EP0000058A1 - Process and apparatus for continuously moulding foamed slabs of rectangular cross-section - Google Patents

Abstract

Foamed slabs (50), the height of which corresponds approximately to their width, are produced by allowing the reaction mixture an initial reaction in an intermediate storage trough (33), then feeding it to the expansion zone (39) and guiding it obliquely downwards at between 0 DEG and 60 DEG , and by levelling the surface along the expansion zone (39). <IMAGE>

Description

The invention relates to a method and a device for the continuous production of foam blocks with a rectangular cross-section from a foamable reaction mixture, in particular based on polyurethane, the reaction mixture being fed into a continuous trough in which the reaction mixture foams to form a block.

Block foam is usually cut to the appropriate size into cushioning material, insulating material, foil material, etc.

The purpose of producing endless foam blocks with a rectangular cross section is to reduce the amount of waste.

Several methods and devices have been developed with which rectangular blocks can be continuously manufactured.

According to DT-OS 2 142 450 (corresponds to US Pat. No. 3,786,122), a block foaming system is known in which the reactive mixture is fed into the bottom of a trough, which is at the inlet current of a conveyor is arranged. The mixture already reacts in the trough to a state in which it is just still flowable, and reaches a sloping plane via a weir, which is arranged in the foaming zone and over which a base film is passed. This inclined plane is inclined in such a way that the surface of the resulting foam block runs horizontally or is aligned parallel to the inclination of the actual conveyor belt which follows the inclined plane and which is inclined approximately between 3 and 10 °. A block with a rectangular cross-section is created; however, it has a leather-like skin on the surface. In addition, the block height is not much larger than about half the block width.

On the other hand, a block foaming system is known from DT-OS 2 12.3 21c (corresponds to US Pat. No. 3,924 925), in which the surface of the resulting block is covered with a cover film along the foaming zone and leveled transversely to the conveying direction by means of a leveling device. This avoids the formation of leather-like skin; as a block height, however, a height is also only slightly above half the block width. It has proven to be disadvantageous that the bottom zone of the foam block has a higher compression, so that special attention must be paid to this deficiency in the further processing of the foam.

The object of the invention is a method and a device with which one can produce endless foam blocks, the height of which is substantially greater than half the block width and have a homogeneous cross section, and also largely have the same density as the core in the bottom zone and in the top zone.

• a) Das Reaktionsgemisch wird vor dem Auftragen anreagieren gelassen;
• b) das aufgetragene Reaktionsgemisch wird in der Aufschäumzone unter einer Neigung zwischen 0 und 60°, bevorzugt zwischen 0 und 30⁰, nach unten geführt;
• c) entlang der Aufschäumzone wird die Oberfläche des aufsteigenden Schaumstoffs quer zur Förderrichtung egalisiert.

From a process engineering point of view, this object is achieved according to the invention by the combination of the following steps:

• a) The reaction mixture is allowed to react before application;
• b) the applied reaction mixture is guided downward in the foaming zone at an inclination between 0 and 60 °, preferably between 0 and 30 ⁰ ;
• c) along the foaming zone, the surface of the ascending foam is leveled transversely to the conveying direction.

As demonstrated at the beginning of the prior art, the individual process steps are known per se. However, it was not immediately obvious to the person skilled in the art that the combination of these measures known per se had to have the desired effect according to the invention; because to produce blocks, the height and width of which are approximately the same size, for example, either twice the amount of mixture has to be applied while maintaining the previously usual belt speeds or the belt speed is reduced by half in the process according to the invention. In both cases, the procedure according to the invention results in a double thickness mixture application in comparison with the previously known methods. From this, the expert had to conclude that precisely because of the higher foaming height, a greater load rests on the bottom zone, which should actually cause an even higher density of the bottom zone. It also had to be assumed that despite the measures known per se for avoiding the surface curvature due to the greater block height, such a curvature had to occur despite the application of the teaching according to the invention. Contrary to the previously known method, in which the reaction mixture is allowed to react before application and the block surface is kept level by the downward reaction of the applied reaction mixture in the foaming zone on the conveying surface or the cover sheet conveyed thereon, the reaction foams in the method according to the invention Mix up beyond that level so that ideally the angle of inclination of the conveying surface and the angle of rise of the foam surface in the foaming zone are the same.

Generating higher blocks results in less production effort and less loss. In the previously known methods, it was necessary to cut off a layer about 2 cm thick from the bottom and top zones, provided the block material was to be used for high demands. The method according to the invention makes it possible to keep the thickness of the layers to be cut away smaller, i. H. to reduce to about 1 cm. If a block is now manufactured, the height of which corresponds to the width, this saves 6 cm of foam compared to the previous manufacturing processes in which the height corresponded to approximately half the width. A layer thickness of 4 cm is saved because only one block is produced, the cross-sectional area of which corresponds to the sum of two cross-sectional areas of blocks produced according to the previously known methods. The additional layer thickness saved by 2 cm results from the better cross-sectional homogeneity in the top and bottom zones.

The process according to the invention is suitable for the production of endless foam blocks made of polyurethane, polycarbodiimide polyisocyanurate or combinations of these plastics. Paper sheets made of normal or plastic-coated kraft paper are used as top or bottom and side foils. Nonwovens, textile webs as well as plastic films and foam films, metal films and combinations of these materials are also used. The more noble materials are only used if the top and / or bottom layer of the foam block is to be used for a particular purpose as a product laminated with the top layer.

To carry out the method, the invention is based on a device consisting of a mixture feed device and a conveyor with side boundaries and unwinding stations for bottom, side and cover foils.

• a) Die Aufgabevorrichtung ist mit einem Zwischenlagerungstrog ausgestattet;
• b) in der Aufschäumzone ist die Förderfläche in einer Neigung von 0 bis 60°, vorzugsweise 0 bis 30°, einstellbar;
• c) in der Aufschäumzone ist eine Egalisiervorrichtung angeordnet.

What is new is the combination of the following features:

• a) The feeder is equipped with an intermediate storage trough;
• b) in the foaming zone, the conveying surface can be set at an incline of 0 to 60 °, preferably 0 to 30 °;
• c) a leveling device is arranged in the foaming zone.

The intermediate storage trough can, as already described in relation to the prior art, be arranged in front of the inlet end of a conveyor. The intermediate storage trough can also be provided on the inlet end of a conveyor.

The conveying surface is inclined downwards in the Aufsehäumzone. The inclination can vary over the length of the conveying surface in order to adapt it to the degree of foaming over time. The conveyor surface can be designed, for example, as a stationary, possibly multi-part plate or as a separate conveyor belt to which the actual conveyor belt is connected. However, only a single conveyor belt can also be provided, the first part of which is guided at a corresponding incline.

A slatted frame, which is particularly lightweight, is preferably used as the leveling device. However, pressure plates can also be provided which are elastically suspended perpendicular to the conveying direction. Skids arranged transversely to the conveying direction and provided with counterweights are also known. Also a circumferential band, the lower strand of which loosely on the surface of the Ge being foamed mixed down, was already used. Such a belt can consist of a rubberized fabric belt, but can also be constructed in the manner of an endless, slatted frame.

The feed device and leveling device are preferably designed to be adjustable in width in a manner known per se.

• Fig. 1 die Vorrichtung gemäß einem ersten Ausführungsbeispiel in der Seitenansicht und
• Fig. 2 die Vorrichtung gemäß einem zweiten Ausführungsbeispiel in der Seitenansicht.

In one drawing, the device according to the invention is shown purely schematically in two exemplary embodiments and explained in more detail below. Show it:

• Fig. 1 shows the device according to a first embodiment in side view
• Fig. 2 shows the device according to a second embodiment in side view.

In Fig. 1, the feed device 1 consists of a mixing head 2 and a trough 3, in the lower area of which leads away from the mixing head 2 feed line 4. An inclined conveying surface 6 is arranged in the foaming zone 5. It consists of a circumferential belt 7, the upper run 8 is backed with adjustable plates 9, 10, 11, so that, seen over the length, the conveying surface 6 has different angles of inclination. A tensioning device 12 ensures constant tension of the belt 7. The actual conveyor belt 13 connects to the belt 7. An insert 14 bridges the gap between the two belts 7, 13. The belts 7, 13 are covered by a base film 15, onto which the mixture which has reacted in the trough 3 is fed. The bands 7, 13 are delimited by side boundaries 16 (only the rear one is shown) which are covered with side foils 17. A cover film 18 is placed on the foaming mixture at the beginning of the foaming zone 5 and guided under a leveling device 19. It consists of a slatted frame 20 which is suspended from a frame 22 by means of belts 21. The height of the block 23 corresponds to its width of 2 m.

In Fig. 2, the feed device 31 consists of a mixing head 32 and a trough 33, to which the reaction mixture is fed from above via a transverse distributor pipe 34 and a guide plate 35. Finally, the mixture passes through a feed plate 36 onto the base sheet 37, which is guided over a table 38 in this area. The bottom film 37 then reaches a conveying surface 40 which is arranged in the foaming zone 39 and is designed as an angle-adjustable plate. Behind it is the actual conveying belt 41 which is correspondingly height-adjustable in order to be able to adapt it to the angular setting of the conveying surface 40. At the beginning of the foaming zone 39, a cover film 42 is placed on the surface of the reaction mixture and carried out under a leveling device 43. This consists of an endless circumferential band 44, the upper strand 45 is guided over rollers 46 and the lower strand 47 loosely hangs down and leveled the surface of the rising foam. The side boundaries 48 (only the rear one is shown) are covered by side foils 49. The finished block 50 has a width of 2.10 m and a height of 1.80 m.

Claims (2)

1. A process for the continuous production of foam blocks with a rectangular cross-section from a foamable reaction mixture, in particular based on polyurethane, the reaction mixture being fed into a continuous trough in which the reaction mixture foams up to the block, characterized by the combination of the following steps: a) The reaction mixture is allowed to react before application; b) the applied reaction mixture is guided downward in the foaming zone at an incline between 0 and 60 °, preferably between 0 and 30 °; c) along the foaming zone, the surface of the ascending foam is leveled transversely to the conveying direction. 2. Device for carrying out the method, consisting of a mixture feed device and a conveyor with side boundaries and unwinding stations for bottom, side and deodorant films, characterized by the combination of the following features: a) The feed device (1, 31) is equipped with an intermediate storage trough (3, 33); b) in the frothing zone (5, 39), the conveying surface (6, 40) can be set at an incline of 0 to 60 °, preferably 0 to 30 °; c) in the frothing zone (5, 39) a leveling device (19, 43) is arranged.

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