JP2858660B2 - Liquid holding structure and absorbent article provided with the liquid holding structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid-retaining structure and an absorbent article represented by a sanitary napkin, a disposable diaper and an incontinence pad provided with the structure, More specifically, the present invention relates to a liquid retaining structure having excellent liquid retention under pressure and an absorbent article provided with the structure.

[Problems to be solved by conventional technology and invention]

Pulp is economical, has flexibility, and has high hydrophilicity, and thus pulp is widely used as an absorbent for sanitary napkins and disposable diapers. However, the absorption and retention of the liquid by the pulp pile are due to the physical properties of the hydrophilic capillary, and therefore, when a force such as compression or bending is applied, the liquid is easily deformed, and the retained liquid is lost. It has the disadvantage that it is easily released. In addition, the piled fabric shows some degree of compression and bending recovery during drying, but significantly decreases when absorbing water,
It has the disadvantage of not showing any recoverability.

As a result, in actual use mounted on the crotch part, the absorber is twisted and set, which is a main cause of leakage. Therefore, the following techniques (1) and (2) have been disclosed in order to compensate for the above-mentioned drawbacks.

(1) As shown in FIG. 3, a liquid-permeable surface material 1, a liquid-impermeable backsheet 2, an absorber 3 mainly composed of hydrophilic fibers.
An absorbent porous body 4 having a shape-retaining property (foam foam, etc.) is installed in the absorbent or non-use surface of a sanitary napkin composed of a napkin to prevent deformation of the absorbent (J. No.).

(2) As shown in FIG. 4, a hydrophilic fiber and / or a water-absorbing polymer 5 is uniformly dispersed in cells (cells) of an elastic porous body 4 (Japanese Patent Laid-Open No. Sho 56-97448).

However, in the case of (1), the shape retention properties of the entire structure are maintained, but the elastic porous body 4 used has insufficient hydrophilicity or has a skeletal structure effective for absorption and retention of liquid. Therefore, the elastic porous body 4 itself does not substantially have a liquid holding property. Therefore, when the deformation is given, the absorber 3 itself mainly composed of the hydrophilic fiber has no recoverability, and as a result, the absorber 3 itself is twisted and set, and the effect is insufficient.

In the case of (2), although the liquid absorbing property and the liquid retaining property are slightly improved, the liquid retaining property of the elastic porous body 4 itself is still poor, and the liquid absorbing and retaining properties of the hydrophilic fiber and the water absorbing polymer are also observed. Since the performance was limited by the bubble diameter, the performance was still insufficient as an absorbent article.

[Means for solving the problem]

Therefore, the present inventors, in order to solve the disadvantages of the prior art as described above, as a result of intensive research, regardless of the material and configuration, by using a hydrophilic porous body having a specific skeletal structure, It has been found that a liquid-retaining structure having extremely excellent deformation recovery properties and sufficient liquid-absorbing and retaining properties can be obtained, and the present invention has been completed.

That is, the present invention provides a liquid-retaining structure having a three-dimensional skeleton structure composed of a polyurethane foam, wherein at least the surface of the skeleton is hydrophilic, and the average cell diameter of the foam is 50 to 700 μm. And an absorbent article comprising the liquid retaining structure.

To explain the present invention in more detail, the liquid-retaining structure of the present invention has a three-dimensional skeletal structure composed of a polyurethane foam, and the foam has an average cell diameter of 50 to 700 μm, In particular, the ethylene oxide residue content obtained by the production method described in the specification of Japanese Patent Application No. 63-294315 (in a polyether polyol which is a structural unit of polyurethane, ethylene accounts for all alkylene oxides in the polyether polyol) A water-absorbing polyurethane-based foam having an oxide content of 20% by weight or more is preferable because preferable hydrophilicity, skeleton structure, compression characteristics, and the like can be imparted relatively easily.

In the present invention, by using a structure having a foam having an average cell diameter of 50 to 700 μm (refer to Examples for measuring method),
Although a liquid-retaining structure having extremely excellent liquid absorption and liquid retention properties can be obtained, when the average bubble diameter is less than 50 μm, the liquid absorption rate is practically insufficient, and conversely, in a structure exceeding 700 μm,
This is not what the present invention intends because the liquid retaining property becomes insufficient.

The shape of the cell membrane of the polyurethane foam of the present invention is in open cells, closed cells may be mixed, but in order to obtain higher absorption performance, open cells are preferable, and even among open-cell foams It is particularly desirable that the porosity of the cell membrane be 40% or more (see Examples for the measuring method).

The bubble film means a thin film extending from the skeleton, and its composition is substantially the same as the skeleton. A bubble in which adjacent bubbles are blocked from each other by the bubble film is called a closed bubble. On the other hand, a bubble film having open pores, that is, continuous pores, in which adjacent bubbles are not blocked from each other is referred to as a continuous bubble.

On the other hand, the average cell (cell) diameter of the foam corresponds to the distance between the skeletons as described above, and therefore needs to be 50 to 700 μm.

Further, in consideration of the absorption rate, the average pore diameter of the communication holes connecting the bubbles (refer to Examples for the measuring method) is preferably 20 to 200 μm, more preferably 60 to 100 μm.

As for the elasticity of the structure of the present invention, it is preferable that the compressive stress at the time of 50% deformation (refer to Examples for measuring method) is 10 to 200 g / cm ² .

The structure of the present invention requires that at least the surface of the skeleton has a certain degree of hydrophilicity. If the material constituting the skeleton is a hydrophobic material, the structure is treated with an appropriate wetting agent, and the hydrophilicity of the surface is increased. It is preferable that the component material itself has a certain degree of hydrophilicity, since it is not necessary to perform a wetting agent treatment and the process is simplified, which is more preferable. The hydrophilicity is quantified as the degree of hydrophilicity by a powder method (for the measuring method, refer to the examples), and the degree of hydrophilicity is preferably 0.3 or more.

The liquid retaining structure according to the present invention as described above can be used for various applications requiring water absorption as an absorbent member. In particular, it is very effective when used as an absorbent member of absorbent articles such as sanitary napkins, disposable diapers, incontinence pads, and the like.

The configuration of the absorbent article provided with the liquid-retaining structure of the present invention is not particularly limited, and a liquid-permeable surface material, a liquid-impermeable backsheet, and the liquid-retaining property of the present invention which are located therebetween. It consists essentially of an absorber having a structure. Sufficient effects can be obtained even if the absorber is constituted solely of the liquid-retaining structure of the present invention. However, the absorber may be combined with pulverized pulp or other absorbing members, for example, absorbing paper or absorbing polymer.

The liquid-permeable surface material used in the absorbent article of the present invention, the liquid-impermeable back sheet is not particularly limited,
Conventionally used absorbent articles can be used.

Absorbent articles having the liquid-retaining structure of the present invention have excellent water absorption and liquid retention properties, and also have elasticity,
It has extremely good absorbability even when used under pressure and for a long time.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Production Examples and Examples, but the present invention is not limited to these Examples.

In the examples, parts and percentages are by weight unless otherwise specified.

Production Example 1 Ethylene oxide (EO) -propylene oxide (PO) block polymer having a molecular weight of 8350 and an ethylene oxide (EO) content of 80% (Pluronic)
F68, 50 parts of Asahi Denka Kogyo Co., Ltd., 50 parts of polyethylene glycol (PEG) having a molecular weight of 2,000, 2 parts of diethanolamine as a cross-linking agent, and 0.7 parts of tetramethylhexamethylenediamine (Kaolyzer No. 1, Kao Corporation) as a catalyst , Water 3
Parts, 1 part of SH-200 (silicone foam stabilizer, Toray Silicone Co., Ltd.) as a foam stabilizer, 1 part of a methyl-capped compound of lauryl alcohol EO 6 mol adduct and 1 part of a sorbitan fatty acid ester EO adduct as an activator. For 15 seconds. Thereafter, an organic polyisocyanate (TDI, Sumidur T-80, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was added, and the mixture was stirred and mixed. After gelation
The reaction was completed by allowing the mixture to stand in a warmer at 50 ° C. for 20 minutes to obtain a polyether-based polyurethane foam (liquid holding structure 1) having an average cell diameter of 385 μm and an EO content of 90%.

Furthermore, the type of the EO-PO block polymer, the mixing ratio with PEG, etc. were changed, and the same operation was repeated to obtain an average cell diameter of 350 μm.
Polyether-based polyurethane foams (liquid holding structures 2 and 3) having m and 280 μm and EO contents of 60% and 80% were obtained.

As a comparative product, a polyether polyurethane foam having an EO content of 80% with an average cell diameter of 40 μm and 800 μm (liquid holding structure 8,
9) got.

Production Example 2 Average bubble diameter using adipic acid and a polyester-based polyol synthesized from ethylene oxide (EO) -propylene oxide (PO) block polymer (Pluronic L31, average molecular weight 1100, Asahi Denka Kogyo KK) as a polyol. An open-cell ester-based polyurethane foam of 340 μm was obtained. This foam is used as a wetting agent perex OTP (sodium dialkyl sulfosuccinate,
Hydrophilic treatment was performed using Kao Corporation, and 3% by weight of a wetting agent was adhered to the entire foam to obtain a hydrophilic polyurethane foam (liquid holding structure 4).

Further, the ester-based polyurethane foam before the wetting agent treatment is placed in a mixed gas of oxygen and propane, ignited, and the blast causes a thin film portion (bubble film) remaining between the bubbles in the polyurethane foam. A polyurethane foam having an average cell diameter of 437 μm, 300 μm, or 243 μm completely removed was obtained, and treated with a wetting agent in the same manner as described above to obtain a hydrophilic polyurethane foam (liquid retaining structures 5, 6, 7).

In addition, the average bubble diameter is 820 μm and 1750 μ respectively as comparative products.
m, and treated with a wetting agent in the same manner as described above to obtain a hydrophilic polyurethane foam (liquid retaining structures 10, 11).

Examples 1 to 7 and Comparative Examples 1 to 5 The liquid retaining structures 1 to 7 (Examples 1 to 7) of the present invention obtained above and comparative liquid retaining structures 8 to 11 (Comparative Example 1)
The average cell diameter, cell membrane opening ratio, average communicating hole diameter, 50% compressive stress, density, and hydrophilicity of each of the samples (1) to (4) were measured by the following methods.

Further, as a comparative product, physical properties of a flocculent pulp having a density of 0.06 g / cm ³ (liquid holding structure 12, Comparative Example 5) were evaluated in the same manner as described above. Table 1 also shows the results.

(1) Measurement of average cell diameter, cell membrane porosity and average communicating hole diameter After photographing a test sample with an electron microscope, the area of each cell was determined using an image analyzer (Avio EXCEL manufactured by Nippon Avionics). The equivalent circle diameter corresponding to the area was defined as the bubble diameter. The average value of 200 cells was taken as the average cell diameter.

 The cell membrane opening ratio α was determined by the following equation (1).

N ₀ : Number of communicating holes connecting each bubble N ₁ : Number of remaining bubble films connecting each bubble without opening (N ₀ + N ₁ = 200 data was used as the bubble film opening ratio Similarly, for the average communicating hole diameter, the area of the hole connecting the bubbles was determined, and the equivalent circle diameter corresponding to the area was defined as the hole diameter. The pores where the cell membrane was not opened were calculated as having a pore diameter of 0, and the average value of 200 pores was taken as the average communicating pore diameter.

(2) Measurement of 50% compressive stress A sample having a size of 100 mm × 50 mm and a thickness of 5 mm is compressed by a Tensilon compression tester at a compression speed of 10 mm / min and a compression area of 10 cm ² . The compressive stress per unit area when the sample reaches 50% (2.5mm) of the initial thickness, 50% compressive stress (g / cm ² )
Asked.

(3) Measurement of hydrophilicity The hydrophilicity is measured using the apparatus shown in FIG.

First, the following operation is performed using ethanol (EtOH) as the measurement liquid 9.

The liquid level at the side port of ethanol in the measuring table 7 and the burette 6 is set at the same level (to make it equal pressure), and the test is performed on the glass filter 8 (No. 1) with a diameter of 80 mm in the measuring table 7. Piece 10
(50mm thick, 40mm × 40mm rectangular parallelepiped) and immediately load 11
(Weight 80 g, load pressure 5 g / cm ² ) and leave for 60 minutes (at this time, air enters from the side port of the burette by the amount of ethanol absorbed by the test piece, and the liquid level of the side port becomes equal. Kept). During this time, the amount of ethanol absorbed by the test piece was determined.

Next, the measurement solution 9 was changed to physiological saline, and the absorption amount of physiological saline was determined in the same manner as above, and the hydrophilicity cos θ (θ: physiological saline and test Contact angle with the piece) was calculated.

The measurement of the degree of hydrophilicity cosθ is also called a powder method.

The liquid retention structures 1 to 7 of the present invention, and the liquid retention structures 8 to 12 of the comparative product, to confirm the effects of liquid absorption, absorption, liquid retention under pressure, etc. The following methods were used to evaluate the amount of absorption, the amount of reduction, and the absorbency.

 The results are shown in Table 2.

A. Absorption time As shown in FIG. 6, a dried test specimen 13 of 10 mm × 10 mm × 5 mm is placed horizontally, and an acrylic plate 15 having an inlet 14 having a diameter of 10 mm is placed thereon. A weight 16 is further placed on the test piece 13 so that a load of 5 g / cm ² is applied (the sum of the weight of the acrylic plate and the weight is
500g). 10 g of horse blood (defibrillation, Japan Biotest Laboratory Co., Ltd.) is injected from the inlet 14 and the time until the liquid is completely absorbed is defined as the absorption time (second).

B. Absorption amount After cutting the dried test piece into 50 mm x 50 mm x 10 mm,
Put into a 300ml beaker. Next, 200 ml of the horse blood used in A was added, and the test piece was forcibly immersed in a wire mesh so as not to float, and allowed to stand for 30 minutes. After that, 5 mesh on 80mesh wire mesh
The sample was left for a while to drain the water, and the weight of the test piece was measured. The absorption amount was determined by the following equation.

Absorption amount (g) = W ₁ -W ₀ W ₀ : Weight of test specimen after drying (g) W ₁ : Weight of test specimen after absorption (g) C. Retention under pressure Test after absorption used for evaluation of absorption Place the piece on the table,
Weight of 1250g thereon (load per unit area 50 g / cm ²⁾
And leave for 3 minutes. Thereafter, the weight was removed and the weight of the test piece was measured. The amount of absorption was determined by the following equation, and was defined as the amount of reduction.

Amount of rolling reduction (g) = W ₂ -W ₀ W ₂ : 50 g / cm ² Weight of test piece after compression under load (g) W ₀ : Weight of test piece after drying determined by B (g) D. Absorbency The absorbency is measured using the apparatus shown in FIG. The liquid level at the side port of the physiological saline 9 in the measuring table 7 and the burette 6 is set at the same level (to make the pressure equal), and the diameter in the measuring table 7
Specimen 10 (10 mm) was placed on an 80 mm glass filter 8 (No. 1).
Thick, 50 mm x 50 mm rectangular parallelepiped) and immediately load 11 (125
g, 5 g / cm ² load) and let stand for 10 minutes (at this time, air enters from the side port of the burette 6 by the amount that the test piece 10 has absorbed the physiological saline, and the liquid level of the side port is equal. Is kept).
The absorption amount of the physiological saline absorbed by the test piece 10 during this period was defined as the absorption power.

Absorbency (ml / 10min) = amount of physiological saline absorbed after 10 minutes From the results shown in Table 2, it is found that all of the foams having an extremely optimized average cell diameter of 50 to 700 μm have a shorter liquid absorption time and a higher elasticity than the flocculent pulp (Comparative Example 5). Therefore, the liquid retention under pressure is excellent.

In the comparative product, when the average bubble diameter is less than 50 μm,
Slow absorption time, insufficient for practical use, average bubble diameter of 700
If it exceeds μm, on the contrary, the absorption amount and the absorption power become insufficient.

Examples 8 to 14 and Comparative Examples 6 to 10 Absorbent articles as shown in FIG. 1 using liquid holding characteristic structures 1 to 7 of the present invention and liquid holding characteristic structures 8 to 12 of comparative products. Was manufactured.

That is, the liquid-retaining structure 21 is cut out to a size of 170 mm × 70 mm and a thickness of 5 mm, the lower surface and side surfaces thereof are covered with a liquid-impermeable back sheet (polyethylene laminated paper) 22, and the entire surface is further made of a liquid-permeable surface material (polyolefin-based material). (Dry-type nonwoven fabric) 23.

In order to confirm the effect of the obtained absorbent article, the dynamic maximum absorption was measured by the following method.

 Table 3 shows the results.

(1) Measurement of dynamic maximum absorption As shown in FIG. 7, a test sample 19 is attached to a movable female waist model 17 as shown in FIG. Simulated blood was injected by the tube pump 18 and the amount absorbed before the occurrence of lateral leakage was measured. The sample was measured at 10 points, and the average was taken as the dynamic maximum absorption.

From the results shown in Table 3, the product of the present invention has an optimum average bubble diameter, so it has extremely good liquid absorption and liquid retention properties, and has an elastic recovery force so that it can be deformed by the movement of the crotch. It can be seen that no horizontal or vertical leakage can be effectively prevented because no twisting or settling occurs.

Examples 15 to 17 and Comparative Examples 11 to 13 Using the liquid holding structures 3, 5, 7 and the liquid holding structures 8, 10, and 12 as comparative products, as shown in FIG. An absorbent article was manufactured.

That is, two sheets of absorbent paper 24 (basis weight 30 g / m ² , 170 mm × 70 mm × 5 mm) are provided under the liquid storage structure 21 (170 mm × 70 mm × 5 mm).
0.3g of superabsorbent polymer 25 (crosslinked polyacrylic acid) between
The sheets were covered with a liquid-impermeable back sheet (polyethylene laminated paper) 22, and the entire surface was further covered with a liquid-permeable surface material (polyolefin-based dry nonwoven fabric) 23.

In order to confirm the effect of the obtained absorbent article, the dynamic maximum absorption was measured in the same manner as in the above example.

 Table 4 shows the results.

From the results shown in Table 4, when the product of the present invention is combined with another absorbent material such as absorbent paper or an absorbent polymer, the product of the present invention exhibited a higher anti-lateral leakage effect.

〔The invention's effect〕

As described above, the liquid-retaining structure of the present invention has an optimum average cell diameter, and is extremely excellent in liquid-absorbing and liquid-retaining properties, and has elasticity. High liquidity. Therefore, even if the liquid-retaining structure of the present invention is used alone or in combination with another absorbent member, when used as an absorbent such as a sanitary napkin or a disposable diaper, the absorbent has extremely low leakage. It became possible to provide goods.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the absorbent article of the present invention,
FIG. 2 is a cross-sectional view showing another embodiment of the absorbent article of the present invention, FIGS. 3 and 4 are cross-sectional views of a conventional absorbent article, respectively, and FIG. FIG. 6 is a cross-sectional view of the device used for measuring the absorption time,
FIG. 7 is a perspective view of a female waist model used for measurement of the dynamic maximum absorption amount, and FIG. 8 is a perspective view showing a state where a test sample is attached to the female waist model. 1: Liquid permeable surface material 2: Liquid impermeable back sheet 3: Absorber mainly composed of hydrophilic fiber 4: Elastic porous body 5: Hydrophilic fiber and / or water-absorbing polymer 6: Buret 7: Measurement table 8 : Glass filter 9: Measurement liquid 10: Test piece 11: Load 12: Rubber stopper 13: Test piece 14: Injection port 15: Acrylic plate 16: Weight 17: Female waist model 18: Tube pump 19: Test sample 21: Liquid holding Structure 22: Liquid impermeable back sheet 23: Liquid permeable surface material 24: Absorbing paper 25: Super absorbent polymer

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-275118 (JP, A) JP-A-62-227354 (JP, A) JP-A-54-15997 (JP, A) JP-A-1- 108216 (JP, A) JP-A-2-140216 (JP, A) JP-B-63-22824 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) A61F 13/15

Claims (7)

(57) [Claims] 1. A liquid having a three-dimensional skeleton structure composed of a polyurethane foam, wherein at least the surface of the skeleton is hydrophilic, and the average cell diameter of the foam is 50 to 700 μm. Retentive structure. 2. The liquid-retaining structure according to claim 1, wherein the foam has a cell membrane porosity of 40% or more. 3. The liquid-retaining structure according to claim 1, wherein an average communicating hole diameter for connecting the cells of the foam is 20 to 200 μm. 4. The method according to claim 1, wherein the skeleton has a hydrophilicity of at least 0.30.
4. The liquid retaining structure according to any one of 3. 5. The liquid retaining structure according to claim 1, wherein a compressive stress at 50% deformation is 10 to 200 g / cm ² . 6. The liquid according to claim 1, wherein in the polyether polyol which is a structural unit of the polyurethane, the content of ethylene oxide in the total alkylene oxide in the polyether polyol is 20% by weight or more. Retentive structure. 7. An absorbent article comprising the liquid retaining structure according to any one of claims 1 to 6.