DE19939084C1 - Continuous fleece manufacture, by splitting sheet to form endless network structure of coherent fibers, employs suction and directly-looped spreading to form structure held by binders - Google Patents

Abstract

The network comprises sheet fibers introduced into a conically enlarging air channel. It is entrained by an airflow driven by suction, simultaneously spreading it. In this form it is laid in a loop onto a recirculating sieve belt to make a fibrous sheet layer. This has an adjustable weight per unit area and high uniformity. Following conventional treatments, the layer is consolidated to a fleece. The network comprises a structure of sheet fibers (9), which are introduced into a conically enlarging air channel (5). It is entrained by an airflow driven by suction, simultaneously spreading it out. In this expanded form it is laid in a looped formation onto a recirculating sieve belt to make a fibrous sheet layer (11). This has an adjustable weight per unit area and high uniformity. Following conventional mechanical and/or chemical and/or thermal treatments, the layer is consolidated to a fleece. An Independent claim is included for corresponding equipment used to manufacture the fleece. It includes a fibrillator (2), a spreader (3), an air channel, a sieve conveyor belt (6), and a blower (8) connected for suction. The front wall of the air channel (5) is perpendicular, The angle ( alpha ) between the channel walls (5a, 5b) is 7-12 deg .

Description

The invention relates to a process for the continuous production of nonwovens from splicable film, the to an endless, mesh-like film structure is split. Foil nonwovens are used primarily in the technical sector.

There are numerous ways of processing foils or foil flat threads Knitting machines known. Flat film threads as warp threads, as weft threads and as sewing threads z. B. for the production of packaging materials, geotextiles or car upholstery materials used. For example, in DE 28 11 986 the processing of film is used instead described by weft threads. Here, the film is shot back and forth in a back and forth Movement of the stitch formation site supplied. The processing of threads in longitudinal and transverse direction, e.g. B. on sewing machines, has the disadvantage that no cross Connections of the individual transverse foil threads are present, so that the cross-laid foil threads do not bring their own share of the longitudinal strength in the knitted fabric.

Furthermore, the production of split fibers by the fibrillation of a film based on Polypropylene and polyethylene are known. The stretching of the extruded film and the Treatment with a needle roller ensures this fibrillation. The fibrillated fibers can u. a. for the production of geotextiles, nets, structural textiles and the Reinforcement of cement can be used.

FR 2 160 738 describes a process for continuous production of nonwovens made of fibrillated film. The film is extruded, thermally stretched fibrillated and fed to a mechanical layer. The fleece is formed exclusively mechanically by longitudinal or transverse paneling of the foil net. The slide layered, but not looped.

It is also known to use nonwoven fabrics with a mass-related proportion of 5 to 50% to produce so-called binding fibers. These binding fibers consist entirely or partially made of a low-melting polymer and with the appropriate exposure to heat in the pile, fleece or nonwoven at the points of contact with each other or with the others Fibers fixed glue or connection points. The binding fibers are used in the nonwoven production in the field of fiber dissolution and fiber mixing with the other fibers mixed. About the work stages of pile formation, fleece laying and / or mechanical Solidification by needles, sewing or swirling with air or water jets the use of binding fibers results in an addition during subsequent thermal treatment consolidation or the pile or the fleece is directly in the form of a thermal treatment the so-called thermal bonding fed and thus solidified to the nonwoven.  

The use of binding fibers is disadvantageous in terms of material and time Production of the binding fibers themselves and for the additional mixing passages. In addition, this classic binder fiber admixture has a limit in the processable Fineness, which is at most 1 dtex and no functional arrangement of the binding fibers allowed in one or more levels (layers) of the nonwoven cross section.

In the patent DD 128 959, the production of a textile composite from fissile Described film and a nonwoven, both components by needling are connected. Here is due to the sandwich-like arrangement of the splittable film despite of the needle composite no binding fiber effect can be achieved. The same applies to the in DD 128 959 described composite.

DE 198 59 782 C1 discloses a strip-like flat binding element laid up the batt. The cross paneling of the fiber web to the nonwoven creates in Fleece cross-section a flat binding layer, from which during the subsequent solidification of the Fleece to the nonwoven mechanically, for example by needles or water jets, fibrous binding elements in the fleece cross section are arranged. This results in mechanical distribution of the fibrous binding elements in certain applications unwanted compaction of the nonwoven. This also requires effective insertion of fibrous binding elements mostly mechanical nonwoven bonding.

Starting from the prior art set out, it is the object of the present invention to develop a process with which a foil nonwoven fabric can be produced in a simple manner can be produced cost-effectively. The task must be solved according to the invention, a targeted guiding and depositing of the spliced film until solidification to the nonwoven.

According to the invention this is achieved by the characterizing features of claim 1. The split into a network-like coherent fiber structure The film is sucked off from the splitting device by means of air flow and spread at the same time, then the spread fiber structure in the required thickness in layers circulating sieve belt and then a system for mechanical, chemical or thermal consolidation is supplied to a nonwoven. With the The inventive method, it is possible to the spliced film without expensive  Steps and additional devices directly into a fleece-like layer to lay the appropriate thickness in a loop and then to a nonwoven solidify. Another major advantage is that when splicing the film resulting cross-connections are present in the film fiber layer and also in Non-woven cross-section are preserved, and through the loop-shaped shelf balanced ratio of longitudinal and transverse strength is achieved, so that the use of Nonwoven film for extensive areas of application, especially in the technical sector is guaranteed. Furthermore, the cross-sectional area of the nonwoven can be variable be designed so that the optimal cross-sectional area for every purpose can be generated. Further advantageous embodiments of the method according to the invention and the device used to carry out the method are in the Subclaims included.

Embodiment

The invention is explained in more detail below using an exemplary embodiment. The accompanying drawing shows the schematic cross section of the device for Implementation of the manufacturing method according to the invention.

To carry out the method according to the invention, a monoaxially stretched film 1 with a thickness of 25 μm and a width of 0.5 m, consisting of a mixture of 70% polyester and 30% high-pressure polyethylene, is continuously fed from a drain rack according to the device shown in the drawing Fibrillator 2 supplied. In the fibrillator 2 , the film 1 is spliced by means of a needle roller, the film running at an angle of 15 ° to the horizontal of the needle roller. The ratio of the rotational speed of the needle roller and take-off roller on the fibrillator is 1.6: 1. The pitch of the needle roller is preferably 20 needles per cm. The spliced foil tape 9 coming from the fibrillator 2 is characterized in that the fineness of the filaments formed by the splicing process is between 1.3 and 1.9 tex and the filaments are connected to one another at a distance of 4 to 7 cm by crossbars. The length of the fiber elements delimited by the cross connections and the fineness of the fiber elements are determined in each case by the type of film used, the splicing technology and the aerodynamic conditions in the air duct 5 . The use of rubberized rollers causes the spliced film strip 9 to be charged electrostatically, as a result of which it can be spread up to 1.5 to 2 times its initial width. After fibrillation the spliced pre-spread band of film 9 is additionally spread by suitable devices 3, for example spherically shaped rolls, curved bars or the like., That is, the film strip 9 is pulled apart cm to a width of about 80 to 100. In this spread form, the film strip 10 is fed to an air duct 5 , the duct walls 5 a; 5 b are arranged symmetrically and at an angle α between 7 ° and 12 °. In another embodiment, the front channel wall 5 a can also run vertically. The air is extracted below the circulating sieve belt 6 and is infinitely adjustable with regard to the volume flow and the suction cross section. The cross section of the air outlet opening 5 c on the air duct 5 is fully opened in the working direction by means of a slide 12 and reduced by 10% on both sides in the transverse direction. The air flow at the belt inlet is in the turbulent or in the transition area from the turbulent to the laminar flow state.

From the suction air flow, the speed of which is set at the narrowest cross section to 2100 m / min, the film strip 10 guided into the air duct 5 is detected. At the same time, it is spread further and thus placed on the rotating sieve belt 6 in a loop shape to form a film fiber layer 11 with an adjustable basis weight and high uniformity. The nonwoven layer 11 is deposited in a width of up to 2.40 m, depending on the required width of use of the nonwoven. As a result, the film sheet 1 provided can be 75 to 80% narrower than the nonwoven fabric width achieved. The mass per unit area is determined by the ratio of film feed speed and tape run-off speed. At a deposition belt speed of 8 in / min, for example, a fleece with a mass per unit area of 150 g / m ^{2 is} produced. By reducing the conveyor belt speed to 2 in / min, the mass per unit area increases to 600 g / m ² .

The deposited film fiber layer 11 is then fed continuously to one of the known consolidation systems 7 , for example a needle machine for mechanical consolidation to form a nonwoven fabric. For thermal consolidation, binder fibers, binders or the like can be metered in in any amount above the film feed point and evenly distributed in the film fiber layer 11 by the air flow.

List of the reference symbols used

1

fed film

2nd

Fibrillator

3rd

Spreader

4th

Deflection roller

5

Air duct

5

a;

5

b channel walls

5

c Air outlet opening

6

Screen belt

7

Consolidation unit

8th

Suction fan

9

fibrillated foil tape

10th

spread foil tape

11

Foil layer

12th

Slider

Claims (12)

1. A process for the continuous production of nonwovens from splicable film, which is split into an endless, network-like continuous film fiber structure , characterized in that the network-like film fiber structure ( 9 ) is supplied to a conically widening air channel ( 5 ), in which it from a suction air stream is recorded and spread at the same time, and in this spread form is placed in a loop on a rotating sieve belt ( 6 ) to form a film fiber layer ( 11 ) with an adjustable basis weight and high uniformity and is then consolidated into a nonwoven fabric by known mechanical and / or chemical or thermal processes . 2. The method according to claim 1, characterized in that the width of the film strip ( 1 ) submitted must only be 20 to 30% of the desired nonwoven width. 3. The method according to claim 1 and 2, characterized in that the film sheet ( 1 ) is preferably used with a thickness of up to 60 microns. 4. The method according to claim 1 to 3, characterized in that the length of the fiber elements delimited by the cross-connections and the fineness of the fiber elements is determined by the type of film used ( 1 ), the splicing technology and the aerodynamic conditions in the air duct ( 5 ). 5. The method according to claim 1 to 4, characterized in that the spliced film strip ( 9 ) can be electrostatically charged by the use of rubber rollers and spread up to 2 times its initial width. 6. The method according to claim 1 to 5, characterized in that the spliced film strip ( 9 ) before entry into the air channel ( 5 ) by spreading elements ( 3 ), such as spherical rollers, bent rods or the like., Can also be spread. 7. The method according to claim 1 to 6, characterized in that the air flow on Belt entry or in the narrowest air duct cross section in turbulent or in Transition area from the turbulent to the laminar flow state.   8. The method according to claim 1 to 7, characterized in that the air suction takes place below the sieve belt ( 6 ) and is infinitely adjustable with respect to the volume flow and the suction cross section. 9. The method according to claim 1 to 8, characterized in that the basis weight of Nonwoven fabric by the ratio of film feed and tape run-off speed is determined. 10. The method according to claim 1 to 9, characterized in that in the sucked Air flow above the film feed point additional binding elements, for example Binding fibers, binders or the like, supplied and evenly in the fleece by the air flow can be distributed. 11. Device for the continuous production of nonwoven film from splicable film according to claims 1 to 9 with a fibrillator, a spreading device, an air duct, an air-permeable storage belt and a suction fan, characterized in that the front wall ( 5 a) of the air duct ( 5 ) is arranged vertically and the angle between the two channel walls ( 5 a; 5 b) is between 7 ° and 12 °. 12. The device according to the preamble of claim 11, characterized in that both air duct walls ( 5 a, 5 b) are arranged symmetrically and the angle (α) between the two duct walls ( 5 a, 5 b) is 7 ° to 12 °.