Weather-resistant temperature-controlling double-layer sunshade net and preparation method thereof

Abstract

The application belongs to the technical field of agricultural sunshade net, and discloses a weather-resistant and temperature-controlling double-layer sunshade net and a preparation method thereof. The preparation method comprises the following steps: S1, preparing reflective master batch, anti-aging master batch I and anti-aging master batch II by using wax dispersant hot melting dispersion; S2, preparing white flat yarn by extrusion stretching; S3, preparing black flat yarn by extrusion stretching; and S4, obtaining the weather-resistant and temperature-controlling double-layer sunshade net by knitting the white flat yarn and the black flat yarn on a numerical control double-needle bed warp knitting machine. The wax dispersant is used for granulating the reflective master batch, the anti-aging master batch I and the anti-aging master batch II, so that the dispersion performance is improved. The synergistic reflective master batch used in the outer white flat yarn can efficiently reflect light and absorb ultraviolet rays, reduces the heat absorption of the inner black net, and avoids the formation of a hot environment. By designing the double-layer sunshade net, the high reflectivity, high light blocking rate and good air permeability are combined, the problems of heat caused by strong light and damage of the sunshade net caused by exposure to the sun are solved. The obtained sunshade net has significant cooling effect and anti-aging property.

Description

Technical Field

[0001] This invention relates to the field of agricultural shade net technology, specifically to a weather-resistant and temperature-controlled double-layer shade net and its preparation method. Background Technology

[0002] Light and temperature are essential for crop growth, but excessive sunlight can scorch fruits and leaves. This is especially true for shade-loving crops such as tea, vegetables, and medicinal herbs, which require controlled direct sunlight during specific growth stages to prevent strong light and high temperatures from affecting crop quality. Shade nets offer multiple functions, including shading, protection against strong typhoons and heavy rain, moisture retention, and pest and disease control, and are widely used in cash crop cultivation. By adjusting the use of shade nets according to weather changes and the needs of different growth stages, precise quality control of cash crops can be achieved throughout their entire lifecycle. For example, moderate shading of tea leaves can improve their color and increase their amino acid content.

[0003] Currently, most shade nets used for cash crops are black, primarily utilizing the heat-absorbing properties of black to cool the crops. They are also densely woven with increased stitch count to increase shading and cooling. However, the heat absorbed by black shade nets is not easily dissipated quickly and can be conducted to the crops, potentially causing scorching. While denser weaving increases shading, overly dense mesh can obstruct airflow and convection, creating a stuffy, humid environment that severely impacts crops. Furthermore, based on long-term experience using black shade nets in matcha cultivation, denser weaving leads to localized high temperatures, hindering air circulation and heat dissipation. This accelerates the photothermal aging of the net, reduces its weather resistance, and makes it brittle and prone to breakage after a period of use, thus shortening its lifespan. Summary of the Invention

[0004] In view of this, and addressing the shortcomings of current black shade nets, such as poor weather resistance and insufficient temperature control, this invention provides a weather-resistant and temperature-controlled double-layer shade net and its preparation method. By designing a double-layer shade net, the outer layer is made of white reflective, weather-resistant flat yarn knitting, and the inner layer is made of black flat yarn knitting. Utilizing the reflection of infrared light and the air convection channels formed by the double layers, it not only achieves high shading efficiency but also provides excellent hot air convection and ventilation. Furthermore, the dispersibility of reflective and anti-aging additives is improved, resulting in flat yarns that, when used in the double-layer shade net, possess excellent reflectivity, temperature control, and weather resistance, significantly extending the service life of the shade net.

[0005] In a first aspect, the present invention provides a method for preparing a weather-resistant and temperature-controlled double-layer shading net, comprising the following steps: S1. Disperse the reflective agent, coupling agent, and dispersant at a mass ratio of 100:(2-3):(15-20) at 90-100℃ using strong dispersion, and cool to obtain a reflective masterbatch; Disperse the light stabilizer 783, ultraviolet absorber UV-360, antioxidant 1010, antioxidant 168, coupling agent, and dispersant at a mass ratio of (7-9):(5-7):(4-5):(1-2):(0.5-0.8):(3-4) at 90-100℃ using strong dispersion. Dispersed and cooled, anti-aging masterbatch I was obtained; light stabilizer 783, antioxidant 1010, antioxidant 168, coupling agent, and dispersant were strongly dispersed at 90-100℃ in a mass ratio of (6-7):(2-3):(1-2):(0.3-0.5):(2-3), and cooled to obtain anti-aging masterbatch II; the reflective agent was composed of rutile titanium dioxide, barium sulfate, and zinc oxide in a mass ratio of 2:(1-2):(1-2); the dispersant was a waxy dispersant; S2. Mix 92-95 parts polyethylene, 4-6 parts reflective masterbatch, 1.2-1.5 parts anti-aging masterbatch I, and 0.3-0.5 parts opening agent evenly in a high-speed mixer according to the weight ratio; feed into a single-screw extruder for melt extrusion, extrude into a film through a flat die, cool and slit into flat filaments, heat and stretch in an oven, cool and shape, and then wind up to obtain white flat filaments; S3. Mix 94-97 parts polypropylene, 2-4 parts black masterbatch, 1.2-1.4 parts anti-aging masterbatch II, and 0.3-0.5 parts opening agent evenly in a high-speed mixer according to the weight ratio; feed into a single-screw extruder for melt extrusion, extrude into a film through a flat die, cool and slit into flat filaments, heat and stretch in an oven, cool and shape, and then wind up to obtain black flat filaments; S4. White flat yarn and black flat yarn are fed into the warp beam through the yarn guide. On a CNC double needle bed warp knitting machine, the white flat yarn is knitted on the front needle bed to form the outer layer mesh, and the black flat yarn is knitted on the rear needle bed to form the inner layer mesh. The white flat yarn is used to alternately form loops between the front and rear needle beds to connect the outer and inner layers mesh. Polyester yarn is used for edge locking to obtain a weather-resistant and temperature-controlled double-layer shade net.

[0006] Preferably, the reflective agent is composed of rutile titanium dioxide, barium sulfate, and zinc oxide in a mass ratio of 2:1:1. Rutile titanium dioxide possesses excellent infrared reflection and ultraviolet absorption properties; barium sulfate exhibits excellent infrared reflection properties, while zinc oxide demonstrates excellent ultraviolet absorption properties. Through the synergistic effect of the composite of rutile titanium dioxide, barium sulfate, and zinc oxide, dispersed in white flat yarn, infrared rays can be efficiently reflected back into the atmosphere, while ultraviolet rays are absorbed. This prevents heat from being directly absorbed and conducted within the flat yarn, resulting in significant cooling and anti-aging effects on the shade net.

[0007] More preferably, the rutile titanium dioxide has a D50 particle size of <300nm; the barium sulfate has a D90 particle size of <5μm; and the zinc oxide has a D50 particle size of <200nm.

[0008] Preferably, the coupling agent is at least one of silane coupling agent KH-560, silane coupling agent KH-550, and silane coupling agent KH-570.

[0009] Preferably, the wax dispersant is one of polyethylene wax, oxidized polyethylene wax, or EVA wax.

[0010] In the preparation of reflective masterbatch, under the action of coupling agent and wax dispersant, the wax dispersant melts, wets and binds the reflective additive. After cooling, the reflective additive powder becomes small particle masterbatch, avoiding dust. When used, it is directly added to plastic. During extrusion, it melts and disperses quickly, ensuring that the reflective additive is evenly dispersed, increasing the smoothness of flat yarn and reflective effect.

[0011] Ultraviolet absorbers and antioxidants are in powder form and added in small quantities. If directly added to plastics, they are prone to electrostatic adsorption and agglomeration. During extrusion, the agglomerates cannot be completely broken up by extrusion shearing, and poor compatibility leads to uneven dispersion. In the preparation of anti-aging masterbatch I and anti-aging masterbatch II, pre-dispersion is achieved through coupling agents and wax dispersants. The wax dispersants are melted and moistened, finally forming granular anti-aging masterbatch, which is rapidly melted and dispersed during plastic extrusion. Conventional commercially available anti-aging masterbatches with resin carriers, although well dispersed, have high dispersion temperatures and poor formulation compatibility. The anti-aging masterbatch I and anti-aging masterbatch II of this invention are easy to disperse, readily available, and easy to modify in formulation.

[0012] Preferably, the polyethylene is selected from high-density polyethylene (HDPE) with a melt index of 0.8-1.5 g / 10 min (190℃, 2.16 g).

[0013] Preferably, the polypropylene is selected as fiber-grade polypropylene with a melt index of 2-5 g / 10 min (230℃, 2.16 kg).

[0014] Preferably, the carbon black content of the masterbatch is 40-50 wt%.

[0015] Preferably, the opening agent is selected from at least one of erucamide, oleamide, and ethylene bis-stearamide.

[0016] Preferably, the warp knitting process involves using knitting needles to bend flat yarns into loops and interlock them. The interlocking process can employ either plain knitting (PZ) or self-locking knitting (ZZ). Self-locking knitting (ZZ), such as the self-locking knitting (ZZ) process in standard T / ZZB2772-2022 (Agricultural Plastic Warp-Knitted Shade Net), is particularly preferred, as it offers excellent longitudinal dimensional stability, good anti-curling properties, good breathability, and a strong sense of crispness.

[0017] Preferably, both the outer and inner mesh layers are 4-pin meshes.

[0018] Secondly, this invention provides a weather-resistant and temperature-controlled double-layer shade net prepared by the above method. The double-layer shade net uses reflective masterbatch and anti-aging masterbatch I in the outer white flat yarn layer to reflect a significant amount of light for primary cooling, while anti-aging masterbatch I prevents photo-oxidative degradation of the plastic and shields against ultraviolet rays, effectively delaying photo-aging. The inner black flat yarn layer uses black masterbatch and anti-aging masterbatch II to absorb residual heat and prevent photo-oxidative aging of the plastic. The double-layer shade net has a three-dimensional mesh, facilitating air convection and heat dissipation. With a low needle count and a large number of mesh openings, the shade net achieves a shading rate greater than 80%, combining high shading rate with good air permeability, resulting in significant temperature control.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention features a double-layered shade net. The outer white net uses synergistic reflective agents to efficiently reflect and absorb ultraviolet rays, while the inner black net absorbs heat, preventing a stuffy environment. It combines high shading rate with good breathability and thermal air convection, solving the problems of high temperature and stuffiness caused by strong sunlight and damage from sun exposure. The shade net exhibits significant temperature control and anti-aging effects.

[0020] 2. This invention addresses the difficulties in dispersing ultrafine powders of reflective additives, as well as the problems of electrostatic adsorption and agglomeration of ultraviolet absorbers and antioxidants, which prevent the extrusion shear from being fully opened during melt extrusion in plastics. By dispersing and granulating reflective masterbatch, anti-aging masterbatch I, and anti-aging masterbatch II with a waxy dispersant, it not only facilitates formula adjustment, has good compatibility, and is easy to mix and add, but also avoids problems such as dust flying and segregation. Moreover, it is easy to disperse in flat filaments, eliminating the need for a twin-screw extruder with high shear force; dispersion can be achieved with a single screw, thus avoiding the decomposition of ultraviolet absorbers caused by high shear and high temperature.

[0021] 3. The shade net of this invention is knitted in one go using a CNC double-needle bed warp knitting machine, which has high production efficiency; the double-layer shade net has a stable structure, obvious shading and cooling effect, and long service life, making it suitable for large-scale application in the refined cooling management and anti-scorching management of economic crops. Detailed Implementation

[0022] To make the technical solution of this invention more apparent and understandable, further detailed descriptions are provided below. Based on common sense that can be understood by those skilled in the art, the raw materials, equipment, and processes not explicitly limited are all conventional choices that can be understood by those skilled in the art. Self-locking knitting is the self-locking knitting (ZZ) weaving process in standard T / ZZB2772-2022 (agricultural plastic warp-knitted shade net); the screw diameter of the single-screw extruder is φ90mm, and the length-to-diameter ratio is 30:1.

[0023] Example 1 S1. 5 kg of rutile titanium dioxide (D50 particle size < 300 nm), 2.5 kg of precipitated barium sulfate (D90 particle size < 5 μm), and 2.5 kg of zinc oxide (D50 particle size < 200 nm) were used as reflective additives. These were then mixed with 0.3 kg of silane coupling agent KH-550 and 2 kg of polyethylene wax in a 100℃ mixer at 200 rpm for 20 minutes with vigorous stirring. The polyethylene wax melted, moistened, dispersed, and bonded the reflective additives. After cooling, the reflective additive powder became small-particle reflective masterbatch. 0.8 kg of light stabilizer 783 and 0.6 kg of ultraviolet absorber U... V-360, 0.5 kg antioxidant 1010, 0.2 kg antioxidant 168, 0.08 kg silane coupling agent KH-560, and 0.4 kg EVA wax were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch I; 0.6 kg light stabilizer 783, 0.3 kg antioxidant 1010, 0.2 kg antioxidant 168, 0.05 kg silane coupling agent KH-560, and 0.3 kg EVA wax were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch II; S2. Mix 95kg HDPE (ZH5000S, melt index 0.9g / 10min, Zhenhai Refining & Chemical), 5kg reflective masterbatch, 1.5kg anti-aging masterbatch I, and 0.5kg opening agent erucamide evenly in a high-speed mixer; feed it into a single-screw extruder for melt extrusion, with the following temperatures for each heating zone: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 230℃; flat die 220℃; extrude into film, cool, and slit into flat filaments, heat in an oven at 100℃, stretch at a 1:5 draw ratio, cool and set, and then wind to obtain white flat filaments with a width of 4mm; S3. Mix 96 kg of fiber-grade polypropylene (T30S, melt index 3.3 g / 10 min, Zhongjing Petrochemical), 3 kg of black masterbatch (carbon black content 40 wt%), 1.3 kg of anti-aging masterbatch II, and 0.5 kg of erucamide opening agent evenly in a high-speed mixer; the temperatures of each heating section are: Zone 1 190℃, Zone 2 210℃, Zone 3 220℃, Zone 4 240℃, Zone 5 240℃; flat die 230℃; extrude into film, cool, slit into flat filaments, heat in an oven at 110℃, stretch at a 1:7 draw ratio, cool and set, and wind up to obtain black flat filaments with a width of 3 mm; S4. White and black flat yarns are fed into the warp beam via yarn guides. On a CNC double-needle bed warp knitting machine, the white flat yarn is self-locked on the front needle bed to form the outer layer mesh, and the black flat yarn is self-locked on the rear needle bed to form the inner layer mesh. Both the outer and inner layers are 4-needle meshes. The white flat yarns are alternately looped between the front and rear needle beds to connect the outer and inner layers. The edges are finished with polyester yarn to obtain a weather-resistant and temperature-controlled double-layer shade net.

[0024] Example 2 S1. 4 kg of rutile titanium dioxide (D50 particle size < 300 nm), 4 kg of precipitated barium sulfate (D90 particle size < 5 μm), and 2 kg of zinc oxide (D50 particle size < 200 nm) were used as reflective additives. These were then mixed with 0.2 kg of silane coupling agent KH-570 and 3 kg of oxidized polyethylene wax in a 100℃ mixer at 200 rpm for 20 minutes with vigorous stirring. The oxidized polyethylene wax melted, moistened, dispersed, and bound the reflective additives. After cooling, the reflective additive powder became small-particle reflective masterbatch. 0.9 kg of light stabilizer 783 and 0.7 kg of ultraviolet absorber UV were also used. -360, 0.5 kg antioxidant 1010, 0.2 kg antioxidant 168, 0.08 kg silane coupling agent KH-560, and 0.4 kg polyethylene wax were vigorously stirred and dispersed at 200 rpm for 15 min at 100℃, and then cooled to obtain anti-aging masterbatch I; 0.6 kg light stabilizer 783, 0.3 kg antioxidant 1010, 0.2 kg antioxidant 168, 0.05 kg silane coupling agent KH-560, and 0.3 kg polyethylene wax were vigorously stirred and dispersed at 200 rpm for 15 min at 100℃, and then cooled to obtain anti-aging masterbatch II; S2. Mix 92kg HDPE (ZH5000S, melt index 0.9g / 10min, Zhenhai Refining & Chemical), 6kg reflective masterbatch, 1.5kg anti-aging masterbatch I, and 0.5kg opening agent oleic amide evenly in a high-speed mixer; feed into a single-screw extruder for melt extrusion, with the following temperatures for each heating zone: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 230℃; flat die 220℃; extrude into film, cool, and slit into flat filaments, heat in an oven at 100℃, stretch at a 1:5 draw ratio, cool and set, and then wind to obtain white flat filaments with a width of 4mm; S3. Mix 94 kg of fiber-grade polypropylene (T30S, melt index 3.3 g / 10 min, Zhongjing Petrochemical), 3 kg of black masterbatch (carbon black content 40 wt%), 1.2 kg of anti-aging masterbatch II, and 0.3 kg of erucamide opening agent evenly in a high-speed mixer; the temperatures of each heating section are: Zone 1 190℃, Zone 2 210℃, Zone 3 220℃, Zone 4 240℃, Zone 5 240℃; flat die 230℃; extrude into film, cool, slit into flat filaments, heat in an oven at 110℃, stretch at a 1:7 stretch ratio, cool and set, and wind up to obtain black flat filaments with a width of 3 mm; S4. White and black flat yarns are fed into the warp beam via yarn guides. On a CNC double-needle bed warp knitting machine, the white flat yarn is self-locked on the front needle bed to form the outer layer mesh, and the black flat yarn is self-locked on the rear needle bed to form the inner layer mesh. Both the outer and inner layers are 4-needle meshes. The white flat yarns are alternately looped between the front and rear needle beds to connect the outer and inner layers. The edges are finished with polyester yarn to obtain a weather-resistant and temperature-controlled double-layer shade net.

[0025] Example 3 S1. 4 kg of rutile titanium dioxide (D50 particle size < 300 nm), 2 kg of precipitated barium sulfate (D90 particle size < 5 μm), and 4 kg of zinc oxide (D50 particle size < 200 nm) were used as reflective additives. These were then mixed with 0.2 kg of silane coupling agent KH-560 and 2 kg of polyethylene wax in a 100℃ mixer at 200 rpm for 20 minutes with vigorous stirring. The polyethylene wax melted, moistened, dispersed, and bonded the reflective additives. After cooling, the reflective additive powder became small-particle reflective masterbatch. 0.7 kg of light stabilizer 783 and 0.6 kg of ultraviolet absorber UV-... 360, 0.4 kg of antioxidant 1010, 0.2 kg of antioxidant 168, 0.08 kg of silane coupling agent KH-560, and 0.4 kg of EVA wax were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch I; 0.7 kg of light stabilizer 783, 0.3 kg of antioxidant 1010, 0.2 kg of antioxidant 168, 0.05 kg of silane coupling agent KH-560, and 0.3 kg of EVA wax were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch II; S2. Mix 95kg HDPE (ZH5000S, melt index 0.9g / 10min, Zhenhai Refining & Chemical), 4kg reflective masterbatch, 1.5kg anti-aging masterbatch I, and 0.5kg opening agent erucamide evenly in a high-speed mixer; feed into a single-screw extruder for melt extrusion, with the following heating zone temperatures: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 230℃; flat die 220℃; extrude into film, cool, and slit into flat filaments, heat in an oven at 100℃, stretch at a 1:5 draw ratio, cool and set, and then wind to obtain white flat filaments with a width of 4mm; S3. Mix 96 kg of fiber-grade polypropylene (T30S, melt index 3.3 g / 10 min, Zhongjing Petrochemical), 4 kg of black masterbatch (carbon black content 40 wt%), 1.4 kg of anti-aging masterbatch II, and 0.5 kg of opening agent ethylene bis-stearamide evenly in a high-speed mixer; the temperatures of each heating section are: Zone 1 190℃, Zone 2 210℃, Zone 3 220℃, Zone 4 240℃, Zone 5 240℃; flat die 230℃; extrude into film, cool, slit into flat filaments, heat in an oven at 110℃, stretch at a 1:7 stretch ratio, cool and set, and wind up to obtain black flat filaments with a width of 3 mm; S4. White and black flat yarns are fed into the warp beam via yarn guides. On a CNC double-needle bed warp knitting machine, the white flat yarn is self-locked on the front needle bed to form the outer layer mesh, and the black flat yarn is self-locked on the rear needle bed to form the inner layer mesh. Both the outer and inner layers are 4-needle meshes. The white flat yarns are alternately looped between the front and rear needle beds to connect the outer and inner layers. The edges are finished with polyester yarn to obtain a weather-resistant and temperature-controlled double-layer shade net.

[0026] Comparative Example 1 S1. 5 kg of rutile titanium dioxide (D50 particle size < 300 nm), 2.5 kg of precipitated barium sulfate (D90 particle size < 5 μm), and 2.5 kg of zinc oxide (D50 particle size < 200 nm) were used as reflective additives and dispersed with 0.3 kg of silane coupling agent KH-550 in a mixer at 100℃ with vigorous stirring at 200 rpm for 20 min. After cooling, a powdery reflective masterbatch was obtained. 0.8 kg of light stabilizer 783, 0.6 kg of ultraviolet absorber UV-360, and 0... 0.5 kg of antioxidant 1010, 0.2 kg of antioxidant 168, and 0.08 kg of silane coupling agent KH-560 were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch I; 0.6 kg of light stabilizer 783, 0.3 kg of antioxidant 1010, 0.2 kg of antioxidant 168, and 0.05 kg of silane coupling agent KH-560 were vigorously stirred and dispersed at 200 rpm for 15 min at 95℃, and then cooled to obtain anti-aging masterbatch II. S2. Mix 95kg HDPE (ZH5000S, melt index 0.9g / 10min, Zhenhai Refining & Chemical), 4.18kg reflective masterbatch, 1.27kg anti-aging masterbatch I, and 0.5kg opening agent erucamide evenly in a high-speed mixer; feed it into a single-screw extruder for melt extrusion. The temperatures of each heating section are: Zone 1 180℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 230℃; flat die 220℃; extrude into film, cool, and slit into flat filaments. Heat in an oven at 100℃, stretch at a 1:5 draw ratio, cool and set, and then wind to obtain white flat filaments with a width of 4mm. S3. Mix 96 kg of fiber-grade polypropylene (T30S, melt index 3.3 g / 10 min, Zhongjing Petrochemical), 3 kg of black masterbatch (carbon black content 40 wt%), 1.03 kg of anti-aging masterbatch II, and 0.5 kg of opening agent erucamide evenly in a high-speed mixer; the temperatures of each heating section are: Zone 1 190℃, Zone 2 210℃, Zone 3 220℃, Zone 4 240℃, Zone 5 240℃; flat die 230℃; extrude into film, cool, slit into flat filaments, heat in an oven at 110℃, stretch at a 1:7 stretch ratio, cool and set, and wind up to obtain black flat filaments with a width of 3 mm; S4. White and black flat yarns are fed into the warp beam via yarn guides. On a CNC double-needle bed warp knitting machine, the white flat yarn is self-locked on the front needle bed to form the outer layer mesh, and the black flat yarn is self-locked on the rear needle bed to form the inner layer mesh. Both the outer and inner layers are 4-needle meshes. The white flat yarns are alternately looped between the front and rear needle beds to connect the outer and inner layers. The edges are finished with polyester yarn to obtain a weather-resistant and temperature-controlled double-layer shade net.

[0027] In this comparative example, conventional coupling dispersion was used when processing reflective additives and anti-aging agents; otherwise, it was the same as in Example 1. The reflective masterbatch was still an ultrafine powder, while the anti-aging masterbatch was an agglomerated powder, which was difficult to depolymerize and disperse in the polymer melt, resulting in limited improvement in the reflective and anti-aging properties of the flat filaments.

[0028] Comparative Example 2 The reflective additives used in this comparative example consisted of 5 kg of rutile titanium dioxide (D50 particle size < 300 nm) and 5 kg of precipitated barium sulfate (D90 particle size < 5 μm), with zinc oxide omitted. The rest was the same as in Example 1.

[0029] Comparative Example 3 The reflective additives used in this comparative example consisted of 5 kg of rutile titanium dioxide (D50 particle size < 300 nm) and 5 kg of zinc oxide, with the precipitated barium sulfate omitted. The rest was the same as in Example 1.

[0030] Comparative Example 4 This comparative example uses a single-layer black shade net with 7 needles knitted from black flat yarn in Example 1, which has a light-blocking rate similar to that of the double-layer shade net in Example 1.

[0031] The aging resistance, thermal cycling resistance, and shading rate of the shade net were comprehensively tested and evaluated in accordance with the relevant technical requirements of QB / T 2000-2017 "Plastic Warp-knitted Shade Net" and T / ZZB2772-2022 "Agricultural Plastic Warp-knitted Shade Net". 1. Light aging resistance test According to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", the same batch of samples underwent ultraviolet lamp exposure aging tests. The cyclic aging conditions were: using a type 1A (UVA-340) lamp, at 340nm, 0.76W / m 2 One cycle consisted of irradiation at 60℃ for 8 hours (irradiated surface being the white outer layer of the shading net) followed by condensation at 50℃ without irradiation for 4 hours. After 1200 cycles, the shading net's resistance to UV aging was evaluated by the retention rate (E) of the tensile breaking strength after UV aging. E = (F / F0) × 100%, where F0 is the initial tensile breaking strength of the sample and F is the tensile breaking strength after exposure aging. The tensile test was conducted with samples cut in the warp and weft directions, each 300 mm long and 50 mm wide, at a tensile rate of 200 mm / min. The test results are shown in Table 1.

[0032] 2. Thermal cycling resistance test The shade net was placed in a thermal shock test chamber, subjected to a high temperature of 60℃ for 4 hours and a low temperature of -20℃ for 4 hours as one cycle, and the experiment was repeated for 3 cycles, for a total of 24 hours. The retention rate of the tensile breaking strength of the shade net after thermal shock was measured. The test results are shown in Table 1.

[0033] Table 1: 3. Opacity Test The shading rate of the shade net was tested according to GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics". The test results are shown in Table 2.

[0034] 4. Cooling effect test A simulation test of the cooling effect of the shade net was conducted: On a sunny day with stable sunlight and wind speed, in an area with no surrounding obstructions, the shade net was erected 1.5 meters above the ground. After shading for 2 hours during the hottest period, the outdoor temperature was continuously measured to obtain the average outdoor temperature. The temperature was also continuously measured at 0.5m and 1.4m above the ground where the shade net was covering the area. The cooling effect of the shade net was objectively evaluated. Data records are shown in Table 2.

[0035] Table 2: Analysis of the test results in Tables 1 and 2 shows that: The double-layer shade net of this invention incorporates dispersed and synergistic reflective and anti-aging agents in its flat yarns. This allows for timely absorption and dissipation of ultraviolet radiation during UV irradiation, resulting in high retention of tensile strength during thermal aging and excellent weather resistance. The outer layer of flat yarns uses a composite reflective agent, combining reflectivity with UV absorption and cooling effects, achieving a temperature reduction exceeding 9.5°C. Near the shade net (at 1.4m), the double-layer shade net's light reflection effect significantly reduces solar radiation absorption, lowering the net's temperature. Good ventilation near the shade net allows heat to dissipate quickly through convection, preventing significant temperature increases.

[0036] In Comparative Example 1, the reflective additives and anti-aging agents were added in powder form after being directly coupled using traditional methods. However, issues such as agglomeration, electrostatic adsorption, and stickiness led to segregation and diffusion obstruction during the flat wire processing, affecting the uniform dispersion of the flat wire and consequently reducing the reflective and cooling effect and weather resistance.

[0037] Comparative Example 2 used rutile titanium dioxide and precipitated barium sulfate as reflective agents, omitting zinc oxide. Precipitated barium sulfate showed a significant reflective effect and a relatively stable cooling effect. However, without zinc oxide, ultraviolet light absorption decreased, and resistance to ultraviolet aging was significantly reduced, with the tensile strength retention rate after ultraviolet aging dropping below 80%.

[0038] Comparative Example 3 used rutile titanium dioxide and zinc oxide as reflective agents, eliminating precipitated barium sulfate. This resulted in reduced infrared reflection, increased ultraviolet absorption, and a significant temperature increase at 1.4m.

[0039] Comparative Example 4, a 7-needle single-layer black shade net with a similar light transmittance to Example 1, serves as a reference. Under the same shading conditions, its cooling effect is significantly reduced. This is mainly because the black shade net has a high absorption rate of solar radiation, leading to an increase in temperature inside the net. The temperature at 1.4m is significantly higher than that in Example 1.

[0040] The foregoing describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a weather-resistant and temperature-controlled double-layer shading net, characterized in that, Includes the following steps: S1. Disperse the reflective agent, coupling agent, and dispersant at a mass ratio of 100:(2-3):(15-20) at 90-100℃ using strong dispersion, and cool to obtain a reflective masterbatch; Disperse the light stabilizer 783, ultraviolet absorber UV-360, antioxidant 1010, antioxidant 168, coupling agent, and dispersant at a mass ratio of (7-9):(5-7):(4-5):(1-2):(0.5-0.8):(3-4) at 90-100℃ using strong dispersion. Dispersed and cooled, anti-aging masterbatch I was obtained; light stabilizer 783, antioxidant 1010, antioxidant 168, coupling agent, and dispersant were strongly dispersed at 90-100℃ in a mass ratio of (6-7):(2-3):(1-2):(0.3-0.5):(2-3), and cooled to obtain anti-aging masterbatch II; the reflective agent was composed of rutile titanium dioxide, barium sulfate, and zinc oxide in a mass ratio of 2:(1-2):(1-2); the dispersant was a waxy dispersant; S2. Mix 92-95 parts polyethylene, 4-6 parts reflective masterbatch, 1.2-1.5 parts anti-aging masterbatch I, and 0.3-0.5 parts opening agent evenly in a high-speed mixer according to the weight ratio; feed into a single-screw extruder for melt extrusion, extrude into a film through a flat die, cool and slit into flat filaments, heat and stretch in an oven, cool and shape, and then wind up to obtain white flat filaments; S3. Mix 94-97 parts polypropylene, 2-4 parts black masterbatch, 1.2-1.4 parts anti-aging masterbatch II, and 0.3-0.5 parts opening agent evenly in a high-speed mixer according to the weight ratio; feed into a single-screw extruder for melt extrusion, extrude into a film through a flat die, cool and slit into flat filaments, heat and stretch in an oven, cool and shape, and then wind up to obtain black flat filaments; S4. White flat yarn and black flat yarn are fed into the warp beam through the yarn guide. On a CNC double needle bed warp knitting machine, the white flat yarn is knitted on the front needle bed to form the outer layer mesh, and the black flat yarn is knitted on the rear needle bed to form the inner layer mesh. The white flat yarn is used to alternately form loops between the front and rear needle beds to connect the outer and inner layers mesh. Polyester yarn is used for edge locking to obtain a weather-resistant and temperature-controlled double-layer shade net.

2. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The reflective additive is composed of rutile titanium dioxide, barium sulfate, and zinc oxide in a mass ratio of 2:1:

1.

3. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The rutile titanium dioxide has a D50 particle size of <300nm; the barium sulfate has a D90 particle size of <5μm; and the zinc oxide has a D50 particle size of <200nm.

4. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The coupling agent is at least one of silane coupling agent KH-560, silane coupling agent KH-550, and silane coupling agent KH-570.

5. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The wax dispersant is one of polyethylene wax, oxidized polyethylene wax, or EVA wax.

6. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The polyethylene selected is high-density polyethylene with a melt index of 0.8-1.5 g / 10 min at 190℃ and 2.

16.

7. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The polypropylene selected is a fiber-grade polypropylene with a melt index of 2-5 g / 10 min at 230℃ and 2.16 kg.

8. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The opening agent is selected from at least one of erucamide, oleamide, and ethylene bis-stearamide.

9. The method for preparing a weather-resistant and temperature-controlled double-layer shading net according to claim 1, characterized in that, The warp knitting process employs either ordinary knitting or self-locking knitting.

10. A weather-resistant and temperature-controlled double-layer shading net obtained by the preparation method according to any one of claims 1-9.

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