EP0242650B1 - Method of manufacturing a building panel - Google Patents

Abstract

Method of manufacturing a building panel, in particular for ceilings and walls, which is composed of at least one cover slab and a central element and the cover slab of which is made of a hygroscopic material, the cover slab being dried and bonded, in the dried state, with the aid of a synthetic-resin adhesive to the central element, which is designed as a grating or as a solid slab, the cover slab being provided furthermore, before or after bonding to the central element, with a coating which reduces the surface pores. For use of the building element in a climate having a transient, mean, minimal relative atmospheric moisture of a%, the cover slab is dried, in the course of manufacture of the building element, down to a relative slab humidity of b% (based on the dry weight) which is smaller and corresponds to the point, assigned to the mean, minimal relative atmospheric moisture, of the relative slab moisture on the equilibrium curve of the relative slab moisture of the cover slab in the moisture exchange with the surrounding air. In this dry state, the cover slab is bonded rigidly to a central element which is free from moisture expansion or exhibits low moisture expansion. Subsequently, the coating is applied to all surfaces of the cover slab having the specified dry state which come into contact with the external air.

Description

The invention relates generically to a method for producing a tabular component, in particular for ceilings and walls, which is constructed from at least one cover plate and a central element and whose cover plate consists of a hygroscopic material, the cover plate being dried and in the dried state with the aid a synthetic resin adhesive is connected to the central element, which is designed as a grating or as a solid plate, wherein the cover plate is further provided with a coating that reduces the surface pores before or after the central element is glued. - In general, such a component is provided with two cover plates, an inner plate and an outer plate. The central element can be a plate, a frame or a grating. If the central element is a frame or a grating, the intermediate space can be filled with an insulating material. Hygroscopic materials are e.g. B. chipboard, fiberboard and esp. Cement chipboard and fiber cement boards.

As part of the measures known from practice, the drying takes place in the course of the production of the cover plates, in accordance with the regulations of the technology, regardless of the later place of use of the component. When gluing, you do not pay attention to whether the adhesive contains water and consequently water enters the aggregate of cover plate and central element. This also applies to the coating, the purpose of which is to form a decorative or protective surface, while no consideration is given to its function as a water vapor barrier by pore closure. The finished components often show disturbing changes in use, namely stretching and shrinking. This limits the use because, for example, in a building that is constructed with such components, appropriate expansion joints must be set up and the component itself cannot be used as a structural load-bearing component and can make only a small contribution to the structural integrity of the building. The components cannot be installed seamlessly. The static load must essentially be transferred to a separate stable framework made of wood, metal or reinforced concrete.

The invention has for its object to carry out the generic method so that the components produced no longer have disturbing expansions and shrinkages and can be installed seamlessly.

To achieve this object, the invention teaches that for the purpose of using the component in a climate with a temporal, average, minimum, relative humidity of a%, the cover plate in the course of the manufacture of the component to a relative plate moisture of b% (based on the Dry mass) is dried down, which is smaller than the point of the relative plate moisture on the equilibrium curve of the relative plate moisture of the cover plate associated with the exchange of moisture with the ambient air, which corresponds to the mean, minimum, relative air humidity, that the cover plate in this drying state is stuck to a central element with a rigid bond is, which is free of moisture expansion or low moisture expansion, and that the coating is then applied to all surfaces of the cover plate having the specified drying state, which come into contact with the outside air. - Climate means not only the metereological climate at a certain geographical location in the context of the invention, but also the environmental conditions that z. B. prevail in a deep-freeze room, a drying chamber or in a commercial kitchen.

Components manufactured according to the invention have the following properties: At the lowest, occurring relative atmospheric humidity at the place of use, there are no shrinkage stresses and no material cracks, since the components subjected to a change in length due to moisture have been processed in the state of their smallest expansion and have been combined with the central element. The shrinkage is thus anticipated. If the relative humidity increases significantly at the point of use, the material moisture of the hygroscopically reacting component is greatly slowed down, ie. H. of the cover plate or cover plates, due to the reduction in the number of pores and the pore area due to the applied coating. If the relative air humidity at the place of use is very long and persistent, the rigid adhesion of the hygroscopic cover plate or cover plates to the substrate, which reacts only slightly or not at all, prevents expansion of these components in length and width. The stresses occurring in the material are deflected in the direction of the material thickness.

There are several options for further developing the method in the context of the invention. A preferred embodiment of the invention is characterized in that a waterproof synthetic resin adhesive is used, which ensures that water is not introduced into the aggregate of cover plate and central element through the adhesive. But you can also work with synthetic resin adhesives that carry water if only the water content is kept sufficiently low. Accordingly, it is advisable to work with a water-free or low-water coating material. According to a preferred embodiment, the number of surface pores is reduced by at least 50%, preferably by approximately 75%, with the coating material.

Metal plates, metal profiles, frames and gratings made of metal profiles come into question as the central element. However, you can also build the central element from wood. In this respect, plywood is particularly suitable, the change in length of which is minimized by suitable multi-layer gluing in both directions. But solid wood profiles can also be used if they are arranged in a frame or in a grating in such a way that the moisture-related dimensional changes of the wood in width and thickness have no effect. In the longitudinal direction parallel to the grain, the moisture-related change in length of wood is known to be negligible, which can be used here. If you work with cover plates, the thickness of which is not particularly large for the production of particularly light components, it is advisable to work with a grating as the central body, the grille bars of which are at a distance which is a maximum of twenty times the thickness of the cover plate or one of the two cover plates corresponds. This prevents the relatively thin cover plates from convexly deforming outwards when water is absorbed.

The invention is explained below on the basis of a graphic representation and on the basis of exemplary embodiments.

The graphic representation explains the behavior of a particle board in relation to the moisture in the plate in exchange with the ambient air. The relative air humidity has been plotted on the ordinate and the relative plate humidity in percent, based on the dry matter, on the abscissa axis. The curve K entered is the equilibrium curve, specifically at a temperature of 20 ° C. It can be seen that at a relative air humidity of 80% the plate moisture is about 9%. At a relative humidity of 90%, the plate moisture is about 15%. It can be seen from this that hygroscopic materials constantly bind a certain amount of water in a finely divided form as moisture. They release this moisture into the ambient air when the air becomes drier. They absorb moisture from the ambient air when it becomes humid. If the parameters are otherwise constant, an equilibrium value is established. The entire length of the curve shown is not important in practice. The range below 30% relative humidity is only important in rare exceptional cases. Likewise, the range above 90% relative humidity is only significant in certain climates.

Example 1:

A prefabricated wall consisting of building elements with cover plates, which are designed as cement chipboards and which have a wooden inner frame, is to be erected in a North African desert area. The climate shows a lowest relative humidity of 30% at 15 ° C. A plate moisture of 3.1% corresponds to these conditions. According to the invention, the cover plates have to be adjusted to this plate moisture by means of drying. The central element is also hygroscopic as a wooden frame. However, its behavior towards changes in air humidity is very different compared to the behavior of the cover plates. At right angles to the grain of the wood there is a significant change in length due to moisture. In parallel to the grain, this change in dimension is negligibly small. In this exemplary embodiment, the cover plates are therefore fixed on the central element parallel to the grain of the wood. It goes without saying that the wood of the central element should also be dried as far as possible, but this is not a mandatory requirement in this case. The cover plates are fixed on this central element with Epoxy resin adhesives, polyurethane adhesives, polyvinyl acetate adhesives and the like. Like., Which have no water or only a low water content. For example, such adhesives can be used in alcohol dispersion. The bonding is carried out in such a way that moisture from the ambient air is not absorbed by the cover plates in this process. The bonding is therefore carried out in a suitably dry room or the cover plates are heated accordingly before the bonding. Then there is the application of a surface pore-reducing coating, it also being possible to work with a plastic coating, e.g. B. with chemically curing two-component paint systems or in the form of dispersions with a high alcohol content and low water content.

Example 2:

Die "feuchte" Abmessung der Deckplatte beträgt demnach

$\text{100,22 x 100,22 x 1,018 cm = 10.224,84 cm³.}$

A cement chipboard that is not rigidly bonded to a substrate as a cover plate of 1000 x 1000 x 10 mm is moved from a climate with 30% relative humidity without changing the temperature to a climate with permanent 95% relative humidity. Your moisture-related volume change is approx .:

The "wet" dimension of the cover plate is accordingly

$\text{100.22 x 100.22 x 1.018 cm = 10,224.84 cm³.}$

This means an increase in volume of

Bei einer erfindungsgemäß starr auf einen nicht hygroskopisch reagierenden Untergrund verklebten, ansonsten völlig gleich gearteten Deckplatte werden Längen- und Breitenänderungen unterbunden, und die durch die Verlagerung in ein Feuchtklima (permanent 95 % relative Luftfeuchtigkeit) bedingte Volumenzunahme wirkt sich ausschließlich in Richtung der Plattendicke aus, d. h. die Deckplatte quillt in der Dicke um 2,2484 % anstatt um 1,8 % bei der nicht verklebten Deckplatte. Die Dicke der Deckplatte wird von 10 mm auf 10,248 mm ansteigen. Diese Dickenänderung ist bei einem Bauelement praktisch bedeutungslos.

In the case of a cover plate which is rigidly bonded to a non-hygroscopically reacting substrate according to the invention and is otherwise of the same type, changes in length and width are prevented, and the increase in volume caused by the shift into a moist climate (permanently 95% relative air humidity) has an effect only in the direction of the plate thickness, ie the cover plate swells in thickness by 2.2484% instead of 1.8% in the case of the non-bonded cover plate. The thickness of the cover plate will increase from 10 mm to 10.248 mm. This change in thickness is practically meaningless for a component.

It has no significant influence on the material structure, nor is it visually perceptible.

Example 3:

Cement chipboards as cover plates as in Example 1 are moved from a climate with 30% relative humidity for a period of 30 days without changing the temperature to a climate with 95% relative humidity and then again exposed to the climate with 30% relative humidity.

In the case of the cover plate which was not rigidly bonded to a substrate, the elongations, width and thickness mentioned under Example 2 occur over the course of about 20 days.

auf 10,186 mm ansteigt.In the case of the cover plate which is rigidly bonded to a central element which does not react hygroscopically and is coated in accordance with the invention, this takes place - due to the reduction in the number of pores and the pore area through the coating - the moisture absorption with a delay. The delay in moisture absorption is approximately proportional to the reduction in the pore area at the cover plate / air interface. With a 50% reduction in this pore area, this means that these cover plates experience only about 3/4 of the volume increase to be expected in a long-term treatment in the 30-day wet climate, that is to say that the thickness increases by

increases to 10.186 mm.

This change in thickness is therefore hardly greater than the change in thickness of the non-bonded and uncoated cover plate with 1.8% to 10.18 mm.

From Examples 2 and 3 it can be seen that, for. B. treated according to the invention cement chipboard to short-term fluctuations in relative humidity (day-night fluctuations, weekly fluctuations) practically no longer respond significantly, and that even with extreme long-term changes from 30% to 95% relative humidity and vice versa the deflection of the elongation forces in a change in thickness runs in such narrowly defined areas that neither material damage (structural change) nor a visible change in volume occurs. Accordingly, according to the invention, the moisture-induced change in length of prefabricated materials is prevented at the expense of a greater swelling in thickness of these materials, this greater swelling in thickness remaining far below the threshold of the physically and optically reasonable limit. As a result, large-area components (walls, ceilings) can be produced without movement or expansion joints.

Claims (5)

1. Method for the production of a building element of panel form, especially for ceilings and walls, which is assembled from at least one cover plate and a central element and the cover plate of which consists of a hygroscopic material, wherein the cover plate is dried and connected in the dried condition with the aid of a synthetic resin adhesive with the central element which is formed as a lattice grid or as a solid plate, while furthermore the cover plate is provided, before or after the sticking with the central element, with a coating which reduces the surface pores, characterised in that for the purpose of using the building element in a climate with a temporal, mean, minimal, relative air humidity of a % the cover plate is dried down in the course of the production of the building element to a relative plate humidity of b % (in relation to the dry mass) which is lower than the point, associated with the mean, minimal, relative air humidity, of the relative plate humidity on the curve of equilibrium of the relative plate humidity of the cover plate in the moisture exchange with the ambient air, in that the cover plate is stuck in this drying condition by rigid bonding on a central element which is free from or low in moisture expansion, and in that thereafter the coating is applied to all surfaces of the cover plate having the stated drying condition which come into contact with the external air.
2. Method according to Claim 1, characterised in that one works with a water-free synthetic resin adhesive.
3. Method according to one of Claims 1 or 2, characterised in that one works with a water-free coating material.
4. Method according to one of Claims 1 to 3, characterised in that with the coating material the number of surface pores is reduced by at least 50% preferably by about 75 %.
5. Method according to one of Claims 1 to 4, in the form of embodiment with a lattice grid as central element, characterised in that one works with a lattice grid the lattice bars of which have a spacing which corresponds at maximum to twenty times the thickness of the cover plate or the added thickness of the cover plates.

Images