JP6929223B2 - Vacuum heat insulating material, manufacturing method of vacuum heat insulating material and outer packaging material for vacuum heat insulating material - Google Patents

Description

The present invention relates to a vacuum heat insulating material, a method for producing the vacuum heat insulating material, and an outer packaging material for the vacuum heat insulating material.

Insulation materials having excellent heat insulation performance are required for heat and cold insulation equipment such as refrigerators and vending machines, and buildings. As such a heat insulating material, the vacuum heat insulating material is being used in place of the conventional glass fiber heat insulating material and the foamed resin heat insulating material. The vacuum heat insulating material has a structure in which the core material is sealed in a vacuum state (decompression state) by an outer packaging material having a gas barrier property.

In order to maintain the heat insulating property of the vacuum heat insulating material, it is important to maintain a high degree of vacuum inside. As a technique for maintaining a high degree of vacuum, in order to adsorb the gas entering from the outside, the adsorbent is sealed with an outer packaging material together with the core material (see Patent Documents 1 and 2), and the pressure is reduced while heating. There has been proposed a method of sealing the core material while volatilizing the water content inside the core material (see Patent Document 3).

On the other hand, as the outer packaging material, a sheet material having a heat-sealing layer and a gas barrier layer arranged in the innermost part is used, and the core material is generally sealed by heat sealing of the sheet material. be. As the heat-sealing layer, polyolefins such as polyethylene are widely used from the viewpoint of having good heat-sealing properties. On the other hand, as a heat-sealing layer, an outer packaging material using an ethylene-vinyl alcohol copolymer (EVOH) having excellent gas barrier properties has been proposed (see Patent Documents 4 and 5). In order to maintain the degree of vacuum inside the vacuum heat insulating material and, by extension, the heat insulating property for a long period of time, it is important for this technology to suppress the infiltration (permeation) of gas from the end face of the heat-sealed heat-sealed layer. It focuses on that.

However, when an outer packaging material having a heat-sealing layer formed of a vinyl alcohol-based resin such as EVOH is used, compared with a case where an outer packaging material having a heat-sealing layer formed of polyethylene or the like is used, Although the heat insulating property is maintained for a long period of time, it has the disadvantage that the heat insulating property at the initial stage is relatively low.

Japanese Unexamined Patent Publication No. 2007-155087 Japanese Unexamined Patent Publication No. 2013-76459 Japanese Unexamined Patent Publication No. 2013-104490 Japanese Unexamined Patent Publication No. 9-309574 Japanese Unexamined Patent Publication No. 2005-305824

The present invention has been made based on the above circumstances, and an object of the present invention is a vacuum heat insulating material having high heat insulating properties from an initial stage and capable of maintaining the heat insulating properties for a long period of time, and a method for producing the vacuum heat insulating material. , As well as providing an outer packaging material used for such a vacuum heat insulating material.

The present inventors include a vacuum heat insulating material using an outer packaging material having a heat-sealing layer formed of polyolefin, and a vacuum heat insulating material using an outer packaging material having a heat-sealing layer formed of a vinyl alcohol-based resin. First found that there are the following differences in the changes in thermal conductivity over time. As schematically shown as a graph in FIG. 2, in the vacuum heat insulating material A using the outer packaging material having a heat-sealing layer formed of polyolefin, its thermal conductivity increases with the passage of time from the initial stage ( A) in FIG. On the other hand, in the vacuum heat insulating material B using the outer packaging material having a heat-sealing layer formed from a vinyl alcohol-based resin, the thermal conductivity at the initial stage is relatively high, and this thermal conductivity is once lowered, and then It starts to rise (B in Fig. 2). In the vacuum heat insulating material B, the rate of increase after the thermal conductivity starts to increase is slower than the rate of increase in the vacuum heat insulating material A due to the high gas barrier property of the vinyl alcohol resin. ..

Furthermore, the inventors have found that the high thermal conductivity at the initial stage of the vacuum heat insulating material B using the encapsulant having a heat-sealing layer formed from the vinyl alcohol resin was formed from the vinyl alcohol resin. It was found that this was due to outgas such as moisture in the heat-sealed layer. The outgas from the heat-sealing layer is not substantially released to the outside by the gas barrier layer existing outside the heat-sealing layer, and the degree of vacuum in the vacuum heat insulating material B, and thus the heat insulating property, is lowered. Therefore, based on these findings, the inventors reduced the thermal conductivity from the initial stage by reducing the water content in the heat-sealed layer formed from the vinyl alcohol-based resin, and the low thermal conductivity. Was maintained for a long period of time, and the present invention was completed.

As described above, although there is a conventional technique for sealing while using an adsorbent or volatilizing the water content of the core material in order to maintain the degree of vacuum of the vacuum heat insulating material, these are heat-sealed. It does not focus on outgas such as moisture from the layer.

That is, the present invention made to solve the above problems is a plate-shaped vacuum heat insulating material including a core material and an outer packaging material that seals the core material in a vacuum state, and the outer packaging material is vinyl alcohol. It has a heat-sealed layer containing a system resin and arranged in the innermost part, and a gas barrier layer laminated on the outer surface side of the heat-sealed layer, and the change in thermal conductivity between the front surface and the back surface with time changes. It is a vacuum heat insulating material that satisfies the following formula (1).

In the formula (1), T ₁ is the minimum value of the thermal conductivity. T ₂ is the maximum value between the initial value and the minimum value of the thermal conductivity.

In the vacuum heat insulating material, the ratio (T ₁ / T ₂ ) of the minimum value (T _{1 ) of the thermal conductivity to the maximum value (T 2} ) between the initial value and the minimum value of the thermal conductivity is 0.8. As described above, the thermal conductivity in the initial stage is relatively reduced, and the heat insulating property is high from the initial stage even though the outer packaging material has a heat-sealing layer including a vinyl alcohol-based resin layer. Can be demonstrated. Further, since the vacuum heat insulating material has a heat-sealing layer containing a vinyl alcohol resin and a gas barrier layer as the outer packaging material, high heat insulating properties can be maintained for a long period of time (C in FIG. 2).

The vacuum heat insulating material preferably further includes an adsorbent sealed in the outer packaging material. Since the adsorbent is sealed, the outgas from the heat-sealing layer generated after the sealing can be adsorbed by the adsorbent, and the heat insulating property at the initial stage can be further improved.

The moisture content of the heat-sealed layer is preferably 2% by mass or less. By setting the water content of the heat-sealing layer to 2% by mass or less, the amount of outgas generated including water can be further reduced, and the heat insulating property at the initial stage can be improved.

It is preferable that the gas barrier layer includes a resin layer containing a vinyl alcohol-based resin and a thin-film deposition layer laminated on at least one surface side of the resin layer. By using such a gas barrier layer, the permeation of gas from the outside is further suppressed, and the heat insulating property can be maintained for a longer period of time. Further, when the gas barrier layer also has a resin layer containing a vinyl alcohol resin as described above, the outgas from the resin layer in the gas barrier layer can also affect the initial value of the thermal conductivity, so that the advantage of adopting the present invention is to be adopted. Is big.

Another invention made to solve the above problems is a method for producing the vacuum heat insulating material, which includes a step of removing volatile components contained in the outer packaging material, and the core material using the outer packaging material. It is a method of manufacturing a vacuum heat insulating material including a step of sealing an object to be sealed by heat fusion. According to the manufacturing method, the generation of outgas from the heat-sealing layer of the outer packaging material after sealing is suppressed by having the step of removing the volatile components contained in the outer packaging material. Therefore, according to the manufacturing method, it is possible to manufacture a vacuum heat insulating material which has high heat insulating properties from the initial stage and can maintain the heat insulating properties for a long period of time.

It is preferable that the removing step and the sealing step are performed in this order. In this way, by separately removing the volatile components contained in the outer packaging material before sealing, the volatile components in the heat-sealing layer can be sufficiently reduced.

It is also preferable to perform the removing step and the sealing step at the same time by performing the sealing step while heating the outer packaging material and the object to be sealed to 40 ° C. or higher. By simultaneously performing the removing step and the sealing step in this way, it is possible to efficiently remove the volatile components in the heat-sealing layer and seal with the outer packaging material from which the volatile components have been removed.

Yet another invention made to solve the above problems is to provide a heat-sealed layer containing a vinyl alcohol-based resin and arranged in the innermost position, and a gas barrier layer laminated on the outer surface side of the heat-sealed layer. It is an external packaging material for a vacuum heat insulating material having a moisture content of the heat-sealed layer of 2% by mass or less. According to the outer packaging material for the vacuum heat insulating material, the generation of outgas from the heat-sealed layer is suppressed, and a vacuum heat insulating material having high heat insulating properties from the initial stage and capable of maintaining the heat insulating properties for a long period of time is obtained. be able to.

According to the present invention, a vacuum heat insulating material having high heat insulating properties from the initial stage and capable of maintaining the heat insulating properties for a long period of time, a method for producing the vacuum heat insulating material, and an external packaging material used for such the vacuum heat insulating material are provided. be able to.

FIG. 1 is a cross-sectional view of the vacuum heat insulating material according to an embodiment of the present invention. FIG. 2 is a graph schematically showing the change over time in the thermal conductivity of the vacuum heat insulating material.

Hereinafter, the vacuum heat insulating material, the method for producing the vacuum heat insulating material, and the outer packaging material for the vacuum heat insulating material according to the embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

<Vacuum heat insulating material>
The vacuum heat insulating material 10 of FIG. 1 includes a core material 11 and an outer packaging material 12 that seals the core material 11 in a vacuum state. Further, the vacuum heat insulating material 10 has a plate shape. The outer packaging material 12 has a heat-sealing layer 13 containing a vinyl alcohol-based resin and arranged inside, and a gas barrier layer 14 laminated on the outer surface side of the heat-sealing layer 13. In the vacuum heat insulating material 10, the peripheral portion of the pair of sheet-shaped outer packaging materials 12 in which the heat-sealing layers 13 are arranged facing each other is heat-sealed to form a bag-shaped outer packaging material 12, and the bag-shaped outer packaging is obtained. The material 12 seals the core material 11.

Here, the vacuum state does not only mean that the vacuum is completely vacuum, but also means that the pressure is sufficiently reduced as compared with the atmospheric pressure. Specifically, the vacuum state refers to, for example, a state of 1000 Pa or less, preferably a state of 100 Pa or less, and more preferably a state of 10 Pa or less.

(Change in thermal conductivity over time)
In the vacuum heat insulating material 10 having a plate shape, the change with time of the thermal conductivity between the front surface and the back surface satisfies the following formula (1).

In the formula (1), T ₁ is the minimum value of the thermal conductivity. T ₂ is the maximum value between the initial value and the minimum value of the thermal conductivity.

The initial value of the thermal conductivity means a measured value 7 days after the vacuum heat insulating material 10 is manufactured (usually, the core material 11 is sealed with the outer packaging material 12). The thermal conductivity measurement period is from 7 days to 147 days after the vacuum heat insulating material 10 is manufactured. This measurement can be performed under the conditions described in the examples. If no minimum value is observed during the measurement period, the minimum value (T ₁ ) shall be the minimum value during the measurement period.

In the vacuum heat insulating material 10, the minimum value of the thermal conductivity with respect to the maximum value (usually the initial value) between the initial value and the minimum value of the thermal conductivity is 0.8 or more. That is, in the vacuum heat insulating material 10, the thermal conductivity at the initial stage is relatively reduced, and the outer packaging material 12 has the heat-sealing layer 13 including the vinyl alcohol-based resin layer. , High heat insulation can be exhibited from the initial stage. Further, in the vacuum heat insulating material 10, since the outer packaging material 12 has a heat-sealing layer 13 containing a vinyl alcohol-based resin and a gas barrier layer 14, high heat insulating properties can be maintained for a long period of time. The lower limit of the minimum value of thermal conductivity with respect to the maximum value between the initial value and the minimum value of thermal conductivity is preferably 0.85, more preferably 0.9.

The upper limit of the initial value of the thermal conductivity of the vacuum heat insulating material is preferably 0.004 W / (m · K), more preferably 0.003 W / (m · K). On the other hand, the lower limit thereof is, for example, 0.0015 W / (m · K) and may be 0.002 W / (m · K).

The initial value of the thermal conductivity of the vacuum heat insulating material 10 has a great influence on the outgas such as moisture from the heat fusion layer 13. Therefore, as will be described later, heat conduction is achieved by removing water or the like from the heat-sealing layer 13 before or during sealing, or by using an adsorbent 16 that absorbs outgas from the heat-sealing layer 13. The vacuum heat insulating material 10 whose rate changes with time satisfies the above formula (1) can be preferably obtained.

(Core material 11)
The core material 11 is usually formed of a material having a high porosity, such as fiber, powder, and foamed resin. By forming the core material 11 from such a material, the inside of the vacuum heat insulating material 10 can be put into a vacuum state. Further, the core material 11 is formed into a plate shape. The core material 11 may be a flexible elastic body or a rigid body.

Examples of the fibers include glass wool, glass fiber, rock wool, alumina fiber, silica fiber, silica alumina fiber, silicon carbide fiber, ceramic fiber and the like. Examples of the powder include silica, carbon black, pearlite and the like. Examples of the foamed resin include urethane foam, phenol foam, and styrene foam.

(External packaging material 12)
The outer packaging material 12 is a laminate having a heat-sealing layer 13, a gas barrier layer 14, and an outer layer 15 in this order from the inside. In the vacuum heat insulating material 10 of FIG. 1, the heat-sealing layers 13 in the peripheral portion of the pair of sheet-shaped outer packaging materials 12 are in a state of heat-sealing. An adhesive for adhering each layer is interposed between the layers of the heat-sealing layer 13, the gas barrier layer 14, and the outer layer 15.

The heat-sealing layer 13 is the innermost layer, that is, the innermost layer, and is a layer that is fused by heating and pressurizing. The heat-sealing layer 13 contains a vinyl alcohol-based resin. Since the heat-sealing layer 13 contains a vinyl alcohol-based resin having a high gas barrier property, it is possible to suppress the permeation of gas from the end face of the heat-sealing layer 13.

The vinyl alcohol-based resin refers to _{a polymer having a vinyl alcohol unit (-CH 2-} CHOH-) as a monomer unit, and may be a copolymer having a monomer unit other than the vinyl alcohol unit. As the vinyl alcohol-based resin, a copolymer containing an α-olefin unit having 4 or less carbon atoms is preferable, and a copolymer containing an ethylene unit, that is, an ethylene-vinyl alcohol copolymer (EVOH) is more preferable. By using such a copolymer, the heat-sealing property and the gas barrier property of the heat-sealing layer 13 itself can be improved.

The lower limit of the content of the vinyl alcohol-based resin in the heat-sealing layer 13 is, for example, 50% by mass, preferably 70% by mass, and more preferably 90% by mass. The heat-sealing layer 13 may contain components other than the vinyl alcohol-based resin. Examples of other components include various additives such as other resins, fillers, and metal salts.

The average thickness of the heat-sealing layer 13 is not particularly limited, but may be, for example, 5 μm as the lower limit and 200 μm as the upper limit. Sufficient heat-sealing properties can be exhibited by setting the average thickness of the heat-sealing layer 13 to be equal to or greater than the above lower limit. On the other hand, by setting the average thickness of the heat-sealing layer 13 to be equal to or less than the above upper limit, the permeation of gas from the end face of the heat-sealing layer 13 can be sufficiently suppressed.

The upper limit of the moisture content of the heat-sealing layer 13 (preferably the moisture content of the heat-sealing layer 13 immediately after sealing the core material 11) is preferably 2% by mass, more preferably 1% by mass, and 0.5. By mass% is even more preferable, 0.3% by mass is even more preferable, and 0.2% by mass is particularly preferable. By setting the moisture content of the heat-sealing layer 13 to the above upper limit or less, the volatilization of water from the heat-sealing layer 13 to the inside of the vacuum heat insulating material 10 can be suppressed, and the heat insulating property from the initial stage can be effectively enhanced. can. On the other hand, the lower limit of this water content is, for example, 0.01% by mass.

A commercially available vinyl alcohol-based resin film can be used for the heat-sealing layer 13. This film may be a non-stretched film or a stretched film.

(Gas barrier layer 14)
The gas barrier layer 14 is laminated on the outer surface side of the heat fusion layer 13. The gas barrier layer 14 allows the vacuum heat insulating material 10 to maintain a high degree of vacuum for a long period of time. Examples of the gas barrier layer include a layer of a metal foil or a thin-film vapor deposition film. The gas barrier layer 14 may be a single layer or a multi-layer. The gas barrier layer 14 may be formed of one metal foil or a vapor-deposited film, or may be formed of a plurality of (for example, two) metal foils or a vapor-deposited film, and may be formed of one or a plurality of metal foils. It may be formed from one or a plurality of thin-film vapor-deposited films. In addition, each metal foil or vapor-deposited film can be bonded in layers with, for example, a known adhesive or the like.

Examples of the metal foil include aluminum foil, stainless steel foil, iron foil and the like, but aluminum foil is preferable. The average thickness of the metal foil can be, for example, 1 μm or more and 100 μm or less.

The thin-film deposition film includes a resin layer and a thin-film deposition layer laminated on the resin layer. Examples of the resin forming the resin layer include vinyl alcohol-based resin, polyethylene terephthalate (PET), polyethylene naphthalate, polyamide, polyimide, nylon, polypropylene and the like. Among these, vinyl alcohol-based resins and PET are preferable. Further, EVOH is preferable as the vinyl alcohol-based resin forming the resin layer. As these resin layers, a known resin film that is stretched or unstretched can be used. Examples of the material for forming the vapor-deposited layer include aluminum, nickel, cobalt, copper, silver, zinc, silica, alumina, and a mixture thereof. The thin-film deposition layer may be laminated only on one surface side of the resin layer, or may be laminated on both sides. The average thickness of the vapor-deposited film can be, for example, 1 μm or more and 100 μm or less.

When the vapor-deposited film has a resin layer containing a vinyl alcohol-based resin, that is, the gas barrier layer 14 comprises a layer containing a vinyl alcohol-based resin and a vapor-deposited layer laminated on at least one surface side of the resin layer. When it is contained, outgas such as water present in the resin layer may affect the initial value of thermal conductivity. Therefore, in this case, as will be described in detail later, there is a great advantage in adopting the present invention that reduces the water content in the outer packaging material 12.

(Outer layer 15)
The outer layer 15 is laminated on the outer surface side of the gas barrier layer 14. The outer layer 15 can be, for example, a resin layer such as PET, polyethylene naphthalate, polyamide, polyimide, nylon, polyethylene, polypropylene or the like. As the resin layer as the outer layer 15, a known stretched or unstretched resin film can be used. The resin layer as the outer layer 15 may be a single layer or a multi-layer.

(Adsorbent 16)
The vacuum heat insulating material 10 further includes an adsorbent 16 sealed by the outer packaging material 12 together with the core material 11. The adsorbent 16 can adsorb outgas and the like from the heat-sealing layer 13 of the outer packaging material 12. As a result, it is possible to suppress a decrease in the degree of vacuum at the initial stage and improve the heat insulating property. It should be noted that this adsorbent also adsorbs the gas that invades from the outside and suppresses the decrease in the degree of vacuum. The location of the adsorbent 16 is not particularly limited, but it is preferably disposed between the core material 11 and the outer packaging material 12, or inside the core material 11.

The adsorbent 16 is not particularly limited, and for example, silica gel, zeolite, hydrotalcite, calcium oxide, magnesium oxide, activated carbon, activated alumina and the like can be used. These can be used alone or in admixture of two or more.

As the adsorbent 16, an alloy-based adsorbent can also be used. As the alloy-based adsorbent, for example, an adsorbent containing a barium-lithium alloy can be used, and a mixture of a transition metal oxide and metallic palladium, a water-absorbing substance, or the like may be further contained.

<Manufacturing method of vacuum heat insulating material>
The vacuum heat insulating material 10 can be obtained by a known method such as sealing the core material 11 together with the adsorbent 16 with the outer packaging material 12, but the dissolved material such as water in the heat-sealing layer 13 is sealed before sealing. It can be preferably obtained by the following production method, which is removed at the time or after sealing.

That is, the method for producing the vacuum heat insulating material according to the embodiment of the present invention is as follows.
A step (A) of removing the volatile components contained in the outer packaging material 12 and a step (B) of using the outer packaging material 12 to seal the object to be sealed including the core material 11 by heat fusion.
To be equipped.

According to the manufacturing method, by having the step (A) for removing the volatile component contained in the outer packaging material 12, the generation of outgas from the heat-sealing layer 13 of the outer packaging material 12 after sealing is suppressed. Therefore, according to the manufacturing method, it is possible to manufacture the vacuum heat insulating material 10 which has high heat insulating properties from the initial stage and can maintain the heat insulating properties for a long period of time.

The manufacturing method includes a manufacturing method (I) in which the removing step (A) and the sealing step (B) are performed in this order, and a manufacturing method (II) in which the removing step (A) and the sealing step (B) are simultaneously performed. , And a manufacturing method (III) in which the sealing step (B) and the removing step (A) are performed in this order.

(Manufacturing method (I))
The manufacturing method (I) is a method in which the removing step (A) and the sealing step (B) are performed in this order. In this way, by separately removing the volatile components contained in the outer packaging material 12 before sealing, the volatile components in the heat-sealing layer 13 can be sufficiently reduced. Hereinafter, the removing step in the manufacturing method (I) will be referred to as a removing step (AI), and the sealing step will be referred to as a sealing step (BI).

The removal step (AI) is preferably performed immediately before the sealing step (BI). This removal step (AI) is intended to remove volatile components contained in the heat-sealing layer 13. Examples of this volatile component include organic substances, oxygen, nitrogen and the like in addition to water.

The method for removing the volatile components in the removal step (AI) is not particularly limited, but it can be carried out by heating, vacuum drying, or a combination thereof. Among these, the combined use of heating and vacuum drying is preferable from the viewpoint of the ability to remove volatile components and the efficiency of removal. When it is carried out by heating, it is preferably carried out by hot air drying. The lower limit of the heating temperature at this time is, for example, 80 ° C., preferably 100 ° C. By setting the heating temperature to the above lower limit or higher, the efficiency of removing volatile components can be improved. On the other hand, the upper limit is, for example, 150 ° C. If the heating temperature exceeds the above upper limit, the heat fusion layer 13 may melt and undesired fusion may occur. The processing time (drying time) of the removal step (A-1) can be, for example, 30 minutes or more and 10 hours or less. This drying can be performed by a known vacuum dryer, hot air dryer, or the like.

In this removal step (AI), the volatile component may be removed from the sheet-shaped outer packaging material 12, or the volatile component may be removed from the bag-shaped outer packaging material 12. The bag-shaped outer packaging material 12 can be obtained by heat-sealing, leaving a part of the peripheral portion of the pair of sheet-shaped outer packaging materials 12 in which the heat-sealing layers 13 are overlapped with each other. Further, the outer packaging material 12 and the core material 11 can be dried at the same time. For example, the core material 11 can be inserted into the bag-shaped outer packaging material 12 and the volatile matter can be removed in the opened state.

The sealing step (BI) is a step of sealing the material to be sealed including the core material 11 by heat fusion using the outer packaging material 12 that has undergone the removal step (AI). In this step (BI), for example, the core material 11 and the adsorbent 16 are inserted into the bag-shaped outer packaging material 12, the pressure is reduced (deaerated) to a predetermined pressure, and then the opening of the bag-shaped outer packaging material 12 is opened. Can be done by heat fusion. The pressure at this time refers to a state of 1000 Pa or less, preferably a state of 100 Pa or less, and more preferably a state of 10 Pa or less. Further, it is preferable that the core material 11 is also dried to sufficiently remove water and the like before being inserted into the outer packaging material 12. This step (BI) can be performed using a known vacuum heat insulating material manufacturing apparatus.

(Manufacturing method (II))
In the production method (II), the sealing step (B) is performed while heating the outer packaging material 12 and the object to be sealed (core material 11 and the adsorbent 16) to 40 ° C. or higher, thereby performing the removing step (B). This is a method in which A) and the sealing step (B) are performed at the same time. By simultaneously performing the removal step (A) and the sealing step (B) in this way, the removal of the volatile components in the heat-sealing layer 13 and the sealing by the outer packaging material 12 from which the volatile components have been removed are efficient. Can be done Hereinafter, in this production method (II), a step of sealing while removing volatile components is referred to as a sealing step (B-II).

In the sealing step (B-II), the manufacturing method (I) is performed except that the outer packaging material 12 and the object to be sealed (core material 11 and adsorbent 16) are sealed while being heated to 40 ° C. or higher. It is the same as the step (BI) in. By this heating, the volatile components in the heat-sealing layer 13 of the outer packaging material 12 can be sufficiently removed. The lower limit of this heating temperature is 40 ° C., but 70 ° C. is preferable, and 90 ° C. is more preferable. On the other hand, the upper limit of the heating temperature is lower than the melting point of the material forming the outer packaging material 12, for example, 150 ° C. By heating below the melting point of the material forming the outer packaging material 12, unwanted deformation and fusion can be prevented.

The heating method in the sealing step (B-II) is not particularly limited, but a method of setting the atmospheric temperature in the step (B-II) to 40 ° C. or higher, or a core material 11 or the like is inserted at the time of sealing. This can be done by a method of pressing the front and / or back of the outer packaging material 12 with a hot plate of 40 ° C. or higher.

(Manufacturing method (III))
In the production method (III), the vacuum heat insulating material 10 obtained after the sealing step (B) is heated to promote the generation of outgas from the heat-sealing layer 13, and the outgas is adsorbed by the adsorbent 16. This is a method in which the removal step (A) is performed after the sealing step (B). Hereinafter, the heating-adsorption step in this manufacturing method (III) will be referred to as a removal step (A-III).

The lower limit of the heating temperature in the removal step (A-III) is 40 ° C, preferably 70 ° C, more preferably 90 ° C. On the other hand, the upper limit of the heating temperature is lower than the melting point of the material forming the outer packaging material 12, for example, 150 ° C.

When the removal step (A-III) is performed, the time when the removal step (A-III) is completed is the time when the vacuum heat insulating material 10 is manufactured. When the removal step (A-III) is completed, for example, the heating may be completed. The time required for the removal step (A-III) can be, for example, 48 hours.

(Other manufacturing methods)
The manufacturing method may be a method other than the above-mentioned manufacturing methods (I) to (III). As another production method, for example, the removal step (AI) of the production method (I) and the sealing step (B-II) of the production method (II) are combined to remove volatile components before sealing. In addition, a method of sealing while removing volatile components can be mentioned. While heating the outer packaging material 12 and the material to be sealed (core material 11 and adsorbent 16) to 40 ° C. or higher, the step of removing the volatile components contained in the outer packaging material 12 (AI), and the heating of the outer packaging material 12 and the material to be sealed (core material 11 and adsorbent 16) According to the manufacturing method including the step (B-II) of sealing the object to be sealed by heat fusion, the thermal conductivity at the initial stage is obtained by removing the volatile components both before and during the sealing. It is possible to obtain the vacuum heat insulating material 10 in which the amount of heat is sufficiently reduced.

<Outer packaging material for vacuum heat insulating material>
The outer packaging material for the vacuum heat insulating material according to the embodiment of the present invention includes a heat-sealing layer containing a vinyl alcohol-based resin and arranged inside, and a gas barrier layer laminated on the outer surface side of the heat-sealing layer. The moisture content of the heat-sealed layer is 2% by mass or less. Here, the inside and outside of the outer packaging material for the vacuum heat insulating material mean the inside and the outside when used as the outer packaging material of the vacuum heat insulating material.

The outer packaging material for the vacuum heat insulating material is the same as the outer packaging material 12 included in the vacuum heat insulating material 10 of FIG. The outer packaging material for the vacuum heat insulating material may be in the form of a sheet having a layered structure, or may be processed into a bag shape or the like. The outer packaging material for the vacuum heat insulating material can be obtained, for example, by laminating the film forming each layer by a known method and then drying it.

According to the outer packaging material for the vacuum heat insulating material, the generation of outgas from the heat-sealed layer is suppressed, and a vacuum heat insulating material having high heat insulating properties from the initial stage and capable of maintaining the heat insulating properties for a long period of time is obtained. be able to.

<Other Embodiments>
The vacuum heat insulating material of the present invention, the method for producing the vacuum heat insulating material, and the outer packaging material for the vacuum heat insulating material are not limited to the above-described embodiments. For example, the outer packaging material of the vacuum heat insulating material may have only a heat-sealing layer and a gas barrier layer and may not have an outer layer. In the vacuum heat insulating material, the adsorbent may not be sealed. Further, the above-mentioned production methods (I) to (III) can also be used for producing a vacuum heat insulating material whose change with time of thermal conductivity does not satisfy or does not satisfy the above formula (1).

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In addition, each measurement in Example and Comparative Example was carried out by the following method.

(1) Thermal conductivity of the vacuum heat insulating material After storing the obtained vacuum heat insulating material at 20 ° C. for 7 days, one of the vacuum heat insulating materials was used using a thermal conductivity measuring device (“HC-074 type” of Eiko Seiki Co., Ltd.). The thermal conductivity of the vacuum heat insulating material was measured by setting the temperature on the surface side of the vacuum heat insulating material to 38 ° C. and the temperature on the other surface side to 10 ° C. After 7 days, the operation of storing the vacuum heat insulating material in an environment of 100 ° C. for 9 hours and then storing it at 20 ° C. for 15 hours was repeated every day. The measurement was performed 7, 37, 82, 117 and 147 days after the vacuum heat insulating material was prepared.

(2) Moisture content of the heat-sealing layer The vacuum heat insulating material immediately after being sealed was promptly opened, and the outer packaging material (outer bag) was cut off. Using a Karl Fischer trace moisture measuring device (Mitsubishi Kasei Corp.'s "CA-06 type"), the amount of moisture generated when the cut outer packaging material was heated at 205 ° C. was measured. Further, by the same method, the amount of water in the laminated body having the structure obtained by removing the heat-sealing layer from the outer packaging material was also measured. This laminated body was fixed to the outer surface of the outer packaging material during the production of the vacuum heat insulating material so that the dried state would be the same (see Example 10 below). The moisture content of the heat-sealing layer was calculated based on the difference between the moisture content of the outer packaging material and the moisture content of the laminate having the structure excluding the heat-sealing layer.

The films and the like used in Examples and Comparative Examples are as follows.
PET film: Biaxially stretched polyester film with an average thickness of 12 μm (Toray Industries, Inc.'s "Lumirror (registered trademark)")
OPA film: Stretched polyamide film with an average thickness of 15 μm (Unitika's "Emblem (registered trademark) ON-BC")
OPP film: Biaxially stretched polypropylene film with an average thickness of 30 μm (Toyobo's "Pilen film-OT (registered trademark)")
VM-PET film: Aluminum-deposited biaxially stretched polyester film with an average thickness of 12 μm (Toray Industries, Inc. “VM-PET1510”)
VM-EVOH film: Aluminum-deposited biaxially stretched ethylene-vinyl alcohol copolymer film with an average thickness of 15 μm (Kuraray's "EVAL (registered trademark) VM-XL")
Aluminum foil: Aluminum foil EVOH film with an average thickness of 6.5 μm: Unstretched ethylene-vinyl alcohol copolymer film with an average thickness of 30 μm (Kuraray's "EVAL (registered trademark) EF-E")
PE film: Polyethylene film with an average thickness of 50 μm (“A-1” from Tamapoli)
Alloy: "Combo Getter (registered trademark)" by Saes Getters SPA

[Example 1]
An outer packaging material having each layer of "PET / OPA / aluminum / EVOH" was prepared by the following method. PET and OAP serve as an outer layer, aluminum serves as a gas barrier layer, and EVOH serves as a heat-sealing layer.

The PET film, OPA film, aluminum foil and EVOH film were prepared. Of these, a two-component adhesive (Mitsui Kagaku Co., Ltd. "A-520" and "A-50") is applied to each of one side of the PET film, OPA film, and EVOH film, and the PET layer / adhesive layer is applied. An outer packaging material was obtained by laminating a PET film, an OPA film, an aluminum foil and an EVOH film so as to have a composition of / OPA layer / adhesive layer / aluminum layer / adhesive layer / EVOH film.

Two pieces of the obtained outer packaging material were cut into a size of 68 cm × 75 cm. The two cut outer packaging materials are overlapped so that the EVOH layers are on the inner surface, and heat-sealed on three sides with a width of 10 mm to obtain an outer bag which is a three-sided bag having an opening on the short side. rice field.

The obtained outer bag (outer packaging material) was placed in a hot air dryer (“PHH-400 type” manufactured by Tabai ESPEC) having an in-machine temperature of 105 ° C., and dried for 3 hours as pre-drying.

A plate-shaped heat-insulating core material made of glass fiber with a flat surface size of 60 cm x 60 cm x 1.5 cm was placed in the machine of a hot air dryer (manufactured by Tanaka Chemical Machinery Works Co., Ltd.) with an in-machine temperature of 160 ° C. It was dried for 1 hour.

After drying for a predetermined time, the outer bag and the core material were taken out from a hot air dryer. After that, promptly insert the core material and the small bag containing calcium oxide as an adsorbent through the opening of the outer bag, and use the vacuum heat insulating panel manufacturing device ("KT500-RD type" of NPC Co., Ltd.). The vacuum heat insulating material of Example 1 was obtained by heat-sealing the opening. The temperature of the hot plate installed in the vacuum chamber was set to 100 ° C., and the outer bag was sealed with an internal pressure of 1.2 Pa. Further, the hot plate is configured to press the surface of the outer bag into which the core material and the adsorbent are inserted, whereby the outer bag and the object to be sealed (core material and the adsorbent) are formed on the hot plate. Will be heated to the temperature of.

[Examples 2-9, 12-16, Comparative Examples 1-5, 7]
Example 2 in the same manner as in Example 1 except that the layer structure of the outer packaging material, the presence or absence of pre-drying, the type and presence or absence of the adsorbent, and the hot plate temperature at the time of sealing are as shown in Table 1. The vacuum heat insulating materials of ~ 9, 12 ~ 16 and Comparative Examples 1 to 5 and 7 were obtained.

[Example 10]
An outer packaging material having each layer of "OPP / aluminum / EVOH" and a laminate having each layer of "OPP / aluminum" were prepared by the following method. In the outer packaging material, OPP is the outer layer, aluminum is the gas barrier layer, and EVOH is the heat-sealing layer.

The above OPP film, aluminum foil and EVOH film were prepared. Of these, a two-component adhesive (Mitsui Kagaku Co., Ltd. "A-520" and "A-50") is applied to each of one side of the OPP film and EVOH film, and the OPP layer / adhesive layer / aluminum layer is applied. An outer packaging material was obtained by laminating an OPP film, an aluminum foil, and an EVOH film so as to have a structure of / adhesive layer / EVOH layer. In addition, a two-component adhesive (Mitsui Chemicals Co., Ltd. "A-520" and "A-50") is separately applied to each of the OPP film and one side of the aluminum foil, and the OPP layer / adhesive layer / aluminum layer / A laminated body was obtained by laminating an OPP film and an aluminum foil so as to form an adhesive layer.

Two pieces of the obtained outer packaging material were cut into a size of 68 cm × 75 cm. The two cut outer packaging materials are overlapped so that the EVOH layers are on the inner surface, and heat-sealed on three sides with a width of 10 mm to obtain an outer bag which is a three-sided bag having an opening on the short side. rice field. Further, the obtained laminated body was cut into a size of 20 cm × 20 cm. The cut laminated body was placed on the outer surface of the outer bag so that the OPP layer was in contact with the outer bag, and the four corners of the laminated body were fixed with adhesive tape.

An outer bag to which the above-mentioned laminate was attached was placed in a hot air dryer (“PHH-400 type” manufactured by Tabai ESPEC) having an in-machine temperature of 105 ° C., and dried for 3 hours as pre-drying.

A plate-shaped heat-insulating core material made of glass fiber with a flat surface size of 60 cm x 60 cm x 1.5 cm was placed in the machine of a hot air dryer (manufactured by Tanaka Chemical Machinery Works Co., Ltd.) with an in-machine temperature of 160 ° C. It was dried for 1 hour.

After drying for a predetermined time, the outer bag and the core material to which the laminated body was attached were taken out from the hot air dryer. After that, promptly insert the core material and the small bag containing calcium oxide as an adsorbent from the opening of the outer bag, and open it using the vacuum heat insulating panel manufacturing device (NPC's "KT500-RD type"). The vacuum heat insulating material of Example 10 was obtained by heat-sealing the portion. The temperature of the hot plate installed in the vacuum chamber was set to 100 ° C., and the outer bag was sealed with an internal pressure of 1.2 Pa. The laminated body attached to the outer surface of the outer bag was used as a reference material when measuring the moisture content of the heat-sealed layer (described later).

[Example 11, Comparative Example 6]
The same as in Example 10 except that the layer structure of the outer packaging material (outer bag), the presence or absence of pre-drying, the type and presence or absence of the adsorbent, and the hot plate temperature at the time of sealing are as shown in Table 1. , Each vacuum heat insulating material of Example 11 and Comparative Example 6 was obtained.

[evaluation]
The thermal conductivity of each of the obtained vacuum heat insulating materials was measured by the method (1) above. The measurement results are shown in Table 1. Further, for the vacuum heat insulating materials of Examples 10 and 11 and Comparative Example 6, the moisture content of the heat-sealed layer was measured by the method (2) above using a laminated body having a structure without a heat-sealed layer. bottom. The measurement results are shown in Table 1.

In Table 1, each layer of the outer packaging material has a laminated structure in the order shown in the table, with the outer layer at the left end being the outermost layer and the heat-sealing layer being the innermost layer. Further, "-" in the "outer layer / gas barrier layer" column indicates that the layer is not provided, and "-" in the "adsorbent" column indicates that no adsorbent is used. A "-" in the "heat-fused layer moisture content" column indicates that the measurement has not been performed.

As shown in Table 2, each vacuum heat insulating material of Examples 1 to 16 has a maximum value (T ₂ : initial value) between the initial value of thermal conductivity (conductivity after 7 days) and the minimum value. The ratio (T ₁ / T ₂ ) of the minimum value (T ₁ ) of the thermal conductivity to) is 0.8 or more and 1 or less. Each of these vacuum heat insulating materials has a low initial value of thermal conductivity of 0.0030 W / (m · K) or less. Further, it can be seen that each of these vacuum heat insulating materials has a thermal conductivity after 147 days of less than or equal to the thermal conductivity (initial value) after 7 days, and excellent heat insulating properties are maintained for a long period of time.

On the other hand, the vacuum heat insulating materials of Comparative Examples 1, 3, 6 and 7 _{having a ratio (T 1} / T _{2) of less than 0.8 have low heat insulating properties at the initial stage.} Further, the vacuum heat insulating materials of Comparative Examples 2, 4 and 5 in which the heat-sealing layer is formed of polyethylene have low thermal conductivity at the initial stage, but the thermal conductivity after 147 days is the thermal conductivity after 7 days ( It is significantly (15% or more) higher than the initial value), and it can be seen that the heat insulating performance is inferior.

The vacuum heat insulating material of the present invention is a heat insulating material for home appliances such as refrigerators, hot water supply facilities, and rice cookers; a residential heat insulating material used for walls, ceilings, attics, floors, etc .; vehicle roofing materials; automatic sales. It can be used for heat insulating panels of machines and the like.

10 Vacuum heat insulating material 11 Core material 12 Outer packaging material 13 Heat fusion layer 14 Gas barrier layer 15 Outer layer 16 Adsorbent

Claims (7)

A plate-shaped vacuum heat insulating material provided with a core material and an outer packaging material that seals the core material in a vacuum state.
The outer packaging material has a heat-sealing layer containing a vinyl alcohol-based resin and arranged inside, and a gas barrier layer laminated on the outer surface side of the heat-sealing layer.
Aging of the thermal conductivity between the surface and the back surface meets the following formula (1),
The moisture content of the heat-sealed layer is 2% by mass or less,
A vacuum heat insulating material in which the vinyl alcohol-based resin is an ethylene-vinyl alcohol copolymer.

(In the formula (1), T ₁ is the minimum value of the _{thermal conductivity. T 2} is the maximum value between the initial value and the minimum value of the thermal conductivity.) The vacuum heat insulating material according to claim 1, further comprising an adsorbent sealed in the outer packaging material. The vacuum heat insulating material according to claim 1 or 2 , wherein the gas barrier layer includes a resin layer containing a vinyl alcohol-based resin and a vapor-deposited layer laminated on at least one surface side of the resin layer. The method for manufacturing a vacuum heat insulating material according to any one of claims 1 to 3.
A method for producing a vacuum heat insulating material, comprising a step of removing volatile components contained in the outer packaging material and a step of using the outer packaging material to seal an object to be sealed containing the core material by heat fusion. The method for manufacturing a vacuum heat insulating material according to claim 4 , wherein the removing step and the sealing step are performed in this order. By performing the sealing step while heating the outer packaging material and the object to be sealed to 40 ° C. or higher,
The method for manufacturing a vacuum heat insulating material according to claim 4 , wherein the removing step and the sealing step are performed at the same time. It has a heat-sealing layer containing a vinyl alcohol-based resin and arranged inside, and a gas barrier layer laminated on the outer surface side of the heat-sealing layer.
Moisture content of the heat fusion layer is Ri der 2 wt% or less,
The vinyl alcohol-based resin is an ethylene - vinyl alcohol copolymer der Ru vacuum heat insulating material for outer material.

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