Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Reexamination Certificate
2004-03-03
2004-12-07
Fortruna, José A. (Department: 1731)
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
C162S117000, C162S158000, C162S204000, C162S132000, C162S164600, C162S113000, C162S179000, C428S156000, C428S172000
Reexamination Certificate
active
06827819
ABSTRACT:
BACKGROUND OF THE INVENTION
In the area of bathroom tissue, softness, absorbency and strength are key attributes considered by consumers. It is highly desirable that the tissue product have a consumer perceived feel of softness. This softness plays a key role in consumer preference. Softness relates both to the product bulk and surface characteristics. In addition to softness, the consumer desires a product that is both strong and absorbent to minimize the amount of the product which must be used to do an effective job.
In a conventional wet press (“CWP”) process and apparatus
10
, as exemplified in
FIG. 1
, a furnish is fed from a silo
50
through conduits
40
,
41
to headbox chambers
20
,
20
′. A web (W) is formed on a conventional wire former
12
, supported by rolls
18
,
19
from a liquid slurry of pulp, water and other chemicals. Materials removed from the web of fabric in the forming zone when pressed against a forming roll
15
are returned to the silo
50
from a saveall
22
through a conduit
24
. The web is then transferred to a moving felt or fabric
14
, supported by a roll
11
for drying and pressing. Materials removed from the web during drying and pressing or from a Uhle box
29
are collected in a saveall
44
and fed to a white water conduit
45
. The web is then pressed by a suction press roll
16
against the surface of a rotating Yankee dryer cylinder
26
which is heated to cause the paper to substantially dry on the cylinder surface. The moisture within the web as it is laid on the Yankee surface causes the web to transfer to the surface. Liquid adhesive may be applied to the surface of the dryer to provide substantial adherence of the web to the creping surface. The web is then creped from the surface with a creping blade
27
. The creped web is then usually passed between calender rollers
30
and rolled up on a roll
28
prior to further converting operations, for example, embossing. The action of the creping blade on the paper is known to cause a portion of the interfiber bonds within the paper to be broken up by the mechanical smashing action of the blade against the web as it is being driven into the blade. However, fairly strong interfiber bonds are formed between the wood pulp fibers during the drying of the moisture from the web. The strength of these bonds in prior art tissues is such that, even after creping, the web typically retains a perceived feeling of hardness, a fairly high density, and low-bulk and water absorbency.
To reduce the strength of the interfiber bonds that inevitably result when wet pressing and drying a web from a slurry, various processes have been utilized. One such process is the passing of heated air through the wet fibrous web after it is formed on a wire and transferred to a permeable carrier—a so-called through-air-drying (“TAD”) process—so that the web is not compacted prior to being dried. The lack of compaction, such as would occur when the web is pressed while on a felt or fabric and against the drying cylinder when it is transferred thereto, reduces the opportunity for interfiber bonding to occur, and allows the finished product to have greater bulk than can be achieved in a wet press process. Because of the consumer perceived softness of these products, and their greater ability to absorb liquids than webs formed in wet press processes, the products formed by the newer TAD processes enjoy an advantage in consumer acceptance.
Felted wet press processes, however, are significantly more energy efficient than processes such as through-air-drying since they do not require heating and moving large quantities of air as required by the TAD process. In wet press operations, excess moisture is mechanically pressed from the web and the final drying of the web is obtained chiefly on the heated Yankee drying cylinder which is maintained at the proper drying temperature.
A conventional TAD process is illustrated in FIG.
2
. In the process, a wet sheet
71
that has been formed on a forming fabric
61
is transferred to a through-air-drying fabric
62
, usually by a vacuum device
63
. TAD fabric
62
is usually a coarsely woven fabric that allows relatively free passage of air through both the fabric
62
and nascent web
71
. While on the fabric
62
, the sheet
71
is dried by blowing hot air through the sheet
71
using a through-air-dryer
64
. This operation reduces the sheet moisture to a value usually between 10 and 65 percent. The partially dried sheet
71
is then transferred to a Yankee dryer
30
where it is dried to its final desired moisture content and is subsequently creped off the Yankee.
In a conventional embossing process according to the prior art as shown in
FIG. 3
, cellulosic webs
11
and
12
are supplied from parent rolls
21
and
22
. The webs are joined together at or prior to the emboss nip which is formed by an emboss roll
31
and a backing roll
41
. The emboss roll
31
has raised protrusions (not shown) on the surface of the roll that make up the emboss pattern. This pattern is transferred to the combined webs by pressing them between the emboss roll
31
and the backing roll
41
, which is usually made of rubber or other like material that allows the pattern on the emboss roll
31
to be impressed into the combined web
13
. The combined web
13
may be further processed by perfing and/or calendering (not shown) before it is wound onto a finished roll
51
.
Thus, the art lacks a method for making a CWP tissue product that achieves high strength, bulk, absorbency, and softness above existing conventional wet pressed tissue, approaching or achieving levels even beyond those found using through-air-drying. The art further lacks a method for making a TAD product that achieves high strength, bulk, absorbency, and softness above existing TAD tissue.
These and other drawbacks of the prior art are overcome by the method of the present invention which can use wet press technology to prepare a strong, ultra soft, bulky tissue. The tissue produced by the method of the present invention exhibits good strength and absorbency while remaining extremely soft. Properties such as those exhibited by the CWP tissue of the present invention have not heretofore been seen in wet press tissue products. The present invention provides a method for making a CWP tissue product that achieves high strength, bulk, absorbency, and softness above existing conventional wet pressed tissue, approaching or achieving levels even beyond those found using through-air-drying. The process according to the present invention is capable of using the cheaper more efficient wet press process and optionally can use less expensive, non-premium fibers. The method of the present invention can also be used to prepare multi-ply tissue products from TAD basesheets. The present invention can be used to make a TAD product that achieves high strength, bulk, absorbency, and softness above existing TAD tissue.
FIELD OF THE INVENTION
The present invention is directed to a method of making an improved ultra soft, bulky, multi-ply product. More particularly, the present invention is directed to a method of making an ultra soft, bulky, multi-ply tissue which can be made from a variety of different furnishes. Still further, the present invention is directed to improving the bulk density and resiliency of a multi-ply product. The present invention is further directed to an ultra soft bathroom tissue.
SUMMARY OF THE INVENTION
Further advantages of the invention will be set forth in part in the description which follows. The advantages of the invention may be realized and attained by virtue of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing advantages and in accordance with the purpose of the invention as embodied and broadly described herein, there is provided a multi-ply tissue product formed by marrying a first embossed ply with a second ply, the first embossed ply having a TMI sidedness of at least about 0.45 and an embossed area of at least about 2%, preferably more th
Dwiggins John H.
Harper Frank D.
Heath Michael S.
Leege Joseph C.
Oriaran T. Philips
Fort James Corporation
Fortruna José A.
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