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

25 30 35 536 128 corrugated cardboard core and covering chipboard. The object is achieved by a method according to claim 1.

The method according to the invention for manufacturing a disc-shaped sandwich material comprises the steps: - providing a disc-shaped core of corrugated cardboard, which core has a top side and a bottom side and in which core the tubular channels of the corrugated board extend substantially perpendicular to the top side and bottom side of the core; applying chips and glue to the top and bottom of the core to form a chip mat on each side; compression of the chip mats by applying compressive force orthogonally to the top and bottom of the core, the adhesive in the chip mats being caused to harden to form hardened chip layers on the top and bottom of the core.

By forming the chip layers by compression and hardening directly on the top and bottom of the corrugated core, the bond between the core and the chip layers becomes strong, as the process allows a thin layer to form in the chip-core interface where chips and glue penetrate the tubular channels of the corrugated board. Another advantage of the method according to the invention is that the chip layers can be made very thin, as these never need to be handled independently of the core but pressed and hardened 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 by the process can thus be made lightweight but still rigid and durable.

According to one embodiment, the chip mats consist of a dry mixture of chips and glue, where the glue is activated during the compression. on which a chip mat is arranged. According to these embodiments, an efficient manufacturing process of sandwich material is allowed as the manufacturing can take place according to the "conveyor belt" principle.

According to one embodiment, a thin barrier layer is applied to the upper side and lower side of the core, respectively, before the application of chips and glue intended for the formation of chip mats. According to 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 becomes lightweight thanks to the channels being largely air-filled.

According to a further embodiment, the barrier layers are applied by applying a wet chip and glue 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 glue mixture as a barrier layer, it is easy to control the degree of penetration of chip and glue mixture into the channels to optimize the weight of the sandwich material while ensuring a good bond between core and surface layer.

According to one embodiment, the core is manufactured by flattening cylindrical corrugated cardboard elements of rolled single wave together side by side with the mantle surfaces against 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 board elements.

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

The density of the core can then be varied by the degree of compression as the corrugated board elements are compressed into a core. Further preferred embodiments of the method of the present invention appear from the claims and the following description. according to the dependent 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 as it is stiff and strong, even lightweight. It also shows a good bond between the core and the chip layer.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in the following with reference to the accompanying drawings, in which: Figs. 1a-c are a schematic diagram showing the steps of 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 to form a barrier layer; Fig. 3 shows a core of corrugated board material with barrier layers and with layers of chip and glue mixture applied before pressing and hardening; 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 Figs. 6a-b show the production of a core of corrugated cardboard material by elements. joining cylindrical corrugated cardboard 10 15 20 25 30 35 535 128 DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION or a layer of chips mixed with glue, where the glue may preferably be in powder form. The term chip layer is used for a hardened and pressed layer of chip and glue.

Figs. 1a-c schematically illustrate a method according to the present invention for producing a disc-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, a lower side 3b and side edges 4. The corrugated board which the core consists of has tubular channels 10, see figure 2, which extend substantially perpendicular to the upper side 3a and lower side 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 compressed as shown in Figure 1b by pressing force F1, F; is applied orthogonally to the top 3a and bottom 3b of the core. The compressed chip mats 5a, 5b are caused to harden under pressure and then form hard chip layers 6 on the upper side 3a and lower side 3b of the core, see figure 1c. A sandwich material 1 comprising a core 2 of corrugated cardboard and chipboard layer 6 on the upper side and the lower side is thereby obtained.

According to the invention, the lower chip mat 5b, which is intended to abut against the underside 3b of a core 2 of corrugated cardboard, can be formed by arranging glued chips in the form of a layer on a conveyor 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 bottom side 3b by means of press rollers or press plates 7, whereby the chip mats are pressed together. During pressing, the adhesive in the chip mats 5a, 5b is activated so that the chips adhere to each other, and the chip layers 6 are cured.

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

According to the invention, the chip mats 5a, 5b preferably consist of dry matter. Preferably, chips that have been glued and dried are used, but also a dry mixture of chips and glue particles, or chips and glue that are applied simultaneously and mixed first in the chip mat can 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 become approximately 3 rnm thick. The thickness of the chip mats 5a, 5b should be more than twice as desired as the desired thickness of the finished chip layers 6. For a final thickness of the chip layers 6 of about 3 mm, the chips should not be more than about 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 upper side 3a and lower side 3b of the core before the application of chips and glue intended for chip nights 5a, 5b.

The barrier layer 8 has as one of its purposes to clog the transverse channels 10 of the corrugated board, in order to prevent chips and glue from the chip mats 5a, 5b penetrating deep into the channels 10 and thereby increase the density of the sandwich material 1. The barrier layers 8 can preferably be formed by a wet chip and glue mixture 9, which is ironed on the upper side 3a and underside 3b of the core by means of applicator 11. The chip and glue mixture 9 can then be cured before chip mats 5a, 5b are arranged on respective sides 3a, 3b as shown in figure 3. It is also It is possible to directly arrange chip mats 5a, 5b on each side 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 takes place in the tubular channels 10 of the corrugated board, as shown in the enlargement in Figure 2, as this increases the bond between barrier layer 8 and core 2. However, the mixture 9 should not penetrate too far , since the density of the core 2 then increases, without 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, at the same time as the chip mats 5a, 5b can be compressed and hardens to clamping 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 made by a method according to the invention is shown in section in Figure 4.

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

The chips used for surface layers and any barrier layers are preferably wood chips, preferably sawdust, as 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 flax straw or hemp chips. The core 2 of corrugated board can be produced in different ways within the scope of the invention. Figure 5 schematically shows an example where a corrugated board web 12 of single well, i.e. corrugated board with a smooth side and a corrugated side, is wound on a roll 13, from which it is rolled off and rolled into a cylinder 14.

Gluing is done by applying glue to the corrugated board web 12 by means of a nozzle 15. The glue can be applied either only on the smooth side of the corrugated board web 12 or on both sides. The glue dries before the corrugated board web 12 is rolled up to 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 a suitable diameter, the corrugated board web 12 is cut, the cylinder 14 is sealed and then cut transversely by a set of knives 16. These are lowered into one or more folds 18 and passed on to a press frame 19, where a number of corrugated cardboard elements 17 are laid side by side with the mantle surfaces 17a against each other as shown in figure 6a. The corrugated cardboard elements 17 are then compressed into a rectangular core 2 by the pressing frame 19 pressing against at least one of the sides which are to form the side edges 4 of the core, see figure 6b, with a pressure adapted to the density and rigidity of the core 2. 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 hardened to join the core 2, alternatively the core can be kept under pressure against the side edges 4 when the barrier layers 8 and / or the chip layers 6 are applied and hardened.

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

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

The core 2 can also be built up of corrugated cardboard sheets which are joined together without first being rolled into cylindrical corrugated cardboard elements. In this case, forms of corrugated cardboard other than single corrugated can be used, such as double corrugated. The core can be manufactured, for example, by joining corrugated cardboard sheets or strips of corrugated cardboard into straight blocks of suitable size, which if necessary are cut with cuts across the tubular channels of the corrugated board so that a core with a top and a bottom side is formed substantially perpendicular to the tubular channels of the corrugated board.

A disc-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 a lower side 3b and sldokanter 4.

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

The sandwich material 1 further comprises on the upper side 3a and lower side 3b of the core chip layers 6, which consist of hardened and compressed chips and glue. In the interface between the core 2 and the chip layers 6 on each side there is a layer where chipboard and glue, alternatively another material which forms a barrier layer 8, penetrated into the tubular channels 10 of the corrugated board and thereby integrated the core 2 with the chip layers 6 or the barrier layers 8. The bond between chip layers 6 and core 2 is therefore good.

The method according to the invention is of course not limited to the embodiments described above, but a number of modifications of these 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).