Anti-aging and anti-yellowing flame-retardant PVC transparent film and preparation method thereof

Abstract

The invention belongs to the technical field of PVC (polyvinyl chloride) transparent films, and particularly relates to an anti-aging, anti-yellowing and flame-retardant PVC transparent film and a preparation method thereof. The PVC transparent film is prepared from the flame retardant and the inorganic and organic anti-aging additives, so that high light transmittance can be kept while the flame retardant property is ensured; and organic and inorganic anti-aging fillers are quantitatively compounded and added to absorb ultraviolet rays in an ultraviolet band, so that serious yellowing of the PVC film caused by degradation and aging can be prevented, and the environmental protection performance meets the requirements of ROHS and REACH.

Description

Technical Field

[0001] This invention belongs to the field of PVC transparent film technology, specifically relating to an aging-resistant, yellowing-resistant, flame-retardant PVC transparent film and its preparation method. Background Technology

[0002] PVC film, due to its excellent transparency, flexibility, ease of processing, chemical resistance, and cost-effectiveness, is widely used in architectural interiors, vehicle interiors, electronic and electrical insulation layers, and high-end packaging. In architectural interiors, to create a high-end and comfortable indoor environment, the film's transparency requires high light transmittance to ensure visual clarity and realism. With fire safety being a major concern, vehicle and architectural interiors place stringent requirements on the flame retardancy of PVC films. The film must meet specific flame retardant standards to slow the spread of fire, reduce fire risk, and protect lives in the event of a fire. In high-end packaging and electronic and electrical insulation applications, the color stability of PVC over long-term use is crucial. The film must maintain color consistency and stability under prolonged exposure to light, temperature changes, and chemical contact, avoiding fading and discoloration to preserve the product's appearance quality and performance reliability.

[0003] Patent CN116790076A discloses a yellowing-resistant and antioxidant PVC film. By adding a self-made stabilizer, it combines the effects of a heat stabilizer, light stabilizer, and antioxidant, resulting in better yellowing resistance and weather resistance. However, this patent only innovates on the yellowing resistance of the product and does not study the yellowing resistance of multi-performance PVC films. Patent CN108912559A discloses a double 85 yellowing-resistant, low-odor, flame-retardant transparent material for optical cable protection sleeves. Through advanced formulation and excellent processing, it possesses good temperature resistance and yellowing resistance, and is environmentally friendly, meeting RoHS and REACH standards. However, its application scenario is optical cable protection, and the testing method used is the double 85 test method, the testing conditions of which are not applicable to the plastic film industry. Patent CN202510413148.6 addresses the flame retardancy, heat stability, and yellowing issues in an environmentally friendly flame-retardant PVC rear projection film, its preparation method, and its uses. However, the yellowing problem addressed in this patent is the yellowing that occurs during processing, not the aging yellowing under actual use conditions.

[0004] Therefore, how to further optimize the transparency, flame retardancy, and color stability of PVC film has become a key issue in meeting current market demands and promoting technological development in the industry. Summary of the Invention

[0005] To address the above problems, the purpose of this invention is to provide an aging-resistant, yellowing-resistant, flame-retardant PVC transparent film and its preparation method.

[0006] First, the present invention provides an aging-resistant, yellowing-resistant, flame-retardant PVC transparent film, which is made from the following raw materials by weight ratio: 75 parts of polyvinyl chloride resin, 17-35 parts of plasticizer, 3-5 parts of stabilizer, 0.2-0.5 parts of gelation accelerator, 16-30 parts of inorganic filler, 1-2 parts of organic ultraviolet absorber, 1-2 parts of ZnO, and 7-10 parts of liquid organic flame retardant.

[0007] Preferably, the plasticizer is selected from at least one of dioctyl terephthalate, diisodecyl terephthalate, and epoxidized soybean oil. More preferably, the plasticizer is dioctyl terephthalate and epoxidized soybean oil, and the amount of dioctyl terephthalate and epoxidized soybean oil used, calculated by weight ratio, is 15-30 parts and 2-5 parts, respectively.

[0008] Preferably, the PVC is SG-3 type PVC with a degree of polymerization of 1000.

[0009] Preferably, the stabilizer is a liquid barium-zinc stabilizer or a liquid calcium-zinc stabilizer.

[0010] Preferably, the gelation accelerator is an acrylate copolymer.

[0011] Preferably, the inorganic filler is composed of calcium powder and inorganic powder flame retardant, wherein the calcium powder is calcium carbonate and the inorganic powder flame retardant is aluminum hydroxide; the amounts of calcium powder and aluminum hydroxide are 3-5 parts and 13-25 parts by weight, respectively.

[0012] Preferably, the organic ultraviolet absorber is selected from at least one of triazine ultraviolet additives, cyanoacrylates, and oxaloylaniline ultraviolet additives.

[0013] Preferably, the liquid organic flame retardant is at least one of toluene diphenyl phosphate, bisphenol A bis(diphenyl) phosphate, diphenyl isooctyl phosphate, xylene phosphate, and tri(butoxyethyl) phosphate.

[0014] Secondly, the present invention provides a method for preparing the aforementioned aging-resistant, yellowing-resistant, flame-retardant PVC transparent film, comprising the following steps:

[0015] Step S1 Material Mixing: Weigh the raw materials according to the weight ratio, add them to a high-speed mixer and mix well, control the temperature at 90℃~110℃, and mix for 6min~10min; after mixing, put the raw materials into a low-speed mixer and mix to cool down to 80℃~100℃ to obtain the mixture.

[0016] Step S2 Plasticizer Preparation: The mixture obtained in step S1 is added to a planetary screw extruder for extrusion plasticization, and the extruder temperature is controlled at 180℃~200℃; it is then transferred to a two-roll mill for further plasticization, and the temperature of the two-roll mill is controlled at 190℃~220℃ to obtain the plasticizer.

[0017] Step S3: Preparation of filter material: The plasticized material obtained in step S2 is filtered through a filter press. The mesh size of the filter screen is selected as 80-120 mesh, and the material temperature is controlled at 170℃-200℃ to obtain the filter material.

[0018] Step S4 Preparation of calendered material: The filter material obtained in step S3 is added to a four-roll calender for calendering, and the temperature is controlled at 175℃~200℃ to obtain calendered material;

[0019] Step S5 Preparation of PVC transparent film: The calendered material obtained in step S4 is sequentially embossed, cold-cut, trimmed, and wound up to obtain the yellowing-resistant and flame-retardant PVC transparent film.

[0020] The technology of the present invention has the following beneficial effects:

[0021] The PVC transparent film of this invention does not use high-cost and environmentally unfriendly antimony trioxide flame retardants. Instead, it is prepared using flame retardants (inorganic and organic flame retardants) and inorganic and organic anti-aging additives. This ensures high light transmittance while maintaining flame retardant performance. The quantitative compounding of organic and inorganic anti-aging fillers absorbs ultraviolet light, preventing severe yellowing due to degradation and aging of the PVC film, and ensuring environmental performance meets RoHS and REACH requirements. Detailed Implementation

[0022] The technical concept, solution, and effects of the present invention are described in detail below through specific embodiments. These embodiments are merely illustrative examples and are not intended to limit the scope of protection of the present invention. In the following embodiments and comparative examples: liquid organic flame retardants: bisphenol A bis(diphenyl) phosphate, diphenyl isooctyl phosphate, and tris(butoxyethyl) phosphate were purchased from Zhejiang Wansheng Co., Ltd. and Shanghai Ruizhe Chemical Co., Ltd., respectively. Inorganic flame retardants: aluminum hydroxide and antimony trioxide are commercially available products. The aluminum hydroxide has a particle size of 1.3 μm to 2.3 μm and a refractive index of 1.57; the antimony trioxide has a particle size of 0.3 μm to 0.9 μm. The PVC is commercially available SG-3 type PVC with a degree of polymerization of 1000. Plasticizers dioctyl terephthalate (DOTP), dioctyl adipate, epoxidized soybean oil, and stabilizers (liquid barium-zinc stabilizer or liquid calcium-zinc stabilizer), gelation accelerators (specifically, acrylate copolymer PA-40), and calcium powder (calcium carbonate, average particle size 3000 mesh) are all commercially available products. Anti-aging additives: Organic UV additives (i.e., organic UV absorbers) are all commercially available products, purchased from Lianlong New Materials Co., Ltd. and Fujian Disheng Technology Co., Ltd.; inorganic UV additive ZnO was purchased from Shijiazhuang Dayuan Chemical Co., Ltd.

[0023] In the following embodiments and comparative examples, where the process parameters are given as range values, thin film preparation and the technical effects of the present invention can be achieved within the parameter fluctuation range. This is something that those skilled in the art can understand based on common knowledge. The parameter values ​​in parentheses after the range values ​​are merely exemplary parameter values ​​for specific embodiments / comparative examples (i.e., specific examples) and are not considered as limitations on the scope of protection.

[0024] The following comparative examples and embodiments describe the preparation methods of PVC transparent films:

[0025] (1) According to the different formulations of the examples and comparative examples, weigh the materials and put them into a high-speed mixer to mix them evenly. Control the temperature at 90℃~110℃ (100℃ in the specific example) and the mixing time at 6min~10min (8min in the specific example). After the mixing is completed, put the raw materials into a low-speed mixer to cool down to 80℃~100℃ (85℃ in the specific example) to obtain a mixture.

[0026] (2) The mixture obtained in step (1) is added to a planetary screw extruder for extrusion plasticization. The temperature of the extruder is controlled at 180℃~200℃ (190℃ in a specific example). The mixture is then transferred to a twin-roll mill for further plasticization. The temperature of the twin-roll mill is controlled at 190℃~220℃ (205℃ in a specific example) to obtain the plasticized material.

[0027] (3) The obtained plasticized material is filtered through a filter press with a mesh size of 80-120 (100 mesh in a specific example) and the material temperature is controlled at 170℃~200℃ (190℃ in a specific example) to obtain the filtered material;

[0028] (4) The filter material obtained in step (3) is fed into a four-roll calender for calendering and forming. The temperature is controlled at 175℃~200℃ (in a specific example, the temperature is controlled at 185℃) to obtain calendered material.

[0029] (5) The calendered material is embossed, cold-cut, trimmed and rolled in sequence to obtain the yellowing-resistant flame-retardant PVC transparent film.

[0030] Example 1: Ingredients (by weight) of yellowing-resistant, flame-retardant PVC transparent film

[0031] 75 parts PVC, 15 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid calcium-zinc stabilizer, 0.4 parts acrylate copolymer, 15 parts aluminum hydroxide, 1.5 parts UV-3039 (cyanoacrylate ultraviolet additive), 5 parts calcium powder, 2 parts zinc oxide, and 8 parts diphenyl isooctyl phosphate.

[0032] Example 2: Ingredients (by weight) of yellowing-resistant and flame-retardant PVC transparent film

[0033] 75 parts PVC, 17 parts DOTP, 4 parts epoxidized soybean oil, 3.2 parts liquid calcium-zinc stabilizer, 0.3 parts acrylate copolymer, 16 parts aluminum hydroxide, 1 part UV-1164 (triazine ultraviolet additive), 5 parts calcium powder, 1.2 parts zinc oxide, and 7.8 parts tri(butoxyethyl) phosphate.

[0034] Example 3: Ingredients (by weight) of yellowing-resistant and flame-retardant PVC transparent film

[0035] 75 parts PVC, 17 parts DOTP, 4 parts epoxidized soybean oil, 3.2 parts liquid calcium-zinc stabilizer, 0.3 parts acrylate copolymer, 16 parts aluminum hydroxide, 1 part UV-3039 (cyanoacrylate ultraviolet additive), 5 parts calcium powder, 1.3 parts zinc oxide, and 7.8 parts diphenyl isooctyl phosphate.

[0036] Example 4: Ingredients of yellowing-resistant and flame-retardant PVC transparent film (parts by weight)

[0037] 75 parts PVC, 15 parts DPHP, 2.4 parts epoxidized soybean oil, 3.7 parts liquid barium zinc stabilizer, 0.2 parts acrylate copolymer, 14.6 parts aluminum hydroxide, 1 part VSU P (oxaloyl aniline UV additive), 3.5 parts calcium powder, 2 parts zinc oxide, and 7.4 parts tri(butoxyethyl) phosphate.

[0038] Example 5: Ingredients (parts by weight) of yellowing-resistant, flame-retardant PVC transparent film

[0039] 75 parts PVC, 15 parts DPHP, 2.4 parts epoxidized soybean oil, 3.7 parts liquid barium zinc stabilizer, 0.2 parts acrylate copolymer, 14.6 parts aluminum hydroxide, 1 part UV-3039 (cyanoacrylate ultraviolet additive), 3.5 parts calcium powder, 1.8 parts zinc oxide, and 7.4 parts diphenyl isooctyl phosphate.

[0040] Example 6: Performance Testing of Yellowing-Resistant and Flame-Retardant PVC Transparent Film

[0041] During the screening and testing process, the following comparative examples of highly transparent PVC films were prepared using the same preparation method as in the examples:

[0042] Comparative Example 1: Ingredients of Yellowing-Resistant Flame-Retardant PVC Transparent Film (by weight)

[0043] 75 parts PVC, 25 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid calcium-zinc stabilizer, 6 parts antimony trioxide, 5 parts calcium powder, and 0.2 parts acrylate copolymer;

[0044] Comparative Example 2: Ingredients of yellowing-resistant and flame-retardant PVC transparent film (parts by weight)

[0045] 75 parts PVC, 25 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid calcium-zinc stabilizer, 5 parts calcium powder, 0.2 parts acrylate copolymer, and 7.5 parts diphenyl isooctyl phosphate.

[0046] Comparative Example 3: Ingredients of Yellowing-Resistant Flame-Retardant PVC Transparent Film (by weight)

[0047] 75 parts PVC, 16 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid calcium-zinc stabilizer, 0.2 parts acrylate copolymer, 5 parts calcium powder, 8 parts bisphenol A diphenyl phosphate, and 13 parts aluminum hydroxide.

[0048] Comparative Example 4: Ingredients of Yellowing-Resistant Flame-Retardant PVC Transparent Film (by weight)

[0049] 75 parts PVC, 23 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid barium zinc stabilizer, 0.2 parts acrylate copolymer, 5 parts calcium powder, 7.5 parts tri(butoxyethyl) phosphate, 13 parts aluminum hydroxide, 1.3 parts UV-3039 (cyanoacrylate ultraviolet additive), and 0.5 parts zinc oxide.

[0050] Comparative Example 5: Ingredients (parts by weight) of yellowing-resistant, flame-retardant PVC transparent film

[0051] 75 parts PVC, 16 parts DOTP, 3 parts epoxidized soybean oil, 4 parts liquid barium zinc stabilizer, 0.2 parts acrylate copolymer, 13 parts aluminum hydroxide, 5 parts calcium powder, 1.3 parts UV-3039 (cyanoacrylate ultraviolet additive), and 5 parts zinc oxide.

[0052] The PVC heads prepared in the examples and comparative examples were subjected to the following performance tests:

[0053] 1. Yellowing Resistance / Anti-aging Performance Test: Anti-aging tests were conducted on the comparative and example samples. The test standard followed ASTM G154 Cycle 1 procedure, using a CONICA MINOLTA CR-400 colorimeter to obtain the lab values ​​of color difference at 0H, 250H, 500H, 750H, and 1000H. Since the film samples were transparent, a white board was used as the background for the tests. The color difference value (ΔE) and yellowing value (Δb) were calculated using Formulas 1 and 2. Higher values ​​indicate more severe aging and yellowing.

[0054]

[0055] Δb = b2 - b1. Formula 2

[0056] The results are shown in Tables 1 and 2.

[0057] Table 1. Anti-aging test results of comparative samples

[0058]

[0059] Table 2. Anti-aging test results of the samples from the examples.

[0060]

[0061]

[0062] As shown in Tables 1 and 2, the addition of antimony trioxide (as in Comparative Example 1) and liquid flame retardants (as in Comparative Example 2, diphenyl isooctyl phosphate, and bisphenol A bis(diphenyl phosphate)) both lead to increased color difference and severe yellowing in the samples. Although Comparative Example 5 (1.3 parts of cyanoacrylate), which contains common organic UV additives, can partially reduce yellowing, its color difference and yellowing values ​​still differ significantly from those of the examples. Furthermore, Comparative Example 4, which includes both organic UV additives and the inorganic anti-aging additive zinc oxide, still fails to meet the anti-aging requirements.

[0063] Adding liquid flame retardants can maintain stable flame retardant performance, but their structure is a phosphate ester structure, with phosphorus atoms in a highly oxidized state. Under ultraviolet irradiation, changes in electron cloud distribution and chemical bonds are easily excited, leading to yellowing and promoting the formation of colored substances. Most liquid flame retardants contain functional groups prone to yellowing, such as unstable chlorine side chains, aromatic rings, and branched alkyl chlorides. Studies have found that a single ultraviolet absorber cannot guarantee efficient ultraviolet absorption because it does not efficiently absorb ultraviolet light. By using a composite anti-aging system to improve the yellowing resistance of materials, samples using organic and inorganic anti-aging additives to cover the sensitive wavelength bands and ultraviolet regions of PVC showed significant reductions in color difference and yellowing values ​​after anti-aging tests, with no obvious yellowing. In the composite anti-aging system, it is also necessary to control the filler content of the inorganic ultraviolet additive. The color difference and yellowing values ​​of Comparative Examples 4 and 5 were significantly lower than those of Comparative Examples 1, 2, and 3, which is consistent with the addition of an anti-aging system formulation (organic ultraviolet additive + inorganic anti-aging additive zinc oxide). The test results of Comparative Example 5 are similar to those of the Example Samples; other performance characteristics will be described in subsequent sections.

[0064] The sample in the example achieved ideal results in terms of color difference, yellowing value, and light transmittance compared to comparative examples 1-5. This is related to the addition of a specific ratio of anti-aging system formulation (the amount of organic UV additive is about 0.5 to 1.25 times the mass of inorganic anti-aging additive zinc oxide).

[0065] 2. Heat Resistance Test: Dynamic heat resistance tests were conducted on the samples of Comparative Example 5 and Examples 1 and 2 using a two-roll mill. The temperature was set to 175℃, the front roller speed was set to 21 rpm, the rear roller speed was set to 18 rpm, and the roller spacing was set to 0.18 mm. The corresponding raw materials were weighed according to the proportions in different formulations, mixed evenly, and then poured into the space between the rollers of the two-roll mill for milling. After milling, a PVC sample was removed from the front roller every 10 minutes until 25 minutes. The sample removed after 10 minutes of milling was used as the original sample. The Lab value of all removed samples was measured using a colorimeter. The results are shown in Table 3.

[0066] Table 3 shows the dynamic heat resistance test results for some comparative examples and embodiments.

[0067]

[0068]

[0069] Table 3 shows that when the ZnO content is increased to 5 parts (e.g., Comparative Example 5), the samples exhibit significant color difference and increased yellowing values ​​after 30 minutes on a two-roll mill. ZnO, as an inorganic anti-aging additive, can absorb some ultraviolet light and react with HCl released during the initial degradation of PVC to form ZnCl2. However, ZnCl2 is a Lewis acid; excessive addition will catalyze the dehydrochlorination, leading to the formation of long conjugated polyene sequences. These polyene sequences, acting as chromophores, absorb specific wavelengths of visible light, causing the originally transparent PVC film to turn yellow under high-temperature heat treatment conditions. In the example samples, reducing the ZnO content to 1-2 parts significantly improved the dynamic heat resistance.

[0070] 3. Flame retardant performance test: The PVC film samples of the comparative example and the embodiment were subjected to oxygen index testing, and the testing standard was in accordance with GB / T 5454-1997 "Textiles - Test for Burning Performance - Oxygen Index Method". The test results are shown in Table 4:

[0071] Table 4. Oxygen index test results of comparative and example samples.

[0072]

[0073] Comparative Example 1 (using antimony trioxide as the flame retardant) had the highest oxygen index. However, antimony trioxide is expensive due to the regulated status of antimony as a strategic resource, making its replacement necessary.

[0074] The samples from the embodiments of the present invention exhibited excellent anti-aging properties (without the use of antimony trioxide), and the oxygen index remained at a level consistent with that of Comparative Example 1 (with antimony trioxide as the flame retardant). This met the flame retardant performance requirements of the samples.

[0075] In the comparative samples, the oxygen index of Comparative Example 2 was significantly reduced after antimony trioxide was replaced with a liquid flame retardant (diphenyl isooctyl phosphate). After adding appropriate amounts of inorganic filler (aluminum hydroxide) and calcium powder, as in Comparative Example 3, the flame retardant performance was slightly improved, but still lower than that of the example samples and Comparative Example 1.

[0076] By subsequently adding an anti-aging compound system (organic UV additive + inorganic anti-aging additive zinc oxide), the flame retardant performance can be comparable to that of the antimony trioxide formulation, because the addition of ZnO promotes the formation of the char layer (as in comparative examples 4 and 5).

[0077] 4. Transmittance Test: The transmittance of the PVC transparent film samples from the comparative and examples was tested using a transmittance densitometer. The film was placed in the middle of the instrument's testing clamp to obtain the transmittance density (OD) and transmittance (T). To ensure the accuracy of the measurement results, the test results were taken three times at different positions, and the average value was calculated as the final measurement result. The relationship between the OD value and transmittance (T) can be calculated using the following formula:

[0078] Formula 3T = 10 -OD .

[0079] The test results are shown in Table 5:

[0080] Table 5. Transmittance of Comparative and Example Samples

[0081]

[0082] Data comparison revealed that, in Comparative Example 1, simply adding antimony trioxide resulted in poor light transmittance. While the light transmittance met the requirements in Comparative Examples 2 and 3 using liquid flame retardants, the flame retardant performance was substandard. Furthermore, in Comparative Example 5, adding excessive ZnO significantly reduced the light transmittance, affecting the product's light transmittance performance. The example sample, which did not use antimony trioxide but employed a liquid flame retardant and controlled the amount of ZnO added, met the flame retardant requirements, maintained a light transmittance >90%, and exhibited good anti-aging effects.

[0083] In summary, the aging-resistant, yellowing-resistant, flame-retardant transparent PVC film and its preparation method provided by this invention have significant advantages, achieving a balance of the "aging-resistant, yellowing-resistant, flame-retardant, and transparent" triangular properties. The product meets the environmental requirements of REACH regulations, maintaining ultra-high light transmittance while also possessing flame-retardant and aging-resistant yellowing properties. The industrial application of this innovative achievement can not only improve product safety standards and quality in fields such as electronics, building decoration, and packaging materials, but also is expected to promote the development of transparent PVC materials towards high performance, possessing significant economic value and social significance.

[0084] Finally, it should be noted that the aging-resistant, yellowing-resistant, flame-retardant PVC transparent films provided in Embodiments 1-5 of the present invention are only partial embodiments. The present invention has been described in detail with reference to preferred embodiments. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flame-retardant PVC transparent film resistant to aging and yellowing, characterized in that, The product is made from the following raw materials in parts by weight: 75 parts polyvinyl chloride resin, 17-35 parts plasticizer, 3-5 parts stabilizer, 0.2-0.5 parts gelation accelerator, 16-30 parts inorganic filler, 1-2 parts organic ultraviolet absorber, 1-2 parts ZnO and 7-10 parts liquid organic flame retardant.

2. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The plasticizer is selected from at least one of dioctyl terephthalate, diisodecyl phthalate, and epoxidized soybean oil.

3. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 2, characterized in that, The plasticizers are dioctyl terephthalate and epoxidized soybean oil, and the amounts of dioctyl terephthalate and epoxidized soybean oil are calculated to be 15-30 parts and 2-5 parts by weight, respectively.

4. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The PVC is SG-3 type PVC with a degree of polymerization of 1000.

5. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The stabilizer is a liquid barium-zinc stabilizer or a liquid calcium-zinc stabilizer.

6. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The gelation accelerator is an acrylate copolymer.

7. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The inorganic filler is composed of calcium powder and inorganic powder flame retardant, wherein the inorganic powder flame retardant is aluminum hydroxide; the amount of calcium powder and aluminum hydroxide used by weight ratio is 3-5 parts and 13-25 parts, respectively.

8. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The organic ultraviolet absorber is selected from at least one of triazine ultraviolet additives, cyanoacrylates, and oxaloylaniline ultraviolet additives.

9. The aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to claim 1, characterized in that, The liquid organic flame retardant is at least one of toluene diphenyl phosphate, bisphenol A bis(diphenyl) phosphate, diphenyl isooctyl phosphate, xylene phosphate, and tri(butoxyethyl) phosphate.

10. A method for preparing an aging-resistant, yellowing-resistant, flame-retardant PVC transparent film according to any one of claims 1 to 9, characterized in that, The preparation method includes the following steps: Step S1 Material mixing: Weigh the raw materials according to the weight ratio, add them to a high-speed mixer and mix well, control the temperature at 90°C~110°C, and mix for 6min~10min; after mixing, put the raw materials into a low-speed mixer and mix to cool down to 80°C~100°C to obtain the mixture. Step S2 Plasticizer Preparation: The mixture obtained in step S1 is added to a planetary screw extruder for extrusion plasticization, and the extruder temperature is controlled at 180°C~200°C; it is then transferred to a two-roll mill for further plasticization, and the temperature of the two-roll mill is controlled at 190°C~220°C to obtain the plasticizer. Step S3 Filter Material Preparation: The plasticized material obtained in step S2 is filtered through a filter press with a mesh size of 80-120 mesh and the material temperature is controlled at 170°C-200°C to obtain the filter material. Step S4 Preparation of calendered material: The filter material obtained in step S3 is added to a four-roll calender for calendering, and the temperature is controlled at 175°C~200°C to obtain calendered material; Step S5 Preparation of PVC transparent film: The calendered material obtained in step S4 is sequentially embossed, cold-cut, trimmed, and rolled up to obtain a yellowing-resistant and flame-retardant PVC transparent film.

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