Flow control within a press fabric using batt fiber fusion methods

#The present invention is directed to the field of papermaker's fabrics, particularly, a press fabric having an anti rewet barrier.

#During the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous slurry, that is, an aqueous dispersion of cellulose fibers, onto a moving forming fabric in the forming section of a paper machine. A large amount of water is drained from the slurry through the forming fabric, leaving the cellulosic fiberous web on the surface of the forming fabric.

#The newly formed cellulosic fibrous web proceeds from the forming section to a press section, which includes a series of press nips. The cellulosic fibrous web passes through the press nips supported by a press fabric, or, as is often the case, between two such fabrics. In the press nips, the cellulosic fibrous web is subjected to compressive forces which squeeze water therefrom, and which adhere the cellulosic fibers in the web to one another to turn the cellulosic fibrous web into a paper sheet. The water is accepted by the press fabric or fabrics and, ideally, does not return to the paper sheet.

#Thus by the present invention its objects and advantages will be realized the description of which should be taken in conjunction with the drawing wherein:

#FIG. 1 is a perspective view of the press fabric of the present invention.

#The manufacture of the press fabric of the present invention utilizes calendering technology. During the manufacture process, layers of staple fiber batt which may be made of polyamide, polyester, polyolefin or other material suitable for purpose, are applied and needled into the base fabric. After needling a number of batt applications, such as two or three, the fabric is subjected to a calendering process where the fiber batt is subjected to high temperatures above the melting point of the polymer material from which the fiber is made and an immediate cool-down. Compression in the calender nip can also be used. After the calendering, the fibers of the fibrous batt are flattened and glazed with very small pores (voids/holes) and almost zero permeability to air creating what will be the anti-rewet barrier of the finished press fabric. The energy applied and the pressure in the calender nip are controlled such that only the upper most surface of the fibrous batt is fused, or the entire batt present at this stage is fused. After completing the calendering processs, a hydrophilic treatment or coating is applied to the barrier layer. Subsequently, additional layers of batt material, in the form of staple fibers is applied and needled into the press fabric on top of this anti-rewet layer. Batt can also be applied to the backside of the base support structure of the press fabric.

#FIG. 1 shows the press fabric 10 of the present invention. Base layer 12 is shown as a woven fabric, and can be formed by any means known to the skilled artisan. Fibrous batt 14 is attached to the base layer by needling. Fibrous batt 14 is in actuality constructed of a plurality of carded layers of batt staple fiber which has been needled to the base fabric.

#Within the interior of the fibrous batt 14, fibrous barrier layer 16 is formed. This layer is formed by the above noted technique, i.e., by calendering fibrous batt 14. A hydrophilic treatment, such as a hydrophilic coating or treatment 18 may optionally be applied to the fused barrier layer 16 preferably by spraying, or any other means suitable for purpose. Other coatings may be applied as well. Additional layers of fibrous batt 20 are applied by needling subsequent to the calendering of the fibrous batt 14.