Thermoformed film and method for manufacturing the same

Abstract

The present invention relates to a thermoformable film, a method for manufacturing the same, and a retort pouch equipped therewith. Specifically, a thermoformable film according to one embodiment of the present invention comprises a first unstretched film layer, a stretched film layer having a transparent deposited layer on one or both sides, and a second unstretched film layer, thereby exhibiting excellent thermoformability, gas barrier properties, and the like.

Description

Detailed description of the invention

[0001] [Technical field] This disclosure relates to a thermoformable film that has excellent gas barrier properties and can improve the long-term preservation of its contents (e.g., food), and to a method for producing the same.

[0002] [Background technology] Thermoformed films are used in the manufacture of retort foods containing meat products. Thermoformed films require heat resistance to withstand heat sterilization and gas barrier properties to block oxygen and / or moisture, enabling long-term preservation of the contents.

[0003] Traditionally, retort foods were manufactured using co-extruded films, which have excellent thermoformability, as the thermoformable film. Specifically, the co-extruded film is placed in a mold inside a chamber. The co-extruded film is molded to the shape of the mold by heating and applying a vacuum. Then, the contents are added and sealed. Next, the sealed contents are heat-sterilized to produce the retort food.

[0004] However, because co-extruded films have a structure where films of the same thickness are joined together (for example, a structure where two polypropylene films are joined together), they become too thin during the stretching process (thermoforming) to match the shape of the molding die, resulting in poor gas barrier properties. If the contents are heat-sterilized in a state with low gas barrier properties, it may adversely affect the contents. Specifically, if the contents are sensitive to heat treatment conditions or gas permeability, discoloration of the contents may occur.

[0005] Therefore, there is a need to develop thermoformable films that possess excellent gas barrier properties and the necessary level of thermoformability even after thermoforming and heat sterilization.

[0006] [Prior art document] [Patent] (Patent Document 1) Korean Patent Publication No. 2010-0085157

[0007] [Overview of the prefecture] [Problems the invention aims to solve] The purpose of this disclosure is to provide a thermoformable film that has the thermoformability and heat resistance required for thermoforming and heat sterilization processes, and that can maintain excellent gas barrier properties even after these processes.

[0008] Furthermore, this disclosure aims to provide a method for manufacturing thermoformed films that can efficiently produce thermoformed films. [Means for solving the problem] To solve the above problem, one aspect of the present disclosure is a thermoformable film comprising a first unstretched film layer, a stretched film layer having a transparent deposited layer on one or both sides thereof, and a second unstretched film layer, In one embodiment, the thermoformed film has an oxygen permeability (OTR) of 20 cc / m² measured after thermoforming at 120-155°C. 2 • It may be less than one day.

[0009] In another embodiment, the thermoformed film has an oxygen permeability (OTR) of 15 cc / m², measured after heating the thermoformed film at 110-130°C for 20-30 minutes. 2 • It may be less than one day.

[0010] In another embodiment, the first unstretched film layer may have a tensile strength of 110-160 MPa in the longitudinal (MD) and transverse (TD) directions, respectively, and an elongation of 400-440% in the longitudinal (MD) and transverse (TD) directions.

[0011] In another embodiment, the stretched film layer may have a tensile strength of 240 to 320 MPa in the longitudinal (MD) and transverse (TD) directions, respectively, and an elongation of 80 to 120% in the longitudinal (MD) and transverse (TD) directions, respectively.

[0012] In another embodiment, the first unstretched film layer has an oxygen permeability (OTR) of 30 cc / m². 2• Less than 250 g / m², and with a water vapor transmission rate (WVTR) of 250 g / m². 2 • It may be less than one day.

[0013] In another embodiment, the stretched film layer has an oxygen permeability (OTR) of 2 cc / m². 2 • Less than 3 days, and with a water vapor transmission rate (WVTR) of 3 g / m³ 2 • It may be less than one day.

[0014] In another embodiment, the first unstretched film layer and the stretched film layer each contain polyamide, and the second unstretched film layer may contain polypropylene.

[0015] In another embodiment, the sum of the thickness of the first unstretched film layer and the thickness of the stretched film layer may be less than the thickness of the second unstretched film layer.

[0016] In another embodiment, the thickness of the first unstretched film layer may be 40 to 60 μm, the thickness of the stretched film layer may be 5 to 25 μm, and the thickness of the second unstretched film layer may be 80 to 120 μm.

[0017] In another embodiment, the first unstretched film layer, the stretched film layer, and the second unstretched film layer may be laminated in sequence.

[0018] In another embodiment, the transparent deposit may contain at least one selected from the group consisting of aluminum oxide, aluminum oxynitride, titanium oxide, silicon oxide, zinc oxide, tin oxide, silicon nitride, aluminum nitride, silicon oxynitride, nickel oxide, and magnesium oxide.

[0019] Another aspect of the present disclosure relates to a method for manufacturing a thermoformable film, which includes preparing a first unstretched film, a stretched film, and a second unstretched film, and sequentially laminating and joining the first unstretched film, the stretched film, and the second unstretched film.

[0020] According to another aspect of the present disclosure, a retort pouch comprising a thermoformed film is provided. [Effects of the invention] The thermoformable film of this disclosure comprises a stretched film layer having gas barrier properties and thermoformability, and first and second unstretched film layers that can enhance thermoformability. Therefore, even after undergoing both thermoforming and heat sterilization treatments, it can retain the necessary thermoformability and exhibit excellent heat resistance, sealing properties, gas barrier properties, etc.

[0021] As a result, when various items such as food, pharmaceuticals, cosmetics, and industrial products are packaged using the thermoformed film of this disclosure, the long-term preservation capacity of the contents can be enhanced. In particular, because the thermoformed film of this disclosure has excellent gas barrier properties even when heat sterilization is performed under conditions more severe than boiling sterilization, it can be advantageously used in the manufacture of retort pouches used to ensure the long-term preservation of processed meat products. [Brief explanation of the drawing]

[0022] [Figure 1] This is a cross-sectional view of a thermoformable film according to one embodiment of the present disclosure. [Figure 2] This flowchart shows a method for manufacturing a thermoformable film according to one embodiment of the present disclosure.

[0023] [Modes for carrying out the invention] The present disclosure will be described in more detail below with reference to embodiments. It should be noted that, as with the present disclosure, various modifications are possible without departing from the spirit of the invention, and this is not limited to the present disclosure.

[0024] In this specification, when an element is formed on, connected to, or joined to another element, it means that one element is formed on, connected to, or joined to the other element directly or indirectly. It should also be understood that the top and bottom reference points of each component may differ depending on the orientation of the object being observed.

[0025] In this specification, the term “equipped with” is used to explicitly identify specific characteristics, areas, processes, treatments, elements, and / or components. Unless explicitly stated otherwise, this does not preclude the presence or addition of other characteristics, areas, processes, treatments, components, elements, and / or components.

[0026] The numerical values ​​and expressions regarding component amounts, reaction conditions, etc., used herein are, unless otherwise specified, to be understood as being modified by the word "abbreviated."

[0027] In this specification, terms such as "1," "2," etc., are used in descriptions of various components. However, these components should not be bound by these terms. Specifically, they are used to distinguish one element from another.

[0028] Thermoformed film This disclosure provides a thermoformable film that has superior gas barrier properties compared to conventional co-extruded films while ensuring thermoformability (stretchability). Specifically, the thermoformable film of this disclosure comprises a first unstretched film layer, a stretched film layer, and a second unstretched film layer, as shown below with reference to Figure 1.

[0029] First unstretched film layer The first unstretched film layer (10) included in the thermoformable film (100) of this disclosure is for ensuring the heat resistance, pinhole resistance, gas barrier properties, etc. of the thermoformable film (100). The first unstretched film layer (10) may be a film containing a polymer resin (first polymer resin), in which case the film may be an unstretched film. The polymer resin (first polymer resin) is not particularly limited, but may specifically contain polyamide. By including polyamide in the first unstretched film layer (10), the pinhole resistance, gas barrier properties, and mechanical strength of the thermoformable film (100) can be improved. Specifically, the polyamide may be at least one selected from the group consisting of nylon 4, nylon 6, nylon 7, nylon 8, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 611, nylon 612, nylon 6T, nylon 6 / 66, nylon 6 / 12, nylon 6 / 6T, nylon 6T (terephthalic acid) / 6I (isophthalic acid), and nylon MXD6.

[0030] According to this disclosure, the first unstretched film layer (10) may have mechanical (physical) properties (e.g., tensile strength, elongation, etc.) controlled to a specific range. This makes it possible to enhance the thermoformability (stretchability) of the thermoformed film (100) while ensuring its gas barrier properties.

[0031] Specifically, the first unstretched film layer (10) can have a tensile strength of 110 to 160 MPa in the longitudinal direction (MD) and the transverse direction (TD), respectively. For example, the tensile strength of the first unstretched film layer (10) in the longitudinal direction (MD) may be 115 to 160 MPa, 120 to 155 MPa, 125 to 155 MPa, 130 to 150 MPa, 135 to 150 MPa, or 135 to 145 MPa. Also, the tensile strength of the first unstretched film layer (10) in the transverse direction (TD) may be 110 to 155 MPa, 115 to 150 MPa, 115 to 145 MPa, 120 to 140 MPa, 125 to 135 MPa, or 125 to 130 MPa. Here, the tensile strength (A) of the first unstretched film layer (10) in the longitudinal direction (MD) can be greater than its tensile strength (B) in the transverse direction (TD) (A > B). The tensile strength of the first unstretched film layer (10) may be measured in accordance with the standard of JIS K 7127 (23°C).

[0032] The first unstretched film layer (10) may have an elongation of 400 to 440% in the longitudinal direction (MD) and the transverse direction (TD), respectively. For example, the elongation of the first unstretched film layer (10) in the longitudinal direction (MD) may be 400 to 435%, 403 to 430%, 405 to 425%, 407 to 420%, or 409 to 415%. Also, the elongation of the first unstretched film layer (10) in the transverse direction (TD) may be 405 to 440%, 410 to 438%, 415 to 435%, 420 to 435%, or 425 to 433%. Here, the elongation (C) of the first unstretched film layer (10) in the longitudinal direction (MD) may be smaller than its elongation (D) in the transverse direction (TD) (C < D). The elongation of the first unstretched film layer (10) may be measured in accordance with the provisions of JIS K 7127 (23°C).

[0033] On the one hand, the first non-stretched film layer (10) may have a tear strength of 130 to 220 N / cm in the longitudinal direction (MD) and the transverse direction (TD), respectively. For example, the tear strength of the first non-stretched film layer (10) in the longitudinal direction (MD) may be 130 to 210 N / cm, 135 to 200 N / cm, 135 to 190 N / cm, 140 to 180 N / cm, 140 to 170 N / cm, or 145 to 155 N / cm. Also, the tear strength of the first non-stretched film layer (10) in the transverse direction (TD) may be 145 to 220 N / cm, 155 to 215 N / cm, 170 to 215 N / cm, 185 to 210 N / cm, or 195 to 205 N / cm. Here, the tear strength (E) of the first non-stretched film layer (10) in the longitudinal direction (MD) may be smaller than the tear strength (F) in its transverse direction (TD) (E < F). The tear strength of the first non-stretched film layer (10) may be measured according to the standard of JIS K 7128 (23 °C).

[0034] Also, the first non-stretched film layer (10) may have a haze of 4% or less, 3.9% or less, 3.8% or less, 3.7% or less, 3.6% or less, or 3.5% or less. The haze of the first non-stretched film layer (10) may be measured according to the standard of JIS K 7105 (23 °C).

[0035] According to the present disclosure, the first non-stretched film layer (10) has an oxygen transmission rate (OTR) of 30 cc / m 2 ·day or less (= 30 cc / m 2 ·day·atm or less), and the water vapor transmission rate (WVTR) can be 250 g / m 2 ·day or less. Specifically, the oxygen transmission rate (OTR) of the first non-stretched film layer (10) is 25 cc / m 2 ·day or less, 20 cc / m 2 ·day or less, 15 cc / m 2 ·day or less, 10 cc / m 2 ·day or less, or 5 cc / m 2 ·day or less, and 0 cc / m 2 ·day or more, 0.0001 cc / m 2·day or more, 0.0002cc / m 2 ·day or more, 0.0003cc / m 2 • More than 1 day, or 0.0004 cc / m³ 2 It can be more than 1 day. Also, the water vapor transmission rate (WVTR) of the first unstretched film layer (10) is 230 g / m². 2 ·day or less, 200g / m 2 ·day or less, 180g / m 2 ·day or less, 165g / m 2 ·day or less, 150g / m 2 It may be less than or equal to 0.00001 g / m². 2 ·day or more, 0.00003g / m 2 ·day or more, 0.00005g / m 2 ·day or more, 0.0001g / m 2 ·day or more, 0.0005g / m 2 It may be more than 1 day. By ensuring that the oxygen permeability (OTR) and water vapor permeability (WVTR) of the first unstretched film layer (10) are within the above range, the gas barrier properties of the thermoformed film (100) can be improved while ensuring the heat resistance and pinhole resistance of the thermoformed film (100). As a result, the long-term storage life of retort pouches manufactured using the thermoformed film (100) can be significantly improved. The oxygen permeability (OTR) of the first unstretched film layer (10) may be measured in accordance with the JIS K 7126 standard (23°C, 0%RH). The water vapor permeability (WVTR) of the first unstretched film layer (10) may be measured in accordance with the JIS K 7129 standard (40°C, 90%RH).

[0036] According to this disclosure, the thickness of the first unstretched film layer (10) can be 40 to 60 μm. Specifically, the thickness of the first unstretched film layer (10) may be 43 to 58 μm, 45 to 55 μm, 48 to 53 μm, or 49 to 51 μm. By having the thickness of the first unstretched film layer (10) within the above range, the gas barrier properties and thermoformability of the thermoformed film (100) can be improved.

[0037] stretched film layer The stretched film layer (20) included in the thermoformable film (100) of this disclosure is provided to enhance the heat resistance, durability, gas barrier properties, and thermoformability of the thermoformable film (100). The stretched film layer (20) may be a film obtained by uniaxially or biaxially stretching an unstretched film containing a polymer resin (second polymer resin). The polymer resin (second polymer resin) is not particularly limited, but may specifically contain polyamide. By providing polyamide in the stretched film layer (20), the gas barrier properties, mechanical strength, and thermoformability of the thermoformable film (100) can be enhanced. Specifically, the polyamide may be at least one selected from the group consisting of nylon 4, nylon 6, nylon 7, nylon 8, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 611, nylon 612, nylon 6T, nylon 6 / 66, nylon 6 / 12, nylon 6 / 6T, nylon 6T (terephthalic acid) / 6I (isophthalic acid), and nylon MXD6.

[0038] The stretched film layer (20) may have a transparent deposited layer on one or both sides. By providing the stretched film layer (20) with a transparent deposited layer, it is possible to provide a thermoformed film (100) that is transparent while increasing the gas barrier properties and mechanical strength of the thermoformed film (100). Therefore, when a retort pouch is manufactured using the thermoformed film (100) of this disclosure, the long-term storage capacity of the contents is greatly improved, while a retort pouch that allows observation of the contents can be provided. This transparent deposited layer is formed on one side of the stretched film layer (20), and the second unstretched film layer (30) and the transparent deposited layer described later may face each other, and the second unstretched film layer (30) and the stretched film layer (20) may be placed (combined).

[0039] According to this disclosure, the transparent deposit layer may contain an inorganic material that is transparent as well as having excellent gas barrier properties. The transparent deposit layer is aluminum oxide (AlO x ), aluminum oxynitride (AlO x Ny ), titanium dioxide (TiO x ), silicon dioxide (SiO₂) x ), zinc oxide (ZnO x ), tin oxide (SnO x ), silicon nitride (SiN x ), aluminum nitride (AlN x ), silicon oxynitride (SiO x N y ), nickel oxide (NiO x ), and magnesium oxide (MgO x It may include at least one selected from the group consisting of ).

[0040] The transparent deposited layer may have a thickness of 5 to 50 nm. Specifically, the thickness of the transparent deposited layer can be 7 to 40 nm, 9 to 35 nm, 10 to 30 nm, or 10 to 25 nm. By having the thickness of the transparent deposited layer within the above range, it is possible to prevent the stretched film layer (20) from being deformed by the transparent deposited layer while improving the gas barrier properties of the thermoformed film (100).

[0041] According to this disclosure, the stretched film layer (20) having a transparent deposited layer can have its mechanical (physical) properties (e.g., tensile strength, elongation, etc.) controlled to a specific range. This can enhance the gas barrier properties and thermoformability (stretchability) of the thermoformed film (100).

[0042] Specifically, the stretched film layer (20) can have a tensile strength of 240 to 320 MPa in the longitudinal direction (MD) and the transverse direction (TD), respectively. For example, the tensile strength of the stretched film layer (20) in the longitudinal direction (MD) can be 240 to 310 MPa, 245 to 300 MPa, 250 to 290 MPa, 250 to 280 MPa, 255 to 270 MPa, or 255 to 265 MPa. Also, the tensile strength of the stretched film layer (20) in the transverse direction (TD) can be 250 to 320 MPa, 260 to 315 MPa, 270 to 315 MPa, 280 to 310 MPa, 290 to 305 MPa, or 295 to 305 MPa. Here, the tensile strength (a) of the stretched film layer (20) in the longitudinal direction (MD) may be smaller than the tensile strength (b) in the transverse direction (TD) (a < b). The tensile strength of the stretched film layer (20) may be measured in accordance with the standard of JIS K 7127 (23°C).

[0043] The stretched film layer (20) may have an elongation of 80 to 120% in the longitudinal direction (MD) and the transverse direction (TD), respectively. For example, the elongation of the stretched film layer (20) in the longitudinal direction (MD) can be 85 to 120%, 90 to 118%, 95 to 115%, 100 to 113%, or 105 to 112%. Also, the elongation of the stretched film layer (20) in the transverse direction (TD) can be 80 to 110%, 82 to 105%, 84 to 100%, 86 to 95%, or 88 to 93%. Here, the elongation (c) of the stretched film layer (20) in the longitudinal direction (MD) is greater than the elongation (d) in the transverse direction (TD) (c > d), and the elongation of the stretched film layer (20) may be measured in accordance with the standard of JIS K 7127 (23°C).

[0044] On the other hand, the stretched film layer (20) may have a total light transmittance of 85% or more, 86% or more, 87% or more, 88% or more, 89% or more, or 90% or more. The total light transmittance of the stretched film layer (20) may be measured in accordance with the standard of JIS K 7361-1 (23°C).

[0045] Furthermore, the stretched film layer (20) may have a haze of 3.5% or less, 3.4% or less, 3.3% or less, 3.2% or less, 3.1% or less, or 3.0% or less. The haze of the stretched film layer (20) may be measured in accordance with the JIS K 7136 standard (23°C).

[0046] Furthermore, the stretched film layer (20) may have a shrinkage rate of 1.8% or less, 1.7% or less, 1.6% or less, or 1.5% or less (for example, 1.3-1.6%) in the longitudinal direction (MD), and a shrinkage rate of 2.3% or less, 2.2% or less, 2.1% or less, or 2.0% or less (for example, 1.9-2.1%) in the transverse direction (TD). The shrinkage rate of the stretched film layer (20) can be measured as a percentage (%) of the length after shrinkage (reduction) of the stretched film after immersing it in water at 95°C for 5 minutes, relative to the initial length.

[0047] According to this disclosure, the stretched film layer (20) has an oxygen permeability (OTR) of 2 cc / m². 2 ·day or less (=2cc / m 2 (less than or equal to 1 day·atm) and water vapor transmission rate (WVTR) of 3 g / m³ 2 It can be less than or equal to 1 day. Specifically, the oxygen permeability (OTR) of the stretched film layer (20) is 1.5 cc / m². 2 ·day or less, 1.3cc / m 2 ·day or less, 1.1cc / m 2 ·day or less, 0.8cc / m 2 ·day or less, 0.6cc / m 2 ·day or less, 0cc / m 2 ·day or more, 0.0001cc / m 2 ·day or more, 0.0002cc / m 2 ·day or more, 0.0003cc / m 2 ·day or more, 0.0004cc / m 2 It may be more than 1 day. Also, the water vapor transmission rate (WVTR) of the stretched film layer (20) is 2.5 g / m². 2 • It may be less than 2.0 g / m². 2 • It may be less than 1.5 g / m². 2It may be less than 1.1 g / m². 2 • It may be less than 0.8 g / m² 2 • It may be less than or equal to 0g / m² 2 It may be more than 0.00001 g / m² 2 • It may be more than 0.00005 g / m² 2 • It may be more than 0.0001 g / m² 2 • May be more than 0.0003 g / m² 2 • It may be more than 0.0005 g / m² 2 It may be more than 1 day. By ensuring that the oxygen permeability (OTR) and water vapor permeability (WVTR) of the stretched film layer (20) are within the above ranges, the heat resistance and pinhole resistance of the thermoformed film (100) can be ensured while improving the gas barrier properties of the thermoformed film (100). As a result, the long-term storage life of retort pouches manufactured using the thermoformed film (100) can be significantly improved. The oxygen permeability (OTR) of the stretched film layer (20) should be measured in accordance with the JIS K 7126 standard (25°C, 80%RH). The water vapor permeability (WVTR) of the stretched film layer (20) should be measured in accordance with the JIS K 7129 standard (40°C, 90%RH).

[0048] According to this disclosure, the stretched film layer (20) may have a thickness of 5 to 25 μm. Specifically, the thickness of the stretched film layer (20) may be 8 to 23 μm, 10 to 20 μm, 12 to 18 μm, or 14 to 16 μm. By having the thickness of the stretched film layer (20) within the above range, the gas barrier properties and thermoformability of the thermoformed film (100) can be improved.

[0049] Second unstretched film layer The second unstretched film layer (30) of the thermoformable film (100) of this disclosure is for ensuring the heat resistance, moisture resistance, sealing properties, and thermoformability of the thermoformable film (100). The second unstretched film layer (30) may be a film containing a polymer resin (third polymer resin), in which case the film may be an unstretched film. The polymer resin (third polymer resin) is not particularly limited, but may specifically contain polypropylene. By including a polymer resin in the second unstretched film layer (30), the heat resistance, sealing properties, and thermoformability of the thermoformable film (100) can be improved. For example, the second unstretched film layer (30) may be a CPP (cast polypropylene) film.

[0050] According to this disclosure, the thickness of the second unstretched film layer (30) can be 80 to 120 μm. Specifically, the thickness of the second unstretched film layer (30) may be 83 to 118 μm, 85 to 115 μm, 90 to 110 μm, or 95 to 105 μm. By having the thickness of the second unstretched film layer (30) within the above range, the sealing and thermoforming properties of the thermoformed film (100) can be improved, while preventing the overall thickness of the thermoformed film (100) from becoming unnecessarily thick.

[0051] On the other hand, according to this disclosure, a first unstretched film layer (10), a stretched film layer (20), and a second unstretched film layer (30) may be sequentially laminated. Specifically, the thermoformable film (100) of this disclosure may have a structure in which a first unstretched film layer (10), a stretched film layer (stretched polyamide base layer and transparent deposited layer) (20), and a second unstretched film layer (30) are laid in this order, as shown in Figure 1. Having such a layer structure makes it possible to have excellent thermoformability. Here, in order to increase the bonding strength between each layer, an adhesive layer may be interposed between the first unstretched film layer (10) and the stretched film layer (20), and / or between the stretched film layer (20) and the second unstretched film layer (30).

[0052] In the thermoformed film (100) of the present disclosure, the sum (T1 + T2) of the thickness (T1) of the first unstretched film layer (10) and the thickness (T2) of the stretched film layer (20) can be smaller than the thickness (T3) of the second unstretched film layer (30) (T1 + T2 < T3). Due to such a thickness difference, in the process of stretching the thermoformed film (100) to fit the mold shape during molding, it is possible to prevent the thickness of the thermoformed film (100) from becoming too thin. Therefore, the gas barrier property of the thermoformed film (100) can be ensured even after molding.

[0053] According to the present disclosure, the thickness ratio (T1: T2: T3) of the first unstretched film layer (10), the stretched film layer (20), and the second unstretched film layer (30) is not particularly limited, but may be 1: 0.1 to 0.5: 1.5 to 2.5, 1: 0.2 to 0.4: 1.7 to 2.3, or 1: 0.2 to 0.3: 1.8 to 2.1.

[0054] The thermoformed film (100) of the present disclosure includes a stretched film layer (20) having high gas barrier properties and thermoformability (stretchability), and a first unstretched film layer (10) and a second unstretched film layer (30) having excellent thermoformability (stretchability). Therefore, even after the thermoforming process, or after the thermoforming process and the heat sterilization process, the gas barrier property can be maintained in an excellent state. That is, the thermoformed film (100) of the present disclosure can have a relatively low oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) even after being subjected to either or both of the thermoforming process or the thermoforming process and the heat sterilization process.

[0055] Specifically, according to the present disclosure, the thermoformed film (100) has an oxygen transmission rate (OTR) measured after thermoforming at 120 to 155 ° C of 20 cc / m 2 ·day or less (= 20 cc / m 2 ·day·atm or less). More specifically, the oxygen transmission rate (OTR) of the thermoformed film (100) after thermoforming may be 15 cc / m 2 ·day or less, may be 13 cc / m 2 ·day or less, or may be 10 cc / m2 • It may be less than 8cc / m 2 • It may be less than 5cc / m 2 It may be less than 1 day. 2 It may be less than or equal to 0 cc / m 2 • It may be more than 0.0001 cc / m 2 • It may be more than 0.001 cc / m². 2 • It may be more than 0.01 cc / m². 2 • It may be more than 0.05 cc / m 2 • It may be more than 0.1 cc / m². 2 • It may be more than a day. Here, there is no particular limit to the time for thermoforming the thermoformable film (100) at 120-155°C (specifically, 125-155°C, 130-155°C, 135-155°C), but it may be 3-15 seconds, 5-13 seconds, or 7-10 seconds. For example, thermoforming the thermoformable film (100) may be carried out by a procedure in which heat treatment is performed at 120-155°C for 3 seconds, and then molding is performed for 5 seconds while maintaining 120-155°C.

[0056] Furthermore, according to this disclosure, by thermoforming the thermoformed film (100) at 120-155°C and heating it at 110-130°C for 20-30 minutes (after both thermoforming and heat sterilization processes), the measured oxygen permeability (OTR) is 15 cc / m². 2 ·day or less (=15cc / m 2 It can be less than or equal to 12 cc / m². More specifically, the oxygen permeability (OTR) of the thermoformed film (100) after thermoforming and heat treatment is 12 cc / m². 2 • Can be less than 9cc / m 2 • Can be less than 7cc / m 2 • Can be less than 5cc / m 2 • Can be less than 3.5cc / m 2 • Can be less than or equal to 0cc / m 2 • It can be more than 0.0001 cc / m 2· It can be more than a certain number of days, and 0.0002 cc / m 2 · It can be more than a certain number of days, and 0.0003 cc / m 2 · It can be more than a certain number of days, and 0.0004 cc / m 2 · It can be more than a certain number of days, and 0.0005 cc / m 2 · It can be more than a certain number of days. Here, the heating of the thermoformed film (100) after thermoforming can be carried out, for example, by storing it in steam under atmospheric pressure at 110 - 130 °C or under a pressure higher than that, or in hot water at 110 - 130 °C for 20 - 30 minutes.

[0057] Method for manufacturing a thermoformed film The present disclosure provides a method for manufacturing a thermoformed film that can efficiently manufacture the above thermoformed film. Specifically, the method for manufacturing a thermoformed film of the present disclosure includes preparing a first unstretched film, a stretched film, and a second unstretched film, and sequentially laminating and combining the first unstretched film, the stretched film, and the second unstretched film (see Figure 2).

[0058] The step of preparing each of the above films may each include preparing a first unstretched film for forming the first unstretched film layer described above, a stretched film for forming the stretched film layer described above, and a second unstretched film for forming the second unstretched film layer described above.

[0059] The first unstretched film may be an unstretched film containing the above-mentioned polymer resin (first polymer resin).

[0060] The above-mentioned stretched film may be a film obtained by subjecting an unstretched film (second unstretched film) containing the above-mentioned polymer resin (second polymer resin) to uniaxial stretching or biaxial stretching and then performing a deposition treatment. Specifically, an unstretched film may be stretched in at least one direction of the longitudinal direction (MD) and the transverse direction (TD), and then a deposition treatment may be performed to obtain a stretched film. The deposition step may be performed by depositing an inorganic substance that is transparent and has excellent gas barrier properties on the stretched film. Here, the inorganic substance is aluminum oxide (AlO x ), aluminum oxynitride (AlO x N y ), titanium oxide (TiO x ), silicon oxide (SiO x ), zinc oxide (ZnO x ), tin oxide (SnO x ), silicon nitride (SiN x ), aluminum nitride (AlN x ), silicon oxynitride (SiO x N y ), nickel oxide (NiO x ), and magnesium oxide (MgO x ), and may contain at least one selected from the group consisting of them. Also, the deposition treatment may be any known deposition process (for example, vacuum deposition using sputter deposition, ion plating, high-frequency heating, electron beam heating, etc.).

[0061] The second unstretched film may be an unstretched film containing the above-mentioned polymer resin (third polymer resin). Specifically, the unstretched film may be a cast polypropylene film (CPP).

[0062] The step of joining the films may include sequentially laminating the first unstretched film, the stretched film, and the second unstretched film and joining them using a known lamination method. Alternatively, the process may include applying an adhesive to at least one of the first unstretched film, the stretched film, and the second unstretched film before laminating each film, and then sequentially laminating and joining these films. The adhesive may be any adhesive commonly used in film manufacturing.

[0063] Retort pouch This disclosure provides a retort pouch comprising the thermoformed film described above. Specifically, the retort pouch of this disclosure is manufactured by laminating an upper film and a lower film and then performing a normal sealing process, wherein at least one of the upper film and the lower film may be the thermoformed film described above. By comprising the thermoformed film described above, the retort pouch of this disclosure can be easily thermoformed into a desired shape and can also have excellent gas barrier properties even after thermoforming. In particular, the retort pouch of this disclosure has excellent gas barrier properties even when heat sterilization is performed under conditions stricter than boiling sterilization, thereby enabling an extension of the shelf life of the contents (e.g., processed meat products).

[0064] The retort pouches of this disclosure may have various forms, such as box pouches, 3-way pouches, T-way pouches, and M-way pouches.

[0065] The present disclosure will be described in detail below based on the following examples. However, the scope of the present disclosure is not limited to the following examples.

[0066] Mode of the invention <Preparation of thermoformed film> Example 1 A 50 μm thick polyamide film was prepared as the first unstretched film, a 15 μm thick polyamide film with silicon oxide deposited on it was prepared as the stretched film, and a 100 μm thick polypropylene film (CPP film) was prepared as the second unstretched film. The properties of each film were summarized in Table 1 below.

[0067] Next, a thermoformed film was manufactured by laminating the first unstretched film layer (polyamide film layer), the stretched film layer (silicon oxide coated polyamide film layer), and the second unstretched film layer (polypropylene film layer) in this order using a lamination method.

[0068] [Table 1]

[0069] Comparative Example 1 A multilayer co-extruded film (manufactured by Shōfu Co., Ltd., 620C) produced using unstretched film was used.

[0070] <Preparation of retort pouches> Example 1 The thermoformed film from Example 1 was laminated and sealed as the top and bottom films used in conventional retort manufacturing to produce a three-way retort pouch.

[0071] Comparative Fabrication Example 1 The co-extruded film of Comparative Example 1 was laminated and sealed using the top and bottom films commonly used in retort manufacturing to produce a three-way retort pouch.

[0072] Test Example 1: Evaluation of Thermoformability Ham products were placed in the retort pouches manufactured in Production Example 1 and Comparative Production Example 1, and the pouches were sealed to produce processed products. Afterward, the four corners of the processed products were visually inspected to check for rounding (the phenomenon of not forming right angles). The results are shown in Table 2 below. ○: No rounding of the four corners △: One or two of the four corners are rounded. ×: All four corners are rounded.

[0073] Test Example 2: Measurement of Oxygen Permeability The thermoformed films produced in Example 1 and Comparative Example 1 were placed in a 10 mm deep mold and thermoformed at 140-155°C for 8 seconds. The thermoformed films were then heat-sterilized at 118°C for 25 minutes. Following this, the oxygen permeability of the thermoformed and heat-sterilized films was measured using a Mocon Oxtran apparatus according to ASTM D3985 (23°C, 50% RH). The results are shown in Table 2 below.

[0074] [Table 2]

[0075] As shown in Figure 2 above, the thermoformable film of this disclosure maintains thermoformability while also possessing excellent gas barrier properties and significantly reduced oxygen permeability even after thermoforming and heat sterilization.

[0076] [Explanation of symbols] 100 Thermoformable Film 10. First unstretched film layer 20 Stretched film layer 30. Second unstretched film layer

Claims

1. The first unstretched film layer, A stretched film layer having a transparent deposited layer on one or both sides thereof, The second unstretched film layer, A thermoformable film equipped with the following features.

2. The oxygen permeability (OTR) measured after thermoforming at 120-155°C was 20 cc / m³. ２ - The thermoformable film according to claim 1, wherein the date is less than or equal to day.

3. The oxygen permeability (OTR) of the thermoformed film, measured after heating at 110-130°C for 20-30 minutes, was 15 cc / m². ２ - The thermoformable film according to claim 2, wherein the date is less than or equal to day.

4. The thermoformable film according to claim 1, wherein the first unstretched film layer has a tensile strength of 110 to 160 MPa in the longitudinal direction (MD) and the transverse direction (TD), and an elongation of 400 to 440% in the longitudinal direction (MD) and the transverse direction (TD), respectively.

5. The thermoformable film according to claim 1, wherein the stretched film layer has a tensile strength of 240 to 320 MPa in the longitudinal direction (MD) and the transverse direction (TD), and an elongation of 80 to 120% in the longitudinal direction (MD) and the transverse direction (TD), respectively.

6. The oxygen permeability (OTR) of the first unstretched film layer is 30 cc / m ２ - It is less than or equal to 250 g / m³ and has a water vapor transmission rate (WVTR) of 250 g / m³. ２ - The thermoformable film according to claim 1, wherein the date is less than or equal to day.

7. The oxygen permeability (OTR) of the stretched film layer is 2 cc / m ２ - The day is less than or equal to 3 g / m³, and the water vapor transmission rate (WVTR) is 3 g / m³. ２ - The thermoformable film according to claim 1, wherein the date is less than or equal to day.

8. The thermoformable film according to claim 1, wherein the first unstretched film layer and the stretched film layer each contain polyamide, and the second unstretched film layer contains polypropylene.

9. The thermoformable film according to claim 1, wherein the sum of the thickness of the first unstretched film layer and the thickness of the stretched film layer is thinner than the thickness of the second unstretched film layer.

10. The thermoformable film according to claim 1, wherein the thickness of the first unstretched film layer is 40 to 60 μm, the thickness of the stretched film layer is 5 to 25 μm, and the thickness of the second unstretched film layer is 80 to 120 μm.

11. The thermoformable film according to claim 1, wherein the first unstretched film layer, the stretched film layer, and the second unstretched film layer are sequentially laminated.

12. The thermoformable film according to claim 1, wherein the transparent deposited layer comprises at least one selected from the group consisting of aluminum oxide, aluminum oxynitride, titanium oxide, silicon oxide, zinc oxide, tin oxide, silicon nitride, aluminum nitride, silicon oxynitride, nickel oxide, and magnesium oxide.

13. A method for manufacturing a thermoformable film, comprising preparing a first unstretched film, a stretched film, and a second unstretched film, and sequentially laminating and joining the first unstretched film, the stretched film, and the second unstretched film.

14. A retort pouch comprising a thermoformed film according to any one of claims 1 to 12.

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