Melamine tableware with hollow interlayer heat insulation structure and compression molding process of melamine tableware

Abstract

The invention discloses melamine tableware with a hollow layer heat insulation structure and a compression molding technology of the melamine tableware, and relates to the field of waste recycling and recycling. The heat insulation structure of the melamine tableware is formed through compression molding of a mold, and raw materials comprise melamine plastic waste powder, modified silicon dioxide aerogel, modified hollow glass beads, a release agent, a coloring agent and a toughening agent. Wherein the melamine plastic waste powder comes from recycling of melamine plastic products, the silicon dioxide aerogel is treated by an amino silane coupling agent, and the hollow glass beads are treated by an aluminate coupling agent; the mold pressing process comprises the specific steps of pre-pressing material preparation, mold pressing forming and the like. The heat insulation property of the melamine tableware is remarkably improved, the technological parameters are reasonable, the forming quality and the mechanical property can be ensured, the melamine tableware is suitable for large-scale production, and meanwhile cyclic utilization and recycling of melamine waste are facilitated.

Description

Technical Field

[0001] This application relates to the field of waste recycling and resource utilization, and in particular to a melamine tableware with a hollow sandwich heat insulation structure and its molding process. Background Technology

[0002] Melamine tableware (i.e., melamine-formaldehyde resin tableware) is widely used in catering, household, and children's products due to its lightweight, drop-resistant, high-temperature resistant, and easy-to-clean properties. However, the excellent properties of melamine tableware also make it difficult to efficiently recycle and reuse melamine resin waste. This means that a large amount of melamine resin waste will be generated in the future, and if it is not effectively recycled, it will inevitably pose a threat to the health of the ecological environment.

[0003] In addition, traditional melamine tableware mostly adopts a single-layer structure. In actual use, although some products improve the heat insulation effect by thickening the edges or designing anti-scalding parts, the heat insulation efficiency is not significantly improved due to the simple structure, and there is still room for improvement in the heat insulation effect. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a melamine tableware with a hollow sandwich insulation structure and its molding process. This melamine tableware exhibits significantly improved insulation, reasonable process parameters, and ensures molding quality and mechanical properties, making it suitable for large-scale production. It also facilitates the recycling and resource utilization of melamine waste.

[0005] To achieve the above objectives, in a first aspect, this application provides a melamine tableware with a hollow sandwich thermal insulation structure, wherein the hollow sandwich thermal insulation structure is obtained by molding using a mold; the raw materials of the melamine tableware include melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, release agent, colorant, and toughening agent; the modified silica aerogel powder is obtained by treating silica aerogel powder with an aminosilane coupling agent; the modified hollow glass microspheres are obtained by treating with an aluminate coupling agent.

[0006] The hollow sandwich thermal insulation structure of the melamine tableware prepared in this application forms a physical thermal insulation barrier through the low thermal conductivity of the gas in the structure; the silica aerogel modified with aminosilane coupling agent has a nanoscale porous structure, and the amino groups introduced on its surface can effectively improve its compatibility with melamine resin, reduce the thermal conductivity of the prepared melamine tableware, and be uniformly dispersed in the melamine resin matrix; the modified hollow glass microspheres also use the hollow cavity to block heat transfer, and at the same time can enhance the interfacial bonding force with melamine resin, avoiding performance degradation caused by filler agglomeration.

[0007] In one feasible implementation, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, release agent, colorant and toughening agent is (70-85):(3-12):(2-8):(1-2):(0.5-1):(5-10).

[0008] The amount of melamine plastic waste powder used can ensure the stability of the matrix; modified silica aerogel and modified hollow glass microspheres form a synergistic heat insulation system. Too high a proportion will lead to increased material brittleness and increase the risk that the components are difficult to disperse and be compatible evenly; mold release agent and toughening agent respectively ensure smooth molding and impact resistance of the tableware, while colorant can achieve the control of appearance color without affecting performance.

[0009] In one feasible embodiment, the aminosilane coupling agent includes any one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl-γ-aminopropyltrimethoxysilane); the aluminate coupling agent includes any one or more of DL-411 aluminate coupling agent, DL-411A aluminate coupling agent, and SG-A1821 aluminate coupling agent.

[0010] Aminosilane coupling agents react with the hydroxyl groups on the surface of silica aerogel powder, introducing amino groups that bind with the triazine rings and imino groups abundant in melamine resin through hydrogen bonds, thereby improving the dispersibility of silica aerogel powder in melamine resin; aluminate coupling agents react with the hydroxyl or carboxyl groups on the surface of hollow glass microspheres through alkoxy groups, transforming them into organophilic groups, thereby enhancing their interfacial bonding with melamine resin and reducing interfacial defects.

[0011] In one feasible implementation, the release agent comprises any one or more of zinc stearate, stearamide, and ethylene bis-stearamide.

[0012] In this application, mold release agents such as zinc stearate migrate to the surface of melamine resin during the compression molding process, forming a lubricating layer, reducing the friction between the mold and the melamine resin, while their chemical inertness prevents adverse reactions with the resin.

[0013] In one feasible implementation, the colorant includes any one or more of titanium dioxide, iron oxide red, iron oxide yellow, iron oxide black, phthalocyanine blue, and phthalocyanine green.

[0014] In this application, inorganic pigments such as titanium dioxide and iron oxide series have high hiding power and chemical stability, while phthalocyanine organic pigments have excellent lightfastness. Both can maintain color fastness during the molding process of melamine resin without affecting the matrix properties.

[0015] In one feasible implementation, the toughening agent comprises any one or more of polyamide, nitrile rubber, and ethylene-vinyl acetate polymers.

[0016] In this application, toughening agents such as polyamide and nitrile rubber form a microphase separation structure in the resin matrix. When the material is subjected to impact, it can absorb energy, prevent crack propagation, and improve the mechanical properties of the melamine tableware.

[0017] In one feasible implementation, the method for preparing the modified silica aerogel powder includes:

[0018] The silica aerogel powder was vacuum dried at 50–80°C for 2–4 hours.

[0019] The dried silica aerogel powder was added to an ethanol-water mixture and ultrasonically dispersed for 10-15 minutes to form a suspension; the mass ratio of silica aerogel powder to ethanol-water mixture was (5-10):(90-95).

[0020] The aminosilane coupling agent was added to the suspension, heated in a water bath at 50-70°C, and stirred at a stirring speed of 200-400 rpm for 1-3 hours; wherein the mass ratio of the aminosilane coupling agent to the silica aerogel powder in the suspension was (1-5):(95-99).

[0021] The modified powder was then collected by vacuum filtration, washed 2-3 times with an ethanol-water mixture, and vacuum dried at 80-100℃ for 4-6 hours to obtain the modified silica aerogel powder.

[0022] In one feasible implementation, the mass ratio of ethanol to water in the ethanol-water mixture is (70-80):(20-30).

[0023] In this application, when silica aerogel powder is modified, vacuum drying can remove adsorbed water on the aerogel surface and avoid excessive hydrolysis and failure of the coupling agent; ultrasonic dispersion ensures uniform suspension of the aerogel; water bath temperature control of 50-70℃ can promote the condensation reaction between the coupling agent and the hydroxyl groups on the aerogel surface, enhance the dispersibility and interfacial bonding of silica aerogel, and give full play to its heat insulation performance in melamine resin tableware.

[0024] In one feasible implementation, the method for preparing the modified hollow glass microspheres includes:

[0025] The hollow glass microspheres were dried in a forced-air drying oven at 80-100℃ for 3-5 hours, cooled to room temperature, and then passed through a 200-300 mesh sieve.

[0026] The dried hollow glass microspheres were added to a high-speed mixer, the speed was controlled at 600-800 rpm, and the mixture was heated to 60-90°C.

[0027] The aluminate coupling agent was heated and melted at 60-80℃ and added to the hollow glass microspheres, and stirred continuously for 30-60 minutes; wherein the mass ratio of the aluminate coupling agent to the hollow glass microspheres was (1-3):(97-99);

[0028] Then stop stirring and allow it to cool naturally to room temperature. Pass it through a 200-300 mesh sieve again to obtain the modified hollow glass microspheres.

[0029] In this application, during the modification process of the hollow glass microspheres, drying and sieving ensure that the microspheres are clean and have uniform particle size, further ensuring that the aluminate coupling agent can uniformly coat the surface of the microspheres; the temperature of 60-90℃ promotes the chemical bonding between the aluminate coupling agent and the surface of the hollow glass microspheres, which also enhances its dispersibility in melamine resin, avoids agglomeration, thereby significantly reducing the thermal conductivity of the obtained melamine resin tableware, while ensuring its mechanical properties.

[0030] Secondly, this application provides a molding process for melamine tableware with a hollow sandwich heat insulation structure, the molding process comprising the following steps:

[0031] Add melamine plastic waste powder, modified silica aerogel powder and modified hollow glass microspheres to a high-speed mixer, heat to 50-60℃, and start stirring at 200 rpm.

[0032] After stirring for 5 to 10 minutes, add the toughening agent and increase the stirring speed to 300 to 400 rpm;

[0033] After stirring for 10-20 minutes, add the colorant and release agent, and stir at 500-600 rpm for 2-5 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0034] The pre-compressed material is evenly filled into the cavity of the hollow mold. The temperature of the upper mold is controlled at 160-180℃ and the temperature of the lower mold is controlled at 150-170℃. The pressure holding operation is carried out at a pressure of 10-30MPa for 2-5 minutes.

[0035] After the pressure holding operation is completed, the pressure is released to normal pressure and the product is removed from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0036] In the molding process of the hollow sandwich thermal insulation structure of melamine tableware in this application, step-by-step stirring and temperature control ensure uniform mixing of raw materials; the temperature difference design of the upper mold at 160-180℃ and the lower mold at 150-170℃ promotes the flow and curing of melamine resin; the pressure of 10-30MPa ensures that the material fills the cavity during the molding process, and the holding time of 2-5min ensures that the pre-pressed material is fully cross-linked during the entire molding process, ultimately achieving the precise molding of a dense hollow sandwich thermal insulation structure, ensuring the dimensional stability and performance uniformity of melamine tableware.

[0037] In one feasible implementation, during the pressure holding operation, the pressure is released 1 to 2 times, each time for 1 to 2 seconds, and each time the pressure is released to 1 to 5 MPa.

[0038] In the molding process of the hollow sandwich thermal insulation structure of the melamine tableware of this application, the residual gas inside the cavity can be released by 1 to 2 brief pressure reliefs during the pressure holding process, so as to avoid too many air bubble defects in the melamine tableware. At the same time, it relieves the internal stress during the curing process of melamine resin, and ultimately reduces the risk of cracking of the melamine tableware.

[0039] This invention, through innovative material formulation, modification process, and molding process, produces a melamine tableware with a hollow sandwich heat insulation structure, significantly improving its overall performance. Compared with existing technologies, the specific beneficial effects are as follows:

[0040] By constructing a hollow sandwich thermal insulation structure and using modified silica aerogel and modified hollow glass microspheres, the macroscopic hollow sandwich structure, the nanoporous structure of silica aerogel, and the hollow structure of hollow glass microspheres are introduced into melamine resin.

[0041] By introducing a gas-containing hollow structure into the melamine tableware through a molding process on a macroscopic scale, a heat conduction-blocking structure is formed, resulting in the largest heat conduction barrier in melamine tableware. The silica aerogel framework is composed of nanoscale silica particles, forming numerous nano-sized pores. These nanopores are primarily filled with air, whose thermal conductivity is much lower than that of melamine resin. Furthermore, the nanoscale pores divide the interior of the melamine resin into a discontinuous structure, blocking the path of heat conduction through the solid. In addition, the hollow glass microspheres have a glass outer shell and a sealed air or other gas interior. When heat is transferred from the resin to the microspheres, it must first pass through the glass shell and then through the low thermal conductivity gas inside. The microspheres are evenly distributed in the resin, further dividing the interior of the melamine resin into a discontinuous structure on a larger scale, avoiding the formation of continuous solid conduction channels. The hollow sandwich insulation structure, silica aerogel, and hollow glass microspheres mutually promote each other's insulation effects at different scales, effectively reducing the heat transfer efficiency of the produced melamine resin and providing better insulation than traditional melamine tableware. Furthermore, the targeted modification with aminosilane and aluminate coupling agents significantly improves the interfacial compatibility between silica aerogel and hollow glass microspheres and melamine resin, resulting in excellent dispersion, no agglomeration affecting performance, and significantly improved mechanical properties such as impact resistance and toughness of the prepared melamine tableware, extending its service life. Finally, the specific molding process parameters and steps of this application ensure uniform mixing of raw materials and precise molding of the hollow sandwich insulation structure, reducing defects in the finished melamine tableware and improving production efficiency and yield. In summary, the melamine tableware prepared in this application has advantages such as excellent thermal insulation, stable mechanical properties, high molding efficiency, and diverse appearances, possessing significant practical value and facilitating the recycling and resource utilization of melamine waste. Attached Figure Description

[0042] Figure 1 This is a photograph of the melamine tableware with a hollow sandwich heat insulation structure prepared in Example 1.

[0043] Figure 2 This is a schematic diagram of the molding process for melamine tableware with a hollow sandwich insulation structure. Detailed Implementation

[0044] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0045] The singular forms “for,” “or,” “a,” and “the” used in this application and the appended claims are intended to include the plural forms unless the context clearly indicates otherwise.

[0046] This application provides a melamine tableware with a hollow sandwich heat insulation structure and its molding process, the flow chart of which is shown below. Figure 2 As shown.

[0047] The following will describe in detail, with reference to different embodiments, a molding process for a melamine tableware with a hollow sandwich heat insulation structure provided in this application.

[0048] Example 1

[0049] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0050] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with γ-aminopropyltrimethoxysilane, and modified hollow glass microspheres treated with DL-411 aluminate coupling agent to a high-speed mixer, heat to 55°C, and start stirring at 200 rpm.

[0051] The mass ratio of γ-aminopropyltrimethoxysilane to silica aerogel powder is 2:98; the mass ratio of DL-411 aluminate coupling agent to hollow glass microspheres is 1:99.

[0052] Step 2: After stirring for 5 minutes, add the ethylene-vinyl acetate polymer and increase the stirring speed to 350 rpm;

[0053] Step 3: After stirring for 15 minutes, add titanium dioxide and zinc stearate, and stir at 550 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0054] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 170℃ and the temperature of the lower mold to 160℃, and perform a pressure holding operation at a pressure of 20MPa for 3 minutes; and during the pressure holding operation, release the pressure once, each time for 1 second, and each time release the pressure to 3MPa.

[0055] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure. A picture of the actual product is shown below. Figure 1 As shown;

[0056] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, zinc stearate, titanium dioxide, and ethylene-vinyl acetate polymer is 75:9:4:1.5:0.5:10.

[0057] Example 2

[0058] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0059] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with γ-aminopropyltriethoxysilane, and modified hollow glass microspheres treated with DL-411A aluminate coupling agent to a high-speed mixer, heat to 50°C, and start stirring at 200 rpm.

[0060] The mass ratio of γ-aminopropyltriethoxysilane to silica aerogel powder is 3:97; the mass ratio of DL-411A aluminate coupling agent to hollow glass microspheres is 2:98.

[0061] Step 2: After stirring for 8 minutes, add polyamide and increase the stirring speed to 300 rpm;

[0062] Step 3: After stirring for 10 minutes, add iron oxide yellow and stearamide, and stir at 500 rpm for 5 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0063] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 160℃ and the temperature of the lower mold to 150℃, and perform a pressure holding operation at a pressure of 10MPa for 5 minutes; and during the pressure holding operation, depressurize twice, each time for 2 seconds, and each time depressurize to 1MPa.

[0064] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0065] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, stearamide, iron oxide yellow and polyamide is 80:5:3:1.2:0.8:10.

[0066] Example 3

[0067] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0068] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and modified hollow glass microspheres treated with SG-A1821 aluminate coupling agent to a high-speed mixer, heat to 60°C, and start stirring at 200 rpm.

[0069] The mass ratio of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane to silica aerogel powder is 5:95; the mass ratio of SG-A1821 aluminate coupling agent to hollow glass microspheres is 3:97.

[0070] Step 2: After stirring for 10 minutes, add nitrile rubber and increase the stirring speed to 400 rpm;

[0071] Step 3: After stirring for 20 minutes, add phthalocyanine blue and ethylene bis-stearamide, and stir at 600 rpm for 2 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0072] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 180℃ and the temperature of the lower mold to 170℃, and perform a pressure holding operation at a pressure of 30MPa for 2 minutes; and during the pressure holding operation, release the pressure once, each time for 2 seconds, and each time release the pressure to 5MPa.

[0073] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0074] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, ethylene bis-stearamide, phthalocyanine blue, and nitrile rubber is 70:10:7:2:1:10.

[0075] Example 4

[0076] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0077] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with γ-aminopropyltrimethoxysilane, and modified hollow glass microspheres treated with DL-411A aluminate coupling agent to a high-speed mixer, heat to 52°C, and start stirring at 200 rpm.

[0078] The mass ratio of γ-aminopropyltrimethoxysilane to silica aerogel powder is 1:99; the mass ratio of DL-411A aluminate coupling agent to hollow glass microspheres is 1:99.

[0079] Step 2: After stirring for 6 minutes, add nitrile rubber and increase the stirring speed to 320 rpm;

[0080] Step 3: After stirring for 12 minutes, add iron oxide red and stearamide, and stir at 520 rpm for 4 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0081] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 165℃ and the temperature of the lower mold to 155℃, and perform a pressure holding operation at a pressure of 15MPa for 4 minutes; and during the pressure holding operation, depressurize twice, each time for 1 second, and each time depressurize to 2MPa.

[0082] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0083] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, stearamide, iron oxide red and nitrile rubber is 82:5:3:1.4:0.6:8.

[0084] Example 5

[0085] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0086] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with γ-aminopropyltriethoxysilane, and modified hollow glass microspheres treated with DL-411 aluminate coupling agent to a high-speed mixer, heat to 58°C, and start stirring at 200 rpm.

[0087] The mass ratio of γ-aminopropyltriethoxysilane to silica aerogel powder is 4:96; the mass ratio of DL-411 aluminate coupling agent to hollow glass microspheres is 2:98.

[0088] Step 2: After stirring for 9 minutes, add polyamide and increase the stirring speed to 380 rpm;

[0089] Step 3: After stirring for 18 minutes, add iron oxide black and ethylene bis-stearamide, and stir at 580 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0090] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 175℃ and the temperature of the lower mold to 165℃, and perform a pressure holding operation at a pressure of 25MPa for 3.5min; and during the pressure holding operation, release the pressure once, each time for 1.5s, and each time release the pressure to 4MPa.

[0091] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0092] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, ethylene bis-stearamide, iron oxide black and polyamide is 76:8:6:1.3:0.7:8.

[0093] Example 6

[0094] like Figure 2 As shown, a molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0095] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and modified hollow glass microspheres treated with SG-A1821 aluminate coupling agent to a high-speed mixer, heat to 56°C, and start stirring at 200 rpm.

[0096] The mass ratio of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane to silica aerogel powder is 3:97; the mass ratio of SG-A1821 aluminate coupling agent to hollow glass microspheres is 3:97.

[0097] Step 2: After stirring for 7 minutes, add the ethylene-vinyl acetate polymer and increase the stirring speed to 360 rpm;

[0098] Step 3: After stirring for 16 minutes, add phthalocyanine green and zinc stearate, and stir at 560 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0099] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 172℃ and the temperature of the lower mold to 158℃, and perform a pressure holding operation at a pressure of 22MPa for 2.5min; and during the pressure holding operation, depressurize twice, each time for 1.5s, and each time depressurize to 3MPa.

[0100] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

[0101] In steps 1 to 5 above, the mass ratio of the polymers of melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, zinc stearate, phthalocyanine green and ethylene vinyl acetate is 73:11:5:1.1:0.9:9.

[0102] Comparative Example 1

[0103] A molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0104] Step 1: Add melamine plastic waste powder and modified hollow glass microspheres treated with DL-411 aluminate coupling agent to a high-speed mixer, heat to 55°C, and turn on the mixer at a speed of 200 rpm.

[0105] The mass ratio of DL-411 aluminate coupling agent to hollow glass microspheres is 1:99.

[0106] Step 2: After stirring for 5 minutes, add the ethylene-vinyl acetate polymer and increase the stirring speed to 350 rpm;

[0107] Step 3: After stirring for 15 minutes, add titanium dioxide and zinc stearate, and stir at 550 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0108] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 170℃ and the temperature of the lower mold to 160℃, and perform a pressure holding operation at a pressure of 20MPa for 3 minutes; and during the pressure holding operation, release the pressure once, each time for 1 second, and each time release the pressure to 3MPa.

[0109] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain melamine tableware with a hollow sandwich heat insulation structure.

[0110] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified hollow glass microspheres, zinc stearate, titanium dioxide, and ethylene-vinyl acetate polymer is 84:4:1.5:0.5:10.

[0111] Comparative Example 2

[0112] A molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0113] Step 1: Add melamine plastic waste powder and modified silica aerogel powder treated with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane to a high-speed mixer, heat to 60°C, and start stirring at 200 rpm.

[0114] The mass ratio of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane to silica aerogel powder is 5:95.

[0115] Step 2: After stirring for 10 minutes, add nitrile rubber and increase the stirring speed to 400 rpm;

[0116] Step 3: After stirring for 20 minutes, add phthalocyanine blue and ethylene bis-stearamide, and stir at 600 rpm for 2 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0117] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 180℃ and the temperature of the lower mold to 170℃, and perform a pressure holding operation at a pressure of 30MPa for 2 minutes; and during the pressure holding operation, release the pressure once, each time for 2 seconds, and each time release the pressure to 5MPa.

[0118] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain melamine tableware with a hollow sandwich heat insulation structure.

[0119] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, ethylene bis-stearamide, phthalocyanine blue, and nitrile rubber is 77:10:2:1:10.

[0120] Comparative Example 3

[0121] A molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0122] Step 1: Add melamine plastic waste powder to a high-speed mixer, heat to 56°C, and turn on the mixer at a speed of 200 rpm.

[0123] Step 2: After stirring for 7 minutes, add the ethylene-vinyl acetate polymer and increase the stirring speed to 360 rpm;

[0124] Step 3: After stirring for 16 minutes, add phthalocyanine green and zinc stearate, and stir at 560 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0125] Step 4: Fill the cavity of the hollow mold evenly with the pre-compressed material, control the temperature of the upper mold to 172℃ and the temperature of the lower mold to 158℃, and perform a pressure holding operation at a pressure of 22MPa for 2.5min. During the pressure holding operation, depressurize twice, each time for 1.5s, and depressurize to 3MPa each time.

[0126] Step 5: After the pressure holding operation is completed, release the pressure to normal pressure and remove the product from the mold to obtain melamine tableware with a hollow sandwich heat insulation structure.

[0127] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, zinc stearate, phthalocyanine green, and ethylene-vinyl acetate polymer is 89:1.1:0.9:9.

[0128] Comparative Example 4

[0129] A molding process for melamine tableware with a hollow sandwich heat insulation structure includes the following steps:

[0130] Step 1: Add melamine plastic waste powder, modified silica aerogel powder treated with γ-aminopropyltriethoxysilane, and modified hollow glass microspheres treated with DL-411 aluminate coupling agent to a high-speed mixer, heat to 58°C, and start stirring at 200 rpm.

[0131] The mass ratio of γ-aminopropyltriethoxysilane to silica aerogel powder is 4:96; the mass ratio of DL-411 aluminate coupling agent to hollow glass microspheres is 2:98.

[0132] Step 2: After stirring for 9 minutes, add polyamide and increase the stirring speed to 380 rpm;

[0133] Step 3: After stirring for 18 minutes, add iron oxide black and ethylene bis-stearamide, and stir at 580 rpm for 3 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material.

[0134] Step 4: Fill the pre-pressed material evenly into the cavity of a regular mold and heat-cur it directly at 200℃.

[0135] Step 5: After curing, cool to room temperature and remove the product from the mold to obtain melamine tableware;

[0136] In steps 1 to 5 above, the mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, ethylene bis-stearamide, iron oxide black and polyamide is 76:8:6:1.3:0.7:8.

[0137] The thermal conductivity and impact strength of the melamine tableware prepared in Examples 1-6 and Comparative Examples 1-4 were tested to demonstrate the heat insulation effect and mechanical properties of the melamine tableware prepared in these examples and comparative examples. The test results are shown in Table 1 below.

[0138] Table 1. Statistical table of performance test results of melamine tableware prepared in Examples 1-6 and Comparative Examples 1-4.

[0139] Thermal conductivity (W / (m·K)) <![CDATA[Impact strength (kJ / m 2 )]]> Example 1 0.07 10.7 Example 2 0.08 10.9 Example 3 0.07 11.2 Example 4 0.09 10.7 Example 5 0.11 10.4 Example 6 0.08 11.3 Comparative Example 1 0.23 7.3 Comparative Example 2 0.25 6.9 Comparative Example 3 0.43 4.6 Comparative Example 4 0.29 8.5

[0140] As shown in Table 1, the melamine tableware prepared in Examples 1-6 has better heat insulation and mechanical properties than Comparative Examples 1-4.

[0141] This is because, in Examples 1 to 6, the hollow sandwich insulation structure, the nanoporous structure of silica aerogel, and the hollow structure of hollow glass microspheres are introduced into melamine resin through the construction of the hollow sandwich insulation structure and the use of modified silica aerogel and modified hollow glass microspheres.

[0142] By introducing a gas-containing hollow structure into the melamine tableware through a molding process on a macroscopic scale, a heat conduction barrier is formed, creating the largest heat conduction barrier in the melamine tableware. The silica aerogel framework is composed of nanoscale silica particles, forming numerous nano-sized pores. These nanopores are primarily filled with air, whose thermal conductivity is much lower than that of melamine resin. Furthermore, the nanoscale pores divide the interior of the melamine resin into a discontinuous structure, blocking the path of heat conduction through the solid. In addition, the hollow glass microspheres have a glass outer shell and a sealed air or other gas interior. When heat is transferred from the resin to the microspheres, it must first pass through the glass shell and then through the low thermal conductivity gas inside. The microspheres are uniformly distributed within the resin, further dividing the interior of the melamine resin into a discontinuous structure on a larger scale, avoiding the formation of continuous solid conduction channels. The hollow sandwich insulation structure, silica aerogel, and hollow glass microspheres mutually promote each other's insulation effects at different scales, effectively reducing the heat transfer efficiency of the produced melamine resin and providing better insulation than traditional melamine tableware. Moreover, the targeted modification of aminosilane and aluminate coupling agent significantly improves the interfacial compatibility between silica aerogel and hollow glass microspheres and melamine resin, resulting in excellent dispersion and no agglomeration that affects performance. This significantly improves the impact resistance and toughness of the prepared melamine tableware and extends its service life.

[0143] Compared to Example 1, Comparative Example 1 did not use modified silica aerogel powder, thus failing to form a large number of nano-sized pores and unable to divide the melamine resin into a discontinuous structure, blocking the path of heat conduction through the solid. Therefore, the final melamine resin had a higher thermal conductivity and poorer heat insulation effect. Moreover, due to the lack of sufficient filling of the melamine resin with modified silica aerogel powder, the mechanical properties of the resulting melamine tableware were poor.

[0144] Compared to Example 3, Comparative Example 2 did not use modified hollow glass microspheres. Therefore, it was impossible to segment the melamine resin into discontinuous structures on a larger scale than the modified silica aerogel powder, thus failing to avoid the formation of continuous solid conductive channels. Consequently, the resulting melamine resin had higher thermal conductivity and poorer heat insulation performance. Similarly, due to the lack of sufficient filling of the melamine resin with modified hollow glass microspheres, the mechanical properties of the resulting melamine tableware were also poor.

[0145] Compared with Example 6, Comparative Example 3 did not use modified silica aerogel powder or modified hollow glass microspheres. Therefore, for the same reason, the heat insulation effect and mechanical properties of the melamine tableware were worse than those of Comparative Example 1 and Comparative Example 2.

[0146] Compared with Example 5, Comparative Example 4 did not form a hollow sandwich structure in the melamine tableware through a molding process. Therefore, it could not form the largest heat conduction blocking structure in the melamine tableware on a macroscopic scale. As a result, the thermal conductivity was also higher and the heat insulation effect was also worse.

[0147] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0148] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A melamine tableware with a hollow sandwich heat insulation structure, characterized in that, The hollow sandwich insulation structure is obtained by molding using a mold; the raw materials of the melamine tableware include melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, release agent, colorant and toughening agent; the modified silica aerogel powder is obtained by treating silica aerogel powder with an aminosilane coupling agent; the modified hollow glass microspheres are obtained by treating with an aluminate coupling agent.

2. A melamine tableware with a hollow sandwich heat insulation structure according to claim 1, characterized in that, The mass ratio of the melamine plastic waste powder, modified silica aerogel powder, modified hollow glass microspheres, release agent, colorant and toughening agent is (70-85):(3-12):(2-8):(1-2):(0.5-1):(5-10).

3. A melamine tableware with a hollow laminated heat-insulating structure according to claim 1, characterized in that, The aminosilane coupling agent includes any one or more of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane; the aluminate coupling agent includes any one or more of DL-411 aluminate coupling agent, DL-411A aluminate coupling agent, and SG-A1821 aluminate coupling agent.

4. A melamine tableware with a hollow laminated heat-insulating structure according to claim 1, characterized in that, The release agent includes any one or more of zinc stearate, stearamide, and ethylene bis-stearamide.

5. A melamine tableware with a hollow laminated heat-insulating structure according to claim 1, characterized in that, The colorant includes any one or more of titanium dioxide, iron oxide red, iron oxide yellow, iron oxide black, phthalocyanine blue, and phthalocyanine green.

6. A melamine tableware with a hollow laminated heat-insulating structure according to claim 1, characterized in that, The toughening agent includes any one or more of polyamide, nitrile rubber, and ethylene-vinyl acetate polymers.

7. A melamine tableware with a hollow sandwich heat insulation structure according to claim 1, characterized in that, The preparation method of the modified silica aerogel powder includes: The silica aerogel powder was vacuum dried at 50–80°C for 2–4 hours. The dried silica aerogel powder was added to an ethanol-water mixture and ultrasonically dispersed for 10-15 min to form a suspension; wherein the mass ratio of silica aerogel powder to ethanol-water mixture was (5-10):(90-95); The aminosilane coupling agent was added to the suspension, heated in a water bath at 50-70°C, and stirred at a stirring speed of 200-400 rpm for 1-3 hours; wherein the mass ratio of the aminosilane coupling agent to the silica aerogel powder in the suspension was (1-5):(95-99). The modified powder was then collected by vacuum filtration, washed 2-3 times with an ethanol-water mixture, and vacuum dried at 80-100℃ for 4-6 hours to obtain the modified silica aerogel powder.

8. A melamine tableware with a hollow laminated heat-insulating structure according to claim 1, characterized in that, The method for preparing the modified hollow glass microspheres includes: The hollow glass microspheres were dried in a forced-air drying oven at 80-100℃ for 3-5 hours, cooled to room temperature, and then passed through a 200-300 mesh sieve. The dried hollow glass microspheres were added to a high-speed mixer, the speed was controlled at 600-800 rpm, and the mixture was heated to 60-90°C. The aluminate coupling agent was heated and melted at 60-80℃ and added to the hollow glass microspheres, and stirred continuously for 30-60 minutes; wherein the mass ratio of the aluminate coupling agent to the hollow glass microspheres was (1-3):(97-99); Then stop stirring and allow it to cool naturally to room temperature. Pass it through a 200-300 mesh sieve again to obtain the modified hollow glass microspheres.

9. The molding process for melamine tableware with a hollow sandwich heat insulation structure according to any one of claims 1 to 8, characterized in that, The steps of the compression molding process include: Add melamine plastic waste powder, modified silica aerogel powder and modified hollow glass microspheres to a high-speed mixer, heat to 50-60℃, and start stirring at 200 rpm. After stirring for 5 to 10 minutes, add the toughening agent and increase the stirring speed to 300 to 400 rpm; After stirring for 10-20 minutes, add the colorant and release agent, and stir at 500-600 rpm for 2-5 minutes. Then cool to room temperature and discharge to obtain a uniformly mixed pre-compressed material. The pre-compressed material is evenly filled into the cavity of the hollow mold. The temperature of the upper mold is controlled at 160-180℃ and the temperature of the lower mold is controlled at 150-170℃. The pressure holding operation is carried out at a pressure of 10-30MPa for 2-5 minutes. After the pressure holding operation is completed, the pressure is released to normal pressure and the product is removed from the mold to obtain the melamine tableware with the hollow sandwich heat insulation structure.

10. The molding process for melamine tableware with a hollow sandwich heat insulation structure according to claim 9, characterized in that, During the pressure holding operation, the pressure is released 1 to 2 times, each time for 1 to 2 seconds, and each time the pressure is released to 1 to 5 MPa.

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