Textiles: manufacturing – Textile product fabrication or treatment – Fiber entangling and interlocking
Reexamination Certificate
2004-02-20
2004-09-28
Vanatta, Amy B. (Department: 3765)
Textiles: manufacturing
Textile product fabrication or treatment
Fiber entangling and interlocking
C028S167000
Reexamination Certificate
active
06796010
ABSTRACT:
TECHNICAL FIELD
For decades, it has been proposed to replace traditional webs (woven fabrics, knitted fabrics) by what are known as “nonwoven” structures which, in general terms, may be classified in three large categories by virtue of the actual process for manufacturing them, to be precise nonwovens known as “by the dry way” and “by the melted way” and nonwovens known as “by the wet way”.
In the rest of the description, the present invention will be described as applied to obtaining nonwovens by the technique known as “by the dry way”, but it is clear that it is not limiting and that, if appropriate, it could be applied to the other two categories of nonwovens.
One of the main problems which arises during the production of nonwovens is that of achieving the cohesion of the structure in order to give the products mechanical characteristics according to the application in question, while maintaining or imparting particular physical characteristics, such as bulk, handle, appearance, etc.
Among the techniques proposed hitherto, such cohesion is obtained by the intermingling of the fibers in the thickness of the web by means of the action of fluid jets and, more particularly, of jets of water under pressure.
Such a technique of treatment by means of water jets has been proposed for decades, as may be gathered from the U.S. Pat. Nos. 3,214,819, 3,508,308 and 3,485,706.
In general terms, this technique involves carrying out the interlacing of the elementary fibers with one another by means of the action of jets of water under pressure which act on the fibrous structure in the manner of needles and make it possible to reorient part of the fibers forming the web in the direction of thickness.
Such a technology has been widely developed at the present time and is used not only for producing what are known as “spunlace” structures for textile use, such as, in particular for applications in the medical and hospital fields, for wiping, filtration and wrappings for teabags, but also for making tiny perforations in continuous supports such as paper, cardboard, films, even sheets of plastic or the like and the articles obtained may be regular and homogeneous and take the form of a plane sheet which, if appropriate, may have perforations, as may be gathered from the patent U.S. Pat. No. 3,508,308, and even, if appropriate, comprise designs resulting from the reorientation of the fibers, this being essentially for an esthetic purpose, as may be gathered from U.S. Pat. No. 3,485,706.
As regards the applications of such products of the “spunlace” type, it has been known for a very long time that the final properties of the product obtained can be adapted by producing mixtures of material, for example by combining with one another a plurality of webs consisting of fibers of different types, for example of natural, artificial or synthetic fibers, even from webs in which the fibers are previously mixed, reinforcements (woven or nonwoven nettings, webs of the “spunbond” type, etc.) being capable, if appropriate, of being incorporated into the nonwoven structure.
Of the numerous applications of nonwovens, mention may be made of wiping products known as “wet wipes”, and of products in the hygiene field.
In addition to good mechanical characteristics both in length and in width, also both in the dry state and in the wet state, such products must also have the essential characteristic of having a good capacity for the absorption and retention of the liquid or treatment product which they support or which they must absorb. Moreover, they must have good dimensional stability and be flexible, soft, bulky and pleasant to handle.
The invention is particularly suitable for producing such articles, and, in the rest of the description, it will be described more particularly for obtaining such products.
PRIOR ART
Hitherto, to produce wiping cloths or wet wipes, it has been conceivable to use nonwoven webs consisting entirely of absorbent fibers, such as cellulose fibers, particularly viscose fibers. In order to give the product good mechanical characteristics, a mixture of synthetic fibers (polyester, polypropylene) and of artificial fibers (viscose) is preferably used.
To produce such articles consisting of a mixture of fibers, either an intimate mixture of said fibers can be produced, which is converted into a homogeneous unitary web, or the combination of two webs previously produced is carried out, to be precise, one web based on discontinuous fibers or on continuous synthetic filaments (polyester, polypropylene) and the second based on artificial fibers (viscose), and said webs are combined by hydraulic entanglement.
It has also been proposed, in order to produce such articles, to replace the artificial fibers which give the web the capacity for the absorption and retention of the liquid with natural cellulose fibers, such as wood fibers, incorporated in the same proportions as the prior products based on artificial or synthetic fibers, said natural cellulose fibers being entangled with the chemical fibers likewise by treatment by means of water jets.
Such a product has good mechanical resistance characteristics, essentially afforded by the synthetic fibers, and good liquid absorption and retention characteristics imparted by the cellulose fibers.
French patents FR-A-2 730 246 and 2 734 285, these patents corresponding respectively to the patents U.S. Pat. No. 5,718,022 and U.S. Pat. No. 5,768,756, describe solutions which make it possible to successfully treat hydrophobic fibers or mixtures of these fibers with other hydrophilic fibers or even webs consisting entirely of natural fibers by means of water jets.
In general terms, according to the teachings of these documents, the treatment involves treating a basic web composed of elementary fibers of the same type or of different types, compressing and moistening this basic web and then intermingling the fibers by means of at least one rack of contiguous jets of water under high pressure acting on the basic web.
For this purpose, the basic web is advanced positively on an endless porous support in motion, and it is brought onto the surface of a perforated rotary cylindrical drum, to the interior of which a partial vacuum is applied.
The basic web is compressed mechanically between the porous support and the rotary drum which both advance substantially at the same speed.
Immediately downstream of the compression zone, a water curtain is directed onto the web and passes successively through the porous support, the compressed basic web and the supporting perforated drum which sucks up the excess water.
The elementary fibers are intermingled continuously, still on the rotary cylindrical drum, by the compressed and wetted web being subjected to the action of at least one rack of jets of water under high pressure. In general, bonding is carried out by means of a plurality of successive racks of water jets which act either on the same face or alternately against the two faces of the web, the pressure within the racks and the velocity of the jets discharged varying from one rack to the next and usually progressively.
Moreover, it is appropriate to note, as may be gathered from FR 2 734 285, that the perforated roller preferably comprises randomly distributed micro-perforations.
If appropriate, after this bonding treatment, the nonwoven structure may be subjected to a second treatment applied to the reverse face.
PRESENTATION OF THE INVENTION
A method has been found, this being the subject of the present invention, which not only makes it possible to produce absorbent nonwovens having excellent physical properties (tensile strength, tearing strength, abrasion resistance) and a good capacity for the absorption and retention of liquid similar to articles of the same composition obtained according to the teachings of FR-2 734 285 but which, moreover, has, in relation to such articles, a more pleasant handle and increased bulk.
In general terms, therefore, the invention relates to a method making it possible to produce a novel type of nonwoven consisting at least parti
Heslin Rothenberg Farley & & Mesiti P.C.
Pietrangelo John
Rieter Perfojet
Vanatta Amy B.
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