Water boiling type heat sealing barrier polyamide film and preparation method thereof

Abstract

The invention relates to the technical field of films for packaging, in particular to a water boiling type heat-sealing barrier polyamide film and a preparation method thereof. The water-boiling type heat-sealing barrier polyamide film comprises a four-layer film layer structure which sequentially comprises a polyamide surface layer, a polyamide core layer, a heat-sealing barrier layer and a heat-sealing polyamide surface layer from top to bottom, the polyamide surface layer comprises the following components: polyamide 6 resin, an anti-blocking agent and a slipping agent; the component of the polyamide core layer comprises polyamide 6 resin; the heat-sealing barrier layer comprises the following components: polyolefin hot melt adhesive resin and a nanosheet layer material; and the heat-sealing polyamide surface layer comprises the following components: copolymerized polyamide resin and a metal compound. The water-boiling type heat-sealing barrier polyamide film has the advantages that the oxygen permeation amount and the water vapor permeation amount are obviously reduced, the water-boiling type heat-sealing barrier polyamide film has good barrier performance, heat-sealing performance and dimensional stability and is suitable for water-boiling packaging, the content of a non-polyamide material is smaller than or equal to 5%, the limitation requirement of a single material on heterogeneous components is met, and the water-boiling type heat-sealing barrier polyamide film is suitable for water-boiling packaging. And a feasible solution is provided for single-material polyamide film packaging.

Description

Technical Field

[0001] The present application relates to the technical field of packaging films, and in particular to a boiled heat-sealed barrier polyamide film and a preparation method thereof. Background Art

[0002] At present, the most commonly used base materials for packaging film materials are PE, PP, PET and PA, and some PS, PVC, etc. Due to the large differences in the performance of different materials themselves, the film-forming process, difficulty and final film performance are all very different. In order to meet the use requirements of packaging materials, multiple film materials need to be compounded. In other words, the packaging bags we see in commercial places (supermarkets, etc.) are generally composed of multiple layers of materials, and each layer has different functions. For example, the base material needs to have heat-sealing properties, and LDPE is usually used. The middle layer needs to have barrier properties, and aluminum foil, aluminized film / aluminum oxide film (metallization deposition for PP, PET, etc.) are usually used. The surface layer needs to have printing function, and BOPP, BOPET, etc. are usually used.

[0003] Single-material packaging refers to unifying multiple layers of different base films in traditional packaging bags into the same material. According to the definition of the European Flexible Packaging Circular Economy Organization (CEFLEX), single material mainly refers to a single polyolefin material (PP and PE), and the content of other components does not exceed 5%. This structure of single-material packaging not only reduces the mixed use of different materials, reduces environmental pollution and resource waste, and is in line with the trend of sustainable development and environmental protection; moreover, this material is easy to separate and recycle in the later stage, which helps to improve the overall recycling efficiency.

[0004] Killing microorganisms is an important method for long-term preservation of food. According to the temperature, it can be divided into pasteurization, boiling sterilization and high-temperature cooking sterilization. Therefore, packaging bags suitable for boiling and cooking sterilization have great market prospects. However, the performance of the existing single polyolefin material is limited and it is not suitable for boiling or cooking sterilization.

[0005] Although biaxially oriented polyamide film (BOPA) has excellent tensile strength, puncture resistance, low temperature resistance, oil resistance and flexibility, and is very suitable for boiling and steaming sterilization, it is widely used in the field of food packaging. However, a single biaxially oriented nylon 6 (polyamide 6) material does not have high barrier properties and heat sealing properties, and it is difficult to overcome the spoilage of food caused by oxygen, temperature, water and pH value. Therefore, how to develop a single-material polyamide film that can be sterilized by boiling in water and can block heat sealing, which is suitable for boiling and steaming sterilization and is convenient for subsequent separation and recycling, has important market value. Summary of the invention

[0006] In order to solve the above-mentioned shortcomings of the prior art: the single-material biaxially oriented nylon 6 material does not have high barrier properties and heat-sealing properties, and it is difficult to overcome the problem of food corruption caused by oxygen, temperature, water and pH value, the present application provides a boiled heat-sealed barrier polyamide film, and its technical solution is as follows: The boiled type heat-sealed barrier polyamide film includes a four-layer film structure, which includes, from top to bottom, a polyamide surface layer, a polyamide core layer, a heat-sealed barrier layer, and a heat-sealed polyamide surface layer; by weight, the components of the polyamide surface layer include 98 to 99.8 parts of polyamide 6 resin, 0.1 to 1 part of an opening agent, and 0.1 to 1 part of a lubricant; the components of the polyamide core layer include polyamide 6 resin; the components of the heat-sealed barrier layer include 98 to 99.5 parts of a polyolefin hot melt adhesive resin and 0.5 to 2 parts of a nanosheet material; the components of the heat-sealed polyamide surface layer include 97 to 99 parts of a copolymerized polyamide resin and 1 to 3 parts of a metal compound.

[0007] In some embodiments, by mass percentage, the components of the polyamide surface layer include 98-99.8% polyamide 6 resin, 0.1-1% anti-blocking agent, and 0.1-1% lubricant; the polyamide core layer is composed of polyamide 6 resin; by mass percentage, the components of the heat-sealing barrier layer include 98-99.5% polyolefin hot melt adhesive resin and 0.5-2% nanosheet material; by mass percentage, the components of the heat-sealing polyamide surface layer include 97-99% copolymerized polyamide resin and 1-3% metal compound.

[0008] In some embodiments, it is composed of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-sealing barrier layer, and a heat-sealing polyamide surface layer from top to bottom; the polyamide surface layer is composed of polyamide 6 resin, an opening agent, and a lubricant; the polyamide core layer is composed of polyamide 6 resin; the heat-sealing barrier layer is composed of polyolefin hot melt adhesive resin and nanosheet material; the heat-sealing polyamide surface layer is composed of copolymerized polyamide resin and metal compounds.

[0009] In some embodiments, the opening agent is one or more combinations of silicon dioxide, talc, calcium carbonate, PMMA particles, and hollow glass microspheres; the lubricant is one or more combinations of erucamide, oleamide, ethylene bisstearamide, polyester silicone wax, polyethylene wax, and amide silicone wax; the polyolefin hot melt adhesive resin is one or more combinations of maleic anhydride grafted metallocene polyethylene wax hot melt adhesive and maleic anhydride grafted metallocene polypropylene wax hot melt adhesive; the nanosheet material is one or more combinations of montmorillonite, titanium dioxide, graphene, mica, and talc. In some embodiments, the particle size of the nanosheet material is 50-200 nm.

[0010] In some embodiments, the metal compound has the general formula MX m; wherein M is one of the metal elements Li, K, Na, Ti, Zr, Zn, Mg, Ca, Fe, and Cu, X is one of the metal elements methoxy, ethoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, acetylacetonato, acetate ion, formate ion, nitrate ion, F group, Cl group, Br group, and I group, and m is a positive integer of 1 to 4.

[0011] In some embodiments, the particle size of the metal compound is 50-100 nm.

[0012] In some embodiments, the copolymerized polyamide is obtained by copolymerizing at least two monomers of polyamide-6, polyamide-66, polyamide-11, polyamide-12, polyamide-1010, and polyamide-1212; and the melting point of the copolymerized polyamide is ≤135°C.

[0013] In some embodiments, the total thickness of the boiled heat-seal barrier polyamide film is 25 to 60 μm; the thickness of the heat-seal barrier layer is 1 to 2 μm; and the thickness of the heat-seal polyamide surface layer is 3 to 6 μm.

[0014] The present application also provides a method for preparing the water-boiled heat-sealed barrier polyamide film as described above, which is characterized by comprising the following preparation steps: The components of the polyamide surface layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a polyamide surface layer masterbatch, and the masterbatch is dried for later use; The components of the heat-sealing barrier layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a heat-sealing barrier layer masterbatch, which is then dried for later use; The components of the heat-sealing polyamide surface layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a heat-sealing polyamide surface layer masterbatch, and the masterbatch is dried for later use; Putting polyamide surface layer masterbatch into the first extruder to make a polyamide surface layer; putting polyamide 6 into the second extruder to make a polyamide core layer; putting heat-sealing barrier layer masterbatch into the third extruder to make a heat-sealing barrier layer; putting heat-sealing polyamide surface layer masterbatch into the fourth extruder to make a heat-sealing polyamide surface layer; wherein the extruder temperature of the polyamide surface layer and the polyamide core layer and the temperature of the T-die head thereof are controlled between 220 and 240°C, and the extruder temperature of the heat-sealing barrier layer and the heat-sealing polyamide surface layer is controlled between 135 and 180°C; The LISIM synchronous stretching method is used to extrude the polyamide surface layer, the polyamide core layer, the heat-seal barrier layer, and the heat-seal polyamide surface layer, and the cast sheet is quenched. The moisture is adjusted and the surface is cleaned in a hot steamer at 60-80°C. The surface of the cast sheet is removed with hot air, and then biaxially stretched. The stretching temperature is 160-190°C, the setting temperature is 180-210°C, and the stretching ratio is 2.6×2.3-3.3×3.3. Then, a water-boiled heat-seal barrier polyamide film can be obtained.

[0015] Based on the above, compared with the prior art, the boiled barrier heat-sealed polyamide film provided in this application has the following beneficial effects: The boiled heat-seal barrier polyamide film provided in the present application has significantly reduced oxygen permeability and water vapor permeability, and has good barrier properties, heat-seal properties and dimensional stability, and is suitable for boiled packaging. In addition, the content of non-polyamide materials in the boiled heat-seal barrier polyamide film is ≤5%, which meets the restriction requirements of a single material on heterogeneous components, and provides a feasible solution for single-material polyamide film packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. The positional relationships described in the drawings in the following description are based on the directions in which the components are drawn in the diagrams, unless otherwise specified.

[0017] Figure 1 This is a structural diagram of a boiled heat-seal barrier polyamide film.

[0018] Figure numerals: 10, polyamide surface layer; 20, polyamide core layer; 30, heat-seal barrier layer; 40, heat-seal polyamide surface layer. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments; the technical features designed in different implementation modes of the present application described below can be combined with each other as long as they do not conflict with each other; based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0020] In the description of this application, it should be noted that all terms (including technical terms and scientific terms) used in this application have the same meanings as those generally understood by ordinary technicians in the field to which this application belongs, and cannot be understood as limitations on this application; it should be further understood that the terms used in this application should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined in this application.

[0021] The present application provides a water-boiled heat-sealed barrier polyamide film, and its technical solution is as follows like Figure 1 As shown, the boiled heat-sealed barrier polyamide film is composed of a four-layer film structure, and the four-layer film structure is, from top to bottom, a polyamide surface layer 10, a polyamide core layer 20, a heat-sealed barrier layer 30, and a heat-sealed polyamide surface layer 40; Among them, by mass percentage, the components of the polyamide surface layer 10 include 98-99.8% of polyamide 6 resin, 0.1-1% of an opening agent, and 0.1-1% of a lubricant; the polyamide core layer 20 is composed of polyamide 6 resin; by mass percentage, the components of the heat-sealing barrier layer 30 include 98-99.5% of a polyolefin hot melt adhesive resin and 0.5-2% of a nanosheet material; by mass percentage, the components of the heat-sealing polyamide surface layer 40 include 97-99% of a copolymerized polyamide resin and 1-3% of a metal compound.

[0022] In the embodiment of the present application, the preparation method of the boiled heat-sealed barrier polyamide film is as follows: Step 1, the components in the polyamide surface layer 10 are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a polyamide surface layer 10 masterbatch, and the masterbatch is dried for standby use; Step 2: Blend the components in the heat-sealing barrier layer 30 in proportion, melt-blend, extrude and granulate through a twin-screw extruder to obtain a masterbatch of the heat-sealing barrier layer 30, and dry the masterbatch for later use; Step 3, the components of the heat-sealing polyamide surface layer 40 are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a masterbatch of the heat-sealing polyamide surface layer 40, and the masterbatch is dried for standby use; Step 4: Put the masterbatch of polyamide surface layer 10 into the first extruder to make the polyamide surface layer 10; put the polyamide 6 into the second extruder to make the polyamide core layer 20; put the masterbatch of heat-sealing barrier layer 30 into the third extruder to make the heat-sealing barrier layer 30; put the masterbatch of heat-sealing polyamide surface layer 40 into the fourth extruder to make the heat-sealing polyamide surface layer 40; wherein, the extruder temperature of the polyamide surface layer 10 and the polyamide core layer 20 and the temperature of the T-die head thereof are controlled between 220 and 240°C, and the extruder temperature of the heat-sealing barrier layer 30 and the heat-sealing polyamide surface layer 40 is controlled between 135 and 180°C; Step 5: Use the LISIM synchronous stretching method to extrude the polyamide surface layer 10, the polyamide core layer 20, the heat-sealing barrier layer 30, and the heat-sealing polyamide surface layer 40, and quench the cast sheet. Adjust the humidity and clean the surface in a 60-80°C hot steamer, use hot air to remove the steam on the surface of the cast sheet, and then perform biaxial stretching. The stretching temperature is 160-190°C, the setting temperature is 180-210°C, and the stretching ratio is 2.6×2.3~3.3×3.3, so as to obtain a boiled heat-sealing barrier polyamide film.

[0023] This application provides the following embodiments: Example 1 1. Structure and formula The boiled heat-seal barrier polyamide film consists of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-seal barrier layer, and a heat-seal polyamide surface layer from top to bottom. Among them, according to mass percentage, the polyamide surface layer component is composed of 99% polyamide 6 resin, 0.5% silicon dioxide, and 0.5% erucamide; the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealing barrier layer component is composed of 98.5% maleic anhydride grafted metallocene polyethylene wax hot melt adhesive and 1.5% nano-montmorillonite; the heat-sealing polyamide surface layer component is composed of 98% copolymer polyamide 6 / 10 / 12 and 2% nano-magnesium oxide.

[0024] Among them, the thicknesses of the polyamide surface layer, polyamide core layer, heat-sealing barrier layer, and heat-sealing polyamide surface layer are 1.5μm, 22μm, 1.5μm, and 5μm respectively; the total thickness of the film is 30μm.

[0025] 2. The preparation process of the film is: Step 1, blending the components of the polyamide surface layer in proportion, melt blending, extruding and granulating through a twin-screw extruder to obtain a polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 2: Blend the components of the heat-sealing barrier layer in proportion, melt-blend, extrude and granulate through a twin-screw extruder to obtain a heat-sealing barrier layer masterbatch, and dry the masterbatch for later use; Step 3, blending the components of the heat-sealing polyamide surface layer in proportion, melt-blending, extruding and granulating through a twin-screw extruder to obtain a heat-sealing polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 4: Put the polyamide surface layer masterbatch into the first extruder to make the polyamide surface layer; put the polyamide 6 into the second extruder to make the polyamide core layer; put the heat-seal barrier layer masterbatch into the third extruder to make the heat-seal barrier layer; put the heat-seal polyamide surface layer masterbatch into the fourth extruder to make the heat-seal polyamide surface layer; Among them, the extruder temperature of the polyamide surface layer and the polyamide core layer and the temperature of the T-die head are controlled at 235°C, and the extruder temperature of the heat-sealing barrier layer and the heat-sealing polyamide surface layer is controlled at 165°C; Step 5: Use the LISIM synchronous stretching method to extrude the polyamide surface layer, polyamide core layer, heat-seal barrier layer, and heat-seal polyamide surface layer, and quench the cast sheet. Adjust the humidity and clean the surface in a 65°C hot steamer. Use hot air to remove the steam on the surface of the cast sheet, and then perform biaxial stretching. The stretching temperature is 175°C, the setting temperature is 195°C, and the stretching ratio is 2.8×3.2. You can get a boiled heat-seal barrier polyamide film.

[0026] Example 2 1. Structure and formula The boiled heat-seal barrier polyamide film consists of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-seal barrier layer, and a heat-seal polyamide surface layer from top to bottom. Among them, according to mass percentage, the polyamide surface layer component is composed of 98% polyamide 6 resin, 1% talc, and 1% EBS (ethylene bisstearamide); the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealing barrier layer component is composed of 98% maleic anhydride grafted metallocene polypropylene wax hot melt adhesive and 2% mica; the heat-sealing polyamide surface layer component is composed of 97% copolymer polyamide 6 / 66 / 10 and 3% nano zinc oxide.

[0027] Among them, the thicknesses of the polyamide surface layer, polyamide core layer, heat-sealing barrier layer, and heat-sealing polyamide surface layer are 1.5μm, 22μm, 1.5μm, and 5μm respectively; the total thickness of the film is 30μm.

[0028] 2. The preparation process of the film is: Step 1, blending the components of the polyamide surface layer in proportion, melt blending, extruding and granulating through a twin-screw extruder to obtain a polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 2: Blend the components of the heat-sealing barrier layer in proportion, melt-blend, extrude and granulate through a twin-screw extruder to obtain a heat-sealing barrier layer masterbatch, and dry the masterbatch for later use; Step 3, blending the components of the heat-sealing polyamide surface layer in proportion, melt-blending, extruding and granulating through a twin-screw extruder to obtain a heat-sealing polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 4: Put the polyamide surface layer masterbatch into the first extruder to make the polyamide surface layer; put the polyamide 6 into the second extruder to make the polyamide core layer; put the heat-seal barrier layer masterbatch into the third extruder to make the heat-seal barrier layer; put the heat-seal polyamide surface layer masterbatch into the fourth extruder to make the heat-seal polyamide surface layer; Among them, the extruder temperature of the polyamide surface layer and the polyamide core layer and the temperature of the T-die head are controlled at 235°C, and the extruder temperature of the heat-sealing barrier layer and the heat-sealing polyamide surface layer is controlled at 165°C; Step 5: Use the LISIM synchronous stretching method to extrude the polyamide surface layer, polyamide core layer, heat-seal barrier layer, and heat-seal polyamide surface layer, and quench the cast sheet. Adjust the humidity and clean the surface in a 65°C hot steamer. Use hot air to remove the steam on the surface of the cast sheet, and then perform biaxial stretching. The stretching temperature is 175°C, the setting temperature is 195°C, and the stretching ratio is 2.8×3.2. You can get a boiled heat-seal barrier polyamide film.

[0029] Example 3 1. Structure and formula The boiled heat-seal barrier polyamide film consists of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-seal barrier layer, and a heat-seal polyamide surface layer from top to bottom. Among them, according to mass percentage, the polyamide surface layer component is composed of 99.8% polyamide 6 resin, 0.1% calcium carbonate, and 0.1% PE wax; the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealing barrier layer component is composed of 99.5% maleic anhydride grafted metallocene polypropylene wax hot melt adhesive and 0.5% nano-graphene; the heat-sealing polyamide surface layer component is composed of 99% copolymer polyamide 6 / 66 / 11 and 1% calcium chloride.

[0030] Among them, the thicknesses of the polyamide surface layer, polyamide core layer, heat-sealing barrier layer, and heat-sealing polyamide surface layer are 1.5μm, 22μm, 1.5μm, and 5μm respectively; the total thickness of the film is 30μm.

[0031] 2. The preparation process of the film is: Step 1, blending the components of the polyamide surface layer in proportion, melt blending, extruding and granulating through a twin-screw extruder to obtain a polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 2: Blend the components of the heat-sealing barrier layer in proportion, melt-blend, extrude and granulate through a twin-screw extruder to obtain a heat-sealing barrier layer masterbatch, and dry the masterbatch for later use; Step 3, blending the components of the heat-sealing polyamide surface layer in proportion, melt-blending, extruding and granulating through a twin-screw extruder to obtain a heat-sealing polyamide surface layer masterbatch, and drying the masterbatch for standby use; Step 4: Put the polyamide surface layer masterbatch into the first extruder to make the polyamide surface layer; put the polyamide 6 into the second extruder to make the polyamide core layer; put the heat-seal barrier layer masterbatch into the third extruder to make the heat-seal barrier layer; put the heat-seal polyamide surface layer masterbatch into the fourth extruder to make the heat-seal polyamide surface layer; Among them, the extruder temperature of the polyamide surface layer and the polyamide core layer and the temperature of the T-die head are controlled at 235°C, and the extruder temperature of the heat-sealing barrier layer and the heat-sealing polyamide surface layer is controlled at 165°C; Step 5: Use the LISIM synchronous stretching method to extrude the polyamide surface layer, polyamide core layer, heat-seal barrier layer, and heat-seal polyamide surface layer, and quench the cast sheet. Adjust the humidity and clean the surface in a 65°C hot steamer. Use hot air to remove the steam on the surface of the cast sheet, and then perform biaxial stretching. The stretching temperature is 175°C, the setting temperature is 195°C, and the stretching ratio is 2.8×3.2. You can get a boiled heat-seal barrier polyamide film.

[0032] This application provides the following comparative examples: Comparative Example 1 Biaxially oriented nylon film (BOPA) is commercially available.

[0033] Comparative Example 2 (the heat-seal barrier layer lacks sheet material, and the heat-seal polyamide surface layer lacks metal compounds) The difference between this comparative example and Example 1 is that the heat-seal barrier layer and the heat-seal polyamide surface layer components are different: The boiled heat-sealed barrier polyamide film is composed of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-sealed barrier layer, and a heat-sealed polyamide surface layer from top to bottom; wherein, according to mass percentage, the polyamide surface layer component is composed of 99% polyamide 6 resin, 0.5% silicon dioxide, and 0.5% erucamide; the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealed barrier layer component is composed of 100% maleic anhydride grafted metallocene polyethylene wax hot melt adhesive; and the heat-sealed polyamide surface layer component is composed of 100% copolymerized polyamide 6 / 10 / 12. Other film formulas and preparation methods are the same as those in Example 1.

[0034] Comparative Example 3 (Heat-sealed polyamide surface lacks metal compounds) The difference between this comparative example and Example 1 is only that the surface components of the heat-sealing polyamide are different: The boiled heat-sealed barrier polyamide film is composed of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-sealed barrier layer, and a heat-sealed polyamide surface layer from top to bottom; wherein, according to mass percentage, the polyamide surface layer component is composed of 99% polyamide 6 resin, 0.5% silicon dioxide, and 0.5% erucamide; the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealed barrier layer component is composed of 98.5% maleic anhydride grafted metallocene polyethylene wax hot melt adhesive and 1.5% nano-montmorillonite; the heat-sealed polyamide surface layer component is composed of 100% copolymerized polyamide 6 / 10 / 12. Other film formulas and preparation methods are the same as those in Example 1.

[0035] Comparative Example 4 (the polyolefin hot melt adhesive resin of the heat seal barrier layer is replaced by EVA resin) The difference between this comparative example and Example 1 is only that the heat seal barrier layer components are different: The boiled heat-sealed barrier polyamide film is composed of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-sealed barrier layer, and a heat-sealed polyamide surface layer from top to bottom; wherein, according to mass percentage, the polyamide surface layer component is composed of 99% polyamide 6 resin, 0.5% silicon dioxide, and 0.5% erucamide; the polyamide core layer component is composed of 100% polyamide 6 resin; the heat-sealed barrier layer component is composed of 98.5% EVA resin and 1.5% nano-montmorillonite; the heat-sealed polyamide surface layer component is composed of 98% copolymerized polyamide 6 / 10 / 12 and 2% nano-magnesium oxide. Other film formulas and preparation methods are the same as those in Example 1.

[0036] Comparative Example 5 (different formulation ratios of heat-seal barrier layer components) The difference between this comparative example and Example 1 is that the heat-sealing barrier layer component is composed of 95% maleic anhydride grafted metallocene polyethylene wax hot melt adhesive and 5% nano-montmorillonite. The other film formulas and preparation methods are the same as those in Example 1.

[0037] The films prepared in the examples and comparative examples were subjected to performance tests, and the test standards were as follows: Thickness: According to GB / T20220-2006 average thickness of plastic film and sheet samples, average thickness of rolls and unit mass area; Heat seal strength: The film heat seal strength test is carried out according to QB / T 2358-98, the heat seal temperature is 125℃, the heat seal pressure is 400kpa, and the heat seal time is 1s; Hygroscopic elongation: The initial size of the film is L0. After being placed in a 23°C / 50% humidity environment for 48 hours, the size becomes L1. The film size unchanged rate is measured: [(L1~L0) / L0]×100%; Thermal shrinkage: GB / T12027-2004 Test method for dimensional change of plastic film and sheet upon heating; Water vapor transmission rate: Test the water vapor transmission rate of the film according to GB / T 1037-1988; Oxygen permeability: Film oxygen permeability test is carried out according to GB / T 1038-2000; the test conditions are 23℃, 50%RH.

[0038] The test evaluation results are shown in Table 1: Table 1

[0039] Notes: 1. The thickness of the heat-sealed barrier layer is 1.5 microns, and the thickness of the heat-sealed polyamide surface layer is 5 microns; 2. The boiling condition is 100°C for 30 minutes.

[0040] It can be seen from Table 1 that compared with the comparative example, the boiled heat-seal barrier polyamide films prepared in Examples 1-3 have better barrier properties, heat-seal properties and dimensional stability, and the barrier properties are further improved after boiling.

[0041] It can be seen that the oxygen permeability and water vapor permeability of the boiled heat-sealed barrier polyamide film provided in the present application are significantly reduced, and it has good barrier properties, heat-sealing properties and dimensional stability, and is suitable for boiled packaging.

[0042] In summary, compared with the prior art, the boiled heat-sealed barrier polyamide film solution provided in this application has the following design concepts and beneficial effects: 1. The heat-sealing barrier layer component in the film is designed with maleic anhydride grafted metallocene polyethylene wax hot melt adhesive or maleic anhydride grafted metallocene polypropylene wax hot melt adhesive, which reasonably utilizes the hydrophobic properties of polyolefins. At the same time, after grafting maleic anhydride, it has good compatibility with polyamide and improves the bonding strength between the layers; 2. Adding nanosheet material to the heat-sealed barrier layer of the film can reduce the path of oxygen and water vapor passing through the substrate, thereby improving the barrier performance. Nanometal compounds can well fill the holes of the polymer, thereby increasing the barrier performance; 3. Nano metal compounds are added to the surface layer of the heat-seal polyamide in the film. During the boiling process, the nano metal compounds are excited by water vapor to produce multivalent metal ions. These metal ions can be transferred and cross-linked with maleic anhydride, so that the barrier properties of the heat-seal barrier layer are further improved; 4. The nanosheet material particles in the film can improve the dimensional stability of the film under different temperature and humidity conditions; the water-boiled heat-sealed barrier polyamide film, the content of non-polyamide materials is ≤5%, which meets the restriction requirements of a single material on heterogeneous components.

[0043] In summary, the boiled-type heat-seal barrier polyamide film provided in the present application has significantly reduced oxygen permeability and water vapor permeability, and has good barrier properties, heat-seal properties and dimensional stability, and is suitable for boiled packaging. In addition, the content of non-polyamide materials in the boiled-type heat-seal barrier polyamide film is ≤5%, which meets the restriction requirements of a single material on heterogeneous components, and provides a feasible solution for single-material polyamide film packaging.

[0044] It should be noted that: In this article, polyamide-6, polyamide-66, polyamide-11, polyamide-12, polyamide-1010, polyamide-1212, copolyamide 6 / 10 / 12, copolyamide 6 / 66 / 10, and copolyamide 6 / 66 / 11 are usually referred to as PA-6, PA-66, PA-11, PA-12, PA-1010, PA-1212, PA6 / 10 / 12, PA6 / 66 / 10, and PA6 / 66 / 11 in the industry. These values ​​are for existing materials.

[0045] As the fourth generation BOPA film technology, LISIM technology is the most advanced synchronous stretching technology in the industry. It uses magnetic levitation technology and takes the advantages of step-by-step stretching and mechanical synchronous stretching to produce a linear synchronous film that combines the advantages of good mechanical strength, good ductility and good balance.

[0046] In this article, “~” is used to indicate a numerical range, and the range indicated by this expression includes two endpoint values.

[0047] In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments conceived by the present application, but are not intended to limit the present application; if no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in the art or in the product manual shall be followed, and the reagents or instruments used without specifying the manufacturer shall all be conventional products that can be purchased commercially.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A boiled heat-seal barrier polyamide film, characterized in that: It includes a four-layer film structure, which is a polyamide surface layer, a polyamide core layer, a heat-sealing barrier layer, and a heat-sealing polyamide surface layer from top to bottom; The components of the polyamide surface layer include 98-99.8 parts of polyamide 6 resin, 0.1-1 parts of an anti-blocking agent, and 0.1-1 parts of a lubricant by weight; The components of the polyamide core layer include polyamide 6 resin; The components of the heat-sealing barrier layer include 98-99.5 parts of polyolefin hot-melt adhesive resin and 0.5-2 parts of nanosheet material; The components of the heat-sealed polyamide surface layer include 97-99 parts of copolymerized polyamide resin and 1-3 parts of metal compound.

2. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: In terms of mass percentage, the components of the polyamide surface layer include 98-99.8% polyamide 6 resin, 0.1-1% anti-blocking agent, and 0.1-1% lubricating agent; The polyamide core layer is composed of polyamide 6 resin; In terms of mass percentage, the components of the heat-sealing barrier layer include 98-99.5% polyolefin hot-melt adhesive resin and 0.5-2% nanosheet material; In terms of mass percentage, the components of the heat-sealed polyamide surface layer include 97-99% copolymerized polyamide resin and 1-3% metal compound.

3. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: It is composed of a four-layer film structure, which is composed of a polyamide surface layer, a polyamide core layer, a heat-sealed barrier layer, and a heat-sealed polyamide surface layer from top to bottom; The polyamide surface layer is composed of polyamide 6 resin, an anti-blocking agent, and a lubricant; The polyamide core layer is composed of polyamide 6 resin; The heat-sealing barrier layer is composed of polyolefin hot-melt adhesive resin and nanosheet material; The heat-sealed polyamide surface layer is composed of copolymerized polyamide resin and metal compounds.

4. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The opening agent is one or more combinations of silicon dioxide, talcum powder, calcium carbonate, PMMA particles, and hollow glass microspheres; The lubricant is one or more combinations of erucamide, oleamide, ethylene bisstearamide, polyester silicone wax, polyethylene wax, and amide silicone wax; The polyolefin hot melt adhesive resin is one or more combinations of maleic anhydride grafted metallocene polyethylene wax hot melt adhesive and maleic anhydride grafted metallocene polypropylene wax hot melt adhesive; The nanosheet material is one or more combinations of montmorillonite, titanium dioxide, graphene, mica and talc.

5. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The particle size of the nanosheet material is 50-200 nm.

6. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The general formula of the metal compound is MX m ; Wherein, M is one of the metal elements Li, K, Na, Ti, Zr, Zn, Mg, Ca, Fe, and Cu, X is one of the metal elements methoxy, ethoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, acetylacetonato, acetate ion, formate ion, nitrate ion, F group, Cl group, Br group, and I group, and m is a positive integer of 1 to 4.

7. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The particle size of the metal compound is 50 to 100 nm.

8. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The copolymerized polyamide is obtained by copolymerizing at least two monomers of polyamide-6, polyamide-66, polyamide-11, polyamide-12, polyamide-1010, and polyamide-1212; The melting point of the copolymerized polyamide is ≤135°C.

9. The boiled heat-seal barrier polyamide film according to claim 1, characterized in that: The total thickness of the boiled heat-sealed barrier polyamide film is 25 to 60 μm; The thickness of the heat-sealing barrier layer is 1 to 2 μm; The heat-sealed polyamide surface layer has a thickness of 3 to 6 μm.

10. A method for preparing a boiled heat-seal barrier polyamide film according to any one of claims 1 to 9, characterized in that: The method comprises the following preparation steps: The components of the polyamide surface layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a polyamide surface layer masterbatch, and the masterbatch is dried for later use; The components of the heat-sealing barrier layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a heat-sealing barrier layer masterbatch, which is then dried for later use; The components of the heat-sealing polyamide surface layer are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder to obtain a heat-sealing polyamide surface layer masterbatch, and the masterbatch is dried for later use; The polyamide surface layer masterbatch is fed into the first extruder to produce the polyamide surface layer; the polyamide 6 is fed into the second extruder to produce the polyamide core layer; The heat-seal barrier layer masterbatch is fed into the third extruder to produce the heat-seal barrier layer; the heat-seal polyamide surface layer masterbatch is fed into the fourth extruder to produce the heat-seal polyamide surface layer; wherein the extruder temperature of the polyamide surface layer and the polyamide core layer and the temperature of the T-die head thereof are controlled between 220 and 240° C., and the extruder temperature of the heat-seal barrier layer and the heat-seal polyamide surface layer is controlled between 135 and 180° C.; The LISIM synchronous stretching method is used to extrude the polyamide surface layer, the polyamide core layer, the heat-seal barrier layer, and the heat-seal polyamide surface layer, and the cast sheet is quenched. The moisture is adjusted and the surface is cleaned in a hot steamer at 60-80°C. The surface of the cast sheet is removed with hot air, and then biaxially stretched. The stretching temperature is 160-190°C, the setting temperature is 180-210°C, and the stretching ratio is 2.6×2.3-3.3×3.

3. Then, a water-boiled heat-seal barrier polyamide film can be obtained.

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