Bio-based multilayer film and method for manufacturing the same

Abstract

The present invention relates to the technical field of optical films, and more specifically, discloses a bio-based multilayer film and a method for producing the same. [Solution] The laminated film is made by alternately laminating two types of resins with different refractive indices, one of which is a bio-based polyester resin, the difference in refractive index between the two resins is 0.05 or more, the laminated film reflects light rays in the wavelength range of 300 to 1200 nm, and the bio-based polyester resin is polyethylene 2,5-franzicarboxylate or polyhydroxyalkanoate ester. The laminated film is biodegradable and also possesses improved mechanical and optical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and more specifically, to a bio-based laminated film and a method for manufacturing the same.

Background Art

[0002] The laminated film technology is realized by alternately laminating two or more materials with different optical properties. By designing the optical thickness of the film layer, the reflection of sunlight passing through multiple interfaces in the laminated film can be caused in different wavelength ranges. Based on this, films with various optical properties, such as infrared reflection films and polarized reflection films, have been gradually developed and applied through different combinations of materials and designs of film layer structures.

[0003] Currently, the resins used in laminated films are generally petrochemical products and do not have biodegradability. As the use of laminated films increases, it becomes difficult to recycle the resins, which is likely to cause environmental pollution and does not contribute to sustainable development.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to solve the environmental problem that all conventional laminated films are derived from petrochemical raw materials and are not environmentally friendly, the present application provides a bio-based laminated film having biodegradability, relatively low haze, and excellent mechanical properties, and a method for manufacturing the same.

Means for Solving the Problems

[0005] In a first aspect, the present application provides a bio-based laminated film and adopts the following technical solutions.

[0006] A bio-based laminated film, This material consists of two resins with different refractive indices layered alternately, one of which is a bio-based polyester resin, the difference in refractive index between the two resins being 0.05 or more, and the bio-based laminated film reflects light rays in the wavelength range of 300 to 1200 nm. The bio-based polyester resin is polyethylene 2,5-franzicarboxylate or polyhydroxyalkanoate ester.

[0007] Furthermore, one of the resins in the bio-based laminated film is polyethylene 2,5-flangecarboxylate, and the other resin is selected from polymethyl methacrylate, polyethylene naphthalate, polyethylene terephthalate-1,4-cyclohexanedimethanol ester, or polyhydroxyalkanoate ester.

[0008] Furthermore, the number of alternating layers in the bio-based multilayer film is 231 to 401 layers.

[0009] Furthermore, the intrinsic viscosity of the resin is 0.8 to 1.0 dL / g.

[0010] Furthermore, the optical thickness of one layer of the resin is 20 to 200 nm.

[0011] Furthermore, the bio-based multilayer film exhibits a difference of 50% or more between its highest and lowest reflectance in the reflection spectrum at wavelengths of 300 to 1200 nm.

[0012] In a second aspect, the present invention provides a method for manufacturing a bio-based multilayer film, employing the following technical solutions.

[0013] A method for manufacturing a bio-based multilayer film, Pretreatment: A step of pre-crystallizing two types of resin particles by vacuum drying, Co-extrusion film formation: A step in which resin particles obtained by pre-crystallization treatment are melted, placed in a distributor, and co-extruded, with the extrusion temperature set to 255-265°C, to obtain a cast slab. The process includes the steps of: stretching the cast slab to a stretching temperature of 95-105°C, setting it in a heating oven after stretching is complete, and heating it to a temperature of 105-115°C to obtain a bio-based laminated film.

[0014] Furthermore, in the aforementioned pretreatment step, the precrystallization temperature is 120-140°C, the precrystallization vacuum level is 0.1-1 Torr, and the precrystallization time is 10-24 hours.

[0015] Furthermore, in the stretching setting step, the stretching ratio is 3 to 5 times, and the stretching speed is 30 to 50 mm / s.

[0016] Furthermore, in the stretching setting step, the airflow speed of the heating oven is 60-80 mm / s.

[0017] Furthermore, in the stretching setting step, the heating and holding time of the heating oven is 70 to 90 seconds. [Effects of the Invention]

[0018] This application has at least the following advantages.

[0019] First, this invention selects a specific bio-based polyester resin as one of the main raw materials for a laminated film. Polyethylene 2,5-franciocarboxylate (PEF) can be decomposed into dicarboxylic acid and furan ethylene glycol by the action of microorganisms. Polyhydroxyalkanoate ester (PHA) is a bio-based material. These two resins, as one of the main raw materials for a laminated film, impart biodegradability to the laminated film and are advantageous for subsequent recycling of bio-based laminated films.

[0020] Next, conventional multilayer polyethylene 2,5-flange carboxylate has low light transmittance. By employing this lamination technology and casting and stretching at an appropriate temperature, the reflected light at the interface between the two resins of the laminated film and the reflected light at the interface between the laminated film and air interfere with each other, improving the light transmittance of the laminated film. This solves the problem of low light transmittance of polyethylene 2,5-flange carboxylate.

[0021] Furthermore, among bio-based polyester resins, the refractive index of PEF differs considerably from that of PMMA, PEN, PETG, and PHA, meeting the needs of optical application scenarios. The intrinsic viscosities of the above-mentioned multiple types of resins are similar, and the flow velocities of the resins in the distributor are also similar. Resins with high intrinsic viscosity are less likely to stretch resins with low intrinsic viscosity, and irregular strain is less likely to occur at the interface between the two types of resins, which improves the transmittance of the laminated film and is advantageous for improving the optical properties of the laminated film.

[0022] All of the above resins have ester groups, exhibit excellent compatibility, and have moderate interlayer bonding strength. When the resins are melted and laminated, the thermal and mechanical stresses at the interface between them are relatively good, and the laminated film has relatively good mechanical properties. Furthermore, due to the structural properties of the resins themselves, when the resins are melted and laminated, the surface tensions at the interface between them differ, making interdiffusion less likely.

[0023] Finally, by pre-crystallizing the resin particles, the manufacturing method of the laminated film is improved, resulting in a more orderly molecular arrangement of the resin particles and enhanced properties such as strength, rigidity, heat resistance, weather resistance, and chemical corrosion resistance of the laminated film. By controlling the extrusion temperature, when the extrusion temperature is 255-265°C, the pellets crystallize completely, reducing the probability of bubble formation between the laminated films and improving the light transmittance of the laminated film. This is advantageous for improving the optical and mechanical properties of the laminated film. By controlling the stretching temperature and the heating oven temperature, the polymer chains of the resin are fully oriented and crystallized, thereby significantly improving the overall mechanical properties of the laminated film after stretching, as well as significantly improving the interlayer bonding strength, thus achieving improvements in both the optical and mechanical properties of the laminated film. [Brief explanation of the drawing]

[0024] [Figure 1] It is the reflection spectrum in the visible light and near-infrared light bands (300 - 1200 nm) of Example 2.

Embodiment for Carrying out the Invention

[0025] Unless otherwise specified, the sources of the raw materials in each structural example and example in this application are as follows. PEF: Refractive index 1.63, intrinsic viscosity 0.85 dL / g, manufactured by Zhejiang Wankai New Materials Co., Ltd. PMMA: Grade HBS006H, obtained from Mitsubishi Corporation PET: Grade FG612, obtained from Yizheng Chemical Fiber Co., Ltd. PEN: Grade 8050SC, obtained from Teijin Limited, Japan PHA: Grade BP330 - 05, obtained from Bluepha Microorganisms Co., Ltd. PETG: Grade S2008, obtained from SK Corporation, South Korea

[0026] <Example 1> The bio-based laminated film is manufactured by the following steps. Material selection: PEF resin particles with a refractive index of 1.63 and PMMA resin particles with a refractive index of 1.49 were selected as the main raw materials of the laminated film. The intrinsic viscosity of the PEF resin particles is, 0.85 dL / g, and the intrinsic viscosity of the PMMA resin particles is 0.9 dL / g. Pretreatment: The PEF resin particles and PMMA resin particles were vacuum-dried and pre-crystallized in separate vacuum drying ovens at a ratio of 56:44. The vacuum pre-crystallization of the PEF resin particles is at a temperature of 120°C, a vacuum degree of 0.5 Torr, and a vacuum time of 12 h, and the vacuum pre-crystallization of the PMMA resin particles is at a temperature of 140°C, a vacuum degree of 0.5 Torr, and a vacuum time of 12 h. Co-extrusion film formation: Pre-crystallized particles were suctioned and transported to the extruder's suction funnel via an insulated pipe. Using different twin-screw extruders, the pellets were co-extruded, passed through a melt metering pump and a filter screen, and transported to a designed multi-layer feed block. In the feed block, molten PET and PMMA resins were sequentially and alternately laminated. A doubling device located after the feed block cut and laminated the alternately laminated melts in the feed block again, doubling the number of layers and forming a slab with an optical thickness of 231 layers, resulting in a total thickness of 26 μm. Next, the melt after lamination was placed in a wedge-shaped die and merged, then stretched laterally within the die before being extruded from the lip. The temperature of the molten resin in the melt pulp was set to 255°C, the temperature of the molten resin in the metering pump was set to 255°C, the temperature of the molten resin before the filter screen was set to 255°C, the temperature of the molten resin after the filter screen was set to 260°C, the temperature of the molten resin in the distributor was set to 260°C, and the temperature of the molten resin in the die was set to 260°C. Using a traction roll and a cooling roll, the sheet flowing from the extruder die was cooled and stretched. At the die, the electrostatic action of an electrostatic wire caused the sheet flowing from the die to adhere completely to the surface of the cooling roll. By adjusting the rotation speed of the cooling roll, a film of the desired thickness was formed. Stretching setting: The cooled film was cut into 110 x 110 mm squares and stretched in two directions using a stretching machine for setting. For a stretch ratio of 4.5 times, the specific stretching parameters were set to a stretching temperature of 95°C, a stretching speed of 30 mm / s, a heating oven cavity temperature of 105°C, a heating oven airflow speed of 60 mm / s, and a heat retention time of 70 s to obtain a bio-based laminated film.

[0027] <Example 2> This is a bio-based multilayer film, and the difference from Example 1 is that in the co-extrusion film formation step, the number of layers is 401, and the thickness of the film layer is 38 μm.

[0028] <Example 3> This is a bio-based multilayer film, and the difference from Example 1 lies in the stretching ratio, stretching temperature, and setting parameters in the stretching setting step. Specifically, these are as follows: The cooled film was cut into 110 x 110 mm squares, stretched in two directions using a stretching machine, and set up. For a stretch ratio of 5, the specific stretching parameters were set as follows: stretching temperature of 105°C, stretching speed of 50 mm / s, heating oven cavity temperature of 115°C, heating oven airflow speed of 80 mm / s, and holding time of 90 s.

[0029] <Example 4> This bio-based laminated film differs from Example 1 in that, in this example, PEF resin particles with a refractive index of 1.63 and PETG resin particles with a refractive index of 1.57 are selected as the main raw materials for the laminated film, and the intrinsic viscosity of the PEF resin particles is 0.85 dL / g, and the intrinsic viscosity of the PETG resin particles is 0.85 dL / g.

[0030] <Example 5> This bio-based laminated film differs from Example 1 in that, in this example, PHA resin particles with a refractive index of 1.49 and PETG resin particles with a refractive index of 1.57 are selected as the main raw materials for the laminated film, and the intrinsic viscosity of the PHA resin particles is 1 dL / g, while the intrinsic viscosity of the PETG resin particles is 0.85 dL / g.

[0031] <Comparative Example 1> This is a bio-based multilayer film, and the difference from Example 1 lies in the process parameters of the co-extrusion film formation step. Specifically, these are as follows: Co-extrusion film formation: Pre-crystallized particles were suctioned and transported to the extruder's suction funnel via an insulated pipe. Using different twin-screw extruders, the pellets were co-extruded, passed through a melt metering pump and a filter screen, and transported to a designed multi-layer feed block. In the feed block, molten PET and PMMA resins were sequentially and alternately laminated. A doubling device located after the feed block cut and laminated the alternately laminated melts in the feed block again, doubling the number of layers and forming a slab with an optical thickness of 231 layers, resulting in a total thickness of 26 μm. Next, the melt after lamination was placed in a wedge-shaped die and merged, then spread laterally within the die before being extruded from the lip. The temperature of the molten resin in the melt pipe was set to 230°C, the temperature of the molten resin in the metering pump was set to 230°C, the temperature of the molten resin before the filter screen was set to 230°C, the temperature of the molten resin after the filter screen was set to 240°C, the temperature of the molten resin in the distributor was set to 240°C, and the temperature of the molten resin in the die was set to 240°C. Using a traction roll and a cooling roll, the sheet flowing from the extruder die was cooled and stretched. At the die, the electrostatic action of an electrostatic wire caused the sheet flowing from the die to adhere completely to the surface of the cooling roll. By adjusting the rotation speed of the cooling roll, a film of the desired thickness was formed.

[0032] <Comparative Example 2> This is a bio-based multilayer film, and the difference from Example 1 lies in the process parameters of the stretching setting step. Specifically, these are as follows: Stretching setting: The cooled film was cut into 110 x 110 mm squares and stretched in two directions using a stretching machine to set it up. For a stretch ratio of 4.5 times, the specific stretching parameters were set to a stretching temperature of 85°C, a stretching speed of 30 mm / s, a cavity temperature of 95°C in the heating oven, an airflow speed of 60 mm / s in the heating oven, and a holding time of 60 s to obtain a bio-based laminated film.

[0033] <Comparative Example 3> This is a laminated film, and the difference from Example 1 is that PEF resin particles with a refractive index of 1.63 and PET resin particles with a refractive index of 1.65 are selected as the main raw materials for the laminated film.

[0034] <Comparative Example 4> This is a laminated film, and the difference from Example 1 is that PET resin particles with a refractive index of 1.65 and PMMA resin particles with a refractive index of 1.49 are selected as the main raw materials for the laminated film.

[0035] <Detected Data> The optical and mechanical properties of Examples 1-5 and Comparative Examples 1-4 were detected, and the detection results are shown below.

[0036] [Table 1]

[0037] [Table 2] Note: Haze was detected using a HAM-200 far-field haze meter. Visible light transmittance, visible light reflectance, and infrared reflectance were all detected using a Shimadzu Model 3600 spectrometer. Figure 1 was acquired using Essential Macleod software.

[0038] When Example 1 and Comparative Example 1 were compared on a one-to-one basis, the main difference was the relatively low extrusion temperature during the co-extrusion film formation step. Comparative Example 1 exhibited high haze, low visible light transmittance and infrared reflectance, and poor optical properties. This is because the low co-extrusion temperature prevented complete crystallization of the pellets, resulting in numerous air bubbles between the laminated films, clouding of the laminated film surface, and consequently, a decrease in the optical properties of the laminated film.

[0039] When Example 1 and Comparative Example 2 were compared on a one-to-one basis, it was found that in the stretching setting step, the stretching setting temperature was relatively low, resulting in incomplete crystal orientation of the polymer within the film. Consequently, the mechanical properties of the laminated film were significantly reduced, and the infrared reflectance was also relatively low.

[0040] When Example 1 and Comparative Example 3 were compared in a one-to-one correspondence, the difference was that two types of resins with a refractive index difference of less than 0.05 were laminated. In actual detection, the laminated film had low visible light reflectivity, relatively low infrared reflectivity, and high haze, failing to meet the needs of optical application scenarios such as thermal insulation.

[0041] A one-to-one comparison of Example 1 and Comparative Example 4 reveals that the difference lies in the lamination of two materials: conventional PET and PMMA. The PET and PMMA used in Comparative Example 4 are conventional polyester materials and are not biodegradable. Furthermore, their mechanical properties are relatively poor, with low tensile strength and elongation at break. In terms of optical properties, their infrared reflectivity is relatively low, and further improvement is needed for optical application scenarios such as heat insulation.

[0042] A one-to-one comparison of Example 1 and Example 2 revealed that increasing the number of layers in the laminated film improves infrared reflectivity, which is advantageous for enhancing the thermal insulation and mechanical properties of the laminated film. However, it also significantly increases the haze of the laminated film, reduces visible light transmittance, and causes the surface of the laminated film to become cloudy, making it impossible to simultaneously consider thermal insulation and high-definition optical requirements. Figure 1 shows the reflection spectrum of Example 2 in the visible and near-infrared light bands. The vertical axis in Figure 1 represents reflectivity. The minimum reflectivity is obtained between 350 and 450 nm, with a minimum reflectivity of 45%. The maximum reflectivity is obtained between 650 and 900 nm, with a maximum reflectivity of 100%. The difference between the maximum and minimum reflectivity is greater than 50%.

[0043] A one-to-one comparison of Example 1 and Example 3 revealed that increasing the stretching ratio, stretching temperature, and setting temperature of the laminated film promoted the growth of crystal nuclei within the film, improving the interlayer density, reducing the haze of the laminated film, improving the visible light transmittance and infrared reflectance, and thus improving the optical properties of the laminated film. However, the rapid formation of crystal nuclei leads to a decrease in crystallinity, resulting in a deterioration of the mechanical properties of the laminated film.

[0044] When Example 1 and Example 4 were compared on a one-to-one basis, Example 4 used PETG with a refractive index of 1.57 instead of PMMA with a refractive index of 1.49. Although the intrinsic viscosity of both materials is the same, the small difference in refractive index resulted in improved haze, decreased infrared reflectivity, and reduced optical properties in the laminated film of Example 4.

[0045] When Example 1 and Example 5 were compared on a one-to-one basis, it was found that in Example 5, the combination of PETG and PHA resin was selected instead of the combination of PEF and PMMA resin. As a result, the difference in refractive index was relatively small, and the difference in intrinsic viscosity was relatively large. Consequently, haze improved, infrared reflectivity decreased, and optical properties deteriorated.

[0046] Based on the above, the present invention provides for the manufacture of a bio-based laminated film that is biodegradable, has a haze of less than 1.5, an infrared reflectivity greater than 35%, a tensile strength greater than 150 MPa, and an elongation at break greater than 90%, and that satisfies the requirements for both optical application scenarios and mechanical properties.

[0047] Any combination of the technical features of the above embodiments is possible, and for the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as these combinations of technical features are inconsistent, they should all be considered to be within the scope of this specification.

[0048] The above examples represent several embodiments of the present invention, and while the descriptions are relatively specific and detailed, this should not be understood as limiting the scope of the patent. Furthermore, for those skilled in the art, several modifications and improvements are possible without departing from the concept of the present invention, and all of these fall within the scope of protection of the present invention. Therefore, the scope of patent protection for the present invention should be in accordance with the attached claims.

Claims

1. A bio-based multilayer film, It is made by alternately laminating two types of resin with different refractive indices, the difference in refractive index between the two types of resin is 0.05 or more, and the infrared reflectance of the laminated film is higher than 35%. One of the resins in the laminated film is polyethylene 2,5-flangecarboxylate, and the other resin is selected from polymethyl methacrylate. The method for manufacturing the bio-based multilayer film is as follows: Pre-treatment: A step of pre-crystallizing two types of resin particles by vacuum drying, wherein the pre-crystallization temperature is 120-140°C, the pre-crystallization vacuum level is 0.1-1 Torr, and the pre-crystallization time is 10-24 hours. Co-extrusion film formation: A step in which resin particles obtained by pre-crystallization treatment are melted, placed in a distributor, and co-extruded, with the extrusion temperature set to 255-265°C, to obtain a cast slab. A bio-based laminated film characterized by comprising the steps of: stretching setting: stretching a cast slab to a stretching temperature of 95 to 105°C, setting it in a heating oven after stretching is complete to a heating temperature of 105 to 115°C, and keeping the heating oven warm for 70 to 90 seconds to obtain a bio-based laminated film.

2. The bio-based laminated film according to claim 1, characterized in that the intrinsic viscosity of both the polyethylene 2,5-flange carboxylate resin and the polymethyl methacrylate resin is 0.8 to 1.0 dL / g.

3. The bio-based multilayer film according to claim 1, characterized in that the number of alternating layers of the bio-based multilayer film is 231 to 401 layers.

4. The method for manufacturing a bio-based laminated film according to claim 1, characterized in that in the stretching setting step, the stretching ratio is 3 to 5 times and the stretching speed is 30 to 50 mm / s.

5. The method for manufacturing a bio-based laminated film according to claim 1, characterized in that, in the stretching setting step, the airflow rate of the heating oven is 60 to 80 mm / s.

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