Textiles: manufacturing – Textile product fabrication or treatment – Fiber entangling and interlocking
Patent
1991-07-26
1993-10-19
Crowder, Clifford D.
Textiles: manufacturing
Textile product fabrication or treatment
Fiber entangling and interlocking
28168, D04H 146
Patent
active
052533972
DESCRIPTION:
BRIEF SUMMARY
The invention concerns the manufacture by hydraulically binding hydrophilic non-wovens based on natural cellulose fibers, for instance from unbleached cotton, flax, hemp or ramie, which were not treated chemically, further to the products made by this method, and to hydrophilic non-wovens comprising chemically untreated natural cellulose fibers.
The purpose of the hydraulic-binding technique is to provide some mechanical strength, independently of any introduction of binder, to a sheet of fibers that initially were not tangled. The binding process consists in subjecting these fibers to very fine pressurized liquid jets, for instance water. As a rule these jets are spaced arrays and are directed at the sheet of fibers which rests on a permeable cloth moving at a specified speed. When moving underneath those arrays, the fibers are driven by the fluid jets passing through the sheet. These jets recoil on the cloth and cause the tangling of the fibers on account of interaction. The links so created ensure the sheet's cohesion.
This procedure makes it possible to make non-wovens from a variety of fibers, whether they be synthetic, natural, long or short, the same or in mixture, chosen in relation to the end use. The products so made as a rule offer superior draping, flexibility and softness to the touch which are superior to those of the non-wovens made by other techniques.
The European patent application 132,028 in particular describes a procedure for making non-wovens from unbleached cotton and consisting in subjecting an initially loose web of unbleached cotton fibers to tangling by water jets which oscillate at low pressure, then in terminating the treatment, prior to drying, by a boiling and bleaching stage of any known technique, for instance by immersion in an autoclave in a solution of caustic soda and oxygenated water at 120.degree. C.
This last stage of the procedure is necessary, according to this patent, because of the use of unbleached cotton. Indeed raw cotton is used, which if cleansed at all was only so mechanically, and of which the fibers comprise a primary coating of waxes and fats that must be eliminated to make the fibers hydrophilic. Accordingly, the object of boiling is to saponify the fats.
The invention is based on the discovery that it is possible, by means of a consolidated water-jet treatment, to impart to a sheet of natural fibers such as of unbleached cotton the property of absorbing liquids, in particular water, in the absence of any chemical treatment.
The method of the invention for making a non-woven from unbleached cotton fibers or other natural ligno-cellulose fibers with a surface coating rending them hydrophobic, comprises the following stages: water-permeable cloth, injector arrays transverse to the direction of motion of the support; it is characterized in that the total energy imparted to the sheet by the set of jets is at least equal to a minimum threshold corresponding to the value at which said sheet becomes hydrophilic.
In particular this threshold depends on the nature and origin of the fibers (new cotton or recovered fibers: stripping, combing noils, etc.), on the sheet structure (superposed card webs, pneumatically made sheets), on the density and thickness of the sheet.
It was found in surprising manner that beyond a given threshold of kinetic energy transmitted by the water jets to the fibers for the purpose of tangling, an action occurs which terminates their initial hydrophobic nature.
Illustratively it was found that for an unbleached cotton from a cotton comber, evincing micronaire number 3 to 5, or new cotton, micronaire 3 to 8, this threshold of injector-dissipated energy is between 0.4 and 1.1 kwh per kg of treated fibers for sheets of which the specific weight is between 25 and 200 g/m.sup.2 and preferably between 30 and 100 g/m.sup.2.
Illustratively when assessing the wetting ability of an unbleached cotton web by measuring the time it needs to sink into water after having been placed on the water surface, it is impossible to measure said ability for a w
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patent: 3494821 (1970-02-01), Evans
patent: 3616175 (1971-10-01), Jung
patent: 4024612 (1977-05-01), Contractor et al.
patent: 4647490 (1987-03-01), Bailey et al.
patent: 4879170 (1989-11-01), Radwanski et al.
Dit Picard Bernard Louis
Neveu Jean-Loup
Crowder Clifford D.
Kaysersberg S.A.
Vanatta Amy Brooke
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