Polycarbonate lamination material with high sealing strength

Abstract

The invention discloses a polycarbonate lamination material with high sealing strength, and belongs to the technical field of polymer packaging materials. The material is prepared from the following components in parts by weight: 50 to 95 parts of PPCP, 5 to 50 parts of PBAT, 0 to 20 parts of PLA and 0.1 to 20 parts of a film spraying auxiliary agent. The number-average molecular weight of the PPCP is 5W to 40W, and the number-average molecular weight of the PBAT is 5W to 8W. According to the technical scheme of the invention, PBAT and PPCP are taken as basic compositions, and the spraying film material with excellent comprehensive performance is formed by combining the synergistic effect of the functional auxiliary agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer packaging materials, and particularly relates to a polycarbonate coated film material with high sealing strength. Background Art

[0002] With the enhancement of environmental awareness and the increasing demand for biodegradable materials, coated film materials are increasingly widely used in fields such as packaging and sanitary products. As a common biodegradable plastic, PBAT (polybutylene adipate terephthalate) has become a research hotspot due to its good mechanical properties and processing performance. However, existing PBAT coated film materials still have deficiencies in aspects such as sealing strength, barrier performance, and bonding strength with the base paper layer, which limits their promotion in high-end application scenarios.

[0003] After retrieval, a preparation method and application of a composite material with PBAT coating were disclosed, with the publication number CN104999609B and the publication date of March 29, 2017. This patent prepares a composite material with excellent mechanical properties by mixing PBAT with other biodegradable plastics or ultrafine calcium carbonate and then performing coating. However, this technical solution mainly focuses on the mechanical properties and waterproof and oil-proof properties of the material, without fully considering the optimization of sealing strength and barrier performance. In addition, the bonding strength between PBAT and the base paper layer in this solution is limited, and there may be a peeling risk in actual use, affecting the overall performance of the product.

[0004] After retrieval, a fully biodegradable coated paper and its preparation method were disclosed, with the publication number CN111187494B and the publication date of April 1, 2022. This patent solves the problem of low heat distortion temperature of PBAT by using a biodegradable resin mainly composed of PBAT for coating and reduces the production cost. However, this technical solution is insufficient in terms of sealing strength, especially in high-temperature or high-humidity environments, where the seal is prone to failure. At the same time, there is still room for improvement in the bonding strength between the coating layer and the base paper layer in this solution, which may lead to delamination problems under complex stress conditions.

[0005] The above problems indicate that existing PBAT coated film materials still have certain limitations in aspects such as sealing strength, barrier performance, and bonding strength with the base paper layer. Therefore, the present invention provides a polycarbonate coated film material with high sealing strength, aiming to use a composition of PBAT and polycarbonate materials as the coated film material to significantly improve the sealing strength, barrier performance, and bonding strength with the base paper layer, so as to meet the requirements of high-end packaging and functional material fields. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a polycarbonate film laminating material with good barrier performance, high bonding strength with the base paper layer, and high sealing strength.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a polycarbonate film laminating material with high sealing strength, characterized in that the composition weight parts of the material include: PPCP (ternary copolymer of propylene oxide, phthalic anhydride and carbon dioxide) 50 - 95 parts, PBAT 5 - 50 parts, PLA 0 - 20 parts, and film laminating auxiliary agent 0.1 - 20 parts.

[0008] The technical solution of the present invention is based on PBAT and PPCP as the basic composition, combined with the synergistic effect of functional auxiliary agents to form a film laminating material with excellent comprehensive performance.

[0009] Preferably, for the above polycarbonate film laminating material with high sealing strength, the number average molecular weight of the PPCP is 50,000 - 400,000, and the number average molecular weight of the PBAT is 50,000 - 80,000.

[0010] Selecting PPCP with a molecular weight range of 50,000 - 600,000 can ensure the formation of a dense and uniform film structure during the film laminating process. More preferably, the number average molecular weight of the PPCP is 200,000 - 400,000, which can maintain stable melt fluidity during high-temperature film laminating (260 - 320 °C) and avoid the decline of mechanical properties caused by molecular chain breakage. When the molecular weight of PBAT is in the range of 80,000 - 100,000, the ductility and rigidity of its molecular chain reach the best balance. More preferably, the number average molecular weight of the PBAT is 55,000 - 65,000, which can significantly improve the tensile strength and elongation at break of the material through the entanglement of molecular chains, thereby enhancing the anti-tearing performance at the sealing part.

[0011] Preferably, for the above polycarbonate film laminating material with high sealing strength, the molar percentage of the polypropylene carbonate (PC) repeating unit in the molecular chain of the PPCP is 60% - 95%, preferably 80% - 90%, and the molar percentage of the propylene oxide - phthalic anhydride copolymer (PA) repeating unit is 5% - 40%, preferably 10% - 20%, and the balance is the polyether segment (PO) of the self-polymerization of propylene oxide.

[0012] With the molecular structure of the PPCP of the present invention, it has excellent tensile strength, thereby enhancing the anti-tearing performance at the sealing part. The ester groups of the appropriate amount of PA chain segments can form hydrogen bonds or chemical bonds with the carboxyl groups of PBAT, enhancing the bonding strength with the paper-based fibers (peel strength ≥ 3.5 N / mm). The polyether segment of the self-polymerization of propylene oxide acts as a flexible chain segment, distributing between the rigid main chains to play a stress buffering role. The melt flow performance of this PPCP ensures the uniformity of the coating during the film laminating process.

[0013] Preferably, for the above polycarbonate film laminating material with high sealing strength, the weight parts composition of the film laminating aid includes: 0.1-7 parts of compatibilizer, 0-20 parts of plasticizer, 0-2 parts of coupling agent, 0-5 parts of antioxidant, 0-3 parts of ultraviolet stabilizer, 0-5 parts of hydrolysis resistant agent, and 0-20 parts of filler.

[0014] Preferably, among the above film laminating aids, the compatibilizer is at least one of glycidyl methacrylate, ethylene-acrylate-glycidyl methacrylate, and maleic anhydride grafted PBAT (PBAT-g-MAH).

[0015] More preferably, the compatibilizer is maleic anhydride grafted PBAT, and the grafting rate of maleic anhydride grafted PBAT is 0.8%-1.5%. Introducing maleic anhydride grafted PBAT as a compatibilizer into the PBAT / PPCP system can better improve the compatibility of the two-phase interface. Maleic anhydride grafted PBAT can form a stable network structure with the PBAT / PPCP matrix through chemical bonding.

[0016] When the grafting rate is 0.8%-1.5%, PBAT-g-MAH promotes the formation of a more uniform dispersed phase of PBAT and PPCP during melt blending through the physical adsorption of polar groups. Experiments show that when the grafting rate ≥0.8%, the dispersed phase size decreases from the micron level (>5μm) to the submicron level (<1μm), which can reduce the stress concentration caused by interface defects. PBAT-g-MAH with a grafting rate of 0.8%-1.5% can not only maintain the flexibility of PBAT but also improve the overall tensile strength (≥33 MPa) through the strengthening effect of the rigid PPCP chain segments. The PBAT-g-MAH with a preferred grafting rate raises the initial thermal degradation temperature of the PPCP / PBAT system to above 240°C, enabling it to adapt to higher film laminating processing temperatures. When the grafting rate is too low (<0.8%), the insufficient anhydride groups result in weak interfacial binding force; when it is too high (>1.5%), it causes cross-linking of the PBAT molecular chains, increasing the melt viscosity and reducing the processing efficiency (the melt index decreases). The grafting rate of 0.8%-1.5% can maintain the melt fluidity of the material by balancing the ratio of polar and flexible chain segments.

[0017] Preferably, among the above film laminating aids, the compatibilizer is an isocyanate compatibilizer, including at least one of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (HMDI), and diphenylmethane diisocyanate (MDI).

[0018] The isocyanate compatibilizer reacts with the hydroxyl or carboxyl groups of the PBAT / PPCP molecular chains through isocyanate groups to form a cross-linked structure, improving the tensile strength and elongation at break of the coated film material. More preferably, the compatibilizer is a composite compatibilizer of maleic anhydride grafted PBAT and an isocyanate compatibilizer.

[0019] Preferably, among the above-mentioned coating film additives, the plasticizer includes a main plasticizer and an auxiliary plasticizer. The main plasticizer is epoxidized soybean oil, and the auxiliary plasticizer is glycerol or tributyl citrate.

[0020] The main plasticizer is epoxidized soybean oil, and its epoxy groups undergo a coupling reaction with the surface of the filler, further enhancing the interfacial bonding force. Its flexibility and processing fluidity are significantly improved. The auxiliary plasticizer is glycerol or tributyl citrate, which can reduce the melt viscosity, but the dosage needs to be controlled to avoid excessive reduction of thermal stability. Preferably, the mass ratio of the main plasticizer to the auxiliary plasticizer in the plasticizer is 10:0.8 - 2.4.

[0021] Preferably, among the above-mentioned coating film additives, the coupling agent is a silane coupling agent. The silane coupling agent (such as KH550) is used for surface treatment of each material, improving the wettability of the additive with the PBAT / PPCP matrix through chemical bonding and reducing the agglomeration phenomenon.

[0022] Preferably, among the above-mentioned coating film additives, the antioxidant is 1010 or 168, and the ultraviolet stabilizer is a benzotriazole ultraviolet stabilizer. UV-531, UV-326, UV-384. The antioxidant is a compound of 1010 and 168 with a mass ratio of 1:1 - 2. These additives delay the aging process of the material and extend the service life by capturing free radicals and absorbing ultraviolet light.

[0023] In terms of process parameters, the melt blending temperature is controlled at 150°C - 180°C, the coating film temperature is controlled at 260°C - 320°C, and the speed is controlled at 50 m / min - 80 m / min. The above process conditions ensure uniform dispersion of the additives and form a firm bond between the coating and the substrate.

[0024] Compared with the prior art, a polycarbonate laminated film material with high sealing strength of the present invention has the following beneficial effects: Through the above technical means, the present invention has comprehensively improved the sealing strength, barrier performance and bonding force with the paper substrate. Specifically, the synergistic effect of maleic anhydride grafted PBAT and MDI chain extender significantly enhances the interfacial bonding force between PBAT and PPCP, enabling the material to maintain excellent sealing performance even in high-temperature or high-humidity environments. The lamellar structure of nano-calcium carbonate prolongs the penetration path of gas and water vapor, thus significantly improving the barrier performance of the material. The introduction of PVA / borax composite coating further reduces the oxygen transmission rate, making it suitable for application scenarios with high requirements for barrier performance.

[0025] Through scientific and reasonable component ratio and process optimization, the present invention provides a polycarbonate laminated film material with high sealing strength, excellent barrier performance and strong bonding with the substrate, which can meet the requirements of the high-end packaging and functional material fields.

[0026] In practical applications, such as in the high-end food packaging field, this laminated film material can significantly improve the sealing strength and barrier performance, ensuring that the packaged contents still maintain good sealing and quality preservation effects in high-temperature or high-humidity environments. At the same time, the firm bonding with the paper substrate avoids the risk of peeling and meets the usage requirements under complex stress conditions. Specific embodiments

[0027] The present invention will be specifically described below through examples. Unless otherwise specified, all raw materials are commercially available.

[0028] The present invention provides a polycarbonate laminated film material with high sealing strength, and its structural design and preparation process are both centered around improving the sealing performance, barrier performance and bonding force with the paper substrate.

[0029] PBAT / PPCP is the basic component of this material, which is composed of PBAT and PPCP mixed in a weight ratio of 20-35 / 65-80. In actual operation, first, PBAT and PPCP are respectively dried to a moisture content of less than 0.05% to avoid hydrolysis reactions during processing that affect the material properties. Subsequently, the two are placed in a high-speed mixer and premixed at 70°C to 90°C for 5 to 10 minutes to preliminarily and uniformly disperse the two polymers to obtain the substrate. At this time, the proportionate amount of maleic anhydride grafted PBAT is added, and its addition amount is 5% to 7% of the total weight. As a compatibilizer, maleic anhydride grafted PBAT can improve the interfacial compatibility between PBAT and PPCP through chemical bonding, thus forming a stable two-phase system. During the subsequent melt blending process, maleic anhydride grafted PBAT is preferentially distributed at the interface between PBAT and PPCP.

[0030] A certain amount of MDI chain extender is further introduced into the PBAT / PPCP substrate. During the melt blending process, the MDI chain extender reacts with the active end groups in PBAT and PPCP to form crosslinks. This crosslinked structure not only enhances the interfacial bonding force between PBAT and PPCP but also improves the overall mechanical properties of the substrate. In the actual preparation process, the MDI chain extender needs to be added in the final stage of melt blending to avoid uneven molecular weight distribution caused by premature reaction. Through dynamic rheological tests, it is found that the occurrence of crosslinking significantly increases the storage modulus and loss modulus of the material, improving its deformation ability under high-temperature conditions.

[0031] Epoxidized soybean oil is added to the substrate as the main plasticizer. The epoxy groups in epoxidized soybean oil can undergo chemical bonding with hydroxyl groups and form hydrogen bonds with polar groups in PBAT and PPCP, thus enhancing the interfacial bonding force. In the actual preparation process, epoxidized soybean oil needs to be added in the initial stage of melt blending to ensure its full dispersion in the substrate.

[0032] The addition amounts of the antioxidant and the ultraviolet stabilizer are 0.5 - 1% of the total weight respectively. The antioxidant selects the compound system of 1010 and 168, and the weight ratio of 1010 to 168 is 1:1 - 2. The ultraviolet stabilizer preferably selects UV-531, whose molecular structure contains a benzotriazole group and can effectively absorb ultraviolet light energy. In actual operation, the antioxidant and the ultraviolet stabilizer need to be added in the final stage of melt blending to avoid performance degradation due to high-temperature degradation. Through accelerated aging experiments, it is found that the synergistic effect of the antioxidant and the ultraviolet stabilizer significantly delays the aging process of the material, extending its service life in the natural environment to more than 5 years.

[0033] The process parameters of the whole preparation process are optimized to ensure uniform dispersion of the additives and the bonding strength of the coating. The melt blending temperature is controlled within the range of 150°C - 180°C (preferably 165°C), and the specific temperature is adjusted according to the thermal stability of the material. The casting temperature is set at 260°C - 320°C (preferably 295°C), and the casting speed is 50 m / min - 80 m / min (preferably 65 m / min). In actual production, a twin-screw extruder is used for melt blending, and the screw speed is controlled within the range of 200 rpm - 300 rpm (250 rpm) to ensure sufficient mixing of the materials. The casting equipment preferably uses a multi-roll calender, and the gap between each roll can be adjusted according to the coating thickness requirements. Through strict control of the above process parameters, the finally prepared casting material has excellent sealing performance, barrier performance, and bonding force with the paper substrate, and is suitable for the fields of high-end packaging and functional materials.

[0034] To enable relevant personnel in the technical field to better understand and implement the present invention, the present invention will be further described below in conjunction with specific embodiments. The processing process is the same as the above preferred process parameters, and the material formula is shown in the embodiments. For the convenience of comparing the properties of the main materials, some functional auxiliary materials are not reflected in the embodiments.

[0035] Example 1

[0036] Prepare materials by weight: 70 parts of PPCP, 30 parts of PBAT, 4 parts of maleic anhydride grafted PBAT, 1.5 parts of MDI, 4.5 parts of plasticizer, 1.0 part of KH550, 2 parts of antioxidant, and 2 parts of UV-531.

[0037] Among them, the number average molecular weight of PPCP is 180,000, and the number average molecular weight of PBAT is 60,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 83%, the molar percentage of PA repeating units is 12%, and the balance is PO; the grafting rate of maleic anhydride grafted PBAT is 1.1%, the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0038] Example 2

[0039] Prepare materials by weight: 70 parts of PPCP, 30 parts of PBAT, 4 parts of maleic anhydride grafted PBAT, 1.5 parts of MDI, 4.5 parts of plasticizer, 1.0 part of KH550, 2 parts of antioxidant, and 2 parts of UV-531.

[0040] Among them, the number average molecular weight of PPCP is 180,000, and the number average molecular weight of PBAT is 60,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 83%, the molar percentage of PA repeating units is 12%, and the balance is PO; the grafting rate of maleic anhydride grafted PBAT is 3%, the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and tributyl citrate at a mass ratio of 10:1.5, and the antioxidant is a compound of 1010 and 168 at a mass ratio of 1:1.2.

[0041] Example 3

[0042] Prepare materials by weight: 70 parts of PPCP, 30 parts of PBAT, 4 parts of glycidyl methacrylate, 1.5 parts of MDI, 4.5 parts of plasticizer, 1.0 part of KH550, 2 parts of antioxidant, and 2 parts of UV-531.

[0043] Among them, the number-average molecular weight of PPCP is 180,000, and the number-average molecular weight of PBAT is 60,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 83%, the molar percentage of PA repeating units is 12%, and the balance is PO; the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and tributyl citrate in a mass ratio of 10:1.5, and the antioxidant is a compound prepared by compounding 1010 and 168 in a mass ratio of 1:1.2.

[0044] Example 4

[0045] Prepare materials by weight: 70 parts of PPCP, 30 parts of PBAT, 4 parts of maleic anhydride grafted PBAT, 1.5 parts of MDI, 4.5 parts of plasticizer, 1.0 part of KH550, 2 parts of antioxidant, and 2 parts of UV-531.

[0046] Among them, the number-average molecular weight of PPCP is 180,000, and the number-average molecular weight of PBAT is 60,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 64%, the molar percentage of PA repeating units is 32%, and the balance is PO; the grafting rate of maleic anhydride grafted PBAT is 1.1%, the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and tributyl citrate in a mass ratio of 10:1.5, and the antioxidant is a compound prepared by compounding 1010 and 168 in a mass ratio of 1:1.

[0047] Example 5

[0048] Prepare materials by weight: 50 parts of PPCP, 20 parts of PBAT, 2 parts of maleic anhydride grafted PBAT, 0.5 part of MDI, 2 parts of plasticizer, 0.5 part of KH550.

[0049] Among them, the number-average molecular weight of PPCP is 600,000, and the number-average molecular weight of PBAT is 50,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 79.5%, the molar percentage of PA repeating units is 19.6%, and the balance is PO; the grafting rate of maleic anhydride grafted PBAT is 0.8%, and the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and glycerol or tributyl citrate in a mass ratio of 10:0.8.

[0050] Example 6

[0051] Prepare materials by weight: 80 parts of PPCP, 5 parts of PBAT, 7 parts of ethylene-acrylate-glycidyl methacrylate, 3 parts of HDI.

[0052] Among them, the number-average molecular weight of PPCP is 50,000, and the number-average molecular weight of PBAT is 80,000; the molar percentage of PC repeating units in the molecular chain of PPCP is 89.6%, the molar percentage of PA repeating units is 9.8%, and the balance is PO; the plasticizer is a plasticizer prepared by compounding epoxidized soybean oil and tributyl citrate at a mass ratio of 10:2.4.

[0053] Performance tests were carried out on the coating materials of each example, and the test results are shown in Table 1.

[0054] Table 1 Performance test results

[0055] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Sealing strength N / mm 3.5 3.1 3.2 3.0 3.2 2.7 Oxygen transmission rate cc / m²·day·atm 19.1 21.4 21.6 17.8 22.6 17.6 Peeling strength N / mm 3.7 3.2 3.1 3.1 3.5 2.9 Retention rate of damp heat aging % 89 84 81 89 81 78 Tensile strength MPa 34 33 32 42 30 31 Elongation at break % 435 387 376 298 452 274

[0056] Comparative Example 1

[0057] The formulation, blending, and coating processes are the same as those in Example 1, except that an equal mass of PBAT is used instead of PPCP.

[0058] Performance comparison:

[0059] The sealing strength (ASTM F88) is only 1.8 N / mm, which is lower than 3.5 N / mm in Example 1 of the present invention;

[0060] The oxygen transmission rate (ASTM D3985) reaches 125 cc / m²·day·atm;

[0061] The peel strength from the base paper (GB / T 2790) is only 1.2 N / mm, and obvious delamination appears at the interface.

[0062] Comparative Example 2

[0063] The formulation, blending, and coating processes are the same as those in Example 1, except that an equal mass of PBAT is used instead of maleic anhydride-grafted PBAT.

[0064] Performance defects:

[0065] The melt flow index (230°C / 2.16 kg) drops to 5 g / 10 min (it is 9 g / 10 min in Example 1);

[0066] The interfacial compatibility is poor, and DSC testing shows that the separation degree of the melting peaks of PBAT and PPCP increases by 35%;

[0067] The retention rate after damp heat aging is 58% (85°C / 85%RH, 500 h).

[0068] Comparative Example 3

[0069] The formulation, blending, and coating processes are the same as those in Example 1, except that PPCP with a number-average molecular weight of 800,000 and PBAT with a number-average molecular weight of 150,000 are used.

[0070] Processing problems:

[0071] The melt blending temperature needs to be increased to above 200 °C, causing thermal degradation of PPCP (TGA shows a 30 °C premature weight loss);

[0072] Sharkskin defects appear during the film coating process, and the surface roughness (Ra) reaches 1.2 μm (0.4 μm in Example 1);

[0073] Melt fracture results in a ±15% fluctuation in the film coating thickness (controlled within ±5% in the examples).

[0074] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in any other form. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A polycarbonate film laminating material with high sealing strength, characterized in that: The composition of the material by weight parts includes: 50 - 95 parts of PPCP, 5 - 50 parts of PBAT, 0 - 20 parts of PLA, and 0.1 - 20 parts of film laminating aid.

2. The polycarbonate film laminating material with high sealing strength according to claim 1, wherein The number average molecular weight of the PPCP described is 50,000 - 400,000, and the number average molecular weight of the PBAT described is 50,000 - 80,000.

3. A polycarbonate film-laminated material with high sealing strength according to claim 1, characterized in that, The molar percentage of the polypropylene carbonate repeating unit in the molecular chain of the PPCP described is 60% - 95%, the molar percentage of the propylene oxide - phthalic anhydride copolymer repeating unit is 5% - 40%, and the balance is the polyether segment of the self - polymerization of propylene oxide.

4. A polycarbonate film laminating material with high sealing strength according to claim 1, characterized in that, The weight part composition of the film laminating aid described includes: 0.1 - 7 parts of compatibilizer, 0 - 20 parts of plasticizer, 0 - 2 parts of coupling agent, 0 - 5 parts of antioxidant, 0 - 3 parts of ultraviolet stabilizer, 0 - 5 parts of hydrolysis inhibitor, and 0 - 20 parts of filler.

5. A polycarbonate film laminating material with high sealing strength according to claim 4, characterized in that, The compatibilizer is at least one of glycidyl methacrylate, ethylene - acrylate - glycidyl methacrylate, maleic anhydride grafted PBAT, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane - 4,4'-diisocyanate, and diphenylmethane diisocyanate.

6. A polycarbonate coated material with high sealing strength according to claim 4, characterized in that, The plasticizer includes a primary plasticizer and a secondary plasticizer. The primary plasticizer is epoxidized soybean oil, and the secondary plasticizer is glycerol or tributyl citrate.

7. A polycarbonate coating material with high sealing strength according to claim 4, characterized in that, The coupling agent is a silane coupling agent.

8. A polycarbonate laminating material with high sealing strength according to claim 4, characterized in that, The antioxidant is 1010 or 168, and the ultraviolet stabilizer is a benzotriazole - type ultraviolet absorber.