A high-barrier boiling-resistant transparent packaging film and preparation method thereof

Abstract

The invention discloses a high-barrier, retort-resistant transparent packaging film and a preparation method thereof, belonging to the technical field of packaging materials. The packaging film comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials by weight: 70-80 parts of binary copolymer polypropylene, 16-18 parts of polyolefin elastomer grafted anhydride, 3.5-4 parts of coupling agent-modified layered filler, and 0.4 parts of lubricant. The preparation method comprises the following steps: the first step, weighing the raw materials of the outer layer and the heat-sealing layer, mixing them respectively, heating them into a molten state, and then extruding, casting, cooling, corona treatment, trimming and rolling to obtain the outer layer and the heat-sealing layer; the second step, using an adhesive to perform solvent-free compounding of the outer layer and the heat-sealing layer with the intermediate layer. The prepared high-barrier, retort-resistant transparent packaging film has good water vapor barrier properties and mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and in particular relates to a high-barrier, retort-resistant transparent packaging film and a preparation method thereof. Background Art

[0002] The packaging film of room temperature food usually adopts single-layer materials such as PE film. When the food needs to be cooked at high temperature, the PE packaging film is not resistant to high temperature and cannot protect the food after high temperature treatment. At the same time, the mechanical strength of the film after high temperature treatment decreases, and it is difficult to prevent perforation for angular food. During the cooking process, it will be exposed to high-temperature water vapor. The packaging material must be able to withstand the corresponding temperature without deformation, cracking, etc. During the cooking process, the packaging needs to prevent excessive external water vapor from entering the packaging. At the same time, it is also necessary to prevent excessive loss of ingredients such as fragrance and juice. For some easily oxidizable ingredients (such as vitamin C, etc.), the packaging must also have good oxygen barrier properties. However, the current packaging film for room temperature food cannot meet the current demand.

[0003] The patent application with publication number CN102173143A discloses a cooking-resistant composite film, comprising a first CPP layer, a PVDC layer and a second CPP layer connected at one time by an adhesive; the second CPP layer comprises in sequence: a corona layer, an intermediate layer and a surface layer in contact with the PVDC layer; the intermediate layer and the corona layer are both binary copolymer PP layers, and the surface layer is a homopolymer PP layer. Compared with the existing cooking-resistant composite film, the outermost layer and the innermost layer in the three-layer structure of the composite film are both PP structures, that is, the three-layer structure of the composite film is symmetrical, so that the composite film maintains a synchronous shrinkage rate in each layer under heating, stretching and shrinking conditions, avoiding curling of the composite film after stretching; but because CPP has poor toughness in low temperature environment (prone to brittle cracking), when stored at low temperature, the composite film will become brittle due to the low temperature and the tear strength will deteriorate, the mechanical properties will decrease, causing the composite film to rupture or crack, and the packaging contents cannot be protected accordingly. Summary of the invention

[0004] The object of the present invention is to provide a high-barrier and retort-resistant transparent packaging film and a preparation method thereof, so as to solve the problem of poor barrier properties of the packaging film.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a high-barrier, retort-resistant, transparent packaging film, which comprises an outer layer, an intermediate layer, and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 70-80 parts of binary copolymer polypropylene, 16-18 parts of polyolefin elastomer grafted anhydride, 3.5-4 parts of coupling agent-modified layered filler, and 0.4 parts of a lubricant.

[0007] Furthermore, the lubricant is selected from at least one of erucamide, stearamide, calcium stearate, zinc stearate, polyethylene wax and polypropylene wax.

[0008] Furthermore, the polyolefin elastomer grafted anhydride is prepared by the following steps:

[0009] After the polyolefin elastomer, the acid anhydride containing double bonds and the initiator are uniformly mixed, the reaction extrusion is carried out to obtain the polyolefin elastomer grafted acid anhydride.

[0010] Further, the mass ratio of the polyolefin elastomer, the acid anhydride containing double bonds and the initiator is 100:4-5:0.5-0.8;

[0011] And / or, during the reaction extrusion process, the screw speed is 250r / min, the temperature of each section of the twin-screw extruder is set to 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, 190°C, 180°C, and purification is carried out after extrusion.

[0012] Furthermore, the acid anhydride containing a double bond is selected from one of nadic anhydride, fumaric anhydride and alkenyl succinic anhydride. Nadic anhydride has good stability and is more suitable for preparing food-related packaging films.

[0013] Furthermore, the initiator is an organic peroxide initiator selected from dicumyl peroxide and dibenzoyl peroxide.

[0014] Furthermore, the coupling agent modified layered filler is prepared by the following steps:

[0015] A silane coupling agent accounting for 5% of the mass of the layered filler is dissolved in an ethanol aqueous solution with a volume fraction of 90%, and then the layered filler is added, stirred for 15-20 minutes, allowed to stand for 1.5-2 hours, filtered and dried to obtain a coupling agent modified layered filler.

[0016] Furthermore, the silane coupling agent is an aminosilane coupling agent; the coupling agent-modified layered filler reacts with the active groups in the polyolefin elastomer grafted anhydride, which not only improves the compatibility between the raw materials but also reduces the proportion of polar groups, and the water vapor barrier effect can be further improved.

[0017] The layered filler is one of graphene oxide, montmorillonite, mica flakes and kaolin. As a barrier material, the layered filler prolongs the permeation path of media such as water vapor and improves the barrier performance.

[0018] In a second aspect, the present invention provides a method for preparing a high-barrier, retort-resistant transparent packaging film, comprising the following steps:

[0019] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them respectively, heat them into a molten state, and then extrude, cast, cool, perform corona treatment, trim and roll them to obtain the outer layer and the heat-sealing layer;

[0020] The second step is to use adhesive to perform solvent-free compounding of the outer layer, the heat-sealing layer and the middle layer to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is a solvent-free retort-resistant adhesive 7735 or 6088 or other composite glue suitable for processing retort-type materials, and after compounding, a retort-resistant composite film is obtained.

[0021] The intermediate layer is a PCTG / PET composite film, which is obtained by mixing polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene terephthalate and additives (N,N'-ethylene bisstearamide and polyethylene wax) and then melt-extruding granulation, extruding, casting and stretching to obtain an intermediate film. The amount ratio of polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene terephthalate, N,N'-ethylene bisstearamide and polyethylene wax is 7:3:0.4:0.2.

[0022] Furthermore, the corona treatment power is 8 kW and the corona roller pressure is 3 bar.

[0023] Beneficial effects of the present invention:

[0024] The invention provides a high-barrier retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive. The prepared high-barrier retort-resistant transparent packaging film has good water vapor barrier properties. The water vapor barrier properties of the high-barrier retort-resistant transparent packaging film are improved by adding a coupling agent-modified layered filler and a polyolefin elastomer grafted anhydride into the raw materials of the outer layer and the heat-sealing layer. The coupling agent-modified layered filler and the polyolefin elastomer grafted anhydride have good dispersibility and reduced interfacial tension, thereby improving the compatibility between the raw materials, which is manifested as improved mechanical properties. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] The present embodiment provides a high-barrier retort-resistant transparent packaging film, which includes an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, and the outer layer and the heat-sealing layer both include the following raw materials in parts by weight: 70 parts of binary copolymer polypropylene, 16 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide.

[0028] The coupling agent modified layered filler is prepared by the following steps:

[0029] γ-aminopropyltriethoxysilane (5% by mass of montmorillonite) was dissolved in an ethanol aqueous solution (90% by volume), and then montmorillonite was added. After stirring for 15 minutes, the mixture was allowed to stand for 2 hours, filtered and dried to obtain a coupling agent-modified layered filler.

[0030] The polyolefin elastomer grafted anhydride is prepared by the following steps:

[0031] A polyolefin elastomer (melt mass flow rate 0.5 g / min; 2.6 kg, 230°C), an acid anhydride containing a double bond (nadic anhydride) and an initiator (dicumyl peroxide) are uniformly mixed and then subjected to reactive extrusion. The screw speed is 250 r / min, and the temperatures of each section of the twin-screw extruder are set to 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, 190°C, 190°C, 180°C. After extrusion, the product is added into xylene and heated to reflux at 140°C. After complete dissolution, the product is cooled and filtered, washed with ethanol and filtered to remove unreacted small molecules, and vacuum dried at 80°C to constant weight to obtain a polyolefin elastomer grafted acid anhydride. The mass ratio of the polyolefin elastomer, the acid anhydride containing a double bond and the initiator is 100:4:0.8.

[0032] The middle layer is a PCTG / PET composite film, which is a mixture of polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene terephthalate and additives (N,N'-ethylene bisstearamide and polyethylene wax) and then melt-extruded and granulated, extruded, cast and stretched to obtain an intermediate film, and the thickness of the intermediate film is controlled to be 15μm. The usage ratio of polyethylene terephthalate-1,4-cyclohexanedimethanol, polyethylene terephthalate, N,N'-ethylene bisstearamide and polyethylene wax is 7:3:0.4:0.2.

[0033] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0034] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0035] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0036] Example 2

[0037] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 75 parts of binary copolymer polypropylene, 17 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; the coupling agent modified layered filler and the polyolefin elastomer grafted anhydride are the same as those in Example 1.

[0038] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0039] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0040] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0041] Example 3

[0042] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 80 parts of binary copolymer polypropylene, 18 parts of polyolefin elastomer grafted anhydride, 4 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; the coupling agent modified layered filler and the polyolefin elastomer grafted anhydride are the same as those in Example 1.

[0043] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0044] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0045] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0046] Example 4

[0047] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 70 parts of binary copolymer polypropylene, 16 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; and the coupling agent modified layered filler is the same as that in Example 1.

[0048] The polyolefin elastomer grafted anhydride is prepared by the following steps:

[0049] A polyolefin elastomer (melt mass flow rate 0.5 g / min; 2.6 kg, 230°C), an acid anhydride containing a double bond (nadic anhydride) and an initiator (dicumyl peroxide) are uniformly mixed and then reactively extruded. The screw speed is 250 r / min, and the temperatures of each section of the twin-screw extruder are set to 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, 190°C, 190°C, 180°C. After extrusion, the product is added into xylene and heated to reflux at 140°C. After being completely dissolved, it is cooled and filtered, washed with ethanol and filtered to remove unreacted small molecules, and vacuum dried at 80°C to constant weight to obtain a polyolefin elastomer grafted acid anhydride. The mass ratio of the polyolefin elastomer, the acid anhydride containing a double bond and the initiator is 100:5:0.8.

[0050] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0051] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0052] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0053] Example 5

[0054] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 75 parts of binary copolymer polypropylene, 17 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; the coupling agent modified layered filler is the same as that in Example 1, and the polyolefin elastomer grafted anhydride is the same as that in Example 4.

[0055] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0056] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0057] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0058] Example 6

[0059] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 80 parts of binary copolymer polypropylene, 18 parts of polyolefin elastomer grafted anhydride, 4 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; the coupling agent modified layered filler is the same as that in Example 1, and the polyolefin elastomer grafted anhydride is the same as that in Example 4.

[0060] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0061] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0062] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0063] Example 7

[0064] This embodiment provides a high barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials by weight: 70 parts of binary copolymer polypropylene, 16 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in embodiment 1. The polyolefin elastomer grafted anhydride is the same as that in embodiment 1.

[0065] The coupling agent is modified into a layered filler by the following steps:

[0066] N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (5% by mass of montmorillonite) was dissolved in an ethanol aqueous solution (90% by volume), and then montmorillonite was added. After stirring for 20 minutes, the mixture was allowed to stand for 1.5 hours, filtered and dried to obtain a coupling agent-modified layered filler.

[0067] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0068] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0069] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0070] Example 8

[0071] The present embodiment provides a high-barrier and retort-resistant transparent packaging film, which comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials in parts by weight: 70 parts of binary copolymer polypropylene, 16 parts of polyolefin elastomer grafted anhydride, 3.5 parts of coupling agent modified layered filler, and 0.4 parts of erucamide; wherein the intermediate layer is the same as that in Example 1; the coupling agent modified layered filler is the same as that in Example 7, and the polyolefin elastomer grafted anhydride is the same as that in Example 4.

[0072] The preparation method of the high-barrier boiling-resistant transparent packaging film comprises the following steps:

[0073] The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them separately, heat them into a molten state, and then extrude, cast, cool, and perform corona treatment. The corona treatment power is 8kW and the corona roller pressure is 3bar. The outer layer and the heat-sealing layer are trimmed and rolled up to obtain the outer layer and the heat-sealing layer. The thickness of the outer layer and the heat-sealing layer is controlled to be 30μm.

[0074] The second step is to compound the outer layer and the heat-sealing layer with the middle layer without solvent to obtain a high-barrier retort-resistant transparent packaging film. The adhesive used is commercially available solvent-free retort-resistant adhesive 7735 as an adhesive to obtain a retort-resistant composite film after compounding.

[0075] Comparative Example 1

[0076] Compared with Example 1, the polyolefin elastomer grafted anhydride was replaced with a polyolefin elastomer (melt mass flow rate 0.5 g / min; 2.6 kg, 230° C.), and the other raw materials and preparation process remained the same as those in Example 1.

[0077] Comparative Example 2

[0078] Compared with Example 1, this comparative example does not add a coupling agent to modify the layered filler, and the other raw materials and preparation process remain the same as those of Example 1.

[0079] Comparative Example 3

[0080] Compared with Example 1, the polyolefin elastomer grafted anhydride is replaced by a polyolefin elastomer (melt mass flow rate 0.5 g / min; 2.6 kg, 230° C.), and the coupling agent modified layered filler is replaced by a self-made coupling agent modified layered filler. The steps are as follows:

[0081] γ-methacryloxypropyltrimethoxysilane (5% by mass of montmorillonite) was dissolved in an ethanol aqueous solution (90% by volume), and then montmorillonite was added. After stirring for 15 minutes, the mixture was allowed to stand for 2 hours, filtered and dried to obtain a coupling agent-modified layered filler.

[0082] The remaining raw materials and preparation process remain the same as in Example 1.

[0083] Comparative Example 4

[0084] Compared with Example 1, in this comparative example, the polyolefin elastomer grafted anhydride is replaced with a polyolefin elastomer (melt mass flow rate 0.5 g / min; 2.6 kg, 230° C.), and no coupling agent-modified layered filler is added. The other raw materials and preparation process remain the same as in Example 1.

[0085] Comparative Example 5

[0086] Compared with Example 1, this comparative example does not add polyolefin elastomer graft anhydride, and the other raw materials and preparation process remain the same as those in Example 1.

[0087] The water vapor transmission rate of Examples 1 to 8 and Comparative Examples 1 to 5 was tested:

[0088] The water vapor transmission rate is tested according to the infrared detector method of GB / T26253-2010 Determination of water vapor transmission rate of plastic film and sheeting at a temperature of 23°C and a relative humidity of 85%:

[0089] The results are shown in Table 1:

[0090]

[0091] As can be seen from Table 1, the high barrier and retort-resistant transparent packaging film prepared by the present invention has good water vapor barrier properties. By adding the coupling agent-modified layered filler and the polyolefin elastomer grafted anhydride into the raw materials of the outer layer and the heat-sealing layer, the water vapor barrier properties of the high barrier and retort-resistant transparent packaging film are improved, but the use of untreated polyolefin elastomer (POE), the use of polyolefin elastomer grafted anhydride or the coupling agent-modified layered filler alone has limited effects. The coupling agent-modified layered filler and the polyolefin elastomer grafted anhydride form hydrogen bonds to enhance the system interface and reduce the interfacial tension, thereby improving the compatibility between the raw materials, which is manifested in the improvement of mechanical properties and barrier properties (water vapor barrier). In Comparative Example 1, polyolefin elastomer (POE) and the coupling agent-modified layered filler are added, and the dispersibility between the polyolefin elastomer (POE) and the coupling agent-modified layered filler is poor (compared with Example 1), and the barrier effect of the layered filler cannot be fully exerted, and the dispersion effect of the polyolefin elastomer (POE) is also affected. In Comparative Example 2, only polyolefin elastomer grafted anhydride was added. Unlike polyolefin elastomer (POE), polyolefin elastomer grafted anhydride has a stronger polarity and its mixing effect with the raw materials is not as good as that of polyolefin elastomer (POE). In Comparative Example 3, polyolefin elastomer (POE) and γ-methacryloxypropyltrimethoxysilane-modified filler were added, but the interfacial strength of the system could not be improved, so the improvement effect was also limited.

[0092] The test samples prepared in Example 1, Example 6 to Example 8 and Comparative Examples 1 to Comparative Examples 5 were tested to test their low-temperature mechanical properties; wherein the low-temperature mechanical properties refer to low-temperature tensile strength and elongation at break. Specifically, the film was placed in a freezer at -10°C for 24 hours, and the tensile strength and elongation at break were tested in accordance with GB / T1040.3-2006 "Determination of Tensile Properties of Plastics"; the results are shown in Table 2 below:

[0093]

[0094] In order to improve the problem that cast polypropylene becomes brittle and has poor tear strength and decreased mechanical properties due to low temperature, polyolefin elastomer grafted anhydride and coupling agent modified layered filler are added in the present invention, wherein hydrogen bonds are formed between the coupling agent modified layered filler and the polyolefin elastomer grafted anhydride to enhance the system interface and reduce the interfacial tension, thereby further improving the compatibility between the raw materials. In comparative example 3, a non-amino silane coupling agent is used, and the polyolefin elastomer grafted anhydride is replaced with a polyolefin elastomer. The interface effect between the coupling agent modified layered filler and the polyolefin elastomer is still relatively poor, but the effect is better than that of other comparative examples. Therefore, in the present invention, the coupling agent modified layered filler and the polyolefin elastomer grafted anhydride can have good compatibility and interfacial strength, thereby further improving the material performance. In summary, it can be seen from Tables 1 and 2 that under the action of polyolefin elastomer grafted anhydride and coupling agent modified layered filler, the barrier effect and mechanical properties of the packaging film samples are improved. Compared with the conventional solution using polyolefin elastomer (POE), not only the low temperature resistance is improved, but also the barrier performance is enhanced.

[0095] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0096] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high barrier and boiling resistant transparent packaging film, characterized in that: It comprises an outer layer, an intermediate layer and a heat-sealing layer connected in sequence by an adhesive, wherein the outer layer and the heat-sealing layer both comprise the following raw materials by weight: 70-80 parts of binary copolymer polypropylene, 16-18 parts of polyolefin elastomer grafted acid anhydride, 3.5-4 parts of coupling agent modified layered filler, and 0.4 parts of lubricant; The polyolefin elastomer grafted anhydride is prepared by the following steps: After uniformly mixing a polyolefin elastomer, an acid anhydride containing double bonds and an initiator, the mixture is subjected to reaction extrusion to obtain a polyolefin elastomer grafted with an acid anhydride; The coupling agent modified layered filler is prepared by the following steps: A silane coupling agent accounting for 5% of the mass of the layered filler is dissolved in an ethanol aqueous solution with a volume fraction of 90%, and then the layered filler is added, stirred for 15-20 minutes, allowed to stand for 1.5-2 hours, filtered and dried to obtain a coupling agent-modified layered filler; the silane coupling agent is an aminosilane coupling agent.

2. The high barrier and boiling resistant transparent packaging film according to claim 1, characterized in that: The lubricant is selected from at least one of erucamide, stearamide, calcium stearate, zinc stearate, polyethylene wax and polypropylene wax.

3. The high barrier and retort-resistant transparent packaging film according to claim 1, characterized in that: The mass ratio of the polyolefin elastomer, the acid anhydride containing double bonds and the initiator is 100:4-5:0.5-0.8; And / or, the screw speed during the reactive extrusion process is 250 r / min, and the temperatures of each section of the twin-screw extruder are set to 165°C, 170°C, 175°C, 180°C, 185°C, 185°C, 190°C, 190°C, 180°C.

4. The high barrier and retort-resistant transparent packaging film according to claim 1, characterized in that: The acid anhydride containing a double bond is selected from one of nadic anhydride, fumaric anhydride and alkenyl succinic anhydride.

5. The high barrier and retort-resistant transparent packaging film according to claim 1, characterized in that: The initiator is an organic peroxide initiator.

6. The high barrier and retort-resistant transparent packaging film according to claim 1, characterized in that: The layered filler is one of graphene oxide, montmorillonite, mica flakes and kaolin.

7. The method for preparing a high barrier and retort-resistant transparent packaging film according to any one of claims 1 to 6, characterized in that: The steps include: The first step is to weigh the raw materials of the outer layer and the heat-sealing layer, mix them respectively, heat them into a molten state, and then extrude, cast, cool, perform corona treatment, trim and roll them to obtain the outer layer and the heat-sealing layer; The second step is to use adhesive to perform solvent-free compounding of the outer layer, the heat-sealing layer and the middle layer.

8. The method for preparing a high barrier and retort-resistant transparent packaging film according to claim 7, characterized in that: The corona treatment power was 8 kW and the corona roller pressure was 3 bar.

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