Bopp adhesive-free laminated film and preparation method thereof

Abstract

This invention relates to the field of thin films, and particularly to a BOPP adhesive-free laminated film and its preparation method. The laminated film comprises a matte layer, a core layer, a barrier layer, and a thermally laminated layer arranged sequentially. The matte layer comprises random copolymer PP and 45-52 wt% HDPE. The core layer comprises homopolymer PP and 0.5-1 wt% antistatic masterbatch. The barrier layer comprises EVOH and 5-10 wt% MAH-g-EVA, with a barrier layer thickness of 1.5-2.3 μm. The thermally laminated layer comprises EVA and 5-8 wt% PB-1 with a melt index of 2.5-4 g / 10 min (190°C, 2.16 kg). The adhesive-free laminated film of this invention can both hinder the migration of antistatic agents and achieve self-anti-blocking at room temperature while allowing EVA to fully wet the target lamination surface during thermal lamination. This improves the problems of weak lamination strength and white spots caused by antistatic agent migration and anti-blocking agent protrusion in traditional laminated films.

Description

Technical Field

[0001] This invention relates to the field of thin films, and in particular to a BOPP adhesive-free laminated film and its preparation method. Background Technology

[0002] BOPP adhesive-free laminated film typically includes a heat-bonded layer mainly composed of EVA. It can be directly laminated with paper without adhesive through a hot-pressing process, replacing the traditional adhesive-coated laminating process. It has the advantages of simple process, green environmental protection and high production efficiency, and has been widely used in the packaging and printing industry.

[0003] Currently, mainstream BOPP adhesive-free laminated films on the market suffer from two major technical pain points, severely limiting the application and mass production stability of high-end products. First, to achieve antistatic effects, small-molecule migratory antistatic agents are often used. These agents can slowly migrate to the thermal lamination layer, forming a weak boundary layer at the paper-plastic lamination interface, significantly reducing the bonding stability of the paper-plastic lamination. Long-term storage of laminated products easily leads to localized delamination and adhesive separation defects. Second, to address the problem of self-adhesion at room temperature due to the adhesiveness of the thermal lamination layer during film roll winding, traditional processes commonly add hard particles such as silica to the thermal lamination layer as anti-adhesion agents. These hard particles continuously protrude at room temperature, not only precipitating on the longitudinal stretching rollers and accelerating equipment wear, but also disrupting the wetting and anchoring of the thermal lamination layer with the paper fibers and other lamination surfaces. This results in large fluctuations in lamination strength, white spots on the film surface, and interlayer separation, severely affecting the appearance quality and lamination stability of high-end packaging. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a BOPP adhesive-free laminated film and its preparation method. By setting a barrier layer to prevent the migration of small molecule antistatic agents in the core layer to the thermal lamination layer, and by adding poly-1-butene (PB-1) to the thermal lamination layer, it achieves room temperature anti-adhesion while ensuring that the ethylene-vinyl acetate copolymer (EVA) in the thermal lamination layer can fully wet the target lamination surface during thermal lamination. This improves the problems of weak lamination strength and white spots after lamination caused by the migration of antistatic agents to the surface of the thermal lamination layer and the inability of EVA to fully contact the target lamination surface due to the protrusion of traditional anti-adhesion agents, thus ensuring excellent lamination effect.

[0005] The technical solution of the present invention is achieved in the following ways: A BOPP adhesive-free laminated film comprises a matte layer, a core layer, a barrier layer, and a heat-bonding layer arranged sequentially. The matte layer comprises random copolymer polypropylene and 45-52 wt% high-density polyethylene. The core layer comprises homopolymer polypropylene and 0.5-1 wt% antistatic masterbatch. The barrier layer comprises ethylene-vinyl alcohol copolymer and 5-10 wt% maleic anhydride-grafted ethylene-vinyl acetate copolymer. The thickness of the barrier layer is 1.5-2.3 μm. The heat-bonding layer comprises ethylene-vinyl acetate copolymer and 5-8 wt% poly-1-butene. The melt index of the poly-1-butene was measured to be 2.5-4 g / 10 min at 190°C and 2.16 kg.

[0006] The BOPP adhesive-free laminated film of the present invention has a matte layer composed of random copolymer polypropylene and high-density polyethylene (HDPE), which gives the film a matte appearance and abrasion resistance; the core layer serves as the core support structure, ensuring the overall mechanical properties of the film and providing antistatic properties.

[0007] Based on this, the BOPP adhesive-free laminated film of the present invention provides a dense, non-porous, homogeneous barrier layer with a thickness of 1.5-2.3 μm formed by ethylene-vinyl alcohol copolymer (EVOH) and 5-10 wt% maleic anhydride-grafted ethylene-vinyl acetate copolymer (MAH-g-EVA) between the core layer and the thermally laminated layer. On the one hand, EVOH prevents the migration of small-molecule antistatic agents from the core layer to the thermally laminated layer, thereby improving the paper-plastic bonding adhesion reduction and local delamination (referring to delamination between the thermally laminated layer and the target laminated surface) caused by the migration of antistatic agents in the thermally laminated layer. On the one hand, the EVA segments in MAH-g-EVA are similar to and compatible with the EVA in the thermally laminated layer. In the molten state, the MAH anhydride groups can undergo esterification with the hydroxyl groups of EVOH to form covalent bonds. The two work together to improve the connection strength between the barrier layer and the thermally laminated layer, and improve the problems such as interlayer peeling, local whitening, and film stripes that easily occur during the stretching, bending, and hot pressing process of the barrier layer containing strong polar EVOH and the thermally laminated layer containing weak polar EVA, which can only rely on weak intermolecular van der Waals forces to bond.

[0008] If the amount of MAH-g-EVA added to the barrier layer is less than 5wt%, the effect on improving the interfacial compatibility between the barrier layer and the thermally laminated layer is insufficient, which may cause delamination at some locations between the barrier layer and the thermally laminated layer. If the amount of MAH-g-EVA added to the barrier layer is greater than 10wt%, the barrier effect of the barrier layer decreases, and the amount of antistatic agent migrating from the core layer to the thermally laminated layer increases. If no MAH-g-EVA is added to the barrier layer, on the one hand, under the action of biaxial tensile shear deformation, a large number of micro gaps and microcracks are easily generated at the interface between EVOH and EVA, providing a bypass channel for the migration of small molecule antistatic agents. The antistatic small molecules in the core layer can bypass the EVOH resin body and migrate to the thermally laminated layer, resulting in a decrease in lamination adhesion and local delamination in the later stage. At the same time, during the stretching, bending, and hot pressing lamination process, the film is also prone to defects such as interlayer delamination, local whitening, and film surface streaks, resulting in poor film product stability.

[0009] If the thickness of the barrier layer is less than 1.5 μm, its ability to block antistatic agents is insufficient. If the thickness of the barrier layer is greater than 3 μm, the tensile properties of EVOH are poor, which will increase the risk of delamination and also increase the cost.

[0010] The BOPP adhesive-free laminated film of this invention also achieves a self-anti-adhesion effect by adding 5-8 wt% (poly-1-butene) PB-1 to the heat-laminating layer. At room temperature, it can form a raised structure on the surface of the heat-laminating layer. This structure works synergistically with the matte layer without the need for external hard particles as an anti-blocking agent. When heat-laminating after unwinding, these PB-1 raised structures can completely melt at the paper-plastic hot-pressing lamination temperature (110-120℃), allowing the EVA in the heat-laminating layer to make more full contact with the target lamination surface, thereby achieving high lamination strength and uniform and stable adhesive-free lamination.

[0011] Specifically, PB-1 is a semi-crystalline, highly isotactic thermoplastic, typically polymerized from 1-butene monomer (butene-1) using a Ziegler-Natta catalyst. Due to the partial incompatibility between PB-1 and EVA, a sea-island structure is formed, with EVA as the marine phase and PB-1 as the island phase. Under the action of the chilled roller, PB-1 initially exists in the heat-coated layer in a metastable tetragonal II crystal form. Then, during the storage of the BOPP adhesive-free laminate at room temperature, PB-1 in the heat-coated layer spontaneously undergoes an irreversible crystal transformation to the thermodynamically stable hexagonal I crystal form. This phase transformation is accompanied by changes in unit cell volume, generating internal stress within the island phase particles. This internal stress is transmitted through the banded molecules and intergranular entanglements within PB-1, causing the PB-1 island phase particles near the film surface to arch outwards, ultimately forming nano- to micron-sized micro-protrusions that are stable at room temperature. The surface of the heat-bonding layer of the BOPP adhesive-free laminating film acts as an anti-adhesion agent. With the synergistic effect of the rough surface of the matte layer, it achieves excellent anti-adhesion performance, ensuring smooth unwinding of the film roll. When the BOPP adhesive-free laminating film is used to laminate with the target laminating surface, because the hot-pressing lamination temperature (110~120℃) is greater than the melting temperature of PB-1 (two melting point peaks of 81℃ and 94℃), the PB-1 island phase particles are completely melted. There are no microscopic protrusions on the surface of the heat-bonding layer that interfere with the EVA wetting of the target laminating surface. EVA can fully wet the target laminating surface, which is conducive to forming a uniform and stable adhesive-free lamination, achieving high lamination strength and no interface defects in adhesive-free lamination, and there will be no hard particles causing wear to the equipment throughout the process.

[0012] If the amount of PB-1 added to the thermally laminated layer is less than 5wt%, there will be too little PB-1 as island phase particles, resulting in excessive noise during unwinding of the master roll and insufficient unwinding smoothness. If the amount of PB-1 added to the thermally laminated layer is greater than 8wt%, the PB-1 in the thermally laminated layer will exhibit a blocky regional distribution characteristic, which is not conducive to the thermal lamination effect of EVA. If the melt index of PB-1 is less than 2.5g / 10min, the melt viscosity of PB-1 is much higher than that of EVA. Under blending shear, the island phase particles will be too large, and visible impurities may appear on the film surface, resulting in uneven film haze. If the melt index of PB-1 is greater than 4g / 10min, the viscosity of PB-1 will be too low. After blending, the island phase particles will be small in size, with insufficient microscopic protrusions, resulting in weak anti-blocking effect. At the same time, the island phase is easily elongated and deformed during biaxial stretching, and cannot form spherical island phases.

[0013] Furthermore, the melt index of the ethylene-vinyl alcohol copolymer was measured to be 3~6 g / 10min at 210℃ and 2.16 kg. If the melt index of EVOH is <3 g / 10min, the melt viscosity is too high, and it does not match the melt viscosity of homopolymer polypropylene and EVA during co-extrusion, resulting in unstable extrusion of the barrier layer and thickness fluctuations. If the melt index of EVOH is >6 g / 10min, the melt is too thin, and interlayer channeling is prone to occur during biaxial stretching, leading to poor thermal stability of the film.

[0014] Furthermore, the ethylene content in the ethylene-vinyl alcohol copolymer is 32-40 mol%. If the ethylene content of EVOH is <32 mol%, on the one hand, EVOH has a high melting point and high rigidity, and is prone to micro-cracks and film breakage during biaxial stretching, resulting in a narrow processing window; on the other hand, EVOH with excessively high hydroxyl content is prone to thermal degradation during melt extrusion blending with MAH-g-EVA. If the ethylene content of EVOH is >40 mol%, there are too many ethylene units, resulting in decreased polarity and significantly insufficient barrier migration ability against small molecule antistatic agents.

[0015] Furthermore, the grafting rate of maleic anhydride in the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 1.0~1.5%. If the grafting rate of MAH in MAH-g-EVA is >1.5%, high grafting brings the risk of thermal degradation, and gelation, yellowing, and carbon buildup on the die head are likely to occur during biaxial stretching. At the same time, excessive cross-linking of the anhydride increases the melt viscosity and the risk of film crystal point formation. If the grafting rate of MAH in MAH-g-EVA is <1%, the number of MAH reactive groups is insufficient, the chemical adhesion between EVOH and EVA is weak, and interlayer delamination is likely to occur between the barrier layer and the thermally bonded layer.

[0016] Furthermore, the VA content of the ethylene-vinyl acetate copolymer in the thermally laminated layer is 16-22 wt%, and the VA content of the ethylene-vinyl acetate copolymer in the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 15-22 wt%. The VA content of the EVA copolymer in MAH-g-EVA is similar to that of the EVA in the thermally laminated layer, which is beneficial for improving the interfacial compatibility between the barrier layer and the thermally laminated layer. However, if the VA content of the EVA copolymer in MAH-g-EVA is <15 wt%, the compatibility between MAH-g-EVA and the thermally laminated layer will deteriorate. If the VA content of the EVA copolymer in MAH-g-EVA is >22 wt%, a large number of highly polar vinyl acetate units are mixed into the EVOH matrix, disrupting the hydrogen bond network of the EVOH molecular chain, reducing the crystallinity of EVOH, and negatively impacting the barrier performance of the barrier layer. In addition, excessively high VA content can also lead to poor thermal stability of MAH-g-EVA, increasing the risk of carbon buildup and gelation in the die.

[0017] Furthermore, the melting point of the poly-1-butene is 80~100℃, the melting point of the ethylene-vinyl acetate copolymer in the thermally laminated layer is 80~90℃, and the melt index of the ethylene-vinyl acetate copolymer in the thermally laminated layer is 15~20g / 10min measured at 190℃ and 2.16kg.

[0018] Furthermore, the density of the high-density polyethylene is 0.952~0.955 g / cm³. 3 The melt flow index of the high-density polyethylene was measured to be 8~12 g / 10min at 190℃ and 21.6 kg. If the density of HDPE is <0.952 g / cm³... 3 The matting effect is poor if the density of HDPE is >0.955 g / cm³. 3 If the melt index of HDPE is less than 8 g / 10 min, the HDPE melt viscosity is high, which cannot be effectively dispersed and has poor fluidity, making it prone to crystal point problems. If the melt index of HDPE is greater than 12 g / 10 min, the phase separation size of HDPE in the matte layer is too small, which cannot provide sufficient roughness and reduce the matte layer effect.

[0019] Furthermore, the melting point of the random copolymer polypropylene is 135~140℃, and the melt index of the random copolymer polypropylene measured at 230℃ and 2.16kg is 8.5~9.5g / 10min. If the melting point of the random copolymer polypropylene is <135℃, the surface of the matte layer is easily scratched. If the melting point of the random copolymer polypropylene is >140℃, the overall film stretching temperature is insufficient, which easily leads to uneven film stretching. If the melt index of the random copolymer polypropylene is <8.5g / 10min, the overall fluidity of the matte layer is poor. If the melt index of the random copolymer polypropylene is >9.5g / 10min, the melt viscosity difference between HDPE and random copolymer polypropylene is too large, which will lead to uneven dispersion of the two phases.

[0020] Furthermore, the melt index of the homopolymer polypropylene was measured to be 2.8~3.6 g / 10 min at 230℃ and 2.16 kg; the effective content of antistatic agent in the antistatic masterbatch was 40 wt%.

[0021] The present invention also provides a method for preparing any of the above-described BOPP adhesive-free laminated films, comprising the following steps: According to the formula, the uniformly mixed matte layer resin, core layer resin, barrier layer resin, and heat-coating layer resin are respectively conveyed to each extruder, and the four layers of melt are melt-extruded. The heat-coating layer melt is used as the roller surface and is laminated into a single melt sheet at the hanger die head. After passing through the chill roller and the water blowing chamber, the sheet is stretched longitudinally and laterally. After shaping, it is corona treated and wound into a master roll to obtain the BOPP adhesive-free laminated film.

[0022] The extrusion temperature of the matte layer is 235~245℃, the extrusion temperature of the core layer is 250~255℃, the extrusion temperature of the barrier layer is 225~235℃, and the extrusion temperature of the thermally laminated layer is 220~230℃. In the longitudinal stretching region, the preheating temperature of the matte layer is 130~133℃ and the stretching temperature is 125~130℃, while the preheating temperature of the thermally laminated layer is 100~120℃ and the stretching temperature is 60~70℃. In the transverse stretching zone, the preheating temperature is 167~172℃, the stretching temperature is 162~166℃, and the setting temperature is 168~172℃.

[0023] It is evident that the BOPP adhesive-free laminated film of the present invention can be adapted to the conventional BOPP biaxial co-extrusion mass production process without the need for equipment modification, exhibiting strong process adaptability and controllable mass production costs.

[0024] To better understand and implement this invention, the invention will be described in detail below. Detailed Implementation

[0025] It should be understood that the described embodiments are merely some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0026] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0027] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims. In the description of this application, it should be understood that the terms "first," "second," "third," etc., are used only to distinguish similar objects and are not necessarily used to describe a specific order or sequence, nor should they be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] It should be understood that the embodiments of this application are not limited to the precise structures already described above, and various modifications and changes can be made without departing from their scope. The scope of the embodiments of this application is limited only by the appended claims.

[0030] This invention provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a heat-bonding layer arranged sequentially. The matte layer comprises random copolymer polypropylene and 45-52 wt% high-density polyethylene. The core layer comprises homopolymer polypropylene and 0.5-1 wt% antistatic masterbatch. The barrier layer comprises ethylene-vinyl alcohol copolymer and 5-10 wt% maleic anhydride-grafted ethylene-vinyl acetate copolymer. The thickness of the barrier layer is 1.5-2.3 μm. The heat-bonding layer comprises ethylene-vinyl acetate copolymer and 5-8 wt% poly-1-butene. The melt index of poly-1-butene was measured to be 2.5-4 g / 10 min at 190°C and 2.16 kg.

[0031] Furthermore, the melt index of the ethylene-vinyl alcohol copolymer was measured to be 3~6 g / 10 min at 210℃ and 2.16 kg.

[0032] Furthermore, the ethylene molar content of the ethylene-vinyl alcohol copolymer is 32~40 mol.

[0033] Furthermore, the grafting rate of maleic anhydride in the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 1.0~1.5%.

[0034] Furthermore, the VA content of the ethylene-vinyl acetate copolymer in the thermally bonded layer is 16~22wt%, and the VA content in the ethylene-vinyl acetate copolymer groups of the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 15~22wt%.

[0035] Furthermore, the melting point of poly-1-butene is 80~100℃, the melting point of the ethylene-vinyl acetate copolymer in the heat-coated layer is 80~90℃, and the melt index of the ethylene-vinyl acetate copolymer in the heat-coated layer is 15~20g / 10min measured at 190℃ and 2.16kg.

[0036] Furthermore, the density of high-density polyethylene is 0.952~0.955 g / cm³. 3The melt index of high-density polyethylene was measured to be 8~12 g / 10 min at 190℃ and 21.6 kg.

[0037] Furthermore, the melting point of random copolymer polypropylene is 135~140℃, and the melt index of random copolymer polypropylene was measured to be 8.5~9.5g / 10min at 230℃ and 2.16kg.

[0038] Furthermore, the melt index of homopolymer polypropylene was measured to be 2.8~3.6 g / 10 min at 230℃ and 2.16 kg; the effective content of antistatic agent in the antistatic masterbatch was 40%.

[0039] Furthermore, the total thickness of the BOPP adhesive-free laminated film is 18~28μm, and the thickness of the thermally laminated layer is 3~5μm.

[0040] Furthermore, the effective content of the antistatic masterbatch is 40wt%, the carrier resin is homopolymer polypropylene, and the antistatic agent is a small molecule migration type antistatic agent. The antistatic agent in the antistatic masterbatch used in the embodiments and comparative examples of the present invention is composed of 40wt% N,N-dihydroxyethyl stearamide (ethoxylated tertiary amine) and 60wt% glyceryl octadecyl acid ester.

[0041] Furthermore, the random copolymer polypropylene can be ethylene-propylene copolymer polypropylene or ethylene-propylene-butene copolymer polypropylene. In the embodiments and comparative examples of this invention, ethylene-propylene copolymer polypropylene is used, specifically Shanghai Petrochemical F800E.

[0042] Furthermore, the melting point of EVOH is between 166 and 178 °C.

[0043] The present invention also provides a method for preparing any of the above-mentioned BOPP adhesive-free laminated films, comprising the following steps: According to the formula, the uniformly mixed matte layer resin, core layer resin, barrier layer resin, and heat-coating layer resin are respectively conveyed to each extruder, and the four layers of melt are melt-extruded. The heat-coating layer melt is used as the roller surface and is laminated into a whole melt sheet at the hanger die head. After passing through the cooling roller and the water blowing chamber, the sheet is stretched longitudinally and laterally. After shaping, it is corona treated and wound into a master roll to obtain BOPP glue-free laminated film.

[0044] The extrusion temperature of the matte layer is 235~245℃, the extrusion temperature of the core layer is 250~255℃, the extrusion temperature of the barrier layer is 225~235℃, and the extrusion temperature of the thermally laminated layer is 220~230℃. In the longitudinal stretching region, the preheating temperature of the matte layer is 130~133℃ and the stretching temperature is 125~130℃, while the preheating temperature of the thermally laminated layer is 100~120℃ and the stretching temperature is 60~70℃. In the transverse stretching zone, the preheating temperature is 167~172℃, the stretching temperature is 162~166℃, and the setting temperature is 168~172℃.

[0045] The physical properties and testing methods of the embodiments or comparative examples of the present invention are as follows: Surface resistivity test of thermally laminated layer: After the film is aged for 72 hours, a sample film between 1 and 1.5 meters from the operating side is taken and placed in an environment of 37±2℃ and 60±5% humidity for 4 days. The surface resistivity of the thermally laminated layer is tested using a two-point electrode tester with a weighted hammer (model SL-030B). The film is contacted with constant pressure, and the surface resistivity is read directly.

[0046] White cardboard peel strength: measured according to GB / T8808 (Method A), unit is N / 15mm.

[0047] Haze: Tested according to GB / T2410-2008.

[0048] The anti-adhesion effect of the thermally laminated layer was evaluated using unwinding noise. The unwinding noise evaluation method is as follows: A master roll with a Shore hardness of 85±0.5 and a length of 8000±5 meters was used as a sample. After aging treatment on an aging rack for 3 days, it was unwound at an unwinding speed of 185 meters / minute. When the master roll was unwound to the 3000th meter, the noise decibel values ​​at positions 2 meters and 4.5 meters away from the operating side of the master roll were recorded using a GM1356 noise meter, and the average value was taken.

[0049] The components and contents of the matte layer, barrier layer, and thermally bonded layer in the embodiments and comparative examples of the present invention are shown in Table 1 below.

[0050] Table 1

[0051] Example 1 This embodiment provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially arranged. The preparation method of each resin layer of the BOPP adhesive-free laminated film in this embodiment includes the following steps: Preparation of matte layer resin: Take 45wt% HDPE (density 0.953g / cm³) 3 The matte layer resin was obtained by mixing 55wt% random copolymer polypropylene (melting point 143℃, melt index measured at 230℃ and 2.16kg with a melt index of 11g / 10min) and 21.6kg at 190℃ with a melt index of 8.7g / 10min) evenly.

[0052] Core layer resin preparation: 99.3 wt% homopolymer polypropylene (melt index of 3.5 g / 10 min measured at 230℃ and 2.16 kg) and 0.7 wt% antistatic masterbatch (effective antistatic agent content of 40 wt%) were mixed evenly to obtain core layer resin.

[0053] Barrier layer resin preparation: 95wt% EVOH (ethylene molar content is 35mol%, melt index is 4.5g / 10min measured at 210℃ and 2.16kg) and 5wt% MAH-g-EVA (VA content in EVA is 20wt%, MAH grafting rate is 1.2%) were mixed evenly to obtain barrier layer resin.

[0054] Preparation of thermally laminated resin: 95wt% EVA (melting point 88℃, VA content 18wt%, melt index of 16g / 10min measured at 190℃ and 2.16kg) and 5wt% PB-1 (melting point 94℃, melt index of 2.5g / 10min measured at 190℃ and 2.16kg) were mixed evenly to obtain thermally laminated resin.

[0055] The method for preparing the BOPP film in this embodiment includes the following steps: According to the formula, the uniformly mixed matte layer resin, core layer resin, barrier layer resin, and heat-coating layer resin are respectively conveyed to each extruder, and the four layers of melt are melt-extruded. The heat-coating layer melt is used as the roller surface and is laminated into a single melt sheet at the hanger die head. After passing through the chill roller and the water blowing chamber, the sheet is stretched longitudinally and laterally. After shaping, it is corona treated and wound into a master roll to obtain the BOPP adhesive-free laminated film.

[0056] The extrusion temperature of the matte layer is 245℃, the extrusion temperature of the core layer is 253℃, the extrusion temperature of the barrier layer is 235℃, and the extrusion temperature of the thermally laminated layer is 230℃. In the longitudinal stretching region, the preheating temperature of the matte layer is 132℃ and the stretching temperature is 128℃, while the preheating temperature of the thermally laminated layer is 105℃ and the stretching temperature is 70℃. In the transverse stretching zone, the preheating temperature is 168℃, the stretching temperature is 165℃, and the setting temperature is 170℃.

[0057] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 1.5µm thick, and the thermal bonding layer is 4µm thick.

[0058] Example 2 This embodiment provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially arranged. The preparation method of each resin layer of the BOPP adhesive-free laminated film in this embodiment includes the following steps: Preparation of matte layer resin: Take 47wt% HDPE (density 0.953g / cm³) 3 The matte layer resin was obtained by uniformly mixing 53 wt% of random copolymer polypropylene (melting point 143℃, melt index measured at 230℃ and 2.16 kg, with a melt index of 11 g / 10 min) and 21 wt% of random copolymer polypropylene (melting point 143℃, melt index measured at 230℃ and 2.16 kg, with a melt index of 8.7 g / 10 min). The core layer resin preparation was the same as in Example 1 and will not be described in detail.

[0059] Barrier layer resin preparation: 93wt% EVOH (ethylene molar content is 35mol%, melt index is 4.5g / 10min measured at 210℃ and 2.16kg) and 7wt% MAH-g-EVA (VA content in EVA is 20wt%, MAH grafting rate is 1.2%) were mixed evenly to obtain barrier layer resin.

[0060] Preparation of thermally laminated resin: 92wt% EVA (melting point 88℃, VA content 18wt%, melt index of 16g / 10min measured at 190℃ and 2.16kg) and 8wt% PB-1 (melting point 94℃, melt index of 2.5g / 10min measured at 190℃ and 2.16kg) were mixed evenly to obtain thermally laminated resin.

[0061] The preparation method of the BOPP adhesive-free laminated film in this embodiment is the same as that in Example 1, so it will not be described again.

[0062] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 1.5µm thick, and the thermal bonding layer is 4µm thick.

[0063] Example 3 This embodiment provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially arranged. The preparation method of each resin layer of the BOPP adhesive-free laminated film in this embodiment includes the following steps: Preparation of matte layer resin: Take 47wt% HDPE (density 0.953g / cm³) 3 The matte layer resin was obtained by uniformly mixing 53 wt% of random copolymer polypropylene (melting point 143℃, melt index measured at 230℃ and 2.16 kg, with a melt index of 11 g / 10 min) and 21 wt% of random copolymer polypropylene (melting point 143℃, melt index measured at 230℃ and 2.16 kg, with a melt index of 8.7 g / 10 min). The core layer resin preparation was the same as in Example 1 and will not be described in detail.

[0064] Barrier layer resin preparation: 90wt% EVOH (ethylene molar content is 35mol%, melt index is 4.5g / 10min measured at 210℃ and 2.16kg) and 10wt% MAH-g-EVA (VA content in EVA is 20wt%, MAH grafting rate is 1.2%) were mixed evenly to obtain barrier layer resin.

[0065] Preparation of thermally laminated resin: 92wt% EVA (melting point 88℃, VA content 18wt%, melt index of 16g / 10min measured at 190℃ and 2.16kg) and 8wt% PB-1 (melting point 94℃, melt index of 4g / 10min measured at 190℃ and 2.16kg) were mixed evenly to obtain thermally laminated resin.

[0066] The preparation method of the BOPP adhesive-free laminated film in this embodiment is the same as that in Example 1, so it will not be described again.

[0067] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0068] Example 4 This embodiment provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially arranged. The preparation method of each resin layer of the BOPP adhesive-free laminated film in this embodiment includes the following steps: Preparation of matte layer resin: Similar to Example 3, the preparation will not be repeated here. The difference is that this example uses 52 wt% HDPE and 48 wt% random copolymer polypropylene. Preparation of core layer resin: Same as Example 1, therefore will not be repeated here.

[0069] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0070] Preparation of thermally bonded resin: The same as in Example 3 will not be repeated here. The difference is that in this example, 92wt% EVA and 8wt% PB-1 were used (the melt index was measured to be 4g / 10min at 190℃ and 2.16kg).

[0071] The preparation method of the BOPP adhesive-free laminated film in this embodiment is the same as that in Example 1, so it will not be described again.

[0072] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2.3µm thick, and the thermal bonding layer is 4µm thick.

[0073] Comparative Example 1 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0074] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0075] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0076] Preparation of thermally bonded resin: The same as in Example 3 will not be repeated here. The difference is that the melt index of PB-1 was measured to be 5.6 g / 10 min at 190 °C and 2.16 kg in this comparative example.

[0077] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0078] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0079] Comparative Example 2 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0080] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0081] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0082] Preparation of thermally bonded resin: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 97wt% EVA and 3wt% PB-1.

[0083] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0084] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0085] Comparative Example 3 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0086] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0087] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0088] Preparation of thermally bonded resin: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 88wt% EVA and 12wt% PB-1.

[0089] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0090] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0091] Comparative Example 4 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0092] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0093] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0094] Preparation of thermally bonded resin: The same as in Example 3 will not be repeated here. The difference is that the melt index of PB-1 was measured to be 1.5 g / 10 min at 190 °C and 2.16 kg in this comparative example.

[0095] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0096] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0097] Comparative Example 5 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0098] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0099] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0100] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0101] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0102] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 1.2µm thick, and the thermal bonding layer is 4µm thick.

[0103] Comparative Example 6 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 43wt% HDPE and 57wt% random copolymer polypropylene.

[0104] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0105] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0106] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0107] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0108] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0109] Comparative Example 7 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 56wt% HDPE and 44wt% random copolymer polypropylene.

[0110] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0111] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0112] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0113] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0114] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0115] Comparative Example 8 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0116] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0117] Preparation of barrier layer resin: Same as in Example 3, so it will not be described in detail.

[0118] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0119] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0120] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2.8µm thick, and the thermal bonding layer is 4µm thick.

[0121] Comparative Example 9 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0122] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0123] Barrier layer resin preparation: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 97wt% EVOH and 3wt% MAH-g-EVA.

[0124] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0125] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0126] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0127] Comparative Example 10 This comparative example provides a BOPP adhesive-free laminated film, comprising a matte layer, a core layer, a barrier layer, and a thermally bonded layer sequentially disposed therefrom. The preparation method of each resin layer of the BOPP adhesive-free laminated film of this comparative example includes the following steps: Preparation of matte layer resin: Same as in Example 3, so it will not be described in detail.

[0128] Core layer resin preparation: Same as in Example 1, so it will not be described in detail.

[0129] Barrier layer resin preparation: The same as in Example 3 will not be repeated here. The difference is that this comparative example uses 85wt% EVOH and 15wt% MAH-g-EVA.

[0130] Preparation of the thermally bonded resin: Same as in Example 3, so it will not be described in detail.

[0131] The preparation method of the BOPP adhesive-free laminated film in this comparative example is the same as that in Example 1, so it will not be described again.

[0132] The total thickness of the film is 22µm, of which the matting layer is 1.9µm thick, the barrier layer is 2µm thick, and the thermal bonding layer is 4µm thick.

[0133] The performance test results of the BOPP adhesive-free laminated films of Examples 1-4 and Comparative Examples 1-10 are shown in Table 2 below.

[0134] Table 2

[0135] Compared to Example 1, Example 2 has a higher PB-1 content in the thermally laminated layer, a rougher matte layer, better overall anti-adhesion effect, and exhibits lower unwinding noise.

[0136] Compared to Example 2, Example 3, while maintaining a similar roughness of the matte layer, increases the melt index of PB-1 in the thermally laminated layer, exhibiting greater unwinding noise, but still within an acceptable range.

[0137] Compared to Example 3, Example 4, while maintaining the same thermally bonded layer, increases the thickness of the EVOH barrier layer, which reduces the migration of small antistatic molecules and improves the peel strength. On the other hand, it further increases the roughness of the matte layer, which improves the anti-adhesion effect and thus exhibits lower unwinding noise.

[0138] It can be seen that the anti-adhesion performance of the BOPP adhesive-free laminated film of the present invention is strongly correlated with the roughness of the matte layer and the content of PB-1 and melt index in the thermally laminated layer.

[0139] Compared to Example 3, the melt index of PB-1 in the thermally laminated layer of Comparative Example 1 is too high, and the island phase size of PB-1 in the thermally laminated layer is too small under high shear, resulting in a decrease in anti-adhesion effect and excessive unwinding noise.

[0140] Compared to Example 3, the content of PB-1 in the thermally laminated layer of Comparative Example 2 is too low, the proportion of protrusions on the surface of the thermally laminated layer is too small, the anti-adhesion effect is poor, and it exhibits greater unwinding noise.

[0141] Compared to Example 3, the content of PB-1 in the thermal lamination layer of Comparative Example 3 is too high, resulting in the enrichment of the PB-1 phase region. The EVA layer and the PB-1 layer are significantly separated, and the thermal lamination layer is damaged during stretching, causing local failure of paper-plastic lamination.

[0142] Compared to Example 3, the melt index of PB-1 in the thermal lamination layer of Comparative Example 4 is too low. Although the PB-1 island phase size is larger, which is beneficial to reduce unwinding noise, the excessively large PB-1 size affects the wetting of the thermal lamination layer and the paper, reduces the peel strength, and causes white spots to appear on the dark lamination background.

[0143] Based on the comprehensive test results, the optimal range is PB-1 addition of 5~8wt% and melt index of 2.5~4g / 10min.

[0144] Compared to Example 1, the EVOH content in the barrier layer of Example 2 was reduced, while the peel strength of the white card did not change significantly. This indicates that the EVOH content was sufficient, and small fluctuations in the EVOH content had no significant impact on its ability to block antistatic agents.

[0145] Analysis of Examples 2-4 shows that the EVA content in the thermally laminated layer of Examples 2-4 is the same, which indicates that the adhesive ability of the thermally laminated layer of the three examples is the same. On this basis, as the thickness of the barrier layer increases, the peel strength of the white card gradually increases, indicating that increasing the thickness of the barrier layer can improve its ability to block small molecule antistatic agents.

[0146] Compared to Example 3, the barrier layer of Comparative Example 5 is too thin and has too weak a barrier ability. The migration of the antistatic agent affects the adhesion between the thermal lamination layer and the paper, and is prone to local spots (delamination and whitening).

[0147] Compared to Example 3, the barrier layer of Comparative Example 8 is too thick. Although the barrier ability is strong, the rigidity of EVOH increases, which is not conducive to biaxial stretching and film formation. The thickness flatness deteriorates or even the film breaks, while also increasing the raw material cost.

[0148] In summary, a barrier layer thickness of 1.5~2.3μm can balance barrier performance, processability, and cost.

[0149] Compared to Example 3, the HDPE content in the matte layer of Comparative Example 6 is too low, resulting in insufficient micro-roughness of the matte layer. This not only leads to uneven, cloud-like matting but also reduces the synergistic anti-sticking effect with the thermally laminated layer PB-1, and increases unwinding noise.

[0150] Compared to Example 3, the HDPE content in the matte layer of Comparative Example 7 is too high, resulting in a mismatch in the melt viscosity of the two phases in the matte layer, large fluctuations in extrusion pressure, and an excessively large HDPE phase, which can easily lead to sticking to the rollers in the longitudinal stretching area and uneven matting in local areas of the film surface.

[0151] Choosing an HDPE content of 45~52wt% in the matte layer can achieve both a matte appearance and an auxiliary anti-sticking effect.

[0152] Compared to Example 3, the content of MAH-g-EVA in the barrier layer of Comparative Example 9 is too low, the chemical bonding between EVOH and EVA layers is insufficient, and micro-gaps are easily formed at the interface under biaxial stretching and hot pressing conditions, forming a small molecule antistatic migration bypass, and delamination occurs between the thermally laminated layer and the composite surface in the later stage.

[0153] Compared to Example 3, the barrier layer of Comparative Example 10 has an excessively high content of MAH-g-EVA, which dilutes the continuous EVOH phase, weakens the barrier effect, increases the extrusion of gel, and results in a poorer thickness.

[0154] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A BOPP adhesive-free laminated film, characterized in that, The material comprises a matte layer, a core layer, a barrier layer, and a heat-bonded layer arranged sequentially. The matte layer comprises random copolymer polypropylene and 45-52 wt% high-density polyethylene. The core layer comprises homopolymer polypropylene and 0.5-1 wt% antistatic masterbatch. The barrier layer comprises ethylene-vinyl alcohol copolymer and 5-10 wt% maleic anhydride-grafted ethylene-vinyl acetate copolymer. The thickness of the barrier layer is 1.5-2.3 μm. The heat-bonded layer comprises ethylene-vinyl acetate copolymer and 5-8 wt% poly-1-butene. The melt index of the poly-1-butene was measured to be 2.5-4 g / 10 min at 190°C and 2.16 kg.

2. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The melt index of the ethylene-vinyl alcohol copolymer was measured to be 3~6 g / 10 min at 210℃ and 2.16 kg.

3. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The ethylene-vinyl alcohol copolymer contains 32-40 mol of ethylene.

4. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The grafting rate of maleic anhydride in the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 1.0~1.5%.

5. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The VA content of the ethylene-vinyl acetate copolymer in the thermally bonded layer is 16~22wt%, and the VA content of the ethylene-vinyl acetate copolymer in the maleic anhydride-grafted ethylene-vinyl acetate copolymer is 15~22wt%.

6. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The melting point of the poly-1-butene is 80~100℃, the melting point of the ethylene-vinyl acetate copolymer in the thermally laminated layer is 80~90℃, and the melt index of the ethylene-vinyl acetate copolymer in the thermally laminated layer is 15~20g / 10min measured at 190℃ and 2.16kg.

7. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The high density polyethylene has a density of 0.952 to 0.955 g / cm 3 The high density polyethylene has a melt index of 8 to 12 g / 10 min measured at 190°C, 21.6 kg.

8. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The random copolymer polypropylene has a melting point of 135~140℃, and the melt index of the random copolymer polypropylene was measured to be 8.5~9.5g / 10min at 230℃ and 2.16kg.

9. The BOPP adhesive-free laminated film according to claim 1, characterized in that, The melt index of the homopolymer polypropylene was measured to be 2.8~3.6 g / 10 min at 230℃ and 2.16 kg; the effective content of antistatic agent in the antistatic masterbatch was 40 wt%.

10. A method for preparing a BOPP adhesive-free laminated film as described in any one of claims 1 to 9, characterized in that, Includes the following steps: According to the formula, the uniformly mixed matte layer resin, core layer resin, barrier layer resin, and heat-coating layer resin are respectively conveyed to each extruder, and the four layers of melt are melted and extruded. The heat-coating layer melt is used as the roller surface and is laminated into a whole melt sheet at the hanger die head. After the sheet passes through the cooling roller and the water blowing chamber, it is stretched longitudinally and laterally. After shaping, it is corona treated and wound into a master roll to obtain the BOPP glue-free laminated film. The extrusion temperature of the matte layer is 235~245℃, the extrusion temperature of the core layer is 250~255℃, the extrusion temperature of the barrier layer is 225~235℃, and the extrusion temperature of the thermally laminated layer is 220~230℃. In the longitudinal stretching region, the preheating temperature of the matte layer is 130~133℃ and the stretching temperature is 125~130℃, while the preheating temperature of the thermally laminated layer is 100~120℃ and the stretching temperature is 60~70℃. In the transverse stretching zone, the preheating temperature is 167~172℃, the stretching temperature is 162~166℃, and the setting temperature is 168~172℃.

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