A recyclable polyethylene agricultural film and its preparation method and application

Abstract

The invention provides a recyclable polyethylene agricultural film and a preparation method and application thereof. The recyclable polyethylene agricultural film comprises an inner layer, a middle layer and an outer layer which are arranged in sequence; the raw material for preparing the middle layer comprises a combination of linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, glass fiber, cellulose nanocrystals and poly(hydroxyethyl methacrylate); by adding ultra-high molecular weight polyethylene and glass fiber to the raw materials for preparing the middle layer, as well as adding cellulose nanocrystals and poly(hydroxyethyl methacrylate) to the raw materials for preparing the middle layer, the mechanical properties, aging resistance and weather resistance of the recyclable polyethylene agricultural film are effectively improved, and the film will not break when recycled after long-term use, thereby enabling the recyclable polyethylene agricultural film to be widely used in the field of mulch films.

Description

Technical Field

[0001] The invention belongs to the technical field of polyethylene films, and in particular relates to a recyclable polyethylene agricultural film and a preparation method and application thereof. Background Art

[0002] As a commonly used packaging material or agricultural basic production material, polyethylene agricultural film has the advantages of low price and easy processing, but it has the disadvantages of being non-degradable and having poor recyclability. With the deepening of the concept of green environmental protection, the degradable plastic industry has gradually become a hot spot of market attention. However, on the one hand, degradable plastics cannot match the growth requirements of crops well in terms of performance, and on the other hand, their manufacturing and use costs are high, and ordinary agricultural users cannot afford the expensive prices, resulting in weak market demand and a long promotion and popularization cycle. Therefore, on the basis of traditional polyethylene agricultural film materials, physical modification is used to enhance the film's strength, modulus and improve its tolerance, while still making it recyclable after the end of its use cycle. This is one of the research directions of many researchers in the field of agricultural films.

[0003] CN108102202A discloses a recyclable mulch film formula, which is formed by combining linear low-density polyethylene with corn starch, polypropylene, gum arabic, dihydroxybenzophenone, microcrystalline wax polybutylene succinate, ethyl paraben and other raw materials to form a recyclable mulch film with high initial mechanical strength, good durability, fast degradation rate, strong UV resistance, low temperature resistance, high mechanical properties and antistatic properties, and fast degradation rate, and no pollution to the environment. However, the recyclable agricultural film provided by the invention ignores the fact that the linear low-density polyethylene and polypropylene used in it cannot be degraded. After the degradation of other components, polyethylene and polypropylene fragments will remain in the farmland, making recycling more difficult.

[0004] CN109789681A discloses a recyclable polyethylene film, which is composed of at least 80% polyethylene material and at most 20% compatible polyolefin material. It adopts a three-layer structure, the main component of which is linear low-density polyethylene, the middle layer of which is composed of linear low-density polyethylene and / or linear metallocene low-density polyethylene, and the outer layer is composed of high-density polyethylene and surrounds the middle layer, wherein the HDPE share of the polyethylene film accounts for at least 60% of the volume, and high rigidity, heat deformation resistance and sufficiently high toughness are achieved by adjusting the thickness of the three layers. This solution only adds polyolefin material, so the rigidity, toughness and heat resistance of the polyolefin material itself are required to be high, but the performance of the polyethylene film product obtained is not significantly improved.

[0005] In summary, from the current modification scheme, simply adding degradable materials to polyethylene agricultural film will give the agricultural film the characteristics of rapid degradation, but the polyethylene material itself cannot be degraded and will still remain. After the degradable material is decomposed, the polyethylene agricultural film will be severely broken, making it more difficult to recycle. Although the use of a variety of polyolefin materials and adjusting the content of different components and the number of different film layers will improve the performance of agricultural film products to a certain extent, the improvement is limited, and the obtained agricultural film still cannot have high rigidity, toughness and heat resistance.

[0006] Therefore, developing a recyclable polyethylene agricultural film with high rigidity, high strength and high tolerance is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a recyclable polyethylene agricultural film and a preparation method and application thereof. The recyclable polyethylene agricultural film comprises an inner layer, a middle layer and an outer layer arranged in sequence. The raw materials for preparing the middle layer are specially limited so that the finally obtained recyclable polyethylene agricultural film has excellent mechanical properties, aging resistance and weather resistance, and does not break when recycled after long-term use, and can be widely used in mulch films in North China, Northwest China, Xinjiang and other regions.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a recyclable polyethylene agricultural film, wherein the recyclable polyethylene agricultural film comprises an inner layer, a middle layer and an outer layer arranged in sequence;

[0010] The raw materials for preparing the middle layer include a combination of linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, glass fiber, cellulose nanocrystal and poly(hydroxyethyl methacrylate).

[0011] The recyclable polyethylene agricultural film provided by the present invention comprises an inner layer, a middle layer and an outer layer arranged in sequence, wherein during use, the inner layer is close to the ground and the outer layer is in direct contact with the air. The raw materials for preparing the middle layer comprise a combination of linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, glass fiber, cellulose nanocrystals and poly(hydroxyethyl methacrylate).

[0012] The present invention adds ultra-high molecular weight polyethylene and glass fiber to the raw materials for preparing the middle layer. On the one hand, the high modulus of the two can effectively improve the overall rigidity and strength of the agricultural film. On the other hand, the low thermal expansion coefficient of the glass fiber itself can effectively improve the weather resistance and aging resistance of the agricultural film.

[0013] At the same time, in order to solve the problem of poor interface compatibility between the polyethylene resin matrix and the glass fiber, the present invention also introduces cellulose nanocrystals and poly(hydroxyethyl methacrylate) as stabilizers in the raw materials for preparing the middle layer. On the one hand, the nano effect of the cellulose nanocrystals and the large amount of hydroxyl groups contained therein are utilized, and the bonding effect of the poly(hydroxyethyl methacrylate) is combined to effectively avoid the problem that the glass fiber is easy to agglomerate and difficult to disperse in the polyethylene resin matrix, thereby enhancing the interface compatibility and interface stability between the polyethylene resin matrix and the glass fiber, so that the characteristics of the polyethylene resin matrix and the glass fiber are fully utilized, and the comprehensive performance of the polyethylene agricultural film is enhanced; on the other hand, the high crystallinity, high modulus and high strength characteristics of the cellulose nanocrystals themselves are utilized to further enhance the mechanical properties and weather resistance of the agricultural film.

[0014] In summary, the present invention specifically limits the raw materials for preparing the middle layer, so that the finally obtained recyclable polyethylene agricultural film has excellent mechanical properties, aging resistance and weather resistance, and does not break when recycled after long-term use, and can be widely used in ground films in North China, Northwest China, Xinjiang and other regions.

[0015] Preferably, the raw materials for preparing the middle layer include the following components in parts by weight:

[0016]

[0017] Wherein, the linear low-density polyethylene (LLDPE) can be 510 parts by weight, 520 parts by weight, 530 parts by weight, 540 parts by weight, 550 parts by weight, 560 parts by weight, 570 parts by weight, 580 parts by weight or 590 parts by weight, etc.

[0018] The metallocene linear low density polyethylene (mLLDPE) may be 110 parts by weight, 120 parts by weight, 130 parts by weight, 140 parts by weight, 150 parts by weight, 160 parts by weight, 170 parts by weight, 180 parts by weight, or 190 parts by weight, etc.

[0019] The high density polyethylene (HDPE) may be 210 parts by weight, 220 parts by weight, 230 parts by weight, 240 parts by weight, 250 parts by weight, 260 parts by weight, 270 parts by weight, 280 parts by weight, or 290 parts by weight.

[0020] The ultra high molecular weight polyethylene (UHMWPE) may be 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, etc.

[0021] The glass fiber may be 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, 5 parts by weight, 5.5 parts by weight, etc.

[0022] The cellulose nanocrystals may be 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, etc.

[0023] The polyhydroxyethyl methacrylate may be 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.75 parts by weight, 0.8 parts by weight, 0.85 parts by weight, 0.9 parts by weight, or 0.95 parts by weight.

[0024] Preferably, the raw materials for preparing the middle layer also include an antioxidant.

[0025] Preferably, the content of antioxidant in the raw materials for preparing the middle layer is 1 to 3.5 parts by weight, for example, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight, 3 parts by weight, 3.2 parts by weight or 3.4 parts by weight, etc.

[0026] Preferably, the raw materials for preparing the inner layer include the following components in parts by weight:

[0027]

[0028] Among them, the linear is 610 parts by weight, 620 parts by weight, 630 parts by weight, 640 parts by weight, 650 parts by weight, 660 parts by weight, 670 parts by weight, 680 parts by weight or 690 parts by weight, etc.

[0029] The low density polyethylene (LDPE) may be 310 parts by weight, 320 parts by weight, 330 parts by weight, 340 parts by weight, 350 parts by weight, 360 parts by weight, 370 parts by weight, 380 parts by weight, 390 parts by weight, etc.

[0030] The antioxidant may be 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, etc.

[0031] The anti-fogging agent may be 0.7 parts by weight, 0.9 parts by weight, 1.1 parts by weight, 1.3 parts by weight, 1.5 parts by weight, 1.7 parts by weight, 1.9 parts by weight, etc.

[0032] Preferably, the raw materials for preparing the outer layer include the following components in parts by weight:

[0033]

[0034]

[0035] As a preferred technical solution of the present invention, by adding ultraviolet absorbers and light stabilizers to the raw materials for preparing the outer layer, the aging resistance and weather resistance of the agricultural film during use are further improved.

[0036] Wherein, the linear low-density polyethylene may be 810 parts by weight, 820 parts by weight, 830 parts by weight, 840 parts by weight, 850 parts by weight, 860 parts by weight, 870 parts by weight, 880 parts by weight or 890 parts by weight.

[0037] The high-density polyethylene may be 110 parts by weight, 120 parts by weight, 130 parts by weight, 140 parts by weight, 150 parts by weight, 160 parts by weight, 170 parts by weight, 180 parts by weight, 190 parts by weight, etc.

[0038] The amount of the ultraviolet absorber may be 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, or 5 parts by weight.

[0039] The antioxidant may be 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, etc.

[0040] The light stabilizer may be 1.6 parts by weight, 1.7 parts by weight, 1.8 parts by weight, 1.9 parts by weight, 2 parts by weight, 2.1 parts by weight, 2.2 parts by weight, 2.3 parts by weight, 2.4 parts by weight, etc.

[0041] Preferably, the thickness ratio of the inner layer, the middle layer and the outer layer is 1:(0.6-1.2):(0.5-0.8).

[0042] Among them, the thickness ratio of the inner layer and the middle layer can be 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1 or 1:1.15, etc.

[0043] The thickness ratio of the middle layer to the outer layer may be 1:0.52, 1:0.54, 1:0.56, 1:0.58, 1:0.6, 1:0.62, 1:0.64, 1:0.66 or 1:0.68, etc.

[0044] Preferably, the total thickness of the recyclable polyethylene agricultural film is 30-100 μm, for example, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm or 90 μm.

[0045] Preferably, the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is ethylene-butene copolymer and / or ethylene-hexene copolymer.

[0046] Preferably, the melt mass flow rate of the linear low density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 0.5 to 3 g / 10min, for example, 0.7 g / 10min, 0.9 g / 10min, 1.1 g / 10min, 1.3 g / 10min, 1.5 g / 10min, 1.7 g / 10min, 1.9 g / 10min, 2.1 g / 10min, 2.3 g / 10min, 2.5 g / 10min, 2.7 g / 10min or 2.9 g / 10min, etc.

[0047] Preferably, the density of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 0.91 to 0.93 g / cm 3 , for example 0.902 g / cm 3 , 0.904g / cm 3 , 0.906g / cm 3 , 0.908g / cm 3 、0.91g / cm 3 , 0.912g / cm 3 , 0.914g / cm 3 , 0.916g / cm 3 or 0.918 g / cm 3 wait.

[0048] Preferably, the weight average molecular weight of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 15×10 4 ~25×10 4 g / mol, for example 16×10 4 g / mol, 17×10 4 g / mol, 18×10 4 g / mol, 19×10 4 g / mol, 20×10 4 g / mol, 21×10 4 g / mol, 22×10 4 g / mol, 23×10 4 g / mol or 24×10 4 g / mol, etc.

[0049] Preferably, the molecular weight distribution width index of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 4 to 7, such as 4.5, 5, 5.5, 6 or 6.5.

[0050] Preferably, the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is ethylene-butene copolymer and / or ethylene-hexene copolymer.

[0051] Preferably, the melt mass flow rate of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 5 to 20 g / 10 min, for example, 7 g / 10 min, 9 g / 10 min, 11 g / 10 min, 13 g / 10 min, 15 g / 10 min, 17 g / 10 min or 19 g / 10 min, etc.

[0052] Preferably, the density of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 0.945-0.96 g / cm 3 , for example 0.947 g / cm 3 , 0.949g / cm 3 , 0.951g / cm 3 , 0.953g / cm 3 、0.955g / cm 3 , 0.957g / cm 3 or 0.959 g / cm 3 wait.

[0053] Preferably, the weight average molecular weight of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 20×10 4 ~30×10 4 g / mol, for example 21×10 4 g / mol, 22×10 4 g / mol, 23×10 4 g / mol, 24×10 4 g / mol, 25×10 4 g / mol, 26×10 4 g / mol, 27×10 4 g / mol, 28×10 4 g / mol or 29×10 4 g / mol, etc.

[0054] Preferably, the molecular weight distribution width index of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 20 to 30, for example, 21, 22, 23, 24, 25, 26, 27, 28 or 29.

[0055] Preferably, the metallocene linear low-density polyethylene is an ethylene-butene copolymer and / or an ethylene-hexene copolymer.

[0056] Preferably, the melt mass flow rate of the metallocene linear low density polyethylene is 0.5 to 5 g / 10 min, for example, 1 g / 10 min, 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min or 4.5 g / 10 min.

[0057] Preferably, the density of the metallocene linear low-density polyethylene is 0.91 to 0.926 g / cm 3 , for example 0.912 g / cm 3 , 0.914g / cm 3 , 0.916g / cm 3 、0.918g / cm 3 , 0.92g / cm 3 , 0.922g / cm 3 , 0.924g / cm 3 or 0.926 g / cm 3 wait.

[0058] Preferably, the weight average molecular weight of the metallocene linear low density polyethylene is 15×10 4 ~25×10 4 g / mol, for example 16×10 4 g / mol, 17×10 4 g / mol, 18×10 4 g / mol, 19×10 4 g / mol, 20×10 4 g / mol, 21×10 4 g / mol, 22×10 4 g / mol, 23×10 4 g / mol or 24×10 4 g / mol, etc.

[0059] Preferably, the molecular weight breadth index of the metallocene polyethylene is 2 to 3, for example, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 or 2.9.

[0060] Preferably, the low density polyethylene is an ethylene homopolymer.

[0061] Preferably, the melt mass flow rate of the low-density polyethylene is 0.2 to 4 g / 10 min, for example, 0.5 g / 10 min, 1 g / 10 min, 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min or 3.5 g / 10 min.

[0062] Preferably, the density of the low-density polyethylene is 0.916-0.93 g / cm 3 , for example 0.918 g / cm 3 , 0.92g / cm 3 , 0.922g / cm 3 , 0.924g / cm 3 , 0.926g / cm 3 or 0.928 g / cm 3 wait.

[0063] Preferably, the weight average molecular weight of the low density polyethylene is 10×10 4 ~18×10 4 g / mol, for example 11×10 4 g / mol, 12×10 4 g / mol, 13×10 4 g / mol, 14×10 4 g / mol, 15×10 4 g / mol, 16×10 4 g / mol or 17×10 4 g / mol, etc.

[0064] Preferably, the molecular weight distribution width index of the low-density polyethylene is 3 to 9, such as 4, 5, 6, 7 or 8.

[0065] Preferably, the ultra-high molecular weight polyethylene is an ethylene homopolymer.

[0066] Preferably, the melt mass flow rate of the ultra-high molecular weight polyethylene is 0.05 to 1.2 g / 10 min, for example, 0.07 g / 10 min, 0.09 g / 10 min, 0.1 g / 10 min, 0.3 g / 10 min, 0.5 g / 10 min, 0.7 g / 10 min, 0.9 g / 10 min or 1.1 g / 10 min.

[0067] Preferably, the density of the ultra-high molecular weight polyethylene is 0.35-0.6 g / cm 3 , for example 0.4g / cm 3 , 0.42g / cm 3 , 0.46g / cm 3 , 0.48g / cm 3 , 0.5g / cm 3 , 0.52g / cm 3 , 0.54g / cm 3 , 0.56g / cm 3 or 0.58g / cm 3 wait.

[0068] Preferably, the molecular weight distribution width index of the ultra-high molecular weight polyethylene is 10 to 15, for example, 10.5, 11, 12, 12.5, 13, 13.5, 14 or 14.5.

[0069] Preferably, the raw material for preparing the cellulose nanocrystals includes any one of wood, cotton or sisal, or a combination of at least two of them.

[0070] Preferably, the diameter of the cellulose nanocrystals is 10 to 50 nm, for example, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm or 45 nm.

[0071] Preferably, the length of the cellulose nanocrystals is 20 to 300 nm, for example, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 170 nm, 190 nm, 210 nm, 250 nm or 280 nm.

[0072] Preferably, the glass fiber is alkali-free glass fiber.

[0073] Preferably, the glass fiber has a diameter of 5 to 30 μm, for example, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 21 μm, 23 μm, 25 μm, 27 μm or 29 μm.

[0074] Preferably, the length of the glass fiber is 40-500 μm, for example, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm or 450 μm.

[0075] Preferably, the weight average molecular weight of the polyhydroxyethyl methacrylate is 12×10 4 ~200×10 4 g / mol, for example 20×10 4 g / mol, 40×10 4 g / mol, 60×10 4 g / mol, 80×10 4 g / mol, 100×10 4 g / mol, 120×10 4 g / mol, 140×10 4 g / mol, 160×10 4 g / mol or 180×10 4 g / mol, etc.

[0076] Preferably, the anti-fogging agent comprises a combination of polyvinyl alcohol, sorbitan fatty acid esters and glycerol esters.

[0077] As a preferred technical solution of the present invention, in addition to adding traditional polyvinyl alcohol as an anti-fogging agent to the raw materials for preparing the inner layer, sorbitan fatty acid esters and glycerol esters are newly added to coordinate with it. The sorbitan fatty acid esters and glycerol esters can also effectively absorb water molecules at low temperatures, thereby having a strong cold anti-fogging effect. At the same time, since the sorbitan fatty acid esters do not have aldehyde groups, the stability of the agricultural film is further enhanced.

[0078] Preferably, the mass ratio of the polyvinyl alcohol, sorbitan fatty acid ester and glycerol ester is 1:(2-3):(6-7).

[0079] Wherein, the mass ratio of the polyvinyl alcohol to the sorbitan fatty acid ester can be 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8 or 1:2.9, etc.

[0080] The mass ratio of the polyvinyl alcohol to glycerol ester may be 1:6.1, 1:6.2, 1:6.3, 1:6.4, 1:6.5, 1:6.6, 1:6.7, 1:6.8 or 1:6.9, etc.

[0081] Preferably, the antioxidants in the raw materials for preparing the inner layer, the middle layer and the outer layer independently include a primary antioxidant and an auxiliary antioxidant.

[0082] Preferably, the primary antioxidant comprises a phosphite antioxidant, more preferably any one of tris(2,4-di-tert-butylphenyl)phosphite, tris(nonylphenyl)phosphite or tetrakis(2,4-di-tert-butylphenyl-4-4'-biphenyl)-bisphosphonate or a combination of at least two thereof.

[0083] Preferably, the auxiliary antioxidant includes a hindered phenol antioxidant, and more preferably any one of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate or 4,4'-thiobis(6-tert-butyl-m-cresol) or a combination of at least two thereof.

[0084] Preferably, the light stabilizer comprises a hindered amine light stabilizer, for example, Tinuvin 622 may be selected.

[0085] Preferably, the ultraviolet absorber includes any one of a salicylate ultraviolet absorber, a benzophenone ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber, a triazine ultraviolet absorber or a hindered amine ultraviolet absorber, or a combination of at least two thereof, and more preferably a salicylate ultraviolet absorber and / or a hindered amine ultraviolet absorber.

[0086] In a second aspect, the present invention provides a method for preparing the recyclable polyethylene agricultural film as described in the first aspect, the preparation method comprising the following steps:

[0087] (1) mixing the raw materials for preparing the inner layer to obtain the inner layer material; mixing the raw materials for preparing the middle layer, extruding and slicing, to obtain the middle layer material; mixing the raw materials for preparing the outer layer to obtain the outer layer material;

[0088] (2) The inner layer material, the middle layer material and the outer layer material obtained in step (1) are melt co-extruded and blown into a film to obtain the recyclable polyethylene agricultural film.

[0089] Preferably, the mixing of the raw materials for preparing the inner layer and the mixing of the raw materials for preparing the outer layer in step (1) are both carried out in a mixer;

[0090] Preferably, the mixing time for mixing the raw materials for preparing the inner layer and mixing the raw materials for preparing the outer layer in step (1) is independently 10 to 20 minutes, for example, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes or 19 minutes, etc.

[0091] Preferably, the mixing of the raw materials for preparing the middle layer in step (1) is carried out in an internal mixer.

[0092] Preferably, the mixing time for mixing the raw materials for preparing the middle layer in step (1) is 3 to 10 minutes, for example, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes or 9 minutes.

[0093] Preferably, the mixing temperature for mixing the raw materials for preparing the middle layer in step (1) is 160-195°C, for example, 165°C, 170°C, 175°C, 180°C, 185°C or 190°C.

[0094] Preferably, the melt coextrusion and film blowing in step (2) are both carried out in a three-layer coextrusion film blowing machine.

[0095] Preferably, the screw speed of the three-layer co-extrusion film blowing machine is 200-600 rpm, for example, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm or 550 rpm.

[0096] Preferably, the barrel temperature of the three-layer co-extrusion film blowing machine is 165-195°C, for example, 165°C, 170°C, 175°C, 180°C, 185°C or 190°C.

[0097] Preferably, the die head temperature of the three-layer co-extrusion film blowing machine is 180-220°C, for example, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C or 215°C.

[0098] Preferably, the blow-up ratio of the three-layer co-extrusion film blowing machine is 1.5-3, for example, 1.7, 1.9, 2.1, 2.3, 2.5, 2.7 or 2.9.

[0099] Preferably, after the film blowing in step (2) is completed, the steps of traction cooling, trimming and winding, and cutting are also included.

[0100] Preferably, the traction speed of the traction cooling is 20-30 m / min, for example, 21 m / min, 22 m / min, 23 m / min, 24 m / min, 25 m / min, 26 m / min, 27 m / min, 28 m / min or 29 m / min.

[0101] Preferably, the temperature of the sealing knife for the cutting process is 150-190°C, for example, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C or 185°C.

[0102] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0103] (1) Mixing the raw materials for the inner layer in a mixer for 3 to 20 minutes to obtain the inner layer material; kneading the raw materials for the middle layer in a mixer at 160 to 195° C. for 3 to 10 minutes, extruding and slicing to obtain the middle layer material; mixing the raw materials for the outer layer in a mixer for 3 to 20 minutes to obtain the outer layer material;

[0104] (2) adding the inner layer material, the middle layer material and the outer layer material obtained in step (1) into a three-layer co-extrusion film blowing machine (the screw speed of the three-layer co-extrusion film blowing machine is 200-600 rpm, the barrel temperature is 165-195° C., the die head temperature is 180-220° C., and the blow-up ratio is 1.5-3), and subjected to melt co-extrusion and blow molding into a film, and then traction cooling, trimming, winding and cutting are performed at a traction speed of 20-30 m / min to obtain the recyclable polyethylene agricultural film.

[0105] In a third aspect, the present invention provides a use of the recyclable polyethylene agricultural film as described in the first aspect in ground film.

[0106] Compared with the prior art, the present invention has the following beneficial effects:

[0107] (1) The recyclable polyethylene agricultural film provided by the present invention comprises an inner layer, a middle layer and an outer layer arranged in sequence, wherein the raw materials for preparing the middle layer comprise a combination of linear low-density polyethylene, metallocene linear low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, glass fiber, cellulose nanocrystals and poly(hydroxyethyl methacrylate). Through the above three-layer structure design and limiting the specific composition of the raw materials for preparing the middle layer, the finally obtained recyclable polyethylene agricultural film has excellent mechanical properties, as well as good aging resistance and weather resistance. After 6 months of use, it can still maintain high tensile load, tensile fracture nominal strain and right-angle tear load performance, and is thus easier to be recycled. At the same time, the preparation process of the recyclable polyethylene agricultural film is simple, and can simultaneously meet the production requirements of polyethylene agricultural film manufacturers and the use needs of downstream customers.

[0108] (2) Before use, the recyclable polyethylene agricultural film provided by the present invention has a tensile load of 2.8 to 3.5 N in the MD direction and a tensile load of 3.0 to 3.7 N in the TD direction; a nominal strain at break in the MD direction of 670 to 790%, and a nominal strain at break in the TD direction of 690 to 750%; a right-angle tear load in the MD direction of 1.9 to 2.1 N, and a right-angle tear load in the TD direction of 2.1 to 2.5 N; and a dart impact strength of 126 to 132 g. ; After six months of use, the tensile load of the recyclable polyethylene agricultural film provided by the present invention in the MD direction is 1.7-2.4N, and the tensile load in the TD direction is 1.7-2.8N; the nominal strain at break of the tensile in the MD direction is 460-610%, and the nominal strain at break of the tensile in the TD direction is 470-580%; the right-angle tear load in the MD direction is 1.0-1.3N, and the right-angle tear load in the TD direction is 1.0-1.5N; the dart impact strength is 85-108g. DETAILED DESCRIPTION

[0109] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0110] The detailed information of the raw materials and equipment involved in the specific implementation of the present invention are shown in Table 1 and Table 2 respectively:

[0111] Table 1

[0112]

[0113] Table 2

[0114] Device Name model factory Universal material testing machine Z010TE ZWICK Electronic tensile testing machine XLW(PC) Labthink Fat loss impact tester RR / FDT-A2 Rayran INSTRON Micrometer Thickness Gauge LS225 Linshang Internal Mixer GE320E Yiyang Machinery Mixer VM-400 Amixon Film Blowing Machine LF-600-COEX Labtech

[0115] Example 1

[0116] A recyclable polyethylene agricultural film, which consists of an inner layer, a middle layer and an outer layer arranged in sequence with a thickness ratio of 1:0.8:0.7, and a total thickness of 60 μm;

[0117] The raw materials for the inner layer, middle layer and outer layer are shown in the following table:

[0118]

[0119] The preparation method of the recyclable polyethylene agricultural film provided in this embodiment comprises the following steps:

[0120] (1) Mixing the raw materials for the inner layer in a mixer for 15 minutes to obtain the inner layer material; putting the raw materials for the middle layer into an internal mixer, mixing at 170° C. for 5 minutes, extruding and slicing to obtain the middle layer material; mixing the raw materials for the outer layer in a mixer for 15 minutes to obtain the outer layer material;

[0121] (2) The inner layer material, the middle layer material and the outer layer material obtained in step (1) are added into a three-layer co-extrusion film blowing machine (the screw speed is 300 rpm, the barrel temperature is 190°C) in a mass ratio of 1:0.8:0.7, and after melt co-extrusion, the film is blown from the film head (the die head temperature is 200°C, and the blow-up ratio is 2), and then traction cooling (traction speed is 25m / min), trimming and winding (the trimming size is 1.8cm), and cutting processing (sealing knife temperature is 170°C, base temperature is 70°C, and winding speed is 196 pieces / roll) to obtain the recyclable polyethylene agricultural film.

[0122] Example 2

[0123] A recyclable polyethylene agricultural film, which consists of an inner layer, a middle layer and an outer layer arranged in sequence with a thickness ratio of 1:0.6:0.5, and a total thickness of 60 μm;

[0124] The raw materials for the inner layer, middle layer and outer layer are shown in the following table:

[0125]

[0126]

[0127] The preparation method of the recyclable polyethylene agricultural film provided in this embodiment is the same as that in Example 1.

[0128] Example 3

[0129] A recyclable polyethylene agricultural film, which consists of an inner layer, a middle layer and an outer layer arranged in sequence with a thickness ratio of 1:1.1:0.8, and a total thickness of 60 μm;

[0130] The raw materials for the inner layer, middle layer and outer layer are shown in the following table:

[0131]

[0132] The preparation method of the recyclable polyethylene agricultural film provided in this embodiment is the same as that in Example 1.

[0133] Example 4

[0134] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no sorbitan fatty acid ester is added to the raw materials for preparing the inner layer, the added amount of polyvinyl alcohol is 0.0125 kg, the added amount of glycerol ester is 0.0875 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0135] Example 5

[0136] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no glycerol ester is added to the raw materials for preparing the inner layer, the added amount of polyvinyl alcohol is 0.033 kg, the added amount of sorbitan fatty acid ester is 0.064 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0137] Example 6

[0138] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no polyvinyl alcohol is added to the raw materials for preparing the inner layer, the added amount of sorbitan fatty acid ester is 0.022 kg, the added amount of glycerol ester is 0.078 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0139] Example 7

[0140] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no ultraviolet absorber is added to the raw materials for preparing the outer layer, the added amount of the light stabilizer is 0.55 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0141] Example 8

[0142] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no light stabilizer is added to the raw materials for preparing the outer layer, the added amount of the ultraviolet absorber is 0.55 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0143] Comparative Example 1

[0144] A recyclable polyethylene agricultural film, which differs from Example 1 only in that glass fiber, cellulose nanocrystals and poly(hydroxyethyl methacrylate) are not added to the raw materials for preparing the middle layer, and other raw materials, dosages and preparation methods are the same as those in Example 1.

[0145] Comparative Example 2

[0146] A recyclable polyethylene agricultural film, which is different from Example 1 only in that cellulose nanocrystals and poly(hydroxyethyl methacrylate) are not added to the raw materials for preparing the middle layer, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0147] Comparative Example 3

[0148] A recyclable polyethylene agricultural film, which differs from Example 1 only in that no cellulose nanocrystals are added to the raw materials for preparing the middle layer, the added amount of polyhydroxyethyl methacrylate is 0.77 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0149] Comparative Example 4

[0150] A recyclable polyethylene agricultural film, which differs from Example 1 only in that poly(hydroxyethyl methacrylate) is not added to the raw materials for preparing the middle layer, the added amount of cellulose nanocrystals is 0.77 kg, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0151] Comparative Example 5

[0152] A recyclable polyethylene agricultural film, which differs from Example 1 only in that UHMWPE is not added to the raw materials for preparing the middle layer, the added amount of LLDPE is 57 kg, the added amount of mLLDPE is 15.6 kg, and the added amount of HDPE is 25.9 kg. Other raw materials, amounts and preparation methods are the same as those in Example 1.

[0153] Comparative Example 6

[0154] A recyclable polyethylene agricultural film, which differs from Example 1 only in that glass fiber is not added to the raw materials for preparing the middle layer, and other raw materials, dosages and preparation methods are the same as those in Example 1.

[0155] Performance Test:

[0156] (1) Tensile load and tensile fracture nominal strain: Tested in accordance with the test method provided in GB / T1040.2-2006;

[0157] (2) Right-angle tear load: Tested in accordance with the test method provided in GB / T529-2008;

[0158] (3) Dart impact strength: tested in accordance with the test method provided in GB / T9639-2006.

[0159] The recyclable polyethylene agricultural films provided in Examples 1 to 8 and Comparative Examples 1 to 6 were tested according to the above test method. The test results are shown in Table 3:

[0160] Table 3

[0161]

[0162] According to the data in Table 3, it can be seen that the recyclable polyethylene agricultural film provided by the present invention has excellent mechanical properties, and also has good aging resistance and weather resistance. After 6 months of use, it can still maintain a high tensile load, tensile fracture nominal strain and right-angle tear load performance, and is thus easier to be recycled. Specifically: The recyclable polyethylene agricultural film obtained in Examples 1 to 8 has a tensile load of 2.8 to 3.5N in the MD direction before use, a tensile load of 3.0 to 3.7N in the TD direction, a tensile fracture nominal strain of 670 to 790% in the MD direction, a tensile fracture nominal strain of 690 to 750% in the TD direction, a right-angle tear load of 1.9 to 2.1N in the MD direction, a right-angle tear load of 2.1 to 2.5N in the TD direction, and a dart impact strength of 1.5N to 2.8N. It is 126-132g; after six months of use, the tensile load in the MD direction is 1.7-2.4N, the tensile load in the TD direction is 1.7-2.8N, the nominal strain at break in the MD direction is 460-610%, the nominal strain at break in the TD direction is 470-580%, the right-angle tear load in the MD direction is 1.0-1.3N, the right-angle tear load in the TD direction is 1.0-1.5N, and the dart impact strength is 85-108g.

[0163] By comparing the performance test data of the recyclable polyethylene agricultural film obtained in Example 1 with those in Comparative Examples 1 to 6, it can be seen that when the thickness of the recyclable polyethylene agricultural film is the same, the recyclable agricultural film provided in Example 1 has a higher tensile load, tensile fracture nominal strain and right-angle tear load before use, and can still maintain a relatively high tensile load, tensile fracture nominal strain and right-angle tear load performance after 6 months of use, which are significantly better than Comparative Examples 1 to 6.

[0164] Further comparison of the data of Example 1 and Examples 4 to 6 shows that the type of antifogging agent in the inner layer will also affect the weather resistance of the finally obtained recyclable polyethylene agricultural film. The lack of any one of polyvinyl alcohol, sorbitan fatty acid ester or glycerol ester will affect the tensile load, tensile break nominal strain and right-angle tear load performance of the obtained recyclable polyethylene agricultural film after 6 months of use.

[0165] Further comparison of the data of Example 1 and Examples 7-8 also shows that the absence of light stabilizer or ultraviolet absorber in the raw materials for preparing the outer layer will also affect the mechanical properties of the agricultural film after use.

[0166] The applicant declares that the present invention illustrates a recyclable polyethylene agricultural film and its preparation method and application through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A recyclable polyethylene agricultural film, characterized in that: The recyclable polyethylene agricultural film comprises an inner layer, a middle layer and an outer layer which are arranged in sequence; The raw materials for preparing the inner layer include the following components in parts by weight: The raw materials for preparing the middle layer include the following components in parts by weight: The raw materials for preparing the outer layer include the following components in parts by weight:

2. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The thickness ratio of the inner layer, the middle layer and the outer layer is 1:(0.6-1.2):(0.5-0.8).

3. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The total thickness of the recyclable polyethylene agricultural film is 30-100 μm.

4. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is ethylene-butene copolymer and / or ethylene-hexene copolymer.

5. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The melt mass flow rates of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer are independently 0.5 to 3 g / 10 min.

6. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The density of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 0.91 to 0.93 g / cm 3 .

7. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The weight average molecular weight of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 15×10 4 ~25×10 4 g / mol.

8. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The molecular weight distribution width index of the linear low-density polyethylene in the raw materials for preparing the inner layer, the middle layer and the outer layer is independently 4-7.

9. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is ethylene-butene copolymer and / or ethylene-hexene copolymer.

10. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The melt mass flow rates of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer are independently 5 to 20 g / 10 min.

11. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The density of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 0.945-0.96 g / cm 3 .

12. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The weight average molecular weight of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 20×10 4 ~30×10 4 g / mol.

13. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The molecular weight distribution width index of the high-density polyethylene in the raw materials for preparing the middle layer and the outer layer is independently 20-30.

14. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The metallocene linear low-density polyethylene is an ethylene-butene copolymer and / or an ethylene-hexene copolymer.

15. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The melt mass flow rate of the metallocene linear low-density polyethylene is 0.5 to 5 g / 10 min.

16. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The density of the metallocene linear low-density polyethylene is 0.91 to 0.926 g / cm 3 .

17. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The weight average molecular weight of the metallocene linear low density polyethylene is 15×10 4 ~25×10 4 g / mol.

18. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The molecular weight breadth index of the metallocene linear low-density polyethylene is 2-3.

19. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The low-density polyethylene is an ethylene homopolymer.

20. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The melt mass flow rate of the low-density polyethylene is 0.2 to 4 g / 10 min.

21. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The density of the low-density polyethylene is 0.916-0.93 g / cm 3 .

22. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The weight average molecular weight of the low density polyethylene is 10×10 4 ~18×10 4 g / mol.

23. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The molecular weight distribution width index of the low-density polyethylene is 3-9.

24. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The ultra-high molecular weight polyethylene is an ethylene homopolymer.

25. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The melt mass flow rate of the ultra-high molecular weight polyethylene is 0.05 to 1.2 g / 10 min.

26. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The density of the ultra-high molecular weight polyethylene is 0.35-0.6 g / cm 3 .

27. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The molecular weight distribution width index of the ultra-high molecular weight polyethylene is 10-15.

28. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The raw materials for preparing the cellulose nanocrystals include any one of wood, cotton or sisal or a combination of at least two of them.

29. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The diameter of the cellulose nanocrystal is 10 to 50 nm.

30. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The length of the cellulose nanocrystal is 20 to 300 nm.

31. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The glass fiber is alkali-free glass fiber.

32. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The diameter of the glass fiber is 5 to 30 μm.

33. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The length of the glass fiber is 40 to 500 μm.

34. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The weight average molecular weight of the polyhydroxyethyl methacrylate is 12×10 4 ~200×10 4 g / mol.

35. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The anti-fogging agent includes a combination of polyvinyl alcohol, sorbitan fatty acid ester and glycerol ester.

36. The recyclable polyethylene agricultural film according to claim 35, characterized in that: The mass ratio of the polyvinyl alcohol, sorbitan fatty acid ester and glycerol ester is 1:(2-3):(6-7).

37. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The antioxidants in the raw materials for preparing the inner layer, the middle layer and the outer layer independently include a primary antioxidant and an auxiliary antioxidant.

38. The recyclable polyethylene agricultural film according to claim 37, characterized in that: The primary antioxidant includes a phosphite antioxidant.

39. The recyclable polyethylene agricultural film according to claim 38, characterized in that: The primary antioxidant is any one of tris(2,4-di-tert-butylphenyl)phosphite, tris(nonylphenyl)phosphite or tetrakis(2,4-di-tert-butylphenyl-4-4'-biphenyl)-bisphosphonate or a combination of at least two thereof.

40. The recyclable polyethylene agricultural film according to claim 37, characterized in that: The auxiliary antioxidant includes a hindered phenol antioxidant.

41. The recyclable polyethylene agricultural film according to claim 40, characterized in that: The auxiliary antioxidant is any one of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate or 4,4'-thiobis(6-tert-butyl-m-cresol) or a combination of at least two thereof.

42. The recyclable polyethylene agricultural film according to claim 1, characterized in that: The light stabilizer includes a hindered amine light stabilizer.

43. The recyclable polyethylene agricultural film according to claim 42, characterized in that: The ultraviolet absorber includes any one of a salicylate ultraviolet absorber, a benzophenone ultraviolet absorber, a substituted acrylonitrile ultraviolet absorber, a triazine ultraviolet absorber or a hindered amine ultraviolet absorber, or a combination of at least two thereof.

44. The recyclable polyethylene agricultural film according to claim 43, characterized in that: The ultraviolet absorber is a salicylate ultraviolet absorber and / or a hindered amine ultraviolet absorber.

45. A method for preparing the recyclable polyethylene agricultural film according to any one of claims 1 to 44, characterized in that: The preparation method comprises the following steps: (1) mixing the raw materials for preparing the inner layer to obtain the inner layer material; mixing the raw materials for preparing the middle layer, extruding and slicing, to obtain the middle layer material; mixing the raw materials for preparing the outer layer to obtain the outer layer material; (2) melt co-extruding and blow-molding the inner layer material, the middle layer material and the outer layer material obtained in step (1) to form a film to obtain the recyclable polyethylene agricultural film; The melt coextrusion and film blowing in step (2) are both carried out in a three-layer coextrusion film blowing machine.

46. ​​The preparation method according to claim 45, characterized in that The mixing of the raw materials for preparing the inner layer and the mixing of the raw materials for preparing the outer layer in step (1) are both carried out in a mixer.

47. The preparation method according to claim 45, characterized in that The mixing time of mixing the raw materials for preparing the inner layer and the mixing of the raw materials for preparing the outer layer in step (1) is independently 10 to 20 minutes.

48. The preparation method according to claim 45, characterized in that In step (1), the raw materials for preparing the middle layer are mixed in an internal mixer.

49. The preparation method according to claim 45, characterized in that The mixing time of mixing the raw materials for preparing the middle layer in step (1) is 3 to 10 minutes.

50. The preparation method according to claim 45, characterized in that: The mixing temperature for mixing the raw materials for preparing the middle layer in step (1) is 160-195°C.

51. The preparation method according to claim 45, characterized in that The screw speed of the three-layer co-extrusion film blowing machine is 200-600 rpm.

52. The preparation method according to claim 45, characterized in that The barrel temperature of the three-layer co-extrusion film blowing machine is 165-195°C.

53. The preparation method according to claim 47, characterized in that: The die head temperature of the three-layer co-extrusion film blowing machine is 180-220°C.

54. The preparation method according to claim 45, characterized in that The blowing ratio of the three-layer co-extrusion film blowing machine is 1.5-3.

55. The preparation method according to claim 45, characterized in that After the film blowing in step (2) is completed, the steps of traction cooling, trimming and winding, and cutting are also included.

56. The preparation method according to claim 55, characterized in that The traction speed of the traction cooling is 20-30 m / min.

57. The preparation method according to claim 55, characterized in that: The sealing temperature of the cutting process is 150-190°C.

58. Use of the recyclable polyethylene agricultural film according to any one of claims 1 to 44 in ground film.

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