Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Patent
1985-04-24
1986-10-28
Chin, Peter
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
162112, 162113, 162123, 162124, 162125, 162127, 162129, 1621641, 1621681, 162169, 428153, 428154, 428327, D21H 524
Patent
active
046197346
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a sanitary paper web having high bulk, bulk softness and surface softness and to a method of manufacturing said web.
Various types of sanitary paper are manufactured from sanitary paper webs, the term "sanitary paper" in substantial referring to the qualities usually known in the branch as "towel" and "tissue", both "toilet tissue", i.e. creped toilet paper, and "facial tissue".
The expression "bulk" refers, as usual to volume per unit weight, i.e. inverted density, and a digital value of the bulk is obtained by dividing the thickness of the web by its weight per unit area. To ensure correct thickness values, a standard contact pressure for the measuring device in the case of sanitary paper, i.e. paper having high bulk, of only 0.2 N/cm.sup.2 as compared with 10 N/cm.sup.2 for paper with low bulk, e.g. newspaper.
"Bulk softness" refers to the feeling of softness perceived when a sample of the paper web is crumpled between the hands. As distinct from this, "surface softness" refers to the feeling of softness perceived when the fingertips are lightly brushed over the surface of the paper web.
Many process-technical measures have been suggested with the object of improving the properties of sanitary paper, e.g. in order to obtain increased bulk, bulk softness and surface softness. Increased bulk softness can generally be obtained by treating the paper web so that bonds between the fibers are torn and broken. Thus, creping a paper web within only selected, spaced surface areas with the aid of a serrated creping blade has been proposed, or creping from a cylinder having grooves in the circumferential direction thereof. However, this method results in the occurrence of weaker lines such that the strength of the finished sheet in some directions will be reduced. Chemical additives have also been proposed. However, these are known to be difficult to apply on the formed sheet and require the use of bath or spray and the extra equipment necessitated thereby. Surface active agents have been mixed into the stock, but the resultant product has not been particularly soften, although its absorption capacity has increased. The patent literature is extremely extensive with respect to suggestions for achieving improved sanitary paper products and improved apparatuses and processes for manufacturing them. The following offers only a small selection.
A basic measure for achieving a soft tissue with low density is to avoid compacting the sanitary paper web. U.S. Pat. No. 3,812,000 describes an apparatus which avoids mechanical compacting of the paper web before it has been dried to a dryness content of about 80%, the paper web being allowed to pass a rotating blow-through dryer located upstream of the Yankee cylinder or other creping cylinder. However, the almost dry paper web does not then adhere to the Yankee cylinder in the desired manner and a creping binding agent must therefore be applied on the surface of the paper web or on the cylinder.
U.S. Pat. No. 3,301,746 suggests compacting the paper web only in spaced-apart areas by means of a specially designed embossing wire effecting impressions in the paper web during its contact with the wire. The paper web thus embossed is then creped by means of a doctor blade when the paper web leaves the Yankee cylinder. Regulating the embossing and creping pattern in connection therewith enables the bulk softness and bulk of the finished product to be increased.
According to U.S. Pat. No. 3,994,771 a layered paper web is produced having improved properties with respect to bulk and surface softness, a web of softwood pulp being combined with a web of hardwood pulp to produce a composite paper web. This is then subjected to embossing by means of an embossing wire before it is caused to pass a through-blow dryer. The increase in bulk is stated to be caused by a re-orientation and penetration of the fibers on the side of the web facing the embossing wire into the mesh openings in the embossing wire.
U.S. Pat. No. 3,476,644 describes a method of improving t
REFERENCES:
patent: 3293114 (1966-12-01), Kenaga et al.
patent: 3556934 (1971-01-01), Meyer
patent: 3941634 (1976-03-01), Nisser et al.
Chin Peter
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