BOPP matte film with optimized cutting performance based on paper-plastic lamination and preparation method thereof

Abstract

The present invention relates to the field of films, and more particularly to a BOPP matt film with optimized cutting performance based on paper-plastic lamination and a preparation method thereof, wherein the BOPP matt film comprises a matt layer, a core layer and a lower surface layer; the matt layer comprises a random copolymerized polypropylene, 40-55wt% high-density polyethylene and 5-10wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer; the core layer comprises homopolypropylene, 10-15wt% styrene-maleic anhydride copolymer, and 3-8wt% maleic anhydride grafted polypropylene; and the lower surface layer comprises homopolypropylene. The present invention optimizes the components of the core layer and the matt layer, improves the brittleness of the core layer and the matt layer, reduces the ability to resist fracture, and makes the laminated product obtained by laminating the BOPP matt film with paper shorten the tail film length or even do not produce a tail film after cutting and breaking the film, meets the application requirements of downstream customers, and can be produced at high speed and automatically.

Description

Technical Field

[0001] The present invention relates to the field of films, in particular to a BOPP matte film with optimized cutting performance based on paper-plastic lamination and a preparation method thereof. Background Art

[0002] Biaxially oriented polypropylene matte film (BOPP matte film) can be matte on one side and glossy on the other, or matte on both sides. Its matte effect is achieved primarily by scattering light. This matte effect can enhance the quality of printed outer packaging, giving it a soft, stylish, and elegant feel, while also reducing eye fatigue. Therefore, BOPP matte film is increasingly being used in the packaging field, and is particularly suitable for deep processing industries and fields such as coating and lamination.

[0003] The BOPP matte film currently used in the packaging industry is primarily composed of a matte layer, a core layer, and a glossy layer. Common applications include paper-plastic lamination (laminated with paper or cartons after applying or pre-applying a glue layer to the glossy surface) and label production. Common thicknesses are 12μm and 15μm. In this application, the glossy layer of the BOPP matte film is continuously laminated to multiple sheets of paper after the glue is applied. A disc cutter then cuts the film according to the paper size, producing several sheets of laminated paper. During cutting, the disc cuts a notch on one side of the laminated paper, then uses the speed difference between the rear and front rollers to perform differential film severing at the location corresponding to the notch.

[0004] Through extensive experience, the inventors discovered that existing BOPP matte films suffer from poor lamination and cutting performance. This poor lamination and cutting performance results in a short section of matte film (tail film) remaining longer than the paper after film cutting. If the tail film is too long, the glue carried by the tail film can cause the two adjacent layers of the paper-plastic laminate to stick together, hindering subsequent processing steps such as UV and hot stamping that require automatic paper removal. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a BOPP matte film with optimized cutting performance based on paper-plastic lamination and a preparation method thereof. By optimizing the components of the core layer and the matte layer and improving the brittleness of the core layer and the matte layer, the ability of the BOPP matte film to resist fracture is significantly reduced, so that the BOPP matte film has good lamination and cutting performance, and does not exhibit excessive deformation tolerance and fracture toughness when subjected to external stress. Furthermore, after cutting and breaking the film, the laminated product obtained by laminating the BOPP matte film with paper can reduce the length of the excess matte film (tail film) on the paper, thereby improving the problem of two adjacent layers of paper-plastic laminated products sticking together due to the glue carried in the tail film, and even eliminating the tail film, thereby meeting the application needs of downstream customers and enabling high-speed automated production.

[0006] The technical solution of the present invention is achieved by the following methods:

[0007] A BOPP matte film with optimized cutting performance based on paper-plastic lamination comprises a matte layer, a core layer and a lower surface layer arranged in sequence; the matte layer comprises random copolymer polypropylene, 40-55wt% high-density polyethylene and 5-10wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer; the core layer comprises homopolypropylene, 10-15wt% styrene-maleic anhydride copolymer and 3-8wt% maleic anhydride grafted polypropylene; and the lower surface layer comprises homopolypropylene.

[0008] The inventors found through practice and analysis that:

[0009] The main reason for the poor lamination and cutting performance of existing BOPP matte film is its excessive toughness and insufficient brittleness. The film's high deformation tolerance and fracture toughness (excessive resistance to fracture), coupled with its significant lack of brittleness, prevent it from effectively breaking when subjected to external stresses such as disc cutting and differential film cutting, resulting in excessively long film tails.

[0010] First, in the three-layer structure of existing BOPP matte film (matt layer, core layer, and lower surface layer), the core layer accounts for the largest proportion and is the layer that primarily reflects the film's mechanical properties. Therefore, the choice of core layer material directly affects the film's brittleness. Currently, the most common core layer substrate is homopolypropylene, which has a glass transition temperature (Tg) of -10°C and exhibits a rubbery phase (highly elastic state) at room temperature. According to the brittle-to-tough transition mechanism of polymers, when the temperature changes from low temperature to room temperature, the system transitions from the low-temperature glassy state to the highly elastic state, and the molecular chain segment mobility becomes active. Therefore, by increasing the Tg of the core layer substrate, the brittle-to-tough transition temperature of the matte film core layer can be moved toward high temperature, so that the core layer substrate of the BOPP matte film remains in a glassy state at room temperature, thereby improving the room-temperature brittleness of the core layer substrate and improving the overall brittleness of the BOPP matte film substrate; specifically, introducing rigid or cross-linking groups into the core layer to form a three-dimensional network structure can enhance the interaction force between polypropylene molecules, limit the movement space and freedom of homopolymer polypropylene molecular chains, help to increase the Tg of the core layer, and help to improve the overall brittleness of the core layer.

[0011] In addition, since the proportion of the matte layer in the BOPP matte film is second only to the core layer, the mechanical properties of the matte layer will also affect the brittleness of the BOPP matte film substrate. The main components of the matte layer are usually random copolymer polypropylene and high-density polyethylene (HDPE). Microscopically, the structure of the matte layer is similar to an "island" structure, in which the random copolymer polypropylene serves as a soft phase encapsulating the dispersed phase of high-density polyethylene. During the slitting process of the BOPP matte film by the disc knife, the random copolymer polypropylene soft phase in the matte layer is the main reflected phase that is cut and stretched. Similarly, according to the brittle-tough transition mechanism of polymers, the overall brittleness of the matte layer can be improved by increasing the Tg of the soft phase, synergistically improving the brittleness of the core layer, and thus improving the overall brittleness of the BOPP matte film. This is beneficial for reducing the length of excess matte film (tail film) on the paper when the BOPP matte film is slid by the disc knife and cut at differential speed in paper-plastic lamination applications, and can even eliminate the tail film and form a neat incision.

[0012] Based on this, the present invention adds 10-15wt% styrene-maleic anhydride copolymer and 3-8wt% maleic anhydride grafted polypropylene to the core layer. Under the synergistic effect of the two, the movement space and freedom of the homopolypropylene molecular chain are restricted, the Tg of the BOPP matte film core layer is increased, the core layer remains in a glassy state at room temperature, and the brittleness of the BOPP matte film core layer is improved. This is beneficial for reducing the length of excess matte film (tail film) on the paper when the BOPP matte film is cut by a disc knife in paper-plastic lamination applications, and can even eliminate the tail film and form a neat incision.

[0013] Specifically, the present invention adds a styrene-maleic anhydride copolymer to the core layer. On the one hand, during the melt blending process, the strongly polar anhydride groups of the maleic anhydride in the styrene-maleic anhydride copolymer and the homopolypropylene are partially bonded to the homopolypropylene molecular chain segments through a free radical grafting reaction, forming physical crosslinking points with the homopolypropylene molecular chains, thereby enhancing the intermolecular interaction force of the homopolypropylene and limiting the movement of the homopolypropylene chain segments to a certain extent. On the other hand, the Tg of the styrene-maleic anhydride copolymer is much higher than that of the homopolypropylene, and the Tg of the entire core layer can be effectively increased through blending. However, since homopolypropylene is a non-polar polymer and has poor compatibility with the polar polymer styrene-maleic anhydride copolymer, the present invention further adds 3-8wt% of maleic anhydride grafted polypropylene to the core layer to improve the compatibility of the homopolypropylene and the polar polymer styrene-maleic anhydride copolymer. The maleic anhydride grafted polypropylene improves the interfacial compatibility of the two phases, allowing the styrene-maleic anhydride copolymer to be evenly dispersed in the homopolypropylene matrix, thereby fully utilizing the rigid structure of the benzene rings in the styrene-maleic anhydride copolymer to further physically restrict the movement of the polypropylene molecular segments.

[0014] On this basis, if the content of styrene-maleic anhydride copolymer in the core layer is less than 10wt%, the styrene-maleic anhydride copolymer cannot effectively enhance the intermolecular interactions of polypropylene and restrict the movement of polypropylene molecular segments, which is not conducive to improving the Tg of the BOPP matte film substrate and thus the brittleness of the BOPP matte film substrate. If the content of styrene-maleic anhydride copolymer is higher than 15wt%, the content of benzene ring rigid groups in the styrene-maleic anhydride copolymer is too high, which increases the risk of film breakage during stretching. If the content of maleic anhydride-grafted polypropylene is less than 3wt%, it is not conducive to improving the compatibility of the styrene-maleic anhydride copolymer with the homopolymer polypropylene matrix, and the cyclic rigid structures in the styrene-maleic anhydride copolymer are not dispersed in the polypropylene matrix to restrict the movement of polypropylene molecular segments, which is not conducive to improving the overall brittleness of the BOPP matte film substrate and reducing the length of the tail film produced when the BOPP matte film is cut by a disc knife in paper-plastic lamination applications. If the content of maleic anhydride grafted polypropylene is higher than 8wt%, the polar groups in maleic anhydride aggregate in the non-polar homopolymer polypropylene matrix to form rigid agglomerates. These agglomerates will produce stress concentration during the biaxial stretching process, affecting the smoothness of production.

[0015] The polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer added to the matt layer of the present invention has polymethyl methacrylate side chains at both ends. On the one hand, the polymethyl methacrylate segment is a rigid segment, which is conducive to restricting the movement of the random copolymerized polypropylene molecular chain. The triblock structure has a hard-soft-hard structural feature, which is more conducive to restricting the movement of the random copolymerized polypropylene molecular chain, thereby increasing the brittleness of the matt layer and cooperating with the core layer to improve the overall brittleness of the matt film. On the other hand, the Tg of the polymethyl methacrylate segment is As high as 105°C, it can effectively increase the Tg of the soft phase random copolymer polypropylene. The two end segments in the triblock structure are both polymethyl methacrylate, which is more conducive to increasing the Tg of the soft phase random copolymer polypropylene, thereby increasing the brittleness of the matte layer. On the other hand, the flexible polybutyl acrylate segment in the triblock copolymer can form a physical bond with the soft phase of random copolymer polypropylene through the entanglement of molecular chains, forming an anchoring effect, reducing the interfacial tension between the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer and the random copolymer polypropylene, and improving compatibility. Furthermore, the polybutyl acrylate segment acts as a flexible elastomer, and the elastomer microdomain, through bridging, can also alleviate the appearance quality problem of cracks in the matte layer during the biaxial stretching of the matte film caused by the addition of the rigid polymethyl methacrylate segment.

[0016] On this basis, if the content of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer in the matte layer is lower than 5wt%, it is not conducive to improving the brittleness of the soft phase of the matte layer, and is not conducive to cooperating with the core layer to improve the overall brittleness of the BOPP matte film substrate; if the content of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is higher than 15wt%, due to the excessive content of polymethyl methacrylate rigid chain segments, the risk of film breakage is increased during the stretching process, affecting the smoothness of production.

[0017] Furthermore, the ester groups in the polymethyl methacrylate (PMMA)-polybutyl acrylate-PMMA triblock copolymer segments that make up the matte layer possess a certain degree of polarity, enabling interaction with the polar maleic anhydride groups in the styrene-maleic anhydride copolymer and maleic anhydride-grafted polypropylene in the core layer. This allows the molecular chains of the matte layer and core layer to interpenetrate and interweave, forming a continuous network structure. This further restricts the freedom of movement of the molecular chains in the matte layer and core layer, requiring higher energy for the molecular chains to move, which helps to increase the overall glass transition temperature of the matte film and reduce interfacial defects and stress concentration points. Furthermore, due to their different chemical properties, the PMMA segments and polybutyl acrylate segments (PBA segments) added to the matte layer form a microphase separation structure. The polymethyl methacrylate segments and the styrene-maleic anhydride copolymer chains in the core layer form an interpenetrating cross-linked network at the interface. This structure not only strengthens the interfacial bonding between the layers but also restricts overall molecular chain motion through segment entanglement, thereby raising the film's glass transition temperature (Tg). Simultaneously, the PBA segments, with their flexible long-chain structure, act as a plasticizer and buffer, effectively absorbing stress during processing by forming an elastic transition layer at the interface. This synergistic mechanism ensures the necessary flexibility for the film, ensuring smooth stretching and forming during production while optimizing cutting performance after subsequent paper-plastic lamination, achieving a balance between rigidity and toughness.

[0018] The BOPP matte film with optimized cutting performance based on paper-plastic lamination disclosed in the present invention optimizes the components of the core layer and the matte layer, thereby increasing the brittleness of the core layer and the matte layer, thereby significantly reducing the BOPP matte film's ability to resist fracture. When subjected to external stress, the film does not exhibit excessive deformation capacity and fracture toughness. Furthermore, after cutting and breaking the laminated product obtained by laminating the BOPP matte film with paper, the length of excess matte film (tail film) on the paper is reduced, and a neat incision can even be formed without any tail film, thereby ensuring that the BOPP matte film has excellent lamination and cutting performance.

[0019] Furthermore, the preparation method of the styrene-maleic anhydride copolymer comprises the following steps: adding styrene and maleic anhydride monomers into a toluene solvent, and performing a free radical copolymerization reaction under the action of an azobisisobutyronitrile initiator; the molar content of the styrene monomer in the styrene-maleic anhydride copolymer is 3-4 mol%. When the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3-4 mol%, the obtained styrene-maleic anhydride copolymer is most effective in increasing the Tg of the core homopolypropylene and improving the brittleness of the core layer of the BOPP matte film. If the molar content of styrene monomer in the styrene-maleic anhydride copolymer is less than 3 mol%, the compatibility of the styrene-maleic anhydride copolymer with the homopolypropylene is poor, resulting in agglomeration of the styrene-maleic anhydride copolymer in the homopolypropylene matrix, increasing the risk of stress concentration during stretching and affecting production smoothness. If the molar content of styrene monomer in the styrene-maleic anhydride copolymer is higher than 4 mol%, the polarity of the styrene-maleic anhydride copolymer is reduced, which is not conducive to forming physical crosslinks between the styrene-maleic anhydride copolymer and the homopolypropylene molecular chain, resulting in weakened intermolecular interaction forces in the homopolypropylene, lowering the Tg of the core homopolypropylene matrix, and not conducive to improving the brittleness of the BOPP matte film, shortening the length of the tail film produced after cutting and breaking the laminated product made of the BOPP matte film and paper, and not conducive to forming a neat incision of the BOPP matte film on the paper.

[0020] Furthermore, the preparation method of the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer comprises the following steps: using toluene and anisole as a mixed solvent, adding methyl methacrylate, pentamethyldiethylenetriamine, and stannous octoate into a reaction flask, and reacting under the action of a double-terminal bromine-based polybutyl acrylate macromolecular initiator and a catalyst CuCl2; the content of the polymethyl methacrylate segment in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is 60-80 mol%, and the content of the polybutyl acrylate segment is 20-40 mol%. If the content of polybutyl acrylate chain segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is greater than 40 mol%, it is not conducive to improving the brittleness of the soft phase (random copolymer polypropylene) of the matte layer, and is not conducive to cooperating with the core layer to improve the overall brittleness of the BOPP matte film; if the content of polybutyl acrylate chain segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is less than 20 mol%, too few polybutyl acrylate chain segments increase the risk of appearance quality problems such as cracks in the matte layer during biaxial stretching.

[0021] Furthermore, the maleic anhydride grafted polypropylene has a maleic anhydride grafting rate of 3-5 wt %, and a melt index of 15-20 g / 10 min, measured at 230° C. and 2.16 kg. The above-defined maleic anhydride grafting rate and melt index are beneficial to the compatibility between the homopolypropylene and the styrene-maleic anhydride copolymer and smooth film production. Preferably, the polypropylene in the maleic anhydride grafted polypropylene is homopolypropylene.

[0022] Furthermore, the melt index of the homopolymerized polypropylene measured at 230° C. and 2.16 kg is 3-8 g / 10 min. Homopolymerized polypropylene within the above-defined melt index range is beneficial to thickness uniformity and smooth production during biaxial stretching.

[0023] Furthermore, the melt index of the high-density polyethylene, measured at 190°C and 2.16 kg, is 9-20 g / 10 min; the melt index of the random copolymer polypropylene, measured at 230°C and 2.16 kg, is 6-10 g / 10 min. The random copolymer polypropylene is a random ethylene-propylene copolymer. High-density polyethylene and random copolymer polypropylene within the above-defined melt index ranges facilitate obtaining a matte layer with a uniform matte effect during biaxial stretching.

[0024] Furthermore, the core layer further comprises 1-3 wt % of an antistatic agent, and the antistatic agent is a quaternary ammonium salt-based methacrylate copolymer.

[0025] Furthermore, the lower surface layer also includes 0.1-0.5wt% of an anti-blocking agent, which is one or more of silicon dioxide, talc, and calcium carbonate, and has a particle size of 3-6μm. Adding an appropriate amount of anti-blocking agent to the lower surface layer is beneficial to increasing the smoothness of winding and unwinding the matte film. If the content of the anti-blocking agent is less than 0.1wt%, it will not have an effective anti-blocking effect. If the content of the anti-blocking agent is higher than 0.5wt%, on the one hand, the anti-blocking agent is likely to fall off during the production process, contaminating the guide rollers. On the other hand, it will increase the haze and reduce the gloss, affecting the appearance of the product.

[0026] The present invention also provides a method for preparing any of the above-mentioned BOPP matte films with optimized cutting performance based on paper-plastic lamination, comprising the following steps:

[0027] Batching and plasticizing: The raw material usage ratio is set in the control system of the biaxial stretch film production line. The batching system then automatically delivers the dried raw materials for each layer to the extruder according to the input ratio. After being melted and plasticized in the extruder, the melt enters the die head through the runner and distributor.

[0028] Casting sheet: After being extruded through the die, the melt immediately contacts the cooling roller to form a thick sheet;

[0029] Longitudinal stretching: The thick sheet is heated to the set temperature by multiple sets of preheating rollers, and then begins longitudinal stretching and then shaping;

[0030] Transverse stretching: After preheating the longitudinally stretched thick sheet to the set temperature, transverse stretching begins, and after transverse stretching, shaping and cooling are carried out;

[0031] Traction and Rewinding: The multi-layer film output from the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the rewinding unit to obtain the parent roll;

[0032] Slitting: The aged mother roll is slit to obtain film rolls of specified width and length.

[0033] Furthermore, the melt extrusion temperature of the matte layer is 200-260°C; the melt extrusion temperature of the core layer and the lower surface layer is 230-260°C; in the process of the melt contacting the cooling roller, the temperature of the chilling water and the cooling roller is 15-50°C; the temperature of the longitudinal stretching zone is 90-130°C; the temperature of the transverse stretching zone is 155-165°C; the longitudinal stretching ratio is 4.5-5.5 times; the transverse stretching ratio is 8-10 times; and the corona power factor of the matte layer is 20-25W·min / m.

[0034] In order to better understand and implement the present invention, the present invention is described in detail below. DETAILED DESCRIPTION

[0035] It should be clear that the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the embodiments of the present application.

[0036] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the embodiments of the present application. The singular forms "a," "the," and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0037] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Instead, they are merely examples of devices and methods consistent with certain 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 are not necessarily used to describe a specific order or precedence, 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 the specific circumstances.

[0038] In addition, in this application, unless otherwise specified, "plurality" refers to two or more. "And / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0039] It should be understood that the embodiments of the present application are not limited to the precise structure described above, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0040] As an embodiment of the present invention, this embodiment provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer and a lower surface layer arranged in sequence; the matte layer comprises random copolymer polypropylene, 40-55wt% high-density polyethylene and 5-10wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer; the core layer comprises homopolypropylene, 10-15wt% styrene-maleic anhydride copolymer, and 3-8wt% maleic anhydride grafted polypropylene; the lower surface layer comprises homopolypropylene.

[0041] Furthermore, the preparation method of the styrene-maleic anhydride copolymer comprises the following steps: adding styrene and maleic anhydride monomers into a toluene solvent, and performing a free radical copolymerization reaction under the action of an azobisisobutyronitrile initiator; the molar content of the styrene monomer in the styrene-maleic anhydride copolymer is 3-4 mol%.

[0042] Furthermore, the preparation method of the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer comprises the following steps: adding methyl methacrylate, pentamethyldiethylenetriamine, and stannous octoate to a reaction flask in a mixed solvent of toluene and anisole, and reacting them in the presence of a double-terminated bromo-polybutyl acrylate macroinitiator and a catalyst of CuCl2 to obtain the copolymer; the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer has a polymethyl methacrylate segment content of 60-80 mol%, and a polybutyl acrylate segment content of 20-40 mol%. The double-terminated bromo-polybutyl acrylate macroinitiator of the present invention is obtained by reacting butyl acrylate, α-bromoisobutyric acid diethylene glycol ester, copper bromide, pentamethyldiethylenetriamine, and stannous octoate reducing agent in a mixed solvent of toluene and anisole; and the α-bromoisobutyric acid diethylene glycol ester of the present invention is obtained by reacting ethylene glycol, triethylamine, and α-bromoisobutyryl bromide in a solvent of tetrahydrofuran.

[0043] Furthermore, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 3-5 wt %, and the melt index of the maleic anhydride grafted polypropylene measured at 230° C. and 2.16 kg is 15-20 g / 10 min.

[0044] Furthermore, the melt index of the homopolypropylene is measured to be 3-8 g / 10 min at 230° C. and 2.16 kg.

[0045] Furthermore, the melt index of the high-density polyethylene measured at 190°C and 2.16kg is 9-20g / 10min; the melt index of the random copolymer polypropylene measured at 230°C and 2.16kg is 6-10g / 10min, and the random copolymer polypropylene is a random ethylene-propylene copolymer.

[0046] Furthermore, the core layer further comprises 1-3 wt % of an antistatic agent, and the antistatic agent is a quaternary ammonium salt-based methacrylate copolymer.

[0047] Furthermore, the lower surface layer further comprises 0.1-0.5 wt% of an anti-adhesive agent, which is one or more of silicon dioxide, talc, and calcium carbonate, and has a particle size of 3-6 μm, preferably 4-5 μm to balance the thickness of the surface layer and the problem of shedding.

[0048] Furthermore, the matt layer has a thickness of 1.8-2.2 μm, the lower surface layer has a thickness of 0.8-1.2 μm, and the total thickness of the biaxially oriented polypropylene matt film is 12-15 μm.

[0049] The present invention also provides a method for preparing any of the above-mentioned BOPP matte films with optimized cutting performance based on paper-plastic lamination, comprising the following steps:

[0050] Batching and plasticizing: The raw material usage ratio is set in the control system of the biaxial stretch film production line. The batching system then automatically delivers the dried raw materials for each layer to the extruder according to the input ratio. After being melted and plasticized in the extruder, the melt enters the die head through the runner and distributor.

[0051] Casting sheet: After being extruded through the die, the melt immediately contacts the cooling roller to form a thick sheet;

[0052] Longitudinal stretching: The thick sheet is heated to the set temperature by multiple sets of preheating rollers, and then begins longitudinal stretching and then shaping;

[0053] Transverse stretching: After preheating the longitudinally stretched thick sheet to the set temperature, transverse stretching begins, and after transverse stretching, shaping and cooling are carried out;

[0054] Traction and Rewinding: The multi-layer film output from the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the rewinding unit to obtain the parent roll;

[0055] Slitting: The aged mother roll is slit to obtain film rolls of specified width and length.

[0056] Furthermore, the melt extrusion temperature of the matte layer is 200-260°C; the melt extrusion temperature of the core layer and the lower surface layer is 230-260°C; in the process of the melt contacting the cooling roller, the temperature of the chilling water and the cooling roller is 15-50°C; the temperature of the longitudinal stretching zone is 90-130°C; the temperature of the transverse stretching zone is 155-165°C; the longitudinal stretching ratio is 4.5-5.5 times; the transverse stretching ratio is 8-10 times; and the corona power factor of the matte layer is 20-25W·min / m.

[0057] The physical properties and testing methods of the embodiments and comparative examples of the present invention are as follows:

[0058] The melt index (melt mass flow rate MFR) is determined according to GB / T3682-2018.

[0059] Lamination and cutting performance: After the matte film is glued and laminated with the paper, the length of the excess matte film on the paper after the film is cut can be judged by visual inspection (good effect: the length of the excess matte film on the paper is 0-1mm; poor effect: the length of the excess matte film on the paper is greater than 1mm).

[0060] Tensile strength: tested according to GB / T1040.3-2006.

[0061] The antistatic agent in the examples and comparative examples of the present invention is a quaternary ammonium salt-based methacrylate copolymer.

[0062] The anti-blocking agent in the examples and comparative examples of the present invention is silicon dioxide with a particle size of 4.5 μm.

[0063] It should be noted that the proportions described in the examples or comparative examples of the present invention are all weight percentages. The components and contents of each layer in the examples and comparative examples of the present invention are shown in Table 1 below.

[0064] Table 1

[0065]

[0066] Example 1

[0067] This embodiment provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this embodiment comprises the following steps:

[0068] Preparation of matt layer resin: 40 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 50 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 10 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 40 mol%, 20 mol% and 40 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0069] Preparation of core layer resin: 86 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 10 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 3 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 3 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain a core layer resin.

[0070] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0071] The method for preparing the BOPP matte film with optimized cutting performance based on paper-plastic lamination of this embodiment comprises the following steps:

[0072] Batching and plasticizing: The raw material usage ratio is set in the control system of the biaxial stretch film production line. The batching system then automatically delivers the dried raw materials for each layer to the extruders of each layer according to the input ratio. After being melted and plasticized in the extruder, the melt of each layer enters the die head through the runner and distributor.

[0073] Casting sheet: After being extruded through the die, the melt immediately contacts the cooling roller to form a thick sheet;

[0074] Longitudinal stretching: The thick sheet is heated to the set temperature by multiple sets of preheating rollers, and then begins longitudinal stretching and then shaping;

[0075] Transverse stretching: After preheating the longitudinally stretched thick sheet to the set temperature, transverse stretching begins, and after transverse stretching, shaping and cooling are carried out;

[0076] Traction and Rewinding: The multi-layer film output from the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the rewinding unit to obtain the parent roll;

[0077] Slitting: The aged mother roll is slit to obtain film rolls of specified width and length with optimized cutting performance of BOPP matte film based on paper-plastic lamination.

[0078] The melt extrusion temperature of the matte layer is 235°C; the melt extrusion temperature of the core layer is 250°C; the melt extrusion temperature of the lower surface layer is 250°C; the temperature of the chilling water and the chilling roller when the melt contacts the cooling roller is 40°C; the temperature of the longitudinal stretching is 125°C; the temperature of the transverse stretching is 160°C; the longitudinal stretching ratio is 5.3 times; the transverse stretching ratio is 8.5 times; the corona power factor of the matte layer is 23.5W·min / m.

[0079] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0080] Example 2

[0081] This embodiment provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this embodiment comprises the following steps:

[0082] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 35 mol%, 30 mol% and 35 mol%, respectively) are mixed uniformly to obtain a matt layer resin. Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 17 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 4 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0083] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0084] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this embodiment is the same as that in Example 1, so it is not described in detail.

[0085] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0086] Example 3

[0087] This embodiment provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this embodiment comprises the following steps:

[0088] Preparation of matt layer resin: 55 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 40 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 5 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin. Preparation of core layer resin: Take 76wt% homopolypropylene (melt index measured at 230℃ and 2.16kg is 3g / 10min), 15wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in styrene-maleic anhydride copolymer is 4mol%), 8wt% maleic anhydride grafted polypropylene (melt index measured at 190℃ and 2.16kg is 20g / 10min, and the grafting rate of maleic anhydride grafted polypropylene in maleic anhydride grafted polypropylene is 5wt%) and 1wt% antistatic agent (quaternary ammonium methacrylate copolymer) and mix them evenly to obtain core layer resin.

[0089] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0090] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this embodiment is the same as that in Example 1, so it is not described in detail.

[0091] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0092] Comparative Example 1

[0093] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0094] Preparation of matt layer resin: 55 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min) and 45 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) are mixed uniformly to obtain matt layer resin.

[0095] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0096] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0097] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0098] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0099] Comparative Example 2

[0100] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0101] Preparation of matt layer resin: 55 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 43 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 2 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0102] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0103] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0104] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0105] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0106] Comparative Example 3

[0107] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0108] Preparation of matt layer resin: 45 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 40 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 15 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0109] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0110] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0111] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0112] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0113] Comparative Example 4

[0114] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0115] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 20 mol%, 60 mol% and 20 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0116] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0117] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0118] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0119] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0120] Comparative Example 5

[0121] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0122] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 45 mol%, 10 mol% and 45 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0123] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0124] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0125] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0126] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0127] Comparative Example 6

[0128] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0129] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0130] Preparation of core layer resin: 94 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain a core layer resin.

[0131] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0132] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0133] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0134] Comparative Example 7

[0135] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0136] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0137] Preparation of core layer resin: 89 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 5 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0138] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0139] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0140] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0141] Comparative Example 8

[0142] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0143] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0144] Preparation of core layer resin: Take 74wt% homopolypropylene (melt index measured at 230℃ and 2.16kg is 3g / 10min), 20wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in styrene-maleic anhydride copolymer is 3mol%), 5wt% maleic anhydride grafted polypropylene (melt index measured at 190℃ and 2.16kg is 20g / 10min, and the grafting rate of maleic anhydride grafted polypropylene in maleic anhydride grafted polypropylene is 5wt%) and 1wt% antistatic agent (quaternary ammonium methacrylate copolymer) and mix them evenly to obtain core layer resin.

[0145] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0146] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0147] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0148] Comparative Example 9

[0149] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0150] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0151] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 6 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain the core layer resin.

[0152] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0153] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0154] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0155] Comparative Example 10

[0156] This comparative example provides a BOPP matte film with optimized cutting performance based on paper-plastic lamination, comprising a matte layer, a core layer, and a lower surface layer arranged in sequence. The method for preparing the resin layers of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example comprises the following steps:

[0157] Preparation of matt layer resin: 50 wt% high-density polyethylene (melt index measured at 190°C and 2.16 kg is 15 g / 10 min), 42 wt% random copolymer polypropylene (melt index measured at 230°C and 2.16 kg is 8 g / 10 min) and 8 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer (the molar contents of the three segments in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer are 30 mol%, 40 mol% and 30 mol%, respectively) are mixed uniformly to obtain a matt layer resin.

[0158] Preparation of core layer resin: 82 wt% homopolypropylene (melt index measured at 230°C and 2.16 kg is 3 g / 10 min), 12 wt% styrene-maleic anhydride copolymer (the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 1 mol%), 5 wt% maleic anhydride grafted polypropylene (melt index measured at 190°C and 2.16 kg is 20 g / 10 min, and the grafting rate of maleic anhydride grafted polypropylene in the maleic anhydride grafted polypropylene is 5 wt%) and 1 wt% antistatic agent (quaternary ammonium methacrylate copolymer) are mixed uniformly to obtain a core layer resin.

[0159] Preparation of the lower surface layer resin: 99.7 wt% homopolypropylene (isotacticity of 96%, melt index of 3 g / 10 min measured at 230°C and 2.16 kg) and 0.3 wt% anti-blocking agent (silicon dioxide, particle size of 4.5 μm) were mixed uniformly to obtain the lower surface layer resin.

[0160] The preparation method of the BOPP matte film with optimized cutting performance based on paper-plastic lamination in this comparative example is the same as that in Example 1, so it will not be described in detail.

[0161] The total thickness of the matte film is 12µm, of which the matte layer is 1.8µm thick and the lower surface layer is 1µm thick.

[0162] The performance test results of the BOPP matte films with optimized cutting performance based on paper-plastic lamination and the lamination cutting performance test results of Examples 1 to 3 and Comparative Examples 1 to 10 are shown in Table 2 below.

[0163] Table 2

[0164]

[0165] It can be seen from the above performance test data that Examples 1-3 of the present invention improve the laminating and cutting performance, so that the BOPP matte film does not exhibit excessive deformation accommodation capacity and fracture toughness when subjected to external stress, that is, its ability to resist fracture is significantly reduced, so that the length of the excess matte film on the paper after the BOPP matte film is cut after the glue is applied and laminated with the paper meets the application requirements of downstream customers and meets the high-speed automated production of BOPP matte film.

[0166] Comparative Example 1: BOPP matte film with improved lamination and cutting performance, in which polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is not added to the matte layer, has strong deformation tolerance and fracture toughness, resulting in low tensile strength and a longer tail film.

[0167] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 2, the content of the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer added to the matte layer is too low, which is not conducive to improving the brittleness of the soft phase of the matte layer and is not conducive to cooperating with the core layer to improve the overall brittleness of the BOPP matte film substrate. As a result, the tensile strength is low and the tail film is long;

[0168] In the comparative example 3, the BOPP matte film with improved lamination and cutting performance had an excessively high content of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer added to the matte layer, which resulted in film breakage during the stretching process, affecting production smoothness.

[0169] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 4, the content of the polybutyl acrylate segment in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer added to the matte layer is too high, which is not conducive to improving the soft phase brittleness of the matte layer and is not conducive to cooperating with the core layer to improve the overall brittleness of the BOPP matte film substrate, resulting in a decrease in tensile strength and an elongation of the tail film;

[0170] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 5, the content of the polybutyl acrylate segment in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer added to the matte layer was too low. During the biaxial stretching process of the BOPP matte film, cracks appeared in the matte layer, which was a problem in appearance quality.

[0171] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 6, no styrene-maleic anhydride copolymer is added to the core layer, and the movement space and degree of freedom of the homopolypropylene molecular chains in the core layer are not restricted. The Tg of the core layer of the BOPP matte film is not increased, and the BOPP matte film substrate is still in a glassy state at room temperature. The overall brittleness of the BOPP matte film substrate is low, resulting in low tensile strength and a long tail film.

[0172] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 7, the content of styrene-maleic anhydride copolymer added to the core layer is too low. The styrene-maleic anhydride copolymer is insufficient in enhancing the interaction between polypropylene molecules and restricting the movement of polypropylene molecular segments in the polypropylene matrix, which is not conducive to improving the Tg of the BOPP matte film substrate and has a poor effect on improving the brittleness of the BOPP matte film substrate. As a result, the tensile strength is low and the tail film is long.

[0173] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 8, the content of styrene-maleic anhydride copolymer added to the core layer was too high, and the content of cyclic rigid groups in the styrene-maleic anhydride copolymer was too high, resulting in film breakage during the stretching process;

[0174] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 9, the molar content of styrene monomer in the styrene-maleic anhydride copolymer in the core layer is too high, resulting in reduced polarity of the styrene-maleic anhydride copolymer, which is not conducive to forming physical crosslinks with homopolypropylene molecular chains and enhancing the interaction between polypropylene molecules. Furthermore, the Tg of the styrene-maleic anhydride copolymer is reduced, which is not conducive to improving the overall brittleness of the BOPP matte film substrate and improving the ability of the BOPP matte film to form a neat cut when cut by a disc knife in paper-plastic lamination applications. As a result, the tensile strength is low and the tail film is long.

[0175] In the BOPP matte film with improved lamination and cutting performance of Comparative Example 10, the molar content of styrene monomer in the styrene-maleic anhydride copolymer in the core layer is too low, and the effect of improving the compatibility of the styrene-maleic anhydride copolymer with homopolypropylene is poor, resulting in agglomeration of the styrene-maleic anhydride copolymer in the homopolypropylene matrix. In addition, due to the influence of the rigid benzene ring group, the film breaks during the stretching process, affecting the smoothness of production.

[0176] The above-described embodiments merely represent several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, and the present invention is intended to encompass such modifications and variations.

Claims

1. A BOPP matte film with optimized cutting performance based on paper-plastic lamination, characterized in that: The invention comprises a matte layer, a core layer and a lower surface layer which are arranged in sequence; the matte layer comprises random copolymerized polypropylene, 40-55 wt% high-density polyethylene and 5-10 wt% polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer, wherein the polymethyl methacrylate segment content in the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer is 60-80 mol% and the polybutyl acrylate segment content is 20-40 mol%; the core layer comprises homopolypropylene, 10-15 wt% styrene-maleic anhydride copolymer and 3-8 wt% maleic anhydride grafted polypropylene, wherein the molar content of styrene monomer in the styrene-maleic anhydride copolymer is 3-4 mol%; and the lower surface layer comprises homopolypropylene.

2. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The preparation method of the styrene-maleic anhydride copolymer comprises the following steps: adding styrene and maleic anhydride monomers into a toluene solvent, and performing free radical copolymerization reaction under the action of an azobisisobutyronitrile initiator to obtain the copolymer.

3. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The preparation method of the polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate triblock copolymer comprises the following steps: using toluene and anisole as a mixed solvent, adding methyl methacrylate, pentamethyldiethylenetriamine, and stannous octoate into a reaction flask, and reacting under the action of a double-terminal bromine-based polybutyl acrylate macromolecular initiator and a catalyst CuCl2 to obtain the copolymer.

4. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 3-5 wt %. The melt index of the maleic anhydride grafted polypropylene measured at 230° C. and 2.16 kg is 15-20 g / 10 min.

5. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The melt index of the homopolypropylene measured at 230° C. and 2.16 kg is 3-8 g / 10 min.

6. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The melt index of the high-density polyethylene measured at 190° C. and 2.16 kg is 9-20 g / 10 min; the melt index of the random copolymer polypropylene measured at 230° C. and 2.16 kg is 6-10 g / 10 min. The random copolymer polypropylene is a random ethylene-propylene copolymer.

7. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The core layer further comprises 1-3 wt % of an antistatic agent, which is a quaternary ammonium salt-based methacrylate copolymer.

8. The BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 1, characterized in that: The lower surface layer further comprises 0.1-0.5 wt% of an anti-adhesive agent, wherein the anti-adhesive agent is one or more of silicon dioxide, talc, and calcium carbonate, and the particle size of the anti-adhesive agent is 3-6 μm.

9. A method for preparing a BOPP matte film with optimized cutting performance based on paper-plastic lamination according to any one of claims 1 to 8, characterized in that: The following steps are involved: Batching and plasticizing: The raw material usage ratio is set in the control system of the biaxial stretch film production line. The batching system then automatically delivers the dried raw materials for each layer to the extruder according to the input ratio. After being melted and plasticized in the extruder, the melt enters the die head through the runner and distributor. Casting sheet: After being extruded through the die, the melt immediately contacts the cooling roller to form a thick sheet; Longitudinal stretching: The thick sheet is heated to the set temperature by multiple sets of preheating rollers, and then begins longitudinal stretching and then shaping; Transverse stretching: After preheating the longitudinally stretched thick sheet to the set temperature, transverse stretching begins, and after transverse stretching, shaping and cooling are carried out; Traction and Rewinding: The multi-layer film output from the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the rewinding unit to obtain the parent roll; Slitting: The aged mother roll is slit to obtain film rolls of specified width and length.

10. The method for preparing a BOPP matte film with optimized cutting performance based on paper-plastic lamination according to claim 9, characterized in that: The melt extrusion temperature of the matte layer is 200-260°C; the melt extrusion temperature of the core layer and the lower surface layer is 230-260°C; during the process of the melt contacting the cooling roller, the temperature of the chill water and the cooling roller is 15-50°C; the temperature of the longitudinal stretching zone is 90-130°C; the temperature of the transverse stretching zone is 155-165°C; the longitudinal stretching ratio is 4.5-5.5 times; the transverse stretching ratio is 8-10 times; the corona power factor of the matte layer is 20-25W·min / m.

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