Environment-friendly degradable rice low-carbon diskless seedling raising film for cold regions and preparation method of environment-friendly degradable rice low-carbon diskless seedling raising film

Abstract

The invention relates to the technical field of rice seedling raising, in particular to an environment-friendly degradable rice low-carbon diskless seedling raising film for cold regions and a preparation method thereof.The preparation method includes the following steps that firstly, plant fibers are soaked through a non-woven fabric technology and a modifier to obtain a basic film; 2, pulping plant straws, mixing the pulped plant straws with a dispersing agent and PLA, and spraying the mixture onto the surface of the basic membrane to obtain a composite membrane; 3, the composite film and the punching film are bonded through an adhesive, needling, calendaring and coiling are conducted, and a finished product is obtained. The seedling raising film prepared by the invention shows remarkable advantages in the aspects of tensile property, degradability and low-temperature performance, and is suitable for rice seedling raising in cold regions.

Description

Technical Field

[0001] The invention relates to the technical field of rice seedling cultivation, and in particular to an environmentally friendly and degradable rice low-carbon discless rice seedling cultivation film for cold regions and a preparation method thereof. Background Art

[0002] Traditional rice seedling raising methods involve raising seedlings on seedling trays and then placing them on seedling beds. These trays must be placed horizontally and vertically, with tight connections and no overlap between them, and close contact with the bed with no gaps. Failure to meet standard tray placement can lead to diseases such as blight and wilt at the 2.5-leaf stage. Farmers typically squat, kneel, and crawl during the entire tray placement process, which is both laborious and time-consuming. Furthermore, plastic trays can deform, break, and become unrecyclable, causing significant pollution. Consequently, trayless rice seedling raising technology has emerged. This technology abandons traditional plastic trays and instead utilizes seedling film and specialized methods. This technology optimizes the seedling raising environment, increasing the temperature and humidity of the bed soil, thereby promoting germination and growth of rice seeds. Trayless rice seedling raising not only improves seedling raising efficiency but also reduces costs. It also adheres to environmental principles and reduces the generation of plastic waste.

[0003] However, the existing rice seedling raising films still have the following technical problems:

[0004] (1) Conventional polyethylene (PE) seedling film is non-degradable, with a recycling rate of less than 30%. Residual fragments lead to soil compaction and microplastic pollution. In cold regions, low temperatures extend the degradation cycle, exacerbating environmental hazards. (2) Ordinary seedling film has poor thermal insulation performance when the temperature difference between day and night is large, and requires heating equipment, which consumes a lot of energy and increases costs by 20%-40%. (3) The brittleness of single PLA / PBAT film increases significantly at low temperatures (tensile strength decreases by ≥40%), and the degradation cycle does not match the seedling period (25-30 days), which makes it prone to early disintegration or difficult degradation in the later stage.

[0005] Therefore, providing a degradable rice discless rice seedling raising film for cold regions becomes a problem to be solved urgently. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides an environmentally friendly and degradable low-carbon rice discless rice seedling raising film for cold regions and a preparation method thereof, which specifically comprises the following steps:

[0007] Step 1: clean the surface of the plant fiber with clean water, dry it, then put the plant fiber into a carding machine for primary web formation, and then put it into an air-laid machine for secondary web formation, soak it in a modifier, and dry it to obtain a base film;

[0008] Step 2: After pulping the plant straws, obtain a slurry. Add a dispersant and PLA to the slurry, stir for several minutes, then spray it onto the surface of the base film and dry it until the moisture content of the surface slurry is ≤5% to obtain a composite film.

[0009] Step 3: Use an adhesive to bond the composite film and the perforated film together, and obtain a preliminary product after rolling. Needle-punch the preliminary product, with the needle-punched surface being the composite film, calender it, and wind it into a roll to obtain the finished product.

[0010] Preferably, the plant fiber is one or more of flax fiber, hemp fiber, ramie fiber, jute fiber, cotton fiber, and short degummed ramie fiber; the plant straws in Step 2 are one or more of rice straws, wheat straws, and corn straws.

[0011] Preferably, the mass ratio of the plant fiber to the modifier in Step 1 is 1:5, and the modifier includes glycerol, chitosan, and water with a mass ratio of 5:1:500. Most preferably, the soaking temperature is 45 - 55°C, the soaking time is 30 - 40 min, the drying temperature is 120 - 130°C, and the drying time is 2 - 3 min.

[0012] Preferably, the mass ratio of the slurry, the dispersant, and PLA in Step 2 is 10:1:1, and the dispersant includes water and carboxymethyl cellulose with a mass ratio of 200:1. Most preferably, the rotation speed is 1500 - 2500 rpm, the stirring time is 30 - 40 min, and the drying temperature is 90 - 120°C.

[0013] Preferably, the pulping treatment in Step 2 is as follows: Mix the plant straws and the soaking agent at a mass ratio of 1:4 and soak them at 70 - 80°C for 2 - 3 h. After taking them out, wash the residual liquid on the surface of the plant straws, then mix them with water and a composite enzyme at a mass ratio of 15:1:50 and enzymatically hydrolyze them at 45 - 55°C for 14 - 16 h. After taking them out, wash the residual liquid on the surface of the plant straws, and then mix them with water at a mass ratio of 1:100 for beating, with the beating degree being 30 - 40°SR. Most preferably, the soaking agent is a sodium hydroxide solution with a mass fraction of 5 - 10% or a hydrogen peroxide solution with a volume fraction of 3 - 5%, and the composite enzyme is ligninase and pectinase with a mass ratio of 2:1.

[0014] Preferably, the mass ratio of the composite film, the adhesive, and the perforated film in Step 3 is 66:1:33. Most preferably, the adhesive is a soybean protein adhesive, the rolling temperature is 70 - 80°C, the rolling pressure is 80 - 100 kN / m, the needle-punching frequency is 1500 - 2000 times / min, and the needle-punching density is 3000 - 5000 needles / m 2 。

[0015] Preferably, the perforated plastic film is made of degradable material, with a thickness of 0.015 mm, a width of 1.5 m, a hole spacing of 3.8 cm × 6 cm, and a hole diameter of 0.6 cm.

[0016] The present invention has the following advantages:

[0017] (1) The present invention uses plant fibers and plant straws as the main raw materials, combines degradable PLA (polylactic acid) and soy protein adhesives, and replaces traditional non-degradable polyethylene (PE) films. Moreover, all components are natural or bio-based materials, ensuring degradability throughout the life cycle.

[0018] (2) The present invention optimizes the ratio of PLA to plant straws in the composite film (the mass ratio of slurry, dispersant, and PLA is 10:1:1), and uses an enzymatic hydrolysis process (a composite treatment of ligninase and pectinase) to regulate the degradation rate, making it highly compatible with the seedling raising period (25 - 30 days) in cold regions, and avoiding problems such as early disintegration or late residue.

[0019] (3) The present invention forms a heat preservation and isolation layer through a three-layer structure of a base film + a surface coating + a perforated film, which can adjust the soil air permeability and reduce heat loss at the same time. The base film is soaked in a glycerol-chitosan modifier to enhance its anti-brittleness at low temperatures. After the heat preservation performance is improved, no additional heating equipment is required, and the seedling raising cost in cold regions is significantly reduced.

[0020] (4) The present invention converts waste materials such as rice straws and wheat straws into slurry raw materials through pulping treatment, which not only reduces incineration pollution but also reduces raw material costs. A composite enzymatic hydrolysis is adopted in the pulping stage to improve the extraction efficiency of straw fibers, and the spraying process ensures uniform coverage of the slurry, reducing raw material waste.

[0021] (5) The combination of the perforated film and the composite film not only maintains soil humidity (through the water absorption of soy protein adhesives) but also enhances air permeability through the microporous structure, promoting root development. The needle punching process enhances the bonding force between the film layers, and the tensile strength of the finished film after calendering treatment is ≥ 25 MPa, meeting the requirements of wind resistance and frost resistance for film covering in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative efforts.

[0023] Figure 1 It is a cross-sectional view of the seedling raising film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Example 1

[0026] Step 1: Take flax fiber, hemp fiber, ramie fiber and jute fiber with a mass ratio of 1:1:1:1, wash the surface with clear water, dry it, then put the above plant fibers into a carding machine for primary web formation, and then put them into an air-laid web machine for secondary web formation. After soaking with a modifier, dry it to obtain a base film 1. Among them, the mass ratio of the plant fiber to the modifier is 1:5, and the modifier includes glycerol, chitosan and water with a mass ratio of 5:1:500. The soaking temperature is 50 °C, the soaking time is 35 min, the drying temperature is 120 °C, and the drying time is 3 min.

[0027] Step 2: Take rice straw and corn straw with a mass ratio of 1:1. Mix the straw and the soaking agent at a mass ratio of 1:4 and soak them at 75 °C for 2.5 h. After taking them out, wash the residual liquid on the surface of the straw, and then mix them with water and a composite enzyme at a mass ratio of 15:1:50 and enzymatically hydrolyze them at 50 °C for 15 h. After taking them out, wash the residual liquid on the surface of the straw, and then mix them with water at a mass ratio of 1:100 for beating, and the beating degree is 35 °SR to obtain a slurry. Add a dispersant and PLA to the slurry, stir at 2000 rpm for 30 min, and then spray it on the surface of the base film 1 to form a coating 2. Dry it at 100 °C until the moisture content of the surface slurry is ≤5% to obtain a composite film. Among them, the soaking agent is a sodium hydroxide solution with a mass fraction of 8%, the composite enzyme is ligninase and pectinase with a mass ratio of 2:1, the mass ratio of the slurry, the dispersant and PLA is 10:1:1, and the dispersant includes water and carboxymethyl cellulose with a mass ratio of 200:1.

[0028] Step 3: Use a soybean protein adhesive 3 to bond the composite film and the perforated film 4 together, and obtain a preliminary product after rolling. Needle-punch the preliminary product, the needle-punched surface is the composite film, calender it, and wind it into a roll to obtain a finished product. Among them, the mass ratio of the composite film, the adhesive and the perforated film is 66:1:33, the rolling temperature is 75 °C, the rolling pressure is 90 kN / m, the needle-punching frequency is 2000 times / min, and the needle-punching density is 4000 needles / m 2 The perforated plastic film is made of PLA material, the thickness of the perforated plastic film is 0.015 mm, the width is 1.5 m, the hole spacing is 2 cm × 2 cm, and the hole diameter is 0.6 cm.

[0029] Test Example 1

[0030] The rice seedling-raising film prepared in Example 1 and common PE films on the market were sent to local testing institutions to test the various properties of the rice seedling-raising film and the PE film respectively. The results are shown in Table 1. The degradation properties of the rice seedling-raising film and the PE film at different temperatures were tested respectively, and the results are shown in Table 2. The tensile properties of the rice seedling-raising film and the PE film at different temperatures were tested respectively, and the results are shown in Table 3. The heat preservation properties of the rice seedling-raising film and the PE film at different temperatures are shown in Table 4.

[0031] Test standards: Tensile strength test (ASTM D638 standard), elongation at break test (ASTM D638 standard), degradation rate test (ISO14855 standard, 25°C for 30 days), degradation cycle test (5°C for 30 days), low-temperature anti-brittle test (-10°C tensile strength), low-temperature elongation at break test (-10°C elongation at break), day-night temperature difference test (simulated temperature -5 - 10°C).

[0032] Table 1

[0033] Seedling-raising film PE film Tensile strength test ≥35Mpa ≤23Mpa Elongation at break test ≥150％ ≤60％ Degradation rate test ≥90％ ≤5％ Degradation cycle test ≥70％ ≤1％ Low-temperature anti-brittle test ≥30Mpa (decrease by about 14%) ≤12Mpa (decrease by about 47%) Low-temperature elongation at break test ≥120％ ≤20％ Day-night temperature difference test Temperature range inside the film ±2℃ Temperature range inside the film ±5℃

[0034] Table 2

[0035]

[0036]

[0037] Table 3

[0038]

[0039] Table 4

[0040] Temperature condition Temperature fluctuation inside the seedling-raising film Temperature fluctuation inside the PE film -5—10℃ ±2℃ ±5℃ -10℃ ±3℃ ±8℃

[0041] As can be seen from Tables 1 - 4, the rice seedling-raising film prepared by the present invention exhibits excellent tensile strength and elongation at break at room temperature (25°C), in cold regions (5°C) and in extremely cold conditions (-10°C), significantly superior to conventional PE films. At room temperature, in cold regions and in extremely cold conditions, the degradation rate of the rice seedling-raising film of the present invention is significantly higher than that of conventional PE films, and it can still maintain a relatively high degradation rate especially in cold regions. In a low-temperature environment, the decline in the tensile strength and elongation at break of the rice seedling-raising film of the present invention is relatively small, showing good low-temperature anti-brittleness. In an environment with a large day-night temperature difference, the temperature fluctuation inside the film of the rice seedling-raising film of the present invention is relatively small, and its heat preservation performance is superior to that of conventional PE films. That is to say, the rice seedling-raising film prepared by the present invention shows significant advantages in terms of tensile performance, degradability and low-temperature performance, and is suitable for rice seedling raising in cold regions.

[0042] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present 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 present invention. Thus, the present invention is not intended 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 preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling-raising film for cold regions, characterized in that, It includes the following steps: Step 1: Wash the surface of plant fibers with clear water, dry them, then put the plant fibers into a carding machine for primary web formation, and then put them into an air-laid machine for secondary web formation. After soaking with a modifier, dry them to obtain a base film; Step 2: After pulping the plant straws, obtain a slurry. Add a dispersant and PLA to the slurry, stir and spray it onto the surface of the base film, and dry it until the moisture content of the surface slurry is ≤5% to obtain a composite film; Step 3: Adhere the composite film and the perforated film together with an adhesive, and obtain a preliminary product after rolling. Needle-punch the preliminary product, with the needle-punched surface being the composite film, calender it, and wind it into a roll to obtain a finished product.

2. The preparation method of an environmentally friendly and degradable low-carbon rice seedling-raising film without a seed tray for cold regions according to claim 1, wherein The plant fibers are one or more of flax fiber, hemp fiber, ramie fiber, jute fiber, cotton fiber, and waste flax short fiber; the plant straws in Step 2 are one or more of rice straw, wheat straw, and corn straw.

3. The preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling raising film for cold regions according to claim 1, wherein, In Step 1, the mass ratio of the plant fibers to the modifier is 1:5, and the modifier includes glycerol, chitosan, and water, with a mass ratio of 5:1:

500.

4. The preparation method of an environmentally friendly and degradable low-carbon rice non-disk seedling-raising film for cold regions according to claim 1, wherein, In Step 2, the mass ratio of the slurry, the dispersant, and PLA is 10:1:1, and the dispersant includes water and carboxymethyl cellulose, with a mass ratio of 200:

1.

5. The preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling raising film for cold regions according to claim 1, characterized in that, The pulping treatment in Step 2 is as follows: Mix the plant straws and the soaking agent at a mass ratio of 1:4 and soak them at 70 - 80°C for 2 - 3 h. After taking them out, wash the residual liquid on the surface of the plant straws, then mix them with water and a composite enzyme at a mass ratio of 15:1:50 and enzymatically hydrolyze them at 45 - 55°C for 14 - 16 h. After taking them out, wash the residual liquid on the surface of the plant straws, and then mix them with water at a mass ratio of 1:100 for beating, with a beating degree of 30 - 40°SR.

6. The preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling-raising film for cold regions according to claim 5, characterized in that The soaking agent is a sodium hydroxide solution with a mass fraction of 5 - 10% or a hydrogen peroxide solution with a volume fraction of 3 - 5%.

7. The preparation method of an environmentally friendly degradable low-carbon diskless rice seedling raising film for cold regions according to claim 5, characterized in that, The composite enzyme is ligninase and pectinase, with a mass ratio of 2:

1.

8. The preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling-raising film for cold regions according to claim 1, characterized in that, The adhesive in Step 3 is a soy protein adhesive.

9. The preparation method of an environmentally friendly and degradable low-carbon diskless rice seedling-raising film for cold regions according to claim 1, characterized in that, In Step 3, the mass ratio of the composite film, the adhesive, and the perforated film is 66:1:3; 10. A rice seedling-raising film without seed trays prepared by the method according to any one of claims 1 - 9.

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