Composite foaming material, preparation method thereof and refrigerator

Abstract

The invention discloses a composite foaming material, a preparation method thereof and a refrigerator, and relates to the technical field of foaming materials. The composite foaming material comprises a matrix, a foaming agent and a nano reinforcing agent, wherein the matrix comprises combined polyether and an isocyanate compound, and the nano reinforcing agent comprises a one-dimensional nano material and a two-dimensional nano material. A one-dimensional nano-material and a two-dimensional nano-material are introduced into the composite foam material, so that the composite foam material can be prepared by increasing nucleation sites, regulating and controlling a foam structure, enhancing the strength of a foam wall, improving mechanical properties of a matrix, improving thermal stability and flame retardance, reducing a heat conductivity coefficient and the like; the mechanical property, the thermal insulation property, the dimensional stability and the durability of the composite foaming material are obviously improved. The one-dimensional nano material mainly provides skeleton support and mechanical enhancement, the two-dimensional nano material mainly provides interface stability and barrier and flame-retardant enhancement, and the comprehensive performance of the composite foam material can be further improved through the synergistic effect of the two nano materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foamed materials, in particular to a composite foamed material, a preparation method thereof and a refrigerator. BACKGROUND

[0002] The refrigerator is a refrigeration equipment that keeps constant low temperature, and is also a product that keeps constant low temperature of food or other objects. The foamed material is a closed-cell rigid foam formed by chemical reaction foaming and solidification in the interlayer of the refrigerator body (the shell and the inner tank). The core function of the foamed material is to build a continuous and uniform heat insulation layer to minimize the heat transfer from the external environment to the interior of the refrigerator, so as to maintain a low temperature environment and reduce energy consumption.

[0003] The nano-enhanced composite material has become a breakthrough in core technology because it can simultaneously improve the mechanical properties and thermal insulation properties of the polyurethane foam. The polyurethane foam is the core material of the refrigerator insulation layer, and its performance directly determines the energy consumption level and service life of the refrigerator. However, the existing nano-enhanced technology still has some problems: single nano-particles are prone to agglomeration, resulting in increased thermal conductivity and decreased mechanical properties; single functional groups and physical modification have poor compatibility, high sedimentation rate, and fast strength decay after multiple high-low temperature cycles; the nano-enhanced and thermal insulation are contradictory, and cannot simultaneously achieve low thermal conductivity and high strength.

[0004] Therefore, the foamed material still needs to be further improved. SUMMARY

[0005] Therefore, the present application provides a composite foamed material, a preparation method thereof and a refrigerator to solve at least one of the above problems.

[0006] In the embodiments of the present application, a composite foamed material includes a polyurethane matrix, a foaming agent and a nano-enhancing agent. The nano-enhancing agent includes one-dimensional nano-material and two-dimensional nano-material.

[0007] Optionally, in some embodiments of the present application, the shape of the one-dimensional nano-material includes nanotubes; the average tube diameter of the nanotubes is 10nm-20nm, and the average length of the nanotubes is 500nm-1000nm. The shape of the two-dimensional nano-material includes nanosheets; the average thickness of the nanosheets is less than or equal to 1.5nm. The one-dimensional nano-material includes carboxylated nano-material; the mass fraction of carboxyl in the carboxylated nano-material is greater than or equal to 2.5wt%; the carboxylated nano-material includes one or more of carboxylated single-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes and carboxylated cellulose nanofibers. The two-dimensional nano-material includes one or more of graphene oxide and boron nitride. The mass ratio of the one-dimensional nanomaterial and the two-dimensional nanomaterial is 1: (2-4).

[0008] Optionally, in some embodiments of the present application, the composite foamed material further comprises a modifier, and the modifier modifies the nanoreinforcement agent; wherein, The modifier comprises one or more of alkoxysilane, hydroxyl-containing acrylate; The alkoxysilane comprises one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane; The hydroxyl-containing acrylate comprises one or more of hydroxyethyl methacrylate, hydroxypropyl methacrylate; The alkoxysilane is connected to the nanoreinforcement agent; The hydroxyl-containing acrylate connects the polyurethane matrix and the nanoreinforcement agent; The mass proportion of the alkoxysilane in the nanoreinforcement agent is 3wt%-5wt%; the mass proportion of the hydroxyl-containing acrylate in the nanoreinforcement agent is 5wt%-8wt%; The mass proportion of the modifier and the nanoreinforcement agent in the polyurethane matrix is 0.5wt%-1.2wt%.

[0009] Optionally, in some embodiments of the present application, the composite foamed material further comprises an initiator; wherein, The initiator comprises one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptyl nitrile, di-tert-butyl peroxide; The mass proportion of the initiator in the nanoreinforcement agent is 0.3wt%-1wt%.

[0010] Optionally, in some embodiments of the present application, the polyurethane matrix is obtained by reaction of a combined polyether and an isocyanate compound; wherein, The hydroxyl value of the combined polyether is 380mg KOH / g-420mg KOH / g; the viscosity of the combined polyether is 1900mPa·s-2100mPa·s; The isocyanate compound comprises one or more of isocyanate, diphenylmethane diisocyanate; The isocyanate index in the polyurethane matrix is 1.08-1.12.

[0011] Optionally, in some embodiments of this application, the blowing agent includes one or more of alkane blowing agents and fluorinated olefin blowing agents; wherein the alkane blowing agent includes one or more of cyclopentane and isopentane; the fluorinated olefin blowing agent includes one or more of 1-chloro-3,3,3-trifluoropropylene, 1,1,1,4,4,4-hexafluoro-2-butene, and 3,3,3-trifluoropropylene; the blowing agent accounts for 12wt%~15wt% of the mass of the polyurethane matrix; The composite foaming material further includes a catalyst; wherein the catalyst includes one or more of organobismuth catalysts, organotin catalysts, amine catalysts, and zinc catalysts; the catalyst accounts for 0.1wt% to 0.3wt% of the mass of the polyurethane matrix.

[0012] Accordingly, embodiments of this application also provide a method for preparing a composite foaming material, providing a nano-reinforcing agent, wherein the nano-reinforcing agent includes one-dimensional nanomaterials and two-dimensional nanomaterials; A composite foam material is obtained by mixing a combination of polyether, isocyanate compound and foaming agent with the nano-reinforcing agent and performing a foaming treatment.

[0013] Optionally, in some embodiments of this application, providing the nano-reinforcing agent further includes: providing a modifier and an initiator, mixing them with the nano-reinforcing agent, and performing a modification treatment; wherein, The one-dimensional nanomaterials include one or more of carboxylated single-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, and carboxylated cellulose nanofibers. The two-dimensional nanomaterials include one or more of graphene oxide and boron nitride; The mass ratio of the one-dimensional nanomaterial to the two-dimensional nanomaterial is 1:(2~4); The modifier includes one or more of alkoxysilanes and hydroxyl-containing acrylates; the alkoxysilane includes one or more of γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane; the hydroxyl-containing acrylate includes one or more of hydroxyethyl methacrylate and hydroxypropyl methacrylate. The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, and di-tert-butyl peroxide; The modification treatment is performed at a temperature of 60℃ to 80℃ for a duration of 3 hours to 8 hours.

[0014] Optionally, in some embodiments of this application, the foaming process includes a nucleation stage and a curing stage performed sequentially, wherein the temperature of the curing stage is higher than the temperature of the nucleation stage; wherein, The temperature of the nucleation stage is 60℃~65℃, and the time of the nucleation stage is 30min~35min; The curing temperature is 70℃~75℃, and the curing time is 25min~30min.

[0015] 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.

[0016] The composite foaming material provided in this application incorporates both one-dimensional and two-dimensional nanomaterials as nano-reinforcing agents. This overcomes the functional limitations and agglomeration defects of single nanoparticles. Through the synergistic compounding of two-dimensional and one-dimensional nanomaterials, the dispersion uniformity of the reinforcing agent is effectively improved, agglomeration is reduced, and the performance degradation caused by stress concentration is resolved. Among the nano-reinforcing agents, the one-dimensional nanomaterials possess a high aspect ratio and excellent mechanical properties. In the composite foaming material, they mainly enhance cell nucleation efficiency, increase cell wall strength, improve the mechanical properties of the matrix, and enhance thermal stability and flame retardant properties. The two-dimensional nanomaterials have a higher specific surface area. The area and excellent barrier properties of these materials play a key role in regulating the cell structure, significantly improving thermal stability and insulation performance, enhancing flame retardancy, and improving the compatibility and interfacial properties of the matrix in composite foam materials. When two types of nanomaterials are introduced together, a three-dimensional network structure of "sheet-tube interweaving" is formed, achieving functional complementarity and producing a synergistic effect: one-dimensional materials provide "skeleton reinforcement" and two-dimensional materials provide "interfacial stability and barrier", making the cell structure more uniform and stable, further improving mechanical properties (strength and toughness), significantly enhancing thermal stability and flame retardancy, and improving dimensional stability and durability, thereby optimizing the overall performance of the foam material. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a flowchart illustrating a method for preparing a composite foamed material according to an embodiment of this application; Figure 2 This is a microstructure diagram of the nano-reinforcing agent modified by the modifier provided in Example 1 of this application; Figure 3 This is another microstructure diagram of the nano-reinforcing agent modified by the modifier provided in Example 1 of this application. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The technical solution of this application is as follows: In a first aspect, embodiments of this application provide a composite foaming material, comprising a polyurethane matrix, a foaming agent, and a nano-reinforcing agent; wherein the nano-reinforcing agent comprises one-dimensional nanomaterials and two-dimensional nanomaterials.

[0025] It should be noted that one-dimensional nanomaterials refer to materials in three-dimensional space where two dimensions are at the nanoscale, and the third dimension is significantly larger than the nanoscale, exhibiting a clear one-dimensional quantum confinement effect, such as nanowires, nanorods, nanotubes, nanofibers, and nanoribbons. Two-dimensional nanomaterials refer to layered or sheet-like materials in three-dimensional space where only one dimension is at the nanoscale, while the other two dimensions are at the macroscopic scale, and their electronic structure and physical properties exhibit strong two-dimensional confinement characteristics.

[0026] The composite foaming material provided in this application incorporates both one-dimensional and two-dimensional nanomaterials as nano-reinforcing agents. This overcomes the functional limitations and agglomeration defects of single nanoparticles. Through the synergistic compounding of two-dimensional and one-dimensional nanomaterials, the dispersion uniformity of the reinforcing agent is effectively improved, agglomeration is reduced, and the performance degradation caused by stress concentration is resolved. Among the nano-reinforcing agents, the one-dimensional nanomaterials possess a high aspect ratio and excellent mechanical properties. In the composite foaming material, they mainly enhance cell nucleation efficiency, increase cell wall strength, improve the mechanical properties of the matrix, and enhance thermal stability and flame retardant properties. The two-dimensional nanomaterials have a higher specific surface area. The area and excellent barrier properties of these materials play a key role in regulating the cell structure, significantly improving thermal stability and insulation performance, enhancing flame retardancy, and improving the compatibility and interfacial properties of the matrix in composite foam materials. When two types of nanomaterials are introduced together, a three-dimensional network structure of "sheet-tube interweaving" is formed, achieving functional complementarity and producing a synergistic effect: one-dimensional materials provide "skeleton reinforcement" and two-dimensional materials provide "interfacial stability and barrier", making the cell structure more uniform and stable, further improving mechanical properties (strength and toughness), significantly enhancing thermal stability and flame retardancy, and improving dimensional stability and durability, thereby optimizing the overall performance of the foam material.

[0027] In some embodiments, the polyurethane matrix is ​​obtained by reacting a combination of polyethers and isocyanate compounds. It is understood that the combination of polyethers and isocyanate compounds are respectively the "white component" and the "black component," and the polyurethane matrix is ​​prepared by nucleation and foaming under the foaming action of a foaming agent.

[0028] In some embodiments, the hydroxyl value of the composite polyether is 380 mg KOH / g to 420 mg KOH / g, for example, it can be 380 mg KOH / g, 390 mg KOH / g, 400 mg KOH / g, 410 mg KOH / g, 420 mg KOH / g, or any range between two of the above values. The viscosity of the composite polyether is 1900 mPa·s to 2100 mPa·s, for example, it can be 1900 mPa·s, 1950 mPa·s, 2000 mPa·s, 2050 mPa·s, 2100 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.

[0029] In some embodiments, the isocyanate compound includes one or more of isocyanates and diphenylmethane diisocyanate (MDI).

[0030] In some embodiments, the isocyanate index in the polyurethane matrix is ​​1.08 to 1.12, for example, it can be 1.08, 1.09, 1.10, 1.11, 1.12, 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.

[0031] In some embodiments, the foaming agent includes one or more of alkane foaming agents and fluorinated olefin foaming agents.

[0032] Furthermore, the alkane blowing agent includes one or more of cyclopentane and isopentane.

[0033] The fluorinated olefin blowing agent includes one or more of 1-chloro-3,3,3-trifluoropropene (HFO-1233zd), 1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz), and 3,3,3-trifluoropropene (HFO-1243zf).

[0034] It should be noted that HFO-1233zd and HFO-1336mzz can be either cis or trans.

[0035] In some embodiments, the foaming agent accounts for 12wt% to 15wt% of the polyurethane matrix by mass, for example, 12wt%, 13wt%, 14wt%, 15wt%, or any range between two of the above values. Within this mass ratio range, it is beneficial to prepare a polyurethane matrix with better foaming performance.

[0036] In some embodiments, the shape of the one-dimensional nanomaterial includes nanotubes.

[0037] Furthermore, the average diameter of the nanotube is 10nm to 20nm, for example, it can be 10nm, 10nm, 12nm, 15nm, 18nm, 20nm, or any range between two of the above values. The average length of the nanotube is 500nm to 1000nm, for example, it can be 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or any range between two of the above values.

[0038] In some embodiments, the shape of the two-dimensional nanomaterial includes nanosheets.

[0039] Furthermore, the average thickness of the nanosheet is less than or equal to 1.5 nm, for example, it can be 1.5 nm, 1.4 nm, 1.3 nm, 1.2 nm, 1.1 nm, 1 nm, etc.

[0040] Within the dimensions of the aforementioned one-dimensional and two-dimensional nanomaterials, the two work together to form a three-dimensional network structure, which can effectively enhance the strength and other properties of composite foam materials.

[0041] In some embodiments, the one-dimensional nanomaterial includes carboxylated nanomaterials. It is understood that carboxylated nanomaterials refer to one-dimensional nanomaterials modified by introducing carboxyl groups onto their surface.

[0042] Furthermore, the mass fraction of carboxyl groups in the carboxylated nanomaterial is greater than or equal to 2.5 wt%, for example, it can be 2.5 wt%, 2.55 wt%, 2.6 wt%, 2.65 wt%, 2.7 wt%, etc. Carboxylation can promote the bonding of one-dimensional nanomaterials with other materials.

[0043] In some embodiments, the carboxylated nanomaterials include one or more of carboxylated single-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, and carboxylated cellulose nanofibers. The carboxylated nanomaterials can enhance mechanical properties and regulate cell nucleation.

[0044] It should be noted that carboxylated nanomaterials can be obtained by carboxylating one-dimensional nanomaterials. Carboxylation can be performed using conventional techniques in this field, such as nitric acid oxidation, sulfuric acid-nitric acid mixed acid oxidation, potassium permanganate oxidation, etc.

[0045] In some embodiments, the two-dimensional nanomaterial includes one or more of graphene oxide and boron nitride. The two-dimensional nanomaterial possesses excellent barrier properties, which can suppress heat conduction and improve the thermal insulation performance of the composite foam material.

[0046] In some embodiments, the mass ratio of the one-dimensional nanomaterial to the two-dimensional nanomaterial is 1:(2~4), for example, it can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any range between the above two values. Within this mass ratio range, it is beneficial for the one-dimensional nanomaterial and the two-dimensional nanomaterial to work synergistically to improve the thermal insulation, structural strength, and other properties of the composite foam material.

[0047] In some embodiments, the composite foam material further includes a modifier that modifies the nano-reinforcing agent.

[0048] In some embodiments, the modifier includes one or more of alkoxysilanes and hydroxyl-containing acrylates.

[0049] Furthermore, the alkoxysilane includes one or more of γ-glycidoxypropyltrimethoxysilane (KH-560) and γ-aminopropyltriethoxysilane (KH-550).

[0050] The hydroxyl-containing acrylate includes one or more of hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (HPMA). The hydroxyl groups of the hydroxyl-containing acrylate can be cross-linked with the matrix to achieve anchoring.

[0051] In some embodiments, the alkoxysilane is linked to the nano-reinforcing agent. Specifically, the surface of the nano-reinforcing agent contains groups such as hydroxyl and carboxyl groups. The alkoxy groups in the alkoxysilane can react with the hydroxyl and carboxyl groups to form a linkage, while the silyl groups in the alkoxysilane can improve the hydrophobic properties of the nano-reinforcing agent and enhance its compatibility with the polyurethane matrix.

[0052] In some embodiments, the hydroxyl-containing acrylate connects the polyurethane matrix and the nano-reinforcing agent. Specifically, the hydroxyl-containing acrylate can undergo graft polymerization with hydroxyl, carboxyl, or other groups in the nano-reinforcing agent, and the isocyanate compound in the polyurethane matrix contains isocyanate groups. The hydroxyl groups in the hydroxyl-containing acrylate can undergo a crosslinking reaction with the isocyanate groups, anchoring the nano-reinforcing agent in the polyurethane matrix.

[0053] By adding modifiers, the nano-reinforcing agents can form stable chemical bonds and interpenetrating network structures with the matrix, solving the problems of poor compatibility and insufficient long-term stability. The modified nano-reinforcing agents form an interpenetrating network structure with the polyurethane matrix, significantly improving the interfacial bonding strength and solving the delamination problem during long-term use.

[0054] In some embodiments, the alkoxysilane accounts for 3wt% to 5wt% of the mass ratio of the nano-reinforcing agent, for example, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any range between two of the above values. The hydroxyl-containing acrylate accounts for 5wt% to 8wt% of the mass ratio of the nano-reinforcing agent, for example, 5wt%, 6wt%, 7wt%, 8wt%, or any range between two of the above values. Thus, within the range of the above mass ratios, it is beneficial for the modifiers to exert their respective functions, promoting the anchoring of the nano-reinforcing agent and improving its stability after graft modification, while preventing its aggregation, thus achieving a dual effect to avoid interfacial delamination.

[0055] In some embodiments, the composite foam material further includes an initiator. The initiator is used during the preparation of the composite foam material to initiate the grafting modification of the nano-reinforcing agent by the modifier.

[0056] Furthermore, the initiator includes one or more of azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), azobisisobutyronitrile (ABVN), and di-tert-butyl peroxide (DTBP).

[0057] In some embodiments, the initiator accounts for 0.3wt% to 1wt% of the mass of the nano-reinforcing agent, for example, it can be 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, or any range between two of the above values. Within this mass ratio range, it is beneficial that during the preparation process, the initiator initiates the generation of free radicals in the modifier, which then graft and modify the active sites of the nano-reinforcing agent.

[0058] In some embodiments, the mass ratio of the modifier and the nano-reinforcing agent to the polyurethane matrix is ​​0.5wt% to 1.2wt%, for example, it can be 0.5wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, or any range between two of the above values. Within the range of the mass ratio, the nano-reinforcing agent, which is beneficial to the modifier, improves the mechanical properties of the composite foam material, while acting as a cell nucleation point to regulate the cell structure and reduce the heat conduction of the composite foam material.

[0059] In some embodiments, the composite foam material further includes a catalyst. The catalyst is introduced during the preparation of the composite foam material to catalyze and improve the foaming nucleation efficiency.

[0060] Furthermore, the catalyst includes one or more of the following: organobismuth catalysts, organotin catalysts (such as dibutyltin dilaurate), amine catalysts (such as triethylenediamine), and zinc catalysts (such as zinc trifluoromethanesulfonate).

[0061] In some embodiments, the catalyst accounts for 0.1 wt% to 0.3 wt% of the polyurethane matrix by mass, for example, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, or any range between two of the above values. Within this mass ratio range, it is beneficial to accelerate the foaming and nucleation rate and improve the quality of the polyurethane matrix.

[0062] The composite foaming material provided in this application, through the synergistic compounding of two-dimensional and one-dimensional nanomaterials, effectively solves the problems of single particle aggregation and functional limitations by employing a "sheet-tube interwoven" three-dimensional network structure compared to single nanoparticles in the prior art. Furthermore, the use of multi-functional reactive grafting modifiers to modify the nano-reinforcing agents, compared to single functional group or physical modification in the prior art, provides a dual "anchoring-compatibility" effect, effectively addressing the issues of poor compatibility and insufficient long-term stability.

[0063] Secondly, 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 nano-reinforcing agent, wherein the nano-reinforcing agent includes one-dimensional nanomaterials and two-dimensional nanomaterials; Step S12: Provide a combination of polyether, isocyanate compound and foaming agent, mix with the nano-reinforcing agent, and perform foaming treatment to obtain a composite foam material.

[0064] The materials and proportions of the combined polyether, isocyanate compound, foaming agent and nano-reinforcing agent can be referred to the content of the first aspect, and will not be repeated here.

[0065] In some embodiments, providing the nano-reinforcing agent further includes: providing a modifier and an initiator, mixing them with the nano-reinforcing agent, and performing a modification treatment.

[0066] The materials and amounts of the modifier and initiator can be referred to in the first aspect, and will not be repeated here.

[0067] It should be noted that one-dimensional and two-dimensional nanomaterials can be dissolved in deionized water to form a solution, and then an appropriate amount of modifier and initiator can be added. After modification, the nano-reinforcing agent is obtained by centrifugation, washing, and freeze-drying.

[0068] In some embodiments, the temperature of the modification treatment is 60℃~80℃, for example, it can be 60℃, 65℃, 70℃, 75℃, 80℃ or any range between two of the above values; the time of the modification treatment is 3h~8h, for example, it can be 3h, 4h, 5h, 6h, 7h, 8h or any range between two of the above values. Under the conditions of the modification treatment, it is beneficial for the modifier to fully modify the nano-reinforcing agent, thereby improving the performance of the nano-reinforcing agent.

[0069] In some embodiments, the foaming process includes a nucleation stage and a curing stage performed sequentially, wherein the temperature of the curing stage is higher than the temperature of the nucleation stage.

[0070] Specifically, in some embodiments, the temperature of the nucleation stage is 60℃~65℃, for example, it can be 60℃, 61℃, 62℃, 63℃, 64℃, 65℃ or any range between two of the above values, and the time of the nucleation stage is 30min~35min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min or any range between two of the above values. The temperature of the curing stage is 70℃~75℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃ or any range between two of the above values, and the time of the curing stage is 25min~30min, for example, it can be 25min, 26min, 27min, 28min, 29min, 30min or any range between two of the above values. Under the aforementioned foaming conditions, the nucleation stage facilitates the reaction between the combined polyether and isocyanate compounds to form a polyurethane matrix. The nucleation effect of the nano-reinforcing agent regulates the cell size and promotes cross-linking between the nano-reinforcing agent and the polyurethane matrix, forming an interpenetrating network structure. Segmented temperature control helps match the reaction rate between the nano-reinforcing agent and the polyurethane matrix, ensuring sufficient chemical bonding and preventing cell collapse.

[0071] Thirdly, 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.

[0072] The composite foaming material provided in this application embodiment is used in refrigerators. Because the foam has a low thermal conductivity and high strength, it can still meet the requirements for heat preservation and structure even with a thin thickness. Therefore, an ultra-thin wall insulation layer of 15mm to 22mm can be prepared. The ultra-thin wall insulation layer saves space in the refrigerator wall material, releases internal storage volume, and improves the volume ratio of the refrigerator.

[0073] 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.

[0074] 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.

[0075] Example 1 This embodiment provides a composite foaming material, which includes a polyurethane matrix, a foaming agent, a modified nano-reinforcing agent, an initiator, and a catalyst.

[0076] The matrix is ​​obtained by reacting a combination of polyether and isocyanate: the combination of polyether (hydroxyl value of 420 mg KOH / g, viscosity of 1900 mPa·s / 25℃) and isocyanate (isocyanate index of 1.1).

[0077] The foaming agent consists of HFO-1336mzz and cyclopentane mixed in a mass ratio of 6:4.

[0078] Modifiers include HEMA and KH-560.

[0079] Nano-reinforcing agents include carboxylated multi-walled carbon nanotubes and graphene oxide.

[0080] Initiators include: AIBN.

[0081] Catalysts include: organic bismuth catalysts.

[0082] The preparation method of composite foamed materials is as follows: Step S21: Take 20g of raw graphene oxide (average thickness 2nm~5nm) and disperse it in 500mL of deionized water. Sonicate at 300W for 30 minutes, centrifuge at 8000r / min for 10 minutes to remove unpeeled sheets, and freeze-dry to obtain 18.2g of graphene oxide (average thickness ≤1.5nm). Take 10g of multi-walled carbon nanotubes and add them to 200mL of 6mol / L nitric acid solution. Reflux at 80℃ for 2h, wash until neutral, and dry to obtain 8.6g of carboxylated multi-walled carbon nanotubes (carboxyl content 2.7wt%). Step S22: Mix 18.2g of graphene oxide with 8.6g of carboxylated multi-walled carbon nanotubes, add 536g of deionized water, and sonicate at 500W for 60min to obtain a suspension. Add 1.34g of HEMA, 0.94g of KH-560 and 0.107g of AIBN to the suspension, stir and react at 75℃ for 5h, centrifuge, wash with deionized water 3 times, and freeze dry to obtain 25.6g of modified nano-reinforcing agent. Step S23: Take 1000g of the combined polyether, heat to 50℃, add 7.5g of the modified nano-reinforcing agent, stir at 1500r / min for 30min, and ultrasonically disperse at 400W for 20min to obtain a pre-dispersion system; add 500g of isocyanate, 180g of foaming agent, and 3.0g of organic bismuth catalyst to the pre-dispersion system, stir rapidly at 2100r / min for 14s, and stir at 58℃ to obtain the foaming material; Step S24: Inject the foaming material into the mold, and sequentially carry out the nucleation stage at 65℃ for 35 minutes and the curing stage at 70℃ for 30 minutes. After cooling to room temperature, demold to obtain the composite foaming material (polyurethane insulation foam).

[0083] Example 2 Example 2 is basically the same as Example 1, except that: In step S22, the mixture of 18.2g graphene oxide and 8.6g carboxylated multi-walled carbon nanotubes is replaced by a mixture of 27.5g graphene oxide and 8.5g carboxylated multi-walled carbon nanotubes. In step S23, the nano-reinforcing agent modified with 7.5g of modifier is replaced with the nano-reinforcing agent modified with 12g of modifier.

[0084] Example 3 Example 3 is basically the same as Example 1, except that: In step S22, the mixture of 18.2g graphene oxide and 8.6g carboxylated multi-walled carbon nanotubes is replaced by a mixture of 36.8g graphene oxide and 9.2g carboxylated multi-walled carbon nanotubes. In step S23, the nano-reinforcing agent modified by adding 7.5g of modifier is replaced by the nano-reinforcing agent modified by adding 18g of modifier.

[0085] Example 4 Example 4 is basically the same as Example 1, except that: In step S22, the mixture of 18.2g graphene oxide and 8.6g carboxylated multi-walled carbon nanotubes is replaced by a mixture of 18.4g graphene oxide and 18.4g carboxylated multi-walled carbon nanotubes.

[0086] Comparative Example 1 Comparative Example 1 and Example 1 are basically the same, except that: In step S22, the nano-reinforcing agent contains only graphene oxide and no carboxylated multi-walled carbon nanotubes; and the modifier contains only KH-560 and no HEMA.

[0087] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that: In step S22, the nano-reinforcing agent contains only carboxylated multi-walled carbon nanotubes and no graphene oxide; and it does not contain the modifiers KH-560 and HEMA.

[0088] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that: In step S22, the nano-reinforcing agents (carboxylated multi-walled carbon nanotubes and graphene oxide) are replaced with SiO2 particles, and the modifier contains only KH-560 and no HEMA.

[0089] Comparative Example 4 Comparative Example 4 is basically the same as Example 1, except that: In step S23, the nano-reinforcing agent was not modified.

[0090] The microstructure of the nano-reinforcing agent modified by the modifier in Example 1 was observed using scanning electron microscopy. See the results below. Figure 2 and Figure 3 .

[0091] from Figure 2 and Figure 3 As can be seen, the graphene oxide sheets and carboxylated carbon nanotubes form a three-dimensional network structure, which can effectively inhibit the aggregation of nano-reinforcing agents.

[0092] The dispersion uniformity, settling rate after 24 hours, density, closed-cell rate, cell uniformity, thermal conductivity, compressive strength, elongation at break, deformation rate, and strength decay rate after 500 high and low temperature cycles of the composite foamed materials in Examples 1-4 and Comparative Examples 1-4 were tested. The test results are shown in Table 1.

[0093] The dispersion uniformity refers to the dispersion uniformity of the modified nano-reinforcing agent in the polyether, and is tested using a laser particle size analyzer in accordance with ISO 13321-1996.

[0094] The sedimentation rate after 24 hours of standing refers to the volume percentage of the supernatant after the modified nano-reinforcing agent has been left to stand in the polyether for 24 hours, as observed in a graduated test tube.

[0095] Density and closed-cell ratio were tested according to GB / T 10799-2008 standard "Determination of open-cell and closed-cell volume percentage of rigid foamed plastics".

[0096] Cell uniformity was tested according to GB / T 12811-2025 standard "Test method for average cell size of rigid foamed plastics".

[0097] 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".

[0098] The compressive strength was tested according to GB / T 8813-2022 standard "Determination of compressive properties of rigid foamed plastics".

[0099] The elongation at break was tested according to GB / T 8813-2022 standard "Determination of compressive properties of rigid foamed plastics".

[0100] The deformation rate was tested under the following conditions: after 10 cycles at -30℃ to 60℃, the dimensional change rate was measured.

[0101] The test conditions for the strength decay rate after 500 high and low temperature cycles are -30℃ to 60℃ for 500 cycles, and then the compressive strength is tested.

[0102] Table 1

[0103] From Table 1, we can obtain: The composite foamed materials of Examples 1-4 of this application are significantly superior to those of Comparative Examples 1-4 in terms of core properties such as thermal conductivity (≤16.3mW / (m·K)), compressive strength (≥1.9kg / cm²), and cell uniformity (≥96.5%), thus breaking the performance contradiction of "reinforcement-insulation" in the prior art. Example 2 exhibits even better performance, with a thermal conductivity as low as 14.8 mW / (m·K) and a compressive strength of 2.3 kg / cm². 2 After 500 cycles of high and low temperatures, the strength decayed by only 3.5%, demonstrating the optimal synergy between the ratio of one-dimensional and two-dimensional nanomaterials and the amount of nano-reinforcing agent added by the modifier. Comparative Examples 1-4, due to the use of single nanoparticles, single functional group modification, or physical modification, suffer from problems such as high sedimentation rate, poor stability, and performance imbalance, and their performance is far inferior to the composite foaming material in the embodiments of this application.

[0104] The composite foam material and its application in refrigerators provided in this application, through the combination of one-dimensional and two-dimensional nanomaterials, achieve a breakthrough improvement in the dispersion performance of the nano-reinforcing agent, increasing the uniformity of the nano-reinforcing agent dispersion in the polyether system. The bifunctional modification of the modifier enables the nano-reinforcing agent and the polyurethane matrix to form an interpenetrating network structure, significantly reducing the compressive strength decay rate after 500 high and low temperature cycles. By controlling the appropriate proportion of the nano-reinforcing agent, the composite foam material exhibits a low thermal conductivity, high compressive strength, and high closed-cell ratio, achieving a coexistence of "reinforcement-insulation" performance. Furthermore, the composite foam material of this application has a simple preparation method, low industrialization cost, and is compatible with existing refrigerator foaming production lines, making it suitable for mass production. Its application in refrigerators can meet the requirements for ultra-thin walls and the need for high-capacity refrigerator upgrades.

[0105] 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 material, characterized in that, It includes a polyurethane matrix, a foaming agent, and a nano-reinforcing agent; wherein the nano-reinforcing agent includes one-dimensional nanomaterials and two-dimensional nanomaterials.

2. The composite foamed material as described in claim 1, characterized in that, The shape of the one-dimensional nanomaterial includes nanotubes; the average diameter of the nanotubes is 10nm~20nm, and the average length of the nanotubes is 500nm~1000nm; The two-dimensional nanomaterial comprises nanosheets; the average thickness of the nanosheets is less than or equal to 1.5 nm. The one-dimensional nanomaterials include carboxylated nanomaterials; the mass fraction of carboxyl groups in the carboxylated nanomaterials is greater than or equal to 2.5 wt%; the carboxylated nanomaterials include one or more of carboxylated single-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, and carboxylated cellulose nanofibers. The two-dimensional nanomaterials include one or more of graphene oxide and boron nitride; The mass ratio of the one-dimensional nanomaterial to the two-dimensional nanomaterial is 1:(2~4).

3. The composite foamed material as described in claim 1, characterized in that, The composite foam material also includes a modifier, which modifies the nano-reinforcing agent; wherein... The modifier includes one or more of alkoxysilanes and hydroxyl-containing acrylates; The alkoxysilane includes one or more of γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane; The hydroxyl-containing acrylate includes one or more of hydroxyethyl methacrylate and hydroxypropyl methacrylate; The alkoxysilane is connected to the nano-reinforcing agent; The hydroxyl-containing acrylate connects the polyurethane matrix and the nano-reinforcing agent; The alkoxysilane accounts for 3wt% to 5wt% of the mass of the nano-reinforcing agent; the hydroxyl-containing acrylate accounts for 5wt% to 8wt% of the mass of the nano-reinforcing agent. The mass ratio of the modifier and the nano-reinforcing agent to the mass ratio of the polyurethane matrix is ​​0.5wt% to 1.2wt%.

4. The composite foamed material as described in claim 3, characterized in that, The composite foam material also includes an initiator; wherein... The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, and di-tert-butyl peroxide; The initiator accounts for 0.3wt% to 1wt% of the mass of the nano-reinforcing agent.

5. The composite foamed material as described in claim 1, characterized in that, The polyurethane matrix is ​​obtained by reacting a combination of polyethers and isocyanate compounds; wherein... The hydroxyl value of the polyether is 380 mg KOH / g to 420 mg KOH / g; the viscosity of the polyether is 1900 mPa·s to 2100 mPa·s. The isocyanate compounds include one or more of isocyanates and diphenylmethane diisocyanate; The isocyanate index in the polyurethane matrix is ​​1.08 to 1.

12.

6. The composite foamed material as described in claim 1, characterized in that, The foaming agent includes one or more of alkane foaming agents and fluorinated olefin foaming agents; wherein the alkane foaming agent includes one or more of cyclopentane and isopentane; the fluorinated olefin foaming agent includes one or more of 1-chloro-3,3,3-trifluoropropylene, 1,1,1,4,4,4-hexafluoro-2-butene, and 3,3,3-trifluoropropylene; the foaming agent accounts for 12wt%~15wt% of the mass of the polyurethane matrix. The composite foaming material further includes a catalyst; wherein the catalyst includes one or more of organobismuth catalysts, organotin catalysts, amine catalysts, and zinc catalysts; the catalyst accounts for 0.1wt% to 0.3wt% of the mass of the polyurethane matrix.

7. A method for preparing a composite foamed material, characterized in that, Provide nano-reinforcing agents, said nano-reinforcing agents comprising one-dimensional nanomaterials and two-dimensional nanomaterials; A composite foam material is obtained by mixing a combination of polyether, isocyanate compound and foaming agent with the nano-reinforcing agent and performing a foaming treatment.

8. The preparation method according to claim 7, characterized in that, The provision of the nano-reinforcing agent further includes: providing a modifier and an initiator, which are mixed with the nano-reinforcing agent to undergo a modification treatment; wherein, The one-dimensional nanomaterials include one or more of carboxylated single-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, and carboxylated cellulose nanofibers. The two-dimensional nanomaterials include one or more of graphene oxide and boron nitride; The mass ratio of the one-dimensional nanomaterial to the two-dimensional nanomaterial is 1:(2~4); The modifier includes one or more of alkoxysilanes and hydroxyl-containing acrylates; the alkoxysilane includes one or more of γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane; the hydroxyl-containing acrylate includes one or more of hydroxyethyl methacrylate and hydroxypropyl methacrylate. The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, azobisisoheptanenitrile, and di-tert-butyl peroxide; The modification treatment is performed at a temperature of 60℃ to 80℃ for a duration of 3 hours to 8 hours.

9. The preparation method according to claim 7, characterized in that, The foaming process includes a nucleation stage and a curing stage performed sequentially, wherein the temperature of the curing stage is higher than the temperature of the nucleation stage; wherein... The temperature of the nucleation stage is 60℃~65℃, and the time of the nucleation stage is 30min~35min; The curing temperature is 70℃~75℃, and the curing time is 25min~30min.

10. A refrigerator, characterized in that, The container includes a housing, the interlayer of which is provided with a composite foam material as described in any one of claims 1 to 6, or includes a composite foam material prepared by the preparation method as described in any one of claims 7 to 9.

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