JP2011196609A - Heat insulating material and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flow-filling property of polyurethane, the thermal insulation performance of a polyurethane heat insulating material, and the power saving of a refrigerator.SOLUTION: A heat insulating material is obtained by reacting polyol and polyisocyanate in the presence of a foaming agent, using a first foaming agent (cyclopentane) and a second foaming agent (carbon dioxide) as the foaming agent, and adding an adsorbent 110 that adsorbs the second foaming agent (carbon dioxide) existing in bubbles after foaming. The mixture liquid can be filled smoothly even into a complex shape since it flows with a low viscosity, and the second foaming agent added for the purpose of increasing the foaming force is removed and the first foaming agent composition used to exert the heat insulating material performance as a base function of the foamed polyurethane heat insulating material becomes predominant and the thermal insulation performance can be maintained.

Description

  The present invention relates to a heat insulating material and a refrigerator using the same.

  In recent years, refrigerators have a social need for improving the heat insulation performance of the heat insulating material used on the wall surface of the refrigerator housing from the viewpoint of energy saving. In order to respond to these demands, refrigerator manufacturers have not neglected their ingenuity, and recently, refrigerators that use vacuum heat insulating materials, which are high performance heat insulating materials, in addition to conventional polyurethane foam heat insulating materials have been commercialized.

  A vacuum insulation material is a vacuum package that encloses a core material, such as powder or glass fiber sintered body, together with a moisture adsorbent, etc., in a jacket bag with excellent air barrier properties. It is difficult to install in a simple shape without a gap. For this reason, generally, a vacuum heat insulating material is pasted in advance on an outer surface material or an inner surface material in the wall surface of the casing, and the remaining space is filled with foamed polyurethane. As a result, the composite thermal conductivity of the casing wall surface can be reduced and the heat insulating performance of the refrigerator casing can be improved as compared with the case of foamed polyurethane alone.

  On the other hand, providing a vacuum heat insulating material in the housing wall surface is not preferable from the viewpoint of filling properties of the polyurethane foam because flow resistance increases and the degree of freedom of the air hole position decreases. The foamed polyurethane is filled in the wall surface of the refrigerator casing while mixing polyol and polyisocyanate and increasing the viscosity (curing) by chemical reaction. That is, if there is a flow-inhibiting factor such as a vacuum heat insulating material at the position where the reaction has progressed, problems such as unfilling due to air entrainment and bubble roughness occur.

  Also, vacuum insulation is often affixed to a relatively smooth outer surface, but in the polyurethane foaming process of the refrigerator housing, the polyurethane material is injected from the inlet provided on the back with the opening side down. In the case of the open side down method, a vacuum heat insulating material is provided on the upper surface side, and therefore air passage design is important (see, for example, Patent Document 1).

  FIG. 6 is a cross-sectional view of the refrigerator described in Patent Document 1. As shown in FIG. The refrigerator body 1 includes an outer box 2, an inner box 3, a heat insulating material 4, a partition wall 5, a freezer compartment door 6, a refrigerator compartment door 7, and a compressor 8. The cold air cooled by the cooler 9 is forcibly blown to the freezer compartment 11 and the refrigerator compartment 12 by the blower 10. The motor 13 drives the blower 10 and is attached via the outer box 2 and the inner box 3 using a motor case 14. On the back surface of the outer box 2, a lid 15 a that covers the stock solution injection port 15 of the foam heat insulating material is provided. The inner box 3 has a gas vent hole 16. A vacuum heat insulating material 17 provided with a gas vent groove is interposed in the heat insulating material 4 in accordance with the gas vent hole 16.

  In this manner, the vacuum heat insulating material 17 with the gas vent groove is embedded in the rigid urethane foam corresponding to the upper ceiling portion of the compressor 8 of the heat insulating wall which becomes the urethane final filling portion in the heat insulating box and the machine room of the box. This prevents the generation of voids, improves cooling efficiency, lowers the center of gravity of the refrigerator body, prevents heat from entering from the upper part of the compressor 8 at a high temperature to the vegetable dedicated room at the lower part of the refrigerator compartment, and expands the internal volume of the vegetable dedicated room I can do it.

JP-A-7-167551

  However, when an air vent groove is provided on the surface like the vacuum heat insulating material 17 used in the conventional refrigerator main body 1, the flow resistance due to air compression is reduced, but the vacuum heat insulating material 17 itself becomes the flow resistance. In some cases, flow in the polyurethane foaming process is hindered.

  The present invention solves the above-described conventional problems, improves the fluid filling properties of polyurethane, is smoothly filled even if there are various flow resistances in the refrigerator casing wall surface, and the heat insulating performance of the polyurethane heat insulating material The purpose is to improve the energy saving of the refrigerator.

  In order to achieve the above object, the present invention provides a foamed polyurethane produced by reacting a polyol and a polyisocyanate in the presence of a foaming agent, wherein the foaming agent comprises a first foaming agent and the first foaming agent. The second foaming agent having a low boiling point is used, and the heat insulating material characterized by adding an adsorbent that adsorbs the second foaming agent present in the bubbles of the foamed polyurethane after foaming is used.

  When the polyol and the polyisocyanate are mixed, the temperature of the mixed solution is raised by self-heating of the urethane reaction. A part of the heat generation is consumed as a heat source for vaporizing the foaming agent. At this time, the second foaming agent having a low boiling point is vaporized from a state where the viscosity of the mixed liquid at the initial stage of the reaction is low, and then the first foaming agent is vaporized to form a foamed polyurethane. From this, since the liquid mixture can flow with a low viscosity, even a complicated shape can be filled smoothly. Further, the second foaming agent is adsorbed and removed by the adsorbent after foaming. For this reason, the second foaming agent added for the purpose of increasing foaming power is removed, and the first foaming agent composition used for the purpose of exhibiting the performance of the heat insulating material as a basic function of the foamed polyurethane heat insulating material becomes dominant, and heat insulating Performance can be maintained.

  INDUSTRIAL APPLICATION While improving the fluid filling property of the polyurethane foam which is a heat insulating material for refrigerators, this invention can provide the refrigerator excellent in energy saving property by maintaining the heat insulation performance.

Schematic of the polyurethane foaming machine used for the heat insulating material in Embodiment 1 of the present invention The characteristic figure which shows the relationship between the amount of carbon dioxide addition in the heat insulating material of the embodiment, and the foaming speed of polyurethane Characteristic chart showing thickening behavior characteristics in polyurethane foaming process in heat insulating material of same embodiment Enlarged schematic diagram showing foamed polyurethane foam, which is a heat insulating material of the same embodiment Longitudinal sectional view of the refrigerator in the second embodiment of the present invention Vertical section of a conventional refrigerator

  The first invention is a foamed polyurethane produced by reacting a polyol and a polyisocyanate in the presence of a foaming agent, the foaming agent having a lower boiling point than the first foaming agent and the first foaming agent. And an adsorbent that adsorbs the second foaming agent present in the foamed polyurethane foam after foaming is added.

  When the polyol and the polyisocyanate are mixed, the temperature of the mixed solution is raised by self-heating of the urethane reaction. A part of the heat generation is consumed as a heat source for vaporizing the foaming agent. At this time, the second foaming agent having a low boiling point is vaporized from a state where the viscosity of the mixed liquid at the initial stage of the reaction is low, and then the first foaming agent is vaporized to form a foamed polyurethane. From this, since the liquid mixture can flow with a low viscosity, even a complicated shape can be filled smoothly.

  Further, the second foaming agent is adsorbed and removed by the adsorbent after foaming. For this reason, the second foaming agent added for the purpose of increasing foaming power is removed, and the first foaming agent composition used for the purpose of exhibiting the performance of the heat insulating material as a basic function of the foamed polyurethane heat insulating material becomes dominant, and heat insulating Performance can be maintained. From this, the filling property can be improved without deteriorating the heat insulating performance of the heat insulating material.

  In the second invention, in particular, in the first invention, the first blowing agent is cyclopentane, and the second blowing agent is carbon dioxide, both of which have a small ozone layer depletion coefficient and a global warming coefficient, Widely used as a foaming agent with excellent environmental properties. Among them, since cyclopentane has a relatively low thermal conductivity, the heat insulation performance can be improved by increasing the composition of foamed polyurethane in the bubbles.

  Carbon dioxide, on the other hand, has a higher thermal conductivity than cyclopentane, but its boiling point is extremely low at 78 degrees below freezing point, so it can be instantly vaporized in the temperature zone (room temperature) of the foaming process, thus increasing the foaming efficiency of polyurethane. And can be sufficiently foamed at the initial stage of the urethane reaction, so that the fluidity can be improved.

  By removing carbon dioxide after foaming, the advantages of both foaming agents can be utilized. From this, it is possible to further improve the filling properties without deteriorating the heat insulating performance of the heat insulating material.

  In the third invention, particularly in the first or second invention, the adsorbent is a porous substance, and physically adsorbs the second foaming agent, and is per unit weight or unit volume of the adsorbent. The surface area can be increased. From this, it is possible to sufficiently remove the second foaming agent even with a small amount of adsorbent addition, so that the first foaming agent can be removed by removing the second foaming agent after foaming without significantly affecting the physical properties of the polyurethane. The advantages of both the foaming agent and the second foaming agent can be utilized. From this, it is possible to further improve the filling properties without deteriorating the heat insulating performance of the heat insulating material.

  In the fourth invention, particularly in the second invention, the adsorbent is an alkaline substance and chemically adsorbs carbon dioxide, and the carbon dioxide is removed by chemically reacting with the adsorbent. For this reason, carbon dioxide once removed cannot be easily removed. From this, the advantages of both the foaming agent of cyclopentane and carbon dioxide can be utilized, and the filling property can be further improved without deteriorating the heat insulating performance of the heat insulating material.

  In the fifth invention, particularly in the second or fourth invention, the adsorbent is obtained by modifying the surface of the porous substrate to be alkaline, chemically adsorbing carbon dioxide, and further increasing the surface area. Carbon dioxide is removed by chemical reaction with the adsorbent. For this reason, carbon dioxide once removed cannot be easily removed. Moreover, the surface area per unit weight or unit volume of the adsorbent can be increased. From this, the second foaming agent can be sufficiently removed even by adding a small amount of adsorbent, so that the physical properties of the polyurethane are not greatly affected. From this, the advantages of both the foaming agent of cyclopentane and carbon dioxide can be utilized, and the filling property can be further improved without deteriorating the heat insulating performance of the heat insulating material.

  6th invention is the heat insulation box provided with the heat insulating material in the space formed between an outer surface material, an inner surface material, and an outer surface material and an inner surface material, Comprising: A compressor, condensation is included in a heat insulation box And a cooling means for circulating the refrigerant in a circulation circuit in which an evaporator is connected by piping, and the heat insulating material uses the heat insulating material of any one of the first to fifth inventions, and the heat insulating material maintains the heat insulating performance. Both improve filling properties. By using this heat insulating material, the degree of freedom in designing the housing wall surface can be improved and a refrigerator excellent in energy saving can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a schematic view of a polyurethane foaming machine used for a heat insulating material in Embodiment 1 of the present invention. FIG. 2 is a characteristic diagram showing the relationship between the amount of carbon dioxide added and the foaming speed of polyurethane in the heat insulating material of the same embodiment. FIG. 3 is a characteristic diagram showing a thickening behavior characteristic in the foaming process of polyurethane in the heat insulating material of the same embodiment. FIG. 4 is an enlarged schematic view showing bubbles of foamed polyurethane, which is a heat insulating material of the same embodiment.

  As shown in FIG. 1, the polyol 101 and the polyisocyanate 102 are collided and mixed by the mixing head 103 and injected into the wall surface of the refrigerator 104. In FIG. 1, an open side down type injection mode in which an inlet (not shown) is provided on the back of the refrigerator 104 is used. You may do it.

  The polyol 101 and the polyisocyanate 102 are a high pressure foaming type that is mixed after being pressurized to about 8 to 15 MPa in a circulation circuit connected by piping through a mixing head 103. The polyol 101 is mixed with a secondary material such as a catalyst, a foam stabilizer, and water.

  As the foaming agent, cyclopentane 105 as the first foaming agent and carbon dioxide 106 as the second foaming agent are used. Since cyclopentane 105 has a boiling point of 49 degrees and is liquid at room temperature, it can be mixed with polyol 101 relatively easily. You may mix beforehand as a premix, and you may provide a mixer and mix separately. On the other hand, carbon dioxide 106 has a boiling point of 78 degrees below freezing point and is a gas at room temperature, so it cannot be premixed with polyol 101. Therefore, it is good to arrange and mix the fixed mixer 107 on the polyol 101 pipe.

  FIG. 2 shows the mixing amount of carbon dioxide 106 and the foaming speed of polyurethane with respect to the total weight of the polyurethane raw material composed of polyol 101 and polyisocyanate 102. Here, the foaming speed is a value obtained by dividing the height of 400 mm by the time until the inside of the jig is filled with foamed polyurethane when a polyurethane raw material is injected into a foam panel jig of width 300 × height 400 × thickness 50 mm. It is.

  As can be seen from FIG. 2, when the amount of carbon dioxide 106 mixed is increased, it can be filled in a short time. In addition, in the polyol 101 used in the present embodiment, when carbon dioxide 106 was mixed by 1% by weight or more, the carbon dioxide 106 was not completely dissolved in the polyol 101, but bumped, but this was dissolved by improving the polyol 101. Therefore, the amount of carbon dioxide 106 is not limited.

  When the carbon dioxide 106 is not mixed, the mixed liquid foams (expands) when the reaction between the polyol 101 and the polyisocyanate 102 starts. This time is called cream time and is about 5 to 10 seconds. When carbon dioxide 106 is mixed, cream time is not recognized because foaming (expansion) occurs immediately after injection.

  Next, with the progress of the reaction, the mixed solution becomes a polymer (resin). This time is called gel time and is an index of the resinification reaction. The gel time of the polyurethane raw material in the present embodiment is 45 to 60 seconds, and as shown in FIG.

  As described above, the use of carbon dioxide 106 as the second foaming agent is characterized by being able to be filled in the wall surface of the refrigerator 104 with a low viscosity because the foaming (expansion) greatly occurs in the initial reaction stage where resinification does not progress much. There is.

  On the other hand, the thermal conductivity of carbon dioxide 106 at 25 degrees is 16.9 mW / mK, which is higher than that of cyclopentane 105 12.4 mW / mK. As shown in FIG. 4, the foamed polyurethane bubbles are composed of a resin part 108 and a gas part 109, and the gas part 109 contains a slight amount of air and water vapor including cyclopentane 105 and carbon dioxide 106. These thermal conductivities are entangled in a complex manner, and the thermal conductance of the gas part 109 is determined.

  For this reason, there is a concern that the heat insulation performance of the polyurethane after foam molding is deteriorated when the carbon dioxide is excessive. Therefore, an adsorbent 110 that physically or chemically adsorbs excess carbon dioxide 106 remaining in the bubbles after foaming may be mixed with the polyol 101 or the polyisocyanate 102.

  As the physical adsorbent, a porous material such as activated carbon, silica gel, or zeolite may be used. On the other hand, as the chemical adsorbent, an alkaline substance can be used, and specifically, calcium hydroxide, ethanolamines, epoxy compounds and the like can be used. Furthermore, the adsorption efficiency of the carbon dioxide 106 is improved by fusing the properties of the physical adsorbent and the chemical adsorbent and modifying the surface of the porous material to be alkaline.

  The heat insulating material configured as described above is a foamed polyurethane produced by reacting polyol 101 and polyisocyanate 102 in the presence of a foaming agent, the foaming agent being a first foaming agent 105 (cyclopentane) and a first foaming agent. The second foaming agent 106 (carbon dioxide) having a boiling point lower than that of the foaming agent 105 is added, and an adsorbent 110 for adsorbing the second foaming agent 106 present in the foamed polyurethane foam is added. When the polyol 101 and the polyisocyanate 102 are mixed, the temperature of the mixed solution is raised by self-heating of the urethane reaction. A part of the heat generation is consumed as a heat source for vaporizing the foaming agent.

  At this time, the second foaming agent 106 having a low boiling point is vaporized from the low viscosity of the mixed liquid at the initial stage of the reaction, and then the first foaming agent 105 is vaporized to form a foamed polyurethane. From this, since the liquid mixture can flow with a low viscosity, even a complicated shape can be filled smoothly.

  Further, the second foaming agent 106 is removed by adsorption with the adsorbent 110 after foaming. Therefore, the second foaming agent 106 added for the purpose of increasing foaming power is removed, and the composition of the first foaming agent 105 used for the purpose of exhibiting the heat insulating material performance as the basic function of the foamed polyurethane heat insulating material is dominant. The heat insulation performance can be maintained.

(Embodiment 2)
FIG. 5 is a cross-sectional view of the refrigerator in the second embodiment of the present invention. In the present embodiment, detailed description of the same components as those in the first embodiment is omitted.

  As shown in FIG. 5, the refrigerator 201 includes a box 202, a door 203, and cooling means 204.

  The box 202 and the door 203 are composed of an outer surface material 205 made of a steel plate or a stainless steel plate, and an inner surface material 206 made of resin such as ABS, polyethylene, polypropylene, and the wall surface formed by the outer surface material 205 and the inner surface material 206 is formed on the wall surface. Polyurethane foam is filled as the heat insulating material 207.

  In addition, as the heat insulating material 207, various foamed resins such as foamed polystyrene can be partially used. Further, a vacuum heat insulating material may be embedded in the heat insulating material 207 in order to improve the heat insulating performance of the box 202.

  The box 202 is composed of a plurality of storage rooms 208. In this embodiment, the box 202 is a refrigerator room, ice making room, freezer room, and vegetable room from the top. The front opening 209 of the storage chamber 208 is provided with a door 203 that can be opened and closed.

  The door 203 can be opened and closed by rotational movement and by forward and backward movement. For example, when a shelf is provided on the inner surface side of the door 203 so that it can be stored, a rotational motion is suitable. The storage chamber 208 is cooled by supplying cool air generated by the cooling means 204 to which the compressor 210, the condenser 211, and the evaporator 212 are connected by piping.

  The polyurethane foam raw material is injected from an inlet 213 provided on the back of the refrigerator 201. The number of the inlets 213 may be appropriately determined according to the capacity of the refrigerator 201. In this embodiment, the injection side is an open side down type in which an inlet 213 is provided on the back of the refrigerator 201. However, the open side up type is used to inject in the horizontal direction from the bottom of the refrigerator 201 with the opening surface facing upward. You may do it.

  The heat insulating material described in Embodiment 1 can be applied to the refrigerator 201 having such a structure.

  In the refrigerator 201 configured as described above, the heat insulating box 202 includes the outer surface material 205, the inner surface material 206, and the heat insulating material 207 in the space formed between the outer surface material 205 and the inner surface material 206. The heat insulating box 202 is provided with a cooling means 204 for circulating the refrigerant in a circulation circuit in which the compressor 210, the condenser 211, and the evaporator 212 are connected by piping, and the heat insulating material 207 is the heat insulating material described in the first embodiment. The heat insulating material 207 achieves both the heat insulating performance maintenance and the filling performance improvement. By using this heat insulating material, the design freedom of the housing wall surface is improved, and the refrigerator 201 excellent in energy saving can be provided.

  As described above, the heat insulating material and the refrigerator according to the present invention can be smoothly foamed and filled without reducing the heat insulating performance of the polyurethane heat insulating material even in a complicated shape such as a refrigerator wall surface. For this reason, it can be applied to refrigerators with increased flow resistance of polyurethane, such as by embedding vacuum insulation materials or harnesses in the refrigerator wall surface, or by reducing the wall thickness in order to improve the volumetric efficiency of the interior of the refrigerator. This can increase the added value of the refrigerator.

101 Polyol 102 Polyisocyanate 104 Refrigerator 105 First blowing agent (cyclopentane)
106 Second foaming agent (carbon dioxide)
DESCRIPTION OF SYMBOLS 110 Adsorbent 201 Refrigerator 202 Heat insulation box 204 Cooling means 205 Outer surface material 206 Inner surface material 207 Heat insulation material (foamed polyurethane)
210 Compressor 211 Condenser 212 Evaporator

Claims (6)

A foamed polyurethane produced by reacting a polyol and a polyisocyanate in the presence of a foaming agent, the foaming agent using a first foaming agent and a second foaming agent having a boiling point lower than that of the first foaming agent. The heat insulating material characterized by adding the adsorbent which adsorb | sucks the said 2nd foaming agent which exists in the bubble of the said said foaming polyurethane later. The heat insulating material according to claim 1, wherein the first blowing agent is cyclopentane, and the second blowing agent is carbon dioxide. The heat insulating material according to claim 1 or 2, wherein the adsorbent is a porous substance and physically adsorbs the second foaming agent. The heat insulating material according to claim 2, wherein the adsorbent is an alkaline substance and chemically adsorbs carbon dioxide. The adsorbent is obtained by modifying the surface of a porous substrate to be alkaline, chemically adsorbing the second foaming agent, and further increasing the surface area. Insulation. An outer surface material, an inner surface material, and a heat insulating box provided with a heat insulating material in a space formed between the outer surface material and the inner surface material, the heat insulating box including a compressor, a condenser, and an evaporation A refrigerator comprising a cooling means for circulating a refrigerant in a circulation circuit connected to a vessel, wherein the heat insulating material uses the heat insulating material according to any one of claims 1 to 5.