A heat-insulating and high-temperature-resistant polyurethane rigid foam material and a low-temperature preparation method thereof

Abstract

This invention discloses a heat-insulating, high-temperature-resistant polyurethane rigid foam material and its low-temperature preparation method, which relates to the field of polyurethane foam materials. Bismaleimide powder is liquefied and dispersed in a polyol through a DA reaction. Lewis acid catalysis shortens the reaction time and is reused as a foaming catalyst. Combined with the excellent high- and low-temperature performance of the polyol, a thermoreversible DA adduct is introduced to achieve endothermic temperature control during the foaming process and low-temperature reconstruction of a rigid cross-linked structure. A low-boiling point primary foaming agent is compounded with methyl formate to reduce the heat of vaporization and system viscosity, and the A / B material preparation temperature is controlled to ≤15°C to avoid foaming agent loss. This solution solves the problems of powder dispersion, viscosity control, and foaming stability at low temperatures, imparting excellent heat-insulating and high-temperature-resistant foam properties.

Description

Technical Field

[0001] The present invention relates to the field of polyurethane foam materials, and in particular to a heat-insulating and high-temperature-resistant polyurethane rigid foam material and a low-temperature preparation method thereof. Background Art

[0002] Polyurethane foam is widely used in construction, energy, transportation, and other fields due to its excellent thermal insulation, lightweight, and designability. In southern regions like Jiangsu, Zhejiang, and Shanghai, where heating facilities are not installed during winter, stringent requirements are placed on polyurethane foam: it must be constructed in low-temperature environments while being resistant to high temperatures and maintaining low thermal conductivity and structural stability. However, the main raw materials for polyurethane foam are currently composed of polyol and isocyanate components. At temperatures as low as 10°C, the foaming rate of these two components decreases or even stops foaming.

[0003] The blowing agent currently used is mostly HCFC-141B, which has a boiling point of 32°C. When the ambient temperature and substrate temperature drop, more heat needs to be condensed during the foaming process to ensure that the physical blowing agent can be vaporized to form polyurethane foam. For example, in order to ensure the progress of the foaming process at a lower temperature, it is often necessary to adjust the heat generated during the foaming process to ensure the smooth progress of the foaming process, such as increasing the amount of chemical blowing agent water or increasing the amount of catalyst in the foaming process, so that it can quickly generate a large amount of heat to counteract the drop in ambient temperature. However, this will cause the temperature inside the foam to rise rapidly. If not controlled properly, it will cause spontaneous combustion and harm the foaming process.

[0004] Some researchers have also used the method of mixing low-temperature foaming agents into component B to solve the problem of high viscosity at low temperatures. For example, the Chinese invention patent with the announcement number CN111647190B adopts the method of changing the formula of components A and B and adding low-temperature foaming agents so that component B can be mixed evenly at 0°C, while component A can be mixed evenly at 50°C, thereby achieving the mixing and foaming of the two components at room temperature. This solves the problem that many low-boiling-point environmentally friendly foaming agents have very low boiling points. When used as components of component A, the material temperature must reach an ultra-low temperature state to prevent overflow. At low temperatures, the viscosity of polyether is high and the viscosity is even higher, making production impossible. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a heat-insulating and high-temperature resistant polyurethane rigid foam material and a low-temperature preparation method thereof.

[0006] The object of the present invention is achieved through the following technical solutions:

[0007] <First Aspect>

[0008] The present invention provides a low-temperature preparation method of a polyurethane rigid foam material, comprising the following steps:

[0009] S1. Mix bismaleimide and polyol at 70-80°C, add diene, and add the first catalyst, and stir to react for 3-5 hours to obtain DA adduct;

[0010] S2. Stirring the DA adduct, polyether polyol, polyether, a second catalyst, a diethylene glycol solution of potassium acetate, a compounded foaming agent, a foam stabilizer, water, and a flame retardant at room temperature to obtain a polyurethane composite material;

[0011] S3. Spraying the polyurethane composite material and polyisocyanate at an ambient temperature of 5-15° C., controlling the temperature of the polyurethane composite material at 8-12° C., and the temperature of the polyisocyanate at 10-15° C., to obtain the polyurethane rigid foam material after complete curing.

[0012] As an embodiment, the polyol is castor oil or epoxidized castor oil.

[0013] In some embodiments, the polyol is castor oil.

[0014] As an embodiment, the diene is selected from one or more of furfural methanol and furfural methylamine.

[0015] In some embodiments, the diene is furanol.

[0016] As an embodiment, the first catalyst is stannous chloride or stannous octoate.

[0017] In some embodiments, the first catalyst is stannous chloride.

[0018] As an embodiment, the stirring parameter in step S1 or S2 is 150-300 rpm.

[0019] In some embodiments, the stirring parameter is 200 rpm.

[0020] As an embodiment, the amount of each substance used, calculated by mass, is 15-25 parts of the bismaleimide, 80-150 parts of the polyol, 5-10 parts of the diene, and 0.05-0.2 parts of the first catalyst.

[0021] In some embodiments, the amounts of the substances used, calculated by weight, are 15-25 parts of the bismaleimide, 100 parts of the polyol, 7 parts of the diene, and 0.1 part of the first catalyst.

[0022] As an embodiment, the polyether polyol is one or more of 4110, 6305, and 8238.

[0023] In some embodiments, the polyether polyol is 4110.

[0024] As an embodiment, the polyether is 403.

[0025] As an embodiment, the second catalyst is one or more of triethanolamine, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine (PC-41), tris(dimethylaminopropyl)hexahydrotriazine, pentamethyldiethylenetriamine (PC-5), A-33, PT303, triethylenediamine (TEDA), stannous octoate, dibutyltin dilaurate (T-12), MB20, and butyl titanate.

[0026] In some embodiments, the second catalyst is composed of tris(dimethylaminopropyl)hexahydrotriazine and pentamethyldiethylenetriamine.

[0027] In some embodiments, the mass ratio of tris(dimethylaminopropyl)hexahydrotriazine to pentamethyldiethylenetriamine in the second catalyst is 5:2.

[0028] As an embodiment, the concentration of the potassium acetate diethylene glycol solution is 30-35 wt.%.

[0029] In some embodiments, the concentration of the potassium acetate diethylene glycol solution is 33 wt.%.

[0030] As an embodiment, the compound foaming agent consists of a low-boiling-point foaming agent and methyl formate, and the low-boiling-point foaming agent is 1,1,1,3,3-pentafluoropropane or monochlorotrifluoropropylene.

[0031] In some embodiments, the compound foaming agent is composed of 1,1,1,3,3-pentafluoropropane and methyl formate.

[0032] In some embodiments, the compound foaming agent is composed of monochlorotrifluoropropylene and methyl formate.

[0033] As an embodiment, the mass ratio of the low-boiling point foaming agent to methyl formate is (7:9):1.

[0034] In some embodiments, the low-boiling point foaming agent is 11 parts and the methyl formate is 1.5 parts by mass.

[0035] As an embodiment, the foam stabilizer is one or more of M-8805, M-8808, M-8809, M-88108, M-88109, M-88716, and M-88719.

[0036] In some embodiments, the foam stabilizer is M-88108.

[0037] As an embodiment, the flame retardant is one or more of TCPP, TCEP, TEP, DEEP, and OP-550.

[0038] In some embodiments, the flame retardant is DEEP.

[0039] As an embodiment, the polyisocyanate is polyphenylpolymethylene polyisocyanate.

[0040] As an embodiment, the polyphenyl polymethylene polyisocyanate is one or more of Wanhua PM200, Covestro 44V20, and Huntsman S5005.

[0041] As an implementation plan, the amount of each substance used, calculated by mass, is: 60-100 parts of DA adduct, 15-25 parts of polyether polyol, 8-12 parts of polyether, 2-3 parts of second catalyst, 1-2 parts of potassium acetate diethylene glycol solution, 10-15 parts of compound foaming agent, 0.5-1.5 parts of foam stabilizer, 0.3-0.5 parts of water, and 8-12 parts of flame retardant.

[0042] In some embodiments, the amount of each substance used, calculated by mass, is: 80 parts of DA adduct, 20 parts of polyether polyol, 10 parts of polyether, 2.8 parts of the second catalyst, 1.5 parts of potassium acetate diethylene glycol solution, 12.5 parts of compound foaming agent, 1 part of foam stabilizer, 0.4 parts of water, and 10 parts of flame retardant.

[0043] As an embodiment, the stirring time of the polyurethane composition in step S2 is 30 to 50 minutes.

[0044] In some embodiments, the stirring time of the polyurethane composition in step S2 is 40 minutes.

[0045] As an embodiment, in step S3, the polyurethane composition and the polyisocyanate are sprayed at a mass ratio of (0.95-1.05):1 by low pressure.

[0046] In some embodiments, in step S3, the polyurethane composition and the polyisocyanate are sprayed at a mass ratio of 1:1 by low pressure.

[0047] <Second Aspect>

[0048] The present invention provides a polyurethane rigid foam material prepared by the above method.

[0049] As an embodiment, the density of the rigid foam material is 44-45 kg / m 3 , the compressive strength is 0.38~0.40MPa, and the thermal conductivity is 0.022~0.023W / (m·K).

[0050] As an embodiment, the dimensional change rate of the rigid foam material after being kept at 250° C. for 5 minutes is ≤0.42%.

[0051] In some embodiments, the dimensional change rate of the rigid foam material after being kept at 250° C. for 5 minutes is between 0.35% and 0.42%.

[0052] As an embodiment, the mass loss rate of the rigid foam material at 250° C. is ≤6.0%.

[0053] In some embodiments, the mass loss rate of the rigid foam material at 250° C. is between 4.5% and 60%.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The polyurethane foam provided by the present invention, which is suitable for preparation in low-temperature environments and has both thermal insulation and high-temperature resistance, achieves performance breakthroughs through multi-dimensional technological innovation, which is mainly reflected in the following aspects:

[0056] (1) Optimized preparation of low-temperature dispersibility and application of high-temperature resistance

[0057] The high-temperature-resistant powder used in this invention is bismaleimide. In the prior art, this is often introduced into the polyurethane foam preparation process as a solid powder. However, as the temperature decreases, the medium viscosity increases, particle mobility and dispersion efficiency decrease, and the particle surface charge or dispersant adsorption decreases, resulting in poor powder dispersibility and increased agglomeration. In this invention, by utilizing bismaleimide to undergo a DA reaction with furan rings, gradually liquefying and dissolving it in a polyol (castor oil or epoxy castor oil), the risks of uneven dispersion of the powder material during the polyurethane foaming process, leading to uneven high-temperature resistance, and reduced foam performance due to powder agglomeration, are avoided. This establishes a foundation for uniform foam performance from the raw material dispersion stage.

[0058] (2) High-efficiency liquefaction reaction process

[0059] This invention uses castor oil as the reaction medium and a Lewis acid (such as stannous chloride or stannous octoate) as a catalyst to accelerate the DA reaction, achieving liquefaction of the bismaleimide powder. Therefore, this process can be achieved without requiring the DA reaction to complete. At 70-80°C, adding 1% catalyst can liquefy the bismaleimide powder through the DA reaction with a furan ring compound within 3 hours. Once the reaction reaches approximately 50% completion, the powder can be used for subsequent polyurethane formulation. This process overcomes the traditional limitation of requiring the DA reaction to complete, allowing subsequent formulation to begin during a partial reaction phase (approximately 50% completion), significantly shortening the production cycle and improving industrial production efficiency.

[0060] (3) Catalyst function reuse and process simplification

[0061] The Lewis acid used in this invention (such as stannous chloride or stannous octoate) exhibits dual catalytic activity. First, it accelerates the bismaleimide (DA) reaction during the DA reaction, achieving liquefaction. Second, it acts as a post-catalyst during the polyurethane foaming stage, reducing the amount of foaming catalysts such as pentamethyldiethylenetriamine. This dual-purpose design simplifies the formulation, reduces raw material costs, and avoids the process complexity associated with the synergistic use of multiple catalysts.

[0062] (4) Co-design of polyol base material performance

[0063] In the present invention, castor oil or epoxy castor oil is selected as the DA reaction medium and as the main polyol of the polyurethane foam. The reason is that the polyol (castor oil or epoxy castor oil) has excellent high-temperature and low-temperature resistance. Its good high-temperature resistance cooperates with bismaleimide to ultimately achieve the high-temperature resistance of the polyurethane foam. In addition, its fluidity and low viscosity under low-temperature conditions ensure the smooth progress of the spraying process of polyurethane foam molding, achieving dual compatibility between material properties and processing technology.

[0064] (5) Intelligent regulation of thermoreversible cross-linking structures

[0065] Bismaleimide and furan compounds undergo a DA reaction in a polyol, introducing a thermally reversible DA adduct into the polyurethane system. During the foaming process, the DA adduct's thermal reversible properties enable the dual advantages of "heat absorption and temperature control—low-temperature reconstruction." On the one hand, when foaming releases instantaneous high heat, causing the system temperature to rise sharply, the DA adduct undergoes a reverse reaction to absorb some of the heat, effectively suppressing the temperature peak, avoiding the risk of spontaneous combustion due to local overheating, and ensuring the safety of the foaming process. On the other hand, after the foam is prepared, as the temperature drops, the reactants generated by the reverse reaction regenerate the DA adduct through a forward DA reaction, supplementing the polyurethane network to form a rigid cross-linked structure. The furan and maleimide rings enhance the high-temperature resistance and mechanical stability of the polyurethane foam, achieving synergistic optimization of thermal runaway prevention and control during processing and maintaining high performance of the final material.

[0066] (6) Synergistic effect of composite foaming agent system

[0067] A unique foaming system is created by combining a low-boiling-point primary blowing agent (1,1,1,3,3-pentafluoropropane / chlorotrifluoropropylene) with methyl formate (optimally in the mass ratio range of 7-9:1). The primary blowing agent reduces the total heat required for vaporization, while methyl formate, with its excellent solvent properties, reduces system viscosity, addressing fluidity issues associated with low-temperature processing. This combination precisely controls foam dimensional stability, avoiding density variations and performance degradation caused by mismatched ratios.

[0068] (7) Preparation process window for precise temperature control

[0069] The optimal preparation temperature of material A (polyurethane composite material) and material B (polyisocyanate) provided by the present invention is not higher than 15°C to prevent serious volatilization of the foaming agent, which causes loss of the foaming agent before foaming, resulting in increased foam density and affecting the mechanical properties and thermal conductivity of the polyurethane foam. DETAILED DESCRIPTION

[0070] The present invention will be described in detail below with reference to the examples. The following examples 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 those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0071] Example 1

[0072] This embodiment provides a low-temperature preparation method for a heat-insulating and high-temperature resistant polyurethane rigid foam material, and the steps are as follows:

[0073] S1. Preparation of furan / maleimide DA adduct

[0074] Bismaleimide and castor oil were mixed, heated to 70°C, and furan methanol was added dropwise. The catalyst stannous chloride was then added. The reaction was continued at a stirring speed of 200 rpm for 3 hours until the reaction system showed a light yellow transparent liquid. The product was named: furan / maleimide DA adduct.

[0075] After testing with a rotational rheometer, the viscosity of the furan / maleimide DA adduct at 10°C was 2840 mPa·s;

[0076] 1H NMR determination showed that the maleimide groups in bismaleimide reacted by 41% before and after the reaction.

[0077] The hydroxyl value of the furan / maleimide DA adduct was determined to be 135 mgKOH / g by acylation titration.

[0078] The raw materials involved in step S1 are as follows by mass:

[0079] Bismaleimide: 25 parts;

[0080] Castor oil: 100 parts;

[0081] Furan methanol: 7 parts;

[0082] Stannous chloride: 0.1 part;

[0083] S2. Preparation of polyurethane composite materials

[0084] The following materials were prepared by mixing 80 parts of furan / maleimide DA adduct, 20 parts of 4110 polyether polyol, 10 parts of 403 polyether, 0.8 parts of pentamethyldiethylenetriamine, 2.0 parts of tris(dimethylaminopropyl)hexahydrotriazine, 1.5 parts of potassium acetate solution in diethylene glycol (concentration of 33 wt.%), 11 parts of 1,1,1,3,3-pentafluoropropane, 1.5 parts of methyl formate, 1 part of foam stabilizer M-88108, 0.4 parts of water, and 10 parts of flame retardant DEEP (diethyl ethylphosphonate) at room temperature and stirring for 40 minutes to obtain a polyurethane composite material.

[0085] After testing with a rotational rheometer, the viscosity of the polyurethane composite material at 10°C was 1240 mPa·s;

[0086] The hydroxyl value of the polyurethane composite material was measured to be 180 mgKOH / g.

[0087] S3. Polyurethane foam spraying preparation

[0088] At an ambient temperature of 10°C, the polyurethane composite material was kept at 10°C, and the polyisocyanate (PM200 produced by Yantai Wanhua in this example) was kept at 15°C. The two materials were sprayed onto a stainless steel surface in a 1:1 mass ratio using a low-pressure spray foaming machine. Testing showed that the milky white time after mixing the two materials was 4 seconds, the wire drawing time was 7 seconds, and the non-stick time was 10 seconds.

[0089] After spraying, leave it at room temperature for 24 hours to cure.

[0090] After the polyurethane foam is completely cured, the crust formed during the spraying process is removed with a blade, and the foam is polished with sandpaper to obtain the low-temperature preparation of the polyurethane foam.

[0091] Example 2

[0092] This embodiment provides a low-temperature preparation method for a heat-insulating and high-temperature resistant polyurethane rigid foam material, and the steps are as follows:

[0093] S1. Preparation of furan / maleimide DA adduct

[0094] Bismaleimide and castor oil were mixed, heated to 70°C, and furan methanol was added dropwise. The catalyst stannous chloride was then added. The reaction was continued at a stirring speed of 200 rpm for 3 hours until the reaction system showed a light yellow transparent liquid. The product was named: furan / maleimide DA adduct.

[0095] The viscosity of the furan / maleimide DA adduct was 2760 mPa·s at 10°C after testing with a rotational rheometer;

[0096] 1H NMR determination showed that the maleimide groups in bismaleimide reacted by 47% before and after the reaction.

[0097] The hydroxyl value of the furan / maleimide DA adduct was determined to be 143 mgKOH / g by acylation titration.

[0098] The raw materials involved in step S1 are as follows by mass:

[0099] Bismaleimide: 20 parts;

[0100] Castor oil: 100 parts;

[0101] Furan methanol: 7 parts;

[0102] Stannous chloride: 0.1 part;

[0103] S2. Preparation of polyurethane composite materials

[0104] The following materials were prepared by mixing 80 parts of furan / maleimide DA adduct, 20 parts of 4110 polyether polyol, 10 parts of 403 polyether, 0.8 parts of pentamethyldiethylenetriamine, 1.5 parts of potassium acetate solution in diethylene glycol (concentration of 33 wt.%), 2.0 parts of tris(dimethylaminopropyl)hexahydrotriazine, 1.5 parts of methyl formate, 1 part of foam stabilizer M-88108, 11 parts of 1,1,1,3,3-pentafluoropropane, 0.4 parts of water, and 10 parts of flame retardant DEEP (diethyl ethylphosphonate) at room temperature and stirring for 40 minutes to obtain a polyurethane composite material.

[0105] After testing with a rotational rheometer, the viscosity of the polyurethane composite material at 10°C was 1180 mPa·s;

[0106] The hydroxyl value of the polyurethane composite material was measured to be 191 mgKOH / g.

[0107] S3. Polyurethane foam spraying preparation

[0108] At an ambient temperature of 10°C, the polyurethane composite material was kept at 10°C, and the polyisocyanate (PM200 produced by Yantai Wanhua in this example) was kept at 15°C. The two materials were sprayed onto a stainless steel surface in a 1:1 mass ratio using a low-pressure spray foaming machine. Testing showed that the milky white time after mixing the two materials was 4 seconds, the wire drawing time was 6 seconds, and the non-stick time was 9 seconds.

[0109] After spraying, leave it at room temperature for 24 hours to cure.

[0110] After the polyurethane foam is completely cured, the crust formed during the spraying process is removed with a blade, and the foam is polished with sandpaper to obtain the low-temperature preparation of the polyurethane foam.

[0111] Example 3

[0112] This embodiment provides a low-temperature preparation method for a heat-insulating and high-temperature resistant polyurethane rigid foam material, and the steps are as follows:

[0113] S1. Preparation of furan / maleimide DA adduct

[0114] Bismaleimide and castor oil were mixed, heated to 70°C, and furan methanol was added dropwise. The catalyst stannous chloride was then added. The reaction was continued at a stirring speed of 200 rpm for 3 hours until the reaction system showed a light yellow transparent liquid. The product was named: furan / maleimide DA adduct.

[0115] The viscosity of the furan / maleimide DA adduct was 2760 mPa·s at 10°C after testing with a rotational rheometer;

[0116] 1H NMR determination showed that the maleimide groups in bismaleimide reacted by 47% before and after the reaction.

[0117] The hydroxyl value of the furan / maleimide DA adduct was determined to be 143 mgKOH / g by acylation titration.

[0118] The raw materials involved in step S1 are as follows by mass:

[0119] Bismaleimide: 20 parts;

[0120] Castor oil: 100 parts;

[0121] Furan methanol: 7 parts;

[0122] Stannous chloride: 0.1 part;

[0123] S2. Preparation of polyurethane composite materials

[0124] The following materials were prepared: 80 parts of furan / maleimide DA adduct, 20 parts of 4110 polyether polyol, 10 parts of 403 polyether, 0.8 parts of pentamethyldiethylenetriamine, 1.5 parts of potassium acetate in diethylene glycol (concentration of 33 wt.%), 2.0 parts of tris(dimethylaminopropyl)hexahydrotriazine, 1.5 parts of methyl formate, 1 part of foam stabilizer M-88108, 11 parts of monochlorotrifluoropropylene, 0.4 parts of water, and 10 parts of flame retardant DEEP (diethyl ethylphosphonate), and stirred at room temperature for 40 minutes to obtain a polyurethane composite material.

[0125] After testing with a rotational rheometer, the viscosity of the polyurethane composite material at 10°C was 1240 mPa·s;

[0126] The hydroxyl value of the polyurethane composite material was measured to be 191 mgKOH / g.

[0127] S3. Polyurethane foam spraying preparation

[0128] At an ambient temperature of 10°C, the polyurethane composite material was kept at 10°C, and the polyisocyanate (PM200 produced by Yantai Wanhua in this example) was kept at 15°C. The two materials were sprayed onto a stainless steel surface in a 1:1 mass ratio using a low-pressure spray foaming machine. Testing showed that the milky white time after mixing the two materials was 3 seconds, the wire drawing time was 6 seconds, and the non-stick time was 8 seconds.

[0129] After spraying, leave it at room temperature for 24 hours to cure.

[0130] After the polyurethane foam is completely cured, the crust formed during the spraying process is removed with a blade, and the foam is polished with sandpaper to obtain the low-temperature preparation of the polyurethane foam.

[0131] Example 4

[0132] This embodiment provides a low-temperature preparation method for a heat-insulating and high-temperature resistant polyurethane rigid foam material, and the steps are as follows:

[0133] S1. Preparation of furan / maleimide DA adduct

[0134] Bismaleimide and castor oil were mixed, heated to 70°C, and furan methanol was added dropwise. The catalyst stannous chloride was then added. The reaction was continued at a stirring speed of 200 rpm for 3 hours until the reaction system showed a light yellow transparent liquid. The product was named: furan / maleimide DA adduct.

[0135] The viscosity of the furan / maleimide DA adduct was 2560 mPa·s at 10°C after rotational rheometer testing;

[0136] 1H NMR determined that the maleimide groups in bismaleimide reacted by 50% before and after the reaction.

[0137] The hydroxyl value of the furan / maleimide DA adduct was determined to be 155 mgKOH / g by acylation titration.

[0138] The raw materials involved in step S1 are as follows by mass:

[0139] Bismaleimide: 15 parts;

[0140] Castor oil: 100 parts;

[0141] Furan methanol: 7 parts;

[0142] Stannous chloride: 0.1 part;

[0143] S2. Preparation of polyurethane composite materials

[0144] The following materials were prepared: 80 parts of furan / maleimide DA adduct, 20 parts of 4110 polyether polyol, 10 parts of 403 polyether, 0.8 parts of pentamethyldiethylenetriamine, 1.5 parts of potassium acetate in diethylene glycol (concentration of 33 wt.%), 2.0 parts of tris(dimethylaminopropyl)hexahydrotriazine, 1.5 parts of methyl formate, 1 part of foam stabilizer M-88108, 11 parts of monochlorotrifluoropropylene, 0.4 parts of water, and 10 parts of flame retardant DEEP (diethyl ethylphosphonate), and stirred at room temperature for 40 minutes to obtain a polyurethane composite material.

[0145] After testing with a rotational rheometer, the viscosity of the polyurethane composite material at 10°C was 1160 mPa·s;

[0146] The hydroxyl value of the polyurethane composite material was measured to be 202 mgKOH / g.

[0147] S3. Polyurethane foam spraying preparation

[0148] At an ambient temperature of 10°C, the polyurethane composite material was kept at 10°C, and the polyisocyanate (PM200 produced by Yantai Wanhua in this example) was kept at 15°C. A single layer of polyisocyanate (polyisocyanate) was sprayed onto a stainless steel surface using a low-pressure spray foaming machine in a 1:1 mass ratio. Testing showed that the milky white time after mixing the two materials was 3 seconds, the wire drawing time was 6 seconds, and the non-stick time was 9 seconds.

[0149] After spraying, leave it at room temperature for 24 hours to cure.

[0150] After the polyurethane foam is completely cured, the crust formed during the spraying process is removed with a blade, and the foam is polished with sandpaper to obtain the low-temperature preparation of the polyurethane foam.

[0151] Comparative Example

[0152] In this comparative example, the reaction time in the preparation method of furan / maleimide DA adduct was regulated, and it was found that:

[0153] The preparation steps are consistent with step S1 in Example 1, except for the reaction time.

[0154] When the reaction time is 1.5 h, no light yellow transparent liquid is obtained, and after stopping the reaction, powders are continuously precipitated, resulting in stratification.

[0155] A reaction time of 3 hours can avoid the problem of stratification caused by precipitation of the prepared DA adduct during storage. This problem can also be achieved when the time is further extended, but it does not significantly improve the performance. Instead, it increases the time and energy consumption of the entire reaction process.

[0156] Test analysis:

[0157] The polyurethane foam prepared in the above example was subjected to performance tests, including foam density, compressive strength, thermal conductivity, foam size change rate after insulation at 250°C for 5 minutes, and thermogravimetric analysis test of foam mass loss rate at 250°C. The results are shown in Table 1:

[0158] Table 1

[0159]

[0160] In summary, this invention utilizes a DA reaction to liquefy and disperse bismaleimide powder in a polyol (such as castor oil or epoxy castor oil). Lewis acid catalysis shortens the reaction time and is reused as a foaming catalyst. Combined with the excellent high- and low-temperature performance of the polyol, a thermoreversible DA adduct is introduced to achieve endothermic temperature control during the foaming process and reconstruct a rigid cross-linked structure at low temperatures. A low-boiling point primary blowing agent is combined with methyl formate to reduce the heat of vaporization and system viscosity, and the A / B material preparation temperature is controlled to ≤15°C to avoid blowing agent loss. This solution addresses the challenges of powder dispersion, viscosity control, and foaming stability at low temperatures, resulting in foams with excellent thermal insulation and high-temperature resistance.

[0161] 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 variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A low-temperature preparation method for polyurethane rigid foam material, characterized in that: The following steps are involved: S1. Mixing bismaleimide and a polyol at 70-80° C., adding a diene, and adding a first catalyst, stirring and reacting for 3-5 hours to obtain a DA adduct, wherein the polyol is castor oil or epoxy castor oil; the diene is furfuryl alcohol and / or furfural; and the first catalyst is stannous chloride or stannous octoate; S2. Stirring the DA adduct, polyether polyol, polyether, a second catalyst, a diethylene glycol solution of potassium acetate, a compounded foaming agent, a foam stabilizer, water, and a flame retardant at room temperature to obtain a polyurethane composition, wherein the compounded foaming agent comprises a low-boiling-point foaming agent and methyl formate, and the low-boiling-point foaming agent is 1,1,1,3,3-pentafluoropropane or monochlorotrifluoropropylene; S3. Under an ambient temperature of 5-15° C., the polyurethane composite material and polyisocyanate are sprayed at low pressure, the temperature of the polyurethane composite material is controlled at 8-12° C., and the temperature of the polyisocyanate is controlled at 10-15° C., and after complete curing, the polyurethane rigid foam material is obtained.

2. The method according to claim 1, characterized in that The amount of each substance used is as follows, calculated by mass: 15-25 parts of the bismaleimide, 80-150 parts of the polyol, 5-10 parts of the diene, and 0.05-0.2 parts of the first catalyst.

3. The method according to claim 1, characterized in that The stirring parameter in step S1 or S2 is 150-300 rpm.

4. The method according to claim 1, wherein By mass, the low-boiling point foaming agent is 11 parts and the methyl formate is 1.5 parts.

5. The method according to claim 1, wherein It also includes one or more of the following technical features: A. The polyether polyol is one or more of 4110, 6305, and 8238; B, the polyether is 403; C. The second catalyst is one or more of triethanolamine, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine (PC-41), tris(dimethylaminopropyl)hexahydrotriazine, pentamethyldiethylenetriamine (PC-5), A-33, PT303, triethylenediamine (TEDA), stannous octoate, dibutyltin dilaurate (T-12), MB20, and butyl titanate; D. The foam stabilizer is one or more of M-8805, M-8808, M-8809, M-88108, M-88109, M-88716, and M-88719; E. The flame retardant is one or more of TCPP, TCEP, TEP, DEEP, and OP-550.

6. The method according to claim 1, characterized in that The amount of each substance used is as follows, by mass: 60-100 parts of DA adduct, 15-25 parts of polyether polyol, 8-12 parts of polyether, 2-3 parts of second catalyst, 1-2 parts of potassium acetate diethylene glycol solution, 10-15 parts of compound foaming agent, 0.5-1.5 parts of foam stabilizer, 0.3-0.5 parts of water, and 8-12 parts of flame retardant.

7. The method according to claim 1, characterized in that The polyisocyanate is polyphenyl polymethylene polyisocyanate.

8. A polyurethane rigid foam material, characterized in that: It is prepared according to the method according to any one of claims 1 to 7.

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