High-water-resistance cooking polyolefin composite film and preparation method thereof

Abstract

The invention provides a high-water-resistance cooking polyolefin composite film and a preparation method thereof, and aims to solve the problems of low water resistance of the existing polyolefin film and cost rise and environmental protection caused by adding a water-resistant coating. The composite film sequentially comprises an outer surface layer (a two-way stretching polyolefin film), a water blocking layer (an interpenetrating network structure formed by polypropylene-polyacrylic acid segmented copolymer and polyvinyl alcohol grafted polyacrylamide), a heat insulation layer (a casting film containing polyolefin elastomer) and a heat sealing layer (a polyolefin film) from outside to inside. Through a specific preparation process, such as a multi-layer co-extrusion film blowing method, effective combination of all layers of materials is realized. The preparation method has the advantages that the water-blocking performance of the film is remarkably improved, the production cost is reduced, the environmental protection requirement is met, and the cyclic utilization of resources is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of composite films, and in particular to a polyolefin thin composite film, and more particularly to a high water barrier and retortable polyolefin thin composite film, and also relates to a preparation method of the composite film. Background Art

[0002] With the increasing requirements for the quality and safety of food, packaging materials need to have good barrier properties, high temperature resistance and other properties to extend the shelf life of food. Traditional packaging materials such as polyethylene and polypropylene films are widely used in packaging materials due to their low price and excellent processing performance. However, they have deficiencies in high-temperature retorting. Specifically, when polyethylene or polypropylene is at a relatively high temperature for a long time, it is prone to softening and deformation. Especially during the retorting process, water vapor will also penetrate into the package through polyethylene, etc. If the characteristic of high water barrier at high temperature is to be satisfied, materials such as aluminum foil or retortable coatings need to be added to the packaging material to achieve this.

[0003] The invention patent application with the publication number of CN113043688A discloses a high-barrier retortable skin stretchable environmentally friendly composite film, which is prepared by laminating a first and a second unidirectionally stretched polyolefin film, a polyvinylidene chloride film, and a polyurethane adhesive after corona treating both sides of the polyvinylidene chloride film online twice. However, the polyvinylidene chloride film contains halogens, and halogen groups may dissociate into liquid food, which is not conducive to health. In addition, the cost of packaging materials similar to those with water barrier coatings is also relatively high, and their applications are limited. Non-single-material packaging materials are also not conducive to environmental protection and recycling.

[0004] Therefore, it is necessary to develop a high water barrier and retortable polyolefin film to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to overcome the technical problems of insufficient water barrier performance of polyolefin films, the increase in cost caused by adding water barrier coatings, and the disadvantage of non-recycling.

[0006] To achieve the above purpose, the technical solution provided by the present invention is as follows: A high water barrier and retortable polyolefin composite film, comprising, from outside to inside in sequence: Outer surface layer: made of a biaxially stretched polyolefin film, preferably made of a BOPE or BOPP film; Water barrier layer: the raw material composition thereof includes a polypropylene - polyacrylic acid block copolymer and a polyvinyl alcohol grafted polyacrylamide, and the two polymers form an interpenetrating network structure. The term "interpenetrating network structure" refers to a polymer blend composed of two or more polymer networks that are crosslinked and interpenetrated with each other.

[0007] Heat insulation layer: A cast film containing polyolefin elastomer; the term "polyolefin elastomer" refers to a thermoplastic elastomer copolymerized from ethylene and propylene or other α-olefins, and the term "cast film" means that this film layer is made by the cast process, such as CPP (cast polypropylene) film.

[0008] Heat-sealing layer: As a preferred embodiment, a polyolefin film material with low-temperature heat-sealing is used. The function of low-temperature heat-sealing can be achieved by adding a plasticizer to the raw material of the heat-sealing layer. The heat-sealing layer is used to achieve the rapid sealing effect of the package.

[0009] Furthermore, the preparation method of the polypropylene-polyacrylic acid block copolymer includes, in a synthesis kettle, at 85 °C, 1 MPa air pressure, in an inert gas atmosphere, introducing propylene gas into an acrylic acid solution, adding initiator (A) and emulsifier and mixing evenly, keeping warm until the reaction is complete, then taking out the product from the solution, washing, and drying to constant weight to obtain the polypropylene-polyacrylic acid block copolymer.

[0010] Furthermore, the preparation method of the polyvinyl alcohol grafted polyacrylamide includes dissolving polyvinyl alcohol in deionized water, after heating and dissolving, adding acrylamide monomer and N,N'-methylenebisacrylamide crosslinking agent, and mixing evenly to obtain a prepolymer solution; then adding initiator (B) to the prepolymer solution, keeping warm until the reaction is complete, then taking out the product from the solution, washing, and drying to constant weight to obtain the polyvinyl alcohol grafted polyacrylamide.

[0011] Furthermore, the grafting rate of the polyvinyl alcohol grafted polyacrylamide ≥ 6%, preferably 6 - 9%.

[0012] Furthermore, the preparation method of the water-blocking layer includes adding the polypropylene-polyacrylic acid block copolymer and the polyvinyl alcohol grafted polyacrylamide to a mixing device according to a mass ratio of 1 - 3:1, adding initiator C, and the mass ratio of the polypropylene-polyacrylic acid block copolymer to initiator C is 100:1 - 3.

[0013] Initiators are used in both the polypropylene-polyacrylic acid block copolymer, the polyvinyl alcohol grafted polyacrylamide, and the water-blocking layer. Since free radical polymerization reactions can be achieved in all three reactions, initiators (A), (B), and (C) can all use free radical initiators such as azobisisobutyronitrile and benzoyl peroxide.

[0014] Furthermore, in the heat insulation layer, by mass percentage, it includes 65 - 75% of polyolefin matrix, 20 - 30% of polyolefin elastomer, and 2 - 5% of processing aids.

[0015] Furthermore, the heat insulation layer and / or the heat-sealing layer are made of high-density polyethylene (HDPE) or high-density polypropylene (HDPP).

[0016] Furthermore, 1,3-butadiene is added to the heat insulation layer and / or the heat sealing layer, and the mass ratio of the 1,3-butadiene to the polyolefin matrix is 2-5:100.

[0017] A method for preparing a high water barrier and retortable polyolefin film (multi-layer co-extrusion blown film method) includes the following steps: A method for preparing a high water barrier and retortable polyolefin film includes the following steps: S1, coating 5-12 mg / ㎡ of polyurethane glue between multi-layer films, and then dry laminating them into one body under a pressure of 3-15 bar; S2, aging the composite film for more than 48 h.

[0018] Furthermore, in S2, the aging temperature of the composite film is 25-60 °C.

[0019] The advantages and beneficial effects of the present invention are as follows: 1. By introducing two materials with good water barrier properties, namely polypropylene-polyacrylic acid block copolymer and polyvinyl alcohol grafted polyacrylamide, into the polyolefin film and forming an interpenetrating network structure between them, the water barrier property of the film is significantly improved. This structure can effectively prevent the penetration of water molecules and ensure that the products inside the package remain dry.

[0020] 2. Compared with the traditional method of adding a water barrier coating, the present invention directly adds water barrier materials during the film preparation process, avoiding additional coating steps, thereby reducing production costs. At the same time, since recyclable polyolefin materials are used, it also meets environmental protection requirements and is conducive to the recycling of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of the composite film provided by the present invention; In the figure: 1 - outer surface layer, 2 - water barrier layer, 3 - heat insulation layer, 4 - heat sealing layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention patent application provides a high water barrier and retortable polyolefin composite film, and its structural composition is as follows.

[0023] Outer surface layer: A biaxially oriented polyolefin film is used. This material has good mechanical strength, heat resistance and dimensional stability, and can provide basic physical property support for the composite film. The biaxial stretching process aligns the molecular chains in both the longitudinal and transverse directions, increasing the intermolecular interaction force, improving the barrier property and stiffness of the film.

[0024] Water-blocking layer: An interpenetrating network structure is formed by two copolymers, namely polypropylene-polyacrylic acid block copolymer and polyvinyl alcohol-grafted polyacrylamide. During the synthesis process, propylene gas is introduced into the acrylic acid solution, and an initiator and an emulsifier are added, and the reaction occurs at a certain temperature and pressure to generate polypropylene-polyacrylic acid block copolymer. The molecular chain contains the carboxyl group of polyacrylic acid. Through the way of block copolymerization, the molecular chain is arranged more closely and orderly, forming a dense water-blocking structure. Dissolve polyvinyl alcohol in deionized water, add acrylamide monomer and N,N'-methylenebisacrylamide crosslinking agent and mix evenly to obtain a prepolymer solution, and then add an initiator to react to obtain polyvinyl alcohol-grafted polyacrylamide. The hydroxyl group and amide group in this copolymer can respectively undergo esterification reaction and nucleophilic addition reaction with the carboxyl group (-COOH) of polyacrylic acid during the subsequent reaction to prepare the water-blocking layer. Among them, the esterification reaction forms an ester bond connecting the two types of polymers, and the nucleophilic addition reaction is the reaction of the carboxyl group with the amino group in the amide group to form an unstable intermediate, and then through mechanisms such as carbon chain rearrangement and elimination, an amide acid connecting the two polymers is generated, greatly improving the intermolecular force. The interpenetrating network structure formed by these two copolymers can improve the barrier ability to water molecules and hinder the penetration of water molecules. At the same time, polyvinyl alcohol-grafted polyacrylamide is also beneficial to the implementation of subsequent composite procedures and improves the processing characteristics during compounding.

[0025] Heat-insulating layer: A cast film containing polyolefin elastomer. The polyolefin elastomer has good flexibility and elasticity, and can absorb and buffer external heat to a certain extent, playing a role in heat insulation and reducing the direct impact of heat on the products inside the package. Specifically, an appropriate amount of polyolefin elastomer is added to the heat-insulating layer, which can enable the composite film to better resist deformation and rupture when subjected to external force impact or stretching, and maintain the integrity of the film. The molecular structure of the polyolefin elastomer is relatively tight, and the arrangement between molecular chains is relatively regular, which can hinder the penetration of small molecules such as water vapor to a certain extent. When it is compounded with other materials such as polyvinyl alcohol-grafted polyacrylamide, the barrier performance of the composite film can be further optimized, the water vapor transmission rate can be reduced, and the waterproof and moisture-proof effects can be better achieved, extending the shelf life of the packaged items. In addition, some polyolefin elastomers (such as ethylene-octene copolymer, styrene-based thermoplastic elastomer, etc.) have excellent low-temperature resistance and can still maintain good elasticity and flexibility in low-temperature environments. This enables the high-barrier water-steam-permeable polyolefin composite film to still effectively play its waterproof and moisture-proof functions under low-temperature storage or transportation conditions, and will not appear brittle or cracked due to temperature reduction, expanding the application range of the composite film.

[0026] Heat-sealing layer: The polyolefin film is used as the heat-sealing layer, which has good heat-sealing performance and can quickly melt and seal with the packaging container or other materials under heating conditions to ensure the tightness of the packaging.

[0027] The composite film shown in the present invention composes laminated materials with different functions together, such that water molecules need to pass through the obstruction of a multi-layer structure to permeate the composite film. By controlling the grafting ratio of polyvinyl alcohol grafted with polyacrylamide and adjusting the composition ratio of the heat-insulating layer, the permeation path is extended. Each layer of material has a certain resistance to the permeation of water molecules, and the combined effect of the multi-layer structure significantly improves the water-blocking performance. The materials of each layer cooperate with each other to form an integral barrier system. For example, the high water-blocking property of the water-blocking layer is combined with the physical barrier effect of the outer surface layer, the heat-insulating property of the heat-insulating layer reduces the risk of increased water molecule permeation caused by temperature changes, and the heat-sealing layer ensures the sealing integrity of the package and prevents water from entering from the edges of the package. The heat-insulating layer and / or the heat-sealing layer are made of high-density polyethylene or high-density polypropylene, which have a relatively high melting point and good thermal stability, and can maintain good sealing performance at high temperatures, ensuring that the items in the package will not deteriorate due to the permeation of water or gas.

[0028] A small amount of 1,3-butadiene is also added to the heat-insulating layer and / or the heat-sealing layer. As a conjugated diene, its molecular structure contains two double bonds. During the polymerization process, it can copolymerize with polyolefins to form a copolymer with a special elastic structure. Unsaturated double bonds are introduced into the main chain of this copolymer, forming side chains containing double bond structures, which increases the rotational freedom and mobility of the molecular chain. The interactions between these side chains and with the main chain increase the flexibility of the molecular chain. When the heat-insulating layer and the heat-sealing layer are in a high-temperature environment, such as during high-temperature treatments like steam sterilization, the polyolefins without the addition of 1,3-butadiene may experience a slight decrease in their steaming performance due to the violent movement of the molecular chain. After adding 1,3-butadiene, the stability of the molecular chain is enhanced, and it can maintain good physical properties at high temperatures, thus ensuring that the heat-insulating, sealing and other functions of the heat-insulating layer and the heat-sealing layer are hardly affected. In addition, adding an appropriate amount of 1,3-butadiene can change the melt viscosity of the polyolefin, enabling it to flow and spread better at the heat-sealing temperature.

[0029] The present invention also provides a method for preparing the above composite film. Among them, for the water-blocking layer, raw materials are put into an extruder for melt extrusion. The blown film method is adopted with a blow-up ratio of 3. After downward blowing, it is cooled to room temperature to cure the film structure. The dry lamination method is used to coat glue between multiple film materials and then roll and laminate them into one body. This method can precisely control the thickness and proportion of each layer, ensure uniform lamination between each layer of materials, and avoid problems such as delamination, bubbles, cracking, or wrinkles. At the same time, during the extrusion process of the water-blocking layer, the material is subjected to shear force and tensile force, and the molecular chains are further oriented and arranged, improving the performance of the film. The blank of the water-blocking layer is blown and cooled by the downward blowing method to form a composite film. The blowing process further stretches the molecular chains of the film in the transverse direction, increasing the transverse strength and barrier performance of the film. The cooling process fixes the shape and structure of the film, making it maintain good performance.

[0030] A preparation method of polypropylene-polyacrylic acid block copolymer. In a synthesis kettle, at 85°C, 1 MPa, in a nitrogen atmosphere, propylene gas is introduced into 500 mL of acrylic acid solution at a speed of 2 mL / s. 2 g of initiator (A) and 5 g of emulsifier (sodium dodecylbenzenesulfonate) are added thereto and mixed evenly. It is kept warm until the reaction is complete, and then the product is taken out of the solution, washed, and dried to constant weight.

[0031] A preparation method of polyvinyl alcohol grafted with polyacrylamide. 20 g of polyvinyl alcohol is dissolved in 500 mL of deionized water, which can be heated to 80°C and assisted by mechanical stirring for dissolution. After dissolution, 20 g of acrylamide monomer and 0.5 g of N,N'-methylenebisacrylamide crosslinking agent are added and mixed evenly to obtain a prepolymer solution; then 0.5 g of initiator (B) is added to the prepolymer solution, and it is kept warm until the reaction is complete. Then the product is taken out of the solution, washed, and dried to constant weight.

[0032] The following combines the drawings and examples to further describe the specific implementation manners of the present invention. The following examples are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0033] Example 1 A high water-blocking and retortable polyolefin composite film is provided, which is sequentially provided from outside to inside with: Outer surface layer: BOPE film; Water-blocking layer: By weight, its composition is as follows: 100 parts of polypropylene-polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted with polyacrylamide, 1 part of initiator C, and the grafting rate of polyvinyl alcohol grafted with polyacrylamide is 6%.

[0034] Heat-insulating layer: By mass percentage, its composition is: 65% of HDPE, 30% of EPM (ethylene-propylene copolymer rubber), 5% of processing aids (including 3% of slip agent and 2% of antiblocking agent), and the casting ratio is 1:2; Heat-sealing layer: HDPE film; The preparation method includes: S1, coat 5 mg / ㎡ of polyurethane glue between each layer of the multi-layer film, and then dry laminate them into one body under a pressure of 3 bar; S2, cure the composite film at 25 °C for 72 h.

[0035] Example 2 A high water-resistant and retortable polyolefin composite film is successively provided from outside to inside with: Outer surface layer: BOPP film; Water-blocking layer: by weight, it is composed of the following: 200 parts of polypropylene-polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted with polyacrylamide, 3 parts of initiator C, and the grafting rate of polyvinyl alcohol grafted with polyacrylamide is 7%.

[0036] Heat-insulating layer: by mass percentage, its composition is: 75% PE, 23% POE (ethylene-octene copolymer elastomer), 2% processing aids (including 1% slip agent and 1% anti-blocking agent), and the casting ratio is 1:3; Heat-sealing layer: PE film; The preparation method includes: S1, coat 8 mg / ㎡ of polyurethane glue between each layer of the multi-layer film, and then dry laminate them into one body under a pressure of 5 bar; S2, cure the composite film at 50 °C for 48 h.

[0037] Example 3 A high water-resistant and retortable polyolefin composite film is successively provided from outside to inside with: Outer surface layer: BOPE film; Water-blocking layer: by weight, it is composed of the following: 300 parts of polypropylene-polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted with polyacrylamide, 2 parts of initiator C, and the grafting rate of polyvinyl alcohol grafted with polyacrylamide is 8%.

[0038] Heat-insulating layer: by mass percentage, its composition is: 70% HDPE, 27% TPV (thermoplastic dynamic vulcanizate), 3% processing aids (including 2% slip agent and 1% anti-blocking agent), and the casting ratio is 1:5; Heat-sealing layer: PE film; The preparation method includes: S1, coat 7 mg / ㎡ of polyurethane glue between each layer of the multi-layer film, and then dry laminate them into one body under a pressure of 10 bar; S2, cure the composite film at 50 °C for 48 h.

[0039] Example 4 A high water - resistant and retortable polyolefin composite film is successively provided from outside to inside with: Outer surface layer: BOPP film; Water - resistant layer: By weight, its composition is as follows: 150 parts of polypropylene - polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted with polyacrylamide, 3 parts of initiator C, and the grafting rate of polyvinyl alcohol grafted with polyacrylamide is 8%.

[0040] Heat - insulating layer: By mass percentage, its composition is: 65% HDPE, 30% EPM (ethylene - propylene rubber), 5% processing aids (including 1% slip agent and 4% anti - blocking agent), and the casting ratio is 1:5; Heat - sealing layer: A film is co - extruded from 1,3 - butadiene and PE with a mass ratio of 5:100.

[0041] The preparation method includes: S1, Coating 12 mg / ㎡ of polyurethane glue between each layer of the multi - layer film, and then dry - laminating them into one body under a pressure of 12 bar; S2, Curing the composite film at 60 °C for 48 h.

[0042] Example 5 A high water - resistant and retortable polyolefin composite film is successively provided from outside to inside with: Outer surface layer: BOPE film; Water - resistant layer: By weight, its composition is as follows: 250 parts of polypropylene - polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted with polyacrylamide, 5 parts of initiator C, and the grafting rate of polyvinyl alcohol grafted with polyacrylamide is 8%.

[0043] Heat - insulating layer: By mass percentage, its composition is: 73.5% PE, 1.5% 1,3 - butadiene, 20% EPM (ethylene - propylene rubber), 5% processing aids (including 2% slip agent and 3% anti - blocking agent), and the casting ratio is 1:3; Heat - sealing layer: A film is co - extruded from 1,3 - butadiene and HDPE with a mass ratio of 2:100.

[0044] The preparation method includes: S1, Coating 10 mg / ㎡ of polyurethane glue between each layer of the multi - layer film, and then dry - laminating them into one body under a pressure of 15 bar; S2, Curing the composite film at 55 °C for 48 h.

[0045] Example 6 A high water - resistant and retortable polyolefin composite film is successively provided from outside to inside with: Outer surface layer: BOPP film; Water-blocking layer: By weight, its composition is as follows: 300 parts of polypropylene-polyacrylic acid block copolymer, 100 parts of polyvinyl alcohol grafted polyacrylamide, 2 parts of initiator C, and the grafting rate of polyvinyl alcohol grafted polyacrylamide is 7%.

[0046] Heat-insulating layer: By mass percentage, its composition is: HDPE 62.7%, 1,3-butadiene 3.3%, POE (ethylene-octene copolymer elastomer) 30%, 4% processing aids (including 2% slip agent and 2% antiblocking agent), and the casting ratio is 1:2; Heat-sealing layer: HDPE film; The preparation method includes: S1, coat 12 mg / ㎡ of polyurethane glue between each layer of the multi-layer film, and then dry laminate them together under a pressure of 10 bar; S2, cure the composite film at 55 °C for 48 h.

[0047] For each of the above embodiments, the water vapor transmission rate was tested in accordance with 《ASTM F 1249-13》; the heat-sealing strength was tested in accordance with 《GB / T19787-2005》; after heat-sealing and enclosing the edges of the composite film in each embodiment to make a packaging bag, it was filled with water containing pigment, and the packaging bag was placed in a pot and steamed for 20 min. It was considered qualified if no bag breakage or leakage occurred.

[0048] The test results are as follows in the table: The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high water-resistant and retortable polyolefin composite film, comprising, from outside to inside in sequence: Outer surface layer: The outer surface layer is made of a biaxially oriented polyethylene film or a biaxially oriented polypropylene film; Water-blocking layer: The water-blocking layer comprises a polypropylene-polyacrylic acid block copolymer and a polyvinyl alcohol-grafted polyacrylamide, and the two polymers form an interpenetrating network structure; Heat-insulating layer: The heat-insulating layer is a cast film containing a polyolefin matrix and a polyolefin elastomer; Heat-sealing layer: The heat-sealing layer is made of polyethylene or polypropylene.

2. The high water-resistant and retortable polyolefin composite film according to claim 1, wherein: The preparation method of the polypropylene-polyacrylic acid block copolymer comprises: in a synthesis kettle, at 85°C and 1 MPa air pressure, in an inert gas atmosphere, introducing propylene gas into an acrylic acid solution, adding an initiator (A) and an emulsifier thereto and mixing evenly, keeping warm until the reaction is complete, then taking out the product from the solution, washing, and drying to constant weight to obtain the polypropylene-polyacrylic acid block copolymer.

3. The high water-resistant and retortable polyolefin composite film according to claim 1, wherein: The preparation method of the polyvinyl alcohol-grafted polyacrylamide comprises: heating and dissolving polyvinyl alcohol in deionized water, adding acrylamide monomers and an N,N'-methylenebisacrylamide crosslinking agent, and mixing evenly to obtain a prepolymer solution; then adding an initiator (B) to the prepolymer solution, keeping warm until the reaction is complete, then taking out the product from the solution, washing, and drying to constant weight to obtain the polyvinyl alcohol-grafted polyacrylamide.

4. The high water-resistant and retortable polyolefin composite film according to claim 3, wherein: The grafting rate of the polyvinyl alcohol-grafted polyacrylamide is 6%-9%.

5. The high water-resistant and retortable polyolefin composite film according to claim 1, wherein: The preparation method of the water-blocking layer comprises: adding the polypropylene-polyacrylic acid block copolymer and the polyvinyl alcohol-grafted polyacrylamide into a mixing device according to a mass ratio of 1-3:1, adding an initiator (C), and the mass ratio of the polyvinyl alcohol-grafted acrylamide to the initiator (C) is 100:1-3.

6. The high water-blocking and retortable polyolefin composite film according to claim 1, wherein: By mass percentage, the heat-insulating layer comprises 65-75% of a polyolefin matrix, 20-30% of a polyolefin elastomer, and 2-5% of a processing aid.

7. The high-barrier water-resistant retortable polyolefin composite film according to any one of claims 1-6, characterized in that: The heat-insulating layer and / or the heat-sealing layer is made of high-density polyethylene or high-density polypropylene.

8. The high-barrier water-resistant retortable polyolefin composite film according to any one of claims 1-6, characterized in that: 1,3-Butadiene is further added to the heat-insulating layer and / or the heat-sealing layer, and the mass ratio of the 1,3-butadiene to the polyolefin matrix is 2-5:

100.

9. A method for preparing a high water-resistant and retortable polyolefin film as described in claim 1, characterized in that, Comprising the following steps: S1, coating 5-12 mg / ㎡ of polyurethane glue between the multi-layer films, and then dry laminating them into one body under a pressure of 3-15 bar; S2, aging the composite film for more than 48 h.

10. The preparation method of the high water-resistant and retortable polyolefin composite film according to claim 9, characterized in that: The aging temperature of the composite film in S2 is 25-60°C.

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