High-barrier, high-modulus, heat-resistant film and preparation method thereof

Abstract

The present invention provides a high-barrier, high-modulus, temperature-resistant film, comprising a film body, wherein the total thickness of the film body is 20-50 μm, and the film body comprises a first layer, a second layer and a third layer stacked; the first layer and the third layer are made of modified polyethylene, and the modified polyethylene comprises high-density polyethylene, hydrogenated petroleum resin and a nucleating agent, wherein the density ρ1 of the high-density polyethylene is 0.950-0.970 g / cm 3 The weight proportion of hydrogenated petroleum resin in the first layer and the third layer is 20-50%, and the weight proportion of nucleating agent is 0.1-1%; the second layer contains metallocene polyethylene and heat stabilizer, wherein the relationship between the density ρ2 of metallocene polyethylene and the density ρ1 of high-density polyethylene satisfies 0.01≤ρ1-ρ2≤0.05, 1≤ρ1 / ρ2≤1.07. The high-barrier high-modulus heat-resistant film of the present invention has low water vapor permeability, stable temperature resistance and high elastic modulus, and is easy to recycle.

Description

Technical Field

[0001] The invention relates to the field of device polymer film processing, in particular to a high-barrier, high-modulus, temperature-resistant film and a preparation method thereof. Background Art

[0002] For the packaging of liquid materials, since it is necessary to avoid the reduction of contents during transportation and storage, recyclable and environmentally friendly packaging with high barrier properties is required (mainly requiring high water vapor barrier properties). At the same time, with the promotion of green environmental protection concepts, recyclable and environmentally friendly packaging is becoming more and more popular in the market. The existing recyclable and environmentally friendly packaging is mainly made of a single type of material. For this reason, the water vapor barrier properties of the packaging bag can be improved by increasing the thickness of the packaging film or increasing the content of high-density polyethylene (recyclable packaging made of polyethylene as the main material). However, the above methods will increase the packaging cost and are not in line with the environmental protection trend of reducing plastics and materials.

[0003] In order to solve the above problems, patent WO2007106671 discloses a solution for manufacturing a cast film with a low water vapor permeability by mixing organic clay into high-density polyethylene for mixed modification. The brittleness of the cast film mixed with organic clay increases, resulting in a decrease in the toughness and drop resistance of the packaging film, which is easy to cause package breakage during packaging transportation and shelf storage and transfer. In addition, the film made of the mixed components will form gaps near the clay particles after being stretched in the mechanical direction. These gaps can allow gas molecules to pass freely, reducing the gas barrier property of the film. In addition, patent CN106633330A discloses a solution for obtaining a polyethylene film with a high modulus by a biaxial stretching process using a polyethylene composition of linear low-density polyethylene, a nucleating agent and a petroleum resin. However, in the above solution, since the main body of the film uses a linear low-density polyethylene with a low melting point and a low softening point, the temperature resistance of the film is poor. During the high-temperature bag-making process, its surface is easily burned by a heat-sealing knife, and it is easy to produce lateral shrinkage deformation after being heated, which affects the appearance and integrity of the packaging bag. In addition, the elastic modulus of the film is limited, which causes the film to be easily stretched and deformed during the printing process, resulting in printing distortion. Therefore, there is an urgent need for a recyclable environmentally friendly packaging material with a low water vapor permeability, stable temperature resistance and a high elastic modulus. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and to provide a high-barrier, high-modulus, heat-resistant film having a low water vapor permeability, stable temperature resistance, a high elastic modulus, and easy recycling.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A high-barrier, high-modulus, heat-resistant film, comprising a film body, the total thickness of which is 20-50 μm, wherein the film body comprises a first layer, a second layer and a third layer stacked together; the first layer and the third layer are made of modified polyethylene, the modified polyethylene comprises high-density polyethylene, hydrogenated petroleum resin and a nucleating agent, wherein the density ρ1 of the high-density polyethylene is 0.950-0.970 g / cm 3 The weight proportion of hydrogenated petroleum resin in the first layer and the third layer is 20-50%, and the weight proportion of nucleating agent is 0.1-1%; the second layer contains metallocene polyethylene and heat stabilizer, wherein the relationship between the density ρ2 of metallocene polyethylene and the density ρ1 of high-density polyethylene satisfies 0.01≤ρ1-ρ2≤0.05, 1≤ρ1 / ρ2≤1.07.

[0007] Compared with the prior art, the high-barrier, high-modulus, heat-resistant film of the present invention has the following beneficial effects:

[0008] (1) The first layer and the third layer of the present invention are made of modified polyethylene containing high-density polyethylene (good water vapor barrier properties), and the second layer is made of metallocene polyethylene (maintaining a certain toughness). The three-layer film has good barrier properties to water vapor (low water vapor permeability);

[0009] (2) The first layer and the third layer of the present invention are made of modified polyethylene containing high-density polyethylene, and the second layer is made of metallocene polyethylene, wherein the density ρ2 of the metallocene polyethylene is close to the density ρ1 of the high-density polyethylene; since the main components of the three-layer structure are all linear polyethylene molecules, the three-layer structure has a good film-forming effect (stable film structure and morphology), and in addition, the density ρ2 of the metallocene polyethylene is close to the density ρ1 of the high-density polyethylene. After being stretched in the mechanical direction, the entire film (three-layer structure) has a higher elastic modulus and maintains a certain transverse toughness to avoid brittle cracking during use;

[0010] (3) The first layer and the third layer of the present invention are made of modified polyethylene containing high-density polyethylene, wherein the crystallization of the polyethylene resin is more perfect (the higher the density), and its heat resistance is also improved accordingly, so that the present invention has higher heat resistance, and when the present invention is used as a packaging film material, it can be suitable for application scenarios under high temperature;

[0011] (4) By adding nucleating agent and hydrogenated petroleum resin to high-density polyethylene, the nucleating agent can promote the formation of more regular and perfect crystals in high-density polyethylene, greatly increasing the path length of gas molecules passing through the film, thereby improving the gas barrier properties. The high softening point and high glass transition temperature of hydrogenated petroleum resin are used to limit the movement of non-crystallized segments of high-density polyethylene after mixing, increasing the difficulty of gas molecules to pass through the amorphous region; the two parts work synergistically to improve the barrier properties of high-density polyethylene to gas molecules, especially water vapor molecules;

[0012] (5) The main components of the membrane are linear polyethylene molecules and additives. The material composition is simple and easy to recycle and reuse.

[0013] Furthermore, the high-density polyethylene has a melt flow rate of 0.1-2.0 g / 10 min at 190° C. under a load of 2.16 kg.

[0014] By selecting high-density polyethylene (high melting point and high density) with suitable density and melt index (melt flow rate), on the one hand, for the processing process, it is beneficial to prepare high-density polyethylene with stable crystallization rate and grain size, so as to facilitate melt extrusion and stretching into film, and it can be stretched and annealed more efficiently during unidirectional stretching, and a higher annealing temperature can be used. On the other hand, for the finished film, it can ensure that the finished film has sufficient toughness, and ensure that the film has good temperature resistance and barrier properties to water vapor.

[0015] Furthermore, the hydrogenated petroleum resin is C5 hydrogenated petroleum resin,

[0016] The C5 hydrogenated petroleum resin used in the present invention is a low molecular weight polymer (a low molecular weight hydrocarbon polymer) and has good compatibility with polyethylene. The C5 hydrogenated petroleum resin has a high softening point and a high glass transition temperature. After mixing, it restricts the movement of the non-crystallized chain segments of high-density polyethylene, increasing the difficulty of gas molecules penetrating in the amorphous region. After hydrogenation, the heat resistance is improved.

[0017] Furthermore, the softening point of the hydrogenated petroleum resin is 110-140°C.

[0018] The softening point of hydrogenated petroleum resin is moderate (the temperature at which the petroleum resin begins to soften. If the softening point is lower than 110°C, it will cause a large difference between its softening and the carrier melting process, affecting efficient mixing).

[0019] Furthermore, the nucleating agent is at least one of hexahydrophthalate, glycerol alcohol salt, sorbitol acetal, cyclic carboxylate, bicyclic carboxylate and stearate.

[0020] The nucleating agent can induce polyethylene to produce a large number of microcrystals and increase the crystallization rate, thereby reducing the unevenness of the crystal size and crystallization rate of polyethylene, helping high-density polyethylene to form more uniform and complete crystals, so that it has a higher degree of crystallinity and a higher melting temperature, and can increase the modulus of the crystalline region, extend the path through which gas molecules pass when passing through the film, thereby improving the barrier properties, that is, improving the gas barrier properties.

[0021] Furthermore, the comonomers of the metallocene polyethylene are hexene and octene, and the density ρB of the metallocene polyethylene is 0.910-0.945 g / cm 3 .

[0022] Metallocene polyethylene whose comonomers are hexene and octene is selected so that the second layer has sufficient toughness.

[0023] Furthermore, the first layer and the third layer each account for 20-45% of the total weight of the film body, and the second layer accounts for 10-60% of the total weight of the film body.

[0024] Another object of the present invention is to provide a method for preparing the above-mentioned high-barrier, high-modulus, heat-resistant film, comprising:

[0025] The raw materials of each layer are added into the corresponding hopper of the multi-layer co-extrusion equipment according to the weight ratio, and the film blank is extruded through the multi-layer co-extrusion compounding mechanism of the multi-layer co-extrusion equipment, and the film blank is blown to form a film body; during the extrusion process, the raw materials of the upper surface layer and the lower surface layer are respectively mixed and modified through the corresponding twin-screw extruders;

[0026] Perform unidirectional stretching of the film in the mechanical direction online or offline;

[0027] The film body is subjected to electron beam irradiation treatment;

[0028] The film body is subjected to surface corona treatment.

[0029] Compared with the prior art, the method for preparing the high-barrier, high-modulus, heat-resistant film of the present invention has the following beneficial effects:

[0030] (1) In the present invention, the uniaxial stretching process in the mechanical direction can orient the molecular chains and crystals of the film along the mechanical direction, thereby increasing the distance that gas molecules need to penetrate when entering and passing through the film, thereby improving the barrier properties of the film;

[0031] (2) By subjecting the film to stretching, electron beam irradiation and corona treatment, a high-specification film assembly can be formed, and the structural strength, barrier properties and processing properties of the film assembly can be improved. In addition, the outer surface of the film assembly after electron beam irradiation and corona treatment forms good adhesion, which is convenient for subsequent processing and use.

[0032] Furthermore, when the film blank is subjected to uniaxial stretching, a stretching roller with negative pressure adsorption is used to stretch the film blank, the negative pressure on the stretching roller is 200-250 mbar, the stretching temperature is 113-118° C., and the stretching ratio is 1:3-1:10.

[0033] The above configuration has the following beneficial effects:

[0034] (1) When the film is stretched and shaped in the longitudinal direction of the machine, there will be lateral shrinkage in the width direction of the film (the width cannot be stretched to the preset length) and edge accumulation at the edge of the film (the edge thickness cannot be stretched to the preset thickness), resulting in the film quality (width and flatness) failing to reach the predetermined target, affecting the subsequent film processing; the present invention uses a stretching roller with negative pressure adsorption to allow the film assembly to be tightly adsorbed on the stretching roller, thereby reducing the lateral shrinkage and edge accumulation during the stretching process. In addition, by setting the negative pressure on the stretching roller to 200-250 mbar, the film thickness of the present invention is controlled within the range of 20-50 μm, which can avoid the film assembly from being damaged and unevenly stretched due to excessive negative pressure suction during the stretching process, and avoid the film assembly from being unable to be tightly attached to the stretching roller due to too small negative pressure suction;

[0035] (2) Regarding the stretching temperature: If the stretching temperature is too low, abnormal defects such as film breakage and holes are likely to occur during the stretching process of the film; if the stretching temperature is too high, the molecular segments and crystals of the film will relax to a certain extent, resulting in limited stretching orientation effect, affecting the effect of improving the barrier properties; Regarding the stretching ratio: If the stretching ratio is too low, the orientation degree of the film is limited and the barrier properties cannot be effectively improved; if the stretching ratio is too high, it is easy to exceed the stretching limit of the polymer film, frequent film breakage occurs, and stable processing cannot be performed. After the film is unidirectionally stretched at a certain ratio at a specific temperature, the film lamellae can be regularly oriented, thereby increasing the elastic modulus in the stretching direction, which helps to resist deformation caused by tensile force in the mechanical direction.

[0036] Furthermore, when the film body is subjected to electron beam irradiation treatment, the electron beam irradiation amount per square meter of the film body is 5-20 mrad.

[0037] By using electron beam irradiation treatment of a specific intensity, free radicals can be generated on the surface of the treated film to cause a certain degree of cross-linking, thereby increasing the molecular weight of the film surface, so that the film body manufactured by the present invention can withstand higher temperature conditions when heat-sealed by a heat-sealing knife. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a cross-sectional view of the present invention. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention in conjunction with the accompanying drawings:

[0040] See also Figure 1The present embodiment provides a high-barrier, high-modulus, and temperature-resistant film, comprising a film body, the total thickness of the film body is 20-50 μm, the film body comprises a first layer 1, a second layer 2, and a third layer 3 stacked, wherein the third layer 3 is used to contact the package or to contact the third layer 3 of another film body; the first layer 1 and the third layer 3 are made of modified polyethylene, the modified polyethylene comprises high-density polyethylene, hydrogenated petroleum resin, and a nucleating agent, wherein the density ρ1 of the high-density polyethylene is 0.950-0.970 g / cm 3 The weight proportion of hydrogenated petroleum resin in the first layer 1 and the third layer 3 is 20-50%, and the weight proportion of the nucleating agent is 0.1-1%; the second layer 2 contains metallocene polyethylene and a thermal stabilizer, wherein the relationship between the density ρ2 of the metallocene polyethylene and the density ρ1 of the high-density polyethylene satisfies 0.01≤ρ1-ρ2≤0.05, 1≤ρ1 / ρ2≤1.07.

[0041] The melt flow rate of high-density polyethylene at 190°C under a load of 2.16 kg is 0.1-2.0 g / 10 min.

[0042] By selecting high-density polyethylene (high melting point and high density) with suitable density and melt index (melt flow rate), on the one hand, for the processing process, it is beneficial to prepare high-density polyethylene with stable crystallization rate and grain size, so as to facilitate melt extrusion and stretching into film, and it can be stretched and annealed more efficiently during unidirectional stretching, and a higher annealing temperature can be used. On the other hand, for the finished film, it can ensure that the finished film has sufficient toughness, and ensure that the film has good temperature resistance and barrier properties to water vapor.

[0043] The hydrogenated petroleum resin is C5 hydrogenated petroleum resin.

[0044] The C5 hydrogenated petroleum resin used in the present invention is a low molecular weight polymer (a low molecular weight hydrocarbon polymer) and has good compatibility with polyethylene. The C5 hydrogenated petroleum resin has a high softening point and a high glass transition temperature. After mixing, it limits the movement of the non-crystallized chain segments of high-density polyethylene, increases the difficulty of gas molecules to penetrate in the amorphous region, and thus improves the gas barrier property.

[0045] The softening point of hydrogenated petroleum resin is 110-140℃.

[0046] The softening point of hydrogenated petroleum resin is moderate (the temperature at which the petroleum resin begins to soften. If the softening point is lower than 110°C, it will cause a large difference between its softening and the carrier melting process, affecting efficient mixing).

[0047] The nucleating agent is at least one of hexahydrophthalate, glycerol alcohol salt, sorbitol acetal, cyclic carboxylate, bicyclic carboxylate and stearate.

[0048] The nucleating agent can induce polyethylene to produce a large number of microcrystals and increase the crystallization rate, thereby reducing the unevenness of the crystal size and crystallization rate of polyethylene, helping high-density polyethylene to form more uniform and complete crystals, so that it has a higher degree of crystallinity and a higher melting temperature, and can increase the modulus of the crystalline region, extend the path through which gas molecules pass when passing through the film, thereby improving the barrier properties, that is, improving the gas barrier properties.

[0049] The comonomers of metallocene polyethylene are hexene and octene, and the density ρB of metallocene polyethylene is 0.910-0.945g / cm 3 .

[0050] Metallocene polyethylene whose comonomers are hexene and octene is selected so that the second layer 2 has sufficient toughness.

[0051] The first layer 1 and the third layer 3 each account for 20-45% of the total weight of the film, and the second layer 2 accounts for 10-60% of the total weight of the film.

[0052] Specifically, the weight ratio of the first layer 1, the second layer 2 and the third layer 3 is 30-45:10-40:30-45, preferably the weight ratio of the first layer 1, the second layer 2 and the third layer 3 is 35-40:20-30:35-40.

[0053] The specific enthalpy of the first layer 1 is H1, the specific enthalpy of the second layer 2 is H2, and the specific enthalpy of the third layer 3 is H3, wherein the relationship between H1, H2 and H3 satisfies H1≥H3≥0.9H1, 2H2≥H1≥1.2H2 (i.e., H1≥H3>H2); the specific enthalpy is the heat required per unit weight of the core layer or surface layer resin to be converted from a solid state to a completely molten state (unit: J / g), and the value of H1 is 270-290J / g.

[0054] Compared with the prior art, the high-barrier, high-modulus, heat-resistant film of the present invention has the following beneficial effects:

[0055] (1) The first layer 1 and the third layer 3 of the present invention are made of modified polyethylene containing high-density polyethylene (good water vapor barrier properties), and the second layer 2 is made of metallocene polyethylene (maintaining a certain toughness). The three-layer film has good water vapor barrier properties (low water vapor permeability);

[0056] (2) The first layer 1 and the third layer 3 of the present invention are made of modified polyethylene including high-density polyethylene, and the second layer 2 is made of metallocene polyethylene, wherein the density ρ2 of the metallocene polyethylene is close to the density ρ1 of the high-density polyethylene; since the main components of the three-layer structure are all linear polyethylene molecules, the three-layer structure has a good film-forming effect (stable film structure and morphology); in addition, the density ρ2 of the metallocene polyethylene is close to the density ρ1 of the high-density polyethylene; after being stretched in the mechanical direction, the entire film (three-layer structure) has a higher elastic modulus and maintains a certain transverse toughness to avoid brittle cracking during use;

[0057] (3) The first layer 1 and the third layer 3 of the present invention are made of modified polyethylene containing high-density polyethylene, wherein the crystallization of the polyethylene resin is more perfect (the higher the density), and its heat resistance is also improved accordingly, so that the present invention has higher heat resistance, and when the present invention is used as a packaging film material, it can be suitable for application scenarios under high temperature;

[0058] (4) By adding nucleating agent and hydrogenated petroleum resin to high-density polyethylene, the nucleating agent can promote the formation of more regular and perfect crystals in high-density polyethylene, greatly increasing the path length of gas molecules passing through the film, thereby improving the gas barrier properties. The high softening point and high glass transition temperature of hydrogenated petroleum resin are used to limit the movement of non-crystallized segments of high-density polyethylene after mixing, increasing the difficulty of gas molecules to pass through the amorphous region; the two parts work synergistically to improve the barrier properties of high-density polyethylene to gas molecules, especially water vapor molecules;

[0059] (5) The main components of the membrane are linear polyethylene molecules and additives. The material composition is simple and easy to recycle and reuse.

[0060] Another object of the present invention is to provide a method for preparing the above-mentioned high-barrier, high-modulus, heat-resistant film, comprising:

[0061] The raw materials of each layer are added into the corresponding hopper of the multi-layer co-extrusion equipment according to the weight ratio, and the film blank is extruded through the multi-layer co-extrusion compounding mechanism of the multi-layer co-extrusion equipment, and the film blank is blown to form a film body; during the extrusion process, the raw materials of the upper surface layer and the lower surface layer are respectively mixed and modified through the corresponding twin-screw extruders;

[0062] Perform unidirectional stretching of the film in the mechanical direction online or offline;

[0063] The film body is subjected to electron beam irradiation treatment;

[0064] The film body is subjected to surface corona treatment.

[0065] When the film blank is subjected to uniaxial stretching, a stretching roller with negative pressure adsorption is used to stretch the film blank. The negative pressure on the stretching roller is 200-250 mbar, the stretching temperature is 113-118° C., and the stretching ratio is 1:3-1:10.

[0066] The above configuration has the following beneficial effects:

[0067] (1) When the film is stretched and shaped in the longitudinal direction of the machine, there will be lateral shrinkage in the width direction of the film (the width cannot be stretched to the preset length) and edge accumulation at the edge of the film (the edge thickness cannot be stretched to the preset thickness), resulting in the film quality (width and flatness) failing to reach the predetermined target, affecting the subsequent film processing; the present invention uses a stretching roller with negative pressure adsorption to allow the film assembly to be tightly adsorbed on the stretching roller, thereby reducing the lateral shrinkage and edge accumulation during the stretching process. In addition, by setting the negative pressure on the stretching roller to 200-250 mbar, the film thickness of the present invention is controlled within the range of 20-50 μm, which can avoid the film assembly from being damaged and unevenly stretched due to excessive negative pressure suction during the stretching process, and avoid the film assembly from being unable to be tightly attached to the stretching roller due to too small negative pressure suction;

[0068] (2) Regarding the stretching temperature: If the stretching temperature is too low, abnormal defects such as film breakage and holes are likely to occur during the stretching process of the film; if the stretching temperature is too high, the molecular segments and crystals of the film will relax to a certain extent, resulting in limited stretching orientation effect, affecting the effect of improving the barrier properties; Regarding the stretching ratio: If the stretching ratio is too low, the orientation degree of the film is limited and the barrier properties cannot be effectively improved; if the stretching ratio is too high, it is easy to exceed the stretching limit of the polymer film, frequent film breakage occurs, and stable processing cannot be performed. After the film is unidirectionally stretched at a certain ratio at a specific temperature, the film lamellae can be regularly oriented, thereby increasing the elastic modulus in the stretching direction, which helps to resist deformation caused by tensile force in the mechanical direction.

[0069] When the film body is subjected to electron beam irradiation treatment, the electron beam irradiation amount per square meter of the film body is 5-20 mrad.

[0070] By using electron beam irradiation treatment of a specific intensity, free radicals can be generated on the surface of the treated film to cause a certain degree of cross-linking, thereby increasing the molecular weight of the film surface, so that the film body manufactured by the present invention can withstand higher temperature conditions when heat-sealed by a heat-sealing knife.

[0071] The first layer and the third layer of the present invention contain hydrogenated petroleum resin, and the second layer contains a heat stabilizer. The hydrogenated petroleum resin and the heat stabilizer can improve the stability of the material. By controlling the content of the hydrogenated petroleum resin in the first layer and the third layer and the content of the heat stabilizer in the second layer, the relationship between the specific enthalpy H1 of the first layer, the specific enthalpy H2 of the second layer and the specific enthalpy H3 of the third layer satisfies H1≥H3≥0.9H1, 2H2≥H1≥1.2H2. It is known that the weight ratio of the first layer, the second layer and the third layer is: 30-45:10-40:30-45. When the specific enthalpy H1 of the first layer, the specific enthalpy H2 of the second layer and the specific enthalpy H3 of the third layer satisfy the above relationship, in the process of multi-layer co-extrusion compounding, by setting an extruder The heating temperature of the barrel of each layer (when determining the material temperature that each layer of material needs to be heated to (each layer of material is heated in a different barrel in the extruder, and the material temperature that the material needs to be heated to is the temperature before the material enters the material compounding section of the extruder), the heating temperature of the barrel corresponding to each layer of material can be calculated according to the mass, specific enthalpy and material temperature that needs to be heated to (the temperature of the material compounding section of the extruder in this application is 160-200°C), so that the temperatures of each layer of the structure in the molten state after heating tend to be close, so that the composite strength between the layers is enhanced when the layers are compounded in the molten state to form a film blank, thereby improving the structural strength of the film body, and in the process of film making and stretching, since the total heat distribution of each layer is evenly distributed Uniform, so that during the stretching process, the temperature difference between each area of ​​the same layer in the horizontal direction is small, while in the vertical direction, heat is transferred from the first layer and the third layer to the second layer, and the heat of the first layer and the third layer is lost outward, causing the temperature of the first layer and the third layer to drop. Since H1≥H3≥0.9H1, 2H2≥H1≥1.2H2, the second layer is sandwiched in the middle and the total heat of the second layer is not greater than that of the first layer and the third layer, so the heat of the second layer will not be lost much, so that the temperature difference between each area in the vertical direction is also small and the melting state is close, so that the shrinkage rate of the film in the length and width directions can be accurately controlled. If 1.2H2>H1 or H1>2H2 (adjust the hydrogenation in the first layer and the third layer The content of petroleum resin or the content of heat stabilizer in the second layer causes the specific enthalpy of each layer to change), the following situations will occur: (1) 1.2H2>H1>H2, which means that the specific enthalpy of the second layer is close to that of the first layer. During the stretching process of the film, the heat of the first layer / third layer will be transferred to the second layer, making the melting state of the second layer different from that of the first layer / third layer, resulting in a poor stretching effect; (2) H1>2H2, which means that the specific enthalpy of the first layer is much larger than the specific enthalpy of the second layer. During the composite process, a large amount of heat from the first layer / third layer is transferred to the second layer, causing the temperature of the second layer / third layer to drop too fast, resulting in the temperature of each layer being different and the composite strength of each layer when forming a film blank being reduced, thereby affecting the structural strength of the film.

[0072] In this embodiment, the high-density polyethylene is selected from commercially available ExxonMobil HTA 108 or Total Lumicene M6012 EP or Dow Elite 5960G or Hanwha F920A.

[0073] In this embodiment, the raw material of the second layer is selected from commercially available ExxonMobilExceed 1018MA or ExxonMobilExceed XP8656 or Dow Elite 5400G, etc. The commercially available materials contain metallocene polyethylene and a heat stabilizer.

[0074] Since the raw materials of the second layer already contain metallocene polyethylene and heat stabilizer, the density of the first layer / third layer is adjusted mainly by adjusting the ratio of hydrogenated petroleum resin in the first layer and the third layer in this embodiment; in the modified polyethylene of this embodiment, the weight ratio of high-density polyethylene, hydrogenated petroleum resin and nucleating agent is 60-75:25-40:0.1-1%.

[0075] In this embodiment, the processing temperature of extrusion compounding is as follows, wherein it is known that the melting temperature of high-density polyethylene is 160-280°C. In this embodiment, the heating temperature of the barrels No. 1 (first layer material) and No. 3 (third layer material) is set to 160-180°C, the heating temperature of the barrel No. 2 (second layer material) is set to 130-150°C, and the temperature of the compounding section is 160-175°C.

[0076] Compared with the prior art, the method for preparing the high-barrier, high-modulus, heat-resistant film of the present invention has the following beneficial effects:

[0077] (1) In the present invention, the uniaxial stretching process in the mechanical direction can orient the molecular chains and crystals of the film along the mechanical direction, thereby increasing the distance that gas molecules need to penetrate when entering and passing through the film, thereby improving the barrier properties of the film;

[0078] (2) By subjecting the film to stretching, electron beam irradiation and corona treatment, a high-specification film assembly can be formed, and the structural strength, barrier properties and processing properties of the film assembly can be improved. In addition, the outer surface of the film assembly after electron beam irradiation and corona treatment forms good adhesion, which is convenient for subsequent processing and use.

[0079] The following provides relevant experimental data of high barrier and high modulus heat resistant films:

[0080] Example 1

[0081] The first layer and the third layer are made of 70% high-density polyethylene resin Total M6012EP, 29.9% C5 hydrogenated petroleum resin ExxonMobil Oppera PR120 and 0.1% nucleating agent Milliken HPN-20E respectively, and the second layer uses polyethylene resin XP8656 (its components are metallocene polyethylene and heat stabilizer). The thickness ratio of the first layer, the second layer and the third layer is 40%:20%:40%, and the film thickness is 25μm.

[0082] Example 2

[0083] The first and third layers are made of 60% high-density polyethylene resin Total M6012EP, 39.9% C5 hydrogenated petroleum resin ExxonMobil Oppera PR120 and 0.1% nucleating agent Milliken HPN-20E respectively, and the second layer uses polyethylene resin XP8656. The thickness ratio of the first layer, the second layer and the third layer is 40%:20%:40%, and the film thickness is 25μm.

[0084] Comparative Example 1 (Comparative Example 1 without stretching treatment)

[0085] The first layer and the third layer are made of 70% high-density polyethylene resin Total M6012EP, 29.9% C5 hydrogenated petroleum resin ExxonMobil Oppera PR120 and 0.1% nucleating agent Milliken HPN-20E respectively, and the second layer uses polyethylene resin XP8656 without stretching treatment. The thickness ratio of the first layer, the second layer and the third layer is 40%:20%:40%, and the film thickness is 25μm.

[0086] Comparative Example 2 (Comparative Example 1 without adding C5 hydrogenated petroleum resin)

[0087] The first and third layers are made of 99.9% high-density polyethylene resin Total M6012EP and nucleating agent Milliken HPN-20E respectively, and the second layer uses polyethylene resin XP8656. The thickness ratio of the first, second and third layers is 40%:20%:40%, and the film thickness is 25μm.

[0088] Comparative Example 3 (Comparative Example 1 without adding nucleating agent)

[0089] The first and third layers are made of 70% high-density polyethylene resin Total M6012EP and 30% C5 hydrogenated petroleum resin ExxonMobil Oppera PR120 respectively, and the second layer uses polyethylene resin XP8656. The thickness ratio of the first, second and third layers is 40%:20%:40%, and the film thickness is 25μm.

[0090] Comparative Example 4 (Comparative Example 1 without irradiation treatment)

[0091] The first and third layers are made of 70% high-density polyethylene resin Total M6012EP, 29.9% C5 hydrogenated petroleum resin ExxonMobil Oppera PR120 and 0.1% nucleating agent Milliken HPN-20E respectively, and the second layer uses polyethylene resin XP8656. The thickness ratio of the first layer, the second layer and the third layer is 40%:20%:40%. No irradiation treatment is performed, and the film thickness is 25μm.

[0092] Comparative Example 5

[0093] With reference to Example 1 of invention patent CN106633327A, resins of LLDPE SP1520 (density 0.913, melt index 190°C 2.0g / 10min) containing hexene comonomer and LLDPE SP1540 (density 0.913, melt index 190°C 3.8g / 10min) containing hexene comonomer are mixed in a weight ratio of 80:20, and then 0.1% of nucleating agent Milliken HPN-20E and 10% of C9 petroleum resin with a softening point of 125°C are added to prepare a film blank, which is formed by MD and TD distributed stretching processes, wherein the MD preheating temperature is 100°C, the stretching temperature is 110°C, the MD stretching ratio is 4 times, the TD preheating temperature is 100°C, the stretching temperature is 115°C, the TD stretching ratio is 8 times, and the shaping temperature is 120°C to obtain a 25um stretched sample film.

[0094] Performance test

[0095] Water vapor transmission rate test: Use Mocon water vapor transmission rate tester to test the water vapor transmission rate of the film;

[0096] Heat resistance test: Use a heat sealing machine to test the sample film at the heating temperatures of the upper and lower heating knives at 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ and 140℃ in sequence, where the upper and lower heat sealing knife temperatures are the same; during the test, the treated surfaces of the two sample films are placed together, the heat sealing time is 1.0s, and the heat sealing pressure is 0.2MPa; the lowest temperature at which the treated surfaces of the sample films stick together is the sticking temperature.

[0097] Elastic modulus test: Tested in accordance with GB-T 1845.2-2021.

[0098] Table 1: Performance test results of embodiments and comparative examples

[0099] name MD elastic modulus / MPa Adhesion temperature <![CDATA[Water vapor transmission rate g / (m 2 ·day·atm)]]> Example 1 1200 135℃ 2.6 Example 2 1250 135℃ 2.5 Comparative Example 1 550 135℃ 15.0 Comparative Example 2 1100 135℃ 9.6 Comparative Example 3 1050 135℃ 6.0 Comparative Example 4 1200 125℃ 2.6 Comparative Example 5 800 115℃ 18.3

[0100] Conclusion 1: By comparing Example 1 and Example 2, it can be seen that the addition amount of C5 hydrogenated petroleum resin increases by 10%, and the addition amount of high-density polyethylene resin decreases by 10%, and the effect on elastic modulus, adhesion temperature and water vapor permeability is not obvious, indicating that within the ratio range of the raw materials of the present application, the film can maintain a high elastic modulus, temperature resistance and low water vapor permeability;

[0101] Conclusion 2: By comparing Example 1 with Comparative Example 1, it can be seen that the elastic modulus and water vapor permeability of the film after uniaxial stretching treatment are improved (both of the above can be greatly improved);

[0102] Conclusion 3: By comparing Example 1 and Comparative Example 2, it can be seen that the addition of C5 hydrogenated petroleum resin can increase the elastic modulus of the film and reduce the water vapor permeability;

[0103] Conclusion 4: By comparing Example 1 and Comparative Example 3, it can be seen that the addition of nucleating agent can increase the elastic modulus of the film and reduce the water vapor permeability;

[0104] Conclusion 5: By comparing Example 1 and Comparative Example 4, it can be seen that the elastic modulus and water vapor transmission resistance of the film after irradiation treatment are improved (both of the above can be greatly improved).

[0105] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a high-barrier, high-modulus, heat-resistant film, characterized in that: Used to prepare a high-barrier, high-modulus, heat-resistant film, the high-barrier, high-modulus, heat-resistant film comprising a film body, the total thickness of the film body is 20-50 μm, and the film body comprises a first layer, a second layer and a third layer stacked; The first layer and the third layer are made of modified polyethylene, which comprises high-density polyethylene, hydrogenated petroleum resin and a nucleating agent, wherein the density ρ1 of the high-density polyethylene is 0.950-0.970 g / cm 3 , the weight proportion of hydrogenated petroleum resin in the first layer and the third layer is 20-50%, and the weight proportion of nucleating agent is 0.1-1%; The second layer comprises metallocene polyethylene and a heat stabilizer, wherein the relationship between the density ρ2 of the metallocene polyethylene and the density ρ1 of the high-density polyethylene satisfies 0.01≤ρ1-ρ2≤0.05, 1≤ρ1 / ρ2≤1.07; The melt flow rate of high-density polyethylene at 190°C under a load of 2.16 kg is 0.1-2.0 g / 10 min; The hydrogenated petroleum resin is C5 hydrogenated petroleum resin; The comonomers of metallocene polyethylene are hexene and octene, and the density ρB of metallocene polyethylene is 0.910-0.945g / cm 3 ; The first and third layers each account for 20-45% of the total weight of the membrane, and the second layer accounts for 10-60% of the total weight of the membrane; The preparation method comprises: The raw materials of each layer are added into the corresponding hopper of the multi-layer co-extrusion equipment according to the weight ratio, and the film blank is extruded through the multi-layer co-extrusion compounding mechanism of the multi-layer co-extrusion equipment, and the film blank is blown to form a film body; during the extrusion process, the raw materials of the upper surface layer and the lower surface layer are respectively mixed and modified through the corresponding twin-screw extruders; Perform unidirectional stretching of the film in the mechanical direction online or offline; The film body is subjected to electron beam irradiation treatment; The film body is subjected to surface corona treatment.

2. The method for preparing a high-barrier, high-modulus, heat-resistant film according to claim 1, characterized in that: The softening point of hydrogenated petroleum resin is 110-140℃.

3. The method for preparing a high-barrier, high-modulus, heat-resistant film according to claim 1, characterized in that: The nucleating agent is at least one of hexahydrophthalate, glycerol alcohol salt, sorbitol acetal, talc, cyclic carboxylate, bicyclic carboxylate and stearate.

4. The method for preparing a high-barrier, high-modulus, heat-resistant film according to claim 1, characterized in that: When the film blank is subjected to uniaxial stretching, a stretching roller with negative pressure adsorption is used to stretch the film blank. The negative pressure on the stretching roller is 200-250 mbar, the stretching temperature is 113-118° C., and the stretching ratio is 1:3-1:

10.

5. The method for preparing a high-barrier, high-modulus, heat-resistant film according to claim 1, characterized in that: When the film body is subjected to electron beam irradiation treatment, the electron beam irradiation amount per square meter of the film body is 5-20 mrad.

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