JPH02239863A - Liquid holdable structural body and absorptive article having this liquid holdable structural body - Google Patents

Abstract

PURPOSE:To obtain the liquid holdable structural body which has excellent recoverability from deformation and sufficient liquid absorbing and holding property by using a hydrophilic porous body having specific skeleton structure. CONSTITUTION:A water absorptive polyurethane foam which is the structural body having the three-dimensional skeleton structure and 50 to 700mum average interskeleton distance and has >=20wt.% content of residual ethylene oxide group is preferable. Open cells are preferable in this case and further, the foam having >=40% porosity is more particularly preferable. On the other hand, the average cell size of the foam corresponds to the interskeleton distance and is, therefore, required to be 50 to 700mum. The average grain size of the open cells is 20 to 200mum and the elasticity of the structural body is preferably 10 to 200g/cm<2> compression repulsion power at 50% deformation. Further, the hydrophilic degree of at least the skeleton is preferably >=0.3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid-retaining structure and absorbent articles including sanitary napkins, disposable diapers, and incontinence pads, including the structure. Specifically, the present invention relates to a liquid-retaining structure with excellent liquid-retaining properties under pressure and an absorbent article including the structure.

[Prior art and problems to be solved by the invention] Pulp iJ is economical, flexible, and has high hydrophilicity, so it can be used as an absorbent material for sanitary napkins, disposable diapers, etc. It has been widely used. However, water absorption and liquid retention by the fiber stack of the valve is due to the physical properties of hydrophilic capillaries, and therefore, when compression, bending, or other forces are applied, they easily deform and the liquid that was being held is lost. It has the disadvantage that it is easily released. Further, when the fiber stack is dried, it exhibits a certain degree of compression and bending recovery, but when it absorbs water, it significantly decreases and shows no recovery at all.

Kneading causes twisting and bending of the absorbent material during actual use when worn on the crotch area, which is the main cause of leakage. Therefore, in order to compensate for the shortcomings of "-", the following (]). A technique as shown in (2) has been disclosed.

(1) As shown in Fig. 3, a liquid-permeable surface material 1, a liquid-impermeable surface material 2, and an absorbent material 3 mainly made of hydrophilic fibers.
In the absorbent body of a sanitary napkin composed of
- The deformation of the absorbent body is prevented by installing an elastic porous body 4 (foam, etc.) with shape-retaining properties on the use side (Japanese Utility Model Publication No. 56-6099).

(2) As shown in FIG. 4, air bubbles (cells) in the elastic porous body 4
Hydrophilic fibers and/or water-absorbing polymer 5 are uniformly dispersed therein (Japanese Unexamined Patent Publication No. 5,697,448).

However, in the case of (]), although the structure retains its shape as a whole, the bullet porous material 4 used may have insufficient hydrophilicity or a skeletal structure that is effective in absorbing and retaining liquid. Therefore, the elastic porous body 4 has substantially no liquid retention property. Therefore, when deformation is applied, the absorbent body 3, which is mainly made of hydrophilic material and 1 fiber, has no recovery properties, and as a result, the absorbent material 3 itself becomes sagging and becomes ineffective. ” minutes.

In case (2), although a slight improvement in liquid absorption and liquid retention is observed, the liquid retention of the elastic porous body is still poor, and the liquid absorption and retention of the hydrophilic fibers and water absorbing polymer are poor. Since the liquid performance is limited by the bubble diameter, its performance as an absorbent article is still insufficient.

[Failure to solve the problem]

Therefore, in order to solve the above-mentioned drawbacks of the prior art, the present inventors, as a result of intensive research, used a hydrophilic porous material having a specific skeleton structure regardless of its quality and structure. The present inventors have discovered that a liquid-retaining structure with extremely excellent deformation recovery properties and sufficient liquid absorption and retention properties can be obtained by applying the same method, and the present invention has been completed.

That is, the present invention provides a liquid-retaining structure having a three-dimensional skeleton structure, at least the surface of the skeleton being hydrophilic, and an average distance between the skeletons being 50 to 700p; The present invention provides an absorbent article characterized by comprising a structure.

To explain the present invention in more detail, the material of the liquid retaining structure of the present invention is not particularly limited as long as it has a three-dimensional skeleton structure and the average distance between the skeletons is 50 to 700p. You can use whatever you want. For example, Boliu I
/ Tan, polystyrene, polyethylene, polyester, polyvinyl alcohol, butadiene styrene rubber (s
IIR), porous bodies made of synthetic polymers such as 21-lyl butadiene rubber, porous bodies made of polysaccharides such as cellulose,
Porous bodies made of inorganic substances such as diatoms, porous bodies made of synthetic fibers (polyethylene (PE), polypropylene (IMP), polyethylene terephthalate (PET), etc.) bonded by heat fusion or adhesive, etc. can be mentioned. Among these, porous bodies made of synthetic polymers, particularly polyurethane-based or polyolefin-based foams, are preferred, and moreover, porous bodies containing ethylene oxide residues obtained by the manufacturing method described in Japanese Patent Application No. 63-294315 are preferred. amount is 2
A water-absorbing polyurethane foam having a content of 0% by weight or more is preferable because preferred hydrophilicity, skeletal structure, compression properties, etc. can be imparted relatively easily.

In the present invention, the average distance between skeletons refers to the average diameter of each cell in a foam (see Examples for measurement method).
In a porous body made of fibers, it means the average distance between adjacent fibers. By using a structure with an average distance between skeletons of 50 to 700 tm,
A liquid-retaining structure with extremely excellent liquid-absorbing and liquid-retaining properties can be obtained, but when the average distance is less than 50 ρ, the liquid absorption rate is insufficient for practical use. This is not the intention of the present invention because the liquid retention property becomes insufficient.

When the structure of the present invention is a foam, the shape of the cell membrane may be open cells mixed with closed cells, but in order to obtain higher absorption performance, open cells are preferable. Furthermore, among open-cell foams, those with a cell membrane porosity (see Examples for measurement method) of 40% or more are particularly desirable.

Note that the bubble membrane refers to a thin film that extends from the skeleton, and its composition is substantially the same as that of the skeleton. Adjacent cells that are separated from each other by this cell membrane are called closed cells. On the other hand, when the cell membrane has open pores, that is, communicating holes, and adjacent cells are not blocked from each other, it is called open cell.

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

In addition, considering the absorption rate, the average pore diameter of the communicating pores that connect the bubbles (see Examples for the measurement method) is 20 to 2001M.
It is preferably 60-100, more preferably 60-100.

In addition, the elasticity of the structure of the present invention is such that the compressive stress at 50% deformation (see Examples for measurement method) is 10 to 200 g/c.
Preferably, it is m2.

The structure of the present invention needs to have at least a certain degree of hydrophilicity on the surface of the skeleton, and if the material composing the skeleton is a hydrophobic material, it is treated with an appropriate wetting agent to make the surface hydrophilic. It is preferable to use the material with improved hydrophilicity, but it is more preferable if the constituent material itself has a certain degree of hydrophilicity, since there is no need for wetting agent treatment and the process is simplified.

This hydrophilicity is quantified as a degree of hydrophilicity by a powder method (see Examples for the measurement method), and this degree of hydrophilicity is preferably 0.3 or more.

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

The composition of the absorbent article comprising the liquid-retaining structure of the present invention is not particularly limited, and includes a liquid-permeable surface material, a liquid-impermeable backsheet, and a liquid-retaining structure of the present invention located between them. It consists essentially of an absorbent body having a structure. A sufficient effect can be obtained even if the absorbent body is composed of the liquid-retentive structure of the present invention alone, but it may also be combined with pulverized pulp or other absorbent materials such as absorbent paper, water-absorbing polymers, etc.

Further, the liquid-permeable surface material used in the absorbent article of the present invention,
The liquid-impermeable hashik sheet is not particularly limited, and those used in conventionally known absorbent articles can be used.

The absorbent article comprising the liquid retaining structure of the present invention has extremely good water absorption and liquid retention properties, and has elasticity, so it has extremely good absorbency even under pressure and long-term use.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to production examples and examples, but the present invention is not limited to these examples.

In addition, parts and percentages in the examples are based on weight unless otherwise specified.

Production Example 1 50 parts of ethylene oxide (EO)-propylene oxide (PO) block polymer (Pluronic F68, Asahi Denka Kogyo ■) with a molecular weight of 8350 and an ethylene oxide (EO) content of 80% as a polyol and a molecular weight of 200%.
0 polyethylene glycol (PEG) 50 parts, diethanolamine 2 parts as a crosslinking agent, tetramethylhexamethylene diamine (Kaolizer No. 1) as a catalyst.
+ Kao ■) 0.7 parts, 3 parts of water, Sll- as a foam stabilizer
1 part of 200 (silicone foam stabilizer, Toray Silicone ■),
As an activator, 1 part of methyl-capped product of 6 mole adduct of lauryl alcohol EO and sorbitan fatty acid ester EO
Add 1 part of adduct and stir at high speed for 15 seconds. Thereafter, an organic polyisocyanate (TDT, Sumidur T-80 manufactured by Sumitomo Hierurethane) was added and stirred and mixed to form a foamed gel in a few minutes. After gelation, the reaction was completed and the average bubble diameter was 3.
A polyether polyurethane foam (liquid retaining structure 1) having an EO content of 90% was obtained at 85 trm.

Furthermore, by changing the blending ratio of EO to PO block polymer and PEG, the average cell diameter was 350 and 111, respectively, by the same operation.
11, 280, polyether-based polyurethane foam with EO content of 60% and 80% (liquid retaining structure 2
．． 3) was obtained.

In addition, as comparative products, we changed the manufacturing conditions such as moisture content, and produced a product with an average cell diameter of 40/M and an EO content of 800 ta, respectively.
A 0% polyether polyurethane foam (liquid retaining structure 8.9) was obtained.

Production Example 2 Adivic acid and ethylene oxide (
An open-cell ester polyurethane foam having an average cell diameter of 340 IIm was obtained using a polyester polyol synthesized from a block polymer (Pluronic L31, average molecular weight 1100, Asahi Denka Kogyo ■). This foam was hydrophilized using Verex OTP (sodium dialkyl sulfosuccinate, Kao ■) as a wetting agent, and 3% by weight of the wetting agent was attached to the entire foam to form a hydrophilic polyurethane foam (liquid-retaining structure 4). I got it.

In addition, the ester-based polyurethane foam before the wetting agent treatment was heat-treated to completely remove the cell membrane, and the average cell diameter was 437 urn, 300 tnn, 243 tr.
rn polyurethane foam was obtained and treated with a wetting agent in the same manner as above to obtain a hydrophilic polyurethane foam (liquid retaining structure 5, 6.7).

In addition, as comparison products, average bubble diameters of 820- and 175
An ester polyurethane foam having a value of 0ρ was obtained and treated with a wetting agent in the same manner as above to obtain a hydrophilic polyurethane foam (liquid-retaining structure 10 and 11).

Examples 1 to 7 and Comparative Examples 1 to 5 Liquid retention structures 1 to 7 of the present invention (Examples 1 to 7) and comparative liquid retention structures 8 to 11 (Comparative Example 1) obtained above
For ~4), the average cell diameter, cell membrane porosity, average communicating pore diameter, 50% compressive stress, density, and hydrophilicity were measured by the following methods, and a series of measurement results are shown in Table 1.

Furthermore, as a comparative product, the physical properties of flocculent pulverized pulp (Liquid Retaining Structure 12, Comparative Example 5) having a density of 0.06 g/cm3 were evaluated in the same manner as above. The results are also shown in Table 1.

(1) Measurement of average bubble diameter, bubble membrane porosity, and average communicating pore diameter After photographing the test sample with an electron microscope, use an image analysis device (AvioEXCEL manufactured by Nippon Avionics Co., Ltd.) to determine the area of each bubble. 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 bubble diameter.

The bubble membrane porosity α was determined by the following equation (1).

N7 No: Number of communication holes connecting each bubble N,: Number of cells remaining without opening in the cell membrane connecting each cell (The data of No + NI = 200 was taken as the cell membrane porosity.) Average Regarding the diameter of the communicating pores, the area of the pores connecting each bubble was similarly determined, and the equivalent circular diameter corresponding to the area was determined as the pore diameter. Calculate the pores where the bubble membrane is not open as having a pore diameter of 0,
The average value a of 200 pores was taken as the average communicating pore diameter.

(2) Measurement of 50% compressive stress A sample of 100 mm x 50 mm and 5 mm thickness is compressed using a Tensilon compression tester at a compression speed of 10 mm/min and a compression area of 10 cm.The sample has an initial thickness of 5 mm.
The compressive stress per unit area when the stress reached 0% (2.5 mm) was determined as 50% compressive stress (g/cm'').

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

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

Set the measuring table 7 and the liquid level at the side port of the puree 6 at the same level (so that the pressure is equal), and place the test sample on the glass filter 8 (No. 1) with a diameter of 80 mm in the measuring table 7. Place piece 10 (.50 mm thickness, 40 mm
Air enters from the side port of the burette by the amount of ethanol absorbed by the test piece, and the liquid level at the side port is maintained at the same level). During this time, the amount of ethanol absorbed by the test piece was determined.

Next, change the measurement solution 9 to physiological saline, calculate the absorbed amount of physiological saline using the same method as above, and use the following formula to determine the hydrophilicity between the physiological saline and the test piece cos θ (θ: between the physiological saline and the test piece) The contact angle with the piece was calculated.

In addition, the measurement of this hydrophilicity cos θ is as follows: is also called.

V plate × 1 2 × ρ 1 Liquid absorbency, absorption capacity, and liquid retention under pressure of liquid-retaining structures 1 to 7, which are products of the present invention, and liquid-retaining structures 8 to 12, which are comparative products. In order to confirm the effects such as absorption time, absorption amount,
The rolling retention amount and absorption capacity were evaluated using the following methods.

The results are shown in Table 2.

As shown in Figure 6, the dry 10mm x 10mm
A test piece 13 with a diameter of 5 mm is placed horizontally, and an acrylic plate 15 with an injection port 14 with a diameter of 10 vn is placed thereon. Test piece 13
A weight 16 is further placed on the plate so that a load of 5 g/cm2 is applied to the plate (the sum of the weight of the acrylic plate and the weight is 500 g). 10 g of horse blood (defibrinated, ■Japan Biotest Institute) is injected through the injection port 14, and the time taken until the liquid is completely absorbed is defined as the absorption time (seconds).

L 1 x 1 dry test piece 50mm x 50mm x 10m
After canting to m, put it in a 300ml beaker.

Next, 200 ml of the horse blood used in Section 8 was added, and the test piece was forcibly immersed with a wire mesh so that it would not float, and left for 30 minutes. Thereafter, the test piece was left on an 80 mesh wire mesh for 5 hours to drain water, and the weight of the test piece was measured. According to the formula shown below,
The amount of absorption was determined.

Absorption amount (g) 1L W6 llIo: Weight of test piece when dry (g) -1: Weight of test piece after absorption! Jt (g) ■Place the test piece after absorption used for the evaluation of absorption amount on a table, and place a 1250g weight (50g/c per unit area) on the table.
m2 load) and leave it for 3 minutes. Thereafter, the weight was removed and the weight of the test piece was measured. The amount of absorption was determined using the formula shown below and was defined as the amount of retention under pressure.

Rolling down holding N (g)-L-Wo Wz: Test piece after compression with 50g/cm2 loadffif
fl (g) tilo: Weight of test piece when dry determined in B (
g) Measure the absorption capacity using the device shown in Figure 5. The measuring table 7 and the liquid level of the side port of the saline 9 in the puree 6 are placed at the same level (so that the pressure is equal), and the diameter of the measuring table 7 is 8.
Test piece 1 on 0mm glass filter 8 (No. 1)
0 (10mm thick, 50mm x 50mm rectangular parallelepiped)
and immediately apply load 11 (125 g, 5 g/cm
2 load) and leave it for 10 minutes (at this time, test piece 1
Air enters from the side port of the puret 6 by the amount that 0 absorbed physiological saline, and the liquid level at the side port is maintained at the same level).

The amount of physiological saline absorbed by the test piece 10 during this period was defined as the absorption capacity.

Absorption power (m!/10min) - Amount of physiological saline absorbed after 10 minutes - Table 2 Absorption performance of the structure From the results shown in Table 2, the structure was designed to have an extremely optimal average bubble diameter of 50 to 700. As for the foams, the liquid absorption time is shorter than that of the flocculent crushed bulb comparative example 5), and since they have elasticity, they have excellent liquid retention properties under pressure.

In the comparison product, if the average bubble diameter is less than 50p, the absorption time is slow and it is not practical enough, and the average bubble diameter is 700p.
If it exceeds tm, the amount of absorption and absorption capacity will be insufficient.

Examples 8 to 14 and Comparative Examples 6 to 10 Absorbent articles as shown in FIG. was manufactured.

That is, the liquid retaining structure 2l is 170 mm x 70 mm.
It was cut out to a thickness of 5 mm, and its lower and side surfaces were covered with a liquid-impermeable backsheet (polyethylene laminate paper) 22, and the entire surface was further covered with a liquid-permeable surface material (polyolefin dry nonwoven fabric) 23.

In order to confirm the effectiveness of the obtained absorbent article, the maximum dynamic absorption amount was measured using the method shown below.

The results are shown in Table 3.

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

Table 3 Performance of absorbent article (1) From the results shown in Table 3, the product of the present invention has an optimal average cell diameter, has extremely good liquid absorption and liquid retention properties, and has excellent elastic recovery power. Because of this, even if it is deformed due to the movement of the crotch, it does not twist or become loose, so it can be seen that side leakage can be effectively prevented.

Examples 15 to 17 and Comparative Examples 11 to 13 Liquid retaining structures 3 and 5 which are products of the present invention. 7 and comparative liquid retaining structures 8 and 10. 12, an absorbent article as shown in FIG. 2 was manufactured.

That is, the liquid retaining structure 21 (170 mm x 70 mm
x 5mm), place two sheets of absorbent paper 24 (basis weight 30g/
super absorbent polymer 25 (polyacrylic acid crosslinked product) 0
．． Absorbent sheets sprinkled with 3 g were installed, and these were covered with a liquid-impermeable octane sheet (polyethylene laminate paper) 22, and the entire surface was further covered with a liquid-permeable surface material (polyolefin dry nonwoven fabric) 23.

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

The results are shown in Table 4.

Table 4 Performance of Absorbent Article (2) From the results shown in Table 4, the product of the present invention showed an even higher lateral leakage prevention effect when combined with other absorbent materials such as absorbent paper and water-absorbing polymers.

〔Effect of the invention〕

As shown above, the liquid-retaining structure of the present invention has an optimal average cell diameter, so it has excellent liquid-absorbing and liquid-retaining properties, and has elasticity, so it retains water under pressure. It is also highly liquid. Therefore, whether the liquid-retaining structure of the present invention is used alone or in combination with other absorbent members, when used as an absorbent material for sanitary napkins, paper diapers, etc., it has extremely low leakage properties. It became possible to provide goods.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an 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 conventional absorbent articles, and FIG. 5 is a cross-sectional view showing another embodiment of the absorbent article of the present invention. Figure 6 is a cross-sectional view of the device used to measure absorption time, Figure 7 is a perspective view of a female waist model used to measure dynamic maximum absorption, and Figure 8 is a female waist model. FIG. 3 is a perspective view showing a state in which a test sample is attached to the device. 1: Liquid-permeable surface material 2: Liquid-impermeable backsheet 3: Absorbent material mainly composed of hydrophilic fibers 4: Elastic porous material 5: Hydrophilic fibers and/or water-absorbing polymer 6: 7 28: 9 = 10: 11: 12= 13: 14: 15: 16: 17: 18: 19: 21: 22: 23: 24: 25: Puree 1- Measuring stand Glass filter Measuring liquid test piece Loading Rubber stopper Test piece Inlet Acrylic Plate weight Female waist model Tube pump test sample Liquid retention structure Body fluid impermeable Hacksy-1 Liquid permeable surface material Absorbent paper Super absorbent polymer

Claims (10)

[Claims] 1. It has a three-dimensional skeleton structure, at least the surface of the skeleton is hydrophilic, and the average distance between the skeletons is 50 to 70.
A liquid retaining structure characterized by having a particle size of 0 μm. 2. The liquid-retaining structure according to claim 1, wherein the liquid-retaining structure is made of a foam. 3. The liquid retaining structure according to claim 2, wherein the foam has an average cell diameter of 50 to 700 μm. 4. The liquid retaining structure according to claim 2 or 3, wherein the foam has a cell membrane porosity of 40% or more. 5. The average communicating pore diameter connecting each cell of the foam is 20
The liquid-retaining structure according to any one of claims 2 to 4, which has a diameter of 200 μm. 6. Claims 1 to 5, wherein the hydrophilicity of the skeleton is 0.30 or more.
The liquid-retaining structure according to any one of the above. 7. Compressive stress at 50% deformation is 10-200g/cm
The liquid retaining structure according to any one of claims 1 to 6, which is ^2. 8. The liquid retaining structure according to any one of claims 2 to 7, wherein the foam is made of polyurethane. 9. Ethylene oxide content of polyurethane is 20
9. The liquid retaining structure according to claim 8, wherein the liquid retention structure is at least % by weight. 10. An absorbent article comprising the liquid retaining structure according to any one of claims 1 to 9.