FR2559793A1 - PROCESS FOR PRODUCING MINERAL FIBER MATTRESSES FROM A MELT MATERIAL - Google Patents

Abstract

THE INVENTION RELATES TO TECHNIQUES FOR THE PRODUCTION OF MATTRESSES OF MINERAL FIBERS. IN THE TECHNIQUES CONSIDERED, A MELTED MATERIAL IS SENT TO A CENTRIFUGER WHOSE PERIPHERY IS PERIPHERED WITH ORIFICES, THE MATERIAL PASSING THROUGH THESE ORIFICES IS PROJECTED OUT OF THE CENTRIFUGE IN THE FORM OF FILAMENTS, A GAS CURRENT LONG THE PERIPHERAL LENGTH THROUGH THE PERIPHERAL. COMPLETING THEIR STRETCHING. THE GAS CURRENT, INITIALLY ANNULAR SHAPED, RESTRICTS DOWNSTREAM OF THE CENTRIFUGE TO THEN FORM A SENSITIVELY CONICAL SHAPE. ACCORDING TO THE INVENTION, ADDITIONAL VEHICLE FIBROUS PARTICLES ARE INTRODUCED BY A GAS CURRENT DIRECTED TRANSVERSALLY TO THE DIRECTION OF PROGRESSION OF THE GAS CURRENT CARRYING THE NEWLY FORMED FIBERS AND ENTERING THE LATTER AT A RUNNING POINT OF THE CURRENT BETWEEN THE ZONE AND THE ZONE CARRYING FIBERS.

Description

IMPROVEMENTS IN THE INTRODUCTION OF FIBROUS BROWN PRODUCTS

  IN A PRODUCTION LINE OF MATTRESSES FROM FIBERS

  The invention relates to the techniques for the production of

telas of mineral fibers.

  Industrially, the most common mode for the formation of mineral fiber felts is to form the fibers from the

  melted material by sending this material to a centrifuge

  riphérie is pierced with orifices. The molten material is ejected from the centrifuge

  runner through these orifices in the form of filaments. A gaseous current

  hot and high speed along the peripheral walls of the

  The fugger pulls the filaments and completes their stretching.

  This method of manufacturing fiber mattresses has been the subject of

  úJ many publications. Among the most recent can be mentioned

  French Patent Application No. 2,443,436 and the application for

European Patent No. 091,866.

  In the production of fiber mattresses, a proportion of

  significant amount of by-products is formed. These are first of all

  or mattress banks that are systematically cut to fit the transverse dimensions and ensure perfect straightness of the edges. It is then all products that are removed from the manufacturing line at any point of it because they

  do not correspond to the chosen standards. All of these sub-

  Fibrous products can represent up to 10% and more, of the whole production. These by-products, as the case may be, are either

  discarded, or reused after transformation.

  Traditionally, in the training techniques of

  telas to which reference was made previously, part of the

255'9793

  less of these by-products is reincorporated into the manufacturing process.

  cation of the mattress. For this purpose, the by-products used are all

  first reduced to small particles or nodules

  by a suitable shredding or grinding operation. The fibrous particles thus formed are carried by a gaseous stream into the chamber where the fibrous mat is formed, where they are more or less well mixed with the fibers which have just been formed before they are collected on a receiving member.

  Returning to the production of fiber mattresses, it is neces-

  to clarify the conditions under which fibers leaving the

  centrifuge are processed to form a mattress.

  Each centrifuge is provided at its periphery with a very large number of orifices, and all the fibers formed, driven by the gas stream along the centrifuge constitutes a kind of veil.

  very regular ring which extends towards a conveyor

  reception. The conveyor, which is permeable to gases, retains the fibers and lets the vehicle gases which are sucked into caissons pass through

  under the conveyor and kept in a vacuum by approved means.

propriate.

  In addition, in their path between the centrifuge and the con-

  reception voyeur, the fibers receive by spraying a binder intended to fix them to each other stably in the mattress

  final. Fiber coating is usually completed by

  the binder, which is done after the mattress is formed by the entanglement of the fibers on the

receiving conveyor.

  In industrial plants, when large production is required, several centrifuges aligned above one

  same conveyor contribute to the formation of the same mattress.

  The introduction of fibrous particles, when practiced

  ticated, is traditionally done between centrifugal devices

  successive. By intercalating the introduction of fibrous particles

  two sources of newly formed fibers, efforts are made to obtain a suitable mixture so that the distribution of the particles in the

  mattress is relatively homogeneous.

  It is indeed important for the properties of mattresses

  formed that the particles are well distributed in the mass of the mate-

  Las. In fact, if the particles are, in view of the fundamental properties of the mattress, such as the newly formed fibers, especially with regard to the thermal resistance, their presence can lead to more or less important property modifications, such as mechanical strength or appearance of the product. In general, it is preferable that the modifications, when they exist, affect the product uniformly. Moreover, the modifications in question are manifested

  for particle contents exceeding certain limits. In repair

  By weaving the particles well in the mattress, it is possible to increase

  the amount of particles without risking exceeding these limits in

any point of the mattress.

  Experience shows that the traditional mode of introduction

  Particle production in the fiber stream does not lead to

  tribution perfectly homogeneous. The particles tend to be deposited in the form of layers more or less integrated into the mass

newly formed fibers.

  In a schematic way, the analysis of the mattress in its thickness seems to show that each centrifuge leads to the deposition of a "layer"

  fiber. The introduction of the particles between two centrifuges results in

  under these conditions, in a privileged way, to the deposition of particles

  between the layers corresponding to these centrifuges.

  The distribution of fibers in the width of the conveyor

  also traditionally problems when the conveyor is relatively

  wide, for example when it reaches or exceeds 2 m. To ensure that the distribution of the fibers is sufficiently regular across the entire width, we usually use means that either

  promote the widening of the gaseous flux carrying the fibers (eg

  gaseous streams directed transversely to the normal path "spread" the veil of fibers), or periodically modify the direction of this

  gaseous flow (for example, they are conduits animated by a movement

  oscillation which alternately move the veil from one edge to the other

the conveyor).

  To distribute the particles in the width of the mattress provisions, the same type as those used for the fibers

  newly formed, could be used. This would require this

  while significantly increasing the complexity of the

  in a relatively small space. For these reasons, we are usually content with less sophisticated solutions but also less

  easily controllable, such as the use of deflecting walls which

  the gaseous flow carrying the particles over the entire width of the conveyor.

  In the best of the previous cases, distribution faults

  bution are minimized but are never perfectly mastered. This

  has the consequence in particular of limiting the overall content of

  which can be introduced in this way in the making of

mineral fiber mattress.

  It is therefore economically desirable to have techniques for achieving a good distribution of the fibrous particles added to the newly formed fibers in order to increase the amount of these recovered particles in the composition of the fibers.

  mattress and this without harming the essential qualities of these mattresses.

This is the purpose of the invention.

  According to the invention, and contrary to the traditional techniques

  the introduction of the fibrous particles, the particles are

  in question in such a way that they enter the veil of

  annular fibers immediately downstream of the centrifuge.

  It is known that the conditions under which the fiber web develops beyond the centrifuge play a vital role in the quality of the prepared mattress. In particular, as far as possible, efforts have traditionally been made to avoid disturbing the gas flow carrying the fibers, in particular to limit as much as possible the

  formation of bricks which break the homogeneity of the distribution of

  - bres in the mattress. Surprisingly, the inventors have found that the penetration of particles carried by a gaseous stream into the

  ring, and near the centrifuge, does not cause

  changes in the appearance of

  and allows a very homogeneous distribution of particles in

newly formed fibers.

  The observation of gas flows at the level of the penetration of

  particles in the annular web can, in part, explain the

  results. Indeed when the penetration in the veil is

  close enough to the centrifuge and under conditions of fast

  which will be discussed later, we observe a breakup of the current

carrying the particles.

  Without studying in detail the mechanism that leads to this

  as a result of good dispersion of the particles in the

  gaseous carrier carrying the fibers, it is possible to recall that the zone under the centrifuge is driven not only by the gaseous currents along the centrifuge, but also by the induced currents.

by these.

  Immediately under the centrifuge a zone is created

  pressure with respect to the ambient atmosphere, which tends to tighten

  fiber veil. Beyond this zone, the initial shaped current

  annular and assembled, is propagated according to a configura-

taper.

  Preferably, according to the invention, the introduction of particles

  is performed near the level of tightening of the veil.

  In this way, the introduced particles are entrained

  in the gas movements resulting in the formation of the current

  appeared, and one leads to a good dispersion of these particles.

  An introduction too far down the tightening zone

  would not allow particle distribution throughout the entire

  bearing the fibers. Likewise, a minimum of distance from the

  centrifuge must be respected so as not to disturb the flow of

  drawing currents at the point where stretching occurs. This

  last distance may nevertheless be relatively small. We can

  It is usually noticeable that beyond 150 mm downstream of the centrifuge,

  formed fibers are stabilized and that the penetration of the

  the particles do not interfere with the drawing conditions.

  To facilitate penetration, the gaseous stream carrying the particles is directed transversely to the drawing gas stream. Preferably, the directions of propagation of these two currents are

  orthogonal to each other or to a posi-

  sine. A certain inclination vis-à-vis the general direction

  flow, that is to say from the vertical, is possible under

  ve this inclination nevertheless leads to the penetration of the current

  carrying the particles in the annular fiber web.

  In addition, the inclined jet must penetrate into the web of

  without hitting the elements of the device which are

  go towards the tightening of the veil, in particular the means of

spraying the binder.

  Taking these conditions into account, the jet

  cules makes an angle of at least 30 with the vertical and preferably

at least 45th.

  The direction of the current carrying the particles is furthermore

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  advantageously located in a vertical plane containing the direction in which the production line extends and therefore the conveyor. A

  different direction (although, as we shall see, the energy developed

  Due to the current carrying the particles is relatively small compared to that of the drawing current) could lead to a deflection of the current carrying the fibers in the direction transverse to the conveyor and consequently change the distribution. By directing the current carrying the particles in a longitudinal plane relative to the conveyor, even if the current carrying the fibers is slightly deflected, this has no problem.

  consequence on the transversal distribution.

  The invention is explained in more detail in the

  following the description that refers to the drawing boards in

  which: - Figure 1 shows, schematically, a part of the production line of mineral fiber mat in which the

  fibers are produced and collected; in this figure, the mode of

  troduction of particles is the traditional way,

  FIG. 2 shows an embodiment, according to the invention

  for the introduction of particles,

  FIG. 3a shows, in section, the type of distribution de-

  fectuous particles that are observed in the traditional modes of introduction, - Figure 3b is a view similar to that of Figure 3a for a product prepared by operating the introduction of particles in

the conditions of the invention.

  Figure i shows three centrifuge devices 1, 2, 3

  for the production of fibers, forming part of the same line. These dis-

  positive are aligned in the upper part of a reception chamber 4 substantially closed. They are located above a conveyor 5 which constitutes the lower part of the receiving chamber. The conveyor 5

is permeable to gases.

  One or more boxes 6, according to the dimensions of the

  chamber 4, are arranged immediately below the conveyor. An aspiration

  tion performed by means not shown maintains the chamber 6 in depression with respect to the atmosphere of the chamber 4. Under the effect of this depression, the gas carrying the fibers through the conveyor and are discharged while the fibers are retained on The conveyor 5. Each of the centrifuges 1, 2, 3 gives rise to a fiber web 7, of shape, which is driven by the drawing gases to the receiving conveyor. After tightening to 8, the current

  of fibers flourishes in a conical form.

  Figure 1 does not respect the proportions of the various

  but endeavors to reproduce in as representative a way as

  possible the flow of the fibers from the centrifuge to the con-

  voyeur. For reasons of economy and space, the various centrifugal devices are as close as possible to one of the

  others so that, in practice and as

  Figure 1 shows the different fluxes of fibers emanating from

  Neighbors tend to mingle before reaching the conveyor.

  This figure did not show the various

  sitives which are usually along the path of the fibers, such as water and binder spray nozzles and possibly means for improving the transverse distribution of the fibers on the conveyor. These means are usually downstream or at the

  the tightening zone 8 of the fiber web.

  Figure i shows three centrifuges. On the lines

  important number of centrifuges, the number of centrifuges can be much higher up to 10 and even 12. As we will see in the

  Therefore, the invention is applicable irrespective of the number of centrifugally

  used and even if there is only one centrifuge while the

  traditional means of introduction of particles implied neces-

  use of several centrifuges.

  The fibers are retained on the conveyor 5 where they are deposited

  feel entangled with each other. The thickness of fibers on

  the conveyor increases from one end of the line to the other by

  successive melting of the fibers from the various centrifuges. At the exit of the reception chamber 4, the collected fiber layer 9

  undergoes various treatments that lead to the final felt. In particular

  bind, a heat treatment is performed to polymerize the composition.

  binder, the fibers of which have been coated and fix the structure of the felt. In the same way, the continuous band of felt is put in the dimensions

required.

  Thus, traditionally, the selvedges are cut as indicated above, and after having undergone a shredding,

  the selvedges are reintroduced as particles or nodules di-

  right in the reception room.

  To transport them from the point where they are formed

  that at the reception chamber 4, the particles are driven by a

gaseous current.

  Traditionally, the particles are introduced into the receiving chamber between two centrifugal devices.

  The pipes 10, 11 leading the gaseous stream charged with parti-

  These spill these essentially in the direction of propagation

  newly produced fiber streams.

  Where appropriate, as we have indicated, a deflector

  killed on the path of the particle-laden gas stream deforms this current so as to disperse the particles across the entire width of the

  conveyor. Such an arrangement is not shown in FIG.

  As is easily understandable, a perfect distribution

  particles in the fiber layer 9 collected on the

  voyeur would imply that one has a perfectly homogeneous mixture of newly produced fiber flows and the gaseous stream carrying the particles. If a certain mixture is actually achieved before these fibers and particles settle on the conveyor, this mixture in practice is generally not sufficient to lead to a product.

perfectly homogeneous.

  The result of this traditional provision, when the

  line is limited to three centrifuge devices and two introduc-

  particles, is of the type shown schematically in Figure 3a. The cup

  a felt in the thickness shows a succession of distinct layers

  your. Especially particles (represented in a darker way

  for the purposes of drawing) are found in a substantial proportion

  higher in two intermediate layers 12 and 13.

  Without resulting in a complete separation of the layers from each other, the distribution is not homogeneous, which in this case leads in this case to limiting the amount of particles that can

  be introduced so that at no point in the felt the particulate content

they do not exceed a certain threshold.

  It should be noted that, if the use of appropriate means such as deflectors makes it possible to obtain a satisfactory cross-section of the particles, these means can not improve the distribution in the thickness of the mattress. This distribution results in

  effect, as is well understood, of a lack of uniformity in the

  fiber / particle in the direction of progression of the conveyor. A zone in which most of the deposit consists of fibers

  newly formed (the one that lies vertically

  geur) succeeds an area where the particles are relatively abundant (vertical to the first introduction of particles) then a

  new zone where the particles are in a very small percentage and

so on.

  The solution according to the invention to obtain a good distribution

  bution is illustrated in Figure 2.

  In this figure, the fiber formation device is

  shown in more detail than in Figure 1. It

  mainly takes a motor assembly schematically denoted 14 which drives in rotation, by means of belts, a hollow shaft 15. The centrifuge device 16 is attached to the end of

  this hollow shaft 15, it is formed of a drum whose peripheral wall

  that is pierced with multiple orifices.

  The molten mineral material is conducted up to the vertical axis of the shaft 15. It is drawn from a die inside the centrifuge 16. The material collected by a basket located in the axis of the shaft 15 is sent from this basket to the peripheral wall of the centrifuge and escapes through the orifices of this wall in form

of filaments.

  To maintain the centrifuge assembly and material under the appropriate temperature conditions for fiber formation, various means are usually employed. Thus, it is advantageous to heat the centrifuge (or at least the lower part thereof which is exposed to faster cooling by its contact

  with the surrounding air) by induction. In Figure 2, a ring of in--

duction is represented in 17.

  The filaments projected out of the centrifuge are driven by an annular gas stream. This gaseous stream is preferably at a high temperature. This may include combustion gas emitted

by an annular burner 18.

  It is also common in this type of device to use

  additional gaseous streams enveloping the draft gas stream.

  These jets can be emitted, for example, from a ring 19

  fed with pressurized gas, and having a series of orifices di-

  rigging jets essentially in the direction of progression of the drawing gases. The formed fibers entrained by the drawing gases form

  a veil 20 whose characteristics have been previously specified.

  The gaseous stream carrying the fibers during its progress

  to the receiving member is then most commonly cooled by spraying water from nozzles 21 arranged in a circle around

  of the gas stream. The nozzles are sufficiently numerous and close

  to lead to a homogeneous treatment of the fibers. In the same way, nozzles 22 disposed around the stream carrying the fibers spray a binder on the fibers to ensure

  subsequently a good cohesion of the entangled fibers in the mat-

las constituted.

  It should be noted in this regard that in traditional modes

* Introduction of fibrous particles, the latter are not di-

  properly subjected to this binder spraying. For this reason, the cohesion of these particles with newly formed fibers is less well achieved in the mattress. This is a factor that can

  in particular to damage the mechanical qualities of the final mattress. In particular

  binding the compression ratio applicable to these mattresses, without compromising their recovery of thickness later, may decrease in the presence of these

  particles less well "bound" to the mass of fibers.

  In the technique according to the invention, the introduction of

  particles is advantageously effected at the level of the tightening of the

  at or above this level as shown in Figure 2. This

  introduction is thus advantageously located upstream of the pulverulent

  binder, so that the fibrous particles undergo

  also feel a coating that promotes cohesion with the fibers

2 -news.

  Particles carried by a gaseous stream are conducted

  close to the fiber veil by means of a pipe 23 with

  only the end is shown in Figure 2.

  Line 23 directs the gaseous stream carrying the

  transversely to the path of the fiber web.

  The respective characteristics (speed, volume or better

  impulse) gaseous draft currents carrying the fibers and

  the particles are chosen in such a way that the second

enters the first.

  The penetration of the current carrying the particles into the

  drawing is accompanied by a kind of "bursting" which causes the

  projection of particles throughout the current carrying the fibers.

  The mechanism that leads to this dispersion has not been fully elucidated

  but it is understandable that the area in question is the seat of tur-

  important bulbs, penetration of the gaseous current bearing the

  particles can only accentuate these turbulences and favor the combination of

  of these two currents and the dispersion of the particles in the

  of these gaseous streams combined.

  As a general rule, the gaseous current used to carry the particles must have a certain speed in order to prevent

  "plugs" are formed in the pipes. Indeed, the journey is

  particles is often relatively long and goes through a number of changes of direction, all of which can lead to irregular

  particles is not vigorous enough.

  As an indication, the distance over which the particles are carried may exceed one hundred meters. This is particularly the case for

  those formed from the selvedges, the cutting operations of

  shredding and returning to the receiving chamber

  then advantageously continuously at the end of the line of

  production, which normally extends over a great length.

  The speed of gases to prevent plugs or

  sedimentation of particles for dimensions of the latter tradition-

  of the order of 10 to 20 mm, is advantageously between 15 and

  m / s and preferably between 20 and 25 m / s.

  For the combination of gaseous currents to be effected satisfactorily, that is to say that the current carrying the particles penetrates well into the current carrying the fibers, without going to cross it completely, it is advantageous to proceed with a pulse ratio of the particle current Ip to the fiber stream If between 1/30 and 1/5 and preferably this ratio is in the vicinity

1/10.

  The impulse of the gaseous current is defined by the expression: I = p.V2.S in which: - P is the density of the gas (in kg / m3), - V is the gas velocity (in m / s) ,

- S is the straight section (in m2).

  The dimensions of the pipe 23 leading the particles

  they are determined by practical considerations. It is necessary

  re that the section of this pipe is sufficient to let the particles pass without difficulty. As an indication, for particles whose average dimensions are of the order of 15 to 20 mm and for a speed of the order of 20 m / s, a section of about 80 mm diameter is suitable.

  A smaller diameter is possible but increases the risk of clogging except to increase the speed of the gas stream. Similarly, a larger diameter can be used but led to blow

  more air to maintain the conditions of vi-

  required to properly train the particles. This second case leads to a greater energy expenditure without the technique being improved. In addition, a gaseous mass which is too large compared to that carrying the new fibers can disturb the balance of

  respective pulses as defined above.

  It may be noted that for a diameter of about 80 mm, the volume of gas carrying the particles is much greater than that which is

  strictly necessary for this pneumatic transport.

  Under the conditions corresponding to the introduction of high levels of particles this equates to a load of the order of 0.25 kg

  of particles per blown m3, which remains a very small amount.

  If one ignores the questions of necessary dimensions,

  of the pipeline, such a pneumatic transport can indeed lead to much greater loads of

of 1 kg / m3 or more.

  As an example of implementation of the invention, the introduction

  fibrous particle was made as previously indicated on a production line equipped with fiberizing machines

  such as that shown in Figure 2.

  The production of each centrifuge is 20 tonnes of

  glasses of glass a day. The insulating product prepared consists of

  very fine bres (micronaire 3.0 under 5g).

  Experience has shown that the sensitivity of the properties

  mattresses to the introduction of particles is all the more

  the fibers are thinner. We have therefore chosen to make these tests on those products for which the introduction of particles is the

  more delicate in order to have fully meaningful results.

  The product is first prepared under the traditional conditions

  which is to say by recycling the milled selvedges representing under the best operating conditions a maximum of 4% of the mass.

  mattress formed. In this first test, the reintroduction of particles

  is carried out between the centrifuge devices as

shown in Figure 1.

  The fiber mat produced has a basis weight of 850 g / m 2, a density of 9.48 kg / m 3 and a thickness of 140 mm.

before compression and storage.

  The mattress is rolled up on itself with a rate of compres-

  4/1, ie in its compressed form its thickness is only about 35 mm. We measure the thickness recovery after 60

  storage days under these compression conditions.

  Still under the traditional conditions of introduction of fibrous particles, when the particle rate is increased by adding crushed products from other sources, it is found, the other conditions remaining the same, a significant loss of recovery of thickness after storage which shows a lower resistance to

  compression (of a less good elasticity).

  As an indication, for a total content of

  troduces (crushed selvedges and articules from other sources) of the order of 10% of the mass of the mattress, the loss of thickness with respect to the product in which only the selvedges are recycled can

  reach 7 to 8%. This loss reaches 12% for a particulate content

the 14%.

  Product observation shows a distribution of

  very inhomogeneous in thickness, of the kind of that represented in

Figure 3a.

  Of course, this bad distribution is all the more

  sensitive in the properties of the mattress that these particles are in pro-

  larger portions. Comparisons established between a mattress consisting solely of newly formed fibers and a mattress in which the crushed selvedges are reintroduced (for a total content representing 4% of the mass) show that the properties are not appreciably modified. In particular, the ability to recover

  thickness is not significantly affected.

  Tests carried out under the conditions of the invention for different contents of particles, lead to a product in which

  the particle distribution in the thickness is practically uni-

  form as shown in Figure 3b.

  In FIGS. 3a and 3b, the particles 24 have been represented

  to allow visualization of the distribution. In fact,

  when the fibrous particles introduced come from a production

  In the case of selvedge or substandard products, the distinction between fiber mass and particles is practically not apparent. It can not be

  found only by careful examination of the fibrous structure. Even-

  the fact that the fibers used in the constitution of these particles have already received a first coating of binder product can lead to a slight shade of color (when the binder tends to

color the fiber of course).

  The improvement of particle distribution is found

  thickness recovery capacity, especially for

  neurs. So, contrary to what we see in the use

  the traditional way of introducing particles, the recovery of

  is virtually unaffected for rates reaching or exceeding

10% of the mass of the mattress.

  For mattresses of very fine fibers (micronaire 3.0 g), the introduction of the 4% of particles corresponding to the selvedges and 7% of particles of other origin, but of the same nature, resulted in a recovery. slightly less good thickness (about 4%). This recovery slightly smaller thickness is less or almost not sensitive when preparing mattresses a little less fine (micronaire 3,5 under 5 g for example or better still 4.0 under 5 g) and which correspond the most common products in the traditional uses of thermal insulation. Also for these

  products, the particle content may reach or exceed 15%.

  In view of these results, it appears that, thanks to the

  vention, it is possible to obtain mineral fiber mat-

  closing increased proportions of particles without affecting the properties of the mattress, while maintaining satisfactory properties. Furthermore, in the case of products mainly intended for thermal insulation, it is important to note that the introduction of particles according to

  the invention, even for a content which may amount to 15%, is practically

  no effect on the thermal conductivity of the mattresses produced.

"5

Claims (10)

  1. Process for producing composite mineral fiber mat   taking the formation of fibers from a molten material, which is sent into a centrifuge whose periphery is pierced with orifices, the material passing through these orifices being thrown out of the centrifuge in the form of filaments, a gaseous current running along the periphery of   centrifuge driving the filaments and completing their stretching, this cou-   initially annular form, narrowing downstream of the centrifuge   to form a current of substantially conical shape, the   fibers entrained by the gaseous stream being directed towards a   reception voyeur where they are collected, a binder composition   being sprayed on the fibers during their journey between the center   trifuge and the conveyor and in which fibrous particles are   also to be deposited on the conveyor with the new fibers   formed with which they are mixed, characterized in that   that the additional fibrous particles are conveyed by a   gaseous flow directed transversely to the direction of progression of the gas stream carrying the newly formed fibers and entering the latter at a point between the centrifuge and the zone of   tightening of the current carrying the fibers.   2. The method of claim 1 wherein the current carrying the particles follows a direction making with the vertical, corresponding to the general direction of progression of the bearing current.   the fibers, an angle of at least 30.   3. A process according to claim 1 or claim 2 wherein the gaseous stream carrying the particles is directed into the direction of the length of the conveyor.   4. Method according to one of the preceding claims, characterized   in that the velocity of the gaseous stream carrying the particles is between 15 and 20 m / s.   5. Method according to one of the preceding claims in   which the ratio of the pulses of the gaseous stream carrying the particles   and the one carrying the fibers 1p / If is between 1/30 and 1/5.   The method of claim 5 wherein the report Ip / If is close to 1/10.   7. Method according to one of the preceding claims in   which the penetration of the particles into the current carrying the fibers   is carried out upstream of the zone in which the fibers are coated. of the binder composition.   8. A process according to any preceding claim   in which the recycled fibrous particles originate for   part of the shredded edges of the mattresses formed on the line.   9. A method according to any preceding claim   in which the content of the mattresses produced in fibrous particles   its additional is equal to or greater than 10%.   10. Fiber mat obtained by the process according to any one   conque of the preceding claims.