A low-carbon high-barrier biodegradable composite film and its preparation method

Abstract

The present invention belongs to the field of polymer films. The present invention relates to a low-carbon, high-barrier biodegradable composite film and a preparation method thereof. The composite film comprises a five-layer film, which includes, in order, a surface substrate layer, a high-barrier layer, an adhesive layer, a transition layer, and an inner substrate layer; the high-barrier layer is vacuum-deposited with aluminum oxide; the surface substrate layer and the high-barrier layer are prepared by double-layer co-extrusion and biaxial stretching, and the high-barrier layer is vacuum-coated; the adhesive layer, the transition layer, and the inner substrate layer are prepared by three-layer co-extrusion and film blowing, wherein the high-barrier layer and the adhesive layer are dry-compounded and aged to obtain a composite film; the composite film can effectively solve the defects of the existing degradable packaging film, such as poor water vapor and oxygen barrier properties and reduced transparency after multi-layer composite, and can reduce carbon emissions by more than 50% compared with traditional composite films.

Description

Technical Field

[0001] The present invention relates to a low-carbon high-barrier biodegradable composite film and a preparation method thereof, and belongs to the field of polymer films. Background Art

[0002] High-barrier packaging film materials offer barrier properties against oxygen and water vapor, extending the shelf life of their contents. They are widely used in packaging for food, pharmaceuticals, cosmetics, and other applications. Food packaging is currently the most widely used application for high-barrier materials. High-barrier packaging films offer a combination of attractive print quality, excellent barrier properties, and outstanding heat-sealing capabilities. However, a single material cannot typically meet all performance requirements. Therefore, current high-barrier packaging films are typically composite films composed of multiple materials, the most typical being a PET / aluminum foil / PE structure, with PA, EVOH, PP, and other materials also being used.

[0003] Given this, multi-layer composite high-barrier packaging materials bring a wealth of convenience to our lives. However, they also place a significant burden on the environment, contributing to severe "white pollution." After several years of practice, biodegradation is recognized as the most fundamental solution to the "white pollution" problem caused by discarded high-barrier composite films.

[0004] Among biodegradable materials, polylactic acid (PLA) is an aliphatic polyester that naturally decomposes into CO2 and water under composting conditions, making it a green and environmentally friendly biodegradable material. It is also the only transparent biodegradable polymer and is used in transparent packaging containers and daily necessities. While PLA boasts excellent biodegradability, processability, and mechanical properties, its brittleness, lack of elasticity, and flexibility significantly limit its application in PLA films. Polybutylene adipate terephthalate (PBAT) exhibits excellent biodegradability, along with good ductility, elongation at break, and impact resistance, but its water vapor barrier properties are relatively poor. Both PLA and PBAT exhibit excellent biodegradability, whether used alone or in blends. However, blending requires addressing compatibility issues. Poor compatibility not only significantly reduces mechanical properties but also compromises film transparency. For food packaging, transparency, allowing for clear visibility of the contents, is a key selling point.

[0005] In addition, the commonly used multi-layer composite films need to achieve water vapor barrier properties (<1 g / m 2 ▪d), oxygen barrier properties (<0.5 cm 3 / m 2▪d ▪0.1MPa), usually requires vacuum coating and then compounding to obtain a composite film. Multi-layer film composites require multiple compounding and aging processes. At the same time, the traditional dry composite aging process needs to be placed at 50-60℃ for about 48 hours, which seriously affects production efficiency and generates large carbon emissions.

[0006] In view of the above problems, modifying PLA and PBAT and combining them with two-step multi-layer co-extrusion, vacuum coating and composite process to prepare low-carbon and high-barrier biodegradable composite films has become a feasible solution. Summary of the Invention

[0007] The purpose of the present invention is to address the defects of the degradable packaging films in the prior art, such as poor water vapor and oxygen barrier properties and reduced transparency after multi-layer composite, and to provide a low-carbon high-barrier biodegradable composite film and its preparation method. It uses homemade plasticizers, compatibilizers and bonding aids to be applied to the corresponding film layers in the composite film. After formula design, the surface substrate layer and the high-barrier layer are first added to the extruder for double-layer co-extrusion and biaxial stretching to prepare composite film A, and the high-barrier layer is vacuum-coated; at the same time, the adhesive layer, transition layer, and inner substrate layer are subjected to three-layer co-extrusion blown film to obtain composite film B, and finally the composite film A and the composite film B are dry-compounded to obtain a low-carbon high-barrier biodegradable composite film. The technical solution adopted by the present invention to solve its technical problems is:

[0008] The present invention provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, which includes a surface substrate layer, a high-barrier layer, an adhesive layer, a transition layer, and an inner substrate layer in sequence; the high-barrier layer is treated with vacuum-evaporated aluminum oxide;

[0009] The surface substrate layer comprises the following raw materials in parts by weight:

[0010] PLA 80-90 parts;

[0011] PBAT 10-20 parts;

[0012] 10-15 parts of plasticizer;

[0013] 1.0-3.0 parts of compatibilizer;

[0014] 0.3-0.5 parts of antioxidant;

[0015] 0.1-0.2 parts of lubricant;

[0016] Among them, the total mass of PLA and PBAT is 100 parts;

[0017] The high barrier layer comprises the following raw materials in parts by weight:

[0018] PLA 70-90 parts;

[0019] PPC-P 10-30 copies;

[0020] 8-12 parts of plasticizer;

[0021] 1.0-2.0 parts of compatibilizer;

[0022] 0.1-0.5 parts of antioxidant;

[0023] 0.1-0.2 parts of lubricant;

[0024] Among them, the total mass of PLA and PPC-P is 100 parts;

[0025] The bonding layer comprises the following raw materials in parts by weight:

[0026] PVAc 90-95 parts;

[0027] PBAT 5-10 parts;

[0028] 0.2-0.5 parts of antioxidant;

[0029] 0.2-0.3 parts of lubricant;

[0030] Among them, the total mass of PVAc and PBAT is 100 parts;

[0031] The transition layer comprises the following raw materials in parts by weight:

[0032] PBAT 100 units;

[0033] 10-20 parts of nanosheet-shaped inorganic filler;

[0034] 0.1-0.3 parts of antioxidant;

[0035] 0.1-0.2 parts of lubricant;

[0036] The inner substrate layer comprises the following raw materials in parts by weight:

[0037] PBAT 100 units;

[0038] 3.0-5.0 parts of bonding agent;

[0039] 1.0-4.0 parts of anti-hydrolysis agent;

[0040] 0.1-0.3 parts of antioxidant;

[0041] 0.5-1.0 parts of lubricant;

[0042] The preparation method of the plasticizer comprises the following steps:

[0043] S11, coupling reaction of a bulky sterically hindered phosphorus chloride with hydroxy acrylate A to obtain intermediate 1I;

[0044] The phosphorus chloride with large steric hindrance and hydroxy acrylate A are added at a molar ratio of chlorine atoms to hydroxyl groups of 1:1;

[0045] S12, subjecting the intermediate product 1I to a Michael addition reaction with an alcoholamine to obtain a target product, i.e., a plasticizer;

[0046] The intermediate product 1I and the alcoholamine are added at a molar ratio of acryloyloxy to amino of 1:1;

[0047] The preparation method of the compatibilizer comprises the following steps:

[0048] S21, coupling reaction of nano-silicon with epoxy silane coupling agent to obtain intermediate product 2I;

[0049] The usage ratio of the nano-silicon to the epoxy silane coupling agent is 1g:5.0-7.0g;

[0050] S22, subjecting the intermediate product 2I to a ring-opening reaction with an aminopolyethylene glycol amino group to obtain the intermediate product 2II;

[0051] The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2;

[0052] S23, reacting the intermediate product 2II with diisocyanate to obtain the target product, i.e., the compatibilizer;

[0053] The intermediate product 2II and diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2;

[0054] The preparation method of the bonding auxiliary agent comprises the following steps:

[0055] S31, performing a ring-opening reaction between an epoxy ring-opening agent containing catechol and an epoxy alkene to obtain an intermediate product 3I;

[0056] The catechol-containing epoxy ring-opener and the epoxy alkene are added at a molar ratio of 1:1 between the epoxy ring-opener and the epoxy group;

[0057] S32, subjecting vinyl acetate, a silane coupling agent containing a carbon-carbon double bond, hydroxy acrylate B, and the intermediate product 3I to free radical polymerization to obtain a target product, i.e., an adhesive additive;

[0058] The usage ratio of the vinyl acetate, the silane coupling agent containing a carbon-carbon double bond, the hydroxy acrylate B, and the intermediate product 3I is 0.1-0.3 mol: 0.2-0.4 mol: 0.1-0.3 mol: 0.2-0.4 mol.

[0059] Furthermore, the bulky steric group is an adamantyl group.

[0060] Furthermore, the number of acryloyloxy functional groups in the hydroxy acrylate A is ≥2.

[0061] Furthermore, the molecular weight of the amino polyethylene glycol amino group is 400-1000.

[0062] Furthermore, the catechol-containing epoxy ring-opener has a structure containing a carboxyl group or an amino group.

[0063] Another object of the present invention is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, comprising the following steps:

[0064] S41, co-extrusion of surface substrate layer and high barrier layer, i.e.

[0065] The raw materials are mixed uniformly according to the formula and placed in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding are performed to obtain composite film A;

[0066] S42, coating treatment of composite film A, namely

[0067] The high barrier layer of composite film A was subjected to corona treatment and vacuum evaporation of aluminum oxide.

[0068] S43, co-extruded blown film of adhesive layer, transition layer and inner substrate layer, i.e.

[0069] The raw materials are mixed uniformly according to the formula, and placed in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding are performed to obtain composite film B; and

[0070] S44, composite treatment, i.e.

[0071] The aluminum oxide-plated surface of the composite film A is composited with the adhesive surface of the composite film B and subjected to aging treatment to obtain the target product, i.e., a low-carbon high-barrier biodegradable composite film.

[0072] Further,

[0073] The transverse stretching ratio of the biaxial stretching is 3.0-5.0, the longitudinal stretching ratio is 3.0-5.0, and the stretching rate is 50-60% / s.

[0074] Furthermore, the aluminum oxide coating has a thickness of 10-50 nm.

[0075] Further,

[0076] The composite process is dry composite, and the composite adhesive includes the following raw materials in parts by weight:

[0077] 50 parts of polyether polyol;

[0078] 5-20 parts of curing agent;

[0079] 5.0-10.0 parts of bonding agent;

[0080] 40-60 parts of ethyl acetate.

[0081] Furthermore, the aging treatment is performed at a aging temperature of 40-50° C. and a aging time of 18-24 hours.

[0082] Beneficial effects of the present invention:

[0083] (1) The present invention provides a low-carbon high-barrier biodegradable composite film, wherein a self-made plasticizer and compatibilizer are added to the composite film A. The plasticizer is a large sterically hindered polyhydroxy small molecule structure. On the one hand, the small molecule polyhydroxy structure has an excellent plasticizing effect and can effectively improve the processing performance and toughness of the composite film; on the other hand, the large steric hindered group gives the plasticizer excellent low migration. The compatibilizer is a long-chain hyperbranched structure with nano-silicon as the core and isocyanate group end capping. First, the long-chain structure is conducive to its effective dispersion in a system mainly composed of PLA; second, the isocyanate group structure can have a high reaction rate with the hydroxyl group in PLA, PBAT, etc., has an excellent reaction chain extension effect, and can improve the mechanical properties; third, the long-chain structure has excellent flexibility and can effectively improve the toughness of the composite film. At the same time, through the synergistic effect of the plasticizer and the compatibilizer, the processability and mechanical properties of PLA can be effectively improved.

[0084] (2) The present invention provides a low-carbon, high-barrier biodegradable composite film, wherein a self-made bonding agent is added to the inner substrate layer and the adhesive in the composite film B, which is an organic polymer chain containing silane, acetate, hydroxyl, and catechol structures. In the inner substrate layer, the bonding agent can migrate to the interface and improve the heat sealing strength of the inner substrate layer during the heat sealing process. In the adhesive, first, the silane structure can enrich it at the interface and improve the bonding strength with the coating; second, the catechol structure has excellent bonding strength and can significantly improve the bonding strength between the coating and the bonding layer; third, the hydroxyl group can participate in the curing process of the polyurethane glue and further improve the bonding strength; fourth, the acetate can provide its bonding strength with the bonding layer and improve the solubility of the bonding agent in the solvent.

[0085] (3) The present invention provides a method for preparing a low-carbon and high-barrier biodegradable composite film. First, the surface substrate layer and the high-barrier layer are double-layer co-extruded and biaxially stretched to prepare a composite film A. On the one hand, compared with the single extrusion, stretching and then composite process, the effect can be effectively improved, and it has a low-carbon and energy-saving effect; on the other hand, biaxial stretching can improve the crystallinity, thereby improving the mechanical properties and barrier properties; second, the high-barrier surface of the composite film A is vacuum-deposited with a nanometer thickness, while improving the barrier properties and maintaining excellent transparency; third, the adhesive layer of PVAc provides additional adhesion to the coating surface on the one hand; on the other hand, it can further improve the barrier properties as a barrier layer; in addition, it can protect the coating surface from damage; fourth, the composite film B is prepared by three-layer co-extrusion and blown film, with mature technology and strong operability; fifth, the composite film A and the composite film B are prepared by dry composite, and the adhesive is modified, the aging cycle is short, and the low-carbon property is improved. DETAILED DESCRIPTION

[0086] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0087] The purpose of this invention is to develop a low-carbon, high-barrier biodegradable composite film. The design concept is as follows: to address the problems of poor water vapor and oxygen barrier properties of degradable packaging films, reduced transparency after multi-layer lamination, and the inherent brittleness of PLA, a multi-layer composite film is designed. The barrier properties are improved through vacuum evaporation; at the same time, the thickness of the coating is controlled to improve transparency. Finally, multi-layer co-extrusion is carried out in conjunction with relevant processes to reduce carbon emissions generated by the number of laminations; and carbon emissions generated by a single lamination must be controlled to achieve a low-carbon effect. In addition, some inherent problems, such as the plasticization of PLA and transparency issues caused by compatibility with other resins, need to be addressed.

[0088] First, the solution to the plasticization problem of PLA is as follows: it is blended with the biodegradable resin PBAT and simultaneously added with a homemade plasticizer and compatibilizer to address the plasticization compatibility issue. Second, the barrier properties of the composite film are enhanced by vacuum evaporation of the high-barrier layer. Given the thinness and susceptibility of the evaporation layer, it is placed as the middle layer of the composite film. Third, the composite film is prepared by co-extruding the surface substrate layer and the high-barrier layer, biaxially stretching them to improve mechanical properties and barrier properties, and evaporation is performed on the high-barrier layer. Simultaneously, a three-layer co-extrusion blown film is produced consisting of a PVAc layer, a transition layer, and an inner substrate layer (containing an adhesive). The PVAc surface and the high-barrier surface layer are then dry-laminated to form the composite film. During this process, the inner substrate layer, containing the adhesive, exhibits high heat-seal strength after heat sealing, meeting the requirements for applications such as packaging bags. This combined process allows the five-layer composite film to be laminated in a single step. Furthermore, the addition of a homemade adhesive during the late-stage lamination process reduces aging time, resulting in low carbon content.

[0089] The theoretical basis for the realization of the above three auxiliary agents is: First, the plasticizer, firstly, the large steric hindered group phosphorus chloride is subjected to a coupling reaction with hydroxy acrylate, and then the acryloyloxy group is subjected to a Michael addition reaction with the amino group in the alcohol amine to obtain a polyhydroxy structure containing a large steric hindered group. Second, the compatibilizer, nano silicon is modified by an epoxy silane coupling agent, and then an amino-terminated epoxy ring-opening reaction is carried out with a high molecular weight diamine, and finally it is reacted with a diisocyanate to form an isocyanate-terminated large molecular weight "hyperbranched" structure. Third, the bonding auxiliary agent, the catechol structure is reacted to obtain catechol containing a carbon-carbon double bond, and then it is free radical copolymerized with the monomer to obtain the bonding auxiliary agent. The above self-made ingredients are added to the extruders of different film layers for co-extrusion and other process treatments to obtain a low-carbon high-barrier biodegradable composite film with improved performance in all aspects; and the bonding auxiliary agent is also used in the adhesive of dry compounding to play a role, and the components work synergistically with each other to effectively improve the barrier properties, mechanical properties, low-carbon performance, etc. The embodiments of the present invention are as follows:

[0090] The embodiment of the present invention provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, which includes, in sequence, a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer, and an inner substrate layer; the high-barrier layer is treated with vacuum-evaporated aluminum oxide;

[0091] The surface substrate layer comprises the following raw materials in parts by weight:

[0092] PLA 80-90 parts;

[0093] PBAT 10-20 parts;

[0094] 10-15 parts of plasticizer;

[0095] 1.0-3.0 parts of compatibilizer;

[0096] 0.3-0.5 parts of antioxidant;

[0097] 0.1-0.2 parts of lubricant;

[0098] Among them, the total mass of PLA and PBAT is 100 parts;

[0099] The high barrier layer comprises the following raw materials in parts by weight:

[0100] PLA 70-90 parts;

[0101] PPC-P 10-30 copies;

[0102] 8-12 parts of plasticizer;

[0103] 1.0-2.0 parts of compatibilizer;

[0104] 0.1-0.5 parts of antioxidant;

[0105] 0.1-0.2 parts of lubricant;

[0106] Among them, the total mass of PLA and PPC-P is 100 parts;

[0107] The bonding layer comprises the following raw materials in parts by weight:

[0108] PVAc 90-95 parts;

[0109] PBAT 5-10 parts;

[0110] 0.2-0.5 parts of antioxidant;

[0111] 0.2-0.3 parts of lubricant;

[0112] Among them, the total mass of PVAc and PBAT is 100 parts;

[0113] The transition layer comprises the following raw materials in parts by weight:

[0114] PBAT 100 units;

[0115] 10-20 parts of nanosheet-shaped inorganic filler;

[0116] 0.1-0.3 parts of antioxidant;

[0117] 0.1-0.2 parts of lubricant;

[0118] The inner substrate layer comprises the following raw materials in parts by weight:

[0119] PBAT 100 units;

[0120] 3.0-5.0 parts of bonding agent;

[0121] 1.0-4.0 parts of anti-hydrolysis agent;

[0122] 0.1-0.3 parts of antioxidant;

[0123] 0.5-1.0 parts of lubricant;

[0124] The preparation method of the plasticizer comprises the following steps:

[0125] S11, adding a bulky sterically hindered phosphorus chloride, hydroxyacrylate A, and triethylamine to N,N-dimethylformamide, stirring at 0°C for 2 hours, slowly warming to room temperature, and stirring overnight; after completion of the reaction, distilling under reduced pressure, dissolving the concentrate in dichloromethane, adding deionized water, shaking, separating the layers, collecting the organic phase, drying it over anhydrous sodium sulfate, filtering, collecting the filtrate, distilling under reduced pressure, and drying it in vacuo at room temperature for 12 hours to obtain intermediate 1I;

[0126] The large sterically hindered phosphorus chloride, hydroxy acrylate A, and triethylamine are added in a molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1;

[0127] The dosage ratio of the hydroxyacrylate A, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g;

[0128] The bulky steric hindered group is adamantyl; that is, the bulky steric hindered phosphorus chloride may be bis(1-adamantyl)phosphonium chloride.

[0129] The number of acryloxy functional groups in the hydroxy acrylate A is ≥2; it may be pentaerythritol triacrylate, α,α-glycerol diacrylate, etc.

[0130] S12, adding the intermediate product 1I and the alcohol amine to N,N-dimethylformamide, stirring at room temperature for 2-6 hours, distilling under reduced pressure, and vacuum drying at 40°C for 8 hours to obtain the target product, i.e., the plasticizer.

[0131] The intermediate product 1I and the alcoholamine are added at a molar ratio of acryloyloxy to amino of 1:1;

[0132] The usage ratio of the intermediate product 1I and N,N-dimethylformamide is 0.1 mol: 200 mL;

[0133] The alcoholamine may be ethanolamine, isopropanolamine, n-butanolamine, diglycolamine, etc., and diglycolamine is preferred.

[0134] The preparation method of the compatibilizer comprises the following steps:

[0135] S21, placing nano-silicon in ethyl acetate A, ultrasonically dispersing for 1 hour, adding epoxy silane coupling agent and deionized water A, slowly heating to 60-80°C, heating and stirring for 6-14 hours. After the reaction is completed, cooling to room temperature, filtering, washing with ethyl acetate B, and vacuum drying at 40°C to constant weight to obtain the target product, i.e., intermediate 2I;

[0136] The usage ratio of the nano-silicon, ethyl acetate A, epoxy silane coupling agent, deionized water A, and ethyl acetate B is: 1.00 g: 50 mL: 5.0-7.0 g: 0.6 g: 200 mL.

[0137] The nano-silicon has an average particle size of 50-100 nm and is purchased from Ningbo Jinlei Nanomaterial Technology Co., Ltd.

[0138] The epoxy silane coupling agent may be silane coupling agent KH560, silane coupling agent A1871, etc., and preferably silane coupling agent KH560.

[0139] S22, add the intermediate product 2I to N,N-dimethylformamide A, sonicate, and add it dropwise to N,N-dimethylformamide B containing aminopolyethylene glycol amino groups via a peristaltic pump, raise the temperature to 40-60°C, continue stirring for 2-4 hours after the addition is completed, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the intermediate product 2II.

[0140] The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2;

[0141] The usage ratio of the intermediate product 2I, N,N-dimethylformyl A, and N,N-dimethylformyl B is 1 g:100 mL:200 mL.

[0142] The molecular weight of the amino polyethylene glycol amino group is 400-1000; it can be 400, 600, 800, 1000, or a range consisting of any two values.

[0143] S23, add the intermediate product 2II to N,N-dimethylformyl C, ultrasonicate, and add it dropwise to N,N-dimethylformyl D containing diisocyanate via a peristaltic pump, stir at room temperature, continue stirring for 2-4 hours after the addition is completed, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the target product, i.e., the compatibilizer.

[0144] The intermediate product 2II and diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2;

[0145] The usage ratio of the intermediate product 2II, N,N-dimethylformyl C, and N,N-dimethylformyl D is 1 g:100 mL:200 mL.

[0146] The diisocyanate is an asymmetric diisocyanate; it can be toluene diisocyanate or isophorone diisocyanate;

[0147] The toluene diisocyanate has an asymmetric structure, and the two isocyanate groups have a certain difference in activity. When one of the highly active isocyanate groups reacts, the activity of the other isocyanate group decreases rapidly. However, the two isocyanate groups of isophorone diisocyanate itself have a large difference in activity. Therefore, the use of an asymmetric diisocyanate can obtain a product with an isocyanate group capped at one end. In addition, isophorone diisocyanate is preferred.

[0148] The preparation method of the bonding auxiliary agent comprises the following steps:

[0149] S31, add a catechol-containing epoxy ring-opener, epoxy olefin, catalyst, and hydroquinone to tetrahydrofuran, react for 6-24 hours, cool to room temperature, add deionized water, shake, add ethyl acetate for extraction, collect the organic phase, dry it over anhydrous sodium sulfate, filter, collect the filtrate, distill it under reduced pressure, and dry it in vacuo at 40°C for 12 hours to obtain the intermediate product 3I.

[0150] The catechol-containing epoxy ring-opener and the epoxy alkene are added at a molar ratio of 1:1 between the epoxy ring-opener and the epoxy group;

[0151] The catechol-containing epoxy ring-opener, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate are added in a ratio of 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g;

[0152] The catechol-containing epoxy ring-opener has a structure containing a carboxyl group or an amino group;

[0153] When containing a carboxyl structure, the epoxy ring-opening agent can be protocatechuic acid or plateau catechuic acid; and, preferably protocatechuic acid;

[0154] When containing an amino structure, the epoxy ring-opener may be dopamine.

[0155] The epoxy alkene may be epoxy acrylate or allyl epoxy;

[0156] The epoxy acrylate may be glycidyl methacrylate or (glycidyloxy)ethyl methacrylate, etc.; and preferably (glycidyloxy)ethyl methacrylate;

[0157] The allyl epoxy may be allyl glycidyl ether, 1,2-epoxy-7-octene, 1,2-epoxy-9-decene, or the like; and preferably allyl glycidyl ether.

[0158] The amount of the catalyst used is 0-0.5 wt % of the total mass of the reactants; and the catalyst can be tetrabutylammonium bromide, triethylamine or triphenylphosphine.

[0159] The amount of hydroquinone used is 0.1wt% of the mass of epoxy olefin.

[0160] S32, vinyl acetate, a silane coupling agent containing a carbon-carbon double bond, hydroxy acrylate B, intermediate product 3I, and initiator AIBN are added to N,N-dimethylformamide, the temperature is raised to 75-85°C, and stirred for 6-10 hours; after the reaction is completed, the temperature is lowered to room temperature, filtered, and the filtrate is distilled under reduced pressure and vacuum dried at 60°C for 6 hours to obtain the target product, i.e., the bonding agent.

[0161] The usage ratio of the vinyl acetate, the silane coupling agent containing a carbon-carbon double bond, the hydroxy acrylate B, the intermediate product 3I, and N,N-dimethylformamide is 0.1-0.3 mol: 0.2-0.4 mol: 0.1-0.3 mol: 0.2-0.4 mol: 1000 mL.

[0162] The silane coupling agent containing a carbon-carbon double bond may be a vinyl silane coupling agent or an acryloxy silane coupling agent;

[0163] The vinyl silane coupling agent may be silane coupling agent KH151, silane coupling agent KH171 or silane coupling agent KH172, etc., and preferably silane coupling agent KH151.

[0164] The acryloxysilane coupling agent may be silane coupling agent KH570, silane coupling agent KH571, silane coupling agent KH670 or silane coupling agent GX572, etc., and preferably silane coupling agent KH570.

[0165] The hydroxyacrylate B may be hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl acrylate, etc., and preferably hydroxypropyl methacrylate.

[0166] The amount of the initiator AIBN used is 1.0 wt% of the total weight of the monomers.

[0167] The PLA, model PT102, was purchased from Pulisi Biotechnology Co., Ltd.

[0168] The PBAT, brand TH801T, was purchased from Xinjiang Lanshan Tunhe Polyester Co., Ltd.

[0169] The PPCP has a glass transition temperature (Tg) of 46° C. and was purchased from Shandong Lianchuang Co., Ltd.

[0170] The antioxidant is a hindered phenol; it can be antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant 2246, etc.; and the antioxidant described in the following examples and comparative examples of the present invention is antioxidant 1010.

[0171] The lubricant can be erucamide, oleamide, ethylene bisstearamide, etc.; and, the lubricant in the following examples and comparative examples of the present invention is erucamide and ethylene bisstearamide mixed in a mass ratio of 2 / 1.

[0172] The PVAc, model VINNEX2504, was purchased from Wacker, Germany.

[0173] The nanosheet-like inorganic filler may be talc, montmorillonite, or graphene oxide, etc., and talc is preferred.

[0174] The anti-hydrolysis agent is a monomeric anti-hydrolysis agent bis(2,6-diisopropylbenzene)carbodiimide, model number HyMax1010, purchased from Shanghai Langyi Functional Materials Co., Ltd.

[0175] Another object of the present invention is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, comprising the following steps:

[0176] S41, co-extrusion of surface substrate layer and high barrier layer, i.e.

[0177] The raw materials are mixed uniformly according to the formula and placed in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding are performed to obtain composite film A;

[0178] The surface substrate layer is set to a temperature of 150-190°C in each zone;

[0179] The high barrier layer is set to a temperature of 155-195°C in each zone;

[0180] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 32:1;

[0181] The die temperature is 180-190°C;

[0182] The transverse stretching ratio of the biaxial stretching is 3.0-5.0, and the longitudinal stretching ratio is 3.0-5.0;

[0183] The stretching temperature is 80-100° C.; the stretching rate is 50-60% / s; and

[0184] The heat setting is a heat treatment at 90-100° C. for 10-20 minutes.

[0185] The thickness of the composite film A is 50 μm.

[0186] S42, coating treatment of composite film A, namely

[0187] The composite film A was corona treated on the high barrier layer, and the surface energy of the corona surface after treatment was ≥42 dyne; then vacuum evaporation of aluminum oxide was performed;

[0188] The vacuum evaporation aluminum oxide process comprises:

[0189] (1) Pretreatment layer evaporation: In a vacuum chamber, high corona first excites plasma, and then uses plasma to excite the surface molecules of the target material to combine with the corona surface, generating an anchoring effect on the organic and inorganic interface to form a pretreatment layer; the pretreatment layer is a Si coating with a thickness of 5nm, and AlO is added. x Adhesion between the coating and the base coating; the pre-treatment layer is in a vacuum chamber, where high corona first excites plasma, and then uses plasma to excite the surface molecules of the Si target to combine with the coating surface, forming an anchoring effect on the organic and inorganic interface.

[0190] (2) Aluminum oxide evaporation: In a high vacuum chamber, the pressure is ≤4.0×10 4 mbar, using high-energy electron beam thermal evaporation or crucible heating evaporation to form nano-AlO x Plating; or under high voltage, plasma is formed, and under the action of controlled electromagnetic field, the Al target is bombarded, and the incoming process gas O2 reacts to generate AlO x Deposited on the surface of the base coating to form a dense nano-coating.

[0191] The thickness of the aluminum oxide coating is 10-50 nm.

[0192] S43, co-extruded blown film of adhesive layer, transition layer and inner substrate layer, i.e.

[0193] The raw materials are mixed uniformly according to the formula, and placed in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding are performed to obtain composite film B; and

[0194] The bonding layer is set to a temperature of 80-160°C in each zone;

[0195] The temperature of each zone of the transition layer is set to 145-175°C;

[0196] The temperature of each zone of the inner substrate layer is set to 140-170°C;

[0197] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 30:1;

[0198] The die temperature is 160-170°C;

[0199] The pulling speed is 6-8m / min, and the blowing ratio is 3.0-4.0;

[0200] The thickness of the composite film B is 75 μm.

[0201] S44, composite treatment, i.e.

[0202] The aluminum oxide-plated surface of the composite film A is composited with the adhesive surface of the composite film B and subjected to aging treatment to obtain the target product, i.e., a low-carbon high-barrier biodegradable composite film.

[0203] The composite process is dry composite, and the coating amount of the adhesive during composite is 3g / m 2 The composite adhesive comprises the following raw materials in parts by weight:

[0204] 50 parts of polyol;

[0205] 5-20 parts of curing agent;

[0206] 0.1 part of catalyst;

[0207] 5.0-10.0 parts of bonding agent;

[0208] 40-60 parts of ethyl acetate.

[0209] The polyol is a mixture of polyether polyol and polyester polyol in a mass ratio of 4 / 1;

[0210] The polyether polyol is polytetrahydrofuran PTMG 2000;

[0211] The polyester polyol is polycaprolactone diol 1000.

[0212] The curing agent is L-75, with a solid content of 75±2%, produced by Mitsui Takeda, Japan.

[0213] The catalyst is stannous octoate.

[0214] The aging treatment is performed at a temperature of 40-50° C. and for a time of 18-24 hours.

[0215] In order to further understand the present invention, a low-carbon high-barrier biodegradable composite film provided by the present invention is described in detail below with reference to specific examples. The protection scope of the present invention is not limited by the following examples.

[0216] Example 1

[0217] This embodiment provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, including a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer, and an inner substrate layer; the high-barrier layer is treated with vacuum-evaporated aluminum oxide;

[0218] The surface substrate layer comprises the following raw materials in parts by weight:

[0219] PLA 85 copies;

[0220] PBAT 15 parts;

[0221] 12 parts of plasticizer;

[0222] 2.0 parts of compatibilizer;

[0223] 0.4 parts of antioxidant;

[0224] 0.15 parts of lubricant;

[0225] The high barrier layer comprises the following raw materials in parts by weight:

[0226] PLA 80 copies;

[0227] PPC-P 20 copies;

[0228] 10 parts of plasticizer;

[0229] 1.5 parts of compatibilizer;

[0230] 0.3 parts of antioxidant;

[0231] 0.15 parts of lubricant;

[0232] The bonding layer comprises the following raw materials in parts by weight:

[0233] PVAc 93 parts;

[0234] PBAT 7 parts;

[0235] 0.3 parts of antioxidant;

[0236] 0.25 parts of lubricant;

[0237] The transition layer comprises the following raw materials in parts by weight:

[0238] PBAT 100 units;

[0239] 15 parts of nano talc;

[0240] 0.2 parts of antioxidant;

[0241] 0.15 parts of lubricant;

[0242] The inner substrate layer comprises the following raw materials in parts by weight:

[0243] PBAT 100 units;

[0244] 4.0 parts of bonding agent;

[0245] 2.0 parts of anti-hydrolysis agent;

[0246] 0.2 parts of antioxidant;

[0247] 0.7 parts of lubricant;

[0248] The preparation method of the plasticizer comprises the following steps:

[0249] S11, bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine were added to N,N-dimethylformamide, stirred at 0°C for 2 hours, slowly warmed to room temperature, and stirred overnight. After the reaction, the concentrate was distilled under reduced pressure, dissolved in dichloromethane, added with deionized water, shaken, separated, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at room temperature for 12 hours to obtain intermediate product 1I.

[0250] The bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine are added in a molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1;

[0251] The usage ratio of the pentaerythritol triacrylate, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g.

[0252] Its infrared data is as follows: 3516cm -1 :-OH does not exist; 1735cm -1 :-C=O exists; 1126cm -1 :-PO-existence; 1609cm -1 , 810cm -1 :-C=C-exists.

[0253] S12, adding the intermediate product 1I and diglycolamine to N,N-dimethylformamide, stirring at room temperature for 4.5 h, distilling under reduced pressure, and drying in vacuo at 40°C for 8 h to obtain the target product, i.e., the plasticizer.

[0254] The intermediate product II and diglycolamine are added at a molar ratio of acryloyloxy to amino of 1:1;

[0255] The usage ratio of the intermediate product 1I and N,N-dimethylformamide is 0.1 mol:200 mL.

[0256] Its infrared data is as follows: 3519cm -1 :-OH exists; 3312cm -1 :-NH- exists; 1735cm -1 :-C=O exists; 1126cm -1 :-PO-existence; 1609cm -1 , 810cm -1 :-C=C- does not exist.

[0257] The preparation method of the compatibilizer comprises the following steps:

[0258] S21, nano-silicon was placed in ethyl acetate A, ultrasonically dispersed for 1 hour, and then silane coupling agent KH560 and deionized water A were added. The temperature was slowly raised to 70°C and heated with stirring for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with ethyl acetate B, and vacuum dried at 40°C to constant weight to obtain the target product, i.e., intermediate 2I;

[0259] The usage ratio of the nano-silicon, ethyl acetate A, silane coupling agent KH560, deionized water A, and ethyl acetate B is: 1.00 g: 50 mL: 6.0 g: 0.6 g: 200 mL.

[0260] Its infrared data is as follows: 3426cm -1 :-OH exists and is significantly weakened; 1265cm -1 、893cm -1 , 825cm -1 : Epoxy groups are present; 1109 cm -1 、801cm -1 :-Si-O- exists.

[0261] S22, add the intermediate product 2I to N,N-dimethylformamide A, sonicate, and add it dropwise to N,N-dimethylformamide B containing aminopolyethylene glycol amino groups via a peristaltic pump, raise the temperature to 50°C, continue stirring for 2.5 hours after the addition is completed, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the intermediate product 2II.

[0262] The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2;

[0263] The usage ratio of the intermediate product 2I, N,N-dimethylformyl A, and N,N-dimethylformyl B is 1 g:100 mL:200 mL.

[0264] The molecular weight of the amino polyethylene glycol amino group is 600.

[0265] Its infrared data is as follows: 3426cm -1:-OH exists (very weak); 3311cm -1 :-NH- exists; 1265cm -1 、893cm -1 , 825cm -1 : Epoxy group does not exist; 1109 cm -1 、801cm -1 :-Si-O- exists.

[0266] S23, add the intermediate product 2II to N,N-dimethylformyl C, ultrasonicate, and add it dropwise to N,N-dimethylformyl D containing isophorone diisocyanate via a peristaltic pump. Stir at room temperature. After the addition is completed, continue stirring for 2.5 hours, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the target product, i.e., the compatibilizer.

[0267] The intermediate product 2II and isophorone diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2;

[0268] The usage ratio of the intermediate product 2II, N,N-dimethylformyl C, and N,N-dimethylformyl D is 1 g:100 mL:200 mL.

[0269] Its infrared data is as follows: 3426cm -1 :-OH exists (very weak); 3311cm -1 :-NH- exists and weakens; 2275cm -1 :-NCO exists; 1109 cm -1 、801cm -1 :-Si-O- exists.

[0270] The preparation method of the bonding auxiliary agent comprises the following steps:

[0271] S31, dopamine, allyl glycidyl ether, a catalyst, and hydroquinone are added to tetrahydrofuran, reacted at room temperature for 6 hours, cooled to room temperature, added with deionized water, shaken, extracted with ethyl acetate, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at 40°C for 12 hours to obtain the intermediate product 3I.

[0272] The dopamine and allyl glycidyl ether are added at a molar ratio of 1:1 between dopamine and epoxy groups;

[0273] The dopamine, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate are added in a ratio of 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0274] The amount of the catalyst used was 0 wt % of the total mass of the reactants; that is, no catalyst was added.

[0275] The amount of hydroquinone used is 0.1wt% of the mass of epoxy olefin.

[0276] Its infrared data are as follows: 3531cm -1 :-OH exists; 3310cm -1 :-NH- exists and weakens; 1616cm -1 :-C=C- exists; 1265cm -1 、893cm -1 , 825cm -1 : Epoxy group does not exist.

[0277] S32, vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and initiator AIBN were added to N,N-dimethylformamide, heated to 80°C, and stirred for 7.5 hours. After the reaction, the mixture was cooled to room temperature, filtered, and the filtrate was distilled under reduced pressure and dried in vacuum at 60°C for 6 hours to obtain the target product, i.e., the bonding agent ( ).

[0278] The usage ratio of the vinyl acetate, the silane coupling agent KH570, the hydroxypropyl methacrylate, the intermediate product 3I, and the N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL.

[0279] Its infrared data are as follows: 3531cm -1 :-OH exists; 3310cm -1 :-NH- exists and weakens; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring exists; 1735cm -1 :-C=O exists; 1109 cm -1 、801cm -1 :-Si-O- exists; 1616cm -1 、1606cm -1 、811cm -1 :-C=C- does not exist.

[0280] The amount of the initiator AIBN used is 1.0 wt% of the total weight of the monomers.

[0281] Another object of this embodiment is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, comprising the following steps:

[0282] S41, co-extrusion of surface substrate layer and high barrier layer, i.e.

[0283] The raw materials are mixed uniformly according to the formula and placed in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding are performed to obtain composite film A;

[0284] The surface substrate layer is set to have temperature zones of 155°C, 165°C, 175°C, 180°C, 185°C, and 185°C respectively;

[0285] The high barrier layer is set at temperature zones of 160°C, 170°C, 180°C, 185°C, 190°C, and 190°C respectively;

[0286] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 32:1;

[0287] The die temperature is 185°C;

[0288] The transverse stretching ratio of the biaxial stretching is 4.0, and the longitudinal stretching ratio is 4.0;

[0289] The stretching temperature is 90° C.; the stretching rate is 55% / s; and

[0290] The heat setting is performed at 95° C. for 15 minutes.

[0291] The thickness of the composite film A is 50 μm, wherein the thickness of the surface substrate layer and the high barrier layer are 25 μm respectively.

[0292] S42, coating treatment of composite film A, namely

[0293] The composite film A was corona treated on the high barrier layer, and the surface energy of the corona surface after treatment was ≥42 dyne; then vacuum evaporation of aluminum oxide was performed;

[0294] The thickness of the aluminum oxide coating is 30 nm.

[0295] S43, co-extruded blown film of adhesive layer, transition layer and inner substrate layer, i.e.

[0296] The raw materials are mixed uniformly according to the formula, and placed in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding are performed to obtain composite film B; and

[0297] The bonding layer is set at temperature zones of 85°C, 105°C, 125°C, 140°C, 150°C and 155°C respectively;

[0298] The temperature zones of the transition layer are set at 150°C, 158°C, 164°C, 168°C, 170°C and 170°C respectively;

[0299] The temperature zones of the inner substrate layer are set at 145°C, 154°C, 160°C, 160°C, 165°C, and 165°C respectively;

[0300] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 30:1;

[0301] The die temperature is 165°C;

[0302] The pulling speed is 7m / min and the blowing ratio is 3.5;

[0303] The thickness of the composite film B is 75 μm; wherein, the thicknesses of the adhesive layer, transition layer, and inner substrate layer are 15 μm, 30 μm, and 30 μm, respectively.

[0304] S44, composite treatment, i.e.

[0305] The aluminum oxide-plated surface of the composite film A is composited with the adhesive surface of the composite film B and subjected to aging treatment to obtain the target product, i.e., a low-carbon high-barrier biodegradable composite film.

[0306] The composite process is dry composite, and the coating amount of the adhesive during composite is 3g / m 2 The composite adhesive comprises the following raw materials in parts by weight:

[0307] 50 parts of polyol;

[0308] 10 parts of curing agent;

[0309] 0.1 part of catalyst;

[0310] 8.0 parts of bonding agent;

[0311] 50 parts of ethyl acetate.

[0312] The aging treatment is performed at a temperature of 45° C. and for a time of 20 h.

[0313] Example 2

[0314] This embodiment provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, including a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer, and an inner substrate layer; the high-barrier layer is treated with vacuum-evaporated aluminum oxide;

[0315] The surface substrate layer comprises the following raw materials in parts by weight:

[0316] PLA 80 copies;

[0317] PBAT 20 parts;

[0318] 10 parts of plasticizer;

[0319] 3.0 parts of compatibilizer;

[0320] 0.3 parts of antioxidant;

[0321] 0.2 parts of lubricant;

[0322] The high barrier layer comprises the following raw materials in parts by weight:

[0323] PLA 70 copies;

[0324] PPC-P 30 copies;

[0325] 8 parts of plasticizer;

[0326] 2.0 parts of compatibilizer;

[0327] 0.1 part of antioxidant;

[0328] 0.2 parts of lubricant;

[0329] The bonding layer comprises the following raw materials in parts by weight:

[0330] PVAc 90 parts;

[0331] PBAT 10 parts;

[0332] 0.2 parts of antioxidant;

[0333] 0.3 parts of lubricant;

[0334] The transition layer comprises the following raw materials in parts by weight:

[0335] PBAT 100 units;

[0336] 10 parts of nano talc;

[0337] 0.1 part of antioxidant;

[0338] 0.2 parts of lubricant;

[0339] The inner substrate layer comprises the following raw materials in parts by weight:

[0340] PBAT 100 units;

[0341] 3.0 parts of bonding agent;

[0342] 4.0 parts of anti-hydrolysis agent;

[0343] 0.1 part of antioxidant;

[0344] 0.5 parts of lubricant;

[0345] The preparation method of the plasticizer comprises the following steps:

[0346] S11, bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine were added to N,N-dimethylformamide, stirred at 0°C for 2 hours, slowly warmed to room temperature, and stirred overnight. After the reaction, the concentrate was distilled under reduced pressure, dissolved in dichloromethane, added with deionized water, shaken, separated, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at room temperature for 12 hours to obtain intermediate product 1I.

[0347] The bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine are added in a molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1;

[0348] The usage ratio of the pentaerythritol triacrylate, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g.

[0349] S12, adding the intermediate product 1I and diglycolamine to N,N-dimethylformamide, stirring at room temperature for 2 h, and then distilling under reduced pressure, and vacuum drying at 40°C for 8 h to obtain the target product, i.e., the plasticizer.

[0350] The intermediate product II and diglycolamine are added at a molar ratio of acryloyloxy to amino of 1:1;

[0351] The usage ratio of the intermediate product 1I and N,N-dimethylformamide is 0.1 mol:200 mL.

[0352] The preparation method of the compatibilizer comprises the following steps:

[0353] S21, nano-silicon was placed in ethyl acetate A, ultrasonically dispersed for 1 hour, and then silane coupling agent KH560 and deionized water A were added. The temperature was slowly raised to 60°C and heated with stirring for 14 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with ethyl acetate B, and vacuum dried at 40°C to constant weight to obtain the target product, i.e., intermediate 2I;

[0354] The usage ratio of the nano-silicon, ethyl acetate A, silane coupling agent KH560, deionized water A, and ethyl acetate B is: 1.00 g: 50 mL: 7.0 g: 0.6 g: 200 mL.

[0355] S22, add the intermediate product 2I to N,N-dimethylformamide A, sonicate, and add it dropwise to N,N-dimethylformamide B containing aminopolyethylene glycol amino groups via a peristaltic pump, raise the temperature to 60°C, continue stirring for 2 hours after the addition is completed, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the intermediate product 2II.

[0356] The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2;

[0357] The usage ratio of the intermediate product 2I, N,N-dimethylformyl A, and N,N-dimethylformyl B is 1 g:100 mL:200 mL.

[0358] The molecular weight of the amino polyethylene glycol amino group is 600.

[0359] S23, add the intermediate product 2II to N,N-dimethylformyl C, ultrasonicate, and add it dropwise to N,N-dimethylformyl D containing isophorone diisocyanate via a peristaltic pump. Stir at room temperature. After the addition is completed, continue stirring for 2 h, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 h to obtain the target product, i.e., the compatibilizer.

[0360] The intermediate product 2II and isophorone diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2;

[0361] The usage ratio of the intermediate product 2II, N,N-dimethylformyl C, and N,N-dimethylformyl D is 1 g:100 mL:200 mL.

[0362] The preparation method of the bonding auxiliary agent comprises the following steps:

[0363] S31, protocatechuic acid, allyl glycidyl ether, tetrabutylammonium bromide, and hydroquinone are added to tetrahydrofuran, heated under reflux for 24 hours, cooled to room temperature, added with deionized water, shaken, extracted with ethyl acetate, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at 40°C for 12 hours to obtain intermediate product 3I.

[0364] The protocatechuic acid and allyl glycidyl ether are added at a molar ratio of protocatechuic acid to epoxy group of 1:1;

[0365] The protocatechuic acid, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate are added in a ratio of 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0366] The amount of tetrabutylammonium bromide used is 0.5 wt % of the total mass of the reactants.

[0367] The amount of hydroquinone used is 0.1wt% of the mass of epoxy olefin.

[0368] S32, vinyl acetate, silane coupling agent KH151, hydroxypropyl methacrylate, intermediate product 3I, and initiator AIBN are added to N,N-dimethylformamide, the temperature is raised to 85°C, and stirred for 6 hours; after the reaction is completed, the temperature is lowered to room temperature, filtered, and the filtrate is taken and distilled under reduced pressure, and vacuum dried at 60°C for 6 hours to obtain the target product, i.e., the bonding agent.

[0369] The usage ratio of the vinyl acetate, silane coupling agent KH151, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL.

[0370] The amount of the initiator AIBN used is 1.0 wt% of the total weight of the monomers.

[0371] Another object of this embodiment is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, comprising the following steps:

[0372] S41, co-extrusion of surface substrate layer and high barrier layer, i.e.

[0373] The raw materials are mixed uniformly according to the formula and placed in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding are performed to obtain composite film A;

[0374] The surface substrate layer is set at temperature zones of 150°C, 160°C, 170°C, 175°C, 180°C, and 180°C respectively;

[0375] The high barrier layer is set to have temperature zones of 155°C, 165°C, 175°C, 180°C, 185°C, and 185°C respectively;

[0376] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 32:1;

[0377] The die temperature is 180°C;

[0378] The transverse stretching ratio of the biaxial stretching is 5.0, and the longitudinal stretching ratio is 5.0;

[0379] The stretching temperature is 100° C.; the stretching rate is 60% / s; and

[0380] The heat setting is a heat treatment at 100° C. for 10 minutes.

[0381] The thickness of the composite film A is 50 μm, wherein the thickness of the surface substrate layer and the high barrier layer are 25 μm respectively.

[0382] S42, coating treatment of composite film A, namely

[0383] The composite film A was corona treated on the high barrier layer, and the surface energy of the corona surface after treatment was ≥42 dyne; then vacuum evaporation of aluminum oxide was performed;

[0384] The thickness of the aluminum oxide coating is 10 nm.

[0385] S43, co-extruded blown film of adhesive layer, transition layer and inner substrate layer, i.e.

[0386] The raw materials are mixed uniformly according to the formula, and placed in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding are performed to obtain composite film B; and

[0387] The temperature zones of the bonding layer are set at 80°C, 100°C, 120°C, 140°C, 145°C and 150°C respectively;

[0388] The temperature zones of the transition layer are set at 145°C, 154°C, 158°C, 161°C, 164°C, and 165°C respectively;

[0389] The temperature zones of the inner substrate layer are set at 140°C, 147°C, 150°C, 155°C, 158°C and 160°C respectively;

[0390] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 30:1;

[0391] The die temperature is 160°C;

[0392] The pulling speed is 6m / min and the blowing ratio is 3.0;

[0393] The thickness of the composite film B is 75 μm; wherein, the thicknesses of the adhesive layer, transition layer, and inner substrate layer are 15 μm, 30 μm, and 30 μm, respectively.

[0394] S44, composite treatment, i.e.

[0395] The aluminum oxide-plated surface of the composite film A is composited with the adhesive surface of the composite film B and subjected to aging treatment to obtain the target product, i.e., a low-carbon high-barrier biodegradable composite film.

[0396] The composite process is dry composite, and the coating amount of the adhesive during composite is 3g / m 2 The composite adhesive comprises the following raw materials in parts by weight:

[0397] 50 parts of polyol;

[0398] 20 parts of curing agent;

[0399] 0.1 part of catalyst;

[0400] 10.0 parts of bonding agent;

[0401] 60 parts of ethyl acetate.

[0402] The aging treatment is performed at a temperature of 40° C. and for a time of 24 hours.

[0403] Example 3

[0404] This embodiment provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, including a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer, and an inner substrate layer; the high-barrier layer is treated with vacuum-evaporated aluminum oxide;

[0405] The surface substrate layer comprises the following raw materials in parts by weight:

[0406] PLA 90 copies;

[0407] PBAT 10 parts;

[0408] 15 parts of plasticizer;

[0409] 1.0 part of compatibilizer;

[0410] 0.5 parts of antioxidant;

[0411] 0.1 part of lubricant;

[0412] The high barrier layer comprises the following raw materials in parts by weight:

[0413] PLA 90 copies;

[0414] PPC-P 10 copies;

[0415] 12 parts of plasticizer;

[0416] 1.0 part of compatibilizer;

[0417] 0.5 parts of antioxidant;

[0418] 0.1 part of lubricant;

[0419] The bonding layer comprises the following raw materials in parts by weight:

[0420] PVAc 95 parts;

[0421] PBAT 5 parts;

[0422] 0.5 parts of antioxidant;

[0423] 0.2 parts of lubricant;

[0424] The transition layer comprises the following raw materials in parts by weight:

[0425] PBAT 100 units;

[0426] 20 parts of nano talc;

[0427] 0.3 parts of antioxidant;

[0428] 0.1 part of lubricant;

[0429] The inner substrate layer comprises the following raw materials in parts by weight:

[0430] PBAT 100 units;

[0431] 5.0 parts of bonding agent;

[0432] 1.0 part of anti-hydrolysis agent;

[0433] 0.3 parts of antioxidant;

[0434] 1.0 part of lubricant;

[0435] The preparation method of the plasticizer comprises the following steps:

[0436] S11, bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine were added to N,N-dimethylformamide, stirred at 0°C for 6 hours, slowly warmed to room temperature, and stirred overnight. After the reaction, the concentrate was distilled under reduced pressure, dissolved in dichloromethane, added with deionized water, shaken, separated, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at room temperature for 12 hours to obtain intermediate product 1I.

[0437] The bis(1-adamantyl)phosphonium chloride, pentaerythritol triacrylate, and triethylamine are added in a molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1;

[0438] The usage ratio of the pentaerythritol triacrylate, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g.

[0439] S12, adding the intermediate product 1I and diglycolamine to N,N-dimethylformamide, stirring at room temperature for 2 h, and then distilling under reduced pressure, and vacuum drying at 40°C for 8 h to obtain the target product, i.e., the plasticizer.

[0440] The intermediate product II and diglycolamine are added at a molar ratio of acryloyloxy to amino of 1:1;

[0441] The usage ratio of the intermediate product 1I and N,N-dimethylformamide is 0.1 mol: 200 mL;

[0442] The preparation method of the compatibilizer comprises the following steps:

[0443] S21, nano-silicon was placed in ethyl acetate A, ultrasonically dispersed for 1 hour, and then silane coupling agent KH560 and deionized water A were added. The temperature was slowly raised to 80°C and heated with stirring for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed with ethyl acetate B, and vacuum dried at 40°C to constant weight to obtain the target product, i.e., intermediate 2I;

[0444] The usage ratio of the nano-silicon, ethyl acetate A, silane coupling agent KH560, deionized water A, and ethyl acetate B is: 1.00 g: 50 mL: 5.0 g: 0.6 g: 200 mL.

[0445] S22, add the intermediate product 2I to N,N-dimethylformamide A, sonicate, and add it dropwise to N,N-dimethylformamide B containing aminopolyethylene glycol amino groups via a peristaltic pump, raise the temperature to 40°C, continue stirring for 4 hours after the addition is completed, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 hours to obtain the intermediate product 2II.

[0446] The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2;

[0447] The usage ratio of the intermediate product 2I, N,N-dimethylformyl A, and N,N-dimethylformyl B is 1 g:100 mL:200 mL.

[0448] The molecular weight of the amino polyethylene glycol amino group is 600.

[0449] S23, add the intermediate product 2II to N,N-dimethylformyl C, sonicate, and add it dropwise to N,N-dimethylformyl D containing isophorone diisocyanate via a peristaltic pump. Stir at room temperature. After the addition is completed, continue stirring for 4 h, distill under reduced pressure, and then dry in a vacuum oven at 40°C for 12 h to obtain the target product, i.e., the compatibilizer.

[0450] The intermediate product 2II and isophorone diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2;

[0451] The usage ratio of the intermediate product 2II, N,N-dimethylformyl C, and N,N-dimethylformyl D is 1 g:100 mL:200 mL.

[0452] The preparation method of the bonding auxiliary agent comprises the following steps:

[0453] S31, dopamine, glycidyloxyethyl methacrylate, a catalyst, and hydroquinone are added to tetrahydrofuran, reacted at room temperature for 6 hours, cooled to room temperature, added with deionized water, shaken, extracted with ethyl acetate, and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and the filtrate was distilled under reduced pressure and dried in vacuo at 40°C for 12 hours to obtain the intermediate product 3I.

[0454] The dopamine and (glycidyloxy)ethyl methacrylate are added at a molar ratio of dopamine to epoxy group of 1:1;

[0455] The dopamine, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate are added in a ratio of 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0456] The amount of the catalyst used was 0 wt % of the total mass of the reactants; that is, no catalyst was added.

[0457] The amount of hydroquinone used is 0.1wt% of the mass of epoxy olefin.

[0458] S32, vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and initiator AIBN are added to N,N-dimethylformamide, the temperature is raised to 75°C, and stirred for 10 hours; after the reaction is completed, the temperature is lowered to room temperature, filtered, and the filtrate is distilled under reduced pressure and vacuum dried at 60°C for 6 hours to obtain the target product, i.e., the bonding agent.

[0459] The usage ratio of the vinyl acetate, the silane coupling agent KH570, the hydroxypropyl methacrylate, the intermediate product 3I, and the N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL.

[0460] The amount of the initiator AIBN used is 1.0 wt% of the total weight of the monomers.

[0461] Another object of this embodiment is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, comprising the following steps:

[0462] S41, co-extrusion of surface substrate layer and high barrier layer, i.e.

[0463] The raw materials are mixed uniformly according to the formula and placed in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding are performed to obtain composite film A;

[0464] The surface substrate layer is set at temperature zones of 160°C, 170°C, 180°C, 186°C, 190°C, and 190°C respectively;

[0465] The high barrier layer is set to have temperature zones of 165°C, 175°C, 185°C, 190°C, 195°C, and 195°C respectively;

[0466] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 32:1;

[0467] The die temperature is 190°C;

[0468] The transverse stretching ratio of the biaxial stretching is 3.0, and the longitudinal stretching ratio is 3.0;

[0469] The stretching temperature is 80° C.; the stretching rate is 50% / s; and

[0470] The heat setting is performed at 90° C. for 20 minutes.

[0471] The thickness of the composite film A is 50 μm, wherein the thickness of the surface substrate layer and the high barrier layer are 25 μm respectively.

[0472] S42, coating treatment of composite film A, namely

[0473] The composite film A was corona treated on the high barrier layer, and the surface energy of the corona surface after treatment was ≥42 dyne; then vacuum evaporation of aluminum oxide was performed;

[0474] The thickness of the aluminum oxide coating is 50 nm.

[0475] S43, co-extruded blown film of adhesive layer, transition layer and inner substrate layer, i.e.

[0476] The raw materials are mixed uniformly according to the formula, and placed in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding are performed to obtain composite film B; and

[0477] The temperature zones of the bonding layer are set at 90°C, 110°C, 130°C, 150°C, 155°C and 160°C respectively;

[0478] The temperature zones of the transition layer are set at 155°C, 162°C, 168°C, 174°C, 175°C, and 175°C respectively;

[0479] The temperature zones of the inner substrate layer are set at 150°C, 158°C, 162°C, 165°C, 168°C, and 170°C respectively;

[0480] The single-screw extruder is a general-purpose screw with a length-to-diameter ratio of 30:1;

[0481] The die temperature is 170°C;

[0482] The pulling speed is 8m / min and the blowing ratio is 4.0;

[0483] The thickness of the composite film B is 75 μm; wherein, the thicknesses of the adhesive layer, transition layer, and inner substrate layer are 15 μm, 30 μm, and 30 μm, respectively.

[0484] S44, composite treatment, i.e.

[0485] The aluminum oxide-plated surface of the composite film A is composited with the adhesive surface of the composite film B and subjected to aging treatment to obtain the target product, i.e., a low-carbon high-barrier biodegradable composite film.

[0486] The composite process is dry composite, and the coating amount of the adhesive during composite is 3g / m 2 The composite adhesive comprises the following raw materials in parts by weight:

[0487] 50 parts of polyol;

[0488] 5 parts of curing agent;

[0489] 0.1 part of catalyst;

[0490] 5.0 parts of bonding agent;

[0491] 40 parts of ethyl acetate.

[0492] The aging treatment is performed at a temperature of 50° C. and for a time of 18 h.

[0493] Example 4

[0494] The rest is the same as in Example 1, except that:

[0495] A method for preparing a plasticizer in a low-carbon high-barrier biodegradable composite film formulation, in S11,

[0496] The pentaerythritol triacrylate is replaced by α,α-glycerol diacrylate.

[0497] Example 5

[0498] The rest is the same as in Example 1, except that:

[0499] A method for preparing a compatibilizer in a low-carbon high-barrier biodegradable composite film formulation, in S22,

[0500] The molecular weight of the amino polyethylene glycol amino group is 400.

[0501] Example 6

[0502] The rest is the same as in Example 1, except that:

[0503] A method for preparing a compatibilizer in a low-carbon high-barrier biodegradable composite film formulation, in S22,

[0504] The molecular weight of the amino polyethylene glycol amino group is 1000.

[0505] Example 7

[0506] The rest is the same as in Example 1, except that:

[0507] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0508] The usage ratio of the vinyl acetate, the silane coupling agent KH570, the hydroxypropyl methacrylate, the intermediate product 3I, and the N,N-dimethylformamide is 0.1 mol: 0.4 mol: 0.1 mol: 0.4 mol: 1000 mL.

[0509] Example 8

[0510] The rest is the same as in Example 1, except that:

[0511] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0512] The usage ratio of the vinyl acetate, the silane coupling agent KH570, the hydroxypropyl methacrylate, the intermediate product 3I, and the N,N-dimethylformamide is 0.3 mol: 0.2 mol: 0.3 mol: 0.2 mol: 1000 mL.

[0513] The following comparative examples are compared with specific embodiment 1:

[0514] Comparative Example 1

[0515] The rest is the same as in Example 1, except that:

[0516] In a low-carbon high-barrier biodegradable composite film formula,

[0517] No plasticizer is added to the raw material formula of the surface substrate layer and the high barrier layer.

[0518] Comparative Example 2

[0519] The rest is the same as in Example 1, except that:

[0520] A method for preparing a plasticizer in a low-carbon high-barrier biodegradable composite film formulation, in S11,

[0521] The pentaerythritol triacrylate was replaced with hydroxyethyl acrylate.

[0522] Comparative Example 3

[0523] The rest is the same as in Example 1, except that:

[0524] In a low-carbon high-barrier biodegradable composite film formula,

[0525] The plasticizer was replaced with glycerol.

[0526] Comparative Example 4

[0527] The rest is the same as in Example 1, except that:

[0528] In a low-carbon high-barrier biodegradable composite film formula,

[0529] No compatibilizer is added to the raw material formula of the surface substrate layer and the high barrier layer.

[0530] Comparative Example 5

[0531] The rest is the same as in Example 1, except that:

[0532] A method for preparing a compatibilizer in a low-carbon high-barrier biodegradable composite film formulation, in S22,

[0533] The amino group of the aminopolyethylene glycol is replaced with ethylenediamine.

[0534] Comparative Example 6

[0535] The rest is the same as in Example 1, except that:

[0536] A method for preparing a compatibilizer in a low-carbon high-barrier biodegradable composite film formulation, in S22,

[0537] The molecular weight of the amino polyethylene glycol amino group is 2000.

[0538] Comparative Example 7

[0539] The rest is the same as in Example 1, except that:

[0540] In a low-carbon high-barrier biodegradable composite film formula,

[0541] No bonding aid is added to the bonding layer raw material formula.

[0542] Comparative Example 8

[0543] The rest is the same as in Example 1, except that:

[0544] In a method for preparing a low-carbon high-barrier biodegradable composite film,

[0545] No bonding aids were added to the adhesive formulation.

[0546] Comparative Example 9

[0547] The rest is the same as in Example 1, except that:

[0548] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0549] The usage ratio of the vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL; that is, no vinyl acetate is added.

[0550] Comparative Example 10

[0551] The rest is the same as in Example 1, except that:

[0552] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0553] The usage ratio of the vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.2 mol: 0 mol: 0.2 mol: 0.3 mol: 1000 mL; that is, the silane coupling agent KH570 is not added.

[0554] Comparative Example 11

[0555] The rest is the same as in Example 1, except that:

[0556] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0557] The usage ratio of vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0 mol: 0.3 mol: 1000 mL; that is, hydroxypropyl methacrylate is not added.

[0558] Comparative Example 12

[0559] The rest is the same as in Example 1, except that:

[0560] A method for preparing a bonding aid in a low-carbon high-barrier biodegradable composite film formulation, in S32,

[0561] The usage ratio of vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0 mol: 1000 mL; that is, the intermediate product 3I is not added.

[0562] Comparative Example 13

[0563] The rest is the same as in Example 1, except that:

[0564] A method for preparing a low-carbon high-barrier biodegradable composite film, in S42,

[0565] No vacuum evaporation treatment was performed.

[0566] Comparative Example 14

[0567] The rest is the same as in Example 1, except that:

[0568] A method for preparing a low-carbon high-barrier biodegradable composite film, in S42,

[0569] The thickness of the aluminum oxide coating is 5 nm.

[0570] Comparative Example 15

[0571] The rest is the same as in Example 1, except that:

[0572] A method for preparing a low-carbon high-barrier biodegradable composite film, in S42,

[0573] The thickness of the aluminum oxide coating is 60 nm.

[0574] Comparative Example 16

[0575] The rest is the same as in Example 1, except that:

[0576] A method for preparing a low-carbon high-barrier biodegradable composite film, in S41,

[0577] The composite film A is not subjected to a biaxial stretching process.

[0578] Comparative Example 17

[0579] The rest is the same as in Example 1, except that:

[0580] A method for preparing a low-carbon high-barrier biodegradable composite film, in S43,

[0581] The composite film B does not contain a PVAc layer.

[0582] The physical properties of the low-carbon high-barrier biodegradable composite films in the examples of the present invention and the comparative examples were measured and the results are shown in Table 1.

[0583] Table 1 Physical test performance of each embodiment

[0584] Example Tensile strength (MPa) longitudinal Tensile strength (MPa) transverse Elongation at break (%) longitudinal Elongation at break (%) transverse Water vapor transmission rate (g / m2▪d) Oxygen permeability (cm3 / m2 ▪d ▪0.1MPa) Light transmittance (%) Heat sealing strength (N / 15mm) Example 1 162 141 110 128 0.58 0.24 78.7 37.65 Example 2 148 134 115 133 0.84 0.43 79.5 33.37 Example 3 159 144 104 109 0.52 0.21 76.2 35.16 Example 4 145 126 102 105 0.67 0.28 77.8 37.44 Example 5 164 145 101 108 0.56 0.23 78.4 37.32 Example 6 137 120 119 137 0.61 0.25 79.0 37.03 Example 7 160 144 109 125 0.55 0.26 78.4 32.28 Example 8 163 140 108 130 0.63 0.29 77.5 33.51 Comparative Example 1 121 102 53 61 1.70 0.68 74.8 30.79 Comparative Example 2 136 113 76 92 1.39 0.51 76.0 34.80 Comparative Example 3 168 149 117 135 0.57 0.26 79.2 32.64 Comparative Example 4 106 87 90 103 2.03 0.74 70.3 28.91 Comparative Example 5 146 121 95 105 1.38 0.66 75.2 33.07 Comparative Example 6 117 98 102 120 1.19 0.57 75.0 33.82 Comparative Example 7 155 134 114 128 0.67 0.30 78.1 22.56 Comparative Example 8 151 143 118 115 0.62 0.29 78.2 18.63 Comparative Example 9 160 141 105 130 0.58 0.26 78.9 30.18 Comparative Example 10 166 132 108 131 0.57 0.25 78.4 28.35 Comparative Example 11 158 144 110 122 0.60 0.27 79.0 29.80 Comparative Example 12 154 146 113 119 0.57 0.26 79.2 26.49 Comparative Example 13 130 113 121 135 53.5 6.61 85.6 37.93 Comparative Example 14 148 130 116 132 1.23 0.56 80.3 37.89 Comparative Example 15 165 144 104 120 0.51 0.20 71.1 37.11 Comparative Example 16 123 106 95 108 1.06 0.53 81.5 35.84 Comparative Example 17 160 143 108 125 1.14 0.47 79.0 30.35

[0585] First, it can be concluded from Examples 1-8 in Table 1 that the low-carbon high-barrier biodegradable composite film of the present invention has excellent mechanical properties (bidirectional mechanical strength > 100 MPa, bidirectional elongation at break > 100%), water vapor barrier properties (< 1 g / m 2▪d), oxygen barrier properties (<0.5 cm 3 / m 2 ▪d ▪0.1MPa), light transmittance (>75%) and heat sealing strength, etc.

[0586] Second, from Example 1 and Comparative Examples 1-3, it can be observed that the low-carbon, high-barrier biodegradable composite film of the present invention, using a homemade plasticizer, significantly improves mechanical properties. Furthermore, the homemade plasticizer exhibits superior heat-sealing strength compared to conventional plasticizers. This is presumably due to the homemade plasticizer's low migration, which prevents it from migrating to the interface and affecting interlayer adhesion.

[0587] It can be observed from Example 1 and Comparative Examples 4-6 that the low-carbon high-barrier biodegradable composite film of the present invention, using a homemade compatibilizer, has a significant effect on improving mechanical properties, light transmittance, etc.

[0588] It can be observed from Example 1 and Comparative Examples 7-12 that the low-carbon high-barrier biodegradable composite film of the present invention, using a homemade bonding aid, has a significant impact on improving the heat seal strength (including interlayer adhesion);

[0589] It can be observed from Example 1 and Comparative Examples 13-15 that the thickness of the low-carbon, high-barrier biodegradable composite film of the present invention, using vacuum-evaporated alumina, has a significant impact on the water vapor, oxygen barrier properties and light transmittance. First, vacuum-evaporated alumina has a significant effect on improving the barrier properties. At the same time, the lower the coating thickness, the worse the barrier properties and the higher the light transmittance. Conversely, the higher the coating thickness, the better the barrier properties and the lower the light transmittance. In summary, at a thickness of 10-50 nm, the effect on the light transmittance is low and the barrier properties are excellent.

[0590] It can be observed from Example 1 and Comparative Example 16 that the mechanical properties and barrier properties of Composite Film A in the low-carbon, high-barrier biodegradable composite film of the present invention are significantly improved after biaxial stretching. This is because after biaxial stretching and orientation, the polymer structure has a certain degree of crystallization, which improves the mechanical properties and barrier properties.

[0591] It can be observed from Example 1 and Comparative Example 17 that the low-carbon high-barrier biodegradable composite film of the present invention has a five-layer structure, wherein the PVAc layer is located between the barrier layer and the transition layer. The PVAc layer has both the effect of improving adhesion and the advantage of barrier performance.

[0592] In summary, the present invention provides a low-carbon, high-barrier biodegradable composite film. On the one hand, through molecular design, homemade plasticizers, high-reactivity compatibilizers and bonding aids are prepared; on the other hand, a five-layer structure is designed through formula; and it is prepared by double-layer co-extrusion, biaxial stretching process, vacuum evaporation and three-layer co-extrusion, blown film, and finally compounded. The low-carbon, high-barrier biodegradable composite film has excellent mechanical properties, barrier properties, transparency, heat sealing strength and other comprehensive properties; and the main raw materials used have the advantage of being completely degradable and have a wide range of applications.

[0593] The test method is as follows:

[0594] (1) Mechanical properties: Tested according to the method described in GB / T 1040.3-2006.

[0595] (2) Water vapor transmission rate: Tested according to the method described in GB / T 1037-2021.

[0596] (3) Oxygen permeability: Tested according to the method described in GB / T 1038.1-2022 at 1 atm.

[0597] (4) Transmittance: UV-visible spectroscopy (UV Vis). The prepared film was tested using an ultraviolet spectrophotometer (UV-2550) with a wavelength range of 200-800 nm.

[0598] (5) Heat seal strength: in accordance with QB / T 2358 1998, the test speed is 300 mm / min.

[0599] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for preparing a low-carbon high-barrier biodegradable composite film, characterized in that: The steps include: S41, respectively, mixing the raw materials of the surface substrate layer and the high barrier layer uniformly, placing them in different extruders for plasticization; co-extrusion, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, pulling, and winding to obtain a composite film A; The raw materials of the surface substrate layer and the high barrier layer are mainly composed of PLA, and contain a plasticizer and a compatibilizer, wherein the plasticizer is a large sterically hindered polyhydroxy small molecule structure, and the compatibilizer is a long-chain hyperbranched structure with nano-silicon as the core and isocyanate-terminated; S42, performing corona treatment and vacuum evaporation aluminum oxide treatment on the high barrier layer of the composite film A; S43, respectively, mixing the raw materials of the adhesive layer, the transition layer, and the inner base material layer, and placing them in different extruders for plasticization; co-extrusion, film blowing, drawing, and winding to obtain a composite film B; The adhesive layer is mainly composed of PVAc, and the transition layer and the inner substrate layer are mainly composed of PBAT; S44, laminating the aluminum oxide-coated surface of composite film A and the adhesive surface of composite film B with an adhesive, and subjecting the composite film to a curing treatment to obtain a target product, namely, a low-carbon, high-barrier, biodegradable composite film; The raw materials of the inner substrate layer and the composite adhesive both contain a bonding agent, which is an organic polymer chain containing silane, acetate, hydroxyl and catechol structures; The preparation method of the plasticizer comprises the following steps: S11, coupling reaction of a bulky sterically hindered phosphorus chloride with hydroxy acrylate A to obtain intermediate 1I; The phosphorus chloride with large steric hindrance and hydroxy acrylate A are added at a molar ratio of chlorine atoms to hydroxyl groups of 1:1; The large sterically hindered phosphorus chloride is bis(1-adamantyl)phosphonium chloride; S12, subjecting the intermediate product 1I to a Michael addition reaction with an alcoholamine to obtain a target product, i.e., a plasticizer; The intermediate product 1I and the alcoholamine are added at a molar ratio of acryloyloxy to amino of 1:1; The number of acryloyloxy functional groups in the hydroxy acrylate A is ≥2; The preparation method of the compatibilizer comprises the following steps: S21, coupling reaction of nano-silicon with epoxy silane coupling agent to obtain intermediate product 2I; The usage ratio of the nano-silicon to the epoxy silane coupling agent is 1g:5.0-7.0g; S22, subjecting the intermediate product 2I to a ring-opening reaction with an aminopolyethylene glycol amino group to obtain the intermediate product 2II; The intermediate product 2I and the amino polyethylene glycol amino group are added at a molar ratio of epoxy group to amino group of 1:2; S23, reacting the intermediate product 2II with diisocyanate to obtain the target product, i.e., the compatibilizer; The intermediate product 2II and diisocyanate are added at a molar ratio of amino group to isocyanate group of 1:2; The molecular weight of the amino polyethylene glycol amino group is 400-1000.

2. The method for preparing the low-carbon high-barrier biodegradable composite film according to claim 1, characterized in that: The surface substrate layer comprises the following raw materials in parts by weight: PLA 80-90 parts; PBAT 10-20 parts; 10-15 parts of plasticizer; 1.0-3.0 parts of compatibilizer; 0.3-0.5 parts of antioxidant; 0.1-0.2 parts of lubricant; Among them, the total mass of PLA and PBAT is 100 parts; The high barrier layer is processed by vacuum evaporation of aluminum oxide, and the high barrier layer comprises the following raw materials in parts by weight: PLA 70-90 parts; PPC-P 10-30 copies; 8-12 parts of plasticizer; 1.0-2.0 parts of compatibilizer; 0.1-0.5 parts of antioxidant; 0.1-0.2 parts of lubricant; The total mass of PLA and PPC-P is 100 parts.

3. The method for preparing the low-carbon high-barrier biodegradable composite film according to claim 1, characterized in that: The bonding layer comprises the following raw materials in parts by weight: PVAc 90-95 parts; PBAT 5-10 parts; 0.2-0.5 parts of antioxidant; 0.2-0.3 parts of lubricant; Among them, the total mass of PVAc and PBAT is 100 parts; The transition layer comprises the following raw materials in parts by weight: PBAT 100 units; 10-20 parts of nanosheet-shaped inorganic filler; 0.1-0.3 parts of antioxidant; 0.1-0.2 parts of lubricant; The inner substrate layer comprises the following raw materials in parts by weight: PBAT 100 units; 3.0-5.0 parts of bonding agent; 1.0-4.0 parts of anti-hydrolysis agent; 0.1-0.3 parts of antioxidant; Lubricant 0.5-1.0 parts.

4. The method for preparing the low-carbon high-barrier biodegradable composite film according to claim 1, characterized in that: The composite process is dry composite, and the composite adhesive includes the following raw materials in parts by weight: 50 parts of polyether polyol; 5-20 parts of curing agent; 5.0-10.0 parts of bonding agent; 40-60 parts of ethyl acetate.

5. The method for preparing the low-carbon high-barrier biodegradable composite film according to claim 3 or 4, characterized in that: The preparation method of the bonding auxiliary agent comprises the following steps: S31, performing a ring-opening reaction between an epoxy ring-opening agent containing catechol and an epoxy alkene to obtain an intermediate product 3I; The catechol-containing epoxy ring-opener and the epoxy alkene are added at a molar ratio of 1:1 between the epoxy ring-opener and the epoxy group; S32, subjecting vinyl acetate, a silane coupling agent containing a carbon-carbon double bond, hydroxy acrylate B, and the intermediate product 3I to free radical polymerization to obtain a target product, i.e., an adhesive additive; The usage ratio of the vinyl acetate, the silane coupling agent containing a carbon-carbon double bond, the hydroxy acrylate B, and the intermediate product 3I is 0.1-0.3 mol: 0.2-0.4 mol: 0.1-0.3 mol: 0.2-0.4 mol; The hydroxyacrylate B is one of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate or hydroxybutyl acrylate.

6. A low-carbon high-barrier biodegradable composite film, characterized in that: The low-carbon high-barrier biodegradable composite film is prepared by the preparation method of any one of claims 1 to 5.