Bamboo-based full-biodegradable mulching film and preparation method thereof

Abstract

The invention belongs to the technical field of biodegradable materials, and relates to a bamboo-based full-biodegradable mulching film and a preparation method thereof, and the preparation method specifically comprises the following steps: step 1, bamboo wood disinfection, and bamboo powder and bamboo fiber separation through steam explosion; secondly, the bamboo powder and the bamboo fibers are dried and ground; 3, bamboo powder, bamboo fibers, degradable plastic, a coupling agent and other auxiliaries are mixed and granulated, and then the bamboo-based full-biodegradable mulching film is prepared; compared with a traditional biodegradable mulching film, the full-biodegradable mulching film prepared from the bamboo wood has the advantages that the production cost is reduced, the mechanical property of the mulching film is improved, the mulching film can be degraded in soil according to an expected degradation period, pollution to the soil environment is reduced, and the requirement of sustainable development is met.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable materials technology, and relates to a bamboo-based fully biodegradable mulch film and its preparation method. Background Technology

[0002] Existing traditional mulch films are mostly made of non-degradable plastic materials such as polyethylene. These films are widely used in agricultural production due to their advantages such as low cost and stable mechanical properties. However, their stable chemical structure makes them difficult to degrade naturally, and their residue in farmland is increasing year by year. This has caused "white pollution" problems such as soil compaction and reduced air and water permeability, which seriously affect crop root development and soil ecological cycle.

[0003] In recent years, although biodegradable mulch films have been proposed as an alternative, they generally suffer from technical bottlenecks such as high production costs (e.g., the use of expensive biodegradable polymer raw materials), mechanical properties that are difficult to meet the actual needs of agriculture (insufficient tensile strength and puncture resistance), and degradation cycles that are difficult to precisely control according to the crop growth cycle. These bottlenecks make it difficult for biodegradable mulch films to be promoted on a large scale.

[0004] Bamboo, as a fast-growing and renewable resource, has a cellulose and lignin content of over 70%. Through a physical pulverization-chemical modification process, it can be combined with bio-based plastics to produce low-cost, high-strength biodegradable mulch films. However, in existing technologies, the polarity difference between bamboo powder and the plastic matrix leads to poor interfacial compatibility (stress concentration points easily form when the dispersed particle size is >50μm). Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a bamboo-based fully biodegradable mulch film and its preparation method. Through innovative processing techniques and composite formulations of bamboo, a biodegradable mulch film with good mechanical properties, a controllable degradation cycle, and low production costs is prepared to meet agricultural production needs and reduce environmental pollution from mulch films. Specifically, the method includes the following steps:

[0006] Step 1: After disinfection, grind the bamboo to 300-500 mesh, steam-explode at 200-230℃ and 2.5-3.5MPa for 3-7 minutes, then hammer and sieve the bamboo to separate bamboo powder and bamboo fiber.

[0007] Preferably, the disinfection treatment involves washing with disinfectant water at 80-90℃ for at least 10 minutes, followed by draining the surface moisture. Most preferably, the disinfectant water comprises a disinfectant, a preservative, and water in a mass ratio of 1:0.2:98.8. Most preferably, the disinfectant is sodium hypochlorite, and the preservative is sodium benzoate.

[0008] Step two: Dry the bamboo powder and bamboo fiber separately, and then grind them to a fineness of 2000 mesh or higher using a 1.0MPa shock wave vortex multi-stage ultra-fine grinding process.

[0009] Step 3: Bamboo powder, bamboo fiber, biodegradable plastic, coupling agent and other additives are mixed in a mass ratio of (10-15):(5-15):(75-80):(0.1-0.3):3, and then co-blended in a twin-screw extruder. The resulting masterbatch melt has a flow rate of 0.28 g / min and is then used to prepare a biodegradable mulch film through a casting process.

[0010] Preferably, during blending, the feeding section is 120-135℃ to prevent bamboo powder pre-agglomeration; the melting section is 150-165℃ to ensure complete melting of PBAT; the mixing section is 165-180℃, at which temperature the titanate coupling agent reaches its peak activity, effectively improving the interfacial compatibility between bamboo powder and PBAT / PPC; and the die head section is 155-170℃ to reduce melt viscosity and ensure smooth discharge. The screw speed is 300-500 rpm; below this value, mixing is insufficient, while above this value, shear overheating (risk of bamboo powder charring) is likely. The feeding rate is 15-25 kg / h, matched with the screw speed, to ensure a melt residence time ≥45 seconds, meeting the requirement for uniform bamboo powder dispersion. The vacuum degree range is (-0.07)-(-0.09) MPa to effectively remove residual moisture from the bamboo powder (reducing moisture content from 1.2% to 0.25%), avoiding granule bubble defects. The pelletizing water temperature is 25-40℃ to ensure a smooth granule surface without adhesion.

[0011] Preferably, the casting process involves drying at 55°C for 4 hours (moisture content ≤0.1%) to eliminate the risk of air bubbles, extruding and casting, with a barrel temperature of 165°C (matching MFI = 2.8g / 10min), bamboo powder dispersion >95% when the T-die temperature is >180°C, die lip gap of 0.7mm (to allow for cooling shrinkage), cooling and shaping, gradient temperature control of the cooling rollers (upper roller 25°C, lower roller 20°C), and roller speed of 20m / min.

[0012] Preferably, the biodegradable plastic is a PBAT / PPC blend, wherein the mass ratio of PBAT to PPC is 80:10.

[0013] Preferably, the coupling agent is aluminate, phthalate and zirconate in a mass ratio of 60:30:10.

[0014] Preferably, the other additives include a plasticizer, erucamide, zinc stearate, chain extender, opening agent, UV stabilizer, and hydrolysis inhibitor, in a mass ratio of 35:12:10:18:8:12:5. Most preferably, the plasticizer is glyceryl monostearate, the chain extender is ADR-4370, the opening agent is 5μm silica, the UV stabilizer is Tinuvin 770, and the hydrolysis inhibitor is Stabaxol P200.

[0015] The present invention has the following advantages:

[0016] (1) The present invention adopts a special bamboo processing technology, which effectively changes the structure of bamboo through steps such as steam explosion, optimizes the performance of bamboo, improves the quality of bamboo powder and bamboo fiber, and thus enhances the mechanical properties of the mulch film, such as tensile strength and tear strength.

[0017] (2) This invention utilizes renewable resources (bamboo) to reduce the production cost of mulch film, and has stronger market competitiveness compared with traditional biodegradable mulch film.

[0018] (3) Bamboo-based fully biodegradable mulch film can degrade in the soil according to the expected degradation cycle, reducing pollution to the soil environment and meeting the requirements of sustainable development. Detailed Implementation

[0019] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] Raw material preparation:

[0022] Disinfectant solution: The mass ratio of sodium hypochlorite, sodium benzoate and water is 1:0.2:98.8.

[0023] Coupling agents: aluminate, phthalate and zirconate in a mass ratio of 60:30:10.

[0024] Other additives: glyceryl monostearate, erucamide, zinc stearate, ADR-4370, 5μm silica, Tinuvin 770 and Stabaxol P200, in a mass ratio of 35:12:10:18:8:12:5.

[0025] PBAT / PPC blend: The mass ratio of PBAT to PPC is 80:10.

[0026] Step 1: Wash the bamboo with 85℃ disinfectant water for more than 10 minutes, then drain the surface water, grind it to 300 mesh, steam it at 200℃ and 2.5MPa for 5 minutes, and then hammer and sieve the bamboo to separate bamboo powder and bamboo fiber.

[0027] Step two: Dry the bamboo powder and bamboo fiber separately, and then grind them to a fineness of 2000 mesh or higher using a 1.0MPa shock wave vortex multi-stage ultra-fine grinding process.

[0028] Step 3: Bamboo powder, bamboo fiber, PBAT / PPC blend, coupling agent, and other additives are mixed in a mass ratio of 12:8:76.8:0.2:3 and co-blended in a twin-screw extruder. The mixture is then extruded and granulated. During blending, the temperatures are: feeding section 130℃, melting section 160℃, mixing section 175℃, die head section 165℃, screw speed 400 rpm, feeding rate 20 kg / h, vacuum degree -0.08 MPa, pelletizing water temperature 30℃. The resulting masterbatch melt has a density of 0.28 g / min. A biodegradable mulch film is then prepared using a casting molding process. This casting molding process involves drying at 55℃ for 4 hours, barrel temperature 165℃, T-die temperature 185℃, die lip gap 0.7 mm, cooling roller (upper roller 25℃, lower roller 20℃), and roller speed 20 m / min.

[0029] Example 1: According to GB / T1040.3-2006 standard, type I dumbbell specimens (15 longitudinal and 15 transverse) were cut from bamboo powder / PBAT / PPC mulch film (thickness 15.2±1.3μm). After pretreatment at 23℃ / 50%RH for 48h, tensile tests were performed using an Instron 5969 testing machine at a rate of 50mm / min. The initial properties were: tensile strength 19.1±0.8MPa (MD) / 18.2±0.6MPa (CD), elongation at break 238±15% (MD) / 225±13% (CD). After 500h of QUV accelerated aging, the strength retention rate was >85%. After 90 days of soil burial, the strength decreased to 12.5±0.9MPa (MD), and the elongation at break decreased to 85±10% (MD), meeting the service life requirements of agricultural mulch film.

[0030] Example 2: Soil burial (25℃ / 60%RH farmland soil) and composting experiments (58℃ / 90%RH) were conducted according to GB / T20197-2006. Samples (20×20mm, 1.0g) were periodically removed, weighed, and their molecular weight was analyzed by GPC.

[0031] Table 1 Mechanical Performance Indicators

[0032]

[0033]

[0034] Table 2 Degradation Cycle Indicators

[0035] Time Node Soil burial weight loss rate Compost weight loss Molecular weight reduction rate Microscopic morphological changes (SEM) 30 days 18.2％±1.5 35.7％±2.1 32％ Micropores (pore size 1-5 μm) appear on the surface. 90 days 57.3％±2.8 78.6％±3.2 68％ Pore ​​enlargement (20-50μm), bamboo powder shedding 180 days 94.3％±3.5 98.1％±0.5 ＞95％ <![CDATA[Skeleton disintegration (residual debris < 1 mm 2 )]]>

[0036] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a bamboo-based fully biodegradable mulch film, characterized in that, Includes the following steps: Step 1: After disinfection, the bamboo is ground, steam-exploded, and then bamboo powder and bamboo fiber are separated. Step two: Dry the bamboo powder and bamboo fiber separately, and grind them into fine powder with a mesh size of 2000 or higher; Step 3: Mix bamboo powder, bamboo fiber, biodegradable plastic, coupling agent and other additives in a mass ratio of (10-15):(5-15):(75-80):(0.1-0.3):3, granulate, and then prepare bamboo-based fully biodegradable mulch film.

2. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 1, characterized in that, The disinfection process described in step one involves rinsing with disinfectant water at 80-90℃ for at least 10 minutes.

3. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 2, characterized in that, The disinfectant solution comprises disinfectant, preservative and water in a mass ratio of 1:0.2:98.

8.

4. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 3, characterized in that, The disinfectant is sodium hypochlorite, and the preservative is sodium benzoate.

5. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 1, characterized in that, The biodegradable plastic described in step three is a PBAT / PPC blend, with a PBAT to PPC mass ratio of 80:

10.

6. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 1, characterized in that, The coupling agent mentioned in step three is aluminate, phthalate and zirconate in a mass ratio of 60:30:

10.

7. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 1, characterized in that, The other additives mentioned in step three include plasticizers, erucamide, zinc stearate, chain extenders, opening agents, UV stabilizers, and hydrolysis inhibitors, in a mass ratio of 35:12:10:18:8:12:

5.

8. The method for preparing a bamboo-based fully biodegradable mulch film according to claim 7, characterized in that, The plasticizer is glyceryl monostearate, the chain extender is ADR-4370, the opening agent is silica, the UV stabilizer is Tinuvin 770, and the hydrolysis stabilizer is Stabaxol P200.

9. The bamboo-based fully biodegradable mulch film prepared by the method according to any one of claims 1-8.

10. The application of the bamboo-based fully biodegradable mulch film according to any one of claims 1-9 in agricultural planting.

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