CN115674838A - Stiffness-enhanced temperature-resistant polyethylene film and preparation method and application thereof - Google Patents
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Abstract
The invention belongs to the technical field of film materials, and particularly discloses a stiffness-increasing and temperature-resisting polyethylene film and a preparation method and application thereof. This polyethylene film is including the top layer, middle level and the inlayer that stack gradually the setting, wherein: the raw material components of the surface layer, the middle layer and the inner layer all comprise metallocene linear low-density polyethylene, high-density polyethylene and a stiffness increasing agent; the stiffness increasing agent comprises petroleum resin. The polyethylene film is prepared by adding a stiffening agent into a blending system of metallocene linear low-density polyethylene and high-density polyethylene and adopting a biaxial stretching method. The metallocene linear low-density polyethylene is utilized to ensure that the integral strength of the film is improved when the biaxial tension preparation is adopted, so that the thickness of the film can be reduced; meanwhile, high-density polyethylene and petroleum resin serving as a stiffness increasing agent are added to improve the overall stiffness and temperature resistance of the film, so that the technical problems of heat shrinkage, seal wrinkling deformation, stretching tearing and the like easily generated during bag making or heat sealing can be effectively solved.
Description
Technical Field
The invention belongs to the technical field of film materials, and particularly relates to a stiffness-increasing and temperature-resisting polyethylene film as well as a preparation method and application thereof.
Background
With the development of polymer synthesis technology and processing equipment technology, the production of Biaxially Oriented Polyethylene (BOPE) films by a flat film method is continuously promoted. In recent years, "reduction, greening and recycling" of flexible packaging materials are the most important development trends. At present, the BOPE film is directly used for a printing layer of packaging and is compounded and matched with other Polyethylene (PE) functional layers for use, and the BOPE film is an effective way for realizing the packaging of all PE single materials. However, most of raw materials for producing the BOPE film are linear low-density polyethylene, the melting point is low, the temperature resistance is poor, the stiffness of the prepared film is low, the temperature resistance is not enough, and particularly after multi-layer compounding, the technical problems of heat shrinkage, seal wrinkling deformation, stretching tearing and the like are easy to generate during bag making or heat sealing. The situation is not beneficial to the application of downstream manufacturers, so that the downstream market is difficult to open, and the development of the BOPE film industry is restricted.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art described above. The invention provides a stiffening and temperature-resistant polyethylene film and a preparation method and application thereof, wherein the polyethylene film adopts a blending system of metallocene linear low density polyethylene (M-LLDPE) and High Density Polyethylene (HDPE), and a stiffening agent is added, and a biaxial tension method is adopted to prepare the polyethylene film with good stiffness and high temperature resistance.
In order to overcome the technical problems, the first aspect of the present invention provides a polyethylene film.
Specifically, the polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked; the raw material components of the surface layer, the middle layer and the inner layer respectively comprise metallocene linear low density polyethylene, high density polyethylene and a stiffening agent; the stiffness agent comprises petroleum resin.
The polyethylene film is formed by compounding a surface layer, a middle layer and an inner layer, wherein metallocene linear low-density polyethylene, high-density polyethylene and a stiffness agent are added in each layer, wherein: the metallocene linear low-density polyethylene can ensure that the integral strength of the film is improved when the biaxial tension preparation is adopted, thereby reducing the thickness of the film; meanwhile, the high-density polyethylene and the stiffness increasing agent petroleum resin are matched, so that the integral stiffness and temperature resistance of the film are improved.
Specifically, the high density polyethylene is prepared by polymerizing ethylene monomers with the concentration of 99.95% under low pressure, and the polymerization process is carried out according to the ionic polymerization reaction process; the high density polyethylene has regular molecular structure, less branched chains, higher density and crystallinity, opacity and higher mechanical property than the conventional Low Density Polyethylene (LDPE).
Linear Low Density Polyethylene (LLDPE) is a molecular structure in which ethylene is copolymerized with a small amount of alpha-olefin to form a linear ethylene backbone with very short comonomer branches. Metallocene linear low density polyethylene (M-LLDPE) is linear low density polyethylene produced by adopting a metallocene catalyst, and the molecular chain structure is more regular than that of the conventional linear low density polyethylene. Compared with the conventional linear low density polyethylene, the metallocene linear low density polyethylene has more excellent tensile property, impact resistance and optical property.
Therefore, the high-density polyethylene and the metallocene linear low-density polyethylene belong to the polyethylene products with regular structures and less branched chains. Researches show that in a raw material system for biaxially stretching metallocene linear low-density polyethylene, high-density polyethylene with a high softening point is added for blending modification, so that the mechanical property and the temperature resistance of the product can be effectively improved.
The polyethylene film of the present invention adopts a blending system of metallocene linear low density polyethylene and high density polyethylene, which is a complex crystalline form. In order to meet the processing requirements of the subsequent biaxial stretching, the two materials need to be uniformly mixed and form a stable crystal form. Therefore, the invention also adds the stiffness agent petroleum resin in the blending system of the metallocene linear low density polyethylene and the high density polyethylene, the petroleum resin not only can play a role of plasticization in the melting state of the blending system, but also plays a good role of stiffness increase in products after biaxial stretching; simultaneously, the polyethylene can also be acted together with metallocene linear low density polyethylene and high density polyethylene to improve the temperature resistance of the product.
As a further improvement of the above aspect, the metallocene linear low density polyethylene has a density of 0.92 to 0.94g/cm 2 The melt index is 0.2-5g/10min. The metallocene linear low-density polyethylene with specific density and melt index range is selected to meet the combined action with high-density polyethylene and stiffness increasing agent, so as to achieve the purposes of temperature resistance and stiffness increase.
As a further improvement of the above aspect, the high density polyethylene has a density of 0.94 to 0.97g/cm 2 The melt index is 0.2-3g/10min. High density polyethylene of a particular density and melt index range is selected and used in combination with metallocene linear low density polyethylene and a stiffness agent to achieve temperature resistance and stiffness in the film.
Preferably, the petroleum resin is a hydrogenated petroleum resin. The hydrogenated petroleum resin is beneficial to improving the viscosity of a blending system of metallocene linear low-density polyethylene and high-density polyethylene, thereby improving the stiffness of the product; and can be used together with metallocene linear low density polyethylene and high density polyethylene to improve the temperature resistance of the product.
As a further improvement of the scheme, the surface layer, the middle layer and the inner layer comprise the following raw material components in parts by weight: 30-68 parts of metallocene linear low-density polyethylene, 30-68 parts of high-density polyethylene and 3-30 parts of a stiffness increasing agent.
Specifically, the optimal proportioning relation among the raw materials is controlled, and the raw materials are synergistic, so that the prepared polyethylene film has excellent stiffness and temperature resistance, the polyethylene film which is not in the component range cannot simultaneously meet the optimization of various properties of the film, and even the low-metallocene linear low-density polyethylene cannot form the film.
As a further improvement of the scheme, the raw material components of the surface layer further comprise a first auxiliary agent, and the addition amount of the first auxiliary agent is 1-7 parts by weight.
As a further improvement of the scheme, the raw material components of the middle layer also comprise a second auxiliary agent, and the addition amount of the second auxiliary agent is 1-5 parts by weight.
As a further improvement of the scheme, the raw material components of the inner layer also comprise a third auxiliary agent, and the addition amount of the third auxiliary agent is 1-7 parts by weight.
As a further improvement of the above scheme, the first auxiliary agent, the second auxiliary agent and the third auxiliary agent are all selected from at least two of a slipping agent, an antioxidant and an anti-sticking agent. The auxiliary agents mainly play their own roles, and further improve the performances of the film such as smoothness, oxidation resistance, adhesion resistance and the like.
Preferably, the first auxiliary agent is an anti-sticking agent and an antioxidant.
Preferably, the second auxiliary agent is a slipping agent and an antioxidant.
Preferably, the third auxiliary agent is a slipping agent, an anti-sticking agent and an antioxidant.
Preferably, the slipping agent is selected from at least one of oleamide and erucamide.
Preferably, the anti-sticking agent is at least one selected from diatomite, calcium carbonate, silica, glass beads and organic silicon micro powder.
Preferably, the antioxidant is selected from phenolic antioxidants or amine antioxidants.
As a further improvement of the above aspect, the thickness of the polyethylene film is 20 to 40 μm; the thickness ratio of the surface layer to the middle layer to the inner layer is 1: (21.5-30.3): (2-2.5).
Specifically, the formula system of the polyethylene film has a wide application range, can meet the thickness requirement of 20-40 mu m, and can obtain better comprehensive performance of products when the thickness of each layer is in a specific range.
The second aspect of the invention provides a preparation method of a polyethylene film.
Specifically, the preparation method of the polyethylene film is used for preparing the polyethylene film, the polyethylene film is prepared by adopting a biaxial stretching method, and the preparation method specifically comprises the following steps:
(1) Compounding: respectively mixing the preparation raw materials of the surface layer, the middle layer and the inner layer, respectively melting and extruding, and compounding to obtain a thick melt;
(2) Casting a sheet: casting and molding the thick sheet melt to obtain a thick sheet;
(3) Stretching: and carrying out longitudinal stretching and transverse stretching on the thick sheet, and carrying out traction and corona treatment to obtain the polyethylene film.
The polyethylene film is prepared by a biaxial stretching method, most of polyethylene films in the packaging material industry at present adopt a film blowing or tape casting processing mode, LDPE or LLDPE is commonly used, and is mostly used for composite layers, heat sealing layers and the like, and the polyethylene film is matched with films with good mechanical properties and barrier property, such as a biaxial stretching polyester film (BOPET), a biaxial stretching nylon film (BOPA) and the like. After the BOPE film of the M-LLDPE formula system is subjected to biaxial stretching, compared with the traditional blow molding PE film, the transparency and the mechanical property of the film are greatly improved due to the high orientation of molecular chains and crystals.
Preferably, the biaxial stretching method is a planar biaxial stretching method.
Specifically, the biaxially oriented plastic film includes a tube film stretching method and a planar biaxial stretching method. The tube-film stretching method is to stretch the film in longitudinal and transverse directions while blowing the bubble tube; the planar biaxial stretching method is to make a melt or solution of a high molecular polymer into a sheet or a thick film by passing through a long and narrow head, then stretch it in two perpendicular directions (longitudinal and transverse) simultaneously or stepwise at a certain temperature and a certain speed in a special stretching machine, and then cool it appropriately or perform special processing (e.g., corona, coating, etc.) to obtain a film. Compared with a tubular film stretching method, the planar biaxial stretching method has the advantages of large stretching magnification, high production efficiency, high mechanical strength, optical performance, high thickness precision and the like, and is more suitable for the production of the polyethylene film.
As a further improvement of the scheme, in the step (1), the melting temperature is 170-250 ℃.
As a further improvement of the scheme, in the step (2), the thickness of the casting sheet is 1.0-1.6mm.
As a further improvement of the scheme, in the step (3), the stretching ratio of the longitudinal stretching is 3.5-5.5, and the temperature is 85-120 ℃.
Preferably, the stretching ratio of the longitudinal stretching is 4 to 5.
As a further improvement of the scheme, in the step (3), the stretching ratio of the transverse stretching is 4-9, and the temperature is 105-135 ℃.
Preferably, the stretching ratio of the transverse stretching is 7-8.
In a third aspect of the invention, there is provided a use of a polyethylene film.
In particular, the polyethylene film of the invention is applied to soft covering materials.
Compared with the prior art, the technical scheme of the invention at least has the following technical effects or advantages:
the polyethylene film is prepared by adding a stiffening agent into a blending system of metallocene linear low-density polyethylene and high-density polyethylene and adopting a biaxial stretching method. The metallocene linear low-density polyethylene is utilized to ensure that the integral strength of the film is improved when the biaxial tension preparation is adopted, thereby reducing the thickness of the film; meanwhile, high-density polyethylene and stiffness increasing agent petroleum resin are added to improve the integral stiffness and temperature resistance of the film. Compared with the conventional BOPE film, the BOPE film is more beneficial to application of downstream manufacturers, and can effectively solve the technical problems of heat shrinkage, seal wrinkling deformation, stretching tearing and the like easily generated during bag making or heat sealing.
Detailed Description
The present invention is specifically described below with reference to examples in order to facilitate understanding of the present invention by those skilled in the art. It should be particularly noted that the examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, as non-essential improvements and modifications to the invention may occur to those skilled in the art, which fall within the scope of the invention as defined by the appended claims. Meanwhile, the raw materials mentioned below are not specified in detail and are all commercial products; the process steps or preparation methods not mentioned in detail are all process steps or preparation methods known to the person skilled in the art.
Example 1
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then respectively extruding by three extruders at 220 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting sheets: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the thick sheet is 0.9mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 120 ℃, wherein the longitudinal stretching multiple is 4; then, performing transverse stretching at 130 ℃, wherein the transverse stretching multiple is 6; and then the polyethylene film sample of the embodiment is prepared by drawing, trimming, thickness measuring and corona, and the thickness of the film is 25 μm.
Example 2
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then, respectively extruding the mixture by three extruders at the extrusion temperature of 220 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting sheets: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the slab is 1.2mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 120 ℃, wherein the longitudinal stretching multiple is 5; then, performing transverse stretching at 130 ℃, wherein the transverse stretching multiple is 8; and then the polyethylene film sample of the embodiment is prepared by drawing, trimming, thickness measuring and corona, and the thickness of the film is 25 μm.
Example 3
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then, respectively extruding the mixture by three extruders at the extrusion temperature of 220 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting a sheet: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the thick sheet is 1.2mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 110 ℃, wherein the longitudinal stretching multiple is 5; then, transverse stretching is carried out at 130 ℃, and the transverse stretching multiple is 8; and then the polyethylene film sample of the embodiment is prepared by drawing, trimming, thickness measuring and corona, and the thickness of the film is 25 μm.
Example 4
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then respectively extruding by three extruders at 230 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting sheets: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the slab is 1.2mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 110 ℃, wherein the longitudinal stretching multiple is 5; then, transverse stretching is carried out at 130 ℃, and the transverse stretching multiple is 8; and then the polyethylene film sample of the embodiment is prepared by drawing, trimming, thickness measuring and corona, and the thickness of the film is 25 μm.
Example 5
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then respectively extruding by three extruders at the extrusion temperature of 210 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting a sheet: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the thick sheet is 1.2mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 100 ℃, wherein the longitudinal stretching multiple is 5; then, transverse stretching is carried out at 130 ℃, and the transverse stretching multiple is 8; it was not stretched to form a film.
Example 6
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the density of the metallocene linear low density polyethylene is 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
A preparation method of a polyethylene film comprises the following steps:
(1) Compounding: respectively weighing the preparation raw materials of the surface layer, the middle layer and the inner layer according to the mass ratio; then mixing the raw materials of each layer respectively; then respectively extruding by three extruders at the extrusion temperature of 210 ℃; finally, compounding by a three-layer die head to prepare a thick melt;
(2) Casting a sheet: molding the thick sheet melt prepared in the step (1) by a sheet casting roller to prepare a thick sheet; the thickness of the thick sheet is 0.9mm, and the thickness ratio of the outer layer, the middle layer and the inner layer is 1:21.5:2.5;
(3) Stretching: firstly, longitudinally stretching the thick sheet prepared in the step (2) at 100 ℃, wherein the longitudinal stretching multiple is 4; then, transverse stretching is carried out at 130 ℃, and the transverse stretching multiple is 6; it was not stretched to form a film.
Comparative example 1
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
96 parts of metallocene linear low-density polyethylene;
1 part of anti-sticking agent diatomite;
3 parts of a phenol antioxidant.
The middle layer comprises the following raw material components in parts by weight:
97 parts of metallocene linear low-density polyethylene;
1.5 parts of a slipping agent oleamide;
1010.5 parts of phenolic antioxidant.
The inner layer comprises the following raw material components in parts by weight:
wherein: the density of the metallocene linear low density polyethylene is 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
The polyethylene film of this comparative example was prepared in the same manner as in example 2.
Comparative example 2
A polyethylene film comprises a surface layer, a middle layer and an inner layer which are sequentially stacked, wherein each layer comprises the following components:
the surface layer comprises the following raw material components in parts by weight:
the middle layer comprises the following raw material components in parts by weight:
the inner layer comprises the following raw material components in parts by weight:
wherein: the metallocene linear low density polyethylene has a density of 0.92g/cm 2 The melt index is 2g/10min; the density of the high density polyethylene is 0.96g/cm 2 The melt index was 0.7g/10min.
The comparative polyethylene film was prepared in the same manner as in example 2.
Performance testing
The polyethylene film samples obtained in the examples and comparative examples were subjected to a performance test according to the Q/FSPG 9-2021 Biaxially Oriented Polyethylene (BOPE) film, product Standard of Fushan Buddha technology group, ltd., and the polyethylene blown film for packaging, GB-T4456-2008.
Wherein: the mechanical property test is executed according to the GB/T1040.3-2006 standard; haze testing was performed according to GB/T2410-2008; and (3) testing the heat-sealing temperature, namely stacking 12 mu m BOPET film on the outer side of the sample, wherein the welding surface pressure is 0.18MPa during heat sealing, the heat-sealing time is 1s, and the heat-sealing strength is more than or equal to the temperature used at 3.0N/15 mm. The test results are characterized by the proportion of each component in the middle layer, and the specific test results are shown in table 1.
Table 1: comparative table of properties of polyethylene film samples prepared in each example and comparative example
As shown in Table 1, the polyethylene films prepared in examples 1-4 all have good stiffness and temperature resistance, which indicates that the stiffness and temperature resistance of the product can be effectively improved by adding HDPE into the biaxially oriented system of the M-LLDPE polyethylene film. Meanwhile, after the stiffening agent is added into the formula system of M-LLDPE and HDPE, the film is easier to stretch in the production process, and the elastic modulus and the stiffness of the film are increased along with the increase of the content of the stiffening agent and the content of HDPE and the increase of the stretching multiple; the haze is reduced; compared with the common BOPE, the heat sealing temperature is improved by about 10 ℃, and the temperature resistance is obviously improved. In examples 5 to 6, the film formation was difficult when the content of M-LLDPE was too much reduced, and the film formation could not be stabilized even when the stretching ratio was reduced. Compared with comparative examples 1-2, the films of examples 1-4 of the invention have obviously higher elastic modulus, greatly improved temperature resistance and improved haze.
It will be obvious to those skilled in the art that many simple derivations or substitutions can be made without inventive effort without departing from the inventive concept. Therefore, simple modifications to the present invention by those skilled in the art based on the present disclosure should be within the scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all similar processes and equivalent variations to those of the present invention should fall within the scope of the present invention.
Claims (10)
1. The polyethylene film is characterized by comprising a surface layer, a middle layer and an inner layer which are sequentially stacked; the raw material components of the surface layer, the middle layer and the inner layer respectively comprise metallocene linear low-density polyethylene, high-density polyethylene and a stiffening agent; the stiffness agent comprises petroleum resin.
2. The polyethylene film of claim 1 wherein the metallocene linear low density polyethylene has a density of from 0.92 to 0.94g/cm 2 The melt index is 0.2-5g/10min.
3. The polyethylene film of claim 1, wherein the high density polyethylene has a density of 0.94 to 0.97g/cm 2 The melt index is 0.2-3g/10min.
4. The polyethylene film according to claim 1, wherein the petroleum resin is a hydrogenated petroleum resin.
5. The polyethylene film according to claim 1, wherein the raw material components of the surface layer, the middle layer and the inner layer all comprise, in parts by weight: 30-68 parts of metallocene linear low-density polyethylene, 30-68 parts of high-density polyethylene and 3-30 parts of a stiffness increasing agent.
6. The polyethylene film according to claim 5, wherein the raw material composition of the surface layer further comprises 1-7 parts by weight of a first auxiliary agent;
the raw material components of the middle layer also comprise 1-5 parts by weight of a second auxiliary agent;
the raw material components of the inner layer also comprise 1-7 parts by weight of a third auxiliary agent;
the first auxiliary agent, the second auxiliary agent and the third auxiliary agent are selected from at least two of slipping agent, antioxidant and anti-sticking agent.
7. Polyethylene film according to any of claims 1 to 6, wherein the polyethylene film has a thickness of 15-60 μm; the thickness ratio of the surface layer to the middle layer to the inner layer is 1: (21.5-30.3): (2-2.5).
8. A preparation method of a polyethylene film, which is used for preparing the polyethylene film of any one of claims 1 to 7, is prepared by a biaxial stretching method, and specifically comprises the following steps:
(1) Compounding: respectively mixing the preparation raw materials of the surface layer, the middle layer and the inner layer, respectively melting and extruding, and compounding to obtain a thick melt;
(2) Casting a sheet: casting and molding the thick sheet melt to obtain a thick sheet;
(3) Stretching: and carrying out longitudinal stretching and transverse stretching on the thick sheet, and carrying out traction and corona treatment to obtain the polyethylene film.
9. The method for preparing a polyethylene film according to claim 8, wherein in the step (1), the temperature of the melting is 170-250 ℃;
in the step (2), the thickness of the casting sheet is 1.0-1.6mm;
in the step (3), the stretching multiple of the longitudinal stretching is 3.5-5.5, and the temperature is 85-120 ℃; the stretching ratio of the transverse stretching is 4-9, and the temperature is 105-135 ℃.
10. Use of a polyethylene film according to any one of claims 1 to 7 in flexible packaging materials.
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| CN117141077A (en) * | 2023-11-01 | 2023-12-01 | 南通金丝楠膜材料有限公司 | Barrier type polyethylene single-material composite antibacterial film and preparation method thereof |
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| CN117141077A (en) * | 2023-11-01 | 2023-12-01 | 南通金丝楠膜材料有限公司 | Barrier type polyethylene single-material composite antibacterial film and preparation method thereof |
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