Wear-resistant biaxially oriented polypropylene matt film and preparation method thereof

Abstract

The invention relates to the field of matt films, in particular to a wear-resistant biaxially oriented polypropylene matt film and a preparation method thereof. The wear-resistant biaxially oriented polypropylene matt film comprises an upper surface matt layer, a middle core layer and a lower surface layer which are sequentially arranged, the upper surface matting layer comprises 45-55 wt% of high-density polyethylene, 42-47 wt% of polypropylene random copolymer and 3-8 wt% of ethylene propylene diene monomer / high-density polyethylene elastomer; the polypropylene random copolymer in the upper surface matting layer is composed of an ethylene-propylene random copolymer chain segment with the leaching temperature T1 belonging to [25, 60] DEG C, an ethylene-propylene block copolymer chain segment with the leaching temperature T2 belonging to [60, 95] DEG C and a homo-polypropylene chain segment with the leaching temperature T3 belonging to [95, 140] DEG C; the content of the ethylene-propylene block copolymer chain segment in the polypropylene random copolymer at the leaching temperature T2 of [60, 95] DEG C is 60-80wt%. By optimizing the material components of the matt layer, the scratch resistance of the matt layer is improved, the problem of powder grinding is reduced, and subsequent processing and production of the BOPP matt film are met.

Description

Technical Field

[0001] The invention relates to the field of matte films, in particular to a wear-resistant biaxially oriented polypropylene matte film and a preparation method thereof. Background Art

[0002] BOPP matte film is usually a BOPP film with matte on one side and glossy on the other side or matte on both sides. It mainly achieves the matte effect by scattering light, which can improve the grade of printed outer packaging. Since the matte film can give people a soft, fashionable and elegant high-end feeling and eliminate eye fatigue, BOPP matte film is increasingly used in the packaging field, especially suitable for deep processing industries and fields such as coating and lamination.

[0003] The matte layer of BOPP matte film currently sold on the market is mainly a combination of high-density polyethylene and random copolymer polypropylene. In the matte masterbatch system, the copolymer polypropylene is the soft phase and the high-density polyethylene is the hard phase. According to the principle of soft-encapsulating-hard, the high-density polyethylene (hard phase) is mostly coated by the copolymer polypropylene (soft phase). The matte principle of matte film is that during the stretching process of the matte masterbatch, because the randomness of copolymer polypropylene is relatively high, the crystallization speed is slow, and the crystallization temperature is relatively low, the copolymer polypropylene will exist as a sea phase; however, due to the high viscosity, high crystallization rate and high crystallinity of high-density polyethylene, high-density polyethylene exists as an island phase; during the film stretching process, when the copolymer polypropylene is still in a relatively soft phase state, the high-density polyethylene has completed part or most of the crystallization, and the crystallized high-density polyethylene becomes a hard phase. Under the action of external stretching force, the high-density polyethylene phase of the matte layer will protrude compared to the soft phase of the copolymer polypropylene during the stretching process, and act as an island phase in the microscopic "island" morphology of the matte film. The sea phase of polypropylene will be coated on the high-density polyethylene, and after biaxial stretching of the film, it will present an "island" structure at the microscopic level, forming a matte surface layer with rough and uneven island morphology, thereby achieving a matte effect. However, the matte film products of the above-mentioned film-making process are often rubbed and left with marks on the matte surface during the secondary slitting and laminating process when in contact with the guide roller, and a thin layer of powder appears on the surface of the guide roller, which seriously affects the packaging effect of the BOPP matte film and the production efficiency of downstream applications. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a wear-resistant biaxially oriented polypropylene matte film and a preparation method thereof, by optimizing the material composition of the matte layer, improving the scratch resistance of the matte layer, reducing the problem of abrasion, meeting the subsequent processing performance requirements, and being able to adapt to high-speed automated production.

[0005] A wear-resistant biaxially stretched polypropylene matte film comprises an upper surface matte layer, an intermediate core layer and a lower surface layer which are arranged in sequence; the upper surface matte layer comprises 45-55wt% of high-density polyethylene, 42-47wt% of random copolymer polypropylene and 3-8wt% of ethylene propylene diene monomer rubber / high-density polyethylene elastomer; the intermediate core layer comprises homopolymer polypropylene; the lower surface layer comprises homopolymer polypropylene; the random copolymer polypropylene in the upper surface matte layer comprises an ethylene-propylene random copolymer segment with an elution temperature T1∈[25,60)°C, an ethylene-propylene block copolymer segment with an elution temperature T2∈[60,95)°C and a homopolymer polypropylene segment with an elution temperature T3∈[95,140]°C; the content of the ethylene-propylene block copolymer segment with an elution temperature T2∈[60,95)°C in the random copolymer polypropylene is 60-80wt%.

[0006] The inventors have found that during the production of BOPP matte film, the powder on the surface of the guide roller is high-density polyethylene, and the main reason for the grinding and scratch resistance of the matte surface of BOPP matte film is that the soft phase wrapped on the hard phase surface is too soft; since copolymer polypropylene is relatively soft, the scratching of BOPP matte film occurs more on the copolymer polypropylene sea phase wrapped in the island phase, so when copolymer polypropylene is used as the surface material of the film, the film surface will be relatively soft, the yield strength and tensile properties of the film surface are poor, and it will easily leave marks when it is squeezed or scratched by displacement, and in severe cases, the original microscopic morphology of the film surface will be destroyed, so the overall scratch resistance is poor. In addition, due to the difference in the order of the stretching area during the stretching process, some parts of the random copolymer polypropylene soft phase wrapped on the surface of the high-density polyethylene hard phase are thicker, while some parts are thinner. When the thin part is subjected to external force, such as being destroyed in the process of contacting the guide roller during the secondary slitting and laminating process, the high-density polyethylene hard phase is in direct contact with foreign objects such as the guide roller, resulting in grinding.

[0007] The EPDM rubber / high-density polyethylene elastomer added to the upper surface matte layer of the wear-resistant biaxially stretched polypropylene matte film of the present invention can accelerate the crystallization speed and increase the crystallization temperature of the random copolymer polypropylene and increase the crystallization temperature in a blended system of random copolymer polypropylene and high-density polyethylene, form more crystal nuclei in a short time, and increase the crystallinity; and can improve the crystallization morphology of the random copolymer polypropylene to form a finer spherulite structure, and the fine spherulite structure can increase the hardness of the random copolymer polypropylene wrapped on the surface of the high-density polypropylene hard phase. Preferably, the content of the EPDM rubber / high-density polyethylene elastomer is 3-8wt%, and the stiffness of the obtained polypropylene matte film is optimal. When the content of EPDM / HDPE elastomer is lower than 3%, the hardness of the soft phase random copolymer polypropylene in the matte layer is insufficient, which is not conducive to forming a core-shell structure and it is difficult to obtain a matte layer with good scratch resistance and low abrasion; when the content of EPDM / HDPE elastomer is higher than 8%, excessive elastomer will cause the mechanical properties of the film to decrease. Adding an appropriate amount of anti-blocking agent to the lower surface layer is conducive to increasing the smoothness of the matte film to be rolled up and unwound; if the content of the anti-blocking agent in the lower surface layer is lower than 1wt%, it will not play an effective anti-blocking role; if the content of the anti-blocking agent is higher than 5wt%, the anti-blocking agent is prone to fall off during the production process, resulting in contamination of the guide roller, while increasing the haze and reducing the glossiness, affecting the appearance of the product.

[0008] In addition, random copolymer polypropylene is a binary copolymer obtained by copolymerizing ethylene as a monomer with propylene. The introduction of ethylene reduces the orderliness of the molecular chain structure; random copolymer polypropylene, as a semi-crystalline polymer, has a certain distribution of chain crystal structures in the molecule. The temperature rise elution classification method is to classify polyolefins according to the degree of crystallinity based on the different effects of chain structure parameters on the crystallization process and degree of crystallinity of polyolefin molecules. The medium crystallinity ethylene-propylene block copolymer chain segment (elution temperature T2∈[60,95)℃) in the matte layer of the wear-resistant biaxially oriented polypropylene matte film of the present invention has a high crystallization temperature, which is more conducive to improving the hardness of the soft phase in the matte layer and obtaining better scratch resistance. In addition, the random copolymer polypropylene has a suitable degree of crystallinity and a slower crystallization speed, which is conducive to the phase separation between high-density polyethylene and random copolymer polypropylene, and ensures the uniformity of matte. By controlling the content of the ethylene-propylene block copolymer segment with medium crystallinity (elution temperature T2∈[60,95)℃), the crystal morphology thereof is improved, and the hardness of the soft phase copolymer polypropylene wrapping the hard phase is increased, so that when the upper surface matte layer is subjected to external force, such as contacting the guide roller during the secondary slitting and laminating process, the soft phase with higher hardness can effectively protect the hard phase from being rubbed off by external objects such as the guide roller, thereby avoiding the occurrence of abrasion. When the content of the ethylene-propylene block copolymer segment with medium crystallinity (elution temperature T2∈[60,95)℃) is less than 60wt%, it is not conducive to improving the hardness of the soft phase in the matte layer, resulting in poor scratch resistance of the matte surface. When the content of the ethylene-propylene block copolymer segment with medium crystallinity (elution temperature T2∈[60,95)℃) is greater than 80wt%, the crystallization temperature of the random copolymer polypropylene is too high, which will lead to an accelerated crystallization rate, and the phase separation effect of the high-density polyethylene and the random copolymer polypropylene will become poor, thereby affecting the matte effect. Controlling the content of the medium crystallinity ethylene-propylene block copolymer segment (elution temperature T2∈[60,95)℃) within the above range is beneficial to improving the hardness of the soft phase in the matte layer, so as to obtain a matte layer with uniform matte effect and good scratch resistance. When the matte layer contacts the guide roller during the secondary slitting and lamination processes, the higher hardness of the soft phase can effectively protect the hard phase (high-density polyethylene) from being rubbed off by foreign objects such as the guide roller, thereby avoiding the occurrence of grinding.

[0009] Furthermore, the upper surface matte layer includes a core-shell structure with the high-density polyethylene as the core and the EPDM rubber / high-density polyethylene elastomer as the shell. In the blending system of random copolymer polypropylene and high-density polyethylene in the upper surface matte layer, the ethylene and propylene groups in the EPDM rubber part in the EPDM rubber / high-density polyethylene elastomer molecular chain are well compatible with the random copolymer polypropylene, and the high-density polyethylene part in the EPDM rubber / high-density polyethylene elastomer molecular chain is compatible with the high-density polyethylene in the matte masterbatch, forming a good physical bridging effect between the random copolymer polypropylene and the high-density polyethylene, reducing interface defects and making the combination of the two closer, and the core-shell structure formed by the EPDM rubber / high-density polyethylene elastomer improves the compatibility of the random copolymer polypropylene and the high-density polyethylene, making the high-density polyethylene more firmly combined with the surrounding random copolymer polypropylene, and even in the secondary slitting and laminating process, it is not easy to be ground even when it contacts with the guide roller. In addition, when the wear-resistant biaxially oriented polypropylene matte film contacts the guide roller during the secondary slitting and laminating process, since the surface of the core-shell structured high-density polyethylene is wrapped with a layer of EPDM rubber / high-density polyethylene elastomer, the EPDM rubber / high-density polyethylene elastomer can effectively absorb and disperse part of the friction energy, thereby avoiding direct contact of the hard phase high-density polyethylene of the matte layer with foreign objects after the thinner soft phase random copolymer polypropylene wrapping some parts of the hard phase surface of the high-density polyethylene is destroyed, thereby improving the scratch and abrasion problems caused by the destruction of the random copolymer polypropylene.

[0010] Furthermore, in the random copolymer polypropylene, the content of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25, 60)°C is 10~35wt%, and the content of the homopolymer polypropylene segment at the elution temperature T3∈[95, 140]°C is 5~10wt%.

[0011] Furthermore, the crystallinity of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25,60)℃ is 10~15%, the crystallinity of the ethylene-propylene block copolymer segment at the elution temperature T2∈[60,95)℃ is 25~35%, and the crystallinity of the homopolypropylene segment at the elution temperature T3∈[95,140]℃ is 40~60%. The wear-resistant biaxially stretched polypropylene matte film obtained by controlling the crystallinity of the ethylene-propylene block copolymer segment within the above range has good matte effect, and can improve the problem of grinding of the guide roller surface and the scratch problem of the matte surface during the secondary slitting and laminating process contacting the guide roller; controlling the ethylene-propylene random copolymer segment with non-crystallization or low crystallinity and the homopolypropylene segment with high crystallinity within the above range is conducive to ensuring the matte effect of the matte layer and improving the hardness of the random copolymer polypropylene. If the crystallinity of the medium-crystallinity ethylene-propylene block copolymer segment (elution temperature T2∈[60,95)℃) is less than 25%, it is not conducive to the improvement of the hardness of the soft phase random copolymer polypropylene in the matte layer, and the scratch resistance cannot be effectively improved; if the crystallinity is greater than 25%, it is not conducive to the phase separation between high-density polyethylene and random copolymer polypropylene, affecting the matte effect of the matte layer.

[0012] Furthermore, the random copolymer polypropylene in the upper surface matte layer has a crystallinity of 25-35%. When the overall crystallinity of the random copolymer polypropylene is lower than 25%, the hardness of the soft phase of the random copolymer polypropylene in the matte layer is insufficient, which is not conducive to enhancing the scratch resistance of the matte layer; when the overall crystallinity of the random copolymer polypropylene is higher than 35%, the high crystallinity affects the compatibility between the random copolymer polypropylene and the high-density polyethylene, which is not conducive to the matte effect; when the crystallinity of the random copolymer polypropylene is 25-35%, the stiffness of the polypropylene matte film obtained is optimal.

[0013] Furthermore, the weight ratio of EPDM to HDPE in the EPDM / HDPE elastomer is (50-60): (40-50). The ethylene and propylene segments in the EPDM have similar compatibility with HDPE and random copolymer polypropylene, reducing the interfacial tension between the two phases and ensuring the mechanical properties of the matte layer. Furthermore, the main chain of the EPDM is a saturated structure, and the side chain non-conjugated diene contains a small amount of double bonds. During the processing, it is partially grafted with the HDPE and random copolymer polypropylene blend system through free radical reaction, further enhancing the interface bonding. When the proportion of EPDM is less than 50wt% and the proportion of HDPE is higher than 50wt%, the high content of HDPE will cause the appearance quality problem of cracks in the matte layer during the stretching process; when the proportion of EPDM is higher than 60wt% and the proportion of HDPE is lower than 40wt%, the high content of EPDM will cause the strength of the HDPE and random copolymer polypropylene blend system to decrease, affecting the mechanical properties of the film.

[0014] Furthermore, the EPDM rubber / high-density polyethylene elastomer is prepared by mixing EPDM rubber and high-density polyethylene using an internal mixer under the action of a crosslinking agent, 1,4-bis(tert-butylperoxyisopropyl)benzene, and a co-crosslinking agent, triallyl isocyanuric acid.

[0015] Furthermore, at 190°C and a load of 2.16kg, the melt index of the EPDM rubber / high-density polyethylene elastomer is 8 to 13g / 10min; the melt index of the high-density polyethylene in the upper surface matte layer is 9 to 20g / 10min at 190°C and a load of 2.16kg; the melt index of the random copolymer polypropylene in the upper surface matte layer is 6 to 10g / 10min at 230°C and a load of 2.16kg; the random copolymer polypropylene in the upper surface matte layer is a random ethylene-propylene copolymer. When the melt index of EPDM rubber / high-density polyethylene elastomer is lower than 8 g / 10min, it is not conducive to forming a more uniform hard phase at the interface, nor is it conducive to increasing the compatibility between the two and reducing interface defects, resulting in the matte layer being scratch-resistant and abrasion-reducing when it contacts the guide roller during the secondary slitting and laminating process; when the melt index of EPDM rubber / high-density polyethylene elastomer is higher than 13 g / 10min, the excessively high melt fluidity is not conducive to its combination at the interface of the matte components high-density polyethylene and random copolymer polypropylene, and it is impossible to form a stable core-shell structure, which affects the scratch resistance and abrasion reduction effect of the matte layer.

[0016] A method for preparing the wear-resistant biaxially oriented polypropylene matte film comprises the following steps: Step 1: Batching and plasticization: The raw material usage ratio is set in the control system of the biaxial stretch film production line, and then the batching system automatically delivers the dried raw materials 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; Step 2: Slab casting: After being extruded through the die head, the melt immediately contacts the chilled roller to form a thick sheet; Step 3: longitudinal stretching: the thick sheet is heated to a set temperature by multiple sets of preheating rollers, and then longitudinal stretching is started and then shaped; the longitudinal stretching ratio is 2 to 6 times; Step 4: Transverse stretching: preheating the longitudinally stretched thick sheet to a set temperature, starting transverse stretching, and then performing shaping and cooling treatment to obtain a multilayer structure film; the transverse stretching ratio is 8 to 10 times; Step 5: traction and reeling: the multi-layer film exiting the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the reeling unit to obtain a parent roll; Step 6: Slitting: Slitting the mother roll after aging treatment to obtain film rolls of specified width and length.

[0017] Furthermore, the melt extrusion temperature of the upper surface matte layer is 200~260°C; the melt extrusion temperature of the intermediate core layer and the lower surface layer is 230~260°C; in the process of the melt contacting the chilled roller, the temperature of the chilled water and the chilled 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 corona power factor of the upper surface matte layer is 20~25W·min / m.

[0018] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the wear-resistant biaxially oriented polypropylene matte film described in Examples 1 to 3 of the present invention and the BOPP matte film described in Comparative Examples 1 to 7. DETAILED DESCRIPTION

[0020] 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. It should be clear in the present application that the embodiments described are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in 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.

[0021] 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 of "a", "said" 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 other meanings. 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.

[0022] Random copolymer polypropylene is a semi-crystalline polymer with a certain distribution of chain crystal structures in its molecules. The temperature-rising elution classification method is to classify polyolefins according to their degree of crystallinity based on the different effects of chain structure parameters on the crystallization process and degree of crystallinity of polyolefin molecules. The random copolymer polypropylene solution is slowly cooled down to gradually crystallize on an inert carrier according to the degree of crystallinity. The component that is most easily crystallized will be deposited first to form an inner layer, while the component that is least likely to crystallize will be deposited on the outer layer last. The temperature is then raised. At a lower temperature, the component with lower crystallinity will dissolve first. As the temperature is gradually increased, the random copolymer polypropylene will be gradually dissolved and eluted in the order of crystallinity from low to high, and finally a temperature-rising elution classification curve of the random copolymer polypropylene is obtained. The random copolymerized polypropylene in the upper surface matte layer of the wear-resistant biaxially stretched polypropylene matte film of the present invention has 8 elution peaks in 8 levels (25, 60, 80, 90, 95, 108, 115, 140) within the range of 25°C to 140°C. Meanwhile, the relative contents of the random copolymerized polypropylene fractions in the different temperature ranges can be obtained by integrating the elution curves in different temperature ranges. The components in the elution temperature T1∈[25, 60)°C are non-crystalline or relatively low-crystalline ethylene-propylene random copolymer segments, the components in the elution temperature range T2∈[60, 95)°C are medium-crystalline ethylene-propylene block copolymer segments, and the components in the elution temperature T3∈[95, 140]°C are relatively high-crystalline homopolymerized polypropylene segments.

[0023] A wear-resistant biaxially oriented polypropylene matte film comprises an upper surface matte layer 1, an intermediate core layer 2 and a lower surface layer 3 which are arranged in sequence; the upper surface matte layer 1 comprises 45-55wt% of high-density polyethylene, 42-47wt% of random copolymer polypropylene and 3-8wt% of ethylene propylene diene monomer rubber / high-density polyethylene elastomer; the intermediate core layer 2 comprises 97-99wt% of homopolymer polypropylene; the lower surface layer 3 comprises 95-99wt% of homopolymer polypropylene; the random copolymer polypropylene in the upper surface matte layer comprises an ethylene-propylene random copolymer segment with an elution temperature T1∈[25,60)°C, an ethylene-propylene block copolymer segment with an elution temperature T2∈[60,95)°C and a homopolymer polypropylene segment with an elution temperature T3∈[95,140]°C; the content of the ethylene-propylene block copolymer segment with an elution temperature T3∈[95,140]°C in the random copolymer polypropylene is 60-80wt%.

[0024] Furthermore, the upper surface matte layer comprises a core-shell structure with the high-density polyethylene as a core and the EPDM rubber / high-density polyethylene elastomer as a shell.

[0025] Furthermore, in the random copolymer polypropylene, the content of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25, 60)°C is 10~35wt%, and the content of the homopolymer polypropylene segment at the elution temperature T3∈[95, 140]°C is 5~10wt%.

[0026] Furthermore, the crystallinity of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25,60)°C is 10~15%, the crystallinity of the ethylene-propylene block copolymer segment at the elution temperature T2∈[60,95]°C is 25~35%, and the crystallinity of the homopolypropylene segment at the elution temperature T3∈[95,140]°C is 40~60%.

[0027] Furthermore, the random copolymer polypropylene in the upper surface matte layer has a crystallinity of 25-35%.

[0028] Furthermore, the weight ratio of EPDM to HDPE in the EPDM / HDPE elastomer is (50-60):(40-50). The EPDM is a copolymer of ethylene, propylene and a small amount of non-conjugated diene, and the EPDM is a highly saturated polymer with a fully saturated main chain.

[0029] Furthermore, the EPDM rubber / high-density polyethylene elastomer is prepared by mixing EPDM rubber and high-density polyethylene using an internal mixer under the action of a crosslinking agent, 1,4-bis(tert-butylperoxyisopropyl)benzene, and a co-crosslinking agent, triallyl isocyanuric acid.

[0030] Furthermore, at 190°C and a load of 2.16kg, the melt index of the EPDM rubber / high-density polyethylene elastomer is 8 to 13g / 10min; the melt index of the high-density polyethylene in the upper surface matte layer is 9 to 20g / 10min at 190°C and a load of 2.16kg; the melt index of the random copolymer polypropylene in the upper surface matte layer is 6 to 10g / 10min at 230°C and a load of 2.16kg; the random copolymer polypropylene in the upper surface matte layer is a random ethylene-propylene copolymer.

[0031] Furthermore, the homopolypropylene of the middle core layer and / or the lower surface layer has a melt index of 3-8 g / 10 min at 230° C. and a load of 2.16 kg.

[0032] Furthermore, the middle core layer also includes 1-3 wt % of an antistatic agent; and the lower surface layer also includes 1-5 wt % of an anti-adhesive agent.

[0033] Furthermore, the antistatic agent is a quaternary ammonium salt-based methacrylate copolymer antistatic agent.

[0034] Furthermore, the anti-adhesive agent is one or more of silicon dioxide, talc, and calcium carbonate, and the particle size is 3 to 6 μm; in order to take into account the surface thickness and shedding problem, it is preferably 4 to 5 μm.

[0035] Furthermore, the thickness of the upper surface matte layer is 1.8-2.2 μm, the thickness of the lower surface glossy layer is 0.8-1.2 μm, and the total thickness of the BOPP matte film is 12-15 μm.

[0036] A method for preparing the wear-resistant biaxially oriented polypropylene matte film comprises the following steps: Step 1: Batching and plasticization: The raw material usage ratio is set in the control system of the biaxial stretch film production line, and then the batching system automatically delivers the dried raw materials 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; Step 2: Slab casting: After being extruded through the die head, the melt immediately contacts the chilled roller to form a thick sheet; Step 3: longitudinal stretching: the thick sheet is heated to a set temperature by multiple sets of preheating rollers, and then longitudinal stretching is started and then shaped; the longitudinal stretching ratio is 2 to 6 times; Step 4: Transverse stretching: preheating the longitudinally stretched thick sheet to a set temperature, starting transverse stretching, and then performing shaping and cooling treatment to obtain a multilayer structure film; the transverse stretching ratio is 8 to 10 times; Step 5: traction and reeling: the multi-layer film exiting the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the reeling unit to obtain a parent roll; Step 6: Slitting: Slitting the mother roll after aging treatment to obtain film rolls of specified width and length.

[0037] Furthermore, the melt extrusion temperature of the upper surface matte layer is 200~260°C; the melt extrusion temperature of the intermediate core layer and the lower surface layer is 230~260°C; in the process of the melt contacting the chilled roller, the temperature of the chilled water and the chilled 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 corona power factor of the upper surface matte layer is 20~25W·min / m.

[0038] The physical properties and test methods of the embodiments or comparative examples of the present invention are as follows: The melt index (melt mass flow rate MFR) is determined according to GB / T3682-2018.

[0039] Appearance of the upper surface matte layer (qualitative): cracks appear / normal.

[0040] Powder loss on the guide roller: In downstream production, after 24 hours of continuous production, observe the powder accumulation on the guide roller that contacts the matte layer and judge by visual inspection (good effect: the guide roller is clean and has no powder accumulation; average effect: there is a layer of white powder accumulation on the guide roller; poor effect: the guide roller is covered with a layer of white powder accumulation, and the guide roller is white).

[0041] The tensile strength is tested according to GB / T1040.3.

[0042] The gloss test is carried out according to GB / T8807-1988 standard.

[0043] The haze test is performed according to GB / T2410-2008.

[0044] The friction resistance test is carried out according to GB / T 454-2020. Specifically, a GM-339 alcohol rubber abrasion tester is used, with a 100g rubber head, to wipe back and forth 20 times to observe the friction of the matte layer.

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0046] Example 1 This embodiment provides a wear-resistant biaxially oriented polypropylene matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. Figure 1 .

[0047] The method for preparing each layer of resin of the wear-resistant biaxially oriented polypropylene matt film of this embodiment comprises the following steps: Preparation of the resin of the upper matte layer 1: Take 42wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 25% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 60wt% and the crystallinity is 25% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 35wt% and the crystallinity is 10% at the elution temperature T1∈[25,60)℃; the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 5wt%, the crystallinity is 40%), 55wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 3wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 50:50) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0048] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0049] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0050] The preparation method of the wear-resistant biaxially oriented polypropylene matte film of the present embodiment comprises the following steps: Batching and plasticization: The proportion of raw materials used is set in the control system of the biaxial stretch film production line, and then the batching system automatically delivers the dried raw materials 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 head, the melt immediately contacts the chilled roller to form a thick sheet; Longitudinal stretching: The thick sheet is heated to a set temperature by multiple sets of preheating rollers, and then begins to be longitudinally stretched and then shaped; Transverse stretching: preheating the longitudinally stretched thick sheet to a set temperature, starting transverse stretching, and then performing shaping and cooling treatment to obtain a multilayer structure film; Traction and reeling: the multi-layer film exiting the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the reeling unit to obtain a parent roll; Slitting: The mother roll after aging treatment is slitting to obtain film rolls of specified width and length.

[0051] The melt extrusion temperature of the upper surface matte layer 1 is 235°C; the melt extrusion temperature of the intermediate core layer 2 is 250°C; the melt extrusion temperature of the lower surface layer 3 is 250°C; when the melt contacts the chilled roller, the temperature of the chilled water and the chilled 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 upper surface layer is 23.5W·min / m.

[0052] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0053] Example 2 This embodiment provides a wear-resistant biaxially oriented polypropylene matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. Figure 1 .

[0054] The method for preparing each layer of resin of the wear-resistant biaxially oriented polypropylene matt film of this embodiment comprises the following steps: Preparation of the resin of the upper matte layer 1: Take 45wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 30% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 70wt% and the crystallinity is 30% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt%, the crystallinity is 50%), 50wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 5wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 60:40) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0055] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0056] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0057] The preparation method of the wear-resistant biaxially oriented polypropylene matte film in this embodiment is the same as that in Example 1.

[0058] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0059] Example 3 This embodiment provides a wear-resistant biaxially oriented polypropylene matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. Figure 1 .

[0060] The method for preparing each layer of resin of the wear-resistant biaxially oriented polypropylene matt film of this embodiment comprises the following steps: Preparation of the resin of the upper matte layer 1: Take 47wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 35% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 80wt% and the crystallinity is 35% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 15wt% and the crystallinity is 15% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 15wt% and the crystallinity is 15% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 5wt%, the crystallinity is 60%), 45wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 8wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 55:45) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0061] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0062] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0063] The preparation method of the wear-resistant biaxially oriented polypropylene matte film in this embodiment is the same as that in Example 1.

[0064] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0065] Comparative Example 1 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0066] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 47wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 30% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 50wt% and the crystallinity is 20% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 40wt% and the crystallinity is 12% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 40wt% and the crystallinity is 12% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt%, the crystallinity is 50%), 45wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 8wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 60:40) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0067] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0068] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0069] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0070] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0071] Comparative Example 2 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0072] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 47wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 30% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 90wt% and the crystallinity is 45% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 5wt% and the crystallinity is 12% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 5wt% and the crystallinity is 12% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 5wt%, the crystallinity is 50%), 45wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 8wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 60:40) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0073] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0074] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0075] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0076] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0077] Comparative Example 3 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0078] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of resin for upper surface matte layer 1: 45wt% random copolymer polypropylene (melt index of 8g / 10min and crystallinity of 30% measured at 230°C and 2.16kg; ethylene-propylene block copolymer segment content of 70wt% and crystallinity of 30% at elution temperature T2∈[60,95)°C; ethylene-propylene random copolymer segment content of 20wt% and crystallinity of 12% at elution temperature T1∈[25,60)°C; homopolymer polypropylene segment content of 10wt% and crystallinity of 50% at elution temperature T3∈[95,140]°C) and 55wt% high-density polyethylene (melt index of 15g / 10min measured at 190°C and 2.16kg) are mixed uniformly to obtain the resin for upper surface matte layer 1.

[0079] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0080] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0081] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0082] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0083] Comparative Example 4 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0084] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 45wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 30% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 70wt% and the crystallinity is 30% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt%, the crystallinity is 50%), 53wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 2wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the weight ratio between EPDM rubber and high-density polyethylene is 60:40) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0085] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0086] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0087] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0088] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0089] Comparative Example 5 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0090] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 45wt% random copolymer polypropylene (the melt index is 8g / 10min and the crystallinity is 30% under the conditions of 230℃ and 2.16kg; the ethylene-propylene block copolymer chain content is 70wt% and the crystallinity is 30% at the elution temperature T2∈[60,95)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T1∈[25,60)℃; the ethylene-propylene random copolymer chain content is 20wt% and the crystallinity is 12% at the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt%, the crystallinity is 50%), 45wt% high-density polyethylene (the melt index is 15g / 10min at 190°C and 2.16kg) and 10wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min at 190°C and 2.16kg; the ratio of EPDM rubber to high-density polyethylene is 60:40) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0091] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0092] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0093] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0094] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0095] Comparative Example 6 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0096] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 45wt% random copolymer polypropylene (the melt index measured at 230℃, 2.16kg is 8g / 10min, and the crystallinity is 30%; the ethylene-propylene block copolymer segment content at the elution temperature T2∈[60,95)℃ is 70wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content at the elution temperature T1∈[25,60)℃ is 20wt%, and the crystallinity is 12%; the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt% and the crystallinity is 50%), 50wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 5wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the ratio of EPDM rubber to high-density polyethylene is 45:55) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0097] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0098] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0099] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0100] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0101] Comparative Example 7 This comparative example provides a BOPP matte film, comprising an upper matte layer 1, an intermediate core layer 2 and a lower surface layer 3 arranged in sequence. The specific structure can be referred to Figure 1 .

[0102] This comparative example provides a method for preparing each layer of resin of a BOPP matte film, comprising the following steps: Preparation of the resin of the upper matte layer 1: Take 45wt% random copolymer polypropylene (the melt index measured at 230℃, 2.16kg is 8g / 10min, and the crystallinity is 30%; the ethylene-propylene block copolymer segment content at the elution temperature T2∈[60,95)℃ is 70wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content at the elution temperature T1∈[25,60)℃ is 20wt%, and the crystallinity is 12%; the elution temperature T3∈[95,140]℃ The homopolymer polypropylene segment content is 10wt% and the crystallinity is 50%), 50wt% high-density polyethylene (the melt index is 15g / 10min measured at 190°C and 2.16kg) and 5wt% EPDM rubber / high-density polyethylene elastomer (the melt index is 10g / 10min measured at 190°C and 2.16kg; the ratio of EPDM rubber to high-density polyethylene is 75:25) are evenly mixed to obtain the upper surface matte layer 1 resin.

[0103] Preparation of the middle core layer 2 resin: 99 wt% homopolypropylene (melt index of 3 g / 10 min measured at 230° C. and 2.16 kg) and 1 wt% antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent) are mixed evenly to obtain the middle core layer 2 resin.

[0104] Preparation of the resin for the lower surface layer 3: 97 wt% homopolypropylene (isotacticity is 96%, and the melt index is 3 g / 10 min at 230°C and 2.16 kg) and 3 wt% anti-blocking agent (silicon dioxide, particle size is 4.5 µm) are mixed evenly to obtain the resin for the lower surface layer 3.

[0105] The preparation method of the BOPP matte film in this comparative example is the same as that in Example 1.

[0106] The total thickness of the film is 12 µm, wherein the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the middle core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0107] The performance test results of the wear-resistant biaxially oriented polypropylene matte films of Examples 1 to 3 and the BOPP matte films of Comparative Examples 1 to 7 are shown in Table 1 below.

[0108] Table 1

[0109] Combined with the above performance test data, we can know that: In the BOPP matte film of Comparative Example 1, the content of ethylene-propylene block copolymer segments with an internal elution temperature T2∈[60,95)°C in the random copolymer polypropylene in the upper surface matte layer is relatively low, which is not conducive to improving the hardness of the soft phase in the upper surface matte layer, resulting in poor scratch resistance of the matte surface and powder loss on the guide roller.

[0110] In the BOPP matte film of Comparative Example 2, the content of ethylene-propylene block copolymer segments with an elution temperature T2∈[60, 95)°C in the random copolymer polypropylene in the upper surface matte layer is relatively high, and the crystallization temperature of the random copolymer polypropylene is too high, which will lead to an accelerated crystallization rate, reduce the difference in crystallization rates between high-density polyethylene and random copolymer polypropylene, and poor phase separation effect, affecting the matte effect.

[0111] In the BOPP matte film of comparative example 3, no EPDM rubber / high-density polyethylene elastomer is added to the upper surface matte layer, which is not conducive to improving the hardness of the soft phase in the matte layer, resulting in very poor scratch resistance of the upper surface matte layer. In subsequent processing, the guide roller loses powder significantly.

[0112] In the BOPP matte film of Comparative Example 4, the content of EPDM rubber / high-density polyethylene elastomer added in the upper surface matte layer is too low, the hardness of the soft phase random copolymer polypropylene in the matte layer is insufficient, and it is not conducive to the formation of the core-shell structure, resulting in poor scratch resistance of the upper surface matte layer and the occurrence of abrasion.

[0113] In the BOPP matte film of Comparative Example 5, the content of EPDM rubber / high-density polyethylene elastomer added in the upper surface matte layer is too high. The excessive elastomer causes the mechanical properties of the film to decrease, resulting in a decrease in the tensile strength of the film. At the same time, the upper surface matte layer has poor scratch resistance and exhibits a grinding phenomenon.

[0114] For the BOPP matte film of Comparative Example 6, when the ratio of EPDM rubber to high-density polyethylene in the EPDM rubber / high-density polyethylene elastomer added to the upper surface matte layer is too low, the increase of high-density polyethylene is beneficial to the improvement of the hardness of the EPDM rubber / high-density polyethylene elastomer, but excessive content will cause appearance quality problems such as cracks in the matte layer during the stretching process.

[0115] In the BOPP matte film of Comparative Example 7, when the ratio of EPDM rubber to high-density polyethylene in the EPDM rubber / high-density polyethylene elastomer added to the upper surface matte layer is too high, the excessive EPDM rubber will cause the strength of the high-density polyethylene and random copolymer polypropylene mixed system to decrease, affecting the mechanical properties of the film, thereby reducing the tensile strength of the film, which is not conducive to film production.

[0116] The wear-resistant biaxially oriented polypropylene matte film of the present invention has good matte effect, can improve the hardness of the soft phase random copolymer polypropylene in the upper surface matte layer, not only improves the mark problem during extrusion or displacement scraping, but also improves the scratch resistance of the film; and can also effectively protect the high-density polyethylene from being rubbed off by foreign objects such as guide rollers when the matte layer is subjected to external force (such as during secondary slitting and laminating process contacting guide rollers), reduce the occurrence of grinding, meet the subsequent processing requirements of the BOPP matte film, and adapt to high-speed automated production.

[0117] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A wear-resistant biaxially oriented polypropylene matte film, characterized in that: The invention comprises an upper surface matte layer, an intermediate core layer and a lower surface layer which are arranged in sequence; the upper surface matte layer comprises 45-55wt% high-density polyethylene, 42-47wt% random copolymer polypropylene and 3-8wt% EPDM rubber / high-density polyethylene elastomer; the intermediate core layer comprises homopolymer polypropylene; the lower surface layer comprises homopolymer polypropylene; the random copolymer polypropylene in the upper surface matte layer comprises an ethylene-propylene random copolymer segment with an elution temperature T1∈[25,60)°C, an ethylene-propylene block copolymer segment with an elution temperature T2∈[60,95)°C and a homopolymer polypropylene segment with an elution temperature T3∈[95,140]°C; the content of the ethylene-propylene block copolymer segment with an elution temperature T2∈[60,95)°C in the random copolymer polypropylene is 60-80wt%.

2. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: The upper surface matte layer comprises a core-shell structure with the high-density polyethylene as a core and the EPDM rubber / high-density polyethylene elastomer as a shell.

3. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: In the random copolymer polypropylene, the content of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25,60)°C is 10~35wt%, and the content of the homopolymer polypropylene segment at the elution temperature T3∈[95,140]°C is 5~10wt%.

4. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: The crystallinity of the ethylene-propylene random copolymer segment at the elution temperature T1∈[25,60)°C is 10~15%, the crystallinity of the ethylene-propylene block copolymer segment at the elution temperature T2∈[60,95]°C is 25~35%, and the crystallinity of the homopolypropylene segment at the elution temperature T3∈[95,140]°C is 40~60%.

5. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: The random copolymer polypropylene in the upper surface matte layer has a crystallinity of 25-35%.

6. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: The weight ratio of EPDM rubber to high-density polyethylene in the EPDM rubber / high-density polyethylene elastomer is (50-60):(40-50).

7. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: The EPDM rubber / high-density polyethylene elastomer is prepared by mixing EPDM rubber and high-density polyethylene in an internal mixer under the action of a crosslinking agent, 1,4-bis(tert-butylperoxyisopropyl)benzene and an auxiliary crosslinking agent, triallyl isocyanuric acid.

8. The wear-resistant biaxially oriented polypropylene matte film according to claim 1, characterized in that: At 190°C and a load of 2.16kg, the melt index of the EPDM rubber / high-density polyethylene elastomer is 8-13g / 10min; the melt index of the high-density polyethylene in the upper surface matte layer is 9-20g / 10min at 190°C and a load of 2.16kg; the melt index of the random copolymer polypropylene in the upper surface matte layer is 6-10g / 10min at 230°C and a load of 2.16kg; the random copolymer polypropylene in the upper surface matte layer is a random ethylene-propylene copolymer.

9. A method for preparing a wear-resistant biaxially oriented polypropylene matte film, characterized in that: The following steps are involved: Step 1: Batching and plasticization: The raw material usage ratio is set in the control system of the biaxial stretch film production line, and then the batching system automatically delivers the dried raw materials 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; Step 2: Slab casting: After being extruded through the die head, the melt immediately contacts the chilled roller to form a thick sheet; Step 3: longitudinal stretching: the thick sheet is heated to a set temperature by multiple sets of preheating rollers, and then longitudinal stretching is started and then shaped; the longitudinal stretching ratio is 2 to 6 times; Step 4: Transverse stretching: preheating the longitudinally stretched thick sheet to a set temperature, starting transverse stretching, and then performing shaping and cooling treatment to obtain a multilayer structure film; the transverse stretching ratio is 8 to 10 times; Step 5: traction and reeling: the multi-layer film exiting the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, enters the reeling unit to obtain a parent roll; Step 6: Slitting: Slitting the mother roll after aging treatment to obtain film rolls of specified width and length.

10. The method for preparing the wear-resistant biaxially oriented polypropylene matte film according to claim 9, characterized in that: The melt extrusion temperature of the upper surface matte layer is 200~260℃; the melt extrusion temperature of the middle core layer and the lower surface layer is 230~260℃; in the process of the melt contacting the chilled roller, the temperature of the chilled water and the chilled roller is 15~50℃; the temperature of the longitudinal stretching zone is 90~130℃; the temperature of the transverse stretching zone is 155~165℃; the longitudinal stretching ratio is 4.5~5.5 times; the corona power factor of the upper surface matte layer is 20~25W·min / m.

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