Polyurethane foam material as well as preparation method and application thereof

Abstract

The invention discloses a polyurethane foam material as well as a preparation method and application thereof. The polyurethane foam material is prepared from the following raw materials in parts by mass: 100 parts of polyol, 2-6 parts of a surfactant, 1.8-9 parts of a catalyst, 1.5-2.1 parts of water, 20-35 parts of LBA, 2-10 parts of an alkane foaming agent and 150-200 parts of isocyanate, 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 foam material has the advantages of low density, low heat conductivity coefficient and excellent thermal stability, can ensure the strength and cost effectiveness of foam, and can be used for preparing a foaming thermal insulation material for household appliances such as an electric water heater. The invention also provides a preparation method of the polyurethane foam material and a household appliance using the polyurethane foam material.

Description

Technical Field

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

[0002] Rigid polyurethane (PU) foam materials are widely used in the insulation field of electric heating appliances such as storage-type electric water heaters due to their good thermal insulation properties. With the proposal of energy conservation and emission reduction goals, the development of low thermal conductivity polyurethane foam materials to meet increasingly stringent energy efficiency requirements has become a hot topic in the research of polyurethane insulation materials.

[0003] The fourth-generation physical foaming agent LBA (trans-1-chloro-3,3,3-trifluoropropene) has a low boiling point and gas phase thermal conductivity, which can effectively reduce the thermal conductivity of the foam and improve the foam strength. However, in applications in heat preservation fields such as water heaters, the stability of the thermal conductivity of polyurethane foam materials prepared using halogen-containing foaming agents such as LBA is poor under heating conditions, making it difficult to ensure long-term thermal insulation effects and reliability. On the other hand, LBA has a large relative molecular mass and high cost. Using it alone will significantly increase production costs. At present, there is still a lack of effective solutions that can balance cost and foam performance. In contrast, polyurethane foams prepared using halogen-free foaming agents are difficult to achieve a lower thermal conductivity (at 22.5°C, the thermal conductivity is generally not less than 20mW / m·K), and in order to maintain the mechanical strength of the foam, the foam density is often high.

[0004] Therefore, there is an urgent need to develop a polyurethane foam material with low thermal conductivity, good thermal stability, high strength, light weight and 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 polyurethane foam material with low density, low thermal conductivity and excellent thermal stability, while ensuring the strength and cost-effectiveness of the foam.

[0006] The invention also provides a method for preparing the polyurethane foam material.

[0007] The invention also provides a household appliance.

[0008] The first aspect of the present invention relates to a polyurethane foam material, comprising the following raw materials in parts by mass: 100 parts of polyol, 2 to 6 parts of surfactant, 1.8 to 9 parts of catalyst, 1.5 to 2.1 parts of water, 20 to 35 parts of LBA, 2 to 10 parts of alkane blowing agent, and 150 to 200 parts of isocyanate; the alkane blowing 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.

[0009] The polyurethane foam material according to the first embodiment of the present invention has at least the following beneficial effects:

[0010] The present invention adopts alkane foaming to replace part of LBA, and designs a foaming agent composed of LBA (main physical foaming agent, medium boiling point), alkane foaming (auxiliary physical foaming agent, including high boiling point alkane) and H 2 O (chemical foaming agent, water reacts with isocyanate to generate carbon dioxide, low boiling point) multi-component foaming system. Through the reasonable combination of high boiling point, medium boiling point and low boiling point foaming agents, an optimized balance is achieved in terms of cost, thermal conductivity, long-term reliability and foam strength, thus obtaining a cost-effective polyurethane foam material.

[0011] LBA has low gas phase thermal conductivity and high vapor pressure. When used as the main foaming agent, it can effectively reduce the thermal conductivity of the foam and improve the strength of the foam. Carbon dioxide, as a low boiling point gas, can increase the internal pressure of the pores and further enhance the strength of the foam. Since carbon dioxide and LBA have low boiling points, the internal pressure of the pores increases in a heated environment, resulting in an enhanced exchange between the gas inside the pores and the outside air, thereby affecting the stability of the thermal conductivity of the foam material. For this reason, the present invention uses high boiling point alkanes to replace part of LBA, which helps to improve the thermal conductivity stability of the foam material under heated conditions and can also reduce the cost of raw materials.

[0012] As a chemical foaming agent, water not only participates in the chemical reaction to generate carbon dioxide, but also has a good nucleation effect, which helps to form a fine cell structure. Fine cells can extend the heat transfer path in the solid phase, reduce the solid phase thermal conductivity, and thus effectively reduce the thermal conductivity of the foam.

[0013] Surfactants can reduce the surface tension between polyols, isocyanates and blowing agents, stabilize the reaction system, and reduce the surface energy of the reaction system, thereby reducing the pressure difference between cells, reducing the phenomenon of cell fusion during cell growth, and promoting the formation of fine cells.

[0014] In summary, the present invention makes full use of the low thermal conductivity of LBA, the effect of LBA and carbon dioxide's low boiling point on the foam strength, and the contribution of high-boiling-point alkanes to the stability of thermal conductivity through reasonable formula design optimization. At the same time, the nucleation effect of water helps to obtain a more delicate pore structure, overcomes the shortcomings of high thermal conductivity of carbon dioxide and high-boiling-point alkanes, and thus maintains the thermal conductivity advantage of the LBA foaming system.

[0015] The polyurethane foam material of the present invention 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 foaming agent is cyclopentane, the foam thermal conductivity can be further reduced to below 18 mW / m·K), good thermal stability, high foam strength, low overall cost, etc. It is particularly suitable for products such as electric water heaters and can significantly improve product energy efficiency.

[0016] According to some embodiments of the present invention, the gas phase thermal conductivity of the high boiling point alkane at 25° C. is less than 15 mW / m·K. The lower the gas phase thermal conductivity, the lower the thermal conductivity of the foam.

[0017] According to some specific embodiments of the present invention, the high boiling point alkane is selected from one or more of cyclopentane, isopentane or normal pentane. Among them, cyclopentane has a higher boiling point and a lower gas phase thermal conductivity, which helps to obtain a foam material with a lower thermal conductivity and higher thermal stability; while isopentane and normal pentane have lower boiling points, which help to improve the compression strength of the foam material.

[0018] According to some specific embodiments of the present invention, the gas phase thermal conductivity of the high boiling point alkane at 25°C is less than 13 mW / m·K. For example, the gas phase thermal conductivity of cyclopentane at 25°C is 12.8 mW / m·K.

[0019] According to some embodiments of the present invention, the alkane foaming agent further includes a low-boiling alkane, and the boiling point of the low-boiling alkane is lower than the boiling point 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 compression strength.

[0020] According to some embodiments of the present invention, the low boiling point alkane includes one or both of n-butane and isobutane. N-butane and isobutane have moderate boiling points, which can improve the strength while reducing the negative impact on the thermal stability of the foam material.

[0021] According to some embodiments of the present invention, in the alkane foaming agent, the mass percentage of the high boiling point alkane is ≥25%, for example, specifically ≥50%, ≥75% or ≥80%. Under the premise of meeting the strength requirements, appropriately increasing the proportion of high boiling point alkanes and reducing the proportion of low boiling point alkanes (for example, the mass percentage of low boiling point alkanes is ≤75%, ≤50%, ≤25% or ≤20%) helps to obtain lower thermal conductivity and higher thermal stability.

[0022] According to some specific embodiments of the present invention, the alkane foaming agent is selected from cyclopentane.

[0023] According to some specific embodiments of the present invention, the alkane foaming agent is selected from a combination of at least one of isopentane, normal pentane, normal butane, isobutane and cyclopentane, wherein the mass percentage of cyclopentane can be ≥25%, ≥50%, ≥75% or ≥80%.

[0024] According to some embodiments of the present invention, the raw materials for preparing the polyurethane foam material also include a flame retardant. Specifically, the flame retardant can be selected from phosphate esters (including halogenated or non-substituted phosphate esters) or inorganic phosphates (such as ammonium phosphate, etc.). Phosphate ester flame retardants are usually preferred because they have better flame retardant properties.

[0025] The present invention successfully achieves a balance between low density and high strength by optimizing the foaming density and strength of the foam material, effectively alleviating the problem of reduced foam strength due to the plasticization caused by the addition of flame retardants. By refining the cell size, the diffusion of combustible gas is further suppressed, and while ensuring good flame retardancy, the amount of flame retardant can be reduced, significantly improving the strength of the foam material, and achieving dual optimization of flame retardancy and strength.

[0026] According to some specific embodiments of the present invention, the flame retardant is selected from one or more halogenated or non-substituted phosphate flame retardants. As a small molecule compound, this type of flame retardant has good flame retardancy, but at the same time has a certain plasticizing effect, which may affect the improvement of foam strength. In comparison, halogenated phosphate flame retardants have more excellent flame retardant properties, but their plasticizing effect is stronger. When the flame retardancy requirements are high, halogenated phosphate flame retardants are preferred; when the foam strength requirements are high, the amount of non-substituted phosphate flame retardants can be appropriately increased. The specific type and ratio of flame retardants can be adjusted according to actual needs. Under the premise of ensuring flame retardant properties, the amount of flame retardant should be reduced as much as possible to reduce its negative impact on foam performance.

[0027] According to some specific embodiments of the present invention, the flame retardant is selected from one or more of tris(2-chloroethyl)phosphate (TCEP), tris(2-chloropropyl)phosphate (TCPP), and triethyl phosphate (TEP). The present invention does not limit the type of flame retardant, and common types can be selected, not limited to the types listed above.

[0028] According to some embodiments of the present invention, based on 100 parts by mass of the polyol, the flame retardant is 10 to 30 parts, for example, 10 to 25 parts, or 10 to 20 parts, or 15 to 25 parts.

[0029] According to some embodiments of the present invention, the polyol is selected from a combination of polyether polyol and polyester polyol. Generally, polyether polyol has better toughness and water resistance, while polyester polyol performs better in mechanical properties, heat resistance and flame retardancy. The rational combination of the two is conducive to the optimization and balance of overall performance.

[0030] According to some specific embodiments of the present invention, the polyether polyol is selected from one or more of a polyether polyol with sucrose as an initiator, a polyether polyol with sorbitol as an initiator, and a polyether polyol with toluenediamine as an initiator. Among them, the polyether polyol with toluenediamine as an initiator has a high reactivity, which helps to quickly establish the viscosity of the system at the initial stage of the reaction and enhance the ability to lock bubbles; the polyether polyol with sucrose or sorbitol as an initiator has a high functionality and the foam strength obtained is also high.

[0031] According to some specific embodiments of the present invention, the polyether polyol is selected from a combination of polyether polyols with sucrose as an initiator, polyether polyols with toluene diamine as an initiator, and polyether polyols with sorbitol as an initiator, so as to better balance the reaction activity and foam strength.

[0032] According to some specific embodiments of the present invention, in the polyether polyol, the mass ratio of the polyether polyol with sucrose as the initiator, the polyether polyol with toluenediamine as the initiator, and the polyether polyol with sorbitol as the initiator is (20-45): (25-55): (5-30), specifically (20-40): (25-40): (5-25), or (20-35): (25-40): (10-20), or (20-35): (30-40): (5-15). The specific collocation of the polyether polyol can be reasonably selected according to the actual application requirements to better balance the reactivity and foam fluidity. Under the premise of ensuring that the performance meets the requirements, the amount of the polyether polyol with toluenediamine as the initiator is reduced as much as possible to reduce the cost of raw materials.

[0033] According to some specific embodiments of the present invention, the polyester polyol is selected from phthalic anhydride polyester polyol. Polyester polyol belongs to primary hydroxyl polyol, has high reactivity with isocyanate (higher than secondary hydroxyl polyether polyol with sucrose or sorbitol etc. as initiator), and is rich in benzene rings in its structure, which helps to improve the flame retardant properties of foam. When polyester polyol is selected from phthalic anhydride polyester polyol, the pore structure is more delicate, and the thermal conductivity of foam is lower, but it may have a greater impact on demoulding property. In the application of traditional cylindrical electric water heaters, demoulding property is not required, and the amount of polyester polyol can be appropriately increased to improve the flame retardant properties of foam.

[0034] 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. The selection of polyether polyol can refer to the above-listed matching methods.

[0035] According to some embodiments of the present invention, the average functionality of the polyol is 3-8.

[0036] According to some embodiments of the present invention, the average hydroxyl value of the polyol is 300 to 500 mgKOH / g.

[0037] Generally speaking, functionality is positively correlated with crosslinking degree and negatively correlated with fluidity; a high hydroxyl value means higher reactivity and faster reaction speed, which is beneficial to improving production efficiency and foam strength. By controlling the functionality and hydroxyl value of polyols within an appropriate range, the requirements of material cost, reactivity, foam fluidity, foam strength, adhesion, etc. can be better taken into account.

[0038] According to some embodiments of the present invention, the catalyst is selected from at least two of a foaming catalyst, a gel catalyst, and a trimerization catalyst. Specifically, the foaming catalyst is selected from one or two of pentamethyldiethylenetriamine and bis(dimethylaminoethyl)ether; the gel catalyst is selected from one or more of N,N-dihexylmethylamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, 1,2-dimethylimidazole, and 1-methylimidazole; the trimerization catalyst is selected from one or more of 2-hydroxypropyltrimethylammonium formate, potassium acetate, and potassium isooctanoate. Among them, the foaming catalyst is used to promote pore formation; the gel catalyst accelerates the gel reaction, plays a role in stabilizing and solidifying the foam, and the trimerization catalyst can increase the foaming rate, and the isocyanate trimerization reaction product has good flame retardancy. The use of different blowing agents is conducive to the formation of a fine and uniform pore structure and improves the flame retardant properties of the foam material. The above catalyst has low or no reaction activity with LBA, which helps to improve the long-term stability of the formula.

[0039] According to some embodiments of the present invention, the catalyst includes at least a gel-type catalyst and a trimerization catalyst.

[0040] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the foaming catalyst is 0 to 1 part.

[0041] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the foaming catalyst is 0.1 to 0.5 parts by mass.

[0042] 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 by mass.

[0043] 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 by mass.

[0044] 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.

[0045] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimerization catalyst is 0.3 to 3 parts.

[0046] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimerization catalyst is 0.3 to 1 part.

[0047] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the trimerization catalyst is 0.5 to 1 part.

[0048] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the catalyst is 2 to 6 parts.

[0049] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the catalyst is 3 to 5 parts.

[0050] According to some embodiments of the present invention, the surfactant is selected from an organosilicon surfactant. The organosilicon surfactant plays the role of emulsification, nucleation and stabilization of foam, which helps to obtain a delicate cell morphology. Common types are polyether-modified organosilicon surfactants, the main structure of which is a polysiloxane-oxidized olefin block or graft copolymer, which has a positive effect in increasing component compatibility, emulsifying materials, stabilizing foam and regulating cells. Specifically, a surfactant with partial nucleation properties known in the art can be selected to obtain a more delicate cell structure.

[0051] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the surfactant is 3 to 6 parts.

[0052] According to some specific embodiments of the present invention, the water is 1.6 to 2 parts based on 100 parts by mass of the polyol. Properly increasing the amount of water is more conducive to the nucleation effect of water, reducing the cell size, further reducing the thermal conductivity of the foam, and obtaining a 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.

[0053] 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.

[0054] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the alkane foaming agent is 4 to 10 parts.

[0055] According to some specific embodiments of the present invention, based on 100 parts by mass of the polyol, the amount of the alkane foaming agent is 6 to 10 parts.

[0056] 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, 22 to 28 parts.

[0057] On the premise that the thermal conductivity meets the requirements, appropriately reducing the amount of LBA and increasing the proportion of cyclopentane will help improve the thermal stability of the foaming material.

[0058] According to some embodiments of the present invention, based on 100 parts by mass of the polyol, the raw materials for preparing the polyurethane foam material include 0 to 3 parts of a nucleating agent. When the nucleating agent is further added, bubble nucleation can be promoted, which helps to obtain a smaller pore size.

[0059] According to some specific embodiments of the present invention, the nucleating aid is selected from one or more of C3-C8 perfluoroolefin compounds, for example, specifically selected from hexafluoropropylene, perfluoro(4-methyl-2-pentene), perfluoro(2-methyl-2-pentene), hexafluorobutadiene or a mixture thereof. Perfluoroolefin compounds have low surface energy, can assist bubble nucleation, and reduce cell size.

[0060] According to some specific embodiments of the present invention, the nucleating agent is 0.5 to 2 parts based on 100 parts by mass of the polyol. The nucleating agent is usually expensive, so its dosage should be reduced as much as possible while ensuring that the foam performance meets the requirements, and in some cases it can even be chosen not to be added.

[0061] 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. The isocyanate is a low-viscosity liquid at room temperature, does not need to be heated and melted when used, is easy to operate, has low volatility, and has high safety.

[0062] According to some embodiments of the present invention, in the raw materials for preparing the polyurethane foam material, the molar ratio of isocyanate to active hydroxyl (or black material index for short) is (1.3-1.6): 1. Both polyol and water have isocyanate reaction activity, and considering that 1 mol of water consumes 2 mol of isocyanate, the molar number of active hydroxyl is calculated as: the sum of the molar number of hydroxyl in the polyol and twice the molar number of water.

[0063] Control the isocyanate group to be appropriately higher than the chemical equivalent to make the reaction more complete. In addition, the isocyanate trimerization product of the black material (under the action of the trimerization catalyst) has excellent flame retardant properties. Properly increasing the black material index helps to improve the flame retardant properties. In order to ensure the fluidity and filling properties of the foam, the black material index should not be too high.

[0064] According to some embodiments of the present invention, the thermal conductivity of the polyurethane foam material at 22.5°C is ≤18.7mW / m·K, more typically ≤18.5mW / m·K, or even ≤18.2mW / m·K; after aging for 24h at 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 <0.8mW / m·K, more typically ≤0.7mW / m·K.

[0065] According to some embodiments of the present invention, the density of the polyurethane foam material in the free foaming state (or free foam density) is less than 24 kg / m 3 Among them, "free foaming" means that the foaming material is not constrained by the mold cavity and foams directly.

[0066] According to some embodiments of the present invention, the compressive strength of the polyurethane foam material is ≥120 kPa, and the test standard is GB / T 8813-2020.

[0067] According to some embodiments of the present invention, the flame retardancy of the polyurethane foam material is HF-1, and the test standard is GB / T 8332-2008. This flame retardancy level can be achieved after further adding a flame retardant (for example, referring to the type and amount of the flame retardant selected in the above embodiment). For water heater applications, excellent flame retardancy is usually required, so it is generally required to reach HF-1 level; while for outdoor application scenarios such as solar water heaters, the flame retardancy requirements are relatively low.

[0068] The second embodiment of the present invention relates to a method for preparing the above-mentioned polyurethane foam material, comprising the following steps: mixing and reacting the raw materials for preparing the polyurethane foam material to obtain the polyurethane foam material.

[0069] The preparation method according to the second aspect of the present invention has at least the following beneficial effects:

[0070] The preparation method is used to prepare the polyurethane foam material, and therefore, at least has all the beneficial effects of the embodiments of the polyurethane foam material. Furthermore, the method can prepare a polyurethane foam material with low density, low thermal conductivity, high strength and excellent thermal stability, and reduce production costs.

[0071] According to some embodiments of the present invention, mixing the raw materials for preparing the polyurethane foam material includes: mixing the raw materials for preparing the polyol, the surfactant, the catalyst, water, the LBA, and the alkane foaming agent to obtain a white material; and mixing the white material with the isocyanate (or black material). Before the foaming reaction, by preparing the white material and the black material in advance, it is helpful to improve the mixing uniformity of the raw materials, thereby improving the overall performance of the foam material.

[0072] According to some specific embodiments of the present invention, the method for preparing the white material comprises the following steps: mixing the raw materials including the polyol, the surfactant, the catalyst, water, and the alkane foaming agent to obtain a first mixture, and mixing the first mixture with the raw materials including the LBA to obtain the white material. The components of the first mixture other than the alkane foaming agent can be premixed by the raw material supplier.

[0073] The use of a graded premixing process for white materials can effectively improve the stability and reliability of the foaming material delivery process. Specifically, by mixing LBA and the catalyst separately, the contact reaction time between LBA and the catalyst is reduced, thereby extending the stability period. Mixing an alkane foaming agent, a surfactant, water and a polyol can reduce the viscosity of the polyol and facilitate material delivery.

[0074] In practical applications, the process of adding LBA to the mixture can be set on the production line foaming platform. In this way, when the first mixture is transported to the production line foaming platform through a long-distance pipeline (alkane foaming agents such as cyclopentane are flammable and explosive, usually far away from the production line, and need to be transported over long distances), there is no problem of LBA contacting the catalyst and causing the catalyst activity to decrease or LBA to fail, thereby improving the stability of the material. At the same time, this solution can also reduce the impact of the temperature rise of the transportation pipeline (especially when the ambient temperature is high in summer), and the production line foaming platform can be set indoors, which helps to slow down the reaction rate of LBA and the catalyst by lowering the material temperature, prolong the stability period of the material, reduce the temperature control cost, and ensure the long-term reliability and stability of the formula.

[0075] According to some embodiments of the present invention, the raw materials for preparing the polyurethane foam material further include a flame retardant, and the method for preparing the white material further includes the step of adding and mixing the flame retardant.

[0076] According to some specific embodiments of the present invention, the raw materials for preparing the polyurethane foam material also include a flame retardant, and the method for preparing the first mixture includes: mixing the raw materials including the polyol, surfactant, catalyst, water, flame retardant, and alkane foaming agent to obtain the first mixture.

[0077] According to some embodiments of the present invention, the raw materials for preparing the polyurethane foam material further include a nucleating agent, and the method for preparing the white material further includes the step of adding and mixing the nucleating agent.

[0078] According to some specific embodiments of the present invention, the raw materials for preparing the polyurethane foam material also include a nucleating aid, and the first mixture is mixed with the raw materials for preparing the LBA, specifically comprising the following steps: mixing the first mixture with the LBA and the nucleating aid. Nucleating aids (such as perfluoroolefin compounds) are similar in structure to LBA, and the two are mutually soluble. Therefore, premixing the nucleating aid with LBA can improve the solubility of the nucleating aid and improve its dispersion uniformity, and is particularly helpful in improving the apparent quality of the foam material, such as reducing surface pore defects. It can be understood that when a flame retardant is further included, the flame retardant can be added to the first mixture for mixing.

[0079] According to some specific embodiments of the present invention, mixing the first mixture with the LBA and the nucleating aid specifically includes: mixing a portion of the LBA with the nucleating aid to obtain a second mixture; and mixing the first mixture, the second mixture and the remaining portion of the LBA.

[0080] The nucleating agent is diluted with some LBA to facilitate accurate measurement of the nucleating agent and production process correction. Since the amount of nucleating agent used is usually small, missing addition may have an adverse effect on the thermal conductivity of the foam. The technical route of nucleating agent dilution, such as missing nucleating agent, will cause the total amount of LBA to change (for example, the missed nucleating agent is replaced by an equal amount of LBA, resulting in an increase in the total amount of LBA), causing the foam density to change. Therefore, through foam density monitoring, abnormalities that may occur in the production process can be discovered in time to ensure long-term stable operation of the production line. If the nucleating agent is added directly, when the nucleating agent is missed, the total amount of the foaming agent will not change, and the impact on the foam density is small, mainly the thermal conductivity is abnormal, 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 many factors, including material temperature, material ratio, gun head pressure, and even abnormalities of polyol raw materials, so it is difficult to quickly find the root cause of the problem.

[0081] According to some specific embodiments of the present invention, in the second mixture, the mass ratio of the nucleating agent to LBA is ≥1:10, and the specific ratio can be selected as needed to ensure that LBA can dissolve the nucleating agent.

[0082] According to some embodiments of the present invention, before the mixing, the material temperatures of the black material and the white material are independently 10 to 30° C., and the material temperature range is controlled to reduce the loss of the foaming agent while ensuring the reaction activity.

[0083] According to some embodiments of the present invention, the mixing gun head pressure is 100-150 bar. Generally, the greater the gun head pressure, the smaller the particle size of the black material and the white material after atomization, 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.

[0084] A third aspect of the present invention provides a household appliance, comprising the polyurethane foam material described above, or the polyurethane foam material prepared by the above preparation method.

[0085] The household appliance according to the third aspect of the present invention has at least the following beneficial effects:

[0086] Given that the above-mentioned polyurethane foam materials have performance advantages such as low density, low thermal conductivity, high strength, excellent thermal stability and low production cost, they can well meet the insulation needs of household appliances such as water heaters.

[0087] According to some embodiments of the present invention, the household appliance includes an electric water heater, a solar water heater or an air energy water heater.

[0088] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 1 is a flow chart of the preparation method of the polyurethane foam material of Example 1 of the present invention. DETAILED DESCRIPTION

[0090] Embodiments of the present invention are described in detail below. The embodiments are exemplary and are only used to explain the present invention, but should not be understood as limiting the present invention.

[0091] Herein, "plurality" means two or more, and "above" or "below" includes the numerical value itself.

[0092] The numerical ranges mentioned include the endpoints and any sub-ranges within the range, such as the range obtained by any combination of the specifically listed numerical values.

[0093] “Mixing the raw materials for preparing…” includes both mixing all the raw materials in one step and mixing in steps. For example, “mixing the raw materials for preparing the polyurethane foam material” includes mixing in one step or mixing in steps. Among them, step-by-step mixing is more suitable for actual foaming production line applications. Specifically, some components including polyols (for example, polyols, surfactants, catalysts, water and physical foaming agents (such as alkane foaming agents and LBA)) can be premixed to form a white material; the white material is mixed with isocyanate (black material) to react to achieve foaming. When a volatile physical foaming agent is added to the white material, the raw material supplier can complete the premixing of the components other than the physical foaming agent, and then further mix these physical foaming agents into 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.

[0094] The present embodiment provides a polyurethane foam material, and the raw materials for preparing the material include: by mass, 100 parts of polyol, 2 to 6 parts of surfactant, 1.8 to 9 parts of catalyst, 1.5 to 2.1 parts of water, 20 to 35 parts of LBA, 2 to 10 parts of alkane foaming agent, and 150 to 200 parts of isocyanate; the alkane foaming agent includes at least high-boiling point alkane, and the boiling point of the high-boiling point alkane is greater than the boiling point of LBA.

[0095] LBA (boiling point 19°C, gas phase thermal conductivity 10.2mW / m·K at 20°C) is used as the main physical foaming agent, alkane foaming agents (including high boiling point alkanes, such as cyclopentane, boiling point 49.2°C, gas phase thermal conductivity 12.8mW / m·K at 25°C) are used as auxiliary physical foaming agents, and water is used as a chemical foaming agent (water reacts with isocyanate to generate carbon dioxide, boiling point -56.6°C). Through a reasonable combination of high boiling point, medium boiling point and low boiling point foaming agents, an optimized balance can be achieved in terms of cost, thermal conductivity, long-term reliability and foam strength, thereby obtaining a cost-effective polyurethane foam material.

[0096] The thermal conductivity of polyurethane foam is mainly affected by solid phase thermal conductivity, gas phase thermal conductivity and radiation thermal conductivity, among which solid phase thermal conductivity accounts for about 20% to 30% and gas phase thermal conductivity accounts for about 60% to 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 a foaming agent with low thermal conductivity to reduce the comprehensive thermal conductivity of the gas phase; reducing solid phase thermal conductivity is achieved by reducing foam density and pore size. At the same density, small-diameter pores have a longer heat transfer path than large-diameter pores, thereby effectively reducing solid phase thermal conductivity.

[0097] LBA has the characteristics of low gas phase thermal conductivity, non-flammable and non-explosive, high vapor pressure, etc., and its use as the main foaming agent helps to obtain lower thermal conductivity and higher foam strength. However, LBA has a high unit price and a large molecular weight, so when used as a single physical foaming agent, the cost is high.

[0098] Unlike polyurethane foam used in cold-keeping applications (such as refrigerators, with internal temperature <10°C), in heat-keeping applications (such as water heaters, with internal water temperature >40°C), when the boiling point of the gas in the pores is low, the internal gas pressure is high and it is easy to exchange gas with the outside air, thus affecting the thermal stability of the foam material. Therefore, in order to ensure the long-term stability of the water heater insulation material, it is usually necessary to control the foam density. For example, the free foam density is much higher than 24kg / m 3 , usually greater than 25kg / m 3 By reducing the foaming ratio, heat exchange can be effectively reduced.

[0099] In this embodiment, high boiling point 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 cost of raw materials. At the same time, a certain amount of chemical foaming agent water is added to fully utilize the low boiling points of carbon dioxide and LBA to increase the internal pressure of the foam cells, effectively improving the strength of the foam.

[0100] During the pore nucleation process, the number and nucleation rate of the original pore nuclei determine the number and size of the final pores. During the pore growth process, the newly generated gas tends to preferentially fill the original bubble nuclei, so the more the original bubble nuclei, the more pores will eventually be formed. The key to controlling pore nucleation is to control the number and nucleation rate of pore nuclei. The more the original pore nuclei, the faster the nucleation rate, and the smaller the size of the formed pores. In the present embodiment, water is used as a chemical foaming agent, which has a good nucleation effect, helps to form a finer pore structure, prolongs the heat transfer path in the solid part, and thus reduces the solid phase thermal conductivity.

[0101] In terms of cell inhibition and cell merging, 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, which makes it easy for small cells to merge with large cells. In order to reduce the phenomenon of cell merging, the use of surfactants is crucial. Surfactants can reduce the surface tension between polyols, isocyanates and foaming agents, stabilize the reaction system, and reduce the pressure difference between cells by reducing the surface energy of the reaction system, thereby reducing the occurrence of cell merging and promoting the formation of fine cells.

[0102] In summary, the present embodiment scheme makes full use of the low thermal conductivity of LBA, the effect of the low boiling points of LBA and carbon dioxide on the foam strength, and the contribution of high boiling point alkanes to the stability of thermal conductivity through reasonable combination of components. At the same time, the nucleation effect of water helps to obtain a more delicate pore structure, overcomes the deficiency of high thermal conductivity of carbon dioxide and cyclopentane, and thus maintains the thermal conductivity advantage of the LBA foaming system.

[0103] Specifically, based on 100 parts by mass of the polyol, the amount of water is 1.5 parts, 1.6 parts, 1.8 parts, 2 parts, 2.1 parts or any value therebetween; and / or the amount of the alkane foaming agent is 2 parts, 4 parts, 6 parts, 8 parts, 10 parts or any value therebetween; and / or the amount of LBA is 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 35 parts or any value therebetween.

[0104] 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 foaming 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 overall cost. It is particularly suitable for electric water heater products and can significantly improve product energy efficiency.

[0105] Referring to Table 1, the performance parameters of LBA, carbon dioxide and commonly used alkane foaming agents are compared. For alkanes with a boiling point higher than LBA, at least one of cyclopentane, isopentane or normal pentane can be selected. If the thermal conductivity and long-term thermal stability are required to be high, cyclopentane or a mixed alkane foaming agent containing a certain proportion of cyclopentane (for example, the mass percentage of cyclopentane in the alkane foaming agent is ≥25%, ≥50%, ≥75% or ≥80%) can be selected (except cyclopentane, the remaining alkanes can be high boiling point alkanes such as isopentane and normal pentane, or low boiling point alkanes such as normal butane and isobutane).

[0106] If the compression strength of the foam is required to be high, alkanes with lower boiling points, such as isopentane and n-pentane, or a combination of high-boiling-point alkanes and low-boiling-point alkanes (such as n-butane and isobutane, etc.) can be selected. By reasonably selecting the ratio of high-boiling-point alkanes to low-boiling-point alkanes (for example, the ratio of high-boiling-point alkanes can be increased for thermal stability requirements; the ratio of low-boiling-point alkanes can be increased for strength requirements), foaming materials that meet different requirements can be obtained.

[0107] Table 1

[0108]

[0109] In the above table: Note 1: The lower the boiling point of the physical foaming agent, the greater the internal pressure it can provide for the pores, which is beneficial to provide sufficient strength for the foam when the foam density is low and meet the use requirements, but the boiling point is too low and the foaming operation is difficult; Note 2: The lower the gas phase thermal conductivity, the lower the gas phase thermal conductivity can be provided for the foam, which is beneficial to reduce 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 produced by the reaction of chemical foaming agent water and isocyanate.

[0110] During the formation of polyurethane foam, the reactions between the components proceed gradually. After adding a high number of blowing agents, the viscosity of the initial mixture is usually not high. For the 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 as soon as possible or external energy cannot be input, the size of the early bubbles in the foaming process will be difficult to continue to grow, which may lead to problems such as bubble collapse. Therefore, from the perspective of controlling the viscosity of the system, select a suitable monomer and catalyst system, reasonably regulate the polymerization reaction rate, ensure the matching of the foaming and polymerization processes, and avoid the collapse of the bubble structure caused by the slow increase in viscosity.

[0111] Based on the above design concept, on the basis of the above-mentioned multi-component foaming agent design, a highly active polymerization reaction system can be selected to rapidly increase the viscosity during the polymerization process and enhance the bubble locking ability. For example, based on a total of 100 parts by mass of the polyol monomer, the polyether polyol is 70 to 90 parts by mass (such as 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or any value between any two), the polyester polyol is 10 to 30 parts by mass (such as 10 parts, 15 parts, 20 parts, 25 parts, 30 parts or any value between any two), the average hydroxyl value is 300 to 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), and the average functionality is 3 to 8 (such as 3, 4, 5, 6, 7, 8 or any value between any two).

[0112] The polyether polyols may specifically include (the total amount is within the target range): 20 to 45 parts by mass of polyether polyols with sucrose as the initiator, 25 to 55 parts by mass of polyether polyols with toluene diamine as the initiator, and 5 to 30 parts by mass of polyether polyols with sorbitol as the initiator. The polyether polyols with toluene diamine as the initiator contain benzene rings in their structure, and have high rigid reactivity, which helps to quickly establish the viscosity of the system at the beginning of the reaction and enhance the ability to lock bubbles; the polyether polyols with sucrose and sorbitol as the initiators have high functionality and the foam strength obtained is high; polyester polyols belong to primary hydroxyl polyols, and have high reactivity with isocyanate (higher than ordinary secondary hydroxyl polyether polyols with sucrose or sorbitol as the initiator), and their structure is rich in benzene rings, which helps to improve the flame retardant properties of the foam. By mixing and matching polyols, the reaction rate and pore morphology can be better adjusted to optimize the foaming process.

[0113] Specifically, non-limiting examples of polyether polyols using sucrose as the initiator include: NJ-8243, NJ-8238, NJ-8345, NJ-8252, NJ-4502, NJ-8209, etc. from Ningwu New Materials, YD-8310, YD-8315, YD-8345, YD-8350, YD-8666, YD-8669, YD-8260, etc. from Hebei Yadong Chemical, R4110B, R8238, R8243, R6001C, etc. from Shandong Yinuowei, SC-450, SC-455, SC-4110, etc. from Guodu Chemical. Non-limiting examples of polyether polyols using sorbitol as an initiator include: NJ-6045, NJ-6256, NJ-6207, NJ-6206, NJ-6249, NJ-6209, NJ-6305B, NJ-6305C, NJ-6305S, etc. from Ningwu New Materials, YD-600, YD-635, YD-6205, etc. from Hebei Yadong Chemical, R6048, R6205, R6207, etc. from Shandong Yinuowei, ST-430, ST-480, ST-481, ST-501, etc. from Guodu Chemical. Non-limiting examples of polyether polyols using toluenediamine as initiator include: NJ-410H, NJ-430H, NJ-410HN, NJ-3445, NJ-406A, etc. from Ningwu New Materials, YD-TD440, etc. from Hebei Yadong Chemical, TD-400, TD-400L, TD-400P, TD-401, TD-405, etc. from Guodu Chemical. Non-limiting examples of polyester polyols include: PS-3152, PS-4051, PS-2352, etc. from Nanjing Stepan Chemical, PE-B503L, etc. from Shandong Yinuowei.

[0114] It should be understood that the specific types or ratios of the polyols listed above do not have exclusive or exhaustive meanings. There are many types and brands of polyols, and different polyol combinations (including different compositions or ratios) may have similar or similar effects. You can refer to the above scheme to select a suitable polyol system. For example, referring to the types and ratio ranges of the polyols listed above, select one or more polyol combinations with a functionality of 3 to 8, and control the average hydroxyl value to 300 to 500 mgKOH / g, or select other polyol combinations with similar properties.

[0115] Surfactant is preferably an organosilicon surfactant with partial nucleation characteristics, including but not limited to one or more of B-8481, B-84813, EP-RS 88, MG-828, MG-945, etc. of Evonik Chemical. This type of surfactant has a positive effect on emulsification and uniform foaming, and helps to reduce bubble merging and bubble breaking. Further, the nucleation ability of bubbles is enhanced by perfluoroolefin efficient nucleation aids, so as to obtain polyurethane foam with small cell size and low thermal conductivity. Nucleation aids can be specifically selected from hexafluoropropylene, perfluoro (4-methyl-2-pentene), perfluoro (2-methyl-2-pentene), hexafluorobutadiene or mixtures thereof, and commercially available grades include PF-5056, FA-188, PF-90, etc.

[0116] Specifically, 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 therebetween; and / or, the nucleating aid is 0 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts or any value therebetween.

[0117] The catalyst should be selected with a low reactivity to LBA to ensure the long-term stability of the formula. Specifically, the catalyst can be selected from a foaming catalyst (such as pentamethyldiethylenetriamine, bis(dimethylaminoethyl)ether, etc.), a gel catalyst (such as N,N-dihexylmethylamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, 1,2-dimethylimidazole, 1-methylimidazole, etc.), a trimerization catalyst (such as 2-hydroxypropyltrimethylammonium formate, potassium acetate, potassium isooctanoate, etc.), which is conducive to regulating the reaction rate and flame retardant properties.

[0118] Based on 100 parts by weight of the polyol, the amount of 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 in between. It is understood that when the catalyst includes multiple types of the above-mentioned foaming catalyst, gel catalyst, and trimerization catalyst, the appropriate amount of the catalyst can be selected with reference to the above-listed ratio range, and the total mass of the catalyst is 1.8 to 9 parts / 100 parts of the polyol.

[0119] Specifically, based on 100 parts by mass of the polyol, the catalyst includes: 0 to 1 part of a foaming catalyst (such as 0 part, 0.2 part, 0.5 part, 0.8 part, 1 part or any value between any two parts), 1.5 to 5 parts of a gel catalyst (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 parts), and 0.3 to 3 parts of a trimerization catalyst (such as 0.3 parts, 0.5 parts, 0.7 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts or any value between any two parts).

[0120] It should be understood that the types of catalysts or their ratios listed above do not have exclusive or exhaustive meanings. It is easy to select a suitable catalyst system by referring to the above scheme, or to select other catalyst systems with similar properties.

[0121] The isocyanate may be liquid polymethylene polyphenyl isocyanate, for example, when the mass fraction of isocyanate is 30wt% to 33wt%, the optional grades include PM-200 and PM-2010 of Wanhua Chemical, 44V20 of Covestro, PAPI27 and PAPI135 of Dow Chemical, M20s of BASF, etc. The amount of isocyanate added is preferably controlled within the range of a black material index of (1.3 to 1.6):1, for example, the black material index is specifically 1.3:1, 1.4:1, 1.5:1, 1.6:1 or any value therebetween.

[0122] When there are higher requirements for flame retardancy, flame retardants can be further added. Through the optimized balance between low foaming density and high strength, the problem of reduced foam strength caused by plasticization caused by flame retardants is alleviated, thereby maintaining low density, high thermal conductivity and stability while ensuring good flame retardancy and foam strength. In addition, the refined cell size helps to inhibit the diffusion of combustible gases and ensure good flame retardancy.

[0123] The flame retardant is selected from one or more of halogenated or non-substituted phosphate flame retardants. Non-limiting examples of halogenated phosphate flame retardants include tris(2-chloroethyl) phosphate (TCEP), tris(2-chloropropyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate, tris(2-chloroisopropyl) phosphate, tris(2,2-dichloroisopropyl) phosphate, tris(1,3-dichloroisopropyl) phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, etc. Non-limiting examples of non-substituted phosphate flame retardants include tricresyl phosphate (TCP), triphenyl phosphate (TPP), N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester (BHAPE), dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), etc. More specifically, the flame retardant is selected from one or more of tris(2-chloroethyl)phosphate (TCEP), tris(2-chloropropyl)phosphate (TCPP), and triethyl phosphate (TEP). The amount of the flame retardant added is 10 to 30 parts, or 10 to 20 parts, based on 100 parts by mass of the polyol.

[0124] The method for preparing a polyurethane foam material is as follows: mixing raw materials including polyol, surfactant, catalyst, water, LBA, and alkane foaming agent to obtain a white material; mixing the white material with isocyanate (or black material), reacting, and obtaining a polyurethane foam material. In practical applications, the raw materials for preparing the white material are mixed in steps, for example, LBA and the catalyst are mixed separately to reduce the contact reaction time between LBA and the catalyst and prolong the material stability period. In addition, premixing the alkane foaming agent with the polyol can reduce the viscosity of the polyol and facilitate material transportation.

[0125] Specifically, when flame retardants and nucleating aids are further added, the preparation method of the white material is as follows: the raw materials including polyols, surfactants, catalysts, water, flame retardants, and alkane foaming agents are mixed to obtain a first mixture; the first mixture is mixed with LBA and nucleating aids. More specifically, in the mixing process of the first mixture with LBA and nucleating aids, the nucleating aid can be premixed with part of the LBA (for example, the mass ratio of the nucleating aid to LBA is ≥1:10), and then mixed with the first mixture and the remaining LBA. The nucleating aid has good compatibility with LBA. Premixing the nucleating aid with LBA can improve the solubility of the nucleating aid and improve its dispersion uniformity, which is particularly helpful 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 error when the nucleating aid is missed during the production process.

[0126] It should be noted that all the above mixing processes can be carried out in static mixers (e.g., tubular static mixers) respectively. The materials after each mixing can be stored in liquid storage tanks for use in subsequent processes. The relevant equipment is commonly used in the art and can be reasonably set according to specific needs.

[0127] Before mixing the white material and the black material, stabilize the temperature of each material at 10-30°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C or any value in between. Control the material temperature range to ensure the reaction activity while reducing the loss of the foaming agent. The temperature of the white material and the black material can be the same or different. In addition, pre-mixing the black material and the white material at a constant temperature close to the reaction temperature helps to improve production efficiency.

[0128] The pressure of the mixing gun head is controlled at 100-150 bar, for example, 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar or any pressure between the two can be selected. The mixing pressure is controlled to ensure the mixing effect and to avoid excessive pressure (such as more than 150 bar) causing excessive load on the equipment.

[0129] The following is a detailed description through specific examples. In the following examples, the relevant raw materials are described as follows:

[0130] Polyols: polyether polyol NJ-8238 (hydroxyl value 380±15mgKOH / g, functionality 5-6) with sucrose as initiator, 30 parts by mass; polyether polyol TD405 (hydroxyl value 397.5±17.5mgKOH / g, functionality 4) with toluene diamine as initiator, 35 parts by mass; polyether polyol NJ-6045 (hydroxyl value 450±15mgKOH / g, functionality 5-6) with sorbitol as initiator, 15 parts by mass; polyester polyol PS-3152 (hydroxyl value 315±15mgKOH / g, functionality 2), 20 parts by mass; average functionality is about 4.3, and average hydroxyl value is about 383mgKOH / g.

[0131] Surfactant: Evonik Chemicals EP-RS 88.

[0132] Flame retardant: mass ratio TCPP:TCEP=11:4.

[0133] Nucleating agent: PF-5056.

[0134] Isocyanate: Wanhua PM-200.

[0135] The relevant test methods are as follows:

[0136] 1. Free foam density: Use the gun tip to spray an appropriate amount of foaming material to foam freely, measure the density by the drainage method, and test it three times in parallel, and take the average value of the results.

[0137] 2. Thermal conductivity: Use a cutting machine to cut the foamed sample into peeled foams of (200±5)mm×(200±5)mm and a thickness of (25±1)mm. Use a thermal conductivity meter to test the thermal conductivity at a temperature of 22.5°C. Take 2 samples and take the average value of the results. Place samples of the same specifications and quantity in an aging box and age them for 24 hours in a dark environment at a humidity of 50%±5% and a temperature of 40°C. Then test their thermal conductivity using the same method.

[0138] 3. Flame retardant performance: The test is based on GB / T 8332-2008 "Test method for combustion performance of foam plastics: horizontal combustion method", and the size of the foam board is 150mm×50mm×13mm.

[0139] 4. Compression strength: The test is based on GB / T 8813-2020 "Rigid Foam Plastics: Determination of Compression Properties", the sample size is (50±1) mm×(50±1) mm×(30±1) mm, the test speed is (5±1) mm / min, and the load is applied to the three directions (length / width / height) of the sample respectively. The number of samples in each direction is 3, and the average value of the 3 test data in each direction is taken. The result is the minimum value of the 3 average values. The compression strength requirement is ≥120kPa.

[0140] Example 1

[0141] The raw material composition and main process parameters of the polyurethane foam materials of Examples 1-1 to 1-6 are shown in Table 2, where:

[0142] The POL compositions of Example 1-1, Example 1-2, Example 1-3, and Example 1-4 are 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), totaling 124.2 parts by mass.

[0143] The POL composition of Examples 1-5 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 parts by mass of pentamethyldiethylenetriamine, 2.7 parts by mass of N,N-dimethylcyclohexylamine, 0.7 parts by mass of potassium acetate), totaling 124.1 parts by mass.

[0144] The POL composition of Examples 1-6 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 parts by mass of pentamethyldiethylenetriamine, 2.3 parts by mass of N,N-dimethylcyclohexylamine, 0.7 parts by mass of potassium acetate), totaling 124.3 parts by mass.

[0145] See also Figure 1 The method for preparing the polyurethane foam material of this embodiment comprises the following steps:

[0146] S1. White material premixing: providing a mixed raw material consisting of polyol, surfactant, water, flame retardant and catalyst (premixing can be completed by the raw material supplier), denoted as POL; mixing POL with LBA, alkane foaming agent (cyclopentane, Cyclopentane, referred to as CP) and nucleating agent to obtain white material;

[0147] S2. Foaming: After the temperature of the white material and the black material (isocyanate) is controlled, they are mixed and reacted through a high-pressure foaming machine gun to achieve foaming.

[0148] Comparative Example 1

[0149] The composition and preparation method of the black material and white material of the polyurethane foam material refer to Examples 1-3, except that the POL composition 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), totaling 124.4 parts by mass. Due to the different masses of POL, the material ratio of black material to white material is slightly different.

[0150] Comparative Example 2

[0151] The composition and preparation method of the black material and white material of the polyurethane foam material refer to Examples 1-3, except that cyclopentane is not added and LBA is increased to 38 parts by mass, as shown in Table 2.

[0152] Table 2

[0153]

[0154] Comparative Examples 1-1 to 1-4 show that, when the amount of water in the chemical foaming agent is fixed, cyclopentane is used as an auxiliary physical foaming agent to replace part of the LBA main foaming agent. As the amount of cyclopentane increases, the thermal conductivity of the resulting foam shows an upward trend, mainly due to the increase in the gas phase thermal conductivity in the pores. At the same time, as the amount of cyclopentane increases, the increase in the thermal conductivity of the foam after 24 hours of thermal aging at 40°C slows down. This is mainly because after replacing part of the LBA with cyclopentane with a higher boiling point, the pressure in the pores decreases, and the exchange between gas and air is weakened, which helps to improve the thermal stability of the foam. In Comparative Example 2, no cyclopentane is added, and the thermal conductivity changes greatly after aging treatment, and a significantly higher amount of LBA is required to achieve a comparable density, which will significantly increase the cost of raw materials.

[0155] By comparing Examples 1-3, 1-5, and 1-6 with Comparative Example 1, it can be seen that when the amount of chemical foaming agent water gradually increases and the amount of physical foaming agent used decreases accordingly, the amount of low-boiling carbon dioxide produced gradually increases, and the gas phase thermal conductivity of the foam also increases accordingly, and the final foam thermal conductivity shows an upward trend. Among them, the thermal conductivity of the foam of Example 1-5 is higher than that of Example 1-3, mainly because the amount of chemical foaming agent water is small, resulting in a weakened nucleation effect. Therefore, although the amount of LBA is high, the thermal conductivity of the obtained foam is still high. At the same time, with the increase in the amount of chemical foaming agent water, the difference in 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 exchange between gas and air is enhanced.

[0156] In Comparative Example 1, the water content is too high (2.4 parts / 100 parts of polyol), and the thermal stability is not improved compared with the conventional solution of simply adding a high content of LBA (Comparative Example 2). On the other hand, the water content should not be too low, because the boiling point of carbon dioxide produced by the reaction of water and isocyanate is low, and the saturated vapor pressure is large. If the amount of water is too little, the cell pressure is too small, which will affect the strength of the foam. In particular, the use of flame retardants will plasticize the foam, which will have an adverse effect on the strength of the foam, and a suitable cell pressure is required to provide support.

[0157] From the above results, it can be seen that the reasonable combination of LBA, alkane foaming agent (cyclopentane) and chemical foaming agent water can not only improve the thermal stability of the foam material, but also take into account the performance advantages of low density and low thermal conductivity, while maintaining a low overall cost. In addition, the flame retardant grade of the foam material reaches HF-1, with excellent flame retardant properties.

[0158] Example 2

[0159] The composition and preparation method of the black material and white material of the polyurethane foam material of Examples 2-1 to 2-3 refer to Example 1-3, except that, before foaming, the white material of Examples 2-1 to 2-3 is placed in a constant temperature box for aging treatment, and the treatment conditions are: dark environment, humidity of 50% ± 5%, aging time of 2 days (45°C), 4 days (45°C) or 10 days (25°C), where 1 day = 24 hours. The main characteristic parameters of the foam are shown in Table 3.

[0160] Table 3

[0161]

[0162]

[0163] In Table 3, aging time of 1 day corresponds to 24 hours; fiber time refers to the time from the mixing of black material and white material until the appearance of fiber-like drawing phenomenon; surface solidification time refers to the time from the mixing of black material and white material until the loss of fluidity and the solidification.

[0164] As can be seen from Table 3, as the aging time increases or the aging temperature rises, the material's stable period shortens, which is manifested in the extension of the fiber time and surface curing time. This indicates that the reaction between the catalyst and LBA causes LBA failure, catalyst loss or decreased activity, which affects the foaming morphology, increases the thermal conductivity, and even causes bubble breaking.

[0165] The chemical reaction between LBA and organic amines is highly dependent on temperature and time. Generally speaking, the higher the temperature, the shorter the stability period of LBA. It can be understood that a graded and step-by-step premixing scheme is adopted, in which LBA is not added first in the primary premixing process of the white material, and LBA is added in the subsequent secondary premixing stage. The secondary premixing can be set on the production line foaming platform, which can reduce the contact time between LBA and the catalyst during the long-distance transportation of the primary premixed material to the production line foaming platform through the pipeline, thereby improving the stability of the material. At the same time, this scheme can also reduce the impact of the temperature rise of the conveying pipeline (especially when the ambient temperature is high in summer), and the secondary premixing module can be set indoors, which helps to slow down the reaction rate of LBA and the catalyst by lowering the material temperature, prolong the stability period of the material, reduce the temperature control cost, and ensure the long-term reliability and stability of the formula.

[0166] 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 there will inevitably be a static process. If the production line is under maintenance or holidays, the parking time of the white material will be longer. At this time, 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 foamed product. Especially when the temperature is high in the summer, long-term storage 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. Although temperature control measures can extend the stability period, the overall temperature control cost and process complexity are high.

[0167] Example 3

[0168] The composition and preparation method of the black material and white material of the polyurethane foam materials of Examples 3-1 to 3-6 refer to those of Example 1-3, except that the amount of the nucleating agent added is different, as shown in Table 4.

[0169] Table 4

[0170]

[0171] It can be seen that the use of nucleating agents can significantly reduce the thermal conductivity of foams, and as the amount of nucleating agents increases, the thermal conductivity of foams shows a trend of gradually decreasing. Since nucleating agents are perfluorocarbon compounds, they have a high unit price, and when the amount exceeds a certain level, the effect of reducing the thermal conductivity of foams tends to be gentle. Therefore, when the thermal conductivity meets the requirements, the amount of nucleating agents should be reduced as much as possible.

[0172] It should be noted that, due to the good compatibility of the nucleating agent with LBA, in the premixing process of the white material, the nucleating agent is first premixed with part of the LBA, and then the premix is ​​used in the white material mixing process, which can improve the dispersion effect of the nucleating agent, help to give full play to its nucleating effect, and especially help to improve the apparent quality of the foam material, such as reducing surface pore defects. This method can also improve the metering accuracy of the nucleating agent, and effectively correct the error when the nucleating agent is missed during the production process. For example, in Examples 1-3, LBA is 26 parts by mass and the nucleating agent is 1.5 parts by mass. If part of LBA (such as 3 parts by mass) is premixed with the nucleating agent first, and then mixed with the other components of the white material, once the nucleating agent is missed and the total amount of LBA increases (that is, the missed nucleating agent is replaced by LBA, so that LBA increases by 1.5 parts), the free bubble density will increase from 23.15kg / m 3 Reduced to about 22.7kg / m 3 Through density monitoring, this abnormality can be discovered in time, and the operation is simple and easy to implement, thus ensuring the stability of the production process.

[0173] Example 4

[0174] The composition and preparation method of the black material and white material of the polyurethane foam materials of Examples 4-1 to 4-5 refer to Example 1-3, except that the type and addition amount of the alkane foaming agent are different, as shown in Table 5.

[0175] Comparative Examples 3 to 4

[0176] The compositions and preparation methods of the black and white materials of the polyurethane foam materials of Comparative Examples 3 to 4 refer to those of Examples 1-3, except that the types and addition amounts of the alkane foaming agents are different, as shown in Table 5.

[0177] Table 5

[0178]

[0179]

[0180] As can be seen from Table 5, compared with the comparative example 2 which completely uses LBA foaming agent, the thermal conductivity of the foam increases to a certain extent in Examples 4-1 to 4-5 using high boiling point alkanes (such as cyclopentane, isopentane, and n-pentane) or a mixture of cyclopentane and low boiling point alkanes (such as n-butane and isobutane) to replace the high-cost LBA foaming agent, but still maintains good thermal insulation performance. In particular, the gas phase thermal conductivity of cyclopentane is significantly lower than that of other alkane foaming agents (such as isopentane, n-pentane, isobutane, and n-butane). Therefore, using cyclopentane partially or entirely as an alkane foaming agent helps to further reduce the thermal conductivity. However, the boiling point of cyclopentane is relatively high, while the boiling points of the above-mentioned other alkane foaming agents are relatively low, so when the latter is used as an alkane foaming agent, a higher foam strength can be obtained. In application scenarios where thermal conductivity is not strictly required, other high-boiling-point alkanes (such as isopentane and n-pentane) can be selected, or high-boiling-point alkanes can be mixed with low-boiling-point alkanes to obtain a more cost-effective foam material.

[0181] Comparing Examples 4-1 and 4-2, it can be seen that when isopentane is used, the thermal conductivity of the foam is slightly higher than that of normal pentane, which may be related to the poor compatibility of isopentane with white material and the low boiling point of isopentane. The low boiling point may cause isopentane to evaporate faster during the foaming process, further affecting the refinement of the pores and ultimately affecting the thermal conductivity of the foam.

[0182] Comparative Examples 3 and 4 only use low-boiling point n-butane or isobutane to replace part of LBA, resulting in decreased thermal stability of the foam.

[0183] Since the polyurethane foam material of this embodiment has the performance advantages of low density, low thermal conductivity, high strength, excellent thermal stability and flame retardancy, and low production cost, it can well meet the insulation needs of household appliances such as water heaters.

[0184] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A polyurethane foam material, characterized in that: The preparation comprises the following raw materials in parts by mass: 100 parts of polyol, 2-6 parts of surfactant, 1.8-9 parts of catalyst, 1.5-2.1 parts of water, 20-35 parts of LBA, 2-10 parts of alkane foaming agent, 150-200 parts of isocyanate; 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 polyurethane foam material 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%.

3. The polyurethane foam material according to claim 1, characterized in that The high boiling point alkane is selected from one or more of cyclopentane, isopentane or n-pentane.

4. The polyurethane foam material according to claim 3, characterized in that: The alkane foaming agent is selected from cyclopentane, or a combination of at least one of isopentane, normal pentane, normal butane, and isobutane and cyclopentane, wherein the mass percentage of cyclopentane is ≥25%.

5. The polyurethane foam material according to claim 1, characterized in that: The polyol is selected from a combination of polyether polyol and polyester polyol; Optionally, the polyether polyol is selected from one or more of a polyether polyol with sucrose as an initiator, a polyether polyol with sorbitol as an initiator, and a polyether polyol with toluenediamine as an initiator; 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.

6. The polyurethane foam material according to claim 5, 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 (20-45):(25-55):(5-30).

7. The polyurethane foam material according to claim 1, characterized in that: The average functionality of the polyol is 3 to 8; And / or, the average hydroxyl value of the polyol is 300 to 500 mgKOH / g.

8. The polyurethane foam material 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.

9. The polyurethane foam material according to claim 8, 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.

10. The polyurethane foam material according to claim 1, characterized in that: The preparation raw materials also include flame retardant; Optionally, the flame retardant is selected from one or more of halogenated or non-substituted phosphate flame retardants; Optionally, based on 100 parts by mass of the polyol, the flame retardant is 10 to 30 parts by mass.

11. The polyurethane foam material according to claim 1, characterized in that: Based on 100 parts by mass of the polyol, the preparation raw material includes 0 to 3 parts of a nucleating aid; Optionally, the nucleating aid is selected from one or more of C3-C8 perfluoroolefin compounds.

12. The polyurethane foam material according to claim 1, characterized in that: In the preparation raw materials, the molar ratio of isocyanate to active hydroxyl is (1.3-1.6):1; and / or, the isocyanate is selected from polymethylene polyphenyl isocyanate.

13. The polyurethane foam material according to claim 1, characterized in that: The surfactant is selected from silicone surfactants.

14. The polyurethane foam material according to claim 1, 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 .

15. The method for preparing a polyurethane foam material according to any one of claims 1 to 14, characterized in that: The following steps are involved: Mixing the preparation raw materials including the polyol, surfactant, catalyst, water, LBA, and alkane foaming agent to obtain a white material; The white material is mixed with the isocyanate to react and obtain the polyurethane foam material.

16. The preparation method according to claim 15, characterized in that: The preparation method of the white material comprises the following steps: The raw materials including the polyol, surfactant, catalyst, water and alkane foaming agent are mixed to obtain a first mixture, and the first mixture is mixed with the raw materials including the LBA to obtain a white material.

17. The preparation method according to claim 16, characterized in that: The raw materials for preparing the polyurethane foam material also include a flame retardant. The method for preparing the first mixture includes: mixing the raw materials including the polyol, a surfactant, a catalyst, water, a flame retardant, and an alkane foaming agent to obtain the first mixture.

18. The preparation method according to claim 16, characterized in that: The raw materials for preparing the polyurethane foam material also include a nucleating agent, and mixing the first mixture with the raw materials for preparing the LBA specifically includes the following steps: mixing the first mixture with the LBA and the nucleating agent; Optionally, the first mixture is mixed with the LBA and the nucleating aid, specifically comprising: mixing a portion of the LBA with the nucleating aid to obtain a second mixture; and mixing the first mixture, the second mixture and the remaining portion of the LBA.

19. A household appliance, characterized in that: A polyurethane foam material comprising the polyurethane foam material according to any one of claims 1 to 14, or a polyurethane foam material prepared by the preparation method according to any one of claims 15 to 18; Optionally, the household appliance includes an electric water heater, a solar water heater or an air energy water heater.

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