Preparation method of floor profile with multilayer structure and product

Abstract

The invention belongs to the technical field of indoor floors, and particularly relates to a preparation process of a floor profile with a composite structure and a corresponding product. According to the scheme, the intermediate with the multi-layer structure is formed through co-extrusion foaming, then the intermediate is pre-shaped through roller cooling, and finally the composite floor with the multi-layer structure is obtained through multiple times of rolling. According to the scheme, the wall thickness uniformity of the multi-layer structure is improved by optimizing the process; the product prepared by the method is the light multilayer structure composite floor, the homogeneity between the structural layers is good, the structural layers can be tightly pressed, and the service life is long; the density of the plate is low, and the transportation cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of indoor flooring, and in particular relates to a composite flooring profile preparation process and corresponding products. Background Art

[0002] In the field of indoor flooring, to reduce density and transportation costs while maintaining mechanical strength, floor profiles typically utilize a composite structure composed of solid and foam materials. Compared to simple two-layer profiles formed by laminating a single layer of solid material with a single layer of foam, three-layer profiles, consisting of two solid skins sandwiching a foam core, offer greater rigidity, improved impact resistance, and suitability for large-area installations. However, these also present a higher level of manufacturing complexity. For example, patent CN112895380 A proposes a co-extruded wood-plastic foam board with a structure of upper and lower surface layers sandwiching a foam core layer. The patent combines the solid material and the foam material through the following process: the molten foam core layer raw material enters the extrusion section of the co-extrusion foaming mold under the action of extrusion, and passes through the expansion section, co-extrusion section and cooling section in sequence. The molten foam core layer raw material foams in the foaming cavity of the expansion section and fills the entire cavity to form a foam core layer. The excess gas is discharged from the exhaust port and then enters the composite cavity. The molten surface layer raw material is synchronously squeezed into the composite cavity from the feed port and co-extruded and composited with the foam core layer to form a surface layer around the foam core layer. The surface layer wraps the foam core layer. The semi-finished product after co-extrusion and composite is sent to the cooling cavity, forced to cool and shape by cold water, and finally pulled by a traction machine to the operating table for sawing to obtain a co-extruded wood-plastic foam board. This solution uses co-extrusion to form a multi-layer structure as a whole, but the bonding effect between the layers is limited. The resulting three-layer profile will experience layer separation and moisture infiltration after long-term use, which will manifest externally as quality problems such as warping, deformation, and bulging, and the service life is insufficient. Summary of the Invention

[0003] In view of this, the present invention hopes to provide a stone-plastic composite floor and a preparation method thereof, which can solve the problems of easy separation between layers and insufficient service life of multi-layer floor structures in the prior art.

[0004] The present invention is achieved through the following technical solutions: A method for preparing a multi-layer floor profile, characterized by comprising the following steps: S1, obtaining upper surface layer raw materials, foaming layer raw materials, and lower surface layer raw materials; S2, extruding the upper surface layer raw material, the foaming layer raw material, and the lower surface layer raw material into a co-extrusion die, completing foaming of the foaming layer in the co-extrusion die, and extruding an intermediate having at least a three-layer structure including the upper surface layer, the foaming layer, and the lower surface layer from an extrusion port of the co-extrusion die; S3, disposing a pair of cooling rollers having a surface temperature lower than that of the intermediate at the extrusion port, wherein the cooling rollers roll the intermediate in conjunction with the extrusion process of the intermediate to obtain a predetermined shape; the contact area between the surfaces of the cooling rollers and the intermediate forms a nip zone, and the distance between the nip zones of the cooling rollers is less than the height of the extrusion port; S4. Rolling the predetermined shape with a roller to reheat the predetermined shape and then set the shape to obtain a multi-layer structure floor profile.

[0005] In production practice, the inventors discovered that the reason floor profiles experience interlayer separation after a period of use is due to the uneven thickness of each layer of material. This causes the deformation and reset process of the floor profile during extrusion to be asynchronous, generating a force that separates the layers. The inventors further investigated the cause of the uneven material thickness. In the co-extrusion foaming process, the upper surface layer, foaming layer, and lower surface layer are co-extruded and foamed inside a mold and then extruded as an intermediate. This intermediate has a relatively high temperature. To quickly shape the intermediate, a cold water mold (cold water setting table) is typically used in the prior art to cool the intermediate. The temperature of the cold water mold (cold water setting table) is controlled within a range of 10-50°C. The cold water mold is internally provided with a cooling channel approximately 1m long to allow the intermediate to pass through. A cooling water tank or cooling water circulation system is also externally provided. After being extruded from the co-extrusion mold's extrusion port, the intermediate immediately enters the cold water mold and is ultimately extruded through the cold water mold's outlet. It is generally believed that the large contact area and high cooling rate between the cold water mold and the intermediate body enable rapid crusting of the intermediate surface, resulting in a smooth and uniform outer surface, which facilitates bonding between the surface layer and the decorative layer in subsequent processes. However, the inventors discovered that it is precisely this cold water mold shaping process that leads to uneven thickness between the layers of multi-layer flooring profiles. The intermediate body continues to foam after leaving the extruder. If the intermediate body's thickness needs to be compressed by the cold water mold, the cold water mold needs to have a large opening to accommodate the intermediate body entering the cooling channel, and then the cooling channel needs to be designed with a shape that gradually narrows in thickness. In this case, the direction of the friction force applied by the cold water mold to the intermediate body is at an angle to the direction of movement of the intermediate body, which is equivalent to the intermediate body being constantly subjected to lateral extrusion during movement, which can easily cause localized material accumulation. Furthermore, since the cold water mold and the intermediate body are in surface contact, and the friction between the two surfaces is positively correlated with the pressure between the two surfaces, the greater the pressure applied by the cold water mold on the intermediate body, the greater the friction. Therefore, the cold water mold cannot exert a large compressive force on the intermediate body, otherwise the intermediate body will jam during passage through the cold water mold.

[0006] This solution uses roller rolling to cool the intermediate to pre-shape it. The area where the surface of the cooling roller contacts the intermediate forms a nip zone, and the nip zone spacing refers to the spacing between the surfaces of the paired cooling rollers. In this solution, the nip zone spacing of the rollers is smaller than the thickness of the die extrusion port. When the intermediate passes between the pair of rollers, the nip zone is a surface with a certain length, and the intermediate achieves heat exchange with the cooling rollers through surface contact. During the heat exchange process, since the foaming layer has a porous structure and the upper and lower skin layers are solid structures, the foaming layer cools down slower than the upper and lower skin layers. This temperature difference will generate thermal stress and pull the structure, resulting in an uneven interface between different material layers and uneven thickness of the material layer itself. Compared to cold water molds, cooling rollers are rotatable, allowing them to apply greater pressure to the intermediate and set smaller nip spacing without hindering the movement of the intermediate. At the same time, the rotatability of the cooling rollers provides a structural basis for adjusting the synchronous movement of the nip and the intermediate. If the linear speed of the cooling rollers is synchronized with the speed of the intermediate, there is no dynamic friction caused by relative sliding between the nip and the intermediate, and the extrusion force is completely perpendicular to the surface of the intermediate. Unlike cold water molds, there will be no lateral extrusion that causes material accumulation. On this basis, the cooling and extrusion processes of the intermediate by the cooling rollers start and stop simultaneously. When the intermediate generates thermal stress and traction, the cooling rollers can apply pressure in real time and continuously to counteract the deformation trend generated within the intermediate, promote the full fusion of the interfaces between the multilayer structure, reduce the generation of microscopic defects between the layers, and form a more continuous and denser interface structure.

[0007] Preferably, in S3, the intermediate is rolled by cooling rollers at least twice, and the nip spacing of the second rolling is larger than the nip spacing of the first rolling.

[0008] This solution uses a gradient roller pressing method to cool the intermediate. Immediately after exiting the extruder, the intermediate is in a hot, molten state and prone to deformation. At this point, the first roller pressing is performed with a smaller spacing. This creates a larger nip area and a greater temperature difference between the nip and the intermediate surface, resulting in high heat transfer efficiency. This allows the SPC board to shrink and solidify at a faster rate during the initial cooling process. The second roller pressing nip spacing is larger than the previous roller pressing spacing, allowing the intermediate to partially rebound as the temperature continues to cool, releasing stress perpendicular to the intermediate thickness.

[0009] Preferably, in S3, the ratio between the diameter of the cooling roller and the thickness compression value of the intermediate after entering the pressing zone is 1000:1 to 2000:1.

[0010] After entering the nip, the intermediate is squeezed by the cooling rollers. Its thickness is limited by the nip spacing, causing the upper and lower epidermal layers of the intermediate to collapse inward, and the overall thickness of the intermediate changes. This change is referred to as the thickness compression value. For example, the intermediate is 6mm thick when entering the nip, and the nip spacing is 4.4mm. At this point, the thickness compression value of the intermediate is 1.6mm. Within the rolling process, the proportional relationship between the diameter of the cooling roller and the thickness compression value of the intermediate determines the size of the nip. Within this parameter range, the area occupied by the nip on the cooling roller surface is relatively small, and the surface temperature of the cooling roller is less likely to fluctuate. Different areas of the intermediate are exposed to the same cooling roller temperature, resulting in uniform process conditions. For the intermediate, a larger nip area and a longer cooling time can further enhance the cooling roller's role in promoting interfacial fusion in multilayer structures.

[0011] Preferably, in S4, the predetermined shape is shaped by at least two roller rolling operations, and the nip spacing of the second rolling operation is greater than the nip spacing of the first rolling operation.

[0012] The pressure zone spacing refers to the spacing between the rollers or the spacing between the pressure rollers and the pressure-bearing plane. In the prior art, after the intermediate extruded from the co-extrusion die is cooled by the cold water die, the internal structure of the foaming layer has been highly shaped. Therefore, during shaping, the pressure zone spacing is gradually narrowed for rolling, with the aim of making the sheet approach the target thickness step by step. The S3 step in this scheme is only for pre-shaping, and further rolling and shaping is required by the rolling of the S4 step. Furthermore, during the first rolling in S4, the spacing between the two rollers is small, and the predetermined shape is squeezed more, which can quickly destroy the large bubbles and hole defects remaining in the foaming layer, and optimize the homogeneity of the foaming layer structure and wall thickness; then the second rolling is carried out, and the pressure zone spacing of the second rolling is larger than that of the first rolling, allowing the predetermined shape to rebound slightly within a controlled range and release residual stress, thereby stabilizing the structure after the first rolling adjustment optimization.

[0013] Preferably, in S4, after the predetermined shape is completed, it is shaped by at least two roller rollings, and during the first rolling, at least one of the decorative layer, the wear-resistant layer, and the UV layer is pressed to the surface of the upper surface layer of the predetermined shape; the pressure zone spacing of the second rolling is greater than the pressure zone spacing of the first rolling.

[0014] The decorative layer is composed of patterned polyvinyl chloride resin, the wear-resistant layer includes polyvinyl chloride resin, stabilizers, plasticizers, etc., and the UV layer is composed of polyurethane-acrylate. All three are surface finishing layers for flooring profiles. The decorative, wear-resistant, and UV layers are introduced during the first rolling process. At this point, the structure and distribution of the microscopic cells in the upper surface layer, foaming layer, and lower surface layer are essentially stable. The alignment of the decorative, wear-resistant, and UV layers with the predetermined shape during pressing is easy to control, achieving higher precision. The first rolling process uses a smaller nip spacing, enabling the surface finishing layer to be quickly and tightly pressed onto the upper surface layer of the predetermined shape. The second rolling process uses a larger nip spacing, providing space for tension adjustment in the surface finishing layer, preventing localized overstretching or wrinkling, and maintaining a uniform thickness across the surface finishing layer.

[0015] Preferably, in the lightweight multi-layer floor profile, the raw materials for the foaming layer include: by weight, 20-30 parts of polyvinyl chloride resin powder, 35-55 parts of calcium carbonate, 1-2 parts of calcium zinc stabilizer, 0.3-0.4 parts of PE wax, 0.2-0.4 parts of stearic acid, 0.05-0.15 parts of OPE wax, 0.8-1.2 parts of plasticizer HL-501, 3-4 parts of plasticizer HL-932, 0.1-0.2 parts of AC foaming agent, and 0.05-0.15 parts of NC foaming agent; The raw materials of the upper surface layer and / or the lower surface layer include: by weight, 20 to 30 parts of polyvinyl chloride resin powder, 50 to 70 parts of calcium carbonate, 1 to 2 parts of calcium zinc stabilizer, 0.2 to 0.4 parts of PE wax, 0.3 to 0.5 parts of stearic acid, 0.4 to 0.6 parts of OPE wax, 0.8 to 1.2 parts of plasticizer HL-501, 0.4 to 0.6 parts of plasticizer chlorinated polyvinyl chloride resin, 0.4 to 0.6 parts of plasticizer dioctyl terephthalate, and 0.04 to 0.06 parts of carbon black.

[0016] In order to improve the bonding effect between the upper and lower surface layers and the foaming layer, the components of the upper and lower surface layers and the foaming layer should be selected as consistent as possible.

[0017] This solution uses a roller cooling process, and there is line contact between the roller and the intermediate. At this time, the force-bearing area of ​​the intermediate is smaller than its force-bearing area in the cold water mold; therefore, in terms of the component ratio of the foaming layer, the feeding ratio of the foaming agent and the polyvinyl chloride resin powder in this solution is lower than that in the prior art. The intermediate is already in a fully foamed state when it is extruded from the co-extrusion mold, preventing rebound due to continued foaming during the pre-forming rolling step.

[0018] Furthermore, the amount of AC foaming agent used in the foaming layer is slightly greater than that of NC foaming agent. The decomposition temperature of AC foaming agent is between 205 and 215°C, while the decomposition temperature of NC foaming agent is between 130 and 150°C. It is generally believed in the prior art that using more high-temperature foaming agent than low-temperature foaming agent will cause gas to be concentrated in the later stages of the foaming phase, and the bubbles generated in the later stages will destroy the bubbles generated in the earlier stages, resulting in uneven density and degraded morphology of the bubble structure in the melt. However, the overall amount of foaming agent used in this solution is low. Slightly increasing the proportion of AC foaming agent can cause the foaming agent to generate bubbles at a stage when the melt viscosity is lower and the fluidity is higher, making the bubble structure more uniform and delicate, and improving the homogeneity of the foam layer structure.

[0019] Preferably, the particle size range of the calcium carbonate used in the foaming layer, the upper surface layer and the lower surface layer is d p Meet 10μm≤ d p ≤15μm.

[0020] Calcium carbonate within this particle size range has a moderate specific surface area and can serve as a foaming core in combination with NC foaming agent and AC foaming agent to form a uniform pore structure. It will not adsorb a large amount of plasticizer due to being too fine, resulting in excessive melt viscosity, nor will it cause uneven flow resistance due to being too coarse.

[0021] Preferably, the thickness of the multi-layer floor profile is 4 mm to 7 mm.

[0022] Preferably, the thickness distribution of the multi-layer floor profile structure is as follows: the thickness of the upper surface layer accounts for 15% to 20% of the thickness of the intermediate body, the thickness of the foam layer accounts for 60% to 70% of the thickness of the intermediate body, and the thickness of the lower surface layer accounts for 15% to 20% of the thickness of the intermediate body.

[0023] In multi-layer floor profiles, the main function of the upper and lower surface layers is to protect and support the foam layer. The main function of the foam layer is to reduce density, provide a slightly bouncy feel, and provide quiet performance. When the thickness of the upper and lower surface layers is large, the thickness of the foam layer is reduced, the difficulty of shaping increases, and it is not conducive to process quality control. When the thickness of the upper and lower surface layers is insufficient, on the one hand, it is impossible to provide sufficient mechanical strength for the profile. On the other hand, the difficulty of extruding the upper and lower surface layers increases, and the friction between the melt and the extrusion port increases. It is necessary to increase the amount of plasticizer in the raw material formula to reduce the melt viscosity and improve the lubricity. However, the plasticizer will evaporate, be extracted or migrate in the subsequent reheating and shaping step, destroying the structure of the upper and lower surface layers, and at the same time hindering the interface bonding between the surface modification layer and the upper surface in the shaping step. Therefore, in this solution, the thickness ratio of the upper surface layer, the foaming layer, and the lower surface layer is controlled at (15~20):(60~70):(15~20). The resulting product has appropriate strength and density, and is also convenient for controlling the thickness of each layer to be stable during processing.

[0024] The present invention also provides a lightweight multi-layer floor profile, which is prepared by any of the aforementioned preparation processes.

[0025] On the premise that the thickness of the profile is the same and the mechanical properties meet the standards, the floor profile obtained by the above process has a core layer of foam material, and its density is lower than that of the profile composed of pure solid materials, making it lightweight and easy to transport.

[0026] The present invention uses the method of in-mold co-extrusion foaming to naturally combine the upper surface layer, the foaming layer and the lower surface layer to form a multi-layer structure, and improves the thickness determination method of the multi-layer structure; in the pre-forming, calendering and embossing steps, the profile is first rolled with a smaller nip spacing to quickly achieve the effect of the step itself, and then the profile is rolled with a larger nip spacing to guide the stress release, so as to achieve the stability of the profile thickness on a time scale and the homogeneity of the spatial structure. The present invention further proposes a lightweight multi-layer floor profile product based on this process, and the mixing formula ratio of the upper and lower surface layers and the foaming layer is adjusted and matched based on the process characteristics, so that the floor profile product not only has a lower density and is easy to transport, but also each layer of the floor structure has a uniform wall thickness, is not easy to produce structural separation under long-term use, has a stable structure, and has a prolonged service life. The density of conventional PVC stone plastic floor profiles is between 2.0 and 2.1 g / cm 3 The thickness of the floor profile obtained by this method is 4mm~7mm, and the mechanical properties are good; the density of the floor profile is 1.3~1.4g / cm 3 , which greatly reduces the weight of the board and reduces transportation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the contact area between the roller and the floor profile being processed Legend mark: 1 roller, 110 pressure zone, d x Nip spacing, L x Nip length, 2 intermediates, 210 upper surface layer, 220 foaming layer, 230 lower surface layer, d 1The thickness of the intermediate when it enters the nip. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below generally represent only a portion of the present invention, rather than all of the embodiments. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0029] Comparative Example The technical solution adopted in the comparative example is a conventional technical solution, that is, after co-extrusion foaming, a cooling water shaping mold is used to shape the intermediate, and no special requirements are made on the particle size of calcium carbonate. The steps of this solution are as follows: 1. Prepare the upper surface layer raw material, lower surface layer raw material and foaming layer raw material according to the following components.

[0030] Raw materials for the upper surface layer: by weight, 25.0 parts of polyvinyl chloride resin powder, 30.0 parts of 325 mesh calcium carbonate, 30.0 parts of 1000 mesh calcium carbonate, 2.0 parts of calcium zinc stabilizer, 0.3 parts of PE wax, 0.4 parts of internal lubricant (HLD-60), 0.5 parts of oxidized polyethylene (OPE wax), 1.0 parts of HL-501, 0.5 parts of chlorinated polyvinyl chloride resin (CPE-S), 1.0 parts of dioctyl terephthalate (DOTP), and 0.05 parts of carbon black.

[0031] Lower surface layer materials: same as upper surface layer materials.

[0032] Raw materials for the foaming layer: by weight, polyvinyl chloride resin powder (special for foaming) accounts for 25.0 parts, 1000 mesh calcium carbonate accounts for 20.0 parts, 325 mesh calcium carbonate accounts for 25.0 parts, calcium zinc stabilizer accounts for 1.0-2.0 parts, PE wax accounts for 0.3-0.4 parts, internal lubricant (HLD-60) accounts for 0.2 parts, oxidized polyethylene (OPE wax) accounts for 0.10 parts, processing aid HL-501 accounts for 1.0 parts, foaming regulator HL-932 accounts for 3.5 parts, azodicarbonamide (AC foaming agent) accounts for 0.15 parts, and sodium bicarbonate (NC foaming agent) accounts for 0.10 parts.

[0033] 2. Place the upper and lower surface layer raw materials in a hot mixer, mix them to 100-120°C, then place them in a cold mixer and cool them to below 50°C; place the foaming layer raw materials in another hot mixer, mix them to 110-130°C, then place them in a cold mixer and cool them to below 50°C; 3. According to the following parameters, the mixed upper and lower surface layer materials are fed into an 80-type extruder for plasticization and extrusion. The mixed foam layer materials are fed into a 92-type extruder for plasticization and extrusion. The materials pass through barrel zones 1 to 5 in sequence, are distributed by the confluence core, and then enter the co-extrusion die (connector zone) in a distribution ratio of upper surface layer thickness: foam layer thickness: lower surface layer thickness = 20:60:20. Melt bonding and foaming of the foam layer materials are carried out in the co-extrusion die. Table 1 Parameters of Type 80 extruder Barrel temperature zone Barrel area 1 Barrel Zone 2 Barrel Zone 3 Barrel Zone 4 Barrel Zone 5 Barrel Zone 6 Converging core area Connector region 1 Connector II Barrel temperature C 200.0 195.0 190.0 180.0 170.0 165.0 170.0 170.0 Recommended host speed (rmin) 14.5 Recommended feeding speed (rmin) 11.74 Recommended host current (A) 65.59 Main machine vacuum degree (Mpa) -0.09 Table 2 Parameters of 92 type extruder Barrel temperature zone Barrel area 1 Barrel Zone 2 Barrel Zone 3 Barrel Zone 4 Barrel Zone 5 Barrel Zone 6 Converging core area Connector region 1 Connector II Barrel temperature / C 195.0 190.0 185.0 180.0 175.0 165.0 170.0 175.0 Recommended host speed (rmin) 12.5 Recommended feeding speed (rmin) 14.5 Recommended host current (A) 117 Main machine vacuum degree (Mpa) -0.07 "Barrel Zone 1" and other terms are commonly used by those skilled in the art to describe the working sections of the Model 80 and Model 92 extruders. Barrel Zone 1, Barrel Zone 2, Barrel Zone 3, Barrel Zone 4, and Barrel Zone 5 correspond to the pre-plasticizing zone, plasticizing zone, homogenizing zone 1, homogenizing zone 2, and extrusion zone, respectively. Missing temperature values ​​in the table indicate that active heating is not performed in that step, the same applies below.

[0034] 4. Extrude an intermediate having a three-layer structure including an upper surface layer, a foaming layer, and a lower surface layer from the extrusion port of the co-extrusion die, with the extrusion port height being 6 mm; 5. Cool the die through the cooling water setting table. The die height is 6.0±0.1mm, the length is 1m, and the cooling water temperature is 25℃. 6. According to the following parameters, the board emerging from the cold water calibrating table mold is rolled through one and two rollers, then passed through a third roller to laminate the decorative layer and the wear-resistant layer. After lamination, it is embossed through four and five rollers to obtain the floor profile. The temperature of the first, second, and third rollers is 170°C to 180°C. The profile is reheated and softened as it passes through the rollers, making it plastic. The nip spacing of the first roller is 5.5±0.1mm, the nip spacing of the second roller is 5.5±0.1mm, the nip spacing of the third roller is 5.5±0.1mm, and the nip spacing of the fourth roller is 5.5±0.1mm. Table 3 Roller area parameters

[0035] 7. The performance of the obtained floor profile was tested and the results are shown in the following table.

[0036] Table 4 Performance test results of the composite floor obtained in the comparative example

[0037] For multi-layer flooring, if the layers are not tightly pressed together, deformation, misalignment, and bulging can easily occur within the composite structure after installation. This quality parameter can be tested using the longitudinal heating rate of change during factory performance testing. As shown in Table 4, the flooring profile prepared in Comparative Example 1 failed the longitudinal heating rate of change test. Example

[0038] The technical solution adopted in the embodiment is an improved solution proposed by the present invention. The steps of this solution are as follows: 1. Prepare the upper surface layer raw material, lower surface layer raw material and foaming layer raw material according to the following components.

[0039] Upper surface layer raw materials: by weight, polyvinyl chloride resin powder accounts for 25.0 parts, 1000 mesh calcium carbonate accounts for 60.0 parts, calcium zinc stabilizer accounts for 2.0 parts, PE wax accounts for 0.3 parts, internal lubricant (HLD-60) accounts for 0.4 parts, oxidized polyethylene (OPE wax) accounts for 0.5 parts, HL-501 accounts for 1.0 parts, chlorinated polyvinyl chloride resin (CPE-S) accounts for 0.5 parts, dioctyl terephthalate (DOTP) accounts for 0.5 parts, and carbon black accounts for 0.05 parts.

[0040] Lower surface layer materials: same as upper surface layer materials.

[0041] Raw materials for the foaming layer: by weight, polyvinyl chloride resin powder (special for foaming) accounts for 25.0 parts, 1000 mesh calcium carbonate accounts for 45.0 parts, calcium zinc stabilizer accounts for 1.0-2.0 parts, PE wax accounts for 0.3-0.4 parts, internal lubricant (HLD-60) accounts for 0.2 parts, oxidized polyethylene (OPE wax) accounts for 0.10 parts, processing aid HL-501 accounts for 1.0 parts, foaming regulator HL-932 accounts for 3.5 parts, azodicarbonamide (AC foaming agent) accounts for 0.15 parts, and sodium bicarbonate (NC foaming agent) accounts for 0.10 parts.

[0042] 2. Place the upper surface layer raw materials and foaming layer raw materials into a hot mixer, mix them in the hot mixer until the temperature reaches 100-120°C, then place them in a cold mixer and cool them down to below 50°C. Place the foaming layer raw materials into the No. 2 hot mixer, mix them in the hot mixer until the temperature reaches 110-130°C, then place them in a cold mixer and cool them down to below 50°C. 3. According to the parameters in the comparative example, the upper surface layer raw materials and the lower surface layer raw materials were added to the 80-type extruder for plasticization and extrusion, and the mixed foam layer raw materials were added to the 92-type extruder for plasticization and extrusion. The materials passed through barrel zones 1 to 5 in sequence, and were distributed by the confluence core before entering the co-extrusion die (connector zone) in a distribution ratio of upper surface layer thickness: foam layer thickness: lower surface layer thickness = 20:60:20. Melt bonding and foaming of the foam layer raw materials were carried out in the co-extrusion die. 4. Extrude an intermediate having a three-layer structure including an upper surface layer, a foaming layer, and a lower surface layer from the extrusion port of the co-extrusion die, with the extrusion port height being 6 mm; 5. The intermediate is pre-shaped by rolling with two sets of cooling rollers; all rollers are 120 cm in diameter, and the surface temperature of the cooling rollers is controlled at 80 ± 5 ° C by the internal oil circulation system; the distance between the extrusion port and the outer surface of the first set of rollers is 15 cm, the nip spacing of the first set of rollers is 4.8 ± 0.1 mm, and the nip spacing of the second set of rollers is 5.4 ± 0.1 mm; the intermediate is cooled to 150 ° C after passing through the first set of rollers and to 130 ° C after passing through the second set of rollers. The nip formed between the rollers and the intermediate is as follows: Figure 1 As shown, the thickness of the intermediate body when entering the nip d1 is about 5~7mm, and the overall thickness compression value of the upper and lower surfaces of the intermediate is about 0.6~1.2mm. At this time, the length of the nip between the cooling roller and the intermediate L x About 1.5~3cm; 6. Following the parameters in the comparative example, the predetermined shape after roller rolling and cooling is rolled through first and second rollers, then through a third roller for laminating the decorative layer and the wear-resistant layer. After lamination, the shape is embossed through fourth and fifth rollers to obtain a flooring profile. The temperatures of the first, second, and third rollers are between 170°C and 180°C, so that the profile is reheated and softened as it passes through the rollers, imparting plasticity. The nip spacing of the first roller is 4.2±0.1mm, the nip spacing of the second roller is 5.5±0.1mm, the nip spacing of the third roller is 4.2±0.1mm, and the nip spacing of the fourth roller is 5.5±0.1mm. 7. The performance of the obtained composite floor was tested and the results are shown in the following table.

[0043] Table 5 Performance test results of the composite floor obtained in the embodiment

[0044] Comparing the Example with the Comparative Example, it was found that, after improving the thickness setting method and the selection of formulation reagents, the flooring material prepared in the Example met the requirements for longitudinal heating rate of change. This demonstrates that the flooring material prepared in this Example has good structural homogeneity, high-quality workmanship, smooth and durable after laying, and a long service life. Furthermore, the composite flooring produced in this solution has a uniform wall thickness and a stable structure after single-roll and double-roll calendering, thus maintaining high alignment accuracy with additional layers such as decorative layers, wear-resistant layers, or UV coatings.

Claims

1. A method for preparing a multi-layer structure floor profile, characterized in that: The steps include: S1, obtaining upper surface layer raw materials, foaming layer raw materials, and lower surface layer raw materials; S2, extruding the upper surface layer raw material, the foaming layer raw material, and the lower surface layer raw material into a co-extrusion die, completing foaming of the foaming layer in the co-extrusion die, and extruding an intermediate having at least a three-layer structure of the upper surface layer, the foaming layer, and the lower surface layer from an extrusion port of the co-extrusion die; S3, disposing a pair of cooling rollers having a surface temperature lower than that of the intermediate at the extrusion port, wherein the cooling rollers roll the intermediate in conjunction with the extrusion process of the intermediate to obtain a predetermined shape; the contact area between the surfaces of the cooling rollers and the intermediate forms a nip zone, and the distance between the nip zones of the cooling rollers is less than the height of the extrusion port; S4. Rolling the predetermined shape with a roller to reheat the predetermined shape and then set the shape to obtain a multi-layer floor profile.

2. The preparation method according to claim 1, characterized in that In S3, the intermediate is rolled by the cooling roller at least twice, and the nip spacing of the second rolling is larger than the nip spacing of the first rolling.

3. The preparation method according to claim 1, characterized in that In S3, the ratio between the diameter of the cooling roller and the thickness compression value of the intermediate after entering the pressing zone is 1000:1 to 2000:

1.

4. The preparation method according to claim 1, characterized in that In the step S4, the predetermined shape is shaped by at least two roller pressings, and the nip spacing of the second rolling is greater than the nip spacing of the first rolling.

5. The preparation method according to claim 4, characterized in that In S4, after the predetermined shape is completed, it is shaped by at least two roller rolling operations, and during the first rolling operation, at least one of the decorative layer, the wear-resistant layer, and the UV layer is pressed onto the surface of the upper surface layer of the predetermined shape; the nip spacing of the second rolling operation is greater than the nip spacing of the first rolling operation.

6. The preparation method according to claim 1, characterized in that The raw materials of the foaming layer include: by weight, 20-30 parts of polyvinyl chloride resin powder, 35-55 parts of calcium carbonate, 1-2 parts of calcium zinc stabilizer, 0.3-0.4 parts of PE wax, 0.2-0.4 parts of stearic acid, 0.05-0.15 parts of OPE wax, 0.8-1.2 parts of plasticizer HL-501, 3-4 parts of plasticizer HL-932, 0.1-0.2 parts of AC foaming agent, and 0.05-0.15 parts of NC foaming agent; The raw materials of the upper surface layer and / or the lower surface layer include: by weight, 20 to 30 parts of polyvinyl chloride resin powder, 50 to 70 parts of calcium carbonate, 1 to 2 parts of calcium zinc stabilizer, 0.2 to 0.4 parts of PE wax, 0.3 to 0.5 parts of stearic acid, 0.4 to 0.6 parts of OPE wax, 0.8 to 1.2 parts of plasticizer HL-501, 0.4 to 0.6 parts of plasticizer chlorinated polyvinyl chloride resin, 0.4 to 0.6 parts of plasticizer dioctyl terephthalate, and 0.04 to 0.06 parts of carbon black.

7. The preparation method according to claim 6, characterized in that The particle size range of calcium carbonate used in the foaming layer, the upper surface layer and the lower surface layer is d p Meet 10μm≤ d p ≤15μm.

8. The preparation method according to claim 1, characterized in that The thickness of the multi-layer floor profile is 4 mm to 7 mm.

9. The preparation method according to claim 8, characterized in that The thickness distribution of the multi-layer floor profile structure is as follows: the thickness of the upper surface layer accounts for 15% to 20% of the thickness of the intermediate body, the thickness of the foam layer accounts for 60% to 70% of the thickness of the intermediate body, and the thickness of the lower surface layer accounts for 15% to 20% of the thickness of the intermediate body.

10. A lightweight multi-layer floor profile, characterized in that: The preparation steps include the preparation method according to any one of claims 1 to 9.

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