Polyurethane and refrigerator comprising same
By using polyurethane with multiple closed and open pores in the refrigerator, the reaction time and pore wall arrangement are controlled, the thermal conductivity is reduced, the existing polyurethane lacks thermal conductivity is solved, and better thermal insulation performance and energy saving are achieved. Effect.
Patent Information
- Application Number
- CN202380038850.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-08-25
- Filing Date
- 2023-05-25
- Publication Date
- 2024-12-31
AI Technical Summary
The insufficient thermal conductivity of existing polyurethanes leads to an increase in refrigerator size or a decrease in storage capacity, which is unable to meet environmental regulations.
Develop a high-performance polyurethane containing multiple closed and open pores. By controlling the reaction time and pore wall arrangement, the thermal conductivity of the polyurethane is from 18.0mW/m·K to 20.5mW/m·K. The diameter of the pore wall is 100 μm to 200 μm, the internal gases are cyclopentane, air and hydrofluoroolefins, and the density is 30 kg/m3 to 35 kg/m3.
Lower thermal conductivity is achieved, thermal insulation performance is improved, and energy savings of 5% or more are expected while maintaining the size and storage capacity of the refrigerator.
Smart Images
Figure CN119234006A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to polyurethane and a refrigerator including the same. Background Art
[0002] Polyurethane used as a heat insulating material is injected into the gap between the refrigerator body and the cavity in a liquid phase and solidified to form a wall. The minimum thermal conductivity of heat insulating materials formed of conventional polyurethane is 20mW / m·K, which cannot meet the environmental regulations that are being strengthened. Summary of the invention
[0003]
Technical issues
[0004] In order to increase the heat insulating effect of the heat insulating material, a method of increasing the thickness of polyurethane has been used. However, in the case of increasing the thickness of polyurethane, problems such as an increase in size or a decrease in storage capacity occur in the refrigerator.
[0005] Therefore, there is a need to develop high-performance polyurethanes having lower thermal conductivity than conventional polyurethanes to meet environmental regulations and minimize consumer inconvenience.
[0006]
Technical solution
[0007] According to aspects of the present disclosure, the polyurethane includes: a plurality of closed cells for accommodating internal gas; a plurality of open cells connected to the outside air; and a cell wall, wherein the cell wall is arranged between at least one of the plurality of closed cells and at least one of the plurality of open cells or between the plurality of closed cells to connect at least one of the plurality of closed cells with at least one of the plurality of open cells or to connect the plurality of closed cells, wherein the diameters of the closed cells in the plurality of closed cells and the open cells in the plurality of open cells are 100 μm to 200 μm.
[0008] Thermal conductivity λ 聚氨酯 The polyurethane may contain 90% or more of the plurality of closed cells and the remaining plurality of open cells by volume fraction. The gas may include cyclopentane (CP), air and hydrofluoroolefin (HFO). The density of the polyurethane is 30 kg / m 3 Up to 35kg / m 3 The average thickness of the pore wall may be 0.35 μm to 0.5 μm.
[0009] According to another aspect of the present disclosure, a method for manufacturing polyurethane includes: forming a polyurethane polymer by reacting a polyol solution with an isocyanate; and forming pores by adding a blowing agent and a foam stabilizer for pore formation. A catalyst can be used to control the reaction rate of the polyurethane polymer forming operation and the pore forming operation. The polyol solution, the isocyanate, the blowing agent, the foam stabilizer and the catalyst are included as follows: based on the 100 parts by weight of the polyol solution, 100 parts by weight of the polyol solution, 100 to 120 parts by weight of the isocyanate, 30 parts by weight or less than 30 parts by weight of the blowing agent, 1 to 3 parts by weight of the foam stabilizer and 1 to 8 parts by weight of the catalyst.
[0010] To control the reaction rate, the cream time (CT) can be 3 seconds to 10 seconds, and the gel time (GT) can be 20 seconds to 60 seconds. The ratio of gel time (GT) to cream time (CT) can be 2 to 10. The polyol solution can include 20 to 80 parts by weight of aromatic polyol solution based on 100 parts by weight of the polyol solution and the remaining amount of aliphatic polyol. The blowing agent can include at least one of cyclopentane (CP), hydrofluoroolefin (HFO) and hydrofluorocarbon (HFC). The catalyst can include 1 to 3 parts by weight of the foaming catalyst based on 100 parts by weight of the polyol solution, 1 to 3 parts by weight of the gel catalyst and the remaining amount of the trimerization catalyst. The foaming catalyst can include at least one of pentamethyldiethylenetriamine (PMDETA) and di(N,N-dimethylaminoethyl) ether (BDMEE). The gel catalyst may include at least one of triethylamine (TEA), triethylenediamine (TEDA), pentamethylenediethylenetriamine (PMDETA), dimethylcyclohexylamine (DMCHA) and tetramethyl-n-hexyldiamine (TMHDA). The trimerization catalyst may include at least one of potassium octoate and TMR-2.
[0011] According to another aspect of the present disclosure, a refrigerator includes: an outer box disposed at the outermost side of the refrigerator; a cavity constituting an inner wall of the refrigerator; and polyurethane disposed between the box and the cavity. The polyurethane may include a plurality of closed cells for accommodating internal gas; a plurality of open cells connected to external air; and a hole wall disposed between at least one of the plurality of closed cells and at least one of the plurality of open cells or between the plurality of closed cells to connect at least one of the plurality of closed cells with at least one of the plurality of open cells or to connect the plurality of closed cells. The diameters of the closed cells in the plurality of closed cells and the open cells in the plurality of open cells may be 100 μm to 200 μm.
[0012]
Beneficial Effects
[0013] In order to solve various problems including the above-mentioned problems, provided are polyurethane having improved thermal insulation performance by reducing thermal conductivity through polyurethane pore refinement performed by controlling a reaction time of the polyurethane, and a refrigerator including the same. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 is a scanning electron microscope (SEM) image of a cross section of a polyurethane according to an embodiment.
[0015] Figure 2 is a schematic diagram illustrating a cross section of a refrigerator according to an embodiment. DETAILED DESCRIPTION
[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. These embodiments are provided to fully convey the concept of the present disclosure to those of ordinary skill in the art. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. In the accompanying drawings, for the clear description of the present disclosure, parts irrelevant to the description are omitted, and for clarity, the size of the element can be enlarged.
[0017] Throughout the specification, unless stated otherwise, the term “comprising” or “including” an element specifies the presence of the specified elements, but does not exclude the presence or addition of one or more elements.
[0018] Unless otherwise specified, an expression used in the singular includes the expression in the plural.
[0019] In order to solve various problems including the above problems, provided are polyurethane having improved thermal insulation performance by reducing thermal conductivity through polyurethane pore refinement performed by controlling a reaction time of polyurethane, and a refrigerator including the same.
[0020] According to one embodiment, a polyurethane having improved thermal insulation performance by reducing thermal conductivity of the polyurethane through pore refinement performed by controlling a reaction time and a refrigerator including the same may be provided.
[0021] However, the effects achieved by the polyurethane according to the embodiments of the present disclosure and the refrigerator including the polyurethane are not limited to those mentioned above, and any other effects not mentioned herein will be understood by those skilled in the art to which the present disclosure pertains.
[0022] The polyurethane according to the embodiment may include a plurality of closed cells containing internal gas; a plurality of open cells connected to the outside air; and cell walls arranged between the closed cells and the open cells or between the plurality of closed cells to connect the closed cells and the open cells or to connect the plurality of closed cells.
[0023] Figure 1 is a scanning electron microscope (SEM) image of a cross section of a polyurethane according to an embodiment.
[0024] refer to Figure 1 , the polyurethane according to the embodiment comprises a plurality of open cells, a plurality of closed cells and cell walls.
[0025] Closed cells refer to closed cells that contain internal gas generated when polyurethane is foamed. Open cells refer to open cells that fail to form closed cells and are connected to the outside air.
[0026] The cell wall refers to a structure arranged between a closed cell and an open cell or between a plurality of closed cells to connect the closed cell and the open cell or to connect a plurality of closed cells. In addition, a strut refers to a point where three or more closed cells or open cells intersect.
[0027] The closed pores of the plurality of closed pores and the open pores of the plurality of open pores may have a diameter of 100 μm to 200 μm.
[0028] The diameter of the closed cells and open cells may be 100 μm to 200 μm.
[0029] Thermal conductivity λ of polyurethane determines the thermal insulation properties of polyurethane 聚氨酯 It can be calculated using the following equation (1).
[0030] Equation (1): λ 聚氨酯 =λ 气体 +λ 固体 +λ 辐射 +λ 对流
[0031] Thermal conductivity λ of polyurethane 聚氨酯 It can be calculated as the thermal conductivity λ of the internal gas contained in the closed pores 气体 , thermal conductivity of the pore wall λ 固体 , the thermal conductivity λ of the radiation energy generated by the entire pore wall and the internal gas 辐射 , and the thermal conductivity λ of the convection generated by the circulation of the internal gas 对流 However, the thermal conductivity λ of the polyurethane in the present disclosure is 聚氨酯 In the calculation of , it is known that the thermal conductivity of convection has little effect on polyurethane, so the thermal conductivity of convection is not considered.
[0032] In order to reduce the thermal conductivity of polyurethane 聚氨酯 , the thermal conductivity λ of the internal gas should be reduced气体 , thermal conductivity of the pore wall λ 固体 and the thermal conductivity λ of the radiated energy 辐射 .
[0033] In the present disclosure, the thermal conductivity λ of the radiated energy is reduced by reducing the diameter of the hole. 辐射 , and the thermal conductivity of the internal gas λ 气体 and the thermal conductivity λ of the pore wall 固体 has a value similar to that of the related art. That is, λ 气体 can have a value of 14mW / m·K to 15mW / m·K, and λ 固体 It can have a value of 2.5 mW / m·K to 3.5 mW / m·K.
[0034] Thermal conductivity λ of radiant energy 辐射 It can be expressed by the following equation (2).
[0035] Equation (2):
[0036]
[0037] In equation (2), K can be expressed by the following equation (3).
[0038] Equation (3):
[0039]
[0040] In equation (3), f s It can be expressed by the following equation (4).
[0041] Equation (4):
[0042]
[0043] In the above equations (2) and (3), σ represents the Stefan-Boltzmann constant, T represents the temperature, K represents the extinction coefficient, and f s represents the pillar fraction, ρ f represents the density of foamed polyurethane, ρ s represents the density of solid non-foamed polyurethane, d represents the average diameter of closed cells, K w represents the extinction coefficient of the pore wall, and t represents the average thickness of the pore wall.
[0044] At the same time, in the calculation, use 5.6704*10 -8 W / m 2 K instead of the Stefan-Boltzmann constant σ, 296 K instead of the temperature T, and 1250 kg / m 3 Instead of ρ s(density of solid non-foamed polyurethane), and 60000m -1 Replace K w (Extinction coefficient of the pore wall).
[0045] The density of the foamed polyurethane should be increased f , and the average diameter d of the closed cells should be reduced to reduce the thermal conductivity λ of the radiated energy 辐射 In addition, no matter whether the average thickness of the hole wall increases or decreases, the thermal conductivity λ of the radiated energy 辐射 calculated to almost the same value.
[0046] Meanwhile, in the present disclosure, average means an average of values measured at five random points.
[0047] In the present disclosure, the diameter of closed and open cells is reduced by optimizing the reaction rate, thereby reducing the thermal conductivity of polyurethane. In particular, by controlling the cream time (CT), gel time (GT) and GT / CT ratio, the refinement of closed and open cells can be obtained.
[0048] The polyurethane according to the embodiment may have a thermal conductivity λ of 18.0 mW / m·K to 20.5 mW / m·K. 聚氨酯 Preferably, the thermal conductivity λ 聚氨酯 The thermal conductivity may be 18.0 mW / m·K to 20.0 mW / m·K, and more preferably, the thermal conductivity may be 18.0 mW / m·K to 19.0 mW / m·K.
[0049] In addition, the polyurethane according to the embodiment may include 90% or more of a plurality of closed cells and the remainder of a plurality of open cells in terms of volume fraction.
[0050] Meanwhile, the internal gas may include cyclopentane (CP), air, and hydrofluoroolefin (HFO).
[0051] The density of polyurethane can be 30kg / m 3 Up to 35kg / m 3 , and the average thickness of the pore wall can be 0.35μm to 0.5μm.
[0052] According to calculation using the above equation (1), although conventional polyurethane has a thermal conductivity of 20 to 22 mW / m·K, the thermal conductivity λ of the polyurethane according to an embodiment of the present disclosure is 聚氨酯 It may be 18.0 mW / m·K to 20.5 mW / m·K. Therefore, since the thermal insulation performance is improved by reducing the thermal conductivity by 10% compared with conventional polyurethane, an energy saving effect of 5% or more can be expected herein.
[0053] Hereinafter, a method of manufacturing polyurethane according to another embodiment of the present disclosure will be described.
[0054] The method for manufacturing polyurethane according to the embodiment includes: forming a polyurethane polymer by reacting a polyol solution with an isocyanate; and forming pores by adding a blowing agent and a foam stabilizer for pore formation, wherein a catalyst is used to control the reaction rates of the polyurethane polymer forming operation and the pore forming operation, and the polyol solution, isocyanate, blowing agent, foam stabilizer and catalyst may be included as follows: based on 100 parts by weight of the polyol solution, 100 parts by weight of the polyol solution, 100 to 120 parts by weight of the isocyanate, 30 parts by weight or less of the blowing agent, 1 to 3 parts by weight of the foam stabilizer and 1 to 8 parts by weight of the catalyst may be included.
[0055] First, as shown in Reaction Scheme 1 below, a polyurethane polymer is prepared via a reaction between an isocyanate and a polyol.
[0056] Reaction scheme 1:
[0057]
[0058] Furthermore, when a foaming agent is added to form internal pores, as shown in the following reaction scheme 2, H 2 O acts as a co-blowing agent to assist in foaming and thus can generate CO 2 and amines.
[0059] Reaction Scheme 2:
[0060]
[0061] Meanwhile, the amine produced in the above reaction scheme 2 is essential in the following reaction (ie, urea and biuret reaction). In the urea and biuret reaction, urea, biuret, etc. act as intermediate reactive groups to enhance the physical bonding strength of polyurethane.
[0062] The polyol solution, isocyanate, blowing agent, foam stabilizer and catalyst may be included as follows: based on 100 parts by weight of the polyol solution, 100 parts by weight of the polyol solution, 100 to 120 parts by weight of isocyanate, 30 parts by weight or less of the blowing agent, 1 to 3 parts by weight of the foam stabilizer and 1 to 8 parts by weight of the catalyst may be included.
[0063] The polyol solution and the isocyanate may be added in a ratio of 1:1 to 1:1.2. In the case of using an excessive amount of the polyol solution, the polyol remains during the reaction, resulting in an increase in the density of the final polyurethane and a decrease in production efficiency. In contrast, in the case of using an excessive amount of isocyanate, the polyurethane will be significantly hardened and pore refinement will not occur sufficiently.
[0064] The foaming agent plays a role in forming pores inside the polyurethane, and the foam stabilizer plays a role in maintaining the formed pores via the action of the surfactant. In the case of using an excessive amount of the foaming agent and an excessive amount of the foam stabilizer, the manufacturing cost will increase and the productivity will decrease.
[0065] Catalysts play a role in increasing or decreasing the rate of a reaction. Excess catalysts can reduce efficiency and increase manufacturing costs.
[0066] In the method of manufacturing polyurethane according to the embodiment, the cream time (CT) may be 3 to 10 seconds, the gel time (GT) may be 20 to 60 seconds, and the gel time (GT) / cream time (CT) ratio may be 2 to 20.
[0067] One of the core technologies of the present disclosure is to achieve pore refinement by controlling CT, GT and GT / CT ratio. In the present disclosure, CT and GT are measured using any method known in the art.
[0068] CT refers to the time period from the point at which foam begins to form to the point at which a color change of the reaction solution is visually recognized as the foam grows. In this regard, the point at which a color change is visually recognized refers to the point at which the ΔE value in the L*a*b* color space exceeds 1 compared to the color of the solution at the point at which foam begins to form.
[0069] GT refers to the period from the reaction start time of the reaction solution to the point at which the polyurethane fibers are formed and solidified.
[0070] In response to a CT of less than 3 seconds, polyurethane is rapidly cured to deteriorate fluidity, making it difficult to fully fill the polyurethane. However, in response to a CT of more than 10 seconds, it may be difficult to obtain the desired polyurethane thermal insulation performance due to the increased pore diameter. Preferably, the CT may be 3 to 7 seconds.
[0071] In response to a GT of less than 20 seconds, the fluidity of the polyurethane is reduced, making it difficult to fill the interior of the refrigerator with polyurethane and causing an excessive increase in density. However, in response to a GT of more than 60 seconds, the pore diameter increases, making it difficult to obtain the desired polyurethane thermal insulation performance. Preferably, the GT may be 20 seconds to 40 seconds.
[0072] In response to a GT / CT ratio of less than 2, the density of polyurethane excessively increases, making it difficult to perform foaming. However, in response to a GT / CT ratio exceeding 20, the diameter of pores increases, making it difficult to obtain the desired polyurethane thermal insulation performance. Preferably, the GT / CT ratio may be 4 to 10.
[0073] The polyol solution may include 20 to 80 parts by weight of the aromatic polyol solution and the remainder of the aliphatic polyol based on 100 parts by weight of the polyol solution.
[0074] Although conventionally, the aromatic polyol is added in an amount of less than 20 parts by weight based on 100 parts by weight of the polyol solution, in the present disclosure, the amount of the aromatic polyol is increased to 20 to 80 parts by weight to control CT and GT.
[0075] The blowing agent may include at least one of cyclopentane (CP), hydrofluoroolefin (HFO), and hydrofluorocarbon (HFC).
[0076] The catalyst may include blowing catalysts, gelling catalysts and trimerization catalysts.
[0077] In the method of manufacturing polyurethane according to the embodiment, the catalyst may include 1 to 3 parts by weight of a foaming catalyst, 1 to 3 parts by weight of a gel catalyst, and the remainder of a trimerization catalyst based on 100 parts by weight of the polyol solution.
[0078] In the present disclosure, the catalyst may play a role in controlling CT and GT.
[0079] The blowing catalyst can control the CT by controlling the blowing reaction between isocyanate and water. The blowing catalyst can include at least one of pentamethyldiethylenetriamine (PMDETA) and di(N,N-dimethylaminoethyl)ether (BDMEE),
[0080] The gel catalyst can control GT by controlling the gelation reaction between the polyol and the isocyanate. The gel catalyst may include at least one of triethylamine (TEA), triethylenediamine (TEDA), pentamethylenediethylenetriamine (PMDETA), dimethylcyclohexylamine (DMCHA), and tetramethyl-n-hexyldiamine (TMHDA).
[0081] The trimerization catalyst may play a role in controlling a trimerization reaction in which three isocyanate molecules react to form an isocyanurate. The trimerization catalyst may include at least one of potassium octoate and TMR-2.
[0082] Hereinafter, a refrigerator according to another embodiment of the present disclosure will be described.
[0083] The refrigerator according to the embodiment includes: an outer box; an inner cavity in the box; and polyurethane arranged between the box and the inner cavity. The polyurethane includes a plurality of closed cells for accommodating internal gas; a plurality of open cells connected to the outside air; and a cell wall, the cell wall being arranged between at least one of the plurality of closed cells and at least one of the plurality of open cells or between the plurality of closed cells to connect at least one of the plurality of closed cells with at least one of the plurality of open cells or to connect the plurality of closed cells, wherein the diameters of the closed cells in the plurality of closed cells and the open cells in the plurality of open cells are 100 μm to 200 μm.
[0084] The refrigerator according to the embodiment includes: an outer box arranged at the outermost side of the refrigerator; a cavity constituting the inner wall of the refrigerator; and polyurethane arranged between the box and the cavity, wherein the polyurethane contains a plurality of closed holes for accommodating internal gas; a plurality of open holes connected to the outside air; and a hole wall, the hole wall is arranged between the closed hole and the open hole or between the plurality of closed holes to connect the closed hole and the open hole or to connect the plurality of closed holes. The diameter of the closed hole in the plurality of closed holes and the open hole in the plurality of open holes may be 100 μm to 200 μm.
[0085] Figure 2 is a schematic diagram illustrating a cross section of a refrigerator according to an embodiment.
[0086] refer to Figure 2 , a refrigerator according to an embodiment includes a box body arranged at the outermost side, a cavity constituting an inner wall of the refrigerator, and polyurethane interposed between the box body and the cavity as a heat insulating material.
[0087] The outer housing may be made of steel, and the inner cavity within the outer housing may be made of plastic.
[0088] Polyurethane may have a thermal conductivity λ of 18.0 mW / m·K to 20.5 mW / m·K 聚氨酯 .
[0089] The polyurethane according to the embodiment may include 90% or more of a plurality of closed cells and a remainder of a plurality of open cells in terms of volume fraction, and the internal gas may include cyclopentane (CP), air, and hydrofluoroolefin (HFO).
[0090] In addition, the density of polyurethane can be 30kg / m 3 Up to 35kg / m 3 , and the average thickness of the pore wall can be 0.35μm to 0.5μm.
[0091] Hereinafter, the present disclosure will be described in more detail with reference to the following examples and comparative examples. However, the following examples are presented only to illustrate the present disclosure, and the scope and effect of the present disclosure are not limited thereto.
[0092] Example
[0093] Polyurethane samples were prepared using initial reaction solutions having composition ranges shown in the following Table 1. The units of the composition ranges in the following Table 1 are based on 100 parts by weight of the polyol solution.
[0094] Table 1
[0095]
[0096] In the following Table 2, CT, GT, GT / CT ratio, pore diameter and polyurethane density of each of the embodiments and comparative examples are shown. CT refers to the time period from the point at which foam begins to form to the point at which the color change of the reaction solution is visually recognized as the foam grows. In this regard, the point at which the color change is visually recognized refers to the time point at which the ΔE value of the L*a*b* color space exceeds 1 compared to the color of the solution at the point at which foam begins to form. GT refers to the time period from the reaction start time of the reaction solution to the point at which polyurethane fibers are formed and can withstand slight impacts. At the same time, GT is measured based on the SPI gel time.
[0097] The pore diameter of the sample was measured using a scanning electron microscope (SEM) image, and the density of the polyurethane sample was measured by using a densitometer at room temperature.
[0098] Table 2
[0099]
[0100] Referring to Table 2, since the samples of Examples 1 to 4 satisfy the composition range of the reaction solution according to the present disclosure, the CT range of 3 seconds to 10 seconds, the GT range of 20 seconds to 60 seconds, and the GT / CT ratio of 2 to 20 are satisfied. Therefore, Examples 1 to 4 satisfy the pore diameter range of 100 μm to 200 μm. That is, it can be seen that in Examples 1 to 4, the thermal insulation performance is improved by reducing the thermal conductivity through pore refinement. However, since the amount of the foaming catalyst and / or gel catalyst of Comparative Examples 1 and 2 does not satisfy the range of 1 to 3, the CT range of 3 seconds to 10 seconds, the GT range of 20 seconds to 60 seconds, and the GT / CT ratio range of 2 to 20 are not satisfied. Therefore, the pore diameter of Comparative Examples 1 and 2 does not satisfy the range of 100 μm to 200 μm. That is, it can be seen that in Comparative Examples 1 and 2, the thermal insulation performance is poor due to insufficient pore refinement. According to the embodiment, a polyurethane having improved thermal insulation performance by reducing thermal conductivity of the polyurethane through pore refinement performed by controlling a reaction time and a refrigerator including the same may be provided.
Claims
1. Polyurethane, comprising: multiple closed cells to contain the internal gas; a hole wall, wherein the hole wall is arranged between at least one of the plurality of closed holes and at least one of the plurality of open holes, or between the plurality of closed holes, so as to connect at least one of the plurality of closed holes and at least one of the plurality of open holes, or to connect the plurality of closed holes, The diameters of the closed pores in the plurality of closed pores and the open pores in the plurality of open pores are in a range of 100 μm to 200 μm.
2. The polyurethane according to claim 1, wherein the thermal conductivity λ 聚氨酯 18.0mW / m·K to 20.5mW / m·K. 3 . The polyurethane according to claim 1 , wherein the polyurethane comprises 90% or more of the plurality of closed cells and the remaining amount of the plurality of open cells in terms of volume fraction.
4. The polyurethane according to claim 1, wherein the internal gas comprises cyclopentane (CP), air, and hydrofluoroolefin (HFO).
5. The polyurethane according to claim 1, wherein the density of the polyurethane is 30 kg / m 3 Up to 35kg / m 3 . The polyurethane according to claim 1 , wherein the average thickness of the cell walls is 0.35 μm to 0.5 μm.
7. A method for producing polyurethane, the method comprising: forming a polyurethane polymer by reacting a polyol solution with an isocyanate; as well as forming pores by adding a foaming agent and a foam stabilizer for pore formation; wherein a catalyst is used to control the reaction rates of the polyurethane polymer forming operation and the pore forming operation, and The polyol solution, the isocyanate, the blowing agent, the foam stabilizer and the catalyst are included as follows: Based on 100 parts by weight of the polyol solution, the invention comprises 100 parts by weight of the polyol solution, 100 to 120 parts by weight of the isocyanate, 30 parts by weight or less of the blowing agent, 1 to 3 parts by weight of the foam stabilizer and 1 to 8 parts by weight of the catalyst.
8. The method of claim 7, wherein the cream time (CT) is 3 to 10 seconds, and the gel time (GT) is 20 to 60 seconds.
9. The method of claim 7, wherein the gel time (GT) / cream time (CT) ratio is 2 to 20. 10 . The method of claim 7 , wherein the polyol solution comprises 20 to 80 parts by weight of an aromatic polyol solution and the remainder of an aliphatic polyol based on 100 parts by weight of the polyol solution.
11. The method of claim 7, wherein the blowing agent comprises at least one of cyclopentane (CP), hydrofluoroolefin (HFO), and hydrofluorocarbon (HFC).
12. The method of claim 7, wherein the catalyst comprises a blowing catalyst, a gelling catalyst, and a trimerization catalyst. 13 . The method according to claim 12 , wherein the catalyst comprises 1 to 3 parts by weight of the blowing catalyst, 1 to 3 parts by weight of the gelling catalyst, and the remainder of the trimerization catalyst based on 100 parts by weight of the polyol solution.
14. The method according to claim 12, wherein the blowing catalyst comprises at least one of pentamethyldiethylenetriamine (PMDETA) and bis(N,N-dimethylaminoethyl)ether (BDMEE), The gel catalyst comprises at least one of triethylamine (TEA), triethylenediamine (TEDA), pentamethylenediethylenetriamine (PMDETA), dimethylcyclohexylamine (DMCHA) and tetramethyl-n-hexyldiamine (TMHDA), and The trimerization catalyst comprises at least one of potassium octoate and TMR-2.
15. Refrigerator, including: A box body disposed at the outermost side of the refrigerator; a cavity constituting an inner wall of the refrigerator; as well as A polyurethane is disposed between the box and the cavity, wherein the polyurethane comprises: multiple closed cells to contain the internal gas; multiple openings connected to the outside air; as well as a hole wall, wherein the hole wall is arranged between at least one of the plurality of closed holes and at least one of the plurality of open holes, or between the plurality of closed holes, so as to connect at least one of the plurality of closed holes and at least one of the plurality of open holes, or to connect the plurality of closed holes, The diameters of the closed pores in the plurality of closed pores and the open pores in the plurality of open pores are in a range of 100 μm to 200 μm.