JP2022112764A - Ultrasonic welding device and side seal part formation method - Google Patents

Abstract

To properly form a side seal part having substantially uniform strength.SOLUTION: In a continuous sheet laminate 9 in which a plurality of absorbent articles continue in the longitudinal direction, a target region T1 that expands in the width direction vertical to the longitudinal direction is set at a constant interval in the longitudinal direction. The target region includes a first region and a second region having a basis weight larger than that of the first region. An ultrasonic welding device comprises: an anvil roller 51 which has a contact surface 511 that is in contact with one target region; an ultrasonic wave application unit which has a head 40 that is opposite to the anvil roller, and applies ultrasonic vibration via the head to a processing position in the target region sandwiched between the contact surface of the anvil roller and an output surface 411 of the head; a movement unit which moves one or both of the contact surface of the anvil roller and the output surface of the head in the width direction with respect to the target region and moves the processing position in the width direction; and a control unit which changes the amplitude of the ultrasonic vibration between the time when the processing position is located in the first region and the time when the processing position is located in the second region.SELECTED DRAWING: Figure 10

Description

The present invention relates to an ultrasonic welding device, a method for forming side seal portions, and an absorbent article.

Conventionally, a pants-type disposable diaper having a body opening at the upper end and a pair of leg openings at the lower end has been used as one of absorbent articles for receiving excrement from a wearer. In the disposable diaper, a side seal portion is formed to join the side edge portion of the front portion and the side edge portion of the rear portion of the exterior sheet.

Patent Document 1 discloses a method for manufacturing a pants-type absorbent article. In this manufacturing method, when a plurality of regions having different thicknesses or different numbers of stacked sheets are provided in the portion where the side seal portion is to be formed, a plurality of ultrasonic horns are arranged corresponding to the plurality of regions. In addition, the clearance between the ultrasonic horn and the anvil corresponding to the area where the thickness is small or the number of sheets laminated is smaller than the clearance between the ultrasonic horn and the anvil corresponding to the area where the thickness is large or the number of sheets laminated is large. Ultrasonic vibrations are applied with a smaller size.

JP 2017-113194 A

By the way, in the side seal portion of the absorbent article, if a portion having excessively high strength (typically, a portion having a large amount of resin that melts and solidifies and has a high tensile strength) is formed, the portion is locally hardened. It may cause pain when worn or damage the wearer's skin. On the other hand, if a portion with excessively low strength is formed, the portion will easily peel off. In the method of Patent Document 1, by adjusting the clearance between the ultrasonic horn and the anvil according to the thickness or the number of laminated sheets, appropriate strength can be obtained at each part of the side seal portion, but the adjustment of the clearance is necessary. requires complicated work. Therefore, there is a demand for a novel technique for appropriately forming side seal portions having substantially uniform strength.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to appropriately form a side seal portion having substantially uniform strength.

According to the first aspect of the invention, in the production of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuously formed, so that each absorbent article is worn by a wearer. An ultrasonic welding device for forming a side seal portion in which the lateral ends of the front portion located on the ventral side of the wearer and the lateral ends of the rear portion located on the back side of the wearer are welded, wherein a plurality of In a continuous sheet laminate in which absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area; and a head facing the anvil, the processing position within the target area sandwiched between the contact surface of the anvil and the output surface of the head. , one or both of the ultrasonic wave applying unit that applies ultrasonic vibrations through the head, the contact surface of the anvil, and the output surface of the head are placed in the width direction with respect to the target area a moving unit that moves the processing position in the width direction; and the target region includes a first region and a second region having a basis weight larger than that of the first region, and the processing When the position is located in the first area and when the position is located in the second area, the amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, the pressure acting on the processing position, or the width direction and a control unit that changes the moving speed of the processing position in.

The invention according to claim 2 is the ultrasonic welding apparatus according to claim 1, wherein the control unit changes the amplitude of the ultrasonic vibration, and the processing position moves in the width direction. during which the pressure acting on the processing position is constant.

The invention according to claim 3 is the ultrasonic welding apparatus according to claim 1 or 2, wherein the amplitude of the ultrasonic vibration when the processing position is located in the first region is It is larger than the amplitude of the ultrasonic vibration when located in the second region.

The invention according to claim 4 is the ultrasonic welding apparatus according to any one of claims 1 to 3, wherein the anvil is a roller that rolls in the width direction, and the outer peripheral surface of the roller is the It is a contact surface, and an uneven pattern is formed on the outer peripheral surface, the roller rolls in the width direction, the processing position reciprocates the target area in the width direction, and the ultrasonic wave applying unit The ultrasonic vibration is applied to the target region on one of the outward and return paths of the reciprocating movement of the processing position, and the ultrasonic vibration is not applied on the other.

In the invention according to claim 5, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuous, so that each absorbent article is worn by the wearer. An ultrasonic welding device for forming a side seal portion in which the lateral ends of the front portion located on the ventral side of the wearer and the lateral ends of the rear portion located on the back side of the wearer are welded, wherein a plurality of In a continuous sheet laminate in which absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. , an anvil having a contact surface that contacts one target area; and a plurality of heads facing the anvil and arranged in the width direction, the contact surface of the anvil and the output surfaces of the plurality of heads. and an ultrasonic wave applying unit that applies ultrasonic vibrations via the plurality of heads to the target region sandwiched between, wherein the target region is a first region and more than the first region an amplitude of the ultrasonic vibration set by a head facing the first region and a head facing the second region among the plurality of heads; The frequency of the ultrasonic vibration or the application time of the ultrasonic vibration is different.

According to the sixth aspect of the present invention, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuous, so that each absorbent article is worn by the wearer. A side seal forming method for forming a side seal portion in which a side end of a front portion located on the ventral side of the wearer and a side end of a rear portion located on the back side of the wearer are welded together, The ultrasonic welding device used in the method for forming the side seal portion spreads in a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, perpendicular to the longitudinal direction and in a width direction along the continuous sheet laminate. Target areas are set at regular intervals in the longitudinal direction, an anvil having a contact surface that contacts one target area, and a head facing the anvil, wherein the contact surface of the anvil and the head An ultrasonic wave applying unit that applies ultrasonic vibrations via the head to a processing position in the target area sandwiched between the output surface of the anvil, the contact surface of the anvil, and the head of the a moving unit that moves one or both of the output surfaces in the width direction with respect to the target area to move the processing position in the width direction, wherein the target area includes a first area and the first a second region having a basis weight larger than that of the region, and the side seal portion forming method includes a) the step of moving the processing position in the width direction by the moving portion; and b) the step a). in parallel with the step of applying the ultrasonic vibration by the ultrasonic wave applying unit to the processing position in the target region, wherein in the step b), the processing position is in the first region The amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, the pressure acting on the processing position, or the speed of movement of the processing position in the width direction at the time of positioning and the time of positioning in the second region. is changed.

According to a seventh aspect of the present invention, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuously arranged, so that each absorbent article is worn by the wearer. A side seal forming method for forming a side seal portion in which a side end of a front portion located on the ventral side of the wearer and a side end of a rear portion located on the back side of the wearer are welded together, The ultrasonic welding device used in the method for forming the side seal portion spreads in a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, perpendicular to the longitudinal direction and in a width direction along the continuous sheet laminate. Target areas are set at regular intervals in the longitudinal direction, an anvil having a contact surface that contacts one target area, and a plurality of heads that face the anvil and are arranged in the width direction. and an ultrasonic wave applying unit that applies ultrasonic vibrations via the plurality of heads to the target area sandwiched between the contact surface of the anvil and the output surface of the plurality of heads, The target area includes a first area and a second area having a basis weight larger than that of the first area, and the method for forming the side seal portions includes the contact surface of the anvil and the contact surface of the plurality of heads. A step of sandwiching the target region between an output surface and a head facing the first region and a head facing the second region among the plurality of heads, wherein the amplitude of the ultrasonic vibration, the and applying the ultrasonic vibration to the target region while varying the frequency of the ultrasonic vibration or the application time of the ultrasonic vibration.

According to an eighth aspect of the present invention, there is provided a pants-type absorbent article comprising: an exterior sheet, which is a sheet laminate having a trunk opening at an upper end and a pair of leg openings at a lower end; An absorbent body attached to the wearer side to absorb excrement from the wearer is provided, and the exterior sheet has a front portion located on the abdomen side of the wearer and a rear portion located on the back side of the wearer. , a crotch portion continuous from the front portion and the rear portion, and a pair of vertically extending side portions formed by ultrasonically welding both side end portions of the front portion and both side end portions of the rear portion. each side seal portion includes a first region having a basis weight of 75 g/m ² or less and a second region having a basis weight of 85 g/m ² or more; The strength is 0.75 times or more the tensile strength in the second region.

According to the present invention, it is possible to appropriately form a side seal portion having substantially uniform strength.

1 is a front view of an absorbent article; FIG. 1 is a rear view of an absorbent article; FIG. 1 is a plan view of an absorbent article in an unfolded state; FIG. FIG. 4 is a cross-sectional view schematically showing the layer structure of the absorbent article in the vicinity of the side seal portion; It is a figure for demonstrating manufacture of an absorbent article. It is a figure which shows the structure of an ultrasonic welding apparatus. FIG. 4 is a cross-sectional view of the welding unit; It is a figure which shows the structure of an ultrasonic wave application part. It is a figure which shows the flow of formation of a side seal part. FIG. 4 shows a continuous sheet stack positioned between the head and the anvil roller; FIG. 12 shows a stack of continuous sheets on the output face of the head; It is a figure which shows the uneven|corrugated pattern on the contact surface of an anvil roller. FIG. 10 is a diagram showing another example of an ultrasonic welding device; It is a figure which shows the flow of formation of a side seal part.

1 and 2 are respectively a front view and a back view (that is, views of the wearer's abdomen and back) of a disposable absorbent article 6 according to one embodiment of the present invention. In the following description, the disposable absorbent article 6 will simply be referred to as the "absorbent article 6". As shown in FIGS. 1 and 2, the absorbent article 6 has a torso opening 61 at its upper end (that is, the upper end in FIGS. 1 and 2) and a pair of leg openings 62 at its lower portion. It is a pants-type disposable diaper. The absorbent article 6 is, for example, an adult disposable diaper. The absorbent article 6 receives excrement from the wearer.

FIG. 3 is a plan view of the absorbent article 6 unfolded and viewed from the wearer's side. In the following description, the vertical direction in FIG. 3 will be referred to as the "longitudinal direction of the article", and the horizontal direction in FIG. 3 will be referred to as the "widthwise direction of the article". The absorbent article 6 includes an exterior sheet 7 and an absorbent body 8 . The body opening 61 and the pair of leg openings 62 (see FIGS. 1 and 2) are provided in the exterior sheet 7 . The exterior sheet 7 includes an exterior sheet main body 70 , a pair of leg elastic members 73 , a pair of body elastic members 74 , and a pair of intermediate elastic members 75 that are joined to the exterior sheet main body 70 . The absorber 8 is a substantially sheet-like member that is attached to the inner surface of the exterior sheet 7 (that is, the wearer's side surface) and absorbs excrement from the wearer.

In the absorbent article 6, the upper part in FIG. 3 covers the wearer's front side (ie, ventral skin), and the lower part in FIG. 3 covers the wearer's back side (ie, back skin). ). In the following description, portions of the exterior sheet 7 located on the wearer's ventral side and back side are referred to as a "front portion 701" and a "rear portion 703", respectively. A portion of the outer sheet 7 between the front portion 701 and the rear portion 703 is called a "crotch portion 702". A crotch portion 702 continues from the front portion 701 and the rear portion 703 . The crotch portion 702 covers the wearer's crotch region. In the absorbent article 6, the exterior sheet 7 has a front portion 701, a crotch portion 702 and a rear portion 703, and the absorbent body 8 extends from the front portion 701 of the exterior sheet 7 to the rear portion 703 via the crotch portion 702. .

As will be described later, when the absorbent article 6 is manufactured, the exterior sheet 7 of FIG. Then, with the crotch portion 702 directed downward, both side end portions of the front portion 701 (both end portions in the width direction of the article) and both side end portions of the rear portion 703 are joined by ultrasonic welding. 1 and 2, a pair of side seal portions 77 are formed. Thereby, the trunk openings 61 are formed at the upper ends of the front portion 701 and the rear portion 703 . A pair of leg openings 62 are formed on the left and right sides of the crotch portion 702 below the front portion 701 and the rear portion 703 . Each side seal portion 77 has a strip shape extending in the vertical direction in FIGS. 1 and 2 .

As shown in FIG. 3, the absorbent body 8 is a substantially sheet-shaped member extending in the longitudinal direction of the article. The absorbent body 8 comprises a top sheet 81 , a back sheet 83 and an absorbent core 82 . The top sheet 81 is a liquid-permeable sheet member. The back sheet 83 is a liquid-impermeable or liquid-repellent sheet member. The absorbent core 82 is a substantially sheet-like member arranged between the top sheet 81 and the back sheet 83 . The top sheet 81 covers the wearer-side surface of the absorbent core 82 . The back sheet 83 covers the surface of the absorbent core 82 opposite to the wearer.

The topsheet 81 quickly captures moisture from the wearer's exudates and transfers the moisture to the absorbent core 82 . The absorbent core 82 absorbs and fixes moisture that permeates the top sheet 81 (that is, moisture in excrement from the wearer). The back sheet 83 prevents water and the like of the excrement reaching the back sheet 83 from seeping out of the absorbent body 8 .

In FIG. 3, the outline of the absorbent core 82 of the absorbent body 8 is drawn with a thick dashed line for easy understanding of the drawing. The same applies to FIGS. 1 and 2 as well. As shown in FIG. 3, the width at both ends of the absorbent core 82 in the longitudinal direction of the article is greater than the width at the central portion of the absorbent core 82 . In other words, the absorbent core 82 has a so-called hourglass shape. The back sheet 83 is bonded onto the exterior sheet 7 with a hot-melt adhesive or the like. Thereby, the absorber 8 is fixed to the exterior sheet 7 . A pair of side sheets forming three-dimensional gathers may be provided on both sides of the absorbent body 8 .

The absorbent core 82 includes at least one of granular or fibrous superabsorbent material and hydrophilic fiber aggregates as an absorbent material, for example. As the superabsorbent material, for example, a granular superabsorbent polymer (SAP (Super Absorbent Polymer)) or a fibrous superabsorbent fiber (SAF (Super Absorbent Fiber)) is used. The aggregate of hydrophilic fibers is formed, for example, from pulverized pulp fibers or cellulose fibers. In the present embodiment, the absorbent core 82 is formed by wrapping a mixture of the above-mentioned hydrophilic fiber assembly with granular SAP in tissue paper, liquid-permeable nonwoven fabric, or the like. As a result, it is possible to prevent the hydrophilic fiber assembly from losing its shape and the SAP from falling off (especially from falling off after liquid absorption).

The top sheet 81 is made of liquid-permeable nonwoven fabric, for example. The nonwoven fabric is formed of, for example, hydrophobic fibers (polypropylene, polyethylene, polyester, polyamide, nylon, etc.) whose surface is hydrophilically treated with a surfactant. The nonwoven fabric may be formed from hydrophilic fibers such as cellulose, rayon or cotton. The nonwoven fabric is, for example, an air-through nonwoven fabric, a point-bonded nonwoven fabric, a spunbonded nonwoven fabric, a spunlaced nonwoven fabric, or the like.

The back sheet 83 is, for example, a liquid-impermeable or liquid-repellent nonwoven fabric (spunbond nonwoven fabric, meltblown nonwoven fabric, SMS (spunbond-meltblown-spunbond) nonwoven fabric, etc.) formed of hydrophobic fibers, or an impermeable It is formed of a liquid or liquid repellent plastic film. The back sheet 83 may be a laminate of the nonwoven fabric and the plastic film. When a plastic film is used for the back sheet 83, a plastic film having moisture permeability (that is, breathability) is used from the viewpoint of preventing stuffiness of the absorbent article 6 and improving the wearer's comfort. preferably.

FIG. 4 is a cross-sectional view schematically showing the layer structure of the absorbent article 6 in the vicinity of the side seal portion 77. As shown in FIG. In FIG. 4, illustration of the leg elastic member 73, the trunk elastic member 74, and the intermediate elastic member 75 is omitted. Also, for convenience of illustration, each layer is drawn separately. As shown in FIG. 4 , an exterior sheet body 70 of the exterior sheet 7 is a sheet laminate, and includes a first sheet 71 and a second sheet 72 . The second sheet 72 is laminated on the inner surface of the first sheet 71 (that is, on the wearer's side) and joined to the first sheet 71 with a hot-melt adhesive or the like. In FIG. 4 , both the portion of the first seat 71 in the front portion 701 and the portion of the first seat 71 in the rear portion 703 are denoted by reference numerals, but actually these portions are the crotch portion 702 . (same for the second sheet 72).

The exterior sheet body 70 further includes two end sheets 76, as shown in FIGS. Each end sheet 76 is laminated on the inner surface of the second sheet 72 and joined to the second sheet 72 with a hot melt adhesive or the like. As shown in FIG. 3, between the two end sheets 76 and the second sheet 72, both ends of the absorbent body 8 in the longitudinal direction of the article are sandwiched and fixed. The end sheet 76 is provided over substantially the entire length of the exterior sheet 7 in the article width direction.

As shown in FIG. 4 , the first sheet 71 has folded portions 711 folded back toward the wearer at the edges 611 of the trunk opening 61 in each of the front portion 701 and the rear portion 703 . The lower end of the folded portion 711 is positioned below the upper end of the end sheet 76 . In addition, the lower end of the folded portion 711 is located above the upper end of the absorber 8 (see FIG. 3). The upper end portion of the end sheet 76 in FIG. 4 is sandwiched between the facing portion 712 of the first sheet 71 that faces the folded portion 711 and the folded portion 711 . The folded portion 711 is joined to the upper end portion of the end sheet 76 . With the above structure, in each of the front portion 701 and the rear portion 703, three ranges R1, R2, and R3 in which the types and numbers of sheets to be stacked in the outer sheet main body 70 are different are sequentially set in the vertical direction in FIG. be done. The ranges R1, R2, and R3 will be described later.

As shown in FIG. 3, a pair of torso elastic members 74 are joined to the front portion 701 and the rear portion 703 along the edge 611 of the torso opening 61 . Typically, each torso elastic member 74 comprises a plurality of thread-like elastic elements arranged in the longitudinal direction of the article. The trunk elastic member 74 is arranged, for example, between the folded portion 711 and the facing portion 712 of the first sheet 71 (see FIG. 4) and joined to the outer sheet main body 70 . In the absorbent article 6 shown in FIGS. 1 and 2, the contraction of the pair of waist elastic members 74 causes the exterior sheet body 70 to contract in the vicinity of the waist opening 61, and the waist gathers contacting the waist of the wearer are formed. It is formed.

As shown in FIGS. 1 and 2, each leg elastic member 73 is positioned partially along the edge of a pair of leg openings 62 . The leg elastic members 73 are joined between the first sheet 71 and the second sheet 72 of the exterior sheet 7 (see FIG. 4). Both ends of one leg elastic member 73 are joined to the front portion 701 of the exterior sheet 7 , and both ends of the other leg elastic member 73 are joined to the rear portion 703 . In addition, portions other than both ends of each leg elastic member 73 (that is, central portions) are joined to crotch portions 702 of the exterior sheet 7 . Typically, each leg elastic member 73 includes a plurality of thread-like elastic elements arranged substantially parallel. In the absorbent article 6, contraction of the pair of leg elastic members 73 causes contraction of the exterior sheet body 70 in the vicinity of the pair of leg openings 62, forming leg gathers around the wearer's legs.

The pair of intermediate elastic members 75 are provided over substantially the entire length in the article width direction in the front portion 701 and the rear portion 703, respectively. Each intermediate elastic member 75 is arranged in a region between both ends of the leg elastic member 73 and the body elastic member 74 in the longitudinal direction of the article. Typically, each intermediate elastic member 75 comprises a plurality of thread-like elastic elements arranged in the longitudinal direction of the article. The intermediate elastic member 75 is joined between the first sheet 71 and the second sheet 72 . In the absorbent article 6, the contraction of the pair of intermediate elastic members 75 causes the outer sheet body 70 to contract, forming intermediate gathers (ie, body-fitting gathers) that contact the lower abdomen and buttocks of the wearer.

The first sheet 71, the second sheet 72, and the end sheets 76 of the exterior sheet main body 70 are, like the back sheet 83, liquid-impermeable or liquid-repellent nonwoven fabrics formed of hydrophobic fibers, or liquid-impermeable. It is formed of a plastic film that is resistant or liquid-repellent. As the plastic film, it is preferable to use a film having moisture permeability. As the first sheet 71 , the second sheet 72 and the end sheets 76 , like the top sheet 81 , a liquid-permeable nonwoven fabric may be used.

As the leg elastic member 73, the body elastic member 74, and the intermediate elastic member 75, for example, polyurethane thread, band-like polyurethane film, or string-like or band-like natural rubber is used. In this embodiment, the leg elastic member 73, the body elastic member 74 and the intermediate elastic member 75 are made of polyurethane thread.

As described with reference to FIG. 4, in each of the front portion 701 and the rear portion 703, three ranges R1, R2, and R3 in which the type and number of stacked sheets differ in the outer sheet main body 70 are arranged vertically. direction. In the uppermost range R3, the folded portion 711 of the first sheet 71, the end sheet 76, and the facing portion 712 of the first sheet 71 overlap. In the range R2 adjacent to the lower side of the range R3, the end sheet 76, the second sheet 72, and the first sheet 71 overlap. In the lowermost range R1, the second sheet 72 and the first sheet 71 overlap. Note that in the present embodiment, the basis weight of the first sheet 71 is slightly larger than the basis weight of the second sheet 72 .

As described above, in each side seal portion 77, the front portion 701 and the rear portion 703 are joined by ultrasonic welding. Therefore, the side seal portion 77 includes a thick region that is included in the range R3 in the vertical direction and in which the six sheets overlap, a medium-thick region that is included in the range R2 and in which the six sheets overlap, and a range A thin area included in R1 and where the four sheets overlap. In the following description, the thick regions included in the range R3 are assigned the same reference numeral R3, the medium regions included in the range R2 are assigned the same reference numerals R2, and the thin regions included in the range R1 are assigned the same reference numerals. Labeled R1. The layer structure of FIG. 4 is merely an example, and may be changed as appropriate. For example, the upper end of the second sheet 72 may be arranged at the same position as the upper end of the end sheet 76, and eight sheets may overlap in the thick region R3. The side seal portion 77 may include only two regions with different types and numbers of sheets, or may include four or more regions.

In this processing example, the total basis weight of the six sheets forming the thick region R3 of the side seal portion 77 (hereinafter simply referred to as "the basis weight of the thick region R3") constitutes the medium region R2. The difference from the total grammage of the six sheets (hereinafter simply referred to as "the grammage of the medium thickness region R2") is slight. On the other hand, the total grammage of the four sheets forming the thin region R1 (hereinafter simply referred to as "the grammage of the thin region R1") is compared with the grammage of each of the thick region R3 and the medium region R2. significantly smaller. When the thin region R1 is called a “first region”, the basis weight of the first region is, for example, 75 g/m ² or less, preferably 70 g/m ² or less, and more preferably 68 g/m ² or less. . When the thick region R3 and the medium region R2 are collectively referred to as the “second region”, the basis weight of the second region is, for example, 85 g/m ² or more, preferably 90 g/m ² or more, more preferably 92 g. /m ² or more. The side seal portion 77 may include a region having a basis weight of more than 75 g/m ² and less than 85 g/m ² .

In the formation of the side seal portion 77, if the first region and the second region having greatly different basis weights are ultrasonically welded under the same conditions, typically, the tensile strength in the first region having a small basis weight is It is much smaller than the tensile strength in the second region where the basis weight is large. In the present embodiment, as will be described later, the conditions for ultrasonically welding the first region are different from the conditions for ultrasonically welding the second region. This reduces the difference between the tensile strength in the first region and the tensile strength in the second region. Preferably, the tensile strength in the first region is at least 0.75 times the tensile strength in the second region, more preferably at least 0.80 times, and even more preferably at least 0.82 times. Typically, the tensile strength in the first region is less than or equal to the tensile strength in the second region. Thus, the absorbent article 6 is provided with the side seal portions 77 having substantially uniform strength. A method for measuring the tensile strength will be described later.

FIG. 5 is a diagram for explaining the manufacturing of the absorbent article 6. FIG. In manufacturing the absorbent article 6, a continuous sheet laminate 9 in which a plurality of absorbent articles 6 in the middle of manufacturing are continuous in the longitudinal direction is produced. Specifically, a first sheet continuum 91 in which a plurality of first sheets 71 (parts to be formed) are continuous, and a second sheet continuum 92 in which a plurality of second sheets 72 are continuous are laminated. Hereinafter, the longitudinal direction of the laminate of the first sheet continuum 91 and the second sheet continuum 92 is referred to as the "laminate longitudinal direction", and the direction perpendicular to the laminate longitudinal direction and along the laminate is referred to as the "laminate body width direction".

Between the first sheet continuum 91 and the second sheet continuum 92, an elastic member continuum in which a plurality of leg elastic members 73 are continuous and an elastic member continuum in which a plurality of intermediate elastic members 75 are continuous are provided. is placed in a stretched state. On the first sheet continuum 91, an elastic member continuum in which a plurality of trunk elastic members 74 are continuous is arranged near each end in the width direction of the laminate. In the laminate of the first sheet continuum 91 and the second sheet continuum 92 , a plurality of absorbent bodies 8 are bonded onto the second sheet continuum 92 at predetermined intervals in the longitudinal direction of the laminate. The absorber 8 extends in the width direction of the laminate. Also, two end sheet continuities 96, in which the plurality of end sheets 76 are continuous, are joined onto the second sheet continuum 92 so as to cover both ends of the plurality of absorbent bodies 8 in the laminate width direction. .

After the end sheet continuous body 96 is joined, both end portions of the first sheet continuous body 91 in the stack width direction are folded back to form folded portions 911 . The folded portion 911 is a portion where the folded portion 711 in FIG. 4 continues in the longitudinal direction of the laminate. Holes 93 corresponding to the leg openings 62 are formed at positions between the absorbent bodies 8 in the longitudinal direction of the laminate. After that, the laminate of the first sheet continuum 91 and the second sheet continuum 92 is folded together with the absorber 8 at the center in the width direction of the laminate. As a result, a continuous sheet laminate 9 is produced in which a plurality of absorbent articles 6 in the course of production are continuous in the laminate longitudinal direction.

Subsequently, side seal portions 77 are formed on the continuous sheet laminate 9 using an ultrasonic welding device 1, which will be described later. In the continuous sheet laminate 9 in which a plurality of absorbent articles 6 are continuous, two side seal portions 77 are formed with a slight gap at the boundary between two adjacent absorbent articles 6 . In FIG. 5, a region T1 in which the two side seal portions 77 are to be formed (hereinafter referred to as "target region T1") is surrounded by a two-dot chain line rectangle. The target regions T1 extend in the width direction of the laminate and are set at regular intervals corresponding to the width of the absorbent article 6 in the longitudinal direction of the laminate. The details of forming the side seal portions 77 will be described later. Thereafter, the continuous sheet laminate 9 is cut between the two side seal portions 77 to obtain a single absorbent article 6 (see the rightmost absorbent article 6 in FIG. 5). The manufacturing flow of the absorbent article 6 is merely an example, and may be changed as appropriate.

FIG. 6 is a diagram showing the configuration of the ultrasonic welding apparatus 1 used for forming the side seal portion 77. As shown in FIG. The ultrasonic welding apparatus 1 includes a welding unit 2, two auxiliary rollers 11, and a control section 10 (see FIG. 8, which will be described later). The control unit 10 is, for example, a computer including a CPU, etc., and is responsible for overall control of the ultrasonic welding apparatus 1 . The welding unit 2 includes a substantially cylindrical sheet holding drum 3 centered on a predetermined central axis J1. The two auxiliary rollers 11 have a substantially cylindrical surface centered on an axis parallel to the central axis J1, and are rotatable about the axis.

In the ultrasonic welding apparatus 1 , the already-described continuous sheet stack 9 is introduced onto the sheet holding drum 3 via one of the auxiliary rollers 11 . In the welding unit 2 , side seal portions 77 are formed for the continuous sheet stack 9 while the continuous sheet stack 9 is held on the outer peripheral surface 30 of the sheet holding drum 3 . The continuous sheet laminate 9 with the side seal portions 77 formed thereon is led out from the ultrasonic welding apparatus 1 via the other auxiliary roller 11 . In the continuous sheet laminate 9 of FIG. 6, the portion where the absorbent body 8 is provided is indicated by a thicker line than the other portions. In the following description, the direction parallel to the central axis J1 is called "drum axial direction". The drum axial direction substantially coincides with the stack width direction of the continuous sheet stack 9 held on the sheet holding drum 3 .

FIG. 7 is a cross-sectional view of the welding unit 2 at the position of arrows VII--VII in FIG. In FIG. 7, the head 40 of the ultrasonic wave imparting unit 4, which will be described later, is shown in a simplified manner, and the illustration of the continuous sheet laminate 9 is omitted. The welding unit 2 includes a sheet holding drum 3 , a plurality of ultrasonic wave applicators 4 , a plurality of anvil units 5 , an anvil holding drum 21 and a cam drum 22 .

As described above, the sheet holding drum 3 has a substantially cylindrical shape centered on the central axis J1. The anvil holding drum 21 has a substantially cylindrical shape centered on the central axis J1. The anvil holding drum 21 and the sheet holding drum 3 are arranged in the axial direction of the drum and fixed to each other. In the example of FIG. 7, the diameter of the anvil retaining drum 21 is smaller than the diameter of the sheet retaining drum 3 . The cam drum 22 has a substantially cylindrical shape centered on the central axis J1. The diameter of the cam drum 22 is smaller than the inner diameter of the anvil retaining drum 21 and the cam drum 22 is arranged inside the anvil retaining drum 21 . The sheet holding drum 3 and the anvil holding drum 21 are integrally rotated about the central axis J1 by a rotating mechanism 12 having a motor or the like. In this embodiment, the sheet holding drum 3 and the anvil holding drum 21 are assumed to rotate continuously counterclockwise in FIG. The cam drum 22 is a fixed body that does not rotate.

A plurality of grooves 31 are provided on the outer peripheral surface 30 of the sheet holding drum 3 . The plurality of grooves 31 are arranged at equal angular intervals in the circumferential direction about the central axis J1. Each groove 31 extends in the axial direction of the drum on the outer peripheral surface 30 . In the example of FIG. 6, six grooves 31 are provided. The number of grooves 31 may be 1 or more, 5 or less, or may be 7 or more (the same applies to the number of ultrasonic wave applying sections 4 and the number of anvil units 5). The heads 40 of the plurality of ultrasonic wave applying units 4 are arranged in the plurality of grooves 31, respectively.

FIG. 8 is a diagram showing the configuration of one ultrasonic wave applicator 4. As shown in FIG. Each ultrasonic applying unit 4 includes an ultrasonic horn 41 , an ultrasonic transducer (converter) 42 and an ultrasonic oscillator 43 . The ultrasonic horn 41 and the ultrasonic vibrator 42 constitute a head 40 arranged in the groove 31 of the sheet holding drum 3 . In the groove portion 31 of FIG. 6, the ultrasonic vibrator 42 is arranged radially inward (center axis J1 side) around the central axis J1, and the ultrasonic horn is arranged outside (the outer peripheral surface 30 side of the sheet holding drum 3). 41 are placed. The ultrasonic oscillator 43 is provided inside or outside the sheet holding drum 3 . The ultrasonic oscillator 43 is electrically connected to the ultrasonic transducer 42 and inputs an electrical signal of a predetermined frequency (for example, 10 kHz to 100 kHz) to the ultrasonic transducer 42 .

The ultrasonic transducer 42 has a piezoelectric element (piezo), and converts an electrical signal input from the ultrasonic oscillator 43 into mechanical vibration by the piezoelectric element. The ultrasonic horn 41 is made of metal (including alloys) such as an aluminum alloy or a titanium alloy. The ultrasonic horn 41 is arranged between the continuous sheet stack 9 on the outer peripheral surface 30 of the sheet holding drum 3 and the ultrasonic vibrator 42 . A radially outer surface 411 (hereinafter referred to as “output surface 411”) of the ultrasonic horn 41 extends in the axial direction of the drum and contacts the entire continuous sheet laminate 9 in the axial direction of the drum. Ultrasonic vibration is input to the ultrasonic horn 41 from the ultrasonic vibrator 42 , and the ultrasonic horn 41 resonates to apply ultrasonic vibration of a constant frequency to the continuous sheet laminate 9 from the output surface 411 . be.

The distance between the output surface 411 and the central axis J1 is substantially the same as the distance between the outer peripheral surface 30 of the sheet holding drum 3 and the central axis J1. The distance between the output surface 411 and the central axis J1 may be slightly larger or slightly smaller than the distance between the outer peripheral surface 30 and the central axis J1. In the ultrasonic wave applying unit 4, an ultrasonic vibration amplifier (booster) that adjusts or amplifies the mechanical vibration from the ultrasonic transducer 42 is provided between the ultrasonic horn 41 and the ultrasonic transducer 42 as necessary. may be provided in The ultrasonic horn 41 may be omitted from the head 40 if sufficient amplitude is obtained.

As shown in FIG. 6, the plurality of anvil units 5 are arranged at the same positions as the plurality of grooves 31 in the circumferential direction. Each anvil unit 5 includes an anvil roller 51 and a roller holder 52 (see FIG. 7). The anvil roller 51 is arranged radially outside the head 40 of the ultrasonic wave applying unit 4 . When the sheet holding drum 3 is viewed along the drum axial direction as shown in FIG. 6, the central axis J1, the head 40 and the anvil roller 51 are arranged in a row in the radial direction. In other words, the anvil roller 51 is arranged on the plane on which the central axis J1 and the head 40 are arranged. The anvil roller 51 has a disc shape centered on a central axis perpendicular to the plane. In the following description, the direction parallel to the central axis of the anvil roller 51 is called "anvil axial direction". The anvil axial direction substantially coincides with the laminate longitudinal direction of the portion of the continuous sheet laminate 9 on the output surface 411 of the head 40 .

The anvil roller 51 faces the head 40 with the continuous sheet laminate 9 interposed therebetween. As will be described later, the anvil roller 51 rolls on the output surface 411 of the head 40 in the axial direction of the drum with the continuous sheet stack 9 interposed therebetween. Anvil roller 51 is an anvil for head 40 . An outer peripheral surface 511 of the anvil roller 51 is a contact surface that contacts one target region T1 (see FIG. 5) of the continuous sheet stack 9. As shown in FIG. As will be described later, the anvil unit 5 may use anvils other than rollers.

As shown in FIG. 7 , the roller holding portion 52 includes a holding portion main body 521 , a holding lever 522 and a biasing portion 523 . As will be described later, the holding portion main body 521 is supported by the anvil holding drum 21 so as to be movable in the drum axial direction. The holding lever 522 is rod-shaped and extends approximately along the axial direction of the drum. In the vicinity of the center of the holding lever 522, a shaft portion A1 is provided that extends in the anvil axial direction (the direction perpendicular to the paper surface of FIG. 7). The shaft portion A1 is connected to the holding portion main body 521, and the holding lever 522 is supported by the holding portion main body 521 so as to be rotatable about the shaft portion A1.

A shaft portion A2 extending in the anvil axial direction is provided at the center of the anvil roller 51 . The shaft A2 is connected to one end of the holding lever 522 (the end on the sheet holding drum 3 side in the drum axial direction), and the anvil roller 51 is rotatably supported by the holding lever 522 about the shaft A2. be. The biasing portion 523 is attached to the other end of the holding lever 522 (the end on the anvil holding drum 21 side in the drum axial direction). The biasing portion 523 biases the other end of the holding lever 522 radially outward so that the anvil roller 51 approaches the head 40 . The biasing portion 523 has, for example, an elastic member such as an air cylinder or a spring.

A plurality of pairs of guide portions 211 are arranged at the same positions as the plurality of groove portions 31 in the circumferential direction on the outer peripheral surface of the anvil holding drum 21 . That is, a pair of guide portions 211 are provided at positions corresponding to the respective anvil units 5 on the outer peripheral surface. The pair of guide portions 211 sandwich the holding portion main body 521 of the anvil unit 5 in the circumferential direction. An engagement groove 212 extending in the axial direction of the drum is provided on a surface of each guide portion 211 facing the holding portion main body 521 . A projection 524 is provided on the surface of the holding portion main body 521 facing each guide portion 211 . By engaging the protrusions 524 with the engaging grooves 212, the holding portion main body 521 is supported by the anvil holding drum 21 in a state in which it can move in the axial direction of the drum.

Further, slits 213 extending in the axial direction of the drum are provided between each pair of guide portions 211 on the outer peripheral surface of the anvil holding drum 21 . The slit 213 is a hole penetrating the peripheral wall of the anvil holding drum 21 . The holding portion main body 521 is provided with a cam protrusion 525 that is inserted into the slit 213 . Cam projection 525 extends to the interior of anvil retaining drum 21 . As already mentioned, a cam drum 22 is arranged inside the anvil retaining drum 21 . A cam groove 221 is provided on the outer peripheral surface of the cam drum 22 . The tip of the cam projection 525 is arranged inside the cam groove 221 . The cam groove 221 moves the cam protrusion 525 in the drum axial direction according to the rotation of the anvil holding drum 21 with respect to the cam drum 22 . That is, while the anvil unit 5 rotates about the central axis J1 together with the anvil holding drum 21, the anvil unit 5 moves in the axial direction of the drum.

Actually, the anvil unit 5 is arranged at a position in the drum axial direction according to the rotational positions (angles) of the sheet holding drum 3 and the anvil holding drum 21 . In one example, in the anvil unit 5 located on the uppermost side in FIG. 6, the anvil roller 51 is arranged near one end in the drum axial direction on the output surface 411 of the head 40 . The sheet holding drum 3 and the anvil holding drum 21 rotate together counterclockwise in FIG. moving axially toward the drum. When the anvil unit 5 is positioned on the lowest side, the anvil roller 51 is arranged near the other end of the output surface 411 . After the anvil unit 5 passes the lowermost position, the anvil roller 51 moves in the drum axial direction toward the one end of the output surface 411 as it approaches the uppermost position. When the anvil unit 5 is positioned on the uppermost side, the anvil roller 51 is arranged near the one end of the output surface 411 .

As described above, in the ultrasonic welding apparatus 1, while the anvil unit 5 makes one rotation about the central axis J1 together with the sheet holding drum 3, the anvil roller 51 sandwiches the continuous sheet stack 9 and the head 40 reciprocates on the output surface 411 of the drum in the axial direction of the drum. In the continuous sheet stack 9, if the position sandwiched between the contact surface (outer peripheral surface) 511 of the anvil roller 51 and the output surface 411 of the head 40 is called a "processing position", the position of the anvil unit 5 during one rotation , the processing position reciprocates the target region T1 (see FIG. 5) of the continuous sheet stack 9 in the stack width direction. In the ultrasonic welding apparatus 1, the rotating mechanism 12, the anvil holding drum 21, and the cam drum 22 shown in FIG. 7 constitute a moving portion that moves the processing position in the width direction of the laminate. As will be described later, the moving section may be realized by other configurations.

Next, formation of the side seal portion 77 using the ultrasonic welding device 1 will be described. As described above, the side seal portion 77 is formed in the target region T1 of the continuous sheet laminate 9 in FIG. Further, the plurality of target regions T1 arranged in the stack longitudinal direction in the continuous sheet stack 9 are sequentially arranged on the plurality of heads 40 as the sheet holding drum 3 rotates. In the following description, formation of the side seal portion 77 for the target region T1 arranged on one head 40 will be described, but the same processing is performed for the target regions T1 arranged on the other heads 40 as well.

FIG. 9 is a diagram showing the flow of forming the side seal portion 77. As shown in FIG. FIG. 10 shows the continuous sheet stack 9 positioned between the head 40 and the anvil roller 51. As shown in FIG. FIG. 10 shows a cross section of the continuous sheet laminate 9 (target region T1) perpendicular to the longitudinal direction of the laminate. FIG. 11 is a view showing the continuous sheet stack 9 on the output surface 411 of the head 40, showing the continuous sheet stack 9 viewed from the anvil roller 51 side.

Similar to the absorbent article 6 in FIG. 4, in the target region T1 of the continuous sheet laminate 9 in FIG. The thin regions R1 where the sheets overlap are arranged in the width direction of the laminate. The thick region R3 includes a folded portion 911 of the first sheet continuous body 91, an end sheet continuous body 96, and a facing portion 912 of the first sheet continuous body 91 corresponding to the front portion 701 and the rear portion 703, respectively. . The medium-thickness region R2 includes an end sheet continuum 96, a second sheet continuum 92, and a first sheet continuum 91 corresponding to the front portion 701 and the rear portion 703, respectively. The thin region R1 includes a second sheet continuum 92 and a first sheet continuum 91 corresponding to the front portion 701 and the rear portion 703, respectively.

As described above, in the ultrasonic welding apparatus 1, the anvil unit 5 rotates together with the sheet holding drum 3 about the central axis J1, and the anvil roller 51 rolls and moves in the width direction of the laminate (drum axial direction). . As a result, the processing position continuously moves in the laminate width direction in the target region T1 arranged on the output surface 411 of the head 40 (step S11). In the example of FIGS. 10 and 11 , in the forward path of the reciprocating movement of the processing position, the distance from the end of the target region T1 on the thick region R3 side (body opening 61 side) to the thin region R1 side (leg opening 62 side) is increased. The processing position moves toward the edge. Further, in the return path, the processing position moves from the end of the target region T1 on the side of the thin region R1 toward the end of the region on the side of the thick region R3. In this processing example, the speed at which the processing position moves on the continuous sheet stack 9 is substantially constant. Further, the pressure applied to the processing position by the anvil roller 51 (biasing force by the biasing portion 523) is also substantially constant.

In the ultrasonic welding apparatus 1, in parallel with the movement of the processing position, ultrasonic vibration is applied to the processing position within the target region T1 by the ultrasonic wave applying unit 4 via the head 40 (step S12). At this time, the control unit 10 controls the ultrasonic wave applying unit 4 in accordance with the rotational position of the sheet holding drum 3 so that when the processing position is located in the first region, which is the thin region R1, and when the processing position is in the thick region R3. And the amplitude of the ultrasonic vibration is changed between when it is located in the second region which is the medium thickness region R2.

In this processing example, the maximum amplitude of ultrasonic vibration that can be applied to the continuous sheet stack 9 by the ultrasonic wave applying unit 4 is defined as an amplitude rate of 100%, and the amplitude of the ultrasonic vibration when the processing position is located in the first region The ratio is 69%, and the amplitude ratio of ultrasonic vibration when the processing position is located in the second region is 50%. In this way, the second region having a larger basis weight than the first region (that is, the second region having a larger amount of resin per unit area than the first region) has an amplitude rate smaller than that of the first region. A sonic vibration is applied. Of course, the amplitude ratios of ultrasonic vibrations for the first region and the second region may be changed as appropriate.

As shown in FIG. 11, two uneven patterns 512 are provided on the contact surface 511 of the anvil roller 51 with a gap therebetween in the longitudinal direction of the laminate (anvil axial direction). Specifically, as shown in FIG. 12 , in each uneven pattern 512 , a plurality of pattern elements 513 are arranged along the entire circumference of the anvil roller 51 . In the target region T<b>1 , the plurality of sheets forming the continuous sheet stack 9 are melted and solidified (welded) only in the regions in contact with the pattern elements 513 . In other words, welding traces are formed by transferring the pattern elements 513 . In this manner, two side seal portions 77 corresponding to the two uneven patterns 512 are formed with a slight gap in the longitudinal direction of the laminate.

Preferably, the plurality of pattern elements 513 arranged at the same position in the longitudinal direction of the laminate have the same shape (same width) and are arranged at a constant pitch in the circumferential direction. As a result, the width of the side seal portion 77 in the longitudinal direction of the laminate becomes constant over the entire width direction of the laminate (from the trunk opening 61 to the leg opening 62), and when the absorbent article 6 is worn, the width of the side seal portion 77 is constant. It is possible to prevent or suppress the occurrence of excessive peeling. Depending on the design of the side seal portion 77, the width of part of the side seal portion 77 may be different from that of other portions. In addition, since the total length of the output surface 411 of the head 40 in the laminate width direction is greater than the total length of the target region T1, the total length of the laminate width direction (from the trunk opening 61 to the leg opening 62) can be reduced. ) The side seal portion 77 can be appropriately formed.

By the way, when ultrasonic vibration is applied to the target region T1 in both the outward and return paths of the reciprocating movement of the processing position, the welding marks formed in the target region T1 in the outward path are shifted from the welding marks formed in the target area T1 in the return path. may be formed. Therefore, in the preferred ultrasonic welding apparatus 1, ultrasonic vibration is applied to the target region T1 in one of the outward and return passes, and ultrasonic vibration is not applied in the other. As a result, it is possible to appropriately form the welding marks having the same pattern as the concave-convex pattern 512 in the side seal portion 77 . Of course, ultrasonic vibration may be applied to the target region T1 both on the outward trip and the return trip.

When the anvil roller 51 reciprocates the output surface 411 of the head 40 in the width direction of the laminate, the formation of the side seal portions 77 is completed. A portion of the continuous sheet stack 9 where the side seal portion 77 is formed is separated from the outer peripheral surface 30 of the sheet holding drum 3 and carried out from the ultrasonic welding apparatus 1 . The processes of steps S11 and S12 are sequentially performed on a plurality of target regions T1 on the continuous sheet stack 9. FIG. The portion of the continuous sheet laminate 9 that has passed through the ultrasonic welding device 1 is cut between the two side seal portions 77 to obtain a single absorbent article 6 .

Next, an experiment for investigating the relationship between the amplitude rate of ultrasonic vibration and the tensile strength of the side seal portion 77 will be described. First, a continuous sheet laminate 9 similar to the above example was prepared. In the continuous sheet laminate 9, the basis weight of the thick region R3 where six sheets are overlapped is 102 g/m ² , the basis weight of the medium thickness region R2 where six sheets are overlapped is 98 g/m ² . The basis weight of the thin region R1 where the sheets overlap was 64 g/m ² . Subsequently, in the ultrasonic welding apparatus 1, the amplitude rate of ultrasonic vibration is set at a constant value of 50%, and ultrasonic vibration is applied to the thick region R3, medium region R2, and thin region R1 of the target region T1. Granted. At this time, the speed at which the processing position moved on the continuous sheet laminate 9 and the pressure (0.3 MPa) applied to the processing position by the anvil roller 51 were substantially constant. After that, the tensile strength of the side seal portion of the obtained absorbent article was measured.

Measurement of tensile strength was performed as follows. First, the absorbent article was cut at the position indicated by the dashed line L1 in FIG. 1 to cut out a portion including each side seal portion. Subsequently, in the cut piece of the side seal portion, the cut piece was cut in the horizontal direction (article width direction) at a position of 40 mm downward from the upper end in the vertical direction of FIG. Obtained. The portion of the side seal portion included in the test piece is almost entirely the thick region R3, and is hereinafter referred to as the "thick region test piece".

Further, the cut piece was horizontally cut at a position of 40 mm upward from the lower end to obtain a test piece with a length of 40 mm. The portion of the side seal portion included in the test piece is almost entirely the thin region R1, and is hereinafter referred to as the "thin region test piece". Further, the cut pieces of the side seal portion were cut horizontally at positions separated by 20 mm vertically from the center in the vertical direction to obtain test pieces with a length of 40 mm. The portion of the side seal portion included in the test piece is almost entirely the medium-thickness region R2, and hereinafter referred to as the "medium-thickness region test piece". In this manner, two thick region test pieces, two medium region test pieces, and two thin region test pieces were produced from one absorbent article 6 .

Subsequently, each test piece was opened 180 degrees with the side seal portion in the center, that is, in a state in which the front portion, the side seal portion, and the rear portion were aligned vertically. , and attached to the upper and lower chucks of a tensile tester (Tensilon Universal Material Testing Machine RTG-1210 manufactured by A&D Co., Ltd.). In the tensile test, the upper chuck was pulled upward at a tensile speed of 300 mm/min, and the maximum strength when the side seal portion was broken or peeled off was obtained as the tensile strength. The tensile strength is a tensile strength value per 40 mm length of the side seal portion in the vertical direction in FIG. 1, and the unit of measurement is [N/40 mm].

In the same manner as described above, the amplitude ratios of the ultrasonic vibrations are set constant at 55% and 57%, respectively, and ultrasonic waves are applied to the thick region R3, the medium region R2 and the thin region R1 of the target region T1. given vibration. After that, the tensile strength of the side seal portion of the obtained absorbent article was measured. Table 1 shows the tensile strength of the thick-walled region test piece, the medium-walled region test piece, and the thin-walled region test piece when the amplitude rate of the ultrasonic vibration is 50%, 55%, and 57%, respectively. (Average value of 15 test pieces) is shown.

As shown in Table 1, when the amplitude rate of ultrasonic vibration is the same, the tensile strength of the test piece in the thick region is the maximum, and the tensile strength of the test piece in the thin region is the minimum. Specifically, the difference in tensile strength between the test piece in the thick region with a small difference in basis weight and the test piece in the medium region is small at any amplitude rate, but the difference in tensile strength is small at any amplitude rate. There was a large difference in tensile strength between the specimens in the thick and thin areas. In addition, the tensile strength increased as the amplitude ratio of the ultrasonic vibration increased in all of the thick-walled region test piece, the medium-walled region test piece, and the thin-walled region test piece.

Subsequently, an ultrasonic vibration with an amplitude rate of 50% was applied to the thick region R3 and the medium thickness region R2 of the target region T1, and an ultrasonic vibration with an amplitude rate of 69% was applied to the thin region R1. After that, the tensile strength of the side seal portion of the obtained absorbent article was measured. Table 2 shows the tensile strength (average value of 15 test pieces) of the thick region test piece, the medium region test piece, and the thin region test piece in the absorbent article. Table 2 also shows the tensile strength when the amplitude rate is constant at 50%.

As shown in Table 2, by applying ultrasonic vibration with a larger amplitude rate to the thin region R1 than the thick region R3 and the medium region R2, the thick region test piece and the thin region test piece The difference in tensile strength between Specifically, when the amplitude ratio is constant at 50%, the tensile strength in the first region, which is the thin region R1, is 0% of the tensile strength in the second region, which is the thick region R3 and the medium region R2. .70 times or less, when applying ultrasonic vibration with a larger amplitude rate than the second region to the first region, the tensile strength in the first region is the tensile strength in the second region 0.87 times or more.

By the way, in the absorbent article, it is preferable that the entire side seal portion has substantially uniform strength. From such a viewpoint, the tensile strength in the first region is preferably 0.75 times or more the tensile strength in the second region, more preferably 0.80 times or more, and 0.82 times or more. It is even more preferable to have From the viewpoint of avoiding application of excessively large amplitude ultrasonic vibrations to the first region (avoiding the occurrence of holes, etc.), the tensile strength in the first region is higher than the tensile strength in the second region. It is preferably 1.10 times or less, more preferably 1.05 times or less, and even more preferably 1.00 times or less.

In the above experiments, the basis weight of the first region was 64 g/m ² and the basis weight of the second region was approximately 100 g/m ² . Considering the above experimental results, the basis weight of the first region is preferably 75 g/m ² or less, more preferably 70 g/m ² or less, and even more preferably 68 g/m ² or less. . The basis weight of the first region is, for example, 40 g/m ² or more, preferably 50 g/m ² or more, more preferably 55 g/m ² or more. Also, the basis weight of the second region is preferably 85 g/m ² or more, more preferably 90 g/m ² or more, and even more preferably 92 g/m ² or more. The basis weight of the second region is, for example, 125 g/m ² or less, preferably 115 g/m ² or less, more preferably 110 g/m ² or less.

As described above, in the ultrasonic welding apparatus 1, by moving the anvil roller 51, the processing position sandwiched between the anvil roller 51 and the head 40 in the target region T1 of the continuous sheet laminate 9 is laminated. Move across the body. In addition, the target region T1 includes a first region and a second region having a larger basis weight than the first region, and when the processing position is positioned in the first region and when positioned in the second region , the amplitude of the ultrasonic vibration is changed. Thereby, the side seal portion 77 having substantially uniform strength (typically, tensile strength) can be easily formed. Further, the amplitude of the ultrasonic vibration when the processing position is located in the first region is larger than the amplitude of the ultrasonic vibration when the processing position is located in the second region, so that the side seal has substantially uniform strength. The portion 77 can be formed more reliably.

By the way, in the apparatus of Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-113194), when changing the size or type of the absorbent article to be processed, the width of a plurality of regions having different thicknesses or the number of laminated sheets (laminated body Since the width in the width direction also changes, it is necessary to separately fabricate a plurality of heads having different widths according to the plurality of regions. In addition, complicated work is required to adjust the clearance between each head and the anvil. On the other hand, in the ultrasonic welding apparatus 1 of FIG. 6, even when the size and type of absorbent article to be processed are changed, the settings related to the amplitude of the ultrasonic vibration (magnitude of amplitude rate and change point) position, etc.) can start processing. Moreover, since there is no need to manufacture a head according to the size and type of absorbent article, it is possible to reduce the cost required for manufacturing the absorbent article.

In the preferred ultrasonic welding apparatus 1, the pressure acting on the processing position is constant while the processing position is moving in the laminate width direction. By pressing the anvil roller 51 toward the continuous sheet stack 9 with a constant force in this way, the anvil roller 51 escapes at a position where the thickness of the continuous sheet stack 9 changes. separation from the laminate 9) can be more reliably prevented. As a result, the side seal portions 77 can be formed without discontinuity in the laminate width direction and with constant strength and hardness.

Here, an experiment for examining the relationship between the pressure acting on the treated position and the tensile strength will be described. In this experiment, by changing the type of elastic member used as the biasing portion 523 of the ultrasonic welding apparatus 1, the pressure applied to the processing position by the anvil roller 51 was changed to 0.25 MPa and 0.3 MPa. The other conditions and the method of measuring the tensile strength were the same as in the above experiment for investigating the relationship between the amplitude ratio of ultrasonic vibration and the tensile strength. Table 3 shows the tensile strength ( mean value of 15 test pieces).

As shown in Table 3, the higher the pressure acting on the treatment position, the higher the tensile strength of the test piece in the thick region, medium region test piece, and thin region test piece. rice field. Therefore, by making the pressure acting on the processing position when the processing position is located in the first region larger than the pressure acting on the processing position when the processing position is located in the second region, the side having substantially uniform strength can be obtained. A seal portion 77 can be formed. In the ultrasonic welding apparatus 1, by using a mechanism with a variable biasing force as the biasing portion 523, it is possible to change the pressure acting on the processing position. For example, as a mechanism with a variable biasing force, a mechanism for changing the position of the other end of an elastic member whose one end is attached to the holding lever 522, a cylinder mechanism, and the like are exemplified.

Further, depending on the design of the ultrasonic wave applying unit 4 (for example, when the ultrasonic horn 41 can be omitted), the frequency of ultrasonic vibration may be changed. In this case, for example, the frequency of ultrasonic vibration when the processing position is located in the first region is made higher than the frequency of ultrasonic vibration when the processing position is located in the second region. Furthermore, in the ultrasonic welding device 1, the moving speed of the processing position in the width direction of the laminate may be changed. In this case, for example, the moving speed of the processing position when the processing position is located in the first area is made smaller than the moving speed of the processing position when the processing position is located in the second area. The moving speed of the processing position in the stack width direction can be changed according to the rotational position of the sheet holding drum 3 (the position of the processing position in the stack width direction) by changing the shape of the cam groove 221 of the cam drum 22, for example. Can be changed. A mechanism that moves the anvil roller 51 in the laminate width direction using a motor or the like may also be employed.

As described above, in the ultrasonic welding apparatus 1, the amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, and the processing position are affected depending on whether the processing position is located in the first region or the second region. If the strength difference between the first region and the second region of the side seal portion 77 is reduced (compared to the case where no change is made) by changing the pressure applied or the moving speed of the processing position in the width direction of the laminate. good. Thereby, the side seal portion 77 having substantially uniform strength can be appropriately formed. Of course, two or more values of the amplitude of ultrasonic vibration, the frequency of ultrasonic vibration, the pressure acting on the processing position, and the moving speed of the processing position may be changed. In this case, if it is possible to appropriately form the side seal portions 77 having substantially uniform strength, for example, the amplitude of the ultrasonic vibration when the processing position is located in the first region is It may be equal to or less than the amplitude of the ultrasonic vibration when positioned in the second region.

FIG. 13 is a diagram showing another example of the ultrasonic welding device. The ultrasonic welding device 1a of FIG. 13 includes an anvil roll 5a and an ultrasonic wave applying section 4a. The anvil roll 5a is a substantially cylindrical anvil centered on the central axis J2, and rotates about the central axis J2. The anvil roll 5a has a block 56 extending in a direction parallel to the central axis J2 on its outer peripheral surface. A continuous sheet laminate 9 is held on the outer peripheral surface of the anvil roll 5a so that the laminate width direction is substantially parallel to the central axis J2. A surface 561 of the block 56 facing outward in the radial direction about the central axis J2 is a contact surface that contacts one target region T1 (see FIG. 5) of the continuous sheet stack 9 . FIG. 13 shows a cross section of the continuous sheet laminate 9 perpendicular to the longitudinal direction of the laminate.

The ultrasonic wave applying unit 4 a has a plurality of heads 46 . A plurality of heads 46 are arranged in the width direction of the laminate. Each head 46 has, for example, an ultrasonic horn and an ultrasonic transducer, similar to the head 40 of FIG. Each head 46 has an output surface 461 facing the outer peripheral surface of the anvil roll 5a. The ultrasonic wave imparting unit 4a applies ultrasonic waves to a target region T1 of the continuous sheet laminate 9 sandwiched between the contact surface 561 of the anvil roll 5a and the output surfaces 461 of the plurality of heads 46 via the plurality of heads 46. Gives sonic vibrations. As in the above-described processing example, the target region T1 includes a first region and a second region having a basis weight larger than that of the first region, and the ultrasonic wave applying unit 4a and the head 46 facing the first region. , and a head 46 facing the second region. Specifically, in the example of FIG. 13, the first region is the thin region R1 and the second region includes the thick region R3 and the medium region R2. The ultrasonic wave applying unit 4a includes a head 46 facing substantially the entire thin region R1, a head 46 facing substantially the entire medium region R2, and a head 46 facing substantially the entire thick region R3.

FIG. 14 is a diagram showing the flow of forming the side seal portion 77 using the ultrasonic welding device 1a. In the formation of the side seal portion 77, a plurality of absorbent articles 6 in the process of being manufactured in the continuous sheet laminate 9 are sequentially introduced onto the outer peripheral surface of the rotating anvil roll 5a, thereby contacting the contact surface 561 of the anvil roll 5a. The target area T1 is sequentially sandwiched between the output surfaces 461 of the plurality of heads 46 (step S21). In the ultrasonic applying unit 4a, the amplitude of the ultrasonic vibration is adjusted by the head 46 facing the first region and the head 46 facing the second region among the plurality of heads 46 under the control of the control unit (not shown). Ultrasonic vibration is applied to the target region T1 while making a difference (step S22). Specifically, the amplitude of ultrasonic vibration in the head 46 facing the first region is greater than the amplitude of ultrasonic vibration in the head 46 facing the second region. As a result, the side seal portion 77 is formed in which the tensile strength of the first region and the tensile strength of the second region are similar.

When the formation of the side seal portions 77 is completed, the portion of the continuous sheet laminate 9 where the side seal portions 77 are formed is separated from the outer peripheral surface of the anvil roll 5a and carried out from the ultrasonic welding apparatus 1a. The processes of steps S21 and S22 are sequentially performed on a plurality of target regions T1 on the continuous sheet stack 9. FIG. In the ultrasonic wave application unit 4a, the amplitude of the ultrasonic vibration differs among the head 46 facing the thin region R1, the head 46 facing the medium region R2, and the head 46 facing the thick region R3. may In this processing example, the pressures applied to the target region T1 by the plurality of heads 46 are substantially the same, but may be different.

In the ultrasonic welding apparatus 1a of FIG. 13, when changing the size or type of the absorbent article to be processed, after replacing with a plurality of heads 46 matching the widths of the first region and the second region in the width direction of the laminate, Processing can be started only by changing the set value of the amplitude rate of ultrasonic vibration. That is, in the ultrasonic welding device 1a, there is no need for the complicated work of adjusting the clearance between the head and the anvil as in the device disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-113194). can be easily formed.

In the ultrasonic wave application unit 4a, the frequencies of the ultrasonic vibrations of the plurality of heads 46 may be different. In this case, for example, the frequency of ultrasonic vibration in the head 46 facing the first area is made higher than the frequency of ultrasonic vibration in the head 46 facing the second area. Moreover, the application time of ultrasonic vibration (the ON time of the heads 46) in the plurality of heads 46 may be different. In this case, for example, the time for applying ultrasonic vibration to the head 46 facing the first region is set longer than the time for applying ultrasonic vibration to the head 46 facing the second region.

As described above, in the ultrasonic welding apparatus 1a, among the plurality of heads 46, the head 46 facing the first region and the head 46 facing the second region set the amplitude of the ultrasonic vibration, the ultrasonic wave The intensity difference between the first region and the second region of the side seal portion 77 may be reduced (compared to the case where the difference is not made) by making the vibration frequency or the application time of the ultrasonic vibration different. Thereby, the side seal portion 77 having substantially uniform strength can be appropriately formed. Of course, two or more set values of the amplitude of ultrasonic vibration, the frequency of ultrasonic vibration, and the application time of ultrasonic vibration are different between the head 46 facing the first region and the head facing the second region. 46 may be different.

Various modifications can be made to the ultrasonic welding devices 1 and 1a, the method of forming the side seal portion 77, and the absorbent article 6 described above.

In the ultrasonic welding apparatus 1 of FIG. 7, the anvil roller 51 moves on the output surface 411 of the head 40 of the ultrasonic applying unit 4, but instead of the anvil roller 51, the anvil roller 51 extends in the width direction of the laminate (drum axial direction). A block-shaped anvil may be provided, and the output surface of the head having a small width in the laminate width direction may move on the contact surface of the anvil in the laminate width direction. Also, both the anvil and the head may move in the laminate width direction with respect to the target region T1. As described above, in the ultrasonic welding apparatus 1, the moving part moves one or both of the contact surface of the anvil and the output surface of the head in the width direction of the laminate with respect to the target region T1. should move in the width direction of the laminate.

For example, when the side seal portion 77 is long, such as a boxer shorts type disposable diaper, and the single head 40 in the ultrasonic welding apparatus 1 shown in FIG. 7 cannot form the entire side seal portion 77. , a plurality of heads 40 may be arranged in the width direction of the laminate, and the anvil roller 51 may move on the output surface 411 of the plurality of heads 40 . Also in this case, the amplitude of the ultrasonic vibration in the head 40 where the processing position is arranged is controlled according to the movement of the processing position.

In the absorbent article 6, when each side seal portion 77 includes a first region and a second region having a basis weight larger than that of the first region, welding per unit length in the vertical direction in the first region By making the area of the trace larger than that of the second region, the side seal portion 77 having substantially uniform strength may be realized.

The absorbent article 6 may be a pants-type disposable diaper for children. Also, the structure of the absorbent article 6 described above may be used for pants-type disposable absorbent articles other than disposable diapers.

The configurations in the above embodiment and each modified example may be combined as appropriate as long as they do not contradict each other.

Reference Signs List 1, 1a ultrasonic welding device 4, 4a ultrasonic applying unit 5a anvil roll 6 absorbent article 7 exterior sheet 8 absorber 9 continuous sheet laminate 10 control unit 12 rotating mechanism 21 anvil holding drum 22 cam drum 40, 46 head 51 anvil Roller 61 Body opening 62 Leg opening 77 Side seal part 411, 461 Output surface 511 Contact surface (of anvil roller) 512 Concavo-convex pattern 561 Contact surface (of anvil roll) 701 Front part 702 Crotch part 703 Rear part R1 Thin region R2 Medium area R3 Thick area S11, S12, S21, S22 Step T1 Target area

The present invention relates to an ultrasonic welding device and a method for forming side seal portions.

According to the first aspect of the invention, in the production of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuously formed, so that each absorbent article is worn by a wearer. An ultrasonic welding device for forming a side seal portion in which the lateral ends of the front portion located on the ventral side of the wearer and the lateral ends of the rear portion located on the back side of the wearer are welded, wherein a plurality of In a continuous sheet laminate in which absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area; and a head facing the anvil, the processing position within the target area sandwiched between the contact surface of the anvil and the output surface of the head. , one or both of the ultrasonic wave applying unit that applies ultrasonic vibrations through the head, the contact surface of the anvil, and the output surface of the head are placed in the width direction with respect to the target area a moving unit that moves the processing position in the width direction; and the target region includes a first region and a second region having a basis weight larger than that of the first region, and the processing A control unit that changes the amplitude of the ultrasonic vibration or the frequency of the ultrasonic vibration depending on whether the position is located in the first area or the second area.

In the invention according to claim 5, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuous, so that each absorbent article is worn by the wearer. An ultrasonic welding device for forming a side seal portion in which the lateral ends of the front portion located on the ventral side of the wearer and the lateral ends of the rear portion located on the back side of the wearer are welded, wherein a plurality of In a continuous sheet laminate in which absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. , an anvil having a contact surface that contacts one target area; and a plurality of heads facing the anvil and arranged in the width direction, the contact surface of the anvil and the output surfaces of the plurality of heads. and an ultrasonic wave applying unit that applies ultrasonic vibrations via the plurality of heads to the target region sandwiched between, wherein the target region is a first region and more than the first region an amplitude of the ultrasonic vibration set by a head facing the first region and a head facing the second region among the plurality of heads; Alternatively , the frequency of the ultrasonic vibration is different.

According to the sixth aspect of the present invention, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuous, so that each absorbent article is worn by the wearer. A side seal forming method for forming a side seal portion in which a side end of a front portion located on the ventral side of the wearer and a side end of a rear portion located on the back side of the wearer are welded together, The ultrasonic welding device used in the method for forming the side seal portion spreads in a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, perpendicular to the longitudinal direction and in a width direction along the continuous sheet laminate. Target areas are set at regular intervals in the longitudinal direction, an anvil having a contact surface that contacts one target area, and a head facing the anvil, wherein the contact surface of the anvil and the head An ultrasonic wave applying unit that applies ultrasonic vibrations via the head to a processing position in the target area sandwiched between the output surface of the anvil, the contact surface of the anvil, and the head of the a moving unit that moves one or both of the output surfaces in the width direction with respect to the target area to move the processing position in the width direction, wherein the target area includes a first area and the first a second region having a basis weight larger than that of the region, and the side seal portion forming method includes a) the step of moving the processing position in the width direction by the moving portion; and b) the step a). in parallel with the step of applying the ultrasonic vibration by the ultrasonic wave applying unit to the processing position in the target region, wherein in the step b), the processing position is in the first region The amplitude of the ultrasonic vibration or the frequency of the ultrasonic vibration is changed depending on whether it is positioned or positioned in the second region.

According to a seventh aspect of the present invention, in the manufacture of pants-type absorbent articles, ultrasonic vibration is applied to a continuous sheet laminate in which a plurality of absorbent articles are continuously arranged, so that each absorbent article is worn by the wearer. A side seal forming method for forming a side seal portion in which a side end of a front portion located on the ventral side of the wearer and a side end of a rear portion located on the back side of the wearer are welded together, The ultrasonic welding device used in the method for forming the side seal portion spreads in a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, perpendicular to the longitudinal direction and in a width direction along the continuous sheet laminate. Target areas are set at regular intervals in the longitudinal direction, an anvil having a contact surface that contacts one target area, and a plurality of heads that face the anvil and are arranged in the width direction. and an ultrasonic wave applying unit that applies ultrasonic vibrations via the plurality of heads to the target area sandwiched between the contact surface of the anvil and the output surface of the plurality of heads, The target area includes a first area and a second area having a basis weight larger than that of the first area, and the method for forming the side seal portions includes the contact surface of the anvil and the contact surface of the plurality of heads. sandwiching the target region between the output surface and the amplitude of the ultrasonic vibration, or and applying the ultrasonic vibrations to the target area while varying the frequency of the ultrasonic vibrations.

A pants-type absorbent article according to the related art of the present invention includes an exterior sheet, which is a sheet laminate having a trunk opening at the upper end and a pair of leg openings at the bottom, and an outer sheet on the wearer side of the exterior sheet An absorbent body is attached to absorb excrement from the wearer, and the outer sheet comprises a front portion located on the abdomen side of the wearer, a rear portion located on the back side of the wearer, and the front portion. and a crotch portion continuous from the rear portion, and a pair of vertically extending side seal portions formed by ultrasonically welding both side end portions of the front portion and both side end portions of the rear portion. Each side seal portion includes a first region having a basis weight of 75 g/m ² or less and a second region having a basis weight of 85 g/m ² or more, and the tensile strength in the first region is the above It is 0.75 times or more the tensile strength in the second region.

Claims (8)

In the manufacture of pants-type absorbent articles, by applying ultrasonic vibration to a continuous sheet laminate in which a plurality of absorbent articles are continuous, the front part of each absorbent article located on the abdomen side of the wearer. An ultrasonic welding device for forming a side seal portion in which a side end portion and a side end portion of a rear portion located on the back side of a wearer are welded together,
In a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area;
A head facing the anvil is provided, and ultrasonic vibration is applied via the head to a processing position within the target area sandwiched between the contact surface of the anvil and the output surface of the head. an ultrasonic applying unit;
a moving unit that moves one or both of the contact surface of the anvil and the output surface of the head in the width direction with respect to the target area to move the processing position in the width direction;
The target area includes a first area and a second area having a basis weight larger than that of the first area, and when the processing position is located in the first area and located in the second area a control unit that changes the amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, the pressure acting on the processing position, or the moving speed of the processing position in the width direction;
An ultrasonic welding device comprising: The ultrasonic welding device according to claim 1,
The control unit changes the amplitude of the ultrasonic vibration,
An ultrasonic welding apparatus, wherein the pressure acting on the processing position is constant while the processing position is moving in the width direction. The ultrasonic welding device according to claim 1 or 2,
The ultrasonic wave, wherein the amplitude of the ultrasonic vibration when the processing position is located in the first region is larger than the amplitude of the ultrasonic vibration when the processing position is located in the second region. Welding equipment. The ultrasonic welding device according to any one of claims 1 to 3,
The anvil is a roller that rolls in the width direction, the outer peripheral surface of the roller is the contact surface, and an uneven pattern is formed on the outer peripheral surface,
The roller rolls in the width direction, and the processing position reciprocates the target region in the width direction,
The ultrasonic wave applying unit applies the ultrasonic vibration to the target region on one of the outward and return paths of the reciprocating movement of the processing position, and does not apply the ultrasonic vibration on the other. Welding equipment. In the manufacture of pants-type absorbent articles, by applying ultrasonic vibration to a continuous sheet laminate in which a plurality of absorbent articles are continuous, the front part of each absorbent article located on the abdomen side of the wearer. An ultrasonic welding device for forming a side seal portion in which a side end portion and a side end portion of a rear portion located on the back side of a wearer are welded together,
In a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area;
Having a plurality of heads facing the anvil and arranged in the width direction, the plurality of an ultrasonic wave applying unit for applying ultrasonic vibrations through the head of
with
The target area includes a first area and a second area having a basis weight larger than that of the first area. An ultrasonic welding apparatus, wherein the set amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, or the application time of the ultrasonic vibration is different between the heads facing each other. In the manufacture of pants-type absorbent articles, by applying ultrasonic vibration to a continuous sheet laminate in which a plurality of absorbent articles are continuous, the front part of each absorbent article located on the abdomen side of the wearer. A side seal portion forming method for forming a side seal portion in which a side end portion and a side end portion of a rear portion located on the back side of a wearer are welded together,
The ultrasonic welding device used in the side seal portion forming method is
In a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area;
A head facing the anvil is provided, and ultrasonic vibration is applied via the head to a processing position within the target area sandwiched between the contact surface of the anvil and the output surface of the head. an ultrasonic applying unit;
a moving unit that moves one or both of the contact surface of the anvil and the output surface of the head in the width direction with respect to the target area to move the processing position in the width direction;
with
The target area includes a first area and a second area having a higher basis weight than the first area,
The method for forming the side seal portion includes
a) moving the processing position in the width direction by the moving unit;
b) in parallel with the step a), applying the ultrasonic vibration to the processing position in the target region by the ultrasonic wave applying unit;
with
In the step b), the amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, and the processing position are influenced when the processing position is positioned in the first region and when the processing position is positioned in the second region. A method for forming a side seal portion, wherein the pressure to apply or the moving speed of the processing position in the width direction is changed. In the manufacture of pants-type absorbent articles, by applying ultrasonic vibration to a continuous sheet laminate in which a plurality of absorbent articles are continuous, the front part of each absorbent article located on the abdomen side of the wearer. A side seal portion forming method for forming a side seal portion in which a side end portion and a side end portion of a rear portion located on the back side of a wearer are welded together,
The ultrasonic welding device used in the side seal portion forming method is
In a continuous sheet laminate in which a plurality of absorbent articles are continuous in the longitudinal direction, target areas that are perpendicular to the longitudinal direction and spread in the width direction along the continuous sheet laminate are set at regular intervals in the longitudinal direction. an anvil having a contact surface in contact with a target area;
Having a plurality of heads facing the anvil and arranged in the width direction, the plurality of an ultrasonic wave applying unit for applying ultrasonic vibrations through the head of
with
The target area includes a first area and a second area having a higher basis weight than the first area,
The method for forming the side seal portion includes
sandwiching the target area between the contact surface of the anvil and the output surfaces of the plurality of heads;
The amplitude of the ultrasonic vibration, the frequency of the ultrasonic vibration, or the application time of the ultrasonic vibration for the head facing the first region and the head facing the second region among the plurality of heads. a step of applying the ultrasonic vibration to the target region while changing the
A method for forming a side seal portion, comprising: A pants-type absorbent article,
an exterior sheet which is a sheet laminate having a trunk opening at the upper end and a pair of leg openings at the lower end;
an absorber that is attached to the wearer side of the exterior sheet and absorbs excrement from the wearer;
with
The outer sheet is
a front part located on the wearer's ventral side;
a rear portion located on the back side of the wearer;
a crotch portion continuous from the front portion and the rear portion;
a pair of vertically extending side seal portions formed by ultrasonically welding both side end portions of the front portion and both side end portions of the rear portion;
with
Each side seal part
a first region having a basis weight of 75 g/m ² or less;
a second region having a basis weight of 85 g/m ² or more;
including
The absorbent article, wherein the tensile strength in the first region is 0.75 times or more the tensile strength in the second region.

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