Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1997-04-23
1998-11-24
Loney, Donald
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428178, 428535, 156209, 156290, 156291, 156292, 162109, B32B 300, B32B 3100, D21H 1100
Patent
active
058404040
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns absorbent papers for household and sanitary uses.
In particular, the invention relates to a multi-layer sheet, i.e., a multi-layer web, for such products as toilet paper, napkins or paper towels, as well as to a manufacturing method for such multi-layer webs.
Use is made in the sanitary and household paper industry of creped absorbent paper of low weight, such as cellulose wadding or tissue paper, for making various products.
Such materials being stretchable on account of creping, are also subject to embossing.
Embossing imparts bulk to the web and improves touch, softness and liquid absorption.
Attempts have been made to increase absorptivity by creating multi-layer webs by combining two or more sheets, also called plies.
Illustratively, U.S. Pat. No. 3,867,225 describes a procedure for making such a product by separately embossing two plies of cellulose wadding into a pattern of protrusions present at a rate of 2 to 30/cm.sup.2, by applying an adhesive to the tops of some of these protrusions, by bringing the plies near one another with their embossed sides facing each other, by nesting the protrusions of one ply between those of the other, and by adhesively bonding the tops of one ply to the cavities of the other.
The empty spaces between the two plies thereby result in a multi-ply structure having increased absorptivity relative to absorbing webs not so designed.
As regards some product applications, where softness is critical, an excessive number of bonding points between the two plies is to be avoided because the total bonded area subtended by such an excessive number substantially contributes to stiffness.
Adhesive deposition is implemented by an adhesive-depositing cylinder and the number of bonding points equals that of the web protrusions receiving glue.
In order to lower the number of bonding points, U.S. Pat. No. 3,867,225 suggests partial glue deposition using an adhesive-depositing cylinder of which the surface is hollowed by alveoles.
However, such a design solution was found to present difficulties in practice on an industrial scale due to rapid cylinder soiling by material accumulation in the alveoles.
U.S. Pat. No. 4,320,162 describes a multi-layer web structure constituted of two embossed plies. Each ply has a wide pattern of first protrusions which are embossed in a relatively deep manner and which are enclosed by a more compact pattern of second protrusions which are embossed more shallowly.
In a first embodiment, the two plies are combined by means of the tops of the first protrusions and in a second embodiment by means of the tops of the first protrusions for one ply and by the tops of the second protrusions for the other ply.
Theoretically such a structure offers more inner empty space than in the design disclosed in U.S. Pat. No. 3,867,225 because the two plies are united by the tops of the protrusions.
However, a web having such a structure will be degraded in its crush resistance.
Even at slight pressures, sagging of the protrusions is observed.
In order to combine the advantages offered by the two above cited procedures while at the same time being free of their drawbacks, French Patent No. 94 07482 already has proposed an absorbent multi-layer web of at least two layers each composed of at least one embossed ply of creped absorbent paper with a specific surface weight between 10 and 40 g/m.sup.2 per ply and having an outer side forming the outside of the multi-layer web and an inner side, where the inner side of the first layer comprises first and second protrusions and the inner side of the second layer comprises third protrusions nested between the protrusions of the first layer, the two layers being bonded to each other at least by a portion of the protrusion tops of the first layer which are glued to the second layer between two third protrusions.
This multi-layer web is characterized in that the adhesive bonding is ensured by the first protrusion tops of the first layer, the second protrusions of the first layer being of a height less than th
REFERENCES:
patent: 4326002 (1982-04-01), Schulz
patent: 5382464 (1995-01-01), Ruppel et al.
Fort James France
Loney Donald
LandOfFree
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