APPARATUS AND METHOD FOR PRODUCING NONWOVENS

Abstract

Apparatus for producing nonwovens, comprising a card drum (1) rotated in a first direction of rotation, a transfer cylinder (2) rotated in a second direction of rotation opposite to the first direction of rotation, at least one doffer (3, 4), at least one condenser (5, 6), at least one stripper roll (7, 8), a first endless conveyor belt (9), a suction drum (10) and a second endless conveyor belt (10).

Claims

1. Apparatus for producing nonwovens in a drylaid process in which fibres travel in a travelling direction, comprising: a card drum (1) rotated in a first direction of rotation and at a first circumferential rotational speed by a first driving means, producing a fibre web in the process, characterised in that the apparatus comprises, immediately downstream of the drum (1) in the direction in which the fibres travel in the apparatus, a transfer cylinder (2) rotated in a second direction of rotation, opposite to the first direction of rotation, and at a second circumferential rotational speed by a second rotation means, the second circumferential rotational speed being greater than the first circumferential rotational speed, the transfer cylinder (2) having, on a periphery, a lining (G) comprising a plurality of teeth (16) that are angled with respect to a radius of the transfer cylinder (2) and are oriented in the second direction of rotation, and, immediately downstream of the transfer cylinder (2), a system that comprises, immediately sequentially in a travelling direction, at least one doffer (3, 4), at least one condenser (5, 6), at least one stripper roll (7, 8), a first endless conveyor belt (9) with an upper side, a suction drum (10), and a second endless conveyor belt (11) with an upper side, the suction drum (10) being adjacent to the upper side of each of the first and second conveyor belts (9, 11) and ensuring the fibres pass from one to the other.

2. The apparatus according to claim 1, characterised in that a ratio of the second circumferential rotational speed to the first circumferential rotational speed is greater than or equal to 1.2.

3. The apparatus according to claim 2, characterised in that a diameter of the transfer cylinder (2) is less than a diameter of the card drum (1).

4. The apparatus according to claim 2, characterised in that a tilt angle of the teeth (16) with respect to a radius of the teeth (16) is between 70° and 80° and a radial height of the teeth (16) is between 0.7 and 1.5 mm.

5. The apparatus according to claim 1, characterised by a suction cylinder (12) adjacent to the upper side of the second endless conveyor belt (11).

6. The apparatus according to claim 1, characterised in that a ratio of a circumferential speed of the at least doffer (3, 4) to that of a circumferential speed of the cylinder (2) is between 0.10 and 0.20, wherein a ratio of a circumferential speed of the at least one condenser (5, 6) to the circumferential speed of the at least one doffer (3, 4) is between 0.35 and 0.55, wherein a ratio of a circumferential speed of the at least one stripper roll (7, 8) to the circumferential speed of the at least one condenser (5, 6) is between 1.50 and 1.75, wherein a ratio of a speed of the first endless conveyor belt (9) to the circumferential speed of the at least one condenser (5, 6) is between 0.95 and 1.10, wherein a ratio of a circumferential speed of the drum (10) to a speed of the first endless conveyor belt (9) is between 0.70 and 0.90, and wherein a ratio of a speed of the second endless conveyor belt (11) to the circumferential speed of the drum (10) is between 0.70 and 0.90.

7. The apparatus according to claim 5, characterised in that a ratio of a circumferential speed of the suction cylinder (12) to that of the second endless conveyor belt (11) is between 0.75 and 1.05.

8. A nonwoven product based on artificial and/or synthetic fibres, having a weight between 45 and 80 g/m.sup.2, wherein the fibres have a titre between 1.3 and 2.2 dtex, a length between 30 and 50 mm, a ratio of strength in a machine direction to strength in a cross direction from 1.0 to 1.5, an elongation in the machine direction between 35 and 70%, and an elongation in the cross direction between 70 and 130%.

9. The nonwoven product according to claim 8, characterised in the fibres are made of viscose, lyocell, polyester or polypropylene.

10. A method for producing nonwovens in a drylaid process in the apparatus according to claim 1, characterised in that the apparatus is operated at the following speed ratios: a ratio of a circumferential speed of the at least one doffer (3, 4) to a circumferential speed of the cylinder (2) is between 0.10 and 0.20; a ratio of a circumferential speed of the at least one condenser (5, 6) to the circumferential speed of the at least one doffer (3, 4) is between 0.35 and 0.55; a ratio of a circumferential speed of the at least one stripper roll (7, 8) to the circumferential speed of the at least one condenser (5, 6) is between 1.50 and 1.75; a ratio of a speed of the first endless conveyor belt (9) to the circumferential speed of the at least one condenser (5, 6) is between 0.95 and 1.10; a ratio of a circumferential speed of the drum (10) to the speed of the first endless conveyor belt (9) is between 0.70 and 0.90; and a ratio of a speed of the second endless conveyor belt (11) to the circumferential speed of the drum (10) is between 0.70 and 0.90.

11. The method according to claim 5, characterised in that a ratio of a circumferential speed of the suction cylinder (12) to a speed of the second endless conveyor belt (11) is between 0.75 and 1.05.

12. The apparatus according to claim 1, characterised in that a diameter of the transfer cylinder (2) is less than a diameter of the card drum (1).

13. The apparatus according to claim 5, characterised in that a ratio of a circumferential speed of the at least one doffer (3, 4) to a circumferential speed of the cylinder (2) is between 0.10 and 0.20, wherein a ratio of a circumferential speed of the at least one condenser (5, 6) to the circumferential speed of the at least one doffer (3, 4) is between 0.35 and 0.55, wherein a ratio of a circumferential speed of the at least one stripper roll (7, 8) to the circumferential speed of the condenser (5, 6) is between 1.50 and 1.75, wherein a ratio of a speed of the first endless conveyor belt (9) to the circumferential speed of the at least one condenser (5, 6) is between 0.95 and 1.10, wherein a ratio of a circumferential speed of the drum (10) to the speed of the first endless conveyor belt (9) is between 0.70 and 0.90, and wherein a ratio of a speed of the second endless conveyor belt (11) to the circumferential speed of the drum (10) is between 0.70 and 0.90.

14. The apparatus according to claim 13, characterised in that a ratio of a circumferential speed of the suction cylinder (12) to the speed of the second endless conveyor belt (11) is between 0.75 and 1.05.

15. The apparatus according to claim 2, characterised in that the ratio of the second circumferential rotational speed to the first circumferential rotational speed is greater than or equal to 1.3.

16. The nonwoven product according to claim 8, wherein the fibres have an elongation in the machine direction between 40 and 60%.

17. The nonwoven product according to claim 8, wherein the fibres have an elongation in the cross direction between 90 and 125%.

Description

[0032] In the accompanying drawings, provided solely by way of example:

[0033] FIG. 1 is a diagram of an apparatus according to the invention, while

[0034] FIGS. 2 and 3 are larger-scale views of the teeth of the lining of the transfer cylinder.

[0035] The apparatus in FIG. 1 comprises at least one card drum 1 driven by its own motor, and a transfer cylinder 2 which is rotated by its own motor and unloads all the fibres from the surface of the drum 1. Following said transfer cylinder 2, one or two doffers 3 and 4, driven by their own motor, take the fibres off the surface of the transfer cylinder 2. Next are the condensers 5 and 6 and the stripper rolls 7 and 8, which are driven by their own motor; then comes a transfer to a conveyor belt 9. The apparatus then comprises a suction drum 10 for condensing and transferring, arranged between the conveyor 9 and an input conveyor belt 11 for a water-jet consolidation apparatus. Advantageously, the water-jet consolidation apparatus conforms to that described in European patent no. 1 554 421. It comprises a first water-jet consolidation cylinder 12, which is tangential to the belt 11 and comprises a pre-wetting injector 13 arranged substantially at the point of transfer between the belt 11 and the cylinder 12 and the consolidation injectors 14 and 15. This first consolidation cylinder 12 may be followed by other water-jet consolidation cylinders, in order to impart better strength on the nonwovens thus produced.

[0036] The various rotating components of the apparatus are driven by their own motor, which are illustrated in FIG. 1 by the arrows indicating the directions of rotation for the two of them the furthest downstream in the division direction of the card web.

[0037] The distance between the drum 11 and the belt 9 and between the belt 11 and the cylinder 12 is between 2 and 15 mm.

[0038] In FIGS. 2 and 3, the transfer cylinder 2 is fitted, on its periphery, with a metal lining G. This lining G is composed of a plurality of teeth 16. In FIG. 2, the double arrow L represents the direction parallel to the longitudinal axis of the transfer cylinder 2, i.e. the direction orthogonal to the plane of FIG. 1. FIG. 3 is a sectional view of the lining of the transfer cylinder 2 in a plane transverse to the longitudinal axis thereof. The teeth 16 of the lining G are aligned in the form of adjacent rows parallel to the longitudinal axis of the transfer cylinder 2. FIG. 2 only shows two adjacent rows of teeth 16. Each tooth 16 of the lining G is angled with respect to the radius of the transfer cylinder 2 at an angle A and faces in the direction of rotation of the cylinder 2 (circumferential speed). The circumferential distance e between two points on two neighbouring teeth is equal to 1.80 mm. The axial length H of a tooth is equal to 1.20 mm.

[0039] The following examples illustrate the invention.

EXAMPLE 1 (COMPARATIVE)

[0040] A fleece weighing approximately 60 g/m.sup.2, composed of 50% polyester fibres of 1.7 dtex measuring 38 mm in length and of 50% viscose fibres of 1.7 dtex measuring 40 mm in length, is produced at a speed of approximately 78 m/min at the cylinder 12.

[0041] For this test, the card is a conventional card without a drum 2 and is controlled according to the optimum production settings for producing nonwovens. The speeds of each component are set out in the table further below.

[0042] The bonding cylinder 12 is covered with a microperforated sleeve as described in French patent no. 2 734 285. The fleece is first wetted by an injector 13 that projects water jets of a diameter of 140 micrometres at a pressure of 10 bar, the jets being spaced apart from one another by 0.9 mm in two rows. The fleece thus wetted and slightly consolidated is then subjected to the action of a series of two hydraulic injectors 14 and 15 that project water jets of a diameter of 120 micrometres at increasing pressures of 70 bar and 90 bar, the jets being spaced apart from one another by 1.4 mm in two rows.

[0043] The bonding cylinder 12 is followed by another bonding cylinder (not shown), which is covered with the same microperforated sleeve as the cylinder 12 and fitted with an injector that projects, on the opposite face to the injectors 14 and 15, water jets of a diameter of 120 micrometres at a pressure of 100 bar.

[0044] The nonwoven thus obtained is then transferred to a suction belt connected to a vacuum generator, and then dried at a temperature of 140° C. in a through-air dryer.

[0045] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance.

EXAMPLE 2 (COMPARATIVE)

[0046] The conditions of example 1 are repeated using an apparatus according to the invention, which now comprises a cylinder 2, but the apparatus is operated at the speeds indicated in the table further below.

[0047] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance but the MD/CD ratio is poor.

EXAMPLE 3

[0048] The conditions of example 2 are repeated. For this test, the speeds of the various components are modified according to the table further below.

[0049] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance and a satisfactory MD/CD ratio.

EXAMPLE 4

[0050] The conditions of example 2 are repeated. For this test, the speeds of the various components are modified according to the table further below.

[0051] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance and an even better MD/CD ratio than in example 3.

EXAMPLE 5

[0052] The conditions of example 2 are repeated. For this test, the speeds of the various components are modified according to the table further below.

[0053] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance and an even better MD/CD ratio than in example 4.

EXAMPLE 6

[0054] The conditions of example 2 are repeated. For this test, the speeds of the various components are modified according to the table further below.

[0055] A nonwoven weighing approximately 60 g/m.sup.2 is obtained. The nonwoven has a uniform appearance and an MD/CD ratio of 1.2, which is altogether exceptional and unexpected.

EXAMPLE 7 (COMPARATIVE)

[0056] Example 1 is repeated using a conventional card not having a transfer cylinder, while applying the speed ratios in example 5 for the doffers up to the cylinder 12. The nonwoven produced has numerous creases in the transverse direction and is unusable or unsellable.

TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Elements Units 1 2 3 4 5 6 Drum 1 m/min 1,300 850 850 850 850 850 Drum 2 m/min 0 1,450 1,450 1,450 1,450 1,450 Doffer 3 m/min 78 78 96 120 146 177 Doffer 4 m/min 77 77 96 120 146 177 Condenser 5 m/min 38 38 45 56 68 83 Condenser 6 m/min 38 38 45 56 68 83 Stripper roll 7 m/min 74 74 74 92 112 136 Stripper roll 8 m/min 74 74 74 92 112 136 Conveyor 9 m/min 74 74 74 93 113 137 Drum 10 m/min 75 75 75 74 90 109 Conveyor 11 m/min 75 75 75 74 73 89 Cylinder 12 m/min 79 79 79 78 77 77 Basis weight g/m2 60.5 60.5 60.0 60.2 60.0 60.4 MD tensile N/50 mm 110.0 103.0 101.3 86.2 79.8 62.9 strength CD tensile N/50 mm 26.2 36.3 41.5 44.8 52.0 54.3 strength MD elongation % 28.9 36.5 42.8 51.2 52.8 59.0 CD elongation % 135.0 125.7 124.8 110.0 108.0 99.8 MD/CD ratio N/A 4.2 2.8 2.4 1.9 1.5 1.2 MD stands for machine direction; CD stands for cross direction. The unit m/min is the unit for the circumferential speed of the various components forming the apparatus.