Coating type light-conversion high-heat-preservation pinhole mulching film used in greenhouse and preparation method

Abstract

The invention belongs to the technical field of agricultural films, and particularly relates to a coating type light-conversion high-heat-preservation pinhole mulching film used in a greenhouse and a preparation method of the coating type light-conversion high-heat-preservation pinhole mulching film. The coating type light-conversion high-heat-preservation pinhole mulching film used in the greenhouse sequentially comprises a coating layer, an outer layer, a secondary outer layer, a middle layer, a secondary inner layer and an inner layer from outside to inside. The outer layer and the inner layer comprise low-density metallocene polyethylene, high-density metallocene polyethylene and long-life master batch; the secondary outer layer and the secondary inner layer comprise a thermal insulation master batch taking linear low-density powder as a carrier, a long-life master batch, low-density metallocene polyethylene and linear low-density polyethylene; and the middle layer comprises a heat preservation master batch taking an ethylene-vinyl acetate copolymer as a carrier, a light conversion master batch, a long-life master batch and the ethylene-vinyl acetate copolymer. According to the coating type light-conversion high-heat-preservation pinhole mulching film used in the greenhouse, the lasting period of dripping fog dissipation is synchronous with the service life, heat preservation is good, and air permeability is good; the invention further provides a preparation method which is reasonable in process, simple and feasible.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural films, and in particular relates to a coated light-converting and high-heat-insulating pinhole mulch film used in greenhouses and a preparation method thereof. Background Art

[0002] Greenhouse mulching technology is a core method for increasing crop yields in modern agriculture. Traditional white mulch, with its high light transmittance, effectively allows daytime solar radiation to penetrate the film layer, accumulating heat in the soil. It also reduces soil moisture evaporation through physical barriers (highly efficient moisture conservation), protecting the roots and promoting growth during the seedling stage. However, it suffers from the following key drawbacks: (1) Poor thermal insulation at night: Due to the lack of effective blocking of far-infrared radiation in the 8-14 μm band, more than 60% of the heat accumulated during the day is lost in the form of thermal radiation at night, causing the ground temperature to fluctuate by more than 10°C between day and night, seriously inhibiting the growth of seedlings.

[0003] (2) Loss of dripping function: When the temperature difference between the inside and outside of the membrane is ≥5°C, the density of condensed water droplets on the inner surface of the membrane can reach 200-500 drops / cm². These water droplets cause incident light scattering due to the difference in refractive index, reducing the actual light flux reaching the ground and significantly weakening the heat storage effect.

[0004] (3) Obstruction of soil gas exchange: The closed environment leads to high CO2 concentration and low O2 concentration in the soil, which directly inhibits root aerobic respiration and causes a decrease in the nutrient absorption efficiency of crops in the later stage.

[0005] To improve thermal insulation, functional ground films containing hydrotalcite-based insulation agents have been introduced. However, these films face significant challenges: high cost, requiring high dosages of hydrotalcite to effectively block infrared rays; processing defects, as high dosages can easily lead to particle aggregation and formation of large crystals, which affect the film's light transmittance; and performance degradation, as the hydrotalcite layered structure easily peels and decomposes under shear forces during processing, resulting in a typically short insulation lifespan.

[0006] CN112210144A discloses a condensation-resistant, specially translucent ground film, comprising Lanhua 7042, high-pressure, EVA, and a functional masterbatch (UV absorber, light-converting agent, heat-insulating agent, dripping agent, defogging agent, ultramarine, paraffin, and zinc stearate). By adding the UV absorber, light-converting agent, and ultramarine, the film avoids insufficient light transmittance during use. However, the film is expensive, has unstable light-converting properties, and cannot combine other properties. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a coated light-converting, high-insulation pinhole ground film for use in greenhouses, the dripping and mist elimination duration of which is synchronized with the service life, with a high far-infrared blocking rate, excellent thermal insulation performance, and good air permeability; the present invention also provides a preparation method thereof, which has a reasonable process and is simple and feasible.

[0008] The coated light-converting and high-heat-insulating pinhole ground film used in the greenhouse of the present invention comprises, from the outside to the inside, a coating layer, an outer layer, a sub-outer layer, a middle layer, a sub-inner layer, and an inner layer; The outer layer and the inner layer are both made of the following raw material components in percentage by mass: 70-80% low-density metallocene polyethylene, 10-20% high-density metallocene polyethylene, and 5-10% long-life masterbatch; the low-density metallocene polyethylene used in the outer layer and the inner layer is preferably 2010RA produced by Mobil Exxon.

[0009] The sub-outer layer and the sub-inner layer are both made of the following raw material components in order of mass percentage: 20-30% thermal insulation masterbatch with linear low-density powder as carrier, 5-10% longevity masterbatch, 20-30% low-density metallocene polyethylene, and 30-40% linear low-density polyethylene; the low-density metallocene polyethylene used in the sub-outer layer and the sub-inner layer is preferably 1018RA produced by Mobil Exxon.

[0010] The middle layer is made of the following raw material components according to mass percentage: 30-40% ethylene-vinyl acetate copolymer as a carrier thermal insulation masterbatch, 5-10% light conversion masterbatch, 5-10% longevity masterbatch, and 40-50% ethylene-vinyl acetate copolymer.

[0011] The mass percentages of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are: outer layer 15%, sub-outer layer 20%, middle layer 30%, sub-inner layer 20%, inner layer 15%. The coating amount of the coating layer is 0.15g / m 2 ~0.2g / m 2 .

[0012] The longevity masterbatch is made of the following raw material components according to mass percentage: 5-8% light stabilizer, 1-2% composite antioxidant, and 90-94% linear low-density polyethylene; The thermal insulation masterbatch with the linear low-density powder as a carrier is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-20% kaolin, 10-20% polysiloxane, and 60-70% linear low-density polyethylene; The thermal insulation masterbatch with ethylene-vinyl acetate copolymer as the carrier is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-20% kaolin, 10-20% polysiloxane, and 60-70% ethylene-vinyl acetate copolymer; The light conversion masterbatch is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-12% light conversion agent, and 86-89% ethylene-vinyl acetate copolymer.

[0013] The ethylene-vinyl acetate copolymer has a melt index of 0.65 g / 10 min and a density of 0.942 g / cm3 at 190° C. and 2.16 kg. 3 , vinyl acetate (VA) content 19%; preferably FL00119 produced by Mobil Exxon.

[0014] The low-density metallocene polyethylene has a melt index of 1 g / 10 min at 190° C. and 2.16 kg, and a density of 0.918-0.920 g / cm 3 ; The high-density metallocene polyethylene has a melt index of 0.2-1 g / 10 min at 190° C. and 2.16 kg, and a density of 0.940-0.96 g / cm 3 ; 4002MC produced by Mobil Exxon is preferred.

[0015] The linear low-density polyethylene has a melt index of 1.8-2 g / 10 min at 190° C. and 2.16 kg, and a density of 0.918-0.923 g / cm 3 , preferably 35BN from Luqing Petrochemical Co., Ltd.

[0016] The mesh number of the kaolin is 10000-15000 mesh; the particle size of the polysiloxane is controlled at 1-3 μm; preferably 5HB produced by BASF and HL100 produced by Yongqi Material Technology (Shanghai) Co., Ltd.

[0017] The composite antioxidant is obtained by compounding a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1, and is preferably B225 produced by Tianjin Lianlong New Materials Co., Ltd.

[0018] The light stabilizer is a hindered amine light stabilizer, preferably the light stabilizer Tiangang® HS-944 produced by Beijing Tiangang Co., Ltd.

[0019] The light conversion agent is a rare earth ion compound, preferably VTFR produced by Changsha Xiweier Co., Ltd. The light conversion agent used converts ultraviolet light of about 350nm into near-infrared light of 690-800nm, thereby achieving a warming effect.

[0020] The pinhole spacing of the coated light-converting high-insulation pinhole mulch is 3 cm in the longitudinal direction and 2 cm in the transverse direction; the diameter of the pinhole is about 0.5 mm; the diameter of the needle roller and needle sleeve is 205 mm; the needle thickness is 2 mm and the needle height is 7.5 mm.

[0021] The coating layer is obtained by applying a coating liquid stock solution. The coating liquid stock solution comprises the following components by weight: 20-30 parts aluminum sol, 15-20 parts silica sol, 10-15 parts surfactant, 5-10 parts organic glue acrylic resin, 3-5 parts defoaming agent, and 20-30 parts purified water. The coating layer is obtained by uniformly mixing the coating liquid stock solution with purified water in a ratio of 1:10, then subjecting the mixture to corona treatment, slurry coating, and drying. The coating liquid stock solution is AG-189 produced by Takemoto Oil & Fats Co., Ltd. of Japan.

[0022] The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film used in a greenhouse comprises the following steps: (1) Preparation of longevity masterbatch: Use an internal mixer to process, add linear low-density polyethylene, light stabilizer, and composite antioxidant in order, stir and shear at high speed for 10-15 minutes, force feed, and send the plasticized masterbatch into the extruder screw, cool and granulate to obtain the longevity masterbatch; (2) Preparation of thermal insulation masterbatch with linear low-density powder as carrier: Use internal mixer to process, add linear low-density polyethylene, kaolin, polysiloxane, and composite antioxidant in order, stir and shear at high speed for 10-15 minutes, force feed, send the plasticized masterbatch into the extruder screw, cool and granulate, and obtain thermal insulation masterbatch with linear low-density powder as carrier; (3) Preparation of thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier: using internal mixer to process, put ethylene-vinyl acetate copolymer, kaolin, polysiloxane, composite antioxidant in order, stir and shear at high speed for 5-10 minutes, force feed, send the plasticized masterbatch into the extruder screw, cool and granulate, and obtain thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier; (4) Preparation of light conversion masterbatch: Use an internal mixer to process, add ethylene-vinyl acetate copolymer, light conversion agent, and composite antioxidant in order, stir and shear at high speed for 5-10 minutes, force feed, and send the plasticized masterbatch into the extruder screw, cool and granulate to obtain the light conversion masterbatch; (5) Preparation of coated light-converting high-insulation pinhole ground film for use in greenhouses: the raw material components of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are uniformly mixed respectively, and the coated multifunctional high-insulation pinhole ground film for use in greenhouses is obtained by blowing, cooling, corona, slurry coating, infiltration, drying, punching and laminating.

[0023] The processing temperature for preparing longevity masterbatch is 140-160℃.

[0024] The processing temperature for preparing thermal insulation masterbatch with linear low-density powder as carrier, thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier, and light conversion masterbatch is 130-150°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a coating process, and the effective period of eliminating mist and dripping can be synchronized with the service life, and can reach a lasting period of at least 6 months.

[0026] (2) The present invention uses a five-layer co-extrusion device, and the formula design is more reasonable and flexible. The high-density metallocene polyethylene used in the outer and inner layers improves the overall puncture resistance of the film, makes the pinholes more uniform, reduces the deformation during punching, and can ensure the mechanical properties of the entire ground film after punching; the middle layer uses ethylene-vinyl acetate copolymer compounded with ethylene-vinyl acetate as a carrier of a new thermal insulation masterbatch to greatly improve the overall thermal insulation performance of the ground film; the sub-outer and sub-inner layers use high-strength metallocene compounded with a linear low-density as a carrier of a new thermal insulation masterbatch, which can ensure the overall physical properties of the film and improve the overall thermal insulation performance of the ground film. The use of five-layer equipment realizes the functional diversification of the ground film.

[0027] (3) The present invention uses a compound of kaolin and polysiloxane as a heat-insulating agent. Compared with traditional hydrotalcite, the haze is low, so that the ground film has a higher far-infrared blocking rate, thereby achieving excellent heat-insulating performance and reducing costs.

[0028] (4) The present invention uses VTFR produced by Changsha Xiweier Co., Ltd. as a light conversion agent. Compared with traditional light conversion agents, it can convert ultraviolet light into near-infrared light with higher energy than visible light, thereby achieving the effect of increasing ground temperature.

[0029] (5) The pinholes punched in the present invention not only meet the functions of air permeability and water permeability, but also have little effect on the mechanical properties of the film, and can meet the requirements of long-term use in the greenhouse. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] The raw materials used in the following examples and comparative examples are: The low-density metallocene polyethylene used in the sub-outer and sub-inner layers is 1018RA produced by Mobil Exxon, which has a melt index of 1g / 10min at 190°C and 2.16kg, and a density of 0.918g / cm 3 .

[0032] The outer and inner layers use low-density metallocene polyethylene: 2010RA produced by Mobil Exxon, which has a melt index of 1g / 10min at 190℃ and 2.16kg, and a density of 0.920g / cm3 .

[0033] The linear low-density polyethylene used in the secondary outer layer and secondary inner layer is 35B from Luqing Petrochemical Co., Ltd., with a melt index of 2g / 10min at 190℃ and 2.16kg, and a density of 0.92g / cm 3 ; The linear low-density polyethylene in the thermal insulation masterbatch with long-life masterbatch and linear low-density powder as carriers uses DGM-1820 from Zhongyuan Petrochemical Company in Puyang, Henan Province. The melt index at 190°C and 2.16kg is 2g / 10min, and the density is 0.923g / cm 3 The high-density metallocene polyethylene used in the outer and inner layers of the embodiment is 4002MC from Mobil Exxon, which has a melt index of 0.25 g / 10 min at 190°C and 2.16 kg, and a density of 0.940 g / cm 3 .

[0034] The high-density linear polyethylene used in the comparative example is 7000F from Mehr Petrochemical Company of Iran, with a melt index of 0.03-0.04 g / 10 min under 2.16 kg conditions and a density of 0.950-0.954 g / cm 3 .

[0035] The raw materials kaolin used in the thermal insulation masterbatch with linear low-density powder as carrier and the thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier in the embodiment are both kaolin produced by BASF, model 5HB; the raw material polysiloxane is produced by Yongqi Material Technology (Shanghai) Co., Ltd., model HL100.

[0036] The heat-insulating agent used in the comparative example is HT-V produced by Sakai Chemical Industry Co., Ltd. of Japan.

[0037] Composite antioxidant: B225 produced by Tianjin Lianlong New Materials Co., Ltd.; (longevity masterbatch, thermal insulation masterbatch with linear low-density powder as carrier, thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier, and light-converting masterbatch all use this raw material).

[0038] The light conversion agents used in the light conversion masterbatch in the examples are all VTFR produced by Changsha Xiweier Co., Ltd.

[0039] The ethylene-vinyl acetate copolymer used in the examples and comparative examples was FL00119 produced by Mobil Exxon, with a melt index of 0.65 g / 10 min under 2.16 kg and a density of 0.942 g / cm 3, vinyl acetate (VA) content 19%. (Light conversion masterbatch, thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier, and middle layer all use this raw material).

[0040] The light stabilizers used are all Tiangang® HS-944 produced by Beijing Tiangang Co., Ltd. The coating liquid stock solution of the coating layer is AG-189 produced by Takemoto Oil & Fats Co., Ltd. of Japan. The coating liquid stock solution is mixed with purified water in a ratio of 1:10 and then coated, calculated in parts by mass.

[0041] Example 1 The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film used in a greenhouse comprises the following steps: (1) Preparation of masterbatch for each layer: The longevity masterbatch is made of the following raw material components according to mass percentage: 5% light stabilizer, 1% composite antioxidant, and 94% linear low-density polyethylene; The thermal insulation masterbatch with the linear low-density powder as the carrier is made of the following raw material components according to mass percentage: 1% composite antioxidant, 20% kaolin, 10% polysiloxane, and 69% linear low-density polyethylene; The thermal insulation masterbatch with ethylene-vinyl acetate copolymer as the carrier is made of the following raw material components according to mass percentage: 1% composite antioxidant, 20% kaolin, 10% polysiloxane, and 69% ethylene-vinyl acetate copolymer; The light conversion masterbatch is made of the following raw material components according to mass percentage: 1% composite antioxidant, 10% light conversion agent, and 89% ethylene-vinyl acetate copolymer; (2) Preparation of various masterbatches: Preparation of longevity masterbatch: Use an internal mixer at 150°C, add linear low-density polyethylene, light stabilizer, and composite antioxidant in that order, stir and shear at high speed for 10 minutes, force feed, and feed the plasticized masterbatch into the extruder screw, cool and granulate to obtain the longevity masterbatch; Preparation of thermal insulation masterbatch with linear low-density powder as carrier: using an internal mixer at 150°C, adding linear low-density polyethylene, kaolin, polysiloxane, and composite antioxidant in that order, stirring and shearing at high speed for 10 minutes, force feeding, feeding the plasticized masterbatch into the extruder screw, cooling and granulating to obtain thermal insulation masterbatch with linear low-density powder as carrier; Preparation of thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier: using an internal mixer at 130°C, adding ethylene-vinyl acetate copolymer, kaolin, polysiloxane, and composite antioxidant in order, stirring and shearing at high speed for 10 minutes, force feeding, feeding the plasticized masterbatch into the extruder screw, cooling and granulating to obtain the thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier; Preparation of light conversion masterbatch: Use an internal mixer at 130°C to add ethylene-vinyl acetate copolymer, light conversion agent, and composite antioxidant in order, stir and shear at high speed for 10 minutes, force feed, and feed the plasticized masterbatch into the extruder screw, cool and granulate to obtain the light conversion masterbatch; (3) Prepare the raw materials for each layer: The outer and inner layers are made of the following raw material components, according to the mass percentage: 70% low-density metallocene polyethylene, 20% high-density metallocene polyethylene, and 10% long-life masterbatch; The sub-outer layer and the sub-inner layer are made of the following raw material components, according to the mass percentage: 30% thermal insulation masterbatch with linear low-density powder as carrier, 10% longevity masterbatch, 30% low-density metallocene polyethylene, and 30% linear low-density polyethylene; The middle layer is made of the following raw material components, according to the mass percentage: 40% ethylene-vinyl acetate copolymer as a carrier thermal insulation masterbatch, 10% light conversion masterbatch, 10% longevity masterbatch, 40% ethylene-vinyl acetate copolymer; (4) Preparation of coated light-converting and high-insulation pinhole film for use in greenhouses: The raw material components of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are uniformly mixed respectively. According to the thickness percentage of each layer, the outer layer is 15%, the sub-outer layer is 20%, the middle layer is 30%, the sub-inner layer is 20%, and the inner layer is 15%. The film thickness is set to 0.015mm by plasticizing and shearing the extruder of each layer. A five-layer co-extruded composite film is obtained. After corona treatment, the coating liquid is applied online at a coating amount of 0.18g / m 2 , dried and shaped to obtain a coated multifunctional high-insulation pinhole film for use in the shed.

[0042] Example 2 The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film used in a greenhouse comprises the following steps: (1) Preparation of masterbatch for each layer: The longevity masterbatch is made of the following raw material components according to mass percentage: 5% light stabilizer, 1% composite antioxidant, and 94% linear low-density polyethylene; The thermal insulation masterbatch with the linear low-density powder as the carrier is made of the following raw material components according to mass percentage: 1% composite antioxidant, 15% kaolin, 15% polysiloxane, and 69% linear low-density polyethylene; The thermal insulation masterbatch with ethylene-vinyl acetate copolymer as the carrier is made of the following raw material components according to mass percentage: 1% composite antioxidant, 15% kaolin, 15% polysiloxane, and 69% ethylene-vinyl acetate copolymer; The light conversion masterbatch is made of the following raw material components according to mass percentage: 1% composite antioxidant, 11% light conversion agent, and 88% ethylene-vinyl acetate copolymer; (2) Preparation of various masterbatches: Preparation of longevity masterbatch: Use an internal mixer at 140°C, add linear low-density polyethylene, light stabilizer, and composite antioxidant in that order, stir and shear at high speed for 15 minutes, force feed, and feed the plasticized masterbatch into the extruder screw, cool and granulate to obtain the longevity masterbatch; Preparation of thermal insulation masterbatch with linear low-density powder as carrier: using an internal mixer at 130°C, linear low-density polyethylene, kaolin, polysiloxane, and composite antioxidant are added in order, stirred and sheared at high speed for 15 minutes, forced feeding, and the plasticized masterbatch is fed into the extruder screw, cooled and granulated to obtain a thermal insulation masterbatch with linear low-density powder as carrier; Preparation of thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier: using an internal mixer at 130°C, adding ethylene-vinyl acetate copolymer, kaolin, polysiloxane, and composite antioxidant in order, stirring and shearing at high speed for 10 minutes, force feeding, feeding the plasticized masterbatch into the extruder screw, cooling and granulating to obtain the thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier; Preparation of light conversion masterbatch: Use an internal mixer at 130°C to add ethylene-vinyl acetate copolymer, light conversion agent, and composite antioxidant in order, stir and shear at high speed for 10 minutes, force feed, and feed the plasticized masterbatch into the extruder screw, cool and granulate to obtain the light conversion masterbatch; (3) Prepare the raw materials for each layer: The outer and inner layers are made of the following raw material components, according to the mass percentage: 70% low-density metallocene polyethylene, 20% high-density metallocene polyethylene, and 10% long-life masterbatch; The sub-outer layer and the sub-inner layer are made of the following raw material components, according to the mass percentage: 30% thermal insulation masterbatch with linear low-density powder as carrier, 10% longevity masterbatch, 30% low-density metallocene polyethylene, and 30% linear low-density polyethylene; The middle layer is made of the following raw material components, according to the mass percentage: 40% ethylene-vinyl acetate copolymer as a carrier thermal insulation masterbatch, 10% light conversion masterbatch, 10% longevity masterbatch, 40% ethylene-vinyl acetate copolymer; (4) Preparation of coated light-converting and high-insulation pinhole film for use in greenhouses: The raw material components of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are uniformly mixed respectively. According to the thickness percentage of each layer, the outer layer is 15%, the sub-outer layer is 20%, the middle layer is 30%, the sub-inner layer is 20%, and the inner layer is 15%. The film thickness is set to 0.015mm by plasticizing and shearing the extruder of each layer. A five-layer co-extruded composite film is obtained. After corona treatment, the coating liquid is applied online at a coating amount of 0.18g / m 2 , dried and shaped to obtain a coated multifunctional high-insulation pinhole film for use in the shed.

[0043] Example 3 The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film used in a greenhouse comprises the following steps: (1) Preparation of masterbatch for each layer: The longevity masterbatch is made of the following raw material components according to mass percentage: 5% light stabilizer, 1% composite antioxidant, and 94% linear low-density polyethylene; The thermal insulation masterbatch with the linear low-density powder as the carrier is made of the following raw material components according to mass percentage: 2% composite antioxidant, 10% kaolin, 20% polysiloxane, and 68% linear low-density polyethylene; The thermal insulation masterbatch with ethylene-vinyl acetate copolymer as the carrier is made of the following raw material components according to mass percentage: 2% composite antioxidant, 10% kaolin, 20% polysiloxane, and 68% ethylene-vinyl acetate copolymer; The light conversion masterbatch is made of the following raw material components according to mass percentage: 2% composite antioxidant, 12% light conversion agent, and 86% ethylene-vinyl acetate copolymer; (2) Preparation of various masterbatches: Preparation of longevity masterbatch: Use an internal mixer at 160°C, add linear low-density polyethylene, light stabilizer, and composite antioxidant in that order, stir and shear at high speed for 10 minutes, force feed, and feed the plasticized masterbatch into the extruder screw, cool and granulate to obtain the longevity masterbatch; Preparation of thermal insulation masterbatch with linear low-density powder as carrier: using an internal mixer at 150°C, adding linear low-density polyethylene, kaolin, polysiloxane, and composite antioxidant in that order, stirring and shearing at high speed for 10 minutes, force feeding, feeding the plasticized masterbatch into the extruder screw, cooling and granulating to obtain thermal insulation masterbatch with linear low-density powder as carrier; Preparation of thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier: using an internal mixer at 150°C, adding ethylene-vinyl acetate copolymer, kaolin, polysiloxane, and composite antioxidant in order, stirring and shearing at high speed for 5-10 minutes, force feeding, feeding the plasticized masterbatch into the extruder screw, cooling and granulating to obtain the thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier; Preparation of light conversion masterbatch: Use an internal mixer at 150°C, add ethylene-vinyl acetate copolymer, light conversion agent, and composite antioxidant in order, stir and shear at high speed for 5 minutes, force feed, and send the plasticized masterbatch into the extruder screw, cool and granulate to obtain the light conversion masterbatch; (3) Prepare the raw materials for each layer: The outer and inner layers are made of the following raw material components, according to the mass percentage: 70% low-density metallocene polyethylene, 20% high-density metallocene polyethylene, and 10% long-life masterbatch; The sub-outer layer and the sub-inner layer are made of the following raw material components, according to the mass percentage: 30% thermal insulation masterbatch with linear low-density powder as carrier, 10% longevity masterbatch, 30% low-density metallocene polyethylene, and 30% linear low-density polyethylene; The middle layer is made of the following raw material components, according to the mass percentage: 40% ethylene-vinyl acetate copolymer as a carrier thermal insulation masterbatch, 10% light conversion masterbatch, 10% longevity masterbatch, 40% ethylene-vinyl acetate copolymer; (4) Preparation of coated light-converting and high-insulation pinhole film for use in greenhouses: The raw material components of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are uniformly mixed respectively. According to the thickness percentage of each layer, the outer layer is 15%, the sub-outer layer is 20%, the middle layer is 30%, the sub-inner layer is 20%, and the inner layer is 15%. The film thickness is set to 0.015mm by plasticizing and shearing the extruder of each layer. A five-layer co-extruded composite film is obtained. After corona treatment, the coating liquid is applied online at a coating amount of 0.18g / m 2 , dried and shaped to obtain a coated multifunctional high-insulation pinhole film for use in the shed.

[0044] Comparative Example 1 The only difference between this comparative example and Example 1 is that the sum of kaolin and polysiloxane in the thermal insulation masterbatch of the middle layer, the sub-inner layer and the sub-outer layer is replaced by pure hydrotalcite thermal insulation agent.

[0045] Comparative Example 2 The only difference between this comparative example and Example 1 is that the kaolin in the thermal insulation masterbatch of the middle layer, the sub-inner layer and the sub-outer layer is removed and replaced with an equal amount of polysiloxane.

[0046] Comparative Example 3 The only difference between this comparative example and Example 1 is that the polysiloxane in the thermal insulation masterbatch of the middle layer, the sub-inner layer and the sub-outer layer is removed and replaced with kaolin in equal amounts.

[0047] Comparative Example 4 The only difference between this comparative example and Example 1 is that the thermal insulation masterbatch of the middle layer is removed and replaced with an equal amount of ethylene-vinyl acetate copolymer.

[0048] Comparative Example 5 The only difference between this comparative example and Example 1 is that the high-density metallocene polyethylene in the inner and outer layers is replaced by high-density linear polyethylene.

[0049] Comparative Example 6 The only difference between this comparative example and Example 1 is that the high-density metallocene polyethylene in the inner and outer layers is replaced by low-density metallocene polyethylene.

[0050] Comparative Example 7 The only difference between this comparative example and Example 1 is that the light-converting masterbatch in the middle layer is removed and replaced with an equal amount of ethylene-vinyl acetate copolymer.

[0051] The performance tests of the ground films prepared in each embodiment and the comparative example were conducted and compared. The total thickness of the ground films was uniformly 0.015 mm, and the thickness percentages of each layer were: outer layer 15%, sub-outer layer 20%, middle layer 30%, sub-inner layer 20%, and inner layer 15%. The test method was as follows: (1) Thermal insulation: The thermal insulation performance is determined by testing the transmittance of the ground film at a wavelength of 7-13 μm using an infrared spectrometer. The higher the transmittance, the worse the thermal insulation effect. The test results are shown in Table 1. (2) Mechanical properties: The tensile strength and elongation at break were tested in accordance with the national ground film standard GB13735-2017. The test results are shown in Table 1. (3) Optical properties: The transmittance and haze values were tested according to GB / T 2410-2008. The test results are shown in Table 1. (4) Punching efficiency: The number of pinholes punched per square meter is divided by the number of all holes, and the result is calculated. The higher the result value, the higher the punching efficiency. The test results are shown in Table 1. (5) Ground temperature test of the film-covered area: The samples blown by the three embodiments and seven comparative examples were laid on the open ground respectively. The ground temperature covered by each sample was tested before 7 o'clock every day in winter (before the sun rises). The test was carried out for 3 consecutive days. The average value of 5 groups was taken in each test. The test results are shown in Table 2. (6) Droplet duration test: The test was conducted in accordance with QB / T4475-2013 standard. The water bath temperature was (60±1)℃ and the water bath was continued for 30 days. The white droplet area ratio was not more than 30% or the transparent droplet area was not more than 50%. The results after 30 days of testing are shown in Table 3.

[0052] Table 1 Test results Table 2 Ground temperature test results in the film-covered area Table 3 Test results of dripping duration As can be seen from Table 1, the thermal insulation performance of Examples 1, 2, and 3 improves with increasing polysiloxane content in the thermal insulation masterbatch. Furthermore, according to the test results in Table 2, the ground temperature also increases with increasing polysiloxane content. However, when the thermal insulation agent in the thermal insulation masterbatch is replaced entirely with polysiloxane, as in Comparative Example 2, while the thermal insulation performance is optimal, the ground temperature test in Table 2 shows that the temperature is even lower than that of Example 1. This is because excessive addition of polysiloxane significantly increases the haze, significantly reducing the light intensity during the day and slowing the accumulation of ground temperature, resulting in lower ground temperature.

[0053] As can be seen from Table 1, when the thermal insulation agent is completely replaced by hydrotalcite, that is, Comparative Example 1, the thermal insulation performance is significantly reduced compared with Examples 1, 2, 3 and Comparative Examples 2 and 3, indicating that the thermal insulation performance of hydrotalcite is worse than that of kaolin and polysiloxane. The temperature test results in Table 2 also show that the ground temperature covered by Comparative Example 1 is the lowest compared with Examples 1, 2, 3 and Comparative Examples 2 and 3.

[0054] As can be seen from Table 1, after the high-density metallocene polyethylene of the outer and inner layers of Comparative Example 5 was replaced with high-density linear polyethylene, although the perforation rate of the film was not affected, the longitudinal and transverse tear strength of the film was reduced, and it failed the test according to the national ground film standard GB13735-2017.

[0055] As can be seen from Table 1, in Comparative Example 6, after the high-density polyethylene of the outer and inner layers is replaced with low-density metallocene polyethylene, although the mechanical properties of the film are significantly improved, the perforation rate per unit square meter is low due to the excessive strength of the film, which cannot meet the actual use effect.

[0056] As can be seen from Tables 1 and 2, after removing the light-converting masterbatch, the far-infrared transmittance test results increased slightly, indicating a slight decrease in thermal insulation, but the impact was not significant. However, when the ground temperature was actually measured, there was a certain difference compared with the other examples and the comparative example. This shows that although the light-converting agent has little effect on the thermal insulation effect of the film, it has a significant impact on the warming effect of the ground, playing a very critical role.

[0057] It can be concluded from Table 3 that no white dew droplets appeared in all embodiments and comparative examples during the test process, and the area ratio of non-flowing transparent droplets did not exceed 40%. The coating effect was able to meet the test standard for a coating film with a one-year service life according to the test standard, proving that the dripping effect of the present invention lasts for at least 6 months.

[0058] Through a series of comparative tests and data analysis, the present invention has achieved a balance of thermal insulation performance, mechanical properties, fog and drip elimination performance, and punching performance through the technical advantages of the formula, and the overall performance is relatively excellent, which plays a good auxiliary role in greenhouse cultivation in winter and improves the ability of crop roots to resist low temperature risks.

Claims

1. A coated light-converting, high-heat-insulating pinhole ground film for use in greenhouses, characterized by: From the outside to the inside, they are coating layer, outer layer, sub-outer layer, middle layer, sub-inner layer, and inner layer; The outer layer and the inner layer are made of the following raw material components, according to the mass percentage: 70-80% low-density metallocene polyethylene, 10-20% high-density metallocene polyethylene, 5-10% long-life masterbatch; The sub-outer layer and the sub-inner layer are both made of the following raw material components, according to the mass percentage: 20-30% thermal insulation masterbatch with linear low-density powder as carrier, 5-10% longevity masterbatch, 20-30% low-density metallocene polyethylene, and 30-40% linear low-density polyethylene; The middle layer is made of the following raw material components according to mass percentage: 30-40% ethylene-vinyl acetate copolymer as a carrier thermal insulation masterbatch, 5-10% light conversion masterbatch, 5-10% longevity masterbatch, and 40-50% ethylene-vinyl acetate copolymer.

2. The coated light-converting and high-heat-insulating pinhole ground film for use in greenhouses according to claim 1, characterized in that: The mass percentages of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are: outer layer 15%, sub-outer layer 20%, middle layer 30%, sub-inner layer 20%, inner layer 15%; the coating amount of the coating layer is 0.15g / m 2 ~0.2g / m 2 .

3. The coated light-converting and high-heat-insulating pinhole ground film for use in greenhouses according to claim 2, characterized in that: The longevity masterbatch is made of the following raw material components according to mass percentage: 5-8% light stabilizer, 1-2% composite antioxidant, and 90-94% linear low-density polyethylene; The thermal insulation masterbatch with the linear low-density powder as a carrier is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-20% kaolin, 10-20% polysiloxane, and 60-70% linear low-density polyethylene; The thermal insulation masterbatch with ethylene-vinyl acetate copolymer as the carrier is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-20% kaolin, 10-20% polysiloxane, and 60-70% ethylene-vinyl acetate copolymer; The light conversion masterbatch is made of the following raw material components according to mass percentage: 1-2% composite antioxidant, 10-12% light conversion agent, and 86-89% ethylene-vinyl acetate copolymer.

4. The coated light-converting and high-heat-insulating pinhole ground film for use in a greenhouse according to claim 3, characterized in that: The ethylene-vinyl acetate copolymer has a melt index of 0.65 g / 10 min and a density of 0.942 g / cm3 at 190° C. and 2.16 kg. 3 , vinyl acetate content 17-19wt.%; The low-density metallocene polyethylene has a melt index of 1 g / 10 min at 190° C. and 2.16 kg, and a density of 0.918-0.920 g / cm 3 ; The high-density metallocene polyethylene has a melt index of 0.2-1 g / 10 min at 190° C. and 2.16 kg, and a density of 0.940-0.96 g / cm 3 ; The linear low-density polyethylene has a melt index of 1.8-2 g / 10 min at 190° C. and 2.16 kg, and a density of 0.918-0.923 g / cm 3 .

5. The coated light-converting and high-heat-insulating pinhole ground film for use in a greenhouse according to claim 3, characterized in that: The mesh number of the kaolin is 10000-15000 mesh; the particle size of the polysiloxane is controlled at 1-3 μm.

6. The coated light-converting and high-heat-insulating pinhole ground film for use in a greenhouse according to claim 3, characterized in that: The composite antioxidant is obtained by compounding a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:1; the light stabilizer is a hindered amine light stabilizer; and the light conversion agent is a rare earth ion compound.

7. The coated light-converting and high-heat-insulating pinhole ground film for use in a greenhouse according to claim 1, characterized in that: The pinhole spacing of the coated light-converting high-insulation pinhole mulch is 3 cm in the longitudinal direction and 2 cm in the transverse direction; the diameter of the pinhole is 0.5 mm; the diameter of the needle roller and needle sleeve is 205 mm; the needle thickness is 2 mm and the needle height is 7.5 mm.

8. A method for preparing the coated light-converting, high-heat-insulating pinhole mulch film for use in greenhouses according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Preparation of longevity masterbatch: Use an internal mixer to process, add linear low-density polyethylene, light stabilizer, and composite antioxidant in order, stir and shear at high speed for 10-15 minutes, force feed, and send the plasticized masterbatch into the extruder screw, cool and granulate to obtain the longevity masterbatch; (2) Preparation of thermal insulation masterbatch with linear low-density powder as carrier: Use internal mixer to process, add linear low-density polyethylene, kaolin, polysiloxane, and composite antioxidant in order, stir and shear at high speed for 10-15 minutes, force feed, send the plasticized masterbatch into the extruder screw, cool and granulate, and obtain thermal insulation masterbatch with linear low-density powder as carrier; (3) Preparation of thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier: using internal mixer to process, put ethylene-vinyl acetate copolymer, kaolin, polysiloxane, composite antioxidant in order, stir and shear at high speed for 5-10 minutes, force feed, send the plasticized masterbatch into the extruder screw, cool and granulate, and obtain thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier; (4) Preparation of light conversion masterbatch: Use an internal mixer to process, add ethylene-vinyl acetate copolymer, light conversion agent, and composite antioxidant in order, stir and shear at high speed for 5-10 minutes, force feed, and send the plasticized masterbatch into the extruder screw, cool and granulate to obtain the light conversion masterbatch; (5) Preparation of coated light-converting high-insulation pinhole ground film for use in greenhouses: the raw material components of the outer layer, sub-outer layer, middle layer, sub-inner layer and inner layer are uniformly mixed respectively, and the coated multifunctional high-insulation pinhole ground film for use in greenhouses is obtained through blow molding, cooling, corona discharge, slurry coating, infiltration, drying, punching and lamination.

9. The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film for use in greenhouses according to claim 8, characterized in that: The processing temperature for preparing longevity masterbatch is 140-160℃.

10. The method for preparing the coated light-converting and high-heat-insulating pinhole mulch film for use in a greenhouse according to claim 8, characterized in that: The processing temperature for preparing thermal insulation masterbatch with linear low-density powder as carrier, thermal insulation masterbatch with ethylene-vinyl acetate copolymer as carrier, and light conversion masterbatch is 130-150°C.

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