CA1241533A

CA1241533A - Process for the continuous production of fiber reinforced webs

Info

Publication number: CA1241533A
Application number: CA000423534A
Authority: CA
Inventors: Gunter H. Tesch
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-03-12
Filing date: 1983-03-14
Publication date: 1988-09-06
Also published as: EP0089018B1; EP0089018A1; JPS58167152A; NZ203527A; DD208638A5; AU1219283A; ATE20254T1; AU563936B2; DE3363879D1

Abstract

ABSTRACT
The invention provides a process for the continuous pro-duction of fiber reinforced webs, wherein the webs even in the unbonded or unvulcanized state possess their own internal coherence, in particular a fiber reinforcement. For this purpose, an elastic unfoamed material, is placed between a cover sheet and a substrate sheet as the core layer, with at least one of the outer layers consisting of actively needle bondable fibers, whereupon the three layers may be needle bonded to each other. Such webs, serving for example as floor coverings, may further be impregnated or coated with binders and the rubber containing core layers may be vulcanized.

Description

~;~41533 The invention concerns a process for the continuous production of fiber reinforced webs.
Fiber reinforced wets are made of highly diverse elastic materials, in which, in addition to the use of raw materials, recycled materials are being increasingly utilized.
It is known from DE-OS 2 162 233 to mix granulated, irreversibly crosslinked elastomers with a thermoplastic binder, heat the mixture to a temperature above the melting point of the binder but under the decomposition temperature of the elastomer, extrude it as a film from a sheet die and cool it between cooled belts of a double belt press to a temperature under the melting point of the binder.
DE-AS 1 089 954 discloses a process for the production of plates or products of other shapes from waste rubber and textile fibers in which impregnated textile filaments ob-tained from cord inserts of used automobile tires by cutting, breaking and grinding, are mixed with a small amount of small pieces of rubber with the addition of binders, such as natural or synthetic resins or adhesives and the mixtures pressed at an elevated temperature.
DE-AS 1 038 266 describes a process for the production of a porous material consisting of textile fibers, in partic-ular textile wastes and binders, in which the textile fibers are agglomerated in the dry state into small units and these fiber agglomerates sprayed with a liquid binder in droplet form while rotating in a drum so that the binder adheres in :`

~L2~ i33 dots to the surface of the fiber agglomerates, whereupon under continued rotation of the mass being formed, a harden-ing agent is sprayed onto it, followed by the shaping, drying and hardening of the mass.
It is known from the production of rubber to prepare elastic webs by vulcanizing a masticated web provided with vulcanizing agents, for example under the action of steam.
It is a common characteristic of all of these known processes that the unhardened or not yet vulcanized web has no coherence over its entire surface. For this reason, the elastic web must be sùpported by a carrier during hardening or vulcanization. If several unhardened or unvulcanized webs are placed upon each other, the individual layers must be separated by separating layers, for example silicone paper. It is not possible to freely move such webs in an unsupported manner, even if for example a masticated rubber sheet is involved.
It is therefore an object of the invention to provide a process for the continuous production of fiber reinforced webs whereby the webs possess their own internal coherence, in particular a fiber reinforcement, even in the unbonded or unvulcanized condition.
The object is attained by the production of fiber rein-forced webs wherein an elastic, unfoamed material is placed as a core layer between a substrate layer and a cover layer, with at least one of the outer layers comprising actively needle bondable fibers thereby forming a composite which is then needle bonded together. The process of needle bonding

-2-known in the textlle industry is used to achieve the needle bonding.
In the so-called needle bonding process, individual fibers or bundles of fibers are inserted from a fiber con-taining layer placed upon another layer by means of needles equipped with barbs into the second layer, in which the fibers remain upon the withdrawal of the needles, thereby bonding the fiber containing layer to the second layer. A
requirement of the needle bonding process is thus the presence of a layer of ''actively needle bondable materials", i.e., a layer consisting of fibrous structures usable for the needle bonding process, or containing such structures. The other layer, in which the actively needle bondable fibers are in--- serted must be at least partially needle bondable, i.e., it must be capable of holding the inserted fibers.
Such a passively needle bondable layer may itself be ; actively needle bondable, but-passively needle bondable layersmay also be formed in a known manner of woven tissue, knits, spunbonds, paper or synthetic plastic sheets, or the like.
Both the cover layer and the substrate layer may be built up of several layers. Thus the substrate layer may consist of a synthetic plastic sheet and a fiber fleece, wherein for example the sheet is facing the core layer.
It has now been surprisingly discovered that an elastic, unfoamed material, such as for example granules of vulcanized rubber, of waste rubber or specially prepared, synthetically pxoduced, unfoamed elastomers, granules with or without binders obtained from needle bonded felt floor coverings, or

-3-~241533 even unvulcanized rubber sheets provided with auxiliary vulcanizing agents, in particular plasticizers, may be needle bonded as the core layer between two outer layers to these outer layers.
By means of the needle bonding of webs of individual layers a plurality of holding fibers may very rapidly be in-serted with a relatively high density into a core layer of unbonded or unvulcanized elastic material whereby the three layers are held together and the elastic materials present in the core layer, together with the potentially added fillers, such as sand particles or the like, are prevented from pene-trating into or through the outer layers.
The fiber reinforced elastic web has its own internal coherence and may be manipulated without a carrier or support surface in a freely suspended manner.
Webs of this type may further be used as an elastic floor in sport or recreational installations, with these unbonded or unvulcanized webs being placed on the floor to be covered ;~ and for example previously provided with an adhesive layer, in order to bond the web to the substrate. This web, adhes-ively bonded to the~floor, is then impregnated with a liquid binder, for example a two-component adhesive such as poly-urethane, and the bonding properly effected with the web installation.
Conventional synthetic fibers of polyester, polyamide, polypropylene or the like, or natural fibers, such as cotton or the like, may be used as the actively needle bondable fibers, with the choice to be effected with regard to the core

-4-..

~L.241533 layer to be needled and the desired properties of the finished web. The second outer layer, which as mentioned hereinabove, must be at least passively needle bondable, may consist of the same fibers, but the aforementioned webs may also be used.
The needle bonding of the three layers leads to the fact that the particles not bonded to each other and the mass of the core layer are not only held between the two outer layers, but are prevented from substantially shifting in the plane of the extent of the web. The solid particles uniformly distri-buted in the manufacturing plant and inserted with a constant layer thickness thus remain even without bonding or vulcan-izing in their predetermined position. This is true even if orifices, such as punched holes, slits, or the like are applied transversely to the plane of the web.
According to a preferred embodiment, the core layer consisting of an elastic, unfoamed material comprises granules which cannot be pierced during needle bonding. The grain size of the granules is chosen in accordance with the final thick-ness desired of the web, preferably, not more than 5 mm. It is, however, also possible to needle bond larger granules; in such cases the stitch density, i.e., the number of needle stitches per unit surface should be lower and bonding needles with a larger diameter should be used. The needle bonded holding fibers are then always located between two or more particles. As a consequence of the elasticity of the granules and the internal pressure generated by the needle bonding, the Ayers are compressed during needling with this densification 3L24~S3;:' being maintained by the holding fibers, the contact surfaces between the granulated particles are increased so that when the granules have an at least rough surface, the particles are prevented from slipping even among themselves.
According to another embodiment, the granules are made from vulcanized rubber, i.e., granulted. This may involve processed rubber waste, obtained for example from used tires or the like. However, a rubber mixture prepared specially for the purpose may also be vulcanized and granulated. It is possible in the process to mix certain desirable additives into the masticated rubber mass. It is further feasible to use as the core layer a mixture of waste rubber with its existing properties and a separately prepared rubber with the desired properties. The waste rubber used may further contain reinforcing fibers, such as cord~inserts or the like. Prior to needle bonding, fillers, such as sand partlcles or the like, may be-mixed with the core layer. When this web is needle bonded it offers a coherence to such a mixture; which in known webs, may be obtained only by hardening, for example, by vulcanizing.
the same is true in the case wherein the core layer consists of rubber granules and/or fillers and foaming elas-tomers, which may be foamed at a much later time. Such foaming elastomers may be present in the form of granules or spheres and may consist of rubber or a synthetic material provided with foaming agents.
According to a preferred embodiment, the rubber particles and possibly the filler particles are provided with a coating prior to their insertion between the two outer layers. The 53;:~

coating may consist of a binder activated by heat and/or pressure, the binder being activated only after the needle bonding of the web.
According to a further feature, the coating consists of one component of a two-component binder, with the second component of this binder being introduced, at the earliest, after the needle bonding of the web, preferably at the location where the needle bonding is performed. The second component may be in a liquid or powder form. ThuS, such a web provided with one component of the binder, may be rolled out on sport fields, whereupon the second component of the binder is sprayed or sprinkled on.
According to a further embodiment, the coating of the particles consists of a slip additive, whereby the sliding of the bonding needles during their insertion along the particles is facilitated and the particles are able to avoid the~needles by a slight lateral shift. After needling, the slip additive, especially when heat is introduced, may evaporate or volatilize.
However, such an additive may also effect cross linking between the individual rubber particles or may be absorbed slowly by the granules without significantly affecting the properties of the latter. Water may be used as a slip additive.
The elastic, unfoamed granule particles may further be coated with a swelling agent, with the surface of the par-ticles swelling to a variable depth. This swelling facilitates the penetration of the core layer by the needles, as not only is the surface of the particles becoming softer, but particles hooked onto the barbs of the needles may be torn out of the .

~4~33 granules without significantly altering the position of the latter. The swelling agent is preferably removed after needle bonding, for example in successive hot calenders.
Granules obtained by the granulating of needle bonded floor coverings may also be considered as an elastic, unfoamed material forming the core layer. In the manufacturing process of needie bonded floor coverings, as a rule as the last work step the so-called selvedge, which as the result of its edge location contains irregularities, is cut off. At the beginning and the end of a floor covering there are further areas which do not meet a predetermined quality standard of the floor covering and which therefore are considered waste. The elasticity of such a needle felted floor covering, which heretofore has been considered unusable was$e, may now be utilized by granulating these waste strips or areas into particles with a grain size of for example 2-5 mm and using them as the core layer in the process according to the inven-tion. The granules are preferably present in the form of small clusters of fibers, bonded preferably at least in part by a binder of rubber latex. If a top layer is used containing coarse, actively needle bondable fibers, for example having a fiber titer of 100 dtex, and these coarse fibers are placed with a low weight per unit area on the core layer so that the core layer is not completely covered, and the fibers are active-ly needle bonded, the granules of the core layer will remain visible between the fibers. A web is obtained in this manner which again may be used as a carpet, which, especially if the granules are of different colors, displays an optically pleasing walking surface. The elastic properties of this web corres-pond essentially to those of the aforedescribed webs consist-ing essentially of rubber particles.
In the above-described needle bonding of rubber particles, the needle process provides the particles which are not bonded together with an internal coherence. If an elastic, unfoamed material is used as the core layer in the form of a rubber sheet treated with vulcanizing agents, the latter receives a fiber reinforcement which reinforces the rubber sheet even before vulcanization. Unvulcanized rubber sheets may be altered in their shape very easily as the result of their plasticity, especially if they are to be handled without a support or carrier surface. This starts as a reduction in cross section and leads by way of a edge tear to tne complete rupture of the sheet.
Even though the insertion of the bonding needles creates openings which act to weaken the rubber sheet, the fact that simultaneously the reinforcing fibers are mechanically bonded to the rubber sheet enhances the inherent stability of such a web. The openings created by the needles are reclosed by the plasticity of the rubber sheet and the pressure applied by the two outer layers to the rubber sheet. In particular,the needle bonded webs containing rubber or carpet granules and possibly fillers, may be impregnated or coated with a binder in the manufacturing plant or at a later application site, wherein the binder may consist of latex, liquid rubber, bitumen, modi-fied polyurethane, a duroplast or construction cement. Such a web may further be impregnated or coated with a solvent, _g_ , ~;24~3~

whereby cross linking is induced between the individual rubber components.
According to one form of embodiment, the needle bonded we is pressed or calendered, in particular compression molded or calendered, with this operation effected prior to the vul-canization or simultaneously with vulcanization of the web.
Vulcanizing may be performed in a known manner, for example with the application of heat and/or pressure. At least the holding fibers connecting the two outer layers are fully bonded into the vulcanizing rubber mass during the vulcanizing pro-cess. If for example, liquid rubber has been applied to a needle bonded web and the web is vulcanized, then at least the outer layer on the side of the application of the liquid rubber is bonded into the rubber mass, so that for example no layer containing fibers or a tissue is visible on the vulcanized web.
It is further possible to have an outer layer containing fibers or a fabric of such a thickness that even after vulcan-izing only these fibers or the fabric are visible, thereby lending the character of a textile to the web. An interesting structure may be obtained by choosing a fiber layer such that even though the fibers remain visible from the outside after vulcanizing, the center layer containing rubber is recognizable between the fibers. A similar effect may be achieved for a web into which textile wastes have been worked, whereby, especially if textile wastes of different colors are used and they remain visible after needle bonding, an interesting color effect may be achieved.

~.24~S33 In addition to the aforementioned pressing or calen-dering the needle bonded web may also be shaped, in particular wound, whereupon the web is vulcanized or bonded in this form.
According to a special embodiment, fibers shrinkable by heat are used as the actively needle bondable fibers and a shrinking process effected after the needle bonding whereby the core layer is further densified.
The webs described hereinabove may be used as carpets.
In contrast to conventional carpets, which in most cases are coated from the direction of the substrate layer with latex or the like, whereby the fibers are further bound for needling, the new webs present a carpet in which the additional bonding is not applied from the outside, but is inserted as the core layer prior to needle bonding.
Depending on how tightly the cover layèr-, wpich usually contains the actively needle bondable fibers, is formed, the core layer containing the elastic material is visible to a greater or lesser extent through the cover layer. It is, however, possible to make the cover layer tight enough so that ~20 the core layer containing rubber particles or the like, is not apparent at all, whereby the web according to the invention displays the appearance of a conventionaI needle felt floor covering, which, however, may be more elastic than the known floor coverings.
The fibers of the cover layer, resting for example on rubber particles and representing the walking surface, provide a sliding surface for the web essentially consisting of rubber, while the rubber core layer prevents the penetration of water and dust particles into or through the web.
Further forms of embodiment and advantages of the invention will become apparent from the following examples of embodiment.
In the drawing Fig. 1 shows a schematic illustration of an instal-lation for the embodiment of the process;
Fig. 2 shows a schematic view of a section through a needle bonded web containing rubber particles and fillers prior to vulcanizing;
Fig. 3 shows a schematic view of a section through a needle bonded elastic web, in which foaming elastomers have been foamed;
Fig. 4 shows a schemativ view of a section through a needle bonded web vulcanized in molds; and Fig. 5 shows a needle bonded elastic web bonded by needling with a needle felt web.
According to Fig. 1, a substrate layer 2 is deposited onto a conveyor i'nstallation, here a conveyor belt 1, onto which, here by means of a metering discharge device 3, the core layer 4 is placed. Actively needle bondable fibers, here in the form of a fiber fleece 5, are deposited onto the core layer 4, whereupon this three layer system is transported to a needle machine 6.
Such needle machines 6 are known from the textile needle felting technology (see: for example Krcma, "Manual of Nonwovensl; page 233 to 23~). In a needle machine of this type the system to be needle bonded, here the three layer system, .

S3~

is guided over a base plate 7 provided with bores. A needle board 9 carrying the needle bonding needles 8 is arranged above the object to be needled, which board is moving constantly up and down (double arrow 10) far enough so that the needle points ll in their lowest position are penetrating entirely through the object to be bonded, while in their uppermost position they have no contact with the object. In this upper-most position the object to be bonded, here the three layer system, may be displaced narrow 12) cyclicly in the advance direction, while it must be at rest during the needle bonding itself. The needle bonding needles 8 carry on their shaft at least one -- here two -- barbs 13, whereby they grip individual fibers or bundles or fibers and draw them into or through the object to be bonded. Upon the retraction of the needles, the fibers or fiber bundles entrained are released from the barbs 13 and remain in the passively bonded layer, here the sub-strate layer 2 and the core layer 4.
While in the needle bonding process in the textile industry, in the production of needle felted carpets with a final thickness of for example 4-6 mm, the needle boards have a plurality of needles arranged in close proximity to each other and may be moved for example with a velocity of 700 strokes per minute, for the needle bonding of elastic, unfoamed materials, such as rubber granules, foamable elastomers, mas-ticated rubber sheets or granules of carpets, to which filler, such as sand particles, may be added, the density of the needles 8 in the needle board 9 must be increased and the number of strokes greatly reduced.

24~53~3 If these criteria are satisfied, a layer containing the aforelisted materials may be subjected to a needle bonding process, wherein the needles are sliding along the rubber or filler particles and possibly slightly shift them aside lat-erally. This sliding and lateral shiftlng may be facilitated by providing the particles with a coating which promotes slip-ping.
As seen in Fig. l, the thickness of the three layer system is reduced during needle bonding, as firstly the fiber contain-ing layer 5 is densified by the needling and secondly thls fiber layer 5 and, depending on its configuration, also the substrate 2 is drawn or pressed into the boundary areas of the core layer as the result of the elasticity of their materials.
Furthermore, the elastic material of the core material itself will be somewhat compressed and remains under a certain stress.
Because of the elasticity of these particles the contact sur-faces themselves may yield. By means of this compression, the subsequent vulcanizing of the web consisting of individual grains is facilitated even if no additional binders, such as latex or liquid rubber, are added.
According to the form of embodiment of the installation for the operation of the process according to the invention, the needle bonded elastic web is guided between two calender rolls 14 and 15, whereby, especially if they are heated, vul-canization may be effected. The two calender rolls 14 and 15, are pressured against each other while transporting the web between them and applying a pressure of 2-5 bar/cm2.

~24~53~

The elastic web 16 leaving the calender rolls has a thickness that is not significantly less than that of the web 16 prior to calendering, as the elastic material expands again after calendering.
Fig. 2 shows a needle bonded web 16 containing rubber particles 17 and filler particles 18 in an enlarged and schematic view, wherein it is seen that the substrate layer 2 is connected with the cover layer 5 by means of the holding fibers 19, which extend through the core layer 4. In the form of embodiment according to Fig. 2 the substrate layer 2 and the cover layer 5 consist of actively needle bondable fiber fleece. The web 16 is here needle bonded from both of the outer sides, which may be seen by the "fiber funnels" 20, formed at the insertion points of the needles 8. Ends and parts of fibers not seized by the barbs 13 are drawn partially into these fiber funnels 20. The holding fibers 19 passing through the web 16 are distributed irregularly over the surface of the web and therefore in a section through such a web in actual practice only very few holding fibers 19 may be seen.
Fig. 3 shows a needle bonded elastic web in which foamable elastomers 21 and filler particles 18 were bonded, whereupon the elastomers were foamed by the activation of the foaming agents. The foamed elastomers 21 fill not only the inter-stices between the filler particles 18, but also contribute to the outward pressure applied to the fibers in the outer layers 2 and 5, leading to a surface structure with small convex bulges of the web. In order to prevent the bursting of the web 16, it is advisable especially in this case to ~L2~533 needle bond the web from both sldes, ln order to maintain an adequate mechanical connection between the two outer layers.
The foaming process may also be effected in a double belt press so that the foaming of the elastomers 21 will be opposed by a further, external resistance. In Fig. 3, the foamed elastomers 21 are shown by shading. Even though it appears therein that the holding fibers 19 are passing through the elastomer 21, they have merely been completely surrounded by it during the foaming process.
To produce the web 16 shown in Fig. 4, rubber granules and filler particles 18, for example grains of sand, are placed between two prebonded fiber fleece sheets, needle bonded from both sides and then vulcanized in a molding press.
This molding press, for example a double belt press, had on one sidè a flat, closed surface, whereby the side of the web at the bottom in Fig. 4 was given a smooth surface, while the other side of the press had a flat surface, in which a plurality - of orifices were provided in a spaced apart manner, so that the web in the area of said orifices was compressed less than in the adjacent areas. The vulcanized web thereby obtained the nap 22 seen in Fig. 4, which is protruding over the sur-face of the web 16. In the region of the nap 22 the web 16 is slightly more elastic than in the adjoining areas.
By using thicker, prebonded fiber fleece webs as the cover layer 5 and/or the bottom layer 2, a web 16 may possibly have the character of a textile on both sides. If such a web is placed on an especially smooth and slippery surface, there is a danger of the web slipping. This may be remedied by cutting of the upper part of one nap 22, as shown in Fig. 4 on the right hand nap, whereby within this area the vulcanized rubber layer will come to the surface. If such a web 16 is placed with its cut nap 22 on a smooth floor so that the pro-truding nap is resting on the floor, i.e., inversely to wha-t is shown in the drawing, the cut off nap is acting as an assurance against slipping. Fig. 5 shows a needle bonded elastic web 16, to which a needle felted 23 has been needle bonded. The holding fibers 24 taken from the needle welt web 23 were needled into the elastic web 16, whereby the two webs are mechanically bonded to each other. This needle bonding of the two webs 16 and ~3 may be effected both prior to the vulcanizing of the elastic web 16 and after it.
According to an example of embodiment, not shown, a masticated rubber sheet provided with vulcanizing agents, is placed between the substrate layer and the cover layer and the three layers needle bonded to each other. Such a web may be manipulated freely, i.e., without a support or carrier layer, without the risk of a change in the thickness of the rubber sheet, of edge tearing or breaking. In place of the discharge device 3 shown in Fig. 1, feeding is effected for example by a belt conveyor or from a roll.
A further form of embodiment, not shown separately, that may be prepared with an installation according to Fig. 1, consists of granules with a grain size of 2-3 mm, made from a needle felted floor covering, as the core layer, which is placed between the two layers 2 and 5 and then needle bonded.
Granules of this type are present in the form of clusters of ~L.2~1533 fibers and in part contain rubber latex. The cover layer 5 consists of coarse fibers, for example Dorix fibers, which are placed in a noncovering manner onto the core layer.
After needle bonding, the core layer consisting of granules of the needle felted floor covering is apparent through the cover layer. By using variously colored granules, for example from different batches of carpet manufacturing, a pattern may be produced. It is possible here again to coat such a needle bonded web 16 with liquid rubber, in order to obtain further strengthening of the particles.
In the above-described examples of embodiment inserts may further be placed into the web prior to needle bonding. It is thus feasible to apply the core layer not by means of the discharge device 4, but to provide several discharge means and to insert between these discharge means cord filaments of a synthetic material or steel wires. Such filaments may be needle bonded as described hereinabove for filler materials.
Metal platelets may be inserted, but precautions must be taken that no needles are inserted in the bonding process in the area of the metal platelets.
The filaments or metal platelets are first suitably pro-cessed so that in the vulcanizing process an adhesive effect will be present between the rubber mass and the inserts.
EXAMPLE:
Two identical fiber fleeces of polyester fibers with 70%
fibers with a titer of 6.7 dtex and 30~ fibers with a titer of 17 dtex, with a weight per unit area of 115 g/m2 and a Bafatex support with a weight by unit area of 25 g/m2, were prepared ~Z~iS33 - by needle bonding from both sides with a stitch density of 24 stitches/cm2.
Rubber particles with a grain size of l mm were placed onto one of the fiber fleeces with a weight per unit area of 3.7 kg/m2, covered with the other fiber fleece and needle bonded with a switch density of 24 stitches/cm2.
The bonded web was covered with 720 g/m2 of a 1:1 mixture of latex and water and dried at 130C for four hours.
An elastic web with a thickness of 4 mm was obtained.
As a swelling agent benzol or light oil can be used.
These swelling agents can be removed by heat after needle bonding the web.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the continuous production of fiber rein-forced webs comprising, placing elastic, unfoamed granules, not penetrable by bonding needles, as a core layer, between an outer substrate layer and an outer cover layer, at least one of which outer layers consists of actively needle bondable fibers, and needle bonding the three layers together, thereby inserting holding fibers between the granules.

2. A process according to claim 1, wherein the layers are needle bonded by means of holding fibers taken from the cover layer and the substrate layer.

3. A process according to claim 1, wherein said granules are obtained from vulcanized rubber.

4. A process according to claim 3, comprising the step of intermixing the core layer, prior to needle bonding, with fillers, such as sand particles or the like.

5. A process according to claim 1, wherein the core layer consists of rubber granules and/or fillers and foamable, unpenetr-able elastomers, and wherein said elastomers are foamed after the needle bonding.

6. A process according to claim 5, wherein the foaming elastomers are present in granule or spherical form.

7. A process according to claim 5, wherein a rubber or a synthetic material provided with foaming agents is used as the foaming elastomer.

8. A process according to claim 4 comprising the step of coating the rubber particles and possibly the filler particles prior to their introduction between the two outer layers.

9. A process according to claim 8, comprising the step of coating the particles with a binder activated by heat and/or pressure.

10. A process according to claim 9, comprising the step of activating the hinder following the needle bonding of the web.

11. A process according to claim 8, wherein the coating is one component of a two-component binder and the second component is introduced after the needle bonding.

12. A process according to claim 8, wherein the particles are coated with a sliding agent.

13. A process according to claim 8, wherein the particles are coated with a swelling agent.

14. A process according to claim 13, comprising the step of removing the swelling agent after needle bonding, preferably during hot calendering.

15. A process according to claim 1, wherein the granules are obtained by granulating needle felt floor coverings.

16. A process according to claim 15, wherein the granules consist of clusters of fibers, bonded together preferably at least in part by means of a rubber latex binder.

17. A process according to claim 1, wherein a cover layer which does not entirely cover the core layer and which comprises coarse, actively needle bondable fibers is used, and wherein said coarse fibers are actively needle bonded.

18. A process according to claim 17, wherein the coarse fibers in the cover layer were deposited with a low weight per unit area so that the core layer is visible between said fibers.

19. A process according to claim 2, comprising the step of impregnating or coating the needle bonded web with a binder.

20. A process according to claim 19, wherein the binder is latex, liquid rubber, or a thermoplastic material such as polyethylene, elastomeric bitumen, or the like.

21. A process according to claim 2, comprising the step of impregnating or coating the needle bonded web with a solvent.

22. A process according to claim 2, wherein the needle comprising the step of pressing or calendering, particularly pressure molding or calendering, the needle bonded web.

23. A process according to claim 2, comprising the step of vulcanizing, bonding or hardening the needle bonded web under heat and/or pressure.

24. A process according to claim 2, comprising the step of winding the needle bonded web.

25. A process according to claim 1, 5 or 16, wherein fibers shrinkable by heat are used as the actively needle bondable fibers and comprising the step of shrinking said fibers following the needle bonding of the web.