An environmentally friendly flame-retardant PVC rear projection film and its preparation method and uses

Abstract

The present invention belongs to the technical field of PVC projection films, and particularly relates to an environmentally friendly flame-retardant PVC rear projection film, its preparation method and uses. The PVC projection film uses inorganic and organic flame retardants. Among them, the organic flame retardant contains at least WSFR-PCF or WSFR-9702; the inorganic powder flame retardant is aluminum hydroxide and modified talc powder. While improving the flame retardancy of the PVC projection film, the light transmittance is not affected or is improved, and problems such as environmental friendliness and white streaks are better solved, meeting the latest regulatory requirements of the European and American markets.

Description

Technical Field

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

[0002] Projection films, as an important optical material, are 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 enclosed projection light, strong resistance to ambient light interference, and visual aesthetics. Currently, rear projection generally uses rear projection screens or rear projection films made of polyvinyl chloride (PVC); mainly focuses on optical properties such as light transmittance, color reproducibility, and clarity, but there are obvious deficiencies in flame retardancy. Although PVC itself has certain flame retardancy, plasticizers are usually added during the production of PVC products, which leads to a significant increase in its flammability. Once a fire occurs, these projection films based on PVC will release a large amount of heat and toxic smoke when burning, hindering the evacuation of personnel and exacerbating the fire hazard.

[0003] Among the similar products in the current market, there are mainly two ways to achieve flame retardancy for common flame-retardant rear projection films. One is to add flame retardants to traditional projection film materials; the other is to adopt a multi-layer composite structure. Although the multi-layer composite structure has certain flame retardant effects, its manufacturing process is cumbersome, the cost is high, and the interlayer bonding stability is poor. Therefore, using flame retardants is a common solution to reduce the flammability of PVC projection films.

[0004] Common flame retardants include halogen-based flame retardants, phosphorus-based flame retardants, antimony trioxide, zinc borate, etc. Among them, halogen-based flame retardants and phosphorus-based flame retardants are organic flame retardants, while antimony trioxide, zinc borate, etc. are inorganic flame retardants. In fields with lower requirements for light transmittance and environmental protection, halogen-based 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 humans, soil, water bodies, etc.) are usually used due to their good flame retardant performance. However, with the increasing environmental protection requirements, the use of such flame retardants has gradually received attention and restrictions. For example, in 2021, the European Union promulgated regulations prohibiting the use of halogen-based flame retardants in the shells and brackets of electronic displays. Antimony trioxide (Sb2O3) is a widely used flame retardant and auxiliary agent, with high flame retardancy and excellent synergistic flame retardant performance. It is often used in combination with halogen-based flame retardants and is difficult to be replaced due to its excellent performance. However, in 2018, antimony trioxide was also considered by the European Union to be included in the RoHS restricted substances list. In 2024, the European Chemicals Agency (ECHA) updated the list of Substances of Very High Concern (SVHC) in the thirty-second batch. In this update, triphenyl phosphate (TPP) was officially added to the candidate list of substances of very high concern, increasing the total number of substances in the EU's SVHC list to 242. This change has brought new compliance requirements and challenges to relevant export enterprises. 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 protection performance of products, making it difficult to develop flame retardant PVC products for the European and American markets.

[0005] At the same time, whether it is organic flame retardants or inorganic flame retardants, for PVC products, there is a contradiction between flame retardancy and light transmittance. Increasing the content of flame retardants can play a better flame retardant role, but it often leads to a decrease in the light transmittance of PVC products, white streaking, color distortion of the picture, brightness decline, etc. CN101935429A provides a PVC rear projection screen that uses organic flame retardant oil, inorganic flame retardants, powder stabilizers, matte PVC resin, etc. However, 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 inevitable and difficult to control. When the target market of the product is the European and American markets, there is an easy compliance risk 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, both antimony trioxide and tolyl xylene phosphate in this patent belong to materials with restricted use or are not environmentally or health-friendly. 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 the main raw materials, and has good transparency, flame-retardant performance, and mildew-proof performance. However, the decabromodiphenyl ether liquid flame retardant also belongs to an environmentally or health-unfriendly material with restricted use. Summary of the Invention

[0007] In view of the above problems, to meet the strict requirements of the European and American markets for the technology and environmental protection of flame-retardant PVC rear projection films, the object of the present invention is to provide an environmentally friendly flame-retardant PVC rear projection film with improved flame retardancy and light transmittance and reduced harmful substance content, as well as its preparation method and uses. For the above object, the technical solution of the present invention is as follows:

[0008] On the one hand, the present invention provides an environmentally friendly flame-retardant PVC rear projection film, which is made of the following materials 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 diffusing agent, 2 - 4 parts of elastomer, 0.2 - 0.5 parts of gelation accelerator, and 10 - 20 parts of inorganic powder flame retardant.

[0009] Preferably, the liquid organic flame retardant is selected from one or more of WSFR-PCF, WSFR-BDP, diphenyl isooctyl phosphate, and WSFR-9702. Among them, WSFR-PCF is a commercially available flame retardant, and its main component is tris(1-chloro-2-propyl) phosphate; WSFR-BDP is a commercially available flame retardant, and its main component is bisphenol (A bisdiphenyl phosphate); WSFR-9702 is a commercially available flame retardant, and its main component is halogen-free phosphate; diphenyl isooctyl phosphate is a commercially available flame retardant, also known as DPOP.

[0010] 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, 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 both 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 diphenyl isooctyl phosphate are not used alone, but in combination with at least one of the other three liquid organic flame retardants. In other words, in a further preferred embodiment, whether the liquid organic flame retardant is a single or a combined liquid organic flame retardant, it contains at least one of WSFR-PCF and WSFR-9702. Wherein the mass percentage content of WSFR-BDP in the combined liquid organic flame retardant is 0% to 35%. The mass percentage content of diphenyl isooctyl phosphate in the combined liquid organic flame retardant is 0% to 50%.

[0011] Preferably, the inorganic powder flame retardant is aluminum hydroxide and modified talc powder, and the mass ratio of aluminum hydroxide to modified talc powder is 1:(1-2).

[0012] In a further preferred embodiment, the refractive index of the aluminum hydroxide is 1.57; the modified talc powder is silicon-coupling agent modified talc powder, and the refractive index is 1.58-1.59. When the refractive indices are similar but the particle sizes are larger, it will also cause a certain degree of decrease in the light transmittance of the projection film. Therefore, the particle sizes of the aluminum hydroxide and the modified talc powder need to be controlled at the micron level or below. For example, the particle size of the aluminum hydroxide is 1.3-2.3 μm; the particle size of the modified talc powder is about 4000 mesh.

[0013] Preferably, the PVC is SG-3 type PVC with a polymerization degree of 1300.

[0014] Preferably, the plasticizer is one or more of dioctyl terephthalate (DOTP), dioctyl adipate (DOA) and epoxidized soybean oil.

[0015] Preferably, the stabilizer is one of liquid barium-zinc stabilizer or liquid calcium-zinc stabilizer.

[0016] Preferably, the calcium carbonate is heavy calcium carbonate with a particle size of about 1500 mesh.

[0017] Preferably, the light diffusing agent is an organosilicon light diffusing agent, and the organosilicon light diffusing agent is at least one of polymethylsilsesquioxane and polymethylhydrogensiloxane.

[0018] Preferably, the elastomer is liquid nitrile rubber or powder nitrile rubber.

[0019] Preferably, the gelling accelerator is an acrylate copolymer.

[0020] In the second aspect of the present invention, there is provided a method for preparing the aforementioned environmentally friendly flame-retardant PVC rear projection film, comprising the following steps:

[0021] S1: Weigh the materials and put them into a high-speed mixer for stirring and mixing evenly, control the temperature at 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 for stirring and cooling to 80°C to 100°C to obtain a mixed material;

[0022] S2: Add the mixed material obtained in step S2 into a planetary screw extruder for extrusion and plasticization, and control the temperature of the extruder at 160°C to 190°C; transfer it to a two-roll calender for further plasticization, and control the temperature of the calender at 190°C to 220°C to obtain a plasticized material;

[0023] S3: Filter the plasticized material obtained in step S2 through a filter, select the mesh number of the filter screen to be 80 to 120 mesh, and control the material temperature at 170°C to 200°C to obtain a filtered material;

[0024] S4: The filtered material obtained in step S3 enters a four-roll calender for calendering and forming, and control the temperature at 165°C to 210°C to obtain a calendered and formed material;

[0025] S5: The calendered and formed material obtained in step S3 is embossed, cold-cut, trimmed, and wound up in sequence to obtain the aforementioned environmentally friendly flame-retardant PVC rear projection film.

[0026] In the third aspect of the present invention, there is provided the application of the aforementioned environmentally friendly flame-retardant PVC rear projection film as a rear projection film, or the application of the aforementioned environmentally friendly flame-retardant PVC rear projection film in a rear projection optical device.

[0027] Advantages of the present invention:

[0028] 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

[0029] 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.

[0030] In the following examples and comparative examples:

[0031] (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.

[0032] (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.

[0033] (3) PVC is commercially available SG-3 type PVC with a degree of polymerization of 1300.

[0034] (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.

[0035] 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.

[0036] Part 1 Preparation of Flame Retardant PVC Rear Projection Film

[0037] This part provides the ingredients and preparation processes of 4 kinds of comparative flame retardant PVC rear projection films and 5 kinds of flame retardant PVC rear projection films of the present invention. The following ingredients are in parts by weight, where 100 parts by weight of PVC is used as the reference benchmark for the ingredient dosage, which is a common form of ingredient representation.

[0038] Comparative Example 1 Ingredients of Flame Retardant PVC Rear Projection Film (in parts by weight)

[0039] 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 part of gelation accelerator, 3.3 parts of powder acrylonitrile-butadiene rubber, 30 parts of DPK.

[0040] Comparative Example 2 Ingredients of Flame Retardant PVC Rear Projection Film (in parts by weight)

[0041] 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 part of gelation accelerator, 3 parts of liquid acrylonitrile-butadiene rubber, 30 parts of DPK, 2 parts of antimony trioxide.

[0042] Comparative Example 3 Ingredients of Flame Retardant PVC Rear Projection Film (in parts by weight)

[0043] 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 part of gelation accelerator, 3 parts of liquid acrylonitrile-butadiene rubber, 33 parts of TBEP, 5 parts of aluminum hydroxide, 10 parts of modified talc powder.

[0044] Comparative Example 4 Ingredients of Flame Retardant PVC Rear Projection Film (in parts by weight)

[0045] 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 part of gelation accelerator, 3 parts of liquid acrylonitrile-butadiene rubber, 20 parts of DPK, 13 parts of WSFR-BDP, 15 parts of aluminum hydroxide.

[0046] Example 1 Ingredients of Flame Retardant PVC Rear Projection Film (in parts by weight)

[0047] 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, 5 parts of modified talc powder.

[0048] Example 2 Ingredients of Flame Retardant PVC Rear Projection Film (by weight)

[0049] 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, 10 parts of modified talc powder.

[0050] Example 3 Ingredients of Flame Retardant PVC Rear Projection Film (by weight)

[0051] 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 polymethylhydrosiloxane, 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, 10 parts of modified talc powder.

[0052] Example 4 Ingredients of Flame Retardant PVC Rear Projection Film (by weight)

[0053] 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, 10 parts of modified talc powder.

[0054] Example 5 Ingredients of Flame Retardant PVC Rear Projection Film (by weight)

[0055] 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, 10 parts of modified talc powder.

[0056] Preparation Method of Flame Retardant PVC Rear Projection Film:

[0057] The preparation methods of the above comparative examples and examples of the flame-retardant PVC rear projection film are as follows:

[0058] (1) Mixing: According to the different formulas of the examples and comparative examples, weigh the corresponding materials and put them into a high-speed mixer to stir and mix evenly. Control the temperature at 120°C ± 10°C and the stirring time at 6 min - 10 min. After stirring, put the raw materials into a low-speed mixer to stir and cool down to 80°C - 100°C;

[0059] (2) Plasticization: Add the raw materials obtained in step (1) into a planetary machine for extrusion and plasticization. Control the temperature of the extruder at 160°C - 190°C. Transfer it to a two-roll calender for further plasticization, and control the temperature of the calender at 190°C - 220°C;

[0060] (3) Filtration: After sufficient plasticization, filter impurities through a filter. Select the mesh number of the filter screen to be 80 - 120 meshes, and control the temperature at 170°C - 200°C;

[0061] (4) Forming: Enter a four-roll calender for calendering and forming, and control the temperature at 165°C - 210°C;

[0062] (5) After forming, perform embossing, cold cutting, edge trimming, and winding in sequence.

[0063] The second part: Performance investigation of the flame-retardant PVC rear projection film

[0064] The following are the tests and results of the performance and other indicators of the flame-retardant PVC rear projection film of the examples and comparative examples.

[0065] 1. Environmental protection

[0066] The European Union's "Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals" is abbreviated as "REACH". This test item aims to investigate whether the product meets the requirements of "REACH".

[0067] According to the formulas of the comparative examples and examples, calculate the content (mass fraction, wt%) of TPP in the environmentally friendly flame-retardant PVC rear projection film. The TPP content is calculated based on the highest content in the raw materials. Among them, the TPP content in the DPK raw material is 11.9%, the TBEP raw material and the WSFR-PCF raw material do not contain TPP, the TPP content in the WSFR-BDP raw material is ≤ 1.5 wt%, the TPP content in the DPOP raw material is below 1000 ppm, and the TPP content in the WSFR-9702 raw material is below 3500 ppm; the calculation results are shown in Table 1:

[0068] Table 1 Content of hazardous substances in the samples of the comparative examples and examples

[0069]

[0070] REACH Regulation - When the mass fraction of substances in the candidate list of substances of very high concern (SVHC) in an article exceeds 0.1%, and the amount of this substance entering the EU per year exceeds 1 ton / year / company, the producer or importer of this 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 Regulation.

[0071] 2. Light transmittance

[0072] The light transmittance of the environmentally friendly flame-retardant PVC rear projection film samples of the comparative examples and the examples was tested. The test method is as follows: Use a transmission densitometer, press the measurement button, and the instrument will automatically measure and display the transmission density value (OD) of the sample. 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 light transmittance (T) can be calculated by the following formula:

[0073]

[0074] The test results are shown in Table 2:

[0075] Table 2 Light transmittance of the samples of the comparative examples and the examples

[0076]

[0077] The environmentally friendly flame-retardant PVC rear projection film prepared by the present invention shows great advantages in terms of light transmittance compared with the sample added with antimony trioxide (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), effectively overcoming the problem of PVC films that cannot balance environmental protection, light transmittance and flame retardancy performance. The light transmittance results shown in the examples of the present invention are not the highest values. During actual production, the light transmittance of the projection film can be further improved by reducing the amount of calcium carbonate. For example: in Comparative Example 3, no calcium carbonate was added, and the light transmittance could reach 85.11%.

[0078] 3. Dynamic heat resistance

[0079] The dynamic heat resistance performance of the samples of Comparative Examples 1 and 3 and Examples 1 and 4 was tested using a two-roll mill. The temperature was set at 180 °C, the rotational speed of the front roller was set at 23 rpm, the rotational speed of the rear roller was set at 18 rpm, and the roller gap was set at 0.3 mm. The corresponding raw materials were weighed according to the ratios in different formulations. After being mixed evenly, they were poured into the gap between the two rollers of the two-roll mill for kneading. After kneading, a PVC sample was taken from the front roller every 5 minutes until 25 minutes. The sample taken at 5 minutes of kneading was used as the original sample. The Lab values of all the taken samples were tested using a color difference meter, and the color difference (ΔE) and yellowness change value (Δb) between them and the original sample were calculated. The larger the value, the worse the thermal stability. The calculation formulas are as follows:

[0080]

[0081]

[0082] The test results are shown in Table 3:

[0083] Table 3 Test Results of Dynamic Heat Resistance Performance of Some Comparative Examples and Examples

[0084]

[0085] From the results of Comparative Example 3, it can be seen that even when the dosage of its heat stabilizer is increased to 7.5 parts, its yellowness change value and color difference value are still much higher than those of other comparative examples and examples. Although Comparative Example 3 uses a phosphorus-based flame retardant and an inorganic flame retardant of aluminum hydroxide + modified talc powder, and has a low TPP content and a high light transmittance, its yellowness change value and color difference value are much higher than those of the flame-retardant rear projection films of the examples.

[0086] 4. Flame Retardancy

[0087] The oxygen index and flame retardancy of the environmentally friendly flame-retardant PVC rear projection film samples of the comparative examples and examples were tested. The test methods refer to the following standards: GB / T 5454-1997 "Textiles - Test for Flammability - Oxygen Index Method"; DIN4102-1 "Fire Performance of Building Materials and Elements - Part 1: Requirements and Classification of Test for Building Materials";

[0088] The test results are shown in Table 4:

[0089] Table 4 Test Results of Combustion Performance of Samples of Comparative Examples and Examples

[0090]

[0091] The oxygen index and flame retardancy of the environmentally friendly flame-retardant PVC rear projection film prepared by the present invention are at the same level as those of the PVC film sample (Comparative Example 2) added with antimony trioxide and DPK; compared with the PVC film sample (Comparative Example 1) only added with DPK, the flame retardancy is improved and can pass the DIN4102 B2 grade; and the flame retardancy is higher than that of the sample of Comparative Example 3 using a phosphorus-based flame retardant and an inorganic flame retardant of aluminum hydroxide + modified talc powder.

[0092] This result clearly shows that on the basis of maintaining the ultra-high light transmittance of the environmentally friendly flame-retardant PVC rear projection film, if we want to further improve the flame retardancy of the film, 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 compared with the prior art.

[0093] 5. Whitening phenomenon

[0094] The whitening phenomenon of PVC refers to the phenomenon that the PVC material turns white at the bent part after being subjected to external forces such as bending. For example, after the PVC edge banding strip is bent into a small arc, the bent part will turn white, and this whitening will not recover even if the edge banding strip is straightened again.

[0095] The environmentally friendly flame-retardant PVC rear projection film samples of the comparative examples and the examples were subjected to whitening detection, and the test method was as follows: under natural light, the tester observed the surface of the PVC projection film with normal vision to check whether there was a whitening phenomenon. The test results are shown in Table 5:

[0096] Table 5 Detection results of whitening phenomenon of samples of comparative examples and examples

[0097]

[0098] It can be seen from the comparison of the results of Comparative Example 4 and the examples that when the content of aluminum hydroxide is relatively high, although the flame retardant effect and the light transmittance effect are good, it will cause the projection film to have a whitening phenomenon, which affects its actual use; while using the compound of modified talc powder and aluminum hydroxide can improve this phenomenon and can maintain the same flame retardant effect as it.

[0099] In summary, the environmentally friendly flame-retardant PVC rear projection film and its preparation method provided by the present invention have significant advantages. The product fully meets the environmental protection requirements of the REACH regulation; while maintaining an ultra-high light transmittance, it also meets the flame-retardant requirements of DIN4102 B2 grade and will not produce other negative effects, such as yellowing, white creasing, etc. This innovative achievement provides a good foundation for improving the compliance of product exports and creating practical 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 helps to promote the PVC material industry to move towards a more green and sustainable direction, injecting new vitality into the long-term development of the industry.

[0100] Obviously, the environmentally friendly flame-retardant rear projection films provided in the above Examples 1-5 of the present invention are only partial examples of the present invention. Within the scope of the present invention, its flame retardancy and transparency can still be further improved, and the environmentally friendly flame-retardant rear projection films provided in Examples 1-5 are only examples that meet the compliance requirements and the basic flame retardancy and light transmittance performance requirements of the rear projection film. 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 light transmittance can reach 89%, and the environmental protection and white creasing phenomena 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 epoxidized soybean oil, 5 parts of liquid barium-zinc stabilizer, 1.3 parts of polymethylsilsesquioxane, 0.3 parts of gelation 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 powder (the preparation method is the same as the first part of the example), the LOI of the sample can reach 29.5%, the light transmittance can reach 89.1%, and the environmental protection and white creasing phenomena 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); the refractive index of the aluminum hydroxide is 1.57; the modified talc is talc modified by a silane coupling agent, and the refractive index is 1.58-1.

59.

2. 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.

3. 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.

4. 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.

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

6. 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.

7. 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.

8. The method for preparing an environmentally friendly flame-retardant PVC rear projection film according to any one of claims 1 to 7, 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 S1 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 S4 is sequentially embossed, cold-cut, trimmed, and rolled to obtain the environmentally friendly flame-retardant PVC rear projection film.

9. Use of the environmentally friendly flame-retardant PVC rear projection film according to any one of claims 1 to 7 as a rear projection film.

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