High-speed and high-stability reverse coating surface treatment process and device

Abstract

A high-speed and high-stability reverse coating surface treatment process and device are provided herein, which comprises the following steps: S1, longitudinal stretching of a film, and surface corona treatment after the longitudinal stretching is completed; S2, single-sided or double-sided, single-layer or multi-layer reverse surface coating of the film subjected to the surface corona treatment; and S3, transverse stretching after the coating is completed. The on-line normal pressure cavity reverse coating processing mode can change the performance of the film surface after the on-line surface treatment of the film, can enhance the adhesion of the aluminum layer or ink of the aluminum printing composite product, and can meet the requirements of various high-performance products after the aluminum printing composite. In the reverse coating process, the precise control of the coating thickness can be realized through the adjustment of the scraper type liquid inlet assembly, the bubbles possibly generated on the film surface can be extruded and broken through the negative pressure adsorption device, so that the stability and uniformity of the overall coating are maintained, and the high-speed coating is realized.

Description

Technical Field

[0001] This article relates to a high-speed and highly stable reverse coating surface treatment process and apparatus. Background Technology

[0002] BOPET film is typically prepared by corona treatment at the traction position, or by applying an external coating to the warp threads of the pre-made base film, depending on the application requirements of the product, to produce various functional products such as aluminized printing base film, adhesive products, release protective base film, and solar base film.

[0003] In applications such as food packaging, industrial products, and electronic products, most products require aluminized printing lamination. Relying solely on simple online corona treatment results in low adhesion of the aluminized film surface. Lamination with printed products requires specialized inks, leading to poor surface printing quality and insufficiently saturated and vibrant colors, failing to meet the requirements of high-performance products. Furthermore, existing off-line coating equipment requires drying the film coating layer in an oven approximately 15 to 40 meters long. This off-line coating method has relatively low production efficiency, resulting in energy waste and redundant investment of various resources, leading to very high manufacturing costs.

[0004] Currently, all coating equipment requires drying the film coating layer in an oven of about 15 to 40 meters. This off-line coating method has low production efficiency, resulting in energy waste and repeated investment of various resources, leading to extremely high production and manufacturing costs.

[0005] Furthermore, with increasingly stringent requirements for food packaging materials, polyester films treated with conventional corona treatment are prone to aluminum layer peeling off during pasteurization or high-temperature sterilization after aluminized composite bag making. This reduces the barrier properties of the packaging material and renders it unsuitable for liquid packaging, failing to fully meet the safety and functionality requirements of food packaging. Polyester films treated with surface corona treatment also exhibit weak adhesion to inks, making them susceptible to ink flaking or peeling during the printing process. Summary of the Invention

[0006] To address the aforementioned issues, this solution provides an integrated online surface treatment solution for the production of biaxially oriented polyester film (BOPET).

[0007] Among them, between the longitudinal stretching exit and the transverse stretching, a brand-new surface treatment method is added to the transverse stretching and drying process in the production process. The surface treatment is carried out on one or both sides of the film surface, adding one or two layers of ultra-thin uniform surface coating. This can change the surface tension of the film, such as enhancing the adhesion of the aluminum layer or ink to aluminized printed composite products, in order to meet the high performance requirements of various high-performance products after aluminized printing composite.

[0008] A high-speed, high-stability reverse coating surface treatment process includes the following steps:

[0009] S1. The film is longitudinally stretched, and after longitudinal stretching, the surface is subjected to corona treatment.

[0010] S2. Perform reverse surface coating on the film that has undergone surface corona treatment, either on one or both sides, or in a single or multiple layer.

[0011] S3. After coating, perform lateral stretching.

[0012] Furthermore, it includes a reverse coating mechanism with multiple atmospheric pressure chambers disposed between the inlet of the transverse tension structure and the outlet of the longitudinal tension structure;

[0013] The atmospheric pressure chamber reverse coating mechanism includes a coating head, a scraper-type liquid inlet assembly, and at least two negative pressure adsorption devices;

[0014] At least one negative pressure adsorption device is provided on both sides of the coating head. A gap is provided between the top of the negative pressure adsorption device and the film to be coated. The direction of rotation of the coating head is opposite to the direction of movement of the film.

[0015] The gap is caused by the film having a certain amount of elastic deformation. After the negative pressure adsorption device below generates adsorption force, the film will move downward. However, due to the presence of the coating head, the film cannot move downward indefinitely, so there is always a certain gap between the film and the negative pressure adsorption device.

[0016] This configuration ensures that the lower surface of the film does not come into contact with any non-processed parts, while also subjecting the film to a continuous downward force. This force causes air bubbles in the coating liquid to be squeezed and burst, thereby preventing the film from moving upward and generating air bubbles during the coating process, thus maintaining the coating quality.

[0017] The coating head includes a rotating shaft, an annular roller, left and right baffles, and annular baffles. The rotating shaft is located at the central axis of the overall coating head and is the drive shaft. An annular roller is sleeved on the upper surface of the rotating shaft and moves together with the rotating shaft. Left and right baffles are provided at both ends of the annular roller, and annular baffles are provided on the inner walls of the left and right baffles.

[0018] The inner wall of the annular baffle, the side walls of the left and right baffles, and the upper surface of the annular roller together form the left and right recovery cavities distributed at both ends of the coating head. The left and right recovery cavities are semi-closed cavity structures, and negative pressure recovery holes are provided inside the left and right recovery cavities.

[0019] The atmospheric pressure chamber reverse coating mechanism is equipped with multiple flattening rollers and guide rollers between the transverse stretching structure and the longitudinal stretching structure.

[0020] To facilitate precise adjustment and control of the coating thickness, the atmospheric pressure chamber reverse coating mechanism is mounted on a precision dovetail slide adjustment device. The coating thickness is adjusted by opening and closing two dovetail slides in the direction of the coating head.

[0021] The atmospheric pressure reverse coating mechanism includes an L-shaped scraper seat, scraper blade, and pressure member. When the L-shaped scraper seat, scraper blade, pressure member, and coating head are close together, they form a U-shaped cavity. Liquid overflows from both sides of the inlet at the bottom, ensuring that the liquid level in the cavity remains constant. Simultaneously, a perforated plate with 3mm diameter pores spaced 4mm apart is installed in the L-shaped scraper seat. The perforated plate is positioned between the inlet hole and the coating head, separating the inlet liquid from the coating liquid and serving to defoam.

[0022] Beneficial effects:

[0023] Compared to existing uncoated processing methods, this system modifies the surface of the thin film by applying a water-based coating, thereby increasing the wet tension of the film surface. Furthermore, it employs a reverse coating method, utilizing multiple atmospheric pressure chambers for reverse coating, with the coating head rotating in the opposite direction to the film's movement, enabling more uniform and meticulous coating.

[0024] Furthermore, the negative pressure adsorption device installed on the coating equipment can better fix the film, reduce shaking and deviation, and ensure the stability of the coating process. The specific structural design of the coating head, including the rotating shaft, annular roller, and baffles, helps to precisely control the coating range and thickness. This method can also promptly remove excess coating material, preventing phenomena such as bubbles, bulging, and dripping during the coating process. Moreover, the multiple atmospheric pressure chamber reverse coating mechanisms can be flexibly adjusted and combined according to specific needs to meet different production requirements. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the overall coating surface treatment solution;

[0026] Figure 2 This is a schematic diagram of a reverse coating apparatus;

[0027] Figure 3 This is a schematic diagram of the reverse coating roller during coating;

[0028] Figure 4 This is a schematic diagram of the reverse coating roller structure;

[0029] 1. Longitudinal stretching machine outlet guide roller; 2. Lower corona device; 3. Upper corona device; 4. Flattening roller one; 5. Guide roller one; 6. Flattening roller two; 7. Film lifting roller one; 8. Edge pressing roller; 9. Lower atmospheric pressure chamber liquid supply device; 10. Coating head one; 11. Edge lifting roller one; 12. Guide roller two; 13. Flattening roller three; 14. Film lifting roller two; 15. Upper atmospheric pressure chamber liquid supply device; 16. Coating head two; 17. Edge lifting roller two; 18. Flattening device; 19. Transverse stretching machine inlet; 91. Scraper-type liquid inlet assembly; 92. Negative pressure adsorption device; 101. Rotating shaft; 102. Annular roller; 103. Left and right recovery chambers; 104. Left and right baffles; 105. Negative pressure recovery hole; 106. Annular baffle; 20. Film to be processed. Detailed Implementation

[0030] To enhance understanding of the present invention, the invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only for explaining the invention and do not constitute a limitation on the scope of protection of the invention.

[0031] Example 1:

[0032] A comprehensive solution for atmospheric pressure chamber reverse coating surface treatment involves adding a single- or double-sided pre-corona treatment and single- or double-sided atmospheric pressure chamber reverse coating machine between the longitudinal stretching outlet and the transverse stretching inlet in the biaxially oriented polyester film (BOPET) process.

[0033] The design principle of this equipment is based on a biaxially oriented polyester film (BOPET) production line with a film width of 6.7m and a maximum linear speed of 350m / min. The basic information of the equipment is as follows:

[0034] Corona treatment: It consists of a corona roller, an electrode device and a guide roller. All rollers are set as driven rollers. The opening and closing of the corona device is interlocked with the speed of the corona roller. The treatment can be controlled independently on one or both sides. Power 15KW*2; exhaust system 3KW.

[0035] The integrated embedded device consists of a frame, flattening rollers, guide rollers, film lifting rollers, edge lifting wheels, an atmospheric pressure chamber liquid supply device, and a coating head. The atmospheric pressure chamber liquid supply device and coating head are integrated as a drawer and placed on the guide rails of the moving trolley. The atmospheric pressure chamber reverse coating frame also has corresponding docking guide rails. The coated film is fed in through the guide rails during production and removed when not in use.

[0036] The scraper-type liquid inlet assembly and coating head are integrated and placed on the guide rail of the mobile trolley. It can be lifted by a hydraulic manual pump, and the heavy-duty rubber wheels are ground-based for movement. After reaching the usage position, it is quickly positioned by a conical device. This means that this online processing equipment can be pulled away from the usage position when not producing online processed products.

[0037] The scraper-type liquid inlet assembly consists of an L-shaped scraper seat, scraper blades, a pressure component, and a defoaming component. The L-shaped scraper seat has an opening at its bottom that connects to the liquid supply pipe, and overflow seals are installed on both sides. The entire assembly is mounted on two precision dovetail slide adjustment devices on the left and right sides. These slides can be adjusted to open and close towards the coating head. When the L-shaped scraper seat, scraper blades, pressure component, and coating head are close together, they form a U-shaped cavity. Liquid overflows from both sides of the bottom inlet, ensuring the liquid level in the cavity remains constant. A perforated plate with 3mm diameter holes spaced 4mm apart is located in the center of the L-shaped scraper seat. This perforated plate is positioned between the liquid inlet and the coating head, separating the inlet and outlet liquids and serving a defoaming function. The entire assembly is fed in by a trolley, lifted and positioned by a hydraulic cylinder, and secured with mechanical bolts. The drive motor is manually engaged and locked with bolts.

[0038] III. Among them:

[0039] 1. After the drawer-type atmospheric pressure chamber liquid supply device and coating head are integrated with the frame and fixed in place, the coating process is achieved by changing the height of one of the lifting rollers 7 in the film conveying process to adjust the contact amount between the film surface and the coating head. Since the lifting roller 7 is a driven roller without an associated mechanism, it is much easier to achieve stable and precise movement of the lifting roller than the former. The structure is also relatively simple and reliable. The feed rate can be adjusted so that the feed rate is 0.2mm per revolution of the adjustment handle, that is, the feed rate is 0.2 / 360 = 0.00056mm per 1° rotation of the handle.

[0040] 2. The edge lifting wheel device also prevents the edge film that cannot be used as a product from being processed, so recycling and granulation are not a problem; at the same time, the edge material does not stick to the coating liquid, and it will not affect the next process of horizontal pulling and clamping.

[0041] 3. The liquid supply pump adopts a peristaltic liquid pump, so the coating liquid only flows in the pipeline and does not come into contact with other easily worn parts, making secondary cleaning of the system very convenient.

[0042] 4. The liquid supply system has good defoaming performance. The liquid supply to the coating head adopts a semi-open atmospheric pressure liquid storage tank, and an additional defoaming porous plate is added to ensure that each concave hole of the coating head is evenly filled with liquid and there are no air bubbles.

[0043] 5. This equipment also uses an arc-shaped roller and an outlet expansion wheel device to make the entire film surface flat, thereby greatly reducing the possibility of leakage treatment.

[0044] Production process such as Figure 1As shown, the movement direction of the film to be coated 20 is from right to left, and the sequence from right to left is longitudinal stretching, corona treatment, reverse coating in the atmospheric pressure chamber, and transverse stretching. The equipment includes a longitudinal stretching machine outlet guide roller 1, a lower corona device 2, an upper corona device 3, a flattening roller 1 4, a guide roller 1 5, a flattening roller 2 6, a film lifting roller 1 7, a pressing roller 8, a lower atmospheric pressure chamber liquid supply device 9, a coating head 1 10, a lifting roller 1 11, a guide roller 2 12, a flattening roller 3 13, a film lifting roller 2 14, an upper atmospheric pressure chamber liquid supply device 15, a coating head 2 16, a lifting roller 2 17, a flattening device 18, and a transverse stretching machine inlet 19.

[0045] During the reverse coating process, the coating head 10 and coating head 26 move in opposite directions to the film 20 to be coated. The coating thickness can be precisely controlled by adjusting the scraper-type liquid inlet component. The air bubbles that may be generated on the film surface are squeezed and broken by the left and right recovery chambers 103 and the negative pressure adsorption device 92, thereby maintaining the stability and uniformity of the overall coating and achieving high-speed coating.

[0046] 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 within the protection scope of the present invention.

Claims

1. A high-speed, high-stability reverse coating surface treatment process, characterized in that, Includes the following steps: S1. The film is longitudinally stretched, and after longitudinal stretching, the surface is subjected to corona treatment. S2. Perform reverse surface coating on the film that has undergone surface corona treatment, either on one or both sides, or in a single or multiple layer. S3. After coating, perform lateral stretching; The processing apparatus of the process includes a plurality of atmospheric pressure chamber reverse coating mechanisms disposed between the inlet of the transverse stretching structure and the outlet of the longitudinal stretching structure. The atmospheric pressure chamber reverse coating mechanism includes a coating head, a scraper-type liquid inlet assembly, and at least two negative pressure adsorption devices; At least one negative pressure adsorption device is provided on both sides of the coating head. A gap is provided between the top of the negative pressure adsorption device and the film to be coated. The direction of rotation of the coating head is opposite to the direction of film movement. The coating head includes a rotating shaft, an annular roller, left and right baffles, and annular baffles. The rotating shaft is located at the central axis of the overall coating head and is the drive shaft. An annular roller is sleeved on the upper surface of the rotating shaft and moves together with the rotating shaft. Left and right baffles are provided at both ends of the annular roller, and annular baffles are provided on the inner walls of the left and right baffles. The inner wall of the annular baffle, the side walls of the left and right baffles, and the upper surface of the annular roller together form the left and right recovery cavities distributed at both ends of the coating head. The left and right recovery cavities are semi-closed cavity structures, and negative pressure recovery holes are provided inside the left and right recovery cavities.

2. The high-speed, high-stability reverse coating surface treatment process according to claim 1, characterized in that, Multiple flattening rollers and guide rollers are provided between the atmospheric pressure chamber reverse coating mechanism and the transverse stretching structure and the longitudinal stretching structure.

3. The high-speed, high-stability reverse coating surface treatment process according to claim 1, characterized in that, The atmospheric pressure chamber reverse coating mechanism is mounted on a precision dovetail slide adjustment device, and is adjusted by opening and closing the two dovetail slides in the direction of the coating head. The atmospheric pressure chamber reverse coating mechanism includes an L-shaped scraper seat, scraper blade, and pressure member. When the L-shaped scraper seat, scraper blade, pressure member, and coating head are close together, they form a U-shaped cavity. Liquid enters from the bottom and overflows from both sides, ensuring that the liquid level in the cavity is always kept at a certain level.

4. The high-speed, high-stability reverse coating surface treatment process according to claim 3, characterized in that, A perforated plate is installed in the L-shaped scraper holder.

5. The high-speed, high-stability reverse coating surface treatment process according to claim 4, characterized in that, The perforated plate has a pore diameter of 3mm and is evenly distributed at 4mm intervals.

6. The high-speed, high-stability reverse coating surface treatment process according to claim 4, characterized in that, The perforated plate is positioned between the liquid inlet and the coating head, separating the liquid inlet from the liquid being used, and its function is to defoam.

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