SE536128C2 - Process for manufacturing sheet-shaped sandwich material with corrugated cardboard and hardened chipboard surface layers - Google Patents

Abstract

SUMMARY A method of manufacturing a sheet-shaped sandwich material (1), comprising the steps of: - providing a sheet-shaped core (2) of corrugated cardboard, which core (2) has an upper side (3a) and a lower side (3b) and in which core (2) the tubular channels (10) of the corrugated board extend substantially perpendicular to the upper side (3a) and lower side (3b) of the core (2); applying chips and glue to the upper side (3a) and lower side (3b) of the core (2) to form a chip mat (5a, 5b) on the respective side; - compression of the chip mats (5a, 5b) by applying compressive force (F1, F2) orthogonally to the upper side (3a) and lower side (3b) of the core, the adhesive in the chip mats (5a, 5b) being hardened to form hard chip layers (6) on the core side of the core. (3a) and underside (3b). (Figure 1)

Description

30 35 536 128 corrugated cardboard core and covering chipboard layer. The object is achieved by a method according to claim 1.

The inventive method for manufacturing a sheet-shaped sandwich material comprises the steps of: - providing a sheet-shaped core of corrugated cardboard, which core has an upper side and a lower side and in which core the tubular channels of the corrugated cardboard extend substantially perpendicular to the upper side and lower side of the core; - applying chips and glue to the upper side and lower side of the core, forming a chip mat on each side; - compressing the chip mats by exerting pressing force orthogonally to the upper side and lower side of the core, whereby the glue in the chip mats is caused to harden, forming hardened chip layers on the upper side and lower side of the core.

By forming the chip layers by pressing and curing directly on the top and bottom of the corrugated cardboard core, the bond between the core and the chip layers becomes strong, since the process allows a thin layer to form at the interface between the chip layer and the core, where the chips and glue have penetrated the tubular channels of the corrugated cardboard. Another advantage of the process according to the invention is that the chip layers can be made very thin, as these never need to be handled separately from the core but are pressed and cured in place. The dimension of the finished sandwich material can thus be adapted so that it corresponds to the standard thickness of a chipboard. The sandwich material produced using the process can thus be made lightweight but still stiff and strong.

According to one embodiment, the chip mats consist of a dry mixture of chips and glue, where the glue is activated during compression. According to another embodiment, the application of chips and glue to the underside of the core is carried out by transferring the core to a surface on which a chip mat is arranged. According to these embodiments, an efficient manufacturing process of sandwich material is allowed, since the manufacturing can be carried out according to the "assembly line" principle.

In one embodiment, a thin barrier layer is applied to the top and bottom of the core, respectively, prior to the application of the chips and glue intended for forming chip mats. In this embodiment, the barrier layer prevents the chip and glue mixture from penetrating too far into the tubular channels of the corrugated board, which ensures that the final sandwich material is lightweight by keeping the channels largely air-filled.

According to a further embodiment, the barrier layers are applied by applying a wet chip and adhesive mixture to the top and bottom of the core and curing to form a thin barrier layer on each side. By applying a wet chip and adhesive mixture as a barrier layer, it is easy to control the degree of penetration of the chip and adhesive mixture into the channels to optimize the weight of the sandwich material while ensuring a good bond between the core and the surface layer.

According to one embodiment, the core is manufactured by joining flat cylindrical corrugated cardboard elements of rolled single corrugated board side by side with the outer surfaces facing each other to form a disc-shaped core. According to this embodiment, the density and size of the core can be easily varied, for example by the number of corrugated cardboard elements.

According to a further embodiment, the core is compressed before the application of chips and glue by exerting pressure substantially orthogonally against at least one of the side edges of the core.

The density of the core can then be varied by the degree of compression when the corrugated cardboard elements are pressed together to form a core. 10 15 20 25 30 35 536 128 Further preferred embodiments of the method of the present invention are apparent from the claims and the following description. according to dependent The invention also relates to a sandwich material manufactured by means of the method according to the invention. The sandwich material is at the same time stiff and strong and also lightweight. It also has a good bond between core and chip layer.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in the following with reference to the accompanying drawings, in which: Fig. 1a-c is a schematic diagram showing the steps in a method according to the invention; Fig. 2 shows the application of a wet chip and glue mixture to a core of corrugated cardboard material during the formation of a barrier layer; Fig. 3 shows a core of corrugated cardboard material with a barrier layer and with layers of chip and glue mixture applied before pressing and curing; Fig. 4 shows a cross-section of a sandwich material according to the invention; Fig. 5 is a schematic diagram showing a method according to the invention; and Fig. 6a-b shows the production of a core of corrugated cardboard material by means of elements. joining of cylindrical corrugated cardboard 10 15 20 25 30 35 535 128 DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION The term chip mat refers in the following to a not yet hardened and pressed layer of glued chips, produced by gluing chips with glue in liquid form or spray form, or a layer of chips mixed with glue, where the glue can preferably be in powder form. The term chip layer is used for a hardened and pressed layer of chips and glue.

Fig. 1a-c schematically illustrates a method according to the present invention for producing a sheet-shaped sandwich material 1.

In the method according to the invention, a disc-shaped core 2 of corrugated cardboard is provided as shown in Figure 1a. The core has an upper side Sa, an underside 3b and side edges 4. The corrugated cardboard of which the core is made has tubular channels 10, see Figure 2, which extend substantially perpendicularly to the upper side 3a and underside 3b of the core. Chips and glue are applied to the upper side 3a and underside 3b of the core, whereby a chip mat 5a, 5b consisting of chips and glue is formed on each side. These chip mats 5a, 5b are then pressed together as shown in Figure 1b by applying pressing forces F1, F; orthogonally to the upper side 3a and underside 3b of the core. The compressed chip mats 5a, 5b are hardened under pressure and then form hard chip layers 6 on the top side 3a and bottom side 3b of the core, see Figure 1c. A sandwich material 1 comprising a core 2 of corrugated cardboard and chip layers 6 on the top side and bottom side is thereby obtained.

The lower chip mat 5b, which is intended to lie against the underside 3b of a core 2 of corrugated cardboard, can according to the invention be formed by arranging glued chips in the form of a layer on a rolling belt. On top of the lower chip mat 5b, the core 2 is placed with the underside 3b directed towards the lower chip mat 5b. An upper chip mat 5a is then formed on the upper side 3a of the core, for example by arranging glued chips in the form of a layer on the upper side 3a of the core. The core 2 with the two chip mats 5a, Sb is then subjected to pressing force P1, F2 orthogonally to the upper side 3a and the underside 3b by means of press rolls or press plates 7, whereby the chip mats are pressed together. During pressing, the glue in the chip mats 5a, 5b is activated so that the chips adhere to each other, and the chip layers 6 are hardened.

Depending on the adhesive used in the tensioning mixture, curing is preferably carried out at an elevated temperature, such as up to 100° C., or in some cases up to approximately 250° C. A press pressure of approximately 100-300 bar can be used during curing.

The chip mats 5a, 5b are preferably made of dry substance according to the invention. Preferably, chips that have been glued and dried are used, but a dry mixture of chips and glue particles, or chips and glue that are applied simultaneously and first mixed into the chip mat can also be used. The chip mats 5a, 5b can, for example, have a thickness of approximately 6-9 mm, in which case the finished chip layers after pressing and curing are approximately 3 mm thick. The thickness of the chip mats 5a, 5b should be just over twice as large as the desired thickness of the finished chip layers 6. For a final thickness of the chip layers 6 of approximately 3 mm, the chips should not be more than approximately 3-5 mm long, preferably less than 3 mm.

Figure 2 shows an embodiment according to the invention where thin barrier layers 8 are applied to the top side 3a and bottom side 3b of the core before the application of chips and glue intended for chip mats 5a, 5b.

The barrier layer 8 has as one of its purposes to block the transverse channels 10 of the corrugated board, to prevent chips and glue from the chip mats 5a, 5b from penetrating deeply into the channels 10 and thereby increasing the density of the sandwich material 1. The barrier layer 8 can preferably be formed from a wet chip and glue mixture 9, which is applied to the top side 3a and bottom side 3b of the core by means of an applicator 11. The chip and glue mixture 9 can then be cured before chip mats 5a, 5b are arranged on the respective sides 3a, 3b as shown in Figure 3. It is also possible to directly arrange 10 15 20 25 30 35 535 128 chip mats 5a, 5b on the respective sides without intermediate curing steps, in which case the barrier layers 8 and the chip layers 6 are cured in the same curing step. It is desirable that a certain penetration of the chip and glue mixture 9 of the barrier layers 8 occurs in the tubular channels 10 of the corrugated cardboard, as shown in the enlargement in Figure 2, since this increases the bond between the barrier layer 8 and the core 2. However, the mixture 9 should not penetrate too far, since the density of the core 2 then increases, but a penetration of around 1 mm is sufficient to achieve good bonding between the core 2 and the chip layers 6. The barrier layers 8 make it possible to maintain a lightweight core 2, while the chip mats 5a, 5b can be pressed together and hardened into a tension layer 6 under high pressure.

The sandwich material 1 thus has a light core 2 and a hard and durable surface. A sandwich material 1 with barrier layer 8 produced by a method according to the invention is shown in cross-section in Figure 4.

The barrier layers can also consist of some other type of putty than a mixture of chips and glue, for example, glue alone can be used as a barrier layer, in which case the glue should be viscous so as not to penetrate too deeply into the tubular channels of the corrugated board. According to one embodiment, the barrier layers can consist of a thin plastic film which is applied to the core. The plastic film can surround the entire core or only cover its top and bottom. The plastic film blocks the channels so that chips and glue are prevented from penetrating into them when applying chips and glue to form the chip mats. The plastic film should be chosen so that it melts when pressing and hardening the chip mats at an elevated temperature, so that chips and glue are allowed to penetrate a little into the channels. Good adhesion of the chip layers to the core is achieved in this way.

The chips used for the surface layer and any barrier layers are preferably wood chips, preferably sawdust because these have a suitable size distribution for forming chip layers with a thickness of a few millimeters. It is also possible to use chips other than wood chips, for example chips of flax straw or hemp. 10 15 20 25 30 35 538 '128 The core 2 of corrugated cardboard can be produced in various ways within the scope of the invention. Figure 5 shows schematically an example where a corrugated cardboard web 12 of single corrugated, that is, corrugated cardboard with a smooth side and a corrugated side, is wound on a roll 13, from which it is unwound and rolled into a cylinder 14.

Pre-gluing is done by applying glue to the corrugated cardboard web 12 using a nozzle 15. The glue can be applied either only to the smooth side of the corrugated cardboard web 12 or to both sides. The glue dries before the corrugated cardboard web 12 is rolled up into the cylinder 14.

The longitudinal axis of the cylinder 14 extends in the same direction as the tubular channels 10 of the corrugated board. When the cylinder 14 has reached the appropriate diameter, the corrugated board web 12 is cut, the cylinder 14 is sealed and then cut transversely by a set of knives 16, whereby flat cylindrical corrugated board elements 17 are formed. These are fed into one or more folds 18 and passed on to a press frame 19, where a number of corrugated board elements 17 are laid side by side with the outer surfaces 17a facing each other as shown in figure 6a. The corrugated board elements 17 are then pressed together to form a rectangular core 2 by the press frame 19 pressing against at least one of the sides that are to constitute the side edges 4 of the core, see figure 6b, with a pressure adapted to the density and stiffness that the core 2 is to have. The degree of compression thus controls the density of the core 2. The adhesive previously applied to the corrugated board web 12 can now be activated and cured to join the core 2, alternatively the core can be held under pressure against the side edges 4 as the barrier layers 8 and/or the chip layers 6 are applied and cured.

It is of course not necessary that the roller 13 and the cylinder 14 are horizontal when producing the flat cylindrical corrugated cardboard elements 17 as shown in Figure 5, but their longitudinal axes can be angled up to 90° to the substrate.

An alternative method for manufacturing the core 2 is that a corrugated cardboard web is pre-glued and then cut into strips, which strips are rolled together to form flat cylindrical corrugated cardboard elements 17. The cylindrical corrugated cardboard elements 17 are joined as described above side by side with the outer surfaces 17a facing each other to form a disc-shaped core 2.

The core 2 can also be made of corrugated cardboard sheets that have been joined together without first being rolled into cylindrical corrugated cardboard elements. In this case, other forms of corrugated cardboard than single corrugated cardboard can be used, such as double corrugated cardboard. The core can, for example, be manufactured by joining corrugated cardboard sheets or strips of corrugated cardboard into rectangular blocks of suitable size, which are, if necessary, cut with a cross-cut transverse to the tubular channels of the corrugated cardboard so that a core with an upper side and an underside substantially perpendicular to the tubular channels of the corrugated cardboard is formed.

A sheet-shaped sandwich material 1 manufactured by the method according to the invention has a core 2 of corrugated cardboard with an upper side 3a and an underside 3b and corrugated edges 4.

The tubular channels 10 of the corrugated cardboard extend substantially perpendicular to the top and bottom of the core.

The sandwich material 1 further comprises on the top side 3a and bottom side 3b of the core chip layers 6, which consist of hardened and compressed chips and glue. At the interface between the core 2 and the chip layers 6 on each side there is a layer where chips and glue, alternatively another material which constitutes a barrier layer 8, have penetrated into the tubular channels 10 of the corrugated cardboard and thereby integrated the core 2 with the chip layers 6 alternatively the barrier layers 8. The bond between the chip layer 6 and the core 2 is therefore good.

The inventive method is of course not limited to the embodiments described above, but a number of modifications thereof should be obvious to a person skilled in the art without the method deviating from the basic idea of the invention as defined in the appended claims.

Claims (3)

A method for manufacturing a sheet-shaped sandwich material (1), comprising the steps of: - providing a sheet-shaped core (2) of corrugated cardboard, which core (2) has a top (3a) and a bottom (3b) and in which core (2) the tubular channels (10) of the corrugated board extend substantially perpendicular to the top (3a) and bottom (3b) of the core (2); applying chips and glue to the upper side (3a) and lower side (3b) of the core (2) to form a chip mat (5a, 5b) on each side; - compressing the chip mats (5a, 5b) by applying compressive force (P1, F2) orthogonally to the top (3a) and bottom side (3b) of the core, causing the adhesive in the chip mats (5a, 5b) to cure at elevated temperature during formation of hard chipboard layers (6) on the upper side (3a) and lower side (3b) of the core. Method for manufacturing a sandwich material (1) according to claim 1, characterized in that the chip mats (5a, 5b) are formed by a dry mixture of chips and glue and that the glue is activated during the compression. . Method for manufacturing a sandwich material (1) according to claim 1 or 2, characterized in that the application of chips and glue on the underside (3b) of the core takes place by transferring the core (2) to a surface on which a chip mat is arranged. Method for manufacturing a sandwich material (1) according to any one of the preceding claims, characterized in that a thin barrier layer (8) is applied to the upper side (3a) and lower side (3b) of the core, respectively, before the application of chip mats (5a, 5b) shavings and glue. 10 15 20 25 30 35 535 128 11. Method for manufacturing a sandwich material (1) according to claim 4, characterized in that the barrier layers (8) are applied by applying a wet chip and glue mixture (9) to the upper side (3a) and lower side (3b) of the core and hardening to form a thin barrier layer (8) on each side. . Method for manufacturing a sandwich material (1) according to claim 4, characterized in that the barrier layers (8) are applied by applying a thin plastic film to the core (2). . Method for manufacturing a sandwich material (1) according to any one of the preceding claims, characterized in that the core (2) is manufactured by joining flat cylindrical corrugated cardboard elements (17) of rolled single wave together side by side with the jacket surfaces (17a) against each other to form a disc-shaped core ( 2). . Method for manufacturing a sandwich material (1) according to claim 7, characterized in that the corrugated board elements (17) are manufactured by rolling a corrugated board web (12) into a corrugated board cylinder (14) with the tubular channels (10) of the corrugated board in the axial direction of the corrugated board cylinder (14) , after which the corrugated board cylinder (14) is cut with a cutting section transverse to the axial direction of the corrugated board cylinder to form said corrugated board element (17). . Method for manufacturing a sandwich material (1) according to claim 7, characterized in that the corrugated board elements (17) are manufactured by cutting a corrugated board web into strips across the tubular channels (10) of the corrugated board, whereupon the strips are rolled up into flat cylindrical corrugated board elements (17). Method for manufacturing a sandwich material (1) according to claim 8 or 9, characterized in that an adhesive layer is applied to the corrugated board web and caused to dry before said rolling up. Method for manufacturing a sandwich material (1) according to one of Claims 7 to 10, characterized in that the core (2) is compressed before the application of chips and glue by applying pressure substantially orthogonally to at least one of the core (2). ) side edges (4). Method for manufacturing a sandwich material (1) according to claim 11 in combination with claim 10, characterized in that the joining of the cylindrical corrugated board elements (17) takes place by activating and curing the adhesive layer, which is applied to the corrugated board web, in the compression of the core (2). ). 1 Sandwich material (1) made by the method according to any one of the preceding claims, comprising a disc-shaped core (2) of corrugated cardboard, which core (2) has an upper side (3a) and a lower side (3b) and in which core (2) corrugated cardboard tubular channels (10) extend substantially perpendicular to the upper side (3a) and lower side (3b) of the core (2), the sandwich material further comprising on the upper side (3a) and lower side (3b) of the core chip layers (6) which consist of hardened and compressed chips and glue and wherein in the interface between the core (2) and the chip layers (6) on each side there is a layer where chip and glue penetrated into the tubular channels (10) of the corrugated board and thereby integrated the core (2) with the chip layers (6).