Polyurethane foam, preparation method thereof and refrigerator

Abstract

The invention relates to the technical field of polyurethane foam, and discloses polyurethane foam, a preparation method thereof and a refrigerator. The polyurethane foam comprises a porous material, the preparation method comprises the following steps: mixing polyol, isocyanate, the porous material and an auxiliary agent in a gun head, and pouring the mixture into a space to be foamed for foaming to prepare the polyurethane foam, and the auxiliary agent comprises a foaming agent. Compared with the method that the porous material is premixed with the polyhydric alcohol or the isocyanate in advance, the abrasion of the porous material to stirring equipment can be reduced.

Description

Technical Field

[0001] This application relates to the technical field of polyurethane foam, and particularly relates to a polyurethane foam, a preparation method thereof, and a refrigerator. Background Art

[0002] Rigid polyurethane foam has low density, high strength, and excellent heat insulation performance, and its molding and processing technology is simple and easy to operate. It is widely used in refrigerators, freezers, cold storage, cold chain logistics, pipeline insulation, and building insulation and other fields.

[0003] The preparation process of rigid polyurethane foam generally adopts the one-step process, that is, the method of mixing the foaming raw materials once and catalyzing foaming. Specifically, polyol, isocyanate, foaming agent, catalyst, etc. are mixed and catalyzed foaming step by step. The one-step process is convenient to operate and simple and feasible, and it is the mainstream method for preparing rigid polyurethane foam at present. The pore size of the polyurethane foam produced by this foaming process is between 200μm and 300μm, and the thermal conductivity is about 19.5mW / (m·K), which is relatively large and not conducive to energy conservation and emission reduction.

[0004] Therefore, studying how to reduce the thermal conductivity of polyurethane foam is of great significance for energy conservation and emission reduction.

[0005] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] To have a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. The summary is not a general review, nor is it intended to identify key / important constituent elements or delineate the protection scope of these embodiments, but rather serves as a preface to the subsequent detailed description.

[0007] The embodiments of the present disclosure provide a polyurethane foam, a preparation method thereof, and a refrigerator to reduce the thermal conductivity of the polyurethane foam.

[0008] According to the first aspect of the embodiments of the present invention, a preparation method of a polyurethane foam is provided. The polyurethane foam includes a porous material, and the preparation method includes: mixing polyol, isocyanate, porous material, and an additive in a gun head; pouring the mixture into a space to be foamed for foaming after mixing to obtain the polyurethane foam; wherein, the additive includes a foaming agent.

[0009] In some embodiments, mixing polyol, isocyanate, porous material, and an additive in a gun head includes: premixing polyol and the additive to obtain a modified polyol; mixing the modified polyol, isocyanate, and porous material in the gun head.

[0010] In some embodiments, the additive also includes a catalyst and a foam stabilizer. Premixing the polyol and the additive to obtain a modified polyol includes: premixing the polyol, the catalyst, and the foam stabilizer to obtain a preliminary mixture; and premixing the preliminary mixture with a blowing agent to obtain the modified polyol.

[0011] An embodiment of the second aspect of the present invention provides a polyurethane foam, which is prepared by the preparation method of the polyurethane foam described in any one of the above embodiments.

[0012] In some embodiments, by weight, it includes the following components: 96 - 104 parts of polyol, 120 - 135 parts of isocyanate, 4 - 10 parts of porous material, and an additive. Among them, the average pore diameter of the pores in the porous material is less than 70 nm.

[0013] In some embodiments, the average particle size of the porous material is less than or equal to 10 μm.

[0014] In some embodiments, the porous material includes a mesoporous silica material.

[0015] In some embodiments, the additive includes a blowing agent; the blowing agent is cyclopentane, and the weight fraction of the blowing agent is 12 - 16 parts; or the blowing agent is LBA, and the weight fraction of the blowing agent is 23 - 32 parts; or the blowing agent is a mixture of cyclopentane and LBA, and the weight fractions of cyclopentane and LBA are 12 - 13.5 parts and 3.5 - 7 parts respectively.

[0016] In some embodiments, the average pore diameter range of the polyurethane foam is 100 - 150 μm; and / or the thermal conductivity range of the polyurethane foam is 14 - 17 mW / (m·K).

[0017] An embodiment of the third aspect of the present invention provides a refrigerator, including: a main body that defines a refrigerating space; an outer shell that is sleeved outside the main body and defines a space to be foamed between the outer shell and the main body; the polyurethane foam described in any one of the above embodiments, which is filled in the space to be foamed.

[0018] The polyurethane foam, its preparation method, and the refrigerator provided by the embodiments of the present disclosure can achieve the following technical effects:

[0019] By adding a porous material, the polyurethane foam is modified with the porous material. The addition of the porous material changes the skeleton structure of the polyurethane foam, and the heat transfer path in the polyurethane foam increases, thereby greatly reducing the thermal conductivity of the polyurethane foam, which is beneficial to achieving energy conservation and emission reduction.

[0020] The preparation method of the polyurethane foam includes: mixing the polyol, the isocyanate, the porous material, and the additive in a gun head. Compared with premixing the porous material with the polyol in advance or premixing it with the isocyanate in advance, the wear of the stirring equipment caused by the porous material can be reduced.

[0021] The above general description and the following description are only exemplary and explanatory, and are not used to limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more embodiments are exemplarily illustrated by corresponding drawings. These exemplary illustrations and the drawings do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements. The drawings do not constitute a scale limitation, and among them:

[0023] Figure 1 is a flowchart of a method for preparing a polyurethane foam provided by an embodiment of the present disclosure;

[0024] Figure 2 is a flowchart of another method for preparing a polyurethane foam provided by an embodiment of the present disclosure;

[0025] Figure 3 is a flowchart of still another method for preparing a polyurethane foam provided by an embodiment of the present disclosure;

[0026] Figure 4 is a schematic diagram of still another method for preparing a polyurethane foam provided by an embodiment of the present disclosure;

[0027] Figure 5 is a schematic diagram of the structure of a gun head provided by an embodiment of the present disclosure;

[0028] Figure 6 is a schematic diagram of the structure of a polyurethane foam provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the protection scope of the present invention.

[0030] The term "and / or" is a description of the associated relationship of an object, indicating that there can be three relationships. For example, A and / or B means: A or B, or, these three relationships of A and B.

[0031] It should be noted that, without conflict, the embodiments in the embodiments of the present disclosure and the features in the embodiments can be combined with each other.

[0032] During the polyurethane foaming process, the heat released by the reaction of polyol and isocyanate is used to heat the blowing agent, and the blowing agent vaporizes when encountering heat and foams. Part of the blowing agent escapes, and the other part remains in the pores of the rigid polyurethane foam.

[0033] The blowing agent expands and vaporizes when heated, becoming the gas phase in the polyurethane foam material. At present, the foaming ratio of most polyurethane foam materials used in refrigerators and freezers has exceeded 30 times. The low gas-phase thermal conductivity and high foaming ratio of the blowing agent gas can greatly reduce the overall thermal conductivity of the polyurethane foam.

[0034] However, at present, the pore size of the polyurethane foam produced by the one-step foaming process is between 200 μm and 300 μm, and the thermal conductivity is about 19.5 mW / (m·K), which is still relatively large and there is still room for further reduction.

[0035] Therefore, the present application provides a polyurethane foam. By weight, there are 96 - 104 parts of polyol, 120 - 135 parts of isocyanate, and 4 - 10 parts of porous material. Among them, the average pore diameter of the pores in the porous material is less than 70 nm.

[0036] On the one hand, the average free path of air molecules is about 70 nm. The average pore diameter of the porous material is less than the average free path of air molecules, which restricts the flow of air molecules in the polyurethane foam. As the average pore diameter of the pores in the porous material decreases, the flow of air molecules in the polyurethane foam will be more restricted and even approximate to a static state, thereby restricting the convective heat transfer of air molecules and further reducing the thermal conductivity of the polyurethane foam. On the other hand, due to the addition of the porous material, the cell structure of the polyurethane foam material is significantly optimized and improved, reducing the radiation heat transfer loss. In addition, because the addition of the porous material changes the skeleton structure, the cell size decreases and the heat transfer path increases, resulting in a significant reduction in the thermal conductivity of the polyurethane foam.

[0037] Optionally, the porous material includes mesoporous silica material. There are a large number of micropores and mesoporous structures in the mesoporous silica material, forming nano-channels. Among them, both the micropores and the mesopores are the pores of the porous material. Moreover, the mesoporous silica has a relatively high hardness and will not be crushed during the mixing or pouring process with polyol or isocyanate, thus not destroying the structure of the porous material, enabling the porous material to effectively improve the heat insulation performance of the polyurethane foam.

[0038] The average pore diameter of the mesoporous silica material is 2 - 50 nm, and the average particle size range is 300 - 800 nm.

[0039] In addition to the mesoporous silica material, the porous material in the present application can also be other materials with pores, among which the average pore diameter of the pores is less than 70 nm.

[0040] Optionally, the average particle size of the porous material is less than or equal to 10 μm, which is beneficial to the mixing of the porous material with polyol and isocyanate, making the interfacial adhesion between the porous material and the surrounding structure in the polyurethane foam good and avoiding reducing the mechanical properties of the polyurethane foam.

[0041] Optionally, the average particle size of the porous material ranges from 300 to 800 nm, such as 300 nm, 400 nm, 600 nm or 800 nm.

[0042] Optionally, by weight parts of the polyurethane foam, the polyol is 100 parts, the isocyanate is 120 - 135 parts, and the porous material is 4 - 10 parts.

[0043] Optionally, by weight parts of the polyurethane foam, the polyol is 100 parts, the isocyanate is 128 parts, and the porous material is 8 parts.

[0044] The weight parts of the blowing agent depend on the type of the blowing agent.

[0045] In some embodiments, the blowing agent is cyclopentane, and the weight parts of the blowing agent are 12 - 16 parts.

[0046] In some embodiments, the blowing agent is an LBA (HFO - 1233zd, 1 - chloro, 3, 3, 3 - trifluoropropene) system, and the weight parts of the blowing agent are 23 - 32 parts.

[0047] In some embodiments, the blowing agent is a mixture of cyclopentane and LBA, and the weight parts of cyclopentane and LBA are 12 - 13.5 parts and 3.5 - 7 parts respectively.

[0048] The average pore size of the polyurethane foam prepared in the prior art is between 200 μm and 300 μm, and the thermal conductivity is about 19.5 mW / (m·K).

[0049] The average pore size of the polyurethane foam prepared by adding the porous material in this application ranges from 100 to 150 μm. The thermal conductivity range of the polyurethane foam is 14 - 17 mW / (m·K).

[0050] It can be seen that the average pore size of the polyurethane foam in this application is significantly reduced, and the thermal conductivity has also been significantly reduced.

[0051] Combined with Figure 1 As shown, this application also provides a preparation method of a polyurethane foam, including:

[0052] Step S101, mixing the polyol, the isocyanate, the porous material and the auxiliary agent in a gun head, and pouring them into the space to be foamed for foaming to obtain the polyurethane foam, wherein the auxiliary agent includes the blowing agent.

[0053] If the porous material is premixed with the polyol to obtain a premix or the porous material is premixed with the isocyanate to obtain a premix, stirring is required by a stirring device during the premixing process. Due to the hardness of the porous material, the stirring device is severely worn.

[0054] Therefore, in the present application, the porous material, polyol and isocyanate are mixed in the gun head, and the mixing is achieved through the gun head, which can avoid the wear of the stirring equipment. Compared with the premixing of the porous material with the polyol or with the isocyanate, by mixing at the gun head in the present application and directly casting after mixing, the addition amount of the porous material can be increased, thereby further reducing the thermal conductivity of the polyurethane foam.

[0055] In a specific embodiment, as Figure 5 shown, the gun head 40 is a high-pressure mixing gun head. A plurality of feed channels are respectively opened on the same side of the high-pressure mixing gun head. The plurality of feed channels include a first feed channel 401, a second feed channel 402 and a third feed channel. Each feed channel is respectively communicated with a high-pressure nozzle. The first feed channel, the second feed channel and the third feed channel are respectively communicated with a first high-pressure nozzle 404, a second high-pressure nozzle 405 and a third high-pressure nozzle. A mixing chamber 407 is opened between the nozzles of the plurality of high-pressure nozzles, and the mixing chamber is communicated with all the high-pressure nozzles.

[0056] During use, the isocyanate in the raw materials is transported by a high-pressure plunger pump through the first feed channel to the first high-pressure nozzle and enters the mixing chamber from its outlet; the polyol in the raw materials is transported by the high-pressure plunger pump through the second feed channel to the second high-pressure nozzle and enters the mixing chamber from its outlet; the porous material in the raw materials is transported by the high-pressure plunger pump through the third feed channel to the third high-pressure nozzle and enters the mixing chamber from its outlet.

[0057] The auxiliary agent can be premixed with the polyol to form a modified polyol, and the modified polyol enters the mixing chamber from the first feed channel.

[0058] The auxiliary agent can also be added separately. For example, at this time, the plurality of feed channels further include a fourth feed channel, and the high-pressure nozzles further include a fourth high-pressure nozzle communicated with the fourth feed channel. The isocyanate in the raw materials is transported by the high-pressure plunger pump through the fourth feed channel to the fourth high-pressure nozzle and enters the mixing chamber from its outlet.

[0059] The polyol, isocyanate, porous material and auxiliary agent are instantaneously mixed under high pressure in the mixing chamber, and then are ejected from the discharge channel 408 through the delivery pipe 409 and injected into the space to be foamed for foaming to form a rigid polyurethane foam product. When the raw materials pass through this mixing gun head, they instantaneously impact and contact under the action of high speed and high pressure, and the mixing is full and uniform. The raw materials react thoroughly and comprehensively, and the generated polyurethane foam has uniform and dense pores, low density, high compressive strength and good product quality. The pressure of the high-pressure nozzle can be adjusted according to production needs.

[0060] The present application provides a method for preparing polyurethane foam for preparing the polyurethane foam as described in any one of the above embodiments, including:

[0061] Prepare each component according to the components and parts by weight of the polyurethane foam described in any one of the above embodiments;

[0062] Mix the polyol, isocyanate, porous material and additives in the gun head, and pour them into the space to be foamed for foaming to obtain the polyurethane foam.

[0063] Step S101, mixing the polyol, isocyanate, porous material and additives in the gun head, includes:

[0064] Pre-mix the polyol and additives to obtain a modified polyol;

[0065] Mix the modified polyol, isocyanate and porous material in the gun head.

[0066] Since the polyol has a relatively high viscosity and its viscoelastic properties are beneficial to the nucleation and growth of the cells, the blowing agent is pre-mixed with the polyol in advance, the foaming ratio of the polyurethane foam is larger, and the cell size is smaller and the cell density is higher. Therefore, the polyurethane foam has a higher compressive strength and compressive modulus.

[0067] In one embodiment, as shown in Figure 2 The embodiments of the present disclosure provide a method for preparing a polyurethane foam, including:

[0068] Step S201, pre-mix the polyol and additives to obtain a modified polyol;

[0069] Step S202, mix the modified polyol, isocyanate and porous material in the gun head, pour them into the space to be foamed for foaming to obtain the polyurethane foam.

[0070] The additives further include a catalyst and a foam stabilizer. Step S201, pre-mix the polyol and additives to obtain a modified polyol, includes:

[0071] Pre-mix the polyol, catalyst and foam stabilizer to obtain a preliminary mixture;

[0072] Pre-mix the preliminary mixture with the blowing agent to obtain a modified polyol.

[0073] The boiling point of the blowing agent is generally relatively low. If the blowing agent, catalyst and foam stabilizer are mixed at the same time, the blowing agent will volatilize, thus affecting the subsequent foaming effect. Therefore, the polyol is first mixed with the catalyst and foam stabilizer, and then the obtained mixture is mixed with the blowing agent.

[0074] As shown in Figure 3 and Figure 4 The embodiments of the present disclosure also provide a method for preparing a polyurethane foam, including:

[0075] Step S301, pre-mix the polyol, catalyst and foam stabilizer to obtain a preliminary mixture;

[0076] Step S302: Premix the initial mixture with a foaming agent to obtain a modified polyol.

[0077] Step S303: Mix the modified polyol, isocyanate, and porous material in a gun head, and pour them into the space to be foamed for foaming to obtain a polyurethane foam.

[0078] Optionally, the polyurethane foam may further include a catalyst, a foam stabilizer, or other additives.

[0079] Optionally, the polyol may be a polyester polyol or a polyether polyol.

[0080] The isocyanate may be MDI (4,4`-diphenylmethane diisocyanate) or TDI (Toluene diisocyanate).

[0081] The foam stabilizer may be HCFC-141b (1,1-dichloro-1-fluoroethane), silicone, etc.

[0082] The catalyst may be triethylenediamine, PC-5 (pentamethyldiethylenetriamine), etc.

[0083] Other additives may be flame retardants, antibacterial agents, biocompatible agents, etc. In practical applications, it is possible to flexibly choose to add or not add other additives according to the requirements for the performance of the polyurethane foam. In the case of addition, it is also possible to flexibly choose the addition amount and / or type of other additives. For example, one additive or multiple additives may be added.

[0084] If the polyurethane foam includes any one of a catalyst, a foam stabilizer, and other additives, the catalyst, the foam stabilizer, and other additives are added in Step S301. That is, the catalyst, the foam stabilizer, and other additives are mixed with the polyol to obtain an initial mixture.

[0085] Optionally, the weight ratio of the catalyst to the polyol is 0.5 - 8:100; the weight ratio of the foam stabilizer to the polyol is 0.5 - 8:100.

[0086] Optionally, the polyurethane foam further includes molecular sieve, and by weight, the molecular sieve is 6 - 10 parts.

[0087] In Figure 4 it, the addition of the molecular sieve is premixed with the isocyanate to obtain a modified isocyanate.

[0088] Molecular sieve modified polyurethane foam is adopted. According to the molecular kinematic radius of the blowing agent molecules, the molecular sieve is used to adsorb and fix the blowing agent molecules, reduce the escape of the blowing agent gas in the polyurethane foam material, and slow down the aging rate of the polyurethane foam.

[0089] After mixing polyol, isocyanate, porous material and additives in the gun head to obtain a mixture, while pouring the mixture into the space to be foamed, gas can also be introduced into the space to be foamed. The gas can be carbon dioxide gas, nitrogen or inert gas, and the pressure in the space to be foamed is maintained at 0.2 - 0.4 MPa. The gas acts on the mixture and exerts a certain force on the mixture, so that a surface layer with a larger thickness is formed on the surface of the foaming layer.

[0090] The polyurethane foam includes a surface layer, a core layer and a transition layer.

[0091] On the one hand, the thickening of the surface layer has a good supporting effect on the core layer and can improve the mechanical properties of the polyurethane foam; on the other hand, the surface layer can slow down the diffusion and escape of the blowing agent molecules in the pores of the core layer and slow down the aging rate of the polyurethane foam.

[0092] As Figure 6 shown, the surface layer 10 defines a closed cavity, and the core layer 20 is located inside the cavity.

[0093] Because the gas is filled into the space to be foamed together with the mixture, the positive-pressure gas can fully diffuse to all positions in the space to be foamed. Therefore, in addition to directly acting on the top surface of the space to be foamed (corresponding to the top wall 403), the gas can also exert a certain pressure on the side surface (corresponding to the side wall 405) and the bottom surface (corresponding to the bottom wall 404) of the space to be foamed.

[0094] Therefore, the surface layer 10 includes a first surface layer 101, a second surface layer 102 and a third surface layer 103. The first surface layer 101 is located on the top surface of the core layer 20, the second surface layer 102 is located on the bottom surface of the core layer 20, and the third surface layer 103 is located on the bottom surface of the core layer 20.

[0095] The gas acts on the top surface of the space to be foamed to form the first surface layer 101, the gas acts on the bottom surface of the space to be foamed to form the second surface layer 102, and the gas acts on the side surface of the space to be foamed to form the third surface layer 103.

[0096] The first surface layer 101, the second surface layer 102 and the third surface layer 103 jointly enclose a closed cavity and wrap the core layer 20 in the cavity in all directions.

[0097] Since the gas can act on the top surface, the bottom surface and the side surface of the space to be foamed, the thicknesses of the first surface layer 101, the second surface layer 102 and the third surface layer 103 are basically the same.

[0098] Optionally, the polyurethane foam further includes a transition layer 30 located between the surface layer 10 and the core layer 20, that is, the transition layer 30 is connected between the surface layer 10 and the core layer 20.

[0099] Among them, the density of the core layer 20, the density of the transition layer 30, and the density of the surface layer 10 increase in sequence.

[0100] The core layer 20 has a cell structure, and the pore diameter of the cells ranges from 200 to 300 μm.

[0101] The transition layer 30 also has a cell structure, but the pore diameter of the cells is smaller than that of the cells in the core layer 20.

[0102] Optionally, the surface layer 10 is a solid structure.

[0103] Due to the pressure of the gas on the mixture, the surface layer 10 forms a solid structure.

[0104] It should be noted that the solid structure does not require a completely solid structure, that is, the solid structure is not strictly without pores, but the volume occupied by the pores is much smaller than the volume occupied by the solid part, and the pore size is small.

[0105] When the porous material is mixed with polyol and isocyanate in the gun head, graphite, such as flake graphite, can also be added to the gun head. By weight, the graphite is 10 - 12 parts. Using graphite to modify the polyurethane foam, the graphite can emit the heat transferred into the polyurethane foam back, thereby reducing the heat transfer caused by thermal radiation and improving the heat insulation performance of the polyurethane foam.

[0106] Example 1:

[0107] For the polyurethane in this Example 1, the polyol is polyether polyol, the foaming agent is cyclopentane, and the porous material is mesoporous silica.

[0108] By weight, the polyol is 100 parts, the isocyanate is 128 parts, the foaming agent is 14 parts, and the porous material is 4 parts.

[0109] The preparation method of the polyurethane foam in this Example 1 is as follows:

[0110] Step 1: Premix the polyol, catalyst, and foam stabilizer to obtain a preliminary mixture.

[0111] Step 2: Mix the preliminary mixture with the foaming agent in a closed container and stir evenly at a stirring speed of 600 rpm to avoid the volatilization of the foaming agent, and prepare a modified polyol containing the foaming agent.

[0112] Step 3: Mix the modified polyol, isocyanate, and porous material at high speed in the gun head, and then pour them into the space to be foamed for foaming to prepare a rigid polyurethane foam material.

[0113] Example 2:

[0114] The only difference from Example 1 is the different weight parts of the porous material. The weight parts of the porous material in Example 2 are 6 parts.

[0115] Example 3:

[0116] The only difference from Example 1 is the different weight parts of the porous material. The weight parts of the porous material in Example 3 are 8 parts.

[0117] Example 4:

[0118] The only difference from Example 1 is the different weight parts of the porous material. The weight parts of the porous material in Example 4 are 10 parts.

[0119] Comparative Example 1

[0120] The only difference from Example 1 is that no porous material is added.

[0121] Specifically, for the polyurethane in Comparative Example 1, the polyol is polyether polyol and the foaming agent is cyclopentane.

[0122] By weight parts, 100 parts of polyol, 128 parts of isocyanate, and 14 parts of foaming agent.

[0123] The preparation method of the polyurethane foam in Comparative Example 1 is as follows:

[0124] Step 1: Mix polyether polyol and cyclopentane evenly in a closed container at a stirring speed of 600 rpm to prepare modified polyether polyol containing a foaming agent.

[0125] Step 2: Mix isocyanate and the modified polyether polyol prepared in Step 1 in a high-speed mixer at a stirring speed of 1200 rpm, and then pour it into a mold for foaming to prepare a rigid polyurethane foam material.

[0126] Experimental Example 1

[0127] Test the thermal conductivity of the polyurethane foams prepared in Examples 1 - 4 and Comparative Example 1 under exactly the same conditions. The test results are shown in Table 1 below.

[0128] Table 1

[0129] Thermal conductivity / mW / (m·K) Example 1 16.82 Example 2 16.69 Example 3 16.58 Example 4 16.37 Comparative Example 1 19.58

[0130] It can be clearly seen from the data in Table 1 that the thermal conductivity of the polyurethane foam prepared by the formulation and method proposed in this application has been significantly reduced. The average thermal conductivity of Examples 1 to 4 is 16.61 mW / (m·K), which is 2.97 mW / (m·K) lower than that in Comparative Example 1.

[0131] An embodiment of the third aspect of this application provides a refrigerator, including a main body and a housing.

[0132] The main body defines a refrigerating space; the housing is sleeved outside the main body, and a space to be foamed is defined between the housing and the main body; the polyurethane foam as described in the above embodiment is filled in the space to be foamed.

[0133] The refrigerator provided by the embodiment of the third aspect of this application, because it includes the polyurethane foam as described in the above embodiment, thus has all the beneficial effects of the polyurethane foam as described in the above embodiment, which will not be elaborated here.

[0134] The polyurethane foam is filled between the main body and the housing. As a heat-insulating material, it can greatly reduce the leakage of cold in the refrigerating space to the outside and the leakage of external heat into the refrigerating space, thereby reducing the energy consumption of the refrigerator.

[0135] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing a polyurethane foam, characterized in that, the polyurethane foam comprises a porous material, and the preparation method comprises: mixing a polyol, an isocyanate, a porous material and an auxiliary agent in a gun head; after mixing, pouring into a space to be foamed for foaming to obtain the polyurethane foam; wherein, the auxiliary agent comprises a blowing agent.

2. The method for preparing a polyurethane foam according to claim 1, characterized in that, mixing a polyol, an isocyanate, a porous material and an auxiliary agent in a gun head, comprising: premixing the polyol and the auxiliary agent to obtain a modified polyol; mixing the modified polyol, the isocyanate and the porous material in the gun head.

3. The method for preparing a polyurethane foam according to claim 2, characterized in that, the auxiliary agent further comprises a catalyst and a foam stabilizer, and premixing the polyol and the auxiliary agent to obtain a modified polyol, comprising: premixing the polyol, the catalyst and the foam stabilizer to obtain a preliminary mixture; premixing the preliminary mixture with the blowing agent to obtain a modified polyol.

4. A polyurethane foam, characterized in that, it is made by using the method for preparing a polyurethane foam according to any one of claims 1 to 3.

5. The polyurethane foam according to claim 4, characterized in that, by weight, the polyol is 96 - 104 parts, the isocyanate is 120 - 135 parts, and the porous material is 4 - 10 parts.

6. The polyurethane foam according to claim 5, characterized in that, the average pore diameter of the pores in the porous material is less than 70 nm; and / or the average particle size of the porous material is less than or equal to 10 μm.

7. The polyurethane foam according to claim 5, characterized in that, the porous material comprises a mesoporous silica material.

8. The polyurethane foam according to claim 4, characterized in that, the blowing agent is cyclopentane, and the weight part of the blowing agent is 12 - 16 parts; or the blowing agent is LBA, and the weight part of the blowing agent is 23 - 32 parts; or the blowing agent is a mixture of cyclopentane and LBA, and the weight parts of cyclopentane and LBA are 12 - 13.5 parts and 3.5 - 7 parts respectively.

9. The polyurethane foam according to any one of claims 4 to 8, characterized in that, the average pore diameter range of the polyurethane foam is 100 - 150 μm; and / or the thermal conductivity range of the polyurethane foam is 14 - 17 mW / (m·K).

10. A refrigerator, characterized in that, comprising: a main body defining a refrigerating space; a housing sleeved outside the main body and defining a space to be foamed between the housing and the main body; the polyurethane foam according to any one of claims 4 to 9 is filled in the space to be foamed.

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