EP0504311B1 - Process for the manufacture of thick-walled shaped articles for use, in particular, for packaging purposes - Google Patents

Abstract

In the process described, the raw material, in particular recycled paper and/or waste cardboard, in the form of an aqueous suspension, is brought by a suction filter out of suspension and on to a perforated surface (3) the shape of which corresponds to that of the packaging article (VS). In order to manufacture shaped articles (VS) of this kind with sufficiently thick walls by suction filtering, the process disclosed calls for the suction effect on the raw material in the suspension to be exerted in the suction filter through spaced holes (5) in the suction surface (3) and through a bed (6), consisting of one or more layers, located directly on the suction surface. This bed, which transmits the suction effect, has mesh apertures which are smaller than the holes in the suction surface.

Description

The invention relates to a method and a suction mold for the production of thick-walled shaped pieces, in particular for packaging purposes.

Methods and suction forms for the stated purpose are known, for example according to the Paper Trade Journal, November 13, 1953, pp. 175-180. Such a method and corresponding suction molds can be used to produce moldings which, however, are only relatively thin-walled and therefore relatively soft, ie are to a certain extent unstable. In order to be able to remove them from the suction mold at all with the appropriate thin walls, these fittings require a dewatering and drying treatment immediately following the suction molding. Such known fittings are sufficient, for example in the form of "egg crates" or bowl-like fruit and vegetable underlays despite their thin walls, but they are not suitable for replacing polystyrene fittings which are necessary for heavier ones To fix objects, for example devices of all kinds or device parts in a packaging box, although this would be highly desirable from an environmental point of view. For this reason, devices, device parts or, for example, wine and champagne bottles are still placed in shape-matched polystyrene moldings and in appropriate cardboard packaging, since only with such moldings can packaging and packaging be protected against breakage and also ensure safe shipping and transport. The replacement of polystyrene fittings by fittings based on easily and environmentally friendly decomposable fibrous material was previously opposed to the fact that with such a raw material, as mentioned, only fittings with small wall thicknesses could be produced which, on the one hand, could not be used immediately after suction molding due to a lack of individual stability in the wet state Suction form can be removed, which would be desirable in the sense of a rational production and the other because of their Thin walls for heavier packaged goods cannot offer the necessary resistance to movement and breakage within a packaging box. With regard to such fittings, reference is made to US Pat. Nos. 3,016,177 and 3,115,450, which, however, can only be produced from appropriately prepared fiber pulp and are thin-walled (up to 3 mm maximum) and which therefore also require a strong rib-like structuring in order to be able to use them to make it sufficiently stiff at all. Relevant suction forms are known from DE-A-26 44 487 and from EP-A-0 153 101, with which molded articles with a wall thickness somewhat larger than 3 mm seem to be producible, but which still leave something to be desired in terms of their stability and cannot readily be used as a replacement for the aforementioned polystyrene packaging moldings.

The invention is therefore based on the object to improve the known method of suction molding and the suction molds necessary for this in such a way that, in particular from waste paper and / or cardboard waste in shredded form, substantially more stable molded articles should be able to be produced.

This object is achieved with a method of the type mentioned according to the invention in that
that at least one other, smaller suction molding tool is kept at a distance from and in the suction molding tool and this smaller suction molding tool is simultaneously placed under suction pressure with the other larger suction tool, and the two resulting molded pieces are formed into a coherent molded piece.

With regard to the suction mold for carrying out the method, it consists of a suction box with a vacuum connection and with a suction surface corresponding to the desired shape of the packaging molding, the suction surface being made of a dimensionally stable support with holes distributed over the suction surface and spaced apart from one another, and that the support is suitable for molding with at least a fine-meshed layer, such as a mesh, grid or fabric layer is covered, the mesh size of which is kept smaller than the cross section of the holes. Based on this, and according to the invention it is provided that at least one further suction surface with a separate suction box is arranged on the suction side is associated with its area close to the other suction surface at a distance that corresponds to a maximum of twice the wall thickness of the packaging molding to be produced.

Surprisingly, it has been shown in this procedure according to the invention in connection with the specially designed suction mold design that wall thicknesses for fittings of this type can be achieved in the connection area which correspond to twice the wall thickness previously achievable, with which moldings produced in this way are not only immediately removed or removed from the suction mold can be removed, but these then have the necessary inherent stability even in the dry state, in order to be able to serve as a replacement for the polystyrene moldings previously used for this purpose.

At the end of the suction process, the negative pressure is maintained for a certain period of time in order to at least roughly dewater the molding, which, however, due to its wall thickness and despite the residual water content that is still present, is already so stable that it can already be removed from the suction mold can while maintaining its specified shape. In addition, however, the larger wall thickness after drying of the shaped part also ensures that it has sufficient stability or rigidity to be able to serve as a replacement for the polystyrene shaped pieces.

In the method according to the invention, waste paper and / or cardboard waste can be used without further notice, which only requires comminution but does not require preparation for fiber digestion, that is to say the wastes comminuted into chips are merely added to the suspension liquid, softened and then the suspension enriched with chips can be used can be processed directly.

It does not matter if the waste contains very isolated plastic film chips, which are often found in paper and cardboard waste. It has been found that the presence of plastic chips in the finished shaped pieces is even advantageous, since these contribute to the increased strength of the shaped pieces, but more than 5% plastic chips should not be included.

As has been shown, it is also not absolutely necessary to add additional binders to a suspension of chips in the water, since in any case sufficient chip cross-links result during the suction process, which then impart a sufficiently stable internal structure to the respective molded part when it is finished. In addition, the raw material to be processed also brings with it a certain proportion of binder that has dissolved in the suspension. If binders are still added to the suspension, then such binders are suitable as are customary in paper production, for example rosin saponified with boiling soda solution or sodium hydroxide solution, but also phenolic resins, coumarone resins, montan resins or resins from pulp liquor. In addition to resin glues, casein, starch, animal glue, water glass or the like can also be used as additives for the sizing.

The method according to the invention, the associated suction form and further advantageous and practical embodiments are explained in more detail below with the aid of exemplary embodiments.

Fig. 1

stark vergrößert einen Abschnitt der Saugfläche mit einem entsprechenden Abschnitt das darauf angesaugten Rohmaterials für die Ausbildung des Formstückes;

Fig. 2

noch stärker vergrößert einen Schnitt durch die erfindungsgemäß ausgebildete Saugfläche;

Fig. 3

eine Draufsicht auf die Saugfläche von der Rohmaterialauflageseite aus gesehen;

Fig. 4

einen Schnitt durch einen Saugkasten Art;

Fig. 5

einen Schnitt durch einen Saugkasten in besonderer Ausführungsform;

Fig. 6

die Ansicht eines Formstückes von der "Rohseite" her gesehen;

Fig. 7

einen Schnitt durch das Formstück gemäß Fig. 6 in Verbindung mit einem zu verpackenden Gegenstand;

Fig. 8, 9

im Schnitt besondere Ausführungsformen der Saugfläche;

Fig. 10

perspektivisch und geschnitten das Beispiel eines Formstückes und

Fig. 11

ein Fließschema des Verfahrens.

It shows schematically

Fig. 1

greatly enlarges a section of the suction surface with a corresponding section of the raw material sucked thereon for the formation of the molding;

Fig. 2

an enlarged section through the suction surface designed according to the invention;

Fig. 3

a plan view of the suction surface seen from the raw material support side;

Fig. 4

a section through a suction box type;

Fig. 5

a section through a suction box in a special embodiment;

Fig. 6

the view of a fitting seen from the "raw side";

Fig. 7

a section through the molding of Figure 6 in connection with an object to be packaged.

8, 9

on average special embodiments of the suction surface;

Fig. 10

perspective and cut the example of a fitting and

Fig. 11

a flow chart of the process.

First, the basic structure of a suction mold is described.
As can be seen from FIG. 4, the suction mold consists of a suction box 1 with a vacuum or vacuum connection 2 and a suction surface 3 adapted to the desired shape of the shaped piece VS. If the suction box 1 is provided with a cover 9, as shown in FIG. 4 is, this has a correspondingly large inflow connection 10 for the suspension, through which the suspension flows when the entire molding box 1 is exchanged for the suspension in the mold cavity. In order to be able to produce shaped pieces VS with a wall thickness S of at least 4 to 6 mm with such a suction mold, the suction surface 3 according to FIG. 1 is designed in such a way that the suction surface 3 consists of a dimensionally stable support 4 with holes distributed over the suction surface and spaced apart from one another 5 (see also FIG. 3), the carrier 4 being covered on the side on which the shaped piece VS is to be formed with at least one fine-mesh layer 6 such as a mesh, grid or fabric layer (for example made of nylon), whose mesh size is kept substantially smaller than the cross section of the holes 5. The holes 5 have a diameter D of 1 to 2 mm, preferably 1.5 mm and a distance A from each other of 4 to 6 mm, preferably 5 mm. 6 wire mesh is preferably used for the layer, which has a wire thickness of 0.2 to 0.4 mm, the wires 7 in the fabric having a distance A 1 of 0.3 to 0.5 mm. It has proven to be particularly advantageous and effective that the crossing wires 7 of the fine-meshed layer 6 extend in two planes E, as illustrated in FIG. 2. The enlarged representation according to FIG. 2 shows and, as indicated by arrows, that there are to a certain extent cross-currents in the layer 6, which are obviously also decisive for the fact that the raw material in the sludge deposits on the layer 6 in the desired large layer thickness can, which is not possible, if only a sieve-like, relatively thin and only a limited negative pressure suction surface was used, which clogged accordingly quickly and thus set the layer thickness too early. Of course, several very thin layers 6 can also be arranged one above the other, each of which has a maximum thickness of only about 1 mm. This layer 6 must therefore not be a correspondingly thin and merely perforated sheet, since no transverse flow can arise on such a sheet. In the case of a multilayer configuration of the layer 6 (see FIG. 8), the mesh size of the individual layers may well be the same or approximately the same as the size of the holes 5, since this results in a staggering of the passages in the depth. Depending on the choice of material for the layers 6, one or more layers 6 can also take over the function of the carrier 4, ie replace it, the layer 6 ′ on the suction side imparting its fine surface structure to the shaped piece. With such a design it is of course a prerequisite that the material for the layers 6 is a dimensionally stable material, ie it must not be a soft textile fabric, for example.

The material to be used for the formation of the layer 6 can be both dimensionally stable and, preferably, dimensionally stable material, in the latter case there being the possibility, for example, of the layer 6 by pressing in corresponding tools of the shape of Adjust carrier 4 and to fix them on the carrier 4 in a suitable manner. The top view (in the direction of arrow P according to FIG. 2) in FIG. 3 corresponds to the dimensions of an actual embodiment in which the holes 5 have a hole size of approximately 1 mm in diameter, the layer 6 having a mesh size two to four times smaller, and further comprising flat F and strip-shaped waste SA, as shown, in the supplied slurry. Flat wastes, i.e. chips, have sizes of about 1 to 6 cm², with which the best results could be achieved. Stiff-shaped, that is, sauerkraut-like waste SA, such as is obtained when comminuting, for example, file papers, has dimensions of about 1 to 5 mm in width and about 10 to 30 cm in length.

The suction surfaces 3 in the mold boxes 1 according to FIGS. 4, 5 are shown there in the simplest form. Other and much more complicated shapes of the carrier 4 and the associated layer 6 are, however, readily possible, care being taken only to ensure that there are no areas in which the suction-effective areas shield one another, which prevents precipitation or suction of raw material particles.

Particularly in view of more complicated shapes of the fittings and the associated, difficult formability of the molded part, but also with simple shapes, as shown, there is an advantageous embodiment of the suction mold F is to make these at least two parts and thus the moldings F₁ and F₂ movable apart . In the case of a simple molding box 1, as shown in FIG. 4, a suitable hinge 14 is sufficient for being able to swing open the upper mold parts 9. However, it is also possible, in particular for complicated molded boxes according to FIG. 5, to provide lifting guides 15, with the aid of which the upper part can be raised. As it has been shown, the shaped piece formed is in a position, owing to its larger wall thickness, to withstand the loads which occur when the shape is divided, ie not to tear. With the greater wall thickness that can be achieved, there is also the advantage of being able to be shaped using divisible molds. In the forms shown in FIGS. 4, 5, the covers 9 result in clean edges on the shaped pieces.

5 is that at least one further suction surface 3 'with a separate suction box 1' is arranged on the suction side F, this suction box 1 'having a separate suction nozzle 1' '. The further suction surface 3 'is associated with its area 8 close to the other suction surface 3 at a distance D 1 which corresponds at most to approximately twice the wall thickness S of the molded part VS to be produced. This makes it possible, and as can be readily recognized, to provide the shaped piece VS with saponifying web formations 11, which contribute significantly to the further stability of the shaped piece VS, in particular as far as the more or less large edge regions 12 of the shaped piece are concerned. For this purpose, reference is made, for example, to FIGS. 6, 7, where FIG. 6 shows a view of a molded part VS produced from the non-smooth side and FIG. 7 shows a section through such a molded part, wherein, as also from FIG. 7 It can be seen that two such shaped pieces serve to fix an article G to be packaged in a cardboard box K. The web cavities 13, as indicated in FIG. 6, result from the suction surfaces 3 ′ additionally arranged in the form F according to FIG. 5.

As far as the spacing of the holes 5 in the carrier 4 from one another is concerned, it is important to note in this regard that on the one hand a sufficiently large suction cross section is created on the one hand and on the other hand the carrier 4 is sufficiently stable to withstand high vacuum (e.g. 120 mb ) not to deform in relation to its specified shape. Here too, the distance values are fluid, since they depend on the hole size, the carrier material, the wall thickness of the carrier and ultimately also on the material of the fine-meshed layer 6 applied directly to the carrier 4. So far, too the hole spacing (for example, corresponding to the diameter of the holes 5) is also a factor to be considered for the wall thickness of the shaped pieces to be achieved.

11 shows the flow diagram of the entire process. The paper waste 16 is brought to the desired shredder size in a suitable shredding machine 17 and is conveyed into the mixing tank 18, to which a sufficient quantity of suspension liquid is fed from a tank 19. This liquid with the chips contained therein and softened then passes into the actual work basin 20, into which the molding boxes 1 are immersed with a suitable lifting mechanism 21, these molding boxes 1 being connected on the suction side to a vacuum pump 24 via a vacuum line 22 and a pressure-tightly closed separating container 23 are. The aspirated liquid is returned from the container 23 to the tank 19 by a pump 25 and from there takes part in the cycle again. As indicated by dashed lines, all tanks and containers are provided twice and are accordingly integrated into the system. This double arrangement serves, in particular, to have sufficient time in the mixing containers 18 for the continuous input of the softening of the batch of chips entered in each case.

Design example:

For this purpose, reference is also made to FIG. 11. The chips produced from the paper waste 16 with the shredding machine 17 have a shape that cannot be defined geometrically, but a cut size of the order of 1 to 6 cm 2. Approx. 500 liters of liquid with a quantity of chips of 3 to 5 kg are prepared and mixed in the mixing container. The liquid temperature corresponds to the normal ambient or line temperature, but can be increased if this is required by the peculiarity of the schnitzel. With a finished weight of the molded part to be manufactured in the dry state of approx. 200 g, which corresponds to a mold box size of approx. 400x400x150 mm³, the suction process lasts with an applied suction pressure of approx. 120 mb on molding box 1 and with a wall thickness of the molding to be produced of 5 to 6 mm only approx. 3 to 5 seconds. The residual moisture in the molding produced depends on how long the suction pressure on molding box 1 remains when it comes from the suspension in the Working pool 20 is lifted out by means of the lifting mechanism 21. After removal from the molding box 1, the molding or the molding is dried in a dryer 26.

The molded part VS that can be produced with the method and the device according to the invention is shown in perspective in FIG. 10, the illustrated shape being to be understood only as an example. It is important here that stiffening web designs 11 are present in the channel 30 on the raw side of the shaped piece VS, which is only indicated by dashed lines at one point, which limit the web cavities 13. Seen from the raw side (in the direction of arrow 31), these web cavity spaces 13 have smooth walls and have a bottom 32 which has twice the wall thickness S of the fitting VS. As can be seen from FIG. 6, a plurality of such web cavities 13 can be provided on the rear or raw side of the shaped piece, i.e. a corresponding number of additional, separate suction boxes 1 'are then arranged in the suction mold according to the invention according to FIG. These additional suction boxes 1 'are attached to the cover 9, which has correspondingly large mass inflow openings 33.

Claims (7)

1. A process for the manufacture of thick-walled preforms, in particular, for packing purposes, especially from waste paper and/or cardboard waste, with the raw material contained in a water wash being sucked from the wash by means of a suction-type pulp moulding tool onto the suction surface conforming to the shape of the packing preform, wherein the suction on the moulding tool is exerted on the washed and sucked-in raw material within the wash, through spaced-apart holes in the suction surface and through a suction-permeable coating composed of one or more layers,with the coating being disposed immediately ahead of the suction surface and being of a mesh size dimensioned smaller than the hole size,
   characterized in
   that at least one additional smaller-sized suction-type pulp moulding tool is kept in spaced relationship from the suction-type moulding tool, and that the said smaller-sized suction-type moulding tool along with the other larger-sized suction-type moulding tool is placed under suction pressure, with the two resultant preforms being formed to constitute one coherent preform.
2. A suction-type pulp mould for carrying out the process according to claim 1, comprising a plenum chamber (1) having a vacuum connection (2) and a suction surface (3) conforming to the desired shape of the packing preform (VS), with the suction surface (3) of a form-stable carrier (4) being provided with spaced-apart holes (5) distributed throughout the suction surface, and with the carrier (4), at the abutment side of the preform being covered by at least one fine-mesh coating (6), such as a grid, lattice or fabric coating the mesh size of which is dimensioned smaller than the cross-section of the holes (5), characterized in that disposed in the divisible suction-type mould (F), at the intake side thereof, is at least one other suction surface (3') having a separate plenum chamber (1'), which suction surface (3') with the area thereof (8) close to the other suction surface (3), is disposed at a space (D₁) which, at best, corresponds to the double wall thickness (S) of the packing preform (VS) to be manufactured.
3. A suction-type mould according to claim 2, characterized in that the suction-type mould (F) is provided with a cover (9) on which is arranged the at least one additional plenum chamber (1') and which is provided with a material in-flow opening (32).
4. A suction-type mould according to claims 2 or 3, characterized in that the crossing cords (7) of the at least one fine-mesh coating (6) extend within two planes (E).
5. A suction-type mould according to claims 2 or 3, characterized in that the at least one coating (6) is of a form-stable configuration and is preformed to conform to the shape of the carrier (4).
6. A suction-type mould according to claims 2 or 3, characterized in that the holes (5) of the carrier (4) are of a diameter (D) of 0.5 to 3 mm, preferably 1 to 2 mm, and that the space (A) of two holes (5) from one another is between 2 and 8 mm, preferably 5 mm.
7. A suction-type mould according to claims 2 or 3, characterized in that the suction-type mould (F) is at least of a bipartite configuration, and the preforms (F₁, F₂) are designed to be movable apart.

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