Long-acting anti-fogdrop agricultural film and preparation method thereof

Abstract

The invention discloses a long-acting anti-fogdrop agricultural film and a preparation method thereof, and belongs to the technical field of anti-fogdrop films. The long-acting anti-fogdrop agricultural film provided by the invention comprises a matrix layer, a bonding layer and an anti-fogdrop functional layer which are arranged in an overlapped manner, a preparation raw material of the matrix layer comprises polyethylene; the bonding layer is prepared from a polyolefin elastomer; the anti-fogdrop functional layer is prepared from at least one of PVA (polyvinyl alcohol) and EVOH (ethylene vinyl alcohol). According to the long-acting anti-fogdrop agricultural film provided by the invention, the anti-fogdrop effect, anti-fogdrop durability, strength, toughness and other mechanical properties of the agricultural film can be effectively improved. The invention also provides a preparation method of the long-acting anti-fogdrop agricultural film.

Description

Technical Field

[0001] The invention relates to the technical field of anti-fog films, in particular to a long-lasting anti-fog droplet agricultural film and a preparation method thereof. Background Art

[0002] Plastic film is widely used in agriculture and has become an effective way to rationally utilize land resources, effectively increase crop yields, and improve agricultural economic benefits.

[0003] During the use of agricultural film, when the surface temperature drops below the dew point, moisture in the air condenses into dew droplets, resulting in a mist. The presence of mist droplets can scatter and reflect light, even acting as lenses. This can reduce the film's light transmittance, directly affecting crop growth. It can also cause localized temperature increases within the greenhouse, harming crops. Furthermore, mist droplets landing on plants can cause stem and leaf rot.

[0004] In order to solve the above problems, two approaches are usually adopted in traditional technologies. One is to add anti-droplet additives to the matrix of the agricultural film, and the other is to provide a functional coating on one or both sides of the agricultural film.

[0005] However, the above two methods have poor anti-droplet effects, and the durability of the anti-droplet effect of agricultural films is poor. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a long-lasting anti-fog agricultural film that can effectively improve the anti-fog effect, anti-fog durability, and mechanical properties such as strength and toughness of the agricultural film.

[0007] The present invention also provides a method for preparing the long-lasting anti-drip agricultural film.

[0008] According to an embodiment of the first aspect of the present invention, there is provided a long-lasting anti-drip agricultural film, comprising a base layer, an adhesive layer and an anti-drip functional layer stacked together;

[0009] The raw material for preparing the base layer includes polyethylene;

[0010] The raw materials for preparing the adhesive layer include polyolefin elastomer (POE);

[0011] The raw material for preparing the anti-fog functional layer is at least one of PVA (polyvinyl alcohol) and EVOH (ethylene-vinyl alcohol copolymer).

[0012] The long-lasting anti-drip agricultural film according to the embodiment of the present invention has at least the following beneficial effects:

[0013] (1) Compared with the traditional agricultural film that uses small molecule anti-droplet additives or is provided with an anti-droplet coating, the agricultural film provided by the present invention directly provides an anti-droplet functional layer, which avoids the migration of small molecules and the shedding of the coating during use. Therefore, the durability of the anti-droplet effect is better.

[0014] (2) The raw materials used in the preparation of the adhesive layer of the present invention are highly compatible with the base layer and the anti-droplet functional layer, so the bonding strength is relatively high. Therefore, the long-lasting anti-droplet agricultural film provided by the present invention has more excellent mechanical properties such as bonding strength and toughness compared with the traditional multi-layer structure.

[0015] (3) In the long-lasting anti-drip agricultural film provided by the present invention, due to the selection of raw materials for preparing the anti-drip functional layer, it has a large number of regularly arranged hydrophilic groups such as hydroxyl groups. Compared with other hydrophilic material layers in traditional technologies, it has better anti-drip performance, especially when PVA and EVOH are used in combination, the effect is even better.

[0016] (4) The long-lasting anti-fog agricultural film provided by the present invention has a base layer with high transparency and high strength, and is a typical hydrophobic layer. Its strong hydrophobicity can also be used to provide an anti-fog effect. In other words, both sides of the long-lasting anti-fog film provided by the present invention have a certain anti-fog effect.

[0017] According to some embodiments of the present invention, the raw material polyolefin for preparing the base layer includes LDPE (low density polyethylene), mLLDPE (metallocene low density polyethylene) and LLDPE (linear low density polyethylene).

[0018] According to some embodiments of the present invention, the mass percentage of the LDPE in the raw materials for preparing the base layer is 55-65%, for example, about 58%, 60% or about 62%.

[0019] According to some embodiments of the present invention, the mass percentage of the mLLDPE in the raw materials for preparing the base layer is 20-25%, for example, about 23% or about 24%.

[0020] According to some embodiments of the present invention, the mass percentage of the LLDPE in the raw materials for preparing the base layer is 10-20%, for example, about 12%, 15% or about 18%.

[0021] According to some embodiments of the present invention, the raw materials for preparing the base layer further include an opening agent.

[0022] According to some embodiments of the present invention, the mass percentage of the anti-fog agent in the raw materials for preparing the base layer is 1-2%, for example, approximately 1.5%. In actual production, antioxidants or anti-UV additives may also be added as needed. However, in order to verify the durability of the anti-fog functional layer, no anti-fog agent has been added.

[0023] According to some embodiments of the present invention, the raw material for preparing the adhesive layer further includes LLDPE.

[0024] According to some embodiments of the present invention, in the raw materials for preparing the adhesive layer, the mass ratio of polyolefin elastomer (POE) to LLDPE is 8.5-10:0.5-1. For example, it can be 8.5-10:1, and more specifically, it can be about 9:1 or about 9.5:1.

[0025] According to some embodiments of the present invention, the anti-fog functional layer is prepared from a mixture of PVA and EVOH, wherein the mass ratio of PVA to EVOH is 2:0.1 to 2. For example, the mass ratio may be approximately 2:0.2, 2:0.5, 2:1, or approximately 2:1.5.

[0026] According to some embodiments of the present invention, the thickness ratio of the anti-fog functional layer to the base layer is 1:15 to 20. For example, it can be about 1:17, 1:18, or about 1:19.

[0027] According to some embodiments of the present invention, the thickness ratio of the anti-fog functional layer to the adhesive layer is 1:1.5 to 2.5, for example, about 1:1.8, 1:2, or about 1:2.2.

[0028] According to some embodiments of the present invention, the thickness of the anti-fog functional layer is 1-5 μm, for example, about 2 μm, 3 μm or about 4 μm.

[0029] According to some embodiments of the present invention, the thickness of the long-lasting anti-drip agricultural film is 20-100 μm, for example, about 30 μm, 40 μm, 50 μm, 60 μm, 70 μm or about 80 μm.

[0030] According to an embodiment of the second aspect of the present invention, a method for preparing the long-lasting anti-drip agricultural film according to the embodiment of the first aspect of the present invention is provided, the preparation method comprising the following steps:

[0031] S1. The raw materials for preparing the base layer, the adhesive layer and the anti-droplet functional layer are plasticized and filtered, and multi-layer co-extrusion is performed using a common die;

[0032] S2. Blow molding the product obtained in step S1.

[0033] Since the preparation method adopts all the technical solutions of the long-lasting anti-drip agricultural film of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0034] According to some embodiments of the present invention, in step S1, the flow channel wall of the die head is provided with a DLC coating (diamond-like carbon coating), thereby improving the smoothness and ensuring smooth extrusion of the anti-droplet functional layer.

[0035] According to some embodiments of the present invention, in step S1, material addition is further included before the plasticizing.

[0036] According to some embodiments of the present invention, in step S1, metering is further included after the plasticizing.

[0037] According to some embodiments of the present invention, in step S1 , the feeding temperature of the base layer is 165-175° C., for example, about 170° C.

[0038] According to some embodiments of the present invention, in step S1, the plasticizing temperature of the base layer is 215-225°C; for example, it may be about 220°C.

[0039] According to some embodiments of the present invention, in step S1, the metering temperature of the base layer is 215-225°C; for example, it may be about 220°C.

[0040] According to some embodiments of the present invention, in step S1, the filtering temperature of the base layer is 215-225°C; for example, it can be about 220°C.

[0041] According to some embodiments of the present invention, in step S1, the feeding temperature of the adhesive layer is 185-195°C; for example, it can be specifically about 190°C.

[0042] According to some embodiments of the present invention, in step S1, the plasticizing temperature of the adhesive layer is 225-235°C, for example, about 230°C.

[0043] According to some embodiments of the present invention, in step S1 , the metering temperature of the adhesive layer is 225-235° C., for example, about 230° C.

[0044] According to some embodiments of the present invention, in step S1 , the filtration temperature of the adhesive layer is 225-235° C., for example, about 230° C.

[0045] According to some embodiments of the present invention, in step S1, the temperature of adding the anti-fog functional layer is 165-175°C, for example, about 170°C.

[0046] According to some embodiments of the present invention, in step S1, the plasticizing temperature of the anti-fog functional layer is 215-225°C, for example, about 220°C.

[0047] According to some embodiments of the present invention, in step S1, the metering temperature of the anti-fog functional layer is 235-245°C, for example, about 240°C.

[0048] According to some embodiments of the present invention, in step S1, the filtration temperature of the anti-droplet functional layer is 235-245°C, for example, about 240°C.

[0049] According to some embodiments of the present invention, in step S1, the temperature of the multi-layer co-extrusion is 235-245°C, for example, about 240°C.

[0050] Unless otherwise specified, the term “about” in the present invention actually means that the error is allowed to be within the range of ±2%, for example, about 100 actually means 100±2%×100.

[0051] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values 2 and 3.

[0052] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0054] Figure 1 Schematic diagram of the structure of the long-lasting anti-drip agricultural film prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0056] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0057] In a specific embodiment, the selection of raw materials for preparation is as follows:

[0058] LDPE, model FELB7000, manufacturer / brand: LG, South Korea;

[0059] LLDPE, model M2320, purchased from Maoming Petrochemical;

[0060] MLLDPE, model SP0511, manufacturer: Japan Prime Polymer Co., Ltd.;

[0061] Antiblocking agent, model HD-22, purchased from Linyi Mingshuo Trading Co., Ltd.

[0062] POE, model PT1450, product name POP was purchased from Dow Chemical;

[0063] EVOH, model EW-3201, was purchased from Chongqing Chuanwei Chemical Co., Ltd. of Sinopec Group.

[0064] PVA, model AKM-CN002, was purchased from Dongguan Aikemei New Material Technology Co., Ltd.

[0065] PLA, model 7032D, brand / manufacturer: NatureWorks, USA.

[0066] Example 1

[0067] In this example, a long-lasting anti-drip agricultural film was prepared. The specific steps are as follows:

[0068] S1. The raw materials for the base layer, adhesive layer, and anti-fog functional layer were plasticized and filtered separately, and then co-extruded using a common die. This process included a feeding stage before plasticization and a metering stage after plasticization. The temperatures of the different layers at each stage are shown in Table 1. The raw materials and thicknesses of the different layers are shown in Table 2.

[0069] Table 1 Temperature limits for multilayer coextrusion in Example 1

[0070] Feeding stage℃ Plasticizing℃ Metering stage℃ Filtration ℃ Die head ℃ base layer 170 220 220 220 240 Adhesive layer 190 230 230 230 240 Anti-droplet functional layer 170 220 240 240 240

[0071] Table 2 Preparation materials and thickness of each layer of the long-lasting anti-drip agricultural film in Example 1

[0072] Preparation raw material ratio Layer thickness ratio% base layer LDPE:mLLDPE:LLDPE:opening agent=60:23.5:15:1.5 85％ Adhesive layer LLDPE:POE=10:90 10％ Anti-droplet functional layer EVOH 5％

[0073] The flow channel wall of the die head has a DLC (diamond-like carbon) coating.

[0074] S2. Blow-molding the product obtained in step S1. The overall thickness of the long-lasting anti-drip agricultural film obtained by blow molding is 40 μm.

[0075] The structural diagram of the anti-drip agricultural film obtained in this example is as follows Figure 1 shown.

[0076] Example 2

[0077] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0078] In step S1, the raw material for preparing the anti-fog functional layer is selected from PVA.

[0079] Example 3

[0080] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0081] In step S1, the raw material for preparing the anti-fog functional layer is a mixture of PVA and EVOH in a mass ratio of 2:1.

[0082] Example 4

[0083] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0084] In step S1 , the raw material for preparing the anti-fog functional layer is a mixture of PVA and EVOH in a mass ratio of 2:0.2.

[0085] Comparative Example 1

[0086] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0087] In step S1, the raw material for preparing the anti-droplet functional layer is replaced with polylactic acid PLA of equal mass.

[0088] Comparative Example 2

[0089] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0090] In step S1, the raw materials for preparing the anti-droplet functional layer are replaced with LLDPE:EVOH=2:1.

[0091] Comparative Example 3

[0092] This example prepares a long-lasting anti-drip agricultural film, which differs from Example 1 in that:

[0093] In step S1, the raw materials for preparing the anti-droplet functional layer are replaced with LLDPE:sorbitol=96:4.

[0094] Test Case

[0095] This example tested the anti-fog performance of the long-lasting anti-fog agricultural film obtained in the Examples and Comparative Examples using the cold mist method specified in the standard document GB / T 31726-2015, on one side of the substrate layer and one side of the anti-fog functional layer. This example also tested the anti-fog durability of the long-lasting anti-fog agricultural film obtained in the Examples and Comparative Examples. Specifically, the anti-fog performance of the anti-fog functional layer was tested using the cold mist method after pretreatment. The pretreatment method involved placing the film over the mouth of a water-containing beaker, with the anti-fog functional layer facing the liquid surface, in a room at an ambient temperature of 23°C, and subjecting it to a 12-hour light shielding treatment followed by a 12-hour AM1.5 / 1000W / m2 exposure. 2 The long-lasting anti-fog agricultural film was treated with simulated sunlight and then air-dried at ambient temperature. The pretreatment durations were 8 days, 31 days, and 60 days. The test results are shown in Table 3.

[0096] This example also tested the mechanical properties of the long-lasting anti-drip agricultural films obtained in the examples and comparative examples. Specifically, the tensile strength and elongation at break were tested according to GB1040-79. The test results are shown in Table 3.

[0097] Table 3 Anti-fog properties of the long-lasting anti-fog agricultural films obtained in the examples and comparative examples

[0098]

[0099]

[0100] The results in Table 3 show that the long-lasting anti-fog agricultural film provided by the embodiment of the present invention has relatively excellent anti-fog properties on both the front and back sides, but the anti-fog properties on both sides are slightly different. In actual production, the appropriate oriented side can be selected according to needs, which improves the flexibility of use. At the same time, the long-lasting anti-fog agricultural film provided by the embodiment of the present invention has relatively excellent durability. When EVOH and PVA are mixed to prepare the anti-fog functional layer, and the anti-fog performance is maintained for 60 days when the ratio is appropriate, this also shows to some extent that there is a certain synergistic effect between EVOH and PVA. Furthermore, it can be found that in the long-lasting anti-fog agricultural film provided by the embodiment of the present invention, since the thickness of the anti-fog functional layer is relatively thin and the mechanical properties of EVOH and PVA are not much different, changing the material selection of the anti-fog functional layer will not significantly affect its mechanical properties.

[0101] If the raw material used to prepare the anti-fog functional layer in the present invention is replaced with conventional PLA, although PLA also has relatively excellent hydrophilicity, the agricultural film produced from it exhibits poor initial and long-term anti-fog performance. This may be due to the poor compatibility between PLA and the adhesive layer. This can easily lead to structural damage in hot and cold test environments, or in environments with temperature differences between the inside and outside of the film, resulting in a decrease in anti-fog performance and, further, a significant reduction in mechanical properties. It is also possible that the arrangement of the hydrophilic groups in PLA differs from that in EVOH / PVA, affecting its anti-fog performance.

[0102] If a conventional polyethylene substrate is modified with hydrophilic polymers or small molecules, the primary and long-term anti-droplet performance will be significantly degraded due to the limited number of hydrophilic groups, the uneven distribution of these groups, and the migration of these groups within the hydrophilic small molecules or polymers. However, the increased proportion of polyethylene used will improve the mechanical properties of the resulting agricultural film to a certain extent.

[0103] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A long-lasting anti-drip agricultural film, characterized in that: It includes a base layer, an adhesive layer and an anti-fog functional layer that are stacked; The raw material for preparing the base layer includes polyethylene; The raw materials for preparing the adhesive layer include polyolefin elastomer; The raw material for preparing the anti-fog functional layer is at least one of PVA and EVOH.

2. The long-lasting anti-drip agricultural film according to claim 1, characterized in that: The raw materials for preparing the base layer are polyolefins, including LDPE, mLLDPE and LLDPE; Preferably, in the raw materials for preparing the base layer, the mass percentage of the LDPE is 55-65%; Preferably, the mass percentage of mLLDPE in the raw materials for preparing the base layer is 20-25%; Preferably, the mass percentage of the LLDPE in the raw materials for preparing the base layer is 10-20%.

3. The long-lasting anti-drip agricultural film according to claim 1, characterized in that: The raw materials for preparing the adhesive layer also include LLDPE.

4. The long-lasting anti-drip agricultural film according to claim 3, characterized in that: In the raw materials for preparing the adhesive layer, the mass ratio of polyolefin elastomer to LLDPE is 8.5-10:0.5-1.

5. The long-lasting anti-drip agricultural film according to claim 1, characterized in that: The thickness ratio of the anti-droplet functional layer to the base layer is 1:15 to 20; Preferably, the thickness ratio of the anti-fog functional layer to the adhesive layer is 1:1.5 to 2.

5.

6. The long-lasting anti-drip agricultural film according to any one of claims 1 to 5, characterized in that: The thickness of the long-lasting anti-drip agricultural film is 20 to 100 μm.

7. A method for preparing a long-lasting anti-drip agricultural film according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1. The raw materials for preparing the base layer, the adhesive layer and the anti-droplet functional layer are plasticized and filtered, and multi-layer co-extrusion is performed using a common die; S2. Blow molding the product obtained in step S1.

8. The preparation method according to claim 7, characterized in that In step S1, a DLC coating is formed on the flow channel wall of the die head.

9. The preparation method according to claim 7, characterized in that In step S1, the temperature of the multi-layer co-extrusion is 235-245°C.

10. The preparation method according to claim 7, characterized in that In step S1, the plasticizing temperature of the base layer is 215-225°C; Preferably, in step S1, the plasticizing temperature of the adhesive layer is 225-235°C; Preferably, in step S1, the plasticizing temperature of the anti-droplet functional layer is 215-225°C.

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