Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1998-12-24
2001-05-08
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S168100, C162S175000, C162S177000, C162S181200, C162S179000, C162S168200, C162S135000, C162S157600, C162S146000
Reexamination Certificate
active
06228218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a water-disintegratable cleaning sheet easily dispersible by water streams. More specifically, it relates to a water-disintegratable cleaning sheet having excellent water disintegratability, wet strength and stability.
2. Related Art Statement
Cleaning sheets are used for wiping human skins such as of hips or for cleaning toilet articles. The cleaning sheets are preferably water-disintegratable so that they can be thrown away to toilets after use. When they are thrown away into a toilet, it would take much time to disperse them in a septic tank unless they are satisfactorily water-disintegratable, and they sometimes clog drainages of the toilet.
Disposable cleaning sheets to be used for wiping are usually marketed while being packaged in a state previously wetted with liquid cleaning medicals in view of convenience and handlability. However, such cleaning sheets must have wet strength sufficient to endure wiping in a state impregnated with liquid cleaning medicals, and are required to be water-disintegratable when thrown away to toilets.
Japanese Patent Publication Hei 7-24636, for example, discloses a water-disintegratable cleaning article comprising a water soluble binder having carboxyl groups, metal ions and an organic solvent. However, the metal ions and the organic solvent are stimulative to skins.
Japanese Patent Laid-Open Hei 3-292924 discloses a water-disintegratable cleaning article comprising fibers containing polyvinyl alcohol and impregnated with an aqueous boric acid solution, and Japanese Patent Laid-Open Hei 6-198778 discloses a water-disintegratable napkin comprising a polyvinylalcohol-containing non-woven fabric incorporated with borate ions and bicarbonate ions. However, polyvinyl alcohol is sensitive to heat, and the wet strength of water-disintegratable articles and water-disintegratable napkins is lowered at 40° C. or higher.
In addition, Japanese Patent Laid-Open Hei 9-170193 discloses a water-disintegratable sheet coated with a water soluble cellulose ether and incorporated with an electrolyte. However, fibrous sheets having more excellent water disintegratability and wet strength have been required.
An object of the present invention is to provide a cleaning sheet having satisfactory water disintegratability, as well as having wet strength so as to be endurable during use in a wet state.
Another object of the present invention is to provide a cleaning sheet of excellent stability not suffering from deterioration of water disintegratability and wet strength even when stored for long time at high temperature in a wet state.
SUMMARY OF THE INVENTION
The foregoing object can be attained according to the present invention by a water-disintegratable cleaning sheet comprising:
a fibrous sheet comprising water-dispersible fibers, having incorporated thereinto, a binder comprising an alkylcellulose; and an electrolyte, and at least one compound selected from the group consisting of:
a) copolymers of the polymerizable acid anhydride compounds and other compounds and
b) amino acid derivatives.
The water-disintegratable cleaning sheet of the present invention can keep sufficient wet strength during wiping even in a wet state incorporated with water. Since it is disintegrated easily when immersed in a large quantity of water after use, it can be thrown away to toilets. In addition, the water-disintegratable cleaning sheet of the present invention is not degraded in the water disintegratability and wet strength even during storage at high temperatures of about 40° C.
In the present invention, a water-disintegratable cleaning sheet highly safe to human bodies can be obtained by selecting the kind of the copolymer incorporated in the fibrous sheet.
In the present invention, the copolymer is preferably a partially sponified alkali metal salt.
In the present invention, the alkyl cellulose is preferably methylcellulose. The content of the alkylcellulose is preferably from 1 to 30 g based on 100 g of the fibers.
In the present invention, the copolymer is preferably at least one compound selected from the group consisting of (meth)acrylic acid(ester)-maleic acid copolymer and (meth)acrylic acid(ester)-fumaric acid copolymer. In this case, it is preferable that the fibrous sheet is impregnated with an aqueous solution of the copolymer at a concentration of from 0.05 to 5.0% by weight to obtain the cleaning sheet.
In the present invention, the amino acid derivative is preferably trimethyl glycine. In this case, it is preferred that the fibrous sheet is impregnated with an aqueous solution of the amino acid derivative at a concentration of from 5 to 15% by weight to obtain the cleaning sheet.
In the present invention, it is preferred that both of the copolymer and the amino acid derivative are dissolved in water, and the fibrous sheet is impregnated with the aqueous solution to obtain the cleaning sheet. In this case, the concentration of the amino acid derivative of the aqueous solution is preferably from 1 to 5% by weight.
In the present invention, the electrolyte is preferably sodium sulfate. The fibrous sheet is preferably impregnated with the electrolyte while being dissolved in an aqueous solution in which the copolymer and/or the amino acid derivative are dissolved. In this case, the concentration of the aqueous solution is preferably from 0.5 to 10% by weight.
In the present invention, preferably, the fibers are made of pulp of conifer, and the basis weight of the fibrous sheet is from 30 to 70 g/m
2
.
The cleaning sheet of the present invention is preferably used in a wet state incorporated with water.
PREFERRED EMBODIMENT OF THE INVENTION
As fibers of the fibrous sheet in the cleaning sheet of the present invention, fibers having satisfactory dispersibility in water, namely, water dispersible fibers are preferably used. The dispersibility in water in this case has the same meaning as water disintegratability, and is such a characteristic that fibers are disintegrated upon contact with a large quantity of water.
As the fibers to be used in the present invention, either or both of natural and chemical fibers may be used. The natural fibers can include, for example, wooden pulp such as pulp of conifer and pulp of hardwood, and chemical fibers can include rayon as regenerated fibers and polypropylene as synthetic fibers. In addition, there can also be adopted those fibers mainly comprising the above-mentioned fibers and incorporated with natural fibers such as cotton, synthetic fibers such as rayon, polypropylene, polyvinyl alcohol, polyester or polyacrylonitrile and inorganic fibers such as synthetic pulp comprising polyethylene and glass wool. Among them, bleached kraft pulp of conifer and bleached kraft pulp of hardwood are especially preferred since they have high water dispersibility.
In the present invention, the basis weight of the fibers is preferably from 20 to 100 g/m
2
. If the basis weight is less than the lower limit, wet strength required when the cleaning sheet is used for wiping in a wet state can not be obtained. If the basis weight is greater than the upper limit, the cleaning sheet lacks in flexibility. The basis weight of the fibers, when used relative to human skins, is more preferably from 30 to 70 g/m
2
with respect to the wet strength and soft feeling.
The fibrous sheet according to the present invention can be produced by using any of dry and wet type process ordinarily adopted. The fibrous sheet mentioned herein comprises fibers formed into a sheet to which a binder is applied. For example, when it is produced by a wet process, a fiber web obtained by paper making is dried, to which an alkylcellulose is applied as a binder by using silk screen and the like. The fiber web is a mass of fibers in the form of a sheet in which the direction of the fibers is aligned to some extent.
Alkylcellulose is a compound in which hydroxyl groups in an glucose ring unit of cellulose are substituted with alkyl groups. The alkylcellulose can include, for example, methylcellulose
Konishi Takayoshi
Kurata Ryuichiro
Matsumoto Masayoshi
Morohashi Nobuo
Takeuchi Naohito
Chin Peter
Darby & Darby
Halpern Mark
Uni-Charm Corporation
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