Procedure of incorporation of powdery products within a fiber pa

Details Procedure of incorporation of powdery products within a fiber pa Procedure of incorporation of powdery products within a fiber pa

1987-02-24

1992-06-02

Davis, Jenna L.

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

156276, 156292, B32B 3120

Patent

active

051183765

DESCRIPTION:

BRIEF SUMMARY
The invention concerns the field of disposable articles, intended for the absorption of fluids and consisting of an absorbent padding made of fibers, and relates to a procedure and device permitting the incorporation of powdery products, especially superabsorbent, within the padding.
In order to reduce the volume of the padding of articles such as baby diapers, pads for incontinents, sanitary napkins, panty liners etc. . . or to increase their absorption ability, it is attempted to incorporate to the padding superabsorbent products, usually called additives with improved water retention, hydroretainers. These products are usually presented in the form of granules, particles, powders; they are compounds which swell in the presence of fluids but are insoluble; they cause the formation of a gel, the volume of which may be several dozens of times the volume of the dry product. The most well known products are alginates, reticular carboxymethylcelluloses, grafted starches, synthetic derivatives of acrylamide or acrylate types.
Since they are materials of a different nature: granules/fibers, their mixture does not remain homogeneous in time. This phenomenon is the more marked as the articles of which they are the components undergo numerous manipulations and deformations during transportation and during usage. As a matter of fact, a migration of the powder towards areas of the padding where it becomes ineffective, is noticed.
The fixation of superabsorbent products on their support was the subject of many studies. They may be fixed by moistening insuring successively their partial gelification, their deposit, then their drying on the support. This technique has the disadvantage of modifying the surface condition of the particles and therefore their efficacy. In addition, the drying stage required by the procedure increases the manufacturing cost of these articles.
It is also possible to insure fixation with binding agents, as described in U.S. Pat. No. 3,903,889 and FR patent 2402474 where the product is maintained by a layer of adhesive material. However, it appeared that the binding agent prevented the expansion of the product and reduced the active surface of the granule:
In the U.S. Pat. Nos. 4,055,180 or 4,381,783 the superabsorbent is encased between support sheets bound together in order to form pockets. These sheets may be impermeable, perforated with apertures to allow the passing of fluids, or they may be permeable. Thus, the migration of particles during manipulation of the article is avoided. But the confinement of the gel is insured: rising towards the material covering the article, on the skin side, is avoided and any risk of contact between gel and the patient's skin is eliminated. However, since the sides of these pockets are not stretchable, the action of the product is limited. In addition, these additional sheets form an obstacle to the passage of fluids and prevent a rapid absorption.
We have also tried to incorporate particles directly into the absorbent padding. The U.S. Pat. No. 3,888,257 described a procedure of incorporation using compressed air jets for the penetration of the particles, previously placed on the surface within the fiber padding. This procedure is a delicate operation since the air jets have a tendency to destabilize the padding which loses its homogeneous characteristic.
The FR patent 2446357 describes a procedure where the powdery product is placed between the padding and a sheet of fibers, bound together along lines or points, in order to define confinement spaces. The binding is performed by simple cold die-casting by means of cylinders engraved with square patterns, or by hot calendering when the fibers are easily melted. The advantage of this solution is it may be carried out quite inexpensively; it insures a good adherence of the particles between the sheets and takes advantage of the elasticity of the fibers to allow the expansion of the gel. However, in this solution, the superabsorbent product remains on the surface of the padding and forms a continuous deposit.

REFERENCES:
patent: 3884741 (1975-05-01), Sexstone
patent: 4055180 (1977-10-01), Karami
patent: 4260443 (1981-04-01), Lindsay
patent: 4333462 (1982-06-01), Holtman
patent: 4333463 (1982-06-01), Holtman
patent: 4662876 (1987-05-01), Wiegner

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