Preparation method of protection and heat insulation composite structure

Abstract

The invention provides a preparation method of a protection and heat insulation composite structure, and relates to the field of functional composites.The protection and heat insulation composite structure comprises a first protection layer, a composite heat insulation layer and a second protection layer, the first protection layer and the second protection layer are each of a metal embossed titanium foil structure, and the composite heat insulation layer is formed by alternately stacking heat resistance layers and reflecting layers; the preparation method comprises the steps that the protective layers are obtained through the embossing process, the reflecting layer is obtained through the magnetron sputtering and imidization process, the thermal resistance layer and the reflecting layer form the composite thermal insulation layer through the sewing process, and integration of the first protective layer, the second protective layer and the composite thermal insulation layer is achieved through the welding process. The protection and heat insulation composite structure prepared by the method can effectively avoid the problems of connection gaps, poor long-term connection stability, large thickness, large weight and the like, and has the advantages of good heat insulation performance, light weight, high efficiency, good long-term protection stability and the like.

Description

[0001] The present invention is a divisional application of patent application number 202411164171.8, and the invention name is “A method for preparing an integrated thermal insulation protective layer”. Technical Field

[0002] The invention relates to the technical field of functional composite materials, and in particular to a method for preparing a protective heat-insulating composite structure. Background Art

[0003] The protective heat-insulating structure is a component used to protect objects or space from high temperatures and heat transfer. It is usually composed of a multi-layer composite structure. The protective heat-insulating structure is widely used in the fields of aerospace and industrial manufacturing. For example, under the influence of the engine radiation heat and aerodynamic heating of the aircraft, the temperature of the parachute cabin is easily increased, which in turn causes the drag parachute to be damaged, affecting the stability and safety of the drag parachute. In order to avoid safety problems caused by heat transfer in the parachute cabin, it is usually necessary to insulate the parachute cabin to ensure that the temperature of the inner cavity of the parachute cabin is controllable, thereby improving the reliability and safety of the drag parachute. At present, protective insulation materials usually use metal foil (such as aluminum foil) as a reflective layer, and use a metal shell as a protective layer of the insulation material to obtain a multi-layer structure with thermal insulation and protection. However, if a smooth metal shell is directly used as a protective layer, when the thermal insulation protection area is large and is an arc-shaped surface or curved surface, the metal structure has low strength and is prone to wrinkles and deformation. During long-term use, cracks and breakages are prone to occur, affecting the thermal insulation and protection effects of the metal shell, and easily causing the outside atmosphere and liquids to penetrate into its interior, causing the reflective layer to be eroded and affecting the overall thermal insulation and protection performance. In addition, traditional thermal insulation and protection structures are usually composited by gluing or mechanical connection: the gluing connection method not only has poor long-term stability and is prone to cracking or gaps, but also cannot withstand external forces such as vibration and impact; mechanical connection is prone to connection gaps, poor anti-infiltration ability, and easy to form temperature convergence points, reducing the overall thermal insulation effect of the composite structure. It can be seen that the existing protective thermal insulation composite structure still has problems such as poor resistance to moisture and heat, salt spray, vibration, and impact resistance, heavy weight, and poor thermal insulation uniformity. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the object of the present invention is to provide a method for preparing a protective heat-insulating composite structure. The protective heat-insulating composite structure prepared by this method can effectively avoid the problems of connection gaps, poor long-term connection stability, large thickness, large weight, etc., and has the advantages of good thermal insulation performance, light weight and high efficiency, and good long-term protection stability.

[0005] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a protective heat-insulating composite structure, wherein the protective heat-insulating composite structure comprises a first protective layer, a composite heat-insulating layer and a second protective layer; the first protective layer and the second protective layer both adopt a metal embossed titanium foil structure, that is, protrusions distributed in an array are arranged on the surface of the flat titanium foil structure; the composite heat-insulating layer is formed by alternatingly stacking a thermal resistance layer and a reflective layer, the number of the thermal resistance layers is n, the number of the reflective layers is n+1, and n is not less than 1 (that is, the layers close to the first protective layer and the second protective layer are all reflective layers); the reflective layer is a sandwich structure formed by an A-side polyimide film, an aluminum-plated layer, and a B-side polyimide film, and the B-side polyimide film is close to the first protective layer (hot side), and the A-side polyimide film is close to the second protective layer (cold side); The specific steps are: Step 1: emboss the flat and smooth titanium foils respectively to obtain protective layer (i.e., the first protective layer and the second protective layer) blanks; Step 2: Aluminum is plated on the A-side polyimide film base by a magnetron sputtering process, and then imidization is performed on the surface of the aluminum-plated layer to form a B-side polyimide film to obtain a reflective layer blank; prepare a thermal resistance layer blank; Step 3: Cut the first protective layer, the second protective layer, the thermal resistance layer, and the reflective layer blanks according to size, and stack and sew the reflective layer and the thermal resistance layer in sequence to form a composite thermal insulation layer; Step 4: Place the composite thermal insulation layer between the first protective layer and the second protective layer, and integrate the protective layers (i.e., the first protective layer and the second protective layer) by welding.

[0006] Through the sandwich design formed by the polyimide film on the A side, the aluminum-plated layer, and the polyimide film on the B side, the aluminum layer is protected by the polyimide film with low surface density, excellent thermal stability, flame retardancy and mechanical properties, so as to prevent the emissivity of the aluminum foil from increasing with the increase of temperature and the influence of external erosion on the aluminum layer, thereby improving the environmental adaptability of the reflective layer such as resistance to moisture and heat, and resistance to salt spray. In addition, the aluminum layer with high reflectivity and low roughness is used as the middle layer of the sandwich structure. First, the aluminum layer is used to achieve the combination of the two layers of polyimide film without adhesive, thereby improving the integrity of the reflective layer; second, an insulating gradient is formed, that is, the inner layer is an aluminum layer with high thermal reflectivity and high thermal conductivity, and the outer layer is a polyimide film with low thermal conductivity. Through interlayer reflection and barrier, effective attenuation of thermal radiation and heat transfer is achieved, thereby improving the thermal insulation performance of the entire reflective layer.

[0007] Based on the further optimization of the above scheme, the protrusions of the first protective layer protrude toward the side away from the composite thermal insulation layer, and the protrusions of the second protective layer protrude toward the side close to the composite thermal insulation layer; the protrusions of the first protective layer and the second protective layer are shaped like rice grains, pearls, or water drops. The thickness of the first protective layer and the second protective layer are both 0.03 to 0.1 mm; the diameter of the protrusions is 1 to 2.5 mm, and the height is 0.4 to 1.0 mm; the distance between two adjacent protrusions is 4 to 8 mm; the number of protrusions per unit area in the protective layer (i.e., the first protective layer or the second protective layer) is 1.5x10 4 ~6x10 4 indivual.

[0008] Through the setting of the protrusions, firstly, the strain hardening effect formed during the pressing process of the protrusions is utilized to improve the stiffness of the first protective layer and the second protective layer, thereby improving the overall stiffness of the protective structure and realizing the protection of the internal composite thermal insulation layer; secondly, by evenly distributing the uneven protrusions and reducing the wrinkles formed during the molding process of the protective layer, the weak points of failure are reduced, the protective layer is avoided from being damaged, and the overall resistance of the protective structure to liquid penetration is improved; thirdly, through the outward protrusions of the first protective layer, the reflective surface of the surface of the protective structure is converted from mirror reflection to dot matrix diffuse reflection, thereby expanding the heat reflection area and improving the reflection efficiency; fourthly, by utilizing the cavity matrix formed between the protrusions of the first protective layer and the composite thermal insulation layer, the interlayer flow field is changed, micro air gaps are formed, heat conduction is effectively blocked, and the thermal insulation effect is improved; fifthly, through the protrusions of the second protective layer, the contact between the second protective layer and the composite thermal insulation layer is converted from surface contact to point contact, thereby reducing the heat conduction area, avoiding the formation of temperature concentration points, and realizing uniform and rapid dissipation of the remaining heat after blocking. In addition, through the cavity matrix formed between the second protective layer and the substrate, the dissipation rate of the residual heat is further increased through the micro air gaps in the interlayer flow field, thereby improving the thermal insulation effect.

[0009] Based on further optimization of the above scheme, the thickness of the thermal resistance layer is 0.5-5 mm; the thermal resistance layer adopts basalt fiber reinforced silica aerogel felt, wherein the diameter of the basalt fiber is not greater than 6 μm, the mass ratio of basalt fiber to silica aerogel is 1:0.78-1, and the thermal conductivity of the basalt fiber reinforced silica aerogel felt at room temperature is 0.017-0.020 W / (m•K).

[0010] Based on the further optimization of the above scheme, the volume density of the basalt fiber reinforced silica aerogel felt is 150-170 kg / m 3 The bulk density of the preform formed by basalt fiber is 80~90kg / m 3 The density of silica aerogel is 70~80kg / m 3Using small diameter basalt fibers as reinforcing fibers for nanoporous silica aerogel can effectively limit the solid heat conduction of the fibers themselves, making the basalt fiber felt itself have a lower thermal conductivity. At the same time, using short diameter basalt fibers to form a low volume density preform can further reduce the volume density while ensuring the mechanical properties of the fiber-reinforced aerogel composite material. The diameter of the fiber preform is close to the wavelength of near-infrared radiation, which can produce a strong diffraction and scattering effect on the near-infrared radiation, thereby further enhancing the high-temperature infrared radiation heat conduction barrier effect. In addition, the addition of basalt fibers can effectively solve the problems of pure aerogel being brittle and easy to break.

[0011] Based on further optimization of the above solution, the thickness of the polyimide film on the A side is 20-30 μm, the thickness of the aluminum plating layer is 100-200 nm, and the thickness of the polyimide film on the B side is 4-6 μm.

[0012] Based on the further optimization of the above scheme, the aluminum plating by magnetron sputtering process in step 2 is specifically as follows: first, open the vacuum chamber, install the film material, measure the film material diameter at the winding and unwinding positions, and adjust the tension; then close the vacuum chamber, turn on the power, and check whether the coating drum can work normally; turn on the cooling water switch of the pump group, turn on the front stage pump group, and start vacuuming after 5 minutes. When the vacuum degree is less than 5×10 -4 Pa, prepare for coating; check the coating drum temperature and deep cooling temperature, turn on the cathode cooling water and pretreatment heater, adjust the tension, and start unwinding; then, rotate the metal aluminum target, adjust the distance between the metal aluminum target and the substrate to 6-12cm; introduce argon gas, clean the gas pipeline, last for 3-5 minutes, keep the pressure at 0.2-1Pa, and start sputtering; after sputtering, turn off the sputtering power and gas. During the aluminum plating process of magnetron sputtering, the flow rate of argon gas is 15-100sccm; the magnetron sputtering power is 50-100W, and the sputtering time is 2-5min.

[0013] Based on further optimization of the above scheme, the imidization processing on the surface of the aluminum-plated layer in the step 2 is specifically as follows: a polyamic acid solution is coated on the aluminum-plated layer surface of the polyimide film on the A side by a scraper method, and baked at step temperatures, and rolled up after the imidization degree is reached; wherein the step temperature range is 20 to 350°C, that is, heating at 20°C to 100°C, 150°C, 200°C, 260°C, and 320°C, and the insulation time for each step temperature is 15 to 90 minutes.

[0014] Based on the further optimization of the above scheme, the sewing process in step three is specifically as follows: except for the first and last stitches, the remaining stitches do not contact the reflective layers close to the first protective layer and the second protective layer (i.e., the outermost reflective layers on both sides), and the first and last stitches respectively penetrate the outermost reflective layers on both sides; the ratio of the distance between two adjacent stitches to the thickness of the composite thermal insulation layer is 1-3:2-5. Due to the difference in expansion coefficient between the reflective layer and the thermal resistance layer, stress concentration is easily generated between the reflective layer and the thermal resistance layer, which leads to interlayer cracking and gradually expands outward, causing the thermal insulation protection structure to fail, the thermal conductivity to increase, and its thermal protection ability to decrease; the present application effectively improves the interlayer shear performance through the laminated structure of the specific thermal resistance layer and the reflective layer and the sewing process, and can inhibit the expansion of delamination damage during the thermal shock process, thereby eliminating interlayer cracking and ensuring the plasticity of the thermal insulation protection structure.

[0015] Based on further optimization of the above scheme, the welding process requirements in step 4 are: using 1 to 3 rows of welding, the welding point spacing is 6±2mm, and the welding point indentation diameter is 1±0.5mm.

[0016] The following are the effects of the technical solution of the present invention: The preparation method of the present invention uses a polyimide film on the A side, an aluminum-plated layer, and a polyimide film on the B side to form a reflective layer of a sandwich structure, and through the alternating superposition between the reflective layer and the thermal resistance layer, the use stability of the reflective layer is improved, and the problem of damage is avoided. At the same time, the layer-by-layer reflection and blocking of heat transfer are achieved, and the heat is attenuated to achieve an excellent thermal insulation effect; the reflective layer and the thermal resistance layer are compounded by a sewing process, which not only effectively suppresses the problems of cracking and crack propagation caused by the difference in thermal expansion coefficient between the reflective layer and the thermal resistance layer, but also avoids the formation of temperature convergence points, thereby performing uniform and efficient thermal insulation. In addition, the welding between the first protective layer and the second protective layer obtained by the embossing process forms an integral metal protective shell. The embossed structure design not only avoids leakage of the external atmosphere, liquid, etc., improves the overall protective ability of the metal protective shell, but also cooperates with the composite thermal insulation layer to achieve uniform and rapid blocking and attenuation of heat, and further improves the overall thermal insulation performance and protective ability of the protective thermal insulation structure.

[0017] The protective heat-insulating composite structure obtained by the present invention is easy to install, stable and reliable, thin in thickness, highly lightweight, and has excellent heat-insulating performance. It can not only be used for thermal protection of aircraft parachute cabins, but also can be used for heat-insulating protection of special equipment in various fields in high-temperature environments of 120 to 350°C, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the protective heat-insulating composite structure in an embodiment of the present invention.

[0019] Figure 2 for Figure 1 A partial enlarged view of middle A.

[0020] Figure 3 Schematic diagram of the structure of the first protective layer of the protective heat-insulating composite structure in an embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the structure of sewing the composite heat insulation layer in an embodiment of the present invention.

[0022] Among them, 10, the first protective layer; 21, the thermal resistance layer; 22, the reflective layer; 221, the polyimide film on the A side; 222, the aluminum plating layer; 223, the polyimide film on the B side; 30, the second protective layer. DETAILED DESCRIPTION

[0023] The present invention is further described in detail in conjunction with the following specific embodiments and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art, and the present invention has no special restrictions; in addition, the described embodiments are not intended to further limit the present invention.

[0024] Embodiment 1: A method for preparing a protective heat-insulating composite structure, see Figure 1 As shown, the protective heat-insulating composite structure includes a first protective layer 10, a composite heat-insulating layer and a second protective layer 30. The first protective layer 10 and the second protective layer 30 both adopt a metal embossed titanium foil structure, that is, protrusions (such as convex protrusions) distributed in an array are arranged on the surface of the flat titanium foil structure. Figure 3 As shown, the protrusion of the first protective layer 10 faces the side away from the composite thermal insulation layer (i.e. Figure 1 The protrusion of the second protective layer 30 is toward the side close to the composite thermal insulation layer (i.e. Figure 1 The first protective layer 10 and the second protective layer 30 have protrusions on the upper side shown in the figure; the protrusions of the first protective layer 10 and the second protective layer 30 are in the shape of rice grains; the thickness of the first protective layer 10 and the second protective layer 30 are both 0.03 mm (the thickness of the titanium foil when the first protective layer 10 and the second protective layer 30 are in a flat state); the diameter of the protrusions is 1 mm and the height is 0.4 mm; the distance between two adjacent protrusions is 4 mm; the number of protrusions per unit area in the protective layer (i.e., the first protective layer 10 or the second protective layer 30) is 6x10 4 indivual.

[0025] The composite thermal insulation layer is formed by alternatingly stacking thermal resistance layers 21 and reflective layers 22, the number of thermal resistance layers 21 is n, the number of reflective layers 22 is n+1, and n is not less than 1 (that is, the reflective layers 22 are close to the first protective layer 10 and the second protective layer 30; the specific number of thermal resistance layers 21 and reflective layers 22 is determined according to the actual insulation effect required, for example, in this embodiment, a structure of five thermal resistance layers 21 + six reflective layers 22 is adopted); the thickness of the thermal resistance layer 21 is 2 mm, and the thermal resistance layer 21 adopts basalt fiber reinforced silica aerogel felt, wherein the diameter of the basalt fiber is not more than 6 μm, the mass ratio of basalt fiber to silica aerogel is 1:0.78, and the thermal conductivity of the basalt fiber reinforced silica aerogel felt at room temperature is 0.020 W / (m•K); the volume density of the basalt fiber reinforced silica aerogel felt is 159.74 kg / m 3 The bulk density of the preform formed by basalt fiber is 89.74kg / m 3 The density of silica aerogel is 70kg / m 3 . Reference Figure 2 As shown: the reflective layer 22 is a sandwich structure formed by an A-side polyimide film 221, an aluminum-plated layer 222, and a B-side polyimide film 223, and the B-side polyimide film 223 is close to the first protective layer 10, and the A-side polyimide film 221 is close to the second protective layer 30 (that is, with respect to the B-side polyimide film 223 and the A-side polyimide film 221 of the single-layer reflective layer 22, the B-side polyimide film 223 is closer to the first protective layer 10 located on the hot side, and the A-side polyimide film 221 is closer to the second protective layer 30 located on the cold side); the thickness of the A-side polyimide film 221 is 20μm, the thickness of the aluminum-plated layer 222 is 100nm, and the thickness of the B-side polyimide film 223 is 4μm.

[0026] The specific steps are: Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to press the titanium foil patterns) to obtain protective layer (ie, the first protective layer 10 and the second protective layer 30) blanks.

[0027] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using magnetron sputtering process. Specifically, first, open the vacuum chamber, install the film material, measure the film material diameter at the winding and unwinding positions, and adjust the tension; then close the vacuum chamber, turn on the power, and check whether the coating drum can work normally; turn on the cooling water switch of the pump group, turn on the front stage pump group, and start vacuuming after 5 minutes. When the vacuum degree is less than 5×10 -4Pa, prepare for coating; check the coating drum temperature and deep cooling temperature, turn on the cathode cooling water and pretreatment heater, adjust the tension, and start unwinding; then, rotate the metal aluminum target, and adjust the distance between the metal aluminum target and the substrate to 6 cm; introduce argon gas, clean the gas pipeline, last for 3 minutes, keep the pressure at 0.4Pa, and start sputtering, where the argon flow rate is 30sccm; the magnetron sputtering power is 50W, and the sputtering time is 5min; after sputtering, turn off the sputtering power and gas. Then, the surface of the aluminum-plated layer 222 is subjected to imidization processing to form a B-side polyimide film 223, and a blank of the reflective layer 22 is obtained, specifically: a polyamic acid solution is coated on the surface of the aluminum-plated layer 222 of the A-side polyimide film 221 by a scraper method, and baked at step temperatures, and rolled up after reaching the imidization degree; wherein the step temperature range is 20-350°C, that is, heating from 20°C to 100°C, 150°C, 200°C, 260°C, and 320°C, and the insulation time of each step temperature is 30 minutes. Prepare the blank of the thermal resistance layer 21 (the thermal resistance layer 21 of the basalt reinforced silica aerogel felt in this embodiment can be prepared by using the conventional preparation method of fiber-reinforced aerogel in the art).

[0028] Step three, respectively cut the blanks of the first protective layer 10, the second protective layer 30, the thermal resistance layer 21, and the reflective layer 22 according to size (i.e., cut the blank size according to the thermal protection area of ​​the equipment to be protected), and stack the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e., stack them in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sew them to form a composite thermal insulation layer. The sewing process is specifically as follows: except for the first and last stitches, the remaining stitches do not touch the reflective layer 22 close to the first protective layer and the second protective layer (i.e., the outermost reflective layer 22 on both sides), and the first and last stitches respectively penetrate the outermost reflective layer 22 on both sides (such as Figure 4 As shown); the ratio of the distance between two adjacent needles to the thickness of the composite insulation layer is 1:2.

[0029] Step 4: Before using the first protective layer 10 and the second protective layer 30, they are first cleaned and dried with ethyl acetate; then, the composite thermal insulation layer is placed between the first protective layer 10 and the second protective layer 30, and the protective layers (i.e., the first protective layer and the second protective layer) are integrated by welding; specifically: first, the composite thermal insulation layer in step 3 is placed on one end face of the protrusion of the second protective layer 30; then, the outer circle of the first protective layer 10 is folded inward to form a package for the second protective layer 30 (after folding, the folded edge part can be knocked with a hammer to fit it to ensure the tightness of the fit); then, check whether there are any problems such as misalignment, abnormal bulging, etc. between the first protective layer 10, the composite thermal insulation layer, and the second protective layer 30. If there is no abnormality, weld the connection between the diameter of the first protective layer 10 and the second protective layer 30. The welding process requirements are: single-row welding method is adopted, the welding point spacing is 6±2mm, and the welding point indentation diameter is 1±0.5mm. Before starting the welding machine each time, it is necessary to select samples of the same structure and thickness for trial welding at 5 points, and formal welding is performed after the tear test is qualified. Finally, the edges of the first protective layer 10 and the second protective layer 30 that have been welded are ground and burrs are removed.

[0030] Embodiment 2: A method for preparing a protective heat-insulating composite structure, see Figure 1 As shown, the protective heat-insulating composite structure includes a first protective layer 10, a composite heat-insulating layer and a second protective layer 30. The first protective layer 10 and the second protective layer 30 both adopt a metal embossed titanium foil structure, that is, protrusions (such as convex protrusions) distributed in an array are arranged on the surface of the flat titanium foil structure. Figure 3 As shown, the protrusion of the first protective layer 10 faces the side away from the composite thermal insulation layer (i.e. Figure 1 The protrusion of the second protective layer 30 is toward the side close to the composite thermal insulation layer (i.e. Figure 1 The first protective layer 10 and the second protective layer 30 have protrusions on the upper side shown in the figure; the protrusions of the first protective layer 10 and the second protective layer 30 are pearl-shaped; the thickness of the first protective layer 10 and the second protective layer 30 is 0.06 mm (the thickness of the titanium foil when the first protective layer 10 and the second protective layer 30 are in a flat state); the diameter of the protrusion is 1.5 mm and the height is 0.7 mm; the distance between two adjacent protrusions is 6 mm; the number of protrusions per unit area in the protective layer (i.e., the first protective layer 10 or the second protective layer 30) is 3.8x10 4 indivual.

[0031] The composite thermal insulation layer is formed by alternatingly stacking thermal resistance layers 21 and reflective layers 22, the number of thermal resistance layers 21 is n, the number of reflective layers 22 is n+1, and n is not less than 1 (that is, the layers close to the first protective layer 10 and the second protective layer 30 are all reflective layers; the specific number of thermal resistance layers 21 and reflective layers 22 is determined according to the actual insulation effect required, for example, in this embodiment, a structure of five thermal resistance layers 21 + six reflective layers 22 is adopted); the thickness of the thermal resistance layer 21 is 2 mm, and the thermal resistance layer 21 adopts basalt fiber reinforced silica aerogel felt, wherein the diameter of the basalt fiber is not more than 6 μm, the mass ratio of basalt fiber to silica aerogel is 1:0.85, and the thermal conductivity of the basalt fiber reinforced silica aerogel felt at room temperature is 0.018 W / (m•K); the volume density of the basalt fiber reinforced silica aerogel felt is 163.24 kg / m 3 The bulk density of the preform formed by basalt fiber is 88.24kg / m 3 The density of silica aerogel is 75kg / m 3 . Reference Figure 2 As shown: the reflective layer 22 is a sandwich structure formed by an A-side polyimide film 221, an aluminum-plated layer 222, and a B-side polyimide film 223, and the B-side polyimide film 223 is close to the first protective layer 10, and the A-side polyimide film 221 is close to the second protective layer 30 (that is, with respect to the B-side polyimide film 223 and the A-side polyimide film 221 of the single-layer reflective layer 22, the B-side polyimide film 223 is closer to the first protective layer 10 located on the hot side, and the A-side polyimide film 221 is closer to the second protective layer 30 located on the cold side); the thickness of the A-side polyimide film 221 is 25μm, the thickness of the aluminum-plated layer 222 is 150nm, and the thickness of the B-side polyimide film 223 is 5μm.

[0032] The specific steps are: Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to press the titanium foil patterns) to obtain protective layer (ie, the first protective layer 10 and the second protective layer 30) blanks.

[0033] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using magnetron sputtering process. Specifically, first, open the vacuum chamber, install the film material, measure the film material diameter at the winding and unwinding positions, and adjust the tension; then close the vacuum chamber, turn on the power, and check whether the coating drum can work normally; turn on the cooling water switch of the pump group, turn on the front stage pump group, and start vacuuming after 5 minutes. When the vacuum degree is less than 5×10 -4Pa, prepare for coating; check the coating drum temperature and deep cooling temperature, turn on the cathode cooling water and pretreatment heater, adjust the tension, and start unwinding; then, rotate the metal aluminum target, and adjust the distance between the metal aluminum target and the substrate to 8 cm; introduce argon gas, clean the gas pipeline, last for 4 minutes, keep the pressure at 0.6 Pa, and start sputtering, where the argon flow rate is 40 sccm; the magnetron sputtering power is 75 W and the sputtering time is 3.5 minutes; after sputtering, turn off the sputtering power and gas. Then, the surface of the aluminum-plated layer 222 is subjected to imidization processing to form a B-side polyimide film 223, and a blank of the reflective layer 22 is obtained. Specifically, a polyamic acid solution is coated on the surface of the aluminum-plated layer 222 of the A-side polyimide film 221 by a scraper method, and baked at step temperatures, and rolled up after reaching the imidization degree; wherein the step temperature range is 20 to 350°C, that is, heating from 20°C to 100°C, 150°C, 200°C, 260°C, and 320°C, and the insulation time of each step temperature is 40 minutes. Prepare the blank of the thermal resistance layer 21 (the thermal resistance layer 21 of the basalt reinforced silica aerogel felt in this embodiment can be prepared by using the conventional preparation method of fiber-reinforced aerogel in the art).

[0034] Step three, respectively cut the blanks of the first protective layer 10, the second protective layer 30, the thermal resistance layer 21, and the reflective layer 22 according to size (i.e., cut the blank size according to the thermal protection area of ​​the equipment to be protected), and stack the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e., stack them in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sew them to form a composite thermal insulation layer. The sewing process is specifically as follows: except for the first and last stitches, the remaining stitches do not touch the reflective layer 22 close to the first protective layer and the second protective layer (i.e., the outermost reflective layer 22 on both sides), and the first and last stitches respectively penetrate the outermost reflective layer 22 on both sides (such as Figure 4 As shown); the ratio of the distance between two adjacent needles to the thickness of the composite insulation layer is 2:3.5.

[0035] Step 4: Before using the first protective layer 10 and the second protective layer 30, they are first cleaned and dried with ethyl acetate; then, the composite thermal insulation layer is placed between the first protective layer 10 and the second protective layer 30, and the protective layers (i.e., the first protective layer and the second protective layer) are integrated by welding; specifically: first, the composite thermal insulation layer in step 3 is placed on one end face of the protrusion of the second protective layer 30; then, the outer circle of the first protective layer 10 is folded inward to form a package for the second protective layer 30 (after folding, the folded edge part can be hammered with a hammer to fit it to ensure the tightness of the fit); then, check whether there are any problems such as misalignment, abnormal bulging, etc. between the first protective layer 10, the composite thermal insulation layer, and the second protective layer 30. If there is no abnormality, weld the connection between the diameter of the first protective layer 10 and the second protective layer 30. The welding process requirements are: double-row staggered welding, welding point spacing of 6±2mm, and welding point indentation diameter of 1±0.5mm. Before starting the welding machine each time, it is necessary to select samples of the same structure and thickness for trial welding at 5 points, and formal welding is performed after the tear test is qualified. Finally, the edges of the first protective layer 10 and the second protective layer 30 that have been welded are ground and burrs are removed.

[0036] Embodiment 3: A method for preparing a protective heat-insulating composite structure, see Figure 1 As shown, the protective heat-insulating composite structure includes a first protective layer 10, a composite heat-insulating layer and a second protective layer 30. The first protective layer 10 and the second protective layer 30 both adopt a metal embossed titanium foil structure, that is, protrusions (such as convex protrusions) distributed in an array are arranged on the surface of the flat titanium foil structure. Figure 3 As shown, the protrusion of the first protective layer 10 faces the side away from the composite thermal insulation layer (i.e. Figure 1 The protrusion of the second protective layer 30 is toward the side close to the composite thermal insulation layer (i.e. Figure 1 The first protective layer 10 and the second protective layer 30 are convex in the shape of a water drop; the thickness of the first protective layer 10 and the second protective layer 30 is 0.1 mm (the thickness of the titanium foil when the first protective layer 10 and the second protective layer 30 are in a flat state); the diameter of the convex is 2.5 mm and the height is 1.0 mm; the distance between two adjacent convexities is 8 mm; the number of convexities per unit area in the protective layer (i.e., the first protective layer 10 or the second protective layer 30) is 1.5x10 4 indivual.

[0037] The composite thermal insulation layer is formed by alternatingly stacking thermal resistance layers 21 and reflective layers 22, the number of thermal resistance layers 21 is n, the number of reflective layers 22 is n+1, and n is not less than 1 (that is, the layers close to the first protective layer 10 and the second protective layer 30 are all reflective layers; the specific number of thermal resistance layers 21 and reflective layers 22 is determined according to the actual insulation effect required, for example, in this embodiment, a structure of five thermal resistance layers 21 + six reflective layers 22 is adopted); the thickness of the thermal resistance layer 21 is 2 mm, and the thermal resistance layer 21 adopts basalt fiber reinforced silica aerogel felt, wherein the diameter of the basalt fiber is not more than 6 μm, the mass ratio of basalt fiber to silica aerogel is 1:1, and the thermal conductivity of the basalt fiber reinforced silica aerogel felt at room temperature is 0.017 W / (m•K); the volume density of the basalt fiber reinforced silica aerogel felt is 160 kg / m 3 The bulk density of the preform formed by basalt fiber is 80kg / m 3 , the density of silica aerogel is 80kg / m 3 . Reference Figure 2 As shown: the reflective layer 22 is a sandwich structure formed by an A-side polyimide film 221, an aluminum-plated layer 222, and a B-side polyimide film 223, and the B-side polyimide film 223 is close to the first protective layer 10, and the A-side polyimide film 221 is close to the second protective layer 30 (that is, with respect to the B-side polyimide film 223 and the A-side polyimide film 221 of the single-layer reflective layer 22, the B-side polyimide film 223 is closer to the first protective layer 10 located on the hot side, and the A-side polyimide film 221 is closer to the second protective layer 30 located on the cold side); the thickness of the A-side polyimide film 221 is 30μm, the thickness of the aluminum-plated layer 222 is 200nm, and the thickness of the B-side polyimide film 223 is 6μm.

[0038] The specific steps are: Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to press the titanium foil patterns) to obtain protective layer (ie, the first protective layer 10 and the second protective layer 30) blanks.

[0039] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using magnetron sputtering process. Specifically, first, open the vacuum chamber, install the film material, measure the film material diameter at the winding and unwinding positions, and adjust the tension; then close the vacuum chamber, turn on the power, and check whether the coating drum can work normally; turn on the cooling water switch of the pump group, turn on the front stage pump group, and start vacuuming after 5 minutes. When the vacuum degree is less than 5×10 -4Pa, prepare for coating; check the coating drum temperature and deep cooling temperature, turn on the cathode cooling water and pretreatment heater, adjust the tension, and start unwinding; then, rotate the metal aluminum target, and adjust the distance between the metal aluminum target and the substrate to 10 cm; introduce argon gas, clean the gas pipeline, last for 5 minutes, keep the pressure at 0.8 Pa, and start sputtering, where the argon flow rate is 50 sccm; the magnetron sputtering power is 100 W and the sputtering time is 2 minutes; after sputtering, turn off the sputtering power and gas. Then, the surface of the aluminum-plated layer 222 is subjected to imidization processing to form a B-side polyimide film 223, and the reflective layer 22 blank is obtained, specifically: a polyamic acid solution is coated on the surface of the aluminum-plated layer 222 of the A-side polyimide film 221 by a scraper method, and baked at step temperatures, and rolled up after reaching the imidization degree; wherein the step temperature range is 20-350°C, that is, heating at 20°C to 100°C, 150°C, 200°C, 260°C, and 320°C, and the insulation time for each step temperature is 50 minutes. Prepare the thermal resistance layer 21 blank (the thermal resistance layer 21 of the basalt reinforced silica aerogel felt in this embodiment can be prepared by the conventional preparation method of fiber-reinforced aerogel in the art); Step three, respectively cut the blanks of the first protective layer 10, the second protective layer 30, the thermal resistance layer 21, and the reflective layer 22 according to size (i.e., cut the blank size according to the thermal protection area of ​​the equipment to be protected), and stack the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e., stack them in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sew them to form a composite thermal insulation layer. The sewing process is specifically as follows: except for the first and last stitches, the remaining stitches do not touch the reflective layer 22 close to the first protective layer and the second protective layer (i.e., the outermost reflective layer 22 on both sides), and the first and last stitches respectively penetrate the outermost reflective layer 22 on both sides (such as Figure 4 As shown); the ratio of the distance between two adjacent needles to the thickness of the composite insulation layer is 3:5.

[0040] Step 4: Before using the first protective layer 10 and the second protective layer 30, they are first cleaned and dried with ethyl acetate; then, the composite thermal insulation layer is placed between the first protective layer 10 and the second protective layer 30, and the protective layers (i.e., the first protective layer and the second protective layer) are integrated by welding; specifically: first, the composite thermal insulation layer in step 3 is placed on one end face of the protrusion of the second protective layer 30; then, the outer circle of the first protective layer 10 is folded inward to form a package for the second protective layer 30 (after folding, the folded edge part can be knocked with a hammer to fit it to ensure the tightness of the fit); then, check whether there are any problems such as misalignment, abnormal bulging, etc. between the first protective layer 10, the composite thermal insulation layer, and the second protective layer 30. If there is no abnormality, weld the connection between the diameter of the first protective layer 10 and the second protective layer 30. The welding process requirements are: adopt three rows of staggered welding, the welding point spacing is 6±2mm, and the welding point indentation diameter is 1±0.5mm. Before starting the welding machine each time, it is necessary to select samples of the same structure and thickness for trial welding at 5 points, and formal welding is performed after the tear test is qualified. Finally, the edges of the first protective layer 10 and the second protective layer 30 that have been welded are ground and burrs are removed.

[0041] Comparative Example 1: A thermal insulation protective layer includes a first protective layer, a composite thermal insulation layer and a second protective layer. The thickness, structure, material, etc. of the first protective layer are consistent with those in Example 2, that is, a metal embossed titanium foil structure; the thickness of the second protective layer is 0.06 mm, and the second protective layer adopts a flat and smooth titanium foil structure. The composite thermal insulation layer is consistent with that in Example 2 (including the thickness, material, number of layers, etc. of the thermal resistance layer and the reflective layer). The preparation method of the thermal insulation protective layer is generally consistent with the preparation method of the thermal insulation protective layer in Example 2, except that: when preparing the protective layer blank in step one, only the first protective layer is embossed, and the second protective layer is not embossed.

[0042] Comparative Example 2: A thermal insulation protective structure includes a first protective layer, a composite thermal insulation layer and a second protective layer. The thickness, structure, material, etc. of the second protective layer are consistent with those in Example 2, that is, a metal embossed titanium foil structure; the thickness of the first protective layer is 0.06 mm, and the first protective layer adopts a flat and smooth titanium foil structure. The composite thermal insulation layer is consistent with that in Example 2 (including the thickness, material, number of layers, etc. of the thermal resistance layer and the reflective layer). The preparation method of the thermal insulation protective layer is generally consistent with the preparation method of the thermal insulation protective layer in Example 2, except that: when preparing the protective layer blank in step one, only the second protective layer is embossed, and the first protective layer is not embossed.

[0043] Comparative Example 3: A heat-insulating protective structure includes a first protective layer, a composite heat-insulating layer and a second protective layer. The thickness, structure, material, etc. of the first protective layer and the second protective layer are consistent with those in Example 2, that is, a metal embossed titanium foil structure; the composite heat-insulating layer is formed by alternating thermal resistance layers and reflective layers, the number of reflective layers is n, the number of thermal resistance layers is n+1, and n is not less than 1 (that is, the thermal resistance layers are close to the first protective layer and the second protective layer; the total number of thermal resistance layers and reflective layers is consistent with that in Example 2), and the thickness, material, etc. of the thermal resistance layers and the reflective layers are consistent with those in Example 2. The preparation method of the heat-insulating protective layer is generally consistent with the preparation method of the heat-insulating protective layer in Example 2, except that: in the process of stacking the composite heat-insulating layer in step three, the stacking is carried out in the order of thermal resistance layer-reflective layer-thermal resistance layer...-reflective layer-thermal resistance layer, and then sewn.

[0044] Comparative Example 4: A heat-insulating protective structure includes a first protective layer, a composite heat-insulating layer and a second protective layer. The thickness, structure, material, etc. of the first protective layer and the second protective layer are consistent with those in Example 2, that is, a metal embossed titanium foil structure; the composite heat-insulating layer is formed by alternating thermal resistance layers and reflective layers, and the number of thermal resistance layers and the number of reflective layers are consistent with those in Example 2; at the same time, the thickness and material of the thermal resistance layer 21 are consistent with those in Example 2, and the reflective layer adopts a smooth and flat aluminum foil structure and the thickness of the reflective layer is consistent with that in Example 2. The preparation method of the heat-insulating protective layer is generally consistent with the preparation method of the heat-insulating protective layer in Example 2, except that: in step 2, the existing aluminum foil is directly used as the reflective layer blank.

[0045] Performance test: The heat insulation protection structure samples obtained in Examples 1 to 3 and Comparative Examples 1 to 4 (the sample sizes are all 400 mm long and 300 mm wide) are fixed on the bracket of the closed inner cavity of the heating equipment. At the same time, three temperature measuring points (i.e., thermocouples) are evenly arranged on the cold surface of the sample, and the cold surface temperature of the sample is continuously collected by the thermocouple; when the hot surface temperature is 300°C, the ambient temperature is 23°C, and the insulation time is 1 hour (the other test conditions of Examples 1 to 3 and Comparative Examples 1 to 4 are consistent), the test results are as follows:

[0046] It can be clearly seen from the above table that the laminated structure combination of the cold surface protection layer + the outer layer of the hot surface protection layer of the specific structure of the present application, and the reflective layer + the thermal resistance layer of the specific material can effectively improve the thermal insulation performance of the protective structure. Under the long-term (i.e., 1 hour) action of the hot surface temperature of 300°C, the average temperature of the cold surface of the thermal insulation protection structure prepared by the present application is not more than 63°C, which is significantly lower than the thermal insulation protection structure and the average temperature of the cold surface prepared in Comparative Examples 1 to 4 (the cold surface temperature in Comparative Examples 1 to 4 is 70°C and above); at the same time, the temperature difference of each temperature measuring point of the thermal insulation protection structure prepared by the present application is small, which proves that the structure of the present application can dissipate heat evenly and there is no temperature concentration point, which also indirectly proves that the interlayer heat insulation effect of the present application is good.

Claims

1. A method for preparing a protective heat-insulating composite structure, characterized in that: The protective heat-insulating composite structure comprises a first protective layer, a composite heat-insulating layer and a second protective layer; the first protective layer and the second protective layer both adopt a metal embossed titanium foil structure, that is, protrusions distributed in an array are arranged on the surface of the flat titanium foil structure; the composite heat-insulating layer is formed by alternatingly stacking thermal resistance layers and reflective layers, the number of thermal resistance layers is n, the number of reflective layers is n+1, and n is not less than 1; the reflective layer is a sandwich structure formed by an A-side polyimide film, an aluminum-plated layer, and a B-side polyimide film, and the B-side polyimide film is close to the first protective layer, and the A-side polyimide film is close to the second protective layer; The specific steps are: Step 1: embossing the flat and smooth titanium foil to obtain a protective layer blank; Step 2: Aluminum is plated on the A-side polyimide film base by magnetron sputtering process, and then imidization is performed on the surface of the aluminum plated layer to form a B-side polyimide film to obtain a reflective layer blank; and a thermal resistance layer blank is prepared; Step 3: Cut the first protective layer, the second protective layer, the thermal resistance layer, and the reflective layer blanks according to size, and stack and sew the reflective layer and the thermal resistance layer in sequence to form a composite thermal insulation layer; Step 4: Place the composite thermal insulation layer between the first protective layer and the second protective layer, and integrate the protective layers by welding; the welding process requirements are: use 1 to 3 rows of welding, the welding point spacing is 6±2mm, and the welding point indentation diameter is 1±0.5mm.

2. The method for preparing a protective heat-insulating composite structure according to claim 1, characterized in that: The protrusions of the first protective layer protrude toward the side away from the composite insulation layer, and the protrusions of the second protective layer protrude toward the side close to the composite insulation layer; the protrusions of the first protective layer and the second protective layer are shaped like rice grains, pearls, or water drops.

3. A method for preparing a protective heat-insulating composite structure according to claim 1 or 2, characterized in that: The thickness of the first protective layer and the second protective layer are both 0.03-0.1 mm.

4. A method for preparing a protective heat-insulating composite structure according to claim 3, characterized in that: The thickness of the thermal resistance layer is 0.5-5 mm; the thermal resistance layer adopts basalt fiber reinforced silica aerogel felt, wherein the diameter of the basalt fiber is not greater than 6 μm, the mass ratio of basalt fiber to silica aerogel is 1:0.78-1, and the thermal conductivity of the basalt fiber reinforced silica aerogel felt at room temperature is 0.017-0.020 W / (m•K).

5. A method for preparing a protective heat-insulating composite structure according to claim 1 or 4, characterized in that: The volume density of the basalt fiber reinforced silica aerogel felt is 150-170 kg / m 3 The bulk density of the preform formed by basalt fiber is 80~90kg / m 3 The density of silica aerogel is 70~80kg / m 3 .

6. The method for preparing a protective heat-insulating composite structure according to claim 3, characterized in that: The thickness of the polyimide film on the A surface is 20-30 μm, the thickness of the aluminum plating layer is 100-200 nm, and the thickness of the polyimide film on the B surface is 4-6 μm.

7. The method for preparing a protective heat-insulating composite structure according to claim 1, characterized in that: The specific steps of the magnetron sputtering aluminum plating process in step 2 are as follows: First, open the vacuum chamber, install the film material, measure the film material diameter at the winding and unwinding positions, and adjust the tension; then close the vacuum chamber, turn on the power, and check whether the coating drum can work normally; Turn on the cooling water switch of the pump group, turn on the front stage pump group, and start vacuuming after 5 minutes. When the vacuum degree is less than 5×10 -4 Pa, prepare for coating; check the coating drum temperature and deep cooling temperature, turn on the cathode cooling water and pretreatment heater, adjust the tension, and start unwinding; then, rotate the metal aluminum target, and adjust the distance between the metal aluminum target and the substrate to 6-12 cm; introduce argon gas, clean the gas pipeline, last for 3-5 minutes, keep the pressure at 0.2-1 Pa, and start sputtering; after sputtering is completed, turn off the sputtering power and gas.

8. The method for preparing a protective heat-insulating composite structure according to claim 1 or 7, characterized in that: In the aluminum plating process of the magnetron sputtering process, the flow rate of argon gas is 15-100 sccm; the magnetron sputtering power is 50-100 W, and the sputtering time is 2-5 minutes.

9. The method for preparing a protective heat-insulating composite structure according to claim 1, characterized in that: The imidization process on the surface of the aluminum-plated layer in the step 2 is specifically as follows: a polyamic acid solution is coated on the aluminum-plated surface of the polyimide film on the A side by a scraper method, and baked at step temperatures, and rolled up after the imidization degree is reached; wherein the step temperature range is 20 to 350°C, that is, heating at 20°C to 100°C, 150°C, 200°C, 260°C, and 320°C, and the insulation time of each step temperature is 15 to 90 minutes.

10. The method for preparing a protective heat-insulating composite structure according to claim 1, characterized in that: The sewing process in step three is specifically as follows: except for the first stitch and the last stitch, the other stitches do not touch the reflective layers close to the first protective layer and the second protective layer, and the first stitch and the last stitch respectively penetrate the outermost reflective layers on both sides; the ratio of the stitch distance between two adjacent stitches to the thickness of the composite insulation layer is 1 to 3:2 to 5.

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