A multifunctional biodegradable mulch film with improved compatibility and preparation method thereof

Abstract

The present invention belongs to the field of new agricultural materials, and relates to a multifunctional biodegradable mulch film with improved compatibility and a preparation method thereof, specifically, a green ionic liquid having plant growth regulating effect and nematode resistance is melt-blended with a fully biodegradable resin, and then extruded and blow-molded to prepare a biodegradable mulch film. By introducing ionic liquid, the compatibility of the biodegradable mulch film can be improved, and the mulch film can also have plant growth regulating effect and nematode resistance, thereby increasing the application value of the biodegradable mulch film, which has a certain reference value for promoting high-value applications and the green development of green polymer materials. The mulch film material is a fully biodegradable resin, which has the characteristics of full biodegradation in the soil, green and environmental protection, and will not cause environmental pollution; the processing technology of the present invention is simple, energy consumption is low, and efficiency is high.

Description

Technical Field

[0001] The invention belongs to the field of new agricultural materials, and particularly relates to a multifunctional biodegradable mulch film with improved compatibility and a preparation method thereof. Background Art

[0002] Using plastic mulch in farmland can increase production, but nowadays plastic mulch is mainly made of non-biodegradable polymer materials such as polyethylene. The large amount of polyethylene mulch fragments left in farmland will deteriorate soil quality, reduce the absorption of water and nutrients by crops, and threaten soil health, thereby reducing crop yield and quality. Therefore, the development of new biodegradable agricultural mulch is the fundamental way to solve the "white pollution" of agriculture.

[0003] Biodegradable mulch refers to a new type of mulch product that is made of bio-based materials or other non-bio-based materials. After a certain period of time and under certain conditions in the natural environment, it will eventually degrade into environmentally friendly substances such as CO2 and water. At present, due to the poor compatibility between the polymers that make up the mulch, the mechanical properties of most mulch are negatively affected. Adding a compatibilizer to the polymer material can effectively reduce the interfacial tension, increase the interfacial adhesion and improve the mechanical properties.

[0004] Ionic liquids are green and environmentally friendly solvents with low melting point, non-flammability, chemical and physical stability, and strong interaction with polymers. Due to these excellent properties, ionic liquids can now be used as interfacial compatibilizers, lubricants, flame retardants, plasticizers, and processing aids for polymers. Among them, ionic liquids are often used as compatibilizers for polymer blends. Nowadays, compounds from natural sources are used as sources of cations and anions to obtain bio-based ionic liquids, which has become a major research hotspot.

[0005] There are related studies on ionic liquid modified fully biodegradable mulch films, such as Yikai Zhou et al. published in the journal Materials Today Communications titled "Enhancing the properties of PBAT / PLA composites with novel phosphorus-based ionic liquid compatibilizers". However, the quaternary phosphorus ionic liquid used in this study only played a role in increasing the capacity, improving mechanical properties and flame retardancy, and did not give the mulch films other functions, limiting their practical application range. Therefore, designing and introducing functional ionic liquids is a wise strategy to increase the application range of composite materials. Summary of the invention

[0006] In view of the problems of poor compatibility, difficulty in degradation, inability to regulate plant growth, and lack of anti-nematode properties in the existing mulch films, the present invention provides a multifunctional biodegradable mulch film with improved compatibility and a preparation method thereof. The preparation method comprises melt blending of functional ionic liquid and fully biodegradable resin, and extrusion blow molding. The preparation process is simple, the film thickness is controllable, and the film has excellent mechanical properties and can be produced and used on a large scale. The prepared mulch film has both anti-nematode properties and plant growth regulating effects, which has certain reference value for promoting high-value applications and the green development of green polymer materials.

[0007] The present invention firstly provides a multifunctional biodegradable mulch film with improved compatibility. The raw material composition of the film comprises, by weight, 75-95 parts of fully biodegradable resin, 5-20 parts of polylactic acid and 0.1-1 part of ionic liquid.

[0008] Preferably, the raw material composition comprises, by weight: 80-90 parts of fully biodegradable resin, 10-20 parts of polylactic acid, and 0.1-1 part of ionic liquid.

[0009] Adding polylactic acid to fully biodegradable resin can improve its rigidity while ensuring biodegradability, so that the product can achieve the best performance balance.

[0010] Preferably, the ionic liquid (IL) is a choline ionic liquid, which can be prepared by a simple acid-base neutralization reaction. Excess acid and choline are dissolved in an appropriate amount of anhydrous ethanol, condensed and refluxed in an oil bath, and after the reaction is completed, the product is subjected to rotary evaporation to remove the solvent. After the product is purified by water, it is rotary evaporated again, and finally the solvent is pumped out with an oil pump to obtain the ionic liquid.

[0011] The acid used is one or more of nonanoic acid, 3-indolebutyric acid, hexanoic acid or amino acid.

[0012] Furthermore, the mass ratio of acid to choline is 2:1-4:1; the volume ratio of acid to anhydrous ethanol is 1:10-1:20; the oil bath temperature is 50-80°C; the reaction time is 5-10h; the condensation reflux stirring speed is 400-600rpm; the rotary evaporation temperature is 40-60°C; the time is 5-10min; and the solvent extraction time is controlled at 8-15h.

[0013] A more specific method for preparing the ionic liquid is:

[0014] 1) First, an excess amount of acid is dissolved in anhydrous ethanol and magnetically stirred, wherein the volume ratio of the acid to the anhydrous ethanol is 1:10-1:20.

[0015] 2) Secondly, choline is dissolved in anhydrous ethanol and slowly added dropwise to the acid solution stirred in an ice bath, the mass ratio of acid to choline is 2:1-4:1, and then the resulting solution is stirred and heated in an oil bath at 50-80°C and condensed and refluxed for 5-10 hours, and the condensation reflux stirring speed is 400-600rpm; after the reaction is completed, the obtained liquid is rotary evaporated at 40-60°C for 5-10 minutes to remove ethanol, and then the product is purified with water, and the obtained liquid is rotary evaporated at 40-60°C for 5-10 minutes to remove water, and finally the product is solvent-drained with an oil pump for 8-15 hours to obtain the target ionic liquid.

[0016] Preferably, the fully biodegradable resin is one or more of polybutylene adipate / terephthalate (PBAT), polylactide (PGA), polypropylene carbonate (PPCP) or polyhydroxyalkanoate (PHA);

[0017] More preferably, the fully biodegradable resin is PBAT.

[0018] Preferably, the particle size of the fully biodegradable resin is 2-4 mm.

[0019] The present invention also provides a method for preparing the multifunctional biodegradable mulch film with improved compatibility, wherein the ionic liquid and the fully biodegradable resin are melt-blended and then extruded and blow-molded to obtain the biodegradable mulch film of the present invention.

[0020] More specifically, the steps for preparing the multifunctional biodegradable mulch film with improved compatibility are as follows:

[0021] Weigh the fully biodegradable resin, polylactic acid and ionic liquid, dry them at 60-100℃ for 8-12h, and add the fully biodegradable resin, polylactic acid and ionic liquid to the twin-screw extruder. There are three continuous temperature zones from the feed part to the die: 130-140℃, 140-150℃, 150-160℃, the feed rate is set to 30-40g / min, and the screw speed is 30-40rpm; then the molten composite material extruded by the twin-screw is cooled under the traction of the traction device, and then granulated by the pelletizer to obtain the composite masterbatch, and the pelletizer speed is 15-30rpm. The obtained composite masterbatch is dried at 80-90℃ for 6-12h, added to the single screw extruder for melt extrusion, and blown into a ground film by a film blowing machine.

[0022] The process temperature of the film blowing is set to 150 / 170 / 165 / 165 / 140°C, the screw speed is 40-60rpm, the traction rate is 20-25Hz, and the collection rate is 15-20Hz, then a multifunctional biodegradable mulch film with improved compatibility can be obtained, which is packaged in black opaque plastic bags and stored in a dry, cool, and dark place.

[0023] The thickness of the multifunctional biodegradable mulch film with improved compatibility obtained by the method is controlled between 20-40 μm by adjusting process parameters such as blowing ratio and pulling rate.

[0024] The beneficial effects of the present invention are as follows:

[0025] The present invention prepares a fully biodegradable mulch film having both plant growth regulating function and nematode resistance by melt blending and extrusion blow molding ionic liquid having plant growth regulating function and nematode resistance, fully biodegradable resin and polylactic acid.

[0026] During use, the ionic liquid molecules loaded inside the ionic liquid will be slowly released into the mulch film matrix, and then further released to the mulch film surface, and finally come into contact with the crop leaves, achieving the effect of promoting plant growth and killing nematodes.

[0027] The fully biodegradable resin used as a ground film material has the characteristic of being degraded in the soil, which has certain reference value for promoting high-value applications and the green development of green polymer materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The photos are the growth effects of lettuce covered with the mulch obtained in Examples 1-3 and Comparative Example 1 and the fully biodegradable mulch without adding ionic liquid (blank film) at different times;

[0029] Figure 2 is the fresh weight of lettuce covered by the mulch obtained in Examples 1-3 and Comparative Example 1 and the fully biodegradable mulch without adding ionic liquid (blank film);

[0030] Figure 3 It is a mechanical property diagram of the mulch films of Examples 1-3 and Comparative Example 1 and a fully biodegradable mulch film (blank film) without adding ionic liquid;

[0031] Figure 4 It is an electron microscope image of the mulch films of Examples 1-3 and Comparative Example 1 and a fully biodegradable mulch film (blank film) without adding ionic liquid. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the technical solution of the present invention in more detail and should not be construed as limiting the protection scope of the present invention.

[0033] Unless otherwise specified, all raw materials in the following examples were purchased from the market.

[0034] Example 1

[0035] The preparation method of the ionic liquid comprises the following steps:

[0036] First, 6.4 g of amino acid was dissolved in 50 mL of anhydrous ethanol and stirred magnetically. Secondly, choline was dissolved in anhydrous ethanol and slowly added dropwise to the amino acid solution stirred in an ice bath (the mass ratio of amino acid to choline was 4:1). The resulting solution was then stirred, heated and condensed under reflux for 5 h in an oil bath at 50 ° C, and the stirring speed of condensation and reflux was 400 rpm. After the reaction was completed, the obtained liquid was rotary evaporated at 40 ° C for 10 minutes to remove ethanol. The product was then purified with water, and the obtained liquid was rotary evaporated at 60 ° C for 10 minutes to remove water. Finally, the product was solvent-drained for 15 h with an oil pump to obtain an amino acid choline ionic liquid.

[0037] A method for preparing a multifunctional biodegradable mulch film with improved compatibility comprises the following steps:

[0038] The ionic liquid, polypropylene carbonate (PPCP) and polylactic acid were dried at 60°C for 8h and added to the twin-screw extruder together. Among them, the mass ratio of PPCP, polylactic acid and ionic liquid is: 80:19:1. There are three continuous temperature zones from the feed part to the die head: 130°C, 140°C, and 150°C. The feeding rate is set to 30g / min and the screw speed is 30rpm. Subsequently, the molten composite material extruded by the twin-screw is cooled under the traction of the traction device, and then granulated by the pelletizer to obtain the composite masterbatch. The pelletizer speed is 15rpm. The obtained composite masterbatch is dried at 80°C for 6h, added to the single-screw extruder for melt extrusion, and blown into a ground film by a film blowing machine. The process temperature of the film blowing is set to 150 / 170 / 165 / 165 / 140°C, the screw speed is 40rpm, the traction rate is 20Hz, and the collection rate is 15Hz. The obtained multifunctional biodegradable mulch film with improved compatibility is packaged in a black light-proof plastic bag and stored in a dry, cool and light-proof place.

[0039] The thickness of the biodegradable mulch was measured by a thickness meter and was found to be 40±1 μm.

[0040] Example 2

[0041] The preparation method of the ionic liquid comprises the following steps:

[0042] The preparation method of the ionic liquid comprises the following steps:

[0043] First, 4.8 g of 3-indolebutyric acid was dissolved in 30 mL of anhydrous ethanol and stirred magnetically. Secondly, choline was dissolved in anhydrous ethanol and slowly added dropwise to the 3-indolebutyric acid solution stirred in an ice bath (the mass ratio of 3-indolebutyric acid to choline was 3:1). The resulting solution was then stirred, heated and condensed under reflux at 60 ° C in an oil bath for 7 h, and the stirring speed of the condensation reflux was 500 rpm. After the reaction was completed, the obtained liquid was rotary evaporated at 50 ° C for 7 minutes to remove ethanol. The product was then purified with water, and the obtained liquid was rotary evaporated at 70 ° C for 8 minutes to remove water. Finally, the product was solvent-drained for 10 h with an oil pump to obtain 3-indolebutyric acid choline ionic liquid.

[0044] A method for preparing a multifunctional biodegradable mulch film with improved compatibility comprises the following steps:

[0045] The ionic liquid, polyhydroxyalkanoate (PHA) and polylactic acid were dried at 80°C for 10 hours and added to the twin-screw extruder together. Among them, the mass ratio of PHA, polylactic acid and ionic liquid is: 85:15:0.5. There are three continuous temperature zones from the feed part to the die: 135°C, 145°C, and 155°C. The feeding rate is set to 35g / min and the screw speed is 35rpm. Subsequently, the molten composite material extruded by the twin-screw is cooled under the traction of the traction device, and then granulated by the pelletizer to obtain the composite masterbatch. The pelletizer speed is 20rpm. The obtained composite masterbatch is dried at 85°C for 10 hours, added to the single-screw extruder for melt extrusion, and blown into a ground film by a film blowing machine. The process temperature of the film blowing is set to 150 / 170 / 165 / 165 / 140°C, the screw speed is 50rpm, the traction rate is 22Hz, and the collection rate is 18Hz. The obtained multifunctional biodegradable mulch film with improved compatibility is packaged in a black light-proof plastic bag and stored in a dry, cool and light-proof place.

[0046] The thickness of the biodegradable mulch was measured by a thickness meter and was found to be 30±1μm.

[0047] Example 3

[0048] The preparation method of the ionic liquid comprises the following steps:

[0049] First, 3.2 g of nonanoic acid was dissolved in 20 mL of anhydrous ethanol and stirred magnetically. Secondly, choline was dissolved in anhydrous ethanol and slowly added dropwise to the nonanoic acid solution stirred in an ice bath (the mass ratio of nonanoic acid to choline was 2:1). The resulting solution was then stirred, heated and condensed under reflux in an 80°C oil bath for 10 h, with a condensation reflux stirring speed of 600 rpm. After the reaction was completed, the obtained liquid was rotary evaporated at 60°C for 5 minutes to remove ethanol. The product was then purified with water, and the obtained liquid was rotary evaporated at 60°C for 5 minutes to remove water. Finally, the product was solvent-drained with an oil pump for 8 h to obtain nonanoic acid choline ionic liquid.

[0050] A method for preparing a multifunctional biodegradable mulch film with improved compatibility comprises the following steps:

[0051] The ionic liquid, polybutylene adipate / terephthalate (PBAT) and polylactic acid were dried at 80°C for 12 hours and added to the twin-screw extruder together. Among them, the mass ratio of PBAT, polylactic acid and ionic liquid is: 90:10:0.1. There are three continuous temperature zones from the feed part to the die head: 140°C, 150°C, and 160°C. The feeding rate is set to 40g / min and the screw speed is 40rpm; then the molten composite material extruded by the twin-screw is cooled under the traction of the traction device, and then granulated by the pelletizer to obtain the composite masterbatch, and the pelletizer speed is 30rpm. The obtained composite masterbatch is dried at 90°C for 12 hours, added to the single-screw extruder for melt extrusion, and blown into a ground film by a film blowing machine. The process temperature of the film blowing is set to 150 / 170 / 165 / 165 / 140°C, the screw speed is 60rpm, the traction rate is 25Hz, and the collection rate is 20Hz. The obtained multifunctional biodegradable mulch film with improved compatibility is packaged in a black light-proof plastic bag and stored in a dry, cool and light-proof place.

[0052] The thickness of the biodegradable mulch was measured by a thickness meter and was found to be 20±1 μm.

[0053] Comparative Example 1

[0054] The PBAT / quaternary phosphorus ionic liquid / PLA mulch film was obtained as Comparative Example 1 based on the synthesis of quaternary phosphorus ionic liquid and the preparation of PBAT / quaternary phosphorus ionic liquid / PLA mulch film described in the paper entitled "Enhancing the properties of PBAT / PLA composites with novel phosphorus-basedionic liquid compatibilizers" published by Yikai Zhou et al. in the journal Materials Today Communications.

[0055] Anti-nematode experiment of ionic liquids:

[0056] The ionic liquid aqueous solutions and clear aqueous solutions with a mass concentration of 1% synthesized in Examples 1-3 and Comparative Example 1 were prepared to conduct a root nematode direct contact killing experiment, and the results are shown in Table 1. At room temperature, a suspension containing 50 root nematodes was dropped into 10 ml of the ionic liquid aqueous solution, and after 24 hours, the dead root nematodes were counted under a microscope, and the root nematode mortality rate was calculated.

[0057] The results show that the ionic liquids synthesized in Examples 1-3 all play a certain role in contact killing of root nematodes compared with the clean water group, and the insecticidal effect of the ionic liquid synthesized in Example 3 is more significant. However, there is no significant difference between the quaternary phosphorus ionic liquid in Comparative Example 1 and the clean water, indicating that the ionic liquid obtained in Comparative Example 1 has no anti-root nematode effect.

[0058] Table 1 Results of direct contact killing experiment of root nematodes

[0059] deal with Number of root nematodes killed Shimizu 2 Example 1 Ionic Liquid 10 Example 2 Ionic Liquid 9 Example 3 Ionic Liquid 47 Comparative Example 1 Ionic Liquid 2

[0060] Crop growth promotion experiment:

[0061] The plant growth promotion experiment was conducted with lettuce as the test object. The experimental design was as follows: 5 flower pots with a diameter of 15 cm and a height of 10 cm were prepared, 500 g of nutrient soil was accurately weighed and placed in the flower pots, and 100 ml of deionized water was sprayed. Lettuce seedlings with the same growth potential were transplanted and then sprayed with the same volume of water.

[0062] Ordinary fully biodegradable mulch, biodegradable mulch prepared in Examples 1-3, and PBAT / quaternary phosphine ionic liquid / PLA mulch prepared in Comparative Example 1 were used as mulch samples. The five mulch samples were cut to the same length, about 30 cm, covered on the flower pots, tied and fixed with rubber strips, and placed on a sunny and well-ventilated balcony to maintain the same environmental conditions. One month after transplanting, the lettuce was harvested, and the fresh weight of the blank film, the biodegradable mulch prepared in Examples 1-3, and the mulch prepared in Comparative Example 1 was weighed using an electronic balance. The results are shown in Table 1. Figure 2 The results show that compared with the blank film, the fresh weight of lettuce did not change significantly when the mulch was prepared using Comparative Example 1, but the fresh weight of lettuce prepared using the biodegradable mulch films prepared using Examples 1-3 became significantly heavier, indicating that it has the effect of promoting plant growth.

[0063] Mechanical properties test:

[0064] The mechanical properties of the ordinary fully biodegradable mulch, the biodegradable mulch prepared in Examples 1-3 and the PBAT / quaternary phosphine ionic liquid / PLA mulch prepared in Comparative Example 1 were tested. Figure 3 . Figure 3The figure in the middle is the result diagram of nominal strain at fracture; the results show that: compared with the blank film, the biodegradable mulch films prepared in Examples 1-3 and the PBAT / quaternary phosphonium ionic liquid / PLA mulch films prepared in Comparative Example 1 both have the effect of improving the toughness of the mulch films, indicating that the ionic liquid can be used as a toughening agent to improve the toughness of the mulch films.

[0065] Electron microscope test:

[0066] The surfaces of the common fully biodegradable mulch films, the biodegradable mulch films prepared in Examples 1-3, and the PBAT / quaternary phosphine ionic liquid / PLA mulch films prepared in Comparative Example 1 were tested using an electron microscope. Figure 4 .

[0067] The results show that compared with the blank film, the surface of the biodegradable mulch films prepared in Examples 1-3 and the PBAT / quaternary phosphine ionic liquid / PLA mulch film prepared in Comparative Example 1 is more dense and uniform, indicating that the ionic liquid has a volume-increasing effect and the compatibility of the mulch film has been improved.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any equivalent substitutions, modifications, etc. made by technicians in this field without any creative work within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multifunctional biodegradable mulch film with improved compatibility, characterized in that: The raw material composition includes, by weight: 75-95 parts of fully biodegradable resin, 5-20 parts of polylactic acid, and 0.1-1 parts of ionic liquid; The ionic liquid is a choline ionic liquid, and the preparation method of the ionic liquid is: preparing through acid-base neutralization reaction, dissolving excess acid and choline in an appropriate amount of anhydrous ethanol, condensing and refluxing in an oil bath, after the reaction is completed, performing rotary evaporation on the product to remove the solvent, purifying the product with water, performing rotary evaporation again, and finally using an oil pump to drain the solvent to obtain the ionic liquid; The acid used is one or more of nonanoic acid, 3-indolebutyric acid, hexanoic acid or amino acid.

2. The multifunctional biodegradable mulch film with improved compatibility according to claim 1, characterized in that: The raw material composition includes, by weight: 80-90 parts of fully biodegradable resin, 10-20 parts of polylactic acid, and 0.1-1 part of ionic liquid.

3. The multifunctional biodegradable mulch film with improved compatibility according to claim 1, characterized in that: The mass ratio of acid to choline is 2:1-4:1; the volume ratio of acid to anhydrous ethanol is 1:10-1:20; the oil bath temperature is 50-80°C; the reaction time is 5-10h; the condensation reflux stirring speed is 400-600rpm; the rotary evaporation temperature is 40-60°C; the time is 5-10min; and the solvent extraction time is controlled at 8-15h.

4. The multifunctional biodegradable mulch film with improved compatibility according to claim 1, characterized in that: The preparation method of ionic liquid is: 1) First, dissolve excess acid in anhydrous ethanol and perform magnetic stirring, wherein the volume ratio of acid to anhydrous ethanol is 1:10-1:20; 2) Secondly, choline is dissolved in anhydrous ethanol and slowly added dropwise to the acid solution stirred in an ice bath, the mass ratio of acid to choline is 2:1-4:1, and then the resulting solution is stirred and heated in an oil bath at 50-80°C and condensed under reflux for 5-10 h, and the condensation reflux stirring speed is 400-600rpm; after the reaction is completed, the obtained liquid is rotary evaporated at 40-60°C for 5-10 minutes to remove ethanol, and then the product is purified with water, and the obtained liquid is rotary evaporated at 40-60°C for 5-10 minutes to remove water, and finally the product is solvent-drained with an oil pump for 8-15 hours to obtain the target ionic liquid.

5. The multifunctional biodegradable mulch film with improved compatibility according to claim 1 or 2, characterized in that: The fully biodegradable resin is one or more of polybutylene adipate / terephthalate, polylactide, polypropylene carbonate or polyhydroxyalkanoate; the particle size of the fully biodegradable resin is 2-4 mm.

6. The multifunctional biodegradable mulch film with improved compatibility according to claim 5, characterized in that: The fully biodegradable resin is polybutylene adipate / terephthalate.

7. The method for preparing the multifunctional biodegradable mulch film with improved compatibility according to claim 1, characterized in that: The specific steps are as follows: Weigh a fully biodegradable resin, polylactic acid and an ionic liquid, dry them at 60-100°C for 8-12 h, and add the fully biodegradable resin, polylactic acid and ionic liquid into a twin-screw extruder; there are three continuous temperature zones from the feed part to the die: 130-140°C, 140-150°C, and 150-160°C, the feed rate is set to 30-40 g / min, and the screw speed is 30-40 rpm; then the molten composite material extruded by the twin-screw is cooled under the traction of a traction device, and then granulated by a pelletizer to obtain a composite masterbatch, and the pelletizer speed is 15-30 rpm; The obtained composite masterbatch is dried at 80-90°C for 6-12 h, added into a single screw extruder for melt extrusion, and blown into a ground film by a film blowing machine.

8. The method for preparing the multifunctional biodegradable mulch film with improved compatibility as claimed in claim 7, characterized in that: The process temperature of the film blowing was set at 150 / 170 / 165 / 165 / 140°C, the screw speed was 40-60 rpm, the pulling rate was 20-25 Hz, and the collection rate was 15-20 Hz.

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