Multilayer pbat / biomass composite active barrier film, method of preparation and use

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a multilayer PBAT / biomass composite active barrier film and a preparation method and application thereof. The preparation method comprises the following steps: S1, pretreating and blending raw materials to obtain an oxygen barrier layer A blend and a water vapor capturing layer B blend; S2, extruding and granulating the blended raw materials: the oxygen barrier layer A blend and the water vapor capturing layer B blend are respectively added into a double-screw extruder for extrusion and granulation, and an oxygen barrier layer A composite modified granule and a water vapor capturing layer B composite modified granule are respectively obtained, and then the granules are subjected to dehumidification and drying treatment; and S3, forming and processing of the composite film: the dried oxygen barrier layer A composite modified granule and the water vapor capturing layer B composite modified granule are blown into a film shape by using a micro-nano multilayer co-extrusion film blowing equipment. The prepared multilayer high polymer composite film can be applied to fields with certain requirements on oxygen barrier performance, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a multilayer PBAT / biomass composite active barrier membrane, its preparation method, and its application. Background Technology

[0002] Biodegradable polybutylene adipate (PBAT) is widely used in various packaging materials due to its good tensile strength and toughness. However, its high oxygen and water vapor permeability coefficient severely limits its application in fields such as food preservation, pharmaceutical packaging, and mulch film where high barrier properties are required.

[0003] Existing technologies have used various methods to regulate the barrier properties of PBAT, such as adding resins with high oxygen barrier properties, such as ethylene-vinyl alcohol copolymer (EVOH), polypropylene carbonate (PPC), and polyglycolic acid (PGA), to PBAT as a barrier phase or using the above polymer resins as a barrier intermediate layer. For example, Chinese patent CN106221165B uses PBAT, PPC, and other resins to reduce the water vapor transmission rate of the degradable mulch film through modified blending. Chinese patent application CN116333459A uses PGA as a barrier phase to fill PBAT, which acts as an organic barrier phase, thereby reducing the water vapor and oxygen transmission rate of the PBAT composite material. Another common method for preparing barrier films is to prepare multilayer biodegradable composite films. For example, Chinese patent CN110583326B prepared a three-layer composite film with good water vapor and oxygen barrier properties using PBAT and PPC as substrates. Chinese patent application CN113211920A prepared a multilayer barrier flexible packaging film with adjustable degradation rate by using PBAT, PCL (polycaprolactone) and PLA (polylactic acid) through multilayer co-extrusion.

[0004] Secondly, low-cost biomass such as starch, protein, and cellulose have the advantage of low oxygen permeability coefficients. Therefore, in biodegradable packaging research, they are often added to the resin matrix to act as oxygen barriers. For example, Chinese patent CN116410496B casts a gelatinized starch solution with eggshell powder into a film, and the oxygen and water vapor permeability coefficients of the film are significantly reduced. Chinese patent application CN105462053A intercalates phosphorylated soy protein isolate with montmorillonite, and then blends and casts a film with an ethylene-vinyl alcohol copolymer solution, and the film's oxygen and water vapor barrier properties are significantly improved. However, most current methods involve solvent casting to coat and mold biomass polymer solutions. However, the above-mentioned biomass processing and preparation are relatively complex and not conducive to industrial production. Plasticizers are typically added to plasticize thermoplastic materials, creating thermoplastic materials similar to thermoplastics. However, the addition of plasticizers increases the volume of free molecular chains in the material, leading to a continuous increase in the oxygen permeability coefficient. Furthermore, since plasticizers are usually low-molecular-weight polyols rich in hydroxyl groups, the resulting thermoplastic materials are highly hygroscopic, and the plasticizers easily leach out. The oxygen permeability coefficient gradually increases with the system's water content, causing the oxygen barrier performance to be compromised after a period of storage, severely impacting its effectiveness and limiting its application as a barrier material. Therefore, there is an urgent need to develop a PBAT / biomass composite active barrier membrane with superior oxygen barrier performance that maintains sufficient oxygen barrier activity even after a period of storage. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a multilayer PBAT / biomass composite active barrier membrane, its preparation method, and its applications. The multilayer PBAT / biomass composite active barrier membrane of the present invention exhibits stable and excellent oxygen and water vapor barrier activity; moreover, the preparation method provided by the present invention is simple and flexible, and easy to mass-produce.

[0006] The technical solution of this invention is:

[0007] A multilayer PBAT / biomass composite active barrier membrane is formed by alternating oxygen barrier layer A and water vapor capture layer B;

[0008] The oxygen barrier layer A comprises the following raw materials in parts by weight: 5-40 parts of biomass premix, 60-95 parts of PBAT, 0.5-5 parts of compatibilizing resin, and 0.1-0.5 parts of polyester tackifier.

[0009] The water vapor trapping layer B comprises the following raw materials in parts by weight: 100 parts PBAT, 5-30 parts inorganic filler, 0.5-5 parts compatibilizer, 0.1-1 parts processing aid, and 0.1-0.3 parts polyester tackifier.

[0010] In the multilayer PBAT / biomass composite active barrier membrane of this invention, the biomass premix and inorganic filler are incompatible with PBAT and have different viscosities. Therefore, during the multiplication process, as the filler phase is repeatedly stacked and stretched, the dispersion of the filler phase is effectively improved, making the gas permeation path more tortuous. When water vapor permeates, it is captured by the water-absorbing inorganic salt in the water vapor trapping layer B, thus reducing the permeation of water vapor into the inner layer. Moreover, the combination of the above materials not only delays the water vapor permeation of the membrane but also protects the biomass filler in the oxygen barrier layer A, thereby inhibiting the decrease in oxygen barrier effect caused by moisture absorption and plasticizer migration. This ensures that the multilayer PBAT / biomass composite active barrier membrane of this invention has excellent and stable oxygen barrier activity.

[0011] Furthermore, the number of alternating oxygen barrier layer A and water vapor trapping layer B ranges from 2. n+1 The layers are n = 4-7, where n is the number of multipliers; and / or, the thickness ratio of the oxygen barrier layer A to the water vapor capture layer B is 1-4:1-4.

[0012] The multilayer PBAT / biomass composite active barrier membrane provided by this invention can flexibly control the required performance by adjusting different layer thickness ratios and the number of layers, making the preparation method simple and flexible, and easy to mass-produce.

[0013] Furthermore, the biomass premix in the oxygen barrier layer A comprises the following raw materials in parts by weight: 100 parts biomass, 15-40 parts compound plasticizer, and 1-2 parts processing aid.

[0014] Furthermore, the biomass in oxygen barrier layer A is plant protein; the compound plasticizer is a blend of glycerol and sorbitol; the processing aid is one or more of glycerol fatty acid esters, stearic acid, calcium stearate, and sodium sulfite; the compatibilizing resin is a resin grafted with PBAT active groups; and / or, the polyester tackifier is an epoxy oligomer.

[0015] Furthermore, the plant protein in the oxygen barrier layer A is soy protein isolate; the resin with PBAT grafted onto the active group is PBAT-g-MA; and the epoxy oligomer is KLE-4370B.

[0016] Furthermore, the inorganic filler in the water vapor trapping layer B is a modified inorganic metal salt; the processing aid is silicone powder; the compatibilizer is a resin polyester with PBAT grafted to active groups; and / or, the polyester tackifier is an epoxy oligomer.

[0017] Further, the modified inorganic metal salt in the water vapor trapping layer B is one of anhydrous calcium chloride, anhydrous magnesium chloride, or anhydrous calcium sulfate; the resin polyester grafted with PBAT for the active groups is PBAT-g-MA; and / or, the modification method of the modified inorganic metal salt is as follows: the inorganic metal salt and stearic acid are mixed and simultaneously pulverized using a pulverizer and then coated for modification. During the pulverization process, hot air is introduced for drying, resulting in a fineness of 5000-10000 mesh and a moisture content of less than 2000 ppm, thereby obtaining the modified inorganic metal salt, which is then sealed and stored. The preferred fineness is 5000-8000 mesh.

[0018] Furthermore, the present invention also provides an application of the multilayer PBAT / biomass composite active barrier film as described above in the preparation of fresh produce packaging materials, pesticide packaging materials, or mulch films.

[0019] Furthermore, this invention provides a method for preparing the multilayer PBAT / biomass composite active barrier membrane as described above, comprising the following steps:

[0020] S1: Raw material pretreatment and blending

[0021] Oxygen barrier layer A: The biomass premix is ​​pre-mixed in a high-speed mixer, and then PBAT, compatibilizing resin and polyester tackifier are added to the pre-mixed biomass premix and mixed evenly to obtain oxygen barrier layer A blend.

[0022] Water vapor trapping layer B: PBAT, processing aids, inorganic fillers, compatibilizers, and polyester tackifiers are pre-blended in a high-speed mixer to obtain water vapor trapping layer B blend;

[0023] S2: Extrusion granulation of blended raw materials

[0024] The oxygen barrier layer A blend and the water vapor capture layer B blend were added to a twin-screw extruder for extrusion and granulation to obtain oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules, respectively, which were then dehumidified and dried.

[0025] S3: Molding and processing of composite films

[0026] Two composite materials, namely the dried oxygen barrier layer A composite modified granules and the water vapor capture layer B composite modified granules, were blown into film using a micro-nano multilayer co-extrusion blown film equipment.

[0027] Furthermore, the blending conditions for the biomass premix in step S1 are: 50-90℃, high-speed mixer speed of 500-1500rpm, and mixing time of 5-15min; the blending conditions for the remaining raw materials are: at room temperature, high-speed mixer speed of 1000-2000rpm, and mixing time of 5-15min.

[0028] The extrusion granulation conditions in step S2 are: extruder temperature range of 100-150℃, rotation speed of 150-250rpm, and feeding rate of 15-30kg / h.

[0029] And / or, the micro-nano multilayer co-extrusion blown film equipment described in step S3 includes a single-screw extruder, a melt pump, a manifold, a multiplier, a layered preform blown film head, a cooling air ring, and a traction winding device; the temperature of the single-screw extruder is 100-150℃, and the rotation speed is 100-200rpm; the temperature of the melt pump, manifold, multiplier, and layered preform blown film head area is 140-160℃.

[0030] In micro / nano multilayer co-extrusion blown film equipment, the working principle of the multiplier is as follows: When two different polymer melts pass through the manifold, they form two stacked melt laminar flows. Then, the multiplier begins to multiply the melt layers. The multiplier cuts the two polymer melt laminar flows into two parts and simultaneously stretches and deforms them. The deformed laminar flows are then stacked to form four alternating layers of the two polymer laminar flows. This process is repeated through multiple multipliers in series to form two layers. n+1 Alternating polymer layers, where n is the number of multipliers in series;

[0031] In micro-nano multilayer co-extrusion blown film equipment, the working principle of the layered tube preform blown film head is as follows: the rectangular polymer laminar flow that has passed through the multiplier is gradually gathered and converged into a ring-shaped polymer laminar flow, and then blown into a film bubble with a multilayer structure by compressed air.

[0032] Multilayer PBAT / biomass composite active barrier membranes with different numbers of layers were obtained according to the aforementioned preparation method.

[0033] Compared with the prior art, the multilayer PBAT / biomass composite active barrier membrane, its preparation method, and its application provided by the present invention have the following advantages:

[0034] This invention first uses a small amount of plasticizer to pregelatinize biomass (plant protein) through blending. Then, a PBAT / protein composite material is prepared as layer A, and a modified water-absorbing metal salt and PBAT composite material is prepared as layer B. Alternating multilayer composite films are then fabricated using a micro / nano multilayer co-extrusion blown film device. In the micro / nano multilayer co-extrusion process, a layer multiplier acts as the core component, repeatedly cutting, stretching, and stacking the melt flow. Because biomass (plant protein) and inorganic fillers are incompatible with PBAT and have viscosity differences, the filler phase is stretched, deformed, and stacked multiple times during the multiplication process, effectively improving the dispersion of the filler phase. After multiple multiplications, the gas permeation path becomes tortuous. See the attached diagram for the fabrication effect. Figure 1In this invention, the biomass (plant protein) in layer A acts as an oxygen barrier, while the modified inorganic metal salt in layer B, which has a hygroscopic function, effectively captures permeated water vapor. Therefore, less water vapor permeates into the inner layers, reducing water vapor transmission through the film and protecting the plant protein filler in layer A. This inhibits the decrease in oxygen barrier effect caused by water absorption and plasticizer migration, ensuring the multilayer PBAT / biomass composite active barrier membrane of this invention exhibits excellent and stable oxygen barrier activity. Furthermore, this invention allows for flexible control of desired performance by adjusting different layer thickness ratios and the number of layers. The preparation method is simple and flexible, facilitating large-scale production. Attached Figure Description

[0035] Figure 1 This is a structural effect diagram of the multilayer PBAT / biomass composite active barrier membrane of the present invention.

[0036] Figure 2 The graph shows the changes in oxygen permeability coefficient before and after storage for the 32, 64, and 256-layer embodiments and comparative examples of the multilayer PBAT / biomass composite active barrier membranes of the present invention.

[0037] Figure 3 The graph shows the changes in oxygen permeability coefficient of the multilayer PBAT / biomass composite active barrier membranes before and after placement in the embodiments and comparative examples of the present invention with 128 layers each. Detailed Implementation

[0038] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0039] Unless otherwise specified, the reagents used in the following examples and comparative examples are conventional reagents and can be purchased from conventional reagent manufacturers and distributors.

[0040] First, the sample composition and preparation of the oxygen barrier layer A composite modified granules and the water vapor trapping layer B composite modified granules of Examples 1 and 1-6 are as follows:

[0041] The modification method of the modified inorganic metal salt in the water vapor capture layer B is as follows: the inorganic metal salt and stearic acid are mixed and simultaneously crushed using a pulverizer and coated for modification. During the crushing process, hot air is introduced for drying. The fineness is 5000-10000 mesh and the water content is less than 2000ppm. The modified inorganic metal salt is obtained and stored in a sealed container.

[0042] The inorganic metal salts are anhydrous calcium chloride, anhydrous magnesium chloride, and anhydrous calcium sulfate.

[0043] Comparative Example 1:

[0044] PBAT is dehumidified and dried.

[0045] Example 1:

[0046] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 15 parts of compound plasticizer (including 10 parts of glycerol and 5 parts of sorbitol), and 2 parts of processing aid (0.6 parts of glycerol fatty acid ester, 0.5 parts of stearic acid, 0.5 parts of sodium sulfite, and 0.4 parts of calcium stearate) were initially blended and pregelatinized in a high-speed mixer at 70℃, 1000 rpm, and 10 min. Then, 20 parts of the pregelatinized product, 80 parts of PBAT, 0.5 parts of PBAT-g-MA, and 0.1 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0047] Water vapor trapping layer B: Take 100 parts of PBAT, 5 parts of 6000 mesh modified anhydrous calcium chloride, 0.5 parts of PBAT-g-MA, 0.1 parts of silicone powder, and 0.3 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0048] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0049] Example 2:

[0050] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 25 parts of compound plasticizer (including 15 parts of glycerol and 10 parts of sorbitol), and 1.5 parts of processing aid (including 0.6 parts of glycerol fatty acid ester, 0.4 parts of stearic acid, and 0.5 parts of sodium sulfite) were initially blended and pregelatinized in a high-speed mixer at 70℃, 1000 rpm, and 10 min. Then, 30 parts of the pregelatinized product, 70 parts of PBAT, 4 parts of PBAT-g-MA, and 0.3 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0051] Water vapor trapping layer B: Take 100 parts of PBAT, 15 parts of 5000 mesh modified anhydrous magnesium chloride, 4 parts of PBAT-g-MA, 0.7 parts of silicone powder, and 0.2 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0052] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0053] Example 3:

[0054] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 40 parts of compound plasticizer (including 25 parts of glycerol and 15 parts of sorbitol), and 1 part of processing aid (including 0.4 parts of glycerol fatty acid ester, 0.3 parts of stearic acid, and 0.3 parts of sodium sulfite) were initially blended and pregelatinized in a high-speed mixer at a temperature of 70℃, a speed of 1000 rpm, and a mixing time of 10 min. Then, 30 parts of the pregelatinized product, 70 parts of PBAT, 4 parts of PBAT-g-MA, and 0.3 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0055] Water vapor trapping layer B: Take 100 parts of PBAT, 30 parts of 8000 mesh modified anhydrous calcium chloride, 5 parts of PBAT-g-MA, 1 part of silicone powder, and 0.1 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0056] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0057] Example 4:

[0058] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 15 parts of compound plasticizer (including 10 parts of glycerol and 5 parts of sorbitol), and 2 parts of processing aid (including 0.6 parts of glycerol fatty acid ester, 0.5 parts of stearic acid, 0.5 parts of sodium sulfite, and 0.4 parts of calcium stearate) were initially blended and pregelatinized in a high-speed mixer at 70℃, 1000 rpm, and 10 min. Subsequently, 5 parts of the pregelatinized product, 95 parts of PBAT, 0.5 parts of PBAT-g-MA, and 0.1 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0059] Water vapor trapping layer B: Take 100 parts of PBAT, 30 parts of 8000 mesh modified anhydrous calcium chloride, 5 parts of PBAT-g-MA, 1 part of silicone powder, and 0.1 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0060] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0061] Example 5:

[0062] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 40 parts of compound plasticizer (including 20 parts of glycerol and 20 parts of sorbitol), and 1.1 parts of processing aid (including 0.4 parts of glycerol fatty acid ester, 0.4 parts of stearic acid, and 0.3 parts of sodium sulfite) were initially blended and pregelatinized in a high-speed mixer at 70℃, 1000 rpm, and 10 min. Then, 30 parts of the pregelatinized product, 70 parts of PBAT, 0.5 parts of PBAT-g-MA, and 0.1 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0063] Water vapor trapping layer B: Take 100 parts of PBAT, 20 parts of 10000 mesh modified anhydrous calcium chloride, 4 parts of PBAT-g-MA, 0.7 parts of silicone powder, and 0.1 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0064] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0065] Example 6:

[0066] Oxygen barrier layer A: 100 parts of plant protein soy protein isolate, 35 parts of compound plasticizer (including 15 parts of glycerol and 20 parts of sorbitol), and 2 parts of processing aid (including 0.6 parts of glycerol fatty acid ester, 0.5 parts of stearic acid, 0.5 parts of sodium sulfite, and 0.4 parts of calcium stearate) were initially blended and pregelatinized in a high-speed mixer at 70℃, 1000 rpm, and 10 min. Then, 40 parts of the pregelatinized product, 60 parts of PBAT, 0.5 parts of PBAT-g-MA, and 0.1 parts of KLE-4370B were taken and blended again in a high-speed mixer to obtain the oxygen barrier layer A blend.

[0067] Water vapor trapping layer B: Take 100 parts of PBAT, 20 parts of 10000 mesh modified anhydrous calcium sulfate, 4 parts of PBAT-g-MA, 0.7 parts of silicone powder, and 0.1 parts of KLE-4370B and pre-mix them in a high-speed mixer to obtain the water vapor trapping layer B blend.

[0068] Oxygen barrier layer A blend and water vapor capture layer B blend were added to a twin-screw extruder for granulation. The temperature range of the extruder was set to 100-150℃, the extruder speed was 180rpm, and the extruder feed rate was 20kg / h. Oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules were obtained, and then dehumidified and dried.

[0069] The oxygen barrier layer A composite modified granules, the water vapor trapping layer B composite modified granules obtained in Examples 1-6, and PBAT from Comparative Example 1 were extruded and blown into film using a micro-nano multilayer co-extrusion blown film equipment with different numbers of layer multipliers. The blown film process conditions were a temperature range of 130-150℃. The layer thickness ratio of the alternating oxygen barrier layer A and water vapor trapping layer B was adjusted by regulating the melt pump frequency of the two single-screw extruders to achieve the feed rate ratio. Different layer numbers were obtained using different layer multipliers. Specific implementation examples and test results are shown in Table 3 below.

[0070] Comparative Example 1 involved direct blown film forming. The oxygen barrier layer A composite modified granules and the water vapor trapping layer B composite modified granules obtained in Example 2 were blown into films separately, as shown in Comparative Examples 2 and 3. Simultaneously, the raw materials from Example 2—the oxygen barrier layer A composite modified granules and the water vapor trapping layer B composite modified granules—were blown into films using a micro-nano multilayer co-extrusion blown film equipment, but with only 16 alternating layers of A and B; this case is known as Comparative Example 4. The raw materials and dosages for Examples 1-6 and Comparative Examples 1-3 of this invention are shown in Tables 1 and 2.

[0071] Table 1: Raw materials and dosages in Examples 1-6 of the present invention

[0072]

[0073] Table 2: Raw materials and dosages of comparative examples 1-3 of the present invention

[0074]

[0075] Table 3: Test results of oxygen permeability coefficient in embodiments and comparative examples of the present invention

[0076]

[0077] Figure 1 This is a structural effect diagram of the multilayer PBAT / biomass composite active barrier membrane of the present invention. Figure 1 As can be seen, water vapor is first captured by the water-absorbing metal salt layer during infiltration, thus effectively delaying the contact between water vapor and the protein biological filler.

[0078] Samples of each multilayer PBAT / biomass composite active barrier membrane were stored at 23°C and 50% RH for 30 days. Their oxygen permeability coefficients were then measured. The test results are shown below. Figure 2 and Figure 3 The changes in permeability coefficient are shown in Table 3.

[0079] Figure 2 These are graphs showing the changes in oxygen permeability coefficient of multilayer PBAT / biomass composite active barrier membranes before and after storage in embodiments of the present invention with 32, 64, and 256 layers, as well as comparative examples. Comparative Example 2 involves the direct blending and blown film production of oxygen barrier layer A (i.e., biomass filler and PBAT). While this reduces the oxygen permeability coefficient of the composite membrane, the hydrophilicity of biomass causes the membrane's oxygen barrier performance to decline due to water absorption during storage, quickly losing its oxygen barrier activity. Comparative Example 3 involves the direct blending and blown film production of water vapor capture layer B (i.e., water-absorbing inorganic metal salt and PBAT). Although the inorganic metal salt can extend the oxygen permeation path within the membrane to some extent, the membrane still exhibits an increase in oxygen permeability coefficient after a period of storage. Secondly, at lower layer counts, such as the 16-layer alternating structure in Comparative Example 4, the improvement in oxygen barrier performance is not particularly significant. The water vapor trapping layer B provides limited protection against oxygen permeability of the film, and the oxygen permeability coefficient also increases significantly after 30 days of storage. In contrast, the test results of the various embodiments of the present invention show that the oxygen permeability coefficient decreases more significantly with the increase in the number of layers. This is because the multiplier can improve the dispersion of the filling phase when cutting and stacking the polymer laminar flow. At the same time, the accumulation of multiple layers also increases the number of B-layers (water-absorbing layers), which also has a positive effect on oxygen barrier performance. The film can maintain oxygen barrier activity for a longer period of time. For example, Example 12 has an alternating 256 structure layer, and its oxygen permeability coefficient decreases significantly. It still maintains high oxygen barrier performance activity after being stored for a period of time.

[0080] Figure 3 This is a graph showing the change in oxygen permeability coefficient of the multilayer PBAT / biomass composite active barrier membrane before and after arrangement, representing an embodiment of the present invention with 128 layers each. It can be seen that as the thickness of layer A and the biomass content in layer A increase, the oxygen permeability coefficient of the membrane decreases to some extent. Although its oxygen barrier activity is slightly reduced after a period of storage, the increased thickness of layer B, which contains water-absorbing filler, effectively ensures that the composite membrane maintains stable oxygen barrier activity for a certain period. Table 3 shows that increasing the number of layers effectively slows down the trend of oxygen permeability coefficient change, but the content and thickness of the water-absorbing filler in the water vapor capture layer B also play an important role in the oxygen permeability coefficient of the composite membrane.

[0081] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A multilayer PBAT / biomass composite active barrier membrane, characterized in that, The multilayer PBAT / biomass composite active barrier membrane is formed by alternating oxygen barrier layer A and water vapor capture layer B; The oxygen barrier layer A comprises the following raw materials in parts by weight: 5-40 parts of biomass premix, 60-95 parts of PBAT, 0.5-5 parts of compatibilizing resin, and 0.1-0.5 parts of polyester tackifier. The biomass premix in the oxygen barrier layer A comprises the following raw materials in parts by weight: 100 parts biomass, 15-40 parts compound plasticizer, and 1-2 parts processing aid; the biomass is plant protein. The water vapor trapping layer B comprises the following raw materials in parts by weight: 100 parts PBAT, 5-30 parts inorganic filler, 0.5-5 parts compatibilizer, 0.1-1 parts processing aid, and 0.1-0.3 parts polyester tackifier; the inorganic filler in the water vapor trapping layer B is a modified inorganic metal salt; In the water vapor capture layer B, the processing aid is silicone powder; the compatibilizer is a resin polyester with PBAT grafted onto its active groups; the polyester tackifier is an epoxy oligomer; and the modified inorganic metal salt is one of anhydrous calcium chloride, anhydrous magnesium chloride, or anhydrous calcium sulfate. The number of alternating oxygen barrier layer A and water vapor trapping layer B ranges from 2. n+1 Layer, n=4-7, where n is the number of multipliers; The thickness ratio of the oxygen barrier layer A to the water vapor capture layer B is 1-4:1-4.

2. The multilayer PBAT / biomass composite active barrier membrane as described in claim 1, characterized in that, In oxygen barrier layer A, the compound plasticizer is a blend of glycerol and sorbitol; the processing aid is one or more of glycerol fatty acid ester, stearic acid, calcium stearate, and sodium sulfite; the compatibilizing resin is a resin grafted with PBAT active groups; the polyester tackifier is an epoxy oligomer; and the plant protein is soy protein isolate.

3. The multilayer PBAT / biomass composite active barrier membrane as described in claim 2, characterized in that, In the oxygen barrier layer A, the resin with PBAT grafted onto the active groups is PBAT-g-MA; the epoxy oligomer is KL-E4370B.

4. The multilayer PBAT / biomass composite active barrier membrane as described in claim 1, characterized in that, In the water vapor capture layer B, the resin polyester grafted with PBAT by the active group is PBAT-g-MA; the modification method of the modified inorganic metal salt is as follows: the inorganic metal salt and stearic acid are mixed and simultaneously pulverized and coated for modification. During the pulverization process, hot air is introduced for drying. The fineness is 5000-10000 mesh and the water content is less than 2000ppm to obtain the modified inorganic metal salt, which is then sealed and stored.

5. The application of the multilayer PBAT / biomass composite active barrier film as described in any one of claims 1-4 in the preparation of fresh produce packaging materials, pesticide packaging materials, or mulch films.

6. A method for preparing a multilayer PBAT / biomass composite active barrier membrane as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Raw material pretreatment and blending Oxygen barrier layer A: The biomass premix is ​​pre-mixed in a high-speed mixer, and then PBAT, compatibilizing resin and polyester tackifier are added to the pre-mixed biomass premix and mixed evenly to obtain oxygen barrier layer A blend. Water vapor trapping layer B: PBAT, processing aids, inorganic fillers, compatibilizers, and polyester tackifiers are pre-blended in a high-speed mixer to obtain water vapor trapping layer B blend; S2: Extrusion granulation of blended raw materials The oxygen barrier layer A blend and the water vapor capture layer B blend were added to a twin-screw extruder for extrusion and granulation to obtain oxygen barrier layer A composite modified granules and water vapor capture layer B composite modified granules, respectively, which were then dehumidified and dried. S3: Molding and processing of composite films Two composite materials, namely the dried oxygen barrier layer A composite modified granules and the water vapor capture layer B composite modified granules, were blown into film using a micro-nano multilayer co-extrusion blown film equipment.

7. The method for preparing the multilayer PBAT / biomass composite active barrier membrane as described in claim 6, characterized in that, The blending conditions for the biomass premix in step S1 are: 50-90℃, high-speed mixer speed of 500-1500rpm, and mixing time of 5-15min; the blending conditions for the other raw materials are: at room temperature, high-speed mixer speed of 1000-2000rpm, and mixing time of 5-15min. The extrusion granulation conditions in step S2 are: extruder temperature range of 100-150℃, rotation speed of 150-250rpm, and feeding rate of 15-30kg / h. The micro-nano multilayer co-extrusion blown film equipment described in step S3 includes a single-screw extruder, a melt pump, a manifold, a multiplier, a layered preform blown film head, a cooling air ring, and a traction winding device; the temperature of the single-screw extruder is 100-150℃, and the rotation speed is 100-200rpm; the temperature of the melt pump, manifold, multiplier, and layered preform blown film head area is 140-160℃.

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