Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
2002-05-13
2003-08-05
Griffin, Steven P. (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
C162S111000, C162S112000, C162S205000, C162S206000, C428S152000, C428S153000, C428S154000
Reexamination Certificate
active
06602387
ABSTRACT:
RELATED APPLICATIONS
The present application is a 371 application of International Application No. PCT/US00/32197 filed Nov. 22, 2000, which claims priority to European Application No. 99123568.0 filed Nov. 26, 1999.
FIELD OF THE INVENTION
The present invention relates to paper tissue, and in particular to facial tissue, and disposable handkerchiefs. In one preferred embodiment a three-ply tissue with embossed middle ply is provided.
BACKGROUND OF THE INVENTION
Paper webs or sheets, sometimes called tissue or paper tissue webs or sheets, or herein called paper tissue, find extensive use in modern society. Such items as facial and toilet tissues are staple items of commerce, all of which are herein referred to as paper tissue. It has long been recognised that important physical attributes of these products are their strength and thickness/caliper, their softness and smoothness, their absorbency, and their lint resistance. Research and development efforts have been directed to the improvement of each of these attributes without seriously affecting the others as well as to the improvement of two or three attributes simultaneously.
Softness and smoothness relate to the tactile sensation perceived by the consumer when holding a particular product, rubbing it across the skin, or crumpling it within the hands. This tactile sensation is a combination of several physical properties. One of the more important physical properties related to the softness and smoothness is generally considered by those skilled in the art to be the surface structure of the paper tissue from which the tissue product is made and which is best captured by the physiological surface smoothness (PSS) parameter as known e.g. from U.S. Pat. No. 5,855,738. As important for the tactile sensation of consumers is the thickness/caliper of a tissue product.
Strength is the ability of the product to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions.
Absorbency is the measure of the ability of a product to absorb quantities of liquid, particularly aqueous solutions or dispersions. Overall absorbency as perceived by the consumer is generally considered to be a combination of the total quantity of a liquid a given mass of paper tissue will absorb at saturation as well as the rate at which the mass absorbs the liquid.
Lint resistance is the ability of the fibrous product, and its constituent webs, to bind together under use conditions, including when wet. In other Words, the higher the lint resistance is, the lower the propensity of the web to lint will be.
WO97/44528 discloses a multi-ply tissue product with high absorbency. Example 4 discloses a product where a patterned, relatively textured ply is disposed between two substantially unpatterned, relatively untextured plies.
EP 0 264 676 discloses a process for the manufacture of multi-ply paper sheets. Example 3 discloses a three-ply product made from wet-formed paper, where the inner web is provided from embossed paper with a weight of 18 g/m
2
and the outer webs are provided from calendered paper with a weight of 14 g/m
2
. The plies are assembled by a cellulose ether adhesive applied by nozzles.
U.S. Pat. No. 5,855,738 discloses a process for making smooth paper tissue comprising a calendering step.
Relatively thick disposable paper products, namely in the form of paper handkerchiefs and facial tissues, are known. For example, Tempo™, sold by The Procter & Gamble Company, has a caliper of about 0.3 mm. A high caliper conveys the idea of high dry and wet strength to the consumer. A high wet strength, also referred to as wet burst strength, in particular prevents tearing or bursting which in turn results in contamination of the user's hand with mucus or other bodily fluids.
Even thicker disposable paper products are known and typically used as kitchen towels, such as Bounty™, sold by The Procter & Gamble Company, which has a caliper of about 0.7 mm and a wet burst strength which is greater than 200 g. However such kitchen towels to a considerable extent owe their caliper to embossing over the whole surface which results in a surface texture which is rough and does not provide a suitably smooth wiping surface for blowing the nose.
Other products with high wet burst strength and typically a relatively high caliper are those produced by through-air-drying. Though-air-drying facilities, however, are not available on conventional paper making machines and the provision of such equipment means a considerable financial investment.
In theory, the wet strength and caliper of a product can be increased by increasing the number of plies to 5, 6 or even more (instead of embossing or the like) and thereby maintaining a smooth outer surface. However, this approach would be very costly and also lead to a stiff product, hence compromising tactile perception.
In attempting to provide a very smooth surface it is common in the art to subject paper tissue to calendering. However, calendering always means a trade-off of caliper and softness for smoothness (as discussed e.g. in U.S. Pat. No. 5,855,738).
In view of the prior art there remains a need for a tissue product, in particular a facial tissue, which:
combines optimal strength, namely wet burst strength, absorbency and lint resistance
further gives an ideal tactile sensation of softness, smoothness and thickness
is cost effective to manufacture and preferably can be manufactured on conventional paper machines
optionally provides skin care benefits
SUMMARY OF THE INVENTION
The present invention relates to a paper tissue, and in particular to facial tissue, and disposable handkerchiefs. Claimed and described is a paper tissue comprising at least two plies, characterised in that the paper tissue has a physiological surface smoothness parameter of less than 700 microns, preferably from 650 microns to 50 microns, more preferably from 650 microns to 300 microns and in combination has a caliper per ply of more than 0.09 mm, preferably from 0.09 mm to 0.5 mm, more preferably from 0.1 mm to 0.2 mm. In one preferred embodiment a three-ply tissue with embossed middle ply is provided. Further is a related process claimed and described.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a cellulose fibrous structure is wet-laid using principles and machinery well-known in the art of paper-making. A suitable pulp furnish for the process of making the paper tissue substrate preferably contains papermaking fibres consisting essentially of cellulose fibres (commonly-known as wood pulp fibres) or cellulose-derived fibres (including, for example, rayon, viscose). Fibres derived from soft woods (gymnosperms or coniferous trees) and hard woods (angiosperms or deciduous trees) are contemplated for use in this invention. The particular species of tree from which the fibres are derived is immaterial. The wood pulp fibers can be produced from the native wood by any convenient pulping process. Chemical processes such as sulfite, sulphate (including the Kraft) and soda processes are suitable. Mechanical processes such as thermochemical (or Asplund) processes are also suitable. In addition, the various semi-chemical and chemi-mechanical processes can be used. Bleached as well as unbleached fibers are contemplated for use. Preferably no non-cellulosic fibres, such as latex, fibres are used.
The paper tissue according to the present invention may contain, as a highly preferred component a wet strength chemical agent. Preferably up to about 3.0%, preferably at least 0.5%, and more preferably at least 0.8% by weight, on a dry fiber weight basis, of wet strength chemical agent, such as water-soluble permanent and temporary wet strength resin, are contained.
Wet strength resins useful herein can be of several types. For example, Wesffelt described a number of such materials and discussed their chemistry in Cellulose Chemistry and Technology, Volume 13, at pages 813-825 (1979).
Usually, the wet strength resins are water-soluble, cationic materials. That is to say, the resins are water-soluble at th
Agouzoul Hasnaa
Bollinger-Krause Claudia Christiane
Loughran Scott Thomas
Malmbak Marianne
Werth Anja
Cook C. Brant
Griffin Steven P.
Halpern M.
The Procter & Gamble & Company
Vitenberg Vladimir
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