EP1554421A2

EP1554421A2 - Method and machine for producing a nonwoven fabric with reduction of displacement speed of the compacted mat

Info

Publication number: EP1554421A2
Application number: EP03775475A
Authority: EP
Inventors: Frédéric NOELLE
Original assignee: Rieter Perfojet SAS
Current assignee: Andritz Perfojet SAS
Priority date: 2002-10-11
Filing date: 2003-10-07
Publication date: 2005-07-20
Anticipated expiration: 2023-10-07
Also published as: IL167871A; WO2004033781A2; FR2845697B1; BR0315245B1; AU2003283501A8; FR2845697A1; DE60333113D1; US7392575B2; AU2003283501A1; BR0315245A; CN1774533A; CN100457996C; WO2004033781A3; US20060080816A1; ATE472002T1; EP1554421B1

Abstract

The procedure for making a non-woven fabric, in which a layer or filaments and fibres is first compacted and then consolidated, reduces the speed of movement before compacting by between 5 and 50 per cent. The layer of filaments/fibres is moistened immediately before the compacting post, where its thickness is reduced by 30 - 99 per cent by compressing it between a conveyor (7) and roller (8). Following compaction, the material is consolidated by hydraulic interlocking, thermal bonding, chemical bonding and/or mechanical felting. Between the compaction and consolidation posts the material is held in place by suction. One version of the machine used for the compaction and consolidation processes has a conveyor frame (1) on legs (2), with supporting (3), tensioning (4) and guide (5) rollers for a water-permeable conveyor belt (6). A cylindrical compacting roller (8) is mounted horizontally above the belt, and a moistening injector (9) beneath it. The compacted material is held against the roller by suction applied in a quadrant (8a) after its lowest point so that it passes in front of water jet injectors (10) that consolidate it.

Description

METHOD AND MACHINE FOR PRODUCING A NON-WOVEN FABRIC FOR REDUCING THE SPEED OF MOVEMENT OF THE TABLECLOTH

COMPACT The present invention relates to processes and machines for producing a nonwoven, consisting of fibers or filaments made of an organic material, in particular natural or synthetic or artificial textile fibers or filaments. The fibers or filaments can in particular be made of polypropylene, polyester, or another plastic material and their mixtures. A process for the production of a nonwoven is already known in which a moving web of filaments or fibers is compacted in the direction of the thickness at a compacting station. Compaction is obtained by passing the moving web in the nip between two movable elements moving in the same direction. One of the movable elements can be a conveyor or a cylinder and the other can also be a conveyor or a cylinder. Downstream of the compacting station, the compacted sheet is consolidated into a consolidated sheet at a consolidation station. Consolidation can be carried out by mechanical needling, by chemical or thermal bonding. Preferably, a hydraulic bonding by water jets is used.

In patent US-A-4 632 685, a process for the production of a nonwoven is described in which the two faces of the web move at first equal speeds in a couple of conveyors, then at second equal speeds, but different from the first speeds, in a second pair of conveyors. The transfer of the sheet from one couple to another poses problems of control of the structure all the more serious as the speed is high. The speed reduction takes place at a point in the path of movement of the sheet other than that where the sheet is compacted.

The nonwovens obtained have a ratio of a property in the long direction, and in particular of the tensile strength, to this same property in the cross direction, which is much greater than one. The long direction is defined by the direction in which the web moves when it is sent to the compacting station, while the cross direction is the direction perpendicular to this direction in the plane of the web. To make many industrial treatments easier and to improve the characteristics of many products, it would be desirable to reduce the ratio of a property of non- woven in the long direction to this property in the cross direction while yet the production processes of veils, sheets and sheets preferentially orient the fibers or filaments in the long direction, while having a high speed of movement and synonymous with a high productivity. The invention provides for this by a process for the production of a nonwoven in which a moving web of filaments or fibers of organic material is compacted in the direction of the thickness, at a point in its travel path at a compacting station, then the compacted sheet is consolidated into a consolidated sheet at a consolidation station downstream, in the direction of movement of the sheet, from the compacting station. According to the invention, the speed of movement of the sheet is reduced to the very point of its travel path where it is compacted.

By compacting and reducing the speed of movement of the sheet simultaneously and at the same point, the fibers or filaments which, due to compacting, cannot move perpendicular to the plane of the sheet, are forced to reorient in the direction through.

Good results have been obtained by reducing the speed of movement which is preferably between 10 and 600 m / min and preferably from 50 to 300 m / min of the sheet at the compacting point by 5 to 50% and preferably by 5 to 30%. Below 5%, the reduction in speed is hardly sufficient to appreciably decrease the ratio of the tensile strength in the long direction to the tensile strength in the cross direction. Above 50% the reorientation is so strong that the uniformity of the sheet is affected. Likewise, it is preferred to reduce the thickness of the sheet at the compaction point from 99% to 30% and, preferably, from 99% to 50%, which gives the best results for the reduction of the resistance to tensile in the long direction to the tensile strength in the cross direction.

The property whose ratio is modified in the process according to the invention is preferably the tensile strength, maximum at break, but it is also the elongation at traction or another property of traction. It has also been found that the process according to the invention makes it possible to improve the resistance of nonwovens to delamination.

According to an embodiment greatly improving the method according to the invention, the sheet is wetted at the compacting station or just downstream from this station. By this wetting, the deformation of the fibers of the tablecloth and thus preserves the relationship between the property of the nonwoven in the long direction and the property of the nonwoven in the cross direction, is obtained at the compacting station, at the outlet thereof while, without fixing by wetting, the fibers tend, after they are no longer compacted, to return, at least in part, to their initial orientation. By just downstream is meant in particular that the wetting takes place before the arrival of the sheet at the consolidation station. One can for example wet the sheet using a hydraulic injector arranged so that the jets extend substantially over the entire width of the sheet and by sending jets whose pressure is between 1 and 50 bars . Depending on the pressure used, this fixation can already have a certain consolidation effect, that is to say entanglement of the fibers. In some cases, it is wetted using a liquid other than pure water.

It is also possible, instead of or in addition to wetting the tablecloth at the compacting station, to maintain it at the exit of the compacting station until it arrives at the consolidation station or simply on part of the path between the two stations , for example by using a vacuum pressing it on a cylinder or on a conveyor.

The compacted sheet is then consolidated into a consolidated sheet at the consolidation station, which is downstream in the direction of movement of the sheet from the compacting station and downstream from the point where, if necessary, the wetting of the sheet . Consolidation can be carried out anywhere known means, in particular by mechanical needling using metal needles, by chemical bonding, by thermal bonding using hot-melt fibers and by using impregnation means such as a scarf. or a spray or foam spray with a binder. However, it is much preferable to carry out the consolidation by hydraulic binding by water jets, where appropriate in addition combined with the other binding means. Hydraulic bonding can be carried out by water jets with a diameter between 50 and 250 microns under pressures between 10 and 1000 bars.

The sheet is preferably a sheet of filaments coming from a machine operating in the melt or from a sheet of fibers coming from a nonwoven card; it can also come from a machine operating by air flow called "ugly air" or from a lapper-stretcher. The invention is particularly applicable for surface weights of 0 to 500 g / m ² and preferably 20 to 300 g / m ² of the sheet.

The invention makes it possible in particular to manufacture filtration products, geotextiles, agrotextiles in civil engineering and in construction, in the automobile, furniture, clothing, in medical applications, in roof seals, products sound and thermal insulation, dry or impregnated wiping products for household and hygiene.

The invention also relates to a machine for producing a nonwoven comprising a first element for sending a sheet to means intended to compact it in the thickness direction, characterized in that said means are also means for reducing the speed of movement of the sheet to the point where it is compacted by the compacting means. The first element is preferably a conveyor, but it can also be a cylinder fed by a conveyor.

The compacting means are produced by the formation of a pinch point between the first element and another mobile element and the reduction in the speed of movement of the sheet is achieved by giving the other mobile element a linear speed less than that of the first element. The other mobile element can be a second conveyor or a second cylinder. The nipping preferably extends over the entire width of the ply, relating to an entire generatrix of the nipping cylinder.

Preferably, the machine comprises means intended to wet the sheet while it is compacted or has just been compacted and before it arrives at consolidation means. Preferably, the consolidation means are arranged so as to consolidate the sheet as it passes over the other mobile element, since the consolidation is all the better the lower the speed of passage of the sheet to the consolidation station. . The invention finally relates to the use of a method or a machine according to the invention for reducing the ratio of a property of a nonwoven in the long direction to this property in the cross direction and more particularly for decrease the ratio of the tensile strength at break of a nonwoven in the long direction to this tensile strength at break in the cross direction. In the accompanying drawings, Figures 1 to 4 are side views of four machines according to the invention.

The machine represented in FIG. 1 comprises a conveyor comprising a frame 1 resting by four feet 2 on the ground S. This frame carries three return rollers 3, a tensioning roller 4 and a guide roller 5 for guiding a mat 6 permeable to conveyor water. Above the upper strand 7 of the conveyor is mounted a cylinder 8 of horizontal axis perpendicular to the direction of movement of the strand 7, while vertically of this cylinder 8 and below the strand 7 is mounted an injector 9 mooring. The distance between the strand 7 and the lowest point of the cylinder 8 is so small that when a sheet is conveyed and passes over the strand 7, it comes into the nip between the strand

7 and the cylinder 8 and is compacted. The tablecloth then passes along the cylinder

8 to arrive in front of two injectors 10 for consolidation by water jets. The cylinder 8 is a hollow cylinder which rotates anticlockwise while the web which passes over the strand 7 goes from left to right in the drawing. The cylinder 8 comprises a quadrant 8a between 4 hours and 6 hours, subjected to a vacuum so that the ply is pressed against the cylinder 8 from the outlet of the nip to the injectors 10.

In FIG. 2, the machine shown is preferred when the thickness of the sheet is greater than 50 mm. It comprises the same elements as the machine of FIG. 1 but, in addition, an additional conveyor carried by four feet 11 and brackets 12. The conveyor has a guide roller 13, a tensioner roller 14, a return roller 15 and the conveyor-permeable mat 15 passes around the cylinder 8 and in the nip between the cylinder 8 and the mat 7.

The machine shown in Figure 3 includes, like that of Figures 1 and 2, a first conveyor 1 to 7, identical to the conveyor of Figure 1, except that it comprises a roller 17 supporting the upper strand 7 of the carpet.

Above the strand 7 is disposed a conveyor 18 having return rollers 19, a tensioning roller 20 and a guide roller 21, the conveyor further has a return roller 22 which is in contact with the upper strand 7 of the belt of the first conveyor and which is disposed on this strand upstream of an injector 23 making it possible to wet a sheet which arrives on the belt 7 from the left to the right in the figure. The roller 17 is just downstream of the injector 23 and it is arranged in such a way with respect to the roller 22 that it maintains the strand 7 in close contact with the lower strand of the belt 24 which passes on the upper conveyor by turning anti-clockwise. The sheet is thus compressed between the upper strand 7 and the lower strand of the mat 24, is wetted at the wetting point 23 and then goes to a preliminary station 25 of consolidation by jets of water before being further consolidated on the cylinder 8 by devices 10 with water jets.

In Figure 4 rests on the ground by feet 27 a conveyor 28 having a deflection roller 29, a tensioning roller 30 and a roller 31 for guiding a mat 32 permeable to water which is wound on a cylinder 33 hollow opposite which are mounted devices 34 of consolidation by water jets. Another conveyor 35, carried by supports 36 and brackets 37, comprises on a frame three return rollers 38, a tensioning roller 39 and a guide roller 40. The conveyor carries a device 41 for spraying water which will be used for mooring. This water spraying device is vertically above the highest point of the cylinder 33. The tablecloth arrives from left to right in the figure on the upper strand of the carpet 32, passes between the cylinder 33 and the lower strand carpet 42 of the upper conveyor where it is compressed while being moistened by the device 41, comes out along the cylinder 33 to be consolidated by the consolidation devices 34, then goes to a cylinder 43 cooperating with additional consolidation devices 44. The following examples illustrate the invention.

In these examples, the following tests were carried out: a) resistance and elongation in the long direction and in the transverse 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 is used for the test, comprising a set of fixed jaws and a set of movable jaws moving at a constant speed. The jaws of the dynamometer have a useful width of 50 mm. The dynamometer is equipped with a recorder which makes it possible to trace the curve of the tensile force as a function of the elongation. 5 samples are cut of 50 mm plus or minus 0.5 mm in width and 250 mm in length, this in the long direction and in the cross direction of the nonwoven. 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 the elongation. We determine the maximum. b) 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 are cut with an area of at least 50,000 mm ² with a cutting device called a cutter. Each sample is weighed on a laboratory balance with an accuracy of 0.1% of the mass of the weighed samples.

Example 1 (comparative) A sheet of approximately 50 g / m ² composed of 100% polyester fibers of 1.7 dtex and 38 mm in length is produced at a speed of 50 m / min. by a card type card for nonwovens.

This sheet is continuously supplied to a transport and compacting conveyor of a binding system by water jets conforming to FIG. 1. The transport conveyor is a polyester fabric of permeability 800 CFM. The transport conveyor has a linear speed of 50 m / min.

The transport conveyor is in contact over a length of 10 nm with the cylinder. The speed of the cylinder is synchronized with the speed of the transport conveyor at a linear speed of 50 / min. The sheet of fibers is compacted between the transport conveyor and the binding cylinder coated with a micro-perforated envelope, the holes being arranged in a random manner, as described in French patent 2,734,285. Immediately after compacting, the sail is wet and slightly consolidated by a hydraulic injector projecting water jets of 140 microns in diameter at a speed of 54 m / s or a pressure of 15 bars. The jets being spaced from each other by a distance of 0.8 mm in two rows.

The veil thus compacted and wet and slightly consolidated is then subjected to the action of two successive hydraulic injectors projecting water jets of 120 microns in diameter at increasing speeds of 100 m / s and

133 m / s, the jets being spaced from each other by 1.2 mm in two rows.

The nonwoven thus obtained is then transferred to a suction mat connected to a vacuum generator and then dried at a temperature of 110 ° C in a through air oven.

A nonwoven weighing about 50 g / m ² is obtained. The nonwoven has a regular, uniform appearance.

Example 2 The conditions of Example 1 are repeated. For this test, the speed of the cylinder is reduced by 10% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the cylinder speed is 45 m / min. The nonwoven has a regular appearance.

Example 3 The conditions of Example 1 are repeated. For this test, the speed of the cylinder is reduced by 20% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the cylinder speed is 40 m / min. The nonwoven is regular.

Example 4 The conditions of Example 1 are repeated. For this test, the speed of the cylinder is reduced by 25% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the cylinder speed is 40 m / min.

The nonwoven is irregular and has wavy fibers in the cross direction.

Example 5 The conditions of Example 1 are repeated. For this test, the transport conveyor is no longer in contact with the cylinder. It is now tangent to it and is about 1 mm away from the cylinder. This new adjustment is obtained by lowering the idler roller of the conveyor immediately downstream of the point of tangency of the conveyor relative to the cylinder. The speed conditions are identical to Example 2 in which the speed of the conveyor is 50 m / min. and the cylinder speed is 45 m / min.

The nonwoven is regular.

Example 6 The conditions of Example 5 are repeated. For this test, the speed of the cylinder is reduced by 20% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the cylinder speed is 40 m / min. The nonwoven is regular. Example 7 The conditions of Example 5 are repeated. For this test, the speed of the cylinder is reduced by 30% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the speed of the cylinder is 35 m / min. The nonwoven is regular.

Example 8 The conditions of Example 5 are repeated. For this test, the speed of the cylinder is reduced by 40% relative to the speed of the conveyor. That is, the speed of the transport and compaction conveyor is always 50 m / min. and the cylinder speed is 30 m / min.

The nonwoven has surface irregularities, wavelets oriented in the cross direction of the web and an irregularity in its opacity.

Example 9 (comparative) A sheet of approximately 90 g / m ² composed of 65% viscose fibers of 1.7 dtex and 40 mm in length and 35% of polyester fibers of 1.7 dtex and 38 mm length is produced at a speed of 25 m / min. by a card type card for nonwovens.

This sheet is continuously supplied to a transport and compacting conveyor of a binding system by water jets conforming to FIG. 2. The installation differs from that of FIG. 1 by the addition of a conveyor upper wrapping around the cylinder.

The transport conveyor is a polyester fabric with a permeability of about 800 CFM. The transport conveyor has a linear speed of 30 m / min. The upper conveyor wrapped around the cylinder is also a polyester fabric with a permeability of approximately 500 CFM.

The transport conveyor is tangent to the second conveyor and the cylinder and is approximately 1.5 mm away from the second conveyor at the point of convergence.

The speed of the upper conveyor and the cylinder is synchronized with the speed of the transport conveyor at a speed of 25 m / min. The sheet of fibers is gradually compacted between the two conveyors immediately after compaction, the web is wet and slightly consolidated by a hydraulic injector projecting water jets of 140 microns in diameter at a speed of 63 m / s or 20 bars of pressure. The jets being spaced from each other by a distance of 0.8 mm in two rows. The veil thus compacted and wet and slightly consolidated is then subjected to the action of two successive hydraulic injectors projecting water jets of 120 microns in diameter at increasing speeds of 125 m / s and

160 m / s, the jets being spaced from each other by 1, 2 mm in two rows.

The nonwoven thus obtained is regular, uniform. Example 10

The conditions of Example 9 are repeated. For this test, the speed of the upper conveyor and of the cylinder is reduced by 20% relative to the speed of the conveyor. In other words, the speed of the transport and compaction conveyor is always 25 m / min. and the speed of the cylinder is 20 m / min.

The nonwoven is regular.

Example 11

Repeating the conditions of Example 9. For this test, the speed of the upper conveyor and the cylinder is reduced by 30% ^* relative to the conveyor speed. In other words, the speed of the transport and compaction conveyor is always 25 m / min. and the cylinder speed is 17.5 m / min.

The nonwoven is regular.

Example 12 The conditions of Example 9 are repeated. For this test, the speed of the upper conveyor and of the cylinder is reduced by 40% relative to the speed of the conveyor. In other words, the speed of the transport and compaction conveyor is always 25 m / min. and the cylinder speed is 17.5 m / min. The nonwoven is slightly irregular with a variation in its opacity which suggests a slip of fibers in the transverse direction.

Example 13 (comparative) A sheet of approximately 60 g / m ² composed of 80% of polyester fibers of 1.7 dtex and 38 mm in length and of 20% of so-called polyester / polyethylene bicomponent fibers of 3 dtex and 38 mm in length is produced at a speed of 30 m / min. by a card type card for nonwovens.

This sheet is continuously supplied to a transport and compacting conveyor XX of a binding system by water jets conforming to FIG. 1. The transport conveyor is a polyester fabric. The transport conveyor has a linear speed of 30 m / min.

The transport conveyor is tangent to a cylinder. The speed of the cylinder is synchronized with the speed of the transport conveyor at a speed of 30 M / min. The sheet of fibers is compacted between the transport conveyor and the binding cylinder coated with a micro-perforated envelope, the holes being arranged in a random manner, as described in French patent 2,734,285. Immediately after compacting, the sail is wet and slightly consolidated by a hydraulic injector projecting 140 micron diameter water jets at a pressure of 70 bars. The jets being spaced from each other by a distance of 1, 2 mm in two rows.

The veil thus compacted and wet and slightly consolidated is then transferred to a suction mat connected to a vacuum generator and then dried at a temperature of 130 ° C in a through air oven.

A nonwoven weighing approximately 60 g / m ^{2 "} is obtained. The nonwoven has a regular, uniform appearance and is bulky.

Example 14

The conditions of Example 9 are repeated. For this test, the speed of the upper conveyor and of the cylinder is reduced by 30% relative to the speed of the conveyor. In other words, the speed of the transport and compaction conveyor is always 30 m / min. and the speed of the cylinder is 21 m / min.

The nonwoven is regular and bulky.

The tests of surface mass measurement, of resistance in long direction and in transverse direction are conducted according to ERT standards of EDANA.

The following table summarizes the long direction and cross direction resistance and long direction to cross direction results obtained for each example.

Claims

1. A method of producing a nonwoven, in which a moving web of filaments or fibers, in an organic material, is compacted in the direction of the thickness, at a point in its travel path, then consolidated downstream, in a consolidation station, the sheet compacted into a consolidated sheet, characterized in that the speed of movement of the sheet is reduced at the very point of its movement path where it is compacted.

2. Method according to claim 1, characterized in that the speed of movement of the sheet is reduced from 5 to 50%.

3. Method according to claim 1 or 2, characterized in that the thickness of the sheet is reduced to compaction from 99% to 30%.

4. Method according to one of claims 1 to 3, characterized in that the web is wetted during compaction or just downstream of compaction.

5. Method according to one of claims 1 to 4, characterized in that the web is consolidated by passing it through the consolidation station at reduced speed.

6. Method according to one of claims 1 to 5, characterized in that the web is consolidated by hydraulic entanglement, by thermal bonding, by chemical bonding and / or by mechanical needling.

7. Method according to one of claims 1 to 6, characterized in that the web is a web of filaments from a machine operating in the melt or a web of fibers from a card for nonwovens or a machine operating by air called "ugly air".

8. Method according to one of claims 1 to 7, characterized in that the web is maintained by applying a vacuum to it between the point where it is compacted and the consolidation station.

9. Machine for producing a nonwoven, comprising a first element (1) for sending a sheet to means (7) intended to compact it in the thickness direction, characterized in that said means (7, 8) are also means intended to reduce the speed of movement of the sheet at the point where it is compacted.

10. Machine according to claim 9, characterized in that the compacting and speed reduction means are produced by the formation of a pinch point between the first element (7) and another mobile element (8) having a speed linear lower than that of the first element.

11. Machine according to claim 10, characterized in that the other mobile element is a conveyor or a second cylinder.

12. Machine according to one of claims 9 to 11, characterized by means (9) intended to wet the web while it is compacted or has just been.

13. Machine according to one of claims 9 to 12, characterized by means (10) for consolidating the ply arranged downstream, in the direction of movement of the ply, compacting means.

14. Machine according to claim 13, characterized in that the consolidation means are arranged so as to consolidate the sheet while it passes over the other mobile element.

15. Machine according to one of claims 13 or 14, characterized by means for maintaining the sheet by vacuum between the compacting means and the consolidation means.

16. The use of a method or a machine according to one of claims 1 to 15 to reduce the ratio of a property of a nonwoven in the long direction to this property in the cross direction.