A load-bearing / insulating integrated insulation structure for a common bottom of a low-temperature storage tank and its forming method and application

Abstract

The present invention discloses a load-bearing / insulating integrated insulation structure for a common bottom of a low-temperature storage tank, and its molding method and application. The insulation layer structure includes epoxy resin low-temperature adhesive, polyurethane low-temperature adhesive, high-pressure lightweight polyurethane foam layer, closed primer, varnish, and polyurea protective layer. The results show that the density of the high-pressure polyurethane foam of the common bottom furnace test piece is not more than 90 kg / m 3 , the compression strength is not less than 0.50 MPa, the thermal conductivity is about 0.022 W / (m·K), and the key performance meets the design indicators. Compared with the current model of the common bottom PMI core material sandwich solution, the processing cycle is reduced by about 85%, the manufacturing cost is reduced by about 94%, and the weight of the insulation layer is reduced by about 38%, achieving cost reduction and efficiency improvement. At the same time, by controlling the scanning speed of the spray gun during the spraying operation, the envelope range is determined, the process margin is guaranteed, and the quality stability of the common bottom product is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of launch vehicles, and in particular relates to a load-bearing / insulating integrated insulation structure for a common bottom of a cryogenic storage tank, and a molding method and application thereof. Background Art

[0002] Under certain environmental conditions, thermal insulation layered materials can block the transfer of heat to isolate the impact of external extreme environments such as high temperature or low temperature.

[0003] Cryogenic fuels such as liquid oxygen / kerosene and liquid oxygen / liquid hydrogen have the characteristics of high combustion heat, non-toxicity and pollution-free, and are advanced propellants for modern space launch vehicles.

[0004] The two sides of the common bottom of a certain type of two-stage tank developed against the background of a new generation of launch vehicles are low-temperature liquid oxygen and room-temperature kerosene media, respectively, and there are ultra-low temperature, large temperature difference, and high load conditions. The common bottom of the tank is a load-bearing / insulating integrated structure. It is in a complex environment of low-temperature gas, liquid, and solid three-phase action. Its main function is to separate the fuel tank and the oxidizer tank so that they can maintain independent operation, and play a role in insulation to maintain the working temperature of the two propellants. The insulation layer in the common bottom interlayer plays a key role in the load-bearing / insulating integrated structure. It not only needs to meet the common bottom insulation requirements, but also needs to bear the internal pressure of the tank. Therefore, the manufacture of a large temperature difference interlayer common bottom is one of the key technologies for cryogenic fuel tanks.

[0005] The applicant has found that there are at least the following technical problems in the prior art: there is a large temperature difference between the front box and the rear box, resulting in low-temperature storage problems with different heat leakage mechanisms such as convection heat transfer and solid heat conduction. At present, the solutions commonly used at home and abroad are two-layer metal shells and a sandwich layer structure located in the middle. The first is a sandwich common bottom structure of a non-metallic honeycomb sandwich aluminum alloy shell represented by the CZ-3B three-stage tank. The heat insulation effect is achieved by vacuuming. The advantage is that the vacuum layer has a very good heat insulation effect and a low thermal conductivity. The disadvantage is that the sandwich common bottom structure is complex, the requirements for the insulation layer are high, and vacuuming is required before testing and use. The efficiency is high and the cost is high, and the preparation time before the launch of the carrier is long.

[0006] The second type is the variable thickness polymethacrylimide (PMI) foam sandwich aluminum alloy panel common bottom tank structure represented by the CZ-6A secondary tank. The advantage is that the structure is relatively simple compared to the vacuum common bottom, and no vacuum is required before testing and use, which shortens the preparation time before the launch of the carrier. The disadvantage is that the PMI foam raw material is expensive, and the upper and lower panels adopt a complex melon slice welding process. The panel size and shape and position tolerances are large, and the foam layer is difficult to fit with the metal shell. VARI technology is required for bonding, and the connection structure of the two common bottom panels is relatively complex, the processing cost is high, and the efficiency is low.

[0007] Both structures emphasize the absolute thermal insulation performance of the two parts of the tank. Non-metallic spacers are used for the parts connecting the inner and outer metal layers. There is no direct contact between the metals. Screws are used to connect the upper and lower panels. Since the upper and lower metal panels of this structure are welded, the structural accuracy of the metal panels is not high, which makes it difficult to fit the hard sandwich core with the upper and lower panels. It has high requirements on equipment and operators, and is time-consuming and labor-intensive.

[0008] In addition, there is a third solution, which is a common bottom configuration of a single metal panel layer + a non-metallic insulation layer, represented by the Chinese invention patent with publication number CN115750142A. The advantages of this configuration are simple structure, relatively simple processing technology, and low manufacturing difficulty, but it also has disadvantages. During operation, the lower surface of the non-metallic insulation layer directly contacts the propellant, and the non-metallic layer contacts the low-temperature propellant, which has the risk of cracking or even falling off.

[0009] Therefore, developing a sandwich common bottom insulation layer forming technology with simple process, high efficiency, low cost and high safety is of great significance for reducing the manufacturing cost of common bottom insulation structure, improving production efficiency and achieving the goal of low cost and rapid manufacturing of my country's new generation of launch vehicles. Summary of the invention

[0010] In view of this, the present invention aims to provide a method and application for forming a load-bearing / heat-insulating integrated insulation layer for the common bottom of a rocket cryogenic tank, so as to solve the problems of difficult processing technology, low efficiency, high cost, low safety, etc. in the prior art. The process method is simple, the manufacturing difficulty is low, the cost is greatly reduced, and it also effectively solves the safety problem of cracking and falling off of the insulation layer, and provides technical support for the manufacture of lightweight, load-bearing / heat-insulating integrated common bottom structures. The results show that the density of the high-pressure polyurethane foam of the common bottom furnace specimen is no more than 90 kg / m 3 , the compression strength is not less than 0.50 MPa, the thermal conductivity is about 0.022W / (m·K), and the key performance meets the design indicators. Compared with the common bottom PMI core material sandwich solution of the current model, the processing cycle is reduced by about 85%, the manufacturing cost is reduced by about 94%, and the weight of the insulation layer is reduced by about 38%, achieving cost reduction and efficiency improvement. At the same time, by controlling the scanning speed of the spray gun during the spraying operation, the envelope range is determined, the process margin is guaranteed, and the quality stability of the common bottom product is effectively improved. The common bottom insulation layer molding process is of great significance to achieving the low-cost, rapid manufacturing, and high-density launch goals of future launch vehicles.

[0011] To achieve the above object, the present invention provides the following technical solutions:

[0012] The present invention provides a load-bearing / insulating integrated insulation structure for a common bottom of a low-temperature storage tank, which comprises a buffer layer, a transition layer, a foam layer, a closed bottom coating layer, a varnish layer, and a protective layer in sequence;

[0013] The buffer layer is an epoxy resin low-temperature adhesive coating;

[0014] The transition layer is a polyurethane low-temperature adhesive coating;

[0015] The foam layer is a high-pressure-bearing lightweight polyurethane foam layer;

[0016] The closed primer coating is a polyisocyanate coating;

[0017] The varnish layer is an isocyanate coating;

[0018] The protective layer is a polyurea protective layer.

[0019] As an embodiment of the present invention, an isolation film layer is further provided on one side of the protective layer of the load-bearing / insulating integrated insulation structure for the common bottom of the cryogenic storage tank. The isolation film includes one of a metal film (aluminum alloy film, such as 5A06, 2219, etc.) and a non-metallic film (such as F46 film, etc.). The isolation film layer can separate the non-metallic insulation layer from the propellant, so that the insulation layer does not directly contact the cryogenic propellant, thereby avoiding the risk of cracking or even falling off.

[0020] As one embodiment of the present invention, the thickness of each layer or the coating amount of the coating is as follows:

[0021] The coating amount of epoxy resin low temperature adhesive is 50~100 g / m 2 ;

[0022] The coating amount of polyurethane low temperature adhesive is 20~100 g / m 2 ;

[0023] The thickness of the foam layer is 19~21 mm; the density of the foam layer is 75~110 kg / m 3 , compression strength is 0.5~1.0MPa, thermal conductivity is 0.022~0.026 W·(m·K) -1 ;

[0024] The thickness of polyisocyanate coating is 0.1-1.5mm;

[0025] The thickness of the varnish is 0.1~0.5 mm;

[0026] The thickness of the polyurea protective layer is 0.2~1.0 mm.

[0027] The present invention provides a molding process method for a load-bearing / heat-insulating integrated insulation layer for a rocket cryogenic tank common bottom, the molding process method comprising the following steps:

[0028] S1, coating epoxy resin low-temperature adhesive on the convex surface of the common bottom metal panel to form a buffer layer;

[0029] S2. Apply polyurethane low-temperature adhesive on the outside of the buffer layer to form a transition layer;

[0030] S3. Spray high-pressure lightweight polyurethane foam on the outside of the transition layer to form a foam layer;

[0031] S4, applying a closed primer on the surface of the foam layer to form a closed primer coating;

[0032] S5, spraying varnish on the surface of the closed primer to form a varnish layer;

[0033] S6. Spray polyurea protective layer material on the surface of the varnish layer to form a protective layer, thereby obtaining a load-bearing / heat-insulating integrated insulation layer.

[0034] Therefore, the present invention solves the problems of difficult processing technology, low efficiency, high cost, low safety, etc. in the prior art by adopting a bearing / insulation integrated insulation layer forming process method for rocket cryogenic tank common bottom. The process method is simple, has low manufacturing difficulty, greatly reduces costs, and effectively solves the safety problem of cracking and falling off of the insulation layer, which has important guiding significance for manufacturing lightweight, bearing / insulation integrated common bottom structure.

[0035] Furthermore, in step S1, the material of the middle common bottom metal panel is aluminum alloy. The middle common bottom metal panel is located at the junction of the liquid oxygen tank and the kerosene tank, and is a common bottom with a convex shape (the side where the insulation layer is located is the kerosene tank, and the other side is the liquid oxygen tank). The buffer layer coating area is the convex area of ​​the metal panel ( Figure 2 ).

[0036] Furthermore, in step S1, before applying the epoxy resin low-temperature adhesive, the convex surface of the common bottom metal panel is first polished to remove the oxide layer. After polishing, compressed air is used to blow away metal chips, and the sprayed surface is scrubbed with anhydrous ethanol 2 to 5 times until there is no metal chips and other dust. After each scrubbing, the next scrubbing is performed after an interval of 5 to 15 minutes. After the last scrubbing, it is left to air for 15 to 30 minutes for use.

[0037] Furthermore, in step S1, when the epoxy resin low-temperature adhesive is prepared, the mass ratio of component A: component B: component C = (20-30): (5-10): (0.5-3).

[0038] Among them, component A is a special epoxy resin, including one or more of bisphenol A epoxy resin, phenolic epoxy resin, polyether epoxy resin, polyester epoxy resin, and polybutadiene epoxy resin; component B is an aromatic amine curing agent, including one or more of diethyltoluenediamine (DETDA), 4,4-diaminodiphenylmethane (DDM), 4,4'-methylene-bis(2-chloroaniline) (MOCA), 4,4-diaminodiphenyl sulfone (DDS), LS-113 aromatic amine epoxy curing agent, meta-phenylenediamine, and meta-phenylenediamine; component C is a coupling agent, including one or more of methyl silane coupling agent, acrylic silane coupling agent, amino silane coupling agent, sulfur-containing silane coupling agent, and epoxy silane coupling agent.

[0039] Furthermore, in step S1, after coating, the coating is cured at room temperature for 24 to 72 hours. During coating, the single amount of adhesive is 1 to 5 kg, and stirred evenly, and 50 to 100 g of epoxy resin low-temperature adhesive per square meter is applied.

[0040] Furthermore, in step S2, the polyurethane low-temperature adhesive is prepared in a mass ratio of component A: component B = (5-10): (1-4).

[0041] Component A is a polyurethane monomer, including one or more of polyether polyurethane, polyester polyurethane, polyimide polyurethane, and polyurea polyurethane. Component B is an amine curing agent. Amine curing agents include one or more of diethyltoluenediamine (DETDA), 4,4-diaminodiphenylmethane (DDM), 4,4'-methylene-bis(2-chloroaniline) (MOCA), 4,4-diaminodiphenyl sulfone (DDS), LS-113 aromatic amine epoxy curing agent, metaphenylenediamine, metaphenylenediamine, and polyetheramine D230.

[0042] Furthermore, in step S2, after coating, curing at room temperature is performed for 24 to 72 hours. During coating, the single amount of adhesive is 1 to 5 kg, and stirred evenly, and 20 to 100 g of polyurethane low-temperature adhesive is applied per square meter.

[0043] Furthermore, in step S3, the high-pressure lightweight polyurethane foam is sprayed by mixing isocyanate (material A) and polyol combination material (material B), atomizing and spraying them on the surface of the transition layer to foam and form a foam layer. After the foam is fully matured (24 hours after spraying), the compression strength and foam density of the foam sample are tested. The foam layer foam density is 75-110 kg / m 3 , compression strength is 0.5~1.0 MPa, thermal conductivity is 0.022~0.026 W·(m·K) -1 .

[0044] Isocyanate (material A) includes one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), and polymethylene polyphenyl polyisocyanate (PAPI); polyol combination material (material B) includes polyol, catalyst, and foaming agent, and the mass ratio is (100~105): (0.6~1.0): (20~40).

[0045] Further, the polyol includes one or more of polyether polyol and polyester polyol;

[0046] The polyester polyol has a hydroxyl value of 300 to 450 mgKOH / g, a molecular weight of 1000 to 4000, and a viscosity of 600 to 1500 mpa·s at 25°C.

[0047] The polyether polyol has a hydroxyl value of 300 to 450 mgKOH / g, a molecular weight of 1000 to 3000, and a viscosity of 700 to 1500 mpa·s at 25°C.

[0048] Further, the catalyst includes one or more of triethanolamine, A-33, PT303, triethylenediamine, stannous octoate, dibutyltin dilaurate, MB20, and butyl titanate mixed in any proportion;

[0049] Furthermore, the foaming agent is one or more of HCFC-141b and H20 mixed in any proportion.

[0050] Furthermore, in step S3, during mixing, two delivery pipes simultaneously deliver isocyanate (material A) and polyol combination material (material B) to the mixing chamber for thorough mixing. The material temperature of isocyanate (material A) is 35-40 °C, and the material temperature of polyol combination material (material B) is 25-30 °C. The pipeline temperature is consistent with the material temperature of material A. During spraying, the pressure readings of the two pipelines are maintained at 1300-1800 psi, the spray gun sweep speed is 0.5-1.0 m / s, and the distance between the gun head and the workpiece is 1-2 m. The thickness of the single-layer foam in the foam body is 4-15 mm (preferably 9 mm-12 mm), and the total thickness of the foam layer is 30-50 mm.

[0051] The spraying of the high pressure-bearing lightweight polyurethane foam is carried out at an ambient temperature of 25° C. and a relative humidity of 50%. The spraying obtains a high pressure-bearing lightweight polyurethane foam.

[0052] Preferably, the pressure readings of the two pipelines are maintained at 1400-1600 psi during spraying, the spray gun sweep speed is 0.6-0.8 m / s, and the thickness of the single layer of foam in the foam is 6-12 mm. Therefore, the foam density of the foam layer under this process parameter is 80-200 kg / m 3 , the compression strength is 0.6~0.8 MPa. It not only ensures the process margin and improves the quality stability of the common bottom product, but also controls the weight of the product insulation layer and reduces production costs.

[0053] Furthermore, in step S4, the foam layer is polished before the closed primer, and the thickness of the foam layer after polishing is 19-21 mm. Free foaming itself has uneven positions, and subsequent polishing is required to achieve a relatively flat and smooth foam layer; the substrate is convex, not horizontal, and there is a phenomenon of sag in the liquid, which to a certain extent causes the thickness of the foam growth to be uneven; in the case of manual foaming, the spraying position and the amount of liquid are not completely uniform.

[0054] For sealing and defect repair of the insulation layer (foam layer), at least one of putty, DW-1 adhesive, and foam powder is allowed to be used as the repair material. Sealing here refers to the use of a closed primer to seal the pores of the foam layer and the foam powder that is difficult to remove. Since there is foam powder on the surface of the foam layer that is difficult to remove after grinding, if the holes are directly sealed with glue, it is very easy to cause "point contact" between the foam powder and the glue liquid, causing the glue layer to debond, and then causing the protective layer to debond. Through the sealing treatment of the insulation layer, the foam powder on the surface of the foam layer can be firmly adhered and compacted on the surface of the foam layer, which is conducive to the close bonding of the subsequent repair material and the foam layer matrix. Defects refer to local small-scale defects caused by uneven foaming of the foam itself, or defects in the foam layer caused by bumps during transportation.

[0055] Furthermore, in step S4, 1 to 3 layers of sealing primer are evenly rolled on the surface of the foam layer, each layer of primer has a thickness of 0.1 to 0.5 mm, and the time interval between each layer of primer is 8 to 24 hours. After curing, local repair and secondary polishing are performed.

[0056] Furthermore, in step S4, before preparing the sealing primer, the primer B component must be fully stirred for 5 to 30 minutes. After stirring until the color is uniform, the sealing primer is prepared according to the mass ratio of component A: component B: component C = (20 to 40): (200 to 240): (5 to 30), and 300 to 400 g is prepared at a time.

[0057] Among them, component A for preparing the closed primer is modified isocyanate, including one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; component B is an amine compound, including one or more of primary amine, secondary amine, and tertiary amine; component C is a sealing aid, including one or more of transparent powder, talcum powder, mica powder, high alumina cement, heavy calcium, light calcium, bentonite, kaolin, diatomaceous earth, wollastonite, silica powder, and barite powder.

[0058] Furthermore, in step S5, the varnish is sprayed on the surface of the primer with a spray gun, and after the spraying is completed and confirmed to be complete, it is cured for 24 to 48 hours.

[0059] Furthermore, in step S5, the matching varnish is prepared according to the mass ratio of component A: component B = (10-50): (150-300), 400-500 g of the ingredients are prepared at a time, and the mixture is used immediately. After spraying, it is cured at room temperature for 12-48 hours.

[0060] Among them, component A is a modified isocyanate, including one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; component B is an amine compound, including one or more of primary amine, secondary amine, and tertiary amine.

[0061] Furthermore, in step S6, the polyurea protective layer material spraying step: the polyurea protective layer material includes component A1 (modified isocyanate), component A2 (liquid flame retardant), and component R (amine compound). The material is prepared according to the mass ratio of component A1: component A2: component R = (30-50): (5-10): (30-60). The R component is fully stirred for 20-30 min as R material; the A1 component and the A2 component are mixed in a prescribed proportion to prepare the A material. The main voltage of the spraying equipment is 220-400 V; the current is 30-100A; the pipeline pressure is set to 2000-3000 psi; the heating temperature of the pipeline, A material, and R material is set to 50-100°C. The distance between the spray gun head and the workpiece to be sprayed is 1-1.5 m.

[0062] Among them, the polyurea protective layer material includes A1 component (modified isocyanate) including one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; A2 component (liquid flame retardant) includes one or more of HFFR type liquid flame retardant, FR type liquid flame retardant, PP type liquid flame retardant, EVA type liquid flame retardant, and PU type liquid flame retardant; R component (amine compound) includes one or more of primary amine, secondary amine, and tertiary amine.

[0063] Furthermore, in step S6, after the protective layer is completely cured, a film layer is used to isolate the thermal insulation layer from the cryogenic propellant. The film layer is pre-connected with the tank barrel section, and then fixedly connected with the top root of the upper panel to form a common bottom structure. The film layer can be made of metal, such as aluminum alloy (5A06, 2219, etc.), or other non-metallic films (such as F46 film, etc.).

[0064] The present invention also provides an application of the load-bearing / heat-insulating integrated thermal insulation structure in the preparation of a rocket cryogenic tank. The load-bearing / heat-insulating integrated thermal insulation structure can be applied to the common bottom of a launch vehicle cryogenic tank.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) Compared with the non-metallic honeycomb core insulation solution, this spraying process solution does not require vacuuming before testing and use, which can effectively shorten the preparation time before the launch of the carrier, simplify the launch site workflow, have high efficiency and low cost, and greatly improve operability.

[0067] (2) Due to the large bonding area, complex profile, and rigid matching (both the foam and the panel are rigid) between the upper and lower panels of the sandwich bottom and the foam core, the debonding defects occur randomly during bonding. The PMI foam bonding solution is difficult, risky, long, and costly. At the same time, the glass cloth is heavy. The foam spraying solution can well overcome the process difficulties brought by the bonding of special-shaped surfaces. Foaming can be performed on any surface. The foam body has no joints, good insulation effect, and is tightly bonded to the attached surface, thus avoiding quality control risks to a large extent. When spraying polyurethane foam, the raw materials are immediately mixed on site, which is well controllable; the raw materials are sprayed in the form of atomized droplets through a spray gun, and the production process has extremely high flexibility. As a result, the spraying process is greatly simplified, and the processing cycle is reduced by about 85% compared with the PMI foam bonding solution. At the same time, the price of the polyurethane foam selected for spraying is greatly reduced compared with PMI foam, and the cost can be reduced by about 94%. The weight of the insulation layer is reduced by about 40%.

[0068] (3) The present invention proposes to use a metal film to separate the non-metallic insulation layer and the propellant during operation, so that the insulation layer does not directly contact the cryogenic propellant, avoiding the risk of cracking or even falling off. At the same time, the thickness of the metal film is greatly reduced compared to the metal panel, achieving weight reduction of the common bottom structure, which can effectively reduce the cost of rocket manufacturing.

[0069] (4) The epoxy resin low-temperature adhesive used in the present invention can improve the bonding strength between the common bottom metal panel and the non-metallic transition layer, and the polyurethane low-temperature adhesive can improve the bonding strength between the non-metallic buffer layer and the foam layer. Compared with a single adhesive, the synergistic combination of the two adhesives can further improve the bonding strength between the insulation layer foam and the common bottom workpiece, thereby ensuring the stability of product quality.

[0070] (5) Since there is foam powder on the surface of the foam layer after grinding, which is difficult to remove, if glue is directly applied to seal the holes, it is very easy to cause "point contact" between the foam powder and the glue liquid, causing the glue layer to debond, and then causing the protective layer to debond. The present invention can effectively avoid the occurrence of the protective layer debonding phenomenon by using a closed primer and a varnish to replace the glue layer (9) in patent CN 115750142 A. The specific implementation method is: after the closed primer is applied, the foam powder on the surface of the foam layer is firmly adhered and compacted on the surface of the foam layer, which is conducive to the close combination of the subsequent repair material and the foam layer substrate. After the second grinding, the varnish is applied to further compact the foam powder produced by the second grinding, thereby ensuring the adhesion of the subsequent protective layer.

[0071] (6) The present invention controls the compressive strength of the insulation layer more accurately by changing the spray gun scanning speed, determines the envelope range of the process parameters, and improves the quality stability of the co-bottom product. Since the faster the scanning speed, the thinner the thickness of the single-layer foam after the foam matures, the superposition of different foam single-layer thicknesses can be achieved by controlling the spray gun scanning speed. Related studies have shown that as the thickness of the single-layer foam decreases, the average density and average compression strength of the foam increase. This is because each layer of foam will form a thin crust on the surface during the foaming and maturation process. The crust has a high density and high strength, and plays a supporting role similar to a skeleton in the foam. Therefore, the crust in the foam can improve the overall compression strength of the foam to a certain extent. The smaller the thickness of the single-layer foam, the more layers of the foam crust of the same thickness, the stronger the supporting force, and thus the higher the overall compression strength of the foam. The test results of the present invention show that even if the thickness of the single-layer foam is ~15 mm, the average compression strength reaches 0.53 MPa, which also meets the design index of not less than 0.5 MPa. In view of this, the present invention proposes that in the actual spraying construction process of the product, the single-layer foam thickness is controlled to be optimally from 9 mm to 12 mm by adjusting the spray gun scanning speed, and the average density of the foam body is not higher than 90 kg / m 3 The compression strength is not less than 0.5 Mpa, which not only ensures the process margin and improves the quality stability of the common bottom product, but also controls the weight of the product's insulation layer and reduces the cost of rocket manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0073] Figure 1 It is a schematic diagram of the heat insulation structure of the present invention;

[0074] Figure 2 This is a schematic diagram of the co-bottom structure of the present invention;

[0075] Figure 3It is the relationship between the average density and average compression strength of the foam and the thickness of a single layer of foam. DETAILED DESCRIPTION

[0076] The present invention is described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some adjustments and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0077] The raw materials used in the examples and comparative examples of the present invention are as follows:

[0078] (1) In the epoxy resin low-temperature adhesive, the special epoxy resin is bisphenol A epoxy resin, the aromatic amine curing agent is m-phenylenediamine, and the coupling agent is aminosilane coupling agent;

[0079] (2) In the polyurethane low-temperature adhesive, the polyurethane monomer is a polyether polyurethane monomer obtained by the reaction of trihydroxy polyoxypropylene ether (N330) and toluene diisocyanate (TDI) (molar ratio: trihydroxy polyoxypropylene ether (N330) / toluene diisocyanate (TDI) = 2 / 3), and the amine curing agent is 4,4'-methylene-bis(2-chloroaniline) (MOCA).

[0080] (3) In the high-pressure lightweight polyurethane foam, the isocyanate (material A) is polymethylene polyphenyl polyisocyanate (PAPI), and the polyol composition includes 100 parts of polyether polyol, 0.8 parts of PT303+MB20 compound catalyst, and 25 parts of HCFC-141b+H2O compound foaming agent.

[0081] (4) When applying the sealing primer, the modified isocyanate is isophorone diisocyanate, the amine compound is a secondary amine, and the sealing aid is bentonite.

[0082] (5) When spraying the varnish layer, the modified isocyanate is hexamethylene diisocyanate and the amine compound is a primary amine.

[0083] (6) When spraying the protective layer, component A1 (modified isocyanate) is benzyl diisocyanate, component A2 (liquid flame retardant) is PU type liquid flame retardant, and component R (amine compound) is primary amine.

[0084] Example 1

[0085] S1. Apply epoxy resin low-temperature adhesive on the convex surface of the middle common bottom metal panel to form a buffer layer.

[0086] The convex surface of the metal panel was polished to remove the oxide layer. After polishing, the metal chips were blown away with compressed air, and the sprayed surface was scrubbed with anhydrous ethanol for 3 times until there was no metal chips and other dust. After each scrubbing, the next scrubbing was done after an interval of 10 minutes. After the last scrubbing, it was left to air for 20 minutes for use. The epoxy resin low-temperature adhesive was prepared according to the mass ratio of special epoxy resin: aromatic amine curing agent: coupling agent = 25:5:1. The single preparation amount of glue was 1.5 kg, and it was stirred evenly, and then 50 g of epoxy resin low-temperature adhesive per square meter was applied. After coating, it was cured at room temperature for 48 hours.

[0087] S2. Apply polyurethane low-temperature adhesive on the outside of the buffer layer to form a transition layer.

[0088] Prepare polyurethane low-temperature adhesive according to the mass ratio of polyurethane monomer: amine curing agent = 5:1, prepare 2 kg of adhesive at a time, stir evenly, and then apply 80 g of polyurethane low-temperature adhesive per square meter. After coating, cure at room temperature for 24 hours.

[0089] S3. At an ambient temperature of 25°C and a relative humidity of 50%, spray a high-pressure lightweight polyurethane foam on the outside of the transition layer. Set the temperature of material A to 38°C, the temperature of material B to 30°C, and the pipeline temperature to 38°C in the foaming machine. During spraying, keep the pressure readings of the two pipelines at around 1500 psi. The isocyanate (material A) and the polyol combination (material B) are simultaneously transported to the mixing chamber by two delivery pipelines for thorough mixing. The spray gun sweep speed is controlled to 1.2 m / s, and the distance between the gun head and the workpiece is 1.5 m. After atomization, spray to the surface of the transition layer to form a foam layer. The thickness of a single layer of foam in the foam is ~9 mm (another experiment with a single layer of foam thickness of ~4 and 15 mm was conducted, see Examples 2 and 3), and the total thickness of the foam layer is 40 mm. After the foam is fully matured for 24 hours, take a sample to test the compressive strength and foam density of the foam sample. The foam layer foam density is 89 kg / m 3 , compression strength is 0.70 MPa, thermal conductivity is 0.024W·(m·K) -1 .

[0090] S4. Stir the B component (amine compound) of the closed primer for 30 minutes until the color is uniform. Prepare the closed primer according to the mass ratio of modified isocyanate: amine compound: sealing aid = 33:220:20, and prepare 353 g at a time. After grinding the foam layer, roll 3 layers of closed primer evenly on the surface of the foam layer (each primer thickness 0.2 mm), with an interval of 8 hours between each primer. The last primer needs to be cured for 24 hours before spraying varnish. The thickness of the foam layer after grinding is ~20 mm. Use DW-1 and foam powder to mix and seal the insulation layer locally and repair defects.

[0091] S5. Prepare varnish according to the mass ratio of modified isocyanate: amine compound = 33:200, 466 g of ingredients at a time, and use it immediately after preparation. Spray the varnish on the surface of the primer with a spray gun (0.3mm). After spraying is completed and confirmed without omission, cure at room temperature for 24 hours.

[0092] S6. Spray a polyurea protective layer generated by the reaction of isocyanate components and amino compound components on the surface of the varnish. Prepare the polyurea protective layer material according to the mass ratio of modified isocyanate (A1): liquid flame retardant (A2): amine compound (R) = 41.9:6.1:40. Stir the R component thoroughly for 30 minutes to prepare the R material; mix the A1 component and the A2 component in a ratio of 41.9:6.1 to prepare the A material. The main voltage of the spraying equipment is 380 V; the current is 60 A; the pipeline pressure is set to 2500 psi; the heating temperature of the pipeline, A material, and R material is set to 65°C. The distance between the spray gun head and the workpiece to be sprayed is 1.2 m. The thickness of the polyurea protective layer is 0.3 mm. After the protective layer is completely cured, if Figure 1 A layer of metal film (aluminum alloy 5A06) is then used to separate the thermal insulation layer from the cryogenic propellant (kerosene), as shown in Figure 2. Figure 2 As shown, the metal membrane is pre-connected with the tank barrel section and then fixedly connected with the top root of the upper panel to form a common bottom structure.

[0093] Example 2

[0094] The difference between this embodiment and embodiment 1 is that the spray gun sweep speed is controlled to 2.0 m / s, and the thickness of the single layer of foam in the foam is ~4 mm. After the foam is fully matured for 24 hours, the compression strength and foam density of the foam sample are tested. The foam layer foam density is 106 kg / m 3 , the compressive strength is 0.84 MPa.

[0095] Example 3

[0096] The difference between this embodiment and embodiment 1 is that the spray gun sweep speed is controlled to 0.6 m / s, and the thickness of the single layer of foam in the foam is ~15 mm. After the foam is fully matured for 24 hours, the compression strength and foam density of the foam sample are tested. The foam layer foam density is 76 kg / m 3 , the compression strength is 0.53 MPa.

[0097] Comparative Example 1

[0098] The only difference between this comparative example and Example 1 is that there is no polyurethane low-temperature adhesive transition layer, and the buffer layer is in direct contact with the foam layer; at the same time, after the foam layer is polished, the epoxy resin low-temperature adhesive is directly coated to form a coating layer, and then a polyurea protective layer is sprayed outside the coating layer.

[0099] Comparative Example 2

[0100] The difference between this comparative example and Example 1 is that there is no buffer layer, and the transition layer is directly scraped and coated on the convex surface of the metal panel.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 1 is that there is no transition layer, and the high-pressure-bearing lightweight polyurethane foam is directly sprayed on the surface of the buffer layer.

[0103] Comparative Example 4

[0104] The only difference between this comparative example and Example 1 is that the foam layer is not prepared by spraying on the direct transition layer, but the foam layer is prepared by the method of step S3, and is contour-processed into a foam prefabricated block with a thickness of 20 mm, which is then attached to the transition layer for subsequent operations.

[0105] Comparative Example 5

[0106] The difference between this comparative example and Example 1 is that the closed primer roller coating is not performed, and the varnish is sprayed directly on the surface of the foam layer.

[0107] Comparative Example 6

[0108] The difference between this comparative example and Example 1 is that after the closed primer is applied, no clear coat is sprayed, and the polyurea protective layer is directly sprayed.

[0109] Performance test example:

[0110] The compressive strength and apparent density of the furnace samples prepared in Examples 1-3 were measured respectively. The compressive strength was tested according to the standard GJB 1585A-2004 "Test Method for Mechanical Properties of Polyurethane Rigid Foam Plastics", and the apparent density was tested according to the standard GB / T6343-2009 "Determination of Apparent Density of Foam Plastics and Rubbers". All measured values ​​were taken as the average of no less than 3 test pieces. The test results are shown in the attached figure of the specification ( Figure 3 ).

[0111] Low temperature impact tests were conducted on the furnace samples in Specific Implementation 1 and Comparative Examples 1-6. The specific test method is: liquid nitrogen is introduced into the test metal box cavity (plate thickness 2mm), and the liquid nitrogen is poured out after standing for 1 minute. After the small sample test piece (size 200mm×200mm×20mm) returns to room temperature, the bonding quality of each layer is re-inspected.

[0112] After low-temperature impact, the sample in Specific Embodiment 1 has good adhesion to the metal substrate and does not debond. At the same time, the protective layer is also tightly bonded to the foam layer through the closed primer and varnish. However, after low-temperature impact, the sample in Comparative Example 1 has obvious debonding between the buffer layer and the foam layer, and between the foam layer and the adhesive layer. After low-temperature impact, the sample in Comparative Example 2 has obvious debonding between the transition layer and the metal panel. After low-temperature impact, the sample in Comparative Example 3 has obvious debonding between the buffer layer and the foam layer. After low-temperature impact, the sample in Comparative Example 4 has obvious debonding between the transition layer and the foam layer. The repair material at the defect of the sample in Comparative Example 5 cannot be tightly bonded to the foam layer matrix, and is very easy to debond, and the protective layer debonds after low-temperature impact. After low-temperature impact, the protective layer of the sample in Comparative Example 6 has debonding.

[0113] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A load-bearing / insulating integrated insulation structure for a common bottom of a low-temperature storage tank, characterized in that: It includes a buffer layer, a transition layer, a foam layer, a closed base coating layer, a varnish layer, and a protective layer in sequence; The buffer layer is an epoxy resin low-temperature adhesive coating; The transition layer is a polyurethane low-temperature adhesive coating; The foam layer is a high-pressure-bearing lightweight polyurethane foam layer; The closed primer coating is a polyisocyanate coating; The varnish layer is an isocyanate coating; The protective layer is a polyurea protective layer; The sealing primer used in the sealing primer coating comprises component A, component B and component C, and the mass ratio is (20-40): (200-240): (5-30); Component A is a modified isocyanate, and the modified isocyanate includes one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; Component B is an amine compound, and the amine compound includes one or more of primary amine, secondary amine and tertiary amine; Component C is a sealing aid, which includes one or more of transparent powder, talcum powder, mica powder, high-alumina cement, heavy calcium, light calcium, bentonite, kaolin, diatomaceous earth, wollastonite, silica powder, and barite powder.

2. The load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 1, characterized in that: The thickness of each layer or the coating amount during preparation is as follows: The coating amount of epoxy resin low temperature adhesive is 50~100 g / m 2 ; And / or, the coating amount of polyurethane low temperature adhesive is 20~100 g / m 2 ; and / or, the thickness of the foam layer is 19 to 21 mm; And / or, the foam layer has a density of 75-110 kg / m 3 , compression strength is 0.5~1.0 MPa, thermal conductivity is 0.022~0.026 W·(m·K) -1 ; and / or, the thickness of the sealing primer layer is 0.1-1.5 mm; and / or, the thickness of the varnish layer is 0.1 to 0.5 mm; And / or, the thickness of the protective layer is 0.2~1.0 mm.

3. A method for forming a load-bearing / insulating integrated insulation structure for a common bottom of a low-temperature storage tank as claimed in claim 1, characterized in that: The molding method comprises the following steps: S1, coating epoxy resin low-temperature adhesive on the convex surface of the common bottom metal panel to form a buffer layer; S2. Apply polyurethane low-temperature adhesive on the outside of the buffer layer to form a transition layer; S3. Spray high-pressure lightweight polyurethane foam on the outside of the transition layer to form a foam layer; S4, applying a closed primer on the surface of the foam layer to form a closed primer coating; S5, spraying varnish on the surface of the closed primer to form a varnish layer; S6. Spray polyurea protective layer material on the surface of the varnish layer to form a protective layer, thereby obtaining a load-bearing / heat-insulating integrated insulation layer.

4. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S1, when the epoxy resin low-temperature adhesive is prepared, the mass ratio of component A: component B: component C = (20-30): (5-10): (0.5-3); Component A is a special epoxy resin, which includes one or more of bisphenol A epoxy resin, phenolic epoxy resin, polyether epoxy resin, polyester epoxy resin, and polybutadiene epoxy resin; Component B is an aromatic amine curing agent, which includes one or more of diethyltoluenediamine, 4,4-diaminodiphenylmethane, 4,4'-methylene-bis(2-chloroaniline), 4,4-diaminodiphenyl sulfone, LS-113 aromatic amine epoxy curing agent, metaphenylenediamine, and metaphenylenediamine; Component C is a coupling agent, which includes one or more of a methyl silane coupling agent, an acrylic silane coupling agent, an amino silane coupling agent, a sulfur-containing silane coupling agent, and an epoxy silane coupling agent.

5. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S2, when the polyurethane low-temperature adhesive is prepared, the mass ratio of component A: component B = (5-10): (1-4); Component A is a polyurethane monomer, which includes one or more of polyether polyurethane, polyester polyurethane, polyimide polyurethane, and polyurea polyurethane; Component B is an amine curing agent, which includes one or more of diethyltoluenediamine, 4,4-diaminodiphenylmethane, 4,4'-methylene-bis(2-chloroaniline), 4,4-diaminodiphenyl sulfone, LS-113 aromatic amine epoxy curing agent, m-phenylenediamine, m-phenylenediamine, and polyetheramine D230.

6. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S3, spraying the high-pressure lightweight polyurethane foam material is to mix the isocyanate and the polyol combination material, atomize and spray it onto the surface of the transition layer to foam and form a foam layer; The isocyanate includes one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, polymethylene polyphenyl polyisocyanate; The polyol combination material includes polyol, catalyst and foaming agent, and the mass ratio is (100~105):(0.6~1.0):(20~40).

7. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S4, 1 to 3 layers of sealing primer are evenly rolled on the surface of the foam layer, each layer of primer has a thickness of 0.1 to 0.5 mm, and the time interval between each layer of primer is 8 to 24 hours. After curing, local repair and secondary grinding are performed; The materials of the sealing primer include component A: component B: component C; Before preparing the sealing primer, the primer B component must be fully stirred for 5-30 minutes. After stirring until the color is uniform, the sealing primer is prepared according to the mass ratio of component A: component B: component C = (20-40): (200-240): (5-30); Component A is a modified isocyanate, including one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; Component B is an amine compound, including one or more of primary amine, secondary amine and tertiary amine; Component C is a sealing aid, including one or more of transparent powder, talcum powder, mica powder, high-alumina cement, heavy calcium, light calcium, bentonite, kaolin, diatomaceous earth, wollastonite, silica powder, and barite powder.

8. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S5, spraying the varnish is to spray the varnish on the surface of the primer with a spray gun, and after spraying is completed and confirmed to be complete, curing for 24 to 48 hours; The varnish is prepared according to the mass ratio of component A: component B = (10~50): (150~300); Component A is a modified isocyanate, and the modified isocyanate includes one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; Component B is an amine compound, and the amine compound includes one or more of primary amine, secondary amine and tertiary amine.

9. The molding method of the load-bearing / insulating integrated insulation structure for the common bottom of a low-temperature storage tank according to claim 3, characterized in that: In step S6, the polyurea protective layer material includes component A1, component A2, and component R; and is prepared according to a mass ratio of component A1: component A2: component R = (30-50): (5-10): (30-60); Component A1 includes one or more of benzyl diisocyanate, hexamethylene diisocyanate, biphenyl diisocyanate, and isophorone diisocyanate; The A2 component includes one or more of HFFR liquid flame retardant, FR liquid flame retardant, PP liquid flame retardant, EVA liquid flame retardant, and PU liquid flame retardant; The R component includes one or more of primary amines, secondary amines, and tertiary amines.

10. An application of the load-bearing / insulating integrated insulation structure for the common bottom of a cryogenic tank as claimed in claim 1 in the preparation of a rocket cryogenic tank.

Images