Patent Publication Number: US-2016236452-A1

Title: Foil-wrapped vacuum insulation element

Description:
The invention is directed to a foil-wrapped vacuum insulation element having a core and a shell surrounding the core. 
     These types of insulation elements often have a sheet- or panel-shaped design, and are used for thermal insulation, for example of buildings, refrigerators or freezers, thermal containers, etc. 
     The functional basis of the vacuum insulation element is that pores that are open, i.e., in communication with one another, are present within the core material which supports the shell, and are evacuated during manufacture. For this reason, within these pores the heat cannot be transported by either thermal conduction or thermal convection, resulting in an extremely good thermal insulation value, so that for the same thermal insulation properties as conventional insulation panels, such vacuum insulation panels have only approximately one-tenth the thickness. 
     However, one problem in the manufacture of such vacuum insulation elements is that during the evacuation, particles may be pulled out of the core, and may then either contaminate the areas of the subsequent sealing seams and make efficient, i.e., pressure-tight, sealing more difficult or even impossible, or they may enter the evacuation pump and damage or even destroy it. 
     To prevent this, it has already been proposed to envelop the core in a nonwoven fabric which is intended to retain entrained particles of the core. However, it has proven to be fairly complicated to completely wrap preformed cores in such a nonwoven fabric; powdered core material cannot be filled into such a nonwoven fabric web anyway. 
     The disadvantages of the described prior art result in the problem on which the object of the invention is based, to refine a generic foil-wrapped vacuum insulation element in such a way that the manufacture may take place easily and preferably by machine, and the particles from the core are reliably retained during evacuation. 
     For a generic foil-wrapped vacuum insulation element having a core and a shell surrounding the core, this object is achieved in that between the core and the shell, one or more layers of paper, cardboard, and/or paperboard are also provided which completely envelop the core, preferably in a powder-tight manner. 
     If the terms paper, cardboard, and paperboard are distinguished from one another in the discussion below, this is to be understood based on common usage, according to which paper has a grammage, i.e., a basis weight, of less than 150 g/m 2 , cardboard has a grammage of 150 g/m 2  to 600 g/m 2 , and paperboard has a grammage of greater than 600 g/m 2 . However, if no distinction is made based on the grammage, the term “paper” may also include cardboard and paperboard. 
     In particular, this is intended to apply to material properties of these substances, which pertain equally to paper, cardboard, and paperboard. These include the following properties: 
     The essential base components of paper, cardboard, and paperboard materials are fibrous materials, in particular wood pulp, semichemical pulp, chemical pulp, and/or recovered paper. Substances for improving the mechanical properties in particular for sizing and impregnation, for example animal glues, resins, paraffins, and waxes, may also be contained in smaller quantities. On the other hand, frequently found fillers such as talc, kaolin, gypsum, barium sulfate, chalk, and titanium white are optional, and are therefore dispensable within the scope of the present invention. Further auxiliary agents such as defoamers, dispersants, etc., are often present for processing reasons. 
     The fibrous materials used, whether wood pulp, semichemical pulp, chemical pulp, and/or recovered paper, contain cellulose. This is a polysaccharide, for example having the empirical chemical formula (C 6 H 10 O 5 ) n . This substance forms the primary component of the cell walls of plants and timber woods. 
     Cellulose is a polymer composed of chain-type macromolecules made up of linked-together monomers in the form of glucose molecules, C 6 H 12 O 6 . Multiple bundles of such chain-type macromolecules constitute so-called micelles, and multiple micelles in turn form so-called fibrils, the base components of the cellulose fibers. 
     In the above-mentioned bundles, there are crystalline regions having a regular molecular arrangement and amorphous regions having an irregular molecular arrangement. The interaction of these different regions results in the typical properties of paper, cardboard, and paperboard, whereby the crystalline regions provide strength and rigidity, while the amorphous regions impart flexibility and elasticity to the substance in question. 
     Within the scope of the invention, all cellulose-containing substances are suitable in principle for paper manufacture. However, since these substances generally do not have to meet any particular requirements, the use of recovered paper, rag, or such recycling materials is particularly suited for this purpose. However, since recovered paper has already been processed once into paper, its fibers are damaged by the previous and new processing, in particular within the scope of the beating step, so that at least further additives should be provided in addition to recycled fibers. Within the scope of the invention, however, this proportion may be kept comparatively low, for example less than or equal to 30% by weight, preferably less than or equal to 20% by weight, in particular less than or equal to 10% by weight. 
     Due to this predominant use of materials which have sometimes been recycled multiple times, on the one hand paper is less expensive than a nonwoven fabric made of a textile material, and on the other hand is thinner, lighter, and more dense, and is therefore better suited for the present purpose than known nonwoven fabric materials, or in any case is just as good. 
     A single paper layer may have a grammage of 40 g/m 2  or more, for example a grammage of 50 g/m 2  or more, preferably a grammage of 60 g/m 2  or more, in particular a grammage of 80 g/m 2  or more, or even a grammage of 100 g/m 2  or more. On the other hand, a single paper layer may have a grammage of 250 g/m 2  or less, for example a grammage of 225 g/m 2  or less, preferably a grammage of 200 g/m 2  or less, in particular a grammage of 175 g/m 2  or less, or even a grammage of 150 g/m 2  or less. The preferred range of the basis weight on the one hand guarantees a high tear strength, but on the other hand limits the added weight thus introduced into the vacuum insulation panel, and ultimately does not significantly increase the thickness of the finished insulation panel; furthermore, paper of this thickness can still be folded well, and may thus have predefined folded edges at the edges of the core in order to support the design of straight edges of the finished vacuum insulation panel. 
     It has proven advantageous to provide multiple, preferably three, layers of paper. The strength of the material, in particular its tear strength, may thus be greatly increased, as the result of which the manufacturing process is less sensitive. 
     It is recommended according to the invention that at least one paper or cardboard layer is joined, preferably glued, to one or two adjoining paper or cardboard layers to form a single layer. Layers of paper or cardboard which are glued together have a higher rigidity than the same number of non-glued layers, due to the fact that the glued layers are not able to move against one another during bending. 
     The flexural strength may be further increased in that at least one of multiple paper or cardboard layers, preferably an inner paper or cardboard layer, has a corrugated profile. Such a corrugated layer allows the distance between the two adjoining layers to be increased. This results in the effect of an upper ply and a lower ply at a distance therefrom, which increases the strength and stability considerably. The result is generally a paperboard, as is also found in larger packaging or moving boxes. 
     It is preferred to provide a total of three paper layers, preferably having a grammage in each case of 40 g/m 2  or more, and/or having a preferred grammage in each case of 250 g/m 2  or less, so that the overall layer made of joined-together layers of paper or cardboard has a total grammage between 120 g/m 2  and 750 g/m 2 , preferably a grammage between 150 g/m 2  and 600 g/m 2 , in particular a grammage between 170 g/m 2  and 500 g/m 2 . An optimal compromise is thus found between maximum tear strength on the one hand and optimal foldability on the other hand. 
     It is within the scope of the invention that the paper is made up of 40% by weight or more of recovered paper, preferably 60% by weight or more of recovered paper, in particular 80% by weight or more of recovered paper. This involves a method for manufacturing the vacuum insulation panels according to the invention in the most environmentally friendly way possible. 
     The ply or layer of paper, cardboard, and/or paperboard may be formed into an open and/or closable hollow body which has approximately the same shape as the finished vacuum insulation element. This results in the option of using an amorphous core material such as a powder or granulate, for example, which is filled into the open and/or closable hollow body and acquires its shape only via the hollow body. The advantage is that the operation of pressing a core may possibly be dispensed with altogether. 
     Due to the fact that the open and/or closable hollow body is produced from a single blank of paper, cardboard, or paperboard, the complexity of manufacturing may be further minimized. The particular shape may be cut out or preferably punched out from a sheet or a roll of the paper, cardboard, or paperboard material in question. 
     Within the scope of one preferred manufacturing method, the paper blank is folded and/or glued in order to form the open and/or closable hollow body. In particular, relatively sharp edges may be produced by folding, which in the finished vacuum insulation panel contribute to avoiding the formation of heat bridges between two adjoining vacuum insulation panels. The desired shape may be stabilized, in particular in the area of the original openings, by gluing. 
     The invention further provides that the paper is formed into a paper bag or into a paperboard box which preferably has approximately the same shape as the finished vacuum insulation element. A paper bag, or also a paperboard box, can completely and seamlessly envelop the enclosed core, and is therefore able to reliably retain the core particles. The paper bag may be a block bottom bag, a square bottom bag, or a cross bottom bag. The bag is preferably folded before it is filled. 
     Further advantages result from the fact that the paper blank is glued to form the paper bag. An adhesive which is suitable for gluing paper may be used for this purpose, for which a wide selection of standard adhesives are commercially available. The blank may preferably first be glued along two longitudinal sides to form a tubular geometry having two ends which are still open. These ends are then glued; preferably, one end is glued prior to filling with the core (material), and the other end is glued after filling with the core (material). 
     In order for a paper bag or a paperboard box to assume the desired shape as exactly as possible, it is folded during manufacture. This may sometimes take place before, between, or after one or more gluing or joining steps. 
     For a paper bag, it is recommended that this be carried out after the first gluing step, in which the blank assumes a tubular shape, and optionally before, during, or after the further method step in which the base is closed, in particular by gluing. 
     In contrast, a folding box may be stabilized and closed without gluing. In this case, the folding preferably takes place immediately after the punching, and when all folded edges are applied, the box shape may be assembled by bending over the folded edges. For the subsequent filling, initially an opening is left which ultimately is closed, for example by a preferably one-piece lid. 
     After being folded up, the box has a preferably rectangular or square base, and a border running along its perimeter, a side wall being folded upwardly in each case along each straight edge section of the base. To keep the filled core material from escaping or trickling out during and after filling of this box body in the area where two such side walls in each case meet in the region of a vertical edge, the invention provides that two adjoining side walls, i.e., vertical border or end-face surfaces, are joined together in the area of their mutual edge, preferably without gaps, up to the filling opening at the top side. 
     This may be achieved on the one hand by applying an adhesive tape above and along the vertical edge on the outside and/or inside. 
     On the other hand, it is also possible to leave a tab in the blank in the area of such an edge, on at least one side wall bordering same; the tab may then be bent over the vertical edge in question in order to lie flatly against the adjoining side wall. 
     This tab may then be joined to this adjoining side wall in a form-fit and/or integrally joined manner. 
     An integral bond is achieved by gluing over the surface, for which purpose an adhesive applied in liquid form is easily sufficient. 
     A form fit may be achieved by the bent-over tab being encompassed on the inside and outside by the adjoining side wall. For this purpose, the adjoining side wall should have an attached tab which, however, is preferably integrally molded onto the free longitudinal edge of the side wall (the subsequent upper edge of the body), or for the blank, is left thereon. If this tab is bent over just to this upper edge of the body, and in particular over the one or two lateral tabs in the area of one or both vertical edges of this side wall, the mutually abutting side walls are joined in a form-fit manner. For this purpose, it is advantageous for the tabs to preferably have a rectangular or trapezoidal shape, and for their parallel extension with respect to the height of the body to correspond to the height thereof, so that when an attempt is made to swing away a side wall, the tabs abut from the inside against the overlapping part between the inner and outer layers of the side wall which is bent over same. 
     To prevent the lid from inadvertently coming open during transport and/or temporary storage, it is recommended that the lid in the closed state is fixed to the body of the box, for example by means of an adhesive tape affixed over the closure gaps. 
     In particular for vacuum elements or vacuum insulation panels having an even border, the basic design may thus be reduced to an appropriate fold of a paper, cardboard, or paperboard blank which is punched out or cut out to size. In vacuum insulation panels commonly used heretofore, the high-barrier foil surrounding the core acquires its dimensional stability from a core which is pressed in the desired shape. The novel structure of a vacuum insulation panel makes it possible to do without a shaped core material. Rather, not only the wrapping foil, but also the core which supports it then acquires its shape solely from the paper, cardboard, or paperboard material which is punched out and folded in the desired shape, provided that this material has sufficient dimensional stability. 
     The invention may be refined in that a paper bag or a paperboard box has at least one filling opening which is closed after filling with the core material. Depending on the manufacturing method, it is possible to fill the core material into this filling opening in the powdered state, so that the core material, optionally together with the wrapping with a foil, is pressed at the earliest after the bag or the box is closed, or a core which is already pressed in the appropriate shape is inserted through the filling opening. In the case of a box, a pressing operation may even be dispensed with altogether, provided that the paperboard of the box is stiff enough to maintain its shape unchanged, at least until the evacuation step. 
     After the core material is filled in, the filling opening of the paper bag may be closed by means of an attached tab, which may be glued, for example. 
     In the closed state, the tab may preferably cover an end face of a panel-shaped vacuum insulation element. Consequently, the paper bag is weakened as little as possible due to the fact that the shape of a deep, flat pocket is relatively stable. 
     In the case of a paperboard box, it may be more advantageous for the filling opening of the paperboard box to be closed by a lid after the core material is filled in, for example by folding shut a lid which hangs on the body on one side, or by placing a loose lid on top. Such a lid may have at least one tongue which is delimited by a folded edge, preferably along a free edge facing away from or opposite from the joining edge between the lid and the body of the box. Such a tongue may then be optionally inserted inside the box in order to stabilize the lid. However, the lid should preferably engage externally over the body so that it does not conflict with an already filled powder or some other mixture when the lid is folded shut or placed on top. Therefore, a lid should have an apron which runs along the base area of the lid and which engages via an edge that protrudes upwardly along the base area of the body. For a loose lid, the apron and the edge should each run along four sides of the base area in question; for a lid which hangs on the body, the apron and the edge need run only along the respective three free sides. 
     To prevent the lid from being inadvertently flipped open, it may be joined to the body of the box with adhesive tape or in some other way after the core material in powdered form, for example, is filled in. 
     Due to the fact that the lid, as further provided by the invention, in the closed state covers a base surface or main surface of a panel-shaped vacuum insulation element, a filling opening of maximum size is available; the filling may therefore be carried out very easily by filling the box from the top with the lid open. On the other hand, the lid, which is still open, generally does not cause an appreciable loss of stability, since the box paperboard used is comparatively solid and stable. 
     A further design condition provides that the paper bag or the paperboard box has at least one ventilation opening which allows the contained air to escape when the core material is filled in and/or when the paper bag is compressed or evacuated. Despite the desired property of the paper bag of reliably retaining the particles of the contained core or core powder, the bag should allow the likewise enclosed air to escape, so that no air cushions adversely affect the process step in question and/or delay the manufacturing process during the filling, pressing, and/or evacuation. 
     To implement the above feature, the invention further provides that a ventilation opening is formed by one or more perforations, in particular one or more needlings. Such a processing step leaves only punctiform openings, which hardly allow particles to escape but which do not represent a hindrance for air. 
     Further optimization may be achieved by the paper bag or the paperboard box having at least one valve or at least one valve area. 
     Such a valve may in particular assist with the function of preferably completely retaining the powder, in that it further reduces the potential clear opening diameter of a ventilation opening. This function is rather comparable to a filter which retains particles but allows gaseous substances to pass through. 
     Due to the fact that such a valve has the structure of a one-way valve, it is able to prevent escaped air from flowing back into the interior of the paper bag. Undesirable aeration during a storage phase within the scope of the manufacturing process is thus hindered or avoided. 
     One option for implementing a valve function is to provide perforations or needlings in all paper layers, but which are offset with respect to one another, in the area of a valve. Air, water vapor, and gas may thus escape from the interior of the paper bag, while particles are retained, since they cannot find a clear opening through which to escape. 
     The core material is preferably made of a powder of a porous, in particular open-pored, material and/or is pressed from such a material. Fumed silica is an example of a suitable material. However, fibrous materials such as glass fibers may also be used. 
     Lastly, the teaching of the invention provides that the shell includes a metal foil, in particular an aluminum foil, and/or a metallized foil, in particular a high-barrier foil. Such a high-barrier foil may have a supporting layer which is made of a plastic, and which is provided on one side with a metallization, and on the opposite side with a sealing layer, preferably a coating of a thermoplastic material. In addition, an aluminum foil should have a low-melting and therefore sealable coating on one side, made of a plastic, in particular a thermoplastic material. 
    
    
     
       Further features, particulars, advantages, and effects based on the invention result from the following description of several preferred embodiments of the invention, and with reference to the drawings, which show the following: 
         FIG. 1  shows a perspective view of a paper bag which is filled with core material, with a cross bottom bag fold, prior to the enveloping in a foil; 
         FIG. 2  shows an illustration, approximately corresponding to  FIG. 1 , of a modified embodiment of the invention with a flat bag fold; 
         FIG. 3  shows another modified embodiment of the invention, with a square bottom bag fold in an illustration corresponding to  FIG. 1 ; and 
         FIG. 4  shows a still unfilled paperboard box for yet another modified embodiment of the invention, in a perspective illustration. 
     
    
    
     The manufacture of a vacuum insulation element according to the invention is as follows: 
     First, a paper bag  1  is produced. 
     For this purpose, paper is selected which, for example, is manufactured using primarily recovered paper, preferably having a basis weight between 50 and 100 g/m 2 . 
     Within the scope of the invention, at least one web or one sheet of the paper is perforated at predefined locations by means of one or more needles. 
     Multiple webs or sheets of this type are then cut off and/or selected and placed on top of one another or joined together in such a way that the perforations in respectively adjoining layers are slightly offset with respect to one another, in particular in such a way that the perforations do not overlap one another at all, but instead preferably even have a fairly large spacing between them. Approximately three paper layers preferably lie one above the other. 
     Next, these overlayered paper sheets or combined paper webs are glued to form a multilayer paper composite. It should be ensured that no adhesive is able to enter the area of the perforations. 
     A blank having a suitable, preferably rectangular, outline is then produced, for example punched out or cut off, from this multilayer paper material. 
     Two oppositely situated longitudinal sides of this blank are then glued together, using an adhesive that is suitable for paper. The paper blank thus acquires the shape of a tube. 
     This tube is then preferably folded in such a way that folded edges  2  extending in the longitudinal direction result. Depending on the manufacturing method, this step could also take place before the longitudinal edges are glued. Two, four, or six folded edges  2  extending in the longitudinal direction of the tube could be provided, depending on the folding method. 
     One end of this tube is then closed. For this purpose, the borders of the blank are folded inwardly at an end which is still open, at fold lines  3  which extend transversely with respect to the longitudinal edges  2 , optionally forming further folded edges  4  in the area of the corners  5  of the future paper bag  1  which are formed by the longitudinally and transversely extending folded edges  2 ,  3 . 
     Next, this end of the tube  1 , which is still open, is closed by gluing together the inwardly turned border areas  6  of the blank, likewise by means of an adhesive that is suitable for paper. 
     The core material is now filled into the paper bag  1 . An open-pored material, for example fumed silica, is used for the core. This material may either be filled into the bag in the powdered state, or prior to filling it may be pressed into the desired shape of the vacuum insulation element in question and then inserted into the paper bag  1  as a block- or panel-shaped body, for example. 
     When this is done, the paper bag  1  is closed at its last remaining open end, likewise by means of an adhesive that is suitable for paper. Either prefolded fold lines  3 ,  4  may be used, in particular when powdered core material is used, or the folds  3 ,  4  in question are made over the edges of a prepressed core body, i.e., by simply folding a corresponding border area  6  over the edges of the core in question. It is possible to provide further folds  4 , in addition to the folded edges  3  which extend transversely with respect to the longitudinal edges  2  of the original tube, in the corner areas  5  where these transverse folded edges  3  meet the longitudinal edges  2 , so that areas of the paper blank which protrude in the corners  5  may be folded over one another in multiple layers. 
     In a subsequent method step the paper bag  1  is closed, in particular glued, at its last remaining open end. 
     Due to the type of blank and its folding and optionally gluing, the finished paper bag  1  now has a flat, cuboidal shape, for example, with two large, approximately rectangular base areas  9  which are joined together at their four mutually corresponding edges by further faces, namely, along their shorter edges  3 , by means of smaller end faces  6  and via longer end faces  8  in the area of the longitudinal edges  2 . Naturally, due to the flexible, foldable paper material, these faces  6 ,  8 ,  9  are not actually flat and stable, and instead are puckered inwardly and outwardly, as seen in  FIG. 1 . However, the above-mentioned faces are at least fairly flat due to the various folds  3 ,  4 ; a folding triangle  10  may be present in the joint areas between every two end faces  6 ,  8  of different lengths in order to fold away excess paper. 
     After this is done, there are multiple method variants. If the core material has been filled in as a powder, the completely closed paper bag  1  may subsequently be pressed into the desired shape of the finished vacuum insulation panel. 
     Otherwise, in particular if a preformed core has been inserted into the paper bag  1 , this work step may be omitted, and instead the operation now described, in which the closed paper bag  1  is wrapped in a foil, takes place immediately. 
     This foil may be a metal foil, for example, in particular an aluminum foil or a high-barrier foil, wherein a supporting foil layer made of a plastic is provided on one side with a metal layer, for example is vapor-deposited with the metal in question, while a sealing layer made of a low-melting thermoplastic is coated on the opposite side. 
     A blank is produced from the selected foil, similarly as for the blank for the paper bag  1 . Ideally, the blank for the foil may be identical to the blank for the paper bag  1 . However, two preferably congruent foil blanks, each of which has a slightly larger surface area than the base area of a panel-shaped core, may also be produced. 
     The foil is now placed around the paper bag  1 . 
     For this purpose, when a single foil blank is used, preferably in a first method step the foil is wrapped completely around the paper bag  1  in one direction until it encloses the paper bag in a tubular manner. A first sealing seam is then created, thus sealing together the two directly adjoining edges of the foil blank after the paper bag  1  is wrapped, resulting in a tubular geometry. 
     At least one of the two ends of this foil tube is completely closed in a subsequent method step. 
     With a flat core body, this may take place in particular in that the two flat end areas lie directly one on top of the other by folding in the end areas in question and sealing them to one another. On the other hand, for this purpose the foil may also be turned inwardly at the narrow sides, and protruding foil sections may be folded away in the corner areas by creating additional folded edges which meet in the area of a corner of the core body or of the paper bag  1  which surrounds it. 
     The oppositely situated tube end of the foil may also be closed, at least partially, preferably leaving an evacuation opening. 
     When two foil blanks are used, they are arranged approximately congruently with respect to one another, above and below the body or paper bag  1 , with their sealing layers facing one another. The core is situated in the appropriate orientation therebetween, similar to the filling between the two pieces of bread in a sandwich. The two protruding border areas of the foil blanks may then be sealed together all around, with only an evacuation opening remaining. 
     An evacuation opening may be situated at any desired location in the area of any sealing seam, or at some other suitable location, but preferably in the vicinity of one or more perforations or other ventilation openings in the paper bag  1 . Normally, a single evacuation opening is sufficient overall, although multiple evacuation openings could be provided. 
     If it has not already been done, the vacuum insulation element which has been finished but not yet evacuated may now be brought into its desired shape, preferably by means of a press, which compresses the vacuum insulation element in particular in a direction perpendicular to its base area. 
     In a subsequent manufacturing step, the vacuum insulation element, which is not yet evacuated, is now placed in a vacuum chamber and evacuated, for example to a pressure of less than 100 mbar, preferably to a pressure of 10 mbar or less, in particular to a pressure of 1 mbar or less. In the process, the air still contained flows outwardly through the perforations in the bag, without particles of the core also being able to follow due to the fact that they are retained by the paper bag  1 , and unlike the air, are not able to escape. 
     The evacuation opening(s) still remaining is/are closed, in particular sealed, during this evacuated state, and the vacuum insulation element is finished. 
     The embodiments of the paper bags  1 ,  1 ′,  1 ″ according to  FIGS. 1 to 3  differ from one another primarily by the folding technique used. 
     A fold of the paper bag  1  according to the cross bottom bag principle is depicted in  FIG. 1 . Visible are only two longitudinal edges  2 , as well as a base which is formed by the folded-over border areas  6  and which extends approximately at right angles to the adjoining faces of the filled paper bag  1 , and which in this application forms an end-face side of the finished vacuum insulation panel. In the cross bottom fold there are two four transverse folded edges  3 , but only two pronounced longitudinal folded edges  2 . 
       FIG. 2  shows a paper bag  1 ′ which is filled with core material and folded according to the flat bag principle. This means that there are no end-face sides characterized by folds, but, rather, similar to an envelope, there are two longitudinal fold edges  2 ′ and an adhesive  7  running in the longitudinal direction, but only two transverse folded edges  3 ′ extending transversely thereto. This paper bag  1 ′ has the approximate shape of an envelope. 
     In contrast,  FIG. 3  shows a paper bag  1 ″ which likewise is filled with core material and provided with folds similar to a square bottom bag. There are once again four pronounced end-face sides here, similarly as for the paper bag  1  according to  FIG. 1 ; however, the two longitudinal end-face sides  8  here, extending in the longitudinal direction, i.e., parallel to the longitudinal edges  2 ″, are separated from the two bag base sides  9  by fold lines  2 ″. Thus, there are a total of four transverse folded edges  3 ″ and a total of six longitudinal folded edges  2 ″, four of which each form a convex edge viewed from the outside, and the two remaining folded edges are originally concavely folded but stretch out in the filled state. 
     All embodiments share the common feature that a valve function is preferably provided, preferably due to offset perforations in the various paper layers of the paper bag  1 ,  1 ′,  1 ″ in question, which allows air to escape from the paper bag  1 ,  1 ′,  1 ″, but not particles of the core material contained therein. 
     The illustration according to  FIG. 4  concerns a slightly modified embodiment of the invention. This is a folded bag which is not made of a lightweight and thus very flexible paper for filling in the core material, but, rather, is a folded box made of a stiffer cardboard or paperboard material. Although this box may generally be made of cardboard or also paperboard, in the following discussion and within the scope of this overall patent application the term “paperboard box” is to be used in a representative sense. The term “paperboard box” is thus intended to also encompass boxes made of cardboard. One difference between cardboard and paperboard was mentioned at the outset, and concerns the grammage, and thus naturally also the strength of the material in question. 
     A further, optional feature is that multiple layers may be present which are joined together, for example glued to one another. It is also possible for an inner layer to have corrugation, so that due to the corrugation there is a distance between two outer layers adjoining the inner layer on both sides which corresponds approximately to the overall height or thickness of the corrugation. Paper or cardboard layers adjoining same on both sides may thus fulfill the function of an upper ply and a lower ply, similarly as for bending of building materials under load. The overall material composite thus acquires much higher flexural strength than one or more single layers that are not joined together. 
     It is also apparent from  FIG. 4  that the paperboard box  11  is made up essentially of a body  17  and a lid  20 . 
     The body  17  as well as the lid  20  preferably each have a large rectangular or square box base area  19 ; these two box base areas  19  have the same shape and also approximately the same size. However, for closing, the lid  20  is pulled over the body  17  and overlaps it, preferably on its outer side; for this reason the lid base area  19  should have approximately twice the thickness of the cardboard or paperboard material, and should be longer and also wider than the body base area  19 . 
     An approximately vertically projecting longitudinal end face  18  adjoins, in each case via one fold each along a front and a rear longitudinal edge  12  of the body base area  19 . 
     Similarly, the body base area  19  continues at its two lateral edges  13 , in each case in the form of a right and a left border face  16 . 
     A vertical edge  14  is situated in the corners  15  of the box base area  19  of the body  17  where a longitudinal end face  18  and a lateral border face  16  meet in each case. Since all faces  16 ,  18  which extend upwardly from the box base area  19  of the body  17  are thus joined together, the body  17  has approximately the shape of a cuboidal trough that is closed at the bottom and at four sides and is open only at the top. Powdered or fibrous core material may be easily filled therein, preferably exactly enough so that the body  17  is filled up to the very top. 
     To prevent the quantity of powder or fibers from falling out along the vertical edges  14 , the faces  16 ,  18  projecting upwardly from the box base area  19  of the body  17  should be joined together in the area of the vertical edges  14 . This may take place, for example, in that on the blank for the body  17 , tabs hang at the lateral end-face edges of the areas which are attached at the front and the rear and which later form the longitudinal end faces  18  by folding upwardly, these tabs in each case protruding outwardly beyond the lateral end-face edges. After these longitudinal end faces  18  are folded up at the folded edges  12 , two tabs each may be folded inwardly over the longitudinal end faces in the area of the same border face  16  along the edges  14 , i.e., folded toward one another until they are in a shared plane. In addition, a tab may hang at the free upper edge of the border face  16  in question, the tab being approximately the same size as the particular border face  16  itself. After a border face  16  is folded up on the outside, next to the tabs of the front and rear longitudinal end faces  16  at this location, this tab may be folded in at its upper edge at the border face  16  in question, and lastly, folded down, so that in each case it engages inwardly around a total of two tabs of the longitudinal end faces  18 . 
     The lid  20  is used for also closing the body  17  of the paperboard box  11  at the top. There are several options for the structure of the lid. 
     In a first embodiment not depicted in the drawing, the lid  20  may be produced as a part that is completely separate from the body  17 , having the same shape as the body but slightly larger, so that in the state which is lowered with respect to the body  17 , wherein the base area  19  of the lid  20  is thus on top, i.e., above the border and end faces laterally adjoining same and extending downwardly therefrom in an apron shape, the lid may be pulled over the body  17  in order to close it. For fixing, adhesive tape may then be affixed along all four edges, with approximately one half of the tape running along the body  17 , and the other half running along the lid  20 . 
     However, in the embodiment depicted in  FIG. 4 , the lid  20  is not separate from the body  17 . 
     Instead, the base area  19  of the lid  20  hangs over a folded edge  21  at the rear longitudinal end face  18  of the body  17 , thus adjoining the upper edge of the body. 
     In each case a border face  24  and end face  25  are situated at the opposite edge  22  of the lid base area  19  and at its two lateral edges  23 , and extend perpendicularly thereto. 
     The heights of the border face  24  and of the two lateral end faces  25  of the lid  20  are preferably equal. 
     The two border faces  18  and the two lateral end faces  16  of the body  17  are likewise preferably the same size. 
     Lastly, the common height of the border faces  24  and end faces  25  of the lid  20  should be equal to the common height of the border faces  18  and end faces  16  of the body  17 . 
     The border faces  24  and end faces  25  of the lid  20  which hang downwardly in an apron-like manner, the same as the border faces  16  and end faces  18  of the body  17 , may be joined together in the areas of the corners  26  or the shared edges, for example based on the folding principle described above with reference to the body  17 . 
     Even for a loose lid, the border faces and end faces  16 ,  18 ;  24 ,  25  of the body  17  and/or of the lid  20  which adjoin one another in each case may be joined together in the area of some or preferably all vertical edges  14  by appropriate folding. 
     If the lid  20  is pivoted downwardly at the folded edge  21  and pulled over the outer faces  16 ,  18  of the body  17 , the overall result is a strictly cuboidal shape with pronounced edges  12 ,  13 ,  22 ,  23  and corners  15 ,  26 . 
     If the paperboard box  11  is thus closed by the lid  20  after filling the body  17  with the core material, the lid  20  may be glued to the lower base area  19  of the body  17  in the area of one or more of its three free edges  27 , and thus closed. 
     The body may then be enveloped by a vacuum-tight foil, and after its contents are evacuated, the enveloping foil which initially incompletely encloses the body may be welded completely, and thus air-tight. Pressing of the contents is possible when the paperboard box  11  is used, in particular when the lid  20  engages over the body  17 . 
     To simplify the evacuation operation, also for the paperboard box  11 , valves which allow air, but not particles, to escape may be mounted at one or more locations. However, the slits in the area of the free end-face edges  27  of the lid  20  may fulfill a similar function; these slits form a type of artificial valve, in particular for a lid  20  which is pressed firmly onto the body  17 , which allows gases such as air to escape, but not particles. In this regard, for adhering the lid  20  to the body  17  it may be advantageous to use an air-permeable adhesive tape in order to allow air to escape on all sides at this location. 
     
       
         
           
               
             
               
                   
               
               
                 List of reference numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1 
                 Paper bag 
               
               
                 2 
                 Longitudinal edge 
               
               
                 3 
                 Folded edge 
               
               
                 4 
                 Folded edge 
               
               
                 5 
                 Corner 
               
               
                 6 
                 Border area 
               
               
                 7 
                 Adhesive 
               
               
                 8 
                 Longitudinal end-face side 
               
               
                 9 
                 Bag base side 
               
               
                 10 
                 Folding triangle 
               
               
                 11 
                 Paperboard box 
               
               
                 12 
                 Longitudinal edge 
               
               
                 13 
                 Folded edge 
               
               
                 14 
                 Edge 
               
               
                 15 
                 Corner 
               
               
                 16 
                 Border face 
               
               
                 17 
                 Body 
               
               
                 18 
                 Longitudinal end face 
               
               
                 19 
                 Box base area 
               
               
                 20 
                 Lid 
               
               
                 21 
                 Folded edge 
               
               
                 22 
                 Edge 
               
               
                 23 
                 Edge 
               
               
                 25 
                 Border face 
               
               
                 25 
                 End face 
               
               
                 26 
                 Corner 
               
               
                 27 
                 Edge