WO1997029234A1

WO1997029234A1 - Nonwoven fabric manufacture

Info

Publication number: WO1997029234A1
Application number: PCT/GB1997/000315
Authority: WO
Inventors: Robert Michael Deeming
Original assignee: Courtaulds Engineering Limited
Priority date: 1996-02-06
Filing date: 1997-02-04
Publication date: 1997-08-14
Also published as: GB9602313D0

Abstract

A hydroentanglement apparatus comprising at least six entanglement rollers (11-17) arranged in a substantially linear array and providing a web path for a web of nonwoven fibres and at least one hydraulic jet assembly (21-27) for jetting water across the jet at each roller. The jet assemblies (21-27) are arranged so that, for each adjacent pair of rollers, water is jetted onto one side of the web as the web passes around one of the adjacent rollers and onto the other side of the web as the web passes around the other of the adjacent rollers. The invention also relates to a method of manufacturing a hydroentangled nonwoven fabric from a web of nonwoven fibres.

Description

NONWOVEN FABRIC MANUFACTURE

TECHNICAL FIELD

This invention relates to a method and apparatus for manufacturing nonwoven fabric.

BACKGROUND ART

It is well known to manufacture nonwoven fabric by introducing fibrous material into a support to provide a fibrous web and then treating the fibrous material with high pressure liquid jets, typically water jets. The treatment causes the individual fibres to entangle with each other in the fibrous web and compacts the fibres to form a paper-like nonwoven material. Such a method is known as hydroentanglement and is described in US-A-3 , 85,706 and US- A-3,508,308.

One method of manufacture of hydroentanglement fabric is described in GB-A-2, 114, 173 and comprises passing a web of fibres over a plurality of water impermeable rollers which are bombarded with water jets. The water jets act directly on the exposed side of the web with water rebounding from the rollers acting on the other side of the web.

US-A-5, 042,722 describes the use of hydroentanglement jets acting on a web supported on a porous cylindrical roller. ^"Typically cylindrical porous rollers may be used in pairs with the web being fed onto one roller for treatment on one of its sides with three or four jet assemblies before passing to the other roller for treatment on its other side by a further three or four jet assemblies. Such a system is shown in GB-A-2, 300, 429. DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided a hydroentanglement apparatus comprising a succession of at least six entanglement rollers arranged in a substantially linear array and providing a web path for a web of nonwoven fibres having opposite sides, and, associated with each roller, at least one hydraulic jet assembly arranged to jet water across the web at the associated roller, the rollers and jet assemblies being arranged so that, in use, for each pair of adjacent rollers along the web path, water is jetted onto one side of the web as the web passes around one of the adjacent rollers and onto the other side of the web as the web passes around the other adjacent roller.

A web which is treated successively on alternate faces for at least three pairs of rollers produces a web which has a good consistent surface finish which is identical on the two faces. The web also has improved mechanical properties in particular the ratio of tensile properties, when measured in the machine direction and transverse direction. This is due to controlled reorientation of the fibre in a cross-laid web.

Preferably each entanglement roller is associated with only a single jet assembly. This reduces energy consumption to a minimum and produces hydroentangled nonwoven material having good mechanical properties.

Preferably the linear surface speeds of the rollers progressively alter from one roller to the next roller along the web path. The speed will typically increase as the web passes through the apparatus.

The progressive increase in speed between adjacent successive treatment surfaces maintains the web under tension as it passes through the apparatus. This has the advantage of preventing the web from sagging, with the possible formation of creases and folds, and therefore prevents the formation of defects resulting from such creases and folds. The progressive increase in speed also:

(i) compensates for any increase in length of the web generated by reorientation of the fibres due to the action of the high pressure jets;

(ii) maintains uniformity in peeling off the fabric from the previous treatment surface and its presentation to the next successive treatment surface; and

(iii) improves the characteristics of the fabrics in the form of an enhanced ratio of machine direction/transverse direction tensile properties.

Preferably the linear surface speeds of the rollers may vary from roller to successive roller by to 50% of the previous roller speed. The increase in speed between successive rollers will be greater at the early stages of the bonding process than at the end of the bonding process.

Preferably there are at least seven, or at least eight, rollers arranged in a series, with the rotational axes of alternate rollers lying in a common first plane and with the rotational axes of the other rollers lying in a common second plane spaced from and parallel to the first plane.

Also according to the invention there is provided a hydroentangled apparatus comprising a plurality of entanglement rollers providing a web path for a web of nonwoven fibres having opposite sides, and a single hydraulic jet assembly for each roller, each jet assembly being arranged to jet water across the web at its associated entanglement roller, the rollers and jet assemblies being arranged so that, in use, for each pair of adjacent rollers along the web path, water is jetted onto one side of the web as the web passes around one of the adjacent rollers and onto the other side of the web as the web passes around the other adjacent roller, wherein the rotational axes of alternate rollers are in a common first plane, with the rotational axes of the other rollers in a common second plane spaced from and parallel to the first plane.

According to another aspect of the present invention there is provided a method of manufacturing a hydroentangled nonwoven fabric from a web of nonwoven fibres comprising passing the web through a succession of at least six rollers arranged in a linear array, each of which rollers has at least one respective jet head assembly associated therewith for jetting water onto the web as it passes around the respective roller, the web being repeatedly treated on opposite sides as it passes from roller to roller, without interruption.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described, by way of example only, and with particular reference to the accompanying drawings, in which:-

Figure 1 is a schematic view of one embodiment of hydroentanglement apparatus according to the present invention and arranged in a generally horizontal configuration; and

Figure 2 is a schematic view of another embodiment of hydroentanglement apparatus according to the present invention and arranged in a generally vertical configuration.

BEST MODES FOR CARRYING OUT THE INVENTION

The apparatus shown in Figure 1 comprises a frame (not shown) mounting a series of at last six rollers. Conveniently from six to eight generally equally spaced apart entanglement or suction rollers are mounted on the frame and, in the example shown, there are seven rollers 11- 17 with provision for adding an eighth roller. A feed roller 18 is provided for introducing a web 10 of nonwoven fibres onto the entanglement or suction rollers 11-17 and a dewatering roller 19 is provided for removing water from the web.

Each of the suction rollers 11-17 is suitably formed from a perforated, corrosion resistant material, e.g. stainless steel or bronze, which is further enclosed in a support mesh with a porous sleeve made from fine woven wire mesh. The rollers 11-17 are arranged in a substantially horizontal array and are mounted in the frame with their axes of rotation substantially parallel. The interior of each roller comprises a static vacuum chamber for the removal of water from the roller. The water is transferred via a series of pipes, filters and separators (not shown) to a reservoir for recirculation.

The rollers 11-17 are driven by electric motors lla-17a which are provided so that each roller can be separately driven at a desired linear surface speed. The speeds of the rollers are controllable directly through their respective motors, or alternatively by means of gearboxes, so that the linear surface speed of the rollers increases progressively through the apparatus from roller 11 to roller 17. The largest increase in speed is between the initial bonding rollers 11-12, and the increases in speed between the successive rollers is gradually reduced. The surface speed of the rollers may be increased in steps of 0.05ms^"1, and the maximum speed difference between successive rollers should not exceed 50% of the speed of the previous roller. Once the roller speeds have been set, all the speeds may be synchronised so that a speed change at one roller automatically causes a speed change for the other rollers so as to maintain a set ratio between the different roller speeds. In Figure 1, synchronising means are generally indicated by the dashed line 18. The increase in linear roller speeds progressively through the apparatus maintains a tension on the web 10 between successive treatment surfaces where the hydroentanglement takes place.

Associated with each suction roller 11-17 is a separate hydraulic jet head assembly 21-27, respectively, preferably of a type disclosed in WO-A-96/09426. Each jet head assembly is generally elongate and extends generally parallel to, but spaced a small distance from, its associated roller. In particular the jet head assemblies 21,23,25 and 27 are positioned to one side, in this case above, the alternate rollers 11,13,15 and 17, respectively, and the jet head assemblies 22,24 and 26 are positioned on the opposite side, in this case below, their associated alternate rollers 12,14 and 16, respectively. The jets of the jet head assemblies are directed substantially radially with respect to their associated rollers, i.e. downwards towards the turning axis of the roller concerned for the jet head assemblies 21,23,25 and 27 and upwards for the jet head assemblies 22,24 and 26.

The rollers 11-17 are arranged so that the axes of rotation of the rollers 11,13,15 and 17 lie in a common first plane and the axes of rotation of the rollers 12,14 and 16 lie in a common second plane spaced from, but parallel to, the first plane.

In use the web 10 is passed onto the feed roller 18 from a wet lay up apparatus (not shown) used to form the web from a slurry of discontinuous fibres. The web 10 is passed around part of each roller 11-17 in turn through the gaps between each roller and its associated spaced apart jet head assembly. Thus in effect the web 10 passe, over rollers 11,13,15,17 and beneath rollers 12,14,1 alternately exposing each side of the web to the action of the hydraulic jets on at least three pairs of adjacent rollers, with no interruptions to the treatment. Thus the web 10 is passed through a succession of generally equally spaced apart rollers and in repeatedly treated on alternate sides as it passes from roller to roller. On emerging from the entanglement rollers 11-17 the web 10 is fed either to a storage roller (not shown) or alternatively to a line oven for drying.

Certain speciality fibres, e.g. bulked or textured fibres, high shrink fibres, are designed to shrink under certain process conditions. During processing of these types of fibres it may be necessary for the rollers 11-17 to run at progressively decreasing speeds so as to control the shrinkage as the web passes through the successive treatments.

An alternative hydroentanglement apparatus is shown in Figure 2 in which a succession of generally equally spaced apart entanglement rollers 31-37 are arranged in a single substantially vertical array. The web 30 is fed into the array of rollers by an open mesh conveyor belt 38 which passes around a series of guide rollers 50A, 50B and 50C. The web 30 then passes downwardly along a web path through the rollers 31-37, without interruption. Although they would be provided in practice, the roller drive means and speed synchronising means of the type shown in Figure 1, have been omitted for simplicity from Figure 2.

The entanglement rollers 31,33,35 and 37 have their rotational axes lying in a common first plane and the rollers 32,34,36 have their rotational axes lying in a common second plane spaced from, and parallel to, the first plane. Thus the axes of the rollers 31-37 are positioned alternately on opposite sides of a central third plane between^", and parallel to, the first and second planes.

Jet head assemblies 41-47 are located on alternate sides of the entanglement rollers 31-37, respectively, so that, in use, water jets from the jet head assemblies are directed radially, relative to the associated rollers, towards the central third plane. As the web 30 passes from the conveyor belt 38 to the first entanglement roller 31 it moves under a curtain of water 52 from a transverse weir 51 consolidating the web. The consolidated web 30 is then passed under a prewetting jet assembly 53 where it is subjected to low pressure water jets before being passed to the entanglement jets. The guide roller 50A is a suction roller which has its axis of rotation lying in the common first plane of the entanglement rollers 32,34 and 36.

The belt 38 speed may also be adjusted relative to the linear speed of the roller 31 so that there is an increase of speed between the belt 38 and the roller 39.

The web 30 passes around each entanglement roller 31-37 between the respective roller and the associated jet head assembly. In this manner first one side and then the other side of the web 30 is exposed to the water jets as the web 30 moves along the web path form one roller to the next.

Typically the jets are spaced from 1-3 cm from the surface of the associated roller and hydraulic pressure in the jet assemblies will conveniently be in the order of 25- 250 bar. The jets suitably having a diameter of about 120 microns and are arranged linearly transversely of the web. Conveniently there are about 40 jets per linear inch (16 jets per linear centimetre) . The web suitably moves past the jet assemblies at a linear speed of from between 8 and 80 meters per minute. On emerging from the entanglement rollers 31-37 the entangled web 30 is passed over a dewatering roller 47.

Claims

1. A hydroentanglement apparatus comprising at least six entanglement rollers (11-17) arranged in a substantially linear array and providing a web path for a web (10) of nonwoven fibres having opposite sides, and, associated with each roller, at least one hydraulic jet assembly (21-27) arranged to jet water across the web at the associated roller, the rollers (11-17) and jet assemblies (21-27) being arranged so that, in use, for each pair of adjacent rollers along the web path, water is jetted onto one side of the web (10) as the web passes around one of the adjacent rollers and onto the other side of the web (10) as the web passes around the other of the adjacent rollers.

2. An apparatus according to claim 1, wherein the rotational axes of alternate rollers (11,13,15,17) are in a common first plane and the rotational axes of the other rollers (12,14,16) are in a common second plane spaced from, and parallel to, the first plane.

3. An apparatus according to claim 1 or 2, in which each entanglement roller is associated with only a single jet assembly.

4. An apparatus according to any one of claims 1 to 3, wherein drive means are provided for driving the rollers and which, in use, can be operated so that the linear surface speed of the rollers alters progressively from one roller to the next roller along the web path.

5. An apparatus according to claim 4, wherein said drive means enable the linear surface speeds of the rollers to alter from roller to roller up to a maximum of 50% of the speed of the previous roller.

6. An apparatus according to claim 5, wherein said drive means enable the linear surface speed of each roller to be altered in steps of up to 0.05ms^"1.

7. An apparatus according to any one of claims 4 to 6, including means for synchronising the speeds of all the rollers so that a change of speed in one roller causes a speed change to the other rollers in order to maintain set speed differentials.

8. An apparatus according to any one of the preceding claims, wherein all the entanglement rollers (11-17) have substantially the same circumference.

9. An apparatus according to any one of the preceding claims, wherein the rollers are arranged in a single vertical or horizontal array.

10. An apparatus according to any one of the preceding claims, comprising a conveyor belt (38) for feeding the web of fibres to the array of entanglement rollers, and means for adjusting the linear belt speed relative to the linear surface speed of the first entanglement roller.

11. A method of manufacturing a hydroentangled nonwoven fabric from a web (10) of nonwoven fibres comprising passing the web in a web path successively around at least six rollers (11-17) arranged in a substantially linear array, and jetting water onto the web from at least one jet head assembly associated with each roller so that, for each adjacent pair of rollers along the web path, water is jetted onto one side of the web as the web passes around one of the adjacent rollers and onto the other side of the web as the web passes around the other of the adjacent rollers.