Environment-friendly flame-retardant PVC (polyvinyl chloride) rear projection film as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of PVC (polyvinyl chloride) projection films, and particularly relates to an environment-friendly flame-retardant PVC rear projection film as well as a preparation method and application thereof. The PVC projection film adopts inorganic and organic flame retardants. Wherein the organic flame retardant at least contains WSFR-PCF or WSFR-9702, and the organic flame retardant is a flame retardant; according to the PVC projection film, the flame retardance is improved, meanwhile, the light transmittance is not affected or improved, the problems of environmental friendliness, whitening and the like are better solved, and the latest regulation requirements of the European and American markets are met.

Description

Technical Field

[0001] The invention belongs to the technical field of PVC projection films, and in particular relates to an environmentally friendly flame-retardant PVC rear projection film and a preparation method and application thereof. Background Art

[0002] As an important optical material, projection film is widely used in the display field. Among them, rear projection technology has gradually become the core solution in the high-end display field due to its advantages such as closed projection light, strong resistance to ambient light interference, and beautiful visual appearance. The current rear projection generally uses a rear projection screen or rear projection film made of polyvinyl chloride (PVC); it mainly focuses on optical properties such as light transmittance, color reproduction and clarity, but has obvious deficiencies in flame retardancy. Although PVC itself has certain flame retardancy, plasticizers usually need to be added when producing PVC products, which greatly increases its flammability. Once a fire occurs, these PVC-based projection films will release a lot of heat and toxic smoke when burning, hindering the evacuation of personnel and exacerbating the fire hazard.

[0003] Among similar products on the current market, there are two main ways for common flame-retardant rear projection films to achieve flame-retardant properties. One is to add flame retardants to traditional projection film materials; the other is to use a multi-layer composite structure. Although the multi-layer composite structure has a certain flame retardant effect, its production process is cumbersome, the cost is high, and the inter-layer bonding stability is poor. Therefore, the use of flame retardants is a common solution to reduce the flammability of PVC projection films.

[0004] Commonly used flame retardants include halogen flame retardants, phosphorus flame retardants, antimony trioxide, zinc borate, etc. Among them, halogen flame retardants and phosphorus flame retardants are organic flame retardants, while antimony trioxide, zinc borate, etc. are inorganic flame retardants. In fields with low requirements for light transmittance and environmental protection, halogen flame retardants (halogen-containing flame retardants will produce a large amount of toxic gases and harmful substances) and antimony trioxide (which will cause pollution to the human body, soil, water, etc.) are usually used because of their good flame retardant properties. However, with the improvement of environmental protection requirements, the use of such flame retardants has gradually received attention and restrictions. For example, the EU issued regulations in 2021 to prohibit the use of halogen flame retardants in electronic display housings and brackets. Antimony trioxide (Sb2O3) is a widely used flame retardant and auxiliary agent with high flame retardancy and excellent performance. It is often used in combination with halogen flame retardants and is difficult to replace due to its excellent performance. However, in 2018, antimony trioxide was also considered by the EU to be included in the RoHS restricted substances list. In 2024, the European Chemicals Agency (ECHA) updated the 32nd batch of Substances of Very High Concern (SVHC) list. In this update, triphenyl phosphate (TPP) was officially added to the candidate list of substances of very high concern, bringing the total number of substances in the EU SVHC list to 242. This change has brought new compliance requirements and challenges to related export companies. This has led to a double squeeze between the technical requirements for improving the flame retardant performance of products and the technical requirements for improving the environmental performance of products, which has brought difficulties to the research and development of flame-retardant PVC products exported to the European and American markets.

[0005] At the same time, whether it is an organic flame retardant or an inorganic flame retardant, there is a contradiction between flame retardancy and light transmittance for PVC products. Increasing the content of flame retardants can play a better flame retardant role, but it often leads to reduced light transmittance, whitening, color distortion, and brightness reduction of PVC products. CN101935429A provides a PVC rear projection screen that uses organic flame retardant oil, inorganic flame retardant, powder stabilizer, matte PVC resin, etc., but even so, it is still necessary to change the conventional embossing process and control the material ratio to achieve the expected optical effect. Phosphorus-based organic flame retardants have good transparency; however, in the production and use of phosphorus-based organic flame retardants, the generation of TPP is difficult to avoid and difficult to control. When the product target market is the European and American markets, it is easy to generate compliance risks of TPP content.

[0006] Patent CN 117820780A provides a highly flame-retardant and light-transmitting PVC ceiling film and its preparation method. By adding a small amount of antimony trioxide, liquid flame-retardant plasticizer and inorganic flame retardant with a refractive index similar to that of PVC, the oxygen index of the film is improved without affecting the light transmittance of the PVC film; however, the antimony trioxide and toluene ditoluene phosphate in this patent are restricted in use or environmentally or health-unfriendly materials. Patent CN 103059472A provides a flame-retardant and mildew-proof rear projection film, which uses PVC resin, silicone resin, citrate plasticizer, stabilizer, flame retardant, mildew-proof agent and elastomer as main raw materials, and has good transparency, flame retardant and mildew-proof properties, but decabromodiphenyl ether liquid flame retardant is also an environmentally or health-unfriendly material and is restricted in use. Summary of the invention

[0007] In view of the above problems, in order to meet the stringent technical and environmental requirements of the European and American markets for flame-retardant PVC rear-projection projection films, the purpose of the present invention is to provide an environmentally friendly flame-retardant PVC rear-projection projection film with improved flame retardancy and light transmittance and reduced content of harmful substances, as well as a preparation method and use thereof. In view of the above objectives, the technical solutions of the present invention are as follows: In one aspect of the present invention, an environmentally friendly flame-retardant PVC rear projection film is provided, which is made of the following materials, measured in parts by weight: 100 parts of polyvinyl chloride (PVC), 15-35 parts of plasticizer, 4-7 parts of stabilizer, 0-13 parts of calcium carbonate, 30-45 parts of liquid organic flame retardant, 1-1.5 parts of light diffuser, 2-4 parts of elastomer, 0.2-0.5 parts of gelling accelerator, and 10-20 parts of inorganic powder flame retardant.

[0008] Preferably, the liquid organic flame retardant is selected from one or more of WSFR-PCF, WSFR-BDP, diphenyl isooctyl phosphate and WSFR-9702. WSFR-PCF is a commercially available flame retardant, the main component of which is tris(1-chloro-2-propyl) phosphate; WSFR-BDP is a commercially available flame retardant, the main component of which is bisphenol (A bis diphenyl phosphate); WSFR-9702 is a commercially available flame retardant, the main component of which is halogen-free phosphate; diphenyl isooctyl phosphate is a commercially available flame retardant, also known as DPOP.

[0009] In a further preferred embodiment, the liquid organic flame retardant is selected from WSFR-PCF; WSFR-9702; a combination of WSFR-BDP and WSFR-PCF and / or WSFR-9702 (i.e. WSFR-BDP+WSFR-PCF, WSFR-BDP+WSFR-9702 or WSFR-BDP+WSFR-PCF+ WSFR-9702); a combination of WSFR-BDP and diphenyl isooctyl phosphate and any one of WSFR-PCF and / or WSFR-9702 (i.e. WSFR-BDP+diphenyl isooctyl phosphate, and then combined with any one or two of WSFR-PCF and WSFR-9702); a combination of diphenyl isooctyl phosphate and WSFR-PCF and / or WSFR-9702 (i.e. diphenyl isooctyl phosphate+WSFR-PCF, diphenyl isooctyl phosphate+WSFR-9702 or diphenyl isooctyl phosphate+WSFR-PCF+WSFR-9702). That is, in a further preferred embodiment, WSFR-BDP and isooctyl diphenyl phosphate are not used alone, but are combined with at least one of the other three liquid organic flame retardants. In other words, in a further preferred embodiment, the liquid organic flame retardant, whether a single or combined liquid organic flame retardant, contains at least one of WSFR-PCF and WSFR-9702. The mass percentage content of WSFR-BDP in the combined liquid organic flame retardant is 0% to 35%. The mass percentage content of isooctyl diphenyl phosphate in the combined liquid organic flame retardant is 0% to 50%.

[0010] Preferably, the inorganic powder flame retardant is aluminum hydroxide and modified talc, and the mass ratio of aluminum hydroxide to modified talc is 1:(1-2).

[0011] In a further preferred embodiment, the aluminum hydroxide has a refractive index of 1.57; the modified talc is a silane coupling agent modified talc, with a refractive index of 1.58-1.59. When the refractive index is similar but the particle size is large, the light transmittance of the projection film will decrease to a certain extent. Therefore, the particle size of aluminum hydroxide and modified talc needs to be controlled at or below the micron level, for example, the particle size of aluminum hydroxide is 1.3-2.3 μm; the particle size of modified talc is about 4000 mesh.

[0012] Preferably, the PVC is SG-3 type PVC with a degree of polymerization of 1300.

[0013] Preferably, the plasticizer is one or more of dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and epoxidized soybean oil.

[0014] Preferably, the stabilizer is one of a liquid barium zinc stabilizer or a liquid calcium zinc stabilizer.

[0015] Preferably, the calcium carbonate is heavy calcium carbonate with a particle size of about 1500 mesh.

[0016] Preferably, the light diffuser is an organosilicon light diffuser, and the organosilicon light diffuser is at least one of polymethylsilsesquioxane and polymethylhydrogensiloxane.

[0017] Preferably, the elastomer is liquid nitrile rubber or powdered nitrile rubber.

[0018] Preferably, the gelling accelerator is an acrylic copolymer.

[0019] The second aspect of the present invention provides a method for preparing the aforementioned environmentally friendly flame-retardant PVC rear projection film, comprising the following steps: S1: Weigh the materials and put them into a high-speed mixer to mix them evenly, control the temperature at 120°C±10°C, and stir for 6min~10min; after stirring, put the raw materials into a low-speed mixer and stir to cool down to 80°C~100°C to obtain a mixture; S2: adding the mixed material obtained in step S2 into a planetary screw extruder for extrusion plasticization, wherein the temperature of the extruder is controlled at 160°C to 190°C; transferring the mixed material to a double-roll mill for further plasticization, wherein the temperature of the double-roll mill is controlled at 190°C to 220°C, to obtain a plasticized material; S3: filtering the plasticized material obtained in step S2 through a filter, wherein the filter mesh number is 80-120 meshes, and the material temperature is controlled at 170° C.-200° C. to obtain a filter material; S4: The filtration material obtained in step S3 is put into a four-roll calender for calendering, and the temperature is controlled at 165°C to 210°C to obtain a calendered material; S5: The calendered molding material obtained in step S3 is sequentially embossed, cold-cut, trimmed, and rolled to obtain the environmentally friendly flame-retardant PVC rear projection film.

[0020] The third aspect of the present invention provides the use of the aforementioned environmentally friendly flame-retardant PVC rear-projection film as a rear-projection film, or the use of the aforementioned environmentally friendly flame-retardant PVC rear-projection film in a rear-projection optical device.

[0021] Beneficial effects of the present invention: The present invention obtains an environmentally friendly flame-retardant PVC rear projection film and a preparation method through the investigation of materials and processes. The environmentally friendly flame-retardant PVC rear projection film not only has good flame retardancy and light transmittance, but also meets the flame retardancy and light transmittance requirements of PVC rear projection film. Its flame retardancy and light transmittance are not lower than or higher than the combination of TPP, etc. / nano inorganic flame retardant (such as aluminum hydroxide or antimony trioxide) which is currently considered to have a good effect. In addition, the environmentally friendly flame-retardant PVC rear projection film also has good environmental friendliness, the TPP content of the obtained product is extremely low, and antimony trioxide, halogen flame retardants, etc. are not used. DETAILED DESCRIPTION

[0022] The technical ideas, solutions, effects, etc. of the present invention are described in detail below through specific embodiments. The embodiments are only exemplary descriptions of the present invention and are not to be regarded as limiting the protection scope of the present invention.

[0023] In the following examples and comparative examples: (1) Liquid organic flame retardants: WSFR-PCF, WSFR-BDP, diphenyl 2-ethylhexyl phosphate (DPOP), WSFR-9702, diphenyl 2-ethylhexyl phosphate (DPK), tris(butoxyethyl) phosphate (TBEP), purchased from Zhejiang Wansheng Co., Ltd. and Shanghai Ruizhe Chemical Co., Ltd., respectively. Among them, TBEP raw material is known to be a TPP-free liquid organic flame retardant.

[0024] (2) Inorganic flame retardants: Aluminum hydroxide, modified talc (silane coupling agent modified talc), and antimony trioxide are all commercially available products. The particle size of aluminum hydroxide is 1.3~2.3 μm, and the refractive index is 1.57; the particle size of modified talc (silane coupling agent modified talc) is about 4000 mesh, and the refractive index is 1.58~1.59; the particle size of antimony trioxide is 0.3~0.9 μm.

[0025] (3) PVC is commercially available SG-3 type PVC with a degree of polymerization of 1300.

[0026] (4) Plasticizers: dioctyl terephthalate (DOTP), dioctyl adipate (DOA), epoxidized soybean oil; and stabilizers (liquid barium zinc stabilizer or liquid calcium zinc stabilizer), silicone light diffusers (polymethylsilsesquioxane, polymethylhydrogensiloxane), elastomers (liquid nitrile rubber or powdered nitrile rubber), gelling accelerators (acrylate copolymers, acrylate copolymer PA-40 used in the examples), and heavy calcium carbonate (particle size of about 1500 mesh) are all commercially available products.

[0027] In the following embodiments and comparative examples, when a process parameter such as temperature adopts a range value, it is the temperature range controlled in production (the fluctuation range of the parameter), which is the process parameter range value that can achieve the technical effect of the present invention.

[0028] Part 1 Preparation of flame retardant PVC rear projection film This section provides ingredients and preparation processes of 4 comparative flame-retardant PVC rear projection films and 5 flame-retardant PVC rear projection films of the present invention. The following ingredients are calculated by weight, among which 100 parts by weight of PVC is used as a reference for the amount of ingredients, which is a commonly used ingredient representation form.

[0029] Comparative Example 1 Ingredients of flame retardant PVC rear projection film (by weight) 100 parts of PVC, 23 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 4 parts of liquid calcium zinc stabilizer, 10 parts of heavy calcium carbonate, 1.4 parts of polymethylsilsesquioxane, 0.4 parts of gelling accelerator, 3.3 parts of powdered nitrile rubber, and 30 parts of DPK.

[0030] Comparative Example 2 Ingredients of flame-retardant PVC rear projection film (by weight) 100 parts of PVC, 23 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 4 parts of liquid barium zinc stabilizer, 10 parts of heavy calcium carbonate, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 30 parts of DPK, and 2 parts of antimony trioxide.

[0031] Comparative Example 3 Ingredients of flame-retardant PVC rear projection film (by weight) 100 parts of PVC, 20 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 7.5 parts of liquid barium zinc stabilizer, 1.4 parts of polymethylsilsesquioxane, 0.4 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 33 parts of TBEP, 5 parts of aluminum hydroxide, and 10 parts of modified talc.

[0032] Comparative Example 4 Ingredients of flame-retardant PVC rear projection film (by weight) 100 parts of PVC, 20 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 5 parts of liquid barium zinc stabilizer, 7 parts of heavy calcium carbonate, 1.4 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 20 parts of DPK, 13 parts of WSFR-BDP, and 15 parts of aluminum hydroxide.

[0033] Example 1 Ingredients of flame retardant PVC rear projection film (by weight) 100 parts of PVC, 18 parts of DOTP, 3 parts of DOA, 2 parts of epoxidized soybean oil, 5 parts of liquid calcium zinc stabilizer, 6 parts of heavy calcium carbonate, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 3.5 parts of liquid nitrile rubber, 15 parts of WSFR-PCF, 5 parts of WSFR-BDP, 17 parts of DPOP, 5 parts of aluminum hydroxide, and 5 parts of modified talc.

[0034] Example 2 Ingredients of flame retardant PVC rear projection film (by weight) 100 parts of PVC, 20 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 5 parts of liquid calcium zinc stabilizer, 6 parts of heavy calcium carbonate, 1.4 parts of polymethylsilsesquioxane, 0.4 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 15 parts of WSFR-PCF, 10 parts of WSFR-BDP, 10 parts of DPOP, 7 parts of aluminum hydroxide, and 10 parts of modified talc.

[0035] Example 3 Ingredients of flame retardant PVC rear projection film (by weight) 100 parts of PVC, 11 parts of DOTP, 5 parts of DOA, 2 parts of epoxidized soybean oil, 6 parts of liquid barium zinc stabilizer, 10 parts of heavy calcium carbonate, 1.2 parts of polymethyl hydrogen siloxane, 0.3 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 15 parts of WSFR-PCF, 15 parts of DPOP, 12 parts of WSFR-9702, 5 parts of aluminum hydroxide, and 10 parts of modified talc.

[0036] Example 4 Ingredients of flame retardant PVC rear projection film (by weight) 100 parts of PVC, 17 parts of DOTP, 8 parts of DOA, 2 parts of epoxidized soybean oil, 5 parts of liquid barium zinc stabilizer, 8 parts of heavy calcium carbonate, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 3 parts of powdered nitrile rubber, 33 parts of WSFR-9702, 5 parts of aluminum hydroxide, and 10 parts of modified talc.

[0037] Example 5 Ingredients of flame retardant PVC rear projection film (in parts by weight) 100 parts of PVC, 15 parts of DOTP, 10 parts of DOA, 2 parts of epoxidized soybean oil, 5 parts of liquid barium zinc stabilizer, 8 parts of heavy calcium carbonate, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 2.7 parts of liquid nitrile rubber, 8 parts of DPOP, 25 parts of WSFR-9702, 5 parts of aluminum hydroxide, and 10 parts of modified talc.

[0038] Preparation method of flame retardant PVC rear projection film: The preparation method of the flame-retardant PVC rear projection film of the above comparative example and embodiment is as follows: (1) Mixing: According to different formulations of the embodiments and comparative examples, weigh the corresponding materials and put them into a high-speed mixer and stir and mix them evenly. The temperature is controlled to be 120°C ± 10°C and the stirring time is 6 min to 10 min. After the stirring is completed, put the raw materials into a low-speed mixer and stir and cool them to 80°C to 100°C. (2) Plasticizing: Add the raw material obtained in step (1) into a planetary extruder for extrusion plasticizing, and control the temperature of the extruder at 160°C to 190°C; move to a double-roll mill for further plasticizing, and control the temperature of the mill at 190°C to 220°C; (3) Filtration: After sufficient plasticization, filter out impurities through a filter with a filter mesh size of 80 to 120 and a temperature of 170°C to 200°C; (4) Forming: Entering into a four-roll calender for calendering and forming, the temperature is controlled at 165°C to 210°C; (5) After forming, embossing, cold cutting, trimming and rolling are carried out in sequence.

[0039] Part II Performance Study of Flame Retardant PVC Rear Projection Film The following are the test results of the performance and other indicators of the flame-retardant PVC rear projection film of the embodiment and the comparative example.

[0040] 1. Environmental protection The EU Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals is referred to as "REACH". This test project is designed to examine whether the product complies with the "REACH" requirements.

[0041] The content of TPP (mass fraction, wt%) in the environmentally friendly flame-retardant PVC rear projection film was calculated according to the formula of the comparative example and the embodiment. The TPP content was calculated by taking the highest content in the raw materials, wherein the TPP content in the DPK raw material was 11.9%, the TBEP raw material and the WSFR-PCF raw material did not contain TPP, the TPP content in the WSFR-BDP raw material was ≤1.5wt%, the TPP content in the DPOP raw material was below 1000ppm, and the TPP content in the WSFR-9702 raw material was below 3500ppm; the calculation results are shown in Table 1: Table 1 Hazardous substance content in comparative examples and examples

[0042] REACH Regulation - When the mass fraction of a substance in the candidate list of substances of very high concern (SVHC) in an article exceeds 0.1%, and the substance enters the EU more than 1 ton / year / company each year, the manufacturer or importer of the article must notify the European Chemicals Agency. From the above results, it can be seen that the environmentally friendly flame-retardant PVC rear projection film prepared by the present invention meets the environmental protection requirements of REACH regulations.

[0043] 2. Light transmittance The environmentally friendly flame-retardant PVC rear projection film samples of the comparative example and the embodiment were tested for transmittance. The test method is as follows: Use a transmission density meter, press the measurement button, and the instrument will automatically measure and display the transmission density value (OD) of the sample. In order to ensure the accuracy of the measurement results, it is usually necessary to measure more than 3 times at different positions, and take the average value as the final measurement result. The relationship between the OD value and the transmittance (T) can be calculated by the following formula:

[0044] The test results are shown in Table 2: Table 2 Light transmittance of comparative examples and example samples

[0045] The environmentally friendly flame-retardant PVC rear projection film prepared by the present invention shows great advantages in light transmittance compared with the sample with antimony trioxide added (Comparative Example 2, DPK combined with antimony trioxide, which is a common flame retardant combination for improving the flame retardancy and light transmittance of PVC), and effectively overcomes the problem of PVC film that cannot take into account environmental protection, light transmittance and flame retardancy. The light transmittance results shown in the embodiments of the present invention are not the highest values. In actual production, the light transmittance of the projection film can be further improved by reducing the amount of calcium carbonate used. For example, in Comparative Example 3, no calcium carbonate is added, and the light transmittance can reach 85.11%.

[0046] 3. Dynamic heat resistance The samples of comparative examples 1 and 3 and examples 1 and 4 were subjected to dynamic heat resistance test using a double-roll mill. The temperature was set to 180°C, the front roller speed was set to 23rpm, the front roller speed was set to 18rpm, and the roller spacing was set to 0.3mm. The corresponding raw materials were weighed according to the ratios in different formulas, and after being mixed evenly, they were poured between the rollers of the double-roll mill for refining. After refining, a piece of PVC sample was taken from the front roller every 5 minutes until 25 minutes. The sample taken after 5 minutes of refining was taken as the original sample. The Lab value of all the taken samples was tested using a colorimeter, and the color difference value (△E) and yellowing value (△b) between them and the original sample were calculated. The larger the value, the worse the thermal stability. The calculation formula is as follows:

[0047]

[0048] The test results are shown in Table 3: Table 3 Dynamic heat resistance test results of some comparative examples and examples

[0049] From the results of Comparative Example 3, it can be seen that even after the amount of heat stabilizer is increased to 7.5 parts, its yellowing value and color difference value are still much higher than those of other comparative examples and embodiments. Although Comparative Example 3 uses phosphorus flame retardant and aluminum hydroxide + modified talcum powder inorganic flame retardant, and has low TPP content and high light transmittance, its yellowing value and color difference value are much higher than those of the flame-retardant rear projection film of the embodiments.

[0050] 4. Flame retardant properties The environmentally friendly flame-retardant PVC rear projection film samples of the comparative example and the embodiment were tested for oxygen index and flame retardancy, and the test methods were in accordance with the following standards: GB / T 5454-1997 "Textile Combustion Performance Test Oxygen Index Method"; DIN4102-1 "Fire resistance of building materials and components Part 1: Classification and grades of building material requirements and tests"; The test results are shown in Table 4: Table 4 Combustion performance test results of comparative examples and example samples

[0051] The oxygen index and flame retardant performance of the environmentally friendly flame-retardant PVC rear projection film prepared by the present invention are maintained at the same level as those of the PVC film sample to which antimony trioxide and DPK are added (Comparative Example 2); compared with the PVC film sample to which only DPK is added (Comparative Example 1), the flame retardant performance is improved and can pass the DIN4102 B2 grade; and the flame retardancy is higher than that of the sample in Comparative Example 3 using a phosphorus flame retardant and aluminum hydroxide + modified talcum powder inorganic flame retardant.

[0052] This result clearly shows that on the basis of maintaining the ultra-high transmittance of the environmentally friendly flame-retardant PVC rear-projection film, if the flame retardant properties of the film are to be further improved, relying solely on a single flame retardant method or relying on the synergistic effect of inorganic powder flame retardants and liquid flame retardants is still not enough, but the technology of the present invention has achieved better results than the prior art.

[0053] 5. Whitening phenomenon PVC whitening refers to the phenomenon that PVC material turns white at the bend after being subjected to external forces such as bending. For example, after the PVC edge banding is bent into a small arc, the edge will turn white, and this whitening will not recover even if the edge banding is straightened again.

[0054] The environmentally friendly flame-retardant PVC rear projection film samples of the comparative example and the embodiment were subjected to folding and whitening test, and the test method was as follows: Under natural light, the test personnel observed the surface of the PVC projection film comprehensively with normal vision to check whether there was folding and whitening phenomenon. The test results are shown in Table 5: Table 5 Whitening phenomenon detection results of comparative examples and example samples

[0055] By comparing the results of Comparative Example 4 with those of the embodiment, it can be seen that when the proportion of aluminum hydroxide is higher, although the flame retardant effect and the light transmittance effect are better, it will cause the projection film to produce a whitening phenomenon, which affects its actual use; and the use of modified talcum powder and aluminum hydroxide in combination can improve this phenomenon and keep the flame retardant effect consistent therewith.

[0056] In summary, the environmentally friendly flame-retardant PVC rear-projection film and the preparation method thereof provided by the present invention have significant advantages. The product fully complies with the environmental protection requirements of the REACH regulations; while maintaining ultra-high light transmittance, it also meets the flame retardant requirements of DIN4102 B2 level, and will not produce other negative effects, such as yellowing, whitening, etc. This innovative achievement provides a good foundation for improving product export compliance and creating tangible economic benefits for other downstream manufacturers; it provides a more environmentally friendly and healthy product option for application fields such as projection films and transparent films. In addition, this achievement will also help to promote the PVC material industry in a greener and more sustainable direction, injecting new vitality into the long-term development of the industry.

[0057] Obviously, the environmentally friendly flame-retardant rear-projection films provided in the above-mentioned embodiments 1-5 of the present invention are only some embodiments of the present invention. Within the scope of the present invention, its flame retardancy and transparency can be further improved, and the environmentally friendly flame-retardant rear-projection films provided in embodiments 1-5 are only embodiments that meet the compliance requirements and the basic flame retardancy and transmittance performance requirements of the rear-projection films. Within the protection scope of the present invention, the LOI of other environmentally friendly flame-retardant rear-projection films can further reach 28~32%, the transmittance can reach 89%, and the environmental protection and whitening phenomenon still meet the requirements. For example, when the formula is 100 parts of PVC, 16 parts of DOTP, 5 parts of DOA, 2 parts of epoxy soybean oil, 5 parts of liquid barium zinc stabilizer, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelling accelerator, 3 parts of liquid nitrile rubber, 12 parts of WSFR-BDP, 25 parts of WSFR-PCF, 6 parts of aluminum hydroxide, and 12 parts of modified talc (the preparation method is the same as that in the first part of the embodiment), the LOI of the sample can reach 29.5%, the transmittance can reach 89.1%, and the environmental protection and whitening phenomenon still meet the requirements.

Claims

1. An environmentally friendly flame-retardant PVC rear projection film, characterized in that: The environmentally friendly flame-retardant PVC rear projection film is made of the following materials in parts by weight: 100 parts of PVC, 15-35 parts of plasticizer, 4-7 parts of stabilizer, 0-13 parts of calcium carbonate, 30-45 parts of liquid organic flame retardant, 1-1.5 parts of light diffuser, 2-4 parts of elastomer, 0.2-0.5 parts of gelling accelerator, and 10-20 parts of inorganic powder flame retardant; the liquid organic flame retardant is selected from one or more of WSFR-PCF, WSFR-BDP, diphenyl isooctyl phosphate, and WSFR-9702, and at least contains WSFR-PCF or WSFR-9702; the inorganic powder flame retardant is aluminum hydroxide and modified talc, wherein the mass ratio of aluminum hydroxide to modified talc is 1:(1-2).

2. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The aluminum hydroxide has a refractive index of 1.57; the modified talc is talc modified by a silane coupling agent, and has a refractive index of 1.58-1.

59.

3. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The PVC is SG-3 type PVC with a degree of polymerization of 1300.

4. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The plasticizer is one or more of dioctyl terephthalate, dioctyl adipate and epoxidized soybean oil.

5. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The stabilizer is one of a liquid barium zinc stabilizer or a liquid calcium zinc stabilizer.

6. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The calcium carbonate is heavy calcium carbonate.

7. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The light diffusing agent is at least one of polymethylsilsesquioxane and polymethylhydrogensiloxane.

8. The environmentally friendly flame-retardant PVC rear projection film according to claim 1, characterized in that: The elastomer is nitrile rubber; the gelling accelerator is an acrylic copolymer.

9. The method for preparing an environmentally friendly flame-retardant PVC rear projection film according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: Weigh the materials and put them into a high-speed mixer to mix them evenly, control the temperature at 120°C±10°C, and stir for 6min~10min; after stirring, put the raw materials into a low-speed mixer and stir to cool down to 80°C~100°C to obtain a mixture; S2: adding the mixed material obtained in step S2 into a planetary screw extruder for extrusion plasticization, wherein the temperature of the extruder is controlled at 160°C to 190°C; transferring the mixed material to a double-roll mill for further plasticization, wherein the temperature of the double-roll mill is controlled at 190°C to 220°C, to obtain a plasticized material; S3: filtering the plasticized material obtained in step S2 through a filter, wherein the filter mesh number is 80-120 meshes, and the material temperature is controlled at 170° C.-200° C. to obtain a filter material; S4: The filtration material obtained in step S3 is put into a four-roll calender for calendering, and the temperature is controlled at 165°C to 210°C to obtain a calendered material; S5: The calendered molding material obtained in step S3 is sequentially embossed, cold-cut, trimmed, and rolled to obtain the environmentally friendly flame-retardant PVC rear projection film.

10. Use of the environmentally friendly flame-retardant PVC rear projection film according to any one of claims 1 to 8 as a rear projection film.

Images