A method of reshaping a deformed label film

Abstract

The present application belongs to the technical field of film production, and particularly relates to a shaping and correcting method of a deformed label film. The shaping and correcting method of the deformed label film comprises the following steps: the deformed label film is heated to a film softening temperature by the action of a hot roller, and then enters a hot air balance area with a length of 15-20 m for processing and then is cooled and shaped; the temperature of the hot air balance area is 20-70 DEG C lower than the film softening temperature, and the temperature of the outlet area of the hot air balance area is lower than the temperature of the inlet area; the hot roller is provided with pressure rollers on both sides, and when the deformed label film is heated on the hot roller, the pressure rollers on both sides are pressed towards the central axis of the hot roller. The method provided by the present application is combined with the processes of high-temperature heating and conditioning, medium-temperature heat balance stress release and cooling and shaping, and is beneficial to fundamentally eliminating the anisotropic internal stress left by the film preparation process, and realizing the deformation correction and size stabilization of loose edges, wavy edges, vertical edges and the like.

Description

Technical Field

[0001] This invention belongs to the field of film production technology, and specifically relates to a method for shaping and correcting deformable label films. Background Technology

[0002] Oriented polypropylene film (OPP) is a type of stretchable polypropylene product. Its characteristics include high tensile strength, high rigidity, good transparency, excellent gloss, and good printability. It has become the mainstream substrate in the label manufacturing industry and is widely used in packaging labels for food, beverage, daily chemical, and pharmaceutical industries.

[0003] In the production and application of OPP label film, the dimensional stability of the film is a key indicator affecting the quality of subsequent printing and die-cutting. However, in the actual production process of OPP film, due to the influence of process formulation, production equipment and technical parameter settings, and precision control, uneven thickness and uneven stretching are unavoidable, leading to deformation problems such as loose edges, wavy edges, and sagging edges. Furthermore, subsequent processing of OPP label film, such as coating, lamination, and molding, generally requires heating, which can exacerbate loose edge and wavy edge deformation, ultimately affecting product quality, increasing product waste, and even scrapping. Therefore, deformation correction is necessary before OPP film is put into production and use.

[0004] Existing technologies for dealing with film deformation typically focus on correcting longitudinal misalignment. For example, some laminating machines use alignment devices that detect the film edge position with photoelectric sensors and drive a moving seat to move the entire roll laterally to achieve edge alignment. However, these devices primarily address the "misalignment" problem during film winding, and their effectiveness in correcting structural deformations such as lateral warping, localized ripples, or uneven tension leading to "loose edges" or "wavy edges" is very limited. Some devices use pressure rollers or crossbars to physically flatten or heat-set the film edges. However, when dealing with OPP films, which are highly rigid and subject to significant deformation stress, these devices relying solely on physical flattening cannot fundamentally eliminate internal stress. Deformation easily recurs after the external force is removed. Furthermore, existing heat-setting processes often combine simple heating and cooling. The orientation stress stored within the OPP film during the stretching process is released during heating. If the heating temperature field is uneven, the stress release will be inconsistent, potentially introducing new deformation. Therefore, the effect on correcting OPP film deformation is limited.

[0005] Therefore, in order to solve the problems of loose edges, wavy edges, and sagging edges caused by uneven thickness and uneven stretching of OPP label film, there is an urgent need for a device that can effectively eliminate the internal stress of OPP label film and efficiently correct deformation. This is of great significance for improving the quality of label products, reducing production losses, and promoting technological progress in the packaging industry. Summary of the Invention

[0006] The purpose of this invention is to address the limitations of existing deformation correction methods for OPP label films in improving deformation issues. This invention provides a deformation correction method for OPP label films that effectively releases and eliminates internal stress, thereby significantly improving issues such as loose edges, wavy edges, and sagging edges, and enhancing film quality.

[0007] This invention provides a method for shaping and correcting deformable label films. The method includes the following steps: the deformable label film is heated to its softening temperature by a hot roller, and then cooled and shaped in a hot air balancing zone of 15-20m in length; the temperature of the hot air balancing zone is 20-70°C lower than the film softening temperature, and the temperature of the outlet area of ​​the hot air balancing zone is lower than the temperature of the inlet area; pressure rollers are provided on both sides of the hot roller, and when the deformable label film is heated on the hot roller, the pressure rollers on both sides press against each other towards the central axis of the hot roller.

[0008] In a preferred embodiment, the deformable label film is an OPP label film.

[0009] In a preferred embodiment, the film softening temperature is 110~150℃, and the temperature of the hot air balance zone is 80~110℃.

[0010] In a preferred embodiment, the hot air balance zone is divided into an inlet zone, a middle zone, and an outlet zone, wherein the temperatures of the inlet zone, the middle zone, and the outlet zone are in the following order from high to low: middle zone temperature > inlet zone temperature > outlet zone temperature, or inlet zone temperature > middle zone temperature > outlet zone temperature.

[0011] In a preferred embodiment, when the temperature of the intermediate zone is higher than the temperature of the inlet zone, the temperature of the inlet zone is 90~99℃, the temperature of the intermediate zone is 100~110℃, and the temperature of the outlet zone is 80~89℃; when the temperature of the intermediate zone is lower than the temperature of the inlet zone but higher than the temperature of the outlet zone, the temperature of the inlet zone is 100~110℃, the temperature of the intermediate zone is 90~99℃, and the temperature of the outlet zone is 80~89℃.

[0012] In a preferred embodiment, the deformable label film exists in the form of a film roll, and the method further includes unwinding the deformable label film using an unwinding roller before softening the film, and winding it up using a winding roller after cooling and shaping by a cooling roller.

[0013] In a preferred embodiment, the process of heating the deformable label film to the film softening temperature is as follows: the film is first heated to a first temperature by the action of a first hot roller, and then heated to a second temperature by the action of a second hot roller, wherein the first temperature is 110~130℃ and the second temperature is 130~150℃.

[0014] In a preferred embodiment, the surfaces of the deformable label film that are heated on the first and second hot rollers are different.

[0015] In a preferred embodiment, the shaping and correction method further includes: controlling the unwinding tension to 15~30N, controlling the film tension in the hot air balance zone to 5~10N, and controlling the winding tension to 10~15N.

[0016] In a preferred embodiment, the method for controlling the unwinding tension is to control the unwinding tension by adjusting the output speed between the unwinding roller and the hot roller; the method for controlling the film tension in the hot air balance zone is to control the film tension in the hot air balance zone by adjusting the output speed between the hot roller and the cooling roller; and the method for controlling the winding tension is to control the winding tension by adjusting the output speed between the cooling roller and the winding roller.

[0017] In a preferred embodiment, the shaping and correction method further includes: controlling the unwinding tension to 15~30N, controlling the film tension between the first hot roller and the second hot roller to 5~10N, controlling the film tension in the hot air balance zone to 5~10N, and controlling the winding tension to 10~15N.

[0018] In a preferred embodiment, the method for controlling the unwinding tension is to control the unwinding tension by adjusting the output speed between the unwinding roller and the hot roller; the method for controlling the film tension between the first hot roller and the second hot roller is to control the film tension between the first hot roller and the second hot roller by adjusting the output speed between the first hot roller and the second hot roller; the method for controlling the film tension in the hot air balance zone is to control the film tension in the hot air balance zone by controlling the output speed between the second hot roller and the cooling roller; and the method for controlling the winding tension is to control the winding tension by adjusting the output speed between the cooling roller and the winding roller.

[0019] In a preferred embodiment, the residence time of the same point on the film in the hot air equilibrium zone is 15-30 seconds.

[0020] In a preferred embodiment, the cooling and shaping temperature is 15~20℃.

[0021] Beneficial effects: The key to this invention lies in processing the deformable label film using a specific combination of processes: first, high-temperature heating to soften it; then, medium-temperature hot air balancing; and finally, cooling and shaping. In the high-temperature stage, the deformable label film is heated and softened, reaching a semi-molten, zero-tension state. In this semi-molten state, the film's molecular chains are freely relaxed, gaining sufficient mobility. Simultaneously, the pressure rollers on both sides of the hot roller exert a pressing effect towards the central axis of the hot roller, keeping the film in a zero-tension (or near-zero) or low-tension state. This allows the orientation stress generated during the manufacturing process to fully relax. In other words, at this point, the film is heated and softened in the high-temperature stage to a semi-molten state and at zero tension. The deformable label film in a low-tension state can be actively tempered, causing the deformed parts of the film to shrink and flatten, and thinner areas can also be compensated, improving thickness uniformity. Then, in the medium-temperature hot air equilibrium zone of 15-20 μm, the film is held below the softening temperature, which can further adjust the stability of the molecular chain and fully release the internal residual stress, helping to overcome the "stress freezing" problem caused by direct cooling and shaping after heating in conventional processes. Finally, cooling rollers are used for cooling and shaping, freezing and stabilizing the structure. The resulting label film shows a significant improvement compared to the deformation problems before treatment, that is, loose edges, wavy edges, and sagging edges are significantly reduced. In summary, the method provided by this invention, by using a combination of high-temperature heating tempering, medium-temperature thermal equilibrium stress release, and cooling and shaping, transforms the molecular chain of the deformable label film from a forced orientation high-stress state to a naturally balanced low-stress state, fundamentally eliminating the anisotropic internal stress left over from the manufacturing process, and achieving deformation correction and dimensional stabilization of loose edges, wavy edges, and sagging edges. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the deformation label film shaping and correction device in Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of the deformation label film shaping and correction device in Embodiment 4 of the present invention.

[0024] Figure 3 This is a schematic diagram of the structure of the deformation label film shaping and correction device in Comparative Example 1 of the present invention.

[0025] Figure 4 This is a schematic diagram of the structure of the deformation label film shaping and correction device in Comparative Example 2 of the present invention.

[0026] The reference numerals in the attached drawings are explained as follows: 11, unwinding roll; 21, first hot roll; 22, rubber pressure roll I; 31, second hot roll; 32, rubber pressure roll II; 41, drying oven; 51, first cooling roll; 52, second cooling roll; 53, first pressure roll; 61, winding roll; 62, second pressure roll; 711, first tension roll; 712, first tension sensor; 721, second tension roll; 722, second tension sensor; 731, third tension roll; 732, third tension sensor; 741, fourth tension roll; 742, fourth tension sensor; 81, drive roll. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Furthermore, unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present invention.

[0028] The shaping and straightening method for deformable label films provided by this invention includes the following steps: the deformable label film is heated to its softening temperature by a hot roller, and then cooled and shaped after entering a hot air balancing zone of 15-20m in length; the temperature of the hot air balancing zone is 20-70°C lower than the film softening temperature, and the temperature of the outlet area in the hot air balancing zone is lower than the temperature of the inlet area; pressure rollers are arranged on both sides of the hot roller, and when the deformable label film is heated on the hot roller, the pressure rollers on both sides press against the central axis of the hot roller, which allows the film on the surface of the hot roller to be in a state of zero tension (or close to zero) or low tension heating. The length of the hot air balancing zone can be 15m, 16m, 17m, 18m, 19m, 20m or any value between them. The temperature of the hot air balancing zone can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or any value between them lower than the film softening temperature, which is beneficial for the film after the previous heating and conditioning steps to release stress without generating new stress. Setting the outlet temperature in the hot air balance zone to be lower than the inlet temperature helps prevent the film from experiencing a large temperature drop shock when it first enters the hot air balance zone. The lower outlet temperature also helps reduce the temperature shock when the film moves from the hot air balance zone to the cooling and shaping stage, thereby reducing new deformation problems caused by sudden temperature changes and improving the deformation correction effect of the film.

[0029] In this invention, the deformable label film is preferably an OPP label film. The film softening temperature is preferably 130~150℃, such as 130℃, 135℃, 140℃, 145℃, 150℃, or any value between them. This temperature is more conducive to the OPP label film softening under heat to reach a semi-molten state with freely relaxed molecular chains. The temperature of the hot air equilibrium zone is preferably 80~110℃, such as 80℃, 90℃, 100℃, 110℃, or any value between them.

[0030] In this invention, the hot air balance zone can be divided into an inlet zone, an intermediate zone, and an outlet zone. The inlet zone is responsible for the stable reception of the film after high-temperature tempering. The intermediate zone is the main area in the hot air balance zone for releasing the internal stress of the film. The outlet zone plays a balancing transition role between the film after the hot air releases stress and the subsequent cooling and shaping. The temperature order of the inlet zone, intermediate zone, and outlet zone from highest to lowest can be: intermediate zone temperature > inlet zone temperature > outlet zone temperature, or inlet zone temperature > intermediate zone temperature > outlet zone temperature.

[0031] In one specific embodiment, when the temperature of the intermediate zone is higher than the temperature of the inlet zone, the temperature of the inlet zone is preferably 90~99℃, such as 90℃, 92℃, 95℃, 97℃, 99℃ or any value between them; the temperature of the intermediate zone is preferably 100~110℃, such as 100℃, 102℃, 105℃, 108℃, 110℃ or any value between them; the temperature of the outlet zone is preferably 80~89℃, such as 80℃, 82℃, 85℃, 87℃, 89℃ or any value between them.

[0032] In one specific embodiment, when the temperature of the intermediate zone is lower than the temperature of the inlet zone but higher than the temperature of the outlet zone, the temperature of the inlet zone is preferably 100~110℃, such as 100℃, 102℃, 105℃, 108℃, 110℃ or any value between them; the temperature of the intermediate zone is preferably 90~99℃, such as 90℃, 92℃, 95℃, 97℃, 99℃ or any value between them; the temperature of the outlet zone is preferably 80~89℃, such as 80℃, 82℃, 85℃, 87℃, 89℃ or any value between them.

[0033] In this invention, the deformable label film exists in the form of a film roll. The method preferably includes unwinding the deformable label film using an unwinding roller before softening the film, and winding it up using a winding roller after cooling and shaping by a cooling roller.

[0034] In this invention, the preferred process for heating the deformable label film to its softening temperature is as follows: the film is first heated to a first temperature by a first hot roller, and then heated to a second temperature by a second hot roller. The first temperature is 110~130℃, such as 110℃, 115℃, 120℃, 125℃, 130℃, or any value between them; the second temperature is 130~150℃, such as 130℃, 135℃, 140℃, 145℃, 150℃, or any value between them. Using a two-step heating method to raise the film to 130~150℃ is more conducive to avoiding thermal shock caused by drastic temperature changes, allowing sufficient time for the molecular chains within the film to relax and rearrange, further improving the deformation correction effect and dimensional stability.

[0035] At this point, two pressure rollers I are symmetrically arranged on both sides of the first hot roller. When the film is heated on the first hot roller, the two pressure rollers I press towards the central axis of the first hot roller, so that the film on the surface of the first hot roller is in a state of zero tension (or close to zero) or low tension heating. Two pressure rollers I are symmetrically arranged on both sides of the second hot roller. When the film is heated on the second hot roller, the two pressure rollers II press towards the central axis of the second hot roller, so that the film on the surface of the second hot roller is in a state of zero tension (or close to zero) or low tension heating. Both pressure rollers I and pressure rollers II are preferably rubber pressure rollers.

[0036] Furthermore, the deformable label film is heated on different sides of the first and second hot rollers, which is more conducive to ensuring that both sides of the film are heated evenly.

[0037] In this invention, the shaping and correction method preferably includes controlling the unwinding tension, the film tension in the hot air balance zone, and the winding tension. The unwinding tension refers to the tension borne by the film from the unwinding roller to the hot air roller. Controlling this unwinding tension is to fully flatten the label film, which is more conducive to uniform heating of the film in subsequent heat treatment. The film tension in the hot air balance zone refers to the tension borne by the film from the hot air roller to the cooling roller. Controlling this film tension in the hot air balance zone can maximize the release and reduction of internal stress in the film. The winding tension refers to the tension borne by the film from the cooling roller to the winding roller. Controlling this winding tension allows the film to be wound and shaped better in a flat state.

[0038] In one specific embodiment, the shaping and correction method may further include: controlling the unwinding tension to 15~30N, such as 15N, 20N, 25N, 30N or any value between them; controlling the film tension in the hot air balance zone to 5~10N, such as 5N, 6N, 7N, 8N, 9N, 10N or any value between them; and controlling the winding tension to 10~15N, such as 10N, 11N, 12N, 13N, 14N, 15N or any value between them.

[0039] In one specific embodiment, the method for controlling the unwinding tension can be to control the unwinding tension by adjusting the output rotational speed between the unwinding roller and the hot roller. The method for controlling the film tension in the hot air balance zone can be to control the film tension in the hot air balance zone by adjusting the output rotational speed between the hot roller and the cooling roller. The method for controlling the winding tension can be to control the winding tension by adjusting the output rotational speed between the cooling roller and the winding roller.

[0040] In this invention, the shaping and correction method preferably includes controlling the unwinding tension, the film tension between the first and second hot rollers, the film tension in the hot air balance zone, and the winding tension. Here, the film tension between the first and second hot rollers refers to the tension borne by the film from the pressure roller I of the first hot roller to the pressure roller II of the second hot roller. Controlling this tension is necessary because the film has already been initially softened by the heat from the first hot roller; controlling this tension prevents the softened film from being subjected to excessive tension, which could lead to uncontrollable and harmful deformation.

[0041] In one specific embodiment, the shaping and correction method preferably further includes: controlling the unwinding tension to 15~30N, such as 15N, 20N, 25N, 30N or any value between them; controlling the film tension between the first hot roller and the second hot roller to 5~10N, such as 5N, 6N, 7N, 8N, 9N, 10N or any value between them; controlling the film tension in the hot air balance zone to 5~10N, such as 5N, 6N, 7N, 8N, 9N, 10N or any value between them; and controlling the winding tension to 10~15N, such as 10N, 11N, 12N, 13N, 14N, 15N or any value between them.

[0042] In one specific embodiment, the method for controlling the unwinding tension can be to control the unwinding tension by adjusting the output rotational speed between the unwinding roller and the heated roller. The method for controlling the film tension between the first heated roller and the second heated roller can be to control the film tension between the first heated roller and the second heated roller by adjusting the output rotational speed between the first heated roller and the second heated roller. The method for controlling the winding tension can be to control the winding tension by adjusting the output rotational speed between the cooled roller and the winding roller.

[0043] In this invention, the dwell time of the same point on the film in the hot air equilibrium zone is preferably 15~30s, such as 15s, 20s, 25s, 30s or any value between them.

[0044] In this invention, the preferred temperature for cooling and setting is 15~20℃, such as 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, or any value between them. In a preferred embodiment, cooling and setting is achieved by the action of cooling rollers, and the number of cooling rollers is set to two. This allows both sides of the film to be cooled and set, further improving the setting effect.

[0045] The present invention will be described in detail below through specific embodiments. These embodiments are intended to explain the invention and should not be construed as limiting it. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0046] Example 1 This embodiment illustrates a method for reshaping and correcting deformed label films. The specific process and required apparatus are as follows: (1) A device for correcting deformed label films: such as Figure 1As shown, the device includes, in sequence, an unwinding unit, an unwinding tension control unit, a first heating unit, a first tension control unit, a second heating unit, a hot air balancing unit, a second tension control unit, a cooling unit, a winding tension control unit, and a winding unit, as well as a control system. The unwinding unit includes an unwinding roller 11 and an unwinding motor driven by the unwinding roller 11. The first heating unit includes a first heating roller 21, a first drive motor driven by the first heating roller 21, and two rubber pressure rollers I 22. The two rubber pressure rollers I 22 are symmetrically arranged on both sides of the first heating roller 21 and do not directly contact each other. During operation, the two rubber pressure rollers I 22 can press towards the central axis of the first heating roller 21. The second heating unit includes a second heating roller 31, a second drive motor driven by the second heating roller 31, and two rubber pressure rollers II 32. The two rubber pressure rollers II 32 are symmetrically arranged on both sides of the second heating roller 31 and do not directly contact each other. During operation, the two rubber pressure rollers II 32 can press towards the central axis of the second heating roller 31. The hot air balancing unit includes a 15m long oven 41. The cooling unit includes a first cooling roller 51, a second cooling roller 52, a first pressure roller 53, and a third drive motor driven by the first cooling roller 51 and the second cooling roller 52. The first cooling roller 51 and the second cooling roller 52 are arranged sequentially along the film's forward direction. The first pressure roller 53 and the first cooling roller 51 form a pair of rollers. The winding unit includes a winding roller 61, a winding motor driven by the winding roller 61, and a second pressure roller 62. The second pressure roller 62 and the unwinding roller 61 form a pair of rollers. The unwinding tension control unit includes a first tension roller 711 and a first tension sensor 712 disposed on the first tension roller 711. The first tension control unit also includes a second tension roller 721 and a second tension sensor 722 disposed on the second tension roller 721. The second tension control unit is located between the hot air balancing unit and the cooling unit. The second tension control unit further includes a third tension roller 731 and a third tension sensor 732 disposed on the third tension roller 731. The winding tension control unit includes a fourth tension roller 741 and a fourth tension sensor 742 disposed on the fourth tension roller 741. The control system is signal-connected to the first tension sensor 712, the second tension sensor 722, the third tension sensor 732, the fourth tension sensor 742, the unwinding motor, the first drive motor, the second drive motor, the third drive motor, and the winding motor.The control system adjusts the output speed of the unwinding motor (speed of the unwinding roller 11) and the first drive motor (speed of the first heated roller 21) based on the detection data of the first tension sensor 712 to regulate the output speed between the unwinding roller 11 and the first heated roller 21, thereby achieving unwinding tension control. The control system is connected to the second tension sensor 722 and the second drive motor. Based on the detection data of the second tension sensor 722, the control system adjusts the output speed of the first drive motor (speed of the first heated roller 21) and the second drive motor (speed of the second heated roller 31) to regulate the output speed between the first heated roller 21 and the second heated roller 31, thereby achieving the first... Film tension control between the hot roller and the second hot roller; the control system adjusts the output speed of the second drive motor (speed of the second hot roller 31) and the third drive motor (speed of the first cooling roller 51) according to the detection data of the third tension sensor 732 to adjust the output speed between the second hot roller 31 and the first cooling roller 51, thereby realizing film tension control within the hot air balance unit; the control system adjusts the output speed of the third drive motor (speed of the first cooling roller 51) and the winding motor (speed of the winding roller 61) according to the detection data of the fourth sensor to adjust the output speed between the first cooling roller 51 and the winding roller 61, thereby realizing winding tension control.

[0047] (2) Method for shaping and correcting deformed label film: This method is carried out in the device described in (1) above. After the OPP label film is fed out from the unwinding roller, it is heated to 120°C by the action of the first hot roller. During heating, the rubber pressure rollers I, which are symmetrically arranged on both sides of the first hot roller, press against the central axis of the first hot roller. Then, the film is further heated to 150°C by the action of the second hot roller. During heating, the rubber pressure rollers II, which are symmetrically arranged on both sides of the second hot roller, press against the central axis of the second hot roller. After that, the OPP label film after conditioning enters a 15m long oven for hot air balancing treatment. The temperature of the inlet area is set to 95°C, the temperature of the middle area is set to 110°C, the temperature of the outlet area is set to 80°C, and the dwell time is 20s. Then, the film is cooled and shaped on both sides at 20°C by the first cooling roller and the second cooling roller. The OPP label film after shaping and correcting is then obtained by winding.

[0048] Specifically, the unwinding tension is controlled at 20N, the film tension between the first and second hot rollers is controlled at 10N, the film tension in the hot air balance zone is controlled at 10N, and the winding tension is controlled at 15N.

[0049] Example 2 This embodiment illustrates a method for reshaping and correcting deformed label films. The specific process and required apparatus are as follows: (1) Reshaping and correcting device for deformed label film: Same as the device described in Example 1 (1).

[0050] (2) Method for shaping and correcting deformed label film: The method described in (2) of Example 1 is followed, except that the first hot roller is heated to 110°C and the second hot roller is heated to 130°C. The following settings are made: the inlet temperature is 90°C, the middle temperature is 100°C, the outlet temperature is 80°C, the unwinding tension is controlled at 30N, the film tension between the first hot roller and the second hot roller is controlled at 10N, the film tension in the hot air balance zone is controlled at 10N, and the winding tension is controlled at 15N. All other conditions are the same as in Example 1. The OPP label film after shaping and correction is obtained by winding.

[0051] Example 3 This embodiment illustrates a method for reshaping and correcting deformed label films. The specific process and required apparatus are as follows: (1) Reshaping and correcting device for deformed label film: Same as the device described in Example 1 (1).

[0052] (2) Method for shaping and correcting deformed label film: The method described in (2) of Example 1 is followed, except that the first hot roller is heated to 130°C and the second hot roller is heated to 150°C. The following settings are made: the inlet temperature is 99°C, the middle temperature is 110°C, the outlet temperature is 85°C, the unwinding tension is controlled at 10N, the film tension between the first hot roller and the second hot roller is controlled at 5N, the film tension in the hot air balance zone is controlled at 5N, and the winding tension is controlled at 10N. All other conditions are the same as in Example 1. The OPP label film after shaping and correction is obtained by winding.

[0053] Example 4 This embodiment illustrates a method for reshaping and correcting deformed label films. The specific process and required apparatus are as follows: (1) A device for correcting deformed label films: such as Figure 2 As shown, the device includes an unwinding unit, an unwinding tension control unit, a first heating unit, a hot air balancing unit, a second tension control unit, a cooling unit, a winding tension control unit, a winding unit, and a control system arranged sequentially. Compared with the device described in Example 1 (1), except for the following differences: the first tension control unit and the second heating unit are not included, and the control system is signal-connected to the first tension sensor 712, the third tension sensor 732, the fourth tension sensor 742, the unwinding motor, the first drive motor, the third drive motor, and the winding motor. The control system adjusts the output speed of the first drive motor (the speed of the first hot roller 21) and the third drive motor (the speed of the first cooling roller 51) according to the detection data of the third tension sensor 732 to adjust the output speed between the first hot roller 21 and the first cooling roller 51, thereby realizing the film tension control in the hot air balancing unit. The rest of the structure and connection method are the same as the device described in Example 1 (1).

[0054] (2) Method for shaping and correcting deformed label film: This method is carried out in the device described in (1) above. After the OPP label film is fed out from the unwinding roller, it is heated to 150°C by the action of the first hot roller. During heating, rubber pressure rollers I are symmetrically set on both sides of the first hot roller and pressed towards the central axis of the first hot roller, so that the film on the surface of the first hot roller is in a state of zero tension heating. Then, the OPP label film after conditioning enters the oven with a length of 15m for hot air balancing treatment. The temperature of the inlet area is set to 95°C, the temperature of the middle area is 110°C, the temperature of the outlet area is 80°C, and the dwell time is 20s. Then, the film is cooled and shaped on both sides at 20°C by the first cooling roller and the second cooling roller. The OPP label film after shaping and correcting is obtained by winding.

[0055] Specifically, the unwinding tension is controlled at 20N, the film tension in the hot air balance zone is controlled at 10N, and the winding tension is controlled at 15N.

[0056] Comparative Example 1 This comparative example illustrates a method for reshaping and correcting deformed label films. The specific process and required equipment are as follows: (1) A device for correcting deformed label films: such as Figure 3 As shown, the device includes an unwinding unit, an unwinding tension control unit, a first heating unit, a second tension control unit, a cooling unit, a winding tension control unit, a winding unit, and a control system arranged sequentially. Compared with the device described in Example 4 (1), except for the following differences: the hot air balancing unit is not included; the control system adjusts the output speed of the first drive motor (speed of the first hot roller) and the third drive motor (speed of the cooling roller) according to the detection data of the third tension sensor 732 to achieve film tension control; the rest of the structure is the same as the device described in Example 4 (1).

[0057] (2) Method for shaping and correcting deformed label film: This method is carried out in the apparatus described in (1) above. After the OPP label film is fed out from the unwinding roller, it is heated to 150°C by the action of the first hot roller. During heating, the rubber pressure rollers I, which are symmetrically arranged on both sides of the first hot roller, press against the central axis of the first hot roller. Then, the OPP label film after conditioning is cooled and shaped on both sides at 20°C by the first cooling roller and the second cooling roller, and then wound up to obtain the shaped and corrected OPP label film.

[0058] Specifically, the unwinding tension is controlled at 20N, the film tension between the heating roller and the cooling roller is controlled at 10N, and the winding tension is controlled at 15N.

[0059] Comparative Example 2 This comparative example illustrates a method for reshaping and correcting deformed label films. The specific process and required equipment are as follows: (1) A device for correcting deformed label films: such as Figure 4 As shown, the device includes an unwinding unit, an unwinding tension control unit, a drive roller, a hot air balancing unit, a second tension control unit, a cooling unit, a winding tension control unit, a winding unit, and a control system arranged in sequence. Compared with the device described in Example 4(1), except for the following differences: the first heating unit is not included; an active roller 81 is provided and is connected to the fourth drive motor; and the control system is signal-connected to the first tension sensor 712, the third tension sensor 732, the fourth tension sensor 742, the unwinding motor, the fourth drive motor, the third drive motor, and the winding motor. The control system adjusts the output speed of the unwinding motor (the speed of the unwinding roller 11) and the fourth drive motor (the speed of the active roller 81) according to the detection data of the first tension sensor 712 to adjust the output speed between the unwinding roller 11 and the active roller 81, thereby realizing unwinding tension control; the control system adjusts the output speed of the fourth drive motor (the speed of the active roller 81) and the third drive motor (the speed of the first cooling roller 51) according to the detection data of the third tension sensor 732 to adjust the output speed between the active roller 81 and the first cooling roller 51, thereby realizing film tension control within the hot air balance unit. The rest of the structure is the same as the device described in Example 4(1).

[0060] (2) Method for shaping and correcting deformed label film: This method is carried out in the device described in (1) above. After the OPP label film is fed out from the unwinding roller, it directly enters the oven with a length of 15m for hot air balancing treatment. The settings are: inlet temperature is 95℃, middle temperature is 110℃, outlet temperature is 80℃, and the dwell time is 20s. Then, the film is cooled and shaped on both sides at 20℃ by the first cooling roller and the second cooling roller. The OPP label film after shaping and correction is obtained by winding.

[0061] Specifically, the unwinding tension is controlled at 20N, the film tension in the hot air balance zone is controlled at 10N, and the winding tension is controlled at 15N.

[0062] Comparative Example 3 This comparative example illustrates a method for reshaping and correcting deformed label films. The specific process and required equipment are as follows: (1) A device for correcting deformed label films: such as Figure 2 As shown, it is the same device as in Example 4.

[0063] (2) Method for straightening deformed label film: This method is carried out in the apparatus described in (1) above. After the OPP label film is fed out from the unwinding roller, it is heated to 150°C by the action of the first hot roller. During heating, rubber pressure rollers I are symmetrically set on both sides of the first hot roller and pressed towards the central axis of the first hot roller, so that the film on the surface of the first hot roller is in a state of zero tension heating. Then, the conditioned OPP label film enters a 15m long oven for hot air balancing treatment. The temperature of the inlet zone, the middle zone and the outlet zone are all set at 150°C, and the dwell time is 20s. Then, the film is cooled and shaped on both sides at 20°C by the first cooling roller and the second cooling roller, and the shaped OPP label film is obtained by winding. In this comparative example, because the temperature of the oven in the hot air balancing zone is too high, the OPP label film shrinks and is scrapped directly.

[0064] Specifically, the unwinding tension is controlled at 20N, the film tension in the hot air balance zone is controlled at 10N, and the winding tension is controlled at 15N.

[0065] Test case The OPP label film obtained by the above-described embodiments was tested for loose edges, wavy edges, and sagging edges using the following methods. The results are shown in Table 1.

[0066] (1) Loose edge test of film: The film sample is mounted on the re-inspection machine. The re-inspection machine is set with a constant tension of 5N. When the loose edge of the film is observed, a mark can be made at this point using a 1000mm span scale. Then the tension is removed, and the loose edge of the film is straightened. The film length value between the two marks is measured. Loose edge value = measured length value - 1000mm.

[0067] (2) Thin film wave edge test: The thin film sample is laid flat on a flat water platform. The valley and peak values ​​of the thin film on the horizontal surface are measured by a non-contact height sensor, and the wave size is calculated: wave amplitude = peak value - valley value.

[0068] (3) Film sag test: Clamp both ends of the film sample on the fixtures of the testing machine, set the fixture spacing to 500 mm, and apply a constant pretension of 0.5 N to straighten the sample. After the sample stabilizes, use a non-contact height sensor to measure the vertical distance between the lowest point of the sample edge and the plane connecting the two end fixtures, which is the sag.

[0069] Table 1

[0070] As can be seen from the results in Table 1, compared with Comparative Examples 1-3, Examples 1-4 of the present invention achieved a very good effect in correcting deformed label films. The label films after treatment all solved deformation problems such as loose edges, wavy edges, and sagging edges. The treatment effect of Comparative Example 1 was not good, and the treatment effect of Comparative Example 2 was better than that of Comparative Example 1, but it was still far from that of the Examples.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for reshaping and correcting deformed label films, characterized in that, The shaping and correction method includes the following steps: the deformable label film is heated to its softening temperature by a hot roller, and then cooled and shaped in a hot air balancing zone of 15-20m in length; the temperature of the hot air balancing zone is 20-70°C lower than the film softening temperature, and the temperature of the outlet area in the hot air balancing zone is lower than the temperature of the inlet area; pressure rollers are set on both sides of the hot roller, and when the deformable label film is heated on the hot roller, the pressure rollers on both sides press against the central axis of the hot roller, so that the film on the surface of the hot roller is in a state of zero tension or low tension heating; the deformable label film is an OPP label film; the film softening temperature is 130-150°C, and the temperature of the hot air balancing zone is 80-110°C.

2. The method for reshaping and correcting deformed label films according to claim 1, characterized in that, The hot air balance zone is divided into an inlet zone, a middle zone, and an outlet zone. The temperature of the inlet zone, the middle zone, and the outlet zone in descending order is: middle zone temperature > inlet zone temperature > outlet zone temperature, or, inlet zone temperature > middle zone temperature > outlet zone temperature.

3. The method for reshaping and correcting deformed label films according to claim 2, characterized in that, When the temperature of the intermediate zone is higher than the temperature of the inlet zone, the temperature of the inlet zone is 90~99℃, the temperature of the intermediate zone is 100~110℃, and the temperature of the outlet zone is 80~89℃. When the temperature of the intermediate zone is lower than that of the inlet zone but higher than that of the outlet zone, the temperature of the inlet zone is 100~110℃, the temperature of the intermediate zone is 90~99℃, and the temperature of the outlet zone is 80~89℃.

4. The method for reshaping and correcting deformed label films according to claim 1, characterized in that, The deformable label film exists in the form of a film roll. The method further includes unwinding the deformable label film using an unwinding roller before softening the film, and winding it up using a winding roller after cooling and shaping by a cooling roller.

5. The method for reshaping and correcting deformed label films according to claim 4, characterized in that, The process of heating the deformable label film to the film softening temperature is as follows: the film is first heated to a first temperature by the action of a first hot roller, and then heated to a second temperature by the action of a second hot roller, wherein the first temperature is 110~130℃ and the second temperature is 130~150℃.

6. The method for reshaping and correcting deformed label films according to claim 5, characterized in that, The deformable label film is heated on different sides of the first and second hot rollers.

7. The method for reshaping and correcting deformed label films according to claim 4, characterized in that, The shaping and correction method further includes: controlling the unwinding tension to 15~30N, controlling the film tension in the hot air balance zone to 5~10N, and controlling the winding tension to 10~15N.

8. The method for reshaping and correcting deformed label films according to claim 7, characterized in that, The method for controlling the unwinding tension is to control the unwinding tension by adjusting the output speed between the unwinding roller and the hot roller; the method for controlling the film tension in the hot air balance zone is to control the film tension in the hot air balance zone by adjusting the output speed between the hot roller and the cooling roller; the method for controlling the winding tension is to control the winding tension by adjusting the output speed between the cooling roller and the winding roller.

9. The method for reshaping and correcting deformed label films according to claim 5, characterized in that, The shaping and correction method further includes: controlling the unwinding tension to 15~30N, controlling the film tension between the first hot roller and the second hot roller to 5~10N, controlling the film tension in the hot air balance zone to 5~10N, and controlling the winding tension to 10~15N.

10. The method for reshaping and correcting deformed label films according to claim 9, characterized in that, The method for controlling the unwinding tension is to control the unwinding tension by adjusting the output speed between the unwinding roller and the hot roller; the method for controlling the film tension between the first hot roller and the second hot roller is to control the film tension between the first hot roller and the second hot roller by adjusting the output speed between the first hot roller and the second hot roller; the method for controlling the film tension in the hot air balance zone is to control the film tension in the hot air balance zone by adjusting the output speed between the second hot roller and the cooling roller; the method for controlling the winding tension is to control the winding tension by adjusting the output speed between the cooling roller and the winding roller.

11. The method for reshaping and correcting deformed label films according to claim 1, characterized in that, The residence time of the same point on the film in the hot air equilibrium zone is 15~30s.

12. The method for reshaping and correcting deformed label films according to claim 1, characterized in that, The cooling and shaping temperature is 15~20℃.

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