CN119159889B

CN119159889B - BOPE extinction film and preparation method thereof

Info

Publication number: CN119159889B
Application number: CN202411657545.XA
Authority: CN
Inventors: 雷炳荣; 赖仲平; 宋涛; 乔胜琦
Original assignee: GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Current assignee: GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Priority date: 2024-11-20
Filing date: 2024-11-20
Publication date: 2025-01-17
Anticipated expiration: 2044-11-20
Also published as: CN119159889A

Abstract

The invention belongs to the field of films, and relates to a BOPE extinction film and a preparation method thereof, wherein the BOPE extinction film comprises an extinction layer, a core layer and a lower surface layer which are sequentially arranged, the extinction layer comprises 22-47.5wt% of first metallocene linear low-density polyethylene, 38-48wt% of polypropylene and 10-30wt% of propylene copolymer, the melting point of the propylene copolymer is 140-160 ℃ and the crystallinity is 5-10%, and the core layer and the lower surface layer both comprise second metallocene linear low-density polyethylene. According to the BOPE extinction film, the propylene-based copolymer with a certain proportion and high melting point, high transparency and low crystallization is added into the extinction layer, so that the temperature resistance of the extinction layer is improved, the extinction effect of the extinction film is improved, and the production efficiency and the use efficiency of the extinction film are improved.

Description

BOPE extinction film and preparation method thereof

Technical Field

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

Background

With the continuous push of single material recycling, biaxially oriented BOPE films are becoming a popular packaging material. Among them, BOPE matt films have attracted attention in packaging because of their softer texture. The extinction principle of the BOPE extinction film is that in the gradual and rapid stretching process of the extinction film thick sheet, the incompatible polyolefin phase of the extinction layer has different responses to stretching force due to the difference of viscosity and crystallization rate, the disperse phase protrudes under stretching to form a rough surface, and the extinction surface layer scatters light to different degrees so as to play a role in adjusting gloss, and the gloss is soft and high-grade packaging texture is provided.

In BOPE matt film production, the polypropylene phase crystallized first in the matt layer is a dispersed phase, commonly called island phase with a sea-island structure, and the continuous phase crystallized later and having low crystallinity is a sea phase with a sea-island structure, because the thermodynamic compatibility of the two phases is poor, the viscosity difference is large, and the island phase crystallized first during stretching is easier to bulge. However, in the BOPE matt film, polyethylene is used as a continuous phase, although the crystallization temperature is lower than that of a dispersed phase, the crystallization rate is relatively faster and the crystallization degree is relatively higher, and the too fast crystallization rate leads to poor adhesion of a thick sheet, narrow stretching window, difficult adjustment of thickness and meanwhile, no good matt effect can be obtained. In addition, the extinction layer of the BOPE extinction film adopts metallocene linear low-density polyethylene as a continuous phase, so that the melting point is low, the temperature resistance is poor when the BOPE extinction film is produced, and the film surface is easy to be scalded by a high-temperature roller to form a film surface flaw, so that a craftsman can produce the BOPE extinction film by cooling, but the production difficulty is increased due to poor roller pasting of thick plates produced by cooling, and the lower production efficiency is one of the reasons for restricting the incapability of expanding the BOPE extinction film.

Disclosure of Invention

Based on the above, the invention aims to provide a BOPE extinction film, which not only improves the temperature resistance of the extinction layer, but also improves the extinction effect of the extinction film, improves the production efficiency and the use efficiency of the extinction film, and has the advantages of wide production temperature range and high production efficiency by adding a certain proportion of high-melting-point, high-transparency and low-crystallization propylene copolymer into the extinction layer.

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

The BOPE extinction film comprises an extinction layer, a core layer and a lower surface layer which are sequentially arranged, wherein the extinction layer comprises 22-47.5wt% of first metallocene linear low-density polyethylene, 38-48wt% of polypropylene and 10-30wt% of propylene-based copolymer, the melting point of the propylene-based copolymer is 140-160 ℃ and the crystallinity is 5-10%, and the core layer and the lower surface layer both comprise second metallocene linear low-density polyethylene.

The surface extinction effect of the BOPE extinction film is mainly generated by the fact that the surface morphology of an extinction layer of the extinction film has certain roughness, and light scattering occurs to different degrees when light irradiates to the film surface so as to generate the extinction effect. The matting layer of the matting film is formed to have a sufficient roughness and requires a portion of the polyolefin phase to be raised. In biaxially stretched matt films, the protrusions are formed by two or more incompatible systems, where the response of different polyolefins to stretching forces is inconsistent at a certain viscosity difference.

The inventor finds that the crystallization temperature difference of two phases in the extinction layer is reasonably utilized, so that the polypropylene disperse phase is easier to harden and bulge during stretching, and the larger the size of the bulged polypropylene disperse phase is, the larger the roughness is. Meanwhile, in order to obtain better roughness, the crystallization temperature or the crystallization degree of the continuous phase should be lower than that of the dispersed phase, because the polyethylene phase with low crystallization temperature or low crystallization degree is easier to extend along the stretching direction when stretching, and the dispersed phase with high crystallization temperature or high crystallization degree is easier to bulge because of high hardness after crystallization. The existing BOPE extinction film uses polyethylene raw materials with generally higher crystallinity and low melt index, the pressure is high during extrusion, the effect of sticking a thick sheet on a roller is poor after the polyethylene is crystallized, the thickness is greatly influenced by the swing of the thick sheet during high-speed production, for this reason, a plurality of technicians can choose to increase the temperature of an extruder for extinction layers of the BOPE extinction film to reduce the extrusion pressure, the temperature of a metallocene linear low-density polyethylene melt at a high-speed stretching roller even reaches 135 ℃, however, the metallocene linear low-density polyethylene melt of extinction layers of the BOPE extinction film has low viscosity and low melting point, is easy to coat on polypropylene, and has slow speed during the longitudinal stretching production stage, and the extinction layers are easy to be burnt due to the first metallocene linear low-density polyethylene with low melting point after the extrusion temperature is increased, so that even though the extrusion temperature is not increased, the extinction surface high-temperature scalding is easy to occur during the film covering of a downstream BOPE extinction film. Therefore, the inventor adds 10-30wt% of propylene-based copolymer with better temperature resistance and lower crystallinity into the extinction layer to replace part of the first metallocene linear low-density polyethylene as a continuous phase, and simultaneously overcomes the defects of poor extinction effect and low temperature resistance of the existing BOPE extinction film. On the one hand, the temperature of a longitudinal stretching area is set to be more than 125-135 ℃ when the BOPE matting film is produced at present, the inventor intuitively improves the temperature resistance of the matting layer by adding a propylene-based copolymer with higher melting point into the matting layer, on the basis, the inventor further discovers that the change of the melting point of the propylene-based copolymer has an influence on the temperature resistance of the matting layer and also has an influence on the matting effect of the matting layer, and particularly, the inventor discovers that the melting point of the propylene-based copolymer added into the matting layer is controlled to be 140-160 ℃ through a large number of practices, if the melting point of the propylene-based copolymer is less than 140 ℃, the propylene-based copolymer cannot effectively resist the temperature of the matting layer, and if the melting point of the propylene-based copolymer is more than 160 ℃, the difference of the melting point is too large, so that poor stretching of the matting surface is easily caused, and preferably, the propylene-based copolymer with the melting point of 140 ℃ is good in compatibility with other materials of the matting layer, can be better dispersed in polyethylene phase and polypropylene phase, and the temperature resistance of the matting layer can be effectively improved. on the other hand, since lowering the crystallization temperature or crystallinity of the continuous phase in the matting layer is favorable for realizing coarsening of the film surface during stretching, the scattering degree of light can be improved by increasing the roughness of the film surface, the inventor adopts a propylene-based copolymer with lower crystallinity and ensures smooth production of the matting film on the basis, specifically, the inventor controls the crystallinity of the propylene-based copolymer to be at a lower level of 5-10%, if the crystallinity of the propylene-based copolymer is less than 5%, the melt viscosity is very low, and certain difficulties are caused for production processing and feeding, and if the crystallinity of the propylene-based copolymer is more than 10%, a larger addition amount is required to obviously lower the total crystallization enthalpy of the continuous phase. Further, the inventors have found that the addition amount of the propylene-based copolymer should be controlled to 10 to 30% by weight, and if the addition amount of the propylene-based copolymer is less than 10% by weight, although the haze of the matting film is improved to some extent by decreasing the total enthalpy of crystallization of the continuous phase, the addition amount of the propylene-based copolymer is low, and after shearing dispersion, it is insufficient to form a continuous amorphous continuous phase, and the effect of improving the temperature resistance of the matting layer is not obvious, and if the addition amount of the propylene-based copolymer is more than 30% by weight, the tensile strength of the BOPE matting film is remarkably reduced and the heat shrinkage ratio of the matting film is increased. According to the invention, the propylene-based copolymer with higher melting point and lower crystallinity is added into the extinction layer, the addition amount of the propylene-based copolymer is controlled to be 10-30wt%, and based on the characteristics that the melting point of the propylene-based copolymer is higher than that of the first metallocene linear low-density polyethylene and the tensile strength of the propylene-based copolymer is lower than that of the first metallocene linear low-density polyethylene, on one hand, the crystallinity of a continuous phase in the extinction layer system is reduced, on the other hand, the polypropylene phase is easier to bulge during stretching, the roughness of the extinction layer is improved, on the other hand, the melting point of the continuous phase is improved, so that the extinction effect of the extinction film is improved, the temperature resistance of the extinction layer of the BOPE extinction film is improved, on the other hand, the extinction film can be smoothly produced, the production efficiency of the BOPE extinction film is improved, and the BOPE extinction film can be applied to wider packaging application and application fields.

Further, the melt index of the first metallocene linear low density polyethylene is measured to be 5-15 g/10min under the conditions of 190 ℃ and 2.16kg, and the melt index of the polypropylene is measured to be 0.1-5 g/10min under the conditions of 230 ℃ and 2.16 kg. The inventor finds out through a great deal of practice that in a BOPE extinction layer composed of metallocene first linear low-density polyethylene and polypropylene, the melt viscosity of the low-melt-index polypropylene is larger, the viscosity of the first metallocene linear low-density polyethylene with relatively higher melt index is low, the low-viscosity polyethylene is compatible with and is easy to cover a high-viscosity polypropylene phase in a shearing plasticizing process, and the larger the two-phase viscosity difference is, the larger the roughness of the extinction layer is caused when the extinction layer is stretched. However, the melt index difference between the metallocene linear low-density polyethylene and the polypropylene is overlarge at present, and the melt viscosity difference is overlarge, so that the high-viscosity polypropylene cannot be uniformly dispersed in the low-viscosity polyethylene phase, and obvious extinction unevenness exists on the film surface even film rupture is caused when the BOPE extinction film is produced. Controlling the melt viscosity difference of two phases, wherein the melt viscosity of the continuous phase first metallocene linear low-density polyethylene is lower than that of the disperse phase polypropylene, limiting the melt index of the first metallocene linear low-density polyethylene to 5-15 g/10min (190 ℃ and 2.16 kg), and limiting the melt index of polypropylene to 0.1-5 g/10min (230 ℃ and 2.16 kg). If the melt viscosity of the continuous phase first metallocene linear low density polyethylene is too small, the dispersion uniformity is poor, and if the melt viscosity of the continuous phase first metallocene linear low density polyethylene is too large, the size of the disperse phase is reduced due to the close viscosity of the two phases, and the roughness is not improved, so that the melt index of the first metallocene linear low density polyethylene is controlled to be 5-15 g/10min, and the melt index of the polypropylene is controlled to be 0.1-5 g/10min.

Further, the melt index of the propylene-based copolymer is controlled to be 5-10 g/10min under the condition of 230 ℃ and 2.16 kg. If the melt index of the propylene-based copolymer is smaller than 5g/10min, the fluidity of the extinction layer is not facilitated, the extinction uniformity at the edge of the extinction film is not facilitated to be improved, and if the melt index of the propylene-based copolymer is larger than 10g/10min, the difference between the melt viscosity and the disperse phase is large, the shearing dispersion is not facilitated, and meanwhile, the mechanical strength of the extinction layer system is also not facilitated to be better maintained.

Further, the propylene-based copolymer is a propylene-1-butene copolymer, wherein the propylene-1-butene copolymer has a propylene sequence isotacticity of 90-93% and a 1-butene sequence isotacticity of 87-90%. It is known to those skilled in the art that, in general, for propylene-1-butene copolymers, the introduction of 1-butene units breaks down the sequence structure of the molecular chains of the polypropylene chains, causing a decrease in the crystallinity of the polymer, the melting temperature decreasing significantly with an increase in 1-butene. However, the propylene-1-butene copolymer selected in the invention is synthesized by adopting an optimized catalytic system for stereospecific polymerization, specifically, an alkylaluminum or alkylaluminum hydride, an external electron donor, a supported titanium catalyst and hydrogen are used as a catalyst system for isotactic polymerization, bulk copolymerization is carried out to obtain the propylene-1-butene copolymer, the isotacticity of a 1-butene sequence and a propylene sequence in the obtained propylene-1-butene copolymer is more than 85%, and the melting temperature of the copolymer is obviously increased along with the increase of the 1-butene content, so that the propylene-1-butene copolymer has a relatively high melting point and relatively low crystallinity. Selecting a propylene-1-butene copolymer composed of a propylene sequence with isotacticity of 90-93% and a 1-butene sequence with isotacticity of 87-90%, wherein if the isotacticity of the propylene sequence is too low, the propylene-1-butene copolymer has too low a melting point and cannot effectively resist temperature protection for the extinction layer, if the isotacticity of the propylene sequence is too high, the propylene-1-butene copolymer has higher crystallinity and is unfavorable for improving haze of an extinction film, and if the isotacticity of the 1-butene sequence is too low, the propylene-1-butene copolymer has too low a melting point and is unfavorable for obtaining a propylene-1-butene copolymer with relatively high melting point, and if the isotacticity of the 1-butene sequence is too high, the propylene-1-butene copolymer can be excessively rigid and is unfavorable for bidirectional stretching;

Preferably, the propylene-1-butene copolymers of the present invention have a 1-butene monomer content ranging from 15 to 35% by weight. If the 1-butene content is less than 15wt%, the isotacticity of the propylene sequence in the propylene-1-butene copolymer is increased, and the increase of the crystallization enthalpy of the propylene-1-butene copolymer is unfavorable for improving the haze of the extinction film, and if the 1-butene content is more than 35wt%, the copolymer may have more branches, increasing the entanglement number of chain segments, making the disentanglement and slippage of the chain difficult, and increasing the extrusion processing pressure of the polymer.

Further, the extinction layer further comprises 0.3-0.5wt% of an antioxidant, the antioxidant comprises an antioxidant 1010 and an antioxidant 168, and the antioxidant 1010 and the antioxidant 168 are 1:3. The antioxidant is mainly added to reduce the cross-linking of the first metallocene linear low-density polyethylene in the high-temperature high-pressure extrusion processing process, so that the crystal point defect of the film surface is caused.

Further, the melt index of the second metallocene linear low density polyethylene is measured to be 3-10 g/10min under the condition of 190 ℃ and 2.16 kg.

Further, the core layer comprises 99-99.5wt% of second metallocene linear low-density polyethylene and 0.5-1wt% of antistatic agent master batch, the matrix resin of the antistatic agent master batch is the second metallocene catalytic linear low-density polyethylene, and the effective content of the antistatic agent in the antistatic agent master batch is 40wt%.

Further, the lower surface layer comprises 99-99.5wt% of second metallocene linear low-density polyethylene and 0.5-1wt% of silica anti-blocking agent master batch.

The invention also provides a preparation method of the BOPE extinction film, which comprises the following steps of weighing and mixing resin raw materials of each layer, respectively carrying out melt extrusion, wherein an extinction layer extruder is a homodromous double-screw extruder, a core layer and a lower surface layer light surface layer are single-screw extruders, and each layer of melt extrusion is combined into a thick sheet, the thick sheet is cooled through a chill roll and a chill tank, longitudinal stretching preheating is carried out on the thick sheet, the preheating temperature is 125 ℃, then longitudinal stretching is carried out, the longitudinal stretching multiple is 5 times, the longitudinal stretching temperature is 128 ℃, then longitudinal stretching shaping is carried out, after the longitudinal stretching shaping, transverse stretching preheating is carried out, then transverse stretching is carried out, the transverse stretching multiple is 8 times, the transverse stretching temperature is 128 ℃, then transverse stretching shaping is carried out, finally corona treatment is carried out, and winding is divided into film finished products.

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 application are not limited to the precise arrangements and instrumentalities 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.

In the determined matting layer formulation, the matting effect is most significantly affected by the addition ratio of the dispersed phase of the matting layer, and for the sake of more convenient explanation of the effect of the present invention, the weight percentages of the dispersed phase are the same in all the following examples, i.e. the polypropylene content in the matting layer is kept unchanged.

According to the BOPE extinction film, the propylene-based copolymer with a certain proportion and high melting point, high transparency and low crystallization is added into the extinction layer, so that the temperature resistance of the extinction layer is improved, the extinction effect of the extinction film is improved, the production efficiency and the use efficiency of the extinction film are improved, and the BOPE extinction film has the advantages of wide production temperature range and high production efficiency.

Further, the melt index of the first metallocene linear low density polyethylene is measured to be 5-15 g/10min under the conditions of 190 ℃ and 2.16kg, and the melt index of the polypropylene is measured to be 0.1-5 g/10min under the conditions of 230 ℃ and 2.16 kg. The inventor finds out through a great deal of practice that in a BOPE extinction layer composed of a first metallocene linear low-density polyethylene and polypropylene, the melt viscosity of the polypropylene with low melt index is larger, the viscosity of the first metallocene linear low-density polyethylene with relatively high melt index is low, the low-viscosity polyethylene is compatible with and is easy to cover a high-viscosity polypropylene phase in a shearing plasticizing process, and the larger the two-phase viscosity difference is, the larger the roughness of the extinction layer is caused when the extinction layer is stretched. However, the melt index difference between the metallocene linear low-density polyethylene and the polypropylene is overlarge at present, and the melt viscosity difference is overlarge, so that the high-viscosity polypropylene cannot be uniformly dispersed in the low-viscosity polyethylene phase, and obvious extinction unevenness exists on the film surface even film rupture is caused when the BOPE extinction film is produced. Controlling the melt viscosity difference of two phases, wherein the melt viscosity of the continuous phase first metallocene linear low-density polyethylene is lower than that of the disperse phase polypropylene, limiting the melt index of the first metallocene linear low-density polyethylene to 5-15 g/10min (190 ℃ and 2.16 kg), and limiting the melt index of polypropylene to 0.1-5 g/10min (230 ℃ and 2.16 kg). If the melt viscosity of the continuous phase first metallocene linear low density polyethylene is too small, the dispersion uniformity is poor, and if the melt viscosity of the continuous phase first metallocene linear low density polyethylene is too large, the size of the disperse phase is reduced due to the close viscosity of the two phases, and the roughness is not improved, so that the melt index of the first metallocene linear low density polyethylene is controlled to be 5-15 g/10min, and the melt index of the polypropylene is controlled to be 0.1-5 g/10min.

Further, the melt index of the propylene-based copolymer is measured at 230 ℃ and under 2.16kg, and is 5-10 g/10min. If the melt index of the propylene-based copolymer is smaller than 5g/10min, the fluidity of the extinction layer is not facilitated, the extinction uniformity at the edge of the extinction film is not facilitated to be improved, and if the melt index of the propylene-based copolymer is larger than 10g/10min, the difference between the melt viscosity and the disperse phase is large, the shearing dispersion is not facilitated, and meanwhile, the mechanical strength of the extinction layer system is also not facilitated to be better maintained.

Further, the propylene-based copolymer is a propylene-1-butene copolymer, wherein the propylene-1-butene copolymer has a propylene sequence isotacticity of 90-93% and a 1-butene sequence isotacticity of 87-90%.

Further, the propylene-1-butene copolymer contains 15-35wt% of 1-butene. The propylene-1-butene copolymer is synthesized by adopting an optimized catalytic system for stereospecific polymerization, specifically, an alkyl aluminum or alkyl aluminum hydride, an external electron donor, a supported titanium catalyst and hydrogen are taken as a catalyst system for isotactic polymerization, and bulk copolymerization is carried out to obtain the propylene-1-butene copolymer. The isotacticity of the 1-butene sequence and the propylene sequence in the obtained propylene-based copolymer is more than 85%, and the melting temperature of the copolymer is not reduced but is obviously increased along with the increase of the 1-butene content. Preferably, the propylene-1-butene copolymer of the present invention has a 1-butene monomer content of 15 to 35wt%, and if the 1-butene content is less than 15wt%, the isotacticity of the propylene sequence in the propylene-1-butene copolymer is increased, and the increase in crystallization enthalpy of the copolymer is detrimental to the improvement in haze of the matted film, and if the 1-butene content is more than 35wt%, the copolymer may have more branches, increasing the number of entanglement of segments, difficulty in disentangling and slipping of chains, and increasing extrusion processing pressure of the polymer.

Further, the thickness of the extinction layer is 2-3 mu m. The BOPE extinction film is 15-40 mu m, and the lower surface layer is 1-1.5 mu m.

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

Melting point and crystallinity were measured by DSC;

The gloss test is carried out according to the GB/T8807-1988 standard, the haze test is carried out according to the GB/T2410-2008 standard, and the mechanical property test is carried out according to the GB/T1040.3-2006 standard.

In the heat shrinkage test, the film sample size was 10 x 10cm, and the film was tested for longitudinal and transverse shrinkage at room temperature cooling after 120 seconds of standing in a 110 ℃ oven.

And detecting flaw points, wherein the rolling and accumulating of an online detector is taken as a counting period, and the particle size of the counted flaw points is 1mm < 2> or more.

It should be noted that the percentages stated in the examples of the present invention or the comparative examples are percentages by weight.

Example 1

The embodiment provides a BOPE extinction film, which 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 matting layer resin was prepared by uniformly mixing 42.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 10wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%; melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 6.1%; melting point of 140 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity of 90%, 1-butene sequence isotacticity of 87%) to obtain the matting layer resin.

Preparation of core resin A core resin was obtained by uniformly mixing 99.5wt% of a second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) with 0.5wt% of an antistatic agent masterbatch.

Preparation of the lower surface layer resin was obtained by uniformly mixing 99wt% of the second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) and 1wt% of the antiblocking agent master batch (fumed silica master batch of the second metallocene linear low density polyethylene, melt index: 4g/10min, wherein the fumed silica effective concentration is 6 wt%).

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

and (3) producing on a bruker production line with the width of 4.2m, weighing and mixing all the resin raw materials, respectively carrying out melt extrusion, wherein a extinction layer extruder is a homodromous double screw, the temperature of the extinction layer extruder is 240 ℃, a core layer and a lower surface layer light surface layer are single screw extruders, the temperatures of the core layer and the lower surface layer extruder are 250 ℃, all the melt extrusion are combined into thick sheets at a T-shaped die after the melt extrusion, the thick sheets are cooled by a chill roll and a chill tank, the thick sheets are firstly subjected to longitudinal stretching preheating at the preheating temperature of 125 ℃, then subjected to longitudinal stretching, the longitudinal stretching multiple is 5 times, the longitudinal stretching temperature is 128 ℃, then subjected to longitudinal stretching shaping, then subjected to transverse stretching preheating, the transverse stretching multiple is 8 times, the transverse stretching temperature is 128 ℃, then subjected to transverse stretching shaping, and finally subjected to corona treatment, and wound into a film finished product.

The total thickness of the matting film was 30. Mu.m, wherein the matting layer had a thickness of 2.8. Mu.m, and the lower surface layer had a thickness of 1.3. Mu.m.

Example 2

The matting layer resin was prepared by uniformly mixing 32.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 20wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%; melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 6.1%; melting point of 140 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity of 90%, 1-butene sequence isotacticity of 90%) to obtain the matting layer resin. Preparation of core resin A core resin was obtained by uniformly mixing 99.5wt% of a second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) with 0.5wt% of an antistatic agent masterbatch.

Preparation of the lower surface resin was obtained by uniformly mixing 99wt% of a second metallocene linear low-density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) and 1wt% of an antiblocking agent master batch (the antiblocking agent master batch is a fumed silica master batch of the second metallocene linear low-density polyethylene, melt index: 4g/10min, wherein the fumed silica effective concentration is 6 wt%).

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 matting layer resin was prepared by uniformly mixing 32.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 20wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 31.3wt%; melt index of 7.1g/10min measured at 230 ℃ C., 2.16 kg; crystallinity: 7.46wt%; melting point 160 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity: 93%, 1-butene sequence isotacticity: 90%) to obtain a matting layer resin. Preparation of core resin A core resin was obtained by uniformly mixing 99.5wt% of a second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16kg, 2.1g/10 min) and 0.5wt% of an antistatic agent.

Preparation of the lower surface layer resin was obtained by uniformly mixing 99% by weight of a second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) and 1% by weight of an antiblocking agent (fumed silica master batch of the second metallocene linear low density polyethylene, melt index: 4g/10min, wherein the fumed silica effective concentration is 6% by weight).

Example 4

The matting layer resin was prepared by uniformly mixing 27.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 25wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene 15wt%; melt index of 7.5g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 6.7%; melting point of 148 ℃ C., propylene sequence isotacticity of 91% and 1-butene sequence isotacticity of 88%) to obtain a matting layer resin. Preparation of core resin A core resin was obtained by uniformly mixing 99.5wt% of a second metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 2.1g/10 min) with 0.5wt% of an antistatic agent masterbatch.

Comparative example 1

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

Preparation of a matting layer resin 52.5wt% of a first metallocene linear low density polyethylene (melt index measured at 190 ℃ C., 2.16 kg: 12g/10 min), 47wt% of a homo-polypropylene (melt index measured at 230 ℃ C., 2.16 kg: 0.3g/10 min) and 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) were homogeneously mixed to obtain a matting 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.

The total thickness of the matting film was 40. Mu.m, wherein the matting layer had a thickness of 2.8. Mu.m, and the lower surface layer had a thickness of 1.3. Mu.m.

Comparative example 2

The matting layer resin was prepared by uniformly mixing 47.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 5wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%; melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 6.1%; melting point of 140 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity of 90%, 1-butene sequence isotacticity of 90%) to obtain the matting layer resin.

Comparative example 3

The matting layer resin was prepared by uniformly mixing 17.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 35wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%; melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 6.1%; melting point of 140 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity of 90%, 1-butene sequence isotacticity of 90%) to obtain the matting layer resin.

Comparative example 4

The matting layer resin was prepared by uniformly mixing 42.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 10wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%; melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity of 4.1%; melting point of 120 ℃ C., propylene-1-butene copolymer, propylene sequence isotacticity of 70%, 1-butene sequence isotacticity of 80%) to obtain the matting layer resin.

Comparative example 5

The mat resin was prepared by uniformly mixing 42.5wt% of a first metallocene linear low-density polyethylene (melt index of 12g/10min measured at 190 ℃ C., 2.16 kg), 47wt% of a homo-polypropylene (melt index of 0.3g/10min measured at 230 ℃ C., 2.16 kg), 0.5wt% of an antioxidant (antioxidant 1010: antioxidant 168=1:3) and 10wt% of a propylene-based copolymer (propylene-1-butene copolymer, comonomer ratio of 1-butene: 23.5wt%, melt index of 8.3g/10min measured at 230 ℃ C., 2.16 kg; crystallinity: 40% and melting point 165 ℃ C., propylene sequence isotacticity: 97% and 1-butene sequence isotacticity: 93%) to obtain a mat resin.

The test results of the properties of the BOPE matt films of examples 1 to 4 and comparative examples 1 to 5 are shown in table 1 below.

TABLE 1

In the invention, the BOPE extinction film produced in all the examples has a good extinction effect, and the haze data of the BOPE extinction film is increased to a certain extent along with the increase of the proportion of the propylene-based copolymer, and the glossiness is reduced in an inverse proportion.

From comparative examples 1 and 2, it was found that when a propylene-based copolymer having a low crystallinity was added to the system, the film surface matting effect of comparative example 2 began to be improved somewhat, and the gloss was lowered. The haze of the propylene-based copolymer of comparative example 3 was very significantly increased when it was added to 35% by weight.

In comparative example 4, the isotacticity of propylene sequence and 1-butene sequence in propylene copolymer is too low, resulting in reduced melting point and crystallinity of propylene copolymer, low melt viscosity in production process, difficulty in production and feeding, influence on production smoothness and production efficiency, and obviously increased defect point of extinction surface of prepared extinction film as seen from data, namely, the extinction layer cannot be effectively temperature-resistant protected, the heat shrinkage rate is increased, the film surface curling of a film can occur to a film coated by a downstream manufacturer, the overprinting positioning deviation is large, and other serious quality problems, but the crystallization degree of the propylene-based copolymer is further reduced, the total crystallization enthalpy value of a continuous phase is more obviously reduced, and therefore, the extinction effect of comparative example 4 is improved to a certain extent.

In comparative example 5, the isotacticity of the propylene sequence and the 1-butene sequence in the propylene-based copolymer is too high, so that the melting point and the crystallinity of the propylene-based copolymer are both increased, the compatibility of the propylene-based copolymer and other materials of the extinction layer is not facilitated, the thick sheet is incompatible, poor extinction surface stretching is caused, the extinction uniformity is poor, and the appearance of the extinction film is affected.

From the comparison of example 2 and example 3, it is revealed that the gloss of the matt layer is increased simultaneously with the increase in crystallinity of the propylene-based copolymer, indicating that the crystallization properties of the continuous phase affect the stretching coarsening of the high viscosity dispersed phase. In the invention, the first linear low-density polyethylene serving as the continuous phase of the extinction layer has good structural regularity, the crystallization enthalpy value is high, the extinction effect of the extinction layer is poor, but the crystallization temperature of polypropylene of the disperse phase is higher, and the melt viscosity of the disperse phase is higher than that of the continuous phase, so that the disperse phase is uniformly distributed in island phase morphology to form a rough surface, and the film surface extinction effect is realized. When the propylene-based copolymer with high melting point and low crystallinity is added into the extinction layer, the polyethylene is continuously and proportionally reduced, and the total crystallinity of the continuous phase is also reduced, so that the polypropylene dispersed phase with early crystallization and higher viscosity is beneficial to protruding out of the surface of the extinction layer in the biaxial stretching process, and the extinction layer is beneficial to forming the appearance with higher roughness.

As seen from the data, the heat shrinkage of BOPE matt films gradually increased as the amount of propylene-based copolymer added increased. The biaxially oriented extinction film is shaped through a transverse stretching shaping area, but the orientation of a high molecular chain segment is an unstable state, the internal stress of the high molecular chain segment always has a tendency to return to random coils, the tendency is particularly obvious at a certain heating temperature, and the heat shrinkage proportion and the crystallinity of the material are in inverse proportion, so that propylene copolymers with different proportions are added, the extinction effect of the BOPE extinction film is improved, the crystallinity of the system is reduced, the internal stress of an amorphous area is easily thawed, the heat shrinkage is increased, and particularly, after the propylene addition amount is increased to 35wt%, the amorphous area gradually forms a regional continuous phase, and the heat shrinkage increase amplitude is larger. When the heat shrinkage ratio exceeds 5%, the film surface curling of the film occurs in the film of the downstream manufacturer, and the offset of the overprinting is large, so that the propylene-based copolymer is not preferably added in an amount exceeding 30% by weight from the viewpoint of the heat shrinkage index. In addition, the propylene-based copolymer is an elastomer material in performance, and has low crystallinity, so that the tensile strength of the BOPE extinction film is reduced, and the addition proportion of the propylene-based copolymer is controlled within 30wt% in order to ensure that the BOPE extinction film has better mechanical strength.

It can also be seen from the present invention that the defect points detected by the in-line detector per ten meters gradually decrease as the amount of the propylene-based copolymer having a high melting point and a low crystallization is increased. This is because the propylene-based copolymer has a melting point of 140℃which is significantly higher than that of the first linear low-density polyethylene in the mat layer, and higher than the longitudinal stretching preheating and stretching temperature, and because of the increase of the high-melting component in the high-speed production, the burn-out of the low-melting component in the longitudinal stretching roller is reduced, and the occurrence of the mat defects is reduced, while comparative examples 2 and 3 show that the higher the melting point of the propylene-based copolymer, the smaller the number of mat defects detected. Therefore, the BOPE extinction film can relatively adapt to higher production temperature or higher speed, and improves the use efficiency of a BOPE downstream industrial chain.

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 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 22-47.5wt% of first metallocene linear low-density polyethylene, 38-48wt% of polypropylene and 10-30wt% of propylene-based copolymer, the propylene-based copolymer has a melting point of 140-160 ℃ and a crystallinity of 5-10%, the propylene-based copolymer is propylene-1-butene copolymer, in the propylene-1-butene copolymer, the isotacticity of a propylene sequence is 90-93%, and the isotacticity of a 1-butene sequence is 87-90%, and the core layer and the lower surface layer both comprise second metallocene linear low-density polyethylene.

2. The BOPE matt film according to claim 1, wherein the melt index of the first metallocene linear low density polyethylene is 5-15 g/10min measured at 190 ℃ and 2.16kg, and the melt index of the polypropylene is 0.1-5 g/10min measured at 230 ℃ and 2.16 kg.

3. The BOPE matt film according to claim 1, wherein the propylene-based copolymer has a melt index of 5 to 10g/10min measured at 230 ℃ and 2.16 kg.

4. The BOPE matt film according to claim 1, wherein the propylene-1-butene copolymer has a 1-butene content of 15 to 35wt%.

5. The BOPE matt film according to claim 1, wherein the matt layer further comprises 0.3-0.5wt% of an antioxidant, the antioxidant comprising an antioxidant 1010 and an antioxidant 168, the antioxidant 1010: the antioxidant 168 being 1:3.

6. The BOPE matt film according to claim 1, wherein the melt index of the second metallocene linear low density polyethylene measured at 190 ℃ and 2.16kg is 3-10 g/10min.

7. The BOPE matt film according to claim 1, wherein the core layer comprises 99 to 99.5wt% of the second metallocene linear low density polyethylene and 0.5 to 1wt% of the antistatic agent masterbatch, the matrix resin of the antistatic agent masterbatch is the second metallocene linear low density polyethylene, and the effective content of the antistatic agent in the antistatic agent masterbatch is 40wt%.

8. The BOPE matt film according to claim 1, wherein the lower skin layer comprises 99 to 99.5wt% of the second metallocene linear low density polyethylene and 0.5 to 1wt% of the silica antiblocking agent masterbatch.

9. A preparation method of the BOPE matt film according to any one of claims 1-8, which is characterized by comprising the steps of weighing and mixing resin raw materials of each layer, respectively carrying out melt extrusion, wherein a matt layer extruder is a homodromous double screw, a core layer and a lower surface layer are single screw extruders, each layer of melt extrusion is combined into a thick sheet, the thick sheet is cooled through a chill roll and a chill tank, longitudinal stretching preheating is carried out on the thick sheet, the preheating temperature is 125 ℃, then longitudinal stretching is carried out, the longitudinal stretching multiple is 5 times, the longitudinal stretching temperature is 128 ℃, then longitudinal stretching shaping is carried out, after the longitudinal stretching shaping, transverse stretching preheating is carried out, then transverse stretching is carried out, the transverse stretching multiple is 8 times, the transverse stretching temperature is 128 ℃, then transverse stretching shaping is carried out, finally corona treatment is carried out, and rolling is divided into film finished products.