A food packaging film for high-temperature retort, a packaging bag, and a production method

Abstract

The application discloses a food packaging film for high-temperature cooking, which is a co-extrusion film and comprises a barrier surface layer, a first adhesive layer, a high-temperature-resistant layer, a second adhesive layer, a first barrier layer, a third adhesive layer, a second barrier layer and a barrier heat-sealing layer which are stacked in sequence; the main components of the barrier surface layer comprise nylon and amorphous nylon; the main components of the first barrier layer comprise nylon; the main components of the second barrier layer comprise mLLDPE and HDPE; and the main components of the barrier heat-sealing layer comprise mLLDPE, HDPE and an opening agent. The food packaging film for high-temperature cooking has a reasonable structure, the barrier performance of the packaging film is improved through the stacked structure of the barrier surface layer, the first barrier layer, the second barrier layer and the barrier heat-sealing layer, and the obtained packaging film is not only soft and puncture-resistant, thereby being suitable for packaging objects with irregular shapes and different softnesses, but also has excellent barrier performance.

Description

Technical Field

[0001] This invention relates to the field of packaging film technology, specifically to a food packaging film, packaging bag, and preparation method for high-temperature cooking. Background Technology

[0002] Commonly available high-temperature retort packaging products are composite films made of nylon film and PP film (polypropylene), which require lamination with high-temperature resistant adhesive. This production process is complex and lengthy, and the lamination process uses adhesive, which is generally solvent-based and can negatively impact food safety. Existing high-temperature retort packaging products also suffer from poor barrier properties, easily leading to a short shelf life for the packaged goods.

[0003] Therefore, it is necessary to improve the existing packaging film and its production. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide a food packaging film for high-temperature cooking. By using a layered structure of a barrier surface layer, a first barrier layer, a second barrier layer, and a barrier heat-sealing layer, the barrier performance of the packaging film is improved. Furthermore, by co-extruding a nylon layer with a polyethylene layer composed of mLLDPE and HDPE, the resulting packaging film is not only soft and puncture-resistant, thus adapting to irregular packaging materials with different hardness and softness, but also has excellent barrier performance.

[0005] To achieve the above-mentioned process effects, the technical solution of the present invention is as follows: a food packaging film for high-temperature cooking, which is a co-extruded film, comprising a barrier surface layer, a first adhesive layer, a high-temperature resistant layer, a second adhesive layer, a first barrier layer, a third adhesive layer, a second barrier layer, and a barrier heat-sealing layer stacked in sequence.

[0006] The main components of the barrier surface layer include nylon and amorphous nylon;

[0007] The main components of the first barrier layer include nylon;

[0008] The second barrier layer mainly consists of mLLDPE and HDPE;

[0009] The main components of the barrier heat seal layer include mLLDPE, HDPE and an opening agent.

[0010] The preferred technical solution is that the high-temperature resistant layer comprises an A layer and a B layer that are composite phases from the outside to the inside;

[0011] The main components of both layer A and layer B include mLLDPE and PP;

[0012] The mass ratio of mLLDPE to PP in layer A is (60-75):(25-40);

[0013] The mass ratio of mLLDPE to PP in layer B is (60-75):(25-40).

[0014] Furthermore, the mass ratio of mLLDPE to PP in layer A is (65–75):(25–35); the mass ratio of mLLDPE to PP in layer B is (65–75):(25–35). Even further, the mass ratio of mLLDPE to PP in layer A is (67–72):(28–33); the mass ratio of mLLDPE to PP in layer B is (67–72):(28–33).

[0015] A preferred technical solution is that the main components of layer A and / or layer B further include CBC, which accounts for 10% to 20% of the total mass of the high-temperature resistant layer; the main components of the second barrier layer also include CBC. Further, layer A comprises CBC.

[0016] A preferred technical solution is as follows: the first adhesive layer comprises mLLDPE and maleic anhydride-modified high-density polyethylene adhesive, and the mass ratio of mLLDPE to maleic anhydride-modified high-density polyethylene adhesive in the first adhesive layer is (1-2.4):1. Further, the mass ratio of mLLDPE to maleic anhydride-modified high-density polyethylene adhesive in the first adhesive layer is (1-2):1.

[0017] The preferred technical solution is as follows: by weight, the main components of the barrier surface layer include 105-115 parts of nylon and 15-25 parts of amorphous nylon;

[0018] The second barrier layer mainly consists of 60-70 parts mLLDPE, 20-30 parts HDPE, and 7-13 parts CBC;

[0019] The main components of the barrier heat seal layer include 70-80 parts of mLLDPE, 20-30 parts of HDPE, and 4-6 parts of opening agent.

[0020] Furthermore, the main components of the barrier surface layer include 110-115 parts nylon and 18-22 parts amorphous nylon. Even further, the main components of the barrier surface layer include 110-113 parts nylon and 19-22 parts amorphous nylon.

[0021] Furthermore, the main components of the second barrier layer include 62-68 parts of mLLDPE, 22-28 parts of HDPE, and 8-12 parts of CBC.

[0022] Furthermore, the main components of the barrier heat seal layer include 72-80 parts of mLLDPE, 20-28 parts of HDPE, and 4-6 parts of opening agent.

[0023] The preferred technical solution is as follows: the thickness ratio of layer A to layer B is (1~2.2):1, the thickness of the high temperature resistant layer accounts for 22%~32% of the total thickness of the packaging film, and the total thickness of the packaging film is 90~200μm.

[0024] The preferred technical solution is that the density of mLLDPE in the high-temperature resistant layer, the second barrier layer, and the barrier heat-sealing layer is all 0.930–0.940 g / cm³. 3 The melt flow index is 0.45–0.56 g / 10 min; the density of PP in the high-temperature resistant layer is 0.880–0.950 g / cm³. 3 The melt flow index is 1.4–2.0 g / 10 min; the density of HDPE in both the second barrier layer and the barrier heat-sealing layer is 0.945–0.955 g / cm³. 3 The melt flow index is 0.9–1.3 g / 10 min; the density of the CBC is 0.92–0.95 g / cm³. 3 The melt index is 1-3 g / 10 min.

[0025] The preferred technical solution is as follows: the mLLDPE grade in the high-temperature resistant layer, the second barrier layer and the barrier heat-sealing layer is 3505MC; the PP grade in the high-temperature resistant layer is RB707CF; the HDPE grade in the second barrier layer is HD3355F; and the CBC grade is ViviOn8210XT.

[0026] The second objective of this invention is to overcome the deficiencies in the prior art and provide a food packaging bag for high-temperature cooking, comprising a first bag surface, wherein the first bag surface is the aforementioned food packaging film for high-temperature cooking, and the heat-sealing barrier layer is the inner surface of the first bag surface.

[0027] The third objective of this invention is to overcome the deficiencies in the prior art and provide a method for preparing a food packaging film for high-temperature retort processing. The food packaging film for high-temperature retort processing is the aforementioned food packaging film for high-temperature retort processing. The extrusion temperature of the barrier surface layer is 260–270°C, the extrusion temperature of the first adhesive layer is 230–240°C, the extrusion temperature of the high-temperature resistant layer is 220–230°C, the extrusion temperature of the second adhesive layer is 230–240°C, the extrusion temperature of the first barrier layer is 260–270°C, the extrusion temperature of the third adhesive layer is 230–240°C, the extrusion temperature of the second barrier layer is 230–240°C, and the extrusion temperature of the heat-sealing barrier layer is 220–230°C.

[0028] The advantages and beneficial effects of this invention are as follows:

[0029] This high-temperature retort food packaging film has a reasonable structure. Through the stacked structure of a barrier surface layer, a first barrier layer, a second barrier layer, and a barrier heat-sealing layer, the barrier performance of the packaging film is improved. Furthermore, by co-extruding a nylon layer with a polyethylene layer composed of mLLDPE and HDPE, the resulting packaging film is not only soft and puncture-resistant, thus adapting to irregular packaging materials with different softness and hardness, but also has excellent barrier performance. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0031] definition

[0032] In this disclosure, the term "mLLDPE" refers to a polymer produced by ethylene polymerization using a metallocene coordination compound as a catalyst.

[0033] In this disclosure, the term "HDPE" refers to high-density polyethylene, which is polymerized from ethylene gas under high temperature and pressure using a catalyst. The molecular chains are essentially linear, and therefore have little or no side chains on the main chain.

[0034] In this disclosure, the term "PP" refers to polypropylene, a thermoplastic resin obtained through the addition polymerization of propylene monomers. The molecular chain of polypropylene is composed of propylene monomer units linked by carbon-carbon single bonds. Each propylene unit contributes a methyl (-CH3) side group to the molecular chain. Based on the arrangement of methyl groups in the molecular chain, polypropylene can be classified into three types: isotactic polypropylene, atactic polypropylene, and syndiotactic polypropylene.

[0035] In this disclosure, the term "CBC" refers to a novel cyclic block copolymer polymer obtained by fully hydrogenating a styrene-conjugated olefin copolymer using a special high-efficiency catalyst.

[0036] model

[0037] The nylon was produced by Nantong Weiming New Materials Co., Ltd., and its trade name is J36TFE.

[0038] The amorphous nylon is manufactured by EMS of Switzerland, with the trade name G21.

[0039] Maleic anhydride modified high-density polyethylene adhesive is produced by Guangzhou Synthetic New Materials Co., Ltd., with the trade name HS3-405Z;

[0040] The cyclic block copolymer (CBC) was purchased from Polymer Chemicals Co., Ltd. in Taiwan, under the brand name ViviOn 8210XT.

[0041] The opening agent is produced by Hong Kong Huayi Company, with the trade name SF109.

[0042] High-temperature retort food packaging film

[0043] The thickness of the barrier layer accounts for 9% to 11% of the total thickness of the packaging film; the thickness of the first, second, and third adhesive layers each accounts for 7% to 9% of the total thickness of the packaging film; the thickness of the high-temperature resistant layer accounts for 22% to 32% of the total thickness of the packaging film; the thickness of the first barrier layer accounts for 9% to 11% of the total thickness of the packaging film; the thickness of the second barrier layer accounts for 8% to 11% of the total thickness of the packaging film; and the thickness of the heat-sealing barrier layer accounts for 17% to 25% of the total thickness of the packaging film.

[0044] Barrier surface

[0045] Amorphous nylon refers to semi-crystalline to crystalline thermoplastic materials. It includes both nylon and amorphous nylon; further, nylon is homopolymer nylon PA6. Homopolymer nylon has a high melting point and thermal stability, which allows it to maintain good physical and mechanical properties under high-temperature cooking conditions, making it less prone to thermal deformation or degradation, thus ensuring the integrity of the packaging. It also has higher tensile strength and rigidity, which helps the packaging material remain tough during high-temperature processing and subsequent logistics, reducing the risk of breakage. It has good resistance to oils, acids, and a certain range of alkaline substances, which is particularly important for food packaging that requires high-temperature cooking, effectively preventing chemical reactions or corrosion of the packaging material when in contact with the food contents. It typically provides good oxygen and water vapor barrier properties, helping to extend the shelf life of food and maintain its freshness.

[0046] The barrier layer is constructed by laminating amorphous nylon with PA6, primarily to improve the transparency of the packaging film. A higher amount of PA6 increases strength and enhances gas barrier properties; conversely, a lower amount of PA6 compromises the mechanical strength of the packaging film.

[0047] High temperature resistant layer

[0048] The packaging consists of two composite layers, A and B, which are formed from the outside in. Both layers primarily consist of mLLDPE and PP. mLLDPE contributes clarity and gloss, making the product's appearance more attractive. It also imparts better flexibility and extensibility, allowing the packaging to better adapt to changes in the shape of its contents, especially during high-temperature processing, resisting internal pressure changes and reducing the risk of breakage. PP ensures the structural stability and shape retention of the packaging film during high-temperature boiling or cooking; it can withstand high temperatures without melting or deforming. PP's excellent impact resistance further enhances the film's tear resistance and extends its service life. The combined use of mLLDPE and PP increases the tear strength and puncture resistance of the packaging film while maintaining good flexibility. Excessive addition of mLLDPE negatively impacts the temperature resistance and rigidity of the packaging film. CBC materials typically have good heat resistance, meaning that their barrier properties do not decrease as rapidly as some plastics during high-temperature cooking or heating, maintaining the integrity of the packaging and preventing contamination of the contents. They also have excellent gas and water vapor barrier properties. The high transparency and low fluorescence properties of CBC, combined with the transparency of mLLDPE, can be used to manufacture packaging or optical products that are both transparent and have low visual interference.

[0049] Second barrier layer and barrier heat seal layer

[0050] The main components of the second barrier layer include mLLDPE and HDPE; the main components of the second barrier layer include mLLDPE, HDPE, and CBC. The main components of the heat-sealing barrier layer include mLLDPE, HDPE, and an opening agent. HDPE has good low-temperature resistance, high mechanical strength, and a certain degree of toughness, which can enhance the physical strength of the film, such as improving tensile strength and abrasion resistance, making the packaging more durable and less prone to damage. HDPE has excellent water vapor resistance, effectively preventing moisture penetration and keeping the contents of the packaging fresh and dry. Due to its good heat resistance, HDPE is suitable as a heat-sealing layer for retort pouches; the addition of mLLDPE further enhances the sealing strength and heat resistance of the heat-sealed area, ensuring the reliability of the packaging seal during high-temperature retort processes and reducing the risk of leakage. mLLDPE complements the high strength and rigidity of HDPE with its high toughness, low brittleness, and good impact resistance, while CBC may provide additional strength and elasticity through its unique structure. As a high-performance material, CBC may have better gas and moisture barrier properties than traditional PE materials. Combining it with mLLDPE and HDPE can enhance the aroma and freshness preservation capabilities of packaging or coatings while maintaining the good mechanical properties of the materials.

[0051] Example 1

[0052] The food packaging film for high-temperature cooking is a co-extruded film, comprising a barrier surface layer, a first adhesive layer, a high-temperature resistant layer, a second adhesive layer, a first barrier layer, a third adhesive layer, a second barrier layer, and a barrier heat-sealing layer stacked sequentially; wherein, the high-temperature resistant layer comprises an A layer and a B layer that are composite phases from the outside to the inside.

[0053] By weight, the barrier surface layer consists of 112.5 parts nylon and 20 parts amorphous nylon; layer A consists of 70 parts mLLDPE and 30 parts PP; layer B consists of 70 parts mLLDPE and 30 parts PP; the first barrier layer consists of 100 parts nylon; the second barrier layer consists of 70 parts mLLDPE and 30 parts HDPE; the barrier heat-sealing layer consists of 75 parts mLLDPE, 25 parts HDPE, and 5 parts opening agent; the first adhesive layer, the second adhesive layer, and the third adhesive layer each include 50 parts mLLDPE (3505MC) and 50 parts maleic anhydride modified high-density polyethylene adhesive.

[0054] The packaging film has a total thickness of 150 μm, a barrier layer thickness of 15 μm, a first adhesive layer, a second adhesive layer, and a third adhesive layer thickness of 12 μm, a high-temperature resistant layer thickness of 42 μm, an A layer thickness of 28.5 μm, a B layer thickness of 13.5 μm, a first barrier layer thickness of 14.25 μm, a second barrier layer thickness of 15.75 μm, and a heat-sealing barrier layer thickness of 27 μm.

[0055] The extrusion temperatures for the barrier surface layer are 220℃, 260℃, 265℃, 265℃, 265℃, 265℃, and 265℃.

[0056] The extrusion temperatures of the first adhesive layer are 80℃, 235℃, 235℃, 235℃, 235℃, 235℃, 235℃;

[0057] The extrusion temperatures for layer A are 80℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃;

[0058] The extrusion temperatures for layer B are 80℃, 225℃, 225℃, 225℃, 225℃, 225℃, 225℃;

[0059] The extrusion temperatures of the second adhesive layer are 80℃, 235℃, 235℃, 235℃, 235℃, 235℃, and 235℃.

[0060] The extrusion temperatures of the first barrier layer are 195℃, 265℃, 265℃, 265℃, 265℃, 265℃, 265℃;

[0061] The extrusion temperatures of the third adhesive layer are 80℃, 235℃, 235℃, 235℃, 235℃, 235℃, and 235℃.

[0062] The extrusion temperatures of the second barrier layer are 80℃, 235℃, 235℃, 235℃, 235℃, 235℃, and 235℃.

[0063] The extrusion temperatures of the barrier heat seal layer are 80℃, 225℃, 225℃, 225℃, 225℃, 225℃, and 225℃.

[0064] Example 2

[0065] Example 2 is based on Example 1, except that layer A contains 70 parts mLLDPE, 30 parts PP, and 30 parts CBC; the second barrier layer consists of 65 parts mLLDPE, 25 parts HDPE, and 10 parts CBC. All other layers remain unchanged.

[0066] Example 3

[0067] Example 3 is based on Example 1, except that layer A contains 70 parts mLLDPE, 30 parts PP, and 30 parts CBC. All other layers remain unchanged.

[0068] Example 4

[0069] Example 4 is based on Example 1, except that the second barrier layer consists of 65 parts mLLDPE, 25 parts HDPE, and 10 parts CBC. All other layers remain unchanged.

[0070] Example 5

[0071] Example 5 is based on Example 2, except that the high-temperature resistant layer includes an A layer and a B layer that are composite phases from the outside to the inside. The composition of the A layer is mLLDPE, and the composition of the B layer is PP. All other layers remain unchanged.

[0072] Example 6

[0073] Example 6 is based on Example 2, except that the total thickness of the packaging film is 90 μm, the thickness of the barrier surface layer is 8.55 μm, the thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer are all 7.2 μm, the thickness of the high temperature resistant layer is 25.2 μm, the thickness of layer A is 18 μm, the thickness of layer B is 7.2 μm, the thickness of the first barrier layer is 8.55 μm, the thickness of the second barrier layer is 7.1 μm, and the thickness of the heat-sealing barrier layer is 19 μm.

[0074] Example 7

[0075] Example 7 is based on Example 2, except that the total thickness of the packaging film remains the same, the thickness of the second barrier layer is 27 μm, the thickness of the heat-sealing barrier layer is 15.75 μm, and the thickness of the other layers remains the same.

[0076] Comparative Example 1

[0077] Comparative Example 1 is based on Example 2, except that the second barrier layer does not contain HDPE, and the second barrier layer is composed of 90 parts mLLDPE and 10 parts CBC.

[0078] Test methods for samples:

[0079] 1. Tensile strength and elongation at break determination: according to the test standard.

[0080] GB / T1040.3-2006;

[0081] 2. Water vapor transmission rate determination: according to test standard GB / T1037-1988;

[0082] 3. Oxygen permeability determination: according to test standard GB / T1038-2000;

[0083] 4. Transmittance measurement: according to test standard GB / T2410-2008;

[0084] 5. Heat seal strength test: according to test standard QB / T2358-1998;

[0085] 6. Heat resistance test: according to test standard GB / T10004-2008.

[0086] 7. Drop Test: Using packaging bags made from the packaging films of the examples and comparative examples, pack 1 kg of rice as a sample. Then, drop the bottom and both sides of the bag from a height of 1 meter. Each test group is tested three times. Observe whether there is any breakage.

[0087] 9. Freezing test: Use the packaging bags made from the packaging films of the examples and comparative examples to pack 1 kg of water as a sample, freeze at -18°C, and then take them out to observe the integrity of the packaging bags, such as whether there is leakage, breakage, and changes in the quality of the contents.

[0088] The test results for the packaging bags in the examples and comparative examples are as follows:

[0089]

[0090]

[0091] Example 1 has a lower barrier performance than Example 2.

[0092] Compared to Example 2, Examples 3 and 4 showed inferior barrier performance.

[0093] Compared to Example 2, Example 5 has a higher rigidity in its packaging film. This makes it difficult to process and can easily lead to instability in the film's layer structure, negatively impacting its mechanical properties and heat resistance. Experiments showed that if layer A is composed of PP and layer B is composed of mLLDPE, the increased thickness of layer A compared to layer B results in greater rigidity of the packaging film, leading to poor performance in drop and freezing tests.

[0094] Compared to Example 2, Example 7 shows that the thickness of the second barrier layer is increased, while the thickness of the heat-sealing barrier layer is too small, which has a negative impact on both heat-sealing strength and barrier performance. Furthermore, the heat-sealed part of the packaging film peels off during the drop test.

[0095] Compared to Example 2, Comparative Example 1 shows that the packaging film obtained by combining HDPE, mLLDPE and CBC in the second barrier layer has better barrier performance.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A food packaging film for high-temperature retorting, which is a co-extruded film, characterized in that, It includes a barrier surface layer, a first adhesive layer, a high-temperature resistant layer, a second adhesive layer, a first barrier layer, a third adhesive layer, a second barrier layer, and a barrier heat-sealing layer, which are stacked in sequence. The main components of the barrier surface layer include nylon and amorphous nylon; The main components of the first barrier layer include nylon; The nylon is homopolymer nylon PA6; The second barrier layer mainly consists of 60-70 parts mLLDPE, 20-30 parts HDPE, and 7-13 parts CBC; The main components of the barrier heat seal layer include 70-80 parts of mLLDPE, 20-30 parts of HDPE, and 4-6 parts of opening agent; The high-temperature resistant layer comprises an A layer and a B layer that are composite phases from the outside to the inside; The main components of both layer A and layer B include mLLDPE and PP; The mass ratio of mLLDPE to PP in layer A is (60~75):(25~40); The mass ratio of mLLDPE to PP in layer B is (60~75):(25~40); The main components of the A layer and / or B layer also include CBC, which accounts for 10% to 20% of the total mass of the high-temperature resistant layer.

2. The food packaging film for high-temperature cooking according to claim 1, characterized in that, The first adhesive layer comprises mLLDPE and maleic anhydride modified high-density polyethylene adhesive, and the mass ratio of mLLDPE to maleic anhydride modified high-density polyethylene adhesive in the first adhesive layer is (1~2.4):

1.

3. The food packaging film for high-temperature cooking according to claim 1, characterized in that, By weight, the main components of the barrier surface layer include 105-115 parts of nylon and 15-25 parts of amorphous nylon.

4. The food packaging film for high-temperature cooking according to claim 1, characterized in that, The thickness ratio of layer A to layer B is (1~2.2):1, the thickness of the high-temperature resistant layer accounts for 22%~32% of the total thickness of the packaging film, and the total thickness of the packaging film is 90~200μm.

5. The food packaging film for high-temperature cooking according to claim 3, characterized in that, The density of mLLDPE in the high-temperature resistant layer, the second barrier layer, and the barrier heat-sealing layer is 0.930~0.940 g / cm³. 3 The melt flow index is 0.45~0.56 g / 10min; the density of PP in the high-temperature resistant layer is 0.880~0.950 g / cm³. 3 The melt flow index is 1.4~2.0 g / 10min; the density of HDPE in the second barrier layer and the barrier heat-sealing layer is 0.945~0.955 g / cm³. 3 The melt flow index is 0.9~1.3 g / 10 min; the density of the CBC is 0.92~0.95 g / cm³. 3 The melt index is 1~3g / 10min.

6. The food packaging film for high-temperature cooking according to claim 1 or 5, characterized in that, The mLLDPE grade in the high-temperature resistant layer, the second barrier layer, and the barrier heat-sealing layer is 3505MC; the PP grade in the high-temperature resistant layer is RB707CF; the HDPE grade in the second barrier layer is HD3355F; and the CBC grade is ViviOn8210XT.

7. A food packaging bag for high-temperature cooking, comprising a first bag face, characterized in that, The first bag surface is a food packaging film for high-temperature cooking as described in any one of claims 1 to 6, and the barrier heat-sealing layer is the inner surface of the first bag surface.

8. A method for preparing a food packaging film for high-temperature cooking, characterized in that, The high-temperature retort food packaging film is the high-temperature retort food packaging film according to any one of claims 1 to 6, wherein the extrusion temperature of the barrier surface layer is 260~270℃, the extrusion temperature of the first adhesive layer is 230~240℃, the extrusion temperature of the high-temperature resistant layer is 220~230℃, the extrusion temperature of the second adhesive layer is 230~240℃, the extrusion temperature of the first barrier layer is 260~270℃, the extrusion temperature of the third adhesive layer is 230~240℃, the extrusion temperature of the second barrier layer is 230~240℃, and the extrusion temperature of the barrier heat-sealing layer is 220~230℃.

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