Tissue with strikethrough resistance

Details Tissue with strikethrough resistance Tissue with strikethrough resistance

1998-06-29

2001-12-25

Chin, Peter (Department: 1731)

Paper making and fiber liberation

Processes and products

Multi-layer waterlaid webs or sheets

C162S112000, C162S129000, C162S130000, C162S132000, C162S134000, C162S135000, C162S158000

Reexamination Certificate

active

06332952

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to the field of paper making, and more specifically, to a tissue with strikethrough resistance.
BACKGROUND
During cleaning after urination the amount of tissue used may be highly variable, but generally about 12 to 15 tissue sheets are used per event for absorbing about 1 milliliter of urine. This tissue amount is about 14 times the actual amount needed based upon tissue's absorption capacity. Using this excessive tissue amount prevents urine from striking through the tissue sheet and reaching the user's hand. Unfortunately, this practice results in tissue waste, which expends economic and degrades environmental resources.
Accordingly, a tissue product that has strikethrough resistance may reduce tissue sheet use by allowing the utilization of the entire absorbency capacity of the tissue, thereby reducing tissue consumption rates and waste.
DEFINITIONS
As used herein, the term “repellant agent” refers to an agent that resists absorption of a liquid, desirably an aqueous liquid. The repellant agent may repel liquids by filling interstitial voids in the fibrous structure of a tissue or coating individual fibers preventing liquids from being absorbed by and passing through the fibers to the interior of the fibrous structure. The repellant agent may be hydrophobic and may include such materials as sizing agents, waxes, and latexes. Furthermore, the repellant agent may be any hydrophobic chemical, such as the agent sold under the trade name REACTOPAQUE by Sequa Chemicals, Inc. at One Sequa Dr., Chester, S.C. 29706. The amount of repellant agent added to the fibers may be from about 1 to about 30 pounds per ton of fiber, more specifically from about 1.2 to about 20 pounds per ton of fiber, and still more specifically, from about 2 to about 10 pounds per ton of fiber.
As used herein, the term “latex” refers to a colloidal water dispersion of high polymers from sources related to natural rubber, such as Hevea tree sap, or of synthetic high polymers that resemble natural rubber. Synthetic latexes may be made by emulsion polymerization techniques from styrene-butadiene copolymer, acrylate resins, polyvinyl acetate, and similar materials.
As used herein, the term “layer” refers to a single thickness, course, stratum, or fold that may lay or lie over or under another. An example of a several layered structure is depicted in
FIG. 3
, where a toilet tissue product
80
includes three layers
84
,
86
, and
88
.
As used herein, the term “ply” refers to a material produced from a headbox having one or more layers. An 30 exemplary toilet tissue product having two-ply structure is depicted in
FIG. 1
, where a product
10
includes two plies
22
and
26
.
As used herein, the term “wax” refers to aqueous emulsions of small particles held in suspension by emulsifying agents and may include materials such as paraffin waxes, microcrystalline wax, or other waxes.
As used herein, the term “sizing agent” refers to any chemical inhibiting liquid penetration to cellulosic fiber structures. Suitable sizing agents are disclosed in a text entitled “Papermaking and Paper Board Making,” second edition, Volume III, edited by R. G. MacDonald, and J. N. Franklin, which is herein incorporated by reference.
Sizing agents are commonly added to control the penetration of aqueous liquids into paper or other fibrous structures. In many cases, a certain resistance is required for end use. When surface treatments are applied with conventional equipment, such as sprayers or applicators, often sizing is required in the base sheet to control pickup of the aqueous solution. Paper grades such as butcher's wrap, milk carton, linerboard, bleached and unbleached bag, fine paper, cylinder board, and corrugated medium are routinely sized.
Internal sizing agents, which are those applied to the fibers within the paper structure, provide a reduced rate of penetration by retarding the rate of flow through the inter-fiber capillaries of the paper, as measured by test procedure ASTM D 779-94. When sizing is accomplished, the contact angle at the fiber surface is 90 degrees or greater, as measured by test procedure ASTM D 5725-95 or TAPPI Test Method T-458. Internal sizing agents function through the use of low surface energy, hydrophobic chemicals which when attached to the surface of cellulose reduce the surface energy of the fiber surface.
Particularly suitable sizing agents are acid or alkaline sizes such as acid rosin, alkenyl succinic anhydride, alkyl ketone dimers and alkenol ketene dimers of the formula:
wherein R
1
and R
2
are based on C
16
-C
18
, aliphatic carbon chains, which can be the same or different. Exemplary commercially available sizing agents of this type are HERCON 79, HERCON 1332, and PRECIS 3000 from Hercules, Inc., 10 Wilmington, Del. The amount of the sizing agent added to the fibers may be from about 0.5 to about 10 pounds per ton of fiber, more specifically from about 1.0 to about 3 pounds per ton of fiber, and still more specifically, from about 2 to about 2.5 pounds per ton of fiber.
As used herein, the term “strikethrough prevention region” refers to an area in a tissue product treated with a repellant agent. The strikethrough prevention region impedes or stops the penetration of liquid from one side of the tissue product to the other. 20 As used herein, the term “cellulosic material” refers to material that may be prepared from cellulose fibers from synthetic source or natural sources, such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. The cellulose fibers may be modified by various treatments such as, for example, thermal, chemical and/or mechanical treatments. It is contemplated that reconstituted and/or synthetic cellulose fibers may be used and/or blended with other cellulose fibers of the fibrous cellulosic material. Desirably, no synthetic fibers are woven into the cellulosic material fibers.
As used herein, the term “pulp” refers to cellulosic fibrous material from sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. Pulp may be modified by various treatments such as, for example, thermal, chemical and/or mechanical treatments. Desirably, no synthetic fibers are woven into the pulp fibers.
As used herein, the term “bleached-chemical-thermo-mechanical pulp” refers to processing cellulosic material with steam, pressure and sodium sulfite or hydrogen peroxide to soften wood lignin between and within cell walls. Furthermore, alkaline peroxide bleaching is added to further soften and brighten the fibers. The term bleached-chemical-thermo-mechanical pulp may be hereinafter abbreviated as “BCTMP” and may be more hydrophobic than Kraft fiber.
As used herein, the term “sulfite pulp” refers to pulp processed chemically with a mixture of sulfurous acid and bisulfite ion. These chemicals attack and solubilize the lignin in the pulp feedstock. Sulfite pulp may be more hydrophobic than Kraft fiber.
As used herein, the term “basis weight” (hereinafter may be referred to as “BW”) is the weight per unit area of a sample and may be reported as gram-force per meter squared. The basis weight may be measured using test procedure ASTM D 3776-96 or TAPPI Test Method T-220.
SUMMARY OF THE INVENTION
The problems and needs described above are addressed by the present invention, which provides a toilet tissue product that may include a first cellulosic ply and a second cellulosic ply. Each ply may further include a single layer. At least one ply may have a region that prevents fluid from striking through the tissue product. Furthermore, at least one ply may be treated with a repellant agent to create a region for preventing fluid strikethrough. Moreover, at least one ply may be printed and/or sprayed with a repellant agent.

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