Retort package and coextruded film for retort package

Abstract

The present invention relates to a retort package having excellent heat resistance at high temperature and high pressure and having excellent moisture and oxygen barrier properties, and to a co-extruded film for the retort package, which is applied for packaging retorted food products. The co-extruded film for the retort package comprises: a first barrier layer and a third barrier layer having moisture barrier properties; a second barrier layer comprising an ethylene vinyl alcohol resin (EVOH) having oxygen barrier properties and located between the first and third barrier layers; an adhesive layer for bonding the first and second barrier layers; an adhesive layer for bonding the second and third barrier layers; and an adhesive layer for bonding the second and third barrier layers; EVOH having an oxygen barrier property, and a second barrier layer comprising an adhesive resin formed between the first and second barrier layers, and between the second and third barrier layers, respectively, and an adhesive layer for bonding each of the barrier layers.

Description

[0001] RETORT PACKAGE AND COEXTRUDED FILM FOR RETORT PACKAGE

[0002] Technical Field

[0003] This invention relates to a packaging or pouch for retort food, and more particularly to a retort package, and a coextruded film for the retort package included therein, which has excellent resistance to high temperatures and high pressures, and excellent moisture and oxygen barrier properties, and is applied for packaging of retort food.

[0004] Background Art

[0005] In general, retort food is a shelf-stable food that is made by sterilizing pre-cooked and processed food by placing it in a plastic bag, sealing it, and placing it in a retort chamber, which is heated to a high temperature and pressure of over 120°C.

[0006] Research on retort food and packaging first began at the U.S. Department of Defense in the 1940s and was used as a military combat ration and space shuttle food in 1958, while industrial use began in Japan when curry was made into a retort food and marketed. In Korea, retort curry was introduced under the name of Ottogi's 3-minute curry as a representative retort food .

[0007] In recent years, as the number of dual-income and singleperson households has increased, retort foods, which are convenient meals, have increased, and the food packaging industry is in the process of developing retort package with excellent freshness retention.

[0008] Retort packages were initially pouch-type, meaning small package, but have recently diversified into cup-type, tray-type, etc .

[0009] In general, pouch-type retort packages are made of laminated films, which are made of three or five layers of plastic film and / or aluminum foil with different properties to improve heat resistance, gas permeability, and heat sealing, which are important elements of retort packages.

[0010] FIG. 1 is a cross-sectional view of a conventional retort package .

[0011] Referring to FIG. 1, a conventional retort package has a structure in which a PET film (Polyester; 11) , an adhesive (Adhesive; 12) , an aluminum foil (Aluminum Foil; 13) , an adhesive (Adhesive; 14) , an oriented nylon (BONY; 15) , an adhesive (Adhesive; 16) , and a sealant layer (CPP Film; 17) are laminated. It is manufactured by applying adhesive to each of the multiple layers of films 11, 13, 15, and 17 and bonding them together through three lamination processes.

[0012] Compared to metal cans, conventional retort pouches are lighter, more portable, and require less heat treatment, resulting in higher quality food, but they are not microwaveable due to the aluminum foil in the package.

[0013] In addition, due to the nature of aluminum foil, it can be easily torn, and it does not have good resistance to pinholes, which can easily be punctured by external stimuli, leading to the possibility of contamination to the foods inside the retort package .

[0014] In addition, conventional retort packages have the disadvantage that the aluminum foil is not transparent, making it difficult to see the deterioration of the food inside the package .

[0015] In addition, conventional retort packages, made of aluminum foil, are not environmentally friendly, causing ongoing problems with environmental pollution when incinerated.

[0016] In addition, conventional retort packages use solvents (VOCs) as adhesives 12, 14, 16 to bond multiple films together, and when sterilization (or pasteurization) is performed at high temperature and pressure, solvent odors are released, which is problematic to the food safety.

[0017] Therefore, considering the freshness and stability of retorted food, retort packages are required to have resistance that can withstand high pressure and high temperature sterilization processes, oxygen and moisture barrier properties that can block the permeation of moisture and oxygen even under high pressure for a long period of time, and pinhole resistance that can maintain the sterilization state of food.

[0018] Disclosure of the Invention

[0019] Technical Problems

[0020] To solve the above problems, the present invention aims to provide a retort package and a co-extruded film for the retort package included therein, which has excellent resistance to high pressure and high temperature, and excellent moisture and oxygen barrier properties even under high pressure for a long time and is applied for packaging retorted food products.

[0021] Another object of the present invention is to provide a microwaveable retort package and a coextruded film for the retort package included therein by further adding a nylon resin layer having excellent pinhole resistance, which is not easily punctured by external impact or stimulation.

[0022] Furthermore, another object of the present invention is to increase the productivity of retort packages by manufacturing a film for retort packages with a multi-layer structure in one step by co-extrusion film technology.

[0023] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be apparent to those who are having packaging knowledge in the packaging technology to which this invention belongs from the following description .

[0024] Technical Solutions

[0025] To accomplish the above-mentioned obj ect s , a coextruded film for retort package according to an embodiment of the present invention comprises : a first barrier layer and a third barrier layer having moisture barrier properties ; a second barrier layer positioned between the f irst barrier layer and the third barrier layer and made of an ethylene vinyl alcohol re sin ( EVOH ) having oxygen barrier propertie s ; an adhe sive layer formed between the first and second barrier layers and between the second and third barrier layers , respectively, for bonding the respective barrier layers .

[0026] In this case , the first barrier layer and the third barrier layer may be including a plastic synthetic re sin formed f rom polyethylene ( PE ) or polypropylene ( PP ) as the main raw material Further , the first and third barrier layers may compri se at least one or more layers for moisture barrier properties and heat resistance .

[0027] Further , the second barrier layer may have a content of Ethylene Vinyl alcohol from 29 mol% to 44 mol% , considering its oxygen barrier propertie s and thermal stability .

[0028] Further , the coextruded film for retort package according to an embodiment of this invention may further comprise a fourth barrier layer formed by a nylon resin having excellent pinhole resistance to increase the puncture re sistance of the first to third barrier layers .

[0029] In this case , the fourth barrier layer may comprise at least one of he following : a first protective layer co-extruded to an outer surface of the first barrier layer to protect the first barrier layer from external stimuli; a second and third protective layers co-extruded to an upper and lower surface of the second barrier layer, respectively, to protect the second barrier layer and the third barrier layer.

[0030] On the other hand, the coextruded film for retort package according to an embodiment of the present invention, wherein the third barrier layer may be an easy peel layer formed mainly of polypropylene (PP) resin.

[0031] The coextruded film for retort package comprising an easy peel film, wherein the first barrier layer may be made of a nylon (Nylon, Polyamide) resin.

[0032] Further, the fourth barrier layer may be made of a Nylon, Polyamide resin.

[0033] A retort package according to an embodiment of the present invention, comprising: a base film; a coextruded film for retort package with a multilayer structured according to claim 1; and an adhesive layer forming a volatile organic compound (VOC) on the base film to bond the base film and the coextruded film for a retort package.

[0034] In this case, the base film comprises at least one of a polyester (PET) film, a polypropylene (PP) film, a nylon film, and a polyethylene (PE) film.

[0035] Specifically, the polypropylene film may comprise a biaxially oriented polypropylene (BOPP) film, the nylon film may comprise a biaxially oriented polyamide (BOPA) film or a biaxially oriented nylon (BONY) film, and the polyethylene film may comprise a biaxially oriented polyethylene (BOPE) film and a mono-axially oriented polyethylene (MOPE) film.

[0036] Furthermore, the coextruded film for retort package prevents components of the volatile organic compound from entering food inside the retort package. Advantageous Effects of the Invention

[0037] According to such an embodiment of the present invention, it has excellent heat resistance to sterilization (or pasteurization) treatment at high temperature and high pressure (e.g. , 120°C to 138°C) , and blocks moisture and oxygen permeation under high pressure for a long period of time (e.g. , 40 minutes to 90 minutes) , making it applicable for packaging retort food.

[0038] In addition, according to an embodiment of the present invention, it is easy to cook by using a microwave oven, has excellent pinhole resistance to impact and tearing, is not easily punctured by external stimuli, and has the effect of preventing contamination by pinholes.

[0039] Furthermore, according to an embodiment of the present invention, productivity can be increased by manufacturing a coextruded film for a retort package with a multi-layer structure at once by a co-extrusion technology, and furthermore, when applied as a pouch-type or tray-type retort package, co-extruded films for retort package manufactured from a single co-extruded film can be easily manufactured by a simple process of bonding the base film to the retort package, thus simplifying the bonding process and improving manufacturing productivity. [Short description of the drawing] .

[0040] FIG. 1 is a cross-sectional view of a conventional retort package .

[0041] FIG.2 is a cross-sectional view of a retort package according to an embodiment of the present invention.

[0042] FIG. 3 is a cross-sectional view of a co-extruded film for a retort package according to the first embodiment of the present invention.

[0043] FIG. 4 is a cross-sectional view illustrating a co-extruded film for a retort package according to a second embodiment of the present invention.

[0044] FIG. 5 is a drawing of a tray-type retort package with a co-extruded film for a retort package according to a third embodiment of the present invention. Best Mode for Invention

[0045] The present invention will be described in more detail below with reference to the drawings.

[0046] Various embodiments of the present invention improve three key requirements for retort package: heat resistance, moisture and oxygen barrier, and pinhole resistance.

[0047] First, the retort package according to an embodiment of the present invention is co-extruded with at least one heat- resistant synthetic resin and is configured to withstand pasteurization treatment at 100°C or higher, as well as sterilization treatment at 125°C to 138°C (high temperature, high pressure) .

[0048] Second, the retort package according to an embodiment of the present invention is co-extruded in a multi-layer structure using a resin having moisture barrier properties and oxygen barrier properties, so that it is configured to block factors (such as rays, moisture, oxygen, etc. ) that adversely affect the freshness of food products even during processing at high temperatures, high pressures, and long periods of time (e.g. , at least 30 minutes to 90 minutes) , as well as during storage at room temperature.

[0049] Third, the retort package according to an embodiment of the present invention is comprised of a multi-layer film using a nylon resin with excellent pinhole resistance, so that the package is not punctured by external stimuli.

[0050] The specific configuration of this is as follows: First, referring to FIG. 2, the configuration of a retort package according to an embodiment of the present invention is illustrated .

[0051] A retort package according to an embodiment of this invention includes a base film 100, an adhesive layer 200, and a coextruded film 300 for a multi-layer retort package, as shown in FIG. 2.

[0052] The base film 100 can be a PET film made of polyester (PET) resin as the main raw material. PET film is thinner, has higher strength and heat resistance, and is more resistant to external scratches than other base films. Therefore, base film 100 is advantageous as an outer surface of the package when the retort package is manufactured for food packaging.

[0053] The base film 100 is preferably, but not exclusively, a PET film having excellent transparency, heat resistance, dimensional stability, impermeability, moisture resistance, water resistance, chemical resistance, etc. suitable for packaging and metallizing, and any transparent film that is resistant to external scratches (tearing) will be applicable. For example, in addition to PET films, one or more of the following can be used: polypropylene films such as BOPP (Biaxially Oriented Polypropylene) films, nylon films such as BOPA (Biaxially Oriented Polyamide) films or BONY (Biaxially Oriented Nylon) films, polyethylene (PE) films such as BOPE (Biaxially Oriented Polyethylene) films and MOPE (Mono-axially Oriented Polyethylene) films.

[0054] The adhesive layer 200 forms a volatile organic compound (VOC) on the base film 100 that serves to bond the base film 100 and the co-extruded film 300 for the multi-layer retort package to each other. In other words, the adhesive layer 200 bonds the two films together using VOC, such as glue, on the base film 100.

[0055] The coextruded film 300 for the multi-layer retort sealant is a multifunctional barrier film, which has the properties of heat resistance, moisture and oxygen barrier, and pinhole resistance as described above. It is also an environmentally friendly material and is transparent.

[0056] In addition, the co-extruded film 300 for the multi-layer retort package prevents volatile organic compounds (VOCs) applied to the adhesive layer 200 from migrating into the food product contained within the package.

[0057] In this case, the co-extruded film 300 for the multi-layer retort package becomes the inner side of the package that comes into contact with the food. Thus, the co-extruded film 300 for the multi-layer retort package is a functional film that can secure the freshness and stability of retorted food by blocking moisture and oxygen permeation, as well as the inflow of volatile organic compounds harmful to food.

[0058] A retort package with this configuration can be manufactured in a simple process as shown below.

[0059] That is, an organic solvent for adhesion is applied to one side of the base film 100, and a multi-layer co-extruded film for retort package 300 is laminated on top of the applied adhesive layer 200, so the base film 100 and the multi-layer coextruded film for retort package 300 are laminated. This results in a laminated-structure product. Since this manufacturing method can shorten the laminating process compared to the manufacturing process of retort package using conventional aluminum foil, it is possible to reduce the work time required for the manufacturing process as well as the process cost, which is expected to improve productivity.

[0060] The manufacturing process of retort package using conventional aluminum foil requires three laminating processes to create the multi-layer structure, as shown in FIG. 1, whereas the manufacturing process of retort package according to an embodiment of the present invention requires only one laminating process between the PET film 100 and the co-extruded film 300 for the retort package, as shown in FIG. 2.

[0061] Next, with reference to FIG.s 3 through 5, a co-extruded film for a retort package according to an embodiment of the present invention will be described in detail.

[0062] FIG. 3 is a cross-sectional view of a co-extruded film for a retort package according to a third embodiment of the present invention .

[0063] The coextruded film 300A for retort package according to the first embodiment includes a first barrier layer 310, a second barrier layer 330, a third barrier layer 350, and adhesive layers 320, 340.

[0064] The first barrier layer 310 and the third barrier layer 350 have moisture barrier properties. To this end, the first barrier layer 310 and the third barrier layer 350 are plastic synthetic resins formed from polyethylene (PE) or polypropylene (PP) .

[0065] Furthermore, the first barrier layer 310 and the third barrier layer 350 may comprise at least one or more layers for moisture barrier and heat resistance. For example, by coextruding two layers as shown, the moisture barrier and heat resistance can be increased.

[0066] In this case, either of the first barrier layer 310 and the third barrier layer 350 can be the inside of the package. For example, if the first barrier layer 310 is the inside that will be in contact with the food product inside, then the third barrier layer 350 will be the outer side that will be bonded to the base film 100 (in FIG. 2) of the retort package. Conversely, if the third barrier layer 350 is the inside that will be in contact with the food inside, the first barrier layer 310 can be the outer side that will be bonded to the base film 100 (in FIG. 2) of the retort package. For ease of understanding, FIG. 3 illustrates a case where the third barrier layer 350 is the inside. The barrier layer to inside is preferably composed of a plastic synthetic resin formed mainly of polypropylene (PP) as the part in direct contact with the food product.

[0067] As shown, assuming that the third barrier layer 350 is the inner side of the package, the third barrier layer 350 may be a synthetic resin comprising polypropylene (PP) and the first barrier layer 310 may be a synthetic resin comprising polyethylene (PE) , such as high-density polyethylene (HDPE) , which has excellent moisture barrier properties.

[0068] The adhesive layers 320, 340 are formed with an adhesive resin between the first barrier layer 310 and the second barrier layer 330, and between the second barrier layer 330 and the third barrier layer 350, respectively, to bond the respective barrier layers .

[0069] Here, the adhesive resin can be a tie resin, which is characterized by excellent interlayer adhesion between the two resins and coextrusion molding when coextruding resins of different materials.

[0070] The second barrier layer 330 is located between the first barrier layer 310 and the third barrier layer 350 and is made of ethylene vinyl alcohol resin (EVOH) , which has excellent oxygen barrier properties .

[0071] Ethylene vinyl alcohol (EVOH) is a copolymer of polyethylene and vinyl acetate, formed by the hydrolysis of polyethylene vinyl acetate obtained by the gas phase copolymerization of ethylene and vinyl acetate, which are usually in solution. Ethylene vinyl alcohol (EVOH) is known to have the best gas barrier properties against gases such as oxygen, nitrogen, and carbon dioxide. In addition, EVOH is a clear, glossy thermoplastic copolymer.

[0072] The oxygen barrier layer 135 according to an embodiment of the present invention may be ethylene vinyl alcohol (EVOH) having these properties, but with a content of ethylene from 27 mol% to 44 mol%, considering its oxygen barrier properties and thermal stability.

[0073] Here, 27 mol% has the highest alcohol content and therefore the best oxygen barrier properties, but it is difficult to produce films with higher content, so EVOH resins with 44 mol% can be used. EVOH resin with 27 mol% or less is very difficult to process with the current equipment in the EVOH manufacturing industry and is not economical, while 44 mol% or more is easy to process, but oxygen barrier properties may decrease rapidly.

[0074] In order for the retort pouch to withstand the high temperature and pressure of sterilization in a retort chamber, a special ethylene vinyl alcohol (EVOH) resin, which is the most oxygen barrier of all ethylene vinyl alcohol (EVOH) resins for retort films, rather than a general ethylene vinyl alcohol (EVOH) resin, is used. If you use regular EVOH resin, it will not withstand the high temperature and pressure of retort sterilization, and the EVOH layer will delaminate and lose its oxygen barrier properties.

[0075] Thus, the coextruded film 300A for the multi-layer retort package according to the first embodiment may comprise HDPE-tie- EVOH-tie-PP or HDPE-HDPE-tie-EVOH-tie-PP-PP sequentially from the first barrier layer 310 to the third barrier layer 350.

[0076] Referring to FIG. 4, FIG. 4 is a cross-sectional view of a co-extruded film for a retort package according to a third embodiment of the present invention.

[0077] The coextruded film 300B for retort package according to the second embodiment may comprise a first barrier layer 410, a second barrier layer 430, a third barrier layer 450, and adhesive layers 420, 440, as in the configuration of the first embodiment, and may further comprise a fourth barrier layer 470 to enhance the puncture resistance of the first to third barrier layers 410, 430, 450.

[0078] Here, the first to third barrier layers 410, 430, 450, and the adhesive layers 420, 440 for bonding each of these layers are the same as described in the first embodiment.

[0079] Describing the fourth barrier layer 470, which is a different configuration from the first embodiment, the fourth barrier layer 470 is a protective layer formed by co-extruding a nylon resin with excellent pinhole resistance, which is included to increase the puncture resistance of the retort package.

[0080] Nylon resins typically have low oxygen permeability and good pinhole resistance (the ability of the film to resist punctures) , making them ideal for packaging applications such as chilled, frozen, and retorted foods.

[0081] Thus, the fourth barrier layer 470 utilizing the nylon resin may further improve the oxygen barrier function as well as the pinhole resistance.

[0082] Specifically, the fourth barrier layer 470 can include at least one of a first protective layer 471 that is co-extruded to an outer surface of the first barrier layer 410 to protect the first barrier layer 410 from external stimuli, and second and third protective layers 472, 473 that are co-extruded to the top and bottom of the second barrier layer 430 and 450, respectively, to protect the second barrier layer 430 and the third barrier layer 450.

[0083] For example, the fourth barrier layer 470 may include only the first protective layer 471 or may include only the first protective layer 471 and the second protective layer 472. Alternatively, it can include both the first protective layer 471 and the third protective layer 473. In this case, the film with the best puncture resistance may be a structure that includes all the first protective layer 471, the second protective layer 472, and the third protective layer 473.

[0084] For example, if the fourth barrier layer 470 includes the second and third protective layers 472, 473, it can protect the second barrier layer 430, which is located in the middle, to maintain its function of being oxygen gas barrier as well as puncture resistant. The second barrier layer 430 is composed of an EVOH resin with excellent oxygen barrier properties, but due to the nature of EVOH, the film is fragile like glass when folded or creased and is weak to high temperature heat, so forming a protective layer of nylon resin on the top and bottom of the second barrier layer 430 can protect the EVOH layer.

[0085] For example, when including the first protective layer 471 as a fourth barrier layer 470, the coextruded film 300B for retort package may further include a third adhesive layer 460 for bonding the first protective layer 471 and the first barrier layer 410.

[0086] The third adhesive layer 460 is formed from the same adhesive resin as the first and second adhesive layers 420, 440, except that the EVOH resin and nylon resin of the second barrier layer 430 adhere to each other without the adhesive resin, making the adhesive layer unnecessary.

[0087] Therefore, the coextruded film 300B for retort package according to the second embodiment may be composed of Nylon (first protective layer) - tie (third adhesive layer) - PP (first barrier layer) - tie (first adhesive layer) - Nylon (second protective layer) - EVOH (second barrier layer) - Nylon (third protective layer) - tie (second adhesive layer) - PP (third barrier layer) from the outer side of the package. This nine-layer structure is considered to be the most stable configuration with the best heat resistance, moisture and oxygen barrier, and pinhole resistance.

[0088] On the other hand, the co-extruded film 300B for retort package according to the second embodiment can be applied as a tray-type retort package 10 that seals a container 20 containing instant food such as instant rice, coffee, fish cake, etc. as shown in FIG. 5.

[0089] FIG. 5 is a drawing of a tray-type retort package with a co-extruded film for a retort package according to a third embodiment of the present invention.

[0090] In this case, the tray-type retort package 10 is the same as the structure previously shown in FIG. 2, and the coextruded film for the retort package included therein may also be formed in the structure of FIG. 3 and 4.

[0091] However, the coextruded film for retort package according to the third embodiment differs in that the third barrier layer (350 in FIG. 3, 450 in FIG. 4) , which is to be the inner sealant layer, is composed of an Easy peel film made of polypropylene (PP) resin.

[0092] Easy peel films are heat sealable, have strong heat seal strength, and easy to remove films that can be sterilized at temperatures above 100°C. These easy peel films are also known as lidding films and are often used as top lidding films for tray product packaging.

[0093] Thus, when the retort package 10, which is composed of a multi-layer film with an inner layer comprising an easy peel resin, moisture and oxygen barrier, and puncture resistance, is sealed over the packaging container 20, the easy peel film is adhered to the packaging container 20 to form a hermetically sealed package and is easily peeled off upon removal of the laminate 20.

[0094] Furthermore, the first barrier layer 410 of the co-extruded film for the retort package according to the third embodiment may be made of a plastic synthetic resin of polyethylene (PE) or polypropylene (PP) , as in the first and second embodiments, but not limited to, a nylon (Nylon, Polyamide) resin.

[0095] Thus, the film for retort package according to the third embodiment may be composed of a multi-layer structure such as a Nylon-tie (third adhesive layer) -PP (or Nylon) -tie-Nylon-EVOH- Nylon-tie-Easy Peel film when the same nylon resin (Nylon, Polyamide) is co-extruded to the first barrier layer (410 of FIG 4) and the fourth barrier layer (470 of FIG. 4) by applying the structure of FIG. 4.

[0096] In this case, the nylon resin of the first barrier layer (410 in FIG. 4) has a thickness of 10 to 25 pm, and the nylon resin of the fourth barrier layer (470 in FIG. 4) can be formed with a thickness of 10 to 15 pm. In this way, the puncture resistance strength is further improved by two layers of nylon with excellent puncture resistance.

[0097] On the other hand, the coextruded films 300A, 300B for the retort package shown in FIG. 3 and 4 above may be manufactured by a coextruded blown or a coextruded cast.

[0098] Go-extrusion is a processing method that uses two or more extruders to produce composite films by simultaneously extruding each molten resin and forming them in multiple layers in the molten state.

[0099] The purpose of coextrusion is to add multiple functions to a film produced in a single layer. In other words, one particular resin has one unique property, and in order to give it a new function, the existing resin and the resin with the new function are coextruded and formed together to create a film with multiple functions .

[0100] In an embodiment of this invention, a co-extrusion method is applied to produce a film having a combination of heat resistance, moisture and oxygen barrier properties, pinhole resistance, and heat seal-ability. Since the coextrusion method is utilized, the interlayer bonding utilizes an adhesive resin, and the film can be manufactured as a single layer using an adhesive resin between each barrier layer.

[0101] For example, using the coextruded cast type, the resin of the raw material to be the first barrier layer, adhesive layer, second barrier layer, adhesive layer, third barrier layer, or fourth barrier layer is put in a manufacturing facility, and when the raw material is extruded at a high temperature at which the raw material melts, a large-diameter cooling roll is placed at the exit from which the resin of each barrier layer is melted and extruded, and the resin of each barrier layer is cooled as it moves on the cooling roll, and is manufactured in the form of a single layer of film or sheet.

[0102] In another example, using the coextruded blown type, the resin of the raw material to be the first barrier layer, adhesive layer, second barrier layer, adhesive layer, third barrier layer, or fourth barrier layer is melted at a high temperature in each extruder and collected in a die cylinder, and air is blown upward using a vertical upward wind called an air ring in the die cylinder, and the resin rises upward like a balloon and cools in contact with the air. Coextruded Blown Film can then be manufactured into rolls of film that are wound on a winder .

[0103] Therefore, the co-extruded film for retort package according to an embodiment of the present invention can be easily manufactured in a simple process, as the multi-layer structure of the film is manufactured in one layer by this coextrusion method, and the productivity can be increased, and even in the process of bonding with the base film for application as a retort package, only the process of bonding the base film and the film for the retort package.

[0104] The features, structures, effects, etc. described above are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified in other embodiments by those who have packaging knowledge in the area to which the embodiments belong. Accordingly, such combinations and modifications are to be construed as being within the scope of the present invention.

[0105] Furthermore, while the above description has been made with reference to embodiments, these are merely illustrative and do not limit the invention, and those having packaging skill in the packaging industry will recognize that many modifications and applications not illustrated are possible without departing from the essential features of the invention. For example, each of the components specifically shown in the embodiments may be practiced with variations. And differences with respect to such variations and applications are to be construed as being within the scope of the invention as defined by the appended claims.

[0106] Industrial Applicability

[0107] The present invention relates to a co-extruded film for retort package applied for packaging retort foods with excellent heat resistance that can withstand high temperatures and high pressures and excellent moisture and oxygen barrier properties, and further forms a nylon res in layer with excellent pinhole resistance , so that it is not easily punctured by external impact or stimulation , and can be used as a packaging material for instant rice or ready-to-eat foods that can be heated in a microwave oven .

[0108] In particular , the manufacturing method using the coextrus ion technology of the present invention is highly applicable to various packaging-related industries as it enable s high-speed and large-scale production , thereby improving productivity . Furthermore , the co-extruded film for retort package of the present invention i s an eco-friendly material that can reduce the emis s ion of chemical s that cause environmental pollution when incinerated , thus expanding its industrial applicability in line with the recent trend of carbon gas emis sion reduction and environmental protection .

Claims

Claims1. A coextruded film for retort packages, comprising:A first and a third barrier layers with moisture barrier properties ;A second barrier layer comprising an ethylene vinyl alcohol resin (EVOH) having oxygen barrier properties, positioned between the first barrier layer and the third barrier layer; andAn adhesive layer formed between the first barrier layer and the second barrier layer, and between the second barrier layer and the third barrier layer, for bonding the respective barrier layers .

2. The coextruded film for retort packages of Claim 1, wherein the first and third barrier layers are including a plastic synthetic resin formed from polyethylene (PE) or polypropylene (PP) as the main raw material.

3. The coextruded film for retort packages of Claim 1, wherein the first and third barrier layers are composed of at least one layer for moisture barrier and heat resistance.4 . The coextruded film for retort packages of Claim 1, wherein the second barrier layer has a content of ethylene ranging from 27 mol% to 44 mol%, taking into account oxygen barrier properties and thermal stability.

5. The coextruded film for retort packages of Claim 1, further comprising:A fourth barrier layer formed by co-extruding a nylon resin having excellent pinhole resistance to increase the punctureresistance of the first to third barrier layers.

6. The coextruded film for retort packages of Claim 5, wherein the fourth barrier layer comprises at least one of the followin :A first protective layer co-extruded to an outer surface of the first barrier layer to protect the first barrier layer from external stimuli; andA second and third protective layer co-extruded above and below the second barrier layer, respectively, to protect the second barrier layer and the third barrier layer.7 . The coextruded film for retort packages of Claim 1 or Claim 5, wherein the third barrier layer is an easy peel layer formed from polypropylene (PP) resin.

8. The coextruded film for retort packages of Claim 7, wherein the first barrier layer is made of nylon (Nylon, Polyamide) resin.

9. The coextruded film for retort packages of Claim 8, Wherein the fourth barrier layer is made of nylon (Nylon, Polyamide) resin.

10. A retort package, comprising:Base film;Coextruded film for retort package with a multilayer structure according to Claim 1; andAn adhesive layer forming a volatile organic compound (VOC) on the base film to bond the base film to the coextruded filmfor retort package.

11. The retort package of Claim 10, wherein the base film comprises at least one of a polyester (PET) film, a polypropylene film, a nylon (Nylon, Polyamide) film, and a polyethylene (PE) film.

12. The retort package of Claim 11, wherein the polypropylene film comprises a biaxially oriented polypropylene (BOPP) film, and wherein the nylon film comprises a biaxially oriented polyamide (BOPA) film or a biaxially oriented nylon (BONY) film, and wherein the polyethylene film comprises a biaxially oriented polyethylene (BOPE) film and a mono-axially oriented polyethylene (MOPE) film.

13. The retort package of Claim 10, wherein the coextruded film for retort package prevents components of the volatile organic compound from entering to food in the retort package .

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