Paper making and fiber liberation – Processes and products – Non-uniform – irregular or configured web or sheet
Reexamination Certificate
2000-03-17
2001-09-11
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-uniform, irregular or configured web or sheet
14, 14, 14
Reexamination Certificate
active
06287419
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water-decomposable non-woven fabric capable of being readily decomposed and dispersed in water flow. More precisely, it relates to a water-decomposable non-woven fabric having high strength in wet but capable of being readily decomposed in water.
2. Description of the Related Art
To wipe the skin of human bodies including the private parts thereof, or to clean toilets and thereabouts, used are cleaning sheets made of paper or non-woven fabric. The cleaning sheets must be decomposable in water so that they could be directly disposed of in toilets after their use. This is because, if hardly water-decomposable cleaning sheets are disposed of in toilets after their use, they will take a lot of time until they are decomposed and dispersed in septic tanks, or will clog the drainpipes around toilets.
For easy and effective use, many disposable cleaning sheets for wiper applications are packaged while being wetted with a cleaning chemical or the like, and are put on the market. Such cleaning sheets must have high strength in wet to such a degree that they are well fit for wiping with them containing a cleaning chemical or the like, but must well decompose in water after they are disposed of in toilets.
For example, Japanese Patent Publication No. 24636/1995 discloses a water-decomposable cleaning article that comprises a carboxyl group-having, water-soluble binder, a metal ion and an organic solvent. However, the metal ion and the organic solvent irritate the skin.
Japanese Patent Laid-Open No. 292924/1991 discloses a water-decomposable cleaning article of polyvinyl alcohol-containing fibers with an aqueous solution of boric acid infiltrated thereinto; and Japanese Patent Laid-Open No. 198778/1994 discloses a water-decomposable napkin of polyvinyl alcohol-containing non-woven fabric with a borate ion and a bicarbonate ion introduced thereinto. However, polyvinyl alcohol is not resistant to heat, and therefore the wet strength of the water-decomposable cleaning article and the water-decomposable napkin is lowered at 40° C. or higher.
On the other hand, Japanese Patent Laid-Open No. 228214/1997 discloses a water-degradable non-woven fabric having a wet strength of from 100 to 800 gf/25 mm as measured according to JIS P-8135, which is produced by mixing fibers having a length of from 4 to 20 mm with pulp followed by entangling them through treatment with high-pressure water jets. Since the constituent fibers are entangled in it, the non-woven fabric disclosed has a bulky feel. However, in producing the non-woven fabric, long fibers are entangled through high-pressure water jet treatment, whereby the non-woven fabric produced could have such a relatively high wet strength. Therefore, according to the technique disclosed, it is difficult to realize well-balanced bulkiness, strength and water-degradability for the non-woven fabric produced, and the non-woven fabric produced is unsuitable to disposal in flush toilets, etc.
SUMMARY OF THE INVENTION
The present invention is to solve the problems in the related art noted above, and its one object is to provide a water-decomposable non-woven fabric which is well decomposed in water and has high wet strength to such a degree that it is well usable in wet even though no binder is added thereto.
Another object of the invention is to provide a water-decomposable non-woven fabric having well balanced wet strength and decomposability in water, even though a relatively smaller amount of binder is added thereto than that in prior art.
The invention provides a water-decomposable non-woven fabric comprising a first regenerated cellulose fiber having a fiber length of 3 mm or more to 5 mm or less, a second regenerated cellulose fiber having a fiber length of 6 mm or more to 10 mm or less, and a natural fiber having a fiber length of 10 mm or less, wherein at least the second cellulose fiber is entangled (or interwoven) with at least one of the first regenerated cellulose fiber, the second regenerated cellulose fiber and the natural fiber.
The water-decomposable non-woven fabric of the invention can keep sufficient strength during wiping works, even when it contains water. In addition, when it is immersed in a large amount of water after used, it is readily decomposed. Therefore, after used, it can be disposed of in toilets, etc. What is more, the water-decomposable non-woven fabric of the invention is highly bulky with soft touch and is composed of materials not harmful to human bodies.
In accordance with the invention, preferably, both the first regenerated cellulose fiber and the second regenerated cellulose fiber have a fineness of 12 denier or less, more preferably, a fineness of 7 denier or less. Furthermore, it is preferable that one of the first and second cellulose fibers has a fineness of more than one denier, while the remaining one has a fineness of one denier or less. In this case, preferably, the fineness (denier value) of the first regenerated cellulose fiber is smaller than the fineness (denier value) of the second regenerated cellulose fiber.
In accordance with the invention, as to the aspect ratio represented by the formula (fiber length divided by denier value)×1,000, the first and second regenerated cellulose fibers are preferably at an aspect ratio of 400 or more to 14,000 or less. In this case, preferably, the first regenerated cellulose fiber is at an aspect ratio of 400 or more to 3,000 or less, while the second regenerated cellulose fiber is at an aspect ratio more than 3,000 to 14,000 or less; and the aspect ratio of the second regenerated cellulose fiber is larger by 300 or more than the aspect ratio of the first regenerated cellulose fiber.
In accordance with the invention, the content of the first and second regenerated cellulose fibers preferably resides in the range of 10 to 50% by weight.
In accordance with the invention, the basis weight (This may be referred to as “METSUKE”) of the water-decomposable non-woven fabric is preferably 30 to 80 g/m
2
.
In accordance with the invention, furthermore, the natural fiber is preferably soft-wood pulp.
The water decomposability of the water-decomposable non-woven fabric of the invention as measured according to JIS P-4501 is preferably at 150 seconds or less. On the other hand, the wet strength of the water-decomposable non-woven fabric of the invention is preferably 100 g/25 mm or more.
The water-decomposable non-woven fabric of the invention can be produced by entangling the fibers at water jetting treatment.
In the water-decomposable non-woven fabric of the invention, additionally, the wet strength thereof can be further enhanced without prominent reduction of the water decomposability, by allowing the water-decomposable non-woven fabric to contain a water-soluble or water-swellable binder. When the water-decomposable non-woven fabric contains the binder, preferably, the water-decomposable non-woven fabric further contains a water-soluble inorganic salt and/or a water-soluble organic salt. Furthermore, it is preferable that the binder is alkyl cellulose, while the water-decomposable non-woven fabric further contains (A) copolymer of a polymerizable acid anhydride compound with another compound; and/or (B) amino acid derivative.
DETAILED DESCRIPTION OF THE INVENTION
The water-decomposable non-woven fabric of the invention can be produced by mixing together a first regenerated cellulose fiber having a relatively short fiber length, a second regenerated cellulose fiber having a relatively long fiber length and a natural fiber having a fiber length of 10 mm or less, and subjecting a fiber web comprising these fibers to for example water-jetting treatment whereby the fibers are entangled together. The water-decomposable non-woven fabric can procure enhanced wet strength by entangling the second regenerated cellulose fiber together and/or entangling the second regenerated cellulose fiber with the first regenerated cellulose fiber and/or the natural fiber. These fibers composing the water-decomp
Konishi Takayoshi
Takeuchi Naohito
Chin Peter
Darby & Darby
Uni-Charm Corportation
LandOfFree
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