Laminated sheet with multiple embossed patterns

Details Laminated sheet with multiple embossed patterns Laminated sheet with multiple embossed patterns

1998-08-24

2000-10-24

Loney, Donald

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

428172, 428212, B32B 300

Patent

active

061364134

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to absorbent papers used for sanitary or household purposes and its objective is a sheet of at least two embossed plies, the sheet being used in the manufacture foremost of toilet paper but also of napkins, handkerchiefs or paper towels.
The sanitary or household paper industry resorts to an absorbent paper generally in creped form and of low specific surface weight, namely cellulose wadding or wadded woven, to manufacture these products. The stretchability imparted, for example by creping, is exploited to emboss the sheet, that is it is deformed permanently in spots and protrusions are created on one side corresponding to hollows on the other.
In the recent past, the trend has been toward softer, more velvety sanitary products by changing their thickness and strength, in particular by embossing. Embossing furthermore allows enhancement of the appearance of the product. Embossing is carried out either on a wet paper, that is in the wet portion of the papermaking machine, or on low-humidity papers, that is during processing. The present invention relates to dry paper processing.
The most commonplace embossing patterns consist of repeating elementary geometric protrusions of simple geometry and low cross-section. U.S. Pat. No. 3,414,459 provides an example relating to a laminated sheet consisting of a plurality of mutually bonded plies. The plies are embossed at a protrusion repetition rate and a protrusion height selected for making water-absorbent products, such as paper towels, the element density being between 5 and 30/cm.sup.2. Applicant furthermore has developed, in particular for toilet paper, patterns in which the element density is higher, being from 30 to 80/cm.sup.2. Necessarily the top surface of each of these elements is very small, being less than 1 mm.sup.2. The latter embodiments offer an appearance like that of woven products. European Patent No. 426,548 describes such an embodiment. This kind of embossing affects foremost the features derived from sheet thickness. However, the attractiveness of its appearance is limited.
It has already been suggested, in order to improve visual attractiveness, to use patterns with much lower repetition rates than those above, preferably with fewer than 2000 elements/m.sup.2 and with a much higher surface per unit of elements constituting the pattern, these elements being within a polygon of 2 to 6 cm.sup.2. Such an embodiment is described in European Patent No. 265,298. In this patent, the protrusions forming these elements assume elongated cross-sections with linearly configured tops. Preferably, the curves so achieved are closed and impart a molleton effect to the pattern elements. Moreover, these elements are comparatively spaced far apart, subtending wide smooth zones of which the softness remains unaffected by embossing. This set of pattern features contributes in endowing the paper with the velvety and soft qualities perceived by the user. On the other hand, however, this pattern only moderately affects the physical properties. In particular, the thickness remains substantially the same. It is observed in this respect that the embossing efficacy is less. The cylinders must be engraved relatively deep to gain some thickness.
The objective of the invention is a laminated sheet of paper for sanitary or household purposes which offers higher thickness and soft and velvety properties imparted by the above patterns.
This objective is attained by means of a laminated sheet constituting at least two plies and made of cellulose wadding or another layer of cellulose fibers having a specific surface weight between 10 and 40 g/m.sup.2. These plies are embossed and assembled so that the protrusions defining the embossed patterns are pointing to the inside of the sheet and subtend cavities between them. This sheet is characterized in that the plies are embossed with different patterns, a first pattern composed of low cross-section first protrusions having a density of at least 30/cm.sup.2 being present on one of the plies and a second

REFERENCES:
patent: 4307141 (1981-12-01), Walbrun
patent: 4320162 (1982-03-01), Schulz
patent: 5382464 (1995-01-01), Ruppel et al.

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