EP1747313B1 - Wide non-woven and methods therefor and production machine - Google Patents

Description

The present invention relates to nonwovens and their processes and manufacturing machines. It relates more specifically to nonwovens of great width, greater than 5 m wide for productions of more than 200 kg per hour and per meter of machine.

In general, light nonwovens, 15 to 80 g / m ² , called "dry" are formed by carding and / or aeraulic route. However, for large production widths, ie for widths greater than 3.5 m, carding is the only dry technique used for high production.

It has been known for a long time to lay transversely the card web or sails to form a heavy ply in wide width, then mechanically stretch it lengthwise to reduce the mass to m ² . This technique is very limited in speed and can not produce both light nonwovens, whose mass per m ² is less than 60 g / m ² , in large width and at production levels of 200 kg / hour and by width meter, and more.

Modern techniques make it possible to construct cards with a maximum width of 5 m and delivering webs of fibers up to 4.7 m wide. Beyond the great technical difficulties of building high precision drums in lengths of 5 m and more, these cards do not allow the production of low mass fleeces of mass ² , with strength ratios of the direction to the sense through less than 3.5.

FR-2846013 discloses a filament nonwoven having a ratio of the resistance in the machine direction to that in the cross direction less than 1.5, a density of less than 0.10g / cm ³ and a filament titer of between 0.9 and 10 dtex . EP 0786428 discloses a web drawing device.

The invention relates to a new light nonwoven fabric, of great width, produced by the so-called "dry method" technique and whose resistance ratio in the long direction in the cross direction is less than 3.5.

It has been found, and this is the subject of the present invention, a lightweight nonwoven and its processes and manufacturing machines, which allow to produce nonwoven "non-woven" high output, wide-width and whose ratio of a mechanical property in the long direction, and in particular of tensile strength, to this same property in the transverse direction is less than 3.5 and, in general, between 1.5 and 3.5 .

The subject of the invention is therefore a nonwoven of a width at least equal to 5 m, with a basis weight of between 15 and 80 g / m ² and, preferably, between 30 and 60 g / m ² and consisting of a length of at least 15 mm and preferably of a length of between 20 and 60 mm, filaments or a mixture of such fibers and filaments, characterized in that the ratio of a mechanical property, particularly of the tensile strength in the long direction at the same property in the cross direction is less than 3.5.

Preferably, said ratio is less than 3 and more preferably 2.5.

The fibers and / or filaments may be made of thermoplastic plastic material, in particular polyolefins such as polypropylene or polyethylene, or polyester or polylactic acid, polyvinyl alcohol, polyamide or an artificial textile material, such as viscose or in a natural textile material, such as cotton, linen, wool, wood. The veil can have different layers.

The subject of the invention is also the process for manufacturing a nonwoven, in which a web of fibers and / or filaments is first consolidated by throwing jets of water under pressure by calendering or by needling to obtain a consolidated sail a first time. The consolidated web is stretched in the width direction a first time to obtain an enlarged web, and then the expanded web is reinforced a second time, preferably by jetting water under pressure. The expanded web is then dried, preferably by a drying device of adjustable width downstream of the second consolidation.

Preferably the pressure of the jets of the second consolidation is greater than the pressure of the jets of the first consolidation. The pressure of the jets of the first consolidation may be for example between 15 and 70 bar and the pressure jets of the second consolidation be greater than 70 bar and for example between 75 to 100 bar. The projection orifices of the jets may have a diameter in particular of between 100 and 200 microns.

In order not to break the nonwovens, at least 30% elongation of nonwovens with a basis weight of less than or equal to 40 g / m ² , less than 40% of nonwoven fabrics with a grammage greater than 40 g / m ² and less than or equal to 60 g / m ² and less than 50% of the basis weight of nonwoven greater than 60 g / m ² and less than or equal to 80 g / m ^2. The percentage of elongation is the ratio of the difference between the dimension after elongation decreased from the dimension before elongation to the dimension before elongation.

Preferably, the temperature of the consolidated web is raised a first time by at least 50 ° C. and not more than 300 ° C. The temperatures of the web before enlargement or during enlargement can be between 15 ° C. and 300 ° C and preferably between 20 ° C and 250 ° C. The heating stage is particularly advantageous for a thermoplastic material having a tendency to crystallize, such as polyester, for which it is thus rapidly crystallized so that the shrinkage is decreased. For polyolefins, heating causes softening which facilitates the broadening and refines the unit diameter of the constituent filaments or fibers.

The invention also relates to a machine for producing a nonwoven comprising a means of transporting a web of fibers or filaments in a consolidation device by jetting water jets, by calendering or by needling, characterized in that it comprises, downstream of the first consolidation device, a firstly consolidated veil widening device. A second consolidation device is provided downstream of the enlargement device. Its effective consolidation width is greater than that of the first consolidation device. We obtain a nonwoven meeting the characteristics mentioned above and in particular having a large width, which reduces falls when it is then cut into smaller strips for the manufacture of finished products.

At US3747161 a nonwoven production machine is described by rearrangement treatments.

The widening device, preferably of adjustable width, may comprise an enlarging roller and preferably a spiral-wound expander roller, or nipples with pins or clamps, especially in the case of heating.

They are flexible rotating rollers whose radius of curvature is adjusted according to the desired enlargement.

The enlargement of the wet nonwoven can also be obtained by two rugs and sprockets guided by guide systems laterally to the edges of the nonwoven and whose spacing increases as the nonwoven advances.

Enlargement is facilitated if the means of transport comprises means for the velocity of the haze to be greater at the exit than at the entrance of the enlarging device. For example, it is possible to provide motor rollers for driving the web at the inlet and the outlet of the widening device and to rotate them at different speeds.

When this second consolidation device comprises a projection of jets of water under pressure, the injection width of the water jets of the second device is greater than that of the first device used for the first consolidation. But the second consolidation can also be carried out by thermoling, calendering, mechanical needling, chemical or other means. The effective consolidation width of the second consolidation device is greater than that of the first consolidation device. The second consolidation device can also give a pattern to the veil.

Preferably, the second consolidation device is followed by an air suction drying device. The drying may be carried out in particular at a temperature of between 110 and 160 ° C. and it is preferably carried out in a through-air oven. Preferably, there is interposed between the drying device and the second consolidation device, a vacuum dehumidification device through a perforated surface comprising means for adjusting the useful width of the perforated surface. This surface may be constituted by a suction belt communicating with a vacuum generator and provided with sliding shutters.

If necessary, the enlargement and reconsolidation operations may be repeated several times.

• la figure 1 est un schéma d'une machine de production d'un nontissé suivant l'invention,
• la figure 2 est une vue en élévation d'un rouleau élargisseur mis en oeuvre dans la machine suivant l'invention, et
• la figure 3 est une vue en plan de l'ensemble d'un rouleau élargisseur et des rouleaux d'entrée et de sortie.

In the accompanying drawings, given solely by way of example:

• the figure 1 is a diagram of a machine for producing a nonwoven according to the invention,
• the figure 2 is an elevational view of an expanding roller implemented in the machine according to the invention, and
• the figure 3 is a plan view of the assembly of an expanding roller and the input and output rollers.

The machine represented in figure 1 comprises an inlet belt conveyor 1, circulating on rollers 2 and feeding on the upper strand a fiber web, schematized by the arrow 3. The web is compacted between a drum 4 and the upper strand of the conveyor 1 with humidification by dispatch water through the conveyor 1 by a humidifier H before winding on the right side of the drum where it receives, as first consolidation, jets of water 5 under high pressure from injectors 6. The thus consolidated sail winds on another drum 7 also provided with injectors 8 to complete what is called, in the sense of the invention, the first consolidation.

The consolidated web a first time arrives at an entry speed in two rollers 9 wideners (separated by three rolls of returns), which is expanded at an output speed which is greater than the entry speed because the drum 7 The enlarged web is returned by the rollers 10 on a drum 11 provided with injectors 12 projecting jets 13 of water on the expanded web to achieve a second consolidation. The roller 11 is provided with a sleeve making it possible to give a pattern to the consolidated veil a second time.

The consolidated web a second time passes over the upper strand of a conveyor 14 provided with a suction box below the upper strand so as to constitute a dehumidification device of the veil. At the exit of the conveyor 14, the web enters a furnace 16 with hot air flow passing through a perforated surface 17 whose length perpendicular to the plane of the drawing can be adjusted to adapt to the width of the web. At the outlet of the dryer the nonwoven 18 is wound on a winder 19.

The expanding roller 21 shown in FIGS. Figures 2 and 3 is tensioned by the bearings 2 which have an adjustable internal device for changing the angle of the axes of the roller relative to the bearings and therefore the radius of curvature of the roll and also the percentage increase of the width of the nonwoven. For lightweight nonwovens, with a basis weight of less than 50 g / m ² , it is preferable to have a motor 23 which drives the expanding roller in rotation.

The nonwoven 24 is first deflected by a motor roller Me then is encircled around the expander roller 6, then is deflected again by a motor roller 27. At the periphery of the expander roller, the nonwoven follows a perpendicular direction. 28 to the longitudinal axis of the roller 26. The surface of the roller 28 is preferably covered with a synthetic material that prevents the nonwoven from sliding on the surface of the roll to obtain maximum expansion.

1. a) Masse au mètre carré :
   • On conditionne un échantillon pendant 24 heures et on effectue l'essai à 23° C et à une humidité relative de 50%.
   • On coupe au moins 3 échantillons d'une surface d'au moins 50000 mm2 avec un appareil de découpe appelé massicot.
   • Chaque échantillon est pesé sur une balance de laboratoire ayant une précision de 0,1 % de la masse des échantillons pesés.
2. b) Résistance et allongement dans le sens long et dans le sens travers :
   • On conditionne un échantillon pendant 24 heures et on effectue l'essai à 23°C et à une humidité relative de 50%. On utilise pour le test un dynamomètre comprenant un jeu de mâchoires fixes et un jeu de mâchoires mobiles se déplaçant à une vitesse constante. Les mâchoires du dynamomètre ont une largeur utile de 50 mm. Le dynamomètre est équipé d'un enregistreur qui permet de tracer la courbe de la force de traction en fonction de l'allongement. On coupe 5 échantillons de 50 mm plus ou mois 0,5 mm de largeur et de 250 mm de longueur, ceci dans le sens long et dans le sens travers du non tissé. Les échantillons sont testés un par un , à une vitesse constante de traction de 100 mm par minute et avec une distance initiale entre mâchoires de 200 mm. Le dynamomètre enregistre la courbe de la force de traction en newtons en fonction de l'allongement.

Laboratory tests for resistance measurement in the long direction and in the cross direction, and mass m ² are conducted according to ERT standards of EDANA (European Disposable and Nonwovens Association) namely:

1. a) Mass per square meter:
   • A sample is conditioned for 24 hours and the test is carried out at 23 ° C. and a relative humidity of 50%.
   • At least 3 samples of an area of at least 50000 mm 2 are cut with a cutting apparatus known as a paper cutter.
   • Each sample is weighed on a laboratory scale with an accuracy of 0.1% of the weight of the weighed samples.
2. b) Resistance and elongation in the long direction and in the cross direction:
   • A sample is conditioned for 24 hours and the test is carried out at 23 ° C. and a relative humidity of 50%. A dynamometer comprising a set of fixed jaws and a set of movable jaws moving at a constant speed is used for the test. The jaws of the dynamometer have a useful width of 50 mm. The dynamometer is equipped with a logger that allows the curve of the tractive force to be plotted as a function of elongation. Five samples of 50 mm plus or 0.5 mm width and 250 mm length were cut in both the long and crosswise directions of the nonwoven fabric. The samples are tested one by one, at a constant tensile speed of 100 mm per minute and with an initial distance between jaws of 200 mm. The dynamometer records the curve of the tensile force in Newtons as a function of elongation.

The following examples illustrate the invention.

Example 1 (comparative)

A haze of about 60 g / m ² composed of 50% of viscose fibers 1.7 dtex and 40 mm in length and 50% of 1.7 dtex polyester fibers and 38 mm in length was produced at a speed of 70 m / min by a carding type card for nonwovens. This veil is delivered continuously to a first consolidation set by water jets followed by a second consolidation set by water jets as described. figure 1 . The first consolidation station consists of a compacting and wetting conveyor followed by two rotating drums each equipped with two hydraulic injectors. The second consolidation station consists of a rotary drum equipped with two hydraulic injectors.

On the first consolidation station, the fiber web is first compacted between the transport conveyor and the first drum. Immediately after compacting, the web is wet and slightly consolidated by a hydraulic injector projecting jets of water of 140 microns in diameter at a pressure of 15 bar. The jets being spaced from each other by a distance of 0.8 mm in two rows.

The thus compacted, wet and slightly consolidated web is then subjected to the action of two successive hydraulic injectors projecting jets of water of 120 .mu.m in diameter and comprising 1666 jets / m of width at increasing pressures of 50 bar and 70 bar.

The nonwoven thus consolidated is transferred to a second drum of the same type as the first and also equipped with two hydraulic injectors and projecting water jets of 120 microns in diameter and having 1,666 jets / m width at pressures of 70 bar each.

The wet nonwoven is then transferred to a last drum equipped with two hydraulic injectors projecting jets of water of 120 microns in diameter and having 1,666 jets / m width at pressures of 80 bar each.

The nonwoven thus obtained is then transferred to a suction belt connected to a vacuum generator and then dried at a temperature of 130 ° C in a through air oven.

We obtain a nonwoven weighing about 60 g / m ² . The expanding roll device located between the second drum and the third drum is inactive in this first example. The nonwoven thus has in this example substantially the same width on all consolidating stations by water jets.

Example 2

The conditions of Example 1 are repeated using the expanding roll device located between the second and the third drum. The width of the wet nonwoven is increased by 15% before being transferred to the third drum. The nonwoven is consolidated on the third drum under the same conditions as Example 1, that is to say by two hydraulic injectors at pressures of 80 bar each.

Then the nonwoven is dried as in Example 1.

Example 3

The conditions of Example 2 are repeated, this time applying a 30% enlargement percentage before transferring the wet nonwoven to the third drum. The other conditions of the test are also identical to those of test 2.

Example 4. (comparative)

The conditions of Example 2 are repeated, this time applying a 50% enlargement percentage before transferring the wet nonwoven to the third drum. The nonwoven tears along longitudinal lines. It is not usable. The test is stopped. Table 1 Characteristics units Comparative Example 1 Example 2 Example 3 Weight per m ² G / m ² 60 52 43 Resistance long N / 50 mm 94 75 58 Resistance meaning across N / 50 mm 26 29 26 Elongation % 33 39 43 Elongation meaning across % 121 95 89 Resistance ratio long direction / cross direction Without units 3.61 2.58 2.23

Claims (9)

1. A nonwoven having a width at least equal to 5 m, a weight between 15 and 80 g/m² and preferably between 30 and 60 g/m², and comprised of fibers having a length of at least 15 mm and preferably a length between 20 and 60 mm, of filaments or of a mixture of such fibers and filaments, characterized in that the ratio of the tensile strength in the machine direction to this same property in the cross direction is less than 3.5.
2. A process for manufacturing a nonwoven as claimed in claim 1, in which a web of fibers and/or filaments is consolidated by projecting water jets thereat, by calendering or by needle bonding in order to obtain a web that has been consolidated a first time, characterized in that the web consolidated a first time is drawn in the width direction, so as to obtain a widened web, then the widened web is consolidated a second time by projecting water jets, in which drawering is carried out to an elongation of less than 30 % for nonwovens having- a weight less than or equal to 40 g/m², of less than 40% for nonwovens having a weight greater than 40 g/m² and less than 50% for nonwovens having a weight greater than 60 g/m² and less than or equal to 80 g/m².
3. The process as claimed in claim 2, characterized in that the pressure of the jets of the second consolidation, which is carried out by projection of jets, is greater than the pressure of the jets of the first consolidation.
4. The process as claimed in one of claims 2 or 3, characterized in that the temperature of a web consolidated for the first time is increased at least of 50°C and at most of 300°C.
5. A machine for manufacturing a nonwoven as claimed in claim 1, comprising a means (1) of transporting a web of fibers or of filaments into a device (1, 6) for consolidation by water jets, by calendering or by needle bonding, characterized in that it comprises, downstream of the first consolidation device, a device (9) for widening the consolidated web and a second consolidation device (12) that is placed downstream of the widening device (9) and having an effective consolidation width that is greater than that of the first consolidation device (6).
6. The machine as claimed in claim 5, characterized in that the widening device (9), preferably of adjustable width, comprises at least one widening roller or pin or clip tenters.
7. The machine as claimed in either of claims 5 and 6, characterized in that the conveying means comprises means (7, 10) so that the web speed is greater at the exit than at the entry of the widening device (9).
8. The machine as claimed in one of claims 5 to 7, characterized in that the second consolidation device (12) is followed by a device (15) for dehumidifying by suction through a perforated surface, comprising means for controlling the working width of the perforated surface.
9. The machine as claimed in one of claims 5 to 8, characterized in that, downstream of the second consolidation device (12), a drying device (16), preferably of adjustable width is provided.

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