Low-carbon high-barrier biodegradable composite film and preparation method thereof

Abstract

The invention belongs to the field of polymeric membranes. The invention relates to a low-carbon high-barrier biodegradable composite film and a preparation method thereof, the composite film comprises five layers of films, and the five layers of films sequentially comprise a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer and an inner substrate layer; the high-barrier layer surface is subjected to aluminum oxide vacuum evaporation treatment; the surface base material layer and the high-barrier layer are prepared through double-layer co-extrusion and two-way stretching, and the surface of the high-barrier layer is subjected to vacuum plating; the bonding layer, the transition layer and the inner base material layer are prepared through three-layer co-extrusion and film blowing, and the high-barrier layer surface and the bonding layer surface are subjected to dry compounding and curing to obtain the composite film; the degradable packaging film can effectively overcome the defects that in the prior art, a degradable packaging film is poor in water vapor and oxygen barrier property, transparency is reduced after multiple layers are compounded and the like, and meanwhile compared with a traditional composite film, carbon emission can be reduced by 50% or above.

Description

Technical Field

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

[0002] High-barrier packaging film materials have the functions of blocking oxygen, water vapor, etc., and can play the role of extending the shelf life of the inner package, and are widely used in the packaging fields of food, medicine, cosmetics, etc. Among them, food packaging is the field where high-barrier materials are most widely used at present. High-barrier packaging films have comprehensive properties such as exquisite printing, excellent barrier properties, and outstanding heat-sealing performance. Usually, a single material cannot meet all performance requirements. Therefore, current high-barrier packaging films are basically composite films of multiple materials. The most typical one is the PET / aluminum foil / PE structure. In addition, there are also multiple materials such as PA, EVOH, and PP.

[0003] In view of this, multilayer composite high-barrier packaging materials bring a great deal of convenience to our lives. However, at the same time, they also cause a great burden on the environment and bring serious "white pollution". After several years of practice, the biodegradation route is considered to be the most fundamental way to solve the "white pollution" problem brought by waste high-barrier composite films.

[0004] Among degradable materials, polylactic acid (PLA) is an aliphatic polyester that naturally decomposes into CO2 and water under composting conditions. It is a green and environmentally friendly bio-based material; moreover, it is the only transparent biodegradable polymer and is used in the fields of transparent packaging containers and daily necessities. Although PLA has good biodegradability, processability, and excellent mechanical properties, it is brittle and fragile, lacks elasticity and flexibility, which greatly limits the application of polylactic acid films. Polybutylene adipate terephthalate (PBAT) has excellent biodegradability, as well as good ductility, elongation at break, and impact resistance, etc., but its water vapor barrier performance is poor. Whether PLA and PBAT are used alone or blended, they both have excellent biodegradability, but when blended, the problem of compatibility needs to be solved. Poor compatibility will not only lead to a significant decline in mechanical properties but also affect the transparency of the film. And as a food packaging bag, being able to achieve transparent packaging and making the packaged contents clearly visible is also a major selling point.

[0005] In addition, currently commonly used multilayer composite films need to achieve water vapor barrier performance (<1 g / m 2 ▪d), oxygen barrier performance (<0.5 cm 3 / m 2▪d ▪0.1 MPa), vacuum coating is usually required, and then a composite film is obtained by lamination. Multiple lamination and curing processes are required for multi-layer film lamination. At the same time, the traditional dry lamination and curing process needs to be placed at 50-60 °C for about 48 h, which seriously affects production efficiency and generates a large amount of carbon emissions.

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

[0007] The purpose of the present invention is to provide a low-carbon, high-barrier biodegradable composite film and its preparation method for the defects of poor water vapor and oxygen barrier properties and reduced transparency after multi-layer lamination in the existing degradable packaging films. Self-made plasticizers, compatibilizers, and bonding aids are used in the corresponding film layers of 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 surface is vacuum coated; at the same time, the bonding layer, transition layer, and inner substrate layer are co-extruded and blown to obtain composite film B. Finally, composite film A and composite film B are dry laminated to obtain a low-carbon, high-barrier biodegradable composite film. The technical solution adopted by the present invention to solve its technical problems is: The present invention provides a low-carbon, high-barrier biodegradable composite film, which includes five layers of films, successively including a surface substrate layer, a high-barrier layer, a bonding layer, a transition layer, and an inner substrate layer; the high-barrier layer surface is treated by vacuum evaporation of aluminum oxide; The surface substrate layer includes the following raw materials in parts by weight: PLA 80-90 parts; PBAT 10-20 parts; Plasticizer 10-15 parts; Compatibilizer 1.0-3.0 parts; Antioxidant 0.3-0.5 parts; Lubricant 0.1-0.2 parts; Among them, the total mass of PLA and PBAT is 100 parts; The high-barrier layer includes the following raw materials in parts by weight: PLA 70-90 parts; PPC-P 10-30 parts; Plasticizer 8-12 parts; Compatibilizer 1.0-2.0 parts; Antioxidant 0.1-0.5 parts; Lubricant 0.1-0.2 parts; Among them, the total mass of PLA and PPC-P is 100 parts; The adhesive layer comprises raw materials in the following parts by weight: PVAc 90 - 95 parts; PBAT 5 - 10 parts; Antioxidant 0.2 - 0.5 part; Lubricant 0.2 - 0.3 part; Among them, the total mass of PVAc and PBAT is 100 parts; The transition layer comprises raw materials in the following parts by weight: PBAT 100 parts; Nanosheet-like inorganic filler 10 - 20 parts; Antioxidant 0.1 - 0.3 part; Lubricant 0.1 - 0.2 part; The inner base material layer comprises raw materials in the following parts by weight: PBAT 100 parts; Adhesion aid 3.0 - 5.0 parts; Hydrolysis inhibitor 1.0 - 4.0 parts; Antioxidant 0.1 - 0.3 part; Lubricant 0.5 - 1.0 part; The preparation method of the plasticizer comprises the following steps: S11, carrying out a coupling reaction between the large steric hindrance group phosphorus chloride and the hydroxyacrylate A to obtain the intermediate product I; The dosage ratio of the large steric hindrance group phosphorus chloride to the hydroxyacrylate A is added according to the molar ratio of chlorine atoms to hydroxyl groups being 1:1; S12, carrying out a Michael addition reaction between the intermediate product I and the alkanolamine to obtain the target product, i.e., the plasticizer; The dosage ratio of the intermediate product I to the alkanolamine is added according to the molar ratio of acryloyloxy groups to amino groups being 1:1; The preparation method of the compatibilizer comprises the following steps: S21, carrying out a coupling reaction between the nano-silicon and the epoxy silane coupling agent to obtain the intermediate product II; The dosage ratio of the nano-silicon to the epoxy silane coupling agent is 1 g:5.0 - 7.0 g; S22, carrying out a ring-opening reaction between the intermediate product II and the amino polyethylene glycol amine to obtain the intermediate product III; The dosage ratio of the intermediate product II to the amino polyethylene glycol amine is added according to the molar ratio of epoxy groups to amino groups being 1:2; S23, carrying out a nucleophilic addition reaction between the intermediate product III and the diisocyanate to obtain the target product, i.e., the compatibilizer; The dosage ratio of the intermediate 2II to the diisocyanate is added according to the molar ratio of amino group to isocyanate group of 1:2; The preparation method of the bonding aid includes the following steps: S31, subject the epoxy ring-opening agent containing catechol and the epoxy group alkene to a ring-opening reaction to obtain an intermediate 3I; The dosage ratio of the epoxy ring-opening agent containing catechol to the epoxy group alkene is added according to the molar ratio of the epoxy ring-opening agent to the epoxy group of 1:1; S32, subject vinyl acetate, the carbon-carbon double bond-containing silane coupling agent, hydroxyacrylate B, and the intermediate 3I to free radical polymerization to obtain the target product, i.e., the bonding aid; The dosage ratio of vinyl acetate, the carbon-carbon double bond-containing silane coupling agent, hydroxyacrylate B, and the intermediate 3I is 0.1 - 0.3 mol: 0.2 - 0.4 mol: 0.1 - 0.3 mol: 0.2 - 0.4 mol.

[0008] Further, the large steric hindrance group is an adamantyl group.

[0009] Further, the number of acryloyloxy functional groups in the hydroxyacrylate A is ≥2.

[0010] Further, the molecular weight of the amino polyethylene glycol amino is 400 - 1000.

[0011] Further, the epoxy ring-opening agent containing catechol has a structure containing a carboxyl group or an amino group.

[0012] Another object of the present invention is to provide a preparation method of a low-carbon high-barrier biodegradable composite film, including the following steps: S41, co-extrusion of the surface substrate layer and the high-barrier layer, that is Mix each raw material evenly according to the formula, place it in different extruders for plasticization; co-extrude, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain a composite film A; S42, plating treatment of the composite film A, that is Subject the composite film A to corona treatment and vacuum evaporation aluminization treatment on the high-barrier surface respectively; S43, co-extrusion and blown film of the bonding layer, the transition layer, and the inner substrate layer, that is Mix each raw material evenly according to the formula, place it in different extruders for plasticization; co-extrude, blow film, traction, and winding to obtain a composite film B; and S44, composite treatment, that is Bond the aluminized surface of the composite film A to the bonding surface of the composite film B, and perform curing treatment to obtain the target product, that is, a low-carbon high-barrier biodegradable composite film.

[0013] Furthermore, the transverse draw ratio of the biaxial drawing is 3.0 - 5.0, and the longitudinal draw ratio is 3.0 - 5.0; and the drawing rate is 50 - 60% / s.

[0014] Furthermore, the thickness of the alumina coating is 10 - 50 nm.

[0015] Furthermore, the composite treatment is dry lamination, and the adhesive for lamination comprises raw materials in the following parts by weight: polyether polyol: 50 parts; curing agent: 5 - 20 parts; bonding assistant: 5.0 - 10.0 parts; ethyl acetate: 40 - 60 parts.

[0016] Furthermore, the curing treatment is carried out at a curing temperature of 40 - 50°C for a curing time of 18 - 24 h.

[0017] Advantages of the present invention: (1) The present invention provides a low-carbon high-barrier biodegradable composite film, in which a self-made plasticizer and compatibilizer are added to composite film A. The plasticizer has a large steric hindrance polyhydroxy small molecule structure. On the one hand, the small molecule polyhydroxy structure has excellent plasticizing effect, which can effectively improve the processing performance and toughness of the composite film; on the other hand, the large steric hindrance group endows the plasticizer with excellent low migration property. The compatibilizer has a long-chain type hyperbranched-like structure with a nano-silicon core and isocyanate group-terminated. First, the long-chain structure is beneficial to its effective dispersion in the PLA-based system; second, the isocyanate group structure can have a high reaction rate with hydroxyl groups in PLA, PBAT, etc., and has excellent reaction chain extension effect, which can improve the mechanical properties; third, the long-chain structure has excellent flexibility, which can effectively improve the toughness of the composite film. At the same time, through the synergistic effect of the plasticizer and compatibilizer, the processability and mechanical properties of PLA can be effectively improved.

[0018] (2) The present invention provides a low-carbon high-barrier biodegradable composite film, in which a self-made bonding assistant is added to the inner substrate layer and the adhesive in composite film B, and it is an organic polymer chain containing silane, acetate, hydroxyl, and catechol structures. In the inner substrate layer, the bonding assistant 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 make it enrich at the interface and improve the bonding force with the coating at the same time; second, the catechol structure has excellent adhesion, which 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 adhesive, further improving the bonding strength; fourth, the acetate can provide its bonding force with the bonding layer and improve the solubility of the bonding assistant in the solvent.

[0019] (3) The present invention provides a method for preparing a low-carbon high-barrier biodegradable composite film. First, a surface substrate layer and a high-barrier layer are co-extruded and biaxially stretched to prepare composite film A. On the one hand, compared with the process of separately extruding, stretching and then laminating, the effect can be effectively improved, and it has the effect of low-carbon energy saving; on the other hand, biaxial stretching can improve crystallinity, thereby improving mechanical properties and barrier properties. Second, a nanoscale-thickness vacuum evaporation coating is performed on the high-barrier surface of composite film A, which can maintain excellent transparency while improving the barrier property. Third, the adhesive layer of PVAc can, on the one hand, supplement and provide the adhesion force with the coating surface; on the other hand, as a barrier layer, it can further improve the barrier property; in addition, it can also protect the coating surface from damage. Fourth, composite film B is prepared by three-layer co-extrusion and blown film, with mature process and strong operability. Fifth, composite film A and composite film B are prepared by dry lamination. After the adhesive is modified, the curing period is short, and the low-carbon property is improved. Detailed Description of the Invention

[0020] The present invention will be described in detail below with reference to the embodiments. It should be understood that the following embodiments are only illustrative examples of the implementation modes of the present invention, rather than limiting the scope of the present invention.

[0021] The object of the present invention is to develop a low-carbon high-barrier biodegradable composite film. The design idea is as follows: aiming at 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, and the barrier property is improved by vacuum evaporation coating; at the same time, the coating thickness is controlled to improve transparency; finally, multi-layer co-extrusion is carried out in combination with relevant processes to reduce the carbon emissions generated by the lamination times; and the carbon emissions generated by a single lamination need to be controlled, so as to achieve a low-carbon effect. In addition, some inherent problems, such as the plasticization problem of PLA and the transparency problem caused by the compatibility with other resins, need to be solved together.

[0022] First, for the plasticization problem of PLA, the solution is as follows: by blending with the biodegradable resin PBAT, and adding homemade plasticizers and homemade compatibilizers to solve the problem of plasticization compatibility. Secondly, for the barrier properties of the composite film, the high barrier layer is improved by vacuum evaporation, and considering that the coating is thin and easy to scratch, it is placed in the middle layer of the composite film. Third, for the preparation of the composite film, the surface substrate layer and the high barrier layer are double-layer co-extruded, and the mechanical properties and barrier properties are improved by biaxial stretching, and the high barrier layer is evaporated; at the same time, the PVAc layer, the transition layer, and the inner substrate layer (containing the bonding aid) are prepared by three-layer co-extrusion blown film; the PVAc surface and the high barrier layer are dry-compounded to obtain a composite film. In this process, the inner substrate layer of the homemade bonding aid has a high heat sealing strength after heat sealing, which meets the application of packaging bags and the like; in combination with the preparation process, that is, the five-layer composite film is only composited once, and at the same time, the late aging of the composite process uses the addition of homemade bonding aids to reduce the aging time, which has low carbon properties.

[0023] 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 coupled with hydroxy acrylate, and then the acryloxy group is subjected to 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, the nano silicon is modified by epoxy silane coupling agent, and then the amino-terminated epoxy ring-opening reaction is carried out with a large molecular weight diamine, and finally the reaction is carried out with 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 the bonding auxiliary agent is obtained by free radical copolymerization with the monomer. 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; 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 properties, etc. The embodiments of the present invention are as follows: The embodiment of the present invention provides a low-carbon high-barrier biodegradable composite film, comprising a five-layer film, which sequentially comprises a surface substrate layer, a high-barrier layer, an adhesive layer, a transition layer, and an inner substrate layer; the high-barrier layer is treated by vacuum evaporation of aluminum oxide; 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; Antioxidant 0.3-0.5 parts; Lubricant 0.1-0.2 parts; Among them, the total mass of PLA and PBAT is 100 parts; The high-barrier layer comprises raw materials in the following parts by weight: 70 - 90 parts of PLA; 10 - 30 parts of PPC-P; 8 - 12 parts of plasticizer; 1.0 - 2.0 parts of compatibilizer; 0.1 - 0.5 part of antioxidant; 0.1 - 0.2 part of lubricant; Among them, the total mass of PLA and PPC-P is 100 parts; The adhesive layer comprises raw materials in the following parts by weight: 90 - 95 parts of PVAc; 5 - 10 parts of PBAT; 0.2 - 0.5 part of antioxidant; 0.2 - 0.3 part of lubricant; Among them, the total mass of PVAc and PBAT is 100 parts; The transition layer comprises raw materials in the following parts by weight: 100 parts of PBAT; 10 - 20 parts of nano-sheet inorganic filler; 0.1 - 0.3 part of antioxidant; 0.1 - 0.2 part of lubricant; The inner base material layer comprises raw materials in the following parts by weight: 100 parts of PBAT; 3.0 - 5.0 parts of adhesion aid; 1.0 - 4.0 parts of hydrolysis inhibitor; 0.1 - 0.3 part of antioxidant; 0.5 - 1.0 part of lubricant; The preparation method of the plasticizer comprises the following steps: S11, adding bulky group phosphoryl chloride, hydroxyacrylate A, and triethylamine into N,N-dimethylformamide, stirring at 0 °C for 2 h, slowly heating to room temperature, and stirring overnight; after the reaction, performing vacuum distillation, dissolving the concentrate in dichloromethane, adding deionized water, shaking, separating the liquid, taking the organic phase, drying with anhydrous sodium sulfate, filtering, taking the filtrate, performing vacuum distillation, and drying in vacuum at room temperature for 12 h to obtain intermediate product 1I; The dosage ratio of the bulky group phosphoryl chloride, hydroxyacrylate A, and triethylamine is added according to the molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1; 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; The large steric hindrance group is an adamantyl group; that is, the phosphorus chloride with a large steric hindrance group can be bis(1-adamantyl)phosphorus chloride.

[0024] The number of acryloyloxy functional groups in the hydroxyacrylate A is ≥2; it can be pentaerythritol triacrylate, α,α-diglycerol diacrylate, etc.

[0025] S12. Add the intermediate 1I and the alkanolamine to N,N-dimethylformamide. Stir at room temperature for 2 - 6 h, then perform vacuum distillation, and dry in vacuo at 40 °C for 8 h to obtain the target product, i.e., the plasticizer.

[0026] The dosage ratio of the intermediate 1I to the alkanolamine is added according to the molar ratio of acryloyloxy to amino group being 1:1; The dosage ratio of the intermediate 1I to N,N-dimethylformamide is 0.1 mol: 200 mL; The alkanolamine can be ethanolamine, isopropanolamine, n-butanolamine, diethylene glycol amine, etc.; and preferably diethylene glycol amine.

[0027] The preparation method of the compatibilizer includes the following steps: S21. Place the nano-silicon in ethyl acetate A, ultrasonically disperse for 1 h, then add an epoxy silane coupling agent and deionized water A, slowly heat up to 60 - 80 °C, heat and stir for 6 - 14 h. After the reaction is completed, cool to room temperature, filter, wash with ethyl acetate B, and dry in vacuo at 40 °C to constant weight to obtain the target product, i.e., the intermediate 2I; The dosage 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.

[0028] The average particle size of the nano-silicon is 50 - 100 nm, purchased from Ningbo Jinlei Nano Materials Technology Co., Ltd.; The epoxy silane coupling agent can be silane coupling agent KH560, silane coupling agent A1871, etc.; and preferably silane coupling agent KH560.

[0029] S22. Add the intermediate 2I to N,N-dimethylformamide A, ultrasonically disperse, and then drip it into N,N-dimethylformamide B containing amino polyethylene glycol amino through a peristaltic pump. Heat up to 40 - 60 °C, continue to stir for 2 - 4 h after the dripping is completed, perform vacuum distillation, and then dry in a vacuum oven at 40 °C for 12 h to obtain the intermediate 2II.

[0030] The dosage ratio of the intermediate 2I to the amino polyethylene glycol amino is added according to the molar ratio of epoxy group to amino group of 1:2; The dosage ratio of the intermediate 2I, N,N-dimethylformamide A, and N,N-dimethylformamide B is 1 g: 100 mL: 200 mL.

[0031] The molecular weight of the amino polyethylene glycol amino is 400-1000; it can be 400, 600, 800, 1000, or a range value composed of any two numerical values.

[0032] S23. Add the intermediate 2II to N,N-dimethylformamide C, ultrasonicate, and drip it into N,N-dimethylformamide D containing diisocyanate through a peristaltic pump. Stir at room temperature. After the dripping is completed, continue to stir for 2-4 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.

[0033] The dosage ratio of the intermediate 2II to the diisocyanate is added according to the molar ratio of amino group to isocyanate group of 1:2; The dosage ratio of the intermediate 2II, N,N-dimethylformamide C, and N,N-dimethylformamide D is 1 g: 100 mL: 200 mL.

[0034] The diisocyanate is an asymmetric diisocyanate; it can be toluene diisocyanate or isophorone diisocyanate; The toluene diisocyanate has an asymmetric structure, and there is a certain activity difference between the two isocyanate groups. When one of the highly active isocyanate groups reacts, the activity of the other isocyanate group decreases rapidly; while there is a large activity difference between the two isocyanate groups of isophorone diisocyanate itself; therefore, using an asymmetric diisocyanate can obtain a product capped with an isocyanate group at one end; and preferably isophorone diisocyanate.

[0035] The preparation method of the adhesion aid includes the following steps: S31. Add the catechol-containing epoxy ring-opening agent, epoxy group alkene, catalyst, and hydroquinone to tetrahydrofuran. After reacting for 6-24 h, cool to room temperature, add deionized water, shake, add ethyl acetate for extraction, take the organic phase, dry with anhydrous sodium sulfate, filter, take the filtrate, distill under reduced pressure, and dry in a vacuum at 40 °C for 12 h to obtain the intermediate 3I.

[0036] The dosage ratio of the catechol-containing epoxy ring-opening agent to the epoxy group alkene is added according to the molar ratio of epoxy ring-opening agent to epoxy group of 1:1; The dosage ratio of the catechol-containing epoxy ring-opening agent, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate is added according to 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g; The catechol-containing epoxy ring-opening agent has a structure containing a carboxyl group or an amino group; When it contains a carboxyl group structure, the epoxy ring-opening agent can be protocatechuic acid or homoprotocatechuic acid; and preferably protocatechuic acid; When it contains an amino group structure, the epoxy ring-opening agent can be dopamine.

[0037] The epoxy group alkene can be epoxy acrylate or allyl epoxy; The epoxy acrylate can be glycidyl methacrylate or glycidyl (methacryloyloxy) ethyl ester, etc.; and preferably glycidyl (methacryloyloxy) ethyl ester; The allyl epoxy can be allyl glycidyl ether, 1,2-epoxy-7-octene or 1,2-epoxy-9-decene, etc.; and preferably allyl glycidyl ether.

[0038] The dosage of the catalyst is 0-0.5 wt% of the total mass of the reactants; and the catalyst can be tetrabutylammonium bromide, triethylamine, triphenylphosphine, etc.

[0039] The dosage of the hydroquinone is 0.1 wt% of the mass of the epoxy group alkene.

[0040] S32, Add vinyl acetate, carbon-carbon double bond-containing silane coupling agent, hydroxyacrylate B, intermediate 3I, initiator AIBN to N,N-dimethylformamide, heat to 75-85 °C, stir for 6-10 h; After the reaction is completed, cool to room temperature, filter, take the filtrate, distill under reduced pressure, and dry in vacuum at 60 °C for 6 h to obtain the target product, i.e., the adhesion promoter.

[0041] The dosage ratio of the vinyl acetate, carbon-carbon double bond-containing silane coupling agent, hydroxyacrylate B, intermediate 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.

[0042] The carbon-carbon double bond-containing silane coupling agent can be a vinyl silane coupling agent or an acryloyloxy silane coupling agent; The vinyl silane coupling agent can be silane coupling agent KH151, silane coupling agent KH171 or silane coupling agent KH172, etc.; and preferably silane coupling agent KH151.

[0043] The acryloyloxy silane coupling agent can 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.

[0044] The hydroxyacrylate B may be hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl acrylate, etc.; and preferably hydroxypropyl methacrylate.

[0045] The dosage of the initiator AIBN is 1.0 wt% of the total mass of the monomers.

[0046] The PLA, with the model number PT102, is purchased from Pulisi Biotechnology Co., Ltd.

[0047] The PBAT, with the brand number TH801T, is purchased from Xinjiang Blueshirt Tunhe Polyester Co., Ltd.

[0048] The PPCP has a glass transition temperature (Tg) of 46 °C and is purchased from Shandong Linkuang Co., Ltd.

[0049] The antioxidant is a hindered phenol type; it may be antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant 2246, etc.; and in the following examples and comparative examples of the present invention, the antioxidant is antioxidant 1010.

[0050] The lubricant may be erucamide, oleamide, ethylene bisstearamide, etc.; and in the following examples and comparative examples of the present invention, the lubricant is a mixture of erucamide and ethylene bisstearamide added in a mass ratio of 2 / 1.

[0051] The PVAc, with the model number VINNEX2504, is purchased from Wacker Chemie AG.

[0052] The nano-sheet-like inorganic filler may be talc, montmorillonite, graphene oxide, etc.; and preferably talc.

[0053] The anti-hydrolysis agent is a monomeric anti-hydrolysis agent bis(2,6-diisopropylphenyl)carbodiimide, with the model number HyMax1010, and is purchased from Shanghai Langyi Functional Materials Co., Ltd.

[0054] 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: S41, co-extrusion of the surface substrate layer and the high-barrier layer, that is Mix all the raw materials evenly according to the formula, plasticize them in different extruders; co-extrude, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain composite film A; The temperature of each zone of the surface substrate layer is set at 150-190 °C; The temperature of each zone of the high-barrier layer is set at 155-195 °C; The single-screw extruder is a general screw with a length-diameter ratio of 32:1; The die head temperature is 180 - 190 °C; The transverse draw ratio of the biaxial stretching is 3.0 - 5.0, and the longitudinal draw ratio is 3.0 - 5.0; The stretching temperature is 80 - 100 °C; the stretching rate is 50 - 60% / s; and The heat setting is heat treatment at 90 - 100 °C for 10 - 20 min.

[0055] The thickness of the composite film A is 50 μm.

[0056] S42, plating treatment of the composite film A, that is The composite film A is subjected to corona treatment on the high-barrier layer surfaces respectively, and the surface energy of the corona-treated surface is ≧ 42 dyne; then vacuum evaporation plating of aluminum oxide is carried out; The vacuum evaporation plating of aluminum oxide treatment includes: (1) Pretreatment layer evaporation plating: In a vacuum chamber, high corona first excites plasma, and then the plasma is used to excite the surface layer molecules of the target material to combine with the corona-treated surface, generating an anchoring effect at the organic-inorganic interface to form a pretreatment layer; the pretreatment layer is a Si plating layer with a thickness of 5 nm, increasing the adhesion between the AlO x plating layer and the bottom coating; the pretreatment layer is formed in a vacuum chamber where high corona first excites plasma, and then the plasma is used to excite the surface layer molecules of the Si target material to combine with the coated surface, forming an anchoring effect at the organic-inorganic interface.

[0057] (2) Aluminum oxide evaporation plating: In a high-vacuum chamber, the air pressure ≤ 4.0×10 4 mbar, and the high-energy electron beam thermal evaporation or crucible heating evaporation method is adopted to form a nano AlO x plating layer; or under high voltage, plasma is formed, and under the action of a controlled electromagnetic field, the Al target material is bombarded, and reacts with the introduced process gas O2 to generate AlO x deposited on the surface of the bottom coating to form a dense nano plating layer.

[0058] The thickness of the aluminum oxide plating layer is 10 - 50 nm.

[0059] S43, co-extrusion blow molding of the adhesive layer, transition layer, and inner substrate layer, that is Mix each raw material evenly according to the formula, place them in different extruders for plasticization; co-extrude, blow mold, draw, and wind up to obtain the composite film B; and The set temperature of each zone of the adhesive layer is 80 - 160 °C; The set temperature of each zone of the transition layer is 145 - 175 °C; The set temperature of each zone of the inner substrate layer is 140 - 170 °C; The single-screw extruder is a general screw with a length-diameter ratio of 30:1; The die head temperature is 160 - 170 °C; The traction speed is 6 - 8 m / min, and the blow-up ratio is 3.0 - 4.0; The thickness of the composite film B is 75 μm.

[0060] S44, composite treatment, that is The aluminum oxide-coated surface of the composite film A is laminated with the adhesive layer surface of the composite film B, and then subjected to curing treatment to obtain the target product, namely a low-carbon high-barrier biodegradable composite film.

[0061] The composite treatment is dry lamination. When laminating, the coating amount of the adhesive is 3 g / m 2 ; The adhesive for lamination includes the following raw materials in parts by weight: Polyol 50 parts; Curing agent 5 - 20 parts; Catalyst 0.1 part; Adhesion aid 5.0 - 10.0 parts; Ethyl acetate 40 - 60 parts.

[0062] The polyol is a mixture of polyether polyol and polyester polyol in a mass ratio of 4 / 1; The polyether polyol is polytetrahydrofuran PTMG 2000; The polyester polyol is polycaprolactone diol 1000.

[0063] The curing agent is L-75, with a solid content of 75 ± 2%, produced by Mitsui Takeda of Japan.

[0064] The catalyst is stannous octoate.

[0065] The curing treatment is carried out at a curing temperature of 40 - 50 °C and a curing time of 18 - 24 h.

[0066] To further understand the present invention, the following provides a detailed description of a low-carbon high-barrier biodegradable composite film provided by the present invention in conjunction with specific embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0067] Example 1 This example provides a low-carbon high-barrier biodegradable composite film, which includes five layers of films, successively including a surface substrate layer, a high-barrier layer, an adhesive layer, a transition layer, and an inner substrate layer; the high-barrier layer surface is treated by vacuum evaporation of aluminum oxide; The surface substrate layer includes the following raw materials in parts by weight: PLA 85 parts; PBAT 15 parts; Plasticizer 12 parts; Compatibilizer 2.0 parts; Antioxidant: 0.4 parts; Lubricant: 0.15 parts; The high-barrier layer comprises raw materials in the following parts by weight: PLA: 80 parts; PPC-P: 20 parts; Plasticizer: 10 parts; Compatibilizer: 1.5 parts; Antioxidant: 0.3 parts; Lubricant: 0.15 parts; The adhesive layer comprises raw materials in the following parts by weight: PVAc: 93 parts; PBAT: 7 parts; Antioxidant: 0.3 parts; Lubricant: 0.25 parts; The transition layer comprises raw materials in the following parts by weight: PBAT: 100 parts; Nano-talc powder: 15 parts; Antioxidant: 0.2 parts; Lubricant: 0.15 parts; The inner substrate layer comprises raw materials in the following parts by weight: PBAT: 100 parts; Adhesive aid: 4.0 parts; Hydrolysis-resistant agent: 2.0 parts; Antioxidant: 0.2 parts; Lubricant: 0.7 parts; The preparation method of the plasticizer comprises the following steps: S11: Add bis(1-adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine into N,N-dimethylformamide, stir at 0 °C for 2 h, slowly heat up to room temperature, and stir overnight; after the reaction is completed, perform vacuum distillation, dissolve the concentrate in dichloromethane, add deionized water, shake, separate the liquid, take the organic phase, add anhydrous sodium sulfate for drying, filter, take the filtrate, perform vacuum distillation, and vacuum dry at room temperature for 12 h to obtain intermediate product 1I; The dosage ratio of bis(1-adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine is added according to the molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1; The dosage ratio of pentaerythritol triacrylate, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g.

[0068] Its infrared data is as follows: 3516 cm -1:-OH does not exist; 1735 cm -1 :-C=O exists; 1126 cm -1 :-P-O- exists; 1609 cm -1 、810 cm -1 :-C=C- exists.

[0069] S12, Add the intermediate 1I and diethanolamine to N,N-dimethylformamide. Stir at room temperature for 4.5 h, then distill under reduced pressure and dry in vacuo at 40 °C for 8 h to obtain the target product, i.e., the plasticizer.

[0070] The dosage ratio of the intermediate 1I to diethanolamine is added according to the molar ratio of acryloyloxy group to amino group of 1:1; The dosage ratio of the intermediate 1I to N,N-dimethylformamide is 0.1 mol:200 mL.

[0071] Its infrared data are as follows: 3519 cm -1 :-OH exists; 3312 cm -1 :-NH- exists; 1735 cm -1 :-C=O exists; 1126 cm -1 :-P-O- exists; 1609 cm -1 、810 cm -1 :-C=C- does not exist.

[0072] The preparation method of the compatibilizer includes the following steps: S21, Place the nano-silicon in ethyl acetate A, ultrasonically disperse for 1 h, then add silane coupling agent KH560 and deionized water A, slowly heat up to 70 °C, heat and stir for 9 h. After the reaction is completed, cool to room temperature, filter, wash with ethyl acetate B, and dry in vacuo at 40 °C to constant weight to obtain the target product, i.e., the intermediate 2I; The dosage 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.

[0073] Its infrared data are as follows: 3426 cm -1 :-OH exists and is significantly weakened; 1265 cm -1 、893 cm -1 、825 cm -1 :-Epoxy group exists; 1109 cm -1 、801 cm -1 :-Si-O- exists.

[0074] S22. Add the intermediate 2I into N,N-dimethylformamide A, sonicate, and then drip it into N,N-dimethylformamide B containing amino polyethylene glycol amine through a peristaltic pump. Heat the mixture to 50 °C, continue stirring for 2.5 h after the addition is completed, perform vacuum distillation, and then dry it in a vacuum oven at 40 °C for 12 h to obtain the intermediate 2II.

[0075] The dosage ratio of the intermediate 2I to amino polyethylene glycol amine is added according to the molar ratio of epoxy group to amino group being 1:2. The dosage ratio of the intermediate 2I, N,N-dimethylformamide A, and N,N-dimethylformamide B is 1 g: 100 mL: 200 mL.

[0076] The molecular weight of the amino polyethylene glycol amine is 600.

[0077] Its infrared data is as follows: 3426 cm -1 : -OH exists (very weak); 3311 cm -1 : -NH- exists; 1265 cm -1 、893 cm -1 、825 cm -1 : Epoxy group does not exist; 1109 cm -1 、801 cm -1 : -Si-O- exists.

[0078] S23. Add the intermediate 2II into N,N-dimethylformamide C, sonicate, and then drip it into N,N-dimethylformamide D containing isophorone diisocyanate through a peristaltic pump. Stir at room temperature, continue stirring for 2.5 h after the addition is completed, perform vacuum distillation, and then dry it in a vacuum oven at 40 °C for 12 h to obtain the target product, i.e., the compatibilizer.

[0079] The dosage ratio of the intermediate 2II to isophorone diisocyanate is added according to the molar ratio of amino group to isocyanate group being 1:2. The dosage ratio of the intermediate 2II, N,N-dimethylformamide C, and N,N-dimethylformamide D is 1 g: 100 mL: 200 mL.

[0080] Its infrared data is as follows: 3426 cm -1 : -OH exists (very weak); 3311 cm -1 : -NH- exists and weakens; 2275 cm -1 : -NCO exists; 1109 cm -1 、801 cm -1 : -Si-O- exists.

[0081] The preparation method of the adhesion aid includes the following steps: S31. Add dopamine, allyl glycidyl ether, catalyst, and hydroquinone into tetrahydrofuran. After reacting at room temperature for 6 h, cool to room temperature, add deionized water, shake, add ethyl acetate for extraction, take the organic phase, dry it with anhydrous sodium sulfate, filter, take the filtrate, distill it under reduced pressure, and dry it in vacuum at 40 °C for 12 h to obtain the intermediate 3I.

[0082] The dosage ratio of dopamine to allyl glycidyl ether is added according to the molar ratio of dopamine to epoxy group of 1:1. The dosage ratio of dopamine, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate is added according to 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0083] The dosage of the catalyst is 0 wt% of the total mass of the reactants; that is, no catalyst is added.

[0084] The dosage of hydroquinone is 0.1 wt% of the mass of allyl epoxy.

[0085] Its infrared data is as follows: 3531 cm -1 : -OH exists; 3310 cm -1 : -NH- exists and weakens; 1616 cm -1 : -C=C- exists; 1265 cm -1 、893 cm -1 、825 cm -1 : The epoxy group does not exist.

[0086] S32. Add vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate 3I, and initiator AIBN into N,N-dimethylformamide. Heat up to 80 °C and stir for 7.5 h; after the reaction is completed, cool to room temperature, filter, take the filtrate, distill it under reduced pressure, and dry it in vacuum at 60 °C for 6 h to obtain the target product, that is, the bonding aid ( ).

[0087] The dosage ratio of vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate 3I, and N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL.

[0088] Its infrared data is as follows: 3531 cm -1 : -OH exists; 3310 cm -1 : -NH- exists and weakens; 3011 cm -1 、1595 cm -1 、1498 cm -1 : Benzene ring exists; 1735 cm -1: -C=O exists; 1109 cm -1 、801 cm -1 : -Si-O- exists; 1616 cm -1 、1606 cm -1 、811 cm -1 : -C=C- does not exist.

[0089] The dosage of the initiator AIBN is 1.0 wt% of the total mass of the monomers.

[0090] Another object of this embodiment is to provide a preparation method of a low-carbon high-barrier biodegradable composite film, including the following steps: S41, co-extrusion of the surface substrate layer and the high-barrier layer, that is Mix each raw material evenly according to the formula, plasticize it in different extruders; co-extrude, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain composite film A; The set temperatures of each zone of the surface substrate layer are 155 °C, 165 °C, 175 °C, 180 °C, 185 °C, 185 °C respectively; The set temperatures of each zone of the high-barrier layer are 160 °C, 170 °C, 180 °C, 185 °C, 190 °C, 190 °C respectively; The single-screw extruder is a general screw with a length-diameter ratio of 32:1; The die head temperature is 185 °C; The transverse stretching ratio of the biaxial stretching is 4.0, and the longitudinal stretching ratio is 4.0; The stretching temperature is 90 °C; the stretching rate is 55% / s; and The heat setting is heat treatment at 95 °C for 15 min.

[0091] The thickness of the composite film A is 50 μm; among them, the surface substrate layer and the high-barrier layer are 25 μm respectively.

[0092] S42, plating treatment of the composite film A, that is Perform corona treatment on the high-barrier surface of the composite film A respectively. After treatment, the surface energy of the corona surface is ≧ 42 dyne; then perform vacuum evaporation plating of aluminum oxide treatment; The thickness of the aluminum oxide plating layer is 30 nm.

[0093] S43, co-extrusion and blown film of the adhesive layer, the transition layer, and the inner substrate layer, that is Mix each raw material evenly according to the formula, plasticize it in different extruders; co-extrude, blown film, traction, and winding to obtain composite film B; and The set temperatures of each zone of the adhesive layer are 85 °C, 105 °C, 125 °C, 140 °C, 150 °C, 155 °C respectively; The set temperatures of each zone of the transition layer are 150 °C, 158 °C, 164 °C, 168 °C, 170 °C, and 170 °C respectively; The set temperatures of each zone of the inner base material layer are 145 °C, 154 °C, 160 °C, 160 °C, 165 °C, and 165 °C respectively; The single-screw extruder is a general-purpose screw with a length-diameter ratio of 30:1; The die head temperature is 165 °C; The traction speed is 7 m / min and the blow-up ratio is 3.5; The thickness of the composite film B is 75 μm; among them, the adhesive layer, the transition layer, and the inner base material layer are 15 μm, 30 μm, and 30 μm respectively.

[0094] S44, composite treatment, that is The aluminum oxide-coated surface of the composite film A is compounded with the adhesive surface of the composite film B, and then subjected to curing treatment to obtain the target product, namely a low-carbon high-barrier biodegradable composite film.

[0095] The composite treatment is dry lamination, and the coating amount of the adhesive during lamination is 3 g / m 2 ; The adhesive for lamination includes the following raw materials in parts by weight: Polyol 50 parts; Curing agent 10 parts; Catalyst 0.1 part; Adhesion aid 8.0 parts; Ethyl acetate 50 parts.

[0096] The curing treatment is carried out at a curing temperature of 45 °C and a curing time of 20 h.

[0097] Example 2 This example provides a low-carbon high-barrier biodegradable composite film, which includes five layers of film, successively including a surface base material layer, a high-barrier layer, an adhesive layer, a transition layer, and an inner base material layer; the high-barrier layer is treated by vacuum evaporation of aluminum oxide; The surface base material layer includes the following raw materials in parts by weight: PLA 80 parts; PBAT 20 parts; Plasticizer 10 parts; Compatibilizer 3.0 parts; Antioxidant 0.3 part; Lubricant 0.2 part; The high-barrier layer includes the following raw materials in parts by weight: PLA 70 parts; PPC-P 30 parts; Plasticizer 8 parts; Compatibilizer: 2.0 parts; Antioxidant: 0.1 part; Lubricant: 0.2 part; The adhesive layer comprises raw materials in the following parts by weight: PVAc: 90 parts; PBAT: 10 parts; Antioxidant: 0.2 part; Lubricant: 0.3 part; The transition layer comprises raw materials in the following parts by weight: PBAT: 100 parts; Nano talcum powder: 10 parts; Antioxidant: 0.1 part; Lubricant: 0.2 part; The inner base material layer comprises raw materials in the following parts by weight: PBAT: 100 parts; Adhesion aid: 3.0 parts; Hydrolysis inhibitor: 4.0 parts; Antioxidant: 0.1 part; Lubricant: 0.5 part; The preparation method of the plasticizer comprises the following steps: S11. Add bis(1-adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine into N,N-dimethylformamide, stir at 0 °C for 2 h, slowly warm up to room temperature, and stir overnight; after the reaction is completed, carry out reduced pressure distillation, dissolve the concentrate in dichloromethane, add deionized water, shake, separate the liquid, take the organic phase, add anhydrous sodium sulfate for drying, filter, take the filtrate, carry out reduced pressure distillation, and vacuum dry at room temperature for 12 h to obtain intermediate product 1I; The dosage ratio of bis(1-adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine is added according to the molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1; The dosage ratio of pentaerythritol triacrylate, N,N-dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol: 200 mL: 200 mL: 300 mL: 20 g.

[0098] S12. Add intermediate product 1I and diethanolamine into N,N-dimethylformamide, stir at room temperature for 2 h, then carry out reduced pressure distillation, and vacuum dry at 40 °C for 8 h to obtain the target product, i.e., the plasticizer.

[0099] The dosage ratio of intermediate product 1I and diethanolamine is added according to the molar ratio of acryloyloxy group and amino group of 1:1; The dosage ratio of the intermediate 1I to N,N-dimethylformamide is 0.1 mol: 200 mL.

[0100] The preparation method of the compatibilizer includes the following steps: S21: Place the nano-silicon in ethyl acetate A, ultrasonically disperse for 1 h, then add silane coupling agent KH560 and deionized water A, slowly heat up to 60 °C, heat and stir for 14 h. After the reaction is completed, cool to room temperature, filter, wash with ethyl acetate B, and vacuum dry at 40 °C until constant weight to obtain the target product, i.e., intermediate 2I. The dosage 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.

[0101] S22: Add intermediate 2I to N,N-dimethylformamide A, ultrasonically disperse, and then drip it into N,N-dimethylformamide B containing amino-polyethylene glycol-amine through a peristaltic pump. Heat up to 60 °C, continue to stir for 2 h after the dripping is completed, perform reduced-pressure distillation, and then dry in a vacuum oven at 40 °C for 12 h to obtain intermediate 2II.

[0102] The dosage ratio of intermediate 2I to amino-polyethylene glycol-amine is added according to the molar ratio of epoxy group to amino group of 1:2. The dosage ratio of intermediate 2I, N,N-dimethylformamide A, and N,N-dimethylformamide B is 1 g: 100 mL: 200 mL.

[0103] The molecular weight of the amino-polyethylene glycol-amine is 600.

[0104] S23: Add intermediate 2II to N,N-dimethylformamide C, ultrasonically disperse, and then drip it into N,N-dimethylformamide D containing isophorone diisocyanate through a peristaltic pump. Stir at room temperature, continue to stir for 2 h after the dripping is completed, perform reduced-pressure distillation, and then dry in a vacuum oven at 40 °C for 12 h to obtain the target product, i.e., the compatibilizer.

[0105] The dosage ratio of intermediate 2II to isophorone diisocyanate is added according to the molar ratio of amino group to isocyanate group of 1:2. The dosage ratio of intermediate 2II, N,N-dimethylformamide C, and N,N-dimethylformamide D is 1 g: 100 mL: 200 mL.

[0106] The preparation method of the adhesion aid includes the following steps: S31. Add protocatechuic acid, allyl glycidyl ether, tetrabutylammonium bromide, and hydroquinone into tetrahydrofuran. After heating under reflux for 24 h, cool to room temperature, add deionized water, shake, add ethyl acetate for extraction, take the organic phase, dry it with anhydrous sodium sulfate, filter, take the filtrate, distill it under reduced pressure, and dry it in vacuum at 40 °C for 12 h to obtain intermediate 3I.

[0107] The dosage ratio of protocatechuic acid to allyl glycidyl ether is added according to the molar ratio of protocatechuic acid to epoxy group of 1:1. The dosage ratio of protocatechuic acid, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate is added according to 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0108] The dosage of tetrabutylammonium bromide is 0.5 wt% of the total mass of the reactants.

[0109] The dosage of hydroquinone is 0.1 wt% of the mass of allyl epoxy.

[0110] S32. Add vinyl acetate, silane coupling agent KH151, hydroxypropyl methacrylate, intermediate 3I, and initiator AIBN into N,N-dimethylformamide, heat up to 85 °C, and stir for 6 h; after the reaction is completed, cool to room temperature, filter, take the filtrate, distill it under reduced pressure, and dry it in vacuum at 60 °C for 6 h to obtain the target product, namely the adhesion promoter.

[0111] The dosage ratio of vinyl acetate, silane coupling agent KH151, hydroxypropyl methacrylate, intermediate 3I, and N,N-dimethylformamide is 0.2 mol: 0.3 mol: 0.2 mol: 0.3 mol: 1000 mL.

[0112] The dosage of initiator AIBN is 1.0 wt% of the total mass of the monomers.

[0113] Another object of this embodiment is to provide a preparation method of a low-carbon high-barrier biodegradable composite film, including the following steps: S41. Co-extrusion of the surface substrate layer and the high-barrier layer, that is Mix each raw material evenly according to the formula, place it in different extruders for plasticization; co-extrude, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain composite film A; The set temperatures of each zone of the surface substrate layer are 150 °C, 160 °C, 170 °C, 175 °C, 180 °C, 180 °C respectively; The set temperatures of each zone of the high-barrier layer are 155 °C, 165 °C, 175 °C, 180 °C, 185 °C, 185 °C respectively; The single-screw extruder is a general-purpose screw with a length-diameter ratio of 32:1; The die head temperature is 180 °C; The transverse draw ratio of the biaxial stretching is 5.0, and the longitudinal draw ratio is 5.0; The stretching temperature is 100 °C; the stretching rate is 60% / s; and The heat setting is heat treatment at 100 °C for 10 min.

[0114] The thickness of the composite film A is 50 μm; among them, the surface base material layer and the high-barrier layer are 25 μm respectively.

[0115] S42, plating treatment of the composite film A, that is The composite film A is subjected to corona treatment on the high-barrier surface respectively, and the surface energy of the corona-treated surface is ≧ 42 dyne; then vacuum evaporation plating of aluminum oxide is carried out; The thickness of the aluminum oxide coating is 10 nm.

[0116] S43, coextrusion blown film of the adhesive layer, the transition layer and the inner base material layer, that is Mix each raw material evenly according to the formula, place it in different extruders for plasticization; coextrude, blow film, draw, and wind up to obtain the composite film B; and The set temperatures of each zone of the adhesive layer are 80 °C, 100 °C, 120 °C, 140 °C, 145 °C, 150 °C respectively; The set temperatures of each zone of the transition layer are 145 °C, 154 °C, 158 °C, 161 °C, 164 °C, 165 °C respectively; The set temperatures of each zone of the inner base material layer are 140 °C, 147 °C, 150 °C, 155 °C, 158 °C, 160 °C respectively; The single-screw extruder is a general-purpose screw with a length-diameter ratio of 30:1; The die head temperature is 160 °C; The draw speed is 6 m / min, and the blow-up ratio is 3.0; The thickness of the composite film B is 75 μm; among them, the adhesive layer, the transition layer and the inner base material layer are 15 μm, 30 μm, 30 μm respectively.

[0117] S44, composite treatment, that is The aluminum oxide-coated surface of the composite film A and the adhesive surface of the composite film B are compounded and subjected to curing treatment to obtain the target product, that is, a low-carbon high-barrier biodegradable composite film.

[0118] The composite treatment is dry lamination, and the coating amount of the adhesive during lamination is 3 g / m 2 ; The adhesive for lamination includes the following raw materials in parts by weight: Polyol 50 parts; 20 parts of curing agent; 0.1 part of catalyst; 10.0 parts of adhesion promoter; 60 parts of ethyl acetate.

[0119] The curing treatment is carried out at a curing temperature of 40 °C for 24 h.

[0120] Example 3 This example provides a low-carbon high-barrier biodegradable composite film, which comprises five layers of film, including a surface base material layer, a high-barrier layer, an adhesion layer, a transition layer, and an inner base material layer in sequence; the high-barrier layer is treated by vacuum evaporation of aluminum oxide; The surface base material layer comprises the following raw materials in parts by weight: 90 parts of PLA; 10 parts of PBAT; 15 parts of plasticizer; 1.0 part of compatibilizer; 0.5 part of antioxidant; 0.1 part of lubricant; The high-barrier layer comprises the following raw materials in parts by weight: 90 parts of PLA; 10 parts of PPC-P; 12 parts of plasticizer; 1.0 part of compatibilizer; 0.5 part of antioxidant; 0.1 part of lubricant; The adhesion layer comprises the following raw materials in parts by weight: 95 parts of PVAc; 5 parts of PBAT; 0.5 part of antioxidant; 0.2 part of lubricant; The transition layer comprises the following raw materials in parts by weight: 100 parts of PBAT; 20 parts of nano-talc powder; 0.3 part of antioxidant; 0.1 part of lubricant; The inner base material layer comprises the following raw materials in parts by weight: 100 parts of PBAT; 5.0 parts of adhesion promoter; 1.0 part of hydrolysis inhibitor; 0.3 part of antioxidant; 1.0 part of lubricant; The preparation method of the plasticizer comprises the following steps: S11. Add bis(1 - adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine into N,N - dimethylformamide. Stir at 0 °C for 6 h, then slowly warm up to room temperature and stir overnight. After the reaction is completed, perform vacuum distillation. Dissolve the concentrate in dichloromethane, add deionized water, shake, separate the layers, take the organic phase, add anhydrous sodium sulfate for drying, filter, take the filtrate, perform vacuum distillation, and dry in vacuum at room temperature for 12 h to obtain intermediate product 1I; The dosage ratio of bis(1 - adamantyl)phosphorus chloride, pentaerythritol triacrylate, and triethylamine is added according to the molar ratio of chlorine atom, hydroxyl group, and triethylamine of 1:1:1; The dosage ratio of pentaerythritol triacrylate, N,N - dimethylformamide, dichloromethane, deionized water, and anhydrous sodium sulfate is 0.1 mol:200 mL:200 mL:300 mL:20 g.

[0121] S12. Add intermediate product 1I and diethanolamine into N,N - dimethylformamide. Stir at room temperature for 2 h, then perform vacuum distillation and dry in vacuum at 40 °C for 8 h to obtain the target product, i.e., the plasticizer.

[0122] The dosage ratio of intermediate product 1I and diethanolamine is added according to the molar ratio of acryloyloxy group and amino group of 1:1; The dosage ratio of intermediate product 1I and N,N - dimethylformamide is 0.1 mol:200 mL; The preparation method of the compatibilizer includes the following steps: S21. Place nano - silicon in ethyl acetate A, ultrasonically disperse for 1 h, then add silane coupling agent KH560 and deionized water A, slowly warm up to 80 °C, heat and stir for 6 h. After the reaction is completed, cool to room temperature, filter, wash with ethyl acetate B, and dry in vacuum at 40 °C to constant weight to obtain the target product, i.e., intermediate product 2I; The dosage ratio of 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.

[0123] S22. Add intermediate product 2I into N,N - dimethylformamide A, ultrasonically disperse, and then drip it into N,N - dimethylformamide B containing amino - polyethylene glycol - amino through a peristaltic pump. Heat up to 40 °C, continue to stir for 4 h after the dripping is completed, perform vacuum distillation, and then dry in a vacuum oven at 40 °C for 12 h to obtain intermediate product 2II.

[0124] The dosage ratio of intermediate product 2I and amino - polyethylene glycol - amino is added according to the molar ratio of epoxy group and amino group of 1:2; The dosage ratio of the intermediate 2I, N,N-dimethylformamide A, and N,N-dimethylformamide B is 1 g: 100 mL: 200 mL.

[0125] The molecular weight of the amino polyethylene glycol amino is 600.

[0126] S23. Add the intermediate 2II into N,N-dimethylformamide C, ultrasonicate, and then dropwise add it into N,N-dimethylformamide D containing isophorone diisocyanate through a peristaltic pump. Stir at room temperature. After the dropping is completed, continue stirring for 4 h. Perform vacuum distillation, and then dry in a vacuum oven at 40 °C for 12 h to obtain the target product, i.e., the compatibilizer.

[0127] The dosage ratio of the intermediate 2II to isophorone diisocyanate is added according to the molar ratio of amino group to isocyanate group of 1:2. The dosage ratio of the intermediate 2II, N,N-dimethylformamide C, and N,N-dimethylformamide D is 1 g: 100 mL: 200 mL.

[0128] The preparation method of the adhesion aid includes the following steps: S31. Add dopamine, glycidyl methacrylate, catalyst, and hydroquinone into tetrahydrofuran. React at room temperature for 6 h, then cool to room temperature, add deionized water, shake, add ethyl acetate for extraction, take the organic phase, dry with anhydrous sodium sulfate, filter, take the filtrate, perform vacuum distillation, and dry in a vacuum at 40 °C for 12 h to obtain the intermediate 3I.

[0129] The dosage ratio of dopamine to glycidyl methacrylate is added according to the molar ratio of dopamine to epoxy group of 1:1. The dosage ratio of dopamine, tetrahydrofuran, deionized water, ethyl acetate, and anhydrous sodium sulfate is added according to 0.1 mol: 100 mL: 150 mL: 200 mL: 10 g.

[0130] The dosage of the catalyst is 0 wt% of the total mass of the reactants; that is, no catalyst is added.

[0131] The dosage of hydroquinone is 0.1 wt% of the mass of the epoxy group alkene.

[0132] S32. Add vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate 3I, and initiator AIBN into N,N-dimethylformamide. Heat to 75 °C and stir for 10 h; after the reaction is completed, cool to room temperature, filter, take the filtrate, perform vacuum distillation, and dry in a vacuum at 60 °C for 6 h to obtain the target product, i.e., the adhesion aid.

[0133] The dosage 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: 0.3 mol: 1000 mL.

[0134] The dosage of initiator AIBN is 1.0 wt% of the total mass of the monomers.

[0135] Another object of this embodiment is to provide a method for preparing a low-carbon high-barrier biodegradable composite film, including the following steps: S41, co-extrusion of the surface substrate layer and the high-barrier layer, that is Mix the raw materials evenly according to the formula, place them in different extruders for plasticization; co-extrude, vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain composite film A; The temperatures of each zone of the surface substrate layer are set to 160 °C, 170 °C, 180 °C, 186 °C, 190 °C, and 190 °C respectively; The temperatures of each zone of the high-barrier layer are set to 165 °C, 175 °C, 185 °C, 190 °C, 195 °C, and 195 °C respectively; The single-screw extruder is a general screw with a length-diameter ratio of 32:1; The die head temperature is 190 °C; The transverse stretching ratio of the biaxial stretching is 3.0, and the longitudinal stretching ratio is 3.0; The stretching temperature is 80 °C; the stretching rate is 50% / s; and The heat setting is heat treatment at 90 °C for 20 min.

[0136] The thickness of composite film A is 50 μm; among them, the surface substrate layer and the high-barrier layer are 25 μm respectively.

[0137] S42, plating treatment of composite film A, that is Corona treatment is carried out on the high-barrier surface of composite film A, and the surface energy of the corona-treated surface is ≧ 42 dyne; then vacuum evaporation plating of alumina is carried out; The thickness of the alumina plating layer is 50 nm.

[0138] S43, co-extrusion and blown film of the adhesive layer, transition layer, and inner substrate layer, that is Mix the raw materials evenly according to the formula, place them in different extruders for plasticization; co-extrude, blow film, traction, and winding to obtain composite film B; and The temperatures of each zone of the adhesive layer are set to 90 °C, 110 °C, 130 °C, 150 °C, 155 °C, and 160 °C respectively; The set temperatures of the respective temperature zones of the transition layer are 155°C, 162°C, 168°C, 174°C, 175°C, and 175°C respectively; The set temperatures of the respective temperature zones of the inner base material layer are 150°C, 158°C, 162°C, 165°C, 168°C, and 170°C respectively; The single-screw extruder is a general-purpose screw with a length-diameter ratio of 30:1; The die head temperature is 170°C; The traction speed is 8 m / min and the blow-up ratio is 4.0; The thickness of the composite film B is 75 μm; among them, the adhesive layer, the transition layer, and the inner base material layer are 15 μm, 30 μm, and 30 μm respectively.

[0139] S44, composite treatment, that is The aluminum oxide-coated surface of the composite film A is compounded with the adhesive surface of the composite film B, and after curing treatment, the target product, that is, a low-carbon high-barrier biodegradable composite film, is obtained.

[0140] The composite treatment is dry lamination, and the coating amount of the adhesive during lamination is 3 g / m 2 ; The adhesive for lamination includes the following raw materials in parts by weight: Polyol 50 parts; Curing agent 5 parts; Catalyst 0.1 part; Adhesion aid 5.0 parts; Ethyl acetate 40 parts.

[0141] The curing treatment is a curing temperature of 50°C and a curing time of 18 h.

[0142] Example 4 Others are the same as in Example 1, the difference is: In the preparation method of the plasticizer in the formula of a low-carbon high-barrier biodegradable composite film, in S11, The pentaerythritol triacrylate is replaced with α,α-diglycerol diacrylate.

[0143] Example 5 Others are the same as in Example 1, the difference is: In the preparation method of the compatibilizer in the formula of a low-carbon high-barrier biodegradable composite film, in S22, The molecular weight of the amino polyethylene glycol amino is 400.

[0144] Example 6 Others are the same as in Example 1, the difference is: In the preparation method of the compatibilizer in the formula of a low-carbon high-barrier biodegradable composite film, in S22, The molecular weight of the amino polyethylene glycol amino group is 1000.

[0145] Example 7 The others are the same as in Example 1, except that: In the preparation method of the adhesion aid in the formula of a low-carbon high-barrier biodegradable composite film, in S32, The dosage ratio of the vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.1 mol: 0.4 mol: 0.1 mol: 0.4 mol: 1000 mL.

[0146] Example 8 The others are the same as in Example 1, except that: In the preparation method of the adhesion aid in the formula of a low-carbon high-barrier biodegradable composite film, in S32, The dosage ratio of the vinyl acetate, silane coupling agent KH570, hydroxypropyl methacrylate, intermediate product 3I, and N,N-dimethylformamide is 0.3 mol: 0.2 mol: 0.3 mol: 0.2 mol: 1000 mL.

[0147] The following comparative examples are all compared with Specific Example 1: Comparative Example 1 The others are the same as in Example 1, except that: In a low-carbon high-barrier biodegradable composite film formula, No plasticizer is added to the surface base material layer and the high-barrier layer raw material formula.

[0148] Comparative Example 2 The others are the same as in Example 1, except that: In the preparation method of the plasticizer in the formula of a low-carbon high-barrier biodegradable composite film, in S11, The pentaerythritol triacrylate is replaced with 2-hydroxyethyl acrylate.

[0149] Comparative Example 3 The others are the same as in Example 1, except that: In a low-carbon high-barrier biodegradable composite film formula, The plasticizer is replaced with glycerol.

[0150] Comparative Example 4 The others are the same as in Example 1, except that: In a low-carbon high-barrier biodegradable composite film formula, No compatibilizer is added to the surface base material layer and the high-barrier layer raw material formula.

[0151] Comparative Example 5 The rest is the same as in Example 1, except that: In the preparation method of the compatibilizer in the formulation of a low-carbon high-barrier biodegradable composite film, in S22, the amino polyethylene glycol amino group is replaced with ethylenediamine.

[0152] Implement Comparative Example 6 The rest is the same as in Example 1, except that: In the preparation method of the compatibilizer in the formulation of a low-carbon high-barrier biodegradable composite film, in S22, the molecular weight of the amino polyethylene glycol amino group is 2000.

[0153] Implement Comparative Example 7 The rest is the same as in Example 1, except that: In a low-carbon high-barrier biodegradable composite film formulation, no adhesion aid is added to the raw material formulation of the adhesive layer.

[0154] Implement Comparative Example 8 The rest is the same as in Example 1, except that: In a preparation method of a low-carbon high-barrier biodegradable composite film, no adhesion aid is added to the adhesive formulation.

[0155] Implement Comparative Example 9 The rest is the same as in Example 1, except that: In the preparation method of the adhesion aid in the formulation of a low-carbon high-barrier biodegradable composite film, in S32, the dosage ratio of 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, vinyl acetate is not added.

[0156] Implement Comparative Example 10 The rest is the same as in Example 1, except that: In the preparation method of the adhesion aid in the formulation of a low-carbon high-barrier biodegradable composite film, in S32, the dosage ratio of 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, silane coupling agent KH570 is not added.

[0157] Implement Comparative Example 11 The rest is the same as in Example 1, except that: A preparation method of a bonding aid in a low-carbon high-barrier biodegradable composite film formulation. In S32, The dosage 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.

[0158] Implement Comparative Example 12 Other conditions are the same as those in Example 1, except that: A preparation method of a bonding aid in a low-carbon high-barrier biodegradable composite film formulation. In S32, The dosage 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, intermediate product 3I is not added.

[0159] Implement Comparative Example 13 Other conditions are the same as those in Example 1, except that: A preparation method of a low-carbon high-barrier biodegradable composite film. In S42, No vacuum evaporation coating treatment is carried out.

[0160] Implement Comparative Example 14 Other conditions are the same as those in Example 1, except that: A preparation method of a low-carbon high-barrier biodegradable composite film. In S42, The thickness of the aluminum oxide coating is 5 nm.

[0161] Implement Comparative Example 15 Other conditions are the same as those in Example 1, except that: A preparation method of a low-carbon high-barrier biodegradable composite film. In S42, The thickness of the aluminum oxide coating is 60 nm.

[0162] Implement Comparative Example 16 Other conditions are the same as those in Example 1, except that: A preparation method of a low-carbon high-barrier biodegradable composite film. In S41, The composite film A is not subjected to a biaxial stretching process.

[0163] Implement Comparative Example 17 Other conditions are the same as those in Example 1, except that: A preparation method of a low-carbon high-barrier biodegradable composite film. In S43, The composite film B does not contain a PVAc layer.

[0164] The physical property results of the low-carbon high-barrier biodegradable composite films in the examples and comparative examples of the present invention were measured separately, as shown in Table 1.

[0165] Table 1 Physical test properties of each example 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 transmission rate (cm3 / m2 ▪d ▪0.1MPa) Light transmittance (%) Heat seal 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 Control Example 1 121 102 53 61 1.70 0.68 74.8 30.79 Control Example 2 136 113 76 92 1.39 0.51 76.0 34.80 Control Example 3 168 149 117 135 0.57 0.26 79.2 32.64 Control Example 4 106 87 90 103 2.03 0.74 70.3 28.91 Control Example 5 146 121 95 105 1.38 0.66 75.2 33.07 Control Example 6 117 98 102 120 1.19 0.57 75.0 33.82 Control Example 7 155 134 114 128 0.67 0.30 78.1 22.56 Control Example 8 151 143 118 115 0.62 0.29 78.2 18.63 Control Example 9 160 141 105 130 0.58 0.26 78.9 30.18 Control Example 10 166 132 108 131 0.57 0.25 78.4 28.35 Control Example 11 158 144 110 122 0.60 0.27 79.0 29.80 Control Example 12 154 146 113 119 0.57 0.26 79.2 26.49 Control Example 13 130 113 121 135 53.5 6.61 85.6 37.93 Control Example 14 148 130 116 132 1.23 0.56 80.3 37.89 Control Example 15 165 144 104 120 0.51 0.20 71.1 37.11 Control Example 16 123 106 95 108 1.06 0.53 81.5 35.84 Control Example 17 160 143 108 125 1.14 0.47 79.0 30.35 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 (biaxial mechanical strength > 100 MPa, biaxial elongation at break > 100%), water vapor barrier property (< 1 g / m 2 ▪d), oxygen barrier property (< 0.5 cm 3 / m 2 ▪d ▪0.1 MPa), light transmittance (> 75%), and heat sealing strength, etc.

[0166] Second, from Examples 1 and Comparative Examples 1-3, it can be observed that for the low-carbon high-barrier biodegradable composite film of the present invention, the use of the self-made plasticizer has a significant effect on improving mechanical properties, etc.; at the same time, the self-made plasticizer has better heat sealing strength compared with conventional plasticizers. It is speculated that the possible reason is that the self-made plasticizer has low migration and will not migrate to the interface to affect the interfacial adhesion; From Examples 1 and Comparative Examples 4-6, it can be observed that for the low-carbon high-barrier biodegradable composite film of the present invention, the use of the self-made compatibilizer has a significant effect on improving mechanical properties, light transmittance, etc.; From Examples 1 and Comparative Examples 7-12, it can be observed that for the low-carbon high-barrier biodegradable composite film of the present invention, the use of the self-made adhesion aid has a significant impact on improving heat sealing strength (including interfacial adhesion); From Examples 1 and Comparative Examples 13-15, it can be observed that for the low-carbon high-barrier biodegradable composite film of the present invention, the thickness of the vacuum-evaporated aluminum oxide has a great influence on water vapor, oxygen barrier properties and light transmittance. First, vacuum-evaporated aluminum oxide has a significant effect on improving barrier properties; at the same time, the lower the coating thickness, the worse the barrier property and the higher the light transmittance; on the contrary, the higher the coating thickness, the better the barrier property and the lower the light transmittance; generally speaking, at a thickness of 10-50 nm, the influence on light transmittance is low and the barrier property is excellent.

[0167] From Examples 1 and Comparative Example 16, it can be observed that after the composite film A in the low-carbon high-barrier biodegradable composite film of the present invention is biaxially stretched, both the mechanical properties and the barrier properties are significantly improved. This is because after biaxial stretching and orientation, the polymer structure has a certain degree of crystallization, improving mechanical properties and barrier properties, etc.; 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, and the PVAc layer has the effects of improving adhesion and the advantages of barrier performance at the same time.

[0168] In summary, a low-carbon high-barrier biodegradable composite film provided by the present invention, on the one hand, through molecular design, self-made plasticizers, highly reactive compatibilizers and bonding aids; on the other hand, through the formulation design of a five-layer structure; and prepared by double-layer co-extrusion, biaxial stretching process, vacuum evaporation and three-layer co-extrusion and blown film respectively, and finally compounded. The low-carbon high-barrier biodegradable composite film has excellent comprehensive properties such as mechanical properties, barrier properties, transparency, heat-sealing strength, etc.; and the main raw materials used have the advantage of being completely biodegradable and are widely used.

[0169] The test methods are as follows: (1) Mechanical properties: Tested according to the method described in GB / T 1040.3-2006.

[0170] (2) Water vapor transmission rate: Tested according to the method described in GB / T 1037-2021.

[0171] (3) Oxygen transmission rate: Tested according to the method described in GB / T 1038.1-2022, and the test condition is 1 atm.

[0172] (4) Light transmittance: Ultraviolet-visible spectroscopy (UV Vis). The prepared film was tested on an ultraviolet spectrophotometer (UV-2550), and the wavelength range was 200-800 nm.

[0173] (5) Heat-sealing strength: In accordance with QB / T 2358 1998, and the test rate was 300 mm / min.

[0174] Inspired by the ideal embodiments of the present invention as described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A preparation method of a low-carbon high-barrier biodegradable composite film, characterized in that, It includes the following steps: S41. Respectively mix the raw materials of the surface base material layer and the high-barrier layer evenly, place them in different extruders for plasticization; co-extrude, carry out vacuum sizing, cooling and shaping, preheating, biaxial stretching, heat setting, traction, and winding to obtain composite film A; The raw materials of both the surface base material layer and the high-barrier layer are mainly composed of PLA, and contain a plasticizer and a compatibilizer. Among them, the plasticizer has a large steric hindrance polyhydroxy small molecule structure, and the compatibilizer has a long-chain hyperbranched-like structure with a nano-silicon core and isocyanate group end-capping; S42. Carry out corona treatment and vacuum evaporation coating of aluminum oxide on the high-barrier surface of composite film A; S43. Respectively mix the raw materials of the adhesive layer, the transition layer, and the inner base material layer evenly, place them in different extruders for plasticization; co-extrude, blow film, traction, and winding to obtain composite film B; Among them, the adhesive layer is mainly composed of PVA, and the transition layer and the inner base material layer are mainly composed of PBAT; S44. Composite the aluminum oxide-coated surface of composite film A with the adhesive surface of composite film B, and carry out aging treatment to obtain the target product, namely a low-carbon high-barrier biodegradable composite film; Both the raw materials of the inner base material layer and the composite adhesive contain a bonding aid, and the bonding aid is an organic polymer chain containing silane, acetate, hydroxyl, and catechol structures.

2. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 1, characterized in that The surface base material layer includes the following raw materials in parts by weight: PLA 80 - 90 parts; PBAT 10 - 20 parts; Plasticizer 10 - 15 parts; Compatibilizer 1.0 - 3.0 parts; Antioxidant 0.3 - 0.5 parts; Lubricant 0.1 - 0.2 parts; Among them, the total mass of PLA and PBAT is 100 parts; The high-barrier surface is treated by vacuum evaporation coating of aluminum oxide, and the high-barrier layer includes the following raw materials in parts by weight: PLA 70 - 90 parts; PPC-P 10 - 30 parts; Plasticizer 8 - 12 parts; Compatibilizer 1.0 - 2.0 parts; Antioxidant 0.1 - 0.5 parts; Lubricant 0.1 - 0.2 parts; Among them, the total mass of PLA and PPC-P is 100 parts.

3. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 1, characterized in that The adhesive layer includes the following raw materials in parts by weight: PVAc 90 - 95 parts; PBAT 5 - 10 parts; Antioxidant 0.2 - 0.5 parts; Lubricant 0.2 - 0.3 parts; Among them, the total mass of PVAc and PBAT is 100 parts; The transition layer includes the following raw materials in parts by weight: PBAT 100 parts; Nano-sheet-like inorganic filler 10 - 20 parts; Antioxidant 0.1 - 0.3 parts; Lubricant 0.1 - 0.2 parts; The inner base material layer includes the following raw materials in parts by weight: PBAT 100 parts; Bonding aid 3.0 - 5.0 parts; Hydrolysis inhibitor 1.0 - 4.0 parts; Antioxidant 0.1 - 0.3 parts; Lubricant 0.5 - 1.0 parts.

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

5. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 2, wherein the preparation method of the plasticizer comprises the following steps: S11, carrying out a coupling reaction between a large steric hindrance group phosphorus chloride and a hydroxyacrylate A to obtain an intermediate product 1I; the dosage ratio of the large steric hindrance group phosphorus chloride to the hydroxyacrylate A is added according to the molar ratio of chlorine atoms to hydroxyl groups of 1:1; S12, carrying out a Michael addition reaction between the intermediate product 1I and an alkanolamine to obtain the target product, i.e., the plasticizer; the dosage ratio of the intermediate product 1I to the alkanolamine is added according to the molar ratio of acryloyloxy groups to amino groups of 1:

1.

6. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 5, wherein the number of acryloyloxy functional groups in the hydroxyacrylate A is ≥2.

7. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 2, wherein the preparation method of the compatibilizer comprises the following steps: S21, carrying out a coupling reaction between nano-silicon and an epoxy silane coupling agent to obtain an intermediate product 2I; the dosage ratio of the nano-silicon to the epoxy silane coupling agent is 1 g: 5.0 - 7.0 g; S22, carrying out a ring-opening reaction between the intermediate product 2I and an amino polyethylene glycol amine to obtain an intermediate product 2II; the dosage ratio of the intermediate product 2I to the amino polyethylene glycol amine is added according to the molar ratio of epoxy groups to amino groups of 1:2; S23, carrying out a nucleophilic addition reaction between the intermediate product 2II and a diisocyanate to obtain the target product, i.e., the compatibilizer; the dosage ratio of the intermediate product 2II to the diisocyanate is added according to the molar ratio of amino groups to isocyanate groups of 1:

2.

8. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 7, wherein the molecular weight of the amino polyethylene glycol amine is 400 - 1000.

9. The preparation method of the low-carbon high-barrier biodegradable composite film according to claim 3 or 4, wherein the preparation method of the bonding aid comprises the following steps: S31, carrying out a ring-opening reaction between a catechol-containing epoxy ring-opening agent and an epoxy alkene to obtain an intermediate product 3I; the dosage ratio of the catechol-containing epoxy ring-opening agent to the epoxy alkene is added according to the molar ratio of the epoxy ring-opening agent to epoxy groups of 1:1; S32, carrying out a radical polymerization on vinyl acetate, a carbon-carbon double bond-containing silane coupling agent, a hydroxyacrylate B, and the intermediate product 3I to obtain the target product, i.e., the bonding aid; the dosage ratio of vinyl acetate, the carbon-carbon double bond-containing silane coupling agent, the hydroxyacrylate 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.

10. A low-carbon high-barrier biodegradable composite film, characterized in that, Prepared by the preparation method of the low-carbon high-barrier biodegradable composite film according to any one of claims 1-9.