Preparation method and application of polyurethane foam material

Abstract

The invention discloses a preparation method and application of a polyurethane foam material. The preparation method of the polyurethane foam material comprises the following steps: mixing preparation raw materials including 100 parts by mass of polyol, 2-6 parts by mass of a surfactant, 1.8-9 parts by mass of a catalyst, 1.5-2.1 parts by mass of water and 2-10 parts by mass of an alkane foaming agent to obtain a white material; the preparation method comprises the following steps: mixing preparation raw materials including 20-35 parts by mass of LBA and 150-200 parts by mass of isocyanate to obtain a black material; mixing the white material with the black material, and reacting to obtain a polyurethane foam material; wherein the alkane foaming agent at least comprises high-boiling-point alkane, and the boiling point of the high-boiling-point alkane is higher than that of the LBA. The polyurethane foam material prepared by the method has the advantages of low heat conductivity coefficient, low density, excellent thermal stability and fewer air pit defects on the surface of the material, and the strength and cost effectiveness of the material can be ensured. The invention also provides application of the preparation method.

Description

Technical Field

[0001] The present invention relates to the field of polyurethane foam materials, and particularly to a preparation method and application of a polyurethane foam material. Background Art

[0002] Rigid polyurethane (PU) foam materials are widely used in the heat insulation field of electric water heaters and other electrothermal appliances due to their good heat insulation performance.

[0003] Currently, the preparation of polyurethane foam materials generally involves the mixing process of black material and white material. Among them, the black material is mainly composed of isocyanate curing agent; the white material usually includes components such as polyol, foaming agent, catalyst and additives. The fourth-generation physical foaming agent LBA (trans-1-chloro-3,3,3-trifluoropropene) has a lower boiling point and gas-phase thermal conductivity, which can effectively reduce the thermal conductivity of the foam and improve the foam strength. However, in the application in heat preservation fields such as water heaters, the thermal conductivity stability of the foam materials prepared with halogen-containing foaming agents such as LBA under high-temperature conditions is poor, and it is difficult to maintain excellent heat insulation performance and reliability for a long time. In addition, LBA has a relatively large relative molecular mass and high cost. Using it alone will significantly increase the production cost, and there is currently no effective solution that takes both cost and foam performance into account.

[0004] In actual production applications, the white material premixing process, as a pre-step of the foaming process, aims to uniformly mix the components of the white material to meet the production requirements for further mixing with the black material, and finally obtain a foaming material that meets the process standards. However, from the completion of the premixing preparation of the white material to the actual foaming use, it usually needs to go through transitional or transportation links such as storage tanks and long-distance pipelines, and these processes require a certain amount of time. Especially during production line maintenance or holidays, the parking time of the white material may be further extended. The traditional premixing process is difficult to ensure the stability and reliability of the white material with LBA as the main foaming agent during long-term storage, resulting in a decrease in the foaming quality of the white material in the pipeline or storage tank during long-term storage, and even causing the phenomenon of foaming failure, seriously affecting the final performance of the foam material. Although taking temperature control measures can extend the stable period of the white material, the temperature control cost and process complexity are relatively high. In addition, after the foam material is formed by the conventional process, air pit defects are easily generated on the surface, affecting the appearance quality and even reducing the use strength of the foam material. Therefore, it is necessary to further optimize the preparation process of polyurethane foam materials to obtain polyurethane foam materials with low thermal conductivity, excellent thermal stability, high strength, low density and good apparent quality, and at the same time having cost advantages. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a polyurethane foam material, and the polyurethane foam material prepared by this method has a low thermal conductivity, a low density, excellent thermal stability, and fewer air pit defects on the material surface, and can ensure the strength and cost-effectiveness of the material.

[0006] The present invention also proposes a polyurethane foam material prepared by the above preparation method.

[0007] The present invention also proposes a household appliance.

[0008] In a first aspect of the present invention, an embodiment relates to a method for preparing a polyurethane foam material, which includes the following steps: mixing a preparation raw material including 100 parts by mass of polyol, 2 - 6 parts by mass of surfactant, 1.8 - 9 parts by mass of catalyst, 1.5 - 2.1 parts by mass of water, and 2 - 10 parts by mass of an alkane foaming agent to obtain a white material; mixing a preparation raw material including 20 - 35 parts by mass of LBA and 150 - 200 parts by mass of isocyanate to obtain a black material; mixing the white material and the black material and reacting to obtain the polyurethane foam material; wherein, the alkane foaming agent at least includes a high-boiling alkane, and the boiling point of the high-boiling alkane is higher than the boiling point of the LBA.

[0009] The method for preparing a polyurethane foam material according to the first aspect of the present invention has at least the following beneficial effects:

[0010] By adding LBA to the black material in the present invention, contact reaction between LBA and the catalyst (such as a commonly used organic amine catalyst) in the white material is avoided, ensuring the long-term stability and reliability of the formulation with LBA as the main foaming agent. In addition, isocyanate has excellent solubility in LBA, which helps to improve the dispersion uniformity of LBA in the system. Compared with the scheme of adding LBA to the white material, this method can significantly reduce the surface air pit defects of the foam material and improve the apparent quality.

[0011] Mixing the alkane foaming agent, surfactant, water and polyol can reduce the viscosity of the polyol and facilitate material transportation.

[0012] The present invention uses an alkane foaming agent to replace part of the LBA, and combines a multi-foaming system of LBA (main physical foaming agent, medium boiling point), alkane foaming agent (auxiliary physical foaming agent, including high-boiling alkane) and water (chemical foaming agent, water reacts with isocyanate to generate carbon dioxide, low boiling point), which can achieve a balance among reducing the thermal conductivity, improving the foam strength and heat resistance, and optimizing the cost.

[0013] Specifically, LBA has a low gas-phase thermal conductivity and a high vapor pressure. When used as the main blowing agent, it can effectively reduce the thermal conductivity of the foam while enhancing the strength of the foam. As a low-boiling gas, carbon dioxide can increase the internal pressure of the pores, further enhancing the foam strength. Since the boiling points of carbon dioxide and LBA are relatively low, the internal pressure of the pores increases in a heated environment, resulting in an enhanced exchange effect between the gas inside the pores and the outside air, thus affecting the stability of the thermal conductivity of the foam material. Therefore, in the present invention, a high-boiling alkane is used to replace part of the LBA, which helps to improve the stability of the thermal conductivity of the foam material under heated conditions and reduce the raw material cost.

[0014] Water, as a chemical blowing agent, not only participates in the chemical reaction to generate carbon dioxide but also has good nucleation ability, which helps to form a fine pore structure. The fine pores can extend the heat transfer path in the solid phase part, reduce the solid-phase thermal conductivity, and thus effectively reduce the thermal conductivity of the foam.

[0015] The surfactant can reduce the surface tension between the polyol, isocyanate, and blowing agent, stabilize the reaction system, and by reducing the surface energy of the reaction system, reduce the pressure difference between the pores, reduce the phenomenon of pore coalescence during the pore growth process, and promote the formation of fine pores.

[0016] Therefore, through the optimization of the formulation design, the low thermal conductivity of LBA, the enhancement effect of the low boiling points of LBA and carbon dioxide on the foam strength, and the contribution of the high-boiling alkane to the thermal conductivity stability are fully utilized. At the same time, the nucleation ability of water helps to obtain a more delicate pore structure, overcome the deficiency of the high thermal conductivity of carbon dioxide and high-boiling alkane, and thus maintain the thermal conductivity performance advantage of the LBA foaming system.

[0017] The polyurethane foam material of the present invention has the advantages of low thermal conductivity (the thermal conductivity of the foam can be as low as below 18.7 mW / m·K at 22.5 °C, especially when the alkane blowing agent is cyclopentane, the thermal conductivity of the foam can be further reduced to below 18 mW / m·K), good thermal stability, high foam strength, low comprehensive cost, etc., and is especially suitable for products such as electric water heaters, which can significantly improve the energy efficiency of the products. In addition, the surface quality of the foam material is significantly improved, and the number of air pit defects with a diameter greater than 3 cm on the material surface is reduced to below 4.55 per square meter.

[0018] According to some embodiments of the present invention, the preparation raw materials of the black material further include a nucleation aid, and the preparation method of the black material includes the following steps: mixing the preparation raw materials including the LBA, nucleation aid, and isocyanate to obtain the black material. Adding a nucleation aid can promote bubble nucleation and help to obtain smaller pore sizes.

[0019] Generally, nucleating agents (such as perfluoroolefin compounds) have good compatibility with LBA. Therefore, adding the nucleating agent and LBA together to the black material helps to improve the solubility of the nucleating agent, enhance its dispersion uniformity, and further improve the appearance quality of the foam material.

[0020] It should be understood that when higher requirements are placed on the appearance quality, the above-mentioned scheme is recommended. When the requirements for appearance quality are relatively low, it is also possible to choose to add the nucleating agent to the white material for mixing, or split the nucleating agent into two parts and add them to the black material and the white material respectively for mixing.

[0021] According to some embodiments of the present invention, the nucleating agent is selected from one or more of perfluoroolefin compounds having 3 to 8 carbon atoms. For example, specifically selected from hexafluoropropene, perfluoro(4-methyl-2-pentene), perfluoro(2-methyl-2-pentene), hexafluorobutadiene or a mixture thereof. Perfluoroolefin compounds have a low surface energy, can assist in bubble nucleation, and reduce the cell size.

[0022] According to some embodiments of the present invention, the mass of the nucleating agent does not exceed 3% of the mass of the polyol. The nucleating agent usually has a high cost. Therefore, on the premise of ensuring that the foam properties meet the requirements, its dosage should be minimized as much as possible, and in some cases, it can even be chosen not to add.

[0023] According to some specific embodiments of the present invention, the mass of the nucleating agent is 0.5% to 2% of the mass of the polyol.

[0024] According to some embodiments of the present invention, the preparation method of the black material specifically includes the following steps: mixing a part of the LBA with the nucleating agent to obtain a first mixture; mixing the first mixture with the isocyanate and the remaining part of the LBA.

[0025] Diluting the nucleating agent with a part of LBA facilitates the accurate metering of the nucleating agent and the rectification of the production process. Since the dosage of the nucleating agent is usually small, missing addition may have an adverse impact on the thermal conductivity of the foam. Adopting the technical route of diluting the nucleating agent, if the nucleating agent is missing, it will cause a change in the total amount of LBA (for example, the missing nucleating agent is replaced by an equal amount of LBA, resulting in an increase in the total amount of LBA), causing a change in the foam density. Thus, through the monitoring of the foam density, abnormalities that may occur during the production process can be detected in a timely manner, ensuring the long-term stable operation of the production line. If the nucleating agent is added directly, when the nucleating agent is missing, the total amount of the blowing agent will not change, and the impact on the foam density is small. The main problem is the abnormal thermal conductivity, which is not conducive to abnormal monitoring (the foam density test is simple to operate and has low requirements for the production line). In addition, the thermal conductivity is affected by various factors, including the material temperature, the material ratio, the gun head pressure, and even the abnormality of the polyol raw material. Therefore, it is difficult to quickly identify the root cause of the problem.

[0026] According to some embodiments of the present invention, in the first mixture, the mass ratio of the nucleating agent to LBA is ≥1:10, and the specific ratio can be selected according to needs to ensure that LBA can dissolve the nucleating agent.

[0027] According to some embodiments of the present invention, the raw materials for preparing the white material further include a flame retardant. The method for preparing the white material includes the following steps: mixing the raw materials including the polyol, surfactant, catalyst, water, flame retardant, and alkane blowing agent to obtain the white material. Among them, all components except the volatile alkane blowing agent can be premixed by the raw material supplier and then further mixed with the alkane blowing agent at the downstream application end to prepare the white material. This method can improve the foaming efficiency of the foaming production line and reduce equipment investment.

[0028] The present invention has successfully achieved a balance between low density and high strength by optimizing the foaming density and strength of the foam material, effectively alleviating the problem of the decrease in foam strength caused by the addition of the flame retardant. By refining the cell size, the diffusion of combustible gases is further inhibited. While ensuring good flame retardancy, the amount of the flame retardant can be reduced, significantly improving the strength of the foam material and achieving dual optimization of flame retardancy and strength.

[0029] Generally, flame retardants can be classified into two categories: reactive flame retardants and additive flame retardants according to whether they participate in chemical reactions. Among them, reactive flame retardants are used as one of the monomer raw materials in the synthesis of resins and become part of the resin molecular chain through chemical reactions. For example, dibromoneopentyl glycol is a commonly used reactive flame retardant for polyurethane foam materials. In contrast, additive flame retardants do not react chemically with polymers but are prepared into flame-retardant polymers through blending. There are many types of additive flame retardants, with lower raw material costs and a wider range of applications. Unless otherwise specified, the flame retardants in the present invention are all additive flame retardants.

[0030] Classified according to chemical composition, flame retardants can be divided into two major categories: organic flame retardants and inorganic flame retardants. Among them, inorganic flame retardants include metal hydroxides (such as aluminum hydroxide, magnesium hydroxide), metal oxides (such as antimony oxide, usually used as a synergistic flame retardant together with organic flame retardants, especially halogen-containing flame retardants), phosphorus-based inorganic flame retardants (such as red phosphorus, ammonium phosphate, calcium phosphate, magnesium phosphate, ammonium polyphosphate), boron-based flame retardants (such as zinc borate), carbon-based flame retardants (such as expanded graphite), etc.

[0031] Organic flame retardants include two major categories: halogen-containing flame retardants and halogen-free flame retardants. Common halogen-containing flame retardants include halogenated phosphate esters (such as tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(1,3-dichloropropyl) phosphate, tris(2,3-dichloropropyl) phosphate, tris(2-chloroisopropyl) phosphate, tris(2,2-dichloroisopropyl) phosphate, tris(1,3-dichloroisopropyl) phosphate, tetra(2-chloroethyl) ethylenediphosphate), halogenated hydrocarbons (hexabromocyclododecane, decabromodiphenylethane, brominated polystyrene, chlorinated paraffin), or halogenated aryl ethers (decabromodiphenyl ether).

[0032] Halogen-free flame retardants include phosphorus-based (mainly halogen-free phosphate esters, such as tricresyl phosphate, triphenyl phosphate, tris(2-ethylhexyl) phosphate, dimethyl methylphosphonate, triethyl phosphate, trimethyl phosphate, tributyl phosphate, tolyldiphenyl phosphate), nitrogen-based (such as melamine, melamine cyanurate), phosphorus-nitrogen intumescent flame retardants (such as N,N-bis(2-hydroxyethyl) aminomethyl diethyl phosphonate, melamine polyphosphate), etc.

[0033] According to some specific embodiments of the present invention, the flame retardant is selected from one or more of phosphate ester flame retardants, including one or more of halogenated phosphate ester flame retardants or halogen-free phosphate ester flame retardants, as described above. Phosphate ester flame retardants have good compatibility with polyurethane and relatively high flame retardancy efficiency, but at the same time have a certain plasticizing effect. In contrast, halogenated phosphate ester flame retardants have better flame retardant properties, but their plasticizing effect is stronger. When higher flame retardancy performance is required, halogenated phosphate ester flame retardants are preferably selected; while when higher foam strength is required, the usage amount of halogen-free phosphate ester flame retardants can be appropriately increased. The specific type and ratio of the flame retardant can be adjusted according to actual needs. On the premise of ensuring the flame retardancy performance, the usage amount of the flame retardant should be reduced as much as possible to minimize its adverse impact on the foam properties.

[0034] According to some specific embodiments of the present invention, the flame retardant is selected from one or more of tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(1,3-dichloropropyl) phosphate, tris(2,3-dichloropropyl) phosphate, tricresyl phosphate, triphenyl phosphate, tris(2-ethylhexyl) phosphate, tributyl phosphate, triethyl phosphate, trimethyl phosphate. The present invention does not limit the type of the flame retardant and is not limited to the types listed above.

[0035] According to some embodiments of the present invention, based on 100 parts by mass of the polyol, the flame retardant is 10 - 30 parts, for example, it can be 10 - 25 parts, or 10 - 20 parts, or 15 - 25 parts.

[0036] According to some embodiments of the present invention, before mixing the white material and the black material, the material temperatures of the two are independently controlled at 10 - 30°C respectively. Controlling the material temperature range can reduce the loss of the blowing agent while ensuring the reaction activity.

[0037] According to some embodiments of the present invention, the white material and the black material are injected and mixed under pressure through a gun head, wherein the gun head pressure is 100 - 150 bar. Generally, the greater the gun head pressure, the smaller the particle size after atomization of the black material and the white material, and the better the mixing effect. However, too high a gun head pressure may affect the long-term service life of the high-pressure foaming machine and increase the operation and maintenance costs of the production line.

[0038] According to some embodiments of the present invention, the gas-phase thermal conductivity of the high-boiling alkane at 25°C < 15 mW / m·K. The lower the gas-phase thermal conductivity, the more conducive it is to reducing the thermal conductivity of the foam.

[0039] According to some specific embodiments of the present invention, the high-boiling alkane is selected from one or more of cyclopentane, isopentane or n-pentane. Among them, cyclopentane has a relatively high boiling point and a relatively low gas-phase thermal conductivity, which is conducive to obtaining a foam material with a lower thermal conductivity and higher thermal stability; while isopentane and n-pentane have relatively low boiling points, which is conducive to improving the compressive strength of the foam material.

[0040] According to some specific embodiments of the present invention, the gas-phase thermal conductivity of the high-boiling alkane at 25°C < 13 mW / m·K. For example, the gas-phase thermal conductivity of cyclopentane at 25°C is 12.8 mW / m·K.

[0041] According to some embodiments of the present invention, the alkane blowing agent further includes a low-boiling alkane, and the boiling point of the low-boiling alkane is lower than that of the LBA. The gas-phase thermal conductivity of the low-boiling alkane is relatively high. When the thermal conductivity and thermal stability of the foam material meet the requirements, adding an appropriate amount of the low-boiling alkane helps to obtain a higher compressive strength.

[0042] According to some embodiments of the present invention, the low-boiling alkane includes one or two of n-butane or isobutane. The boiling points of n-butane and isobutane are moderate, which can improve the strength while reducing the negative impact on the thermal stability of the foam material.

[0043] According to some embodiments of the present invention, in the alkane blowing agent, the mass percentage of the high-boiling alkane ≥ 25%, for example, specifically ≥ 50%, ≥ 75% or ≥ 80%. On the premise of meeting the strength requirements, appropriately increasing the proportion of the high-boiling alkane and reducing the proportion of the low-boiling alkane (for example, the mass percentage of the low-boiling alkane ≤ 75%, ≤ 50%, ≤ 25% or ≤ 20%) helps to obtain a lower thermal conductivity and higher thermal stability.

[0044] According to some specific embodiments of the present invention, the alkane blowing agent is selected from cyclopentane.

[0045] According to some specific embodiments of the present invention, the alkane blowing agent is selected from a combination of at least one of isopentane, n-pentane, n-butane, isobutane and cyclopentane. The mass percentage of cyclopentane can be ≥25%, ≥50%, ≥75% or ≥80%.

[0046] According to some embodiments of the present invention, the polyol is selected from a combination of polyether polyol and polyester polyol. Generally, polyether polyols have better toughness and water resistance, while polyester polyols perform better in mechanical properties, heat resistance and flame retardancy. By reasonably matching the two, it is beneficial to achieve the optimization and balance of overall performance.

[0047] According to some specific embodiments of the present invention, the polyether polyol is selected from one or more of polyether polyols initiated with sucrose, polyether polyols initiated with sorbitol, and polyether polyols initiated with toluene diamine. Among them, the polyether polyol initiated with toluene diamine has higher reactivity, which helps to quickly establish the system viscosity in the initial stage of the reaction and enhance the foam-locking ability; the polyether polyols initiated with sucrose or sorbitol have higher functionality and the foam strength obtained is also higher.

[0048] According to some specific embodiments of the present invention, the polyether polyol is selected from a combination of polyether polyols initiated with sucrose, polyether polyols initiated with toluene diamine, and polyether polyols initiated with sorbitol, so as to better balance the reactivity and foam strength.

[0049] According to some specific embodiments of the present invention, in the polyether polyol, the mass ratio of the polyether polyol initiated with sucrose, the polyether polyol initiated with toluene diamine, and the polyether polyol initiated with sorbitol is (0.6 - 9):(0.8 - 11):1, specifically it can be (0.8 - 8):(1 - 8):1, or (1 - 7):(2 - 8):1, or (1 - 3.5):(1 - 4):1. The specific combination of polyether polyols can be reasonably selected according to actual application requirements to better balance the reactivity and foam fluidity. On the premise of ensuring that the performance meets the requirements, the dosage of the polyether polyol initiated with toluene diamine is reduced as much as possible to reduce the raw material cost.

[0050] According to some specific embodiments of the present invention, the polyester polyol is selected from phthalic anhydride-based polyester polyols. Polyester polyols belong to primary hydroxyl polyols and have a relatively high reactivity with isocyanate groups (higher than secondary hydroxyl polyether polyols starting with sucrose or sorbitol, etc.), and their structures are rich in benzene rings, which helps to improve the flame retardancy of the foam. When the polyester polyol is selected from phthalic anhydride polyester polyols, the cell structure is relatively delicate and the thermal conductivity of the foam is lower, but it may have a greater impact on the demolding property. In the application of traditional cylindrical electric water heaters, the requirement for demolding property is not high, and the amount of polyester polyol can be appropriately increased to improve the flame retardancy of the foam.

[0051] According to some embodiments of the present invention, based on 100 parts by mass of the polyol, the polyol includes: 70 - 90 parts of polyether polyol and 10 - 30 parts of polyester polyol. Among them, for the selection of polyether polyol, the matching methods listed above can be referred to.

[0052] According to some embodiments of the present invention, the average functionality of the polyol is 3 - 8.

[0053] According to some embodiments of the present invention, the average hydroxyl value of the polyol is 300 - 500 mgKOH / g.

[0054] Generally speaking, functionality is positively correlated with crosslinking degree and negatively correlated with fluidity; while a high hydroxyl value means higher reactivity and faster reaction rate, which is beneficial to improving production efficiency and foam strength. By controlling the functionality and hydroxyl value of the polyol within a suitable range, the requirements in terms of material cost, reactivity, foam fluidity, foam strength, adhesiveness, etc. can be better balanced.

[0055] According to some embodiments of the present invention, the catalyst is selected from at least two of foaming catalysts, gelling catalysts, and trimerization catalysts. Specifically, the foaming catalyst is selected from one or two of pentamethyldiethylenetriamine and bis(dimethylaminoethyl) ether; the gelling catalyst is selected from one or more of N,N - dihexylmethylamine, N,N - dimethylcyclohexylamine, N,N - dimethylbenzylamine, triethylenediamine, dibutyltin dilaurate, bis(dodecylthio)dibutyltin, 1,2 - dimethylimidazole, and 1 - methylimidazole; the trimerization catalyst is selected from one or more of tris(dimethylaminopropyl)hexahydrotriazine, 2 - hydroxypropyltrimethylformate ammonium salt, potassium acetate, and potassium isooctanoate. Among them, the foaming catalyst is used to promote pore formation; the gelling catalyst accelerates the gel reaction and plays a role in stabilizing and solidifying the foam, and the trimerization catalyst can increase the foaming rate, and the reaction product of isocyanate trimerization has good flame retardancy. Using different combinations of foaming agents is beneficial to forming a fine and uniform cell structure and improving the flame retardancy of the foam material. The above catalysts have low reactivity or no reaction with LBA, which helps to improve the long - term stability of the formulation.

[0056] According to some embodiments of the present invention, the catalyst at least includes a gel-type catalyst and a trimer-type catalyst.

[0057] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the blowing catalyst is 0 to 1 part.

[0058] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the blowing catalyst is 0.1 to 0.5 part.

[0059] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the gel-type catalyst is 1.5 to 5 parts.

[0060] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the gel-type catalyst is 1.5 to 3 parts.

[0061] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the gel-type catalyst is 2 to 3 parts.

[0062] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimer-type catalyst is 0.3 to 3 parts.

[0063] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimer-type catalyst is 0.3 to 1 part.

[0064] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimer-type catalyst is 0.5 to 1 part.

[0065] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the catalyst is 2 to 6 parts.

[0066] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the catalyst is 3 to 5 parts.

[0067] According to some embodiments of the present invention, the surfactant is selected from silicone surfactants. The silicone surfactant plays roles in emulsification, nucleation, and foam stabilization, and helps to obtain a fine cell morphology. The common type is polyether-modified silicone surfactants, and the main structure is a polysiloxane-oxyalkylene block or graft copolymer, which has positive effects in increasing component compatibility, emulsifying materials, stabilizing foam, and regulating cells. Specifically, a surfactant with a partial nucleation characteristic known in the art can be selected to obtain a finer cell structure.

[0068] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the surfactant is 3 to 6 parts.

[0069] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the water is 1.6 to 2 parts. Appropriately increasing the amount of water is more conducive to exerting the nucleation effect of water, reducing the cell size, further reducing the thermal conductivity of the foam, and obtaining higher foam strength. The amount of water should not be too high to reduce the adverse effects of carbon dioxide on the gas-phase thermal conductivity and thermal stability.

[0070] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the water is 1.8 to 2 parts.

[0071] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the alkane blowing agent is 4 to 10 parts.

[0072] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the alkane blowing agent is 6 to 10 parts.

[0073] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the LBA is 22 to 30 parts, for example, it can be 22 to 28 parts.

[0074] On the premise that the thermal conductivity meets the requirements, appropriately reducing the amount of LBA and increasing the proportion of cyclopentane helps to improve the thermal stability of the foaming material.

[0075] According to some embodiments of the present invention, the isocyanate is selected from polymethylene polyphenyl isocyanate, which has a high average functionality (generally > 2.6) and can significantly improve the foam strength. This isocyanate is a low-viscosity liquid at room temperature, does not need to be heated and melted during use, is convenient to operate, and has low volatility and high safety.

[0076] According to some embodiments of the present invention, the molar ratio of isocyanate groups in the black material to the active hydroxyl groups in the white material (or simply referred to as the black material index) is (1.3 to 1.6):1. Both polyol and water have reactivity with isocyanate groups. Considering that 1 mol of water consumes 2 mol of isocyanate groups, the molar number of active hydroxyl groups is calculated as: the sum of the molar number of hydroxyl groups in the polyol and twice the molar number of water.

[0077] Controlling the isocyanate groups to be slightly higher than the chemical equivalent makes the reaction more complete. In addition, the trimerization product of isocyanate groups in the black material (under the action of a trimerization catalyst) has excellent flame retardant properties. Appropriately increasing the black material index helps to improve the flame retardant properties. To ensure the fluidity and filling property of the foam, the black material index should not be too high.

[0078] The second aspect of the present invention provides a polyurethane foam material prepared by the above preparation method.

[0079] The polyurethane foam material according to the second aspect of the present invention has at least the following beneficial effects:

[0080] The above polyurethane foam material is prepared by the above preparation method. Therefore, it has at least all the beneficial effects brought by the embodiments of the above preparation method. Furthermore, this material has characteristics such as a low thermal conductivity, low density, and excellent thermal stability. At the same time, there are fewer air pit defects on the material surface, and the strength and cost-effectiveness of the material can be ensured.

[0081] According to some embodiments of the present invention, the thermal conductivity of the polyurethane foam material at 22.5 °C is ≤ 18.7 mW / m·K (for example, 17.4 - 18.7 mW / m·K), more typically ≤ 18.5 mW / m·K (for example, 17.4 - 18.4 mW / m·K), and even ≤ 18.2 mW / m·K (for example, 17.4 - 18.2 mW / m·K); after being subjected to a 24-hour aging treatment under the conditions of a humidity of 50% ± 5% and a temperature of 40 °C, the increase in the thermal conductivity of the material at 22.5 °C is < 0.8 mW / m·K (for example, 0.5 - 0.8 mW / m·K, and not including 0.8 mW / m·K), more typically ≤ 0.7 mW / m·K (for example, 0.5 - 0.7 mW / m·K).

[0082] According to some embodiments of the present invention, the density of the polyurethane foam material in the free foaming state (or free foam density) < 24 kg / m 3 , for example, specifically 23 - 23.5 kg / m 3 . Among them, "free foaming" means that the foaming material is not restricted by the mold cavity and directly foams.

[0083] According to some embodiments of the present invention, calculated per square meter, the number of air pit defects on the surface of the polyurethane foam material with a diameter greater than 3 cm is less than 5, for example, specifically 4 - 4.6. It should be noted that this defect number is based on the surface air pit defect number measured for the polyurethane foam material prepared by the conventional pressure injection mold foaming process. Among them, the injection pressure can be controlled at 100 - 150 bar.

[0084] According to some embodiments of the present invention, the compression strength of the polyurethane foam material ≥ 120 kPa, and the test standard is GB / T 8813 - 2020.

[0085] According to some embodiments of the present invention, the flame retardancy of the polyurethane foam material is HF-1 level, and the test standard is GB / T 8332-2008. After further adding a flame retardant (for example, selected according to the type and dosage of the flame retardant in the above embodiments), this flame retardant level can be achieved. For water heater applications, excellent flame retardancy is usually required, so generally it is required to reach HF-1 level; while for outdoor application scenarios such as solar water heaters, the requirement for flame retardancy is relatively low.

[0086] The third aspect of the present invention provides a household appliance, including the above-mentioned polyurethane foam material, or the polyurethane foam material prepared by the above-mentioned preparation method.

[0087] The household appliance according to the third aspect of the present invention has at least the following beneficial effects:

[0088] In view of the performance advantages of the polyurethane foam material prepared by the above method, such as low density, low thermal conductivity, high strength, high apparent quality, excellent thermal stability, and low production cost, it can well meet the heat insulation requirements of household appliances such as water heaters.

[0089] According to some embodiments of the present invention, the household appliance includes an electric water heater, a solar water heater, or an air source heat pump water heater.

[0090] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0091] Figure 1 is a flowchart of the preparation method of the polyurethane foam material in Example 1-1 of the present invention. Detailed Embodiments

[0092] The embodiments of the present invention will be described in detail below. The embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention.

[0093] In this article, "a plurality of" means more than two, and "above", "below", or "not exceeding" all include the numerical value itself.

[0094] The numerical ranges involved all include the endpoint values and cover any sub-range within this range, for example, the range obtained by any combination of the specifically listed numerical values.

[0095] "Mixing the raw materials for the preparation of..." includes both mixing all the raw materials for preparation in one step and the method of step-by-step mixing. For example, "mixing the raw materials for the preparation of the polyurethane foam material" includes the method of one-step mixing or step-by-step mixing. Among them, step-by-step mixing is more suitable for actual foaming production lines. Specifically, some components including polyol (for example, polyol, surfactant, catalyst, water, and physical blowing agents (such as alkane blowing agents and LBA), etc.) can be premixed to form the white material; the white material is mixed with isocyanate (black material) for reaction to achieve foaming. When a volatile physical blowing agent is added to the white material, the raw material supplier can complete the premixing of the components other than this physical blowing agent, and then further mix these physical blowing agents at the downstream application end to prepare the white material. This method can improve the foaming efficiency of the foaming production line and reduce equipment investment.

[0096] The method for preparing the polyurethane foam material of this embodiment includes the following steps:

[0097] S1. Mix the raw materials for preparation including 100 parts by mass of polyol, 2 - 6 parts by mass of surfactant, 1.8 - 9 parts by mass of catalyst, 1.5 - 2.1 parts by mass of water, and 2 - 10 parts by mass of alkane blowing agent to obtain the white material;

[0098] S2. Mix the raw materials for preparation including 20 - 35 parts by mass of LBA and 150 - 200 parts by mass of isocyanate to obtain the black material;

[0099] S3. Mix the white material and the black material, and react to obtain the polyurethane foam material;

[0100] Among them, the alkane blowing agent includes at least high-boiling alkanes, and the boiling point of the high-boiling alkanes is higher than the boiling point of LBA.

[0101] It should be noted that the description order of steps S1 to S3 is only for exemplary illustration and does not mean that there is a strict sequence between the steps.

[0102] By mixing LBA separately from the white material, it is avoided to contact-react with the commonly used organic amine catalyst in the white material, ensuring that the formulation with LBA as the main blowing agent has excellent long-term stability and reliability. At the same time, premixing the alkane blowing agent with good chemical stability with the polyol can reduce the viscosity of the polyol, facilitate the material transportation, and will not affect the stability of the white material.

[0103] The traditional premixing process adopts a one-step method, that is, cyclopentane and other alkane foaming agents, LBA and nucleating agents are added to POL at one time, stored in the premixing station and transported to the white material working tank of the high-pressure foaming machine through a pipeline (for electric water heater products, the white material and the black material are mixed by the high-pressure foaming machine and injected into the cavity of the water heater product for foaming, and the final product is obtained through subsequent assembly processes). These transitions or transportations require a certain amount of time (cyclopentane and other alkane foaming agents are flammable and explosive. Based on safety considerations, traditional premixing stations are built far away from the production line) and inevitably have a parking process. Therefore, the nucleophilic reaction of LBA with the organic tertiary amine catalyst is inevitable, which may produce fluoride ions, chloride ions, ammonium ions, etc. The above reaction will not only consume the organic tertiary amine catalyst and affect the subsequent foaming chemical reaction rate, but also make the main foaming agent LBA ineffective, thereby affecting the density and thermal conductivity of the foam product. Especially when the temperature is high in the summer, long-term parking will inevitably affect the stability and long-term reliability of the foaming white material, and have an adverse effect on the energy consumption, strength and other properties of the final product. This solution effectively solves the above problems by mixing LBA and white material separately to avoid long-term contact between LBA and organic amine catalyst.

[0104] In addition, adding LBA to the black material and making full use of the solubility of isocyanate in LBA can effectively reduce the air pit defects in the foam molding process. The number of air pit defects with a diameter greater than 3 cm on the surface of the foam material is reduced to less than 4.55 per square meter, significantly improving the apparent quality of the foam material.

[0105] From the perspective of formula design, this embodiment uses LBA (boiling point 19°C, gas phase thermal conductivity 10.2mW / m·K at 20°C) as the main physical foaming agent, alkane foaming agent (including high boiling point alkanes, such as cyclopentane, boiling point 49.2°C, gas phase thermal conductivity 12.8mW / m·K at 25°C) as the auxiliary physical foaming agent, and water as the chemical foaming agent (water reacts with isocyanate to generate carbon dioxide, boiling point -56.6°C). Through the reasonable combination of high boiling point, medium boiling point and low boiling point foaming agents, it is possible to achieve an optimized balance in terms of cost, thermal conductivity, long-term reliability and foam strength, thereby obtaining a cost-effective polyurethane foam material.

[0106] The thermal conductivity of polyurethane foam is mainly affected by solid-phase thermal conductivity, gas-phase thermal conductivity, and radiative thermal conductivity. Among them, the proportion of solid-phase thermal conductivity is about 20% - 30%, and the proportion of gas-phase thermal conductivity is about 60% - 70%. Therefore, reducing the thermal conductivity of polyurethane foam requires focusing on two factors: solid-phase thermal conductivity and gas-phase thermal conductivity. The main method to reduce gas-phase thermal conductivity is to use blowing agents with low thermal conductivity to reduce the overall thermal conductivity of the gas phase; reducing solid-phase thermal conductivity is achieved by reducing the foam density and cell size. At the same density, smaller-diameter cells have a longer heat transfer path compared to larger-diameter cells, thus effectively reducing solid-phase thermal conductivity.

[0107] LBA has the characteristics of low gas-phase thermal conductivity, being non-flammable and non-explosive, and high vapor pressure. Using it as the main blowing agent helps to obtain a lower thermal conductivity and higher foam strength. However, LBA has a relatively high unit price and large molecular weight, resulting in a high cost when used as a single physical blowing agent.

[0108] Different from polyurethane foam used in cold insulation applications (such as refrigerators with an internal temperature < 10°C), in heat insulation applications (such as water heaters with an inner tank water temperature > 40°C), when the boiling point of the gas inside the cells is relatively low, the internal gas pressure is relatively high, making it easy to have gas exchange with the outside air, thus affecting the thermal stability of the foam material. Therefore, to ensure the long-term stability of the water heater insulation material, it is usually necessary to control the foam density, such as the free foam density being much higher than 24 kg / m 3 , usually greater than 25 kg / m 3 . By reducing the foaming ratio, heat exchange can be effectively reduced.

[0109] In this embodiment, high-boiling alkanes are used to replace a part of LBA, which can improve the thermal conductivity stability of the foam under heating conditions and reduce the raw material cost. At the same time, adding a certain amount of chemical blowing agent water makes full use of the low boiling points of carbon dioxide and LBA to increase the internal cell pressure, effectively enhancing the foam strength.

[0110] During the cell nucleation process, the number and nucleation rate of the original cell nuclei determine the final number and size of the cells. During the cell growth process, the newly generated gas often preferentially fills the original gas bubbles. Therefore, the more the number of original gas bubbles, the more the number of finally formed cells. The key to controlling cell nucleation is to control the number and nucleation rate of cell nuclei. The more the number of original cell nuclei and the faster the nucleation rate, the smaller the formed cell size. In the solution of this embodiment, using water as the chemical blowing agent has a good nucleation effect, which helps to form a finer cell structure and extend the heat transfer path in the solid part, thereby reducing the solid-phase thermal conductivity.

[0111] In terms of cell suppression and cell coalescence, there are differences in the gas pressure of cells with different pore sizes. The internal pressure of small-sized cells is greater than that of large-sized cells, resulting in the tendency of small cells to merge into large cells. To reduce cell coalescence, the use of surfactants is crucial. Surfactants can reduce the surface tension between polyols, isocyanates, and blowing agents, stabilize the reaction system, and reduce the pressure difference between cells by decreasing the surface energy of the reaction system, thereby reducing the occurrence of cell coalescence and promoting the formation of fine cells.

[0112] Therefore, through the reasonable combination of components in this embodiment, the low thermal conductivity of LBA, the promotion of foam strength by the low boiling points of LBA and carbon dioxide, and the contribution of high-boiling alkanes to the stability of thermal conductivity are fully utilized. At the same time, the nucleation effect of water helps to obtain a more delicate cell structure, overcome the deficiency of the high thermal conductivity of carbon dioxide and cyclopentane, and thus maintain the thermal conductivity advantage of the LBA foaming system.

[0113] The polyurethane foam material of this embodiment has the advantages of low thermal conductivity (the foam thermal conductivity can be as low as below 18.7 mW / m·K at 22.5°C, especially when the alkane blowing agent is cyclopentane, the foam thermal conductivity can be further reduced to below 18 mW / m·K), good thermal stability, high foam strength, and low comprehensive cost. Further, through the improvement of the mixing process, the surface quality of this foam material has been significantly improved, reducing apparent defects such as air pits, thus better meeting the requirements of heat preservation application fields such as electric water heaters and helping to improve the energy efficiency of products.

[0114] Specifically, when a nucleating aid is further added, the preparation method of the black material includes the following steps: mixing the preparation raw materials including LBA, nucleating aid, and isocyanate, and that's it. More specifically, the preparation method of the black material may include the following steps: mixing a part of LBA with the nucleating aid (for example, the mass ratio of the nucleating aid to LBA ≥ 1:10) to obtain a first mixture; mixing the first mixture with isocyanate and the remaining part of LBA, and that's it. The nucleating aid has good compatibility with LBA. Therefore, adding the nucleating aid and LBA together to the black material helps to improve the solubility of the nucleating aid and enhance its dispersion uniformity, especially helps to improve the apparent quality of the foam material, such as reducing surface pore defects. In addition, this method can improve the metering accuracy of the nucleating aid and effectively correct the situation of missing addition of the nucleating aid during the production process.

[0115] Specifically, the nucleating agent is selected from one or more of C3-C8 perfluoroolefin compounds. For example, it can specifically be selected as hexafluoropropene, perfluoro(4-methyl-2-pentene), perfluoro(2-methyl-2-pentene), hexafluorobutadiene or a mixture thereof. The commercially available grades include PF-5056, FA-188, PF-90, etc. The mass of the nucleating agent does not exceed 3% of the mass of the polyol. For example, the nucleating agent is 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or any value between any two of the mass of the polyol.

[0116] Specifically, when a higher requirement for flame retardancy is needed, a flame retardant can be further added. Then the preparation method of the white material includes the following steps: mixing the preparation raw materials including polyol, surfactant, catalyst, water, flame retardant, and alkane blowing agent, and that is it. Through the optimized balance of low foam density and high strength, the problem that the foam strength is reduced due to the plasticizing effect caused by the flame retardant is alleviated. Furthermore, while ensuring good flame retardancy and foam strength, low density, high thermal conductivity and stability are maintained. In addition, the refined cell size helps to inhibit the diffusion of combustible gases and ensures good flame retardancy.

[0117] Among them, the flame retardant is selected from one or more of phosphate flame retardants (including halogenated phosphate esters and non-halogenated phosphate esters). Non-limiting examples of halogenated phosphate esters include tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate (TDCP), tris(2,3-dichloropropyl) phosphate (TDCPP), tris(2-chloroisopropyl) phosphate, tris(2,2-dichloroisopropyl) phosphate, tris(1,3-dichloroisopropyl) phosphate, tetra(2-chloroethyl) ethylenediphosphate, etc. Non-limiting examples of non-halogenated phosphate esters include tricresyl phosphate (TCP), triphenyl phosphate (TPP), tris(2-ethylhexyl) phosphate (TEHP), dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), trimethyl phosphate (TMP), tributyl phosphate (TBP), etc. More specifically, the flame retardant is selected from one or more of tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, tris(1,3-dichloropropyl) phosphate, tris(2,3-dichloropropyl) phosphate, tricresyl phosphate, triphenyl phosphate, tris(2-ethylhexyl) phosphate, tributyl phosphate, triethyl phosphate, trimethyl phosphate. Examples of the addition amount of the flame retardant: based on 100 parts by mass of the polyol, the flame retardant is 10-30 parts, or 10-20 parts.

[0118] It should be noted that all the above mixing processes can be carried out separately in a static mixer (such as a tubular static mixer). The materials after each mixing can be stored separately in a liquid storage tank for use in subsequent processes. The related equipment is commonly used in this field and can be reasonably set according to specific requirements.

[0119] Before mixing the white material and the black material, first stabilize their respective temperatures at 10 - 30 °C. For example, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C or any value between any two of them can be selected. Controlling the material temperature range can ensure the reaction activity while reducing the loss of the blowing agent. The temperatures of the white material and the black material can be the same or different. In addition, pre - maintaining the temperatures of the black material and the white material at a constant value close to the reaction temperature during mixing helps to improve production efficiency.

[0120] The pressure of the mixing nozzle is controlled at 100 - 150 bar. For example, 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar or the pressure between any two of them can be selected. Controlling the mixing pressure can ensure the mixing effect and avoid excessive pressure (such as exceeding 150 bar) causing too large an operating load on the equipment.

[0121] Specifically, based on 100 parts by mass of the polyol, water is 1.5 parts, 1.6 parts, 1.8 parts, 2 parts, 2.1 parts or any value between any two of them; and / or, the alkane blowing agent is 2 parts, 4 parts, 6 parts, 8 parts, 10 parts or any value between any two of them; and / or, LBA is 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 35 parts or any value between any two of them.

[0122] Referring to Table 1, the performance parameters of LBA, carbon dioxide and common alkane blowing agents are compared. For alkanes with a boiling point higher than that of LBA, at least one of cyclopentane, isopentane or n - pentane can be selected. If higher requirements are placed on the thermal conductivity and long - term thermal stability, cyclopentane or a mixed alkane blowing agent containing a certain proportion of cyclopentane (for example, the mass percentage of cyclopentane in the alkane blowing agent ≥ 25%, ≥ 50%, ≥ 75% or ≥ 80%) can be selected. (Except for cyclopentane, the other alkanes can be high - boiling - point alkanes such as isopentane, n - pentane, or low - boiling - point alkanes such as n - butane, isobutane).

[0123] If higher requirements are placed on the compressive strength of the foam, alkanes with a lower boiling point, such as isopentane, n - pentane, or a combination of high - boiling - point alkanes and low - boiling - point alkanes (such as n - butane, isobutane, etc.) can be selected. By reasonably selecting the ratio of high - boiling - point and low - boiling - point alkanes (for example, increasing the proportion of high - boiling - point alkanes for thermal stability requirements and increasing the proportion of low - boiling - point alkanes for strength requirements), foaming materials that meet different requirements can be obtained.

[0124] Table 1

[0125]

[0126] In the above table: Note 1: The lower the boiling point of the physical blowing agent, the greater the internal pressure it can provide for the pores, which is beneficial to providing sufficient strength for the foam when the foam density is low to meet the usage requirements. However, if the boiling point is too low, the foaming operation is difficult. Note 2: The lower the gas-phase thermal conductivity, the lower the gas-phase thermal conductivity it can provide for the foam, which is beneficial to reducing the thermal conductivity of the foam. The gas-phase thermal conductivity is related to the test temperature. Generally, the higher the test temperature, the higher the gas-phase thermal conductivity. Note 3: Carbon dioxide is generated by the reaction of the chemical blowing agent water with isocyanate groups.

[0127] During the formation process of polyurethane foam, the reactions between various components proceed step by step. After adding a high amount of blowing agent, the viscosity of the initial mixture is usually not high. For a foaming system with LBA as the main blowing agent, since the boiling point of LBA is only 19°C, if the viscosity of the reaction system cannot be increased quickly or external energy is not input, the size of the early pores during the foaming process will be difficult to continuously increase, which may lead to problems such as pore collapse. Therefore, from the perspective of controlling the system viscosity, select a suitable monomer and catalyst system, and reasonably regulate the polymerization reaction rate to ensure the matching of the foaming and polymerization processes to avoid the collapse of the pore structure caused by too slow an increase in viscosity.

[0128] Based on the above design concept, on the basis of the foregoing multi-component blowing agent design, a highly active polymerization reaction system can be selected to rapidly increase the viscosity during the polymerization process and enhance the foam-locking ability. For example, calculated based on a total of 100 parts by mass of polyol monomers, among them, polyether polyol is 70 - 90 parts by mass (such as 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or any value between any two of them), polyester polyol is 10 - 30 parts by mass (such as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts or any value between any two of them), the average hydroxyl value is 300 - 500 mgKOH / g (such as 300 mgKOH / g, 350 mgKOH / g, 400 mgKOH / g, 450 mgKOH / g, 500 mgKOH / g or any value between any two of them), and the average functionality is 3 - 8 (such as 3, 4, 5, 6, 7, 8 or any value between any two of them).

[0129] The polyether polyols may specifically include (meeting the total amount within the target range): 20-45 parts by mass of polyether polyol initiated with sucrose, 25-55 parts by mass of polyether polyol initiated with toluenediamine, and 5-30 parts by mass of polyether polyol initiated with sorbitol. The polyether polyol initiated with toluenediamine contains a benzene ring in its structure, has high rigid reactivity, helps to quickly establish the system viscosity in the initial stage of the reaction, and enhances the foam-locking ability; the polyether polyols initiated with sucrose and sorbitol have high functionality and the resulting foams have high strength; the polyester polyol belongs to primary hydroxyl polyol and has a higher reactivity with isocyanate groups (higher than that of secondary hydroxyl polyether polyols initiated with common substances such as sucrose or sorbitol), and its structure is rich in benzene rings, which helps to improve the flame retardancy of the foam. Through the mixed combination of polyols, the reaction rate and cell morphology can be better adjusted, and the foaming process can be optimized.

[0130] Specifically, non-limiting examples of the polyether polyol initiated with sucrose include: NJ-8243, NJ-8238, NJ-8345, NJ-8252, NJ-4502, NJ-8209, etc. of Ningwu New Materials; YD-8310, YD-8315, YD-8345, YD-8350, YD-8666, YD-8669, YD-8260, etc. of Hebei Yadong Chemical Industry; R4110B, R8238, R8243, R6001C, etc. of Shandong Yinuowei; SC-450, SC-455, SC-4110, etc. of Guodu Chemical Industry. Non-limiting examples of the polyether polyol initiated with sorbitol include: NJ-6045, NJ-6256, NJ-6207, NJ-6206, NJ-6249, NJ-6209, NJ-6305B, NJ-6305C, NJ-6305S, etc. of Ningwu New Materials; YD-600, YD-635, YD-6205, etc. of Hebei Yadong Chemical Industry; R6048, R6205, R6207, etc. of Shandong Yinuowei; ST-430, ST-480, ST-481, ST-501, etc. of Guodu Chemical Industry. Non-limiting examples of the polyether polyol initiated with toluenediamine include: NJ-410H, NJ-430H, NJ-410HN, NJ-3445, NJ-406A, etc. of Ningwu New Materials; YD-TD440 of Hebei Yadong Chemical Industry; TD-400, TD-400L, TD-400P, TD-401, TD-405, etc. of Guodu Chemical Industry. Non-limiting examples of the polyester polyol include: PS-3152, PS-4051, PS-2352, etc. of Nanjing Stepan Chemical; PE-B503L of Shandong Yinuowei.

[0131] It should be understood that the specific types or ratios of the polyols listed above do not have an exclusive or exhaustive meaning. There are numerous types and grades of polyols, and different polyol combinations (including different compositions or ratios) may have similar or comparable effects. The appropriate polyol system can be selected with reference to the above solutions. For example, referring to the types and ratio ranges of the polyols listed above, one or more polyol combinations with a functionality of 3 to 8 are selected, and the average hydroxyl value is controlled to be 300 to 500 mgKOH / g, or other polyols with similar properties are selected for combination.

[0132] The surfactant is preferably an organosilicon surfactant with a preferential nucleation property, including but not limited to one or more of B-8481, B-84813, EP-R-S 88, MG-828, MG-945, etc. of Evonik Industries. Such surfactants play an active role in emulsification and foam homogenization, helping to reduce bubble coalescence and foam breakage. Further, a perfluoroolefin-based highly efficient nucleation aid is used to enhance the nucleation ability of the bubbles, thereby obtaining a polyurethane foam with small cell size and low thermal conductivity. Based on 100 parts by mass of the polyol, the mass of the surfactant is 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, or any value between any two of them.

[0133] Since LBA is added to the black material, LBA will basically not come into contact with the catalyst and react before foaming, so there will be no stability problems. Therefore, in this solution, the type of catalyst selected is not subject to specific restrictions. Specifically, the catalyst can be selected from blowing catalysts (such as pentamethyldiethylenetriamine, bis(dimethylaminoethyl) ether, etc.), gelling catalysts (such as N,N-dihexylmethylamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, triethylenediamine, dibutyltin dilaurate, bis(dodecylthio)dibutyltin, etc.), and trimerization catalysts (such as tris(dimethylaminopropyl)hexahydrotriazine, 2-hydroxypropyltrimethylformate ammonium salt, potassium acetate, potassium isooctanoate, etc.) for combination, which is beneficial to regulating the reaction rate and flame retardancy performance.

[0134] Based on 100 parts by mass of the polyol, the catalyst is 1.8 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or any value between any two of them. It can be understood that when the catalyst includes multiple types of the above-mentioned blowing catalysts, gelling catalysts, and trimerization catalysts, the appropriate catalyst dosage can be selected with reference to the ratio ranges listed above, and the total mass of the catalyst should meet 1.8 to 9 parts / 100 parts of polyol.

[0135] Specifically, based on 100 parts by mass of the polyol, the catalyst includes: the foaming catalyst is 0 to 1 part (such as 0 part, 0.2 part, 0.5 part, 0.8 part, 1 part or any value between any two of them), the gelling catalyst is 1.5 to 5 parts (such as 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts or any value between any two of them), and the trimerization catalyst is 0.3 to 3 parts (such as 0.3 part, 0.5 part, 0.7 part, 1 part, 1.5 part, 2 part, 2.5 part, 3 part or any value between any two of them).

[0136] It should be understood that the types or their ratios of the catalysts listed above do not have an exclusive or exhaustive meaning. It is easy to select a suitable catalyst system with reference to the above scheme, or select other catalyst systems with similar properties.

[0137] The isocyanate can be a liquid polymethylene polyphenyl isocyanate. For example, when the mass fraction of isocyanate groups is 30 wt% to 33 wt%, the optional grades include Wanhua Chemical PM-200, PM-2010, Covestro 44V20, Dow Chemical PAPI27, PAPI135, BASF M20s, etc. The addition amount of the isocyanate is preferably controlled within the range of making the black material index (1.3 to 1.6):1. For example, the specific black material index is 1.3:1, 1.4:1, 1.5:1, 1.6:1 or any value between any two of them.

[0138] The following is a detailed description through specific examples. In the following examples, the relevant raw materials are described as follows:

[0139] Polyol: Polyether polyol NJ-8238 (hydroxyl value 380 ± 15 mgKOH / g, functionality 5 - 6) starting from sucrose, 30 parts by mass; polyether polyol TD405 (hydroxyl value 397.5 ± 17.5 mgKOH / g, functionality 4) starting from toluenediamine, 35 parts by mass; polyether polyol NJ-6045 (hydroxyl value 450 ± 15 mgKOH / g, functionality 5 - 6) starting from sorbitol, 15 parts by mass; polyester polyol PS-3152 (hydroxyl value 315 ± 15 mgKOH / g, functionality 2), 20 parts by mass; average functionality is about 4.3, and average hydroxyl value is about 383 mgKOH / g.

[0140] Surfactant: Evonik Chemical EP-R-S 88.

[0141] Flame retardant: mass ratio of TCPP:TCEP = 11:4.

[0142] Nucleating aid: PF-5056.

[0143] Isocyanate: Wanhua PM-200.

[0144] The relevant test methods are as follows:

[0145] 1. Free foam density: Spray an appropriate amount of foaming material with a pipette tip to foam freely, measure the density by the water displacement method, conduct parallel tests 3 times, and take the average of the results.

[0146] 2. Thermal conductivity: Cut the foamed sample into peeled foam with dimensions of (200 ± 5) mm × (200 ± 5) mm and a thickness of (25 ± 1) mm using a cutting machine, and measure the thermal conductivity at a temperature of 22.5 °C using a thermal conductivity meter. Take 2 samples, and take the average of the results; additionally, place samples of the same specification and quantity in an aging oven, and conduct an aging treatment for 24 h under the conditions of a dark environment, a humidity of 50% ± 5%, and a temperature of 40 °C, and then measure its thermal conductivity according to the same method.

[0147] 3. Number of surface air pit defects: Prepare foam blocks using a standard Laneige mold (cavity size: 110 cm × 30 cm × 5 cm), and count the number of air pit defects with a diameter greater than 3 cm on both side surfaces (110 cm × 30 cm).

[0148] 4. Flame retardancy performance: The test is based on GB / T 8332-2008 "Test Method for Combustion Performance of Cellular Plastics: Horizontal Burning Method", and the size of the foam board is 150 mm × 50 mm × 13 mm.

[0149] 5. Compressive strength: The test is based on GB / T 8813-2020 "Rigid Cellular Plastics - Determination of Compressive Properties", the specimen size is (50 ± 1) mm × (50 ± 1) mm × (30 ± 1) mm, the test speed is (5 ± 1) mm / min, apply loads to the specimen in three directions (length / width / height) respectively, the number of specimens in each direction is 3, take the average of the 3 test data in each direction, and take the minimum value of the 3 averages. The requirement for compressive strength is ≥ 120 kPa.

[0150] Example 1 and Comparative Example 1

[0151] The raw material compositions and main process parameters of Example 1-1, Example 1-2, Comparative Example 1-1, and Comparative Example 1-2 are shown in Table 2. Among them, POL (which can be premixed by the raw material supplier) is composed as follows: 100 parts by mass of polyol, 4.0 parts by mass of surfactant, 1.8 parts by mass of water, 15 parts by mass of flame retardant, 3.4 parts by mass of catalyst (0.2 parts by mass of pentamethyldiethylenetriamine, 2.5 parts by mass of N,N-dimethylcyclohexylamine, 0.7 parts by mass of potassium acetate), with a total of 124.2 parts by mass.

[0152] Example 1-1

[0153] See Figure 1, the preparation method of the polyurethane foam material in this embodiment includes the following steps:

[0154] S1. Premixing of the white material: Provide a mixed raw material composed of polyol, surfactant, water, flame retardant, and catalyst, denoted as POL; mix POL with an alkane blowing agent (cyclopentane, abbreviated as CP) to obtain the white material;

[0155] S2. Premixing of the black material: Add LBA and nucleating aid to the isocyanate and mix to obtain the black material;

[0156] S3. Foaming: After controlling the temperature of the white material and the black material, mix them through the high-pressure foaming machine gun head (the gun head pressures of the white material and the black material are both 130 bar), and react to achieve foaming.

[0157] Example 1-2

[0158] Compared with Example 1-1, the difference is that before step S3, both the white material and the black material are placed in an incubator and aged under the conditions of a dark environment, a relative humidity of 50% ± 5%, and a temperature of 45°C. The aging times are 10 days and 20 days respectively (1 day = 24 hours).

[0159] Comparative Example 1-1

[0160] The preparation method of the polyurethane foam material includes the following steps:

[0161] S1. Premixing of the white material: Provide a mixed raw material composed of polyol, surfactant, water, flame retardant, and catalyst, denoted as POL; mix POL with LBA, an alkane blowing agent (CP), and a nucleating aid to obtain the white material;

[0162] S2. Foaming: After controlling the temperature of the white material and the black material (isocyanate), mix them through the high-pressure foaming machine gun head and react to achieve foaming.

[0163] Comparative Example 1-2

[0164] Compared with Comparative Example 1-1, the difference is that before step S2, both the white material and the black material are placed in an incubator and aged under the conditions of a dark environment, a relative humidity of 50% ± 5%, and a temperature of 45°C. The aging times are 2 days and 4 days respectively (1 day = 24 hours).

[0165] The main characteristic parameters of the foam materials of Example 1-1, Example 1-2, Comparative Example 1-1, and Comparative Example 1-2 are shown in Table 2.

[0166] Table 2

[0167]

[0168] In Table 2, the fiber time refers to the time from the start of mixing the black material and the white material until the appearance of fibrous drawing; the surface curing time refers to the time from the start of mixing the black material and the white material until the loss of fluidity and the appearance of a solidified state.

[0169] From the comparison between Comparative Example 1-1 and Comparative Example 1-2, it can be seen that as the aging time prolongs or the aging temperature increases, the stable period of the material significantly shortens, manifested as the prolongation of the fiber time and the surface curing time. This indicates that the reaction between the catalyst and LBA causes the failure of LBA, the loss or decrease in the activity of the catalyst, thereby affecting the foaming morphology, resulting in an increase in the thermal conductivity, and even the occurrence of bubble bursting. Therefore, the chemical reaction between LBA and organic amine has a strong dependence on temperature and time. Generally, the higher the temperature and the longer the contact time, the shorter the stable period of LBA. When LBA is added to the white material, after aging at 45°C for 4 days, the foaming performance significantly deteriorates, and phenomena such as bubble bursting occur.

[0170] Comparing Example 1-1 and Example 1-2, it can be seen that adding LBA to the black material can effectively avoid the contact between LBA and the organic amine catalyst. Even after aging at 45°C for 20 days, no obvious deterioration problem occurs in the foaming performance. Therefore, the mixing process of adding LBA to the black material can effectively extend the stable period of LBA, thereby ensuring the long-term reliability and stability of the formulation. Based on the physical and chemical properties of the blowing agent, adding cyclopentane with good chemical stability to the white material can not only effectively reduce the viscosity of the polyol, improve the fluidity of the material, but also have no impact on the stability of the white material.

[0171] In addition, adding LBA to the black material (Example 1-1) makes full use of the good solubility of the black material in the physical blowing agent. Compared with adding all the physical blowing agents to the white material (Comparative Example 1-1), the foam material prepared by this process has fewer defects in appearance, which helps to improve the appearance quality of the final product.

[0172] Example 2

[0173] The compositions of the black material and the white material and the preparation method of the polyurethane foam materials in Examples 2-1 to 2-6 refer to Example 1-1, except that the addition amounts of the nucleating aids are different, as shown in Table 3 specifically.

[0174] Table 3

[0175]

[0176] It can be seen that the use of nucleating agents can significantly reduce the thermal conductivity of the foam, and with the increase in the dosage of nucleating agents, the thermal conductivity of the foam shows a gradually decreasing trend. Since nucleating agents belong to perfluorohydrocarbon compounds and have a relatively high unit price, and when the dosage exceeds a certain level, the effect of reducing the thermal conductivity of the foam tends to level off. Therefore, when the thermal conductivity meets the requirements, the dosage of nucleating agents should be reduced as much as possible.

[0177] Example 3

[0178] The POL compositions of Examples 3-1 to 3-2 are the same as those of Example 1-1. For the relevant raw material compositions and main process parameters, please refer to Table 4.

[0179] Example 3-1

[0180] A method for preparing a polyurethane foam material, comprising the following steps:

[0181] S1. Premixing of the white material: Provide a mixed raw material composed of polyol, surfactant, water, flame retardant, and catalyst, denoted as POL; mix POL with an alkane blowing agent (CP) to obtain the white material;

[0182] S2. Premixing of the black material: Take 3 parts by mass of LBA and 1.5 parts by mass of nucleating agent and mix them. The obtained mixture is mixed with the remaining LBA (23 parts by mass) and isocyanate to obtain the black material;

[0183] S3. Foaming: After controlling the temperature of the white material and the black material, mix them through the nozzle of a high-pressure foaming gun and react to achieve foaming.

[0184] Example 3-2

[0185] Compared with Example 3-1, the difference lies in that step S2 is as follows, and the other steps are the same as those of Example 3-1:

[0186] S2. Premixing of the black material: Take 4.5 parts by mass of LBA and 1.5 parts by mass of nucleating agent and mix them. The obtained mixture is mixed with the remaining LBA (21.5 parts by mass) and isocyanate to obtain the black material.

[0187] Table 4

[0188]

[0189]

[0190] In Table 4, Simulation Example 3-1 and Simulation Example 3-2 indicate that according to the schemes of Example 3-1 and Example 3-2, assuming that the metering of the nucleating agent is abnormal and not added, the mixture of LBA and the nucleating agent is completely replaced by LBA, that is, LBA is 27.5 parts by mass and the nucleating agent is 0 part by mass.

[0191] As can be seen from the above data, after diluting the nucleating agent with a certain quality of LBA and then adding it to the black material, the main properties of the foam are comparable to those of Example 1-1 where all the LBA and the nucleating agent are directly mixed. However, once the scheme of diluting the nucleating agent in this example is adopted, if the metering of the nucleating agent is abnormal and the nucleating agent fails to be added successfully, the parameters such as the thermal conductivity and the density of free bubbles of the final foam will show obvious abnormalities (such as an increase in thermal conductivity and a decrease in the density of free bubbles of the foam). Among them, the abnormal thermal conductivity will directly affect the energy efficiency performance of the final product and cause adverse effects.

[0192] Since in the daily production process, the production line usually regularly monitors the foam density, but rarely monitors the thermal conductivity, diluting and adding the nucleating agent can enable the production line to detect abnormalities in a timely manner during the normal production process, facilitating early investigation and taking corresponding measures, thereby improving the stability and reliability of the production process.

[0193] Example 4

[0194] For the composition of the black material and the white material of the polyurethane foam materials in Examples 4-1 to 4-5 and the preparation method, refer to Example 1-1, the difference is that the type and addition amount of the alkane blowing agent are different, as shown in Table 5 specifically.

[0195] Comparative Examples 2 to 3

[0196] For the composition of the black material and the white material of the polyurethane foam materials in Comparative Examples 2 to 3 and the preparation method, refer to Example 1-1, the difference is that the type and addition amount of the alkane blowing agent are different, as shown in Table 5 specifically.

[0197] Table 5

[0198]

[0199]

[0200] As can be seen from Table 5, in Examples 4-1 to 4-5, high-boiling alkanes (such as cyclopentane, isopentane, n-pentane) or a mixture of cyclopentane and low-boiling alkanes (such as n-butane, isobutane) are used to replace the high-cost LBA blowing agent. Although the thermal conductivity of the foam increases to a certain extent, it can still maintain good heat insulation performance. In particular, the gas-phase thermal conductivity of cyclopentane is significantly lower than that of other alkane blowing agents (such as isopentane, n-pentane, isobutane, n-butane). Therefore, using cyclopentane partially or entirely as the alkane blowing agent helps to further reduce the thermal conductivity. However, cyclopentane has a higher boiling point, while the above-mentioned other alkane blowing agents have lower boiling points. Therefore, when using the latter as the alkane blowing agent, higher foam strength can be obtained. In application scenarios where strict requirements for thermal conductivity are not imposed, other high-boiling alkanes (such as isopentane, n-pentane) can be selected, or high-boiling alkanes can be mixed with low-boiling alkanes to obtain a more cost-effective foam material.

[0201] Comparing Comparative Examples 4-1 and 4-2, it can be seen that when using isopentane, the thermal conductivity of the foam is slightly higher than that of n-pentane, which may be related to the poor compatibility of isopentane with the white material and the relatively low boiling point of isopentane. The lower boiling point may cause isopentane to volatilize faster during the foaming process, further affecting the refinement degree of the cell structure and ultimately the thermal conductivity of the foam.

[0202] In Comparative Examples 2 and 3, only low-boiling n-butane or isobutane is used to replace part of the LBA, resulting in a decrease in the thermal stability of the foam.

[0203] Comparative Example 4

[0204] The raw material compositions and main process parameters of the polyurethane foam materials in Comparative Examples 4-1 to 4-5 are shown in Table 6, where:

[0205] The POL compositions of Comparative Examples 4-1, 4-2, and 4-3 are the same as those in Example 1-1.

[0206] The POL composition of Comparative Example 4-4 is as follows: 100 parts by mass of polyol, 4.0 parts by mass of surfactant, 1.5 parts by mass of water, 15 parts by mass of flame retardant, 3.6 parts by mass of catalyst (0.2 part by mass of pentamethyldiethylenetriamine, 2.7 parts by mass of N,N-dimethylcyclohexylamine, 0.7 part by mass of potassium acetate), with a total of 124.1 parts by mass.

[0207] The POL composition of Comparative Example 4-5 is as follows: 100 parts by mass of polyol, 4.0 parts by mass of surfactant, 2.1 parts by mass of water, 15 parts by mass of flame retardant, 3.2 parts by mass of catalyst (0.2 part by mass of pentamethyldiethylenetriamine, 2.3 parts by mass of N,N-dimethylcyclohexylamine, 0.7 part by mass of potassium acetate), with a total of 124.3 parts by mass.

[0208] Preparation method of polyurethane foam material, comprising the following steps:

[0209] S1. Premixing of white material: Provide a mixed raw material composed of polyol, surfactant, water, flame retardant, and catalyst (premixing can be completed by the raw material supplier), denoted as POL; mix POL with LBA, alkane blowing agent (CP), and nucleating aid to obtain the white material;

[0210] S2. Foaming: After controlling the temperature of the white material and the black material (isocyanate), mix them through a high-pressure foaming machine gun head, react, and achieve foaming.

[0211] It can be seen from the comparison between Example 1-1 and Comparative Example 1-1 that for the scheme of adding LBA to the white material, the foam properties are basically equivalent to the results of adding LBA to the black material in this scheme. This example mainly compares the influence of different blowing agent compositions on the foam properties. Therefore, adopting the scheme of adding all the blowing agents to the white material can highlight the influence of the blowing agent composition.

[0212] Comparative Example 5

[0213] The composition and preparation method of the black material and white material of the polyurethane foam material refer to Example 1-3, the difference is that the composition of POL is as follows: 100 parts by mass of polyol, 4.0 parts by mass of surfactant, 2.4 parts by mass of water, 15 parts by mass of flame retardant, 3.0 parts by mass of catalyst (0.2 parts by mass of pentamethyldiethylenetriamine, 2.2 parts by mass of N,N-dimethylcyclohexylamine, 0.6 parts by mass of potassium acetate), with a total of 124.4 parts by mass. Due to the different mass of POL, there are slight differences in the material ratio of the black material and the white material.

[0214] Comparative Example 6

[0215] The composition and preparation method of the black material and white material of the polyurethane foam material refer to Example 1-3, the difference is that cyclopentane is not added, and the amount of LBA is increased to 38 parts by mass, as shown in Table 6.

[0216] Table 6

[0217]

[0218]

[0219] From the comparison of Comparative Examples 1-1, 4-1 to 4-3, it can be seen that when the amount of water in the chemical blowing agent is fixed, using cyclopentane as an auxiliary physical blowing agent to replace part of the LBA main blowing agent, as the amount of cyclopentane increases, the thermal conductivity of the resulting foam shows an upward trend. This is mainly because the thermal conductivity of the gas phase in the pores increases. At the same time, as the amount of cyclopentane increases, the increase in the thermal conductivity of the foam after thermal aging at 40 °C for 24 hours slows down. This is mainly because after using cyclopentane with a higher boiling point to replace part of the LBA, the pressure in the pores decreases, and the gas-air exchange effect weakens, which helps to improve the thermal stability of the foam. In Comparative Example 6, cyclopentane was not added, and the change in thermal conductivity after aging treatment was relatively large, and a significantly higher amount of LBA was required to achieve a comparable density, which would significantly increase the raw material cost.

[0220] From the comparison of Comparative Examples 1-1, 4-4, 4-5 and Comparative Example 5, it can be seen that when the amount of water in the chemical blowing agent gradually increases and the amount of the physical blowing agent decreases accordingly, the amount of low-boiling-point carbon dioxide generated gradually increases, and the thermal conductivity of the gas phase in the foam also increases, and the final thermal conductivity of the foam shows an upward trend. Among them, the thermal conductivity of the foam in Comparative Example 4-4 is higher than that in Comparative Example 1-1, mainly because the amount of water in the chemical blowing agent is less, resulting in a weakened nucleation effect. Therefore, although the amount of LBA is high, the thermal conductivity of the prepared foam is still high. At the same time, as the amount of water in the chemical blowing agent increases, the difference in the thermal conductivity of the foam after thermal aging at 40 °C for 24 hours increases, mainly because the boiling point of carbon dioxide is low, the pressure in the pores increases, and the gas-air exchange effect is enhanced.

[0221] In Comparative Example 5, the water content is too high (2.4 parts / 100 parts of polyol). Compared with the conventional scheme of simply adding a high content of LBA (Comparative Example 6), the thermal stability is not improved. On the other hand, the water content should not be too low, because the carbon dioxide generated by the reaction of water and isocyanate has a low boiling point and a large saturated vapor pressure. If the amount of water is too small, the pore pressure will be too small, which will affect the strength of the foam. Especially the use of flame retardants will have a plasticizing effect on the foam, which will further have an adverse effect on the strength of the foam, and a suitable pore pressure is required to provide support.

[0222] From the above results, it can be seen that through the reasonable combination of LBA, alkane blowing agents (cyclopentane) and chemical blowing agent water, not only can the thermal stability of the foam material be improved, but also the performance advantages of low density and low thermal conductivity can be taken into account, while maintaining a relatively low comprehensive cost. In addition, the flame retardant grade of the foam material reaches HF-1 level, with excellent flame retardant performance.

[0223] In view of the performance advantages of the polyurethane foam material of this embodiment, such as low density, low thermal conductivity, high strength, excellent thermal stability and flame retardancy, and low production cost, it can well meet the heat insulation requirements of household appliances such as water heaters.

[0224] The present invention has been described in detail above in conjunction with the embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A method for preparing a polyurethane foam material, characterized in that: The following steps are involved: Mixing raw materials including 100 parts by mass of polyol, 2 to 6 parts by mass of surfactant, 1.8 to 9 parts by mass of catalyst, 1.5 to 2.1 parts by mass of water and 2 to 10 parts by mass of alkane foaming agent to obtain a white material; Mixing raw materials including 20 to 35 parts by mass of LBA and 150 to 200 parts by mass of isocyanate to obtain a black material; The white material and the black material are mixed and reacted to obtain the polyurethane foam material; Wherein, the alkane foaming agent at least includes high-boiling-point alkanes, and the boiling point of the high-boiling-point alkanes is higher than the boiling point of the LBA.

2. The preparation method according to claim 1, characterized in that: The raw materials for preparing the black material also include a nucleating aid, and the preparation method of the black material includes the following steps: Mixing the preparation raw materials including the LBA, the nucleating aid and the isocyanate to obtain the black material; Optionally, the nucleating aid is selected from one or more of C3-C8 perfluoroolefin compounds; Optionally, the mass of the nucleating aid does not exceed 3% of the mass of the polyol.

3. The preparation method according to claim 2, characterized in that: The preparation method of the black material specifically comprises the following steps: mixing a portion of the LBA with the nucleating aid to obtain a first mixture; mixing the first mixture with the isocyanate and the remaining portion of the LBA; In the first mixture, the mass ratio of the nucleating aid to LBA is ≥1:

10.

4. The preparation method according to claim 1, characterized in that: The raw materials for preparing the white material also include a flame retardant, and the preparation method of the white material includes the following steps: Mixing the preparation raw materials including the polyol, surfactant, catalyst, water, flame retardant, and alkane foaming agent to obtain the white material; Optionally, the flame retardant is selected from one or more of phosphate flame retardants; Optionally, based on 100 parts by mass of the polyol, the flame retardant is 10 to 30 parts by mass.

5. The preparation method according to claim 1, characterized in that: Before mixing the white material and the black material, the material temperatures of the two materials are independently controlled at 10 to 30° C.; And / or, the white material and the black material are injected and mixed under pressure through a gun tip, wherein the gun tip pressure is 100-150 bar.

6. The preparation method according to claim 1, characterized in that: The gas phase thermal conductivity of the high boiling point alkane at 25°C is less than 15 mW / m·K; And / or, the alkane foaming agent further includes low-boiling-point alkanes, and the boiling point of the low-boiling-point alkanes is lower than the boiling point of the LBA; And / or, in the alkane foaming agent, the mass percentage of the high boiling point alkane is ≥ 25%.

7. The preparation method according to claim 1, characterized in that: The high boiling point alkane is selected from one or more of cyclopentane, isopentane or n-pentane; and / or, the surfactant is selected from silicone surfactants; And / or, the polyol is selected from a combination of polyether polyol and polyester polyol, the average functionality of the polyol is 3 to 8, and the average hydroxyl value of the polyol is 300 to 500 mgKOH / g.

8. The preparation method according to claim 7, characterized in that: The polyether polyol is selected from a combination of a polyether polyol with sucrose as an initiator, a polyether polyol with toluene diamine as an initiator, and a polyether polyol with sorbitol as an initiator, wherein the mass ratio of the three is (0.6-9):(0.8-11):1; Optionally, the polyester polyol is selected from phthalic anhydride type polyester polyol; Optionally, based on 100 parts by mass of the polyol, the polyol comprises: 70 to 90 parts by mass of polyether polyol and 10 to 30 parts by mass of polyester polyol.

9. The preparation method according to claim 1, characterized in that: The catalyst is selected from at least two of a foaming catalyst, a gel catalyst, and a trimerization catalyst.

10. The preparation method according to claim 9, characterized in that: Based on 100 parts by mass of the polyol, the foaming catalyst is 0 to 1 part; And / or, the gel-type catalyst is 1.5 to 5 parts; And / or, the trimerization catalyst is 0.3 to 3 parts.

11. The preparation method according to claim 1, characterized in that: The molar ratio of isocyanate in the black material to active hydroxyl in the white material is (1.3-1.6):1; And / or, the isocyanate is selected from polymethylene polyphenyl isocyanate.

12. A polyurethane foam material, characterized in that: The polyurethane foam material is prepared by the preparation method according to any one of claims 1 to 11.

13. The polyurethane foam material according to claim 12, characterized in that: The thermal conductivity of the polyurethane foam material at 22.5°C is ≤18.7mW / m·K; after aging for 24 hours at a humidity of 50%±5% and a temperature of 40°C, the thermal conductivity increase of the material at 22.5°C is <0.8mW / m·K; And / or, the density of the polyurethane foam material in the free foaming state is less than 24kg / m 3 ; And / or, the number of air pit defects with a diameter greater than 3 cm on the surface of the polyurethane foam material is less than 5 per square meter.

14. A household appliance, characterized in that: It comprises a polyurethane foam material prepared by the preparation method according to any one of claims 1 to 11, or a polyurethane foam material according to any one of claims 12 to 13.

15. The household appliance according to claim 14, characterized in that: The household appliance includes an electric water heater, a solar water heater or an air energy water heater.

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