Wear-resistant biaxially oriented polypropylene matte film and its preparation method

Abstract

The present invention relates to the field of matte films, and particularly to a wear-resistant biaxially oriented polypropylene matte film and a preparation method thereof. The wear-resistant biaxially oriented polypropylene matte film of the present 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 45-55 wt% of high-density polyethylene, 42-47 wt% of random copolymer polypropylene and 3-8 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer; the random copolymer polypropylene in the upper surface matte layer is composed of an ethylene-propylene random copolymer chain segment with an elution temperature T1 ∈ [25, 60) °C, an ethylene-propylene block copolymer chain segment with an elution temperature T2 ∈ [60, 95) °C and a homopolypropylene chain segment with an elution temperature T3 ∈ [95, 140] °C; the content of the ethylene-propylene block copolymer chain segment with an elution temperature T2 ∈ [60, 95) °C in the random copolymer polypropylene is 60-80 wt%. By optimizing the composition of the matte layer material, the present invention improves the scratch resistance of the matte layer, reduces the problem of grinding powder, and meets the subsequent processing and production of BOPP matte films.

Description

Technical Field

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

[0002] BOPP matte films are usually BOPP films with one matte side and one shiny side or both sides matte. The matte effect is mainly achieved by scattering light, which can enhance the grade of printed outer packaging. Since the matte effect of the matte film gives a soft, fashionable and elegant high-class feeling and eliminates eye fatigue, BOPP matte films are increasingly widely used in the packaging field, especially suitable for deep processing industries and fields such as coating and lamination.

[0003] At present, the matte layer of the BOPP matte films sold on the market is mainly composed of a combination of high-density polyethylene and random copolymer polypropylene. In the masterbatch system for matte, the copolymer polypropylene is the soft phase and the high-density polyethylene is the hard phase. According to the principle of soft wrapping hard, the high-density polyethylene (hard phase) is mostly coated by the copolymer polypropylene (soft phase). The matte principle of the matte film is that during the stretching process of the matte masterbatch, because the randomness of the copolymer polypropylene is relatively high, the crystallization speed is slow, and the crystallization temperature is relatively low, the copolymer polypropylene will exist as the continuous phase; however, due to the high viscosity, high crystallization rate and high crystallinity characteristics of the high-density polyethylene, the high-density polyethylene exists as the dispersed phase. During the film-forming stretching process, when the copolymer polypropylene is still in a relatively soft state, the high-density polyethylene has completed partial or most of the crystallization. The crystallized high-density polyethylene forms a hard phase. Under the action of external tensile force, the high-density polyethylene phase in the matte layer will protrude compared with the copolymer polypropylene soft phase during the stretching process. In the microscopic "island" morphology of the matte film, it is the dispersed phase, and the continuous-phase polypropylene will coat the high-density polyethylene. After the film is biaxially stretched, a "island" structure is microscopically presented, forming a matte surface layer with uneven roughness, thereby achieving the matte effect. However, in the process of secondary slitting and laminating of the matte film products prepared by the above film-forming process and contacting the guide rollers, the matte surface is often scratched, and a thin layer of powder appears on the surface of the guide rollers, seriously affecting the packaging effect of the BOPP matte film and the production efficiency of downstream applications. Summary of the Invention

[0004] Based on this, the object of the present invention is to provide a wear-resistant biaxially oriented polypropylene matte film and a preparation method thereof. By optimizing the composition of the matte layer material, the scratch resistance of the matte layer is improved, the problem of grinding powder is reduced, the requirements for subsequent processing performance are met, and it can adapt to high-speed automated production.

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

[0006] Through the research of the inventor, it is found that during the production process of BOPP matte film, the powder appearing on the surface of the guide roller is high-density polyethylene, and the main reasons for the matte surface abrasion and scratch resistance of BOPP matte film are that the soft phase wrapping the hard phase surface is too soft; since the copolymer polypropylene is relatively soft, the scratching of BOPP matte film mostly occurs on the copolymer polypropylene sea phase wrapping the island phase. Therefore, when the 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 scratches are likely to remain when it is subjected to extrusion or displacement scratching. In severe cases, the original microscopic morphology of the film surface is damaged, so the overall scratch resistance is poor. In addition, due to the sequential order of the stretching areas during the stretching process, some parts of the random copolymer polypropylene soft phase wrapping the high-density polyethylene hard phase surface are thicker, while some parts are thinner. When the thin parts are damaged by external forces, such as during secondary slitting and contact with the guide roller during the film laminating process, the high-density polyethylene hard phase directly contacts external objects such as the guide roller, resulting in the phenomenon of powdering.

[0007] In the matting layer on the upper surface layer of a wear-resistant biaxially oriented polypropylene matting film of the present invention, ethylene propylene diene monomer / high density polyethylene elastomer is added. In the blend system of random copolymer polypropylene and high density polyethylene, the ethylene propylene diene monomer / high density polyethylene elastomer serves as a homogeneous nucleating agent, which can accelerate the crystallization rate of random copolymer polypropylene and increase the crystallization temperature, forming more crystal nuclei in a short time and increasing the crystallinity. Moreover, it can improve the crystallization morphology of random copolymer polypropylene, making it form a finer spherulite structure, and the finer spherulite structure can improve the hardness of the random copolymer polypropylene wrapping the surface of the high density polypropylene hard phase. Preferably, the content of the ethylene propylene diene monomer / high density polyethylene elastomer is 3-8 wt%, and the stiffness of the prepared polypropylene matting film is the best. When the content of the ethylene propylene diene monomer / high density polyethylene elastomer is less than 3%, the hardness of the soft-phase random copolymer polypropylene in the matting layer is insufficient, which is not conducive to the formation of a core-shell structure, and it is difficult to obtain a matting layer with good scratch resistance and less powdering. When the content of the ethylene propylene diene monomer / high density polyethylene elastomer is higher than 8%, the excessive elastomer will cause a decline in the mechanical properties of the film. Adding an appropriate amount of anti-blocking agent to the lower surface layer is beneficial to increasing the smoothness of the winding and unwinding of the matting film; if the content of the anti-blocking agent in the lower surface layer is less than 1 wt%, it cannot play an effective anti-blocking role; if the content of the anti-blocking agent is higher than 5 wt%, problems such as the shedding of the anti-blocking agent are likely to occur during the production process, resulting in the contamination of the guide rollers, and at the same time, it will increase the haze and reduce the gloss, 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. As a semi-crystalline polymer, there is a certain distribution of the chain crystallization structure in random copolymer polypropylene. The temperature rising elution fractionation method classifies polyolefins according to the crystallinity based on the different effects of chain structure parameters on the crystallization process and crystallinity of polyolefin molecules. The ethylene-propylene block copolymer segments with medium crystallinity (the elution temperature T2 ∈ [60, 95) °C) in the matte layer of a wear-resistant biaxially oriented polypropylene matte film of the present invention have a high crystallization temperature, which is more conducive to improving the hardness of the soft phase in the matte layer, and is beneficial to obtaining better scratch resistance. In addition, it also makes the random copolymer polypropylene have a suitable crystallinity and a slow crystallization rate, which is conducive to the phase separation between high-density polyethylene and random copolymer polypropylene, ensuring the uniformity of matting. By controlling the content of the above-mentioned ethylene-propylene block copolymer segments with medium crystallinity (the elution temperature T2 ∈ [60, 95) °C), the crystallization morphology is improved, and the hardness of the soft-phase copolymer polypropylene wrapping the hard phase is increased. When the upper surface matte layer is subjected to external forces, such as during secondary slitting and film laminating processes when contacting guide rollers, etc., the soft phase with a higher hardness can effectively protect the hard phase from being rubbed off by external objects such as guide rollers, avoiding the occurrence of powdering. When the content of the ethylene-propylene block copolymer segments with medium crystallinity (the elution temperature T2 ∈ [60, 95) °C) is less than 60 wt%, 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 segments with medium crystallinity (the elution temperature T2 ∈ [60, 95) °C) is greater than 80 wt%, the crystallization temperature of the random copolymer polypropylene is too high, which will lead to an accelerated crystallization rate and a poor phase separation effect between high-density polyethylene and random copolymer polypropylene, thus affecting the matting effect. Controlling the content of the ethylene-propylene block copolymer segments with medium crystallinity (the elution temperature T2 ∈ [60, 95) °C) within the above range is conducive to improving the hardness of the soft phase in the matte layer, obtaining a matte layer with uniform matting effect and good scratch resistance, so that the soft phase with a higher hardness can effectively protect the hard phase (high-density polyethylene) from being rubbed off by external objects such as guide rollers during the processes of secondary slitting and film laminating, avoiding the occurrence of powdering.

[0009] Furthermore, the upper surface matting layer comprises a core-shell structure with the high-density polyethylene as the core and the ethylene-propylene-diene monomer / high-density polyethylene elastomer as the shell. In the blend system of random copolymer polypropylene and high-density polyethylene in the upper surface matting layer, the ethylene and propylene groups in the ethylene-propylene-diene monomer part of the ethylene-propylene-diene monomer / high-density polyethylene elastomer molecular chain are well compatible with the random copolymer polypropylene, while the high-density polyethylene part in the ethylene-propylene-diene monomer / high-density polyethylene elastomer molecular chain is compatible with the high-density polyethylene in the matting masterbatch, forming a good physical bridging effect between the random copolymer polypropylene and the high-density polyethylene, reducing interface defects, making their combination closer. The core-shell structure formed by the ethylene-propylene-diene monomer / high-density polyethylene elastomer improves the compatibility between the random copolymer polypropylene and the high-density polyethylene, making the combination of the high-density polyethylene and the surrounding random copolymer polypropylene firmer, and it is not easy to appear the phenomenon of powdering even when contacting the guide roller during the secondary slitting and film laminating processes. In addition, when the wear-resistant biaxially oriented polypropylene matting film contacts the guide roller during the secondary slitting and film laminating processes, since the surface of the core-shell structure high-density polyethylene is wrapped with a layer of ethylene-propylene-diene monomer / high-density polyethylene elastomer, the ethylene-propylene-diene monomer / high-density polyethylene elastomer can effectively absorb and disperse part of the frictional energy, avoiding the direct contact of the hard-phase high-density polyethylene of the matting layer with external objects after the destruction of some parts of the soft-phase random copolymer polypropylene with a relatively thin surface wrapping the high-density polyethylene hard phase, and improving the scratch and powdering 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 chain segment with the elution temperature T1 ∈ [25, 60) °C is 10 - 35 wt%, and the content of the homopolypropylene chain segment with the elution temperature T3 ∈ [95, 140] °C is 5 - 10 wt%.

[0011] Furthermore, the crystallinity of the ethylene-propylene random copolymer segment with a rinsing temperature T1 ∈ [25, 60) °C is 10 - 15%, the crystallinity of the ethylene-propylene block copolymer segment with a rinsing temperature T2 ∈ [60, 95) °C is 25 - 35%, and the crystallinity of the homopolypropylene segment with a rinsing temperature T3 ∈ [95, 140] °C is 40 - 60%. The wear-resistant biaxially oriented polypropylene matte film obtained by controlling the crystallinity of the ethylene-propylene block copolymer segment within the above range has a good matte effect, and can improve the problems of grinding powder on the surface of the guide roller and matte surface scratches during the processes of secondary slitting and laminating and contacting the guide roller. Controlling the ethylene-propylene random copolymer segment with no crystallization or low crystallinity and the homopolypropylene segment with high crystallinity within the above range is beneficial to ensuring the matte effect of the matte layer and improving the hardness of the random copolymer polypropylene. If the crystallinity of the ethylene-propylene block copolymer segment with medium crystallinity (rinsing temperature T2 ∈ [60, 95) °C) is less than 25%, it is not conducive to improving the hardness of the soft-phase random copolymer polypropylene in the matte layer and cannot effectively improve the scratch resistance performance; 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 crystallinity of the random copolymer polypropylene in the upper surface matte layer is 25 - 35%. When the overall crystallinity of the random copolymer polypropylene is lower than 25%, the hardness of the soft-phase random copolymer polypropylene in the matte layer is insufficient, which is not conducive to enhancing the scratch resistance performance of the matte layer; when the overall crystallinity of the random copolymer polypropylene is higher than 35%, too high crystallinity affects the compatibility between the random copolymer polypropylene and high-density polyethylene, which is not conducive to the matte effect; the polypropylene matte film prepared with the crystallinity of the random copolymer polypropylene being 25 - 35% has the optimal stiffness.

[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:

[0017] Step 1: Batching and Plasticizing: Set the proportion of raw materials used in the control system of the biaxially stretched film production line. Then, the batching system automatically conveys the dried raw materials to the extruder according to the input proportion. After melting and plasticizing in the extruder, the melt enters the die through the flow channel and distributor;

[0018] Step 2: Casting: After being extruded from the die, the melt immediately contacts the chill roll to form a thick sheet;

[0019] Step 3: Longitudinal Stretching: The thick sheet is heated to a set temperature by multiple groups of preheating rolls, starts longitudinal stretching, and then is shaped; the longitudinal stretching ratio is 2 - 6 times;

[0020] Step 4: Transverse Stretching: The thick sheet that has undergone longitudinal stretching is preheated to a set temperature, starts transverse stretching, and then is shaped and cooled to obtain a multi-layer structured film; the transverse stretching ratio is 8 - 10 times;

[0021] Step 5: Traction and Rewinding: The multi-layer structured film exiting the transverse stretching unit enters the traction unit, and after thickness measurement and corona treatment, it enters the rewinding unit to obtain a master roll;

[0022] Step 6: Slitting: The master roll that has undergone aging treatment is slit to obtain a film roll with a specified width and length.

[0023] Furthermore, the melting and extrusion temperature of the upper surface matting layer is 200 - 260 °C; the melting and extrusion temperatures of the middle core layer and the lower surface layer are 230 - 260 °C; in the process where the melt contacts the chill roll, the temperature of the chill water and the chill roll 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 matting layer is 20 - 25 W·min / m.

[0024] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the wear-resistant biaxially stretched polypropylene matting film described in Embodiments 1 - 3 of the present invention and the BOPP matting film described in Comparative Examples 1 - 7. Detailed Embodiments

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

[0027] The terms used in the embodiments of the present application are 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 "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0028] In the random copolymer polypropylene, there is a certain distribution in the chain crystallization structure within the semi-crystalline polymer molecule. The temperature rising elution fractionation method grades polyolefins according to the crystallinity based on the different effects of chain structure parameters on the crystallization process and crystallinity of polyolefin molecules. The random copolymer polypropylene solution is slowly cooled, and it gradually crystallizes on the inert carrier according to the crystallinity from high to low. The most easily crystallized component will deposit first to form the inner layer, while the least easily crystallized component deposits last on the outer layer. Then, the temperature is raised. At a lower temperature, the component with a lower crystallinity dissolves first. As the temperature gradually increases, the random copolymer polypropylene is gradually dissolved and eluted in the order of increasing crystallinity, and finally the temperature rising elution fractionation curve of the random copolymer polypropylene is obtained. In the random copolymer polypropylene in the surface extinction layer of a wear-resistant biaxially stretched polypropylene extinction film of the present invention, within the range of 25°C to 140°C, there will be 8 elution peaks in 8 levels (25, 60, 80, 90, 95, 108, 115, 140). At the same time, by integrating the elution curves in different temperature ranges, the relative content of the random copolymer polypropylene fractions in different temperature ranges can be obtained. Among them, the component with the elution temperature T1 ∈ [25, 60) °C is an ethylene-propylene random copolymer chain segment with no crystallization or low crystallinity, the component with the elution temperature range T2 ∈ [60, 95) °C is an ethylene-propylene block copolymer chain segment with medium crystallinity, and the component with the elution temperature T3 ∈ [95, 140] °C is a homopolypropylene chain segment with high crystallinity.

[0029] 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 arranged in sequence; the upper surface matte layer 1 comprises 45-55 wt% high-density polyethylene, 42-47 wt% random copolymer polypropylene, and 3-8 wt% ethylene-propylene-diene monomer / high-density polyethylene elastomer; the intermediate core layer 2 comprises 97-99 wt% homopolypropylene; the lower surface layer 3 comprises 95-99 wt% homopolypropylene; the random copolymer polypropylene in the upper surface matte layer is composed of an ethylene-propylene random copolymer chain segment with a elution temperature T1 ∈ [25, 60) °C, an ethylene-propylene block copolymer chain segment with a elution temperature T2 ∈ [60, 95) °C, and a homopolypropylene chain segment with a elution temperature T3 ∈ [95, 140] °C; the content of the ethylene-propylene block copolymer chain segment with a elution temperature T3 ∈ [95, 140] °C in the random copolymer polypropylene is 60-80 wt%.

[0030] Further, the upper surface matte layer comprises a core-shell structure with the high-density polyethylene as the core and the ethylene-propylene-diene monomer / high-density polyethylene elastomer as the shell.

[0031] Further, in the random copolymer polypropylene, the content of the ethylene-propylene random copolymer chain segment with a elution temperature T1 ∈ [25, 60) °C is 10-35 wt%, and the content of the homopolypropylene chain segment with a elution temperature T3 ∈ [95, 140] °C is 5-10 wt%.

[0032] Further, the crystallinity of the ethylene-propylene random copolymer chain segment with a elution temperature T1 ∈ [25, 60) °C is 10-15%, the crystallinity of the ethylene-propylene block copolymer chain segment with a elution temperature T2 ∈ [60, 95) °C is 25-35%, and the crystallinity of the homopolypropylene chain segment with a elution temperature T3 ∈ [95, 140] °C is 40-60%.

[0033] Further, the crystallinity of the random copolymer polypropylene in the upper surface matte layer is 25-35%.

[0034] Further, the weight ratio of ethylene-propylene-diene monomer to high-density polyethylene in the ethylene-propylene-diene monomer / high-density polyethylene elastomer is (50-60):(40-50). The ethylene-propylene-diene monomer is a copolymer of ethylene, propylene, and a small amount of non-conjugated diene, and the ethylene-propylene-diene monomer is a highly saturated polymer with a completely saturated main chain.

[0035] Further, the ethylene-propylene-diene monomer / high-density polyethylene elastomer is prepared by mixing ethylene-propylene-diene monomer and high-density polyethylene in a mixer under the action of a cross-linking agent 1,4-bis(tert-butylperoxyisopropyl)benzene and a co-cross-linking agent triallyl isocyanurate.

[0036] Further, at 190 °C and a load of 2.16 kg, the melt index of the ethylene-propylene-diene rubber / high-density polyethylene elastomer is 8-13 g / 10 min; the melt index of the high-density polyethylene in the upper surface matting layer at 190 °C and a load of 2.16 kg is 9-20 g / 10 min; the melt index of the random copolymer polypropylene in the upper surface matting layer at 230 °C and a load of 2.16 kg is 6-10 g / 10 min; the random copolymer polypropylene in the upper surface matting layer is a random ethylene-propylene copolymer.

[0037] Further, the melt index of the homopolypropylene in the middle core layer and / or the lower surface layer at 230 °C and a load of 2.16 kg is 3-8 g / 10 min.

[0038] Further, the middle core layer further comprises 1-3 wt% of an antistatic agent; the lower surface layer further comprises 1-5 wt% of an antiblocking agent.

[0039] Further, the antistatic agent is a quaternary ammonium salt-based methacrylate copolymer antistatic agent.

[0040] Further, the antiblocking agent is one or more of silica, talc, and calcium carbonate, with a particle size of 3-6 μm; preferably 4-5 μm in order to balance the surface layer thickness and the peeling problem.

[0041] Further, the thickness of the upper surface matting 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 matting film is 12-15 μm.

[0042] A method for preparing the wear-resistant biaxially oriented polypropylene matting film comprises the following steps:

[0043] The first step: batching and plasticizing: Set the raw material usage ratio in the control system of the biaxially oriented film production line, and then the batching system automatically conveys the dried raw materials to the extruder according to the input ratio. After melting and plasticizing in the extruder, the melt enters the die through the runner and the distributor;

[0044] The second step: casting: After being extruded from the die, the melt immediately contacts the chill roll to form a thick sheet;

[0045] The third step: longitudinal stretching: The thick sheet is heated to a set temperature by multiple groups of preheating rolls, starts longitudinal stretching, and then is shaped; the longitudinal stretching ratio is 2-6 times;

[0046] The fourth step: transverse stretching: The thick sheet after longitudinal stretching is preheated to a set temperature, starts transverse stretching, and then is shaped and cooled to obtain a multi-layer structure film; the transverse stretching ratio is 8-10 times;

[0047] Step 5: Traction and Rewinding: The multi-layer structured film exiting the transverse stretching unit enters the traction unit, undergoes thickness measurement and corona treatment, and then enters the rewinding unit to obtain the master roll.

[0048] Step 6: Slitting: The master roll that has undergone aging treatment is slit to obtain film rolls with specified widths and lengths.

[0049] Furthermore, the melting and extrusion temperature of the upper surface matting layer is 200 - 260 °C; the melting and extrusion temperatures of the middle core layer and the lower surface layer are 230 - 260 °C; in the process where the melt contacts the chill roll, the temperature of the chill water and the chill roll is 15 - 50 °C; the temperature in the longitudinal stretching zone is 90 - 130 °C; the temperature in 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 matting layer is 20 - 25 W·min / m.

[0050] The physical property indexes and their testing methods of the embodiments or comparative examples of the present invention are specifically as follows:

[0051] The melt mass-flow rate (MFR) is measured according to GB / T3682-2018.

[0052] Appearance of the upper surface matting layer (qualitative): Cracks appear / Normal condition.

[0053] Powder dropping situation of the guide roll: During downstream production, after continuous production for 24 hours, observe the powder accumulation on the guide roll in contact with the matting layer, and judge by visual inspection (Good effect: The guide roll is clean without powder accumulation; General effect: There is a layer of white powder accumulation on the guide roll; Poor effect: The guide roll is covered with a layer of white powder and the guide roll turns white).

[0054] The tensile strength is tested according to GB / T1040.3.

[0055] The glossiness test is carried out according to the standard of GB / T8807-1988.

[0056] The haze test is carried out according to GB / T2410-2008.

[0057] The friction resistance performance test is carried out according to GB / T 454-2020. Specifically, use a GM-339 alcohol rubber abrasion resistance testing machine, use a rubber head of 100 g, wipe back and forth 20 times, and observe the friction situation of the matting layer.

[0058] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention.

[0059] Example 1

[0060] This embodiment provides an abrasion-resistant biaxially oriented polypropylene matte film, which includes an upper surface matte layer 1, an intermediate core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, reference can be made to Figure 1 .

[0061] The preparation method of the resins of each layer of the abrasion-resistant biaxially oriented polypropylene matte film in this embodiment includes the following steps:

[0062] Preparation of the resin of the upper surface matte layer 1: Take 42 wt% of random copolymer polypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 8 g / 10 min, and the crystallinity is 25%); the ethylene-propylene block copolymer chain segment content with a leaching temperature T2 ∈ [60, 95) °C is 60 wt%, and the crystallinity is 25%; the ethylene-propylene random copolymer chain segment content with a leaching temperature T1 ∈ [25, 60) °C is 35 wt%, and the crystallinity is 10%; the homopolypropylene chain segment content with a leaching temperature T3 ∈ [95, 140] °C is 5 wt%, and the crystallinity is 40%), 55 wt% of high-density polyethylene (the melt index measured under the conditions of 190 °C and 2.16 kg is 15 g / 10 min), and 3 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (the melt index measured under the conditions of 190 °C and 2.16 kg is 10 g / 10 min; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 50:50), and mix them evenly to obtain the resin of the upper surface matte layer 1.

[0063] Preparation of the resin of the intermediate core layer 2: Take 99 wt% of homopolypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min), 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin of the intermediate core layer 2.

[0064] Preparation of the resin of the lower surface layer 3: Take 97 wt% of homopolypropylene (the isotacticity is 96%, and the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin of the lower surface layer 3.

[0065] The preparation method of the abrasion-resistant biaxially oriented polypropylene matte film in this embodiment includes the following steps:

[0066] Batching and plasticization: Set the raw material usage ratio in the control system of the biaxially oriented film production line, and then the batching system automatically conveys the dried raw materials to the extruder according to the input ratio. After melting and plasticizing in the extruder, the melt enters the die head through the runner and distributor;

[0067] Sheet casting: After being extruded from the die head, the melt immediately contacts the chill roll to form a thick sheet;

[0068] Longitudinal stretching: The thick sheet is heated to a set temperature by multiple groups of preheating rollers, starts longitudinal stretching, and then is shaped.

[0069] Transverse stretching: After preheating the thick sheet that has undergone longitudinal stretching to a set temperature, transverse stretching is started, and then shaping and cooling treatments are carried out to obtain a multi-layer structure film.

[0070] Traction and winding: The multi-layer structure film exiting the transverse stretching unit enters the traction unit, undergoes thickness measurement and corona treatment, and then enters the winding unit to obtain a master roll.

[0071] Slitting: The master roll that has undergone aging treatment is slit to obtain a film roll with a specified width and length.

[0072] The melting and extrusion temperature of the upper surface matte layer 1 is 235 °C; the melting and extrusion temperature of the intermediate core layer 2 is 250 °C; the melting and extrusion temperature of the lower surface layer 3 is 250 °C; when the melt contacts the chill roll, the temperature of the chilled water and the chill roll is 40 °C; the temperature of longitudinal stretching is 125 °C; the temperature of 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 23.5 W·min / m.

[0073] The total thickness of the film is 12 µm, where the thickness of the upper surface matte layer 1 is 1.8 µm, the thickness of the intermediate core layer 2 is 9.2 µm, and the thickness of the lower surface layer 3 is 1 µm.

[0074] Example 2

[0075] This example provides a wear-resistant biaxially stretched polypropylene matte film, which includes an upper surface 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 .

[0076] The preparation method of the resins of each layer of the wear-resistant biaxially stretched polypropylene matte film in this example includes the following steps:

[0077] Preparation of the resin for the upper surface extinction layer 1: Take 45 wt% of random copolymer polypropylene (with a melt index of 8 g / 10 min measured under the conditions of 230 °C and 2.16 kg, and a crystallinity of 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 50 wt% of high-density polyethylene (with a melt index of 15 g / 10 min measured under the conditions of 190 °C and 2.16 kg), and 5 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (with a melt index of 10 g / 10 min measured under the conditions of 190 °C and 2.16 kg; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 60:40), and mix them evenly to obtain the resin for the upper surface extinction layer 1.

[0078] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0079] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (isotacticity is 96%, with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0080] The preparation method of the wear-resistant biaxially oriented polypropylene extinction film in this example is the same as that in Example 1.

[0081] The total thickness of the film is 12 µm, among which the thickness of the upper surface extinction 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.

[0082] Example 3

[0083] This example provides a wear-resistant biaxially oriented polypropylene extinction film, which includes an upper surface extinction layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0084] The preparation method of the resin for each layer of the wear-resistant biaxially oriented polypropylene extinction film in this example includes the following steps:

[0085] Preparation of the resin for the upper surface extinction layer 1: Take 47 wt% of random copolymer polypropylene (with a melt index of 8 g / 10 min measured under the conditions of 230 °C and 2.16 kg, and a crystallinity of 35%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 80 wt%, and the crystallinity is 35%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 15 wt%, and the crystallinity is 15%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 5 wt%, and the crystallinity is 60%), 45 wt% of high-density polyethylene (with a melt index of 15 g / 10 min measured under the conditions of 190 °C and 2.16 kg), and 8 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (with a melt index of 10 g / 10 min measured under the conditions of 190 °C and 2.16 kg; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 55:45), and mix them evenly to obtain the resin for the upper surface extinction layer 1.

[0086] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0087] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (isotacticity is 96%, with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0088] The preparation method of the wear-resistant biaxially oriented polypropylene extinction film in this example is the same as that in Example 1.

[0089] The total thickness of the film is 12 µm, among which the thickness of the upper surface extinction 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.

[0090] Comparative Example 1

[0091] This comparative example provides a BOPP extinction film, including an upper surface extinction layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0092] The preparation method of the resin for each layer of the BOPP extinction film provided in this comparative example includes the following steps:

[0093] Preparation of the resin for the upper surface matting layer 1: Take 47 wt% of random copolymer polypropylene (with a melt index of 8 g / 10 min measured under the conditions of 230 °C and 2.16 kg, and a crystallinity of 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 50 wt%, and the crystallinity is 20%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 40 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 45 wt% of high-density polyethylene (with a melt index of 15 g / 10 min measured under the conditions of 190 °C and 2.16 kg), and 8 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (with a melt index of 10 g / 10 min measured under the conditions of 190 °C and 2.16 kg; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 60:40), and mix them evenly to obtain the resin for the upper surface matting layer 1.

[0094] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0095] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (isotacticity is 96%, with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0096] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0097] The total thickness of the film is 12 µm, among which the thickness of the upper surface matting 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.

[0098] Comparative Example 2

[0099] This comparative example provides a BOPP matting film, which includes an upper surface matting layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0100] The preparation method of the resin for each layer of the BOPP matting film provided in this comparative example includes the following steps:

[0101] Preparation of the resin for the upper surface extinction layer 1: Take 47 wt% of random copolymer polypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 8 g / 10 min, and the crystallinity is 30%); the ethylene-propylene block copolymer segment content with the elution temperature T2 ∈ [60, 95) °C is 90 wt%, and the crystallinity is 45%; the ethylene-propylene random copolymer segment content with the elution temperature T1 ∈ [25, 60) °C is 5 wt%, and the crystallinity is 12%; the homopolypropylene segment content with the elution temperature T3 ∈ [95, 140] °C is 5 wt%, and the crystallinity is 50%), 45 wt% of high-density polyethylene (the melt index measured under the conditions of 190 °C and 2.16 kg is 15 g / 10 min), and 8 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (the melt index measured under the conditions of 190 °C and 2.16 kg is 10 g / 10 min; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 60:40), and mix them evenly to obtain the resin for the upper surface extinction layer 1.

[0102] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0103] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (the isotacticity is 96%, and the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 3 wt% of antiblocking agent (silica, with a particle size of 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0104] The preparation method of the BOPP extinction film in this comparative example is the same as that in Example 1.

[0105] The total thickness of the film is 12 µm, among which the thickness of the upper surface extinction 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.

[0106] Comparative Example 3

[0107] This comparative example provides a BOPP extinction film, which includes an upper surface extinction layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0108] The preparation method of the resin for each layer of the BOPP extinction film provided in this comparative example includes the following steps:

[0109] Preparation of the resin for the upper surface extinction layer 1: Take 45 wt% of random copolymer polypropylene (with a melt index of 8 g / 10 min measured under the conditions of 230 °C and 2.16 kg, and a crystallinity of 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), and 55 wt% of high-density polyethylene (with a melt index of 15 g / 10 min measured under the conditions of 190 °C and 2.16 kg), and mix them evenly to obtain the resin for the upper surface extinction layer 1.

[0110] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0111] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (isotacticity is 96%, with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0112] The preparation method of the BOPP extinction film in this comparative example is the same as that in Example 1.

[0113] The total thickness of the film is 12 µm, among which the thickness of the upper surface extinction 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.

[0114] Comparative Example 4

[0115] This comparative example provides a BOPP extinction film, which includes an upper surface extinction layer 1, a middle core layer 2 and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0116] The preparation method of the resin for each layer of the BOPP extinction film provided in this comparative example includes the following steps:

[0117] Preparation of the resin for the upper surface matting layer 1: Take 45 wt% of random copolymer polypropylene (with a melt index of 8 g / 10 min measured under the conditions of 230 °C and 2.16 kg, and a crystallinity of 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 53 wt% of high-density polyethylene (with a melt index of 15 g / 10 min measured under the conditions of 190 °C and 2.16 kg), and 2 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (with a melt index of 10 g / 10 min measured under the conditions of 190 °C and 2.16 kg; the weight ratio between ethylene-propylene-diene monomer and high-density polyethylene is 60:40), and mix them evenly to obtain the resin for the upper surface matting layer 1.

[0118] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0119] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (isotacticity is 96%, with a melt index of 3 g / 10 min measured under the conditions of 230 °C and 2.16 kg) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0120] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0121] The total thickness of the film is 12 µm, among which the thickness of the upper surface matting 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.

[0122] Comparative Example 5

[0123] This comparative example provides a BOPP matting film, which includes an upper surface matting layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0124] The preparation method of the resin for each layer of the BOPP matting film provided in this comparative example includes the following steps:

[0125] Preparation of the resin for the upper surface matting layer 1: Take 45 wt% of random copolymer polypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 8 g / 10 min, and the crystallinity is 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 45 wt% of high-density polyethylene (the melt index measured under the conditions of 190 °C and 2.16 kg is 15 g / 10 min), and 10 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (the melt index measured under the conditions of 190 °C and 2.16 kg is 10 g / 10 min; the ratio between ethylene-propylene-diene monomer and high-density polyethylene is 60:40), and mix them evenly to obtain the resin for the upper surface matting layer 1.

[0126] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0127] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (the isotacticity is 96%, and the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 3 wt% of antiblocking agent (silica, with a particle size of 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0128] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0129] The total thickness of the film is 12 µm, among which the thickness of the upper surface matting 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.

[0130] Comparative Example 6

[0131] This comparative example provides a BOPP matting film, which includes an upper surface matting layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0132] The preparation method of the resin for each layer of the BOPP matting film provided in this comparative example includes the following steps:

[0133] Preparation of the resin for the upper surface extinction layer 1: Take 45 wt% of random copolymer polypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 8 g / 10 min, and the crystallinity is 30%); the ethylene-propylene block copolymer segment content with a elution temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the ethylene-propylene random copolymer segment content with a elution temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the homopolypropylene segment content with a elution temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 50 wt% of high-density polyethylene (the melt index measured under the conditions of 190 °C and 2.16 kg is 15 g / 10 min), and 5 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (the melt index measured under the conditions of 190 °C and 2.16 kg is 10 g / 10 min; the ratio between ethylene-propylene-diene monomer and high-density polyethylene is 45:55), and mix them evenly to obtain the resin for the upper surface extinction layer 1.

[0134] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0135] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (the isotacticity is 96%, and the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 3 wt% of antiblocking agent (silica, particle size is 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0136] The preparation method of the BOPP extinction film in this comparative example is the same as that in Example 1.

[0137] The total thickness of the film is 12 µm, among which the thickness of the upper surface extinction 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.

[0138] Comparative Example 7

[0139] This comparative example provides a BOPP extinction film, which includes an upper surface extinction layer 1, a middle core layer 2, and a lower surface layer 3 arranged in sequence. For the specific structure, please refer to Figure 1 .

[0140] The preparation method of the resin for each layer of the BOPP extinction film provided in this comparative example includes the following steps:

[0141] Preparation of the resin for the upper surface matting layer 1: Take 45 wt% of random copolymer polypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 8 g / 10 min, and the crystallinity is 30%); the content of ethylene-propylene block copolymer segments with a leaching temperature T2 ∈ [60, 95) °C is 70 wt%, and the crystallinity is 30%; the content of ethylene-propylene random copolymer segments with a leaching temperature T1 ∈ [25, 60) °C is 20 wt%, and the crystallinity is 12%; the content of homopolypropylene segments with a leaching temperature T3 ∈ [95, 140] °C is 10 wt%, and the crystallinity is 50%), 50 wt% of high-density polyethylene (the melt index measured under the conditions of 190 °C and 2.16 kg is 15 g / 10 min), and 5 wt% of ethylene-propylene-diene monomer / high-density polyethylene elastomer (the melt index measured under the conditions of 190 °C and 2.16 kg is 10 g / 10 min; the ratio between ethylene-propylene-diene monomer and high-density polyethylene is 75:25), and mix them evenly to obtain the resin for the upper surface matting layer 1.

[0142] Preparation of the resin for the middle core layer 2: Take 99 wt% of homopolypropylene (the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 1 wt% of antistatic agent (quaternary ammonium salt-based methacrylate copolymer antistatic agent), and mix them evenly to obtain the resin for the middle core layer 2.

[0143] Preparation of the resin for the lower surface layer 3: Take 97 wt% of homopolypropylene (the isotacticity is 96%, and the melt index measured under the conditions of 230 °C and 2.16 kg is 3 g / 10 min) and 3 wt% of antiblocking agent (silica, with a particle size of 4.5 µm), and mix them evenly to obtain the resin for the lower surface layer 3.

[0144] The preparation method of the BOPP matting film in this comparative example is the same as that in Example 1.

[0145] The total thickness of the film is 12 µm, among which the thickness of the upper surface matting 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.

[0146] The performance test results of the wear-resistant biaxially oriented polypropylene matting films in Examples 1 to 3 and the BOPP matting films in Comparative Examples 1 to 7 are shown in Table 1 below.

[0147] Table 1

[0148]

[0149] Combined with the above performance test data, it can be seen that:

[0150] For the BOPP matting film of Comparative Example 1, the content of ethylene-propylene block copolymer segments with the internal flushing temperature T2 of random copolymer polypropylene in the upper surface matting layer being in the range of [60, 95) °C is relatively low, which is not conducive to improving the hardness of the soft phase in the upper surface matting layer, resulting in poor scratch resistance of the matting surface and powder falling off the guide roller.

[0151] For the BOPP matting film of Comparative Example 2, the content of ethylene-propylene block copolymer segments with the internal flushing temperature T2 of random copolymer polypropylene in the upper surface matting layer is relatively high, and the crystallization temperature of random copolymer polypropylene is too high, which will lead to an accelerated crystallization rate, reduce the crystallization rate difference between high-density polyethylene and random copolymer polypropylene, and result in poor phase separation effect, affecting the matting effect.

[0152] For the BOPP matting film of Comparative Example 3, no ethylene-propylene-diene monomer / high-density polyethylene elastomer is added to the upper surface matting layer, which is not conducive to improving the hardness of the soft phase in the matting layer, resulting in very poor scratch resistance of the upper surface matting layer. During subsequent processing, obvious powder falling off occurs on the guide roller.

[0153] For the BOPP matting film of Comparative Example 4, the content of ethylene-propylene-diene monomer / high-density polyethylene elastomer added to the upper surface matting layer is too low, and the hardness of the soft-phase random copolymer polypropylene in the matting layer is insufficient, which is also not conducive to the formation of the core-shell structure, resulting in poor scratch resistance of the upper surface matting layer and powdering phenomenon.

[0154] For the BOPP matting film of Comparative Example 5, the content of ethylene-propylene-diene monomer / high-density polyethylene elastomer added to the upper surface matting layer is too high. Due to the excessive elastomer, the mechanical properties of the film decrease, resulting in a reduction in the tensile strength of the film. At the same time, the upper surface matting layer has poor scratch resistance and powdering phenomenon.

[0155] For the BOPP matting film of Comparative Example 6, when the proportion of ethylene-propylene-diene monomer to high-density polyethylene in the ethylene-propylene-diene monomer / high-density polyethylene elastomer added to the upper surface matting layer is too low, although the increase in high-density polyethylene is beneficial to improving the hardness of the ethylene-propylene-diene monomer / high-density polyethylene elastomer, too much content will cause appearance quality problems such as cracks in the matting layer during stretching.

[0156] For the BOPP matting film of Comparative Example 7, when the proportion of ethylene-propylene-diene monomer to high-density polyethylene in the ethylene-propylene-diene monomer / high-density polyethylene elastomer added to the upper surface matting layer is too high, too much ethylene-propylene-diene monomer will lead to a decrease in the strength of the high-density polyethylene and random copolymer polypropylene mixed system, affecting the mechanical properties of the film, thereby reducing the tensile strength of the film and being not conducive to film production.

[0157] A wear-resistant biaxially oriented polypropylene (BOPP) matte film of the present invention has a good matting effect, can improve the hardness of the soft-phase random copolymer polypropylene in the upper surface matting layer, not only improve the problem of scratches left during extrusion or displacement scratching, and enhance the scratch resistance of the film; but also effectively protect the high-density polyethylene from being rubbed off by external objects such as guide rollers when the matting layer is subjected to external forces (such as during secondary slitting and laminating processes when contacting guide rollers), reduce the occurrence of powdering phenomenon, meet the subsequent processing requirements of BOPP matte films, and adapt to high-speed automated production.

[0158] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and variations.

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 with a crystallinity of 25-35% 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 ethylene-propylene random copolymer chain segments with an elution temperature T1∈[25,60)°C, 60-80wt% ethylene-propylene block copolymer with an elution temperature T2∈[60,95)°C and a crystallinity of 25-35% The terpolymer EPDM rubber / high-density polyethylene elastomer is prepared by mixing terpolymer EPDM rubber and high-density polyethylene in a weight ratio of (50-60): (40-50) under the action of a crosslinking agent 1,4-bis(tert-butylperoxyisopropyl)benzene and a co-crosslinking agent triallyl isocyanuric acid using an internal mixer, and the melt index is 8-13 g / 10 min at 190°C and a load of 2.16 kg; the upper surface matte layer includes a core-shell structure with the high-density polyethylene as the core and the terpolymer EPDM rubber / high-density polyethylene elastomer as the shell.

2. 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%.

3. 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%, and the crystallinity of the homopolymerized polypropylene segment at the elution temperature T3∈[95,140]°C is 40-60%.

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

5. The method for preparing the wear-resistant biaxially oriented polypropylene matte film according to any one of claims 1 to 4, 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.

6. The method for preparing the wear-resistant biaxially oriented polypropylene matte film according to claim 5, 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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