Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Nonwoven fabric has an elastic quality
Reexamination Certificate
2000-12-20
2004-06-15
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Nonwoven fabric has an elastic quality
C028S103000, C028S104000, C028S107000, C028S116000, C028S112000
Reexamination Certificate
active
06750166
ABSTRACT:
The invention concerns a procedure to make a fleece consisting of fibers with numerous hole structures extending over the entire cross-section, and a fleece manufactured according to this procedure.
One-layer or multilayer fleeces with hole structures extending over the entire cross-section are e.g. used for coverstock materials for articles of hygiene such as sanitary napkins and diapers, or for other textile or technical uses. The hole structures serve to quickly drain bodily fluids, tissue components and feces into the liquid-absorbing material of diapers, sanitary napkins, etc. Depending on the application, the fleeces can be single-layer or multilayer, whereby multilayer fleeces can be bonded with other sheet media such as films.
There are several prior-art procedures to introduce hole structures into a one-layer or multilayer fleece, whereby the common element of the prior-art procedures is that the hole structures are created in the finished fleece after bonding and especially thermobonding.
For example, a prior-art procedure in EP 0 687 757 A2 introduces hole structures into the bonded fleece by passing the fleece between heated stamps that are pressed together to melt holes in the bonded fleece. A similar prior-art procedure, a hot-needle punching procedure, is in U.S. Pat. No. 5,709,829.
The advantage of this procedure is that the bond of the fleece structure is held due to the melted edges that arise around the holes. A disadvantage is that the softness is negatively influenced by the relatively hard melted edges. A fleece obtained in this manner feels relatively hard and can be unpleasant to users.
In DE 34 16 004 A1, there is a prior-art process in which an unbonded fleece of thermoplastic fibers is fed to a calender roller arrangement, and the thermoplastic material is melted and displaced by pressure in the area of the holes by the calender roller arrangement. This produces a liquid bump at the edge of the holes to form a bonded grid to stabilize and fix the remaining fleece sheet. A hard melted edge is specifically created to reinforce the fleece sheet which is positive for the strength of the fleece sheet, but is disadvantageous due to the hardness of the melted edges.
In another prior-art procedure, the hole structures are created by (cold) stamping/cutting the fibers out of the bonded fleece. Such procedures have the advantage that hard stamped or melted edges do not arise, and materials obtained in this manner are soft. A disadvantage is that this procedure can only be done when the fleece is conveyed at a slow speed. In addition, the fibers are shortened along the holes which decreases the strength of the fleece.
A disadvantage of the cited procedures is that material is unnecessarily destroyed or wasted by hot and cold stamping or burning.
In another prior-art procedure in EP 0 214 608 A2, the fleece is manufactured and the hole structures are created by two rollers between which the fleece is guided. One roller has numerous heated needles, and the other roller has corresponding holes to receive the needles of the first roller. The needles purportedly displace the fibers while forming the hole structures and simultaneously form recesses around the hole structures, and they seal the edges of the hold structures by melting the fibers. In this procedure, the fibers are not shortened or destroyed, however hard melted edges arise that negatively influence the softness. In addition, it is involved and expensive to introduce hole structures after the fleece is thermobonded.
The problem of the invention is therefore to create a procedure that enables professionals to manufacture a fleece with hole structures that feels soft, the bond of the fibers is not weakened by introducing hole structures, the procedure can be done without waste, and it is simple and economical.
This problem is solved with a procedure of the initially-cited type that has the features of patent claim
1
.
According to the invention, the fibers are randomly deposited on a screen belt to form a fibrous web in a first step of a procedure to create a fleece made of fibers with numerous hole structures extending over the entire cross-section of the fleece. In a second step, the fibrous web is transported to a hole-structure-creating machine; in a third step, the hole structures are created by mechanically displacing the fibers. The displacement of the fibers does not influence their mechanical and chemical structure. In a fourth step, the fibrous web with the hole structures is bonded in a bonding unit to form a fleece.
The invention is therefore based on the surprising knowledge that, to generate hole structures, it is sufficient to displace the fibers that cover the area of the holes to be formed and compress the fibers in this area and/or the neighboring area without having to destroy or impair the fibrous web in the area of the holes to be formed and/or its general appearance. In brief, the fibers of the fibrous web are reoriented in the area of the hole structures or diverted from their prior course in the procedure according to the invention before manufacturing the fleece by bonding and possibly thermobonding without requiring a heat treatment or simultaneous compression.
Suitable fibers or filaments for creating a fleece by the procedure according to the invention are any fibers or filaments suitable to form fleeces according to the various procedures, especially staple fibers, endless filaments, and bicomponent fibers and filaments. In particular, staple fibers are highly suitable.
It is particularly advantageous that no unnecessary waste or lost material arises, that the fibers are not shortened or destroyed in the area of the hole structures, and that the softness of the finished fleece is very good, and that no additional hardening at the edge of the hole structures impairs the softness of the finished fleece.
Such a solution has not been pursed to date since in particular in a prior-art process in EP 0 214 608 A2 it is assumed that the fibers would tend to return to their original position after being displaced due to the return effect which would eliminate the created hole structures. It was surprisingly shown that this return effect is irrelevant in the procedure according to the invention.
Before the third step, the fibrous web can be bonded to one or more fleeces and/or with another sheet medium such as a film.
In addition, the danger of the fibers springing back can be advantageously countered by feeding the fibrous web directly to the bonding unit after creating the hole structure. In such a bonding unit, e.g. a calender roller arrangement, the fibrous web is compressed to create the finished fleece and, in an advantageous embodiment of the invention, it is simultaneously thermobonded. A very short path is desirable so that the hole structure is not lost while the fleece is being transported from the hole-structure-creating unit to the bonding unit.
In another advantageous embodiment of the invention, the fibrous web is prebonded before the third step so that the tensile strength of the prebonded fibrous web is 0.1 to 75% and especially 50% of the tensile strength of the bonded fleece.
The unbonded fibrous web is more-or-less held by a few widely-spaced bonding points or by applying pressure and/or heat. This provides a certain amount of mechanical stability to the fibrous web so that it can be transported faster to the hole-structure-creating unit. The faster speed enables faster manufacturing.
In an advantageous embodiment of the procedure, the fibers surrounding the hole structures are fixed before feeding the fibrous web to the bonding unit. This serves to prevent the hole structures from stretching while transporting the fibrous web with the hole structures. Fixing the fibers, i.e., slightly adhering the fibers around the hole structure can be done with suitable means such as by applying heat and/or pressure to the fibrous web, e.g. by smooth rollers.
In addition, the fourth step can be carried out with the hole-structure-creating unit directly after the third step. In thi
Bauer Joachim
Etzold Stefan
Collard & Roe P.C.
Corovin GmbH
Juska Cheryl A.
Salvatore Lynda
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