An environmentally friendly degradable composite film and its preparation method

Abstract

The present invention discloses an environmentally friendly degradable composite film and a preparation method thereof, relating to the technical field of packaging materials, which includes a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from outside to inside; the protective outer layer contains the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano-silica, 2-3 parts of epoxy chain extender and 0.5-0.8 part of antioxidant; the barrier layer contains the following raw materials in parts by weight: 60-80 parts of PBAT, 30-50 parts of PHA-MAH copolymer, 8-12 parts of nano-montmorillonite, 2-4 parts of graphene oxide, etc. The present invention realizes the full-component degradability, improves the environmental friendliness, enhances the tensile strength of the composite film by using nano-fillers and modifying with chain extenders, has excellent mechanical strength, far exceeding that of ordinary degradable films, and at the same time has excellent barrier performance, the degradation is controllable and does not affect the stability of drugs, meeting the strict requirements of pharmaceutical packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and specifically relates 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), polypropylene (PP), etc. These packaging films are difficult to decompose in the natural environment, and a large amount of accumulation causes serious "white pollution", which greatly damages the soil and water ecosystem. With the enhancement of environmental awareness and the tightening of environmental protection regulations, it is urgent to develop environmentally friendly degradable packaging films.

[0003] However, in the prior art, existing single degradable polymers, such as polylactic acid (PLA), although having degradability, have defects such as insufficient toughness and poor barrier performance, and cannot meet the strict requirements of packaging, especially pharmaceutical 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 problems in the above background art that existing single degradable polymers, such as polylactic acid (PLA), although having degradability, have defects such as insufficient toughness and poor barrier performance, and cannot meet the strict requirements of packaging, especially pharmaceutical packaging.

[0005] To achieve the above purpose, 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 outside to inside;

[0006] The protective outer layer contains the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano-silica, 2-3 parts of epoxy chain extender, and 0.5-0.8 parts of antioxidant;

[0007] The barrier layer contains the following raw materials in parts by weight: 60-80 parts of PBAT, 30-50 parts of PHA-MAH copolymer, 8-12 parts of nano-montmorillonite, 2-4 parts of graphene oxide, and 0.2-0.4 parts of ultraviolet absorber;

[0008] The heat-sealing layer contains the following raw materials in parts by weight: 70-90 parts of PEG-PHA copolymer, 20-30 parts of PLA, 1-2 parts of erucamide, and 0.5-0.8 parts of calcium stearate.

[0009] Preferably, the epoxy chain extender is selected from any one of epoxy soybean oil and polyethylene glycol diglycidyl ether.

[0010] Preferably, the ultraviolet absorber is selected from any one of UV-531, UV-326, and UV-9.

[0011] A preparation method of an environmentally friendly degradable composite film, comprising the following steps:

[0012] Ⅰ. Weigh nano-silica, nano-montmorillonite and graphene oxide respectively, and vacuum dry them at 80 - 100 °C for 4 - 6 hours. Use silane coupling agent KH550 to conduct surface modification treatment on nano-silica and nano-montmorillonite;

[0013] Ⅱ. Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, barrier layer and heat-sealing layer respectively according to the proportion;

[0014] Ⅲ. Conduct three-layer co-extrusion casting on the blended material, and after temperature control and shaping, cool it to room temperature through a cooling roller;

[0015] Ⅳ. Conduct on-line corona treatment on the cooled film and then wind it up to obtain the composite film;

[0016] Ⅴ. Cut and wind up the finished composite film according to the set size and conduct vacuum packaging.

[0017] Preferably, in step Ⅰ, the surface modification treatment of nano-silica and nano-montmorillonite using silane coupling agent KH550 comprises the following steps:

[0018] A1. Mix KH550 and absolute ethanol at a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550:water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution;

[0019] A2. Mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and conduct ultrasonic treatment for 30 minutes with a power of 500 W and a frequency of 40 kHz to obtain a nano-silica suspension and a nano-montmorillonite suspension respectively;

[0020] A3. Dropwise add the hydrolysis solution into the nano-silica suspension and the nano-montmorillonite suspension, and stir and react in a water bath at 70 °C for 4 hours;

[0021] A4. Centrifuge at a speed of 8000 rpm for 10 minutes, and wash with ethanol 3 times to remove the unreacted coupling agent;

[0022] A5. Vacuum dry at 80 °C for 6 hours, grind and sieve, and the particle size ≤ 50 μm.

[0023] Preferably, in step Ⅱ, the melt blending of the raw materials comprises the following steps:

[0024] B1. Preparation of masterbatch using a twin-screw extruder: For the protective outer layer masterbatch: temperature 160 - 180 °C, screw speed 200 rpm; for the intermediate layer masterbatch: temperature 170 - 190 °C, screw speed 180 rpm; for the inner layer masterbatch: temperature 150 - 170 °C, screw speed 220 rpm;

[0025] B2. All masterbatches are vacuum-dried at 80 °C for 4 - 6 hours, with a moisture content ≤ 0.1%.

[0026] Preferably, in step III, the three-layer coextrusion casting molding includes the following steps:

[0027] C1. Select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer coextrusion die head, and set the temperature zones.

[0028] C2. Set the feeding of the protective outer layer, barrier layer, and heat-sealing layer in a ratio of 5:3:2: For the protective outer layer: add the outer layer masterbatch through the main feeder, with a feeding rate of 20 kg / h; for the barrier layer: add the barrier layer masterbatch through side feeder 1, with a rate of 12 kg / h; for the heat-sealing layer: add the heat-sealing layer masterbatch through side feeder 2, with a rate of 8 kg / h.

[0029] C3. Each layer of raw material enters an independent screw section and is melted through shear heat and external heating.

[0030] C4. The melt is guided to the five-layer coextrusion die head through a layered flow channel distributor and laminated in the order of protective outer layer - barrier layer - heat-sealing layer.

[0031] C5. Extrusion from the die head, die head temperature: outer layer 170 °C, barrier layer 180 °C, heat-sealing layer 160 °C, draw speed 15 - 25 m / min, and quickly cooled and shaped through a cooling roll at 20 - 25 °C.

[0032] C6. Extrude the melt through the die head onto the casting roll, control the temperature of the cooling roll at 25 - 30 °C to form a film with a thickness of 20 - 50 μm, and perform stretching treatment: longitudinal stretching ratio 1.5 - 2.0 times, transverse stretching ratio 1.2 - 1.5 times.

[0033] Preferably, in step IV, the process of online corona treatment for the cooled film is as follows: Pass the cooled composite film between the electrodes of the corona treatment equipment. Under the action of the high-voltage electric field generated by the electrodes, air is ionized to generate corona discharge, thereby performing corona treatment on the surface of the continuously passing film.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. In the present invention, by using PHA, PBAT, PLA bio-based or biodegradable materials for compounding, all components can be degraded, improving environmental protection. The use of nano-fillers for reinforcement and chain extenders for modification enhances the tensile strength of the composite film, with excellent mechanical strength, far exceeding that of ordinary biodegradable films. At the same time, it has excellent barrier performance against oxygen and water vapor, passing the OTR / WVTR medical-grade test, and the degradation is controllable without affecting the stability of drugs, meeting the strict requirements of pharmaceutical packaging.

[0036] 2. In the present invention, the heat-sealing layer is composed of a PEG-PHA copolymer and PLA in combination, with high heat-sealing strength and meeting low-temperature heat-sealing requirements for high-speed packaging production lines. The proportion of each layer is precisely controlled through twin-screw co-extrusion technology, with excellent interfacial bonding strength. Combined with corona treatment, it improves the ink adhesion, adapting to diverse printing requirements.

[0037] 3. In the present invention, through material compounding and process optimization, while ensuring biodegradability, it breaks through the bottlenecks of poor mechanical properties and insufficient barrier properties of traditional single biodegradable films, and is applicable to the high-end pharmaceutical packaging field. Detailed implementation mode

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Next, the present invention will be further described in conjunction with the embodiments.

[0040] Embodiment 1: This embodiment provides an environmentally friendly biodegradable composite film, including a protective outer layer, a barrier layer, and a heat-sealing layer arranged in sequence from outside to inside; the protective outer layer contains the following raw materials in parts by weight: 50 parts of PHA, 30 parts of PBAT, 5 parts of nano-silica, 2 parts of epoxy chain extender, and 0.5 part of antioxidant; the barrier layer contains 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 part of ultraviolet absorber; the heat-sealing layer contains the following raw materials in parts by weight: 70 parts of PEG-PHA copolymer, 20 parts of PLA, 1 part of erucic acid amide, and 0.5 part of calcium stearate.

[0041] Among them, the epoxy chain extender is selected as epoxy soybean oil, and the ultraviolet absorber is selected as UV-531.

[0042] A preparation method of an environmentally friendly biodegradable composite film includes the following steps:

[0043] Step 1: Weigh nano-silica, nano-montmorillonite, and graphene oxide separately and vacuum dry them at 80 - 100 °C for 4 - 6 hours. Surface modification treatment of nano-silica and nano-montmorillonite is carried out using silane coupling agent KH550.

[0044] The specific process of surface modification treatment is as follows: First, mix KH550 and absolute ethanol at a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution. Then, mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and perform ultrasonic treatment for 30 minutes with a power of 500 W and a frequency of 40 kHz to obtain nano-silica suspension and nano-montmorillonite suspension respectively. Then, add the hydrolysis solution dropwise to the nano-silica suspension and nano-montmorillonite suspension, and stir and react in a water bath at 70 °C for 4 hours. Centrifuge at a speed of 8000 rpm for 10 minutes, and wash with ethanol 3 times to remove unreacted coupling agent. Finally, vacuum dry at 80 °C for 6 hours, grind and screen, and the particle size ≤ 50 μm.

[0045] Step 2: Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, barrier layer, and heat-sealing layer in proportion.

[0046] The specific process of raw material melting and blending is as follows: The twin-screw extruder is used for masterbatch preparation: Protective outer layer masterbatch: temperature 160 - 180 °C, screw speed 200 rpm; Intermediate layer masterbatch: temperature 170 - 190 °C, screw speed 180 rpm; Inner layer masterbatch: temperature 150 - 170 °C, screw speed 220 rpm; All masterbatches are vacuum dried at 80 °C for 4 - 6 hours, and the moisture content ≤ 0.1%.

[0047] Step 3: Carry out three-layer coextrusion casting molding on the blended material. Select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer coextrusion die head, and set the temperature zones. 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, and the feeding rate is 20 kg / h; Barrier layer: Add the barrier layer masterbatch through side feeder 1, and the rate is 12 kg / h; Heat-sealing layer: Add the heat-sealing layer masterbatch through side feeder 2, and the rate is 8 kg / h; The raw materials of each layer enter the independent screw section respectively, are melted by shear heat and external heating, and the melt is guided to the five-layer coextrusion die head through a layered flow channel distributor, and laminated in the order of protective outer layer - barrier layer - heat-sealing layer. Extrude from the die head, die head temperature: outer layer 170 °C, barrier layer 180 °C, heat-sealing layer 160 °C, traction speed 15 - 25 m / min; The melt is extruded from the die head to the casting roll, and the temperature of the cooling roll is controlled at 25 - 30 °C to form a film with a thickness of 20 - 50 μm. Tensile treatment: longitudinal tensile ratio 1.5 - 2.0 times, transverse tensile ratio 1.2 - 1.5 times, and after temperature control and shaping, it is cooled to room temperature through the cooling roll.

[0048] Step 4: Pass the cooled composite film between the electrodes of the corona treatment device. Under the action of the high-voltage electric field generated by the electrodes, air is ionized to generate corona discharge, so as to corona-treat the surface of the continuously passing film and then wind it up to obtain the composite film;

[0049] Step 5: Slit and wind up the finished composite film according to the set size and vacuum package it.

[0050] Example 2: This example provides an environmentally friendly degradable composite film, which includes a protective outer layer, a barrier layer and a heat-sealing layer arranged in sequence from outside to inside; the protective outer layer contains the following raw materials in parts by weight: 65 parts of PHA, 40 parts of PBAT, 6 parts of nano-silica, 2.5 parts of epoxy chain extender and 0.6 part of antioxidant; the barrier layer contains 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 part of ultraviolet absorber; the heat-sealing layer contains the following raw materials in parts by weight: 80 parts of PEG-PHA copolymer, 25 parts of PLA, 1.5 parts of erucic acid amide and 0.6 part of calcium stearate.

[0051] Among them, the epoxy chain extender is selected as polyethylene glycol diglycidyl ether, and the ultraviolet absorber is selected as UV-326.

[0052] A preparation method of an environmentally friendly degradable composite film includes the following steps:

[0053] Step 1: Weigh nano-silica, nano-montmorillonite and graphene oxide respectively and vacuum dry them at 80-100 °C for 4-6 hours, and perform surface modification treatment on nano-silica and nano-montmorillonite with silane coupling agent KH550;

[0054] The specific process of the surface modification treatment is as follows: First, mix KH550 and absolute ethanol in a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution; then mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and perform ultrasonic treatment for 30 minutes, with a power of 500 W and a frequency of 40 kHz, to obtain a nano-silica suspension and a nano-montmorillonite suspension respectively; then add the hydrolysis solution dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and react with stirring in a water bath at 70 °C for 4 hours; centrifuge and separate at a speed of 8000 rpm for 10 minutes, and wash with ethanol 3 times to remove the unreacted coupling agent; finally, vacuum dry at 80 °C for 6 hours, grind and sieve, and the particle size ≤ 50 μm;

[0055] Step 2: Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, the barrier layer and the heat-sealing layer respectively according to the ratio;

[0056] Among them, the specific process of raw material melt blending is as follows: The masterbatch is prepared by a twin-screw extruder: For the protective outer layer masterbatch: the temperature is 160 - 180 °C, and the screw speed is 200 rpm; for the intermediate layer masterbatch: the temperature is 170 - 190 °C, and the screw speed is 180 rpm; for the inner layer masterbatch: the temperature is 150 - 170 °C, and the screw speed is 220 rpm; all masterbatches are vacuum-dried at 80 °C for 4 - 6 hours, and the moisture content ≤ 0.1%.

[0057] Step 3: The blended material is subjected to three-layer coextrusion casting. A co-rotating twin-screw extruder is selected, equipped with a three-channel loss-in-weight feeder and a five-layer coextrusion die head, and the temperature zoning is set; The protective outer layer, the barrier layer, and the heat-sealing layer are fed in a ratio of 5:3:2: The protective outer layer: The outer layer masterbatch is added through the main feeder, and the feeding rate is 20 kg / h; The barrier layer: The barrier layer masterbatch is added by side feeder 1, and the rate is 12 kg / h; The heat-sealing layer: The heat-sealing layer masterbatch is added by side feeder 2, and the rate is 8 kg / h; The raw materials of each layer enter the independent screw section respectively, are melted by shear heat and external heating, and the melt is guided to the five-layer coextrusion die head through the stratified flow channel distributor, and are laminated in the order of protective outer layer - barrier layer - heat-sealing layer; Extrusion from the die head, the die head temperature: the outer layer is 170 °C, the barrier layer is 180 °C, the heat-sealing layer is 160 °C, and the traction speed is 15 - 25 m / min; The melt is extruded from the die head to the casting roll, and the temperature of the cooling roll is controlled at 25 - 30 °C to form a film with a thickness of 20 - 50 μm. Tensile treatment: The longitudinal draw ratio is 1.5 - 2.0 times, and the transverse draw ratio is 1.2 - 1.5 times. After temperature control and shaping, it is cooled to room temperature by the cooling roll;

[0058] Step 4: The cooled composite film is passed between the electrodes of the corona treatment equipment. Under the action of the high-voltage electric field generated by the electrodes, the air is ionized to generate corona discharge, so as to corona-treat the surface of the continuously passing film and then wind it up to obtain the composite film;

[0059] Step 5: The finished composite film is slit and wound according to the set size and vacuum-packed.

[0060] Example 3: This example provides an environmentally friendly degradable composite film, which includes a protective outer layer, a barrier layer, and a heat-sealing layer arranged in sequence from outside to inside; The protective outer layer contains the following raw materials in parts by weight: 80 parts of PHA, 50 parts of PBAT, 8 parts of nano-silica, 3 parts of epoxy chain extender, and 0.8 part of antioxidant; The barrier layer contains 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 part of ultraviolet absorber; The heat-sealing layer contains the following raw materials in parts by weight: 90 parts of PEG-PHA copolymer, 30 parts of PLA, 2 parts of erucic acid amide, and 0.8 part of calcium stearate.

[0061] Among them, the epoxy chain extender is selected as epoxy soybean oil, and the ultraviolet absorber is selected as UV-531.

[0062] A preparation method of an environmentally friendly degradable composite film, comprising the following steps:

[0063] Step 1: Weigh nano-silica, nano-montmorillonite and graphene oxide respectively, and vacuum dry them at 80-100°C for 4-6 hours. Use silane coupling agent KH550 to conduct surface modification treatment on nano-silica and nano-montmorillonite;

[0064] The specific process of the surface modification treatment is as follows: First, mix KH550 and absolute ethanol in a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution; Then mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and ultrasonically treat for 30 minutes, with a power of 500W and a frequency of 40kHz, to obtain nano-silica suspension and nano-montmorillonite suspension respectively; Then drop the hydrolysis solution into the nano-silica suspension and nano-montmorillonite suspension drop by drop, and stir and react in a water bath at 70°C for 4 hours; Centrifuge and separate at a speed of 8000rpm for 10 minutes, and wash with ethanol 3 times to remove the unreacted coupling agent; Finally, vacuum dry at 80°C for 6 hours, grind and sieve, and the particle size ≤ 50μm;

[0065] Step 2: Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, barrier layer and heat-sealing layer in proportion;

[0066] Among them, the specific process of the raw material melt blending is as follows: The twin-screw extruder is used for masterbatch preparation: The masterbatch of the protective outer layer: temperature 160-180°C, screw speed 200rpm; The masterbatch of the middle layer: temperature 170-190°C, screw speed 180rpm; The masterbatch of the inner layer: temperature 150-170°C, screw speed 220rpm; All masterbatches are vacuum dried at 80°C for 4-6 hours, and the moisture content ≤ 0.1%

[0067] Step 3: Perform three-layer co-extrusion casting on 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 zones. The feeding settings for the protective outer layer, barrier layer, and heat-sealing layer are in a ratio of 5:3:2: Protective outer layer: Add the outer layer masterbatch through the main feeder at a feeding rate of 20 kg / h; Barrier layer: Add the barrier layer masterbatch through side feeder 1 at a rate of 12 kg / h; Heat-sealing layer: Add the heat-sealing layer masterbatch through side feeder 2 at a rate of 8 kg / h. The raw materials for each layer enter independent screw sections, are melted by shear heat and external heating, and the melt is guided to the five-layer co-extrusion die head through a layered flow channel distributor and laminated in the order of protective outer layer - barrier layer - heat-sealing layer. Extrude from the die head, with the die head temperatures: 170 °C for the outer layer, 180 °C for the barrier layer, and 160 °C for the heat-sealing layer, and the traction speed is 15 - 25 m / min. The melt is extruded from the die head onto the casting roll, and the temperature of the cooling roll is controlled at 25 - 30 °C to form a film with a thickness of 20 - 50 μm. Tensile treatment: The longitudinal tensile ratio is 1.5 - 2.0 times, and the transverse tensile ratio is 1.2 - 1.5 times. After temperature control and shaping, it is cooled to room temperature by the cooling roll.

[0068] Step 4: Pass the cooled composite film between the electrodes of the corona treatment equipment. Under the action of the high-voltage electric field generated by the electrodes, air ionization generates corona discharge, thereby corona-treating the surface of the continuously passing film and then winding it up to obtain the composite film.

[0069] Step 5: Slit and wind up the finished composite film according to the set size and perform vacuum packaging.

[0070] Example 4: This example provides an environmentally friendly degradable composite film, including a protective outer layer, a barrier layer, and a heat-sealing layer arranged from outside to inside in sequence; The protective outer layer contains the following raw materials in parts by weight: 60 parts of PHA, 35 parts of PBAT, 5 parts of nano-silica, 2 parts of epoxy chain extender, and 0.5 part of antioxidant; The barrier layer contains 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 part of ultraviolet absorber; The heat-sealing layer contains the following raw materials in parts by weight: 75 parts of PEG-PHA copolymer, 25 parts of PLA, 1.2 parts of erucic acid amide, and 0.6 part of calcium stearate.

[0071] Among them, the epoxy chain extender is selected as polyethylene glycol diglycidyl ether, and the ultraviolet absorber is selected as UV-531.

[0072] A preparation method of an environmentally friendly degradable composite film includes the following steps:

[0073] Step 1: Weigh nano-silica, nano-montmorillonite, and graphene oxide respectively and vacuum dry them at 80 - 100 °C for 4 - 6 hours, and perform surface modification treatment on nano-silica and nano-montmorillonite with silane coupling agent KH550.

[0074] The specific process of surface modification treatment is as follows: First, mix KH550 and absolute ethanol in a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution; then mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and perform ultrasonic treatment for 30 minutes, with a power of 500W and a frequency of 40kHz, to obtain a nano-silica suspension and a nano-montmorillonite suspension respectively; then add the hydrolysis solution dropwise to the nano-silica suspension and the nano-montmorillonite suspension, and stir and react in a water bath at 70°C for 4 hours; centrifuge and separate at a rotation speed of 8000 rpm for 10 minutes, and wash 3 times with ethanol to remove the unreacted coupling agent; finally, dry in vacuum at 80°C for 6 hours, grind and sieve, and the particle size ≤ 50μm;

[0075] Step 2: Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, the barrier layer, and the heat-sealing layer in proportion;

[0076] Among them, the specific process of raw material melt blending is as follows: The twin-screw extruder is used for masterbatch preparation: Protective outer layer masterbatch: temperature 160 - 180°C, screw speed 200 rpm; Intermediate layer masterbatch: temperature 170 - 190°C, screw speed 180 rpm; Inner layer masterbatch: temperature 150 - 170°C, screw speed 220 rpm; All masterbatches are dried in vacuum at 80°C for 4 - 6 hours, and the moisture content ≤ 0.1%

[0077] Step 3: Perform three-layer coextrusion casting on the blended material. Select a co-rotating twin-screw extruder, equipped with a three-channel loss-in-weight feeder and a five-layer coextrusion die head, and set the temperature zones; The protective outer layer, the barrier layer, and the heat-sealing layer are fed in a ratio of 5:3:2: Protective outer layer: Add the outer layer masterbatch through the main feeder, and the feeding rate is 20 kg / h; Barrier layer: Add the barrier layer masterbatch through side feeder 1, and the rate is 12 kg / h; Heat-sealing layer: Add the heat-sealing layer masterbatch through side feeder 2, and the rate is 8 kg / h; The raw materials of each layer enter the independent screw sections respectively, are melted by shear heat and external heating, and the melt is guided to the five-layer coextrusion die head through the stratified flow channel distributor, and are laminated in the order of protective outer layer - barrier layer - heat-sealing layer; Extrude from the die head, die head temperature: outer layer 170°C, barrier layer 180°C, heat-sealing layer 160°C, traction speed 15 - 25 m / min; The melt is extruded from the die head to the casting roll, and the temperature of the cooling roll is controlled at 25 - 30°C to form a film with a thickness of 20 - 50μm. Tensile treatment: The longitudinal tensile ratio is 1.5 - 2.0 times, and the transverse tensile ratio is 1.2 - 1.5 times. After temperature control and shaping, it is cooled to room temperature through the cooling roll;

[0078] Step 4: Pass the cooled composite film between the electrodes of a corona treatment device. Under the action of the high-voltage electric field generated by the electrodes, air is ionized to generate corona discharge, thereby corona-treating the surface of the continuously passing film and then winding it up to obtain a composite film;

[0079] Step 5: Slit and wind up the finished composite film according to the set size and perform vacuum packaging.

[0080] Example 5: This example provides an environmentally friendly degradable composite film, which includes a protective outer layer, a barrier layer, and a heat-sealing layer arranged in sequence from outside to inside; the protective outer layer contains the following raw materials in parts by weight: 50 parts of PHA, 50 parts of PBAT, 5 parts of nano-silica, 2 parts of epoxy chain extender, and 0.6 part of antioxidant; the barrier layer contains 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 part of ultraviolet absorber; the heat-sealing layer contains the following raw materials in parts by weight: 70 parts of PEG-PHA copolymer, 30 parts of PLA, 1.4 parts of erucic acid amide, and 0.6 part of calcium stearate.

[0081] Among them, the epoxy chain extender is selected as epoxy soybean oil, and the ultraviolet absorber is selected as UV-9.

[0082] A preparation method of an environmentally friendly degradable composite film includes the following steps:

[0083] Step 1: Weigh nano-silica, nano-montmorillonite, and graphene oxide respectively and vacuum-dry them at 80-100 °C for 4-6 hours, and perform surface modification treatment on nano-silica and nano-montmorillonite with silane coupling agent KH550;

[0084] The specific process of the surface modification treatment is as follows: First, mix KH550 and absolute ethanol at a volume ratio of 1:9, add an acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution; then mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and perform ultrasonic treatment for 30 minutes, with a power of 500W and a frequency of 40kHz, to obtain a nano-silica suspension and a nano-montmorillonite suspension respectively; then dropwise add the hydrolysis solution into the nano-silica suspension and the nano-montmorillonite suspension, and stir and react in a water bath at 70 °C for 4 hours; centrifuge and separate at a speed of 8000 rpm for 10 minutes, wash with ethanol 3 times to remove the unreacted coupling agent; finally, vacuum-dry at 80 °C for 6 hours, grind and sieve, and the particle size ≤ 50 μm;

[0085] Step 2: Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, the barrier layer, and the heat-sealing layer in proportion respectively;

[0086] Among them, the specific process of raw material melt blending is as follows: The masterbatch is prepared by a twin-screw extruder: For the protective outer layer masterbatch: the temperature is 160 - 180°C, and the screw speed is 200 rpm; for the intermediate layer masterbatch: the temperature is 170 - 190°C, and the screw speed is 180 rpm; for the inner layer masterbatch: the temperature is 150 - 170°C, and the screw speed is 220 rpm; all masterbatches are vacuum dried at 80°C for 4 - 6 hours, and the moisture content ≤ 0.1%

[0087] Step 3: The blended material is subjected to three-layer coextrusion casting. A co-rotating twin-screw extruder is selected, equipped with a three-channel loss-in-weight feeder and a five-layer coextrusion die head, and temperature zoning is set; The protective outer layer, barrier layer, and heat-sealing layer are fed in a ratio of 5:3:2: For the protective outer layer: the outer layer masterbatch is added through the main feeder, and the feeding rate is 20 kg / h; for the barrier layer: the barrier layer masterbatch is added by side feeder 1, and the rate is 12 kg / h; for the heat-sealing layer: the heat-sealing layer masterbatch is added by side feeder 2, and the rate is 8 kg / h; The raw materials of each layer enter independent screw sections respectively, are melted by shear heat and external heating, and the melt is guided to the five-layer coextrusion die head through a layered flow channel distributor, and are laminated in the order of protective outer layer - barrier layer - heat-sealing layer; Extrusion from the die head, die head temperature: 170°C for the outer layer, 180°C for the barrier layer, 160°C for the heat-sealing layer, and the traction speed is 15 - 25 m / min; The melt is extruded from the die head to the casting roll, and the temperature of the cooling roll is controlled at 25 - 30°C to form a film with a thickness of 20 - 50 μm. Tensile treatment: The longitudinal tensile ratio is 1.5 - 2.0 times, and the transverse tensile ratio is 1.2 - 1.5 times. After temperature control and shaping, it is cooled to room temperature by the cooling roll;

[0088] Step 4: The cooled composite film is passed between the electrodes of a corona treatment device. Under the action of the high-voltage electric field generated by the electrodes, air is ionized to generate corona discharge, so as to perform corona treatment on the surface of the continuously passing film and then wind it up to obtain the composite film;

[0089] Step 5: The finished composite film is slit and wound according to the set size and vacuum packaged.

[0090] Comparative Example 1: An environmentally friendly degradable composite film and its preparation method provided in this example are generally the same as those in Example 3. The main difference is that the surface modification treatment is not performed on the nano-fillers.

[0091] Comparative Example 2: An environmentally friendly degradable composite film and its preparation method provided in this example are generally the same as those in Example 3. The main difference is that a single-layer film formula is adopted: 50 parts of PHA, 30 parts of PBAT, 5 parts of unmodified nano-silica, 2 parts of epoxy soybean oil, and 0.5 part of antioxidant; The layered coextrusion is cancelled, and only the protective outer layer formula is used. The film is formed by single-layer casting, with a thickness of 50 μm.

[0092] 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, with the main difference being that graphene oxide is not added to the barrier layer.

[0093] The performance tests of Examples 1-5 and Comparative Examples 1-3 were respectively conducted on the products prepared, including mechanical properties, barrier properties, heat sealing properties, degradation properties and surface properties, and the relevant data were recorded in Table 1;

[0094] 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

[0095] As can be seen from Table 1, 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. It has passed the OTR / WVTR pharmaceutical grade test, and the degradation is controllable without affecting the stability of the drug. The heat sealing performance is reliable and adaptable to high-speed packaging production lines. In addition, the degradation rate within 180 days is ≥90%, and all components are degradable, which is green and environmentally friendly.

[0096] The present invention adopts a layered composite structure: a protective outer layer with high hardness and enhanced scratch resistance through nano-silicon dioxide, while taking into account surface printability; a barrier layer with dual-network MMT + graphene oxide to achieve ultra-high barrier, extending the shelf life of food and medicine; a heat-sealing layer with flexibility and smoothness to ensure sealing strength and ease of tearing, and a corona treatment with a dyne value of ≥38 mN / m to improve ink adhesion, adapting to diverse printing needs.

[0097] 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 scope of protection 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 from outside to inside in sequence; The protective outer layer contains the following raw materials in parts by weight: 50-80 parts of PHA, 30-50 parts of PBAT, 5-8 parts of nano-silica surface-modified by silane coupling agent KH550, 2-3 parts of epoxy chain extender, and 0.5-0.8 part of antioxidant; The barrier layer contains the following raw materials in parts by weight: 60-80 parts of PBAT, 30-50 parts of PHA-MAH copolymer, 8-12 parts of nano-montmorillonite surface-modified by silane coupling agent KH550, 2-4 parts of graphene oxide, and 0.2-0.4 part of ultraviolet absorber; The heat-sealing layer contains the following raw materials in parts by weight: 70-90 parts of PEG-PHA copolymer, 20-30 parts of PLA, 1-2 parts of erucic acid amide, and 0.5-0.8 part 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. An 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 preparation method of an environment-friendly degradable composite film, characterized in that, To prepare an environmentally friendly degradable composite film according to any one of claims 1-3, it includes the following steps: Ⅰ. Weigh nano-silica, nano-montmorillonite, and graphene oxide respectively and vacuum-dry them at 80-100 °C for 4-6 hours, and use silane coupling agent KH550 to conduct surface modification treatment on nano-silica and nano-montmorillonite; Ⅱ. Use a twin-screw extruder to melt and blend the raw materials of the protective outer layer, the barrier layer, and the heat-sealing layer in proportion; Ⅲ. Conduct three-layer co-extrusion casting on the blended materials, and after temperature control and shaping, cool them to room temperature through a cooling roller; Ⅳ. Conduct on-line corona treatment on the cooled film and then wind it up to obtain a composite film; Ⅴ. Cut and wind up the finished composite film according to the set size and conduct vacuum packaging.

5. The preparation method of an environment-friendly degradable composite film according to claim 4, characterized in that, In step Ⅰ, the surface modification treatment of nano-silica and nano-montmorillonite with silane coupling agent KH550 includes the following steps: A1. Mix KH550 and absolute ethanol in a volume ratio of 1:9, add acetic acid aqueous solution with pH = 4, KH550: water = 1:1, and stir magnetically for 30 minutes to form a hydrolysis solution; A2. Mix the dried nano-silica and nano-montmorillonite with deionized water respectively, and conduct ultrasonic treatment for 30 minutes, with a power of 500W and a frequency of 40kHz, to obtain a nano-silica suspension and a nano-montmorillonite suspension respectively; A3. Dropwise add the hydrolysis solution into the nano-silica suspension and the nano-montmorillonite suspension, and stir and react in a water bath at 70 °C for 4 hours; A4. Centrifuge and separate at a rotation speed of 8000 rpm for 10 minutes, and wash with ethanol 3 times to remove the unreacted coupling agent; A5. Vacuum-dry at 80 °C for 6 hours, grind and sieve, and the particle size ≤ 50 μm.

6. The preparation method of an environmentally friendly degradable composite film according to claim 4, characterized in that, In step Ⅱ, the melting and blending of the raw materials includes the following steps: B1. Preparation of masterbatch using a twin-screw extruder: For the protective outer layer masterbatch: temperature 160 - 180 °C, screw speed 200 rpm; for the intermediate layer masterbatch: temperature 170 - 190 °C, screw speed 180 rpm; for the inner layer masterbatch: temperature 150 - 170 °C, screw speed 220 rpm. B2. All masterbatches are vacuum dried at 80 °C for 4 - 6 hours, with a moisture content ≤ 0.1%.

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

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