A fully biodegradable multilayer paper-plastic composite film for food and a preparation method and application thereof

Abstract

The application provides a full-biodegradable multilayer paper-plastic composite film for food and a preparation method and application thereof. The composite film comprises, in sequence, a corona layer, an adhesive layer, a barrier layer, a paper layer and a heat sealing layer. The blend of high-molecular-weight polypropylene carbonate (PPCH) and PBAT is used as the barrier layer, so that the water and oxygen barrier properties of the composite film can be effectively improved; the low-molecular-weight polypropylene carbonate (PPCL) hot melt adhesive is used as the adhesive layer, so that the adhesion and barrier effects can be achieved. In addition, the multilayer paper-plastic composite film provided by the application uses raw materials with the full-biodegradable characteristic, so that the environmental friendliness is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of food packaging technology, specifically relating to a fully biodegradable multilayer paper-plastic composite film for food, its preparation method, and its application. Background Technology

[0002] Traditional petroleum-based plastics are difficult to degrade naturally in the environment. In recent years, with the increasing awareness of environmental protection, seeking biodegradable alternatives to alleviate the increasingly serious environmental problems has become a research hotspot. Currently, among many biodegradable plastics, polylactic acid (PLA), polybutylene terephthalate (PBAT), and polypropylene carbonate (PPC) have attracted much attention due to their good biodegradability.

[0003] Food packaging films are essential for preserving food's freshness and nutritional value, making them a indispensable item in the food industry. Traditional food packaging films are primarily made of PP or PE resin composites, offering puncture resistance and high strength, but generally lacking high barrier properties and biodegradability. This necessitates special collection and treatment to prevent environmental pollution. Furthermore, most food packaging films use paper-plastic composites, and the adhesives used contain organic solvents, resulting in solvent residues in the composite film that can be harmful to human health when used to package food.

[0004] In contrast, biodegradable plastics can achieve or even surpass the performance of traditional plastics in certain aspects, and they also have similar applications in terms of practicality. For example, in terms of mechanical properties, PLA has high tensile strength and modulus similar to PP, while PBAT has high toughness and tear resistance similar to PE. However, PLA and PBAT generally perform poorly in terms of gas barrier properties, significantly lagging behind PP and PE, which limits their application in high-barrier packaging materials.

[0005] Based on the above problems, US 4133784 modified PE by blending ethylene-acrylic acid copolymer with starch. However, due to the high starch content and poor compatibility, the barrier properties of the film decreased. CN 202011645101.6 used PLA as the matrix layer and polyvinyl alcohol (PVA) as the adhesive layer to improve the barrier properties of the film. However, PVA is not water-resistant, resulting in poor water vapor barrier properties. At the same time, the cost is high and the process is complex.

[0006] Therefore, finding a biodegradable food packaging film with good barrier properties remains an urgent problem to be solved. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a fully biodegradable multilayer paper-plastic composite film for food, its preparation method, and its application. The composite film possesses excellent biodegradability and barrier properties.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a fully biodegradable multilayer paper-plastic composite film for food, characterized in that it comprises, in sequence, a corona layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer.

[0010] Preferably, the adhesive layer comprises PPCL, which is a first MMA-co-GMA copolymer modified polypropylene carbonate, wherein the mass ratio of MMA to GMA in the first MMA-co-GMA5 copolymer is (80~90):(10~20).

[0011] Preferably, both the barrier layer and the heat-sealing layer comprise PPCH and PBAT, wherein the PPCH is polypropylene carbonate modified with a second MMA-co-GMA copolymer, and the mass ratio of MMA to GMA in the second MMA-co-GMA copolymer is (91~99):(1~9).

[0012] Preferably, the mass ratio of MMA to GMA in the first MMA-co-GMA copolymer is 90:10.

[0013] Preferably, the mass ratio of MMA to GMA in the second MMA-co-GMA5 copolymer is 95:5.

[0014] Preferably, the Mn of the first MMA-co-GMA copolymer is 6.0 × 10⁻⁶. 4 ~7.0×10 4 Mw is 12.0 × 10 4 ~13.5×10 4 The PDI is 1.8~2.5.

[0015] Preferably, the Mn of the second MMA-co-GMA copolymer is 7.2 × 10⁻⁶. 4 ~9.0×10 4 Mw is 14.0 × 10 4 ~16.0×10 4 The PDI is 1.8~2.5.

[0016] Preferably, the Mn of the PPCH is 25 × 10⁻⁶. 5 ~40×10 5 Mw is 55×10 5 ~70.0×10 5The PDI is 1.8~2.5.

[0017] Preferably, the Mn of the PPCL is 10 × 10 5 ~15×10 5 Mw is 20×10 5 ~30.0×10 5 The PDI is 1.8~2.5.

[0018] Preferably, the corona layer comprises toughening agent-modified polylactic acid.

[0019] Preferably, the toughening agent is selected from one or more of the following: core-shell particles (e.g., MBS, Methyl methacrylate-Butadiene-Styrene, a terpolymer of methyl methacrylate (M), butadiene (B), and styrene (S); ACR: a core-shell polymer with butyl acrylate (BA) as the core and methyl methacrylate (MMA) as the shell), acrylate compounds, epoxy compounds, or polyolefin copolymers.

[0020] Preferably, the thickness of the corona layer is 20~30 μm, more preferably 25 μm.

[0021] Preferably, the thickness of the barrier layer is 10~20 μm, more preferably 15 μm.

[0022] Preferably, the thickness of the heat-sealed layer is 10~20 μm, more preferably 15 μm.

[0023] Preferably, the thickness of the adhesive layer is 5~10 μm, more preferably 5 μm.

[0024] Preferably, an ink layer is further disposed between the corona layer and the adhesive layer.

[0025] Preferably, the thickness of the ink layer is 5~10 μm, more preferably 5 μm.

[0026] Secondly, the present invention also provides a method for preparing the above-mentioned fully biodegradable multilayer paper-plastic composite film for food, comprising the following steps:

[0027] A barrier layer and a heat-sealed layer are laminated on both sides of the paper layer by means of coating and bonding.

[0028] An adhesive layer is formed on the side of the barrier layer away from the paper layer;

[0029] After laminating an optional ink layer onto the adhesive layer, a corona layer is then laminating the ink layer.

[0030] Specifically, the barrier layer and the heat-sealing layer are both formed by blending and casting PPCH and PBAT into a film, and then laminated onto both sides of the paper layer by a coating process.

[0031] The adhesive layer comprises PPCL adhesive, which can be formed by coating the barrier layer on the side away from the paper layer with PPCL adhesive using a coating machine.

[0032] The ink layer is bonded to the adhesive layer by means of adhesion.

[0033] After applying adhesive to the ink layer, a corona layer is then laminated onto the adhesive.

[0034] Thirdly, the present invention also provides a packaging film, wherein the above-mentioned technical solution involves a fully biodegradable multilayer paper-plastic composite film for food.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] This invention provides a multilayer paper-plastic composite film, comprising, in sequence, a corona layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Specifically, this invention uses a blend of high molecular weight polypropylene carbonate (PPCH) and PBAT as the barrier layer, which effectively improves the water and oxygen barrier properties of the composite film; it uses low molecular weight polypropylene carbonate (PPCL) hot melt adhesive as the adhesive layer, which increases the bonding strength between layers while improving barrier properties; and it uses a blend of high molecular weight polypropylene carbonate (PPCH) and PBAT as the heat-sealing layer, which effectively improves the heat-sealing strength and sealing performance. Furthermore, the corona layer further enhances the corona resistance of the composite film.

[0037] The multilayer paper-plastic composite film provided by this invention uses raw materials that are fully biodegradable, which greatly improves its environmental friendliness. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the fully biodegradable multilayer paper-plastic composite film for food prepared in Examples 1-4 of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] This invention provides a fully biodegradable food-grade multilayer paper-plastic composite film, comprising, in sequence, a corona layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer.

[0041] In this invention, since corona treatment is required during the preparation of the composite film, a corona layer is preferably provided on the outer surface of the composite film to improve the printability and composite performance of the film. In this invention, the corona layer is made of toughening agent-modified polylactic acid (PLA) to improve the toughness and tear resistance of the film; the toughening agent is selected from any one or more of core-shell particles, acrylate compounds, epoxy compounds, or polyolefin copolymers, specifically core-shell particles.

[0042] In this invention, the thickness of the corona layer is generally 20~30 μm, preferably 22~28 μm, and more preferably 25 μm.

[0043] In some embodiments of the present invention, the corona layer is prepared by biaxial stretching of modified PLA to form a biaxially stretched film (BOPLA).

[0044] For example, the following steps are included:

[0045] PLA was melt-extruded with toughening agents of different compositions using a twin-screw extruder. The screw speed was 200 rpm, the feed rate was 30 kg / h, and the barrel temperature was set to 190°C. o C. Then, the PLA is processed into 0.5 mm sheets using a specialized sheeting machine, with the barrel temperature set at 180°C. o C up to 200 o C-segment setting, die head temperature set to 200 o C. The prepared sheet is then processed into a film using a bistretching apparatus at a stretching speed of 1 m / min, resulting in a film thickness of 25 μm.

[0046] The specific parameters set above can be adjusted within a reasonable range.

[0047] In this invention, the adhesive layer is made of low molecular weight polypropylene carbonate (PPCL), and the Mn of the PPCL is 10 × 10⁻⁶. 5 ~15×10 5 Preferably 12×10 5 ~14×10 5 Mw is 20×10 5 ~30.0×10 5 Preferably 22×10 5 ~28.0×10 5 The PDI is 1.8~2.5, preferably 1.9~2.2. The thickness of the adhesive layer is generally 3~5 μm, preferably 3.5~4 μm.

[0048] Specifically, in some embodiments of the present invention, the PPCL is obtained by modifying polypropylene carbonate (i.e., PPC) with a first MMA-co-GMA copolymer.

[0049] The first MMA-co-GMA copolymer is a low molecular weight MMA-co-GMA copolymer, and the Mn of the first MMA-co-GMA copolymer is 6.0 × 10⁻⁶. 4 ~7.0×10 4 Preferably 6.5×10 4 ~7.0×10 4 Mw is 12.0 × 10 4 ~13.5×10 4 Preferably 12.5×10 4 ~13.4×10 4 The PDI is 1.8~2.5, preferably 1.9~2.2.

[0050] In some embodiments of the present invention, the mass ratio of MMA to GMA in the first MMA-co-GMA copolymer is (80~90):(10~20), preferably (85~90):(10~15), and more preferably 90:10.

[0051] In some embodiments of the present invention, PPCL is preferably obtained in the following manner:

[0052] PPC and the first MMA-co-GMA in 60 o The sample was dried in a vacuum oven at C for 12 h, and then processed by a twin-screw extruder through melt extrusion reaction.

[0053] The parameters for the twin-screw extruder are set as follows:

[0054] Screw speed: 200 rpm, length-to-diameter ratio: 52, feeding speed: 30 kg / h;

[0055] The temperature settings for each zone of the barrel are as follows:

[0056] Zone 1: 80 o C, Zone 2: 130 o C, Zone 3: 180 o C, Zone 4: 190 o C, Zone 5: 190 o C, Zone 6: 190 o C, Zone 7: 190 o C, Zone 8: 190 o C, Zone 9: 190 o C.

[0057] During the above reaction process, the epoxy functional groups in the first MMA-co-GMA copolymer undergo ring-opening reactions with the carboxyl and hydroxyl groups in PPC, resulting in chain extension or network structures. The chemical reaction process is shown below, which is the main reason for the change in the molecular weight of PPC.

[0058] ;

[0059] .

[0060] The present invention uses the above-mentioned low molecular weight polypropylene carbonate as an adhesive layer, which not only facilitates the application of adhesive but also provides a certain barrier function.

[0061] In this invention, the barrier layer is a mixture of high molecular weight polypropylene carbonate (PPCH) and PBAT. The mass ratio of PPCH to PBAT is (50~100):(0~50), specifically 100:0, 90:10, 80:20, 70:30, 60:40, or 50:50.

[0062] In this invention, the Mn of the PPCH is 25 × 10⁻⁶. 5 ~40×10 5 Preferably 27×10 5 ~35×10 5 Mw is 55×10 5 ~70.0×10 5 Preferably 60×10 5 ~68×10 5 The PDI is 1.8~2.5, preferably 1.9~2.2. The thickness of the barrier layer is 10~20 μm, preferably 12~18 μm, and more preferably 15 μm.

[0063] Specifically, in some embodiments of the present invention, the PPCH is obtained by modifying PPC with a second MMA-co-GMA copolymer, and the modification process is described above.

[0064] The second MMA-co-GMA copolymer is a high molecular weight MMA-co-GMA copolymer, and the Mn of the second MMA-co-GMA copolymer is 7.2 × 10⁻⁶. 4 ~9.0×10 4 Preferably 7.5×10 4 ~8.5×10 4 Mw is 14.0 × 10 4 ~16.0×10 4 The preferred value is 14.2 × 10⁻⁶. 4 ~15.5×104 The PDI is 1.8~2.5, preferably 1.9~2.2.

[0065] In some embodiments of the present invention, the mass ratio of MMA to GMA in the second MMA-co-GMA copolymer is (91~99):(1~9), preferably 95:5.

[0066] The present invention uses the above-mentioned high molecular weight polypropylene carbonate as a barrier layer, which can effectively improve the water and oxygen barrier properties of the material.

[0067] In this invention, the paper layer is specifically kraft paper, and its thickness is not specifically limited.

[0068] In this invention, when the composite film is used as a packaging film, a heat-sealing layer is provided to ensure the adhesion between the composite film and the substrate being packaged. Simultaneously, the heat-sealing layer also improves heat-sealing strength and enhances sealing performance. The heat-sealing layer is a mixture of high molecular weight polypropylene carbonate (PPCH) and PBAT. The mass ratio of PPCH to PBAT is (50~100):(0~50), specifically 100:0, 90:10, 80:20, 70:30, 60:40, or 50:50.

[0069] In this invention, the thickness of the heat-sealed layer is 10~20 μm, preferably 12~18 μm, and more preferably 15 μm.

[0070] The thickness of the adhesive layer is 5~10 μm, preferably 5~8 μm, and more preferably 5 μm.

[0071] It should be noted that in some embodiments of the present invention, an ink layer is further provided between the corona layer and the adhesive layer, depending on actual needs.

[0072] In some embodiments of the present invention, the fully biodegradable food-grade multilayer paper-plastic composite film comprises, in sequence, a corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer.

[0073] This invention also provides a method for preparing the above-mentioned fully biodegradable multilayer paper-plastic composite film for food, comprising the following steps:

[0074] A barrier layer and a heat-sealed layer are laminated on both sides of the paper layer by means of coating and bonding.

[0075] An adhesive layer is formed on the side of the barrier layer away from the paper layer;

[0076] After laminating an ink layer onto the adhesive layer, a corona layer is then laminating the ink layer.

[0077] Specifically, the barrier layer and the heat-sealing layer are both formed by blending and casting PPCH and PBAT into a film, and then laminated onto both sides of the paper layer by means of coating and bonding.

[0078] The adhesive layer comprises PPCL adhesive, which can be formed by coating the barrier layer on the side away from the paper layer with PPCL adhesive using a coating machine.

[0079] The ink layer is laminated onto the adhesive layer by ink printing. After applying adhesive to the ink layer, a corona layer is laminated onto the adhesive, preferably a biaxially oriented laminar flow (BOPLA) film.

[0080] In the preparation method provided by this invention, the corona layer and the adhesive layer are bonded together, which ensures that the thickness of each layer is uniform and dense, and has a high degree of mechanization, enabling continuous production. At the same time, the barrier layer is also formed into a composite film by coating, thus forming a continuous and dense barrier and light-shielding layer. This avoids the problem of uneven distribution caused by insufficient PPC melt strength in traditional blend film preparation, resulting in excellent barrier performance.

[0081] This invention also provides a packaging film comprising the fully biodegradable multilayer paper-plastic composite film for food described above. The packaged material can be grains, dried fruits, or other moisture-absorbing and light-sensitive foods.

[0082] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0083] Preparation Example 1 - Preparation of a copolymer of methyl methacrylate and glycidyl methacrylate (abbreviated as: MMA-co-GMA copolymer)

[0084] MMA-co-GMA copolymers were prepared using a continuous solution polymerization method. First, a mixture of two-thirds MMA (methyl methacrylate), GMA (glycidyl methacrylate), toluene, and an initiator (di-tert-butyl peroxide) was pre-charged into the reactor. Then, the mixture was heated to 155°C using an oil bath. o C. Begin continuous polymerization. The remaining one-third of the mixture of MMA, GMA, toluene, and initiator is continuously injected into the reactor at a rate of 500 mL / h using a feed pump. Simultaneously, the reaction product in the reactor is continuously pumped into a twin-screw extruder at the same rate as the feed pump to remove solvent and residual monomer. The MMA-co-GMA melt is then cooled and granulated. The MMA-co-GMA copolymer prepared in this example and its molecular properties are shown in Table 1, where PDI refers to molecular weight distribution.

[0085] Table 1

[0086]

[0087] Preparation Example 2 - Preparation of High Molecular Weight Polypropylene Carbonate (PPCH)

[0088] PPC was mixed with MMA-co-GMA5 obtained in Preparation Example 1 at 60°C. o After drying in a vacuum oven for 12 h, the mixture was processed by a twin-screw extruder through melt extrusion reaction to obtain PPCH;

[0089] The parameter settings for the twin-screw extruder are as follows:

[0090] Screw speed: 200 rpm, length-to-diameter ratio: 52, feeding speed: 30 kg / h;

[0091] The temperature settings for each zone of the barrel are as follows:

[0092] Zone 1: 80 o C, Zone 2: 130 o C, Zone 3: 180 o C, Zone 4: 190 o C, Zone 5: 190 o C, Zone 6: 190 o C, Zone 7: 190 o C, Zone 8: 190 o C, Zone 9: 190 o C.

[0093] Preparation Example 3 - Preparation of Low Molecular Weight Polypropylene Carbonate (PPCL)

[0094] The MMA-co-GMA10 obtained in Preparation Example 1 was prepared at 60°C. o After drying in a vacuum oven for 12 h, the mixture was processed by a twin-screw extruder through melt extrusion reaction to obtain PPCL;

[0095] The parameter settings for the twin-screw extruder are the same as in Preparation Example 2.

[0096] The molecular weights and molecular weight distributions of PPCH and PPCL obtained in Preparation Examples 2 and 3 above are shown in Table 2 below:

[0097] Table 2

[0098]

[0099] Preparation Example 4 - Preparation of a Highly Transparent Corona Layer

[0100] PLA and MBS were melt-extruded using a twin-screw extruder at a screw speed of 200 rpm, a feed rate of 30 kg / h, and a barrel temperature of 190°C. oC. Then, the PLA is processed into 0.5 mm sheets using a specialized sheeting machine, with the barrel temperature set at 180°C. o C up to 200 o C-segment setting, die head temperature set to 200 o C. The prepared sheet is then processed into a biaxially oriented polylactic acid (BOPLA) film using a biaxial stretching device at a stretching speed of 1 m / min. The BOPLA film thickness is 25 μm. The film is then set aside for later use.

[0101] Example 1

[0102] This invention provides a fully biodegradable multilayer paper-plastic composite film for food, the structural schematic of which is shown below. Figure 1 As shown, the structure comprises the following six layers stacked sequentially: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. The high-transparency corona layer is a toughening agent-modified BOPLA film obtained in Preparation Example 3, with a thickness of 25 μm; the adhesive layer is made of PPCL adhesive, with a thickness of 5 μm; the barrier layer is made of a PPCH / PBAT blend film with a weight ratio of 100:0 and a thickness of 15 μm; the heat-sealing layer is made of a PBAT / PPCH blend film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer has a thickness of 100 μm, and the ink layer has a thickness of 5 μm.

[0103] The preparation method is as follows:

[0104] (1) First, according to the above proportions, PPCH and PBAT are blended in different proportions and then melt-extruded to prepare PPCH / PBAT blends. Then, barrier layers are laminated on one side of the paper layer using a paper-plastic coating extruder. The parameters of the paper-plastic coating extruder are set as follows:

[0105] Zone 1: 80℃, Zone 2: 130℃, Zone 3: 180℃, Zone 4: 190℃, Zone 5: 190℃, Zone 6: 190℃, Zone 7: 190℃, Zone 8: 190℃, Zone 9: 190℃;

[0106] The die head has five temperature zones, with the temperature controlled at 230℃.

[0107] (2) Apply hot melt adhesive PPCL to the side of the barrier layer away from the paper layer using a coating device to form an adhesive layer;

[0108] (3) The designed patterns, texts, etc. are printed on the adhesive layer to form an ink layer;

[0109] (4) After applying glue to the ink layer with a coating machine, the corona layer is glued to the ink layer to finally obtain a fully biodegradable food multilayer paper-plastic composite film.

[0110] Example 2

[0111] A fully biodegradable multilayer paper-plastic composite film for food, as shown in the schematic diagram below. Figure 1 As shown, the structure comprises the following six layers stacked sequentially: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. The high-transparency corona layer is a toughening agent-modified BOPLA film obtained in Preparation Example 3, with a thickness of 25 μm; the adhesive layer is made of PPCL adhesive, with a thickness of 5 μm; the barrier layer is made of a PPCH / PBAT blend film with a weight ratio of 80:20 and a thickness of 15 μm; the heat-sealing layer is made of a PBAT / PPCH blend film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer has a thickness of 100 μm, and the ink layer has a thickness of 5 μm.

[0112] The preparation method is the same as in Example 1.

[0113] Example 3

[0114] A fully biodegradable multilayer paper-plastic composite film for food, as shown in the schematic diagram below. Figure 1 As shown, the structure comprises the following six layers stacked sequentially: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. The high-transparency corona layer is a toughening agent-modified BOPLA film obtained in Preparation Example 3, with a thickness of 25 μm; the adhesive layer is made of PPCL adhesive, with a thickness of 5 μm; the barrier layer is made of a PPCH / PBAT blend film with a weight ratio of 70:30 and a thickness of 15 μm; the heat-sealing layer is made of a PBAT / PPCH blend film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer has a thickness of 100 μm, and the ink layer has a thickness of 5 μm.

[0115] The preparation method is the same as in Example 1.

[0116] Example 4

[0117] A fully biodegradable multilayer paper-plastic composite film for food, as shown in the schematic diagram below. Figure 1 As shown, the structure comprises the following six layers stacked sequentially: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. The high-transparency corona layer is a toughening agent-modified BOPLA film obtained in Preparation Example 3, with a thickness of 25 μm; the adhesive layer is made of PPCL adhesive, with a thickness of 5 μm; the barrier layer is made of a PPCH / PBAT blend film with a weight ratio of 60:40 and a thickness of 15 μm; the heat-sealing layer is made of a PBAT / PPCH blend film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer has a thickness of 100 μm, and the ink layer has a thickness of 5 μm.

[0118] The preparation method is the same as in Example 1.

[0119] Example 5

[0120] A fully biodegradable multilayer paper-plastic composite film for food, as shown in the schematic diagram below. Figure 1 As shown, the structure comprises the following six layers stacked sequentially: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. The high-transparency corona layer is a toughening agent-modified BOPLA film obtained in Preparation Example 3, with a thickness of 25 μm; the adhesive layer is made of PPCL adhesive, with a thickness of 5 μm; the barrier layer is made of a PPCH / PBAT blend film with a weight ratio of 50:50 and a thickness of 15 μm; the heat-sealing layer is made of a PBAT / PPCH blend film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer has a thickness of 100 μm, and the ink layer has a thickness of 5 μm.

[0121] The preparation method is the same as in Example 1.

[0122] Barrier performance test

[0123] The oxygen permeability and water vapor permeability of the composite membrane obtained above were tested according to the GB / T1038-2000 standard.

[0124] Among them, the oxygen permeability is ≤3 cm 3 / (m 2 A pressure of 0.1 MPa (24 h) indicates excellent oxygen barrier performance, with a range of 3-10 cm. 3 / (m 2 A pressure of 0.1 MPa (24 h) indicates good oxygen barrier properties, and the pressure ranges from 10 to 50 cm. 3 / (m 2 • 24 h • 0.1 MPa) indicates good oxygen barrier properties, 50~100 cm 3 / (m 2 A pressure of 0.1 MPa (24 h) indicates that the oxygen barrier properties are acceptable, ≥100 cm. 3 / (m 2 (24h·0.1 MPa) indicates poor oxygen barrier properties.

[0125] Water vapor transmission rate ≤10 g / m 2 • 24 h indicates excellent water vapor barrier performance, 10~20 g / m 2 • 24 h indicates good water vapor barrier properties, 20~50 g / m 2 • 24 h indicates good water vapor barrier properties, 50~100 g / m 2 • 24 h indicates that the nitrogen barrier performance is qualified, ≥100 g / m 2 • 24 h indicates poor water vapor barrier properties.

[0126] The test results are shown in Table 1 below:

[0127] Table 3

[0128]

[0129] As can be seen from Table 1, the composite film provided by the present invention combines a biodegradable layer and a barrier layer with paper, and has the advantages of low water and oxygen permeability, good barrier properties, and good preservation.

[0130] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fully biodegradable multilayer paper-plastic composite film for food, characterized in that, It consists of the following layers stacked in sequence: corona layer, adhesive layer, barrier layer, paper layer, and heat-sealed layer; The adhesive layer comprises PPCL, which is polypropylene carbonate modified with a first MMA-co-GMA copolymer, wherein the mass ratio of MMA to GMA in the first MMA-co-GMA copolymer is (80~90):(10~20); and the Mn of the PPCL is 10×10⁻⁶. 5 ~15×10 5 Mw is 20×10 5 ~30.0×10 5 The PDI is 1.8~2.5; Both the barrier layer and the heat-sealing layer comprise PPCH and PBAT. The PPCH is polypropylene carbonate modified with a second MMA-co-GMA copolymer, wherein the mass ratio of MMA to GMA in the second MMA-co-GMA copolymer is (91~99):(1~9); and the Mn of the PPCH is 25×10⁻⁶. 5 ~40×10 5 Mw is 55×10 5 ~70.0×10 5 The PDI is 1.8~2.

5.

2. The fully biodegradable multilayer paper-plastic composite film for food as described in claim 1, characterized in that, The mass ratio of MMA to GMA in the first MMA-co-GMA copolymer is 90:10; The mass ratio of MMA to GMA in the second MMA-co-GMA copolymer is 95:

5.

3. The fully biodegradable multilayer paper-plastic composite film for food according to claim 1 or 2, characterized in that, The Mn of the first MMA-co-GMA copolymer is 6.0 × 10⁻⁶. 4 ~7.0×10 4 Mw is 12.0 × 10 4 ~13.5×10 4 The PDI is 1.8~2.5; The Mn of the second MMA-co-GMA copolymer is 7.2 × 10⁻⁶. 4 ~9.0×10 4 Mw is 14.0 × 10 4 ~16.0×10 4 The PDI is 1.8~2.

5.

4. The fully biodegradable multilayer paper-plastic composite film for food according to claim 1, characterized in that, The corona layer comprises toughening agent-modified polylactic acid; The toughening agent is selected from any one or more of core-shell particles, acrylate compounds, epoxy compounds, or polyolefin copolymers.

5. The fully biodegradable multilayer paper-plastic composite film for food according to claim 1, characterized in that, The thickness of the corona layer is 20~30 μm; The thickness of the barrier layer is 10~20 μm; The thickness of the heat-sealed layer is 10~20 μm; The thickness of the adhesive layer is 5~10 μm.

6. The fully biodegradable multilayer paper-plastic composite film for food according to claim 1, characterized in that, An ink layer is also provided between the corona layer and the adhesive layer.

7. The fully biodegradable multilayer paper-plastic composite film for food according to claim 6, characterized in that, The thickness of the ink layer is 5~10 μm.

8. A method for preparing a fully biodegradable multilayer paper-plastic composite film for food as described in any one of claims 1 to 7, characterized in that, Includes the following steps: A barrier layer and a heat-sealed layer are respectively laminated on both sides of the paper layer by coating and bonding. An adhesive layer is formed on the side of the barrier layer away from the paper layer; After laminating an optional ink layer onto the adhesive layer, a corona layer is then laminating the ink layer.

9. A packaging film, characterized in that, The fully biodegradable multilayer paper-plastic composite film for food as described in any one of claims 1 to 7, or the fully biodegradable multilayer paper-plastic composite film for food prepared by the preparation method according to claim 8.

Images