DK175937B1 - Flexible felt of fiber material with random fiber orientation - Google Patents

Description

in DK 175937 B1

The invention relates to a felt of mineral wool, in particular a so-called crepe felt, that is, in which the orientation of the fibers rather than being parallel to a plane is virtually random.

5 Creped filters are designed for various applications, in particular where they can either be subjected to pressure without causing excessive flat pressure or a perpendicular to the surface without causing delamination. However, unlike conventional layered filters, the 10 are very sensitive to bending, and as soon as they bend, even to a slight extent, they strike cracks perpendicular to their surface. This phenomenon greatly limits the field of application of creped filters. It is a desire to be able to make this area bigger.

Traditionally, filters of mineral fibers are layered as they are built up continuously, the fibers moving by gas streams deposited on a conveyor. The conveyor holds the fibers and releases the gases.

Before being deposited on the conveyor, the fibers 20 are coated with an adhesive composition adapted to bond the fibers to each other, thus providing adhesion to the built-up felt. The adhesive composition applied in liquid form is cured by a heat treatment performed on the felt which is already applied to the desired shape in thickness and density.

The traditional ways of making filters end up in products whose properties do not quite meet the requirements of particular applications. Thus, in addition to the insulating properties required in a very ordinary way, it is sometimes necessary that the products used have very specific mechanical properties. This is e.g. This is the case for products that carry building elements and which thus have to withstand large compressions, such as the products that serve to insulate 35 roof terraces that are accessible to traffic. This is also the case for products used for external insulation and which should in particular be able to withstand tearing forces.

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In order to provide products with these particular properties, it is necessary to change the traditional methods of making the filters.

With the conventional method, the formation of the filters by depositing fibers on a receiving conveyor, or on a corresponding means, leads to an infiltration which is not uniform in all directions. It is found in experiments that the fibers have a high tendency to place parallel to the receiving surface. This added flexibility is all the more pronounced when the fibers are longer. This felt structure is beneficial in terms of longitudinal insulating properties and tensile strength. Thus, such a structure is advantageous in many applications.

However, it should be understood that such a structure is not the most suitable when the product e.g. shall be able to withstand compression or tearing in its thickness direction.

Methods are known which give the fibers a virtually random orientation. In European patent application no.

0 133 083, it is proposed that the felt fibers received on the receiving means, optionally after having undergone thickness compression, be continuously compressed longitudinally through passage from a pair of conveyors moving at one speed to a pair of conveyors. at a lower rate than the previous one. Higher degrees of compression can be achieved when compression is performed in several successive steps, especially with filters where compression without folding is difficult to achieve. To achieve the same final degree of compression, the properties of the products produced can be improved if the compression is performed in 30 multiple steps.

In another document, European Patent Application No. 0 434 536, a felt of mineral fibers with improved properties is proposed, the fibers having virtually random orientations, and the felt being formed of 35 fibers having a diameter mostly of 2.5 and 4.5 μτη, a length of 2 to 15 cm, and a density not exceeding 40 kg / m. In this application it is contemplated that the DK 175937 B1 3 mat may have a covering layer, i.e. be coated with one or more adhesive layers of paper, aluminum, polyethylene or PVC.

The 5 mats made of creped mineral fibers produced by the techniques described above are usually transported and used in the form in which they are made, ie. like flat panels. However, it would be interesting to be able to bend the creped mats - temporarily or permanently - and possibly with small radii of curvature.

10 The interest in being able to roll the creped mats together to allow transport and storage of large lengths, without using too much space, is obvious. In the industrial field of scratched mats, the insulation of large pipelines or cylindrical containers on which to walk can be an application where sustained curvature of a crepe may be very useful.

Still in the prior art regarding crepe mineral wool filters, European Patent Specification No. 20,472,532 is known, which proposes a technique for making a crepe sheet coated with a single-sided coating. According to this method, after the scraping done in the usual manner, a glass tissue is deposited on the two surfaces of the mat before the thermal treatment of the glue which constitutes the binder. At the end, the mat is split in the thickness direction to form two identical mats coated on a single side. This technique makes it possible to provide a sheet which can be bent, leaving the glass tissue to form the concave side. The document clearly shows that bending in the other direction (glass tissue on the convex side) is impossible. The intermediate with the web on the two surfaces is described as rigid, but after cleavage, the fibers in the free side "are not subjected to tensile and compressive forces in the direction of the fibers, but perpendicular to the fibers when the plate is bent.

35 The sheet made by the method bends well thanks to the absence of horizontal bonds on the back The assembly of these two properties, namely the stiffness of the sheet having a coating on its two surfaces, and the flexibility of the slit in the thickness direction plate, shows that it is under tension that the glass tissue is undeformable and that the curvature cannot occur in any other way than with the coating on the concave side. The mounting technique described in the document, namely that the edges of the plate in the ceiling are "in contact with T-profiles", as in the case of a vault, confirm this.

The invention aims to provide a product in the form of a mat of creped fibers which can be rolled up on itself without deterioration for the purpose of permitting transport and storage.

It is also an object of the invention to allow the use of mats with creped mineral fibers on 15 curved surfaces without losing their good properties, especially with respect to insulation.

In order to achieve these objects, the invention proposes a felt of crepe mineral wool, which felt on at least one of its surfaces is provided with a covering layer and is adapted to undergo a temporary or sustained curvature, the surface of which is arranged to be convex, is equipped with a covering layer whose breaking strength is greater than 300 kPa.

This layer is preferably made from kraft paper. In order to be able to achieve even the required property with respect to breaking strength, it should have a surface density 2 greater than or equal to 60 g / m.

In order to be easy to roll up on itself and to retain all properties once placed on a curved surface, the creped felt according to the invention preferably has a degree of creep of between 4 and 5 and a surface density less than 2 kg / m.

In an advantageous embodiment of the invention, the product has on the surface opposite the cover layer 35 fibers which are substantially perpendicular to the surface. Such an arrangement is provided if the felt of scraped mineral fibers is formed as a result of a division in the thickness of a thicker felt, with the opposite surface being coated with the covering layer according to the invention formed by the splitting.

The invention will be better understood and the advantages will become more apparent from the drawings and the following description. In the drawing, FIG. 1 shows the result of a curvature applied to a known crepe mat; FIG. 2 and 3 a mat according to the invention, respectively 10 before and after curvature.

The creped filters, of which this is the case, are made from mineral wool, glass wool or so-called stone wool. These products are most often made from fibers produced by centrifugation techniques, as the case may be, through passage through openings in a centrifuge or simply by throwing on the surface of high speed rotating rollers.

The filter forming plant comprises, first and foremost, one or more machines of the above described kind for producing fibers. The ejected fibers are collected by suction in the lower section of the machines on a conveyor belt which forms the bottom of a receiving chamber.

Within this chamber, organs throw a liquid binder mixture onto the fibers. It is usually attempted to perform this in such a way that the distribution of binder on the fiber is as uniform as possible, so as to distribute the binder uniformly in the felt unit.

The felt coming out of this chamber is usually relatively light. Its average density is small 30 for such a large thickness. In addition, as a result of the fabric manufacturing method, the fibers are generally oriented in directions parallel to the conveyor.

In conventional plants for the production of mineral fiber filters, the felt exiting the receiving chamber immediately enters a heat treatment which causes the binder to harden.

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In making a crepe felt, however, a further operation is continued before the binder hardens: It is a matter of changing the dominant orientation of the fibers. Several methods are possible. There are e.g.

5 the possibility of "running" the felt with needles which, by their action, orient the fibers perpendicular to the surface of the felt. Another method allows the felt, after the changes, to obtain a substantially increased density and a different orientation of the fibers.

The changes according to the latter method preferably include a compression of the felt in the thickness direction. This compression is achieved e.g. by passing the felt through two conveyors, the distance separating the two conveyors becoming smaller and smaller in the direction of feeding of the felt.

The thus compressed felt then passes between other conveyor pairs, the speed of each pair being less than the previous pair, which causes a longitudinal compression of the felt.

During this series of changes, the felt is held in by the barrier to prevent it from assuming at least part of its original volume, and is subsequently introduced directly into the heating cabinet, where the heat treatment provides the curing of the binder and the stabilization of the product.

By taking a sample of the crepe felt formed by one of the methods described above and subjecting it to bending, generally, even for very large radii of curvature, a deterioration of the product is obtained. Between the 30 fibers in the convex side, cracks occur which extend to the interior of the product. In FIG. 1 shows an illustration of this phenomenon. Such cracks destroy the lateral stability of the product and severely impair its adhesion. Indeed, the breaking of the bond between the fibers on each side of the crack 35 is irreversible, being the chemical bonds established in the binder during curing thereof that no longer exist.

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The above-described phenomenon makes it impossible to bend a crepe felt, even temporarily, without destroying its properties. It is e.g. For this reason, if a glass wool crepe felt with an o 5 density of 16 kg / m and a thickness of 120 mm is used to insulate a horizontally placed cylindrical container with a diameter of 1 m - the use of the crepe material should allow continuous good insulation - cracks occur on the convex side, which cracks are identical to those in FIG. 1, which greatly impairs the heat insulation of the shroud of crepe felt.

In the same context, when using a crepe felt with a width of 1.20 m and a length of 10 m with a density of 30 kg / m 2 and a thickness of 30 mm industrial, it is interesting to be able to produce the product in rolls where the felt is rolled up on itself. In such a case, even if the outer windings of the roll have a large radius of curvature, which only causes cracks with a small depth on the convex side, it will generally go differently in the center of the roll 20, where the radii of curvature are of the same order as the thickness of the felt and thus poor probably exceeds 30 mm. Here the deteriorations are unacceptable. However, it is particularly interesting to have creped filters in rolls, ie. of indefinite length, since it is thus possible at the construction site 25 to precisely cut the piece that is needed without creating waste which involves waste.

The inventors have thus been given the idea of equipping one of the product's surfaces with a covering layer, whose essential function is to avoid an extension of the convex side of the product, which is to undergo a curvature.

Experiments with many different materials have been carried out, using films made of plastic (polyethylene), of metals (aluminum) and different types of paper (power). These are both simple films and composite materials.

The latter appears in sandwich form, e.g. an aluminum film which, over its entire surface, is connected to a polyethylene film, or in the form of a single reinforced film.

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Thus, kraft papers reinforced with reinforcing gratings made of fiberglass or polyester wires have been tested.

In the following, an example will be described of an operation which provides a solution to the problem posed. In a glass wool manufacturing line where the fibers are produced by forcing them to pass through openings in a centrifuge, a creped felt and the conveyor belt which carries them prior to introduction into the heat treatment plant where the curing of the binder takes place are introduced. cover paper of kraft paper with a surface density of 90 g / m. This is glued to the felt at the beginning of manufacture and continues to accompany it, the finished product being shown in FIG. 2. The felt has a density 15 of 43 kg / nV * and a thickness of 60 mm. Its degree of creep, ie. the longitudinal concentration of fibers produced during the creeping operation is 4.5 (which is equal to the ratio of the velocities at the entrance to the creeping zone and at the exit, and so is the increase in density 20). Attempts to roll the felt thus formed on themselves have been made, since the kraft paper has been on the convex side. After keeping the roller locked for a week, it has been rolled out and found that once flattened, the felt has no memory, retaining its flatness. Finally, a destructive test in which the kraft paper was separated from the felt surface showed the absence of cracks, that is, the product did not change in any way during the roll-up.

An attempt to roll up the felt in the other direction, 30 with the paper on the concave side, has given the felt that shown in FIG. 1, i.e. a plurality of cracks which, taking into account the average thickness of the felt, crosses it completely through several places.

In contrast, when the paper is on the convex side, the result is that of FIG. 3 showed where it is seen that the felt does not move except the compression of the concave side alone.

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A comparative experiment with an identical paper, but with a smaller surface density (60 g / m), failed during the roll-up of the felt as the paper was torn in several places.

5 Finally, studies that have been conducted with. various materials such as cover layers, shown that a necessary condition for good functioning of the invention is that the breaking strength of the layer must be greater than a certain limit, namely 300 kPa. Surprisingly, it has been found that this limit did not depend on the properties of the felt. From a creeping degree greater than 4, regardless of the thickness or density of the felt, it is possible to perform large curves all the way up to the roll-up on itself, provided that the cover layer is located on the convex side and has a breaking strength of over 300 kPa. .

The breaking strength is a characteristic size for the stability of thin films designed for packaging.

The measurement was carried out in accordance with the standard DIN 53 113 (June 1990).

20 The only limitations found were the large thicknesses of the filters that arose due to large bulk densities. The results become less certain when, for example, a blanket of 60 kg / m has a thickness of 120 mm. Thus, it is still possible to apply a blanket to the felt where the blanket is arranged to insulate a curved support, but reeling the felt on itself, leaving no void other than the center of the roll, is impossible. It has been found that as long as the density of the product multiplied by the thickness remains within certain limits, the reeling is still possible. If the density in kg / m3 multiplied by the thickness in meters (ie the surface density) remains below 2 kg / m, it can still be possible to roll the product according to the invention on itself, even with a creeping degree of more than 4.

Claims (5)

A felt of crepe mineral wool, which felt on at least one of its surfaces is provided with a covering layer and is adapted to undergo a temporary or continuous curvature, characterized in that the surface arranged to be convex , is equipped with a covering layer whose breaking strength is greater than 300 kPa. Mineral wool felt according to claim 1, characterized in that the cover layer is kraft paper-based. Mineral wool felt according to claim 2, characterized in that the cover layer is constituted by a kraft paper whose surface density is greater than or equal to 60 g / m3. Mineral wool felt according to one of claims 1-3, characterized in that its degree of creep is greater than 4 and its surface density is less than 2 kg / m, and that it is wound on itself to form a roll. Mineral wool felt according to one of the preceding claims, characterized in that it is the result of a thickness distribution in the thickness direction of a thicker felt.