FR2726012A1 - FELT OF FIBROUS MATERIAL FOR RANDOM RANDOM ORIENTATION - Google Patents

Abstract

The invention relates to crimped mineral wool felts, that is to say in which the orientation of the fibers, instead of being parallel to a plane, is quasi-random. To allow the felts to be bent temporarily or permanently, they are fitted on the convex side of a surfacing sheet with a burst strength greater than 300 kPa, such as for example kraft paper with a basis weight greater than 60 g / m ** 2.

Description

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FELT OF FIBROUS MATERIAL

CURRENT RANDOM ORIENTATION

  The invention relates to mineral wool felts and more particularly felts said "creped" that is to say in which the orientation of the fibers, instead of being parallel to a plane, is quasialéatoire. o0 The creped felts are intended for a variety of uses, in particular

  when one wants to be able to exert on them, either a pressure without

  too much, ie traction perpendicular to the surface without delamination. However, unlike the usual laminated felts, they are very sensitive to bending and as soon as they are bent, even slightly, they crack perpendicular to their surface. This phenomenon significantly limits the field of use of creped felts. We

  wish to expand this area.

  In the traditional way, the mineral fiber felts are laminated, they

  are constituted continuously by depositing on a conveyor the fibers which are

  abutted by gaseous currents. Conveyor retains fibers and passes

gas.

  Before they are deposited on the conveyor, the fibers are coated with a resinous composition intended to bind the fibers together, thus giving cohesion to the constituted felt. The resinous composition applied in form

  liquid is crosslinked by a heat treatment carried out on the felt

  have been reduced to the desired thickness and density conditions.

  Traditional felting patterns result in products whose properties do not fully meet all the requirements of particular applications. In addition to the insulating qualities required in a very general way, it is sometimes necessary that the products used have very specific mechanical properties. This is the case for example products supporting masonry elements and which must therefore withstand strong compressions such as products used for -2Iisolation of roof terraces accessible to traffic. This is also the case for products used in isolation from the outside and which, in particular, must be able to

  resist the efforts to tear.

  In order to obtain products having these particular properties, it is necessary to modify the traditional felting processes. In the traditional process, the formation of felts by deposition of fibers

  on the receiving conveyor or on a similar device leads to an

  clothing that is not homogeneous in all directions. There is experi-

  mentally that the fibers have a strong tendency to stand parallel to the receiving surface. This tendency is all the more accentuated as the fibers are longer. This felt structure is favorable to their insulating properties and also to their tensile strength in the longitudinal direction. For

  Many uses such a structure is therefore advantageous.

  However, it is understood that such a structure is not the most suitable when for example the product must resist compression or tearing

in the direction of its thickness.

  Methods are known that provide a quasi-random orientation of the fibers. Thus, the European patent application EP-A-0 133 083 proposes that the fiber felt collected on the receiving member, possibly after compression in the direction of the thickness, be compressed continuously in the longitudinal direction by passing a pair of animated conveyors

  of a certain speed to a pair of conveyors of speed lower than the preceding

  toothed. Higher compression rates can be achieved when

  pressure is carried out in several successive stages, in particular with the felts for which the compression without formation of folds is the most difficult to obtain. Similarly, for the same final compression ratio, the properties of the products obtained can be improved when the compression is conducted in

many stages.

  In another document, the European patent application EP-A-0 434 536, is proposed a mineral fiber felt with improved properties where the fibers have quasi-random orientations and which is formed of fibers having, for the most part, between them, a diameter of between 2.5 and 4.5

  length of 2 to 15 centimeters and has a mass. volume not greater than

  Less than 40 kg / m3. In this application, it is envisaged that the mattress may have a surfacing, that is to say be coated with one or two adherent sheets

  paper, aluminum, polyethylene or PVC.

  The creped mineral fiber mattresses obtained by the techniques just described are generally transported and used in the form they have

  been made, that is to say as flat panels. It would, however, be

  striving for power - temporarily or permanently - bending the mattresses

  pancakes, possibly even with small radii of curvature.

  The advantage of being able to wrap creped mattresses to allow the transfer

  The port and storage of large lengths without using too much space is obvious. In the field of industrial use of pancake mattresses, the isolation of large pipes or cylindrical tanks on which one must be able to walk is an application in which the permanent curvature of a mattress

creped would be very useful.

  Still in the field of the prior art, mineral wool felts

  creped, we know the European patent EP-B-O 472 532 which proposes a

  to make a crepe plate coated with a single-side surfacing sheet. According to this method, after creping in the usual manner, is deposited on both sides of the mattress a glass cloth before proceeding to heat treatment of the resin which will constitute the binder. To the output,

  the mattress is split into the thickness to obtain two identical mattresses

  faceted on one side. This technique makes it possible to obtain a plate that can be

  arched leaving the glass fabric concave side. The document clearly states

  bending in the other direction (convex side glass fabrics) is impossible. Indeed, the intermediate product with the fabric on both sides is described as rigid but, after scission, the fibers of the free side "are not subjected to tension and compression forces in the direction of the fibers when the plate is bent but perpendicularly to the fibers, so the plate produced by the method curves well because of the absence of horizontal links at the back. " The approximation of these two phenomena, the rigidity of the plate coated on both sides and the flexibility of the split plate in its thickness, shows that it is in tension that the glass fabric is indeformable and that the

  curvature can only be achieved with concave side coating. The technology

  The mounting plate described in the document with the edges of the ceiling plate "resting on T-sections" as in the case of an arch, confirms this. The invention is intended to provide a product, creped fiber mat, which can, without deterioration, be wound on itself, in order to

  put his transport and storage.

  It is also an object of the invention to allow the use of creped mineral fiber mattresses on curved surfaces without losing

  their performance, insulation in particular.

  To obtain these results, the invention proposes a creped mineral wool felt, equipped on at least one of its faces with a surfacing sheet and intended to undergo a temporary or definitive curvature whose face to be convex is equipped a surfacing sheet whose resistance to bursting

is greater than 300 kPa.

  This sheet is advantageously based on kraft paper. This alone to achieve the performance of bursting resistance required must

  have a mass per unit area greater than or equal to 60 g / m2.

  To wind easily on itself and to keep all its performance

  when used on a curved surface, the creped felt of the invention

  preferably has a creping rate of between 4 and 5 and a surface weight of

less than 2 kg / m2.

  An advantageous variant of the product of the invention has on the face

  opposite to that coated with the surfacing sheet of the invention the fibers practically

  all perpendicular to the surface. Such a provision is ensured if

  the creped mineral wool felt results in particular from the division in the thick-

  thicker felt, the face opposite to that coated with the surface foil

  of the invention resulting from the split.

  The following figures and description will help you understand

  the invention and to take advantage of it.

  In the figures, FIG. 1 represents the result of a curvature imposed on a creped mattress of the prior art, FIG. 2 a mattress according to the invention.

  before and FIG. 3, after curvature.

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  The crepe felts mentioned here are made from mineral wool.

  rales, glass wool or so-called rock wool. These products are most often made from fibers obtained by centrifugation techniques, depending on the case with passing through the orifices of a centrifuge or simply by ejection on the surface of rollers rotating at high speed. The felting installation firstly comprises one or more machines of the above type, fiber generators. The ejected fibers are collected at the bottom of the machines by suction on a

  carpet-conveyor constituting the bottom of a reception chamber.

  Inside the chamber, devices project onto the fibers a liquid binder composition. It has traditionally been endeavored to ensure that the distribution of the binder on the fiber is as uniform as possible so that subsequently

  the binder is distributed homogeneously throughout the felt.

  The felt coming out of the room is usually relatively light. Its average density is low for a large thickness. Moreover, because of the mode of formation of the felt, the fibers are mainly oriented

  following directions parallel to the conveyor.

  In traditional installations for the manufacture of mineral fiber felts, the felt coming from the reception chamber immediately enters

  the heat treatment chamber which allows the binding of the binder.

  On the other hand when making a creped felt is carried out an additional operation before the setting of the binder: it is a question of modifying the dominant orientation of the fibers. Several methods are possible. For example, it is possible to "work" the felt with needles which, by their action, orient the fibers perpendicularly to the surface of the felt. Another method allows that, by a succession of modifications, the felt is brought to a very high density.

  significantly increased and at a different fiber orientation.

  The modifications, according to the latter method, preferably include

  felt compression of the felt in the direction of the thickness. This compression is obtained for example by passing the felt between two conveyors, the

  distance separating the two conveyors decreasing in the direction of pro-

gression of the felt.

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  The felt thus compressed then passes between other pairs of

  voyeurs, the speed of each pair being lower than that of the pairs of

  voyeurs preceding, which causes a continuous longitudinal compression

felt.

  During this succession of modifications, the felt is confined permanently

  In order to prevent it from taking up at least part of its initial volume, it is then introduced directly into the oven where the heat treatment ensures the

  crosslinking of the binder and the stabilization of the product.

  When a sample of creped felt obtained according to one of the preceding methods is subjected to bending, it is generally obtained even for

  very large radii of curvature, a degradation of the product. Cracks appear

  fall between the fibers of the convex face that propagate inside the product. We see in Figure 1 an illustration of this phenomenon. Such cracks destroy the lateral stability of the product and its cohesion is severely degraded. Indeed, the rupture of the bond between the fibers on either side of the crack is irreversible: it is the chemical bonds established in the binder during

  its crosslinking that no longer exist.

  The phenomenon just described has the effect that it is impossible to

  bend a crepe felt, even temporarily without degrading its properties.

  For example, if a glass wool crepe felt with a density of 16 kg / m3 and a thickness of 120 mm is used to isolate a cylindrical tank one meter in diameter placed horizontally - The use of the creped material to allow to achieve good continuous insulation - cracks appearing on the convex side, identical to those of Figure 1, they

  significantly degrade the thermal insulation of the creped felt coat.

  In the same vein, it is interesting to market a crepe felt with a width of 1.20 m in lengths of 10 m with a density of 30 kg / m3 and a thickness of 30 mm. condition the product in rolls where the felt is wound on itself. In such a case, even if the outer turns of the roll have a large radius of curvature which causes only shallow cracks of the convex side, it is different in the center of the roll where the radii of curvature are of the same order as the thickness of the felt and therefore, to. hardly more than 30 mm. There, the degradations are unacceptable. It is however particularly interesting to be able to have crepe felts presented in rolls, that is to say with an indefinite length because on the building site, it is then possible to cut exactly the section of which one has

  need without creating falls that are a waste.

  The inventors then had the idea of equipping one of the faces of the product with a surfacing sheet whose essential function is to avoid lengthening the

  convex face of the product which must undergo a curvature.

  Tests with many different materials have been attempted, plastic films (polyethylene), metals (aluminum) and different

  papers (kraft). They were either simple films or composite materials.

  The latter are in the form of sandwiches such as an aluminum film associated throughout its surface with a polyethylene film, or in the form of a single reinforced film. We have tested kraft paper reinforced with

  reinforcement grids made of glass or polyester threads.

  By way of example, an operation is described below which has made it possible to provide a solution to the problem posed. On a glass wool production line o

  the fibers are obtained by forcing them to pass through the orifices of a cen-

  trifuge was introduced between the creped felt and the conveyor belt that supports it before entering the thermal conditioning installation o is carried out

  crosslinking of the binder, a kraft paper surfacing foil with a surface

  90 g / m2. It is glued to the felt in the packaging chamber and it accompanies definitively, the product obtained is shown in Figure 2. The felt had a density of 43 kg / m3 and a thickness of 60 mm. Its creping rate, ie the longitudinal concentration of the fibers made during the creping operation was 4.5 (it is also the ratio of the speeds at the entrance to the crepe area and at the exit it is also the increase in density achieved). Winding tests on itself of the felt thus equipped were made taking care to leave the kraft on the convex side. After keeping the roll tight for a week, we proceeded to its recovery, it was found that once laid flat the felt had no memory, once flattened, it keeps its flatness. Subsequently, a destructive examination in which the kraft paper was separated from the felt surface showed no cracks:

  the product has not been altered in any way by being rolled.

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  An attempt to wind in the other direction, the paper being on the opposite side

  cellar, gave to the felt the appearance of Figure 1, a multitude of cracks which, given the average thickness of the felt, passed right through

several places.

  On the other hand, when the paper is on the convex side, the result is that of FIG. 3 where it can be seen that the felt works only on compression, on the concave side only.

  A comparative test conducted with identical paper but with a surface mass

  weaker test (60 g / m2) was unsuccessful during the winding up of the

  o felt, the paper tore in several places.

  Studies continued with different materials such as

  Finally, they have shown that a condition necessary for the proper functioning of the invention is that the burst strength of the sheet is greater than a certain threshold: 300 kPa. Quite surprisingly, it appeared that this limit did not depend on the characteristics of the felt: from the moment when the crepe rate is greater than 4: whatever the thickness or the density of the felt, it is able to undergo strong curvatures up to the winding on itself insofar as the surfacing sheet is placed on the convex side and has a resistance to bursting that exceeds

300 kilopascals.

  Burst strength is a characteristic of the strength of thin films for packaging. The measurement is made according to the standard

DIN 53113 (June 1990).

  The only limitations observed were the large thicknesses of felts associated with the large densities. The results become less reliable when, for example, a felt of 60 kg / m3 has a thickness of 120 mm. It is then still possible to impose a curvature felt to isolate a curved support, but the winding of the felt on itself leaving the center of the roll no vacuum, is impossible. It was found that to the extent that the product density multiplied by the thickness remained within certain limits, winding was still possible. If the density in kg / m3 multiplied by the thickness in meters (that is to say, the basis weight) remains at the maximum of -9- 2 kg / m2, then the winding on itself of the product according to the invention, even with

  a crepe rate higher than 4 is always possible.

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Claims (5)

  1. Felt of mineral wool creped, equipped on at least one of its faces with a surfacing sheet, and intended to undergo a temporary or permanent curvature characterized in that the face intended to be convex is equipped with a sheet   surfacing with a burst strength greater than 300 kPa.   2. Felt mineral wool according to claim 1 characterized in that   the surfacing sheet is based on kraft paper.   3. felt mineral wool according to claim 2 characterized in that the surfacing sheet is made of a kraft paper of a mass per unit area greater than or equal to 60 g / m2.   4. Felt of mineral wool according to one of claims 1 to 3   characterized in that its creping rate is greater than 4 and its basis weight less than 2 kg / m2 and that it is wound on itself for constitute a roll.   5. Mineral wool felt according to one of the preceding claims   characterized in that it results from the division in the thickness of a thicker felt.