Special material for halogen-free flame-retardant recycled PET sheet for steel coil packaging and preparation method thereof

Abstract

The present invention relates to a PET sheet, specifically a special material for halogen-free flame-retardant recycled PET sheet for steel coil packaging and a preparation method thereof, belonging to the technical field of PET sheet manufacturing. It includes PET resin, antioxidant, toughening agent, glass fiber cloth and crystallization accelerator. The intrinsic viscosity value of the PET resin is 0.53 - 0.65 dl / g. The antioxidant uses fat-soluble natural materials. The toughening agent is selected from maleic anhydride graft compatibilizers. The crystallization accelerator is used to improve the crystallization rate of the material. The PET resin is processed and formed by injection molding. High-quality dimethyl terephthalate and ethylene glycol ester materials are selected and combined in a ratio of 1:3, and synthesized by the esterification method. And the glass fiber cloth is laid flat in the middle layer of the mold, so that the glass fiber is completely wrapped and fixed inside the PET resin. By adding an integrally formed glass fiber cloth inside the sheet, the rigidity of the sheet can be improved, the tear resistance of the material can be enhanced, and the flame-retardant protection effect of the sheet can be comprehensively improved.

Description

Technical Field

[0001] The present invention relates to a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging and a preparation method thereof, belonging to the technical field of PET sheet manufacturing. Background Art

[0002] PET sheets, white, are a kind of material, mainly composed of polyethylene terephthalate PET and polybutylene terephthalate PBT. Polyethylene terephthalate glycol is also commonly known as polyester resin. It is a condensate of terephthalic acid and ethylene glycol, and together with PBT is collectively called thermoplastic polyester, or saturated polyester. PET and PBT, as thermoplastic polyesters together, become one of the five major engineering plastics. The main characteristics of PET sheets: high mechanical strength, stiffness, and hardness. Good sliding performance and wear resistance, good electrical insulation, very good creep resistance, low and stable friction coefficient, excellent wear resistance (better than nylon), very good dimensional stability (better than POM), physiological inertness (suitable for contact with food). Good weather resistance, good chemical resistance stability, low water absorption, resistant to weak acids and organic solvents, but not resistant to hot water immersion and not resistant to alkalis.

[0003] A prior art special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging (publication number CN109735065B) is prepared from recycled PET, toughening agent, aluminum diethylphosphinate, polyacrylonitrile powder, and antioxidant raw materials. The weight parts of each raw material are: 100 parts of recycled PET, 5 - 10 parts of toughening agent, 5 - 9 parts of aluminum diethylphosphinate, 2 - 5 parts of polyacrylonitrile powder, and 0.5 - 1.5 parts of antioxidant. The preparation method of the special material is also disclosed, including the following steps: 1) drying the recycled PET; 2) stirring and mixing the dried recycled PET with the toughening agent, aluminum hypophosphite, polyacrylonitrile powder, and antioxidant to obtain a mixture; 3) melt-extruding and pelletizing the mixture through a twin-screw extruder under vacuum conditions. The recycled PET sheets prepared with the special material of the present invention have the characteristics of high tensile strength, excellent flame-retardant effect, good impact resistance, and good processing fluidity, and can be used in the field of steel coil packaging.

[0004] The materials of the finished products obtained by the above method have relatively balanced performances in all aspects and excellent protection effects on external devices. However, its overall rigidity is weak, the tear resistance is poor, and it is easily scratched by sharp objects from the outside. Summary of the Invention

[0005] The purpose of the present invention is to provide a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging and a preparation method thereof, which can improve the tear resistance of the finished product and enhance the protection effect of the material.

[0006] The present invention realizes the above object through the following technical solutions. A special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging and a preparation method thereof, including PET resin, antioxidant, toughening agent, glass fiber cloth and crystallization accelerator. The intrinsic viscosity value of the PET resin is 0.53 - 0.65 d l / g. The antioxidant uses fat-soluble natural materials. The toughening agent is selected from maleic anhydride graft compatibilizers. The crystallization accelerator is used to increase the crystallization rate of the material.

[0007] Preferably, in order to improve the flexibility during material production, the PET resin is chemically synthesized from dimethyl terephthalate and ethylene glycol ester, and terephthalic acid and ethylene glycol ester. The PET resin selects one of APET, RPET and PETG.

[0008] Preferably, in order to improve the strength of the glass fiber cloth, the glass fiber cloth is made of glass raw materials and sizing agent raw materials. The glass raw materials are processed through glass components. The sizing agent raw materials use styrene-butadiene rubber and pure acrylic emulsion. The glass raw materials are prepared by adding 14.5% - 16.7% of zirconia and 6% of titanium dioxide to the glass components.

[0009] Preferably, in order to improve the protection effect of the material, the antioxidant is selected from alcohol ester antioxidants, phenolic ester antioxidants, and phosphite antioxidants. The mass ratio between the antioxidant and the PET resin is 2:1000.

[0010] Preferably, in order to improve the strength of the finished product, the mass ratio between the toughening agent and the PET resin is 5:1000. The maleic anhydride graft compatibilizer includes styrene-butadiene thermoplastic elastomer, methyl methacrylate-butadiene-styrene terpolymer, acrylonitrile-butadiene-styrene copolymer, chlorinated polyethylene, and ethylene-vinyl acetate copolymer.

[0011] Preferably, in order to accelerate the manufacturing efficiency of the PET resin, the crystallization accelerator is selected from various aluminides. The mass ratio between the crystallization accelerator and the PET resin is 8:1000.

[0012] A preparation method of a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging, the steps are as follows:

[0013] S2. Manufacture the glass fiber cloth.

[0014] S21. Manufacture glass fibers. The prepared glass raw materials are melted at a high temperature of 1600 °C and drawn into continuous filaments by a platinum leak, and then combined and twisted into textile glass fibers. A film is evenly formed on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency.

[0015] S22. Weaving and forming: Weave the glass fiber into a gauze shape, then evenly apply the sizing agent raw material on its surface, and use the skills of constant temperature, constant speed and constant tension control to make it adhere fully.

[0016] S3. Fusion and shaping: Process and form the PET resin by injection molding, and lay the glass fiber cloth flat in the middle layer of the mold, so that the glass grid is completely wrapped and fixed inside the PET resin, and then carry out cooling and shaping.

[0017] S4. Adding a protective layer: Use the masterbatch of the PET resin made of environmentally friendly flame retardant material to process and form a flame retardant film by stretching the film, and use the flame retardant film to cover both sides of the shaped product to be cooled. Then, while carrying out secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0018] Preferably, in order to improve the convenience of material manufacturing, the esterification method includes indirect esterification method and direct esterification method. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid and excessive ethylene glycol at 200 °C into low-polymerization-degree polyethylene terephthalate, and then carry out final polycondensation at 280 °C into high-polymerization-degree final polyester products.

[0019] The beneficial effects of the present invention are: By adding an integrally formed glass fiber cloth inside the sheet, the rigidity of the sheet can be improved, the tear resistance of the material can be enhanced, and the flame retardant and protective effect of the sheet can be comprehensively improved. Description of the Drawings

[0020] Figure 1 It is a flow chart of the preparation method of the present invention.

[0021] Figure 2 It is an experimental data table of the present invention. Detailed Embodiments

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0023] Please refer to Figure 1-2As shown, a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging and its preparation method include PET resin, antioxidant, toughening agent, glass fiber cloth, and crystallization accelerator. The intrinsic viscosity value of the PET resin is 0.53 - 0.65 dL / g. The antioxidant is a fat-soluble natural material. The toughening agent is selected from maleic anhydride graft compatibilizers. The crystallization accelerator is used to increase the crystallization rate of the material.

[0024] As Figure 1 shown, the PET resin is chemically synthesized from dimethyl terephthalate and ethylene glycol ester, and terephthalic acid and ethylene glycol ester. The PET resin is selected from one of APET (polyethylene terephthalate), RPET (recycled polyethylene terephthalate), and PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester) to improve the flexibility during material production.

[0025] As Figure 1 shown, the glass fiber cloth (a mesh material made of glass fiber) is made from glass raw materials and sizing agent raw materials. The glass raw materials are processed from glass components. The sizing agent raw materials use styrene-butadiene rubber and pure acrylic emulsion. The glass raw materials are prepared by adding 14.5% - 16.7% zirconia and 6% titanium dioxide to the glass components to improve the strength of the glass fiber cloth.

[0026] As Figure 1 shown, the antioxidant is selected from alcohol ester antioxidants, phenol ester antioxidants, and phosphite antioxidants. The mass ratio between the antioxidant and the PET resin is 2:1000 to improve the protection effect of the material.

[0027] As Figure 1 shown, the mass ratio between the toughening agent and the PET resin is 5:1000. The maleic anhydride graft compatibilizer includes styrene-butadiene thermoplastic elastomer, methyl methacrylate-butadiene-styrene terpolymer, acrylonitrile-butadiene-styrene copolymer, chlorinated polyethylene, and ethylene-vinyl acetate copolymer to improve the strength of the finished product.

[0028] As shown, the crystallization accelerator is selected from various aluminum compounds. The mass ratio between the crystallization accelerator and the PET resin is 8:1000 to accelerate the manufacturing efficiency of the PET resin.

[0029] As shown, a preparation method for a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging has the following steps:

[0030] S2. Manufacture the glass fiber cloth.

[0031] S21. Manufacture fiberglass. Melt the prepared glass raw materials at a high temperature of 1600 °C, draw them into continuous filaments by a platinum leak, twist and splice them into textile fiberglass, and uniformly form a film on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency;

[0032] S22. Weave and shape. Weave the fiberglass into a leno shape, then evenly apply the sizing agent raw materials on its surface, and use the skills of constant temperature, constant speed and constant tension control to make it fully adhered;

[0033] S3. Fusion and shaping. Process the PET resin by injection molding, and lay the glass grid cloth flat in the middle layer of the mold, so that the glass grid is completely wrapped and fixed inside the PET resin, and then cool and shape it;

[0034] S4. Add a protective layer. Use the masterbatch of the PET resin made of environmentally friendly flame retardant materials to draw a film into a flame retardant film, and use the flame retardant film to cover both sides of the shaped product to be cooled. Then, while performing secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0035] As Figure 1 shown, the esterification method includes indirect esterification method and direct esterification method. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid and excess ethylene glycol into low-polymerization-degree polyethylene terephthalate at 200 °C, and then carry out final polycondensation into high-polymerization-degree final polyester products at 280 °C to facilitate the manufacturing convenience of the materials.

[0036] When the present invention is in use,

[0037] Example 1

[0038] Select an appropriate amount of PET resin made of APET material, antioxidant, toughening agent, fiberglass cloth, and crystallization accelerator materials, and adjust the ratio among the PET resin, antioxidant, toughening agent, fiberglass cloth, and crystallization accelerator to 1000:2:5:300:8. The intrinsic viscosity value of the PET resin is 0.60 d l / g. Select alcohol ester-based antioxidants, and select styrene-butadiene thermoplastic elastomer as the toughening agent. Add 15% zirconia and 6% titanium dioxide to the glass raw materials. Use fat-soluble natural materials for the antioxidant, select from maleic anhydride graft compatibilizers for the toughening agent. The crystallization accelerator is used to increase the crystallization rate of the material. Select high-quality dimethyl terephthalate and ethylene glycol ester materials and combine them in a ratio of 1:3, and use the esterification method for synthesis. The esterification method includes indirect esterification and direct esterification. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid and excessive ethylene glycol at 200 °C into low-polymerization-degree polyethylene terephthalate, and then conduct final polycondensation at 280 °C into high-polymerization-degree final polyester products. The methyl esterification is the reaction of terephthalic acid and slightly excessive methanol to first esterify into dimethyl terephthalate; distill out water, excessive methanol, methyl benzoate and other low-boiling substances, and then obtain pure dimethyl terephthalate through rectification. The transesterification refers to at 190 - 200 °C, using cadmium acetate and antimony trioxide as catalysts to conduct transesterification reaction between dimethyl terephthalate and ethylene glycol to form polyester oligomers. Distill out methanol to make the transesterification sufficient; the final polycondensation refers to at a temperature higher than the melting point of polyester, such as 283 °C, using antimony trioxide as a catalyst to conduct self-condensation or transesterification of polyethylene terephthalate glycol ester, and continuously distill out the by-product ethylene glycol under reduced pressure and high temperature to gradually increase the degree of polymerization.

[0039] Melt the prepared glass raw materials at a high temperature of 1600 °C, draw them into continuous filaments by a platinum leak, and twist them into textile glass fibers. Uniformly form a film on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency. Weave the glass fibers into a leno shape. Then, evenly apply the sizing agent raw materials on its surface and use the constant temperature, constant speed, and constant tension control technology to make it adhere fully. Use injection molding to process the PET resin into a shape, and lay the fiberglass cloth flat in the middle layer of the mold, so that the fiberglass grid is completely wrapped and fixed inside the PET resin, and then conduct cooling and shaping. Use the masterbatch of the PET resin made of environmentally friendly flame-retardant material to conduct film drawing to process into a flame-retardant film, and use the flame-retardant film to double-cover the shaped product after cooling. Then, while conducting secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0040] Example 2

[0041] Select an appropriate amount of PET resin made of APET material, antioxidant, toughening agent, fiberglass mesh cloth, and crystallization accelerator material, and adjust the ratio between the PET resin, antioxidant, toughening agent, fiberglass mesh cloth, and crystallization accelerator to 1000:2:5:200:8. The intrinsic viscosity value of the PET resin is 0.60 d l / g. Select alcohol ester-based antioxidants, and use styrene-butadiene thermoplastic elastomer as the toughening agent. Add 15% zirconium dioxide and 6% titanium dioxide to the glass raw materials. Use fat-soluble natural materials for the antioxidant, and select the toughening agent from maleic anhydride graft compatibilizers. The crystallization accelerator is used to increase the crystallization rate of the material. Select high-quality dimethyl terephthalate and ethylene glycol ester materials, and combine them in a ratio of 1:3, and use the esterification method for synthesis. The esterification method includes indirect esterification and direct esterification. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid with excess ethylene glycol at 200 °C to form low-polymerization-degree polyethylene terephthalate, and then carry out final polycondensation at 280 °C to form a high-polymerization-degree final polyester product. The methyl esterification is the reaction of terephthalic acid with slightly excess methanol to first esterify into dimethyl terephthalate; distill out water, excess methanol, methyl benzoate and other low-boiling substances, and then through rectification, pure dimethyl terephthalate is obtained. The transesterification refers to reacting dimethyl terephthalate with ethylene glycol at 190-200 °C using cadmium acetate and antimony trioxide as catalysts to carry out transesterification reaction to form polyester oligomers. Distill out methanol to make the transesterification sufficient; the final polycondensation refers to at a temperature higher than the melting point of polyester, such as 283 °C, using antimony trioxide as a catalyst, making polyethylene terephthalate self-condense or transesterify, and continuously distill out the by-product ethylene glycol under reduced pressure and high temperature to gradually increase the degree of polymerization.

[0042] Melt the prepared glass raw materials at a high temperature of 1600 °C, draw them into continuous filaments by a platinum leak, splice and twist them into textile glass fibers, and uniformly form a film on the raw filaments to reduce the fiber hairiness of the raw filaments and improve the weaving production efficiency. Weave the glass fibers into a gauze shape, and then evenly apply the sizing agent raw materials on its surface, and use the constant temperature, constant speed, and constant tension control technology to make it adhere fully. Process the PET resin by injection molding, and lay the fiberglass mesh cloth flat in the middle position of the mold, so that the fiberglass mesh is completely wrapped and fixed inside the PET resin, and carry out cooling and shaping. Use the masterbatch of the PET resin made of environmentally friendly flame-retardant material to carry out film drawing to process into a flame-retardant film, and use the flame-retardant film to double-cover the shaped product after cooling. Then, while carrying out secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0043] Example 3

[0044] Select an appropriate amount of PET resin made of APET material, antioxidant, toughening agent, fiberglass cloth, and crystallization accelerator materials, and adjust the ratio between the PET resin, antioxidant, toughening agent, fiberglass cloth, and crystallization accelerator to 1000:2:5:500:8. The intrinsic viscosity value of the PET resin is 0.60 d l / g. Select alcohol ester-based antioxidants, and choose styrene-butadiene thermoplastic elastomer as the toughening agent. Add 15% zirconium dioxide and 6% titanium dioxide to the glass raw materials. Use fat-soluble natural materials for the antioxidant, and select from maleic anhydride graft compatibilizers for the toughening agent. The crystallization accelerator is used to increase the crystallization rate of the material. Select high-quality dimethyl terephthalate and ethylene glycol ester materials and combine them in a ratio of 1:3, and use the esterification method for synthesis. The esterification method includes indirect esterification and direct esterification. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid and excess ethylene glycol at 200 °C into low-polymerization-degree polyethylene terephthalate, and then finally polycondense it into a high-polymerization-degree final polyester product at 280 °C. The methyl esterification is the reaction of terephthalic acid with slightly excess methanol to first esterify into dimethyl terephthalate; distill out water, excess methanol, methyl benzoate and other low-boiling substances, and then obtain pure dimethyl terephthalate through rectification. The transesterification refers to the transesterification reaction of dimethyl terephthalate and ethylene glycol at 190 - 200 °C using cadmium acetate and antimony trioxide as catalysts to form polyester oligomers. Distill out methanol to make the transesterification sufficient; the final polycondensation refers to self-condensation or transesterification of polyethylene terephthalate at a temperature higher than the melting point of polyester, such as 283 °C, using antimony trioxide as a catalyst, continuously distilling out the by-product ethylene glycol under reduced pressure and high temperature, and gradually increasing the degree of polymerization.

[0045] Melt the prepared glass raw materials at a high temperature of 1600 °C, draw them into continuous filaments by a platinum leak, and twist and combine them into textile glass fibers. Uniformly form a film on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency. Weave the glass fibers into a leno shape, and then evenly apply the sizing agent raw materials on its surface, and use the constant temperature, constant speed, and constant tension control technology to make it adhere fully. Use the injection molding method to process and form the PET resin, and lay the fiberglass cloth flat in the middle layer of the mold, so that the fiberglass grid is completely wrapped and fixed inside the PET resin, and then cool and shape it. Use the masterbatch of the PET resin made of environmentally friendly flame-retardant material to perform film drawing processing into a flame-retardant film, and use the flame-retardant film to double-cover the shaped product after cooling. Then, while performing secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0046] Example 4

[0047] Select an appropriate amount of PET resin made of APET material, antioxidant, toughening agent, fiberglass mesh cloth, and crystal accelerator materials, and adjust the ratio between the PET resin, antioxidant, toughening agent, fiberglass mesh cloth, and crystal accelerator to 1000:2:5:300:16. The intrinsic viscosity value of the PET resin is 0.60 d l / g. Select alcohol ester-based antioxidants, and choose styrene-butadiene thermoplastic elastomer as the toughening agent. Add 15% zirconium dioxide and 6% titanium dioxide to the glass raw materials. Use fat-soluble natural materials as the antioxidant, and select from maleic anhydride graft compatibilizers as the toughening agent. The crystal accelerator is used to increase the crystallization rate of the material. Select high-quality dimethyl terephthalate and ethylene glycol ester materials and combine them in a ratio of 1:3, and use the esterification method for synthesis. The esterification method includes indirect esterification and direct esterification. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method is to first esterify terephthalic acid with excessive ethylene glycol at 200°C into low-polymerization-degree polyethylene terephthalate, and then carry out final polycondensation at 280°C into high-polymerization-degree final polyester products. The methyl esterification is the reaction of terephthalic acid with slightly excessive methanol to first esterify into dimethyl terephthalate; distill out water, excess methanol, methyl benzoate and other low-boiling substances, and then through rectification, pure dimethyl terephthalate can be obtained. The transesterification refers to at 190 - 200°C, using cadmium acetate and antimony trioxide as catalysts to carry out transesterification reaction between dimethyl terephthalate and ethylene glycol to form polyester oligomers. Distill out methanol to make the transesterification sufficient; the final polycondensation refers to at a temperature higher than the melting point of polyester, such as 283°C, using antimony trioxide as a catalyst to carry out self-condensation or transesterification of ethylene glycol terephthalate, and continuously distill out the by-product ethylene glycol by reducing pressure and increasing temperature to gradually increase the degree of polymerization.

[0048] Melt the prepared glass raw materials at a high temperature of 1600°C, draw them into continuous filaments by a platinum leak, and twist and combine them into textile glass fibers. Uniformly form a film on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency. Weave the glass fibers into a gauze shape, and then evenly apply the sizing agent raw materials on its surface, and use the constant temperature, constant speed, and constant tension control technology to make it fully adhered. Use the injection molding method to process and form the PET resin, and lay the fiberglass mesh cloth flat in the middle position of the mold, so that the fiberglass mesh is completely wrapped and fixed inside the PET resin, and then carry out cooling and shaping. Use the masterbatch of the PET resin made of environmentally friendly flame-retardant material to carry out film drawing to process into a flame-retardant film, and use the flame-retardant film to double-cover the shaped product after cooling. Then, while carrying out secondary heating, extrude it to make the bonding surfaces fuse with each other.

[0049] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0050] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A special material for halogen-free flame-retardant recycled PET sheets used for steel coil packaging, characterized in that: It includes PET resin, antioxidant, toughening agent, glass fiber cloth and crystallization accelerator. The intrinsic viscosity value of the PET resin is 0.53 - 0.65 dl / g. The antioxidant uses fat-soluble natural materials. The toughening agent is selected from maleic anhydride graft compatibilizers. The crystallization accelerator is used to increase the crystallization rate of the material.

2. The special material for halogen-free flame-retardant recycled PET sheet used for steel coil packaging according to claim 1, wherein: The PET resin is chemically synthesized from dimethyl terephthalate and ethylene glycol ester, terephthalic acid and ethylene glycol ester. The PET resin selects one of APET, RPET and PETG.

3. The special material for halogen-free flame-retardant recycled PET sheet used for steel coil packaging according to claim 1, wherein: The glass fiber cloth is made of glass raw materials and sizing agent raw materials. The glass raw materials are processed through glass components. The sizing agent raw materials use styrene-butadiene rubber and pure acrylic emulsion. The glass raw materials are prepared by adding 14.5% - 16.7% of zirconium dioxide and 6% of titanium dioxide to the glass components.

4. The special material for halogen-free flame-retardant recycled PET sheets used for steel coil packaging according to claim 1, wherein: The antioxidant is selected from alcohol ester antioxidants, phenolic ester antioxidants, and phosphite antioxidants. The mass ratio between the antioxidant and the PET resin is 2:1000.

5. The special material for halogen-free flame-retardant recycled PET sheets used for steel coil packaging according to claim 1, wherein: The mass ratio between the toughening agent and the PET resin is 5:1000. The maleic anhydride graft compatibilizer includes styrene-butadiene thermoplastic elastomer, methyl methacrylate-butadiene-styrene terpolymer, acrylonitrile-butadiene-styrene copolymer, chlorinated polyethylene, and ethylene-vinyl acetate copolymer.

6. The special material for halogen-free flame-retardant recycled PET sheet used for steel coil packaging according to claim 1, wherein: The crystallization accelerator is selected from various aluminides. The mass ratio between the crystallization accelerator and the PET resin is 8:1000.

7. A preparation method of a special material for halogen-free flame-retardant recycled PET sheet for steel coil packaging, characterized in that, According to any one of claims 1 to 6, a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging, when being prepared, its steps are as follows: S1. Synthesize the PET resin, select high-quality dimethyl terephthalate and ethylene glycol ester materials, combine them in a ratio of 1:3, and use the esterification method for synthesis; S2. Manufacture the glass fiber cloth; S21. Manufacture glass fibers, melt the prepared glass raw materials at a high temperature of 1600 °C, draw them into continuous filaments by a platinum leak, twist and splice them into textile glass fibers, and form a film evenly on the raw filaments to reduce the hairiness of the raw filaments and improve the weaving production efficiency; S22. Weave and form, weave the glass fibers into a leno shape, then evenly apply the sizing agent raw materials on its surface, and use the skills of constant temperature, constant speed and constant tension control to make it fully adhered; S3. Fusion molding, use injection molding to process and form the PET resin, and lay the glass fiber cloth flat in the middle position of the mold, so that the glass grid is completely wrapped and fixed inside the PET resin, and then carry out cooling molding; S4. Add a protective layer, use the masterbatch of the PET resin made of environmentally friendly flame-retardant materials to draw a film into a flame-retardant film, and use the flame-retardant film to cover both sides of the molded product to be cooled. Then, while performing secondary heating, extrude it to make the bonding surfaces fuse with each other.

8. The preparation method of a special material for halogen-free flame-retardant recycled PET sheets for steel coil packaging according to claim 7, characterized in that: The esterification method includes an indirect esterification method and a direct esterification method. The direct esterification method consists of three steps: methyl esterification, transesterification, and final polycondensation. The direct esterification method involves esterifying terephthalic acid with excessive ethylene glycol at 200°C to form a low-degree-of-polymerization polyethylene terephthalate first, and then performing final polycondensation at 280°C to form a final polyester product with a high degree of polymerization.

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