High-performance biaxially oriented aluminized film and preparation method thereof

Abstract

The invention discloses a high-performance biaxially oriented aluminized film and a preparation method thereof.The biaxially oriented aluminized film comprises a base material layer, a middle layer, an interface synergistic layer and an aluminized layer which are sequentially arranged from bottom to top, and the middle layer comprises pearlescent master batch, homo-polypropylene and polymethyl methacrylate-polypropylene block copolymer; the interface synergistic layer contains co-polypropylene and norbornene dianhydride grafted polyolefin elastomer, the aluminum-plated layer adopts a vacuum evaporation aluminum layer, and the upper end part of the aluminum-plated layer is coated with an aluminum oxide protective layer. According to the technical scheme, the surface tension of the film is large and lasting, the adhesive force is good, the uniformity of a metal aluminum plating layer is high, the metal feeling is strong, the compounding fastness is high, the mechanical property, the barrier property and the aluminum plating binding force of the film are improved, the service life of the film is effectively prolonged, and the performance stability of the film is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thin films, and particularly relates to a high-performance biaxially oriented aluminized film and a preparation method thereof. Background Art

[0002] Biaxially oriented polypropylene film (BOPP) is generally a multi-layer co-extruded film. It is made by co-extruding polypropylene particles into a sheet and then stretching it in both the longitudinal and transverse directions. Due to molecular orientation during stretching, this film has good physical stability, mechanical strength, and airtightness, high transparency and gloss, and is tough and wear-resistant. It is a widely used printing film, generally with a thickness of 20 - 40 μm, and the most widely used is 20 μm. The main disadvantage of biaxially oriented polypropylene film is its poor heat-sealing property, so it is generally used as the outer layer film of composite films. For example, when compounded with polyethylene film, its moisture resistance, transparency, strength, stiffness, and printability are all ideal, and it is suitable for packaging dry foods. Since the surface of biaxially oriented polypropylene film is non-polar, has a high degree of crystallinity, and low surface free energy, its printing performance is poor, and its adhesion to inks and adhesives is poor. Therefore, surface treatment is required before printing and compounding.

[0003] With the continuous improvement of global environmental awareness, environmentally friendly packaging materials have become the development trend of the packaging industry. As an important packaging material, BOPP film is widely used in many industries such as food, medicine, and cosmetics.

[0004] However, most of the aluminized layers of the existing BOPP aluminized films on the market are formed by the transfer method, which has many process steps, low efficiency, high cost, and the aluminized layer is prone to peeling off, affecting the service life and performance of the film. Summary of the Invention

[0005] The main purpose of the present invention is to propose a high-performance biaxially oriented aluminized film and a preparation method thereof, aiming to solve the technical problems that the aluminized layer of the existing BOPP aluminized film is formed by the transfer method, with many process steps, low efficiency, high cost, and the aluminized layer is prone to peeling off, affecting the service life and performance of the film.

[0006] To achieve the above object, the high-performance biaxially oriented aluminized film proposed by the present invention includes a substrate layer, an intermediate layer, an interfacial synergistic layer, and an aluminized layer arranged in sequence from bottom to top. The substrate layer is formed of BOPP or BOPET material. The intermediate layer contains pearlescent masterbatch, homopolypropylene, and poly(methyl methacrylate - polypropylene) block copolymer. The interfacial synergistic layer contains copolymerized polypropylene and norbornene dianhydride grafted polyolefin elastomer. The aluminized layer is a vacuum-evaporated aluminized layer, and an alumina protective layer is coated on the upper end of the aluminized layer.

[0007] Optionally, the thickness of the base material layer ranges from 12 μm to 50 μm, the thickness of the intermediate layer ranges from 20 μm to 60 μm, and the thickness of the interface enhancing layer ranges from 10 μm to 30 μm.

[0008] Optionally, by mass percentage, the intermediate layer contains 15% to 40% of pearlescent masterbatch and 2% to 5% of poly(methyl methacrylate - polypropylene) block copolymer, with the balance being homopolypropylene.

[0009] Optionally, the base material layer is formed of low - melting - point terpolymerized polypropylene.

[0010] Optionally, the thickness of the aluminized layer ranges from 0.02 to 0.05 μm.

[0011] Optionally, by mass percentage, the interface enhancing layer contains 20% to 30% of norbornene anhydride - grafted polyolefin elastomer, with the balance being copolymerized polypropylene.

[0012] On the other hand, the present invention also provides a method for preparing a high - performance biaxially stretched aluminized film, and the preparation method includes the following steps: Raw material pretreatment: The prepared raw materials enter the main extruder and the auxiliary extruder through the feeding port. Under the environment of high temperature and high pressure, through the shearing and extrusion of the screw rod, they are gradually melted, plasticized, and mixed to ensure the uniformity of melting. Co - extrusion casting: The filtered melt enters the die head of the extruder through the melt pipeline, and under the push of pressure, it passes through the die lip. Under the action of the air knife, the polypropylene melt flowing out of the die head in a viscous flow state is tightly attached to the surface of the chill roll. There is flowing cooling water inside the chill roll. Under the combined cooling of the air knife, the surface of the chill roll, and the water bath, the temperature drops to 20 - 35 °C, and it is rapidly cooled and cast into a sheet to form a multi - layer base film structure. Longitudinal stretching: The cooled sheet enters the longitudinal stretching device for longitudinal stretching treatment. Through the steps of pre - heating, longitudinal stretching, and shaping, the sheet is longitudinally elongated by the stretching rollers at a magnification speed difference, and the molecular chains are oriented along the longitudinal direction. Transverse stretching: The sheet after longitudinal stretching enters the transverse stretching device for transverse stretching treatment. Through the steps of film feeding, pre - heating, transverse stretching, shaping, and cooling, the transverse stretching process is completed to form a uniform planar orientation structure. Heat setting: The stretched film is heat - set at a high temperature to fix the arrangement of the molecular chains and reduce subsequent shrinkage. Coating of the interface enhancing layer: A layer of polyurethane - acrylic composite glue is coated on the surface layer of the base film, and after drying and curing, a dense coating is formed to fill the surface roughness and enhance the adhesion of the aluminized layer. Surface pretreatment: The surface of the base film is corona-treated to increase the surface energy. In a vacuum chamber, high-purity aluminum wire is heated and evaporated by resistance heating or arc melting. The evaporation temperature is 1100-1400°C. The gaseous aluminum molecules are rapidly cooled by a cooling system, and the aluminum vapor condenses and uniformly deposits on the surface of the base film to form an aluminized layer; After cooling, an aluminum oxide protective layer is coated on the surface of the aluminized layer, and the internal stress is eliminated by aging treatment, and then slitting and winding are carried out to finally obtain the finished product.

[0013] Adopting the technical solution of the present invention has the following beneficial effects: The technical solution of the present invention, through the substrate layer, intermediate layer, interfacial synergistic layer and aluminized layer arranged in sequence from bottom to top, the substrate layer is formed of BOPP or BOPET material, the intermediate layer contains pearlescent masterbatch, homopolypropylene and polymethyl methacrylate-polypropylene block copolymer, the interfacial synergistic layer contains copolymerized polypropylene and norbornene dianhydride grafted polyolefin elastomer, and the aluminized layer adopts a vacuum aluminized layer, so that the surface of the plastic film has a metallic luster, and the surface tension of the film is large and the surface tension is persistent, the adhesion is good, the uniformity of the aluminum layer is high, the metallic feeling is strong, the composite fastness is high, the process steps of the aluminized layer are simple, the cost is low, the efficiency is high, the energy and materials are saved, the cost is reduced, the aluminized layer can form a heat barrier, slow down the heat conduction, and has excellent barrier performance, has excellent folding resistance and good toughness, the aluminized layer has good electrical conductivity and can eliminate the electrostatic effect; its sealing performance is good, especially when packaging powdery products, it will not contaminate the sealing part and ensure the sealing performance of the package. It has both the characteristics of plastic film and the characteristics of metal, has good adaptability to post-processing such as printing and compounding, the aluminized layer can block light and prevent ultraviolet irradiation, extend the shelf life of the contents, has low price, beautiful appearance and good barrier performance. The present invention adopts a multi-layer composite structure design, uses modified polyester to improve the surface activity to enhance the adhesion of the aluminized layer, further optimizes the bonding strength and barrier performance of the aluminized layer through the interfacial synergistic layer, improves the crystallinity and uniformity through biaxial stretching, and adopts a vacuum evaporation process to deposit a nano-scale aluminum layer on the surface of the interfacial synergistic layer, endowing the film with high barrier properties, thereby improving the mechanical properties, barrier properties and aluminized bonding force of the aluminized film, and effectively improving its service life and performance stability. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0015] Figure 1Schematic diagram of the decomposition structure of a high-performance biaxially stretched aluminized film according to an embodiment of the present invention; Figure 2 Flow chart of the steps of a preparation method of a high-performance biaxially stretched aluminized film according to an embodiment of the present invention.

[0016] The realization of the object of the present invention, functional features and advantages will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0019] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of the technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0020] The present invention provides a high-performance biaxially stretched aluminized film and a preparation method thereof.

[0021] In an embodiment of the present invention, as Figure 1 shown, the high-performance biaxially stretched aluminized film includes a substrate layer 101, an intermediate layer 102, an interface enhancement layer 103, and an aluminized layer 104 arranged in sequence from bottom to top. The substrate layer 101 is formed of BOPP or BOPET material. The intermediate layer 102 contains pearlescent masterbatch, homopolypropylene, and poly(methyl methacrylate)-polypropylene block copolymer. The interface enhancement layer 103 contains copolymerized polypropylene and norbornenedicarboxylic anhydride grafted polyolefin elastomer. The aluminized layer 104 is a vacuum-evaporated aluminized layer. An alumina protective layer is coated on the upper end of the aluminized layer 104. A silica or talcum powder opening agent layer is provided on the lower end wall of the substrate layer 101.

[0022] Specifically, the thickness range of the substrate layer 101 is 12 μm to 50 μm, the thickness range of the intermediate layer 102 is 20 μm to 60 μm, and the thickness range of the interfacial enhancement layer 103 is 10 μm to 30 μm.

[0023] Specifically, by mass percentage, the intermediate layer 102 contains 15% to 40% of pearlescent masterbatch and 2% to 5% of polymethyl methacrylate - polypropylene block copolymer, and the balance is homopolypropylene.

[0024] Specifically, the substrate layer 101 is formed of low - melting - point terpolymer polypropylene.

[0025] Specifically, the thickness range of the aluminized layer is 0.02 to 0.05 μm.

[0026] Specifically, by mass percentage, the interfacial enhancement layer contains 20% to 30% of norbornene anhydride - grafted polyolefin elastomer, and the balance is copolymerized polypropylene. The interfacial enhancement layer can also adopt modified polyester or PP containing polar groups (such as carboxylate ester) to enhance the aluminizing adhesion, and the extrusion temperature is 260 - 280 °C.

[0027] On the other hand, the present invention also provides a method for preparing a high - performance biaxially oriented aluminized film, and the preparation method includes the following steps: S100: Raw material pretreatment, the polyester (PET) or polypropylene (PP) raw materials need to be dried (humidity ≤ 50 ppm), and functional masterbatches (such as anti - blocking agent, slip agent) are mixed. The prepared raw materials enter the main extruder and the auxiliary extruder through the feeding port, and under the environment of high temperature and high pressure, through the shearing and extrusion of the screw rod, they are gradually melted, plasticized and mixed to ensure the melting uniformity. S200: Co - extrusion casting, the filtered melt enters the die head of the extruder through the melt pipeline, and under the push of pressure, it passes through the die lip. Under the action of the air knife, the polypropylene melt flowing out of the die head in a viscous flow state is tightly attached to the surface of the chill roll. There is flowing cooling water inside the chill roll. Under the combined cooling of the air knife, the surface of the chill roll and the water bath, the temperature drops to 20 - 35 °C, and it is quenched and cast into a sheet, forming an amorphous thick sheet (crystallinity < 5%). S300: Longitudinal stretching, the cooled sheet enters the longitudinal stretching device for longitudinal stretching treatment. Through the steps of pre - heating, longitudinal stretching and shaping, the sheet is longitudinally elongated by the stretching rollers in a way of magnification speed difference, and the molecular chains are oriented longitudinally. Pre - heating temperature: 130 - 135 °C for PET base film, 120 - 125 °C for PP base film; stretching ratio: 3 - 5 times for PET, 5 - 6 times for PP, and the longitudinal orientation of molecular chains is achieved through multi - roll differential stretching. S400: Transverse stretching. The sheet after longitudinal stretching enters the transverse stretching device for transverse stretching treatment. Through the steps of film feeding, preheating, transverse stretching, shaping and cooling, the transverse stretching process is completed to form a uniform planar orientation structure. Preheating temperature: 90 - 100°C for PET, 160 - 165°C for PP. Stretching ratio: 2.5 - 4 times for PET, 8 - 10 times for PP. Transverse expansion is carried out using a chain clip type tenter frame, and synchronous cooling: immediately cooled to 40 - 50°C after stretching to lock the molecular chain orientation structure; S500: Heat setting: The stretched film is heat set at a high temperature to fix the molecular chain arrangement and reduce subsequent shrinkage. Heat setting temperature: 200 - 220°C for PET, 160 - 165°C for PP, lasting for 5 - 10 seconds to eliminate internal stress; Corona treatment on the film surface (power 5 - 10 kW) to make the surface energy ≥ 45 mN / m to improve the adhesion of subsequent coating; S600: Coating of the interfacial enhancement layer. A layer of polyurethane - acrylic composite glue is coated on the surface layer of the base film and dried and cured to form a dense coating to fill the surface roughness and enhance the adhesion of the aluminized layer. Specifically, polyurethane - acrylic composite emulsion (solid content 20% - 30%), adding nano - titanium dioxide (particle size 20 - 50 nm) to improve the barrier property, solvent system: water / ethanol mixed solvent (ratio 7:3), viscosity controlled at 50 - 100 cps, using micro - gravure coating method, coating amount 0.5 - 1.5 g / m², coating speed 150 - 300 m / min, drying conditions: step - by - step gradient heating (80°C → 120°C → 90°C), curing time 10 - 15 seconds to form a 0.1 - 0.5 μm dense coating; S700: Surface pretreatment. Corona treatment is carried out on the surface layer of the base film to increase the surface energy. In a vacuum chamber, high - purity aluminum wire is heated and evaporated by resistance heating or arc melting. The evaporation temperature is 1100 - 1400°C. The gaseous aluminum molecules are rapidly cooled by the cooling system, and the aluminum vapor condenses and uniformly deposits on the surface of the base film to form an aluminized layer. Specifically, the surface pretreatment steps are: Glow cleaning: bombarding the coating surface with argon ions (vacuum degree ≤ 5×10⁻³ Pa) to remove impurities and activate the surface; Aluminum target undercoating: pre - depositing an aluminum layer (thickness 1 - 2 nm) with a small current (0.5 - 1 A) to enhance the bonding force; Aluminum layer deposition: Evaporation source: electron beam evaporation of high - purity aluminum ingot (purity ≥ 99.99%), evaporation power 10 - 30 kW, deposition rate: 0.5 - 2 nm / s, final aluminum layer thickness 20 - 50 nm (optical density 2.5 - 3.5), base film temperature: controlled at - 10 to 10°C to avoid thermal deformation; S800: After cooling, an alumina protective layer is coated on the surface of the aluminized layer, and the internal stress is eliminated through aging treatment. Then, it is slit and wound to finally obtain the finished product. Specifically, the aging treatment: the aluminized film is left standing for 24 hours in a constant temperature and humidity environment (25°C / 50%RH) to eliminate the residual stress; slitting and winding: slitting accuracy: width deviation ≤ ±0.2 mm, tension control 10 - 15 N, winding hardness: Shore hardness 70 - 80 HA, to avoid damaging the film layer; The working principle and process of the present invention are as follows: By sequentially arranging a substrate layer, an intermediate layer, an interface enhancing layer, and an aluminized layer from bottom to top, the substrate layer is formed of BOPP or BOPET material, the intermediate layer contains pearlescent masterbatch, homopolypropylene, and poly(methyl methacrylate - polypropylene) block copolymer, the interface enhancing layer contains copolymerized polypropylene and norbornene dianhydride grafted polyolefin elastomer, and the aluminized layer is a vacuum aluminized layer. Thus, the surface of the plastic film has a metallic luster, and the surface tension of the film is large and persistent, with good adhesion, high uniformity of the aluminum layer, strong metallic feeling, high composite fastness, simple process steps for the aluminized layer, low cost, high efficiency, saving energy and materials, reducing costs, the aluminized layer can form a heat barrier, slow down heat conduction, have excellent barrier performance, have excellent folding resistance and good toughness, good electrical conductivity of the aluminized layer, and can eliminate the electrostatic effect; its sealing performance is good, especially when packaging powdery products, it will not contaminate the sealing part, ensuring the sealing performance of the packaging. It has both the characteristics of plastic film and metal, has good adaptability to post - processing such as printing and lamination. The aluminized layer can block light and prevent ultraviolet radiation, extending the shelf life of the contents, and has the advantages of low price, beauty, and good barrier performance. By adopting a multi - layer composite structure design, the present invention improves the mechanical properties, barrier properties, and aluminized bonding strength, thus effectively improving the service life.

[0028] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural transformations made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A high-performance biaxially oriented aluminum-coated film, characterized in that: The biaxially oriented aluminized film comprises a substrate layer, an intermediate layer, an interface enhancement layer and an aluminized layer which are arranged in sequence from bottom to top, the substrate layer is formed of BOPP or BOPET material, the intermediate layer contains pearlescent masterbatch, homopolypropylene and polymethyl methacrylate-polypropylene block copolymer, the interface enhancement layer contains copolymer polypropylene and nadic anhydride grafted polyolefin elastomer, the aluminized layer is a vacuum evaporated aluminum layer, and the upper end of the aluminized layer is coated with an aluminum oxide protective layer.

2. The high performance biaxially oriented aluminum-plated film according to claim 1, characterized in that: The thickness of the substrate layer ranges from 12 μm to 50 μm, the thickness of the intermediate layer ranges from 20 μm to 60 μm, and the thickness of the interface enhancement layer ranges from 10 μm to 30 μm.

3. The high performance biaxially oriented aluminum-plated film according to claim 1, characterized in that: In terms of mass percentage, the middle layer contains 15% to 40% of pearlescent masterbatch and 2% to 5% of polymethyl methacrylate-polypropylene block copolymer, and the remainder is homopolymer polypropylene.

4. The high-performance biaxially oriented aluminum-plated film according to claim 1, characterized in that: The substrate layer is formed by low melting point terpolymer polypropylene.

5. The high performance biaxially oriented aluminum-plated film according to claim 1, characterized in that: The thickness of the aluminum plating layer is in the range of 0.02 to 0.05 μm.

6. The high-performance biaxially oriented aluminum-plated film according to claim 1, characterized in that: In terms of mass percentage, the interface enhancement layer contains 20% to 30% of nadic anhydride grafted polyolefin elastomer, and the remainder is copolymerized polypropylene.

7. A method for preparing a high-performance biaxially oriented aluminum-plated film according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: Raw material pretreatment: the prepared raw materials are fed into the extruder and auxiliary extruder through the feed port. Under high temperature and high pressure, they are gradually melted, plasticized and mixed through the shearing and extrusion of the screw rod to ensure melting uniformity; Co-extrusion casting sheet, the filtered melt enters the extruder die through the melt pipe, and passes through the die lip under the pressure. Under the action of the air knife, the polypropylene melt flowing out of the die in a viscous flow state is tightly attached to the surface of the chilling roller. The chilling roller is filled with flowing cooling water. Under the joint cooling of the air knife, the chilling roller surface and the water bath, the temperature drops to 20-35°C, and the sheet is cast into a sheet by rapid cooling to form a multi-layer base film structure; Longitudinal stretching: the cooled sheet enters the longitudinal stretching device for longitudinal stretching. After preheating, longitudinal stretching and shaping, the sheet is longitudinally stretched by the stretching roller at a speed difference, and the molecular chains are arranged in the longitudinal direction. Transverse stretching: After longitudinal stretching, the sheet enters the transverse stretching device for transverse stretching. After film feeding, preheating, transverse stretching, shaping and cooling, the transverse stretching process is completed to form a uniform planar orientation structure. Heat setting: After stretching, the film is heat set at high temperature to fix the molecular chain arrangement and reduce subsequent shrinkage; Interface enhancement layer coating: a layer of polyurethane-acrylic composite glue is applied to the surface of the base film, which is then dried and cured to form a dense coating to fill the surface roughness and enhance the adhesion of the aluminum coating; Surface pretreatment: corona treatment is performed on the surface of the base film to increase the surface energy. In the vacuum chamber, high-purity aluminum wire is melted by resistance heating or arc melting, and the aluminum wire is heated and evaporated. The evaporation temperature is 1100-1400℃. The gaseous aluminum molecules are quenched by the cooling system, and the aluminum vapor condenses and evenly deposits on the surface of the base film to form an aluminum coating. After cooling, an aluminum oxide protective layer is applied on the surface of the aluminum-plated layer, and internal stress is eliminated through aging treatment. The product is then slit and rolled to obtain the finished product.

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