Composite foaming agent, composite foaming material, preparation method of composite foaming material and refrigerator

Abstract

The invention discloses a composite foaming agent, a composite foaming material, a preparation method of the composite foaming material and a refrigerator, and relates to the technical field of foaming materials. The composite foaming agent comprises a supercritical fluid, a bio-based alkane and a bio-based furan derivative. The compound foaming agent provided by the invention breaks through the barrier of a binary system, adopts the ternary foaming agent for compounding, and realizes the synergistic effect of environmental protection and thermal insulation through the high diffusivity and nucleation ability of the supercritical fluid, the low thermal conductivity of the bio-based alkane and the compatibility and stabilization of the bio-based furan derivative; the solubility parameter difference between a foaming agent system and polyurethane is reduced, the phase uniformity is improved, the foam structure is optimized, the heat conductivity coefficient is reduced, and good foaming driving force and phase stability are kept at low temperature.

Description

Technical Field

[0001] This application relates to the field of foaming materials technology, and in particular to a composite foaming agent, a composite foaming material and its preparation method, and a refrigerator. Background Technology

[0002] A refrigerator is a refrigeration device that maintains a constant low temperature, and it is also a product that keeps food or other items at a constant low temperature. Foamed material is a closed-cell rigid foam that is chemically foamed and cured in the space between the refrigerator's outer shell and inner liner. The core function of foamed material is to create a continuous and uniform thermal insulation layer, minimizing the transfer of heat from the external environment to the refrigerator's interior, thereby maintaining a low-temperature environment and reducing energy consumption.

[0003] Supercritical foaming technology has become the core direction for upgrading cold chain insulation materials. However, existing foaming materials have not broken through the triple barrier of "binary system - single regulation - single-function additive". Conventional single foaming systems or binary foaming systems have problems such as insufficient compatibility with extreme environments, lack of coordinated regulation of pressure-temperature-depressurization leading to poor cell stability, and single foaming agent being unable to balance strength and weather resistance. Summary of the Invention

[0004] In view of this, this application provides a composite foaming agent, a composite foaming material and its preparation method, and a refrigerator.

[0005] The embodiments of this application are implemented as follows: a composite foaming agent includes a supercritical fluid, a bio-based alkane, and a bio-based furan derivative.

[0006] Optionally, in some embodiments of this application, the supercritical fluid includes one or more of supercritical carbon dioxide, supercritical nitrous oxide, and supercritical propane; The bio-based alkanes include one or more of bio-based pentane, bio-based hexane, and bio-based cyclopentane; The bio-based furan derivatives include one or more of bio-based 2-methylfuran, bio-based furan, and bio-based 2-ethylfuran; The mass ratio of the supercritical fluid, the bio-based alkane, and the bio-based furan derivative is (5~6):(2~3):2.

[0007] Accordingly, embodiments of this application also provide a composite foaming material, including a matrix and the above-mentioned composite foaming agent, wherein the matrix includes a combination of polyethers and isocyanate compounds.

[0008] Optionally, in some embodiments of this application, the hydroxyl value of the combined polyether is 400 mg KOH / g to 440 mg KOH / g; The viscosity of the polyether composition is 1800 mPa·s to 2000 mPa·s; The isocyanate compounds include one or more of isocyanates and diphenylmethane diisocyanate; The isocyanate index in the matrix is ​​1.1~1.15. The mass ratio of the matrix to the composite foaming agent is 100:(12~16).

[0009] Optionally, in some embodiments of this application, the composite foaming material further includes a composite foaming agent; the composite foaming agent includes a polyether-modified epoxy compound and a bio-based polyol ester; wherein, The molecular weight of the polyether-modified epoxy compound is 5000~7000; The polyether-modified epoxy compound includes one or more of polyether-modified ethylene oxide and polyether-modified propylene oxide; The bio-based polyol esters include one or more of castor oil-modified polyol esters and soybean oil-modified polyol esters; The mass ratio of the matrix to the composite foaming agent is 100:(1~2).

[0010] Accordingly, this application also provides a method for preparing a composite foamed material, comprising the following steps: A matrix is ​​provided, the matrix comprising a combination of polyethers and isocyanate compounds; The above-mentioned composite foaming agent is mixed with the matrix and foamed to obtain a composite foamed material.

[0011] Optionally, in some embodiments of this application, the supercritical fluid includes one or more of supercritical carbon dioxide, supercritical nitrous oxide, and supercritical propane; The bio-based alkanes include one or more of bio-based pentane, bio-based hexane, and bio-based cyclopentane; The bio-based furan derivatives include one or more of bio-based 2-methylfuran, bio-based furan, and bio-based 2-ethylfuran; The isocyanate compounds include one or more of isocyanates and diphenylmethane diisocyanate; The matrix supply further includes: providing a composite foaming agent, which is mixed with the matrix; optionally, the composite foaming agent includes a polyether-modified epoxy compound and a bio-based polyol ester.

[0012] Optionally, in some embodiments of this application, the foaming includes a sequentially performed wetting stage, nucleation stage, expansion stage, and curing stage; wherein, The pressure during the nucleation stage is greater than the pressure during the expansion stage, which in turn is greater than the pressure during the solidification stage, which is greater than the pressure during the wetting stage. The temperature of the curing stage is greater than the temperature of the nucleation stage, which is greater than the temperature of the expansion stage, which is greater than the temperature of the wetting stage.

[0013] Optionally, in some embodiments of this application, the pressure of the impregnation stage is 6MPa~8MPa, the pressure of the nucleation stage is 18MPa~22MPa, the pressure of the expansion stage is 13MPa~15MPa, and the pressure of the curing stage is 10MPa~12MPa. The temperature of the wetting stage is 45℃~50℃, the temperature of the nucleation stage is 65℃~70℃, the temperature of the expansion stage is 62℃~65℃, and the temperature of the curing stage is 75℃~80℃. The wetting stage lasts for 40-50 minutes, the nucleation stage lasts for 30-35 minutes, the expansion stage lasts for 25-30 minutes, and the solidification stage lasts for 30-35 minutes. The pressure relief rate during the nucleation stage is 0.3 MPa / min to 0.5 MPa / min, the pressure relief rate during the expansion stage is 0.6 MPa / min to 0.8 MPa / min, and the pressure relief rate during the solidification stage is 0.3 MPa / min to 0.4 MPa / min. During the foaming process, the pressure change rate between two adjacent stages is 0.5 MPa / min to 1 MPa / min.

[0014] Accordingly, this application also provides a refrigerator, including a cabinet, the interlayer of which is provided with the above-mentioned composite foam material, or includes the composite foam material prepared by the above-mentioned preparation method.

[0015] The compounded foaming agent provided in this application breaks through the barrier of binary systems and adopts a ternary foaming agent compound. Through the high diffusivity and nucleation ability of supercritical fluids, the low thermal conductivity of bio-based alkanes, and the compatibility and stabilization effect of bio-based furan derivatives, it achieves a synergistic effect that balances environmental protection and thermal insulation performance. It also reduces the difference in solubility parameters between the foaming agent system and polyurethane, improves phase uniformity, optimizes cell structure, reduces thermal conductivity, and maintains good foaming driving force and phase stability at low temperatures. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for preparing a composite foamed material provided in an embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0019] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the orientation shown in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0020] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0021] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0022] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0023] Existing foaming systems have at least the following problems: 1. Insufficient compatibility of binary foaming system with extreme environments: The solubility of foaming agent is low under extreme high and low temperature cycles in the cold chain, the uniformity of cell size is low, and the foaming agent is prone to precipitation, which leads to cell collapse.

[0024] 2. Lack of coordinated control of pressure, temperature and depressurization rate: It is difficult to dynamically match cell nucleation, expansion and solidification, resulting in large dimensional deformation rate and rapid degradation of mechanical properties after cold chain cycle.

[0025] 3. Single-function foaming agents have limited performance: Single-function additives usually only improve a single property, and the effect is limited.

[0026] 4. Limited room for environmental protection and performance upgrades: The existing binary system has low bio-based content, high GWP (Global Warming Potential) value, and long production cycle, making it difficult to meet dual carbon targets and large-scale requirements.

[0027] The technical solution of this application solves at least one of the above-mentioned problems.

[0028] The technical solution of this application is as follows: In a first aspect, embodiments of this application provide a composite foaming agent, comprising supercritical fluid, bio-based alkane, and bio-based furan derivative.

[0029] It should be noted that the state in which the pressure and temperature of a substance simultaneously exceed its critical pressure and critical temperature is called the supercritical state. Liquids in the supercritical state, that is, liquids whose temperature and pressure are both above the critical point, are called supercritical fluids.

[0030] Bio-based alkanes are saturated hydrocarbon compounds produced from renewable biomass resources through bio-fermentation, bioconversion, thermochemical conversion, or other sustainable processes. Their carbon skeletons are derived from organic carbon in biomass (such as plant oils, starch, cellulose, lignin, sugars, or lipids synthesized by microorganisms themselves).

[0031] Bio-based furan derivatives refer to a series of compounds containing furan ring structures obtained from renewable biomass (such as agricultural and forestry waste and non-grain crops) through chemical or biocatalytic transformation. Specifically, in this application, bio-based furan derivatives can be prepared from agricultural waste such as corn cobs and straw through a process of high-temperature cellulose hydrolysis at 120°C, anaerobic fermentation at 37°C, and vacuum distillation purification.

[0032] The composite foaming agent provided in this application comprises a combination of three phases: supercritical fluid, bio-based alkane, and bio-based furan derivative. The supercritical fluid provides nucleation motive force, the bio-based alkane ensures thermal insulation performance, and the bio-based furan derivative exhibits amphiphilic properties: the furan ring is a weakly polar aromatic heterocycle, and substituents can exist on the ring to adjust the polarity. This structure can simultaneously adapt to the characteristics of both supercritical fluid and polyurethane. Specifically, the π-electron cloud of the furan ring can form a dipole-induced dipole interaction with the dipole of the supercritical fluid, and the substituents can also form weak hydrogen bonds with the supercritical fluid, improving the solubility of the supercritical fluid in the system. The furan ring can also form weak hydrogen bonds with the supercritical fluid through hydrogen bonding and π-π interactions. The interaction between the bio-based furan derivative and the dipolar-dipolar interaction with polyurethane creates a bidirectional effect, making the furan derivative a "molecular bridge" between the two phases. This can break the phase separation tendency caused by the polarity difference between the supercritical fluid and polyurethane. The bio-based furan derivative is enriched at the supercritical fluid / polyurethane interface, reducing interfacial tension through its amphiphilic structure. Furthermore, the solubility parameter of the bio-based furan derivative is between that of the supercritical fluid and polyurethane. According to the principle of "like dissolves like," it can dissolve in both phases simultaneously. Through molecular diffusion, the overall solubility parameter distribution of the system becomes more uniform, reducing the difference in solubility parameters between the supercritical fluid and polyurethane, inhibiting phase separation, improving compatibility, and promoting the application of composite foaming agents in polyurethane foam.

[0033] The composite foaming agent provided in this application has environmental benefits: the supercritical fluid itself is non-volatile, non-flammable, and non-toxic, and its GWP (Global Warming Potential) is far lower than that of traditional foaming agents, significantly reducing the environmental burden of the foaming process. Bio-based alkanes and bio-based furan derivatives are derived from renewable resources, have short carbon cycles, reducing dependence on fossil resources, and are biodegradable in the environment. Bio-based furan derivatives further enhance environmental friendliness by reducing interfacial tension and minimizing the escape of the foaming agent during the cell nucleation and growth stages.

[0034] The composite foaming agent provided in this application has a thermal insulation effect: supercritical fluids diffuse quickly and have high solubility, which can form a large number of uniform nucleation points in the polymer, making the cells finer; bio-based alkanes have a lower thermal conductivity than air, and filling the cells can reduce the overall thermal conductivity of the foam and improve the thermal insulation performance; bio-based furan derivatives regulate the viscosity and interfacial tension of the system, making it difficult for the cells to merge or collapse during the growth stage, forming a uniform and closed cell structure, reducing the heat transfer through convection between cells; the three work together to form a "fine, closed, low thermal conductivity gas" cell structure, which ultimately significantly reduces the thermal conductivity of the foamed material and improves the thermal insulation performance of the foam.

[0035] The composite foaming agent provided in this application breaks through the barrier of binary systems and adopts a ternary foaming agent compound. Through the high diffusivity and nucleation ability of supercritical fluids, the low thermal conductivity of bio-based alkanes, and the compatibility and stabilization effect of bio-based furan derivatives, it achieves a synergistic effect that balances environmental protection and thermal insulation performance. It also reduces the difference in solubility parameters between the foaming agent system and polyurethane, improves phase homogeneity, optimizes cell structure, reduces thermal conductivity, and maintains good foaming driving force and phase stability at low temperatures.

[0036] In some embodiments, the supercritical fluid includes one or more of supercritical carbon dioxide, supercritical nitrous oxide, and supercritical propane. The supercritical fluid has advantages such as low GWP, high permeability, and compatibility with ternary systems, and can be combined with bio-based alkanes and bio-based furan derivatives to improve the nucleation performance of composite foaming agents in promoting foaming.

[0037] In some embodiments, the bio-based alkane includes one or more of bio-based pentane, bio-based hexane, and bio-based cyclopentane. The bio-based alkane can effectively match the solubility parameters and thermodynamic properties of supercritical fluids and bio-based furan derivatives, and can be combined with supercritical fluids and bio-based furan derivatives to improve the foaming and insulation performance of composite foaming agents.

[0038] In some embodiments, the bio-based furan derivative includes one or more of bio-based 2-methylfuran, bio-based furan, and bio-based 2-ethylfuran. The bio-based furan derivative has advantages such as high compatibility with supercritical fluids and bio-based alkanes, low GWP, and suitable boiling point. It can also improve the compatibility of the composite blowing agent with the polyurethane blowing material and reduce the difference in solubility parameters.

[0039] In some embodiments, the mass ratio of the supercritical fluid, the bio-based alkane, and the bio-based furan derivative is (5~6):(2~3):2, for example, it can be 5:3:2, 5.2:2.8:2, 5.5:2.5:2, 5.8:2.2:2, 6:2:2, or any range between two of the above ratios. Within this mass ratio range, it is beneficial for the supercritical fluid, the bio-based alkane, and the bio-based furan derivative to synergistically improve the environmental friendliness, heat insulation, stability, and other properties of the composite foaming agent.

[0040] Secondly, embodiments of this application provide a composite foaming material, including a matrix and a composite foaming agent, wherein the matrix includes a combination of polyethers and isocyanate compounds.

[0041] The composite foaming agent can refer to the composite foaming agent in the first aspect above, and will not be repeated here.

[0042] It should be noted that the composite foaming material is a polyurethane foam material prepared by nucleation and foaming of a combination of polyethers and isocyanate compounds in the matrix under the action of a composite foaming agent. The combination of polyethers and isocyanate compounds are respectively "white material" and "black material", which can generate rigid polyurethane foam through chemical reaction.

[0043] In some embodiments, the hydroxyl value of the composite polyether is 400 mg KOH / g to 440 mg KOH / g, for example, it can be 400 mg KOH / g, 410 mg KOH / g, 420 mg KOH / g, 430 mg KOH / g, 440 mg KOH / g, or any range between two of the above values. The viscosity of the composite polyether is 1800 mPa·s to 2000 mPa·s, for example, it can be 1800 mPa·s, 1850 mPa·s, 1900 mPa·s, 1950 mPa·s, 2000 mPa·s, or any range between two of the above values. It should be noted that the hydroxyl value is used as an indicator to characterize the hydroxyl content in a substance, specifically defined as the number of milligrams of potassium hydroxide equivalent to the hydroxyl content in 1 gram of sample. The viscosity in this application represents the force required to move two layers of fluid 1 meter apart at a speed of 1 meter per second relative to each other at 25°C. Under the above conditions, the composite polyether has suitable performance and is suitable for preparing polyurethane foam.

[0044] In some embodiments, the isocyanate compound includes one or more of isocyanates and diphenylmethane diisocyanate (MDI).

[0045] In some embodiments, the isocyanate index in the matrix is ​​1.1 to 1.15, for example, it can be 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, or any range between two of the above values. It should be noted that the isocyanate index is a key formulation parameter in polyurethane foam synthesis, representing the equivalent ratio of isocyanate groups (-NCO) in the isocyanate compound to hydroxyl groups (-OH) in the polyether. Within the range of the isocyanate index, the polyether and the isocyanate compound can effectively nucleate and foam to prepare polyurethane foam.

[0046] In some embodiments, the mass ratio of the matrix to the composite foaming agent is 100:(12~16), for example, it can be 100:12, 100:13, 100:14, 100:15, 100:16, or any range between two of the above values. Within this mass ratio range, it is beneficial for the matrix to react under the action of the composite foaming agent to obtain polyurethane foam.

[0047] In some embodiments, the composite foaming material further includes a composite foaming aid.

[0048] In some embodiments, the composite foaming agent comprises a polyether-modified epoxy compound and a bio-based polyol ester.

[0049] Furthermore, the molecular weight of the polyether-modified epoxy compound is 5000-7000, for example, it can be 5000, 5500, 6000, 6500, 7000, or any two of the above values. Within the aforementioned molecular weight range, the degree of crosslinking between the polyether-modified epoxy compound and the polyurethane prepared from the matrix is ​​more well matched, ensuring the cell wall strength of the composite foam material and meeting suitable compatibility requirements.

[0050] In some embodiments, the polyether-modified epoxy compound includes one or more of polyether-modified ethylene oxide and polyether-modified propylene oxide.

[0051] In some embodiments, the bio-based polyol ester includes one or more of castor oil-modified polyol esters and soybean oil-modified polyol esters.

[0052] It should be noted that castor oil modified polyol esters can be prepared by conventional methods in the art. For example, castor oil is pretreated (dehydrated and impurities removed under reduced pressure at 100°C~120°C), then excess low-carbon alcohol (such as methanol) and a catalyst (such as sodium hydroxide) are added, and the mixture is stirred at 60°C~80°C for 2h~4h. Excess alcohol and impurities are then removed by reduced pressure distillation to obtain castor oil modified polyol esters.

[0053] In some embodiments, the mass ratio of the matrix to the composite foaming agent is 100:(1~2), for example, it can be 100:1, 100:1.2, 100:1.5, 100:1.8, 100:2, or any range between the above two values. Within this mass ratio range, it is beneficial for the epoxy groups in the polyether-modified epoxy compound to crosslink with the hydroxyl groups of the polyurethane, thereby improving the cell wall strength. The long-chain structure of the bio-based polyol ester enhances the flexibility and high and low temperature resistance of the foam. The synergistic effect of both effectively improves the cell wall strength and optimizes the high and low temperature cycling performance. Furthermore, the composite foaming agent and the ternary composite foaming agent have excellent compatibility, which can promote the uniform dispersion of the foaming agent, further improve the cell uniformity, and reduce the thermal conductivity.

[0054] Thirdly, please refer to Figure 1 This application also provides a method for preparing a composite foamed material, comprising the following steps: Step S11: Provide a matrix, the matrix comprising a combination of polyethers and isocyanate compounds; Step S12: Provide a composite foaming agent, mix it with the matrix, and perform a foaming treatment to obtain a composite foamed material.

[0055] The composite foaming agent can refer to the composite foaming agent in the first aspect above, and the matrix can refer to the matrix in the second aspect above, which will not be repeated here.

[0056] In some embodiments, the provision of the matrix further includes: providing a composite foaming agent, which is mixed with the matrix. It is understood that the matrix can be obtained by mixing a combination of polyethers and isocyanate compounds. During the mixing process, a composite foaming agent can be added, and stirring or other operations can be used to promote full contact and mixing of the components to form a homogeneous premixed system, which is then mixed with the subsequent composite foaming agent.

[0057] The ratio of the combined polyether and isocyanate compounds, as well as the materials and dosage of the composite foaming agent, can be referred to the second aspect, and will not be repeated here.

[0058] In some embodiments, the foaming process includes a sequentially occurring impregnation stage, a nucleation stage, an expansion stage, and a curing stage. It should be noted that the pressure and temperature are different between any two adjacent stages.

[0059] Furthermore, the pressure during the nucleation stage is greater than the pressure during the expansion stage, which in turn is greater than the pressure during the solidification stage, which is greater than the pressure during the wetting stage.

[0060] The temperature of the curing stage is greater than the temperature of the nucleation stage, which is greater than the temperature of the expansion stage, which is greater than the temperature of the wetting stage.

[0061] More specifically, the pressure during the impregnation stage is 6 MPa to 8 MPa, for example, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, or any range between two of the above values; the pressure during the nucleation stage is 18 MPa to 22 MPa, for example, 18 MPa, 19 MPa, 20 MPa, 21 MPa, 22 MPa, or any range between two of the above values; the pressure during the expansion stage is 13 MPa to 15 MPa, for example, 13 MPa, 13.5 MPa, 14 MPa, 14.5 MPa, 15 MPa, or any range between two of the above values; and the pressure during the curing stage is 10 MPa to 12 MPa, for example, 10 MPa, 10.5 MPa, 11 MPa, 11.5 MPa, 12 MPa, or any range between two of the above values. Under the aforementioned dynamic gradient pressure conditions, low-pressure wetting is beneficial for promoting the full penetration of the composite foaming agent, high-pressure burst nucleation is beneficial for increasing the nucleation density, medium-pressure precise expansion is beneficial for controlling the size of the cells, and finally, low-pressure stable curing is beneficial for stabilizing the cell structure.

[0062] In some embodiments, the temperature of the impregnation stage is 45℃~50℃, for example, it can be 45℃, 46℃, 47℃, 48℃, 49℃, 50℃ or any two of the above values; the temperature of the nucleation stage is 65℃~70℃, for example, it can be 65℃, 66℃, 67℃, 68℃, 69℃, 70℃ or any two of the above values; the temperature of the expansion stage is 62℃~65℃, for example, it can be 62℃, 63℃, 64℃, 65℃ or any two of the above values; the temperature of the curing stage is 75℃~80℃, for example, it can be 75℃, 76℃, 77℃, 78℃, 79℃, 80℃ or any two of the above values. Under the above-mentioned intelligent segmented temperature control conditions, low-temperature preheating impregnation is beneficial to promoting the dissolution of each raw material, high-temperature activation of nucleation is beneficial to accelerating the nucleation efficiency, medium-temperature controlled expansion is beneficial to suppressing excessive expansion, and finally high-temperature cross-linking curing is beneficial to promoting full cross-linking.

[0063] In some embodiments, the impregnation stage lasts for 40 to 50 minutes, for example, 40, 42, 45, 48, or 50 minutes, or any range between two of these values; the nucleation stage lasts for 30 to 35 minutes, for example, 30, 31, 32, 33, 34, or 35 minutes, or any range between two of these values; the expansion stage lasts for 25 to 30 minutes, for example, 25, 26, 27, 28, 29, or 30 minutes, or any range between two of these values; and the curing stage lasts for 30 to 35 minutes, for example, 30, 31, 32, 33, 34, or 35 minutes, or any range between two of these values. Under appropriate temperature, pressure, and time conditions, it is beneficial to prepare polyurethane foam with excellent performance.

[0064] In some embodiments, the pressure relief rate of the nucleation stage is 0.3 MPa / min to 0.5 MPa / min, for example, it can be 0.3 MPa / min, 0.35 MPa / min, 0.4 MPa / min, 0.45 MPa / min, 0.5 MPa / min, or any range between any two of the above values; the pressure relief rate of the expansion stage is 0.6 MPa / min to 0.8 MPa / min, for example, it can be 0.6 MPa / min, 0.65 MPa / min, 0.7 MPa / min, 0.75 MPa / min, 0.8 MPa / min, or any range between any two of the above values; the pressure relief rate of the solidification stage is 0.3 MPa / min to 0.4 MPa / min, for example, it can be 0.3 MPa / min, 0.32 MPa / min, 0.35 MPa / min, 0.8 MPa / min, 0.4 MPa / min, or any range between any two of the above values. Under the aforementioned adaptive pressure relief rate coupling control, the nucleation stage can avoid cell merging, the expansion stage is conducive to promoting uniform expansion, and the solidification stage is conducive to stabilizing cells.

[0065] In some embodiments, during the foaming process, the pressure change rate between two adjacent stages is 0.5 MPa / min to 1 MPa / min, for example, it can be 0.5 MPa / min, 0.6 MPa / min, 0.7 MPa / min, 0.8 MPa / min, 0.9 MPa / min, 1 MPa / min, or any range between two of the above values. Within the range of the pressure change rate, cell rupture caused by sudden pressure changes can be avoided.

[0066] It should be noted that the rate of pressure change between two adjacent stages can be either the rate of pressure increase or the rate of pressure decrease.

[0067] It should also be noted that the pressure relief rate of each stage refers to the rate at which pressure is released after being maintained at a certain pressure for a period of time within the stage. The pressure after the pressure is released is still within the pressure range of that stage. The pressure change rate between two adjacent stages refers to the rate at which the pressure after the pressure is released in the previous stage is adjusted to the target pressure of the next stage.

[0068] It should be further noted that after the pressure is released during the curing stage, the pressure is reduced to normal pressure at the same rate as the pressure changes in the two adjacent stages mentioned above. After cooling, the material is demolded to obtain polyurethane insulation foam.

[0069] The method for preparing composite foamed materials disclosed in this application overcomes the shortcomings of single-parameter control, such as uneven cell nucleation and high deformation rate, by coupling dynamic gradient pressure, intelligent segmented temperature control, and adaptive pressure relief rate (breaking through the barrier of single control). Through four-stage pressure, four-stage temperature control, and adaptive pressure relief, the deformation rate is effectively reduced, and the yield of high-quality composite foamed materials is improved. Furthermore, based on the existing reactor of a cold-chain foaming production line, only three modules need to be upgraded: ① pressure control system (adding a dynamic pressure feedback regulating valve); ② temperature control module (writing an intelligent segmented temperature control program); ③ pressure relief system (installing an adaptive pressure relief controller). The total modification cost is transparent, no core equipment needs to be replaced, and the production cycle can be optimized.

[0070] Fourthly, embodiments of this application also provide a refrigerator, which includes a cabinet, and the interlayer of the cabinet is provided with the above-mentioned composite foam material, or the composite foam material prepared by the above-mentioned preparation method.

[0071] In addition to refrigerator insulation, the composite foam material provided in this application embodiment can also be widely used in cold chain equipment such as cold chain containers and refrigerated trucks, and has broad market application prospects.

[0072] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0073] Example 1 This embodiment provides a composite foaming material, which includes a matrix, a composite foaming agent, and a composite foaming aid.

[0074] The matrix includes: a polyether (hydroxyl value of 420 mg KOH / g, viscosity of 1900 mPa·s / 25℃) and an isocyanate (isocyanate index of 1.12).

[0075] The composite foaming agent includes: supercritical carbon dioxide, bio-based pentane (GWP=20), and bio-based furan derivative (2-methylfuran, GWP=5).

[0076] The composite foaming agent includes: polyether-modified propylene oxide (molecular weight 6000, hydroxyl value 130mg KOH / g) and bio-based castor oil-modified polyol ester (hydroxyl value 90mg KOH / g).

[0077] The preparation method of composite foamed materials is as follows: Step S21: Take 1000g of combined polyether, heat to 48℃, add 1120g of isocyanate and 31.8g of composite foaming agent (1.5wt%, the mass ratio of polyether modified propylene oxide to bio-based castor oil polyol ester is 6.5:3.5), stir at 1800r / min for 25min to form a uniform premixed system; Step S22: The premixed system is fed into an existing cold chain foaming high-pressure reactor, sealed, and then a composite foaming agent (supercritical carbon dioxide, bio-based pentane, and bio-based furan derivative are compounded in a mass ratio of 5.5:2.5:2) is introduced. The total amount added is 302.8g (14wt%). The injection pressure is controlled at 7MPa, the temperature at 48℃, and the mixture is stirred and soaked at 400r / min for 45min. Step S23: Parameter adjustment is performed sequentially for the nucleation, expansion, and solidification stages. ① Nucleation stage: The pressure is increased to 20MPa and the temperature is increased to 68℃ at a rate of 0.9MPa / min, maintained for 32min, and simultaneously depressurized to 19MPa at a rate of 0.4MPa / min; ②Expansion phase: Adjust the pressure to 14MPa at a rate of 0.6MPa / min, reduce the temperature to 63℃, maintain for 28min, and then depressurize to 13MPa at a rate of 0.7MPa / min; ③ Curing stage: Stabilize the pressure to 11MPa at a rate of 0.4MPa / min, raise the temperature to 78℃, hold for 32min, and depressurize to 10MPa at a rate of 0.35MPa / min; Step S24: Slowly reduce the pressure to atmospheric pressure at a rate of 0.5 MPa / min, cool to room temperature, and then demold to obtain the composite foam material (polyurethane insulation foam).

[0078] Examples 2-5, Comparative Examples 1-3 Examples 2-5 and Comparative Examples 1-3 are basically the same as Example 1. For specific differences, please refer to Table 1.

[0079] Table 1

[0080] It should be noted that the proportions in the composite foaming agent refer to the mass ratio of supercritical carbon dioxide, bio-based pentane, and bio-based furan derivatives; the proportions in the composite co-foaming agent refer to the mass ratio of polyether-modified propylene oxide and bio-based castor oil-modified polyol ester. Pressure gradient refers to the pressure changes during the wetting, nucleation, expansion, and curing stages; temperature control segmentation refers to the temperature changes during the wetting, nucleation, expansion, and curing stages; and pressure relief rate refers to the pressure relief rate changes within the nucleation, expansion, and curing stages, where the pressure change rate remains constant between adjacent stages.

[0081] The cell diameter, uniformity, closed-cell ratio, thermal conductivity, compressive strength, elongation at break, deformation rate after 15 cycles at -40℃ to 70℃, strength decay after 15 cycles at -40℃ to 70℃, solubility, DWP, and bio-based content of the composite foamed materials in Examples 1-5 and Comparative Examples 1-3 were tested. The test results are shown in Table 2.

[0082] The bubble diameter was observed and recorded using SEM, with 50 bubble diameters randomly measured and the average value taken.

[0083] Cell uniformity was tested according to GB / T 12811-2025 standard "Test method for average cell size of rigid foamed plastics".

[0084] The closed-cell rate was tested according to GB / T 10799-2008 standard "Determination of open-cell and closed-cell volume percentage of rigid foamed plastics".

[0085] The thermal conductivity was tested according to the GB / T 10294-2008 standard "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method".

[0086] The compressive strength was tested according to GB / T 8813-2022 standard "Determination of compressive properties of rigid foamed plastics".

[0087] The elongation at break was tested according to GB / T 8813-2022 standard "Determination of compressive properties of rigid foamed plastics".

[0088] The high and low temperature cyclic deformation rate was tested according to GB / T 8811-2008 "Test Method for Dimensional Stability of Rigid Foamed Plastics".

[0089] Cyclic strength decay is calculated as (compressive strength before cycling - compressive strength after cycling) / strength before cycling × 100%.

[0090] The solubility was tested by gravimetric method, and the amount of solubility was obtained by calculating the change in mass of the system before and after mixing.

[0091] The GWP (Global Warming Potential) is calculated using the IPCC accounting method, Σ(component mass fraction × component GWP value).

[0092] The bio-based content was tested using the GB / T 29649-2013 standard, "Determination of Bio-based Content in Bio-based Materials by Liquid Scintillation Counter Method".

[0093] Table 2

[0094] From Table 2, we can obtain: The composite foaming material provided in this application has a cell uniformity of ≥99%, a solubility of ≥99.2%, a GWP of ≤15, and a bio-based content of ≥40wt%, which is significantly better than that of control examples 1-3 (uniformity ≤96%, solubility ≤93.5%, GWP ≥18, and bio-based content ≤32wt%). This proves that the composite foaming agent effectively improves the compatibility, environmental friendliness, and cell fineness of the composite foaming material. The high and low temperature cycle deformation rate of the composite foamed materials in Examples 1-5 is ≤0.21% and the strength decay is ≤2.9%, which is far better than that of Comparative Examples 1-3 (deformation rate ≥0.58% and decay ≥10.8%). Moreover, the closed-cell rate is ≥99.7% and the thermal conductivity is ≤13.3mW / (m·K), indicating that the pressure-temperature-pressure relief coupling control has solved the problem of cell stability. The compressive strength of the composite foamed materials in Examples 1-5 is ≥2.5 kg / cm². 2 The elongation at break is ≥25%, which is better than that of comparative examples 1~3 (strength ≤2.0kg / cm², elongation ≤22%), proving that the composite foaming agent achieves a synergistic improvement in strength and flexibility; Examples 1-5 underwent high and low temperature cycling tests from -40℃ to 70℃, with a strength decay of ≤3%, which is far superior to Comparative Examples 1-3 (strength decay ≥10%), and the long-term weather resistance is significantly improved.

[0095] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A composite foaming agent, characterized in that, This includes supercritical fluids, bio-based alkanes, and bio-based furan derivatives.

2. The composite foaming agent as described in claim 1, characterized in that, The supercritical fluid includes one or more of supercritical carbon dioxide, supercritical nitrous oxide, and supercritical propane. The bio-based alkanes include one or more of bio-based pentane, bio-based hexane, and bio-based cyclopentane; The bio-based furan derivatives include one or more of bio-based 2-methylfuran, bio-based furan, and bio-based 2-ethylfuran; The mass ratio of the supercritical fluid, the bio-based alkane, and the bio-based furan derivative is (5~6):(2~3):

2.

3. A composite foaming material, characterized in that, It includes a matrix and a composite foaming agent as described in any one of claims 1 to 2, wherein the matrix comprises a combination of polyethers and isocyanate compounds.

4. The composite foamed material as described in claim 3, characterized in that, The hydroxyl value of the combined polyether is 400 mg KOH / g to 440 mg KOH / g; The viscosity of the polyether composition is 1800 mPa·s to 2000 mPa·s; The isocyanate compounds include one or more of isocyanates and diphenylmethane diisocyanate; The isocyanate index in the matrix is ​​1.1~1.

15. The mass ratio of the matrix to the composite foaming agent is 100:(12~16).

5. The composite foaming material as described in claim 3, characterized in that, The composite foaming material also includes a composite foaming aid; the composite foaming aid includes a polyether-modified epoxy compound and a bio-based polyol ester; wherein... The molecular weight of the polyether-modified epoxy compound is 5000~7000; The polyether-modified epoxy compound includes one or more of polyether-modified ethylene oxide and polyether-modified propylene oxide; The bio-based polyol esters include one or more of castor oil-modified polyol esters and soybean oil-modified polyol esters; The mass ratio of the matrix to the composite foaming agent is 100:(1~2).

6. A method for preparing a composite foamed material, characterized in that, Includes the following steps: A matrix is ​​provided, the matrix comprising a combination of polyethers and isocyanate compounds; A composite foaming agent as described in any one of claims 1 to 2 is provided, mixed with the matrix, and foamed to obtain a composite foam material.

7. The preparation method according to claim 6, characterized in that, The supercritical fluid includes one or more of supercritical carbon dioxide, supercritical nitrous oxide, and supercritical propane. The bio-based alkanes include one or more of bio-based pentane, bio-based hexane, and bio-based cyclopentane; The bio-based furan derivatives include one or more of bio-based 2-methylfuran, bio-based furan, and bio-based 2-ethylfuran; The isocyanate compounds include one or more of isocyanates and diphenylmethane diisocyanate; The matrix supply further includes: providing a composite foaming agent, which is mixed with the matrix; optionally, the composite foaming agent includes a polyether-modified epoxy compound and a bio-based polyol ester.

8. The preparation method according to claim 6, characterized in that, The foaming process includes, sequentially, an impregnation stage, a nucleation stage, an expansion stage, and a curing stage; wherein... The pressure during the nucleation stage is greater than the pressure during the expansion stage, which in turn is greater than the pressure during the solidification stage, which is greater than the pressure during the wetting stage. The temperature of the curing stage is greater than the temperature of the nucleation stage, which is greater than the temperature of the expansion stage, which is greater than the temperature of the wetting stage.

9. The preparation method according to claim 8, characterized in that, The pressure during the wetting stage is 6 MPa to 8 MPa, the pressure during the nucleation stage is 18 MPa to 22 MPa, the pressure during the expansion stage is 13 MPa to 15 MPa, and the pressure during the solidification stage is 10 MPa to 12 MPa. The temperature of the wetting stage is 45℃~50℃, the temperature of the nucleation stage is 65℃~70℃, the temperature of the expansion stage is 62℃~65℃, and the temperature of the curing stage is 75℃~80℃. The wetting stage lasts for 40-50 minutes, the nucleation stage lasts for 30-35 minutes, the expansion stage lasts for 25-30 minutes, and the solidification stage lasts for 30-35 minutes. The pressure relief rate during the nucleation stage is 0.3 MPa / min to 0.5 MPa / min, the pressure relief rate during the expansion stage is 0.6 MPa / min to 0.8 MPa / min, and the pressure relief rate during the solidification stage is 0.3 MPa / min to 0.4 MPa / min. During the foaming process, the pressure change rate between two adjacent stages is 0.5 MPa / min to 1 MPa / min.

10. A refrigerator, characterized in that, The container includes a housing, the interlayer of which is provided with the composite foam material as described in any one of claims 3 to 5, or includes the composite foam material prepared by the preparation method as described in any one of claims 6 to 9.

Images