A method for preparing an integrated thermal insulation protective layer

Abstract

The present invention provides a method for preparing an integrated heat-insulating protective layer, which relates to the field of functional composite materials. The heat-insulating protective layer comprises 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; the composite heat-insulating layer is formed by alternately stacking a heat-resistance layer (21) and a reflective layer (22); 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). The steps include: embossing to obtain a protective layer blank; obtaining a reflective layer (22) and a heat-resistance layer (21) blank; stacking and sewing to obtain a composite heat-insulating layer; and welding the protective layer to obtain a heat-insulating protective structure. The heat-insulating protective layer prepared by the method is an integrated structure, which can effectively avoid problems such as connection gaps, poor long-term connection stability, large thickness, and large weight.

Description

Technical Field

[0001] The present invention relates to the technical field of functional composite materials, and in particular to a method for preparing an integrated heat-insulating protective layer. Background Art

[0002] At present, in order to prevent the radiant heat from the engine, exhaust system, etc. from affecting other equipment (for example, the radiant heat from the engine can easily cause the temperature of the parachute cabin to be too high, which in turn causes damage to the parachute's own fabric, carbonization of the compressed oil, and other problems), it is usually necessary to prepare a heat insulation layer on the surface of the equipment to achieve high-temperature thermal protection of the equipment, ensure the stability and safety of the equipment function, and improve the service life of the equipment in a high-temperature environment. However, the existing heat insulation protection structure usually uses aluminum foil as a reflective layer, and its (i.e., aluminum foil) emissivity will increase with the increase of temperature, resulting in a decrease in reflective ability; at the same time, the existing heat insulation protection structure usually uses a metal layer as a protective layer of the heat insulation material. When the smooth metal structure is directly used as a protective layer, when the area of ​​the equipment to be heat-insulated is large and has an arc surface, the metal structure has low strength and is prone to wrinkles and deformation. Problems such as cracks and breakage are prone to occur during long-term use, which in turn affects the heat insulation and protection effects of the metal protective layer, causing the external atmosphere, liquids, etc. to penetrate into the heat insulation protection structure, causing the reflective layer to be eroded, and then resulting in a decrease in the heat insulation performance of the heat insulation layer. In addition, in the prior art, the connection method of the metal protective layer also directly affects its overall thermal insulation performance and may even cause thermal insulation failure. For example, if the metal protective layer is connected by adhesive bonding, firstly, the long-term connection stability is poor, and cracking and gaps are prone to occur during long-term high-temperature use (i.e., there is currently a lack of organic adhesives on the market that can be used for a long time in a high-temperature environment of 350°C); secondly, the adhesive strength is low, and the metal protective layer after bonding has poor vibration and impact resistance. If the metal protective layer is mechanically connected, firstly, connection gaps are prone to occur, and the ability to prevent liquid and atmospheric leakage is poor; secondly, temperature convergence points are prone to occur at the connection (i.e., the temperature of the connectors such as screws or bolts, which are heat-conducting), reducing the overall thermal insulation performance of the thermal insulation protective layer; thirdly, the thickness and weight of the thermal insulation protective layer are easily increased, which does not meet the requirements of a lightweight thermal insulation protective layer. Summary of the invention

[0003] 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 an integrated thermal insulation and protective layer. The thermal insulation and protective layer prepared by this method is an integrated structure, that is, the thermal insulation layer is located in an integrated metal mold cavity, which can effectively avoid the problems of connection gaps, poor long-term connection stability, large thickness, large weight, etc., and obtain a thermal insulation and protective layer with good thermal insulation performance, light weight and high efficiency, and good long-term protection stability.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for preparing an integrated heat-insulating protective layer, the heat-insulating protective layer comprising 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 thermal resistance layers is n, the number of 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);

[0006] The specific steps are:

[0007] Step 1: embossing the flat and smooth titanium foils respectively to obtain protective layer (i.e., first protective layer and second protective layer) blanks;

[0008] Step 2: Aluminum is plated on the A-side polyimide film base by magnetron sputtering process, and then imidization is applied 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;

[0009] 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;

[0010] Step 4: Place the composite thermal insulation layer between the first protective layer and the second protective layer, and integrate the protective layers (ie, the first protective layer and the second protective layer) by welding.

[0011] 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.

[0012] Based on 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 have any one of rice grain, pearl, and water drop shapes.

[0013] Based on the further optimization of the above scheme, the thickness of the first protective layer and the second protective layer are both 0.03-0.1 mm; the diameter of the protrusion is 1-2.5 mm and the height is 0.4-1.0 mm; the distance between two adjacent protrusions is 4-8 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.

[0014] 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 damage of the protective layer is avoided, and the overall liquid penetration resistance of the protective structure 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.

[0015] 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).

[0016] 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 3The density of silica aerogel is 70~80kg / m 3 .

[0017] Using 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-density preform can further reduce the density of the fiber-reinforced aerogel composite while ensuring its mechanical properties. 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.

[0018] 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.

[0019] Based on the further optimization of the above scheme, the aluminum plating by magnetron sputtering process in step 2 is specifically as follows:

[0020] 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 coiling; then, rotate the metal aluminum target, 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.

[0021] Based on further optimization of the above scheme, during 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 min.

[0022] Based on further optimization of the above scheme, the imidization process of coating the aluminum-plated layer surface in 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.

[0023] Based on further optimization of the above scheme, the sewing process in step three is specifically as follows: except for the first stitch and the last stitch, 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 stitch and the last stitch penetrate the outermost reflective layers on both sides respectively; the ratio of the stitch distance between two adjacent stitches to the thickness of the composite thermal insulation layer is 1 to 3:2 to 5.

[0024] 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 a laminated structure of a specific thermal resistance layer and a reflective layer and a 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.

[0025] 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.

[0026] The following are the effects of the technical solution of the present invention:

[0027] The present application forms a composite thermal insulation layer by staggeredly stacking the reflective layer and the thermal resistance layer, which can effectively reflect and block heat transfer, thereby repeatedly realizing heat attenuation and achieving excellent thermal insulation effect; the stacking and sewing process of the reflective layer and the thermal resistance layer is utilized to effectively suppress the cracking and crack propagation between the reflective layer and the thermal resistance layer due to the difference in thermal expansion coefficient during the thermal shock process, thereby ensuring the overall thermal insulation performance of the composite thermal insulation layer structure; at the same time, in the reflective layer, a sandwich structure of polyimide film-aluminum-plated layer-polyimide film is prepared by a magnetron sputtering process, thereby improving the long-term use stability and thermal insulation performance of the reflective layer and preventing the reflective layer from being easily damaged.

[0028] In addition, the present application forms an integrated protective metal shell outside the composite thermal insulation layer through welding between the first protective layer and the second protective layer. At the same time, the embossed structure design between the first protective layer and the second protective layer is utilized to prevent leakage of external atmosphere, liquid, etc., and enhance the protective capability of the metal protective shell. It also cooperates with the composite thermal insulation layer to achieve uniform and rapid heat blocking and attenuation, and prevent rapid heat transfer, thereby further enhancing the overall thermal insulation performance of the thermal insulation protective layer, and enhancing the protective capability of the metal shell, and avoiding problems such as leakage prevention performance and severe reduction in thermal insulation performance caused by easy damage to the metal shell.

[0029] The thermal insulation protective layer prepared by the method of the present application can be bonded to the surface of the equipment to be thermally protected, is easy to install, stable and reliable, highly lightweight, thin, and has excellent thermal insulation performance. It can be used for thermal insulation 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

[0030] Figure 1 Schematic diagram of the overall structure of the heat insulation protection structure in an embodiment of the present invention.

[0031] Figure 2 for Figure 1 A partial enlarged view of middle A.

[0032] Figure 3 Schematic diagram of the structure of the first protective layer of the thermal insulation protective structure in an embodiment of the present invention.

[0033] Figure 4 It is a schematic diagram of the structure of sewing the composite heat insulation layer in an embodiment of the present invention.

[0034] 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

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Embodiment 1:

[0037] A method for preparing an integrated thermal insulation protective layer, see Figure 1 As shown, the heat insulation protective layer includes a first protective layer 10, a composite heat insulation 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 1The 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.

[0038] 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 .

[0039] 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.

[0040] The specific steps are:

[0041] Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to emboss the titanium foil patterns) to obtain protective layer (i.e., first protective layer 10 and second protective layer 30) blanks;

[0042] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using a magnetron sputtering process, specifically:

[0043] 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 coiling; 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 5 minutes; after sputtering, turn off the sputtering power and gas.

[0044] Then, the surface of the aluminum-plated layer 222 is coated with imidization processing to form a B-side polyimide film 223, and the reflective layer 22 blank is obtained. Specifically, the 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 30min;

[0045] Prepare a 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 a conventional method for preparing fiber-reinforced aerogel in the art);

[0046] Step 3, respectively cutting 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. cutting the blank size according to the thermal protection area of ​​the equipment to be protected), and stacking the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e. stacking in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sewing them to form a composite thermal insulation layer;

[0047] The sewing process is as follows: except for the first stitch and the last stitch, the remaining stitches do not contact 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 stitch and the last stitch respectively penetrate the outermost reflective layer 22 on both sides (i.e., Figure 4 As shown); the ratio of the distance between two adjacent needles to the thickness of the composite insulation layer is 1:2.

[0048] 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 heat 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:

[0049] First, place the composite heat insulation layer in step 3 on the raised end face of the second protective layer 30; then, fold the outer circle of the first protective layer 10 inward to form a package for the second protective layer 30 (after folding, the folded edge can be hammered to fit it to ensure the tightness of the fit); then, check whether there are any problems such as misalignment and abnormal bulging between the first protective layer 10, the composite heat 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, welding point spacing 6±2mm, welding point indentation diameter 1±0.5mm. Before starting the welding machine each time, it is necessary to select 5 points of samples with the same structure and thickness for trial welding, and formally weld after passing the tear test.

[0050] Finally, the edges of the welded first protective layer 10 and the second protective layer 30 are ground and burrs are removed.

[0051] Embodiment 2:

[0052] A method for preparing an integrated thermal insulation protective layer, see Figure 1 As shown, the heat insulation protective layer includes a first protective layer 10, a composite heat insulation 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 a pearl-like protrusion shape; 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 flat); 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 3.8 x 10 4 indivual.

[0053] 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 .

[0054] 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.

[0055] The specific steps are:

[0056] Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to emboss the titanium foil patterns) to obtain protective layer (i.e., first protective layer 10 and second protective layer 30) blanks;

[0057] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using a magnetron sputtering process, specifically:

[0058] 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 coiling; 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.

[0059] Then, the surface of the aluminum-plated layer 222 is coated with imidization processing to form a B-side polyimide film 223, and the reflective layer 22 blank is obtained. Specifically, the 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 40min;

[0060] Prepare a 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 a conventional method for preparing fiber-reinforced aerogel in the art);

[0061] Step 3, respectively cutting 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. cutting the blank size according to the thermal protection area of ​​the equipment to be protected), and stacking the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e. stacking in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sewing them to form a composite thermal insulation layer;

[0062] The sewing process is as follows: except for the first stitch and the last stitch, the remaining stitches do not contact 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 stitch and the last stitch respectively penetrate the outermost reflective layer 22 on both sides (i.e., 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.

[0063] 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 heat 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:

[0064] First, place the composite heat insulation layer in step three on the raised end face of the second protective layer 30; then, fold the outer circle of the first protective layer 10 inward to form a package for the second protective layer 30 (after folding, the folded 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 and abnormal bulging between the first protective layer 10, the composite heat 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: use double-row 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 5 points of samples with the same structure and thickness for trial welding, and formally weld after passing the tear test.

[0065] Finally, the edges of the welded first protective layer 10 and the second protective layer 30 are ground and burrs are removed.

[0066] Embodiment 3:

[0067] A method for preparing an integrated thermal insulation protective layer, see Figure 1 As shown, the heat insulation protective layer includes a first protective layer 10, a composite heat insulation 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.

[0068] 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 .

[0069] 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.

[0070] The specific steps are:

[0071] Step 1: emboss the flat and smooth titanium foils respectively (conventional embossing in the art, such as roller embossing, can be used to emboss the titanium foil patterns) to obtain protective layer (i.e., first protective layer 10 and second protective layer 30) blanks;

[0072] Step 2: Aluminum is plated on the polyimide film 221 base layer on the A side by using a magnetron sputtering process, specifically:

[0073] 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 coiling; then, rotate the metal aluminum target, 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.

[0074] Then, the surface of the aluminum-plated layer 222 is coated with imidization processing to form a B-side polyimide film 223, and the reflective layer 22 blank is obtained. Specifically, the 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 50min;

[0075] Prepare a 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 a conventional method for preparing fiber-reinforced aerogel in the art);

[0076] Step 3, respectively cutting 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. cutting the blank size according to the thermal protection area of ​​the equipment to be protected), and stacking the reflective layer 22 and the thermal resistance layer 21 in sequence (i.e. stacking in the order of reflective layer 22-thermal resistance layer 21-reflective layer 22…-thermal resistance layer 21-reflective layer 22), and sewing them to form a composite thermal insulation layer;

[0077] The sewing process is as follows: except for the first stitch and the last stitch, the remaining stitches do not contact 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 stitch and the last stitch respectively penetrate the outermost reflective layer 22 on both sides (i.e., Figure 4 As shown); the ratio of the distance between two adjacent needles to the thickness of the composite insulation layer is 3:5.

[0078] 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 heat 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:

[0079] First, place the composite heat insulation layer in step three on the raised end face of the second protective layer 30; then, fold the outer circle of the first protective layer 10 inward to form a package for the second protective layer 30 (after folding, the folded 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 and abnormal bulging between the first protective layer 10, the composite heat insulation layer, and the second protective layer 30. If there are no abnormalities, weld the connection between the diameter of the first protective layer 10 and the second protective layer 30. The welding process requirements are: use 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 5 points of samples with the same structure and thickness for trial welding, and formally weld after passing the tear test.

[0080] Finally, the edges of the welded first protective layer 10 and the second protective layer 30 are ground and burrs are removed.

[0081] Comparative Example 1:

[0082] A heat-insulating protective layer 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 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 heat-insulating 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).

[0083] The preparation method of the heat-insulating protective layer is substantially the same as the preparation method of the heat-insulating protective layer in Example 2, except that when preparing the protective layer blank in step 1, only the first protective layer is embossed, and the second protective layer is not embossed.

[0084] Comparative Example 2:

[0085] A heat insulation protection structure includes a first protection layer, a composite heat insulation layer and a second protection layer. The thickness, structure, material, etc. of the second protection layer are consistent with those in Example 2, that is, a metal embossed titanium foil structure; the thickness of the first protection layer is 0.06 mm, and the first protection layer adopts a flat and smooth titanium foil structure. The composite heat 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).

[0086] The preparation method of the heat-insulating protective layer is substantially the same as the preparation method of the heat-insulating protective layer in Example 2, except that when preparing the protective layer blank in step 1, only the second protective layer is embossed, and the first protective layer is not embossed.

[0087] Comparative Example 3:

[0088] A heat-insulating protective structure comprises 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 alternatingly stacking 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 layer and the reflective layer are consistent with those in Example 2.

[0089] The preparation method of the thermal insulation protective layer is substantially the same as that of the thermal insulation protective layer in Example 2, except that: during the stacking process of the composite thermal insulation layer in step three, the stacking is performed in the order of thermal resistance layer-reflection layer-thermal resistance layer...-reflection layer-thermal resistance layer, and then sewn.

[0090] Comparative Example 4:

[0091] A heat-insulating protective structure comprises 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 alternatingly stacking a thermal resistance layer and a reflective layer, and the number of the thermal resistance layers and the number of the 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, 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.

[0092] The preparation method of the heat-insulating protective layer is substantially the same as 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.

[0093] 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:

[0094]

[0095] 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 an integrated thermal insulation protective layer, characterized in that: The heat-insulating protective layer 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.

2. The method for preparing an integrated heat-insulating protective layer 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. The method for preparing an integrated heat-insulating protective layer 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. The method for preparing an integrated heat-insulating protective layer 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. The method for preparing an integrated heat-insulating protective layer 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.

6. The method for preparing an integrated heat-insulating protective layer 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.

7. The method for preparing an integrated heat-insulating protective layer 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.

8. The method for preparing an integrated heat-insulating protective layer 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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