KR20230151370A - Urethane with improved insulation performance and refrigerator using the same - Google Patents

Abstract

Disclosed is a urethane having improved thermal insulation performance by reducing the thermal conductivity of the urethane, and a refrigerator applied with the same. The urethane with improved thermal insulation performance according to one embodiment of the present invention can comprise: a plurality of closed cells containing an internal gas; a plurality of open cells connected to an external atmosphere; and a cell wall between the closed cells and the open cells, or between the plurality of closed cells, connecting the closed cells and the open cells, or the plurality of closed cells, wherein the internal gas comprises CO_2, and wherein the CO_2 content can be greater than 0 and less than or equal to 0.1 by mole fraction.

Description

Urethane with improved insulation performance and refrigerator using it {Urethane with improved insulation performance and refrigerator using the same}

The present invention relates to urethane with improved thermal insulation performance and a refrigerator to which it is applied. More specifically, it relates to urethane with improved thermal insulation performance by lowering the thermal conductivity of urethane and a refrigerator to which it is applied.

Urethane, which is used as an insulating material, is injected as a liquid between the cabinet and cavity of the refrigerator, and forms the wall in a hardened state. The lowest thermal conductivity limit of conventional insulation materials made of urethane is 20 mW/m·K, making it difficult to meet strengthening environmental regulations.

In order to increase the insulation effect of the insulation material, there is a way to increase the thickness of the urethane. However, when the thickness of urethane is increased, problems arise such as the size of the refrigerator becoming larger or the storage capacity becoming smaller.

The thermal conductivity of urethane itself is largely contributed by the thermal conductivity of the internal gas. In particular, as the CO ₂ fraction of the internal gas increases, the thermal conductivity of urethane increases. Therefore, in order to lower the thermal conductivity of urethane, it is necessary to minimize the CO2 fraction.

The purpose of the present invention to solve the above problems is to provide urethane with improved thermal insulation performance and a refrigerator to which it is applied by minimizing the amount of CO ₂ generated in the urethane foaming reaction and lowering the thermal conductivity of urethane.

Urethane with improved thermal insulation performance according to an embodiment of the present invention includes a plurality of closed cells containing internal gas; a plurality of open cells connected to the external atmosphere; and a cell wall provided between the closed cell and the open cell or between the plurality of closed cells to connect the closed cell and the open cell or the plurality of closed cells, wherein the internal gas contains CO2. Included, the CO ₂ content may be greater than 0 and less than or equal to 0.1 in terms of mole fraction.

In addition, urethane with improved thermal insulation performance according to an embodiment of the present invention may have a thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K.

In addition, the urethane with improved thermal insulation performance according to an embodiment of the present invention may include, in terms of volume fraction, 92 to 93% of the plurality of closed cells and 7 to 8% of the plurality of open cells.

Additionally, in the urethane with improved insulation performance according to an embodiment of the present invention, the internal gas may further include CP (cyclopentane) and atmosphere (air).

Additionally, in the urethane with improved thermal insulation performance according to an embodiment of the present invention, the density of the urethane may be 33 to 37 kg/㎥.

Additionally, in the urethane with improved thermal insulation performance according to an embodiment of the present invention, the average diameter of the closed cells may be 220 to 270 ㎛.

Additionally, in the urethane with improved thermal insulation performance according to an embodiment of the present invention, the average thickness of the cell walls may be 0.35 to 0.5 ㎛ or less.

In addition, a method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention includes the step of reacting isocyanate and polyol liquid to form a urethane polymer; A closed cell forming step of foaming by adding a foaming agent to create internal voids, wherein the polyol liquid contains not more than 2 parts by weight of H ₂ O 2 and the remaining polyol, based on 100 parts by weight of the polyol liquid, and the foaming agent may be CP (Cyclopentane).

Additionally, in the method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention, the polyol liquid may further include separate amines.

In addition, in the method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention, the separate amines are at least one of amines to which an allyl group, an aryl group, and an alkyl group are bonded. It could be one.

In addition, the method for manufacturing urethane with improved thermal insulation performance according to an embodiment of the present invention may mix nano-filler before the closed cell forming step.

Additionally, in the method for manufacturing urethane with improved thermal insulation performance according to an embodiment of the present invention, the nano-filler may be at least one of nanofibers, nanotubes, nanoporous materials, metal organic framework (MOF), and airgel.

In addition, in the method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention, the surface of the nano-filler is modified with an epoxide group, and the polyol is added to promote the reaction between the epoxide group and CO ₂ A catalyst can be added to the liquid.

In addition, in the method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention, the catalyst is at least one of tetrabutylammonium bromide (Bu ₄ NBr) and tetrabutylammonium iodide (Bu ₄ NI) as a main catalyst. Contains one, and as a cocatalyst, it may include at least one of cerium oxide (CeO ₂ ), zinc chloride (ZnCl ₂ ), nickel zinc cyanide (Ni-Zn cyanide) complex, and perfluorinated triol. there is.

In addition, a refrigerator with improved thermal insulation performance according to an embodiment of the present invention includes a cabinet provided on the outermost side of the refrigerator; Cavity forming the inner wall of the refrigerator; and urethane provided between the outer case and the inner case, wherein the urethane includes: a plurality of closed cells containing internal gas; a plurality of open cells connected to the external atmosphere; and a cell wall provided between the closed cell and the open cell or between the plurality of closed cells to connect the closed cell and the open cell or the plurality of closed cells, wherein the internal gas contains CO2. Included, the CO ₂ content may be greater than 0 and less than or equal to 0.1 in terms of mole fraction.

Additionally, in a refrigerator with improved thermal insulation performance according to an embodiment of the present invention, the thermal conductivity (λ _urethane ) of the urethane may be 17.6 to 18.7 mW/m·K.

Additionally, in the refrigerator with improved insulation performance according to an embodiment of the present invention, the internal gas may further include CP (Cyclopentane) and atmosphere (air).

Additionally, in the refrigerator with improved thermal insulation performance according to an embodiment of the present invention, the density of the urethane may be 33 to 37 kg/㎥.

Additionally, in a refrigerator with improved thermal insulation performance according to an embodiment of the present invention, the average diameter of the closed cells may be 220 to 270 ㎛.

Additionally, in a refrigerator with improved thermal insulation performance according to an embodiment of the present invention, the average thickness of the cell walls may be 0.35 to 0.5 ㎛.

According to an example of the present invention, by minimizing the amount of CO ₂ generated in the urethane foaming reaction and lowering the thermal conductivity of urethane, urethane with improved thermal insulation performance and a refrigerator to which it is applied can be provided.

However, the effects that can be achieved by the urethane with improved thermal insulation performance according to the embodiments of the present invention and the refrigerator to which it is applied are not limited to those mentioned above, and other effects not mentioned can be obtained from the description below. It will be clearly understandable to those with ordinary knowledge in the relevant technical field.

Figure 1 is a cross-sectional photograph of urethane according to an example of the present invention taken with a scanning electron microscope (SEM) .
Figure 2 is a schematic diagram showing a cross section of a refrigerator according to an example of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are presented to sufficiently convey the idea of the present invention to those skilled in the art. The present invention is not limited to the embodiments presented herein and may be embodied in other forms. In order to clarify the present invention, the drawings may omit illustrations of parts unrelated to the description and may slightly exaggerate the sizes of components to aid understanding.

Throughout the specification, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

Singular expressions include plural expressions unless the context clearly makes an exception.

Urethane with improved thermal insulation performance according to an embodiment of the present invention includes a plurality of closed cells containing internal gas; a plurality of open cells connected to the external atmosphere; and a cell wall provided between the closed cell and the open cell or between the plurality of closed cells to connect the closed cell and the open cell or the plurality of closed cells.

Figure 1 is a cross-sectional photograph of urethane according to an example of the present invention taken with a scanning electron microscope (SEM) .

Referring to FIG. 1, urethane according to an example of the present invention includes a plurality of open cells, a plurality of closed cells, and a cell wall.

The closed cell refers to a closed cavity containing internal gas generated during urethane foaming. The open cell refers to an open pupil that does not constitute a closed cell and is connected to the external atmosphere.

The cell wall refers to a structure provided between the closed cell and the open cell, or between the plurality of closed cells, and connecting the closed cell and the open cell, or the plurality of closed cells. Additionally, a strut refers to a point where three or more closed cells or open cells meet.

The internal gas includes CO ₂ , and the CO ₂ content may be greater than 0 and less than or equal to 0.1 in terms of mole fraction.

CO ₂ is a gas with high thermal conductivity. As the fraction of CO ₂ in the internal gas increases, the thermal conductivity of the internal gas increases. In particular, since the thermal conductivity of the internal gas has a high contribution to the thermal conductivity of the urethane itself, lowering the CO ₂ fraction is very effective in lowering the thermal conductivity of the urethane itself.

In the case of conventional urethane, the CO ₂ mole fraction is about 0.52 to 0.56. However, the present invention seeks to lower the urethane thermal conductivity by more than 10% compared to the prior art by lowering the CO ₂ mole fraction from more than 0 to 0.1 or less by using the urethane production method described later.

Urethane with improved thermal insulation performance according to an example of the present invention may have a thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K.

In addition, the urethane with improved thermal insulation performance according to an example of the present invention may include, in terms of volume fraction, 92 to 93% of the plurality of closed cells and 7 to 8% of the plurality of open cells.

Meanwhile, the internal gas may further include CP (Cyclopentane) and atmosphere (Air).

Urethane thermal conductivity (λ _urethane ), which determines the insulation performance of urethane, can be calculated using equation (1) below.

Equation (1): λ _urethane = λ _gas + λ _solid + λ _radiation + λ _convection

Urethane thermal conductivity (λ _urethane ) is the internal gas thermal conductivity (λ _gas ) contained in the closed cell, the cell wall thermal conductivity (λ _solid ), and the thermal conductivity (λ) due to radiant energy generated throughout the cell wall and internal gas. It can be calculated as the sum of _radiation ) and convection heat conductivity (λ _convection ) generated by circulation of internal gas. However, since convective thermal conductivity is generally known to have little effect inside urethane, it is not considered when calculating urethane thermal conductivity (λ _urethane ) in the present invention.

In order to lower the urethane thermal conductivity (λ _urethane ), the internal gas thermal conductivity (λ _gas ), the cell wall thermal conductivity (λ _solid ), and the thermal conductivity due to radiant energy (λ _radiation ) must be lowered.

In the present invention, the internal gas thermal conductivity (λ _gas ) is intended to be lowered, and the cell wall thermal conductivity (λ _solid ) and thermal conductivity due to radiant energy (λ _radiation ) have similar values to those of the prior art. That is, λ _solid is 2.5 to 3.5 mW/m·K, and λ _radiation has a value of about 2.0 to 3.0 mW/m·K.

The internal gas thermal conductivity (λ _gas ) can be expressed as equation (2) below.

Equation (2):

In equation (2) above, A _ij can be expressed as equation (3) below.

Equation (3):

In equation (3) above, a _ij can be expressed as equation (4) below.

Equation (4):

In the above equations (2), (3) and (4), λ _g means λ _gas , _ni or n _j means the mole fraction of any gas i or j, and λ _i means any It means the thermal conductivity of gas i, M _i and M _j mean the molar molecular weight of any gas i or j, and μ _i or μ _j means the viscosity coefficient of any gas i or j.

The mole fraction means the volume ratio of the internal gas divided by 100.

Among the internal gases, the molar molecular weight of CO ₂ is 44, the thermal conductivity of CO ₂ is 15.7 mW/m·K, and the viscosity coefficient of CO ₂ is 1.44*10 ^-5 .

In addition, among the internal gases, the molar molecular weight of CP (Cyclopentane) is 70, the thermal conductivity of CP is 12.7 mW/m·K, and the viscosity coefficient of CP is 4.37*10 ^-4 .

Additionally, among the internal gases, the molar molecular weight of air is 30, the thermal conductivity of the air is 25 mW/m·K, and the viscosity coefficient of the air is 1.79*10 ^-5 .

In order to lower the internal gas thermal conductivity (λ _gas ), the mole fraction of air and CO ₂ must be small and the mole fraction of CP (Cyclopentane) must be high. Meanwhile, it is difficult to control the mole fraction of air due to the open cell structure that inevitably occurs during urethane foaming. Therefore, in the present invention, the thermal conductivity (λ _gas ) of the internal gas is attempted to be lowered by controlling the mole fraction of CO ₂ to be low.

The density of the urethane may be 33 to 37 kg/㎥, and the average diameter of the closed cells may be 220 to 270 ㎛. Additionally, the average thickness of the cell walls of the urethane may be 0.35 to 0.5 ㎛ or less.

Meanwhile, in the present invention, average refers to the average value of values measured at five arbitrary points.

When calculated with reference to Equation (1), the thermal conductivity of conventional urethane is 20 to 22 mW/m·K, while the thermal conductivity (λ _urethane ) of urethane according to an embodiment of the present invention is 17.6 to 18.7 mW. It can be /m·K. Therefore, by lowering thermal conductivity by more than 10% compared to conventional urethane and improving insulation performance, energy savings of more than 5% can be expected.

Next, a method for manufacturing urethane with improved thermal insulation performance according to another aspect of the present invention will be described.

A method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention includes the step of reacting isocyanate and polyol liquid to form a urethane polymer; A closed cell forming step of foaming by adding a foaming agent to create internal voids, wherein the polyol liquid contains not more than 2 parts by weight of H ₂ O 2 and the remaining polyol, based on 100 parts by weight of the polyol liquid, and the foaming agent may be CP (Cyclopentane).

First, as shown in Scheme 1 below, urethane polymer is formed by reacting isocyanate and polyol.

Scheme 1:

Conventionally, H ₂ O was used as a co-blowing agent to aid foaming while adding a blowing agent to create internal voids. Therefore, CO ₂ and an amine were formed, as shown in Scheme 2 below.

Scheme 2:

Since CO ₂ generated when using H ₂ O increases the thermal conductivity of the internal gas, in the present invention, in order to minimize the CO ₂ generated, the H ₂ O content is set to 2 parts by weight or less based on 100 parts by weight of polyol liquid. Control.

Meanwhile, the amine generated in Scheme 2 is required for the next reaction, the urea and biuret reaction. In the urea and biuret reaction, urea, biuret, etc. act as intermediate reactors and strengthen the physical bonding force of urethane.

In the method for producing urethane with improved thermal insulation performance according to an embodiment of the present invention, the polyol liquid may further include separate amines.

Referring to Scheme 2 above, in the present invention, a small amount of H ₂ O is added to minimize CO ₂ generation, so less amines required in the urea and biuret reactions are generated. Therefore, by adding additional amines to the polyol solution, the insufficient amines are supplemented.

The separate amines may be at least one of amines to which an allyl group, an aryl group, and an alkyl group are bonded. However, it is not limited to this.

In the urethane manufacturing method with improved thermal insulation performance according to an embodiment of the present invention, nano-filler may be mixed before the closed cell forming step.

Even if a small amount of H ₂ O is added, a small amount of CO ₂ may be generated according to Scheme 2 above. Therefore, in the present invention, in order to additionally remove the small amount of CO ₂ generated, foaming can be performed by mixing a nanofiller capable of continuously removing CO ₂ . Here, the nano filler includes an adsorber or reactor capable of reacting with CO ₂ and may serve to remove CO ₂ .

The nanofiller may be at least one of nanofibers, nanotubes, nanoporous materials, metal organic framework (MOF), and airgel, but is not limited thereto.

The surface of the nano-filler is modified with epoxide groups, and a catalyst can be added to the polyol liquid to promote the reaction between epoxide groups and CO ₂ .

CO ₂ can be continuously removed by modifying the surface of the nano filler with an epoxide group so that it can react with CO ₂ . At this time, the reaction between the epoxide group and CO ₂ can be promoted using a catalyst.

The catalyst includes at least one of tetrabutylammonium bromide (Bu ₄ NBr) and tetrabutylammonium iodide (Bu ₄ NI) as a main catalyst, and cerium oxide (CeO ₂ ) and zinc chloride ( It may include at least one of ZnCl ₂ ), nickel zinc cyanide (Ni-Zn cyanide) complex, and perfluorinated triol. However, it is not limited to this, and any type of catalyst that can promote the reaction between nanofiller and CO ₂ can be used.

Next, a refrigerator with improved thermal insulation performance according to another aspect of the present invention will be described.

A refrigerator with improved thermal insulation performance according to an embodiment of the present invention includes a cabinet provided on the outermost side of the refrigerator; Cavity forming the inner wall of the refrigerator; and urethane provided between the outer case and the inner case, wherein the urethane includes: a plurality of closed cells containing internal gas; a plurality of open cells connected to the external atmosphere; and a cell wall provided between the closed cell and the open cell or between the plurality of closed cells to connect the closed cell and the open cell or the plurality of closed cells, wherein the internal gas is CO ₂ It includes, and the CO ₂ content may be greater than 0 and less than or equal to 0.1 in terms of mole fraction.

Figure 2 is a schematic diagram showing a cross section of a refrigerator according to an example of the present invention.

Referring to FIG. 2, the refrigerator with improved thermal insulation performance according to an example of the present invention is provided with an outer shell on the outermost layer, an inner shell forms the inner wall of the refrigerator, and urethane is included as an insulating material between the outer shell and the inner shell. can do.

The outer case may be made of steel, and the inner case may be made of plastic.

The thermal conductivity (λ _urethane ) of the urethane is 17.6 to 18.7 mW/m·K, and the internal gas may further include Cyclopentane (CP) and air.

Additionally, the density of the urethane may be 33 to 37 kg/㎥, the average diameter of the closed cells may be 220 to 270 ㎛, and the average thickness of the cell walls may be 0.35 to 0.5 ㎛.

Below, examples and comparative examples are described to aid understanding of the present invention. However, the following description only corresponds to an example of the content and effects of the present invention, and the scope and effects of the present invention are not necessarily limited thereto.

{Example}

Table 1 below shows the calculated values of λ _gas and λ _urethane according to the mole fraction of the internal gas. The calculated value of λ _gas was calculated using Equation (2), Equation (3), and (4) above, and the calculated value of λ _urethane was calculated using Equation (1) above. At this time, λ _solid was substituted as 2.5mW/mK, and λ _radiation was substituted as 2.0mW/mK.

mole fraction λ _gas calculated value
(mW/mK) λ _urethane calculated value
(mW/mK) Air _CO2 CP Example 1 0.1 0.01 0.89 13.1 17.6 Example 2 0.2 0.05 0.75 13.5 18.0 Example 3 0.1 0.1 0.8 14.2 18.7 Comparative Example 1 0.3 0.2 0.5 15.7 20.2 Comparative example 2 0.1 0.3 0.5 16.8 21.3 Comparative Example 3 0.2 0.5 0.3 18 22.5

Referring to Table 1, Examples 1 to 3 satisfied that the CO ₂ content was greater than 0 and less than 0.1 in mole fraction. Therefore, Examples 1 to 3 were able to satisfy urethane thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K.

However, Comparative Examples 1 to 3 did not satisfy the CO ₂ content of more than 0 and less than 0.1 in mole fraction. Therefore, Comparative Examples 1 to 3 did not satisfy the urethane thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K. In other words, since urethane thermal conductivity was high, it could be evaluated that the thermal insulation performance was inferior.

Claims (20)

a plurality of closed cells containing gas therein;
a plurality of open cells connected to the external atmosphere; and
It includes a cell wall provided between the closed cell and the open cell or between the plurality of closed cells, connecting the closed cell and the open cell or the plurality of closed cells,
The internal gas includes CO ₂ ,
Urethane with improved thermal insulation performance, wherein the CO ₂ content is greater than 0 and less than or equal to 0.1 in mole fraction. In claim 1,
Urethane with improved thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K. In claim 1,
In terms of volume fraction, the plurality of closed cells comprises 92 to 93%, and the plurality of open cells comprises 7 to 8%. In claim 1,
The internal gas is urethane with improved thermal insulation performance, further containing CP (Cyclopentane) and air. In claim 1,
Urethane with improved thermal insulation performance, wherein the urethane has a density of 33 to 37 kg/㎥. In claim 1,
Urethane with improved thermal insulation performance, wherein the closed cells have an average diameter of 220 to 270 ㎛. In claim 1,
Urethane with improved thermal insulation performance, with an average cell wall thickness of 0.35 to 0.5 ㎛. A step of forming a urethane polymer by reacting isocyanate and polyol liquid;
It includes a closed cell forming step of foaming by adding a foaming agent to create internal voids,
The polyol liquid contains not more than 2 parts by weight of H ₂ O 2 and the remaining polyol, based on 100 parts by weight of the polyol liquid,
A method of manufacturing urethane with improved thermal insulation performance, wherein the foaming agent is CP (Cyclopentane). In claim 8,
A method for producing urethane with improved thermal insulation performance, wherein the polyol liquid further contains separate amines. In claim 9,
The separate amines are at least one of amines to which an allyl group, an aryl group, and an alkyl group are bonded. A method of producing urethane with improved thermal insulation performance. In claim 8,
A method for manufacturing urethane with improved thermal insulation performance, wherein nano-filler is mixed before the closed cell forming step. In claim 11,
The nanofiller is at least one of nanofibers, nanotubes, nanoporous materials, metal organic framework (MOF), and airgel. A method of manufacturing urethane with improved thermal insulation performance. In claim 11,
The surface of the nano-filler is modified with an epoxide group,
A method for producing urethane with improved thermal insulation performance by adding a catalyst to the polyol liquid to promote the reaction between epoxide groups and CO ₂ . In claim 13,
The catalyst is,
As a main catalyst, it contains at least one of tetrabutylammonium bromide (Bu ₄ NBr) and tetrabutylammonium iodide (Bu ₄ NI),
As a cocatalyst, urethane with improved thermal insulation performance containing at least one of cerium oxide (CeO ₂ ), zinc chloride (ZnCl ₂ ), nickel-zinc cyanide (Ni-Zn cyanide) complex, and perfluorinated triol. Manufacturing method. A cabinet provided on the outermost side of the refrigerator;
Cavity forming the inner wall of the refrigerator; and
Including urethane provided between the outer box and the inner box,
The urethane is,
a plurality of closed cells containing gas therein;
a plurality of open cells connected to the external atmosphere; and
It includes a cell wall provided between the closed cell and the open cell or between the plurality of closed cells, connecting the closed cell and the open cell or the plurality of closed cells,
The internal gas includes CO ₂ ,
A refrigerator with improved thermal insulation performance, wherein the CO ₂ content is greater than 0 and less than or equal to 0.1 in mole fraction. In claim 15,
A refrigerator with improved insulation performance, wherein the urethane has a thermal conductivity (λ _urethane ) of 17.6 to 18.7 mW/m·K. In claim 15,
The internal gas further includes Cyclopentane (CP) and air. A refrigerator with improved insulation performance. In claim 15,
A refrigerator with improved insulation performance, wherein the density of the urethane is 33 to 37 kg/㎥. In claim 15,
A refrigerator with improved thermal insulation performance, wherein the closed cell has an average diameter of 220 to 270 ㎛. In claim 15,
A refrigerator with improved thermal insulation performance, wherein the cell wall has an average thickness of 0.35 to 0.5 ㎛.