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1 METHOD FOR PRODUCING DISPOSABLE WORN ARTICLE
The present invention relates to a method for producing a disposable worn article using a laminated stretchable sheet.
In the prior art, there are cases where a laminated stretchable sheet including two non-woven fabrics and a thermoplastic elastic sheet placed therebetween is used as a composite sheet for use in a disposable diaper, or the like, particularly, as a composite sheet for use in a waist portion of a pants-type diaper, or the like, in order to improve the fit of the diaper (see the first and second patent documents).
[First Patent Document] Japanese Laid-Open Patent Publication No. 2001-129016 (Abstract)
[Second Patent Document] U.S. Pat. No. 6,994,761 B2
DISCLOSURE OF THE INVENTION
Japanese Laid-Open Patent Publication No. 2001-129016 describes a method for producing a disposable worn article by intermittently bonding elastic sheet pieces on front and rear girth webs, and placing absorbent body webs between adjacent elastic sheet pieces.
However, when elastic sheet pieces are bonded by an adhesive on girth webs, it is not possible to obtain sufficient stretching of the elastic sheet pieces. Moreover, the use of an adhesive for the bonding introduces stiffness to the girth web or deteriorates the feel of the girth web.
On the other hand, the specification of U.S. Pat. No. 6,994, 761 describes attaching an elastic sheet piece to a web at a plurality of positions by thermal welding or ultrasonic attachment.
With this method, however, it is diflicult to attach the elastic sheet piece to the web while holding the elastic sheet piece in a stretched state.
It is therefore a primary object of the present invention to provide a method for producing a disposable worn article with a sufficient stretchability, a good feel, and a desirable productivity.
A method for producing a disposable worn article of the present invention is a method for producing a disposable worn article including a torso portion covering a torso of a wearer, and a crotch portion covering a crotch of the wearer, the method including: a step of forming stretched elastic sheet pieces from a continuous elastic sheet; a step of carrying a continuous web to be the torso portion in a longitudinal direction of the continuous web; a step of placing the elastic sheet pieces intermittently on the continuous web, with a stretch direction of the stretched elastic sheet pieces being aligned with the longitudinal direction; a step of bonding opposite end portions of each of the elastic sheet pieces in the longitudinal direction to the continuous web by an adhesive, during the placing step; an ultrasonic attachment step of applying a vibration energy on an overlap portion in which an interrnediate portion of one of the elastic sheet pieces between the opposite end portions and the continuous web overlap with each other, thereby welding the intermediate portion to the continuous web, and forming a laminated stretchable sheet; a placement step of placing a core portion to be the crotch portion between adjacent ones of the elastic sheet pieces on
the laminated stretchable sheet; and a step of cutting off the laminated stretchable sheet between adjacent ones of the core portions.
According to the present invention, the elastic sheet and the continuous web are welded to each other by applying a vibration energy on an overlap portion therebetween, and it is therefore not necessary to use an adhesive. As a result, it is possible to achieve a good feel and a suflicient stretchability.
Since the attachment is done by applying a vibration energy on the intermediate portion between the opposite end portions of the elastic sheet piece in the longitudinal direction, i.e., the flow direction, after the opposite end portions are bonded to the continuous web, the elastic sheet piece can be ultrasonically attached to the web while holding the elastic sheet piece in a stretched state. Therefore, since it is not necessary to separately provide an apparatus, etc ., for holding the elastic sheet piece in a stretched state, the process is easy, and the productivity will not be lowered.
In the present invention, it is preferred that the method further includes: a step of stretching the elastic sheet in a longitudinal direction; a step of carrying a non-woven fabric, which forms a portion of the torso portion and which is to be an inner sheet to be in contact with a skin surface of the wearer; a step of laying the elastic sheet in a stretched state on the non-woven fabric; a step of bonding by an adhesive a portion of an overlap portion between the non-woven fabric and the elastic sheet laid on each other; and a step of cutting off the non-woven fabric and the elastic sheet, which have been bonded together, to thereby obtain a cut-off panel including one of the elastic sheet pieces therein, wherein the step of forming the elastic sheet piece is performed by these steps.
In the present invention, it is preferred that bonding portions in which the non-woven fabric and the elastic sheet are bonded together are formed in the opposite end portions of the elastic sheet piece in the stretch direction; and the placement step is performed so that the core portion covers at least a portion of the bonding portion.
According to this embodiment, the bonding portions, which have been hardened by an adhesive, are covered by the soft core portion to be in contact with the skin surface of the wearer, and therefore the bonding portions will not be in contact with the skin surface of the wearer. Therefore, it is possible to suppress stiffness and discomfort, and to thus further improve the wearability, etc.
In one embodiment of the present invention, the torso portion includes a front torso portion covering an abdominal portion of the wearer, and a rear torso portion covering a back portion of the wearer; and the elastic sheet piece is placed on each of the torso portions, with the core portion placed so as to bridge between the front torso portion and the rear torso portion.
In such a case, the front and rear torso portions are both stretchable.
In such a case, it is preferred that the front torso portion and the rear torso portion are a pair of continuous webs placed apart from each other, and the method includes a step of carrying the pair of continuous webs in parallel to each other.
According to such an embodiment, it is possible to efliciently produce a pants-type diaper.
In one embodiment, the method may further include, after the placement step, a step of slitting the laminated stretchable sheet into a plurality of pieces along a carrying direction of the laminated stretchable sheet.
It gives a higher productivity to slit a single laminated stretchable sheet into two or more pieces, than to separately produce a pair of laminated stretchable sheet pieces.
In one embodiment of the present invention, the method further includes a step of sandWiching the elastic sheet piece betWeen the continuous Web and another Web different from the continuous Web, Wherein the tWo Webs are non-Woven fabrics containing thermoplastic fibers therein, and the elastic sheet is a thermoplastic resin sheet, Wherein the ultrasonic attachment step is performed by applying a vibration energy, at a plurality of attachment positions, on an overlap portion betWeen the tWo non-Woven fabrics and the elastic sheet piece, thereby Welding together the tWo non-Woven fabrics and the elastic sheet piece; and in the ultrasonic attachment step, vent holes are formed in the elastic sheet piece, only in a portion of an outer edge of the attachment positions.
According to this production method, the non-Woven fabrics and the elastic sheet pieces are attached together by the application of a vibration energy, Without using an adhesive, and thus there Will be no stiffness, etc., due to an adhesive. Therefore, it is possible to produce a laminated stretchable sheet that Will not deteriorate the Wearability or the feel.
In the ultrasonic attachment step, the vibration energy is applied to the attachment positions for Welding the tWo nonWoven fabrics With the elastic sheet piece, While ripping a portion of the outer edge of the attachment positions to thereby form vent holes in the elastic sheet. Therefore, there is no need for a separate step for forming vent holes.
Note that the “elastic sheet” may be a film-like elastic sheet, Which is an elastic film, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective vieW shoWing a method for producing a laminated stretchable sheet according to one embodiment of the present invention.
FIG. 2A is a schematic cross-sectional vieW of a composite stretchable sheet, FIG. 2B is an enlarged schematic plan vieW of an elastic sheet, and FIG. 2C is a schematic plan vieW of a composite stretchable sheet.
FIG. 3 is a schematic side vieW shoWing a sealing apparatus.
FIGS. 4A, 4B and 4C are enlarged schematic side vieWs shoWing a method for producing a laminated stretchable sheet.
FIG. 5 is a schematic plan vieW shoWing a method for producing a Worn article.
FIG. 6 is a schematic plan vieW shoWing a method for producing a Worn article.
DESCRIPTION OF THE REFERENCE NUMERALS
31: Front torso portion
32: Rear torso portion
33: Crotch portion
A1, A2: Bonding area (bonding portion) C: Core portion
F: Elastic sheet
F1: Elastic sheet piece
P: Cut-off panel
W1: First non-Woven fabric (Non-Woven fabric to be inner sheet)
X: Carrying direction (floW direction)
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention Will be understood more clearly from the folloWing description of preferred embodiments taken in conjunction With the accompanying draWings. Note hoWever that the embodiments and the draWings are merely illustrative and should not be taken to define the scope of the present invention. The scope of the present invention shall be defined only by the appended claims. In the accompanying draWings, like reference numerals denote like components throughout the plurality of figures.
One embodiment of the present invention Will noW be described With reference to the draWings.
The folloWing description Will be directed to a diaper, as an example of a disposable Worn article.
As shoWn in FIG. 6, a diaper 3 includes torso portions 31 and 32 covering the torso of the Wearer, and a crotch portion 33 covering the crotch of the Wearer. The crotch portion 33 is formed by a core portion C including an absorbent body.
The torso portions 31 and 32 include the rear torso portion 31 covering a back portion of the Wearer, and the front torso portion 32 covering an abdominal portion of the Wearer. The core portion C is placed so as to bridge betWeen the rear torso portion 31 and the front torso portion 32.
The rear torso portion 31 and the front torso portion 32 are divided laminated sheets Wa and Wb, respectively, Which are obtained by dividing a laminated stretchable sheet W in the Width directionY. The laminated stretchable sheet W Will noW be described.
Laminated Stretchable Sheet W:
First, a square cut-off panel P shoWn in FIG. 1 is produced. The cut-off panel P is obtained by laying an elastic sheet F in a stretched state on a first non-Woven fabric W1 to be the inner sheet to be in contact With the skin surface of the Wearer, and then cutting the laminate. The cut-off first non-Woven fabric W1 and a cut-off elastic sheet piece F1 in the cut-off panel P are bonded to each other by an adhesive in first bonding areas A1 and A1 along opposite end portions of the cut-off panel P in the longitudinal direction X, Which are portions of the overlap portion therebetWeen.
Then, the cut-off panels P are placed at a predetermined interval on a second non-Woven fabric W2, Which is a continuous Web, to thereby form composite sheet W3 portions. Note that the cut-off panel P is placed on the surface to be in contact With the skin surface of the Wearer, and is bonded to the second non-Woven fabric W2 by an adhesive in second bonding areas A2 andA2 along opposite end portions thereof.
Therefore, in the composite sheet W3 portion, the thermoplastic elastic sheet piece F1 is sandWiched betWeen the tWo, first and second, non-Woven fabrics W1 and W2 containing thermoplastic fibers therein. In the composite sheet W3, opposite end portions P2 of the elastic sheet piece F1 are bonded to the non-Woven fabrics W1 and W2 by an adhesive in the first and second bonding areas A1 and A2.
At a plurality of attachment positions M of an intermediate portion P1 of the composite sheet W3, the opposite sides (both surfaces) of the elastic sheet piece F1 are Welded respectively to the non-Woven fabrics W1 and W2 by ultrasonic attachment to be described beloW, thereby producing the laminated stretchable sheet W.
In the laminated stretchable sheet W, the elastic sheet piece F1 is attached to the first non-Woven fabric W1 and the second non-Woven fabric W2 at the attachment positions M in the intermediate portion P1 of the composite sheet W3, as shoWn