Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-02-23
2002-03-26
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S219000, C156S220000, C156S290000
Reexamination Certificate
active
06361638
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonwoven fabric which is used in a disposable diaper, a sanitary napkin or kitchen utensils. More specifically, the present invention relates to a nonwoven fabric which has a solid, soft appearance, looks solid and soft and which can maintain a satisfactory bond strength of fibers, as well as to a process for producing the same.
2. Prior Art
There is a nonwoven fabric having a base weight of at least 15 g/m
2
and at most 45 g/m
2
which fabric is embossed to have a raised line pattern (embossed pattern). In this nonwoven fabric, fibers on the surface of the fibrous web formed of fluffed fibers are adhered relatively densely by a predetermined method, for example, by heat-welding or entangling, and the adhered portions are recessed. The embossed pattern has been provided through this adhesion.
Since, however, the embossed pattern is formed densely throughout this nonwoven fabric, the difference in height between the recessed portion given through this embossing and the other portion in the nonwoven fabric is small. Accordingly, the surface of the nonwoven fabric is less raised, that is, it has a less solid appearance. Consequently, it does not look soft, nor does it feel soft when one touches it.
Meanwhile, as shown in
FIG. 9
, in a product in which welded dot portions M are formed in a fibrous web W at a fixed pitch, a specific volume (volume/weight) is relatively large in the portions other than the welded portions M, and it can easily be given a solid appearance.
Nevertheless, in the product shown in
FIG. 9
, the area of the welded portion M is small, the outer periphery of each welded portion M is short, and the nonwoven fabric is less raised. Therefore, the difference in volume between the welded portion M and the surrounding portion is small, so that the raising of the nonwoven fabric is unsatisfactory. Thus, the pattern is monotonous, lacking variety when it is adhered to, for example, an outer surface of an outer film in a disposable diaper.
Further, a nonwoven fabric shown in
FIG. 9
is laminated on the outer surface of the outer film in a disposable diaper or the like, and a resin film of the outer film and the nonwoven fabric are welded; this welded portion has a pattern or a figure. However, in case the nonwoven fabric having welded dot portions M as shown in
FIG. 9
is further welded to the resin film, the portions welded to the resin film are overlapped with the welded dot portions M, and the area of the welded portions is larger than the area of the nonwoven fabric. Thus, the line pattern formed by the welded portions M lacks sharpness, and the nonwoven fabric does not look solid. Further, as the resin film and the nonwoven fabric are welded to each other in the welded portions M, these portions feel stiff. Further, when an air-permeable film is used as the resin film and patterned or figured welded portions are formed in the resin film and the nonwoven fabric, the air permeability of the resin film is reduced as a whole.
Besides the conventional nonwoven fabric is formed of an uncolored fibrous web in many cases. Even if it is formed of a colored web, the overall nonwoven fabric has a single color. For this reason, there is not a product which has a color contrast and in which a pattern is expressed upon using a bulkiness of the nonwoven fabric.
SUMMARY OF THE INVENTION
The present invention aims to solve the above-mentioned problems associated with the prior art. It is an object of the present invention to provide a nonwoven fabric which makes vivid a line pattern formed with press-welded portions by improving the shape of the press-welded portions, which can be rendered bulky by raising the non-press-welded portions, which looks soft and feels soft when touched with the hand, as well as a process for producing the same.
Another object of the present invention is to provide a nonwoven fabric which can have a pattern or a figure by improving the shape of the press-welded portions, for example, which can have a pattern or a figure in the outer surface when used as an outer sheet of a disposable diaper for babies or little children, which can increase a beautiful appearance and in which the presence or absence of urine in a diaper can visually be observed in the press-welded portions from outside the diaper, as well as a process for producing the same.
Still another object of the present invention is to provide a nonwoven fabric in which the shape of the press-welded portions is improved to make bulky the non-press-welded portions and the press-welded portions can provide a clearer pattern to give a color contrast, as well as a process for producing the same.
The present invention is to provide a nonwoven fabric having partially press-welded portions that are recessed in the surface of a fibrous web, characterized in that the press-welded portions have a continuous line or uncontinuous line (broken line) pattern with a curved or square part, and the portions other than the continuous line or uncontinuous line press-welded portions in the fibrous web have a raised pattern relative to the recess of the press-welded portions.
As the fibrous web which is a material of this nonwoven fabric, the web formed of relatively dense fibers having a base weight of at least 15 g/m
2
and at most 45 g/m
2
is preferably used. When the specific volume of the press-welded portions is at least 3 cm
3
/g and at most 10 cm
3
/g and the specific volume of the non-press-welded portions is at least 10 cm
3
/g and at most 30 cm
3
/g, the non-press-welded portions in the fibrous web become bulky, and the boundary between the press-welded portions and the non-press-welded portions make clear and the nonwoven fabric comes to look solid.
The portion surrounded with the continuous line or uncontinuous line press-welded portions is formed in the above-mentioned non-woven fabric, and the fibrous web in the surrounded portion is preferably raised relative to the recessed press-welded portions.
It is further preferable to form a plurality of press-welded dot portions other than the continuous line or uncontinuous line press-welded portions. In this case, it is advisable that the press-welded dot portions are formed where these portions do not overlap with the continuous line or uncontinuous line press-welded portions of the fibrous web. The continuous line or uncontinuous line press-welded portions are preferably spaced apart from the adjacent press-welded dot portions by at least 1 mm, preferably at least 1 mm and at most 5 mm.
It is still further preferable that the total area of the press-welded dot portions in the nonwoven fabric is the same as, or less than, the total area of the continuous line or uncontinuous line press-welded portions.
It is furthermore preferable to use fibers having a square or uneven cross-section as a starting material of the fibrous web.
It is moreover preferable that a color sheet is overlaid on the reverse surface of the nonwoven fabric and they are adhered so that the color of the color sheet is seen through the press-welded portions of the nonwoven fabric. This procedure gives the sharp color contrast between the recessed press-welded portions of the fibrous web and the bulky portions of the fibrous web and makes clear the pattern drawn by the press-welded portions.
A process for producing a nonwoven fabric in the present invention comprises a step of forming a fibrous web from starting fibers, a step of feeding the fibrous web between a hot roller provided on the surface with curved or square line or uncontinuous line projected portions and a hot roller having a smooth surface, and a step of holding the fibrous web between the hot rollers provided on the surface with the projected portions and the hot roller having the smooth surface, and press-welding the fibers of the fibrous web with the projected portions on the surface of the hot roller to partially recess the fibrous web and form the press-welded portions.
A plurality of dot-shaped projected portions, in addition
Shibata Akira
Takai Hisashi
Koda & Androlia
Uni-Charm Corporation
Yao Sam Chuan
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