PVB (polyvinyl butyral) anti-sticking film production device and production process

Abstract

The invention relates to the technical field of film sticking prevention, in particular to a PVB (polyvinyl butyral) anti-sticking film production device and a PVB anti-sticking film production process. The PVB anti-sticking film production device comprises a casting die head, a cooling water tank, a water driving roller, a main cooling roller and a winding device which are sequentially arranged along a production line; according to the invention, the online embossing system is additionally arranged between the water driving roller and the main cooling roller, so that the surface of the produced film has micron-sized convex anti-sticking textures, the contact area between the films is greatly reduced under the conditions of rolling transportation and the like of the films, the anti-sticking stripping force is reduced from 2.4 N / cm to an extremely low level of 0.5 N / cm, and the production efficiency is greatly improved. Compared with the technical means of relying on low-temperature storage and adding an isolating membrane in the prior art, the cost is greatly reduced, and the film with the greatly improved anti-sticking effect is obtained by slightly sacrificing haze and bonding strength under the condition that the production cost and the process complexity are not excessively increased and the industrial standard is met.

Description

Technical Field

[0001] This invention relates to the field of anti-stick film technology, specifically to a PVB anti-stick film production apparatus and production process. Background Technology

[0002] Polyvinyl butyral (PVB) film, as an important intermediate material for safety glass, is widely used in automotive windshields and architectural laminated glass. PVB resin is typically formed by the condensation of polyvinyl alcohol and butyral under acid catalysis. Its molecular chain contains a large number of hydroxyl groups, which gives PVB resin good compatibility with plasticizers, but also results in a strong adhesive surface on the film. This adhesiveness makes PVB film prone to self-adhesion during storage, transportation, and processing, causing significant inconvenience to production operations.

[0003] The industry commonly uses methods such as low-temperature storage (approximately 5°-15°C) or the addition of a release liner to prevent PVB films from sticking together. However, these measures increase production costs and complexity, and also introduce quality risks. For variants of standard PVB sheets (such as PVB sheets with added high plasticizer content to improve sound insulation), sticking can still occur even under low-temperature conditions. Therefore, there is an urgent need to develop a technology for producing anti-stick films that can effectively solve the self-adhesion problem of PVB films while maintaining their excellent optical and adhesive properties, without excessively increasing production costs and process complexity.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to design an apparatus and process for producing anti-adhesive films, which effectively solves the self-adhesion problem of PVB films while maintaining their excellent optical and adhesive properties, without excessively increasing production costs and process complexity, thus addressing the aforementioned shortcomings in the technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a PVB anti-stick film production apparatus, comprising a casting die, a cooling water tank, a water-removing roller, a main cooling roller, and a winding device arranged sequentially along a production line, wherein the water-removing roller and the main cooling roller are further provided with: Guide rollers and an online embossing system, the online embossing system comprising a front embossing unit and a rear embossing unit arranged sequentially along the film travel direction; The front embossing unit includes an upper front embossing roller and a lower front embossing roller arranged opposite to each other. The roller surface of the upper front embossing roller has a pit structure for forming a micro-convex anti-stick texture on the front side of the film. The rear embossing unit includes an upper rear embossing roller and a lower rear embossing roller arranged opposite to each other, and the roller surface of the upper rear embossing roller has the recessed structure; Furthermore, hot oil is circulated inside the front embossing upper roller, the front embossing lower roller, the rear embossing upper roller, and the rear embossing lower roller, so that the contacting film is heated to the plastic temperature range for embossing, while accelerating the evaporation of water vapor, and the rear embossing lower roller adheres to the film on the guide roller; The heat from the lower embossing roller accelerates the removal of moisture from the front side of the film, improving the printing effect of the upper embossing roller on the front side of the film. At the same time, the heat from the lower embossing roller accelerates the removal of moisture from the back side of the film, improving the printing effect of the upper embossing roller on the back side of the film.

[0007] Preferably, the pit structure is non-periodicly distributed on the roller surface, and the cross-sectional shape of the pit structure is a frustum-shaped cone without sharp edges.

[0008] Preferably, the recessed structure has multiple recesses distributed spirally on the roller surface, and the recessed structure has N interruptions that divide the recessed structure into N+1 anti-sticking holes, the length of the anti-sticking holes is 240±5μm, and the length of the interruptions is 25±5μm.

[0009] Preferably, the interruption filler and the adjacent interruption filler along the film travel direction are spaced apart in the length direction of the roller surface.

[0010] Preferably, the depth of the pit structure is 85±5μm, and the distance between the deepest points of two adjacent pit structures is 275-300μm.

[0011] Preferably, the angle between the length direction of the pit structure and the film travel direction is 45°.

[0012] Preferably, the cross-section of the pit structure is asymmetrical, with the slope between one side of the pit structure and the film being greater than that between the other side and the film. Both sides of the pit structure are smooth curved surfaces, and the cross-sectional shape of one pit structure is different from that of the adjacent pit structures.

[0013] Secondly, the present invention also provides a PVB anti-stick film production process for operating the production apparatus, comprising the following steps: S1: Preliminary film forming: The molten film is discharged from the casting die and passes through the cooling water tank and the water-dripping roller in sequence to obtain the preliminary film forming; S2: Front embossing: The pre-formed film is passed through the front embossing unit, and the front side of the film is embossed at the film temperature T1 to obtain a pit structure. The embossing pressure is P1. S3: Post-embossing: The film is passed through the post-embossing unit, and a pit structure is embossed on the back of the film at a film temperature of T2. The embossing pressure is P2, and then the film is cooled by the main cooling roller. S4: Winding up, the film is wound up to obtain the finished PVB anti-stick film.

[0014] Preferably, the film temperatures T1 and P1 in S2 and the film temperatures T2 and P2 in S3 satisfy the following relationship: T1 > T2, P1 < P2, and the temperature range of T1 and T2 is controlled between 100℃ and 180℃ according to the film travel speed.

[0015] The technical effects and advantages provided by the present invention in the above technical solution are as follows: This invention adds an online embossing system between the water-driving roller and the main cooling roller, resulting in a micron-level raised anti-stick texture on the surface of the produced film. This significantly reduces the contact area between films during winding and transportation, and lowers the anti-sticking peel force from 2.4 N / cm to an extremely low level of 0.5 N / cm. Compared with existing technologies that rely on low-temperature storage and the addition of a release film, the cost is significantly reduced. This invention designs the pit structure on the roller surface, adopting a non-periodic distribution and intermittent filling structure. Without affecting the anti-sticking effect, it can effectively disrupt the reflection, refraction, and diffraction paths of light in the film. This not only controls the haze of the film product to 1.1%, but also avoids optical interference images such as moiré patterns caused by periodic structures, breaking the traditional understanding of achieving both high light transmittance and low haze. The present invention features an asymmetrical structure with different slopes on both sides of the pit structure and a smooth curved surface. At the same time, the end is a frustum-shaped cone without sharp edges. This design avoids stress concentration when the film is rolled up and can further disrupt the paths of light reflection, refraction, and diffraction within the film, thereby further reducing the generation of optical interference images. This invention achieves a film with significantly improved anti-sticking effect by slightly sacrificing haze and adhesive strength, without excessively increasing production costs and process complexity, while meeting industry standards. In this invention, by designing guide rollers and adjusting the layout of the front embossing unit and the rear embossing unit, when the film comes out of the cooling water tank and most of the moisture is removed by the water-removing roller, the residual moisture on the front and back of the film does not require additional drying equipment. Instead, the high temperature of 100℃-180℃ on the lower rear embossing roller removes most of the moisture on the front of the film, improving the printing effect of the upper front embossing roller on the front of the film. At the same time, the high temperature of 100℃-180℃ on the lower front embossing roller removes most of the moisture on the back of the film, improving the printing effect of the upper rear embossing roller on the back of the film. This invention utilizes the characteristic that the front embossing unit and the rear embossing unit need to heat the film surface to 100℃-180℃ during printing, and uses the heat wasted in the air to remove residual moisture on the film surface after the water-removing roller, which not only saves the cost of setting up drying equipment, but also reduces the floor space required. The asymmetrical design of the pit structure and the smooth curved surfaces on both sides in this invention not only produces a film with a slight sacrifice in haze and adhesion strength, resulting in a significant improvement in anti-sticking effect, but also removes moisture from the film surface through the water-removing roller, the front embossing unit, and the rear embossing unit. Even if a little moisture remains, it will be heated within the pit structure and most of it will be discharged from both sides in time, without affecting the formation of the film of the expected quality. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 This is a schematic diagram of the overall structure and flow of the production device of the present invention; Figure 2 This is a schematic diagram showing the distribution of the pit structure on the roller surface of the present invention; Figure 3 For the present invention Figure 2 Enlarged view of the A-section structure; Figure 4 This is a schematic cross-sectional view of the recess structure of the present invention; Figure 5 This is a schematic diagram of the distribution of micro-convex anti-stick texture on the film of the present invention; Figure 6 This is a simplified schematic diagram of the micro-convex anti-stick texture of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Casting die head; 2. Cooling water tank; 3. Water-dripping roller; 4. Main cooling roller; 5. Rewinding device; 6. Front embossing unit; 601. Front embossing upper roller; 602. Front embossing lower roller; 7. Rear embossing unit; 701. Rear embossing upper roller; 702. Rear embossing lower roller; 8. Roller surface; 9. Dent structure; 901. Interval filling; 902. Anti-sticking hole; 10. Guide roller. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0021] This invention provides, for example Figures 1-6 The PVB anti-stick film production apparatus shown includes a casting die 1, a cooling water tank 2, a water-repelling roller 3, a main cooling roller 4, and a winding device 5 arranged sequentially along the production line. Unlike the existing technology that uses low-temperature storage at 5℃-15℃ or the addition of a release film to prevent the film from self-adheding, this technical solution also includes an online embossing system. The online embossing system includes a front embossing unit 6 and a rear embossing unit 7 arranged sequentially along the film's travel direction. The front embossing unit 6 includes a front embossing upper roller 601 and a front embossing lower roller 602 arranged opposite each other, and the rear embossing unit 7 includes a rear embossing upper roller 701 and a rear embossing lower roller 702 arranged opposite each other. The roller surfaces 8 of the front embossing upper roller 601 and the rear embossing upper roller 701 both have pit structures 9 for forming micro-convex anti-stick textures on the front and back sides of the film.

[0022] To achieve excellent anti-sticking performance while maintaining the superior optical and adhesive properties of PVB film, we configured multiple recessed structures 9, arranged in a spiral pattern on the roller surface 8. The angle between the length direction of the recessed structure 9 and the film travel direction is 45°, the depth of the recessed structure 9 is 85±5μm, and the distance between the deepest points of two adjacent recessed structures 9 is 275-300μm. The cross-section of the recessed structure 9 is asymmetrical, with the slope of one side contacting the film being greater than that of the other side. To reduce stress concentration of the micro-protrusion anti-sticking texture on the film, the cross-sectional shape of the recessed structure 9 is a frustum-shaped cone without sharp edges, and the sides and ends are rounded. This can also further reduce the impact of residual moisture on the film surface during printing on the forming quality, as the moisture is easily discharged from both sides after being heated.

[0023] To avoid optical interference patterns on the film caused by the micro-convex anti-stick texture, the cross-sectional shapes of two adjacent pit structures 9 are different. Simultaneously, the pit structure 9 has multiple interrupted fillers 901 along its length, dividing it into multiple anti-stick holes 902. The length of each anti-stick hole 902 is 240±5μm, and the length of each interrupted filler 901 is 25±5μm. Furthermore, two adjacent interrupted fillers 901 along the film's travel direction are spaced apart along the length of the roller surface 8. This results in the micro-convex anti-stick texture on the film exhibiting a pattern similar to... Figure 5 The pattern shown avoids the generation of optical interference patterns.

[0024] To ensure that residual moisture on the film surface after passing through the dewatering roller 3 does not affect the film's production quality, a guide roller 10 is installed between the dewatering roller 3 and the main cooling roller 4. The layout of the front embossing unit 6 and the rear embossing unit 7 is also altered. Hot oil is circulated through the front embossing upper roller 601, front embossing lower roller 602, rear embossing upper roller 701, and rear embossing lower roller 702 to raise the temperature to 100℃-180℃, a temperature commonly used in printing. This heats the contacting film to the plastic temperature range for embossing, while simultaneously accelerating moisture evaporation. The rear embossing lower roller 702 adheres to the film on the guide roller 10. The heat from the rear embossing lower roller 702 accelerates the removal of moisture from the front of the film, improving the printing effect of the front embossing upper roller 601 on the front of the film. Simultaneously, the heat from the front embossing lower roller 602 accelerates the removal of moisture from the back of the film, improving the printing effect of the rear embossing upper roller 701 on the back of the film.

[0025] Example 1: The PVB film produced using the above-described production apparatus has a micro-raised anti-stick texture on its surface, as shown in the example below. Figure 5 Figure 6 As shown, the height of the micro-convex anti-adhesion texture is 85±5μm, the distance between the two adjacent highest points of 85±5μm is 275-300μm, the length of the micro-convex anti-adhesion texture is 240±5μm, and the distance between two adjacent micro-convex anti-adhesion textures along the length direction is 25±5μm.

[0026] Comparative Example 1 is a textureless film produced using existing embossing rollers, i.e., a PVB film of the same material. The only difference between it and Example 1 is that the film surface does not have micro-protrusion anti-stick texture.

[0027] Comparative Example 2, the film produced using the above-described production apparatus differs from Example 1 only in that the height of the micro-convex anti-stick texture is 30±5μm, while other parameters are the same.

[0028] Comparative Example 3, the film produced using the above-described production apparatus, differs from Example 1 only in that the spacing between two adjacent micro-convex anti-stick textures along the film's travel direction is 200±10μm, while other parameters are the same.

[0029] Comparative Example 4 uses a film produced by the above-mentioned production equipment. The only difference from Example 1 is that the micro-convex anti-stick texture is not broken into a spiral line along the length direction, that is, the pit structure 9 does not have a break-filling 901. All other parameters are the same.

[0030] The above five films were tested, mainly for the following: For the bonding strength, the film and glass are laminated to form a sample, which is then placed in an autoclave for treatment. The peel strength between the glass and the film is then tested. According to GB / T 7124-2008, the bonding strength is tested. The film sample size is 125mm×50mm. The specific method is as follows: the film and glass are laminated to form a sample, and the peel strength between the film and the glass is tested using a universal testing machine. Optical performance: The haze value of the film was measured using a haze meter, referring to GB / T 2410-2008. The haze of the film was tested with a film size of 100mm×100mm. The specific method was to use a haze meter to test the haze of the film. To assess the anti-adhesion effect, two films were stacked under the same pressure and temperature for 24 hours. The force required to peel them off was then tested using a tensile testing machine. In accordance with GB / T 7124-2008, the adhesive strength was tested. The film sample size was 125mm × 50mm. The specific method was as follows: the two films were stacked to form a template, and the peel strength between the films was tested using a universal testing machine.

[0031] The test results of Example 1 and each comparative example are shown in the table below:

[0032] The anti-adhesion peel force determines the anti-adhesion effect of the film. As can be seen from Example 1 to Comparative Example 4, the anti-adhesion peel force of the film in Example 1 is the smallest. Although the anti-adhesion peel force increases with the reduction of the spacing and height of the micro-convex anti-adhesion texture, it is still much smaller than that of the smooth film. This indicates that the film with micro-convex anti-adhesion texture has excellent anti-adhesion effect.

[0033] Haze determines the optical properties of the thin film. The smaller the value, the better the optical properties. As can be seen from the table, the smooth thin film has the best optical properties. In Example 1, Comparative Example 2 and Comparative Example 3, although the haze increased, the increase was not high and was within an acceptable range. However, in Comparative Example 4, not only did the haze increase significantly, but moiré patterns, which are part of optical interference, also appeared.

[0034] The adhesion strength to glass determines the initial adhesion strength between the PVB film and the glass. As can be seen from the table, except for the smooth film, the adhesion strength decreases to some extent, but the decrease is small and within an acceptable range.

[0035] As can be seen, compared to the smooth and textureless Comparative Example 1, the film produced by this production apparatus in Example 1 achieves excellent anti-sticking improvement. The peel force decreases from 2.4 N / cm to 0.5 N / cm, while the haze increases only slightly from 0.8% to 1.1%, and the adhesive strength decreases slightly from 38 N / cm to 34 N / cm, remaining above the standard requirement of >70 N / cm. This proves that the film produced by this equipment, through improvements in the production equipment, generates a non-periodic distributed micro-convex anti-sticking texture on the film surface through micro-nano-level topological structure design. This achieves excellent anti-sticking performance with a slight sacrifice in peel force and haze, while also avoiding optical interference.

[0036] Secondly, the present invention also provides a PVB anti-stick film production process for operating a production apparatus, comprising the following steps: S1: Preliminary film forming: The molten film is discharged from the casting die 1 and passes through the cooling water tank 2 and the water-dripping roller 3 in sequence to obtain a preliminarily formed film; S2: Front embossing: The pre-formed film is passed through the front embossing unit 6, and the front side of the film is embossed at the film temperature T1 to obtain the pit structure 9. The embossing pressure is P1. S3: Post-embossing: The film is passed through the post-embossing unit 7, and the back of the film is embossed to create a pit structure 9 when the film temperature is T2. The embossing pressure is P2, and then the film is cooled by the main cooling roller 4. S4: Winding up, the film is wound up to obtain the finished PVB anti-stick film.

[0037] The film temperatures T1 and P1 in S2 satisfy the relationship with the film temperatures T2 and P2 in S3: T1 > T2, P1 < P2. By utilizing the synergistic process of high-temperature and low-pressure preliminary molding and medium-temperature and high-pressure finishing, high-fidelity reproduction of texture and dimensional stability are ensured.

[0038] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape and proportion of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), installation arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application.

Claims

1. A PVB anti-stick film production apparatus, comprising a casting die (1), a cooling water tank (2), a water-repelling roller (3), a main cooling roller (4), and a winding device (5) arranged sequentially along a production line, characterized in that: A further means is provided between the water-driving roller (3) and the main cooling roller (4): Guide roller (10) and online embossing system, the online embossing system comprising a front embossing unit (6) and a rear embossing unit (7) arranged sequentially along the film travel direction; The front embossing unit (6) includes a front embossing upper roller (601) and a front embossing lower roller (602) arranged opposite to each other. The roller surface (8) of the front embossing upper roller (601) has a pit structure (9) for forming a micro-convex anti-stick texture on the front side of the film. The rear embossing unit (7) includes a rear embossing upper roller (701) and a rear embossing lower roller (702) arranged opposite to each other, and the roller surface (8) of the rear embossing upper roller (701) has the recessed structure (9). Furthermore, hot oil is circulated inside the front embossing upper roller (601), the front embossing lower roller (602), the rear embossing upper roller (701), and the rear embossing lower roller (702), so that the contacting film is heated to the plastic temperature range for embossing, while accelerating the evaporation of water vapor. The rear embossing lower roller (702) is in contact with the film on the guide roller (10). The heat on the lower embossing roller (702) accelerates the removal of moisture from the front side of the film, improving the printing effect of the upper embossing roller (601) on the front side of the film. At the same time, the heat on the lower embossing roller (602) accelerates the removal of moisture from the back side of the film, improving the printing effect of the upper embossing roller (701) on the back side of the film.

2. The PVB anti-stick film production apparatus according to claim 1, characterized in that: The pit structure (9) is distributed non-periodically on the roller surface (8), and the cross-sectional shape of the pit structure (9) is a frustum without sharp edges.

3. The PVB anti-stick film production apparatus according to claim 1, characterized in that: The recessed structure (9) has multiple recesses distributed in a spiral shape on the roller surface (8). The recessed structure (9) has N interrupted fillers (901) that divide the recessed structure (9) into N+1 anti-sticking holes (902). The length of the anti-sticking hole (902) is 240±5μm, and the length of the interrupted filler (901) is 25±5μm.

4. The PVB anti-stick film production apparatus according to claim 3, characterized in that: The interruption filler (901) and the adjacent interruption filler (901) along the film travel direction are spaced apart in the length direction of the roller surface (8).

5. The PVB anti-stick film production apparatus according to claim 1, characterized in that: The depth of the pit structure (9) is 85±5μm, and the distance between the deepest point of two adjacent pit structures (9) is 275-300μm.

6. The PVB anti-stick film production apparatus according to claim 1, characterized in that: The angle between the length direction of the pit structure (9) and the direction of film travel is 45°.

7. The PVB anti-stick film production apparatus according to claim 1, characterized in that: The cross-section of the pit structure (9) is asymmetrical. The slope of one side of the pit structure (9) relative to the film is greater than that of the other side relative to the film. Both sides of the pit structure (9) are smooth curved surfaces, and the cross-sectional shape of one pit structure (9) is different from that of the adjacent pit structure (9).

8. A PVB anti-stick film production process, using the production apparatus as described in any one of claims 1-7, characterized in that: Includes the following steps: S1: Preliminary film forming: The molten film is discharged from the casting die (1) and passes through the cooling water tank (2) and the water-dripping roller (3) in sequence to obtain the preliminarily formed film; S2: Front embossing: The pre-formed film is passed through the front embossing unit (6) and the front side of the film is embossed at the film temperature T1 to obtain a pit structure (9). The embossing pressure is P1. S3: Post-embossing: The film is passed through the post-embossing unit (7), and a pit structure (9) is formed on the back of the film when the film temperature is T2. The embossing pressure is P2, and then the film is cooled by the main cooling roller (4). S4: Winding up, the film is wound up to obtain the finished PVB anti-stick film.

9. The PVB anti-stick film production process according to claim 8, characterized in that: The film temperatures T1 and P1 in S2 are related to the film temperatures T2 and P2 in S3 as follows: T1 > T2, P1 < P2.

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