A fiber / powder composite VIP core material based on DLP technology and a preparation method and application thereof

Abstract

The application discloses a kind of fiber / powder composite VIP core material based on DLP technology and its preparation method and application, belong to vacuum insulation panel manufacturing technical field.The preparation method of the core material includes the following steps: (1) glass fiber, fumed silica powder, photocuring resin, dispersing agent, photoinitiator are stirred and mixed uniformly, to obtain printing material;(2) according to the three-dimensional model of preset structure, the printing material in (1) is used to print out fiber / powder composite VIP core material, drying, cooling;(3) the core material in (2) is placed into barrier film, and getter is added, packaging is carried out, and it is obtained.There are beneficial effects: through careful optimization of material composition and structure design, especially based on the directional layered arrangement of fiber that DLP printer is conducive to realize can effectively reduce solid-phase heat conduction, after composite fumed silica, can further fill fiber pore.The synergies among the components make the thermal conductivity of VIP can be as low as 0.0025~0.0035 W / (m·K), compared with traditional VIP, there is significant improvement.

Description

Technical Field

[0001] This invention relates to the field of vacuum insulation panel manufacturing technology, and in particular to a fiber / powder composite VIP core material based on DLP technology, its preparation method and application. Background Technology

[0002] Vacuum insulation panels (VIPs), as a highly efficient insulation material, have broad application prospects in many fields with strict requirements for thermal insulation performance, such as cold chain logistics, building energy conservation, and aerospace. Their basic principle is to vacuum-seal insulation core materials such as fibers, powders, and foams within a barrier membrane, achieving excellent insulation effects through macroscopic control of three heat transfer modes: heat conduction, heat convection, and heat radiation. However, traditional VIP core material preparation methods have significant limitations in practical applications.

[0003] In terms of structured design and fabrication, traditional processes struggle to achieve precise control over the microstructure of the core material. This makes it impossible to design and fabricate core materials with specific pore structures, fiber distributions, and dimensions tailored to different application scenarios and thermal requirements, resulting in poor product adaptability and versatility. For example, in applications with specific requirements for thermal insulation and mechanical properties, such as insulation layers for high-temperature and high-pressure equipment or insulation jackets for complex-shaped cryogenic containers, traditional VIP structures cannot meet the demands for structural precision. Furthermore, traditional processes lack precise control over the thickness of the VIP core material, directly impacting its thermal insulation performance and overall dimensional accuracy. In space-constrained applications, such as the thermal insulation encapsulation of precision instruments or thermal insulation facilities in confined spaces, thickness deviations can prevent proper installation or use, severely limiting the application range of VIPs.

[0004] In core material molding and VIP (Visible Container) fabrication, traditional processes cannot guarantee high-quality core material molding and long-lasting VIP fabrication. Ultrafine glass fiber (UGF) core VIPs are known to have the lowest thermal conductivity and the most mature fabrication process among existing VIPs. However, they are highly dependent on the vacuum environment; with the influence of external conditions and the aging of the barrier film itself, vacuum leakage is easily caused, leading to a loss of thermal insulation performance. Some researchers have proposed fiber / powder composite core materials, which, by introducing powder particles, further control the fiber pore size, thereby reducing its pressure sensitivity and extending its service life. However, during the fiber-powder mixing process, due to the lack of effective mixing methods and process control conditions, the fibers and powders often cannot be fully and uniformly mixed. This not only affects the overall thermal insulation performance of the core material but also leads to inhomogeneity in the internal structure of the material, making the core material prone to localized thermal bridging during use and reducing product reliability. Furthermore, uneven mixing may also cause powder shedding, which may affect the VIP packaging quality and further reduce its service life.

[0005] Digital Light Processing (DLP) additive manufacturing technology, as an advanced 3D printing technology, utilizes digital micromirrors to project light onto the surface of a liquid photocurable resin, causing the resin to solidify layer by layer. This technology features high precision, high resolution, and the ability to rapidly prototyping complex structures, and has been widely applied and has achieved significant results in numerous industrial manufacturing and scientific research fields. Given its unique advantages in material forming, combined with diverse structural designs and digital projection printing technology, this technology offers a novel approach to the preparation of VIP core materials.

[0006] Chinese patent application CN102942305A discloses a method for preparing a novel mineral wool VIP core material, comprising the following steps: 1) adding rock wool fibers to a dispersing machine, then adding sulfuric acid and water for dispersion, dispersing the rock wool fibers to a diameter of less than 1.5 μm; then sending the dispersed rock wool fibers to a storage and stirring tank, adding sulfuric acid and water to adjust the pH value to 3.5–4.5 and the mass concentration to 3%–4% slurry; 2) diluting the slurry obtained in step 1) to a mass concentration of 0.2%–0.4%, and then performing slag removal treatment; then conveying the slurry to an inclined wire forming machine for wet forming to obtain wet paper; then dehydrating the wet paper under a vacuum of 0.01–0.05 MPa; 3) drying the wet paper obtained in step 2) at 200–300℃. However, the VIP core material prepared by this patent has poor thermal conductivity, and therefore needs further improvement. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to solve the problem of poor performance of existing vacuum insulation panel (VIP) core materials.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] The first aspect of this invention provides a method for preparing a fiber / powder composite VIP core material based on DLP technology, comprising the following steps:

[0010] (1) Mix glass fiber, fumed SiO2 powder, photocurable resin, dispersant and photoinitiator to obtain printing material;

[0011] (2) Based on the three-dimensional model of the preset structure, the fiber / powder composite VIP core material is printed using the printing material in (1), dried, and cooled;

[0012] (3) Place the core material from (2) into the barrier film, add getter, and encapsulate to obtain the final product.

[0013] Preferably, in step (1), the volume ratio of the glass fiber, fumed SiO2 powder, photocurable resin, dispersant, and photoinitiator is: (28-32): (53-55): (13-17): (1-1.5): (2.5-3.5).

[0014] Preferably, the glass fiber has a length of 4–10 mm and a diameter of 4–12 μm.

[0015] Preferably, the particle size of the gaseous SiO2 powder is 8–25 nm.

[0016] Preferably, the photocurable resin is an acrylic photocurable resin, specifically selected from any one of HEA, HDDA, and TMPTA.

[0017] Preferably, the dispersant is selected from any one of CPD01, CPD02, and CPD03.

[0018] Preferably, the photoinitiator is selected from any one of CPI01, CPI06, and TPO.

[0019] Preferably, in step (1), the stirring speed is 50-200 r / min and the stirring time is 4-10 h.

[0020] Preferably, in step (2), during printing, the light source wavelength is 385nm and the light intensity is 12-16mW / cm². 2 The exposure time is 1.8 to 2.5 seconds, and the printing layer thickness is 40 μm to 50 μm.

[0021] Preferably, the drying temperature is 90-110°C and the drying time is 5-12 hours.

[0022] Preferably, a gap of 2-3 mm is reserved between the barrier film and the core material, and the gap is filled with polyurethane foam particles as cushioning material.

[0023] Preferably, the barrier film is a composite aluminum-plastic film or a polyimide film.

[0024] A second aspect of the present invention provides a fiber / powder composite VIP core material prepared by the above preparation method.

[0025] A third aspect of the present invention proposes the application of the above-mentioned fiber / powder composite VIP core material as an insulation material in the field of thermal insulation.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention proposes a fiber / powder composite VIP core material based on DLP technology, comprising glass fiber, fumed SiO2 powder, photocurable resin, dispersant, and photoinitiator. The glass fiber has a small diameter and short length, which helps to extend the solid-phase heat transfer path, thereby reducing the thermal conductivity. Fumed SiO2 has high porosity and low thermal conductivity, which helps to improve the thermal insulation performance of the core material. Through carefully optimized material composition and structural design, the fiber directional layered arrangement realized by DLP printer can effectively reduce solid-phase heat conduction. The synergistic effect between the components improves the performance of the VIP core material, making the thermal conductivity of the VIP as low as 0.0025~0.0035W / (m·K), which is significantly improved compared with traditional VIP.

[0028] 2. The core material of this invention possesses excellent compressive strength and controllable thickness. The structural design of the composite core material and the synergistic effect of fibers and resin endow it with good compressive strength, capable of withstanding external pressures of 2–4 MPa. (Compared to traditional materials, fiber-based core materials: 0.1–0.5 MPa, powder-based core materials: 0.2–0.8 MPa, and foam-based core materials: 0.3–1.2 MPa). Furthermore, the thickness of the core material can be precisely controlled using DLP printing technology, adjustable within the range of 8–20 mm according to actual needs, and does not undergo significant volume shrinkage during the vacuum process.

[0029] 3. The core material of this invention has a long service life. Based on DLP technology, it is possible to prepare fiber / powder composite core material with controllable density and a pore size printing accuracy of up to 5μm. At the same time, it has good compressive strength and therefore exhibits extremely low pressure sensitivity. The change in thermal conductivity after vacuum leakage is not significant, which effectively improves the service life of VIP and can achieve a long service life of more than 80 years.

[0030] 4. Customized core material structure design: Based on DLP technology, fiber / powder composite core materials (VIPs) with different pore structures, fiber distributions, and external dimensions can be designed and fabricated according to different application scenarios and thermal requirements, meeting diverse market demands and improving product adaptability and competitiveness. DLP layer-by-layer printing technology facilitates the layered and oriented distribution of fibers within the core material, especially their tendency towards horizontal alignment, thereby significantly reducing solid-phase heat conduction and greatly improving the VIP's thermal insulation performance.

[0031] 5. The fiber / powder composite core material VIP based on DLP technology provided by this invention effectively overcomes the problems of uncontrollable process, uncontrollable thickness, and uncontrollable structure in traditional VIP preparation technology, and provides a new solution for long-lasting and diversified VIP manufacturing. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the fiber / powder composite VIP core material structure in Embodiment 1 of the present invention; wherein 1 is a barrier membrane, 2 is the fiber / powder composite core material, and 3 is a getter;

[0033] Figure 2 This is a three-dimensional model diagram of the core material as preset in Embodiment 1 of the present invention;

[0034] Figure 3 This is a three-dimensional model diagram of the core material preset in Embodiment 2 of the present invention;

[0035] Figure 4 This is a three-dimensional model diagram of the core material preset in Embodiment 3 of the present invention;

[0036] Figure 5 This is a three-dimensional model diagram of the core material preset in Embodiment 4 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0039] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0040] Experimental Example 1:

[0041] A method for preparing a fiber / powder composite VIP core material based on DLP technology includes the following steps:

[0042] (1) Using an anchor-type stirring paddle, glass fiber (6mm in length, 6μm in diameter), fumed SiO2 powder (12nm in particle size), photocurable resin (HEA), dispersant (CPD01), and photoinitiator (CPI01) were thoroughly mixed at a volume ratio of 30:55:14:1.2:3.5 to obtain the printing material; the stirring paddle speed was controlled at 100r / min for 8h.

[0043] (2) Based on the preset three-dimensional model of the core material ( Figure 2 (As shown) was printed using a light source with a wavelength of 385nm and a light intensity of 13mW / cm². 2 The exposure time was 2 seconds, and the printing layer thickness was 40 μm. The printed fiber / powder composite core material was placed in an oven and heated to 100°C for 8 hours. Then it was allowed to cool naturally to room temperature.

[0044] (3) Place the core material from (2) into the composite aluminum-plastic barrier film and add a getter; leave a 3mm gap between the barrier film and the core material, and fill the gap with polyurethane foam particles as buffer material. Use a vacuum sealing device to seal the film, deeply evacuate the air, reduce the internal pressure to 0.001Pa, the evacuation rate is 5L / s, and maintain the pressure for 2h to obtain the composite aluminum-plastic film fiber / powder composite VIP core material.

[0045] Experimental Example 2:

[0046] A method for preparing a fiber / powder composite VIP core material based on DLP technology includes the following steps:

[0047] (1) Using an anchor-type stirring paddle, glass fiber (7mm in length, 6μm in diameter), fumed SiO2 powder (10nm in particle size), photocurable resin (HEA), dispersant (CPD02), and photoinitiator (CPI06) were thoroughly mixed at a volume ratio of 32:50:14:1.2:2.8 to obtain the printing material; the stirring paddle speed was controlled at 150r / min for 6h.

[0048] (2) Based on the preset three-dimensional model of the core material ( Figure 3 Printing was performed using a light source with a wavelength of 385nm and a light intensity of 15mW / cm². 2 The exposure time was 2.5s, and the printing layer thickness was 50μm. The printed fiber / powder composite core material was placed in an oven and heated to 110℃ for 5 hours. Then it was allowed to cool naturally to room temperature.

[0049] (3) Place the core material from (2) into the polyimide barrier membrane and add a getter; leave a 2mm gap between the barrier membrane and the core material, and fill the gap with polyurethane foam particles as a buffer material; use a vacuum sealing device to seal, deeply evacuate the air, reduce the internal pressure to 0.001Pa, the evacuation rate is 5L / s, and maintain the pressure for 3h to obtain the polyimide membrane fiber / powder composite VIP core material.

[0050] Comparative Example 1:

[0051] Commercially available ultra-fine glass fiber VIP core material.

[0052] Comparative Example 2:

[0053] Commercially available fumed silica VIP core material.

[0054] Comparative Example 3:

[0055] Commercially available polyurethane foam VIP core material.

[0056] The material properties of Examples 1 and 2 were tested, and the specific test methods were as follows:

[0057] (1) Thermal conductivity

[0058] Using a Netzsch HFM446 thermal conductivity meter as the testing equipment, a VIP sample with dimensions of 300*300*10mm was prepared. The preheated VIP sample was placed in the testing area of ​​the instrument, ensuring it was in close contact with the heat flow sensor and temperature sensor. Care was taken to avoid air gaps between the sample and the sensors to prevent affecting the measurement results. The relevant test parameters were set through the instrument's operating interface. For VIP, the hot plate temperature is typically set between 20℃ and 50℃, and the cold plate temperature is set between 0℃ and 20℃ to create a suitable temperature difference. After confirming that the parameter settings were correct, the measurement was started. The thermal conductivity of the VIP was obtained once the measurement system reached a stable state.

[0059] (2) Compressive strength

[0060] Using a universal testing machine as the testing equipment, a VIP sample with dimensions of 10*10*5mm is prepared and placed between the upper and lower pressure plates of the universal testing machine. The position of the pressure plates is adjusted to ensure uniform contact with the sample. The loading rate is set, generally 0.5~1mm / min. The equipment is started, and the real-time changes in the pressure value are observed during the loading process. When the sample ruptures or the pressure value changes drastically, the pressure value at this time is recorded. The compressive strength is calculated by dividing the pressure value by the force-bearing area of ​​the sample. The test process must be carried out under standard ambient temperature and humidity conditions to ensure the accuracy and reliability of the test results.

[0061] (3) Service life

[0062] Refer to Appendix E of GB / T 37608-2019 Vacuum Insulation Panels for the evaluation method A of the service life of vacuum insulation panels.

[0063] The test results are shown in Table 1 below:

[0064] Table 1

[0065] Thermal conductivity / W / (m·K) Compressive strength / MPa Service life / year Example 1 0.0035 2.7 80 Example 2 0.0025 3.2 82 Comparative Example 1 0.002 0.2 30 Comparative Example 2 0.006 0.7 50 Comparative Example 3 0.008 0.2 30

[0066] Example 3:

[0067] A method for preparing a fiber / powder composite VIP core material based on DLP technology includes the following steps:

[0068] (1) Using an anchor-type stirring paddle, glass fiber (4 mm in length, 12 μm in diameter), fumed SiO2 powder (8 nm in particle size), photocurable resin (HDDA), dispersant (CPD03), and photoinitiator (TPO) were thoroughly mixed at a volume ratio of 28:53:17:1.5:2.5 to obtain the printing material; the stirring paddle speed was controlled at 50 r / min for 10 h.

[0069] (2) Based on the preset three-dimensional model of the core material ( Figure 4 (As shown) Printing was performed using a light source with a wavelength of 385nm and a light intensity of 12mW / cm². 2 The exposure time was 1.8s, and the printing layer thickness was 45μm. The printed fiber / powder composite core material was placed in an oven, heated to 90℃, and kept at that temperature for 12h. Then it was allowed to cool naturally to room temperature.

[0070] (3) Place the core material from (2) into the composite aluminum-plastic barrier film and add a getter; leave a 2.5mm gap between the barrier film and the core material, and fill the gap with polyurethane foam particles as buffer material. Use a vacuum sealing device to seal the film, deeply evacuate the air, reduce the internal pressure to 0.001Pa, the evacuation rate is 5L / s, and maintain the pressure for 2h to obtain the composite aluminum-plastic film fiber / powder composite VIP core material.

[0071] Example 4:

[0072] A method for preparing a fiber / powder composite VIP core material based on DLP technology includes the following steps:

[0073] (1) Using an anchor-type stirring paddle, glass fiber (10 mm in length, 4 μm in diameter), fumed SiO2 powder (25 nm in particle size), photocurable resin (TMPTA), dispersant (CPD03), and photoinitiator (TPO) were thoroughly mixed at a volume ratio of 30.5:54.2:15.5:1.4:2.6 to obtain the printing material; the stirring paddle speed was controlled at 200 r / min for 4 hours.

[0074] (2) Based on the preset three-dimensional model of the core material ( Figure 5 (As shown) Printing was performed using a light source with a wavelength of 385nm and a light intensity of 16mW / cm². 2 The exposure time was 1.8s, and the printing layer thickness was 48μm. The printed fiber / powder composite core material was placed in an oven, heated to 90℃, and kept at that temperature for 12h. Then it was allowed to cool naturally to room temperature.

[0075] (3) Place the core material from (2) into the composite aluminum-plastic barrier film and add a getter; leave a 2.6 mm gap between the barrier film and the core material, and fill the gap with polyurethane foam particles as buffer material. Use a vacuum sealing device to seal the film, deeply evacuate the air, reduce the internal pressure to 0.001 Pa, the evacuation rate is 5 L / s, and maintain the pressure for 2 hours to obtain the composite aluminum-plastic film fiber / powder composite VIP core material.

[0076] The core materials prepared in Examples 3 and 4 have similar properties to those in Example 1.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing fiber / powder composite VIP core material based on DLP technology, characterized in that, Includes the following steps: (1) Glass fiber, fumed SiO2 powder, photocurable resin, dispersant, and photoinitiator are stirred and mixed to obtain printing material; the volume ratio of glass fiber, fumed SiO2 powder, photocurable resin, dispersant, and photoinitiator is (28~32):(53~55):(13~17):(1~1.5):(2.5~3.5); (2) Based on the three-dimensional model of the preset structure, the fiber / powder composite VIP core material is printed using the printing material in (1), dried, and cooled; during printing, the light source wavelength is 385nm, the light intensity is 12~16mW / cm², the exposure time is 1.8~2.5s, and the printing layer thickness is 40μm~50μm; (3) Place the core material from (2) into the barrier film, add getter, and encapsulate to obtain the product.

2. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of the glass fiber, fumed SiO2 powder, photocurable resin, dispersant and photoinitiator is 30:55:14:1.2:3.

5.

3. The preparation method according to claim 1, characterized in that, The glass fiber has a length of 4~10mm and a diameter of 4~12μm.

4. The preparation method according to claim 1, characterized in that, The particle size of the gaseous SiO2 powder is 8~25nm.

5. The preparation method according to claim 4, characterized in that, The particle size of the vapor-phase SiO2 powder is 12 nm.

6. The preparation method according to claim 1, characterized in that, In step (1), the stirring speed is 50~200 r / min and the stirring time is 4~10 h.

7. The preparation method according to claim 1, characterized in that, In step (2), the light intensity is 13mW / cm², the exposure time is 2 s, and the printing layer thickness is 40μm.

8. The preparation method according to claim 1, characterized in that, The drying temperature is 90~110℃, and the drying time is 5~12h.

9. The fiber / powder composite VIP core material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the fiber / powder composite VIP core material as described in claim 9 as an insulation material in the field of thermal insulation.

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