JP2001157692A - Disposable diaper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disposable diaper wherein bonding strengths among members constituting the diaper are improved. SOLUTION: In the disposable diaper provided with a top sheet 2, a back sheet 3 and an absorbent body 4 placed between both sheets, a hot melt adhesive with a melt viscosity of 10-1,000 Pa.s at 140 deg.C is used for bonding either part between members comprising the diaper 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disposable diaper having improved joining strength between members constituting the diaper, for example, a side flap and a fastening tape.

[0002]

2. Description of the Related Art In a so-called deployable (flat type) disposable diaper, a fastening tape for fastening a diaper is disposed on side flaps formed on both left and right sides of a back side of the diaper. Have been. The fastening tape is sandwiched between a top sheet and a back sheet that constitute side flaps, and is fixedly joined by a hot melt adhesive. In recent years, a breathable material such as a nonwoven fabric has been used as a constituent material of the side flap in order to enhance the breathability of the diaper side portion.

[0003] However, since the nonwoven fabric has relatively large voids between fibers, it is not easy to bond and fix the fastening tape to the nonwoven fabric using a hot melt adhesive. In particular, it is not easy to simultaneously satisfy the shear resistance property and the high-speed 180 ° peel strength property, which are important properties for joining and fixing the fastening tape. A similar problem may occur when a hot-melt pressure-sensitive adhesive is used for bonding between other members constituting the diaper.

For the purpose of simultaneously satisfying the shear resistance and the high-speed 180 ° peel strength with respect to the joining and fixing of the fastening tape, for example, as shown in FIG. A diaper in which one end of a fastening tape 18 'is fixed, one end of an auxiliary tape 23' is fixed to the other surface of the side flap 10 ', and the other end of the auxiliary tape 23' is fixed to the fastening tape 18 'is proposed. Have been. But,
In this diaper, an additional material is required for the auxiliary tape 23 ', and the manufacturing cost is increased.

Accordingly, an object of the present invention is to provide a disposable diaper having improved joining strength between members constituting the diaper. Another object of the present invention is to provide a disposable diaper in which the bonding strength between the side flap and the fastening tape is improved while maintaining the air permeability of the side portion.

[0006]

According to the present invention, there is provided a disposable diaper having a liquid-permeable top sheet, a liquid-impermeable back sheet, and a liquid-retentive absorber interposed between the two sheets. The melt viscosity at 140 ° C. is 10 to 1000 Pa ·
The above object has been achieved by providing a disposable diaper using the hot-melt pressure-sensitive adhesive of s.

The present invention also provides a preferable method for producing the disposable diaper, wherein the hot melt adhesive in the tank of the applicator is sent out to a coating head via a transport pipe, and the diaper is moved by the coating head. After applying the hot melt adhesive to one of the constituent members, when manufacturing the diaper by bonding and fixing the other member of the diaper to the one member, the hot melt adhesive in the tank is manufactured. The agent is heated and melted to a predetermined temperature,
Another object of the present invention is to provide a method of manufacturing a disposable diaper in which the temperature of the hot melt adhesive in the coating head is set lower than the temperature of the hot melt adhesive in the tank.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. In FIG.
FIG. 2 is a perspective view of the disposable diaper according to an embodiment of the present invention in a use state, and FIG. 2 is a plan view and a cross-sectional view of the disposable diaper shown in FIG.

The diaper 1 of the present embodiment has a crotch C positioned at the crotch of the wearer when worn, and an abdomen positioned before and after the crotch C and positioned on the abdomen and back of the wearer when worn. S, and a back side portion B, comprising a liquid-permeable top sheet 2, a liquid-impermeable back sheet 3, and a liquid-retentive absorber 4 interposed between the two sheets 2, 3. . The absorber 4 has a vertically long rectangular shape. Similarly,
Each of the top sheet 2 and the back sheet 3 also has a vertically long rectangular shape, and extends from both left and right side edges and the front and rear end edges of the absorber 4. That is, the top sheet 2 and the back sheet 3 have outer shapes larger than the outer shape of the absorber. At the front and rear ends of the diaper 1, a plurality of elastic members 5, 5,... Are joined and fixed between the top sheet 2 and the back sheet 3 along the width direction of the diaper 1 in an extended state. Thus, waist gathers 6 are formed at the front and rear ends of the diaper 1.

The top sheet 2 is formed of a liquid-permeable sheet such as a nonwoven fabric or a perforated film, and the back sheet 3 is formed of a liquid-impermeable sheet such as a plastic film. Further, the back sheet 3 may be formed of a microporous sheet having moisture permeability. Further, the back sheet may be a laminated sheet of a liquid-impermeable inner layer sheet with or without moisture permeability and an outer layer sheet made of a nonwoven fabric.

Exterior nonwoven fabrics 8 and 8 are continuously connected to the left and right side edges of the back sheet 3 by an adhesive 7 such as a hot melt adhesive, and the exterior nonwoven fabrics 8 extend outward from the left and right side edges of the back sheet 3. Is extended. An interior nonwoven fabric 9 is overlaid on the exterior nonwoven fabric 8. The two nonwoven fabrics 8 and 9 are adhered to each other by the adhesive 7 so that a bonded portion and a non-bonded portion are formed. The outer nonwoven fabric 8 and the inner nonwoven fabric 9 bonded together form side flaps 10, 10 extending outward from both left and right edges of the back sheet 3. Since the side flaps 10 are made of a non-woven fabric, the side flaps have air permeability. As a result, when the diaper 1 is attached, the air permeability of the diaper side portion is maintained, and stuffiness and skin irritation caused by the heat are effectively prevented. .

The exterior nonwoven fabric 8 is composed of a single-layer nonwoven fabric.
Or a laminate of a plurality of nonwoven fabrics. Exterior
When the nonwoven fabric 8 is composed of a laminate, the laminate is
Melt blown spunbond (SMS) non-woven fabric
Or spunbond / spunbond (SS) nonwoven fabric
Can be. The outer nonwoven fabric has a basis weight of 7 to 30 g /
m ^Two, Especially 10 to 25 g / m^TwoTo be breathable,
Securing the strength of the fixing portion of the fastening tape 18 described later,
Adhesion with hot melt adhesive, e
Prevents exudation of hot melt adhesive, texture, workability, etc.
It is preferable from the point of view. Interior nonwoven fabric 9 is the same as exterior nonwoven fabric 8
May be composed of a single layer of nonwoven fabric,
A laminate of cloth may be used. The interior nonwoven fabric 9 will be described later.
As a three-dimensional guard to prevent lateral leakage of excrement
From the viewpoint of performance, it is preferable to have water repellency.
The interior nonwoven fabric 9 has a basis weight of 7 to 30 g / m.^Two, Especially 1
0 to 25 g / m^TwoCan be breathable, hot melt
Adhesiveness with adhesive, hot melt viscosity after long-term storage
Preferred from the viewpoint of prevention of exudation of the adhesive, texture, workability, etc.
New

The outer edge 11 of the side flap 10 forms left and right side edges of the diaper 1, and a portion corresponding to the diaper crotch C of the outer edge 11 is concavely curved. Slightly inside the outer edge 11, a plurality of elastic members 12, 12,... Are joined and fixed between the exterior nonwoven fabric 8 and the interior nonwoven fabric 9 along the concavely curved outer edge 11. I have. As a result, leg gather 1 is placed on the crotch C of the diaper 1.
3 and 13 are respectively formed.

The interior nonwoven fabric 9 has an extension 1 extending inward (in the direction of the longitudinal center line of the diaper 1) from the inner edge of the exterior nonwoven fabric 8.
Four. The front and rear ends of the extension portion 14 are joined and fixed to the top sheet 2 in an inward state. The extension 14 has a fixed end 15 and a free end 16. The fixed end 15 is formed by joining and fixing the vicinity of the inner edge of the exterior nonwoven fabric 8 in the extension portion 14 to the top sheet 2 by the adhesive 9 along the longitudinal direction of the diaper 1.
The free end 16 is formed by folding the inner edge of the interior nonwoven fabric 9 into a sleeve shape. In this sleeve, an elastic member 17 is joined and fixed in an extended state, so that when the diaper 1 is mounted, the extension portion 14 stands up in the longitudinal direction of the diaper 1 to prevent lateral leakage of excrement. Functions as a three-dimensional guard to prevent.

Fastening tapes 18 for fastening the diaper are provided on the side flaps 10 on the right and left sides of the back side B of the diaper 1. Fastening tape 18
Has a vertically long shape, and is composed of a base sheet 19 made of a thick nonwoven fabric or a plastic film and a hook member 20 of a mechanical fastener. The base sheet 19 has a free end 19a and a fixed end 19b at both ends in the longitudinal direction. A hook member 20 of a mechanical fastener is fixed near the free end 19a. On the other hand, the fixed end 19b is joined and fixed on the exterior nonwoven fabric 8 in the side flap 10 by the hot melt adhesive 21. When the diaper 1 is worn, the hook member 20 of the fastening tape 18 engages with the loop member 22 of the mechanical fastener disposed on the back sheet 3 of the diaper ventral side S.

In the diaper 1 of the present embodiment, the hot melt adhesive 21 for joining and fixing the base sheet 19 of the fastening tape 18 and the nonwoven fabric 8 of the side flap 10 has a melt viscosity at 140 ° C. 10 to 1000 Pa · s, preferably 10 to
800 Pa · s, more preferably 15 to 500 Pa ·
s, more preferably 30 to 100 Pa · s. When a nonwoven fabric and a fastening tape are bonded and fixed by a hot melt adhesive that has been conventionally used, it is not easy to simultaneously satisfy the shear resistance property and the high-speed 180 ° peel strength property, but the hot melt adhesive having a melt viscosity within the above range is not easy. , These two characteristics can be satisfied simultaneously. More specifically, if the melt viscosity is less than 10 Pa · s, the shear resistance and high speed 1
80 ° peel strength cannot be satisfied at the same time.
If it exceeds 00 Pa · s, it will be difficult to apply the hot melt adhesive to the base sheet 19 stably. The melt viscosity is measured with a B-type viscometer (Tokyo Keiki Co., Ltd.).

[0017] In the present specification, the shear resistance property means a property that the fastening tape is hard to be peeled off from the side flap under a predetermined temperature at a predetermined temperature while applying a predetermined load to the fastening tape. As shown in FIG. 3, refers to the property that the fastening tape is hard to peel off from the side flap when the fastening tape is pulled at a high speed in the direction of 180 ° with respect to the side flap.

The hot melt pressure-sensitive adhesive 21 can be used without any particular limitation as long as the melt viscosity is within the above range. Examples thereof include a styrene-based hot melt pressure-sensitive adhesive and an olefin-based hot melt pressure-sensitive adhesive. And the like. Considering processability and adhesive strength, a styrene-based hot melt adhesive is particularly preferred.

The hot melt adhesive 21 preferably comprises a base polymer, a tackifier which is solid at room temperature, a softener component and an antioxidant as constituents.

As the base polymer, styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer Coalescing (SEB
S), styrene-ethylene-propylene-styrene block copolymer (SEPS) and the like. When the total amount of the tackifier component and the softener component is 100 parts by weight,
It is preferably used in a range of from 130 to 130 parts by weight, particularly from 40 to 120 parts by weight.

Examples of the tackifier include C ₅ petroleum resin,
C ₉ petroleum resins, dicyclopentadiene-based petroleum resins, rosin-based petroleum resins, polyterpene resins, terpene phenol resins, and the like, in a total amount of 100 parts by weight of the tackifying component and softening agent component, 60 to 99 parts by weight, Especially 70-9
It is preferably used in the range of 5 parts by weight.

Examples of the softener include process oils having a softening point of 10 ° C. or lower and an average molecular weight of 200 to 700, mineral oil, various plasticizers, polybutene, and liquid tackifier resins. Total amount of ingredients 10
It is preferably used in an amount of 1 to 40 parts by weight, particularly 5 to 30 parts by weight in 0 parts by weight.

As the antioxidant, a phenolic antioxidant, an amine antioxidant, a phosphorus antioxidant, a benzimidazole antioxidant and the like are used, and the total of the base polymer, the tackifier and the softener is used. When the amount is 100 parts by weight, it is preferably used in the range of 0.5 to 3 parts by weight.

The hot-melt pressure-sensitive adhesive 21 may contain, in addition to these components, components normally used in pressure-sensitive adhesives such as an ultraviolet absorber.

The hot melt pressure-sensitive adhesive 21 is 20 to 100
g / m ^2, it is particularly applied at a basis weight of 40 and 80 g / m ^2, anti-shear properties and high-speed 180 ° peel strength properties are simultaneously satisfied, and that the hot melt adhesive does not exude during storage Is preferred.

The diaper 1 of this embodiment is preferably manufactured by the method described below. That is, the hot-melt adhesive 21 in the tank of the applicator is sent out to the coating head via the transport pipe, and the hot-melt adhesive 21 is applied to the fixed end 19b of the base sheet 19 in the fastening tape 18 by the coating head. Is applied, and the fixed end 19b is joined and fixed on the exterior nonwoven fabric 8 in the side flap 10, whereby the diaper 1 is manufactured. At this time, the hot-melt adhesive 21 in the tank is heated and melted to a predetermined temperature, and the temperature of the hot-melt adhesive 21 in the coating head is adjusted to the hot-melt adhesive 2 in the tank.
1 and the temperature of the hot melt adhesive 21 in the transport pipe is set to the temperature of the hot melt adhesive 21 in the coating head and the temperature of the hot melt adhesive 21 in the tank. Set between.

When applying the hot melt pressure-sensitive adhesive 21 used in the present invention by a conventional hot-melt pressure-sensitive adhesive coating method, that is, a method in which the temperatures of the tank, the conveying pipe and the coating head are all the same. However, there are the following inconveniences. That is, when the melting temperature of the hot melt adhesive 21 is low, the hot melt adhesive 21 does not circulate smoothly in the applicator, and a large load is applied to the motor of the circulation pump. On the other hand, when the melting temperature of the hot melt adhesive 21 is high, the base sheet 19 of the fastening tape 18 is thermally damaged when coming into contact with the coating head. On the other hand, the inconvenience is solved by applying the hot melt adhesive 21 by the above-mentioned method.

When applying the hot-melt adhesive 21, the temperature of the hot-melt adhesive 21 in the tank and the coating head is set to 150 to 200 ° C. and 120 to 150 ° C., particularly 160 ~ 180 ° C
And 130 to 140 ° C. are preferable in order to suppress thermal deterioration such as carbonization in the tank and to reduce the motor load of the circulating pump. In addition, in the coating head portion, coating stability and It is preferable from the viewpoint of reducing thermal damage to the base sheet.

When the hot melt adhesive 21 is applied, the melt viscosity of the hot melt adhesive 21 in the tank and the coating head is 5 to 50 P each.
a · s and 10 to 500 Pa · s, especially 5 to
40 Pa · s and 10 to 300 Pa · s,
It is preferable from the viewpoint of reducing the load on the pump of the applicator and the coating stability of the coating head.

The method of applying the hot-melt adhesive 21 may be either in-line coating or off-line coating. However, it is generally better to join immediately after applying the hot-melt adhesive because the bonding performance is generally better. Coating is preferred.

The present invention is not limited to the above embodiment. For example, the fastening position of the fastening tape 18 is
Not limited to the above, the fastening tape 18 may be fixed on the interior nonwoven fabric 9 or between the exterior nonwoven fabric 8 and the interior nonwoven fabric 9. Further, as shown in FIG. 4, the fastening tape 18 is fixed between the exterior nonwoven fabric 8 and the interior nonwoven fabric 9,
Further, the interior nonwoven fabric 9 and the fastening tape 18 may be fixed via the auxiliary tape 23. However, the hot-melt adhesive used in the present invention is a non-woven fabric,
9 and the peeling strength between the nonwoven fabrics 18 and 19 and the fastening tape 18 is high, so that sufficient performance can be obtained without using the auxiliary tape 23, as is clear from the examples described later. Therefore, the disposable diaper of the present invention also has an advantage of cost reduction. In this case, the auxiliary tape 23, the interior nonwoven fabric 9 and the fastening tape 18
It is preferable to use the hot-melt pressure-sensitive adhesive 21 for the bonding and fixing. The use of the auxiliary tape 23 is advantageous when the bonding area between the external nonwoven fabric 8 or the internal nonwoven fabric 9 and the fastening tape 18 cannot be sufficiently ensured due to diaper design reasons.

In place of the hook member 20 of the mechanical fastener in the fastening tape 18, a coating layer of an adhesive may be formed. In this case, instead of the loop member 22 of the mechanical fastener disposed on the back sheet 3 of the diaper ventral side S, a plastic film to which the coating layer of the adhesive can be attached is used.

The bonding between the constituent members of the diaper by the hot melt adhesive 21 is not limited to the bonding between the side flaps 10 and the fastening tape 18, but also includes the outer nonwoven fabric 8 and the inner nonwoven fabric 9, the backsheet 3 and the outer Non-woven fabric 8, bonding of top sheet 2 and back sheet 3 and the like.

[0034]

The present invention will be described in more detail with reference to the following examples.

Examples 1-3 and Comparative Examples 1 and 2 The disposable diapers shown in FIGS. 1 and 2 were produced. Table 1 shows the melt viscosity at 140 ° C. of the hot melt pressure-sensitive adhesive used for bonding and fixing the fastening tape to the side flaps. Table 1 also shows the types of the outer nonwoven fabric forming the side flaps. The base sheet of the fastening tape was a spunbond nonwoven fabric made of polypropylene. In Examples 1 and 2, when applying the hot melt adhesive, the temperature and melt viscosity of the hot melt adhesive in the tank of the applicator and in the coating head were 160 to 180 ° C. and 130 to 14, respectively.
0 ° C, and 5 to 20 Pa · s and 12 to 100 Pa · s
s. The same hot-melt pressure-sensitive adhesive as that of Example 2 was used as the hot-melt pressure-sensitive adhesive of Example 3. In Comparative Examples 1 and 2, the temperature of the hot-melt pressure-sensitive adhesive in the tank of the applicator, the inside of the transport tube, and the inside of the coating head was all set to 140 ° C. The melt viscosity of the hot melt adhesive at 140 ° C. was 7 Pa ·
s (Comparative Example 1) and 8 Pa · s (Comparative Example 2).

The diapers obtained in each of the examples and comparative examples were evaluated for shear resistance and high-speed 180 ° peel strength by the following methods. Table 1 shows the results. FIG.
Shows temperature-viscosity curves of the hot melt pressure-sensitive adhesives used in Examples 1 to 3 and Comparative Examples 1 and 2. The viscosity of the hot melt adhesive was measured using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd.). The rotor No. 4 was used for the measurement, and the rotation speed of the rotor was 6 rpm.

[Shear Resistance] The longitudinal direction of the fastening tape is set to be vertical, and a load of 9.8 N is applied to the tip of the fastening tape in an environment of 40 ° C. until the fastening tape is sheared off from the side flaps. Was measured.

[High-Speed 180 ° Peeling Strength Characteristics] As shown in FIG. 3, the maximum load when the fastening tape was pulled at 100 m / min in the 180 ° direction with respect to the side flap was measured. In Table 1, material destruction means that the fastening tape did not peel off from the side flaps during the measurement.
This means that the side flap near the joint with the side flap was broken.

[0039]

[Table 1]

As is evident from the results shown in Table 1, the disposable diapers of each embodiment in which the fastening tape was bonded and fixed to the side flaps using a hot melt adhesive having a specific melt viscosity had shear resistance and high speed. 18
It can be seen that both the 0 ° peel strength characteristics are satisfied.
In contrast, in the disposable diapers of each comparative example,
It can be seen that although the high-speed 180 ° peel strength characteristics are satisfied, the shear resistance characteristics are insufficient, or conversely, the high-speed 180 ° peel strength characteristics are insufficient although the shear resistance characteristics are observed. Although not shown in the table, no thermal damage was observed on the fastening tape of the diaper of each example due to the application of the hot melt adhesive.
In Example 3, as in the other examples, both the shear resistance and the high-speed 180 ° peel strength were satisfied, but the sample stored for one month in an environment of 40 ° C. and 80 RH% was obtained. Some of the hot melt pressure-sensitive adhesive was exuded in some of them. In Examples 1 and 2, such exudation was not observed. For reference, when an auxiliary tape is used in combination with the fastening tape of the diaper of Comparative Example 1, the same shear resistance as the diaper of Example 1 was obtained.

[0041]

According to the present invention, a disposable diaper having improved joining strength between members constituting the diaper is provided.
In particular, by forming the side flaps from a nonwoven fabric, the bonding strength between the side flaps and the fastening tape is improved while maintaining the air permeability of the side portions. In this case, sufficient bonding strength can be ensured without using an auxiliary tape, so that the material can be reduced and the manufacturing cost can be reduced. In addition, since the amount of the back sheet used can be reduced as compared with the conventional diaper, the manufacturing cost can be suppressed from this point as well.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a disposable diaper according to an embodiment of the present invention in use.

FIG. 2 (a) is a plan view of the disposable diaper shown in FIG. 1 when viewed from the top sheet side.
2 (b) and FIG. 2 (c) respectively show I in FIG. 2 (a).
FIG. 2 is a cross-sectional view taken along line I-II and line II-II.

FIG. 3 is a schematic view showing a method for measuring a high-speed 180 ° peel strength.

FIG. 4 is a schematic view (corresponding to FIG. 2 (c)) showing another fixing method of the fastening tape.

FIG. 5 is a diagram showing a temperature-viscosity curve of the hot melt pressure-sensitive adhesive used in Examples 1 to 3 and Comparative Examples 1 and 2.

FIG. 6 is a schematic diagram (corresponding to FIG. 2 (c)) showing a method of fixing a fastening tape in a conventional disposable diaper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disposable diaper 2 Top sheet 3 Back sheet 8 Exterior nonwoven fabric 9 Interior nonwoven fabric 10 Side flap 18 Fastening tape 21 Hot melt adhesive

Continued on the front page (72) Inventor Takahiro Arimura 2606 Kabane-cho, Akaga-cho, Haga-gun, Tochigi Prefecture F-term in the Kao Corporation Research Laboratories (reference)

Claims (5)

[Claims] 1. A disposable diaper provided with a liquid-permeable top sheet, a liquid-impermeable back sheet, and a liquid-retentive absorber interposed between the two sheets. 140 for joining
A disposable diaper using a hot melt adhesive having a melt viscosity at 10 ° C of 10 to 1000 Pa · s. 2. A side flap is formed on each of the left and right sides of a back portion located on the back side of a wearer when worn, and fastening tapes for fastening a diaper are disposed on the side flaps, respectively. 2. The disposable diaper according to claim 1, wherein the disposable diaper is formed of a nonwoven fabric, and the fastening tape is bonded and fixed to the side flaps with the hot melt adhesive. 3. The method for producing a disposable diaper according to claim 1, wherein the hot melt adhesive in a tank of the applicator is sent out to a coating head via a transport pipe, and the hot melt adhesive is fed by the coating head. After applying the hot melt adhesive to one member constituting the diaper, when manufacturing the diaper by bonding and fixing the other member constituting the diaper to the one member, A method for producing a disposable diaper, wherein a melt adhesive is heated and melted to a predetermined temperature, and the temperature of the hot melt adhesive in the coating head is set lower than the temperature of the hot melt adhesive in the tank. 4. The temperature of the hot-melt pressure-sensitive adhesive in the tank and the coating head is set to 150 to 100, respectively.
The method for producing a disposable diaper according to claim 3, wherein the temperature is 200C and 120 to 150C. 5. The melt viscosity of the hot melt adhesive in the tank and the coating head is 5 to 5, respectively.
The pressure is set to 50 Pa · s and 10 to 500 Pa · s.
Or the manufacturing method of the disposable diaper of 4.