JP4772887B2 - Core material for vacuum heat insulating material, vacuum heat insulating material, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a vacuum heat insulating material core, a vacuum heat insulating material, and a manufacturing method thereof.

  Conventionally, heat insulating materials having various structures and performances have been used in refrigerators, cold boxes, and warm boxes used for heating, cooling, and warming various foods. Among heat insulating materials, vacuum heat insulating materials are excellent in heat insulating performance, and are widely used in devices such as household refrigerators that require heat insulation. A vacuum heat insulating material is generally obtained by filling a core material made of an inorganic material into an outer packaging material, sealing the outer packaging material, and maintaining the inside of the outer packaging material in a reduced pressure state. The core material of such a vacuum heat insulating material is formed using the glass wool which consists of the glass fiber manufactured by the flame method or the centrifugation method among inorganic materials.

  For example, the vacuum heat insulating material described in JP-A-2005-265038 (Patent Document 1) uses, as a core material, a laminate of a plurality of inorganic fiber sheets obtained by wet-making glass wool made of glass fibers as inorganic fibers. The shot content rate with a particle diameter of 30 μm or more in the inorganic fiber is 0.1 mass% or less, the average fiber diameter in the inorganic fiber is 0.2 to 6 μm, and the inorganic fiber is horizontal to the sheet surface Arranged in the direction.

Moreover, in the vacuum heat insulating material described in Japanese Patent Application Laid-Open No. 2006-17169 (Patent Document 2), a core material made of glass wool made of glass fiber as an inorganic fiber laminated material is sealed under reduced pressure in a jacket material. In addition, the density of the core material in the vacuum heat insulating material is 200 to 270 kg / m ³ , and the core material after opening the outer cover material contains 75% or more of glass fibers having a fiber length of 100 μm or more.

JP 2005-265038 A JP 2006-17169 A

  FIG. 8 is a plan view schematically showing a distribution state of glass fibers in glass wool that has been conventionally used as a core material of a vacuum heat insulating material. FIG. 9 is a planar electron micrograph (magnification 100 times) showing a distribution state before compression of glass fibers in glass wool, which has been conventionally used as a core material of a vacuum heat insulating material, and FIG. 10 shows a similar distribution state. It is an electron micrograph (magnification 100 times) of a section.

  As shown in FIG. 8, in the glass wool 500, it can be seen that a large number of glass fibers 510 having various fiber lengths extend in various directions and are randomly distributed. Further, as shown in FIGS. 8 and 9, in glass wool manufactured by a flame method or a centrifugal method, a short fiber having a fiber length of 1 mm or less or a fine fiber having a fiber diameter of 1 μm or less with respect to the main fiber. It is in a state in which various fibers are mixed. Such short fibers and fine fibers are filled between the main fibers or entangled between the main fibers, and heat conduction occurs between the fibers, along the thickness direction of the core material. It is considered that the heat insulation performance is lowered by causing heat conduction. Moreover, in such glass wool, it turns out that the main fiber also includes many fibers that are bent or twisted.

  Since glass wool is thus configured, as described in JP-A-2005-265038 (Patent Document 1), when forming a sheet by wet papermaking, the glass fiber is oriented in a horizontal direction with respect to the sheet surface. It is very difficult to align most of the glass fibers even if they are arranged in the same manner.

Further, as described in Japanese Patent Application Laid-Open No. 2006-17169 (Patent Document 2), a core material containing 75% or more of glass fibers having a fiber length of 100 μm or more has a core material density of 200 to 270 kg / m ^3. Even if the glass wool is pressed so that it is difficult to align most glass fibers.

  Therefore, in the core material of the vacuum heat insulating material described in any of the above-mentioned publications, it is difficult to prevent a decrease in heat insulating performance due to the occurrence of heat conduction between fibers. For this reason, the heat conductivity of the obtained vacuum heat insulating material is about 2 mW / m · K, and the improvement of the heat insulating performance of the vacuum heat insulating material is limited by the conventional improvement method.

  Accordingly, an object of the present invention is to provide a vacuum insulation core material that can exceed the improvement limit of conventional heat insulation performance, has excellent heat insulation performance, and can be industrially mass-produced, and its core material. It is providing the vacuum heat insulating material provided with these, and these manufacturing methods.

  As a result of intensive studies to solve the problems of the core material that has been used in conventional vacuum heat insulating materials, the present inventors have produced a fiber constituting the core material for vacuum heat insulating material by a continuous filament method. It has been found that the above object can be achieved by including at least a plurality of inorganic fibers formed. Here, the continuous filament method is a fiber manufacturing method in which molten filaments are continuously drawn down through a bushing nozzle, drawn, and fiberized to produce continuous filaments. Based on this knowledge, the core material for a vacuum heat insulating material according to the present invention has the following characteristics.

  The core material for a vacuum heat insulating material according to the present invention is a core material for a vacuum heat insulating material configured by laminating a plurality of nonwoven fabrics. The nonwoven fabric includes at least a plurality of inorganic fibers produced by a continuous filament method. In the nonwoven fabric, most of the plurality of inorganic fibers extend in a direction substantially parallel to the surface of the nonwoven fabric.

  According to the continuous filament method, a large number of fibers with extremely small variations in fiber diameter can be mass-produced. Moreover, the inorganic fiber manufactured by the continuous filament method has very high straightness of each fiber. For this reason, by cutting a large number of inorganic fibers produced by the continuous filament method into a substantially constant length, a large number of inorganic fibers having almost the same length with a very small variation in fiber diameter can be obtained. It can be obtained in a very high state.

Since the nonwoven fabric constituting the core material of the present invention includes at least a plurality of inorganic fibers produced by the continuous filament method, each inorganic fiber is formed into a nonwoven fabric when forming a nonwoven fabric using such a plurality of inorganic fibers. When trying to arrange in a direction parallel to the surface, a plurality of inorganic fibers can be easily aligned so that most of the inorganic fibers extend in a direction substantially parallel to the surface of the nonwoven fabric. At this time, most of the plurality of inorganic fibers extend in a direction substantially parallel to the surface of the nonwoven fabric, but are in close contact with each other and do not align with the parallel direction, and are in a random direction within the plane forming the surface of the nonwoven fabric. the to array to disperse facing. As a result, the presence of inorganic fibers filling between the plurality of inorganic fibers constituting the core material can be minimized, and the presence of inorganic fibers entangled between the plurality of inorganic fibers can be minimized. Therefore, it is possible to prevent heat conduction between the inorganic fibers. For this reason, by preventing the occurrence of heat conduction along the thickness direction of the core material, the thermal conductivity of the core material can be reduced, and it becomes possible to exceed the improvement limit of the conventional heat insulation performance, The core material for vacuum heat insulating materials which has the heat insulation performance can be obtained.

  By the way, the non-woven fabric made of, for example, glass fibers used as the core material for a vacuum heat insulating material configured as described above has no bonding force between fibers. For this reason, it is necessary to use a binder in the paper making process in order to prevent the glass fibers from falling off in the manufacturing process of the nonwoven fabric and to prevent the mold from being lost in the subsequent processing process.

  The liquid binder tends to gather around a portion where a plurality of glass fibers intersect due to surface tension. For this reason, even if the adjacent glass fibers are in contact with each other at a point, the binder may cover the contact portion. As a result, heat conduction through the binder is expected to occur, so a liquid binder is considered to be undesirable. Therefore, it is conceivable to use a granular or fibrous binder.

  When a granular binder or a fibrous binder is used as a binder, and these binders are dispersed and mixed in a glass chopped strand to produce a nonwoven fabric by a wet papermaking method, most of the binders are separated by a binder between the fibers other than the fiber contact point. It can be considered to bridge. Such bridging is very delicate and is expected to have very little possibility of generating heat conduction. However, in order to increase the heat insulation performance to the limit, it is necessary to suppress heat conduction by such a binder.

  Therefore, in order to prevent slight heat conduction due to the bridging of the binder and increase the heat insulation performance to the limit, the heat insulation performance is further improved by removing or reducing the binder in the core material by a method such as thermal decomposition before vacuum sealing. It is conceivable to improve.

  That is, before encapsulating the core material in the outer packaging material, only the binder is removed by pyrolysis by processing at a temperature higher than the thermal decomposition temperature of the binder and lower than the melting point of the glass fiber used as an example of the inorganic fiber. It is possible to do. In addition, when a water-soluble resin binder such as polyvinyl alcohol (PVA) is used as the binder, it may be possible to remove or reduce the binder by washing with warm water or the like in addition to the above method.

  However, in order to remove the binder in the core material using the above method, a long heating step or washing step is required, and the core material after removing the binder is very weak, It takes time to enclose the outer packaging material. Therefore, although a vacuum heat insulating material having excellent heat insulating performance can be obtained, a new problem arises that it is difficult to industrially mass-produce with conventional vacuum heat insulating material manufacturing equipment.

  Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors include at least a plurality of fibers produced by the continuous filament method in the fibers constituting the vacuum insulation core material. It has been found that the above new problem can be solved by using a very small amount of a liquid binder as the binder in the vacuum heat insulating material core. Here, the liquid binder means one obtained by dissolving a binder component into a liquid state, or one obtained by emulsifying a binder component into a liquid state.

  When granular or fibrous binders are used, in order to suppress heat conduction by the binder component, if the binder component content in the nonwoven fabric is reduced to the limit, the binder component will be uniformly present in the nonwoven fabric, resulting in strength. Not only decreases, but also the fibers easily fall off on the surface of the nonwoven fabric, and a large amount of fibers dropped on the drying equipment in the nonwoven fabric manufacturing process adheres, causing problems such as difficulty in continuous production.

  On the other hand, when a liquid binder is used, even if the binder component content in the nonwoven fabric is extremely reduced, sufficient strength can be obtained for continuous production compared to the case where a granular or fibrous binder is used. It has been found by the present inventors that not only the heat insulation performance is excellent but also the heat insulation performance is excellent. The reason is estimated as follows.

  Liquid binders tend to move together with the binder when the moisture inside the nonwoven web evaporates during the heating and drying process when manufacturing the nonwoven fabric. appear.

  In addition, the liquid binder tends to gather around a portion where a plurality of fibers intersect due to surface tension. This is not preferable from the viewpoint of heat conduction, but is preferable from the viewpoint of strength. Therefore, when using a liquid binder, the binder concentrated on both surfaces of the non-woven fabric is reduced between the fibers even if the content of the binder component in the non-woven fabric is extremely reduced compared to when using a granular or fibrous binder. Are bonded relatively firmly, the overall strength is increased, and the strength required in the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process can be obtained.

  Furthermore, in the inside of the nonwoven fabric, the content of the binder component is further less than the surface of the nonwoven fabric, so that the heat conduction through the binder is very small.

  For these reasons, when a very small amount of liquid binder is used, the fibers near the surface of the nonwoven fabric are effectively bonded to each other. Therefore, the core material for vacuum heat insulating material of the present invention is industrially mass-produced. However, the amount of the binder can be extremely reduced inside the nonwoven fabric.

  When a granular or fibrous binder is used, a phenomenon that the binder moves in the nonwoven fabric in the heating and drying process unlike the liquid binder hardly occurs.

  Based on the above findings of the inventors, the vacuum heat insulating core material according to the present invention further includes the following characteristics.

The core material for a vacuum heat insulating material according to the present invention is a core material for a vacuum heat insulating material configured by laminating a plurality of nonwoven fabrics. The nonwoven fabric includes at least a plurality of inorganic fibers that are manufactured by a continuous filament method and have an average fiber diameter of 3 μm to 15 μm, an average fiber length of 3 mm to 15 mm, and extremely high straightness. In the non-woven fabric, in the two inorganic fiber layers laminated in the non-woven fabric, most of the plurality of inorganic fibers forming the upper layer and most of the plurality of inorganic fibers forming the lower layer are in a direction substantially parallel to the surface of the non-woven fabric. Extending and in close contact with each other, not aligned in a parallel direction, contact at points between adjacent fibers, and disperse in a random direction within each plane forming the upper and lower layers of the nonwoven fabric It is arranged to do. In the core material for a vacuum heat insulating material having such a configuration, a relatively large amount of liquid binder component is present in the surface layer portion of the nonwoven fabric, and a relatively small amount of liquid binder component is present inside the nonwoven fabric. Is further characterized.

  In the core for vacuum heat insulating material according to the present invention, the content of the binder component is preferably 0.1% by mass or more and 1.5% by mass or less with respect to the nonwoven fabric.

  If the content of the binder component is less than 0.1% by mass, the strength of the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process will be insufficient, and there will be a phenomenon that the fibers fall off or scatter on the surface of the nonwoven fabric. Since many occur, it becomes difficult to mass-produce industrially. In addition, when the content of the binder component exceeds 1.5% by mass, the heat insulating performance for the vacuum heat insulating material is equal to or less than that when a granular or fibrous binder is used, and the effect of using the liquid binder Cannot be obtained.

In vacuum insulation material for a core material of this invention, the average fiber diameter of the inorganic fibers is 3μm or 15μm or less, an average fiber length of the inorganic fibers Ru der least 15mm below 3 mm. Thereby , the thermal conductivity of a core material can be reduced most and the core material for vacuum heat insulating materials which has the most excellent heat insulation performance can be obtained.

  In the core material for vacuum heat insulating material of the present invention, the inorganic fiber is preferably a glass fiber. In this case, since the glass fiber has a smaller thermal conductivity than other inorganic fibers, for example, ceramic fibers, the heat insulating performance of the core material can be further improved by reducing the thermal conductivity of the material itself.

  The vacuum heat insulating material according to the present invention includes an outer packaging material and a core material accommodated in the outer packaging material. The outer packaging material is configured so that the inside can be kept in a reduced pressure state. The core material includes at least one vacuum heat insulating material core material having any of the above-described characteristics.

  The manufacturing method of the core material for vacuum heat insulating material according to the present invention includes a step of manufacturing a nonwoven fabric by a wet papermaking method using at least a plurality of inorganic fibers manufactured by a continuous filament method and a liquid binder, In the step, the method includes a step of extending most of the plurality of inorganic fibers in a direction substantially parallel to the surface of the manufactured nonwoven fabric, and further laminating the plurality of nonwoven fabrics.

  In the manufacturing method of the core material for vacuum heat insulating materials of this invention, the some inorganic fiber manufactured by the continuous filament method and a liquid binder are used at least. Using such a plurality of inorganic fibers, when producing a nonwoven fabric by wet papermaking, when trying to arrange each inorganic fiber in a direction parallel to the surface of the nonwoven fabric, most of the inorganic fibers are separated from the surface of the nonwoven fabric. A plurality of inorganic fibers can be easily aligned so as to extend in a substantially parallel direction.

At this time, most of the plurality of inorganic fibers extend in a direction substantially parallel to the surface of the nonwoven fabric, but are in close contact with each other and do not align with the parallel direction, and are in a random direction within the plane forming the surface of the nonwoven fabric. the to array distributed facing. Thereby, even if a plurality of non-woven fabrics are laminated to constitute the core material, the inorganic fibers filling between the plurality of inorganic fibers can be eliminated as much as possible, and entangled between the plurality of inorganic fibers. Since inorganic fibers can be eliminated as much as possible, it is possible to prevent heat conduction from occurring between inorganic fibers arranged in a direction substantially parallel to the surface of the nonwoven fabric.

  Moreover, in the drying process at the time of manufacturing a nonwoven fabric, as the water or solvent inside the nonwoven fabric evaporates, the liquid binder concentrates on both surface layers of the nonwoven fabric as it moves to the surface of the nonwoven fabric. Therefore, even if the binder contained in the nonwoven fabric is very small, the strength of the surface of the nonwoven fabric is increased, so that scattering of fibers on the surface of the nonwoven fabric is suppressed, and the strength required in the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process is Not only can it be obtained, but the binder content inside the nonwoven fabric is further reduced, so the heat conduction through the binder is also very small.

  For this reason, by preventing the heat conduction along the thickness direction of the core material as much as possible, the thermal conductivity of the core material can be reduced and the improvement limit of the conventional heat insulation performance can be exceeded. Thus, a core material for vacuum heat insulating material having excellent heat insulating performance can be obtained.

  In addition, even if the amount of binder contained in the nonwoven fabric is very small, it has the necessary strength in the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process, and there is little scattering and dropping of fibers from the surface of the nonwoven fabric. A core material for a vacuum heat insulating material can be obtained as an intermediate material that can be industrially mass-produced.

  The method for producing a vacuum heat insulating material according to the present invention includes a step of producing a nonwoven fabric by a wet papermaking method using at least a plurality of inorganic fibers produced by a continuous filament method and a liquid binder, A step of extending most of the plurality of inorganic fibers in a direction substantially parallel to the surface of the manufactured nonwoven fabric, and further laminating the plurality of nonwoven fabrics, and laminating the plurality of nonwoven fabrics inside the outer packaging material And a step of maintaining the inside of the outer packaging material in a reduced pressure state.

In the manufacturing method of the vacuum heat insulating material of this invention, the some inorganic fiber manufactured by the continuous filament method and a liquid binder are used at least. Using such a plurality of inorganic fibers, when producing a nonwoven fabric by wet papermaking, when trying to arrange each inorganic fiber in a direction parallel to the surface of the nonwoven fabric, most of the inorganic fibers are separated from the surface of the nonwoven fabric. A plurality of inorganic fibers can be easily aligned so as to extend in a substantially parallel direction. At this time, most of the plurality of inorganic fibers extend in a direction substantially parallel to the surface of the nonwoven fabric, but are in close contact with each other and do not align with the parallel direction, and are in a random direction within the plane forming the surface of the nonwoven fabric. the to array to disperse facing. As a result, even if a plurality of non-woven fabrics are laminated to constitute the core material, the presence of inorganic fibers filling between the plurality of inorganic fibers can be minimized, and the plurality of inorganic fibers are entangled. Since the presence of such inorganic fibers can be minimized, it is possible to prevent heat conduction from occurring between the inorganic fibers. And a vacuum heat insulating material can be manufactured by accommodating the laminated | stacked several nonwoven fabric in the inside of an outer packaging material, and keeping the inside of an outer packaging material in a pressure-reduced state.

  Furthermore, since the content of the binder component inside the nonwoven fabric is very small, the probability that the binder component adheres to a location where a plurality of inorganic fibers intersect is very small. Therefore, the heat conduction through the binder is negligible.

  In this way, heat conduction can be prevented from occurring along the thickness direction of the core material. For this reason, the thermal conductivity of a core material can be reduced. Thereby, it becomes possible to exceed the improvement limit of the conventional heat insulation performance, and the vacuum heat insulating material which has the outstanding heat insulation performance can be obtained.

  Furthermore, a small amount of binder effectively bonds the fibers on the surface of the nonwoven fabric. For this reason, strength required in the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process can be ensured in the nonwoven fabric. Thereby, it is possible to industrially mass-produce the vacuum heat insulating material.

  As described above, according to the present invention, by using at least a plurality of inorganic fibers produced by the continuous filament method and a liquid binder, the thermal conductivity of the core material can be reduced, and the conventional heat insulation performance can be reduced. It is possible to exceed the improvement limit, and it is possible to obtain a vacuum heat insulating material core material having excellent heat insulating performance and a vacuum heat insulating material provided with the core material.

  In addition, according to the present invention, a relatively large amount of binder component is present in the surface layer portion of the nonwoven fabric, and a relatively small amount of binder component is present inside the nonwoven fabric. In spite of the extremely low heat conduction by the binder, the necessary strength in the nonwoven fabric manufacturing process and the vacuum heat insulating material manufacturing process can be ensured in the nonwoven fabric. It becomes possible to produce.

As one embodiment of this invention, it is sectional drawing which shows typically the mode (B) of the inside of a vacuum heat insulating material when arrangement | positioning (A) of a core material and an outer packaging material, and the inside of an outer packaging material is pressure-reduced. . As one embodiment of this invention, it is a perspective view showing typically an arrangement (A) of a core material and an outer packaging material, and a state (B) inside a vacuum heat insulating material when the inside of the outer packaging material is decompressed. . It is a top view which shows typically the distribution state of the glass fiber which comprises the nonwoven fabric used for the core material of a vacuum heat insulating material as one embodiment of this invention. It is a scanning electron micrograph (magnification 100 times) which shows the distribution state before compression of the glass fiber which comprises the nonwoven fabric used for the core material of a vacuum heat insulating material as one embodiment of this invention. It is an electron micrograph (magnification 100 times) of the section which shows the distribution state before compression of the glass fiber which constitutes the nonwoven fabric used for the core material of a vacuum heat insulating material as one embodiment of the present invention. It is sectional drawing which shows typically the distribution state of the granular or fibrous binder in the nonwoven fabric used for the core material of a vacuum heat insulating material as one comparative form of this invention in the thickness direction of a nonwoven fabric. It is sectional drawing which shows typically the distribution state of the liquid binder in the nonwoven fabric used for the core material of a vacuum heat insulating material as one embodiment of this invention in the thickness direction of a nonwoven fabric. It is a top view which shows typically the distribution state of the glass fiber in the glass wool conventionally used as a core material of a vacuum heat insulating material. It is the electron microscope photograph (100 times magnification) of the plane which shows the distribution state before compression of the glass fiber in the glass wool conventionally used as a core material of a vacuum heat insulating material. It is the electron micrograph (100-times multiplication factor) of the cross section which shows the distribution state before compression of the glass fiber in the glass wool conventionally used as a core material of a vacuum heat insulating material.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a vacuum heat insulating material as one embodiment of the present invention. FIG. 1A shows a state before the inside of the outer packaging material is decompressed, and FIG. 1B shows a state when the inside of the outer packaging material is decompressed.

  As shown in FIG. 1, in the vacuum heat insulating material 1, a core material 100 is accommodated inside a gas barrier outer packaging material 200 formed in a bag shape.

  As shown to (A) of FIG. 1, the core material 100 is comprised by laminating | stacking the some nonwoven fabric 110. FIG. Each nonwoven fabric 110 is produced by a papermaking method using glass fibers which are examples of inorganic fibers and a small amount of binder.

As shown in FIG. 1B, when the inside of the outer packaging material 200 is depressurized, the core material 100 is compressed by the atmospheric pressure outside the outer packaging material 200, and the nonwoven fabrics 110 constituting the core material 100 are pressed against each other. Touch as you can. The density of the core material 100 in a state where the inside of the outer packaging material 200 is decompressed is included in the range of 100 to 400 kg / m ³ .

  A nonwoven fabric is comprised as mentioned above, a nonwoven fabric is laminated | stacked, a core material is comprised, a core material is arrange | positioned inside an outer packaging material, and it pressure-reduces, and comprises a vacuum heat insulating material.

  FIG. 2 schematically shows an arrangement (A) of the core material and the outer packaging material and an internal state (B) of the vacuum heat insulating material when the inside of the outer packaging material is decompressed as one embodiment of the present invention. It is a perspective view. Only a part of each nonwoven fabric, core material, and outer packaging material is shown.

  As shown in FIG. 2A, the core material 100 is formed by laminating a plurality of nonwoven fabrics 110. The core material 100 is covered with an outer packaging material 200. The outer packaging material 200 is gas barrier, is formed in a bag shape, and covers the entire core material 100.

  As shown in FIG. 2B, when the inside of the bag-shaped outer packaging material 200 is decompressed, the core material 100 is compressed. When the core material 100 is compressed, the nonwoven fabrics 110 come into contact with each other so as to be pressed against each other.

  As a result of intensive studies to improve the heat insulating performance of the vacuum heat insulating material 1 configured as described above, the present inventors have made a nonwoven fabric 110 configured to include inorganic fibers and a binder under specific conditions. By using as the core material 100, the heat insulation performance of the vacuum heat insulating material 1 was found to be significantly improved, and the present invention was achieved.

  Therefore, as shown in FIG. 1, the nonwoven fabric 110 constituting the core material 100 used in the vacuum heat insulating material 1 of the present invention is configured to include at least a plurality of inorganic fibers manufactured by a continuous filament method and a liquid binder. The

  Moreover, as shown in FIG. 1, the vacuum heat insulating material 1 of this invention is provided with the outer packaging material 200 and the core material 100 accommodated in the inside of the outer packaging material 200, and the outer packaging material 200 keeps an inside in a pressure-reduced state. The core material 100 is configured by laminating the nonwoven fabric 110. The nonwoven fabric 110 includes at least a plurality of inorganic fibers manufactured by a continuous filament method and a liquid binder.

  Examples of inorganic fibers include glass fibers, ceramic fibers, rock wool fibers, etc., but small diameter fibers necessary for constituting the core material of the present invention are distributed at a relatively low price due to mass production, In view of the low thermal conductivity of the material itself, glass fibers are preferably used as the inorganic fibers.

  In one embodiment of the present invention, a nonwoven fabric 110 manufactured by a wet papermaking method using glass fibers cut to a certain length is used as the core material 100 of the vacuum heat insulating material. Here, the glass fiber cut into a certain length is a glass fiber which is a filamentous continuous filament having a uniform thickness, formed by drawing molten glass from a number of nozzles by a continuous filament method. Thousands are bundled and wound into a strand, and the strand is cut to a predetermined length with a guillotine cutter or the like. What cut | disconnected the strand of glass fiber in this way is called glass chopped strand.

  The glass fiber thus obtained is a continuous filament cut into a predetermined length to obtain a predetermined length. Therefore, the glass fiber is extremely straight and highly rigid, and is a substantially uniform fiber. It has a diameter and a substantially circular cross section. That is, according to the continuous filament method, a large number of fibers with extremely small variation in fiber diameter can be produced. Moreover, the inorganic fiber manufactured by the continuous filament method has very high straightness of each fiber. For this reason, by cutting a large number of inorganic fibers produced by the continuous filament method into a substantially constant length, a large number of inorganic fibers having almost the same length with a very small variation in fiber diameter can be obtained. It can be obtained in a very high state.

For this reason, when the nonwoven fabric 110 is manufactured using this glass fiber by a wet papermaking method, the fibers extend in a direction substantially parallel to the surface of the nonwoven fabric 110, but in a random direction within the plane forming the surface of the nonwoven fabric 110. it is possible to obtain an array nonwoven 110 to disperse facing.

  FIG. 3 is a plan view schematically showing a distribution state of glass fibers constituting a nonwoven fabric used as a core material of a vacuum heat insulating material as one embodiment of the present invention. FIG. 3 shows a nonwoven fabric composed of two glass fiber layers. FIG. 4 is a plane electron micrograph (magnification 100 times) showing the distribution state before compression of the glass fibers constituting the nonwoven fabric used for the core material of the vacuum heat insulating material as one embodiment of the present invention, FIG. Is an electron micrograph (magnification 100 times) of a cross section showing a similar distribution state.

As shown in FIG. 3, the plurality of glass fibers 111 forming the upper layer and the glass fibers 112 forming the lower layer extend in a direction substantially parallel to the surface of the nonwoven fabric 110, but in close contact with each other in the parallel direction. not aligned, it is array to distribute randomly oriented in the plane forming the surface of the nonwoven fabric 110. Moreover, as shown in FIG. 4 and FIG. 5, it turns out that the straightness of each fiber is very high. Also, the majority of the fibers extend in a direction substantially parallel to the surface of the nonwoven fabric 110, but it can be understood that the array so as to disperse randomly oriented in the plane forming the surface of the nonwoven fabric 110.

Thus, since the nonwoven fabric 110 which comprises the core material 100 of this invention contains at least the glass fiber 111,112 which is an example of the some inorganic fiber manufactured by the continuous filament method, such a some glass fiber 111, 112, when forming the nonwoven fabric 110, if the glass fibers 111 and 112 are arranged in a direction parallel to the surface of the nonwoven fabric 110, most of the glass fibers 111 and 112 are almost the same as the surface of the nonwoven fabric 110. The plurality of glass fibers 111 and 112 can be easily aligned so as to extend in parallel directions. At this time, most of the plurality of glass fibers 111 and 112 extend in a direction substantially parallel to the surface of the nonwoven fabric 110, but do not align with each other in close contact with each other and form a surface of the nonwoven fabric 110. to array to distribute randomly oriented within. Thereby, the presence of glass fibers filling between the plurality of glass fibers 111 and 112 constituting the core material 100 can be eliminated as much as possible, and the glass fibers entangled between the plurality of glass fibers 111 and 112. Therefore, it is possible to prevent heat conduction from occurring between the glass fibers 111 and 112. For this reason, by preventing heat conduction from occurring along the thickness direction of the core material 100, the thermal conductivity of the core material 100 can be reduced, and the improvement limit of the conventional heat insulation performance can be exceeded. The vacuum heat insulating material core 100 having excellent heat insulating performance and the vacuum heat insulating material 1 including the core material 100 can be obtained.

  The composition of the glass fibers 111 and 112 is not particularly limited, and C glass, D glass, E glass, and the like can be used, but E glass (aluminoborosilicate glass) is preferably employed because of its availability.

  As described above, the inorganic fibers forming the nonwoven fabric 110 as the core material of the present invention are the glass fibers 111 and 112 obtained by cutting a continuous filament into a predetermined length and having a predetermined length. It has a circular cross section. Therefore, unless the plurality of glass fibers 111 and 112 dispersed in a random direction are aligned and aligned in parallel, the glass fibers 111 and 112 are in contact with each other at a point, so that heat conduction between the glass fibers 111 and 112 is performed. Is significantly suppressed.

  Although other materials may be used in place of the glass fibers 111 and 112, generally, inorganic fiber materials such as alumina chopped strands using alumina fibers are more expensive than the glass fibers 111 and 112, and are thermally conductive. Since the rate is high, it is not preferable.

  Organic materials generally have lower thermal conductivity than inorganic materials, but do not have rigidity. For this reason, an organic fiber material deform | transforms a fiber by the external pressure in the location where a fiber cross | intersects, and causes the reduction | decrease in the surface contact of fibers and a vacuum space ratio. As a result, a vacuum heat insulating material using an organic fiber as a core material is not preferable because of its high thermal conductivity.

  The nonwoven fabric 110 made of the glass fibers 111 and 112 used as the vacuum heat insulating material core 100 of the present invention does not have a bonding force between the fibers. For this reason, it is necessary to use a binder in the paper making process in order to prevent the glass fibers 111 and 112 from falling off in the manufacturing process of the non-woven fabric 110 and to prevent mold deformation in the subsequent processing process. However, since the nonwoven fabric 110 is finally included in the outer packaging material 200 as the core material 100 of the vacuum heat insulating material 1, it is necessary to minimize the amount of binder used.

  The binder used in the present invention is not a granular or fibrous binder but a liquid binder according to the following knowledge of the present inventors.

  When a liquid binder is used, even if the binder component content in the nonwoven fabric 110 is extremely reduced, sufficient strength can be obtained for continuous production as compared with the case where a granular or fibrous binder is used. It has been found by the present inventors that not only the heat insulation performance is excellent. The reason is estimated as follows.

  In the heating and drying process at the time of manufacturing the nonwoven fabric 110, the liquid binder moves together with the binder when the moisture in the nonwoven fabric 110 web evaporates. Therefore, the binder gathers on both surfaces of the nonwoven fabric 110, and the binder inside the nonwoven fabric 110 Tend to decrease.

  In addition, the liquid binder tends to gather around a portion where the plurality of glass fibers 111 and 112 intersect due to surface tension. This is not preferable from the viewpoint of heat conduction, but is preferable from the viewpoint of strength. Therefore, when the liquid binder is used, the binder concentrated on both surfaces of the nonwoven fabric 110 is reduced even if the content of the binder component in the nonwoven fabric 110 is extremely reduced as compared with the case where a granular or fibrous binder is used. Since the glass fibers 111 and 112 are bonded relatively firmly, the overall strength is increased, and the strength required in the manufacturing process of the nonwoven fabric 110 and the manufacturing process of the vacuum heat insulating material 1 can be obtained.

  Furthermore, since the content of the binder component is further less than the surface of the nonwoven fabric 110 inside the nonwoven fabric 110, the heat conduction through the binder is extremely reduced.

  For these reasons, when a very small amount of a liquid binder is used, the glass fibers 111 and 112 in the vicinity of the surface of the nonwoven fabric 110 are effectively bonded to each other. In addition, while sufficient strength is exhibited for mass production, the amount of the binder can be extremely reduced inside the nonwoven fabric 110.

  FIG. 6 is a cross-sectional view schematically showing a distribution state of a granular or fibrous binder in a nonwoven fabric used as a core material of a vacuum heat insulating material as one comparative embodiment of the present invention in the thickness direction of the nonwoven fabric. FIG. 7 is a cross-sectional view schematically showing the distribution state of the liquid binder in the nonwoven fabric used for the core material of the vacuum heat insulating material as one embodiment of the present invention in the thickness direction of the nonwoven fabric. In FIG. 6, the portion indicated by dots represents the distribution state of the binder. In FIG. 7, shades of black represent the distribution state of the binder.

  As shown in FIG. 6, when a granular or fibrous binder is used, the binder component shown in the form of dots is uniformly dispersed in the thickness direction of the nonwoven fabric. On the other hand, as shown in FIG. 7, when a liquid binder is used in the present invention, a relatively large amount of binder component is present in the surface layer portion of the nonwoven fabric in the thickness direction of the nonwoven fabric, and a relatively small amount. The binder component is present inside the nonwoven fabric. The content of the liquid binder is preferably in the range of 0.1% by mass to 1.5% by mass with respect to the nonwoven fabric.

  In addition, although it is also possible to use an inorganic binder for the liquid binder, if an inorganic binder is used, the fiber assembly, that is, the nonwoven fabric is not flexible enough to be folded, and the cost when used as a product is organic. Since it becomes expensive compared with the case where a binder is used, it is preferable to use an organic binder.

  The liquid binder in the present invention is an acrylic resin, an epoxy resin, a phenol resin, a styrene resin, an emulsion such as polyethylene, polypropylene, or a polyester resin, or a solution in which these are dissolved in a solvent, or polyvinyl alcohol (PVA) or starch. Although it will not specifically limit if it is a liquid thing, such as an aqueous solution of a water-soluble binder, Acrylic resin emulsion or a polyvinyl alcohol aqueous solution etc. are suitable from the relation of strength and cost.

  In one embodiment of the method for manufacturing the vacuum heat insulating material core 100 of the present invention, first, glass fibers 111 and 112 which are examples of a plurality of inorganic fibers manufactured by a continuous filament method, and at least a liquid binder are used. Then, the nonwoven fabric 110 is manufactured by a wet papermaking method. Thereby, most glass fibers 111 and 112 are made to extend in the direction substantially parallel to the surface of the manufactured nonwoven fabric 110 among several glass fibers. Further, a plurality of nonwoven fabrics 110 are laminated.

  Moreover, in one embodiment of the manufacturing method of the vacuum heat insulating material 1 of the present invention, first, a nonwoven fabric is formed by a wet papermaking method using at least a plurality of glass fibers 111 and 112 manufactured by a continuous filament method and a liquid binder. 110 is manufactured. Thereby, most glass fibers 111 and 112 are made to extend in the direction substantially parallel to the surface of the manufactured nonwoven fabric 110 among several glass fibers. Further, a plurality of nonwoven fabrics 110 are laminated. Thereafter, the laminated nonwoven fabrics 110 are accommodated in the outer packaging material 200, and the interior of the outer packaging material 200 is kept in a reduced pressure state.

  In one embodiment of the manufacturing method of the vacuum heat insulating material core 100 or the vacuum heat insulating material 1 of the present invention, a liquid binder such as an emulsion of the above resin or an aqueous solution of the above resin is used. It is preferable to adopt a method in which a liquid binder is attached to the glass fibers 111 and 112 by a method such as spraying the glass fibers 111 and 112 by spraying or the like.

In one embodiment of the method for manufacturing a vacuum heat insulating material of the present invention, at least a plurality of glass fibers 111 and 112 manufactured by a continuous filament method and a liquid binder are used. When a plurality of glass fibers 111 and 112 are used to manufacture the nonwoven fabric 110 by a wet papermaking method, when the glass fibers are arranged in a direction parallel to the surface of the nonwoven fabric 110, most of the glass fibers A plurality of glass fibers can be easily aligned such that 111 and 112 extend in a direction substantially parallel to the surface of the nonwoven fabric 110. At this time, most of the plurality of glass fibers 111 and 112 extend in a direction substantially parallel to the surface of the nonwoven fabric 110, but do not align with each other in close contact with each other and form a surface of the nonwoven fabric 110. to array to distribute randomly oriented within. Thereby, even if a plurality of non-woven fabrics 110 are laminated to constitute the core material 100, the presence of glass fibers that fill between the plurality of glass fibers can be minimized, and between the plurality of glass fibers. Since the presence of the glass fiber entangled with the glass fiber can be eliminated as much as possible, it is possible to prevent heat conduction from occurring between the glass fibers. And the vacuum heat insulating material 1 can be manufactured by accommodating the some nonwoven fabric 110 laminated | stacked inside the outer packaging material 200, and keeping the inside of the outer packaging material 200 in a pressure-reduced state. Thus, by preventing heat conduction from occurring along the thickness direction of the core material 100, the thermal conductivity of the core material 100 can be lowered, and the improvement limit of the conventional heat insulation performance may be exceeded. It becomes possible and the core material 100 which has the outstanding heat insulation performance and the vacuum heat insulating material 1 provided with the core material 100 can be obtained.

  The nonwoven fabric 110 made of glass fibers 111 and 112 used in the present invention is manufactured by a wet papermaking method. In the wet papermaking method, by adding an appropriate dispersant, glass chopped strands obtained by cutting glass fibers into a certain length are monofilamentized and dispersed and arranged in layers, and are made of glass fibers 111 and 112 with very little binding. The nonwoven fabric 110 can be obtained. For this reason, the number of glass fibers 111 and 112 arranged in parallel is very small, and most glass fibers 111 and 112 are in contact with each other at points between adjacent fibers. In this way, the nonwoven fabric 110 having a high compressive strength and a very low thermal conductivity in the thickness direction can be produced. Therefore, such a nonwoven fabric 110 is suitable as the core material 100 of the vacuum heat insulating material 1. .

  Fabrication of the non-woven fabric 110 by the wet papermaking method employed in the production method of the present invention is possible by using a known papermaking machine such as a long net papermaking machine, a short netting papermaking machine, or an inclined wire type papermaking machine.

  Usually, the nonwoven fabric which consists of glass fibers is used as a heat insulating material which has heat resistance, a heat insulating material which has fire resistance, or an electrical insulator. For this reason, the nonwoven fabric is required to have a fabric strength that can withstand tearing and breaking, and often requires entanglement of fibers. Nonwoven fabrics made of glass fibers used for such applications are often manufactured by a papermaking method using a long net paper machine or a short net paper machine.

  On the other hand, since the nonwoven fabric 110 made of the glass fibers 111 and 112 used in the present invention is accommodated in the outer packaging material 200 as the core material 100, the strength as a cloth is not so required. Further, the papermaking method in which the fiber directions are easily aligned increases the contact area between the fibers, and thus is not preferable for producing the nonwoven fabric 110 made of the glass fibers 111 and 112 used in the present invention. On the other hand, in order to improve the heat insulation performance in the thickness direction, it is desirable that the glass fibers 111 and 112 have less entanglement.

  Therefore, as the paper machine for making the nonwoven fabric 110 made of the glass fibers 111 and 112 used in the present invention, an inclined wire type paper machine capable of making paper at a low inlet concentration is suitable, but is not limited thereto. is not.

  As for the glass chopped strand which is an example of the inorganic fiber used for this invention, it is preferable that the structural ratio of the glass fibers 111 and 112 with a fiber diameter of 3-15 micrometers and a fiber length of 3-15 mm is 99% or more.

  A glass chopped strand having a fiber diameter of less than 3 μm or a fiber length of less than 3 mm is expected to be unsuitable for use in the nonwoven fabric 110 constituting the vacuum heat insulating material core 100 of the present invention as described below. .

  Since the glass fibers 111 and 112 having a fiber diameter of less than 3 μm have low fiber rigidity, when the nonwoven fabric 110 is manufactured by the wet papermaking method, the fibers are bent and entanglement between the fibers occurs, and the fibers contact each other. Increases area. Thereby, since heat conduction becomes large and the heat insulation performance of the core material 100 is deteriorated, the glass fibers 111 and 112 having a fiber diameter of less than 3 μm are not preferable.

  When the non-woven fabric 110 is produced by the wet papermaking method, the glass fibers 111 and 112 having a fiber length of less than 3 mm are obtained by dispersing the fibers located in the upper layer on the fibers located in the lower layer already dispersed. The fibers of the upper layer cannot bridge the lower layer fibers, and the upper layer fibers are more likely to be supported on the lower layer fibers. For example, one end of the upper layer fibers hang down to the lower layer and the other Is expected to be positioned in a form that protrudes in the thickness direction. As described above, when a certain fiber is bridged in the thickness direction between a plurality of fibers, heat conduction in the length direction of the fiber occurs, and the contact area between the fibers increases. Thereby, heat conduction becomes large and the heat insulation performance of the core member 100 is deteriorated, so that glass fibers having a fiber length of less than 3 mm are not preferable.

  When the non-woven fabric 110 is formed using the glass fibers 111 and 112 having a fiber diameter of 15 μm or more, and the core material 100 is formed by laminating the plurality of non-woven fabrics 110, the number of fiber layers in the thickness direction of the core material 100 decreases. The heat transfer path in the thickness direction is shortened, and the pore diameter is increased when the nonwoven fabric 110 is formed. Thereby, the glass fiber having a fiber diameter of 15 μm or more is not preferable because the heat insulation performance of the core material 100 is lowered due to the influence of the thermal conductivity of the gas.

  When glass fibers 111 and 112 having a fiber length of 15 mm or more are used, the fiber length increases with respect to the fiber diameter, so that the rigidity of the fiber is lowered and the fiber is liable to be bent. The contact area increases. Thereby, heat conduction becomes large and the heat insulation performance of the core material 100 is deteriorated, so that glass fibers having a fiber length of 15 mm or more are not preferable.

The basis weight of the nonwoven fabric 110 made of the glass fibers 111 and 112 used as the vacuum heat insulating material core 100 of the present invention is preferably 30 to 600 g / m ² . When the non-woven fabric 110 has a basis weight of less than 30 g / m ² , the influence of the thermal conductivity of the gas is increased by increasing the diameter of the voids existing in the nonwoven fabric 110. Thereby, since the heat insulation performance of the core material 100 falls and the intensity | strength of the core material 100 becomes weak, it is not preferable if the rice paper weight of the nonwoven fabric 110 is less than 30 g / m < ² >. On the other hand, when the basis weight of the nonwoven fabric 110 exceeds 600 g / m ² , the drying efficiency when the nonwoven fabric 110 is produced from the glass fibers 111 and 112 is lowered, and the productivity is lowered.

  Here, the US basis weight is generally a unit of measurement of the thickness of paper, and represents the mass of paper per square meter, and is also referred to as metric basis weight. Here, rice tsubo is used as a unit for measuring the thickness of the nonwoven fabric 110 made of the glass fibers 111 and 112 manufactured by the wet papermaking method.

  By the way, for example, JP-A-2006-17169 (Patent Document 2) describes that the average diameter of inorganic fibers such as glass wool constituting the core material of the vacuum heat insulating material is preferably 1 to 5 μm. . And when the average diameter of the inorganic fiber exceeds 5 μm, it is described that the heat insulation performance of the finally obtained vacuum heat insulating material itself is lowered. Certainly, the heat insulation performance of the vacuum heat insulating material increases as the diameter of the inorganic fibers constituting the core material is smaller. On the other hand, fine inorganic fibers are expensive and have the disadvantages of reducing the dewatering efficiency and reducing the productivity when producing nonwoven fabrics by wet papermaking. On the other hand, in the present invention, as an example of the inorganic fiber, by selecting the optimum conditions for improving the heat insulation performance for the fiber parameters such as the fiber diameter of the inorganic fiber, the fiber length, and the adhesion state between the fibers, Even when a glass chopped strand having a relatively large fiber diameter is used, it is possible to realize the vacuum heat insulating material 1 that can obtain heat insulating performance far higher than that of the conventional vacuum heat insulating material.

  Moreover, even if a glass chopped strand with a fiber diameter thinner than 6 μm is used, the improvement width of the heat insulating performance of the finally obtained vacuum heat insulating material is almost the same as when using a glass chopped strand with a fiber diameter of 10 μm. It is negligible. Therefore, if the aspects of productivity, price, and performance are taken into consideration, the preferred fiber diameter of the glass chopped strand is 6 to 15 μm. When the glass fibers 111 and 112 in this range are used, the vacuum heat insulating material 1 having a heat insulating performance higher than that of the conventional vacuum heat insulating material can be obtained at an appropriate manufacturing cost.

  The vacuum heat insulating material 1 of this invention can be manufactured by a known method using the core material 100 provided with the characteristics mentioned above. As a representative method, in the configuration of the vacuum heat insulating material 1 shown in FIG. 1, the core material 100 is accommodated inside a gas barrier outer packaging material 200 formed in a bag shape. The outer packaging material 200 for storing the core material 100 in a decompressed state has a high gas barrier property and a protective layer against heat-sealing layers, scratches, etc., and can keep the inner packaging material 200 in a decompressed state for a long period of time. Use something. Further, a plurality of films having such characteristics may be laminated to form the outer packaging material 200.

  As a specific example of the structure of the outer packaging material 200, the outermost layer is made of polyethylene terephthalate (PET) resin, the intermediate layer is made of an ethylene-vinyl alcohol copolymer resin having an aluminum vapor deposition layer, and the innermost layer is made of high-density polyethylene. Examples thereof include a gas barrier film using a resin, a gas barrier film using nylon as an outermost layer, two layers of an aluminum-deposited PET resin and an aluminum foil as an intermediate layer, and a high-density polyethylene resin as an innermost layer.

  In order to maintain the initial heat insulation performance and the temporal heat insulation performance of the vacuum heat insulating material 1, it is preferable to use a getter agent such as a gas adsorbent or a water adsorbent in the vacuum heat insulating material 1.

  Hereinafter, although some examples of the present invention are described, the present invention is not limited to these.

(Examples 1-5, Comparative Example 1)
A glass chopped strand (manufactured by Owens Corning Corporation) having an average fiber diameter of 10 μm and an average fiber length of 10 mm is poured into water so that its concentration is 0.5% by mass, and used as a dispersant. Emanon (registered trademark) 3199 (manufactured by Kao Corporation) was added to 1 part by mass with respect to 100 parts by mass of the glass chopped strand, and stirred to prepare a glass chopped strand slurry.

  Using the obtained glass chopped strand slurry, paper was made by a wet paper making method to prepare a web. The obtained web was appropriately diluted and impregnated with a liquid binder of the binder type shown in Table 1, and the nonwoven fabric was adjusted by sucking moisture so that the binder content shown in Table 1 was obtained. Then, the nonwoven fabric 110 used for the core material 100 for vacuum heat insulating materials was produced by drying a web. Table 1 shows the rice paper weight and binder content of the nonwoven fabric 110 obtained.

  In the description of the binder type in Table 1, the liquid acrylic is an acrylic emulsion (GM-4 manufactured by Dainippon Ink & Chemicals, Inc.), and the liquid PVA is a PVA aqueous solution (PVA117 manufactured by Kuraray dissolved in warm water). ).

(Comparative Examples 2 to 4)
Using the glass chopped strands used in Examples 1 to 5 and Comparative Example 1, glass chopped strand slurries were produced in the same manner as in Examples 1 to 5 and Comparative Example 1.

  Granular PVA (OV-N manufactured by Unitika Ltd.) was added to water so as to have a concentration of 10% and stirred to prepare a granular binder slurry.

  Using a slurry obtained by adding granular binder slurry to the obtained glass chopped strand slurry and stirring and mixing so as to have the binder content shown in Table 1 with respect to the nonwoven fabric, papermaking is performed by a wet papermaking method. Then, a web was produced. Then, the nonwoven fabric 110 used for the core material 100 for vacuum heat insulating materials was produced by drying the obtained web. Table 1 shows the rice paper weight and binder content of the nonwoven fabric 110 obtained.

(Conventional example)
As a core material used for a conventional vacuum heat insulating material, a non-woven fabric was prepared as a sheet-like fiber aggregate made of glass wool having an average fiber diameter shown in Table 1.

  In addition, the binder content shown in Table 1 is obtained by removing the organic component by heating the nonwoven fabric 110 used for the core material 100 for vacuum heat insulating material at a temperature of 600 ° C. for 30 minutes, and calculating from the mass difference before and after the heating by the following formula. It was.

  Binder content (mass%) = [{(mass before heating) − (mass after heating)} / (mass before heating)] × 100

Ten nonwoven fabrics 110 manufactured according to the above Examples 1 to 5 and Comparative Examples 1 to 4 were laminated to obtain the core material 100. With a compression force of 1 kgf / cm ² (about 98 kPa) applied in the thickness direction to the upper and lower surfaces of each core member 100 made of the obtained laminate through spacers, the degree of vacuum is 0.01 Torr (about A vacuum state of 1.3 Pa) was maintained. In each of the held vacuum steady state core materials 100, the thermal conductivity was calculated by measuring the temperature of the upper and lower surface portions of each core material 100 made of a laminate and the heat flow flowing through each core material 100. . The measurement results of the obtained thermal conductivity are shown in the “thermal conductivity” column of Table 1. In addition, about a prior art example, the thermal conductivity of the nonwoven fabric which consists of conventional glass wool is shown in the column of "the thermal conductivity" of Table 1.

  From the results shown in Table 1, the vacuum heat insulating materials 1 according to Examples 1 to 5 of the present invention had a thermal conductivity of 0.85 mW / m · K or less, and industrially stable production was possible. .

  On the other hand, the vacuum heat insulating material 1 according to Comparative Examples 1 and 2 was industrially stable, but the thermal conductivities were 1.50 mW / m · K and 0.90 mW / m, respectively.・ It was K. Further, in Comparative Example 3, a vacuum heat insulating material having a thermal conductivity of 0.80 mW / m · K was obtained, but the non-woven fabric 110 was cut to a size according to the non-woven fabric manufacturing process and the outer packaging material 200 of the vacuum heat insulating material 1. In this process, a large amount of glass fibers 111 and 112 dropped off from the surface of the nonwoven fabric 110, and paper breakage occurred during delivery between rolls, so that stable production was difficult. In Comparative Example 4, a vacuum heat insulating material 1 having a thermal conductivity of 0.60 mW / m · K was obtained. However, a long time was required for the process of removing the binder, and the outer packaging material 200 of the vacuum heat insulating material 1 was used. In the process of encapsulating the core material 100 made of the nonwoven fabric 110, the nonwoven fabric 110 tends to lose its shape, making it difficult to industrially mass-produce. In addition, the heat conductivity of the conventional vacuum heat insulating material was 1.70 mW / m · K.

  Therefore, by using the vacuum heat insulating material according to the present invention, it is possible to industrially stably produce a vacuum heat insulating material having excellent heat insulating performance, and to provide equipment such as a refrigerator excellent in energy saving. It becomes possible.

  It should be considered that the embodiments and examples disclosed above are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of the claims, and includes all modifications and variations within the meaning and scope equivalent to the scope of the claims.

  1: vacuum heat insulating material, 100: core material, 200: outer packaging material, 110: non-woven fabric, 111, 112: glass fiber.

Claims (6)

A core material for vacuum heat insulating material constituted by laminating a plurality of nonwoven fabrics,
The nonwoven fabric includes a plurality of inorganic fibers manufactured by a continuous filament method, having an average fiber diameter of 3 μm to 15 μm, an average fiber length of 3 mm to 15 mm, and extremely high straightness,
In the nonwoven fabric, in the two inorganic fiber layers laminated in the nonwoven fabric, most of the plurality of inorganic fibers forming the upper layer and most of the plurality of inorganic fibers forming the lower layer are substantially parallel to the surface of the nonwoven fabric. Extending in the same direction and in close contact with each other, not aligned in parallel directions, but in contact between adjacent fibers at points, and in a random direction within each plane forming the upper and lower layers of the nonwoven fabric It is arranged so that it faces and
A core material for a vacuum heat insulating material, wherein a relatively large amount of a liquid binder component is present in a surface layer portion of the nonwoven fabric, and a relatively small amount of a liquid binder component is present inside the nonwoven fabric.   The core material for vacuum heat insulating materials according to claim 1, wherein a content of the binder component is 0.1% by mass or more and 1.5% by mass or less with respect to the nonwoven fabric.   The core material for a vacuum heat insulating material according to claim 1 or 2, wherein the inorganic fiber is a glass fiber. Outer packaging materials,
A core material housed inside the outer packaging material,
The outer packaging material is configured to be able to keep the inside in a reduced pressure state,
The vacuum heat insulating material in which the said core material contains at least 1 or more sheets of the core material for vacuum heat insulating materials of any one of Claim 1- Claim 3. It is a manufacturing method of the core material for vacuum heat insulating materials given in any 1 paragraph of Claims 1-3,
A step of producing a nonwoven fabric by a wet papermaking method using at least a plurality of inorganic fibers produced by a continuous filament method and a liquid binder, and in this step, in a direction substantially parallel to the surface of the produced nonwoven fabric. , Extending most of the plurality of inorganic fibers,
The manufacturing method of the core material for vacuum heat insulating materials provided with the step which laminates | stacks the said some nonwoven fabric. It is a manufacturing method of the vacuum heat insulating material of Claim 4, Comprising:
A step of producing a nonwoven fabric by a wet papermaking method using at least a plurality of inorganic fibers produced by a continuous filament method and a liquid binder, and in this step, in a direction substantially parallel to the surface of the produced nonwoven fabric. , Extending most of the plurality of inorganic fibers,
Laminating a plurality of the nonwoven fabrics;
A method of manufacturing a vacuum heat insulating material, comprising: storing a plurality of laminated nonwoven fabrics in an outer packaging material, and maintaining the interior of the outer packaging material in a reduced pressure state.