CN118852793B

CN118852793B - BOPE extinction master batch, extinction film and preparation method thereof

Info

Publication number: CN118852793B
Application number: CN202411336335.0A
Authority: CN
Inventors: 赖仲平; 雷炳荣; 宋涛
Original assignee: GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Current assignee: GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Priority date: 2024-09-25
Filing date: 2024-09-25
Publication date: 2025-01-10
Anticipated expiration: 2044-09-25
Also published as: CN118852793A

Abstract

本发明涉及薄膜领域，特别是涉及一种BOPE消光母料、消光膜及其制备方法，BOPE消光母料包括30‑50wt%线性低密度聚乙烯、30‑50wt%聚丙烯、5‑10wt%长链支化聚乙烯、8‑15wt%聚丙烯接枝线性低密度聚乙烯和2‑3wt%PPA加工助剂。本发明所述的BOPE消光母料，通过加入特定配比的长链支化聚乙烯、聚丙烯接枝线性低密度聚乙烯和PPA加工助剂，提高了线性低密度聚乙烯对聚丙烯的包覆力，提高了消光母料熔体强度和耐热性，有效减少消光母料熔体破裂、减少了模头析出、延长了制膜连续生产周期。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

BOPE extinction master batch, extinction film and preparation method thereof

Technical Field

The invention relates to the field of films, in particular to a BOPE extinction master batch, an extinction film and a preparation method thereof.

Background

Biaxially Oriented Polyethylene (BOPE) film is a biaxially oriented film using polyethylene with a special structure as a main raw material, and has excellent impact resistance and pinhole resistance at low temperature. The BOPE film is taken as a recyclable material of a single material, is light in weight and environment-friendly, realizes the green and recyclable development of the material, and is widely applied to the industries of rice packaging, laundry detergent, frozen food packaging and the like. BOPE films have been developed over the years and are becoming increasingly interesting and useful to the market and clients, with BOPE matt films being especially touted. BOPE matt films are films that have a matt or matte effect due to diffuse reflection of light by the surface or internal microstructure of the film when light is incident on the film. The extinction film is used for product packaging, gives people a soft, fashionable and elegant high-grade feel, and can eliminate visual fatigue of people, so that the BOPE extinction film is widely applied to the packaging field.

At present, a BOPE extinction film is used for realizing an extinction effect in a common mode that an extinction layer is added with an extinction master batch and then is subjected to biaxial stretching, the melt viscosity difference between two phases is large, the copolymerized polyethylene in the extinction master batch system is a continuous phase, the polypropylene is a disperse phase, and the polypropylene (hard phase) is coated by the copolymerized polyethylene (soft phase) according to a soft-coating hard principle.

However, the existing BOPE extinction master batch still has the defects that firstly, the extinction master batch cannot bear the internal and external pressure difference of a die head, so that a melt is broken, the die head is quickly precipitated, the extinction master batch is easily adsorbed on a die lip, precipitation and accumulation are excessive, a film is uneven in longitudinal stripes and thickness, and the like, secondly, the heat resistance is insufficient, the accumulation on the die head is easily carbonized and falls to cause film breakage, so that frequent shutdown is required for cleaning the die head, and the production efficiency of a production line and the economic benefits of enterprises are seriously influenced.

Disclosure of Invention

The inventors have found from a lot of researches that, firstly, the melt fracture of BOPE matt master batch is caused by that, from the material characteristic, linear Low Density Polyethylene (LLDPE) has a plurality of short and regular branched chains on a molecular chain, which weakens the melt strength, and has insufficient coating capability on polypropylene (PP), and when the melt flows in a die head, the weak coating state is difficult to maintain a stable flow structure, and the melt fracture is easy to be initiated. In addition, the elastic effect of the extinction master batch outlet can be further enhanced, namely, when the melt leaves a narrow channel of a die head, extrusion swelling occurs, in the die head, the melt is sheared and stretched, molecular chains are in a certain orientation state, restraint disappears after the melt leaves the die head, the molecular chains try to recover a random curling state, the outlet is expanded, and further melt fracture is caused, and secondly, from the flowing state, the extinction master batch melt can generate wall sliding phenomenon in the die head, so that the whole flow of the melt is unstable, and once the flow loses stability, the melt fracture is very easy to occur.

In summary, in order to reduce melt fracture of the extinction master batch, reduce die head precipitation, improve coating force of the linear low-density polyethylene on polypropylene, improve melt strength and heat resistance of the extinction master batch, and prolong continuous production period of film making, the inventor finds that the addition of long-chain branched polyethylene (LCBPE) and polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) has obvious synergistic effect, and has key influence on the performance of the extinction master batch. On the one hand, LCBPE by virtue of the unique high melt strength and obvious strain hardening characteristics and the long-chain branched chain structure on the main chain, not only can the melt strength of the extinction master batch be effectively improved, the risk of melt fracture is reduced, but also the heat resistance of the extinction master batch can be improved. LCBPE has a star-branched structure, as if a stable frame is built inside the melt, the stability and deformation resistance of the melt are enhanced, and a solid foundation support is provided for the whole system. On the other hand, PP-g-LLDPE is focused on improving the coating properties between linear low density polyethylene and polypropylene. The linear low-density polyethylene can wrap polypropylene more tightly through the special grafting structure, so that the problems of phase separation and precipitation caused by poor compatibility are reduced, the die head precipitation is reduced, the quality of products and the continuity of production are improved, LCBPE stabilizes the internal structure of melt, PP-g-LLDPE optimizes the interfacial compatibility among different polymers, and the two cooperate to reduce melt fracture and further improve the coating force of the linear low-density polyethylene on the polypropylene, so that the extinction master batch has more excellent melt strength and processing performance on the premise of ensuring extinction effect, greatly prolongs the continuous production period of film making, and realizes the comprehensive improvement of the product performance.

It is known to those skilled in the art that, to achieve a matting effect, a dispersed phase (hard phase) and a matrix phase (soft phase) in a matting master batch have certain incompatibility between them at a certain stretching temperature, and the melt viscosity of the dispersed phase is higher than that of the matrix phase, when the crystallization speed or crystallinity of the dispersed phase is obviously higher than that of the matrix phase, the dispersed phase is easier to crystallize in a two-phase system to form a hard island phase, and when the matrix phase is relatively soft, uniform roughening of a film surface is achieved by stress stretching.

Based on the above, the invention aims to provide the BOPE extinction master batch, and the long-chain branched polyethylene (LCBPE), the polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) and the PPA processing aid are added in a specific proportion, so that the coating force of the linear low-density polyethylene (soft phase) to the polypropylene (hard phase) is improved, the melt strength and the heat resistance of the extinction master batch are improved, the melt fracture of the extinction master batch is effectively reduced, the die head precipitation is reduced, and the continuous production period of film making is prolonged.

The technical scheme of the invention is realized by the following steps:

A BOPE extinction master batch 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.

LCBPE has a long chain branch structure, when added into a delustering master batch system composed of LLDPE and PP, on the one hand, the long chain branches can interpenetrate and intertwine with molecular chains of LLDPE and PP, and the intertwining action is like forming a temporary 'network structure' among the molecular chains, so that the free movement of the molecular chains in a melt state is limited. The presence of long chain branches can also increase the relaxation time of the molecular chain. When the external force is applied, the molecular chains in the melt have more time to transfer and disperse the stress, so that the system can bear larger tensile stress without breaking, and the melt strength is further enhanced. LCBPE also has an effect on the crystallization process of LLDPE and PP, LCBPE can change the crystal form and size of the system, and smaller crystal size and irregular crystal form can reduce stress concentration among crystals, so that the system is more uniform and stable in a melt state, and the improvement of the melt strength is facilitated.

LCBPE long chain branches can also interact better with the molecular chains of LLDPE, increasing the entanglement density between the molecular chains, and can significantly increase the melt strength, especially at high temperatures and high shear rates. On the other hand, the long-chain branched structure of LCBPE forms more irregular forms, interface areas and refractive index difference areas on microscopic scale in LLDPE and PP systems, and becomes a light scattering center, which increases a tiny granular structure and interface discontinuous areas in the system, improves the light scattering probability, and realizes the extinction effect.

The invention limits that the adding amount of LCBPE-10wt% is limited, when the adding amount of LCBPE is less than 5wt%, the entanglement degree of the long-chain branched chains of LCBPE and LLDPE and PP molecular chains is lower, the melt strength is improved to a limited extent, and when the adding amount of LCBPE is more than 10wt%, on one hand, LCBPE can form a more complex microstructure in an LLDPE and PP system, and the complex structure can lead the scattering behavior of light rays in the material to become difficult to control, on the other hand, excessive long-chain branched chains can lead to local uneven areas in the material, the refractive index difference of the areas is increased, thereby causing irregular scattering of the light rays, leading the glossiness of the surface of the material to become extremely uneven, leading to 'mottled' visual effect, seriously affecting the appearance quality of products, and on the other hand, the fluidity of a extinction master batch melt can be excessively reduced, and the processability is affected.

The invention also adds a certain amount of polypropylene grafted linear low density polyethylene (PP-g-LLDPE) into the extinction master batch, on one hand, the PP chain segment and LLDPE chain segment in the PP-g-LLDPE are respectively interacted with PP and LLDPE in the system, so that the interface combination is improved, the phase separation is reduced, the system is uniform and stable, the coating of LLDPE on the PP is enhanced, on the other hand, the crystallization of the LLDPE and the PP system is uniformly refined by the aid of the PP-g-LLDPE, so that extinction is more uniform, and on the other hand, the grafting chain segment and the LLDPE molecular chain form a physical crosslinking point, so that the entanglement degree of the molecular chain of the system can be increased, the melt strength is improved, and the thermal stability of the extinction master batch is improved. On the basis, the invention also limits the content of the polypropylene grafted linear low-density polyethylene to 8-15wt%, if the content of the polypropylene grafted linear low-density polyethylene is less than 8wt%, the microstructure change of LLDPE and PP master batch system is limited, enough physical crosslinking points and entanglement points cannot be formed, the strength of melt is improved to a limited extent, the problem of quick precipitation of a die head cannot be effectively solved, and if the content of the polypropylene grafted linear low-density polyethylene is more than 15wt%, the microstructure of LLDPE and PP system is formed, a complex heterogeneous phase structure is formed, local agglomeration light scattering irregularity occurs, extinction uniformity is damaged, certain areas are dull, certain areas have higher glossiness, the surface flatness of the material is also influenced, optical performance parameters are difficult to control and stabilize, meanwhile, the melt viscosity is greatly increased, the fluidity is reduced, and the processing difficulty is increased.

The invention also adds a certain amount of PPA processing aid into the extinction master batch, and utilizes the characteristics that the PPA processing aid can move towards the outer layer of the melt and adhere to the surface of the die head to form a lubricating layer, thereby reducing friction, lowering shear rate and viscous drag, delaying melt fracture, weakening melt slip of the extinction master batch, and achieving dynamic balance during continuous extrusion so as to stabilize the extrusion process and product quality. Furthermore, the invention also limits the dosage of the PPA processing aid to be 2-3wt%, if the dosage of the PPA processing aid is more than 3wt%, the die lip PPA accumulation can influence the smoothness and efficiency of film making, and if the dosage of the PPA processing aid is less than 2wt%, the continuous lubrication layer is not formed, and the melt sliding and the production stability are influenced.

Further, the linear low density polyethylene has a melt index of 5 to 15g/10min measured at 190 ℃ under a load of 2.16kg, the linear low density polyethylene comprises one or more of a binary copolymer polyethylene formed by copolymerizing one of propylene, butene, hexene or octene with ethylene, and a ternary copolymer polyethylene comprising an ethylene-propylene-butene terpolymer, and the polypropylene has a melt index of 1 to 4g/10min measured at 230 ℃ under a load of 2.16kg, the polypropylene comprises one or more of a homo-polypropylene and a co-polypropylene, and the co-polypropylene comprises one or more of an ethylene-propylene binary copolymer and an ethylene-propylene-butylene terpolymer. The melt index of the linear low-density polyethylene and the melt index of the polypropylene are limited, so that a certain melt index difference is kept between the polypropylene and the linear low-density polyethylene, the overall haze of the extinction master batch is in a more ideal state, extinction effect is facilitated, however, if the melt index difference is too large, the polypropylene is difficult to disperse and crystal points are easy to generate, so that extinction effect is poor, and if the melt index difference is too small, the two-phase compatibility is good, and extinction film haze is reduced.

Further, the melting point of the long chain branched polyethylene is 135-140 ℃, the melt index of the long chain branched polyethylene is 3-5g/10min measured under the load of 2.16 kg at 190 ℃, and the branching degree is 0.4-0.9%. The melt point of the long-chain branched polyethylene is limited to 135-140 ℃, so that the extinction master batch has certain temperature resistance, the problem of carbonization drop of die head deposit is improved, the production smoothness is improved, on the other hand, long-chain branches of LCBPE can fully interact with molecular chains of LLDPE and PP to form more entanglement points and physical crosslinking points, the entanglement points and the crosslinking points can effectively limit the movement of the molecular chains, the elasticity and the tensile property of a melt are increased, the melt strength is improved, the problem of quick die head precipitation is effectively improved, the melt index of the long-chain branched polyethylene is limited to 3-5g/10min, the branching degree is 0.4-0.9%, the extinction master batch is favorable for maintaining reasonable melt strength and fluidity, a proper amount of branching can form certain entanglement among the molecular chains of the polymer, the entanglement can limit the movement of the molecular chains, and the fluidity of the melt is matched, so that the melt strength is improved. If the branching degree is less than 0.4%, the melt index of the long-chain branched polyethylene is too high, on one hand, the scattering and refraction of light in the material are less, the extinction effect is poor, on the other hand, the too low branching degree means that the entanglement degree among molecular chains is low, the molecular chains are relatively easy to slide, the melt is easy to flow and deform under the action of external force, the melt strength is low, if the branching degree is more than 0.9%, the melt index of the long-chain branched polyethylene is too low, on the one hand, the extinction effect is reduced, on the other hand, the polymer molecular chains form an excessively complex network structure, the fluidity of the melt is greatly reduced, and the processing difficulty is remarkably increased.

Further, the preparation method of the long chain branched polyethylene is a melt branching method, and comprises the following steps of uniformly mixing high-density polyethylene, an initiator and an ethylene-based polyfunctional monomer in proportion, extruding at 200 ℃, drawing, cooling, drying, granulating, vibrating and sieving, packaging to obtain the long chain branched polyethylene, wherein the melt index of the high-density polyethylene is 6-8g/10min under the load of 2.16 kg at 190 ℃. The melt branching method can realize continuous production of long-chain branched polyethylene, improves production efficiency, and preferably, the melt index of high-density polyethylene for preparing 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 extinction master batch.

Further, the melt index of the polypropylene grafted linear low density polyethylene is 0.5 to 2g/10min, and the grafting ratio of the linear low density polyethylene in the polypropylene grafted linear low density polyethylene is 0.8 to 1.1% measured under a load of 2.16kg at 230 ℃. Limiting the melt index of the polypropylene grafted linear low-density polyethylene to be 0.5-2g/10min, maintaining the extinction effect and melt processing fluidity of the extinction master batch, reducing melt fracture and die head precipitation, if the grafting rate of the polypropylene grafted linear low-density polyethylene is less than 0.8%, improving the melt strength is limited, the coating of the polypropylene by the linear low-density polyethylene is not facilitated, the precipitation cannot be effectively improved, the extinction effect is not facilitated to be ensured, the BOPP extinction film production efficiency is affected, and if the grafting rate of the polypropylene grafted linear low-density polyethylene is more than 1.1%, the melt fluidity is deteriorated, and the film making film is affected.

Further, the PPA processing aid is a fluoropolymer.

Further, the preparation method of the BOPE extinction master batch comprises the following steps of uniformly mixing linear low-density polyethylene, polypropylene, long-chain branched polyethylene, polypropylene grafted linear low-density polyethylene and PPA processing aid according to a proportion, extruding at 220-245 ℃, cooling, drying, granulating and sieving the extruded strips to obtain the BOPE extinction master batch.

The invention further provides a BOPE extinction film, which comprises an extinction layer, a core layer and a lower surface layer which are sequentially arranged, wherein the extinction layer comprises any one of the BOPE extinction master batches, the core layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1wt% of antistatic agent master batch, when the lower surface layer is a light surface layer, the lower surface layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1.0wt% of anti-blocking agent master batch, and when the lower surface layer is an extinction layer, the lower surface layer comprises 45-55wt% of copolymerized polyethylene and 45-55wt% of polypropylene.

Further, the copolymer polyethylene in the lower surface layer and the core layer comprises one or more of binary copolymer polyethylene and ternary copolymer polyethylene, the melt index of the copolymer polyethylene is 2-5g/10min measured under the load of 2.16kg at 190 ℃, the effective content of the antistatic agent in the antistatic agent master batch is 20-40wt%, the carrier is polyethylene, the effective content of the anti-blocking agent in the anti-blocking agent master batch is 6wt%, the anti-blocking agent is fumed silica, the D50 is 5 mu m, and the carrier is polyethylene.

The invention also provides a preparation method of the BOPE extinction film, which comprises the following steps:

under the condition of drying, the raw materials of the extinction layer, the core layer and the lower surface layer are weighed according to the proportion and uniformly mixed to obtain each layer of resin, and the resin is added into each extruder;

The resin of each layer is melted and plasticized in each extruder and then metered by a metering pump, and is converged at a T-shaped die through different extruder runners;

and cooling the thick sheet by a chill roll, performing shaping, performing longitudinal stretching in a longitudinal stretching region, performing transverse stretching in a transverse stretching region, performing trimming and trimming after the biaxial stretching of the film is completed, and performing corona and rolling to obtain the BOPE matt film.

The invention is described in detail below for a better understanding and implementation.

Detailed Description

It should be understood that the described embodiments are merely some, but not all embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the application, are intended to be within the scope of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.

The implementations described in the following exemplary examples do not represent all implementations consistent with the application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the application as detailed in the accompanying claims. In the description of the present application, it should be understood that the terms "first," "second," "third," and the like are used merely to distinguish between similar objects and are not necessarily used to describe a particular order or sequence, nor should they be construed to indicate or imply relative importance. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

Furthermore, in the description of the present application, unless otherwise indicated, "a plurality" means two or more. "and/or" describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate that there are three cases of a alone, a and B together, and B alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.

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

The BOPE extinction master batch of the embodiment 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. By adding long-chain branched polyethylene (LCBPE), polypropylene grafted linear low-density polyethylene (PP-g-LLDPE) and PPA processing aid in a specific proportion, the coating force of the linear low-density polyethylene on polypropylene is improved, the melt strength and heat resistance of the extinction master batch are improved, the melt fracture of the extinction master batch is effectively reduced, the die head precipitation is reduced, and the continuous production period of film making is prolonged.

Further, the linear low density polyethylene has a melt index of 5 to 15g/10min measured at 190 ℃ under a load of 2.16kg, the linear low density polyethylene comprises one or more of a binary copolymer polyethylene formed by copolymerizing one of propylene, butene, hexene or octene with ethylene, and a ternary copolymer polyethylene comprising one or more of an ethylene-propylene-butene terpolymer, and the polypropylene has a melt index of 1 to 4g/10min measured at 230 ℃ under a load of 2.16kg, the polypropylene comprises one or more of a homo-polypropylene and a co-polypropylene, and the co-polypropylene comprises one or more of an ethylene-propylene-butylene terpolymer. The melt index of the linear low-density polyethylene and the melt index of the polypropylene are limited, so that a certain melt index difference is kept between the polypropylene and the linear low-density polyethylene, the overall haze of the extinction master batch is in a more ideal state, extinction effect is facilitated, however, if the melt index difference is too large, the polypropylene is difficult to disperse and crystal points are easy to generate, so that extinction effect is poor, and if the melt index difference is too small, the two-phase compatibility is good, and extinction film haze is reduced.

Further, the long chain branched polyethylene has a melting point of 135-140 ℃, a melt index of 3-5g/10min, and a degree of branching of 0.4-0.9% measured at 190 ℃ under a load of 2.16 kg. The melting point of the long-chain branched polyethylene is limited to 135-140 ℃, on one hand, the extinction master batch has certain temperature resistance, the problem of carbonization dropping of die head deposit is improved, the production smoothness is improved, on the other hand, long-chain branches of LCBPE can fully interact with molecular chains of LLDPE and PP to form more entanglement points and physical crosslinking points, on the other hand, the entanglement points and the crosslinking points can effectively limit the movement of the molecular chains, the elasticity and the tensile property of a melt are increased, the melt strength is improved, the problem of quick die head precipitation is effectively improved, the melt index of the long-chain branched polyethylene is limited to 3-5g/10min, the branching degree is 0.4-0.9%, the extinction master batch is favorable for keeping proper melt strength and fluidity, and a proper amount of branching can form certain entanglement among the molecular chains of the polymer, the entanglement effect can limit the movement of the molecular chains and is favorable for the fluidity matching of the melt, so that the melt strength is improved. If the branching degree is less than 0.4%, the melt index of the long-chain branched polyethylene is too high, on one hand, the scattering and refraction of light in the material are less, the extinction effect is poor, on the other hand, the too low branching degree means that the entanglement degree among molecular chains is low, the molecular chains are relatively easy to slide, the melt is easy to flow and deform under the action of external force, the melt strength is low, if the branching degree is more than 0.9%, the melt index of the long-chain branched polyethylene is too low, on the one hand, the extinction effect is reduced, on the other hand, the polymer molecular chains form an excessively complex network structure, the fluidity of the melt is greatly reduced, and the processing difficulty is remarkably increased.

Further, the method for preparing the long chain branched polyethylene is a melt branching method, comprising the steps of adding 85.5wt% of high density polyethylene (melt index of 6-8g/10min measured under the load of 190 ℃ and 2.16 kg), 0.5wt% of initiator (DCP) and 4wt% of vinyl-based polyfunctional monomer into a high-speed mixer in proportion for premixing, uniformly mixing, adding the premixed materials into a double-screw extruder, extruding at the processing temperature of 200 ℃, drawing, cooling, drying, granulating, vibrating screen and packaging to obtain the long chain branched polyethylene. The melt branching method can realize continuous production of long-chain branched polyethylene, improves production efficiency, and preferably, the melt index of the high-density polyethylene for preparing 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 extinction master batch.

Further, the preparation method of the polypropylene grafted linear low density polyethylene comprises the following steps:

PP-g-MAH and ethylenediamine with 2 times of molar weight are dissolved in dimethylbenzene and react for 6 hours at 80 ℃ under the protection of nitrogen to generate PP-g-NH ₂;

PP-g-NH ₂ and LLDPE-g-MAH are dissolved in dimethylbenzene and react for 6 hours at 80 ℃ under the protection of nitrogen to generate PP-g-LLDPE with a long-chain branched structure;

The melt index of the polypropylene grafted linear low density polyethylene is 0.5-2g/10min measured under the load of 2.16kg at 230 ℃, and the grafting rate of the linear low density polyethylene in the polypropylene grafted linear low density polyethylene is 0.8-1.1%. The polypropylene adopts copolymerized polypropylene, the melt index is 1-4g/10min (230 ℃ and 2.16 kg), which is favorable for LLDPE grafting, and the melt index of the linear low-density polyethylene is 5-15g/10min (190 ℃ and 2.16 kg), which is the same as that of the linear low-density polyethylene used for the extinction master batch, and is favorable for improving the coating property between the linear low-density polyethylene and the polypropylene. Limiting the melt index of the polypropylene grafted linear low-density polyethylene to be 0.5-2g/10min, maintaining the extinction effect and melt processing fluidity of the extinction master batch, reducing melt fracture and die head precipitation, if the grafting rate of the polypropylene grafted linear low-density polyethylene is less than 0.8%, improving the melt strength is limited, the coating of the polypropylene by the linear low-density polyethylene is not facilitated, the precipitation cannot be effectively improved, the extinction effect is not facilitated to be ensured, the BOPP extinction film production efficiency is affected, and if the grafting rate of the polypropylene grafted linear low-density polyethylene is more than 1.1%, the melt fluidity is deteriorated, and the film making film is affected.

Further, the PPA processing aid is a fluoropolymer.

Further, the preparation method of the BOPE extinction master batch comprises the following steps of 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 proportion, fully mixing, stably feeding the mixed materials into a double-screw extruder at a set flow, controlling the extrusion temperature between 220 ℃ and 245 ℃ for extrusion, and cooling, drying, granulating and sieving the extruded strips to obtain the BOPE extinction master batch.

The invention further provides a BOPE extinction film which comprises an extinction layer, a core layer and a lower surface layer which are sequentially arranged, wherein the extinction layer comprises BOPE extinction master batch, the core layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1wt% of antistatic agent master batch, when the lower surface layer is a light surface layer, the lower surface layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1.0wt% of anti-blocking agent master batch, and when the lower surface layer is an extinction layer, the lower surface layer comprises 45-55wt% of copolymerized polyethylene and 45-55wt% of polypropylene.

Further, the copolymer polyethylene in the core layer and the lower surface layer comprises one or more of binary copolymer polyethylene and ternary copolymer polyethylene, the melt index of the copolymer polyethylene is 2-5g/10min measured under the load of 2.16kg at 190 ℃, the effective content of the antistatic agent in the antistatic agent master batch is 20-40wt%, the carrier is polyethylene, the effective content of the anti-blocking agent in the anti-blocking agent master batch is 6wt%, the anti-blocking agent is fumed silica, the D50 is 5 mu m, and the carrier is polyethylene.

Further, the thickness of the matting layer is 1.4-2.0 μm, the thickness of the lower surface layer is 0.8-1.0 μm, and the total thickness of the BOPE matting film is 12-22 μm.

under the condition of drying raw materials of the extinction layer, the core layer and the lower surface layer, weighing and uniformly mixing the raw materials according to a proportion, and adding each layer of resin obtained after the raw materials are uniformly mixed into each extruder;

The physical property indexes of the embodiment or the comparative example and the testing method thereof are specifically as follows:

the glossiness is measured according to GB/T10003-2008 standard by adopting a 45-degree angle method;

Haze measurement was performed according to GB/T10003-2008 standard;

Melt index determination was determined according to GB/T3682.1-2018 standard.

The shutdown interval time refers to the time from film making, start-up production to shutdown cleaning of the die lip.

The extinction uniformity is judged according to haze indexes of different positions of the extinction film and by combining visual observation of film surface quality.

It should be noted that the percentages by weight of the examples of the present invention and the comparative examples are shown in Table 1 below.

TABLE 1

The linear low-density polyethylene adopts ethylene-butene binary copolymer with the melt index of 10g/10min, the polypropylene adopts homo-polypropylene with the melt index of 1.5g/10min, the copolymerization polyethylene adopts propylene-ethylene binary copolymerization polyethylene with the melt index of 4g/10min, the antistatic agent master batch comprises glycerol monostearate as an effective component, the anti-blocking agent master batch is fumed silica with the D50 of 5 mu m, and the carrier is polyethylene.

Example 1

The embodiment provides a BOPE extinction master batch for preparing an extinction layer of a BOPE extinction film, wherein the BOPE extinction film comprises an extinction layer, a core layer and a lower surface layer which are sequentially arranged. The preparation method of the BOPE matt film resin comprises the following steps:

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40 wt% of polypropylene (melt index is 1.5g/10 min), 5wt% of LCBPE (melt index is 3g/10min, melting point is 140 ℃ and branching degree is 0.9%), 15wt% of PP-g-LLDPE (melt index is 2g/10min, grafting rate is 0.8%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, vibrating screen, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

The preparation of the core layer resin comprises the steps of uniformly mixing 99.2 weight percent of copolymerized polyethylene (with the melt index of 4g/10 min) and 0.8 weight percent of antistatic agent master batch (glycerol monostearate with the effective content of 30 weight percent and polyethylene as a carrier) to obtain the core layer resin.

The preparation of the lower surface layer resin comprises the steps of uniformly mixing 99.4wt% of copolymerized polyethylene (melt index is 4g/10 min) and 0.6wt% of anti-blocking agent master batch (fumed silica, D50 is 5 mu m and carrier polyethylene) to obtain the lower surface layer resin.

The preparation method of the BOPE extinction film of the embodiment comprises the following steps:

Under the condition of drying, the raw materials of the extinction layer, the core layer and the lower surface layer are weighed according to a proportion and uniformly mixed to obtain each layer of resin, and the resin is added into each extruder, wherein the temperature of the core layer and the lower surface layer extruder is 240 ℃, and the temperature of the extinction layer extruder is 245 ℃;

After being cooled by a chill roll, the thick sheet is longitudinally pulled and preheated, longitudinally pulled and shaped, the longitudinal pulling multiple is 5 times, the longitudinal pulling temperature is 110 ℃, the longitudinal pulling and shaping are carried out, the transverse pulling and preheating are carried out after the longitudinal pulling and shaping, the transverse pulling multiple is 8 times, the transverse pulling temperature is 125 ℃, the trimming and trimming are carried out after the two-way pulling of the film is completed, and then the BOPE matt film is obtained through corona and winding.

The total film thickness was 22. Mu.m, wherein the matting layer had a thickness of 1.6. Mu.m, the core layer had a thickness of 19.6. Mu.m, and the lower skin layer had a thickness of 0.8. Mu.m.

Example 2

This embodiment provides a BOPE extinction master batch, including extinction layer, sandwich layer and the lower top layer that sets gradually. The preparation method of the BOPE matt film resin comprises the following steps:

The preparation of the extinction layer resin comprises the steps of taking 39.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 10wt% of LCBPE (melt index is 5g/10min, melting point is 135 ℃ and branching degree is 0.4%), 8wt% of PP-g-LLDPE (melt index is 0.5g/10min, grafting rate is 1.1%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin. The preparation of the core layer resin comprises the steps of uniformly mixing 99.2 weight percent of copolymerized polyethylene (with the melt index of 4g/10 min) and 0.8 weight percent of antistatic agent master batch (glycerol monostearate with the effective content of 30 weight percent and polyethylene as a carrier) to obtain the core layer resin.

The preparation method of the BOPE matt film in this embodiment is the same as that in embodiment 1, and thus a description thereof will be omitted.

Example 3

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 4g/10min, melting point is 138 ℃ and branching degree is 0.6%), 12wt% of PP-g-LLDPE (melt index is 1.2g/10min, grafting rate is 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin. The preparation of the core layer resin comprises the steps of uniformly mixing 99.2 weight percent of copolymerized polyethylene (with the melt index of 4g/10 min) and 0.8 weight percent of antistatic agent master batch (glycerol monostearate with the effective content of 30 weight percent and polyethylene as a carrier) to obtain the core layer resin.

Example 4

The lower surface layer resin was prepared by uniformly mixing 54wt% of a copolymer polyethylene (melt index: 4g/10 min) and 46wt% of a polypropylene (melt index: 4g/10 min) to obtain a lower surface layer resin, the lower surface layer in this example being a matt layer.

Comparative example 1

This comparative example provides a BOPE matting masterbatch comprising a matting layer, a core layer and a lower surface layer set in sequence. The preparation method of the BOPE matt film resin of the comparative example comprises the following steps:

The preparation of the extinction layer resin comprises the steps of taking 47.5wt% of linear low-density polyethylene (with the melt index of 10g/10 min), 50wt% of polypropylene (with the melt index of 1.5g/10 min), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at the extrusion temperature of 245 ℃, cooling, drying, granulating, vibrating and sieving the extruded material strips, and packaging to obtain the BOPE extinction master batch, wherein the extinction master batch is used as the extinction layer resin.

The preparation method of the BOPE matting film of this comparative example is the same as that of example 1, and thus a description thereof will be omitted.

Comparative example 2

The preparation of the extinction layer resin comprises the steps of taking 49.5wt% of linear low density polyethylene (with a melt index of 10g/10 min), 40wt% of polypropylene (with a melt index of 1.5g/10 min), 8wt% of LCBPE (with a melt index of 4g/10min, a melting point of 138 ℃ and a branching degree of 0.6%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at an extrusion temperature of 245 ℃, cooling, drying, granulating, vibrating screen, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as extinction layer resin.

Comparative example 3

The preparation of the extinction layer resin comprises the steps of taking 45.5wt% of linear low density polyethylene (with a melt index of 10g/10 min), 40wt% of polypropylene (with a melt index of 1.5g/10 min), 12wt% of PP-g-LLDPE (with a melt index of 1.2g/10min and a grafting rate of 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at the extrusion temperature of 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as extinction layer resin.

Comparative example 4

The preparation of the extinction layer resin comprises the steps of taking 32wt% of linear low density polyethylene (melt index is 10g/10 min), 32.5wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 4g/10min, melting point is 138 ℃ and branching degree is 0.6%), 25wt% of PP-g-LLDPE (melt index is 1.2g/10min, grafting rate is 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

Comparative example 5

The preparation of the extinction layer resin comprises the steps of taking 32wt% of linear low density polyethylene (melt index is 10g/10 min), 33.5wt% of polypropylene (melt index is 1.5g/10 min), 20wt% of LCBPE (melt index is 4g/10min, melting point is 138 ℃ and branching degree is 0.6%), 12wt% of PP-g-LLDPE (melt index is 1.2g/10min, grafting rate is 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

Comparative example 6

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 7g/10min, melting point is 128 ℃ and branching degree is 0.1%), 12wt% of PP-g-LLDPE (melt index is 1.2g/10min, grafting rate is 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

Comparative example 7

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 2g/10min, melting point is 145 ℃ and branching degree is 1.5%), 12wt% of PP-g-LLDPE (melt index is 1.2g/10min, grafting rate is 0.9%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

The film processing difficulty of this comparative example is greater than that of example 1.

Comparative example 8

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 4g/10min, melting point is 138 ℃ and branching degree is 0.6%), 12wt% of PP-g-LLDPE (melt index is 5g/10min, grafting rate is 0.2%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, vibrating sieving and packaging the extruded materials to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

Comparative example 9

The preparation of the extinction layer resin comprises the steps of taking 37.5wt% of linear low density polyethylene (melt index is 10g/10 min), 40wt% of polypropylene (melt index is 1.5g/10 min), 8wt% of LCBPE (melt index is 4g/10min, melting point is 138 ℃ and branching degree is 0.6%), 12wt% of PP-g-LLDPE (melt index is 0.2g/10min, grafting rate is 1.8%), adding 2.5wt% of PPA processing aid into a high-speed mixer for fully mixing, adding the mixed materials into a double-screw extruder, extruding at 245 ℃, cooling, drying, granulating, sieving, packaging to obtain the BOPE extinction master batch, and taking the extinction master batch as the extinction layer resin.

The test results of properties of the BOPE matt concentrates and matt films of examples 1-4 and comparative examples 1-9 are shown in table 2 below.

TABLE 2

Comparative example 1 is a conventional matt film, in which only 8wt% of LCBPE is added, no PP-g-LLDPE is added, in which only 12wt% of PP-g-LLDPE is added, and no LCBPE is added, in which both the melt indices of the matt masterbatch systems of comparative example 2 and comparative example 3 are reduced, and the downtime is only slightly prolonged, indicating that the effect of improving the die precipitation is not obvious;

the addition of excessive LCBPE in comparative example 4 results in a matting masterbatch system with a melt index that is too low, a masterbatch melt that adheres more easily to the die, resulting in a reduced downtime interval, and also detrimental to matting uniformity, difficulty in formation, and draw film formation.

The addition of excess PP-g-LLDPE in comparative example 5 also resulted in too low a melt index of the matting masterbatch system, which resulted in too low a melt index of the matting masterbatch system, and the masterbatch melt was more likely to adhere to the die head, resulting in reduced downtime, detrimental to matting uniformity, difficult formation, and detrimental to stretch film formation.

As can be seen from the results of comparative examples 6 and 7, the branching degree of less than 0.4% results in a high LCBPE melt index, on the one hand, the haze of the extinction film is reduced, the extinction uniformity is also poor, on the other hand, the extinction effect is poor, mainly because the scattering and refraction of light inside the material are small, on the other hand, the shutdown interval time is remarkably shortened, mainly because the branching degree is low, the entanglement degree among molecular chains is low, the molecular chains are relatively easy to slide, the melt is easy to flow and deform when being acted by external force, the melt strength is low, the die head is still seriously analyzed, if the branching degree is more than 0.9%, the LCBPE melt index is excessively low, on the one hand, the haze of the extinction film is reduced, the extinction uniformity is also poor, the extinction effect is reduced, and on the other hand, the shutdown interval time is remarkably shortened, mainly because the polymer molecular chains form an excessively complex network structure, the fluidity of the melt is greatly reduced, and the master batch melt is easier to adsorb on the die head. As can be seen from the results of comparative examples 8 and 9 in Table 2, the grafting ratio of PP-g-LLDPE is less than 0.8%, the average haze value of the extinction film is reduced, the extinction uniformity is also deteriorated, the shutdown interval time is remarkably shortened, mainly because the extinction master batch has limited melt strength improvement, the coating of linear low density polyethylene on polypropylene is not facilitated, precipitation cannot be effectively improved, the extinction effect is not facilitated to be ensured, the BOPE extinction film production efficiency is influenced, the grafting ratio of PP-g-LLDPE is more than 1.1%, the average haze value of the extinction film is reduced, the extinction uniformity is also deteriorated, and the shutdown interval time is remarkably shortened, mainly because the melt flowability is deteriorated, and film forming is influenced.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the spirit of the invention, and the invention is intended to encompass such modifications and improvements.

Claims

1. The BOPE extinction master batch is characterized by comprising 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;

The linear low density polyethylene has a melt index of 5 to 15g/10min measured at 190 ℃, a melt index of 1 to 4g/10min measured at 230 ℃, a melt index of 2.16kg, a melt index of 135 to 140 ℃, a melt index of 3 to 5g/10min measured at 190 ℃, a melt index of 2.16kg, a branching degree of 0.4 to 0.9%, a melt index of 0.5 to 2g/10min measured at 230 ℃, a melt index of 2.16kg, and a grafting ratio of 0.8 to 1.1%.

2. The BOPE matt concentrate of claim 1, wherein the linear low density polyethylene comprises one or more of a binary copolymer polyethylene formed by copolymerizing one of propylene, butene, hexene, or octene with ethylene, and a ternary copolymer polyethylene comprising an ethylene-propylene-butene terpolymer, wherein the polypropylene comprises one or more of a homo-polypropylene and a copolymer polypropylene, and wherein the copolymer polypropylene comprises one or more of an ethylene propylene binary copolymer and an ethylene propylene butylene terpolymer.

3. The BOPE matt master batch according to claim 1, wherein the preparation method of the long chain branched polyethylene is a melt branching method, comprising the steps of extruding high density polyethylene, initiator and vinyl-based polyfunctional monomer at 200 ℃ after uniformly mixing the materials in proportion, drawing, cooling, drying, granulating, sieving and packaging to obtain the long chain branched polyethylene, wherein the melt index of the high density polyethylene is 6-8g/10min measured under the load of 190 ℃ and 2.16 kg.

4. A BOPE matt masterbatch according to claim 1, characterized in that said PPA processing aid is a fluoropolymer.

5. The BOPE extinction master batch according to claim 1, wherein the preparation method of the BOPE extinction master batch comprises the following steps of uniformly mixing linear low density polyethylene, polypropylene, long chain branched polyethylene, polypropylene grafted linear low density polyethylene and PPA processing aid according to a proportion, extruding at 220-245 ℃, cooling, drying, granulating and sieving the extruded strips to obtain the BOPE extinction master batch.

6. A BOPE extinction film is characterized by comprising an extinction layer, a core layer and a lower surface layer which are sequentially arranged, wherein the extinction layer comprises the BOPE extinction master batch according to any one of claims 1-5, the core layer comprises 99-99.5wt% of copolymerized polyethylene and 0.5-1 wt% of antistatic agent master batch, the lower surface layer is a gloss surface layer, and the lower surface layer comprises copolymerized polyethylene.

7. A BOPE matt film according to claim 6, wherein said co-polyethylene in said lower skin layer and said core layer comprises one or more of a binary co-polyethylene and a ternary co-polyethylene, said co-polyethylene having a melt index of from 2 to 5g/10min measured at 190 ℃ under a load of 2.16 kg.

8. A process for producing a BOPE matt film as claimed in any of claims 6 to 7, comprising the steps of:

after the resin of each layer is melted and plasticized in each extruder, the resin is measured by a metering pump, and is converged at a T-shaped die through different extruder runners to form a thick sheet;