A method for preparing cassava starch-based liquid mulch film

Abstract

The invention discloses a method for preparing a cassava starch-based liquid mulch film, the preparation method comprising the following steps: (1) preparing an orthosilicic acid hydrolyzate by dissolving tetraethyl orthosilicate, ethanol, deionized water and 0.8-1.2 mol / L hydrochloric acid, stirring at room temperature until completely hydrolyzed, and obtaining a silica sol as a cross-linking agent; (2) adding cassava starch to the silica sol, stirring and mixing, and obtaining a starch solution containing a cross-linking agent; (3) adding carboxymethyl cellulose and carbodiimide to the starch solution containing a cross-linking agent, stirring and mixing to obtain an emulsion, i.e., a cassava starch-based liquid mulch film. The mulch film emulsion prepared by the present invention is easy to spray and use, can help keep the soil moist, reduce water evaporation and rainwater loss, maintain the surface temperature, and reduce soil heat loss.

Description

Technical Field

[0001] The invention provides a method for preparing a biodegradable liquid mulch film, belonging to the technical field of agricultural mulch films. Background Art

[0002] my country has been a major agricultural country since ancient times. Today, the total area of ​​crop planting in China has reached 2.5 billion mu, of which the planting of vegetables and fruit trees requires mulch protection. The total area of ​​vegetable planting in my country is about 322 million mu, accounting for about 12.8% of the total area of ​​crop planting, and the area of ​​orchards is nearly 200 million mu, accounting for about 7.56% of the total area of ​​crop planting in the country.

[0003] Since the introduction of agricultural mulch film in my country, polyethylene (PE) mulch film has been rapidly and widely promoted and applied throughout the country. The effect of covering crops with mulch film on agricultural water saving and increasing production is very significant. It can increase the water utilization efficiency and yield of crops by about 30% respectively, making great contributions to increasing production and income of agricultural products, ensuring food security, and year-round supply of vegetables. It generates direct economic benefits of 120 billion to 140 billion yuan in the country each year.

[0004] In order to solve the recycling and degradation problems caused by the use of traditional PE mulch, researchers have tried to prepare mulch based on various biodegradable materials to replace PE mulch, such as PBAT, PLA, PBS and other mulch. These mulch have excellent biodegradability and environmentally friendly properties. However, they are difficult to promote due to cost or production process.

[0005] Among them, starch-based biodegradable mulch only requires a simple production process. Moreover, cassava is defined by the Chinese government as a non-grain energy crop and is known as the "king of starch." In 2022, my country's cassava starch production was about 220,000 tons, mainly used for modified starch, alcohol, feed, etc., which is rarely consumed and therefore has low cost. However, the fatal flaw of starch-based biodegradable mulch is that it degrades quickly and has a short shelf life, making it difficult to commercialize. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method for preparing a biodegradable liquid mulch film using cassava starch as a basic raw material. The method has a simple preparation process, readily available raw materials, a long shelf life, and adjustable degradation time. The prepared mulch film has heat preservation, moisture retention and seedling protection properties.

[0007] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0008] A method for preparing a cassava starch-based liquid mulch film comprises the following steps:

[0009] (1) preparing an orthosilicic acid hydrolyzate by mixing tetraethyl orthosilicate, ethanol, deionized water and 0.8-1.2 mol / L hydrochloric acid, stirring the solution at room temperature until the solution is completely hydrolyzed, thereby obtaining a silica sol as a crosslinking agent; wherein the mass ratio of tetraethyl orthosilicate to ethanol, water and hydrochloric acid is 25-55:23:9:0.08-0.2;

[0010] (2) adding cassava starch to silica sol in a mass ratio of 8 to 15:100, stirring and mixing to obtain a starch solution containing a crosslinking agent;

[0011] (3) adding carboxymethyl cellulose and carbodiimide to a starch solution containing a crosslinking agent, wherein the mass ratio of carboxymethyl cellulose: carbodiimide: starch solution is 9-15: 0.009-0.015: 1000, and stirring and mixing to obtain an emulsion, namely, a cassava starch-based liquid mulch film.

[0012] Preferably, in step (1), a mixture of ethanol and water is first prepared, and then ethyl orthosilicate is added, followed by hydrochloric acid, and the mixture is stirred and mixed, and then hydrolyzed at room temperature for 1-2 hours.

[0013] Preferably, in step (1), the concentration of hydrochloric acid is 1 mol / L.

[0014] Preferably, the cassava starch in step (2) is industrial grade starch.

[0015] Preferably, the stirring and mixing to obtain the starch solution in step (2) refers to adding cassava starch to the silica sol and stirring until the starch is completely dissolved, and cross-linking occurs while stirring to form a network structure, thereby forming a uniform and stable mixture.

[0016] Preferably, the stirring and mixing in step (3) is to disperse the starch mixture to which carboxymethyl cellulose and carbodiimide are added evenly through a homogenizer, so that carbodiimide catalyzes the starch and carboxymethyl cellulose at room temperature, and the two begin to undergo an esterification reaction, and the mixture is left for 1-1.5 hours to allow the mixed emulsion to fully react to form a micro-cross-linked structure.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The mulch film emulsion prepared by the present invention is easy to spray and use, and a single person can quickly and conveniently form a thin film on a large-scale field surface through a sprayer. The starch-based mulch film prepared by the present invention can help keep the soil moist, reduce water evaporation and rainwater loss, maintain the surface temperature, and reduce soil heat loss.

[0019] (2) The liquid mulch emulsion of the present invention has low synthesis cost, simple formula, and convenient process, and can be prepared and used in various places.

[0020] (3) The liquid mulch film of the present invention is a disposable mulch film without any non-degradable additives and is a completely biodegradable material, which reduces plastic pollution in the fields and complies with national policy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the process of hydrolysis of ethyl orthosilicate into orthosilicic acid under the catalysis of ethanol and hydrochloric acid.

[0022] Figure 2 The left picture shows the structural formula of cassava starch, and the right picture shows the simplified structural formula.

[0023] Figure 3 Cross-linking occurs due to dehydration condensation of orthosilicic acid and cassava starch.

[0024] Figure 4 The esterification reaction of carboxymethyl cellulose and cassava starch occurs under the action of carbodiimide. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the present invention, not all of it. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be obtained by conventional technical means or purchased commercially.

[0027] Embodiment 1:

[0028] (1) 556.5 g of tetraethyl orthosilicate was added to a mixture of 96.4 g of water and 246.1 g of ethanol, 1 g of 1 mol / L hydrochloric acid was added dropwise, and the mixture was stirred and hydrolyzed at room temperature for 1 hour to obtain a silica sol as a crosslinking agent.

[0029] (2) adding 90 g of cassava starch to the silica sol, stirring and mixing, to obtain nearly 1 kg of starch solution containing a cross-linking agent;

[0030] (3) 9 g of carboxymethyl cellulose and 0.009 g of carbodiimide were added to a starch solution containing a crosslinking agent, and the mixture was dispersed evenly at a speed of 2000 r / m for 10 min using a homogenizer, and then allowed to stand for 1 hour to allow the reaction to fully proceed and form a micro-crosslinked structure, thereby obtaining an emulsion, i.e., a cassava starch-based liquid mulch film.

[0031] (4) Three containers (without covers) with length, width and height of 30 cm, 30 cm and 20 cm respectively were filled with completely dry sand with a diameter of 100 to 300 μm. 1 kg of water was evenly sprayed into each container using a spray bottle. After the water completely penetrated the sand, liquid mulch emulsion was sprayed until the surface of the sand was completely covered. The sand was weighed and marked as No. 1, No. 2 and No. 3. After being placed at room temperature for two days, the weight was weighed. The average moisture retention rate was 78%.

[0032] Table 1

[0033]

[0034]

[0035] Embodiment 2:

[0036] The liquid mulch and sand containers were the same as in Example 1, but two thermometers were inserted into the three sand containers to a depth of 10 cm, and the temperature displayed was recorded as 1-1, 1-2, 2-1, 2-2, 3-1, and 3-2. The three sand containers were heated to 50°C in an oven, placed at room temperature for 24 hours, and the temperatures before and after were recorded. Compared with the control group, the thermal insulation effect of spraying mulch was significant.

[0037] Table 2

[0038]

[0039] Embodiment 3:

[0040] The other steps were the same as in Example 1, but 10 peanut seeds were planted separately at a depth of 5 cm in sand containers No. 1, No. 2, and No. 3, respectively, and the germination rates were recorded after waiting for 10 days.

[0041] Table 3

[0042]

[0043] Embodiment 4:

[0044] The other steps are the same as those in Example 1, but the sand containers No. 1, No. 2, and No. 3 are placed outdoors to observe when the ground film on the surface of the sand is completely degraded.

[0045] Table 4

[0046] sample Days when the ground film is basically intact Days for complete degradation of mulch film 1 38 51 2 41 55 3 40 53

[0047] Embodiment 5:

[0048] The other steps are the same as in Example 1, but the amount of ethyl orthosilicate is changed to obtain a liquid mulch film. Then, the operation is carried out according to Example 2 and Example 4 to observe the heat preservation capacity and degradation days of the liquid mulch film.

[0049] Table 5

[0050]

[0051]

[0052] Embodiment 6:

[0053] The other steps were the same as in Example 1, but the amount of carboxymethyl cellulose was changed to obtain a liquid mulch film. The water retention rate and degradation days of the liquid mulch film were observed.

[0054] Table 6

[0055] Carboxymethyl cellulose addition amount (g) Water retention rate (%) Days for complete degradation of mulch film 10.5 81 50 12 85 53 13.5 86 53

[0056] Comparative Example 1:

[0057] The other steps are the same as in Example 1, but the liquid mulch film is not sprayed, and the samples are placed at room temperature for two days and then weighed.

[0058] Table 7

[0059]

[0060] By comparing Example 1 with Control Example 1, it can be seen that spraying the liquid mulch film can help keep the soil moist and reduce water evaporation.

[0061] Comparative Example 2:

[0062] The rest is the same as in Example 2, but without spraying the liquid ground film. The ground is left at room temperature for 24 hours, and the temperature before and after is compared.

[0063] Table 8

[0064]

[0065] By comparing Example 2 with Control Example 2, it can be seen that spraying the liquid ground film can help maintain the ground surface temperature and reduce soil heat loss.

[0066] Comparative Example 3:

[0067] The rest was the same as in Example 3, but the liquid mulch film was not sprayed, and the germination of the peanuts was recorded after 10 days.

[0068] Table 9

[0069]

[0070]

[0071] By comparing Example 3 and Control Example 3, it can be seen that the germination rate and sprout length of peanuts in the container sprayed with liquid mulch are better than those of peanuts not sprayed with liquid mulch.

Claims

1. A method for preparing a cassava starch-based liquid mulch film, characterized in that: The preparation method comprises the following steps: (1) preparing an orthosilicic acid hydrolyzate by mixing tetraethyl orthosilicate, ethanol, deionized water and 0.8-1.2 mol / L hydrochloric acid, stirring the solution at room temperature until the solution is completely hydrolyzed, thereby obtaining a silica sol as a crosslinking agent; wherein the mass ratio of tetraethyl orthosilicate to ethanol, water and hydrochloric acid is 25-55:23:9:0.08-0.2; (2) adding cassava starch to silica sol in a mass ratio of 8 to 15:100, stirring and mixing to obtain a starch solution containing a crosslinking agent; (3) adding carboxymethyl cellulose and carbodiimide to a starch solution containing a crosslinking agent, wherein the mass ratio of carboxymethyl cellulose: carbodiimide: starch solution is 9-15: 0.009-0.015: 1000, and stirring and mixing to obtain an emulsion, namely, a cassava starch-based liquid mulch film.

2. The preparation method according to claim 1, characterized in that: In step (1), a mixture of ethanol and water is first prepared, and then ethyl orthosilicate is added, followed by hydrochloric acid, which is stirred and mixed and then hydrolyzed at room temperature for 1-2 hours.

3. The preparation method according to claim 1, characterized in that: In step (1), the concentration of hydrochloric acid is 1 mol / L.

4. The preparation method according to claim 1, characterized in that: The stirring and mixing to obtain the starch solution in step (2) refers to adding cassava starch to the silica sol and stirring until the starch is completely dissolved, and cross-linking occurs while stirring to form a network structure, thereby forming a uniform and stable mixture.

5. The preparation method according to claim 1, characterized in that: The stirring and mixing in step (3) is to disperse the starch mixture to which carboxymethyl cellulose and carbodiimide are added evenly through a homogenizer, and then place the mixture for 1-1.5 hours to allow the mixed emulsion to fully react and form a micro-crosslinked structure.

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