JP3093413B2 - Absorbent articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorbent article such as a disposable diaper, and more particularly, to a non-sticky non-woven fabric surface when used because the adhesive has a low tackiness. The present invention relates to an absorbent article in which a certain softener or the like exudes, that is, a so-called “through phenomenon” is less likely to occur.

[0002]

2. Description of the Related Art A general disposable diaper has a structure in which an absorbent is interposed between a nonwoven fabric in contact with the skin and a moisture-permeable sheet, and predetermined portions thereof are adhered and fixed with an adhesive. The pressure-sensitive adhesive has tackiness in a wide temperature range (0 to 60 ° C.) in order to adhere a member that is difficult to adhere. Adhesives that can be adhered regardless of time (called open time) are used.

[0003] The above-mentioned pressure-sensitive adhesive is a low-viscosity rubber obtained by reducing the proportion of a base elastomer and increasing the proportion of a tackifier and a softener in order to develop tackiness and improve coating suitability. Rubber-based hot-melt adhesives are the mainstream in consideration of productivity and the like. Normally, in the rubber-based pressure-sensitive adhesive, the molecular weight of the base rubber (styrene-based block polymer) is large (70,000 to 100,000), and the ratio of the softener component is increased to reduce the melt viscosity.

[0004] As the above-mentioned moisture-permeable sheet, a moisture-permeable sheet made of porous polyolefin is usually used in order to prevent the diaper from becoming uneven when used.

[0005]

The above-mentioned pressure-sensitive adhesive having tackiness in a wide temperature range, which is used for ordinary absorbent articles, is suitable for bonding a material having a rough surface such as a nonwoven fabric. When the coating amount is large or when a high pressure is applied to the coating portion, there is a drawback that the nonwoven fabric seeps through and gives a sticky feeling. For this reason, use of an adhesive with reduced tackiness is conceivable.

However, there is a limit in reducing the tackiness of the rubber-based pressure-sensitive adhesive. When the tackiness is reduced, when the rubber-based pressure-sensitive adhesive is melted and applied, since the time from the molten state to the solid state is short, the solid state is obtained before the base material is bonded, At that time, if the tackiness is low, the adhesive strength to a substrate having a small contact area such as a non-woven fabric is not developed, which causes inconvenience for use in an absorbent article.

Further, in the rubber-based pressure-sensitive adhesive which easily exhibits tackiness in a wide range, the ratio of the tackifier and the softening agent is large and the ratio of the base elastomer is small, so that the softening agent and the like are hardly retained in the pressure-sensitive adhesive. Under the influence of heat or the like, a so-called "through-through phenomenon" occurs that seeps into the surface of the moisture-permeable sheet. When this see-through phenomenon occurs, the surface of the moisture-permeable sheet becomes sticky, adversely affects various physical properties of the diaper, blocking of the diapers occurs during storage of the pack, and changes in the adhesive composition cause the adhesive physical properties to change. Various inconveniences such as a change over time occur.

Accordingly, an object of the present invention is to provide an absorbent article having good adhesiveness to a substrate during the production thereof, and having a low tackiness and no stickiness during use. It is an object of the present invention to provide an absorbent article which has good properties and has almost no "through phenomenon" in which the exuding component such as a softening agent, which is a composition component in the adhesive, exudes to the surface of the moisture-permeable sheet.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object can be achieved by using a specific adhesive. The present invention has been made based on the above findings, and has a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorber interposed between these two sheets, and an absorbent integrated with an adhesive. in sexual article, the adhesive, which contains the amorphous poly-α-olefins and tackifier resins, moisture permeation amount of the backsheet, Ri 0.7~2.8g / 100cm ² · h der, upper
After applying the above-mentioned adhesive to the above-mentioned back sheet, 5 days at 60 ° C.
On the side opposite to the coating side of the back sheet after the passage of time
Decreasing rate of the reflectance, it is to provide an absorbent article, characterized in der Rukoto within 20%.

Hereinafter, the absorbent article of the present invention will be described in detail. The absorbent article of the present invention has a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorber interposed between these sheets, and is integrated with an adhesive.

The pressure-sensitive adhesive used in the absorbent article of the present invention includes an amorphous polyalphaolefin (hereinafter referred to as A
An APAO-based pressure-sensitive adhesive containing PAO) and a tackifier resin and, if necessary, a softener is used.

As the above-mentioned APAO, for example, a propylene / ethylene copolymer and a propylene / ethylene / butene-1 copolymer having a molecular weight of 1,000 to 20,000 are preferable.

[0013] Examples of the tackifier resin, softening point of 80 ° C. or higher, C ₅ petroleum resins molecular weight of 400 to 2,000, C ₉ petroleum resins, C ₅ / C ₉ petroleum resins A polyterpene resin which is a polymer of α-pinene, β-pinene or dipentene; a rosin-based resin, a DCPD (dicyclopentadiene) -based petroleum resin, and hydrogenated products thereof.

The softening agent has a softening point of 10
Preferred are process oils, various plasticizers, polybutenes, liquid resins and the like having an average molecular weight of 200 to 700 at a temperature of not more than ° C.

The preferred composition of the APAO-based pressure-sensitive adhesive is 50 to 200 parts by weight of the tackifier resin per 100 parts by weight of APAO (more preferably 70 to 15 parts by weight).
0 parts by weight) and 1 to 50 parts by weight (more preferably 1 to 30 parts by weight) of the above softener. When the content of the tackifier resin is less than 50 parts by weight, the fluidity at the temperature at which the base material is bonded becomes small, and the adhesive strength of a small contact area such as a nonwoven fabric becomes small. When the amount of the tackifier resin is more than 200 parts by weight, or when the amount of the softener is 5
If the content is more than 0 parts by weight, tackiness is exhibited in the operating temperature range of the absorbent article, and the stickiness is increased, and the phenomenon of strike-through of the moisture-permeable sheet may be increased. Above AP
As a method of coating the AO-based pressure-sensitive adhesive, beads, spirals, slots, gravure coating, and the like can be used, but beads and spiral coating are preferable in consideration of application to a moisture-permeable sheet having low heat resistance. The coating amount of the APAO pressure-sensitive adhesive is preferably 30 to 100 mg / m in the case of a bead. When the coating amount of the pressure-sensitive adhesive is less than 30 mg / m, it is difficult to obtain an adhesive force necessary for fixing the absorbent article. 100 coated adhesive
If it is more than mg / m, oozing from the surface material occurs,
There is a possibility that blocking at the time of product production and stickiness at the time of wearing may occur.

The APAO-based pressure-sensitive adhesive includes the AP
It is preferable to further add an antioxidant in addition to AO, the tackifier resin, and the softener.

Examples of the antioxidant include Irganox 1010, Irganox 1076 (manufactured by Ciba-Geigy Co., Ltd.), Sumilizer GM (Sumitomo Chemical Co., Ltd.) and the like. The amount of the antioxidant added is APAO1
It is preferably 1 to 3 parts by weight with respect to 00 parts by weight.

The above AP used in the absorbent article of the present invention
The AO-based pressure-sensitive adhesive has a long time to solidify from a molten state, maintains fluidity in a temperature range in which a substrate is bonded, and contributes to tackiness and adhesive strength by tackling to the substrate. it can.

In order to eliminate the sticky feeling of the adhesive when using the absorbent article of the present invention integrated using the APAO-based adhesive, the use temperature range of the absorbent article is 0 to 40 ° C. In this case, the tackiness of the pressure-sensitive adhesive may be reduced, so that the elastic modulus of the APAO-based pressure-sensitive adhesive at 0 to 40 ° C. is 10 ⁷ to 10
It is preferably ⁸ Pa. In addition, in order to develop tackiness at the time of bonding the substrate, the elastic modulus of the APAO-based pressure-sensitive adhesive at 40 to 60 ° C., which is the temperature range for bonding the substrate, is preferably 10 ⁵ to 10 ⁷ Pa. .

The elastic modulus of the APAO based adhesive at 0 to 40 ° C. is, if it is 10 ⁸ Pa greater, there is a possibility that the texture of the absorbent article is deteriorated, and if it is less than 10 ⁷ Pa, tackiness May be caused, which may cause stickiness and blocking.

Further, when the elastic modulus of the APAO-based pressure-sensitive adhesive at 0 to 40 ° C. is out of the above range, the elastic modulus range at which tackiness is exhibited at 40 to 60 ° C., which is the temperature range for bonding the substrate. no longer fall within the modulus range of 10 ⁵ to 10 ⁷ Pa is, the adhesive strength may be lowered.

40 to 6 in the temperature range for bonding the substrate
At 0 ° C., the elastic modulus of the APAO-based pressure-sensitive adhesive is 1
0 is less than ⁵ Pa, without cohesive force of the pressure-sensitive adhesive is expressed, the adhesive strength is lowered, there is a risk that tackiness will also expressed at the use temperature range of the absorbent article, also 10 ⁷
If it is more than Pa, tackiness may not be easily exhibited, so that the adhesive strength may be reduced.

In order to extend the time from the molten state to the solidification of the APAO-based pressure-sensitive adhesive, the loss tangent (tan δ) peak temperature determined from the dynamic viscoelasticity curve of the pressure-sensitive adhesive is 0 to 40 ° C. Is preferred.

If the tan δ peak temperature is higher than 40 ° C., the fluidity is reduced in the temperature range in which the substrate is bonded, and the adhesive strength may be reduced. Further, when the tan δ peak temperature is less than 0 ° C., the fluidity in the temperature range in which the substrate is bonded is maintained, but in the use temperature range of the absorbent article, tackiness may be developed, Also,
Due to an increase in low molecular weight components, there is a possibility that the “through phenomenon” in which these low molecular components seep onto the surface of the moisture-permeable sheet may increase.

Incidentally, the above "penetration phenomenon" means that when an adhesive is applied to a moisture-permeable sheet, a oozing component such as a softening agent in the adhesive wets the surface of the moisture-permeable sheet and strikes through (penetration). When the frosted glass is wet with water, light is transmitted and the outside becomes visible through the frosted glass.

The present inventors have attempted to quantify the above-mentioned “through-through phenomenon” by utilizing such a phenomenon.

That is, as shown in FIG. 1, a black plate 4 is disposed on the back side of the sample 3 in which the adhesive is applied to the back side of the moisture-permeable sheet. The plate 5 is arranged, and while blue incident light having a wavelength of 459 nm is irradiated from the surface side of the sample 3 (the transparent glass plate 5 side), the reflectivity of the reflected light from the sample 3 is measured, so that the strikethrough occurs. Degree (degree of exudation)
Was quantified. According to this method, when the degree of strikethrough is large (the degree of seepage is large), the blue incident light passes through the sample 3 and reaches the black plate 4, is absorbed by the black plate 4, and When the reflectivity of the reflected light from the sample 3 decreases and the degree of strikethrough is small (the degree of seepage is small), the incident blue light rarely passes through the sample 3 and reaches the black plate 4. The light is reflected by the sample 3 without being absorbed by the black plate 4, and the reflectance of the reflected light from the sample 3 increases.

As the surface sheet used for the absorbent article of the present invention, a liquid-permeable sheet used for ordinary absorbent articles such as a woven fabric and a nonwoven fabric can be suitably used. The back sheet used in the absorbent article of the present invention
Is a moisture permeable sheet having a moisture permeability of 0.7 to 2.8 g / 100 cm ² · h. Further, as the absorbent used in the absorbent article of the present invention, an absorbent used in ordinary absorbent articles such as defibrated pulp can be suitably used.

Further, in the absorbent article of the present invention, the coating in order to reduce the extent to which the "strike-through" phenomenon occurs from the backsheet, the APAO based adhesive to the back sheet (moisture-permeable sheet) After the working, the reduction rate of the reflectance on the surface opposite to the coated surface of the back sheet after 5 days at 60 ° C. is set to be within 20%. When the decrease rate of the reflectance is more than 20%, the back sheet surface may have a sticky feeling, adversely affect various physical properties of the absorbent article, may cause blocking between the absorbent articles at the time of pack storage, and may have an adhesive property. Various inconveniences may occur, such as a change in the adhesive properties with time due to a change in the agent composition.

The above AP used in the absorbent article of the present invention
Since the molecular weight of APAO itself is smaller than the rubber component of the rubber-based pressure-sensitive adhesive and the molecular weight can be arbitrarily adjusted, the AO-based pressure-sensitive adhesive has a hot melt viscosity that can be used for absorbent articles even if the softener component is small. It is possible to use a melt pressure-sensitive adhesive, so that the rate of decrease in the reflectance can be suppressed within 20%.

[0031]

In the absorbent article of the present invention, the elastic modulus is in an elastic modulus region where tackiness is not exhibited in a temperature range when the absorbent article is used, and tackiness is exhibited in a temperature range in which a substrate is bonded. According to the absorbent article of the present invention, by using an APAO-based pressure-sensitive adhesive that is in an elastic modulus region, and the tan δ peak temperature is in a range suitable for prolonging the time from the molten state to the solidification, In the use temperature range of the article, there is no stickiness or blocking between the substrates during storage, while in the temperature range in which the substrates are bonded, adhesion can be achieved with sufficient strength due to tackiness and fluidity.
Further, since the APAO-based pressure-sensitive adhesive can be blended to reduce the amount of the softener component, the "penetration phenomenon" in which the softener component is stained on the surface of the moisture-permeable sheet is suppressed.

[0032]

EXAMPLE As the base polymer, amorphous poly-α-olefin (APAO), propylene
Using butene-1 copolymer, as a tackifier resin, C
_Ninth petroleum resin, a naphthenic process oil as a softening agent, and an antioxidant, Irganox 1010 "pentaerythrityl-tetrakis [3- (3,5-di-t) manufactured by Ciba Geigy Co., Ltd.] -Butyl-4-
Hydroxyphenyl) propionate] ”and kneaded with a kneader under the conditions of a temperature of 150 ° C. and a time of 40 minutes to obtain two types of APAO having the properties shown in the following [Table 1].
A base adhesive was prepared. For comparison, SEBS, a styrenic block polymer, was used as the base polymer.
(Styrene-ethylene-butylene-styrene block copolymer), and the other components were the same.
Two kinds of pressure-sensitive adhesives having the properties shown in the following [Table 1] were prepared in the same manner as the AO-based pressure-sensitive adhesive. The content of the antioxidant was 3% by weight with respect to the base polymer in all the pressure-sensitive adhesives.

Each of the above pressure-sensitive adhesives was applied as a hot melt (HM) at 150 ° C. on a non-woven fabric in a bead shape at a coating amount of 70 mg / m, and the temperature of the bead HM became 45 ° C. At this time, the nonwoven fabric was permeable to moisture at a rate of 1.7 g / 100 c.
Each sample of the present invention products 1 and 2 and the comparative products 1 and 2 was prepared by attaching to a m ² · h moisture permeable sheet. For each of the above samples, the adhesive strength, stickiness, and the blocking strength between diapers (absorbent articles) during storage of the pack (40)
° C, blocking strength due to the flow of the adhesive under pressure), and the degree of strike-through by exudation when stored at 60 ° C for 2 days, according to the following <adhesive strength>, <blocking strength> and <exuding, respectively. Through-through> was measured or evaluated. The results are shown in Table 1 below.

<Adhesive Strength> Under the atmosphere of 20 ° C. and 65% RH, as shown in FIG. 2, the nonwoven fabric 6 constituting the sample 3 was fixed to the nonwoven fabric 6 at both ends by the chuck 8. 6 and hot melt adhesive 1 as described above
Speed 300 from the moisture-permeable sheet 7 attached by
mm / min. And the resistance was determined.

<Blocking Strength> As shown in FIG.
Two of the above samples 3 are superimposed and 100 g / c from the top
m ^TwoAnd stored at 40 ° C. for 7 days. afterwards,
Leave in an atmosphere of 20 ° C. and 65% RH for 30 minutes or more.
Both surfaces on the overlapping surface caused by the flow of the adhesive
Adhesive force between sample 3 and 3 is the same as <Adhesive force>
It was evaluated by the method.

<Tear-through by Exudation> After the above sample was stored at 60 ° C. for 2 days, strike-through of the moisture-permeable sheet due to exudation was visually observed. The symbol "o" in Table 1 indicates that almost no bleeding occurred.
Indicates that a large amount of bleeding occurred. In order to quantitatively measure the degree of bleeding, a black plate 4 was placed on the sample 3 as shown in FIG.
The reflectivity of 9 nm blue incident light was measured. The reduction rate was calculated based on the measured reflectance, and is also shown in [Table 1]. The reflectance was measured using a color difference meter (manufactured by NEC Corporation). The rate of decrease in the reflectance was calculated by the following [Equation 1].

[0037]

(Reduction rate of reflectance) = (ab) / a = 1− (b / a) [%] a: reflectance of blank b: reflectance after 2 days

The tan δ peak temperature of each sample was measured using a viscoelasticity measuring device (DM manufactured by Seiko Electronics Co., Ltd.).
S-110) was measured by the following method. The measurement was performed in a bending mode at a frequency of 1 Hz. T against temperature
An δ was plotted, and the temperature at the maximum value was determined.

[0039]

[Table 1]

As is clear from Table 1 above, the products 1 and 2 of the present invention exhibited an adhesive force between the nonwoven fabric and the moisture-permeable sheet, and almost no blocking occurred between the samples.

That is, in this system, in the temperature range in which the base material is bonded, the pressure-sensitive adhesive has tackiness and a certain degree of fluidity. ) In the operating temperature range, since the pressure-sensitive adhesive had no tackiness, no adhesive force was exhibited, and no blocking or stickiness between substrates occurred. In addition, it was confirmed that in the products 1 and 2 of the present invention, almost no "through phenomenon" caused by seepage of the oil component of the pressure-sensitive adhesive.

On the other hand, in Comparative Examples 1 and 2, since the base polymer of the pressure-sensitive adhesive was a styrene-based block polymer, the ratio of the softener component had to be increased. It is smaller than the APAO-based pressure-sensitive adhesive used in the invention, and exhibits tackiness in the temperature range in which the base material is bonded, and in the diaper (absorbent article) use temperature range. Blocking and stickiness between the substrates occurred. Comparative product 3 is
Although APAO is used as the base polymer, it contains a large amount of petroleum resin (tackifier resin), so its elastic modulus is low, the temperature range for bonding the base material, and the use of diapers (absorbent articles) Since the tackiness was developed in the temperature range, the adhesive strength was developed, and blocking and stickiness between the substrates occurred.

[0043]

As described above, the absorbent article of the present invention has good adhesiveness to a substrate when the absorbent article is manufactured, and has a low tackiness and no stickiness when used. Has good adhesiveness, and there is almost no "through-through phenomenon" in which exuding components such as a softening agent, which are constituent components of the pressure-sensitive adhesive, exude to the surface of the moisture-permeable sheet.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of peeling a sample in an adhesive strength test.

FIG. 2 is a diagram showing a method of pressurizing a sample in a blocking test.

FIG. 3 is a diagram illustrating a measurement principle of a method of quantitatively measuring a “through phenomenon”.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adhesive 3 Sample 4 Black plate 5 Transparent glass plate 6 Nonwoven fabric 7 Moisture permeable sheet 8 Chuck

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-86676 (JP, A) JP-A-58-149303 (JP, A) JP-A-3-37062 (JP, A) JP-A-2- 82974 (JP, A) JP-A-2-209936 (JP, A) JP-B-57-3712 (JP, B2)

Claims (4)

(57) [Claims] 1. An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet and an absorber interposed between these sheets, and integrated with an adhesive, wherein the adhesive is , Containing an amorphous poly-α-olefin and a tackifier resin, the moisture permeability of the back sheet,
0.7~2.8g / 100cm ² · h der is, the pressure-sensitive
5 days at 60 ° C after applying the agent on the back sheet
Reflectance on the surface opposite to the coated surface of the back sheet afterwards
The absorbent article reduction rate, characterized in der Rukoto within 20%. 2. The absorbent article according to claim 1, wherein the pressure-sensitive adhesive contains a softener. 3. The pressure-sensitive adhesive has an elastic modulus of 10 ⁷ at 0 to 40 ° C.
To 10 ⁸ Pa, absorbent article according to claim 1 or 2, wherein it is a 10 ⁵ to 10 ⁷ Pa at 40 to 60 ° C.. 4. The absorbent article according to claim 1, wherein a peak loss temperature (tan δ) of the dynamic viscoelasticity curve of the pressure-sensitive adhesive is in a range of 0 to 40 ° C.