Compound sheets made of absorbent paper

Details Compound sheets made of absorbent paper Compound sheets made of absorbent paper

1993-10-05

2001-09-11

Dixon, Merrick (Department: 1774)

Stock material or miscellaneous articles

Structurally defined web or sheet

Weight per unit area specified

C428S218000, C428S220000, C428S191000, C428S193000, C428S212000

Reexamination Certificate

active

06287676

ABSTRACT:

The present invention concerns novel compound sheets of absorbent paper.
More particularly, the objects of the invention are papers for household use, especially cellulose-wool type crepe paper. In this field, highly absorbent paper with high softness and mechanical strength is much sought after.
For a number of years already, papers having several plies have been used in this field, as a rule two or three plies, which previously had been embossed and then slightly bonded to each other with the adhesive being deposited at the tops of projections created during embossing.
Presently, two different systems for embossing, assembling and bonding are being used whereby two different kinds of structures are made. A first kind consists in identically embossing two separate paper plies so as to obtain projections from the sheets and to form a laminate from these two sheets. The projections of the two sheets point to the inside of the laminate and are bonded at their tops. This procedure leads to what shall be called tip-to-tip assembly. Such a procedure as well as the laminates so made, are described in U.S. Pat. No. 3,414,459. It is essentially possible thereby to make two-ply papers having the structure shown in
FIG. 6
of the patent. Another variation described therein consists in sandwiching an unembossed sheet between the two embossed sheets before the tips are bonded together.
Another procedure is described in U.S. Pat. No. 3,867,225 and consists in making a laminate between two embossed sheets arrayed in such a manner that the projections point inward of the laminate, i.e., the projection tips of one of the two sheets are coated with glue and the bonding is carried out in such a position that the projections of one of the sheets will nest between two projections of the other sheet. Such structures are called “nested”.
The object of the present invention is to improve the touch, flexibility and appearance of the known absorbent-paper compound sheets of the prior art and, in particular, to improve the products assembled in nested or tip-to-tip manner wherein each ply evinces an embossed pattern with the height of the bosses being between approximately 0.5 and 2.5 mm and evincing a density between 3 and 20 bosses per cm
2
while amounting to 5 to 60% of the total area.
This result is achieved in the invention using a compound sheet of the above described paper which is characterized by the embossed sheet comprising a second embossing pattern with bosses 0.1 to 0.30 mm high enclosing the bosses of the first pattern.
This second embossing, which can be called microembossing, imparts a more pleasant textile look to the sheet because the spaces between the bosses of greater depth are occupied. Furthermore, such embossing improves the sheet's feel and flexibility.
Preferably, the density of the second pattern is between 20 and 300 bosses per cm
2
, and in particular between 40 and 100. Beyond 300, the bosses no longer can be seen, the sheet then appearing smooth.
Advantageously, the ratio of the density of the second pattern to the first pattern exceeds 2 whereby at least one micro-boss is located between any two bosses of the first pattern.
Applicant is aware of U.S. Pat. No. 4,320,162 proposing a two-sheet paper structure wherein each sheet comprises two embossing patterns, namely, a first and relatively spaced-apart pattern with wide bosses that are 1 to 2.3 mm deep and a more compact pattern of thin bosses enclosing the former and only 0.38 to 1.27 mm deep. The two sheets are bonded to each other by the tips of the first-pattern bosses. This patent specifies that the comparatively wide spacing between the bosses of the first pattern allows the second-pattern bosses to make contact by their tips on account of the bending of the sheet. Accordingly, this second pattern imparts softness, absorption and bulk to the second sheet and improves its appearance.
The compound sheet of the present invention differs from that of the '162 patent in that the first pattern evinces a density of more than 3 bosses/cm
2
while the covered area is 5 to 60%, whereas the patent comprises comparatively wide bosses each reproducing, for example, a flower design, and are widely spaced apart. Moreover, whereas in the present invention the bosses of the second pattern are at most 0.3 mm deep (the selected depth depending predominantly on the specific weight and being 0.1 mm for low specific weights and 0.30 mm for higher specific weights). The bosses of the second pattern of U.S. Pat. No. 4,320,162 are 0.38 to 1.27 mm deep depending on the specific weight of the embossed sheet, their purpose being to make contact by their tips because of the wide spacing between the bosses of the first pattern.


REFERENCES:
patent: 2043351 (1936-06-01), Fourners et al.
patent: 2854336 (1958-09-01), Gutkwecht
patent: 3142599 (1964-07-01), Chavannes
patent: 3399101 (1968-08-01), Magid
patent: 3414459 (1968-12-01), Wells
patent: 3466212 (1969-09-01), Clayton
patent: 3547723 (1970-12-01), Gresham
patent: 3708366 (1973-01-01), Donnelly
patent: 3867225 (1975-02-01), Nystrand
patent: 3868205 (1975-02-01), Thomas
patent: 4320162 (1982-03-01), Schulz

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