EP1936016A2 - Method for adjusting the local characteristics of a non-woven fabric and corresponding installation - Google Patents

Abstract

The process for making non-woven textile sheet, comprises determining orientations (OVB, OVC) of fibers in function of its position according to a bandwidth direction by dynamic adjustment, establishing different distributions of fiber orientation in different points of the bandwidth, and making and then strengthening a fibrous layer. The distribution of the orientation of fibers is selected in a direction to standardize a size representative of the mechanical resistance or lengthening of the textile non-woven material. A card supplying veil (421) is superposed on transverse segments. The process for making non-woven textile sheet, comprises determining orientations (OVB, OVC) of fibers in function of its position according to a bandwidth direction by dynamic adjustment, establishing different distributions of fiber orientation in different points of the bandwidth, and making and then strengthening a fibrous layer. The distribution of the orientation of fibers is selected in a direction to standardize a size representative of the mechanical resistance or lengthening of the textile non-woven material. A card supplying veil (421) is superposed on successive transverse segments for forming a cloth in a distributor layer. In a spectrum of orientation of fibers, a component parallel to a width of the cloth is larger than a longitudinal component. The dynamic adjustment moves a carriage of the distributor layer along a transverse direction of the cloth. The dynamic adjustment is influenced on a connection between a speed to which the cloth leaves the distributor layer and a speed to which a point of veil moves along the width of the cloth, and on a scrolling speed of an exit apron of the distributor layer supplied with fibrous veil presenting an anisotropic orientation. The fibrous layer is strengthened by mechanical needle punching and/or by thermal or chemical water jet cutting. The dynamic adjustment belongs to a regulation loop having a unit for measuring a physical size relating to the sheet, and a unit to control the dynamic adjustment according to the measured physical size. The measured physical size is the width removed from the sheet during the strengthening process. The physical size relative to the orientation is determined by an image analysis. An other regulation takes place on a surface weight of the sheet in different width points while influencing a second dynamic adjustment without an effect on the orientation of fibers. The second dynamic adjustment affects the quantity of fibers collected by a fiber comber of the card. An independent claim is included for an installation for producing a non-woven.

Description

The present invention relates to a method for producing a nonwoven fabric having locally determined characteristics, particularly in terms of mechanical strength. The invention also relates to an installation for implementing this method.

Technical area

It is known to produce a continuous web in a crosslapper fed with one or more webs produced in a card.

In the crosslapper, the web is folded alternately in one direction and the other on an exit carpet, thereby providing a web of overlapping web segments, alternately inclined in one direction and the other relative to one another. to the direction of the width of the sheet. The folds between successive segments are aligned along the lateral edges of the sheet produced. The fiber web obtained is generally intended for subsequent consolidation treatment, for example by needling, by coating, and / or etc. to give the desired nonwoven fabric, with a certain coherence and having a certain number of characteristics. mechanical resistance, especially in tensile strength.

The patent FR-A-2,234,395 teaches the velocity relationships that must be respected in the crosslapper to control the weight of the web at all points of its width.

The needling consolidates the web by entangling the fibers together and interpenetrating the different layers. Planks filled with very many needles perpendicular to the plane of the sheet regularly hit the sheet of fibers passing through the needling. Fibers of the different layers are thus driven from one layer to another, and there follows a felting effect which gives the sheet a certain resistance.

During its consolidation, the sheet undergoes changes in the distribution of the fibers. Due to the interpenetration and entanglement of the fibers, the sheet is compacted mainly by reducing its thickness. However, it is also observed that the width of the sheet decreases slightly. In addition, the surface weight of the sheet is often affected by the consolidation process, typically being increased on the edges of the web.

A disadvantage of these alterations of the tablecloth is that it is necessary to increase the overall quantity of fibers so that the lightest point of the consolidated sheet satisfies the criteria for weight per unit area requested by the buyer. The heavier areas of the sheet, ie the edges, then correspond to an unnecessary consumption of fibers which is not profitable on sale, as well as an unnecessary increase in the total weight of the sheet with the subsequent disadvantages, for example during handling or implementation.

So far, it has been sought to overcome this disadvantage by producing a web having before needling a greater surface weight in its center than on its edges.

Thus, the patent EP-B-0 371 948 describes a method for pre-compensating defects occurring during the subsequent consolidation, in particular needling, by locally varying the weight of the web of lapping introduced into the crosslapper. This is achieved by automatically adjusting the speed of a doffer of the card with respect to the speed of the drum of the card. The faster the dancer turns with respect to the drum, the lighter the veil formed by the doffer. The lightest areas of the web are those intended to form the edges of the web.

The patent EP-A-1,036,227 discloses a method for producing a web whose weight per unit area has a determined profile over the width of the web, again by locally varying the surface weight of the web of lapping introduced into the crosslapper. This is achieved by varying at the card a dynamic adjustment affecting the weight of the veil, for example by changing the distance between the doffer and the drum to change the amount of fibers removed by the doffer, or in "Condensing" the fibers in a variable manner downstream of the doffer. It is said that a card web is "condensed" when, in particular in a device called "condenser", the web is longitudinally compressed to increase its surface weight and at the same time make the veil pass from an initial state where the fibers are longitudinally oriented to a condensed state where the fibers have a less unidirectional orientation distribution, i.e. at least a portion of the fibers having over at least part of their length an orientation at an angle to the longitudinal direction of the web.

According to WO 00/73547 A1 , the dynamic weight adjustment means are part of a regulation loop comprising means for detecting the surface weight profile of the consolidated web. Typically, the speed of rotation of the cardboard is readjusted according to the difference between the result of this detection and a setpoint. The detection detects at the same time the width of the consolidated web and the regulation corrects the length of the course of the lapper-lapper carriage as a function of the difference between the detected width and a set nominal width, so to give the web a real width as close as possible to the desired nominal width. In an improved version, the longitudinal profile of the web weights of the web is also regulated. The consolidated web thus obtained has a width and a surface weight very uniform and very close to the respective nominal values. The EP 1 057 906 B1 discloses another method of dynamically adjusting the weight profile of a web.

Increasingly, buyers take into account certain criteria, in particular tensile strength values, measured in particular in different directions of the nonwoven, for example in the direction of the width of the nonwoven ("Cross Direction"). and in the longitudinal direction of the nonwoven ("Machine Direction").

• la résistance à la rupture en traction dans le sens longitudinal du textile (ou de la nappe), qualifiée de "Machine Direction";
• la résistance à la rupture en traction dans le sens de la largeur du textile (ou de la nappe), qualifiée de "Cross Direction";
• le rapport entre ces deux valeurs de résistance, noté MD/CD, c'est à dire la résistance "Machine Direction" divisée par la résistance "Cross Direction".

For example, a criterion commonly required for nonwovens, in particular in the field of geotextiles, is expressed in the form of the following quantities:

• the tensile strength in the longitudinal direction of the textile (or web), referred to as "Machine Direction";
• tensile strength in the width direction of the textile (or web), referred to as "Cross Direction";
• the ratio between these two resistance values, denoted MD / CD, ie the resistance "Machine Direction" divided by the resistance "Cross Direction".

When the mechanical characteristics obtained in the consolidated sheet do not correspond to the requirements, the current practice is to strengthen the entire sheet by increasing the amount of fiber, locally or generally. To satisfy one of these characteristics, it often comes to use more fiber than requires the other characteristic, which goes against an optimization of the amount of fiber consumed.

For example, if the two resistors MD and CD must have the same minimum value, to optimize fiber consumption by ensuring sufficient resistance in both directions, the MD / CD ratio should be as close as possible to the value 1: 1

In addition, it is often found that the ratio MD / CD has a rather different value on the edges of the web relative to the central part. Even if the surface weight of the nonwoven is uniform over its entire width, thanks in particular to the weight compensations performed according to the prior art, the ratio MD / CD of a nonwoven according to the prior art is generally not uniform, because the orientation distribution of the fibers is not the same in all points of the width of the nonwoven. For example, consolidation by needling tends to favor the transverse orientation of the fibers near the center of the sheet rather than near the edges of the sheet.

If the distribution of the observed resistance values does not correspond to the required characteristics, and in particular if the required values are the same over the entire width of the sheet, it will then be necessary to reinforce the sheet over its entire width so that the lowest value be sufficient.

Furthermore, it may be useful to be able to choose a distribution of these resistance values within the width of the web according to a non-uniform profile meeting the needs of a particular specification. It may be for example to obtain a profile having one or more specifically stronger, or lower, resistance values in one or more areas of such a profile.

• une ou plusieurs caractéristiques mécaniques locales maîtrisées en une ou plusieurs régions;
• une répartition uniforme de ses valeurs de résistance longitudinale (résistance MD), ou transversale (résistance CD), ou du rapport de ces valeurs;
• une répartition non-uniforme de ces valeurs, de façon distribuée selon un profil déterminé;
• une combinaison de telles répartitions des valeurs de résistance avec une répartition de poids surfacique distribuée selon un profil déterminé.

An object of the invention is thus to make it possible to obtain a nonwoven fabric having in its width at least one of the following characteristics:

• one or more local mechanical characteristics controlled in one or more regions;
• a uniform distribution of its longitudinal resistance values (MD resistance), or transverse resistance (CD resistance), or the ratio of these values;
• a non-uniform distribution of these values, distributed according to a given profile;
• a combination of such distributions of the resistance values with a distribution of distributed surface weight according to a given profile.

The invention also seeks to optimize the amount of fibers necessary to obtain a nonwoven fabric, all parts of which have certain minimum characteristics, as well as to optimize the weight or volume of such a nonwoven fabric.

For this purpose, the invention proposes a method for manufacturing non-woven fabrics in a strip, characterized in that by at least one dynamic adjustment, the orientation distribution of the fibers is influenced in a targeted manner as a function of the position of said fibers according to the direction of the width of the band.

"Dynamic adjustment" means a setting that is revised and, if necessary, changed continuously or repeatedly (for example at regular time intervals) while the installation is operating in production.

The invention is based on the idea of differentiating the fiber orientations as a function of the location of the fibers along the width of the web, either to obtain different mechanical characteristics in different zones of the width of the web, or to pre-compensate for uniformity defects introduced into the mechanical characteristics of the sheet during subsequent stages of the manufacturing process, especially during consolidation and more particularly needling. In the case of the precompensation, knowing that needling tends to "longitudinalize" the fibers close to the edges, it is possible to use the invention to give the fibers close to the edges of the ply before needling a distribution of orientations favoring the transversal orientation only for the fibers forming the central zone of the web.

In some cases, for example for textiles intended to be easily cut, separated or torn, the control sought may aim at providing one or more zones of lesser resistance, or a sufficiently low resistance in all points of the textile.

The relevant mechanical characteristics, in particular in the field of geotextiles, include characteristics of resistance to traction in the plane of the textile, for example the elongation before breaking and especially the breaking strength. For a given category of textile, these characteristics must have sufficient value in all regions of the textile, and in particular over its entire width. In the case of characteristics such as breaking strength, this sufficient value will generally correspond to a minimum value, and the present description will focus essentially on this type of characteristic. However, for other characteristics such as elongations, this sufficient value may in fact correspond to a maximum value, without departing from the scope of the invention.

In the context of the present invention, the concept of "distribution of orientations" is used. This notion accounts for the different orientations present in a given zone, and the greater or lesser abundance of each orientation in this zone. We can illustrate a distribution by a closed curve having a center. The distance between each point of the curve and the center indicates the percentage of fibers having the orientation indicated by the vector from the center to that point. In the simplest case of a non-condensed carded web, the fibers are typically all parallel to the web length (flattened orientation distribution curve to give a single segment). If this web is then napped in successive segments that overlap in zig-zag as will be described later, the distribution in the resulting web has a preponderance parallel to the width of the web, with however a longitudinal dimension resulting from the obliquity sail segments with respect to the width of the web. We could speak of bidirectional distribution represented by a more or less flattened "X".

In the more complex case of a condensed card web, the initially longitudinal fibers of the non-condensed web have been folded back on themselves and / or "transverse" by the condensation so that the orientation distribution is no longer unidirectional but omnidirectional, represented by an oval.

In a first embodiment or preferred embodiment, the orientation of the fibers in the web is affected. Such dynamic adjustment on the web is performed before folding the web on itself to form the web. For example, it is possible to influence the orientation distribution of the fibers in the web within the assembly forming the card, but also during transport to the crosslapper or the input circuit of the crosslapper. The fiber orientation distribution is adjusted in the successive areas of the length of the web as a function of the position that these areas will take along the width of the web.

In particular, it is possible to influence the orientation of the fibers by means of an adjustable condensation of the web. Such condensation of the web can itself be obtained in several ways that can be used as desired or even be combined with one another.

Typically dynamically adjustable condensation according to the invention is obtained at least in part by varying with respect to each other the speeds of at least two rotary members of the card contributing to the manufacture or transport of the web.

Alternatively in the context of this first embodiment of the invention, the condensation is obtained at least in part by adjusting a displacement of at least one carriage of the spreader-lapper in a direction substantially transverse to the web, for example by giving this carriage a speed different from that which ensures that the sail leaves the lapper carriage with a running speed equal to the speed of movement of the lapper carriage.

If, at a given point in the course of the lapper carriage, the lapper carriage is moved less rapidly than the veil is scrolled through the lapper carriage, the veil condenses locally at the exit of the lapper carriage.

If, on the contrary, at a given point in the course of the lapper carriage, the movement of the lapper carriage is faster than the movement of the web through the lapper carriage, the web is stretched at the exit of the lapper carriage. This can for example locally reduce the effect of a pre-existing condensation of the web and thus modify the local distribution of fiber orientations to make it closer to a longitudinal unidirectional distribution relative to the web.

And if at a given point in the course of the lapper carriage the speed of movement of the lapper carriage is equal to the speed of movement of the web through the lapper carriage, the web is deposited substantially unchanged on the exit apron of the lapper. lapper.

In a second embodiment, possibly combinable with the first embodiment, the relationship between the repository is affected. the sail on the exit apron of the spreader-lapper and the running speed of the output apron conveying the forming web towards the exit of the lapping spreader.

This modifies the direction in which the web is deposited on the web, ie the angle that this direction forms with the axes of the web, and thus the angle formed by the fibers deposited with the axes of the web. web, especially when the fibers of the web are longitudinal relative to the web. In particular the angle of inclination of the sail segments in the web depends on the ratio between the speed of the apron output and the speed of movement of the lapper carriage. For example, if the speed of the exit apron is reduced not only in absolute terms but also with respect to the speed of the lapper carriage which is itself decreasing when the lapping carriage is in the vicinity of its end purposes. stroke, the fibers of the web are deposited with a smaller inclination with respect to the width of the web in the vicinity of the edges of the web; which pre-qualifies the defect introduced later by a consolidation process by needling.

The invention combines very advantageously with the methods known per se to achieve a predetermined distribution of surface weights over the width of the web.

In particular, it is possible to reduce the degree of condensation of the parts of the web intended to be at the edge of the web so that the fibers are "more transverse" in the web in the vicinity of the edges of the web before consolidation. This results in principle in the vicinity of the edges of the sheet a variation in surface weight. To obtain the desired surface weight profile, there is added to this first variation a second variation which is substantially without effect on the orientation distribution of the fibers, for example a variation of the spacing between the doffer and the carding drum, or still a variation of the speed of the doffer and a proportional variation of the fiber transport members located downstream of the doffer. In principle, downstream of the comb is provided an accumulator means capable of absorbing speed fluctuations so that the transport speed of the fibers downstream of the accumulator is not affected by these fluctuations. Such an accumulator may for example be constituted by an apparatus interposed between the card and the spreader, or by an accumulator placed at the exit of the lapping spreader, or by the accumulator carriage of the spreader-lapper as described in EP-A-1,036,227 .

Preferably, the method according to the invention comprises a regulation of the dynamic adjustment of the orientation of the fibers as a function of a detection of at least one representative quantity of the orientation distribution of the fibers in the nonwoven, preferably the non-woven after consolidation.

The measured quantity may be the withdrawal suffered by the sheet during its consolidation by needling. Such a withdrawal is interpretable in terms of modification of the fiber orientation distribution in the edge zones of the web. The dynamic adjustment consists of pre-compensating this modification by one of the orientation means described above, namely the condensation in the card, between the card and the spreader, or at the exit of the lapper carriage, or the adjustment of the speed of the exit apron of the spreader with respect to the speed of movement of the lapper carriage.

Alternatively, the measured magnitude can be derived from an image of the web that is analyzed to determine the local distribution of orientations, or a numerical value or a set of numerical values that represents that distribution, for example its bidirectional spectrum such as it will be defined later.

According to a second aspect, the invention relates to a plant for producing nonwovens comprising a card providing at least one web of fibers, a spreader-lapper having the web in successive transverse segments on an exit apron to form a web, and a consolidating machine such as a needling machine or a device for binding by water jet, thermal or chemical downstream of the exit apron, characterized in that it further comprises orientation means for influencing the distribution of orientations of the fibers according to their position along the width of the web.

• les figures 1a à 1c illustrent un exemple de variation des caractéristiques de résistance mécanique au sein d'une nappe selon l'art antérieur, en particulier :
  • la figure 1a représente une coupe transversale de la nappe avant et après consolidation selon l'art antérieur, sans compensation de poids surfacique;
  • la figure 1b est analogue à la figure 1a mais avec compensation de poids surfacique;
  • la figure 1c représente le profil de variation du rapport MD/CD suivant la largeur de la nappe consolidée de la figure 1b, toujours selon l'art antérieur;
• la figure 2 est une vue de dessus de la nappe avant et après le traitement de consolidation, illustrant le procédé selon l'invention;
• les figures 3a et 3b représentent les distributions d'orientation d'une nappe non consolidée lorsque le voile est non-condensé (figure 3a) et lorsque le voile est condensé (figure 3b) ;
• les figures 4 à 6 illustrent l'invention dans son premier mode de réalisation, en particulier :
  • la figure 4 est une vue de côté de la carde et de l'étaleur-nappeur, illustrant certaines variantes du premier mode de réalisation de l'invention ;
  • la figure 5 est une vue schématique de dessus de l'étaleur-nappeur (partiellement éclaté) et de ses entrée et sortie, dans un exemple de mise en oeuvre du premier mode de réalisation de l'invention;
  • la figure 6 est une vue de côté de la carde dans une autre configuration, illustrant certaines variantes du premier mode de réalisation de l'invention;
  • la figure 7 est une vue de dessus de l'étaleur-nappeur (partiellement éclaté) et de ses entrée et sortie, dans un exemple de mise en oeuvre du deuxième mode de réalisation de l'invention; et
  • la figure 8 est une vue de côté des chariots de l'étaleur-nappeur, illustrant certaines variantes du deuxième mode de réalisation de l'invention.

Other features and advantages of the invention will become apparent from the detailed description of non-limiting embodiments, and the accompanying drawings, in which:

• the Figures 1a to 1c illustrate an example of variation of the mechanical strength characteristics within a ply according to the prior art, in particular:
  • the figure 1a represents a cross section of the web before and after consolidation according to the prior art, without surface weight compensation;
  • the figure 1b is analogous to the figure 1a but with surface weight compensation;
  • the figure 1c represents the variation profile of the MD / CD ratio according to the width of the consolidated water table of the figure 1b still according to the prior art;
• the figure 2 is a top view of the web before and after the consolidation treatment, illustrating the process according to the invention;
• the Figures 3a and 3b represent the orientation distributions of an unconsolidated web when the web is non-condensed ( figure 3a ) and when the veil is condensed ( figure 3b );
• the Figures 4 to 6 illustrate the invention in its first embodiment, in particular:
  • the figure 4 is a side view of the card and the crosslapper, illustrating certain variants of the first embodiment of the invention;
  • the figure 5 is a schematic top view of the spreader-lapper (partially exploded) and its input and output, in an exemplary implementation of the first embodiment of the invention;
  • the figure 6 is a side view of the card in another configuration, illustrating certain variants of the first embodiment of the invention;
  • the figure 7 is a top view of the spreader-lapper (partially exploded) and its input and output, in an exemplary implementation of the second embodiment of the invention; and
  • the figure 8 is a side view of the trolleys of the crosslapper, illustrating certain variants of the second embodiment of the invention.

As illustrated in figure 1a in the known configurations where the fibers are regularly deposited to form a substantially rectangular sheet of section 430a, the consolidation gives a nonwoven fabric having a profile 440a whose edges are significantly heavier, by example with a surface weight of the order of 115 to 120 for the edges if the center weight is 100. This increase in the surface weight near the edges is fed by a lateral withdrawal dc of the consolidated web with respect to the tablecloth non-consolidated.

According to the prior art, compensation for surface weight variations is typically obtained by depositing more fibers in the central part of the sheet. This produces a curved profile 430b as shown in dotted lines in figure 1b . Consolidation then gives a nonwoven fabric having a substantially uniform weight profile 440b.

Despite the uniformity of surface weight thus obtained, the different tensile strengths obtained in the transverse direction CD and in the longitudinal direction MD have a certain heterogeneity between the edges and the central part of the consolidated web of the prior art. As illustrated in figure 1c the ratio MD / CD between these two tensile strengths can in some cases be 40% greater near the edges than in the central part. The tensile strength in the longitudinal direction of the web (MD strength) is higher near the edges of the web than in its central region, compared to the tensile strength in the width direction of the web (resistance). CD). This heterogeneity is believed to be due to the fact that the orientation of the fibers near the edge of the web is altered by the needling process, together with the appearance of the dc shrinkage. According to this theory, the fibers of the edge of the consolidated web tend to form on average a greater angle with the width of the web, than the fibers of the central region of the web.

The tablecloth 430 ( figure 2 ) is typically obtained by superposition of several S430 web segments overlapping each other. The segments are interconnected by folds extending along the edges of the web. The fibers of the ply 430 have different orientations resulting from the orientation of the fibers within each of these segments, as well as the angle A430 according to which these segments are deposited on the moving apron carrying the ply. Typically, a web made of non-condensed web, whose fibers are therefore longitudinal in the web, has a much greater tensile strength in the transverse direction of the web (CD) than in its longitudinal direction (MD) because the longitudinal direction of the veil, and hence the direction of the fibers, are almost transverse in the tablecloth. If the web used is condensed, the orientation distribution in the web is more homogeneous, but the transverse or quasi-transverse orientations remain preferred. Therefore, the resistance CD remains higher than the resistance MD, although the ratio between the two is less than 1: 1 that when the fog used is not condensed.

In a given zone of the ply 430, the distribution of the orientation of all the fibers present may be represented by a closed curve C _F linked to this zone and having a center of symmetry Cs. The figure 3a represents an example of curve C _F for a sheet made of non-condensed veil and the figure 3b an example of curve C _F for a web made of condensed web. Each point P of the curves C _F indicates by its distance at the center Cs the proportion of fibers having an orientation identical to that of the vector ray CSP connecting the center Cs to this point P.

From a curve C _F can be established a representation comprising an FM arrow parallel to the longitudinal direction and an arrow FC parallel to the width of the web. The two arrows then each have a length proportional to the sum of the longitudinal components and respectively to the sum of the transverse components of the vector rays. CSP a quadrant (arbitrarily chosen between the four possible) of the curve C _F. The ratio between the lengths of the arrows FM and FC gives an idea of the MD / CD ratio at the center Cs. The set formed by the two arrows FM and FC at a given point of a web or a web will be called "bidirectional spectrum of orientations".

In the example shown in figure 2 the orientation of the fibers in the ply 430 has been influenced so as to obtain, in the central part of the unfilled ply, an orientation spectrum ON2 different from the orienting spectrum ON1 in those parts of the ply close to its boundaries. edges.

Compared to the prior art illustrated in figure 1c it will often be sought for the needle-ahead ply an orientational spectrum ON2 in the center of the ply 430 in which the component FM ₂ parallel to the longitudinal axis A43 of displacement of this ply is greater than the corresponding component FM ₁ of the spectrum Orientation ON1 near the edges, so as to pre-compensate the variations of the ratio MD / CD found in the prior art after needling, and after needling a spectrum of orientations which is substantially the same in all points of the width of the consolidated web.

The orientation of the fibers in a given part of the ply 430 is influenced by a dynamic adjustment effected upstream of the consolidation treatment in the needling machine 3. More particularly, in this example, the adjustment affects each region of the length of the veil depending on the position that this region of the length of the veil will take in the sheet.

The fibers of the web regions intended to be placed at the edges of the web are given an orientation spectrum having a greater longitudinal preponderance (relative to the web) than the fibers of the web intended to be placed in the central region of the web. the tablecloth.

A first embodiment will be described, with particular reference to the Figures 4 to 6 .

The figure 4 illustrates a non-woven production facility comprising a card 1 producing a web 421 feeding a spreader-lapper 2. The card comprises a feed roller 11 collecting fibers 411 directly or indirectly in a reserve, for feeding a card drum 12. The periphery of the drum 12 is equipped with known means not shown for working the fibers driven by the drum. These fibers are taken from the drum 12 by a doffer roll 13, then transferred successively to a first condenser roll 14 and a second condenser roll 15. The web 421 thus formed is detached by a detacher roll 16 rotating in the same direction as the last condenser roller and depositing the veil on a conveyor belt 17 leading to the input 20 of the spreader-lapper 2. The fibers are oriented circumferentially on the doffer 13. In conventional machines, the condensers 14 and 15 are used to increase the surface weight of the veil, reduce the velocity of the veil and give the fibers a more varied orientation than on the doffer. The condensation effect is obtained by giving the second condensation roller 15 a peripheral speed less than that of the first condensation roller 14, the peripheral speed of which is itself lower than that of the doffer 13.

The crosslapper 2 comprises an entrance mat or front mat 24 and a rear mat 25 each forming a closed loop. These loops are external to each other and bypass various rollers rotating around fixed axes, as well as rollers carried by an accumulator carriage 21 and others carried by a lapper carriage 22. Each of the two belts 24 and 25 is driven by one of the fixed axis rollers associated with it and which is coupled to a respective electric servo motor.

At the entrance 20 of the crosslapper 2, the web 421 is conveyed to the accumulator truck 21 by the entrance belt or front belt 24, a region of which may constitute the conveyor belt 17, as shown. The web crosses down the first accumulator carriage 21, then the lapper carriage 22. The lapper carriage 22 is reciprocating M22 in a direction perpendicular to the width of the web, and thus lays the web 421 in successive segments on a deck of output 28 moving in a direction parallel to the width of the sail. The successive accumulated and offset segments formed by the web 421 deposited on the exit apron 28 form the sheet 431 ( Fig 5 ) which is routed to consolidation processing 3 ( figure 2 ). The accumulator carriage 21 is in reciprocating movement M21 in the same direction as the lapper carriage 22 with a displacement law calculated to adjust the distance to be traveled by the web between the entry 20 of the crosslapper and the lapper carriage 22. Said distance is more particularly adjusted to combine with one another the entry speed of the web 421 in the crosslapper with the speed at which the web passes through the lapper carriage 22. The entry speed is equal to 20 at the speed of production of the card, as modified if necessary at each moment by the doffer 13 which can be variable speed and by the variable condensation that will be described. The speed with which the web passes through the lapper carriage 22 is equal to the speed of movement of the lapper carriage 22 if the web is to be deposited without the addition of condensation or stretching, or different if the web is to be condensed or stretched when deposited on the exit apron of the spreader-lapper.

In the first embodiment, the dynamic adjustment according to the invention affects the preparation or transport of the web 421, that is to say upstream of the deposition of the web on the exit apron 28 by the lapper carriage 22.

In the embodiment illustrated in figure 5 , this adjustment modification produces in the web 421 penetrating in the crosslapper 2 an alternating structure having, along the longitudinal direction of the sail 421, an alternation of areas VC and VB which differ in their fiber orientation distributions.

The zones VB are intended to compose the edge areas B1 of the ply 431, while the zones VC are intended to compose its central part. In the areas VB corresponding to the edges of the web, the fibers of the web have a certain OVB orientation spectrum, while in the VC areas corresponding to the center of the web, the fibers of the web have another OVC orientation spectrum.

When an attempt is made to increase the MD / CD ratio of the central zone of the ply 431, the dynamic adjustment is operated so as to increase the transverse component of the OVC orientation spectrum of the VC zones of the web 421. These VC zones produce then in the layer a central zone where the fibers have an orientation spectrum ON2 ( figure 2 ) having a longitudinal component FM2 larger. After consolidation, this same central area has a higher MD / CD ratio. As, in turn, the MD / CD ratio of the edge zones of the consolidated web has been increased by the effect of the needling described with reference to the figure 1c both MD / CD ratios can be made equal.

In a manner analogous to that just described for the standardization of the MD / CD ratio in the consolidated web, the process according to the invention can be used to produce other types of distribution profile of the orientation spectra of the The invention thus makes it possible to produce a nonwoven having, after consolidation, mechanical strengths distributed according to a chosen profile, preferably taking into account the variations directly induced by the consolidation in the layers of the web. edge areas as shown in figure 1c .

Such selected profiles may allow for example to produce a textile that will tear more easily along a selected longitudinal area, for example to facilitate separation or cutting in such a zone.

In some cases, the orientation of the fibers in the ply 431, such as that represented in FIG. figure 5 which is symmetrical with respect to the longitudinal axis of the sheet 431, the periodicity of variation of the settings affecting the orientation of the fibers corresponds to a half-working period of the crosslapper 2, corresponding to a sequence of a VC area and a VB area on the sail 421. In the general case such as that of a non-symmetrical profile, the adjustment variation period corresponds to a full working period of the crosslapper.

In the exemplary embodiment illustrated in Figures 4 to 6 the orientation of the fibers of the web 421 is influenced by condensation in the VC portions of the web.

However, certain combinations of zones and settings give particularly interesting results in the field of fiber orientation, as well as the distribution of mechanical strength and elongations after consolidation.

Indeed, tests have shown that the reorientation of the fibers by condensation of the web, in particular upstream of the lapper-spreader carriages or within the card, had on the anisotropy of the mechanical strength in the nonwoven final a dramatic effect in comparison with the degree of condensation chosen.

Thus, a condensation of the order of 17% by weight per unit area can vary by approximately 40% the value of MD / CD in the consolidated sheet, in the case of a geotextile based on polypropylene fibers.

Preferably, the variable condensation is carried out within the card, during the production or transport of the web, by varying with respect to each other the speeds of at least two rotating members of the card or transport. One of these bodies rotates for example at a given speed and one or more subsequent organs rotate at a lower speed when the condensation must be effective.

For example, if the dancer roll 13 rotates at a circumferential speed of 130 m / min while the detacher 16 is rotating at 100 m / min, the haze produced will have a condensation of 30%. This condensation may for example be carried out in several intermediate phases, with the first condenser roll 14 rotating at 80 m / min and the second condenser roll 15 rotating at 50 m / min.

In another configuration not shown, the card may comprise a single condenser roll. Such a condensation of 30% can then be obtained with a doffer roll rotating at 130 m / min, the condenser roll rotating at 80 m / min, and the detacher rotating at 100 m / min.

In another configuration illustrated in figure 6 a combing roll 13 is directly followed by a detaching roll 16. Such a condensation of 30% can then be carried out directly between the doffer rotating at 130 m / min and the detacher rotating at 100 m / min.

Alternatively or in combination with the dynamic adjustment of the condensation in the card 1, condensation can also be dynamically adjusted on the transport path or within the crosslapper 2.

The transport path may thus comprise one or more condensation devices. It may be for example one or more condenser rollers whose circumferential speed is dynamically adjusted. Dynamically adjustable condensation can be achieved with a drawing or compression device as described in FIG. WO 02/101130 A1 where the FR-A3-2 828 696 placed between the actual card and the crosslapper proper. These devices may for example, according to the invention, operate in variable stretching to cancel at least partially, and variably, a constant condensation at the output of the card. Thus, both a surface weight adjustment and a setting of the orientation spectrum are carried out, since the areas of the length of the web undergoing the strongest stretch, intended to be placed near the edges of the web, are at the same time. lenght (reduced surface weight) and at the same time "longitudinal" in terms of fiber orientation, while the other, less stretched zones retain the higher weight and the more homogeneous orientation spectrum resulting from condensation at the outlet of the card.

A dynamic condensation of the web can also be achieved in the crosslapper 2, for example by modifying the displacement law of one or two of its carriages 21 and 22 so as to adjust the speed at which the sail passes through the lapper carriage 22 with respect to the speed of movement of the lapper carriage 22. Instead of adjusting the condensation for each point of the lapping carriage stroke, and therefore for each point of the width of the web, adjustments can also be made by areas, for example the two edge areas and the central area.

A second embodiment, which will be described with reference to Figures 7 and 8 can be implemented as an alternative to the first embodiment or in combination with it.

In this second embodiment, a dynamic adjustment is carried out affecting the preparation or transport of the sheet 432, that is to say at the stage or downstream of the deposition of the web 422 on the exit apron 28 in the crosslapper 2.

As illustrated in figure 7 this adjustment modification produces a modification of the veil deposition diagram to form each of the transverse segments composing the ply 432, by modifying the inclination of the segment relative to the width of the ply. Within the ply 432, the longitudinal direction DB or DC of each segment forms with the width of the ply an angle AB or AC respectively.

In some conventional lapping spreaders, the exit apron such as 28 is advancing at a constant speed. The ratio between this constant speed and the speed of movement of the lapper carriage as defined by the angle between the width of the web and the longitudinal direction of the sail segments.

It is known to slow down the exit apron when the lapper carriage slows in the vicinity of its reversal points, so as to maintain constant the ratio between the speed of the apron output and the speed of the lapper carriage. Thus the angle formed by a segment with the width of the web is constant from one edge to the other of the web according to the state of the art.

With the present invention, the exit apron is further slowed down so that the angle AB in the edge regions B2 is smaller than the angle AC in the central region of the web, as shown in FIG. figure 7 .

From a dominant orientation OV2 of the fibers in the web 422, the variation of the direction of deposition of the web on the exit apron thus produces a desired variation of the orientations of the fibers along the width of the web.

Thus, by dynamically adjusting the deposition direction of the web so as to increase the deposition angle AC in the central area relative to the deposition angle AB in the edge regions B2, the orientation spectrum ON2 in the center the web is less elongated in the width direction of the web than the orientation spectrum ON1 in the edge areas. After consolidation, the edge zones have an MD / CD ratio close to that of the central zone.

In the same way as specified for the first embodiment, this second embodiment can also be used to obtain a chosen non-uniform profile, with regard to the distribution of the resistances within the textile obtained, and not simply a uniform profile.

Preferably, the installation according to the invention combines the means described up to now aimed at controlling the distribution of orientations of the fibers over the width of the sheet, with means such as according to the EP-1 036 227 to control the profile of the surface weights over the width of the sheet.

For this, once adjustments have been made to provide the desired distribution of the orientation distributions over the width of the web and / or the desired distribution, over the width of the web, of the quantities, such as the ratio MD / CD, relating to the mechanical strength of the web, a second dynamic adjustment is carried out affecting the surface weight of the web but having substantially no effect on the orientation of the fibers. The second setting may be a setting varying the amount of fiber drawn by the doffer on the card drum. More specifically, the second adjustment may for example consist in varying the speed of rotation of the doffer (the faster the dancer rotates less it collects fiber at each turn, and more the veil it produces is light) or the spacing of the doffer relative to the drum of the card (the more the comb is removed from the drum, the less fiber it withdraws at each turn, and the more the veil it produces is light).

In a concrete example, the speed of the doffer is dynamically adjusted to produce a web whose weight is non-uniform along its longitudinal direction as for example described in FIG. EP-A-1036 227 and controlling the fiber orientation distribution in the web by dynamically varying the rate of condensation of the web, i.e. for example the ratio of the speed of a detacher to the speed of the web. comber. Therefore, if at a given moment the speed of the doffer varies and the rate of condensation must remain constant, it is typically necessary that the speed of the detacher varies in the same proportion as the speed of the doffer.

It is intended according to the invention to regulate the dynamic adjustment affecting the orientation of the fibers in the sheet. In a favorite version, this regulation is combined with a regulation of the surface weight profile such as according to the WO 00/073547 where the EP 1 057 906 B1 .

For this, as shown in figure 2 above the sheet emerging from the needling machine 3, a transverse detector 41 of the type described in FIG. WO 00/073547 comprising a series of sensors aligned parallel to the width of the web or, alternatively, a single sensor called "traveling" making trips back and forth over the web. The transverse detector 41 detects the width of the consolidated ply 440 and the surface weight at different points of the width of the ply. The detection of the width of the web allows a computer 42 to calculate the lateral shrinkage suffered by the web during consolidation, or by difference with a width detection (not shown) upstream of the needling machine 3, or by difference with the travel length of the lapper carriage of the spreader-lapper 2. This running length is known to the computer 42 because the lapping carriage is actuated precisely by a servomotor (not shown) also controlled by this computer.

The width of the edge zone of the web which is altered in connection with the shrinkage phenomenon is known from experience or from preliminary tests. A simple arithmetic calculation and / or preliminary tests make it possible to evaluate the impact of this shrinkage on the orientation distribution of the fibers in the edge zone affected by the shrinkage. Based on this evaluation, the computer 42 controls an adjustment of the orientation means.

For example, according to said evaluation, the calculator 42 calculates a condensation rate that must be applied to the parts of the web intended to form the central zone of the web so that this central zone has in the consolidated web an orientation distribution. , or in any case a bidirectional spectrum of orientation, which is substantially equal to that of the edge areas. Simultaneously or alternating temporally with this regulation of the orientation distributions, the computer 42 receives from the detector 41 measurements of the area weight at different points of the width of the consolidated sheet 440 and regulates the surface weight profile of the consolidated sheet and the width of the consolidated web as described in WO 00/073547 , influencing parameters, such as those described above (speed of the doffer, spacing of the doffer), not affecting or practically no orientation of the fibers in the web. The figure 4 schematically illustrates the computer 42 sending commands 43 to the condensers 14, 15 and the detacher 16 for the dynamic adjustment of the condensation, orders 44 to the doffer 13 for the dynamic adjustment of the weight without affecting the orientation of the fibers, and orders 46 the lapping spreader 2 to adjust and define at each instant the position of the two lapper carriages 21, 22 in their movements back and forth M21, M22 and the speed of circulation of the belts 24, 25. The lines 43, 44, 46 are bidirectional to transmit back to the computer 42, information on the actual values of the operating parameters of the card and the crosslapper in particular.

In another embodiment of the regulation, it is envisaged to use at the output of the needling machine 3, in addition to the detector 41, at least one image sensor (not shown) in one of the edge zones. , and preferably at least three image sensors for the two edge areas and the central area respectively. The images produced by these sensors are analyzed to determine the orientation distribution of the fibers in the images obtained. The calculator 42 then calculates, for example, the bidirectional orientation spectra corresponding to the observed distributions, and controls the orientation means in a direction tending to equalize, or maintain equal, these bidirectional spectra.

The invention is not limited to the examples described and shown.

In particular, the regulation based on a detection of the transverse shrinkage of the sheet could be carried out without being combined with a regulation of the surface weight profile.

The orientation means controlled in the context of the regulation of distributions or orientation spectra can be any of those described, for example the driving motor of the output deck of the crosslapper 2 as described in FIG. reference to the figure 7 .

The invention is also not limited to the use of specific mathematical parameters such as orientation distributions or bidirectional orientation spectra defined above.

Claims (28)

A method of manufacturing a web-nonwoven fabric (440) characterized in that dynamically adjusting the fibers (OVB, OVC) according to the position of said fibers according to direction of the width of the web (430, 440). Method according to claim 1, characterized in that different orientation distributions (OVB, OVC) are established at different points of the web width at an intermediate stage of manufacture (430) so that the nonwoven fabric obtained at a later stage of manufacture (440) has at different points of the width of the textile respective desired distributions with respect to mechanical strength and / or elongation. Process according to Claim 2, characterized in that the orientation distributions of the fibers are chosen in the direction tending to standardize in all points of the width of the nonwoven fabric a quantity (MD / CD) representative of the mechanical strength or the lengthening of the nonwoven fabric. Process according to Claim 1, in which a sheet of fibers is produced and this sheet of fibers is consolidated, in particular by needling, characterized in that in the fiber orientation spectrum (430, 431, 432) a component parallel to the width of the ply before needling is greater, with respect to a longitudinal component, in two edge regions of the ply than in a central region of the ply. Method according to one of claims 1 to 4, wherein a card (1) provides at least one web (421, 422) which is superimposed in overlapping successive substantially transverse segments to form in a crosslapper (2). a web (430, 431, 432) then undergoing consolidation treatment (3), characterized in that said dynamic adjustment influences the orientation of the fibers in successive regions (VB, VC) of the length of the web (421). ). Method according to claim 5, characterized in that said dynamic adjustment influences a degree of condensation of the web (421). A method according to claim 6, characterized in that the dynamic control affecting the condensation is at least partly an adjustment of the relative speeds with respect to each other of at least two rotary members (12 to 17) of the card which contributes to the manufacture or the transport of the veil (421). A method according to claim 7, characterized in that said relative speeds are those of a detacher (16) and respectively a doffer (13) of the card. Method according to claim 7, characterized in that said relative speeds are those of a condenser (15; 14) and respectively of another condenser (14) or a doffer (13) of the card. Method according to claim 7, characterized in that said relative speeds are those of a detacher (16) and respectively a condenser (15, 15) of the card. A method according to claim 5, characterized in that the dynamic adjustment affects the movement (M21, M22) of at least one carriage (21, 22) of the crosslapper (2) in a direction substantially transverse to the web. Method according to claim 11, characterized in that the dynamic adjustment influences the ratio between a speed at which the web exits the crosslapper and a speed at which a web deposition point (422) on the forming web within the crosslapper (2) moves along the width of the web. Method according to one of claims 5 to 12, characterized in that the at least one dynamic adjustment affects a running speed of an outlet apron (28) of the vaporizer-spreader (2) fed with a veil fibers having an anisotropic orientation distribution, preferably with a longitudinal predominance of the web. Process according to one of Claims 4 to 13, characterized in that the consolidation step comprises mechanical needling and / or water jet bonding, thermal or chemical. Method according to one of claims 1 to 14, characterized in that the dynamic adjustment is part of a control loop further comprising measuring means (31) of at least one physical quantity relative to the band, and control means for modifying the dynamic adjustment according to the measured physical quantity. A method according to claim 15, characterized in that the measured physical quantity is the width shrinkage (dc) experienced by the web during the consolidation process. Method according to claim 15 or 16, characterized in that the physical quantity relates to the distribution of orientations. Method according to Claim 17, characterized in that the physical quantity relating to the distribution of orientations is determined by image analysis. Process according to one of Claims 15 to 18, characterized in that a double regulation is carried out, on the one hand, the aforesaid regulation influencing the fiber orientation distributions and, on the other hand, a regulation on the weight. surface of the strip at different points of its width by influencing a second dynamic setting which is substantially without effect on the orientation of the fibers. Process according to one of Claims 1 to 19, characterized in that the surface weight of the web at different points of its width is influenced by a second dynamic adjustment which has substantially no effect on the orientation of the fibers. A method according to claim 19 or 20, characterized in that the second dynamic setting affects the amount of fiber collected by a cardboard comb. Non-woven production facility comprising: - a card (1) providing at least one fiber web (421, 422); - a spreader-lapper (2) having the web in successive transverse segments on an exit apron (28) to form a web (431, 432); - A consolidating machine such as a needling machine (3), or a water jet binding apparatus, thermal or chemical, downstream of the output apron (28); characterized in that it further comprises orientation means for influencing the orientation distribution of the fibers as a function of their position along the width of the web, in a method according to one of claims 1 to 21 . Installation according to claim 22, characterized in that the orientation means comprise means for adjusting a condensation rate upstream of the crosslapper. Apparatus according to claim 22 or 23, characterized in that it further comprises weight adjustment means for focussing on the local web weight of the web at different points of its width, the adjustment means of weight being substantially without effect on the orientation of the fibers. Apparatus according to claim 24, characterized in that the weight adjustment means comprises means for adjusting the amount of fiber taken by a doffer (13) of the card (1) on a drum (12) of the card. Plant according to claim 24 or 25, characterized by detection means (41) for detecting at least indirectly the surface weights of the web at different sites of its width and for controlling the weight adjustment means according to the result of this detection. Installation according to one of claims 22 to 26, characterized in that detection means, in particular those of claim 25, at least indirectly detect the width of the consolidated web, and the installation comprises means for controlling the means orientation based on the detected width. Installation according to one of claims 22 to 26, characterized in that it comprises image analysis means for detecting the orientation distribution of the fibers of the sheet, the orientation means being controlled according to the result of this analysis.

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