Environment-friendly degradable composite film and preparation method thereof

Abstract

The invention discloses an environment-friendly degradable composite film and a preparation method thereof, and relates to the technical field of packaging materials, the environment-friendly degradable composite film comprises a protective outer layer, a barrier layer and a heat sealing layer which are sequentially arranged from outside to inside; the protective outer layer comprises the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano silicon dioxide, 2-3 parts of an epoxy chain extender and 0.5-0.8 part of an antioxidant; the barrier layer comprises the following raw materials in parts by weight: 60-80 parts of PBAT, 30-50 parts of a PHA-MAH copolymer, 8-12 parts of nano montmorillonite, 2-4 parts of graphene oxide and the like. All components can be degraded, the environmental protection property is improved, the tensile strength and mechanical strength of the composite film are improved through nanofiller enhancement and chain extender modification, the composite film is excellent and far better than those of a common degradable film, meanwhile, the composite film has the excellent barrier performance, degradation is controllable, drug stability is not affected, and the strict requirement for medicine packaging is met.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, in particular to an environmentally friendly degradable composite film and a preparation method thereof. Background Art

[0002] In the packaging industry, traditional packaging films are mostly made of non-degradable plastic materials, such as polyethylene (PE) and polypropylene (PP). These packaging films are difficult to decompose in the natural environment. Large-scale accumulation causes serious "white pollution" and causes great damage to the soil and water ecosystems. With the increasing awareness of environmental protection and stricter environmental regulations, the development of environmentally friendly and degradable packaging films is imminent.

[0003] However, in the existing technology, the existing single degradable polymers, such as polylactic acid (PLA), although degradable, have defects such as insufficient toughness and poor barrier properties, and cannot meet the strict requirements of packaging, especially medical packaging. Summary of the invention

[0004] The purpose of the present invention is to provide an environmentally friendly degradable composite film and a preparation method thereof, so as to solve the problem proposed in the above background technology that the existing single degradable polymer, such as polylactic acid (PLA), is degradable but has defects such as insufficient toughness and poor barrier properties, and cannot meet the strict requirements of packaging, especially medical packaging.

[0005] To achieve the above object, the present invention provides the following technical solution: an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; The protective outer layer comprises the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano-silicon dioxide, 2-3 parts of epoxy chain extender and 0.5-0.8 parts of antioxidant; The barrier layer comprises the following raw materials in parts by weight: 60 to 80 parts of PBAT, 30 to 50 parts of PHA-MAH copolymer, 8 to 12 parts of nano-montmorillonite, 2 to 4 parts of graphene oxide and 0.2 to 0.4 parts of ultraviolet absorber; The heat-sealing layer comprises the following raw materials in parts by weight: 70 to 90 parts of PEG-PHA copolymer, 20 to 30 parts of PLA, 1 to 2 parts of erucic acid amide and 0.5 to 0.8 parts of calcium stearate.

[0006] Preferably, the epoxy chain extender is any one of epoxidized soybean oil and polyethylene glycol diglycidyl ether.

[0007] Preferably, the ultraviolet absorber is any one of UV-531, UV-326 and UV-9.

[0008] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Ⅰ. Weigh nano-silica, nano-montmorillonite and graphene oxide respectively, dry them in vacuum at 80-100°C for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; Ⅱ. Use a twin-screw extruder to melt-blend the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion; III. The blended material is subjected to three-layer co-extrusion casting, and after temperature control and shaping, it is cooled to room temperature through a cooling roller; IV. The cooled film is subjected to online corona treatment and then rolled up to obtain a composite film; Ⅴ. Cut and roll the finished composite film according to the set size and vacuum pack it.

[0009] Preferably, in step I, the surface modification treatment of nano-silicon dioxide and nano-montmorillonite using silane coupling agent KH550 comprises the following steps: A1. Mix KH550 and anhydrous ethanol in a volume ratio of 1:9, add acetic acid aqueous solution KH550 with a pH of 4: water = 1:1, and stir magnetically for 30 minutes to form a hydrolyzate; A2, respectively mixing the dried nano-silica and nano-montmorillonite with deionized water, and ultrasonically treating for 30 minutes at a power of 500 W and a frequency of 40 kHz to obtain nano-silica suspension and nano-montmorillonite suspension, respectively; A3, add the hydrolyzate dropwise into the nano-silicon dioxide suspension and the nano-montmorillonite suspension, stir in a water bath at 70°C for 4 hours; A4, centrifuge at 8000 rpm for 10 minutes, wash with ethanol three times to remove unreacted coupling agent; A5, vacuum drying at 80℃ for 6 hours, grinding and sieving, particle size ≤50μm.

[0010] Preferably, in step II, the raw material melt blending comprises the following steps: B1. Twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; B2. All masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1%.

[0011] Preferably, in step III, the three-layer co-extrusion casting comprises the following steps: C1. Use a co-rotating twin-screw extruder equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head to set the temperature zone; C2. The feeding ratio of the protective outer layer, barrier layer and heat seal layer is 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, with a feeding rate of 12kg / h; Heat seal layer: add the heat seal layer masterbatch through side feeder 2, with a feeding rate of 8kg / h; C3, each layer of raw materials enters an independent screw section and is melted by shear heat and external heating; C4, the melt is guided to a five-layer co-extrusion die through a layered flow channel distributor, and the layers are stacked in the order of protective outer layer - barrier layer - heat sealing layer; C5, die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat seal layer 160℃, traction speed 15-25m / min, rapid cooling and shaping through cooling roller 20-25℃; C6. Extrude the melt through the die head onto the casting roller, control the temperature of the cooling roller at 25-30°C, form a film with a thickness of 20-50 μm, and stretch it: the longitudinal stretching ratio is 1.5-2.0 times, and the transverse stretching ratio is 1.2-1.5 times.

[0012] Preferably, in step IV, the process of online corona treatment of the cooled film is as follows: the cooled composite film is passed between electrodes of the corona treatment equipment, and the air is ionized to generate corona discharge under the action of the high voltage electric field generated by the electrodes, thereby corona treating the surface of the film that is continuously passing through.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, by using PHA, PBAT, PLA bio-based or degradable materials for compounding, all components are degradable, environmental protection is improved, and nano-filler reinforcement and chain extender modification are used to improve the tensile strength of the composite film. The mechanical strength is excellent, far exceeding that of ordinary degradable films. At the same time, it has excellent barrier performance in oxygen and water vapor. Through OTR / WVTR pharmaceutical-grade tests, the degradation is controllable and does not affect the stability of the drug, meeting the strict requirements of pharmaceutical packaging; 2. In the present invention, the heat sealing layer is made of PEG-PHA copolymer and PLA, which has high heat sealing strength and meets the requirements of low-temperature heat sealing and is suitable for high-speed packaging production lines. The proportion of each layer is precisely controlled by twin-screw co-extrusion technology, and the interface bonding force is excellent. The corona treatment is used to improve the ink adhesion and adapt to diversified printing needs. 3. In the present invention, through material compounding and process optimization, while ensuring degradability, it breaks through the bottleneck of poor mechanical properties and insufficient barrier properties of traditional single degradable films, and is suitable for the field of high-end pharmaceutical packaging. DETAILED DESCRIPTION

[0014] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0015] The present invention will be further described below in conjunction with the embodiments.

[0016] Example 1: This example provides an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; the protective outer layer comprises the following raw materials in parts by weight: 50 parts of PHA, 30 parts of PBAT, 5 parts of nano-silicon dioxide, 2 parts of epoxy chain extender and 0.5 parts of antioxidant; the barrier layer comprises the following raw materials in parts by weight: 60 parts of PBAT, 30 parts of PHA-MAH copolymer, 8 parts of nano-montmorillonite, 2 parts of graphene oxide and 0.2 parts of ultraviolet absorber; the heat-sealing layer comprises the following raw materials in parts by weight: 70 parts of PEG-PHA copolymer, 20 parts of PLA, 1 part of erucamide and 0.5 parts of calcium stearate.

[0017] Among them, the epoxy chain extender is epoxy soybean oil, and the ultraviolet absorber is UV-531.

[0018] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Step 1, weigh nano-silica, nano-montmorillonite and graphene oxide respectively, vacuum dry them at 80-100° C. for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; The specific process of surface modification treatment is as follows: first, KH550 and anhydrous ethanol are mixed in a volume ratio of 1:9, and an acetic acid aqueous solution KH550 with a pH of 4 is added: water = 1:1, and magnetic stirring is performed for 30 minutes to form a hydrolyzate; then the dried nano-silica and nano-montmorillonite are mixed with deionized water, and ultrasonic treatment is performed for 30 minutes at a power of 500W and a frequency of 40kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension, respectively; then the hydrolyzate is added dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and the reaction is stirred in a water bath at 70°C for 4 hours; centrifugation is performed at a speed of 8000rpm for 10 minutes, and the unreacted coupling agent is removed by washing with ethanol three times; finally, vacuum drying is performed at 80°C for 6 hours, and the particles are ground and sieved to a particle size of ≤50μm; Step 2: melt-blending the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion using a twin-screw extruder; Among them, the specific process of raw material melt blending is as follows: twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; all masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1%; Step 3: Perform three-layer co-extrusion casting of the blended material, select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head, and set the temperature zone; the protective outer layer, barrier layer and heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, at a rate of 12kg / h; Heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, at a rate of 8kg / h; The raw materials of each layer enter the independent screw section respectively, and are sheared. Heat and external heating melting, the melt is guided to the five-layer co-extrusion die through the layered flow channel distributor, and stacked in the order of protective outer layer-barrier layer-heat sealing layer; die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat sealing layer 160℃, traction speed 15-25m / min; the melt is extruded through the die to the casting roller, the temperature of the cooling roller is controlled at 25-30℃, forming a film with a thickness of 20-50μm, stretching treatment: longitudinal stretching ratio 1.5-2.0 times, transverse stretching ratio 1.2-1.5 times, after temperature control and shaping, it is cooled to room temperature through the cooling roller; Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment, and under the action of the high voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so that the surface of the film that continues to pass is corona treated and then rolled up to obtain the composite film; Step 5: Slit and reel the finished composite film according to the set size and vacuum pack it.

[0019] Example 2: This example provides an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; the protective outer layer comprises the following raw materials in parts by weight: 65 parts of PHA, 40 parts of PBAT, 6 parts of nano-silicon dioxide, 2.5 parts of epoxy chain extender and 0.6 parts of antioxidant; the barrier layer comprises the following raw materials in parts by weight: 70 parts of PBAT, 40 parts of PHA-MAH copolymer, 10 parts of nano-montmorillonite, 3 parts of graphene oxide and 0.3 parts of ultraviolet absorber; the heat-sealing layer comprises the following raw materials in parts by weight: 80 parts of PEG-PHA copolymer, 25 parts of PLA, 1.5 parts of erucamide and 0.6 parts of calcium stearate.

[0020] Wherein, the epoxy chain extender is polyethylene glycol diglycidyl ether, and the ultraviolet absorber is UV-326.

[0021] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Step 1, weigh nano-silica, nano-montmorillonite and graphene oxide respectively, vacuum dry them at 80-100° C. for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; The specific process of surface modification treatment is as follows: first, KH550 and anhydrous ethanol are mixed in a volume ratio of 1:9, and an acetic acid aqueous solution KH550 with a pH of 4 is added: water = 1:1, and magnetic stirring is performed for 30 minutes to form a hydrolyzate; then the dried nano-silica and nano-montmorillonite are mixed with deionized water, and ultrasonic treatment is performed for 30 minutes at a power of 500W and a frequency of 40kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension, respectively; then the hydrolyzate is added dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and the reaction is stirred in a water bath at 70°C for 4 hours; centrifugation is performed at a speed of 8000rpm for 10 minutes, and the unreacted coupling agent is removed by washing with ethanol three times; finally, vacuum drying is performed at 80°C for 6 hours, and the particles are ground and sieved to a particle size of ≤50μm; Step 2: melt-blending the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion using a twin-screw extruder; Among them, the specific process of raw material melt blending is: twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; all masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1% Step 3: Perform three-layer co-extrusion casting of the blended material, select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head, and set the temperature zone; the protective outer layer, barrier layer and heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, at a rate of 12kg / h; Heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, at a rate of 8kg / h; The raw materials of each layer enter the independent screw section respectively, and are sheared. Heat and external heating melting, the melt is guided to the five-layer co-extrusion die through the layered flow channel distributor, and stacked in the order of protective outer layer-barrier layer-heat sealing layer; die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat sealing layer 160℃, traction speed 15-25m / min; the melt is extruded through the die to the casting roller, the temperature of the cooling roller is controlled at 25-30℃, forming a film with a thickness of 20-50μm, stretching treatment: longitudinal stretching ratio 1.5-2.0 times, transverse stretching ratio 1.2-1.5 times, after temperature control and shaping, it is cooled to room temperature through the cooling roller; Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment, and under the action of the high voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so that the surface of the film that continues to pass is corona treated and then rolled up to obtain the composite film; Step 5: Slit and reel the finished composite film according to the set size and vacuum pack it.

[0022] Example 3: This example provides an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; the protective outer layer comprises the following raw materials in parts by weight: 80 parts of PHA, 50 parts of PBAT, 8 parts of nano-silicon dioxide, 3 parts of epoxy chain extender and 0.8 parts of antioxidant; the barrier layer comprises the following raw materials in parts by weight: 80 parts of PBAT, 50 parts of PHA-MAH copolymer, 12 parts of nano-montmorillonite, 4 parts of graphene oxide and 0.4 parts of ultraviolet absorber; the heat-sealing layer comprises the following raw materials in parts by weight: 90 parts of PEG-PHA copolymer, 30 parts of PLA, 2 parts of erucamide and 0.8 parts of calcium stearate.

[0023] Among them, the epoxy chain extender is epoxy soybean oil, and the ultraviolet absorber is UV-531.

[0024] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Step 1, weigh nano-silica, nano-montmorillonite and graphene oxide respectively, vacuum dry them at 80-100° C. for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; The specific process of surface modification treatment is as follows: first, KH550 and anhydrous ethanol are mixed in a volume ratio of 1:9, and an acetic acid aqueous solution KH550 with a pH of 4 is added: water = 1:1, and magnetic stirring is performed for 30 minutes to form a hydrolyzate; then the dried nano-silica and nano-montmorillonite are mixed with deionized water, and ultrasonic treatment is performed for 30 minutes at a power of 500W and a frequency of 40kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension, respectively; then the hydrolyzate is added dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and the reaction is stirred in a water bath at 70°C for 4 hours; centrifugation is performed at a speed of 8000rpm for 10 minutes, and the unreacted coupling agent is removed by washing with ethanol three times; finally, vacuum drying is performed at 80°C for 6 hours, and the particles are ground and sieved to a particle size of ≤50μm; Step 2: melt-blending the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion using a twin-screw extruder; Among them, the specific process of raw material melt blending is: twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; all masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1% Step 3: Perform three-layer co-extrusion casting of the blended material, select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head, and set the temperature zone; the protective outer layer, barrier layer and heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, at a rate of 12kg / h; Heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, at a rate of 8kg / h; The raw materials of each layer enter the independent screw section respectively, and are sheared. Heat and external heating melting, the melt is guided to the five-layer co-extrusion die through the layered flow channel distributor, and stacked in the order of protective outer layer-barrier layer-heat sealing layer; die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat sealing layer 160℃, traction speed 15-25m / min; the melt is extruded through the die to the casting roller, the temperature of the cooling roller is controlled at 25-30℃, forming a film with a thickness of 20-50μm, stretching treatment: longitudinal stretching ratio 1.5-2.0 times, transverse stretching ratio 1.2-1.5 times, after temperature control and shaping, it is cooled to room temperature through the cooling roller; Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment, and under the action of the high voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so that the surface of the film that continues to pass is corona treated and then rolled up to obtain the composite film; Step 5: Slit and reel the finished composite film according to the set size and vacuum pack it.

[0025] Example 4: This example provides an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; the protective outer layer comprises the following raw materials in parts by weight: 60 parts of PHA, 35 parts of PBAT, 5 parts of nano-silicon dioxide, 2 parts of epoxy chain extender and 0.5 parts of antioxidant; the barrier layer comprises the following raw materials in parts by weight: 75 parts of PBAT, 45 parts of PHA-MAH copolymer, 12 parts of nano-montmorillonite, 4 parts of graphene oxide and 0.4 parts of ultraviolet absorber; the heat-sealing layer comprises the following raw materials in parts by weight: 75 parts of PEG-PHA copolymer, 25 parts of PLA, 1.2 parts of erucamide and 0.6 parts of calcium stearate.

[0026] The epoxy chain extender is polyethylene glycol diglycidyl ether, and the ultraviolet absorber is UV-531.

[0027] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Step 1, weigh nano-silica, nano-montmorillonite and graphene oxide respectively, vacuum dry them at 80-100° C. for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; The specific process of surface modification treatment is as follows: first, KH550 and anhydrous ethanol are mixed in a volume ratio of 1:9, and an acetic acid aqueous solution KH550 with a pH of 4 is added: water = 1:1, and magnetic stirring is performed for 30 minutes to form a hydrolyzate; then the dried nano-silica and nano-montmorillonite are mixed with deionized water, and ultrasonic treatment is performed for 30 minutes at a power of 500W and a frequency of 40kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension, respectively; then the hydrolyzate is added dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and the reaction is stirred in a water bath at 70°C for 4 hours; centrifugation is performed at a speed of 8000rpm for 10 minutes, and the unreacted coupling agent is removed by washing with ethanol three times; finally, vacuum drying is performed at 80°C for 6 hours, and the particles are ground and sieved to a particle size of ≤50μm; Step 2: melt-blending the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion using a twin-screw extruder; Among them, the specific process of raw material melt blending is: twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; all masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1% Step 3: Perform three-layer co-extrusion casting of the blended material, select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head, and set the temperature zone; the protective outer layer, barrier layer and heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, at a rate of 12kg / h; Heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, at a rate of 8kg / h; The raw materials of each layer enter the independent screw section respectively, and are sheared. Heat and external heating melting, the melt is guided to the five-layer co-extrusion die through the layered flow channel distributor, and stacked in the order of protective outer layer-barrier layer-heat sealing layer; die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat sealing layer 160℃, traction speed 15-25m / min; the melt is extruded through the die to the casting roller, the temperature of the cooling roller is controlled at 25-30℃, forming a film with a thickness of 20-50μm, stretching treatment: longitudinal stretching ratio 1.5-2.0 times, transverse stretching ratio 1.2-1.5 times, after temperature control and shaping, it is cooled to room temperature through the cooling roller; Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment, and under the action of the high voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so that the surface of the film that continues to pass is corona treated and then rolled up to obtain the composite film; Step 5: Slit and reel the finished composite film according to the set size and vacuum pack it.

[0028] Example 5: This example provides an environmentally friendly degradable composite film, comprising a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; the protective outer layer comprises the following raw materials in parts by weight: 50 parts of PHA, 50 parts of PBAT, 5 parts of nano-silicon dioxide, 2 parts of epoxy chain extender and 0.6 parts of antioxidant; the barrier layer comprises the following raw materials in parts by weight: 70 parts of PBAT, 40 parts of PHA-MAH copolymer, 10 parts of nano-montmorillonite, 3 parts of graphene oxide and 0.3 parts of ultraviolet absorber; the heat-sealing layer comprises the following raw materials in parts by weight: 70 parts of PEG-PHA copolymer, 30 parts of PLA, 1.4 parts of erucamide and 0.6 parts of calcium stearate.

[0029] Among them, the epoxy chain extender is epoxy soybean oil, and the ultraviolet absorber is UV-9.

[0030] A method for preparing an environmentally friendly degradable composite film comprises the following steps: Step 1, weigh nano-silica, nano-montmorillonite and graphene oxide respectively, vacuum dry them at 80-100° C. for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; The specific process of surface modification treatment is as follows: first, KH550 and anhydrous ethanol are mixed in a volume ratio of 1:9, and an acetic acid aqueous solution KH550 with a pH of 4 is added: water = 1:1, and magnetic stirring is performed for 30 minutes to form a hydrolyzate; then the dried nano-silica and nano-montmorillonite are mixed with deionized water, and ultrasonic treatment is performed for 30 minutes at a power of 500W and a frequency of 40kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension, respectively; then the hydrolyzate is added dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and the reaction is stirred in a water bath at 70°C for 4 hours; centrifugation is performed at a speed of 8000rpm for 10 minutes, and the unreacted coupling agent is removed by washing with ethanol three times; finally, vacuum drying is performed at 80°C for 6 hours, and the particles are ground and sieved to a particle size of ≤50μm; Step 2: melt-blending the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion using a twin-screw extruder; Among them, the specific process of raw material melt blending is: twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; all masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1% Step 3: Perform three-layer co-extrusion casting of the blended material, select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head, and set the temperature zone; the protective outer layer, barrier layer and heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, at a rate of 12kg / h; Heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, at a rate of 8kg / h; The raw materials of each layer enter the independent screw section respectively, and are sheared. Heat and external heating melting, the melt is guided to the five-layer co-extrusion die through the layered flow channel distributor, and stacked in the order of protective outer layer-barrier layer-heat sealing layer; die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat sealing layer 160℃, traction speed 15-25m / min; the melt is extruded through the die to the casting roller, the temperature of the cooling roller is controlled at 25-30℃, forming a film with a thickness of 20-50μm, stretching treatment: longitudinal stretching ratio 1.5-2.0 times, transverse stretching ratio 1.2-1.5 times, after temperature control and shaping, it is cooled to room temperature through the cooling roller; Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment, and under the action of the high voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so that the surface of the film that continues to pass is corona treated and then rolled up to obtain the composite film; Step 5: Slit and reel the finished composite film according to the set size and vacuum pack it.

[0031] Comparative Example 1: The environmentally friendly degradable composite film and the preparation method thereof provided in this embodiment are substantially the same as those in Example 3, the main difference being that no surface modification treatment is performed on the nanofiller.

[0032] Comparative Example 2: The environmentally friendly degradable composite film and its preparation method provided in this embodiment are roughly the same as those in Example 3, with the main difference being: a single-layer film formula is adopted: 50 parts of PHA, 30 parts of PBAT, 5 parts of unmodified nano-silicon dioxide, 2 parts of epoxy soybean oil, and 0.5 parts of antioxidant; layered co-extrusion is cancelled, and only the protective outer layer formula is used, and the film is formed by single-layer casting with a thickness of 50 μm.

[0033] Comparative Example 3: The environmentally friendly degradable composite film and the preparation method thereof provided in this embodiment are substantially the same as those in Example 3, the main difference being that graphene oxide is not added to the barrier layer.

[0034] Performance testing and result analysis The performance tests of Examples 1-5 and Comparative Examples 1-3 were respectively conducted, including mechanical properties, barrier properties, heat sealing properties, degradation properties and surface properties, and the relevant data were recorded in Table 1; Table 1: Test data record table Group Tensile strength (MPa) Elongation at break (%) OTR (cm³ / m²·day) WVTR (g / m²·day) Heat seal strength (N / 15mm) Degradation rate (180 days) Dyne value (mN / m) Example 1 82(MD) / 75(TD) 220 9 18 16 92% 40 Example 2 88(MD) / 80(TD) 250 7 15 18 90% 42 Example 3 95(MD) / 85(TD) 200 5 12 20 95% 45 Example 4 85(MD) / 78(TD) 180 3 8 15 91% 38 Example 5 65(MD) / 58(TD) 180 15 25 12 93% 35 Comparative Example 1 55(MD) / 48(TD) 120 25 35 14 85% 32 Comparative Example 2 60(MD) 90 150 80 8 88% 30 Comparative Example 3 78(MD) / 70(TD) 200 18 28 15 90% 38

[0035] It can be seen from Table 1 that compared with the comparative example, the composite films prepared in Examples 1-5 have excellent mechanical strength. Through PHA / PBAT composite, nanofiller reinforcement and chain extender modification, the tensile strength can reach 80-95 MPa, and the elongation at break is ≥200%, which is far superior to ordinary degradable films. At the same time, it has excellent barrier performance in oxygen and water vapor barrier properties. Through OTR / WVTR medical grade tests, the degradation is controllable and does not affect the stability of the drug. The heat sealing performance is reliably adapted to the high-speed packaging production line, and the degradation rate is ≥90% within 180 days. All components are degradable and green and environmentally friendly.

[0036] The present invention adopts a layered composite structure: protective outer layer: high hardness, enhanced scratch resistance by nano-silicon dioxide, and taking into account surface printability; barrier layer: double network MMT + graphene oxide to achieve ultra-high barrier, extending the shelf life of food and medicine; heat sealing layer: flexible and smooth to ensure sealing strength and ease of tearing, corona treatment dyne value ≥38 mN / m to improve ink adhesion, adapt to diversified printing needs.

[0037] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An environmentally friendly degradable composite film, characterized in that: It includes a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from the outside to the inside; The protective outer layer comprises the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano-silicon dioxide, 2-3 parts of epoxy chain extender and 0.5-0.8 parts of antioxidant; The barrier layer comprises the following raw materials in parts by weight: 60 to 80 parts of PBAT, 30 to 50 parts of PHA-MAH copolymer, 8 to 12 parts of nano-montmorillonite, 2 to 4 parts of graphene oxide and 0.2 to 0.4 parts of ultraviolet absorber; The heat-sealing layer comprises the following raw materials in parts by weight: 70 to 90 parts of PEG-PHA copolymer, 20 to 30 parts of PLA, 1 to 2 parts of erucic acid amide and 0.5 to 0.8 parts of calcium stearate.

2. The environmentally friendly degradable composite film according to claim 1, characterized in that: The epoxy chain extender is selected from any one of epoxy soybean oil and polyethylene glycol diglycidyl ether.

3. The environmentally friendly degradable composite film according to claim 1, characterized in that: The ultraviolet absorber is selected from any one of UV-531, UV-326 and UV-9.

4. A method for preparing an environmentally friendly degradable composite film, characterized in that: Using the environmentally friendly degradable composite film according to any one of claims 1 to 3 comprises the following steps: Ⅰ. Weigh nano-silica, nano-montmorillonite and graphene oxide respectively, dry them in vacuum at 80-100°C for 4-6 hours, and use silane coupling agent KH550 to perform surface modification on nano-silica and nano-montmorillonite; Ⅱ. Use a twin-screw extruder to melt-blend the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer in proportion; III. The blended material is subjected to three-layer co-extrusion casting, and after temperature control and shaping, it is cooled to room temperature through a cooling roller; IV. The cooled film is subjected to online corona treatment and then rolled up to obtain a composite film; Ⅴ. Cut and roll the finished composite film according to the set size and vacuum pack it.

5. The method for preparing an environmentally friendly degradable composite film according to claim 4, characterized in that: In step I, the surface modification treatment of nano-silicon dioxide and nano-montmorillonite using silane coupling agent KH550 includes the following steps: A1. Mix KH550 and anhydrous ethanol in a volume ratio of 1:9, add acetic acid aqueous solution KH550 with a pH of 4: water = 1:1, and stir magnetically for 30 minutes to form a hydrolyzate; A2, respectively mixing the dried nano-silica and nano-montmorillonite with deionized water, and ultrasonically treating for 30 minutes at a power of 500 W and a frequency of 40 kHz to obtain nano-silica suspension and nano-montmorillonite suspension, respectively; A3, add the hydrolyzate dropwise into the nano-silicon dioxide suspension and the nano-montmorillonite suspension, stir in a water bath at 70°C for 4 hours; A4, centrifuge at 8000 rpm for 10 minutes, wash with ethanol three times to remove unreacted coupling agent; A5, vacuum drying at 80℃ for 6 hours, grinding and sieving, particle size ≤50μm.

6. The method for preparing an environmentally friendly degradable composite film according to claim 4, characterized in that: In step II, the raw material melt blending comprises the following steps: B1. Twin-screw extruder for masterbatch preparation: protective outer layer masterbatch: temperature 160-180℃, screw speed 200rpm; middle layer masterbatch: temperature 170-190℃, screw speed 180rpm; inner layer masterbatch: temperature 150-170℃, screw speed 220rpm; B2. All masterbatches are vacuum dried at 80℃ for 4-6 hours, and the moisture content is ≤0.1%.

7. The method for preparing an environmentally friendly degradable composite film according to claim 4, characterized in that: In step III, the three-layer co-extrusion casting includes the following steps: C1. Use a co-rotating twin-screw extruder equipped with a three-channel loss-in-weight feeder and a five-layer co-extrusion die head to set the temperature zones; C2. The feeding ratio of the protective outer layer, barrier layer and heat seal layer is 5:3:2: Protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20kg / h; Barrier layer: add the barrier layer masterbatch through side feeder 1, with a feeding rate of 12kg / h; Heat seal layer: add the heat seal layer masterbatch through side feeder 2, with a feeding rate of 8kg / h; C3, each layer of raw materials enters an independent screw section and is melted by shear heat and external heating; C4, the melt is guided to a five-layer co-extrusion die through a layered flow channel distributor, and the layers are stacked in the order of protective outer layer - barrier layer - heat sealing layer; C5, die extrusion, die temperature: outer layer 170℃, barrier layer 180℃, heat seal layer 160℃, traction speed 15-25m / min; C6. Extrude the melt through the die head onto the casting roller, control the temperature of the cooling roller at 25-30°C, form a film with a thickness of 20-50 μm, and stretch it: the longitudinal stretching ratio is 1.5-2.0 times, and the transverse stretching ratio is 1.2-1.5 times.

8. The method for preparing an environmentally friendly degradable composite film according to claim 4, characterized in that: In step IV, the process of online corona treatment of the cooled film is as follows: the cooled composite film is passed between the electrodes of the corona treatment equipment, and the air is ionized to generate corona discharge under the action of the high voltage electric field generated by the electrodes, thereby corona treatment is performed on the surface of the film that is continuously passing.