Retort sterilization film laminate and packaging material containing the same

Abstract

A retort sterilization film laminate according to one embodiment of the present invention includes a first OPP film made of oriented polypropylene (OPP), a first CPP film made of cast polypropylene (CPP) and bonded to one side of the first OPP film, a second OPP film made of oriented polypropylene and bonded to one side of the first CPP film, and a second CPP film made of cast polypropylene and bonded to one side of the second OPP film.

Description

[Technical Field]

[0001] The present invention relates to a retort sterilized film laminate and a packaging material including the same, and more particularly to a retort sterilized film laminate that maintains interlayer adhesive strength even after retorting, and a packaging material including the same. [Background technology]

[0002] As is already well known, retort pouch packaging materials are constructed by replacing the layer structure of existing laminated films made of different materials (for example, PET, Al, Ny, PP, etc.) with a layer structure of laminated films made of only PP (Polypropylene).

[0003] PP-only laminated films have limitations when transporting heavy goods due to the hard and fragile properties of PP. Furthermore, because the non-polar PP material is used as the laminate, PP-only laminated films suffer from a decrease in interlayer adhesive strength after retort sterilization. This decrease in interlayer adhesive strength reduces the peel strength and impact strength of the laminated film. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a retort sterilization film laminate that enhances interlayer adhesive strength. Another object of the present invention is to provide a retort sterilization film laminate that prevents breakage during distribution. Another object of the present invention is to provide a packaging material including the retort sterilization film laminate. [Means for solving the problem]

[0005] A retort sterilization film laminate according to one embodiment of the present invention includes a first OPP film made of oriented polypropylene (OPP), a first CPP film made of cast polypropylene (CPP) and bonded to one side of the first OPP film, a second OPP film made of oriented polypropylene and bonded to one side of the first CPP film, and a second CPP film made of cast polypropylene and bonded to one side of the second OPP film.

[0006] At least one of the first OPP film and the second OPP film may be formed of a barrier OPP film that blocks oxygen or moisture.

[0007] The barrier OPP film may be formed of a transparent film on which AlOx is vapor-deposited.

[0008] The barrier OPP film may be formed of a transparent film on which an SiOx type inorganic material is vapor-deposited.

[0009] The first CPP film may be corona treated on both sides to have a textured surface.

[0010] The first CPP film and the second CPP film may have a thickness ratio of 1:1 to 1:2.5.

[0011] The first CPP film and the second CPP film may contain a rubber component.

[0012] The first OPP film, the first CPP film, the second OPP film, and the second CPP film may have dry lamination layers between them.

[0013] A packaging material according to one embodiment of the present invention includes a retort sterilization film laminate, a first film laminate forming one side of the packaging material in the thickness direction, a second film laminate forming the other side of the packaging material in the thickness direction, and a sealing part forming an outer shell of the first film laminate and the second film laminate, the sealing part being bonded with a second CPP film facing each other.

[0014] The thickness of the second CPP film at the sealing portion may be formed to be thicker than the thickness of the first CPP film disposed between the first OPP film and the second OPP film. [Effects of the Invention]

[0015] As described above, in one embodiment of the present invention, the first CPP film is provided between the first OPP film and the second OPP film, thereby enhancing the interlayer adhesive strength and preventing breakage during distribution.

[0016] One embodiment comprises a first CPP film and a second CPP film, which allows the interlayer adhesive strength to be strengthened while maintaining the same overall thickness of the film laminate, and the sealing portion is formed with the second CPP film containing a rubber component, allowing the sealing properties of the packaging material to be maintained.

[0017] In addition, in one embodiment, the thickness of the second CPP film is formed to be thicker than the thickness of the first CPP film, so that the sealing performance at the sealing portion of the packaging material can be improved and maintained. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of a retort sterilization film laminate according to one embodiment of the present invention. [Figure 2] 1 is a perspective view of a packaging material including a retort sterilization film laminate according to one embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unnecessary for the explanation are omitted in order to clearly explain the present invention, and the same reference numerals are used throughout the specification to refer to the same or similar components.

[0020] 1 is a cross-sectional view of a retort sterilization film laminate according to one embodiment of the present invention. Referring to FIG. 1, the retort sterilization film laminate 100 of one embodiment includes a first OPP film 11, a first CPP film 21, a second OPP film 12, and a second CPP film 22.

[0021] The first OPP film 11, the first CPP film 21, the second OPP film 12 and the second CPP film 22 are bonded to one another with a dry lamination layer (DL) therebetween. The first OPP film 11 may have a printing layer.

[0022] The first OPP film 11, the first CPP film 21, the second OPP film 12 and the second CPP film 22 are formed from a single material to have excellent recyclability, and form a film laminate 100 suitable for retort use, which is difficult to replace due to limitations on the use of materials due to the heat treatment process.

[0023] The first OPP film 11 and the second OPP film 12 are made of oriented polypropylene (OPP). For example, the first OPP film 11 and the second OPP film 12 may have a thickness of 15 to 30 μm.

[0024] The first OPP film 11, which forms the top layer in Fig. 1, provides printability and heat resistance to prevent heat damage, while the second OPP film 12, which forms the third layer from the top, reinforces the film to maintain its strength.

[0025] At least one of the first OPP film 11 and the second OPP film 12 may be formed of a barrier OPP film that blocks oxygen or moisture. For example, the first OPP film 11 and the second OPP film 12 may have a thickness of 15 to 30 μm.

[0026] When the first OPP film 11, which is the first paper feed, is formed from a barrier OPP film, the barrier OPP film has a barrier property against oxygen or moisture, provides properties that enable printing, and provides heat resistance to prevent heat damage during retort sterilization and sealing.

[0027] For example, the barrier OPP film may be formed of a transparent film vapor-deposited with AlOx. Alternatively, the barrier OPP film may be formed of a transparent film vapor-deposited with an SiOx-type inorganic material. Alternatively, the barrier OPP film may be formed of an organic-inorganic hybrid vapor-deposited transparent film that combines an organic compound with AlOx or SiOx to improve the hard and brittle properties of inorganic materials.

[0028] The barrier OPP film may be formed as a transparent film containing barrier materials by mixing plate-like materials such as nanoclay to improve barrier properties, or as a barrier coating film.The barrier OPP film may be formed as an OPP-based barrier film.

[0029] The first CPP film 21 and the second CPP film 22 are made of cast polypropylene (CPP). For example, the first CPP film 21 and the second CPP film 22 may have a total thickness of 60 to 120 μm for retort packaging. The first CPP film 21 and the second CPP film 22 are used for retort packaging and contain a rubber component for impact reinforcement.

[0030] The first CPP film 21, which forms the second layer from the top, contains a rubber component to enhance impact strength. The second CPP film 22, which forms the fourth layer from the top, improves sealing performance and orange peel resistance. In other words, since sealing adhesion is important for the second CPP film 22, it can contain a higher amount of rubber component than the first CPP film 21, which allows for smooth sealing at low temperatures.

[0031] After a film laminate is retorted (usually at 121°C), its heat resistance decreases, and when heat resistance decreases, the contents of the film laminate penetrate into the film laminate, causing the film laminate to become uneven like orange peel, resulting in a significant decrease in the appearance quality of the film laminate product.

[0032] Orange peel resistance is a term used in the packaging and film industries and refers to the ability to prevent deterioration in the appearance quality of film laminates. The second CPP film 22 can improve sealing properties and orange peel resistance due to the rubber component.

[0033] On the other hand, the first CPP film 21 has been corona treated on both sides to have surface irregularities on both sides, and one side thereof is bonded to one side of the first OPP film 11, and the other side is bonded to one side of the second OPP film 12.

[0034] Corona treatment creates physical irregularities on the non-polar surface of the first CPP film 21, but the electrical discharge oxidizes and polarizes the surface, so the first CPP film 21 improves adhesion between the first OPP film 11 and the second OPP film 12, and the surface irregularities further improve physical adhesion.

[0035] In other words, the first OPP film 11 and the second OPP film 12 have very smooth and even surfaces due to stretching, so they can be polarized even by corona treatment, but the formation of physical irregularities is difficult, resulting in low adhesive strength. However, the first CPP film 21 can be placed between the first OPP film 11 and the second OPP film 12 to increase the mutual adhesive strength on both sides.

[0036] The first CPP film 21 can be used at a minimum thickness to provide adhesion between the first OPP film 11 and the second OPP film 12 while still achieving the required impact strength. The first CPP film 21 provided at a minimum thickness can provide excellent adhesion due to the surface irregularities and wetting tension of the double-sided corona treatment.

[0037] Generally, for the interlayer adhesive strength of an adhesive to be at least the required level, the film must have a minimum wet tension of 36 dynes or more. The first CPP film 21 has a wet tension of 37 to 42 dynes through double-sided corona treatment, which allows it to fully achieve the interlayer adhesive strength.

[0038] That is, by subjecting the first CPP film 21 to a corona discharge treatment, radicals / ions are generated on the surface, polarizing it and thereby maximizing the adhesive strength of the adhesive. Corona treatment also roughens the surface of the first CPP film 21, forming irregularities on the surface, which simultaneously provides a physical adhesive effect that allows the adhesive to adhere better.

[0039] The first CPP film 21, with its strong impact strength as a retort CPP film, can compensate for the drawback of the first OPP film 11 and the second OPP film 12 being hard and prone to bursting. As shown in the figure, the sandwich structure in which the first CPP film is positioned between the first OPP film 11 (first feed) and the second OPP film 12 (third feed) primarily serves to cushion the first OPP film 11 (first feed) from a drop or external impact, thereby improving the overall strength of the retort sterilization film laminate 100.

[0040] The second CPP film 22 is intended to provide sealing properties to the packaging material 200 using the film laminate 100, and may be used in a thickness range obtained by subtracting the thickness of the first CPP film 21 from the total thickness of the first CPP film 21 and the second CPP film 22. The first CPP film 21 and the second CPP film 22 have a thickness ratio of 1:1 to 1:2.5. For example, if the thickness of the first CPP film 21 is 30 to 50 μm, the thickness of the second CPP film 22 may be 30 to 70 μm.

[0041] In one embodiment, the divided first CPP film 21 and second CPP film 22 use the same amount, i.e., the same thickness, of CCP film compared to the conventional use of a single CCP film, thereby not causing an increase in thickness, but improving the adhesion performance of the first OPP film 11 and the second OPP film 12, and also improving and maintaining sealing performance by forming the second CPP film 22 thicker than the first OPP film 11.

[0042] Figure 2 is a perspective view of a packaging material including a retort sterilization film laminate according to one embodiment of the present invention, and Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Referring to Figures 2 and 3, a packaging material 200 according to one embodiment includes the retort sterilization film laminate 100 of Figure 1.

[0043] The packaging material 200 may be formed in a free-standing form (eg, a standing pouch) or a non-free-standing form (eg, a three-sided sealing pouch), and is shown here as a free-standing form for convenience.

[0044] The first film laminate 110 forming one side of the packaging material 200 and the second film laminate 120 forming the other side form a sealing portion 300 by attaching upper and lower second CPP films 22 facing each other internally. For convenience, the printing layer and dry lamination layer are omitted from Figure 3.

[0045] That is, the sealing portion 300 is formed by symmetrically arranging the first film laminate 110 and the second film laminate 120 and attaching them with two facing second CPP films 22. The facing two second CPP films 22 provide sufficient sealing performance to the sealing portion 300 of the packaging material 200.

[0046] The excellent performance of the example will be explained below by taking a film laminate 100 of an example and a film laminate of a comparative example. The film laminate of the comparative example includes a first OPP film, a second OPP film, and one CPP film (corresponding to the second CPP film of the example, but not the first CPP film).

[0047] The overall thickness of the film laminate 100 of the example and the film laminate of the comparative example is the same, and the total thickness of the first CPP film 21 and the second CPP film 22 of the example is the same as the thickness of the CPP film of the comparative example. In other words, the overall amount of material used is the same. In the comparative example, the first feed is OPP film, the second feed is OPP film, and the third feed is CPP film.

[0048] [Table 1]

[0049] In the example, the interlayer adhesive strength of the first paper feed / second paper feed before retorting was 310 gf / 15 mm. 2The interlayer adhesive strength of the second and third feeds is 225gf / 15mm. 2 The interlayer adhesive strength of the 3rd paper feed / 4th paper feed is 240gf / 15mm 2 In the comparative example, the interlayer adhesive strength of the first paper feed / second paper feed before retorting was 190 gf / 15 mm. 2 The interlayer adhesive strength of the second and third feeds is 205gf / 15mm. 2 is.

[0050] In the example, the loads on both sides of the second paper feed are 310 and 225 gf / 15 mm. 2 The comparative example has an interlayer adhesive strength of 190 and 250 gf / 15 mm on both sides of the second paper feed. 2 It can be seen that before retorting, the adhesive strength of the Example is significantly superior to that of the Comparative Example.

[0051] In the example, after retorting, the interlayer adhesive strength of the first paper feed / second paper feed was 275gf / 15mm. 2 The interlayer adhesive strength of the second and third feeds is 230gf / 15mm. 2 The interlayer adhesive strength of the 3rd paper feed / 4th paper feed is 250gf / 15mm 2 In the comparative example, the adhesive strength of the first paper feed / second paper feed after retorting was 205 gf / 15 mm. 2 The interlayer adhesive strength of the second and third feeds is 230gf / 15mm. 2 is.

[0052] In the example, the loads on both sides of the second paper feed are 275 and 230 gf / 15 mm. 2 The comparative example has an interlayer adhesive strength of 205 and 230 gf / 15 mm on both sides of the second paper feed. 2 It can be seen that even after retorting, the interlayer adhesive strength of the example is significantly superior to the interlayer adhesive strength of the comparative example.

[0053] It was confirmed that the embodiment using the first CPP film 21 and the second CPP film 22 had a significantly increased interlayer adhesive strength both before and after retort compared to the comparative example using a single CPP film.

[0054] On the other hand, when comparing the interlayer strength by material, compared to the comparative example having a laminated structure between OPP film / OPP film, the example having a CPP film between OPP film / OPP film can increase the interlayer adhesive strength due to the wettability caused by the surface unevenness of the CPP film and the anchorage effect resulting from the wettability.

[0055] [Table 2]

[0056] Looking at the interlayer adhesive strength by material, OPP film and OPP film have an average of 180 (gf / 15mm 2 ), and the average for OPP film and CPP film is 301 (gf / 15mm 2 ) The interlayer adhesive strength between OPP films and CPP films is much higher than the interlayer adhesive strength between OPP films. The Example embodies a strong interlayer adhesive strength between the first CPP film 21 and the first OPP film 11 and between the first CPP film 21 and the second OPP film 12, which is not disclosed in the Comparative Example.

[0057] The excellent performance of the embodiment will be explained below by taking a packaging material 200 using the film laminate 100 of the embodiment and a packaging material of a comparative example. When the film laminate 100 is applied to a packaging material, the ratio of the thickness of each layer to the total thickness can be changed for heating efficiency.

[0058] At the top of the film laminate 100, i.e., the outside of the packaging material 200, the first and second OPP films 11 and 12, which are high-strength material layers, are formed thicker than the first and second CPP films 21 and 22. At the bottom of the film laminate 100, i.e., the inside of the packaging material 200, is a retort layer that has a greater impact on heating efficiency. Of the retort layers, the second CPP film 22, which is located on the inner side, is formed thicker than the first CPP film 21, which is located in the middle.

[0059] The surface characteristics of the first and second OPP films 11, 12 and the first and second CPP films 21, 22 ensure increased interlayer adhesion strength and impact strength, and ultimately ensure distribution stability while using the same or similar amount of PP raw material.

[0060] However, the thickness and ratio of the first and second OPP films 11, 12 and the first and second CPP films 21, 22 can be increased or decreased to adjust general physical properties such as tensile strength and sealing strength in addition to interlayer adhesive strength depending on the distribution environment for distribution stability.

[0061] The retort efficiency of the packaging material 200 was confirmed. Dart strength is used as an index that can predict impact strength and distribution safety due to improvement in interlayer adhesive strength. It was confirmed that the dart strength was higher in the example compared to the comparative example, and that the dart strength was maintained at the same level in the example compared to the comparative example even after retort.

[0062] The dart strength is a strength measured by the impact resistance of the film laminate 100 and the packaging material 200 using a free-fall dart method with a Dart Drop Impact Tester.

[0063] [Table 3]

[0064] In the Example, the peak force of the dart before retorting was 44 kgf, which decreased to 42 kgf after retorting, resulting in a change of 4% in the peak force of the dart before and after retorting. In contrast, in the Comparative Example, the peak force of the dart before retorting was 41 kgf, which decreased to 33 kgf after retorting, resulting in a change of 21% in the peak force of the dart before and after retorting.

[0065] Therefore, considering that the film laminate 100 and packaging material 200 of the embodiment have a much smaller rate of change in dart strength before and after retort than the comparative example, it can be considered that they have a structure optimized for cooking or distribution procedures.

[0066] Although one embodiment of the present invention has been described above, the present invention is not limited to this and can be implemented in various modified forms within the scope of the claims, the description of the invention, and the accompanying drawings, and it is natural that this also falls within the scope of the present invention. [Explanation of symbols]

[0067] 11: First OPP film 12: Second OPP film 21: 1st CPP film 22: Second CPP film 100: Film laminate 110: First film laminate 120: Second film laminate 200, 400: Packaging materials 300: Sealing part 410: Upper area 411:Top edge 420: Lower area 421: Bottom edge DL: Dry lamination layer

Claims

1. a first OPP film formed of oriented polypropylene (OPP); a first CPP film made of cast polypropylene (CPP) and bonded to one surface of the first OPP film; a second OPP film made of oriented polypropylene and attached to one side of the first CPP film; and a second CPP film made of unstretched polypropylene and attached to one side of the second OPP film; 1. A retort sterilization film laminate comprising:

2. At least one of the first OPP film and the second OPP film is 10. The retort sterilizable film laminate of claim 1, which is formed from a barrier OPP film that blocks oxygen or moisture.

3. The barrier OPP film is 3. The retort sterilizable film laminate of claim 2, which is formed from a transparent film vapor-deposited with AlOx.

4. The barrier OPP film is 3. The retort sterilizable film laminate of claim 2, which is formed of a transparent film vapor-deposited with an SiOx-type inorganic material.

5. The first CPP film is 2. The retort sterilizable film laminate of claim 1, which has been corona-treated on both sides to have a textured surface.

6. The first CPP film and the second CPP film are 10. The retort sterilizable film laminate of claim 1 having a thickness ratio of 1:1 to 1:2.

5.

7. The retort sterilizable film laminate of claim 1 , wherein the first CPP film and the second CPP film contain a rubber component.

8. The first OPP film, the first CPP film, the second OPP film, and the second CPP film are 10. The retort sterilizable film laminate of claim 1, comprising a dry lamination layer therebetween.

9. A packaging material comprising the retort sterilization film laminate according to at least one of claims 1 to 8, a first film laminate forming one side of the packaging material in a thickness direction; a second film laminate forming the other thickness-wise side of the packaging material; and a sealing portion that forms an outer periphery of the first film stack and the second film stack; Including, The sealing portion is adhered to a second CPP film facing each other.

10. The thickness of the second CPP film at the sealing portion is: The packaging material according to claim 9 , which is formed to have a thickness greater than that of the first CPP film disposed between the first OPP film and the second OPP film.

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