JP2009210072A - Vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum heat insulating material using, as a core material, a non-woven inorganic fiber layer mainly containing inorganic fibers having average fiber diameters of 4 μm or smaller, the core material consisting of the inorganic fiber layer being substantially formed of inorganic materials only, where inorganic fibers are bound to each other with inorganic binder, to maintain improved pressure resistance and improved heat insulating performance over a long period while maintaining good softness and flexibility and suppressing the degradation of heat insulating performance due to better heat conduction between the surface and the reverse. <P>SOLUTION: The vacuum heat insulating material comprises the core material consisting of the non-woven inorganic fiber layer mainly containing the inorganic fibers having average fiber diameters of 4 μm or smaller, packed with a gas-barrier skin material, and sealed with internal pressure reduced. In this case, the core material is substantially formed of the inorganic materials only, where the inorganic fibers on the surface on at least one of the surface and the reverse of the inorganic fiber layer are bound to each other with the inorganic binder formed of swollen layered clay mineral. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vacuum heat insulating material having a non-woven inorganic fiber layer as a core material.

  Conventionally, as a vacuum heat insulating material, a core material composed of an inorganic fiber layer formed by a dry manufacturing method such as a needling mat or felt, or a wet manufacturing method such as a papermaking sheet, with inorganic fibers as a main constituent, polyester, polyethylene, etc. A plastic film and metal foil or metal vapor deposition or other metal laminated and laminated, wrapped in a gas barrier outer covering material, the air inside is removed, and then sealed and molded. ing.

  The thermoplastic film has a function of imparting flexibility and fusing workability, and the metals have a gas barrier function of preventing external air from entering. In order to enhance the heat insulation, the core material has a function of reducing the heat convection space and slowing the movement of heat, so that the diameter of the inorganic fiber can be reduced to 1 μm or less, or the shot in the inorganic fiber (unfiberized) The thermal conductivity is lowered by decreasing the content ratio of the granular material) or by arranging inorganic fibers in a direction perpendicular to the heat transfer direction (for example, Patent Documents 1 and 2). .

  When the inorganic fiber diameter is reduced, the joint area between the fibers decreases, the heat transfer path becomes complicated, and the heat insulation performance is improved. Inorganic fibers with an average fiber diameter of 4 μm or less are wool fibers produced by spinning from a molten material such as a normal flame method or a centrifugal method, and blowing away with a high-speed flame or high-speed air current. , Relatively large size compared to the original inorganic fiber, such as those with teardrop-shaped clumps at the end of the fiber, partially thickened fibers, or thick fibers left before being blown away A small amount of particulate matter or fibrous material having a particle size (this is called a shot), and especially a shot with a large particle size causes large pores in the heat insulating material, causing convective heat transfer of gas, gas molecules The heat insulation performance can be improved by reducing the shot content in order to promote the heat transfer due to the collision. Moreover, in the inorganic fiber layer, by arranging the fibers in a direction perpendicular to the heat transfer direction of the heat insulating material, the heat transfer path between the front and back surfaces of the heat insulating material can be complicated, maze, and heat conduction time can be extended. Therefore, the heat insulation performance is improved.

  The vacuum insulation materials described above are used as heat insulation materials for promoting energy conservation in household and commercial appliances such as refrigerators, rice cookers, water heaters and vending machines, and for medical and cold storage containers for maintaining freshness. As a heat insulating material, and recently, it has been applied as a heat insulating material for a cold clothing and a heat insulating material for an unheated house, and is responding to the demand for high-performance heat insulation by reducing the thickness.

  However, since the vacuum heat insulating material core material like patent document 1-2 is comprised only from the inorganic fiber in order to suppress heat conduction low, when it vacuum-reduces and seals, the thickness direction of a core material will be by atmospheric pressure. The thickness is reduced to 30-40%. Thereby, the distance between fibers becomes short, the contact area between fibers increases, heat conduction increases, and there exists a problem that heat insulation performance falls.

  Therefore, in a vacuum heat insulating material core made of an inorganic fiber layer, an organic binder (for example, Patent Documents 3 to 4), a repellent synthetic fiber, or an inorganic binder (for example, a patent) is used to improve the thickness loss due to reduced pressure. It is conceivable to introduce documents 5 to 6).

  However, when organic substances such as organic binders and synthetic fibers are introduced, there is a problem in that the degree of vacuum cannot be increased due to gas generation from unreacted components and surface treatment agent at the time of vacuum exhaust. There is a problem that the heat insulation performance is gradually lowered due to gas generation. As a countermeasure, a so-called getter agent (adsorbent) may be introduced, but it is an auxiliary solution and not a fundamental solution. In addition, there are problems such as a decrease in heat insulation at the portion where the getter agent is introduced and an increase in the number of processing steps. Therefore, it is not preferable to introduce organic substances such as organic binders and synthetic fibers.

  Moreover, when silica emulsion (inorganic oxide sol) etc. generally used as an inorganic binder like patent documents 5-6 are introduced, since the intersection of inorganic fibers is well adhered and solidified, Although improved, since the inorganic fibers are completely bonded to each other, the bonded portion acts as a thermal bridge (shortening the heat transfer path), shortening the heat transfer distance between the front and back of the vacuum heat insulating material, and improving the heat conduction There is a problem that the heat insulation performance is lowered. In addition, since the inorganic fiber layer bonded with the inorganic oxide sol has reduced flexibility and flexibility and becomes a hard and brittle layer, there are also problems such as being unable to be used for curved surface installation and being unable to roll the raw fabric. . In addition, since the inorganic fiber layer is a hard and brittle layer, cracks and chips are likely to occur, and a hard damaged material may damage the gas barrier outer covering material and lose its function as a vacuum heat insulating material. In addition, since the inorganic binder easily forms a film, there is also a problem that the depressurization exhaust time is prolonged due to the film.

  In addition, as a method not using an organic binder or an inorganic binder, there is a method (for example, Patent Documents 7 to 9) in which inorganic fibers are bound together by a melting or dissolving component of the inorganic fiber itself. Melting or dissolution causes a decrease in strength of the inorganic fiber, and there is a problem that the fiber is easily broken. In addition, in the case of melting, it is difficult to heat and melt only the intersections of the fibers, and when performing a normal heat treatment, the fibers are easily melted together and bonded, the inorganic fibers become thicker and heat conduction is increased, There is a problem that the inorganic fiber layer becomes hard and is liable to be cracked or chipped, resulting in a hard breakage.

  In addition, in the method of binding the intersections of inorganic fibers with an inorganic binder and preventing the settling of the thickness, there is a problem that the bonded portion of the inorganic fibers acts as thermal cross-linking and heat conduction is improved, and the inorganic fiber layer becomes hard and cracks. In order to solve the problem that chipping is likely to occur, a method has been proposed in which an inorganic binder is attached to only a part of the inorganic fiber layer or a part with a small amount of inorganic binder is provided (for example, Patent Documents 10 to 10). 11).

JP 2005-265038 A JP 2007-239931 A Japanese Patent Laid-Open No. 9-138058 JP 2001-108186 A JP-A-10-115396 JP 2004-084847 A JP 7-139691 A JP 7-167376 A JP 2006-002314 A JP 2003-148687 A JP 2004-011707 A

  As described above, in the vacuum heat insulating material having the inorganic fiber layer as a core material, from the viewpoint of assembling property, thickness uniformity, shape retention after vacuum sealing, etc., the inorganic fiber layer has a board shape, a mat shape, Therefore, the inorganic fiber layer that forms the molded body must be formed by excluding a special molding method that breaks the fiber array, such as the needling method (the fiber is insulated). It is important to have a structure in which the fibers are joined to each other because it is oriented in the heat transfer direction of the material), but the method of introducing an organic substance as a binder involves gas generation. It is not suitable, and the inorganic fiber layer needs to be composed essentially of inorganic substances. However, the method of introducing an inorganic binder such as a general inorganic oxide sol is a method of completely cross-linking inorganic fibers and heat-crosslinking action. By It is not preferable because heat conduction increases and heat insulation performance deteriorates, and the inorganic fiber layer becomes hard and easily cracks and chipped. This is not preferable, and the method of bonding inorganic fibers with the melted or dissolved components of the inorganic fiber itself is the strength of the inorganic fiber. This is not preferable because it involves a decrease.

On the other hand, if we look at the improvement in thickness sag under approximately atmospheric pressure (approx. 1 kg / cm ² pressurization) after vacuum sealing of the vacuum heat insulating material core composed of an inorganic fiber layer, melting of the inorganic fiber itself Or the method of patent document 7, which is a method of binding inorganic fibers with a dissolved component, shows a thickness of 30 to 40%. This is an improvement over the 50% to 70% thickness when paper is made under neutral conditions. However, there is a further improvement to meet the demand for high performance insulation by reducing the thickness in recent years. It is necessary.

  Therefore, in view of the above-described conventional problems, the present invention provides a vacuum heat insulating material using a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less as a core material. The core material consisting of is composed of only inorganic material that binds inorganic fibers with an inorganic binder, while maintaining good flexibility and flexibility, and heat insulation performance by improving heat conduction between the front and back It aims at providing the vacuum heat insulating material which is excellent in pressure resistance, and can maintain the heat insulation performance excellent over the long term, suppressing the fall of this.

  In order to achieve the above object, the vacuum heat insulating material according to the present invention is a gas barrier jacket material comprising a core material composed of an inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less. In the vacuum heat insulating material formed by packing and depressurizing the inside and sealing, the core material is an inorganic material in which the inorganic fibers in the surface portion of at least one surface of the inorganic fiber layer are made of a swellable layered clay mineral. It is characterized by being composed of only an inorganic substance bound by a binder.

In order to achieve the above object, the vacuum heat insulating material of the present invention is a core material comprising a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less as described in claim 2. In a vacuum heat insulating material which is packed with a gas barrier outer covering material and is depressurized and hermetically sealed, the core material is a swellable layered clay having self-forming properties on at least one of the front and back surfaces of the inorganic fiber layer An air-permeable coating made of mineral is formed, and is substantially composed only of an inorganic material.
The vacuum heat insulating material according to claim 3 is the vacuum heat insulating material according to claim 1 or 2, characterized in that the inorganic fiber layer is composed of a nonwoven fabric sheet mainly composed of the inorganic fibers.
According to a fourth aspect of the present invention, there is provided the vacuum heat insulating material according to the third aspect, wherein the inorganic fiber layer is a wet papermaking sheet mainly composed of the inorganic fibers.
The vacuum heat insulating material according to claim 5 is the vacuum heat insulating material according to any one of claims 1 to 4, wherein the inorganic fiber layer is mainly composed of inorganic fibers having an average fiber diameter of 1.5 μm or less. It is characterized by that.
The vacuum heat insulating material according to claim 6 is the vacuum heat insulating material according to any one of claims 1 to 5, wherein the inorganic fiber layer is substantially composed only of the inorganic fiber and the swellable layered clay mineral. It is characterized by being configured.
The vacuum heat insulating material according to claim 7 is the vacuum heat insulating material according to any one of claims 1 to 6, wherein the swellable lamellar clay mineral is a smectite group.

  According to the present invention, in the vacuum heat insulating material using a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less as a core material, the core material made of the inorganic fiber layer is substantially Is composed of only inorganic substances, has high heat resistance, does not generate gas that causes lowering of vacuum degree or heat insulation performance, and the inorganic fibers on the surface portion of at least one of the front and back surfaces of the inorganic fiber layer Are bonded with an inorganic binder made of a swellable layered clay mineral, and the inorganic fiber layer maintains its flexibility without being hard and brittle, even though the inorganic fibers have a bonded structure with the inorganic binder. Therefore, it is possible to prevent cracks and chipping and damage to the jacket material due to burrs, and it can also be used for curved surface installation and widen the application range, and when the inorganic fiber layer is made of paper sheet etc. Sheet Since the film formed by the inorganic binder has air permeability, it is possible to prevent prolonged decompression exhaust time, and furthermore, the pressure resistance is greatly improved. Further, it is possible to provide a vacuum heat insulating material that can prevent the thickness settling after vacuum sealing as much as possible and maintain excellent heat insulating performance over a long period of time.

Further, the core material made of the inorganic fiber layer has a micron thickness breathable film made of a swellable layered clay mineral having self-forming properties on at least one of the front and back surfaces of the inorganic fiber layer. In addition, since it exhibits excellent pressure resistance that is not easily crushed by pressurization at atmospheric pressure (about 1 kg / cm ² ), the thickness set after sealing under reduced pressure is greatly improved, and the insulation performance is maintained by maintaining the thickness over a long period of time. It can be applied to fields of residential and architectural applications that have a long product life.

  The vacuum heat insulating material core of the present invention comprises a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less, and the inorganic fibers on the surface portion of at least one of the front and back surfaces of the inorganic fiber layer They are bound together by an inorganic binder made of a swellable layered clay mineral and are substantially composed of only an inorganic substance. Further, the vacuum heat insulating material core material is substantially composed only of an inorganic material in which a breathable film made of a swellable layered clay mineral having self-forming properties is formed on at least one of the front and back surfaces of the inorganic fiber layer. It may be. The inorganic fibers on the surface of the inorganic fiber layer are bound together with an inorganic binder made of a swellable layered clay mineral having self-forming properties, and the surface of the inorganic fiber layer has a micron level thickness made of a swellable layered clay mineral. Therefore, the pressure applied in the thickness direction is applied to the entire surface of the sheet, so that excellent pressure resistance is exhibited. In this sense, in order to pursue the pressure resistance of the vacuum heat insulating material core material, in the above configuration, the inorganic fibers on the front and back surfaces of the inorganic fiber layer are bonded with an inorganic binder made of a swellable layered clay mineral. It is preferable that a breathable film made of a swellable layered clay mineral having self-forming properties is formed on both the front and back surfaces of the inorganic fiber layer.

  The inorganic fiber layer consisting only of the inorganic substance mainly composed of the inorganic fiber may be mixed with an auxiliary material such as inorganic powder in addition to the inorganic fiber and the swellable layered clay mineral depending on the purpose and purpose. Although it is possible, from the viewpoint of pursuing the object of the present invention, it is preferable that the inorganic fiber and the swellable layered clay mineral are used alone.

  The inorganic fiber layer is mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less. Here, “mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less” means that the inorganic fiber material constituting the inorganic fiber layer is composed only of inorganic fiber materials having an average fiber diameter of 4 μm or less, This includes the case where an inorganic fiber material having a fiber diameter of 4 μm or less and an inorganic fiber material having an average fiber diameter exceeding 4 μm are mixed (provided that the average fiber diameter of the entire inorganic fiber layer is 4 μm or less).

  More preferably, the inorganic fiber layer is mainly composed of inorganic fibers having an average fiber diameter of 1.5 μm or less. In the case of a core material composed of a non-woven inorganic fiber layer, the thinner the inorganic fibers, the smaller the joint area between the fibers, the more complicated the heat transfer path, and the better the heat insulation performance. The average fiber diameter of the inorganic fibers in the inorganic fiber layer is preferably 1.5 μm or less, and more preferably 1 μm or less. Moreover, when the average fiber diameter of the inorganic fibers of the inorganic fiber layer is 1.5 μm or less, and further 1 μm or less, particularly when the inorganic fiber layer is composed of a nonwoven fabric sheet or a wet papermaking sheet, As the entanglement increases and the sheet strength increases, the thickness uniformity of the sheet increases and the uniformity of the heat insulating performance can be improved. Moreover, it is preferable that the average fiber diameter of the said inorganic fiber is 0.2 micrometer or more. When the average fiber diameter is less than 0.2 μm, when the inorganic fiber layer is composed of a wet papermaking sheet, it is possible to form a sheet by wet papermaking, but the manufacturing cost increases due to poor drainage, resulting in an industrial product. As a disadvantage, it is not suitable for practical use.

  The non-woven inorganic fiber layer is preferably composed of a wet papermaking sheet mainly composed of the inorganic fibers. Non-woven inorganic fiber layer forms include non-woven sheets of the inorganic fibers, a laminate of a plurality of the sheets, a simple collection of wool-like inorganic fibers without forming a sheet, and the like. In the case of the wet papermaking sheet mainly composed of the inorganic fibers, the thickness uniformity of the core material can be increased, so that the surface smoothness of the vacuum heat insulating material can be improved and the uniformity of the heat insulating properties can be improved. Enhanced. An inorganic fiber layer made of a wet papermaking sheet is superior to an inorganic fiber layer obtained by collecting and compressing wool-like inorganic fibers and compressing them, and can be made to have a stable quality. Moreover, when the thickness per sheet of wet papermaking sheets is made thin and laminated, the degree of arrangement of inorganic fibers in the horizontal direction of the core material (perpendicular to the stacking direction of the sheets) is It becomes high, and the glass fibers aligned in the horizontal direction with respect to the heat conduction in the front and back direction of the core material inhibit the heat conduction, and the heat insulation performance of the vacuum heat insulating material is improved.

  As the inorganic fiber, glass fiber, alumina fiber, silica fiber, ceramic fiber, slag wool fiber, rock wool fiber, and the like can be used, and glass fiber is preferable because inorganic fibers having a small fiber diameter can be easily obtained. Glass fibers have a lower melting temperature and can be easily made into fine fibers than other inorganic fibers. The fine glass fiber is, for example, a wooly glass having an average fiber diameter of 0.2 to 4 μm obtained by melting and spinning acid-resistant C glass at about 1100 ° C., applying energy with a flame of a burner, and blowing it off. Fiber is preferred.

  The swellable layered clay mineral of the present invention is an inorganic substance, and has a self-forming property and functions as an inorganic binder by being dissolved in a solvent and used in a wet state and dried. In particular, the swellable layered clay mineral of the smectite group (mineral names such as saponite, hectorite, saumanite, montmorillonite, beidellite, nontronite) is a nano-sized scaly structure, and when this layer is layered and dried It exhibits a hard and strong film shape. However, since the swellable layered clay mineral alone causes cracks, it is difficult to obtain a complete film. However, when, for example, an inorganic fiber nonwoven fabric sheet, which is a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less according to the present invention, is coated or impregnated, the distance between the inorganic fibers is 4 μm or less. Therefore, a film can be easily formed between inorganic fibers.

  The swellable layered clay mineral having self-forming properties has high thixotropy and maintains a viscosity of 4000 to 8000 mPa · s (measured with a B-type viscometer) even in an aqueous solution of only 1% by weight. Therefore, the average fiber diameter of the present invention is 4 μm. For example, if the surface of an inorganic fiber nonwoven fabric sheet that becomes a non-woven inorganic fiber layer mainly composed of the following inorganic fibers is coated, the swellable lamellar clay mineral does not enter the interior of the nonwoven fabric sheet. A coating having a thickness of micron can be easily formed on the sheet surface.

  When the swellable layered clay mineral is dispersed in water, it swells and disperses in a scale of several nanometers, and when this aqueous solution is dried, a flexible film in which the clay is overlapped in a scale form can be easily obtained. A pressure-resistant film made of an inorganic substance having a thickness of micron and having flexibility can be obtained only on the surface of the target inorganic fiber layer. Further, since this film is scaly like graphite graphite, there is an advantage that slipping is good and it is easy to insert the core material into the jacket material. Furthermore, in manufacturing, for example, the inorganic fiber nonwoven fabric sheet that becomes the inorganic fiber layer of the present invention may be applied or impregnated with an aqueous solution of a swellable layered clay mineral, and then dried, so that the equipment cost is also reduced. There is an advantage that it can be reduced. The heat resistant temperature of the smectite-based swellable layered clay mineral is 700 ° C.

  The swellable layered clay mineral can be used as a natural product or a synthetic product. In the case of a natural product, although it is very inexpensive, it contains impurities such as iron and has a hue such as gray, so it is not suitable for applications that dislike metal impurities. In the case of a synthetic product, the hue is usually colorless and transparent, and has the advantage of not containing impurities, but is 20 times more expensive than a natural product.

  Oxide sol is known as a conventional general inorganic binder, but it has no property of being laminated and self-forming, and the oxide sol was treated in order to firmly bind and fix the intersection of inorganic fibers. It is considered that the inorganic fiber nonwoven fabric sheet loses flexibility and becomes a hard and brittle sheet, which may cause generation of foreign substances that damage the outer cover material. In addition, since the intersection of the inorganic fibers is firmly bound and fixed, the heat conduction through this portion is improved and the heat insulation performance is hindered. Further, natural mica and synthetic mica are known as conventional scaly inorganic binders, but those having an average particle diameter of 3 μm or less cannot be obtained, and the size is large, so that it is difficult to obtain adhesive strength as a binder.

  The vacuum heat insulating material core of the present invention comprises an inorganic fiber layer in which at least one surface of the front and back surfaces of the inorganic fiber layer is an adhesion surface of the swellable layered clay mineral, and the inorganic fiber layer is inorganic. It is preferable that the inorganic fiber nonwoven fabric sheet mainly composed of fibers is formed as a single layer or laminated. As a specific example of the inorganic fiber layer, when the inorganic fiber layer is composed of an inorganic fiber layer having a single layer structure composed of one inorganic fiber nonwoven fabric sheet, at least one surface of the front and back surfaces of one inorganic fiber nonwoven fabric sheet May be an adhesion surface of the swellable layered clay mineral, and when the inorganic fiber layer is composed of an inorganic fiber layer having a multilayer structure composed of a plurality of inorganic fiber nonwoven fabric sheets, at least of the plurality of inorganic fiber nonwoven fabric sheets At least one surface of the front and back surfaces of one inorganic fiber nonwoven fabric sheet is used as a surface for attaching the swellable layered clay mineral, and at least one surface of the front and back surfaces of the inorganic fiber layer is used as a surface for attaching the swellable layered clay mineral. They may be laminated, and in any case, single layer or multiple layers, as a result, at least one surface of the front and back surfaces of the inorganic fiber layer may be configured to be an adhesion surface of the swellable layered clay mineral. .

Next, a specific method for producing the vacuum heat insulating material of the present invention will be described using an example thereof.
(1) An inorganic fiber, for example, a predetermined amount of fine glass fiber is uniformly dispersed and mixed in water by a separator such as a mixer or a pulper to obtain a papermaking type and stored in a tank.
(2) A paper sheet is continuously supplied from a tank to a circular net, a long net or an inclined paper machine, wet-made, and dried to obtain an inorganic fiber paper-making sheet having a predetermined thickness.
(3) The raw fabric sheet is cut into a predetermined size to obtain an inorganic fiber nonwoven fabric sheet.
(4) Weigh smectite group swellable layered clay mineral to a specified concentration.
(5) Water (which may be tap water) and smectite group swellable layered clay mineral are put into a stirrer (homogenizer) and stirred for 5 minutes to uniformly disperse to obtain a thixotropic swellable layered clay mineral solution.
(6) A prescribed amount of the swellable layered clay mineral solution is adhered to the surface of the inorganic fiber nonwoven fabric sheet obtained in (3) by a coating method such as spray, roll coater, doctor coater or the like, or an impregnation method using a dipping tank or the like. Let However, in the present invention, the meaning of providing the adhering portion of the swellable lamellar clay mineral is to form a thin reinforcing film that enhances pressure resistance, and any method can be used as long as it is attached to at least the surface portion.
(7) Dry with a general dryer (circulating hot air drying furnace or the like) to obtain an inorganic fiber nonwoven fabric sheet provided with an adherent surface of the swellable layered clay mineral.
(8) Inorganic fiber nonwoven fabric sheet A obtained in (1) to (7) and, if necessary, other inorganic fiber nonwoven fabric sheets obtained in (1) to (3) (swellability to the front and back surfaces of the sheet) The setting of the adhesion surface of the layered clay mineral is optional) B, C... Are laminated so that at least one of the front and back surfaces is the adhesion surface of the swellable layered clay mineral. An inorganic fiber layer is produced and used as a vacuum heat insulating material core.
(9) After the heat treatment (180 ° C., 5 hours) with a hot air drier to evaporate and remove the adsorbed trace moisture of the vacuum heat insulating material core material, the bag-like gas barrier covering material is immediately prevented while preventing re-adsorption of moisture. And vacuum evacuation (5.32 Pa, 10 minutes), and fusion-sealed to obtain a vacuum heat insulating material.

  In the above-described specific production example of the vacuum heat insulating material of the present invention, the heat drying method and its temperature and time are not particularly limited, and the degree of vacuuming is not particularly limited. It can be about 10.64 Pa or less. In addition, the gas barrier covering material is not particularly limited as long as the inside can be kept in a vacuum state, and examples thereof include a multilayer laminate film made of a film of aluminum foil and polyester, polyethylene or the like. Can do.

  As described above, in the inorganic fiber layer forming the vacuum heat insulating material core of the present invention, one or both surfaces of the front and back surfaces of the inorganic fiber layer of the present invention are used as the adhesion surface of the swellable layered clay mineral of the present invention. Then, on the adhesion surface (surface portion), the inorganic fibers are bound to each other by the binder function of the swellable layered clay mineral, and a film is formed on the entire adhesion surface by the self-forming function of the swellable layered clay mineral. The film is a film formed by innumerable layers of nano-sized scaly layers, and has a very dense structure. It is a thin film of about several μm (usually 5 μm or less) and a high-strength film, but flexible. In addition, it has air permeability. Therefore, the inorganic fibers are bound on one or both sides of the front and back surfaces of the inorganic fiber layer and a high-strength film is formed, thereby significantly improving the pressure resistance of the inorganic fiber layer and the swelling of the inorganic fiber layer. Since the adhesion surface of the porous layered clay mineral maintains flexibility, it is possible to roll the original fabric with less cracking and chipping, and the adhesion surface of the swellable layered clay mineral in the inorganic fiber layer has air permeability. Since it is maintained, it is possible to prevent the decompression exhaust time from being prolonged. In the present invention, the main purpose of providing the adhesion portion of the swellable layered clay mineral on the inorganic fiber layer is to improve the pressure resistance of the inorganic fiber layer. Since the purpose can be achieved if at least one side of the back surface is an adhesion part, only the front and back surface parts (and only a thickness of several μm) should be the adhesion part of the swellable layered clay mineral in the entire inorganic fiber layer. It has become. That is, in the idea of the inorganic fiber layer of the present invention, since there is a main purpose of improving pressure resistance, an adhesive material (swelling layered clay mineral) is intentionally introduced into the inorganic fiber layer that is originally composed of only inorganic fibers. However, there are naturally harmful effects of introducing the adhering material (including those that hinder the basic function and performance of the vacuum heat insulating material core). In that sense, in the inorganic fiber layer of the present invention, in order to achieve the main object, only the front and back surface portions (thickness of several μm) should be the adhesion portion of the swellable layered clay mineral in the entire inorganic fiber layer. In the example of Example 2 described later, a smectite clay coating is 4 μm × 2 layers on a 3000 μm thick glass fiber nonwoven fabric sheet, and the adhering part of the swellable layered clay mineral is an inorganic fiber layer. Therefore, the effect of the invention is very great in that the adverse effects of achieving the main objective can be minimized. That is, in the entire inorganic fiber layer of the present invention, the adhesion portion of the swellable layered clay mineral is only a few μm in thickness on the front and back surface portions (about 0.13% of the inorganic fiber layer), and the inner layer portion The surface part of the other surface that does not become the adhesion surface (about 99.87% of the inorganic fiber layer) maintains the original flexibility without adhesion of the swellable layered clay mineral, so the entire inorganic fiber layer is also highly flexible The surface part of the other side which does not become the inner layer part or the adhesion surface (about 99.87% of the inorganic fiber layer) Since there is no adhesion of the swellable layered clay mineral and the inorganic fibers are not bound to each other, it is possible to shorten the heat transfer distance between the front and back surfaces of the inorganic fiber layer and suppress the thermal cross-linking action that reduces the heat insulation performance.

Next, examples of the present invention will be described in detail together with comparative examples and conventional examples.
Example 1
100% by weight of C-glass composition wool fiber glass having an average fiber diameter of 1.0 μm is dispersed and mixed in water, then wet-made with a normal paper machine, dried at 105 ° C., and has a thickness of 3.0 mm. A glass fiber papermaking sheet having an amount of 420 g / m ² was obtained.
Next, 10 g of synthetic smectite clay (Lucentite SWN manufactured by Co-op Chemical Co., Ltd.) is collected as a swellable layered clay mineral having self-forming properties and a binder function. L4R manufactured by Son Co., Ltd.) was stirred and dispersed uniformly for 5 minutes to obtain a clay aqueous solution having a concentration of 1% by weight with thixotropic properties.
Next, 134 g (solid content 1.3 g) of the clay aqueous solution is uniformly applied with a knife coater to one surface of the front and back surfaces of a sheet (weight 67.2 g) obtained by cutting the glass fiber paper sheet into a size of 400 mm × 400 mm. Then, it is dried with a hot air dryer at 105 ° C., and an adhesion surface of the synthetic smectite clay is formed only on one surface of the front and back surfaces, and the glass fibers on the surface portion are bound and fixed with the synthetic smectite clay, and the synthetic smectite is fixed on the surface. A glass fiber nonwoven fabric sheet (amount of 2% by weight of synthetic smectite clay) on which a breathable coating film of clay was formed was obtained.
Next, two glass fiber nonwoven fabric sheets on which the synthetic smectite clay adhering surface was formed only on one side were laminated so that the adhering surface would be the front and back surfaces, and the vacuum heat insulating material core material of Example 1 was obtained.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1.

(Example 2)
A glass fiber papermaking sheet having a thickness of 3.0 mm and a basis weight of 420 g / m ² was obtained in the same manner as in Example 1, and a clay aqueous solution having a concentration of 2% by weight was obtained in the same procedure as in Example 1.
Next, 134 g (solid content 2.6 g) of the clay aqueous solution is uniformly applied with a knife coater to one side of the front and back surfaces of a sheet (weight 67.2 g) obtained by cutting the glass fiber paper sheet into a size of 400 mm × 400 mm. And dried with a hot air dryer at 105 ° C., and a glass fiber nonwoven fabric sheet having a synthetic smectite clay adhering surface formed on only one surface as in Example 1 to form fiber binding and film formation (about 4 μm thickness) A synthetic smectite clay adhesion amount of 4% by weight) was obtained.
Next, these two glass fiber nonwoven fabric sheets were laminated so that the clay adhering surfaces were the front and back surfaces, and the vacuum heat insulating material core material of Example 2 was obtained.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1. Moreover, the fine structure of the said glass fiber nonwoven fabric sheet was observed with the scanning electron microscope (SEM). The results are shown in FIGS.

(Example 3)
A glass fiber papermaking sheet having a thickness of 3.0 mm and a basis weight of 420 g / m ² was obtained in the same manner as in Example 1, and a clay aqueous solution having a concentration of 4% by weight was obtained in the same procedure as in Example 1.
Next, 134 g (solid content: 5.2 g) of the clay aqueous solution is uniformly applied with a knife coater to one surface of the front and back surfaces of a sheet (weight: 67.2 g) obtained by cutting the glass fiber paper sheet into a size of 400 mm × 400 mm. And dried with a hot air dryer at 105 ° C., and a synthetic smectite clay adhering surface is formed only on one side as in Example 1 to form a fiber binding and film formation (adhesion amount of synthetic smectite clay) 8% by weight) was obtained.
Next, these two glass fiber nonwoven fabric sheets were laminated so that the clay adhering surfaces were the front and back surfaces, and the vacuum heat insulating material core material of Example 3 was obtained.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1.

(Comparative Example 1)
600 g of wool glass fiber raw cotton having an average fiber diameter of 3.5 μm is sampled to form a 1 m ² laminated sheet so that the glass fibers are as uniform as possible, and a metal hot plate so that the density is 0.20 g / cm ^3. It was sandwiched between and heated at 200 ° C. for 2 hours to obtain a nonwoven glass fiber sheet having a thickness of about 3 mm.
Next, two sheets obtained by cutting the sheet into a size of 400 mm × 400 mm were laminated so that the smoother surface was on the outside, and the vacuum heat insulating material core material of Comparative Example 1 was obtained.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1.
In addition, although the said laminated sheet is produced so that the raw fiber of wool-like glass fiber may be extract | collected and glass fiber may become as uniform as possible, it processes directly into a uniform sheet form from an irregular-shaped wool-like glass fiber. The sheet thickness uniformity is inferior to that of the sheet made by the paper making method as in Examples 1 to 3 and the conventional examples described later.

(Comparative Example 2)
In the same manner as in Example 1, a glass fiber papermaking sheet having a thickness of 3.0 mm and a basis weight of 420 g / m ² was obtained.
Next, colloidal silica (Snowtex O, manufactured by Nissan Chemical Industries, Ltd.) was prepared as an inorganic binder, and an aqueous silica gel solution having a concentration of 2% by weight was obtained in the same procedure as in Example 1.
Next, 134 g (solid content 2.6 g) of the silica gel aqueous solution is uniformly applied with a knife coater to one side of the front and back surfaces of a sheet (weight 67.2 g) obtained by cutting the glass fiber paper sheet into a size of 400 mm × 400 mm. And dried with a hot air dryer at 105 ° C. to obtain a glass fiber nonwoven fabric sheet (silica gel adhesion amount of 4% by weight) having a silica gel adhesion surface formed on only one surface.
Next, the two glass fiber nonwoven fabric sheets were laminated so that the silica gel adhering surfaces were the front and back surfaces, and the vacuum heat insulating material core material of Comparative Example 2 was obtained.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1. Moreover, the fine structure of the said glass fiber nonwoven fabric sheet was observed with the scanning electron microscope (SEM). The results are shown in FIG.

(Conventional example)
^Two sheets (weight: 67.2 g) obtained by cutting a glass fiber paper sheet having a thickness of 3.0 mm and a basis weight of 420 g / m ² obtained in the same manner as in Example 1 into a size of 400 mm × 400 mm were laminated, and a conventional example. It was set as the vacuum heat insulating material core material.
Next, the dried core material was inserted into a bag-shaped gas barrier jacket material, vacuumed and fused and sealed to obtain a vacuum heat insulating material, and the thickness and heat insulating characteristics during pressurization were measured. The results are shown in Table 1. The microstructure of the glass fiber papermaking sheet was observed with a scanning electron microscope (SEM). The results are shown in FIG.

From the results shown in Table 1 and FIGS. In addition, FIG. 5 is a graph showing the result of the thickness under pressure measured by pressing the core material of each example at 0.2 to 3.0 kg / cm ² (however, the thickness of the vertical axis is 0.00. 2 kg / cm ² relative thickness with 100% thickness at the time of pressurization).
(1) In the vacuum heat insulating materials of Examples 1 to 3 of the present invention, the front and back surfaces of the inorganic fiber layer are smectite clay 2 to 8 wt% adhering surfaces as the core material composed of the inorganic fiber layer. Part of the glass fiber is fixed with smectite clay and a high-strength film (reinforcing film) is formed on the entire adhering surface, thereby reducing the thickness under a pressure of 0.2 to 3.0 kg / cm ² (thickness). Is significantly improved as compared with the conventional example and Comparative Examples 1 and 2. For example, when the atmospheric pressure equivalent 1.0 kg / cm ² pressure, 0.2 kg / cm ² pressure圧厚Thickness reduction rate from the (reference the "thickness" of the inorganic fiber nonwoven fabric sheet of the present invention) 3.8 to 9.6%, 30.1% of the conventional example that did not use the adhering material, 15.2% of Comparative Example 1 in which thick glass raw cotton was laminated and thermoformed, and the adhering material was Compared to 27.9% of Comparative Example 2 in which silica gel was used, it was greatly improved. Therefore, when the vacuum heat insulating material of the present invention is applied to structural deformation such as pressurization over a long period of time, it is highly possible that the performance can be maintained.
(2) In the vacuum heat insulating materials of Examples 1 to 3, 2 to 8% by weight of an adhesion material that gives fiber binding and film formation to the inorganic fiber layer as a core material composed of the inorganic fiber layer mainly for the purpose of improving pressure resistance. Although introduced, the initial thermal conductivity (thermal conductivity under atmospheric pressure in Table 1) has not deteriorated over the conventional example in which no adhering material was introduced, and the thermal conductivity is kept low, and the heat insulation High performance.
(3) Assuming more excessive deformation, the thermal conductivity under pressure of 2.0 kg / cm ² and 3.0 kg / cm ² is measured. 0 kg / cm ² ) about 0-4% under pressure of 2.0 kg / cm ² and about 4-16% under pressure of 3.0 kg / cm ^2. About 20% and about 40% of the conventional example in which no adhering material was used, about 7% and about 27% of Comparative Example 1 in which thick glass raw cotton was laminated and heat-molded, and Comparative Example 2 in which the adhering material was silica gel Compared to about 17% and about 33%, it is greatly improved. In Comparative Example 1, since the glass fiber diameter is as thick as 3.5 μm, the initial thermal conductivity (thermal conductivity under atmospheric pressure in Table 1) is higher than that of the conventional example in which the glass fiber diameter is 0.7 μm. Although it was inferior by about 20%, the thickness reduction rate was affected by the fact that the density was reduced to about 15% because the density was previously increased to 0.20 g / cm ³ by applying pressure during heat molding. It is estimated that the thermal conductivity under a pressure of 0 kg / cm ² is only about 7%, which is a relatively slight deterioration.
(4) In Comparative Example 2 in which the adhering material was silica gel, the inorganic binder was seen to cover the entire glass fiber and became generally hard, but no improvement effect was seen with respect to thickness reduction. Moreover, because the glass fibers are firmly bonded to each other, the initial thermal conductivity (thermal conductivity under atmospheric pressure in Table 1) is about 20% worse than that of the conventional example in which no adhesive material is used. As described above, this is in contrast to the results of Examples 1 to 3 in which no deterioration was observed from the conventional example in which the adhesion material was not used even though the adhesion material was used.
(5) When FIG. 1 which observed the glass fiber nonwoven fabric sheet of Example 2 is seen, it is confirmed that the smectite clay layer covers the whole surface by the thickness of several micrometers on the surface of a glass fiber nonwoven fabric sheet. No smectite clay is seen inside the sheet, and the smectite clay is solidified only on the glass fiber on the surface of the sheet, and the inside of the sheet maintains the original flexible structure of the papermaking sheet. It is estimated that it can resist without breaking. In nature and industrial materials, it is similar to lightweight and high strength bone and honeycomb structures. As for the reason why such a structure is formed, in the case of a glass fiber nonwoven sheet (porous sheet), when a general binder solution is attached, it easily penetrates from the opening on the surface of the porous sheet, but the smectite clay solution is thixotropic. Therefore, when the smectite clay solution is attached to a nonwoven fabric sheet having a small fiber diameter and a small opening according to the present invention, it cannot penetrate inside, and only adheres in a film form only to the sheet surface. It is to become. FIG. 2 is an enlarged view of the smectite clay adhering portion in FIG. 1. The smectite clay coating is only 4 μm thick, but it consists of hundreds of nano-sized dense clay layers, It can be confirmed that a firm coating is formed on the fiber nonwoven fabric sheet surface and the glass fibers on the sheet surface are firmly fixed.
(6) When FIG. 3 which observed the glass fiber papermaking sheet | seat of the prior art example is seen, since the adhering material is not used at all and the structure is only maintained by the friction between glass fibers, a vacuum heat insulating material core When the material is sealed under reduced pressure as a material, the thickness is reduced by about 30%, and it is difficult to reduce the thickness in recent years and exhibit the performance sufficient to meet the demand for high performance heat insulation.
(7) When FIG. 4 which observed the glass fiber nonwoven fabric sheet of the comparative example 2 is seen, the state which the inorganic binder adhering to the sheet | seat surface has osmose | permeated the inside of a sheet | seat can be confirmed, and the film | membrane of the sheet | seat surface like an Example Cannot be confirmed.

It is a SEM photograph (photographing magnification 1000 times) which image | photographed the surface layer part of the glass fiber nonwoven fabric sheet (cross section) of Example 2 of this invention. It is the SEM photograph (photographing magnification 20000 times) which expanded further the smectite clay adhesion part of FIG. It is the SEM photograph (100 times of imaging magnification) which image | photographed the surface layer-inner layer part of the glass fiber papermaking sheet | seat (cross section) of a prior art example. It is a SEM photograph (photographing magnification 200 times) which photoed the surface layer-inner layer part of the glass fiber nonwoven fabric sheet (cross section) of comparative example 2. It is a graph which shows the result of the thickness at the time of pressurizing and measuring the core material of each example by 0.2-3.0 kg / cm < ² >.

Claims (7)

  In the vacuum heat insulating material, in which a core material composed of a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less is packed with a gas barrier outer covering material, and the inside is decompressed and sealed, the core material However, the inorganic fibers on the surface portion of at least one of the front and back surfaces of the inorganic fiber layer are bound by an inorganic binder made of a swellable layered clay mineral and are substantially composed of only an inorganic substance. Features vacuum insulation.   In the vacuum heat insulating material, in which a core material composed of a non-woven inorganic fiber layer mainly composed of inorganic fibers having an average fiber diameter of 4 μm or less is packed with a gas barrier outer covering material, and the inside is decompressed and sealed, the core material However, it is characterized in that a breathable film made of a swellable layered clay mineral having self-forming properties is formed on at least one of the front and back surfaces of the inorganic fiber layer and is substantially composed of only an inorganic substance. Vacuum insulation.   The vacuum heat insulating material according to claim 1 or 2, wherein the inorganic fiber layer is made of a nonwoven fabric sheet mainly composed of the inorganic fibers.   The vacuum heat insulating material according to claim 3, wherein the inorganic fiber layer is a wet papermaking sheet mainly composed of the inorganic fibers.   The vacuum heat insulating material according to any one of claims 1 to 4, wherein the inorganic fiber layer is mainly composed of inorganic fibers having an average fiber diameter of 1.5 µm or less.   The vacuum heat insulating material according to any one of claims 1 to 5, wherein the inorganic fiber layer is substantially composed only of the inorganic fiber and the swellable layered clay mineral.   The vacuum heat insulating material according to any one of claims 1 to 6, wherein the swellable layered clay mineral is a smectite group.