IE63564B1 - Mineral fiber based composite material apparatus for production and application of the composite material - Google Patents

Abstract

The invention relates to a composite product formed of flock - to which is added a binder - obtained by shredding a felt (1) based on insulating mineral fibres. The said flock is obtained by means of a carding device for a felt of insulating mineral fibres, which device comprises a unit (2, 3) for feeding in the felt, a brush equipped with flexible bristles (5), and a comb (7).

Description

MINERAL FIBER BASED COMPOSITE MATERIAL, APPARATUS FOR PRODUCTION AND APPLICATION OF THE COMPOSITE MATERIAL The invention relates to a composite material and the device for obtaining it. The material according to the invention is based on mineral fibres, in particular glass fibres, obtained by reconstitution of a mineral fibre mat containing a binder. It is used for example as a primary substance for obtaining moulded parts.

It is known to obtain parts, optionally shaped parts, which are dense or, on the contrary, very lightweight, by moulding a primary substance based on natural or synthetic fibres and comprising a binder. Textile fibres having a s relatively high average diameter of more than 10 μχη, which is not very favourable from the point of view of sound and heat·-proofing performance, are used in particular as natural fibres. Mineral fibres, in particular so-called insulating fibres such as glass fibres, rock fibres or slag fibres, which are more fine and are furthermore produced at extremely low cost, are more particularly preferred from among the synthetic fibres.

Patent application FR 2 SOS 964 for example describes the use of glass fibre-based mats to obtain moulded parts such as motor vehicle trims for example. In this case the primarysubstances are sections of mats of glass fibres obtained by the high-speed centrifuging of molten glass with gaseous drawing of the filaments; the fibres are received on a continuous conveyor belt closing a hood in which they are sprinkled with an organic binder in aqueous solution; the sheet obtained in this way is then shaped in a furnace in which the binder polymerises, and the sheet is '10 finally cut to the desired dimensions so as to form the mat.

Other fibre-drawing processes can also be used, in particular those processes known as free centrifuging processes or processes in which the 15 molten material is introduced into the area in which two gaseous currents interact at high temperatures and high velocities. However, regardless of the fibre-drawing process selected, reception is characterised by the suction of the fibres collected on the continuous belt under which a vacuum chamber is provided. Consequently, although it is partially possible to overcome this by operating in suitable fibre-drawing and suction conditions, the mineral fibres or mats obtained in this manner always have a degree of anisotropy, the fibres preferably being positioned in horizontal planes. This is manifested by ) anisotropy of certain physical properties, in particular resistance to traction, the anisotropy also having certain advantages in particular as regards the insulating capacity of the felt formed.

A further disadvantage encountered is that of the limited choice of pulverised resins used as size in agueous solution. In order to optimise the distribution of the binder in the mat and in particular to bring about the satisfactory wetting of the fibres by the latter in order to form a protective matrix, it is preferable to spray the binder in the fibre-drawing hood before the fibres have accumulated to form a mat. In view of the temperature conditions prevailing in the fibre-drawing hood and in order to avoid any risk of ignition, it is essential to use a resin in solution in water. This excludes the majority of conventional adhesives of the heat melting or " thermosetting type. Generally a phenolic resin of the resol resin type is used which is known to decompose at an operating temperature of more than 350°C which, however, in particular restricts the possibilities of using products based on fibres which on the other hand are able to withstand temperatures far in excess of 500°C for example without damage. ) 4 Furthermore it is known, for example from Patent FR 2 591 621, to reconstitute mineral fibre products from fibrous flakes which are themselves produced from a mat - again known as felt - by a carding operation using counter-rotating brushes or even rotary flails beating the felt which has preferably already been cut into strips. The carding process is preferably followed by a process in which the flakes are whipped or θ conveyed pneumatically in order to release the residual stresses. The flakes produced are conventionally used as such. They are for example distributed in layers over the floor for the heat or soundproofing of roofs which have not been 15 fitted out or are even used as material for filling chambers to form internal partitions for example.

The insulating layers obtained from flakes of this type are clearly more high20 performance than blown layers of wool obtained in a traditional manner but with respect to many points, in particular heat conductivity, the difference between the properties of these layers and those of the original mat is still very noticeable. ί '4 5 The decline noted in the resistance to heat is explained by the nature of the flakes. It is well known that free fibres, ie. fibres which are not stuck to one another by a binder, tend by their nature to combine with one another in the form of spheres. Thus, in all carding operations, it is sought to untangle this mass to recover the complete fibres. However, mineral fibres such as glass fibres or even rock fibres are extremely θ fragile and thus the carding process breaks the fibres and reduces them totally to dust if the operation is continued for too long. Consequently the tendency is to use gentle carding means such as those described in patent FR 2 591 621 with, on 1 A the other hand, less satisxactory gaps between the flakes which signifies that a large number of them (approximately 1 out of 2 in the best instance) always consist of a central nodule about which a few rare single fibres radiate. As these nodules are particularly dense, they do not enable a great amount of air to be trapped and this is known to reduce the insulating capacity of a fibrous product. Thus the amount of product required has to be increased in order to achieve a given degree of insulation.

In addition to this already great disadvantage there is the fact that it is very t6 difficult to impregnate or wet these nodules with a binder, whether the binder is in the liquid state or even in the solid state in the form of a powder and is thus not very suitable for penetrating the core of the nodules by capillary action. Typically, as the majority of binders display coloration after polymerisation, this phenomenon is manifested by a speckled appearance of the product after polymerisation, the nodules not impregnated with binder not having the same colour as the remainder of the product.

In contrast, it should be noted to the advantage of this process that a binder can be added before the flakes are combined again, at a temperature and in conditions which are free from any constraint owing to the fibre preparation process. In addition, the flakes can be received simply by deposition under gravity, ie. in conditions which do not result in fibres being oriented in any preferred direction and which thus lead to products which are more isotropic.

Furthermore, the published version of patent AU-A-75746/87 discloses a process for obtaining an insulating fibrous product containing a uniformly distributed binder, although the product is based on fibres which are difficult to Ί 7 impregnate, such as plant or animal fibres. This process - which can also be applied to mineral fibres - consists in the carding of felt in order to separate the fibres to a substantial extent then, in order to complete this separation process, in liquifying them by entraining them with a gaseous current, the binder being sprayed onto the separate fibres before they are deposited. This publication does not propose any fi specific carding means for the mineral fibres such that what is to be understood by mineral fibres is glass fibres known as textiles - also known as reinforcing glass fibres - ie. fibres which are produced by means of a die plate and a mechanical drawing process and of which the average diameter is more than 10 gm. It should be remembered that so-called insulating fibres have an average diameter of less than o gm and generally of the order of 3 gm. In addition, the so-called textile fibres are practically always combined to form threads in the fashion of natural fibres which renders them totally different from insulating fibres from the point of view of their behaviour, in particular during the carding process.

Moreover, this technique uses a pneumatic system for transporting the fibres which poses the problem of eliminating the gaseous currents generated and results in the need for suction Ί chambers which, as indicated above, lead to anisotropic products.

The subject of the present invention is a composite product based on mineral fibres obtained by the reconstitution of an insulating mineral fibre mat or felt of which the thermal output (compared to a mass of identical product) is at least 93% of that of the initial felt and which comprises a binder which can be subseguently 1 θ activated and is selected independently of the technique used for obtaining the said initial felt. The composite product according to the invention consists of flakes to which a binder which can subsequently be activated is added and which are obtained by the shredding of an insulating mineral fibre-based felt, less than 10% of the flakes comprising a dense nodule of which the average diameter is moreover defined as being less than 7 mm and which has a degree of impregnation with reactivable binder which is less than the remainder of the product.

From this definition it emerges that the term flakes is in practice incorrect since the felt is shredded in such a way that the fibres are practically completely separated and that, as soon as this has occurred, the process reverts to a stage where the fibres are practically all in the unitary state as was the case when they were drawn into fibres.

For this purpose the flakes are produced from a mineral fibre felt which is shredded by means of a carder consisting of a single brush with flexible bristles and cleaned by a comb. In contrast to the means known from the art, the operation is thus performed with a device which is 0 greatly simplifed but which gives unexpectedly superior results. A carder with counter-rotating brushes in accordance with FR2 591 621 produces flakes of which half have dense nodules (and it is impossible to overcome this defect by extending the time during which the flakes remain between the brushes since the flakes are then reduced to dust).

In addition to the flakes, the composite product according to the invention contains a binder which can be activated subsequently. What is to be understood by subsequently is a duration fixed by the user which can optionally be a few seconds in the case where a polymerisation oven is provided immediately downstream of the line or, in contrast, several days or even several months, the latter case being encountered more particularly ϊ when the reconstituted product is used as primary substance to obtain parts which are moulded into shape.

Evidently the duration of this period depends on the type of binder used, intermediate storage of the product only being possible with resins of which the action does not occur (or only occurs extremely slowly) at ambient temperature. This is the case for example with thermofusible or heat-setting resins added in powder form to the fibres. Novolac phenol formaldehyde resins, epoxy resins, silicones, polyurethane, polyethylene and polypropylene can be cited for example.

In any event, the fact that the resin is added to cold fibres, far away from any fibredrawing installation, implies that the choice of binder is entirely open (resin or mineral binder).

In liquid form, the binder is sprayed onto the fibres equally well during the carding operation or after this operation, when it is in its powdery form, the binder is preferably added after carding, the binder being in suspension in a gas for optimum distribution. Ί The flakes are preferably collected by simple deposition under gravity and without additional suction. The products reconstituted in this manner are far more isotropic than the standard products obtained directly under the fibre-drawing hood, which is more particulary advantageous for the preparation of parts moulded into shape which can subseguently be subjected to relatively high level stresses which is certainly not the case when the flakes are used in bulk.

Further details and advantageous features of the invention are described below with reference to the attached sheets of drawings, in which: - Figure 1 shows a diagram of a line for a composite product according to the invention; - Figure 2 shows a more a detailed view of the carder from Figure 1; - Figure 3 shows the development curves 2θ of heat conductivity as a function of density; - Figure 4 shows the curves comparing the values of the resistances specific to the passage of the air as a function of density; and - Figure 5 shows the curves comparing the relative deformation values as a function of the force exerted.

The composite product according to the invention is prepared as shown very schematically in Figure 1. The initial felt 1 which is also known as standard felt - or the two felts as illustrated here - is a mineral fibre felt. A glass wool felt can be used for example, the fibres being obtained by a process according to which the molten glass is introduced into a centrifuging plate which rotates at high speed and from which it escapes in the form of filaments via a series of openings provided in the wall of the plate, the filaments being drawn in the form of fibres by a high-speed, high-temperature gaseous current generated by burners surrounding the plate. The temperature conditions of the glass and the gases, the pressures and speeds used are for example those defined in European patent No. 91866. The size is advantageously sprayed onto the fibres before they are collected by a receiving member. This size is preferably an aqueous solution with 10% ox a formophenolic resin comprising as a dry portion 55 weight % of resol resin and a silane acting inter alia as a dustpreventing agent. By way of example, a felt is used of which the density is 11 kg/m , the heat resistance is 2 m2oC/Watt and the specific resistance to the passage of air is 6.4 Rayls/cm (resistance measured perpendicular to the plane on ’ which the glass fibres are deposited). The felt, made up in the form of a roll, is mounted on an unwinding device (not illustrated).

As illustrated more precisely with reference to Figure 2, the carding unit is 1θ supplied by means of a cylinder 2 and a countercylinder 3 advancing the product. The felt 1 is simply compressed between the cylinders 2, 3 without being cut, which simplifies the device performing these operations. Advantageously, these two cylinders also hold the felt by retaining it somewhat.

The carding unit 4, surrounded by a casing, advantageously consists of a single brush 5. The outer diameter of this brush is 300 mm for 20 example. It is provided with thin bristles 5 which are mounted af a sufficient free height (in this case 45 mm) to allow them a given degree of flexibility. These bristles are approximately 0.5 aim in diameter for example and are preferably undulating. In accordance with the invention they are made of metal, the best results being obtained Ί with hardened steel. The choice of metal may appear to be unexpected insofar as it is known that bristles of synthetic material, for example of polyamide, are more resistant to attack from abrasion by the glass. In effect, it has been noted in accordance with the invention that bristles of synthetic materials - and thus, owing to given technological constraints, of necessity of more than 1 mm in diameter - heat up to an 0 extremely high degree during the carding operation and that consequently they wear far more rapidly than bristles made of a material which is less resistant overall but which are finer. In addition, using fine bristles permits better adaptation of the dimensions of the cutting tool which they constitute to those of the fibres which it is desired to separate.

Advantageously a brush of this type having fine metal bristles enables the number of bristles to be increased and the counter-brush, which disadvantageously increases the treatment time of the mineral fibre felt and thus increases its degree of wear, to be omitted. The density of the bristles should be sufficiently great to allow the mat to be completely shredded and over a small portion of the brush but without reaching a value such that it prevents the bristles acting ύ separately. In practice a spacing between the bristles at the periphery of between 2 and 5 mm is satisfactory, the best results being obtained with approximately 1500 bristles, that is one bristle every 3.5 mm for a brush which is 300 mm in diameter.

The rotational speed of the brush is approximately 1000 rpm for example when the unit is supplied with an 11 kg/m felt.

In order to clean the brush, a simple comb 7 is used which consists of tips mounted on a plate 8 which are preferably very fine and very pointed. These points are for example metal needles of at least 0.2 mm diameter at the tip which penetrate -the brush at a depth of 2 mm for example, it being possible for this depth to be varied by means of the position-regulating mechanism 9.

After carding, the flakes are collected by deposition under gravity in an enclosed chamber , without being transported pneumatically. The disadvantage of pneumatic transportation is that, when the air is extracted, the flakes tend to be oriented in a preferred direction parallel to the direction of the carrying gas and in addition it substantially increases the cost price of the product. In order to avoid flakes accumulating as a result of static electricity, the enclosed receiving chamber 10 is preferably made completely of plastics material. if the resultant flakes are examined under the microscope, it can be seen that they consist of relatively long fibres, ie, approximately 2 cm, whilst the fibres of the initial felt are approximately 10 cm long; fi evidently this is a value which has been averaged after a small sample has been estimated, the actual measuring process being particularly awkward. These shorter fibres are less subject to stratification problems, on the other hand their length is still sufficient to ensure that a large amount of air is trapped. Moreover these fibres are distributed in an extremely uniform manner, less than 10% of the flakes comprising a dense central nodule of which the diameter is less than 7 mm or being in the form of a tuft.

In this respect it appears moreover that the fibres are almost in a state which is more unitary than at the moment when the initial felt is manufactured. One explanation for this unexpected condition is perhaps the presence of the binder used as size for the Initial felt which acts as a lubricant between the fibres there - in the manner of that which is required of any size and which moreover encourages the fibres to be spaced apart - this property being sought to increase the thickness recovery capacity of the product.

The second aspect of the invention is the addition of a binder; after being metered (via pumps 11, 12), the binder is led via a pipe 13 to the fibres. In general, a liquid binder tends to be sprayed at a level located after the carding unit, in order, if possible, to avoid the latter unit being fouled; on the contrary, a binder in powder form with a reduced wetting effect is 1 ζ delivered to the flakes at the carding unit. However, as indicated above, this is only a general tendency, the problem depending more precisely on the type of binder used. On the other hand, it should further be noted that the very large gaps between the flakes obtained according to the invention enable the binder to be distributed extremely homogeneously as necessary even after carding.

The fibres are deposited on a reception 25 belt 14 which closes the carding hood 10. As shown in Figure 1, this hood 10 entirely closes λ the system which leads to an almost 100% material output. At the hood outlet, the mat is brought to the desired thickness by a calender roller 15, then the product is optionally guided through a chamber 16 in which the circulation of hot air is established for setting the binder (for example in a binder melting furnace if the product is heatmeltable). Simultaneously or following these operations, it will be appreciated that the various cutting operations 17 necessary are performed before the finished product is obtained.

A further particularly advantageous application of the process according to the invention is the production of primary moulding ζ substances and in this case the product is made up directly after being calendered, the binder then setting during the moulding operation.

Products have been produced with extremely varied amounts of binder. Tests have been performed for example with a very low percentage of binder of between 10 and 15 %, for a binder which can be activated by heat and is intended as a primary substance for products moulded hot on the press. On the other hand, composite products comprising more than 70% of a mineral binder which can be activated by the addition of water have also been prepared.

By way of examples of use as primary moulding substances three series a, b, c of products containing respectively 30% of an epoxy type binder, constituted by waste from the production of paint by electrostatic spraying, 50% of polypropylene and 17% of a phenolic binder (bakelite) are produced, the percentages of binder * θ being given relative to the mass of finished product. These dry primary substances can be kept for as long as necessary before being pressed in the hot state. The values of the breaking stresses (in MPa) and moduli in flexure (in GPa) are then measured in accordance with standard NFB-51224 for different densities (in kg/m3). A fourth series of measurements is taken by way of comparison based on conventional moulded products prepared by the wet process and comprising 18% of ? 0 phenolic resins. The results are given in the following table: . binder j thickness : kg/m3 : MBa ϊ GB& 9 9 0 a 9 5-7 rom 300 500 600 970 5,8 21,0 36,0 37,0 0,3 0,7 2.3 4.3 9 to 4 »5 mm 210 1,6 0,2 » 420 7,6 0,8 Ο <0 - 590 12,8 1,3 : 850 25,6 2,9 ® I5J 10 : 1030 36,1 3,8 to © Ol c 5-7 rom 320 6,4 0,7 to 500 · 16,3 1,6 ob s> u 6 700 27,0 2,9 : 9 9 890 45,9 4,2 : 15 (2k a 5-7 200 2,5 0,3 X : 300 6 0,7 : to u 500 22 2,3 5 800 43 4,3 to The values measured for products a, c and d are practically identical. Thus the process according to the invention indeed enables final products to be obtained which are highly comparable to those of the art but which can be produced according to a process in two different stages, thus rendering the moulding stage independent of the fibre preparation stage.

A further aspect of the device according to the invention is that of the recycling of the fibres. It is known that insulating products can be prepared from the waste of textile glass fibre felt. For this purpose the so-called textile fibres are recovered by carding a felt using a carder conventionally used by the textile industry. Felts based on so-called insulating fibres such as those envisaged by the present θ invention are not suitable since the carder transforms these more fragile fibres into dust. With a carder according to the invention some of the textile fibres can be replaced by insulating fibres. It is thus possible to produce without any particular difficulty a reconstituted felt having a gsm substance of 1.2 kg/m3, for a density of 25 kg/m3, consisting of 12% of flakes according to the invention, 74% of textile glass fibres and 14% of a phenolic binder. The proportion of insulating mineral fibres can optionally be increased to 20 or 25%, which is particularly advantageous when the available amount of textile fibre waste is insufficient to meet the demand of reconstituted insulating products. 'Ί The performance of the product according to the invention will appear more particularly from the three attached graphs.

The first of these graphs (Figure 3) illustrates the heat conductivity Lambda measured in mW/m °K as a function of the density of the prepared product (fibres and binders). This graph is directly connected to the insulating capacity of a product and the heat conductivity is defined θ as being equal to the ratio of the thickness of the product to its heat resistance. Curve A is the characteristic curve of a standard product obtained by the centrifuging process with gaseous drawing as explained above, the fineness of the fibres being characterised by a permeability coefficient of 3 at 5 g. The permeability coefficient F is defined in a standardised manner as the flow rate of a gaseous current measured after this gaseous current discharged in highly 20 specific pressure conditions has passed through a highly compressed 5 g fibre sample. It should be noted that the permeability coefficient thus provides an indication of the braking of the gaseous current by the glass fibres and is thus characteristic of the fineness of the fibres. A. permeability coefficient of this type of 3 at 5 g is characteristic of extremely fine glass fibres.

Curve B is the curve obtained with products reconstituted according to the invention whilst curves C and D are obtained respectively for reconstituted products obtained in accordance with the teaching of FR 2 591 621 and for blown glass wool obtained in a conventional manner. A comparison of these 4 curves shows that for an equivalent degree of insulation (Lambda = 40 rnW/m °K for example), approximately 1 further density θ point is required with the products according to the invention (ie. approximately 6.6% more product) whilst 2 points are necessary (ie. approximately 13% more product) with the products according to FR 2 591 621, the conventional products requiring more than 50% of additional products to give a comparable degree of insulation. It should also be noted that curves A and B are practically parallel and that consequently the difference between the initial 2θ product (according to curve A) and the reconstituted product according to the invention is considered to be between 5 and 7% over the entire density range. In other words, the composite product according to the invention can very easily be substituted for the standard product without deterioration in the qualities being noticeable in practice; in particular very lightweight products, typically of 10 kg/m or less, can be produced whilst the products made of blown fibres always have a density of more than 15 kg/m3 (and in this case have an insulating capacity which is very low as compared with standard felts) and that the lower limit is approximately 12-13 kg/m3 for products according to FR 2 591 621.

This first test enables it to be demonstrated that the reconstituted products according to the invention have an insulating capacity which is very similar to that of the initial products used in their manufacture. In addition, the method of obtaining and receiving the flakes leads to a great reduction in the anisotropy of the material. For example this emerges from the values of a product's specific resistance to the passage of air measured for different product densities. Contrary to the measurement of the permeability coefficient, which is performed on a very small sample and which is 2θ above all highly compressed, the measurement of the specific resistance to the passage of air characterises the arrangement of the fibres in the product, and in particular their orientation, far better. This test is performed on an actual product and on a sample of which the size is 20 x 20 cm, ie. just as the permeability coefficient is a characteristic of the fibres, so the specific resistance to the passage of air is characteristic of the finished product.

The measurements, expressed in [Rayl/cm Rs], of which the results are shown in Figure 4, are taken on a plane parallel to the fibre deposition plane (parallel specific resistance or Rs //) and in a plane perpendicular thereto (perpendicular specific resistance or R"). If the product is perfectly isotropic, the parallel *θ and perpendicular resistance curves coincide; if, on the other hand, the fibres are oriented preferentially along one of these planes, parallel thereto, the air passes through the product in corridors parallel to the fibres whilst 15 perpendicularly thereto it systematically has to pass around the fibres in order to force a passage. The curves 21 and 22 are obtained with the previously defined standard product. It is noted that, for a given density, the parallel 0 specific resistance is far less than the perpendicular specific resistance. For the reconstituted product according to the invention, the curve 24 of parallel specific resistance practically coincides with the curve 22 of the standard product; in contrast, the perpendicular specific resistance (curve 23) is slightly less. This explains the product's reduction in 2δ insulating performance (cf. heat conductivity curve) but shows moreover that the anisotropy of the product has decreased.

The amount of this decrease is shown up more particularly by the curve in Figure 5 which shows the stresses exerted on a product (in kN/m ) along the X axis and the corresponding relative deformations on the Y axis.

The curve 31 corresponds to a standard product, again as defined above and of which the density is 45 kg/m3. Practically vertical at the outset - which corresponds to a great increase in the relative deformation even at a low stress the curve bends slightly for higher stresses but remains permanently concave. In addition it is noted that a 50% relative deformation rate is achieved for a stress of 18 kg/m .

With the products according to the invention and having the same density, it is noted on the other hand that firstly the curve 32 is relatively flat, in other words the increase in the relative deformation is less rapid than that of the force exerted. In effect this corresponds to the presence of vertically disposed fibres which can curve whilst, in the horizontal plane, the relative deformation results directly from the deformation of the fibres themselves under the effect of stresses.

Once the stress value corresponding to the buckling point of the vertical fibres has been reached, the relative deformation curve becomes identical to that of the standard product but starting from an initial value which is not zero.

It is noted in fact that for a given relative 10 deformation, the stress to be exerted is approximately 12 k'N/m2 greater with a reconstituted product.

These different tests thus demonstrate the fact that the carding operation performed in -j 5 the conditions of the invention enables products to be reconstituted which have a very great ability from the point of view of heat insulation and have advantageous mechanical properties.

Claims (14)

1. A device for manufacturing a reconstituted product formed from flakes which are impregnated with a reactivatable binder and based on 5 insulating mineral fibres, characterised in that it comprises a felt supply unit, a carding unit (4) comprising a brush (5) provided with flexible metal bristles, which are preferably undulating, a comb (7) and a unit (11, 12, 13) for supplying 10 binder in liguid or powder form.

2. A device according to Claim 1, characterised in that the bristles on the brush (5) are approximately 0.5 mm in diameter.

3. A device according to either of Claims 1 15 and 2, characterised in that the distance between the bristles on the brush (5) at its periphery is between 2 and 5 mm.

4. A device according to any one of Claims 1 to 3, characterised in that it comprises a felt 2θ retaining device (1). 5. A device according to any one of Claims 1 to 4, characterised in that the felt supply unit and/or the felt retaining device are formed by a Λ cylinder associated with a counter cylinder (2, 3).

5. A process for using the device according to any one of Claims 1 to 5, characterised in that 5 the carding unit (4) is supplied with a mineral fibre based felt (1), the said felt is shredded into flakes by means of a brush (5) and a comb (7) without the use of pneumatic force, a reactivatable binder is sprayed onto the flakes 1θ during or after the shredding operation and the flakes impregnated with binder are then collected by gravity.

6. 7. A reconstituted product formed from flakes which are impregnated with a reactivatable binder 15 and formed from a felt (1) based on insulating mineral fibres and obtained by the process according to Claim 6, characterised in that at least 10% of the said flakes comprise a dense nodule of which the diameter remains less than 10 20 mm; in that its thermal output relative to an identical mass of product is at least 93% of that of the initial felt (1); and in that it has a more marked isotropic nature than the initial felt (1).

7. 8. A reconstituted product formed from flakes 25 which are impregnated with a reactivatable binder ν η and obtained from a mineral fibre based felt (1) by the process according to Claim 6, characterised in that at least 10% of the said flakes comprise a dense nodule of which the diameter remains less 5 than 7 mm; in that, for a given relative deformation, the value of the stress to be applied to the said product is approximately 12 kN/m 2 higher than that exerted on the initial felt (1); and in that it has a more marked isotropic nature 1 θ than the initial felt (1).

8. 9. A product according to either of Claims 7 and 8, characterised in that the fibres in the flakes are approximately 2 cm long.

9. 10. A product according to any one of Claims 7 1 ζ to 9, characterised in that the reactivatable binder is thermosetting or thermoplastic and in particular selected from among epoxy, phenolic and polypropylene resins.

10. 11. An application of the product according to 20 any one of Claims 7 to 10 as heat insulating material.

11. 12. An application of the product according to any one of Claims 7 to 10 as a primary substance for moulding composite parts.

12. 13. An application of the product according to any one of Claims 7 to 10 in the preparation of a felt reconstituted from 12 to 25% of the said flake-based product, 60 to 74% of recycled textile 5 fibres and approximately 15% of phenolic binder»

13. 14» A device for manufacturing a reconstituted product formed from flakes, according to any one of Claims 1 to 5, substantially as herein described with reference to and as shown in the accompanying drawings. 10 15. A reconstituted product formed from flakes which are impregnated with a reactivatable binder according to any one of Claims 7 to 10, substantially as herein described. 16. An application of the product, according to any

14. 15 one of Claims 11 to 13, substantially as herein described.