EP1190125B1 - Installation for making a nonwoven textile web and method for using such an installation - Google Patents

Abstract

The invention concerns an installation comprising at least an extruder (1) for a melted organic polymer feeding a die (2) for producing a curtain of filaments (3); a cooling zone (4) for providing at least surface solidification of said extruded filaments; a suction device (5) in the form of a narrow chamber with rectangular cross-section, wherein the curtain of filaments is subjected to the action of high speed air streams causing the filaments to be drawn; means (6) for deflecting and slowing down the air flow at the outlet of the drawing slot and for distributing the filaments homogeneously on a receiving belt (7). The invention is characterised in that the means for producing the different operational phases, namely the extruding means, the cooling means, the filament drawing assembly and the distributing means, are separate from one another and can be individually adjusted, not only based on the production to be obtained (type of polymers, elementary yarn count of the filaments produced, weight per unit area of the web produced), but also at the beginning of production.

Description

Technical area

The present invention relates to an improved installation allowing the manufacture of a nonwoven textile tablecloth, commonly known as generic "spunbond" and which is formed by synthetic filaments continuous

It also relates to a method of implementing such an installation.

Previous techniques

• à extruder un polymère organique fondu au travers d'une filière percée de trous, de manière à former un faisceau ou rideau de filaments ;
• puis, à orienter les filaments extrudés par étirage au moyen d'un ou plusieurs dispositifs à jets de fluide, notamment à air comprimé,
• et enfin, à recevoir le faisceau de filaments sous la forme d'une nappe sur un tapis transporteur mobile, en général soumis à une source d'aspiration, et dont la vitesse est réglée en fonction des caractéristiques de la nappe, grammage notamment, que l'on souhaite obtenir.

The production of spunbond type nonwoven tablecloths dates back decades and generally consists of:

• extruding a molten organic polymer through a die pierced with holes, so as to form a bundle or curtain of filaments;
• then orienting the extruded filaments by drawing by means of one or more fluid jets devices, in particular with compressed air,
• and finally, to receive the bundle of filaments in the form of a sheet on a movable conveyor belt, generally subjected to a suction source, and the speed of which is adjusted according to the characteristics of the sheet, in particular grammage, that we wish to obtain.

After completion, the sheet is consolidated, for example by carrying out a sizing or calendering, preferably hot, so that the filaments are linked to each other.

Other consolidation treatments can also be performed, such as that for example a needling treatment (conventional or by jets of fluid), and / or the deposition on the surface or inside the sheet of a binding material.

Many proposals have been made to make such sheets, all aimed at obtaining the most homogeneous sheet or veil possible with high productivity and, increasingly with elementary filaments of great finesse with a titer less than 2 dtex if possible.

Among the oldest documents allowing such tablecloths to be produced, there may be mentioned GB-A-932 482, in which the filaments, after extrusion, travel in the open air leaving the die for a sufficient distance to allow at least superficial solidification of said extruded filaments before introduce them inside a suction and stretching nozzle creating the high speed annular airflow.

To obtain the bursting of the bundle of filaments, these receive a electrostatic charge which can be obtained by an electrostatic generator causing a Corona-like effect located upstream or downstream of the nozzle suction.

Among the different parameters that must be taken into account for the production of good quality tablecloths, depending on the polymers extruded, to adapt the distance between the outlet of the die and the entry inside the stretching system, the air speed inside the nozzle and also the speed of filament exit from the latter so that the deposit on the receiving belt do it regularly.

To solve this problem of homogeneity of the deposit on the conveyor belt, it has been proposed in patent US-A-3,286,896, to produce the suction device in the form of a chamber of rectangular section, of small width and of very long, such an assembly comprising at the inlet a suction chamber for extruded filaments followed by an additional chamber into which is injected air at low pressure and a very long channel inside which flows air at high speed. In order to obtain a good distribution of the filaments on the receiving surface, a deflector assembly which slows the air flow is arranged in exit from the drawing chamber thus allowing a better distribution of filaments.

Such systems in which the filaments pass inside a rectangular suction and drawing chamber, possibly have the width of the sheet of extruded filaments, have been proposed like this is particularly apparent from French patent 2,064,087 (corresponding to US-A-3,802 817), the curtain of filaments being subjected on its two sides to the action of veins air at high speed causing them to stretch.

Furthermore, US-A-4,064,605 describes an improvement to such a technique which consists in providing an additional assembly for cooling the filaments, before introduction into the drawing chamber proper, in subjecting the bundle of filaments to a transverse air flow.

Finally, the evolution of the technique has led to installations in which the drawing of the filaments at the outlet of the die and their transfer on a carpet receiver, is achieved by eliminating any passage in the open air of the filaments at the outlet of the sector thanks to an integrated assembly allowing cooling to be carried out, the stretching and depositing of the filaments on the carpet as is apparent in particular from the US Patent 4,627,811 as well as US 5,814,349.

Such an installation design makes it possible to obtain non-woven sails. can be of low grammage and good regularity but it is complex and delicate to implement.

Furthermore, such installations lack versatility by the fact that it it is not possible to easily adjust the cooling conditions at the outlet of die which vary according to the polymers and the title of the filaments which are wishes to produce and final characteristics of the tablecloth.

In addition, such installations are unsuitable for producing filaments. of great finesse.

Consequently, to date, no satisfactory solution has been proposed for set up a production facility for spunbond type nonwovens allowing to obtain a high productivity when the filaments are fine, that is to say having a titer less than 2 dtex, which implies having a perfect stretch extremely regular filaments without breaking them during this phase stretching.

Now to obtain a high production, i.e. a flow rate of polymers important at the end of the die, this implies on the one hand that the drawing speed is increased in the stretching slot, thus causing a large air flow coupled at a relatively high temperature of the filaments before drawing in order to retain some plasticity.

Furthermore, stretching of the filaments, coupled with high productivity, also involves being able to brake the air streams coming out of the slit drawing to obtain a regular deposit of the filaments on the receiving conveyor and the production of a good quality veil.

Statement of the invention

Now we have found, and this is what is the subject of the invention, a new type installation allowing the realization of nonwoven textile tablecloths from continuous synthetic filaments, which solves all the problems supra.

In general, the installation according to the invention is of the type defined in claim 1.

Thanks to such a design, which goes against technical evolution in this area, evolution which tended to realize sets completely integrated for cooling, stretching and distributing the filaments on the belt carrier, it has been found that such a dissociation of the different phases each other’s operating systems had a huge number of advantages, particularly with regard to flexibility of use and the possibility of paying production much more easily depending on the yarn titles and the weight of tablecloth that we wish to obtain.

• la zone de refroidissement en sortie de filière et la zone d'étirage des filaments est constituée par une pluralité de modules élémentaires juxtaposés les uns aux autres en fonction de la largeur de production, le système d'ouverture des filaments étant, quant à lui, constitué par un ensemble s'étendant sur toute la largeur de la nappe produite ;
• le refroidissement en sortie de filière est obtenu au moyen d'un ensemble comportant plusieurs zones successives permettant de soumettre le rideau de filaments à un courant d'air transversal dont la vitesse et la température peuvent être ajustées de façon indépendante dans chacune des zones.
• le système d'ouverture des filaments qui est espacé de la sortie du système d'étirage est constitué par un ensemble qui dévie latéralement le flux d'air, réduisant la vitesse de celui-ci et celle des filaments, et facilitant le dépôt uniforme sur le convoyeur en éliminant tout rebond au moment de ce dépôt, avantageusement le système d'ouverture des filaments est également associé à un ensemble chargeant électrostatiquement lesdits filaments avant dépôt sur le tapis de réception et qui peut être disposé soit immédiatement à la sortie dudit système d'ouverture ou intégré à l'intérieur de ce dernier ;
• l'installation comporte des moyens de contrôle par ordinateur de la totalité des sous-ensembles permettant de réaliser automatiquement la montée en vitesse de la ligne de production.

Advantageously and in practice, in accordance with the invention:

• the cooling zone at the outlet of the die and the zone for drawing the filaments is constituted by a plurality of elementary modules juxtaposed to each other as a function of the production width, the system for opening the filaments being, for its part, consisting of an assembly extending over the entire width of the sheet produced;
• cooling at the outlet of the die is obtained by means of an assembly comprising several successive zones making it possible to subject the curtain of filaments to a transverse stream of air whose speed and temperature can be adjusted independently in each of the zones.
• the filament opening system which is spaced from the outlet of the drawing system is constituted by an assembly which laterally deflects the air flow, reducing the speed of this and that of the filaments, and facilitating uniform deposition on the conveyor eliminating any rebound at the time of this deposition, advantageously the filament opening system is also associated with an assembly electrostatically charging said filaments before deposition on the receiving mat and which can be disposed either immediately at the exit of said system of opening or integrated inside the latter;
• the installation includes means of computer control of all the sub-assemblies making it possible to automatically increase the speed of the production line.

• lors de la phase de lancement, la température de l'air à l'intérieur de chaque zone de refroidissement décroít d'une zone à la suivante, la vitesse de l'air traversant dans chaque zone étant réglable et pouvant être comprise entre 0,5 m/seconde et 3 m/seconde dans chacune desdites zones, la fente d'étirage étant maintenue en position écartée,
• on augmente ensuite progressivement la vitesse de production, les paramètres de la zone de refroidissement et de mise en température des filaments étant modifiée pour :
  • augmenter la vitesse d'air de la première zone, la température demeurant inchangée,
  • augmenter la température de la deuxième zone pour l'amener au niveau de celle de la première zone et augmenter la vitesse d'air de cette zone,
  • augmenter la température de l'air de la troisième zone et augmenter la vitesse d'air de cette zone ;
• simultanément, on réduit progressivement la largeur de la fente d'étirage pour atteindre une valeur nominale de fonctionnement, la pression de l'air d'étirage étant augmentée progressivement

The invention also relates to a method for implementing such an installation, which method is characterized in that:

• during the launching phase, the air temperature inside each cooling zone decreases from one zone to the next, the speed of the air passing through each zone being adjustable and can be between 0, 5 m / second and 3 m / second in each of said zones, the stretching slot being maintained in the separated position,
• the production speed is then gradually increased, the parameters of the cooling and temperature setting of the filaments being modified to:
  • increase the air speed of the first zone, the temperature remaining unchanged,
  • increase the temperature of the second zone to bring it to that of the first zone and increase the air speed of this zone,
  • increase the air temperature of the third zone and increase the air speed of this zone;
• simultaneously, the width of the stretching slot is gradually reduced to reach a nominal operating value, the pressure of the stretching air being gradually increased

It should be noted that in the process according to the invention, the air temperature inside each cooling zone is generally included in a range which can range from 5 ° C to 60 ° C.

Brief description of the drawings

• la figure 1 est une vue d'ensemble d'une installation réalisée conformément à l'invention ;
• la figure 2 est une vue schématique de détail de l'ensemble de refroidissement ou plus précisément de contrôle de la température des filaments avant introduction dans la fente d'étirage proprement dite ;
• la figure 3 est une vue schématique montrant la structure générale d'une fente d'étirage.

The invention and the advantages which emerge therefrom will be better understood thanks to the example of embodiment which follows given by way of indication but not limitation, and which is illustrated by the appended diagrams in which:

• Figure 1 is an overview of an installation produced according to the invention;
• Figure 2 is a schematic detail view of the cooling assembly or more precisely of controlling the temperature of the filaments before introduction into the drawing slot proper;
• Figure 3 is a schematic view showing the general structure of a stretching slot.

Way of realizing the invention

Referring to Figure 1 attached, the installation according to the invention is therefore essentially consists of at least one extruder, designated by the general reference (1) supplying synthetic polymer such as polyamide, polyethylene, polyester ..., a die (2) allowing the formation of a curtain of filaments (3).

From a practical point of view, as an indication, the sector can be constituted a perforated plate comprising 5000 holes, for example 0.5 mm in diameter, per meter of width. These holes are distributed over a plurality of parallel rows, for example on eighteen rows and this, on a die outlet width of 140 mm.

At the outlet of this die, is arranged the cooling assembly (4) allowing the regulation of the temperature of the filaments as a function of the polymer and which, according to the invention, consists of three successive zones (4a, 4b, 4c) allowing the filament curtain (3) to be subjected to through air flows, speed and temperature can be adjusted.

As an indication, the length of this cooling zone is of the order of 1200 mm and the temperature and speed of each of the zones decreasing by the first zone (4a) to the third zone (4c).

The air temperature in this area will generally be between 15 and 60 ° C, the speed of the through air being between 0.5 m / s and 3 m / s.

Downstream of this cooling zone, the stretching assembly is arranged. proper (5) which is in the form of a closed enclosure comprising a slot (6) inside which air is injected at a pressure of 0.5 to 1.5 bar.

In general, such a stretching system can be designed in a similar to the teachings of FR 1,582,147 or GB 932,482 (Figure 3) and which allows to obtain the suction of the curtain of filaments and its training by high speed air streams for stretching.

As shown in Figure 3 where such a stretching assembly (5) is represented schematically, this consists essentially of a proper stretching slot (10), the air coming from a collector (11) being introduced inside this chamber (10) through a distributor (12) and an acceleration chamber (13).

Such a suction / stretching assembly is however preferably designed to that the width (F) of the slot (10) can be changed during operation of the installation, which allows on the one hand to regulate the flow speed of the veins of air and, consequently, the delicacy of the title which one wishes to obtain and on the other hand, facilitates the launch operation as will be seen in the following description.

In general, for a production of filaments having a titer between 1.5 dtx and 3 dtx, the width (F) of the slot will be between 3 mm and 10 mm, this gap spacing can be increased to 25 mm during the launch phase.

At the outlet of the drawing assembly (5), the bundle of filaments (3) is projected on the receiving belt (7) not directly as is apparent from FR 2 064 087 or US 4,064,605, but through a set (6) causing a deviation of the air jet leaving the slot (5) and a slowing down of this air jet, causing opening the curtain of filaments and distributing them on the carpet receiver (7).

Such an assembly can for example be in the form of a slot divergent walls.

In addition, to amplify the bursting of the curtain of filaments and the distribution random on the receptive surface, which can be loaded electrostatically, by means of a “Corona” type system associated with the distributor element (6), and in a manner similar to the teachings of the British patent 932,482.

Possibly, the means allowing the electrostatic charge of the filaments, can be integrated at the entrance of the divergent walls of the element distributor (6).

Example of implementation

On an installation of the type illustrated by the appended figures, a nonwoven web consisting of continuous filaments from polypropylene, in the present case of 38 MSR. The polymer is melted in an extruder with five melting zones and at the exit of the extruder, it is filtered on a filter composed of stainless steel mesh before being introduced into the chain itself (2).

To do this, the machine has two dies (1) arranged in series, each comprising 5000 holes of 0.5mm in diameter per meter of width.

Furthermore, in accordance with the invention, the cooling zone (4) and the stretching zone (5) preferably consists of a plurality of modules elementary each having a width of 50 cm.

On the other hand, the distributor element (6) arranged at the outlet of the stretching zone (5) has, in turn, a continuous slot extending over the entire width of the installation and having the shape of a divergent whose width is 15 mm in looking at the exit area of the filaments from the slot (5) and 100 mm opposite the receiving mat (7).

The distributor assembly (6) can possibly be associated with means also allowing electrostatic charging of the filaments thus improving the bursting of the beam and their distribution on the carpet receiver (7).

The line is started at low production with a flow of polymer set at 0.2 g / min and per hole.

• zone (4a)
  • température de l'air : 35°C
  • vitesse de l'air : 1 m/seconde
• zone (4b)
  • température de l'air : 20°C
  • vitesse de l'air : 1 m/seconde
• zone (4c)
  • température de l'air : 15°C
  • vitesse de l'air :0,5 m/seconde.

During this start-up phase, the following parameters are observed in the warm-up zone, using a cooling zone (4) comprising three successive zones (4a, 4b, 4c) having a total length of approximately 1200 mm during from which the bundle of extruded filaments (3) is subjected to a flow of through air coming from each of these zones, under the following conditions:

• zone (4a)
  • air temperature: 35 ° C
  • air speed: 1 m / second
• zone (4b)
  • air temperature: 20 ° C
  • air speed: 1 m / second
• zone (4c)
  • air temperature: 15 ° C
  • air speed: 0.5 m / second.

During this start-up cooling phase, the width (F) of the stretching slot (5) is adjusted to 25 mm, the pressure of the air injected into said slot being 0.3 bar.

The stretched beam passes, at the outlet of the stretching slot (5), into the system (6) of opening and of distribution of said beam which is in the form of a divergent, having a width at the entrance of 20 mm and an opening at the base of the order of 100 mm.

During this entire start-up period, the polymer is collected on a conveyor belt (7) by means of a "leader" which is unwound on said belt and which prevents drops of molten polymer from clogging it.

When a uniform flow of polymer is established in the die, the speed of line production is gradually increased.

• augmentation de la vitesse de l'air de la première zone (4a) à 1,5 mètres/seconde, la température demeurant inchangée ;
• augmentation de la temperature de l'air de la deuxième zone (4b) qui est portée à 30°C, sa vitesse étant portée à 1,3 mètre/seconde ;
• augmentation de la température de l'air de la troisième zone (4c) à 20°C et augmentation de la vitesse qui est portée à 1 mètre/seconde.

During this entire period of speed increase, the parameters of the zone (4) for cooling and warming up the filaments, are gradually modified, namely:

• increasing the air speed of the first zone (4a) to 1.5 meters / second, the temperature remaining unchanged;
• increase in the temperature of the air in the second zone (4b) which is brought to 30 ° C, its speed being brought to 1.3 meters / second;
• increase of the air temperature of the third zone (4c) to 20 ° C and increase of the speed which is brought to 1 meter / second.

Such a procedure ensures solidification at least surface of the extruded filaments which do not stick together when enter the drawing slot (5).

Regarding this stretching slot (5), during the entire setting period road, its width is gradually reduced from 25 mm to 5 mm and, simultaneously, the pressure of the drawing air is gradually increased from 0.3 to 1 bar approximately.

The temperature of the stretching air is controlled and remains constant throughout this period.

Thanks to such a procedure, it is possible to realize, from an installation in which the different zones remain fixed, one by compared to others, polymers of different nature and also facilitate the production of filaments having a very fine titer of the order of 1.7 dtex, or even less.

Indeed, the fact of gradually raising the temperature of the air used in the last two cooling zones (4b) and (4c), increases the plasticity of the polymer and thus facilitates its stretching, allowing greater fineness of the filaments.

Finally, being able to adjust on-the-fly, both the air pressure and the width of the stretching slot optimizes the conditions drawing, which, of course, results in obtaining a high production associated with the production of very fine filaments.

The structure of the filament opening system located downstream of the stretching system and independent of it also promotes regular deposition and homogeneous filaments on the receiving surface (7).

Indeed, the production of filaments with very fine titles is accompanied of a high speed, of the order of 5000 m / min of the filaments leaving the slot stretching. The device (6) used in the installation according to the invention allows a slowing down of the speed of said filaments as well as of the air flow leaving the stretching slot, favoring their distribution on the conveyor belt by the fact that it eliminates rebound phenomena likely to disrupt regular deposition and homogeneous.

All unit settings are made and checked automatically by a "process" computer which operates on the principle known as "fuzzy logic" or "fuzzy logic" allowing to take into account a multitude of parameters independent.

The concrete example given previously makes it possible to obtain filaments having a titre of 1.7 dtex with a polymer flow rate of 0.65 g / hole / minute.

The veils obtained can weigh from 10 to 150 g / m ² , are very regular, and can be used for various applications such as hygiene products (baby diapers), products for medical or industrial use.

If such an installation allows very fine filaments to be obtained, it is of course also possible to significantly increase the production of the line when the title of the filaments is increased.

As an indication, if in the previous example, we had made filaments having a titer of 2 dtex, the flow rate of polymer could have been increased to 0.8 g / hole / minute.

Claims (7)

1. Installation for making a nonwoven textile web comprising :

   at least one extruder (1) for a melted organic polymer feeding a spinneret (2) for producing a curtain of filaments (3);

   a cooling zone (4) for bringing about at least surface solidification of the said extruded filaments;

   a drawing device (5) in the form of a narrow chamber of rectangular cross-section as a drawing slot (F), inside which the curtain of filaments is subjected to the action of high-speed air streams causing the said filaments to be drawn;

   means (6) for deflecting and slowing down the air flow at the outlet of the drawing slot and for distributing the filaments homogeneously over a receiving belt (7);

      in which the means for carrying out the different operational phases, namely extruding means, cooling means, filament-drawing assembly and distributing means, are separate from one another,
      characterised by means for adjusting the width of the drawing slot (F).
2. Installation according to claim 1, characterised in that the cooling zone (3) at the spinneret outlet and the filament-drawing zone (5) consist of a plurality of elementary modules placed side by side according to the production width, the filament-opening system consisting, for its part, of an assembly extending over the entire width of the web produced.
3. Installation according to one of claims 1 and 2, characterised in that the cooling at the spinneret (2) outlet is brought about by means of an assembly (4) having a plurality of successive zones (4a, 4b, 4c) for subjecting the curtain of filaments to a transverse air current, the speed and temperature of which may be adjusted independently in each of the zones.
4. Installation according to one of claims 1 to 3, characterised in that the filament-opening system (6), which is spaced from the outlet of the drawing system, consists of an assembly which laterally deflects the air flow, reducing the speed thereof and that of the filaments, and facilitating the uniform deposition on the conveyor (7) by eliminating any rebound at the moment of this deposition.
5. Installation according to claim 4, characterised in that the filament-opening system (6) is associated with an assembly which electrostatically charges the said filaments before deposition on the receiving belt.
6. Installation according to one of claims 1 to 5, characterised in that it has means for controlling, by computer, all of the subassemblies making it possible to bring about the increase in speed of the production line automatically.
7. Method for using an installation according to one of claims 3 to 6, characterised in that:

   during the start-up phase, the temperature of the air inside each cooling zone (4a, 4b, 4c) decreases from one zone to the next, it being possible for the speed of the traversing air in each zone to be adjusted and to be between 0.5 m/second and 3 m/second in each of the said zones, the drawing slot being maintained in the separated position,

   the production speed is then increased progressively, the parameters of the zone (4) for cooling and heating up the filaments being modified in order to:

   increase the air speed in the first zone (4a), the temperature remaining unchanged,

   increase the temperature in the second zone (4b) to bring it to the level of that of the first zone and increase the air speed in this zone,

   increase the air temperature in the third zone (4c) and increase the air speed in this zone;

   simultaneously, the width of the drawing slot is progressively reduced to attain a nominal operating value, the pressure of the drawing air being progressively increased.

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