Preparation method and device of modified CNC / PVA coating high oil-resistant and water-resistant baking paper

Abstract

The invention provides a preparation method and device of modified CNC / PVA coating high-oil-resistance and water-resistance baking paper, and relates to the technical field of paper production, the preparation method comprises the following steps: step 1, base material pretreatment: base material paper is conveyed to a pretreatment mechanism through an unwinding mechanism; step 2, preparing a modified CNC / PVA coating liquid, performing carboxymethylation modification on CNC, and mixing the CNC with PVA according to a mass ratio of 1: 3-1: 5; 3, coating and drying, wherein a coating mechanism deposits a coating at the speed of 15-30 m / min; and 4, cooling and rolling. The device comprises an unwinding mechanism, a pretreatment mechanism is arranged on the rear side of the unwinding mechanism, a coating mechanism is arranged on the rear side of the pretreatment mechanism, a drying mechanism is arranged on the rear side of the coating mechanism, and a winding mechanism is arranged on the rear side of the drying mechanism; according to the invention, the grease barrier property and the water vapor barrier property are obviously improved, the heat-resistant cycle performance of the coating is improved, the stable long-term use performance is maintained, the device can realize slit type and lead screw type switching, and the process can be matched according to the characteristics of the coating liquid.

Description

Technical Field

[0001] The present invention relates to the technical field of paper production, and in particular to a method and device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper. Background Art

[0002] In the field of food packaging materials, baking paper is a key consumable material that comes into direct contact with food, and its functional requirements are constantly increasing with the development of the baked food industry. Traditional baking paper mostly uses pure polyvinyl alcohol (PVA) coating or fluorine-containing compound coating, but both types of materials have significant technical bottlenecks. Although pure PVA coating has the advantage of biodegradability, its molecular chain structure has poor regularity and is prone to forming microporous defects, resulting in prominent problems with the penetration of oil and water vapor molecules, especially in high-temperature baking environments, where the barrier performance is significantly attenuated. Although fluorine-containing coatings can achieve anti-stick effects through low surface energy properties, the environmental residue risks and bioaccumulation of perfluorinated compounds (PFCs) strictly limit their application.

[0003] In addition, the technical bottlenecks of existing coating equipment further restrict the industrial application of high-performance coatings. Traditional slit coating heads are prone to nozzle clogging due to slurry deposition when processing particle-containing slurries, while screw-type coating heads have insufficient precision in low-viscosity fluid coating scenarios. Poor equipment adaptability makes it difficult to handle coating fluids of different viscosities and different particle contents on the same production line, severely limiting process flexibility. If a different coating process is required, the entire coating die head needs to be replaced, which is inconvenient to use and has low material discharge. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and apparatus for preparing a modified CNC / PVA coated highly oil- and water-resistant baking paper.

[0005] The present invention provides a method for preparing a modified CNC / PVA coating highly oil-resistant and water-resistant baking paper, comprising the following steps:

[0006] Step 1: Substrate pretreatment: The substrate paper is transported to the pretreatment mechanism through the unwinding mechanism, and the spray head is cleaned at a pressure of 1.5 MPa;

[0007] Step 2: Preparation of modified CNC / PVA coating solution: CNC is modified by carboxymethylation and mixed with PVA at a mass ratio of 1:3-1:5, and dispersed at high speed;

[0008] Step 3: coating and drying: the coating mechanism deposits the coating at a speed of 15-30 m / min, and the drying mechanism dries the coating to achieve gradient evaporation of the solvent;

[0009] Step 4: Cooling and winding: reduce the paper temperature to below 25°C, and wind it through the winding mechanism. The winding tension is controlled at 50-80N.

[0010] According to a preferred technical solution, in step 2, 2% by mass of nano-silicon dioxide with a particle size of 20-50 nm and 0.5-2% by mass of a silane coupling agent are added.

[0011] A device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper, comprising an unwinding mechanism, a pretreatment mechanism disposed at the rear of the unwinding mechanism, a coating mechanism disposed at the rear of the pretreatment mechanism, a drying mechanism disposed at the rear of the coating mechanism, and a winding mechanism disposed at the rear of the drying mechanism;

[0012] The coating mechanism includes side fixing plates, an upper template is set between the side fixing plates for sliding up and down, a lower template is set between the side fixing plates and directly below the upper template for sliding up and down, the lower template opens and closes with the upper template through up and down movement, a slit is set between the front sides of the upper and lower templates, a mold cavity communicating with the slit is set on the upper inner side of the lower template, a coating liquid inlet communicating with the mold cavity is set on the upper template, and an opening and closing mechanism for controlling the opening and closing of the lower template and the upper template is set on the side fixing plates.

[0013] According to the preferred technical solution, the opening and closing mechanism includes a pushing frame horizontally slidingly arranged between the side fixed plates, and a first rotating handle and a second rotating handle are hingedly arranged at the front of both ends of the pushing frame respectively. The end of the first rotating handle away from the pushing frame is hinged to the side of the upper template, and the end of the second rotating handle away from the pushing frame is hinged to the side of the lower template. A horizontal plate is fixedly arranged between the rear ends of the side fixed plates, and a pushing cylinder is horizontally arranged between the horizontal plate and the pushing frame.

[0014] In the preferred technical solution, corresponding screw grooves are provided between the interior of the upper template and the lower template, and the screw grooves are located at the rear of the mold cavity. A shaft hole is provided at the position corresponding to the screw groove between the side portions of the upper template and the lower template. When the upper template and the lower template are closed, the screw groove is isolated from the mold cavity. A pipe groove is provided on the lower side of the interior of the upper template, and a liquid inlet pipe is provided in the pipe groove. The two ends of the pipe groove extend to both sides of the upper template. The pipe groove is located at the rear side of the screw groove, and the lower side of the liquid inlet pipe is evenly provided with a liquid outlet. A coating is provided in the screw groove. Screw, a horizontal slide is provided on the side fixed plate and corresponding to the side of the upper template and the lower template, a horizontal slide is provided for sliding inside the horizontal slide, both ends of the coating screw are rotatably connected to the horizontal slide through the shaft hole, both ends of the liquid inlet pipe are fixedly connected to the horizontal slide, a transmission motor is fixedly provided on the horizontal slide, the transmission motor is transmission-connected to the coating screw, the end side of the horizontal slide cooperates with the pushing frame, and when the upper template and the lower template are closed, there is a gap between the end side of the horizontal slide and the front side of the pushing frame.

[0015] According to a preferred technical solution, a positioning plate slidably connected to the horizontal slide is provided at the front end of the horizontal slide, and an adjusting screw is provided between the positioning plate and the side fixing plate.

[0016] According to a preferred technical solution, an air hood is fixedly provided between the side fixing plates and at the rear side of the upper template and the lower template, and an air outlet of the air hood faces the gap between the upper template and the lower template.

[0017] In a preferred technical solution, the length of the first rotating handle is greater than the length of the second rotating handle.

[0018] According to a preferred technical solution, guide rollers are respectively provided between the unwinding mechanism, the pretreatment mechanism, the coating mechanism, the drying mechanism and the winding mechanism.

[0019] Technical effects and advantages of the present invention:

[0020] 1. By combining carboxymethylated CNC with PVA and combining it with nano-silica to create a "nano-barrier layer," the high surface area and surface activity of the nano-silica form a dense barrier network, significantly improving both grease and water vapor barrier properties, overcoming the limitations of traditional PVA coatings in terms of permeability. Surface modification with a silane coupling agent significantly enhances the interfacial bonding strength of the nanoparticles, improving the coating's resistance to thermal cycling. The anchoring effect of the nano-silica imparts excellent friction resistance to the coating, maintaining stable performance over long-term use.

[0021] 2. The nano-size effect of CNC forms a three-dimensional interpenetrating network with PVA, significantly improving the tensile strength and elongation at break of the coating, effectively solving the brittleness problem of PVA coating.

[0022] 3. Slit / screw switching mechanism can match the process according to the characteristics of the coating liquid: Slit type: suitable for low-viscosity coating liquid, achieving high-precision and high-speed coating. Screw type: suitable for high-viscosity coating liquid containing particles, ensuring coating uniformity.

[0023] 4. The differential opening and closing mechanism enables precise control of the template spacing to ensure coating accuracy. The dynamic air curtain eliminates coating bubbles and reduces coating defect rates. The screw position fine-tuning device adapts to substrates of different thicknesses, improving equipment adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0025] Figure 2 It is a schematic structural diagram of the coating mechanism and the opening and closing mechanism of the present invention;

[0026] Figure 3 This is a structural diagram of the present invention when the upper template and the lower template are closed;

[0027] Figure 4 This is a schematic cross-sectional view of the upper and lower templates of the present invention when coordinated with other components;

[0028] Figure 5 This is a schematic diagram of the cross-sectional structure of the upper template and the lower template of the present invention when they are separated from other components;

[0029] Figure 6 For the present invention Figure 2 A schematic diagram of the enlarged structure of part A;

[0030] For example: 1. Unwinding mechanism; 2. Pretreatment mechanism; 3. Coating mechanism; 4. Drying mechanism; 5. Rewinding mechanism; 6. Opening and closing mechanism; 7. Guide roller; 21. Side fixing plate; 22. Upper template; 23. Lower template; 24. Slit; 25. Mold cavity; 26. Coating liquid inlet; 27. Screw groove; 28. Axis hole; 29. Pipe groove; 210. Liquid inlet pipe; 211. Liquid outlet; 212. Coating screw; 213. Horizontal slide; 214. Horizontal slide; 215. Transmission motor; 216. Positioning plate; 217. Adjusting screw; 218. Air hood; 61. Pushing frame; 62. First rotating handle; 63. Second rotating handle; 64. Horizontal plate; 65. Pushing cylinder. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] like Figures 1 to 6 shown

[0033] A method for preparing a modified CNC / PVA coated highly oil- and water-resistant baking paper comprises the following steps:

[0034] Step 1: Substrate pretreatment: the substrate paper is transported to the pretreatment mechanism 3 via the unwinding mechanism 1, and the spray head is cleaned at a pressure of 1.5 MPa;

[0035] Step 2: Preparation of modified CNC / PVA coating solution: CNC is modified by carboxymethylation and mixed with PVA at a mass ratio of 1:3-1:5. High-speed dispersion is performed at a speed of ≥3000 rpm for 30-60 min.

[0036] Step 3: coating and drying, the coating mechanism 2 deposits the coating at a speed of 15-30 m / min, and the drying mechanism 4 performs drying to achieve gradient evaporation of the solvent;

[0037] Step 4: Cooling and winding: reduce the paper temperature to below 25°C and wind it through the winding mechanism 5. The winding tension is controlled at 50-80N.

[0038] In step 2, 2% by mass of nano-silicon dioxide with a particle size of 20-50 nm and 0.5-2% by mass of a silane coupling agent are added.

[0039] like Figure 1 As shown, a device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper includes an unwinding mechanism 1, a pretreatment mechanism 3 disposed on the rear side of the unwinding mechanism 1, a coating mechanism 2 disposed on the rear side of the pretreatment mechanism 3, a drying mechanism 4 disposed on the rear side of the coating mechanism 2, and a winding mechanism 5 disposed on the rear side of the drying mechanism 4;

[0040] like Figure 2 and Figure 3As shown, the coating mechanism 2 includes side fixing plates 21, an upper template 22 is provided between the side fixing plates 21 for sliding up and down, a lower template 23 is provided between the side fixing plates 21 and directly below the upper template 22 for sliding up and down, the lower template 23 opens and closes with the upper template 22 through up and down movement, a slit 24 is provided between the front sides of the upper template 22 and the lower template 23, a mold cavity 25 communicating with the slit 24 is provided on the inner upper part of the lower template 23, a coating liquid inlet 26 communicating with the mold cavity 25 is provided on the upper template 22, and an opening and closing mechanism 6 for controlling the opening and closing of the lower template 23 and the upper template 22 is provided on the side fixing plates 21.

[0041] like Figure 1 and Figure 2 As shown, the opening and closing mechanism 6 includes a pushing frame 61 that is horizontally slidably arranged between the side fixed plates 21, and a first rotating handle 62 and a second rotating handle 63 are hingedly arranged at the front of both ends of the pushing frame 61. The end of the first rotating handle 62 away from the pushing frame 61 is hinged to the side of the upper template 22, and the end of the second rotating handle 63 away from the pushing frame 61 is hinged to the side of the lower template 23. A cross plate 64 is fixed between the rear ends of the side fixed plates 21, and a pushing cylinder 65 is horizontally arranged between the cross plate 64 and the pushing frame 61.

[0042] like Figures 1 to 4 As shown, corresponding screw grooves 27 are provided between the interior of the upper template 22 and the lower template 23. The screw groove 27 is located at the rear of the mold cavity 25. An axial hole 28 is provided at the position corresponding to the screw groove 27 between the sides of the upper template 22 and the lower template 23. When the upper template 22 and the lower template 23 are closed, the screw groove 27 is isolated from the mold cavity 25. A pipe groove 29 is provided on the lower side of the interior of the upper template 22. A liquid inlet pipe 210 is provided in the pipe groove 29. Both ends of the pipe groove 29 extend to both sides of the upper template 22. The pipe groove 29 is located at the rear side of the screw groove 27. Liquid outlets 211 are evenly provided on the lower side of the liquid inlet pipe 210. A coating screw 212 is provided in the screw groove 27. A horizontal slot 213 is provided on the side fixing plate 21, corresponding to the sides of the upper and lower mold plates 22 and 23. A horizontal slide 214 is slidably mounted within the slot 213. The ends of the coating screw 212 are rotatably connected to the slide 214 through the axial hole 28. The ends of the liquid inlet pipe 210 are fixedly connected to the slide 214. A transmission motor 215 is fixedly mounted on the slide 214, which is in transmission connection with the coating screw 212. The distal end of the slide 214 engages with the pusher frame 61. When the upper and lower mold plates 22 and 23 are closed, a gap is formed between the distal end of the slide 214 and the front side of the pusher frame 61. A hood 218 is fixedly mounted between the side fixing plates 21 and located behind the upper and lower mold plates 22 and 23. The air outlet of the hood 218 faces the gap between the upper and lower mold plates 22 and 23. The length of the first handle 62 is greater than that of the second handle 63.

[0043] like Figure 2 and Figure 6 As shown, a positioning plate 216 is provided at the front end of the horizontal slide groove 213 and is slidably connected to the horizontal slide groove 213 , and an adjusting screw 217 is provided between the positioning plate 216 and the side fixing plate 21 .

[0044] like Figure 1 As shown, guide rollers 7 are respectively provided between the unwinding mechanism 1 , the pretreatment mechanism 3 , the coating mechanism 2 , the drying mechanism 4 and the winding mechanism 5 .

[0045] The preparation method of the present invention improves the compatibility of CNC and PVA through carboxymethylation modification, achieving uniform dispersion of nanoparticles in the polymer matrix. The nano-size effect and high aspect ratio of CNC significantly enhance the mechanical properties and barrier properties of the coating, breaking through the limitations of traditional PVA coatings such as high brittleness and insufficient permeability. Nano-silica is introduced as a functional filler, and its high specific surface area and surface activity are utilized to construct a "nano-barrier layer" that effectively blocks the penetration of oil and water molecules. At the same time, the chemical modification of the silane coupling agent further strengthens the interfacial bonding between the nanoparticles and the matrix, avoiding agglomeration and shedding, and improving the long-term stability of the coating.

[0046] The present invention can select different coating methods during coating, specifically, a slit coating method and a screw coating method. When nano-silica and a silane coupling agent are not added in step 2, the coating solution has a low viscosity and does not contain granular nano-materials, so the slit coating method is more suitable. The slit coating method has higher coating precision and faster coating speed. When nano-silica and a silane coupling agent are added in step 2, the coating solution has a high viscosity and poor fluidity. The granular material may cause sedimentation when flowing, so the slit coating method is not suitable. The screw coating method has a better coating effect.

[0047] like Figures 1 to 6 shown

[0048] When the slit coating method is selected in the present invention, the cylinder 65 is pushed in a retracted state. Under the action of the first rotating handle 62 and the second rotating handle 63, the upper template 22 and the lower template 23 are in a closed state, and the coating screw 212 and the liquid inlet pipe 210 are respectively located in the screw groove 27 and the tube groove 29. At this time, the screw groove 27 and the tube groove 29 are isolated from the mold cavity 25, which plays a role in protecting the coating screw 212 and the liquid inlet pipe 210. The coating liquid in the mold cavity 25 cannot enter the screw groove 27 and the tube groove 29. Then the front side of the upper template 22 and the lower template 23 constitutes a slit-type coating structure. Specifically, the coating liquid enters from the coating liquid inlet 26 and is sprayed out from the slit 24 to coat the substrate passing through the slit 24 at a uniform speed.

[0049] When the screw coating method is selected in the present invention, the push cylinder 65 is in an extended state. In the process of extending the push cylinder 65, the push frame 61 is first driven and the upper template 22 and the lower template 23 are separated through the first rotating handle 62 and the second rotating handle 63. When the distance between the upper template 22 and the lower template 23 is sufficient for the coating screw 212 and the liquid inlet pipe 210 to pass through, the push cylinder 65 begins to contact the rear end side of the horizontal slide 214 and pushes the horizontal slide 214 to slide forward in the horizontal slide 213. When the horizontal slide 214 slides forward, The coating screw 212 and the liquid inlet pipe 210 are driven to move forward until the front end side of the horizontal slide 214 presses against the positioning plate 216, pushing the cylinder 65 to stop extending. At this time, the lower part of the coating screw 212 is located in the mold cavity 25, and the front side of the coating screw 212 is located at the slit of the original slit coating. Then the transmission motor 215 is turned on, and the transmission motor 215 drives the coating screw 212 to rotate. The liquid inlet pipe 210 continuously replenishes the coating liquid into the mold cavity 25, so that the coating screw 212 can coat the surface of the substrate passing through the front side of the coating screw 212.

[0050] During the screw coating process, the upper template 22, the lower template 23, the horizontal slide 214 and the wind shield 218 make the coating screw 212 and the liquid inlet pipe 210 in a relatively isolated environment, with only the front coating area of the coating screw 212 exposed to the outside, thus protecting the coating screw 212, the liquid inlet pipe 210 and the coating liquid. A ventilation channel is formed between the upper template 22, the lower template 23 and the horizontal slide 214. When the wind shield 218 blows air, the wind will blow from the back side of the ventilation channel to the front side, which not only prevents the coating liquid from splashing into the screw groove 27 when entering the mold cavity 25, causing waste or even outflow of the coating liquid, but also removes bubbles in the coating liquid, thereby improving the coating effect. The present invention also provides a positioning plate 216, the position of which can be adjusted by adjusting the screw 217, that is, adjusting the position of the horizontal slide 214 moving forward, so that the position of the front side of the coating screw 212 can be fine-tuned to adapt to substrates of different thicknesses. In the present invention, when the upper template 22 and the lower template 23 are opened, especially when the distance between the upper template 22 and the lower template 23 is the largest, it is convenient to clean the various components without disassembly.

[0051] It should be pointed out that, in the process of changing to the screw-type coating method of the present invention, the opening and closing mechanism 6 first controls the distance between the upper template 22 and the lower template 23 to gradually increase. When the first rotating handle 62 and the second rotating handle 63 are vertically arranged up and down, the distance between the upper template 22 and the lower template 23 reaches the maximum. At this time, the coating screw 212 and the liquid inlet pipe 210 are about to reach the preset position, pushing the cylinder 65 to continue to extend, and the distance between the upper template 22 and the lower template 23 begins to shrink again, and finally the coating screw 212 and the liquid inlet pipe 210 reach the preset position, and the lower part of the coating screw 212 is located inside the mold cavity 25, that is, the distance between the upper template 22 and the lower template 23 is a process of first increasing and then decreasing, so as to ensure that the lower part of the coating screw 212 accurately enters the interior of the mold cavity 25. Since the mold cavity 25 of the present invention is located on the upper side of the lower template 23, the distance the upper template 22 rises needs to be greater than the distance the lower template 23 falls, so as to ensure that the upper side of the upper template 22 will not touch the upper side of the coating screw 212, thereby causing interference. Therefore, the length of the first rotating handle 62 of the present invention is greater than the length of the second rotating handle 63, so that when the pushing cylinder 65 is extended, the distance the upper template 22 rises is greater than the distance the lower template 23 falls, thereby avoiding interference.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper, characterized by: The following steps are included Step 1: pretreatment of substrate, substrate paper is transported to pretreatment mechanism (3) via unwinding mechanism (1), and the spray head is cleaned at a pressure of 1.5 MPa; Step 2: Preparation of modified CNC / PVA coating solution: CNC is modified by carboxymethylation and mixed with PVA at a mass ratio of 1:3-1:5, and dispersed at high speed; Step 3: coating and drying, the coating mechanism (2) deposits the coating at a speed of 15-30 m / min, and the drying mechanism (4) performs drying to achieve gradient evaporation of the solvent; Step 4: Cooling and rewinding: lower the paper temperature to below 25°C and rewind it through the rewinding mechanism (5). The rewinding tension is controlled at 50-80N.

2. The method for preparing a modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 1, characterized in that: In the step 2, 2% by mass of nano-silicon dioxide with a particle size of 20-50 nm and 0.5-2% by mass of a silane coupling agent are added.

3. The device for preparing a modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 1 or 2, characterized in that: The invention comprises an unwinding mechanism (1), a pre-treatment mechanism (3) is provided on the rear side of the unwinding mechanism (1), a coating mechanism (2) is provided on the rear side of the pre-treatment mechanism (3), a drying mechanism (4) is provided on the rear side of the coating mechanism (2), and a rewinding mechanism (5) is provided on the rear side of the drying mechanism (4); The coating mechanism (2) includes side fixing plates (21), an upper template (22) is provided between the side fixing plates (21) for sliding up and down, a lower template (23) is provided between the side fixing plates (21) and directly below the upper template (22) for sliding up and down, the lower template (23) opens and closes with the upper template (22) through up and down movement, a slit (24) is provided between the front sides of the upper template (22) and the lower template (23), a mold cavity (25) communicating with the slit (24) is provided on the inner upper part of the lower template (23), a coating liquid inlet (26) communicating with the mold cavity (25) is provided on the upper template (22), and an opening and closing mechanism (6) for controlling the opening and closing of the lower template (23) and the upper template (22) is provided on the side fixing plates (21).

4. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 3, characterized in that: The opening and closing mechanism (6) includes a pushing frame (61) horizontally slidably arranged between the side fixing plates (21), and the front parts of the two ends of the pushing frame (61) are respectively hingedly provided with a first rotating handle (62) and a second rotating handle (63), the end of the first rotating handle (62) away from the pushing frame (61) is hinged to the side of the upper template (22), and the end of the second rotating handle (63) away from the pushing frame (61) is hinged to the side of the lower template (23), a horizontal plate (64) is fixedly arranged between the rear ends of the side fixing plates (21), and a pushing cylinder (65) is horizontally arranged between the horizontal plate (64) and the pushing frame (61).

5. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 4, characterized in that: A corresponding screw groove (27) is provided between the interior of the upper template (22) and the lower template (23), and the screw groove (27) is located at the rear of the mold cavity (25). An axial hole (28) is provided at the position corresponding to the screw groove (27) between the side of the upper template (22) and the lower template (23). When the upper template (22) and the lower template (23) are closed, the screw groove (27) is isolated from the mold cavity (25). A pipe groove (29) is provided on the lower side of the interior of the upper template (22), and a liquid inlet pipe (210) is provided in the pipe groove (29). Both ends of the pipe groove (29) extend to both sides of the upper template (22). The pipe groove (29) is located at the rear side of the screw groove (27). The lower side of the liquid inlet pipe (210) is evenly provided with a liquid outlet (211). A coating screw (212) is provided in the screw groove (27). ), a horizontal slide groove (213) is provided on the side fixing plate (21) and at a position corresponding to the side of the upper template (22) and the lower template (23), a horizontal slide plate (214) is provided inside the horizontal slide groove (213), and the two ends of the coating screw (212) are respectively rotatably connected to the horizontal slide plate (214) through the shaft hole (28), and the two ends of the liquid inlet pipe (210) are fixedly connected to the horizontal slide plate (214), and a transmission motor (215) is fixedly provided on the horizontal slide plate (214), and the transmission motor (210) is transmission-connected to the coating screw (212), and the end side of the horizontal slide plate (214) cooperates with the pushing frame (61), and when the upper template (22) and the lower template (23) are closed, there is a gap between the end side of the horizontal slide plate (214) and the front side of the pushing frame (61).

6. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 5, characterized in that: A positioning plate (216) slidably connected to the horizontal slide groove (213) is provided at the front end of the horizontal slide groove (213), and an adjusting screw (217) is provided between the positioning plate (216) and the side fixing plate (21).

7. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 5, characterized in that: An air hood (218) is fixedly provided between the side fixing plates (21) and at the rear side of the upper template (22) and the lower template (23), and the air outlet of the air hood (218) faces the gap between the upper template (22) and the lower template (23).

8. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 5, characterized in that: The length of the first rotating handle (62) is greater than the length of the second rotating handle (63).

9. The device for preparing modified CNC / PVA coated highly oil- and water-resistant baking paper according to claim 5, characterized in that: Guide rollers (7) are respectively provided between the unwinding mechanism (1), the pretreatment mechanism (2), the coating mechanism (3), the drying mechanism (4) and the winding mechanism (5).

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