Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
2002-05-23
2004-09-28
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C162S111000, C162S113000, C162S130000, C162S129000, C162S127000, C162S123000, C162S125000, C162S117000
Reexamination Certificate
active
06797114
ABSTRACT:
BACKGROUND OF THE INVENTION
Strength and softness are important attributes in consumer tissue products such as facial tissue, bathroom tissue, towels, and napkins. Strength and softness are strongly influenced by the sheet structure of a tissue product. Mechanical treatment of fibers and fiber slurries in the manufacture of tissue products is an important factor in determining the strength and softness of products that are produced thereby.
Strength and softness usually are inversely related. That is, the stronger a given sheet, the less softness that sheet is likely to provide. Likewise, a softer sheet is usually not as strong. Thus, an inverse relationship that exists between the properties of strength and softness results in consistent efforts in the industry to produce sheets or webs having strength levels which are at least as great as conventional sheets, but with improved softness. Also, a sheet or web that is at least as soft as previously known sheets, but with improved strength, also is desirable.
As a general rule, fibers having superior softness are provided in outer layers of tissue products—i.e., those layers that routinely contact the skin of consumers. This is true for bath tissue, for example. The inner layers of such products often comprise softwood fibers that provide strength. Further, debonding agents have also traditionally be utilized to further soften the tissue product.
Unfortunately, however, sloughing sometimes is increased by the use of debonding agents. Sloughing may be described generally as the loss of paper particles from the surface of the paper due to surface abrasion. Many consumers react negatively to paper that exhibits a high degree of sloughing. Therefore, efforts are commonly made to provide a tissue product that exhibits a minimal amount of sloughing. Many changes that are made to paper manufacture to decrease sloughing have the undesirable side effect of stiffening the tissue (i.e., reducing softness). Thus, in the manufacture of tissue products it is a constant struggle to reduce sloughing of such products without adverse effects upon softness levels.
One conventional tissue product is a two-ply product in which each ply has two layers. In particular, each ply usually contains a hardwood layer that faces the consumer and a softwood layer that faces the softwood layer of the other ply. Thus, the inner softwood layers of each ply are in contact with each other. Another conventional tissue product is a single ply product having three layers. The outer layers usually contain hardwood fibers, while the inner layer contains softwood fibers. Although these products may be soft due to the presence of hardwood fibers, they also tend to generate a significant level of slough.
Thus, it would be desirable to provide a process, system and product that is capable of providing a high degree of softness and strength, with reduced amounts of sloughing. Furthermore, a layered tissue product that reveals reduced sloughing with a minimal or negligible effect upon softness levels would be desirable.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a multi-ply tissue product is disclosed that comprises a first ply and a second ply. The first ply comprises a first hardwood layer, a second hardwood layer, and a softwood layer positioned between the first and second hardwood layers of the first ply. The second ply comprises a first hardwood layer, a second hardwood layer, and a softwood layer positioned between the first and second hardwood layer of the second ply, wherein the second hardwood layer of the first ply is positioned adjacent to the first hardwood layer of the second ply. In one embodiment, for example, a two-ply tissue product can be formed in which the first hardwood layer of the first ply and the second hardwood layer of the second ply define an outer surface of the product. The resulting tissue product may exhibit reduced sloughing, with little or no sacrifice in softness.
In some embodiments, the tissue product further comprises a third ply. The third ply comprises a first hardwood layer, a second hardwood layer, and a softwood layer positioned between the first and second hardwood layers of the third ply, wherein the first hardwood layer of the third ply is positioned adjacent to the second hardwood layer of the second ply. In one embodiment, a three-ply tissue product can be formed in which the first hardwood layer of the first ply and the second hardwood layer of the third ply define outer surfaces of the product.
Further, in some embodiments, the tissue product can further comprise a fourth ply. The fourth ply comprises a first hardwood layer, a second hardwood layer, and a softwood layer positioned between the first and second hardwood layers of the fourth ply, wherein the first hardwood layer of the fourth ply is positioned adjacent to the second hardwood layer of the third ply. In one embodiment, a four-ply tissue product can be formed in which the first hardwood layer of the first ply and the second hardwood layer of the fourth ply define outer surfaces of the product.
Other features and aspects of the present invention are discussed in greater detail below.
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Chin Peter
Dority & Manning P.A.
Halpern Mark
Kimberly--Clark Worldwide, Inc.
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