A polyolefin composite film, a solar backsheet, and a method for manufacturing the same

Abstract

The application provides a polyolefin composite film, a solar back sheet and a preparation method thereof. The polyolefin composite film comprises an outer layer, an intermediate layer and an inner layer; the preparation raw materials of the outer layer comprise, in terms of mass percentage, 30-70% of polypropylene, 10-40% of polyethylene, 5-15% of a toughening agent, 5-30% of an anti-UV master batch and 1-10% of a compatilizer; the preparation raw materials of the intermediate layer comprise, in terms of mass percentage, 50-90% of polypropylene, 5-20% of polyethylene, 1-10% of an ultraviolet absorber, 1-10% of a light stabilizer and 1-10% of titanium white; and the preparation raw materials of the inner layer comprise, in terms of mass percentage, 20-50% of polypropylene, 40-70% of polyethylene, 1-8% of an ultraviolet absorber, 1-8% of a light stabilizer and 1-8% of an antioxidant. The application solves the problems of poor heat resistance and poor impact resistance of the existing solar back sheet through specific composition and proportion of the three-layer raw materials of the polyolefin composite film.

Description

Technical Field

[0001] This invention relates to the field of solar backsheet technology, and in particular to a self-polyolefin composite film, a solar backsheet, and a method for preparing the same. Background Technology

[0002] The solar backsheet, located on the outer layer of the solar cell, must not only resist environmental damage including ultraviolet radiation, moisture erosion, temperature fluctuations, and alternating hot and cold cycles to protect the cell's lifespan, but also possess high heat resistance to prevent hot spots and bulging. Traditional PET backsheets use a fluoropolymer film as the outer layer, which has poor barrier properties and is difficult to recycle. Polyolefin materials, on the other hand, offer high weather resistance and high barrier properties. Using polyolefin films in the backsheet effectively improves its performance, enabling the solar backsheet to provide efficient protection even in harsh environments.

[0003] Currently, the backsheets using polyolefin materials on the market mainly include those with a solid polyolefin material and those with a polyolefin film inner layer. Backsheets with a solid polyolefin material have poor mechanical properties and poor impact resistance; backsheets with a polyolefin film inner layer have poor heat resistance due to the melting point of polyolefin material being 160℃, making them prone to bulging due to hot spots, and DTI is easily lost.

[0004] CN103066141A discloses a solar backsheet and its preparation method, comprising an inner surface layer, a core layer, and an outer surface layer from the inside out, with a mass ratio of inner surface layer:core layer:outer surface layer = 10-20:20-40:40-60. The inner and outer surface layers are made of polyamide resin, fillers, and additives. The core layer is made of a modified polypropylene resin composition. The modified polypropylene resin composition includes the following components: 100 parts polypropylene resin, 5-50 parts grafted polyethylene, 0-2.5 parts additives, and 0-100 parts fillers. The polyamide resin in the inner and outer surface layers of this solar backsheet can improve the water absorption rate and water vapor transmission rate of the backsheet to a certain extent. The outer layer has poor mechanical properties and impact resistance, while the inner layer has poor heat resistance, making it prone to bulging due to hot spots.

[0005] CN112721374A discloses a low-temperature resistant polypropylene film for protecting photovoltaic backsheet substrates and its manufacturing process. The film has a three-layer structure consisting of an outer layer, a core layer, and an inner layer. The middle layer is the core layer, the inner layer is a corona-treated layer, and the outer layer is an untreated layer. The middle layer, i.e., the core layer, consists of 1-3% antistatic masterbatch, 1-3% anti-UV masterbatch, 10-30% low-temperature resistant masterbatch, and 60-89% homopolymer polypropylene. The inner layer consists of 3-5% anti-blocking masterbatch, 1-3% anti-UV masterbatch, 5-10% low-temperature resistant masterbatch, 1-3% antistatic masterbatch, and 82-91% homopolymer polypropylene. The outer layer consists of 3-5% anti-blocking masterbatch, 1-3% anti-UV masterbatch, 5-10% low-temperature resistant masterbatch, and 85-92% homopolymer polypropylene. This film also suffers from poor mechanical properties, poor impact resistance, poor heat resistance, and is prone to bulging due to hot spots, as well as easy loss of DTI.

[0006] In conclusion, existing solar backsheets still need improvement.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] One objective of this invention is to provide a polyolefin composite film comprising an outer layer, a middle layer, and an inner layer. This invention, through three layers of raw materials with different compositions and proportions, yields an air separator for solar panel backsheets, effectively solving the technical problems of poor heat resistance and impact resistance in existing solar panel backsheets.

[0009] The second objective of this invention is to provide a method for preparing the polyolefin composite film, the method comprising the following steps: mixing the raw materials for the outer layer, the raw materials for the middle layer, and the raw materials for the inner layer according to the raw material ratio, and then placing them in the three channels of a twin-screw extruder, and obtaining the polyolefin composite film by melt plasticizing, extrusion, and stretching.

[0010] A third objective of this invention is to provide a solar backsheet comprising an air layer, a substrate layer, and an adhesive layer; wherein the air layer is the aforementioned three-layer polyolefin composite film; and the inner layer of the polyolefin composite film is bonded to the substrate layer. This invention provides a high-performance multilayer solar backsheet with excellent heat resistance, weather resistance, and high UV performance, and does not use fluorine film materials, making it environmentally friendly.

[0011] The fourth objective of this invention is to provide a method for preparing the solar backsheet, the method comprising the following steps: coating one side of the substrate layer with a fluorocarbon coating and coating the other side of the substrate layer with polyurethane adhesive, then attaching the polyolefin composite film, performing a thermosetting treatment, and then performing a curing treatment to obtain the solar backsheet.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] In a first aspect, the present invention provides a polyolefin composite film, the polyolefin composite film comprising an outer layer, a middle layer and an inner layer;

[0014] The raw materials for preparing the outer layer, by mass percentage, include: 30-70% polypropylene, 10-40% polyethylene, 5-15% toughening agent, 5-30% UV-resistant masterbatch, and 1-10% compatibilizer.

[0015] The raw materials for preparing the intermediate layer include, by mass percentage: 50-90% polypropylene, 5-20% polyethylene, 1-10% ultraviolet absorber, 1-10% light stabilizer, and 1-10% titanium dioxide.

[0016] The raw materials for preparing the inner layer, by mass percentage, include: 20-50% polypropylene, 40-70% polyethylene, 1-8% ultraviolet absorber, 1-8% light stabilizer, and 1-8% antioxidant.

[0017] In this invention, a highly weather-resistant polyolefin composite film (PO film) is obtained by using the above three layers of raw materials with different compositions and proportions. When used as the air layer of a solar panel backsheet, it forms a multi-layered protective barrier. Compared to fluorocarbon coatings and fluorine films, this PO film has better barrier properties and higher mechanical strength, effectively protecting the solar cells from environmental corrosion and improving the aging resistance of the backsheet. Simultaneously, as an outer layer, the PO film is unaffected by lamination, providing a high DTI (effective insulation thickness), comparable to the thickness of PET, effectively reducing costs, and the backsheet is not affected by hot spots during use.

[0018] Based on the total mass of the raw materials used to prepare the outer layer as 100%, the polypropylene content is 30-70%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, etc., preferably 40-65%, and more preferably 45-60%.

[0019] Based on the total mass of the raw materials used to prepare the outer layer (100%), the content of polyethylene is 10-40%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc., preferably 15-35%, and more preferably 18-30%.

[0020] Based on the total mass of the raw materials used to prepare the outer layer as 100%, the content of the toughening agent is 5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., preferably 5-12%, and more preferably 8-12%.

[0021] In this invention, the toughening agent is dispersed in the resin in the form of a dispersed phase and has good compatibility with the main resin. Under the action of external force, the toughening agent becomes a stress concentration point, which can generate silver crimp and shear energy consumption without being converted into destructive cracks, thereby enhancing the toughness of the PO film.

[0022] Based on the total mass of the raw materials used to prepare the outer layer as 100%, the content of the UV-resistant masterbatch is 5-30%, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc., preferably 8-25%, and more preferably 10-20%.

[0023] Based on the total mass of the raw materials used to prepare the outer layer as 100%, the content of the compatibilizer is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably 1-8%, and more preferably 1-7%.

[0024] Based on the total mass of the raw materials used to prepare the intermediate layer as 100%, the polypropylene content is 50-90%, for example, it can be 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, etc., preferably 58-80%, and more preferably 65-78%.

[0025] Based on the total mass of the raw materials used to prepare the intermediate layer as 100%, the content of polyethylene is 5-20%, for example, it can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., preferably 8-18%, and more preferably 10-15%.

[0026] Based on the total mass of the raw materials used to prepare the intermediate layer as 100%, the content of the ultraviolet absorber is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 2-8%, and more preferably 3-7%.

[0027] Based on the total mass of the raw materials used to prepare the intermediate layer as 100%, the content of the light stabilizer is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 2-8%, and more preferably 3-7%.

[0028] Based on the total mass of the raw materials used to prepare the intermediate layer as 100%, the content of titanium dioxide is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 2-8%, and more preferably 3-7%.

[0029] Based on the total mass of the raw materials used to prepare the inner layer as 100%, the content of polypropylene is 20-50%, for example, it can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, etc., preferably 25-45%, and more preferably 30-40%.

[0030] Based on the total mass of the raw materials used to prepare the inner layer as 100%, the content of polyethylene is 40-70%, for example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, etc., preferably 40-65%, and more preferably 45-60%.

[0031] Based on the total mass of the raw materials used to prepare the inner layer as 100%, the ultraviolet absorber is 1-8%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., preferably 2-8%, and more preferably 2-6%.

[0032] Based on the total mass of the raw materials used to prepare the inner layer as 100%, the light stabilizer is 1-8%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., preferably 2-8%, and more preferably 2-6%.

[0033] Based on the total mass of the raw materials used to prepare the inner layer as 100%, the antioxidant content is 1-8%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., preferably 2-8%, and more preferably 2-6%.

[0034] Preferably, the thickness ratio of the outer layer, the middle layer and the inner layer is (1-5):(8-18):(1-3);

[0035] Among them, "1 to 5" can be, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.;

[0036] Among them, "8 to 18" can be, for example, 8, 10, 12, 14, 16, 18, etc.

[0037] Among them, "1 to 3" can be, for example, 1, 1.5, 2, 2.5, 3, etc.

[0038] Preferably, the total thickness of the polyolefin composite film is 100-250 μm, for example, it can be 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, etc., preferably 120-230 μm, and more preferably 150-200 μm.

[0039] Preferably, the thickness of the outer layer is 10 to 50 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., more preferably 15 to 40 μm, and more preferably 20 to 30 μm.

[0040] Preferably, the thickness of the intermediate layer is 80-180 μm, for example, it can be 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, etc., preferably 90-180 μm, and more preferably 120-150 μm.

[0041] Preferably, the thickness of the inner layer is 10 to 30 μm, for example, it can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 22 μm, 26 μm, 28 μm, 30 μm, etc., more preferably 12 to 25 μm, and more preferably 15 to 20 μm.

[0042] Preferably, the raw materials for preparing the UV-resistant masterbatch include, by weight percentage: 40-70% polypropylene, 5-15% UV absorber, 1-10% light stabilizer, 1-10% antioxidant, and 10-30% titanium dioxide.

[0043] Based on the total mass of the raw materials for preparing the UV-resistant masterbatch as 100%, the polypropylene content is 40-70%, for example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, etc., preferably 45-65%, and more preferably 48-60%.

[0044] Based on the total mass of the raw materials for preparing the UV-resistant masterbatch as 100%, the content of the UV absorber is 5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., preferably 5-12%, and more preferably 6-12%.

[0045] Based on the total mass of the raw materials for preparing the UV-resistant masterbatch as 100%, the content of the light stabilizer is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 1-8%, and more preferably 2-8%.

[0046] Based on the total mass of the raw materials for preparing the UV-resistant masterbatch as 100%, the content of titanium dioxide is 10-30%, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc., preferably 12-28%, and more preferably 15-25%.

[0047] Based on the total mass of the raw materials for preparing the UV-resistant masterbatch as 100%, the antioxidant is 1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 1-8%, and more preferably 2-8%.

[0048] Preferably, the polypropylene is selected from any one or a combination of at least two of homopolymer polypropylene, block polypropylene, or atactic polypropylene.

[0049] Preferably, the melt index of the polypropylene is 0.1 to 25 g / 10 min, for example, it can be 0.1 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 4 g / 10 min, 6 g / 10 min, 8 g / 10 min, 10 g / 10 min, 12 g / 10 min, 14 g / 10 min, 16 g / 10 min, 18 g / 10 min, 20 g / 10 min, 22 g / 10 min, 24 g / 10 min, 25 g / 10 min, etc.

[0050] Preferably, the polyethylene is selected from any one or a combination of at least two of ultra-high molecular weight polyethylene, high-density polyethylene, low-density polyethylene, or linear low-density polyethylene.

[0051] Preferably, the melt index of the polyethylene is 0.1 to 10 g / 10 min, for example, it can be 0.1 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 2 g / 10 min, 4 g / 10 min, 6 g / 10 min, 8 g / 10 min, 10 g / 10 min, etc.

[0052] Preferably, the toughening agent is selected from any one or a combination of at least two of ethylene-propylene binary rubber, ethylene-propylene ternary rubber, or ethylene-octene copolymer.

[0053] Preferably, the compatibilizer is selected from any one or a combination of at least two of the following: polypropylene maleic anhydride graft, ethylene-octene copolymer maleic anhydride graft, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-acrylate-maleic anhydride copolymer, or ethylene-methacrylate-maleic anhydride copolymer.

[0054] Preferably, the ultraviolet absorber is selected from any one or a combination of at least two of salicylate ultraviolet absorbers, benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, hindered amine ultraviolet absorbers, substituted acrylonitrile ultraviolet absorbers, or triazine ultraviolet absorbers.

[0055] Preferably, the light stabilizer is selected from any one or a combination of at least two of the following: o-hydroxybenzophenone light stabilizers, benzotriazole light stabilizers, triazine light stabilizers, or salicylate light stabilizers.

[0056] Preferably, the antioxidant is selected from any one or a combination of at least two of hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, or thioester antioxidants.

[0057] Preferably, the titanium dioxide is selected from rutile titanium dioxide.

[0058] In a second aspect, the present invention provides a method for preparing a polyolefin composite film as described in the first aspect, the method comprising the following steps:

[0059] The raw materials for the outer layer, the middle layer, and the inner layer are mixed according to the raw material ratio and then placed in the three channels of a twin-screw extruder. Through melt plasticizing, extrusion, and stretching, the polyolefin composite film is obtained.

[0060] Preferably, the melting and plasticizing temperature is 180 to 250°C, for example, it can be 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0061] Preferably, the extrusion temperature is 180-270°C, for example, it can be 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, etc.

[0062] Preferably, the stretching speed is 5 to 20 m / min, for example, it can be 5 m / min, 6 m / min, 8 m / min, 10 m / min, 12 m / min, 14 m / min, 16 m / min, 18 m / min, 20 m / min, etc.

[0063] Preferably, the method for preparing the polyolefin composite film further includes a granulation step:

[0064] Polypropylene, UV absorber, light stabilizer, antioxidant, and titanium dioxide are mixed in a twin-screw extruder according to the raw material ratio and then granulated to obtain UV-resistant masterbatch.

[0065] Preferably, during the granulation process, the temperature of the granulation extruder is 180-270℃, for example, it can be 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, etc.

[0066] Thirdly, the present invention provides a solar backsheet, the solar backsheet comprising an air layer, a substrate layer and an adhesive layer; wherein the air layer is the polyolefin composite film described in the first aspect; and the inner layer of the polyolefin composite film is bonded to the substrate layer.

[0067] Preferably, the substrate layer is a polyethylene terephthalate film (PET film).

[0068] Preferably, the thickness of the polyethylene terephthalate film is 125-305 μm, for example, it can be 125 μm, 150 μm, 200 μm, 250 μm, 285 μm, 305 μm, etc.

[0069] Preferably, the adhesive layer is a fluorocarbon coating.

[0070] Preferably, the thickness of the fluorocarbon coating is 5 to 20 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc., preferably 8 to 17 μm, and more preferably 8 to 12 μm.

[0071] Preferably, the inner layer of the polyolefin composite film and the substrate layer further include an adhesive layer.

[0072] Preferably, the adhesive layer is a polyurethane adhesive layer.

[0073] Preferably, the thickness of the polyurethane adhesive layer is 5 to 12 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.

[0074] Fourthly, the present invention provides a method for preparing a solar backsheet according to the third aspect, the method comprising the following steps:

[0075] A fluorocarbon coating is applied to one side of the substrate layer, and polyurethane adhesive is applied to the other side of the substrate layer. The polyolefin composite film is then applied, followed by thermosetting and curing treatment to obtain the solar backsheet.

[0076] Preferably, the temperature of the thermosetting treatment is 140-160℃, for example, 140℃, 145℃, 150℃, 155℃, 160℃, etc., and the time is 1-5min, for example, 1min, 2min, 3min, 4min, 5min, etc.

[0077] Preferably, the aging process is carried out at a temperature of 40-60°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, etc., and for a time of 48-72 hours, such as 48 hours, 50 hours, 52 hours, 54 hours, 56 hours, 58 hours, 60 hours, 62 hours, 64 hours, 66 hours, 68 hours, 70 hours, 72 hours, etc.

[0078] Compared with the prior art, the present invention has the following beneficial effects:

[0079] (1) This invention develops a highly weather-resistant PO film and uses it in the air layer of a solar backsheet to form a multi-layer protective barrier;

[0080] (2) The PO film of the present invention has better barrier properties and higher mechanical strength, which can effectively protect the battery cells from environmental corrosion and further improve the aging resistance of the back sheet.

[0081] (3) The PO film described in this invention is used as an outer layer and is not affected by lamination. It can provide a high DTI (effective insulation thickness), bear the thickness of PET, effectively reduce costs, and the backing is not affected by hot spots during use. Attached Figure Description

[0082] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0083] Figure 1 This is a schematic diagram of the structure of the polyolefin composite membrane described in this invention.

[0084] Among them, 10 is the outer layer, 11 is the middle layer, and 12 is the inner layer.

[0085] Figure 2 This is a schematic diagram of the structure of the solar backsheet described in this invention.

[0086] Among them, 1 is the air layer, 10 is the outer layer, 11 is the middle layer, 12 is the inner layer, 2 is the substrate layer, and 3 is the adhesive layer. Detailed Implementation

[0087] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0088] It should be noted that specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0089] Figure 1 This is a schematic diagram of the structure of the polyolefin composite film described in this invention. Figure 1 As shown, the polyolefin composite film includes an outer layer 10, a middle layer 11, and an inner layer 12.

[0090] Figure 2 This is a schematic diagram of the structure of the solar backsheet described in this invention. Figure 2 As shown, the solar backsheet includes an air layer 1, a substrate layer 2, and an adhesive layer 3; wherein, the air layer 1 is... Figure 1 The polyolefin composite film shown; and the inner layer 12 of the polyolefin composite film is bonded to one side of the substrate layer 2.

[0091] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0092] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0093] Example 1

[0094] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0095] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 5 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0096] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0097]

[0098] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0099]

[0100]

[0101] The solar backsheet is prepared by the following method:

[0102] S1. Preparation of UV-resistant masterbatch:

[0103] According to the formula, the raw materials of the above-mentioned UV-resistant masterbatch are placed in a twin-screw extruder for mixing and granulation to obtain the UV-resistant masterbatch; wherein, the temperature of the granulation extruder is 220℃.

[0104] Preparation of S2 and PO membranes:

[0105] The raw materials for the outer layer, the middle layer, and the inner layer are mixed evenly according to the formula, and then placed into the three channels A, B, and C of a twin-screw extruder. After melting and plasticizing, the PO film is obtained by extrusion and stretching. The melting and plasticizing temperature is 220℃, the extrusion temperature is 220℃, and the stretching speed is 8m / min.

[0106] S3, Preparation of Solar Backsheet

[0107] The PET film substrate is unwound, coated with a fluorocarbon adhesive layer on one side, and coated with a polyurethane adhesive on the other side to bond an air layer PO film (the inner layer is bonded to the substrate layer). It is then placed in a circulating oven for thermosetting, followed by curing and slitting to obtain a high-performance multilayer solar backsheet. The circulating oven temperature is 150℃, the curing time is 2 minutes, and the curing reaction temperature is 50℃ for 48 hours.

[0108] Example 2

[0109] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0110] The substrate layer is a PET film with a thickness of 250 μm; the PET film is of type E510; the adhesive layer is a fluorocarbon coating with a thickness of 7 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5910.

[0111] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0112]

[0113]

[0114] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0115]

[0116] The preparation method of the solar backsheet is the same as that in Example 1.

[0117] Example 3

[0118] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0119] The substrate layer is a PET film with a thickness of 250 μm; the PET film is of type E510; the adhesive layer is a fluorocarbon coating with a thickness of 5 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0120] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0121]

[0122]

[0123] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0124]

[0125] The preparation method of the solar backsheet is the same as that in Example 1.

[0126] Example 4

[0127] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0128] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 20 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5000.

[0129] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0130]

[0131] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0132]

[0133] The preparation method of the solar backsheet is the same as that in Example 1.

[0134] Example 5

[0135] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0136] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 17 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0137] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0138]

[0139]

[0140] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0141]

[0142] The preparation method of the solar backsheet is the same as that in Example 1.

[0143] Example 6

[0144] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0145] The substrate layer is a PET film with a thickness of 250 μm; the PET film is of type KP20; the adhesive layer is a fluorocarbon coating with a thickness of 10 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5000.

[0146] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0147]

[0148]

[0149] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0150]

[0151] The preparation method of the solar backsheet is the same as that in Example 1.

[0152] Example 7

[0153] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0154] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 15 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5000.

[0155] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0156]

[0157] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0158]

[0159] The preparation method of the solar backsheet is the same as that in Example 1.

[0160] Example 8

[0161] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0162] The substrate layer is a PET film with a thickness of 285 μm; the PET film is of type M48; the adhesive layer is a fluorocarbon coating with a thickness of 8 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0163] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0164]

[0165] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0166]

[0167]

[0168] The preparation method of the solar backsheet is the same as that in Example 1.

[0169] Example 9

[0170] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0171] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 10 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0172] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0173]

[0174]

[0175] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0176]

[0177] The preparation method of the solar backsheet is the same as that in Example 1.

[0178] Example 10

[0179] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0180] The substrate layer is a PET film with a thickness of 305 μm; the PET film is of type DS10; the adhesive layer is a fluorocarbon coating with a thickness of 9 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5000.

[0181] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0182]

[0183]

[0184] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0185]

[0186] The preparation method of the solar backsheet is the same as that in Example 1.

[0187] Example 11

[0188] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0189] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 10 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0190] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0191]

[0192] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0193]

[0194] The preparation method of the solar backsheet is the same as that in Example 1.

[0195] Example 12

[0196] This embodiment provides a solar backsheet comprising a polyolefin composite film, wherein the solar backsheet comprises an air layer, a substrate layer and an adhesive layer in sequence; the air layer is a PO film, which comprises an outer layer, a middle layer and an inner layer in sequence; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0197] The substrate layer is a PET film with a thickness of 150 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 12 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0198] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage: The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0199]

[0200]

[0201] The preparation method of the solar backsheet is the same as that in Example 1.

[0202] Comparative Example 1

[0203] This comparative example provides a commercially available conventional TPC solar backsheet, which sequentially includes an air layer, a substrate layer, and an adhesive layer; the air layer is a polyvinyl fluoride (PVF) film with a thickness of 25 μm; the substrate layer is a PET film with a thickness of 280 μm; and the adhesive layer is a fluorocarbon coating with a thickness of 8 μm.

[0204] Comparative Example 2

[0205] This comparative example provides a commercially available conventional TPO solar backsheet, which sequentially includes an air layer, a substrate layer, and an adhesive layer; the air layer is a polyvinyl fluoride (PVF) film with a thickness of 25 μm; the substrate layer is a PET film with a thickness of 250 μm; and the adhesive layer is a commercially available PO film with a thickness of 60 μm.

[0206] Comparative Example 3

[0207] This comparative example provides a solar backsheet, which sequentially includes an air layer, a substrate layer, and an adhesive layer; the air layer is a PO film, which sequentially includes an outer layer, a middle layer, and an inner layer; and the inner layer of the polyolefin composite film is bonded to one side of the substrate layer, and the adhesive layer is coated on the other side of the substrate layer.

[0208] The substrate layer is a PET film with a thickness of 125 μm; the PET film is of type M60; the adhesive layer is a fluorocarbon coating with a thickness of 10 μm; the fluorocarbon coating is formed by curing a fluorocarbon coating applied to the other side of the substrate layer; the air layer and the substrate interlayer are bonded by adhesive, the adhesive is a polyurethane adhesive, and the adhesive is of type D-5902.

[0209] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0210]

[0211]

[0212] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0213]

[0214] The preparation method of the solar backsheet is the same as that in Example 1.

[0215] Comparative Example 4

[0216] This comparative example provides a solar backsheet containing a polyolefin composite film. The difference from Example 1 is that the PO film does not have an outer layer, the thickness of the middle layer is increased to 250 μm, and the thickness of the inner layer is increased to 50 μm. All other settings are completely the same as in Example 1.

[0217] Comparative Example 5

[0218] This comparative example provides a solar backsheet containing a polyolefin composite film. The difference from Example 1 is that the PO film does not contain an intermediate layer, the thickness of the outer layer is increased to 200 μm, and the thickness of the inner layer is increased to 100 μm. All other settings are completely the same as in Example 1.

[0219] Comparative Example 6

[0220] This comparative example provides a solar backsheet containing a polyolefin composite film. The difference from Example 1 is that the PO film does not contain an inner layer, the thickness of the outer layer is increased to 125 μm, and the thickness of the inner layer is increased to 175 μm. All other settings are completely the same as in Example 1.

[0221] Comparative Example 7

[0222] This comparative example provides a solar backsheet containing a polyolefin composite film. The difference from Example 1 is that the PO film has only one layer structure and its thickness is 300 μm.

[0223] The raw materials for each layer of the PO membrane specifically include the following components by mass percentage:

[0224]

[0225] The raw materials of the UV-resistant masterbatch specifically include the following components by mass percentage:

[0226]

[0227] Test case

[0228] Test samples: Solar backsheets containing polyolefin composite films provided in Examples 1-12, and solar backsheets provided in Comparative Examples 1-7;

[0229] Test method:

[0230] (1) Water vapor transmission rate (WVTR): The water vapor transmission rate of the solar backsheet was tested by electrolysis according to the standard GB / T 31034-2014 "Insulating backsheet for crystalline silicon solar cell modules". The test conditions were 38℃ and 90% relative humidity.

[0231] (2) DTI test: The test method refers to IEC TS 62788-2:2017 "Measurement procedures for materials used in photovoltaic modules - Part 2: Polymeric materials - Frontsheets and backsheets".

[0232] A higher DTI value indicates better insulation performance. A high DTI provided by the outer film allows for a reduction in the thickness of the PET substrate, thereby lowering the cost of the backsheet. (Solar backsheets at 1500V require a DTI of over 300 micrometers. If the outer film has a high DTI, the thickness of the PET substrate can be reduced. Since the cost of the outer film is lower than that of the PET substrate, the overall cost of the backsheet can be reduced.)

[0233] (3) QUV aging treatment: According to the standard GB / T 31034-2014 "Insulating backsheet for crystalline silicon solar cell modules", the sample was treated with a UV aging lamp. The irradiated surface was the outer layer of the PO film. The accumulated UV energy reached 200 kWh / m². The sample was taken out to observe its appearance, and the yellowing Δb and the elongation at break of the sample were tested. The elongation at break after aging was recorded as the elongation at break, and the elongation at break retention rate was calculated.

[0234] (4) Damp heat aging treatment: In accordance with the standard GB / T 31034-2014 "Insulating backsheet for crystalline silicon solar cell modules", the temperature was set at 85℃ and the humidity at 85% in a high temperature and high humidity chamber for a cumulative time of 2000h. The samples were taken out to observe their appearance, and the yellowing Δb and the elongation at break of the samples were tested. The elongation at break after aging was recorded as the elongation at break, and the elongation at break retention rate was calculated.

[0235] (5) Wet freeze aging treatment: Set up the program according to the wet freeze aging test method in IEC61215:2016, complete 30 cycles, test the yellowing Δb and the elongation at break of the sample, record it as the elongation at break after aging, and calculate the elongation at break retention rate.

[0236] (6) Elongation at break: The elongation at break of the unaged sample was tested according to GB / T 13542.2-2009 standard and recorded as the initial elongation at break.

[0237] Elongation at break retention rate = Elongation at break after aging / Initial elongation at break × 100%

[0238] The specific test results are shown in Table 1 below:

[0239] Table 1

[0240]

[0241]

[0242] As shown in Table 1, the PO film and solar backsheet provided by this invention possess high weather resistance, high barrier properties, and high insulation. Examples 5-8 are preferred embodiments, exhibiting good barrier properties, high DTI, and maintaining an elongation at break greater than 60% under QUV aging, damp heat aging, and wet freeze aging, with a yellowing value less than 2.5. Examples 8-10 are optimal embodiments, with a WVTR less than 1.2 g / m³. 2 For days, the DTI is greater than 300 μm, and the elongation at break during QUV aging, wet heat aging, and wet freeze aging remains above 80%.

[0243] Furthermore, the test results from the above embodiments and comparative examples show that the solar backsheet provided by the present invention has excellent performance, high barrier properties, high insulation properties, and excellent resistance to UV aging, damp heat aging, and wet freeze aging, effectively protecting solar cell modules from environmental corrosion. Comparative Examples 1 and 2 show that the solar backsheet provided by the present invention has better barrier properties than existing solar backsheets on the market. Comparative Example 2 shows that using the PO film as the outer layer of the solar backsheet improves its insulation. Comparative Example 3 shows that without the addition of a toughening agent, the toughness of the solar backsheet deteriorates, and the elongation at break after aging is low, failing to meet the requirements of photovoltaic modules. This is because the toughening agent is dispersed in the resin as a dispersed phase and has good compatibility with the main resin. Under external force, the toughening agent becomes a stress concentration point, generating crimps and shear energy consumption without converting into destructive cracks, thereby enhancing the toughness of the PO film. Comparative Examples 4-7 show that the PO film maintains a superior three-layer structure with excellent weather resistance.

[0244] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polyolefin composite film, characterized in that, The polyolefin composite film includes an outer layer, a middle layer, and an inner layer; The raw materials for preparing the outer layer, by weight percentage, include: 40-65% polypropylene, 15-35% polyethylene, 5-12% toughening agent, 8-25% UV-resistant masterbatch, and 1-8% compatibilizer; The raw materials for preparing the UV-resistant masterbatch, by weight percentage, include: 40-70% polypropylene, 5-15% UV absorber, 1-10% light stabilizer, 1-10% antioxidant, and 10-30% titanium dioxide; the compatibilizer is selected from any one or a combination of at least two of the following: polypropylene maleic anhydride graft, ethylene-octene copolymer maleic anhydride graft, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-acrylate-maleic anhydride copolymer, or ethylene-methacrylate-maleic anhydride copolymer. The raw materials for preparing the intermediate layer, by weight percentage, include: 58-80% polypropylene, 8-18% polyethylene, 2-8% ultraviolet absorber, 2-8% light stabilizer, and 2-8% titanium dioxide; The raw materials for preparing the inner layer include, by mass percentage: 25-45% polypropylene, 40-65% polyethylene, 2-8% ultraviolet absorber, 2-8% light stabilizer, and 2-8% antioxidant.

2. The polyolefin composite film according to claim 1, characterized in that, The thickness ratio of the outer layer, the middle layer and the inner layer is (1~5):(8~18):(1~3).

3. The polyolefin composite film according to claim 1, characterized in that, The total thickness of the polyolefin composite film is 100~250 μm.

4. The polyolefin composite film according to claim 1, characterized in that, The outer layer has a thickness of 10~50 μm, the middle layer has a thickness of 80~180 μm, and the inner layer has a thickness of 10~30 μm.

5. The polyolefin composite film according to claim 1, characterized in that, The polypropylene is selected from any one or a combination of at least two of homopolymer polypropylene, block polypropylene, or atactic polypropylene.

6. The polyolefin composite film according to claim 1, characterized in that, The melt index of the polypropylene is 0.1~25 g / 10min.

7. The polyolefin composite film according to claim 1, characterized in that, The polyethylene is selected from any one or a combination of at least two of ultra-high molecular weight polyethylene, high-density polyethylene, low-density polyethylene, or linear low-density polyethylene.

8. The polyolefin composite film according to claim 1, characterized in that, The melt index of the polyethylene is 0.1~10 g / 10min.

9. The polyolefin composite film according to claim 1, characterized in that, The toughening agent is selected from any one or a combination of at least two of ethylene-propylene binary rubber, ethylene-propylene ternary rubber, or ethylene-octene copolymer.

10. The polyolefin composite film according to claim 1, characterized in that, The ultraviolet absorber is selected from any one or a combination of at least two of the following: salicylates, benzophenones, benzotriazoles, hindered amines, substituted acrylonitrile, or triazines.

11. The polyolefin composite film according to claim 1, characterized in that, The light stabilizer is selected from any one or a combination of at least two of the following: o-hydroxybenzophenone light stabilizers, benzotriazole light stabilizers, triazine light stabilizers, or salicylate light stabilizers.

12. The polyolefin composite film according to claim 1, characterized in that, The antioxidant is selected from any one or a combination of at least two of the following: hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, or thioester antioxidants.

13. The polyolefin composite film according to claim 1, characterized in that, The titanium dioxide is selected from rutile titanium dioxide.

14. A method for preparing a polyolefin composite film according to any one of claims 1 to 13, characterized in that, The preparation method includes the following steps: The raw materials for the outer layer, the middle layer, and the inner layer are mixed according to the raw material ratio and then placed in the three channels of a twin-screw extruder. Through melt plasticizing, extrusion, and stretching, the polyolefin composite film is obtained.

15. The method for preparing the polyolefin composite film according to claim 14, characterized in that, The melting and plasticizing temperature is 180~250℃.

16. The method for preparing the polyolefin composite film according to claim 14, characterized in that, The extrusion temperature is 180~270℃.

17. The method for preparing the polyolefin composite film according to claim 14, characterized in that, The stretching speed is 5~20 m / min.

18. The method for preparing the polyolefin composite film according to claim 14, characterized in that, The method for preparing the polyolefin composite film also includes a granulation step: Polypropylene, UV absorber, light stabilizer, antioxidant, and titanium dioxide are mixed in a twin-screw extruder according to the raw material ratio and then granulated to obtain UV-resistant masterbatch.

19. The method for preparing the polyolefin composite film according to claim 18, characterized in that, During the granulation process, the temperature of the granulation extruder is 180~270℃.

20. A solar backsheet, characterized in that, The solar backsheet includes an air layer, a substrate layer, and an adhesive layer; wherein the air layer is a polyolefin composite film as described in any one of claims 1 to 19; and the inner layer of the polyolefin composite film is bonded to the substrate layer.

21. The solar backsheet according to claim 20, characterized in that, The substrate layer is a polyethylene terephthalate film.

22. The solar backsheet according to claim 21, characterized in that, The thickness of the polyethylene terephthalate film is 125~305 μm.

23. The solar backsheet according to claim 20, characterized in that, The adhesive layer is a fluorocarbon coating.

24. The solar backsheet according to claim 23, characterized in that, The thickness of the fluorocarbon coating is 5~20 μm.

25. The solar backsheet according to claim 20, characterized in that, The inner layer of the polyolefin composite film and the substrate layer also include an adhesive layer.

26. The solar backsheet according to claim 25, characterized in that, The adhesive layer is a polyurethane adhesive layer.

27. The solar backsheet according to claim 26, characterized in that, The thickness of the polyurethane adhesive layer is 5~12 μm.

28. A method for preparing a solar backsheet according to any one of claims 20-27, characterized in that, The preparation method includes the following steps: A fluorocarbon coating is applied to one side of the substrate layer, and polyurethane adhesive is applied to the other side of the substrate layer. The polyolefin composite film is then applied, followed by thermosetting and curing treatment to obtain the solar backsheet.

29. The method for preparing a solar backsheet according to claim 28, characterized in that, The temperature for the thermosetting treatment is 140~160℃, and the time is 1~5 min.

30. The method for preparing a solar backsheet according to claim 28, characterized in that, The aging process is carried out at a temperature of 40-60°C for 48-72 hours.

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