Low-thermal-conductivity, high-strength and thermal-shock-resistant hard polyurethane insulating material for cryogenic storage and transportation liquid cargo tank and preparation method thereof

Abstract

The invention discloses a low-thermal-conductivity, high-strength and thermal-shock-resistant hard polyurethane insulating material for a cryogenic storage and transportation liquid cargo tank and a preparation method of the low-thermal-conductivity, high-strength and thermal-shock-resistant hard polyurethane insulating material. The premixed polyether polyol comprises the following raw materials in parts by weight: the insulating material comprises premixed polyether polyol and polyisocyanate in a weight ratio of 1: (1.3-1.9); the premixed polyether polyol comprises the following components in parts by weight: 20 to 50 parts of high-functionality polyether polyol a, 10 to 20 parts of long-chain polyether polyol b, 10 to 20 parts of structural flame-retardant polyether polyol c, 20 to 40 parts of high-strength polyester polyol d, 2 to 5 parts of a chain extender, 2 to 8 parts of a nano modifier, 1.5 to 5 parts of a composite catalyst, 2 to 5 parts of a surfactant, 10 to 15 parts of a flame retardant, 0.5 to 1.5 parts of a chemical foaming agent and 15 to 35 parts of a physical foaming agent. According to the invention, the combined polyether reacts with the isocyanate, and the high-functionality polyether polyol, the polyester polyol and the nano reinforcing agent have a synergistic effect, so that the polyurethane insulating material can be used for preparing the low-heat-conductivity, high-strength and thermal-shock-resistant hard polyurethane insulating material for the cryogenic storage and transportation liquid cargo tank.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic insulating materials, and particularly relates to a low-thermal-conductivity, high-strength and thermal-shock-resistant rigid polyurethane insulating material for a deep-cold storage and transportation liquid cargo tank and a preparation method thereof. BACKGROUND

[0002] According to the International Code on the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code), the independent liquid cargo tank of a liquefied gas ship, that is, a self-supporting type, is divided into three types: an A-type independent liquid cargo tank, a B-type independent liquid cargo tank and a C-type independent liquid cargo tank. The functions of the independent liquid cargo tank include but are not limited to transporting liquefied gas, serving as a liquefied gas fuel tank and the like, and the liquefied gas loaded in the tank includes but is not limited to liquefied natural gas (LNG), liquid ammonia fuel (NH3), liquefied ethylene gas (LEG) and the like. In the prior art, the ultra-low-temperature deep-cold liquid cargo tank usually adopts insulating materials such as sprayed polyurethane, polyurethane insulating board, polystyrene, polyethylene and phenolic foam to control the temperature and pressure of the ship body. The liquefied gas ship is long-term operated at sea and is subjected to harsh weather conditions such as severe cold and heat and sea tossing and vibration, and thus is at risk of fatigue failure and crack propagation during the operation, thereby causing leakage of the low-temperature liquefied gas. Therefore, the insulating material used in the liquid cargo tank should not only have good heat preservation performance, but also have certain strength and impact resistance and good dimensional stability to ensure the insulating effect of the liquid cargo tank during long-term operation.

[0003] The existing liquid cargo tank insulating material has the following problems: 1) high thermal conductivity, resulting in a thick insulating layer or poor heat preservation effect and large cold energy loss; 2) poor strength, especially under deep cold conditions, the material is hard and brittle, the mechanical properties decrease, the structural stability is poor, and there is a safety hazard; 3) poor impact resistance, the material is prone to cracking and deformation under vibration and deep cold conditions; 4) poor dimensional stability, the material shrinks and deforms severely under deep cold conditions; 5) the on-site sprayed polyurethane insulation has high requirements for the environment, high technical requirements for the gun operator, great difficulty in quality control, poor strength and impact resistance, and is prone to cracking and deformation under deep cold and vibration conditions. SUMMARY

[0005] The application provides a low-thermal-conductivity, high-strength and thermal-shock-resistant rigid polyurethane insulating material for a deep-cold storage and transportation liquid cargo tank and a preparation method thereof, and aims to solve the problems in the background art.

[0006] In one aspect, the application provides a low-thermal-conductivity, high-strength and thermal-shock-resistant rigid polyurethane insulating material for a deep-cold storage and transportation liquid cargo tank, which is prepared from combined polyether and polyisocyanate at a weight ratio of 1:1.3-1.9.

[0007] The combination polyether includes the following weight percentage components: high functionality polyether polyol a: 20-50 parts, long chain polyether polyol b: 10-20 parts, structural flame-retardant polyether polyol c: 10-20 parts, high-strength polyester polyol d: 20-40 parts, chain extender: 2-5 parts, nano modifier: 2-8 parts, composite catalyst: 1.5-5 parts, surfactant: 2-5 parts, flame retardant: 10-15 parts, chemical foaming agent: 0.5-1.5 parts, physical foaming agent: 15-35 parts.

[0008] Further, the polyisocyanate includes any one of diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate, the content of isocyanate (-CNO) in the polyisocyanate is 30-33 wt%, and the viscosity is 100-300 mPa•s.

[0009] Further, the functionality of the high functionality polyether polyol a is 5-7, preferably 6-7; the hydroxyl value is 380-550 mg KOH / g, preferably 460-500 mg KOH / g; and the viscosity is 9000-22000 mPa•s.

[0010] Further, the molecular weight of the long chain polyether polyol b is 1500-5000 g / mol, preferably 2000-5000 g / mol; the functionality is 2-6, preferably 2-4; the hydroxyl value is 30-150 mg KOH / g; and the viscosity is 120-600 mPa•s.

[0011] Further, the structural flame-retardant polyether polyol c is one or more of a phosphorus-containing flame-retardant element and a heterocyclic structure polyether polyol, a phosphorus-nitrogen-containing flame-retardant polyether polyol, preferably a phosphorus-containing flame-retardant element and a heterocyclic structure polyether polyol; the hydroxyl value of the structural flame-retardant polyether polyol c is 100-400 mg KOH / g, the viscosity is 300-15000 mPa•s, and the functionality is 2-5.

[0012] Further, the high-strength polyester polyol d is a high-aromatic-content polyester polyol, the hydroxyl value is 240-315 KOH / g, the viscosity is 2000-4500 mPa•s, the functionality is 2-3, and the molecular weight is 300-500 g / mol.

[0013] Further, the chain extender is a dihydric alcohol containing an ether bond, which can increase the flexibility and water resistance of the product, the functionality of the chain extender is 2-3, the hydroxyl value is 1030-1850 mg KOH / g, and the viscosity is 30-50 mPa•s.

[0014] Further, the nano modifier is a surface-modified nano-SiO2 with a particle size of 15-50 nm.

[0015] Further, the catalyst is a mixture of amine catalyst, organic metal catalyst and quaternary ammonium salt catalyst, the amine catalyst includes one or more of N,N-dimethylcyclohexylamine, pentamethyldiethylene triamine, N-(2-hydroxypropyl)trimethylene diamine, N,N-dimethylbenzylamine, the organic metal catalyst includes one or more of potassium iso-octoate or potassium acetate; the mass ratio of the amine catalyst, the organic metal catalyst and the quaternary ammonium salt catalyst in the catalyst is (0.1-0.2):(1-2):(0.5-1.2).

[0016] Further, the chemical foaming agent is deionized water; the physical foaming agent is a hydrofluorocarbon foaming agent. Further, the surfactant is one or more of polyether modified polysiloxane and polysiloxane polymer; preferably one or more of B8462, B8547, B8525, L-6863, L-6900, AK8860 and AK8805.

[0017] Further, the flame retardant is one or more of triethyl phosphate (TEP), tris (2-chloropropyl) phosphate (TCPP), tris (chloroethyl) phosphate (TCEP) and dimethyl methylphosphonate (DMMP), preferably the flame retardant TEP and the flame retardant TCPP.

[0018] The application also provides a preparation method of a low-thermal-conductivity, high-strength and thermal-shock-resistant rigid polyurethane insulating material for a cryogenic storage and transportation liquid cargo hold, comprising the following steps: Step one, preparation of a combined polyether: sequentially weigh high-functionality polyether polyol a, long-chain polyether polyol b, structure-type flame-retardant polyether polyol c, high-strength polyester polyol d, chain extender, nano modifier, catalyst, surfactant, flame retardant, chemical foaming agent and physical foaming agent according to weight fractions, and then stir and mix them uniformly to obtain a combined polyether; Step two: the combined polyether and polyisocyanate are drawn into a high-pressure foaming machine according to a mass ratio, the temperature of the combined polyether and polyisocyanate is controlled to be 17-30 DEG C, the pressure of the high-pressure foaming machine is 100-130 bar, and the product is prepared by mixing the combined polyether and polyisocyanate through the gun head of the high-pressure foaming machine and then injecting them into a mold with a mold temperature of 30-45 DEG C.

[0019] Advantages: The rigid polyurethane insulating material prepared by optimizing the formula and selecting suitable polyether / polyester polyols and additives has fine pores, uniform density and low thermal conductivity, meets the requirements of energy saving and emission reduction, has good strength, good dimensional stability, good thermal shock resistance and vibration resistance, has good flexibility and strength under cryogenic conditions and vibration conditions, and can meet the requirements of long-term operation of a liquid cargo hold at sea.

[0020] The present application improves the heat preservation performance and strength of the foam block through the synergistic effect of high-functionality polyether polyol, high-strength polyester polyol and surface-modified nano-SiO2, and the prepared foam block has low thermal conductivity and high strength; the high-strength polyester polyol has better compatibility with the poly-methylene polyphenyl polyisocyanate component, can increase the foam fineness of the polyurethane rigid foam material, and thus improve the heat preservation performance thereof; meanwhile, by introducing more aromatic ring structures into the polyurethane rigid foam skeleton, the strength and dimensional stability of the polyurethane rigid foam material can also be increased, and the heat resistance and flame resistance are also improved; by adding long-chain polyether polyol, the flexibility thereof is increased, and the toughness thereof under low-temperature conditions is ensured, so as to meet the performance requirements under low-temperature thermal shock and vibration conditions; by adding structural flame-retardant polyether polyol, the mechanical properties and dimensional stability of the foam are enhanced, and the flame-retardant properties of the foam are also improved due to the phosphorus-nitrogen flame-retardant elements contained in the molecules; by adding a chain extender, the toughness and strength of the foam block are enhanced, and the foam block is prevented from being brittle and deformed under low-temperature and vibration conditions.

[0021] The combined polyether (component A) and the polyisocyanate (component B) are mixed at a mass ratio of 1:1.3-1.9, the polyisocyanate is excessive, and in the polymerization reaction, in addition to the generation of urethane groups, the excessive -NCO groups trimerize to generate cyclic isocyanurate groups, the cyclic isocyanurate groups are introduced into the polyurethane structure, and the strength, dimensional stability, low-temperature resistance, aging resistance and other properties of the prepared polyurethane foam are improved.

[0022] The hard polyurethane insulation material provided by the present application solves the problems that the on-site spraying requires high technical requirements for the sprayer and the spraying environment and quality are difficult to control, and the material size and quality are easy to control in factory processing and prefabrication, and the on-site construction period is reduced. DETAILED DESCRIPTION

[0023] In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In the description of the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0024] In addition, the terms "first", "second", etc. are used only for descriptive purposes and do not connote or imply relative importance or a quantity of the indicated technical features. Thus, features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly and specifically limited.

[0025] The technical solutions of the present application are further illustrated by the specific embodiments. The reference numbers correspond to different components and process steps, which will be described in detail in the specific embodiments.

[0026] The raw materials used in the present application are all obtained from commercially available materials unless otherwise specified.

[0027] Example 1 The present embodiment provides a low thermal conductivity, high strength, and thermal shock resistant rigid polyurethane insulation material for cryogenic storage and transportation liquid cargo tank. The insulation material is prepared from a combination of polyether and polyisocyanate in a weight ratio of 1:1.5. The combination of polyether includes the following components by weight: high functionality polyether polyol a: 30 parts, long chain polyether polyol b: 10 parts, structural flame-retardant polyether polyol c: 15 parts, high-strength polyester polyol d: 40 parts, chain extender: 2 parts, nano modifier: 3 parts, catalyst: 2.48 parts, surfactant: 4 parts, flame retardant: 15 parts, chemical foaming agent: 1.2 parts, physical foaming agent HFC-245fa: 25 parts.

[0028] In the present embodiment, the high functionality polyether polyol a is purchased from Jiangong Ningwu New Material Co., Ltd., model NJ6207, functionality: 5-6, hydroxyl value: 460±20 mgKOH / g, viscosity (25℃): 14000±2000 mPa·s, molecular weight 580-760 g / mol.

[0029] The long chain polyether polyol b is purchased from Dow Chemical, model VORANOL 2000LM, functionality: 2, hydroxyl value: 56 mgKOH / g, dynamic viscosity (25℃): 370 mPa·s, molecular weight: 2000 g / mol.

[0030] The structural flame-retardant polyether polyol c is purchased from Shanghai Xinxue Chemical Technology Co., Ltd., model F-7190, functionality: 2-3, hydroxyl value: 190 mgKOH / g, viscosity (25℃): about 7000 mPa·s, molecular weight: 590-886 g / mol.

[0031] High-strength polyester polyol d was purchased from Nanjing Jinling Stepan Chemical Co., Ltd., model PS-3152, hydroxyl value 315 mgKOH / g, viscosity 2000-3000 mPa·s; functionality at 2, molecular weight 356 g / mol.

[0032] The chain extender is diethanolamine purchased from Dow Chemical, model DEA, functionality at 3, molecular weight 105 g / mol, viscosity 30-50 mPa·s, hydroxyl value at 1030-1050 mg KOH / g; The nano-modifier is modified SiO2; the flame retardant is TCPP; the chemical foaming agent is deionized water; the physical foaming agent is HFC-245fa; the surfactant is B8547, AK8805 prepared according to a mass ratio of 1:1; the catalyst includes 0.18 parts of amine catalyst, including 0.1 parts of PC-5 and 0.08 parts of PC-8, 1.3 parts of organic metal catalyst PC-46, and 1 part of quaternary ammonium salt catalyst DabcoTMR-21.

[0033] The polyisocyanate is purchased from Huntsman, model Suprasec 5005, isocyanate (-CNO) content 30.7wt%, viscosity 225 mPa·s (25℃). In the present application, the polyisocyanate can be selected from one or more of the following products: Suprasec 5005, Suprasec 5008, M20S, PM-200, 44V20L.

[0034] The application also provides a preparation method of a low-thermal-conductivity, high-strength, and thermal-shock-resistant rigid polyurethane insulation material for cryogenic storage and transportation liquid cargo holds, comprising the following steps: Step one, preparation of combined polyether: sequentially weigh high-functionality polyether polyol a, long-chain polyether polyol b, structure-type flame-retardant polyether polyol c, high-strength polyester polyol d, chain extender, nano-modifier, catalyst, surfactant, flame retardant, chemical foaming agent, and physical foaming agent according to the weight parts, and then stir and mix them uniformly to obtain a combined polyether; Step two: the combined polyether and the polyisocyanate are drawn into a high-pressure foaming machine according to a mass ratio, the temperature of the combined polyether and the polyisocyanate is controlled at 23℃, the pressure of the high-pressure foaming machine is 110 bar, and the product is prepared by mixing through the gun head of the high-pressure foaming machine and then injecting into a mold with a mold temperature of 40℃.

[0035] Example 2 This embodiment provides a low thermal conductivity, high strength, and thermal shock resistant rigid polyurethane insulation material for cryogenic storage and transportation liquid cargo tanks. The insulation material comprises a polyether and a polyisocyanate in a weight ratio of 1:1.7. The polyether comprises the following components in parts by weight: high-functionality polyether polyol a: 40 parts, long-chain polyether polyol b: 15 parts, structural flame-retardant polyether polyol c: 10 parts, high-strength polyester polyol d: 30 parts, chain extender: 2 parts, nano-modifier: 2 parts, catalyst: 2.15 parts, surfactant: 4 parts, flame retardant: 15 parts, chemical foaming agent: 1.5 parts, and physical foaming agent: 20 parts.

[0036] In this embodiment, the high-functionality polyether polyol a was purchased from Jurong Ningwu New Material Co., Ltd., model NJ8238, with a functionality of 6, a hydroxyl value of 380±15mgKOH / g, a viscosity (25℃) of 11250±1250mPa•s, and a molecular weight of 852~922g / mol.

[0037] The long-chain polyether polyol b was purchased from Dow Chemical, model VORANOL 2471, with a functionality of 3, a hydroxyl value of 33 mg KOH / g, a viscosity of 860 mPa•s (room temperature), and a molecular weight of 4957 g / mol.

[0038] The structural flame-retardant polyether polyol C was purchased from Shanghai Xinrui Chemical Technology Co., Ltd., model F-7190, with functionality of 2-3, hydroxyl value of 190 mgKOH / g, viscosity (25℃) of approximately 7000 mPa•s, and molecular weight of 590-886 g / mol.

[0039] High-strength polyester polyol d was purchased from Nanjing Jinling Stepan Chemical Co., Ltd., model PS-1752, with a functionality of 2, hydroxyl value of 175 mg KOH / g, viscosity (25℃) of approximately 3800 mPa•s, and molecular weight of 641 g / mol.

[0040] The chain extender was diethylene glycol, purchased from Shenghong Refining & Chemical Co., Ltd., model DEG, with a functionality of 2, a hydroxyl value of 1030-1050 mgKOH / g, and a viscosity of 30-50 mPa•s.

[0041] The nano-modifier is modified SiO2; the flame retardant is TEP; the chemical foaming agent is deionized water; the physical foaming agent is HFC-245fa; the surfactants are B8462 and L6863 formulated in a 1:1 mass ratio; the catalyst contains 0.15 parts of amine catalyst, including 0.05 parts of PC-5 and 0.1 parts of PC-8, 1.5 parts of organometallic catalyst K-15, and 0.5 parts of quaternary ammonium salt catalyst DabcoTMR-2.

[0042] The polyisocyanate was purchased from Huntsman, model Suprasec 5008, with an isocyanate (-CNO) content of 31 wt% and a viscosity of 200–300 mPa•s (25°C).

[0043] This application also provides a method for preparing a rigid polyurethane insulation material with low thermal conductivity, high strength, and thermal shock resistance for cryogenic liquid storage and transportation tanks, comprising the following steps: Step 1: Preparation of the composite polyether: The high-functionality polyether polyol a, long-chain polyether polyol b, structural flame-retardant polyether polyol c, high-strength polyester polyol d, chain extender, nano-modifier, catalyst, surfactant, flame retardant, chemical foaming agent and physical foaming agent are weighed according to their weight parts and stirred and mixed evenly to obtain the composite polyether. Step 2: The polyether and polyisocyanate are pumped into a high-pressure foaming machine at a mass ratio. The temperature of the polyether and polyisocyanate is controlled at 23°C and the pressure of the high-pressure foaming machine is 110 bar. After being mixed by the nozzle of the high-pressure foaming machine, the mixture is injected into a mold with a mold temperature of 35°C to obtain the product.

[0044] Example 3 This embodiment provides a low thermal conductivity, high strength, and thermal shock resistant rigid polyurethane insulation material for cryogenic storage and transportation liquid cargo tanks. The insulation material comprises a polyether and a polyisocyanate in a weight ratio of 1:1.9. The polyether comprises the following components in parts by weight: high-functionality polyether polyol a: 50 parts, long-chain polyether polyol b: 12 parts, structural flame-retardant polyether polyol c: 20 parts, high-strength polyester polyol d: 20 parts, chain extender: 2 parts, nano-modifier: 5 parts, catalyst: 2.93 parts, surfactant: 5 parts, flame retardant: 15 parts, chemical foaming agent: 0.9 parts, and physical foaming agent: 30 parts.

[0045] In this embodiment, the high-functionality polyether polyol a was purchased from Jurong Ningwu New Material Co., Ltd., model NJ450L, with a functionality of 6, a hydroxyl value of 450±15mgKOH / g, a viscosity (25℃) of 7000~10000mPa•s, and a molecular weight of 724~774g / mol.

[0046] The long-chain polyether polyol b was purchased from Shandong Lanxing Dongda, model 330N, with a functionality of 3, hydroxyl value of 32.5~35.5mgKOH / g, viscosity of 800~1000mPa·s (25℃), and molecular weight of 5000.

[0047] The structural flame-retardant polyether polyol C was purchased from Jiangsu Changneng Energy-Saving New Material Technology Co., Ltd., model EDS-5083H, with a functionality of 3, hydroxyl value of 140 mg KOH / g, viscosity of 13000 mPa·s (25℃), and molecular weight of 1200 g / mol.

[0048] The high-strength polyester polyol d was purchased from Nanjing Jinling Stepan Chemical Co., Ltd., model PS-2412, with a functionality of 2, hydroxyl value of 240±15mgKOH / g, viscosity of 3500±1000mPa·s (25℃), and molecular weight of 400~500.

[0049] The chain extender is ethylene glycol, model EG, functionality: 2, hydroxyl value: 1800mgKOH / g, viscosity: 26mPa•s (25℃), molecular weight: 62g / mol.

[0050] The nano-modifier is modified SiO2; the flame retardant is 5 parts TEP and 10 parts TCPP; the chemical foaming agent is deionized water; the physical foaming agent is HFC-245fa; the surfactant is B8525 and L-6900 formulated in a 1:1 mass ratio; the catalyst contains 0.13 parts amine catalyst, including 0.05 parts PC-5 and 0.08 parts PC-8, 1.2 parts organometallic catalyst K-15, 0.8 parts PC-46, and 0.5 parts quaternary ammonium salt catalyst JD-18.

[0051] The polyisocyanate was purchased from Huntsman, model Suprasec 5008, with an isocyanate (-CNO) content of 31 wt% and a viscosity of 200–300 mPa•s (25°C).

[0052] This application also provides a method for preparing a rigid polyurethane insulation material with low thermal conductivity, high strength, and thermal shock resistance for cryogenic liquid storage and transportation tanks, comprising the following steps: Step 1: Preparation of the composite polyether: The high-functionality polyether polyol a, long-chain polyether polyol b, structural flame-retardant polyether polyol c, high-strength polyester polyol d, chain extender, nano-modifier, catalyst, surfactant, flame retardant, chemical foaming agent and physical foaming agent are weighed according to their weight parts and stirred and mixed evenly to obtain the composite polyether. Step 2: The polyether and polyisocyanate are pumped into a high-pressure foaming machine at a mass ratio. The temperature of the polyether and polyisocyanate is controlled at 23°C and the pressure of the high-pressure foaming machine is 130 bar. After being mixed by the nozzle of the high-pressure foaming machine, the mixture is injected into a mold with a mold temperature of 45°C to obtain the product.

[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that the insulating material is prepared by combining polyether and polyisocyanate in a weight ratio of 1:1, while the other components and ratios are the same as in Example 1.

[0054] Comparative Example 2 The difference between this comparative example and Example 1 is that no nano-modifier is added to the polyether combination, while the other components and proportions are the same as in Example 1.

[0055] Comparative Example 3 The difference between this comparative example and Example 1 lies in the weight proportions of the polyether components. Specifically: high-functionality polyether polyol a: 10 parts, long-chain polyether polyol b: 30 parts, structural flame-retardant polyether polyol c: 40 parts, high-strength polyester polyol d: 15 parts, chain extender: 2 parts, nano-modifier: 3 parts, catalyst: 2.48 parts, surfactant: 4 parts, flame retardant: 15 parts, chemical foaming agent: 1.2 parts, physical foaming agent: 25 parts. Other components and proportions are the same as in Example 1.

[0056] The insulating materials prepared in the above embodiments and comparative examples were tested for their properties, and the corresponding test results are shown in Table 1 below. The testing standards for apparent density are ASTM D1622 GB / T6343; compressive strength and compressive modulus are ASTM D1621 GB / T 8813; coefficient of linear expansion is ASTM E228 GB / T 20673; thermal conductivity is ASTM C177 GB / T 10294; closed-cell ratio is ASTM D6226 GB / T10799; and water absorption is ASTM D2842 GB / T 8810.

[0057] The test method for thermal shock resistance is as follows: Immerse the standard plate of insulating material in liquid nitrogen (below -165℃) for 20 minutes, take it out and let it stand for 2 hours, and repeat this process 5 times.

[0058] The vibration resistance test method is as follows: Install the standard plate of insulating material on the AL disk, with an acceleration of 0.35G and a frequency of 15Hz for 500,000 cycles; and with an acceleration of 0.7G and a frequency of 15Hz for 50 cycles.

[0059] Table 1. Performance test results of the polyurethanes prepared in the examples and comparative examples. Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Apparent density / Kg / m 3 ]] 42.5 41.7 40.9 40 42 42.3 Compressive strength / KPa 330 324 311 205 280 195 Compressive elastic modulus / MPa 8.1 7.8 7.6 4.8 7.5 4.5 Thermal conductivity W / m·k 0.0192 0.0193 0.0189 0.023 0.025 0.02 Linear expansion coefficient, 1 x 10 -6 / °C, (25°C to -165°C) 44 48 53 67 64 65 Closed cell ratio / % 95 97 96 90 92 91 Water absorption / % 0.9 1.0 0.8 1.9 1.4 1.8 Oxygen index / % 30.1 30.5 30.2 26 27 32 Thermal shock resistance Surface intact, no cracks, no damage Surface intact, no cracks, no damage Surface intact, no cracks, no damage Material shrinkage deformation, cracks Surface has slight deformation, small cracks Material shrinkage deformation, cracks Vibration resistance Surface intact, no cracks, no damage Surface intact, no cracks, no damage Surface intact, no cracks, no damage Material deformation damage Surface intact, no cracks, no damage Material deformation damage Analysis of experimental results: The rigid polyurethane insulation material prepared in the embodiments of the present invention has excellent strength and thermal conductivity, and can be used in the liquid cargo tanks of cryogenic storage and transportation ships.

[0060] In Comparative Example 1, the insulation material was prepared by mixing polyether and polyisocyanate in a 1:1 weight ratio. Changing the ratio of polyether and polyisocyanate significantly reduced the density, strength, dimensional stability, and closed-cell rate of the resulting polyurethane foam. Reducing the blowing ratio (usually referring to the isocyanate index) of rigid polyurethane foam essentially reduces the isocyanate (-NCO) content in the system. This directly affects two major chemical reactions: 1. Foaming reaction: -NCO + H2O → CO2 (gas) + urea. Water is a chemical foaming agent, producing CO2 which causes the foam to expand.

[0061] 2. Gel reaction: -NCO + -OH → urethane (polyurethane). This forms the polymer backbone of the foam, providing strength.

[0062] When the ratio of polyether (component A) to polyisocyanate (component B) is changed, and there is no excess polyisocyanate, there are no extra -NCO groups that trimerize to form cyclic isocyanurate groups. As a result, it is impossible to introduce cyclic isocyanurate groups into the polyurethane structure, and the strength, dimensional stability, low temperature resistance, closed-cell rate, and anti-aging properties of the prepared polyurethane foam are reduced.

[0063] Reducing the component ratio leads to a softer foam structure and decreased mechanical strength because isocyanates are crucial for forming the polyurethane polymer network (hard segments). A reduction in NCO content results in fewer urethane and urea bonds. These chemical bonds form the foam's "skeleton," and a sparser skeleton naturally makes the foam softer and weaker. The closed-cell rate decreases because the strength supporting the cell walls is insufficient, leading to larger, uneven cells. Dimensional stability deteriorates, and the risk of shrinkage increases dramatically due to insufficient gel strength; during foaming, a sufficiently rapid gel reaction is required to "lock" the cell structure. Insufficient NCO content leads to a slow and incomplete gelation reaction, resulting in insufficient strength for the foam to resist external atmospheric pressure and internal gas condensation after cooling. This causes shrinkage (the CO2 and vaporized physical blowing agent produced during foaming fill the cells; when the foam cools, these gases condense, causing the internal pressure of the cells to be lower than the external atmospheric pressure. If the cell wall strength is insufficient, i.e., insufficient gelation, the foam will be "flattened" by atmospheric pressure, manifesting as shrinkage and deformation, especially in thick products or at low temperatures, where visible shrinkage, depressions, and deformation are easily observed). Decreased foam density and premature cell rupture cause gas escape, forming open cells, disrupting the gelation reaction equilibrium, resulting in lower or uneven density.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and not restrictive in all respects. Furthermore, it should be understood that although this specification describes embodiments, it does not encompass only one technical solution. This descriptive method is merely for clarity, and those skilled in the art should consider the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low thermal conductivity, high strength, thermal shock resistant rigid polyurethane insulation material for cryogenic liquid cargo tanks, characterized by: The insulating material is a combination of polyether and polyisocyanate with a weight ratio of 1:1.3-1.9; the combination of polyether includes the following components in parts by weight: high functionality polyether polyol a: 20-50 parts, long chain polyether polyol b: 10-20 parts, structural flame-retardant polyether polyol c: 10-20 parts, high-strength polyester polyol d: 20-40 parts, chain extender: 2-5 parts, nano modifier: 2-8 parts, composite catalyst: 1.5-5 parts, surfactant: 2-5 parts, flame retardant: 10-15 parts, chemical foaming agent: 0.5-1.5 parts, and physical foaming agent: 15-35 parts.

2. The low thermal conductive, high strength, and thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank according to claim 1, characterized in that: The polyisocyanate includes any one of diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate, the content of isocyanate in the polyisocyanate is 30-33 wt%, and the viscosity is 100-300 mPa·s.

3. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane insulation material for cryogenic liquid shipping tank cargo holds of claim 1, wherein: The functionality of the high functionality polyether polyol a is 5-7, the hydroxyl value is 380-550 mg KOH / g, and the viscosity is 9000-22000 mPa·s.

4. The low thermal conductive, high strength, and thermal shock resistant rigid polyurethane foam insulation material for the cryogenic liquid cargo hold according to claim 1, characterized in that: The molecular weight of the long chain polyether polyol b is 1500-5000 g / mol, the functionality is 2-6, the hydroxyl value is 30-150 mg KOH / g, and the viscosity is 120-600 mPa·s.

5. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank as defined in claim 1, wherein: The structural flame-retardant polyether polyol c is one or more of polyether polyols containing phosphorus-based flame-retardant elements and heterocyclic structures, and phosphorus-nitrogen-based flame-retardant polyether polyols; the hydroxyl value is 100-400 mg KOH / g, the viscosity is 300-15000 mPa·s, and the functionality is 2-5.

6. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank as defined in claim 1, wherein: The high-strength polyester polyol d is a high-aromatic-content polyester polyol, the hydroxyl value is 240-315 mg KOH / g, the viscosity is 2000-4500 mPa·s, the functionality is 2-3, and the molecular weight is 300-500 g / mol.

7. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank as defined in claim 1, wherein: The chain extender is a dihydric alcohol containing an ether bond, the functionality of the chain extender is 2-3, the hydroxyl value is 1030-1850 mg KOH / g, and the viscosity is 30-50 mPa·s.

8. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank as claimed in claim 1, wherein: The nano modifier is surface-modified nano-SiO2 with a particle size of 15-50 nm, the surfactant is one or more of polyether-modified polysiloxanes and polysiloxane polymers, the flame retardant is one or more combinations of triethyl phosphate, tris (2-chloropropyl) phosphate, trichloroethyl phosphate, and dimethyl methylphosphonate, the chemical foaming agent is deionized water, and the physical foaming agent is a hydrogen fluorocarbon foaming agent.

9. The low thermal conductivity, high strength, thermal shock resistant rigid polyurethane foam insulation material for cryogenic liquid shipping tank as defined in claim 1, wherein: The catalyst is a mixture of amine catalysts, organic metal catalysts, and quaternary ammonium salt catalysts, the amine catalysts include one or more of N,N-dimethylcyclohexylamine, pentamethyldiethylene triamine, N-(2-hydroxypropyl) trimethylene diamine, and N,N-dimethylbenzylamine, the organic metal catalysts include one or more of potassium iso-octoate or potassium acetate, and the mass ratio of the amine catalysts, the organic metal catalysts, and the quaternary ammonium salt catalysts in the catalyst is (0.1-0.2):(1-2):(0.5-1.2).

10. The process for producing a low-conductive, high-strength, and thermal shock resistant rigid polyurethane insulation material for a cryogenic liquid cargo tank according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: Step one, preparation of the combined polyether: sequentially weigh high-functionality polyether polyol a, long-chain polyether polyol b, structure type flame-retardant polyether polyol c, high-strength polyester polyol d, chain extender, nano modifier, catalyst, surfactant, flame retardant, chemical foaming agent, and physical foaming agent according to weight fractions, and then stir and mix uniformly to obtain the combined polyether; Step two: the combined polyether and the polyisocyanate are drawn into a high-pressure foaming machine according to a mass ratio, the temperature of the combined polyether and the polyisocyanate is controlled to be 17-30 DEG C, the pressure of the high-pressure foaming machine is 100-130 bar, the combined polyether and the polyisocyanate are mixed after passing through a gun head of the high-pressure foaming machine, and then the product is prepared by being injected into a mold with a mold temperature of 30-45 DEG C.