Multi-layer paper-plastic composite film for full-biodegradable food as well as preparation method and application of multi-layer paper-plastic composite film

Abstract

The invention provides a multilayer paper-plastic composite film for full-biodegradable food as well as a preparation method and application of the multilayer paper-plastic composite film. The composite film comprises a corona layer, a bonding layer, a blocking layer, a paper layer and a heat sealing layer which are stacked in sequence. According to the invention, a 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; and a low-molecular-weight polypropylene carbonate (PPCL) hot melt adhesive is used as the bonding layer, so that a bonding effect and a barrier effect can be achieved. In addition, according to the multilayer paper-plastic composite film provided by the invention, the adopted raw materials have the characteristic of full biodegradation, so that the environmental friendliness of the multilayer paper-plastic composite film is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging, and in particular relates to a multi-layer paper-plastic composite film for fully biodegradable food, and a preparation method and application thereof. Background Art

[0002] Traditional petroleum-based plastic products are difficult to degrade naturally in the ecological environment. In recent years, with the improvement of people's environmental awareness, seeking biodegradable alternatives to alleviate the increasingly serious environmental problems has become a research hotspot. At present, among many biodegradable plastics, polylactic acid (abbreviated as: PLA), polybutylene terephthalate adipate (abbreviated as: PBAT), and carbon dioxide copolymer polypropylene carbonate (abbreviated as: PPC) have attracted much attention due to their good biodegradability.

[0003] Food packaging film can be used to package and store food to ensure the freshness and nutrition of food, and has become an indispensable item in the food industry. Traditional food packaging films are mainly made of PP or PE resin composites, which have puncture resistance and high strength properties, but generally do not have high barrier and degradation properties, resulting in the need for special collection and treatment of packaging films to avoid environmental pollution. In addition, most food packaging films use paper-plastic composite films, and the glue used contains organic solvents, resulting in solvent residues in the composite film, which is harmful to the human body when packaging food.

[0004] On the other hand, biodegradable plastics can achieve or exceed the performance of traditional plastics in certain characteristics, and also have similar applications in practicality. For example, in terms of mechanical properties, PLA has higher tensile strength and modulus similar to PP, and PBAT has higher toughness and tear resistance similar to PE, but PLA and PBAT have average performance in gas barrier properties, which is much different from PP and PE, limiting 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, but the high starch content and poor compatibility resulted in decreased barrier properties of the film. CN 202011645101.6 used PLA as the base layer and polyvinyl alcohol (PVA) as the adhesive layer to improve the barrier properties of the film, but PVA is not water-resistant and has poor water vapor barrier properties. It also has high costs and complex processes.

[0006] Therefore, seeking a biodegradable food packaging film with good barrier properties is still an urgent problem to be solved. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a fully biodegradable multi-layer paper-plastic composite film for food and a preparation method and application thereof. The composite film has excellent degradability and barrier properties.

[0008] To achieve this object, the present invention adopts the following technical solutions:

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

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

[0011] Preferably, the barrier layer and the heat-sealing layer both include PPCH and PBAT, the PPCH is polypropylene carbonate modified by 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 4 ~7.0×10 4 , Mw is 12.0×10 4 ~13.5×10 4 , PDI is 1.8~2.5.

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

[0016] Preferably, the Mn of the PPCH is 25×10 5 ~40×10 5 , Mw is 55×10 5 ~70.0×10 5, 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 , 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 any one or more of core-shell particles (such as MBS, Methyl methacrylate-Butadiene-Styrene, which is a terpolymer of methyl methacrylate (abbreviated as: M), butadiene (abbreviated as: B) and styrene (abbreviated as: S); ACR: a core-shell structure polymer with butyl acrylate (abbreviated as: BA) as the core and methyl methacrylate (abbreviated as: MMA) as the shell), acrylic acid ester 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-sealing 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 provided 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] In a second aspect, the present invention further provides a method for preparing the above-mentioned fully biodegradable multi-layer paper-plastic composite film for food, comprising the following steps:

[0027] The barrier layer and the heat-sealing layer are respectively compounded on both sides of the paper layer by laminating and bonding;

[0028] forming an adhesive layer on a side of the barrier layer away from the paper layer;

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

[0030] Specifically, the barrier layer and the heat-sealing layer are formed by casting a blend of PPCH and PBAT and then laminated on both sides of the paper layer.

[0031] The adhesive layer includes PPCL adhesive, and can be formed by coating the PPCL adhesive on the side of the barrier layer away from the paper layer using a coater.

[0032] The ink layer is compounded on the adhesive layer by bonding.

[0033] After glue is applied on the ink layer, a corona layer is compounded on the glue.

[0034] In a third aspect, the present invention further provides a packaging film, wherein the above technical solution relates to a multi-layer paper-plastic composite film for fully biodegradable food.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention provides a multilayer paper-plastic composite film, which includes: a corona layer, an adhesive layer, a barrier layer, a paper layer and a heat-sealing layer stacked in sequence. Among them, the present invention uses a blend of high molecular weight polypropylene carbonate (PPCH) and PBAT as a barrier layer, which can effectively improve the water and oxygen barrier properties of the composite film; uses a low molecular weight polypropylene carbonate (PPCL) hot melt adhesive as an adhesive layer, which can increase the bonding strength between layers while improving the barrier properties; uses a blend of high molecular weight polypropylene carbonate (PPCH) and PBAT as a heat-sealing layer, which can effectively improve the heat-sealing strength and increase the sealing performance. In addition, the provision of the corona layer can further improve the corona resistance of the composite film.

[0037] The multi-layer paper-plastic composite film provided by the present invention uses raw materials that are fully biodegradable, thereby greatly improving its environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the multi-layer paper-plastic composite film for fully biodegradable food prepared in Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with 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.

[0040] The invention provides a multi-layer paper-plastic composite film for fully biodegradable food, which comprises: a corona layer, an adhesive layer, a barrier layer, a paper layer and a heat-sealing layer which are stacked in sequence.

[0041] In the present invention, since corona treatment is required in the preparation process of the composite film, the present invention preferably provides a corona layer on the outer surface of the composite film to improve the printing performance and composite performance of the film. In the present invention, the material of the corona layer is polylactic acid (i.e., PLA) modified by a toughening agent 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, and specifically core-shell particles can be selected.

[0042] In the present 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, during the preparation of the corona layer, a biaxially stretched film BOPLA is prepared by using modified PLA through a biaxially stretched method.

[0044] Exemplarily, the steps include:

[0045] PLA and toughening agents of different components were melt extruded through a twin-screw extruder with a screw speed of 200 rpm, a feed rate of 30 kg / h, and a barrel temperature of 190 o C. Then, PLA was made into 0.5 mm thin sheets through a dedicated sheet making machine, and the barrel temperature was increased from 180 o C up to 200 o C segment setting, die head temperature is set to 200 o C. The prepared sheet was made into a film by a double-stretching device, with a stretching speed of 1 m / min and a film thickness of 25 μm.

[0046] The specific parameters of the above settings can be adjusted within a reasonable range.

[0047] In the present invention, the material of the adhesive layer is low molecular weight polypropylene carbonate (abbreviated as PPCL), and the Mn of the PPCL is 10×10 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 , 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 (ie, 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 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 ; 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 First MMA-co-GMA at 60 o The samples were dried in a vacuum oven at 4000 C for 12 h and then processed by melt extrusion reaction using a twin-screw extruder.

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

[0054] Screw speed: 200 rpm, aspect ratio: 52, feeding rate: 30 kg / h;

[0055] The temperature settings of 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 VI: 190 o C, District 7: 190 o C, Zone 8: 190 o C, District 9: 190 o C.

[0057] In the above reaction process, the epoxy functional groups in the first MMA-co-GMA copolymer undergo a ring-opening reaction with the carboxyl and hydroxyl groups in PPC to produce a chain extension or network structure. 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 low molecular weight polypropylene carbonate as the adhesive layer, which is convenient for glue coating and can not only play an adhesive role but also play a certain barrier role.

[0061] In the present invention, the material of the barrier layer is a mixture of high molecular weight polypropylene carbonate (PPCH for short) 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 the present invention, the Mn of the PPCH is 25×10 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 , 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 thereof refers to the above-mentioned related content.

[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 4 ~9.0×10 4 , preferably 7.5×10 4 ~8.5×10 4 , Mw is 14.0×10 4 ~16.0×10 4 , preferably 14.2×10 4 ~15.5×104 , 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 high molecular weight polypropylene carbonate as a barrier layer, which can effectively improve the water and oxygen barrier properties of the material.

[0067] In the present invention, the paper layer is specifically kraft paper, and the thickness thereof is not particularly limited.

[0068] In the present invention, when the composite film is used as a packaging film, in order to ensure the adhesion between the composite film and the packaged substrate, the composite film is provided with a heat-sealing layer. At the same time, the heat-sealing layer can also improve the heat-sealing strength and increase the sealing performance. The material of the heat-sealing layer is a mixture of high molecular weight polypropylene carbonate (abbreviated as: 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 the present invention, the thickness of the heat-sealing 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 according to actual needs.

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

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

[0074] The barrier layer and the heat-sealing layer are respectively compounded on both sides of the paper layer by laminating and bonding;

[0075] forming an adhesive layer on a side of the barrier layer away from the paper layer;

[0076] After the ink layer is laminated on the adhesive layer, a corona layer is laminated on the ink layer.

[0077] Specifically, the barrier layer and the heat-sealing layer are formed by casting a blend of PPCH and PBAT, and then laminated on both sides of the paper layer by laminating and bonding.

[0078] The adhesive layer includes PPCL adhesive, and can be formed by coating the PPCL adhesive on the side of the barrier layer away from the paper layer using a coater.

[0079] The ink layer is compounded on the adhesive layer by ink printing. After glue is applied on the ink layer, a corona layer is compounded on the glue, and the corona layer is preferably a double-stretched film BOPLA.

[0080] In the preparation method provided by the present invention, the corona layer and the adhesive layer are bonded to ensure uniform and fine thickness of each layer, and the mechanization degree is high, and continuous production is possible. At the same time, the barrier layer is also formed into a composite film by laminating to form a continuous and dense barrier and light-shielding layer, avoiding the problem of insufficient PPC melt strength in the traditional blend film making and uneven distribution in the film preparation process, so the barrier performance is good.

[0081] The present invention also provides a packaging film, which includes the multi-layer paper-plastic composite film for fully biodegradable food involved in the above technical solution, wherein the packaged material can be grains, dried fruits and other foods that are easy to absorb moisture and afraid of light.

[0082] In order to further illustrate the present invention, the following examples are provided for detailed description. The experimental raw materials used in the following examples of the present invention are all common 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 by continuous solution polymerization. First, two-thirds of a mixture of MMA (methyl methacrylate), GMA (glycidyl methacrylate), toluene, and an initiator (di-tert-butyl peroxide) was pre-charged into the reactor, and then the mixture was heated to 155°C in an oil bath. o C, and continuous polymerization begins. The remaining one-third of the MMA, GMA, toluene, and initiator mixture is continuously injected into the reactor by a feed pump at a rate of 500 mL / h, and the reaction product in the reactor is continuously pumped into a twin-screw extruder by a melt pump at the same rate as the feed pump to remove the solvent and residual monomers, and then the MMA-co-GMA melt is cooled into balls. The MMA-co-GMA copolymer prepared in this preparation example and its molecular properties are shown in Table 1, and PDI refers to molecular weight distribution.

[0085] Table 1

[0086]

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

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

[0089] The parameters of the twin-screw extruder are set as follows:

[0090] Screw speed: 200 rpm, aspect ratio: 52, feeding rate: 30 kg / h;

[0091] The temperature settings of 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 VI: 190 o C, District 7: 190 o C, Zone 8: 190 o C, District 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 heated to 60 o After drying in a vacuum oven at C for 12 h, the mixture was processed by melt extrusion reaction using a twin-screw extruder to obtain PPCL;

[0095] The parameter settings of the twin-screw extruder were the same as those in Preparation Example 2.

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

[0097] Table 2

[0098]

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

[0100] PLA and MBS were melt extruded through a twin-screw extruder with a screw speed of 200 rpm, a feed rate of 30 kg / h, and a barrel temperature of 190 oC. Then, PLA was made into 0.5 mm thin sheets through a dedicated sheet making machine, and the barrel temperature was increased from 180 o C up to 200 o C segment setting, die head temperature is set to 200 o C. The prepared sheet is made into a biaxially oriented polylactic acid film (referred to as BOPLA film) through a double-stretching device, the stretching speed is 1 m / min, and the BOPLA film thickness is 25 μm, and it is set aside.

[0101] Example 1

[0102] The present invention provides a multi-layer paper-plastic composite film for fully biodegradable food, the structural schematic diagram of which is shown in Figure 1 As shown, the following six layers are stacked in sequence: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Among them, 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 glue with a thickness of 5 μm; the barrier layer is made of PPCH / PBAT blended film with a weight ratio of 100:0 and a thickness of 15 μm; the heat-sealing layer is made of PBAT / PPCH blended film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer is 100 μm thick, and the ink layer is 5 μm thick.

[0103] The preparation method is as follows:

[0104] (1) First, according to the above ratio, PPCH and PBAT are blended in different ratios and then melt-extruded to prepare the PPCH / PBAT blend, and then a barrier layer is laminated on one side of the paper layer by a paper-plastic laminating extruder; the parameters of the paper-plastic laminating 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, and the temperature is controlled at 230°C;

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

[0108] (3) Printing the designed pattern, text, etc. on the adhesive layer by ink to form an ink layer;

[0109] (4) After applying glue on the ink layer using a coating machine, the corona layer is glued to the ink layer, and finally a multi-layer paper-plastic composite film for fully biodegradable food is obtained.

[0110] Example 2

[0111] The present invention is a fully biodegradable multi-layer paper-plastic composite film for food, the structural schematic diagram of which is as follows Figure 1 As shown, the following six layers are stacked in sequence: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Among them, 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 glue, with a thickness of 5 μm; the barrier layer is made of PPCH / PBAT blended film, with a weight ratio of 80:20 and a thickness of 15 μm; the heat-sealing layer is made of PBAT / PPCH blended film, with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer is 100 μm thick, and the ink layer is 5 μm thick.

[0112] The preparation method is similar to that of Example 1.

[0113] Example 3

[0114] The present invention is a fully biodegradable multi-layer paper-plastic composite film for food, the structural schematic diagram of which is as follows Figure 1 As shown, it includes the following six layers stacked in sequence: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Among them, 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 glue with a thickness of 5 μm; the barrier layer is made of PPCH / PBAT blended film with a weight ratio of 70:30 and a thickness of 15 μm; the heat-sealing layer is made of PBAT / PPCH blended film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer is 100 μm thick, and the ink layer is 5 μm thick.

[0115] The preparation method is similar to that of Example 1.

[0116] Example 4

[0117] The present invention is a fully biodegradable multi-layer paper-plastic composite film for food, the structural schematic diagram of which is as follows Figure 1 As shown, it includes the following six layers stacked in sequence: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Among them, 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 glue, with a thickness of 5 μm; the barrier layer is made of PPCH / PBAT blended film, with a weight ratio of 60:40 and a thickness of 15 μm; the heat-sealing layer is made of PBAT / PPCH blended film, with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer is 100 μm thick, and the ink layer is 5 μm thick.

[0118] The preparation method is similar to that of Example 1.

[0119] Example 5

[0120] The present invention is a fully biodegradable multi-layer paper-plastic composite film for food, the structural schematic diagram of which is as follows Figure 1 As shown, the following six layers are stacked in sequence: a high-transparency corona layer, an ink layer, an adhesive layer, a barrier layer, a paper layer, and a heat-sealing layer. Among them, 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 glue with a thickness of 5 μm; the barrier layer is made of PPCH / PBAT blended film with a weight ratio of 50:50 and a thickness of 15 μm; the heat-sealing layer is made of PBAT / PPCH blended film with a weight ratio of 50:50 and a thickness of 15 μm; the paper layer is 100 μm thick, and the ink layer is 5 μm thick.

[0121] The preparation method is similar to that of Example 1.

[0122] Barrier performance test

[0123] The oxygen permeability and water vapor permeability of the composite film obtained above were tested in accordance with the GB / T1038-2000 standard.

[0124] Among them, the oxygen permeability is ≤3 cm 3 / (m 2 ·24 h·0.1 MPa) indicates that the oxygen barrier performance is very good, 3~10cm 3 / (m 2 ·24 h·0.1 MPa) indicates good oxygen barrier properties, 10~50 cm 3 / (m 2 ·24 h·0.1 MPa) indicates good oxygen barrier properties, 50~100 cm 3 / (m 2 ·24 h·0.1 MPa) indicates that the oxygen barrier property is qualified, ≥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 very good water vapor barrier performance, 10~20 g / m 2 24 h indicates good water vapor barrier, 20~50 g / m 2 24 h indicates good water vapor barrier, 50~100 g / m 2 24 h indicates that the nitrogen barrier property 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] It can be seen from Table 1 that the composite film provided by the present invention, in which the degradable layer and the barrier layer are composited by paper, has the advantages of low water and oxygen permeability, good barrier properties, and good freshness preservation.

[0130] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fully biodegradable multi-layer paper-plastic composite film for food, characterized in that: It includes: a corona layer, an adhesive layer, a barrier layer, a paper layer and a heat-sealing layer stacked in sequence; The adhesive layer includes PCL, the PPCL is polypropylene carbonate modified by a first MMA-co-GMA copolymer, and the mass ratio of MMA to GMA in the first MMA-co-GMA copolymer is (80-90):(10-20); The barrier layer and the heat-sealing layer both include PPCH and PBAT, wherein the PPCH is polypropylene carbonate modified by 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).

2. The fully biodegradable multi-layer paper-plastic composite film for food according to 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 multi-layer 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 4 ~7.0×10 4 , Mw is 12.0×10 4 ~13.5×10 4 , PDI is 1.8~2.5; The Mn of the second MMA-co-GMA copolymer is 7.2×10 4 ~9.0×10 4 , Mw is 14.0×10 4 ~16.0×10 4 , PDI is 1.8~2.

5.

4. The fully biodegradable multi-layer paper-plastic composite film for food according to any one of claims 1 to 3, characterized in that: The Mn of the PPCH is 25×10 5 ~40×10 5 , Mw is 55×10 5 ~70.0×10 5 , PDI is 1.8~2.5; The Mn of the PPCL is 10×10 5 ~15×10 5 , Mw is 20×10 5 ~30.0×10 5 , PDI is 1.8~2.

5.

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

6. The fully biodegradable multi-layer paper-plastic composite film for food according to any one of claims 1 to 5, 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-sealing layer is 10-20 μm; The thickness of the adhesive layer is 5-10 μm.

7. The fully biodegradable multi-layer paper-plastic composite film for food according to any one of claims 1 to 6, characterized in that: An ink layer is also arranged between the corona layer and the adhesive layer.

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

9. A method for preparing a fully biodegradable multilayer paper-plastic composite film for food as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: The barrier layer and the heat-sealing layer are respectively compounded on both sides of the paper layer by laminating and bonding; forming an adhesive layer on a side of the barrier layer away from the paper layer; After laminating an optional ink layer on the adhesive layer, a corona layer is laminated on the ink layer.

10. A packaging film, characterized in that: The invention comprises the fully biodegradable multi-layer paper-plastic composite film for food according to any one of claims 1 to 8 or the fully biodegradable multi-layer paper-plastic composite film for food prepared by the preparation method according to claim 9.

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