Multilayer foamed flooring and manufacturing method therefor

Abstract

The present invention relates to the technical field of composite flooring. Disclosed are a multilayer foamed flooring and a manufacturing method therefor. The multilayer foamed flooring comprises surface layers and a core layer, and adopts a surface layer - core layer - surface layer structural form. The surface layer is composed of the following raw materials in parts by mass: 40-60 parts of PVC resin powder, 80-110 parts of calcium carbonate, 35-60 parts of a common recycled material, 2-4 parts of a calcium-zinc stabilizer, 2-4 parts of a foaming processing aid, 2-4 parts of a toughening agent, 0.5-3 parts of an internal lubricant, 0.5-3 parts of an external lubricant, and 0.1-0.5 parts of carbon black. The core layer is composed of the following raw materials in parts by mass: 40-60 parts of PVC resin powder, 80-100 parts of calcium carbonate, 40-60 parts of a foamed recycled material, 3-5 parts of a calcium-zinc stabilizer, 1-3 parts of a foaming processing aid, 5-10 parts of a foaming regulator, 0.1-0.5 parts of a yellow foaming agent, 0.1-0.3 parts of a white foaming agent, 0.5-3 parts of an internal lubricant, and 0.5-3 parts of an external lubricant. In the multilayer foamed flooring prepared in the present invention, the problem of warpage on the back surface of the product can be effectively controlled, the thermal stability of the flooring can be improved, and better comprehensive performance are exhibited.

Description

A multi-layer foamed floor and its preparation method

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411965410.X, filed on December 30, 2024, entitled "A Multi-Layer Foamed Floor and Its Preparation Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of composite flooring technology, and in particular to a multi-layer foamed flooring and its preparation method. Background Technology

[0004] In recent years, the PVC flooring market has shown rapid growth. The global market continues to expand, with Europe and the United States becoming major consumer markets, while China is a major producer and exporter, with its export value increasing year by year.

[0005] In terms of competition, international brands dominate the high-end market, while domestic brands are numerous but have low market concentration, with some companies emerging based on quality and R&D. Products are developing towards environmental friendliness, multifunctionality, and aesthetics. However, the market suffers from inferior products and is affected by fluctuations in raw material prices. Overall, the prospects are broad, but challenges coexist.

[0006] Today's flooring market has new requirements for products. Flooring with good toughness, stability, and lighter weight has become the focus of the market. Good toughness can withstand impacts and pressure, while good stability can adapt to various environments and avoid deformation. Lighter flooring is more convenient for both transportation and installation. Flooring that meets these characteristics is urgently needed by the market and will lead the development direction of the flooring industry.

[0007] However, traditional PVC flooring still falls short in meeting the aforementioned characteristics. For example, it is difficult to balance toughness and stability, especially in high-temperature environments where it is prone to warping and shrinkage. Furthermore, compared to conventional SPC flooring, how to maintain or even improve mechanical properties such as static bending strength and modulus of elasticity while reducing weight remains a problem that current technology urgently needs to solve. Summary of the Invention

[0008] To address the shortcomings of existing flooring in terms of weight, toughness, and high-temperature stability, this invention aims to provide a multi-layer foamed PCV flooring formulation and its preparation and manufacturing process.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution after research:

[0010] A first aspect of the present invention provides a multi-layer foamed flooring, comprising a surface layer and a core layer; the surface layer is composed of the following raw materials in parts by weight: 40-60 parts of polyvinyl chloride (PVC) resin powder, 80-110 parts of calcium carbonate, 35-60 parts of ordinary recycled material, 2-4 parts of calcium-zinc stabilizer, 2-4 parts of foaming processing aid, 2-4 parts of toughening agent, 0.5-3 parts of internal lubricant, 0.5-3 parts of external lubricant, and 0.1-0.5 parts of carbon black.

[0011] Preferably, the surface layer is composed of the following raw materials in parts by weight: 50 parts PVC resin powder, 100 parts calcium carbonate, 40 parts ordinary recycled material, 3.6 parts calcium zinc stabilizer, 3 parts foaming processing aid, 2.2 parts toughening agent, 1 part internal lubricant, 0.8 parts external lubricant, and 0.3 parts carbon black.

[0012] Furthermore, the PVC resin powder is a conventional SG5 powder.

[0013] Furthermore, the calcium carbonate mentioned is 400 mesh calcium carbonate.

[0014] Furthermore, the foaming processing aid is an acrylic copolymer (ACR).

[0015] Furthermore, the toughening agent is modified chlorinated polyvinyl chloride (CPVC) resin particles.

[0016] In some embodiments, the modified CPVC resin particles are composed of the following raw materials in parts by weight: 100 parts of CPVC with 67% chlorine content, 4 parts of chlorinated polyethylene (CPE) with 35% chlorine content, 10 parts of SG-5 type PVC powder, 10 parts of MBS (Methyl methacrylate-Butadiene-Styrene) resin, 5 parts of calcium-zinc stabilizer, and 0.4 parts of polyethylene wax (PE wax).

[0017] In some embodiments, the core layer of the multi-layer foamed flooring is composed of the following raw materials in parts by weight: 40-60 parts PVC resin powder, 80-100 parts calcium carbonate, 40-60 parts recycled foaming material, 3-5 parts calcium-zinc stabilizer, 1-3 parts foaming processing aid, 5-10 parts foaming regulator, 0.1-0.5 parts yellow foaming agent, 0.1-0.3 parts white foaming agent, 0.5-3 parts internal lubricant, and 0.5-3 parts external lubricant.

[0018] Preferably, the core layer is composed of the following raw materials in parts by weight: 50 parts PVC resin powder, 85 parts calcium carbonate, 40 parts recycled foaming material, 4 parts calcium-zinc stabilizer, 2.5 parts foaming processing aid, 6 parts foaming regulator, 0.25 parts yellow foaming agent, 0.1 parts white foaming agent, 0.95 parts internal lubricant, and 0.8 parts external lubricant.

[0019] Furthermore, the PVC powder is a conventional SG8 powder.

[0020] Furthermore, the calcium carbonate mentioned is 1250 mesh calcium carbonate.

[0021] Furthermore, the foaming processing aid is an acrylic copolymer (ACR).

[0022] Furthermore, the foaming regulator is a high molecular weight acrylate PVC processing aid with a molecular weight in the range of 5 million to 6.5 million Daltons.

[0023] Furthermore, the raw materials of the foaming regulator include methacrylate, butyl acrylate, 4-fluoro-2-methyl-1-styrene, emulsifier, and initiator; the mass ratio of methacrylate to butyl acrylate is 1:(1.5-3), and the mass ratio of methacrylate to 4-fluoro-2-methyl-1-styrene is 1:(0.1-0.3).

[0024] In some embodiments, the multilayer foamed flooring consists of a surface layer-core layer-surface layer structure.

[0025] In some embodiments, the thickness of the surface layer is 0.8-1.2 mm, and the thickness of the core layer is 2.5-12.5 mm.

[0026] A second aspect of the present invention provides a method for preparing multi-layer foamed flooring, comprising the following steps:

[0027] S1. Stir and heat the surface layer and core layer materials separately to 110-120℃;

[0028] S2. After cooling, it is conveyed to the extruder;

[0029] S3. The core layer material is injected into the mold through the confluence core, and the surface layer material is injected into the mold through the confluence core and the flow channel. The structure of surface layer-core layer-surface layer is realized by the distributor.

[0030] S4. The board is extruded into shape using a mold, cooled and shaped, coated, trimmed and cut to obtain the finished flooring product.

[0031] Furthermore, the temperature of the confluence core in S3 is 170–200°C, and / or the temperature of the flow channel is 170–180°C.

[0032] Furthermore, the temperature of the confluence core in S3 is 170–180°C.

[0033] Further, the mold in S4 includes a cooling roller, a mold roller 1, a mold roller 2, a mold roller 3, a mold roller 4, and a mold roller 5. The rotational speed of the cooling roller is 200-230 R / min, the rotational speed of the mold roller 1 is 180-200 R / min, the rotational speed of the mold roller 2 is 180-200 R / min, the rotational speed of the mold roller 3 is 160-180 R / min, the rotational speed of the mold roller 4 is 160-180 R / min, and the rotational speed of the mold roller 5 is 220-240 R / min.

[0034] Furthermore, the extrusion molding of the sheet material by the mold involves passing the sheet material sequentially through a cooling roller, a mold roller 1, a mold roller 2, a mold roller 3, a mold roller 4, and a mold roller 5.

[0035] Furthermore, the temperature of the cooling roller is 0–5°C.

[0036] The parameters are set within a range optimized based on actual conditions, which can better ensure the stability of the prepared product.

[0037] The beneficial effects of the present invention include at least the following:

[0038] 1) By using toughening agents, the static bending strength, elastic modulus, displacement and other indicators of the sheet can be effectively improved, thereby enhancing the toughness of the material.

[0039] 2) By adopting a surface layer-core layer-surface layer structure, the warping problem on the back of the product can be effectively controlled, and the stability of the flooring can be improved. After being kept at 80℃ for 6 hours, the shrinkage and warping stability of the foamed flooring of this invention is superior to that of current cold-applied multi-layer flooring.

[0040] 3) By adopting core layer foaming technology, the foamed flooring of the present invention is at least 20% lighter than conventional SPC flooring, which makes the foamed flooring more convenient to transport and install, while retaining higher mechanical properties. Detailed Implementation

[0041] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0042] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0043] The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or device that includes a series of steps is not limited to the steps or modules listed, but may optionally include steps not listed, or may optionally include other steps inherent to such process, method, product, or device.

[0044] I. Surface Extrusion Formulation and Preparation Method:

[0045] The surface extrusion formulation of this invention consists of the following components in parts by weight: 40-60 parts PVC resin powder, 80-100 parts 400-mesh heavy calcium carbonate, 40-60 parts ordinary recycled material, 2-4 parts calcium-zinc stabilizer, 2-4 parts ACR processing aid, 2-4 parts toughening agent, 0.5-3 parts internal lubricant, 0.5-3 parts external lubricant, and 0.1-0.5 parts carbon black.

[0046] The selected PVC powder is conventional SG5 powder. SG5 is a commonly used grade among the various types of PVC resin.

[0047] The selected calcium carbonate powder has a particle size of 400 mesh. Too coarse particles will cause the product to scorch easily, while too fine particles will increase the cost and make the product too brittle.

[0048] The selected recycled material is shredded PVC flooring material; from an environmental perspective, it can reduce resource waste, lower carbon emissions, and reduce waste pollution; from an economic perspective, it can reduce production costs and improve resource utilization.

[0049] The selected calcium-zinc stabilizer is a non-toxic and environmentally friendly PVC calcium-zinc stabilizer, which is composed of zinc soap, calcium soap, auxiliary stabilizers, lubricants, etc. It has the characteristics of being non-toxic, highly efficient, stable, producing fine foam cells, excellent demolding performance, excellent processing performance, and long production cycle.

[0050] The selected foaming processing aid is an acrylic copolymer (ACR), which is a copolymer of methyl methacrylate (MMA) and acrylates. ACR can promote the plasticizing properties of PVCU during processing and improve its flowability.

[0051] The selected internal lubricant is G60, which is a lubricant whose main component includes stearic acid.

[0052] The selected external lubricant is PE wax.

[0053] The toughening agent used is modified CPVC resin granules, and its preparation formula and process are as follows:

[0054] (1) Weigh 100 parts by weight of CPVC with 67% chlorine content; weigh 4 parts by weight of CPE with 35% chlorine content, whose main function is to act as a compatibilizer to increase the bonding force between CPVC and PVC and enhance mechanical properties; weigh 10 parts by weight of SG-5 type PVC powder; weigh 10 parts by weight of MBS resin (a terpolymer of methyl methacrylate (M), butadiene (B) and styrene (S), since its solubility parameters are similar to those of PVC, the two have good thermodynamic compatibility, which means that PVC has high impact strength at room temperature or low temperature; weigh 5 parts by weight of calcium zinc stabilizer; weigh 0.4 parts by weight of PE wax;

[0055] (2) After weighing the materials mentioned in step (1), put them into the mixer in the order of weighing and mix them. First, mix them in a low-speed mixer, then switch to a high-speed mixer, and feed them after the temperature reaches 90°C.

[0056] (3) After the above operation in step (2), the feeding part is sent to the conical twin-screw extruder for extrusion, and the temperature is set to 180-200℃;

[0057] (4) Following step (3) extrusion molding, the temperature is cooled by cooling the die head, and then traction cooling is performed until the molding is complete and the next step can be carried out.

[0058] (5) Continue with step (4) to granulate and sieve.

[0059] The carbon black used is used to color the board.

[0060] II. Core Layer Extrusion Formulation and Preparation Method:

[0061] Core layer extrusion formulation design: 40-60 parts PVC resin powder, 80-100 parts 1250 mesh calcium carbonate, 40-60 parts recycled foaming material, 3-5 parts calcium-zinc stabilizer, 1-3 parts ACR processing aid, 5-10 parts foaming regulator, 0.1-0.5 parts yellow foaming agent, 0.1-0.3 parts white foaming agent, 0.5-3 parts internal lubricant, and 0.5-3 parts external lubricant.

[0062] The selected PVC powder is conventional SG8 powder, because the core layer is used for foaming. SG-8 PVC resin powder has a degree of polymerization of 740-650 and a K value of 59-55, which is more suitable for foaming.

[0063] The selected calcium carbonate powder is 1250 mesh. When the particle size of calcium carbonate matches the foaming agent, it can act as a nucleating agent, thereby promoting foaming. Suitable calcium carbonate particle sizes are less than or equal to 10 μm and do not agglomerate. This allows for better adsorption of foaming gas to form bubble nuclei, controlling the number of bubbles and resulting in finer bubbles. Firstly, calcium carbonate acts as a nucleating agent, adsorbing foaming gas to form bubble nuclei, controlling the number of bubbles and resulting in finer bubbles; secondly, it improves melt properties: calcium carbonate itself has high rigidity, which can slow down melt deformation and movement, thereby inhibiting excessively rapid bubble expansion and controlling the bubble size to be finer. When the calcium carbonate particle size is less than or equal to 10 μm, it can act as a nucleating agent to promote foaming. If the calcium carbonate particle size is greater than 20 μm, or too fine, causing self-agglomeration, it will affect the foaming effect.

[0064] The selected recycled foam material is pulverized material from foamed boards.

[0065] The selected calcium-zinc stabilizer is a non-toxic and environmentally friendly PVC calcium-zinc stabilizer, which is composed of zinc soap, calcium soap, auxiliary stabilizers, lubricants, etc. It has the characteristics of being non-toxic, highly efficient, stable, producing fine foam cells, excellent demolding performance, excellent processing performance, and long production cycle.

[0066] The selected foaming processing aid is ACR, which is a copolymer of MMA and acrylates. It can promote the plasticizing properties of PVCU during processing and improve its flowability.

[0067] The selected internal lubricant is G60, a type of lubricant whose main components include stearic acid. It is a dicarboxylic acid ester containing fatty alcohols.

[0068] The selected external lubricant is PE wax.

[0069] The selected foaming regulator is actually an acrylic processing aid, possessing all the basic characteristics of PVC processing aids. The only difference from general PVC processing aids lies in its molecular weight. The foaming regulator is a high-molecular-weight acrylic PVC processing aid, with a molecular weight far exceeding that of PVC resin (generally between 50,000 and 110,000). The higher molecular weight of the foaming regulator, typically between 5 million and 6.5 million Daltons, allows it to better bind PVC molecules together, forming a gel network. This improves melt strength, prevents bubble formation and gas leakage, and ensures the quality and density of the foamed product.

[0070] In some embodiments, the raw materials of the foaming regulator include methacrylate, butyl acrylate, 4-fluoro-2-methyl-1-styrene, emulsifier, and initiator; the mass ratio of methacrylate to butyl acrylate is 1:(1.5-3), and the mass ratio of methacrylate to 4-fluoro-2-methyl-1-styrene is 1:(0.1-0.3).

[0071] The selected yellow foaming agent has a gas emission rate of 220-230 ml / g, a decomposition temperature of 195-205℃, and a volatility of ≤0.2% (110℃ 1H).

[0072] The selected white foaming agent has a gas emission rate of 130-140 ml / g, a decomposition temperature of 157-165℃, and a volatility of ≤0.5% (110℃ 1H).

[0073] This invention utilizes core-layer foaming technology, resulting in foamed flooring that is at least 20% lighter than conventional SPC flooring. For example, 5mm thick foamed flooring weighs 2kg less per square meter than conventional SPC flooring. This makes the foamed flooring easier to transport and install, while retaining superior mechanical properties.

[0074] III. A multi-layer co-extruded PVC flooring substrate extrusion process, the specific steps of which are as follows:

[0075] S1. Add the materials for the surface layer and core layer formulations, calcium carbonate, and PVC powder to a high-speed mixer. Then add plasticizers, stabilizers, lubricants, and other additives. Mix and stir, then heat to 110-120℃ before discharging and cooling. (The surface layer and core layer are placed in separate reactors.)

[0076] S2. When the mixture from S1 is cooled to 65°C, it is placed into the storage silo and the mixture from the storage silo is conveyed to the screw extruder through the screw feeding system.

[0077] S3. Prepare the surface layer structure substrate using one twin-screw extruder (material formulation as described above for surface layer extrusion formulation design), and prepare the core layer structure substrate using another twin-screw extruder (material formulation as described above for core layer extrusion formulation design).

[0078] The specific operation involves injecting the core layer material into the mold through a confluence core, and injecting the surface layer material into the mold through the confluence core and flow channels. The mold distributor distributes the surface layer and core layer according to the different injection channels of the core layer and surface layer, so that the surface layer and core layer materials are combined in the mold to form a multi-layer structure of surface layer-core layer-surface layer.

[0079] S4. The board is extruded into shape, cooled and shaped, coated, trimmed and cut to obtain a multi-layer flooring product consisting of a surface layer, a core layer and a surface layer.

[0080] The specific operating method includes the following steps: equipment preparation before starting the machine, starting the machine, discharging the material and pulling the plate, and turning off the machine.

[0081] 1. Equipment preparation before startup mainly includes the following steps: equipment inspection and equipment heating / pre-cooling.

[0082] The equipment inspection includes, but is not limited to, checking and ensuring that the power supply system and cooling water system are functioning properly; checking and ensuring that the mold, distributor, and vacuum device are installed correctly.

[0083] The heating / precooling of the equipment includes the following steps:

[0084] 1-1. Set the mold opening temperature (170~180℃), mold temperature (180~190℃), and side plate temperature (190~210℃). Turn on the mold, mold opening, and side plate to heat for about 2 hours.

[0085] 1-2. Set the extruder temperature according to the diagram below. Adjust the temperature appropriately while ensuring stable product extrusion. Turn on the heating for about 2.5 hours (Note: Main unit numbers 7 and 8 are the confluence core temperatures).

[0086] 1-3. Set the distributor temperature according to the diagram below. Adjust it appropriately while ensuring stable product extrusion. Turn on the heating for about 0.5 hours.

[0087] 1-4. Set the temperature of the mold rollers (190℃ for roller 1, 190℃ for roller 2, 180℃ for roller 3, and cold water rollers for rollers 4 and 5). It is permissible and should be adjusted appropriately while ensuring stable extrusion of the product. Turn on the heating for about 1.5 hours.

[0088] 1-5. Set the shaping and cooling rollers, and ensure that the cooling water is circulating at around 15℃.

[0089] 2. Powering on the device mainly includes the following steps:

[0090] First, start the screw extruder. Then, set the 80# auxiliary extruder speed to 200 RPM and the feed speed to 120 RPM. After the 80# auxiliary extruder discharges material, set the 92# main extruder speed to 200 RPM and the feed speed to 90 RPM. Slowly increase the speed multiple times, increasing by 20-40 RPM each time. Stabilize the speed, feed speed, and current according to the diagram below, adjusting them appropriately while ensuring stable product extrusion. (Note: When increasing the speed, observe the current; increase slowly to avoid high current alarms.)

[0091] Taking the production of 6.5mm products as an example, the following roller speeds are set as a reference:

[0092] The following are references for the settings of the traction device, bracket, and lampshade:

[0093] 3. Sheet extrusion and processing mainly include the following steps:

[0094] During the extrusion process, the machine is moved closer to the die orifice to prepare for sheet extrusion. After the extruded sheet emerges from the die, it is manually transferred to the cooling and shaping rollers. Once the flatness and thickness of each layer of the extruded sheet are adjusted and confirmed, the lampshade is turned on for lamination. The edges are then trimmed by adjusting the spacing of the rotary cutters according to the required width of the laminated sheet. After passing through the cooling zone, the laminated sheet is cut into the required dimensions using a shearing machine.

[0095] 4. Shutdown and Cleanup

[0096] Turn off the heating system, conveyor belt, and cooling system; shut down the hopper, screw compressor, and die roller system. Simultaneously, clean the dust accumulated at the top of the main unit's feed hopper. Determine whether to replace the material based on the actual amount of material remaining in the screw compressor.

[0097] IV. Setup Example:

[0098] The specific formulations of Examples 1, 2, and 3 are shown in Table 1; the preparation process of the examples is carried out according to the specific steps of "III. An extrusion process for a multilayer co-extruded PVC flooring substrate" above.

[0099] Table 1. Formulations of multi-layer foamed flooring in each embodiment.

[0100] Compare with Example 1

[0101] This comparative example prepared conventional flooring, and its formulation and manufacturing process are as follows:

[0102] 1. Formulation: The base material consists of 75 parts PVC resin powder, 250 parts heavy calcium carbonate, 7 parts stabilizer, 0.7 parts external lubricant PE wax, and 1.7 parts internal lubricant CA80.

[0103] The selected PVC powder is conventional SG5 powder;

[0104] The selected calcium carbonate powder needs to be 400 mesh. Too coarse particles will cause the product to scorch easily, while too fine particles will increase the cost and make the product too brittle.

[0105] The stabilizer selected is a non-toxic and environmentally friendly calcium-zinc stabilizer.

[0106] The selected internal lubricant is stearic acid;

[0107] The selected external lubricant is PE wax;

[0108] 2. The extrusion process of this substrate, its characteristics, and the selection of the backing film include the following steps:

[0109] 2.1 Add 400-mesh heavy calcium carbonate, PVC powder, and some recycled material to a high-speed mixer, then add plasticizer, stabilizer, and lubricant. Mix and heat to 110-120℃, then discharge and cool.

[0110] 2.2 When the mixture from 2.1 is cooled to 65°C, it is placed into the storage silo. The mixture in the storage silo is then conveyed to the twin-screw extruder (a conical twin-screw extruder) through a screw feeding system.

[0111] 2.3 The barrel temperature is controlled at 160-180℃, the die temperature is controlled at 200-220℃, and the die opening cooling temperature is controlled at 100-140℃. After extrusion, the material is shaped by the die, and then the thickness is adjusted and shaped by rolling rollers 1 and 2. Roller 3 is used to bond the color film and wear-resistant layer, and rollers 4 and 5 are used for embossing. After cooling, the material is cut to obtain the sheet material.

[0112] Compare with Example 2

[0113] This comparative example prepared a conventional cold-laid multilayer flooring, the formula and manufacturing process of which are as follows:

[0114] 1. Conventional cold-laid multi-layer flooring: Its base material composition is 400 parts PVC resin powder, 1700 parts calcium carbonate, 150 parts DOTP oil, 7 parts stabilizer, and 3 parts carbon black.

[0115] The selected PVC powder is conventional SG5 powder;

[0116] The selected calcium carbonate powder needs to be 400 mesh;

[0117] The selected stabilizer is a calcium-zinc stabilizer.

[0118] 2. The extrusion process of this substrate, its characteristics, and the selection of the backing film include the following steps:

[0119] 2.1 Add 400-mesh heavy calcium carbonate and PVC powder together to a mixer, then add stabilizer, carbon black and DOTP oil for mixing.

[0120] 2.2 The mixture from 2.1 is subjected to open milling and LVT substrate layer is formed by calendering.

[0121] 2.3 The wear-resistant layer, color film, and LVT substrate layer are hot-pressed together using a hot press.

[0122] 2.4 The above semi-finished products are bonded to the purchased wood-plastic composite substrate using adhesive.

[0123] 2.5 The semi-finished product from 2.4 is bonded to the LVT substrate layer again with adhesive to obtain cold-laid multilayer flooring.

[0124] Test Example 1: The flooring prepared in the Example and Comparative Examples was subjected to physical property tests, and the results are shown in Table 2.

[0125] Table 2. Comparison of physical property tests

[0126] As shown in Table 2, the multi-layer foamed flooring of this application (Examples 1-3) is significantly superior to the cold-laid multi-layer flooring (Comparative Example 2) in terms of static bending strength, elastic modulus and residual indentation. This indicates that the formulation design of its surface layer and core layer and the "surface layer-core layer-surface layer" structure have significant advantages, resulting in better synergistic effects and exhibiting superior comprehensive performance.

[0127] Test Example 2: The flooring prepared in the Example and Control Example was compared for installation warping. The results are shown in Table 3.

[0128] Table 3. Comparison of Pavement Warpage (Unit: mm)

[0129] Note: The floor warping comparison is conducted by placing the floor in a constant temperature room and cycling it for 35℃*12H, 0℃*12H, for one day.

[0130] As shown in Table 3, the warpage values ​​of Examples 1-3 were significantly lower than those of conventional cold-applied multilayer flooring (control group 2) throughout the entire experimental period, indicating that the multilayer foam structure can effectively improve the anti-warpage performance.

[0131] Among them, the warpage value of Example 1 was only 0.16 mm on the seventh day, lower than the other two examples. This is because the surface layer and core layer formulations in Example 1 are superior, and the surface layer and core layer formulations, along with the "surface layer-core layer-surface layer" structural design, produced an unexpected synergistic effect. This effectively reduced stress accumulation inside the flooring, making it more stable under temperature differences. In addition, the foamed core layer provided good cushioning, reducing the impact of thermal expansion of the flooring.

[0132] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A multi-layer foamed flooring, characterized in that, It includes a surface layer and a core layer; the surface layer is composed of the following raw materials in parts by weight: 40-60 parts of polyvinyl chloride (PVC) resin powder, 80-110 parts of calcium carbonate, 35-60 parts of ordinary recycled material, 2-4 parts of calcium-zinc stabilizer, 2-4 parts of foaming processing aid, 2-4 parts of toughening agent, 0.5-3 parts of internal lubricant, 0.5-3 parts of external lubricant, and 0.1-0.5 parts of carbon black.

2. The multi-layer foamed flooring according to claim 1, characterized in that, The surface layer is composed of the following raw materials in parts by weight: 50 parts PVC resin powder, 100 parts calcium carbonate, 40 parts ordinary recycled material, 3.6 parts calcium zinc stabilizer, 3 parts foaming processing aid, 2.2 parts toughening agent, 1 part internal lubricant, 0.8 parts external lubricant, and 0.3 parts carbon black.

3. The multi-layer foamed flooring according to claims 1-2, characterized in that: The PVC resin powder is conventional SG5 powder; and / or; The calcium carbonate mentioned is 400 mesh calcium carbonate; and / or; The foaming processing aid is an acrylic copolymer (ACR); and / or; The toughening agent is modified chlorinated polyvinyl chloride (CPVC) resin particles.

4. The multi-layer foamed flooring according to claim 3, characterized in that, The modified CPVC resin granules are composed of the following raw materials in parts by weight: 100 parts of CPVC with 67% chlorine content, 4 parts of chlorinated polyethylene (CPE) with 35% chlorine content, 10 parts of SG-5 type PVC powder, 10 parts of MBS (Methyl methacrylate-Butadiene-Styrene) resin, 5 parts of calcium-zinc stabilizer, and 0.4 parts of polyethylene (PE) wax.

5. The multi-layer foamed flooring according to claim 1, characterized in that, The core layer is composed of the following raw materials in parts by weight: 40-60 parts PVC resin powder, 80-100 parts calcium carbonate, 40-60 parts recycled foaming material, 3-5 parts calcium-zinc stabilizer, 1-3 parts foaming processing aid, 5-10 parts foaming regulator, 0.1-0.5 parts yellow foaming agent, 0.1-0.3 parts white foaming agent, 0.5-3 parts internal lubricant, and 0.5-3 parts external lubricant.

6. The multi-layer foamed flooring according to claim 5, characterized in that, The core layer is composed of the following raw materials in parts by weight: 50 parts PVC resin powder, 85 parts calcium carbonate, 40 parts recycled foaming material, 4 parts calcium-zinc stabilizer, 2.5 parts foaming processing aid, 6 parts foaming regulator, 0.25 parts yellow foaming agent, 0.1 parts white foaming agent, 0.95 parts internal lubricant, and 0.8 parts external lubricant.

7. The multi-layer foamed flooring according to any one of claims 5-6, characterized in that: The PVC powder is conventional SG8 powder; and / or; The calcium carbonate mentioned is 1250 mesh calcium carbonate; and / or; The foaming processing aid mentioned is ACR.

8. The multi-layer foamed flooring according to any one of claims 5-6, characterized in that, The foaming regulator is an acrylic PVC processing aid with a molecular weight in the range of 5,000,000 to 6,500,000 Daltons.

9. The multi-layer foamed flooring according to any one of claims 5-6, characterized in that, The raw materials of the foaming regulator include methacrylate, butyl acrylate, 4-fluoro-2-methyl-1-styrene, emulsifier, and initiator; the mass ratio of methacrylate to butyl acrylate is 1:(1.5-3), and the mass ratio of methacrylate to 4-fluoro-2-methyl-1-styrene is 1:(0.1-0.3).

10. The multi-layer foamed flooring according to claim 1, characterized in that, The multi-layer foamed flooring consists of a surface layer-core layer-surface layer structure.

11. A method for preparing multi-layer foamed flooring as described in any one of claims 1-10, characterized in that, Includes the following steps: S1. Stir and heat the surface layer and core layer materials separately to 110-120℃; S2. After cooling, it is conveyed to the extruder; S3. The core layer material is injected into the mold through the confluence core, and the surface layer material is injected into the mold through the confluence core and the flow channel. The structure of surface layer-core layer-surface layer is realized by the distributor. S4. The board is extruded into shape using a mold, cooled and shaped, coated, trimmed and cut to obtain the finished flooring product.

12. The preparation method according to claim 11, characterized in that, The temperature of the confluence core in S3 is 170–200°C, and / or the temperature of the flow channel is 170–180°C.

13. The preparation method according to claim 11, characterized in that, The mold in S4 includes a cooling roller, a mold roller 1, a mold roller 2, a mold roller 3, a mold roller 4, and a mold roller 5. The cooling roller has a rotational speed of 200-230 R / min, the mold roller 1 has a rotational speed of 180-200 R / min, the mold roller 2 has a rotational speed of 180-200 R / min, the mold roller 3 has a rotational speed of 160-180 R / min, the mold roller 4 has a rotational speed of 160-180 R / min, and the mold roller 5 has a rotational speed of 220-240 R / min.

14. The preparation method according to claim 13, characterized in that, The process of extruding the sheet material through a mold involves passing the sheet material sequentially through a cooling roller, mold roller 1, mold roller 2, mold roller 3, mold roller 4, and mold roller 5.

15. The preparation method according to claim 13, characterized in that, The temperature of the cooling roller is 0 to 5°C.

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