Continuous production combined polyether for LNG (Liquefied Natural Gas), polyurethane foam and preparation method thereof

Abstract

The invention discloses premixed polyether polyol for continuous production of LNG (liquefied natural gas), polyurethane foam and a preparation method of the premixed polyether polyol. The premixed polyether polyol comprises the following raw materials in parts by weight: 80-105 parts of composite polyol; 3-5 parts of a nano reinforcing agent; 2-4 parts of a composite catalyst; 2-4 parts of a foam stabilizer; 20-30 parts of a physical foaming agent; 1.0-2.0 parts of a chemical foaming agent; and 20-30 parts of a flame retardant. The polyurethane foam comprises the combined polyether and polymerized diphenylmethane diisocyanate, and is prepared by mixing the combined polyether and the polymerized diphenylmethane diisocyanate according to a certain proportion. According to the low-temperature-resistant, low-thermal-conductivity and high-strength polyurethane foam for the LNG, the combined polyether reacts with the isocyanate, and through the synergistic effect of the high-functionality polyether polyol, the polyester polyol and the nano reinforcing agent, the low-temperature-resistant, low-thermal-conductivity and high-strength polyurethane foam for the LNG can be continuously produced; the density is uniform; the heat conductivity coefficient is low; and the strength is high.

Description

Technical Field

[0001] This invention belongs to the field of functional polyether materials technology, specifically a combined polyether for continuous production of LNG, polyurethane foam, and its preparation method. Background Technology

[0002] The storage and transportation of LNG (liquefied natural gas) requires extremely low temperatures (-162°C), placing stringent demands on the performance of insulation materials. Polyurethane foam insulation material boasts the lowest thermal conductivity and best energy-saving performance among organic insulation materials. The foaming agents used in this insulation material have undergone over 40 years of development and evolution, from first-generation Freon-based foaming agents (F-11) to second-generation chlorofluorocarbon (HCFC) foaming agents, to third-generation hydrofluorocarbon (HFC) foaming agents, and finally to fourth-generation hydrofluoroolefin (HFO) foaming agents, continuously improving in terms of energy saving, environmental protection, and energy consumption.

[0003] Existing technologies, such as Chinese Patent Publication No. CN114133509A, provide high-density, high-strength, and environmentally friendly LNG padding materials and their preparation methods, employing an all-aqueous system to solve the problems of low strength and mold cracking associated with high-density padding materials prepared using all-aqueous systems. However, the polyether compositions and polyurethane materials provided by existing technologies still have the following problems: 1) Traditional rigid polyurethane foam is prone to embrittlement at low temperatures, resulting in decreased mechanical properties and affecting structural stability; 2) High thermal conductivity leads to insufficient insulation efficiency and increased energy consumption; 3) Intermittent production processes have low production efficiency and poor batch stability, making it difficult to meet the needs of large-scale industrialization. Therefore, developing a continuously produced LNG-specific polyether composition that produces polyurethane foam with low-temperature resistance, low thermal conductivity, and high strength, while achieving stable industrial production, is a technical challenge that urgently needs to be solved in the industry. Summary of the Invention

[0004] This application provides a method for the continuous production of combined polyethers and polyurethane foams for LNG, and aims to solve the problems described in the background art.

[0005] On one hand, this application provides a composite polyether for continuous production of LNG, the composite polyether comprising the following components by weight fraction: 80-105 parts of composite polyol; 3-5 parts of nano-reinforcing agent; 2-4 parts of composite catalyst; 2-4 parts of foam stabilizer; 20-30 parts of physical foaming agent; 1.0-2.0 parts of chemical foaming agent; and 20-30 parts of flame retardant.

[0006] Furthermore, the composite polyol comprises 25-35 parts of polyether polyol A, 5-15 parts of polyether polyol B, 20-30 parts of polyester polyol C, and 30-50 parts of polyester polyol D. The polyether polyol A has a functionality ≥6 and a hydroxyl value of 470-500 mg KOH / g, the polyether polyol B has a functionality of 3 and a hydroxyl value of 32-36 mg KOH / g, the polyester polyol C has a hydroxyl value of 170-180 mg KOH / g, and the polyester polyol D has a hydroxyl value of 235-240 mg KOH / g.

[0007] Furthermore, the composite polyol comprises 25-35 parts of polyether polyol A, 5-15 parts of polyether polyol B, 20-30 parts of polyester polyol C, and 30-50 parts of polyester polyol D. The polyether polyol A has a functionality ≥6 and a hydroxyl value of 470-500 mg KOH / g, the polyether polyol B has a functionality of 3 and a hydroxyl value of 32-36 mg KOH / g, the polyester polyol C has a hydroxyl value of 170-180 mg KOH / g, and the polyester polyol D has a hydroxyl value of 235-240 mg KOH / g.

[0008] Furthermore, the nano-reinforcing agent is modified nano-silica, and the nano-silica particle size is ≤30 nm.

[0009] Furthermore, the composite catalyst is a mixture of a tertiary amine catalyst and an organometallic catalyst. The tertiary amine catalyst is one of pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, and N,N-dimethylbenzylamine, or a mixture of several in any proportion. The organometallic catalyst is one of potassium isooctanoate or potassium acetate, or a mixture of two in any proportion. The weight ratio of the tertiary amine catalyst to the organometallic catalyst in the composite catalyst is (0.05-1.5):(1.0-2.5).

[0010] Furthermore, the foam stabilizer is a non-hydrolyzable silicon-carbon surfactant, the physical foaming agent is trans-1-chloro-3,3,3-trifluoropropylene, the chemical foaming agent is deionized water, and the flame retardant is tri-(2-chloropropyl)phosphate (TCPP).

[0011] This application also provides a polyurethane foam for continuous production of LNG, the polyurethane foam comprising component A and component B, wherein component A is the above-mentioned combined polyether; and component B is polymeric diphenylmethane diisocyanate.

[0012] Furthermore, the weight ratio of component A to component B is 1:1.5-1.7.

[0013] This invention also provides a method for preparing polyurethane foam for continuous production of LNG, comprising the following steps: Step 1: Add the composite polyol, nano-reinforcing agent, composite catalyst, foam stabilizer, physical foaming agent, chemical foaming agent and flame retardant in sequence and mix. Stir at room temperature for 1-1.5 hours to obtain component A; Step 2: Mix component A and component B according to the weight ratio to prepare the product.

[0014] Beneficial effects: The combined polyether and isocyanate prepared by this invention react to produce LNG polyurethane foam with low temperature resistance, low thermal conductivity, and high strength through the synergistic effect of high-functionality polyether polyol, polyester polyol, and nano-reinforcing agents. The prepared material exhibits high toughness at extremely low temperatures, as well as uniform density, low thermal conductivity, and high strength. Typical performance indicators meet the following requirements: thermal conductivity: ≤0.018 W / (m·K) (-196℃); compressive strength (10% deformation): ≥280 kPa (-196℃); low-temperature dimensional stability: ≤0.8% (-196℃, 168 h); closed-cell ratio: ≥95%. This invention employs continuous production and an LBA foaming system in its preparation method, ensuring batch consistency and increasing production capacity by 40%, making it suitable for large-scale industrial applications. It also meets the requirements of environmental protection, high production efficiency, and low energy consumption for large-scale production, significantly reducing overall production costs and making it suitable for large-scale industrial applications. Detailed Implementation

[0015] The embodiments or implementations described in this specification adopt a progressive approach, with each embodiment focusing on its differences from other embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with an implementation or example that are included in at least one implementation or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same implementation or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more implementations or examples.

[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0017] The technical solution of this application is further illustrated below through specific embodiments.

[0018] Unless otherwise specified, all materials used in this application are derived from commercially available materials.

[0019] This invention provides a polyurethane foam for continuous production of LNG, wherein the polyurethane foam comprises component A and component B, wherein component A and component B are composed of the following raw materials in parts by weight: 80-105 parts of composite polyol; 3-5 parts of nano-reinforcing agent; 2-4 parts of composite catalyst; 2-4 parts of foam stabilizer; 20-30 parts of physical foaming agent; 1.0-2.0 parts of chemical foaming agent; 20-30 parts of flame retardant; and component B is polymeric diphenylmethane diisocyanate.

[0020] The weight ratio of component A to component B in polyurethane foam is 1:1.5-1.7, preferably 1:1.6.

[0021] Component A comprises 25-35 parts of polyether polyol A, 5-10 parts of polyether polyol B, 20-30 parts of polyester polyol C, and 30-50 parts of polyester polyol D. Polyether polyol A has a functionality ≥6 and a hydroxyl value of 470-500 mg KOH / g. Polyether polyol B has a functionality of 3 and a hydroxyl value of 32-36 mg KOH / g. Polyether polyol A has a hydroxyl value of 170-180 mg KOH / g and 235-240 mg KOH / g.

[0022] The nano-reinforcing agent is silane coupling agent modified nano-silica, and the nano-silica particle size is ≤30 nm.

[0023] The composite catalyst is a mixture of a tertiary amine catalyst and an organometallic catalyst. The tertiary amine catalyst is one of pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, or N,N-dimethylbenzylamine, or a mixture of several in any proportion. The organometallic catalyst is one of potassium isooctanoate or potassium acetate, or a mixture of two in any proportion. The weight ratio of the tertiary amine catalyst to the organometallic catalyst in the composite catalyst is (0.05-1.5):(1.0-2.5).

[0024] The foam stabilizer is a non-hydrolyzable silicon-carbon surfactant, purchased from Jiangsu Meiside Chemical Co., Ltd., product model M-88313. The physical blowing agent is trans-1-chloro-3,3,3-trifluoropropylene, purchased from Honeywell Solstics LBA. The chemical blowing agent is deionized water, and the flame retardant is tri-(2-chloropropyl)phosphate (TCPP).

[0025] This application also provides a method for preparing a composite polyether for continuous production of polyurethane LNG, comprising the following steps: Step 1: Add the composite polyol, nano-reinforcing agent, composite catalyst, foam stabilizer, physical foaming agent, chemical foaming agent and flame retardant in sequence and mix. Stir at room temperature for 1-1.5 hours to obtain component A; Step 2: Mix component A and component B according to the weight ratio, and foam at 20-25℃ to obtain the product.

[0026] This application is prepared according to the above-described embodiments, and there are the following examples and comparative examples. The components and proportions of the examples and comparative examples are shown in Table 1 below, and the preparation methods of the examples and comparative examples are the same.

[0027] The difference between Example 2 and Example 1 is that the component ratios of the combined polyether and polyurethane foam are different, as shown in Table 1 below.

[0028] The difference between Example 3 and Example 1 is that the component ratios of the combined polyether and polyurethane foam are different, as shown in Table 1 below.

[0029] The difference between Comparative Example 1 and Example 1 is that no polyether polyol A was added, while the other components and proportions were the same as in Example 1.

[0030] The difference between Comparative Example 2 and Example 1 is that no nano-reinforcing agent was added, but the other components and proportions are the same as in Example 1.

[0031] The difference between Comparative Example 3 and Example 1 is that the mass ratio of component A to component B in the polyurethane foam is 1:1.2, while the other components and proportions are the same as in Example 1.

[0032] The corresponding test results are shown in Table 2 below.

[0033] Table 1. Weight proportions of each component in the examples and comparative examples. Table 2 Performance test table of polyurethanes prepared in the examples and comparative examples Analysis of experimental results: In Comparative Example 1, the polyurethane foam prepared without high-functionality and high-hydroxyl-value polyether polyols exhibited decreased low-temperature dimensional stability and compressive strength. This is because these polyethers primarily function to construct a high-crosslinking-density network in this invention. During the polyurethane reaction, isocyanates (-NCO) react with the hydroxyl groups (-OH) of the polyether to form urethane bonds (-NH-COO-), linking the molecular chains. High functionality means that a single molecule can react with multiple isocyanate molecules simultaneously; high hydroxyl value means a high density of reaction sites per unit mass. The combination of these two factors allows for the rapid formation of a dense three-dimensional crosslinked network structure within the system, significantly improving the material's hardness and rigidity. Higher crosslinking density results in greater constraint on molecular chain movement, making the material less prone to deformation and enhancing dimensional stability.

[0034] In Comparative Example 2, without the addition of nano-reinforcing agents, the compressive strength, dimensional stability, thermal conductivity, closed-cell ratio, and toughness of the prepared polyurethane foam all decreased. This is because in the initial stage of the polyurethane foaming reaction, the system generates CO2 or low-boiling-point blowing agents that vaporize to form bubble nuclei. Homogeneous nucleation (spontaneous bubble formation in pure liquid) requires very high energy, while nano-silica particles provide a huge specific surface area and abundant nucleation sites. Gas molecules preferentially aggregate at the interface between the nanoparticles and the polymer matrix to form bubble nuclei. This significantly lowers the nucleation energy barrier, resulting in finer and more uniform pores, a sharp increase in the number of nucleation sites, and more and more uniform bubble nuclei. Ultimately, this leads to a foam structure with smaller and more uniformly distributed pores, resulting in a lower thermal conductivity. By controlling the number and dispersion of nanoparticles, the stability of the pore walls can be indirectly affected, helping to obtain an ideal closed-cell structure and improve the closed-cell ratio. Nano-silica is a rigid inorganic particle with extremely high specific strength and modulus. When uniformly dispersed within a polyurethane organic polymer matrix, nanoparticles act similarly to the reinforcing steel in reinforced concrete, significantly improving compressive and tensile strength. Physical interactions (van der Waals forces, hydrogen bonds, etc.) exist between nanoparticles and polyurethane molecular chains, restricting chain movement, hindering microcrack propagation, and improving toughness. Appropriate amounts of nanoparticles can prevent crack propagation and absorb more energy.

[0035] In Comparative Example 3, adjusting the material ratio in the relative embodiment resulted in a significant decrease in the density, strength, dimensional stability, and closed-cell rate of the prepared polyurethane foam. Reducing the foaming ratio (typically 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.

[0036] 2. Gel reaction: -NCO + -OH → urethane (polyurethane). This forms the polymer backbone of the foam, providing strength.

[0037] 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.

[0038] 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 composite polyether for continuous production of LNG, characterized in that: The composite polyether comprises the following components by weight fraction: 80-105 parts of composite polyol; 3-5 parts of nano-reinforcing agent; 2-4 parts of composite catalyst; 2-4 parts of foam stabilizer; 20-30 parts of physical foaming agent; 1.0-2.0 parts of chemical foaming agent; and 20-30 parts of flame retardant.

2. The combined polyether for LNG produced continuously according to claim 1, characterized in that: The composite polyol comprises the following components in parts by weight: 25-35 parts of polyether polyol A; 5-15 parts of polyether polyol B; 20-30 parts polyester polyol C; 30-50 parts polyester polyol D; The polyether polyol A has a functionality of ≥6 and a hydroxyl value of 470-500 mg KOH / g; the polyether polyol B has a functionality of 3 and a hydroxyl value of 32-36 mg KOH / g; the polyester polyol C has a hydroxyl value of 170-180 mg KOH / g; and the polyester polyol D has a hydroxyl value of 235-240 mg KOH / g.

3. The combined polyether for LNG produced continuously according to claim 1, characterized in that: The nano-reinforcing agent is modified nano-silica, and the nano-silica particle size is ≤30 nm.

4. The combined polyether for LNG produced continuously according to claim 1, characterized in that: The composite catalyst is a mixture of a tertiary amine catalyst and an organometallic catalyst. The tertiary amine catalyst is one of pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine, and N,N-dimethylbenzylamine, or a mixture of several of them in any proportion. The organometallic catalyst is one of potassium isooctanoate or potassium acetate, or a mixture of two of them in any proportion. The weight ratio of the tertiary amine catalyst to the organometallic catalyst in the composite catalyst is (0.05-1.5):(1.0-2.5).

5. The combined polyether for LNG produced continuously according to claim 1, characterized in that: The foam stabilizer is a non-hydrolyzable silicon-carbon surfactant, the physical foaming agent is trans-1-chloro-3,3,3-trifluoropropylene, the chemical foaming agent is deionized water, and the flame retardant is one or a combination of triethyl phosphate, tri(2-chloropropyl) phosphate, trichloroethyl phosphate, and dimethyl methylphosphonate.

6. A polyurethane foam for continuous production of LNG, characterized in that: The polyurethane foam comprises component A and component B, wherein component A is the combined polyether as described in any one of claims 1-5; and component B is polymeric diphenylmethane diisocyanate.

7. The polyurethane foam for LNG produced continuously according to claim 6, characterized in that: The weight ratio of component A to component B is 1:1.5-1.

7.

8. The method for preparing polyurethane foam for continuous production of polyurethane LNG according to any one of claims 6-7, characterized in that: Includes the following steps: Step 1: Add the composite polyol, nano-reinforcing agent, composite catalyst, foam stabilizer, physical foaming agent, chemical foaming agent and flame retardant in sequence and mix. Stir at room temperature for 1-1.5 hours to obtain component A; Step 2: Mix component A and component B according to the weight ratio to prepare the product.

Images