Open-cell urethane foam, vacuum insulation material using the same, and use thereof

Abstract

To provide an open-cell urethane foam capable of achieving better heat insulating performance when used as a core material of a vacuum heat insulating material.SOLUTION: The open-cell urethane foam is used as a core material of a vacuum heat insulating material, and is a plate-shaped foam having open cells communicating with each other. A thickness direction of the open cell urethane foam is a heat conduction direction of the vacuum heat insulating material, and the open cell includes an ellipsoidal cell having an ellipsoidal shape and disposed so that a major axis direction thereof intersects with the heat conduction direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an open-cell urethane foam having interconnected cells, a vacuum insulation material comprising this open-cell urethane foam as a core material, and uses of this vacuum insulation material. [Background technology]

[0002] Vacuum insulation materials have a structure in which a core material is enclosed in an outer covering material in a reduced pressure sealed state (near-vacuum state). The outer covering material has gas barrier properties to maintain the approximate vacuum state inside. Known core materials for vacuum insulation materials include fibrous materials and foam materials.

[0003] For example, Patent Document 1 discloses an insulator (vacuum insulation material) configured using an open-cell rigid urethane foam as a core material. In this Patent Document 1, in order to produce the open-cell rigid urethane foam, a polyether polyol using an aromatic diamine as an initiator, an organic polyisocyanate, a foam stabilizer, and a catalyst are used, and in order to ensure good fluidity during foam generation and to avoid localized density reduction, a blowing agent and a cell-opening agent made of HCFCs (halogenated hydrocarbons containing hydrogen and fluorine) are further used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 04-351621 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, the vacuum insulation material disclosed in Patent Document 1 not only has good fluidity during foaming, but also uses a polyether polyol with an aromatic diamine as an initiator to achieve finer open cells (communicating cells). Therefore, the good fluidity during foaming results in fine, spherical communicating cells overall, which not only effectively prevents the rigid urethane foam from having extremely poorly oriented communicating cells, but also achieves excellent insulating performance. However, in recent years, there has been a trend toward even better insulating performance for vacuum insulation materials.

[0006] The present disclosure has been made to solve these problems, and aims to provide an open-cell urethane foam that can achieve even better insulating performance when used as the core material of a vacuum insulation material. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the open-cell urethane foam according to the present disclosure is used as a core material for a vacuum insulation material, and is a plate-shaped foam having interconnected open cells, the thickness direction of which is the direction of thermal conduction of the vacuum insulation material, and the open cells include ellipsoidal cells that are ellipsoidal in shape and are arranged so that their major axis direction intersects the direction of thermal conduction.

[0008] According to the above configuration, the cells of the open-cell urethane foam include ellipsoidal cells, which are open cells with an ellipsoidal shape. This allows for a longer heat flow path length in the insulating direction compared to a case where the open cells are spherical, assuming that conditions such as the thickness of the urethane foam and the size of the open cells are the same. Therefore, using this type of open-cell urethane foam as the core material of a vacuum insulation material can further improve the insulating performance of the vacuum insulation material.

[0009] In addition, the vacuum insulation material disclosed herein comprises an outer covering material having gas barrier properties and a core material sealed inside the outer covering material in a reduced pressure and sealed state, and is configured to use the above-described open-cell urethane foam as the core material.

[0010] Furthermore, the present disclosure also includes an insulated box provided with the vacuum insulation material having the above-described configuration, a refrigeration cycle device provided with the insulated box, and a refrigeration cycle device such as a refrigerator. [Effects of the Invention]

[0011] The present disclosure has the effect of providing an open-cell urethane foam with the above-described configuration that can achieve even better insulating performance when used as a core material for vacuum insulation materials. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing an example of the configuration of a vacuum insulator according to a representative embodiment of the present disclosure. [Figure 2] 1A is a schematic perspective view showing an example of the configuration of an open-cell urethane foam according to the present disclosure, used as the core material of the vacuum insulation material shown in FIG. 1; FIG. 1B is a schematic cross-sectional view showing an example of a cross section of the open-cell urethane foam shown in FIG. 1A in the heat conduction direction, as viewed from the direction of the arrow II; and FIG. 1C is a schematic cross-sectional view showing an example of a cross section of the open-cell urethane foam shown in FIG. 1A in the heat conduction direction, as viewed from the direction of the arrow II-II. [Figure 3] (A) is a micrograph showing a specific example of the ellipsoidal cells of the open-cell urethane foam shown in Figures 2(A) and (B), (B) is a schematic diagram illustrating the horizontal and vertical Feret diameters of the ellipsoidal cells shown in (A), and (C) is a schematic diagram showing the relationship between the orientation of the ellipsoidal cells shown in (B) and the direction of heat conduction and the direction of urethane foam flow. [Figure 4] 1 is a graph showing the relationship between the Feret orientation rate and the cell thickness position (the position of the cells in the thickness direction of the open-cell urethane foam) in an open-cell urethane foam according to a representative example of the present disclosure. [Figure 5] 1 is a graph showing the relationship between the Feret orientation rate and the proportion of cells that are not laterally oriented in an open-cell urethane foam according to a representative example of the present disclosure. [Figure 6] 1 is a graph showing the relationship between the thermal conductivity of a vacuum insulation material manufactured using an open-cell urethane foam according to a representative example of the present disclosure and the Feret orientation rate of the open-cell urethane foam. [Figure 7] 1 is a graph showing the relationship between the thermal conductivity of a vacuum insulation material manufactured using an open-cell urethane foam according to a representative example of the present disclosure and the urethane density of the open-cell urethane foam. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Findings that formed the basis of this disclosure) In general, open-cell urethane foams are produced by injecting a urethane raw material composition into a mold, sealing it, and foaming it. As a result, the shape of the open cells is generally spherical, as in the open-cell rigid urethane foam disclosed in Patent Document 1, for example.

[0014] The present inventors have conducted extensive research, particularly into the urethane foam core material, to further improve the thermal insulation performance of vacuum insulation materials, and have independently discovered an open-cell urethane foam with ellipsoidal open cells. In this new open-cell urethane foam, the open cells are formed so that the longitudinal direction of the ellipsoid intersects the direction of heat conduction.

[0015] With this new open-cell urethane foam, when conditions such as foam thickness and cell size of the open cells are kept the same, the length of the heat flow path in the insulating direction can be made longer than with conventional urethane foam with spherical open cells. This makes it possible to achieve even better insulating properties in the heat conduction direction than with conventional urethane foam, thereby making it possible to further improve the insulating performance of the vacuum insulation material, leading to the completion of the technology of the present disclosure.

[0016] Representative embodiments of the present disclosure will be described below with reference to the drawings. Note that the same or corresponding elements will be designated by the same reference numerals throughout the drawings, and redundant description thereof will be omitted.

[0017] The open-cell urethane foam according to the present disclosure is used as a core material for vacuum insulation materials, and is a foam plate having interconnected cells whose thickness direction corresponds to the direction of thermal conduction of the vacuum insulation material. The open cells of the open-cell urethane foam include ellipsoidal cells that are oriented such that their major axis (or longitudinal direction) intersects the direction of thermal conduction.

[0018] [Vacuum insulation material] First, a representative example of a vacuum insulation material to which the open-cell urethane foam according to the present disclosure is applied will be described with reference to Figure 1 and Figures 2(A) and (B). As shown in Figure 1, a vacuum insulation material 10 according to this embodiment includes an outer covering material (outer packaging material) 20 and a core material 30 enclosed in the outer covering material 20 in a reduced pressure, sealed state (a substantially vacuum state).

[0019] The outer covering material 20 is a bag-shaped member with gas barrier properties, and in this embodiment, for example, the bag shape is formed by placing two laminated sheets opposite each other and sealing their peripheries. The sealed area around the periphery is configured as a sealed portion 11 where the laminated sheets are in contact with each other and there is no core material 30 inside. This sealed portion 11 is, for example, in the form of a fin extending from the main body of the vacuum insulation material 10 toward the periphery. Of course, the specific configuration of the vacuum insulation material 10 according to the present disclosure is not limited to the example configuration shown in FIG. 1.

[0020] The specific configuration of the outer covering material 20 is not particularly limited, and known sheets or films having gas barrier properties can be suitably used. A typical example of the outer covering material 20 is a laminated sheet having a multilayer structure. Such an outer covering material 20 can be exemplified by a laminated sheet having one or more gas barrier layers and a heat-sealing layer. By providing the outer covering material 20 with a heat-sealing layer, as will be described later, the outer covering material 20 can be easily processed into a bag shape, thereby simplifying the manufacturing process of the vacuum insulation material 10.

[0021] The core material 30 is not particularly limited as long as it is a typical vacuum insulation material 10 and has thermal insulation properties, but in the present disclosure, the aforementioned open-cell urethane foam is used as the core material 30. As shown in FIG. 2(A), the open-cell urethane foam 31 according to this embodiment may be a plate-shaped foam having a rectangular plate shape. The direction of the block arrow Dh in FIG. 2(A) is the direction of heat conduction, which corresponds to the thickness direction of the open-cell urethane foam 31. This heat conduction direction Dh can also be said to be the insulating direction of the vacuum insulation material 10.

[0022] The open-cell urethane foam 31 can be described as a rectangular parallelepiped hexahedron having opposing flat surfaces 31a and 31b and four surrounding surfaces that are side surfaces 31c to 31f. For ease of explanation, one of the flat surfaces 31a and 31b is referred to as a first flat surface 31a, and the other is referred to as a second flat surface 31b. In Figure 2(A), the first flat surface 31a is shown facing downward, and the second flat surface 31b is shown facing upward.

[0023] 2(A), the open-cell urethane foam 31 has a longitudinal direction extending laterally from the plane of the drawing. Therefore, the side surfaces 31c-31f can be divided into side surfaces 31c and 31d that face each other along the longitudinal direction and side surfaces 31e and 31f that face each other along a shorter direction perpendicular to the longitudinal direction. For ease of explanation, these side surfaces 31c-31f will be referred to as the first side surface 31c, the second side surface 31d, the third side surface 31e, and the fourth side surface 31f, respectively.

[0024] A typical method for producing the open-cell urethane foam 31 is "free foam molding," which involves foam-molding a urethane raw material composition in an open system using a mold with an open, flat cavity, as described below. During free foam molding, for example, the first side surface 31c corresponds to the bottom surface of the mold cavity, and the third side surface 31e and the fourth side surface 31f each correspond to the inner side surfaces of the cavity. The first flat surface 31a and the second flat surface 31b also each correspond to the main inner surfaces of the cavity.

[0025] Meanwhile, because the upper surface of the cavity is open as an opening, the urethane raw material composition flows upward while foaming as the reaction progresses in the cavity. Therefore, for convenience, the direction in which the urethane raw material composition flows is referred to as the urethane foaming flow direction. In the example shown in FIG. 2(A), as indicated by the block arrow Df, the shorter direction perpendicular to the longitudinal direction (the direction along the third side surface 31e and the fourth side surface 31f) is the urethane foaming flow direction Df.

[0026] Unlike the flat surfaces 31a and 31b and the side surfaces 31c, 31e, and 31f, the second side surface 31d, which is located downstream in the urethane foaming flow direction Df, is not in contact with the inner surface of the cavity. Therefore, immediately after removal from the mold, the open-cell urethane foam 31 does not have the second side surface 31d, and the urethane foam has an irregular shape (a shape that is irregular) due to the urethane foaming and hardening in a bulging state. Therefore, the final open-cell urethane foam 31 is obtained by cutting the irregularly shaped portion. Therefore, when free foam molding is employed, the second side surface 31d of the open-cell urethane foam 31 is not a "molded surface" formed during foam molding like the other surfaces, but rather a "cut surface" formed by cutting after foam molding.

[0027] For example, assume that the central portion of the open-cell urethane foam 31 shown in Figure 2(A) is sampled in the thickness direction (thermal conduction direction Dh) to form a columnar (e.g., rectangular columnar) shape to obtain a heat conduction direction cross-sectional sample 31g. Figure 2(B) corresponds to a schematic cross-sectional view of this heat conduction direction cross-sectional sample 31g as viewed from the direction of arrow II indicated by the dashed line in Figure 2(A), i.e., a direction perpendicular to the urethane foaming flow direction Df, and Figure 2(C) corresponds to a schematic cross-sectional view as viewed from the direction of arrows II-II indicated by the dashed line in Figure 2(A), i.e., from the upstream side of the urethane foaming flow direction Df.

[0028] As shown in Fig. 2(B), a large number of ellipsoidal cells 32 are formed as interconnected cells in the heat conduction direction cross-sectional sample 31g. The ellipsoidal cells 32 are formed so that the major axis direction (longitudinal direction of the ellipsoid) of the ellipsoid intersects with the heat conduction direction Dh (thickness direction). In Fig. 2(B), the major axis direction of the ellipsoidal cells 32 is illustrated by a dotted line Lx. In this example, the major axis direction Lx of the ellipsoidal cells 32 is perpendicular to the heat conduction direction Dh, but the present disclosure is not limited to this. The major axis direction Lx of the ellipsoidal cells 32 may be any direction as long as it intersects with the heat conduction direction Dh.

[0029] In this way, in the open-cell urethane foam 31 according to the present disclosure, the communicating cells are ellipsoidal cells 32, and the ellipsoidal cells 32 are arranged so that the long axis direction Lx intersects with the heat conduction direction Dh, thereby making it possible to relatively increase the length of the heat flow path in the heat conduction direction Dh, thereby further improving the heat insulation properties of the open-cell urethane foam 31 in the thickness direction.

[0030] As described above, FIG. 2(B) shows a cross section of the heat conduction direction cross-sectional sample 31g viewed from a direction perpendicular to the urethane foaming flow direction Df. When viewed from this direction, the cross sections of the ellipsoidal cells 32, which are interconnected cells, are elliptical. In contrast, as shown schematically in FIG. 2(C), when the heat conduction direction cross-sectional sample 31g is viewed from the upstream side of the urethane foaming flow direction Df (the forward direction of the urethane foaming flow direction Df), the cross sections of the ellipsoidal cells 32 are circular. Therefore, a more specific shape of the ellipsoidal cells 32 in this embodiment is a prolate ellipsoid. As described above, in the interconnected-cell urethane foam 31 according to the present disclosure, the shape of the interconnected cells may be ellipsoidal rather than spherical, but a more typical shape is a prolate ellipsoid.

[0031] [Example of a specific configuration of an ellipsoidal cell] Next, a more specific example of the configuration of the ellipsoidal cells 32 of the open-cell urethane foam 31 according to the present disclosure will be described with reference to FIGS. 2(B), (C) and 3(A) to (C).

[0032] In the heat conduction direction cross-sectional sample 31g shown in FIG. 2(B), for ease of explanation, all ellipsoidal cells 32 are shown as being the same size, with the polyurethane portion shaded in black. However, as shown in the micrograph in FIG. 3(A), the actual size of the ellipsoidal cells 32 varies. Furthermore, as will be described later, not all cells (cells) in the open-cell urethane foam 31 are necessarily open cells, and some may be closed cells. Similarly, not all cells (open cells and closed cells) are necessarily ellipsoidal cells 32, and some may be spherical.

[0033] Furthermore, in the open-cell urethane foam 31 according to the present disclosure, the degree of orientation of the ellipsoidal cells 32 with respect to the heat conduction direction Dh is not particularly limited. As a representative example, as shown schematically in Fig. 3(B), when the heat conduction direction Dh (thickness direction) of the ellipsoidal cells 32 is the vertical direction and the direction perpendicular to this vertical direction is the horizontal direction, and the vertical Feret diameter Fv and the horizontal Feret diameter Fh are set, the horizontal Feret diameter Fh is larger than the vertical Feret diameter Fv (Fh>Fv).

[0034] In other words, when the ratio of the horizontal Feret diameter Fh to the vertical Feret diameter Fv is defined as the Feret orientation Of (Of = Fh / Fv), the Feret orientation Of of the ellipsoidal cells 32 exceeds 1 (Of > 1). The vertical Feret diameter Fv and the horizontal Feret diameter Fh can be calculated (measured) by sampling a cross-sectional sample 31g (see Figures 2(A) and (B)) in the heat conduction direction from the open-cell urethane foam 31 and analyzing the image taken with a microscope using analysis software.

[0035] In the present disclosure, the reason why the Feret diameter is used to evaluate the ellipsoidal cells 32 is that the major axis directions (or longitudinal directions) of all the ellipsoidal cells 32 contained in all the cells are not all oriented in a uniform direction, but rather there is variation as described above (see FIG. 3(A)). Note that, as described above, not all the cells are necessarily ellipsoidal cells 32 (they may include spherical cells), so the Feret diameter is also useful for evaluating the ellipsoidal cells 32 contained in all the cells.

[0036] For example, as shown in Fig. 3(C), if the ellipsoidal cell 32 has a prolate ellipsoidal shape, and the heat conduction direction Dh, i.e., the thickness direction of the open-cell urethane foam 31, is taken as the Z axis, and the urethane foam flow direction Df is perpendicular to the Z axis (heat conduction direction Dh), then the axis parallel to the urethane foam flow direction Df can be set as the X axis, and the axis perpendicular to the urethane foam flow direction Df can be set as the Y axis. Ideally, the long axis of the ellipsoidal cell 32 is along the urethane foam flow direction Df, i.e., the X axis. In this case, the ellipsoidal cell 32 can be evaluated using the XZ plane indicated by the dashed dotted line in Fig. 3(C) as a cross section.

[0037] In the ideal case shown in Figure 3(C), the ellipsoidal cell 32 can be evaluated based on the length in the major axis direction (major axis diameter) on the XZ plane. However, in reality, the orientation of the ellipsoidal cell 32 is such that the major axis direction is not necessarily perpendicular to the heat conduction direction Dh, but intersects at various angles. The Feret diameter is a suitable evaluation index for the ellipsoidal cell 32 because the vertical and horizontal lengths of a rectangle circumscribing the target shape are the vertical Feret diameter and horizontal Feret diameter, respectively.

[0038] In the schematic example shown in Figure 3(C), the X-axis is set to the direction along the urethane foaming flow direction Df. However, in the present disclosure, the setting of the X-axis is not limited to the direction along the urethane foaming flow direction Df. For example, the Y-axis may be set to the direction along the urethane foaming flow direction Df, and the X-axis may be set to the direction perpendicular to the Y-axis and Z-axis. In other words, in the present disclosure, the X-axis and Y-axis may be set so that the urethane foaming flow direction Df is perpendicular to the heat conduction direction Dh (Z-axis).

[0039] In the example shown in Figure 3(C), as described above, the shape of the ellipsoidal cell 32 is illustrated as a prolate ellipsoid, and therefore the cross-sectional shape of the ellipsoidal cell 32 is elliptical in the XZ plane cross section indicated by the dashed line. In contrast, when the YZ plane cross section indicated by the dashed line in Figure 3(C) is taken as the cross section, the cross section of the ellipsoidal cell 32 is circular. Therefore, in the present disclosure, the X-axis and Y-axis may be set so that the direction in which the cross section of the ellipsoidal cell 32 is elliptical is the XZ plane.

[0040] In this embodiment, a prolate ellipsoid is exemplified as the shape of the ellipsoidal cell 32. Therefore, the cross section of the ellipsoidal cell 32 along the longitudinal direction (i.e., the XZ plane) is elliptical, and the cross section along the direction perpendicular to the longitudinal direction (i.e., the YZ plane) is approximately circular. Therefore, in the present disclosure, a prolate ellipsoid can be defined as having a three-dimensional structure in which the shape of a first cross section along the longitudinal direction is elliptical and the shape of a second cross section perpendicular to the first cross section is (approximately) circular. Note that the cross section of the heat conduction direction cross-sectional sample 31g shown in FIG. 2(B) corresponds to the XZ plane in FIG. 3(C), and the cross section of the heat conduction direction cross-sectional sample 31g shown in FIG. 2(C) corresponds to the YZ plane in FIG. 3(C).

[0041] In the open-cell urethane foam 31 according to the present disclosure, ideally, the ellipsoidal cells 32 should be orthogonal (perpendicular to) the heat conduction direction Dh, as shown in the heat conduction direction cross-sectional sample 31g in Figure 2(B). However, in practice, the orientation of the ellipsoidal cells 32 varies depending on various conditions, such as the specific composition of the urethane raw material composition, the foaming conditions, and the cavity shape of the mold. Therefore, the orientation of the ellipsoidal cells 32 can be evaluated using the difference between the horizontal Feret diameter Fh and the vertical Feret diameter Fv, or the Feret orientation Of.

[0042] When the horizontal Feret diameter Fh and the vertical Feret diameter Fv are the same, that is, when the difference between the horizontal Feret diameter Fh and the vertical Feret diameter Fv is 0 or the Feret orientation Of is 1, the ellipsoidal cell 32 is determined to be not substantially ellipsoidal but substantially spherical. If the ellipsoidal cell 32 is substantially spherical, the heat flow path length cannot be made relatively long, so better heat insulation performance cannot be achieved.

[0043] Also, when the horizontal Feret diameter Fh is smaller than the vertical Feret diameter Fv (Fh < Fv) or the Feret orientation Of is less than 1 (Of < 1), the ellipsoidal cell 32 is oriented along the heat conduction direction Dh without the major axis direction Lx intersecting the heat conduction direction Dh. If the orientation in which the ellipsoidal cell 32 intersects the heat conduction direction Dh is, for convenience, referred to as the "lateral orientation", the orientation in which the ellipsoidal cell 32 is along the heat conduction direction Dh can be referred to as the "vertical orientation". When the ellipsoidal cell 32 is vertically oriented in this way, the heat flow path length becomes relatively short, so better heat insulation performance cannot be achieved.

[0044] In the open-cell urethane foam 31 according to the present disclosure, the orientation of the ellipsoidal cell 32 can be evaluated by another method based on the Feret diameter. Specifically, the Feret orientation ratio Rf can be defined by the following formula (1). Rf = (Fh - Fv) / Fh ···(1)

[0045] In the open-cell urethane foam 31, for a plurality of cells arranged at different positions along the heat conduction direction Dh (thickness direction), the Feret orientation ratio Rf is calculated for each cell, the average value of these Feret orientation ratios Rf is calculated, and this average value can be used for evaluating the orientation of the ellipsoidal cell 32. As described above, since the open-cell urethane foam 3 may include spherical cells, the cells selected when calculating the Feret orientation ratio Rf are not necessarily limited to the ellipsoidal cells 32. Specifically, although the average value of the Feret orientation ratio Rf is not particularly limited, typically it can be 0.2 or more.

[0046] Here, the position of a cell along the heat conduction direction Dh can be defined as the position in the thickness direction relative to one of the flat surfaces 31a, 31b of the open-cell urethane foam 31. Specifically, as shown in FIG. 2(B), for example, in the heat conduction direction cross-sectional sample 31g, the first flat surface 31a (the lower surface in the figure) is used as the reference surface, and the distance in the thickness direction, i.e., the heat conduction direction Dh, from this reference surface to any cell can be defined as the cell thickness position Pc. For multiple cells with different cell thickness positions Pc, the Feret orientation ratio Rf can be calculated for each cell, and the average value can be calculated and evaluated.

[0047] As shown in the examples described later, for example, 16 cells are extracted from a heat conduction direction cross-sectional sample 31g of an open-cell urethane foam 31 along the heat conduction direction Dh (thickness direction), the Feret orientation ratios Rf of these cells are calculated, and the average of the calculated Feret orientation ratios Rf is calculated (Table 2 described later). As will be explained in the examples described later, it has been revealed that this average Feret orientation ratio Rf has a good proportional relationship with the thermal conductivity λ of a vacuum insulation material 10 using an open-cell urethane foam 31 as the core material 30 (see FIG. 6). Based on the results of this proportional relationship, in the present disclosure, a lower limit of 0.2 or more can be cited as a preferred example for the average Feret orientation ratio Rf.

[0048] Furthermore, as will be explained in the examples below, it has been revealed that in the open-cell urethane foam 31 according to the present disclosure, the change in the cell Feret orientation ratio Rf with increasing cell thickness position Pc may include peaks showing maximum and minimum values, depending on the position in the open-cell urethane foam 31. Note that the change in the Feret orientation ratio Rf here refers to the change in all cells (including ellipsoidal cells 32 and other cells) contained in the open-cell urethane foam 31.

[0049] The maximum or minimum value at the peak of change in the Ferret orientation ratio Rf is not particularly limited, but typically, the maximum value of the Ferret orientation ratio Rf is 0.3 or greater, and the minimum value of the Ferret orientation ratio Rf is 0.1 or greater. Note that, depending on the position of the open-cell urethane foam 31, a peak indicating a maximum or minimum may not appear. Therefore, in the present disclosure, the average value of the Ferret orientation ratio Rf is sufficient as long as it is 0.2 or greater. Furthermore, in the present disclosure, a portion of the open-cell urethane foam 31 with a high Ferret orientation ratio Rf can be selected and used as the core material 30. This allows for a further reduction in the thermal conductivity of the core material 30.

[0050] As shown in the examples described later, as the cell thickness position Pc changes, peaks showing maximum values ​​of the Feret orientation ratio Rf can be confirmed both near the first flat surface 31a, which is the reference surface, and near the second flat surface 31b, which is the opposing surface (Table 2 described later). On the other hand, peaks showing minimum values ​​of the Feret orientation ratio Rf can be confirmed near the center in the thickness direction (Table 2 described later). Although the specific numerical values ​​of these maximum and minimum values ​​are not particularly limited, the results of the examples described later show that if the maximum value of the Feret orientation ratio Rf with changes in the cell thickness position Pc is 0.3 or more and the minimum value is 0.1 or more, the insulating performance of the vacuum insulation material 10 can be further improved.

[0051] In addition, as shown in the examples described later, the value of the Feret orientation rate Rf for the cell thickness position Pc in the XZ plane is larger than the value of the Feret orientation rate Rf for the cell thickness position Pc in the YZ plane (Table 3 and Figure 4 described later). In addition, in both the XZ plane and the YZ plane, a peak showing a maximum or minimum can be confirmed in the Feret orientation rate Rf with a change in the cell thickness position Pc. In particular, the average value of the change in the Feret orientation rate Rf in the YZ plane is within the range of 0 to 0.10, and can be considered to be close to 0 when compared with the average value in the XZ plane (Table 3 and Figure 4 described later).

[0052] 3(C), the present embodiment illustrates a case in which the Z axis is set to the heat conduction direction Dh, the X axis is set to the urethane foam flow direction Df, and the Y axis is set to a direction perpendicular to the Z axis and the X axis. In this case, the XZ plane (indicated by the dashed line in the figure) is a plane along the urethane foam flow direction Df, and the YZ plane (indicated by the broken line in the figure) is a plane perpendicular to the urethane foam flow direction Df.

[0053] The fact that the average value of the change in the Feret orientation ratio Rf in the YZ plane is close to 0 means that the cross section of the ellipsoidal cell 32 is circular or a shape close to that (substantially circular) in the YZ plane perpendicular to the urethane foaming flow direction Df. Furthermore, the fact that the Feret orientation ratio Rf in the XZ plane is greater than the Feret orientation ratio Rf in the YZ plane means that the cross section of the ellipsoidal cell 32 is elliptical rather than substantially circular in the XZ plane along the urethane foaming flow direction Df. Therefore, as described above, it can be seen that the shape of the ellipsoidal cell 32 in this embodiment tends to be a prolate ellipsoid with the longitudinal direction along the urethane foaming flow direction Df.

[0054] In the present disclosure, there are no particular limitations on the limit value of the cell thickness position Pc (the distance between the first flat surface 31a and the second flat surface 31b) relative to the first flat surface 31a, i.e., the thickness of the open-cell urethane foam 31. The thickness of the core material 30 can be set appropriately depending on the application of the vacuum insulation panel 10 using the open-cell urethane foam 31 as the core material 30. Typical thicknesses of the core material 30 are within the range of 10 to 50 mm. The upper limit of the thickness of the core material 30 may be 40 mm or less, or 30 mm or less. The lower limit of the thickness of the core material 30 may be 15 mm or more, or 20 mm or more.

[0055] As will be described later, in the present disclosure, a typical application of the vacuum insulation material 10 can be a refrigeration cycle device such as a refrigerator. When the vacuum insulation material 10 according to the present disclosure is used as a heat insulating member for a refrigeration cycle device, the thickness of the core material 30 can be, for example, in the range of 20 to 30 mm.

[0056] [Example of manufacturing open-cell urethane foam] Next, a typical example of manufacturing an open-cell urethane foam 31 according to the present disclosure will be described. The open-cell urethane foam 31 can be obtained by mixing a polyol component and an isocyanate component and foam-molding the mixture while allowing a condensation polymerization reaction to occur. Specifically, the hydroxyl groups (-OH) of the polyol component and the isocyanate groups of the isocyanate component form urethane bonds (-NH-CO-O-) (urethanization reaction). This reaction can be accompanied by foaming using a known blowing agent. In this disclosure, the pre-reaction composition containing the polyol component and the isocyanate component is referred to as the urethane raw material composition.

[0057] The polyol component used in the urethane raw material composition is not particularly limited, and any known polyol compound can be appropriately selected and used. Typical examples include polyether polyols, polyester polyols, polyetherester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, polyolefin polyols, acrylic polyols, vinyl monomer-modified polyols, polyhydric alcohols, vegetable oil polyols, and hydroxyl group-containing diene polymers.

[0058] More specifically, examples of polyether polyols include compounds obtained by adding a cyclic ether or alkylene oxide to a polyhydric alcohol, sugar, alkanolamine, polyamine, polyhydric phenol, or other initiator. Examples of polyhydric alcohols that can be used include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, and pentaerythritol. Examples of sugars that can be used include sucrose, dextrose, and sorbitol. Examples of alkanolamines that can be used include diethanolamine and triethanolamine. Examples of polyamines that can be used include ethylenediamine, toluenediamine, diaminodiphenylmethane, and polymethylenepolyphenylamine. Examples of polyhydric phenols that can be used include bisphenol A, bisphenol S, and phenolic resin-based initial condensates.

[0059] Examples of polyester polyols include polyols based on polyhydric alcohol-polycarboxylic acid condensation, polyols based on cyclic ester ring-opening polymers, aromatic polyester polyols, etc. Examples of polyhydric alcohols that can be used include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, and bisphenol A. Examples of polycarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid; aliphatic carboxylic acids such as ricinoleic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as hexahydrophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid; and acid esters or acid anhydrides thereof. Examples of cyclic esters include lactones such as ε-caprolactone, α-methyl-ε-caprolactone, and methylvalerolactone.

[0060] Examples of polyetherester polyols include those obtained by reacting the aforementioned polyether polyols with polycarboxylic acids to form polyesters, those obtained by addition polymerization of alkylene oxides with the aforementioned polyester polyols, and copolymers having both polyether and polyester segments in one molecule. Examples of alkylene oxides that can be used include ethylene oxide, propylene oxide, and butylene oxide.

[0061] Examples of polycarbonate polyols include those obtained by the dealcoholization reaction of the aforementioned polyhydric alcohol with a carbonate. Examples of the carbonate that can be used include dialkyl carbonate, dialkylene carbonate, and diphenyl carbonate.

[0062] Examples of polyurethane polyols include polyester polyurethane polyols, polyether polyurethane polyols, polycarbonate polyurethane polyols, and polyester polyether polyurethane polyols.

[0063] Examples of epoxy polyols include those obtained by reacting a low-molecular-weight polyol having two or more hydroxyl groups (hydroxy groups) and a molecular weight of 60 to 300 with a polyfunctional halohydrin. Examples of low-molecular-weight polyols that can be used include the polyhydric alcohols described above. Examples of polyfunctional halohydrins that can be used include epichlorohydrin and β-methylepichlorohydrin.

[0064] Examples of polyolefin polyols include polybutadiene polyols (polybutadiene having two or more hydroxyl groups), polyisoprene polyols (polyisoprene having two or more hydroxyl groups), hydrogenated polybutadiene polyols, and hydrogenated polyisoprene polyols.

[0065] Examples of acrylic polyols include copolymers of (meth)acrylic acid esters (acrylic acid esters and / or methacrylic acid esters) and (meth)acrylic acid hydroxy compounds having one or more hydroxyl groups (acrylic acid hydroxy compounds and / or methacrylic acid hydroxy compounds).

[0066] Examples of vinyl monomer-modified polyols include copolymers of a high-molecular-weight polyol having two or more hydroxyl groups and a vinyl monomer. The high-molecular-weight polyol may be a polyol having a number-average molecular weight (typically, a standard polyoxyethylene-equivalent molecular weight measured by GPC) of 250 to 10,000, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, silicone polyols, fluorine polyols, and vinyl monomer-modified polyols. Examples of vinyl monomers that can be used include alkyl (meth)acrylates (alkyl acrylates and / or alkyl methacrylates), styrene, and vinyl esters.

[0067] Examples of plant-derived polyols include castor oil-based polyols, soybean oil-based polyols, palm oil-based polyols, palm kernel oil-based polyols, coconut oil-based polyols, cashew oil-based polyols, olive oil-based polyols, cottonseed oil-based polyols, safflower oil-based polyols, sesame oil-based polyols, sunflower oil-based polyols, and linseed oil-based polyols.

[0068] Examples of hydroxyl group-containing diene polymers include those obtained by polymerizing a single conjugated diene monomer or a combination of two or more conjugated diene monomers. Examples of conjugated diene monomers that can be used include unsubstituted or substituted diolefin-type unsaturated diene compounds having 4 to 12 carbon atoms, specifically 1,3-butadiene, isoprene, chloroprene, 2-cyano-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, etc. Examples of the substituent in the substituted diene compound include, in addition to the cyano group, an alkyl group, an aryl group, a halogen, a nitro group, etc. Furthermore, a portion of the conjugated diene monomer can be replaced with an ethylenically unsaturated monomer.

[0069] These polyol compounds may be used alone or in appropriate combination of two or more. Furthermore, the compounds used for synthesizing (polymerizing) these polyol compounds may be used alone or in appropriate combination of two or more.

[0070] The isocyanate component used in the urethane raw material composition is not particularly limited, and any known isocyanate compound can be selected and used. Typical examples include aromatic, alicyclic, and aliphatic polyisocyanates having two or more isocyanate groups, as well as modified polyisocyanates obtained by modifying these.

[0071] Examples of aromatic polyisocyanates include tolylene diisocyanate (TDI), phenylene diisocyanate, diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), Examples of the isocyanate include dimethylphenylene diisocyanate, dibenzyl diisocyanate, anthracene diisocyanate, dimethyldiphenyl diisocyanate, diphenyl diisocyanate, naphthalene diisocyanate (NDI), toluidine diisocyanate (TODI), diphenyl ether diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl polyisocyanate, and diisocyanate diethylbenzene.

[0072] Examples of the aliphatic polyisocyanate include cyclopentane diisocyanate, cyclopentene diisocyanate, cyclohexane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate, dimethyldicyclohexylmethane diisocyanate, methylenebis(cyclohexylisocyanate) (H12MDI), methylcyclohexane diisocyanate, norbornane diisocyanate (NBDI), and bis(isocyanatomethyl)cyclohexane (H6XDI).

[0073] Examples of aliphatic polyisocyanates include methylene diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, butylene diisocyanate, pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate, and diisocyanate methylcaprate.

[0074] Examples of modified polyisocyanates include the above-mentioned polyisocyanate multimers, the above-mentioned prepolymer-type modified polyisocyanates, the above-mentioned isocyanurate-modified polyisocyanates, the above-mentioned urea-modified polyisocyanates, the above-mentioned allophanate-modified polyisocyanates, the above-mentioned polyol-modified polyisocyanates, the above-mentioned biuret-modified polyisocyanates, the above-mentioned oxadiazinetrione-modified polyisocyanates, the above-mentioned carbodiimide-modified polyisocyanates, the above-mentioned uretdione-modified polyisocyanates, the above-mentioned uretonimine-modified polyisocyanates, and polymethylene polyphenyl isocyanates, which are polyisocyanate derivatives. The position of the substituent in these compounds is not particularly limited.

[0075] These isocyanate compounds and modified compounds (including derivatives) may be used alone or in appropriate combination of two or more kinds.

[0076] A known catalyst can be used for the condensation polymerization reaction of the polyol component and the isocyanate component. Therefore, the urethane raw material composition used in the present disclosure may contain a catalyst. Specific examples of the catalyst include, but are not limited to, amine catalysts such as dimethylethanolamine, triethylenediamine, dimethylcyclohexylamine, 1,2-dimethylimidazole, pentamethyldiethylenetriamine, and bis(2-dimethylaminoethyl)ether; metal compound catalysts such as lead octoate and dibutyltin dilaurate; and isocyanuration catalysts such as tris(dimethylaminopropyl)hexahydro-S-triazine, potassium acetate, and potassium octoate. These catalysts may be used alone or in combination.

[0077] The open-cell urethane foam 31 according to the present disclosure is foamed by reacting a urethane raw material composition. Therefore, the urethane raw material composition used in the present disclosure may contain a foaming agent. The foaming agent may be a foamable substance that vaporizes due to the heat of reaction generated by the chemical reaction between the polyisocyanate component and the polyol component, or a gaseous component that is generated by the reaction. Specific examples of the foaming agent include water, carbon dioxide, lower hydrocarbons having 6 or fewer carbon atoms, hydrofluorocarbons (HFCs), and hydrofluoroolefins (HFOs). Among these, water is preferably used as the foaming agent in the present disclosure, as shown in the examples described below.

[0078] The urethane raw material composition used in the present disclosure can contain various additives (or other components) as needed. Specific additives are not particularly limited, but representative examples include foam stabilizers, crosslinking agents, curing accelerators, flame retardants, dispersants, antioxidants, antibacterial agents, mold release agents, and fillers. In the examples described below, the urethane raw material composition contains a foam stabilizer. The use of a foam stabilizer makes it possible to suppress variation in the size of the interconnected cells formed by foaming.

[0079] Specific examples of the foam stabilizer include, but are not limited to, silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, surfactants, etc. Examples of silicone-based foam stabilizers include those mainly composed of siloxane chains, those in which the siloxane chain and polyether chain form a linear structure, those having branched chains, and those in which the polyether chain is modified with the siloxane chain.

[0080] The urethane raw material composition used in the present disclosure is not particularly limited in the amounts of the polyol component, isocyanate component, catalyst, blowing agent, foam stabilizer, and other additives. The amounts of these components can be adjusted appropriately within known ranges depending on various conditions, such as the physical properties required of the open-cell urethane foam 31 or the aforementioned adjustment of the Ferret orientation ratio Rf.

[0081] In the present disclosure, the open-cell urethane foam 31 may be prepared by mixing a polyol component and an isocyanate component and reacting them with a blowing agent, and the mixing ratio of the polyol component and the isocyanate component is not particularly limited. In the examples described below, a premix polyol containing three low-molecular-weight polyols and one high-molecular-weight polyol is prepared, and this premix polyol is mixed with an isocyanate component as the polyol component to prepare a urethane raw material composition.

[0082] In the present disclosure, high-molecular-weight polyols and low-molecular-weight polyols used as polyol components can be classified, for example, by whether their number-average molecular weight Mn is 1000 or more or less than 1000. The specific number-average molecular weight Mn of the high-molecular-weight polyol is not particularly limited, but can be, for example, in the range of 1000 to 6000. The more specific number-average molecular weight Mn of the low-molecular-weight polyol is not particularly limited, but can be, for example, in the range of 600 or less.

[0083] As the low molecular weight polyol, for example, dihydric alcohols such as ethylene glycol or propylene glycol can be used as described above.Low molecular weight polyol compounds that do not have a polymer structure, such as dihydric alcohols, can be evaluated by the molecular weight derived from the chemical formula, not by the number average molecular weight Mn.Therefore, the lower limit of the number average molecular weight Mn of the low molecular weight polyol does not need to be specified.

[0084] In the present disclosure, the conditions for reacting the urethane raw material composition, i.e., the reaction conditions between the polyol component and the isocyanate component and the molding conditions, are not particularly limited, and known conditions can be used depending on the physical properties required of the open-cell urethane foam 31 or various conditions, such as the adjustment of the Feret orientation ratio Rf described above, or known conditions can be appropriately adjusted and set.

[0085] As described above, the open-cell urethane foam 31 according to the present disclosure has ellipsoidal cells 32 arranged so that their major axes intersect the heat conduction direction Dh. While there are no particular limitations on the method for forming such ellipsoidal cells 32, a typical example is "free foam molding," in which a urethane raw material composition is foam-molded using a mold having a flat cavity with the cavity open and not sealed. An example of a mold having a flat cavity is a mold (metal mold) having a slit-shaped cavity.

[0086] The open-cell urethane foam 31 according to the present disclosure may be a plate-shaped foam containing open cells, but may also contain some closed cells. The upper limit of the closed cell content of the open-cell urethane foam 31 according to the present disclosure is not particularly limited, but may be, for example, 5% or less, or may be 1% or less, or 0.1% or less. In other words, the open-cell urethane foam 31 according to the present disclosure may be such that at least 95% of all cells are open cells. The lower limit of the closed cell content is ideally 0% or more. In the present disclosure, the closed cell content was measured using an analytical measuring instrument (analyzer) in the Accupyc II 1345 series (product name) manufactured by Shimadzu Corporation.

[0087] Furthermore, as described above, in the open-cell urethane foam 31 according to the present disclosure, not all of the open cells need to be ellipsoidal cells 32, and some may be spherical open cells. In the open-cell urethane foam 31 according to the present disclosure, the lower limit of the ratio of ellipsoidal cells 32 to all cells (ellipsoidal cell ratio) is not particularly limited, but may be 85% or more, 90% or more, 95% or more, or 98% or more.

[0088] As mentioned above, the lower limit of the average value of the Feret orientation ratio Rf can be 0.2 or more. As shown in the examples described later, when the Feret orientation ratio Rf is around 0.2, the proportion of cells that are not horizontally oriented (oriented intersecting the thermal conduction direction Dh) among all cells is less than 15% (see Table 4 and Figure 5). Therefore, the ellipsoidal cell ratio among all cells should be 85% or more.

[0089] The ellipsoidal cell ratio can be calculated backward from the ratio of cells that are not laterally oriented, as described in the Examples below. As mentioned above, not all cells in the open-cell urethane foam 31 are necessarily ellipsoidal cells 32. Therefore, not only cells that are vertically oriented (oriented along the thermal conduction direction Dh) but also spherical cells and the like can be collectively referred to as "cells that are not laterally oriented." The ratio of cells that are not laterally oriented can be calculated by sampling a cross-sectional sample 31g (see Figures 2(A) and (B)) from the open-cell urethane foam 31 in the thermal conduction direction and analyzing images taken with a scanning microscope using image analysis and measurement software, as described in the Examples below.

[0090] Furthermore, the density of the open-cell urethane foam 31 according to the present disclosure is not particularly limited, and a suitable density can be selected depending on the thermal insulation performance required of the vacuum insulation material 10. As will be shown in the examples described later, a good proportional relationship can sometimes be found between the density of the open-cell urethane foam 31 and the thermal insulation properties of the vacuum insulation material 10 (see FIG. 7). It is generally considered that the upper limit of the thermal conductivity λ of the vacuum insulation material 10 should be 7.0 mW / m·K or less. Therefore, as described above, when a proportional relationship can be found between density and thermal insulation properties, the upper limit of the density of the open-cell urethane foam 31 should be 85 kg / m 3 On the other hand, the lower limit of the density of the open-cell urethane foam 31 is not particularly limited.

[0091] [Vacuum insulation panel manufacturing method and its uses] As described above, the open-cell urethane foam 31 according to the present disclosure is used as the core material 30 of the vacuum insulation material 10. In the present disclosure, there are no particular limitations on the specific manufacturing method for the vacuum insulation material 10, and known manufacturing methods can be suitably used. A representative manufacturing method is to form the outer covering material 20 into a bag shape, insert the core material 30 and, if necessary, other components (for example, a gas adsorbent) inside it, and then hermetically seal the bag-shaped outer covering material 20 in a reduced pressure environment (approximately a vacuum state).

[0092] There are no particular limitations on the method for forming the outer covering material 20 into a bag shape, but as mentioned above, when a laminated film having a heat-sealing layer is used as the outer covering material 20, one method for forming the bag shape is to prepare two sheets of laminated film that will become the outer covering material 20, and heat-seal the majority of the peripheral edges with the heat-sealing layers facing each other. Specifically, for example, if the outer covering material 20 is rectangular, only one of the four sides may be left as an opening, and the remaining part of the peripheral edges excluding the opening may be heat-sealed so as to surround the central part (the part where the core material 30 is housed).

[0093] Next, the open-cell urethane foam 31, which is the core material 30, is inserted into the bag-shaped outer covering material 20 through the opening, and the pressure is reduced, for example, in a decompression chamber or other decompression equipment. As a result, the inside of the bag-shaped outer covering material 20 (inside the bag) is sufficiently reduced in pressure through the opening, creating a substantial vacuum. Thereafter, the opening is hermetically sealed by heat welding in the same way as the other peripheral edges, thereby obtaining the vacuum insulation material 10 shown in FIG.

[0094] The conditions for heat welding, decompression, etc. are not particularly limited, and various known conditions can be suitably adopted. Furthermore, the bag-shaped outer covering material 20 is not limited to a configuration using two laminated films. For example, a bag-shaped outer covering material 20 having an opening can be obtained by folding one laminated film in half and heat welding both side edges. Alternatively, the laminated film can be formed into a cylindrical shape and one opening can be sealed.

[0095] The vacuum insulation material 10 manufactured in this manner not only has a reduced pressure sealed state (almost a vacuum state) inside, but also uses the aforementioned open-cell urethane foam 31 as the core material 30, so it can exhibit extremely excellent insulation performance.

[0096] The vacuum insulation material 10 according to the present disclosure can be suitably used for a variety of insulation applications. A typical example of an insulation application is a home appliance. While the specific type of home appliance is not particularly limited, examples include refrigerators, water heaters, rice cookers, and thermos pots. Another example of an insulation application is residential walls. Yet another example of an insulation application is transportation equipment. While the specific type of transportation equipment is not particularly limited, examples include ships such as tankers, automobiles, and aircraft. Yet another example of an insulation application is a cold storage container such as a cooler box, or a thermal storage container such as a thermal jar.

[0097] Among these insulation applications, a particularly representative application can be a refrigeration cycle device such as a refrigerator. For example, in the case of a refrigerator, the vacuum insulation material 10 according to the present disclosure can be applied to the insulating box body, which is the main body of the refrigerator. The refrigerator can be for home use or for commercial use. Furthermore, the specific configuration of the refrigeration cycle device is not particularly limited, and it can be configured so that components such as a compressor, a condenser, an expansion means, and an evaporator are connected by piping. Specific examples of refrigeration cycle devices are not limited to refrigerators, and can also be, for example, showcases, ice makers, vending machines, etc.

[0098] In this way, the open-cell urethane foam according to the present disclosure is used as the core material of a vacuum insulation material, and is a plate-shaped foam having interconnected interconnected cells, the thickness direction of which is the thermal conduction direction of the vacuum insulation material, and the interconnected cells include ellipsoidal cells that are ellipsoidal in shape and are arranged so that their major axis direction intersects the thermal conduction direction.

[0099] According to this configuration, the cells of the open-cell urethane foam include ellipsoidal cells, which are open cells with an ellipsoidal shape. This allows for a longer heat flow path length in the insulating direction than when the open cells are spherical. By using this type of open-cell urethane foam as the core material of a vacuum insulation material, the insulation performance of the vacuum insulation material can be further improved. [Example]

[0100] The present disclosure will be described in more detail based on examples, but the present disclosure is not limited thereto. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

[0101] (Example of manufacturing open-cell urethane foam) A premix polyol was prepared by blending three commercially available low-molecular-weight polyols, Polyol A, Polyol B, and Polyol C, a high-molecular-weight polyol, water as a blowing agent, and a commercially available foam stabilizer and catalyst in the blending amounts (mass ratio) shown in Table 1. This premix polyol and a commercially available polyisocyanate were blended and mixed in the blending ratio (mass ratio) shown in Table 1 to obtain a urethane raw material composition.

[0102] [Table 1]

[0103] This urethane raw material composition was injected into a mold (approximately 60°C) with a slit-shaped space, and the urethane raw material composition was allowed to react and foam with the mold opening open (free foam molding). After sufficient reaction and foaming were confirmed, the mold was demolded to obtain a foam plate. This foam plate was used as an evaluation sample for the open-cell urethane foam of this example. Multiple evaluation samples were produced in the same manner.

[0104] In the obtained evaluation sample, numerous ellipsoidal cells were observed as interconnected cells arranged crosswise to the thickness direction (thermal conduction direction) (see Figure 3(A)). The horizontal Feret diameter Fh of these ellipsoidal cells was larger than the vertical Feret diameter Fv.

[0105] (Change in cell Feret orientation rate) Among the multiple evaluation samples, the first and second evaluation samples were selected as representative evaluation samples for evaluating the XZ direction. A total of 16 cells were selected from each evaluation sample in the thickness direction (thermal conduction direction) of the foam plate. The cell thickness position Pc and the Feret orientation ratio Rf were measured from the first flat surface (surface), which served as the reference plane. The cell thickness position Pc and the Feret orientation ratio Rf were calculated (measured) by analyzing cross-sectional samples (see Figures 2(A)-(C)) taken in the thermal conduction direction from each evaluation sample using a scanning electron microscope (Hitachi High-Tech Corporation, product name: FlexSEM 1000 II) and image analysis and measurement software (Mitani Corporation, product name: WinROOF CLOUD Ver. 2.4.0). The results are shown in Table 2.

[0106] [Table 2]

[0107] As shown in Table 2, in the first evaluation sample, the change in the cell's Feret orientation ratio Rf with increasing cell thickness position Pc included peaks indicating maximum values ​​(near Pc = 4.27 mm and Pc = 15.29 mm) and peaks indicating minimum values ​​(near Pc = 10.38 mm). The maximum values ​​of the Feret orientation ratio Rf were 0.61 and 0.58, and the minimum value was 0.03. The average value of the Feret orientation ratio Rf was 0.24.

[0108] Similarly, in the second evaluation sample, the change in the cell's Feret orientation ratio Rf with increasing cell thickness position Pc included peaks indicating maximum values ​​(near Pc = 4.15 mm and Pc = 14.68 mm) and peaks indicating minimum values ​​(near Pc = 7.65 mm). The maximum values ​​of Feret orientation ratio Rf were 0.42 and 0.48, and the minimum value was 0.29. The average value of Feret orientation ratio Rf was 0.33.

[0109] As such, in both the first evaluation sample and the second evaluation sample, the maximum value of the Feret orientation ratio Rf relative to the cell thickness position Pc is 0.3 or more, and the minimum value of the Feret orientation ratio Rf is 0.1 or more.

[0110] (3D shape of ellipsoidal cell) As with the change in the cell's Feret orientation ratio described above, a third evaluation sample was selected as a representative evaluation sample for evaluating the XZ direction from among the multiple evaluation samples. A cross-sectional sample in the heat conduction direction (see Figures 2(A) to 2(C)) was sampled from this third evaluation sample, and images taken with a scanning electron microscope were analyzed using image analysis and measurement software to calculate (measure) the cell thickness position Pc and Feret orientation ratio Rf in the XZ direction (see Figure 2(B) / XZ plane in Figure 3(C)) and YZ direction (see Figure 2(C) / YZ plane in Figure 3(C)). The results are shown in Table 3 and Figure 4. In Figure 4, the vertical axis represents the Feret orientation ratio Rf, and the horizontal axis represents the cell thickness position Pc (unit: mm).

[0111] [Table 3]

[0112] As shown in Table 3 and Figure 4, at the same cell thickness position Pc, the value of the Ferret orientation rate Rf in any XZ plane was larger than the value of the Ferret orientation rate Rf in the YZ plane. In Figure 4, the open circular symbol (open circle) represents the Ferret orientation rate Rf in the XZ plane (in Figure 4, it is written as "Ferret orientation rate (XZ)"), and the filled-in circular symbol (black circle) represents the Ferret orientation rate Rf in the YZ plane (in Figure 4, it is written as "Ferret orientation rate (YZ)").

[0113] Furthermore, in both the XZ and YZ planes, peaks indicating maximum and minimum values ​​were observed in the Ferret orientation ratio Rf as the cell thickness position Pc changed. Of these, the maximum value of the Ferret orientation ratio Rf in the XZ plane was 0.55 or 0.52. Meanwhile, the minimum value of the Ferret orientation ratio Rf was 0.26, which was greater than 0.1. Furthermore, as shown in Table 3, the average value of the Ferret orientation ratio Rf in the XZ plane was 0.32, while the average value of the Ferret orientation ratio Rf in the YZ plane was 0.05. Thus, the average value of the Ferret orientation ratio Rf in the YZ plane was within the range of 0 to 0.10, and can be considered to be close to 0 when compared to the average value of the Ferret orientation ratio Rf in the XZ plane.

[0114] Because the average change in the Feret orientation ratio Rf in the YZ plane is close to 0, it can be determined that the cross section of the ellipsoidal cell 32 is circular or a shape close to that (substantially circular) in the YZ plane perpendicular to the urethane foaming flow direction Df. Furthermore, because the Feret orientation ratio Rf in the XZ plane is greater than the Feret orientation ratio Rf in the YZ plane, it can be determined that the cross section of the ellipsoidal cell 32 is elliptical rather than substantially circular in the XZ plane along the urethane foaming flow direction Df. Therefore, in this example, it can be seen that the shape of the ellipsoidal cell 32 tends to be a prolate ellipsoid with its longitudinal direction aligned with the urethane foaming flow direction Df.

[0115] (Ratio of ellipsoidal cells to all cells) For the cross-section sample of the third evaluation sample in the heat conduction direction, which was sampled in the three-dimensional shape of the ellipsoidal cell described above, the photographed image of the XZ plane was analyzed using image analysis and measurement software, and the proportion of cells that were not laterally oriented at an arbitrary cell thickness position Pc was calculated as a percentage. The results are shown in Table 4.

[0116] [Table 4]

[0117] As shown in Table 4, when the Feret orientation rate Rf is 0.16, the proportion of cells that are not horizontally oriented is 22.4% (cell thickness position Pc = 1.85 mm) or 17.35% (cell thickness position Pc = 18.25 mm). The relationship between the proportion of cells that are not horizontally oriented and the Feret orientation rate Rf is shown in a graph in Figure 5. In Figure 5, the vertical axis represents the proportion (%) of cells that are not horizontally oriented, and the horizontal axis represents the Feret orientation rate Rf.

[0118] The lower limit of the average value of the Feret orientation ratio Rf can be 0.2 or more. Therefore, considering the value at Rf=0.16, which is close to Rf=0.2 in FIG. 5, it can be seen that the proportion of cells that are not horizontally oriented should be 15% or less. In other words, it can be seen that the proportion of ellipsoidal cells 32 among all cells should be 85% or more.

[0119] (Example of vacuum insulation material manufacturing) The vacuum insulation materials of this example were manufactured as described above using the first evaluation sample or the second evaluation sample as the core material and a laminate film having gas barrier properties as the outer covering material. The vacuum insulation materials using the first evaluation sample were designated as the first evaluation vacuum insulation material and the second evaluation vacuum insulation material, respectively.

[0120] The thermal conductivity of these evaluation vacuum insulation panels was measured using the heat flow meter method described in the steady-state method of JIS A1412-2. The relationship between the obtained thermal conductivity λ and the average value of the Feret orientation ratio Rf is shown in a graph in Figure 6.

[0121] In Figure 6, the vertical axis is thermal conductivity λ (unit: mW / m K) and the horizontal axis is the average value of the Feret orientation factor Rf. In addition, the circular symbols in the figure represent the results for the first evaluation vacuum insulation material, and the diamond symbols represent the results for the second evaluation vacuum insulation material. Furthermore, the triangular symbols in the figure represent the results (Feret orientation factor Rf and thermal conductivity) for the reference evaluation vacuum insulation material manufactured using a total of six samples other than the first and second evaluation samples as core materials.

[0122] As is clear from the results in Figure 6, the thermal conductivity λ of the second evaluation vacuum insulation material is lower than that of the first evaluation vacuum insulation material, indicating good thermal insulation performance. Furthermore, from the results of the first evaluation vacuum insulation material and the second evaluation vacuum insulation material, as well as the results of the six reference evaluation vacuum insulation materials, it is clear that there is a good proportional relationship between the thermal conductivity λ and the Feret orientation ratio Rf. Therefore, from the results in Figure 6, it is clear that vacuum insulation materials using the open-cell urethane foam according to the present disclosure as a core material have good thermal insulation performance. It is also clear that even better thermal insulation performance can be achieved if the average Feret orientation ratio Rf is 0.2 or higher.

[0123] Furthermore, as mentioned above, the second evaluation vacuum insulation material exhibits better insulation performance than the first evaluation vacuum insulation material, so it is clear that the second evaluation sample is better as a core material. Therefore, according to the results of the second evaluation sample shown in Table 2, it is clear that it is more preferable that the maximum value of the cell Feret orientation ratio Rf is 0.3 or more and the minimum value is 0.1 or more in the change in the cell thickness position Pc.

[0124] The relationship between the thermal conductivity λ of the evaluation vacuum insulation material of this example and the density (urethane density) ρ of the evaluation sample (open-cell urethane foam) used as the core material is plotted in a graph in Figure 7. The density of the evaluation sample was measured by the method of dividing the mass by the volume as specified in JIS A9521.

[0125] As shown in Figure 7, there is a good proportional relationship between the urethane density ρ of the evaluation sample and the thermal conductivity λ of the evaluation vacuum insulation material. Based on this result, although there is no particular limitation on the upper limit of the urethane density of the open-cell urethane foam according to the present disclosure, for example, a preferred upper limit is 85 kg / m, which corresponds to the preferred upper limit of thermal conductivity λ of 7.0 mW / m K or less. 2 It is possible to specify the following:

[0126] (Addendum) Based on the description of the above embodiments, the following techniques are disclosed in this specification. (Technology 1) An open-cell urethane foam used as the core material of a vacuum insulation material, which is a plate-shaped foam having interconnected cells, the thickness direction of which is the direction of thermal conduction of the vacuum insulation material, and the interconnected cells include ellipsoidal cells that are ellipsoidal in shape and are arranged so that their major axes intersect the direction of thermal conduction.

[0127] (Technology 2) The open-cell urethane foam according to Technology 1, wherein the ellipsoidal cells have a Feret diameter in the horizontal direction larger than the Feret diameter in the vertical direction when the heat conduction direction is the vertical direction.

[0128] (Technology 3) The ellipsoidal cell has a Feret diameter when the heat conduction direction is the vertical direction, and when the horizontal Feret diameter is Fh and the vertical Feret diameter is Fv, the Feret orientation rate Rf is defined by the following formula (1), Rf = (Fh - Fv) / Fh (1) 3. The open-cell urethane foam according to claim 1, wherein the average value of the Feret orientation coefficient Rf of the plurality of ellipsoidal cells arranged at different positions along the heat conduction direction is 0.2 or more.

[0129] (Technology 4) An open-cell urethane foam according to Technology 3, wherein, when one of the opposing flat surfaces of the foam plate is taken as a reference plane and the distance in the thickness direction of the cells contained in the foam plate from the reference plane is taken as the cell thickness position, the change in the Feret orientation ratio Rf of the cells with an increase in the cell thickness position includes a peak indicating a maximum and a peak indicating a minimum, and the maximum value of the Feret orientation ratio Rf is 0.3 or more and the minimum value is 0.1 or more.

[0130] (Technical 5) The open-cell urethane foam according to any one of Technical 1 to Technical 4, wherein the ellipsoidal shape of the ellipsoidal cells is a prolate ellipsoid.

[0131] (Technology 6) Density is 85 kg / m 3 The open-cell urethane foam according to any one of Techniques 1 to 5, which is as follows:

[0132] (Technology 7) A vacuum insulation material comprising an outer covering material having gas barrier properties and a core material sealed inside the outer covering material under reduced pressure and in a sealed state, wherein the core material uses the open-cell urethane foam described in any one of Technology 1 to Technology 6.

[0133] (Technology 8) An insulated box body equipped with the vacuum insulation material described in Technology 7.

[0134] (Technology 9) A refrigeration cycle device comprising the heat-insulating box according to Technology 8.

[0135] (Technology 10) The refrigeration cycle device according to Technology 9, which is a refrigerator.

[0136] The present invention is not limited to the description of the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments or multiple modified examples are also included in the technical scope of the present invention. [Industrial Applicability]

[0137] The present disclosure can be suitably used in the field of core materials for vacuum insulation materials, and can also be suitably used widely in vacuum insulation materials and various fields that use vacuum insulation materials, such as insulated boxes, refrigeration cycle devices such as refrigerators, or home appliances or residential walls. [Explanation of symbols]

[0138] 10: Vacuum insulation material 11: Sealing part 20: Outer cover material 30: Core material 31: Open cell urethane foam 31a: First flat surface (reference surface) 31b: Second flat surface 31c: First side (bottom side during molding) 31d: Second side (cut surface) 31e: Third side (side during molding) 31f: Fourth side (side during molding) 31g: Cross-sectional sample in the direction of heat conduction 32: Ellipsoidal cell Df: Direction of urethane foam flow Dh: Heat conduction direction Fh: horizontal ferret diameter Fv: Vertical Feret diameter Pc: Cell thickness position

Claims

1. Used as the core material of vacuum insulation materials, a plate-shaped foam having interconnected cells, the thickness direction of which is the heat conduction direction of the vacuum insulation material; The communicating cells include ellipsoidal cells that are ellipsoidal in shape and are arranged such that their major axes intersect with the heat conduction direction. Open-cell urethane foam.

2. The ellipsoidal cell has a Feret diameter in which the horizontal Feret diameter is larger than the vertical Feret diameter when the heat conduction direction is the vertical direction. The open-cell urethane foam according to claim 1 .

3. The ellipsoidal cell has a Feret diameter when the heat conduction direction is the vertical direction, where Fh is the horizontal Feret diameter and Fv is the vertical Feret diameter. The Feret orientation ratio Rf is defined by the following formula (1): Rf=(Fh-Fv) / Fh...(1) The average value of the Feret orientation ratio Rf in the plurality of ellipsoidal cells arranged at different positions along the heat conduction direction is 0.2 or more, The open-cell urethane foam according to claim 1 .

4. When one of the opposing flat surfaces of the foam plate is taken as a reference plane and the distance in the thickness direction of the cells contained in the foam plate from the reference plane is taken as a cell thickness position, The change in the Feret orientation ratio Rf of the cell with an increase in the cell thickness position includes a peak indicating a maximum and a peak indicating a minimum, The maximum value of the Feret orientation ratio Rf is 0.3 or more, and the minimum value is 0.1 or more. The open-cell urethane foam according to claim 3.

5. The ellipsoid shape of the ellipsoid cell is a prolate ellipsoid. The open-cell urethane foam according to claim 1 .

6. Density is 85 kg / m 3 Below is the The open-cell urethane foam according to claim 1 .

7. The container comprises an outer covering material having gas barrier properties and a core material sealed in the outer covering material under reduced pressure and in a sealed state, The core material is an open-cell urethane foam according to any one of claims 1 to 6. Vacuum insulation material.

8. An insulating box comprising the vacuum insulating material according to claim 7.

9. A refrigeration cycle device comprising the heat-insulating box according to claim 8.

10. The refrigeration cycle apparatus according to claim 9, which is a refrigerator.

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