Liquid mulch film and its preparation method

Abstract

This invention belongs to the field of agricultural mulch film technology, specifically relating to a liquid mulch film and its preparation method. The liquid mulch film provided by this invention comprises the following raw materials: lignite ethanol extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, and water. By combining lignite ethanol extract, lignite-based humic acid, film-forming agent, and plasticizer, the liquid mulch film provided by this invention can improve the hydrophobicity and toughness of the resulting liquid mulch film, thereby enhancing its heat retention and moisture retention effects on the soil.

Description

Technical Field

[0001] This invention relates to the field of agricultural mulch film technology, specifically to a liquid mulch film and its preparation method. Background Technology

[0002] Liquid mulch is typically composed of film-forming agents, plasticizers, additives, and water to form a relatively uniform liquid. When sprayed onto the soil surface, it forms a thin film after a certain period of time, which has the effect of heat preservation and moisture retention on the soil. Most importantly, liquid mulch can be naturally degraded by microorganisms in the natural environment, thereby replacing white plastic film and solving the problem of white pollution.

[0003] In existing liquid mulches, polyvinyl alcohol (PVA) is commonly used as a film-forming agent. However, PVA has strong hydrophilicity and is prone to cracking due to uneven soil surfaces after spraying, which affects its moisture retention. Chinese patent application CN107936583A discloses a multifunctional liquid mulch film made of montmorillonite resin and its preparation method. Its main components include montmorillonite resin, resin co-solvent, potassium permanganate, PVA, triethanolamine, and trimethylolpropane. Using this liquid mulch film can increase soil temperature by 0.5-1.1℃ and increase soil moisture content by 1.8-4.0%. However, there is still room for improvement in the moisture retention effect of this mulch film. Summary of the Invention

[0004] The purpose of this invention is to provide a liquid mulch film and its preparation method, aiming to further improve the moisture retention effect of the obtained liquid mulch film by improving its hydrophobicity and toughness.

[0005] To achieve the above-mentioned objectives, the present invention provides a liquid mulch film comprising the following raw materials: lignite alcohol extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, and water.

[0006] In some embodiments, the liquid mulch film also contains an antifoaming agent.

[0007] In some embodiments, the mass ratio of the lignite extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, defoamer, and water is (14-30):10:(0.03-0.096):(20-70):(1-4):(0.00-0.14):(368-584).

[0008] In some embodiments, the emulsifier is castor oil phosphate.

[0009] In some embodiments, the film-forming agent is polyvinyl alcohol.

[0010] In some embodiments, the plasticizer is selected from at least one of glycerol and sorbitol.

[0011] In some embodiments, the defoamer is at least one of ethanol, propanol, and butanol.

[0012] The present invention also provides a method for preparing a liquid mulch film, comprising:

[0013] It provides lignite alcohol extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, water, and optionally, defoamer;

[0014] The lignite extract, the emulsifier, and water are mixed to obtain a lignite extract emulsion; the lignite-based humic acid is mixed with water to obtain a lignite-based humic acid solution; the film-forming agent is mixed with water and optionally an antifoaming agent to obtain a film-forming agent solution.

[0015] The lignite ethanol extract emulsion, the plasticizer, and the lignite-based humic acid solution are added sequentially to the film-forming agent solution and stirred to obtain a liquid mulch film.

[0016] In some embodiments, the preparation method of the lignite ethanol extract includes: mixing and stirring ethanol and lignite at a volume ratio of (1.2-1.5):1, filtering, removing ethanol from the filtrate, and obtaining the lignite ethanol extract.

[0017] In some embodiments, the preparation method of the lignite-based humic acid includes: grinding lignite into powder, mixing it with an alkaline solution, letting it stand, taking the supernatant and filtering it, adding acid to adjust the pH until stratification occurs, and then letting it stand and filtering it again. The resulting solid is lignite-based humic acid.

[0018] In some embodiments, the mass ratio of the lignite extract to the emulsifier is 1000:(1-3).

[0019] In some preferred embodiments, the alkaline solution is a sodium hydroxide solution and the acid is hydrochloric acid.

[0020] In some preferred embodiments, the mass concentration of lignite extract in the lignite extract emulsion is 25-35%.

[0021] In some preferred embodiments, the mass concentration of lignite-based humic acid in the lignite-based humic acid solution is 45-55%.

[0022] In some preferred embodiments, the mass concentration of the film-forming agent in the film-forming agent solution is 8-12%.

[0023] In some preferred embodiments, the mass ratio of the film-forming agent solution: the plasticizer: the lignite-based humic acid solution: the lignite alcohol extract emulsion is (272-612):(1-4):(26-38):(50-160).

[0024] The liquid mulch film provided by this invention is sprayed onto the soil surface to form a thin film for soil heat preservation and moisture retention.

[0025] The present invention has the following beneficial effects:

[0026] The liquid mulch film provided by this invention is a biodegradable liquid mulch film. It incorporates a lignite extract rich in resin acids, characterized by its high carboxyl group content. One end of the carboxyl group forms a network structure with polyvinyl alcohol, while the long carbon chain and hydrophobic aromatic rings at the other end slow down the erosion of the mulch film by water molecules, increasing its water retention capacity. Simultaneously, the addition of lignite-based humic acid not only improves soil fertility but also accelerates the degradation of the liquid mulch film. The addition of a plasticizer reduces the hardness of the resulting liquid mulch film, making it easier to adhere to the soil and reducing cracking. The liquid mulch film provided by this invention, through the combination of lignite extract, lignite-based humic acid, film-forming agent, and plasticizer, improves the hydrophobicity and toughness of the resulting liquid mulch film, enhancing its heat retention and moisture retention effects on the soil. Furthermore, the liquid mulch film provided by this invention does not require the addition of oxidants such as potassium permanganate, eliminating the oxidation reaction step and improving the stability of the mulch film product. The liquid mulch film provided by this invention is easy to use; it can be sprayed onto the soil surface using a sprayer. After the liquid mulch film forms, seedlings can naturally emerge from it, saving a significant amount of manual work. After crop emergence, there is no need to remove the mulch film; it remains in the soil and degrades naturally, while simultaneously enhancing the capillary action of soil particles and improving soil permeability, thus acting as a soil conditioner. Therefore, the liquid mulch film provided by this invention not only increases soil organic matter but also solves the problem of "white pollution," which is of great significance for promoting agricultural development and environmental protection. Attached Figure Description

[0027] Figure 1 This is the infrared spectrum of the lignite alcohol extract provided by the present invention;

[0028] Figure 2 This is a photograph of the liquid mulch film provided by the present invention after it has been cast into a film on a glass plate;

[0029] Figure 3 This is a photograph showing the formation of a thin film on the soil surface after the liquid mulch film provided by this invention is sprayed onto the soil surface and about 1-2 hours later. Detailed Implementation

[0030] This invention provides a liquid mulch film comprising the following raw materials: lignite alcohol extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, and water.

[0031] Specifically, the inventors of this invention discovered in their research that by subjecting lignite to alcohol extraction, the resulting lignite alcohol extract, rich in resin acids, exhibits a high acid value, typically ranging from 30-60 mg KOH / g. For example... Figure 1 As shown in the infrared spectrum of the lignite ethanol extract provided by this invention, 1734 cm⁻¹ -1 There is a very significant characteristic peak of carboxyl group C=O at 2848 cm⁻¹, and also at 2848 cm⁻¹. -1 2916cm -1 The long-chain -CH2- characteristic peak is also significant (mainly hydrophobic groups), which can improve the hydrophobicity of liquid mulch film, thereby enhancing the heat preservation and moisture retention effect on the soil after application.

[0032] In some embodiments, the lignite extract is a lignite ethanol extract.

[0033] In some preferred embodiments, the preparation method of the lignite ethanol extract includes: mixing and stirring ethanol and lignite at a volume ratio of (1.2-1.5):1, filtering, and removing the ethanol from the filtrate to obtain the lignite ethanol extract. The ethanol in the filtrate can be removed by evaporation. Further, the mixing and stirring time is 1-4 hours.

[0034] To ensure a more uniform distribution of the lignite extract in the polyvinyl alcohol solution, an emulsifier is used to prepare the lignite extract into an emulsion. In some embodiments, the emulsifier is castor oil phosphate.

[0035] In some embodiments, the preparation method of the lignite extract emulsion includes: dissolving the lignite extract and an emulsifier in water at 60-90°C, and emulsifying by stirring. Preferably, the mass ratio of the lignite extract to the emulsifier is 1000:(1-3).

[0036] Lignite-based humic acid is a type of humic acid extracted from lignite. In this invention, it is used to improve soil fertility and accelerate the degradation of liquid mulch films. In some embodiments, the preparation method of the lignite-based humic acid includes: grinding lignite into powder, mixing it with an alkaline solution, allowing it to stand (i.e., the first standing), taking the supernatant and filtering it, adding acid to adjust the pH until stratification occurs, and then allowing it to stand (i.e., the second standing) and filtering. The resulting solid is lignite-based humic acid. By first treating with alkali and then adjusting the pH with acid, the molecular weight of the obtained lignite-based humic acid can be made moderate, effectively controlling the time when the mulch film begins to decompose. Preferably, the alkaline solution is a 20% sodium hydroxide solution by mass percentage; the acid is hydrochloric acid.

[0037] Preferably, the first settling time is 24-48 hours; the second settling time is 12-24 hours.

[0038] Preferably, the pH is adjusted to 2 using hydrochloric acid.

[0039] In some embodiments, the film-forming agent is polyvinyl alcohol (PVA).

[0040] In some embodiments, the plasticizer is selected from at least one of glycerol and sorbitol.

[0041] Polyvinyl alcohol (PVA) is prone to foaming during dissolution, which can lead to unevenness and localized breakage in the final product. In this embodiment of the invention, the lignite extract has defoaming properties, which can solve this problem to some extent. In some embodiments, the raw material for the liquid mulch film also includes a defoamer. Adding a defoamer further enhances the defoaming effect during the preparation of the film-forming agent solution.

[0042] In some embodiments, the defoamer is at least one of ethanol, propanol, and butanol.

[0043] In some preferred embodiments, the mass ratio of the lignite extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, defoamer, and water is (14-30):10:(0.03-0.096):(20-70):(1-4):(0.00-0.14):(368-584).

[0044] The liquid mulch film provided in this embodiment of the invention can be prepared by the preparation method provided by this invention.

[0045] Accordingly, embodiments of the present invention also provide a method for preparing a liquid mulch film, comprising:

[0046] (1) Provides lignite alcohol extract, lignite-based humic acid, emulsifier, film-forming agent, plasticizer, water and optionally defoamer;

[0047] (2) The lignite extract, the emulsifier and water are mixed to obtain a lignite extract emulsion; the lignite-based humic acid is mixed with water to obtain a lignite-based humic acid solution; the film-forming agent is mixed with water and optionally an antifoaming agent to obtain a film-forming agent solution.

[0048] (3) Add the lignite extract emulsion, the plasticizer, and the lignite-based humic acid solution to the film-forming agent solution and stir to obtain a liquid mulch film.

[0049] Specifically, in step (1), the lignite extract and its preparation method, the lignite-based humic acid and its preparation method, the emulsifier, the film-forming agent, the defoamer and the plasticizer are as described above, and will not be repeated here.

[0050] In step (2), a lignite ethanol extract emulsion, a lignite-based humic acid solution, and a film-forming agent solution are prepared separately for subsequent preparation of liquid mulch film. The preparation method of the lignite ethanol extract emulsion is as described above and will not be repeated here. In some embodiments, the lignite ethanol extract concentration in the lignite ethanol extract emulsion is 25-35%, preferably 30%, at which point the resulting lignite ethanol extract emulsion has a suitable viscosity, facilitating operation.

[0051] In some embodiments, when the lignite-based humic acid is mixed with water to obtain a lignite-based humic acid solution, the mass concentration of the lignite-based humic acid in the lignite-based humic acid solution is 45-55%, preferably 50%, at which point the lignite-based humic acid is more uniformly dispersed.

[0052] In some embodiments, when the film-forming agent is mixed with the defoamer and water to obtain a film-forming agent solution, the film-forming agent is polyvinyl alcohol, and the mixture is heated to 85-90°C simultaneously. Preferably, the mass concentration of the film-forming agent (i.e., polyvinyl alcohol) in the film-forming agent solution is 8-12%, more preferably 10%.

[0053] In step (3), the step of sequentially adding the lignite ethanol extract emulsion, the plasticizer, and the lignite-based humic acid solution to the film-forming agent solution and stirring is preferably carried out as follows: the lignite ethanol extract emulsion is added to the film-forming agent solution at 85-90°C and stirred for 30-60 minutes; then the plasticizer is added and stirred for another 10 minutes; finally, the lignite-based humic acid solution is added and stirred for another 30-60 minutes.

[0054] In some embodiments, the mass ratio of the film-forming agent solution: the plasticizer: the lignite-based humic acid solution: the lignite alcohol extract emulsion is (272-612):(1-4):(26-38):(50-160).

[0055] like Figure 2 and Figure 3 As shown, the liquid mulch film provided in this embodiment of the invention can be cast into a film, and therefore can be sprayed onto the soil surface to form a thin film for soil insulation and moisture retention. Furthermore, the liquid mulch film provided in this embodiment of the invention is biodegradable, making it more environmentally friendly than plastic mulch film.

[0056] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the liquid mulch film and its preparation method in the embodiments of the present invention, the above technical solutions are illustrated below through multiple embodiments.

[0057] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0058] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0059] The preparation method of the lignite ethanol extract emulsion in the following examples is as follows: ethanol and lignite are mixed at a volume ratio of 1.5:1, stirred at room temperature for 1 hour, filtered, and the ethanol in the filtrate is removed by evaporation to obtain the lignite ethanol extract. The lignite ethanol extract and castor oil phosphate are dissolved in water at 80°C at a mass ratio of 998:2, stirred, emulsified, and cooled to obtain the lignite ethanol extract emulsion, wherein the mass concentration of the lignite ethanol extract is 30%.

[0060] The preparation method of the lignite-based humic acid solution in the following examples is as follows: Lignite is ground into powder with a particle size of 0.2-0.45 mm, mixed with a 20% sodium hydroxide solution at a mass ratio of 1:8, stirred evenly, and allowed to stand at room temperature for 24 hours. The supernatant is collected and filtered, and the pH is adjusted to 2 with hydrochloric acid. Layering occurs, and the mixture is allowed to stand for 24 hours. After filtration, the filter cake is washed to obtain lignite-based humic acid. Water is added to this lignite-based humic acid to obtain a lignite-based humic acid solution, wherein the mass concentration of lignite-based humic acid is 50%.

[0061] The film-forming agent solution in the following examples is prepared by adding polyvinyl alcohol particles (film-forming agent) and ethanol (defoamer) to water at a mass ratio of 1000:2, heating to 85-90°C and stirring until fully dissolved to obtain a film-forming agent solution, wherein the mass concentration of polyvinyl alcohol is 10%.

[0062] Example 1

[0063] The lignite extract emulsion was added to the film-forming agent solution, heated to 90℃ and stirred for 30 min; glycerol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 30 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: glycerol: lignite extract emulsion = 30:400:2:116. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0064] Example 2

[0065] The lignite extract emulsion was added to the film-forming agent solution, heated to 90℃ and stirred for 30 min; sorbitol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 30 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: sorbitol: lignite extract emulsion = 26:435:2:110. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0066] Example 3

[0067] The lignite extract emulsion was added to the film-forming agent solution, heated to 80℃ and stirred for 60 min; glycerol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 60 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: glycerol: lignite extract emulsion = 21:612:1:50. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0068] Example 4

[0069] The lignite ethanol extract emulsion was added to the film-forming agent solution, heated to 80℃ and stirred for 60 min; glycerol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 30 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: glycerol: lignite ethanol extract emulsion = 18:525:2:87. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0070] Example 5

[0071] The lignite extract emulsion was added to the film-forming agent solution, heated to 80℃ and stirred for 60 min; glycerol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 30 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: glycerol: lignite extract emulsion = 8:367:4:110. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0072] Example 6

[0073] The lignite extract emulsion was added to the film-forming agent solution, heated to 80℃ and stirred for 60 min; glycerol (plasticizer) was added dropwise, and stirring continued for 10 min; lignite-based humic acid solution was added, and stirring continued for 30 min to obtain a liquid mulch film. The mass ratio of each component was lignite-based humic acid solution: film-forming agent solution: glycerol: lignite extract emulsion = 32:272:3:160. The obtained liquid mulch film was sprayed onto the soil surface, and the temperature and moisture content were measured.

[0074] The soil temperature and soil moisture content measured in Examples 1-6 are shown in Tables 1 and 2.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] Degradation rate evaluation: 10g of the liquid mulch film from Examples 1-6 was weighed and cast onto a 10×10cm glass plate. After drying, the entire film was peeled off, dried, and weighed. The mass of the film at this point was recorded as m0. The film was buried 10cm deep in soil and periodically removed. After cleaning the soil off the film surface, it was dried and weighed again. The mass of the film at this point was recorded as m1. The degradation rate D was calculated using the following formula, and the results are shown in Table 3.

[0080] D = (m0 - m1) / m0 × 100%

[0081] Table 3

[0082]

[0083] As shown in Tables 1 and 2, spraying the liquid mulch film of this invention can increase soil temperature by 2-4℃ and soil moisture content by 2-4.9%. As the mulch film gradually degrades, its heat-insulating and moisture-retaining properties gradually decrease. The reduced temperature difference indicates that the integrity of the mulch film can be maintained for more than 30 days. Furthermore, the data also show that the moisture-retaining performance of the liquid mulch film of this invention increases with the addition of lignite extract. However, more lignite extract is not necessarily better; excessive addition can lead to decreased toughness of the liquid mulch film, causing micro-cracks and affecting its moisture-retaining properties. Table 3 shows that the degradation rate of the liquid mulch film of this invention is very slow initially, with a slight acceleration starting around 30 days, followed by gradual degradation. Based on the later degradation rate, complete degradation is estimated to take approximately 90-180 days.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A liquid mulch film, characterized in that, It contains the following ingredients: lignite alcohol extract, lignite-based humic acid, emulsifier, polyvinyl alcohol, plasticizer, defoamer, and water; The mass ratio of the lignite extract, lignite-based humic acid, emulsifier, polyvinyl alcohol, plasticizer, defoamer, and water is (14-30):10:(0.03-0.096):(20-70):(1-4):(0.00-0.14):(368-584). The preparation method of lignite ethanol extract includes: mixing ethanol and lignite in a volume ratio of (1.2-1.5):1, stirring, filtering, removing ethanol from the filtrate, and obtaining lignite ethanol extract; The preparation method of the lignite-based humic acid includes: grinding lignite into powder, mixing it with an alkaline solution, letting it stand, taking the supernatant and filtering it, adding acid to adjust the pH until stratification occurs, and then letting it stand and filtering it again. The resulting solid is lignite-based humic acid.

2. The liquid mulch film according to claim 1, characterized in that, The emulsifier is castor oil phosphate; and / or The plasticizer is selected from at least one of glycerin and sorbitol; and / or The defoamer is at least one of ethanol, propanol, and butanol.

3. A method for preparing a liquid mulch film, characterized in that, include: It provides lignite alcohol extract, lignite-based humic acid, emulsifier, polyvinyl alcohol, plasticizer, water, and defoamer; The lignite extract, the emulsifier, and water are mixed to obtain a lignite extract emulsion; the lignite-based humic acid is mixed with water to obtain a lignite-based humic acid solution; and the polyvinyl alcohol is mixed with water and an antifoaming agent to obtain a polyvinyl alcohol solution. Add the lignite alcohol extract emulsion, the plasticizer, and the lignite-based humic acid solution to the polyvinyl alcohol solution and stir to obtain a liquid mulch film; The preparation method of lignite ethanol extract includes: mixing ethanol and lignite in a volume ratio of (1.2-1.5):1, stirring, filtering, removing ethanol from the filtrate, and obtaining lignite ethanol extract; The preparation method of the lignite-based humic acid includes: grinding lignite into powder, mixing it with an alkaline solution, letting it stand, taking the supernatant and filtering it, adding acid to adjust the pH until stratification occurs, and then letting it stand and filtering it again. The resulting solid is lignite-based humic acid. The mass ratio of the polyvinyl alcohol solution, the plasticizer, the lignite-based humic acid solution, and the lignite alcohol extract emulsion is (272-612): (1-4): (26-38): (50-160).

4. The preparation method according to claim 3, characterized in that, The mass ratio of the lignite extract to the emulsifier is 1000:(1-3).

5. The preparation method according to claim 3 or 4, characterized in that, The mass concentration of lignite extract in the lignite extract emulsion is 25-35%; and / or The mass concentration of lignite-based humic acid in the lignite-based humic acid solution is 45-55%; and / or The polyvinyl alcohol concentration in the polyvinyl alcohol solution is 8-12%.

6. The use of the liquid mulch film according to claim 1 or 2 or the liquid mulch film prepared by the preparation method according to any one of claims 3-5 in soil heat preservation and moisture retention.

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