Biodegradable polyester composite material with gas barrier property and thermal shrinkage based on PPC / PVA and preparation method of biodegradable polyester composite material

Abstract

The invention relates to the field of biodegradable packaging materials, in particular to a biodegradable polyester composite material with gas barrier property and thermal shrinkage based on PPC / PVA and a preparation method of the biodegradable polyester composite material. The biodegradable polyester composite material mainly comprises biodegradable polyester, flaky nano silicon dioxide, a compatilizer, a lubricant and an antioxidant, and the biodegradable polyester, polypropylene carbonate (PPC) and polyvinyl alcohol (PVA) are mixed according to the mass ratio of (595-795): (150-350). The raw materials are mixed at a high speed, extruded and diced to obtain a biodegradable polyester composite material, and the biodegradable film is obtained through extrusion and film blowing. The biodegradable film disclosed by the invention has good gas barrier property and thermal shrinkage, can be biodegraded under a matured compost condition, the biodegradation rate is 90.30%, the relative biodegradation rate is 92.41%, and products are carbon dioxide and water and meet the GB / T 38082-2019 standard requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biodegradable packaging materials, and discloses a biodegradable polyester composite material based on PPC / PVA and having gas barrier property and heat shrinkability, and a preparation method thereof. BACKGROUND

[0002] Traditional polyethylene (PE) film is less affected by salt, corrosive gas, high humidity and high temperature, has high gas barrier property, prevents water vapor and oxygen in the air from entering the package, and is thus widely used in the fields of packaging and transportation of food, medicine and metal products. However, PE material is difficult to degrade in the environment, and discarded film causes serious pollution to land, sea and water sources. Biodegradable polymer material is a widely available renewable resource, can be biodegraded in a natural environment without causing pollution, and has a wide application in barrier packaging materials.

[0003] Polypropylene carbonate (PPC) is an aliphatic polycarbonate that can be completely degraded into carbon dioxide and water under microbial conditions, and is a biodegradable polymer. PPC has excellent tensile strength, elongation at break, flexibility and water vapor barrier property, and is mainly applied in the fields of film and barrier materials. However, the oxygen barrier property of PPC film is poor, which limits its application. Polyvinyl alcohol (PVA) is a vinyl polymer with biodegradable property, can be decomposed by bacteria in soil, and can be finally degraded into carbon dioxide and water. PVA film has good toughness and large tensile strength, and has excellent oil resistance, organic solvent resistance and other properties. However, the water vapor barrier property of PVA film is not ideal, but the oxygen barrier property is excellent. Sheet-shaped nano-silicon dioxide (fn-SiO2) has a sheet or sheet-like aggregate structure and a tetrahedral crystal structure, contains a large number of Si-OH groups on the surface and has a large specific surface area. Blending PPC with PVA and using fn-SiO2 as a filler can not only improve the mechanical property and oxygen barrier property of PPC film, but also endow the film with good heat shrinkability. SUMMARY

[0004] In view of the problems existing in the biodegradable polymer barrier materials at present, the purpose of the present application is to provide a biodegradable polyester composite material with gas barrier property and heat shrinkage property based on PPC / PVA and a preparation method thereof. The present application first places polypropylene carbonate (PPC), polyvinyl alcohol (PVA), flaky nanosilica (fn-SiO2), a compatibilizer, a lubricant, an antioxidant and other additives in a high-speed mixer, controls a certain temperature, stirs at high speed for a certain time, discharges, and obtains a modified mixture. The modified mixture is placed in a twin-screw extruder for melt blending, extrusion and granulation to obtain a PPC / PVA biodegradable polyester composite material with good processing performance and excellent mechanical properties, and then blown into a film in a film blowing machine to obtain a biodegradable film with good gas barrier property and good heat shrinkage property.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a biodegradable polyester composite material with gas barrier property and heat shrinkage property based on PPC / PVA, which is prepared by taking biodegradable polypropylene carbonate (PPC) as the main base material, polyvinyl alcohol (PVA) as the auxiliary resin, flaky nanosilica (fn-SiO2) as the filler, and a compatibilizer, a lubricant and an antioxidant as the additives. The particle size d of the flaky nanosilica is 1-100 nm.

[0006] The compatibilizer is one of PEG-6000, PEG-400, citric acid and KT-915A; the lubricant is two of glycerol, calcium stearate, solid paraffin, polyethylene wax, stearic acid and oleic acid amide; and the antioxidant is one of antioxidant B225, antioxidant 168 or antioxidant B215.

[0007] The mass ratio of the PPC, the PVA, the flaky nanosilica, the compatibilizer, the lubricant, the antioxidant B225 is 500-850:100-500:10-80:8-30:4-10:1-4.

[0008] Preferably, the filler is fn-SiO2 with an average particle size d of 55 nm, the compatibilizer is PEG-6000, the lubricant is glycerol and calcium stearate, and the antioxidant is B225.

[0009] Preferably, the mass ratio of the PPC and the PVA is 595-795:150-350.

[0010] Preferably, the mass ratio of the PPC, fn-SiO2, PEG-6000, glycerol, calcium stearate and B225 is 595-795:30:10:6:8:1.

[0011] Preferably, the mass ratio of the PVA, fn-SiO2, PEG-6000, glycerol, calcium stearate and B225 is 150-350:30:10:6:8:1.

[0012] A preparation method of a biodegradable polyester composite material with gas barrier property and heat shrinkage based on PPC / PVA, comprising the following steps:

[0013] (1) Preparation of modified mixture: PPC, PVA, filler, compatibilizer, lubricant and antioxidant are weighed and added into a high-speed mixer, and the temperature is controlled to stir for a certain time before discharging to obtain the modified mixture.

[0014] Preferably, the temperature in the mixer is 85℃.

[0015] Preferably, the stirring speed is 15 Hz.

[0016] Preferably, the stirring time is 15 min.

[0017] (2) Preparation of biodegradable polyester composite material: the modified mixture is placed in a twin-screw extruder, and the temperature of each zone is controlled for melt blending, extrusion and granulation to obtain the biodegradable polyester composite material.

[0018] Preferably, the temperature of each zone of the twin-screw extruder is: zone 1 150℃, zone 2 155℃, zone 3 155℃, zone 4 160℃, and zone 5 160℃.

[0019] A biodegradable film with gas barrier property and heat shrinkage based on PPC / PVA: the biodegradable polyester composite material is placed in a film blowing machine, and the temperature of each zone is controlled to blow the film to obtain the biodegradable film.

[0020] Preferably, the temperature of each zone of the film blowing machine is: zone 1 150℃, zone 2 155℃, zone 3 155℃, zone 4 160℃, and zone 5 160℃, and the thickness of the film is 0.05 mm.

[0021] The beneficial effects of the present application are:

[0022] Compared with the prior art, the advantages of the present application are as follows: (1) the present application uses sheet-shaped nano-silicon dioxide (fn-SiO2) (d=55 nm) as a filler, which not only improves the mechanical properties of the PPC / PVA composite film, but also improves the gas barrier property of the film. Because the fn-SiO2 with a sheet structure can form a layer-by-layer structure in the film, the resistance of water vapor and oxygen to penetrate the film increases, the amount of water vapor and oxygen penetrating the film decreases, and the barrier property improves. When the average particle size (d=90 nm) of fn-SiO2 is relatively large, relatively more pores are formed in the film, the resistance of water vapor and oxygen to penetrate the film decreases, the amount of water vapor and oxygen penetrating the film increases, and the barrier property decreases. When the average particle size (d=25 nm) of fn-SiO2 is relatively small, relatively large particles are formed due to agglomeration and defects are generated, the number of pores in the film increases and the uniformity decreases, resulting in a decrease in the resistance of water vapor and oxygen to penetrate the film, an increase in the amount of water vapor and oxygen penetrating the film, and a decrease in the barrier property. Therefore, in the present application, the fn-SiO2 particles with an average particle size d=55 nm have the best gas barrier property and mechanical properties; (2) using PPC as the main base material and blending with a certain proportion of PVA resin, not only can the poor oxygen barrier property of pure PPC film be effectively overcome, but also the mechanical properties of the film can be further improved, and the film has good thermal shrinkage, and the shrinkage rate can be adjusted by the proportion of PPC and PVA; (3) the raw materials in the present application are easy to obtain, there is no solvent, the process is simple, the processing conditions are mild, and it is suitable for continuous large-scale industrial production. The biodegradable film can be biodegraded under composting conditions (test period of 126 days), the biodegradation rate is 90.30%, the relative biodegradation rate is 92.41%, the product is carbon dioxide and water, and it meets the standard requirements of GB / T 38082-2019. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a photograph of biodegradable polyester composite material 1 (A) and film 1 (B).

[0024] Figure 2 is a photograph of biodegradable polyester composite material 2 (A) and film 2 (B).

[0025] Figure 3 is a photograph of biodegradable polyester composite material 3 (A) and film 3 (B).

[0026] Figure 4 is a photograph of biodegradable polyester composite material 4 (A) and film 4 (B).

[0027] Figure 5 is a photograph of biodegradable polyester composite material 5 (A) and film 5 (B).

[0028] Figure 6is a photograph of a biodegradable polyester composite 6 (A) and a film 6 (B).

[0029] Figure 7 is a photograph of a biodegradable polyester composite 7 (A) and a film 7 (B).

[0030] Figure 8 is a graph showing the change in the amount of carbon dioxide generated over time for the biodegradable film 1.

[0031] Figure 9 is a graph showing the change in the biodegradation rate over time for the biodegradable film 1. DETAILED DESCRIPTION

[0032] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not intended to limit the claims of the present application.

[0033] Example 1: A PPC / PVA-based biodegradable polyester composite 1 having gas barrier properties and heat shrinkability and a method for preparing the same

[0034] 1. Preparation of a modified mixture

[0035] 7.95 kg of PPC, 1.5 kg of PVA, 0.3 kg of fn-SiO2 (d = 55 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate, and 0.01 kg of B225 were weighed into a high-speed mixer, the material temperature was controlled at 85°C, the stirring speed was controlled at 15 Hz, and the mixture was stirred for 15 min before discharging to obtain a modified mixture.

[0036] 2. Preparation of a biodegradable polyester composite 1

[0037] The modified mixture described above was placed in a twin-screw extruder, the temperature of each zone was controlled at 150°C for zone 1, 155°C for zone 2, 155°C for zone 3, 160°C for zone 4, and 160°C for zone 5, and the mixture was melt-blended and extruded to obtain the biodegradable polyester composite 1. A photograph of the biodegradable polyester composite 1 is shown in Figure 1 (A).

[0038] 3. Preparation of a biodegradable film 1

[0039] The biodegradable polyester composite 1 was placed in a film blowing machine, the temperature of each zone was controlled at 150°C for zone 1, 155°C for zone 2, 155°C for zone 3, 160°C for zone 4, and 160°C for zone 5, and the film was blown to obtain the biodegradable film 1. A photograph of the film 1 is shown in Figure 1 (B). The film thickness was 0.05 mm, and the water vapor transmission rate was 46 g / (m 2• day atm), oxygen transmission rate: 68 cm 3 / (m 2 • day atm), elongation at break: 385% in the longitudinal direction, 362% in the transverse direction, tensile strength: 30 MPa in the longitudinal direction, 27 MPa in the transverse direction, shrinkage (shrinkage temperature 120°C): 71% in the longitudinal direction, 19% in the transverse direction.

[0040] Example 2: A biodegradable polyester composite 2 based on PPC / PVA with gas barrier property and heat shrinkability and a preparation method thereof

[0041] 1. Preparation of modified mixture

[0042] 6.95 kg of PPC, 2.5 kg of PVA, 0.3 kg of fn-SiO2(d=55 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate and 0.01 kg of B225 were weighed into a high-speed mixer, the material temperature was controlled at 85°C, the stirring speed was 15 Hz, and the stirring time was 15 min, and then the modified mixture was obtained.

[0043] 2. Preparation of biodegradable polyester composite 2

[0044] The modified mixture was placed in a twin-screw extruder, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C, and then the biodegradable polyester composite 2 was obtained by melt blending and extrusion granulation. The photo of the biodegradable polyester composite 2 is shown in Figure 2 (A).

[0045] 3. Preparation of biodegradable film 2

[0046] The biodegradable polyester composite 2 was placed in a film blowing machine, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C, and then the biodegradable film 2 was obtained by film blowing. The photo of the film 2 is shown in Figure 2 (B). The film thickness is 0.05 mm, the water vapor transmission rate is 51 g / (m 2 · day atm), the oxygen transmission rate is 49 cm 3 / (m 2 · day atm), the elongation at break is 397% in the longitudinal direction and 376% in the transverse direction, the tensile strength is 34 MPa in the longitudinal direction and 31 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) is 75% in the longitudinal direction and 22% in the transverse direction.

[0047] Example 3: A biodegradable polyester composite 3 based on PPC / PVA with gas barrier property and heat shrinkability and a preparation method thereof

[0048] 1. Preparation of modified mixture

[0049] Weigh 5.95 kg of PPC, 3.5 kg of PVA, 0.3 kg of fn-SiO2(d=55 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate and 0.01 kg of B225 into a high-speed mixer, control the material temperature at 85°C, the stirring speed at 15 Hz, stir for 15 min and discharge to obtain a modified mixture.

[0050] 2. Preparation of biodegradable polyester composite material 3

[0051] Put the above modified mixture into a twin-screw extruder, control the temperature of the first zone at 150°C, the second zone at 155°C, the third zone at 155°C, the fourth zone at 160°C and the fifth zone at 160°C, melt blend and extrude to obtain biodegradable polyester composite material 3. The photo of biodegradable polyester composite material 3 is shown in Figure 3 (A).

[0052] 3. Preparation of biodegradable film 3

[0053] Put the biodegradable polyester composite material 3 into a film blowing machine, control the temperature of the first zone at 150°C, the second zone at 155°C, the third zone at 155°C, the fourth zone at 160°C and the fifth zone at 160°C, and blow film to obtain biodegradable film 3. The photo of film 3 is shown in Figure 3 (B). The film thickness is 0.05 mm, the water vapor transmission rate is 57 g / (m 2 ·day·atm), the oxygen transmission rate is 35 cm 3 / (m 2 ·day·atm), the elongation at break is 412% in the longitudinal direction and 394% in the transverse direction, the tensile strength is 38 MPa in the longitudinal direction and 34 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) is 81% in the longitudinal direction and 24% in the transverse direction.

[0054] As can be seen from the above three examples, within a certain range, as the PVA content in the polyester composite material gradually increases, the water vapor transmission rate of the film gradually increases, the oxygen transmission rate gradually decreases, and the elongation at break, the tensile strength and the shrinkage gradually increase, so the gas barrier property, the mechanical property of the film can be adjusted by the content of PVA.

[0055] Comparative Example 1: A biodegradable polyester composite material 4 based on PPC / PVA with gas barrier property and thermal shrinkage and a preparation method thereof

[0056] 1. Preparation of modified mixture

[0057] The 7.85 kg of PPC, 1.5 kg of PVA, 0.4 kg of fn-SiO2(d=55 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate and 0.01 kg of B225 were weighed into a high-speed mixer, the material temperature was controlled at 85°C, the stirring speed was 15 Hz, and the stirring time was 15 min, and then the modified mixture was discharged.

[0058] 2, Preparation of biodegradable polyester composite 4

[0059] The modified mixture was placed in a twin-screw extruder, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C. The biodegradable polyester composite 4 was obtained by melt blending and extrusion granulation. The photo of the biodegradable polyester composite 4 is shown in Figure 4 (A).

[0060] 3, Preparation of biodegradable film 4

[0061] The biodegradable polyester composite 4 was placed in a film blowing machine, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C. The biodegradable film 4 was obtained by film blowing. The photo of the film 4 is shown in Figure 4 (B). The film thickness was 0.05 mm, the water vapor transmission rate was 39 g / (m 2 ·day·atm), the oxygen transmission rate was 57 cm 3 / (m 2 ·day·atm), the elongation at break was 378% in the longitudinal direction and 357% in the transverse direction, the tensile strength was 33 MPa in the longitudinal direction and 29 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) was 68% in the longitudinal direction and 17% in the transverse direction.

[0062] Compared with Example 1, the amount of filler fn-SiO2 in Comparative Example 1 was increased from 0.3 kg to 0.4 kg (increased by 33%), and the water vapor transmission rate and the oxygen transmission rate of the film were reduced, and the tensile strength was increased. The reason is that within a certain range, as the content of fn-SiO2 increases, the compactness of the film increases, and the gas barrier property and the tensile strength improve.

[0063] Comparative Example 2: A biodegradable polyester composite 5 based on PPC / PVA with gas barrier property and thermal shrinkage and a preparation method thereof

[0064] 1, Preparation of modified mixture

[0065] The 7.95 kg of PPC, 1.5 kg of PVA, 0.3 kg of sn-SiO2(d=55 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate and 0.01 kg of B225 were weighed into a high-speed mixer, the material temperature was controlled at 85°C, the stirring speed was 15 Hz, and the stirring time was 15 min, and then the modified mixture was discharged. The modified mixture was obtained.

[0066] 2. Preparation of biodegradable polyester composite 5

[0067] The modified mixture was placed in a twin-screw extruder, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C. The biodegradable polyester composite 5 was obtained by melt blending and extrusion granulation. The photo of the biodegradable polyester composite 5 is shown in Figure 5 (A).

[0068] 3. Preparation of biodegradable film 5

[0069] The biodegradable polyester composite 5 was placed in a film blowing machine, and the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, and the temperature of the fifth zone was controlled at 160°C. The biodegradable film 5 was obtained by film blowing. The photo of the film 5 is shown in Figure 5 (B). The film thickness was 0.05 mm, the water vapor transmission rate was 56 g / (m 2 ·day·atm), the oxygen transmission rate was 83 cm 3 / (m 2 ·day·atm), the elongation at break was 389% in the longitudinal direction and 366% in the transverse direction, the tensile strength was 27 MPa in the longitudinal direction and 24 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) was 72% in the longitudinal direction and 19% in the transverse direction.

[0070] Compared with Example 1, in Comparative Example 2, the filler was replaced by sn-SiO2 with the same mass and average particle size d=55 nm instead of fn-SiO2 with the average particle size d=55 nm. The water vapor transmission rate and the oxygen transmission rate of the film increased, and the tensile strength decreased. The reason is that sn-SiO2 cannot form the layer-by-layer structure of fn-SiO2 in the film, the resistance of gas molecules passing through the film is small, and the gas barrier property decreases.

[0071] Comparative Example 3: A biodegradable polyester composite 6 based on PPC / PVA with gas barrier property and heat shrinkage and a preparation method thereof

[0072] 1. Preparation of modified mixture

[0073] Take 7.95 kg PPC, 1.5 kg PVA, 0.3 kg fn-SiO2(d=90 nm), 0.1 kg PEG-6000, 0.06 kg glycerol, 0.08 kg calcium stearate and 0.01 kg B225 into a high-speed mixer, control the material temperature at 85°C, the stirring speed at 15 Hz, stir for 15 min and discharge to obtain a modified mixture.

[0074] 2, Preparation of biodegradable polyester composite 6

[0075] Put the modified mixture above into a twin-screw extruder, control the temperature of the first zone at 150°C, the second zone at 155°C, the third zone at 155°C, the fourth zone at 160°C, and the fifth zone at 160°C, melt blend, extrude and pelletize to obtain biodegradable polyester composite 6. The photo of biodegradable polyester composite 6 is shown in Figure 6 (A).

[0076] 3, Preparation of biodegradable film 6

[0077] Put biodegradable polyester composite 6 into a film blowing machine, control the temperature of the first zone at 150°C, the second zone at 155°C, the third zone at 155°C, the fourth zone at 160°C, and the fifth zone at 160°C, and blow film to obtain biodegradable film 6. The photo of film 6 is shown in Figure 6 (B). The film thickness is 0.05 mm, the water vapor transmission rate is 51 g / (m 2 ·day·atm), the oxygen transmission rate is 77 cm 3 / (m 2 ·day·atm), the elongation at break is 382% in the longitudinal direction and 360% in the transverse direction, the tensile strength is 28 MPa in the longitudinal direction and 21 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) is 72% in the longitudinal direction and 17% in the transverse direction.

[0078] Compared with Example 1, in Comparative Example 3, the filler is replaced by fn-SiO2 with an average particle size d=90 nm instead of fn-SiO2 with an average particle size d=55 nm, and the water vapor transmission rate and the oxygen transmission rate of the film increase, and the tensile strength decreases. The reason is that relatively large fn-SiO2 particles form more pores in the film, the resistance of water vapor and oxygen to pass through the film decreases, the barrier property decreases, and the tensile strength also decreases.

[0079] Comparative Example 4: A biodegradable polyester composite 7 based on PPC / PVA with gas barrier property and heat shrinkability and a preparation method thereof

[0080] 1, Preparation of modified mixture

[0081] The 7.95 kg of PPC, 1.5 kg of PVA, 0.3 kg of fn-SiO2(d=25 nm), 0.1 kg of PEG-6000, 0.06 kg of glycerol, 0.08 kg of calcium stearate and 0.01 kg of B225 were weighed into a high-speed mixer, the material temperature was controlled at 85°C, the stirring speed was 15 Hz, the stirring time was 15 min, and the modified mixture was discharged. The modified mixture was obtained.

[0082] 2, Preparation of biodegradable polyester composite 7

[0083] The modified mixture was placed in a twin-screw extruder, the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, the temperature of the fifth zone was controlled at 160°C, and the biodegradable polyester composite 7 was obtained by melt blending and extrusion granulation. The photo of the biodegradable polyester composite 7 is shown in Figure 7 (A).

[0084] 3, Preparation of biodegradable film 7

[0085] The biodegradable polyester composite 7 was placed in a film blowing machine, the temperature of the first zone was controlled at 150°C, the temperature of the second zone was controlled at 155°C, the temperature of the third zone was controlled at 155°C, the temperature of the fourth zone was controlled at 160°C, the temperature of the fifth zone was controlled at 160°C, and the biodegradable film 7 was obtained by film blowing. The photo of the film 7 is shown in Figure 7 (B). The film thickness was 0.05 mm, the water vapor transmission rate was 60 g / (m 3 ·day·atm), the oxygen transmission rate was 88 cm 2 / (m v / d ·day·atm), the elongation at break was 380% in the longitudinal direction and 358% in the transverse direction, the tensile strength was 25 MPa in the longitudinal direction and 21 MPa in the transverse direction, and the shrinkage (shrinkage temperature 120°C) was 70% in the longitudinal direction and 18% in the transverse direction.

[0086] Compared with Example 1, in Comparative Example 4, the filler was replaced by fn-SiO2 with an average particle size d=25 nm instead of fn-SiO2 with an average particle size d=55 nm, and the water vapor transmission rate and the oxygen transmission rate of the film were increased, and the tensile strength was decreased. The reason is that when the particle size is relatively small, relatively large particles are formed due to agglomeration and defects are generated, the number of pores in the film increases and the uniformity decreases, resulting in a decrease in the resistance of water vapor and oxygen to pass through the film, a decrease in the barrier property, and a decrease in the tensile strength.

[0087] The biodegradation performance of the biodegradable film 1 was commissioned by the Jilin Provincial Product Quality Supervision and Inspection Institute to be tested, and the testing method was GB / T 19277.1-2011 “Determination of the ultimate aerobic biodegradation capacity of materials under controlled composting conditions - Method for the determination of released carbon dioxide - Part 1: General method”. The reference material in the experimental data was provided by the Jilin Provincial Product Quality Supervision and Inspection Institute, and the results are shown in Table 1. Figure 8 、 Figure 9 , Table 1, can be biodegraded under composting conditions (test period 126 days), the biodegradation rate is 90.30%, the relative biodegradation rate is 92.41%, the product is carbon dioxide and water, which meets the standard requirements of GB / T38082-2019.

[0088] Table 1 Biodegradation film 1 and reference material biodegradation rate data

[0089] Relevant information Biodegradable film 1 Reference material (cellulose) Inoculum Composted manure Composted manure total volatile solids ratio mat v / d ]] 71.47% 99.99% Biodegradation rate at 45 days 60.63% 76.13% Final biodegradation rate 90.30% 97.72% Test period 126 days 126 days

[0090] It can be understood that the above specific description of the present application is only used to illustrate the present application and is not limited to the technical solutions described in the embodiments of the present application. Those skilled in the art should understand that the present application can still be modified or replaced equivalently to achieve the same technical effect, as long as it meets the use requirements, and it is within the protection scope of the present application.

Claims

1. A biodegradable polyester composite material based on PPC / PVA with gas barrier and heat shrinkage properties, characterized in that, The biodegradable polyester composite material mainly includes biodegradable polyester, sheet-like nano silica, compatibilizer, lubricant and antioxidant. The biodegradable polyester is a mixture of polypropylene carbonate (PPC) and polyvinyl alcohol (PVA) in a mass ratio of 595~795:150~350.

2. The biodegradable polyester composite material based on PPC / PVA with gas barrier and heat shrinkage properties according to claim 1, characterized in that, The particle size of the sheet-like nano-silica is d=1~100 nm.

3. The biodegradable polyester composite material based on PPC / PVA with gas barrier and heat shrinkage properties according to claim 1, characterized in that, The compatibilizer is one of PEG-6000, PEG-400, citric acid, and KT-915A; the lubricant is two of glycerin, calcium stearate, solid paraffin, polyethylene wax, stearic acid, and oleamide; and the antioxidant is one of antioxidant B225, antioxidant 168, or antioxidant B215.

4. A biodegradable polyester composite material based on PPC / PVA with gas barrier and heat shrinkage properties according to claim 3, characterized in that, The compatibilizer is PEG-6000, the lubricant is a mixture of glycerin and calcium stearate in a mass ratio of 5~20:3~10, and the antioxidant is antioxidant B225.

5. A biodegradable polyester composite material based on PPC / PVA with gas barrier and heat shrinkage properties as described in claim 1, characterized in that, The mass ratio of PPC, PVA, sheet-like nano silica, compatibilizer, lubricant, and antioxidant B225 is 500~850:100~500:10~80:8~30:4~10:1~4.

6. A method for preparing a PPC / PVA-based biodegradable polyester composite material with gas barrier and heat shrinkage properties as described in any one of claims 1-5, characterized in that, Includes the following steps: 1) Weigh out biodegradable polyester, flake nano silica, compatibilizer, lubricant and antioxidant and place them in a high-speed mixer. Control the temperature and stir at high speed for a certain time to discharge the material to obtain the modified mixture. 2) The modified mixture is placed in a twin-screw extruder, and the temperature of each zone is controlled for melt blending. After extrusion and pelletizing, a biodegradable polyester composite material is obtained.

7. A method for preparing a PPC / PVA-based biodegradable polyester composite material with gas barrier and heat shrinkage properties according to claim 6, characterized in that, In step 1), the temperature is 80~90℃, the stirring speed is 10~20 Hz, and the stirring time is 10~30 min.

8. A method for preparing a PPC / PVA-based biodegradable polyester composite material with gas barrier and heat shrinkage properties according to claim 6, characterized in that, In step 2), the temperatures of each zone of the twin-screw extruder are as follows: Zone 1 150~155℃, Zone 2 155~160℃, Zone 3 155~160℃, Zone 4 160~165℃, and Zone 5 160~165℃.

9. A biodegradable film based on PPC / PVA with gas barrier and heat shrinkage properties, characterized in that, The biodegradable polyester composite material according to any one of claims 1-5 is placed in a blown film machine, and the temperature of each zone is controlled to blow film a biodegradable film.

10. A biodegradable film based on PPC / PVA with gas barrier and heat shrinkage properties as described in claim 9, characterized in that, The temperatures of each zone of the blow molding machine are as follows: Zone 1 150~155℃, Zone 2 155~160℃, Zone 3 155~160℃, Zone 4 160~165℃, Zone 5 160~165℃, and the film thickness is 0.05~0.15 mm.

Images