CA2069295A1 - Process for the production of thick-walled shaped articles especially for packaging uses - Google Patents

Abstract

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 the shape of which corresponds to that of the packaging article. In order to manufacture shaped articles 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 in the suction surface and through a bed, 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

~9295 Process for the production of thick walled shaped articles especially for packaqina uses.
The invention relates to a process and a suction mould for producing thick-walled shaped articles, having particular application to packaging.

Process and suction moulds for the above mentioned purpose are known in the art, an example of which was featured in the Paper Trade Journal of 13/11/1953, pages 175-180. This prior art process and the corresponding suction forms permit production only of relatively thin-walled and thus relatively soft, shaped articles which are therefore somewhat unstable. Such shaped articles, especially those having thin walls, need to be specially dewatered and dried immediately following the suction moulding step. Although such conventional shaped articles can serve as egg boxes or shell-like fruit and vegetable containers and meet the strength requirements of that role, they are not suited to replace shaped articles made of polystyrol, which must be used for packing heavier objects such as machinery, or machine parts that must be immobilized for shipment inside a packing .1 carton. It would, however, be suitable from an environmental viewpoint if such replacement were possible. For this reason, therefore, machines, machine parts or even wine and champagne ~ bottles, are packed in form-fitting polystyrol shaped articles.
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Only with such packaging articles is it possible to ship the objects in the carton without danger of shifting or breakage.

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Shaped articles comprising light and environmentally friendly degradable fibrous material have, until the present, been prevented from effectively replacing polystyrol shaped articles, because the raw material used in producing such shaped articles can only be produced with limited wall strength, which, because of low inherent stability when wet, cannot be removed immediately following the suction-moulding stage. Although rapid removal of the moulded articles would serve the efficiency of the moulding process, the thin cardboard walls could not prevent sliding or breakage of the packed objects during shipment. Prior art examples of such moulded articles have been disclosed in U.S.-A-3 016 177 and 3 315 450. These however, produced from a fibrous pulp mash, have thin walls (to a maximum of 3 mm) and thus required a very pronounced ribbing structure for stiffness.
Until now, it seems that shaped articles made from fibrous raw material could only have thin walls because the suction bed of the conventional suction moulds plugs up too rapidly which, despite continuous vacuum pressure being applied to the suction form, prevents further accretion of wet fibre material along the walls of the mould. This prevents both formation of thicker walls and creation of a durable bond with the raw material already sucked onto the sides of the mould.
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The object of the invention, therefore, is the improvement both of the prior art process for suction moulding and the suction moulds that are used to produce shaped articles of adequate wall : . : .,- , - .

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~ 3 thickness from shredded waste paper and/or cardboard. ~he proposed process and apparatus enable production of an article having greater stability while permitting its practically ; immediate removal from the suction mould.
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The object of the invention is satisfied by a prior art process of the type mentioned above, wherein suction applied to the suction moulding apparatus through a plurality of separate holes provided in the suction surface and through at least one bed located in front of the suction surface serving to permit :' suctional flow via mesh apertures that are smaller than the apertures, suctions raw material held in a suspension and whereby furthermore the suction mould used according to the invention comprises a suction surface having a stable frame provided with holes that are separated from each other and distributed over such surface and whereby, furthermore, the frame is covered on the side facing the moulded article deposit with a bed having fine mesh apertures such as net, wire or woven meshing, the size of whose apertures is smaller than the cross section of the holes in the suction surface. Advantageous and practical alternate embodiments of the invention will be described later in greater detail.

The expression "approximately", which appears in the subsidiary claims, is used in the disclosure because the actual limits cannot be precisely defined. It will be appreciated in this ' - 20~929~

respect that t is unavoidable to have precise data on the dimensions of the raw material to be processed since such material is, prior to processing, not shredded to correspond to the dimensional variations of differently shaped articles. This relationship can have a variety of results when the raw material is placed in suspension.

It was surprising to note that use of the process according to the invention in conjunction with the specially-designed suction form permitted production of walls whose thicknesses were double that of conventionally-moulded articles. In addition to which, the shaped articles produced by the process according to the invention could not only be removed immediately from the suction moulding apparatus, but, when dried, exhibited the stability required to serve as a replacement for polystyrol packaging articles which had, up to now, been used for packaging purposes.
It is crucial to the operation of the invention that suction is no longer applied directly through a finely-meshed suction surface whose apertures can become clogged. In the apparatus contemplated in the invention, the raw material in suspension flows through a frame having relatively large holes and at least one suction flow-through bed whose mesh size is smaller than the size of the holes contained in the frame. The very surprising effect achieved with the apparatus according to the invention, which is to produce by means of suction a product having thicker walls, can be explained in part by the emergence of cross suction .
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between the frame and the finely meshed suction flow area. It is believed that such cross flow permits the suction to act for a longer period of time on the deposited raw material. The result of this arrangement is that, in general, thicker material deposits are produced, which could not be produced either with a frame containing alone or with a finely meshed sieve-like mould.
Another salient feature of the apparatus according to the invention is a stable frame that permits the application of vacuum pressure to the mould, which permits the material deposited on the sides of the mould to be thicker.

At the end of the suction step, vacuum pressure is maintained for a certain length of time to allow the moulded article to be dewatered at least to some extent. Due to its thick wall and despite the water remaining in the raw material, the moulded article is basically stable enough to permit its removal from the suction form prior to complete drying while retaining the originally intended shape. In addition, the increased thickness of the walls of the moulded article provide the latter with a degree of stability or stiffness that enables the article to effectively replace conventional shaped articles produced from polystyrol.

One obvious advantage of the process according to the invention is that waste paper and/or waste cardboard board can be shredded without further preparation. In other words, the shredded waste 20~929~

material is merely added to the suspension liquid, in which it is softened; the resulting liquid is then transferred without further modification to the suction moulding process.

It is irrelevant in this respect whether or not isolated pieces of plastic sheeting or film become mixed with the waste, even though such plastic is often found mixed in with paper and cardboard waste. It has been demonstrated that the presence of plastic shreds in finished moulded articles can even be advantageous since their presence serves to increase the rigidity of the formed articles, although it is not advisable that the raw material used contain more than 5~ of plastic scraps.

Although the main advantage of the process according to the invention is the ability to process shredded raw material and to produce moulded articles of greater wall thickness, it is also possible to preprocess paper waste into single fibres and to use such fibres, or, for example, wood shavings, in the raw material suspension.

As has been demonstrated, it is not absolutely necessary to add a bonding agent to the aqueous shred suspension, since it has been found in every case that sufficient crosslinkage of the shredded material occurs during the suction phase, which then later imparts to the finished shaped article a sufficiently stable internal structure. In addition, the raw material used for ::
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processing usually contains a percentage of bonding agent that is released into solution when placed in suspension. If bonding agents are to be added to the suspension, it is adv~sable to use those compounds that are normally used in paper making.
Examples are: a boiled soda solution, i.e., caustic soda, saponified resin, phenolic resins, montanic resins, or resins derived from cellulose liquors. Also suitable are paper-making resin, bonding casein, starch, animal glue, sodium silicate, or similar substances.

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The process according to the invention, the suction mould to be used in conjunction with the process, and further advantageous and practical alternative embodiments of the invention will next be described in greater detail by means of the following drawings of embodiment examples.

Schematically shown are:

Figure 1. a greatly enlarged section of the suction surface with a corresponding section through the raw material being ~ sucked dry to form the moulded article;

; Figure 2. shown still larger is a section through the suction surface which has been designed as proposed;

Figure 3. a plan view of the suction surface viewed from the side :.~

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upon which the raw material is deposited;

Figure 4. a section through a suction box;

Figure 5. a section through a special design of a suction box;

Figure 6. a view of a moulded article as seen from the side on which the raw material is deposited:

Figure 7. a section through the moulded article shown in Figure 6 in connection with an obiect that is to be packed;

Figure 8, 9.

special embodiment examples of the suction surface in section;

Figure 10 a perspective view of a section of an embodiment example of a moulded article; and Figure 11 a flow chart of the process.

In Figure 4, the proposed suction form comprises a suction box 1, provided with a vacuum or low-pressure connection 2, and a suction surface 3 corresponding to the desired shape of the moulded article VS. If, as illustrated in Figure 4, suction box 1 is provided with a cover 9, such cover possesses an inflow ,:

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connection 10 of a diameter capable of permitting the raw material suspension to flow into the mould cavity when the entire mould box 1 is immersed in the suspension. In order to be able to produce moulded articles VS having a wall thickness S of at least 4 to 6 mm by using such a suction mould, the special design of suction surface 3 shown in Figure 1 must comprise a frame 4 having a stable shape and separate holes 5 that are distributed over the suction surface (also see Figure 3). In this arrangement, frame 4 is covered on the side on which moulded article VS is to be formed with at least one finely meshed bed 6 comprising netting, wire or woven material (e.g., of nylon) the mesh apertures of which are significantly smaller than the cross section of holes 5. In this special embodiment, the holes have a diameter D between 1 and 2 mm, preferably 1.5 mm and are separated from each other by a distance A of from between 4 and 6 mm, preferably 5 mm. It is preferable if a copper wire mesh be used for bed 6 and have a thickness of between 0.2 and 0.4 mm whereby wires 7 comprised in the mesh are separated from each other by a distance A1 which is between 0.3 and 0.5 mm. A
particularly advantageous and effective arrangement comprises that the interwoven wires 7 of the finely woven bed 6 extend over two planes E as illustrated in Figure 2. It will be appreciated from the enlarged illustration shown in Figure 2 and highlighted with arrows that cross flows are produced to a certain extent in bed 6. Such crossflows are clearly responsible for increasing, as necessary, the depth of the layers of the suspended raw material , ", , .
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deposited on bed 6, a result previously unobtainable by using conventional processes involving use of a relatively thin sieve-like sheet that permitted use only of a limited vacuum pressure and which accordingly clogged very quickly and thus prematurely limited the amount of material that could be deposited. Of course, several very thin beds 6 can be arranged one on top of the other, whereby the thickness of each individual bed is only approximately 1 mm. Bed 6, in addition, should not comprise a thin sheet having only holes, because such a sheet would be unable to facilitate the creation of cross flows. If bed 6 is designed to comprise a plurality of layers (see Figure 8), the mesh width of the individual layers can even be equal to or nearly equal to the diameters of apertures 5, because the depth of the layers causes the apertures in bed 6 to be somewhat staggered. Depending on the choice of material used for bed 6, for example, one or more beds 6 can assume the role of frame 4, i.e., replace the latter, in which case bed 6' located on the suction side would come into contact with the moulded article via its fine surface structure. A precondition to such a design is naturally that the material used for bed 6 has a stable shape, i.e., a soft textile weave should not be employed.
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- Although it is preferable that form-stable material be used in bed 6, it is also possible to use a material of unstable shape which would allow bed 6 to be pressed into the shape of frame 4 by means of equipment and be mounted on frame 4. The plan view ., :' , ', - ~ ~ . ... ~. . . . ,, - . .
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(shown in the direction of arrow P, as per Figure 2) shown in Figure 3 corresponds to the dimensions of an actual practical embodiment, wherein holes 5 have a diameter of approximately 1 mm and whereby the mesh size of bed 6 is from 2 to 4 times smaller than apertures 5 and whereby furthermore, flat F and strip-shaped waste material SA are as shown held in suspension. Flat waste material, strips for example, have in this arrangement a size of approximately 1 to 6 cm2 which produces the best results. Strip-shaped waste material, i.e. waste material having the appearance of sauerkraut, which is produced by shredding office paper, are approximately 1 to 5 mm wide and approximately 10 to 30 cm long.

Suction surfaces 3 comprised by mould box 1 shown in Figures 4 and 5 are shown in their most basic form. Further and significantly more complex mould designs of frame 4 and corresponding bed 6 are easily obtainable, the only precondition being that no zones exist in which suction beds mutually block each other off, the result of which could be to prevent the deposit or suctioning of raw material particles.

Production of more complex mould designs and the ability to mould simple articles, can benefit from a suction mould F comprising two parts, whereby mould sections F1 and F2 designed so as to be able to separate from each other. In a basic configuration of mould box 1, as illustrated in Figure 4, all that is required is a constructed hinge 14, which allows the upper part 9 of the -, . . . : ,. .. . . . .
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12mould to swing open. It is also possible, especially for more complicated moulding box designs, as shown in Figure 5, to provide vertical guides 15, by means of which the upper part can be raised. It has already been demonstrated that the finished moulded packaging article is, due to its increased wall thickness, entirely capable of withstanding, i.e. will not tear apart in the presence of loads produced when the form is pulled apart. The increased wall thickness that can be obtained by using the process according to the invention also affords the advantage of moulding with the aid of moulds that can be pulled apart. In the mould versions shown in Figures 4 and 5, the provision of covers 9 provides the moulded articles with clean edges.

The novelty of the design of suction mould F, as shown in Figure 5 owes to the fact that arranged in mould F on the suction side is at least one further suction surface 3' comprising a separate suction box 1', whereby suction box 1' is provided with a separate suction connection 1''. The additional suction surface 3' is in this arrangement arranged to function in conjunction with the other suction surface 3 located at a distances D1 from nearby zone 8, which corresponds to at most approximately double the wall thickness S of the articles VS that are to be moulded.
This arrangement permits moulded article VS to be provided with a stiffening rib arrangement 11, which contributes considerably to increasing the stability of moulded article VS, particularly in .~

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the relatively wide edge regions 12. In this connection, reference should be made to Figures 6 and 7, for example, wherein Figure 6 shows a view of a finished moulded article VS from the unsmoothed side, while Figure 7 shows a section through the same moulded article. Figure 7 also shows two such moulded articles being used to immobilize an object G which is to be packed inside a carton K. The mould cavities 13 are, as indicated in Figure 6, formed in this design by the suction surfaces 3' which are provided additionally in mould F, and have a corresponding shape;
this is shown in Figure 5.

It is very important that the spaces separating holes 5 of frame 4, permit formation on one side of the holes of a suction cross section whose size is sufficient to increase material thickness while on the other side of frames 4 allows enough stability to prevent the frame from deforming under high vacuum pressure (e.g.
120 millibar). In the arrangement of the apertures, the spaces separating the holes in the frame can vary greatly since these depend on the size of the aperture, the material from which the frame is made, the wall thickness of the frame and lastly on the material used to produce the finely meshed bed 6 that is applied directly over the frame 4. Furthermore, the distances between the holes (for example, corresponding to the diameter of holes 5) also influences the thickness of the finished moulded articles.

Figure 11 shows the flow chart for the basic configuration of the :
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overall process. Waste paper 16 is reduced in a shredding machine 17 to the required particle size and then transferred to a mixing tank 18 into which a sufficient quantity of suspension fluid is pumped from a tank 19. This fluid, together with the particles which it contains and which become softened by such liquid flow into a proce~sing bath 20, into which the mould boxes 1, which are fitted with a raising mechanism 21 are immersed.
Mould boxes 1 are connected via a vacuum line 22 and a pressure sealed separation vessel 23 to a vacuum pump 24 located on the side on which suction is applied. The suctioned fluid is pumped by means of a pump 25 from container 23 back into tank 19 from which point it recirculates through the system. As indicated by the broken line, all tanks and containers are provided in double and are connected inside the system. The main purpose of this double arrangement is to allow sufficient time for the waste particles which have been poured into the mixing vessels containers to be softened while the moulding process continues without stoppage.

Configuration example:

Reference is made here to Figure 11. The paper shreds which have been produced from waste paper 16 with the aid of a shredding machine 17 are geometrically undefined, but have an average size ranging from 1 to 6 cmZ. Approximately five hundred litres of liquid containing approx. 3 to 5 kg of waste paper particulate, 20~929~

is poured into the mixing vessel and agitated. The temperature of the liquid in the mixing vessel corresponds to ambient temperature, i.e. the temperature of the transfer lines, but can be raised if the particular characteristics of the waste paper ; particles being used so require. In the present example, the finished dry weight of the moulded article is approx. 200 g which corresponds roughly to a moulded box of approximately 400 x 400 x 150 mm3. If the vacuum pressure applied to suction box 1 is approx. 120 mb and the required thickness of the article wall is approx. 5 to 6 mm, the suction phase lasts approximately 3 to 5 seconds. The moisture remaining in the moulded article depends on how long the vacuum pressure is applied to moulding box 1, after the latter has been withdrawn from the suspension in the immersion bath by means of raising mechanism 21. After being removed from moulding box 1, the moulded article or articles are dried inside a dryer 26.

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Claims (7)

16 Patent Claims

1. Process for producing thick walled moulded articles with particular application to packaging, more particularly packaging using waste paper and/or cardboard waste whereby the raw material held in an aqueous suspension is suctioned out of the suspension by means of a suction mould implement on to the suction surface which corresponds to the shape of the moulded packaging article, characterized in that suction is applied to the suspended material to be suctioned and held in suspension through holes of the suction surface that are separated from each other and through suction -admitting beds comprising one or more layers, being arranged directly in front of the suction surface and having mesh apertures that are smaller than the holes, a further, smaller suction mould implement is held at a distance from and inside the suction mould implement and this smaller suction mould implement is, together with the other larger suction mould implement subjected simultaneously to vacuum pressure, by means of which both moulded articles so produced are formed into a continuous moulded article.

2. Suction mould for implementing the process in accordance with Claim 1, comprising a suction box (1) with vacuum connection (2) and a suction surface (3) corresponding to the desired shape of moulded packaging article (VS), whereby suction surface (3) comprises a form-stable frame (4) provided with holes (5) that are separated from one another and are distributed over the suction surface, and whereby frame (4) is covered on the side on which the deposit for the moulded article is made with at least one finely-meshed bed (6) characterized in that arranged in mould (F) on the side where suction is being applied is at least one further suction surface (3') comprising a separate suction box (1') located in surrounding region (8) which is separated from the other suction surface (3) by a distance (D1) corresponding at most to double the wall thickness of the packaging article VS to be produced.

3. Suction mould in accordance with Claim 2 characterized in that mould (F) is provided with a cover (9) on which is arranged at least one additional suction box (1') and which is provided with a mesh inlet opening (32).

4. Suction mould in accordance with Claim 2 or 3 characterized in that the interwoven strands (7) of at least one finely meshed bed, extend across two planes (E).

5. Suction mould in accordance with Claim 2 or 3 characterized in that at least one bed is designed to have a stable shape and is preshaped to conform to the shape of frame (4).

6. Suction mould in accordance with Claim 2 or 3 characterized in that holes (5) of frame (4) have a diameter (D) ranging between 0.5 and 3 mm, preferably between 1 and 2 mm, and whereby the distance (A) separating holes (5) from each other is between 2 and 8 mm, preferably 5 mm.

7. Suction mould in accordance with Claim 2 or 3, characterized in that mould (F) is designed to comprise at least two parts and whereby mould parts (F1, F2) can be moved apart from each other.