A biaxially stretched polyethylene-based film, a preparation method thereof, and a tape film

Abstract

The present invention relates to the field of thin films, and particularly to a biaxially oriented polyethylene-based film, a preparation method thereof, and a tape film. The base film sequentially comprises a release functional layer, a core layer, and an adhesive-enhancing surface layer. The release functional layer comprises linear low-density polyethylene, 5-10 wt% of ethylene-propylene copolymer polyethylene, and 20-30 wt% of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer. The fluorinated polysiloxane chain segment is copolymerized and connected by 3 to 4 fluorinated siloxane units, and the ethylene-norbornene chain segment is copolymerized and connected by 1 to 2 ethylene-norbornene units. The core layer comprises linear low-density polyethylene. The adhesive-enhancing surface layer comprises ethylene-propylene copolymer polyethylene and 10-20 wt% of PMMA-g-EVA. The present invention can reduce the peel force of the release functional layer and improve the barrier property on the premise of ensuring release uniformity, so that the winding and unwinding of the prepared base film and tape film are smooth, and the peel force of the adhesive-enhancing surface layer is increased. The adhesive force between the adhesive-enhancing surface layer and the adhesive layer can be ensured without coating a bottom coating, which is beneficial to the use of the tape film in a high-humidity environment for a long time.

Description

Technical Field

[0001] The present invention relates to the field of thin films, and particularly to a biaxially oriented polyethylene film, a preparation method thereof, and a tape film. Background Art

[0002] Existing tape films generally include a substrate layer, a bottom coating layer, and an adhesive layer from bottom to top. The substrate layer is usually a biaxially oriented polypropylene film (referred to as BOPP film for short) or a biaxially oriented polyester film (referred to as BOPET film for short), with a thickness of 12 - 40 μm. However, with the continuous implementation of single - material recyclability, the biaxially oriented polyethylene film (BOPE film) has gradually become a popular packaging material, which has the characteristics of recyclability, multi - functionality, and light weight, and is increasingly valued by the packaging industry. However, there are few studies on using BOPE films as tape films at present.

[0003] In practical applications, the tape film is usually wound up and stored. After winding, the adhesive layer covers the other surface of the substrate layer. However, due to the low surface energy of the BOPE film and the very strong polarity of the adhesive used to prepare the adhesive layer, the adhesive layer is likely to adhere to the other surface of the substrate layer, resulting in phenomena such as inability to unwind, detachment of the adhesive layer from the bottom coating layer, or detachment of the adhesive layer with the bottom coating layer from the substrate layer. Therefore, when using a BOPE film as the substrate layer, it is generally necessary to coat a material with a lower surface energy, such as silicone oil, on the other surface of the substrate layer to make the other surface of the substrate layer and the adhesive layer easily peelable during use.

[0004] However, through a large number of practices, the inventor found that the existing tape films still have the following defects after coating with silicone oil: First, coating a material with a lower surface energy, such as silicone oil, on the other surface of the substrate layer requires a coating process, which increases the production process and processing cost. It is difficult to ensure the uniformity of coating during coating, and the silicone oil is prone to migration after coating, affecting the adhesion strength between the adhesive layer and the bottom coating layer; Second, when the existing tape films are exposed to a high - humidity environment for a long time, there is usually a problem of insufficient adhesiveness; Third, the adhesion between the adhesive layer and the substrate layer of the existing tape films is insufficient, resulting in the phenomenon that when the tape film is unwound or the already - pasted tape film is torn off for re - pasting, the adhesive layer detaches from the substrate layer, and it is necessary to cut off the part where the adhesive layer detaches or use a new tape film for pasting. Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a biaxially stretched polyethylene-based film and a preparation method thereof. For the biaxially stretched polyethylene-based film of the present application, on the one hand, by adding a certain amount of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer to the release functional layer, the release force of the release functional layer is reduced on the premise of ensuring the compatibility of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer with linear low-density polyethylene, and the smooth winding of the tape film and the biaxially stretched polyethylene-based film can be achieved without coating silicone oil; on the other hand, by adding polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA-g-EVA) to the tackifying surface layer, the adhesion between the tackifying surface layer and the adhesive layer can be ensured without coating a primer layer on the tackifying surface layer, the release force of the tackifying surface layer is enhanced, which is beneficial to ensuring that the adhesive layer will not separate from the tackifying surface layer when the prepared tape film is unrolled and can be smoothly torn off for repeated use after use. In addition, the addition of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer also improves the barrier performance of the release functional layer. Under the synergistic effect of the enhanced release force of the tackifying surface layer, it is beneficial for the tape film to still maintain a high adhesive force in a high-humidity environment and can be used in a high-humidity environment for a long time.

[0006] The technical solution of the present invention is achieved in the following manner:

[0007] A biaxially stretched polyethylene-based film, comprising a release functional layer, a core layer and a tackifying surface layer arranged in sequence; the release functional layer comprises linear low-density polyethylene, 5-10 wt% of ethylene-propylene copolymer polyethylene and 20-30 wt% of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer, the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is copolymerized from a fluorinated polysiloxane chain segment and an ethylene-norbornene chain segment, the fluorinated polysiloxane chain segment is copolymerized and connected by 3 to 4 fluorinated siloxane units, and the ethylene-norbornene chain segment is copolymerized and connected by 1 to 2 ethylene-norbornene units; the core layer comprises linear low-density polyethylene; the tackifying surface layer comprises ethylene-propylene copolymer polyethylene and 10-20 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer.

[0008] For the biaxially oriented polyethylene film of the present application, on the one hand, a certain amount of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer and ethylene-propylene copolymerized polyethylene are added to the release functional layer. On the premise of ensuring the compatibility between the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer and linear low-density polyethylene, the release force of the release functional layer is reduced, and the smooth winding of the tape film and the biaxially oriented polyethylene film can be achieved without coating silicone oil. On the other hand, by adding polymethyl methacrylate grafted ethylene vinyl acetate copolymer (PMMA-g-EVA) to the tackifying surface layer, the adhesion between the tackifying surface layer and the adhesive layer can be ensured without coating a primer on the tackifying surface layer, the release force of the tackifying surface layer is enhanced, which is beneficial to ensuring that the adhesive layer will not separate from the tackifying surface layer when the prepared tape film is unwound and can be smoothly torn off for reuse after use. In addition, the addition of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer also improves the barrier performance of the release functional layer. With the synergistic effect of the enhanced release force of the tackifying surface layer, it is beneficial for the tape film to maintain a high adhesive force in a high-humidity environment and can be used in a high-humidity environment for a long time.

[0009] In the present application, 20-30 wt% of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is added to the release functional layer and the molecular chain composition thereof is defined. While improving the release effect of the release functional layer, the barrier performance of the release functional layer is also improved. The smooth winding and unwinding of the tape film and the biaxially oriented polyethylene film can be achieved without coating silicone oil. With the synergistic effect of the enhanced release force of the tackifying surface layer, it is beneficial for the tape film to be used in a high-humidity environment for a long time and maintain the adhesion between the adhesive layer and the substrate in a high-humidity environment. Specifically, if the content of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is less than 20 wt%, the improvement of the release effect is not obvious, which is not conducive to the smooth winding and unwinding of the base film itself, and will also have a certain adverse effect on the release force of the tackifying surface layer; if the content of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is higher than 30 wt%, it is not conducive to the effective coextrusion of the release functional layer and the core layer, and is not conducive to the smoothness of biaxial stretching, and cracks will occur during production; if the number of ethylene-norbornene units in a single ethylene-norbornene chain segment is greater than 2, it will cause the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer to be too rigid and not conducive to biaxial stretching. If the number of polysiloxane units in a single polysiloxane chain segment is greater than 4, it may lead to poor compatibility between the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer and other components of the release functional layer, which is not conducive to the uniformity of the release effect and results in a poor final release effect.

[0010] On this basis, to ensure the compatibility between the fluorosilicone-functionalized ethylene-norbornene block copolymer and linear low-density polyethylene in the release functional layer, the present application also adds 5-10 wt% of ethylene-propylene copolymerized polyethylene with relatively better melt fluidity to the release functional layer to ensure that the fluorosilicone-functionalized ethylene-norbornene block copolymer can be evenly dispersed in the release functional layer.

[0011] On the other hand, to directly coat the adhesive layer on the tackifying surface layer and ensure the adhesion between the tackifying surface layer and the adhesive layer, the present application also adds 10-20 wt% of polymethyl methacrylate-grafted ethylene vinyl acetate copolymer to the tackifying surface layer. Since the polymethyl methacrylate-grafted ethylene vinyl acetate copolymer introduces amorphous polymethyl methacrylate (PMMA) through a graft polymerization process, it disrupts the packing of the crystalline polyethylene segments, reduces the crystallinity, is conducive to forming a smooth microstructure, has a high adhesion area, and increases the content of polar ester groups, which is more conducive to improving the adhesion between the tackifying surface layer and the adhesive layer, thus eliminating the need for coating a primer layer. In addition, the PMMA-g-EVA has a short PMMA graft chain, which is conducive to forming a uniform interpenetrating polymer network at the interface between the tackifying surface layer and the adhesive layer, enabling effective compatibilization between the tackifying surface layer and the adhesive layer and having high adhesion, which is conducive to achieving the coating of the adhesive layer without coating a primer layer.

[0012] Further, the melt index of the fluorosilicone-functionalized ethylene-norbornene block copolymer is measured to be 50-100 g / 10 min under the conditions of 190 °C and 2.16 kg. Using the fluorosilicone-functionalized ethylene-norbornene block copolymer within the defined melt index range is conducive to improving the melt fluidity required for the release functional layer and ensuring the conformability between the longitudinal drawing roller and the thick sheet during the production process.

[0013] Further, the tackifying surface layer also includes 0.5-1 wt% of crosslinked polymethyl methacrylate microparticles. Considering that the tackifying surface layer contains polymethyl methacrylate-grafted ethylene vinyl acetate copolymer, compared with the commonly used silica-based anti-blocking agents, the crosslinked polymethyl methacrylate microparticles can be more evenly dispersed in the tackifying surface layer. Adding crosslinked polymethyl methacrylate microparticles to the tackifying surface layer is conducive to ensuring the smoothness of the winding and unwinding of the biaxially oriented polyethylene film.

[0014] Further, the content of polymethyl methacrylate in the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 20-40 wt%; the number average molecular weight of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 20,000-22,000 g / mol. The present application also limits the content of PMMA in PMMA-g-EVA. If the PMMA content is greater than 40 wt%, it will cause the viscosity of PMMA-g-EVA to be too high, which is not conducive to the compatibility with ethylene-propylene copolymerized polyethylene, is not conducive to obtaining a thick sheet suitable for biaxial stretching, and may have the problem of sticking to the roller; if the PMMA content is less than 20 wt%, it is impossible to effectively form a uniform interpenetrating polymer network at the interface between the tackifying surface layer and the adhesive layer, which is not conducive to the adhesion between the tackifying surface layer and the adhesive layer. Within the limited number average molecular weight range, the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer has good melt matching with the ethylene-propylene copolymerized polyethylene in the tackifying surface layer.

[0015] Further, the melting point of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 90-100 °C. EVA usually has a relatively low melting point and poor thermal stability. Controlling the melting point of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer to be 90-100 °C has better thermal stability than EVA and is also conducive to the smooth unwinding and rewinding of the biaxially stretched polyethylene film itself.

[0016] Further, the melting point of the ethylene-vinyl acetate copolymer used to prepare the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 80-90 °C, and the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 15-25 wt%, which is conducive to maintaining the thermal stability of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer and will not degrade at the processing temperature of the present invention.

[0017] Further, the thickness of the release functional layer is 1-2 μm, the thickness of the tackifying surface layer is 1-2 μm, and the thickness of the biaxially stretched polyethylene film is 20-40 μm. If the thickness of the release functional layer > 2 μm, it will cause the haze of the biaxially stretched polyethylene film to increase and increase the production cost; if the thickness of the release functional layer < 1 μm, it is difficult to achieve a good release effect and is not conducive to smooth unwinding and use in the application of the tape film.

[0018] Further, at 230 °C and under the condition of 2.16 kg, the melt index of the ethylene-propylene copolymerized polyethylene is measured to be 5-10 g / 10 min, which is conducive to the compatibility between the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer and the linear low-density polyethylene in the release functional layer to ensure that the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer can be evenly dispersed in the release functional layer.

[0019] Further, the melt index of the linear low-density polyethylene was measured to be 1-5 g / 10 min at 190°C and 2.16 kg.

[0020] Further, the release functional layer further comprises 0.5-1 wt% of an anti-blocking agent.

[0021] Further, the core layer further comprises 0.5-1 wt% of an antistatic agent.

[0022] The present invention also provides a method for preparing the biaxially stretched polyethylene-based film described above, comprising the following steps: co-extruding and cooling the tackifying surface layer, the core layer and the release functional layer to form a resin sheet; longitudinally stretching and transversely stretching the resin sheet; subjecting the tackifying surface layer to corona treatment and winding it up. The extrusion temperatures of the tackifying surface layer and the core layer are both 220°C to 250°C, and the extrusion temperature of the release functional layer is 200°C to 250°C. The present application adopts a co-extrusion one-step forming process, which simplifies the processing technology and reduces the cost; corona treatment of the tackifying surface layer is beneficial to enhancing the surface tension of the tackifying surface layer, enabling the tackifying surface layer of the biaxially stretched polyethylene-based film to have good adhesion, and enabling the coating of glue process on the tackifying surface layer without a primer, which is applied to the preparation of tape films. The biaxially stretched polyethylene-based film prepared by the biaxial stretching process of the present invention has good bonding strength among the tackifying surface layer, the core layer and the release functional layer, so that they can be smoothly co-extruded. The release functional layer has good release effect, and the winding and unwinding are smooth, reducing the cost and improving the production efficiency.

[0023] The present invention also provides a tape film comprising the biaxially stretched polyethylene-based film described above, further comprising an adhesive layer, and the release functional layer, the core layer, the tackifying surface layer and the adhesive layer are arranged in sequence. For the tape film of the present invention, the peeling force required between the biaxially stretched polyethylene-based film and the adhesive layer after winding is small, it has a good release effect, and the winding and unwinding are smooth.

[0024] Further, the adhesive layer comprises at least one of an aqueous acrylate adhesive and a styrene-butadiene-styrene triblock copolymer.

[0025] For better understanding and implementation, the present invention will be described in detail below. Detailed Embodiments

[0026] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the embodiments of the present application.

[0027] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present application. The singular forms "a", "the" and "said" used in the embodiments of the present 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 encompasses any and all possible combinations of one or more of the associated listed items.

[0028] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0029] In addition, in the description of the present application, unless otherwise specified, "a plurality" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0030] It should be understood that the embodiments of the present application are not limited to the exact structure described above and various modifications and changes can be made without departing from its scope. The scope of the embodiments of the present application is only limited by the appended claims.

[0031] As an embodiment of the present invention, this embodiment provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence; the release functional layer includes linear low-density polyethylene, 5-10 wt% of ethylene-propylene copolymer polyethylene, and 20-30 wt% of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer. The fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is copolymerized from a fluorinated polysiloxane chain segment and an ethylene-norbornene chain segment. The fluorinated polysiloxane chain segment is copolymerized and connected by 3 to 4 fluorinated siloxane units, and the ethylene-norbornene chain segment is copolymerized and connected by 1 to 2 ethylene-norbornene units; the core layer includes linear low-density polyethylene; the tackifying surface layer includes ethylene-propylene copolymer polyethylene and 10-20 wt% of poly(methyl methacrylate) grafted ethylene-vinyl acetate copolymer.

[0032] Further, the melt index of the fluorine-containing polysiloxane-functionalized ethylene-norbornene block copolymer was measured to be 50-100 g / 10 min under the conditions of 190 °C and 2.16 kg.

[0033] Further, the tackifying surface layer further comprises 0.5-1 wt% crosslinked polymethyl methacrylate particles.

[0034] Further, the content of polymethyl methacrylate in the polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer is 20-40 wt%; the number average molecular weight of the polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer is 20,000-22,000 g / mol.

[0035] Further, the melting point of the polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer is 90-100 °C.

[0036] Further, the melting point of the ethylene-vinyl acetate copolymer used to prepare the polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer is 80-90 °C, and the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 15-25 wt%.

[0037] Further, the thickness of the release functional layer is 1-2 μm, the thickness of the tackifying surface layer is 1-2 μm, and the thickness of the biaxially stretched polyethylene film is 20-40 μm.

[0038] The present invention also provides a method for preparing the biaxially stretched polyethylene film as described in any one of the above, comprising the following steps: co-extruding and cooling the tackifying surface layer, the core layer, and the release functional layer to form a resin sheet; longitudinally stretching and transversely stretching the resin sheet; corona treating the tackifying surface layer and winding it up. The extrusion temperature of the tackifying surface layer and the core layer is 220 °C to 250 °C, and the extrusion temperature of the release functional layer is 200 °C to 250 °C.

[0039] The present invention also provides a tape film of the biaxially stretched polyethylene film as described in any one of the above, further comprising an adhesive layer, and the release functional layer, the core layer, the tackifying surface layer, and the adhesive layer are arranged in sequence.

[0040] Further, the adhesive layer comprises at least one of an aqueous acrylate adhesive and a styrene-butadiene-styrene triblock copolymer.

[0041] The physical property indexes and their testing methods of the examples or comparative examples of the present invention are specifically as follows:

[0042] The melt index (melt mass flow rate MFR) was measured according to GB / T3682-2018;

[0043] 180° peel strength test of the release film. The peel strength of the base film was determined with reference to the national standard GB / T 25256-2010 as follows: (1) Evaluation of the peel strength of the release functional layer: A 3M standard pressure-sensitive tape with a width of 25 mm was adhered to the BOPE base film (bonded to the release functional layer) of this patent with a width of 25 mm. A pressure roller was used to roll back and forth twice at a speed of about 10 mm / s, and it was placed for 20 h under the conditions of a temperature of 23°C ± 2°C, a relative humidity of 80% ± 5%, and a pressure of 70 g / cm 2 Then, it was tested at 180° with a tensile machine, and the relative humidity of the test environment was 80% ± 5%; (2) Evaluation of the peel strength of the tackifying surface layer: A 3M standard pressure-sensitive tape with a width of 25 mm was adhered to the release film (bonded to the surface layer) of this patent with a width of 25 mm. A pressure roller was used to roll back and forth twice at a speed of about 10 mm / s, and it was placed for 20 h under the conditions of a temperature of 23°C ± 2°C, a relative humidity of 80% ± 5%, and a pressure of 70 g / cm 2 Then, it was tested at 180° with a tensile machine, and the relative humidity of the test environment was 80% ± 5%.

[0044] The melt index of linear low-density polyethylene is: 1.7 g / 10 min (test conditions: 190°C, 2.16 kg);

[0045] The melt index of ethylene-propylene copolymer polyethylene is: 7.5 g / 10 min (test conditions: 230°C, 2.16 kg);

[0046] The melt index of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer is: 60 g / 10 min (test conditions: 190°C, 2.16 kg);

[0047] The fluorosiloxane unit is methyl(trifluoropropyl)siloxane;

[0048] The melting point of the ethylene-vinyl acetate copolymer used to prepare the polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer is 85°C, and the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 20 wt%;

[0049] The anti-blocking agent in the release functional layer is silica;

[0050] The antistatic agent in the core layer is glycerol monostearate;

[0051] The adhesive used for coating is a styrene-butadiene-styrene triblock copolymer adhesive.

[0052] It should be noted that the proportions described in the examples or comparative examples of the present invention are all weight percentages.

[0053] Example 1

[0054] This embodiment provides a biaxially oriented polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially oriented polyethylene film in this embodiment includes the following steps:

[0055] Preparation of the release functional layer resin: Take 71 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 20 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is connected by 1 ethylene-norbornene copolymer unit, and the fluorinated polysiloxane copolymer segment is connected by 3 fluorinated siloxane copolymer units), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0056] Preparation of the core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0057] Preparation of the tackifying surface layer resin: Take 89 wt% ethylene-propylene copolymer polyethylene, 10 wt% polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 20 wt%, number average molecular weight Mn is 20000 g / mol, melting point Tm is 90 °C), and 1 wt% cross-linked PMMA microparticles, and mix them evenly to obtain the tackifying surface layer resin.

[0058] The preparation method of the BOPE film in this embodiment includes the following steps: Introduce the tackifying surface layer resin, the core layer resin, and the release functional layer resin into an extruder for co-extrusion. After passing through a runner distributor, they converge at a T-die to form a resin melt. The extrusion temperature of the tackifying surface layer and the core layer is 230 °C, and the extrusion temperature of the release functional layer is 210 °C; the resin melt is then cooled by a chill roll at 28 °C and cast into a sheet; the resin sheet is preheated at 120 °C and then longitudinally stretched 5 times, then introduced into a transverse stretching device, transversely stretched 8.5 times after preheating at 143 °C, and finally wound up after corona treatment (corona power 30 w.min / m); then aging treatment is carried out, and it is slit into the required specifications and packaged to obtain the biaxially oriented polyethylene film.

[0059] The thickness of the biaxially oriented polyethylene film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the winding and unwinding are smooth.

[0060] Coat a layer of adhesive on the tackifying surface layer of the biaxially oriented polyethylene film in this embodiment to form an adhesive layer with a thickness of 5 μm, and obtain a tape film. During the preparation process, the winding and unwinding are smooth.

[0061] Example 2

[0062] This embodiment provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene film in this embodiment includes the following steps:

[0063] Preparation of release functional layer resin: Take 66 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin. Preparation of core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0064] Preparation of tackifying surface layer resin: Take 84 wt% ethylene-propylene copolymer polyethylene, 15 wt% polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21000 g / mol, melting point Tm is 95 °C), and 1 wt% crosslinked PMMA particles, and mix them evenly to obtain the tackifying surface layer resin.

[0065] The preparation method of the biaxially stretched polyethylene film in this embodiment is the same as that in Embodiment 1, so it will not be elaborated here.

[0066] The thickness of the biaxially stretched polyethylene film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the winding and unwinding are smooth.

[0067] Coat a layer of adhesive on the tackifying surface layer of the biaxially stretched polyethylene film in this embodiment to form an adhesive layer with a thickness of 5 μm, and obtain a tape film. During the preparation process, the winding and unwinding are smooth.

[0068] Embodiment 3

[0069] This embodiment provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene film in this embodiment includes the following steps:

[0070] Preparation of release functional layer resin: Take 61 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 30 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 4 fluorinated siloxane copolymer units connected), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin. Preparation of core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0071] Preparation of tackifying surface layer resin: 79 wt% of ethylene-propylene copolymerized polyethylene, 20 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 40 wt%, number average molecular weight Mn is 20,000 g / mol, melting point Tm is 100 °C), and 1 wt% of crosslinked PMMA particles are mixed evenly to obtain the tackifying surface layer resin.

[0072] The preparation method of the biaxially stretched polyethylene-based film in this example is the same as that in Example 1, so it will not be elaborated here.

[0073] The thickness of the biaxially stretched polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the winding and unwinding are smooth.

[0074] A layer of adhesive is coated on the tackifying surface layer of the biaxially stretched polyethylene-based film in this example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding are smooth.

[0075] Comparative Example 1

[0076] This comparative example provides a biaxially stretched polyethylene-based film, including a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation methods of the resins of each layer of the biaxially stretched polyethylene-based film in this comparative example include the following steps:

[0077] Preparation of release functional layer resin: 66 wt% of linear low-density polyethylene, 8 wt% of ethylene-propylene copolymerized polyethylene, 25 wt% of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected), and 1 wt% of anti-blocking agent are mixed evenly to obtain the release functional layer resin.

[0078] Preparation of core layer resin: 99 wt% of linear low-density polyethylene and 1 wt% of antistatic agent are mixed evenly to obtain the core layer resin.

[0079] Preparation of tackifying surface layer resin: 91 wt% of ethylene-propylene copolymerized polyethylene, 8 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21,000 g / mol, melting point Tm is 95 °C), and 1 wt% of crosslinked PMMA particles are mixed evenly to obtain the tackifying surface layer resin.

[0080] The preparation method of the biaxially stretched polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0081] The biaxially stretched polyethylene film has a thickness of 20 μm, among which the release functional layer has a thickness of 2 μm, the core layer has a thickness of 17 μm, and the tackifying surface layer has a thickness of 1 μm. During the preparation process, the unwinding and rewinding are smooth.

[0082] A layer of adhesive is coated on the tackifying surface layer of the biaxially stretched polyethylene film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the unwinding and rewinding are smooth.

[0083] Comparative Example 2

[0084] This comparative example provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene film in this comparative example includes the following steps:

[0085] Preparation of the release functional layer resin: Take 66 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is connected by 2 ethylene-norbornene copolymer units, and the fluorinated polysiloxane copolymer segment is connected by 3 fluorinated siloxane copolymer units), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0086] Preparation of the core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0087] Preparation of the tackifying surface layer resin: Take 76 wt% ethylene-propylene copolymer polyethylene, 23 wt% polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer (the PMMA content is 30 wt%, the number-average molecular weight Mn is 21000 g / mol, and the melting point Tm is 95 °C), and 1 wt% cross-linked PMMA particles, and mix them evenly to obtain the tackifying surface layer resin.

[0088] The preparation method of the biaxially stretched polyethylene film in this comparative example is the same as that of Example 1, so it will not be elaborated here.

[0089] The biaxially stretched polyethylene film has a thickness of 20 μm, among which the release functional layer has a thickness of 2 μm, the core layer has a thickness of 17 μm, and the tackifying surface layer has a thickness of 1 μm. During the preparation process, the unwinding and rewinding are not smooth enough, and there is a situation of sticking to the roller.

[0090] A layer of adhesive is coated on the tackifying surface layer of the biaxially stretched polyethylene film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the unwinding and rewinding are smooth.

[0091] Comparative Example 3

[0092] This comparative example provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene film in this comparative example includes the following steps:

[0093] Preparation of the release functional layer resin: Take 73 wt% linear low density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 18 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0094] Preparation of the core layer resin: Take 99 wt% linear low density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0095] Preparation of the tackifying surface layer resin: Take 84 wt% ethylene-propylene copolymer polyethylene, 15 wt% polymethyl methacrylate grafted ethylene vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21000 g / mol, melting point Tm is 95 °C), and 1 wt% cross-linked PMMA microparticles, and mix them evenly to obtain the tackifying surface layer resin.

[0096] The preparation method of the biaxially stretched polyethylene film in this comparative example is the same as that of Example 1, so it will not be elaborated.

[0097] The thickness of the biaxially stretched polyethylene film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the winding and unwinding are smooth.

[0098] Coat an adhesive on the tackifying surface layer of the biaxially stretched polyethylene film in this comparative example to form an adhesive layer with a thickness of 5 μm, and obtain a tape film. During the preparation process, the winding and unwinding are not smooth enough.

[0099] Comparative Example 4

[0100] This comparative example provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene film in this comparative example includes the following steps:

[0101] Preparation of the release functional layer resin: Take 59 wt% linear low density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 32 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0102] Preparation of core layer resin: 99 wt% linear low density polyethylene and 1 wt% antistatic agent were mixed evenly to obtain the core layer resin.

[0103] Preparation of tackifying surface layer resin: 84 wt% ethylene-propylene copolymerized polyethylene, 15 wt% polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21000 g / mol, melting point Tm is 95 °C) and 1 wt% crosslinked PMMA particles were mixed evenly to obtain the tackifying surface layer resin.

[0104] The preparation method of the biaxially stretched polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated.

[0105] The thickness of the biaxially stretched polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the production smoothness was poor and it was difficult to stretch into a film.

[0106] A layer of adhesive was coated on the tackifying surface layer of the biaxially stretched polyethylene-based film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding were smooth.

[0107] Comparative Example 5

[0108] This comparative example provides a biaxially stretched polyethylene-based film, including a release functional layer, a core layer and a tackifying surface layer arranged in sequence. The preparation methods of the resins of each layer of the biaxially stretched polyethylene-based film in this comparative example include the following steps:

[0109] Preparation of release functional layer resin: 66 wt% linear low density polyethylene, 8 wt% ethylene-propylene copolymerized polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer chain segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer chain segment is composed of 3 fluorinated siloxane copolymer units connected) and 1 wt% anti-blocking agent were mixed evenly to obtain the release functional layer resin.

[0110] Preparation of core layer resin: 99 wt% linear low density polyethylene and 1 wt% antistatic agent were mixed evenly to obtain the core layer resin.

[0111] Preparation of tackifying surface layer resin: 84 wt% ethylene-propylene copolymerized polyethylene, 15 wt% ethylene-vinyl acetate copolymer (the content of vinyl acetate (VA) is 20 wt%, and the melt index of the ethylene-vinyl acetate copolymer measured under the conditions of 230 °C and 2.16 kg is 15 g / 10 min, melting point Tm is 85 °C) and 1 wt% crosslinked PMMA particles were mixed evenly to obtain the tackifying surface layer resin.

[0112] The preparation method of the biaxially oriented polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0113] The thickness of the biaxially oriented polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the production smoothness is good.

[0114] A layer of adhesive is coated on the tackifying surface layer of the biaxially oriented polyethylene-based film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding are not smooth enough, and there is a phenomenon of glue peeling off.

[0115] Comparative Example 6

[0116] This comparative example provides a biaxially oriented polyethylene-based film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation methods of the resins of each layer of the biaxially oriented polyethylene-based film in this comparative example include the following steps:

[0117] Preparation of the release functional layer resin: Take 66 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0118] Preparation of the core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0119] Preparation of the tackifying surface layer resin: Take 84 wt% ethylene-propylene copolymer polyethylene, 15 wt% polymethyl methacrylate-grafted ethylene-vinyl acetate copolymer (PMMA content is 50 wt%, number average molecular weight Mn is 21000 g / mol, melting point Tm is 95 °C), and 1 wt% cross-linked PMMA particles, and mix them evenly to obtain the tackifying surface layer resin.

[0120] The preparation method of the biaxially oriented polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0121] The thickness of the biaxially oriented polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the production smoothness is poor, and there is a situation of sticking to the roller.

[0122] A layer of adhesive is coated on the tackifying surface layer of the biaxially oriented polyethylene-based film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding are not smooth enough.

[0123] Comparative Example 7

[0124] This comparative example provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins for each layer of the biaxially stretched polyethylene film in this comparative example includes the following steps:

[0125] Preparation of the release functional layer resin: Take 66 wt% linear low-density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% blend of fluorinated polysiloxane and ethylene-norbornene copolymer (the molar ratio of the blend of fluorinated polysiloxane and ethylene-norbornene copolymer is 3:2, and the melt index of the blend is 60 g / 10 min (test conditions: 190 °C, 2.16 kg)) and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0126] Preparation of the core layer resin: Take 99 wt% linear low-density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0127] Preparation of the tackifying surface layer resin: Take 84 wt% ethylene-propylene copolymer polyethylene, 15 wt% polymethyl methacrylate grafted ethylene vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21000 g / mol, and melting point Tm is 95 °C) and 1 wt% cross-linked PMMA particles, and mix them evenly to obtain the tackifying surface layer resin.

[0128] The preparation method of the biaxially stretched polyethylene film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0129] The thickness of the biaxially stretched polyethylene film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the production smoothness is good.

[0130] Coat an adhesive on the tackifying surface layer of the biaxially stretched polyethylene film in this comparative example to form an adhesive layer with a thickness of 5 μm, and obtain a tape film. During the preparation process, the winding and unwinding are not smooth enough.

[0131] Comparative Example 8

[0132] This comparative example provides a biaxially stretched polyethylene film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins for each layer of the biaxially stretched polyethylene film in this comparative example includes the following steps:

[0133] Preparation of the release functional layer resin: Take 66 wt% linear low density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 3 ethylene-norbornene copolymer units connected together, and the fluorinated polysiloxane copolymer segment is composed of 3 fluorinated siloxane copolymer units connected together), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0134] Preparation of the core layer resin: Take 99 wt% linear low density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0135] Preparation of the tackifying surface layer resin: Take 84 wt% ethylene-propylene copolymer polyethylene, 15 wt% polymethyl methacrylate grafted ethylene vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21000 g / mol, melting point Tm is 95 °C), and 1 wt% crosslinked PMMA microparticles, and mix them evenly to obtain the tackifying surface layer resin.

[0136] The preparation method of the biaxially stretched polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0137] The thickness of the biaxially stretched polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the production smoothness is poor and it is difficult to form a film by biaxial stretching.

[0138] Coat an adhesive on the tackifying surface layer of the biaxially stretched polyethylene-based film in this comparative example to form an adhesive layer with a thickness of 5 μm, and obtain a tape film. During the preparation process, the winding and unwinding are smooth.

[0139] Comparative Example 9

[0140] This comparative example provides a biaxially stretched polyethylene-based film, which includes a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene-based film in this comparative example includes the following steps:

[0141] Preparation of the release functional layer resin: Take 66 wt% linear low density polyethylene, 8 wt% ethylene-propylene copolymer polyethylene, 25 wt% fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected together, and the fluorinated polysiloxane copolymer segment is composed of 1 fluorinated siloxane copolymer unit connected together), and 1 wt% anti-blocking agent, and mix them evenly to obtain the release functional layer resin.

[0142] Preparation of the core layer resin: Take 99 wt% linear low density polyethylene and 1 wt% antistatic agent, and mix them evenly to obtain the core layer resin.

[0143] Preparation of tackifying surface layer resin: 84 wt% of ethylene-propylene copolymerized polyethylene, 15 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21,000 g / mol, melting point Tm is 95 °C), and 1 wt% of crosslinked PMMA particles are mixed evenly to obtain the tackifying surface layer resin.

[0144] The preparation method of the biaxially stretched polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0145] The thickness of the biaxially stretched polyethylene-based film is 20 μm, among which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 17 μm, and the thickness of the tackifying surface layer is 1 μm. During the preparation process, the winding and unwinding are not smooth enough.

[0146] A layer of adhesive is coated on the tackifying surface layer of the biaxially stretched polyethylene-based film in this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding are not smooth enough.

[0147] Comparative Example 10

[0148] This comparative example provides a biaxially stretched polyethylene-based film, including a release functional layer, a core layer, and a tackifying surface layer arranged in sequence. The preparation method of the resins of each layer of the biaxially stretched polyethylene-based film in this comparative example includes the following steps:

[0149] Preparation of release functional layer resin: 66 wt% of linear low-density polyethylene, 8 wt% of ethylene-propylene copolymerized polyethylene, 25 wt% of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer (the ethylene-norbornene copolymer segment is composed of 2 ethylene-norbornene copolymer units connected, and the fluorinated polysiloxane copolymer segment is composed of 5 fluorinated siloxane copolymer units connected), and 1 wt% of anti-blocking agent are mixed evenly to obtain the release functional layer resin.

[0150] Preparation of core layer resin: 99 wt% of linear low-density polyethylene and 1 wt% of antistatic agent are mixed evenly to obtain the core layer resin.

[0151] Preparation of tackifying surface layer resin: 84 wt% of ethylene-propylene copolymerized polyethylene, 15 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer (PMMA content is 30 wt%, number average molecular weight Mn is 21,000 g / mol, melting point Tm is 95 °C), and 1 wt% of crosslinked PMMA particles are mixed evenly to obtain the tackifying surface layer resin.

[0152] The preparation method of the biaxially stretched polyethylene-based film in this comparative example is the same as that in Example 1, so it will not be elaborated here.

[0153] The biaxially stretched polyethylene-based film has a thickness of 20 μm, of which the release functional layer has a thickness of 2 μm, the core layer has a thickness of 17 μm, and the tackifying surface layer has a thickness of 1 μm. During the preparation process, the winding and unwinding are smooth.

[0154] A layer of adhesive is coated on the tackifying surface layer of the biaxially stretched polyethylene-based film of this comparative example to form an adhesive layer with a thickness of 5 μm, obtaining a tape film. During the preparation process, the winding and unwinding are smooth.

[0155] The performance test results of the biaxially stretched polyethylene-based films of Examples 1-3 and Comparative Examples 1-10 are shown in Table 1 below.

[0156] Table 1

[0157]

[0158] From the above performance test data, it can be seen that:

[0159] For the biaxially stretched polyethylene-based films of Examples 1-3, on the one hand, the release functional layer has a low peel force. Without coating silicone oil, it can be ensured that the tackifying surface layer and the adhesive layer will not adhere to the release functional layer during unwinding, realizing the smooth winding of the tape film and the biaxially stretched polyethylene-based film and improving the barrier performance of the release functional layer, which is beneficial to maintaining the adhesion between the adhesive layer and the substrate of the tape film in a high-humidity environment and can be used in a high-humidity environment for a long time. On the other hand, the tackifying surface layer has a high peel force. Without coating a primer layer, it can ensure good adhesion between the tackifying surface layer and the adhesive layer, which is beneficial to ensuring that the adhesive layer of the prepared tape film will not separate from the tackifying surface layer during unwinding and can be smoothly torn off after use for repeated use. In addition, the addition of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer also improves the barrier performance of the release functional layer. Under the synergistic effect of the enhanced surface peel force, it is beneficial to maintain the high adhesion of the tape film in a high-humidity environment and can be used in a high-humidity environment for a long time.

[0160] According to the data of Comparative Example 1 and Example 2, under the condition of the same release functional layer, the content of polymethyl methacrylate grafted ethylene vinyl acetate copolymer in the tackifying surface layer of Comparative Example 1 is too low, and the peel force of the tackifying surface layer of Comparative Example 1 is significantly lower than that of the tackifying surface layer of Example 2, which is not conducive to ensuring the bonding force between the tackifying surface layer and the adhesive layer of the tape film, there is a risk of delamination, and it is not suitable for use in a high-humidity environment.

[0161] According to the data of Comparative Example 2 and Example 2, under the same conditions of the release functional layer, the content of polymethyl methacrylate grafted ethylene vinyl acetate copolymer in the tackifying surface layer of Comparative Example 2 is too high, resulting in the tackifying surface layer being too sticky. The peel force of the tackifying surface layer of Comparative Example 2 is significantly higher than that of the tackifying surface layer of Example 2. However, during the production process, the film-forming property is poor, and the phenomenon of sticking to the roller will occur, and the smoothness of winding and unwinding between the base films themselves is poor.

[0162] According to the data of Comparative Example 3 and Example 2, under the same conditions of the tackifying surface layer, the content of fluorinated polysiloxane-functionalized ethylene norbornene in the tackifying surface layer of Comparative Example 3 is too low, and the improvement of the release effect is not obvious. The peel force of the release functional layer of Comparative Example 3 is significantly higher than that of the release functional layer of Example 2, which is not conducive to the desorption of the adhesive layer and the release functional layer. The tape film prepared has a problem of insufficient smoothness in winding and unwinding, and it is also not conducive to the smoothness of winding and unwinding of the BOPE base film itself. In addition, the too low content of fluorinated polysiloxane-functionalized ethylene norbornene block copolymer leads to a decrease in the barrier property of the release functional layer, and the surface peel force of Comparative Example 3 is also slightly lower than that of Example 2.

[0163] According to the data of Comparative Example 4 and Example 2, under the same conditions of the tackifying surface layer, the content of fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer in the release functional layer of Comparative Example 4 is too high. The peel force of the release functional layer of Comparative Example 4 is significantly lower than that of the release functional layer of Example 2, but the biaxially oriented polyethylene base film of Comparative Example 4 has poor film-forming property during production.

[0164] According to the data of Comparative Example 5 and Example 2, Comparative Example 5 directly uses unmodified ethylene vinyl acetate copolymer without grafting polymethyl methacrylate. The tackifying effect is not as good as that of polymethyl methacrylate grafted ethylene vinyl acetate copolymer. The peel force of the tackifying surface layer of Comparative Example 5 is significantly lower than that of the tackifying surface layer of Example 2, which is not conducive to effectively ensuring the bonding force between the tackifying surface layer and the adhesive layer of the tape film, and there is a risk of delamination, and it is also not conducive to application in a high-humidity environment.

[0165] According to the data of Comparative Example 6 and Example 2, the content of PMMA in the polymethyl methacrylate grafted ethylene vinyl acetate copolymer of Comparative Example 6 is on the high side. Although the peel force of the tackifying surface layer of Comparative Example 6 is significantly higher than that of the tackifying surface layer of Example 2, the tackifying surface layer of the biaxially oriented polyethylene base film of Comparative Example 6 is too sticky, and the film-forming property is poor during the production process, and smooth production cannot be carried out.

[0166] According to the data of Comparative Example 7 and Example 2, what is added to the release functional layer of Comparative Example 7 is a blend of fluorinated polysiloxane and ethylene-norbornene copolymer, and its compatibility and dispersion uniformity in the release functional layer will be worse than that of fluorinated polysiloxane-functionalized ethylene norbornene block copolymer. There are bright spots on the surface of the BOPE base film of Comparative Example 7.

[0167] According to the data of Comparative Example 8 and Example 2, the number of ethylene-norbornene copolymer units constituting the ethylene-norbornene chain segment in the release functional layer of Comparative Example 8 is excessive, and Comparative Example 8 has the problem that it is difficult to stretch into a film, which is not conducive to the smoothness of biaxial stretching.

[0168] According to the data of Comparative Example 9 and Example 2, under the same conditions of the tackifying surface layer, the amount of fluorinated polysiloxane constituting the fluorinated polysiloxane chain segment in Comparative Example 9 is too small, and the improvement of the release effect is not obvious. The peeling force of the release functional layer of Comparative Example 9 is significantly higher than that of the release functional layer of Example 2, which is not conducive to the desorption of the adhesive layer and the release functional layer. The prepared tape film has the problem that the winding and unwinding are not smooth enough, and it is also not conducive to the smoothness of the winding and unwinding of the BOPP base film itself.

[0169] According to the data of Comparative Example 10 and Example 2, the amount of fluorinated polysiloxane constituting the fluorinated polysiloxane chain segment in the release functional layer of Comparative Example 10 is excessive, and its compatibility and dispersion uniformity in the release functional layer will be worse than those of the fluorinated polysiloxane-functionalized ethylene-norbornene block copolymer. Although the peeling force of the release functional layer of Comparative Example 10 is lower than that of the release functional layer of Example 2, there are bright spots on the surface of the BOPP base film of Comparative Example 10, which is not conducive to the uniformity of release.

[0170] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and deformations.

Claims

1. A biaxially oriented polyethylene-based film, characterized in that, It includes a release functional layer, a core layer, and an adhesion-promoting surface layer arranged in sequence; the release functional layer includes linear low-density polyethylene, 5-10 wt% of ethylene-propylene copolymer polyethylene, and 20-30 wt% of fluorosilicone-functionalized ethylene-norbornene block copolymer. The fluorosilicone-functionalized ethylene-norbornene block copolymer is copolymerized from a fluorosilicone segment and an ethylene-norbornene segment. The fluorosilicone segment is copolymerized and connected by 3 to 4 fluorosilicone units, and the ethylene-norbornene segment is copolymerized and connected by 1 to 2 ethylene-norbornene units; the core layer includes linear low-density polyethylene; the adhesion-promoting surface layer includes ethylene-propylene copolymer polyethylene and 10-20 wt% of polymethyl methacrylate grafted ethylene-vinyl acetate copolymer, and the content of polymethyl methacrylate in the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 20-40 wt%.

2. The biaxially oriented polyethylene-based film according to claim 1, characterized in that, The adhesion-promoting surface layer further includes 0.5-1 wt% of cross-linked polymethyl methacrylate microparticles.

3. The biaxially oriented polyethylene-based film according to claim 1, characterized in that, Under the conditions of 190 °C and 2.16 kg, the melt index of the fluorosilicone-functionalized ethylene-norbornene block copolymer is 50-100 g / 10 min.

4. The biaxially oriented polyethylene-based film according to claim 1, wherein The number-average molecular weight of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 20,000-22,000 g / mol.

5. The biaxially oriented polyethylene film according to claim 1, wherein The melting point of the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 90-100 °C.

6. The biaxially oriented polyethylene film according to claim 1, wherein The melting point of the ethylene-vinyl acetate copolymer used to prepare the polymethyl methacrylate grafted ethylene-vinyl acetate copolymer is 80-90 °C, and the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 15-25 wt%.

7. The biaxially oriented polyethylene film according to claim 1, wherein The thickness of the release functional layer is 1-2 μm, the thickness of the adhesion-promoting surface layer is 1-2 μm, and the thickness of the biaxially stretched polyethylene film is 20-40 μm.

8. A method for preparing a biaxially stretched polyethylene film as described in any one of claims 1 to 7, characterized in that, It includes the following steps: Coextrude the adhesion-promoting surface layer, the core layer, and the release functional layer and cool to form a resin sheet; longitudinally stretch and transversely stretch the resin sheet; Perform corona treatment on the adhesion-promoting surface layer and wind it up. The extrusion temperature of both the adhesion-promoting surface layer and the core layer is 220 °C - 250 °C, and the extrusion temperature of the release functional layer is 200 °C - 250 °C.

9. A tape film comprising a biaxially stretched polyethylene-based film as described in any one of claims 1 to 7, characterized in that, It further includes an adhesive layer, and the release functional layer, the core layer, the adhesion-promoting surface layer, and the adhesive layer are arranged in sequence.

10. The tape film according to claim 9, wherein The adhesive layer includes at least one of aqueous acrylate adhesives and styrene-butadiene-styrene triblock copolymers.

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