Degradable mulching film and preparation method thereof

Abstract

The invention belongs to the technical field of agricultural mulching films, and relates to a degradable mulching film and a preparation method thereof. The invention provides a degradable mulching film. The degradable mulching film is prepared from polypropylene, a humectant, an emulsifier, a stabilizer and a modified filler, a preparation method of the modified filler comprises the following steps: mixing kapok fiber, nano silicate and beryllium oxide, adding a modified hydrogen-containing silicone oil cross-linking agent, stirring and reacting at 50-60 DEG C for 3-5 hours, cleaning and drying, thereby obtaining the modified filler. The modified hydrogen-containing silicone oil cross-linking agent is obtained by modifying a hydrogen-containing silicone oil cross-linking agent with vinyltriethoxysilane and distearoyloxy isopropyl aluminate. The degradable mulching film disclosed by the invention not only has very high degradability, but also can promote plant growth.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural mulch films and relates to a degradable mulch film and a preparation method thereof. Background Art

[0002] Ground film is a ground covering film. It is widely used in agricultural production because of its significant functions of warming, moisture conservation, weed control, and production promotion. It is considered to be one of the most important agricultural production materials besides fertilizers, seeds, and pesticides. A large number of practices have shown that ground film covering technology can gradually extend the suitable planting area of ​​many crops from the central region to the northwest, northeast, and south, and from low altitudes to high altitudes, extend the frost-free period by 10 to 15 days, increase the water utilization rate of dry land by 30% to 50%, and generally increase crop yields by 30% to 50% and value added by 40% to 60%. With the extensive use of ground film and the long-term emphasis on use and neglect of recycling, the amount of residual ground film in farmland has increased year by year. A large amount of residual film has entered the soil, reducing the air permeability of the cultivated soil, hindering the absorption of water and nutrients by crops, and affecting the quality of mechanical operations, becoming a prominent problem affecting the sustainable development of agriculture.

[0003] In recent years, biodegradable mulch has been recognized as a substitute for polypropylene mulch because of its similar functions to polypropylene mulch. Based on this, various degradable mulch films have appeared on the market, such as photodegradable mulch films, biodegradable mulch films, liquid mulch films, etc. However, these degradable mulch films all have limitations to varying degrees, which limits their widespread use. For example, the degradation limitation of photodegradable mulch films is that the part of the mulch film buried in the soil or shaded cannot be degraded or degrades slowly, and can only solve the problem of residual film in the surface of the cultivated land; biodegradable mulch films are weak in the ability to increase temperature and retain moisture, which affects the growth and development of crops; compared with traditional mulch films, the use of liquid mulch films requires specific spraying equipment and techniques, which increases the difficulty of operation.

[0004] Therefore, in the field of agricultural mulch film technology, it is particularly important to provide a mulch film that is highly degradable and can promote plant growth. Summary of the invention

[0005] The object of the present invention is to provide a degradable mulch film which not only has high degradability but also can promote plant growth.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a degradable mulch film, the degradable mulch film comprising polypropylene, a moisturizer, an emulsifier, a stabilizer and a modified filler;

[0008] The preparation method of the modified filler is as follows: kapok fiber, nano silicate and beryllium oxide are mixed, and a modified hydrogen-containing silicone oil cross-linking agent is added, and the mixture is stirred at 50-60° C. for 3-5 hours, and the mixture is washed and dried to obtain the modified filler;

[0009] The modified hydrogen-containing silicone oil cross-linking agent is obtained by modifying the hydrogen-containing silicone oil cross-linking agent with vinyl triethoxysilane and distearoyloxyisopropylaluminate.

[0010] Preferably, in terms of weight percentage, the degradable mulch film is composed of 40-60 parts of polypropylene, 2-3 parts of moisturizer, 1-3 parts of emulsifier, 3-5 parts of stabilizer and 20-25 parts of modified filler.

[0011] Preferably, the mass ratio of the kapok fiber, the nano-silicate and the beryllium oxide is 10:5-6:3-5.

[0012] Preferably, the mass ratio of the hydrogen-containing silicone oil crosslinking agent, the vinyl triethoxysilane and the distearoyloxyisopropylaluminate is 1:0.2-0.3:0.4-0.5.

[0013] Preferably, the humectant is chitosan or sodium hydroxymethylcellulose.

[0014] Preferably, the emulsifier is sorbitol or ethylene glycol.

[0015] Preferably, the stabilizer is antioxidant 1076, antioxidant 1010 and light stabilizer 770.

[0016] More preferably, the mass ratio of the antioxidant 1076, the antioxidant 1010 and the light stabilizer 770 is 0.5-1:0.3-0.5:1.

[0017] In a second aspect, a method for preparing the degradable mulch film of the present invention is provided, comprising the following steps:

[0018] S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and react at 60-90°C for 3-4h;

[0019] S2. The reactants, moisturizer, emulsifier and stabilizer are mixed evenly, extruded into granules by a twin-screw extruder, and blown into a film by a blow molding machine to obtain a degradable mulch film.

[0020] Preferably, the method comprises the following steps:

[0021] S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and react at 60-90°C for 3-4h;

[0022] S2. The above reactants, moisturizer, emulsifier and stabilizer are mixed evenly, and granulated by extrusion using a twin-screw extruder at 155-170°C; when the temperature of the first zone of the blow molding machine is 150-160°C, the temperature of the second zone is 160-170°C, the temperature of the third zone is 170-180°C, and the temperature of the blow molding machine head is 165-170°C, the film is blow-molded by a blow molding machine, and the film is cooled to obtain a degradable mulch film.

[0023] In a third aspect, a degradable mulch film for promoting corn growth is provided, comprising the degradable mulch film described in the present invention.

[0024] In a fourth aspect, there is provided application of the degradable mulch film of the present invention in promoting plant growth.

[0025] Preferably, the plant is corn, sugar cane or tobacco.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The degradable mulch film of the present invention uses a specific modified filler, which is composed of kapok fiber, nano-silicate, beryllium oxide and a modified hydrogen-containing silicone oil cross-linking agent; this combination makes the mulch film highly degradable and avoids the long-term pollution problem of traditional plastic mulch films on soil and crops. The applicant speculates that on the one hand, it may be due to: when vinyl triethoxysilane and distearyloxyisopropylaluminate are introduced into the hydrogen-containing silicone oil cross-linking agent, they may interact with the hydrogen-containing silicone oil by chemical bonding. This interaction may change the structure and properties of the hydrogen-containing silicone oil cross-linking agent, so that it has a high degradability when combined with the polypropylene mulch film. On the other hand, it may be due to: kapok fiber, nano-silicate and beryllium oxide are combined with the modified hydrogen-containing silicone oil cross-linking agent to form a filler with a special structure and properties. This filler increases the contact area and friction between the mulch film and the soil, thereby accelerating the physical degradation process; this filler can provide a place for microorganisms to attach and reproduce, thereby accelerating the degradation process of the mulch film. These factors work together to make the mulch film more easily decomposed by microorganisms and chemically degraded in the soil, while the physical degradation process is also accelerated, resulting in the degradable mulch film of the present invention having higher degradability.

[0028] (2) The degradable mulch film of the present invention can provide a suitable temperature, humidity, air permeability and nutrient supply conditions for plant growth, thereby improving and optimizing the plant growth environment, thereby promoting plant growth and development. The applicant speculates that on the one hand, it may be due to the following: the modified filler not only improves the mechanical properties of the mulch film, but also has a positive impact on the soil environment; for example, the combination of kapok fiber, nanosilicate and beryllium oxide may increase the air permeability and water permeability of the soil, and may also provide nutrients for plants, and may also improve the structure and fertility of the soil; thereby facilitating the growth and development of plant roots. On the other hand, it may be due to the following: the modified hydrogen-containing silicone oil crosslinker is obtained by modifying the hydrogen-containing silicone oil crosslinker with vinyl triethoxysilane and distearyloxyisopropylaluminate. This modifier not only improves the crosslinking degree and stability of the filler, but also has a positive impact on plant growth. Specifically, compared with unmodified hydrogen-containing silicone oil, the modified hydrogen-containing silicone oil crosslinker can better improve the drought resistance, cold resistance and disease resistance of plants. At the same time, the modified hydrogenated silicone oil crosslinker may also form a protective film on the soil surface, reducing the evaporation of soil moisture and the loss of nutrients, thereby providing better environmental conditions for plant growth.

[0029] (3) Through reasonable formulation and preparation process, the degradable mulch film of the present invention not only maintains good degradability and promotes plant growth, but also has sufficient mechanical properties (such as strength, etc.) to meet the use requirements in agricultural production (such as covering, heat preservation, moisturizing, etc.). DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0031] The technical scheme of the present invention is described below in conjunction with the examples, but the present invention is not limited to the following examples. The experimental methods and detection methods described in each example are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0032] Example 1

[0033] This embodiment provides a degradable mulch film, which is composed of 40 parts of polypropylene, 2 parts of chitosan, 1 part of sorbitol, 3 parts of stabilizer and 20 parts of modified filler in terms of mass percentage;

[0034] The preparation method of the modified filler is as follows: kapok fiber, nano-silicate and beryllium oxide are mixed in a mass ratio of 10:5:3, and a modified hydrogen-containing silicone oil cross-linking agent is added to react at 50° C. for 3 hours by stirring, and then washed with deionized water for 4 times, and dried in an oven at 40° C. for 10 minutes.

[0035] The modified hydrogenated silicone oil crosslinking agent is obtained by modifying the hydrogenated silicone oil crosslinking agent with vinyl triethoxysilane and distearoyloxy isopropyl aluminate, and the mass ratio of the hydrogenated silicone oil crosslinking agent, vinyl triethoxysilane and distearoyloxy isopropyl aluminate is 1:0.2:0.4;

[0036] The stabilizers are antioxidant 1076, antioxidant 1010 and light stabilizer 770, and the mass ratio of antioxidant 1076, antioxidant 1010 and light stabilizer 770 is 0.5:0.3:1;

[0037] The method for preparing the degradable mulch film of this embodiment comprises the following steps:

[0038] S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and then react at 60°C for 3h;

[0039] S2. The above reactants, chitosan, sorbitol and stabilizer are mixed evenly, and granulated by extrusion using a twin-screw extruder at 155°C; film is blow-molded by a blow molding machine under the conditions that the temperature of zone 1 of the blow molding machine is 150°C, the temperature of zone 2 is 160°C, the temperature of zone 3 is 170°C, and the temperature of the blow molding machine head is 165°C, and the film is cooled to obtain a degradable mulch film.

[0040] Example 2

[0041] This embodiment provides a degradable mulch film, which is composed of 60 parts of polypropylene, 3 parts of sodium hydroxymethyl cellulose, 3 parts of ethylene glycol, 5 parts of stabilizer and 25 parts of modified filler in terms of mass percentage;

[0042] The preparation method of the modified filler is as follows: kapok fiber, nano-silicate and beryllium oxide are mixed in a mass ratio of 10:6:5, and a modified hydrogen-containing silicone oil cross-linking agent is added to react at 60° C. for 5 hours by stirring, and then washed with deionized water for 4 times, and dried in an oven at 40° C. for 10 minutes.

[0043] The modified hydrogenated silicone oil crosslinking agent is obtained by modifying the hydrogenated silicone oil crosslinking agent with vinyl triethoxysilane and distearoyloxy isopropyl aluminate, and the mass ratio of the hydrogenated silicone oil crosslinking agent, vinyl triethoxysilane and distearoyloxy isopropyl aluminate is 1:0.3:0.5;

[0044] The stabilizers are antioxidant 1076, antioxidant 1010 and light stabilizer 770, and the mass ratio of antioxidant 1076, antioxidant 1010 and light stabilizer 770 is 1:0.5:1;

[0045] The method for preparing the degradable mulch film of this embodiment comprises the following steps:

[0046] S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and then react at 90°C for 4h;

[0047] S2. Evenly mix the above reactants, moisturizer, emulsifier and stabilizer, extrude and granulate them at 170°C using a twin-screw extruder; blow-mold into a film using a blow molding machine when the temperature of zone 1, zone 2 and zone 3 is 160°C, 170°C, 180°C, and the head temperature of the blow molding machine is 170°C, and cool to obtain a degradable mulch film.

[0048] Example 3

[0049] This embodiment provides a degradable mulch film, which is composed of 50 parts of polypropylene, 3 parts of chitosan, 2 parts of sorbitol, 4 parts of stabilizer and 21 parts of modified filler in terms of mass percentage;

[0050] The preparation method of the modified filler is as follows: kapok fiber, nano-silicate and beryllium oxide are mixed in a mass ratio of 10:5:4, a modified hydrogen-containing silicone oil cross-linking agent is added, the mixture is stirred and reacted at 55°C for 4 hours, the mixture is washed with deionized water for 4 times, and the mixture is dried in an oven at 40°C for 10 minutes.

[0051] The modified hydrogenated silicone oil crosslinking agent is obtained by modifying the hydrogenated silicone oil crosslinking agent with vinyl triethoxysilane and distearoyloxy isopropyl aluminate, and the mass ratio of the hydrogenated silicone oil crosslinking agent, vinyl triethoxysilane and distearoyloxy isopropyl aluminate is 1:0.2:0.5;

[0052] The stabilizers are antioxidant 1076, antioxidant 1010 and light stabilizer 770, and the mass ratio of antioxidant 1076, antioxidant 1010 and light stabilizer 770 is 0.6:0.4:1;

[0053] The method for preparing the degradable mulch film of this embodiment comprises the following steps:

[0054] S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and then react at 70°C for 4h;

[0055] S2. The above reactants, chitosan, sorbitol and stabilizer are mixed evenly, and granulated by extrusion using a twin-screw extruder at 160°C; film is blow-molded by a blow molding machine under the conditions that the temperature of zone 1 of the blow molding machine is 157°C, the temperature of zone 2 is 160°C, the temperature of zone 3 is 170°C, and the temperature of the blow molding machine head is 166°C, and the film is cooled to obtain a degradable mulch film.

[0056] Comparative Example 1

[0057] This comparative example is the same as Example 3, except that the kapok fiber in the modified filler is replaced by carbon fiber.

[0058] Comparative Example 2

[0059] This comparative example is the same as Example 3, except that vinyltriethoxysilane is replaced by 3-aminopropyltriethoxysilane.

[0060] Comparative Example 3

[0061] This comparative example is the same as Example 3, except that no modified filler is added.

[0062] Comparative Example 4

[0063] This comparative example is the same as Example 3, except that the modified filler is replaced by a hydrogen-containing silicone oil cross-linking agent.

[0064] Effect verification

[0065] Experimental objects: the degradable mulch films of Examples 1-3 and Comparative Examples 1-4;

[0066] Experimental methods:

[0067] The test site is a corn planting base in Weinan City, Shaanxi Province. The test corn variety is Zhongdan No. 2. The field soil is fertile and well-drained, and the previous crop does not affect the growth of corn. The area of ​​the test plot is 30m 2 , density is 60,000 plants / hm 2 ; Film covering was carried out on April 23, and sowing was carried out on April 25. The degradation and damage of the degradable film were observed, and the effect of the degradable film on plant growth was analyzed;

[0068] Experimental results:

[0069] Result 1:

[0070] During the same growth period, the leaf area was measured by a leaf area meter. The results of the effect of degradable mulch on the leaf area of ​​corn are shown in Table 1.

[0071] Table 1 Effect of degradable mulch film on corn leaf area

[0072] Experimental Group <![CDATA[Leaf area / m 2 > Example 1 928.0 Example 2 932.1 Example 3 1231.2 Comparative Example 1 657.0 Comparative Example 2 660.2 Comparative Example 3 562.2 Comparative Example 4 613.4

[0073] As can be seen from Table 1, the corn leaf area obtained by covering the degradable mulch film of the present invention is 928.0-1231.2, wherein, covering the degradable mulch film of Example 3 of the present invention can significantly increase the corn leaf area, specifically 1231.2; the corn leaf area obtained by covering the degradable mulch film without the modified filler of the present invention is 562.2-660.2. The more leaf area, the better the plant grows. Leaf area is one of the important indicators for measuring plant growth potential. The larger the leaf area, the more photosynthesis the plant can carry out, the more energy it accumulates, and thus promotes growth and development; leaves play a key role in the life activities of plants. They are the core areas of photosynthesis and respiration, and are extremely sensitive to light and water supply. The size of the leaf area directly reflects the strength of the crop growth potential. The larger the leaf area, the more luxuriant the growth, the better the growth potential, and the more dry matter accumulation. Therefore, compared with not covering the degradable mulch film of the present invention, covering the degradable mulch film of the present invention can well promote the growth and development of corn.

[0074] Result 2:

[0075] The results of the effects of degradable mulch on the growth period of corn plants are shown in Table 2.

[0076] Table 2 Effects of degradable mulch on the growth period of corn plants

[0077]

[0078] It can be seen from Table 2 that, on the one hand, each growth period of the corn covered with the degradable mulch film of the present invention is earlier than that of the corn not covered with the degradable mulch film of the present invention. Specifically, compared with the corn not covered with the degradable mulch film of the present invention, the sowing period, emergence period, three-leaf period, jointing period, tasseling period, silking period and maturity period of the corn covered with the degradable mulch film of the present invention are all advanced, rather than only one or several growth periods being advanced. This further proves that covering with the degradable mulch film of the present invention can well promote the growth and development of corn. On the other hand, the full growth period of corn covered with the degradable mulch film of the present invention is much earlier than that of corn not covered with the degradable mulch film of the present invention. Specifically, the full growth period of corn covered with the degradable mulch film of the present invention is 117-126 days, and the full growth period of corn not covered with the degradable mulch film of the present invention is 145-154 days. Among them, the full growth period of corn covered with the degradable mulch film of Example 3 of the present invention is the shortest, which is 117 days; the full growth period of corn covered with the degradable mulch film of Comparative Example 3 is the longest, which is 154 days. The time difference between the two is 37 days, which shows that the degradable mulch film of the present invention has excellent warming and heat preservation effects, and can well promote the growth and development of plants, especially the growth and development of corn.

[0079] Result 3:

[0080] Through field observation, it can be seen that after 40 days of covering with the degradable mulch film of Example 1-Example 2, large vertical and horizontal cracks of 20-25 cm appeared, and after 70 days of covering, 25-30% were degraded into fragments of varying sizes, and after 100 days of covering, more than 35% were degraded into fragments of 1-3 cm, and the unbroken part had lost its elasticity. The degradable mulch film buried in the soil 1-10 cm has begun to decompose after 50 days; after 90 days, about 25% have begun to decompose. After 40 days of covering with the degradable mulch film of Example 3, large vertical and horizontal cracks of 20-25 cm appeared, and after 70 days of covering, 40-45% were degraded into fragments of varying sizes, and after 100 days of covering, more than 50% were degraded into fragments of 1-3 cm, and the unbroken part had lost its elasticity. The degradable mulch film buried in the soil 1-10 cm has begun to decompose after 50 days; after 90 days, about 40% have begun to decompose. The degradation degree of the degradable mulch films of Comparative Examples 1 to 4 was 15-20% by the corn harvest period.

[0081] In order to further demonstrate the beneficial effects of the present invention, the tensile properties of the degradable mulches of Examples 1-3 and Comparative Examples 1-4 were measured transversely and longitudinally in the examples of the present invention. The results showed that the mechanical properties of the degradable mulches of Examples 1-3 of the present invention were good and better than the mechanical properties of the degradable mulches of Comparative Examples 1-4. Among them, the mechanical properties of the degradable mulches of Example 3 were the best.

[0082] In order to further demonstrate the beneficial effects of the present invention, the water vapor permeability of the degradable mulches of Examples 1-3 and Comparative Examples 1-4 was measured in the present invention, and the results showed that the degradable mulches of Examples 1-3 of the present invention can greatly reduce the water vapor permeability, thereby making the prepared degradable mulches have good moisturizing effect, among which the degradable mulches of Example 3 have the best moisturizing effect. The moisturizing effect of the degradable mulches of Comparative Examples 1-4 is average.

[0083] Through the effect verification experiment, it can be known that the formula system of the degradable mulch provided by the present invention is a whole. Specifically, the functions of the raw materials in the degradable mulch support each other and there is an interactive relationship. It is precisely because the functions of the raw materials support each other and there is an interactive relationship that the degradable mulch of the present invention has good degradation performance, good moisturizing effect, good mechanical properties, and good effect of promoting plant growth.

[0084] It should be understood that the disclosed invention is not limited only to the specific method, scheme and material of description, because these all can change.It should also be understood that the terminology used herein is only for the purpose of describing specific embodiment scheme, rather than being intended to limit the scope of the present invention, and the scope of the present invention is only limited to the appended claims.

Claims

1. A degradable mulch film, characterized in that: The degradable ground film is composed of polypropylene, a moisturizer, an emulsifier, a stabilizer and a modified filler; The preparation method of the modified filler is as follows: kapok fiber, nano silicate and beryllium oxide are mixed, and a modified hydrogen-containing silicone oil cross-linking agent is added, and the mixture is stirred at 50-60° C. for 3-5 hours, and the mixture is washed and dried to obtain the modified filler; The modified hydrogen-containing silicone oil crosslinking agent is obtained by modifying the hydrogen-containing silicone oil crosslinking agent with vinyl triethoxysilane and distearoyloxyisopropylaluminate.

2. The degradable mulch film according to claim 1, characterized in that: In terms of weight percentage, the degradable mulch film is composed of 40-60 parts of polypropylene, 2-3 parts of moisturizer, 1-3 parts of emulsifier, 3-5 parts of stabilizer and 20-25 parts of modified filler.

3. The degradable mulch film according to claim 1, characterized in that: The mass ratio of the kapok fiber, the nano-silicate and the beryllium oxide is 10:5-6:3-5.

4. The degradable mulch film according to claim 1, characterized in that: The mass ratio of the hydrogen-containing silicone oil crosslinking agent, the vinyl triethoxysilane and the distearoyloxyisopropylaluminate is 1:0.2-0.3:0.4-0.

5.

5. The degradable mulch film according to claim 1, characterized in that: The moisturizing agent is chitosan or sodium hydroxymethylcellulose.

6. The degradable mulch film according to claim 1, characterized in that: The emulsifier is sorbitol or ethylene glycol.

7. The degradable mulch film according to claim 1, characterized in that: The stabilizers are antioxidant 1076, antioxidant 1010 and light stabilizer 770, and the mass ratio of the antioxidant 1076, the antioxidant 1010 and the light stabilizer 770 is 0.5-1:0.3-0.5:

1.

8. The method for preparing the degradable mulch film according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Add polypropylene and modified filler into the reactor and disperse them evenly by ultrasonication, and react at 60-90°C for 3-4h; S2. The reactants, moisturizer, emulsifier and stabilizer are mixed evenly, extruded into granules by a twin-screw extruder, and blown into a film by a blow molding machine to obtain a degradable mulch film.

9. A degradable mulch film for promoting corn growth, characterized in that: The invention comprises the degradable mulch film according to any one of claims 1 to 7.

10. Use of the degradable mulch film according to any one of claims 1 to 7 in promoting plant growth.

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