Biodegradable film material for promoting growth of microorganisms as well as preparation and application of biodegradable film material

Abstract

The invention belongs to the field of packaging materials, and particularly relates to a biodegradable film material for promoting microbial growth and preparation and application thereof. The biodegradable film material is prepared by taking PBAT and P34HB as substrates and uniformly mixing humic acid-loaded biochar, an antioxidant, an anti-blocking agent, a chain extender, a plasticizer and a biodegradation accelerant. The biodegradable film prepared from the biodegradable film material releases nutrients, repairs soil, promotes the growth of microorganisms, achieves the fertility increasing effect, enriches the functions of the biodegradable film, and provides a new path for the development of the biodegradable film.

Description

Technical Field

[0001] The present invention belongs to the field of packaging materials, and in particular relates to a biodegradable film material for promoting microbial growth and a preparation and application thereof. Background Art

[0002] Traditional polyethylene (PE) mulch is widely used for its moisture conservation, temperature control, and weed control properties, but its non-degradability leads to serious "white pollution." Studies have shown that PE mulch takes a long time to completely decompose in the soil, and its decomposed residues damage the soil, hinder water flow, affect microbial activity, and spread to water bodies and ecosystems, causing cross-regional pollution. For example, in Northeast my country's black soil, long-term mulch coverage has led to soil compaction and increased cadmium contamination, directly affecting crop yields. Therefore, the development of degradable mulch has become an urgent need for sustainable agricultural development.

[0003] Among the synthetic materials for ground films, polybutylene terephthalate-adipate (PBAT) has a molecular structure that contains a combination of flexible butylene adipate (BA) and rigid butylene terephthalate (BT) segments (BA accounts for 56% and BT accounts for 44%). It has both processing plasticity and mechanical properties, and maintains a thermal insulation effect comparable to polyethylene (PE). However, its high cost and low thermomechanical properties limit its application, and it needs to be improved through blending modification. The fourth-generation polyhydroxyalkanoate (PHA) material P34HB is made by copolymerizing 3-hydroxybutyrate (3-HB) and 4-hydroxybutyrate (4-HB). By adjusting the proportion of 4-HB, the hardness and ductility of the material can be controlled, significantly improving thermal stability and processing performance. Studies have shown that after PBAT and P34HB are compounded using melt blending technology, the addition of P34HB not only improves the compatibility of the blend system (tensile strength reaches 21MPa when added at 5wt%), but also reduces the glass transition temperature through the plasticizing effect, while improving the elongation at break (up to 1018%) and melt viscoelasticity. In addition, the addition of epoxy chain extenders can further optimize interfacial bonding, increasing the fracture strength and elongation of the blend by 91.8% and 58.7%, respectively. This composite strategy effectively compensates for the inherent defects of PBAT and expands its application potential in fields such as agricultural films.

[0004] Loading humic acid onto biochar combines the advantages of both: the porous biochar skeleton provides physical adsorption sites, while the active functional groups of humic acid enhance chemical chelation. Studies have shown that a 0.5% humic acid-rice husk biochar composite can reduce soil cadmium levels by 40% while increasing corn yields by 15%. Such composite materials, as additives for mulch films, have the potential to continuously release nutrients during degradation and remediate contaminated soils.

[0005] The present invention applies humic acid-loaded biochar to the film-making field, hoping to obtain a biodegradable film that promotes microbial growth, regulates the film degradation rate, and achieves the effect of soil fertility at the same time. Summary of the Invention

[0006] The present invention provides a biodegradable film material that promotes the growth of microorganisms. The biodegradable film material regulates the degradation rate of the film while releasing nutrients, repairing the soil, and promoting the growth of microorganisms to achieve a fertilization effect.

[0007] The technical solution of the present invention is a biodegradable film material that promotes microbial growth, which is based on PBAT and P34HB and mixed with the following substances:

[0008] Biochar loaded with humic acid: 1%-5% of substrate mass;

[0009] Antioxidant: 0.1%-0.5% of substrate mass;

[0010] Anti-adhesion agent: 2%-6% of substrate mass;

[0011] Chain extender: 1%-2% of substrate mass;

[0012] Plasticizer: 1%-2% of substrate mass;

[0013] Biodegradation promoter: 2%-8% of substrate mass;

[0014] The mass ratio of PBAT and P34HB is 8-10:1.

[0015] The humic acid loading in the humic acid-loaded biochar is 20-40% of the mass of the biochar. The humic acid-loaded biochar is obtained by low-temperature ball milling. Adding only humic acid causes the humic acid to be inactivated at the high temperature of the extrusion casting process. Therefore, the humic acid is ball-milled into the biochar to protect it.

[0016] Specifically, 2.5-5 mm zirconia balls are used as ball milling media, and the weight ratio of the ball milling media to the humic acid / biochar mixture is 1-5:1. The ball milling is carried out at 400-600 rpm for 2-4 hours in a low temperature environment (-10°C) to obtain humic acid-loaded biochar.

[0017] The antioxidant is BHA and / or Basf 245.

[0018] The anti-blocking agent is kaolin and / or oleamide.

[0019] The chain extender is ADR4368 and / or ADR4380.

[0020] The plasticizer is one or more of glycerol, triethyl citrate, tributyl citrate, polyethylene glycol 4000 or epoxidized soybean oil.

[0021] The biodegradation accelerator is malic acid.

[0022] By mixing humic acid-loaded biochar into PBAT / P34HB and extruding it into a casting film, a biodegradable film that can promote microbial growth is obtained. This biodegradable film can not only degrade quickly but also achieve the effect of increasing fatness.

[0023] The biodegradable film prepared by the biodegradable film material has uniform thickness, which can reach 20 to 40 μm, tensile strength of 15 to 28 MPa, and elongation at break of 100 to 120%.

[0024] The present invention also provides a biodegradable film comprising the above-mentioned biodegradable film material of the present invention.

[0025] The present invention also provides a method for preparing a biodegradable film, comprising the following steps:

[0026] (1) mixing the biodegradable film material according to any one of claims 1 to 7;

[0027] (2) melting and granulating the mixed biodegradable film material to obtain mixed particles;

[0028] (3) Casting the mixed particles into a film to obtain the biodegradable film.

[0029] The melt granulation temperature is 120-165° C., and the screw speed is 80-120 rpm; the casting temperature is 120-175° C., and the screw speed is 100-130 rpm.

[0030] By adopting the following scheme, the beneficial effects of the present invention are:

[0031] By mixing humic acid-loaded biochar into PBAT / P34HB and then extruding it into a casting film, a biodegradable film that promotes microbial growth was prepared and its fertility-enhancing effect was investigated. When the added humic acid-loaded biochar accounted for 1-5% of the total mass, the degradation rate of the biodegradable film prepared by the present invention reached 95%, and soil fertility was also increased after film degradation. Therefore, the film prepared by the present invention has a certain soil fertility-enhancing effect, enriches the functionalities of biodegradable membranes, and provides a new path for the development of biodegradable membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The tensile strength of the biodegradable film with different contents (0, 1%, 2%, 3%, 4%, 5%) of humic acid-loaded biochar added.

[0033] Figure 2 Elongation at break of biodegradable films with different contents (0, 1%, 2%, 3%, 4%, 5%) of humic acid-loaded biochar added.

[0034] Figure 3 The water vapor permeability and oxygen permeability of the biodegradable membranes added with different contents (0, 1%, 2%, 3%, 4%, 5%) of humic acid-loaded biochar.

[0035] Figure 4 The degradation rate of the biodegradable film with different contents (0, 1%, 2%, 3%, 4%, 5%) of humic acid-loaded biochar added at 10d, 20d, 30d and 50d.

[0036] Figure 5 These are the test results of pH, organic carbon, total nitrogen and microbial colony in three groups of soil: biodegradable film of biochar loaded with 3% humic acid, commercially purchased PLA film and bare soil. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0038] Below in conjunction with embodiment, the present invention is further described:

[0039] Example 1

[0040] Preparation of DAP2-loaded biochar

[0041] Humic acid and biochar were ground using a ball mill (MITR QM-QX-0.4L). 15 g of biochar was dried at 80°C for 12 hours, and 5 g of humic acid was added to a zirconia ball mill container. Zirconia balls of 2.5 mm, 4 mm, and 5 mm were used as milling media, and the weight ratio of these three zirconia balls to the humic acid / biochar mixture powder was 5:1. The humic acid / biochar mixture was ball milled at a stable low temperature of -10°C at a speed of 500 rpm for 5 hours and was recorded as BM-B-HA (humic acid / biochar mixture).

[0042] Example 2

[0043] (1) Base blending: 90 parts of PBAT and 10 parts of P34HB were dried at 60-80°C for 12 hours. 1 wt% of BM-B-HA, 5 wt% of kaolin, 1.5 wt% of ADR4368, 1 wt% of glycerol, 0.2 wt% of BASF 245, and 5 wt% of malic acid were weighed and physically blended.

[0044] (2) Extrusion granulation: The mixed materials were added to the feeder of the ML130 film granulator. The materials entered the screw through the feeder, were melt-mixed and uniformly mixed by the screw, extruded into granules, and dried at 60-80°C for 8 hours to obtain PBAT / P34HB mixed granules. The processing temperatures of extruder zones 1 to 10 were 120, 140, 145, 160, 162, 165, 162, 155, 150, and 145°C, respectively, and the screw speed was 100 rpm.

[0045] (3) Casting: The PBAT / P34HB mixed particles were blown into films using an SJM-FM1600 plastic extrusion blow molding auxiliary machine with a thickness of 40-50 μm. The processing temperatures of zones 1 to 10 of the blow molding machine were 120, 140, 145, 150, 155, 162, 175, 162, 155, and 150°C, respectively, and the screw speed was 100 rpm.

[0046] Example 3

[0047] (1) Base blending: 90 parts of PBAT and 10 parts of P34HB were dried at 60-80°C for 12 hours. 2 wt% of BM-B-HA, 5 wt% of kaolin, 1.5 wt% of ADR4368, 1 wt% of triethyl citrate, 0.2 wt% of BASF 245, and 5 wt% of malic acid were weighed and physically blended.

[0048] (2) Extrusion granulation: The mixed materials were added to the feeder of the ML130 film granulator. The materials entered the screw through the feeder, were melt-mixed and uniformly mixed by the screw, extruded into granules, and dried at 60-80°C for 8 hours to obtain PBAT / P34HB mixed granules. The processing temperatures of extruder zones 1 to 10 were 120, 140, 145, 160, 162, 165, 162, 155, 150, and 145°C, respectively, and the screw speed was 100 rpm.

[0049] (3) Casting: The PBAT / P34HB mixed particles were blown into films using an SJM-FM1600 plastic extrusion blow molding auxiliary machine with a thickness of 40-50 μm. The processing temperatures of zones 1 to 10 of the blow molding machine were 120, 140, 145, 150, 155, 162, 175, 162, 155, and 150°C, respectively, and the screw speed was 100 rpm.

[0050] Example 4

[0051] (1) Base blending: 90 parts of PBAT and 10 parts of P34HB were dried at 60-80°C for 12 hours. 3 wt% of BM-B-HA, 5 wt% of kaolin, 1.5 wt% of ADR4368, 1 wt% of tributyl citrate, 0.2 wt% of BASF 245, and 5 wt% of malic acid were weighed and physically blended.

[0052] (2) Extrusion granulation: The mixed materials were added to the feeder of the ML130 film granulator. The materials entered the screw through the feeder, were melt-mixed and uniformly mixed by the screw, extruded into granules, and dried at 60-80°C for 8 hours to obtain PBAT / P34HB mixed granules. The processing temperatures of extruder zones 1 to 10 were 120, 140, 145, 160, 162, 165, 162, 155, 150, and 145°C, respectively, and the screw speed was 100 rpm.

[0053] (3) Casting: The PBAT / P34HB mixed particles were blown into films using an SJM-FM1600 plastic extrusion blow molding auxiliary machine with a thickness of 40-50 μm. The processing temperatures of zones 1 to 10 of the blow molding machine were 120, 140, 145, 150, 155, 162, 175, 162, 155, and 150°C, respectively, and the screw speed was 100 rpm.

[0054] Example 5

[0055] (1) Base blending: 90 parts of PBAT and 10 parts of P34HB were dried at 60-80°C for 12 hours. 4 wt% of BM-B-HA, 5 wt% of kaolin, 1.5 wt% of ADR4368, 1 wt% of polyethylene glycol 4000, 0.2 wt% of BASF 245, and 5 wt% of malic acid were weighed and physically blended.

[0056] (2) Extrusion granulation: The mixed materials were added to the feeder of the ML130 film granulator. The materials entered the screw through the feeder, were melt-mixed and uniformly mixed by the screw, extruded into granules, and dried at 60-80°C for 8 hours to obtain PBAT / P34HB mixed granules. The processing temperatures of extruder zones 1 to 10 were 120, 140, 145, 160, 162, 165, 162, 155, 150, and 145°C, respectively, and the screw speed was 100 rpm.

[0057] (3) Casting: The PBAT / P34HB mixed particles were blown into films using an SJM-FM1600 plastic extrusion blow molding auxiliary machine with a thickness of 40-50 μm. The processing temperatures of zones 1 to 10 of the blow molding machine were 120, 140, 145, 150, 155, 162, 175, 162, 155, and 150°C, respectively, and the screw speed was 100 rpm.

[0058] Example 6

[0059] (1) Base blending: 90 parts of PBAT and 10 parts of P34HB were dried at 60-80°C for 12 hours. 5 wt% of BM-B-HA, 5 wt% of kaolin, 1.5 wt% of ADR4368, 1 wt% of epoxidized soybean oil, 0.2 wt% of BASF 245, and 5 wt% of malic acid were weighed and physically blended.

[0060] (2) Extrusion granulation: The mixed materials were added to the feeder of the ML130 film granulator. The materials entered the screw through the feeder, were melt-mixed and uniformly mixed by the screw, extruded into granules, and dried at 60-80°C for 8 hours to obtain PBAT / P34HB mixed granules. The processing temperatures of extruder zones 1 to 10 were 120, 140, 145, 160, 162, 165, 162, 155, 150, and 145°C, respectively, and the screw speed was 100 rpm.

[0061] (3) Casting: The PBAT / P34HB mixed particles were blown into films using an SJM-FM1600 plastic extrusion blow molding auxiliary machine with a thickness of 40-50 μm. The processing temperatures of zones 1 to 10 of the blow molding machine were 120, 140, 145, 150, 155, 162, 175, 162, 155, and 150°C, respectively, and the screw speed was 100 rpm.

[0062] Comparative Example 1

[0063] Comparative Example 1 is identical to Example 2 in other implementation conditions, except that no BM-B-HA is added during the substrate blending (i.e., 0% BM-B-HA content). The content of each component is expressed in parts by weight.

[0064] The biodegradable films of Comparative Example 1 and Examples 2 to 6 were recorded as 0%, 1%, 2%, 3%, 4%, and 5% according to the content of BM-B-HA.

[0065] Film index test

[0066] The above films were tested in various ways. The test results are shown in Figures 1 to 5 And Tables 1 to 4.

[0067] Mechanical properties

[0068] Using an XLW(EC) intelligent electronic tensile testing machine, a 100mm x 15mm film sample was placed in a fixture with a 50mm spacing. The tensile speed was set to 50mm / min, and the tensile strength and elongation at break were measured. The test results are shown in Table 1 below:

[0069] Table 1 Mechanical properties test results

[0070]

[0071] Note: The superscript letters in a, b, and c represent significant differences. The same letters indicate insignificant differences (P>0.05), and different letters indicate significant differences (P<0.05).

[0072] BM-B-HA affects mechanical properties in polymer modification primarily by enhancing interfacial compatibility and functional group activity. Humic acid is rich in polar functional groups such as hydroxyl and carboxyl groups, which can promote hydrogen bonding between polymer chains and improve dispersion uniformity; biochar provides a porous structure and surface active sites, increasing the material's energy dissipation capacity. When the addition amount increases from 1% to 3%, the mechanical properties of the film gradually increase. This is because the functional groups of humic acid / biochar act like chain extenders, forming bonds and interacting to reduce phase separation, thereby improving strength. When the addition amount exceeds 3%, the rigid particles of biochar may cause agglomeration, increase internal defects, and thus reduce the mechanical properties of the film.

[0073] Barrier properties

[0074] Barrier properties include water vapor transmission rate test and oxygen transmission rate test, where the water vapor transmission rate test is as follows:

[0075] Using a PERMATRAN-W1 / 50G water vapor transmission rate tester, circular specimens with a diameter of 100 mm were placed in test chambers A, B, and C, respectively. The water vapor transmission rate was measured continuously for 12 hours at 38°C and 100% RH.

[0076] The oxygen transmission rate test is as follows:

[0077] Using a G2-32 gas permeation tester, place the film tightly in the test chamber and test at 25°C, 50% RH for 6 hours to measure the oxygen transmission rate.

[0078] The barrier performance test results are shown in Table 2 below:

[0079] Table 2 Barrier performance test results

[0080]

[0081] Note: The superscript letters in a, b, and c represent significant differences. The same letters indicate insignificant differences (P>0.05), and different letters indicate significant differences (P<0.05).

[0082] Table 2 shows the film's barrier properties. The water vapor transmission rate gradually increases, while the oxygen transmission rate decreases. This is likely due to the porous structure of the biochar, which prolongs the gas diffusion path and reduces the film's oxygen transmission rate. Furthermore, the addition of the humic acid hydrophilic groups plasticizes the film, thereby increasing its water vapor transmission rate.

[0083] Degradation experiment

[0084] The biodegradable film containing 3% BM-B-HA prepared in Example 4 was subjected to degradation experiments and soil fertility monitoring, and a control group used commercially available PLA mulch film.

[0085] Film degradation was measured by weight loss during burial in soil for 5 cm. 3% BM-B-HA biodegradable film and commercially available PLA mulch were cut into square samples with a side length of 5 cm. The samples were dried at 40°C for 24 hours and then buried in soil. The samples were removed at 10, 20, 30, and 50 days of degradation. The samples were washed with deionized water and dried at 40°C for 4 hours. The test was repeated five times. The degradation rate was measured using formula (1):

[0086]

[0087] Where W is the degradation rate (%), M1 (g) and M2 (g) are the weights of the membrane before and after degradation, respectively.

[0088] Table 3 Film degradation test results

[0089]

[0090] The degradation performance of the film is shown in Table 3. The degree of degradation gradually increased with time. Furthermore, with increasing BM-B-HA content, the degradation rate of the film initially increased and then decreased. This is because humic acid provides active functional groups (carboxyl and phenolic hydroxyl groups) that promote enzyme binding, and biochar pores adsorb degrading bacteria (such as Bacillus). However, when the biochar content is greater than 3%, excess biochar hinders microbial-membrane contact, resulting in a decrease in the degradation rate.

[0091] Soil fertility monitoring

[0092] The prepared 3% BM-B-HA biodegradable film and commercially available PE mulch were laid in the field, and a degradation film coverage area was set up. The pH, soil organic carbon, total nitrogen and microbial colony at 50 days were compared with those of bare soil.

[0093] The pH was tested by the potentiometric method (soil-water ratio was 1:5); the organic carbon and total nitrogen were tested by the Walkley-Black wet oxidation method and the Kjeldahl method; and the microbial colonies were determined by the pour plate method (beef extract peptone medium).

[0094] Table 4 Soil fertility test results

[0095]

[0096] Note: The superscript letters in a, b, and c represent significant differences. The same letters indicate insignificant differences (P>0.05), and different letters indicate significant differences (P<0.05).

[0097] The results of soil fertility after film degradation are shown in Table 3. The PBAT-P34HB film with 3% humic acid biochar loaded rapidly releases active substances, significantly optimizing the chemical and biological properties of the soil. The fertility indicators are significantly better than those of the PLA film and the control group (p < 0.05).

[0098] It should be noted that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those familiar with the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A biodegradable film material that promotes microbial growth, characterized in that: Use PBAT and P34HB as the base and mix the following substances: Biochar loaded with humic acid: 1%-5% of substrate mass; Antioxidant: 0.1%-0.5% of substrate mass; Anti-adhesion agent: 2%-6% of substrate mass; Chain extender: 1%-2% of substrate mass; Plasticizer: 1%-2% of substrate mass; Biodegradation promoter: 2%-8% of substrate mass; The mass ratio of PBAT and P34HB is 8-10:

1.

2. The biodegradable film material according to claim 1, characterized in that The loading amount of humic acid in the humic acid-loaded biochar is 20-40% of the mass of the biochar.

3. The biodegradable film material according to claim 1, characterized in that The antioxidant is BHA and / or Basf245.

4. The biodegradable film material according to claim 1, characterized in that The anti-blocking agent is kaolin and / or oleamide.

5. The biodegradable film material according to claim 1, characterized in that The chain extender is ADR4368 and / or ADR4380.

6. The biodegradable film material according to claim 1, characterized in that The plasticizer is one or more of glycerol, triethyl citrate, tributyl citrate, polyethylene glycol 4000 or epoxidized soybean oil.

7. The biodegradable film material according to claim 1, characterized in that: The biodegradation accelerator is malic acid.

8. The biodegradable film material according to any one of claims 1 to 7 is used for preparing biodegradable film.

9. A biodegradable film, characterized in that Contains the biodegradable film material according to any one of claims 1 to 7.

10. A method for preparing a biodegradable film, characterized in that the steps include: (1) mixing the biodegradable film material according to any one of claims 1 to 7; (2) melting and granulating the mixed biodegradable film material to obtain mixed particles; (3) The mixed particles are cast into a film to obtain the biodegradable film.

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