Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Reexamination Certificate
2001-12-31
2003-11-18
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
C162S109000, C162S111000, C162S113000, C162S125000, C428S153000, C428S154000, C428S156000, C428S166000, C428S172000, C428S198000, C428S212000, C156S209000, C156S295000
Reexamination Certificate
active
06649025
ABSTRACT:
BACKGROUND OF THE INVENTION
Products made from paper webs such as bath tissues, facial tissues, paper towels, industrial wipers, food service wipers, napkins, medical pads and other similar products are designed to include several important properties. For example, the product should have a relatively soft feel and, for most applications, should be highly absorbent. The product should also have stretch characteristics and should resist tearing in the environment in which they are used. The above properties are especially important when trying to develop a disposable paper wiping product that can serve as a substitute for conventional cloth products.
In the past, various paper wiping products have been developed. For instance, in order to optimize various properties, in the past two or more embossed conventional paper webs have been laminated together. The present invention is directed to further improvements in such laminated wiping products. In particular, the present invention is directed to a wiping product made from separate plies that has different surface characteristics on each side of the product as will be described in greater detail below.
SUMMARY OF THE INVENTION
In general, the present invention is directed to a paper wiping product made from at least two plies. The two outer plies of the product have different properties for producing a laminate that has different surface characteristics on each side of the product. In particular, the wiping product of the present invention includes a rough or textured side and a smooth and soft side. The product can be used in numerous applications, particularly to clean or polish any adjacent surface or object.
In one embodiment, the paper wiping product includes a first outer ply made from an uncreped, throughdried paper web. The first outer ply can have a basis weight of from about 15 gsm to about 80 gsm, and in one embodiment, from about 20 gsm to about 27 gsm. The first outer ply includes a textured surface having an Overall Surface Depth of greater than about 0.1 mm, and particularly greater than about 0.2 mm. The first outer ply can contain softwood fibers, hardwood fibers and high-yield fibers. For example, in one embodiment, the first outer ply includes high-yield fibers in an amount up to about 30% by weight in combination with softwood fibers. The density of the first outer ply can be less than about 0.3 g/cm
3
.
The paper wiping product includes a second outer ply bound or laminated to the first outer ply. The second outer ply is generally softer and smoother than the first outer ply. The second outer ply has a basis weight less than the first outer ply and can be made from softwood fibers, hardwood fibers and high-yield fibers. In one embodiment, the second outer ply is made from a combination of high-yield fibers and softwood fibers and/or hardwood fibers.
The second outer ply can be made from various paper making processes. For instance, the second outer ply can be creped or uncreped. The second outer ply can also be throughdried or can be dried on a heated cylinder or drum, such as a felted Yankee drum dryer.
The first outer ply can be laminated to the second outer ply by any suitable process. For example, in one embodiment, the first outer ply and the second outer ply are embossed and nested together. Alternatively, one or both of the plies are embossed and secured together in an pin-to-pin or random pin-to-pin (unnested) arrangement. As used herein, a “pin-to-pin” arrangement refers to laminating together two embossed plies in which the raised or embossed areas of each ply contact each other.
Various binder materials, such as adhesives, can be used to secure the layers together. The adhesive can be, for instance, a polyvinyl alcohol, an acetate or a starch adhesive. Alternatively, other binder materials, such as binder fibers, can be inserted between the plies and heated causing the plies to attach together. The binder fibers can be made from, for instance, any suitable thermoplastic polymer, such as polyester, polyethylene or polypropylene. In one embodiment, the binder fibers can be bicomponent fibers. For some applications, the first outer ply and the second outer ply should be bonded together over the entire surface area of the adjacent plies. Alternatively, the binder materials can be applied at selected areas for attaching the plies together. For example, the binder material can be applied to the raised areas on one of the plies.
The binder material can be applied to the plies according to any suitable process. For example, the adhesive, such as a latex adhesive, can be sprayed or printed onto the plies. Binder fibers, however, can be sprayed onto the plies or applied by other means. For example, in one embodiment, an air forming system can be used to apply the binder fibers in between the adjacent layers. Other features, and aspects of the present invention are discussed in greater detail below.
DEFINITIONS AND TEST METHODS
As used herein, “dry bulk” is measured with a thickness gauge having a circular platen 3 inches in diameter such that a pressure of 0.05 psi is applied to the sample, which should be conditioned at 50% relative humidity and at 73° F. for 24 hours prior to measurement. The webs can have a dry bulk of 3 cc/g or greater. The uncreped throughdried webs can have a dry bulk of 6 cc/g or greater, particularly 9 cc/g or greater, and more particularly between 8 cc/g and 28 cc/g.
As used herein, “high-yield pulp fibers” are those papermaking fibers produced by pulping processes providing a yield of about 65 percent or greater, more specifically about 75 percent or greater, and still more specifically from about 75 to about 95 percent. Yield is the resulting amount of processed fiber expressed as a percentage of the initial wood mass. Such pulping processes include bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP) pressure/pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high-yield sulfite pulps, and high-yield kraft pulps, all of which leave the resulting fibers with high levels of lignin. High-yield fibers are well known for their stiffness (in both dry and wet states) relative to typical chemically pulped fibers. The cell wall of kraft and other non-high-yield fibers tends to be more flexible because lignin, the “mortar” or “glue” on and in part of the cell wall, has been largely removed. Lignin is also nonswelling in water and hydrophobic, and resists the softening effect of water on the fiber, maintaining the stiffness of the cell wall in wetted high-yield fibers relative to kraft fibers. The preferred high-yield pulp fibers can also be characterized by being comprised of comparatively whole, relatively undamaged fibers, high freeness (250 Canadian Standard Freeness (CSF)or greater, more specifically 350 CFS or greater, and still more specifically 400 CFS or greater), and low fines content (less than 25 percent, more specifically less than 20 percent, still more specifically less that 15 percent, and still more specifically less than 10 percent by the Britt jar test).
“Noncompressive drying” refers to drying methods for drying cellulosic webs that do not involve compressive nips or other steps causing significant densification or compression of a portion of the web during the drying process. Such methods include through air drying; air jet impingement drying; non-contacting drying such as air flotation drying, as taught by E. V. Bowden, E. V., Appita J., 44(1): 41 (1991); through flow or impingement of superheated steam; microwave drying and other radio frequency or dielectric drying methods; water extraction by supercritical fluids; water extraction by nonaqueous, low surface tension fluids; infrared drying; drying by contact with a film of molten metal; and other methods. It is believed that the three-dimensional basesheets of the present invention could be dried with any of the above mentioned noncompressive drying means without causing significant web densification or a significant loss of their three
Barta Thomas
Behm Rick
Mills Russell P.
Paquot Laurent
Chin Peter
Dority & Manning P.A.
Halpern M.
Kimberly--Clark Worldwide, Inc.
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