Patent Application
20130078368
The present invention is directed towards a fabric used in combination with a melt-bonding apparatus to form, transport and bond a web into a non-woven fabric.
There presently exists apparatus for the production of spun-bond webs, structures or articles formed from filaments or fibers typically made from a thermoplastic resin. Such an apparatus is disclosed in U.S. Pat. No. 5,814,349 issued Sep. 29, 1998, the disclosure of which is incorporated herein by reference. These typically include a spinneret for producing a curtain of strands and a process-air blower for blowing process air onto the curtain of strands for cooling the same to form thermoplastic filaments. The thermoplastic filaments are then typically, aerodynamically entrained by the process air for aerodynamic stretching of the themoplastic filaments which are then, after passing through a diffuser, deposited upon a continuously circulating sieve belt for collecting the interentangled filaments and forming a web thereon. The web, structure or article, so formed, is then subject to further processing.
Apparatus of this type, particularly for high-speed melt-bond web production are currently available from Reifenhäuser GmbH Co. Maschinenfabrik, Spicher Strabe D-53839 Troisdort, Germany and sold under the name Reicofil®. The latest generation of such high-speed spun-bond lines is referred to as the Reicofil® 3 type system.
Another manufacturer of such equipment is Nordson Corporation, 28601 Clemens Road, Westlake, Ohio 44145. Other manufacturers are STP Impianti, Rieter Perfojet, Kobelco, Ason and NWT.
During the forming process, a high air flow volume is used to deposit the fibers on the forming fabric. This air volume is drawn through the forming fabric typically by vacuum boxes positioned thereunder. Oftentimes the area around the nip of the press rolls is rendered air tight to avoid any disturbance thereabout. Typically, four press rolls are involved which are a pair of top and bottom rolls through which the forming fabric with the web thereon passes. The air volume is provided between the successive nips.
In high speed operations with high air flow, air leakage can occur between the top press roll and the forming fabric surface or through the fabric itself. Air leakage can result in undesired disturbance to the formation of the web. Excessive air carried by the fabric during web transportation may result in causing the web to flutter. The cause of such air being carried is divided between the fabric's permeability and the fabric roughness and raw material. The proportions are on the order of 80% to 20% air respectively.
Accordingly, it is desirable to minimize air leakage particularly such leakage which is caused by the movement of the forming fabric.
In addition, in a melt-bonding process (which incidentally can produce spun-bond or melt-blown or any combination of the two), there is a large amount of static electricity generated. Normally a negative charge builds up on the filaments or fibers as they are being processed. Successive layers of fibers, since they are the same polarity, tend to repel each other. Charged fibers tend to cling to the press rolls. They also tend to be repelled from the forming fabric, since it will develop a charge thereon during the processing of the charged fibers. This charge tends to accumulate.
In European Patent Application No. EP 0 950 744 A1 it proposes using press rolls having a dielectric surface which is charged with a polarity that will repel the fibers. The forming fabric is also made from a dielectric material and charged such that it is opposite to that of the fibers, thereby attracting the fibers thereto.
In summary, during the production of the non-woven web, structure or article provisions of some nature need to address the electric charges that are typically generated whether it be to dissipate them or use them in an advantageous fashion as disclosed in the aforesaid application.
It is therefore a principal object of the invention to provide for the production of non-woven webs, structures or articles through, for example, the melt-bonding process, which minimizes air leakage, particularly that caused by the forming fabric.
It is a further object of the invention to provide for a forming fabric for the production of non-woven webs, structures or articles that minimizes or eliminates web flutter.
A yet further object of the invention is to provide for a forming fabric for use in the production of non-woven webs, structures or articles which provides for the effect of static electricity during production.
These and other objects and advantages are achieved by the present invention. In this regard the invention is directed towards generally a forming fabric for use in the production of non-woven webs, structure or articles. The forming fabric comprises a woven structure having flat monofilament yams in at least either the machine direction or cross machine direction. The use of the flat yarns in the forming fabric improve the fabric surface and decrease the empty volume in the fabric. The forming fabric may be single or multi-layered and is directed towards decreasing the disturbance caused by air whilst maintaining the desired permeability of the fabric. In addition, so as to address the static electricity problem, the flat monofilaments can be made of a conductive material which allows the dissipation of the static electricity on the web through the forming fabric to ground.
Thus by the present invention, its objects and advantages will be realized, the description of which should be taken in conjunction with the drawings wherein:
Turning now more particularly to the figures where like elements will be similarly numbered,
Intermediate the presses 14 and 16 is a melt-bonding apparatus 30 which typically includes a spinneret, blower, attenuator and diffuser which produces and deposits the filaments onto forming fabric 12. Air flow is indicated by arrow 32. Beneath apparatus 30 is a vacuum or suction box 34 which applies suction to the underside of fabric 12. The area between presses 14 and 16 may be sealed which may be in a manner as set forth in U.S. Pat. No. 5,814,349 so as to avoid any disturbance.
Air leakage can result in a disturbance of the web. As shown in
As can be seen in
The present invention is directed towards providing in combination with a melt-bonding apparatus, a forming fabric which reduces the empty volume for carrying air and reduces the fabric roughness. In this regard, as shown in
This can also be readily seen in comparing
Note that the flat yarns have been illustrated generally. The cross section of the yarns may vary, for example, the ratio between the thickness and the width could be from 1/1 to 1/5. Also, while shown as rectangular in shape (i.e. having parallel sides), they can be barrel-shaped (i.e. parallel sides with slightly curved top and bottom) or ellipitcal shape.
As for the material used for the flat yarns, it can be any material suitable for the purpose. Note, however, as aforenoted during the operation of the melt-bonding machines, a large amount of static electricity builds up. In order to dissipate it, some of the yarns used in the fabric can be conductive. Accordingly, it is desirable that a portion of the flat CMD yarns and/or MD yarns be made of a conductive material or coated with a conductive material in order to dissipate the static electricity from the web 28 to the ground, through the fabric 12′.
Accordingly, the fabric 12′ of the present invention is a woven, single or multi-layer structure having flat CMD and/or MD with a portion of which are conductive. Such a fabric 12 reduces air disturbance during spun-bonding production whilst providing a desired permeability in the web production process.
Although a preferred embodiment has been disclosed and described in detail herein, its scope should not be limited thereby; rather its scope should be determined by that of the appended claims.
This application is a continuation of U.S. patent application Ser. No. 13/018,053 filed Jan. 31, 2011 which is a continuation of U.S. patent application Ser. No. 10/142,512 filed May 9, 2002, now abandoned, the disclosures of which are herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13018053 | Jan 2011 | US |
| Child | 13602972 | US | |
| Parent | 10142512 | May 2002 | US |
| Child | 13018053 | US |
