High-strength temperature-increasing composite agricultural mulching film and preparation method thereof

Abstract

The invention relates to the technical field of polymer films, and provides a high-strength temperature-increasing composite agricultural mulching film and a preparation method thereof. The high-strength temperature-increasing composite agricultural mulching film comprises a surface layer and a base layer, and the surface layer is prepared from PBAT, PLA, silicon dioxide and a first compatilizer; the base layer is prepared from the following raw material components: PBAT, PLA, silicon dioxide and a second compatilizer; the molecular structure of the first compatilizer comprises a phenyl group and an epoxy group; the molecular structure of the second compatilizer comprises an epoxy group and does not comprise a phenyl group; 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. According to the technical scheme, the problem of low strength of the mulching film prepared from the PLA and PBAT blended material in the prior art is solved.

Description

Technical Field

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

[0002] Agricultural film is a kind of polymer compound and is a plastic film popularized and applied in agriculture by the country, which has the functions of increasing temperature and humidity and promoting crop growth. With the continuous enhancement of human awareness of environmental protection, China has focused on the research and development of degradable agricultural films. There are currently photodegradable agricultural films, biodegradable agricultural films, and controllable photodegradable and microbial degradable agricultural films.

[0003] The currently researched and developed degradable agricultural film materials include polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), poly(propylene carbonate) (PPC), polyhydroxyalkanoates (PHA), etc. The commonly used blend material of PLA and PBAT has poor compatibility between PLA and PBAT, resulting in low strength of the agricultural film. Summary of the Invention

[0004] The present invention provides a high-strength heat-increasing composite agricultural film and a preparation method thereof, which solves the problem of low strength of the agricultural film prepared from the blend material of PLA and PBAT in the related art.

[0005] The technical solution of the present invention is as follows: A high-strength heat-increasing composite agricultural film includes a surface layer and a base layer. The raw materials of the surface layer include the following components: PBAT, PLA, silicon dioxide, and a first compatibilizer; The raw materials of the base layer include the following components: PBAT, PLA, silicon dioxide, and a second compatibilizer; The molecular structure of the first compatibilizer includes a phenyl group and an epoxy group; the molecular structure of the second compatibilizer includes an epoxy group and does not include a phenyl group; 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] In the composite agricultural film provided by the present invention, the surface layer uses PBAT as the main material. The excellent flexibility and ductility of PBAT endow the agricultural film with good tensile and tear resistance, which can effectively resist external force damage; the base layer uses PLA as the main material, and its rigid characteristics cooperate with the surface layer to enhance the overall structural stability of the agricultural film, making the agricultural film not easily damaged during laying and use, and extending its service life. The addition of silicon dioxide can effectively absorb and store solar radiation heat, increase the soil temperature through heat conduction, be beneficial to crop growth, and promote the root development and metabolism of crops.

[0007] The composite agricultural film provided in the present invention uses PBAT and PLA, both of which are biodegradable materials. After the usage cycle of this film is completed, it can be gradually degraded in the natural environment, reducing white pollution in farmland and contributing to the green and sustainable development of agriculture. In addition, different raw material ratios in the surface layer enable the film to have good heat preservation and moisture retention properties, which can effectively reduce soil moisture evaporation, maintain soil humidity, reduce irrigation frequency, achieve water conservation and efficiency increase, create an excellent soil environment for crop growth, and improve crop yield and quality.

[0008] In the present invention, the first compatibilizer can be any one or more compounds containing phenyl and epoxy groups in the molecular structure. For example, it can be one or more of 4-[2-(2-epoxyethyl)ethoxy]benzoic acid 4-[2-(2-epoxyethyl)ethoxy]phenyl ester, methyl 4-(oxiranylmethoxy)phenylpropionate, diglycidyl phthalate, resorcinol diglycidyl ether, 1,4-bis(epoxypropyl)benzene, preferably one or more of 4-[2-(2-epoxyethyl)ethoxy]benzoic acid 4-[2-(2-epoxyethyl)ethoxy]phenyl ester, methyl 4-(oxiranylmethoxy)phenylpropionate, diglycidyl phthalate, and more preferably diglycidyl phthalate.

[0009] In the present invention, the second compatibilizer can be any one or more compounds containing epoxy groups and not including phenyl in the molecular structure. For example, it can be one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(7-oxabicyclo[4.1.0]heptan-3-ylmethyl) adipate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, 4,5-epoxytetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, 1,6-hexanediol diglycidyl ether, preferably one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(7-oxabicyclo[4.1.0]heptan-3-ylmethyl) adipate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, 4,5-epoxytetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, and more preferably adipic acid diglycidyl ester.

[0010] As a further technical solution, the mass ratio of PBAT to PLA in the surface layer is 60 to 70:30, for example, it can be 60:30, 61:30, 61.5:30, 62:30, 62.5:30, 63:30, 64:30, 65:30, 65.5:30, 66:30, 66.5:30, 67:30, 67.5:30, 68:30, 69:30, 70:30, etc., and preferably 60:30 or 70:30.

[0011] As a further technical solution, the mass ratio of PLA to PBAT in the base layer is 60 to 70:30, for example, it can be 60:30, 61:30, 61.5:30, 62:30, 62.5:30, 63:30, 64:30, 65:30, 65.5:30, 66:30, 66.5:30, 67:30, 67.5:30, 68:30, 69:30, 70:30, etc., and preferably 60:30 or 70:30.

[0012] 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 silica is 90 to 100:10, for example, it can be 90:10, 91:10, 91.5:10, 92:10, 92.5:10, 93:10, 93.5:10, 94:10, 94.5:10, 95:10, 95.5:10, 96:10, 96.5:10, 97:10, 97.5:10, 98:10, 99:10, 100:10, etc., and preferably 90:10 or 100:10.

[0013] 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 silica is 90 to 100:5, for example, it can be 90:10, 91:10, 91.5:10, 92:10, 92.5:10, 93:10, 93.5:10, 94:10, 94.5:10, 95:10, 95.5:10, 96:10, 96.5:10, 97:10, 97.5:10, 98:10, 99:10, 100:10, etc., and preferably 90:10 or 100:10.

[0014] 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 the first compatibilizer is 100:1 to 5, for example, it can be 100:1, 100:1.2, 100:1.5, 100:1.7, 100:2, 100:2.5, 100:2.8, 100:3, 100:3.5, 100:4, 100:4.2, 100:4.5, 100:4.7, 100:5, etc., and preferably 100:1 or 100:5.

[0015] 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 the second compatibilizer is 100:1 to 5. For example, it can be 100:1, 100:1.2, 100:1.5, 100:1.7, 100:2, 100:2.5, 100:2.8, 100:3, 100:3.5, 100:4, 100:4.2, 100:4.5, 100:4.7, 100:5, etc. Preferably, it is 100:1 or 100:5.

[0016] In the present invention, the thickness ratio of the surface layer to the base layer can be any ratio. For example, it can be 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. Preferably, it is 1:4 to 4:1.

[0017] The present invention also provides a method for preparing a high-strength heat-increasing composite agricultural film for preparing the high-strength heat-increasing composite agricultural film, which includes the following steps: respectively melting and uniformly mixing the raw materials of the surface layer and the raw materials of the base layer, then co-extruding, blow molding, and cooling to obtain the high-strength heat-increasing composite agricultural film.

[0018] In the present invention, the composite agricultural film is prepared by a melt mixing co-extrusion blow molding process. The raw materials of the surface layer and the base layer are respectively melt mixed to ensure uniform mixing of PBAT, PLA, and silicon dioxide in each layer, laying a foundation for the high-strength performance of the agricultural film. At the same time, the co-extrusion process enables the surface layer and the base layer to be tightly combined, forming a continuous and stable composite structure, effectively avoiding delamination phenomena, greatly ensuring the overall tensile resistance and puncture resistance of the agricultural film, enabling it to withstand the damage of mechanical external forces, etc. during the laying and use processes, and extending the service life. In addition, the blow molding process endows the agricultural film with good uniformity and appropriate thickness, ensuring that the agricultural film fits tightly with the soil when covering the farmland, reducing heat loss, and ensuring the heat-increasing and heat-preserving effects.

[0019] The present invention also provides the application of the high-strength heat-increasing composite agricultural film or the high-strength heat-increasing composite agricultural film prepared by the preparation method in agricultural films.

[0020] The working principle and beneficial effects of the present invention are as follows: In the present invention, a compound including phenyl and epoxy groups in its molecular structure is added as a compatibilizer to the surface layer, and a compound including epoxy groups but not including phenyl in its molecular structure is added as a compatibilizer to the base layer, improving the compatibility of the PLA and PBAT blend material and achieving the effect of improving the strength of the composite agricultural film. Detailed implementation manners

[0021] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. 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.

[0022] 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 silicon dioxide is 20 nm.

[0023] Example 1 S1. After uniformly mixing 75 parts of PBAT, 25 parts of PLA, 10 parts of silicon dioxide, and 3 parts of resorcinol diglycidyl ether at 175 °C, a surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 60 parts of PLA, 5 parts of silicon dioxide, and 3 parts of 1,6 - hexanediol diglycidyl ether at 175 °C, a base layer raw material is obtained; S3. Co - extrude, blow - mold, and cool the surface layer raw material and the base layer raw material at 180 °C to obtain a high - strength temperature - increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0024] Example 2 S1. After uniformly mixing 70 parts of PBAT, 30 parts of PLA, 10 parts of silicon dioxide, and 5 parts of resorcinol diglycidyl ether at 175 °C, a surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 70 parts of PLA, 5 parts of silicon dioxide, and 5 parts of 1,6 - hexanediol diglycidyl ether at 175 °C, a base layer raw material is obtained; S3. Co - extrude, blow - mold, and cool the surface layer raw material and the base layer raw material at 180 °C to obtain a high - strength temperature - increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0025] Example 3 S1. After uniformly mixing 60 parts of PBAT, 30 parts of PLA, 10 parts of silicon dioxide, and 1 part of resorcinol diglycidyl ether at 175 °C, a surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 60 parts of PLA, 5 parts of silicon dioxide, and 1 part of 1,6 - hexanediol diglycidyl ether at 175 °C, a base layer raw material is obtained; S3. Co-extrude the surface layer raw material and the base layer raw material at 180 °C, blow mold, and cool to obtain a high-strength temperature-increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0026] Example 4 The difference from Example 2 is only that resorcinol diglycidyl ether is replaced with an equal amount of diglycidyl phthalate.

[0027] Example 5 The difference from Example 4 is only that 1,6-hexanediol diglycidyl ether is replaced with an equal amount of diglycidyl adipate.

[0028] Comparative Example 1 S1. After uniformly mixing 70 parts of PBAT, 30 parts of PLA, 10 parts of silica, and 5 parts of resorcinol diglycidyl ether at 175 °C, the surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 70 parts of PLA, 5 parts of silica, and 5 parts of resorcinol diglycidyl ether at 175 °C, the base layer raw material is obtained; S3. Co-extrude the surface layer raw material and the base layer raw material at 180 °C, blow mold, and cool to obtain a high-strength temperature-increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0029] Comparative Example 2 S1. After uniformly mixing 70 parts of PBAT, 30 parts of PLA, 10 parts of silica, and 5 parts of 1,6-hexanediol diglycidyl ether at 175 °C, the surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 70 parts of PLA, 5 parts of silica, and 5 parts of 1,6-hexanediol diglycidyl ether at 175 °C, the base layer raw material is obtained; S3. Co-extrude the surface layer raw material and the base layer raw material at 180 °C, blow mold, and cool to obtain a high-strength temperature-increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0030] Comparative Example 3 S1. After uniformly mixing 70 parts of PBAT, 30 parts of PLA, 10 parts of silica, and 5 parts of 1,6-hexanediol diglycidyl ether at 175 °C, the surface layer raw material is obtained; S2. After uniformly mixing 30 parts of PBAT, 70 parts of PLA, 5 parts of silica, and 5 parts of resorcinol diglycidyl ether at 175 °C, the base layer raw material is obtained; S3. Co-extrude the surface layer raw material and the base layer raw material at 180 °C, blow mold, and cool to obtain a high-strength temperature-increasing composite agricultural film with a surface layer: base layer thickness ratio of 4:1.

[0031] The composite agricultural mulch films with a thickness of 0.01 mm obtained in Examples 1-5 and Comparative Examples 1-3 were tested for tensile load according to the method in GB / T 35795-2017; the test results were recorded in Table 1.

[0032] Table 1 Tensile Load of Composite Agricultural Mulch Films

[0033] As can be seen from Table 1, compared with Comparative Examples 1-3, the composite agricultural mulch films provided in Examples 1-5 have a high tensile load and meet the requirements of various indicators in GB / T 35795-2017, indicating that adding a compound with phenyl and epoxy groups in the molecular structure as a compatibilizer to the surface layer and adding a compound with epoxy groups but without phenyl in the molecular structure as a compatibilizer to the base layer improve the strength of the composite agricultural mulch film.

[0034] In addition, compared with the mulch films in the prior art, after using the composite agricultural mulch film provided by the present invention, the soil temperature at a distance of 5 cm from the mulch film is 2-3 °C higher after testing, indicating that the composite agricultural mulch film provided by the present invention has good heat increase and heat preservation effects.

[0035] 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 high-strength heat-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, silica, and a first compatibilizer; The raw materials of the base layer include the following components: PBAT, PLA, silica, and a second compatibilizer; The molecular structure of the first compatibilizer includes a phenyl group and an epoxy group; the molecular structure of the second compatibilizer includes an epoxy group and does not include a phenyl group; 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 high-strength temperature-increasing composite agricultural film according to claim 1, characterized in that, The first compatibilizer includes one or more of 4-[2-(2-epoxyethyl)ethoxy]benzoic acid 4-[2-(2-epoxyethyl)ethoxy]phenyl ester, methyl 4-(oxiranylmethoxy)phenylpropionate, diglycidyl phthalate, resorcinol diglycidyl ether, 1,4-bis(epoxypropyl)benzene; The second compatibilizer includes one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(7-oxabicyclo[4.1.0]heptan-3-ylmethyl) adipate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, 4,5-epoxytetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, 1,6-hexanediol diglycidyl ether; 3. The high-strength temperature-increasing composite agricultural film according to claim 2, characterized in that, The first compatibilizer includes one or more of 4-[2-(2-epoxyethyl)ethoxy]benzoic acid 4-[2-(2-epoxyethyl)ethoxy]phenyl ester, methyl 4-(oxiranylmethoxy)phenylpropionate, diglycidyl phthalate; 4. The high-strength temperature-increasing composite agricultural film according to claim 2, wherein The second compatibilizer includes one or more of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(7-oxabicyclo[4.1.0]heptan-3-ylmethyl) adipate, cyclohexane-1,2-dicarboxylic acid diglycidyl ester, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, 4,5-epoxytetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester; 5. The high-strength heat-increasing composite agricultural film according to claim 1, characterized in that, 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.

6. The high-strength temperature-increasing composite agricultural film according to claim 1, wherein, In the surface layer, the mass ratio of the sum of the masses of PBAT and PLA to silica is 90 - 100:10; In the base layer, the mass ratio of the sum of the masses of PBAT and PLA to silica is 90 - 100:

5.

7. The high-strength temperature-increasing composite agricultural film according to claim 1, wherein In the surface layer, the mass ratio of the sum of the masses of PBAT and PLA to the first compatibilizer is 100:1 - 5; In the base layer, the mass ratio of the sum of the masses of PBAT and PLA to the second compatibilizer is 100:1 - 5.

8. A high-strength heat-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 high-strength heat-increasing composite agricultural film, which is used to prepare the high-strength heat-increasing composite agricultural film according to any one of claims 1 to 8, and is 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 high-strength heat-increasing composite agricultural film.

10. Use of the high-strength heat-increasing composite agricultural film according to any one of claims 1 to 8 or the high-strength heat-increasing composite agricultural film prepared by the preparation method according to claim 9 in agricultural films.

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