Degradable warming composite agricultural mulching film and preparation method thereof

Abstract

The invention relates to the technical field of polymer films, and provides a degradable warming composite agricultural mulching film and a preparation method thereof. The degradable temperature-increasing composite agricultural mulching film comprises a surface layer and a base layer, and the surface layer is prepared from PBAT, PLA and silane modified silicon dioxide containing benzene rings; the base layer is prepared from the following raw material components: PBAT, PLA and silane modified silicon dioxide containing no benzene ring; the mass of the PBAT in the surface layer is greater than that of the PLA; the mass of the PBAT in the base layer is less than that of the PLA. By means of the technical scheme, the problems that in the prior art, a warming mulching film is not prone to degradation and low in strength are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer films, and specifically, to a degradable and temperature-increasing composite agricultural film and a preparation method thereof. Background Art

[0002] Agricultural plastic films, namely plastic films for agricultural use, belong to high molecular compounds and have functions such as heat preservation, water retention, fertilizer retention, improvement of physical and chemical properties of soil, improvement of soil fertility, inhibition of weed growth, reduction of diseases, promotion of plant growth and development, earlier flowering and fruiting, increase in yield, and reduction of labor costs.

[0003] At present, commonly used agricultural plastic films include polyvinyl chloride agricultural plastic films, polyethylene agricultural plastic films, etc., which have strong pollution and are not easily degradable. With the continuous enhancement of human awareness of environmental protection, the application of degradable agricultural plastic films will be more extensive. In addition, in order to ensure the temperature-increasing and heat-preserving effects of agricultural plastic films, silicon dioxide is often added to the raw materials of agricultural plastic films. Although the addition of a large amount of silicon dioxide can improve the temperature-increasing and heat-preserving effects of agricultural plastic films, due to the easy agglomeration of silicon dioxide itself and the easy uneven dispersion, the strength of the agricultural plastic films decreases. Summary of the Invention

[0004] The present invention provides a degradable and temperature-increasing composite agricultural film and a preparation method thereof, which solve the problems of difficult degradation and low strength of temperature-increasing agricultural plastic films in the related art.

[0005] The technical solution of the present invention is as follows: A degradable and temperature-increasing composite agricultural film, comprising a surface layer and a base layer. The raw materials of the surface layer include the following components: PBAT, PLA, and benzene ring-containing silane-modified silicon dioxide; The raw materials of the base layer include the following components: PBAT, PLA, and benzene ring-free silane-modified silicon dioxide; The mass of PBAT in the surface layer > the mass of PLA; the mass of PBAT in the base layer < the mass of PLA.

[0006] As a further technical solution, the mass ratio of PBAT to PLA in the surface layer is 60-70:30.

[0007] In the present invention, it is only necessary that the mass of PBAT in the surface layer > the mass of PLA to ensure the flexibility of the agricultural plastic film. Preferably, the mass ratio of PBAT to PLA in the surface layer is 60-70:30, for example, it can be 60:30, 61.5:30, 62:30, 63:30, 64.5:30, 65:30, 66:30, 67.4:30, 68:30, 69:30, 70:30, etc., and more preferably 60:30, 70:30.

[0008] As a further technical solution, the mass ratio of PLA to PBAT in the base layer is 60-70:30.

[0009] In the base layer of the present invention, the mass of PBAT < the mass of PLA is sufficient to ensure the rigidity and support force of the plastic film. Preferably, the mass ratio of PLA to PBAT in the base layer is 60-70:30. For example, it can be 60:30, 61.5:30, 62:30, 63:30, 64.5:30, 65:30, 66:30, 67.4:30, 68:30, 69:30, 70:30, etc. More preferably, it is 60:30, 70:30.

[0010] As a further technical solution, the mass ratio of the sum of the masses of PBAT and PLA in the surface layer to the mass of benzene ring-containing silane-modified silica is 90-100:10. For example, it can be 90:10, 90.5:10, 91:10, 91.5:10, 92:10, 93:10, 93.5:10, 94:10, 95:10, 96.5:10, 97:10, 98:10, 99:10, 100:10, etc. More preferably, it is 90:10, 100:10.

[0011] As a further technical solution, the mass ratio of the sum of the masses of PBAT and PLA in the base layer to the mass of benzene ring-free silane-modified silica is 90-100:5. For example, it can be 90:5, 90.5:5, 91:5, 91.5:5, 92:5, 93:5, 93.5:5, 94:5, 95:5, 96.5:5, 97:5, 98:5, 99:5, 100:5, etc. More preferably, it is 90:5, 100:5.

[0012] As a further technical solution, the surface layer further includes benzene ring-free silane-modified silica, and the mass of the benzene ring-containing silane-modified silica ≥ 1.5 times the mass of the benzene ring-free silane-modified silica; the base layer further includes benzene ring-containing silane-modified silica, and the mass of the benzene ring-free silane-modified silica ≥ 1.5 times the mass of the benzene ring-containing silane-modified silica.

[0013] In the present invention, it is defined that the surface layer further includes benzene ring-free silane-modified silica, and the mass of the benzene ring-containing silane-modified silica ≥ 1.5 times the mass of the benzene ring-free silane-modified silica; at the same time, the base layer further includes benzene ring-containing silane-modified silica, and the mass of the benzene ring-free silane-modified silica ≥ 1.5 times the mass of the benzene ring-containing silane-modified silica, further improving the strength of the temperature-increasing plastic film.

[0014] As a further technical solution, the mass ratio of the benzene ring-containing silane-modified silica and the non-benzene-ring-containing silane-modified silica in the surface layer is 3:1 to 1.5; the mass ratio of the non-benzene-ring-containing silane-modified silica and the benzene ring-containing silane-modified silica in the base layer is 3:1 to 1.5.

[0015] In the present invention, the mass ratio of the benzene ring-containing silane-modified silica and the non-benzene-ring-containing silane-modified silica in the surface layer is defined as 3:1 to 1.5, and at the same time, the mass ratio of the non-benzene-ring-containing silane-modified silica and the benzene ring-containing silane-modified silica in the base layer is 3:1 to 1.5, further improving the strength of the temperature-increasing ground film.

[0016] As a further technical solution, the raw materials of the benzene ring-containing silane-modified silica in the surface layer include a benzene ring-containing silane and silica with a mass ratio of 0.1 to 1:10; the raw materials of the non-benzene-ring-containing silane-modified silica include a non-benzene-ring-containing silane and silica with a mass ratio of 0.1 to 1:10.

[0017] As a further technical solution, the raw materials of the non-benzene-ring-containing silane-modified silica in the base layer include a non-benzene-ring-containing silane and silica with a mass ratio of 0.1 to 1:10; the raw materials of the benzene ring-containing silane-modified silica include a benzene ring-containing silane and silica with a mass ratio of 0.1 to 1:10.

[0018] The benzene ring-containing silane in the present invention can be any one or more benzene ring-containing silanes in the art. For example, it can be divinyltetraphenyldisilane, 3,5-diphenyloctamethyltetrasilane, 3-phenylheptamethyltrisilane, trimethyl-1,3,5-triphenylcyclotrisilane, 1,1,5,5-tetramethyl-3,3-diphenyltrisilane, hexaphenyldisilane, ethoxytriphenylsilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldimethoxysilane, triethoxy-p-tolylsilane, phenyltrimethoxysilane, etc.

[0019] The non-benzene-ring-containing silane in the present invention can be any one or more non-benzene-ring-containing silanes in the art. For example, it can be a non-benzene-ring-containing amino silane, a non-benzene-ring-containing epoxy silane, a non-benzene-ring-containing vinyl silane, a non-benzene-ring-containing mercapto silane, a non-benzene-ring-containing alkyl silane, etc. Preferably, it is a non-benzene-ring-containing alkyl silane. For example, it can be octyltrimethoxysilane, n-hexyltrimethoxysilane, triethoxypentylsilane, N-propyltriethoxysilane, octylmethyldiethoxysilane, dimethyldimethoxysilane, etc.

[0020] The preparation method of the silane-modified silica in the present invention can be any conventional silane modification method in the art. Preferably, silica is dispersed in water, a silane is added for modification, and then dried to obtain the silane-modified silica.

[0021] In the present invention, the thickness ratio of the surface layer to the base layer can be any ratio, such as 1:99, 1:89, 1:79, 1:69, 1:59, 1:49, 1:39, 1:29, 1:19, 1:9, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 9:1, 19:1, 29:1, 39:1, 49:1, 59:1, 69:1, 79:1, 89:1, 99:1, etc., and preferably 1:4 to 4:1.

[0022] The present invention also provides a method for preparing a degradable temperature-increasing composite agricultural film for preparing the above-mentioned degradable temperature-increasing composite agricultural film, which includes the following steps: separately melting and uniformly mixing the raw materials of the surface layer and the raw materials of the base layer, and then co-extruding, blow molding, and cooling to obtain the degradable temperature-increasing composite agricultural film.

[0023] In the present invention, the technology of independently melting and mixing the raw materials of the surface layer and the base layer and then co-extruding is adopted to realize the compounding of raw materials with different properties, effectively improving the uniformity and stability of the film forming of the agricultural film, and ensuring the consistency of product quality.

[0024] The present invention also provides the application of the above-mentioned degradable temperature-increasing composite agricultural film or the degradable temperature-increasing composite agricultural film prepared by the above-mentioned preparation method in agricultural films.

[0025] The agricultural film provided by the present invention has excellent temperature-increasing characteristics, can significantly increase the soil temperature, create a good warm environment for crop growth, promote the root development and metabolism of crops, and help increase the yield and quality of crops; at the same time, its mechanical properties are outstanding, with both high strength and flexibility, and can resist external forces such as wind and sand and mechanical operations during field use, extending the service life of the agricultural film. In addition, the degradable raw materials adopted can be gradually degraded in the natural environment through microbial decomposition, photo-oxidative degradation and other ways after the agricultural film completes its service cycle, effectively solving problems such as soil pollution caused by the residue of traditional agricultural films, and providing strong technical support for promoting the green and low-carbon development of agriculture and building an eco-friendly agriculture.

[0026] The working principle and beneficial effects of the present invention are as follows: 1. The degradable temperature-increasing composite agricultural film provided in the present invention includes a surface layer and a base layer. The surface layer uses PBAT as the main base material to endow the film with good flexibility, which can effectively resist external forces such as scraping by farm tools and pushing by crop roots, and ensure the integrity of the film during the service life. The base layer uses PLA as the main base material, which improves the rigidity and support force of the film, avoids collapse and deformation in the soil due to gravity or external forces, and enhances the overall stability. In addition, the degradable characteristics of PBAT and PLA enable the film to be gradually decomposed by microbial action in the natural environment after use, avoiding various problems caused by the residue of traditional films and promoting the green and sustainable development of agriculture.

[0027] 2. The addition of silica in the present invention can effectively absorb, store and conduct heat, realize the increase of soil temperature, provide a suitable warm environment for the early growth of crops, and promote seed germination and seedling development. In addition, by adding silane-modified silica containing benzene rings in the surface layer and silane-modified silica without benzene rings in the base layer, the strength of the temperature-increasing film is improved. Specific Embodiments

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0029] The parameters of the raw materials in the following examples and comparative examples are as follows: PBAT is PBAT TH801T; PLA is PLA LX175; The particle size of silica is 20 nm.

[0030] Example 1 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain silane-modified silica containing benzene rings; S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyl dimethoxysilane for modification, and dry to obtain silane-modified silica without benzene rings; S3. After melting and uniformly mixing the raw materials of the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of silane-modified silica containing benzene rings) and the raw materials of the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of silane-modified silica without benzene rings) respectively, co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0031] Example 2 S1. Disperse 10 parts of silica in 100 parts of water, add 0.5 part of diphenyldimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Disperse 10 parts of silica in 100 parts of water, add 0.5 part of octylmethyldiethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S3. After melting and uniformly mixing the raw materials for the surface layer (60 parts of PBAT, 30 parts of PLA, 10 parts of benzene ring-containing silane-modified silica) and the raw materials for the base layer (30 parts of PBAT, 60 parts of PLA, 5 parts of benzene ring-free silane-modified silica) respectively, co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0032] Example 3 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyldimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyldimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S3. After melting and uniformly mixing the raw materials for the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of modified silica composed of benzene ring-containing silane-modified silica and benzene ring-free silane-modified silica with a mass ratio of 3:4) and the raw materials for the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of modified silica composed of benzene ring-free silane-modified silica and benzene ring-containing silane-modified silica with a mass ratio of 3:4) respectively, co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0033] Example 4 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyldimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyldimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S3. Respectively melt and uniformly mix the raw materials for the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of modified silica composed of a 1:1 mass ratio of benzene ring-containing silane-modified silica and benzene ring-free silane-modified silica), and the raw materials for the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of modified silica composed of a 1:1 mass ratio of benzene ring-free silane-modified silica and benzene ring-containing silane-modified silica), then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0034] Example 5 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica. S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyl dimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica. S3. Respectively melt and uniformly mix the raw materials for the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of modified silica composed of a 3:2 mass ratio of benzene ring-containing silane-modified silica and benzene ring-free silane-modified silica), and the raw materials for the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of modified silica composed of a 3:2 mass ratio of benzene ring-free silane-modified silica and benzene ring-containing silane-modified silica), then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0035] Example 6 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica. S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyl dimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica. S3. Respectively melt and uniformly mix the raw materials for the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of modified silica composed of a 3:1.5 mass ratio of benzene ring-containing silane-modified silica and benzene ring-free silane-modified silica), and the raw materials for the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of modified silica composed of a 3:1.5 mass ratio of benzene ring-free silane-modified silica and benzene ring-containing silane-modified silica), then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0036] Example 7 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyldimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S3. Respectively melt and mix the surface layer raw materials (70 parts of PBAT, 30 parts of PLA, 10 parts of modified silica composed of benzene ring-containing silane-modified silica and benzene ring-free silane-modified silica with a mass ratio of 3:1), and the base layer raw materials (30 parts of PBAT, 70 parts of PLA, 5 parts of modified silica composed of benzene ring-free silane-modified silica and benzene ring-containing silane-modified silica with a mass ratio of 3:1) evenly, then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0037] Comparative Example 1 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Respectively melt and mix the surface layer raw materials (70 parts of PBAT, 30 parts of PLA, 10 parts of benzene ring-containing silane-modified silica), and the base layer raw materials (30 parts of PBAT, 70 parts of PLA, 5 parts of benzene ring-containing silane-modified silica) evenly, then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0038] Comparative Example 2 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyldimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S2. Respectively melt and mix the surface layer raw materials (70 parts of PBAT, 30 parts of PLA, 10 parts of benzene ring-free silane-modified silica), and the base layer raw materials (30 parts of PBAT, 70 parts of PLA, 5 parts of benzene ring-free silane-modified silica) evenly, then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0039] Comparative Example 3 S1. Disperse 10 parts of silica in 100 parts of water, add 1 part of methylphenyl dimethoxysilane for modification, and dry to obtain benzene ring-containing silane-modified silica; S2. Disperse 10 parts of silica in 100 parts of water, add 1 part of dimethyldimethoxysilane for modification, and dry to obtain benzene ring-free silane-modified silica; S3. Respectively melt and uniformly mix the raw materials of the surface layer (70 parts of PBAT, 30 parts of PLA, 10 parts of benzene-ring-free silane-modified silica), and the raw materials of the base layer (30 parts of PBAT, 70 parts of PLA, 5 parts of benzene-ring-containing silane-modified silica), then co-extrude, blow mold, and cool to obtain a degradable temperature-increasing composite agricultural film with a surface layer:base layer thickness ratio of 4:1.

[0040] The composite agricultural films with a thickness of 0.01 mm obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were tested for tensile load according to the method in GB / T 35795-2017; the test results are recorded in Table 1.

[0041] Table 1 Tensile Load of Composite Agricultural Films

[0042] As can be seen from Table 1, compared with Comparative Examples 1 to 3, the composite agricultural films provided in Examples 1 to 7 have a high tensile load and meet the requirements of various indicators in GB / T 35795-2017, indicating that adding benzene-ring-containing silane-modified silica in the surface layer and benzene-ring-free silane-modified silica in the base layer improves the strength of the composite agricultural film.

[0043] In addition, compared with the plastic films in the prior art, after using the composite agricultural film provided by the present invention, the soil temperature at a distance of 5 cm from the plastic film is 3 - 4 °C higher after testing, indicating that the composite agricultural film provided by the present invention has good temperature-increasing and heat-preserving effects.

[0044] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A degradable temperature-increasing composite agricultural film, comprising a surface layer and a base layer, characterized in that, The raw materials of the surface layer include the following components: PBAT, PLA, and benzene ring-containing silane-modified silica; The raw materials of the base layer include the following components: PBAT, PLA, and benzene ring-free silane-modified silica; In the surface layer, the mass of PBAT > the mass of PLA; in the base layer, the mass of PBAT < the mass of PLA.

2. The biodegradable temperature-increasing composite agricultural film according to claim 1, wherein, In the surface layer, the mass ratio of PBAT to PLA is 60-70:30; in the base layer, the mass ratio of PLA to PBAT is 60-70:

30.

3. The degradable temperature-increasing composite agricultural film according to claim 2, wherein, In the surface layer, the mass ratio of the sum of the masses of PBAT and PLA to benzene ring-containing silane-modified silica is 90-100:10; In the base layer, the mass ratio of the sum of the masses of PBAT and PLA to benzene ring-free silane-modified silica is 90-100:

5.

4. The degradable temperature-increasing composite agricultural film according to claim 3, characterized in that, The surface layer further includes benzene ring-free silane-modified silica, and the mass of the benzene ring-containing silane-modified silica ≥ 1.5 times the mass of the benzene ring-free silane-modified silica; the base layer further includes benzene ring-containing silane-modified silica, and the mass of the benzene ring-free silane-modified silica ≥ 1.5 times the mass of the benzene ring-containing silane-modified silica.

5. The degradable temperature-increasing composite agricultural film according to claim 4, characterized in that, In the surface layer, the mass ratio of the benzene ring-containing silane-modified silica to the benzene ring-free silane-modified silica is 3:1-1.5; in the base layer, the mass ratio of the benzene ring-free silane-modified silica to the benzene ring-containing silane-modified silica is 3:1-1.

5.

6. The degradable temperature-increasing composite agricultural film according to claim 5, wherein The raw materials of the benzene ring-containing silane-modified silica in the surface layer include benzene ring-containing silane and silica with a mass ratio of 0.1-1:10; the raw materials of the benzene ring-free silane-modified silica include benzene ring-free silane and silica with a mass ratio of 0.1-1:

10.

7. The degradable temperature-increasing composite agricultural film according to claim 6, characterized in that, The raw materials of the benzene ring-free silane-modified silica in the base layer include benzene ring-free silane and silica with a mass ratio of 0.1-1:10; the raw materials of the benzene ring-containing silane-modified silica include benzene ring-containing silane and silica with a mass ratio of 0.1-1:

10.

8. A degradable temperature-increasing composite agricultural film according to any one of claims 1 to 7, characterized in that, The thickness ratio of the surface layer to the base layer is 1:4-4:

1.

9. A preparation method of a degradable and temperature-increasing composite agricultural film for preparing the degradable and temperature-increasing composite agricultural film according to any one of claims 1 to 8, characterized in that, It includes the following steps: respectively melt and mix the raw materials of the surface layer and the raw materials of the base layer evenly, then co-extrude, blow mold, and cool to obtain a degradable and heat-increasing composite agricultural film. 1°. The application of the degradable and heat-increasing composite agricultural film according to any one of claims 1-8 or the degradable and heat-increasing composite agricultural film prepared by the preparation method according to claim 9 in agricultural films.

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