Three-color composite mulching film and preparation method thereof

Abstract

The invention discloses a three-color composite mulching film and a preparation method thereof. The three-color composite mulching film comprises a transparent bottom layer, a middle black layer, a surface silver layer and a transparent layer located in the middle of the film. The transparent bottom layer has hydrophilicity, and does not form dewdrops on the surface of the film layer to reflect sunlight, so that the light transmittance of the mulching film is effectively increased, and the ground temperature and the soil energy storage are improved. And the middle black layer can efficiently block light rays and can effectively inhibit growth of various weeds. The surface silver layer can highly reflect sunlight, can improve photosynthesis of bottom leaves of crops, and can avoid aphids at the same time.

Description

Technical Field

[0001] This invention relates to the field of agricultural plastic products technology, specifically to a three-color composite mulch film and its preparation method. Background Technology

[0002] Mulch film is a plastic film used to cover the surface of planting soil. Its functions are to maintain soil temperature and moisture, preserve soil structure, prevent pests from attacking crops, and prevent microbial diseases, thereby promoting plant growth. While the application of plastic mulch film is widespread, some problems still exist, such as unreasonable thickness settings, poor mechanical properties, and limited functionality.

[0003] Currently, plastic film has evolved from ordinary film to single-color film (such as black and white film), and then to multi-color film (such as black and white striped film and three-color composite film). Existing research shows that black film has low light transmittance, making it difficult for heat to be transferred to the soil, which can prevent soil moisture evaporation and significantly inhibit weed growth; however, it can also lead to unfavorable crop growth, causing delayed maturity and reduced yield. At the same time, black has a significant heat absorption effect, making the film prone to accelerated aging due to heat absorption, thus reducing its lifespan. Transparent film, due to its better light transmittance, has a good effect on warming and moisturizing the soil after covering it, but it can also cause weeds to grow vigorously under the film, thus affecting crop yield. Black and white striped film, i.e., film with black sides and a white middle, also suffers from premature aging due to heat absorption. The mulch film exhibits the drawback of rotting, which can pollute the soil and affect crop yields. Furthermore, in silver-gray and black composite mulch films, if the silver-gray layer does not reflect light effectively, the film is prone to aging faster due to heat absorption, thus reducing its lifespan.

[0004] CN 109220420B discloses a high-strength, three-layer, two-color agricultural mulch film and its preparation method. The film includes an inner layer, a middle layer, and an outer layer. The inner layer is prepared using a black masterbatch, the middle layer using a white masterbatch, and the outer layer using silver-gray masterbatch. The resulting mulch film has a black bottom layer and a silver-gray outer layer. However, this invention does not disclose the composition of the silver-gray masterbatch, and the reflectivity of the outer film to sunlight is unknown. Furthermore, this invention requires the addition of long-life masterbatch containing lanthanum trifluoromethanesulfonate and alkyl samarium compounds, resulting in high manufacturing costs.

[0005] CN 111955248B discloses a three-layer composite black and white alternating color mulch film of polyethylene and its preparation method. The resulting mulch film has a solid white composite layer as the middle layer, and black and white covering layers as the inner and outer layers, respectively. The black and white alternating color scheme of the mulch film is that the white part is in the middle and the black parts are on both sides. However, the function of this three-layer composite black and white alternating color mulch film is still limited, and it is difficult to effectively promote increased crop yields and income. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a three-color composite mulch film and its preparation method. The three-color composite mulch film of this invention comprises a transparent bottom layer, a middle black layer, a surface silver layer, and a transparent layer located in the middle of the composite mulch film. Its transparent bottom layer is hydrophilic, preventing the formation of dew on the film surface and thus avoiding sunlight reflection. Therefore, the transparent bottom layer can effectively increase the film's light transmittance, improve ground temperature, and enhance soil energy storage. The middle black layer can efficiently... By blocking light, it can effectively suppress the growth of various weeds. The silvery surface layer can highly reflect sunlight, which can improve the photosynthesis of the lower leaves of crops, while also repelling aphids.

[0007] One objective of this invention is to provide a three-color composite mulch film, comprising a bottom layer, an intermediate layer, and a top layer. The bottom layer is a transparent layer A, and a transparent layer B is disposed above the transparent layer A. The intermediate layer is disposed on the bottom layer and located on both sides of the transparent layer B, and the top layer is disposed on the intermediate layer and located on both sides of the transparent layer B. The intermediate layer is a black layer, and the top layer is a silver layer. The silver-black composite film formed by the black intermediate layer and the silver top layer is arranged alternately with the thin film of the transparent layer B. The composite film composed of the transparent layer B and the transparent layer A constitutes the intermediate transparent layer of the composite mulch film.

[0008] The raw materials for preparing the transparent layer A include polyethylene and hydrophilic additives, and the light transmittance of the transparent layer A is ≥85%.

[0009] Preferably, the light transmittance of the transparent layer A obtained by the present invention is >90%. Because of the presence of a hydrophilic additive in the transparent layer A, dew droplets are less likely to form on the surface of the transparent layer film, thereby improving the light transmittance of the transparent layer A.

[0010] The polyethylene is at least one of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene. The type of polyethylene can be selected by those skilled in the art based on the application performance requirements of the composite film.

[0011] Preferably, the raw materials for preparing the transparent layer A include the following components in parts by weight: 75-87 parts linear low-density polyethylene, 2-10 parts low-density polyethylene, 1-10 parts hydrophilic additives, and 0.5-5 parts processing aids.

[0012] The processing aids include at least one of antioxidants, ultraviolet absorbers, and lubricants.

[0013] The hydrophilic additive can be at least one of nonionic surfactants, anionic surfactants, and amphoteric surfactants. And / or, the hydrophilic additive can be commercially available anti-fogging masterbatch for agricultural films.

[0014] The transmittance of the transparent layer A can be obtained by testing according to the test method described in GB / T 2410–2008.

[0015] The raw materials for preparing the black layer include polyethylene and black pigment, and the light transmittance of the black layer is ≤5%.

[0016] The polyethylene is at least one of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene.

[0017] Preferably, the raw materials for preparing the black layer include the following components in parts by weight: 75-85 parts linear low-density polyethylene, 2-10 parts low-density polyethylene, 1-8 parts black pigment, and 0.5-5 parts processing aids.

[0018] The processing aids include at least one of antioxidants, ultraviolet absorbers, and lubricants.

[0019] The black pigment can be a common powdered black pigment such as carbon black, Ketjen black, or graphite. Preferably, the average particle size of the carbon black is 10-40 nm. And / or, the black pigment can be a black masterbatch comprising black pigment.

[0020] Preferably, the black pigment is a black masterbatch.

[0021] The transmittance of the black layer can be tested using the test method described in GB / T 2410–2008.

[0022] The raw materials for preparing the silver layer include polyethylene and a silver-gray dye. Its solar reflectivity is ≥85%.

[0023] The polyethylene is at least one of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene.

[0024] Preferably, the raw materials for preparing the silver layer include the following components in parts by weight: 75-85 parts linear low-density polyethylene, 2-10 parts low-density polyethylene, 1-8 parts silver-gray dye, and 0.5-5 parts processing aids.

[0025] The processing aids include at least one of antioxidants, ultraviolet absorbers, and lubricants.

[0026] The silver-gray dye comprises flake-shaped aluminum powder. The average particle size of the aluminum powder is 2~50 μm.

[0027] The aluminum powder can be added directly or introduced into the raw materials for preparing the silver layer in the form of a masterbatch. Preferably, the silver-gray dye is a masterbatch comprising flake aluminum powder.

[0028] The solar reflectivity of the silver layer can be tested using the test method described in GB / T 2410–2008.

[0029] The raw materials for preparing the transparent layer B include polyethylene, hydrophobic agent, and heat-insulating agent.

[0030] Preferably, the raw materials for preparing the transparent layer B include the following components in parts by weight: 70-80 parts linear low-density polyethylene, 2-10 parts low-density polyethylene, 1-10 parts hydrophobic agent, 5-15 parts heat-insulating agent, and 0.5-5 parts processing aid.

[0031] The hydrophobic agent includes silane-modified silica; preferably, the silane is hexamethyldisilazane.

[0032] The silane-modified silica has an average particle size of 10-100 nm, and can be specifically selected from... At least one of Aerosil® R812, Huifu HB-612, HB-615, HB-620, and HB-630.

[0033] The heat-insulating agent is hydrotalcite; preferably, the average particle size of the hydrotalcite is 0.5~5μm, more preferably, the average particle size of the hydrotalcite is 1~3μm.

[0034] When preparing the raw materials for transparent layer B, the hydrophobic agent and the heat-insulating agent can be added directly or introduced in the form of masterbatch.

[0035] The linear low-density polyethylene and low-density polyethylene in the above-mentioned transparent layer A, black layer, silver layer, and transparent layer B can be the same or different. Preferably, the melt flow rate of the linear low-density polyethylene at 190°C and 2.16 kg is 0.5~5 g / 10 min; the melt flow rate of the low-density polyethylene at 190°C and 2.16 kg is 0.5~5 g / 10 min.

[0036] The antioxidants, UV absorbers, lubricants, etc., in the processing aids of the above-mentioned transparent layer A, black layer, silver layer, and transparent layer B can be the same or different.

[0037] A method for preparing a three-color composite mulch film, characterized in that the preparation method includes the following steps: Step S1: Prepare the raw materials for the preparation of transparent layer A, black layer, silver layer and transparent layer B respectively.

[0038] In step S2, the raw materials for preparing transparent layer A, black layer, silver layer and transparent layer B are added to the barrels of four extruders respectively, and co-extruded using the four extruders. After being compounded by a composite die, the mixture is extruded and blow-molded into a film.

[0039] Furthermore, the preparation methods of the transparent layer A, black layer, silver layer, and transparent layer B... The preparation methods for each material independently include the following steps: The raw material components are mixed evenly, added to an extruder for melt extrusion, pelletized, and dried to obtain particles.

[0040] The thickness of the three-color composite mulch film is 5~30μm, preferably 10~25μm.

[0041] The thickness of the transparent layer A, the black layer, and the silver layer in the three-color composite mulch film can be the same or different, and their thicknesses are each 3~9μm.

[0042] The thickness of the transparent layer B is the sum of the thicknesses of the black layer and the silver layer.

[0043] The width of the silver-black composite layer, composed of a black layer and a silver layer, and the width of the intermediate transparent layer, composed of a transparent layer B and a transparent layer A, in the three-color composite mulch film can be set according to application requirements.

[0044] Beneficial effects The three-color composite mulch film of this invention has a bottom transparent layer containing a hydrophilic additive. This transparent layer prevents dew droplets from forming and thus avoids sunlight reflection, effectively increasing the film's light transmittance, improving soil temperature and energy storage, and promoting crop growth. Secondly, the silver surface layer of the mulch film contains flake-like alumina, which reflects sunlight, thereby enhancing photosynthesis in the lower leaves of plants. Thirdly, the mulch film also includes a transparent layer B, located in the middle. The hydrophobic additive in transparent layer B imparts a hydrophobic effect, allowing rainwater to easily clean dust from the film surface, further increasing the light transmittance of transparent layer B and thus better enhancing soil temperature. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the structure of the three-color composite mulch film in an embodiment of the present invention, wherein ① is the transparent layer B and ② is the transparent layer A. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0049] Example 1 The raw materials for preparing transparent layer A are shown below in parts by weight: 85 parts of linear low-density polyethylene (ExxonMobil LL-3001, melt index 1.5 g / 10 min); 5 parts of low-density polyethylene (Sinopec LDPE 2426H, melt index 1.9 g / 10 min); 7 parts of hydrophilic additive (agricultural film anti-fogging masterbatch, Belt Collins); 1 part of antioxidant 1010; 1 part of ultraviolet light absorber UV-531; 1 part of polyethylene wax.

[0050] The raw materials for preparing the black layer are shown below in parts by weight: 87 parts of linear low-density polyethylene (ExxonMobil LL-3001, melt index 1.5 g / 10 min); 5 parts of low-density polyethylene (Sinopec LDPE 2426H, melt index 1.9 g / 10 min); 5 parts of black pigment (carbon black masterbatch, Xinyang New Materials); 1 part of antioxidant 1010; 1 part of ultraviolet absorber UV-531; 1 part of polyethylene wax.

[0051] The raw materials for preparing the silver surface layer are shown below in parts by weight: 87 parts of linear low-density polyethylene (ExxonMobil LL-3001, melt index 1.5 g / 10 min); 5 parts of low-density polyethylene (Sinopec LDPE 2426H, melt index 1.9 g / 10 min); 5 parts of silver-gray dye (flaky alumina, Silver Arrow ZLG-9081C, average particle size 6 μm); 1 part of antioxidant 1010; 1 part of ultraviolet absorber UV-531; 1 part of polyethylene wax.

[0052] The raw materials for preparing the transparent layer B are as follows, in parts by weight: 77 parts of linear low-density polyethylene (ExxonMobil LL-3001, melt index 1.5 g / 10 min); 5 parts low-density polyethylene (Sinopec LDPE 2426H, melt index 1.9g / 10min); 5 parts hydrophobic agent (Evonik Aerosil® R812); 10 parts thermal insulation agent (hydrotalcite, D50 1.9μm, Anhe Technology); 1 part antioxidant 1010; 1 part ultraviolet absorber UV-531; 1 part polyethylene wax.

[0053] The method for preparing the composite mulch film includes the following steps: S1, the raw material components of transparent layer A, black layer, silver layer and transparent layer B are mixed and added to a twin-screw extruder, melt extruded and granulated to obtain the raw materials (particles) for preparing transparent layer A, black layer, silver layer and transparent layer B respectively.

[0054] S2, the raw materials (particles) for preparing transparent layer A, black layer, silver layer, and transparent layer B are respectively added to the barrels of four extruders, and co-extruded using the four extruders. After being compounded by a composite die, the mixture is extruded and blow-molded into a film. The barrel temperature of the extruders is 160℃~190℃, and the film thicknesses of transparent layer A, black layer, silver layer, and transparent layer B are approximately 5μm, 5μm, 5μm, and 10μm, respectively. The thickness of the composite film is approximately 15μm.

[0055] Example 2 Based on Example 1, the amount of low-density polyethylene in transparent layer A was adjusted to 89 parts, and the amount of hydrophilic additive was adjusted to 3 parts; the amount of low-density polyethylene in silver surface layer was adjusted to 89 parts, and the amount of silver-gray dye was adjusted to 3 parts; the amount of hydrophobic agent in transparent layer B was adjusted to 8 parts; and the amount of heat-insulating agent was adjusted to 7 parts.

[0056] Comparative Example 1 Based on Example 1, without the transparent layer B in the middle, the composite mulch film... The structure consists of a transparent layer A at the bottom, a black layer in the middle, and a silver layer on top.

[0057] Comparative Example 2 Based on Example 1, the amount of hydrophobic agent in transparent layer B was adjusted to 15 parts, and the amount of heat-insulating agent was adjusted to 0 parts.

[0058] Comparative Example 3 Based on Example 1, the amount of hydrophobic agent in transparent layer B was adjusted to 0 parts, and the amount of heat-insulating agent was adjusted to 15 parts.

[0059] Comparative Example 4 Based on Example 1, the heat-insulating agent in the transparent layer B was adjusted to calcium carbonate with an average particle size of 2 μm.

[0060] Comparative Example 5 Based on Example 1, the amount of hydrophilic additive in transparent layer A was adjusted to 0 parts, and the amount of linear low-density polyethylene was adjusted to 92 parts.

[0061] Comparative Example 6 Based on Example 1, the amount of hydrophilic additive in transparent layer A was adjusted to 12 parts, and the amount of linear low-density polyethylene was adjusted to 80 parts.

[0062] Comparative Example 7 Based on Example 1, the amount of hydrophobic agent in transparent layer B was adjusted to 12 parts, and the amount of linear low-density polyethylene was adjusted to 70 parts.

[0063] Comparative Example 8 Based on Example 1, the amount of hydrophobic agent in transparent layer B was adjusted to 0 parts, and the amount of linear low-density polyethylene was adjusted to 82 parts.

[0064] Application performance testing Optical performance testing: According to GB / T 2410–2008, the transmittance of the silver / black dual-color layer film and the transmittance of the intermediate composite transparent layer film were tested using a transmittance-haze tester.

[0065] Hydrophobic / hydrophilic performance testing: A contact angle tester was used to measure the water contact angle of the surface layer (transparent layer B) and the bottom layer (transparent layer A) of the intermediate composite transparent film. For transparent layer B, a larger water contact angle indicates better hydrophobicity and better dustproof performance of the composite mulch film; for transparent layer A, a smaller water contact angle indicates better hydrophilicity and better dew-proof performance of the composite mulch film.

[0066] Mechanical properties: Using a tensile testing machine, the silver composite film and transparent composite film of the three-color composite mulch film were tested according to the performance test standard of GB / T 4455-2006 "Agricultural Polyethylene Blown Greenhouse Film". Both films have a thickness of 15μm and a side length of 1200mm. The tensile composite (N), nominal strain at break (%), and right angle tear load (N) were obtained.

[0067] Table 1. Light transmittance and surface properties of composite mulch films As shown in Table 1, the test results of Examples 1-2 indicate that the visible light transmittance of the silver / black bicolor layer of the composite mulch film obtained by this invention is ≤5%, indicating that it has a good reflective effect on visible light; while the visible light transmittance of the transparent composite film layer is greater than 90%, indicating that the transparent composite film layer of the composite mulch film has a good solar transmittance effect. Furthermore, the bottom layer of the transparent film of the composite mulch film has a certain hydrophilic effect, which can prevent dew droplets; while the surface of the top layer of the transparent film has a certain hydrophobic effect, which is beneficial for rainwater to clean the dust on the surface of the mulch film, thereby facilitating the transmission of visible light.

[0068] The test results of Comparative Examples 1-8 show that if the amount of hydrophilic additive in transparent layer A is not within the specified range, or if the amount of hydrophobic agent and heat-insulating agent in transparent layer B is not within the specified range... Within a limited range, the light transmittance of the intermediate composite transparent layer will decrease, making it difficult to achieve a transmittance greater than 85%. It will also affect the anti-drip effect of the bottom film or the hydrophobic effect of the top film of the composite transparent membrane to some extent. It is speculated that changes in the amount of hydrophilic or hydrophobic additives will affect their dispersion effect after blown film deposition, thus affecting the transmittance of the single-layer membrane and the surface energy of the membrane surface, consequently affecting the transmittance and other application performance of the composite membrane.

[0069] Table 2 Mechanical properties of composite mulch films As can be seen from the test results of Examples 1-2 in Table 2, the composite mulch film obtained by the present invention has good mechanical properties and can be applied in the field of mulch film. As can be seen from the test results of Comparative Examples 1-8, although the mechanical properties of the mulch films obtained in Comparative Examples 1-8 meet the national standard requirements, the mechanical properties of the mulch films corresponding to Comparative Examples 1-8 are still inferior to those of the mulch films obtained in the examples. Furthermore, the visible light transmittance and surface properties of the mulch films obtained in the comparative examples are poor, making it difficult to meet the multi-functional requirements of mulch films.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A three-color composite mulch film, characterized in that, It includes a bottom layer, a middle layer, and a top layer. The bottom layer is a transparent layer A, and a transparent layer B is disposed on top of the transparent layer A. The middle layer is disposed on the bottom layer and located on both sides of the transparent layer B. The top layer is disposed on the middle layer and located on both sides of the transparent layer B. The middle layer is a black layer, and the top layer is a silver layer.

2. A three-color composite mulch film as described in claim 1, characterized in that, The raw materials for preparing the transparent layer A include polyethylene and hydrophilic additives, and the light transmittance of the transparent layer is ≥85%.

3. A three-color composite mulch film as described in claim 1, characterized in that, The raw materials for preparing the black layer include polyethylene and black pigment, and the light transmittance of the black layer is ≤5%.

4. A three-color composite mulch film as described in claim 1, characterized in that, The raw materials for preparing the silver layer include polyethylene and silver-gray dye, and the solar reflectance of the silver layer is ≥85%.

5. A three-color composite mulch film as described in claim 1, characterized in that, The raw materials for preparing the transparent layer B include polyethylene, hydrophobic agent, and heat-insulating agent.

6. A three-color composite mulch film as described in claim 5, characterized in that, The hydrophobic agent includes silane-modified silica; preferably, the silane is hexamethyldisilazane.

7. A three-color composite mulch film as described in claim 5, characterized in that, The heat-insulating agent is hydrotalcite; preferably, the average particle size of the hydrotalcite is 0.5~5μm.

8. A three-color composite mulch film as described in claim 4, characterized in that, The silver-gray dye comprises flake aluminum powder.

9. A three-color composite mulch film as described in claims 1-8, characterized in that, The thickness of the mulch film is 8~30μm.

10. A method for preparing a three-color composite mulch film as described in claims 1-8, characterized in that, The preparation method includes the following steps: Step S1: Prepare the raw materials for the preparation of transparent layer A, black layer, silver layer and transparent layer B respectively. In step S2, the raw materials for preparing transparent layer A, black layer, silver layer and transparent layer B are added to the barrels of four extruders respectively, and co-extruded using the four extruders. After being compounded by a composite die, the mixture is extruded and blow-molded into a film.

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