method: Contact angle meter (Dataphysics OCA50, Germany), testing the static contact angle of deionized water (average of 3 points) according to GB / T 30693-2014. Anti-fogging aging: Placing in a constant humidity chamber at 40 °C / 90% RH, recording the time when the contact angle rises back to 45°.

[0066] 4. Microporous structure and anchoring effect Method: AFM (Bruker Dimension Icon) scanning the surface topography (5×5 μm² area), analyzing the pore size distribution and roughness (Ra). Chemical bonding rate: Characterizing the intensity change of the characteristic peak of the anti-fog agent ( ester group) by FTIR (Nicolet iS50).

[0067] III. Functional efficacy testing 5. Antibacterial and antifungal properties Antibacterial rate: Calculating the bacteriostatic rate after inoculating Escherichia coli (ATCC 25922) for 24 h according to GB / T 31402-2015. Antifungal grade: According to ASTM G21 standard, spraying Aspergillus niger spore suspension, observing the moldy area after 28 days (Grade 0: no mold; Grade 4: >60% mold spots). Silver ion migration amount is tested according to GB 31604.8-2021; VOCs are detected by headspace-GC / MS method according to GB / T 23296.26-2009, not detected (detection limit 0.01 mg / m²).

[0068] 6. Physical stability Thickness deviation: Continuously measuring 10 points with a laser thickness gauge (Mitutoyo LSM-6200), calculating the standard deviation. Interlayer peeling strength: GB / T 8808-1988, tensile speed 50 mm / min. The performance test results are shown in Table 1 below: Table 1 Performance test results of the anti-fogging, anti-mildew and antibacterial fresh-keeping film base films prepared in each example and comparative example

[0069] From the above data, it can be seen that the process of the present invention (Examples 1-3) is comprehensively superior to the traditional method in terms of core performance: the anti-fogging time is increased by 3 times: up to 75-80 hours (only 12-25 hours in the comparative example); there is a breakthrough in safety: the silver ion migration amount ≤ 0.042 mg / kg (the comparative example exceeded the standard up to 0.198-0.205 mg / kg), and the antibacterial rate > 99.5% (the comparative example ≤ 78.6%); the precision is improved: the thickness deviation ≤ ±2.8% (up to ±7.2% in Comparative Example 3), and the defective product rate < 1.5% (the industry average > 5%).

[0070] In summary, the present invention completely solves the industry pain points of the fresh-keeping film such as functional failure, high safety risk and low yield rate through gradient mixing (migration rate > 85%), plasma anchoring (contact angle stability ≤ 35°) and five-layer coextrusion layer thickness optimization (peeling strength 4.3-4.7 N / 15 mm).

[0071] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A production process of anti-fogging, anti-mildew and antibacterial plastic food wrap, characterized in that, It includes the following steps: S1. Prepare the matrix resin: Put 55 - 75 wt% of low - density polyethylene with a melt index of 2 - 5 g / 10min and 25 - 45 wt% of linear low - density polyethylene with a density of 0.915 - 0.925 g / cm³ into a high - speed mixer, premix at 60 - 80 °C for 5 - 10 min to form a matrix resin blend; S2. Compound the functional raw materials: To the matrix resin blend prepared in step S1 above, add the following masterbatches and additives in the following weight percentages based on the total weight percentage of the final mixture: anti - fog masterbatch 3 - 5%, antibacterial and mildew - proof composite masterbatch 3 - 6%, processing aid 0.6 - 1.3%. After mixing evenly, stir at low speed under nitrogen protection to obtain a functional raw material mixture; S3.

1. Prepare the anti - fog melt: Add 3 - 5% of anti - fog masterbatch by weight percentage to the matrix resin blend prepared in step S1 above, mix at 50 - 60 °C for 10 min. After the anti - fog agent is evenly dispersed, prepare the anti - fog melt; S3.

2. Prepare the raw material gradient - distribution blended melt: Put the functional raw material mixture prepared in step S2 above into a gradient - distribution mixing system, conduct primary dynamic shear and secondary laminar - flow guiding blending in sequence, and then output a composite melt with a core - layer antibacterial and mildew - proof - surface - layer anti - fog gradient structure; S4. Multi - layer co - extrusion blown - film forming: Inject the matrix resin blend prepared in step S1 into the second - layer and fourth - layer runners respectively, inject the anti - fog melt prepared in step S3.1 into the first - layer and fifth - layer runners respectively, inject the composite melt with a core - layer antibacterial and mildew - proof - surface - layer anti - fog gradient structure prepared in step S3.2 into the third - layer runner, and conduct blown - film forming to prepare a base film; S5. Plasma surface modification: Guide the base film prepared in step S4 above through traction into an atmospheric - pressure dielectric - barrier - discharge plasma region for plasma surface modification to obtain an anti - fog, mildew - proof, and antibacterial plastic food wrap, and then obtain the finished product after winding and cutting; 2. The production process of an anti-fog, anti-mildew and antibacterial plastic food wrap according to claim 1, characterized in that, The anti - fog masterbatch described in step S2 is a masterbatch prepared by compounding glycerol monostearate and polyoxyethylene sorbitan monooleate in a mass ratio of 1:(1 - 2) and then granulating with a twin - screw granulator, with a particle size of 2 - 3 mm; The antibacterial and mildew - proof composite masterbatch is prepared by dry - mixing silver - loaded zeolite, nano - zinc oxide, organosilicon quaternary ammonium salt, and linear low - density polyethylene carrier resin in a mass ratio of 2:1:1:4, and then melt - coating at 120 - 140 °C with an enclosed mixer; The processing aid is a powder obtained by mixing erucic acid amide and antioxidant 1010 evenly in a mass ratio of (4 - 5):1; The silver - loaded zeolite has a particle size of 50 - 100 nm, and the silver - ion loading amount is ≥2.5 wt%. The nano - zinc oxide has a particle size of 20 - 50 nm.

3. According to the production process of an anti - fog, mildew - proof, and antibacterial plastic food wrap as described in claim 1, characterized in that, In step S4, the melt distribution thickness ratio is: the first layer: the second layer: the third layer: the fourth layer: the fifth layer = 0.8:1.2:1.5:1.2:0.8, where the first layer is the air contact surface, the fifth layer is the food contact surface, and the third layer is the core layer; the die head temperature is 160 - 190 °C, blown film forming is carried out according to a blow-up ratio of (2.0 - 2.5):1, and the traction speed is 15 - 25 m / min to obtain a base film with a thickness of 20 - 50 μm.

4. The production process of an anti-fogging, anti-mildew and antibacterial plastic food wrap according to claim 1, characterized in that, The processing parameters of the plasma surface modification described in step S5 are as follows: power density 0.8 - 1.0 W / cm 2 , electrode spacing 2 - 3 mm, argon gas flow rate 10 - 15 L / min, film running speed 15 - 25 m / min; surface etching: plasma bombardment forms a microporous structure with pore diameters of 50 - 200 nm and a density of pores / cm² on the surface layer, AFM roughness Ra = 120 - 150 nm, surface contact angle reduced to below 35°, and anti-fogging aging time ≥ 72 hours.

5. The production process of an anti-fog, anti-mildew and antibacterial plastic food wrap according to claim 1, characterized in that, Step S4 is carried out in a five-layer co-extrusion blown film unit, and the five-layer co-extrusion blown film unit includes a mounting frame (1) and a blown film die head (2). Five shunt channels are arranged in the blown film die head (2); an extruder (3) is arranged on one side of the blown film die head (2), and the output end of the extruder (3) is communicated with the feeding end of a shunt channel in the blown film die head (2). A bubble stabilizing frame (4) is fixedly connected above the blown film die head (2) on the mounting frame (1), a herringbone flattening row (5) is installed above the bubble stabilizing frame (4) on the mounting frame (1), a traction rewinder (6) is arranged on one side of the mounting frame (1), an air ring (7) is arranged above the blown film die head (2), a die core (10) is installed at the top end of the blown film die head (2), and an annular film outlet gap is formed between the blown film die head (2) and the die core (10); the discharging ends of the respective shunt channels are communicated with the annular film outlet gap; the air ring (7) is installed through an installation mechanism (8), and the die core (10) is installed at the top end of the blown film die head (2) through a connection mechanism (9).

6. A production process of an anti-fogging, anti-mildew and antibacterial plastic food wrap according to claim 5, characterized in that, The installation mechanism (8) includes a positioning ring (801), the positioning ring (801) is arranged at the top end of the blown film die head (2), positioning columns (802) are symmetrically and fixedly installed on both sides of the positioning ring (801), an installation ring (803) is fixedly connected to the bottom end of the air ring (7), vertical grooves (804) are symmetrically opened at the bottom end of the inner wall of the installation ring (803), a rotating ring (805) is rotatably connected to the outer wall of the installation ring (803), a bevel gear (806) is rotatably connected to the inner wall of the installation ring (803) inside the rotating ring (805), a lead screw (807) is fixedly connected to one end of the bevel gear (806), a positioning frame (808) is connected to the outer wall of the lead screw (807), the positioning frame (808) is slidably connected to the inside of the installation ring (803), one end of the positioning frame (808) extends to the inner wall of the vertical groove (804), a clamping groove (809) is opened on the outer wall of the rotating ring (805), a clamping block (810) is rotatably connected to the outer wall of the installation ring (803) above the rotating ring (805), and a counterweight block (811) is fixedly connected to the outer wall of the clamping block (810).

7. A production process of an anti-fogging, anti-mildew and antibacterial plastic food wrap according to claim 6, characterized in that, The connecting mechanism (9) includes a threaded post (901) fixedly connected to the bottom end of the die core (10). A threaded groove (902) for the connection of the threaded post (901) to enter is provided inside the film blowing machine die head (2). First threaded holes (903) are symmetrically provided at the top end of the die core (10). Second threaded holes (904) are symmetrically provided on the outer wall of the positioning ring (801). One end of the positioning post (802) is fixedly connected to a threaded rod (905). A round hole (906) is provided on the outer wall of the positioning post (802). Connecting grooves (907) are symmetrically provided at the top end of the film blowing machine die head (2). Fixed grooves (908) are symmetrically provided on the inner wall of the connecting grooves (907). Connecting blocks (909) are symmetrically and fixedly connected to the bottom end of the positioning ring (801). Fixed blocks (910) are symmetrically and slidably connected inside the connecting blocks (909). One end of the fixed block (910) is rotatably connected to a connecting rod (911). One end of the connecting rod (911) is rotatably connected to a displacement frame (912). The displacement frame (912) is slidably connected inside the positioning ring (801) and the connecting block (909). A spring (913) is connected between the displacement frame (912) and the positioning ring (801). An extrusion rod (914) is slidably connected inside the positioning ring (801) on one side of the displacement frame (912). The extrusion rod (914) extends into the inner cavity of the second threaded hole (904).

8. The production process of an anti-fog, anti-mildew and antibacterial plastic food wrap according to claim 6, characterized in that, The inner wall of the mounting ring (803) is in contact with the outer wall of the film blowing machine die head (2). The inner wall of the vertical groove (804) is in contact with the outer wall of the positioning post (802).

9. A production process of an anti-fog, anti-mildew and antibacterial plastic food wrap according to claim 6, characterized in that, Toothed grooves are provided on the inner wall of the rotating ring (805) and are engaged with the bevel gears (806). Connecting holes are provided on the outer wall of the positioning frame (808). Threads matching the lead screw (807) are provided on the inner wall of the connecting holes. The inner wall of the card slot (809) is in contact with the outer wall of the card block (810).

10. A production process of an anti-fog, anti-mildew and antibacterial plastic food wrap according to claim 7, characterized in that, The threaded post (901) is matched with the threaded groove (902). The inner wall of the connecting groove (907) is in contact with the outer wall of the connecting block (909). The inner wall of the fixed groove (908) is in contact with the outer wall of the fixed block (910). An inclined surface is provided on one side of the displacement frame (912). The extrusion rod (914) is in contact with the inclined surface. Both the second threaded hole (904) and the first threaded hole (903) are matched with the threaded rod (905).

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