FR2639868A1 - COMPOSITE MATERIAL BASED ON MINERAL FIBERS. DEVICE FOR OBTAINING AND APPLYING THE COMPOSITE MATERIAL - Google Patents

Abstract

The invention relates to a composite product formed from flakes - to which a binder is added - obtained by shredding a felt based on mineral insulating fibers. Said flakes are obtained by means of a carding device for felt in mineral insulating fibers comprising a felt feeding unit, a brush provided with flexible bristles and a comb.

Description

COMPOSITE MATERIAL BASED ON MINERAL FIBERS

  OBTAINING DEVICE AND APPLICATION

COMPOSITE MATERIAL

  The subject of the invention is a composite material and its production device. The material according to the invention is based on mineral fibers, especially fibers of

  glass, obtained by reconstitution of a mat of mineral fibers

  balls containing a binder. It serves for example as a primitive

  for obtaining molded parts.

  It is known to obtain parts, possibly shaped, dense or on the contrary very light, by molding a primitive based on natural or synthetic fibers comprising a binder. As natural fibers are used in particular textile fibers which have a fairly large average diameter, greater than 10 microns which is not very favorable from the point of view of the performance of acoustic and thermal insulation. Among the synthetic fibers are

  more particularly preferred mineral fibers, no

  particularly the so-called insulation fibers such as glass fibers, rock fibers or slag fibers which

  - are finer and are also produced at ex-

very weak.

  Patent application FR 2 608 964 describes, for example, the use of glass fiber mats for obtaining molded parts such as, for example, fittings for automobile parts. The primitives are in this case sections of glass fiber mats obtained by high speed centrifugation of molten glass with a

  gaseous drawing of the filaments; the fibers being received

  worked on an endless conveyor belt closing a hood in which they are sprayed with an organic binder in aqueous solution; the sheet thus obtained being subsequently shaped in an oven where polymerization of the binder occurs, and then cut to dimensions

desired to form the mat.

  Other fiberizing methods can be used.

  in particular, so-called free centrifugation processes

  or processes in which the molten material is in-

  troduit in the interaction zone of two gas streams at high temperatures and high speeds. However whatever the fiberizing method chosen, the reception is characterized by an aspiration of the fibers being collected on the endless strip under which a vacuum chamber is provided. Consequently and even if it is possible to partially remedy it by operating under conditions

  of suitable fiberizing and suction, mats or mid fibers

  minerals thus obtained always exhibit anisotropy, the fibers preferably being positioned in planes

  horizontal. This results in an anisotropy of certain

  certain physical properties, in particular of the tensile strength, anisotropy which moreover has certain advantages in particular as regards the insulating power of

felt formed.

  Another disadvantage encountered is that of the

  limitation in the choice of spray resin as

  collage in aqueous solution. In fact, to optimize the distribution of the binder in the mat and in particular to obtain a good wetting of the fibers in order to form a protective matrix, it is preferable to spray the binder in the fiber hood, before the fibers have accumulated to form a mattress. However, given the temperature conditions prevailing in the fiber hood and to avoid any risk of ignition, it is

  imperative to use a resin in solution in water.

  This excludes most of the usual adhesives of type -3-

  hot-melt or thermosetting. In general, we use

  read a phenolic resin of the resol resin type which

  knows that it decomposes at a higher usage temperature

  below 350 C, which significantly restricts the possibilities

  application capabilities of products, however, based on fibers which are, on the other hand, capable of withstanding without damage

  temperatures for example well above 500 C.

  Furthermore, it is known for example from French patent 2,591,621 to reconstitute mineral fiber products from fibrous flakes themselves produced from a mat - also called felt - by a carding operation using brushes contra-rotary or by means of rotary flails beating the felt preferably pre-cut in strip. Carding is preferably followed by whipping the flakes or pneumatic transport in order to release the residual stresses. The flakes produced are usually used as such. They are for example spread in layers on the ground for thermal or acoustic insulation of undeveloped attics or still serve as filling material for boxes for example

  for the formation of interior partitions.

  The insulating layers obtained from such flakes are significantly better than the blown wool layers obtained in the traditional way, but on many points, in particular the thermal conductivity, the difference between the properties of these layers and those of the

  original mat is still very sensitive.

  The observed deterioration in thermal resistance

  mique is explained by the nature of the flakes. Indeed, it is well known that free fibers, that is to say fibers not bonded together by a binder, tend naturally

  to associate in the form of balls. Also in any opera-

  tion of carding, we are trying to untangle these clumps to re-

  find healthy fibers. However, mineral fibers

  rales such as glass fibers and even more rock fibers are extremely fragile, so carding breaks

  the fibers and if we continue the operation a little too long

  ration, completely reduces them to dust. Consequently, the tendency is to operate with "soft" carding means, such as those described in patent FR 2 591 621 with, in return, a less good opening of the flakes which means that a large number of between them (about 1 in 2 in the best of cases) are always formed by central nodules around which radiate some rare unitary fibers. These nodules being particularly

  dense, they do not allow the imprisonment of a quan-

  high air content, which is known to decrease the insulating power of a fibrous product. Also for insulation

  given should we increase the amount of product needed.

  To this already very great drawback is added the fact that it is very difficult to impregnate or "wet" these nodules with a binder, whether this is in the liquid state or even more in the solid state in pulverulent form and therefore able to penetrate capillary into the heart of

  nodules. Typically, like most pre-

  feel a color after polymerization, this phenomenon

  results in a speckled appearance of the product after pol-

  ymerization, nodules not impregnated with binder do not pre-

  not feeling the same color as the rest of the product.

  On the other hand, to the advantage of this process it should be noted that the addition of binder can be carried out before the flakes are reunited again, at a temperature and under conditions free from any stress due to the process for preparing the fibers. . In addition, the reception

  flakes can be done simply by depositing under gra-

  vity, that is to say under conditions which do not give rise to preferential orientation of the fibers and which lead

  therefore to more isotropic products.

  On the other hand, patent publication AU-A-75 746/87 teaches a process for obtaining an insulating fibrous product containing a uniformly distributed binder, even if the product is based on fibers which are difficult to impregnate such as vegetable fibers. or animal. This process - which

  can also be applied to mineral fibers -

  is to card a felt to substantially separate the

  fibers and then to complete this separation to the fluids

  say by entraining them by a gaseous current, the binder being sprayed on the separated fibers before these

- 5 -

  have not settled. In this publication, we do not

  no specific carding means for fibers

  so that mineral fibers are to be understood

  rales, so-called textile glass fibers - also called reinforcing glass fibers - that is to say fibers produced by means of a die with mechanical drawing

  and whose average diameter is greater than 10 microns. Rap-

  pelons that so-called insulation fibers have an average diameter less than 6 microns, generally of the order of 3

  microns. In addition, the so-called textile fibers are practical-

  always grouped in threads like natural fibers

  which removes them completely from the fibers of iso-

  from the point of view of their behavior, particularly in carding. On the other hand, this technique calls for pneumatic transport of the fibers which poses the problem of eliminating the gas streams generated and leads to the need for suction boxes which, as indicated above.

  lead to anisotropic products.

  The subject of the present invention is a product

  composite based on mineral fibers obtained by reconstituting

  tution of a mat or felt made of mineral insulating fibers, whose thermal performance (based on an identical mass of product) is at least equal to 93% of that of

  initial felt and comprising an activatable binder

  laughingly, chosen independently of the technique used to obtain said initial felt. The composite product according to the invention is formed from flakes to which a subsequently activatable binder is added, obtained by shredding a felt based on mineral insulating fibers, less than 10% of the flasks comprising a dense nodule whose average diameter is further defined as less than 7 mm and which has a degree of impregnation with reactivable binder

less than the rest of the product.

  From this definition, it appears that the term flakes is practically abusive because the shredding of the felt is carried out in such a way that individualization

  of fibers is practically total and that therefore

  goes through a stage where the fibers are practically all in the unitary state, as was the case at the time of their 6-fiberizing. To do this, the flakes are produced from a felt of mineral fibers which is shredded by means of a carding machine constituted by a single soft bristle brush cleaned by a comb. In relation to the means

  known in the art, we therefore operate with an extreme device

  simplified but which nevertheless gives surprising results

  particularly superior. Indeed, a brush carder

  contra-rotating machines conforming to FR-2 591 621 produces flo-

  cons comprising for half of them dense nodules (and it is not possible to remedy this defect by extending the time of presence of the flakes between the

  brushes because then the fibers are reduced to dust).

  In addition to the flakes, the composite product according to the invention contains a binder which can be activated subsequently. By subsequently is meant a duration set by the user which may possibly be a few seconds, in the case where a polymerization oven is provided immediately downstream of the line or on the contrary several days and even

  several months the latter case finding itself more

  when the reconstituted product is used at full

  primitive for obtaining shaped molded parts. The duration of this period depends of course on the type of binder used, intermediate storage of the product is only possible with resins whose action does not

  does not - or extremely slowly - produce at am-

  biante. This is the case for example of the-

  melts or thermosets, added in powder form to the fibers. Let’s quote for example resins

  novolak phenol formaldehyde, epoxy resins, si-

  licones, polyurethane, polyethylene and polypropylene. Anyway, the fact that the resin is added

  on cold fibers, far from any installation of

  brage, gives complete freedom in the choice of binder

(resin or mineral binder).

  In liquid form, the binder is sprayed onto the fibers, either at the time of or after the carding operation. When in its form

  pulverulent, the addition of the binder is preferably carried out

  after carding, the binder being suspended in

  a gas for optimal distribution.

  The flakes are preferably collected by

  simple removal under gravity, without additional suction.

  The products thus reconstituted are much more iso-

  tropes than standard products obtained directly under the fiber hood, which is more particularly advantageous for the preparation of shaped molded parts

  likely to be subject to further

  traced to fairly high levels, which of course is

  not the case when flakes are used in bulk.

  Other details and advantageous characteristics of the invention are described below with reference to the appended plates which represent: FIG. 1: a diagram of a line for composite product according to the invention,

  - Figure 2: a more detailed view of the car-

Figure 1 deuse,

  - Figure 3: the evolution curves of the con-

  thermal ductivity as a function of density, - Figure 4: the compared curves of the values

  specific resistances to the passage of air during

  density, - Figure 5: the compared curves of the values of

  relative deformation as a function of the stress exerted.

  - The composite product according to the invention is pre-

  trimmed as shown very schematically in Figure 1. The

  initial felt 1 which we still call standard felt -

  or the 2 felts as shown here - is a felt made of mineral fibers. A glass wool felt can be used for example, the fibers being obtained by a process according to which the molten glass is introduced inside a centrifugation plate rotating at high speed from which it escapes in the form of filaments by a series

  holes on the wall of the plate, the threads

  elements being drawn in the form of fibers by a current

  zeux at high speed and high temperature, generated by -8 -

  burners surrounding the plate. The temperature conditions

  tures of glass and gases, the pressures and speeds used being for example those defined in the patent

  European EP-91866. The gluing is advantageously sprayed

  laughed at the fibers before they are collected by a receiving organ. This sizing is preferably a 10% aqueous solution of a formo-phenolic resin comprising in the dry part 55% by weight of resol resin and a silane acting among other actions as an anti-dust agent. For example, we used a felt whose density is 11 kg / m3, the thermal resistance of 2 m2eC / Watt and the specific resistance to the passage of air of 6.4 Rayls / cm (resistance measured perpendicularly glass fiber deposition plan). Felt conditioned

  the roll state is mounted on a reel here not shown

  smelled. As more precisely represented with the aid of FIG. 2, the supply of the carding unit is obtained by means of a cylinder 2 and a counter-cylinder 3 ensuring the advancement of the product. The felt 1 is simply compressed between the cylinders 2, 3, without cutting, which simplifies the device for these operations. Advantageously, these two cylinders also ensure the maintenance of the felt by the

holding back somewhat.

  The carding unit 4, surrounded by a casing, is advantageously constituted by a single brush 5. This brush has an outside diameter of for example 300 mm. It is provided with 6 fine bristles, mounted at a sufficient free height (within 45 mmn to allow them a certain flexibility. These bristles, for example, have a diameter of the order of 0.5 nmmn and are preferably wavy. the invention, they are preferably made of metal, the best results have been obtained with hardened steel The choice of metal may seem surprising since it is known that bristles made of synthetic materials, for example of resistant polyamide better for attack by abrasion of glass. In fact, it has been found according to the invention that

  bristles of synthetic materials - and therefore of certain

  some technological constraints necessarily of a -9 - diameter of more than 1 mm - heat up enormously during the carding operation and that consequently they wear out much more quickly than hairs in a less resistant material in the absolute but finer. In addition, the use of fine bristles allows a better match between the dimensions of the cutting tool which they constitute.

  and those of the fibers that we are trying to separate.

  Advantageously, such a metal bristle brush

  fine liquids increases the number of hairs and

  remove the counter brush which has the disadvantage of

  lengthening the processing time of the felt in mineral fibers and therefore accentuates its degradation. The density of hairs

  must be large enough to allow tearing

  complete quetting and on a small portion of the brush,

  but without however reaching a value such that it in-

  terdise a separate action of each hair. In practice a spacing of the bristles at the periphery of between 2 and 5 - mm is satisfactory, better results having been obtained with approximately 1500 bristles, ie 1 bristle every 3.5 mm

  for a brush 300 mm in diameter.

  The speed of rotation of the brush is for example close to 1000 revolutions per minute when the unit is

  fed by a felt of 11 kg / m3.

  To clean the brush, a simple comb 7 is used, consisting of points mounted on a plate 8, preferably very fine and very pointed. These points are for example metal needles of less than 0.2 mm in diameter at the point which penetrate into the brush at a depth - of for example 2 mm, this depth possibly

  vary thanks to the position adjustment mechanism 9.

  After carding, the flakes are collected by gravity deposit in a closed enclosure 10, without

  transport by pneumatic means. This tire transport

  matic has the drawback during extraction

  tion of air to favor a preferential orientation of the flakes parallel to the direction of the carrier gas and moreover, it appreciably increases the cost price of the product. To avoid the accumulation of flakes due to static electricity, the closed enclosure 10 for receiving

- 10 -

  is preferably made entirely of plastic.

  Observation under the microscope of the flakes obtained shows them to be made up of relatively long fibers, that is to say of approximately 2 cm while the fibers of the initial felt have a length of approximately 10 cm; this is of course an average value after estimation on a

  sample reduced size the actual measurement being by-

  particularly delicate. These shorter fibers are less prone to stratification problems, however their

  length is still sufficient to ensure imprisonment-

  large amount of air. In addition, these fibers are distributed in an extremely homogeneous manner, less than 10% of the flakes comprising a dense central nodule whose diameter is less than 7 mm or which is in the form

wick.

  In this regard, it seems moreover that the fibers are almost in a more unitary state than at the time of the manufacture of the initial felt. An explanation for this unexpected state is perhaps the presence of the binder used as glue for the initial felt which plays a role there.

  lubricant between the fibers - like what is re-

  sought by any size - and which moreover favors

  fiber spacing - property sought for aug-

  lie about the thickness recovery capacities of the product.

  The other aspect of the invention is the addition of a binder; after dosing (by pumps 11, 12) the binder is led through a pipe 13 to the fibers. As a general rule, a binder in liquid form will rather be sprayed at a level located after the carding unit, this in order to avoid if possible fouling of the latter against a binder in powder form, with "wetting" power. lesser, will be sent to him on the flakes at

  level of the carding unit. But as indicated above

  This is only a general trend, the pro-

  problem more precisely for each binder used.

  What should be noted, however, is that the extreme or-

  verture of the flakes obtained according to the invention allows if necessary a very homogeneous distribution of the binder even after

carding.

- 11 -

  The fibers are deposited on a receiving mat 14

  closing the carding hood 10. As shown in figure

  gure 1, this hood 10 completely closes the system which leads to yields of materials close to 100%. On leaving the hood, the mattress is brought back to the thickness

  hatched by a calender 15 then the product is

  tually led into an enclosure 16 in which is established a circulation of hot air ensuring the setting of the

  binder (for example in a melting furnace the binder is

  health of a hot-melt product). In parallel or at the

  Following these operations, we of course proceed to the diff-

  various cutting operations 17 required before the

attention to the finished product.

  Another particularly interesting application-

  health of the process according to the invention is the realization of

  molding primitives and in this case the product is di-

  rectified after calendering, the setting of the binder taking place later during the molding operation. Products have been produced with extremely diverse amounts of binder. Tests have been carried out

  for example with a very low percentage of binder

  taken between 10 and 15%, for a heat-activatable binder

  primed to a hot press molded product. In contrast, we also prepared products

  composites containing more than 70% of an active mineral binder

separable by addition of water.

  The performance of the product according to the invention emerges more particularly from the study of the 3 curves

attached.

  The first of these curves (Figure 3) is a representation of the Lambda thermal conductivity measured in mW / m. K, depending on the density of the prepared product (fibers and binders). This curve relates directly to

  the insulation capacity of a product in fact the conducti-

  thermal life is defined as equal to the ratio of the thickness of the product to its thermal resistance. The

  curve A is the characteristic curve of a standard product

  dart obtained by the centrifugal process with gas drawing

- 12 -

  discussed above, the fineness of the fibers being characteristic

  laughed at by a micronaire of 3 for 5 g. The micronaire F is

  defined in a standardized way as the flow of a current

  zeux measured after this gas stream emitted in con-

  ditions of well-fixed pressures passed through a very compressed sample of 5 g of fibers. Note that the micronaire therefore gives an indication of the braking of the gas stream by the glass fibers and is therefore characteristic of the fineness of the fibers. Such a micronaire of 3 for 5 g is

  characteristic of very large glass fibers

  nesse. Curve B is that obtained with products reconstituted according to the invention, while curves C and

  D are respectively obtained for reconstituted products

  killed obtained in accordance with the teaching of FR 2,591,621 and for blown glass wool obtained in a conventional manner. The comparison of these 4 curves shows that for

  equivalent insulation (Lambda = 40 mW / m.OK for example-

  ple), it takes about i point more density with products according to the invention (or about 6.6% more product) while 2 points are necessary (or about 13% more product) with products according to FR 2,591,621, traditional products requiring more than 50

  % of additional products for comparative insulation

  corn. It should also be noted that curves A and B

  are practically parallel and therefore the diff

  reference between the initial product (along curve A) and the reconstituted product according to the invention is for all

  density range considered between 5 and 7%. At-

  in other words, the composite product according to the invention can very easily replace the standard product, without

  that a deterioration in qualities is practically cons-

  tatable; we can especially produce very light products, typically 10 kg / m3 or less while the

  Blown fiber products always have a den-

  sity greater than 15 kg / m3 (and in this case with very low insulating power compared to standard felts), and that the lower limit is close to 12-13 kg / m3 for

of products according to FR 2 591 621.

- 13 -

  This first test demonstrated that the

  reconstituted products according to the invention have a potential

  see insulation very similar to that of the initial products used for their manufacture. In addition, the method of obtaining and receiving the flakes leads to a very significant reduction in the anisotropy of the material. This is apparent, for example, from the values of the specific resistance to the passage of air in a product, measured for different densities of products. Contrary to the measurement of the micronaire which is carried out on a sample of very small size and especially very strongly compressed, the measurement of the specific resistance to the passage of air characterizes much better the arrangement of the fibers in the product and in particular their orientation. This test is indeed carried out on a real product, and on a sample whose dimension is 20 x

  cm, so the micronaire is a characteristic

  fibers, both the specific resistance to

  air passage is characteristic of the finished product.

  The measurements, expressed in [Rayl / cm Rs], the results of which are shown in FIG. 4, were taken in a plane parallel to the fiber deposition plane (resistance

  specific parallel or Rs //) and in a plane perpendicular to

  water to it (perpendicular specific resistance or R-). If the product is perfectly isotropic, the curves

  of parallel and perpendicular resistances are con-

  fondues; if on the other hand the fibers are oriented preferably-

  tiially according to one of these planes, parallel to this, the air passes through the product in "corridors" parallel to the fibers while perpendicular to it it must systematically go around the fibers to spawn

  a path. Curves 21 and 22 are obtained with the pro-

  standard product defined previously. We note that for a given density, the parallel specific resistance is

  significantly lower than the specific resistance perpendicular

  cular. For the product reconstituted according to the invention, the

* curve 24 of the parallel specific resistance is practi-

  only confused with curve 22 of the standard product; on the other hand, the perpendicular specific resistance (curve 23) is a little lower. this explains

- 14 -

  the weakening of the insulation performance of the product (see thermal conductivity curve) but also shows

  that the anisotropy of the product has decreased.

  The importance of this decrease is more

  particularly highlighted by the curve of Figure 5 o are indicated on the abscissa the stresses exerted on a

  product (in kN / m2) and on the ordinate the relative deformations

corresponding tives.

  Curve 31 corresponds to a standard product, always in the sense defined above, whose density is 45 kg / m3. Practically vertical at the start - which corresponds to a significant increase in deformation

  relative even for a weak stress, the curve becomes

  slightly bends for higher stresses but remains permanently concave. In addition, one notes that a rate of 50% of relative deformation is reached for

a stress of 18 kg / m.

  With the products according to the invention and of the same density, it is noted, on the other hand, that at first,

  curve 32 is relatively flat, in other words the increase

  mentation of the relative deformation is slower than that of the stress exerted. This corresponds in fact to the presence of fibers arranged vertically which have the possibility of bending whereas in the horizontal plane the relative deformation is directly the result of the

  deformation of the fibers themselves under the effect of

  treacherous. Once reached, the value of the stress which corresponds to the point of buckling of the vertical fibers, the curve of the relative deformation becomes identical to that of the standard product, but starting from an initial value

  not zero. We note indeed that for a relative deformation

  given the constraint to be exercised is approximately 12 kN / m2

  higher with a reconstituted product.

  These various tests thus highlight the

  that the carding operation performed under the conditions

  tions of the invention makes it possible to reconstitute very efficient products from the point of view of thermal insulation

  and having valuable mechanical properties.

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  RMVENDICATIOfS 1. Composite product formed of flakes - to which a binder is added - obtained by shredding a felt based on mineral insulating fibers, characterized in that the binder can be reactivated later and in that less than 10% of the flakes have a dense nodule, the

  diameter of said nodules being less than 7 mm.

  2. Composite product according to claim 1, characterized. in that the binder is thermosetting or

hot melt.

  - 3. Carding device for felt in mineral insulating fibers comprising a supply unit

  in felt, a brush with soft bristles and a comb.

  4. Device according to claim 3, character-

  laughed in that the brush is provided with metallic bristles.

  5. Device according to claim 3 or 4, ca-

  characterized in that the hairs have a diameter close to 0.5 mm.

  6. Device according to one of claims 3 to

  5, characterized in that the spacing of the bristles at the peri

  brush pitch is between 2 and 5 mm.

  7. Device according to one of claims 3 to

  6, characterized in that the bristles are wavy.

  -8. Device according to one of claims 3 to

  7, characterized in that it comprises a hand-held device

your felt.

  9. Device according to one of claims 3 to

  8, characterized in that it comprises a supply unit

  tion by binding in liquid or powder form. -

  10. Application of the product according to one of the res-

  1 to 2 instructions for making molded shaped parts.