NZ231549A

NZ231549A - Carding device for mineral fibres

Info

Publication number: NZ231549A
Application number: NZ231549A
Authority: NZ
Inventors: Yves Demars; Christian Decoopman; Francois Szalata
Original assignee: Saint Gobain Isover
Priority date: 1988-12-01
Filing date: 1989-11-28
Publication date: 1992-09-25
Also published as: KR900010113A; PT92480B; FR2639868A1; DK604989D0; DE68906863T2; ES2042043T3; PT92480A; AU4478189A; CA2004360A1; DE68906863D1; EP0371847B1; IE63564B1; FI895742A0; KR970009655B1; NO894725L; EP0371847A1; IE893798L; DK604989A; FR2639868B1; ZA898987B

Description

<div id="description" class="application article clearfix"> No.: Date: Priority D- I \~L-3*3 231 54 Spsc-'ii..«4«- ... Class: Putoiicatton Date: ... P.O. Jouinal, No: r ITsep'J??.! \'^4dO NEW ZEALAND \ PATENTS ACT, 1953 COMPLETE SPECIFICATION "MINERAL FIBER BASED COMPOSITE MATERIAL DEVICE FOR OBTENTION AND APPLICATION OF THE COMPOSITE MATERIAL" 11 We, ISOVER SAINT-GOBAIN, a French company of Siege Social 18, avenue d'Alsace 92400 Courbevoie, Cedex 27-92096, Paris, France hereby declare the invention for which I / we pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 1 5 MINERAL FIBER BASED COMPOSITE MATERIAL DEVICE FOR OBTENTION AND APPLICATION OF THE COMPOSITE MATERIAL The subject of the invention is a composite material and its obtention device. The material according to the invention is based on mineral fibers, particularly glass fibers, obtained by reconstitution of a mineral fiber mat containing a binder. It serves for example as a primitive (an intermediate product made from fibers and a binder, the binder being not polymerized) for obtaining moulded parts. It is known that dense or on the contrary very light, possibly shaped, parts can be obtained by moulding a natural or synthetic fiber based primitive comprising a binder. As regards natural fibers, textile fibers of fairly large average diameter in excess of 10 microns can be used, which is not very favorable from the point of view of the soundproofing and heat insulation performances. Of synthetic fibers, those particularly preferred are mineral fibers, especially so-called insulating fibers such as glass fibers, rock fibers or slag fibers which are finer and in addition produced at extremely low costs. Patent application FR E 60S 96describes for example the use of glass fiber based mats to obtain moulded parts such as the gaskets on automobile parts, for example. In this case the primitives are sections of glass fiber mats obtained by high speed centrifugation of molten glass with the filaments drawn out by gas ; the fibers being received on an endless conveyor belt closing a hood inside which they are sprayed with an organic binder in an aqueous solution; the sheet thus obtained being later shaped in an oven where the binder is polymerized, and then cut to the desired dimensions to form the mat. Other processes can be used for drawing out fibers , namely so—called free centrifugation processes or processes in which t the molten matter is introduced into the zone of interaction of two high temperature high speed gas flows. However, whatever the fiber drawing out process chosen, collection is characterized by suction, the fibers being collected on the « endless belt under which Is provided a chamber at negative pressure- Consequently, and even if it possible partially to remedy this by operating in suitable fiber drawing and suction conditions, the mats or mineral fibers thus obtained are always anisotropic, the fibers preferably positioning themselves in horizontal planes. This results in an anisotropy of certain physical properties, particularly tensile strength, an anisotropy which otherwise offers some advantages especially as regards the insulating ability of the felt formed. Another disadvantage found is the limited choice of resin sprayed as size in an aqueous solution. Indeed, to optimize distribution of the binder in the mat and in particular to obtain good wetting of the fibers by the binder in order to form a protective gangue, it is preferable to spray the binder in a fiber drawing hood, before the fibers accumulate to form a mattress. However, given the temperature conditions reigning in the fiber drawing hood and to avoid all risk of igniting, it is essential to use a water-soluble resin. This excludes most usual thermofusing or thermosetting type adhesives. Generally speaking a phenolic resin of resol resin type is used, which is known to break down at a utilization temperature over 350°C, which considerably restricts the application possibilities of products which in spite of being fiber based are however capable of withstanding without damage temperatures for example we11 over 5000 C. In addition, we learnt from French patent £ 591 6S1 for example how to reconstitute mineral fiber products from fibrous products themselves produced from a mat - still called felt -by a carding operation using counter-rotary brushes or yet again by rotary threshers beating the felt preferably pre—cut into strips. Carding is preferably followed by whipping of ■flakes or air conveyance in order to release the residual stresses. The flakes produced are usually used as they are. They are for example spread in layers on the floor for heat insulation or soundproofing of unused attics or may serve as cavity filling material, for example in forming interior .... '*** artitions. Insulating layers obtained from such flakes perform considerably better than blown wool layers obtained by conventional methods, but on many points, particularly thermal conductivity, there remains a considerable difference between the properties of these layers and those ©f the original »a*. - 4 - 23154-9 The observed deterioration of temperature stability can be explained by the nature of the flakes. Indeed, it is well known that free fibers, i.e. not glued together by a binder, have a natural tendency to associate in the form of balls. Thus, in any carding operation, an attempt is made to loosen these matted fibers to obtain whole fibers again. However, mineral fibers such as glass fibers and even more so rock fibers are extremely fragile therefore carding breaks the fibers and if the operation is carried on for too long, reduces them completely to dust. Consequently, the tendency is to work with "gentle" carding means, such as those described in patent FR 2 591 6E1 the counterpart being less good opening of the flakes which signifies that a large number of them (approximately 1 in £ in the best of cases) still consist of central nodules around which radiate a few rare single fibers. As these nodules are particularly dense, they cannot capture a large quantity of air, which is known to reduce the insulating ability of a fibrous material. Thus for a given insulation rate the quantity of product needs to be increased. To this already big disadvantage is added the fact that it is very difficult to impregnate or "wet" these nodules with a binder, whether this latter is in liquid state or even more so in solid state in the form of a powder and therefore little apt to penetrate by capillarity action to the heart of the nodules. Typically, as most binders take on a color after polymerization, this phenomenon results in a mottled appearance of the product after polymerization, the nodules not impregnated with binder not looking the same as the rest of the product. On the other hand, to the advantage of this process one should note that the binder can be added before the flakes are re-united, at a temperature and in conditions free of any stresses due to the fiber preparation process. In addition, can be collected simply by deposition due to ^flavity, i.e. in conditions which do not lead to a preferential U.i Orientation of the fibers therefore resulting in more isotropic products. Also, publication of patent AU-A-75 746/B7 teaches a - 5 - /31549 a uniformly distributed binder, even if the product is based on difficultly impregnable fibers such as vegetable or animal fibers. This process - which can also be applied to mineral fibers - consists of carding a felt to substantially separate the fibers then, to complete this separation, fluidising them by drawing them out by a gas current, the binder being sprayed onto the separated fibers before they are deposited. In this publication, no specific carding means are proposed for mineral fibers so that by mineral fibers one must understand so-called textile glass fibers - otherwise referred to as reinforcement glass fibers - i.e. fibers having an average diameter in excess of 10 microns and produced using a mechanical drawing machine. As a reminder, so-called insulation fibers have an average diameter of under 6 microns, generally around 3 microns. In addition, so-called textile fibers are practically always grouped in threads like natural fibers which makes them totally different from insulation fibers from the point of view of their behaviour particularly during carding. In addition, this technique calls for air conveyance of the fibers which poses the problem of eliminating the gas currents generated and results in the need for suction chambers which as indicated above leads to anisotropic products. The aim of this invention is a composite product based on mineral fibers obtained by reconstitution of a mat or felt in insulation mineral fibers, whose thermal performances (in relation to an identical product mass) are at least equal to 93tf of those of the initial felt and comprising a binder which can be activated at a. later time, chosen independently of the technique used to obtain the said initial felt. The composite product according to the invention is formed of flakes to which a subsequently activable binder is added, obtained by shredding felt based on insulating mineral fibers, less than 10% of the ||[lakes comprising a dense nodule whose mean diameter is in addition defined as less than 7 mm and which presents a lesser gree of impregnation by the reactivable binder than the rest the product. From this definition, the term flakes turns out to be 4b / / ^virtual abusive since the felt is shredded in such a manner ; that the fibers are virtually all separated and therefore one j ^ *1 ' if* * 231549 returns to a stage in which the fibers are practically all in a single state, as was the case at the time of fiber forming. To do this, the flakes are produced from a felt in mineral fibers which is shredded by a carding machine consisting of a single brush with flexible bristles cleaned by a comb. Compared with the known means of the art, one therefore operates with an extremely simplified device yet which however gives astonishingly better results. Indeed, a carding machine with counter-rotating brushes conforming to FR-a 591 621 produces flakes half of which comprise dense nodules (and it is not possible to remedy this defect by extending the period of time the flakes remain between the bristles for this then reduces the fibers to dust). In addition to the flakes, the composite product accordinq to the invention contains a subsequently activable binder. Subsequently is understood to mean a period of time set by the user, which may possibly be only a few seconds, in the case where polymerization is carried out immediately downstream on the production line or on the contrary from several days to several months, this latter case occurring particularly when the reconstituted product is used as a primitive in obtaining parts moulded to shape. The length of time depends of course on the type of binder used, intermediate storage of the product being possible only with resins whose action does not take place - or takes place only slowly - at ambient temperature. This is the case for sxample with thermofusing or thremosetting resins added in powder form to the fibers. We mention for example novo lac phenol-formaldehyde resins, epoxy resins, silicones, polyurethane, polyethylene and polypropylene. In any case, the fact that the resin is added onto cold fibers, away from any fiber-forming installation, gives full freedom of choice as regards the binder (resin or mineral »r) . i ISfln liquid form, it does not matter whether the binder is flayed onto the fibers during the carding operation or V Mjterwards. In powder form, the binder is added preferably ^28 FEB 1992^1 |ter carding, the binder being suspended in gas for optimum /31549 The flakes are preferably collected simply by gravity deposition, without further suction. The products thus reconstituted are much more isotropic than standard products obtained directly under the fiber-forming hood, which is particularly advantageous for the preparation of parts moulded into shape and likely subsequently to be subject to fairly high level stresses, which is not of course the case when the flakes are used in bulk. Other details and advantageous characteristics of the invention are described below in reference to the appended illustrations which show : - Figure 1 : diagram of a production line for a composite product according to the invention, - Figure 2 : a more detailed view of the carding machine shown in figure 1, - Figure 3 : curves showing the evolution of thermal conductivity in relation to density, - Figure ^ : comparative curves of values of specific resistances to air passage in relation to density. - Figure 5 : the comparative curves of relative deformation values in relation to the stress extertsd. The composite product according to the invention is prepared as indicated very summarily in figure 1. The initial ■felt 1 which we still call standard felt - or the £ felts as represented here - is a felt of mineral fibers. One can use ■for example a felt in glass wool, the fibers being obtained by a process according to which the molten glass is introduced into a centrifuging deck revolving at high speed from which it escapes in the form of filaments through a series of holes perforated in the wall of the deck, the filaments being drawn out in the form of fibers by a high speed high temperature gas current, generated by burners surrounding the deck. The conditions of temperature glass and gases, pressures and speeds Mm? being for example those defined in European patent EF'- f||j66. The size is advantageously sprayed onto the fibers ''$0" erore they are collected in the collection device- This size preferably a 10% aqueous solution of a formo-phenolic resin omprising 55% by dry weight of resol resin and a si lane acting among other actions as a dustproofing agent. As an example, a © - 3 - 231549 felt was used having a density of 11 kg/m3, the thermal resistance of 2 m'C/Watt and specific resistance to air passage of 6.4- Rayls/cm (resistance measured perpendicularly to the glass fibers deposition plane). The felt conditioned in roll form is mounted on a spool not represented here. As more precisely represented in figure 2, the carding machine is fed using a cylinder 2 and an opposite cylinder 3 ensuring product advancement. The felt 1 is simply compressed between cylinders 2 ans 3 without cutting, which simplifies the device for these operations. Advantageously, these two cylinders also help maintain the felt by retaining it slightly. The carding machine A- surrounded by a casing, is advantageously constituted by a single brush 5. This brush has an external diameter of 300 mm for example. It is equipped with fine bristles 6, mounted with sufficient free height (45 mm in this case) to enable a degree of flexibility. These bristles for example have a diameter of around 0.5 mm and are preferably wavy. According to the invention, they are preferably in metal, best results have been obtained with hardened steel. The choice of metal may appear surprising inasmuch as it is known that bristles in synthetic materials, ) for example in polyamide, better withstand attack due to abrasion by the glass. Indeed, it has been seen according to the invention that bristles in synthetic materials - and therefore due to certain technological restrictions mandatorily of a diameter over 1 mm - become exceedingly hot during the carding operation and consequently wear much more quickly than bristles of less resistant material in absolute terms, but finer. In addition, using fine bristles enables better matching the dimensions of the cutting machine they are used on to those of the fibers that it is wanted to separate. ^jj^pjRn the positive side, a fine metal bristled brush such as fh ifflllal lows a larger number of bristles and removes the need «*k'< opposite brush which has the disadvantage of prolonging * processing time from felt to mineral fibers and thus IP p£gt99&c^3ntuates its deterioration. The bristles must be sufficiently dense to enable total shredding and over a small ^•^!J?#':;portiori of the brush, but without however reaching a value such 1 1 w - 9 - 251549 bristles between 2 to 5 mm apart around the periphery are satisfactory, best results having been obtained with approximately 1500 bristles i.e. 1 bristle at 3.5 mm intervals for a 300 mm diameter brush. The brush rotation speed is for example around 1000 revolutions per minute when the machine is fed with felt of density 11 kg/m2. To clean the brush, a simple comb 7 is used consisting of points mounted on a plate 9, preferably very fine and very pointed. These points are for example metal needles of under 0.2 mm diameter at the tip which penetrate into the brush to a depth of for example 2 mm, this depth being variable depending on position adjusting mechanism 9. After carding, the flakes are deposited by gravity and collected in a closed chamber 10, without conveyance by air means. This air conveyance indeed has the disadvantage, when extracting the air, of encouraging a preferential orientation of flakes parallel to the direction of the carrier gas and, in addition, distinctly increases the product cost price. To avoid the accumulation of flakes due to static electricity, the closed collection chamber 10 is preferably entirely of a plastic material. Observation of the flakes obtained under the microscope shows they are composed of relatively long fibers, i.e. approximately 2 cm long whereas the fibres of the initial felt were approximately 10 cm long ; this of course is an average value obtained by estimation of a sample of reduced sine, true measurement being particularly tricky. These shorter fibers are less subject to stratification problems, on the other hand they remain sufficiently long to capture a large amount of air. In addition these fibers are distributed extremely homogeneously, less than 10% of flakes have a dense central nodule whose diameter is less than 7 mm or in meshed form. -On this subject, it also seems that the fibres are ly in a more unitary state than at the time the initial , - w, Jfe^f't- was manufactured. An explanation of this unexpected state * ''vu is perhaps the presence of the binder used as size for the initial felt which then acts as a lubricant between the fibers is the intention of all sizing - and m addition o - 10 - 2:3)549 encourages fiber separation - a property sought after to increase the ability of the product to regain its thickness, •"""s The other aspect of the invention is the addition of a binder ; after dosing it (using pumps 11, IE) the binder is conveyed through tube 13 up to the fibers. As a general rule, a binder in liquid form will rather be sprayed at a point situated after the carding machine, this in order if possible r N to avoid clogging this latter, however a binder in powder form with less "wetting" power, will be sent onto the fibers inside the carding machine. But as indicated above, this is only a general tendency, the problem being posed more precisely for each binder used. On the other hand, what must be noted is that the extreme openness of the flakes obtained accordinq to the invention enables where relevant a very homogeneous distribution of the binder even after carding. The fibers are deposited on a collection mat 1^ closing the carding hood 10. As shown on figure 1, this hood 10 totally closes the system which leads to material yields of around 100*/.. Qn leaving the hood, the mattress is brouqht to the desired thickness using a calendar 15 then the product is eventually taken into a chamber 16 in which hot air is (^) circulated to set the binder (for example in a binder melting oven if the product is thermofusing type). At the same time as or following these operations, the various cutting operations 17 necessary to obtain the finished product are carried out. Another particularly useful application of the process \WJ according to the invention is the realization of moulding primitives and in this case, the product is directly packaged after passing through the calendar, the binder setting later during the moulding operation. Products have been realized using extremely diverse quantities of binder. Tests have been carried out for example with a very low percentage of binder between lO and 15V., for a thermo-activable binder intended for a primitive for products moulded using a hot press. At the other end of the range ^-ssstest^ ^^c'mij&'site products were also produced which comprised over 707, mineral binder activable by adding water. % jfcf' ^) - 11 - /315 49 As examples of applications of the invention as an intermediate product (a primitive) for moulding purposes, 3 series of products, a) , b) , and c), were made, each containing an epoxy-type binder (30%) consisting of waste products of paint production by electrostatic discharge, polypropylene (50%), and a phenolic binder (Bakelite) (17%), with the percentages for the binders being calculated in relation to the mass of the finished product. These dry intermediate products can be kept for as long as necessary before they are hot-pressed. Then the breaking strengths in (MPa) and the bending strengths in (GPa) for different densities (in kg/m3) were measured in accordance with the French standard NF-B-51224. A fourth series of measurements was made, by way of comparison, on ordinary moulded products prepared by the wet process and containing 18% phenolic resins. The results are shown in the following table: binder thickness kg/m3 MPa GPa a 5-7 mm 300 5/8 0,3 500 21,0 0,7 600 36,0 2,3 970 57,0 4,3 b 4-5 mm 210 1,6 0,2 420 7,6 0,8 590 12,8 1,3 850 25,6 2,9 1030 36,1 3,8 c 5-7 mm 320 6,4 0,7 500 16,3 1,6 700 27,0 2,9 890 45,9 4,2 d 5-7 mm 200 2,5 0,3 300 6 0,7 500 22 2,3 800 45 4,3 ... r 2315 49 The measurements for products a, c, and d are practically identical. Thus the process as per the invention makes it possible to produce end products that are very comparable with those of the state of the art but which can be produced r$ in two stages separated in time, thus making the moulding stage independent of the fibre-preparation stage. Another aspect of the device as per the invention is the recycling of fibres. It is is known, in the art, how to prepare insulating products from waste felt made from textile glass-fibres. Textile fibres for this purpose are recovered by carding a felt, by means of a carding machine of the kind traditionally used in the textile industry. Felts based on insulating-fibres as envisaged by the present invention are not suitable because the carding machine turns these more fragile fibres into dust. With a carding machine as per the invention, however, it is possible to replace part of the textile fibres with insulating-fibres. Thus it was possible, without any particular difficulty, to produce a reconstituted fibre weighing 1.2 kg/m3 fibres and with a density of 25 kg/m3, consisting of 12% "flakes" as per the invention, 74% textile glass-fibres, and 14% phenolic binder. The proportion of mineral insulating fibres can, if applicable, be increased to 2 0 or 25%, which is particularly worthwhile when the quantity of waste textile fibres available is insufficient to' meet the demand for reconstituted insulating products. O / v 13 ?31549 A study of the three appended carves particularly highlights the performances of the product according to the i riven t i on. The first of these curves (figure 3) is a representation of thermal conductivity Lambda measured in mW/m.°K, in relation to the density of the prepared product (fibers and binders). This curve is directly associated to the insulating ability of a product indeed the thermal conductivity is defined as equal to the ratio of product's thickness to its thermal resistance. Curve A is the characteristic curve of a standard product obtained by the gas-drawn centrifuge process indicated earlier, the fineness of the fibers being characterized by a micron value of 3 for 5 g. The micron value F is defined in standardized manner as the yield of a gas current measured after this gas current emitted in stable sat pressure conditions had crossed a highly compressed sample of 5 q of fibers. We note that the micron value therefore gives an indication of gas current inhibition by the glass fibers and is therefore characteristic of the fineness of the fibers. A micron value such as 3 for 5 g is characteristic of extremely fine glass fibers. Curve B is that obtained with reconstituted products according to the invention, whereas curves C and D are respectively obtained for reconstituted products obtained in compliance with the teaching of FR E 591 6E1 and for blown glass wool obtained in the conventional manner. Comparison of these 4 curves shows that for an equivalent insulation (Lambda — 40 ffiW/m.°K for example), approximately 1 point more density is needed with products according to the invention (i.e. approximately 6.6*/. more product) whereas E points are necessary ^.(i.e. approximately 13% more product) with products according FR E 591 6E1, conventional products requiring more than 50% C'% extra products for comparable insulation. It must also be <p|DC'ted that curves A and B are practically parallel and that 1 jitisequerit ly, the difference between the initial product (WURccording to curve A) and the reconstituted product accordinq invention is, for the entire density range concerned, betwperr 5 and 7*A. In other words, the composite product • ggStfcording to the invention may very easily be substituted for 2' 31 54-9 the standard product, practically without any noticeable deterioration in the qualities ; one can in particular manufacture very light products, typically of 10 kg/m3 or under whereas blown fiber products always have a density exceeding 15 kg/m3 (and in this case with very low insulating ability compared with standard felts), and that the bottom limit is around 12-13 kq/m3 for products according to FR 2 591 621. This first test demonstrated that the reconstituted products according to the invention present an insulating ability very similar to that of the initial products serving for their manufacture. In addition, the method of obtaining and collecting the flakes leads to a very big reduction in the anisotropy of the material. This is demonstrated for example by the specific resistance values as air passes through the product, measured for different product densities. Contrary to measurement of the micron value which is done on a very small sized and above all highly compressed sample, measurement of the specific resistance on air passage much better characterizes the arrangement of the fibers in the product and particularly their orientation. This test is indeed carried out on an actual product, and on a sample of dimension 20 x 20 cm, therefore the micron value is a data as characteristic of the fibers as the specific resistance to air passage is characteristic of the finished product. The measurements, expressed in [Rayl/cm Rs3 whose results are given in figure 4 were carried out in a plane parallel to the fiber deposition plane (parallel specific resistance or Rs //) and in a perpendicular plane to this (perpendicular specific resistance or R). If the product is perfectly isotropic, the parallel and perpendicular resistance curves are the same ; if on the other hand the fibers are oriented preferentially along one of these planes, parallel to this one, '^he air crosses throuqh the product in "corridors" parallel to the fibers whereas perpendicularly to this it must siematically go round the fibers to find its way. Curves 21 d 3^are obtained with the standard product defined earlier. no^|^especial ly that for a given density, the parallel specific resistance est distinctly less than perpendicular soecific resistance. For the reconstituted product according - 15 - 231549 to the invention., parallel specific resistance carve 24 is practically the same as the standard product curve EE; however the perpendicular specific resistance (curve 23) is slightly weaker. This explains the attentuation of the product's insulating performances (see thermal conductivity curve) but also shows that the product's anisotropy has reduced. The extent of this reduction is more particularly highlighted by the curve in figure 5 where the stresses exerted on a product (en kN/rr.E) are indicated along the x-axis and the corresponding relative deformations along the y-axis. Curve 31 corresponds to a standard product, still in the sense defined earlier, whose density is 45 kg/m3. Practically vertical at outset - which corresponds to a high increase in relative deformation even for a small stress, the curve bends inwards slightly for higher stresses but always remains concave. In addition, we note that a relative deformation rate of 50% is reached for a stress of 13 kg/m2. With the products according to the invention and of the same density, we note on the other hand that in the first instance curve 3E is relatively flat, in other words relative deformation increases less rapidly than the stress exterted. This corresponds in fact to the presence of fibers laid vertically which are able to sag whereas in the horizontal plane relative deformation is directly the result of the fibers themselves deforming under the effect of the stresses. Once reached, the stress value which corresponds to the vertical fibers buckling point, the relative deformation curve becomes identical to that of the standard product, but starting from an initial value which is not nil. We note indeed that for a given relative deformation, the stress exerted is approximately 12 kN/m2 higher than with a reconstituted product. These different tests highlight the fact that the carding operation practised in the conditions of the invention enable reconstituting highly performing products from the thermal insulation viewpoint and presenting valuable mecahnical </div>

Claims

<div id="claims" class="application article clearfix printTableText"> - 16 - 2 315 '1 WHAT WE CLAIM IS:

1. A carding device for forming flakes from a felt made from insulating mineral fibers, the device comprising: a felt feed unit, a brush with flexible bristles and a comb, the felt feed unit being arranged to guide the felt to the brush and comb where the brush cards the felt into flakes and the comb cleans the brush.

2. A device according to claim 1, characterized in that the brush is fitted with metal bristles.

3. A device according to claim 1 or 2, characterized in that the bristles have a diameter of approximately 0.5 mm.

4. A device according to any one of claims 1 to 3, characterized in that the intervals between bristles around the brush periphery is between 2 and 5 mm.

5. A device according to any one of claims 1 to 4, characterized in that the bristles are wavy.

6. A device according to any one of claims 1 to 5, characterized in that it further comprises a felt holding device.

7. A device according to any one of claims 1 to 6, characterized in that it further comprises a binder supply unit supplying binder in liquid or powder form.

8. A carding device substantially as herein described with reference to the accompanying drawings. &Q(Xf Cninb. _ fy bis/their authorised Agfiate, a. i. pars: & sow. T 'V Ss, p- a i \ </div>