A multilayer material for SMC recycling, a mold for its preparation, and a preparation method thereof.

Abstract

This invention discloses a multi-layer material for recycling and reusing SMC, a preparation mold, and a preparation method. The multi-layer material includes a semi-finished SMC product and a foamed material layer. The semi-finished SMC product includes a top plate and a surrounding edge around the outer edge of the top plate, forming a cavity. The foamed material layer fills the cavity, and the foamed material layer is uniformly filled with crushed recycled SMC material. This invention provides a multi-layer material for recycling and reusing SMC, which achieves efficient recycling of waste SMC while ensuring mechanical properties. The foamed material layer reduces density, improves sound insulation properties, optimizes processing adaptability, and reduces production costs, offering both environmental and economic advantages.

Description

Technical Field

[0001] This invention relates to the field of SMC (Sheet Molding Compound) technology, and more specifically, to a multilayer material for recycling SMC, a mold for its preparation, and a method for its preparation. Background Technology

[0002] SMC (Sheet Molding Compound) is a high-strength, high-rigidity composite material widely used in automotive, aerospace, and construction industries. However, SMC is mainly composed of unsaturated polyester resin, glass fiber, and fillers. Its thermosetting properties make it difficult to melt and reshape after curing, limiting the feasibility of traditional mechanical or chemical recycling methods. Currently, the disposal of end-of-life SMC parts mainly relies on incineration or landfill, but these methods have certain environmental problems: incineration may release harmful gases, such as styrene monomers or dioxins, while landfill may lead to long-term environmental pollution. In addition, due to the high density of SMC, it occupies a lot of landfill space, which also increases the cost of waste management. Summary of the Invention

[0003] This invention aims to address one of the technical problems in related technologies to a certain extent. To this end, embodiments of this invention propose a multi-layered material for the recycling and reuse of SMC. This multi-layered material ensures mechanical properties while achieving efficient recycling of waste SMC. The filling of the foam material layers reduces density, improves sound insulation properties, optimizes processing adaptability, and simultaneously reduces production costs, thus possessing both environmental and economic advantages.

[0004] This invention also proposes a mold for preparing the above-mentioned SMC recycled multilayer material.

[0005] This invention also proposes a method for preparing the above-mentioned SMC recyclable multilayer material.

[0006] The technical solution adopted by the present invention is to provide a multi-layer material for SMC recycling, including SMC semi-finished product and foam material layer. The SMC semi-finished product includes a top plate and a surrounding edge arranged around the outer edge of the top plate. The top plate and the surrounding edge form a cavity. The foam material layer fills the cavity, and the interior of the foam material layer is uniformly filled with crushed SMC recycled material.

[0007] By adopting the above structure, this multi-layered material can effectively recycle waste SMC materials while ensuring mechanical properties. Specifically, the filling of the foam material layer not only reduces the overall material density, making it lighter, but also improves the material's sound insulation properties. Since the crushed SMC recycled material is uniformly dispersed in the foam material, this recycled material can partially replace virgin foamable material, thereby reducing production costs and improving resource utilization. Furthermore, this structure maintains good processing adaptability without affecting the overall strength and durability of the material, making it suitable for molding products of different shapes and sizes. Compared to traditional landfill and incineration methods, the technical solution of this invention has significant advantages in terms of environmental friendliness and economic feasibility, providing a new approach for the sustainable development of SMC materials.

[0008] According to one embodiment of the present invention, the SMC recycled material is a particle with a particle size range of 0.1 mm to 20 mm, preferably a particle with a particle size range of 2 mm to 5 mm.

[0009] According to one embodiment of the present invention, the mass ratio of the SMC recycled material to the foam material in the foaming material layer is 5:100 to 80:20, preferably 20:80 to 30:70.

[0010] According to one embodiment of the present invention, the foam material includes at least one of the following: foamed polyethylene, foamed polypropylene, foamed polystyrene, foamed ethylene-vinyl acetate, and foamed polyurethane.

[0011] A multilayer material preparation mold includes an SMC molding mold and a foaming molding mold. The SMC molding mold is used to prepare an SMC semi-finished product, and the foaming molding mold is used to fill the cavity of the SMC semi-finished product with foam material containing recycled SMC material and cool it to form a foam material layer.

[0012] According to one embodiment of the present invention, when the upper mold core of the foaming mold is closed, it contacts the edge of the SMC semi-finished product to seal the cavity of the SMC semi-finished product.

[0013] According to one embodiment of the present invention, the foaming molding mold includes a first foaming mold and a second foaming mold. The first foaming mold is used to foam and form a first foam material layer in the cavity of the SMC semi-finished product, and the second foaming mold is used to form a second foam material layer on the surface of the first foam material layer.

[0014] According to one embodiment of the present invention, the combination of the first foamed material layer and the second foamed material layer constitutes the foamed material layer.

[0015] A method for preparing a multilayer material, such as SMC, which is recycled and reused, includes the following steps:

[0016] S1. Prepare SMC semi-finished products using SMC molding dies;

[0017] S2. Place the SMC semi-finished product in the first foaming mold, and fill and form the first foaming material layer in its cavity.

[0018] A method for preparing a multilayer material for SMC recycling and reuse, characterized by comprising the following steps:

[0019] S1. Prepare SMC semi-finished products using SMC molding dies;

[0020] S2. Place the SMC semi-finished product in the first foaming mold, and fill and form the first foaming material layer in its cavity;

[0021] S3. Place the SMC semi-finished product containing the first foaming material layer into the second foaming mold, and form the second foaming material layer on the surface of the first foaming material layer. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional view of the SMC mold in an embodiment of the present invention.

[0024] Figure 2 This is a cross-sectional view of the SMC semi-finished product in an embodiment of the present invention.

[0025] Figure 3 This is a cross-sectional view of the first foaming mold in an embodiment of the present invention.

[0026] Figure 4 This is a cross-sectional view of the multilayer material in an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the structure of the first foaming mold in an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the structure of the second foaming mold in an embodiment of the present invention.

[0029] Explanation of the labels in the diagram:

[0030] 10. SMC mold; 20. Multilayer material; 30. First foaming mold; 40. Second foaming mold;

[0031] 21. SMC semi-finished product; 22. First foaming material layer; 23. Second foaming material layer;

[0032] 21a. Top plate; 21b. Surrounding edge; 21c. Cavity. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] In this embodiment, the SMC filler is made from crushed waste SMC material, and its composition is as follows:

[0035] Components Content (wt%) SMC fragments (particle size 2mm-5mm) 70-90 Calcium carbonate 5-15 Glass fiber (chopped fibers, 3-6mm in length) 5-15

[0036] SMC filler undergoes screening, cleaning, and drying to ensure good dispersibility when filled into the foam material layer and to form a stable bond with the foam material.

[0037] SMC semi-finished products are made from sheet molding compound, and their main components are as follows:

[0038] Components Content (wt%) Unsaturated polyester resin 20-35 Glass fiber (chopped fiber, length 25-50mm) 25-40 Calcium carbonate filler 15-30 Initiator (peroxide) 1-3 Toughening agents (styrene monomers or vinyl monomers) 3-7 Other additives (release agents, diluents, etc.) 1-5

[0039] SMC semi-finished products are molded to form a shell-like structure with a top plate and surrounding edges, providing a closed cavity for subsequent filling with foam material layers.

[0040] The foamed material layer is composed of a polymer foaming system and SMC filler, with the following formula:

[0041] Components Content (wt%) Polyurethane or foamed polyethylene 50-80 SMC packing (crushed SMC particles) 10-40 Foaming agents (such as AC foaming agent) 1-5 Crosslinking agent 0.5-2 stabilizer 0.5-2

[0042] In some other embodiments, the foam material is one or more of expanded polypropylene, expanded polystyrene, expanded ethylene-vinyl acetate, and expanded polyurethane.

[0043] Examples 1 and 2

[0044] like Figure 1-4 As shown in the figure, this embodiment discloses a multi-layer material for SMC recycling, including SMC semi-finished product and foam material layer. The SMC semi-finished product includes a top plate and a surrounding edge arranged around the outer edge of the top plate. The top plate and the surrounding edge form a cavity. The foam material layer fills the cavity, and the interior of the foam material layer is uniformly filled with crushed SMC recycled material.

[0045] This embodiment also discloses a mold for preparing multilayer materials, including an SMC molding mold and a foaming molding mold. The SMC molding mold is used to prepare SMC semi-finished products, and the foaming molding mold is used to fill the cavity of the SMC semi-finished product with foam material containing recycled SMC material, and then cool and solidify it to form a foam material layer. When the mold is closed, the upper mold core of the foaming molding mold contacts the edge of the SMC semi-finished product to seal the cavity of the SMC semi-finished product. The foaming molding mold includes a foaming mold, which is used to foam and solidify a foam material layer within the cavity of the SMC semi-finished product.

[0046] In this embodiment, the method for preparing the mold includes the following steps:

[0047] S1. SMC semi-finished products are prepared using SMC molding dies. The SMC used is ordinary SMC sheet molding compound, with dimensions of 1000mm-1500mm in width and 2mm in thickness. The SMC sheet is placed into the SMC molding die, which is preheated to 120℃-160℃ to promote resin curing. Simultaneously, a release agent is applied to the die surface to prevent adhesion of the molded product. Then, pre-cut SMC sheets are placed into the die cavity according to the set weight and shape, ensuring uniform material distribution to guarantee the structural integrity of the molded product. The upper and lower molds are closed, and high pressure (usually 5-15MPa) is applied. Under high temperature and pressure, the resin gradually flows and fills the cavity, while a cross-linking and curing reaction occurs. Glass fiber plays a reinforcing role during molding, giving the molded SMC semi-finished product good mechanical properties. After a certain curing time (generally 30-300 seconds, depending on the material formulation; in this example, curing time is 120 seconds), the SMC semi-finished product reaches the designed strength and dimensional stability, and is then cooled to the demolding temperature.

[0048] S2. The SMC semi-finished product is placed in a foaming mold, and a foamed material layer is filled and formed in its cavity. Specifically, the shell-shaped SMC semi-finished product is placed into the foaming mold with its opening facing the injection end of the mold. When the upper mold of the foaming mold closes, the upper mold core contacts the edge of the SMC semi-finished product to seal its cavity. Then, foaming material mixed with recycled SMC is injected into the cavity. The foaming agent decomposes upon heating or undergoes a chemical reaction to generate gas, causing the material to expand and form a uniform porous structure. As the reaction proceeds, the foaming material gradually fills the entire mold cavity and solidifies within a certain time, ultimately obtaining a dimensionally stable and uniformly dense foamed product. The mass ratio of recycled SMC to the foam material in the foaming material layer is 5:100.

[0049] The difference between Example 2 and Example 1 is that in Example 2, the mass ratio of SMC recycled material to foam material in the foaming material layer is 80:20.

[0050] Examples 3 to 8

[0051] Combination Figure 5-6 As shown, this embodiment differs from Embodiment 1 in that the foaming material layer in Embodiment 1 adopts a single-layer structure, while the foaming material layer in this embodiment adopts a double-layer structure.

[0052] This embodiment also discloses a mold for preparing a multilayer material, including an SMC molding mold and a foaming molding mold. The SMC molding mold is used to prepare an SMC semi-finished product, and the foaming molding mold is used to fill the cavity of the SMC semi-finished product with foam material containing recycled SMC material, and then cool and solidify it to form a foamed material layer. When the mold is closed, the upper core of the foaming molding mold contacts the edge of the SMC semi-finished product to seal the cavity. The foaming molding mold includes a first foaming mold and a second foaming mold. The first foaming mold is used to foam and form a first foamed material layer within the cavity of the SMC semi-finished product, and the second foaming mold is used to form a second foamed material layer on the surface of the first foamed material layer. The combination of the first foamed material layer and the second foamed material layer constitutes the foamed material layer.

[0053] In this embodiment, the method for preparing the mold includes the following steps:

[0054] S1. SMC semi-finished products are prepared using SMC molding dies. The SMC used is ordinary SMC sheet molding compound, with dimensions of 1000mm-1500mm in width and 2mm in thickness. The SMC sheet is placed into the SMC molding die, which is preheated to 120℃-160℃ to promote resin curing. Simultaneously, a release agent is applied to the die surface to prevent adhesion of the molded product. Then, pre-cut SMC sheets are placed into the die cavity according to the set weight and shape, ensuring uniform material distribution to guarantee the structural integrity of the molded product. The upper and lower molds are closed, and high pressure (usually 5-15MPa) is applied. Under high temperature and pressure, the resin gradually flows and fills the cavity, while a cross-linking and curing reaction occurs. Glass fiber plays a reinforcing role during molding, giving the molded SMC semi-finished product good mechanical properties. After a certain curing time (generally 30-300 seconds, depending on the material formulation; in this example, curing time is 120 seconds), the SMC semi-finished product reaches the designed strength and dimensional stability, and is then cooled to the demolding temperature.

[0055] S2. The SMC semi-finished product is placed in the first foaming mold, and the cavity is filled and formed with a first foaming material layer. Specifically, the shell-shaped SMC semi-finished product is placed into the first foaming mold, with the opening of the SMC semi-finished product facing the injection end of the first foaming mold. When the upper mold of the first foaming mold closes, the upper mold core contacts the edge of the SMC semi-finished product to seal the cavity. Then, the first foaming mold injects foaming material into the cavity. The foaming material contains recycled SMC material. Under suitable temperature and pressure, the foaming agent decomposes thermally or reacts chemically to generate gas, causing the material to expand in volume and form a uniform porous structure. As the reaction proceeds, the foaming material gradually fills the entire mold cavity and solidifies within a certain time, ultimately obtaining a dimensionally stable and uniformly dense foamed product.

[0056] S3. Place the SMC semi-finished product in the second foaming mold, and fill and form a second foaming material layer in its cavity. Specifically, place the shell-shaped SMC semi-finished product into the second foaming mold, with the opening of the SMC semi-finished product facing the injection end of the second foaming mold. When the upper mold of the second foaming mold closes, the upper mold core contacts the edge of the SMC semi-finished product to seal its cavity. Then, the second foaming mold injects foaming material into the cavity. The foaming material contains recycled SMC material. The foaming agent decomposes upon heating or undergoes a chemical reaction to generate gas, causing the material to expand and form a uniform porous structure. As the reaction proceeds, the foaming material gradually fills the entire mold cavity and solidifies within a certain time, ultimately obtaining a dimensionally stable and uniformly dense foamed product.

[0057] The mass ratio of recycled SMC to foam material in the foaming material layer is:

[0058] First foaming material layer Second foaming material layer Example 3 5:100 80:20 Example 4 30:100 80:20 Example 5 50:100 60:20 Example 6 80:20 5:100 Example 7 80:20 30:100 Example 8 60:20 50:100

[0059] As shown in the table above, in Examples 3 to 5, the mass proportion of SMC recycled material in the second foaming material layer is greater than that in the first foaming material layer. In Examples 6 to 8, the mass proportion of SMC recycled material in the first foaming material layer is greater than that in the second foaming material layer. In this embodiment, the multilayer material made from recycled SMC is used for outdoor weather-resistant flooring, with applications including parks and garden bridges. The thickness of the multilayer material is 20-100mm. Therefore, the multilayer material made from recycled SMC was used as the test group, and sound insulation tests were conducted using the standard ASTM E2179-09. The test results are shown in the table below:

[0060] Test Items Thickness (mm) Improvement in pedestrian noise (%) Impact noise reduction (%) Example 1 48 23 12 Example 2 48 28 17 Example 3 48 24 13 Example 4 48 26 15 Example 5 48 26 16 Example 6 48 30 21 Example 7 48 32 24 Example 8 48 29 23

[0061] The test results above show that the improvement effects of multilayered materials made from recycled SMC on walking noise and impact noise vary depending on the mass ratio of recycled SMC to foam material. Specifically, Example 7 showed the highest improvement in walking noise at 32%, while Example 6 showed the highest improvement in impact noise at 21%.

[0062] Further analysis of the test results revealed that the mass ratio of SMC recycled material in the first and second foaming material layers significantly impacts the sound insulation performance of the final product. When the mass ratio of SMC recycled material in the first foaming material layer is higher (as in Examples 6 and 7), the improvement in impact noise is better, which is presumably related to the reinforcing effect of the SMC recycled material and the structural characteristics of the foaming material. Conversely, when the mass ratio of SMC recycled material in the second foaming material layer is higher (as in Examples 2 and 5), the improvement in walking noise is relatively better, possibly because the second foaming material layer is closer to the surface and has a stronger ability to absorb high-frequency noise. The final product in Example 8 exhibits the best overall sound insulation performance, significantly improving both impact noise and walking noise.

[0063] Furthermore, from an overall trend perspective, appropriately increasing the proportion of recycled SMC can improve noise suppression performance; however, excessively high recycled SMC content may affect the uniformity and mechanical properties of the foamed material layers. Therefore, in specific applications, the ratio of recycled SMC in the first and second foamed material layers needs to be adjusted according to actual requirements to achieve optimal noise suppression performance.

[0064] In summary, this invention provides a multi-layer material based on recycled SMC, which not only effectively recycles SMC waste and achieves resource reuse, but also exhibits excellent sound insulation performance in outdoor weather-resistant flooring applications. By adjusting the ratio of recycled SMC in the first and second foaming material layers, the sound insulation effect can be optimized for different application scenarios.

[0065] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A multilayer material for SMC recycling and reuse, characterized in that: The product includes SMC semi-finished product and foam material layer. The SMC semi-finished product includes a top plate and a surrounding edge provided around the outer edge of the top plate. The top plate and the surrounding edge form a cavity. The foam material layer fills the cavity and is uniformly filled with crushed SMC recycled material inside the foam material layer. The multilayer material is used for outdoor weather-resistant flooring, with a thickness of 20-100mm. The foamed material layer is composed of a polymer foaming system and SMC filler, with the following formula: 50-80wt% foamed polyurethane or foamed polyethylene, 10-40wt% recycled SMC, 1-5wt% foaming agent, 0.5-2wt% crosslinking agent, and 0.5-2wt% stabilizer. The foamed material layer includes a first foamed material layer and a second foamed material layer. First, the cavity of the SMC semi-finished product is filled and formed into a first foamed material layer. Then, a second foamed material layer is formed on the surface of the first foamed material layer. The mass ratio of SMC recycled material in the first foamed material layer is greater than that in the second foamed material layer.

2. The multilayer material for SMC recycling and reuse according to claim 1, characterized in that: The SMC recycled material consists of particles with a particle size range of 0.1 mm to 20 mm.

3. A multilayer material for SMC recycling and reuse according to claim 1, characterized in that: The mass ratio of the SMC recycled material to the foam material in the foaming material layer is 5:100 to 80:

20.

4. A method for preparing a multilayer material for SMC recycling and reuse as described in any one of claims 1-3, characterized in that... Includes the following steps: S1. Prepare SMC semi-finished products using SMC molding dies; S2. Place the SMC semi-finished product in the first foaming mold, and fill and form the first foaming material layer in its cavity; S3. Place the SMC semi-finished product containing the first foaming material layer into the second foaming mold, and form the second foaming material layer on the surface of the first foaming material layer.

Images