Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Special forms and forming
Patent
1997-09-02
1998-06-30
Crowder, C. D.
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Special forms and forming
D06B 1101
Patent
active
057715173
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for treating a natural fiber lap, for example a cotton fiber lap, and in particular the stage during which the fibers are rinsed to eliminate the chemical products that impregnated the lap before the treatment.
Illustratively, when preparing absorbent cotton from crude cotton, the leaves, twigs or other foreign materials acquired in cotton picking are first eliminated. Next, the sheaths of waxy and fatty materials of the fibers are stripped by a chemical boiling-off treatment consisting in impregnating a lap formed by the crude fibers, for example with a soda-based liquor which is made to react while heated in evaporating equipment. Following treatment, the lap is neutralized and then rinsed with water. Depending on need, the fibers will be bleached and/or oiled. In bleaching, the fibers are made to contact an aqueous oxygenated solution that is allowed to react at an appropriate temperature before the fibers are neutralized and then rinsed again with water.
Boiling-off and bleaching may be carried out batch-wise in liquor-containing tubs. However, recently continuous treatment processes have been developed in order to lower costs when absorbent cotton is manufactured on a large scale. In this field, applicant developed a continuous process allowing the making of a lap offering a given cohesion and which can be used in some applications, such as for packed surgical cotton, dressings or cosmetic pads, without needing to rework the lap mechanically, that is to shred it in order to card it or to form a lap in some other manner.
Such a process is described in French Patent Application No. 90 04647.
In the process, the impregnation stages by the various liquors for boiling-off, bleaching or neutralization rinsing are carried out by pouring liquid sheets on the lap under such conditions as to control the amount of liquid carried away by the sheet and simultaneously to achieve its homogeneous impregnation. Overall process efficiency is improved thereby, also the material quality following treatment of the features vary little from one production run to the next. Applying liquid in such a manner assures firming of the lap because of the energy of the liquid transferred to it.
Attempts have been made to further improve this process, in particular rinsing efficacy, because large quantities of water are required to eliminate the chemical products, in particular the surfactants needed during the initial impregnation phase of the crude cotton. Rinsing before the final finishing or prior to drying is especially significant in that regard because of the desirability of minimizing as much as possible the proportion of residual products, in particular in the light of the Codex. Moreover, considering the ever present desire to maintain and, if possible, to improve product quality without incurring higher costs, rinsing must not degrade the lap's mechanical properties during treatment. This condition only applies where it is desired to use the lap, after it was dried without having to work on it again, in such conventional uses as absorbent cotton or makeup removal pads.
The invention provides a process for treating natural cellulose fibers, in particular cotton fibers, comprising the stages of depositing fibers on a permeable conveyor wire to form a lap having a specific surface weight of 100 to 800 g/m.sup.2, impregnating with a treatment liquor, and treatment then of rinsing using an aqueous liquid, being characterized in that rinsing is carried out by applying the liquid in the form of jets directed at one side of the lap perpendicularly to its direction of advance and imparting to the lap an energy between 2 and 100 kwh/ton of treated product.
The jets are created by injectors such as used in hydrodynamic binding of non-wovens, each injector illustratively comprising an elongated chamber closed lengthwise by a perforated plate with one or more rows of many small-diameter (about 100 .mu.m) orifices. The chamber is fed with pressurized liquid issuing from the orifices in the form of fine,
REFERENCES:
patent: 3864079 (1975-02-01), Gregg
patent: 4132524 (1979-01-01), Hasselschwert
patent: 5253397 (1993-10-01), Neven et al.
Dit Picard Bernard Louis
Neveu Jean-Louis
Crowder C. D.
Fort James France
Worrell Jr. Larry D.
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