A BOPE matte masterbatch, matte film and preparation method thereof

Abstract

The present invention relates to the field of films, and in particular to a BOPE matte masterbatch, a matte film and a preparation method thereof, wherein the BOPE matte masterbatch comprises 30-50wt% linear low-density polyethylene, 30-50wt% polypropylene, 5-10wt% long-chain branched polyethylene, 8-15wt% polypropylene grafted linear low-density polyethylene and 2-3wt% PPA processing aid. The BOPE matte masterbatch of the present invention improves the coating force of the linear low-density polyethylene on the polypropylene, improves the melt strength and heat resistance of the matte masterbatch, effectively reduces the melt fracture of the matte masterbatch, reduces die head precipitation, and prolongs the continuous production cycle of film making by adding a specific ratio of long-chain branched polyethylene, polypropylene grafted linear low-density polyethylene and PPA processing aid.

Description

Technical Field

[0001] The invention relates to the field of films, and in particular to a BOPE matte masterbatch, a matte film and a preparation method thereof. Background Art

[0002] Biaxially oriented polyethylene (BOPE) film is a biaxially oriented film made of special structural polyethylene as the main raw material. It has excellent impact resistance and pinhole resistance at low temperatures. As a single material recyclable material, BOPE film is lightweight and environmentally friendly, realizing the green and recyclable development of materials. It is widely used in rice packaging, laundry detergent, frozen food packaging and other industries. After years of development, BOPE film has received more and more attention and application from the market and customers, among which BOPE matte film is particularly popular. BOPE matte film is a film with matte or matte effect, which is caused by the diffuse reflection of light on the surface or internal microstructure of the film when light is incident on the film. Matt film is used for product packaging to give people a soft, stylish and elegant high-end feeling. At the same time, it can also eliminate people's visual fatigue. Therefore, the application of BOPE matte film in the packaging field will become more and more extensive.

[0003] At present, in order to achieve the matte effect of BOPE matte film, the common method is to add the matte masterbatch to the matte layer and then stretch it in both directions. The melt viscosity between the two phases is quite different. In the matte masterbatch system, the copolymer polyethylene is the continuous phase and the polypropylene is the dispersed phase. According to the principle of soft-encapsulating-hard, the polypropylene (hard phase) is mostly coated by the copolymer polyethylene (soft phase).

[0004] However, the existing BOPE matte masterbatch still has the following shortcomings: First, the matte masterbatch cannot withstand the pressure difference between the inside and outside of the die head, resulting in melt rupture, which leads to rapid die head precipitation, and the matte masterbatch is very easy to adsorb on the die lip, precipitate and accumulate too much, resulting in longitudinal stripes and uneven thickness of the film; second, the heat resistance is insufficient, the deposits on the die head are easily carbonized and fall off, causing film breakage, resulting in frequent shutdowns to clean the die head, seriously affecting the production efficiency of the production line and the economic benefits of the enterprise. Summary of the invention

[0005] The inventors have found through extensive research that the melt fracture of BOPE matte masterbatch is mainly caused by the following two reasons: First, from the perspective of material properties, there are many short and regular side chains on the molecular chain of linear low-density polyethylene (LLDPE), which weakens its melt strength and has insufficient coating ability for polypropylene (PP). When the melt flows in the die, this weak coating state is difficult to maintain a stable flow structure and easily causes melt fracture. In addition, the elastic effect of the matte masterbatch outlet will also aggravate this phenomenon: when the melt leaves the narrow channel of the die, extrusion swell will occur. In the die, the melt is sheared and stretched, and the molecular chain is in a certain orientation state. After leaving the die, the constraints disappear, and the molecular chain tries to restore the random curling state, resulting in expansion at the outlet, which in turn causes melt fracture; second, from the perspective of flow state, the matte masterbatch melt will experience wall slip inside the die, which makes the overall melt flow unstable. Once the flow loses stability, melt fracture is very likely to occur.

[0006] In summary, in order to reduce the melt fracture of the matte masterbatch, reduce die precipitation, improve the coating force of linear low-density polyethylene on polypropylene, improve the melt strength and heat resistance of the matte masterbatch, and extend the continuous production cycle of film making, the inventors found that the addition of long-chain branched polyethylene (LCBPE) and polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) has a significant synergistic effect, which plays a key role in improving the performance of the matte masterbatch. On the one hand, LCBPE, with its unique high melt strength and obvious strain hardening characteristics, as well as the long branched chain structure on the main chain, can not only effectively improve the melt strength of the matte masterbatch, reduce the risk of melt fracture, but also improve the heat resistance of the matte masterbatch. LCBPE has a star-shaped branched structure, which is like building a stable framework inside the melt, enhancing the stability and deformation resistance of the melt, and providing a solid foundation support for the entire system. On the other hand, PP-g-LLDPE focuses on improving the coating between linear low-density polyethylene and polypropylene. Through its special grafting structure, linear low-density polyethylene can wrap polypropylene more tightly, reducing phase separation and precipitation problems caused by poor compatibility, thereby reducing die head precipitation and improving product quality and production continuity; LCBPE stabilizes the internal structure of the melt, while PP-g-LLDPE optimizes the interface compatibility between different polymers. The two work synergistically to reduce melt fracture while further improving the coating force of linear low-density polyethylene on polypropylene, so that the matting masterbatch has better melt strength and processing performance while ensuring the matting effect, greatly extending the continuous production cycle of film making and achieving an overall improvement in product performance.

[0007] It is well known to those skilled in the art that in order to achieve the matte effect of BOPE matte film, under a certain stretching temperature, there must be a certain incompatibility between the dispersed phase (hard phase) and the matrix phase (soft phase) in the matte masterbatch, and the melt viscosity of the dispersed phase must be higher than that of the matrix phase. When the crystallization rate or degree of crystallinity of the dispersed phase is significantly higher than that of the matrix phase, the dispersed phase is more likely to crystallize first in the two-phase system to form a hard island phase. When the matrix phase is relatively soft, uniform coarsening of the film surface can be achieved through stress stretching.

[0008] Based on this, the purpose of the present invention is to provide a BOPE matte masterbatch, which improves the coating force of linear low-density polyethylene (soft phase) on polypropylene (hard phase) by adding a specific ratio of long-chain branched polyethylene (LCBPE), polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) and PPA processing aid, improves the melt strength and heat resistance of the matte masterbatch, effectively reduces the melt fracture of the matte masterbatch, reduces die head precipitation, and extends the continuous production cycle of film making.

[0009] The technical solution of the present invention is achieved by the following methods:

[0010] A BOPE matte masterbatch comprises 30-50wt% of linear low-density polyethylene, 30-50wt% of polypropylene, 5-10wt% of long-chain branched polyethylene, 8-15wt% of polypropylene grafted linear low-density polyethylene and 2-3wt% of PPA processing aid.

[0011] LCBPE has a long chain branch structure. When it is added to the matte masterbatch system composed of LLDPE and PP, on the one hand, its long chain branches can interweave and entangle with the molecular chains of LLDPE and PP. This entanglement is like forming a temporary "net structure" between the molecular chains, which limits the free movement of the molecular chains in the melt state. The presence of long chain branches can also increase the relaxation time of the molecular chains. When subjected to external forces, the molecular chains in the melt have more time to transmit and disperse stress, so that the system can withstand greater tensile stress without breaking, further enhancing the melt strength. LCBPE also affects the crystallization process of LLDPE and PP. LCBPE may change the crystal morphology and size of the system. Smaller crystal size and irregular crystal morphology can reduce stress concentration between crystals, making the system more uniform and stable in the melt state, which is conducive to improving melt strength.

[0012] The long chain branches of LCBPE can also better interact with the molecular chains of LLDPE, increase the entanglement density between the molecular chains, and significantly improve the melt strength, especially at high temperature and high shear rate. On the other hand, the long chain branch structure of LCBPE forms more irregular shapes, interface areas and refractive index difference areas on a microscopic scale in the LLDPE and PP system, becoming a light scattering center, which increases the tiny granular structure and interface discontinuous areas in the system, increases the probability of light scattering, and achieves an extinction effect.

[0013] The present invention limits the addition amount of LCBPE to 5-10wt%. When the addition amount of LCBPE is less than 5wt%, the degree of entanglement between the long chain branches of LCBPE and the molecular chains of LLDPE and PP is low, and the improvement of melt strength is limited. When the addition amount of LCBPE is greater than 10wt%, on the one hand, LCBPE will form a more complex microstructure in the LLDPE and PP system. This complex structure makes the scattering behavior of light inside the material difficult to control. On the other hand, too many long chain branches may cause local uneven areas to appear inside the material. The difference in refractive index of these areas increases, thereby causing irregular scattering of light, making the glossiness of the material surface extremely uneven, resulting in a "mottled" visual effect, seriously affecting the appearance quality of the product, and on the other hand, the fluidity of the matte masterbatch melt may be excessively reduced, affecting the processing performance.

[0014] The present invention also adds a certain amount of polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) into the matte masterbatch. On the one hand, the PP segment and the LLDPE segment in the PP-g-LLDPE are used to interact with the PP and LLDPE in the system respectively, so as to improve the interface bonding, reduce the phase separation, make the system uniform and stable, and enhance the coating of the PP by the LLDPE; on the other hand, the crystallization of the LLDPE and PP system is refined and uniform by means of the PP-g-LLDPE, so that the matte is more uniform; on the other hand, the grafted segment forms a physical cross-linking point with the LLDPE molecular chain, which can increase the entanglement degree of the molecular chain of the system, improve the melt strength and improve the thermal stability of the matte masterbatch. On this basis, the present invention further limits the content of polypropylene grafted linear low-density polyethylene to 8-15wt%. If the content of polypropylene grafted linear low-density polyethylene is less than 8wt%, the microstructure of the LLDPE and PP masterbatch system will be limited, and sufficient physical crosslinking points and entanglement points cannot be formed, so that the strength of the melt is limited, and the problem of fast die precipitation cannot be effectively improved; if the content of polypropylene grafted linear low-density polyethylene is greater than 15wt%, the microstructure of the LLDPE and PP system will form a complex and inhomogeneous phase structure, and local agglomeration will occur, resulting in irregular light scattering, destroying the extinction uniformity, making some areas dark and some areas high in gloss, and also affecting the surface flatness of the material, and making it difficult to control the stability of optical performance parameters, while greatly increasing the melt viscosity, reducing fluidity, and increasing the difficulty of processing.

[0015] The present invention also adds a certain amount of PPA processing aid to the matte masterbatch, utilizing the characteristics that the PPA processing aid will move to the outer layer of the melt and adhere to the surface of the die to form a lubricating layer, thereby reducing friction, reducing shear rate and viscous drag, delaying melt fracture, weakening the melt slip of the matte masterbatch, and achieving dynamic balance during continuous extrusion to stabilize the extrusion process and product quality. Furthermore, the present invention also limits the amount of PPA processing aid to 2-3wt%; if the amount of PPA processing aid is greater than 3wt%, it will cause PPA accumulation on the die lip, affecting the smoothness and efficiency of film making; if the amount of PPA processing aid is less than 2wt%, it is not conducive to the formation of a continuous lubricating layer, affecting melt slip and production stability.

[0016] Further, the melt index of the linear low-density polyethylene measured at 190°C and a load of 2.16kg is 5-15g / 10min, the linear low-density polyethylene includes one or more of a binary copolymer polyethylene and a ternary copolymer polyethylene, the binary copolymer polyethylene is formed by copolymerizing ethylene with one of propylene, butene, hexene or octene; the ternary copolymer polyethylene includes an ethylene-propylene-butene ternary copolymer; the melt index of the polypropylene measured at 230°C and a load of 2.16kg is 1-4g / 10min, the polypropylene includes one or more of a homopolymer polypropylene and a copolymer polypropylene; the copolymer polypropylene includes one or more of an ethylene-propylene binary copolymer polypropylene and an ethylene-propylene-butene ternary copolymer polypropylene. By limiting the melt index of linear low-density polyethylene and the melt index of polypropylene, a certain melt index difference is maintained between polypropylene and linear low-density polyethylene, so that the overall haze of the matte masterbatch reaches a more ideal state, which is beneficial to the matte effect; however, if the difference in melt index is too large, polypropylene is difficult to disperse and crystal points are easily generated, resulting in a poor matte effect; and if the difference in melt index is too small, the compatibility of the two phases is better, which will reduce the haze of the matte film.

[0017] Furthermore, the melting point of the long-chain branched polyethylene is 135-140° C.; the melt index of the long-chain branched polyethylene measured at 190° C. and a load of 2.16 kg is 3-5 g / 10 min, and the degree of branching is 0.4-0.9%. The melting point of the long-chain branched polyethylene is limited to 135-140°C. On the one hand, it can make the matte masterbatch have a certain temperature resistance, improve the problem of carbonization and falling of die deposits, and improve production smoothness. On the other hand, the long branches of LCBPE can fully interact with the molecular chains of LLDPE and PP to form more entanglement points and physical cross-linking points. These entanglement points and cross-linking points can effectively limit the movement of the molecular chains, increase the elasticity and tensile properties of the melt, thereby improving the melt strength and effectively improving the problem of fast die precipitation; the melt index of the long-chain branched polyethylene is limited to 3-5g / 10min and the branching degree is 0.4-0.9%, which is conducive to the matte masterbatch to maintain reasonable melt strength and fluidity. The right amount of branching can form a certain entanglement between the polymer molecular chains. This entanglement can limit the movement of the molecular chains and match the fluidity of the melt, thereby improving the melt strength. If the degree of branching is less than 0.4%, the melt index of the long-chain branched polyethylene will be too high. On the one hand, the light is less scattered and refracted inside the material, and the extinction effect is poor. On the other hand, too low a degree of branching means that the degree of entanglement between the molecular chains is low, and the molecular chains are relatively easy to slide. When subjected to external forces, the melt is prone to flow and deformation, and the melt strength is low. If the degree of branching is greater than 0.9%, the melt index of the long-chain branched polyethylene will be too low. On the one hand, the extinction effect is reduced, and on the other hand, the polymer molecular chains form an overly complex network structure, which greatly reduces the fluidity of the melt and significantly increases the difficulty of processing.

[0018] Furthermore, the preparation method of the long-chain branched polyethylene is a melt branching method, comprising the following steps: high-density polyethylene, an initiator and a vinyl multifunctional monomer are uniformly mixed in proportion, extruded at 200°C, stretched, cooled, dried, pelletized, vibrated, and packaged to obtain long-chain branched polyethylene, and the melt index of the high-density polyethylene is 6-8g / 10min at 190°C and a load of 2.16kg. The melt branching method can realize the continuous production of long-chain branched polyethylene and improve the production efficiency. Preferably, the melt index of the high-density polyethylene used to prepare the long-chain branched polyethylene is 6-8g / 10min, which can make the prepared long-chain branched polyethylene have better flow matching with other components in the matte masterbatch.

[0019] Furthermore, the melt index of the polypropylene grafted linear low-density polyethylene was measured to be 0.5-2g / 10min at 230°C and a load of 2.16kg, and the grafting rate of the linear low-density polyethylene in the polypropylene grafted linear low-density polyethylene was 0.8-1.1%. The melt index of the polypropylene grafted linear low-density polyethylene is limited to 0.5-2g / 10min, which can maintain the matting effect of the matting masterbatch and the melt processing fluidity, reduce melt fracture and die head precipitation; if the grafting rate of the polypropylene grafted linear low-density polyethylene is less than 0.8%, the melt strength is limited, which is not conducive to the coating of the linear low-density polyethylene on the polypropylene, and cannot effectively improve the precipitation, which is not conducive to ensuring the matting effect, and affects the production efficiency of the BOPP matt film; if the grafting rate of the polypropylene grafted linear low-density polyethylene is greater than 1.1%, the melt fluidity becomes poor, which affects the film formation.

[0020] Furthermore, the PPA processing aid is a fluorine-containing polymer.

[0021] Furthermore, the preparation method of the BOPE matte masterbatch comprises the following steps: linear low-density polyethylene, polypropylene, long-chain branched polyethylene, polypropylene grafted linear low-density polyethylene, and PPA processing aid are uniformly mixed according to a ratio, extruded at 220-245° C., and the extruded strips are cooled, dried, pelletized, and vibrated to obtain the BOPE matte masterbatch.

[0022] Furthermore, the present invention also provides a BOPE matte film, comprising a matte layer, a core layer and a lower surface layer arranged in sequence, the matte layer comprising any of the above-mentioned BOPE matte masterbatches; the core layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1wt% of antistatic agent masterbatch; when the lower surface layer is a glossy layer, it comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1.0wt% of anti-blocking agent masterbatch, and when the lower surface layer is a matte layer, it comprises 45-55wt% of copolymerized polyethylene and 45-55wt% of polypropylene.

[0023] Furthermore, the copolymer polyethylene in the lower surface layer and the core layer includes one or more of binary copolymer polyethylene and ternary copolymer polyethylene, and the melt index of the copolymer polyethylene is measured to be 2-5g / 10min at 190°C and a load of 2.16kg; the effective content of the antistatic agent in the antistatic agent masterbatch is 20-40wt%, and the carrier is polyethylene; the effective content of the antiblocking agent in the antiblocking agent masterbatch is 6wt%, the antiblocking agent is fumed silica, D50 is 5µm, and the carrier is polyethylene.

[0024] The present invention also provides a method for preparing any of the above-mentioned BOPE matte films, comprising the following steps:

[0025] The raw materials of the matt layer, the core layer and the lower surface layer are weighed and mixed according to the ratio under dry conditions, and the obtained resins of each layer are added into each extruder;

[0026] The resin of each layer is melted and plasticized in each extruder, and then metered by a metering pump, and converges at the T-die through different extruder flow channels;

[0027] The thick sheet is cooled by a chilled roller. After shaping, it first enters the longitudinal stretching area for longitudinal stretching, and then enters the transverse stretching area for transverse stretching. After the biaxial stretching of the film is completed, the edges are trimmed and then corona treated and rolled to obtain the BOPE matte film.

[0028] In order to better understand and implement the present invention, the present invention is described in detail below. DETAILED DESCRIPTION

[0029] It should be clear that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of the present application.

[0030] 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.

[0031] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0032] In addition, in the description of this application, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0033] It should be understood that the embodiments of the present application are not limited to the structures described above, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0034] The BOPE matte masterbatch of this embodiment includes 30-50wt% linear low-density polyethylene, 30-50wt% polypropylene, 5-10wt% long-chain branched polyethylene, 8-15wt% polypropylene grafted linear low-density polyethylene and 2-3wt% PPA processing aid. By adding a specific ratio of long-chain branched polyethylene (LCBPE), polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) and PPA processing aid, the coating force of linear low-density polyethylene on polypropylene is improved, the melt strength and heat resistance of the matte masterbatch are improved, the melt fracture of the matte masterbatch is effectively reduced, the die head precipitation is reduced, and the continuous production cycle of film making is extended.

[0035] Further, the melt index of the linear low density polyethylene measured at 190°C and a load of 2.16 kg is 5-15 g / 10 min, the linear low density polyethylene includes one or more of a binary copolymer polyethylene and a ternary copolymer polyethylene, the binary copolymer polyethylene is formed by copolymerizing ethylene with one of propylene, butene, hexene or octene; the ternary copolymer polyethylene includes one or more of ethylene-propylene-butene ternary copolymers; the melt index of the polypropylene measured at 230°C and a load of 2.16 kg is 1-4 g / 10 min, the polypropylene includes one or more of a homopolymer polypropylene and a copolymer polypropylene; the copolymer polypropylene includes one or more of an ethylene-propylene binary copolymer polypropylene and an ethylene-propylene-butene ternary copolymer polypropylene. By limiting the melt index of linear low-density polyethylene and the melt index of polypropylene, a certain melt index difference is maintained between polypropylene and linear low-density polyethylene, so that the overall haze of the matte masterbatch reaches a more ideal state, which is beneficial to the matte effect; however, if the difference in melt index is too large, polypropylene is difficult to disperse and crystal points are easily generated, resulting in a poor matte effect; and if the difference in melt index is too small, the compatibility of the two phases is better, which will reduce the haze of the matte film.

[0036] Furthermore, the melting point of the long-chain branched polyethylene is 135-140° C.; the melt index of the long-chain branched polyethylene measured at 190° C. and a load of 2.16 kg is 3-5 g / 10 min, and the degree of branching is 0.4-0.9%. The melting point of the long-chain branched polyethylene is limited to 135-140°C. On the one hand, it can make the matting masterbatch have a certain temperature resistance, improve the problem of carbonization and falling of die deposits, and improve production smoothness. On the other hand, the long branches of LCBPE can fully interact with the molecular chains of LLDPE and PP to form more entanglement points and physical cross-linking points. On the one hand, these entanglement points and cross-linking points can effectively limit the movement of the molecular chains, increase the elasticity and tensile properties of the melt, thereby improving the melt strength and effectively improving the problem of fast die precipitation; the melt index of the long-chain branched polyethylene is limited to 3-5g / 10min and the branching degree is limited to 0.4-0.9%, which is conducive to the matting masterbatch to maintain appropriate melt strength and fluidity. The right amount of branching can form a certain entanglement between the polymer molecular chains. This entanglement can limit the movement of the molecular chains, which is conducive to the fluidity matching of the melt, thereby improving the melt strength. If the degree of branching is less than 0.4%, the melt index of the long-chain branched polyethylene will be too high. On the one hand, the light is less scattered and refracted inside the material, and the extinction effect is poor. On the other hand, too low a degree of branching means that the degree of entanglement between the molecular chains is low, and the molecular chains are relatively easy to slide. When subjected to external forces, the melt is prone to flow and deformation, and the melt strength is low. If the degree of branching is greater than 0.9%, the melt index of the long-chain branched polyethylene will be too low. On the one hand, the extinction effect is reduced, and on the other hand, the polymer molecular chains form an overly complex network structure, which greatly reduces the fluidity of the melt and significantly increases the difficulty of processing.

[0037] Furthermore, the preparation method of long-chain branched polyethylene is a melt branching method, comprising the following steps: 85.5wt% high-density polyethylene (melt index measured at 190°C and 2.16kg load is 6-8g / 10min), 0.5wt% initiator (DCP), and 4wt% vinyl multifunctional monomer are added to a high-speed mixer in proportion for premixing to make them uniformly mixed, the premixed materials are added to a twin-screw extruder, extruded at a processing temperature of 200°C, and the long-chain branched polyethylene is obtained by drawing, cooling, drying, pelletizing, vibrating, and packaging. The melt branching method can realize the continuous production of long-chain branched polyethylene and improve the production efficiency; preferably, the melt index of the high-density polyethylene used to prepare the long-chain branched polyethylene is 6-8g / 10min, so that the prepared long-chain branched polyethylene can have better flow matching with other components in the matte masterbatch.

[0038] Furthermore, the preparation method of polypropylene grafted linear low-density polyethylene comprises the following steps:

[0039] PP-g-MAH and 2 times the molar amount of ethylenediamine were dissolved in xylene and reacted at 80°C for 6 hours under nitrogen protection to generate PP-g-NH2;

[0040] PP-g-NH2 and LLDPE-g-MAH were dissolved in xylene and reacted at 80°C for 6 hours under nitrogen protection to generate PP-g-LLDPE with a long-chain branched structure.

[0041] The melt index of polypropylene grafted linear low-density polyethylene is measured at 230°C and a load of 2.16kg to be 0.5-2g / 10min, and the grafting rate of linear low-density polyethylene in polypropylene grafted linear low-density polyethylene is 0.8-1.1%. The polypropylene adopts copolymerized polypropylene, and the melt index is 1-4g / 10min (230°C, 2.16kg), which is conducive to LLDPE grafting; the melt index of the linear low-density polyethylene is 5-15g / 10min (190°C, 2.16kg), which is the same as the linear low-density polyethylene used in the matte masterbatch, which is conducive to improving the coating between the linear low-density polyethylene and the polypropylene. The melt index of polypropylene grafted linear low-density polyethylene is limited to 0.5-2g / 10min, which can maintain the matting effect of the matting masterbatch and the melt processing fluidity, and reduce melt fracture and die head precipitation; if the grafting rate of polypropylene grafted linear low-density polyethylene is less than 0.8%, the melt strength is limited, which is not conducive to the coating of polypropylene by linear low-density polyethylene, and cannot effectively improve precipitation, which is not conducive to ensuring the matting effect and affecting the production efficiency of BOPP matt film; if the grafting rate of polypropylene grafted linear low-density polyethylene is greater than 1.1%, the melt fluidity will deteriorate, affecting film making and film formation.

[0042] Furthermore, the PPA processing aid is a fluorine-containing polymer.

[0043] Furthermore, the preparation method of the BOPE matte masterbatch comprises the following steps: adding linear low-density polyethylene, polypropylene, long-chain branched polyethylene, polypropylene grafted linear low-density polyethylene, and PPA processing aid into a high-speed mixer according to a ratio for thorough mixing, feeding the mixed materials stably into a twin-screw extruder at a set flow rate, controlling the extrusion temperature between 220-245° C. for extrusion, cooling, drying, pelletizing, and vibrating the extruded strips to obtain the BOPE matte masterbatch.

[0044] Furthermore, the present invention also provides a BOPE matte film comprising a matte layer, a core layer and a lower surface layer which are arranged in sequence, the matte layer comprising a BOPE matte masterbatch; the core layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1wt% of an antistatic agent masterbatch; when the lower surface layer is a glossy layer, it comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1.0wt% of an anti-blocking agent masterbatch, and when the lower surface layer is a matte layer, it comprises 45-55wt% of copolymerized polyethylene and 45-55wt% of polypropylene.

[0045] Furthermore, the copolymer polyethylene in the core layer and the lower surface layer includes one or more of binary copolymer polyethylene and ternary copolymer polyethylene, and the melt index of the copolymer polyethylene is measured to be 2-5g / 10min at 190°C and a load of 2.16kg; the effective content of the antistatic agent in the antistatic agent masterbatch is 20-40wt%, and the carrier is polyethylene; the effective content of the antiblocking agent in the antiblocking agent masterbatch is 6wt%, the antiblocking agent is fumed silica, D50 is 5µm, and the carrier is polyethylene.

[0046] Furthermore, the thickness of the matt layer is 1.4-2.0µm, the thickness of the lower surface layer is 0.8-1.0µm, and the total thickness of the BOPE matt film is 12-22µm.

[0047] The present invention also provides a method for preparing any of the above-mentioned BOPE matte films, comprising the following steps:

[0048] The raw materials of the matt layer, the core layer and the lower surface layer are weighed and mixed in a dry state according to the ratio to obtain the resins of each layer, and then added into each extruder;

[0049] The resin of each layer is melted and plasticized in each extruder, and then metered by a metering pump, and converges at the T-die through different extruder flow channels;

[0050] The thick sheet is cooled by a chilled roller. After shaping, it first enters the longitudinal stretching area for longitudinal stretching, and then enters the transverse stretching area for transverse stretching. After the biaxial stretching of the film is completed, the edges are trimmed and then corona treated and rolled to obtain the BOPE matte film.

[0051] The physical properties and test methods of the embodiments or comparative examples of the present invention are as follows:

[0052] Glossiness is measured according to GB / T 10003-2008 standard, using the 45° angle method;

[0053] The haze is measured according to GB / T 10003-2008 standard;

[0054] The melt index is determined according to GB / T 3682.1-2018 standard.

[0055] The downtime interval refers to the time from starting film production to stopping to clean the die lip.

[0056] The matt uniformity is determined by the haze index at different positions of the matt film combined with visual observation of the film surface quality.

[0057] It should be noted that the proportions described in the embodiments of the present invention or comparative examples are all weight percentages. The components and contents of each layer in the embodiments of the present invention and comparative examples are shown in Table 1 below.

[0058] Table 1

[0059]

[0060] Among them, the linear low-density polyethylene adopts ethylene-butene binary copolymer with a melt index of 10g / 10min; the polypropylene adopts homopolymer polypropylene with a melt index of 1.5g / 10min; the copolymer polyethylene adopts propylene-ethylene binary copolymer polyethylene with a melt index of 4g / 10min; the effective component of the antistatic agent masterbatch is propylene monostearate; the anti-blocking agent masterbatch is fumed silica with a D50 of 5µm and a carrier of polyethylene.

[0061] Example 1

[0062] The present embodiment provides a BOPE matte masterbatch for preparing a matte layer of a BOPE matte film, wherein the BOPE matte film comprises a matte layer, a core layer and a lower surface layer arranged in sequence. The method for preparing each layer of resin of the BOPE matte film of the present embodiment comprises the following steps:

[0063] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 5wt% LCBPE (melt index of 3g / 10min, melting point of 140°C, branching degree of 0.9%), 15wt% PP-g-LLDPE (melt index of 2g / 10min, grafting rate of 0.8%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0064] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0065] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0066] The preparation method of the BOPE matte film of this embodiment comprises the following steps:

[0067] The raw materials of the matt layer, the core layer and the lower surface layer are weighed and mixed in a dry state according to a ratio to obtain resins of each layer, and then added to each extruder; wherein the temperature of the extruders of the core layer and the lower surface layer is 240°C, and the temperature of the extruder of the matt layer is 245°C;

[0068] The resin of each layer is melted and plasticized in each extruder, and then metered by a metering pump, and converges at the T-die through different extruder flow channels;

[0069] After the thick sheet is cooled by the chilled roller, it is first preheated by longitudinal stretching, then stretched longitudinally, the longitudinal stretching multiple is 5 times, the longitudinal stretching temperature is 110°C, then it is shaped by longitudinal stretching, and after longitudinal stretching and shaping, it is preheated by transverse stretching, and then stretched transversely, the transverse stretching multiple is 8 times, the transverse stretching temperature is 125°C. After the biaxial stretching of the film is completed, the edges are trimmed and then corona treated and rolled to obtain the BOPE matte film.

[0070] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0071] Example 2

[0072] The present embodiment provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of the present embodiment comprises the following steps:

[0073] Preparation of matt layer resin: 39.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 10wt% LCBPE (melt index of 5g / 10min, melting point of 135°C, branching degree of 0.4%), 8wt% PP-g-LLDPE (melt index of 0.5g / 10min, grafting rate of 1.1%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin. Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0074] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0075] The preparation method of the BOPE matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0076] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0077] Example 3

[0078] The present embodiment provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of the present embodiment comprises the following steps:

[0079] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin. Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0080] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0081] The preparation method of the BOPE matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0082] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0083] Example 4

[0084] The present embodiment provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of the present embodiment comprises the following steps:

[0085] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin. Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0086] Preparation of lower surface layer resin: 54wt% copolymerized polyethylene (melt index is 4g / 10min) and 46wt% polypropylene (melt index is 4g / 10min) are mixed evenly to obtain a lower surface layer resin. The lower surface layer of this embodiment is a matte layer.

[0087] The preparation method of the BOPE matte film of this embodiment is the same as that of Embodiment 1, so it is not described in detail.

[0088] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0089] Comparative Example 1

[0090] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0091] Preparation of matte layer resin: 47.5wt% linear low-density polyethylene (melt index of 10g / 10min), 50wt% polypropylene (melt index of 1.5g / 10min), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, and extruded at an extrusion temperature of 245°C. The extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matte masterbatch, which is used as the matte layer resin.

[0092] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0093] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0094] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0095] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0096] Comparative Example 2

[0097] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0098] Preparation of matte layer resin: 49.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, degree of branching of 0.6%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, and vibrated, and packaged to obtain BOPE matte masterbatch, which is used as the matte layer resin.

[0099] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0100] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0101] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0102] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0103] Comparative Example 3

[0104] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0105] Preparation of matt layer resin: 45.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, which is used as the matt layer resin.

[0106] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0107] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0108] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0109] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0110] Comparative Example 4

[0111] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0112] Preparation of matt layer resin: 32wt% linear low-density polyethylene (melt index of 10g / 10min), 32.5wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 25wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0113] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0114] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0115] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0116] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0117] Comparative Example 5

[0118] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0119] Preparation of matt layer resin: 32wt% linear low-density polyethylene (melt index of 10g / 10min), 33.5wt% polypropylene (melt index of 1.5g / 10min), 20wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0120] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0121] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0122] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0123] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0124] Comparative Example 6

[0125] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0126] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 7g / 10min, melting point of 128°C, branching degree of 0.1%), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0127] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0128] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0129] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0130] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0131] Comparative Example 7

[0132] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0133] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 2g / 10min, melting point of 145°C, branching degree of 1.5%), 12wt% PP-g-LLDPE (melt index of 1.2g / 10min, grafting rate of 0.9%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0134] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0135] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0136] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0137] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0138] The film processing difficulty of this comparative example is greater than that of Example 1.

[0139] Comparative Example 8

[0140] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0141] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 12wt% PP-g-LLDPE (melt index of 5g / 10min, grafting rate of 0.2%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0142] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0143] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0144] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0145] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0146] Comparative Example 9

[0147] This comparative example provides a BOPE matte masterbatch, comprising a matte layer, a core layer and a lower surface layer arranged in sequence. The preparation method of each layer of resin of the BOPE matte film of this comparative example comprises the following steps:

[0148] Preparation of matt layer resin: 37.5wt% linear low-density polyethylene (melt index of 10g / 10min), 40wt% polypropylene (melt index of 1.5g / 10min), 8wt% LCBPE (melt index of 4g / 10min, melting point of 138°C, branching degree of 0.6%), 12wt% PP-g-LLDPE (melt index of 0.2g / 10min, grafting rate of 1.8%), and 2.5wt% PPA processing aid are added to a high-speed mixer for thorough mixing, and the mixed materials are added to a twin-screw extruder, extruded at an extrusion temperature of 245°C, and the extruded material strips are cooled, dried, pelletized, vibrated, and packaged to obtain BOPE matt masterbatch, and the matt masterbatch is used as the matt layer resin.

[0149] Preparation of core layer resin: 99.2wt% copolymer polyethylene (melt index is 4g / 10min) and 0.8wt% antistatic agent masterbatch (propylene glycol monostearate, effective content is 30wt%, carrier is polyethylene) are uniformly mixed to obtain core layer resin.

[0150] Preparation of lower surface layer resin: 99.4wt% copolymer polyethylene (melt index is 4g / 10min) and 0.6wt% anti-blocking agent masterbatch (fumed silica, D50 is 5µm, carrier polyethylene) are mixed evenly to obtain the lower surface layer resin.

[0151] The preparation method of the BOPE matte film in this comparative example is the same as that in Example 1, so it is not described in detail.

[0152] The total thickness of the film is 22µm, of which the matte layer is 1.6µm, the core layer is 19.6µm, and the lower surface layer is 0.8µm.

[0153] The performance test results of the BOPE matte masterbatch and matte film of Examples 1-4 and Comparative Examples 1-9 are shown in Table 2 below.

[0154] Table 2

[0155]

[0156] Comparative Example 1 is a conventional matte film, in Comparative Example 2, only 8 wt% LCBPE is added, and no PP-g-LLDPE is added, and in Comparative Example 3, only 12 wt% PP-g-LLDPE is added, and no LCBPE is added. Compared with Comparative Example 1, the melt index of the matte masterbatch system of Comparative Example 2 and Comparative Example 3 is reduced, and the downtime interval is only slightly extended, indicating that the effect of improving die head precipitation is not obvious;

[0157] In Comparative Example 4, excessive LCBPE was added, resulting in a too low melt index of the matte masterbatch system. The masterbatch melt was more likely to adhere to the die head, resulting in a shortened downtime interval, and was not conducive to the uniformity of matte, molding difficulties, and stretching film formation.

[0158] Adding an excessive amount of PP-g-LLDPE in Comparative Example 5 also results in too low a melt index of the matte masterbatch system, which makes the masterbatch melt more easily adhere to the die head, resulting in a shortened downtime interval, which is not conducive to the uniformity of matte, difficulty in molding, and not conducive to stretching and film forming.

[0159] It can be seen from the results of Comparative Examples 6 and 7 that a degree of branching less than 0.4% will result in an excessively high melt index of LCBPE. On the one hand, the haze of the matte film is reduced, the matte uniformity is also deteriorated, and the matte effect is poor, mainly because the light is less scattered and refracted inside the material, and on the other hand, the downtime interval is significantly shortened, mainly because the low degree of branching leads to a low degree of entanglement between molecular chains, and the molecular chains are relatively easy to slide. When subjected to external forces, the melt is prone to flow and deformation, the melt strength is low, and die head segregation is still serious; if the degree of branching is greater than 0.9%, the LCBPE melt index will be too low. On the one hand, the haze of the matte film is reduced, the matte uniformity is also deteriorated, and the matte effect is reduced. On the other hand, the downtime interval is significantly shortened, mainly because the polymer molecular chains form an overly complex network structure, which greatly reduces the fluidity of the melt and makes the masterbatch melt more easily adsorbed on the die head. Combining the results of Comparative Examples 8 and 9 in Table 2, it can be seen that the grafting rate of PP-g-LLDPE is less than 0.8%, the average value of the haze of the matte film is reduced, the matte uniformity is also deteriorated, and the shutdown interval is significantly shortened. This is mainly because the melt strength of the matte masterbatch is limited, which is not conducive to the coating of linear low-density polyethylene on polypropylene, and cannot effectively improve precipitation, which is not conducive to ensuring the matte effect and affecting the production efficiency of BOPE matte film; the grafting rate of PP-g-LLDPE is greater than 1.1%, the average value of the haze of the matte film is reduced, the matte uniformity is also deteriorated, and the shutdown interval is significantly shortened, mainly because the melt fluidity is deteriorated, which affects the film formation.

[0160] 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 BOPE matte masterbatch, characterized in that: It includes 30-50wt% linear low-density polyethylene, 30-50wt% polypropylene, 5-10wt% long-chain branched polyethylene, 8-15wt% polypropylene grafted linear low-density polyethylene and 2-3wt% PPA processing aid; The melt index of the linear low-density polyethylene measured at 190°C and a load of 2.16kg is 5-15g / 10min, the melt index of the polypropylene measured at 230°C and a load of 2.16kg is 1-4g / 10min, the melting point of the long-chain branched polyethylene is 135-140°C, the melt index of the long-chain branched polyethylene measured at 190°C and a load of 2.16kg is 3-5g / 10min, the degree of branching of the long-chain branched polyethylene is 0.4-0.9%, the melt index of the polypropylene-grafted linear low-density polyethylene measured at 230°C and a load of 2.16kg is 0.5-2g / 10min, and the grafting rate of the linear low-density polyethylene in the polypropylene-grafted linear low-density polyethylene is 0.8-1.1%.

2. The BOPE matte masterbatch according to claim 1, characterized in that: The linear low-density polyethylene includes one or more of a binary copolymer polyethylene and a ternary copolymer polyethylene, the binary copolymer polyethylene is formed by copolymerizing one of propylene, butene, hexene or octene with ethylene, and the ternary copolymer polyethylene includes an ethylene-propylene-butene ternary copolymer; the polypropylene includes one or more of a homopolymer polypropylene and a copolymer polypropylene; the copolymer polypropylene includes one or more of an ethylene-propylene binary copolymer polypropylene and an ethylene-propylene-butene ternary copolymer polypropylene.

3. The BOPE matte masterbatch according to claim 1, characterized in that: The preparation method of the long-chain branched polyethylene is a melt branching method, comprising the following steps: high-density polyethylene, an initiator and a vinyl multifunctional monomer are uniformly mixed in proportion, extruded at 200° C., stretched, cooled, dried, pelletized, vibrated, and packaged to obtain long-chain branched polyethylene. The melt index of the high-density polyethylene is measured to be 6-8 g / 10 min at 190° C. and a load of 2.16 kg.

4. The BOPE matte masterbatch according to claim 1, characterized in that: The PPA processing aid is a fluorine-containing polymer.

5. The BOPE matte masterbatch according to claim 1, characterized in that: The preparation method of the BOPE matte masterbatch comprises the following steps: linear low-density polyethylene, polypropylene, long-chain branched polyethylene, polypropylene grafted linear low-density polyethylene, and PPA processing aid are uniformly mixed according to a proportion, extruded at 220-245° C., and the extruded strips are cooled, dried, pelletized, and vibrated to obtain the BOPE matte masterbatch.

6. A BOPE matte film, characterized in that: It comprises a matte layer, a core layer and a lower surface layer arranged in sequence, the matte layer comprises the BOPE matte masterbatch described in any one of claims 1 to 5; the core layer comprises 99-99.5wt% of copolymer polyethylene and 0.5-1wt% of antistatic agent masterbatch; the lower surface layer is a glossy layer, and the lower surface layer comprises copolymer polyethylene.

7. The BOPE matte film according to claim 6, characterized in that: The copolymer polyethylene in the lower surface layer and the core layer includes one or more of binary copolymer polyethylene and ternary copolymer polyethylene, and the melt index of the copolymer polyethylene measured at 190° C. and a load of 2.16 kg is 2-5 g / 10 min.

8. A method for preparing a BOPE matte film as claimed in any one of claims 6 to 7, characterized in that: The following steps are involved: The raw materials of the matt layer, the core layer and the lower surface layer are weighed and mixed according to the ratio under dry conditions, and the obtained resins of each layer are added into each extruder; The resin of each layer is melted and plasticized in each extruder, and then metered by a metering pump, and then converged at the T-die through different extruder flow channels to form a thick sheet; The thick sheet is cooled by a chilled roller. After shaping, it first enters the longitudinal stretching area for longitudinal stretching, and then enters the transverse stretching area for transverse stretching. After the biaxial stretching of the film is completed, the edges are trimmed and then corona treated and rolled to obtain the BOPE matte film.

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