Temperature-controlled agricultural film and preparation method thereof

Abstract

A temperature-controlled agricultural mulch film and its preparation method are technologies for producing temperature-controlled plastic film. This technology overcomes the challenges of other existing technologies, such as a lack of cooling and sunshade properties, high costs, and complex manufacturing processes. It utilizes the principle that water-absorbing substances automatically release water at high temperatures. Steam condenses at the top of the two film layers, turning the transparent film opaque and reducing light exposure and temperature. When the temperature drops, the water droplets are absorbed by the water-absorbing substance, turning the film transparent. This method can also be used in combination with other temperature-control technologies to promote or control high temperatures.

Description

Technical Field

[0001] The invention relates to a production technology of a temperature-controllable plastic film, in particular to a temperature-controllable agricultural film and a preparation method thereof. Background Art

[0002] Agricultural films and ground films control heat loss during use, increase internal film temperatures, and provide insulation. However, during the hot summer months, high soil temperatures can hinder plant growth, limiting their effectiveness in providing shade and cooling. Spraying agricultural films with a milky white, adhesive sunscreen to reduce light and temperature not only has a short-lived effect but can also lead to insufficient light in winter, hampering plant growth.

[0003] Other technologies have also been proposed, but they all have some problems, such as CN107254150A, a method for preparing a degradable mulch film with thermal insulation and water control. This invention discloses a method for preparing a degradable mulch film with thermal insulation and water control, comprising the following steps: 1. selecting raw materials, wherein the raw materials include polylactic acid, polycarbonate, polyethylene adipate, and a grafted compatibilizer in mass fractions; 2. first baking the polylactic acid and polycarbonate in a vacuum environment in steps; 3. placing the polylactic acid, polyethylene adipate, and grafted compatibilizer in a blender according to a weight ratio and stirring; 4. placing the evenly mixed raw materials in a melt granulator for a first melt copolymerization; 5. placing the product A particles and the baked polycarbonate in a blender and stirring evenly, and then placing them in a melt granulator again after stirring for a second melt copolymerization; 6. transferring the product B particles to a film blowing machine for film blowing operation to produce a mulch film; and 7. conducting a strength test on the prepared mulch film product. This invention has a high degradation rate, high overall mechanical properties, and good water retention, but the manufacturing process is relatively complicated and it only has a heat preservation function.

[0004] There is also a smart microporous ground film, such as CN101990836B smart microporous temperature-controlled breathable ground film. This invention provides a smart microporous temperature-controlled breathable ground film, comprising a non-woven fabric, elongated channels on the non-woven fabric, an intelligent moisture regulator embedded in the center of the channels, and suction cups interspersed on the bottom surface of the non-woven fabric. This ground film is thin and lightweight, easy to transport and construct, inexpensive, and easy to promote. During use, the underside of the mat has strong adaptability, can improve water penetration and reduce water evaporation, effectively reducing production and management costs in agriculture, forestry, and other fields, and facilitating the efficient and economical use of water resources. It is mainly used in agriculture, forestry, and other fields. This ground film can intelligently control temperature, but the process is complex and the cost is too high.

[0005] CN217608641U A high-strength mulch film with good temperature control. This invention provides a high-strength mulch film with good temperature control, including a light-colored mulch film and a black mulch film. The light-colored mulch film is connected to a black mulch film at each end. The black mulch film and the connection between the light-colored and black mulch films are provided with longitudinal mechanical zones, while the light-colored mulch film is provided with transverse mechanical zones. The light-colored mulch film is an infrared-blocking film, which facilitates light exposure for crops, minimizes the temperature difference between day and night, and can achieve a certain degree of weed control. This invention utilizes infrared blocking, which can only reduce the temperature difference to a certain extent.

[0006] CN114793722B - Method for preparing a water-droplet-free ground film with controlled air permeability using a load-type negative thermal material. This invention provides a water-droplet-free ground film with controlled air permeability using a load-type negative thermal material. The film comprises, from top to bottom, a surface mask layer, a temperature-regulated ventilation layer, and a hydrophilic layer. The surface mask layer is provided with air holes. The temperature-regulated ventilation layer is composed of a composite negative thermal material of butyl acrylate, styrene, and chlorosulfonated polyethylene (PVC). The negative thermal material is ZrW2O8 loaded with benzoyl peroxide. The hydrophilic layer is composed of a hydroxypropyl acrylate, styrene, and chlorosulfonated polyethylene (PVC) copolymer. The resulting ground film increases carbon dioxide concentration and reduces ammonia concentration in the space covered by the film. At the same time, no water droplets form on the inner surface of the film, maintaining a relatively high soil temperature. The negative heat material in the temperature-regulatable ventilation layer is ZrW2O8 loaded with benzoyl peroxide. Benzoyl peroxide can trigger free radical polymerization of organic monomers with double bonds. Consequently, the loaded ZrW2O8 triggers polymerization of butyl acrylate and styrene monomers on the surface of the negative heat material particles, forming a strong and dense polymer shell that encapsulates the surface of the negative heat material particles. This facilitates the formation of temperature-regulatable pores in the ventilation layer. This invention utilizes a loaded negative heat material to generate relative strain, thereby forming gaps to achieve gas exchange, but the process is relatively complex.

[0007] JP2001078591A Film for agriculture. This invention provides an agricultural film whose light transmittance can be automatically controlled according to the amount of sunlight. The agricultural film is formed by extrusion molding, blow molding, or calendering a resin composition comprising 100 parts by weight of a water-insoluble or slightly water-soluble thermoplastic resin, such as a polyvinyl chloride resin, and 0.001 to 10 parts by weight of a photochromic compound. The film is preferably a laminated film. The film has excellent durability and, by treating the resin composition comprising the thermoplastic resin, can be effectively used for cultivating crops in greenhouses, etc. For example, the ratio of the water-insoluble thermoplastic resin to the photochromic compound is determined by extrusion molding, etc.

[0008] In summary, the preparation of temperature-controlling agricultural land film with cooling and sun-shading effects has not yet been found. Summary of the Invention

[0009] The present invention aims to provide a temperature-controlled agricultural mulch film and its preparation method. This method overcomes the challenges of other existing technologies, such as the lack of cooling and sunshade functions, high costs, and complex manufacturing processes. This objective is achieved by utilizing the principle that water-absorbing substances automatically release water at high temperatures. Steam condenses at the top of the two layers of film, turning the transparent film opaque, reducing light exposure and lowering the temperature. When the temperature drops, the water droplets are absorbed by the water-absorbing substance, turning the film transparent. This method can also be used in combination with other temperature-control technologies to promote or control high temperatures.

[0010] The composite cooling agricultural film of the present invention comprises two or more layers with a water-absorbing material sandwiched between them. The two layers contain a grid that divides the water-absorbing material into small, isolated areas. This can be achieved by adding the water-absorbing material to the middle layer through multi-layer co-extrusion technology, or by first blowing the film and then thermally laminating the film to fill the middle layer with the water-absorbing material.

[0011] The two layers have one upward facing layer and one downward facing layer. The upward facing layer faces the sky (sun), while the downward facing layer faces the ground. The upward facing layer has a greater water barrier effect than the downward facing layer. This can be achieved by adjusting the thickness or material of the upward and downward layers. The goal is to allow moisture from the ground to penetrate through the downward layer to the middle, allowing the water-absorbing material to fully absorb the water.

[0012] The water-absorbing material includes but is not limited to sodium carbonate, sodium sulfate, calcium chloride, calcium oxide or a mixture thereof, preferably sodium carbonate, because the water loss temperature of sodium carbonate decahydrate is 33.5° C., and above this temperature, most crops will be unsuitable for growth.

[0013] The significance of the invention is as follows: First, the invention utilizes the water-absorbing material in the middle layer of the agricultural film to automatically release water at high temperature, forming steam condensation water droplets on the top between the two layers of film, turning the transparent film into opaque, thereby reducing light, lowering the temperature, and achieving the effect of cooling and shading; it fills a major gap in the application performance of agricultural film and has great market value; second, it has a high reuse rate and a long service life, and the moisture on the ground can penetrate from the lower layer to the middle, allowing the water-absorbing material to fully absorb water to increase the recycling of the water-absorbing material; third, the application process method is simple to operate, with low cost, and is easy to promote; fourth, it is green and environmentally friendly, the ingredients will not affect the soil itself, and the controlled temperature is conducive to the growth of most crops. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the principle and implementation process.

[0015] Figure 2 It is a table diagram of the blank control group of the present invention. DETAILED DESCRIPTION

[0016] The present invention utilizes the principle that water-absorbing substances automatically release water at high temperatures, forming steam condensation water droplets at the top between the two layers of film, turning the transparent film opaque, reducing light and lowering the temperature; when the temperature drops, the water droplets are absorbed by the water-absorbing substance and the film becomes transparent.

[0017] The present invention is composed of two or more layers and a water-absorbing material sandwiched in the middle; there is a grid between the two layers, which divides the water-absorbing material into small isolated areas. This can be achieved by adding the water-absorbing material to the middle layer through multi-layer co-extrusion technology, or by first blowing a film and then filling the water-absorbing material into the middle layer by heat lamination; the two layers have one side as an upward layer and the other side as a downward layer; when in use, the upward layer faces the sky (sun) and the downward layer faces the ground, and the upward layer has a greater water barrier effect than the downward layer, which can be achieved by adjusting the thickness or material of the upward and downward layers; the purpose is to allow moisture on the ground to penetrate into the middle through the downward layer, allowing the water-absorbing material to fully absorb water.

[0018] The water-absorbing material includes but is not limited to sodium carbonate, sodium sulfate, calcium chloride, calcium oxide or a mixture thereof, preferably sodium carbonate, because the water loss temperature of sodium carbonate decahydrate is 33.5° C., and above this temperature, most crops will be unsuitable for growth.

[0019] The preparation method is as follows: solid sodium carbonate is ground into fine powder of 0.001mm to 0.003mm, and then made into masterbatch particles containing 25% to 35% sodium carbonate. The other 65-75% of the material is ordinary low-density polyethylene particles (7050 of Sinopec), which are heated to 200℃ for melting and then drawn and pelletized; before entering the film blowing machine, a mixer is used to stir the masterbatch and other main materials for more than 8 minutes to evenly distribute the sodium carbonate particles therein, and the masterbatch is added to the middle layer to control the sodium carbonate content in the middle layer to 8% to 10%. The other raw materials of the middle layer are 7050, and the other layers are 100% 7050. The temperatures of the three-stage screw are 200℃, 220℃, and 240℃ respectively, and the die head temperature is 225℃ to 230℃. Normally, a film of 0.008mm to 0.12mm is blown, and the thickness of the upper layer is higher than that of the lower layer, which is normally used in the field.

[0020] Furthermore, the sodium carbonate solid is ground into a fine powder of 0.002mm, and then made into masterbatch particles containing 30% sodium carbonate. The other 70% material is ordinary low-density polyethylene particles (Sinopec's 7050), which are heated to 200°C to melt and then drawn and pelletized; before entering the film blowing machine, a mixer is used to stir the masterbatch and other main materials for more than 8 minutes to ensure that the sodium carbonate particles are evenly distributed. The masterbatch is added to the middle layer, and the sodium carbonate content in the middle layer is controlled to be 9%. The other raw materials in the middle layer are 7050, and the other layers are 100% 7050. The temperatures of the three-stage screw are 200°C, 220°C, and 240°C, respectively, and the die head temperature is 227°C. Normally, a 0.08mm film is blown, the upper layer thickness is 0.05mm, the middle layer thickness is 0.02mm, and the lower layer thickness is 0.01mm, which is normally used in the field.

[0021] During the use of this product, the temperature, haze and transmittance on both sides of the inner and outer sides of the membrane were respectively detected, and a blank control group was set up; the transmittance and haze were tested using a WGT-S transmittance / haze meter; during the use of this product, the temperature, haze and transmittance on both sides of the inner and outer sides of the membrane were respectively detected, and a blank control group was set up; when used, the higher the temperature outside the membrane of the present invention, the lower the transmittance and the higher the haze, and the temperature inside the membrane of the present invention is lower than that of the control group not using this technology.

[0022] The above technical solutions only reflect the preferred technical solutions of the technical solutions of the present invention. Any changes that may be made to certain parts thereof by those skilled in the art can reflect the principles of the present invention and fall within the scope of protection of the present invention.

Claims

1. A temperature-controlled agricultural film, characterized in that: The invention is composed of two or more layers of film and a water-absorbing material sandwiched in the middle layer. The middle layer of the two or more layers of film has a grid, which divides the water-absorbing material into small isolated areas. The water-absorbing material is added to the middle layer by multi-layer co-extrusion technology, or the film is blown first and then the water-absorbing material is filled into the middle layer by heat lamination. The two or more layers of film have one side as an upward layer and the other side as a downward layer. When in use, the upward layer faces the sky and the downward layer faces the ground. The upward layer has a greater water barrier effect than the downward layer. This is achieved by adjusting the thickness or material of the upward layer and the downward layer. The purpose is to allow the moisture on the ground to penetrate into the middle layer through the downward layer, allowing the water-absorbing material to fully absorb water. The principle that the water-absorbing material automatically releases water at high temperature is used to form steam condensation water droplets on the top between the two layers of film, turning the transparent film opaque, reducing light and lowering the temperature. When the temperature drops, the water droplets are absorbed by the water-absorbing material and the film becomes transparent.

2. The temperature-controlled agricultural film according to claim 1, characterized in that: The water-absorbing substance includes one or more of sodium carbonate, sodium sulfate, calcium chloride, and calcium oxide.

3. The temperature-controlled agricultural film according to claim 2, characterized in that: The water-absorbing substance is sodium carbonate.

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