A food packaging bag for microwave oven

Abstract

The present invention relates to the technical field of microwave heating bags, and specifically to a food packaging bag for a microwave oven, comprising a bag body and a cavity formed in the bag body, the bag body comprising a first co-extruded film and a second co-extruded film heat-pressed and edge-sealed with the first co-extruded film, an opening portion is provided at the top of the bag body, the bag body is provided with a heat-sealed block formed by heat-pressing and bonding the first co-extruded film and the second co-extruded film, and the heat-sealed block is provided with an internal pressure exhaust hole that penetrates the bag body; when the bag body is sealed and the bag body expands, the heat-sealed block is separated, and the cavity is connected to the internal pressure exhaust hole. When in use, food is loaded into the bag body through the opening portion, and when the bag body is sealed and the bag body is expanded by microwave heating, the heat-sealed block is separated by the internal pressure of the bag body, and at this time the cavity is connected to the internal pressure exhaust hole, and the water vapor in the bag body is discharged to the outside of the bag body through the internal pressure exhaust hole, thereby avoiding the expansion and bursting of the bag body and causing food to splash in the microwave oven.

Description

Technical Field

[0001] The invention relates to the technical field of microwave heating bags, in particular to a food packaging bag for microwave ovens. Background Art

[0002] When existing vacuum-sealed food packaging is heated in a microwave oven, the moisture in the food forms water vapor under microwave heating, causing excessive air pressure in the bag, which can easily cause the bag to expand and burst, causing food to splash into the microwave. Summary of the invention

[0003] In order to overcome the shortcomings and deficiencies in the prior art, an object of the present invention is to provide a vacuum-sealed microwave-safe food packaging bag that is resistant to bursting due to microwave heating.

[0004] The objective of the present invention is achieved through the following technical scheme: A food packaging bag for a microwave oven comprises a bag body and a cavity formed in the bag body, the bag body comprises a first co-extruded film and a second co-extruded film heat-pressed and edge-sealed with the first co-extruded film, an opening is arranged on the top of the bag body, the first co-extruded film and the second co-extruded film are both provided with a heat-sealed exhaust adjustment area, the heat-sealed exhaust adjustment area of ​​the first co-extruded film and the heat-sealed exhaust adjustment area of ​​the second co-extruded film are heat-pressed and bonded to form a heat-sealed block, the heat-sealed block is provided with an internal pressure exhaust hole; when the bag body is sealed and the bag body expands, the heat-sealed block is separated, and the cavity is connected to the internal pressure exhaust hole.

[0005] Preferably, the bag body also includes a third co-extruded film folded in half and arranged between the first co-extruded film and the second co-extruded film, one end of the third co-extruded film is heat-pressed and sealed with the bottom end of the first co-extruded film, and the other end of the third co-extruded film is heat-pressed and sealed with the bottom end of the second co-extruded film.

[0006] Preferably, the bottom of the bag body is provided with a first heat-seal reinforcement portion and a second heat-seal reinforcement portion, the first heat-seal reinforcement portion is formed by heat-sealing the first co-extruded film and the third co-extruded film, and the second heat-seal reinforcement portion is formed by heat-sealing the second co-extruded film and the third co-extruded film.

[0007] Preferably, a first yielding heat seal and a second yielding heat seal symmetrical to the first yielding heat seal are provided on the side of the third co-extruded film.

[0008] Preferably, a plurality of air-conducting ridges are evenly distributed on a side of the second co-extruded film close to the first co-extruded film.

[0009] Preferably, the outer side wall of the bag body is provided with an easy-tear notch.

[0010] Preferably, the layered structure of the first co-extruded film includes a barrier layer, an adhesive layer, a first stiffness layer, a second stiffness layer, a third stiffness layer, a toughness layer and a heat-sealing layer arranged in sequence from the outside to the inside, and the layered structure of the second co-extruded film and the layered structure of the third co-extruded film are the same as the layered structure of the first co-extruded film.

[0011] Preferably, the raw materials of the barrier layer include a melting temperature of 230-250°C and a density of 1.08-1.18 g / cm 3 of nylon;

[0012] The bonding layer comprises the following raw materials in parts by weight: 20-40 parts of adhesive resin TIE and 60-80 parts of copolymerized polypropylene;

[0013] The first stiffness layer comprises the following raw materials in parts by weight: 20-40 parts by weight of homopolymer polypropylene and 60-80 parts by weight of copolymer polypropylene.

[0014] By adopting the above technical scheme, the raw material of the barrier layer is nylon with a specific melting temperature and density, which can effectively block water and oxygen, and preserve the freshness and flavor of the food in the microwave food packaging bag after vacuum heat sealing. The bonding layer is compounded by bonding resin TIE and copolymer polypropylene in a specific ratio, which completely avoids the existing composite film using solvent-based adhesives, can greatly reduce solvent residues, and meets food grade requirements. It is applied between the barrier layer and the first stiffness layer. Its bonding strength is 2 times higher than that of the existing composite film using solvent-based adhesives, and it is more environmentally friendly. The first stiffness layer is blended with homopolymer polypropylene and copolymer polypropylene in a specific ratio, which not only improves the hardness and stiffness of the first co-extruded film, avoids the bag body from being soft and unable to stand upright, but also improves the puncture resistance and toughness of the first co-extruded film, and avoids the bag body from being easily scratched and affecting the touch and appearance of the microwave food packaging bag. Furthermore, the melt index of the copolymerized polypropylene used in the bonding layer is 6.5-9.5 g / 10 min; the melt index of the homopolymerized polypropylene used in the first stiffness layer is 3-6 g / 10 min; the melt index of the copolymerized polypropylene used in the first stiffness layer is 6.5-9.5 g / 10 min. The melt indexes referred to in the present invention are all measured at 230° C. and 2.16 kg load.

[0015] Preferably, the second stiffness layer comprises the following raw materials in parts by weight: 20-40 parts of homopolymer polypropylene and 60-80 parts of copolymer polypropylene;

[0016] The third stiffness layer comprises the following raw materials in parts by weight: 20-40 parts of homopolymer polypropylene and 60-80 parts of copolymer polypropylene;

[0017] The raw material of the toughness layer includes copolymerized polypropylene with a melt index of 6.5-9.5 g / 10min;

[0018] The heat sealing layer comprises the following raw materials in parts by weight: 20-40 parts of metallocene polypropylene and 60-80 parts of copolymer polypropylene.

[0019] By adopting the above technical scheme, the second and third stiffness layers are further added on the basis of the first stiffness layer, so as to further improve the hardness and stiffness of the first co-extruded film, avoid the bag body being soft and unable to stand upright, improve the puncture resistance and toughness of the first co-extruded film, and avoid the bag body being easily scratched and affecting the touch and appearance of the microwave food packaging bag. The toughness layer adopts copolymer polypropylene with a melt index of 6.5-9.5g / 10min, further improves the puncture resistance and toughness of the first co-extruded film, avoids the bag body being easily scratched, and cooperates with the heat sealing layer to improve the heat sealing and sealing strength of the first co-extruded film. The heat sealing layer adopts metallocene polypropylene and copolymer polypropylene blend to improve the puncture resistance and sealing strength, and the blending of metallocene polypropylene greatly reduces the sealing temperature, which is convenient for using a low-power vacuum sealer to tightly seal the opening of the bag body, improving its home convenience. Furthermore, the melt index of the homopolypropylene used in the second stiffness layer is 3-6 g / 10 min; the melt index of the copolymer polypropylene used in the second stiffness layer is 6.5-9.5 g / 10 min; the melt index of the homopolypropylene used in the third stiffness layer is 3-6 g / 10 min; the melt index of the copolymer polypropylene used in the third stiffness layer is 6.5-9.5 g / 10 min; the melt index of the metallocene polypropylene is 7-8 g / 10 min; and the melt index of the copolymer polypropylene used in the heat sealing layer is 6.5-9.5 g / 10 min.

[0020] Furthermore, the raw materials of each layer of the second co-extruded film and the raw materials of each layer of the third co-extruded film are the same as the raw materials of each layer of the first co-extruded film; the first co-extruded film formed by the above-mentioned raw materials is resistant to high temperatures of 121°C, and is particularly resistant to microwave heating; compared with existing food packaging bag films, the microwave food packaging bag made from the above-mentioned first co-extruded film, the second co-extruded film and the third co-extruded film avoids the microwave food packaging bag from melting, shrinking, burning and releasing odorous gas during microwave heating, thereby contaminating food; and the microwave food packaging bag has a higher light transmittance, and the food in the bag can be observed more clearly. Since the polyamide used in the barrier layer has excellent self-lubricity and wear resistance, the barrier layer is placed on the outer surface of the microwave food packaging bag to improve the good touch and quality of the microwave food packaging bag. However, its self-lubricity leads to low viscosity and poor adhesion with the first stiffness layer. Therefore, a bonding layer with high bonding strength is added between the barrier layer and the first stiffness layer. The first stiffness layer, the second stiffness layer, the third stiffness layer, the toughness layer and the heat-sealing layer all use polypropylene raw materials, which have good compatibility and good mutual adhesion. Therefore, the addition of the bonding layer is omitted, which greatly saves the cost of raw materials. Since the second co-extruded film is provided with a plurality of air-conducting ridges, the first stiffness layer, the second stiffness layer and the third stiffness layer work together to improve the overall stiffness hardness of the second co-extruded film, thereby greatly increasing the supporting force of the air-conducting ridges, achieving the effect of rapid exhaust and improving the vacuuming effect.

[0021] The first co-extruded film, the second co-extruded film and the third co-extruded film are all environmentally friendly and harmless, are co-extruded using environmentally friendly materials, have no solvent residue hazards, comply with RoHS, REACH, HF, phthalate, PFOS, and DMF standards, and are suitable for home use.

[0022] The microwaveable food packaging bag is easy to use and can be used with a low-power vacuum sealer (or a small household vacuum packaging machine) and a microwave oven. Since the second co-extruded film is provided with an air-conducting ridge, the opening of the bag body of the low-power vacuum sealer can be directly used for vacuuming, which is convenient for quickly vacuuming and preserving various foods. The material of the bag body can withstand high-temperature heating in a microwave oven for a long time without melting or bursting.

[0023] Preferably, the method for preparing the first co-extruded film comprises the following steps:

[0024] (S1), adding the raw materials of each layer into the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer;

[0025] (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank;

[0026] (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:1.25-2.5 and a temperature of 180-250°C, and then water-cooled to obtain the first co-extruded film.

[0027] The preparation method of the above-mentioned first co-extruded film is simple to operate, easy to control, high in production efficiency, and low in production cost, and can be used for large-scale industrial production. Wherein, in step (S1), the raw materials of each layer are added to the extruders of each layer respectively for melt plasticization to obtain the molten materials of each layer, so that the layers can be combined into one during the co-extrusion process. In step (S2), the film blank formed by co-extrusion has an integrated structure; after the film is blown in step (S3), the first co-extruded film is formed; in step (S3), the film is blown at a blowing ratio of 1:1.25-2.5 and a temperature of 180-250°C, which is conducive to adjusting the thickness of the first co-extruded film, giving full play to the performance of the processed material, while maintaining the best dimensional accuracy, so that the function of the film can be quantitatively controlled.

[0028] Furthermore, in the step (S1), the processing temperature of the barrier layer is 230-260°C, the processing temperature of the bonding layer is 220-250°C, the processing temperature of the first stiffness layer is 250-270°C, the processing temperature of the second stiffness layer is 250-270°C, the processing temperature of the third stiffness layer is 250-270°C, the processing temperature of the toughness layer is 230-250°C, and the processing temperature of the heat sealing layer is 230-250°C.

[0029] Furthermore, in the step (S2), the molten material of the barrier layer, the molten material of the bonding layer, the molten material of the first stiffness layer, the molten material of the second stiffness layer, the molten material of the third stiffness layer, the molten material of the toughness layer and the molten material of the heat sealing layer enter the stacked die head in a weight ratio of 14-17:10-13:13-16:13-16:13-16:12-16:12-16, so as to give full play to the performance of the processed materials while maintaining the best dimensional accuracy, so that the function of the film can be quantitatively controlled.

[0030] Furthermore, in the step (S3), the water temperature of the water cooling and shaping is controlled at 10-25°C to avoid water lines on the co-extruded film due to excessively high water temperature. Compared with the existing composite film, the preparation method does not have an organic solvent volatilization odor, has less impact on the health of the workers, and does not cause contamination to food under microwave heating conditions.

[0031] The beneficial effects of the present invention are as follows: when the food packaging bag for the microwave oven of the present invention is used, food is loaded into the bag body through the opening, and then the opening is vacuumized and heat-sealed to seal the bag body; when the bag body is heated by microwaves, moisture in the food is heated by microwaves to form water vapor, which expands the bag body, and the internal pressure of the bag body separates the heat-sealed blocks, and the first co-extruded film and the second co-extruded film at the heat-sealed blocks change from a hot-pressed bonding state to a non-bonded state, at which time the cavity is connected to the internal pressure exhaust hole, and the water vapor in the bag body is discharged to the outside of the bag body through the internal pressure exhaust hole, thereby achieving a pressure relief effect, thereby avoiding the expansion and bursting of the bag body, which causes food to splash in the microwave oven. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the structure of the present invention;

[0033] Figure 2 yes Figure 1 Cross-section of the middle AA;

[0034] Figure 3 is a schematic structural diagram of the third co-extruded film of the present invention;

[0035] Figure 4 is a schematic diagram of the layered structure of the first co-extruded film of the present invention;

[0036] Figure 5 It is a schematic diagram of the structure of the present invention after food is loaded;

[0037] Figure 6 is a schematic diagram of placing the food packaging bag of group A on a baking tray of a microwave oven in Example 6;

[0038] Figure 7 This is a microwave heating time record diagram of the food packaging bag of Group A in Example 6;

[0039] Figure 8 is a schematic diagram of the food packaging bag of Example 2 after microwave heating of Group A in Example 6;

[0040] Fig. 9 is a schematic diagram of the food packaging bag of Comparative Example 1 after microwave heating of Group A in Example 6;

[0041] Fig.10 is a schematic diagram of the food packaging bag of Example 2 after the sealing of Group B in Example 6;

[0042] Fig.11 is a schematic diagram of the food packaging bag of Comparative Example 1 after sealing of Group B in Example 6;

[0043] Fig.12 is a schematic diagram of the food packaging bag of Example 2 after microwave heating of Group B in Example 6;

[0044] Fig.13It is a schematic diagram of the food packaging bag of Comparative Example 1 after microwave heating of Group B in Example 6.

[0045] The accompanying drawings are marked as follows: 1. cavity; 2. first co-extruded film; 21. barrier layer; 22. adhesive layer; 23. first stiffness layer; 24. second stiffness layer; 25. third stiffness layer; 26. toughness layer; 27. heat sealing layer; 3. second co-extruded film; 4. opening; 5. heat sealing block; 6. internal pressure exhaust hole; 7. third co-extruded film; 8. first heat sealing reinforcement portion; 9. second heat sealing reinforcement portion; 10. first yielding heat seal port; 11. second yielding heat seal port; 12. air guide ridge; 13. easy-tear port. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0047] Example 1

[0048] like Figure 1-5 As shown, a food packaging bag for a microwave oven comprises a bag body and a cavity 1 formed in the bag body, the bag body comprises a first co-extruded film 2 and a second co-extruded film 3 heat-pressed and sealed with the first co-extruded film 2, an opening 4 is arranged on the top of the bag body, the first co-extruded film 2 and the second co-extruded film 3 are both provided with a heat-seal exhaust adjustment area, the heat-seal exhaust adjustment area of ​​the first co-extruded film 2 and the heat-seal exhaust adjustment area of ​​the second co-extruded film 3 are heat-pressed and bonded to form a heat-seal block 5, and the heat-seal block 5 is provided with an internal pressure exhaust hole 6; when the bag body is sealed and the bag body expands, the heat-seal block 5 is separated, and the cavity 1 is connected with the internal pressure exhaust hole 6. The cavity 1 is formed by the first co-extruded film 2 and the second co-extruded film 3 being heat-pressed and sealed. The heat-seal block 5 and the internal pressure exhaust hole 6 are combined to form an internal pressure exhaust valve.

[0049] When in use, food is loaded into the bag through the opening 4, and then the opening 4 is vacuumed and heat-sealed to seal the bag. The first co-extruded film 2 and the second co-extruded film 3 are bonded to each other in the heat-sealing block 5, and the cavity 1 is in a sealed state. When the bag is heated by microwaves, the moisture in the food is heated by microwaves to form water vapor, which expands the bag. The heat-sealing block 5 is separated by the internal pressure of the bag, and the first co-extruded film 2 and the second co-extruded film 3 at the heat-sealing block 5 change from a hot-pressed bonding state to a non-bonded state. At this time, the cavity 1 is connected to the internal pressure exhaust hole 6, and the water vapor in the bag is discharged to the outside of the bag through the internal pressure exhaust hole 6, achieving a pressure relief effect, thereby preventing the bag from expanding and bursting and causing food to splash in the microwave. Furthermore, the heat sealing block 5 controls the bonding force by controlling the temperature and pressure of the hot-pressing bonding, so that the first co-extruded film 2 and the second co-extruded film 3 at the heat sealing block 5 change from a hot-pressing bonding state to a non-bonded state under an internal pressure condition of 3-5N, so that when the bag body is sealed and the bag body expands, the heat sealing block 5 is separated, and the cavity 1 is connected with the internal pressure exhaust hole 6; in this embodiment, the heat sealing block 5 is rectangular, the internal pressure exhaust hole 6 is circular, and the width of the heat sealing block 5 is greater than the diameter of the internal pressure exhaust hole 6, so that when the microwave food packaging bag is not subjected to microwave heating, the cavity 1 and the internal pressure exhaust hole 6 remain isolated, that is, the cavity 1 and the internal pressure exhaust hole 6 are not connected; the number of the heat sealing blocks 5 is 2, and the two heat sealing blocks 5 are symmetrically arranged on both sides of the bag body, and the two heat sealing blocks 5 do not abut against the side of the bag body. Preferably, each of the heat sealing blocks 5 is provided with two internal pressure exhaust holes 6, and the two internal pressure exhaust holes 6 are respectively arranged in the heat sealing exhaust adjustment area of ​​the first co-extruded film 2 and the heat sealing exhaust adjustment area of ​​the second co-extruded film 3 and respectively penetrate the corresponding heat sealing exhaust adjustment areas.

[0050] In this embodiment, the bag body also includes a third co-extruded film 7 which is folded between the first co-extruded film 2 and the second co-extruded film 3, one end of the third co-extruded film 7 is hot-pressed and sealed with the bottom end of the first co-extruded film 2, and the other end of the third co-extruded film 7 is hot-pressed and sealed with the bottom end of the second co-extruded film 3.

[0051] By adopting the above technical solution, the bottom of the microwave food packaging bag is stretched open (ie the folded third co-extruded film 7 is stretched open), so that the microwave food packaging bag can be placed upright and the accommodating space of the cavity 1 is increased.

[0052] In this embodiment, a first heat-seal reinforcement portion 8 and a second heat-seal reinforcement portion 9 are provided at the bottom of the bag body. The first heat-seal reinforcement portion 8 is formed by heat-sealing the first co-extruded film 2 and the third co-extruded film 7, and the second heat-seal reinforcement portion 9 is formed by heat-sealing the second co-extruded film 3 and the third co-extruded film 7.

[0053] The above technical solution is adopted to improve the structural strength of the bottom of the bag body, and prevent the third co-extruded film 7 from detaching from the bag body and causing the bag to pierce. Specifically, the first heat-seal reinforcement part 8 is arranged at the bottom of the bag body on the side opposite to the second heat-seal reinforcement part 9.

[0054] In this embodiment, a first heat seal 10 and a second heat seal 11 symmetrical to the first heat seal 10 are formed on the side of the third co-extruded film 7 .

[0055] By adopting the above technical solution, the first co-extruded film 2 and the second co-extruded film 3 are heat-pressed and bonded via the first yield heat seal 10 and the second yield heat seal 11, providing a support point for the microwave food packaging bag when it is placed upright. Furthermore, the number of the first yield heat seal 10 is 2, the number of the second yield heat seal 11 is 2, the two first yield heat seals 10 are respectively arranged on the two sides of the third co-extruded film 7, and the two second yield heat seals 11 are respectively arranged on the two sides of the third co-extruded film 7.

[0056] In this embodiment, a plurality of air-conducting ridges 12 are evenly distributed on a surface of the second co-extruded film 3 close to the first co-extruded film 2 .

[0057] With the above technical solution, when the bag is vacuum-sealed, the internal space of the bag gradually shrinks until the inner walls on both sides of the bag abut against each other. Since the inner wall of the other side of the bag is evenly distributed with a plurality of air-guiding ridges 12, the gas remaining in the internal space of the bag is more easily circulated between two adjacent air-guiding ridges 12 and discharged toward the opening 4, thereby avoiding gas residue. Furthermore, the air-guiding ridge 12 is formed by the outer wall of the side wall being pressed inwardly, and the outer wall of the side wall forms a concave blind groove corresponding to the air-guiding ridge 12.

[0058] In this embodiment, an easy-tear notch 13 is provided on the outer side wall of the bag body.

[0059] By adopting the above technical solution, it is convenient to tear open the sealed microwave food packaging bag along the easy-tear opening 13 .

[0060] In this embodiment, the layered structure of the first co-extruded film 2 includes a barrier layer 21, an adhesive layer 22, a first stiffness layer 23, a second stiffness layer 24, a third stiffness layer 25, a toughness layer 26 and a heat-sealing layer 27, which are arranged in sequence from the outside to the inside. The layered structure of the second co-extruded film 3 and the layered structure of the third co-extruded film 7 are the same as the layered structure of the first co-extruded film 2.

[0061] By adopting the above technical solution, the barrier layer 21 is used to prevent the outside air from penetrating into the cavity 1 through the outer surface of the bag body, thereby improving the vacuum sealing effect of the microwave food packaging bag after vacuum heat sealing; the adhesive layer 22 bonds the barrier layer 21 to the first stiffness layer 23; the first stiffness layer 23, the second stiffness layer 24 and the third stiffness layer 25 are all used to improve the hardness and stiffness of the co-extruded film to prevent the bag body from being soft and unable to stand upright; the toughness layer 26 is used to improve its puncture resistance and toughness; the heat sealing layer 27 improves the heat sealing strength, and the heat sealing layers 27 of the two co-extruded films can be tightly bonded to each other by hot pressing during heat sealing. In addition, all layers of the first co-extruded film 2, all layers of the second co-extruded film 3 and all layers of the third co-extruded film 7 are extruded and formed at the same time, so there will be no other non-plastic materials such as aluminum foil and paper, and there is no odor from the volatilization of organic solvents, which has less impact on the health of the staff.

[0062] The raw materials of each layer of the second co-extruded film and the raw materials of each layer of the third co-extruded film are the same as the raw materials of each layer of the first co-extruded film; the preparation method of the second co-extruded film and the preparation method of the third co-extruded film are the same as the preparation method of the first co-extruded film.

[0063] Example 2

[0064] The difference between this embodiment and embodiment 1 is that:

[0065] The raw materials of the barrier layer include a melting temperature of 240°C and a density of 1.13 g / cm 3 of nylon;

[0066] The bonding layer comprises the following raw materials in parts by weight: 30 parts of bonding resin TIE and 70 parts of copolymerized polypropylene; the melt index of the copolymerized polypropylene used in the bonding layer is 8g / 10min; the model of the bonding resin TIE is QB515;

[0067] The first stiffness layer comprises the following raw materials in parts by weight: 30 parts of homopolypropylene and 70 parts of copolymer polypropylene. The melt index of the homopolypropylene used in the first stiffness layer is 5 g / 10 min; the melt index of the copolymer polypropylene used in the first stiffness layer is 8 g / 10 min.

[0068] The second stiffness layer comprises the following raw materials in parts by weight: 30 parts of homopolypropylene and 70 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the second stiffness layer is 5g / 10min; the melt index of the copolymer polypropylene used in the second stiffness layer is 8g / 10min;

[0069] The third stiffness layer comprises the following raw materials in parts by weight: 30 parts of homopolypropylene and 70 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the third stiffness layer is 5g / 10min; the melt index of the copolymer polypropylene used in the third stiffness layer is 8g / 10min;

[0070] The raw material of the toughness layer includes copolymerized polypropylene with a melt index of 8g / 10min;

[0071] The heat seal layer comprises the following raw materials in parts by weight: 30 parts of metallocene polypropylene and 70 parts of copolymer polypropylene. The melt index of the metallocene polypropylene is 7.5 g / 10 min; the melt index of the copolymer polypropylene used for the heat seal layer is 8 g / 10 min.

[0072] The preparation method of the first co-extruded film comprises the following steps:

[0073] (S1), adding the raw materials of each layer into the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer;

[0074] (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank;

[0075] (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:2.0 and a temperature of 220°C, and then water-cooled to obtain the first co-extruded film.

[0076] In the step (S1), the processing temperature of the barrier layer is 245°C, the processing temperature of the bonding layer is 235°C, the processing temperature of the first stiffness layer is 260°C, the processing temperature of the second stiffness layer is 260°C, the processing temperature of the third stiffness layer is 260°C, the processing temperature of the toughness layer is 240°C, and the processing temperature of the heat sealing layer is 240°C.

[0077] In the step (S2), the molten material of the barrier layer, the molten material of the adhesive layer, the molten material of the first stiffness layer, the molten material of the second stiffness layer, the molten material of the third stiffness layer, the molten material of the toughness layer and the molten material of the heat sealing layer enter the stacked die in a weight ratio of 15:12:15:15:15:14:14.

[0078] In the step (S3), the water temperature of the water cooling and shaping is controlled at 20°C.

[0079] Example 3

[0080] The difference between this embodiment and embodiment 1 is that:

[0081] The raw materials of the barrier layer include a melting temperature of 230° C. and a density of 1.08 g / cm 3of nylon;

[0082] The bonding layer comprises the following raw materials in parts by weight: 20 parts of bonding resin TIE and 60 parts of copolymerized polypropylene; the melt index of the copolymerized polypropylene used in the bonding layer is 6.5 g / 10 min; the model of the bonding resin TIE is QB515;

[0083] The first stiffness layer comprises the following raw materials in parts by weight: 20 parts of homopolypropylene and 60 parts of copolymer polypropylene. The melt index of the homopolypropylene used in the first stiffness layer is 3 g / 10 min; the melt index of the copolymer polypropylene used in the first stiffness layer is 6.5 g / 10 min.

[0084] The second stiffness layer comprises the following raw materials in parts by weight: 20 parts of homopolypropylene and 60 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the second stiffness layer is 3 g / 10 min; the melt index of the copolymer polypropylene used in the second stiffness layer is 6.5 g / 10 min;

[0085] The third stiffness layer comprises the following raw materials in parts by weight: 20 parts of homopolypropylene and 60 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the third stiffness layer is 3g / 10min; the melt index of the copolymer polypropylene used in the third stiffness layer is 6.5g / 10min;

[0086] The raw material of the toughness layer includes copolymerized polypropylene with a melt index of 6.5 g / 10 min;

[0087] The heat seal layer comprises the following raw materials in parts by weight: 20 parts of metallocene polypropylene and 60 parts of copolymer polypropylene. The melt index of the metallocene polypropylene is 7 g / 10 min; the melt index of the copolymer polypropylene used for the heat seal layer is 6.5 g / 10 min.

[0088] The preparation method of the first co-extruded film comprises the following steps:

[0089] (S1), adding the raw materials of each layer into the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer;

[0090] (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank;

[0091] (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:1.25 and a temperature of 180°C, and then water-cooled to obtain the first co-extruded film.

[0092] In the step (S1), the processing temperature of the barrier layer is 230°C, the processing temperature of the bonding layer is 220°C, the processing temperature of the first stiffness layer is 250°C, the processing temperature of the second stiffness layer is 250°C, the processing temperature of the third stiffness layer is 250°C, the processing temperature of the toughness layer is 230°C, and the processing temperature of the heat sealing layer is 230°C.

[0093] In the step (S2), the molten material of the barrier layer, the molten material of the adhesive layer, the molten material of the first stiffness layer, the molten material of the second stiffness layer, the molten material of the third stiffness layer, the molten material of the toughness layer and the molten material of the heat sealing layer enter the stacked die in a weight ratio of 14:10:13:13:13:12:12.

[0094] In the step (S3), the water temperature of the water cooling and shaping is controlled at 10°C.

[0095] Example 4

[0096] The difference between this embodiment and embodiment 1 is that:

[0097] The raw materials of the barrier layer include a melting temperature of 250° C. and a density of 1.18 g / cm 3 of nylon;

[0098] The bonding layer comprises the following raw materials in parts by weight: 40 parts of bonding resin TIE and 80 parts of copolymerized polypropylene; the melt index of the copolymerized polypropylene used in the bonding layer is 9.5 g / 10 min; the model of the bonding resin TIE is QB515;

[0099] The first stiffness layer comprises the following raw materials in parts by weight: 40 parts of homopolypropylene and 80 parts of copolymer polypropylene. The melt index of the homopolypropylene used in the first stiffness layer is 6 g / 10 min; the melt index of the copolymer polypropylene used in the first stiffness layer is 9.5 g / 10 min.

[0100] The second stiffness layer comprises the following raw materials in parts by weight: 40 parts of homopolypropylene and 80 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the second stiffness layer is 6 g / 10 min; the melt index of the copolymer polypropylene used in the second stiffness layer is 6.5-9.5 g / 10 min;

[0101] The third stiffness layer comprises the following raw materials in parts by weight: 40 parts of homopolypropylene and 80 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the third stiffness layer is 6 g / 10 min; the melt index of the copolymer polypropylene used in the third stiffness layer is 9.5 g / 10 min;

[0102] The raw material of the toughness layer includes copolymerized polypropylene with a melt index of 9.5 g / 10 min;

[0103] The heat seal layer comprises the following raw materials in parts by weight: 40 parts of metallocene polypropylene and 80 parts of copolymer polypropylene. The melt index of the metallocene polypropylene is 8 g / 10 min; the melt index of the copolymer polypropylene for the heat seal layer is 9.5 g / 10 min.

[0104] The preparation method of the first co-extruded film comprises the following steps:

[0105] (S1), adding the raw materials of each layer into the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer;

[0106] (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank;

[0107] (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:2.5 and a temperature of 250°C, and then water-cooled to obtain the first co-extruded film.

[0108] In the step (S1), the processing temperature of the barrier layer is 260°C, the processing temperature of the bonding layer is 250°C, the processing temperature of the first stiffness layer is 270°C, the processing temperature of the second stiffness layer is 270°C, the processing temperature of the third stiffness layer is 270°C, the processing temperature of the toughness layer is 250°C, and the processing temperature of the heat sealing layer is 250°C.

[0109] In the step (S2), the molten material of the barrier layer, the molten material of the adhesive layer, the molten material of the first stiffness layer, the molten material of the second stiffness layer, the molten material of the third stiffness layer, the molten material of the toughness layer and the molten material of the heat sealing layer enter the stacked die in a weight ratio of 17:13:16:16:16:16:16.

[0110] In the step (S3), the water temperature of the water cooling and shaping is controlled at 25°C.

[0111] Example 5

[0112] The difference between this embodiment and embodiment 1 is that:

[0113] The raw materials of the barrier layer include a melting temperature of 235°C and a density of 1.16 g / cm 3 of nylon;

[0114] The bonding layer comprises the following raw materials in parts by weight: 25 parts of bonding resin TIE and 65 parts of copolymerized polypropylene; the melt index of the copolymerized polypropylene used in the bonding layer is 7.5 g / 10 min; the model of the bonding resin TIE is QB515;

[0115] The first stiffness layer comprises the following raw materials in parts by weight: 33 parts of homopolypropylene and 67 parts of copolymer polypropylene. The melt index of the homopolypropylene used in the first stiffness layer is 4 g / 10 min; the melt index of the copolymer polypropylene used in the first stiffness layer is 8.5 g / 10 min.

[0116] The second stiffness layer comprises the following raw materials in parts by weight: 24 parts of homopolypropylene and 76 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the second stiffness layer is 5 g / 10 min; the melt index of the copolymer polypropylene used in the second stiffness layer is 7.5 g / 10 min;

[0117] The third stiffness layer comprises the following raw materials in parts by weight: 38 parts of homopolypropylene and 62 parts of copolymer polypropylene; the melt index of the homopolypropylene used in the third stiffness layer is 4 g / 10 min; the melt index of the copolymer polypropylene used in the third stiffness layer is 7.0 g / 10 min;

[0118] The raw material of the toughness layer includes copolymerized polypropylene with a melt index of 8.0 g / 10 min;

[0119] The heat seal layer comprises the following raw materials in parts by weight: 23 parts of metallocene polypropylene and 77 parts of copolymer polypropylene. The melt index of the metallocene polypropylene is 7.2 g / 10 min; the melt index of the copolymer polypropylene for the heat seal layer is 6.8 g / 10 min.

[0120] The preparation method of the first co-extruded film comprises the following steps:

[0121] (S1), adding the raw materials of each layer into the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer;

[0122] (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank;

[0123] (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:2.3 and a temperature of 205°C, and then water-cooled to obtain the first co-extruded film.

[0124] In the step (S1), the processing temperature of the barrier layer is 235°C, the processing temperature of the bonding layer is 240°C, the processing temperature of the first stiffness layer is 265°C, the processing temperature of the second stiffness layer is 255°C, the processing temperature of the third stiffness layer is 260°C, the processing temperature of the toughness layer is 235°C, and the processing temperature of the heat sealing layer is 245°C.

[0125] In the step (S2), the molten material of the barrier layer, the molten material of the adhesive layer, the molten material of the first stiffness layer, the molten material of the second stiffness layer, the molten material of the third stiffness layer, the molten material of the toughness layer and the molten material of the heat sealing layer enter the stacked die in a weight ratio of 16:11:14:15:16:12:14.

[0126] In the step (S3), the water temperature of the water cooling and shaping is controlled at 18°C.

[0127] Comparative Example 1

[0128] The difference between this comparative example and Example 2 is:

[0129] The bonding layer comprises the following raw materials in parts by weight: 25 parts of adhesive resin TIE and 65 parts of LLDPE;

[0130] The first stiffness layer comprises the following raw materials in parts by weight: 35 parts of LDPE and 50 parts of LLDPE;

[0131] The second stiffness layer comprises the following raw materials in parts by weight: 35 parts of LDPE and 50 parts of LLDPE;

[0132] The third stiffness layer comprises the following raw materials in parts by weight: 35 parts of LDPE and 50 parts of LLDPE;

[0133] The raw material of the toughness layer is LLDPE;

[0134] The heat sealing layer comprises the following raw materials in parts by weight: 20 parts by weight of MLLDPE and 80 parts by weight of LLDPE.

[0135] The LDPE used in this comparative example has a melt index of 2.0 g / 10 min and a density of 0.923 g / cm 3 The LLDPE used in this comparative example is a melt index of 1.5g / 10min and a density of 0.916g / cm 3 The MLLDPE used in this comparative example is a linear low-density polyethylene with a melt index of 0.8g / 10min and a density of 0.911g / cm 3 Metallocene linear low density polyethylene.

[0136] The type of the adhesive resin TIE used in this comparative example is NF377.

[0137] Example 6 Performance Test

[0138] I. Microwave heating resistance test:

[0139] (1) Group A: Take the food packaging bag of Example 2 and the food packaging bag of Comparative Example 1 and place them on the baking tray of a microwave oven. Figure 6As shown, microwave heating is performed on them at the same time, and the heating time is as follows Figure 7 Then, the food packaging bag of Example 2 and the food packaging bag of Comparative Example 1 were taken out, and their changes were observed and recorded. After microwave heating, the food packaging bag of Example 2 was as follows: Figure 8 As shown, the food packaging bag of Comparative Example 1 after microwave heating is as follows Fig. 9 As shown;

[0140] From above Figure 8-9 By comparison, the food packaging bag of Example 2 showed no obvious shrinkage or mutual adhesion, while the first co-extruded film and the second co-extruded film of the food packaging bag of Comparative Example 1 showed obvious adhesion, indicating that the food packaging bag of Example 2 is resistant to microwave heating.

[0141] (2) Group B: The food packaging bags of Example 2 and Comparative Example 1 were taken, and pork of the same weight was placed in each of the food packaging bags, vacuum-sealed, and then heated in a microwave oven for 7 min. The food packaging bags were taken out, and the changes before and after were observed and recorded. The food packaging bags of Example 2 after sealing were as follows: Fig.10 As shown, the food packaging bag of Comparative Example 1 after sealing is as follows Fig.11 As shown, the food packaging bag of Example 2 after microwave heating is as follows Fig.12 As shown, the food packaging bag of Comparative Example 1 after microwave heating is as follows Fig.13 As shown;

[0142] The food packaging bag of Comparative Example 1 emits an obvious pungent odor during the microwave heating experiment, while the food packaging bag of Example 2 has no obvious pungent odor during the microwave heating experiment. Figure 12-13 By comparison, it can be seen that after microwave heating, the food packaging bag of Example 2 showed no shrinkage or melting, while the food packaging bag of Comparative Example 1 showed obvious shrinkage and melting, which further illustrates that the food packaging bag of Example 2 is also resistant to microwave heating after food is placed in it.

[0143] II. Mechanical properties test

[0144] The first co-extruded films and food packaging bags of Examples 2-5 and Comparative Example 1 were tested for puncture strength, tensile strength, elongation at break and heat-sealing strength, respectively, and the test methods were as follows:

[0145] Puncture strength: According to the provisions of 6.6.13 of GB / T 10004-2008, the puncture strength of the first co-extruded film is tested;

[0146] Tensile strength: According to the provisions of 6.6.3 of GB / T 10004-2008, the tensile strength of the first co-extruded film is tested;

[0147] Elongation at break: According to the provisions of GB13022-91, type II specimens were selected to test the elongation at break of the first co-extruded film;

[0148] Heat seal strength: Test the heat seal strength of food packaging bags in accordance with the provisions of 6.6.2 of GB / T 10004-2008.

[0149] The test results are shown in Table 1 below:

[0150] Table 1

[0151] Puncture strength (N) Breaking force(N / 15mm) Heat sealing strength (N / 15mm) Elongation at break (%) Example 2 6 25 28 233 Example 3 4 21 22 217 Example 4 7 26 26 250 Example 5 5 23 24 238 Comparative Example 1 2 40 44 425

[0152] It can be seen from Table 1 above that the puncture strength of the microwave food packaging bag of the present invention is 4-7N, the tensile force is 21-26N / 15mm, the heat sealing strength is 22-28N / 15mm, and the elongation at break is 210-250%; compared with comparative example 1, embodiment 2 has higher puncture strength and better puncture resistance, while the elongation at break of embodiment 2 is lower than that of comparative example 1, which avoids the easy deformation of the bag body after the microwave food packaging bag is filled with food.

[0153] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A food packaging bag for a microwave oven, comprising a bag body and a cavity formed in the bag body, characterized in that: The bag body comprises a first co-extruded film and a second co-extruded film heat-pressed and edge-sealed with the first co-extruded film, an opening is arranged on the top of the bag body, the first co-extruded film and the second co-extruded film are both provided with heat-sealed exhaust adjustment areas, the heat-sealed exhaust adjustment areas of the first co-extruded film and the heat-sealed exhaust adjustment areas of the second co-extruded film are heat-pressed and bonded to form a heat-sealed block, and the heat-sealed block is provided with an internal pressure exhaust hole; when the bag body is sealed and the bag body expands, the heat-sealed block is separated, and the cavity is connected to the internal pressure exhaust hole; The layered structure of the first co-extruded film comprises a barrier layer, an adhesive layer, a first stiffness layer, a second stiffness layer, a third stiffness layer, a toughness layer and a heat-sealing layer arranged in sequence from outside to inside, and the layered structure of the second co-extruded film and the layered structure of the third co-extruded film are the same as the layered structure of the first co-extruded film; The raw materials of the barrier layer include a melting temperature of 230-250°C and a density of 1.08-1.18 g / cm 3 Nylon; the bonding layer comprises the following parts by weight of raw materials: 20-40 parts of adhesive resin TIE and 60-80 parts of copolymerized polypropylene; the first stiffness layer comprises the following parts by weight of raw materials: 20-40 parts of homopolymerized polypropylene and 60-80 parts of copolymerized polypropylene; The second stiffness layer comprises the following raw materials in parts by weight: 20-40 parts of homopolypropylene and 60-80 parts of copolymer polypropylene; the third stiffness layer comprises the following raw materials in parts by weight: 20-40 parts of homopolypropylene and 60-80 parts of copolymer polypropylene; the raw material of the toughness layer comprises copolymer polypropylene with a melt index of 6.5-9.5 g / 10min; the heat sealing layer comprises the following raw materials in parts by weight: 20-40 parts of metallocene polypropylene and 60-80 parts of copolymer polypropylene.

2. A food packaging bag for microwave oven according to claim 1, characterized in that: The bag body also includes a third co-extruded film folded in half and arranged between the first co-extruded film and the second co-extruded film, one end of the third co-extruded film is heat-pressed and sealed with the bottom end of the first co-extruded film, and the other end of the third co-extruded film is heat-pressed and sealed with the bottom end of the second co-extruded film.

3. A food packaging bag for microwave oven according to claim 2, characterized in that: The bottom of the bag body is provided with a first heat-seal reinforcement part and a second heat-seal reinforcement part, wherein the first heat-seal reinforcement part is formed by heat-sealing the first co-extruded film and the third co-extruded film, and the second heat-seal reinforcement part is formed by heat-sealing the second co-extruded film and the third co-extruded film.

4. A food packaging bag for microwave oven according to claim 2, characterized in that: The side edge of the third co-extruded film is provided with a first heat seal and a second heat seal symmetrical to the first heat seal.

5. A food packaging bag for microwave oven according to claim 1, characterized in that: A plurality of air-conducting ridges are evenly distributed on a side of the second co-extruded film close to the first co-extruded film.

6. A food packaging bag for microwave oven according to claim 1, characterized in that: The outer side wall of the bag body is provided with an easy-tear opening.

7. The food packaging bag for microwave oven according to claim 1, characterized in that: The preparation method of the first co-extruded film comprises the following steps: (S1), adding the raw materials of each layer to the extruder of each layer respectively for melting and plasticizing to obtain molten materials of each layer; (S2), the molten materials of each layer obtained in step (S1) enter the stacked die head to complete co-extrusion to form a film blank; (S3) The film blank formed in step (S2) is blown at a blowing ratio of 1:1.25-2.5 and a temperature of 180-250°C, and then water-cooled to obtain the first co-extruded film.

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