A weather-resistant high-branched polyolefin protective film and a preparation process thereof

Abstract

The application provides a weather-resistant high-branched polyolefin protective film and a preparation process thereof, and relates to the technical field of surface protection materials, and comprises a tack control layer, a core layer and a weather-resistant surface layer, wherein the tack control layer, the core layer and the weather-resistant surface layer each contain a high-branched polyolefin resin; the high-branched polyolefin resin is a polymer formed by ethylene and propylene and C4-C10 alpha-olefin or a reaction-extrusion long-chain branched modified product thereof; and the total branching degree of the high-branched polyolefin resin is 10-30 per 1000 carbon atoms according to 13C-NMR. Since the high-branched polyolefin resin reduces the crystallization regularity and improves the melt strength, the protective film is more easily obtained in the processes of film blowing and casting, and the film roll is of uniform thickness, few fish eyes and good interlayer flow matching, and the problems that the existing polyolefin protective film is generally low in melt strength and has large thickness fluctuation amplitude while realizing high transparency and weather resistance are solved.

Description

Technical Field

[0001] This invention relates to the field of surface protection materials technology, and in particular to a weather-resistant highly branched polyolefin protective film and its preparation process. Background Technology

[0002] Existing polyolefin protective films mostly use LDPE, LLDPE, metallocene polyethylene, POE, or their compound systems with tackifying resins to achieve initial tack, transparency, or a certain level of mechanical strength, and are widely applicable to outdoor building panels, color-coated steel sheets, and other panels.

[0003] While existing polyolefin protective films achieve high transparency and weather resistance, they generally suffer from defects such as low melt strength, large fluctuations in blown film thickness, and rapid aging rate after long-term use. The polyolefin molecular structure in the protective film lacks long-chain branched structure, which leads to the deterioration of the resin melt processing rheological properties and increases the difficulty of molding and processing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a weather-resistant, highly branched polyolefin protective film and its preparation process. This addresses the common defects mentioned in the background art, such as low melt strength, large fluctuations in blown film thickness, and rapid aging rate after long-term use, while existing polyolefin protective films achieve high transparency and weather resistance. Furthermore, the lack of long-chain branched structures in the polyolefin molecular structure of the protective film leads to deterioration of the resin melt processing rheological properties and increased difficulty in molding and processing.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: This invention relates to a weather-resistant, highly branched polyolefin protective film, specifically comprising: a control layer, a core layer, and a weather-resistant surface layer. The control layer, core layer, and weather-resistant surface layer are distributed sequentially from the inside to the outside of the protected substrate surface, and each layer contains a highly branched polyolefin resin. The highly branched polyolefin resin is a polymer formed from ethylene and propylene with C4-C10 α-olefins, or a reaction-extruded long-chain branched modified product thereof. The highly branched polyolefin resin has a total branching degree of 10-30 branches per 1000 carbon atoms according to ^13C-NMR, a weight-average molecular weight of 8×10^4-3×10^5, and a gel content not exceeding 2.0%. The control layer comprises, by weight, 35-65 parts of highly branched polyolefin resin. The composition includes: 10-30 parts polyolefin elastomer and SEBS, 8-22 parts tackifying resin, 2-10 parts maleic anhydride-grafted polyolefin, and 0.05-0.5 parts antioxidant; the core layer comprises, by weight: 45-85 parts highly branched polyolefin resin, 10-35 parts linear polyolefin, 2-10 parts compatibilizer, and 0-8 parts inorganic filler; the weather-resistant surface layer comprises, by weight: 55-85 parts highly branched polyolefin resin, 5-20 parts polypropylene and cyclic olefin copolymer, 0.2-1.2 parts ultraviolet absorber, 0.1-0.8 parts hindered amine light stabilizer, 0.1-3.0 parts surface-treated nano-cerium oxide and rutile titanium dioxide, 0.05-0.5 parts antioxidant, and 0.05-0.8 parts polysiloxane.

[0006] Furthermore, the total thickness of the protective film is 40-150 μm, and the thickness ratio of the control layer, core layer and weather-resistant surface layer is 10-25:30-80:5-20; the density of the highly branched polyolefin is 0.880-0.915 g / cm³, and the melt mass flow rate is 0.5-8.0 g / 10 min.

[0007] Furthermore, the outer surface of the control layer has a micro-textured structure, and a release layer is provided on the outer side of the control layer; the tackifying resin is at least one of hydrogenated C5 resin, hydrogenated C9 resin, and hydrogenated C5 / C9 copolymer resin, with a softening point of 85-130℃.

[0008] Furthermore, the linear polyolefin is selected from one or two of metallocene linear low-density polyethylene, random polypropylene, and polyolefin elastomers; the compatibilizer is one or more of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, or ethylene-acrylate grafts.

[0009] Furthermore, the ultraviolet absorber is selected from one or two of benzotriazole and triazine ultraviolet absorbers; the hindered amine light stabilizer is a polymeric or low-volatility hindered amine light stabilizer; the surface-treated nano-cerium oxide and rutile titanium dioxide have an average particle size of 10-80 nm and are surface modified using silane, fatty acid salt or polyolefin grafting agent.

[0010] Furthermore, a surface modification layer is provided on the outer side of the weather-resistant surface layer; the surface modification layer is a siloxane hybrid curing layer with a dry film thickness of 0.05-0.8 μm; the siloxane hybrid curing layer is formed by curing a sol system containing 3-glycidoxypropyltrimethoxysilane and tetraethyl orthosilicate.

[0011] Furthermore, a preparation process for a weather-resistant, highly branched polyolefin protective film includes the following steps: Step 1: Prepare highly branched polyolefin resin; Step 2: The control layer, core layer and weather-resistant surface layer are respectively mixed with highly branched polyolefin resin according to their respective formulas and melted, and then granulated by twin-screw extrusion to obtain masterbatches for each layer; Step 3: A three-layer co-extrusion blown film method is used to form a composite film of the control layer, core layer and weather-resistant surface layer. The melt temperature during film formation is 165-230℃ and the die temperature is 180-235℃. Step 4: Perform corona treatment or plasma treatment on the outer surface of the membrane to achieve a surface tension of 38-46 dyn / cm. Step 5: Apply siloxane hybrid hardening liquid to the outer surface of the weather-resistant surface layer, and heat-cur it at 80-140℃ for 30-300s or under UV conditions to form a surface modification layer. Step six involves sequentially ripening, slitting, and rewinding the prepared protective film.

[0012] Furthermore, the highly branched polyolefin resin in step one is obtained by insertion polymerization of ethylene and propylene with one or more of 1-butene, 1-hexene, and 1-octene, with a polymerization temperature of 40-90℃ and a total pressure of 0.5-3.0MPa.

[0013] Furthermore, during the co-extrusion blown film formation in step three, the extrusion swell ratio is 2.2-3.5, the traction speed is 12-40 m / min, and the cooling air ring temperature is 10-25℃.

[0014] Furthermore, the protective film in step six is ​​cured at 40-70℃ for 24-72 hours before slitting, and the surface modified layer reaches grade 0-1 after curing through a cross-cut test.

[0015] The present invention has the following beneficial effects: Since the highly branched polyolefin resin reduces the crystal regularity and increases the melt strength, the protective film is easier to obtain film rolls with uniform thickness, fewer fisheyes and good interlayer flow matching during blown film and casting processes, and the molding and processing difficulty is reduced. Therefore, it can maintain more stable optical performance and significantly improve weather resistance without increasing the thickness.

[0016] In addition, the addition of the surface modification layer significantly improves the surface hardness, scrub resistance and fingerprint resistance of the highly branched polyolefin protective film, and reduces surface abrasion caused by friction during outdoor construction and board handling. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0018] The accompanying drawings described below are only related to some embodiments of the invention and are not intended to limit the invention.

[0019] In the attached diagram: Figure 1 A schematic diagram of the layer structure of the highly branched polyolefin protective film of the present invention is shown; Figure 2 A schematic diagram of the preparation process of the highly branched polyolefin protective film of the present invention is shown; Figure 3 A causal correspondence diagram is shown between the distinguishing features of the present invention and the target technical effect; List of reference numerals 1. Control layer; 2. Core layer; 3. Weather-resistant surface layer; 4. Release layer; 5. Surface modification layer. Detailed Implementation

[0020] Please refer to Figures 1 to 3 : Example 1: This invention proposes a weather-resistant highly branched polyolefin protective film and its preparation process, comprising: a control layer 1, a core layer 2, and a weather-resistant surface layer 3. The control layer 1, core layer 2, and weather-resistant surface layer 3 are distributed sequentially from the inside to the outside of the protected substrate surface, and each of the control layer 1, core layer 2, and weather-resistant surface layer 3 contains highly branched polyolefin resin. The highly branched polyolefin resin is a polymer formed by ethylene and propylene with C4-C10 α-olefins or a reaction-extruded long-chain branched modified product thereof. The highly branched polyolefin resin has a total branching degree of 10-30 branches / 1000 carbon atoms according to ^13C-NMR, a weight-average molecular weight of 8×10^4-3×10^5, and a gel content of not more than 2.0%. The control layer 1 comprises, by weight, highly branched polyolefin resin. The core layer 2, by weight, comprises: 35-65 parts of highly branched polyolefin resin, 10-30 parts of polyolefin elastomer and SEBS, 8-22 parts of tackifying resin, 2-10 parts of maleic anhydride grafted polyolefin, and 0.05-0.5 parts of antioxidant; the weather-resistant surface layer 3, by weight, comprises: 45-85 parts of highly branched polyolefin resin, 10-35 parts of linear polyolefin, 2-10 parts of compatibilizer, and 0-8 parts of inorganic filler; the weather-resistant surface layer 3, by weight, comprises: 55-85 parts of highly branched polyolefin resin, 5-20 parts of polypropylene and cyclic olefin copolymer, 0.2-1.2 parts of UV absorber, 0.1-0.8 parts of hindered amine light stabilizer, 0.1-3.0 parts of surface-treated nano-cerium oxide and rutile titanium dioxide, 0.05-0.5 parts of antioxidant, and 0.05-0.8 parts of polysiloxane. The total thickness of the protective film is 40-150 μm, and the thickness ratio of the control layer 1, core layer 2, and weather-resistant surface layer 3 is 10-25:30-80:5-20; the density of the highly branched polyolefin is 0.880-0.915 g / cm³, and the melt flow rate is 0.5-8.0 g / 10 min; the outer surface of the control layer 1 has a micro-textured structure, and a release layer 4 is provided on the outer side of the control layer 1; the tackifying resin is at least one of hydrogenated C5 resin, hydrogenated C9 resin, and hydrogenated C5 / C9 copolymer resin, with a softening point of 85-130℃; the linear polyolefin is selected from one or two of metallocene linear low-density polyethylene, random polypropylene, and polyolefin elastomer; the compatibilizer is maleic anhydride graft. One or more of the following: grafted polyethylene, maleic anhydride-grafted polypropylene, or ethylene-acrylate grafts; UV absorber selected from one or two of benzotriazole and triazine UV absorbers; hindered amine light stabilizer is a polymeric or low-volatility hindered amine light stabilizer; the average particle size of the surface-treated nano-cerium oxide and rutile titanium dioxide is 10-80 nm, and the surface is modified by silane, fatty acid salt, or polyolefin grafting agent; a surface modification layer 5 is provided on the outside of the weather-resistant surface layer 3; the surface modification layer 5 is a siloxane hybrid hardening layer with a dry film thickness of 0.05-0.8 μm; the siloxane hybrid hardening layer is formed by curing a sol system containing 3-glycidoxypropyltrimethoxysilane and tetraethyl orthosilicate; A process for preparing a weather-resistant, highly branched polyolefin protective film includes the following steps: Step 1: Prepare a highly branched polyolefin resin that meets the requirements for branching degree, molecular weight and gel content. The highly branched polyolefin resin is obtained by insertion polymerization of ethylene and propylene with one or more of 1-butene, 1-hexene and 1-octene. The polymerization temperature is 40-90℃ and the total pressure is 0.5-3.0MPa. Step 2: Mix highly branched polyolefin resin with the control layer 1, core layer 2 and weather-resistant surface layer 3 according to their respective formulas and melt them. Then, granulate them by twin-screw extrusion to obtain masterbatches for each layer. Step 3: A three-layer co-extrusion blown film method is used to form a composite film of control layer 1, core layer 2 and weather-resistant surface layer 3. During film formation, the melt temperature is 165-230℃, the die temperature is 180-235℃, the extrusion swell ratio is 2.2-3.5, the traction speed is 12-40m / min, and the cooling air ring temperature is 10-25℃. Step 4: Perform corona treatment or plasma treatment on the outer surface of the membrane to achieve a surface tension of 38-46 dyn / cm. Step 5: Apply siloxane hybrid hardening liquid to the outer surface of weather-resistant surface layer 3, and heat-cur it at 80-140℃ for 30-300s or under UV conditions to form surface modification layer 5; Step 6: The prepared protective film is successively cured, slit and rewound. Before slitting, the protective film is cured at 40-70℃ for 24-72 hours, and the surface modification layer 5 reaches level 0-1 after curing through a cross-cut test.

[0021] Example 2: Application of highly branched polyolefin protective film as a transparent protective film on outdoor architectural color-coated aluminum panels. First, 2.0 liters of deoxygenated n-hexane were added to a 5-liter high-pressure reactor. The temperature was raised to 55°C and stirred at a rate of 500 rpm. α-Diimide nickel catalyst and modified methylaluminoxane co-catalyst were added sequentially. The molar ratio of ethylene, 1-octene, and propylene was controlled at 88:8:4. The total system pressure was 1.2 MPa, and the reaction time was 90 minutes. After the reaction, the mixture was quenched with a 2% hydrochloric acid methanol solution. After washing and filtration, the mixture was vacuum dried at 55°C for 12 hours to obtain highly branched polyolefin resin. The total weight is 652 grams. The highly branched polyolefin resin contains 18 branches per thousand carbon atoms, with a weight-average molecular weight of 1.62 × 10^5, a density of 0.892 g / cm³, and a gel content of 0.4%. The raw materials for the control layer 1, core layer 2, and weather-resistant surface layer 3 are formulated according to the following weight parts: Control layer 1 consists of 48 parts highly branched polyolefin resin, 18 parts polyolefin elastomer, 8 parts styrene-ethylene-butene-styrene block copolymer, 16 parts hydrogenated C5 petroleum resin, 8 parts maleic anhydride-grafted polyethylene, 0.20 parts antioxidant 1010, and 0.20 parts benzotriazole UV absorber 326. Core layer 2 consists of 64 parts highly branched polyolefin resin... The weather-resistant surface layer 3 consists of branched polyolefin resin, 20 parts metallocene linear low-density polyethylene, 8 parts polyolefin elastomer, 5 parts maleic anhydride grafted polyethylene, 2 parts nano-silica, 0.20 parts antioxidant 1010, and 0.20 parts antioxidant 168. It is composed of 70 parts highly branched polyolefin resin, 15 parts atactic polypropylene, 0.60 parts benzotriazole UV absorber 326, 0.35 parts polymerizable hindered amine light stabilizer 944, 0.80 parts surface-treated cerium dioxide-titanium dioxide composite powder, 0.20 parts antioxidant 1010, 0.20 parts antioxidant 168, 0.25 parts polysiloxane, and 0.80 parts... The film is composed of an anti-sticking agent and is produced using a co-extrusion blown film process. The die temperature is 210℃, the expansion ratio is 2.8, the traction speed is 18 m / min, and the total film thickness is controlled at 80±4 micrometers. The thickness ratio of the three layers is 12:56:12. After the film is formed, the weather-resistant surface layer 3 is corona treated, and then coated with a mixed curing liquid of 3-glycidyl etheroxypropyltrimethoxysilane and tetraethyl orthosilicate by gravure coating process. After curing, a surface modification layer 5 with a thickness of about 0.28 micrometers is formed. The film has excellent comprehensive performance before and after aging, with no adhesive residue on the surface, a cross-cut grade of 0, and a small decrease in abrasion resistance and washability.

[0022] Example 3: Application of highly branched polyolefin protective film as a temporary protective film for transparent photovoltaic backsheets. Highly branched polyolefin resin was prepared using a reactive extrusion long-chain branching process. Random polypropylene and ethylene-octene elastomer were used as the base raw materials. Based on 100 parts of the base raw materials, 0.35 parts of vinyltrimethoxysilane, 0.08 parts of dicumyl peroxide, 0.12 parts of trimethylolpropane triacrylate, and 0.20 parts of antioxidant were added. The reactive extrusion process was carried out in a twin-screw extruder at a screw speed of 260 rpm, maintaining a system vacuum of -0.08 MPa. The final product was highly branched polyolefin granules. This resin contained 11 branches per thousand carbon atoms, had a weight-average molecular weight of 1.08 × 10^5, a melt flow rate of 3.6 g / 10 min, and a gel content of 0.6%. The raw materials for each layer—control layer 1, core layer 2, and weather-resistant surface layer 3—are formulated according to their respective weight proportions. Control layer 1 consists of 52 parts highly branched polyolefin resin, 22 parts polyolefin elastomer, 14 parts hydrogenated C5 / C9 copolymer resin, 8 parts maleic anhydride-grafted polypropylene, 0.20 parts antioxidant 1010, and 0.15 parts benzotriazole UV absorber 326. Core layer 2 consists of 60 parts highly branched polyolefin resin, 22 parts metallocene linear low-density polyethylene, 10 parts cyclic olefin copolymer, 6 parts maleic anhydride-grafted polypropylene, 0.20 parts antioxidant 1010, and 0.20 parts antioxidant 168. Weather-resistant surface layer 3 consists of 68 parts highly branched polyolefin resin, 12 parts cyclic olefin copolymer, 0.75 parts triazine UV absorber 1577, and 0.40 parts hindered polymerization amine. The film is composed of light stabilizer 944, 0.60 parts surface-treated nano-cerium dioxide, 0.20 parts antioxidant 1010, 0.20 parts antioxidant 168, and 0.30 parts polysiloxane. Film formation was performed using a casting machine with a melt temperature range of 185-225℃, a T-die temperature of 228℃, a cooling roller temperature of 28℃, a draw ratio of 3.2, and a total film thickness of 65±3 micrometers. The three-layer thickness ratio was 10:45:10. After plasma treatment to a surface tension of 44 dynes / cm, a siloxane curing liquid was applied to form a surface-modified layer with a dry film thickness of approximately 0.12 micrometers. After 1500 hours of xenon lamp aging and high-temperature and high-humidity environmental testing, the film maintained good mechanical and optical properties, low yellowing, stable peel strength, and no residual adhesive on the surface.

[0023] Compared with Example 2, a common linear metallocene linear low-density polyethylene / low-density polyethylene / polyolefin elastomer system was used to replace the highly branched polyolefin, and the remaining formulation components and proportions were kept as consistent as possible with Example 2; Comparative Example 3: The highly branched polyolefin was retained, but the nano-cerium dioxide-titanium dioxide composite powder and polymeric hindered amine light stabilizer compound system were removed, and only conventional ultraviolet absorbers were added.

[0024] In summary, the weather-resistant highly branched polyolefin protective film of the present invention comprises, from the inside out, a control layer 1, a core layer 2, and a weather-resistant surface layer 3. A release layer 4 is provided on the outer side of the control layer 1, and a surface modification layer 5 is provided on the outer side of the weather-resistant surface layer 3. All three main structural layers contain highly branched polyolefin resin. The control layer 1 contains 35-65 parts of highly branched polyolefin resin, 10-30 parts of polyolefin elastomer and styrene-ethylene-butene-styrene block copolymer, 8-22 parts of hydrogenated C5 / C9 tackifying resin with a softening point of 85-130℃, 2-10 parts of maleic anhydride-grafted polyolefin, and 0.05-0.5 parts of antioxidant. The core layer 2 contains 45-85 parts of highly branched polyolefin resin, 10-35 parts of... The product consists of linear polyolefin, 2-10 parts compatibilizer and 0-8 parts inorganic filler; weather-resistant surface layer 3 contains 55-85 parts highly branched polyolefin resin, 5-20 parts polypropylene and cyclic olefin copolymer, 0.2-1.2 parts UV absorber, 0.1-0.8 parts polymeric or low-volatility hindered amine light stabilizer, 0.1-3.0 parts surface-modified nano-cerium dioxide and rutile titanium dioxide, 0.05-0.5 parts antioxidant and 0.05-0.8 parts polysiloxane; tack control layer 1 solves the adhesion and peel balance; core layer 2 solves mechanical strength and thickness uniformity; weather-resistant surface layer 3 solves UV, thermal oxygen and damp heat; and surface modification layer 5 solves wear resistance, scrub resistance and stain resistance.

Claims

1. A weather-resistant, highly branched polyolefin protective film, characterized in that, include: The control layer (1), core layer (2), and weather-resistant surface layer (3) are distributed sequentially from the inside to the outside of the protected substrate surface, and each of the control layer (1), core layer (2), and weather-resistant surface layer (3) contains highly branched polyolefin resin. The highly branched polyolefin resin is a polymer formed by ethylene and propylene with C4-C10 α-olefin. The highly branched polyolefin resin has a total branching degree of 10-30 branches per 1000 carbon atoms according to ^13C-NMR, a weight-average molecular weight of 8×10^4-3×10^5, and a gel content of not more than 2.0%. The control layer (1) includes, by weight: 35-65% highly branched polyolefin resin. The core layer (2) comprises, by weight: 45-85 parts of highly branched polyolefin resin, 10-35 parts of linear polyolefin, 2-10 parts of compatibilizer, and 0-8 parts of inorganic filler; the weather-resistant surface layer (3) comprises, by weight: 55-85 parts of highly branched polyolefin resin, 5-20 parts of polypropylene copolymer, 0.2-1.2 parts of ultraviolet absorber, 0.1-0.8 parts of hindered amine light stabilizer, 0.1-3.0 parts of surface-treated nano-cerium oxide, 0.05-0.5 parts of antioxidant, and 0.05-0.8 parts of polysiloxane.

2. The weather-resistant highly branched polyolefin protective film according to claim 1, characterized in that, The total thickness of the protective film is 40-150μm, and the thickness ratio of the control layer (1), the core layer (2) and the weather-resistant surface layer (3) is 10-25:30-80:5-20; the density of the highly branched polyolefin is 0.880-0.915g / cm³, and the melt mass flow rate is 0.5-8.0g / 10min.

3. The weather-resistant highly branched polyolefin protective film according to claim 2, characterized in that, The outer surface of the control layer (1) has a micro-textured structure, and a release layer (4) is provided on the outer side of the control layer (1); the tackifying resin is hydrogenated C5 resin with a softening point of 85-130℃.

4. The weather-resistant highly branched polyolefin protective film according to claim 3, characterized in that, The linear polyolefin is selected from metallocene linear low-density polyethylene; the compatibilizer is maleic anhydride-grafted polyethylene.

5. The weather-resistant, highly branched polyolefin protective film according to claim 4, characterized in that, The ultraviolet absorber is selected from benzotriazoles; the hindered amine light stabilizer is a polymeric hindered amine light stabilizer; the surface-treated nano-cerium oxide has an average particle size of 10-80 nm and is surface-modified using silanes and fatty acid salts.

6. The weather-resistant, highly branched polyolefin protective film according to claim 5, characterized in that, A surface modification layer (5) is provided on the outside of the weather-resistant surface layer (3); the surface modification layer (5) is a siloxane hybrid hardening layer with a dry film thickness of 0.05-0.8 μm; the siloxane hybrid hardening layer is formed by curing a sol system containing 3-glycidyl etheroxypropyltrimethoxysilane and tetraethyl orthosilicate.

7. A process for preparing a weather-resistant, highly branched polyolefin protective film according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Prepare highly branched polyolefin resin; Step 2: The control layer (1), core layer (2) and weather-resistant surface layer (3) are respectively mixed with highly branched polyolefin resin according to their respective formulas and melted, and then granulated by twin-screw extrusion to obtain masterbatches for each layer; Step 3: A three-layer co-extrusion blown film method is used to form a composite film of the control layer (1), core layer (2) and weather-resistant surface layer (3). The melt temperature during film formation is 165-230℃ and the die temperature is 180-235℃. Step 4: Perform corona treatment or plasma treatment on the outer surface of the membrane to achieve a surface tension of 38-46 dyn / cm. Step 5: Apply siloxane hybrid hardening liquid to the outer surface of the weather-resistant surface layer (3) and heat-cur it at 80-140℃ for 30-300s or under UV conditions to form a surface modification layer (5). Step six involves sequentially ripening, slitting, and rewinding the prepared protective film.

8. The preparation process of a weather-resistant highly branched polyolefin protective film according to claim 7, characterized in that, The highly branched polyolefin resin in step one is obtained by insertion polymerization of ethylene and propylene with 1-butene at a polymerization temperature of 40-90℃ and a total pressure of 0.5-3.0MPa.

9. The preparation process of a weather-resistant highly branched polyolefin protective film according to claim 7, characterized in that, When forming a film using the co-extrusion blown film method in step three, the extrusion swell ratio is 2.2-3.5, the traction speed is 12-40 m / min, and the cooling air ring temperature is 10-25℃.

10. The preparation process of a weather-resistant highly branched polyolefin protective film according to claim 7, characterized in that, The protective film in step six is ​​cured at 40-70℃ for 24-72h before slitting, and the surface modification layer (5) reaches level 0-1 after curing by cross-cutting test.

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