Microporous membrane for covering cherry crown and preparation method thereof

Abstract

The invention provides a microporous membrane for covering a cherry crown and a preparation method of the microporous membrane, and belongs to the technical field of polymer membranes. The microporous film for covering the cherry crown comprises a microporous plastic film body layer, a non-woven fabric reinforcing moisture-conducting layer and a protective plastic film layer which are bonded into a whole by adopting continuous glue or a continuous hot-pressing process. The non-woven fabric reinforcing moisture-conducting layer is positioned on the inner side of the microporous plastic film body layer; the protective plastic film layer is located on the inner side of the non-woven fabric reinforcing moisture guiding layer, and a plurality of rectangular holes or round holes are formed in the protective plastic film layer in a rectangular array mode. According to the invention, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer are added; the microporous plastic film body layer is a main structural layer for realizing rain prevention, ventilation and heat preservation; the non-woven fabric reinforcing moisture-conducting layer can enhance the puncture resistance and the heat preservation property of the microporous plastic film body layer, and can also be used as a channel for absorbing water vapor and guiding discharge at the same time, so that water vapor condensation and aggregation are reduced; and the protective plastic film layer plays a role in protecting the non-woven fabric reinforcing moisture-conducting layer.

Description

Technical Field

[0001] The invention relates to the technical field of polymer films, and in particular to a microporous film for covering cherry tree crowns and a preparation method thereof. Background Art

[0002] Cherry includes subgenus Prunus, subgenus Sour Prunus, subgenus Laurus, etc. The fruit can be eaten as a fruit, with bright color, crystal clear and beautiful, red like agate, yellow like cream, and rich in sugar, protein, vitamins, calcium, iron, phosphorus, potassium and other elements. It is one of the important economic crops. However, cherry trees are a species with poor stress resistance and are not tolerant to low temperatures. They are suitable for growing in places with an average annual temperature of 10℃~14℃. Therefore, in areas with low temperatures and strong winds in winter, it is particularly important to cover the crowns of cherry trees in winter to keep them warm.

[0003] Cherry tree crowning treatment often uses polyethylene or polypropylene microporous membranes to achieve rainproof, breathable and heat-insulating effects. However, the existing microporous membranes are easily damaged due to the thorns of cherry tree branches during use, affecting the rainproof, breathable and heat-insulating effects; on the other hand, after using the microporous membrane to cover the cherry tree crown, the inner side of the microporous membrane (the side facing the cherry tree) is prone to condensation and aggregation due to untimely moisture release, affecting the ventilation effect. Summary of the invention

[0004] The present invention aims to provide a microporous film for covering cherry tree crowns and a preparation method thereof, which adds a non-woven fabric reinforcing moisture-conducting layer and a protective plastic film layer; the microporous plastic film body layer is the main structural layer for achieving rainproof, breathable and heat-insulating properties; the non-woven fabric reinforcing moisture-conducting layer can enhance the puncture resistance and heat-insulating properties of the microporous plastic film body layer, and can also serve as a channel for absorbing and guiding the discharge of water vapor, thereby reducing condensation and aggregation of water vapor; the protective plastic film layer plays a role in protecting the non-woven fabric reinforcing moisture-conducting layer.

[0005] The technical solution adopted by the present invention is:

[0006] A microporous membrane for covering a cherry tree crown, comprising:

[0007] Microporous plastic film body layer;

[0008] A non-woven fabric reinforcing moisture-conducting layer, wherein the non-woven fabric reinforcing moisture-conducting layer is located on the inner side of the microporous plastic film body layer;

[0009] A protective plastic film layer, the protective plastic film layer is located on the inner side of the non-woven fabric reinforcing moisture-conducting layer, and is provided with a plurality of 1~2mm*1~2mm rectangular holes, φ1~2mm circular holes or φ1~2mm tapered holes with a wide end diameter of 1~2mm in the form of a rectangular array; from the two edges of the protective plastic film layer in the width direction to the middle position, the protective plastic film layer, the non-woven fabric reinforcing moisture-conducting layer and the microporous plastic film body layer are integrated into one by using a dispersed point gluing or dispersed point hot pressing process.

[0010] Furthermore, in the width direction, the width of the microporous plastic film main layer is greater than the width of the non-woven fabric reinforced moisture-conducting layer; in the width direction, the surplus edges on both sides of the microporous plastic film main layer are bent to cover the corresponding edges of the non-woven fabric reinforced moisture-conducting layer, and then the microporous plastic film main layer, the non-woven fabric reinforced moisture-conducting layer and the microporous plastic film main layer are combined into one by continuous glue bonding or continuous hot pressing process.

[0011] Furthermore, the width of the microporous plastic film body layer is 2-5 cm larger than that of the non-woven fabric; when the non-woven fabric reinforcing moisture-conducting layer is located on the inner side of the microporous plastic film body layer, both sides of the microporous plastic film body layer in the width direction are uniformly 1-2.5 cm surplus.

[0012] Furthermore, the width of the protective plastic film layer is 10 to 15 cm smaller than the width of the non-woven reinforced moisture-conductive layer; when the protective plastic film layer is located on the inner side of the non-woven reinforced moisture-conductive layer, the non-woven reinforced moisture-conductive layer has a uniform surplus of 5 to 7.5 cm on both sides in the width direction, and except for the edge of the non-woven reinforced moisture-conductive layer which is bent and wrapped by the microporous plastic film body layer, there is an area of ​​approximately 4 to 5 cm on both sides in the width direction of the non-woven reinforced moisture-conductive layer that is not covered by the protective plastic film layer.

[0013] Furthermore, in the width direction, the surface of the microporous plastic film body layer corresponding to the edge region of the non-woven fabric reinforcing moisture-conducting layer not covered by the protective plastic film layer is coated with a black heat-absorbing coating.

[0014] Furthermore, the thickness of the microporous plastic film body layer is 35-40 μm, and the porosity is 45-47%; the thickness of the non-woven fabric reinforcement moisture-conducting layer is 0.08-0.5 mm; and the thickness of the protective plastic film layer is 15-100 μm.

[0015] Furthermore, the total opening area per square centimeter of the protective plastic film layer is 0.4-0.7 cm 2 .

[0016] Based on the same inventive concept, the present invention also provides a method for preparing a microporous membrane for covering a cherry tree crown, comprising the following steps:

[0017] Step S1, using 45-55wt% of calcium carbonate powder with a D50 particle size of less than 50nm, 1-8wt% of polyethylene wax, 1-5wt% of silane coupling agent, 0.1-1wt% of anti-aging agent, 25-35wt% of metallocene polyethylene with an ethylene content of 80-99wt% and a melt flow rate of 2.5-10g / 10min, 5-15wt% of linear low-density polyethylene with a melt flow rate of 2-5g / 10min, and 5-10wt% of low-density polyethylene with a melt flow rate of 3-6 g / 10min as raw materials by melt extrusion, casting and uniaxial stretching;

[0018] Step S2, using 25-50 wt% of low-density polyethylene with a melt flow rate of 2-5 g / 10 min and 50-75 wt% of linear low-density polyethylene with a melt flow rate of 1-2 g / 10 min as raw materials, by blow molding, cooling and punching, to prepare a protective plastic film layer;

[0019] Step S3, cutting the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer to a preset size, and then laying the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer in sequence, from the two edges in the width direction of the protective plastic film layer to the middle position, using dispersed point gluing or dispersed point hot pressing technology to combine them into one, and the interval between adjacent bonding points is 2~5cm; then the surplus edges on both sides of the width direction of the microporous plastic film main layer are bent to cover the edges of the non-woven fabric reinforcing moisture-conducting layer, and are combined into one by continuous glue bonding or continuous hot pressing technology to obtain a microporous film for covering the cherry tree crown.

[0020] Furthermore, in step S1, the casting temperature is 200-230° C.; during uniaxial stretching, the stretching temperature is 60-90° C., the stretching ratio is 1.5-4.0, the stretching speed is 80-120 mm / min, and the shaping time after stretching is 15-40 min.

[0021] Furthermore, when the hot pressing process is adopted in step S3, the hot pressing temperature is 170-180° C., and the hot pressing time is 1-5 s.

[0022] The beneficial effects of the present invention are:

[0023] 1. The microporous film for cherry tree crown covering in the present invention is composed of a microporous plastic film body layer, a non-woven fabric reinforcing moisture-conducting layer and a protective plastic film layer. Among them, the microporous plastic film body layer is the main structural layer for achieving rainproof, air permeability and heat preservation; the non-woven fabric reinforcing moisture-conducting layer can enhance the puncture resistance and heat preservation of the microporous plastic film body layer, and can also serve as a channel for water vapor absorption and discharge guidance, reducing water vapor condensation and aggregation; the protective plastic film layer plays a role in protecting the non-woven fabric reinforcing moisture-conducting layer.

[0024] 2. The preparation method of the microporous membrane for covering the cherry tree crown in the present invention has easy-to-obtain raw materials and is relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 Schematic diagram of the microporous membrane used for covering the cherry tree crown in Example 1.

[0027] Figure 2 Schematic diagram of water vapor migration.

[0028] The accompanying drawings are marked as follows:

[0029] 100-microporous plastic film main body layer, 200-non-woven fabric reinforcement moisture-conducting layer, 300-protective plastic film layer. DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0032] The embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0033] Example 1

[0034] Figure 1 Schematic diagram of the microporous membrane used for covering the cherry tree crown in Example 1. Figure 1As shown in the figure, the microporous film for covering the cherry tree crown includes a microporous plastic film body layer 100; the microporous plastic film body layer 100 is the main structural layer for achieving rain protection, air permeability and heat preservation after covering the cherry tree crown.

[0035] Specifically, in terms of mass percentage, the raw materials of the microporous plastic film body layer 100 include: 45-55wt% of calcium carbonate powder with a D50 particle size less than 50nm, 1-8wt% of polyethylene wax, 1-5wt% of silane coupling agent, 0.1-1wt% of anti-aging agent, 25-35wt% of metallocene polyethylene with an ethylene content of 80-99wt% and a melt flow rate of 2.5-10g / 10min, 5-15wt% of linear low-density polyethylene with a melt flow rate of 2-5g / 10min, and 5-10wt% of low-density polyethylene with a melt flow rate of 3-6 g / 10min. The preparation of the microporous plastic film body layer 100 includes the following steps: (1) heating the calcium carbonate powder to 75-80°C, adding a silane coupling agent as a modifier, and stirring to obtain an intermediate material; grinding the intermediate material with a grinder, filtering and extracting the material through a vacuum pump and a screen, and then sending it to a dryer for drying, and then grinding it with a high-speed ball mill to obtain ultrafine calcium carbonate powder; (2) mixing the ultrafine calcium carbonate powder, polyethylene wax, metallocene polyethylene, linear low-density polyethylene and low-density polyethylene, and mixing and extruding the mixture through a twin-screw extruder at a twin-screw speed of 200-500 rpm and a heating temperature of 170-200°C to obtain polyethylene particles; (3) forming a film from the polyethylene particles by a casting method at a film forming temperature of 200-230°C to obtain a polyethylene cast film; (4) uniaxially stretching the polyethylene cast film at a stretching temperature of 60-90°C and a stretching ratio of 1.5-4.0. The stretching speed is 80-120 mm / min, and the microporous plastic film body layer 100 is prepared after the stretching for 15-40 minutes. The microporous plastic film body layer 100 has a thickness of 35-40 μm and a porosity of 45-47% (determined by ASTM D-2873 liquid absorption method).

[0036] like Figure 1As shown in the figure, a non-woven fabric reinforcing moisture-conducting layer 200 is provided on the inner side of the microporous plastic film main layer 100 (i.e., the side facing the cherry tree); the thickness of the non-woven fabric reinforcing moisture-conducting layer 200 is 0.08~0.5mm, and the width of the non-woven fabric 200 is 2~5cm smaller than the width of the microporous plastic film main layer 100; at the same time, in order to ensure a good moisture-conducting effect, the non-woven fabric reinforcing moisture-conducting layer 200 preferably adopts cotton fiber non-woven fabric, polylactic acid non-woven fabric, etc. with good moisture absorption. When the non-woven fabric reinforcing moisture-conducting layer 200 is located on the inner side of the microporous plastic film main layer 100, the two sides of the microporous plastic film main layer 100 in the width direction are uniformly surplus by 1~2.5cm, and the surplus edge of the microporous plastic film main layer 100 is bent to wrap the width edge of the non-woven fabric reinforcing moisture-conducting layer 200, and the three layers in the thickness direction are combined into one by continuous glue bonding or continuous hot pressing process; when the hot pressing process is adopted, the hot pressing temperature is 170~180℃, and the hot pressing time is 1~5s. In this embodiment, the non-woven fabric reinforcing moisture-conducting layer 200 can provide structural reinforcement for the entire microporous film as a whole, improve puncture resistance, and reduce the phenomenon of cherry branches being scratched and damaged; at the same time, the moisture absorption of the non-woven fabric reinforcing moisture-conducting layer 200 itself can serve as a migration channel for moisture in the film, reducing the large amount of moisture accumulation in the film; furthermore, the non-woven fabric reinforcing moisture-conducting layer 200 can also play a certain role in heat preservation. Finally, the edge of the microporous plastic film main layer 100 is hemmed with the edge of the non-woven fabric reinforcing moisture-conducting layer 200, which is beneficial to prolong the service life of the non-woven fabric reinforcing moisture-conducting layer 200 and reduce the phenomenon of separation from the edge.

[0037] like Figure 1 As shown in , a protective plastic film layer 300 is provided on the inner side of the non-woven fabric reinforcing moisture-conducting layer 200 (ie, the side facing the cherry tree); the protective plastic film layer 300 is mainly a protective structural layer of the non-woven fabric reinforcing moisture-conducting layer 200 .

[0038] Specifically, in terms of mass percentage, the raw materials of the protective plastic film layer 300 include: 25-50 wt% of low-density polyethylene with a melt flow rate of 2-5 g / 10 min and 50-75 wt% of linear low-density polyethylene with a melt flow rate of 1-2 g / 10 min. The process of preparing the protective plastic film layer 300 is as follows: low-density polyethylene and linear low-density polyethylene are mixed, gradually fed into a twin-screw extruder, melted and plasticized, fed into a die head, extruded and blown, cooled by air, fed into an upper traction device, and rolled into a film to obtain the protective plastic film layer 100; wherein, the temperature of the twin-screw extruder is 140-160° C., the extrusion pressure is 220-250 bar; the die head temperature is 175-180° C.; the thickness of the protective plastic film layer 100 is 15-100 μm.

[0039] The protective plastic film layer 300 is punched with a plurality of 1~2mm*1~2mm rectangular holes, φ1~2mm circular holes or 1~2mm wide end diameter conical holes (the narrow end of the conical hole faces the non-woven fabric reinforcing moisture conductive layer 200) in a rectangular array form by using a laser punching machine or a plastic film punching machine; the total opening area per square centimeter on the protective plastic film layer 300 is 0.4~0.7cm 2 . On the one hand, the size of the rectangular holes or circular holes on the protective plastic film layer 300 is relatively small, and it is not easy to hook with the branches of the cherry tree; on the other hand, the rectangular holes or circular holes can ensure that the two sides of the protective plastic film layer 300 are connected. The width of the protective plastic film layer 300 is 10~15cm smaller than the width of the non-woven fabric reinforcing moisture-conducting layer 200; when the protective plastic film layer 300 is located on the inner side of the non-woven fabric reinforcing moisture-conducting layer 200, the width direction of the non-woven fabric reinforcing moisture-conducting layer 200 is uniformly 5~7.5cm surplus on both sides, and except for the width edge of the non-woven fabric reinforcing moisture-conducting layer 200 that is bent and wrapped by the microporous plastic film body layer 100, there is an area of ​​approximately 4~5cm on both sides of the width direction of the non-woven fabric reinforcing moisture-conducting layer 200 that is not covered by the protective plastic film layer 300, and this area can be the evaporation release area of ​​the water vapor absorbed by the non-woven fabric reinforcing moisture-conducting layer 200. At the same time, from the two edges in the width direction of the protective plastic film layer 200 to the middle position, the microporous plastic film main layer 100, the non-woven fabric reinforcing moisture-conducting layer 200 and the protective plastic film layer 300 are combined into one by using dispersed point gluing (i.e., gluing at multiple non-continuous dispersed points) or dispersed point hot pressing technology (i.e., hot pressing at multiple non-continuous dispersed points respectively); when the hot pressing technology is used, the hot pressing temperature is 170~180℃, and the hot pressing time is 1~5s.

[0040] The microporous membrane used for covering the cherry tree crowns in this embodiment is composed of a microporous plastic film main layer, a non-woven fabric reinforced moisture-conducting layer and a protective plastic film layer, wherein the microporous plastic film main layer is the main structural layer for achieving rainproof, breathable and heat-insulating properties; the non-woven fabric reinforced moisture-conducting layer can enhance the puncture resistance and heat-insulating properties of the microporous plastic film main layer, and also serves as a channel for absorbing and guiding the discharge of water vapor, reducing condensation and aggregation of water vapor; the protective plastic film layer plays the role of protecting the non-woven fabric reinforced moisture-conducting layer.

[0041] In this embodiment, in order to accelerate the release of water vapor absorbed by the non-woven fabric reinforcing moisture-conducting layer 200 from the area not covered by the microporous plastic film body layer 100 and the protective plastic film layer 300, a black heat-absorbing coating (which can be a black pigment) is coated on the surface of the corresponding microporous plastic film body layer 100; the black heat-absorbing coating can increase the local temperature of the corresponding area, accelerate the evaporation and release of water vapor, and accelerate the migration of water to a drier area, thereby further reducing the condensation and aggregation of water vapor on the inner side of the film, such as Figure 2 as shown in .

[0042] Example 2

[0043] A method for preparing a microporous membrane for covering a cherry tree crown comprises the following steps:

[0044] Step S1, in terms of mass percentage, using 45-55wt% of calcium carbonate powder with a D50 particle size of less than 50nm, 1-8wt% of polyethylene wax, 1-5wt% of silane coupling agent, 0.1-1wt% of anti-aging agent, 25-35wt% of metallocene polyethylene with an ethylene content of 80-99wt% and a melt flow rate of 2.5-10g / 10min, 5-15wt% of linear low-density polyethylene with a melt flow rate of 2-5g / 10min, and 5-10wt% of low-density polyethylene with a melt flow rate of 3-6 g / 10min as raw materials, through melt extrusion, casting and uniaxial stretching to prepare a microporous plastic film body layer.

[0045] Specifically, the step includes the following processes: (1) heating the calcium carbonate powder to 75-80°C, adding a silane coupling agent as a modifier, and stirring to obtain an intermediate material; grinding the intermediate material with a grinder, filtering and extracting the material through a vacuum pump and a screen, and then sending it to a dryer for drying, and then grinding it with a high-speed ball mill to obtain ultrafine calcium carbonate powder; (2) mixing the ultrafine calcium carbonate powder, polyethylene wax, metallocene polyethylene, linear low-density polyethylene and low-density polyethylene, and mixing and extruding and granulating them with a twin-screw extruder at a speed of 200-500rpm and a heating temperature of 170-200°C to obtain polyethylene particles; (3) forming a film from the polyethylene particles by a casting method at a film forming temperature of 200-230°C to obtain a polyethylene cast film; (4) uniaxially stretching the polyethylene cast film at a stretching temperature of 60-90°C and a stretching ratio of 1.5-4.0. The stretching speed is 80-120 mm / min, and the film is shaped for 15-40 minutes after stretching to obtain the microporous plastic film body layer.

[0046] Step S2, by mass percentage, using 25-50wt% of low-density polyethylene with a melt flow rate of 2-5g / 10min and 50-75wt% of linear low-density polyethylene with a melt flow rate of 1-2g / 10min as raw materials, through blow molding, cooling and punching to prepare a protective plastic film layer.

[0047] Specifically, the step includes the following process: (1) After mixing low-density polyethylene and linear low-density polyethylene, gradually feed them into a twin-screw extruder, melt and plasticize them, feed them into a die head, extrude and blow film, cool them by air cooling, enter the upper traction device, and roll them into a film to obtain a protective plastic film layer 100; wherein, the temperature of the twin-screw extruder is 140-160°C, the extrusion pressure is 220-250bar; the die head temperature is 175-180°C; (2) a laser punching machine or a plastic film punching machine is used to open a plurality of 1-2mm*1-2mm rectangular holes, φ1-2mm circular holes or φ1-2mm tapered holes with a wide end diameter of 1-2mm in a rectangular array to obtain a protective plastic film layer.

[0048] Step S3, cutting the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer to a preset size, and then laying the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer in sequence, from the two edges in the width direction of the protective plastic film layer to the middle position, using dispersed point gluing or dispersed point hot pressing technology to combine them into one, and the interval between adjacent bonding points is 2~5cm; then the surplus edges on both sides of the width direction of the microporous plastic film main layer are bent to cover the edges of the non-woven fabric reinforcing moisture-conducting layer, and are combined into one by continuous glue bonding or continuous hot pressing technology to obtain a microporous film for covering the cherry tree crown.

[0049] The preparation method of the microporous membrane for covering the cherry tree crown in this embodiment has readily available raw materials and is relatively simple.

[0050] It should be noted that the order of step S1 and step S2 in this example can be swapped or performed simultaneously.

Claims

1. A microporous membrane for covering cherry tree crowns, characterized in that: include: Microporous plastic film body layer; A non-woven fabric reinforcing moisture-conducting layer, wherein the non-woven fabric reinforcing moisture-conducting layer is located on the inner side of the microporous plastic film body layer; A protective plastic film layer, the protective plastic film layer is located on the inner side of the non-woven fabric reinforcing moisture-conducting layer, and is provided with a plurality of 1~2mm*1~2mm rectangular holes, φ1~2mm circular holes or φ1~2mm tapered holes with a wide end diameter of 1~2mm in the form of a rectangular array; from the two edges of the protective plastic film layer in the width direction to the middle position, the protective plastic film layer, the non-woven fabric reinforcing moisture-conducting layer and the microporous plastic film body layer are integrated into one by using a dispersed point gluing or dispersed point hot pressing process.

2. The microporous membrane for covering the cherry tree crown according to claim 1, characterized in that: In the width direction, the width of the microporous plastic film main layer is greater than the width of the non-woven fabric reinforcing moisture-conducting layer; In the width direction, the surplus edges on both sides of the microporous plastic film body layer are bent to cover the corresponding edges of the non-woven fabric reinforcing moisture-conducting layer, and then the microporous plastic film body layer, the non-woven fabric reinforcing moisture-conducting layer and the microporous plastic film body layer are combined into one by continuous glue bonding or continuous hot pressing process.

3. The microporous membrane for covering the cherry tree crown according to claim 2, characterized in that: The width of the microporous plastic film main layer is 2-5 cm larger than that of the non-woven fabric; when the non-woven fabric reinforcing moisture-conducting layer is located on the inner side of the microporous plastic film main layer, both sides of the microporous plastic film main layer have an even surplus of 1-2.5 cm in the width direction.

4. The microporous membrane for covering the cherry tree crown according to claim 2 or 3, characterized in that: The width of the protective plastic film layer is 10 to 15 cm smaller than that of the non-woven reinforced moisture-conductive layer; when the protective plastic film layer is located on the inner side of the non-woven reinforced moisture-conductive layer, the non-woven reinforced moisture-conductive layer has a uniform surplus of 5 to 7.5 cm on both sides in the width direction, and except for the edge of the non-woven reinforced moisture-conductive layer which is bent and wrapped by the microporous plastic film body layer, there is an area of ​​approximately 4 to 5 cm on both sides in the width direction of the non-woven reinforced moisture-conductive layer that is not covered by the protective plastic film layer.

5. The microporous membrane for covering the cherry tree crown according to claim 4, characterized in that: In the width direction, the surface of the microporous plastic film body layer corresponding to the edge area of ​​the non-woven fabric reinforcing moisture-conducting layer not covered by the protective plastic film layer is coated with a black heat-absorbing coating.

6. The microporous membrane for covering the cherry tree crown according to claim 4, characterized in that: The thickness of the microporous plastic film main body layer is 35-40 μm, and the porosity is 45-47%; the thickness of the non-woven fabric reinforcement moisture-conducting layer is 0.08-0.5 mm; and the thickness of the protective plastic film layer is 15-100 μm.

7. The microporous membrane for covering the cherry tree crown according to claim 5 or 6, characterized in that: The total opening area of ​​the protective plastic film layer is 0.4-0.7 cm per square centimeter. 2 .

8. A method for preparing a microporous membrane for covering cherry tree crowns, characterized in that: The following steps are involved: Step S1, using 45-55wt% of calcium carbonate powder with a D50 particle size of less than 50nm, 1-8wt% of polyethylene wax, 1-5wt% of silane coupling agent, 0.1-1wt% of anti-aging agent, 25-35wt% of metallocene polyethylene with an ethylene content of 80-99wt% and a melt flow rate of 2.5-10g / 10min, 5-15wt% of linear low-density polyethylene with a melt flow rate of 2-5g / 10min, and 5-10wt% of low-density polyethylene with a melt flow rate of 3-6 g / 10min as raw materials by melt extrusion, casting and uniaxial stretching; Step S2, using 25-50 wt% of low-density polyethylene with a melt flow rate of 2-5 g / 10 min and 50-75 wt% of linear low-density polyethylene with a melt flow rate of 1-2 g / 10 min as raw materials, by blow molding, cooling and punching, to prepare a protective plastic film layer; Step S3, cutting the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer to a preset size, and then laying the microporous plastic film main layer, the non-woven fabric reinforcing moisture-conducting layer and the protective plastic film layer in sequence, from the two edges in the width direction of the protective plastic film layer to the middle position, using dispersed point gluing or dispersed point hot pressing technology to combine them into one, and the interval between adjacent bonding points is 2~5cm; then the surplus edges on both sides of the width direction of the microporous plastic film main layer are bent to cover the edges of the non-woven fabric reinforcing moisture-conducting layer, and are combined into one by continuous glue bonding or continuous hot pressing technology to obtain a microporous film for covering the cherry tree crown.

9. The method for preparing a microporous membrane for covering cherry tree crowns according to claim 8, characterized in that: In the step S1, the casting temperature is 200-230° C.; during uniaxial stretching, the stretching temperature is 60-90° C., the stretching ratio is 1.5-4.0, the stretching speed is 80-120 mm / min, and the shaping after stretching takes 15-40 minutes.

10. The method for preparing a microporous membrane for covering cherry tree crowns according to claim 8, characterized in that: When the hot pressing process is adopted in step S3, the hot pressing temperature is 170-180° C. and the hot pressing time is 1-5 seconds.

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