The present invention relates to a foamed heat-insulating material production method and a foamed heat-insulating material.
A foamed heat-insulating material is a cell structure encapsulating a gas in spaces defined by walls of a resin and having a diameter of less than approximately 1 mm. In order to secure a thermal conductivity of, for example, less than 0.04 W/mK, which is close to an upper limit of thermal conductivity of foamed plastic heat-insulating materials that is provided in Japanese Industrial Standards “Thermal Insulating Materials and Products for Buildings”, the foamed heat-insulating material needs to encapsulate a large amount of the gas therein and have a relative density of less than 1/10 with respect to the resin of the same volume. In order to implement higher heat insulating performance, methods such as micronizing cells while maintaining a high expansion ratio, using a resin of a low thermal conductivity or a gas of a low thermal conductivity, and minimizing radiant heat are adopted.
As a foamed heat-insulating material of high heat insulating performance, rigid urethane foam using hydrocarbon as a foaming agent is known. The rigid urethane foam encapsulates in foam cells hydrocarbon such as pentane and butane, which has a lower thermal conductivity than air, and carbon dioxide generated by urethane reaction so as to obtain a thermal conductivity of approximately 0.02 W/mK lower than the air. However, the rigid urethane foam has disadvantages including lower heat resistance and lower flame resistance, molding time as long as several minutes, and need of explosion-protected construction of a production plant and equipment, which increases cost for capital investment.
In view of this, the rigid urethane foam is replaced with a mold beads foaming method of forming a foamed heat-insulating material into a shape of a product to be installed by a single molding step. This mold beads foaming method includes a preliminary foaming step of dissolving an evaporation foaming agent such as hydrocarbon in bead-shaped resin particles, and heating the resin to vaporize the foaming agent and expand the beads. After the preliminary foaming step, the preliminarily foamed beads are filled in a forming die. Then, the beads are heated by heated vapor or the like and re-foamed to fuse surfaces of the particles to one another. A formed product thus obtained is kept still in a drying chamber for approximately a whole day and night to dry and stabilize shrinkage after forming.
Exemplary resins used for the above-described mold beads foaming method include polystyrene, polypropylene, and polyethylene. Exemplary hydrocarbons include butane, propane, and pentane. The hydrocarbon gas in the foam cells is replaced with air while kept still after forming.
As a method for improving heat insulating performance of a foamed heat-insulating material obtained by the mold beads foaming method, a production method including adding a substance to decrease a radiant component is known as disclosed in, for example, JP-A-2003-192821 (Patent Literature 1).
Foamed heat-insulating materials obtained by mold beads foaming methods including the above-described example of the related art have air filled in foam cells irrespective of kinds of resins, kinds of foaming agents, and production methods. This makes it impossible to make a thermal conductivity lower than the thermal conductivity of air, which is 0.024 W/mK.
Since the production method for improving the heat insulating performance disclosed in patent document 1 produces an effect limited to decreasing radiant heat, an improvement effect that compensates for an increase in material cost by adding the additive cannot be unfortunately obtained.
The invention has been made to solve the above problems, and an object of the invention is to provide a foamed heat-insulating material production method and a foamed heat-insulating material that yield high heat insulating performance.
A foamed heat-insulating material production method according to the invention is characterized by comprising: a step of preliminarily foaming high-melting point beads that keep internal gas lower in thermal conductivity than air at a mold beads forming temperature; a step of mixing the foamed high-melting point beads with low-temperature foam beads and filling a mixture in a forming die; and a step of heating the high-melting point beads and the low-temperature foam beads that have been filled in the forming die at the mold beads forming temperature. The low-temperature foam beads after mold beads forming have a smaller size than the high-melting point beads.
The foamed heat-insulating material production method according to the invention causes the high-melting point beads to be preliminarily foamed by a forming method different from beads foaming. Consequently, the gas having a lower thermal conductivity than air can be filled in cells, and the cells can be micronized so as to secure high heat insulating performance and reduce energy consumption of a product to be installed.
The preferred embodiments of a foamed heat-insulating material production method and a foamed heat-insulating material according to the invention will be described below with reference to the drawings. In the drawings, the same or corresponding components are denoted with identical reference numerals and signs and will not be described repeatedly.
As illustrated in
When the low-temperature foam beads 3 are re-foamed and expanded, the material is filled in the beads forming die cavity 4b with no gaps. Moreover, surfaces of the low-temperature foam beads 3 soften to fuse the low-temperature foam beads 3 to one another so as to maintain the shape even after removed from the die. While the low-temperature foam beads 3 are changing as described above, the high-melting point beads 2 do not soften and are not re-foamed, and keep internal gas lower in thermal conductivity than air and are maintained in a state prior to being filled in the beads forming die cavity 4b.
Next, production methods of the high-melting point beads 2 will be described. However, production methods of the high-melting point beads 2 according to the invention are not limited to these.
A foaming agent from a foaming agent supply source 6a is increased to a predetermined pressure by a foaming agent supply pump 6b and mixed with the molten resin in the screw cylinder 5a. The foaming agent is dissolved in the resin by mixing by the screw 5d and a pressure of the resin in the screw cylinder 5a, and the mixture is extruded from the die 5e. Reduced in pressure when extruded from the die 5e, the dissolved foaming agent is vaporized, and the molten resin is cooled and solidified to form a foam molded product of the resin. After formed, the foam molded product is passed through a device, such as a pulverizer and a pelletizer, to cut the resin to a predetermined length, thereby forming the high-melting point beads 2.
As illustrated in
Alternatively, similarly to foamed beads of the related art, after immersing bead-shaped resin particles in a foaming agent, and when the resin is heated to vaporize the foaming agent, the preliminary foaming step may not be performed but the resin particles may be expanded to a predetermined foam expansion ratio to form the high-melting point beads 2.
When substances such as polyethylene terephthalate, nylon, and ethylene-vinyl alcohol copolymer resin are used as a resin material of the high-melting point beads 2, internal gas is less likely to transmit than three substances used for mold beads foaming of the related art, namely, polystyrene, polypropylene, and polyethylene. When hydrocarbons such as carbonic acid gas, butane, and pentane, and hydro-fluoro-olefin that have lower thermal conductivity than air are used as a foaming agent, the high-melting point beads 2 can maintain a lower thermal conductivity than the foamed beads of the related art.
According to the first embodiment, the gas having a lower thermal conductivity than air can be filled in foam cells of the high-melting point beads 2 in advance at a step prior to mold beads foaming, and the gas is less likely to transmit from the inside of the form cells so as to maintain a low thermal conductivity.
Next, a second embodiment of the invention will be described.
As illustrated in
According to the second embodiment, the ratio of the high-melting point beads 2 having high heat insulating performance in the volume can be increased to obtain still higher heat insulating performance. Because the low-temperature foam beads 3 are more likely to fuse to one another, a shape of the foamed heat-insulating material 1 can be more easily maintained.
Next, a third embodiment of the invention will be described.
As illustrated in
Methods of forming the coating layer 2c include spray coating and immersion in a coating liquid tank, but are not limited to these. Alternatively, the foamed heat-insulating material 1 may include no low-temperature foam beads 3 but may have the coating layers 2c fused to one another by vapor heating at the time of mold beads forming to maintain the shape.
According to the third embodiment, the gas barrier property of the high-melting point beads 2 can be improved to maintain high heat insulating performance on a long-term basis. Moreover, the coating layers 2c are softened by vapor heating at the time of mold beads forming to make the high-melting point beads 2 have fusibility to eliminate need of the low-temperature foam beads 3. Even higher heat insulating performance can be obtained, and time for mold beads forming can be shortened to reduce production cost of the foamed heat-insulating material.
Next, a fourth embodiment of the invention will be described.
As illustrated in
The high-melting point bead 2 illustrated in the fourth embodiment is produced by extrusion molding, that is, multilayer forming of supplying two or more kinds of resins into a single die or by forming the inner layer 2d at a first extrusion molding step and adhering the outer layer 2e to an outer periphery of the inner layer 2d in a forming die while supplying the inner layer 2d from an upstream side of the die at a second extrusion molding step.
The high-melting point bead 2 may be obtained by supplying a foaming agent to an extruder of each of the inner layer 2d and the outer layer 2e and performing foam extrusion molding similarly to the first embodiment or by extrusion molding followed by autoclave foaming. Alternatively, similarly to foamed beads of the related art, after immersing a bead-shaped resin particle in a foaming agent for each of the inner layer 2d and the outer layer 2e, and when the resin is heated to vaporize the foaming agent, the preliminary foaming step may not be performed but the resin particle may be expanded to a predetermined foam expansion ratio to form the high-melting point bead 2. The number of layers is not be limited to 2.
According to the fourth embodiment, because the inner layer 2d is covered with the outer layer 2e, materials that have a low melting temperature and a low gas barrier property and are inexpensive and easy to foam and form, such as polyethylene and polystyrene, may be used for the inner layer 2d to reduce production cost and material cost.
At the time of forming high-melting point beads, for example, a crystalline nucleating agent and a polymer chain extender may be added to materials.
When the high-melting point beads 2 are formed by foam extrusion molding described in the first embodiment, the crystalline nucleating agent and the polymer chain extender may be kneaded and dispersed in the high-melting point beads 2 in advance or the crystalline nucleating agent, the polymer chain extender and the like may be introduced from the material supply unit 5b (see
According to the fifth embodiment, when a foaming agent is vaporized and expanded, addition of the crystalline nucleating agent increases the number of foam nuclei generated to micronize foam cells, and addition of the polymer chain extender improves viscosity of resin when foamed to stabilize bubbles in a micronized state, thus further improving heat insulating performance of the high-melting point beads 2.
A radiation reducing agent may be added to high-melting point beads. Examples of the radiation reducing agent include carbon black, graphite, and titanium oxide. The radiation reducing agent may be added not only to the high-melting point beads but also to low-temperature foam beads or to both of the high-melting point beads and the low-temperature foam beads. When the high-melting point beads 2 are formed by foam extrusion molding described in the first embodiment, the radiation reducing agent maybe kneaded and dispersed in the high-melting point beads 2 in advance or maybe introduced from the material supply unit 5b (see
According to the sixth embodiment, radiant heat can be reduced to obtain even higher heat insulating performance.
Next, a seventh embodiment of the invention will be described.
As illustrated in
According to the seventh embodiment, even when the gas barrier property of the high-melting point beads 2 alone is insufficient for use time of the foamed heat-insulating material 1, the gas barrier property can be secured, and even when the high-melting point beads 2 and the low-temperature foam beads 3 do not fuse to each other by heating and foaming, the film 9 maintains the outer peripheral shape to secure the shape as a component. Thus, the high-melting point beads 2, the low-temperature foam beads 3, and the film 9 that are worth the production cost and the material cost can be selected to produce the foamed heat-insulating material 1 at more appropriate cost.
Next, an eighth embodiment of the invention will be described.
As illustrated in
According to the eighth embodiment, even when the high-melting point beads 2 need higher production cost and higher material cost than the low-temperature foam beads 3, use amounts of the beads can be appropriately adjusted in accordance with the specification required for the product so as to reduce the production cost and the material cost.
Next, a ninth embodiment of the invention will be described.
As illustrated in
According to the ninth embodiment, even without beads forming equipment, the foamed heat-insulating material 1 having a low thermal conductivity can be produced by equipment for producing the low-temperature foam filler 10, and it is unnecessary to use hydrocarbon such as cyclopentane for the low-temperature foam filler 10, thus reducing equipment investment cost.
Next, a tenth embodiment of the invention will be described.
As illustrated in
The high-melting point bead 2 illustrated in the tenth embodiment is produced by extrusion molding, that is, by multilayer forming of supplying two or more kinds of resins into a single die or by forming the inner layer 2d at a first extrusion molding step and adhering the outer layer 2e to an outer periphery of the inner layer 2d in the forming die while supplying the inner layer 2d from an upstream side of the die at a second extrusion molding step.
The high-melting point bead 2 may be obtained by supplying a foaming agent to an extruder of each of the inner layer 2d and the outer layer 2e and performing foam extrusion molding similarly to the first embodiment or by extrusion molding followed by autoclave foaming. Alternatively, similarly to foamed beads of the related art, after immersing a bead-shaped resin particle in a foaming agent for each of the inner layer 2d and the outer layer 2e, and when the resin is heated to vaporize the foaming agent, the preliminary foaming step may not be performed but the resin particle may be expanded to a predetermined foam expansion ratio to form the high-melting point bead 2. The number of layers is not be limited to 2.
According to the tenth embodiment, because the outer layers 2e are fused to one another at the time of beads forming to eliminate need of the low-temperature foam beads 3. Even when the outer layers 2e soften to allow gas of a low thermal conductivity to transmit, the whole heat-insulating material can be prevented from increasing the thermal conductivity so as to reduce production cost and material cost.
Although the first to tenth embodiments of the invention have been described heretofore, the embodiments of the invention can be freely combined and suitably modified and omitted within the scope of the invention.
1 . . . foamed heat-insulating material, 1a . . . main portion, 1b . . . flange, 1c . . . protrusion, 1d . . . hole, 2 . . . high-melting point bead, 2a . . . cell wall, 2b . . . foam cell, 2c . . . coating layer, 2d . . . inner layer, 2e . . . outer layer, 3 . . . low-temperature foam bead, 4a . . . material supply port, 4b . . . beads forming die cavity, 5 . . . extrusion molder, 5a . . . screw cylinder, 5b . . . material supply unit, 5c . . . motor, 5d . . . screw, 5e . . . die, 6 . . . foaming agent supply device, 6a . . . foaming agent supply source, 6b . . . foaming agent supply pump, 7 . . . coupling valve, 8 . . . autoclave, 8a . . . material placement portion, 8b . . . discharge valve, 9 . . . film, 10 . . . low-temperature foam filler
Number | Date | Country | Kind |
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2016-237257 | Dec 2016 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2017/041954 | 11/22/2017 | WO | 00 |