A high-filler rPET substrate composite material and its preparation method, composite flooring

Abstract

This invention discloses a high-filler rPET substrate composite material and its preparation method, as well as a composite flooring, belonging to the field of polymer composite material technology. The composite material uses recycled PET (rPET) as the matrix, combined with 50-500 parts of multi-element inorganic mineral fillers, and compounded with toughening agents, lubricants, and optional processing aids. The high-filler rPET substrate is prepared through pretreatment, mixing, melt extrusion, calendering, and cooling processes. This substrate is then laminated with a surface decorative wear-resistant layer and a balanced backing layer to obtain the composite flooring. This invention overcomes the processing bottleneck of high-filler rPET, achieving ultra-high filling of inorganic minerals. The composite material possesses low cost, high rigidity, good processing stability, and excellent mechanical properties. Furthermore, it can be produced using existing SPC flooring production lines, offering significant environmental benefits and aligning with the circular economy and "dual-carbon" policy guidelines.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a composite material for flooring made of recycled polyethylene terephthalate (rPET) as the matrix, using a variety of inorganic minerals as highly filled fillers, and achieving stable extrusion through a compound toughening and lubrication system, as well as the preparation method thereof. Background Technology

[0002] In the field of building decoration materials such as SPC (stone-plastic composite flooring) and WPC (wood-plastic composite flooring), inorganic fillers are often added to the polymer matrix to reduce production costs and improve material rigidity. However, in traditional processes, the amount of inorganic fillers added is generally low due to limitations in material compatibility, processing fluidity, and final mechanical properties. For every 100 parts of resin, the filler content is usually less than 150 parts. Excessive filler content can lead to increased material brittleness, a sharp decrease in melt strength, difficulties in extrusion molding, and easy product breakage, making industrial-scale production difficult.

[0003] Recycling rPET, as an environmentally friendly recycled polymer material, can effectively reduce waste plastic pollution and dependence on virgin petroleum-based resins. However, the melt viscosity, crystallization behavior, and mechanical properties of rPET are far less stable than those of virgin PET, posing greater technical challenges to its application in high-filled inorganic mineral systems. While existing technologies have explored modifying rPET using elastomer grafts such as POE-g-GMA, these studies primarily focus on low-filled systems or solely on toughening effects, failing to systematically address the issue of stable industrial production of rPET under ultra-high filler conditions exceeding 200 parts per second. Furthermore, the design of the lubrication system is particularly critical in high-filled polymer systems. Existing lubrication schemes are often singular or poorly formulated, failing to simultaneously meet the dual requirements of internal lubrication to reduce melt viscosity and improve flowability, and external lubrication to prevent melt adhesion to processing equipment and improve demolding efficiency, further limiting the high-filler applications of rPET.

[0004] Therefore, there is an urgent need to develop a composite material formulation and molding process that can achieve high filling of rPET inorganic minerals, good processing stability, and excellent mechanical properties, while taking into account production costs and environmental protection, adapting to existing flooring production lines, and realizing industrial application. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing rPET composite materials, such as low filler ratio, high cost, and poor processing stability. It provides a composite material that can achieve high inorganic mineral filling in rPET, its preparation method, and a composite floor made from the composite material. This invention achieves a technological leap from fillable to high-filler stable production of rPET, while ensuring the material's high rigidity, good mechanical properties, and processability, reducing production costs, and improving environmental benefits.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a high-filler rPET substrate composite material, comprising the following components in parts by weight:

[0008] 100 portions of recycled PET (rPET) granules;

[0009] Inorganic mineral filler, 50-500 parts;

[0010] Toughening agent 5-30 parts;

[0011] 2-20 parts lubricant;

[0012] Processing aids 1-5 parts;

[0013] The processing aids include at least one of antioxidants, light stabilizers, coupling agents, and nucleating agents; the lubricant is a compound system containing at least one internal lubricant and at least one external lubricant.

[0014] As a further embodiment of the present invention, the inorganic mineral filler is 200-400 parts by weight, the toughening agent is 10-20 parts by weight, and the lubricant is 5-15 parts by weight.

[0015] As a further embodiment of the present invention, the inorganic mineral filler is 300-400 parts by weight and the lubricant is 10-15 parts by weight.

[0016] As a further embodiment of the present invention, the inorganic mineral filler is at least one of calcium carbonate, calcium sulfate, talc, kaolin, wollastonite, and mica powder.

[0017] As a further aspect of the present invention, the rPET particles are granulated from beverage bottle crushed material or polyester textile recycled material that has been modified by thickening or chain extension.

[0018] As a further aspect of the present invention, the toughening agent is selected from at least one of the following categories:

[0019] (1) Grafted elastomer toughening agent: at least one of the following: polyolefin elastomer grafted with glycidyl methacrylate (POE-g-GMA), ethylene propylene rubber grafted with glycidyl methacrylate (EPDM-g-GMA), polypropylene grafted with glycidyl methacrylate (PP-g-GMA), polypropylene grafted with maleic anhydride (PP-g-MAH), and low-density polyethylene grafted with acrylic acid (LDPE-g-AA);

[0020] (2) Copolymerized acrylate toughening agent: at least one of the following: ethylene-acrylate-glycidyl methacrylate terpolymer, methyl methacrylate-n-butyl acrylate-glycidyl methacrylate copolymer (GMA-MMA-BA), and isobornyl methacrylate-n-butyl acrylate-glycidyl methacrylate copolymer (GMA-IBOMA-BA);

[0021] (3) Thermoplastic elastomer: at least one of dynamic vulcanized thermoplastic elastomer (TPV), styrene-butadiene-styrene block copolymer (SBS), and styrene-ethylene-butene-styrene block copolymer (SEBS).

[0022] As a further aspect of the present invention, the lubricant is selected from at least two of the following categories:

[0023] (1) Hydrocarbon lubricants: polyethylene wax, oxidized polyethylene wax, paraffin wax, microcrystalline wax;

[0024] (2) Fatty acid lubricants: stearic acid, hydroxystearic acid;

[0025] (3) Fatty acid salt lubricants: calcium stearate, zinc stearate, magnesium stearate;

[0026] (4) Fatty acid ester lubricants: butyl stearate, glyceryl monostearate, pentaerythritol stearate;

[0027] (5) Polyester lubricants: polyethylene glycol fatty acid esters, polyester waxes;

[0028] (6) Amide lubricants: stearamide, oleamide, erucamide, ethylene bis-stearamide (EBS).

[0029] Secondly, the present invention also provides a method for preparing a high-filler rPET substrate composite material, comprising the following steps:

[0030] Pretreatment: Dry the inorganic mineral filler at 100-130℃ for ≤1 hour, controlling the moisture content to be below 0.5%;

[0031] Mixing: Place 100 parts of modified rPET granules, 50-500 parts of dry inorganic mineral filler, 5-30 parts of toughening agent, 2-20 parts of lubricant and optional processing aids into a high-speed mixer and mix at 80-120℃ for 5-15 minutes to make the additives evenly coat the surface of the filler.

[0032] Melt extrusion molding: The mixed material is fed into a 110-type conical twin-screw extruder. Gradient temperature control is adopted, with the temperature of each section controlled between 160-230℃, screw speed 15-30rpm, and vacuum degree -0.06 to -0.09MPa, so that the material is fully plasticized and degassed.

[0033] Calendering and cooling: After the molten material is extruded through a T-die, it is calendered, cooled, and drawn by a three-roll calender to obtain a substrate of a specified thickness.

[0034] Thirdly, the present invention also provides a composite flooring, comprising, from top to bottom, at least:

[0035] Surface decorative wear-resistant layer: a printed layer and a transparent wear-resistant layer stacked in sequence, or a wear-resistant layer with a printed pattern;

[0036] Core substrate layer: a highly filled rPET substrate obtained using composite materials and their preparation methods;

[0037] Balanced backing layer: a functional layer attached to the lower surface of the substrate layer, selected from at least one of IXPE foam, EVA foam, cork, and PET padding.

[0038] As a further aspect of the present invention, the materials of the printed layer and the transparent wear-resistant layer are each independently selected from at least one of PET, PETG, PE, and PP.

[0039] As a further embodiment of the present invention, the surface decorative wear-resistant layer is composited with the core substrate layer by a hot pressing process. The film is heated before entering the embossing roller, with the heating temperature between 75-120°C, the temperature of the embossing roller being 65-130°C, the pressure being 0.5-2.0 MPa, and the time from embossing to plate collection being 30-90 seconds. After composite, a UV coating hardening treatment is performed on the surface of the transparent wear-resistant layer.

[0040] As a further aspect of the present invention, the composite flooring is sawn and grooved, and then bonded to a balanced backing layer with an environmentally friendly adhesive to obtain the finished product.

[0041] Compared with the prior art, the high-filling rPET substrate composite material and its preparation method, as well as the composite flooring of the present invention, realize the stable industrial production of high-filling rPET inorganic minerals, and have the following beneficial effects:

[0042] 1. Diversified filling materials and wide adaptability of raw materials: Inorganic mineral fillers are no longer limited to calcium carbonate alone, but have been expanded to include calcium sulfate, talc, kaolin and other inorganic fillers commonly used in the flooring industry. They can be flexibly selected according to the cost and supply of raw materials, which greatly reduces the risk of material procurement and production costs.

[0043] 2. Optimized filling ratio, resulting in significant economic benefits: The inorganic mineral filling amount is expanded to 50-500 parts, covering the full range from conventional filling to extreme filling. The high filling range of 200-400 parts achieves the best balance between cost and performance, making the raw material cost of the flooring substrate significantly lower than that of traditional SPC flooring and conventionally filled rPET boards.

[0044] 3. Systematized toughening system with adjustable performance: Toughening agents cover three major categories of modified materials: grafted elastomers, copolymer acrylates, and thermoplastic elastomers. Different types of toughening agents play a synergistic role. For example, toughening agents containing epoxy groups (GMA) can react with rPET end groups, and have both toughening and chain extension functions. By compounding different toughening agents, a wide range of performance control of composite materials from high rigidity to high toughness can be achieved to meet the needs of different application scenarios.

[0045] 4. The lubrication system has been fully optimized to overcome the bottleneck of high-filler processing: the lubricants have been expanded to six categories and a compound lubrication design has been adopted. Polyester lubricants have excellent compatibility with rPET and provide high-temperature long-lasting lubrication. Amide lubricants have excellent external lubrication and demolding effects, which effectively solves engineering problems such as poor material flowability, easy sticking, uneven plasticization and melt fracture under high-filler systems, and ensures continuous industrial production.

[0046] 5. The substrate of this invention is mainly composed of recycled PET and natural inorganic minerals, which greatly reduces the dependence on virgin petroleum-based resins, while realizing the high-value recycling of waste plastics, reducing environmental pollution from waste plastics, and meeting the requirements of the circular economy and the "dual carbon" policy. It can be produced directly using existing mature SPC flooring production lines (110 type conical twin extruder and subsequent pressing and grooving equipment) without major equipment modifications, reducing the industrialization investment of enterprises and achieving rapid mass production.

[0047] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] Example 1

[0050] This invention provides a high-filled rPET substrate composite material, which belongs to a high-filled calcium carbonate system and comprises the following components by weight:

[0051] 100 parts of modified rPET particles;

[0052] 350 parts of dried heavy calcium carbonate (800 mesh);

[0053] 15 parts of POE-g-GMA toughening agent;

[0054] 14 parts of compound lubricant (calcium stearate: polyethylene wax: EBS = 2:1:1);

[0055] Antioxidant 0.5 parts.

[0056] In this embodiment, the method for preparing the composite material includes the following steps:

[0057] 1. Pretreatment: Dry the heavy calcium carbonate at 120℃ for 1 hour, controlling the moisture content to ≤0.5%;

[0058] 2. Mixing: Add all raw materials to a high-speed mixer according to the above proportions and mix at 100°C for 10 minutes;

[0059] 3. Melt extrusion: The mixture is fed into a 110-type conical twin-screw extruder, with the gradient temperature set at 170℃, 185℃, 195℃, 200℃, 205℃, and 200℃, the screw speed at 18 rpm, and the vacuum at -0.08 MPa for melt extrusion.

[0060] 4. Calendering and Cooling: After melt extrusion, the substrate is calendered, cooled, and drawn by a three-roll calender to obtain a high-filled rPET substrate A with a thickness of 4.5 mm.

[0061] In this embodiment, when preparing composite flooring based on high-fill rPET substrate A, the surface decorative wear-resistant layer of PET printing layer and PET transparent wear-resistant layer is laminated with substrate A. Before the film enters the embossing roller, it is heat-treated. The heating temperature is 120°C, the embossing roller temperature is 85°C, and the pressure is 1.0MPa. The time from embossing to board retraction of the embossing roller is 60 seconds. After UV coating and hardening, the groove is sawn and grooved. The IXPE foam balance backing layer is laminated with environmentally friendly adhesive to obtain the finished composite flooring.

[0062] Performance metrics:

[0063] Substrate: The surface is smooth and dense, with no visible pores or cracks; the bending strength is ≥25MPa, and there is no breakage when subjected to a falling ball impact (500g steel ball, 1m height); the dimensional shrinkage rate is ≤0.3%; the melt flow rate is stable; and there is no stick clamping or melt breakage during the extrusion process.

[0064] Composite flooring: abrasion resistance ≥6000 revolutions, scratch resistance ≥3 level, excellent dimensional stability, no warping or cracking in temperature and humidity cycle tests, excellent abrasion resistance, comfortable underfoot feel, and good dimensional stability.

[0065] Example 2

[0066] This invention provides a high-filler rPET substrate composite material, which belongs to a talc-filled system and comprises the following components by weight:

[0067] 100 parts of modified rPET particles;

[0068] 300 parts of dried talc powder (1250 mesh);

[0069] 12 parts of ethylene-acrylate-glycidyl methacrylate terpolymer;

[0070] 10 parts of compounded lubricant (pentaerythritol stearate: oxidized polyethylene wax = 1:1);

[0071] 0.8 parts of coupling agent.

[0072] In this embodiment, the preparation method of the composite material includes the following steps:

[0073] 1. Mixing: The high-speed mixer temperature is 85℃, the mixing time is 12 minutes, and the remaining mixing operations are the same as in Example 1;

[0074] 2. Melt extrusion: The extruder temperature gradient zone, screw speed, and vacuum level are completely consistent with those in Example 1;

[0075] 3. Calendering and cooling: Same as in Example 1, to obtain a high-filling rPET substrate B.

[0076] In this embodiment, during the preparation of the composite flooring, the surface decorative wear-resistant layer is a PETG printed wear-resistant integrated layer. The film is heated before entering the embossing roller. The heating temperature is 95°C, the embossing roller temperature is 90°C, the pressure is 0.8MPa, and the time from embossing to board retraction is 50 seconds. After UV coating and hardening, a composite EVA foam balanced backing layer is applied. The remaining processes are the same as in Example 1.

[0077] Performance metrics:

[0078] Substrate: Excellent rigidity, flexural modulus ≥2800MPa, heat distortion temperature 5-8℃ higher than calcium carbonate filled system, reaching 78-82℃, better high temperature resistance; smooth surface, no powdering or delamination, continuous and stable extrusion processing;

[0079] Composite flooring: It has better high-temperature resistance than calcium carbonate flooring, and can withstand short-term baking at 100℃ without deformation. It is suitable for underfloor heating, high-temperature workshops and other similar applications.

[0080] Example 3

[0081] This invention provides a high-filler rPET substrate composite material, which belongs to a calcium sulfate / calcium carbonate composite filler system and includes the following components by weight:

[0082] 100 parts of modified rPET particles;

[0083] 200 parts of dried calcium sulfate (600 mesh);

[0084] 150 parts of dried calcium carbonate (800 mesh);

[0085] 18 portions of TPV / LDPE-g-AA compound toughening system;

[0086] 12 parts of compound lubricant (zinc stearate: polyethylene glycol fatty acid ester = 1.5:1).

[0087] In this embodiment, the preparation method 1 of the composite material includes the following steps:

[0088] 1. Mixing: The high-speed mixer temperature is 90℃, the mixing time is 11 minutes, and the remaining mixing operations are the same as in Example 1;

[0089] 2. Melt extrusion: The extruder vacuum was adjusted to -0.07 MPa, and the remaining extrusion parameters were the same as in Example 1;

[0090] 3. Calendering and cooling: Same as in Example 1, to obtain a high-filling rPET substrate C.

[0091] In this embodiment, during the preparation of the composite flooring, the surface decorative wear-resistant layer consists of a PP printed layer and a PET transparent wear-resistant layer. The film is heated before entering the embossing roller at a temperature of 75°C. The temperature of the embossing roller is also 75°C, and the pressure is 1.2 MPa. The time from embossing to board retraction is 70 seconds. The composite cork balance backing layer is also included. The remaining processes are the same as in Embodiment 1.

[0092] Performance metrics:

[0093] Substrate: It has balanced comprehensive mechanical properties, with bending strength ≥23MPa, impact strength ≥4.5kJ / m², good processing fluidity, and raw material procurement costs are 8%-10% lower than those of a single calcium carbonate system, resulting in a significant cost advantage.

[0094] Composite flooring: It feels warm underfoot, has better sound insulation than single-filler systems, and is resistant to chemical corrosion, able to withstand the corrosion of common household cleaning agents.

[0095] Example 4

[0096] This invention provides a high-filler rPET substrate composite material, which belongs to a high-toughness formulation system and includes the following components by weight:

[0097] 100 parts of modified rPET particles;

[0098] 250 parts of dried calcium carbonate (800 mesh);

[0099] 20 parts of GMA-MMA-BA acrylate copolymer toughening agent;

[0100] 5 parts of SEBS elastomer;

[0101] 15 parts of compound lubricant (stearamide: polyethylene wax = 1:2).

[0102] In this embodiment, the preparation method of the composite material includes the following steps:

[0103] 1. Mixing: The high-speed mixer temperature is 95℃, the mixing time is 13 minutes, and the remaining mixing operations are the same as in Example 1;

[0104] 2. Melt extrusion: The extruder screw speed was adjusted to 20 rpm, the vacuum degree was -0.09 MPa, and the other temperature parameters were the same as in Example 1;

[0105] 3. Calendering and cooling: Same as in Example 1, to obtain a high-filling rPET substrate D.

[0106] In this embodiment, during the preparation of the composite flooring, the surface decorative wear-resistant layer is a PET high wear-resistant printing layer. The film is heated before entering the embossing roller. The heating temperature is 80°C, the embossing roller temperature is 65°C, the pressure is 0.9MPa, and the time from embossing to board retraction is 60 seconds. The composite PET pad layer balances the backing layer, and the remaining processes are the same as in Embodiment 1.

[0107] Performance metrics:

[0108] Substrate: Excellent toughness, the impact strength of simply supported beam is more than 30% higher than that of conventional high-filler formulations, ≥6.0kJ / m², the bending strength is ≥22MPa, there is no melt fracture during processing, and the substrate has both toughness and rigidity.

[0109] Composite flooring: It has outstanding impact resistance and is suitable for public decoration scenarios with high personnel density and easy impact, such as shopping malls, office buildings, and kindergartens, where high toughness is required. It also has excellent flexural resistance and will not crack after repeated bending.

[0110] Comparative Example 1:

[0111] The composite material formulation and all preparation processes of Example 1 were used in full, except that the amount of compound lubricant added was changed from 14 parts to 3 parts. The rest of the ratio of calcium stearate: polyethylene wax: EBS remained 2:1:1, with corresponding addition amounts of 1.5 parts: 0.75 parts: 0.75 parts.

[0112] The low-lubricant-content system prepared during processing exhibited severe rod sticking during the extrusion stage, with material adhering heavily to the screw and barrel, resulting in uneven plasticization and unstable melt output, making continuous industrial production impossible. The resulting substrate had a rough surface with numerous pores and pits, and internal delamination and slag inclusions, making subsequent composite processing impossible. The unqualified substrate lacked effective mechanical property data and could not meet the basic requirements for flooring substrates.

[0113] Therefore, when using the formulation of Example 1 but with only 3 parts of lubricant, severe sticking occurred during extrusion, the material was not plasticized evenly, the surface of the sheet was rough and had air holes, and continuous production was not possible.

[0114] Comparative Example 2

[0115] The composite material formulation and all preparation processes of Example 4 were used entirely, except that the compound toughening agent was replaced with 25 parts of a single thermoplastic elastomer, SEBS, and the GMA-MMA-BA acrylate copolymer was removed. In terms of interfacial compatibility, the resulting single toughening agent system showed poor interfacial bonding between SEBS and rPET and calcium carbonate filler, resulting in uneven dispersion of the filler in the matrix and obvious filler agglomeration on the substrate cross-section. The simply supported beam impact strength decreased by approximately 40% compared to Example 4, reaching only 3.5-3.8 kJ / m², and cracks appeared in the falling ball impact test. The toughness could not meet the impact resistance requirements of public packaging applications. The melt strength decreased slightly, and burrs easily appeared at the substrate edges during extrusion, increasing the difficulty of subsequent cutting and grooving processes.

[0116] Therefore, using the formulation of Example 4 but only SEBS (acrylate-free copolymer), the interfacial bonding between rPET and calcium carbonate is poor, and the impact strength decreases by about 40%.

[0117] This invention discloses a high-filler rPET substrate composite material and its preparation method, as well as a composite flooring. The filler is not limited to calcium carbonate but extends to various inorganic mineral fillers such as calcium sulfate, talc, and kaolin, allowing for flexible selection based on raw material costs and supply, significantly reducing material procurement risks and production costs. By expanding the filler content, it covers the entire range from conventional to extreme fillers. Particularly in the high-filler range of 200-400 parts, it achieves an optimal balance between cost and performance, making the raw material cost of the flooring substrate significantly lower than that of traditional SPC flooring and conventionally filled rPET sheets.

[0118] This invention expands toughening agents to three major categories: grafted elastomers, copolymerized acrylates, and thermoplastic elastomers, covering the mainstream technical routes in the current rPET modification field. Among them, toughening agents containing epoxy groups (GMA) can react with the end groups of rPET, possessing both toughening and chain-extending functions; acrylate toughening agents (such as GMA-MMA-BA) can significantly improve the impact strength of rPET; maleic anhydride grafts (PP-g-MAH) can improve interfacial compatibility. Through the compounding of different toughening agents, a broad spectrum of performance control from "high rigidity" to "high toughness" can be achieved. Lubricants are expanded to six major categories: hydrocarbons, fatty acids, fatty acid salts, fatty acid esters, polyesters, and amides, covering all functional requirements for internal lubrication, external lubrication, and metal soap lubrication. Polyester lubricants exhibit excellent compatibility with rPET and can provide long-lasting lubrication at high temperatures; amide lubricants (such as EBS) have excellent external lubrication and mold release effects. Through compound design, engineering problems such as poor material flowability, easy sticking, uneven plasticization, and melt fracture in high-filler systems are effectively solved.

[0119] In this invention, the substrate is mainly composed of recycled PET and natural minerals (calcium carbonate, talc, etc.), which significantly reduces dependence on virgin petroleum-based resins and environmental pollution from waste plastics, aligning with the circular economy and "dual-carbon" policy guidelines. It can be produced directly using existing mature SPC flooring production lines (a 110-type conical twin extruder and subsequent pressing and grooving equipment) without major equipment modifications, allowing for rapid industrialization.

[0120] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A high-filled rPET substrate composite, characterized in that, Based on parts by weight, it comprises the following components: 100 portions of recycled PET pellets; Inorganic mineral filler, 50-500 parts; Toughening agent 5-30 parts; 2-20 parts lubricant; Processing aids 1-5 parts; The processing aids include at least one of antioxidants, light stabilizers, coupling agents, and nucleating agents; the lubricant is a compound system containing at least one internal lubricant and at least one external lubricant.

2. The high-filled rPET-based substrate composite of claim 1, wherein, The inorganic mineral filler comprises 200-400 parts by weight, the toughening agent comprises 10-20 parts by weight, and the lubricant comprises 5-15 parts by weight.

3. The high-filler rPET substrate composite material according to claim 2, characterized in that, The inorganic mineral filler is 300-400 parts by weight, and the lubricant is 10-15 parts by weight.

4. The high-filler rPET substrate composite material according to claim 1, characterized in that, The inorganic mineral filler is at least one of calcium carbonate, calcium sulfate, talc, kaolin, wollastonite, and mica powder.

5. The high-filler rPET substrate composite material according to claim 1, characterized in that, The rPET granules are granulated from beverage bottle crushed material or polyester textile recycled material that has undergone thickening or chain extension modification.

6. The high-filler rPET substrate composite material according to claim 1, characterized in that, The toughening agent is selected from at least one of the following categories: Grafted elastomer toughening agents: at least one of the following: polyolefin elastomer grafted with glycidyl methacrylate, ethylene propylene rubber grafted with glycidyl methacrylate, polypropylene grafted with glycidyl methacrylate, polypropylene grafted with maleic anhydride, and low-density polyethylene grafted with acrylic acid. Copolymerized acrylate toughening agents: at least one of the following: ethylene-acrylate-glycidyl methacrylate terpolymer, methyl methacrylate-n-butyl acrylate-glycidyl methacrylate copolymer, and isobornyl methacrylate-n-butyl acrylate-glycidyl methacrylate copolymer; Thermoplastic elastomers: at least one of dynamically vulcanized thermoplastic elastomers, styrene-butadiene-styrene block copolymers, and styrene-ethylene-butene-styrene block copolymers.

7. The high-filler rPET substrate composite material and its preparation method, and the composite flooring according to claim 6, characterized in that, The lubricant is selected from at least two of the following categories: Hydrocarbon lubricants: polyethylene wax, oxidized polyethylene wax, paraffin wax, microcrystalline wax; Fatty acid lubricants: stearic acid, hydroxystearic acid; Fatty acid salt lubricants: calcium stearate, zinc stearate, magnesium stearate; Fatty acid ester lubricants: butyl stearate, glyceryl monostearate, pentaerythritol stearate; Polyester-based lubricants: polyethylene glycol fatty acid esters, polyester waxes; Amide lubricants: stearamide, oleamide, erucamide, ethylene bis-stearamide.

8. A method for preparing a high-filler rPET substrate composite material as described in any one of claims 1-7, and a composite flooring, characterized in that, Includes the following steps: Pretreatment: Dry the inorganic mineral filler at 100-130℃ for ≤1 hour, controlling the moisture content to be below 0.5%; Mixing: Place 100 parts of modified rPET granules, 50-500 parts of dry inorganic mineral filler, 5-30 parts of toughening agent, 2-20 parts of lubricant and optional processing aids into a high-speed mixer and mix at 80-120℃ for 5-15 minutes to make the additives evenly coat the surface of the filler. Melt extrusion molding: The mixed material is fed into a 110-type conical twin-screw extruder. Gradient temperature control is adopted, with the temperature of each section controlled between 160-230℃, screw speed 15-30rpm, and vacuum degree -0.06 to -0.09MPa, so that the material is fully plasticized and degassed. Calendering and cooling: After the molten material is extruded through a T-die, it is calendered, cooled, and drawn by a three-roll calender to obtain a substrate of a specified thickness.

9. A composite flooring, characterized in that, From top to bottom, it includes at least: Surface decorative wear-resistant layer: a printed layer and a transparent wear-resistant layer stacked in sequence, or a wear-resistant layer with a printed pattern; Core substrate layer: a highly filled rPET substrate obtained by using the composite material and preparation method described in any one of claims 1-7; Balanced backing layer: a functional layer attached to the lower surface of the substrate layer, selected from at least one of IXPE foam, EVA foam, cork, and PET padding.

10. The composite flooring according to claim 9, characterized in that, The surface decorative wear-resistant layer is laminated with the core substrate layer through a hot pressing process. Before the film enters the embossing roller, it is heated at a temperature between 75-120°C, the temperature of the embossing roller is 65-130°C, the pressure is 0.5-2.0 MPa, and the time from embossing to plate collection is 30-90 seconds. After lamination, a UV coating hardening treatment is applied to the surface of the transparent wear-resistant layer.