Preparation method of biodegradable weeding film

Abstract

The invention discloses a preparation method of a biodegradable weeding film, and belongs to the technical field of weeding films. The biodegradable weeding film is prepared from polylactic acid, bamboo tar and a bamboo powder extract, and meanwhile, the preparation method of the biodegradable weeding film comprises the steps that the raw materials are dissolved in dichloromethane or ethyl acetate, a uniform mixture is obtained through ultrasonic and magnetic stirring, and the film is prepared through a solvent tape casting method. The prepared weeding film can be completely biologically degraded and is remarkable in weeding effect, and compared with the prior art, the independently researched and developed biodegradable weeding film is derived from degradable materials, has the advantages of being simple in preparation process, environmentally friendly and the like, facilitates comprehensive utilization of bamboo processing by-products and is wide in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of weed control films, and in particular relates to a method for preparing a biodegradable weed control film. Background Art

[0002] Weeds compete with crops for nutrients, water and sunlight, causing significant damage to the yield and quality of crops. More than 85% of my country's farmland is damaged by weeds. At present, the main method of weed control is chemical herbicides. With the excessive and long-term irregular use of chemical herbicides, weeds have developed resistance and caused problems such as pesticide residues and ecological pollution. Weed film is a mulch covering that inhibits the germination or growth of weeds by controlling light, temperature and other physical methods. Weed film can effectively control various weeds in the field, reduce the use of chemical herbicides, and avoid food safety and ecological safety problems caused by herbicides. With the improvement of my country's environmental protection requirements, the research and development and promotion of degradable weed film have been intensified, and the future market potential is huge.

[0003] Traditional mulch films are widely used, and their main component is polyethylene. This type of mulch film is difficult to degrade in the natural environment. The mulch film fragments remain in the soil, which will destroy the soil pore structure and cause problems such as soil compaction. The materials used in biodegradable weed control films can be degraded into harmless components in the natural environment and will not damage the soil and ecological environment. At present, there are two main strategies for the development of weed control films: one is to make the color of the mulch film black to achieve the purpose of weed control by inhibiting the photosynthesis of weeds; the other is to add chemical herbicides to the mulch film and use herbicides to achieve the purpose of weed control. Both strategies have shortcomings. For example, black mulch films are easy to absorb too much sunlight radiation, causing the soil temperature to be too high, which may affect the normal growth of the root system of crops. The herbicides added to the mulch film still have the risk of causing pesticide residues.

[0004] There are different types of by-products in the bamboo processing process, such as bamboo tar produced by processing bamboo charcoal and bamboo powder produced by processing boards. These by-products have not been effectively utilized, resulting in a waste of resources. Our research group has also conducted research on the herbicidal activity of bamboo powder extracts in the early stage, and found that the bamboo powder extracts obtained by combining low eutectic solvents with microwave chemical conversion and extraction have significant herbicidal activity.

[0005] The main strategies for developing the herbicidal film of the present invention are: first, replacing the difficult-to-degrade film material with an easily degradable material; second, adding the bamboo wood powder extract with significant herbicidal activity to the herbicidal film; third, bamboo tar has a characteristic absorption spectrum, which makes the herbicidal film light brown in color and rich in phenolic substances, which is beneficial to the growth of crop roots. Therefore, the biodegradable herbicidal film of the present invention has a herbicidal effect and promotes the resource utilization of bamboo processing byproducts, and has broad application prospects. Summary of the invention

[0006] The invention provides a method for preparing a biodegradable weed control film.

[0007] A method for preparing a biodegradable weed control film, characterized in that biodegradable plastics such as polylactic acid, bamboo tar and bamboo wood powder extract are dissolved in an organic solvent, and then the film-forming materials are dissolved and mixed evenly by ultrasonic wave, stirring and the like, and after homogenization, a film is formed by solvent casting method, such as forming a film on a glass plate by solvent casting method.

[0008] Furthermore, the biodegradable plastic is dissolved in an organic solvent, and then an organic solvent containing bamboo tar and an organic solvent containing bamboo wood powder extract are added, and then the film-forming material is dissolved and mixed evenly by ultrasonic wave, stirring, etc. After homogenization, a film is formed by solvent casting method, such as forming a film on a glass plate by solvent casting method.

[0009] The mass ratio of biodegradable plastic, bamboo tar and bamboo wood powder extract is (50-60):(5-8):(0.8-1.2), preferably 54:6:1.

[0010] Specifically, the biodegradable plastic is selected from one or more of polylactic acid (PLA), polybutylene terephthalate-adipate (PBAT), polyhydroxyalkanoate (PHA), and polybutylene succinate (PBS).

[0011] The organic solvent is selected from one or more of ethyl acetate, dichloromethane, chloroform, tetrahydrofuran, acetone, acetonitrile, dichloroacetic acid, and propylene glycol carbonate. The organic solvent for dissolving bamboo tar is preferably a mixed solvent of ethyl acetate and dichloromethane in a volume ratio of 10-90% and 10-90%.

[0012] The bamboo tar is selected from a dark brown oily thick liquid produced in the process of preparing bamboo charcoal by dry distillation and pyrolysis of bamboo materials or processing residues. During use, solid particle precipitation such as carbon powder is removed by filtering. The filtered liquid is concentrated under reduced pressure in a 50-70°C water bath to obtain viscous bamboo tar, and the concentrated viscous bamboo tar is preferred.

[0013] The bamboo powder extract is prepared by adding bamboo powder to a low eutectic solvent (such as a solvent in which the molar ratio of choline chloride to lactic acid is 2:1 to 1:10) and heating it under microwave conditions (power 420W-1000W) for 1-30 minutes until the sample solution turns brown, then adding it to an aqueous solution, filtering to remove the filter residue, extracting the aqueous phase with ethyl acetate, discarding the aqueous phase, and obtaining an ethyl acetate phase concentrate, that is, obtaining the bamboo powder extract.

[0014] The bamboo powder is selected from one or more of bamboo stalks, bamboo branches and bamboo whips remaining after bamboo stalk processing, preferably the stem of moso bamboo.

[0015] The thickness of the biodegradable weed control film is 0.015-0.1 mm.

[0016] Taking red clover as the target plant, the herbicidal activity experiment was carried out using the water agar medium method. The inhibition rates of polylactic acid film and biodegradable herbicidal film on the root length and shoot length of red clover were compared. It was found that the growth inhibition rate of the film added with bamboo tar and / or bamboo powder extract on the target plant was significantly better than that of the blank polylactic acid film.

[0017] The weed control film prepared by the invention is light brown in color because the characteristic absorption wavelength of ultraviolet-visible light of polylactic acid is changed by adding bamboo tar and bamboo powder extract.

[0018] The invention has the following advantages: polylactic acid can be prepared from plants such as straw as raw materials and is a biodegradable material; bamboo tar and bamboo powder extracts are both from bamboo processing byproducts; therefore, the main components of the herbicidal film are all from natural plants, which is environmentally friendly and has no problems such as pesticide residues. The preparation method of the biodegradable herbicidal film in the invention is simple and has low requirements for equipment conditions. Compared with the prior art, the independently developed biodegradable herbicidal film has the effect of weed control, and is conducive to the resource utilization of bamboo processing byproducts, and has the characteristics of ecological safety, simplicity and high efficiency. With people's attention to environmental protection, the herbicidal film has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Comparison of small samples of the biodegradable herbicidal film of the present invention with that of a polylactic acid film.

[0020] Figure 2 The ultraviolet-visible absorption spectra of the biodegradable herbicidal film of the present invention and that of the polylactic acid film are compared. Specific implementation methods

[0022] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0023] Example 1: Preparation method of biodegradable weed control film

[0024] 5.4g of polylactic acid of 80 mesh is added to 70mL of dichloromethane, 0.6g of bamboo tar after filtration is taken, and 10mL of ethyl acetate: dichloromethane=1:1 (v / v) is used to dissolve the bamboo tar, 100mg of bamboo powder extract is taken and dissolved with 10mL of dichloromethane, the mixed solution of polylactic acid, tar and bamboo powder extract is stirred with a glass rod and ultrasonicated for 5min, and magnetically stirred for 30min at room temperature to obtain a solution with a suitable mass fraction. The mixed solution is evenly divided into 8 portions, each portion is poured into a glass dish (the glass dish is placed horizontally), and taken out after ventilation and standing overnight in a fume hood, which is the biodegradable weed control film of the present invention.

[0025] Example 2: Experiment on the weed killing activity of biodegradable weed killing film

[0026] The biodegradable herbicidal film and polylactic acid film of the present invention were used as test samples, and the treatment without the film was used as the control group. The water agar culture medium method was used to carry out a weed control experiment on the target plant red clover. The results are shown in Table 1. The corresponding film thickness is 0.07 mm.

[0027] Table 1 The weed control effect of the tested herbicidal films on target plants

[0028]

[0029] As shown in Table 1, the biodegradable herbicidal film of the present invention has a strong inhibitory effect on target plants, and the inhibition rates of root length, shoot length and fresh weight of red clover are all 100%, which is significantly better than that of polylactic acid film.

Claims

1. A method for preparing a biodegradable herbicidal film, characterized in that: Biodegradable plastics, bamboo tar and bamboo powder extract are dissolved in an organic solvent, and then ultrasonic and stirring methods are used to dissolve and mix the film-forming materials evenly. After homogenization, a solvent casting method is used to form a film.

2. The method according to claim 1, characterized in that The biodegradable plastic is added into an organic solvent to dissolve, and then an organic solvent containing bamboo tar and an organic solvent containing bamboo wood powder extract are added, and then ultrasonic and stirring methods are used to dissolve and mix the film-forming materials uniformly.

3. The method according to claim 1, characterized in that The mass ratio of biodegradable plastic, bamboo tar and bamboo wood powder extract is (50-60):(5-8):(0.8-1.2), preferably 54:6:

1.

4. The method according to claim 1, characterized in that The biodegradable plastic is selected from one or more of polylactic acid (PLA), polybutylene terephthalate-adipate (PBAT), polyhydroxyalkanoate (PHA), and polybutylene succinate (PBS).

5. The method according to claim 1, characterized in that The organic solvents are selected from one or more of ethyl acetate, dichloromethane, chloroform, tetrahydrofuran, acetone, acetonitrile, dichloroacetic acid, and propylene glycol carbonate; the organic solvent for dissolving bamboo tar is preferably a mixed solvent of ethyl acetate and dichloromethane in a volume ratio of 10-90% and 10-90%.

6. The method according to claim 1, characterized in that The bamboo tar is selected from a dark brown oily thick liquid produced in the process of preparing bamboo charcoal by dry distillation and pyrolysis of bamboo materials or processing residues. During use, solid particle precipitation such as carbon powder is removed by filtering. The filtered liquid is concentrated under reduced pressure in a 50-70°C water bath to obtain viscous bamboo tar, and the concentrated viscous bamboo tar is preferred.

7. The method according to claim 1, characterized in that The bamboo powder extract is prepared by adding bamboo powder to a low eutectic solvent (such as a solvent in which the molar ratio of choline chloride to lactic acid is 2:1 to 1:10) and heating it under microwave conditions (power 420W-1000W) for 1-30 minutes until the sample solution turns brown, then adding it to an aqueous solution, filtering to remove the filter residue, extracting the aqueous phase with ethyl acetate, discarding the aqueous phase, and obtaining an ethyl acetate phase concentrate, that is, obtaining the bamboo powder extract.

8. The method according to claim 7, characterized in that The bamboo powder is selected from one or more of bamboo stalks, bamboo branches and bamboo whips remaining after bamboo stalk processing, preferably the stem of moso bamboo.

9. The biodegradable herbicidal film prepared by the method according to any one of claims 1 to 8, wherein the thickness of the biodegradable herbicidal film is 0.015-0.1 mm.

10. Use of the biodegradable herbicidal film prepared by the method according to any one of claims 1 to 8 for weed control, for eradication of roots, shoots and whole grass.

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